Off-topic question - power density at sample - calculation/estimation

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Jacqui Ross Jacqui Ross
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Off-topic question - power density at sample - calculation/estimation

*****
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*****

Hi everyone,

I've been contacted by someone in our faculty who needs to estimate/calculate the power density of the fluorescence light source at the sample. He knows the lamp power and the objective lens  (water lens) and NA. We also know the field of view.

I've looked online but haven't found a method for working this out as yet.

Can anyone help?

Kind regards,

Jacqui

Jacqueline Ross
Lead Technologist
Optical Microscopy & Image Analysis
Biomedical Imaging Research Unit (BIRU)
School of Medical Sciences
Faculty of Medical & Health Sciences
The University of Auckland
Private Bag 92019
Auckland 1142, NEW ZEALAND

Telephone: Ext 87438; DDI:  +64 9 923 7438

Website:    http://www.auckland.ac.nz/biru
Craig Brideau Craig Brideau
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Re: Off-topic question - power density at sample - calculation/estimation

*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
Post images on http://www.imgur.com and include the link in your posting.
*****

The absorption of the microscope optics, and losses due to the exact way
the light source is coupled into the system, can lead to widely varying
actual power levels at the sample. Typically I would measure this with an
appropriate power meter at the sample plane to get a precise number. Trying
to estimate the losses is probably a losing battle and could put you off by
an order of magnitude in some cases.

Craig

On Thu, May 28, 2020 at 3:31 PM Jacqueline Ross <[hidden email]>
wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> Hi everyone,
>
> I've been contacted by someone in our faculty who needs to
> estimate/calculate the power density of the fluorescence light source at
> the sample. He knows the lamp power and the objective lens  (water lens)
> and NA. We also know the field of view.
>
> I've looked online but haven't found a method for working this out as yet.
>
> Can anyone help?
>
> Kind regards,
>
> Jacqui
>
> Jacqueline Ross
> Lead Technologist
> Optical Microscopy & Image Analysis
> Biomedical Imaging Research Unit (BIRU)
> School of Medical Sciences
> Faculty of Medical & Health Sciences
> The University of Auckland
> Private Bag 92019
> Auckland 1142, NEW ZEALAND
>
> Telephone: Ext 87438; DDI:  +64 9 923 7438
>
> Website:    http://www.auckland.ac.nz/biru
>
Jacqui Ross Jacqui Ross
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Re: Off-topic question - power density at sample - calculation/estimation

*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
Post images on http://www.imgur.com and include the link in your posting.
*****

Thanks Craig,

I was thinking the same actually. Excuse my ignorance but what kind of power meter would we need? Something similar to what is used for measuring laser power at the objective lens?

Kind regards,

Jacqui

-----Original Message-----
From: Confocal Microscopy List <[hidden email]> On Behalf Of Craig Brideau
Sent: Friday, May 29, 2020 10:37 AM
To: [hidden email]
Subject: Re: Off-topic question - power density at sample - calculation/estimation

*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
Post images on http://www.imgur.com and include the link in your posting.
*****

The absorption of the microscope optics, and losses due to the exact way
the light source is coupled into the system, can lead to widely varying
actual power levels at the sample. Typically I would measure this with an
appropriate power meter at the sample plane to get a precise number. Trying
to estimate the losses is probably a losing battle and could put you off by
an order of magnitude in some cases.

Craig

On Thu, May 28, 2020 at 3:31 PM Jacqueline Ross <[hidden email]>
wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> Hi everyone,
>
> I've been contacted by someone in our faculty who needs to
> estimate/calculate the power density of the fluorescence light source at
> the sample. He knows the lamp power and the objective lens  (water lens)
> and NA. We also know the field of view.
>
> I've looked online but haven't found a method for working this out as yet.
>
> Can anyone help?
>
> Kind regards,
>
> Jacqui
>
> Jacqueline Ross
> Lead Technologist
> Optical Microscopy & Image Analysis
> Biomedical Imaging Research Unit (BIRU)
> School of Medical Sciences
> Faculty of Medical & Health Sciences
> The University of Auckland
> Private Bag 92019
> Auckland 1142, NEW ZEALAND
>
> Telephone: Ext 87438; DDI:  +64 9 923 7438
>
> Website:    http://www.auckland.ac.nz/biru
>
Craig Brideau Craig Brideau
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Re: Off-topic question - power density at sample - calculation/estimation

*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
Post images on http://www.imgur.com and include the link in your posting.
*****

Yes, those will work, but you need to consider two things: Lamp sources
will be broadband, and most of the "at the objective lens" sensors are
silicon based, which have a specific wavelength response. You typically set
the wavelength on the meter to the wavelength of your laser to get the
correct measurement. Since the lamp will be broadband, the meter will only
be usable if you are band-pass filtering the light. This is typical for
excitation filters in most fluorescent regimes, but not effective for white
light illumination. Since you mention fluorescence in your message I assume
your user is working with a particular excitation band. Simply set the
wavelength of your power meter to the middle of the band and you should get
a reasonably accurate reading. For instance if the excitation filter is
490/20 (490nm centered in 20nm bandwidth) then set the wavelength of the
meter to 490nm.
The second consideration is that the spot from the lamp will be larger than
a laser spot since it illuminates the entire field of view. Your sensor
will have to be large enough to collect the entire spot. It is also
recommended that you do not place the surface of your power meter directly
at the focus, so you will want do defocus the point of light on the meter
rather than having minimum spot size. The reason for this is that a large
area silicon detector can give incorrect results if the majority of the
sensor surface is not illuminated: It is better to spread the power out
over a wider area of sensor so that it is evenly distributed rather than
having a single high-intensity point in the middle of the active detection
area. Note this also applies for measuring lasers; do not put a focused
laser spot on your active sensor area.

Craig

On Thu, May 28, 2020 at 4:40 PM Jacqueline Ross <[hidden email]>
wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> Thanks Craig,
>
> I was thinking the same actually. Excuse my ignorance but what kind of
> power meter would we need? Something similar to what is used for measuring
> laser power at the objective lens?
>
> Kind regards,
>
> Jacqui
>
> -----Original Message-----
> From: Confocal Microscopy List <[hidden email]> On
> Behalf Of Craig Brideau
> Sent: Friday, May 29, 2020 10:37 AM
> To: [hidden email]
> Subject: Re: Off-topic question - power density at sample -
> calculation/estimation
>
> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> The absorption of the microscope optics, and losses due to the exact way
> the light source is coupled into the system, can lead to widely varying
> actual power levels at the sample. Typically I would measure this with an
> appropriate power meter at the sample plane to get a precise number. Trying
> to estimate the losses is probably a losing battle and could put you off by
> an order of magnitude in some cases.
>
> Craig
>
> On Thu, May 28, 2020 at 3:31 PM Jacqueline Ross <
> [hidden email]>
> wrote:
>
> > *****
> > To join, leave or search the confocal microscopy listserv, go to:
> > http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> > Post images on http://www.imgur.com and include the link in your
> posting.
> > *****
> >
> > Hi everyone,
> >
> > I've been contacted by someone in our faculty who needs to
> > estimate/calculate the power density of the fluorescence light source at
> > the sample. He knows the lamp power and the objective lens  (water lens)
> > and NA. We also know the field of view.
> >
> > I've looked online but haven't found a method for working this out as
> yet.
> >
> > Can anyone help?
> >
> > Kind regards,
> >
> > Jacqui
> >
> > Jacqueline Ross
> > Lead Technologist
> > Optical Microscopy & Image Analysis
> > Biomedical Imaging Research Unit (BIRU)
> > School of Medical Sciences
> > Faculty of Medical & Health Sciences
> > The University of Auckland
> > Private Bag 92019
> > Auckland 1142, NEW ZEALAND
> >
> > Telephone: Ext 87438; DDI:  +64 9 923 7438
> >
> > Website:    http://www.auckland.ac.nz/biru
> >
>
Cvic Innocent Cvic Innocent
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Re: Off-topic question - power density at sample - calculation/estimation

In reply to this post by Jacqui Ross
*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
Post images on http://www.imgur.com and include the link in your posting.
*****

Hello Jacqui

Consider a power meter like this:
https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=3341

Comes in quite handy as there are a variety of sensors from which to
choose, including a slide sensor (S170C) which would suit your needs well
(other sensors are designed for measuring at different locations of your
optical path).

Cordially,
cvic
.....
On Thu, May 28, 2020 at 5:31 PM Jacqueline Ross <[hidden email]>
wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> Hi everyone,
>
> I've been contacted by someone in our faculty who needs to
> estimate/calculate the power density of the fluorescence light source at
> the sample. He knows the lamp power and the objective lens  (water lens)
> and NA. We also know the field of view.
>
> I've looked online but haven't found a method for working this out as yet.
>
> Can anyone help?
>
> Kind regards,
>
> Jacqui
>
> Jacqueline Ross
> Lead Technologist
> Optical Microscopy & Image Analysis
> Biomedical Imaging Research Unit (BIRU)
> School of Medical Sciences
> Faculty of Medical & Health Sciences
> The University of Auckland
> Private Bag 92019
> Auckland 1142, NEW ZEALAND
>
> Telephone: Ext 87438; DDI:  +64 9 923 7438
>
> Website:    http://www.auckland.ac.nz/biru


On Thu, May 28, 2020 at 6:40 PM Jacqueline Ross <[hidden email]>
wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> Thanks Craig,
>
> I was thinking the same actually. Excuse my ignorance but what kind of
> power meter would we need? Something similar to what is used for measuring
> laser power at the objective lens?
>
> Kind regards,
>
> Jacqui
>
> -----Original Message-----
> From: Confocal Microscopy List <[hidden email]> On
> Behalf Of Craig Brideau
> Sent: Friday, May 29, 2020 10:37 AM
> To: [hidden email]
> Subject: Re: Off-topic question - power density at sample -
> calculation/estimation
>
> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> The absorption of the microscope optics, and losses due to the exact way
> the light source is coupled into the system, can lead to widely varying
> actual power levels at the sample. Typically I would measure this with an
> appropriate power meter at the sample plane to get a precise number. Trying
> to estimate the losses is probably a losing battle and could put you off by
> an order of magnitude in some cases.
>
> Craig
>
> On Thu, May 28, 2020 at 3:31 PM Jacqueline Ross <
> [hidden email]>
> wrote:
>
> > *****
> > To join, leave or search the confocal microscopy listserv, go to:
> > http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> > Post images on http://www.imgur.com and include the link in your
> posting.
> > *****
> >
> > Hi everyone,
> >
> > I've been contacted by someone in our faculty who needs to
> > estimate/calculate the power density of the fluorescence light source at
> > the sample. He knows the lamp power and the objective lens  (water lens)
> > and NA. We also know the field of view.
> >
> > I've looked online but haven't found a method for working this out as
> yet.
> >
> > Can anyone help?
> >
> > Kind regards,
> >
> > Jacqui
> >
> > Jacqueline Ross
> > Lead Technologist
> > Optical Microscopy & Image Analysis
> > Biomedical Imaging Research Unit (BIRU)
> > School of Medical Sciences
> > Faculty of Medical & Health Sciences
> > The University of Auckland
> > Private Bag 92019
> > Auckland 1142, NEW ZEALAND
> >
> > Telephone: Ext 87438; DDI:  +64 9 923 7438
> >
> > Website:    http://www.auckland.ac.nz/biru
> >
>
leavesley leavesley
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Re: Off-topic question - power density at sample - calculation/estimation

*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
Post images on http://www.imgur.com and include the link in your posting.
*****

Hi All,

If you're using an arc lamp for a widefield system, my personal
preference is a fiber-coupled spectrometer with integrating sphere (or
other sampling accessory), calibrated to a NIST-traceable light source. 
It is fascinating what you start learning about the transmission
properties of your filters and other components of the microscope when
you start poking around with a spectrometer. Checking all your filters
in the filter cube for cross-talk and has helped us to identify the
source of strange signals in several cases.

