Patent ID: 6800843
Filing Date: 2004-10-05
Classification: G01D,G01L

Abstract:
An optical displacement sensor comprising:a source of optical radiation; an array of radiation detectors, the detector array including a two-dimensional array of detector elements; at least one modulating element disposed between the source of optical radiation and the array of radiation detector, said modulating element having alternating first and second modulating regions circumferentially spaced around a central axis of the element, the first and second regions having different optical characteristics and the transition between adjacent first and second regions being defined by a substantially radially extending edge, the modulating element being displaceable relative to the array of detectors so that the first and second regions are exposed to optical radiation from the source and pass by the two-dimensional detector array of elements to cause the detector array to form a two dimensional image of said first and second regions of the modulating element on the array; a data processor connected to the detector array to receive therefrom respective signals dependent upon the radiation falling on the detectors, the processor being adapted to identify the orientation of at least two different radially extending edges of regions on the at least one modulating element from the two-dimensional image produced by the detector array and to determine the position of the centre of the element from the determined orientation of the edges.