Study On The Fringe Projection System Based On Three-dimensional Profilometry Measurement

The 3D object surface measurement is very important in several aspects such as industrial inspection, quality controlling, machine vision and reverse engineering. The traditional measuring method of contact, point and line structured light cannot have a good balance between speed and precsion. In order to meet the requirement of high precision and fast when measuring the 3D free-form surface in industrial field, the paper proposes a design scheme of micro projection system based on DMD(Digital Micromirror Device), which is combined with the method of fringe projection. This system converts the digital image to digital light which is then reflected by micro display device and projected by projection lens. The continuous phase distribution of the light field is modulated by 3D surface when the frame synchronous trigger signal is sent to CCD camera to capture the fringe image.The digital fringe projection system has several advantages as follows:1. Because of the continuous phase of sinusoidal grating image distributed in space, the 3D surface can be completely covered in a projection and measured by extraction of phase information, which brings advantage of high speed and high precision. 2. Fringe patterns with any phase can be generated easily according to the actual requirement, which overcome various disadvantages brought by using physical grating. 3. The method that the input information of digital image is directly converted to the output information of digital light can avoid noise interference during D/A procession and improve the quality of projected images. 4. Using monochrome fringe patterns to be projected can avoids crosstalk between color channels.This paper has completed several main work as follows:1. According to the needs and appilication of the projection system in industral field, the design requirement and meaning of this system was analyzed and a projection system solution based on DMD was put forward. 2. Complete the selection of hardware system and illumination source. 3. Design the hardware drive circuits based on DLPC350 to complete the control of DMD and LED. 4. Design the control platform through USB protocol under the Windows. 5. Complete the design of driving board and the test of its electrical performance,and also the experimental verification of each functional mudule. Analyse the error brought by digital projection in thee-dimensional profilometry measurement in detail and the method of restraining error, and complete the experimental verification.