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.

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.