CREATING CUTS IN A TRANSPARENT MATERIAL USING OPTICAL RADIATION

Abstract

A method for creating cuts in a transparent material using optical radiation, the optical radiation being focused onto the material in a focal point and the focal point being shifted along a curve: A simple or double harmonic curve is used when seen at a right angle to a main direction of incidence of the radiation and preferably successively traveled curves do not lie on top of each other.

Claims

1-17. (canceled)

18. A method for creating cuts in a transparent material in eye surgery using femtosecond optical radiation of a femtosecond laser device, comprising: focusing the femtosecond optical radiation of the femtosecond laser device at a focus in the material; shifting the focus along a path; using a simple or double harmonic curve; and wherein adjacent paths are not superimposed in a main direction of incidence of radiation.

19. The method according to claim 18, further comprising additionally shifting the focus this is along the main direction of incidence of the radiation and relative to the main direction of incidence.

20. The method according to claim 18, further comprising rotating adjacent paths against each other.

21. The method according to claim 18, further comprising shifting adjacent paths against each other.

22. The method according to claim 18, farther comprising stretching adjacent paths against each other.

23. The method according to claim 18, further comprising shifting adjacent curves against each other in the phase.

24. The method according to claim 18, further comprising: defining a cut area; using a path which is larger than the cut area; and switching off or modifying the optical radiation on sections of the path which lies outside of the cut area such that the optical radiation does not create cuts in the transparent material.

25. The method according to claim 18, further comprising forming the cuts as a skewed grid structure.

26. The method according to claim 18, further comprising forming the cuts as a grid structure by shifting the paths repeatedly in several height levels stacked along a direction of incidence of the radiation.

27. The method according to claim 18, further comprising providing between at least two height levels, an intermediate plane lying parallel to the height levels, and providing a path with which a contiguous cut is formed.

28. A method for producing control data for a femtosecond laser device which creates cuts in a transparent material in eye surgery by focusing femtosecond optical radiation, wherein the control data predetermine a path for a shift of a focus of the femtosecond optical radiation in the material, the method comprising: producing the control data such that the path for the shift of the focus is a simple or double harmonic curve when seen perpendicular to a main direction of incidence of the radiation; and wherein adjacent paths are not superimposed in the main direction of incidence of radiation.

29. The method according to claim 28, further comprising additionally shifting the focus this is along the main direction of incidence of the femtosecond optical radiation and relative to the main direction of incidence.

30. The method according to claim 28, further comprising rotating adjacent paths against each other.

31. The method according to claim 28, further comprising shifting adjacent paths against each other.

32. The method according to claim 28, further comprising stretching adjacent paths against each other.

33. The method according to claim 28, further comprising shifting adjacent curves against each other in the phase.

34. The method according to claim 28, further comprising defining a cut area; using a path which is larger than the cut area; and switching off or modifying the femtosecond optical radiation on sections of the path which lies outside of the cut area such that the optical radiation does not create cuts in the transparent material.

35. The method according to claim 28, further comprising forming the cuts as a skewed grid structure.

36. The method according to claim 28, further comprising forming the cuts as a grid structure by shifting the paths repeatedly in several height levels stacked along a direction of incidence of the femtosecond optical radiation.

37. The method according to claim 28, further comprising providing between at least two height levels, an intermediate plane lying parallel to the height levels, and providing a path with which a contiguous cut is formed.

38. A treatment apparatus for creating cuts in a transparent material in eye surgery, the treatment apparatus comprising: a femtosecond laser device, which emits pulsed laser radiation and which creates cuts in a transparent material by focusing optical radiation; a control device which is connected to the laser device and controls the laser device such that the laser device shifts a focus of the optical radiation in the material along a path; wherein the control device controls the laser device such that the path is a simple or double harmonic curve in a view perpendicular to a main direction of incidence of the radiation, and wherein adjacent paths don't superimpose each other in the main direction of incidence of the radiation.

39. The treatment apparatus according to claim 38, wherein the control device controls the laser device such that adjacent paths are rotated against each other and/or are shifted against each other and/or are stretched against each other and/or are shifted in a phase against each other.

40. The treatment apparatus according to claim 38, wherein the control device controls the laser device such that when the path lies outside of a predetermined cut area, the optical radiation is switched off or modified such that it does not create cuts in the transparent material.

41. The treatment apparatus according to claim 38, wherein the control device controls the laser device such that the cuts are formed as a grid structure by the paths being shifted repeatedly in several height levels stacked along a direction of incidence of the radiation.