Best regards,

Silas


On 5/28/2020 7:19 PM, Cvic Innocent wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> Hello Jacqui
>
> Consider a power meter like this:
> https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=3341
>
> Comes in quite handy as there are a variety of sensors from which to
> choose, including a slide sensor (S170C) which would suit your needs well
> (other sensors are designed for measuring at different locations of your
> optical path).
>
> Cordially,
> cvic
> .....
> On Thu, May 28, 2020 at 5:31 PM Jacqueline Ross <[hidden email]>
> wrote:
>
>> *****If
>> To join, leave or search the confocal microscopy listserv, go to:
>> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
>> Post images on http://www.imgur.com and include the link in your posting.
>> *****
>>
>> Hi everyone,
>>
>> I've been contacted by someone in our faculty who needs to
>> estimate/calculate the power density of the fluorescence light source at
>> the sample. He knows the lamp power and the objective lens  (water lens)
>> and NA. We also know the field of view.
>>
>> I've looked online but haven't found a method for working this out as yet.
>>
>> Can anyone help?
>>
>> Kind regards,
>>
>> Jacqui
>>
>> Jacqueline Ross
>> Lead Technologist
>> Optical Microscopy & Image Analysis
>> Biomedical Imaging Research Unit (BIRU)
>> School of Medical Sciences
>> Faculty of Medical & Health Sciences
>> The University of Auckland
>> Private Bag 92019
>> Auckland 1142, NEW ZEALAND
>>
>> Telephone: Ext 87438; DDI:  +64 9 923 7438
>>
>> Website:    http://www.auckland.ac.nz/biru
>
> On Thu, May 28, 2020 at 6:40 PM Jacqueline Ross <[hidden email]>
> wrote:
>
>> *****
>> To join, leave or search the confocal microscopy listserv, go to:
>> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
>> Post images on http://www.imgur.com and include the link in your posting.
>> *****
>>
>> Thanks Craig,
>>
>> I was thinking the same actually. Excuse my ignorance but what kind of
>> power meter would we need? Something similar to what is used for measuring
>> laser power at the objective lens?
>>
>> Kind regards,
>>
>> Jacqui
>>
>> -----Original Message-----
>> From: Confocal Microscopy List <[hidden email]> On
>> Behalf Of Craig Brideau
>> Sent: Friday, May 29, 2020 10:37 AM
>> To: [hidden email]
>> Subject: Re: Off-topic question - power density at sample -
>> calculation/estimation
>>
>> *****
>> To join, leave or search the confocal microscopy listserv, go to:
>> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
>> Post images on http://www.imgur.com and include the link in your posting.
>> *****
>>
>> The absorption of the microscope optics, and losses due to the exact way
>> the light source is coupled into the system, can lead to widely varying
>> actual power levels at the sample. Typically I would measure this with an
>> appropriate power meter at the sample plane to get a precise number. Trying
>> to estimate the losses is probably a losing battle and could put you off by
>> an order of magnitude in some cases.
>>
>> Craig
>>
>> On Thu, May 28, 2020 at 3:31 PM Jacqueline Ross <
>> [hidden email]>
>> wrote:
>>
>>> *****
>>> To join, leave or search the confocal microscopy listserv, go to:
>>> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
>>> Post images on http://www.imgur.com and include the link in your
>> posting.
>>> *****
>>>
>>> Hi everyone,
>>>
>>> I've been contacted by someone in our faculty who needs to
>>> estimate/calculate the power density of the fluorescence light source at
>>> the sample. He knows the lamp power and the objective lens  (water lens)
>>> and NA. We also know the field of view.
>>>
>>> I've looked online but haven't found a method for working this out as
>> yet.
>>> Can anyone help?
>>>
>>> Kind regards,
>>>
>>> Jacqui
>>>
>>> Jacqueline Ross
>>> Lead Technologist
>>> Optical Microscopy & Image Analysis
>>> Biomedical Imaging Research Unit (BIRU)
>>> School of Medical Sciences
>>> Faculty of Medical & Health Sciences
>>> The University of Auckland
>>> Private Bag 92019
>>> Auckland 1142, NEW ZEALAND
>>>
>>> Telephone: Ext 87438; DDI:  +64 9 923 7438
>>>
>>> Website:    http://www.auckland.ac.nz/biru
>>>
--
Silas J. Leavesley, Ph.D.
Professor
Department of Chemical and Biomolecular Engineering
Department of Pharmacology
Center for Lung Biology
University of South Alabama
150 Jaguar Drive, SH4129
Mobile, AL 36688
ph: (251)-460-6160
fax: (251)-461-1485
web: http://www.southalabama.edu/centers/bioimaging
google scholar: http://scholar.google.co.uk/citations?user=knkwcj4AAAAJ
Jacqui Ross Jacqui Ross
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Re: Off-topic question - power density at sample - calculation/estimation

In reply to this post by Cvic Innocent
*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
Post images on http://www.imgur.com and include the link in your posting.
*****

Thanks Cvic,

I will look into this.

Kind regards,

Jacqui

-----Original Message-----
From: Confocal Microscopy List <[hidden email]> On Behalf Of Cvic Innocent
Sent: Friday, May 29, 2020 12:19 PM
To: [hidden email]
Subject: Re: Off-topic question - power density at sample - calculation/estimation

*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
Post images on http://www.imgur.com and include the link in your posting.
*****

Hello Jacqui

Consider a power meter like this:
https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=3341

Comes in quite handy as there are a variety of sensors from which to
choose, including a slide sensor (S170C) which would suit your needs well
(other sensors are designed for measuring at different locations of your
optical path).

Cordially,
cvic
.....
On Thu, May 28, 2020 at 5:31 PM Jacqueline Ross <[hidden email]>
wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> Hi everyone,
>
> I've been contacted by someone in our faculty who needs to
> estimate/calculate the power density of the fluorescence light source at
> the sample. He knows the lamp power and the objective lens  (water lens)
> and NA. We also know the field of view.
>
> I've looked online but haven't found a method for working this out as yet.
>
> Can anyone help?
>
> Kind regards,
>
> Jacqui
>
> Jacqueline Ross
> Lead Technologist
> Optical Microscopy & Image Analysis
> Biomedical Imaging Research Unit (BIRU)
> School of Medical Sciences
> Faculty of Medical & Health Sciences
> The University of Auckland
> Private Bag 92019
> Auckland 1142, NEW ZEALAND
>
> Telephone: Ext 87438; DDI:  +64 9 923 7438
>
> Website:    http://www.auckland.ac.nz/biru


On Thu, May 28, 2020 at 6:40 PM Jacqueline Ross <[hidden email]>
wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> Thanks Craig,
>
> I was thinking the same actually. Excuse my ignorance but what kind of
> power meter would we need? Something similar to what is used for measuring
> laser power at the objective lens?
>
> Kind regards,
>
> Jacqui
>
> -----Original Message-----
> From: Confocal Microscopy List <[hidden email]> On
> Behalf Of Craig Brideau
> Sent: Friday, May 29, 2020 10:37 AM
> To: [hidden email]
> Subject: Re: Off-topic question - power density at sample -
> calculation/estimation
>
> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> The absorption of the microscope optics, and losses due to the exact way
> the light source is coupled into the system, can lead to widely varying
> actual power levels at the sample. Typically I would measure this with an
> appropriate power meter at the sample plane to get a precise number. Trying
> to estimate the losses is probably a losing battle and could put you off by
> an order of magnitude in some cases.
>
> Craig
>
> On Thu, May 28, 2020 at 3:31 PM Jacqueline Ross <
> [hidden email]>
> wrote:
>
> > *****
> > To join, leave or search the confocal microscopy listserv, go to:
> > http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> > Post images on http://www.imgur.com and include the link in your
> posting.
> > *****
> >
> > Hi everyone,
> >
> > I've been contacted by someone in our faculty who needs to
> > estimate/calculate the power density of the fluorescence light source at
> > the sample. He knows the lamp power and the objective lens  (water lens)
> > and NA. We also know the field of view.
> >
> > I've looked online but haven't found a method for working this out as
> yet.
> >
> > Can anyone help?
> >
> > Kind regards,
> >
> > Jacqui
> >
> > Jacqueline Ross
> > Lead Technologist
> > Optical Microscopy & Image Analysis
> > Biomedical Imaging Research Unit (BIRU)
> > School of Medical Sciences
> > Faculty of Medical & Health Sciences
> > The University of Auckland
> > Private Bag 92019
> > Auckland 1142, NEW ZEALAND
> >
> > Telephone: Ext 87438; DDI:  +64 9 923 7438
> >
> > Website:    http://www.auckland.ac.nz/biru
> >
>
Jacqui Ross Jacqui Ross
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Re: Off-topic question - power density at sample - calculation/estimation

In reply to this post by leavesley
*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
Post images on http://www.imgur.com and include the link in your posting.
*****

Thanks Silas,

I may be able to get someone from our Physics Dept to help with this approach.

