A Measurement System For The 3-Dimensional Object Surface Based On Projected Grating Phase Method

With the development of computer and signal processing technology, the application of 3D object surface measurement plays an important role in many domain. There are many ways of 3D object surface measurement, but the phase measurement method is one of most promising methods because of its high precision and fastness of data acquisition. This dissertation studies the theories and application of phase measurement system.The mathematical model of each phase measurement method and the relationship between the phase and the height are analyzed. At the same time, the FTP theory and process of engineering measurement are studied.The depth of field of camera is studied and the relationship of the area out of focus in the image and the phase errors is presented to improve the precision of the measurement system,A measurement system that consists of LCD, CCD camera, and image card is designed. At the same time, a software system that integrates the function of system calibration, image processing and also image analyzing is developed with Visual C++ 6.0.The availability of the measurement system is proved by a lot of practical measurements. The system errors and the random errors are analyzed and the improvement scheme is proposed.To improve phase measurement method the wavelet transform is applied to FTP. The theory of wavelet transform is described. The image is processed with db4 wavelet to eliminate the light of background. It will also direct the choosing of multi-frequency grating and the construction of self-adaptive grating.