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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 beam is projected on the relief grating, the diffracted light spot passing through the grating reflects the surface information of the relief grating. A high-precision diffraction measurement method of embossed rectangular grating groove depth is proposed. Two laser wavelengths were used to perpendicularly incident on the grating surface respectively, and the 0th and 1st order diffracted light intensities of the grating were measured to measure the grating groove depth indirectly. The theoretical accuracy of this measurement method is better than 1nm. The experimental results of the quartz relief rectangular grating are given. The salient features of this measurement method are: the equipment used is simple, insensitive to environmental noise, fast measurement speed, especially suitable for on-line detection.