Aperture sampling coherence sensor and method
AssigneeEnvironmental Research Institute of Michigan
InventorsAnthony M. Tai, John N. Cederquist
Life of this patent
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Abstract
In a speckle imaging process, the contribution of non-uniform, incoherent background illumination is removed via an aperture sampling technique. A pair of uncorrelated speckle images are produced and subtracted from one another to eliminate the non-coherent background contribution. The result of this subtraction is rectified so as to provide a signal which may be displayed on a video display. Disclosed are techniques for real time video display of enhanced speckle images as well as techniques for visualizing vibrational modes and surface roughness mapping.
Claims17
Apparatus for providing a speckle image of an object having reduced contributions from non-uniform, incoherent illumination, said apparatus including:
- a source of at least partially coherent light disposed to illuminate an object so as to produce a light field reflected therefrom;
- sampling means operative to (1) sample a first portion of the reflected light field so as to provide a first speckle image therefrom and (2) sample a second portion of the reflected light field spatially separated from the first portion by a distance sufficient to provide a second speckle image therefrom which is uncorrelated with said first image;
- and
- processing means operative to (1) subtract said first speckle image from said second speckle image so as to provide an output signal and (2) rectify the output signal.
A method for the reduction of the nonuniform, incoherent background of a speckle image of an object, the method including the steps of:
- illuminating an object with a source of at least partially coherent light so as to provide a reflected field of light;
- sampling a first portion of the reflected field so as to provide a first speckle image therefrom;
- sampling a second portion of the reflected field spatially separated from the first portion by at least a diameter of a speckle, so as to provide a second speckle image uncorrelated with the first;
- subtracting the first and second speckle images so as to provide an output signal;
- and,
- rectifying the output signal, whereby the contribution of non-coherent light to the speckle image is removed.
Dependencies are inferred from the claim text.