Optical system with movable lens for ophthalmic surgical laser
An eye-surgical laser system includes a laser source, to generate a laser beam, an XY scanner, to scan a focal spot of a received laser beam in an XY direction essentially transverse to an optical axis of the laser system, and a lens group, disposed in the optical path between the laser source and the XY scanner, to receive the laser beam generated by the laser source, to precompensate an aberration of the laser beam, and to forward the precompensated laser beam to the XY scanner, the lens group having a movable lens, movable in a Z direction along an optical axis.
1. An eye-surgical laser system, comprising:
a laser source configured to generate a laser beam;
an XY scanner disposed between a laser source and a Z scanner, the XY scanner configured to:
receive the laser beam; and
scan a focal spot of the received laser beam in an XY direction essentially transverse to an optical axis of the laser system;
the Z scanner, configured to:
receive the laser beam from the XY scanner; and
scan the focal spot of the received laser beam in a Z direction along the optical axis of the laser system within a depth scanning range, the depth scanning range suitable for surgical procedures on a cornea and a crystalline lens of an eye;
a computation controller communicatively coupled to a memory;
a position actuator, controlled by the computational controller, configured to move a precompensating movable lens;
a lens group, disposed in an optical path between the laser source and the XY scanner, and comprising the precompensating movable lens, movable in a Z direction along the optical axis, the lens group configured
to receive the laser beam generated by the laser source and forward a precompensated laser beam to the XY scanner;
wherein the computation controller is configured to:
receive focal coordinates (z, r) corresponding to a scanning pattern in a target region, wherein z corresponds to a Z focal depth and r corresponds to a radial distance from the optical axis;
determine an aberration measure corresponding to the received focal coordinates (z, r); and
cause the position actuator to move the precompensating movable lens to compensate for the determined aberration.
2. The eye-surgical laser system of claim 1 , wherein:
the computation controller is configured to cause the position actuator to move the precompensating movable lens within a Z scanning range, a length of the Z scanning range being in the range of 0.3-4 millimeters.
3. The eye-surgical laser system of claim 1 , wherein:
the computation controller is configured to cause the position actuator to move the precompensating movable lens within a Z scanning range, a length of the Z scanning range being in the range of 0.5-2 millimeters.
4. The eye-surgical laser system of claim 1 , wherein:
the computation controller is configured to cause the position actuator to move the precompensating movable lens to a position where a Strehl ratio S of the laser system is higher than a value S(movable); and
the Strehl ratio S of the laser system is lower than S(movable) at least at one point along a Z moving range of the movable lens, wherein
S(movable) is one of 0.6, 0.7, 0.8 and 0.9.
5. The eye surgical laser system of claim 1 , wherein:
the computation controller is configured to cause the position actuator to move the precompensating movable lens to vary a Strehl ratio S of the laser system in the range of S(min) to S(max), wherein
S(min)=0.6 and S(max)=0.95.
6. The eye surgical laser system of claim 1 , wherein:
the computation controller is configured to cause the position actuator to move the precompensating movable lens in a Z moving range to vary a Strehl ratio S of the laser system in the range of S(min) to S(max), wherein
S(min)=0.7 and S(max)=0.95.
7. The eye-surgical laser system of claim 1 , wherein:
the XY scanner is configured to move the focal spot of the laser system in the XY direction with an XY scanning speed in a target region; and
the precompensating movable lens is configured to move the focal spot of the laser beam in the Z direction with a Z scanning speed in the target region, wherein
the ratio of the Z scanning speed and a maximal XY scanning speed is greater than a scanning speed ratio, wherein
the scanning speed ratio is one of 5%, 10%, and 20%.
8. The eye-surgical laser system of claim 1 , wherein:
the computation controller is configured to cause the position actuator to move the precompensating movable lens to move the focal spot of the laser system in the Z direction by 0.5-1 millimeter in a Z scanning time, wherein
the Z scanning time is in one of the ranges of 10-100 nanoseconds, 100 nanoseconds-1 millisecond, 1-10 milliseconds, and 10-100 milliseconds.
