Environmental Research Institute of Michigan

John N Cederquist

Anthony M Tai

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.

Aperture sampling coherence sensor and method

A method for producing multicolor holographic optical elements useful in presentation of multicolor holographic images in a head-up display (HUD) system. Because of restricted geometries, such HUDs should allow for reconstruction of wavefronts employing all readout beams coming from the same direction, with the reconstructed wavefront being cast in a specified direction. A first method for producing a multicolor HOE satisfying these conditions makes all recording at the same wavelength but with varying record geometries. A second method for producing multicolor HOEs employs the same record geometries but uses varying wavelengths of recording light. This allows the recording to be made under conditions where the diffraction efficiency of the resulting HOEs is controlled, as are the displayed colors. As the consequence of this, the multicolor HOE can be made under conditions which allow the Bragg condition to be satisfied for each of the readout wavelengths allowing a uniformly bright multicolor wavefront to be reconstructed. A third method for producing such HOEs is to further change the recording geometry by redirecting all the recording wavefronts through the same angular interval. This minimizes the crosstalk which occurs between images recorded at different wavelengths. Also disclosed are apparatus for display of each of the HOEs.

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Ann Arbor, MI, United States of America

John N Cederquist