42. The treatment apparatus according to claim 38, wherein the control device provides, between at least two height levels, an intermediate plane lying parallel to the height levels and controls the laser device such that a contiguous cut is formed in the intermediate plane.

43. The treatment apparatus according to claim 38, wherein the focus is shifted by application of a scanning device which includes two scanning mirrors which deflect about axes that cross each other and wherein the focus is shifted by a focus-shifting device which shifts the focus perpendicularly thereto and along a main direction of incidence, wherein the control device controls the focus-shifting device such that, after one pass through the path, the focus position is shifted contrary to the main direction of incidence, by a distance to generate a contiguous material cutting of the successive passes through the non-superimposed paths.

44. The treatment apparatus according to claim 38, wherein the femtosecond laser device, emits pulsed laser radiation at a pulse repetition frequency between 10 kHz and 10 MHz.

45. The treatment apparatus according to claim 38, wherein the femtosecond laser device, emits pulsed laser radiation with a pulse duration of 50 femtoseconds to 800 femtoseconds.

46. The treatment apparatus according to claim 38, wherein the femtosecond laser de vice, emits pulsed laser radiation with a pulse duration of 100 femtoseconds to 400 femtoseconds.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The invention is explained in further detail below by way of example with reference to the attached drawings which also disclose features of embodiments of the invention. There are shown in:

[0049] FIG. 1 is a schematic representation of a treatment apparatus for ophthalmology procedures, in particular for correcting defective vision,

[0050] FIG. 2 is a schematic representation with regard to the structure of the treatment apparatus of FIG. 1,

[0051] FIG. 3 depicts a basic principle for introducing pulsed laser radiation into the eye with the treatment apparatus of FIG. 1,

[0052] FIG. 4 is a schematic representation to illustrate a first grid of cuts which is to be created with the treatment apparatus of FIG. 1,

[0053] FIG. 5 is a schematic representation to illustrate the creation of the schematically represented cut of FIG. 4,

[0054] FIG. 6 is a representation similar to FIG. 5, but with a delimitation of cuts to a machining zone

[0055] FIG. 7 depicts a hypotrochoid as a sample curve

[0056] FIG. 8 depicts a hypocycloid as a sample curve

[0057] FIG. 9 depicts different curves from Gerono as a sample curve

[0058] FIG. 10 depicts the application of a curve from Gerono for segmentation

[0059] FIG. 11 depicts the application of a curve from Gerono for a planar cut

[0060] FIG. 12 is a schematic representation to clarify a second grid from cut surfaces that is supposed to be created with the treatment apparatus of FIG. 1,

[0061] FIG. 13 is a schematic representation to clarify the creation of the schematically shown cut surface of FIG. 12,

[0062] FIG. 14 is a representation similar to FIG. 13, but with a limitation of cut surfaces on a treatment area.

[0063] FIG. 15 depicts a further representation to clarify the creation of the schematically shown cut surface of FIG. 12 for a larger z area.

[0064] FIG. 16 is a schematic representation of more cut surface designs

[0065] FIG. 17 is a schematic representation of another cut surface design

DETAILED DESCRIPTION

[0066] FIG. 1 depicts a treatment apparatus 1 for eye surgery. For example an eye-surgery process which is similar to that described in EP 1 159 986 A2 or U.S. Pat. No. 5,549,632 can be carried out with it. The treatment apparatus 1 creates a material cutting in transparent material using treatment laser radiation 2. This material cutting can be e.g. a creation of cuts, in particular the treatment apparatus for correcting defective vision can bring about a change on an eye 3 of a patient 4. The defective vision can include hyperopia, myopia, presbyopia, astigmatism, mixed astigmatism (astigmatism in which there is hyperopia in one direction and myopia in a direction at right angles thereto), aspheric errors and higher-order aberrations. The material cutting can, however, also be used in the field of ophthalmology on other tissues of the eye, e.g. for sectioning the crystalline lens in cataract surgery. Where reference is made to eye surgery below, this is to be understood in each case only by way of example and not as limiting.

[0067] In the embodiment example described, the components of the apparatus 1 are controlled by an integrated control unit, which, however, can of course also be formed as a stand-alone unit.

[0068] FIG. 2 depicts the treatment apparatus 1 schematically. In this variant it has at least three pieces of devices or modules. Laser device L emits the laser beam 2 onto the material, e.g. the eye 3, and adjusts the position of the focus in the material in three spatial directions x, y, z. The adjustment along the main direction of incidence of the optical radiation (z-axis) is called z-axis adjustment, the x- and y-axis adjustment is preferably carried out perpendicular to the z-axis by scanners.

