British United Shoe Machinery Ltd.

Peter M Witty

David C Reedman

Stephen J Marshall

Hugh G Sasse

An optical system and method for digitizing a last or other irregularly shaped article comprises a laser device fixed on a base directing a light beam at a last supported for rotation about an axis, perpendicular to which the light beam is directed. Two cameras are fixed to the base, one at each side of the laser device, and each comprises an array of cells for detecting the point of incidence of the light beam on the last surface. As the last is rotated, the point of incidence varies in relation to a datum, e.g. the axis of rotation, and the point maximum intensity of illumination on the array of cells will vary across the array accordingly. By a correlating technique, the distance of the point of incidence from the datum can be determined according to the point of maximum intensity of the array. Thus, for digitizing the last, it is necessary merely to rotate it and also move it in a direction along its length for a large number of point positions to be detected, these being then stored as digitized coordinate axis value (R-theta-z). Because the last is an irregularly shaped object, in certain circumstances it is necessary to provide more digitized point positions than in other areas. These are all catered for either by flagging for a subsequent in-fill operation or by back-stepping over reduced angles of rotation of the last.

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Leicester, United Kingdom

Peter M Witty