Renishaw Plc

Iain Robert Gordon-Ingram

Andrew Paul Gribble

Alan James Holloway

Simon Eliot McAdam

Michael Homer

A position encoder apparatus, including a scale having a series of position features; and a readhead configured to read the series of position features via a snapshot capture process. The snapshot capture process is adaptable so as to compensate for the relative speed between the scale and readhead.

Position encoder apparatus

A position encoder kit, including: a scale comprising a series of position features; and a readhead. The readhead includes a detector for receiving configuration information from a configuration item. The readhead is configured to operate in accordance with the configuration information. The readhead also includes a receiver interface via which the readhead can supply position information to a receiver.

This invention relates to a method of operating an absolute encoder apparatus comprising a scale having features defining absolute position information in at least one measuring dimension, and a readhead configured to read the features. The method comprises: obtaining at least one representation of at least some of the features defining absolute position information; analyzing the at least one representation to determine at least one parameter indicative of the quality of the representation; and providing an output indicative of the relative setup of the scale and readhead based at least in part on the at least one parameter.

Absolute encoder setup indication

An absolute measurement scale has an incremental scale with light reflecting lines alternating with non-light reflecting lines in which absolute data, in the form of discrete codewords, is embedded in the incremental scale by removing light reflecting lines. The codewords are arranged such that the scale is palindromic and cyclic. A look-up table is used to determine a coarse absolute position by comparing absolute position data extracted from the scale with absolute codewords in the look-up table. The absolute position is determined by combining the coarse absolute position with the position of the start of the first codeword in the data extracted. The absolute position may be determined to within a scale pitch by combining the absolute position with the incremental position.

Absolute position measurement

The invention relates to a reference mark detector for use with a metrological scale or encoder () having a patterned reference mark rm movable relative to the reference mark detector. The detector may comprise a photodetector array () for detecting the patterned reference mark, the array comprising at least two sets of detector elements A and B each set being formed as a pattern which relates to the pattern of the reference mark. The two sets may be separate rows of photodectors or different elements of the same row of photodetectors. The pattern is preferably irregular.

Reader for a scale marking

A measurement scale () is movable in plane x relative to a mask () and photodetector (). When a pattern of apertures in the mask () are in correlation with a pattern of apertures e.g. a reference mark in the scale () then light bands a b and c may propagate to the detector (). The relative sizes of the patterns is such that the light bands converge at the detector (). Other embodiments show light divergent and light inversion correlation of incongruent patterns.

Position determination system for determining the position of one relatively moveable part relative to another relatively movable part

A scale and scale reader are disclosed which may be used to determine absolute position of the reader with respect to the scale in two directions. In an embodiment of the invention a chequered pattern is produced on a scale and block of the pattern may be imaged on a detector and decoded. The blocks contain bits of information which define an absolute position. The pattern may be used also for incremental measurement.

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Marshfield, United Kingdom

Iain Robert Gordon-Ingram