Method for scanning a pulsed laser beam
Systems and methods of photoaltering a region of a material using a pulsed laser beam. The method includes scanning the pulsed laser beam in a first portion of the region with a first pattern, scanning the pulsed laser beam in a second portion of the region with a second pattern, and separating a flap of the material at the region. The system includes a laser, a controller selecting at least first and second patterns, and a scanner operable in response to the controller. The first pattern has a first maximum acceleration associated with the second portion, and the second pattern has a second maximum acceleration associated with the second portion. The second maximum acceleration is less than the first maximum acceleration. The scanner scans the pulsed laser beam from the laser in the first portion with the first pattern and in the second portion with the second pattern.
1. A method of photoaltering a sub-surface region of a patient's cornea using a pulsed laser beam to create a corneal flap, the sub-surface region having an outer periphery, a first portion defined within and circumscribed by the periphery, and a second portion smaller than and located within the first portion, the method comprising the steps of:
transmitting the pulsed laser beam with a scanner to the first portion of the region in accordance with only a first laser scan pattern based on a continuous scan of the pulsed laser beam, the first laser scan pattern requiring a first maximum scanner movement acceleration associated with the second portion;
transmitting the pulsed laser beam with a scanner to the second portion of the region in accordance with only a second laser scan pattern based on a continuous scan of the pulsed laser beam and that is different than the first laser scan pattern, the second laser scan pattern requiring a second maximum scanner movement acceleration associated with the second portion that is less than the first maximum scanner movement acceleration; and
separating a corneal flap of the material at the region.
2. The method of claim 1 , wherein at least some of the second portion of the region overlaps at least some of the first portion of the region to form a third portion of the region, and wherein the step of transmitting the pulsed laser beam in the second portion comprises blanking the pulsed laser beam while transmitting the pulsed laser beam with the second laser scan pattern in the third portion.
3. The method of claim 1 , wherein the region has a periphery, and wherein the step of transmitting the pulsed laser beam in a first portion comprises transmitting the pulsed laser beam in a spiral laser scan pattern beginning from the periphery of the region.
4. The method of claim 1 , wherein the step of transmitting the pulsed laser beam in the second portion comprises transmitting the pulsed laser beam in an uninterrupted compound laser scan pattern.
5. The method of claim 1 , wherein the step of transmitting the pulsed laser beam in the second portion comprises transmitting the pulsed laser beam in a traveling circular laser scan pattern.
6. The method of claim 1 , wherein the step of transmitting the pulsed laser beam in the second portion comprises transmitting the pulsed laser beam in a sinusoidal laser scan pattern.
7. The method of claim 1 , wherein the step of transmitting the pulsed laser beam in the second portion comprises transmitting the pulsed laser beam in a progressive oval laser scan pattern.
8. The method of claim 1 , further including transmitting the pulsed laser beam to create a side cut around a desired perimeter of the flap while leaving an uncut segment to serve as a hinge for the flap, and wherein transmission of the pulsed laser beam in the first and second laser scan patterns forms a resection bed the perimeter of which is approximately defined by and slightly greater than the side cut.
9. The method of claim 1 , wherein the first laser scan pattern and second laser scan pattern are defined over a dome-shaped area of the sub-surface region.
10. A method of photoaltering a sub-surface region of a patient's cornea using a pulsed laser beam to create a corneal flap, the sub-surface region having an outer periphery, a first portion defined within and circumscribed by the periphery, and a second portion smaller than and located within the first portion, the method comprising the steps of:
transmitting the pulsed laser beam with a scanner having a mass in the first portion of the sub-surface region with a first laser scan pattern, the first laser scan pattern requiring a first maximum scanner mass acceleration when traversing the region, wherein the first laser scan pattern comprises scanning the pulsed laser beam in a spiral pattern beginning from the periphery of the region and successively tracing smaller rotations toward the second portion;
transmitting the pulsed laser beam with the scanner in the second portion of the sub-surface region with a second laser scan pattern, the second laser scan pattern requiring a second maximum scanner mass acceleration less than the first maximum scanner movement acceleration, wherein the second laser scan pattern comprises scanning the pulsed laser beam in a raster laser scan pattern; and
separating a corneal flap at the region.
11. The method of claim 10 , wherein the first laser scan pattern and second laser scan pattern are defined over a dome-shaped area of the sub-surface region.
12. The method of claim 10 , wherein the step of scanning the pulsed laser beam in the first portion comprises scanning the pulsed laser beam with the first laser scan pattern having the first maximum scanner movement acceleration, the first maximum scanner movement acceleration associated with the second portion, and wherein the step of scanning the pulsed laser beam in the second portion comprises scanning the pulsed laser beam with the second laser scan pattern having the second maximum scanner movement acceleration, the second maximum scanner movement acceleration associated with the second portion.
13. The method of claim 10 , wherein at least some of the second portion of the region overlaps at least some of the first portion of the region to form a third portion of the region, and wherein the step of scanning the pulsed laser beam in the second portion comprises blanking the pulsed laser beam while scanning the pulsed laser beam with the second laser scan pattern in the third portion.
14. The method of claim 10 , wherein the step of scanning the pulsed laser beam in the second portion comprises scanning the pulsed laser beam in an uninterrupted compound laser scan pattern.
15. The method of claim 14 , wherein the step of scanning the pulsed laser beam in an uninterrupted compound pattern comprises scanning the pulsed laser beam in a hypotrochoid laser scan pattern.
16. The method of claim 10 , wherein the step of scanning the pulsed laser beam in the second portion comprises combining scanning the pulsed laser beam with a sinusoidal laser scan pattern.
17. The method of claim 16 , wherein the step of scanning the pulsed laser beam with a sinusoidal laser scan pattern comprises blanking the pulsed laser beam when scanning the sinusoidal pattern where it overlaps the spiral pattern.
18. The method of claim 10 , further including transmitting the pulsed laser beam to create a side cut around a desired perimeter of the flap while leaving an uncut segment to serve as a hinge for the flap, and wherein transmission of the pulsed laser beam in the first and second laser scan patterns forms a resection bed the perimeter of which is approximately defined by and slightly greater than the side cut.