Kind regards,

Jacqui

-----Original Message-----
From: Confocal Microscopy List <[hidden email]> On Behalf Of Silas Leavesley
Sent: Friday, May 29, 2020 1:22 PM
To: [hidden email]
Subject: Re: Off-topic question - power density at sample - calculation/estimation

*****
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Hi All,

If you're using an arc lamp for a widefield system, my personal
preference is a fiber-coupled spectrometer with integrating sphere (or
other sampling accessory), calibrated to a NIST-traceable light source. 
It is fascinating what you start learning about the transmission
properties of your filters and other components of the microscope when
you start poking around with a spectrometer. Checking all your filters
in the filter cube for cross-talk and has helped us to identify the
source of strange signals in several cases.

Best regards,

Silas


On 5/28/2020 7:19 PM, Cvic Innocent wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> Hello Jacqui
>
> Consider a power meter like this:
> https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=3341
>
> Comes in quite handy as there are a variety of sensors from which to
> choose, including a slide sensor (S170C) which would suit your needs well
> (other sensors are designed for measuring at different locations of your
> optical path).
>
> Cordially,
> cvic
> .....
> On Thu, May 28, 2020 at 5:31 PM Jacqueline Ross <[hidden email]>
> wrote:
>
>> *****If
>> To join, leave or search the confocal microscopy listserv, go to:
>> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
>> Post images on http://www.imgur.com and include the link in your posting.
>> *****
>>
>> Hi everyone,
>>
>> I've been contacted by someone in our faculty who needs to
>> estimate/calculate the power density of the fluorescence light source at
>> the sample. He knows the lamp power and the objective lens  (water lens)
>> and NA. We also know the field of view.
>>
>> I've looked online but haven't found a method for working this out as yet.
>>
>> Can anyone help?
>>
>> Kind regards,
>>
>> Jacqui
>>
>> Jacqueline Ross
>> Lead Technologist
>> Optical Microscopy & Image Analysis
>> Biomedical Imaging Research Unit (BIRU)
>> School of Medical Sciences
>> Faculty of Medical & Health Sciences
>> The University of Auckland
>> Private Bag 92019
>> Auckland 1142, NEW ZEALAND
>>
>> Telephone: Ext 87438; DDI:  +64 9 923 7438
>>
>> Website:    http://www.auckland.ac.nz/biru
>
> On Thu, May 28, 2020 at 6:40 PM Jacqueline Ross <[hidden email]>
> wrote:
>
>> *****
>> To join, leave or search the confocal microscopy listserv, go to:
>> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
>> Post images on http://www.imgur.com and include the link in your posting.
>> *****
>>
>> Thanks Craig,
>>
>> I was thinking the same actually. Excuse my ignorance but what kind of
>> power meter would we need? Something similar to what is used for measuring
>> laser power at the objective lens?
>>
>> Kind regards,
>>
>> Jacqui
>>
>> -----Original Message-----
>> From: Confocal Microscopy List <[hidden email]> On
>> Behalf Of Craig Brideau
>> Sent: Friday, May 29, 2020 10:37 AM
>> To: [hidden email]
>> Subject: Re: Off-topic question - power density at sample -
>> calculation/estimation
>>
>> *****
>> To join, leave or search the confocal microscopy listserv, go to:
>> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
>> Post images on http://www.imgur.com and include the link in your posting.
>> *****
>>
>> The absorption of the microscope optics, and losses due to the exact way
>> the light source is coupled into the system, can lead to widely varying
>> actual power levels at the sample. Typically I would measure this with an
>> appropriate power meter at the sample plane to get a precise number. Trying
>> to estimate the losses is probably a losing battle and could put you off by
>> an order of magnitude in some cases.
>>
>> Craig
>>
>> On Thu, May 28, 2020 at 3:31 PM Jacqueline Ross <
>> [hidden email]>
>> wrote:
>>
>>> *****
>>> To join, leave or search the confocal microscopy listserv, go to:
>>> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
>>> Post images on http://www.imgur.com and include the link in your
>> posting.
>>> *****
>>>
>>> Hi everyone,
>>>
>>> I've been contacted by someone in our faculty who needs to
>>> estimate/calculate the power density of the fluorescence light source at
>>> the sample. He knows the lamp power and the objective lens  (water lens)
>>> and NA. We also know the field of view.
>>>
>>> I've looked online but haven't found a method for working this out as
>> yet.
>>> Can anyone help?
>>>
>>> Kind regards,
>>>
>>> Jacqui
>>>
>>> Jacqueline Ross
>>> Lead Technologist
>>> Optical Microscopy & Image Analysis
>>> Biomedical Imaging Research Unit (BIRU)
>>> School of Medical Sciences
>>> Faculty of Medical & Health Sciences
>>> The University of Auckland
>>> Private Bag 92019
>>> Auckland 1142, NEW ZEALAND
>>>
>>> Telephone: Ext 87438; DDI:  +64 9 923 7438
>>>
>>> Website:    http://www.auckland.ac.nz/biru
>>>
--
Silas J. Leavesley, Ph.D.
Professor
Department of Chemical and Biomolecular Engineering
Department of Pharmacology
Center for Lung Biology
University of South Alabama
150 Jaguar Drive, SH4129
Mobile, AL 36688
ph: (251)-460-6160
fax: (251)-461-1485
web: http://www.southalabama.edu/centers/bioimaging
google scholar: http://scholar.google.co.uk/citations?user=knkwcj4AAAAJ
Jacqui Ross Jacqui Ross
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Re: Off-topic question - power density at sample - calculation/estimation

In reply to this post by Craig Brideau
*****
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*****

Thanks Craig,

I appreciate the clarification. Yes, the filter set is a bandpass on the excitation side, emission is LP.

I will give this a try.

Kind regards,

Jacqui

-----Original Message-----
From: Confocal Microscopy List <[hidden email]> On Behalf Of Craig Brideau
Sent: Friday, May 29, 2020 11:38 AM
To: [hidden email]
Subject: Re: Off-topic question - power density at sample - calculation/estimation

*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
Post images on http://www.imgur.com and include the link in your posting.
*****

Yes, those will work, but you need to consider two things: Lamp sources
will be broadband, and most of the "at the objective lens" sensors are
silicon based, which have a specific wavelength response. You typically set
the wavelength on the meter to the wavelength of your laser to get the
correct measurement. Since the lamp will be broadband, the meter will only
be usable if you are band-pass filtering the light. This is typical for
excitation filters in most fluorescent regimes, but not effective for white
light illumination. Since you mention fluorescence in your message I assume
your user is working with a particular excitation band. Simply set the
wavelength of your power meter to the middle of the band and you should get
a reasonably accurate reading. For instance if the excitation filter is
490/20 (490nm centered in 20nm bandwidth) then set the wavelength of the
meter to 490nm.
The second consideration is that the spot from the lamp will be larger than
a laser spot since it illuminates the entire field of view. Your sensor
will have to be large enough to collect the entire spot. It is also
recommended that you do not place the surface of your power meter directly
at the focus, so you will want do defocus the point of light on the meter
rather than having minimum spot size. The reason for this is that a large
area silicon detector can give incorrect results if the majority of the
sensor surface is not illuminated: It is better to spread the power out
over a wider area of sensor so that it is evenly distributed rather than
having a single high-intensity point in the middle of the active detection
area. Note this also applies for measuring lasers; do not put a focused
laser spot on your active sensor area.

Craig

On Thu, May 28, 2020 at 4:40 PM Jacqueline Ross <[hidden email]>
wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> Thanks Craig,
>
> I was thinking the same actually. Excuse my ignorance but what kind of
> power meter would we need? Something similar to what is used for measuring
> laser power at the objective lens?
>
> Kind regards,
>
> Jacqui
>
> -----Original Message-----
> From: Confocal Microscopy List <[hidden email]> On
> Behalf Of Craig Brideau
> Sent: Friday, May 29, 2020 10:37 AM
> To: [hidden email]
> Subject: Re: Off-topic question - power density at sample -
> calculation/estimation
>
> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> The absorption of the microscope optics, and losses due to the exact way
> the light source is coupled into the system, can lead to widely varying
> actual power levels at the sample. Typically I would measure this with an
> appropriate power meter at the sample plane to get a precise number. Trying
> to estimate the losses is probably a losing battle and could put you off by
> an order of magnitude in some cases.
>
> Craig
>
> On Thu, May 28, 2020 at 3:31 PM Jacqueline Ross <
> [hidden email]>
> wrote:
>
> > *****
> > To join, leave or search the confocal microscopy listserv, go to:
> > http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> > Post images on http://www.imgur.com and include the link in your
> posting.
> > *****
> >
> > Hi everyone,
> >
> > I've been contacted by someone in our faculty who needs to
> > estimate/calculate the power density of the fluorescence light source at
> > the sample. He knows the lamp power and the objective lens  (water lens)
> > and NA. We also know the field of view.
> >
> > I've looked online but haven't found a method for working this out as
> yet.
> >
> > Can anyone help?
> >
> > Kind regards,
> >
> > Jacqui
> >
> > Jacqueline Ross
> > Lead Technologist
> > Optical Microscopy & Image Analysis
> > Biomedical Imaging Research Unit (BIRU)
> > School of Medical Sciences
> > Faculty of Medical & Health Sciences
> > The University of Auckland
> > Private Bag 92019
> > Auckland 1142, NEW ZEALAND
> >
> > Telephone: Ext 87438; DDI:  +64 9 923 7438
> >
> > Website:    http://www.auckland.ac.nz/biru
> >
>
Craig Brideau Craig Brideau
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Re: Off-topic question - power density at sample - calculation/estimation

*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
Post images on http://www.imgur.com and include the link in your posting.
*****

The integrating sphere and spectrometer Silas mentions will give very
detailed information of the instrument spectral response, but the equipment
can be expensive. The key advantage is it can record the absolute spectral
power density response for broadband sources. For lamps with narrow filters
and laser sources it is probably overkill and a power meter like Cvic
mentioned will be sufficient.
In full disclosure Dr. Pina Colarusso and I assisted Thorlabs with the
design of the model Cvic mentioned. We both received free prototypes from
the company as thanks for our help with the details.
When I use them I try to fill the sensor area by about half to two thirds
with the circle of light from the objective. Fiddle with the focus while
watching the reading and it will be fairly steady when you have good sensor
fill. Be careful to not contact the surface of the sensor with the tip of
the lens as the sensor uses a thin coverglass similar to a coverslip to
properly material match the refractive indices. It is water and oil proof
so you can use the medium your lens is designed for directly on the sensor
for a more accurate reading. It cleans up with alcohol and lens tissues,
and works fine with air lenses as well. I use mine with 1.1 and 1.25 NA
water dipping lenses and 1.4 NA oil. Don't forget to set the correct
wavelength on the control box before recording the power.

