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# VL53L5CX Distances Don't Match Theory - What am I missing?

Associate II

I am on a robotic forum where we have been studying using this VL53L5CX for robotic vision, mapping and SLAM for the last two months. We are on page 12 of this thread: "<link provided if requested and I'm permitted>"

The problem we have run into concerns the distance readings we're getting out of it. The problem is explained in detail in the second half of this post "<link provided if requested and I'm permitted>" with pictures and previous posts to that thread give detailed output from the sensor.

Since I am new to this forum and can't provide the links, I'll summarize the problem here:

1. We have the sensor square-on to a wall 1000 mm away.
2. The wall is house-painted white
3. The ambient lighting is very low (barely readable)
4. Since the FoV angle from corner to corner is ~64 degrees, the corner distances should follow standard Trigonometry theory and be further away than the central pixels.

Theory says, if the center is 1000 mm away, the distance to the center of all four corner pixels should be ~1112 mm away. The sensor is only returning values close to 1018 mm away. IOW, Not anywhere near close to theory. We have tried many different settings for Integration Time (5 to 100 ms) and Sharpness Percent (0 to 99%).

Because it is SO wrong, I feel like I'm missing something fundamental here. Maybe someone here can enlighten me. No one on our forum has seen a problem with our logic and expectations.

VBR,

Inq

12 REPLIES 12
Associate II

BTW - Are you allowed to elaborate on the VL53L7 any? FoV, Range, Resolution, Rates???

ST Employee

I can do better than that!

You get the databrief that answers the easy ones, and the full datasheet which should answer everything.

But if you know lots about the VL53L5, you know it all already. All we did was change the FoV with a lens change. (And of course the Rad-to-Perpendicular adjustments.)

As for scholarly articles, google DTOF theory. There are lots of articles. If you find one that mentions Histograms, you are on the right track.

Instead of posting on the community page, you can create a support ticket. (click on the support tab on ST.com) It's a more formal way for us to talk.

If this or any post solves your issue, please mark them as 'Accept as Solution' It really helps. And if you notice anything wrong do not hesitate to 'Report Inappropriate Content'. Someone will review it.
Associate II
John,
Thank you for the even quicker response. I'll definitely search for the scholarly papers and bone-up on it.
And... we did see some other strange issues, so I will follow up directly with a ticket next time. But I want to re-address our perpendicular and oblique testing with our new-found knowledge first. 😉... so we can get a warm-fuzzy-feeling back. The HC-SR04 contingent needs their Binky taken away.
VBR,
Dennis