VL53L9CX - Temporal Noise Reduction

[Ian Buehring]

I wish to get a better understanding of how the TNR works. The precision figures given in the DS are with the TNR enabled. What is not clear from this is what impact it has on the frequncy response of the sensor. So, suppose I have a linear actuator moving sinusoidally at 3Hz over a few mm radially to the sensor, will this be picked up cleanly without attentuation with the TNR enabled or would I need to disable it? I can operate the sensor at 30fps up to 100fps for data capture. 

thanks    

[fichotti]

Hello Ian,

Regarding how TNR works, we have prepared a post-processing guideline available on st.com, link is the following: VL53L9CX postprocessing pipeline - Technical note

 

Regarding your specific example, a displacement of only a few millimeters could potentially be partially smoothed by TNR. When motion is detected, TNR automatically avoids applying local noise reduction in that area, to prevent averaging real motion and introducing additional error. However, with a small displacement, it is possible that the variation between frames is not large enough for the motion to be fully preserved, so the movement may appear attenuated.

At 30 fps up to 100 fps, a 3 Hz motion is well sampled, so the main concern is not temporal resolution but possible smoothing of the amplitude by TNR.

If the objective is to observe or measure the displacement amplitude as accurately as possible, we would recommend comparing results with TNR enabled and disabled.

 

Hope this helps!

 

Cheers,

Timothee