Myopia-preventing lens with continuous effect distribution

Abstract

The invention relates in particular to an eyeglass lens having at least one diffractive effect region as at least part of a see-through region of the eyeglass lens, such that the eyeglass lens comprises diffractive microstructures in the diffractive effect region, the diffractive microstructures produce at least one base effect or a myopia prevention effect deviating from the base effect in each perspective point of a diffractive effect region, where the diffractive effect region includes a combination region in which the diffractive microstructures produce a combination of the base effect and the myopia prevention effect simultaneously.

Description

Technical Field

[0001] The invention relates to a spectacle lens with a diffractive microstructure for simultaneously producing at least two different effects on at least one partial region of the spectacle lens in order to increase long-term wearing comfort. Background Art

[0002] Particularly in the case of spectacle lenses for correcting myopia, a pronounced trend towards myopia progression often means that the wearing comfort of the spectacle lenses after they have been dispensed as well as the spectacle wearer's satisfaction and tolerance of the spectacles decrease again after a short time.

[0003] In general, myopia is increasing dramatically worldwide, especially in Asia. The WHO estimates that by 2050, more than 50% of the population will suffer from myopia. As myopia increases in an individual, the risk of related eye diseases such as retinal detachment, glaucoma, cataracts and macular degeneration also increases dramatically. Therefore, there is a great interest in slowing the increase in myopia. There are several methods to slow the progression of myopia by optical aids (vision aids). However, what all these methods have in common is that they are very complex and costly, and are also inflexible when it comes to adapting to rapidly changing circumstances (e.g. changes in eyeglass prescriptions, demands on the visual system).

[0004] To date, various optical effects related to the tolerance and comfort of ophthalmic lenses, especially spectacle lenses, have been studied for their influence on myopia and / or hyperopia and their progression or development, based on optical and physiological mechanisms aimed at explaining or slowing down the progression or development (especially degeneration). Existing methods are essentially based on imaging the image in front of the retina, as this aims to slow down the length growth of the eye. It has been shown that it is sufficient (or even better) if this is only in the periphery of the retina.

[0005] One possible approach is to use bifocal lenses and / or progressive addition lenses (PAL). On the one hand, by addition, the area is imaged in the peripheral zone in front of the retina when looking at distance, and on the other hand, the image is not imaged behind the retina when looking at near, at least in the case of insufficient autofocus. This works better for children with insufficient autofocus and / or hyperconvergence. However, with this approach, acceptable results can only be achieved in a smaller group of hyperconvergence. Bifocal lenses are aesthetically unacceptable, especially for children.

[0006] Another approach is based on special PALs (or radially symmetric PALs) with a central focusing effect and peripheral addition (eg DE 10 2009 053 467 A1).

[0007] Like both methods, PAL also has areas with large aberrations. If the power of the spectacle lens is changed, which is often the case in children, a new, expensive spectacle lens has to be produced, which is laborious. Furthermore, due to the aberrations, the quality of both peripheral vision and foveal vision when viewing through the periphery of the lens is greatly compromised. If high demands are placed on the visual system (e.g. in road traffic), this can only be solved with a second pair of single-vision glasses. This further increases the effort and costs when changing prescriptions. Therefore, the acceptance of such solutions is also often low.

[0008] Other approaches are based on special contact lenses, for example. For example, research has been conducted on progressive contact lenses that have a higher additive effect in the peripheral zone than in the central zone. However, in practice, this also impairs foveal vision. In addition, if the power is changed, new lenses must be produced at great expense. Furthermore, for children, operability and reliability are limited. This is particularly true for young children, and is made even more difficult by the fact that measures to slow myopia would actually achieve the greatest effect if taken from an early age.

[0009] Another approach using contact lenses utilizes so-called Ortho-K contact lenses, which can be worn at night but deform the cornea. This aims to correct myopia centrally and to produce an additive effect in the periphery (compared to the center). However, each contact lens has its own specific requirements here and new lenses must also be produced at great expense, for example in the case of a new prescription. Furthermore, the effects of corneal deformation on the metabolism and structure of the cornea are still unclear, especially in young children.

[0010] The progression of myopia leads to the following problems for spectacle wearers: the wearing comfort of the spectacle wearer for a one-time fit continuously decreases. One possible way to control myopia is to use spectacle lenses with small additional lenses (so-called lenslets) with additional positive power. These additional lenses are formed by bump-like structures. The additional effect leads to a local shift of the focus in front of the retina and is therefore intended to counteract the excessive length growth of the eye.

[0011] In the area with lenslets (hereinafter referred to as the "active area"), the distribution of the effect is not continuous: the image becomes blurred in the area of ​​the lenslets and becomes sharp in the area between them. When looking through the area, these lenslets are irritating because they locally prevent sharp imaging. When the eye moves through this area, other irritations occur because the arrangement of the lenslets in front of the pupil changes depending on the gaze direction. Summary of the invention

[0012] The object of the invention is therefore to improve the long-term compatibility of spectacles and thus to achieve long-term wearing comfort in an economically efficient manner. According to the invention, this object is achieved by a spectacle lens having the features specified in the independent claim. Preferred embodiments are the subject matter of the dependent claims.

[0013] Therefore, the present invention provides a spectacle lens having at least one diffraction effect zone as at least a part of a perspective zone of the spectacle lens, so that the spectacle lens includes a diffraction microstructure in the diffraction effect zone, wherein the diffraction microstructure produces at least one basic effect or a myopia prevention effect that deviates from the at least one basic effect in each perspective point of the diffraction effect zone, wherein the diffraction effect zone includes a combination zone, wherein the diffraction microstructure simultaneously produces a combination of the basic effect and the myopia prevention effect.

[0014] A basic effect is understood to be a refractive effect which corresponds to a spherical equivalent to compensate for the defective refraction of the eye of the spectacle wearer. A myopia blocking effect is a refractive effect which deviates from the basic effect. By realizing the basic effect and the myopia blocking effect by means of a diffractive microstructure of the combined zone, it is now possible to achieve a local transition of the intensity ratio (i.e. the ratio of basic effect to myopia blocking effect) without visible jumps and noticeable inhomogeneities in the transparency of the spectacle lens. For example, an area with a pure basic effect (e.g. in the center of a spectacle lens) can be converted quasi-continuously into (e.g. annular) areas in which a myopia blocking effect is additionally or predominantly produced, without these areas having significantly different transparency. This reduces irritation to the eye during eye movements, for example, compared with the use of refractive microlenses to locally produce additional focal areas.

[0015] A basic effect or a myopia-preventing effect is understood here to be the corresponding overall effect of the lens at the corresponding perspective point. This may also be influenced by the refractive effect of the lens body or the curvature of its surface. For example, a diffractive microstructure of a spectacle lens can be formed on a first spectacle lens surface, which has a base curve (curvature) and which, together with an opposite second spectacle lens surface, produces a refractive effect as a positive lens (converging lens) or a negative lens (diffusing lens). However, the overall effect of the spectacle lens is then split by the diffractive microstructure into a basic effect and a myopia-preventing effect (with different focal lengths). The diffractive microstructure preferably produces a sharp image, at least for the basic effect. For the myopia-preventing effect, it is not absolutely necessary to produce a single sharp image (with different focal lengths). It is also possible to realize a plurality of focal lengths with different diffraction orders.

