Multifocal lenses

Abstract

At least three principal powers (D F ,D M ,D N The multifocal lens (1) has a plurality of concentric annular main zones (Z i ), each of which is divided into inner and outer annular subzones (2, 3) of different refractive powers (D1, D2). The lens (1) has no geometric steps between all the subzones (2, 3). The refractive powers (D1) of all the inner subzones (2) are equal to one another, and the refractive powers (D2) of all the outer subzones (3) are equal to one another. All the inner and outer subzones (3) are separated by their respective main zones (Z i ) are shared in equal area ratios within the range of 30:70 to 70:30.

Description

Detailed Description of the Invention

[0001] The present invention relates to a multifocal lens with at least three main refractive powers, which has a plurality of concentric annular main zones adjacent to each other, each of which is divided into inner and outer annular subzones of different refractive powers, and which has no geometric steps between all the subzones.

[0002] Such lenses are often used as ophthalmic lenses (eg, contact lenses, intraocular lenses (IOLs), intracorneal lenses, or spectacle lenses).

[0003] Trifocal lenses have been known for a long time. In most cases, they are diffractive lenses with equal-area ring-shaped zones (so-called "Fresnel zones") between which geometric steps are provided. In such trifocal lenses, the step heights usually vary alternately. Figure 1 shows the through-focus response (TFR) of such a lens with 28 zones. The steps between the equal-area annular zones are alternately higher, resulting in optical path length differences of 0.65 λ and 1.35 λ (λ is the wavelength of light). However, the fabrication of such steps is complex, resulting in high manufacturing costs.

[0004] Furthermore, trifocal refractive-divergent lenses are known in which the steps are replaced by so-called "phase subzones" with small areas. In such trifocal refractive-divergent lenses, the refractive power of the phase subzones is substantially different from the refractive power of the other so-called "phase main zones." This allows corresponding optical path length differences to be realized between the phase main zones (e.g., EP 1 194 797 B1, EP 2 564 265 B1). Such trifocal lenses exhibit a complex refractive power profile from the inside to the outside, with the area ratio between the phase subzones and the phase main zone changing. Therefore, the manufacture of such trifocal lenses is generally complex.

[0005] An object of the present invention is to create a multifocal lens with at least three principal refractive powers that is easy and economical to manufacture.

[0006] This object is achieved by a multifocal lens of the type mentioned at the outset, which is characterized in that, according to the invention, the refractive powers of all inner subzones are in each case equal to one another, the refractive powers of all outer subzones are in each case equal to one another, and all inner and outer subzones share their respective main zones in an equal area ratio within the range of 30:70 to 70:30.

[0007] The basis of the present invention is the explicit consideration of interference phenomena between light from various subzones or the main zone. By combining alternating subzone powers with a specific area ratio between the inner and outer subzones, the present invention creates multifocal lenses that can have three or more main powers, at least one of which is diffractive. The simple surface profile of the alternating subzone powers, with equal area ratios for the pairs of subzones that form the main zones and no geometric steps, makes the multifocal lenses of the present invention particularly easy and economical to manufacture. Furthermore, the lenses of the present invention allow for a variable division of light intensity into their main powers, for example, an equal division for better vision at distance, intermediate, and near distances.

[0008] In a preferred embodiment, all main zones have the same area. As a result, the main zones have the area ratio of a Fresnel zone lens. This simplifies the generation of at least one diffractive main power by interference between the sub-zones and the main zone. In an alternative embodiment, the areas of the main zones increase or decrease monotonically from the inside to the outside. This allows the individual main powers to be dependent on the aperture size (e.g., pinhole or eye pupil).

[0009] The area of ​​each main zone is 2.2πmm 2 less than π mm 2 less than 2π / 3 mm, and particularly preferably 2 If the diffractive main power of the lens is less than 1000 .mu.m, the diffractive main power of the lens can be generated particularly easily for visible light.

[0010] In one embodiment that is particularly preferred from the viewpoint of manufacturing technology, the above-mentioned area ratio is preferably within the range of 40:60 to 60:40, and particularly preferably 50:50.

[0011] The lens may have any number of main zones, for example, more than 50 or more than 100. If the lens has 5 to 50 main zones, preferably 10 to 20 main zones, its surface profile can be kept simple and its at least one main diffractive power can be formed by light diffraction in the sub-zones and main zones at a sharp focus.

