Patent ID: 6600509
Filing Date: 2003-07-29
Classification: G01B,G06K,G06T,G07C,G08B

Abstract:
A detection system for detecting movement of an object relative to the system, said system comprising:a light source for projecting light in a projection direction to form an intersection with an obstructing surface, the intersection extending across a detection zone of the system and comprising a line of light which is one of a continuous line of light and a line defined by a series of separate regions of light; imaging apparatus comprising at least one camera for providing an image of the intersection of said light with the obstructing surface, the imaging apparatus: responsive to said light, having an optical axis which is offset from the projection direction, producing a line image of a profile of the intersection of the projected light with the obstructing surface in an image plane of the camera, and where at least part of the obstructing surface is not that of a reference surface, at least part of its imaged profile is displaced in the image plane relative to an image position corresponding to intersection of projected light with the reference surface; image processing apparatus, said image processing apparatus: responsive to deflection of the imaged profile of the light intersection caused by relative movement of an object through the detection zone providing a change of obstructing surface position, and detecting a line image deflection pattern produced by the obstructing surface profile relative to image deflection produced by at least one elongate reference profile; and the deflection pattern comprising in perpendicular displacements (dshift 1) of line image components in a line image of the obstructing surface profile from positions of corresponding line image components in a reference line image, said displacements being described at the imaging apparatus' image plane by an equation as follows: dshift&UpTee;=fd&UpTee;&it;hbodyhc&it;(hc-hbody)where d1 is the perpendicular distance from the imaging apparatus to a light sheet associated with the line image of the obstructing surface profile,f is the focal length of the imaging apparatus, hC is the distance between the imaging apparatus and the bounding surface and hbody is a parameter indicating the body surface's distance from the reference surface at each point that it intersects the light sheet.