OPHTHALMOLOGICAL OPTICAL ELEMENT AND METHOD FOR DESIGNING AN OPHTHALMOLOGICAL OPTICAL ELEMENT

Description

[0001] The present application relates to an ophthalmic optical element for correcting visual defects, in particular a spectacle lens, comprising a first refractive optical substrate and a first and a second diffractive optical element. The present application further relates in particular to a computer-implemented method for designing an ophthalmic optical element, spectacles, and a head-mounted display with such an ophthalmic optical element.

[0002] Traditionally, prescription eyeglasses are manufactured using methods that have proven successful for decades. By selecting an outer radius of curvature (object-side) and a outer radius (eye-side) of curvature for the lens, the required visual acuity is achieved. For aesthetic and manufacturing reasons, the outer radius (object-side) is generally spherical, assuming a specific predefined value for each diopter range, which can be found in so-called preferred radius tables. The precise visual acuity is then generated using the inner radius (eye-side). In the simplest case, this can also be a spherical radius. Special visual properties, such as astigmatism (including the rotation angle of the astigmatism) or imaging properties for peripheral vision, can also be achieved via the inner radius.The outer radius is advantageously selected so that the correction possibilities offered by the inner radius are not negatively affected. For example, a relatively short outer radius should be chosen for strongly positive diopter values.

[0003] Depending on the required diopter value, the resulting lens can be more or less curved, which, at high diopter values, can sometimes result in a less aesthetically pleasing appearance and poor wearing comfort. In particular, with sports lenses and their desired close-fitting shape, it is very difficult to create negative diopter values.

[0004] It is also known that a dioptric effect can be generated by means of a diffractive optical element (DOE). Since diffractive optical elements have a very strong dispersion compared to refractive optics, their effect can only be used in very measured doses. At an effect of ±2 diopters, strong chromatic aberrations occur, especially lateral color fringing at the field edge, which are no longer tolerable.

[0005] Color aberrations include longitudinal chromatic aberration, which creates different foci for different wavelengths. This is also known as axial deviation or longitudinal chromatic aberration. In addition to longitudinal chromatic aberration, another type of color aberration is lateral chromatic aberration, which manifests as color fringes or edges in the image plane, or, in the case of corrective lenses, on the retina of the eye. These fringes are perceived by the user and, above a certain intensity, are considered bothersome. Lateral chromatic aberration is also known as chromatic magnification error or transverse chromatic aberration. German patent DE 10 2010 047 846 A1 discloses a combination of a first lens element and a second lens element that interact at least partially achromatically. However, the use of a diffractive optical element is not disclosed in this context. Instead, conventional lens elements are employed.

[0006] Document US 2006 / 0050234 A1 discloses a diffractive lens for correcting refractive errors. The lens comprises a combination of a first diffractive optical element (WSD) and a second diffractive optical element (MOD). The second diffractive element provides the basic refractive power, or the primary focusing effect of the lens. The first diffractive element provides only additive near-vision correction.

[0007] In US 2006 / 0050234 A1, the second diffractive element is a so-called multiorder diffractive (MOD) lens, which directs light of several different wavelengths from different diffraction orders to a common focal distance. For example, green light (λg = 550 nm) from the fifth diffraction order and blue light (λb = 471 nm) from the seventh diffraction order are directed to the same focal distance. Such a MOD structure is also referred to as a polychromatic diffractive lens.

[0008] In addition to the basic refractive power of the second diffractive element (MOD), the first diffractive element (WSD) provides an additive focusing effect for near-field correction. For this purpose, light of different diffraction orders is simultaneously directed to two or more different focal distances. The first optical element is referred to as a "wavefront splitting diffractive structure" (WSD). Here, too, only a limited amount of diffractive power can be added in order to keep chromatic aberration within acceptable limits.

[0009] The first and second diffractive elements of US 2006 / 0050234 A1 work together in such a way that the MOD provides a basic refractive power and the WSD creates a multifocal effect. Because the WSD has a much lower optical refractive power than the MOD, chromatic aberration caused by the first diffractive element (WSD) is kept to a minimum. However, mutual compensation of chromatic aberration is not disclosed.

[0010] One disadvantage of this approach, however, is that chromatic aberration, particularly lateral chromatic aberration, remains. Furthermore, unlike progressive lenses, WSDs provide multiple focal distances simultaneously rather than separating them geographically on the lens, which is only partially desirable. DE 10 2006 061 066 A1 discloses a double DOE arrangement that strongly separates unwanted orders, which are then blocked by subsequent lens mounts and / or apertures as the light propagates through the optical system in the direction of useful light propagation, or arrive outside the intended image area when passing through the optical system. US 5,117,306 discloses a bifocal diffractive optical lens with two focal points or focal distances. It is proposed to provide different or matched chromatic aberrations for the different focal points.EP 1 072 906 A2 discloses a diffractive optical element which is intended to improve the wavelength dependence of a diffraction efficiency.

[0011] The invention is therefore based on the objective of providing an improved ophthalmological optical element, improved spectacles and a head-worn display device with such an ophthalmological optical element, an improved computer-implemented method for designing an ophthalmological optical element, an improved method for manufacturing an ophthalmological optical element, and a corresponding computer program product, which at least partially overcome the disadvantages of conventional prescription spectacles and the prior art described above.

