VL53L1X test with a foggy area and distance impacted!

[leo su]

Posted on June 12, 2018 at 10:28

Description:

We use 4 -VL53L1X sensors in our product and we have a closed box (rectangular shape), in which we place a 

foggy stuff for a worst air condition to see object distance impact or not.

Before the foggy stuff in, 

ideal distance of S1 S2 S3 S4 in cm areS1 ~ 1cm, (blue plot)

S2 ~ 39cm,  (red plot)

S3 ~ 18cm, (purple plot)

S4 ~ 10cm, (green plot).

From 4 plots, during foggy period in middle time, from red plot, distance is dropped from among 39cm to near 25cm (14cm), if it can be proportional to a linear impact, if desired object distance is near 200cm, and during foggy period, it may be impact by 14cm * 5 (200cm/40cm) = 70cm; it seems a lot distance drop. Is there any referred statistics of foggy test from ST sensor chip? Then I can base on them for more tests. 

TKS. 

[John E KVAM]

Fog is an interesting problem. Generally 940nm light is absorbed by water vapor. That is why there is less 940nm light in the atmosphere (at sea level) than other frequencies.

But at the boundary of air and water there is some reflection. And a lot of transmission.

So in your experiment you are seeing several effects.

Absorption, reflection, and transmission. But keep in mind that light slows down in water so you might be getting some of that as well.

It all makes water and fog a real issue.

the only thing I can think to do is a lot of testing and calibration of your environment.

[S.Ma]

There is no perfect sensor in the real world, need to combine several types to try to remove the false positive. We got more than 2 eyes...