[0016] Preferably, the myopia blocking effect has a shorter focal length than the basic effect, especially in each perspective point of the combined zone. The difference in focal length is also referred to here as the additional effect (of the myopia blocking effect compared to the basic effect). The additional effect is preferably in the range of about 1.5 dpt to about 5 dpt, especially in the range of about 2 dpt to about 4 dpt. As long as the basic effect causes a clear image on the retina, imaging can be achieved in front of the retina, especially when a shorter focal length is produced, thereby reducing the excessive length growth of the eye, thus effectively achieving long-term wearing comfort of the spectacle lens. The present invention does not necessarily require that the basic effect and the myopia blocking effect are the same on the entire spectacle lens, or even only on the diffraction effect zone. On the contrary, it is well known that, for example, for conventional progressive lenses, both the basic effect and the myopia blocking effect may be different for different visual directions. However, it is particularly preferred if at least the additional effect (i.e., the difference between the focal lengths of the basic effect and the myopia blocking effect) remains essentially constant in the combined zone, i.e., there is no significant difference for different perspective points within the combined zone, especially not more than about 2 dpt, preferably not more than about 1 dpt. In other words, while the basic effect across the spectacle lens (especially the combination zone) is varied, the myopia preventing effect is preferably also continued.

[0017] The reference here to the simultaneous generation of a basic effect and a myopia blocking effect (in the combined zone) is intended to express the fact that the diffractive microstructure simultaneously generates both effects (basic effect and myopia blocking effect) by interacting around the corresponding perspective point through the pupil of the eyeglass wearer in an environment representing the cross section of the light beam associated with the object point. This environment can preferably be considered as a disk with a diameter in the range of about 1.5 mm to about 8 mm, preferably in the range of about 3 mm to about 6 mm, even more preferably in the range of not more than about 5 mm or even not more than about 4 mm or even not more than 3 mm.

[0018] Since the diffraction effect is produced as an interference of wavefronts with limited lateral extent, it is of interest to consider such an environment around the respective perspective point, in which the geometry of the diffractive microstructure (e.g. periodicity, amplitude or transition / jump height, glaze angle, etc.) varies. This is particularly true if the basic effect and the myopia-blocking effect are produced by spatially separated diffractive substructures within the combination zone, i.e. the basic effect is produced by one of the substructures and the myopia-blocking effect by the other substructure. In this case, however, the two substructures are so close together (in particular alternating with each other) that the environment around each perspective point of the observed combination zone always contains both substructures. Therefore, the basic effect and the myopia-blocking effect are not perceived by the eye as being spatially separated from each other. For such a characterization of the diffractive microstructure (in particular such a substructure) and its optical effect on the respective perspective point (in particular within the combination zone), a circular environment around the perspective point can be considered in particular, the diameter of which is not greater than 3 mm, or even not greater than 2 mm, or even not greater than 1 mm.

[0019] Preferably, the diffractive microstructure is formed in an annular shape around the center of the spectacle lens. Particularly preferably, the diffractive microstructure is formed rotationally symmetrically.

[0020] Preferably, the diffractive microstructure has a sawtooth shape in cross section. Preferably, the diffractive microstructure has a constant step height. However, the radial spacing of the steps preferably depends on the distance from the center and in particular decreases inversely proportional to the distance from the center.

[0021] In a preferred embodiment, the basic effect and the myopia preventing effect are respectively caused by corresponding diffraction orders of light diffraction by the diffractive microstructure. Particularly preferably, the basic effect and / or the myopia preventing effect is produced as the zeroth diffraction order of the diffractive microstructure.

[0022] In a preferred embodiment, for each perspective point (of a plurality of perspective points) within the combined region, the diffractive microstructure has at least substantially a single periodicity, wherein the basic effect and the myopia blocking effect are caused by different diffraction orders of the (single) diffraction grating formed thereby. The respective diffraction orders of the basic effect and the myopia blocking effect differ from one another, particularly preferably by 1.

[0023] In a preferred embodiment, the diffractive microstructure comprises, for each perspective point, a plurality of perspective points within the combined area:

[0024] - at least one first diffractive substructure, substantially producing the basic effect; and

[0025] - at least one second diffractive substructure, substantially producing a myopia blocking effect.

[0026] Particularly preferably, at least one first substructure is formed by a first periodic diffraction grating with a first grating period and a first grating amplitude, and at least one second substructure is formed by a second periodic diffraction grating with a second grating period and a second grating amplitude. The term "grating amplitude" here does not refer to the influence of a conventional amplitude grating on the local attenuation of the light waves. Instead, it generally means a local influence on the light waves. This can indeed be the attenuation of the light waves by a conventional amplitude grating. However, within the scope of the present invention, it is preferred to use phase gratings with the aid of refractive index transitions. In particular for the preferred case of phase gratings (due to refractive index transitions), the "grating amplitude" here means describing the spatially variable (especially periodic) influence on the optical path length (e.g. the local layer thickness of a layer forming a diffractive microstructure with a refractive index different from the refractive index of the main body of the spectacle lens). For example, in the case of sawtooth microstructures, the grating amplitude can be described by the step height of the sawtooth cross section of the microstructure.

[0027] In a particularly preferred embodiment, the first grating amplitude and the second grating amplitude differ from each other, while preferably the first grating period and the second grating period substantially coincide. In this case, "substantially" particularly means that deviations from an exact match should be possible, these deviations particularly achieving a global radial variation of the grating period over the entire spectacle lens.

[0028] In this embodiment, the diffraction factors of the two substructures correspond to a certain extent in the case of (substantially) the same grating period. However, they differ from each other in the shape factor. This will be explained in more detail later. Due to the different grating amplitudes (shape factors), different diffraction orders of the respective substructures can be specifically selected to provide a basic effect and a myopia blocking effect.

[0029] In a further preferred embodiment, the first grating period and the second grating period are different from each other, while preferably the first grating amplitude and the second grating amplitude substantially coincide. This embodiment provides a particularly high degree of flexibility, since the absolute values ​​of the basic effect and the myopia blocking effect as well as their relative positions, i.e. the additional effect, can be adjusted relatively freely (in particular steplessly) via the continuously selectable grating period. In particular, there is no restriction to a specific choice of diffraction orders (i.e. in steps).

[0030] In principle, it is also possible for the grating amplitude and the grating period of the two substructures to differ from each other, which in turn may provide greater freedom for selecting / adapting the basic effect and the myopia blocking effect.

[0031] Preferably, the diffractive microstructure comprises a plurality of first substructures and a plurality of second substructures, wherein the plurality of first substructures and the plurality of second substructures are arranged alternately with each other. In other words, at least in the combination region, a second substructure is usually present between two first substructures, and vice versa.

[0032] In particular, when a plurality of alternatingly arranged first and second substructures are used, it is particularly preferred that along a continuous path within the combined area (in particular extending radially on the lens), the number of a plurality of first grating periods of the first substructures and the number of second grating periods of the second substructures change successively in opposite directions. In other words, along a continuous path alternating across the first and second substructures, one number of grating periods increases, while the other number of grating periods decreases along the same path. This means that the corresponding areas of one type of substructure increase (quasi-)continuously along the path, while the corresponding areas of the other type of substructure decrease (quasi-)continuously. This results in a (quasi-)continuous change in the proportion of the basic effect relative to the proportion of the myopia-blocking effect, wherein the eye does not perceive any (step-like) inhomogeneities of the glass.

[0033] Preferably, the number of grating periods in each substructure is in the range of about 2 to about 200, preferably, in the range of at least about 5, more preferably, in the range of at least about 10; and / or in the range of not more than about 100. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In the following, the present invention is further described with reference to the accompanying drawings by means of preferred embodiments. The accompanying drawings show:

[0035] Figures 1A to 1D a schematic cross section through an exemplary eyeglass lens illustrating a diffraction grating formed by a diffractive microstructure;

[0036] Figure 2 Schematic illustration for determining the phase difference of two adjacent light beams on an arbitrary (not necessarily) periodic surface;

[0037] Figure 3 The backside grating has a prism with a blaze angle to make the local periodic microstructure visible;

[0038] Figure 4 Prisms with complex grating structures: sections within a period are divided into different subsections that can represent substructures;

[0039] Figure 5 Distribution of diffraction factor, shape factor and total intensity as a function of the exit angle φ' for a blaze angle β = 3.8°;

[0040] Figure 6The course of the intensity at the 0th and -1st orders and the sum of the remaining orders as a function of the blaze angle;

[0041] 7A to 7D Schematic cross section of a preferred diffractive microstructure based on several substructures;

[0042] Figure 8 Distribution of diffraction factor, shape factor and total intensity as a function of exit angle φ' for another example of a diffractive microstructure;

[0043] Fig. 9 Intensity distribution at different orders as a function of the number of grating periods per substructure;

[0044] Fig. 10A and Fig. 10B Example of a particularly simple microstructure. DETAILED DESCRIPTION

[0045] Thus, the present invention provides a spectacle lens in which, in the active zone (diffraction effect zone or combined zone), at least part of the light enables sharp imaging on the retina of the spectacle wearer, while another part of the light is focused so as to provide a stimulus to prevent an increase in eye length that leads to myopia. In contrast to conventional spectacle lenses, the spectacle lens according to the present invention can also provide a substantially uniform image in the active zone. In particular, a continuous visual impression is produced when the pupil moves.

