Abstract
An ophthalmic lens includes a lens body with a predetermined refractive effect and a ring-shaped, diffractive structuring. The ring-shaped, diffractive structuring (4-4) has a waveform in the radial direction which differs from a sinusoidal waveform by an asymmetry and/or a flattening and/or a periodicity, wherein the asymmetry and/or flattening and/or periodicity is constant or changes strictly monotonically over the entire radial curve of the waveform. Further, a method for designing an ophthalmic lens is disclosed.
Claims
1-21. (canceled)
22. An ophthalmic lens comprising: a lens body with a predetermined refractive effect; and a ring-shaped, diffractive structuring, wherein the ring-shaped, diffractive structuring has a waveform in a radial direction which differs from a sinusoidal waveform of a square of a radius by an asymmetry, which is constant or changes strictly monotonically over an entire radial curve of the waveform, wherein the asymmetry is such that a maximum absolute value of the gradient of a falling edge is greater than the maximum absolute value of the gradient of a rising edge in respective periods of the waveform, and wherein a ratio of the maximum absolute value of the gradient of the falling edge to the maximum absolute value of the gradient of the rising edge is at least 1.5.
23. The ophthalmic lens as claimed in claim 22, wherein the waveform is periodic over the square of the radius of the lens body in the radial direction.
24. The ophthalmic lens as claimed in claim 22, wherein an entire waveform of the ring-shaped, diffractive structuring has a continuously differentiable curve in the radial direction.
25. The ophthalmic lens as claimed in claim 22, wherein the asymmetry is such that the curve of the waveform in the radial direction is not mirror symmetric with respect to a local maximum of a respective asymmetric period.
26. The ophthalmic lens as claimed in claim 22, wherein the strictly monotonic change in the asymmetry is expressed as a strictly monotonic increase or a strictly monotonic decrease in the asymmetry.
27. The ophthalmic lens as claimed in claim 22, wherein the ring-shaped, diffractive structuring is arranged on a surface of the lens body.
28. The ophthalmic lens as claimed in claim 22, wherein the refractive effect of the lens body is at least partially spherical, aspheric, or toric.
29. The ophthalmic lens as claimed in claim 22, wherein the ring-shaped, diffractive structuring is formed concentrically about an optical axis of the ophthalmic lens.
30. The ophthalmic lens as claimed in claim 22, wherein the asymmetry is such that an average and/or the maximum absolute value of the gradient of the rising edge differs from the average or the maximum absolute value of the gradient of the falling edge in the respective periods of the waveform.
31. The ophthalmic lens as claimed in claim 22, wherein the ophthalmic lens is multifocal.
32. The ophthalmic lens as claimed in claim 22, wherein the ring-shaped, diffractive structuring is formed such that at least one negative order of diffraction of the ring-shaped, diffractive structuring has a greater polychromatic diffraction efficiency than a zeroth order of diffraction and/or a first positive order of diffraction.
33. An ophthalmic lens comprising: a lens body with a predetermined refractive effect; and a ring-shaped, diffractive structuring, wherein the ring-shaped, diffractive structuring has a waveform in a radial direction which differs from a sinusoidal waveform of a square of a radius by an asymmetry, and wherein the asymmetry changes strictly monotonically over an entire radial curve of the waveform.
34. An ophthalmic lens comprising: a lens body with a predetermined refractive effect; and a ring-shaped, diffractive structuring, wherein the ring-shaped, diffractive structuring has a waveform in a radial direction which differs from a sinusoidal waveform of a square of a radius by an asymmetry, which is constant or changes strictly monotonically over an entire radial curve of the waveform, and wherein the asymmetry is such that a maximum absolute value of a gradient of a rising edge is greater than the maximum absolute value of the gradient of a falling edge in the respective periods.
35. The ophthalmic lens as claimed in claim 34, wherein a ratio of the maximum absolute value of the gradient of the rising edge to the maximum absolute value of the gradient of the falling edge is at least 1.5.
