当激光束投射在浮雕光栅上,透过光栅的衍射光斑就反映了浮雕光栅的表面信息。提出一种浮雕矩形光栅刻槽深度的高精度衍射测量方法。分别采用两个激光波长垂直入射光栅表面,测量透过光栅的0级和1级衍射光强比,实现对光栅刻槽深度的间接测量。此测量方法理论精度优于1nm。给出了对石英浮雕矩形光栅的实验测量结果。该测量方法的突出特点是:所用仪器设备简单,对环境噪声不敏感,测量速度快,特别适用于在线检测。

When the laser beams project in the relief gratings,its transmission diffraction patterns represent the surface informations of the relief gratings. A new method of high accuracy to measure the groove depth of rectangular relief gratings by laser diffraction is proposed. Using two respective lasers of different wavelength to incident vertically on the surface of the gratings,the intensity ratio of zero-order diffraction to the 1st-order diffraction through the grating is measured. So the groove depth of rectangular relief gratings can be measured indirectly. The theoretical accuracy of groove depth is better than 1nm by this measurement method. The experimental results of measuring the quartz rectangular relief gratings are given in this paper. The method is characterized by simple equipments,less sensitive to noise,higher measurement speed,and is especially suitable for on-line testing.