Problems with the Chessboard and Calibration Board during calibration

[oneday1992]

1. When the chessboard is calibrated, is the chessboard fixed in one position? When the camera shoots the chessboard, the camera position: up, down, left, right, front and back Can you change it at will?

2. Calibration Board When calibrating, is the calibration Board fixed in one position? Do the SLR camera and hollens2 need to be bound together? Hollens2 position: up, down, left, right, front and back, can you change it at will?

3. What is the positional relationship of chessboard and calibration board? Are they in the same position? How to place them?

who can help me ? Very anxious！ Thanks！

[genereddick]

It's been a while, so not fresh in my mind. Broadly, for Intrinsics I move the Chessboard and for Extrinsics I move the camera/hololens rig.

Here are some notes I took:

INTRINSICS Move Chessboard to capture different angles / corners.

Distance to camera can remain stable.

Angles of 45° or less to camera

Capture 9-20 images

Capture corners, edges and center at various angles.

The higher the focal length the more photos you may need. We have had success at >40° and 12+ photos.

Press: “Take Photo” button to capture the image. If successful will appear in one of the quad windows in the Game view. When you have captured enough images, press “Calculate Camera Intrinsics” button

Check Reprojection Error. Should be < 1.0 minimum and as close to 0 as possible

EXTRINSICS Move camera rig around QRCode / ARUCO Board to capture all Marker Pairs

Board needs to be close to Camera (<1 meter)

When a new Marker Pair is captured you will see it appear in the Device Portal (remember there is a delay of several seconds to the Portal).

After a Marker Pair appears you can move the rig to capture more pairs.

The Marker Pairs do not need to align to the current position of the board (what matters is their relative positions at the time of the capture).

Once you have captured all the Marker Pairs (but at least n)

• Back on PC press Capture Extrinsics button
• Check that the CalibrationData.json file has been created in the Calibration Folder
• Optional: Spot check some of the values for accuracy.
• The values in e03, e13, e23 represent the position offset in meters. If the Hololens is exactly centered and above the Camera (may be hard to judge as it is the focal point of the camera lens and the center of the Hololens which is a little unclear) you would want e03 and e23 to be close to 0; e13 would be the vertical offset (negative if above the Camera).
• The rotation offset consist of several Quaternion values (in en0, en1, en2) so not easy to do a simple visual check for accuracy, but generally should be either close to 0.0n or 1.0 – if you are seeing values in the 0.n range, there could be an issue (either a calibration issue or just that the HoloLens is rotated in some way which may be undesirable).