Intermittent Flashing pattern in VL53L7CX ToF Sensor Data During In-Cabin Mapping

[Aju004]

Hi,

We are trying to mount the VL537CX ToF(Pololu) sensor on roof of a car and map a certain area of the cabin. The sensor is pointed downwards.

But we are observing the a pattern flashing (appearing for a single frame of ToF data) at an interval varying from 0.2 to 5 seconds. The pattern is not constant, there will be slight changes each time.

There are textured hard plastic surfaces (black color & white color) in the locations corresponding to  the zones where flashing occurs. The windshield is close to the sensor, but is out of its FoV.­­­­­­

What could be the reason for this behavior? What can be done to avoid this flashing behavior?

Attached the images of normal zone values and zone values during flashing for reference.

[John_Kvam]

The sensor sends out a flash of light and measures the timing of the return signal. (Actually, it sends out maybe a million flashes, but that's just a detail.)

But no matter what you do, there is going to be something 'at the edge' of detectability. So the sensor sees that object, 'sometimes'. And that will lead to the symptom you see. 

What you want to do is take a look at the range status. I'll bet a lot of times you get a 'low signal' warning. In this case you can use the distance, but you must realize that the accuracy of the measurement will not be great due the low number of photons received. 

You might also find that some of the zones return a 'merged signal' warning. This means that there are two distances in the zone, and the sensor is warning you that your distance is an average of two different distances. (If the distances were greater than 60cm, you would get both distances, but the sensor needs 60cm separation to resolve both distances.)

So in addition to those distances, print out the Return status. That will tell you want is going on, and you can decide what to do about it. 

But if you get this osculation, something is on the edge of detection.

- john