A new, relatively simple experimental technique for generating arbitrary, two-dimensional patterns with high visibility and higher resolution than allowed by the Rayleigh criterion has been developed. The theoretical and experimental details of the method, based on repeated phase-coherent interference of four beams on a multiphoton absorber, are described. A sample pattern generated by numerical computer simulation of the technique is also shown.
The transverse component of velocity for a moving laser-illuminated target is determined using computer image processing. Active imaging is employed in which the target is coherently illuminated producing a speckled image in the pupil plane of a CCD array. Multiple image scans are recorded following the same procedure used to retrieve the incoherent target image. This data is electronically processed to produce an interference pattern dependent upon the distance traveled between image scans. The velocity component transverse to the line of sight of the system is calculated using the distance traveled and time elapsed between scans. The axial component of velocity is shown to reduce the visibility of the interference pattern.
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