Patent ID: 6248994
Filing Date: 2001-06-19
Classification: G01B,G01L

Abstract:
A method for determining angular displacements of one or more parts of an object, said method comprising:a) directing at least one beam of substantially coherent and substantially parallel electromagnetic radiation towards said one or more parts of the object positioned in a first position;b) detecting in at least one first image sensor, a first one or more distributions of speckles provided by at least a part of the electromagnetic radiation scattered from said one or more parts of the object in said first position;c) angularly displacing said one or more parts of the object to a second position;d) detecting in said at least one first image sensor, a second one or more distributions of speckles provided by at least a part of the electromagnetic radiation scattered from said angularly displaced one or more parts of the object in said second position; ande) determining one or more displacements of the first and second detected distributions of the speckles as a function of the angular displacements of said one of more parts of the object between said first and second positions;whereinf) the at least a part of electromagnetic radiation scattered from said one or more parts of the object is Fourier transformed by at least one Fourier-transforming means having a Fourier plane, andg) the at least one first image sensor is positioned in a detector plane in or near said Fourier plane of said at least one Fourier-transforming means.