用变频条纹图扫描技术测量陡峭物体的三维轮廓

针对传统条纹投影方法不能测量陡峭物体三维轮廓的问题，提出了一种基于相移的变频条纹图扫描测量技术．采用投影装置投射一系列频率随时间变化的正弦条纹图到被测物体上，且在每个频率下完成相移条纹扫描．用电荷耦合器件(CCD)和图像采集卡记录这些变形的条纹图，对这些条纹图沿时间轴提取相位并进行处理，可以得到图像上每个像素点的相位和沿时间轴的相位变化率，由此得到的每个像素点的相位值在像面内都是相互独立的，而相位变化率包含物体的高度信息，因此可以得到物体的三维轮廓．实验证明，该技术能够成功地测量陡峭物体的轮廓．

Three-Dimensional Profile Measurements of Objects with Large Height Steps by Frequency Conversion Fringe Pattern Scanning Technology

To solve the problem that traditional technique is unable to measure three-dimensional profile for objects with spatially isolated surfaces, a new technique, which is a combination of phase shift fringe analysis and frequency conversion fringe pattern scanning, is proposed. A sequence of sinusoidal fringe patterns with a varying pitch is projected onto objects tested, and the temporal variation of the fringe signal is recorded with a charge couple device(CCD) camera. The phase of the temporal fringe signal is detected at each pixel by the phase shift technique, independently of the other pixels. The temporal frequency of the fringe signal estimated from the time slope of the unwrapped phase provides the information about the absolute surface heights of the objects. The experimental results indicate that the technique enables to measure object with large discontinuities and spatially isolated surfaces more successfully and accurately.