Laser illumination with speckle reduction
First Claim
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1. A speckle reduction system for a coherent optical source comprising:
- a beamsplitter that divides a pulse of coherent radiation into a series of pulselets having substantially common cross-sectional areas with the pulse;
a delay line that separates the series of pulselets into a succession of temporally spaced pulselets;
an aberrator that spatially distinguishes wavefront shapes of the pulselets within the succession of pulselets; and
the succession of aberrated pulselets being sufficiently temporally spaced and aberrated to produce a succession of different speckle patterns that accumulate incoherently over an interval for reducing speckle contrast.
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Abstract
A speckle reduction system divides pulses of coherent radiation into successions of temporally separated and spatially aberrated pulselets. One or more beamsplitters divide the pulses into the successions of pulselets that are circulated through delay lines. Spatial aberrators located along the delay lines modify wavefront shapes of the pulselets. Together, the temporal separation and spatial aberration of the pulselets produce a succession of different speckle patterns that can be averaged together within the integration interval of a detector to reduce speckle contrast.
262 Citations
27 Claims
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1. A speckle reduction system for a coherent optical source comprising:
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a beamsplitter that divides a pulse of coherent radiation into a series of pulselets having substantially common cross-sectional areas with the pulse;
a delay line that separates the series of pulselets into a succession of temporally spaced pulselets;
an aberrator that spatially distinguishes wavefront shapes of the pulselets within the succession of pulselets; and
the succession of aberrated pulselets being sufficiently temporally spaced and aberrated to produce a succession of different speckle patterns that accumulate incoherently over an interval for reducing speckle contrast. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of reducing speckle contrast comprising the steps of:
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dividing a pulse of coherent radiation into a series of pulselets having coaxial wavefronts;
temporally separating at least some of the pulselets beyond a coherence length of the radiation; and
spatially aberrating the coaxial wavefronts of the temporally separated pulselets with respect to each other so that the temporally separated pulselets produce different speckle patterns. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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21. A speckle reduction system of an illuminator comprising:
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a source of substantially coherent radiation having a limited coherence length;
a beam divider that divides a pulse of the coherent radiation into a series of pulselets that are directed along optical pathways distinguished in optical length by at least the coherence length of the radiation;
a plurality of spatial aberrators that are located along the optical pathways and that change wavefront shapes of the pulselets directed along the optical pathways; and
a beam combiner that combines pulselets into a succession of overlapping pulses that are sufficiently temporally spaced and spatially aberrated to produce a corresponding succession of different speckle patterns. - View Dependent Claims (22, 23, 24, 25, 26, 27)
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Specification