A code plate of an optical encoder has a nonplanar incident part on a first major surface for transmitting light emitted from a light emitter to the inside of the code plate, and a planar primary reflection part for fully reflecting the transmitted light. The first major surface is also provided with a code pattern part which extends in a ring shape around the rotation axis at a position different from the incident part to switch transmission/non-transmission of the totally reflected light in accordance with a rotation position of the code plate. The code pattern part has nonplanar exit parts which transmit the totally reflected light, and planar secondary reflection parts which again totally reflect the totally reflected light. The secondary reflection parts and exit parts are alternately arranged in the circumferential direction about the rotation axis.

A position detecting device detects the position of a moving body by using first and second detected signals that have voltage values changing in connection with a movement of the moving body. The position detecting device includes a difference computing unit that computes first and second difference values, the first being the difference between a center voltage of the first detected signal and the voltage value of the first detected signal, and the second being the difference between a center voltage of the second detected signal and the voltage value of the second detected signal. A ratio computing unit computes a difference-sum ratio index in accordance with the ratio of the difference value between the absolute values of the first and second difference values and the absolute value of the second difference value to the sum of the absolute values of the first and second difference values.

An optical encoder of the present invention includes a light-receiving element unit 5, moving slit 2 and fixed slit 3. The light-receiving element unit 5 includes a pattern 5B for detecting infiltration of liquid.

A rotation angle measurement device includes: relative angle detection means including a reference support whose rotation is regulated in a fixed range in an arbitrary direction of a rotation axis, and a driving rotating body which is coupled to the reference support and is axially supported so as to be all-round rotatable with respect to the reference support, the relative angle detection means which detects a relative rotation angle of the rotating body with respect to the reference support; and non-contact angle detection means which detects a rotation angle of the reference support with reference to a position that does not contact with the rotating body and the reference support. This provides improved accuracy in indexing the rotation angle of a rotating moving shaft and easy installation onto the rotating moving shaft.

A scale is provided with a two-level code pattern according to a pseudo random code sequence along a length measurement direction. Each code of the two-level code pattern indicates a code “1” or “0”, each code includes two bits, and each bit 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 by 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. The scale is commonly used in a reflective type encoder or transmissive type encoder. A detection head part includes an inversion processing unit which performs inversion processing to a detection image of the scale as required.

Provided is an encoder apparatus capable of reducing frequency of maintenance of a battery. An encoder apparatus includes: a position detection system including a detector that detects position information on a mover; an electric signal generator that generates an electric signal in response to movement of the mover; and a battery that supplies at least a part of power consumed by the position detection system in accordance with the electric signal generated by the electric signal generator.

A rotary encoder includes a rotor, a stator, and a casting compound. The casting compound has a first surface facing the stator. The first surface has a first predetermined shape and is fixed in relation to the stator. The casting compound has a second surface facing away from the stator, the second surface having a second predetermined shape.

A measuring device includes a measure, a reel around which the measure is wound, the reel rotating according to pulling-out of the measure and being provided with a code pattern that changes along a rotation direction, a reader configured to optically read the code pattern, and a calculator configured to calculate a measurement value of the measure from a reading result by the reader.

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.