Optimal shape for PnP on calibration pattern

asked 2016-09-26 03:50:36 -0500

Mehdi gravatar image

updated 2016-09-26 03:50:52 -0500

I have a setup where I need extrinsic calibration of an actuator where a camera is mounted. The camera is already calibrated relative to the actuator and now I need to calibrate the whole system relative to some kind of shelf. I need the distance from that shelf and the angle relative to that shelf. I tried using AR markers (AR track alvar) on the shelf but the accuracy is highly dependent on the print quality and even then it is still relatively unstable. When I visualize the marker's detection in Rviz (a ROS software) I see that the markers are not always collinear, where in reality they are just put next to each other on a planar surface. This planar surface is the only free place where I can put markers and it has dimensions of 30x3 cm. I thought about putting a calibration pattern there (the black dots). However, this calibration pattern will not be close to a square shape and will be much thinner and longer. Do you have any suggestions on what I should consider before doing that? Would it still work well with a 3x20 shape? I am targeting accuracy ranges under one millimeter and one degree. The intrinsic calibration of the camera returns a re-projection error under 1 pixel.

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