[0012] In a further preferred embodiment, the lens has a distance power, an intermediate power, and a near power as its principal refractive powers, and the difference between the near and far powers is in the range of 1 to 6 diopters, preferably in the range of 2.0 to 4.5 diopters. In this case, near and far objects can be well focused, especially when the lens is used as an IOL. Furthermore, intermediate objects can also be well focused when the difference between the intermediate and far powers is in the range of 1.4 to 2 diopters, preferably in the range of 1.6 to 1.8 diopters.

[0013] In principle, the lens could have one or two main refractive powers that match the refractive powers of the inner and / or outer sub-zones. In an advantageous embodiment, all sub-zones combine to form a diffraction grating that generates at least three of the main refractive powers of the lens by diffraction. As a result, none of the main refractive powers of the lens matches the refractive power of any of its sub-zones, and the main refractive power can be determined purely by taking into account interference phenomena between the light from the various sub-zones or main zone.

[0014] In a preferred combination of the latter two embodiments, the distance power can be generated by the negative first diffraction order (also referred to as the "diffraction order") of the lens. While the use of this diffraction order for distance power has traditionally been discouraged due to its axial chromatic aberration, it has now been recognized for the first time that this same axial chromatic aberration can be advantageously used to simulate or correct the refractive chromatic aberration present in the human or animal lens. In particular, the negative first diffraction order of the lens for light between 450 nm and 650 nm can have a diffractive axial chromatic aberration in the range of 0.1 to 1.2 diopters, preferably in the range of 0.3 to 0.7 diopters, and particularly preferably in the range of 0.35 to 0.55 diopters.

[0015] In one advantageous embodiment of the lens, particularly as an IOL, the refractive power of the inner subzone or the refractive power of the outer subzone is in the range of -2.5 to 2.5 diopters around the smallest of the primary powers, preferably in the range of -2.0 to 2.0 diopters around the smallest of the primary powers. This allows the primary powers of the lens to be within the range of the refractive power of the human crystalline lens. For the same purpose, in a further advantageous embodiment, which can be optionally combined with this, the refractive power of the inner subzone or the refractive power of the outer subzone can be in the range of -2.5 to 2.5 diopters around the largest of the primary powers, preferably in the range of -2.0 to 2.0 diopters around the largest of the primary powers.

[0016] The subzones may all be homogeneous. Alternatively, at least one inner or outer subzone may be divided into a plurality of partial zones, the averaged refractive power of which corresponds to the refractive power of each of the subzones. In this case, one or more subzones may have, for example, a discrete or continuous through-focus response. This allows for various manufacturing options for the lens and a variety of available diffraction patterns.

[0017] The invention will now be explained in more detail with reference to exemplary embodiments shown in the accompanying drawings, in which: FIG. 1 is an intensity-power graph showing the through-focus response (TFR) obtained with a prior art trifocal lens at an optical wavelength of 550 nm; FIG. 2 shows a first embodiment of a trifocal lens according to the invention in a half-section perpendicular to its axis of rotational symmetry A; FIG. 3 shows a central detail III of the lens of FIG. 2 in a half-section perpendicular to the axis A, with the x-axis elongated so that it can be better appreciated; FIG. 4 is an intensity-power graph showing the through-focus response obtained with the lenses of FIGS. 2 and 3 at an optical wavelength of 550 nm; Figure 5 is a contrast-line graph showing the modulation transfer function (MTF) obtained with the lenses of Figures 2 and 3; FIG. 6 is an intensity-power graph showing the through-focus response obtained with an exemplary variation of the lens of FIGS. 2 and 3 at an optical wavelength of 550 nm; FIG. 7 is an intensity-power graph showing the through-focus response obtained with a trifocal lens according to a second embodiment of the invention at an optical wavelength of 550 nm; FIG. 8 is an intensity-power graph showing the through-focus response obtained with a trifocal lens according to a third embodiment of the invention at an optical wavelength of 550 nm; Figure 9 is an intensity-power graph showing the through-focus response obtained with the lenses of Figures 2 and 3 for polychromatic light with wavelengths between 450 nm and 650 nm; 10a and 10b are intensity-power graphs showing in each case three through-focus responses obtained with a trifocal lens according to the invention with different area ratios of the successive main zones at a light wavelength of 550 nm (FIG. 10a) or for polychromatic light with wavelengths between 450 nm and 650 nm (FIG. 10b); Figure 11 is a power-wavelength graph showing the dependence of the refractive power of the human eye on the wavelength of light; FIG. 12 is an intensity-power graph showing the diffractive axial chromatic aberration using two through-focus responses obtained with the lenses of FIGS. 2 and 3 at optical wavelengths of 450 nm and 650 nm.

