Research On Three-dimensional Measurement Method For Specular Surface

In order to solve the problem of three-dimensional shape measurement of objects with pecular surface,a three-dimensional measurement system based on digital micromirror device(DMD)is build,and it can realize three-dimensional shape measurement of objects with pecular surface.This paper proposes a way to slove the problem of over-saturation area of coded image.To remove the over-saturation area,we add DMD in monocular vision measurement and realize high dynamic range imaging with digital micromirror device.Study of this paper is based on monocular vision measurement system combined with the imaging principle of DMD camera And build optical model of DMD camera and three-dimensional measurement.Combined with the matching method of gray code,three-dimensional coordinates is obtained.Camera and projector calibration are Zhengyou Zhang calibration algorithm to obtain internal parameters and external parameters.In order to complete the matching between camera image and projector image,gray code desigedn as coding structured light is projected on the surface.Finally,the three-dimensional coordinate is obtained by calculation.The main content of this paper is as follow:1、The three-dimensional topography measurement system design of objects with specular surface based on DMD.This paper proposes that DMD generates the mask for over-saturation area in image according to the principle of DMD imaging.DMD camera is built for high dynamic range imaging and the new measurement system is build to obtain three-dimensional shape.2、System calibration.Research of system calibration mainly include camera imaging model and calibration algorithm--Zhengyou Zhang calibration algorithm.Calibration is the process of the the internal and external parameters calculation.the result obtained is the optical parameters and geometric parameters of camera and the relative position of the camera coordinate system and world coordinate system.3、Study on the algorithm of three-dimensional measurement.Based on monocular vision measurement,mathematical model is established for measuring system.According to the gray code encoding and decoding method,the computer generates nine horizontal and vertical gray code imges,corresponding to its radix-minus-one complement.the method of gray code is used in this system for matching between camera image and projector image and radix-minus-onecomplement can effectively be removed the effects of the ambient light.The experimental results show that the system has a positive effect on object with high dynamic range of surface reflectivity and achieve high dynamic range of three-dimensional measurement.