An encoder includes an optical component and an enclosing device having a first surface portion and a second surface portion. The first surface portion is arranged to receive from an ambient environment a first radiation beam. The second surface portion is arranged to receive from the ambient environment a second radiation beam. The optical component is arranged to combine the first and second radiation beams. The enclosing device is arranged to propagate the first radiation beam along a first path. The first path is between the first surface portion and the optical component. The enclosing device is arranged to propagate the second radiation beam along a second path. The second path is between the second surface portion and the optical component. The enclosing device is arranged to enclose a space, so as to isolate the first path and the second path from the ambient environment.

The invention relates to a system and a method for active grating position tracking in X-ray differential phase contrast imaging and dark-field imaging. The alignment of at least one grating positioned in an X-ray imaging device is measured by illuminating a reflection area located on the grating with a light beam, and detecting a reflection pattern of the light beam reflected by the reflection area. The reflection pattern is compared with a reference pattern corresponding to an alignment optimized for X-ray differential phase contrast imaging, and the X-ray imaging device is controlled upon the comparison of the reflection pattern and the reference pattern.

The photoelectric rotary encoder includes: a generally disk-shaped scale with a grating-like pattern formed with a predetermined period along a measurement direction, the measurement direction being a direction of rotation of a measurement target that rotates on a predetermined axis, the scale being plate-like and centered on an axis of rotation; and a head that detect, from the scale, the amount of displacement caused by the rotation of the measurement target. The head includes a light source, a diffraction unit with grating parts, and a light-receiving unit with light-receiving elements. The grating parts of the diffraction unit are formed as deformed grating parts that spread cut wide, from the center on the axis of rotation, along the grating-like pattern of the scale. The light-receiving elements are formed as linear grating parts.

A device for position determination includes a light source and a planar measurement reflector movable along a measurement direction oriented perpendicular to the measurement reflector. A detector device is disposed such that a beam emitted by the light source strikes the detector device after impinging on the measurement reflector so that, in an event of a movement of the measurement reflector along the measurement direction, a signal results which is dependent on a position of the measurement reflector and from which a reference signal is generatable at a defined reference position. A deflection unit is disposed so as to deflect the beam such that the beam strikes the measurement reflector twice and therebetween passes through the deflection unit. The deflection unit is arranged so that a deviation in beam direction, resulting after the first reflection from a tilt of the measurement reflector, is compensated after the second reflection.

A device for position determination includes a light source and a planar measurement reflector movable along a measurement direction oriented perpendicular to the measurement reflector. A detector device is disposed such that a beam emitted by the light source strikes the detector device after impinging on the measurement reflector so that, in an event of a movement of the measurement reflector along the measurement direction, a signal results which is dependent on a position of the measurement reflector and from which a reference signal is generatable at a defined reference position. A deflection unit is disposed so as to deflect the beam such that the beam strikes the measurement reflector twice and therebetween passes through the deflection unit. The deflection unit is arranged so that a deviation in beam direction, resulting after the first reflection from a tilt of the measurement reflector, is compensated after the second reflection.

A position detector includes a detection unit configured to detect light from a first diffraction grating including a first pattern disposed in a first direction, and light from a second diffraction grating including a second pattern disposed in the first direction, and a control unit configured to obtain a relative position between the first and the second diffraction gratings based on the light detected by the detection unit. The position detector has a third pattern formed in a second direction different from the first direction at edges of the first pattern of the first diffraction grating, the third pattern has a width smaller than a width of the first pattern of the first diffraction grating.

A position detector includes a detection unit configured to detect light from a first diffraction grating including a first pattern disposed in a first direction, and light from a second diffraction grating including a second pattern disposed in the first direction, and a control unit configured to obtain a relative position between the first and the second diffraction gratings based on the light detected by the detection unit. The position detector has a third pattern formed in a second direction different from the first direction at edges of the first pattern of the first diffraction grating, the third pattern has a width smaller than a width of the first pattern of the first diffraction grating.

A displacement detection apparatus capable of stably and accurately detecting the amount of displacement. The length of a polarization maintaining fiber for transmitting the light from a light source to a displacement detector is set not to be equal to a length obtained by dividing, by the wavelength of the light source, a product of an even integral multiple of a length, which is obtained by multiplying twice the length of a resonator by the refractive index of the resonator, and a beat length obtained by a difference between the propagation constants of two polarization modes. Alternatively, the length of the polarization maintaining fiber is set to be larger than a length, which is obtained by dividing, by the wavelength of the light source, a product of a coherence length and a beat length obtained from a difference between the propagation constants of two polarization modes.

A displacement detection apparatus capable of stably and accurately detecting the amount of displacement. The length of a polarization maintaining fiber for transmitting the light from a light source to a displacement detector is set not to be equal to a length obtained by dividing, by the wavelength of the light source, a product of an even integral multiple of a length, which is obtained by multiplying twice the length of a resonator by the refractive index of the resonator, and a beat length obtained by a difference between the propagation constants of two polarization modes. Alternatively, the length of the polarization maintaining fiber is set to be larger than a length, which is obtained by dividing, by the wavelength of the light source, a product of a coherence length and a beat length obtained from a difference between the propagation constants of two polarization modes.

Rotary encoders suitable for inclusion within small form factor devices (e.g., as input devices to small form factor electronic devices) are disclosed. In one aspect, a light source can illuminate a pattern on a rotatable shaft in order to reflect the pattern onto an array of optical sensors. Each optical sensor from the array of optical sensors can be polled at the same time to yield a snapshot vector. The snapshot vector can be projected onto a subspace spanned by two vectors selected in part on the pattern of the rotatable shaft and the distance separating the shaft and array. The resulting projection can be used to determine error and phase of the reflected pattern across the array of optical sensors. The phase of the reflected pattern can correlate to rotation of the shaft.