Maximum distance limit in VL53L1X

[kbsh]

Hi

I want to use the VL53L1X to measure the distance of a target less than 30 cm away and about 1 cm in size.
Is it possible to ignore the measurements above 30 cm?
I would like to know the settings to ignore the area above 30 cm when calculating a distance histogram in the sensor.

[John E KVAM · Accepted solution]

That's a tough question. The VL53L1X has a lens on the receive side, so one can limit the Region of Interest to about 5 degrees. 

At 30cm and 5 degrees, the target would be about 2.6cm in diameter. So we are getting close. But all the photons received in this area are averaged together. Thus your target would be influenced by the wall behind it. 

But if you used the VL53L1CB, we use a different detection mechanism. With this a target can be isolated if there are no other targets with 80cm of separation. 

So a target at 30cm could be separated from a wall at a bit over 1M. 

Combined with the Region of Interest, it might work. 

If you could make your target especially reflective, and your background very dull, the influence of the background would be very small. 

With 20million photons from the target, <0.5M photons from the wall behind would average to give you a reasonable accurate answer. 

 - john

[kbsh]

Thank you, John.

I’ll try using the VL53L1CB.

By the way, I think the minimum FoV of the VL53L1X is 15 degrees. Is there a setting to reduce it to 5 degrees?
The minimum size of the ROI is 4×4, right?

[John E KVAM]

The cone of illumination goes out at 27 degrees. Mapped across a 16x16 square SPAD array, gives about 20 degreesx20 degrees. (This is all pretty iffy, as the lens on the receive side is deliberately a bit out of focus.)

But that means that the 4x4 smallest region is 1/4 the 20 degrees, and that's how I get to 5 degrees square. 

To be sure if one uses a reflective target at close distance and tries to determine the detection angle, you will come up with a wider zone. Bit with a medium reflective target at a farther distance you will get closer to the 5 degrees. And at a longer distance you will get less than 5 degrees.  

if you have not already done so, try the P-nucleo-53L1A2. It will allow you to make all these experiments rather easily.

- john