[0069] The operation of the laser device L is fully automatic, controlled by integrated or separate control device C. In response to a corresponding start signal the laser device L starts to deflect the laser beam 2 and thereby creates cuts which are constructed in a manner yet to be described.

[0070] The control device C operates according to control data which either have been produced by it or have been supplied to it. In the latter case, which is shown in FIG. 2, the control data necessary for operation are supplied from a planning device P to the control device C beforehand as a control data set via control lines not identified in more detail. The determination or transmission of the control data takes place prior to operation of the laser device L. Naturally, the communication can also be wireless. As an alternative to direct communication, it is also possible to arrange the planning unit P physically separated from the laser device L, and to provide a corresponding data transmission channel.

[0071] In ophthalmology, the defective vision of the eye 3 is for example, measured with one or more pieces of measuring device M before the treatment apparatus 1 is used. The measured values are then supplied to the control device or the planning device P and form the basis for the production of the control data. In particular, the position and/or extent of an area to be treated, in particular to be sectioned, can be measured.

[0072] The control device or the planning device P produces the control data set from the measurement data which have been determined, e.g. for the eye to be treated. They are supplied to the planning device P via an interface S and, in the embodiment represented, come from measuring device M which has previously taken measurements of the eye of the patient 4. Naturally, the measuring device M can transfer the corresponding measurement data to the planning device P or directly to the control device C in any desired manner.

[0073] For example, the control data set is transmitted to the control device and, in another example, operation of the laser device L is blocked until there exists a valid control data set at the laser device L. A valid control data set can be a control data set which in principle is suitable for use with the laser device L of the treatment apparatus 1. Additionally, however, the validity can also be linked to further tests being passed, for example whether details additionally stored in the control data set concerning the treatment apparatus 1, e.g. an apparatus serial number, or concerning the patient, e.g. a patient identification number, correspond to other details that for example have been read out or input separately at the treatment apparatus as soon as the patient is in the correct position for the operation of the laser device L.

[0074] The transmission of the measurement data and/or of the control data can be by means of memory chips (e.g. by USB or memory stick), magnetic storage (e.g. disks), or other data storage devices, by radio (e.g. WLAN, UMTS, Bluetooth) or wired connection (e.g. USB, Firewire, RS232, CAN-Bus, Ethernet etc.). A direct radio or wired connection has the advantage that the use of incorrect measurement data is ruled out with the greatest possible certainty. This applies in particular when the patient is transferred from the measuring device M or pieces of measuring device to the laser device L by use of a support device (not represented in the figure) which interacts with the measuring device M and the laser device L respectively such that the respective devices recognize whether the patient 4 is in the respective position for measurement or introduction of the laser radiation 2. The transmission of the measurement and defective-vision data to the treatment apparatus 1 can also take place simultaneously with bringing the patient 4 from the measuring device M to the laser device L.

[0075] It is, for example, facilitated that the control device or the planning device P always produces the control data set belonging to the patient 4 and an erroneous use of an incorrect control data set for a patient 4 is as good as ruled out.

[0076] In the embodiment described, the laser radiation 2 is emitted as a pulsed laser beam focused into the material, e.g. the eye 3. The pulse duration produced by the laser device L in this case is e.g. in the femto-second range, and the laser radiation 2 acts by non-linear optical effects in the material, e.g. the crystalline lens or cornea. The laser beam has e.g. 50 to 800 fs short laser pulses (preferably 100-400 fs) with a pulse repetition frequency of between 10 kHz and 10 MHz The type of material-cutting effect which the treatment apparatus 1 uses with the laser radiation, however, is of no further relevance for the following description, in particular there is no need to use pulsed laser radiation. The only important thing is that a focus of machining radiation 2 in the material is shifted along a path.

[0077] The treatment apparatus 1 forms a cut in the material, the shape of which cut depends on the pattern with which the laser-pulse foci are/become arranged in the tissue. The pattern in turn depends on the path along which the focus is shifted. The path predetermines target points for the focus position at which one or more laser pulse(s) is (are) emitted and ultimately defines the shape and position of the cut.

[0078] A possible mode of operation of the laser beam 2 is indicated schematically in FIG. 3. It is focused into the material, e.g. the cornea 5 or lens of the eye, by means of a lens system of the laser device L not identified in more detail. As a result there forms in the material a focus 6 in which the energy density of the laser radiation is so high that, in combination with the pulse length, a non-linear effect occurs. For example, each pulse of the pulsed laser radiation 2 can create at the respective site of the focus 6 an optical breakthrough in the material, e.g. in the cornea 5 or lens, which is indicated schematically in FIG. 3 by way of example by a plasma bubble. As a result, material, e.g. tissue, is cut owing to this laser pulse. When a plasma bubble forms, the tissue layer cutting comprises a larger zone than the spot covered by the focus 6 of the laser radiation 2, although the conditions for creating the breakthrough are achieved only in the focus. In order for an optical breakthrough to be created by every laser pulse, the energy density, i.e. the fluency, of the laser radiation must be above a certain threshold value which is dependent on pulse length. This relationship is known to a person skilled in the art from, for example, DE 695 00 997 T2.

