METHOD FOR PRODUCING A TRANSMISSIVE OPTICS

Abstract

In a method for the manufacture of a transmissive optical system from a blank, material ablation is achieved on the blank with an ablative laser, and the pulse duration of the ablative laser is less than 1 ns, and preferably lies between 3 fs and 100 fs, or between 100 fs and 10 ps.

Claims

1-43. (canceled)

44: A method for the manufacture of a transmissive optical system (1) from a blank (2), wherein material ablation (4) is achieved on the blank (2) with an ablative laser (3), wherein, the pulse duration of the ablative laser (3) is less than 1 ns and preferably lies between 3 fs and 100 fs, or between 100 fs and 10 ps.

45: The method in accordance with claim 44, wherein the blank (2), initially treated with the ablative laser (3), is further processed with a polishing laser (20).

46: The method in accordance with claim 44, wherein a blank (40) with a circular cross-section is used, which has an optical density towards the center (41) that differs from that towards the edge (42).

47: The method in accordance with claim 44, wherein during processing, the process temperature is monitored and/or controlled with a pyrometer (7).

48: The method in accordance with claim 44, wherein the blank is symmetrically formed on one side, and on another side is processed asymmetrically or in a free-form manner.

49: The method in accordance with claim 44, wherein an eye of a patient is first measured and a data set is thereby generated, and the ablative laser and/or the polishing laser is subsequently controlled on the basis of the data of this data set.

50: The method in accordance with claim 44, wherein with the laser radiation the material of the blank is altered such that the finished lens has an optical density gradient.

51: The method in accordance with claim 44, wherein the optical system is an intraocular lens (IOL).

52: The method in accordance with claim 44, wherein the ablative laser is operated such that it effects a material ablation of of 0.02 μm to 5 μm and particularly of 0.02 μm to 0.5 μm.

53: The method in accordance with claim 44, wherein the ablative laser is operated with a laser wavelength of less than 400 nm, such as, in particular, between 193 nm and 370 nm.

54: The method in accordance with claim 44, wherein the focal diameter of the ablative laser lies between 5 and 50 μm, and preferably at approx. 20 μm.

55: The method in accordance with claim 44, wherein the scanning rate of the ablative laser lies between 500 and 5,000 mm/s, and preferably at approx. 1,000 mm/s.

56: The method in accordance with claim 44, wherein the pulse energy of the ablative laser lies between 0.1 μJ and 10 μJ, and preferably at approx. 1 μJ.

57: The method in accordance with claim 44, wherein the repetition rate of the ablative laser lies between 5 kHz and 5,000 kHz, and preferably between 50 kHz and 200 kHz.

58: The method in accordance with claim 44, wherein the polishing laser is operated with a laser wavelength between 1 and 12 μm, and particularly preferably between 9 μm and 11 μm.

59: The method in accordance with claim 44, wherein the polishing laser is operated continuously.

60: The method in accordance with claim 44, wherein the polishing laser is formed into a “quasi-line” by means of a scanning movement, with a scanning rate of 500 mm/s to 20,000 mm/s.

61: The method in accordance with claim 44, wherein with the polishing laser less than 30, and preferably 1 to 10, passes are carried out.

62: A lens manufactured in accordance with the method of claim 44, wherein the lens has a density that is at least 1% lower in one region than in another region of the lens.

Description

[0062] Inventive examples of embodiment are illustrated in the figures and are described in what follows. Here:

[0063] FIG. 1 shows schematically a blank for the manufacture of a lens,

[0064] FIG. 2 shows schematically the blank during the laser processing,

[0065] FIG. 3 shows schematically the processed blank after the laser processing,

[0066] FIG. 4 shows schematically the impingement of a laser beam onto a lens surface,

[0067] FIG. 5 shows schematically the melt and the vapour generated after the laser beam impinges onto the surface,

[0068] FIG. 6 shows schematically the evaporation of the generated vapour,

[0069] FIG. 7 shows schematically a crater created on the lens surface,

[0070] FIG. 8 shows schematically the smoothing of a lens surface with a laser beam,