[0012] According to a first aspect of the invention, it is therefore proposed to provide an ophthalmological optical element for correcting visual defects, witha first refractive optical substrate having a positive or negative first optical refractive power; a first diffractive optical element having a second optical refractive power; a second diffractive optical element having a third optical refractive power; wherein the first diffractive optical element and the second diffractive optical element have opposite optical refractive powers, and the sum of the second optical refractive power of the first diffractive optical element and the third optical refractive power of the second diffractive optical element divided by the difference between the second optical refractive power and the third optical refractive power is less than 1 / 10, in particular less than 1 / 15, and in particular less than 1 / 20. In particular, the first diffractive optical element and the second diffractive optical element interact at least partially achromatically.In particular, the first diffractive optical element and the second diffractive optical element can interact achromatically together with the first refractive optical element.

[0013] The dioptric power of the ophthalmic optical element results primarily from the sum of the first, second, and third refractive powers. Since the first diffractive optical element (DOE) and the second diffractive optical element have opposite refractive powers, or refractive powers with opposite signs, the contributions of the second and third refractive powers at least partially cancel each other out. The inventors discovered that, surprisingly, combining the two diametrically opposed DOEs, or DOEs with opposite refractive powers, reduces lateral chromatic aberration, making it even lower than that of conventional, classically optimized refractive lenses. Therefore, by using two DOEs with opposite refractive powers, a specific diopter requirement can be met while simultaneously achieving good optical performance even at the periphery of the field of vision.

[0014] The first diffractive optical element and the second diffractive optical element have approximately equal optical refractive powers. The magnitude of the sum of the second optical refractive power of the first diffractive optical element and the third optical refractive power of the second diffractive optical element, divided by the magnitude of the difference between the second optical refractive power and the third optical refractive power, is less than 1 / 10, in particular less than 1 / 15, and in particular less than 1 / 20. K = D 2 + D 3 D 2 − D 3 ≤ x mit x ≤ 1 10 , insbesondere x ≤ 1 15 , insbesondere x ≤ 1 20 , where D2 denotes the second optical refractive power and D3 the third optical refractive power. Since D2 and D3 have opposite signs, the magnitude of the sum | D 2 +D 3| less than the absolute value of the difference | D 2- D 3|. The quotient given in equation (1) can also be referred to as contrast or contrast value K.

[0015] It is proposed to provide an ophthalmic optical element with a first refractive optical substrate having a positive or negative first optical refractive power; a first diffractive optical element having a second optical refractive power; a second diffractive optical element having a third optical refractive power; wherein the first diffractive optical element and the second diffractive optical element have opposite optical refractive powers, wherein the magnitude of a sum of the second optical refractive power of the first diffractive optical element and the third optical refractive power of the second diffractive optical element divided by a magnitude of a difference between the second optical refractive power and the third optical refractive power may be less than 1 / 10, in particular less than 1 / 15, in particular less than 1 / 20.

[0016] Contrary to the usual practice of those skilled in the art, which is to select the smallest possible refractive power of a single DOE due to the typically strong chromatic aberration of DOEs, it is proposed to provide two DOEs with higher refractive power and opposite signs. The resulting refractive power is obtained, in particular, from the sum of the second and third refractive powers. The inventors have recognized that by having the first and second DOEs have approximately the same optical refractive power, as defined by the above, advantageous mutual compensation of chromatic aberrations, including lateral chromatic aberrations, can be achieved. The first and second DOE can thus interact at least partially achromatically. The additional refractive power resulting from the sum of the two DOEs can constitute a very significant portion of the total refractive power. Typically, for example, + / - 3 diopters can be added by the two DOEs.When using a single DOE, typically only a refractive power of approximately 0.1 to 0.3 diopters can be added for comparison, otherwise the chromatic aberrations would increase too much.

[0017] Another advantage of the proposed solution is that only a few first optical substrates need to be kept on hand. Preferably, only one or two optical substrates with positive or negative refractive power are required. Further adjustment to the user's visual acuity can be made by the first and second DOE.

[0018] A further advantage of the proposed solution is that an aesthetically pleasing lens shape can be achieved even with high positive or negative diopter values. Correction beyond the refractive power of the first refractive optical substrate can be achieved using DOEs. Preferably, this eliminates the need for lenses with high center or edge thickness, resulting in a reduction in material and weight.

[0019] Another advantage of the proposed solution may be that almost any optical effect can be achieved, since the DOE effect can be based on mathematically general xy-DOEs.

[0020] Another advantage of the proposed solution is that progressive lens or multi-area functions, such as those found in bifocal glasses, can also be implemented without significant effort.

[0021] Another advantage of the proposed solution is that sports glasses or glasses with a predetermined strong front curvature can also be fitted with refractive corrections.

[0022] Unless otherwise stated, the terminology used in this application corresponds to the definitions in the standard DIN EN ISO 13666:1998-11 of the German Institute for Standardization (DIN).

[0023] Within the scope of this disclosure, an "ophthalmological optical element" can be understood to mean an optical element that serves to correct visual defects, in particular eyeglasses or spectacle lenses, contact lenses, but also an intraocular implant or the like. With regard to materials, for example, a spectacle lens includes not only inorganic or mineral glass but also organic material or plastic.

[0024] Refractive power is defined as the reciprocal of the focal length f. The unit of refractive power is the diopter (1 dptr = 1 m - 1). In other words, refractive power can be used to specify the dioptric effect, particularly a focusing effect, of a refractive lens or diffractive optical element. The required effect should occur at a design reference point, which may be located on the back surface of the respective element. A prismatic effect can occur at a prism reference point, which may differ from the design reference point.

[0025] In the context of the present invention, "at least partially interacting achromatically" or "interacting achromatically" means that the color error or errors are not necessarily completely eliminated, but at least reduced.

[0026] The term "optical axis" refers to a straight line that is perpendicular to both optical surfaces of a spectacle lens and along which light passes through the spectacle lens without deflection, cf. No. 4.8 of the standard DIN EN ISO 13666.

