Have there been any optical interface material compatibility tests for the VL53L1X?

[JLitt.1]

We wish to use the sensor in a freezer behind a protective plastic cover. We expect some frost and dirt to be an issue on the outside of the glass. We are considering an optically clear adhesive between the glass and the VL53L1X to prevent frost and outgassing contamination problems inside the glass. Is there a recommended adhesive?

[John E KVAM]

The VL53L1X sensor does have issues with what we call 'coverglass'. One needs a coverglass, but anything that prevents the light from going out, hitting the target and coming back causes an effect we call crosstalk.

There is a video on the subject that might help you understand the issue:

VL53L1X Dirty Cover Glass: https://youtu.be/BHM2CZVXZGc

The good thing is that 940nm light really does not see water, snow or ice. The light tends to go right through it.

The bad thing is I've not seen too many adhesives that are really transparent at 940nm.

But if you can come up with an adhesive that sticks to the case and has holes to let the light thorough, that would work.

There is one company - Hornix in Taiwan, that builds an integrated coverglass and sensor.

You could buy that, and install the sensor simply buy drilling a hole in the sidewall and putting the assembly into it.

It's described in an appnote AN5231 - available from ST.com. Just do a search.

• john