[0046] In general, the active area, i.e. the diffractive effect area and / or the combined area, is not limited to certain areas on the lens. In principle, the diffractive effect can be used anywhere on the lens. However, it is particularly preferred that the combined area leaves at least one central perspective area of ​​the spectacle lens (e.g. with a diameter of about 10 mm or even about 15 mm). It is further preferred that the combined area fills an annular area with a radius between about 20 mm and about 35 mm or even a radius between about 20 mm and about 40 mm or even a radius between about 15 mm and about 50 mm.

[0047] With the spectacle lens according to the invention, it is achieved in particular that part of the light is directed to the first effect (basic effect, S G ) is focused on the retina, while another part of the light is focused on the retina as a secondary effect (myopia blocking effect, S M ) is focused in front of the retina, and this second effect is more active than the basic effect to reach a third effect (additional effect ΔS).

[0048] Fourth effect (basic glass S KThe effect of the diffractive microstructure contributes to both the basic effect and the myopia prevention effect. This effect can also be zero or can vary over the area of ​​the glass. The special diffractive microstructure also contributes to the myopia prevention effect and / or the basic effect. At least the basic effect and the myopia prevention effect are caused by the diffractive microstructure. This will be described in more detail later. Figures 1A to 1D An example of a possible structure of a spectacle lens is schematically illustrated, the spectacle lens comprising a base lens and a diffractive microstructure. Both are preferably formed in one piece from the same material. Nevertheless, the macro curvature of the base lens with refractive effect can be distinguished from the microstructure with diffractive effect, at least as a model.

[0049] As described in more detail below, the preferred axial extent of the diffraction microstructure depends on the diffraction order used. In particular, it is determined as the product of the diffraction order and the design wavelength divided by the difference in the refractive index of the two media. In preferred embodiments, the first diffraction order is used. The lateral dimensions of the corresponding diffraction grating are typically in the range of about 1 mm to about 0.01 mm. However, more specific details of specific embodiments are explained later.

[0050] The lateral extent of the individual grating elements (periods) of a diffraction grating results from the design of the structure. For simple gratings, the principle is that the lateral extent is linearly inverse with the prismatic effect of the glass at this time. For a given sphero-cylindrical effect, it must increase from the center to the edge of the glass according to the Prentice formula Prism = Effect * Radius. Therefore, the extent is specifically inverse with the radius. The Prentice formula also shows that the prismatic effect increases with the desired sphero-cylindrical effect. This results in a wide range of lateral extents of individual grating elements. This will also be explained later. The change in order of magnitude can be clearly explained by the fact that, for example, in the case of a diffraction lens with an effect of around 10 dpt, the grating constant near the center of the lens is of the order of magnitude of about 1 mm, while via the 1 / r law, the grating constant in the periphery is typically of the order of magnitude of 1 / 30 of this number, i.e. 0.03 mm or slightly less.

[0051] Diffraction gratings (i.e., diffractive microstructures) can resist air, e.g. Figures 1A to 1D As shown. Nevertheless, it is also possible to apply thin layers which do not significantly change the structure, for example as a hard layer, anti-reflection layer or topcoat. In a preferred embodiment, the structure is covered with a covering layer which is thicker than the structure height and preferably provides a flat surface. The refractive index of this layer must then be taken into account in the effect of the structure.

[0052] In a preferred embodiment, the diffractive structure is designed rotationally symmetrically around the center or main perspective point or far point of the lens. This avoids undesired prismatic effects and makes it particularly easy to define the design of the lens around the corresponding point.

[0053] In another preferred embodiment, the periodicity or course of the grating is rotationally symmetric around the center, but not necessarily the structure height. This enables, for example, structures in which the intensity distribution depends on the polar angle.

[0054] The basic effect consists of the effect of the base glass and the mth diffraction structure of the diffraction grating. G Effect of diffraction order S diff,G The myopia blocking effect is the effect of the base glass and (at least one) the mth M (at least one) effect of order S diff,M Therefore, the mth G Diffraction order and mth M The difference between the effects of the diffraction orders is the additional effect ΔS.

[0055] Enter the basic effect (mth G The proportion of incident radiation that enters (at least one) myopic blocking effect (mth order) M The proportion of incident radiation that is diffracted (ie, the order of the diffraction) is determined by the structure (eg, height) of the diffraction grating. This can be determined in such a way that a desired intensity distribution is achieved. This is explained in more detail below.

[0056] Part of the incident radiation may also be diffracted into other orders. This may not be desirable and can be reduced as much as possible. This can be achieved in particular by choosing a suitable structure height (or amplitude or step height) of the diffractive microstructure, as explained in more detail below.

[0057] As only a single m M As an alternative to diffraction orders, the myopia blocking effect can also be formed by several diffraction orders. This is possible because its main purpose is to provide a stimulus to prevent further growth of the eye length, rather than to produce a sharp image.

[0058] In a preferred case, the basic effect m G and myopia blocking effect M The orders are directly adjacent to each other (m M =m G ±1). In this case, the grating can have a sawtooth shape and the intensity distribution can be controlled by the height of the corresponding peaks. In the simplest case, m G =0, so m M = ±1. Therefore, the basic effect is not affected by the diffractive structure and corresponds to the effect of the base glass. Therefore, the diffractive structure provides an additional effect. However, other m G This allows to reduce the effect of the base lens while maintaining the same basic effect, thereby reducing the curvature of the surface and ultimately reducing the thickness of the lens. Furthermore, by cleverly choosing the effect of the base lens and the mthG The effect of the step grating can reduce the color error of the basic effect.

[0059] As a first approximation, the refractive effect S of a diffraction grating with given grating parameters A is diff It is linearly related to the wavelength λ at the diffraction order m:

[0060]

[0061] The grating parameter A describes the periodicity of the grating as a function of the distance from the center. Details regarding the structure of the grating and the definition of the grating parameters are discussed in more detail below.

[0062] While it is advantageous to minimize (or at least not increase) the color error of the image due to the basic effect, (larger) color errors of the image due to the myopia blocking effect can be accepted, since no sharp image is formed on the retina anyway. The overall effect distribution between the refractive component (the effect of the basic lens) and the diffractive component required to fully compensate for the color error depends on the refractive index n of the material of the lens body. K and any covering layer n S and the Abbe number ν of the lens material K The details of this aspect, including the definition of the color error parameter σ as a function of material parameters, are discussed in more detail below.

[0063] It is not necessary to fully compensate for the color error. It is sufficient if the color error is partially compensated or partially overcompensated, ie a smaller color error (in the normal or abnormal direction) remains than a purely refractive lens would have.

[0064] Improvements can already be achieved if the following conditions are met:

[0065]

[0066] Where σ0 is a constant that depends on the Abbe number and the refractive index, as will be explained later. With conventional materials, σ0 is approximately 0.09.

[0067] Table 1 summarizes some examples.

