Studies On 3D Vision Measuring System Based On Lcd Grating Technology

A 3D vision measuring system based on stereovision theory and LCD grating projection technique is studied in this thesis. The system is brevity and portable, it can get three-dimensional coordinates of the free form at field. The measuring is non-contact and quickly. Regular point images of LCD are projected to the measured surface. The images modulated by the surface are received by binocular vision sensor. A special image processing software is developed to deal with the LCD images. Characteristic points are obtained accurately by rough-precise match technology. The coordinates of 3D data points are calculated by binocular sensor that is calibrated precisely. These points define a surface equation based on NURBS theory. It supplies interface to industry manufacture. The main works of this thesis are summarized as follows:1. A new binocular vision sensor based on LCD grating technique is developed. It has the functions of three traditional vision sensors: point scanning, line scanning and grating code. The deficiency of the sensor is analyzed. The structure of the sensor is optimized.2. Optical rejection system is designed; the depth of field of the projection system is calculated. The control module of measuring system is designed. An experimental system is developed.3. Characteristic points are established through projecting images of regular points to measured surface. Space dimidiate coding method which is called rough match and correlation technology, centroid technology, corner detect technology which are called precise match are used to acquire characteristic points accurately. The coordinates of these points are calculated by binocular vision sensor that is calibrated precisely.4. A special image processing software is programmed according to the characteristic of LCD image. Median filter, auto-threshold and morphological technology are used for rough-precise match.5. NURBS surface reconstruction method is studied. The 3D data points obtained above are topological rectangles, which are required by NURBS theory. The reconstruction using NURBS method supplies standard interface for industry manufacture.