VL53L1X ambient rate drops with better target reflectance

[mf101]

It looks like the ambient rate delivered by the sensor drops, the better the reflector is (the higher the signal rate is). In a practical evaluation the ambient rate dropped from 40 kcps to 0 kcps when the signal rate increased from 400 kcps to 12000 kcps.

Is this behaviour normal ? How does the sensor measure the ambient rate ?

[John E KVAM]

When the signal rate goes up beyond a limit, the sensor starts turing off SPADS. We don't need the extra signal, and it degrades the math. So you are going to have to work in signal per SPAD and ambient per SPAD.

So take the signal you get and divide by the number of SPADS. I sometimes normalize this by multiplying it by 200 (the approximate max number of SPADs).

This will give you a better indication of the amount of light you are seeing.

Then take the ambient and pull the same trick.

See if the ambient/#of SPADs *200 is more constant than is ambient alone.

I'm going to guess that is is not perfect, but it's going to be a lot closer.

• john