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Just to follow on with what Mark said, if all you want is to measure 
distortion, you don't even need a reflection image of your grid. Just 
use a transmission detector and, if you don't have one (assuming 
inverted optics), a PIN diode sitting on the top of the slide should 
do nicely, as TPE usually has a massive (mW) beam.

JP

>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.
>*****
>
>Unfortunately, it is extremely difficult to record the reflection mode
>image in our microscope, as the NIR light will not pass through the
>dichroic, and even if we changed out the dichroic for a beam splitter,
>out PMTs are not sensitive to NIR light.
>
>Translating a bead though is a very interesting idea.  We use a high
>precision thorlabs MLS stage.  I will double check the repeatability,
>but in theory I could program it to perform an extremely high
>resolution distortion measurement.  Of course, getting a single bead
>onto a coverslip (or else programming software to automatically
>identify the same bead across hundreds of frames) will be somewhat
>tricky.
>
>Its a shame that getting targets for multiphoton is so difficult.
>Ideal I suppose would be something etched in glass so that I could
>flow my own fluorophore through it.  I will have to look around and
>see if I can get a lithography facility to make something like that.
>
>Thanks,
>Mike
>
>On Wed, Jul 23, 2014 at 3:19 AM, Mark Cannell
><[log in to unmask]> wrote:
>>  *****
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>>
>>  Thinking about this a bit more, I realised that your existing grid 
>>is perfectly suitable as you don't need 2P excitation to measure 
>>field distortion at the wavelength you are using, Just turn the 
>>power down a lot and record a reflection image,
>>
>>  Cheers Mark
>>
>>>>
>>>>  Hi Mark,
>>>>
>>>>  I'm assuming you mean beads deposited in a grid or something similar?
>>>>  Could you point me to where you found this?
>>>>
>>>>  Thanks,
>>>>  Mike
>>>>
>>>>  On Tue, Jul 22, 2014 at 3:58 AM, Mark Cannell
>>>>  <[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
>>>>>  Post images on http://www.imgur.com and include the link in your
>>>>  posting.
>>>>>  *****
>>>>>
>>>>>  Hi Michael
>>>>>
>>>>>  I've always used beads to test the microscope. They are relatively cheap
>>>>  and if you blow one up it don't matter. As you say, evaporated metal
>>>>  targets are too easily damaged (as Jim Pauley and I discovered 
>>>>when testing
>>>>  my microscope back in '95!)
>>>>>
>>>>>  HTH
>>>>>
>>>>>  Mark
>>>>>
>>>>>  On 22/07/2014, at 4:30 am, Michael Giacomelli <[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
>>>>>>  Post images on http://www.imgur.com and include the link in your
>>>>  posting.
>>>>>>  *****
>>>>>>
>>>>>>  Could someone recommend a good multiphoton distortion target?
>>>>>>  Preferably one that is relatively robust against damage.
>>>>>>
>>>>>>  Currently I am using a thorlabs wire grid target with fluorophore
>>>>>>  behind it.  The beam is attenuated by the metal, resulting in an image
>>>>>>  of the grid.  However, passing through the entire 1 mm slide greatly
>>>>>>  reduces my resolution, and unless I am extremely careful, the grid is
>>>>>>  ablated by the beam.
>>>>>>
>>>>>>  Thanks,
>>>>>>  Michael
>>>>>
>>>>>
>>>>>  Mark  B. Cannell Ph.D. FRSNZ
>>>>>  Professor of Cardiac Cell Biology
>>>>>  School of Physiology &  Pharmacology
>>>>>  Medical Sciences Building
>>>>>  University of Bristol
>>>>>  Bristol
>>>>>  BS8 1TD UK
>>>>>
>>>>>  [log in to unmask]
>  >>>
>>
>>
>>
>>  Mark  B. Cannell Ph.D. FRSNZ
>>  Professor of Cardiac Cell Biology
>>  School of Physiology &  Pharmacology
>>  Medical Sciences Building
>>  University of Bristol
>>  Bristol
>>  BS8 1TD UK
>>
>>  [log in to unmask]


-- 
Prof. James  Pawley, Shangri La Hotel, Harbin,
email <[log in to unmask]>,   China Cell phone  15636810175