tailieunhanh - Advances in Measurement Systems Part 2

Tham khảo tài liệu 'advances in measurement systems part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 36 Advances in Measurement Systems Zhang Huang 2006b proposed a new structured light system calibration method. In this method the fringe images are used as a tool to establish the mapping between the camera pixel and the projector pixel so that the projector can capture images like a camera. By this means the structured light system calibration becomes a well studied stereo system calibration. Since the projector and the camera are calibrated independently and simultaneously the calibration accuracy is significantly improved and the calibration speed is drastically increased. Fig. 4 shows a typical checkerboard image pair captured by the camera and the projector image converted by the mapping method. It clearly shows that the projector checkerboard image is well captured. By capturing a number of checkerboard image pairs and applying the software algorithm developed by Bouguet http bouguetj calib_doc both the camera and the projector are calibrated at the same time. Fig. 4. Checkerboard image pair by using the proposed technique by Zhang and Huang Zhang Huang 2006b . a The checkerboard image captured by the camera b The mapped checkerboard image for the projector which is regarded as the checkerboard image captured by the projector. b Following the work by Zhang Huang 2006b a number of calibration approaches have been developed Gao et al. 2008 Huang Han 2006 Li et al. 2008 Yang et al. 2008 . All these techniques are essentially the same to establish the one-to-one mapping between the projector and the camera. Our recent work showed that the checker size of the checkerboard plays a key role Lohry et al. 2009 and a certain range of checker size will give better calibration accuracy. This study provides some guidelines for selecting the checker size for precise system calibration. Once the system is calibrated the xyz coordinates can be computed from the absolute phase which will be addressed in the next subsection. 3-D coordinate .