A scale includes a diffraction grating configured to condense diffracted light in a periodic direction of the diffraction grating in order to detect a reference position. A light receiving element array is configured to receive light from the diffraction grating. The light receiving element array includes first to fourth light receiving elements configured to output signals having phases different from each other. The first light receiving element and the second light receiving element are adjacent to each other and are arranged between the third light receiving element and the fourth light receiving element. The processing unit generates a signal representing the reference position based on a differential signal between a signal from the first light receiving element and a signal from the third light receiving element and a differential signal between a signal from the second light receiving element and a signal from the fourth light receiving element.

A photon momentum sensor includes: a reflector plate that includes: a central disk including a mirror; an annular member; a plurality of spring legs interposed between the central disk and the annular member, such that: the spring legs are interleaved; neighboring spring legs are spaced apart; and the spring legs individually are arranged in an Archimedean spiral that provides orthogonal motion of the central disk relative to the plane of the annular member; and a bias plate disposed opposing the reflector plate such that: the central disk of the reflector plate moves orthogonally to a plane of the bias plate in response to reflection of laser light, and the central disk and the bias plate are arranged spaced apart as a capacitive structure.

A method for determining a position of a mirror of an optical system comprises: a) providing at least one parameter from a mechanical model of the mirror, b) interferometrically detecting a temporal change in a distance of a point of a curved mirror effective surface; and c) ascertaining an amplitude and a phase of N eigenmodes from the temporal change in the distance and the at least one parameter to determine the position of the mirror.

Example position detection means and displacement detection devices are described. A relative position detection means optically detects a relative position of displacement of an object to be measured in a measuring direction, including a target mounted on the object to be measured and irradiated with light from a light source; a light receiver for detection of relative position for receiving light by changing polarization state of reflected light at the target with respect to the light; and a relative position information output unit for outputting relative position information based on displacement of the target in the measuring direction based on change of polarization state of the reflected light. The target includes a reflector mounted on the object to be measured and a birefringent member on the reflector and having a thickness changing from a tip to a base end along the measuring direction.

A system determines a position of a rotating object in a device and controls the device according to the determined position of the rotating object. The system includes a reflecting region on the rotating object and a light source located in the device. Emitted light is emitted by the light source onto the reflecting region and reflected light is reflected off the rotating object. The reflected light has an intensity. The system also includes a detector that detects the reflected light and measures the intensity of the reflected light. The reflecting region has a feature configured to effect a change in the intensity of the reflected light as the rotating object rotates. The change in the intensity of the reflected light corresponds to a change in a signal associated with a determined position of the rotating object. The device is controlled according to the determined position of the rotating object.

In some examples, an optical encoder may consist of a light source that shines light onto a wheel which then reflects the light onto a sensor. Using information encoded in the reflected light, the rotation of the wheel may be determined. In some examples, rotation of the wheel may be determined by detecting an encoding pattern in light reflected from an exterior surface of the wheel. In some examples, the encoding pattern can be a pattern of light and dark stripes. In some examples, a pattern of light stripes can be generated from light reflecting off of reflective portions of the wheel. Some examples of the disclosure relate to using a surface topology for a wheel that can be used to generate an encoding pattern of light and dark stripes in light reflected from the surface of the wheel, even when the surface of the wheel is uniformly reflective.

An apparatus, a system and a method for detecting position of a movable object in a device and using the same for controlling the device. A distance and/or an intensity of emitted light may be measured by using a sensor to emit light and detect light to determine the location of the movable object. The movable element absorbs emitted light from the sensor. The sensor determines and/or measures an intensity of the emitted light from the sensor which is not absorbed by the movable object. The intensity of emitted light is related to the position of the movable object in the device. A microprocessor may determine the position of the movable object based on the intensity of emitted light detected by the sensor. The position of a rotating object on a crankshaft in an engine may be detected.

A photon momentum sensor includes: a reflector plate that includes: a central disk including a mirror; an annular member; a plurality of spring legs interposed between the central disk and the annular member, such that: the spring legs are interleaved; neighboring spring legs are spaced apart; and the spring legs individually are arranged in an Archimedean spiral that provides orthogonal motion of the central disk relative to the plane of the annular member; and a bias plate disposed opposing the reflector plate such that: the central disk of the reflector plate moves orthogonally to a plane of the bias plate in response to reflection of laser light, and the central disk and the bias plate are arranged spaced apart as a capacitive structure.

A position sensing device comprises a frame, a guide bearing, a motion element, a position sensitive detector, a light source, and a position indicating emitter. The motion element is guided by the guide bearing over a measuring range along a measuring axis direction. The light source is configured to radiate source light. The position indicating emitter moves with the motion element. The position indicating emitter comprises an emitter material that absorbs source light and outputs excitation light from the emitter material to form a measurement spot on the position sensitive detector. The measurement spot moves along the sensing axis direction of the position sensitive detector corresponding to the position of the motion element along the measuring axis direction. The position sensitive detector outputs at least one signal in response to the measurement spot which is indicative of the position of the motion element along the measuring axis direction.

A position sensing device comprises a frame, a guide bearing, a motion element, a position sensitive detector, a light source, and a position indicating emitter. The motion element is guided by the guide bearing over a measuring range along a measuring axis direction. The light source is configured to radiate source light. The position indicating emitter moves with the motion element. The position indicating emitter comprises an emitter material that absorbs source light and outputs excitation light from the emitter material to form a measurement spot on the position sensitive detector. The measurement spot moves along the sensing axis direction of the position sensitive detector corresponding to the position of the motion element along the measuring axis direction. The position sensitive detector outputs at least one signal in response to the measurement spot which is indicative of the position of the motion element along the measuring axis direction.