Abstract: An incremental encoder apparatus including: a scale including a series of periodic features defining an optical incremental scale, and at least one magnetic reference mark; and a readhead. The readhead includes at least one incremental sensor configured to detect light from the optical incremental scale and to output at least one signal dependent thereon, and at least two analogue Hall sensors, each including at least two output terminal pairs, and each configured to switch repeatedly between each output terminal pair so as to reduce any inherent offset in the output of the analogue Hall sensor. The apparatus is configured to determine the presence of the reference mark from the outputs of the at least two analogue Hall sensors.

Abstract: An encoder apparatus including a scale including a series of features defining at least one scale track and a readhead for reading the scale's features. The readhead includes at least one light source for illuminating the scale and at least one detector. The configuration of the at least one light source is such that there is a structure in the light projected toward the scale. The readhead is configured such that the structure is angled so that it is substantially misaligned with respect to the scale's features so as to reduce measurement error in the signal output by the readhead.

Abstract: An encoder apparatus comprising a readhead moveable relative to a scale, configured to produce a position signal, as well as to produce a reference mark signal when the readhead passes over a reference mark on the scale, configured such that the process for producing the reference mark signal adapts automatically in response to a change in circumstance so as to at least pursue maintenance of a given relationship between the position and reference mark signals.

Abstract: A method of operating a measurement device such as position measurement encoder comprising a scale comprising a series of features and a readhead for reading the scale's features and supplying position signals, the readhead operable in a plurality of different modes of operation. The method comprises the measurement device such as a readhead outputting on at least one signal channel to an external device at least one mode of operation signal indicating the measurement device's (e.g. the readhead's) mode of operation.

Abstract: An encoder apparatus including a scale including a series of features defining at least one scale track and a readhead for reading the scale's features. The readhead includes at least one light source for illuminating the scale and at least one detector. The configuration of the at least one light source is such that there is a structure in the light projected toward the scale. The readhead is configured such that the structure is angled so that it is substantially misaligned with respect to the scale's features so as to reduce measurement error in the signal output by the readhead.

Abstract: A method of manufacturing a measurement device (such as a position measurement encoder including a scale and a readhead) the measurement device including at least one sensor, the method including positioning at least one component of the measurement device using the output from the sensor.

Abstract: Encoder apparatus enabling relative position measurement between a scale and a readhead along a measurement direction. The scale includes features that define a series of incremental scale marks and at least one reference mark. The readhead includes a light source for illuminating the incremental scale marks and at least one reference mark and at least one reference mark photodetector channel. The at least one reference mark is configured to provide an increase in light from the common light source reaching the at least one reference mark photodetector channel at the at least one reference position. The at least one reference mark and/or the at least one reference mark photodetector channel can be featured to interact with light from the common light source non-uniformly across its extent in a dimension perpendicular to the measurement direction to reduce the intensity of light detected by the at least one reference mark photodetector channel.

Abstract: Scale reading apparatus having a scale and readhead moveable relative to one another. The scale has a first incremental scale pattern with a fine pitch and a second incremental scale pattern with a coarse pitch. The readhead has a detector to detect each of the incremental scale patterns. The scale reading apparatus can be used for both slow speed and fast speed measurements. The second incremental scale pattern may be provided in a scale track which has a dual function (e.g. limit track or reference mark) and the readhead may be configured to decode the signal to produce an output suitable for the desired function.

Abstract: Apparatus for determining angular alignment of a readhead with respect to a scale. The apparatus comprises a scale and readhead. The readhead has at least one sensor which produces an output which is dependent on the angular alignment of the readhead relative to the scale.