数字微镜器件的时空特性对相位测量轮廓术影响的实验研究

Study of effect on the phase measuring profilometer to the spatiotemporal characteristic of DMD

数字微镜(DIMD)投影机具有亮度高、对比大、像质好、全数字,系统体积小等特点,将它用在相位测量轮廓术(PMP)中可以实现高精度的相移提高三维测量的精度,同时可以实现系统的小型化。然而,DMD投影机采用数字光处理技术(DLP) ,它对摄像—投影系统的时间匹配要求较高。如果时间不匹配,会引入光强测量误差,导致三维测量精度降低。本文根据DMD投影原理及探测器积分情况,先分析了当测量系统时间不匹配时,光强测量误差与积分时间的关系;通过实验研究了摄像机积分时间与投影周期的匹配关系对相位测量的影响。得出了积分时间为投影周期的整数倍时,相位测量误差最小;当积分时间与投影周期为非整数倍关系时,积分时间越长,测量误差越小的结论。为优化投影参数,选择合适的相移算法及测量数据预处理算法提供了依据。

There are many characteristics of digital micromirror device (DMD) projector such as high brightness, high contrast, good image quality, full digital and small volume etc. When the DMD projector is used in phase measuring profilometer(PMP), the precision of profile measurement will increase due to the precision of phase-shift increases and the measure system is miniaturized as well. But high precision of schedule match between camera and projector is needed as a result of that the digital light processing technology is used in DMD projector. The schedule mismatch will lead to light intensity measurement error which results in decrease of the profile measurement precision. To study the effect on profile measurement error caused by the schedule mismatch, the relationship between the measurement error of light intensity and the integrating period is analysed at first based the theory of DMD projector and integration of detector, and then the effect is studied through experimentation. It is drawed that the measurement error is minimum when the integrating period is multiple of the projecting period and the integrating period is longer the measurement error littler. The result can give the guidance for the application of DMD in structured illumination three dimensional sensing.