VL53L8 crosstalk calibration

[smenet13]

Hello,

I plan to use a cover glass on top of a VL53L8CX sensor. I understand that I need to perform a calibration to account for the crosstalk effect. According to the forum and datasheet, this calibration requires using an object with a known reflectance percentage. I have two questions about this process:

1. Can I use a board covered with printing paper, setting the reflectance percentage to 88%, and place it approximately 1 meter away from the sensor for calibration, as suggested in the comments?

2. The datasheet mentions measuring reflectance with "vl53l8 REFLECTANCE_PERCENT." Can I use the value obtained from measuring my detected object's reflectance to calibrate the sensor when the cover glass is applied?

Thank you.

[John E KVAM]

The absolute best way to calibrate the sensor is to point it out into space and hit the calibrate button. We are looking for the light that is reflected by the coverglass. As we have a 2-ns pulse, we have to worry if you have any object within 60 cm. The user manual shows:

But 3% reflective is kind of hard to come by. But 5% is just a good quality flat black paint. Chalkboard paint is good for this. 

If you have the space, put that really black (5%) target 70cm away, and use that for your calibration. But while testing in the lab, just point it at the ceiling and calibrate it. 

- john 

[smenet13]

Thank you for your reply, if I understand correctly, I have two options for calibration:

1) Point the sensor towards the ceiling with nothing in its field of view and set the reflectance to 5%, then perform the calibration.
2) Use a board painted with chalkboard paint, place it 70 cm away from the sensor, and calibrate. However, does the board need to cover the entire field of view of the sensor during this process?

[John E KVAM]

That 70cm target is there only to keep anyone from standing front of the sensor when it calibrates. 

At your desk, you are paying attention, but on the factory floor, one kind of has to mark off that 70cm and it's a big area. Thus, you really should mark out an area.

[smenet13]

So, if I understand correctly, during calibration, I need to ensure there is nothing within 60 cm below the sensor. I can either point the VL53L8 towards the ceiling or into empty space and set the reflectance to 5%, or I can use a black painted board placed 70 cm away (and also set to 5% reflectance)just to be sure that there is nothing below 60 cm from the sensor ?

[John E KVAM · Accepted solution]

Exactly!

[smenet13]

Thank you for the explanations