Investigation of cross-polarized heterodyne technique for measuring refractive index and thickness of glass panels

A new mathematical model of cross-polarized heterodyning is proposed for measuring glass panels. An optical system is presented for obtaining relative thickness variation and difference distribution of refractive indices simultaneously, and the dual-balanced coherent demodulation technique is used. The experiment results show that the transmittance of light beam can be less than 0.5% when the vibration amplitude of the glass panels is equal to 5 mm. It takes about 200 s to scan the whole glass sample with size of 1430 × 1360 mm². The resolution of the thickness variation is 0.3 μm, and the lateral sampling resolution is 1 mm.     

双平衡式相干接收原理及其在外差干涉仪中的应用研究

利用琼斯矩阵理论推导了光学双平衡式相干接收的原理,得到了具有正交相关性的包含全部光学信息的IQ信号,给出了基于IQ正交信号解调待测光信号信息的信号处理算法.基于该原理设计了一种高速微机电系统扫描式激光外差干涉仪,得到了待测玻璃的厚度信息分布图.该干涉仪的波前相位差提取准确度可高达0.01 rad、测量速度可达40 frame/s、最大测量直径可达到300 mm,在实时光学检测方面有广阔的应用价值.