Conventional white-light scanning interferometers cannot measure exactly large thickness of glass plates because of a great dispersion effect. In this paper a compensation glass plate is used to reduce the dispersion effect. Moreover, a fixed reference surface is added behind the object and four-step measurements are performed. By this method a front surface profile and a thickness distribution of the object can be measured exactly without knowing the refractive index of the object, the thickness of the compensation glass, and dispersion effect containing in the interferometer. Due to the difficulty in scanning the reference surface at a constant speed over a long distance for a large thickness of the object, a piezoelectric transducer stage with a high positioning resolution are utilized together with an additional interferometer which measures the movement of this stage. Experimental results show that the error in thickness measurement is less than 60 nm and 170 nm for 1 mm and 5 mm-thickness glass plates, respectively.

由于色散效应很大，传统的白光扫描干涉仪无法准确测量大厚度的玻璃板。本文采用补偿玻璃板来减少色散效应。此外，在物体后面添加了一个固定的参考面，并进行了四步测量。通过这种方法，可以在不知道物体的折射率、补偿玻璃的厚度以及干涉仪中包含的色散效应的情况下，准确地测量物体的前表面轮廓和厚度分布。由于难以对大厚度物体进行长距离恒速扫描，具有高定位分辨率的压电换能器平台与测量该平台运动的附加干涉仪一起使用。实验结果表明，1mm和5mm厚的玻璃板的厚度测量误差分别小于60nm和170nm。