[0068]

[0069]

[0070] Table 1: where m M =m G Examples of ±1 effects and diffraction orders

[0071] In addition, as described below, a small portion of the incident light may also reach adjacent diffraction orders (mainly directly adjacent diffraction orders m M -1 and m M +2 or m M -2 and m M +1). However, this is acceptable and does not prevent coating, as long as the quality of the structure is sufficient and the diffraction into undesired orders is not too high. Preferably, in the areas where full correction is to be achieved (especially in the central perspective area and / or the far vision area and / or the near vision area, i.e. in the perspective area of ​​the lens mainly used), the proportion of diffraction into undesired orders is not more than about 5%, even more preferably not more than about 3%, most preferably not more than about 1%. In other areas, a proportion of 20% or more in undesired orders can still be tolerated. There are cases in which the proportion of extraneous orders cannot be reduced further. If, for example, two adjacent orders have the same intensity, the theoretical minimum is just above 20% of the energy that ends up unintentionally entering the other order. However, there is not a clear theoretical limit in every case.

[0072] Using adjacent diffraction orders of the sawtooth structure avoids unnecessary complexity and provides sufficient flexibility for most applications. All desired additional effects can be achieved by selecting the grating parameter A. However, there is a certain dependency between the basic effect and the additional effect due to equation (E1):

[0073]

[0074] However, in many cases this margin is sufficient because, for example, color error correction is more relevant for high effects than for low effects.

[0075] For some applications, it is useful to have more flexibility in setting these effects by not constraining them to adjacent diffraction orders. This allows for distributions of effects with arbitrary integer ratios.

[0076]

[0077] This enables, for example, color error correction for lower basic effects or higher additional effects and enables better adjustment of the color errors of the base glass. Furthermore, if the basic effect is to be produced only or mainly by the grating, the additional effect can be fine-tuned.

[0078] Table 2 summarizes some examples.

[0079]

[0080] Table 2: where m M ≠m GExamples of effects and diffraction orders of ± 1. Compared to the situation in Table 1, here the color error compensation is almost complete and the additional effects are significantly higher.

[0081] Secondary maxima may also occur in the intensity distribution. For the basic effect, the goal should be to use only one maximum (or closely adjacent secondary maxima) in order to ensure a sharp image. For the myopia blocking effect, on the other hand, several maxima (especially secondary maxima) with larger distances between them may also be used, since a sharp image is less important here.

[0082] In summary, the factors affecting the design of diffractive microstructures can be better understood through the following basic explanations.

[0083] For example, US 2013 / 0229619 A1 (and US 2013 / 0235337 A1) describe the optical properties of a surface, in particular an at least partially flat surface, according to the equation:

[0084] z D (x+d)=z D (x), 0≤x≤Nd (1)

[0085] With periodic arrow height z D If a parallel beam (flat wavefront) is incident on such a surface at any angle, covering the entire width 0≤x≤Nd, the incident light has an angular intensity distribution I=I F ×I D , the angular intensity distribution can be summarized as the diffraction factor I D and shape factor I F The diffraction factor (except for the angle of incidence) depends only on the period d and the number of periods N. On the other hand, the shape factor is independent of N but depends on the function z D (x) Shape within a period.

[0086] The background for the use of diffractive structures in US 2013 / 0229619 A1 is the possibility of color fringe correction. In contrast, it is now proposed to use diffraction gratings to improve the long-term wearing comfort of spectacle lenses by inhibiting myopia progression. The desired optical properties are as follows: In addition to the basic effect, the lens also produces a second image created in front of the retina, where the additional effect is typically around +3 dpt. In general, this additional effect is preferably in the range of around +1.5 dpt to around +5 dpt.

[0087] To illustrate the principle, for simplicity, a prism or a flat surface with equidistant gratings will be considered below. This already provides a very good local description (i.e. for a specific perspective point and its local environment). The results can then be transferred to a lens, similar to the approach in US 2013 / 0229619 A1. It is explained below how the intensity distribution changes if more complex structures are allowed within the grating period, such as different grating constants in the substructures and different blaze angles.

[0088] For a better overview, the initial case of equidistant gratings from US 2013 / 0229619 A1 is summarized here again, but with slightly different naming. Assume the case of a finite equidistant grating with N periods, where the grating profile can initially be arbitrary. The normal of the surface on which the grating is applied points in the z direction, and the grating consists of a profile z D (x) Definition, according to equation (1), 0≤x≤x0=Nd.

[0089] If light (coherent across the entire width of the grating) is incident on the grating at an angle of incidence φ relative to the surface normal, it makes sense to first determine the phase shift that occurs as a function of x. Figure 2 , it can be seen that even with an arbitrary, not necessarily periodic, grating, two adjacent beams will enter into a phase relationship. If the penetration point is given by:

[0090]

[0091] Then the projection parts λ1 and λ2 can be calculated by the following formula:

[0092] ((P1+λ1N′)-P2)N′=0 (3)

[0093]

[0094] The phase difference between beam 2 and beam 1 is now:

[0095]

[0096] The abbreviations are as follows:

[0097] p s (φ,φ′)=(n′sinφ′-n sinφ); p c (φ,φ′)=(n′cosφ′-n cosφ) (7)

[0098] If the refractive surface is actually flat, that is, z D (x)≡0, the second term is omitted; and the law of refraction is derived from the first term by requiring that the phase differences for all x vanish.

[0099] Under the assumption that z D When (0)=0, the phase of any beam, defined as the phase difference relative to the beam when x=0, is as follows:

[0100] Φ(φ,φ′,x)=x(n′sinφ′-n sinφ)+z D (x)(n′cosφ′-n cosφ) (8)

[0101] Conveniently, we can also introduce the phase as a function:

[0102] Φ(p s , p c , x) = xp s +z D (x)p c (9)

[0103] The amplitude φ′ in the emission direction is as follows:

[0104]

[0105] where k = 2π / λ (sizing factors are neglected here, these should take into account the fact that different angular points on the grating are hit by different "numbers" of beams per unit area).

[0106] If now k = 2π / λ and the periodicity condition of equation (1) holds, equation (10) can be rewritten as:

[0107]

[0108] where the periodicity is exploited after the permutation. The prefactor is the shape factor U F (d,p s , p c ), and then factor U D (N, d, p s ) takes the periodicity of the diffraction grating into account, i.e., it is the diffraction factor.

[0109] Therefore, the intensity distribution is given by:

[0110]

[0111] For practical reasons, new names are now introduced for the arguments:

[0112]

[0113] The diffraction factor can be rewritten as:

[0114]

[0115] as well as

[0116]

[0117] It is known that the function sin(Nx) / sin x has a sharp maximum where x=πm, m∈Z. This means that the maximum occurs where

[0118]

[0119] This is the well-known diffraction extension of the law of refraction.

[0120] The shape factor is given by:

[0121]

[0122] and cannot be simplified further without additional assumptions. However, for the special case of a sawtooth grating, the following applies:

[0123] z D (x)=-x tanβ,0≤x≤d (18)

[0124] where β is the so-called blaze angle. Its sign is initially arbitrary and is chosen below so that β>0 describes the rear grating on a prism with a base at the bottom (see Figure 3 ) magnifying prism. Therefore,

[0125]

[0126] where β is included as an additional independent variable.

[0127] factor

[0128] q:=(p s -p c tanβ) (20)

[0129] has a very descriptive meaning, i.e.