[0018] See introduction for prior art FIG. 1.

[0019] 2 and 3 show a multifocal lens 1 according to the invention. The multifocal lens 1 has at least three main refractive powers, in particular a distance power D F , middle refractive power D M , and near refractive power D N (Figure 4) Far refractive power D F , intermediate refractive power D M , and near power D N are related to the perception of distant, intermediate, and near objects, respectively. Lens 1 may be used, for example, as an ophthalmic lens (e.g., a contact lens, an intraocular lens (IOL), an intracorneal lens, or a spectacle lens) or as an optical element (e.g., a mirror lens, a converging lens, or a diverging lens). Lens 1 may be made of any material suitable for this purpose (e.g., glass, acrylic, silicone, hydrogel, polymethyl methacrylate (PMMA), etc.).

[0020] The lens 1 is arranged concentrically around an axis of rotational symmetry A and has several (2, 3 or more) main zones Z i (i=1, 2, ..., I). i are adjacent to each other, i.e. from the inside to the outside (in the radial direction R in Fig. 3), the second main zone Z2 is adjacent to the first main zone Z1 at its inner radius r1 (measured from the optical axis A), the third main zone Z3 is adjacent to the second main zone Z2 at its inner radius r2, etc., in each case without any further intervening optical zones. i The number I>1 is the overall diameter of the lens 1 and the near power D N and far refractive power D F The difference may be determined depending on the desired difference between the two, and is usually in the range of 5 to 50, particularly in the range of 10 to 20.

[0021] Each main zone Z i is subdivided into inner subzones 2 and outer subzones 3. The inner subzones 2 and outer subzones 3 have different refractive powers, which are denoted herein by the formula symbols "D1" and "D2," respectively. The refractive power D1 of all inner subzones 2 and the refractive power D2 of all outer subzones 3 are the same in each case. That is, each inner subzone 2 has a refractive power D1, and each outer subzone 3 has a refractive power D2.

[0022] In addition, each main zone Z i The area ratio of the inner subzone 2 to the outer subzone 3 is equal and is within the range of 30:70 to 70:30. Therefore, the main zone Z of each inner subzone 2 i The area ratio of each outer subzone 3 to the main zone Z is p1. i If the area ratio of p1 to p2 is p2, then the inequality 30:70≦p1:p2≦70:30 holds. In most embodiments, the area ratio p1:p2 is 40:60 to 60:40, and in some embodiments, it is substantially 50:50.

[0023] As can be seen from Figure 3, the lens 1 has no steps between all the sub-zones 2, 3. That is, the lens 1 has no steps between the main zone Z i There are no steps between the sub-zones 2, 3 or between their respective sub-zones 2, 3. The multifocal lens surface 4 of the lens 1 is therefore continuous.

[0024] Primary refractive power D of lens 1 F , D M , D N At least one of the sub-zones 2, 3 or main zone Z is diffractive, i.e., is produced by diffractive effects in the lens 1. Therefore, the basis of the lens 1 disclosed herein is the various sub-zones 2, 3 or main zone Z. i The aim is to explicitly take into account the interference phenomenon between the light from each main zone Z i The area of ​​is 2.2πmm 2 For example, π mm 2 or less than 2π / 3mm 2 In some embodiments, all sub-zones 2, 3 combined may be selected to have all (in this case three, alternatively four or more) principal powers D of lens 1. F , D M , D N , .... At this time, all the principal refractive powers D F , D M , D N , ... are diffractive, and the refractive powers D1, D2 in the subzones 2, 3 are in most embodiments the principal refractive power D of the resulting multifocal lens 1. F , D M , D N , ... does not match the principal refractive power of any of the

