The invention provides an angle detecting device, which comprises absolute encoders provided on a rotation member which rotates at a constant speed, a clock signal generating component, a counter circuit, an angle calculating component, and a trigger signal generating component, wherein an angle trigger signal is inputted to the absolute encoders and the counter circuit at a predetermined time interval, the absolute encoders input rotation angles for each angle trigger signal to the angle calculating component, the counter circuit outputs the number of clock counts to the angle calculating component from the moment when a rotation angle measuring trigger signal is inputted by inputting the rotation angle measuring trigger signal for detecting the rotation angle of the rotation member to the counter circuit, and wherein the angle calculating component detects the rotation. angle of the rotation member based on the rotation angles from the absolute encoders and on the number of the clock counts.

An absolute encoder includes: a scale including an optical pattern that includes code patterns for a plurality of cycles; an illumination unit that outputs light for illuminating the scale; a light detection unit that detects light from the scale; a section determination unit that determines, for a region of the optical pattern divided into a plurality of sections, the section to which a code string belongs; and an absolute position calculation unit that obtains an absolute position of the scale on the basis of the section determined and the code string. When N is the number of the cycles of the code patterns on the scale, in a case where N is equal to two, the number of the sections is three or more, and in a case where N is equal to three or more, the number of the sections is N or more.

The invention is a rotational sensor to sense an object's angle and methods to analyze the sensor output. The sensor has a first emitting source, to either emit onto, or from the object, a first receiving sensor, to receive emissions from the first emitting source, either directly or indirectly, the emissions received dependent on said angle, first receiving sensor outputting a first signal a course measurement of the angle. Also present is a second emitting source, to emit onto, or from the object and a second receiving sensor, to receive emissions from the second emitting source, either directly or indirectly the emissions received again dependent on said angle, second receiving sensor outputting a second signal, as a fine measurement of the angle. A method of use of the sensor is disclosed together with a method of combining the fine and course measurements to output a signal with zero error.

A position measurement system to determine a position of a first object relative to a second object, includes an encoder head mounted on the first object, a grating mounted on the second object, wherein the grating includes a first array of grating lines in a first direction and a second array of grating lines in a second direction to diffract a measurement beam incident on the first and second arrays in at least one first diffracted beam in the first direction and in at least one second diffracted beam in the second direction, wherein the first diffracted beam is for position measurement in the first direction and the second diffracted beam is for position measurement in the second direction, wherein the measurement beam has a power quantity, and the grating is configured to distribute the power quantity unevenly over the first and second diffracted beams.

Provided are an absolute position measurement method, an absolute position measurement apparatus, and a scale. The scale includes a scale pattern formed by replacing repeatedly arranged pseudo-random-codes with a sequence of a linear feedback shift register of N stages using a first symbol with first width representing a first state and a second symbol with second width representing a second state. The first is divided into two or more first symbol areas of different structures, and the second symbol is divided into two or more second symbol areas of different structures. There is at least one overlap area in which the first symbol and the second symbol overlap each other to have the same structure.

A light source in a rotary optical encoder can illuminate a pattern on a rotatable shaft and an optical sensor can detect either the light that is reflected or transmitted based on the pattern. A sampling rate of the optical sensor is dynamically adjusted based on a rotational speed of the rotatable shaft. A pulse rate of the light source may also be dynamically adjusted based on the sampling rate of the optical sensor.

To obtain a position detection device capable of detecting highly accurate and robust position by suppressing affect of error detection of an edge, provided is a configuration for performing a validity determination of edges detected by binarizing an image signal (21) converted by a light-receiving element (3) for receiving light irradiated from a light source (1) toward a scale (2) having a code pattern, and performing position detection after removing the edges determined to be invalid as edges that have been affected by foreign matter and the like among the edges on which the validity determination has been performed.

An electronic absolute position encoder is provided having a scale, a detector, and a signal processor configured to determine an absolute position of the detector along the scale. The scale includes a signal modulating scale pattern comprising a periodic pattern component and a gradual pattern variation component. The detector includes N spatial phase sensing elements (e.g., conductive windings) and at least one reference sensing element, which is spaced apart along the measuring axis direction by a distance corresponding to an integer multiple of 360 degrees of spatial phase shift relative to a first one of the N spatial phase sensing elements. A first reference signal from the first reference sensing element and a first signal from the first one of the N spatial phase sensing elements include nominally similar signal contributions from the periodic pattern component, and a difference between the two signals is due to a difference in their signal contributions from the gradual pattern variation component. The difference may be used to determine a scale factor M1 for a gradual signal variation exhibited by the detector signals output from the detector.

An electronic absolute position encoder is provided having a scale, a detector, and a signal processor configured to determine an absolute position of the detector along the scale. The scale includes a signal modulating scale pattern comprising a periodic pattern component and a gradual pattern variation component. The detector includes N spatial phase sensing elements (e.g., conductive windings) and at least one reference sensing element, which is spaced apart along the measuring axis direction by a distance corresponding to an integer multiple of 360 degrees of spatial phase shift relative to a first one of the N spatial phase sensing elements. A first reference signal from the first reference sensing element and a first signal from the first one of the N spatial phase sensing elements include nominally similar signal contributions from the periodic pattern component, and a difference between the two signals is due to a difference in their signal contributions from the gradual pattern variation component. The difference may be used to determine a scale factor M1 for a gradual signal variation exhibited by the detector signals output from the detector.

There is provided an absolute position detection type photoelectric encoder which improves robustness to dirt while maintaining high resolution. A two-level code pattern according to a pseudo random code sequence is provided on a scale along a length measurement direction. Each code of the two-level code pattern indicates a code 1 or a code 0, and includes two bits. Each of the two bits is L or H. The code 1 is represented by an A pattern which is a combination of L and H, and the code 0 is represented by a B pattern which is a combination of L and L or a C pattern which is a combination of H and H. When the codes 0 are continued, the B pattern and the C pattern are alternately used.