Lenslet array for beam homogenization
View Patent ↗Apparatus for homogenizing a laser beam includes a lenslet array. In some embodiments, the lenslets have a negative power. The lenslet array may include from 16 to 36 effective lenslets in some embodiments, or any other suitable number in alternative embodiments. Some embodiments additionally include a re-focusing lens for directing the beamlets onto a target so that the beamlets overlap and the energy distribution is homogenized. In an alternative embodiment, the lenslet array and re-focusing lens are combined in one optic.
1. A method for homogenizing an energy distribution across a laser beam, the method comprising:
generating the laser beam with a laser, the laser beam comprising an unequal divergence in two axes;
passing a laser beam through a lenslet array having a pattern to transmit the laser beam as multiple beamlets;
moving the lenslet array about a longitudinal axis extending along the laser beam to avoid coupling of the pattern with the unequal divergence of the two axes; and
directing the beamlets onto a target using at least one lens, so that the beamlets overlap and the energy distribution is homogenized.
2. A method as in claim 1 , wherein the lenslet array comprises a negative power lenslet array, and wherein passing the beam through the lenslet array forms diverging beamlets.
3. A method as in claim 1 , wherein passing the laser beam through the lenslet array generates at least 16 beamlets.
4. A method as in claim 1 , further comprising rotating the lenslet array about a longitudinal axis extending along the laser beam.
5. A method as in claim 4 , wherein the lenslet array rotates such that each pulse of a pulsed laser beam passes through the array in an angular window of acceptance about 45° diagonal axes, thus avoiding 0° and 90° orientations of the array relative to the laser beam.
6. A method as in claim 5 , wherein the angular window of acceptance comprises a range of 10° on both sides of the 45° diagonal axes.
7. A method as in claim 4 , further comprising rotating the lens about the longitudinal axis.
8. A method as in claim 1 , further comprising adjusting a cross-sectional dimension of the laser beam by passing the beam through a telescope before passing the beam through the lenslet array.
9. A method as in claim 1 , wherein directing the beamlets onto a target comprises focusing the beamlets on an aperture disposed apart from the lens.
10. A method as in claim 1 , further comprising directing at least some of the beamlets through an aperture.
11. A method as in claim 10 , wherein directing the beamlets through the aperture causes the beamlets to arrive collimated at an ablation plane.
12. A method as in claim 10 , wherein a cross-sectional dimension of the aperture is selected to provide the laser beam with a desired cross-sectional dimension at an ablation plane.
13. A method of providing a laser beam having a homogenized energy distribution to an eye of a patient, the method comprising:
passing a laser beam having an unequal divergence in two axes through a lenslet array having a pattern to transmit the laser beam as multiple beamlets;
directing the beamlets through at least one lens, so that the beamlets overlap and the energy distribution is homogenized;
directing at least some of the beamlets through an aperture; and
rotating the lenslet array about an axis of rotation to avoid coupling of the pattern with the unequal divergence in two axes.
14. A method as in claim 13 , wherein the lenslet array comprises a negative power lenslet array, and wherein passing the beam through the lenslet array forms diverging beamlets.
15. A method as in claim 13 , wherein the array rotates within an angular window of acceptance about 45° diagonal axes, relative to the direction of the laser beam.
16. A method as in claim 15 , wherein the angular window of acceptance comprises a range of 10° on both sides of the 45° diagonal axes.
17. A method as in claim 13 , further comprising rotating the lens about the longitudinal axis.
18. A method as in claim 13 , further comprising adjusting a cross-sectional dimension of the laser beam, by passing the beam through a telescope before passing the beam through the lenslet array.
19. A method as in claim 13 , wherein directing the beamlets through the aperture causes the beamlets to arrive collimated at an ablation plane.
20. A method as in claim 13 , wherein a cross-sectional dimension of the aperture is selected to provide the laser beam with a desired cross-sectional dimension at an ablation plane.