Multi-Camera Wand Calibration

http://www.ee.surrey.ac.uk/CVSSP/VMRG/WandCalibration/에 있는 내용중 일부입니다.

Multi-Camera Wand Calibration
The use of multiple CCD cameras for generating three-dimensional data of visual scenes is becoming more and more widespread. Once such example is the Prometheus Project, using multiple cameras to generate 3D television content. As part of the project, a fast wand-based method was developed to calibrate the cameras so they can be used for accurate 3D reconstruction. As an aid to researchers working in this area, this site contains linux binaries, a full C++ implementation of the calibration technique, and details of the method.

Calibration Wand
The calibration wand used in this work is shown on the right. Its purpose is to provide two spheres separated by a known distance and easily distinguishable by their colour. We used two standard tennis balls, spray-painted bright red and bright green. The balls are held a fixed distance apart by a piece of wooden dowel passing through them both. This can be done simply by puncturing each ball using a bradawl.

This wand must be waved throughout the capture volume for several seconds whilst video is recorded simultaneously from all cameras. The digitised frames of video can then be fed to the software for processing. The method is robust to clutter provided the colour of objects in the scene is different from the colours chosen for the balls. It does work best, however, when the background is plain since this provides consistently good contrast with the wand.

Tests were performed using PAL cameras, an analog-to-SDI interface, and SDI frame grabbers. It would be interesting to hear from anyone using the method, especially with other camera systems. Please send feedback, comments and suggestions to joel@codamotion.com .


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