36. The ophthalmic lens as claimed in claim 34, wherein the ophthalmic lens is monofocal.
37. The ophthalmic lens as claimed in claim 34, wherein the ring-shaped, diffractive structuring is formed such that a polychromatic diffraction efficiency of at least one negative order of diffraction of the ring-shaped, diffractive structuring is at least 75% of a diffraction efficiency of a zeroth order of diffraction and/or a first positive order of diffraction.
38. The ophthalmic lens as claimed in claim 22, wherein the ophthalmic lens is an intraocular lens or a contact lens.
39. An ophthalmic lens comprising: a lens body with a predetermined refractive effect; and a ring-shaped, diffractive structuring, wherein the ring-shaped, diffractive structuring has a waveform in a radial direction which differs from a sinusoidal waveform of a square of a radius by a periodicity, and wherein the periodicity is constant or changes strictly monotonically over an entire radial curve of the waveform.
40. The ophthalmic lens as claimed in claim 22, wherein the strictly monotonic change in periodicity is expressed as a waveform period length which increases or decreases in the radial direction.
41. The ophthalmic lens as claimed in claim 31, wherein the ophthalmic lens is trifocal.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Further details and advantages of the disclosure should now be explained in more detail on the basis of the following examples and exemplary embodiments with reference being made to the figures, in which:
[0029] FIGS. 1A and 1B show schematic illustrations of a plan view and a cross-sectional view of an ophthalmic lens;
[0030] FIGS. 2A and 2B show the wave-shaped height profile of the diffractive structuring of the lens from FIGS. 1A and 1B;
[0031] FIGS. 3A to 3C show further illustrations of the wave-shaped curve of the diffractive structuring;
[0032] FIGS. 4A and 4B show the polychromatic diffraction efficiency of the lens according to the first exemplary embodiment;
[0033] FIGS. 5A and 5B show the phase profile and monochromatic diffraction intensity as a function of the added diffractive power;
[0034] FIGS. 6A to 6C show the curve of a further diffractive structuring, the first derivative, and the absolute value of the derivative for a lens with a refractive index of n.sub.IOL=1.56;
[0035] FIGS. 7A and 7B show an ophthalmic lens according to a further exemplary embodiment;
[0036] FIGS. 8A and 8B show the curve and the height profile of the wave-shaped diffractive structuring according to the second exemplary embodiment;
[0037] FIGS. 9A to 9C show further illustrations of the wave-shaped curve of the diffractive structuring;
[0038] FIGS. 10A and 10B show the polychromatic diffraction efficiency of the lens according to the second exemplary embodiment;
[0039] FIGS. 11A to 11D show the phase profile and monochromatic diffraction intensity;
[0040] FIGS. 12A to 12D show the influence of various parameters on the curve of the waveform of the diffractive structuring.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0041] The same or similar elements in the various exemplary embodiments are denoted by the same reference signs in the following figures for reasons of simplicity.
[0042] Different ophthalmic lenses according to exemplary embodiments of the disclosure are explained with reference to the following figures.
[0043] FIGS. 1A and 1B show schematic illustrations of a plan view (FIG. 1A) and a cross-sectional view (FIG. 1B) of an ophthalmic lens 10. In this case, the ophthalmic lens 10 is designed as a multifocal intraocular lens (IOL).
[0044] The lens 10 comprises a lens body 12 which has a refractive effect on account of its material properties, in particular its refractive index, and its shape. On the front side 12a of the lens body 12, the lens 10 has a diffractive structuring 14, as a result of which the lens 10 also has a diffractive effect in addition to the refractive effect. According to the exemplary embodiment shown, the diffractive structuring is wave-shaped, with the structuring having a wave-shaped depth profile in the radial direction. It should be noted that these are only schematic illustrations in which the waveform of the diffractive structuring is shown in greatly exaggerated fashion for better identification. In actual configurations, both the amplitude and the period of the waveform can have a significantly smaller and more delicate design in comparison with the dimensions of the lens body 12.