[0130]

[0131] This gives:

[0132]

[0133] as well as

[0134]

[0135] Here sincx = sinx / x is the diffraction amplitude of a single slit. It has a maximum value where the independent variable x = 0, and at all other zero points of the counter, x = πm F,m F ∈Z\{0}, there is zero. This means that:

[0136]

[0137] The maximum is to be expected, i.e., in the direction in which refraction would also occur in a classical manner, i.e., without light wave properties. In alternative notation, the zero point exists when the following holds, where m F ≠0,

[0138]

[0139] For practical reasons (to support a normalized representation of the diffraction factor, shape factor and total intensity), normalized functions of the diffraction factor and shape factor are introduced, which have the value 1 at the central maximum:

[0140]

[0141] Figure 3 Complex or combined gratings are illustrated and variants with different substructures are shown. For its mathematical description, the period of length d can be subdivided according to the following expression based on the arrow height in equation (18):

[0142]

[0143] Preferably, the portion d1 is divided into M1 grating lines with a blaze angle β1, and the portion d2 is divided into M2 grating lines with a blaze angle β2.

[0144] δ1(d1,M1)=d1 / M1

[0145] δ2(d2,M2)=d2 / M2 (30)

[0146] The height of the arrow in this section d1 is then described by:

[0147]

[0148] The height of the arrow in section d2 is described by:

[0149]

[0150] The total intensity is then still described by equation (12), but the shape factor can be described by the sum of two parts rather than by the magnitude from equation (22):

[0151]

[0152] For this part d h , which yields:

[0153]

[0154] The abbreviations are as follows:

[0155] q h =p s -p c tanβ h ,h=1,2 (35)

[0156] After simplification, the following formula is obtained (where the exponent 'h' is omitted from the empty variable):

[0157]

[0158] as well as

[0159]

[0160] If, as in equation (13), the following abbreviations are used:

[0161] but

[0162]

[0163] And according to equation (33), in total:

[0164]

[0165] in

[0166]

[0167] Right now,

[0168]

[0169] In summary, the strength of the form factor is as follows:

[0170]

[0171] According to equation (27), the normalized shape factor intensity is as follows:

[0172]

[0173] where for the intensity of the sub-grating, the abbreviations are:

[0174]

[0175] And for distractors, abbreviations:

[0176]

[0177] An introduction has already been made.

[0178] The normalized diffraction factor intensity is given by equation (26), thus giving the total normalized intensity as:

[0179]

[0180] The method presented here can be used to design the structure of eyeglass lenses with myopia prevention effect. The specific procedure will be explained using three examples of preferred embodiments. Even if these examples are described separately, specific measures for the design of diffractive microstructures can also be combined.

[0181] A first example is presented of how (especially adjacent) diffraction orders of a simple grating can be specifically used for the fundamental effect and the near-sighted blocking effect. In order to analyze the intensity distribution over the different orders, the energy content of each diffraction order must be evaluated by integral formation. However, if the peak of the diffraction factor is sufficiently sharp, it is sufficient to evaluate the shape factor at the position of the corresponding angle of incidence belonging to a specific diffraction order.

[0182] For this purpose, a simple diffraction grating (i.e., without splitting) with a blaze angle of β = 3.8° is considered. If we assume that the intensity I0 (p s 、p c , d, 0, β, β, 1, 1, N), then for the exit angle φ′0 at order m=0 = 15.09°, which gives an intensity I0 = 0.1564. For the exit angle φ′ at order m=-1 -1 =12.15°, and the corresponding intensity is I0=0.6791. The obtained spectrum is as follows Figure 5 shown. Figure 5 The diffraction factor I is shown as a function of the angle of incidence φ′ for a blaze angle β=3.8° D0 (blue), shape factor I F0 (red) and the distribution of the total intensity I0 (black). In this case, order m=0 and order m=-1 are the dominant orders, but other orders are also occupied.

[0183] By appropriate variation of the blaze angle β, the intensity can be divided between the different diffraction orders. The dependence of the intensity on the blaze angle for orders m = 0 and m = -1 is given by Figure 6 shown. Figure 6 Plots of the intensity at orders m=0 (blue) and m=-1 (orange) and the sum of the remaining orders (green) as a function of the blaze angle β are shown. The blaze angle of 3.8° is shown with Figure 5For β≈2.85° (ie, tan β≈0.0497), the two orders m=0 and m=−1 are assigned the same proportion of I0=0.3956, while the remaining 20% ​​is assigned to the other orders.

[0184] This change in the blaze angle obviously corresponds to a change in the jump height between the difference of an integer multiple of the design wavelength divided by the refractive index of the medium and the difference of the next higher integer multiple of the design wavelength divided by the refractive index of the medium. This means that the above-described embodiments of using adjacent diffraction orders for the basic effect and the myopia blocking effect can be well implemented and optimized in a targeted manner.

[0185] In the second example, it is explained in more detail how to construct a diffractive microstructure using substructures with different effects. In order to obtain additional degrees of freedom compared to a simple grating, two desired effects (basic effect and myopia blocking effect) can be provided by different subgratings (substructures). In the simplest case, these two effects correspond to the m1-th and m2-th diffraction orders of a grating with a grating constant (δ).

[0186] Therefore, by using two substructures (i.e., with corresponding grating parameters A G The first substructure and has grating parameters A M Another flexibility is achieved by using a second substructure of the first substructure instead of a single periodic structure with grating parameter A. Preferably starting from the center and preferably starting from the first structure, they alternate outwards in an annular zone. G (j) The fork (number of the first grating period) is followed by the Z of the second substructure M (j) Prong (number of second grating periods), then Z of the first substructure G (j+1) points, and so on. The parameter j is a continuous variable used to number individual regions (or substructures of the same type of substructure, ie, the first substructure or the second substructure).

[0187] Select the grating parameters A G and A M and the diffraction order m G and m M , so that the expected effect S can be achieved diff,G and S diff,M In each case, "G" stands for the basic effect and "M" stands for the myopia prevention effect. Number of prongs Z G (j) and Z M (j) (i.e. the number of corresponding grating periods) can be used to control the intensity distribution between the two effects. This is described in more detail below. G (j) or Z MThe number of (j) can vary with j.

[0188] The division of the structure into regions or substructures may lead to interference between adjacent regions of different substructure types and / or interference between consecutive regions of the same substructure type. These effects must be taken into account when designing the structure.

[0189] For example, interference between adjacent regions of different substructures may result in intensities at undesired (secondary) orders. This effect can be reduced by increasing Z, since wider regions may reduce interference between adjacent regions. Furthermore, by appropriately placing A G or A M With Z G (j) or Z M (j)Matching each other can minimize this effect.

[0190] 7A to 7D Different arrangements of the diffractive microstructures are compared. Fig. 7A A periodic grating with only one (locally constant) grating period is shown. FIG. 7B to FIG. 7D The diffractive microstructures are schematically illustrated, each having two substructures. In the schematic representation, the two substructures can be distinguished by different shading and can otherwise differ technically, in particular by different grating constants or grating periods. FIG. 7B to FIG. 7D In the case of the first substructure (with vertical stripes) is not interrupted by the second substructure (with horizontal stripes). FIG. 7B to FIG. 7D In the detail of FIG. 1 , two separate regions are shown for the first part structure, which are separated from each other by a region of the second part structure.

[0191] If the number of forks is chosen so that the (j+1)th region of a substructure of this type is Figure 7B , Figure 7C and Fig.7D ) is interrupted by a sharp cross with horizontal stripes in the middle, and runs relative to the jth region as if it had not yet been interrupted by another substructure ( Fig. 7A and Fig.7D If the substructure is interrupted by a vertically striped fork in the figure, then there is no problem for interference between successive regions of the same type of substructure. In this case, constructive interference occurs between two consecutive regions of one substructure type.

[0192] This can be achieved by ensuring that the sum of the widths of the individual prongs of the other substructures that are interrupted corresponds to the sum of the widths of the individual prongs of the one substructure that is displaced. Figure 7C ). However, this is related to the correspondence constraints on the effects of the two substructures.

[0193] If the phase of a substructure in region j+1 where an interruption occurs is selected so that it corresponds to the phase in the case where it is not interrupted ( Fig. 7A ), this constraint can be avoided.