[0071] FIG. 9 shows schematically the surface of an untreated lens blank,

[0072] FIG. 10 shows schematically the lens surface after laser ablation,

[0073] FIG. 11 shows schematically the lens surface after polishing,

[0074] FIG. 12 shows schematically the feed of a laser during processing,

[0075] FIG. 13 shows schematically the dependence of the feed rate on the laser power,

[0076] FIG. 14 shows schematically a plan view onto a lens with a density gradient,

[0077] FIG. 15 shows schematically a section through the lens shown in FIG. 14,

[0078] FIG. 16 shows schematically the variation of pulse intensity over time,

[0079] FIG. 17 shows schematically the local variation of pulse intensity,

[0080] FIG. 18 shows schematically a pulse with a central intensity sink,

[0081] FIG. 19 shows schematically the alignment of the laser beam relative to the lens,

[0082] FIG. 20 shows schematically the laser processing in the interior of the lens,

[0083] FIG. 21 shows schematically ablation craters with different spatial separations on the lens surface,

[0084] FIG. 22 shows schematically a lens with an increased density in the interior of the lens,

[0085] FIG. 23 shows schematically a lens with an increased density at the surface of the lens,

[0086] FIG. 24 shows schematically a plan view onto the lens shown in FIG. 23,

[0087] FIG. 25 shows schematically a lens with an increased density in the radially outer region of the lens,

[0088] FIG. 26 shows schematically a plan view onto the lens shown in FIG. 25,

[0089] FIG. 27 shows schematically a lens with a density altering in the radial direction and

[0090] FIG. 28 shows schematically a plan view onto the lens shown in FIG. 27.

[0091] FIG. 1 shows a lens blank 2 as a transmissive optical system 1. FIG. 2 shows how this blank 2 is processed by means of an ablative laser 3. In the example shown in FIG. 2, the indicated material ablation 4 has already been achieved on the left-hand side of the lens 2 with the laser 3. After the material has been ablated, the measuring device 5 measures the shape 6 of the lens 2 in the region of the processed surface. On the basis of the measured values, this makes it possible to adjust the type of pulse of the laser 3, preferably whilst still in the course of processing. In addition, the process temperature is already monitored during the processing with the pyrometer 7. The process temperature can also be influenced and, if required, can even be controlled, by adjustment of the nature of the laser beam of the laser 3.

[0092] After ablation, the blank 2 has the shape shown in FIG. 3, with a reduced volume that is to be attributed to the material ablation 4.

[0093] The blank is a plastic and in the present case is an acrylate 8. The said blank can also comprise other materials, such as other plastics, or glass. However, the surface of the blank to be reworked is made of plastic. FIG. 4 shows how the laser beam 9 impinges onto the surface 10 of the acrylate 8, and thereby penetrates into the acrylate in the shape of a cup in the region 11. The pulse duration of the ablative laser is about 100 femtoseconds and the acrylate is thereby vaporised in the region 11. This creates a cup-shaped region 12 of an acrylate melt, and, within this cup-shaped region 12, a region 13 of vapour.

[0094] FIG. 6 shows how the melt 12 solidifies again and the vapour 13 evaporates. Thus, at the end of the process, the crater 14 shown in FIG. 7 remains in the acrylate region 8.

[0095] By the arrangement of a plurality of craters of this type in close proximity to each other, a planar material ablation 4 is achieved. The resulting surface structure is rough as a result of the linking together of the craters. By minimising the depth of the crater, and minimising the distances between the craters, the roughness of the plastic surface can be reduced.

[0096] It is advantageous for the smoothing of the surface if the laser intensity is minimised, and/or the footprint of the laser on the surface to be processed is increased, so that material is only melted, and, as far as possible, no material evaporates. A polishing laser 20 is usually used for this purpose, which is scanned along the line 21 with a scanning rate (V.sub.scan) and a footprint width 22, 23 over the surface 24. The polishing laser 20 is moved forward at a feed rate (V.sub.feed) in the direction of the arrow 25, at right angles to the line 21.

[0097] As a consequence, as shown in FIGS. 9 to 11, the blank 2 is first processed with the ablative laser to achieve material ablation 4, resulting in a rough surface of the blank 2. The subsequent laser polishing produces the smooth surface 26 of the blank 2 shown in FIG. 11.

