Optical system for ophthalmic surgical laser
A laser system for ophthalmic surgery includes a laser source to produce a surgical pulsed laser beam, an XY scanner to scan the surgical pulsed laser beam in XY transverse directions, a Z scanner, to scan the XY scanned laser beam along a Z axis, an objective, to focus the XYZ scanned beam into a focal spot in a target region, and a computational controller, to use a computational process to control at least one of the Z scanner and the XY scanner, to control an optical distortion of the focused scanned beam.
1. A laser system for ophthalmic surgery, comprising:
a laser source to produce a surgical pulsed laser beam;
an XY scanner to scan the surgical pulsed laser beam in XY transverse directions;
a Z scanner, to scan the XY scanned laser beam along a Z axis;
an objective, to focus the XYZ scanned beam into a focal spot in a target region; and
a computational controller, configured
to compute scanner coordinates of at least one of the Z scanner and the XY scanner that correspond to focal coordinates along a scanning pattern via a transfer matrix algorithm without utilizing a position feedback to generate a diffraction limited laser beam at a focal spot of the laser beam.
2. The laser system of claim 1 , wherein:
the optical distortion is one of an aberration, a field curvature, a barrel distortion, a pincushion distortion, a curved focal plane, and a bent scanning line.
3. The laser system of claim 1 , wherein:
the computational controller is configured to receive at least one of input (z k , r l ) focal coordinates and input elements of a focal matrix S kl , corresponding to the scanning pattern in the target region with reduced optical distortion, and
the computational controller is configured to compute at least one of (ζ i , χ j ) scanner coordinates and elements of a scanner matrix C ij , using a predetermined inverse transfer matrix (T l ) ijkl , corresponding to the input (z k , r l ) focal coordinates or elements of the focal matrix S kl .
4. The laser system of claim 3 , wherein:
the computational controller is configured
to control at least one of the XY scanner and the Z scanner according to the computed (ζ i , χ j ) scanner coordinates,
to scan the focal spot according to the input (z k ,r l ) focal coordinates or elements of the focal matrix S kl .
5. The laser system of claim 3 , wherein:
the computational controller is configured
to receive input (z k , r l )focal coordinates corresponding to a focal plane with a curvature below a critical curvature; and
to control at least one of the XY scanner and the Z scanner according to (ζ i , χ j )scanner coordinates, computed from the input (z k , r 1 ) focal coordinates.
6. The laser system of claim 3 , wherein:
the computational controller is configured
to receive input (z k , r l )focal coordinates corresponding to a focal plane with a predetermined shape; and
to control at least one of the XY scanner and the Z scanner according to (ζ i , χ j ) scanner coordinates, computed from the input (z k , rd focal coordinates.
7. The laser system of claim 1 , further comprising:
a distortion-precompensator, disposed between the laser source and the XY scanner.
8. The laser system of claim 7 , wherein:
the distortion-precompensator has a movable lens
to perform partial Z scanning of the pulsed laser beam
before the pulsed laser beam enters the XY scanner.
9. The laser system of claim 1 , wherein:
the Z scanner is configured
to adjust a Z focal depth of the focal spot and
a numerical aperture NA of the focused XYZ scanned beam essentially independently.
10. The laser system of claim 1 , the Z scanner further comprising:
a first beam expander; and
a movable beam scanner.
11. The laser system of claim 1 , wherein:
the Z scanner is located before and separately from the objective.
12. The laser system of claim 1 , wherein:
the diffraction limited laser beam has a Strehl ratio S larger than 0.8.
13. The laser system of claim 1 , wherein:
the computational controller is configured to achieve the diffraction limited laser beam at a focal spot by computing numerical apertures corresponding to the scanner coordinates.
14. A method of computationally controlling a surgical laser system, the laser system comprising a laser source to output a pulsed laser beam; an XY scanner to scan the pulsed laser beam in transverse directions, a Z scanner to scan the XY scanned beam in a Z direction, and an objective, focusing the XYZ scanned beam into a focal spot in a target region, the method comprising the steps of:
receiving at least one of input focal coordinates and elements of a focal matrix corresponding to a scanning pattern with reduced optical distortion in the target region;
computing or recalling from memory at least one of scanner coordinates and elements of a scanner matrix, corresponding to the input focal coordinates or elements of the focal matrix, using a predetermined inverse transfer matrix; and
controlling at least one of the Z scanner and the XY scanner according to the computed scanner coordinates or computed scanner matrix elements to scan the focal spot according to the input focal coordinates or elements of the focal matrix, using an optical distortion measure of the XYZ scanned beam as a control factor.
15. The method of claim 14 , wherein:
at least one of the receiving, the computing and the controlling steps is performed by a computational controller.
16. The method of claim 14 , wherein the controlling step comprises:
controlling an optical distortion of the XYZ scanned beam.
17. The method of claim 16 , comprising:
reducing the optical distortion compared to the optical distortion of an analogous laser system not practicing the method of computationally controlling the laser system.
18. The method of claim 14 , wherein:
the optical distortion is one of
an aberration, a field curvature, a barrel distortion, a pincushion distortion, a curved focal plane, and a bent scanning line.
19. The method of claim 18 , wherein:
the receiving step comprises receiving input focal coordinates corresponding to a focal plane with a curvature below a critical curvature; and
the controlling step comprises controlling at least one of the XY scanner and the Z scanner according to scanner coordinates, computed from the input focal coordinates.
20. The method of claim 18 , wherein:
the receiving step comprises receiving input focal coordinates corresponding to a focal plane with a predetermined shape; and
the controlling step comprises controlling at least one of the XY scanner and the Z scanner according to scanner coordinates, computed from the input focal coordinates.