The Calibration Methods Of Near-infrared Vein Display System

Venipuncture is a common procedure in many clinical situations. The near-infrared vein display device is an auxiliary visualization equipment of venipuncture. In the vein display device, the accuracy and efficiency of calibration determines the reliability of the system. This dissertation aims to study the methods of calibration the camera-projector system in the non-coaxial vein display system. In this paper, mapping function between camera image and projector image is established with two different methods. Based on the research of calibration methods, an experimental vein display system is realized. The main works accomplished in this paper are as follows:1) Based on the analyses of the mapping relationship between camera image and projector image in the non-coaxial vein display system, two different methods are presented to solve the calibration issue from two perspectives respectively: efficiency and accuracy.2) The fast calibration method based on circular mark pattern is designed and completed. The feature point correspondences can be obtained through the circular markers. A mapping function called homography can be established between camera image and projector image. The mapping function can be obtained fast and automatically with only two images.3) The accurate calibration method based on structured light is designed and completed. An under-sampling of mapping function is obtained by gray encoding and decoding. Combining with local homography, a local linear mapping function can be established, while combining with bilinear interpolation algorithm, an accurate mapping function establishing the correspondence of each pixel of a projector image to a pixel of the camera image is defined. Both the two methods can be applied to curved projection surface.4) The experimental system is set up and both of two calibration methods are verified on the system. The hand dorsal vein displaying experiment is also designed and accomplished on this system.The experimental results show that the presented methods can automatically calibrate the near-infrared vein display system. With the calibration procedure, the experimental system can get accurate display results.