[0098] In the example of embodiment, the material surface shown in FIG. 10 is created by selective material ablation of an intraocular lens 2 from the initial shape shown in FIG. 9, and the said material surface is then smoothed by laser polishing until it is transparent. This creates the material surface shown in FIG. 11.

[0099] During material ablation 4 with the ablative laser 3, care is taken to ensure that systematically localised material ablation is achieved by the action of ultra-short pulses of laser radiation of about 100 or 200 femtoseconds only at the point of impingement of the laser onto the surface, without any thermal damage to the surrounding material. In the example of embodiment, a laser wavelength of 343 nm is used, so that the laser radiation is absorbed near the surface as a result of the small optical penetration depth of this laser wavelength in the acrylate.

[0100] By comparing the initial shape and the target shape of the surface, the required ablation depth and thus the required number of laser pulses at each point on the surface are determined. In this manner the material ablation 4 can be determined by the number of laser pulses per unit surface area without altering the nature of the laser radiation. Here the laser beam 30 can be guided in a meandering manner over the surface to be processed, in particular for the laser material ablation. On the basis of the calculated number of laser pulses per unit surface area, the laser is switched on and off during its passage over the surface to be processed.

[0101] In the example of embodiment shown in FIG. 12, a beam diameter 31 of the laser radiation on the material surface of approx. 20 μm, a repetition rate of 100 kHz, and a scanning rate 32 of 1,000 mm/s are used. This results in a feed rate 33 (V.sub.feed), with which the laser 30 is guided over the lens 34.

[0102] For the subsequent laser polishing, a laser with a wavelength of 10.6 μm is used, since this wavelength is also absorbed near the surface in the material. The laser is operated continuously and the laser power is in the range of 50 to 100 watts. As a consequence the material surface is melted by the action of the laser radiation during laser polishing, and is then smoothed by the surface tension before it solidifies once again.

[0103] In the example of embodiment shown in FIG. 12, 20 iterations (the number of passes) are carried out, so as to polish the surface gradually, whereby each iteration reduces the surface roughness until the target roughness is achieved. A pause of 20 seconds is envisaged between the iterations to prevent the sample from overheating.

[0104] The processing strategy for the iteration shown in FIG. 12 is characterised by the use of a bi-directional scanning strategy, with a scanning rate of 5,000 mm/s, thereby creating a quasi-line focus. The said quasi-line focus 35 is guided with the feed rate 33 of 30 to 40 mm/s over the surface of the lens 34 to be polished. In this example of embodiment, the beam diameter 31 at the workpiece is 6 mm. Temperature control is preferably also used so as to improve the stability of the laser polishing further.

[0105] With a higher average laser power a higher feed rate is to be used, and with a lower average laser power the feed rate is reduced. This process can therefore be scaled. The dependence between feed rate 33 and average laser power 36 is shown in FIG. 13. This results in the hatched preferred working region 37.

[0106] FIG. 14 shows a particular blank 40 that is manufactured by injection moulding. As a consequence of the injection moulding method this blank has a density gradient. Here the central region 41 is formed with a higher density than the edge region 42. This density gradient can be generated in injection moulding by the pressure conditions during the injection process, or also by a multi-component injection moulding process in which different plastics are used. In particular, in the case of additive production from a powder-form, liquid or gaseous material, a blank can easily be manufactured with a density gradient or from different materials. This density gradient leads to a particular refraction of the light by the lens 40. In order that the different densities of the blank 40 do not impair the process of material ablation and polishing, a region with a different density can also be provided in the interior of the lens 40, while the surface to be processed with the surface region relevant to the processing has a uniform density.

[0107] It is advantageous if the pulse energy is varied during ablation and/or polishing. To this end FIG. 16 shows the intensity of different pulses 50 to 55, which follow each other in time and have different intensities 56, but the same pulse durations 57 (only numbered in an exemplary manner). Thus the intensity 56 of the pulses 50 to 55 varies over time 58. Correspondingly, the pulse duration 57 of the individual pulses 50 to 55 can also vary, while the pulse intensity remains constant. Finally, both the intensity 56 and the pulse duration 57 can be varied and preferably controlled over time, in order to influence the ablation or polishing process in an optimal manner, and in order to achieve rapid processing without overheating.

