The photoelectric encoder 1 includes a scale 2, and a detection head 3 including a light emitting unit 4, an index 5, and a detection unit 6. The index 5 includes a first index portion 50 consisting of diffraction portions and non-diffraction portions alternately juxtaposed at a predetermined pitch along the longitudinal direction of the scale 2, and a second index portion 51 consisting of diffraction portions and non-diffraction portions alternately juxtaposed at twice the pitch of the first index portion 50. The scale 2 is configured to include a first pattern portion 20 consisting of diffraction portions and non-diffraction portions alternately juxtaposed at a predetermined pitch along the longitudinal direction of the scale 2, and a second pattern portion 21 consisting of diffraction portions and non-diffraction portions arranged in a checkered pattern.

The instant disclosure provides an optical scanning light-guiding encoder including a light-guiding grating wheel, a light-emitting module and an optical sensing module. The optical sensing module includes a plurality of sensor elements adjacent to the light-guiding grating wheel, and a plurality of exposed sensor areas of the plurality of sensor elements are offset in the transverse direction and are arranged along a plurality of different horizontal lines parallel to each other. The optical scanning light-guiding encoder provided by the instant disclosure utilizes the coordination of the light projected on the optical sensing module and the plurality of exposed sensor areas to increase the resolution thereof without increasing the size of the encoder and the number of blades thereof.

An optical sensor, an optical encoder, a torque detection apparatus, and an electric power steering apparatus less affected by fluctuations in the amount of detected light and with an improved resolution are provided. The optical sensor includes a first polarizing layer that splits incident light to light with a first polarization direction, a first photoreceiver that receives first polarized light split by the first polarizing layer, a second polarizing layer that splits the incident light to light with a second polarization direction, and a second photoreceiver that receives second polarized light split by the second polarizing layer. The first photoreceiver and the second photoreceiver are positioned alternatingly and spaced uniformly with each other.

A displacement measuring system is disclosed. The system may implement a code carrier formed from a data storage medium which includes a relative displacement measurement code channel which is an arrangement of pit lines and bump lines. A composite subsystem may include an optical laser assembly, a signal processing unit, and a power driver, and can scan and decode the code carrier by focusing a laser beam on the code carrier and obtaining a group of radio frequency electric signals from the reflection of the laser beam which represents the bumps and pits of the code carrier. A central control and signal output unit can process the electric signals produced by multiple composite subsystems and output information representing incremental and absolute displacement.

A stage assembly for positioning a device along a first axis, the stage assembly comprising: a base; a stage that retains the device and moves above the base; a mover assembly that moves the stage along the first axis relative to the base; a first sensor system that monitors the movement of the stage along the first axis, the first sensor system generating a first signal, the first sensor system having a first sensor accuracy; a second sensor system that monitors the movement of the stage along the first axis, the second sensor system having a second sensor accuracy that is different from the first sensor accuracy of the first sensor system, the second sensor generating a second signal; and a control system that controls the mover assembly using at least one of the first sensor and the second signal.

An encoding device includes a sensing unit having a signal transmitting element and a signal receiving element. The signal transmitting element and the signal receiving element are respectively disposed on different carrier members. Accordingly, when performing the rectification and alignment processes between the signal receiving element and the signal unit, the other components are prevented from hindering the rectification and alignment processes, whereby the rectification and alignment processes can be easily performed.

A length-measuring device includes a scale and a mounting element. The mounting element has a first fastening portion by which the mounting element is stationarily attached to the scale and a second fastening portion configured to be stationarily attached to a support. An arrangement of a plurality of flexible struts is provided between the first fastening portion and the second fastening portion which, through flexure, allows the first fastening portion to move relative to the second fastening portion perpendicularly to the longitudinal direction. The arrangement of struts is configured to compensate for a flexure-induced change in length of the struts in such a way that no movement will result from the flexure-induced change in length between the first fastening portion and the second fastening portion in the longitudinal direction.

There is provided an absolute encoder advantageous in accuracy of an output thereof against a defect in a scale thereof. In the absolute encoder, a detector detects a part of an array of marks of the scale, and outputs a data sequence corresponding to the part. A processor stores information indicating a correspondence between each of a plurality of code sequences and an absolute coordinate of motion of the scale, and outputs information of the absolute coordinate based on the data sequence and the information. The processor detects an error of the data sequence, and performs rewriting of the information based on the detected error.

The encoder includes a scale and a sensor relatively movable in a first direction. The sensor includes first and second readers reading a first pattern. The encoder acquires a first position in a first direction by using an output signal from the first reader and acquires a second position in the first direction by using an output signal from the second reader. The encoder acquires a period of the first pattern by using the first and second positions, and acquires first and second shift amounts between the scale and the first and second readers in a second direction orthogonal to the first direction. The encoder produces position information by using the first and second positions, the period and the first and second shift amounts.

There is provided an interpolation circuit of an optical encoder including a phase shifter circuit, two multiplexers, two digital circuits and four comparators. The phase shifter circuit receives signals sequentially have a 90 degrees phase shift and outputs multiple phase shifted signals. Each of the two multiplexers receives a half of the multiple phase shifted signals and outputs two pairs of phase shifted signals, each pair having 180 degrees phase difference, respectively to two comparators connected thereto. Each of the two digital circuits controls the corresponding multiplexer to select the two pairs of phase shifted signals from the half of the multiple phase shifted signals.