I am working with the D415 module, which is mounted in a custom aluminum frame. I have tried to calibrate multiple modules (using the same aluminum frame), using the procedure outlined in the "self-calibration white paper" (Rev 2.7):
- On-chip calibration
- Focal length calibration
- Tare calibration (including automatic calculation of the ground truth distance)
For all steps I have been using the "GaussianBlur30x100x175back-11x17-1.pdf" image printed at 100% scale. The RealSense tools (Viewer and Depth Quality) are version 2.50.0.
I get very different results when I perform the calibration, which is the reason for this post. For most devices I need to perform multiple on-chip calibrations before I get a satisfactory "health check" value. And I have tried to redo on-chip calibration when focal length calibration has been performed if "large" focal length corrections have been made.
Never the less, and despite decent looking values, for some devices I end up with a far from satisfactory result! One example could be the following, where the "health check" was very close to 0, focal length imbalance was 0.012% and estimated tilt angle 0.217 deg:
After the calibration, in the Depth Quality tool, the estimated angle was 1.32 deg, fill rage = 99.99%, Plane fit RMS error = 0.25% and subpixel RMS error = 0.11%. The calculated ground truth was 1046 mm which was well in line with the measured ground truth.
Never the less, in the above picture, the depth in the lower right hand corner is just below 1000 mm and in the upper right hand corner just below 1080 mm. In other words, a difference of almost 8 cm within what should have been a completely flat depth map with the used camera and target alignment.
The "shown" D415 module had never been used before, and came directly from a "foam-protected" box. The good question now is:
Assuming I purchase the OEM calibration target (and therefore get access to the OEM calibration software), is it likely that I would be able to end up with a better calibration? And in a bigger perspective: when calibrating multiple D415 modules, can I make them more similar from a calibration-point-of-view, if I use the OEM calibration rather than the self-calibration procedure?
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