An optical element for generating diffraction orders for an encoder apparatus, in which the optical element includes an array of diffraction features arranged such that the spacing between the centres of adjacent diffraction features varies irregularly from one pair of adjacent features to the next.

An encoder comprises first and second sensors which reads first and second tracks, the first and second sensors being arranged in a radial direction to face each other, and a processor which generates a first position signal based on first and second periodic signals based on a signal obtained by reading the first and second tracks by the first sensor, and generates a second position signal based on third and fourth periodic signals based on a signal obtained by reading the first and second tracks by the second sensor, wherein the processor generates an absolute position signal indicating an absolute position of at least one of the scale, the first sensor, or the second sensor based on the first and second position signals and the first and third periodic signals.

An encoder comprises first and second sensors which reads first and second tracks, the first and second sensors being arranged in a radial direction to face each other, and a processor which generates a first position signal based on first and second periodic signals based on a signal obtained by reading the first and second tracks by the first sensor, and generates a second position signal based on third and fourth periodic signals based on a signal obtained by reading the first and second tracks by the second sensor, wherein the processor generates an absolute position signal indicating an absolute position of at least one of the scale, the first sensor, or the second sensor based on the first and second position signals and the first and third periodic signals.

There is provided an optical encoder with alignable relative positions between elements including an encoding medium, a sensor package and a memory. The sensor package includes a photodiode array and two alignment photodiodes opposite to the encoding medium. The memory records an alignment pattern associated with output signals of the two alignment photodiodes when the encoding medium and the sensor package are at nominal operating positions. When the encoding medium and the sensor package are not at the nominal operating positions, the relative position alignment is performed by adjusting current relative positions between the encoding medium and the sensor package to cause a current pattern associated with output signals of the two alignment photodiodes to be identical to the alignment pattern.

A method of optical sensing is disclosed. The method comprises coupling an excitation optical signal into a first optical fiber to induce Rayleigh backscattering, thereby providing a backscattered signal; coupling the backscattered signal into a second optical fiber, spatially separated from the first optical fiber; and optically amplifying the backscattered signal in the second optical fiber, thereby generating a sensing signal.

A method of optical sensing is disclosed. The method comprises coupling an excitation optical signal into a first optical fiber to induce Rayleigh backscattering, thereby providing a backscattered signal; coupling the backscattered signal into a second optical fiber, spatially separated from the first optical fiber; and optically amplifying the backscattered signal in the second optical fiber, thereby generating a sensing signal.

A method of determining a direction of rotation of a shaft is disclosed, as well as an integrated circuit chip that uses the disclosed method. The method includes receiving a first binary signal and a second binary signal from a transducer attached to the shaft, with the first and second binary signals being in quadrature. A present quadrant identification number, QID.sub.PRESENT, is determined as a two-digit binary number by left-shifting a value of the first signal and adding a value of the second signal. After a sampling interval has elapsed, the method sets a past quadrant identification number, QID.sub.PAST, to the value of said QID.sub.PRESENT, determines a new value of QID.sub.PRESENT and calculates a value of a transition code using an equation that operates on QID.sub.PRESENT and QID.sub.PAST. The method uses the transition code to determine a direction of rotation of the shaft.

In order to measure a distance in a construction machine having a caterpillar chain drive, at least one contactless sensor for being arranged at a chassis of the construction machine is provided such that the contactless sensor is directed to a caterpillar chain of the caterpillar chain drive of the construction machine. An evaluating unit is connected to the contactless sensor and operative to determine a distance covered by the construction machine based on the signals received by the contactless sensor.

In order to measure a distance in a construction machine having a caterpillar chain drive, at least one contactless sensor for being arranged at a chassis of the construction machine is provided such that the contactless sensor is directed to a caterpillar chain of the caterpillar chain drive of the construction machine. An evaluating unit is connected to the contactless sensor and operative to determine a distance covered by the construction machine based on the signals received by the contactless sensor.

The present invention provides: a rotary encoder checking an eccentricity state of a scale by sensor units; and related matters. The scale moves, relatively to the sensor units, around a rotational axis line. The pair of sensor units are arranged opposite to each other sandwiching the rotational axis line C0 therebetween. A processing system acquires output signals from each of the sensor units, at a plurality of rotation angles at which the scale has moved relatively to the sensor units. The processing system determines first phase information based on the output signal obtained from the sensor unit, and second phase information based on the output signal obtained from the sensor unit. The processing system determines eccentricity information based on a differential value between any one of the first phase information and the second phase information and an average value of the first phase information and the second phase information.