[0194] If this condition is not met ( Figure 7C ), then two coherent regions of a substructure (i.e., a substructure type) may interfere constructively or incompletely in the direction where constructive interference may be desired, and at least partially in the direction where (as completely as possible) destructive interference is desired. This can reduce the intensity of the desired effect and the diffraction intensity of the undesired effect or in the undesired direction.

[0195] As in the case of interference between adjacent regions of different substructures, this effect can be reduced by choosing higher Zs, since wider regions may reduce interference between different regions.

[0196] Nevertheless, a higher Z allows a finer control of the intensity distribution with approximately the same ratio. Conversely, a too high Z may result in individual perceptible zones. This may be desirable if, for example, a basic effect is to be provided only in a central zone. However, this may not be desirable if the basic effect and the myopia blocking effect are to be present in a zone. The decisive factor here is the area on the lens through which the light passes through the pupil when the eye is deflected accordingly. In order to avoid this, at least one area of ​​each type of substructure may be located in an area surrounding the perspective point, which area corresponds to the so-called effective pupil. The effective pupil can be calculated from the effect of the lens and the size of the physical pupil and is typically between 2 mm and 8 mm.

[0197] In the simplest case, the first diffraction order is used for both substructures. This simplifies the analytical view and ensures a homogeneous structure that is as low as possible. However, higher diffraction orders can also be used. The resulting larger structure may be easier to produce with the necessary accuracy. However, the used diffraction order can also be varied between the two substructures or even between individual areas of the same substructure. This creates an additional degree of freedom in the design of the structure, which can be used to optimize the diffraction behavior of the overall structure.

[0198] The same applies to the individual structures according to the description for the significance of the secondary maxima in the basic effect or the myopic blocking effect, as well as for the design for reducing the color error and its significance in the basic effect or the myopic blocking effect.

[0199] According to the form described below, two desired effects are achieved by combining two sub-gratings (sub-structures) having in particular the same grating constant (δ1=δ2=δ) but different step heights (and blaze angles). This provides greater flexibility compared to the example with only one periodic grating. The latter only allows the use of two adjacent diffraction orders, while any diffraction order can be combined by varying the blaze angle.

[0200] This can be considered based on a supergrating consisting of two sub-gratings with specified properties. As a basis, a grating that acts in the first diffraction order and is used as a first sub-grating (first substructure) can be considered. The same grating period can be used for the second sub-grating (second substructure), but where the step height corresponds to three times the diffraction order.

[0201] For M1=M2=1, a relatively broad distribution of four peaks around the central diffraction order of the individual gratings is obtained for I0 (see Figure 8 ). This behavior can be understood phenomenologically by the strong interference of the two substructures. Even by a moderate increase in the parameters M1 and M2, this broadening can be reduced, such as with M1 = M2 = 2 ( Fig. 9A )、M1=M2=5( Fig. 9B )、M1=M2=10( Fig. 9C ) and M1=M2=50( Fig.9D ). Phenomenologically, this can be understood by the change in the phase offset of the elements of the sub-grating relative to each other. A narrow distribution is particularly important for the basic effect and is desirable at least for the myopic blocking effect. As shown above, this can be achieved by a moderate increase in the parameters M1 and M2.

[0202] Furthermore, a completely different effect can be exploited: In the approximation used for the model presented here, an infinite coherence length is assumed. In reality, however, we are dealing with light of finite coherence length ("in the approximate average wavelength (of the order of 10-6 m)"). This means that interference only occurs between reasonably adjacent grating elements. By choosing higher parameters M1 and M2, this effect leads to a suppression of parasitic interference between elements of different sub-gratings compared to the interference within the corresponding sub-gratings. For the grating constant, the area of ​​the spectacle lens occupied by the light beam that passes through the pupil of the eye and contributes to the imaging on the retina can be chosen to be large enough to achieve a correspondingly large M (synonymous with M1 and / or M2) without causing irregularities in the visual impression. The preferred value of M is preferably in the range of 5 to 200, particularly preferably 10 to 100. Furthermore, M can also vary over the entire range. As the grating constant decreases towards the periphery, M can increase towards the periphery, where the vignetting through the entrance pupil of the eye is the same. By using higher diffraction orders, parasitic interference can be further suppressed. This is because for a given coherence length, the number of grating elements participating in diffraction is further reduced.

[0203] As mentioned previously, a third example is a grating consisting of two sub-gratings with different grating constants and adapted blaze angles, as has been schematically described with reference to Figure 7. The structures of the respective regions differ in the used diffraction orders and not (necessarily) in the grating constant. This enables a wider selection of effects, since the effects of the two sub-structures no longer depend on different diffraction orders of the same grating constant, but the grating constant can be freely selected according to the desired effect of each region (sub-structure).

[0204] In the formalism used here, two desired effects can be achieved by combining two sub-gratings with the same step height but different grating constants (and blaze angles).

[0205] This is again analyzed using a supergrating consisting of two sub-gratings with specified properties. As a basis, a grating acting in the first diffraction order and used as a first substructure can be considered. A grating with four times the grating constant is considered as the second subgrating. Since the intensity contribution of each subgrating depends on the area it occupies, for each grating element from the grating with the higher grating constant, a corresponding number of grating elements from the grating with the lower grating constant can be selected in order to obtain the same intensity. However, if a different (especially locally different) intensity distribution is to be achieved, it is preferable to deviate from this in a targeted manner.

[0206] Here, for M1=1 and M2=4 for I0, a relatively broad distribution of five peaks around the central diffraction order of the individual gratings is also obtained. Again, this broadening can be reduced by a moderate increase in Ms, as shown in simulations with M1=2, 5 and 10 (and M2=4M1). What has been described with respect to the second example applies analogously for the phenomenological understanding, the application for constructing supergratings with two narrow intensity distributions and exploiting the finite coherence length of natural radiation.

[0207] In spectacle lenses, in contrast to prisms, the grating "constant" is preferably not constant over the entire lens, but varies slowly. In particular in the case of lenses, the prior art discloses a dependency according to d(r) ≈ 1 / r, where r is the distance from the center of the lens (see, for example, US 2013 / 0235337 A1). Figures 1A to 1D This reduction of the grating period towards the edge is also schematically illustrated. Since, as a good approximation, the step height of the grating tines can also be chosen to be a constant for the eyeglass lens, and since the blaze angle is given by tanβ=h / d(r), the increase in the steepness of the grating tines for increasing radius corresponds to tanβ~r.

[0208] In particular, the method presented here can be used to simulate the effects of a supergrating consisting of two sub-gratings in the approximation of Fraunhofer diffraction and infinite coherence length. Three different grating concepts were investigated as examples. It was shown that undesired interferences occur between the sub-gratings for this application. These lead to a broadening of the actual desired sharp diffraction orders. In practice, however, these can be substantially reduced by increasing the grating factor M. Additionally, since in natural radiation the coherence length and therefore the ability to interfere with more distant grating elements (laterally and axially) is limited, these parasitic interferences can be suppressed by transitioning to higher M and / or higher diffraction orders.

[0209] Even though gratings with a prismatic effect and a constant grating constant were investigated, the results and the design principles can be transferred to other gratings according to the invention with a refractive effect and a defined variation of the grating constant.

[0210] The invention is not limited to the structures described above in an analytical manner. Other possibilities include holographic structures, where the structure is determined based on the desired light distribution under a given illumination or is manufactured as a holographic structure.

[0211] The intensity distribution between the basic effect and the myopia-preventing effect can be constant or variable over the entire glass, depending on the respective position on the glass. This allows, for example, the formation of areas with only the basic effect, areas with both effects and areas with only the myopia-preventing effect. For example, the areas can be ring-shaped, full-sector-shaped or ring-sector-shaped. One advantage of the invention is that not only can a distinction be made between areas with the basic effect and areas with the myopia-preventing effect, but also a continuous transition can be formed.

