An absolute surface encoder with a planar scale grating of variable periods
An absolute surface encoder with a planar scale grating of variable periods
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DOI：
10.1016/j.precisioneng.2020.09.007
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发表时间：
2021-01-01
影响因子：
3.6
通讯作者：
Gao, Wei
中科院分区：
文献类型：
--
作者：
Shimizu, Yuki;Ishizuka, Ryo;Gao, Wei
提出了一种利用锁模飞秒激光器和周期沿着正交方向可变的平面光栅实现面内绝对位置测量的绝对式面内光栅编码器。该方法通过观察正、负一阶衍射锁模飞秒激光在平面光栅上单点出射的耦合群光谱来测量面内绝对位置。由于具有可变周期的平面标度光栅的色散效应，每个衍射模式具有与绝对位置信息相关联的唯一衍射角。因此，可以通过获得由双检测器单元接收的耦合的正和负一阶衍射光束的光谱中的峰值频率来检测绝对面内位置。光学头的双检测器配置还有助于提高绝对位置测量相对于平面标度光栅的角误差运动的鲁棒性。此外，在双检测器配置下可以产生能够用于改善绝对位置测量的干涉信号。文中给出了理论验证的数值计算结果、用干涉光刻法制作可变周期光栅（VLS光栅）、光学头的设计和研制，以及用研制的光学头和VLS光栅进行基础实验的结果。
An absolute surface encoder for measurement of absolute in-plane position with a mode-locked femtosecond laser and a planar scale grating having variable periods along the two orthogonal directions is proposed. In the proposed method, the absolute in-plane position is measured through observing the spectra of the coupled groups of the positive and negative first-order diffracted mode-locked femtosecond laser emanated from a single point on the planar scale grating. Due to the dispersive effect of the planar scale grating having variable periods, each of the diffracted modes has a unique angle of diffraction associated with the absolute position information. Therefore, the absolute in-plane position can be detected by obtaining the peak frequencies in the optical spectra of the coupled positive and negative first-order diffracted beams received by dual detector units. The dual detector configuration of the optical head also contributes to improving the robustness of the absolute position measurement against the angular error motion of the planar scale grating. Furthermore, interference signals capable of being used for the improvement of the absolute position measurement can be generated under the dual detector configuration. Results of the numerical calculations for the theoretical verification of the proposed method, fabrication of a scale grating having a variable period (VLS grating) with interference lithography, design and development of the optical head, as well as the results of basic experiments by using the developed optical head and the VLS grating, are reported.