Patent ID: 7432485

Claim:
Optical apparatus comprising an optical system ( 6 , 7 ) for providing a coherent radiation beam ( 2 ), a strongly scattering object ( 5 ) located in the path of said coherent radiation, and a pixelated photo-detector ( 6 ) for detecting a speckle pattern incident thereon, said speckle pattern being produced by said coherent radiation being incident on said strongly scattering object ( 5 ), wherein the size of the pixels of said photo-detector ( 6 ) is determined by the location thereof in said optical apparatus relative to said strongly scattering object ( 5 ) and is set at substantially the same size as that of bright and dark patches present in said speckle pattern as determined by λ/NA, where λ is the wavelength of said coherent radiation, and NA is the numerical aperture of said optical system ( 6 , 7 ).