Craig

On Thu., May 28, 2020, 10:01 p.m. Jacqueline Ross, <
[hidden email]> wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> Thanks Craig,
>
> I appreciate the clarification. Yes, the filter set is a bandpass on the
> excitation side, emission is LP.
>
> I will give this a try.
>
> Kind regards,
>
> Jacqui
>
> -----Original Message-----
> From: Confocal Microscopy List <[hidden email]> On
> Behalf Of Craig Brideau
> Sent: Friday, May 29, 2020 11:38 AM
> To: [hidden email]
> Subject: Re: Off-topic question - power density at sample -
> calculation/estimation
>
> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> Yes, those will work, but you need to consider two things: Lamp sources
> will be broadband, and most of the "at the objective lens" sensors are
> silicon based, which have a specific wavelength response. You typically set
> the wavelength on the meter to the wavelength of your laser to get the
> correct measurement. Since the lamp will be broadband, the meter will only
> be usable if you are band-pass filtering the light. This is typical for
> excitation filters in most fluorescent regimes, but not effective for white
> light illumination. Since you mention fluorescence in your message I assume
> your user is working with a particular excitation band. Simply set the
> wavelength of your power meter to the middle of the band and you should get
> a reasonably accurate reading. For instance if the excitation filter is
> 490/20 (490nm centered in 20nm bandwidth) then set the wavelength of the
> meter to 490nm.
> The second consideration is that the spot from the lamp will be larger than
> a laser spot since it illuminates the entire field of view. Your sensor
> will have to be large enough to collect the entire spot. It is also
> recommended that you do not place the surface of your power meter directly
> at the focus, so you will want do defocus the point of light on the meter
> rather than having minimum spot size. The reason for this is that a large
> area silicon detector can give incorrect results if the majority of the
> sensor surface is not illuminated: It is better to spread the power out
> over a wider area of sensor so that it is evenly distributed rather than
> having a single high-intensity point in the middle of the active detection
> area. Note this also applies for measuring lasers; do not put a focused
> laser spot on your active sensor area.
>
> Craig
>
> On Thu, May 28, 2020 at 4:40 PM Jacqueline Ross <
> [hidden email]>
> wrote:
>
> > *****
> > To join, leave or search the confocal microscopy listserv, go to:
> > http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> > Post images on http://www.imgur.com and include the link in your
> posting.
> > *****
> >
> > Thanks Craig,
> >
> > I was thinking the same actually. Excuse my ignorance but what kind of
> > power meter would we need? Something similar to what is used for
> measuring
> > laser power at the objective lens?
> >
> > Kind regards,
> >
> > Jacqui
> >
> > -----Original Message-----
> > From: Confocal Microscopy List <[hidden email]> On
> > Behalf Of Craig Brideau
> > Sent: Friday, May 29, 2020 10:37 AM
> > To: [hidden email]
> > Subject: Re: Off-topic question - power density at sample -
> > calculation/estimation
> >
> > *****
> > To join, leave or search the confocal microscopy listserv, go to:
> > http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> > Post images on http://www.imgur.com and include the link in your
> posting.
> > *****
> >
> > The absorption of the microscope optics, and losses due to the exact way
> > the light source is coupled into the system, can lead to widely varying
> > actual power levels at the sample. Typically I would measure this with an
> > appropriate power meter at the sample plane to get a precise number.
> Trying
> > to estimate the losses is probably a losing battle and could put you off
> by
> > an order of magnitude in some cases.
> >
> > Craig
> >
> > On Thu, May 28, 2020 at 3:31 PM Jacqueline Ross <
> > [hidden email]>
> > wrote:
> >
> > > *****
> > > To join, leave or search the confocal microscopy listserv, go to:
> > > http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> > > Post images on http://www.imgur.com and include the link in your
> > posting.
> > > *****
> > >
> > > Hi everyone,
> > >
> > > I've been contacted by someone in our faculty who needs to
> > > estimate/calculate the power density of the fluorescence light source
> at
> > > the sample. He knows the lamp power and the objective lens  (water
> lens)
> > > and NA. We also know the field of view.
> > >
> > > I've looked online but haven't found a method for working this out as
> > yet.
> > >
> > > Can anyone help?
> > >
> > > Kind regards,
> > >
> > > Jacqui
> > >
> > > Jacqueline Ross
> > > Lead Technologist
> > > Optical Microscopy & Image Analysis
> > > Biomedical Imaging Research Unit (BIRU)
> > > School of Medical Sciences
> > > Faculty of Medical & Health Sciences
> > > The University of Auckland
> > > Private Bag 92019
> > > Auckland 1142, NEW ZEALAND
> > >
> > > Telephone: Ext 87438; DDI:  +64 9 923 7438
> > >
> > > Website:    http://www.auckland.ac.nz/biru
> > >
> >
>
Jacqui Ross Jacqui Ross
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Re: Off-topic question - power density at sample - calculation/estimation

*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
Post images on http://www.imgur.com and include the link in your posting.
*****

Thanks Craig,

Appreciate the additional information and disclosure. I think something like this would be useful to us.

Kind regards,

Jacqui

-----Original Message-----
From: Confocal Microscopy List <[hidden email]> On Behalf Of Craig Brideau
Sent: Friday, May 29, 2020 4:51 PM
To: [hidden email]
Subject: Re: Off-topic question - power density at sample - calculation/estimation

*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
Post images on http://www.imgur.com and include the link in your posting.
*****

The integrating sphere and spectrometer Silas mentions will give very
detailed information of the instrument spectral response, but the equipment
can be expensive. The key advantage is it can record the absolute spectral
power density response for broadband sources. For lamps with narrow filters
and laser sources it is probably overkill and a power meter like Cvic
mentioned will be sufficient.
In full disclosure Dr. Pina Colarusso and I assisted Thorlabs with the
design of the model Cvic mentioned. We both received free prototypes from
the company as thanks for our help with the details.
When I use them I try to fill the sensor area by about half to two thirds
with the circle of light from the objective. Fiddle with the focus while
watching the reading and it will be fairly steady when you have good sensor
fill. Be careful to not contact the surface of the sensor with the tip of
the lens as the sensor uses a thin coverglass similar to a coverslip to
properly material match the refractive indices. It is water and oil proof
so you can use the medium your lens is designed for directly on the sensor
for a more accurate reading. It cleans up with alcohol and lens tissues,
and works fine with air lenses as well. I use mine with 1.1 and 1.25 NA
water dipping lenses and 1.4 NA oil. Don't forget to set the correct
wavelength on the control box before recording the power.

Craig

On Thu., May 28, 2020, 10:01 p.m. Jacqueline Ross, <
[hidden email]> wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> Thanks Craig,
>
> I appreciate the clarification. Yes, the filter set is a bandpass on the
> excitation side, emission is LP.
>
> I will give this a try.
>
> Kind regards,
>
> Jacqui
>
> -----Original Message-----
> From: Confocal Microscopy List <[hidden email]> On
> Behalf Of Craig Brideau
> Sent: Friday, May 29, 2020 11:38 AM
> To: [hidden email]
> Subject: Re: Off-topic question - power density at sample -
> calculation/estimation
>
> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> Yes, those will work, but you need to consider two things: Lamp sources
> will be broadband, and most of the "at the objective lens" sensors are
> silicon based, which have a specific wavelength response. You typically set
> the wavelength on the meter to the wavelength of your laser to get the
> correct measurement. Since the lamp will be broadband, the meter will only
> be usable if you are band-pass filtering the light. This is typical for
> excitation filters in most fluorescent regimes, but not effective for white
> light illumination. Since you mention fluorescence in your message I assume
> your user is working with a particular excitation band. Simply set the
> wavelength of your power meter to the middle of the band and you should get
> a reasonably accurate reading. For instance if the excitation filter is
> 490/20 (490nm centered in 20nm bandwidth) then set the wavelength of the
> meter to 490nm.
> The second consideration is that the spot from the lamp will be larger than
> a laser spot since it illuminates the entire field of view. Your sensor
> will have to be large enough to collect the entire spot. It is also
> recommended that you do not place the surface of your power meter directly
> at the focus, so you will want do defocus the point of light on the meter
> rather than having minimum spot size. The reason for this is that a large
> area silicon detector can give incorrect results if the majority of the
> sensor surface is not illuminated: It is better to spread the power out
> over a wider area of sensor so that it is evenly distributed rather than
> having a single high-intensity point in the middle of the active detection
> area. Note this also applies for measuring lasers; do not put a focused
> laser spot on your active sensor area.
>
> Craig
>
> On Thu, May 28, 2020 at 4:40 PM Jacqueline Ross <
> [hidden email]>
> wrote:
>
> > *****
> > To join, leave or search the confocal microscopy listserv, go to:
> > http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> > Post images on http://www.imgur.com and include the link in your
> posting.
> > *****
> >
> > Thanks Craig,
> >
> > I was thinking the same actually. Excuse my ignorance but what kind of
> > power meter would we need? Something similar to what is used for
> measuring
> > laser power at the objective lens?
> >
> > Kind regards,
> >
> > Jacqui
> >
> > -----Original Message-----
> > From: Confocal Microscopy List <[hidden email]> On
> > Behalf Of Craig Brideau
> > Sent: Friday, May 29, 2020 10:37 AM
> > To: [hidden email]
> > Subject: Re: Off-topic question - power density at sample -
> > calculation/estimation
> >
> > *****
> > To join, leave or search the confocal microscopy listserv, go to:
> > http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> > Post images on http://www.imgur.com and include the link in your
> posting.
> > *****
> >
> > The absorption of the microscope optics, and losses due to the exact way
> > the light source is coupled into the system, can lead to widely varying
> > actual power levels at the sample. Typically I would measure this with an
> > appropriate power meter at the sample plane to get a precise number.
> Trying
> > to estimate the losses is probably a losing battle and could put you off
> by
> > an order of magnitude in some cases.
> >
> > Craig
> >
> > On Thu, May 28, 2020 at 3:31 PM Jacqueline Ross <
> > [hidden email]>
> > wrote:
> >
> > > *****
> > > To join, leave or search the confocal microscopy listserv, go to:
> > > http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> > > Post images on http://www.imgur.com and include the link in your
> > posting.
> > > *****
> > >
> > > Hi everyone,
> > >
> > > I've been contacted by someone in our faculty who needs to
> > > estimate/calculate the power density of the fluorescence light source
> at
> > > the sample. He knows the lamp power and the objective lens  (water
> lens)
> > > and NA. We also know the field of view.
> > >
> > > I've looked online but haven't found a method for working this out as
> > yet.
> > >
> > > Can anyone help?
> > >
> > > Kind regards,
> > >
> > > Jacqui
> > >
> > > Jacqueline Ross
> > > Lead Technologist
> > > Optical Microscopy & Image Analysis
> > > Biomedical Imaging Research Unit (BIRU)
> > > School of Medical Sciences
> > > Faculty of Medical & Health Sciences
> > > The University of Auckland
> > > Private Bag 92019
> > > Auckland 1142, NEW ZEALAND
> > >
> > > Telephone: Ext 87438; DDI:  +64 9 923 7438
> > >
> > > Website:    http://www.auckland.ac.nz/biru
> > >
> >
>
Alex Gramann Alex Gramann
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Re: Off-topic question - power density at sample - calculation/estimation