[0045] As is evident from FIGS. 1A and 1B, the diffractive structuring 14 is ring-shaped, with the rings 14a of the diffractive structuring 14 running concentrically around the optical axis 12b of the lens 10. The waveform deviates from a sinusoidal waveform of the square of the radius in that the waveform is periodic in the radial direction of the lens body with respect to the linear radius of the lens body 12 and the individual periods, which is to say the sections from one local maximum to the next local maximum, are asymmetric.
[0046] The graphs in FIGS. 2A and 2B show the wave-shaped height profile of the diffractive structuring 14 of the lens 10 from FIGS. 1A and 1B. In this case, the height profile relative to the otherwise smooth surface of the front side 12a of the lens body 12 is given on the vertical axis in micrometers. The height profile of the unstructured front side 12a or surface of the lens body 12 represents a base line, which was subtracted from the overall curve of the height contour in order to create the graphs shown, with the result that the wave-shaped curve of the diffractive structuring 14 in the radial direction can be seen unaffected by the curvature of the front side 12a of the lens body 12.
[0047] In FIG. 2A, the curve of the diffractive structuring is plotted as a function of the (linear) radius r, which is to say that the linear radius r is plotted on the horizontal axis in millimeters, starting from the optical axis 12b of the lens 10. By contrast, FIG. 2B shows the wave-shaped curve as a function of the square of the radius r, which is to say that the square of the radius r.sup.2 is plotted along the horizontal axis in mm.sup.2.
[0048] What is evident here is that the diffractive structuring 14 of the lens body 12 according to the exemplary embodiment shown runs periodically with the square of the radius along the radial direction. That is to say the curve has a periodicity in a plot against r.sup.2, with the result that the local maxima are spaced equidistantly. A period is plotted in exemplary fashion in FIG. 2B and provided with the reference sign 1000. By contrast, if the wave-shaped curve is considered linearly, which is to say in a plot against the linear radius r, as provided in FIG. 2A, the local maxima are not arranged equidistantly, but are compressed with increasing radius. Nevertheless, the individual sections of the curve from one maximum to the next maximum are referred to as a period for the sake of simplicity. The periodicity of the wave-shaped curve of the diffractive structuring 14 with the square of the radius offers the advantage that a greater diffractive effect can be achieved in the radially outer areas than in the radially inner areas, and this allows focusing of the incident and diffracted light to be achieved. The periodicity with the square of the radius leads to approximately the same surface areas being formed between the individual rings 14a of the ring-shaped, diffractive structuring 14.
[0049] FIGS. 2A and 2B further illustrate that the waveform has asymmetry and deviates from a sinusoidal waveform in this way. In this case, the falling edge, which is to say the edges that lead away from a local maximum, is steeper than the rising edges that lead to a local maximum. This allows the diffraction intensity of the individual orders of diffraction to be changed, and in particular allows the diffraction intensity of the first negative order of diffraction to be increased and the diffraction intensity of the first positive order of diffraction to be reduced.
[0050] The wave-shaped profile of the diffractive structuring 14 can be used, for example, for a lens body 12 with a refractive index of n.sub.IOL=1.46.
[0051] FIGS. 3A to 3C show a more detailed representation of the wave-shaped curve of the diffractive structuring 14 plotted against the radius squared r.sup.2.
[0052] In this case, FIG. 3A corresponds to the curve of the wave-shaped profile, as in FIG. 2B; FIG. 3B corresponds to the first derivative (in units of mm/mm) with respect to the radius; and FIG. 3C corresponds to the absolute value of the first derivative (correspondingly also in units of mm/mm). The individual periods are identified as Z1 to Z5. As a precaution, reference is made to the fact that only a part of the wave-shaped curve, is shown and the actual waveform may have significantly more than five periods.
