prism for 2mm grin len

[rnleao]

Hi all,

There was a post on the old forum regarding perpendicular imaging. Well, in that post the user had fixed the issue with focusing. I was wondering if anyone know where I can get prism to glue on my 2mm grin lenses. Many thanks!

Richardson

[Daniel Aharoni]

Hi Richardson,
A prism adds additional glass that needs to be imaged through effectively requiring the optics of the Miniscope system to have a larger working distance. For instance, if you are interested in using a 1mm prism, this adds an additional 1mm of distance between the bottom of the GRIN lens and the brain structure you want to image. The standard 1.8mm or 2mm diameter objective GRIN lenses used in the Miniscope have a pitch of 0.25 and, in conjunction with the achromatic lens, have a maximum working distance of around 200um. This means your focal plane will be stuck inside your prism. The solution is to have custom GRIN lenses made with a shorter pitch to shift the focal plane past the prism. A while back we got a batch of GRIN lenses made by Grintech to do just this and obtained very promising results. Unfortunately Grintech has now stopped providing custom GRIN lens solutions to neuroscience labs that don't use Inscopix's nVista system.

That all being said, I can suggest 2 possibly solutions:

• The official statement from Inscopix is they are willing to sell their own relay GRIN lenses (and relay+prism lenses) to Miniscope users. In actuality it appears that they have ignored the requests of almost all Miniscope users. Still, you can try and contact them to request a quote.
• We have been working closely with GoFoton to develop an alternate GRIN lens solution and supply chain. They are very close to commercially releasing 1mm diameter relay GRIN lenses for imaging with the Miniscope system. Once these are available they will likely be able to make custom GRIN lenses to work with prisms. This is actually something we are interested in as well and will push forward with them when we have time.

[rnleao]

Thanks Daniel,

Looking forward to hear more about the developments w GoFoton. if you need more people to increase the order size for GoFoton custom grin please let me know. Best

richardson (neurodynamics lab, brain institute, Natal/RN - brazil)

[Lee Hyeonju]

Hi Daniel! I have a question for your answer.

I have 1mm diameter GRIN lens with attached prism for perpendicular view. Its working distance is infinite and 0.25pitch.
I checked it can make image without lens. Because of prism, it's hard to see fluorescent samples with lens so i couldn't check it. i just confirm that optic path is fine.
And if I put lens and miniscope on a head of mouse, it shows nothing.

Do you think that prism is a cause of this problem?
But at fact sheet, the GRIN lens has infinite working distance so i think those prism is not affect on focal length.
Is there any specific formula to calculate working distance of achromatic lens+GRIN lens?

-------------------------------------------------------------------------------------------------------
I found there was a blood clot. But i am still concerned about my lens system.

Hyeonju Lee

[Daniel Aharoni]

Hi Hyeonju Lee,
Thanks for the question. Unfortunately the GRIN lens you have will not work in conjunction with a prism for the following reasons:
1) The only ~0.25 pitch GRIN lens that you should use with the Miniscope is a larger 1.8mm or 2mm diameter GRIN lens (this is what we usually call the GRIN objective lens). 0.25pitch GRIN lenses with a smaller diameter will result in much more difficult focal plane adjustment.
2) When imaging through a 1mm x 1mm x 1mm prism, you are adding an additional 1mm of glass you need to image through. The optics and lenses of the Miniscope were designed to only image a few hundred micrometers, not over a millimeter.

When using a prism you will need to get a custom GRIN lens made which will extend the effective working distance of the entire system past the additional glass of the prism. Inscopix already sells GRIN lens + prism systems that should be compatible with your Miniscope. Hope this helps.

[Lee Hyeonju]

Thank you Daniel. I just understand your answer. We have to buy another lens.

[hoogland]

• We have been working closely with GoFoton to develop an alternate GRIN lens solution and supply chain. They are very close to commercially releasing 1mm diameter relay GRIN lenses for imaging with the Miniscope system. Once these are available they will likely be able to make custom GRIN lenses to work with prisms. This is actually something we are interested in as well and will push forward with them when we have time.

Hi Daniel, w/ GoFoton now providing custom GRIN lenses has the UCLA miniscope team pursued the use of a custom lens w/ a prism further? Cheers, Tycho.

[Daniel Aharoni]

Hi Tycho,
We haven't tried out GoFoton lenses in conjunction with prisms yet but I imagine they should work well. If you are interested you can contact Walter at GoFoton (walter.boyles@gofoton.com) and request custom 1mm diameter CLH lenses. You will just have to provide him with the new front working distance of the lens which will be their standard working distance plus the size of your prism. So for a 1mm x 1mm prism you would just ask them to cut some GRIN lenses to increase the front working distance by 1mm.

[hoogland]

Perfect, thanks.