[0027] In the context of this application, a "cross-sectional plane" is understood to be a cross-section through the ophthalmic optical element that lies parallel to a user's intended principal line of sight through the optical element. The cross-sectional plane may be a meridian plane if the optical element has an optical axis. For example, if a spectacle lens does not have an optical axis, the cross-sectional plane may contain the geometric center according to section 5.5 of the standard DIN EN ISO 13666, namely the intersection of the horizontal and vertical center lines of the lens box, relative to the shape of the unrimmed spectacle lens. A "geometric central axis" then runs through the geometric center parallel to an intended principal line of sight through the optical element. Thus, the cross-sectional plane may contain the point of sight according to section 5.11 of the standard DIN EN ISO 13666, namely the intersection of the fixation line with the back surface of the optical element.

[0028] According to a second aspect of the invention, a computer-implemented method for designing an ophthalmic optical element, in particular a spectacle lens, for a user is further proposed, wherein the ophthalmic optical element a first optical substrate having a positive or negative first optical refractive power; a first diffractive optical element having a second optical refractive power; and a second diffractive optical element having a third optical refractive power; wherein the first diffractive optical element and the second diffractive optical element have opposite optical refractive powers; wherein the method comprises the following steps: selection of the first optical substrate having a positive or negative first optical refractive power according to a diopter range to be corrected; provision of the first diffractive optical element having the second optical refractive power and the second diffractive optical element having the third optical refractive power.In particular, the first diffractive optical element and the second diffractive optical element interact at least partially achromatically.

[0029] In this way, an ophthalmic optical element can be designed that offers the advantages described above. The selection of the first optical substrate, which has a first positive or negative optical refractive power, can preferably be based on a diopter range to be corrected. In other words, the first optical substrate can provide a base refractive power for a range of diopter values ​​to be corrected for users. For example, one first optical substrate can serve as the base for a range of, say, 0 to +4 diopters, and an alternative first optical substrate can be selected for a range of, say, +4 to +8 diopters. Adjusting the resulting effect of the ophthalmic optical element to the user's diopter value to be corrected in the respective range can then be achieved using the first and second diffractive optical elements.

[0030] The first and second diffractive optical elements are selected such that they have approximately equal optical refractive powers. The first and second diffractive optical elements are selected such that the sum of the second optical refractive power of the first diffractive optical element and the third optical refractive power of the second diffractive optical element, divided by the difference between the second and third optical refractive powers, is less than 1 / 10, in particular less than 1 / 15, and in particular less than 1 / 20.

[0031] According to a third aspect of the invention, a method for manufacturing an ophthalmic optical element is further proposed, comprising the steps of designing the ophthalmic optical element according to the second aspect of the invention and further comprising the step of manufacturing the ophthalmic optical element.

[0032] In this way, an ophthalmic optical element can be produced that has the advantages described above.

[0033] According to a fourth aspect of the invention, a computer program product with program code is further proposed which is designed to execute a method according to the second aspect of the invention or one of its embodiments when the computer program product is executed on a data processing device.

[0034] The computer program product thus enables the design of an ophthalmic optical element as described above and therefore has the same advantages.

[0035] According to a fifth aspect of the invention, a pair of glasses with a frame and a first and a second lens is further proposed, wherein the first and / or second lens is an ophthalmological optical element according to the first aspect of the invention or one of its embodiments.

[0036] The glasses can therefore offer the advantages described above. In particular, the glasses can have a predetermined strong front curvature and still be fitted with refractive error correction. This is especially advantageous for close-fitting glasses such as sports glasses.

[0037] In one embodiment of the ophthalmic optical element according to the first aspect of the invention, it can be provided that the first optical substrate has a front surface and a rear surface, wherein the first diffractive optical element is arranged on the side of the front surface and / or the second diffractive optical element is arranged on the side of the rear surface.

[0038] The term "front surface" or "object-side surface" refers to the surface of the first optical refractive substrate that faces away from the user's eye when the ophthalmic optical element is used as intended. The term "back surface" or "eye-side surface" refers to the surface of the first optical refractive substrate that faces towards the user's eye when the ophthalmic optical element is used as intended. The terms "first optically active surface" and "second optically active surface" may also be used instead of "front surface" and "back surface."

[0039] In one embodiment of the ophthalmic optical element according to the first aspect of the invention, it may be provided that the ophthalmic optical element has a second optical substrate which includes the first diffractive optical element and / or the second diffractive optical element.

[0040] In this way, the first refractive optical substrate can preferably be used unchanged for a large number of users. This simplifies and standardizes manufacturing.

[0041] In a further development of this embodiment, the first optical substrate can have a front surface and a rear surface, wherein the second optical substrate is arranged on the side of the front surface or the rear surface of the first optical substrate.

[0042] Preferably, the second optical substrate is arranged on the back surface of the first optical substrate. Furthermore, the second optical substrate preferably comprises both the first and the second DOE. In this way, one or more standardized first refractive optical substrates can be used, which can then be adapted or customized for the user by selecting the DOEs on the second optical substrate.

[0043] In particular, the second optical substrate can be a film, glass, or plastic shell. For example, the second optical substrate can be a film incorporating both the first and second DOE. Such a film can preferably be applied to the back surface of the first refractive optical substrate. The first optical substrate can provide the necessary mechanical stability to the arrangement. In particular, a film or plastic shell can be manufactured cost-effectively. By arranging the second optical substrate on the back surface of the first optical substrate, it can be protected from damage such as scratching.

[0044] In one embodiment of the ophthalmic optical element, a cement layer or an air gap can be provided between the first optical substrate and the second optical substrate. More generally, a medium with a different refractive index can be located between the first optical substrate and the second optical substrate.

