研究了一套投影正弦光栅条纹,测量表面有大梯度或非连续结构等复杂形貌微小物体的三维测量系统。针对所测量物体大小,通过将体视显微镜、相机和投影仪组合,研制了具有较小视场的条纹投影系统。软件产生具有最佳条纹个数的三组正弦条纹图,每组包含四个彼此间有90°相位移动的条纹。根据所测量物体表面颜色和纹理特性,选择投影系统的合适颜色通道投射软件所产生的正弦条纹序列到被测物表面。相机从另一角度获取经被测表面调制的变形条纹图。通过四步相移和最佳条纹选择方法分别计算得到折叠相位图和展开相位图。利用水平精密移动台定位一水平白板到几个已知位置,建立绝对相位和深度之间的关系,获得系统深度方向的数据。微小物体的三维形貌测量实验证明了所研制成像系统的可行性和准确性。

A 3D small-field imaging system was established by using the fringe projection technique to measure the small objects having large slopes and/or discontinuous surface. A stereo microscope was used to generate a small-field projecting field and to capture the deformed fringe patterns on the measured small objects. Three fringe sets having the optimum fringe numbers were coded into one major color channel to generate color fringe patterns having the maximum fringe contrast of the captured fringe images. Through one channel of the stereo microscope, a Digital Light Processing(DLP) projector projected these generated color fringe pattern images onto the measured objects surface. From another channel, the fringe patterns were deformed with regard to the object surface and captured by a color CCD camera. The absolute phase of each pixel could be calculated from the captured fringe patterns by using the optimum three-fringe numbers selection method. The relationship between the absolute phase and depth was established to move a white plate to several known positions by using an accurate linear translating stage, so the 3D shape data of the measured objects were obtained. Experimental results on measuring 3D shape of small objects show the accuracy and availability of the developed 3D imaging system.