VL531X effective FOV for reliable results

[sjgc]

Although the data sheet specifies a field of view of either 27 degrees or 36 degrees (depending on where about it is mention in the data sheet, I have found the effective FOV to be aound 8 degrees. Setup as follows

  sensor.setDistanceMode(VL53L1X::Medium);

 sensor.setMeasurementTimingBudget(33000);

  sensor.setROISize(16, 16);

 startcontnuous(100);

with all other sensor settings at default

A large all black target set up at 140 cm from the sensor, reulted in a invalid reading. I then moved a white target in from one side until a valid reading was made, marked the position and repeated this for the other side top and bottom.

This resulted in an area in the middle of about 20 x 25 cm which represents a FOV of around 8 degrees. Any target outside this selected area will reults in an invalid reading (i..e canot be trusted). Targets with in ths area will be detected although the accuracy is very dependent on the refectivity of the oblect, the variation between measured and actual by as much as 30 cm.

Is this effective FOV and accuracy to be expected (ambiant was about 4.7 during testing)

 

[John_Kvam]

I spent a long time thinking about how to measure the field of view - and it’s not as simple as it might seem. 

The 27 degrees comes from the spot of illumination created by the VCSEL (laser). And even that is a fuzzy answer as the VCSEL light rolls off at the edges. 

If you take a really large, bright white target (Printer paper is 88%) and start moving it in from the edge you are going to get a range as soon as enough photons hit the paper and return. But if you take the same paper, but reduce its size to a couple square inches, you might not get a range until the entire target is well within the field of view - and depending on the distance that target might have to be in the dead center of the FoV where the illumination is strongest.

This is the reason, your FoV numbers are so variable.

In order to fully characterize the FoV, you need to do it based on target reflectivity, target size and target distance. 

You end up with a shape that has a wide FoV up close, and it narrows as the target gets farther away. 

• john