Patent ID: 7071461
Filing Date: 2006-07-04
Classification: G01D

Abstract:
1. An optical encoder including a graduation plate inscribed with graduation lines along a predetermined direction and an optical reader for optically reading the graduation lines on the graduation plate, wherein a corresponding electric signal is outputted from the optical reader in accordance with movement of the graduation plate and the optical reader relative to each other; and wherein the optical reader includes a light projecting optical system for irradiating light from a light projecting source to the graduation plate and a light receiving optical system for focusing light from the graduation plate on a light receiving portion and the light receiving optical system comprises a telecentric optical system, wherein the optical reader further includes an object lens, a pin hole plate arranged at a focal position of the object lens, and a light receiving portion arranged at an image plane of light after passing through the pin hole plate and including a light receiving array pattern in correspondence with images of the group of the graduation lines, wherein the light receiving portion includes a light blocking plate having a slit pattern in correspondence with images of the group of the graduation lines and a light receiving element disposed on a back side of the light blocking plate for receiving light transmitting through the slit pattern and the light receiving array pattern is formed by exposing the light receiving element from the slit pattern.