Spatio-temporal beam modulator for surgical laser systems
A surgical laser system can include a laser engine to generate a laser beam of laser pulses; a scanning delivery system to direct the laser beam to a target region and to scan the laser beam along a scan-pattern in the target region; and a spatio-temporal modulator to perform a space- and time dependent modulation of the laser beam. The spatio-temporal modulation of the phases or amplitudes of the beam components can reduce or even eliminate uncut regions in the target region, caused by the destructive interference of the beam components brought about by a wrinkling of a portion of the target or by other beam distorting factors.
1. A surgical laser system, comprising:
a laser engine, configured to generate a laser beam of laser pulses;
a scanning delivery system, configured
to direct the laser beam to a target region, and
to scan the laser beam along a scan-pattern in the target region; and
a spatio-temporal modulator, configured to perform a space- and time dependent modulation of the laser beam by randomizing at least one of a phase and an amplitude of beam components of the laser beam.
2. The surgical laser system of claim 1 , wherein:
the spatio-temporal modulator is operable without at least one of a beam diagnostic system, a wavefront analyzer and a feedback system.
3. The surgical laser system of claim 1 , wherein:
the spatio-temporal modulator is configured to randomize at least one of a phase and an amplitude of beam components of the laser beam on a modulation length and a modulation time.
4. The surgical laser system of claim 1 , wherein:
the spatio-temporal modulator is configured to reduce a length of an un-photo-disrupted scan-segment left behind when the laser beam is scanned through a distorted region of the target region by a factor of more than 2 compared to the length of an un-photo-disrupted scan-segment left behind when the same surgical laser system is scanned through the same target region but without the spatio-temporal modulator.
5. The surgical laser system of claim 1 , wherein:
the spatio-temporal modulator is configured to perform the space- and time dependent modulation having a spatial variation with a transverse modulation length less than a beam diameter at the spatio-temporal modulator.
6. The surgical laser system of claim 1 , wherein:
the spatio-temporal modulator is configured to perform the space- and time dependent modulation within a modulation time less than 10 times a pulse repetition time of the laser pulses.
7. The surgical laser system of claim 1 , wherein:
the spatio-temporal modulator is configured to perform the space- and time dependent modulation within a modulation time less than a return time of the scan-pattern, wherein
the scan-pattern includes a set of closely spaced lines, and
the return time is a time the scan of the laser beam takes between passing a first point on a first line of the scan-pattern and a second point on a second line of the scan-pattern nearest to the first point.
8. The surgical laser system of claim 1 , wherein:
the spatio-temporal modulator is configured to perform the space- and time dependent modulation within a modulation time less than a return time of the scan-pattern, wherein
the scan-pattern includes a set of closely spaced scan segments, and
the return time is a time the scan of the laser beam takes between passing a first point on a first scan-segment of the scan-pattern and a second point on a second scan-segment of the scan-pattern nearest to the first point.
9. The surgical laser system of claim 1 , wherein:
the scanning delivery system is configured to rescan the laser beam with a second modulation along a portion of the scan-pattern that has been already scanned with a first modulation, wherein
the first modulation is different from the second modulation.
10. The surgical laser system of claim 1 , wherein:
the scanning delivery system comprises
at least one of a first Z scanner-expander and a second Z scanner-expander,
an XY scanner, and
an objective; and
the spatio-temporal modulator is positioned at one of a location along an optical path of the laser beam
before the first Z scanner-expander,
between the first Z scanner-expander and the XY scanner,
between the XY scanner and the second Z scanner-expander, and
between the second Z scanner and the objective.
11. The surgical laser system of claim 1 , wherein:
the spatio-temporal modulator is at least one of a transmissive modulator, an absorptive modulator and a reflective modulator.
12. The surgical laser system of claim 1 , wherein:
the spatio-temporal modulator is configured to perform a space- and time dependent phase modulation of the laser beam.
13. The surgical laser system of claim 12 , wherein:
the spatio-temporal modulator is configured to introduce a spatially dependent phase modulation of the laser beam with a maximum phase modulation of at least π/4.
14. The surgical laser system of claim 12 , the spatio-temporal modulator comprising:
a rotatable wheel configured to cause an optical path length variation with an amplitude between 0.1λ and 10λ, wherein λ is a wavelength of the laser beam.
15. The surgical laser system of claim 12 , the spatio-temporal modulator comprising:
an array of electronically controllable electro-optical phase modulators.
16. The surgical laser system of claim 12 , the spatio-temporal modulator comprising:
an acousto-optical phase modulator.
17. The surgical laser system of claim 12 , the spatio-temporal modulator comprising:
a deformable mirror, deformable by an array of mechanical actuators.
18. The surgical laser system of claim 1 , wherein:
the spatio-temporal modulator is configured to perform a time-dependent phase modulation that is a non-linear function of a coordinate across a beam aperture.
19. The surgical laser system of claim 1 , wherein:
the spatio-temporal modulator is configured to perform a space- and time dependent amplitude modulation of the laser beam.
20. The surgical laser system of claim 19 , the spatio-temporal modulator comprising:
a rotatable wheel with a transmission coefficient varying at a transmission length shorter than a beam diameter at the spatio-temporal modulator.
21. The surgical laser system of claim 19 , the spatio-temporal modulator comprising:
an array of variable transparency pixels.
22. A method of homogenizing a laser beam, the method comprising:
generating a laser beam of laser pulses with a laser engine;
directing the laser beam to a target region with a scanning delivery system;
scanning the laser beam along a scan-pattern in the target region with the scanning delivery system; and
performing a space- and time dependent modulation of the laser beam with a spatio-temporal modulator by randomizing at least one of a phase and an amplitude of beam components of the laser beam.
23. The method of claim 22 , wherein:
the space- and time dependent modulation is performed within a modulation time less than 10 times a pulse repetition time of the laser pulses.
24. The method of claim 22 , the performing a space- and time dependent modulation comprising:
performing a space- and time dependent phase modulation of the laser beam.