What colors and material do you recommend we try for a cover glass. (imported query)

PMMA and Acrylic are pretty transparent to 940nm light. Both have been used by customers.

And the color does not seem to matter much if you avoid the white ones.

And of course all kinds of glass works too.

The best coverglass (CG) would be thin, transparent, smooth, and mounted very close to the sensor.

I would start with the coverglass from Hornix. See if that works for you. They use PMMA.

    http://www.hornix.com.tw/en/product-list-3/ - all the way at the bottom

   There is also a Hornix distributer in Vancouver BC, Canada. This guy distributes the Hornix glass, but he’s also really good at designing systems like you are using. You might give him a call. 

Attila Bene, 4036197011

AB Embedded Systems Ltd. (Canada)

info@abmbed.com

1. Pricing

https://www.dropbox.com/s/5iy8qr3zamjk0ru/2018%20Hornix%20Price%20List%

ST uses a 1mm thick Acrylic in a smoky color.

But here is what I recommend you do.

Get a bit of the material you are thinking of using. Place it on the P-Nucleo-53L1A1 EVK and do a Crosstalk calibration.

It will tell you how ‘clear’ the cover glass is. Then make your decision from there.

​Thanks John for your great answer, I would like to add some important information : the material is important for the crosstalk performance but the cover glass width and the air gap (the space between the top surface of the sensor and the cover glass) are determinant and main contributors for the crosstalk performances.