直接相位测量偏折术 (Direct Phase Measuring Deflectometry,DPMD)解决了非连续镜面物体的测量问题,其通过数学模型直接建立了相位与深度之间的关系。在DPMD系统中,采用液晶显示屏 (Liquid Crystal Display,LCD)显示具有高对比度的条纹图案,通过相机采集经被测镜面反射的变形条纹图像,但是LCD透明层的折射效应导致DPMD测量结果出现误差。因此,提出了一种补偿DPMD系统中显示屏折射效应的方法。先建立单层折射模型,并利用光线方程标定透明层厚度及折射率。然后利用系统几何关系标定折射角角度。最后基于标定好的参数计算偏移量,对系统的深度数据进行补偿。对一个镜面台阶和一个凹面镜进行了测量,结果表明,测试精度提高了30%。因此,该方法有效提高了偏折术的测量精度。

Direct phase measuring deflectometry (DPMD) solves the measurement problem of discontinuous mirror objects. It uses a new mathematical model to directly establish the relationship between phase and depth. In the DPMD system, a liquid crystal display (LCD) is used to display a high-contrast fringe pattern, and a camera captures the deformed fringe image reflected by the mirror surface to be tested. However, the refractive effect of the LCD transparent layer causes errors in the DPMD measurement results. Therefore, we propose a method for compensating the refraction effect of the display in the DPMD system. By establishing a single layer refraction model, the thickness and refractive index of the transparent layer are first calibrated using the light equations, and then the refraction angle is calibrated using the system’s geometric relationship. Finally, the offset is calculated based on the calibrated parameters to compensate the system's depth data. The measurement results of a specular step and a concave mirror show that the measurement accuracy is enhanced by 30%. Therefore, this method effectively increases the measurement accuracy of the DPMD.