Optical System for Ophthalmic Surgical Laser
A laser delivery system for ophthalmic surgery includes a laser engine, configured to generate a laser beam, an optical block, to receive the laser beam generated by the laser engine and to precompensate an aberration of the laser beam, and an XY scanner, to receive, directly or indirectly, the precompensated laser beam outputted by the optical block and to scan the laser beam in a direction essentially transverse to an optical axis of the laser delivery system.
1 . A laser delivery system for ophthalmic surgery, comprising:
a laser engine, configured to generate a laser beam;
an optical block, to receive the laser beam generated by the laser engine and to precompensate an aberration of the laser beam; and
an XY scanner, to receive, directly or indirectly, the precompensated laser beam outputted by the optical block and to scan the laser beam in a direction essentially transverse to an optical axis of the laser delivery system.
2 . The laser delivery system of claim 1 , wherein:
the precompensated aberration is one of a spherical aberration, a chromatic aberration and an off-axis aberration.
3 . The laser delivery system of claim 1 , wherein:
the precompensated aberration is an aberration corresponding to at least one of five reference points in a target region.
4 . The laser delivery system of claim 3 , wherein:
the five reference points are determined by their cylindrical coordinates (z, r) in the target region as P 1 =(0,0), P 2 =(2,6), P 3 =(5,0), P 4 =(8,0), P 5 =(8,3), all in millimeters, at any azimuth angle φ, wherein
z denotes a distance along the optical axis and r denotes the corresponding cylindrical coordinate, and
the (0,0) of the cylindrical coordinate system denotes a front and center point of the target region.
5 . The laser delivery system of claim 1 , wherein:
the optical block precompensates an aberration by introducing a precompensating aberration which is opposite in sign and comparable in magnitude as the aberration being precompensated.
6 . The laser delivery system of claim 1 , wherein:
the optical block precompensates an aberration developed by the laser beam along a portion of an optical path of the laser delivery system.
7 . The laser delivery systems of claim 1 , wherein:
the optical block precompensates an aberration developed by the laser beam in a surgical target tissue.
8 . The laser delivery system of claim 1 , wherein:
the laser delivery system comprising the optical block has a Strehl ratio S higher than a value S(precomp); and
a corresponding laser delivery system not having the optical block has a Strehl ratio S lower than the value S(precomp), wherein
S(precomp) is one of the values of 0.6, 0.7, 0.8, and 0.9.
9 . The laser delivery system of claim 8 , wherein:
the Strehl ratio S corresponds to laser beam with a wavelength in the range of 0.4 microns to 1.1 microns.
10 . The laser delivery system of claim 8 , wherein:
the Strehl ratio S corresponds to at least one of five reference points in a target region, wherein
the five reference points are determined by their cylindrical coordinates (z, r) in the target region as P 1 =(0,0), P 2 =(2,6), P 3 =(5,0), P 4 =(8,0), P 5 =(8,3), all in millimeters, at any azimuth angle φ, relative to the front and center of the target region being at (0, 0).
11 . The laser delivery system of claim 1 , wherein:
the laser delivery system comprising the optical block has a numerical aperture NA smaller than a value NA(precomp); and
a corresponding laser delivery system not having the optical block has a numerical aperture NA higher than the value NA(precomp), wherein
NA(precomp) is one of 0.2, 0.25, 0.3, 0.35.
12 . The laser delivery system of claim 11 , wherein:
the numerical aperture NA corresponds to at least one of five reference points in a target region, wherein
the five reference points are determined by their cylindrical coordinates (z, r) in the target region as P 1 =(0,0), P 2 =(2,6), P 3 =(5,0), P 4 =(8,0), P 5 =(8,3), all in millimeters, at any azimuth angle φ, relative to the front and center of the target region being at (0, 0).
13 . The laser delivery system of claim 1 , wherein:
the laser delivery system comprising the optical block has a focal spot radius r f smaller than a value r f (precomp); and
a corresponding laser delivery system not having the optical block has a focal spot radius r f larger than a value r f (precomp), wherein
r f (precomp) is one of 2, 3, and 4 micrometers.
14 . The laser delivery system of claim 13 , wherein:
the focal spot radius r f corresponds to at least one of five reference points in a target region, wherein
the five reference points are determined by their cylindrical coordinates (z, r) in the target region as P 1 =(0,0), P 2 =(2,6), P 3 =(5,0), P 4 =(8,0), P 5 =(8,3), all in millimeters, at any azimuth angle φ, relative to the front and center of the target region being at (0, 0).
15 . The laser delivery system of claim 1 , wherein:
the laser delivery system comprising the optical block has a wavefront RMS value ω smaller than a value ω(precomp); and
a corresponding laser delivery system not having the optical block has a wavefront RMS value ω larger than a value ω(precomp), wherein
ω(precomp) is one of 0.06, 0.07, 0.08 or 0.09, in units of the wavelength of the laser beam.
16 . The laser delivery system of claim 15 , wherein:
the wavefront RMS value ω corresponds to at least one of five reference points in a target region, wherein
the five reference points are determined by their cylindrical coordinates (z, r) in the target region as P 1 =(0,0), P 2 =(2,6), P 3 =(5,0), P 4 =(8,0), P 5 =(8,3), all in millimeters, at any azimuth angle φ, relative to the front and center of the target region being at (0, 0).