[0045] Preferably, the first optical substrate and the second optical substrate can be cemented together. In cementing, adjacent surfaces, in this case, for example, a back surface of the first optical substrate and a front surface of the second optical substrate, are bonded together using a thin, transparent cement layer. For example, a synthetic resin can be used for this purpose. Furthermore, it is also possible to connect the first optical substrate and the second optical substrate by pressure bonding. This manufacturing method is also known as pressure bonding. Here, the surfaces are joined together by molecular attraction forces.

[0046] In one embodiment, the first and / or second diffractive optical element can be manufactured by laser beam writing, stamping, holographic exposure, and / or photolithography.

[0047] In this way, it is possible to provide a cost-effective first and / or second DOE according to requirements, for example by stamping. Alternatively or additionally, more complex DOEs can also be realized using processes such as holographic exposure and / or photolithographic processes.

[0048] In one embodiment of the ophthalmic optical element, the first and / or second diffractive optical element can be rotationally symmetric about an optical axis.

[0049] One advantage of this embodiment is its cost-effective manufacturing. The first and / or second DOE can be provided with a rotationally symmetric phase function and optionally the same coordinate origin. Likewise, in the case of holographic exposure, the DOEs can be designed as holographic optical elements (HOEs), which are optionally exposed axially symmetrically and have the same origin. From a manufacturing perspective, HOEs can be exposed independently and sequentially, preferably onto appropriately thin plastic sheets, and then bonded to the first diffractive optical element. Mounting using spacers is also possible if, for example, an air gap is used instead of a cement layer.

[0050] In one embodiment, the first and / or second DOE in the cross-sectional plane can be described by a second- or higher-order polynomial. In particular, a third- or fourth-order polynomial can be provided, for example. A third-order polynomial can, for example, be formed in the form P(y) = A|y| 3< +B|y| 2< +C|y|+D, where A, B, C, and D are constants.

[0051] The coefficients of the polynomial can be optimized using a ray tracing method. Such ray tracing methods are generally familiar to the average person. They are described, for example, in "Robert R. Shannon, The Art and Science of Optical Design, Cambridge University Press, 1997". In this way, it is possible to design an ophthalmic optical element, at least approximately, in accordance with the second aspect of the present disclosure and to further optimize the design. The optimization step can be performed significantly faster, particularly due to the solutions initially found, at least approximately. Furthermore, this saves resources on the data processing equipment used for this purpose.

[0052] Preferably, the first and second diffractive optical element (21,22) in a cross-sectional plane can each be described by a second- or higher-order phase polynomial, wherein between a first coefficient a 1 ,DOE 1 of the phase polynomial of the first diffractive optical element and a first coefficient a 1 ,DOE 2 of the phase polynomial of the second diffractive optical element with a tolerance range of ±20%, in particular ±10%, in particular ±5%, the following relationship applies: a 1 , DOE 1 a 1 , DOE 1 + a 1 DOE 2 = 20 D d , where D represents a resultant additional optical refractive power due to the first and second diffractive optical elements, and d is a distance between the first and second diffractive optical elements. According to the opposite signs of the second and third refractive powers of the first and second diffractive optical elements, the coefficients can be a 1 ,DOE 1 and a 1 ,DOE The values ​​of the first and second diffractive optical elements have different signs. Furthermore, the following relationship can hold, also with the tolerances mentioned above: a 1 , DOE 1 − a 1 DOE 2 = D 1000 where λ 0 specifies a design wavelength of, for example, 546nm.

[0053] In one embodiment, the ophthalmic optical element can further exhibit an astigmatic effect and / or a differently focusing effect in the near and far parts.

[0054] An additional corrective effect can generally be provided, in particular astigmatism correction and / or progressive or near-vision correction. This effect can be achieved by the first refractive optical element and / or by the first and / or second DOE, or any combination thereof. In particular, an additional corrective effect can be advantageously achieved when manufacturing a DOE by holographic exposure with, for example, deformed wavefronts. Furthermore, astigmatism correction, including the necessary rotation angle, can be provided, for example, by incorporating a cylindrical optic.

[0055] In one embodiment, the method according to the second aspect of the present invention can be further characterized in that the selection of the first optical substrate is made from a set of predetermined first optical substrates. Each of the predetermined optical substrates can serve as the basis for a diopter range to be corrected. For example, the set of predetermined first optical substrates comprises at least one of the following diopter ranges: 0...+5 dptr, 0...-5 dptr, +5...+8 dptr, and -5...-8 dptr.

[0056] One advantage of this design is that only a limited number of first optical substrates need to be kept on hand. This is particularly advantageous for a head-mounted display device, as described in the sixth aspect, which will be explained further below.

[0057] The grating frequencies required to ensure the necessary optical functions increase the further a user's desired diopter value deviates from the initially selected diopter value of the first refractive optical element. To avoid excessive spread, it may therefore be advisable to provide a set of predefined optical substrates, each covering a portion of a larger range.

[0058] In a further embodiment, one substrate of the set of predefined first optical substrates can, for example, serve as the basis for a diopter range of at least 2, in particular at least 3, and in particular at least 4 diopters. The diopter ranges can overlap.

[0059] According to a sixth aspect of the invention, a head-mounted display (HMD) with an ophthalmic optical element according to the first aspect of the present invention is proposed, wherein the ophthalmic optical element further comprises a coupling optic configured to couple an image to be displayed by means of the first optical substrate of the ophthalmic optical element.

[0060] A head-mounted display (HMD) is a visual output device worn on the head or worn on the head. In particular, it can be an overhead display (OHMD), which allows the user to see through the display. Such devices are especially advantageous in augmented reality applications. An HMD can present images, particularly on a screen close to the eye, or project them directly onto the retina.

