acrylic glass & infrared light

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Is colorful Acrylic glass transparent to Infrared Light?

hover over the image above to find out ­čÖé

some days ago i bought a breakout-board for the VL53L1X Time Of Flight (TOF) distance sensor. It can measure the distance of an ‘object’ in the range of ~4-400cm.

My plan was to integrate this into the amulet – so the colors can change if somebody comes in view.. just one of the ‘interactive’ ideas..

for this i need some sort of ‘cover glass’ to protect the sensor.
after a short search i found this video of a good solution for cover glass windows.

it describes a method of using two separate windows – one for the transmitter and one for the receiver – with a light-blocking barrier in between. this way the sensor is not fooled by reflections inside the glass..

i want to try and implement this concept.
for the light barrier i want to use black solid acrylic glass – and for the transparent parts i want to use some – to the human eye – very dark color.
so that the ‘sandwich’ of different materials is more of a ‘dark area’.

but for the sensor it should be as clear as possible.
the sensor operates in the ‘near infrared band’ (940 nm).

so i had to find what acrylic glass colors are transparent to infrared.
as i have found no spectral transmission plots / datasheets from the manufacture (i limited my search to Evonik) i just ordered some samples in interesting colors and tested theme myself.

My Results:

seems very transparent:

blocks some amount

milky / translucent (expected as they are for led diffusion…)

  • LED Black & White (7H25)
  • LED Black & White (9H04) SC

so i will likely use the dark blue one ­čÖé

as Filter for my USB-Webcam i used this IR HIGH pass filter.
it blocks the visible light up to about 825nm. all above is let through.