Patent ID: 8993954
Filing Date: 2015-03-31
Classification: G01D

Abstract:
1. An optical encoder comprising: a light source; a scale configured to be irradiated by the light source and have a fine pitch pattern and a coarse pitch pattern in a measuring direction in one track; a photo detector array configured to be used for both the fine pitch pattern and the coarse pitch pattern and detect transmitting light or reflected light from the scale, the transmitting light and the reflected light being emitted from the light source; a signal processing unit including a first initial-stage amplifier unit configured to generate a position detection signal from the photo detector array; and a control unit configured to use an output signal from the first initial-stage amplifier unit to control a light amount variation of the light source, wherein the optical encoder is configured to operate in a high resolution detection mode to form an arrangement of a light receiving surface of the photo detector array at a first pitch in the measuring direction to detect the fine pitch pattern and a low resolution detection mode to form an arrangement of a light receiving surface of the photo detector array at a second pitch in the measuring direction to detect the coarse pitch pattern, the optical encoder includes a second initial-stage amplifier unit to which an output of an unused photo detector of the photo detector array is inputted when there is the unused photo detector which is not used to detect position in at least one of the high resolution detection mode and the low resolution detection mode, and the control unit controls the light amount variation of the light source on the basis of a sum signal of output signals from the first initial-stage amplifier unit and the second initial-stage amplifier unit when there is the unused photo detector.