[0079] Alternatively, a material-cutting effect can also be produced by the pulsed laser radiation by emitting several laser radiation pulses in one area, wherein the spots 6 overlap for several laser radiation pulses. Several laser radiation pulses then interact to achieve a tissue-cutting effect. For example the treatment apparatus 1 can use the principle which is described in WO 2004/032810 A2.

[0080] The treatment apparatus 1 creates in the cornea 5 or in the lens of the eye 1 a sectioning of the tissue by forming cuts as a grid (naturally, this is not limited to ophthalmology). By this grid represented schematically in FIG. 4, transparent material 1a is to be sectioned, with the result that it can be removed.

[0081] In the transparent material 1a, a grid of cuts 10, 11, 12 is created by shifting the focus 6 of the laser radiation 2, which propagates along a direction of propagation 3a, inside the transparent material 1a along a path 6a. The path 6a is chosen such that it follows the cuts 10, 11 and 12 and travels along these.

[0082] When controlling the laser device L, the control device C makes sure that the cuts 10, 11 and 12 are constructed by the trajectory 6a only contrary to the main direction of propagation 3a of the laser beam 2. Otherwise, the focus 6 would be disrupted by material cuts that are already present (for example cuts) in the incident light cone 4a. This problem is in principle posed in the case of material cutting by focused optical radiation and is particularly great at crossover points 5a of the cuts 10, 11 and 12 in the use described by way of example.

[0083] The cut 12 represented by a dashed line illustrates that the path 6a is arranged in different height levels in order to avoid the mentioned laser focus disruption in the incident light cone 4a. The path 6a is therefore formed such that it works through all cuts 10, 11 and 12 in the lowest height level first, i.e. in the height level that is the furthest removed from the laser device L in relation to the main direction of incidence 3a. If, with the path 6a, the cut lines of all cuts 10, 11 and 12 were worked through with it in this height level, the same is carried out for the next height level which lies closer to the laser device L in relation to the main direction of incidence 3a.

[0084] To provide a better overview, the individual paths 24 are used to create the cut surfaces 10, 11, 12 from FIG. 12 are depicted by way of example once more.

[0085] In order to avoid a time-consuming deceleration and re-positioning or acceleration of the focus deflection, the grid of cuts represented schematically in FIG. 4 is generated by movement of the biaxial deflection of the laser device L on a path 23 in the shape of a planar path, which is represented in FIG. 5. The basic figure only has to be provided in respect of the x-/y-deflection, thus as seen along the main direction of incidence 3a. Only from this view must a closed, thus periodic, path 6a be provided.

[0086] There are thus two variants: Firstly, the path 6a can lie in one height plane. Then the z-position of the focus 6 remains constant as long as the basic figure is traveled, and the path 6a is also closed in three-dimensional space. The control data or the control by the control device thus effect in each height level a closed path 23 on which the focus is guided. This is called variant 1 below. Secondly, the z-adjustment can adjust the position of the focus, while the basic figure is being traveled. This is called variant 2 below. Unless differences in these two variants are explicitly discussed, the statements made here apply to both variants.

[0087] The basic figure is preferably formed by a superimposition of harmonic oscillations, x-/y-deflection devices can thus be moved continuously with harmonic sine or cosine movements. A high working speed is the result.

[0088] In sections 23 of the path 6a which run outside of the zone in which the intended cuts are to be created (the cut surface 10 is also drawn in by way of example in FIG. 5), the laser beam is blanked, i.e. switched off or deactivated in respect of its treatment effect. The laser radiation is active and cuts tissue only in sections 24 of the path 6a which run inside the zone in which cuts are to lie. FIG. 5 shows, dotted, the sections 23 of the path 6a, in which the laser beam is blanked. The sections 24 of the path 6a in which the radiation brings about a material cutting are drawn in with continuous lines.

[0089] FIG. 5 shows furthermore the spacing 8 between the height levels, in which in each case the basic figure is traveled. In contrast to the state of the art, the desired sectioning of the transparent material 1a can also be achieved, when the basic figure is stretched or compressed a bit, its origin is slightly shifted or it is rotated as is shown by way of example on the angle 25.

