| Summary: | 博士 === 國立臺灣科技大學 === 機械工程系 === 106 === This thesis is discussing fabricating and analyzing optical encoder. Two femtosecond lasers have been used for fabricating optimal and precise reflecting grating on the Invar alloy. Several gratings were made with different laser parameters in two regimes: constant repetition rates and constant average laser power. The efficiency of diffraction gratings is measured in an off-plane configuration by determining the power of diffracted points, image processing of Talbot image and also the pitch of gratings has been measured by an improved Littrow configuration setup. It has been shown that Talbot image setup has capability to be an online NDT test machine for grating in the optical encoder fabrication line. The method of improving Littrow pitch measuring setup could remove the error of installation up to 0.03º.
An optical path has been introduced for making interference between orders of diffraction grating and according to this optical path, M-encoder has been designed and fabricated. The result of measurement in different traveling distances and in different installation situations has been showed that the total error of fabricating grating, installing error, environment, signal processing and circuits is less than ±195nm /100mm. The installation tolerance and size of M-encoder is compatible to the other encoders in the market.
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