[0025] In the exemplary embodiment of lens 1 shown in Figures 2 and 3, it is an intraocular lens (IOL) with a refractive index of 1.458. The primary refractive power D of lens 1 is F , D M , D Nare 20 diopters, 21.7 diopters and 23.4 diopters, the inner subzone 2 has a refractive power D1 of 19.8 diopters and the outer subzone 3 has a refractive power D2 of 23.8 diopters. The anterior side 5 of the lens 1 has a lens surface 4 which generates multifocality by all the subzones 2, 3. Alternatively or additionally, the posterior side 6 of the lens 1 also has a lens surface 4 which generates multifocality by all the subzones 2, 3. i and such lens surface 4 having subzones 2, 3. In one embodiment, the lens 1 is a toric lens, and the lens surface facing away from the lens surface 4 has the shape of a torus cap.

[0026] The different refractive powers D1, D2 present in the individual sub-zones 2, 3 cannot be seen in the scale drawing of FIG. 2. For this reason, the individual main zones Z i Detail III of the center of lens surface 4 is shown in FIG. 3 such that the x-axis parallel to optical axis A is stretched by a factor of 13.3 so that the different curvatures at θ are clearly visible.

[0027] 2 and 3, it can be seen that the lens 1 disclosed herein is easier to manufacture than, for example, prior art diffractive lenses that have steps between individual zones. In particular, the lens 1 in this regard can have a continuous lens surface 4 on the anterior side 5 and / or posterior side 6.

[0028] In the exemplary embodiment shown in Figures 2 and 3, the lens 1 has a diameter of 6.02 mm and is divided into 14 main zones Z of equal area. i (i.e., Fresnel zones). The diameter d1=2r1 of the central main zone Z1 is 1.6088 mm. The inner diameter d1=2r1 of the ring-shaped second main zone Z2 adjacent to this main zone Z1 is 1.6088 mm, and the outer diameter d2=2r2 of the second main zone Z2 is 1.6088√2 mm. The outer diameter d3=2r3 of the third main zone Z3 is 1.6088√3 mm. i Inner diameter d i-1 =2r i-1 is 1.6088√(i-1)mm, and the i-th main zone Zi Outer diameter d i =2r i In the present embodiment, the area components p1 of the inner subzones 2 are each the area components p1 of the respective main zones Z i The area component p2 of the outer subzone 3 corresponds to 52.5% of the area of ​​each main zone Z i This corresponds to 47.5% of the area.

[0029] The resulting through focus response (TFR) of Lens 1 is shown in FIG. 4 in a graph of intensity I versus power D. As can be seen from FIG. 4, the three principal powers D F = 20 diopters, D M = 21.7 diopters, and D N Integrated intensity I at = 23.4 diopters F , I M , I N The sum of these is 84% ​​of the total integrated intensity, with the remaining 16% of the intensity occurring at secondary maxima appearing at 18.3 and 25.1 diopters, respectively.

[0030] The modulation transfer function (MTF) is often used to evaluate the imaging quality. In Figure 5, the three principal refractive powers D for the lens 1 of Figures 2 and 3 for light of wavelength 550 nm are shown. F , D M , D N The MTF at F For curve 7, the intermediate refractive power D M For curve 8, near power D N For the lens 1 in question, the MTF for each principal power at intermediate and near distances (curves 8 and 9) is virtually the same, while the MTF for the distance power (curve 7) is slightly higher than the MTFs for the other two principal powers.

[0031] In addition, near refractive power D N and far refractive power D F It should be noted that a conventional diffractive trifocal lens with the same power interval of 3.4 diopters between main zone Z and main zone Z , and the same diameter of 6.02 mm, would require 28 Fresnel zones with 27 steps to achieve the through-focus response shown in Figure 1, i.e., discontinuities between these zones. On the other hand, lens 1 of the present disclosure has only 28 Fresnel zones with 27 steps between main zone Z and main zone Z . i No steps are required between subzones 1 and 2, or between subzones 2 and 3.

[0032] For the exemplary lens 1 of FIGS. 2 and 3, the following parameters were selected: D1=19.8 diopters, D2=23.8 diopters, D F = 20 diopters, D M = 21.7 diopters, D N = 23.4 diopters, p1 = 0.525, and p2 = 0.475. As can be seen, the resulting primary power D of Lens 1 is F , D M , D N Each of the refractive powers D1 and D2 is not equal to the refractive power D1 and D2 and may therefore be due to interference phenomena.