[0090] When creating the cut surfaces 10, 11, and 12, in accordance with variant 1, the curved path 6a may comprise a complete run at each vertical level (or several runs as mentioned in the general part of the description) through the basic figure.

[0091] To create the cut surfaces it is however also possible, according to variant 2, to execute the deflection along the main direction of incidence 3a during the basic figure. The control device or the control data created by the planning unit effect a z-adjustment of the focus 6 either in a short path section that then represents a transition between two vertical levels of variant 1, or a continuous z-adjustment of the focus 6. With reference to the equations mentioned above, during which the scan path repeats with a basic frequency f.sub.0, during continuous z-adjustment of the focus 6, the z-coordinate of the focus 6 moves in the duration 1/f.sub.0 by the desired distance 8 that superimposed curved path sections should have.

[0092] FIG. 6 shows, by way of example, a sectioning of a crystalline lens 30, which is carried out for cataract surgery or also of a different lens-shaped area (i.e. also in the cornea of the eye). The treatment apparatus 1 creates cuts 31, by travelling the curved path 6a. In sections 32 of the path which lie inside the lens 30, the laser radiation 2 is active. In sections 32 of the curved path which lie outside of the crystalline lens 30, the laser radiation 2 is blanked. Naturally, this principle can also be applied to other materials and illustrates that the combination of activating the laser radiation inside a desired volume and blanking outside of the desired volume makes possible a rapid construction of crossing cuts.

[0093] Particularly preferred curved paths or basic figures are clarified in the following.

[0094] FIG. 7 shows a hypotrochoid with the parameters

[00006]$a=7,b=3,\frac{1}{k}=k=\frac{a-b}{b}$

[0095] The general formula for this curve is provided by

[00007]$x\left(t\right)=\frac{R}{2}.Math.\left[\cos \left(\omega .Math..Math.t\right)+\cos \left(\frac{\omega .Math..Math.t}{k}\right)\right]$$y\left(t\right)=\frac{R}{2}.Math.\left[\sin \left(\omega .Math..Math.t\right)-\sin \left(\frac{\omega .Math..Math.t}{k}\right)\right]$$z\left(t\right)=\frac{R}{2}.Math.\left(e^{+i.Math..Math.\omega .Math..Math.t}+e^{-\frac{i.Math..Math.\omega .Math..Math.t}{k}}\right)$

[0096] R is thereby the radius of the circle describing the surface to be processed and w is the maximum angular velocity of the scanners used.

[0097] The periodicity T therefore results from

[00008]$T=\left(a-b\right).Math.\frac{2.Math.\pi }{\omega }=4.Math.\frac{2.Math.\pi }{\omega }$

and the effective processing time (laser-on time) from

[00009]$T_{\mathrm{on}}=\frac{T}{2}=2.Math.\frac{2.Math.\pi }{\omega }$

[0098] The total length of the curve to be traveled is

L=24.407−R

[0099] Whereby the effective length is

[00010]$l=\frac{L}{2}=7.204.Math.R.$

[0100] FIG. 8 shows a hypocycloid with the parameters

[00011]$a=7,b=3,k=\frac{a-b}{b}$

[0101] The general formula for this curve is provided by

[00012]$x\left(t\right)=\frac{R}{1+k}.Math.\left[\cos \left(\omega .Math..Math.t\right)+k.Math.\cos \left(\frac{\omega .Math..Math.t}{k}\right)\right]$$y\left(t\right)=\frac{R}{1+k}.Math.\left[\sin \left(\omega .Math..Math.t\right)-k.Math.\sin \left(\frac{\omega .Math..Math.t}{k}\right)\right]$$z\left(t\right)=\frac{R}{k+1}.Math.\left(e^{+i.Math..Math.\omega .Math..Math.t}+k.Math.e^{-\frac{i.Math..Math.\omega .Math..Math.t}{k}}\right)$

[0102] The periodicity T thus results from

[00013]$T=\left(a-b\right).Math.\frac{2.Math.\pi }{\omega }=4.Math.\frac{2.Math.\pi }{\omega }$

and the effective processing time (laser-on time) from

[00014]$T_{\mathrm{on}}=\left(1-0.037\right).Math.T=3.852.Math.\frac{2.Math.\pi }{\omega }$

