Patent ID: 7646494

Claim:
A system for detecting the displacement, of a plurality of elements forming part of an array, said system comprising: a light source arranged to emit a light beam towards the array; an optical position detector arranged to receive the light beam upon reflection of said light beam by said array, said position detector being arranged to provide a first output indicative of a position of incidence of the reflected light beam on said position detector, whereby said position of incidence is determined by the displacement of the corresponding element, scanning means for displacing the light beam along the array so that the light beam is sequentially reflected, by the individual elements along said array, towards the position detector; and reflection detecting means for detecting when the light beam is reflected by an element; the system being arranged so that when the reflection detecting means detect that the light beam is reflected by an element, the corresponding first output is taken as an indication of the displacement of said element, wherein the scanning means comprise: means for carrying out a first continuous scan of the array by continuously displacing the light beam along said array, by moving at least one scan element from a first to a second position in order that the light beam, during movement of said scan element from said first to said second position, be sequentially reflected by the individual elements along said array; means for recording selected positions of said scan element during said first scan, said selected positions corresponding to positions in which reflections are detected by the reflection detecting means; means for carrying out subsequent scans of the array by displacing the scan element stepwise from one selected position to a subsequent selected position.