[0061] Preferably, the first optical substrate is designed to guide light of the image to be displayed through total internal reflection in the first optical substrate and further comprises a combiner optic as coupling optic which, when used as intended, lies from the eye to the

[0062] The problem with head-mounted displays (HMDs) is that different diopter requirements usually necessitate the design of a new HMD coupling optic for each one, or the use of a combination with a standard prescription lens. This either results in significant complexity or the use of a sandwich-like construction, which would make the overall glasses very thick.

[0063] According to the proposed solution, a standardized first refractive optical element (DOE) can be used for an entire diopter range or sub-range, incorporating HMD coupling and output optics. Individualization is achieved by providing a first and second DOE, as described above, on the rear surface of the first optical element. This allows the DOEs to function for both the transmitted and reflected light channels, enabling the same HMD or first optical element to be used for multiple prescriptions. This simplifies manufacturing and reduces costs.

[0064] In one embodiment, the ophthalmic optical element can have an input optic and / or output optic for an HMD, which is configured to couple in and / or out an image to be displayed by means of the first optical substrate of the ophthalmic optical element. It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified, but also in other combinations or individually, without departing from the scope of the present invention.

[0065] Embodiments of the invention are illustrated in the drawing and explained in more detail in the following description. The drawing shows: Fig. 1 a sectional view of an ophthalmic optical element according to a first embodiment; Fig. 2 a sectional view of an ophthalmic optical element according to a second embodiment; Fig. 3 a top view of an ophthalmic optical element according to a further embodiment; Fig. 4 a schematic representation of a head-mounted display device (HMD) with an ophthalmic optical element similar to the first embodiment. Fig. 1 Fig. 5 a flowchart of a method for designing an ophthalmic optical element; Fig. 6 another flowchart of a method for designing an ophthalmic optical element; Fig. 7 a representation of a lateral chromatic aberration in an ophthalmic optical element according to one aspect of the present invention; Fig. 8 a representation of a lateral chromatic aberration in a conventional spectacle lens; Fig. 9 another representation of a lateral chromatic aberration in an ophthalmic optical element according to one aspect of the present invention; Fig. 10 another representation of a lateral chromatic aberration in a conventional spherical spectacle lens; Fig. 11 a representation of an MTF in an ophthalmic optical element according to one aspect of the present invention; Fig. 12 a representation of an MTF in a conventional spectacle lens with a spherical inner radius; and Fig.13. A representation of an MTF in a conventional spectacle lens with a freeform inner surface.

[0066] Fig. 1 Figure 1 shows a cross-sectional view of an ophthalmic optical element 1 according to a first embodiment, for example, a spectacle lens. The ophthalmic optical element 1 comprises a first refractive optical substrate 10, which has a positive or negative first optical refractive power, a first diffractive optical element (DOE) 21, which has a second optical refractive power, and a second diffractive optical element 22, which has a third optical refractive power, wherein the first diffractive optical element 21 and the second diffractive optical element 22 have opposite optical refractive powers and wherein the first diffractive optical element 21 and the second diffractive optical element 22 interact at least partially achromatically.The first diffractive optical element 21 and the second diffractive optical element 22 can have approximately the same refractive power, but with different signs, so that the first diffractive optical element 21 and the second diffractive optical element 22 interact at least partially achromatically.

[0067] Fig. 1 Figure 1 shows a preferred embodiment in which an object-side front surface 11 of the first optical substrate 10 is convex for aesthetic reasons. Preferably, an eye-side rear surface 12 of the first optical substrate 10 is concave, also for aesthetic reasons. The refractive power of the first refractive optical substrate 10 is determined in particular by the radii of the front surface 11, the rear surface 12, and the thickness of the substrate 10.

[0068] In the Fig. 1 In the illustrated embodiment, a second optical substrate 30 is arranged on the rear surface 12 of the first optical substrate 10. The second optical substrate 30 has the first diffractive optical element 21 on an object-side front surface 31 and the second diffractive optical element 22 on an eye-side rear surface 32. Alternatively, the second diffractive optical element 22 can also be arranged on the rear surface 12 of the first optical substrate 10.

[0069] The second optical substrate 30 can, for example, be a plastic tray or film, such as a grating film with a front-side, first diffraction grating for the first diffractive optical element 21 and a rear-side, second diffraction grating for the second diffractive optical element 22.

[0070] The second optical substrate 30 can be bonded or cemented to the first optical substrate 10. Mounting using spacers is also possible if, for example, an air gap is used instead of a cement layer. For this purpose, the [missing information] is located in the Fig. 1 In the example shown, an air gap or cement layer 13 exists between the back surface 12 of the first optical substrate 10 and the front surface 31 of the second optical substrate 30. The air gap or cement layer 13 can have a refractive index that differs from that of the first and / or second optical substrate 10, 30.

[0071] A protective layer 40 can optionally be provided on the rear surface 32 of the second optical substrate 30, which protects the second DOE 22, for example, from mechanical damage. The protective layer 40 has a refractive index that differs from that of the second optical substrate 30. A protective layer can also optionally be provided on the front surface 11 of the first optical substrate 10.

[0072] In Fig. 1 Furthermore, examples of incident beams 40a, 40b from infinity are shown, which are directed to an entrance pupil 41 of a user's eye through the ophthalmic optical element 1.

