VL810X doesn't detect hand movement when covered with an opaque black film

[SKalk.2]

We are working on an application where we are making VL6180X detect an approaching hand towards it. We would like to understand how can this application work when sensor is covered by an opaque black film. Is there a special calibration required? The hand movement is being done behind the opaque black film. Will it ever detect such movement? Would appreciate appropriate technical support.

[Peter BENSCH]

The VL6180 uses a infrared Laser with a wavelength of 850nm.

What does the term "opaque" refer to in your case?

What attenuation does the film have at the 850nm of the laser?

Regards

/Peter

[John E KVAM · Accepted solution]

The trick to doing this is finding a plastic film that stops most visible light, but is transparent at the frequency of the sensor.

(the VL6180 runs at 850nm)

If you really want an opaque black film, (and are not too far along) you can use the VL53L0X. It uses 940nm light, and this frequency generally goes right through most plastics. Plastics are darkened by adding dye, which stops visible light, but does NOT stop 940nm light.

It takes some experiementation, but a good plastic vendor can find what you want.

Dark is easy, Stay away from white plastic though; that's almost impossible.

Unfortuantely the VL53L0X is neither footprint compatable nor software compatable with the VL6180. It's about the same size, so there is some work could be salvaged.

But if your application doesn't have to be completely black, you can find some pretty dark plastics that let the 850nm light through.

All the plastic vendors should be able to give you a spec sheet that shows the transmissivity at both 850 and 940nm light.

I'm sure you can find something.

By the way, if you don't need the Ambient Light Sensor in the VL6180X, the VL6180V1 is the same silicon - and a bit cheaper.