光学式エンコーダ装置

Optical encoder device

Abstract

(57)【要約】 【課題】本発明は光源とスケールの相対的位置変化で生 じる光強度の変化で、光源とスケールの相対的位置変化 を読み取る光学式エンコーダ装置を提供する。 【解決手段】光学式エンコーダ装置10は、光源11か らスリット12に向かって出射された光を、スリット1 2で遮蔽するとともに透過させ、光源11からの光を開 口部12aを透過する透過光と、開口部12aを点光源 として放射する回折光と、に分ける。透過光は、光の直 進性により光源11とスリット12の開口部12aを結 ぶ直線に沿って直進してスケール13に入射し、回折光 は、互いに干渉を起こして、2つの開口部12aからの 距離が光の波長の整数倍になる角度に沿って放射する状 態で進行してスケール13に入射する。この透過光と回 折光の重なるピッチがスケール13のスリット16のピ ッチの整数倍となるように配置されており、透過光と回 折光をスケール13のスリット16を通して受光素子に 入射させて、光源11とスケール13の相対位置を検出 できる。
PROBLEM TO BE SOLVED: To provide an optical encoder device with which a change in the relative position of a light source with respect to a scale is read out, on the basis of a change in a light intensity generated due to the change in the relative position of the light source to the scale. SOLUTION: In the optical encoder device 10, a light which is radiated form the light source 11 toward a slit 12 is shielded and transmitted by the slit 12, and the light is divided into a transmitted light, in which the light form the light source 11 is transmitted through aperture parts 12a and diffracted light, which is radiated by using the aperture parts 12a as point light sources. The transmitted light travels straight along a straight line, which connects the light source 11 to the aperture parts 12a in the slit 12 due to the linearly advancing property of light, and it is incident on the scale 13. The diffracted light interfers mutually, it advances in a state in which it is radiated along an angle at which a distance from the two aperture parts 12a becomes an integral multiple of a wavelength and is incident on the scale 13. The scale 13 is arranged, in such a way that a pitch at which the transmitted light and the diffracted light are overlapped becomes an integral multiple of the pitch of slits 16 in the scale 13. The transmitted light and the diffracted light are made incident on a light receiving element, through the slits 16 in the scale 13, and the relative position of the light source 11 to the scale 13 is detected.

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