Decapod Stereo Camera Calibration Workflows and Alternatives

Owned by Jonathan Hung
Last updated: Sept 21, 2012Version comment
2 min read

Stereo Calibration

Stereo calibration requires:
1. 22 stereo images of the checkerboard
2. Outer corners should be visible in all images

Issues

1. Long process: 30s per stereo pair for capturing. 6 minutes for calibration script.
2. Unknown expectation: what is needed for calibration? What angles? What is the criteria for good images vs bad?

Approach 1: Move the Rig

Description:

  • Reposition tripod, adjust pitch and height to capture images.
  • Can have a systematic approach: 3 positions with 4 different height adjustments. At each high adjustment, adjust pitch 2 times = 24 frames (3 x 4 x 2)

Pros:

  • Pattern stays in one spot.

Cons:

  • User is required to move the rig around increasing likelihood of bumping cameras, or pulling cables out.
  • Rig may be heavy.
  • Tedious

Approach 2: Move the pattern with timer

Description:

  • User marks / mentally notes the boundaries of the camera views
  • initiates automatic calibration.
  • User moves and tilts randomly in front of cameras until 25 images are taken.
  • Optionally, the user can review the images and delete the bad ones and retake another sample.

Pros:

  • Automatic: User can just move the pattern around until done.
  • User doesn't have to move camera: reduces possible error.

Cons:

  • Higher change of user doesn't position pattern properly.
  • Timer may be too long, or too short depending on the user's ability.
  • User needs to hold pattern really still. Each camera captures one after the other (not simultaneous). Any movement of pattern between left-right shots will throw off calibration.

Approach 3: Move the pattern, prop up without timer

Description:

  • User marks / mentally notes the boundaries of the camera views
  • User positions the pattern in front, propping it up different ways for each shot.
  • Manually trigger cameras.
  • Optionally, the user can review the images and delete the bad ones and retake another sample.

Pros:

  • User doesn't have to hold pattern - little chance of pattern moving between camera exposures.

Cons:

  • Manual process: position, prop, capture - repeat 22 times.
  • User needs to think of different ways on how to prop pattern.