[0073] In a specific embodiment, the first optical element 1 can be designed for a diopter range of 0 to -4 dptr, a pupil diameter of 3 mm, and a field of view of + / - 25 degrees. For cost-effective manufacturing, one or more front and / or back surfaces can be spherical. In this example, R1 denotes a radius of a back surface 42 of the protective layer 40, R2 the radius of the back surface 32 of the second optical element 30, R3 the radius of the front surface 31 of the second optical element, R4 the radius of the back surface 12 of the first optical element 10, and R5 the radius of the front surface 11 of the first optical element 10. In this example, D1 denotes a thickness of the protective layer 40, D2 a thickness of the second optical element 30, D3 a thickness of the cement layer 13, and D4 a thickness of the first optical element 10. The values ​​for the first optical element 1 according to this embodiment can be chosen as follows: R1 = 112.17 mm (cc) D1 = 0.1 mm R2 = 112.27 mm (cc) D2 = 0.25 mm R3 = 112.57 mm (cc) D3 = 0.1 mm R4 = 112.67 mm (cc) D4 = 2.0 mm R5 = 120.00 mm (cc) The abbreviation "cc" indicates that the surface can be concave. This allows for an appealing aesthetic.

[0074] The first and / or second diffractive optical element 21, 22 can be provided with a rotationally symmetric phase function and optionally the same coordinate origin. Such a structure is shown as an example in the top view in Fig. 3 shown. Section II denotes the cross-sectional plane according to Fig. 1 .

[0075] In this embodiment, a sixth-order phase polynomial can be chosen for the first DOE 21 and for the second DOE 22. In the present example, preferably only the even terms are considered, with: P y : = ∑ i = 1 N a i y 2 i λ H mit i = 1 … N und N = 3 , where y is a radial height on the DOE, i.e., a radial distance from the center (see 0 in Fig. 3 ) specifies the diopter value and λH is a design wavelength, for example, λH = 546 nm. The coefficients ai can be selected according to a desired diopter value. The design wavelength λH can optionally already be included in the coefficients ai. In the coefficient sets given below as examples, the design wavelength λH is already included in the coefficients ai.

[0076] One advantage of this solution is that the same first refractive optical element 10 can serve as the basis for several desired diopter values ​​for different users. This allows the manufacturing of the first optical element to be standardized, thereby reducing production costs. Adaptation to a user's desired diopter value can be achieved by selecting the coefficients ai of the phase polynomial of the first and second DOEs 21, 22. In the present example, the following coefficient sets can be chosen: Coefficient set at -1 dptr Koeffizient DOE1 DOE2 a1 -0.4274E-01 0.4363E-01 a2 -0.2732E-04 0.2791E-04 a3 0.2187E-06 -0.2270E-06 Coefficient set at -2 diopters Koeffizient DOE1 DOE2 a1 0.3751E-01 -0.3616E-01 a2 -0.7081E-04 0.6560E-04 a3 0.2261E-06 -0.2001E-06 Coefficient set at -3 diopters Koeffizient DOE1 DOE2 a1 0.4882E-01 -0.4671E-01 a2 -0.1107E-03 0.1015E-03 a3 0.3310E-06 -0.2871E-06 Coefficient set at -4 diopters Koeffizient DOE1 DOE2 a1 0.6123E-01 -0.5808E-01 a2 -0.1668E-03 0.1512E-03 a3 0.4874E-06 -0.4139E-06

[0077] In the present example, the first optical substrate 10 and the second optical substrate 30 are made of a first transparent material, here polycarbonate. The cement layer 13 and protective layer 40 are made of a second transparent material, here PMMA, which has a different refractive index. Polycarbonate can have a refractive index n1 = 1.49 and PMMA a refractive index n2 = 1.6.

[0078] It is understood that the respective numerical values, i.e. radii of the respective surfaces and / or coefficients of the first and second DOEs 21, 22, can be obtained by computer-aided optical simulation or optimization for a respective desired diopter value and a desired geometry.

[0079] According to one aspect of the present disclosure, the interpretation of the first DOE 21 and the second DOE 22 is subject to the boundary condition that the magnitude of the sum of the second optical refractive power of the first diffractive optical element 21 and the third optical refractive power of the second diffractive optical element 22, divided by the magnitude of the difference between the second optical refractive power and the third optical refractive power, is less than 1 / 10, in particular less than 1 / 15, and in particular less than 1 / 20. By choosing the second and third refractive powers to be approximately equal in magnitude and to have opposite signs, a low lateral chromatic aberration can be achieved. This quotient, also given in equation (1), can be referred to as the contrast or contrast value K.

[0080] For an additional diopter value D to be corrected by the combination of first and second DOE 21, 22 and a distance between the first and second DOE d, exemplary contrast values ​​K are given below: D [dptr] d [mm] K = D 2 + D 3 D 2 − D 3 1 0.5 54.7 1 1.0 38.9 1 1.5 31.8 2 0.5 38.5 2 1.0 27.4 2 1.5 22.5 3 0.5 31.3 3 1.0 22.3 3 1.5 18.3 4 0.5 26.9 4 1.0 19.2 4 1.5 15.8 For the same diopter value, the contrast values ​​at different distances of the DOEs are preferably proportional to d1 / d2 , where d1 and d2 specify the distances between the DOEs. A distance between the DOEs can be defined as the distance between the DOEs along the optical axis.

[0081] As described at the beginning, the grating frequencies that a diffractive optical element must achieve to guarantee an optical effect, such as a desired refractive power, are higher the greater the desired additional effect of the combination of the first and second DOEs 21, 22. However, a high grating frequency and the associated small feature sizes can increase the manufacturing requirements. It is therefore recommended to subdivide a diopter range to be covered, for example, from -8 Dptr to +8 Dptr, into several diopter ranges. For example, into the ranges -8 Dptr to -4 Dptr, -4 Dptr to 0 Dptr, 0 Dptr to +4 Dptr, and 4 Dptr to 8 Dptr. The final adjustment to the user's value can then be made using the first and second DOEs.