In reply to this post by Jacqui Ross
*****
To join, leave or search the confocal microscopy listserv, go to:
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*****

**COMMERCIAL RESPONSE**

Hi Jacqui,

Totally agree with everything Craig said. Just wanted to add some further points -

If your microscope is equipped with a field stop and aperture stop, you'll want to make sure they're opened to the correct position. I'd assume that for your application you'll want the aperture stop opened all the way (for maximum power & irradiance at the sample plane). The field stop's position will be dependent on what your desired FOV is. Just open it up until the aperture lies just outside the FOV when looking through the eyepiece / at a screen (the sample will have to be in focus in order to do this). The field/aperture stop may need centering and can be done so using an Allen key. If your system doesn't have a field stop, then you'll need to get creative to limit your illumination so that it is within your FOV. I've been able to do this successfully by sticking a precision pinhole onto the entrance of an integrating sphere and positioning this such that the pinhole lies at the sample plane.

Another thing to note is that the light source will have to be configured for Kohler Illumination. This isn't a concern if you're dealing with a light source that connects to the microscope via LLG / LLG epi-port. There's plenty of literature on configuring most light sources for Kohler illumination.

To convert your power measurement into irradiance, simply divide by the area, which is equal to the following
Area [mm^2] = pi * (FOV diameter [mm] / 2)^2

If you don't know the FOV of your system, or would like a sanity check, the FOV diameter can be calculated using the following equation
FOV [mm] = f.n. [mm] / M,

Where f.n. is the eyepiece/camera field number and M is the magnification of the objective.

If you want some further reading, we've created a white paper on measuring irradiance.
https://www.coolled.com/wp-content/uploads/2019/10/Measuring-illumination-intensity-with-accuracy-and-precision-final-1.pdf

Hope this helps,

Alex
Craig Brideau Craig Brideau
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Re: Off-topic question - power density at sample - calculation/estimation

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Good points! In theory Kohler should also provide even illumination if
configured correctly as Alex says. You can verify this by putting a pinhole
into a piece of foil and covering your sensor with it. Move the pinholed
sensor across the spot and you can check for spatial intensity variability.

Craig

On Fri., May 29, 2020, 4:20 a.m. Alex Gramann, <[hidden email]>
wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> **COMMERCIAL RESPONSE**
>
> Hi Jacqui,
>
> Totally agree with everything Craig said. Just wanted to add some further
> points -
>
> If your microscope is equipped with a field stop and aperture stop, you'll
> want to make sure they're opened to the correct position. I'd assume that
> for your application you'll want the aperture stop opened all the way (for
> maximum power & irradiance at the sample plane). The field stop's position
> will be dependent on what your desired FOV is. Just open it up until the
> aperture lies just outside the FOV when looking through the eyepiece / at a
> screen (the sample will have to be in focus in order to do this). The
> field/aperture stop may need centering and can be done so using an Allen
> key. If your system doesn't have a field stop, then you'll need to get
> creative to limit your illumination so that it is within your FOV. I've
> been able to do this successfully by sticking a precision pinhole onto the
> entrance of an integrating sphere and positioning this such that the
> pinhole lies at the sample plane.
>
> Another thing to note is that the light source will have to be configured
> for Kohler Illumination. This isn't a concern if you're dealing with a
> light source that connects to the microscope via LLG / LLG epi-port.
> There's plenty of literature on configuring most light sources for Kohler
> illumination.
>
> To convert your power measurement into irradiance, simply divide by the
> area, which is equal to the following
> Area [mm^2] = pi * (FOV diameter [mm] / 2)^2
>
> If you don't know the FOV of your system, or would like a sanity check,
> the FOV diameter can be calculated using the following equation
> FOV [mm] = f.n. [mm] / M,
>
> Where f.n. is the eyepiece/camera field number and M is the magnification
> of the objective.
>
> If you want some further reading, we've created a white paper on measuring
> irradiance.
>
> https://www.coolled.com/wp-content/uploads/2019/10/Measuring-illumination-intensity-with-accuracy-and-precision-final-1.pdf
>
> Hope this helps,
>
> Alex
>
Julio MATEOS_LANGERAK Julio MATEOS_LANGERAK
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Re: Off-topic question - power density at sample - calculation/estimation

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*****

Hi everyone,

Does Thorlabs S170C Microscope Slide Power Sensor Head seem to be an option?

https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=2191&pn=S170C#8120

Best, Julio


On 29 May 2020, at 21:14, Craig Brideau <[hidden email]<mailto:[hidden email]>> wrote:

*****
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Post images on http://www.imgur.com and include the link in your posting.
*****

Good points! In theory Kohler should also provide even illumination if
configured correctly as Alex says. You can verify this by putting a pinhole
into a piece of foil and covering your sensor with it. Move the pinholed
sensor across the spot and you can check for spatial intensity variability.

Craig

On Fri., May 29, 2020, 4:20 a.m. Alex Gramann, <[hidden email]<mailto:[hidden email]>>
wrote:

*****
To join, leave or search the confocal microscopy listserv, go to:
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*****

**COMMERCIAL RESPONSE**

Hi Jacqui,

Totally agree with everything Craig said. Just wanted to add some further
points -

If your microscope is equipped with a field stop and aperture stop, you'll
want to make sure they're opened to the correct position. I'd assume that
for your application you'll want the aperture stop opened all the way (for
maximum power & irradiance at the sample plane). The field stop's position
will be dependent on what your desired FOV is. Just open it up until the
aperture lies just outside the FOV when looking through the eyepiece / at a
screen (the sample will have to be in focus in order to do this). The
field/aperture stop may need centering and can be done so using an Allen
key. If your system doesn't have a field stop, then you'll need to get
creative to limit your illumination so that it is within your FOV. I've
been able to do this successfully by sticking a precision pinhole onto the
entrance of an integrating sphere and positioning this such that the
pinhole lies at the sample plane.

Another thing to note is that the light source will have to be configured
for Kohler Illumination. This isn't a concern if you're dealing with a
light source that connects to the microscope via LLG / LLG epi-port.
There's plenty of literature on configuring most light sources for Kohler
illumination.

To convert your power measurement into irradiance, simply divide by the
area, which is equal to the following
Area [mm^2] = pi * (FOV diameter [mm] / 2)^2

If you don't know the FOV of your system, or would like a sanity check,
the FOV diameter can be calculated using the following equation
FOV [mm] = f.n. [mm] / M,

Where f.n. is the eyepiece/camera field number and M is the magnification
of the objective.

If you want some further reading, we've created a white paper on measuring
irradiance.

https://www.coolled.com/wp-content/uploads/2019/10/Measuring-illumination-intensity-with-accuracy-and-precision-final-1.pdf

Hope this helps,

Alex

Glen MacDonald Glen MacDonald
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Re: Off-topic question - power density at sample - calculation/estimation

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*****

S170C is a useful detector.  Downside is the S170C it won’t accept high angle rays from immersion objectives.  

You can get around this by estimating the transmission efficiency for an immersion objective relative to a lower NA dry objective. (This is working from memory, haven’t done this in a while).  Focus a low NA lens on a clean, cover slipped slide, setting Koehler illumination, then collect a camera image.  Switch to immersion objective, reset the condenser and collect another image.  The ratio of intensities between the  2 images approximates transmission by the immersion lens.  Add filters to light source for spectral behavior.

I had a 75 mmx25 mm metal holder machined to hold the S170C.   A frosted plastic disk, about US$0.50 from local plastics suppler, of the same diameter as the S170C, could be dropped into the holder as a target for focus and alignment of lens or condenser.  Then the disk replaced by the S170C for measurement.
One could also use a Chroma fluorescent slide for fluorescence.  

Glen

> On May 30, 2020, at 3:30 AM, Julio MATEOS_LANGERAK <[hidden email]> wrote:
>
> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> Hi everyone,
>
> Does Thorlabs S170C Microscope Slide Power Sensor Head seem to be an option?
>
> https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=2191&pn=S170C#8120
>
> Best, Julio
>
>
> On 29 May 2020, at 21:14, Craig Brideau <[hidden email]<mailto:[hidden email]>> wrote:
>
> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> Good points! In theory Kohler should also provide even illumination if
> configured correctly as Alex says. You can verify this by putting a pinhole
> into a piece of foil and covering your sensor with it. Move the pinholed
> sensor across the spot and you can check for spatial intensity variability.
>
> Craig
>
> On Fri., May 29, 2020, 4:20 a.m. Alex Gramann, <[hidden email]<mailto:[hidden email]>>
> wrote:
>
> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> **COMMERCIAL RESPONSE**
>
> Hi Jacqui,
>
> Totally agree with everything Craig said. Just wanted to add some further
> points -
>
> If your microscope is equipped with a field stop and aperture stop, you'll
> want to make sure they're opened to the correct position. I'd assume that
> for your application you'll want the aperture stop opened all the way (for
> maximum power & irradiance at the sample plane). The field stop's position
> will be dependent on what your desired FOV is. Just open it up until the
> aperture lies just outside the FOV when looking through the eyepiece / at a
> screen (the sample will have to be in focus in order to do this). The
> field/aperture stop may need centering and can be done so using an Allen
> key. If your system doesn't have a field stop, then you'll need to get
> creative to limit your illumination so that it is within your FOV. I've
> been able to do this successfully by sticking a precision pinhole onto the
> entrance of an integrating sphere and positioning this such that the
> pinhole lies at the sample plane.
>
> Another thing to note is that the light source will have to be configured
> for Kohler Illumination. This isn't a concern if you're dealing with a
> light source that connects to the microscope via LLG / LLG epi-port.
> There's plenty of literature on configuring most light sources for Kohler
> illumination.
>
> To convert your power measurement into irradiance, simply divide by the
> area, which is equal to the following
> Area [mm^2] = pi * (FOV diameter [mm] / 2)^2
>
> If you don't know the FOV of your system, or would like a sanity check,
> the FOV diameter can be calculated using the following equation
> FOV [mm] = f.n. [mm] / M,
>
> Where f.n. is the eyepiece/camera field number and M is the magnification
> of the objective.
>
> If you want some further reading, we've created a white paper on measuring
> irradiance.
>
> https://www.coolled.com/wp-content/uploads/2019/10/Measuring-illumination-intensity-with-accuracy-and-precision-final-1.pdf
>
> Hope this helps,
>
> Alex
>
Craig Brideau Craig Brideau
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Re: Off-topic question - power density at sample - calculation/estimation

