Development of Optical Encoder with Large Enconder Gap

• Main Authors: Hung-lin Huang, 黃鴻麟
• Other Authors: Hua-sheng Lu
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/36583320640272766333

碩士 === 逢甲大學 === 光電研究所 === 97 === This study proposes a new optical encoder with a large gap between the index grating and main grating. Compared with conventional optical encoders, the large-gap encoder is easily assembled and provides displacement signals with good quality. Thus the proposed encoders are well suited for the accurate positioning of high-speed linear stages. Two different index gratings, one- (1D) and two-dimensional (2D) phase gratings, are designed according to the theory of image formation using Talbot effect. The profile and self-imaging quality of the phase gratings are investigated by a scanning white-light microscope and transmission microscope, respectively. Experimental results show that an optical encoder with the 1D or 2D phase grating can work successfully at an encoder gap of one- or three-quarter Talbot distance. However, the optical encoder with the 2D phase grating has superior capabilities to reject the common-mode noise and to eliminate the DC offset in the displacement signals. In addition, a high-precision gap measurement technology based on low-coherence interferometry is also presented and verified experimentally in this study.