[0033] Furthermore, the relation is: intermediate primary refractive power D M holds true: D M =D1·p1+D2·p2(1) Difference D N -D F does not depend on the selection of the refractive power D1 and the refractive power D2, but only on the area of ​​the main zone or sub-zones 2 and 3. For example, when multiple main zones 2 have the same area, the difference D N -D F is D N -D F =(2.2πmm) / (F·10 3 ), where F is the area of ​​the main zone (unit: mm 2 ) is shown.

[0034] Therefore, either the refractive power D1 or the refractive power D2 can be freely selected within certain limits. For example, if D1 is freely selected, the following holds: D1·p1+D2·p2=D M =D1·p1+D2·(1-p1) (2) From this formula, the following follows: D2=(D M -D1·p1) / (1-p1) (3) According to equation (3), for example, the value of D1 is set to 20.5 diopters, and D M is again 21.7 diopters, then when the area components p1=0.525 and p2=0.475, the value of D2 is 23.0263 diopters.

[0035] Instead of D1, D2 can also be specified, in which case D1 will be obtained from the following relation: D1=(D M -D2·p2) / (1-p2) (4) As will be explained, for example, for lens 1, the trifocality is divided into I main zones Z i is achieved by subdividing the subzones 2 and 3 into two subzones 2 and 3, each of which has a different refractive power D1 and D2. For completeness, it should be noted that the individual subzones 2 and 3 could also be subdivided into further partial zones (not shown). If the refractive powers of all the partial zones of subzone 2 or subzone 3, averaged over the subzone area, correspond to the refractive power D1 or D2, the through-focus response is substantially the same as if only a single refractive power D1 or D2 were used per subzone 2 and 3. In general, the individual refractive powers D1 and D2 of subzones 2 and 3 may each be replaced by any continuous power distribution within the subzones 2 and 3, as long as the average value of this power distribution over the subzone area corresponds to the required individual power D1 or D2.

[0036] FIG. 6 shows the through-focus response for a variation of lens 1 of FIGS. 2 and 3. Each subzone 2, 3 consists of two equal-area subzones. The two subzones of each inner subzone 2 have 19.5 diopters and 20.1 diopters, respectively, and the two subzones of each outer subzone 3 have 23.4 diopters and 24.2 diopters, respectively. Therefore, the average value of each subzone 2 is 19.8 diopters, and the average value of each subzone 3 is 23.8 diopters. The other parameters correspond to those of lens 1 of FIGS. 2 and 3. As shown, the through-focus responses of FIGS. 4 and 6 are virtually identical. Alternatively, subzone 2 and subzone 3 may each have varying refractive power profiles, their respective average values ​​being given by D1 and D2.

[0037] 7 shows the through-focus response of a further embodiment of lens 1 to monochromatic light at 550 nm. i The area components of subzones 2 and 3 in are equal, i.e., p1 = p2 = 0.5. Here, inner subzone 2 has a refractive power D1 of 18 diopters and outer subzone 3 has a refractive power D2 of 25 diopters. As shown, lens 1 has three primary refractive powers D1 of 18.5 diopters, 21.5 diopters, and 24.5 diopters. F , D M , D N and each of which has approximately equal intensity I F , I M , I N It has.

[0038] In the embodiments described so far, the resulting primary refractive power D of the lens 1 F , D M , D N The sub-zone powers D1, D2 are not matched. Figure 8 shows the through-focus response of an alternative embodiment. F corresponds to the refractive power D1 of the inner subzone 2 and the near refractive power D Ncorresponds to the refractive power D2 of the outer sub-zone 3. Both types of sub-zones 2 and 3 are located within each main zone Z i 8, the intermediate refractive power D M Intensity I M are the other two principal powers D F ,D N Intensity I F ,I N Higher than.

