Patent ID: 7075097

Claim:
A position measuring device usable for measuring a relative position between the position measuring device and a target member, the position measuring device comprising: an array detector; an optical path array element comprising a plurality of similar optical path elements that each provide an input and an output for light rays, wherein the optical path elements are arranged such that their inputs are arranged along two dimensions corresponding to an input face of the optical path array element and their outputs are arranged along two dimensions corresponding to an output face of the optical path array element; and an angular filter portion that only transmits respective light rays outputted from the optical path array element along a respective operable direction that is approximately parallel to an optical axis of the angular filter portion, wherein: the position measuring device is positionable to provide an image on the array detector that corresponds to at least a portion of the target member, the image arising from the transmitted light rays; and the image on the array detector is usable to determine at least one measurement value that corresponds to at least one degree of freedom of the relative position between the position measuring device and the target member.