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To get the full power at the back aperture I check the Laser power using a 25mm diameter F100mm lens mounted in a 1" SMS tube with an SMS-RMS thread adapter (Thor Labs). I place the nose piece in the lowest position, replace my objective with the F100mm lens assembly and use the X-Cite power meter (XR2100) with the XP750 slide mounted sensor for my measurements. I repeat this with the objective of interest after I focus on a specimen. Make sure the brightfield condenser is centered so that you can align the sensor over the objective.
I have no commercial interest in Thor Labs or X-Cite
Eric Marino
Senior Imaging Specialist
Immune Disease Institute
Harvard Medical School
200 Longwood Ave
WAB 133D
Boston, MA 02115
Lab: 617 713-8885
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On May 24, 2012, at 6:08 PM, James Pawley wrote:
> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> *****
>
>> *****
>> To join, leave or search the confocal microscopy listserv, go to:
>> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
>> *****
>>
>> Hi Louis, you might consider this product from Lumen dynamics (no commercial interest):
>>
>> http://www.ldgi-xcite.com/products-xr2100-xp750.php
>>
>> A regular power meter will work as well provided you can hold it in a fixed position above your objective.
>>
>> Just be aware that power meters like these have a certain acceptance angle and won't work with high NA or immersion objectives. You're better off measuring the power at the nosepiece after removing the objective of interest and then calculating the resulting power that gets through the objective based on it's wavelength transmission curve in those cases.
>> Also be aware that these devices don't tell over what area your power is projected in or extending beyond your field of view. There other ways and devices you can use to determine that.
>>
>> Cheers
>>
>>
>> John Oreopoulos
>> Research Assistant
>> Spectral Applied Research
>> Richmond Hill, Ontario
>> Canada
>> www.spectral.ca
>
>
> I agree with John about the problems of "getting the light out of high-NA immersion lenses and into the sensitive area of the power meter", but we need to add that not all of the light getting to the nosepiece will actually enter the entrance pupil of the objective.
>
> So you need to compensate for the NA and magnification of the objective as well as its transmission.
>
> If the illumination optics have been designed to "fill" (Fuzzy definition here: How uniforml or peaked is this light bundle?) a 40x 1.2, then you switch to a 100x 1.2, the area of the pupil of the latter will be 6.25x smaller. Depending on how uniform (or peaked) the laser light is in the BFP, this may mean that the light striking the glass part of the 40x will represent about 5x more photons than that striking the glass part of the 100x.
>
> This should be remembered when setting the Laser power level. And also when comparing the overall performance of 40x, 63x and 100x lenses (The differences you thought that you saw may be mostly due to more power striking the specimen at 40x),
>
> Cheers,
>
> Jim Pawley
>
>
>>
>>
>> On 2012-05-24, at 10:22 AM, [log in to unmask] wrote:
>>
>>> *****
>>> To join, leave or search the confocal microscopy listserv, go to:
>>> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
>>> *****
>>>
>>> Bonjour à tous,
>>>
>>> I would like to have some suggestions in order to buy a power meter for
>>> checking the LASERs intensities at the objective level.
>>>
>>> Thanks for your help!
>>>
>>> Louis
>>>
>>> Louis Villeneuve
>>> Research Associate - Confocal Microscopy
>>> Montreal Heart Institute- Research Center
>>> 5000 East Belanger
>>> Montreal (Qc), Canada
>>> H1T 1C8
>>>
>>> 514-376-3330 ext 3511
>>> 514-376-1355 (Fax)
>>>
>>> [log in to unmask]
>
>
> --
> James and Christine Pawley, 21 N. Prospect Ave. Madison, WI, 53726 Phone: 608-238-3953
> <[log in to unmask]>
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