9. The eye-surgical laser system of claim 1 , wherein:
the computation controller is configured to cause the position actuator to move the precompensating movable lens in a Z moving range to reduce a first aberration measure by at least a movable percentage P(movable), wherein
the first aberration measure is one of a spherical aberration coefficient a 40 , an RMS wavefront error ω, and a focal spot radius r {dot over (f)} , and
the movable percentage P(movable) is one of 10%, 20%, 30% and 40%.
10. The eye-surgical laser system of claim 1 , wherein:
the computation controller is configured to cause the position actuator to move the precompensating movable lens in a Z moving range to increase an aberration measure by at least a movable percentage P(movable), wherein
the second aberration measure is a Strehl ratio S; and
the movable percentage P(movable) is one of 10%, 20%, 30% and 40%.
11. The eye-surgical laser system of claim 1 , wherein:
the computation controller is configured to cause the position actuator to move the precompensating movable lens to change one of characteristics of the laser system essentially independently from the other three characteristics, wherein the characteristics of the laser system comprise
a numerical aperture, a focal spot depth, an aberration measure and a beam diameter of the laser system.
12. The eye-surgical laser system of claim 1 , the lens group further comprising:
a second movable lens, wherein
the computation controller is configured to cause the position actuator to move the precompensating movable lens and second movable lens to change two of characteristics of the laser system essentially independently from the other two characteristics, wherein the characteristics of the laser system comprise
a numerical aperture, a focal spot depth, an aberration measure and a beam diameter of the laser system.
13. The eye-surgical system of claim 1 , wherein:
the computational controller is configured to cause the position actuator to move the precompensating movable lens without using a feedback from an imaging system.
14. The eye-surgical system of claim 1 , wherein the lens group comprises one of:
three lenses with refractive powers in the range of D1*a*t1, D2*a*t2, and D3*a*t3, separated by distances d1/a and d2/a, wherein
D1 is in the range of −3 l/m to −5 l/m, D2 is in the range of 3 l/m to 5 l/m, and D3 is in the range of −3.5 l/m to −6 l/m;
d1 is in the range of 60 mm to 100 mm, and d2 is in the range of 3 mm to 9 mm, wherein at least one of d1 and d2 is a variable distance;
a is in the range of 0.3 to 3; and
t1, t2, and t3 are in the range of 0.8 to 1.2; and
four lenses with refractive powers in the range of D1*a*t1, D2*a*t2, D3*a*t3, D4*a*t4, separated by distances d1/a, d2/a and d3/a, wherein
D1 is in the range of −15 l/m to −20 l/m, D2 is in the range of −5 l/m to −8 l/m, D3 is in the range of −25 l/m to −3.5 l/m, and D4 is in the range of 7 l/m to 10 l/m;
d1 is in the range of 100 mm to 130 mm, d2 is in the range of 32 mm to 41 mm, and d3 is in the range of 33 mm to 45 mm, wherein at least one of d1, d2 and d3 is a variable distance;
a is in the range of 0.2 to 5; and
t1, t2, t3, and t4 are in the range of 0.7 to 1.3.
15. An ophthalmic laser system, comprising:
a laser source configured to generate a laser beam;
a first precompensating lens arranged between the laser source and an XY scanner, the first precompensating lens configured to move in a Z direction along the optical axis of the laser system;
the XY scanner, configured to scan a focal spot of the laser beam in an XY direction essentially transverse to an optical axis of the laser system, the XY scanner arranged between the precompensating lens and a Z scanner;
the Z scanner, configured to scan the focal spot of the laser beam in a Z direction along the optical axis of the laser system within a Z scanning range suitable for surgical procedures on a cornea and a crystalline lens of an eye;
a controller communicatively coupled to a memory and configured to adjust a position of the XY scanner, the Z scanner, and the precompensating lens;
wherein the controller is configured to:
receive focal coordinates (z k , r l ) corresponding to a scanning pattern in a target region, wherein z k corresponds to a Z focal depth and r l corresponds to a radial distance from the optical axis of the laser system;
determine an aberration measure corresponding to the received focal coordinates;
cause the first precompensating lens to move to a position at which the precompensating lens compensates for the determined aberration; and
cause the XY scanner and Z scanner to scan a focal spot according to the input focal coordinates.