提出一种基于数字信号处理器(DSP)的嵌入式三维数字成像系统设计方案。该方案的硬件平台由条纹投影模块、数据采集模块、条纹自动分析模块及储存器等其他辅助电路组成。条纹投影模块将DSP输出的正弦光栅条纹, 经视频编码后用DLP投射到物体表面; 数据采集模块通过CCD相机采集被物体表面三维信息调制后的变形条纹图, 并进行视频解码; 条纹自动分析模块中利用相移算法计算折叠相位, 再结合相位展开算法求绝对相位分布。系统软件采用多线程技术并行控制三个模块。在相位解调过程中以软件流水线为主综合运用了循环展开、数据预取和内联函数等多种方法优化解调程序。实验结果表明, 该系统可以高速、准确地实现三维轮廓测量,优化后相位展开程序速度是优化前的7倍。

An embedded three-dimensional (3D) imaging system based on digital signal processor (DSP) is presented. The hardware platform of this prototype is composed of fringe projection, data acquisition, automatic fringe analysis as well as other supporting circuits and memories. The fringe projection module encoded the fringe patterns that is realized by the DSP software, and projected it on object surface through the digital light projection (DLP) to create structural light illumination. The deformed fringe patterns reflected from object surface is detected by a CCD camera and then acquired by data acquisition module that decodes the video signal. The module of automatic fringe analysis is utilized to demodulate the phase distributions of deformed fringe patterns with phase shifting technique, and followed by a phase unwrapping procedure to create continuous phase maps that correlate the height variation of object surface. Three major modules are controlled by the multi-thread technique to accomplish multi-tasks in a parallel fashion. The phase demodulation algorithm, the most time-consuming calculation, is optimized by the software pipeline combined with other strategies such as loop unfolding, data prefetching and inline functions, etc. Experimental results show that the proposed approach can implement the 3D shape measurement with fast speed and good accuracy. The optimized speed of phase unwrapping program is 7 times faster than it before.