[0039] The operating principle of lens 1 for monochromatic light has been described above. Figure 9 shows the through-focus response of lens 1 of Figures 2 and 3 for polychromatic light having a spectrum between 450 and 650 nm. At a distance power D of 20 diopters F corresponds to the negative first order diffraction of Lens 1, with a near power D of 23.4 diopters N corresponds to positive first order diffraction and has an intermediate refractive power D of 21.7 diopters M corresponds to the zeroth diffraction order. The positive and negative first diffraction orders each exhibit chromatic diffraction aberration. Consequently, the peak intensities I at these diffraction orders for polychromatic light are F,p , I N,p is the peak intensity I in the 0th diffraction order M,p As can be inferred from FIG. 9, the individual primary refractive powers D F , D M , D N Integral intensity I F , I M , I N are almost the same. This means that the three principal refractive powers D F , D M , D N This means that the imaging quality at

[0040] In the illustrated embodiment, lens 1 is made of a material that exhibits negligible refractive chromatic aberration, i.e., its refractive index is substantially independent of the wavelength of light. Exemplary materials are glass, acrylic, silicone, hydrogel, and PMMA. Alternatively, lens 1 may be made of a different material.

[0041] The embodiments described so far have the same area as the main zone Z i i.e., it has a so-called Fresnel ring zone. i outer radius r i For , the following holds: r i =r1·i 0.5 (5) In such an embodiment of the lens 1, the individual principal refractive powers D F , D M , D N remains substantially independent of the optical pupil size, whether this is provided by a pinhole diaphragm or by the pupil of the eye. Nevertheless, the individual principal refractive powers D F , D M , D N It may be desirable to depend on the pupil size, for example by using the radius r according to i This can be achieved by selecting r i =r1·i z (z≠0.5) (6)

[0042] For example, the near refractive power D is greater for larger pupils than for smaller pupils. N may be intended to be slightly larger. For this purpose, the main zone Z i The area of ​​the near power D may decrease (z<0.5) with increasing distance from the optical axis A. Conversely, for example, with increasing pupil size, N To reduce the main zone Z i The area of ​​may increase with increasing distance from the optical axis A (z>0.5).

[0043] 10a and 10b show the through-focus response for monochromatic light with a wavelength of 550 nm (FIG. 10a) and polychromatic light with wavelengths between 450 nm and 650 nm (FIG. 10b) for various values ​​of the parameter z. A value of z of 0.5 is shown by the solid line 10, a value of z of 0.48 is shown by the dashed line 11, and a value of z of 0.52 is shown by the line with triangles 12. As shown, the primary refractive power D F , D M , D N , their associated intensities I F , I M , I N , and their respective maxima vary with the parameter z. However, the intensity I F , I M , I N The sum of does not change.

[0044] Conventionally, in diffractive bifocal lenses or diffractive trifocal lenses, the diffractive power of the zeroth order diffraction is called the refractive power D F This is because the zeroth diffraction order does not have chromatic diffraction aberration. However, as will be described later, in one embodiment of the lens 1 disclosed herein, the diffractive power of the negative first diffraction order is used as the far power D, for example, to mimic the chromatic aberration of the crystalline lens. F It is used as.

[0045] Figure 11 shows the refractive power D of the human eye as a function of the wavelength λ of light. A(Charman WN, Jennings JAM (1976), "Objective Measurement of the longitudinal chromatic aberration of the human eye", Vision Res. 16:999-1005). As Figure 11 shows, the longitudinal chromatic aberration of the human eye between 450 nm and 650 nm is about 1.3 diopters, and the refractive power for 450 nm (blue light) is greater than the refractive power for 650 nm (red light). According to the standard work Bergmann - Scha (umlaut) fer: Optik, Verlag Walter de Gruyter, 1993, the refractive power of the entire human eye is 58.8 diopters, and the refractive power of the crystalline lens is 20.2 diopters. Assuming that the chromatic aberration of the entire eye and the crystalline lens within it is proportional to their respective refractive powers, the magnitude of the chromatic aberration of the crystalline lens can be estimated to be 1.3 20.2 / 58.8 = 0.447 ≒ 0.45 diopters. In this case, blue light is refracted more strongly than red light.

