Speckle free laser probe beam
First Claim
1. An apparatus for generating a speckle free probe beam comprising:
- a radiation source producing a narrow coherent light beam of predetermined beam size, power, and wavelength;
a holographic phase plate disposed in the path of said coherent light beam and modulating relative phase across said coherent light beam;
a mechanical mechanism scanning said holographic phase plate speedily and continuously across said coherent light beam to randomize relative phase across said coherent light beam; and
focal optics positioned to refocus/collimate said modulated coherent light beam into a narrow and near collimated probe beam;
wherein said narrow and near collimated probe beam forms said speckle free probe beam with its temporal coherence unchanged from said coherent light beam but its spatial coherence randomized rapidly in time.
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Abstract
The present invention contemplates a method and apparatus to generate a laser probe beam free of speckles. The present invention employs a holographic phase plate inserted in a laser beam path to modulate the relative phase across the beam. The holographic phase plate is designed to optimize the phase modulation across the beam while to minimize the degradation of the beam quality. The modulated laser beam has only a small and confined divergent angle and can then be refocused or collimated into a narrow and near collimated probe beam. The present invention further rotates the holographic phase plate to randomize the speckles in a time sequence. As a result, the probe beam preserves substantially the beam quality of a laser and produces substantially no speckles on image of its, intersection with a surface or material.
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Citations
18 Claims
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1. An apparatus for generating a speckle free probe beam comprising:
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a radiation source producing a narrow coherent light beam of predetermined beam size, power, and wavelength;
a holographic phase plate disposed in the path of said coherent light beam and modulating relative phase across said coherent light beam;
a mechanical mechanism scanning said holographic phase plate speedily and continuously across said coherent light beam to randomize relative phase across said coherent light beam; and
focal optics positioned to refocus/collimate said modulated coherent light beam into a narrow and near collimated probe beam;
wherein said narrow and near collimated probe beam forms said speckle free probe beam with its temporal coherence unchanged from said coherent light beam but its spatial coherence randomized rapidly in time. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An apparatus for generating a speckle free probe beam for an eye diagnosis instrument comprising:
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a radiation source producing a narrow coherent light beam of predetermined beam size, power, and wavelength;
a holographic phase plate disposed in the path of said coherent light beam and modulating relative phase across said coherent light beam;
a mechanical mechanism scanning said holographic phase plate speedily and continuously across said coherent light beam to randomize relative phase across said coherent light beam;
focal optics positioned to refocus/collimate said modulated coherent light beam into a narrow and near collimated probe beam; and
means to direct said narrow and near collimated probe beam into a subject eye and to intersect with the retina;
wherein said narrow and near collimated probe beam forms said speckle free probe beam having a small spot on said retina and having its temporal coherence unchanged from said coherent light beam but its spatial coherence randomized rapidly in time. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. A method for generating a speckle free probe beam, comprising the steps of:
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providing a radiation source producing a narrow coherent light beam of predetermined beam size, power, and wavelength;
providing a holographic phase plate;
disposing said holographic phase plate in the path of said coherent light beam to modulate relative phase across said coherent light beam;
scanning said holographic phase plate rapidly and continuously across said coherent light beam to randomize relative phase across said coherent light beam; and
providing a focal optics to refocus/collimate said modulated coherent light beam into a narrow and near collimated probe beam;
wherein said narrow and near collimated probe beam forms said speckle free probe beam with its temporal coherence unchanged from said coherent light beam but its spatial coherence randomized rapidly in time.
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Specification