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*****

On Sat, May 30, 2020 at 11:54 AM Glen MacDonald <[hidden email]> wrote:

> S170C is a useful detector.  Downside is the S170C it won’t accept high
> angle rays from immersion objectives.
>

Hi Glen, when I worked with Thor on the design for this sensor, one of the
key issues was ensuring that it *would* work with high angles. I was
dissatisfied with existing sensors with limited angles and worked to solve
this explicitly. There is a special index-matching gel under the coverslip
to ease the light into the silicon detector. If you want to calculate the
maximum NA, calculate the Fresnel equations for Air/Water to glass
depending on what medium the lens is using. An oil lens of course doesn't
need to worry since the medium index is the same as the coverslip. You'll
find the error is quite small up to very large NA even for air lenses. The
Brewster angle air-to-glass is around 57 degrees at which point you are
looking at approximately a 5-10% measurement error, depending on the
polarization of the light out of the objective. Practically most air lenses
will be much less than this.
With high NA Water and Oil lenses, you will of course have a large
measurement error unless you *put a drop of water or oil on the
sensor* (the S170C
is designed for this) and measure through the medium. The sensor is
designed for this and so you can get the proper measurement. I've found
emperically for NA > ~1.0 you can notice a significant difference. Try it
for yourself; get a high NA oil lens and measure the power coming out of
the objective without oil on the sensor. Then add a drop of oil, dip the
lens in, ease focus back to enlarge the spot size on the sensor while
maintaining the oil link between the tip of the lens and the sensor. You
will get a higher power reading as more light will properly enter the
coverglass thanks to the presence of the oil. You can also do this with a
drop of water for water lenses. Just be sure not to break contact of the
drop of medium between the tip of the lens and the sensor, and don't
accidentally ram the tip of the objective into the fragile sensor face.
After using oil, clean the sensor with Isopropyl or Methanol and a lens
tissue. After using water just wipe it off with a lens tissue.

Craig


>
> I had a 75 mmx25 mm metal holder machined to hold the S170C.   A frosted
> plastic disk, about US$0.50 from local plastics suppler, of the same
> diameter as the S170C, could be dropped into the holder as a target for
> focus and alignment of lens or condenser.  Then the disk replaced by the
> S170C for measurement.
> One could also use a Chroma fluorescent slide for fluorescence.
>

This is a good idea. I use the Chroma slides pretty extensively in this
way. Various plastics shops also sell fluorescent acrylic for cheap and
will often cut to custom sizes.

Craig



>
> Glen
>
> > On May 30, 2020, at 3:30 AM, Julio MATEOS_LANGERAK <
> [hidden email]> wrote:
> >
> > *****
> > To join, leave or search the confocal microscopy listserv, go to:
> > http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> > Post images on http://www.imgur.com and include the link in your
> posting.
> > *****
> >
> > Hi everyone,
> >
> > Does Thorlabs S170C Microscope Slide Power Sensor Head seem to be an
> option?
> >
> >
> https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=2191&pn=S170C#8120
> >
> > Best, Julio
> >
> >
> > On 29 May 2020, at 21:14, Craig Brideau <[hidden email]<mailto:
> [hidden email]>> wrote:
> >
> > *****
> > To join, leave or search the confocal microscopy listserv, go to:
> > http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> > Post images on http://www.imgur.com and include the link in your
> posting.
> > *****
> >
> > Good points! In theory Kohler should also provide even illumination if
> > configured correctly as Alex says. You can verify this by putting a
> pinhole
> > into a piece of foil and covering your sensor with it. Move the pinholed
> > sensor across the spot and you can check for spatial intensity
> variability.
> >
> > Craig
> >
> > On Fri., May 29, 2020, 4:20 a.m. Alex Gramann, <[hidden email]
> <mailto:[hidden email]>>
> > wrote:
> >
> > *****
> > To join, leave or search the confocal microscopy listserv, go to:
> > http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> > Post images on http://www.imgur.com and include the link in your
> posting.
> > *****
> >
> > **COMMERCIAL RESPONSE**
> >
> > Hi Jacqui,
> >
> > Totally agree with everything Craig said. Just wanted to add some further
> > points -
> >
> > If your microscope is equipped with a field stop and aperture stop,
> you'll
> > want to make sure they're opened to the correct position. I'd assume that
> > for your application you'll want the aperture stop opened all the way
> (for
> > maximum power & irradiance at the sample plane). The field stop's
> position
> > will be dependent on what your desired FOV is. Just open it up until the
> > aperture lies just outside the FOV when looking through the eyepiece /
> at a
> > screen (the sample will have to be in focus in order to do this). The
> > field/aperture stop may need centering and can be done so using an Allen
> > key. If your system doesn't have a field stop, then you'll need to get
> > creative to limit your illumination so that it is within your FOV. I've
> > been able to do this successfully by sticking a precision pinhole onto
> the
> > entrance of an integrating sphere and positioning this such that the
> > pinhole lies at the sample plane.
> >
> > Another thing to note is that the light source will have to be configured
> > for Kohler Illumination. This isn't a concern if you're dealing with a
> > light source that connects to the microscope via LLG / LLG epi-port.
> > There's plenty of literature on configuring most light sources for Kohler
> > illumination.
> >
> > To convert your power measurement into irradiance, simply divide by the
> > area, which is equal to the following
> > Area [mm^2] = pi * (FOV diameter [mm] / 2)^2
> >
> > If you don't know the FOV of your system, or would like a sanity check,
> > the FOV diameter can be calculated using the following equation
> > FOV [mm] = f.n. [mm] / M,
> >
> > Where f.n. is the eyepiece/camera field number and M is the magnification
> > of the objective.
> >
> > If you want some further reading, we've created a white paper on
> measuring
> > irradiance.
> >
> >
> https://www.coolled.com/wp-content/uploads/2019/10/Measuring-illumination-intensity-with-accuracy-and-precision-final-1.pdf
> >
> > Hope this helps,
> >
> > Alex
> >
>
Glen MacDonald Glen MacDonald
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Re: Off-topic question - power density at sample - calculation/estimation

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*****

Craig, thanks for the background.

Sorry, I realize that I misspoke (mistyped?).  I was using the S120C.  For some reason I typed S170C, despite having the Thor page open for the S120C.  Unfortunately, the S170C  came out after I already had purchased the S120C and couldn’t justify another sensor, no matter how great that design is for working with immersion lenses.  

Regards,
Glen



> On May 30, 2020, at 12:16 PM, Craig Brideau <[hidden email]> wrote:
>
> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> On Sat, May 30, 2020 at 11:54 AM Glen MacDonald <[hidden email]> wrote:
>
>> S170C is a useful detector.  Downside is the S170C it won’t accept high
>> angle rays from immersion objectives.
>>
>
> Hi Glen, when I worked with Thor on the design for this sensor, one of the
> key issues was ensuring that it *would* work with high angles. I was
> dissatisfied with existing sensors with limited angles and worked to solve
> this explicitly. There is a special index-matching gel under the coverslip
> to ease the light into the silicon detector. If you want to calculate the
> maximum NA, calculate the Fresnel equations for Air/Water to glass
> depending on what medium the lens is using. An oil lens of course doesn't
> need to worry since the medium index is the same as the coverslip. You'll
> find the error is quite small up to very large NA even for air lenses. The
> Brewster angle air-to-glass is around 57 degrees at which point you are
> looking at approximately a 5-10% measurement error, depending on the
> polarization of the light out of the objective. Practically most air lenses
> will be much less than this.
> With high NA Water and Oil lenses, you will of course have a large
> measurement error unless you *put a drop of water or oil on the
> sensor* (the S170C
> is designed for this) and measure through the medium. The sensor is
> designed for this and so you can get the proper measurement. I've found
> emperically for NA > ~1.0 you can notice a significant difference. Try it
> for yourself; get a high NA oil lens and measure the power coming out of
> the objective without oil on the sensor. Then add a drop of oil, dip the
> lens in, ease focus back to enlarge the spot size on the sensor while
> maintaining the oil link between the tip of the lens and the sensor. You
> will get a higher power reading as more light will properly enter the
> coverglass thanks to the presence of the oil. You can also do this with a
> drop of water for water lenses. Just be sure not to break contact of the
> drop of medium between the tip of the lens and the sensor, and don't
> accidentally ram the tip of the objective into the fragile sensor face.
> After using oil, clean the sensor with Isopropyl or Methanol and a lens
> tissue. After using water just wipe it off with a lens tissue.
>
> Craig
>
>
>>
>> I had a 75 mmx25 mm metal holder machined to hold the S170C.   A frosted
>> plastic disk, about US$0.50 from local plastics suppler, of the same
>> diameter as the S170C, could be dropped into the holder as a target for
>> focus and alignment of lens or condenser.  Then the disk replaced by the
>> S170C for measurement.
>> One could also use a Chroma fluorescent slide for fluorescence.
>>
>
> This is a good idea. I use the Chroma slides pretty extensively in this
> way. Various plastics shops also sell fluorescent acrylic for cheap and
> will often cut to custom sizes.
>
> Craig
>
>
>
>>
>> Glen
>>
>>> On May 30, 2020, at 3:30 AM, Julio MATEOS_LANGERAK <
>> [hidden email]> wrote:
>>>
>>> *****
>>> To join, leave or search the confocal microscopy listserv, go to:
>>> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
>>> Post images on http://www.imgur.com and include the link in your
>> posting.
>>> *****
>>>
>>> Hi everyone,
>>>
>>> Does Thorlabs S170C Microscope Slide Power Sensor Head seem to be an
>> option?
>>>
>>>
>> https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=2191&pn=S170C#8120
>>>
>>> Best, Julio
>>>
>>>
>>> On 29 May 2020, at 21:14, Craig Brideau <[hidden email]<mailto:
>> [hidden email]>> wrote:
>>>
>>> *****
>>> To join, leave or search the confocal microscopy listserv, go to:
>>> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
>>> Post images on http://www.imgur.com and include the link in your
>> posting.
>>> *****
>>>
>>> Good points! In theory Kohler should also provide even illumination if
>>> configured correctly as Alex says. You can verify this by putting a
>> pinhole
>>> into a piece of foil and covering your sensor with it. Move the pinholed
>>> sensor across the spot and you can check for spatial intensity
>> variability.
>>>
>>> Craig
>>>
>>> On Fri., May 29, 2020, 4:20 a.m. Alex Gramann, <[hidden email]
>> <mailto:[hidden email]>>
>>> wrote:
>>>
>>> *****
>>> To join, leave or search the confocal microscopy listserv, go to:
>>> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
>>> Post images on http://www.imgur.com and include the link in your
>> posting.
>>> *****
>>>
>>> **COMMERCIAL RESPONSE**
>>>
>>> Hi Jacqui,
>>>
>>> Totally agree with everything Craig said. Just wanted to add some further
>>> points -
>>>
>>> If your microscope is equipped with a field stop and aperture stop,
>> you'll
>>> want to make sure they're opened to the correct position. I'd assume that
>>> for your application you'll want the aperture stop opened all the way
>> (for
>>> maximum power & irradiance at the sample plane). The field stop's
>> position
>>> will be dependent on what your desired FOV is. Just open it up until the
>>> aperture lies just outside the FOV when looking through the eyepiece /
>> at a
>>> screen (the sample will have to be in focus in order to do this). The
>>> field/aperture stop may need centering and can be done so using an Allen
>>> key. If your system doesn't have a field stop, then you'll need to get
>>> creative to limit your illumination so that it is within your FOV. I've
>>> been able to do this successfully by sticking a precision pinhole onto
>> the
>>> entrance of an integrating sphere and positioning this such that the
>>> pinhole lies at the sample plane.
>>>
>>> Another thing to note is that the light source will have to be configured
>>> for Kohler Illumination. This isn't a concern if you're dealing with a
>>> light source that connects to the microscope via LLG / LLG epi-port.
>>> There's plenty of literature on configuring most light sources for Kohler
>>> illumination.
>>>
>>> To convert your power measurement into irradiance, simply divide by the
>>> area, which is equal to the following
>>> Area [mm^2] = pi * (FOV diameter [mm] / 2)^2
>>>
>>> If you don't know the FOV of your system, or would like a sanity check,
>>> the FOV diameter can be calculated using the following equation
>>> FOV [mm] = f.n. [mm] / M,
>>>
>>> Where f.n. is the eyepiece/camera field number and M is the magnification
>>> of the objective.
>>>
>>> If you want some further reading, we've created a white paper on
>> measuring
>>> irradiance.
>>>
>>>
>> https://www.coolled.com/wp-content/uploads/2019/10/Measuring-illumination-intensity-with-accuracy-and-precision-final-1.pdf
>>>
>>> Hope this helps,
>>>
>>> Alex
>>>
>>
Craig Brideau Craig Brideau
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Re: Off-topic question - power density at sample - calculation/estimation

