Changing the cross-talk calibration distances for the VL6180X

[AGome.7]

Hello!

So in the project I am working on, we are using ToF sensors (with a cover glass) to accurately measure the distance of a white object within the ranges of 30-70mm. We would like to create a calibration fixture that also falls within these distances, but reading up on the datasheet the recommended distance to account for cross-talk is set to 100mm. Could we still get away with setting the calibration distance for cross-talk at 70mm?

[John E KVAM]

To set the offset you need a lot of photons, so a close distance and a nice white target are required.

White printer paper works well for this.

But crosstalk is different, you need a target and a distance that return photons in the same order of magnitude as your crosstalk.

To find this distance, you need to range on an object until you find one that under-ranges by about 10 or 20 percent.

The crosstalk routine can then take the known distance, the returned distance and the signal strength to determine how may photon hits are from the coverglass.

A white object at 70mm will give you a range that is so close to the acutal that you won;t get a good crosstalk measurment.

You need either a longer distance or a blacker target.

If you could replace your white target with a very dull one, it might work out that 70mm will give you enough difference between your range and acutal.

But try this first. With your white target at 70cm, do your offset calibration. It should give you 70.

Then change your setup to th 30mm and collect that data point.

Crosstalk causes dull targets at the longer distances to range 'short'. But unless your crosstalk is really bad it might not take effect until you are past 10cm or so on a white target. (Which means you may not need it at all.)

• john

i'm saying you might not even need it.

[John E KVAM]

You might also consider the VL6180V1. If you are not using the ALS the V1 is EXACTLY the same silicon. We just plugged the ALS hole, saving us the cost of calibration. So the V1 is a touch less expensive.

• john