[0103] The total length of the curve to be traveled is

[00015]$L=\frac{96}{7}.Math.R=13.714.Math.R$

whereby the effective length is

l=0.942−.Math.L=12.922.Math.R

[0104] The double harmonic curves presented in 7 and 8 are examples from the favorably selected parameters from the classes of the hypotrochoids or hypocycloids, so that a small periodicity, many overlaps of the central zone and a sufficiently constant path velocity are reached in the central zone. In both cases, the frequencies act like 4:3. The amplitude ratios are 1:1 (Hypotrochoids) or 4:3 (Hypocycloids). If one sets the cut-off frequency of the angular scanners to 250 Hz by way of example, there will be a fast movement component at 250 Hz and a slow one at 187.5 Hz. The time required for a complete rotation is 16 ms. If one additionally adds the radius of the enveloping of 3.5 mm, it results in a path velocity of about 3 m/s. In case of a repetition rate of the laser of, for instance 2 MHz, one achieves pulse intervals of a typical 1.5 μm in the material to be cut. If superimposed cuts are supposed to have the same distance, the overall time for 2,000 layers (3 mm axial length) is 32 seconds. As can be seen easily, these basic figures are especially suited for the sectioning by use of cut surfaces in parallel to the direction of incidence of the optical radiation.

[0105] FIG. 9 shows a group of so-called curves (or lemniscates) of Gerono.

[0106] The general formula for this curve is given by

[00016]$x\left(t\right)=r.Math.R.Math.\sin \left(\omega .Math..Math.t\right)$$y\left(t\right)=2.Math.r.Math.R.Math.\sin \left(\frac{\omega .Math..Math.t}{2}\right)$$z\left(t\right)=\frac{R}{2}\left[i\left(e^{-i.Math..Math.\omega .Math..Math.t}-e^{+i.Math..Math.\omega .Math..Math.t}\right)+2.Math.r\left(e^{+\frac{i.Math..Math.\omega .Math..Math.t}{2}}-e^{-\frac{i.Math..Math.\omega .Math..Math.t}{2}}\right)\right]$

[0107] With r=0.7 it thus results in a curve of the area to be processed limited precisely by the radius R, the optical radiation therefore doesn't affect any areas located outside of the treatment zone.

[0108] The periodicity T results from

[00017]$T=2.Math.\frac{2.Math.\pi }{\omega }$

and the effective processing time (laser-on time) from

[00018]$T_{\mathrm{on}}=0.369.Math.T=0.738.Math.\frac{2.Math.\pi }{\omega }$

[0109] The total length of the curve to be traveled is

L=8.536.Math.R

whereby the effective length is

l=0.471.Math.L=4.017.Math.R

[0110] By travelling this basic figure under a different angle as shown in FIG. 10, a sectioning can be realized by use of cut surfaces parallel to the direction of incidence of the optical radiation just like in the examples of FIGS. 7 and 8. The basic figure was thereby traveled twice at an angle of 45°, which results in 8 sections.

[0111] But it is equally possible to realize a cut vertically to the direction of incidence of the optical radiation by a travelling the basic figure against each other multiple times. The basic figure was traveled 32 times with a respective rotation of 90°/32=28,125° in FIG. 11 by way of example, thus resulting in a very smooth cut.

[0112] An alternative embodiment of the invention is described in the following.

[0113] The treatment apparatus 1 creates in the cornea 1 or in the lens of the eye 1 a sectioning of the tissue by forming cuts as a grid (naturally, this is not limited to ophthalmology). By this grid represented schematically in FIG. 12, transparent material 1a is to be sectioned, with the result that it can be removed.

[0114] In the transparent material 1a, a grid of cuts 10, 11, 12 is created by shifting the focus 6 of the laser radiation 2, which propagates along a direction of propagation 3a, inside the transparent material 1a along a path 6a. The path 6a is chosen such that it follows the cuts 10, 11 and 12 and travels along these.

[0115] When controlling the laser device L, the control device C makes sure that the cuts 10, 11 and 12 are constructed by the trajectory 6a only contrary to the main direction of propagation 3a of the laser beam 2. Otherwise, the focus 6 would be disrupted by material cuts that are already present (for example cuts) in the incident light cone 4a. This problem is in principle posed in the case of material cutting by focused optical radiation and is particularly great at crossover points 5a of the cuts 10, 11 and 12 in the use described by way of example.

[0116] The cut 12 represented by a dashed line illustrates that the path 6a has to be arranged in different height levels in order to avoid the mentioned laser focus disruption in the incident light cone 4a. The path 6a is therefore formed such that it works through all cuts 10, 11 and 12 in the lowest height level first, i.e. in the height level that is the furthest removed from the laser device L in relation to the main direction of incidence 3a. If, with the path 6a, the cut lines of all cuts 10, 11 and 12 were worked through with it in this height level, the same is carried out for the next height level which lies closer to the laser device L in relation to the main direction of incidence 3a. But the basic figure of the path 6a is now modified such that it is not superimposed with the path just traveled in the main direction of incidence 3a.