[0046] FIG. 12 shows the principal refractive power D of the lens 1 of FIGS. 2 and 3 for two wavelengths, 450 nm (dashed curve 13) and 650 nm (solid curve 14). F , D M , D N As can be inferred from FIG. 12, (refractive power D F The axial chromatic aberration in the negative 1st diffraction order (for the intermediate refractive power D) is 0.51 diopters for the parameters selected as an example (see the two peaks 15 and 16 on the left side of Figure 12). This value is close to the value mentioned above for the crystalline lens. M ), the axial chromatic aberration of the lens 1 is zero (see the two peaks 17 and 18 in the center of FIG. 12), and the first diffraction order (near power D N), the diffractive axial chromatic aberration is −0.51 diopters (see the two peaks 19, 20 on the right side of FIG. 12), i.e., red light is refracted more strongly than blue light, thereby canceling the chromatic aberration of the rest of the eye. That is, Lens 1 exhibits approximately the chromatic aberration of the crystalline lens for distance, no chromatic aberration for intermediate distance, and approximately the chromatic aberration of the crystalline lens with the opposite sign for near distance.

[0047] The parameters of the lens 1 may be selected according to other estimates of the chromatic aberration of the eye itself or may be adapted to the individual (previously measured) crystalline lens of the patient. For example, a negative first order diffraction of the lens for light between 450 nm and 650 nm may have a diffractive axial aberration in the range of 0.1 to 1.2 diopters, e.g., in the range of 0.3 to 0.7 diopters, and in particular in the range of 0.35 to 0.55 diopters (close to the above estimates).

[0048] Of course, the refractive powers D1 and D2 of subzones 2 and 3 of lens 1, and their respective main zones Z i their area components p1, p2, and the associated principal power D F , D M , D N , ... may deviate from the illustrated embodiment or several of the presented embodiments may be combined. For example, the near refractive power D N and far refractive power D F The difference between the intermediate refractive power D and the intermediate refractive power D may be in the range of 1 to 6 diopters, for example, in the range of 2.0 to 4.5 diopters. M and far refractive power D F The difference between the powers D1 and D2 of the subzones 2 and 3 may be in the range of 1.4 to 2 diopters, for example, in the range of 1.6 to 1.8 diopters. FAlternatively or additionally, the other of the powers D1 and D2 of the subzones 2 and 3 may be, for example, a near power D N The diopter may be in the range of -2.5 to 2.5 diopters, and particularly in the range of -2.0 to 2.0 diopters.

[0049] The invention is not limited to the embodiments presented, but includes all variations, modifications and combinations that fall within the scope of the appended claims. [Brief explanation of the drawings]

[0050] [Figure 1] 1 is an intensity-power graph showing the through-focus response (TFR) obtained with a prior art trifocal lens at an optical wavelength of 550 nm. [Figure 2] A first embodiment of a trifocal lens according to the invention is shown in a half-section perpendicular to its axis of rotational symmetry A. [Figure 3] A central detail III of the lens of FIG. 2 is shown in a half-section perpendicular to the axis A, with the x-axis elongated so that it can be better appreciated. [Figure 4] 4 is an intensity-power graph showing the through-focus response obtained with the lenses of FIGS. 2 and 3 at an optical wavelength of 550 nm. [Figure 5] 4 is a contrast line graph showing the modulation transfer function (MTF) obtained with the lenses of FIGS. 2 and 3. [Figure 6] 4 is an intensity-power graph showing the through-focus response obtained with an exemplary variation of the lens of FIGS. 2 and 3 at an optical wavelength of 550 nm. [Figure 7] 10 is an intensity-power graph showing the through-focus response obtained with a trifocal lens according to a second embodiment of the invention at an optical wavelength of 550 nm; [Figure 8]10 is an intensity-power graph showing the through-focus response obtained with a trifocal lens according to a third embodiment of the invention at an optical wavelength of 550 nm; [Figure 9] 4 is an intensity-power graph showing the through-focus response obtained with the lens of FIGS. 2 and 3 for polychromatic light with wavelengths between 450 nm and 650 nm. [Figure 10a] 1 is an intensity-power graph showing three through-focus responses obtained with a trifocal lens according to the invention with different area ratios of successive main zones at a light wavelength of 550 nm. [Figure 10b] 1 is an intensity-power graph showing three through-focus responses obtained with a trifocal lens according to the invention with different area ratios of successive main zones for polychromatic light with wavelengths between 450 nm and 650 nm; [Figure 11] 1 is a power-wavelength graph showing the dependence of the refractive power of the human eye on the wavelength of light. [Figure 12] 4 is an intensity-power graph showing diffractive axial chromatic aberration using two through-focus responses obtained with the lenses of FIGS. 2 and 3 at optical wavelengths of 450 nm and 650 nm.

