Optical Absolute Encoder Using Spatial Filter

Toshitsugu Ueda; Fusao Kohsaka; Toshio Iino; Kunio Kazami; Hiroshi Nakayama

doi:10.1117/12.941698

17 February 1987 Optical Absolute Encoder Using Spatial Filter

Toshitsugu Ueda, Fusao Kohsaka, Toshio Iino, Kunio Kazami, Hiroshi Nakayama

Proceedings Volume 0814, Photomechanics and Speckle Metrology; (1987) https://doi.org/10.1117/12.941698
Event: 31st Annual Technical Symposium on Optical and Optoelectronic Applied Sciences and Engineering, 1987, San Diego, CA, United States

Abstract

This paper describes a vernier-type optical encoder for absolute angular measurement. The vernier encoder has only two tracks, so it is much smaller and simpler than conven-tional Gray code encoders. Two "spatial filter" detectors are used with the vernier to provide interpolation between encoder slit positions. Each detector consists of a LED light source on one side of the disk, and two photodiode arrays (PDA) -- one for each track of the vernier -- on the other. The two detectors are placed at diametrically-opposed positions, and the intensities of the LED light sources are modulated in quad-rature by a sinusoidal signal. The signals from the detector arrays are combined to generate two vernier signals, and the difference between these vernier signals is a high-precision "absolute vernier" signal. The accuracy of angular measurement for a prototype encoder was as high as 1/10,000 (2.2 arc-min).

Citation Download Citation

Toshitsugu Ueda, Fusao Kohsaka, Toshio Iino, Kunio Kazami, and Hiroshi Nakayama "Optical Absolute Encoder Using Spatial Filter", Proc. SPIE 0814, Photomechanics and Speckle Metrology, (17 February 1987); https://doi.org/10.1117/12.941698

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