Re-calibration of D435 often needed

[MBerg22]

We are calibrating the D435 cameras, with your tools, and that works very well. After a calibration the depth error is really low and the depth image works well with no artifacts etc.

HOWEVER, we quite often need to re-calibrate!! Suddenly we see that the depth data contains a lot of artifacts (ghost objects that are much too close than what they really are). A re-calibration fixes the issue and everything is fine for a while. The D435 is mounted on a DJI drone.

Do you have any info on what can cause this?

1) Can it be that the vibrations from the electric motors/props slowly destroys the calibration? Or something else?

2) What is it that happens within the D435 when a re-calib is needed? Are there mechanical/physical "things" that move within the cam? Or ... ? Can we maybe fasten some parts of the cam better?

regards,

Mats B

[MartyG · Accepted solution]

The stereo algorithms on the 400 Series cameras are very robust again vibration up to a certain point, where they may start to become an issue if the vibration is severe enough. There was a recent case on the RealSense GitHub site where a user who is using the camera with agricultural machinery was having their camera signal drop because of excessive vibration, even when using a USB cable with a screw-lock to firmly fix the cable in the camera's USB port so it could not work its way loose during motion.

I suggested using some form of "vibration suppression" pad like those that can be placed on the feet of a tripod to dampen vibrations so less of it is passed through the camera mount to the camera. Google for 'vibration suppression pad' to see the products available, please.

I do also recall though that there was a previous case of artifacts on a drone equipped with a D435. The user provided a short video of the flight and the artifacts during it.

https://forums.intel.com/s/question/0D50P0000490XM0SAM/noise-in-realsense-d435-pointcloud?language=en_US

The camera should not usually need re-calibrating unless it has received physical shocks such as a hard knock or a drop on the ground. I guess severe physical vibration could fall into the 'physical shock' category!

The standard D435 inside is essentially the Vision Processor D4 board (which does processing on the captured data), the D430 Depth Camera Module with a pair (left and right) of IR imagers on it, and a separately-attached RGB sensor connected via a cable. Unlike the D435i model, it does not have an IMU unit with gyro and accelerometer. It is the imager sensor parts of the camera that the Dynamic Calibration process adjusts.