Claims

1. At least three principal powers (D Ｆ , D Ｍ , D Ｎ ) a multifocal lens having Multiple concentric circular main zones (Z ｉ ) and each of the annular main zones (Z ｉ ), Each of them has a different refractive power (D １ , D ２ ) into inner and outer annular subzones (2, 3), the lens (1) is free of geometric steps between all the subzones (2, 3), The refractive power (D １ ) are in each case equal to one another, The refractive power (D ２ ) are in each case equal to one another, All inner and outer subzones (2, 3) are connected to their respective main zones (Z ｉ ) in equal area ratios within the range of 30:70 to 70:

30.

2. All the main zones (Z ｉ 2. The multifocal lens of claim 1, wherein each of the first and second lenses has the same area.

3. A plurality of the main zones (Z ｉ 2. The multifocal lens of claim 1, wherein the area of ​​each of the first and second corneas increases or decreases monotonically from the inside to the outside.

4. Each main zone (Z ｉ ) has an area of ​​2.2π mm ２ less than π mm ２ It is particularly preferably less than 2π / 3 mm ２ A multifocal lens according to any one of claims 1 to 3, wherein the .lambda.

5. A multifocal lens according to any one of claims 1 to 4, wherein the area ratio is in the range of 40:60 to 60:40, preferably 50:

50.

6. The lens (1) has 5 to 50 main zones (Z ｉ ), and preferably has 10 to 20 main zones (Z ｉ 6. The multifocal lens according to claim 1, wherein

7. The lens (1) has a distance refractive power, an intermediate refractive power, and a near refractive power (D Ｆ , D Ｍ , D Ｎ ) The near refractive power (D Ｎ ) and the far refractive power (D Ｆ 7. A multifocal lens according to claim 1, wherein the difference between the first and second diopters is in the range of 1 to 6 diopters, preferably in the range of 2.0 to 4.5 diopters.

8. The intermediate refractive power (D Ｍ ) and the far refractive power (D Ｆ 8. A multifocal lens according to claim 7, wherein the difference between the first and second diopters is in the range of 1.4 to 2 diopters, preferably in the range of 1.6 to 1.8 diopters.

9. All subzones (2, 3) are combined to provide at least three of the principal refractive powers (D Ｆ , D Ｍ , D Ｎ ) by diffraction, preferably having exactly three principal diffractive powers (D Ｆ , D Ｍ , D Ｎ 9. A multifocal lens according to claim 1, which forms a diffraction grating that generates a

10. The far refractive power (D Ｆ 10. A multifocal lens according to claims 7 and 9 or a multifocal lens according to claims 8 and 9, wherein the first diffraction order of the lens (1) is generated by the negative first diffraction order of the lens (1).

11. The multifocal lens of claim 10, wherein the negative first diffraction order of the lens (1) for light of 450 nm to 650 nm has a diffractive axial chromatic aberration in the range of 0.1 to 1.2 diopters, preferably in the range of 0.3 to 0.7 diopters, and particularly preferably in the range of 0.35 to 0.55 diopters.

12. The refractive power (D １ ) or the refractive power (D ２ ) is the primary refractive power (D Ｆ , D Ｍ , D Ｎ ) is in the range of -2.5 to 2.5 diopters, with the smallest principal refractive power of the principal refractive power (D Ｆ , D Ｍ , D Ｎ 12. The multifocal lens according to claim 1, wherein the minimum principal refractive power is in the range of -2.0 to 2.0 diopters, centered on the minimum principal refractive power of the multifocal lens.

13. The refractive power (D １ ) or the refractive power (D ２ ) is the primary refractive power (D Ｆ , D Ｍ , D Ｎ ) is in the range of -2.5 to 2.5 diopters, with the maximum principal refractive power of the principal refractive power (D Ｆ , D Ｍ , D Ｎ 13. The multifocal lens according to claim 1, wherein the maximum principal refractive power of the multifocal lens is in the range of -2.0 to 2.0 diopters, with the maximum principal refractive power being the center.

14. At least one inner or outer subzone (2, 3) is subdivided into a plurality of partial zones, The averaged refractive power of the plurality of partial zones is the refractive power (D １ , D ２ 14. A multifocal lens according to any one of claims 1 to 13, which conforms to the above formula:

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