[0053] The vertical dashed lines 1002 and 1004, which extend across all three graphs, mark those locations at which the falling edge (line 1002) and the rising edge (line 1004) have their respective maximum absolute value of the gradient in the period Z1. Here, it is evident from the graph in FIG. 3C in particular that, according to the exemplary embodiment shown, the absolute value of the gradient of the falling edge is significantly greater than the absolute value of the gradient of the rising edge. For further clarification, the numerical values are given, with the absolute value of the gradient of the falling edges being 0.03 mm/mm and the absolute value of the gradient of the rising edge being 0.0087 mm/mm. The absolute value of the gradient of the falling edge is accordingly significantly greater than the absolute value of the gradient of the rising edge in this exemplary embodiment, with the ratio being approximately 3.45. In the period Z5, where the absolute values of the gradient are given as 0.0215 mm/mm for the falling edge and 0.007 mm/mm for the rising edge, the ratio is approximately 3.07. Accordingly, all periods have an asymmetry, with the asymmetry not being the same for all periods but being subject to a strictly monotonic change, specifically a strictly monotonic decrease. As a result, a distribution of the diffraction intensity between the diffraction maxima which is advantageous for the multifocal IOL can be achieved, with the result that the polychromatic diffraction intensity for the first negative order of diffraction is greater than the zeroth and the first positive orders of diffraction, even if the material dispersion of the lens body 12 is also taken into account.
[0054] The polychromatic diffraction efficiency for the lens 10 described in FIGS. 1A to 3C is shown in arbitrary units in FIGS. 4A and 4B, with FIG. 4A illustrating the polychromatic order of diffraction without taking into account the material dispersion of the lens body 12 and FIG. 4B illustrating the polychromatic order of diffraction taking into account the material dispersion of the lens body 12. The latter is decisive for the optical performance of the lens. The horizontal axis specifies the added diffractive power (add power) in dioptres, by which the refractive effect of the lens body is modified by the diffractive effect. The zeroth order of diffraction, which reflects the unmodified refractive effect of the lens body, accordingly has an added diffractive power of zero dioptres. The positive orders of diffraction have a positive added diffractive power since they bend the incident light toward the optical axis of the lens 10 and correspondingly amplify the refractive effect of the (convex) lens body 12. By contrast, the negative orders of diffraction have a negative added diffractive power since they reduce the effective refractive effect of the lens 10 since the diffractive power counteracts the refractive effect of the lens body 12. Thus, the first negative order of diffraction has an added diffractive power of approx. ?1.3 dioptres and the first positive order of diffraction has an added diffractive power of about 1.3 dioptres.
[0055] As shown in FIG. 4A, the diffractive structuring with the properties as explained with reference to the previous FIGS. leads to the polychromatic diffraction intensity of the first negative order of diffraction being significantly greater than the polychromatic diffraction intensity of the zeroth and first positive orders of diffraction.
[0056] However, since the dispersion is in the same direction as the material dispersion and amplifies the latter accordingly in the case of the negative orders of diffraction, the ratio of the diffraction intensities is less pronounced when the material dispersion is taken into account, as shown in FIG. 4B. Nevertheless, what can be achieved with the lens according to the explained exemplary embodiment is that the polychromatic diffraction intensity of the first negative order of diffraction is greater than the polychromatic diffraction intensity of each of the zeroth and the first positive orders of diffraction, even when the material dispersion is taken into account. Consequently, a lens according to the explained exemplary embodiment offers the advantage that the greatest polychromatic diffraction intensity can be achieved in the first negative order of diffraction in particular, which is to say in that order of diffraction which is typically used for distance focus. This offers the advantage that the patient's visual experience can be significantly improved in comparison with lenses with a sinusoidal diffractive structuring. This also offers the advantage that this creates a continuous transition area between the distance focus (first negative order of diffraction) and the intermediate focus (zeroth order of diffraction), which has a positive effect on the depth of focus and improves the lens even further.
