为了通过结构光投影的方法测量微小物体, 构建了一套微小物体三维形貌测量系统, 视场范围可达1.8 cm×1.6 cm。这套测量系统利用了Light Crafter 4500数字投影组件的高速投影、立体显微镜的低畸变缩放、远心镜头的大景深与低畸变成像的特性。先利用立体显微镜对Light Crafter 4500投影的相移条纹图进行低畸变缩小, 再投影到待测物体表面, 采用配有远心镜头的相机同步记录受到物体表面形貌调制而发生形变的条纹, 利用三步相移法计算出条纹对应的截断相位图, 再根据可靠路径跟踪相位展开算法求取连续的相位分布, 重建被测物体的三维表面形貌。实验成功重建了以BGA芯片为代表的微小物体表面三维形貌。实验结果表明, 系统测量精度达到11 μm, 系统的有效深度测量范围为700 μm。

In order to measure micro-objects by the method of structured light projection,a set of three-dimensional topography measurement system for micro-objects was built, and the field rangecould reach 1.8 cm×1.6 cm.This measurement system took advantage of the high-speed projection feature of Light Crafter 4 500 digital projection module, low distortion scaling feature of stereoscopic microscope, extended depth of field and low distortion imaging feature of telecentric lenses. First the phase shift fringes projected by Light Crafter 4 500 were scaled down with low distortion by stereoscopic microscope, then projected it to the surface of the measured object, and the camera equipped with telecentric lens synchronously recorded deformable fringes that were modulated by the object surface topography. The corresponding truncation phase diagram was calculated by using three-step phase shift method, and then the continuous phase distribution by phase-unwrapping algorithm based on reliable path tracking was also sought for. The three-dimensional surface topography of the measured object was reconstructed. The experiment successfully reconstructs the three-dimensional topography of micro-objects surface such as BGA chips, and the results show that the system measurement accuracy reaches 11 μm, as well as the effective depth measurement range of the system is 700 μm.