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.

An optical encoder comprises an emitter; a receiver; a reflector; and a code carrier, wherein the emitter emits electromagnetic radiation along an emission axis in the direction of the reflector and the reflector deflects the electromagnetic radiation along a reception axis in the direction of the receiver. The code carrier is movably supported and has a sequence of code sections to interrupt or to give way for the emitted electromagnetic radiation to impinge on the detector in dependence on the position of the code carrier, wherein the emission axis and the reception axis extend at an alignment angle with respect to one another that has a value in the range from 30 degrees to 150 degrees.

An optical position-measurement device includes a reflection measuring standard and a scanning unit, which is movable in relation thereto in at least one measurement direction. The reflection measuring standard has an incremental measuring graduation and a reference marking in at least one reference position. In addition to scanning device(s) for the incremental signal generation, the scanning unit includes for the reference signal generation at least one light source, imaging optics, a diaphragm structure arranged in a diaphragm plane, and a plurality of detector elements. Via the imaging optics, imaging of the reference marking onto the diaphragm structure is implemented. The reference marking is provided on the reflection measuring standard and is integrated into the incremental measuring graduation. In addition, the imaging optics has a variable, object-side focal length along a transversal direction oriented perpendicular to the measurement direction.

An optical position-measuring device includes a scale and a scanning unit. The scale is connected to a first object, extends along a measurement direction and includes a first track having an incremental measuring graduation, and a second track having an absolute measuring graduation. The scanning unit is connected to a second object and includes a light source, a detector having an absolute detector arrangement configured to detect an aperiodic light pattern transmitted from the absolute measuring graduation onto a detection plane and an incremental detector arrangement configured to detect a periodic light pattern transmitted from the incremental measuring graduation onto a detection plane, and a fiber-optic plate arranged as a continuous component in front of the absolute detector arrangement and the incremental detector arrangement, wherein both absolute track information and incremental track information in the respective detection planes are transmitted via the fiber-optic plate in this manner.

There is provided an optical encoder including an encoding medium, multiple photodiodes and a signal processing circuit. The encoding medium includes an index track. The index track includes a first index pattern and a second index pattern. The multiple photodiodes include a first index photodiode, a second index photodiode and a reference index photodiode for receiving modulated light from the first index pattern and the second index pattern. When the first index photodiode is aligned with the first index pattern and the second index photodiode is aligned with the second index pattern, the signal processing circuit outputs a triggering signal.

An encoder connected to an object is provided. The encoder includes a plate, a sensor, a memory and a processor. The plate has a pattern thereon. The sensor is configured to obtain an image of a portion of the pattern. The memory is configured to store a first set of reference images corresponding to a portion of the pattern and angle and/or position information corresponding to the first set of images. The processor is configured to shift the first set of reference images to obtain a second set of reference images and to compare the obtained image with the first set of reference images and/or the second set of reference images.

There is provided an optical encoder including an encoding medium, multiple photodiodes and a signal processing circuit. The encoding medium includes an index track. The index track includes a first index pattern and a second index pattern. The multiple photodiodes include a first index photodiode, a second index photodiode and a reference index photodiode for receiving modulated light from the first index pattern and the second index pattern. When the first index photodiode is aligned with the first index pattern and the second index photodiode is aligned with the second index pattern, the signal processing circuit outputs a triggering signal.

A length measuring instrument for measuring length with a measure includes: a measure on which a code is printed, a plurality of patterns each allotted to a different number being arranged, each of the patterns having digits to which an N-notation number (N being 3 or greater) is allotted, each of the digits having a different color corresponding to the allotted numerical value, the patterns being arranged in ascending order or descending order, a Hamming distance between patterns adjacent to each other in an array direction being 1, an amount of change in numerical value at the same digit between the adjacent patterns being 1 in the code; a reading unit that optically reads patterns printed on the measure; and a measuring unit that measures a length of a measurement target from a result of the reading by the reading unit.

A measuring instrument includes a plurality of first readers that optically read a plurality of patterns from a measure having a color pattern including the plurality of patterns arranged at a regular interval in a length direction, the plurality of first readers being arranged at the regular interval in the length direction, a converter that converts the plurality of patterns read by the plurality of first readers into a value of an N-ary number (N is 3 or more), and a calculator that calculates a scale value of the measure based on data that defines a relationship between the value of the N-ary number and the scale value of the measure.

A method includes imaging, with an optical read head attached to a second mechanical component, a portion of an encoder track disposed on a first mechanical component. The encoder track has a first encoder scale extending along the encoder track and a second encoder scale extending along the encoder track, and the imaged portion of the encoder track includes a first portion of the first encoder scale and a second portion of the second encoder scale. The method further includes transforming an imaged portion of the encoder track to a spatial frequency domain; identifying a pair of frequency bins in the spatial frequency domain; determining a phase difference between a first frequency bin and a second frequency bin in the pair of frequency bins; and mapping the phase difference to a positional relationship between the first mechanical component and the second mechanical component.