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TOF VL53L1 Calibration Process

Vraj_patel
Visitor

 

Hello ST Team,

We have integrated the TOF sensor into our hardware, and we would like to clarify the following:

  1. How can we calibrate the TOF sensor?
  2. When does the calibration occur—during device power-on or reboot?
  3. What are the results of the TOF sensor calibration?

Thank you for your assistance!

1 REPLY 1
John E KVAM
ST Employee

All of that is documented in the user manual. But we kind of hide the user manual. Download the API from ST.com and it's in the documentation section. Or look in the documentation section of the devices web page. Just search on ST.com for the VL53L1.

There are two devices VL53L1X and VL53L1CB (this is sometimes shorted to VL53L1). So, it's a little confusing.

With the L1X all the work is done on chip, so you can set thresholds and only get interrupted when some condition is met. The L1CB does some processing on your MCU, so you get a better answer, but you have to process every range. 

The user manual for the L1CB is UM2133. 

The user manual for the L1X is UM2510.

During reflow, the chip changes ever so slightly so there is an offset calibration. Set up a white sheet of paper at 14cm or so and range on it a lot. The difference between the average of these ranges and the actual distance is the offset. 

(There is a function call that does this.)

Crosstalk is slightly more difficult. On the VL53L1X range on a relatively dull target. A bit of cardboard painted with flat black paint works well. Find a distance where the range result is 10-20 percent short of what it should be. Knowing the number of photons we got back, the correct distance and the ranged distance we can work out how many photons stuck the coverglass and reflected back to the sensor. 

There is a 3rd calibration; but just call the function. You don't need any setup. 

On the VL53L1CB, the crosstalk calibration is slightly different. As we can directly measure the number of photons we get back no target is required. Just open space for a meter or so.

But read the manuals - it's in there.

- john

 


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