[0057] In order to characterize the optical performance of the lens 10, it seems necessary to consider the polychromatic diffraction intensity taking into account the material dispersion of the lens body 10, since the dispersion can have a significant influence on the optical power. This is illustrated in FIGS. 5A to 5D. FIGS. 5A and 5B show, respectively, the phase profile (as a function of linear radius) and monochromatic diffraction intensity as a function of added diffractive power (in dioptres), in each case without taking the material dispersion into account. FIGS. 5C and 5D show, respectively, the phase profile (as a function of linear radius) and monochromatic diffraction intensity as a function of added diffractive power (in dioptres), in each case with the material dispersion being taken into account. From this, it is evident that, for an optimization of the optical performance of a lens 10, the material dispersion of the lens body must also be taken into account in order to achieve the best possible result.
[0058] FIGS. 6A to 6C show the curve of a further diffractive structuring, the first derivative, and the absolute value of the derivative for a lens 10 with a refractive index of n.sub.IOL=1.56. The refractive index of the surrounding medium in the eye is unchanged, n.sub.MED=1.336. The illustration corresponds to that from FIGS. 3A to 3C, but in a configuration for a lens with a different refractive index. With regard to the explanations of the information presented, reference is therefore made to the explanations of FIGS. 3A to 3C. It is evident from the graphs that the ratio of the absolute values of the falling edges relative to the absolute values of the rising edges is 3.54 and 3.0 for periods Z1 and Z5, respectively. Accordingly, variations in the asymmetry may be advantageous for the adaptation to the respective refractive index.
[0059] FIGS. 7A and 7B show an ophthalmic lens 10 according to a further exemplary embodiment of the disclosure, the lens 10 being designed as a monofocal intraocular lens (IOL) with an extended depth of focus. Such a lens is also referred to as an EDoF lens (EDoF=enhanced depth of focus). Like in the case of the IOL according to the exemplary embodiment explained above (FIGS. 1A and 1B) as well, this lens 10 also comprises a lens body 12 with a refractive effect, and a ring-shaped, diffractive structuring 14 which is attached to the front side 12a of the lens body 12 and has a plurality of rings 14a running concentrically around the optical axis of the lens 10. Like in FIGS. 1A and 1B as well, the illustrations shown here are also of a purely schematic nature and, in particular, the dimensions of the diffractive structuring are shown in greatly exaggerated fashion relative to the lens body.
[0060] According to this second exemplary embodiment, the diffractive structuring 14 is optimized with regard to its periodicity, the change in periodicity, the asymmetry, and the flattening, in such a way that the optical properties of the diffractive structuring 14 increase the depth of focus achievable with the lens 10 in comparison with a lens with regular, ring-shaped, diffractive structuring with a sinusoidal curve.
[0061] In FIGS. 8A and 8B, the curve or the height profile of the wave-shaped diffractive structuring 14 is plotted (in micrometers) relative to the curve of the otherwise smooth surface 12a of the lens body 12, which represents a subtracted base line, starting radially from the optical axis 12a of the lens 10, with the linear radius r being plotted on the horizontal axis in FIG. 8A and the radius squared r.sup.2 being plotted in FIG. 8B. It is evident here that the periodicity of the waveform of the diffractive structuring is subject to a strictly monotonic change, both in the plot against the linear radius r and in the plot against the radius squared r.sup.2. As is evident from the graphs, the periodicity in the radial direction decreases with increasing radius, with the result that the waveform is increasingly compressed. This is a feature in which the shown lens 10 according to the second exemplary embodiment differs from the lens 10 according to the first exemplary embodiment. In this case, the strictly monotonic change in the periodicity offers the advantage that the depth of focus of the lens 10 can be increased.
[0062] A more detailed consideration of the asymmetry of the waveform of the radial curve of the diffractive structuring 14 is shown in FIGS. 9A to 9C, which, corresponding to FIGS. 3A to 3C, show the profile of the waveform against r.sup.2 (FIG. 9A), the first derivative with respect to the radius in mm/mm (FIG. 9B), and the absolute value of the first derivative in mm/mm. In this case, the dashed vertical lines 1002 to 1008 indicate those locations at which the waveform has the locations that locally have the gradient with the greatest absolute value.
