| 摘要 |
PURPOSE:To detect a rotational position with high resolution even when the width of a vernier slit is reduced by setting the slit number of the vernier slit as the least significant digit signal of a counter and thus obtaining fast responding performance. CONSTITUTION:Light from a light source 21 is collimated 22 into parallel light 22, which is projected on a main scale slit plate 23 at intervals of DELTAtheta. Then light passed through the slit plate 23 is passed through a lens 24 and a pinhole plate 25 to remove diffracted light of high order diffracted by a main slit 33, thereby guiding only diffracted light of 0th order to a lens 26. Then the light is expanded again by the lens 26 into a parallel beam, which is projected on the subscale slit plate 27 and photodiodes 28 are arranged corresponding to vernier slits 27a of the slit plate 27 to convert light passed through the slits 27a into current signals. Then the current signals are converted and amplified 29 into voltage signals, which are processed through a comparator 30 and counters 31 (the least significant digit) and 32 to obtain a value proportional to the angle of rotation. Thus, fast response is obtained and the rotational position can be detected with high resolution.
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