A Surface Encoder Based on Wave Optics

• Published in: Journal of the Japan Society for Precision Engineering, Contributed Papers Vol. 71; no. 8; pp. 1051 - 1055
• Main Authors: WATANABE, Yoji, GAO, Wei, KIYONO, Satoshi, SHIMIZU, Hiroki
• Format: Journal Article
• Language: English
• Published: Tokyo The Japan Society for Precision Engineering 2005; Japan Science and Technology Agency
• Subjects: measurement; multi-cell photodiode; optical simulation; surface encoder
• ISSN: 1348-8724; 1881-8722
• DOI: 10.2493/jspe.71.1051

A surface encoder, which is composed of a 2D angle grid and a 2D slope sensor, is analyzed in wave optics. Based on the wave optics model, behavior of optical diffraction pattern on the photo-detector caused by 5-degree-of-freedom motions of the angle grid, which are the X- (Y-) movement, tilt motion about the X- (Y-) axis and rotation about the Z-axis, are investigated. The diffraction pattern on the photo-detector show different behavior in each of the motions. In addition, a new 5 degree-of-freedom measurement method is proposed based on the analysis results. This method uses a multi-cell photodiode instead of the QPD in the slope sensor. The principle of the new surface encoder and the design of the multi-cell photodiode are described. Simulation results based on the wave optics model are also presented.