Patent ID: 8546746
Filing Date: 2013-10-01
Classification: G01B,G01D

Abstract:
1. A photoelectric encoder comprising: a scale in which diffraction gratings are formed at predetermined pitches in a measurement axis direction; a detection head which is relatively movable with respect to the scale, and which includes an illuminating portion configured to illuminate the scale, and a light receiving portion configured to receive light reflected by or transmitted through the diffraction gratings of the scale; a signal processing device configured to process a light reception signal output from the light receiving portion of the detection head, the signal processing device comprising a display unit configured to display information indicating an attachment posture of the detection head with respect to the scale; a signal transmitting unit configured to transmit a signal between the detection head and the signal processing device; and a plurality of transmission type diffraction gratings, which are placed on a light receiving surface of the light receiving portion and are placed at an equal distance from the illuminating portion, wherein the light receiving portion includes a displacement detection light receiving portion configured to detect pitching of the light receiving surface with respect to the scale about the illuminating portion, and a posture monitor light receiving portion configured to detect rolling and yawing of the light receiving surface with respect to the scale about the illuminating portion, the display unit is configured to display the pitching, rolling, and yawing, the displacement detection light receiving portion has four displacement detection light receiving surfaces, which are equally placed about the illuminating portion in the measurement axis direction and a direction that is perpendicular to the measurement axis direction, and on which transmission type diffraction gratings of four phases that are shifted by 90° from each other are placed, the posture monitor light receiving portion has two monitor light receiving surfaces, which are equally placed about the illuminating portion in a direction that is perpendicular to the measurement axis direction and on which a pair of transmission-type diffraction gratings is placed, and the signal processing device is configured to detect pitching of the light receiving surfaces from an amplitude difference of light reception signals of the displacement detection light receiving portion, to detect rolling from an amplitude difference of light reception signals of the posture monitor light receiving portion, and to detect yawing from a phase difference of the light reception signals of the posture monitor light receiving portion.