*****
To join, leave or search the confocal microscopy listserv, go to:
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Post images on http://www.imgur.com and include the link in your posting.
*****

I started out with the S121C, which is the same as the 120 but has lower
sensitivity so that it can handle higher power levels. It was good for
measuring lower power Ti:Saph beams prior to the scan head, after power
stepdowns. Of course you want to use a multi-watt thermopile for measuring
the laser itself, but usually by the time you have it at the scan head it
is <500mW, which was the limit of the 121. You can also use the 120 and 121
to measure the collimated beam out of the objective turret by removing the
lenses, as this eliminates the NA issue. Be sure to wear eye protection
when doing this though as any reflections of a collimated beam risks
sending substantial optical power flying around the room. The fluorescent
ring around the sensor area helps you find the NIR laser beam while wearing
appropriate NIR blocking goggles. This also assumes your beam diameter is
less than that of the sensor (<10mm), or at least the beam as limited by
the back aperture of your objective. A good trick is to use a foil hole to
emulate the back aperture of your objective and place it over the sensor to
estimate the power actually entering the lens itself. You can also do this
with the 170 (and handle wider beams), but the 121 has higher power
handling capability.

Craig

On Sat, May 30, 2020 at 3:58 PM Glen MacDonald <[hidden email]> wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> Craig, thanks for the background.
>
> Sorry, I realize that I misspoke (mistyped?).  I was using the S120C.  For
> some reason I typed S170C, despite having the Thor page open for the
> S120C.  Unfortunately, the S170C  came out after I already had purchased
> the S120C and couldn’t justify another sensor, no matter how great that
> design is for working with immersion lenses.
>
> Regards,
> Glen
>
>
>
> > On May 30, 2020, at 12:16 PM, Craig Brideau <[hidden email]>
> wrote:
> >
> > *****
> > To join, leave or search the confocal microscopy listserv, go to:
> > http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> > Post images on http://www.imgur.com and include the link in your
> posting.
> > *****
> >
> > On Sat, May 30, 2020 at 11:54 AM Glen MacDonald <[hidden email]> wrote:
> >
> >> S170C is a useful detector.  Downside is the S170C it won’t accept high
> >> angle rays from immersion objectives.
> >>
> >
> > Hi Glen, when I worked with Thor on the design for this sensor, one of
> the
> > key issues was ensuring that it *would* work with high angles. I was
> > dissatisfied with existing sensors with limited angles and worked to
> solve
> > this explicitly. There is a special index-matching gel under the
> coverslip
> > to ease the light into the silicon detector. If you want to calculate the
> > maximum NA, calculate the Fresnel equations for Air/Water to glass
> > depending on what medium the lens is using. An oil lens of course doesn't
> > need to worry since the medium index is the same as the coverslip. You'll
> > find the error is quite small up to very large NA even for air lenses.
> The
> > Brewster angle air-to-glass is around 57 degrees at which point you are
> > looking at approximately a 5-10% measurement error, depending on the
> > polarization of the light out of the objective. Practically most air
> lenses
> > will be much less than this.
> > With high NA Water and Oil lenses, you will of course have a large
> > measurement error unless you *put a drop of water or oil on the
> > sensor* (the S170C
> > is designed for this) and measure through the medium. The sensor is
> > designed for this and so you can get the proper measurement. I've found
> > emperically for NA > ~1.0 you can notice a significant difference. Try it
> > for yourself; get a high NA oil lens and measure the power coming out of
> > the objective without oil on the sensor. Then add a drop of oil, dip the
> > lens in, ease focus back to enlarge the spot size on the sensor while
> > maintaining the oil link between the tip of the lens and the sensor. You
> > will get a higher power reading as more light will properly enter the
> > coverglass thanks to the presence of the oil. You can also do this with a
> > drop of water for water lenses. Just be sure not to break contact of the
> > drop of medium between the tip of the lens and the sensor, and don't
> > accidentally ram the tip of the objective into the fragile sensor face.
> > After using oil, clean the sensor with Isopropyl or Methanol and a lens
> > tissue. After using water just wipe it off with a lens tissue.
> >
> > Craig
> >
> >
> >>
> >> I had a 75 mmx25 mm metal holder machined to hold the S170C.   A frosted
> >> plastic disk, about US$0.50 from local plastics suppler, of the same
> >> diameter as the S170C, could be dropped into the holder as a target for
> >> focus and alignment of lens or condenser.  Then the disk replaced by the
> >> S170C for measurement.
> >> One could also use a Chroma fluorescent slide for fluorescence.
> >>
> >
> > This is a good idea. I use the Chroma slides pretty extensively in this
> > way. Various plastics shops also sell fluorescent acrylic for cheap and
> > will often cut to custom sizes.
> >
> > Craig
> >
> >
> >
> >>
> >> Glen
> >>
> >>> On May 30, 2020, at 3:30 AM, Julio MATEOS_LANGERAK <
> >> [hidden email]> wrote:
> >>>
> >>> *****
> >>> To join, leave or search the confocal microscopy listserv, go to:
> >>> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> >>> Post images on http://www.imgur.com and include the link in your
> >> posting.
> >>> *****
> >>>
> >>> Hi everyone,
> >>>
> >>> Does Thorlabs S170C Microscope Slide Power Sensor Head seem to be an
> >> option?
> >>>
> >>>
> >>
> https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=2191&pn=S170C#8120
> >>>
> >>> Best, Julio
> >>>
> >>>
> >>> On 29 May 2020, at 21:14, Craig Brideau <[hidden email]
> <mailto:
> >> [hidden email]>> wrote:
> >>>
> >>> *****
> >>> To join, leave or search the confocal microscopy listserv, go to:
> >>> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> >>> Post images on http://www.imgur.com and include the link in your
> >> posting.
> >>> *****
> >>>
> >>> Good points! In theory Kohler should also provide even illumination if
> >>> configured correctly as Alex says. You can verify this by putting a
> >> pinhole
> >>> into a piece of foil and covering your sensor with it. Move the
> pinholed
> >>> sensor across the spot and you can check for spatial intensity
> >> variability.
> >>>
> >>> Craig
> >>>
> >>> On Fri., May 29, 2020, 4:20 a.m. Alex Gramann, <
> [hidden email]
> >> <mailto:[hidden email]>>
> >>> wrote:
> >>>
> >>> *****
> >>> To join, leave or search the confocal microscopy listserv, go to:
> >>> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> >>> Post images on http://www.imgur.com and include the link in your
> >> posting.
> >>> *****
> >>>
> >>> **COMMERCIAL RESPONSE**
> >>>
> >>> Hi Jacqui,
> >>>
> >>> Totally agree with everything Craig said. Just wanted to add some
> further
> >>> points -
> >>>
> >>> If your microscope is equipped with a field stop and aperture stop,
> >> you'll
> >>> want to make sure they're opened to the correct position. I'd assume
> that
> >>> for your application you'll want the aperture stop opened all the way
> >> (for
> >>> maximum power & irradiance at the sample plane). The field stop's
> >> position
> >>> will be dependent on what your desired FOV is. Just open it up until
> the
> >>> aperture lies just outside the FOV when looking through the eyepiece /
> >> at a
> >>> screen (the sample will have to be in focus in order to do this). The
> >>> field/aperture stop may need centering and can be done so using an
> Allen
> >>> key. If your system doesn't have a field stop, then you'll need to get
> >>> creative to limit your illumination so that it is within your FOV. I've
> >>> been able to do this successfully by sticking a precision pinhole onto
> >> the
> >>> entrance of an integrating sphere and positioning this such that the
> >>> pinhole lies at the sample plane.
> >>>
> >>> Another thing to note is that the light source will have to be
> configured
> >>> for Kohler Illumination. This isn't a concern if you're dealing with a
> >>> light source that connects to the microscope via LLG / LLG epi-port.
> >>> There's plenty of literature on configuring most light sources for
> Kohler
> >>> illumination.
> >>>
> >>> To convert your power measurement into irradiance, simply divide by the
> >>> area, which is equal to the following
> >>> Area [mm^2] = pi * (FOV diameter [mm] / 2)^2
> >>>
> >>> If you don't know the FOV of your system, or would like a sanity check,
> >>> the FOV diameter can be calculated using the following equation
> >>> FOV [mm] = f.n. [mm] / M,
> >>>
> >>> Where f.n. is the eyepiece/camera field number and M is the
> magnification
> >>> of the objective.
> >>>
> >>> If you want some further reading, we've created a white paper on
> >> measuring
> >>> irradiance.
> >>>
> >>>
> >>
> https://www.coolled.com/wp-content/uploads/2019/10/Measuring-illumination-intensity-with-accuracy-and-precision-final-1.pdf
> >>>
> >>> Hope this helps,
> >>>
> >>> Alex
> >>>
> >>
>
Jacqui Ross Jacqui Ross
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Re: Off-topic question - power density at sample - calculation/estimation

*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
Post images on http://www.imgur.com and include the link in your posting.
*****

Hi everyone,

Thanks to Craig/Glen/Julio/Alex/Silas/Cvic for their valuable advice and explanations. We had a long weekend so I'm now about to read and digest all of these suggestions.

