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Tutorial: Calibration by Checkerboard (stereo)

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Chris Chronopoulos edited this page Aug 12, 2023 · 2 revisions

This page is up-to-date as of Parallax version 0.28.2

This tutorial generates a stereo camera calibration by auto-detecting the corners of a checkerboard, saving these across multiple checkerboard poses, and then using these as calibration points.

Note: Currently, the checkerboard parameters (number of rows, number of columns, square size) are fixed to those of this reticle (20 mm diameter): 19x19 corners, 500 um pitch.

This page is up-to-date as of Parallax version 0.28.1

Instructions

  1. In the main window, click on Tools > Checkerboard Tool (stereo). This will open a new window for the Checkerboard Tool.

  2. In the Checkerboard Tool, right-click on each view port and select the camera for that view (Right Click -> Parallax -> Camera).

  3. Position your checkerboard so that it's in both cameras' views.

  1. Confirm that the view ports are detecting the checkerboard corners correctly; zoom in to see the placement of the rainbow-colored overlay.

  1. (Optional, Recommended) By default, the filter on the view ports is set to "Checkerboard (fast)". For slower, but more accurate corner detection, right click on BOTH view ports, and select Parallax > Filters > Checkerboard (smooth). This filter implements a 5-frame boxcar smoothing, so you will see some latency in the corner updates as you move the checkerboard around.

  2. Click "Grab Corners" to grab the latest set of corners from the view ports. If you selected Checkerboard (smooth) in the previous step, make sure you wait for the corners to settle before grabbing them.

  3. Change the pose/orientation of your checkerboard, and grab another set of corners.

The count in the Save button will increment with each added pose.

  1. Repeat step 7 for several poses (at least 10) at different angles and different parts of the field of view. Make sure the checkerboard is in both camera views simultaneously.

  2. Click "Save Corners" to save the data to disk. Close the Checkerboard Tool.

  3. In the main window, click Tools > Calibration from Stereo Corners. A dialog window will pop up.

  1. Click "Load Corners" to load your data file from step 9.

  2. Provide a name for the calibration; this field will be auto-populated with a name based on the current date and time.

  3. (Optional) Check the "Provide Intrinsics" option if you wish to fix the intrinsics in the calibration to those determined from a monocular calibration.

  4. Click "Generate Calibration". This can take a few (~10) seconds for large pose counts. When complete, the new calibration will be loaded into the model and selectable via the Calibration Panel on the main window.

  5. (Optional, Recommended) With your calibration selected in the Calibration Panel dropdown, click "Save" to save this calibration to disk.

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