| 摘要 |
An optical arrangement of at least a coherent light source (1), a strongly scattering object (5) (the PUF), and a pixelated photo-detector (6), wherein the pixels are comparable in size with the bright and dark patches of the speckle pattern produced by coherent radiation traversing the scattering object (5). Quantitively, the pixel size should be roughly lambda/NA, where lambda is the wavelength, and (i) NA=a/z for free-space geometry, with a being the beam radius and z being the distance between the exit surface of the PUF (5) and the pixelated detector (6), or (ii) NA is the numerical aperture of a lens (7) in an imaging geometry. In a preferred embodiment of the invention, there are tentative requirements that the pixels should be at least smaller than etamaxlambda/ NA and preferably larger than etamaxlambda/NA, where (in an exemplary embodiment) etamax =5 and etamin = 0.05, say. It will be understood by a person skilled in the art that the present invention is concerned with the optical arrangement of the PUF (5) and the photo- detector (6), rather than the photo -detector (6) per se.
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