| 摘要 |
PROBLEM TO BE SOLVED: To provide a condensing optical encoder which is small and compact. SOLUTION: In an optical encoder 10, a polarizing device 22 divides an emission light from a laser light source 21 into a diffraction zero dimension light (main beam) L0 and diffraction plus/minus one dimension light (sub-beams) L1, L2. Those main beam L0 and sub-beams L1, L2 are collected to a scale plate 40 by an objective lens 25. A condensing position A(0) of the main beam L0 and a condensing position A(-) of the sub-beam L2 are set to be away from each other at a distance of (1+1/4)λwith the proviso that a cycle of forming of patterns of a reflection section 421 on the scale plate 40 is designated asλ. As a result, a first encode pulse signal formed based on the main beam L0 and a second encode pulse signal formed based on the sub-beams L1, L2 are in a relationship that the phases thereof are shifted 1/4 cycle with each other. Therefore, a phase A signal and a phase B signal of which phases are shifted 1/4 cycle with each other can be obtained by utilizing a single optical unit, thereby reducing the condensing optical encoder in size.
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