A position detection apparatus detects a position of an object, and the position detection apparatus includes a detector, a scale having a periodic pattern, the scale and the detector being movable relatively to each other, and a signal processor configured to generate a reference signal indicating a reference position of the scale, and the signal processor is configured to generate the reference signal based on a ratio of a first phase signal and a second phase signal from the detector.

A linear encoder has a stationary part and a moving part, and measures and encodes a relative displacement between the stationary part and the moving part along a linear extent of displacement. The encoder comprises multiple machine sensible elements arranged on one of the parts in a predetermined, pattern; and multiple evenly placed sensors arranged along the other part along the entire linear extent, thereby to measure and encode the displacement. The encoder may be an absolute encoder and may be based on magnetic or optical or any other kind of sensing.

A position detection apparatus (100) includes a scale (20) including a reference position grating (22), a detector (10), a detection grating (19), and a signal processor (10), the signal processor acquires a relative reference position between the scale and the detector by using a light intensity distribution of a divergent light beam obtained via the reference position grating and the detection grating, the detection grating has a first spatial frequency that is offset by a predetermined frequency offset amount with respect to a local spatial frequency of an interference image from the reference position grating, the detection grating is provided in an optical path between the scale and a light receiver of the detector, and the light receiver detects a component of a second spatial frequency that is lower than the first spatial frequency in the light intensity distribution transmitting through the detection grating.

Embodiments of the present disclosure provide an optical encoder for an electronic device. The optical encoder comprises an elongated shaft having an encoding pattern made up of axial markings and radial markings. The encoding pattern may be disposed around a circumference of the elongated shaft. The optical encoder also includes an optical sensor. In embodiments, the optical sensor includes an emitter and a photodiode array. The emitter causes light to shine on the encoding pattern. The encoding pattern reflects the light back to the photodiode array and the photodiode array determines movement of the shaft based on the reflected light.

A scale is provided with a reference mark and an incremental pattern. A detection head is relatively movable in a measurement direction with respect to the scale, and detects a light intensity distribution of diffracted beams if beams radiated onto the scale are diffracted by the reference mark, and outputs the detection result. A signal processing unit detects a reference position based on a position in the light intensity distribution where light intensity is lower than a predetermined value. The reference position has a plurality of pattern areas having a plurality of patterns arranged with a predetermined pitch in the measurement direction. At least one pattern area of the plurality of pattern areas is disposed with an offset from a neighboring pattern area in the measurement direction.

A scale has a first pattern area and a second pattern areas disposed with an offset from the first pattern area in a measurement direction by 1/(2s) of pitch. A detection head detects interference fringes caused by positive s-th-order diffracted beams and negative s-th-order diffracted beams diffracted by the scale, and output a detection result. A signal processing unit detects a reference position based on a position where light intensity is lower than a predetermined value which appears in a light intensity distribution of the interference fringes, and detects incremental positions based on the interference fringes which appear at other positions. The detection head includes a light source, a detecting unit configured to output the detection result of the beams radiated onto light receiving devices to the signal processing unit, and an optical system configured to image positive s-th-order diffracted beams and negative s-th-order diffracted beams on the detecting unit.

A scale includes a grating pattern arranged in a measurement direction. A detection head can be moved relative to the scale in the measurement direction and outputs an electric signal indicating a result of detection of the pattern. An operation unit calculates a relative displacement of the detection head relative to the scale. The detection head irradiates the scale with light. A light-receiving unit includes a light-receiving element array arranged in the measurement direction and outputs a result of detection of the irradiation light applied to the light-receiving element array as the electric signal. An optical system forms light from the scale into interference fringes on a light-receiving surface of the light-receiving unit by using lens arrays arranged in the measurement direction. A lens array pitch between neighboring lenses of the lens arrays is not equal to an integral multiple of a pitch of the grating pattern.

System for determining positions along a direction of advance, having a first sensor, particularly a line sensor, having a scanning length (L) for scanning a first 2D pattern and producing a scan signal. The first 2D pattern has pattern elements that each form a first code word on at least one portion of the scanning length (L), which first code word codes a position along the direction of advance absolutely. In addition, the first code word can be taken as a basis for determining a deviation from an ideal position for the first sensor in relation to the first 2D pattern.

An encoder apparatus including a reflective scale and a readhead. The readhead includes at least one light emitting element, at least one sensor and at least one optical device, which together with the scale form an optical system in which the optical device forms an image of an illuminated region of the reflective scale onto the sensor. The system's optical path, from the light emitting element to the sensor, passes through the optical device on its way toward and after reflection from the scale, and includes an unreflected optical path between the light emitting element and the optical device and an unreflected optical path between the optical device and the sensor.

A liquid crystal exposure apparatus that exposes a substrate with an illumination light via a projection optical system is equipped with: a substrate holder that holds the substrate; a substrate encoder system that includes head units and scales, and acquires the position information of the substrate holder on the basis of the output of the head units; and a drive section that relatively moves one of the head units and the scales on the substrate holder with respect to the other.