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Parameters for camera_pose_calibration

asked 2017-03-27 14:31:12 -0500

AndyZe gravatar image

updated 2017-03-27 15:00:05 -0500

I'm trying to use the camera_pose_calibration package, which seems easy to use. Thank you! Can you help me understand some of the parameters:

PatternParameters pattern_width: Is this the # of dots in a row?

PatternParameters pattern_height: # of dots in a column?

PatternParameters pattern_distance: distance between circle centers? in meters?

neighbor_distance: The readme says this is distance between pixels. In meters, I guess? I think this should be a small number with a RealSense camera, like 0.1mm

Finally, is this OpenCV "asymmetric circle grid" the type of pattern to use?

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Are you referring to the old version, or the new package?

gvdhoorn gravatar image gvdhoorn  ( 2017-03-28 05:55:03 -0500 )edit
AndyZe gravatar image AndyZe  ( 2017-03-28 07:07:56 -0500 )edit

Yeah, so the Indigo version?

gvdhoorn gravatar image gvdhoorn  ( 2017-03-28 07:23:46 -0500 )edit

Ah, yes. Indigo.

AndyZe gravatar image AndyZe  ( 2017-03-28 09:52:35 -0500 )edit

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answered 2017-04-25 15:00:55 -0500

AndyZe gravatar image

updated 2017-04-26 10:11:08 -0500

The parameters that worked for me with a RealSense R200 and the circles pattern from (printed on US letter size) were:

srv.request.tag_frame = "calibration_circles_frame"; // This is defined in a URDF. It's known.
srv.request.camera_frame = "camera_ee_depth_frame"; // Unknown pose. Find its relation to target_frame
srv.request.target_frame = "base_link"; // This is defined in a URDF. It's fixed

  camera_pose_calibration::PatternParameters circle_pattern;
  circle_pattern.pattern_width = 4; // 4 circles wide
  circle_pattern.pattern_height = 11; // 11 circles long
  circle_pattern.pattern_distance = 0.038; // Distance between circle centers. [m]
  circle_pattern.neighbor_distance = 1; // Expected distance between pixels of image
  circle_pattern.valid_pattern_ratio_threshold = 0.5; // Min. ratio of valid pixels to NaN's
  srv.request.pattern = circle_pattern;

I still had an unexplained 45 degree rotation and a Z-offset, but those were easy enough to correct manually. So it was easier than calibrating by hand, for sure.

The RealSense is more tricky than most cameras, I think, because the point cloud is published in the frame camera_depth_optical_frame, which is a child of camera_depth_frame. So camera_depth_frame is what actually needs to be attached to camera_link in the URDF. Maybe this was the cause of the extra rotation -- which I corrected for with an extra transformation matrix.

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answered 2017-03-28 08:12:10 -0500

Ronald gravatar image

It's all in accordance with OpenCV:

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^This helped a little bit with pattern_width and pattern_height. So, thanks! But I'm still having issues. Maybe I'll ask a new question.

AndyZe gravatar image AndyZe  ( 2017-03-28 17:52:16 -0500 )edit

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Asked: 2017-03-27 14:31:12 -0500

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Last updated: Apr 26 '17