[0117] To provide a better overview, the individual paths 20, 21, 22, which are used to create the cut surfaces 10, 11, 12 from FIG. 12 are illustrated in FIG. 13 once again by way of example. As can be clearly seen, the paths 20, 21, 22 are not superimposed, but are offset to each other by an angle 25 as the travel of the basic figure from the z-level illustrated by way of example to the next z-level was modified as described above.

[0118] In order to avoid a time-consuming deceleration and re-positioning or acceleration of the focus deflection, the grid of cuts represented schematically in FIG. 12 is generated by movement of the biaxial deflection of the laser device L on a planar path 23, which is represented in FIG. 14. The basic figure only has to be provided in respect of the x-/y-deflection, thus as seen along the main direction of incidence 3a. Only from this view must a closed, thus periodic, path 6a be provided.

[0119] There are thus two variants: Firstly, the path 6a can lie in one height plane. Then the z-position of the focus 6 remains constant as long as the basic figure is traveled, and the path 6a is also closed in three-dimensional space. The control data or the control by the control device thus effect in each height level a closed path 23 on which the focus is guided. This is called variant 1 below. Secondly, the z-adjustment can adjust the position of the focus, while the basic figure is being traveled. This is called variant 2 below. Unless differences in these two variants are explicitly discussed, the statements made here apply to both variants.

[0120] The basic figure is preferably formed by superimposition of harmonic scintillations, x-/y-deflection devices with harmonic sine or cosine movements can thus be moved continuously. A high working speed is the result.

[0121] In sections 23 of the path 6a which run outside of the zone in which the intended cuts are to be created (the cut 10 is also drawn in by way of example in FIG. 5), the laser beam is blanked, i.e. switched off or deactivated in respect of its treatment effect. The laser radiation is active and cuts tissue only in sections 24 of the path 6a which run inside the zone in which cuts are to lie. FIG. 5 shows, dotted, the sections 23 of the path 6a, in which the laser beam is blanked. The sections 24 of the path 6a in which the radiation brings about a material cutting are drawn in with continuous lines.

[0122] FIG. 14 furthermore shows the spacing 8 between the height levels in which in each case the basic figure is traveled. Contrary to the state of the art, the desired sectioning of the transparent material 1a is also achieved, if the basic figure is stretched or compressed a bit in each height level, if its origin is slightly shifted, or if it is rotated as is represented at angle 25 by way of example.

[0123] To create the cuts 10, 11 and 12, according to variant 1 the path 6a can comprise, in each height level, one full pass (or, as mentioned in the general part of the description, several passes) through the basic figure.

[0124] To create the cuts, according to variant 2 it is, however, likewise possible to carry out the shift along the main direction of incidence 3a during the basic figure. The control device or the control data produced by the planning device effecting a z-adjustment of the focus 6 either in a short path section, which then represents a transition between two height levels of variant 1, or effecting a continuous z-adjustment of the focus 6. In relation to the above-mentioned equations, in which the scanning path is repeated with a base frequency f.sub.0, the z-coordinate of the focus 6 moves, in the case of continuous z-adjustment of the focus 6, in the time period 1/f.sub.0, by the desired distance 8 which path sections lying one above the other are to have.

[0125] FIG. 15 shows once again by way of example the ratios with a 4-digit basic figure that is rotated by a low angle after each travel. When this angle is determined such that just a quarter circle (due to the basic figure that is tetramerous) was filled with paths 24, it is easy to see that the treating physician can thereby follow the progress of the division of the crystalline lens in a simple manner. If the entire surface was filled with paths, the treatment has been completed and the intended section of the crystalline eye lens has been divided into removable parts. The following features can additionally be realized:

[0126] The laser radiation can also be blanked on particular sections of the path inside an area in which cuts lie if the course of the path on the basic figure in those areas does not correspond to a desired cutting pattern.

[0127] The height levels need not be planes in the mathematical sense. In particular in the case of a curvature of the image field and/or when curved material is machined, the height levels can be curved 2D manifolds.

[0128] In the control of scanners, the amplitude attenuation and phase retardation of the x-/y-deflection device can be determined and taken into account by providing corresponding counterbalancing offsets of the amplitude and phase of the deflection control at high frequencies.

[0129] The frequencies of the deflection on the basic figures can take into account the maximum spacing of spots which successive laser pulses are to strike.

