VL53L4CD configuration and minimum distance reading

[TheRaprus]

Hi to all.

I'm trying the VL53L4CD nucleo expansion board. My goal is to use this ToF sensor to detect a very small change in  distace, starting from about 5 mm.

The idea is use this VL53L4CD  sensor to detect if the distace become greater than 5mm. (5 mm could be from 2 to 6. No measurement is necessary).

I have read the other posts and I agre than VL53L4CD can't be used for measurement < 7mm (better 10).

But can it be used as a  "switch"? Is this VL53L4CD  the correct choice?

[John E KVAM · Accepted solution]

The problem is the light. 

When the flash goes out, the sensor expects it to hit the target and return. But in the really close case the light reflects, then reflects against the sensor's structure and reflects again. This really messes with the range. 

One can paint the sensor's structure black, which can help a little, but that light is pretty bright at that short distance. 

(Keep in mind that each flash of light is 2nano-seconds long. But light takes 66pico seconds to traverse 1cm (out and back.)

This means the sensor's job is easier past 15cm. It still works at the close distances, but there are more issues there. 

If you are looking for a small change, then you are going to have issues.

But if the change is large - say from 5mm to 5cm then it would work fine.

- john