[0212] A simple grating with a single diffraction order can only provide one effect. The simplest structure according to the invention is probably a simple grating (especially with a grating constant decreasing outwards and with) a step height depending on the radius, which controls the effect distribution between the basic effect (0th diffraction order) and the myopic blocking effect (1st diffraction order).

[0213] A simple exemplary embodiment of a myopia blocking glass may be as follows: A diffraction grating applied to the lens and having a grating constant d(r)=A / r has an optical power of -mλ / A at a wavelength λ and in diffraction order m, where r is the distance from the center of the glass. If the intensity is to land at the mth diffraction order, the jump height is h=mλ / (n-1). If it is desired to create a myopia blocking glass with no additional diffraction effects at order m=1 in the center of the glass, not on the outside, the jump height may have a transition between h=0 and h=λ / (n-1).

[0214] If the myopic blocking effect at wavelength λ = 550 nm is to be approximately ΔS = 2.3 dpt, then a constant A = 2.4 × 10-7 m2 is required. A grating with a constant myopic blocking effect ΔS is as follows: Fig. 10A If a transition is to be installed with zero effect at the center but with ΔS at the periphery, the center can be damped, as Fig. 10B shown.

[0215] Exemplary details of the shapes and dimensions of preferred diffractive microstructures for use in the present invention will be presented below. In particular, diffractive microstructures with a single periodicity will be discussed first. In these diffractive microstructures, one diffraction order (full intensity in one diffraction order) or, for example, two adjacent diffraction orders can be used.

[0216] like Figures 1A to 2 As shown in the exemplary embodiment of D, the diffractive microstructure is preferably rotationally symmetrical about the center of the glass so that the definition of the cross section along the meridian is sufficient. Preferably, in each case a defined time interval r1, r2, r3, ..., one edge follows in succession, where r iThe measurement is preferably made from the center of the glass in the vertical plane (i.e. the tangent plane at the center of the glass) as a projection perpendicular to the vertical plane. Preferably, the step height of all edges is substantially the same, at least locally h. Preferably, this is also measured perpendicular to the vertical plane. However, it can also be measured perpendicular to the glass surface. The differences are usually small and are not relevant for this approximation. Preferably, the same curvature k G d is present anywhere on the edge-free portion of the diffractive microstructure (i.e. between the edges). This means that the edges in the cross section shown preferably form a grating with a radially variable grating constant d. In particular, d i =r i+1 -r i or i =r i -r i-1 The grating constant d can particularly preferably be defined as a function d(r) of r (thus, in the discrete case, the variable d is actually a function of i i It can also be written as r i Preferably, the function d(r) is a Laurent series.

[0217] In a preferred embodiment, the grating pitch, ie the distance between edges, is given by d(r) = A / r, so

[0218] d i =d(r i )=A / r i (A1)

[0219] In another preferred embodiment, the radius r i It is directly given by:

[0220]

[0221] Equation (A2) is obtained from equation (A1) by treating i as a real variable and interpreting equation (A1) itself as a differential equation. Its solution is equation (A2). For large values ​​of i, this equation (A2) gives the same curve as equation (A1), but for small values, especially for i≤10, it deviates significantly from equation (A1). Therefore, equation (A2) is given here as an independent embodiment.

[0222] The dioptric effect of a grating with a grating constant d(r) is given by the fact that the contribution of the diffraction grating to the prism deflection angle is

[0223]

[0224] is understood as a function of r and the effect is defined as the derivative:

[0225]

[0226] In the preferred embodiment where d(r)=A / r, this effect is constant and, at diffraction order m at wavelength λ, is given by equation (A1), where the grating parameter is A.

[0227] Grating curvature k G , that is, the curvature of the cross section of the diffractive microstructure along the meridian is given by:

[0228] k G =k1+k diff (A5)

[0229] Where k1 is the curvature of the base curve, k diff is the change in curvature due to the diffraction grating. diff Preferably matches the effect, i.e.

[0230] (n S -n K ) diff =S diff (A6)

[0231] where n K is the refractive index of the body, n S is the refractive index of the outer or covering layer.

[0232] The jump height h of the diffractive microstructure is given by the following formula: D The maximum diffraction intensity and diffraction order m Max Matches:

[0233]

[0234] where φ K is the angle of the beam within the body, φS is the angle within the cover, and the second subexpression without the cosine term corresponds to the small angle approximation at nearly normal incidence.

[0235] On the other hand, if we want to change the proportion p G Diffraction to the order m of the fundamental effect G , and diffract as much of the remaining proportion as possible to the order m of the myopic blocking effect M =m G ±1, the jump height is calculated as follows:

[0236]

[0237] where x depends on p G The number of which sinc 2 x=p GOf course, with this type of grating, not all residuals are of scale 1-p, since the residual orders will usually also have intensities G Both can be prepared to diffract to the order of myopia blocking effect.

[0238] If the strength of the base effect and the myopia blocking effect are the same (just below 40%), the following applies:

[0239]

[0240] In this case, about 10% of the fraction ends up falling into the adjacent diffraction order m. G -1 and m G +2 or m G -2 and m G +1 in each adjacent diffraction order.

[0241] If the grating is not used for color fringing correction, the radius r i (or function d(r)), the step height h and the grating curvature k g The values ​​of are independent of the base lens, especially the lens material. If, on the other hand, a grating is to be applied to its effect S K If it is a pure refractive lens, the grating should be adjusted for color fringe correction. i or the value of the function d(r), the step height h and the grating curvature k g The value of is preferably defined by:

[0242] -Material at design wavelength λ D The refractive index n

[0243] - Abbe number v of the material d

[0244] -The refractive power S of the base glass at the design wavelength K

[0245] -Base arc k1

[0246] In this embodiment (full color fringe compensation), the grating parameter A is given by:

[0247]

[0248] where according to the (so-called old) definition, the Abbe number is given by:

[0249]

[0250] where n K 、n F 、n C are the refractive indices at constant wavelengths.

[0251]

[0252] The Abbe number is

[0253]

[0254] The derivative of the refractive index according to wavelength n′(λ D ) are approximately related.

[0255] Since A according to equation (A2) depends on the basic effect S K , so the radius is the counting index i and S K The function r i (S K ). In the case of a refractive base glass, the diffraction change in curvature is determined by:

[0256]

[0257] This means that the curvature of the entire grating is a function of the base curve and the base effect k G =k G (k1,k S ).

[0258] For at least partial compensation of color errors, this effect can be understood as a function of wavelength and two orders of magnitude m G and Δm function S(λ, m G , Δm), where Δm: =m M -m G If the relative longitudinal color error FL rL It is defined as the derivative of the total effect S, according to the wavelength λ and the basic effect (receptor effect) S as a derivative G related

[0259]

[0260] At a specific design wavelength (reference wavelength) λ D If we analyze the linear equation

[0261] FL rL =aσ+b (B2)

[0262] As a function of the variable σ,

[0263]

[0264] and where the line parameters are given by:

[0265]

[0266] The longitudinal color error vanishes at the zero point of the linear equation, i.e.,

[0267]

[0268] The zero point itself is also n′(λ D ) or Abbe number.

[0269] In order to reduce color errors, so-called MODs (multi-order diffraction structures) can be used in the basic effect zone and the myopia prevention effect zone. With a simple diffraction structure, the diffraction order with the highest intensity is the same for all wavelengths. With MOD, on the other hand, the structure is designed so that the diffraction maxima for different spectral ranges are at different orders. In this way, the dispersion can be controlled and the color errors are minimized. The structure is designed so that the diffraction structure does not introduce additional color errors. Preferably, the structure is also designed so that it (additionally) compensates for the color errors of the refractive effect of the base glass, thereby minimizing the overall color error. Such a structure can also be used in the basic effect zone and / or the myopia prevention effect zone.

[0270] In general, the diffractive microstructures can be located on the front or back surface of the lens. They are preferably located on the front surface. The basic effect can then be determined by the shape of the back surface using conventional techniques (shell grinding) or free-form techniques.