[0130] Naturally, the cutting pattern created with the basic figure can be supplemented by further cut elements, for example a cylinder jacket as outer delimitation of the treated volume area. In order additionally to also divide the parts of the transparent material 1a created by the cuts 10, 11 and 12 perpendicular to the direction of propagation 3a, cuts which extend substantially perpendicular to the main direction of incidence 3a can also be created between individual height levels.

[0131] The cuts created using the basic figure can be used to section eye tissue, for example the crystalline lens or the cornea. It is also possible to effect by the crossed cuts a targeted weakening of a material. In the field of eye surgery, this can be e.g. an intrastromal weakening of the cornea in order to influence the balance between intraocular pressure and cornea strength such that a desired change in the shape of the front surface of the cornea is achieved.

[0132] The harmonic movement may also be superimposed by other movements. A parts scanning system that has a large scan area and whose scanning course is freely programmable, however therefore has a comparatively slower scanning speed may be enabled to a quickest possible execution of the scanning figure by programming it with a harmonic scanning path. In the meantime, a fast scanner that has however only a smaller scan area or is also limited in the selection of the scanning curve (e.g. resonant scanner), may superimpose a small fast scanning motion and may therefore execute a scanning area in the form of a band along the harmonic figure.

[0133] This way, cut shapes deviating from the cylinder shape may be generated. The basic figures per the invention are thus also suited for the capsulotomy with cut shapes deviating from the cylinder shape. A respective cut shape is represented in FIG. 16 and can be described with the function

x+iy=e.sup.iω+0,26e.sup.2iω

Instead of a circular opening, an opening can thus be created that deviates from the circular form and possesses a preferred axial direction. A preferred embodiment of the opening is shown in FIG. 16b. This basic figure type can be described with the function

x+iy=e.sup.iω+0,12e.sup.3iω

for example. The harmonic movement in the x/y level is thereby superimposed through a quick up-down motion in z-direction, which can be executed by a resonant scanner, for example and does not need to be synchronized with the harmonic movement.

[0134] Conversely, a quick scanning system may also perform a harmonic movement and may be superimposed on a slow “feed motion”. For instance, tunnel-shaped areas may be scanned this way, whereas the quick harmonic motion determines the tunnel cross-section and specifies the slow “feed motion”, the direction of the tunnel.

[0135] Toric IOL can preferably be implanted with such an opening, especially when its outer shape is adapted to the shape of the opening.

[0136] With the basic figures per the invention, it is possible to cut the capsulotomy required for implanting the IOL precisely with a high quality and a high speed.

[0137] Lamé curves are also usable as opening geometry for a capsulotomy. Lame curves can be described with the function:

[00019]${.Math.\frac{x}{a}.Math.}^n+{.Math.\frac{y}{b}.Math.}^n=1.$

[0138] A and b are thereby the half-axes, whereby 1.05 a<b<1.3 a preferably applies. What is preferred is n greater or equal 2 so that the result is a super ellipse as the geometric shape. It has proved to be especially advantageous if n lies in the range of 2 to 8 and all the more in the range of 3 to 5. Opening geometries of this type are represented in FIG. 17.

[0139] The basic figures per the invention are furthermore suited to quickly and effectively perform cuts in the vitreous body. Vitreous strands that exert a pull on the retina can thus be separated. Level cuts according to Gerono that are created according to FIG. 1 are particularly suited for the separation. The planar cutting pattern is thereby selected so that the diameter of the cutting figure is adapted to the diameter of the vitreous strand in the planned cutting level.

[0140] It is also within the framework of the invention to create cuts for the protection of the retina. The level cuts according to Gerono according to FIG. 11 are also suited for it. A section plane may thus be generated before the retina that is characterized, at least in part, by a higher absorption for the radiation of the laser. This plane forms a protective shield for the retina for the work of the laser in the area between the cornea and this plane.

[0141] The cutting pattern according to FIG. 11 is especially well suited, in particular, since the density of the set spot is higher in the middle area and as the area of the fovea is especially protected.

[0142] In one embodiment, cutting patterns are generated by superimposition of a slow and a fast movement each. By means of the slow scanning movement, the focus can, with 3 scanners for the x-, y-, and z-direction, for example, be positioned on each point of the eye to be worked on. The cutting patterns themselves are then formed through fast harmonic movements in the three coordinate directions by means of three more scanners for the x-, y-, and z-direction. The amplitude of the fast movement is thereby preferably in the range of 1 to 3 mm.

[0143] It is also within the framework of the invention to execute slow and fast scanning movements simultaneously. Cutting patterns may thus be generated in a preferred manner, in which traveled paths are arranged offset to one another in different depth positions, as is represented in FIG. 14 by way of example.