[0082] In the Fig. 2 Figure 1 is a schematic cross-sectional view of another possible embodiment of an ophthalmic optical element 1. The same elements are again labelled with the same reference numerals and are not described again. Only the differences are discussed below.

[0083] In the Fig. 2 In the illustrated embodiment, the first DOE 21 is arranged on an object-side front surface 11 of the first refractive optical substrate 10. The second DOE 22 can be arranged on an eye-side rear surface 12 of the first refractive optical substrate 10. Preferably, a protective layer 40 can be provided which protects the first and / or second DOE 21, 22.

[0084] Fig. 4 Figure 1 shows a simplified schematic representation of a head-mounted display device (HMD) 60 with a further development of an ophthalmic optical element 1 according to one aspect of the present invention, as described with reference to Figure 2. Fig. 1 described.

[0085] The ophthalmic optical element 1 further comprises a coupling optic 61, which is designed to couple an image to be displayed by means of the first optical substrate 10 of the ophthalmic optical element 1.

[0086] The HMD 60 further comprises an image source 62 which provides an image to be displayed. The image to be displayed can optionally be coupled into the first optical substrate 10 via another element 63.

[0087] In the Fig. 4 In the example shown, the components of the HMD are greatly simplified. For instance, the image to be displayed is coupled from the image source 62 into the first optical substrate 10 via a first mirror 63 and coupled out of the optical substrate via a second mirror 61, or rather coupled into the beam path to the eye. Preferably, the mirror 61 can be a semi-transparent mirror, so that the user can still perceive light 40a from their surroundings. This is particularly advantageous for augmented reality applications.

[0088] The HMD can also utilize diffractive input and output coupling structures, as described, for example, in Levola, "Diffractive optics for virtual reality displays", Journal of the Society for Information Display, Volume 14, Issue 5, pages 467-475, May 2006.

[0089] An advantage of this embodiment is that the same first optical substrate 10 can be used for several different diopter values. Final diopter adjustment can be achieved by the first and second DOE 21, 22, which are arranged on the side of a rear surface 12 of the first optical substrate 10. For this purpose, a second optical substrate 30 can be provided, as described with reference to Fig. 1 described.

[0090] Fig. 5 Figure 1 shows a flowchart of a computer-implemented method for designing an ophthalmic optical element 1, in particular a spectacle lens, for a user, wherein the ophthalmic optical element comprises a first optical substrate having a positive or negative first optical refractive power; a first diffractive optical element having a second optical refractive power; and a second diffractive optical element having a third optical refractive power; wherein the first diffractive optical element and the second diffractive optical element have opposite optical refractive powers and wherein the first diffractive optical element and the second diffractive optical element preferably interact at least partially achromatically.

[0091] In the first step, S101, a first optical substrate, which has a positive or negative first optical refractive power, is selected according to the diopter range to be corrected. The first optical substrate can be selected from a set of predefined first optical substrates, each of which serves as the basis for a diopter range to be corrected. For example, if the user requires a correction of -3 dptr, then a first optical substrate designed for a diopter range of -4 dptr to 0 dptr can be selected.

[0092] In a second step S102, the first diffractive optical element, which has the second optical refractive power, and the second diffractive optical element, which has the third optical refractive power, are selected.

[0093] The first and second diffractive optical elements are preferably selected such that the sum of the second optical refractive power of the first diffractive optical element and the third optical refractive power of the second diffractive optical element divided by the difference between the second optical refractive power and the third optical refractive power is less than 1 / 10, in particular less than 1 / 15, in particular less than 1 / 20.

[0094] Fig. 6 Figure 1 shows another flowchart of a method for designing an ophthalmic optical element. With such a method, a required diopter value, or optionally a specifically optimized refractive error correction, can preferably be achieved from a few, easily manufactured, and optically appealing basic shapes of the first optical substrate.

[0095] In a first step S201, a diopter range to be corrected with an identical first refractive optical substrate, also referred to as carrier glass, is selected, for example from -4 dptr to 0 dptr or from +4 dptr to +7 dptr.

[0096] In a second step S202, the radius of the front surface 11 and the radius of the rear surface 12 of the first refractive optical substrate 10 can be optimized using conventional methods for, for example, a mean diopter value from this diopter range. This determines the first optical refractive power of the first refractive optical substrate 10. Preferably, the front surface 11 and the rear surface 12 are spherical. An advantage is the simple, cost-effective manufacturing with high quality.

[0097] In a third step S203, a first diffractive optical element (DOE) 21 with a second refractive power and a second diffractive optical element 22 with a second refractive power are provided, in particular the following possibilities: (a) One DOE is applied to the front surface of the first optical substrate 10 and the other DOE is applied to the rear surface of the first optical substrate 10, as for example in Fig. 2 (b) A second optical substrate is provided, wherein one DOE is applied to the front surface of the second optical substrate and the other DOE is applied to the rear surface of the second optical substrate, as shown, for example, in Fig. 1 shown. (c) A hybrid form can be chosen, wherein one DOE is applied to a front or back surface of the first optical substrate and the other DOE is applied to a front or back surface of the second optical substrate.

[0098] The first and second DOE 21, 22 are selected such that they possess approximately the same optical power in magnitude, but with opposite signs, for the corresponding diopter requirement. As described at the beginning, the resulting refractive power of the ophthalmic optical element 1 is obtained, in particular, from the sum of the first, second, and third refractive powers.

[0099] In a fourth step S204, a simultaneous optimization for several support points, i.e., several desired diopter values, can be carried out from the diopter range to be corrected, e.g. -4 dptr to 0 dptr, in which the coefficients of the DOEs 21, 22 are optimized together with the specified first optical substrate from step S202.

