Patent ID: 7307736

Claim:
A position measuring device usable for measuring a relative position between two members, the position measuring device comprising: an imaging array detector; and a structured light generating target member comprising at least three respective target sources that output at least three respective structured light patterns, the output structured light patterns being in a fixed relationship relative to the target member, wherein: the imaging array detector and the structured light generating target member are positionable to provide a structured light image on the imaging array detector; each of the at least three respective target sources gives rise to a corresponding respective image feature in the image on the imaging array detector; and a size characteristic of each of the at least three corresponding respective image features in the image is usable to determine a z-coordinate value for a respective reference point that is fixed relative to the corresponding respective target source, the z-coordinate value corresponding to a translational degree of freedom along a z-axis that extends along a direction of varying separation between the imaging array detector and the target member.