Optical encoder using metallic surface grating

With an intense thermal variation, optical encoder yields measuring error because of the generation of nonlinear strain due to the difference of the thermal expansion coefficient between a glass scale and a metallic parts of machines. In this study, a method of using a grating which is directly manufactured on a metallic surface of parts of machines is proposed. Using this method, the thermal strain is made linear and the error becomes simplified to calibrate. Furthermore, it realizes a miniaturization of the system and improves its vibration-resistance. This paper shows the process of making a grating on a metallic surface by photolithography using some methods and ascertains the sufficient performance of this scale in an optical encoder.