Study On Non-Contact On-Line Measurement Of Free-Form Surface

Aimed at realizing on-line measurement of free-form surface, Achievements on this field have been analyzed and every step of a non-contact measurement system of free-form surface by using linear structured light has been researched. Then, a new approach of on-line measurement by using "digitized templet" which is made of data extracted from CAD-file is proposed.Several methods of non-contact measurement are compared. Laser scanning measurement using linear structured light is taken as emphases of research works according to the present conditions and development status of non-contact measurement. A mathematic model is set up on triangulation principle and a new algorithm of extracting the light strip center is developed.Combined with characteristics of a linear structured light image, the technique of processing the linear structured light image has been gained. Several methods of image segmentation have been compared and analyzed, and a new method named search-region square error has been proposed. By the new method, the linear structured image under simple background can be separated effectively. Then ,the format of DIB(Device Independent Bitmap) is briefly introduced. Having Analyzed the format of CAD-files with a example of a mesh surface obtained by AutoCAD, a method of directly extracting data from CAD-files is proposed and realized in VC++. With Basic principles of B-Spline curve surface studied, a method of obtaining intersection of curve surface and plane is developed and testified.Calibration of image measurement system is studied. The measurement system has been simply calibrated by experiment and factors that affect precision of the measurement system are analyzed.