[0063] In this context, it is evident from the graphs that the rising edges, which is to say the sections that run towards a maximum, have a gradient with a greater absolute value than the falling edges, which run away from a maximum. In the first period Z1, a maximum gradient of the falling edge has an absolute value of 0.0024 mm/mm and a maximum gradient of the rising edge has an absolute value of 0.0047 mm/mm, and these maximum gradients therefore have a ratio of 1:1.96. In the period Z5, a maximum gradient of the falling edge has an absolute value of 0.0018 mm/mm and a maximum gradient of the rising edge has an absolute value of 0.0041 mm/mm, and these maximum gradients therefore have a ratio of 1:2.28. It is evident that the asymmetry or the ratio of the gradients within the respective period is also subject to a strictly monotonic change, which contributes to providing the increased depth of focus.
[0064] In FIGS. 10A and 10B, the polychromatic diffraction efficiency (in arbitrary units) resulting from the diffractive structuring 14 of the lens 10 according to the second exemplary embodiment is plotted against added diffraction power (in dioptres), without the material dispersion of the lens body being taking into account (FIG. 10A) and with the material dispersion of the lens body 12 being taking into account (FIG. 10B). In this case, it is evident from FIG. 10A that the diffraction intensity of the first positive order of diffraction is approximately 0.32, the diffraction intensity of the zeroth order of diffraction is approximately 0.3 and the diffraction intensity of the first negative order of diffraction is approximately 0.2. The individual orders of diffraction are clearly separated from one another when the material dispersion is not taken into account (FIG. 10A). A significant superposition of the orders of diffraction arises when the material dispersion of the lens body 12 is taken into account, with the result that an approximately 2 dioptre wide range of diffraction intensities arises around the zeroth order of diffraction, which provides the lens with a greatly increased depth of focus in comparison with a conventional monofocal lens.
[0065] FIGS. 11A and 11B show, respectively, the phase profile (as a function of linear radius) and monochromatic diffraction intensity as a function of added diffractive power in dioptres, in each case without taking the material dispersion into account, for the lens 10 according to the second exemplary embodiment. FIGS. 11C and 11D show, respectively, the phase profile (as a function of linear radius) and monochromatic diffraction intensity as a function of added diffractive power in dioptres, in each case with the material dispersion being taken into account. From this, it is evident that, for an optimization of the optical performance of a lens 10, the material dispersion of the lens body must also be taken into account in order to achieve the best possible result.
[0066] In the following, an example is used to explain how the mathematical description of an asymmetric waveform for the radial curve of a ring-shaped, diffractive structure can take place, without however the disclosure being limited thereto.
[0067] According to the example explained below, a regularly symmetrical shape of a sinusoidal curve is altered toward an asymmetrically undulated structure. The asymmetry in the diffraction profile achievable in this way allows the asymmetry already explained above with regard to the diffraction efficiencies of the different orders of diffraction in relation to the zeroth order of diffraction to be achieved, whereby one or more degrees of freedom for the design of lenses are provided, for example for the design of distance-dominant intensity distributions for multifocal intraocular lenses.
[0068] For example, the deviation of the profile from a sinusoidal curve can be described using the following mathematical formula f:
[00001]
[0069] The parameters and variables are explained below: [0070] r radial position on the lens surface [0071] ? parameters for the diffractive spacing of the orders of diffraction [0072] a phase angle deviation in multiples of the design wavelength [0073] c phase offset [0074] sf(r) shape factor form (flattening) [0075] ?(r) asymmetry parameter [0076] ?0 lateral phase shift [0077] sync parameters for varying the periodicity
[0078] The effects of the individual parameters and their respective variation on the profile of the wave curve are illustrated below in exemplary fashion. For the sake of completeness, it should be mentioned that the mathematical function given above is only an example and other mathematical functions, for instance modified functions, functions based on Fourier series, an at least piecewise definition via polynomials and/or splines, may also be suitable for specifying an asymmetric wave profile for the radial curve of the diffractive structure.
