VL53L1X in a tube.. Tips and tricks?.

[CBarr.3]

I like the VL53L1X because the ROI is narrow, and I have seen other posts about a TOF in an opaque tube, but have a few questions still. I get that the beam can be narrowed to 15 degrees, and I have seen that the suggestion is to use matte black internal walls and a reflective survace at the end.

It seems to me if the tube the sensor is in is a tight diameter say 6mm by 2000 mm you could have a shiny surface as the light would be mainly bouncing in the right direction. If you had a 100mm diameter tube you wojuld want to absorb the light.

What is the best chance of success? Round tube or square tube? Shiny walls or Matte Black. Matte black with texture like sandblasted or even felt?

For reflective survace... white paint, shiny surfaface like polished aluminum, or an actual mirror (behind glass) best?

I would like to be able to meaure 500-3000mm length ranges in the smallest diameter tube as possible.. Perhaps 8mm to 25mm diameter.

Or does none of the above really matter if I just do some measurements and make a lookup table?

How about a concave reflective surface so that None of the photons take a straight path back?

Polarizing filter that blocks photons that come in at an angle?

Setting up a test this weekend and would love to stand on the shoulders of some experience... I have never worked with a TOF sensor before.

Concept is to get an absolute measurement of a telescoping tube.

Thanks!

[John E KVAM]

great questions.

I think your only chance is if you have a tube that has a mirror-finish on the inside. That way, when the photons hit the side walls they continue on their way and don't bounce back.

Chrome maybe?

You might try black annodized polished Aluminum but make the target a mirror finish.

I might consider the VL53L4CX as the beam starts out at 17 or 18 degrees. Given your geometery the light is going to fill the tube once the side walls get into the act, so the lens on the VL53L1 is not going to help you much.

polorizing filters don't help with coherent light. But if your light hits all those walls it may not be coherent any longer. You'd have to check that.

I'd make the piston in your tube as shiny as possible.

I'd invent the $56 and buy the eval kit. Then get a polished bit of chrome pipe from a plumbing store.

If that works, try to find some longer pipe.

Unless you really polish that interior surface you are going to get too much light back from the sides the lookup table is not going to help.

Good luck

• john