17 . The laser delivery system of claim 1 , wherein:
the laser delivery system comprising the optical block has a spherical aberration coefficient a 40 smaller than a value a 40 (precomp); and
a corresponding laser delivery system not having the optical block has a spherical aberration coefficient a 40 larger than a value a 40 (precomp), wherein
a 40 (precomp) is one of 2, 3, and 4 micrometers.
18 . The laser delivery system of claim 17 , wherein:
the spherical aberration coefficient a 40 corresponds to at least one of five reference points in a target region, wherein
the five reference points are determined by their cylindrical coordinates (z, r) in the target region as P 1 =(0,0), P 2 =(2,6), P 3 =(5,0), P 4 =(8,0), P 5 =(8,3), all in millimeters, at any azimuth angle φ, relative to the front and center of the target region being at (0, 0).
19 . The laser delivery system of claim 1 , wherein:
a first aberration measure of the laser delivery system comprising the optical block increases by at least a precompensation percentage P(precomp) compared to a corresponding laser delivery system not including the optical block, wherein
the precompensation percentage P(precomp) is one of 10%, 20%, and 30%; and
the first aberration measure is one of a spherical aberration coefficient a 40 , an RMS wavefront error ω, and a focal spot radius r f .
20 . The laser delivery system of claim 1 , wherein:
a second aberration measure of the laser delivery system comprising the optical block decreases by at least a precompensation percentage P(precomp) compared to a corresponding laser delivery system not including the optical block, wherein
the precompensation percentage P(precomp) is one of 10%, 20%, 30% and 40%; and
the second aberration measure is a Strehl ratio S.
21 . The laser delivery system of claim 1 , wherein:
a radius of the laser beam exiting the laser delivery system is larger than a precompensated radius r(precomp); and
the radius of a corresponding laser beam exiting the laser delivery system not having the optical block is smaller than the precompensated radius r(precomp), wherein
the precompensated radius r(precomp) is one of 5 mm and 8 mm.
22 . The laser delivery system of claim 1 , wherein:
the aberration precompensated by the optical block is a spherical aberration; and
the optical block does not increase an RMS wavefront error ω corresponding to other aberrations by more than 0.075, or does not reduce a Strehl ratio S, corresponding to other aberrations, below 0.8.
23 . The laser delivery system of claim 1 , wherein:
the laser engine is configured to generate laser pulses with at least one of the following laser parameters:
a pulse duration in the 1 femtosecond to 1000 femtosecond range;
an energy per pulse in the 0.1 microJoule to 1000 microJoule range; and
a repeat frequency in the 10 kHz to 100 MHz range.
24 . The laser delivery system of claim 1 , wherein:
the optical block is configured to precompensate an aberration measure to a Strehl ratio S above 0.8 or an RMS wavefront error ω below 0.075 for pulses having an associated bandwidth at least an order of magnitude larger than the bandwidth of laser pulses with a duration of one picosecond.
25 . The laser delivery system of claim 1 , wherein:
the optical block precompensates an off-axis aberration, generated in a segment of the optical pathway.
26 . The laser delivery system of claim 1 , wherein:
the optical block performs a beam conditioning function.
27 . The laser delivery system of claim 1 , wherein:
the optical block performs a beam expanding function.
28 . The laser delivery system of claim 1 , wherein:
the optical block comprises one to five lenses.
29 . The laser delivery system of claim 1 , wherein:
the optical block comprises 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 mm to −5 mm, D2 is in the range of 3 mm to 5 mm, and D3 is in the range of −3.5 mm to −6 mm;
d1 is in the range of 60 mm to 100 mm, and d2 is in the range of 3 mm to 9 mm;
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.
30 . The laser delivery system of claim 1 , wherein:
the optical block comprises 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 mm to −20 mm, D2 is in the range of −5 mm to −8 mm, D3 is in the range of −25 mm to −35 mm, and D4 is in the range of 7 mm to 10 mm;
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;
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.
31 . A surgical laser system comprising:
a laser engine, for generating a laser beam;
a beam expander, for receiving the laser beam generated by the laser engine directly or indirectly and for expanding a diameter of the laser beam; and
an XY scanner, for receiving, directly or indirectly, the expanded laser beam outputted by the beam expander and to scan the laser beam in a direction essentially transverse to an optical axis of the laser delivery system, wherein:
the beam expander is configured to precompensate an aberration of the laser beam, associated with a subsequent segment of an optical pathway of the surgical laser system and a target region.
32 . The surgical laser system of claim 31 , wherein:
a Strehl ratio S of the laser beam exiting the surgical laser system with the beam expander is higher than S(precomp), and
the Strehl ratio S of the laser beam exiting the laser delivery system not having the beam expander is lower than S(precomp), wherein
S(precomp) is one of 0.7 and 0.8.
33 . A method of precompensating a surgical laser beam, the method comprising the steps of:
generating the laser beam;
precompensating an aberration of the laser beam before coupling the laser beam into an XY scanner; and
coupling the precompensated laser beam into an XY scanner.
34 . The method of claim 33 , wherein the precompensating step comprises:
introducing a compensating aberration which is opposite in sign and comparable in magnitude as the precompensated aberration.
35 . The method of claim 33 , wherein:
the precompensating step includes increasing a Strehl ratio S of the laser beam to a value greater than S(precomp), wherein the laser beam without the precompensating step has a Strehl ratio S less than S(precomp), wherein
S(precomp) is one of 0.6, 0.7, 0.8 and 0.9.