[0079] The effect of varying shape factor sf(r), which influences the flattening of the wave profile, is shown in FIG. 12A. Here, an amplitude profile of the waveform (in arbitrary units) is plotted against the squared radius r.sup.2 for different values of the shape factor sf(r). Even though the shape factor sf(r) may vary strictly monotonically with radius, the waveform for a radius-independent shape factor is shown in FIG. 12A for the sake of clarity. Here, the waveform according to equation (1) is plotted for different values of the shape factor sf, with the value range running from sf=0 to sf=10. The waveform experiences progressive flattening for increasing values of sf. The arrows 1010 elucidate the development of the flattening of the waveform with increasing sf, with the direction in which the respective arrows point indicating the direction of the development for increasing values of the shape factor sf. In this case, it is evident that for sf=0 the waveform has a strong resemblance to a sinusoidal waveform, whereas the waveform for sf=10 has been flattened into an almost rectangular waveform.
[0080] FIG. 12B shows an amplitude profile of the waveform (in arbitrary units) against the squared radius r.sup.2 for different values of the asymmetry parameter ?(r). Even though the asymmetry parameter ?(r) may vary strictly monotonically with radius, the waveform for a radius-independent asymmetry parameter is shown in FIG. 12B for the sake of clarity. In this case, the value range runs from ?=0 to ?=0.7. In this case, increasing values of the asymmetry parameter ?increasingly influence the asymmetry of the waveform, with the result that the edges of the waveform increasingly deviate from a mirror symmetric curve with respect to the local maximum. For an increasing asymmetry parameter ?, the edge running toward a local maximum loses steepness, while the edge running away from the local maximum increases in steepness. The development of the waveform asymmetry with increasing asymmetry parameter is indicated by the arrows 1010, with the arrows pointing in the direction of development for an increasing asymmetry parameter ?.
[0081] FIG. 12C shows an amplitude profile of the waveform (in arbitrary units) against the squared radius r.sup.2 for different values of the sync parameter, which defines the periodicity. In this case, a value sync=1 means that the waveform is periodic with r, which is to say with the linear radius. If the sync parameter has a value of 2 or 3, the waveform is periodic with respect to r.sup.2 and r.sup.3, respectively. Naturally, values that differ from the values mentioned as examples are also possible for the sync parameter, in particular values that are not integers as well. As a result of the graph in FIG. 12C being plotted against the square of the radius, the waveform with synch=2 appears periodic. The waveform with sync=3 experiences a compression with increasing radius, while the waveform with sync=1 is stretched with increasing radius in the quadratic plot. Accordingly, FIG. 12C illustrates how the parameter sync can be used to obtain the periodicity of the waveform and, in particular, a strictly monotonic variation of the periodicity of the waveform. The arrow 1010 elucidates the increasing distortion of the waveform with increasing sync parameter.
[0082] FIG. 12D shows an amplitude profile of the waveform (in arbitrary units) against the squared radius r.sup.2 for different values of the 60 parameter, which specifies the lateral phase shift. A variation of this parameter correspondingly leads to a radial offset of the periodic waveform, without however affecting its wavelength, flattening, and asymmetry. In other words, a variation of the parameter 60 represents a shift in the waveform in the radial direction. The arrow 1010 indicates the increasing lateral shift of the waveform with increasing 60.
LIST OF REFERENCE SIGNS
[0083] 10 (Ophthalmic) lens [0084] 12 Lens body [0085] 12a Front side or surface of the lens body [0086] 14 Diffractive structuring [0087] 14a Rings of diffractive structuring [0088] 1000 Period length [0089] 1002 . . . 1008 Locations with the maximum absolute value of the gradient [0090] 1010 Tendency of changes as each parameter increases [0091] Z1 . . . Z5 Periods of the waveform