I am very grateful for this sharing of expertise. Always learning more!

Kind regards,

Jacqui

-----Original Message-----
From: Confocal Microscopy List <[hidden email]> On Behalf Of Craig Brideau
Sent: Monday, June 1, 2020 10:02 AM
To: [hidden email]
Subject: Re: Off-topic question - power density at sample - calculation/estimation

*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
Post images on http://www.imgur.com and include the link in your posting.
*****

I started out with the S121C, which is the same as the 120 but has lower
sensitivity so that it can handle higher power levels. It was good for
measuring lower power Ti:Saph beams prior to the scan head, after power
stepdowns. Of course you want to use a multi-watt thermopile for measuring
the laser itself, but usually by the time you have it at the scan head it
is <500mW, which was the limit of the 121. You can also use the 120 and 121
to measure the collimated beam out of the objective turret by removing the
lenses, as this eliminates the NA issue. Be sure to wear eye protection
when doing this though as any reflections of a collimated beam risks
sending substantial optical power flying around the room. The fluorescent
ring around the sensor area helps you find the NIR laser beam while wearing
appropriate NIR blocking goggles. This also assumes your beam diameter is
less than that of the sensor (<10mm), or at least the beam as limited by
the back aperture of your objective. A good trick is to use a foil hole to
emulate the back aperture of your objective and place it over the sensor to
estimate the power actually entering the lens itself. You can also do this
with the 170 (and handle wider beams), but the 121 has higher power
handling capability.

Craig

On Sat, May 30, 2020 at 3:58 PM Glen MacDonald <[hidden email]> wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> Craig, thanks for the background.
>
> Sorry, I realize that I misspoke (mistyped?).  I was using the S120C.  For
> some reason I typed S170C, despite having the Thor page open for the
> S120C.  Unfortunately, the S170C  came out after I already had purchased
> the S120C and couldn’t justify another sensor, no matter how great that
> design is for working with immersion lenses.
>
> Regards,
> Glen
>
>
>
> > On May 30, 2020, at 12:16 PM, Craig Brideau <[hidden email]>
> wrote:
> >
> > *****
> > To join, leave or search the confocal microscopy listserv, go to:
> > http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> > Post images on http://www.imgur.com and include the link in your
> posting.
> > *****
> >
> > On Sat, May 30, 2020 at 11:54 AM Glen MacDonald <[hidden email]> wrote:
> >
> >> S170C is a useful detector.  Downside is the S170C it won’t accept high
> >> angle rays from immersion objectives.
> >>
> >
> > Hi Glen, when I worked with Thor on the design for this sensor, one of
> the
> > key issues was ensuring that it *would* work with high angles. I was
> > dissatisfied with existing sensors with limited angles and worked to
> solve
> > this explicitly. There is a special index-matching gel under the
> coverslip
> > to ease the light into the silicon detector. If you want to calculate the
> > maximum NA, calculate the Fresnel equations for Air/Water to glass
> > depending on what medium the lens is using. An oil lens of course doesn't
> > need to worry since the medium index is the same as the coverslip. You'll
> > find the error is quite small up to very large NA even for air lenses.
> The
> > Brewster angle air-to-glass is around 57 degrees at which point you are
> > looking at approximately a 5-10% measurement error, depending on the
> > polarization of the light out of the objective. Practically most air
> lenses
> > will be much less than this.
> > With high NA Water and Oil lenses, you will of course have a large
> > measurement error unless you *put a drop of water or oil on the
> > sensor* (the S170C
> > is designed for this) and measure through the medium. The sensor is
> > designed for this and so you can get the proper measurement. I've found
> > emperically for NA > ~1.0 you can notice a significant difference. Try it
> > for yourself; get a high NA oil lens and measure the power coming out of
> > the objective without oil on the sensor. Then add a drop of oil, dip the
> > lens in, ease focus back to enlarge the spot size on the sensor while
> > maintaining the oil link between the tip of the lens and the sensor. You
> > will get a higher power reading as more light will properly enter the
> > coverglass thanks to the presence of the oil. You can also do this with a
> > drop of water for water lenses. Just be sure not to break contact of the
> > drop of medium between the tip of the lens and the sensor, and don't
> > accidentally ram the tip of the objective into the fragile sensor face.
> > After using oil, clean the sensor with Isopropyl or Methanol and a lens
> > tissue. After using water just wipe it off with a lens tissue.
> >
> > Craig
> >
> >
> >>
> >> I had a 75 mmx25 mm metal holder machined to hold the S170C.   A frosted
> >> plastic disk, about US$0.50 from local plastics suppler, of the same
> >> diameter as the S170C, could be dropped into the holder as a target for
> >> focus and alignment of lens or condenser.  Then the disk replaced by the
> >> S170C for measurement.
> >> One could also use a Chroma fluorescent slide for fluorescence.
> >>
> >
> > This is a good idea. I use the Chroma slides pretty extensively in this
> > way. Various plastics shops also sell fluorescent acrylic for cheap and
> > will often cut to custom sizes.
> >
> > Craig
> >
> >
> >
> >>
> >> Glen
> >>
> >>> On May 30, 2020, at 3:30 AM, Julio MATEOS_LANGERAK <
> >> [hidden email]> wrote:
> >>>
> >>> *****
> >>> To join, leave or search the confocal microscopy listserv, go to:
> >>> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> >>> Post images on http://www.imgur.com and include the link in your
> >> posting.
> >>> *****
> >>>
> >>> Hi everyone,
> >>>
> >>> Does Thorlabs S170C Microscope Slide Power Sensor Head seem to be an
> >> option?
> >>>
> >>>
> >>
> https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=2191&pn=S170C#8120
> >>>
> >>> Best, Julio
> >>>
> >>>
> >>> On 29 May 2020, at 21:14, Craig Brideau <[hidden email]
> <mailto:
> >> [hidden email]>> wrote:
> >>>
> >>> *****
> >>> To join, leave or search the confocal microscopy listserv, go to:
> >>> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> >>> Post images on http://www.imgur.com and include the link in your
> >> posting.
> >>> *****
> >>>
> >>> Good points! In theory Kohler should also provide even illumination if
> >>> configured correctly as Alex says. You can verify this by putting a
> >> pinhole
> >>> into a piece of foil and covering your sensor with it. Move the
> pinholed
> >>> sensor across the spot and you can check for spatial intensity
> >> variability.
> >>>
> >>> Craig
> >>>
> >>> On Fri., May 29, 2020, 4:20 a.m. Alex Gramann, <
> [hidden email]
> >> <mailto:[hidden email]>>
> >>> wrote:
> >>>
> >>> *****
> >>> To join, leave or search the confocal microscopy listserv, go to:
> >>> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> >>> Post images on http://www.imgur.com and include the link in your
> >> posting.
> >>> *****
> >>>
> >>> **COMMERCIAL RESPONSE**
> >>>
> >>> Hi Jacqui,
> >>>
> >>> Totally agree with everything Craig said. Just wanted to add some
> further
> >>> points -
> >>>
> >>> If your microscope is equipped with a field stop and aperture stop,
> >> you'll
> >>> want to make sure they're opened to the correct position. I'd assume
> that
> >>> for your application you'll want the aperture stop opened all the way
> >> (for
> >>> maximum power & irradiance at the sample plane). The field stop's
> >> position
> >>> will be dependent on what your desired FOV is. Just open it up until
> the
> >>> aperture lies just outside the FOV when looking through the eyepiece /
> >> at a
> >>> screen (the sample will have to be in focus in order to do this). The
> >>> field/aperture stop may need centering and can be done so using an
> Allen
> >>> key. If your system doesn't have a field stop, then you'll need to get
> >>> creative to limit your illumination so that it is within your FOV. I've
> >>> been able to do this successfully by sticking a precision pinhole onto
> >> the
> >>> entrance of an integrating sphere and positioning this such that the
> >>> pinhole lies at the sample plane.
> >>>
> >>> Another thing to note is that the light source will have to be
> configured
> >>> for Kohler Illumination. This isn't a concern if you're dealing with a
> >>> light source that connects to the microscope via LLG / LLG epi-port.
> >>> There's plenty of literature on configuring most light sources for
> Kohler
> >>> illumination.
> >>>
> >>> To convert your power measurement into irradiance, simply divide by the
> >>> area, which is equal to the following
> >>> Area [mm^2] = pi * (FOV diameter [mm] / 2)^2
> >>>
> >>> If you don't know the FOV of your system, or would like a sanity check,
> >>> the FOV diameter can be calculated using the following equation
> >>> FOV [mm] = f.n. [mm] / M,
> >>>
> >>> Where f.n. is the eyepiece/camera field number and M is the
> magnification
> >>> of the objective.
> >>>
> >>> If you want some further reading, we've created a white paper on
> >> measuring
> >>> irradiance.
> >>>
> >>>
> >>
> https://www.coolled.com/wp-content/uploads/2019/10/Measuring-illumination-intensity-with-accuracy-and-precision-final-1.pdf
> >>>
> >>> Hope this helps,
> >>>
> >>> Alex
> >>>
> >>
>