LASER ILLUMINATION SYSTEM WITH REDUCED SPECKLE
First Claim
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1. A despeckle unit, comprising:
- a first transparent element comprising a plurality of microlenses to receive collimated light having a coherence length and to output a beamlet from each of the microlenses; and
a second transparent element comprising a plurality of steps having a one-to-one correspondence with the plurality of microlenses, wherein each of the steps receives one of the beamlets and outputs the beamlet to an image plane, where a height of each step of at least two of the steps is configured to produce an optical path difference of the beamlet longer than the coherence length,wherein the second transparent element is disposed approximately at a foci of the beamlets output from the first transparent element.
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Abstract
A despeckling device and method in which an optical path difference staircase element is disposed between a fly'"'"'s eye lens array and the image plane in a position near the focus position of the fly'"'"'s eye lens array, and a laser generating unit generates and transmits pulsed laser beams to the optical path difference staircase element, wherein the pulsed laser beams are driven at a very short pulsed rate.
37 Citations
36 Claims
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1. A despeckle unit, comprising:
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a first transparent element comprising a plurality of microlenses to receive collimated light having a coherence length and to output a beamlet from each of the microlenses; and a second transparent element comprising a plurality of steps having a one-to-one correspondence with the plurality of microlenses, wherein each of the steps receives one of the beamlets and outputs the beamlet to an image plane, where a height of each step of at least two of the steps is configured to produce an optical path difference of the beamlet longer than the coherence length, wherein the second transparent element is disposed approximately at a foci of the beamlets output from the first transparent element. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A despeckle unit, comprising:
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a first transparent element comprising a plurality of microlenses to receive collimated light having a coherence length and to output a beamlet from each of the microlenses; and a second transparent element comprising a plurality of steps having a one-to-one correspondence with the plurality of microlenses, wherein each of the steps receives one of the beamlets and outputs the beamlet to an image plane, wherein a height of each step of at least two of the steps is configured to produce an optical path difference of the collimated light longer than the coherence length, wherein the second transparent element is disposed in a location relative to the first transparent element such that edges of the second transparent element parallel to an optical path of the beamlets exiting the second transparent element do not diffract the beamlets. - View Dependent Claims (8)
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9. A despeckling laser unit to despeckle a laser beam, comprising:
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a laser generating unit to generate a pulsed laser beam having a coherence length; a first transparent element comprising a plurality of microlenses to receive the pulsed laser beam and to output a beamlet from each of the microlenses; and a second transparent element comprising a plurality of steps corresponding to the plurality of microlenses, wherein each of the steps receives one of the beamlets and outputs the beamlet to an image plane, wherein a height of each step of at least two of the steps is configured to produce an optical path difference of the pulsed laser beam longer than the coherence length; wherein the second transparent element is disposed approximately at the foci of the beamlets output from the first transparent element. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A one-dimensional crossed despeckling unit, comprising:
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a first transparent element comprising; a first surface having a first plurality of first microlenses to receive collimated light having a coherence length, and output a first plurality of first beamlets corresponding to the first plurality of microlenses, and a second surface having a second plurality of second microlenses to receive the collimated light, and output a second plurality of second beamlets corresponding to the second plurality of microlenses; and a second transparent element comprising; a first plurality of first steps oriented such that at least one of the first steps corresponds to at least one of the first beamlets; and a second plurality of second steps oriented such that at least one of the second steps corresponds to at least one of the second beamlets, wherein; a height of each step of at least two steps from among the first steps and the second steps is configured to produce an optical path difference of the pulsed laser beam longer than the coherence length, and the second transparent element is disposed approximately at a foci of the first beamlets and the second beamlets output from the first transparent element. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28)
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29. A method to despeckle a laser beam, comprising:
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generating a pulsed laser beam having a coherence length; transmitting the pulsed laser beam through a first transparent element comprising a plurality of microlenses so that the pulsed laser beam is output as a beamlet from each of the microlenses; and transmitting each one of the beamlets through a respective step included in a second transparent element comprising a plurality of the steps having a one-to-one correspondence with the plurality of microlenses, to an image plane, wherein a height of each step of at least two of the steps is configured to produce an optical path difference of the beamlets longer than the coherence length, wherein the second transparent element is disposed approximately at the foci of the beamlets output from the first transparent element. - View Dependent Claims (30, 31, 32, 33, 34, 35)
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36. A two-dimensional despeckling unit, comprising:
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a first transparent element comprising; a surface having a plurality of microlenses to receive collimated light having a coherence length from a pulsed laser beam, each of the microlenses configured to output a beamlet which is shaped in two-dimensions; and a second transparent element comprising; a light incident surface forming a two-dimensional area comprising two first boundaries and two second boundaries perpendicular to and connecting the two first boundaries; and a plurality of steps protruding out from the light incident surface and arranged in rows, wherein the steps in each row are configured to increase in height along a first direction parallel to the first boundaries, and the rows increase in height along a second direction parallel to the second boundaries, each of the steps having a different height from each other, and each of the steps being configured to receive a corresponding one of the beamlets; wherein; the height of each step is configured to produce an optical path difference longer than the coherence length, and the light incident surface is disposed approximately at a foci of the beamlets output from the first transparent element.
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Specification