[0271] In particular when used in combination with a base curve system, the effect of the diffractive microstructure can be defocusing ("spherical"), while the refractive effect of the opposite surface can be an additional defocus component and an astigmatism component ("cylindrical"). This means that the rotational symmetry of the front surface can be preserved while providing a spectacle lens with a cylindrical base effect. Of course, a cylindrical effect of the diffractive microstructure is also possible, but this requires a non-rotationally symmetric structure.

[0272] The diffractive microstructures can also be protected by covering the diffractive microstructures with a material having a refractive index different from that of the spectacle lens. Such a covering layer can be used both during use and during downstream production steps (e.g., mechanical processing of the opposite surface of the lens) and can also be covered by other layers (e.g., hard layers, anti-reflective layers and / or topcoats). It can also act as a hard layer itself.

[0273] The diffractive microstructure can be incorporated directly into the lens (e.g. by machining or embossing). Alternatively, a negative image of the diffractive microstructure can be introduced into a casting mold (e.g. by machining or embossing) and transferred into the spectacle lens during casting. Alternatively, the structure can also be introduced as a negative image (e.g. by machining, embossing or casting) into a transfer layer remaining on a subsequent spectacle lens as a protective layer, and the spectacle lens can be molded onto the structure.

[0274] Furthermore, one or more casting molds (having a negative image structure) for eyeglass lenses can be manufactured by molding a direct-build master mold (having a positive image structure). This is advantageous for the following reasons: First, molding is generally more cost-effective than direct-build. Second, materials that are well suited for direct-build (e.g., nickel alloys) are often not well suited for molding eyeglass lens materials, and vice versa (e.g., hardened crown glass).

[0275] Furthermore, the structuring can be done photolithographically (e.g. through a mask or by direct laser exposure). This applies to the spectacle lens itself, any transfer layer, any casting mould and any master mould.

[0276] These structures can also be achieved by locally changing the refractive index of the spectacle lens material inside the spectacle lens.

[0277] If these structures are rotationally symmetric, they can be easily realized by (precision) lathes or other rotational production systems (e.g., lasers).

[0278] If the periodicity of the gratings is rotationally symmetric around the center, but the structure height is not, they can also be produced using (precision) lathes or other rotational production systems (e.g., lasers). In this case, however, the tool position or the energy must be varied with the polar angle.

[0279] The following are non-exclusive examples of materials used.

[0280] Materials of eyeglass lenses:

[0281] - Perfalit 1.5 (chemical name: polyethylene glycol bisallyl carbonate, based on CR39 (Columbia Resin 39) from PPG, refractive index 1.5, Abbe number 58),

[0282] -PCM 1.54 (chemical name: polyethylene glycol dimethacrylate, refractive index 1.54, Abbe number 43)

[0283] -Polycarbonate (refractive index 1.59, Abbe number 29)

[0284] -Perfalit 1.6 (chemical name: polythiocarbamate, refractive index 1.60, Abbe number 41)

[0285] -Perfalit 1.67 (chemical name: polythiocarbamate, refractive index 1.67, Abbe number 32)

[0286] -Perfalit 1.74 (chemical name: polythiocarbamate, refractive index 1.74, Abbe number about 32)

[0287] Transfer layer material:

[0288] - TS56T (3) from Tokuyama (refractive index 1.49).

[0289] -IM-9200 from SDC Technologies (optical power between 1.585 and 1.605)

[0290] - Transhade from Tokuyama (if necessary, use a primer (Transhade-SC-P) as an adhesion promoter, refractive index 1.54)

[0291] -Hi Guard 1080 from PPG

[0292] Furthermore, the materials mentioned under Materials for Spectacle Lenses can also be used for the transfer layer.

[0293] Casting mold material:

[0294] - Crown glass (e.g. tempered crown glass type CH-W0991 (S-3) based on Schott material from Barberini GmbH)

[0295] -Quartz glass ("fused silica")

[0296] -Metals (e.g. steel, nickel, nickel alloys)

[0297] -Plastics (e.g. polycarbonate (PC), polyamide (PA), polymethyl methacrylate (PMMA)

[0298] Carrier substrate material:

[0299] - Materials listed under Materials for eyeglass lenses

[0300] - Materials listed under Casting Mold Materials

[0301] The preferred material combination is as follows: Spectacle lens: Perfalit 1.6 or 1.67; Transfer layer: Transshade; Casting mold: Crown glass CH-W 0991; Carrier substrate: Perfalit 1.5

[0302] In principle, a wide variety of materials can be used, such as plastic, glass or metal, both individually and in combination. Individual materials can be layered and / or structured on a surface.

Claims

1. A spectacle lens having at least one diffraction effect zone as at least a part of a perspective zone of the spectacle lens, so that the spectacle lens includes a diffraction microstructure in the diffraction effect zone, and the diffraction microstructure produces at least one basic effect or a myopia prevention effect that deviates from the at least one basic effect in each perspective point of the diffraction effect zone, wherein the diffraction effect zone includes a combination zone, in which the diffraction microstructure simultaneously produces a combination of the basic effect and the myopia prevention effect.

2. The spectacle lens according to claim 1, wherein the myopia preventing effect has a shorter focal length in each perspective point of the combined zone than the basic effect. 3 . The spectacle lens according to claim 1 , wherein the diffractive microstructure is formed annularly around the center of the spectacle lens, in particular rotationally symmetrically.

4. The spectacle lens according to any one of the preceding claims, wherein the diffractive microstructure has a sawtooth shape in cross section.

5. Spectacle lens according to any one of the preceding claims, wherein the diffractive microstructure has a constant step height.

6. A spectacle lens according to any one of the preceding claims, wherein the basic effect and the myopia preventing effect are respectively caused by corresponding diffraction orders of the light diffraction by the diffractive microstructure.

7. Spectacle lens according to any of the preceding claims, wherein the basic effect and / or the myopia-preventing effect is produced as a zeroth diffraction order of the diffractive microstructure.

8. An eyeglass lens according to any of the preceding claims, wherein the diffraction microstructure has at least essentially a single periodicity for each of a plurality of perspective points within the combined zone, wherein the basic effect and the myopia-preventing effect are caused by different diffraction orders of the diffraction grating formed thereby.

9. The spectacle lens according to claim 8, wherein the respective diffraction orders of the basic effect and the myopia preventing effect differ from each other by 1.

10. The spectacle lens according to any one of the preceding claims, wherein for each perspective point, the diffractive microstructure comprises a plurality of perspective points within the combination zone: - a first diffractive substructure, which substantially produces the basic effect; and - a second diffractive substructure, said second diffractive substructure substantially producing said myopia preventing effect.

11. The eyeglass lens according to claim 10, wherein the first substructure is formed by a first periodic diffraction grating having a first grating period and a first grating amplitude, and wherein the second substructure is formed by a second periodic diffraction grating having a second grating period and a second grating amplitude.

12. The spectacle lens according to claim 11, wherein the first grating amplitude and the second grating amplitude are different from each other, while preferably the first grating period and the second grating period substantially coincide.

13. The spectacle lens according to claim 11, wherein the first grating period and the second grating period are different from each other, while preferably the first grating amplitude and the second grating amplitude substantially coincide. 14 . The spectacle lens according to claim 11 , wherein the diffractive microstructure comprises a plurality of first substructures and a plurality of second substructures, and the plurality of first substructures and the plurality of second substructures are respectively arranged alternately with each other.

15. The spectacle lens according to claim 14, wherein along a continuous path within the combination zone, the number of the first grating periods of the first substructure and the number of the second grating periods of the second substructure change successively in opposite directions.

16. The eyeglass lens according to any one of claims 11 to 15, wherein the number of grating periods in each substructure is in the range of about 2 to about 200, preferably in the range of at least about 5, more preferably in the range of at least about 10; and / or in the range of not more than about 100.

Images