[0108] The local intensity distribution of a pulse 60 on the spatial axes 61 and 63 is shown in an exemplary manner in FIG. 17. This pulse shows a locally bounded higher pulse energy 62 on the left-hand side than on the right-hand side. For example, the pulse can drop slowly along the surface 64, or rapidly along the curved surface 65, so that the right-hand side of the pulse has a significantly lower energy concentration than its left-hand side. This makes it possible, for example, to vary the radiation intensity applied to a surface region over time as a laser beam moves over a surface.

[0109] FIG. 18 shows a particular local energy distribution of a pulse 70, in which a higher energy is present in the edge region 71 of the pulse 70 than in the central region 72. When the pulse impinges onto the surface of a lens this results in a higher energy being applied to the edge region of the resulting crater than to the central region of the crater. The crater is therefore given less of a cup shape and more of a rectangular shape, so that a plurality of craters placed side-by-side form an approximately planar surface.

[0110] In order to optimise this effect, it is proposed that the pulse energy distribution be varied transverse to the direction of radiation during processing.

[0111] In order to achieve homogeneous processing of a lenticular surface 80 of a lens 81, it is advantageous if the laser beam 82 is maintained essentially at right angles to a tangent 83 at the point of intersection 84 of the laser beam 82 and the lens 81. This can be achieved by varying the alignment of the laser beam during processing and maintaining the position of the lens 81 constant, or by altering the alignment of the lens 81 relative to the laser beam 82 by moving the lens 81 during processing. Needless to say, both the lens and laser can be moved so as to align the laser beam 82 as nearly at right angles as possible to the normal 83 on the surface of the lens. Moreover, instead of moving the laser, the laser beam can also be aligned with the aid of a mirror so that it impinges onto the lens surface as nearly at right angles as possible.

[0112] As in the example of the lens shown in FIGS. 14 and 15, the density of the lens can be varied by the choice of material or by the material processing of the blank. However, the density can also be altered during processing by material ablation and/or polishing. This makes it possible to provide, by the nature of the laser beam, densities on the lens surface that differ in terms of gradient and are locally bounded. The density on the material surface can be increased such that reflections are prevented by the altered refractive index. However, the density can also be altered with the laser beam, or by means of a plurality of laser beams 91, 92, in the interior 90 of a lens 93 such that the refraction of the finished lens does not result from the surface shape of the lens, but rather from a density gradient in the surface region 94 of the lens 93 and/or in the interior region 90 of the lens 93.

[0113] The arrangement of the ablation craters 100 on the surface 101 of a lens 102 is shown in FIG. 21. Here the craters 100 are spaced further apart in the edge region 103 than in the central region 104. This is just one example to show how the nature of the processing of the surface can be varied by means of the number of craters per unit surface area.

[0114] The lens 110 shown in FIG. 22 has a central region 111, which has a greater density than the radially outer region 112.

[0115] The inverted density distribution was implemented with the lens 120 shown in FIG. 23. There an outer region is illustrated as graphically darker so as to indicate the higher density, while the interior region 122 is illustrated as brighter so as to indicate the lower density.

[0116] In the plan view shown in FIG. 24, a uniform density can be discerned, if just the visible surface is considered. In both examples of embodiment a density gradient is therefore present in the direction of the optical axis 113 or 123.

[0117] FIG. 25 shows a lens 130 with a radial density gradient. In the region of the optical axis 133, there is a region 132 with a lower density than in the radially outer region 131. The plan view in FIG. 26 therefore shows a darker radially outer region 131 and a brighter central region 132 with a lower density.

[0118] FIG. 27 shows a lens 140 with a multi-focal density gradient. Here, regions 143 and 144 with a lower optical density alternate outwards in the radial direction from a central region 141 on the optical axis 142; between these there is a region 145 with a higher optical density.

[0119] FIG. 28 shows in a plan view that the regions of higher and lower optical density are annular in form.

[0120] In all the examples of embodiment shown, the optical density can migrate via a gradient into an altered optical density, and, alternatively, regions of different optical densities can lie clearly bounded next to each other. Here the varying optical density can be used to influence the refractive behaviour of the lens when a light beam passes through it, and its deflection. Alternatively or cumulatively, the reflection properties, especially at the boundary surface of the lens surface, can be influenced by way of its density and the hardness that usually accompanies the latter.