[0100] Preferably, in this optimization, the radius of the front surface 11 of the first refractive optical substrate 10 can be kept constant, whereas, in particular, the radius of the rear surface 12 of the first optical substrate 10 and, if applicable, the radii of the optional second optical substrate 30 as well as the distances of the DOEs within permissible limits can be optimized. This allows for an appealing aesthetic design.

[0101] Computer-aided optimization methods, including ray tracing techniques, are generally familiar to the average professional. For example, commercially available products such as Code V or Zemax can be used. However, the crucial factor when using such solutions is the choice of boundary conditions in order to achieve a favorable result.

[0102] In particular, the inventors have recognized that a low lateral chromatic aberration can be achieved if the first and second diffractive optical elements are selected such that the sum of the second optical refractive power of the first diffractive optical element and the third optical refractive power of the second diffractive optical element, divided by the difference between the second optical refractive power and the third optical refractive power, is less than 1 / 10, in particular less than 1 / 15, in particular less than 1 / 20.

[0103] The Fig. 7 bis Fig. 13 show exemplary simulation results of ophthalmic optical elements according to aspects of the present invention in comparison to conventional classic spectacle lenses.

[0104] Fig. 7 bis Fig. 10 These graphs show representations of lateral chromatic aberration. The horizontal axis indicates the lateral chromatic aberration µ in millimeters. The vertical axis indicates the viewing angle θ of the visual field from 0° to 25°. The scale of the axes is in Fig. 7 bis Fig. 10 For better comparability, the values ​​are identical. The chromatic aberration for long-wavelength light, for example at a wavelength of 643 nm, is represented by a dashed line 71. A chromatic aberration for short-wavelength light, for example at 480 nm, is represented by a solid line 72. A maximum chromatic aberration over the angular range from 0° to 25° is indicated by a double arrow 73.

[0105] Fig. 7 und Fig. 8 show the lateral chromatic aberration at a dioptric power of +3 dptr. Fig. 9 und Fig. 10 show the lateral chromatic aberration at a dioptric power of +4 dptr.

[0106] Fig. 7 and Fig. 9 show a representation of a lateral chromatic aberration in an ophthalmic optical element according to one aspect of the present invention, as for example in Fig. 1 depicted. Fig. 8 and Fig. 10 show a corresponding representation of a lateral chromatic aberration for a conventional spherical spectacle lens.

[0107] As can be seen from the comparison of the Fig. 7 with the Fig. 8 and the comparison of Fig. 9 with the Fig. 10 As can be seen, the chromatic aberration can be advantageously reduced with the ophthalmic optical element 1 according to one aspect of the present invention. In particular, the proposed solution thus enables improved optical performance even at the edge of the image field.

[0108] Fig. 11 bis Fig. 13 The graphs show the modulation transfer function (MTF), also known as the modulation transfer function or contrast transfer function, at a diopter value of 4 diopters. The horizontal axis indicates the spatial frequency ω in cycles per millimeter. The vertical axis indicates the amplitude of an achievable modulation M.

[0109] Fig. 11 shows an MTF for an ophthalmic optical element 1 according to one aspect of the present invention, as for example in Fig. 1 depicted. Fig. 12 shows an MTF for a classic spherical spectacle lens. Fig. 13 shows an MTF for a classic spectacle lens with a freeform surface.

[0110] In the diagrams, the dashed curve 81 indicates the diffraction-limited maximum of the MTF. The other curves 82 indicate the achievable modulation at different viewing angles.

[0111] From the comparison of Fig. 11 with Fig. 12 und Fig. 13It becomes clear that with the ophthalmic optical element 1 according to one aspect of the present invention, an improved transmission function can be achieved over a large field of vision compared to classic spectacle lenses.

Claims

1. Ophthalmological optical element (1) for correcting visual defects, in particular a spectacle lens, having a first refractive optical substrate (10), which has a positive or negative first optical power (D1); a first diffractive optical element (21), which has a second optical power (D2); a second diffractive optical element (22), which has a third optical power (D3); wherein the first diffractive optical element (21) and the second diffractive optical element (22) have opposite optical powers, and characterized in that the absolute value of a sum of the second optical power (D2) of the first diffractive optical element (21) and the third optical power (D3) of the second diffractive optical element (22) divided by an absolute value of a difference between the second optical power (D2) and the third optical power (D3) is less than 1 / 10, in particular less than 1 / 15 and in particular less than 1 / 20.

2. Ophthalmological optical element according to Claim 1, wherein the first diffractive optical element (21) and the second diffractive optical element (22) interact in an achromatic manner together with the first refractive optical substrate (10).

3. Ophthalmological optical element according to either of the preceding claims, characterized in that the first optical substrate (10) has a front surface (11) and a back surface (12) and wherein the first diffractive optical element (21) is arranged on the side of the front surface (11) and / or the second diffractive optical element (22) is arranged on the side of the back surface (12).

4. Ophthalmological optical element according to any of the preceding claims, having a second optical substrate (30) that has the first diffractive optical element (21) and / or the second diffractive optical element (22); in particular wherein the first optical substrate has a front surface (11) and a back surface (12) and wherein the second optical substrate (30) is arranged on the side of the front surface (11) or the back surface (12) of the first optical substrate (10).

5. Ophthalmological optical element according to Claim 5, wherein the second optical substrate (30) has a film, a glass or a plastics shell; and / or wherein a cemented layer (13) or an air gap is arranged between the first optical substrate (10) and the second optical substrate (30).

6. Ophthalmological optical element according to any of the preceding claims, wherein the first and / or second diffractive optical element (21, 22) is rotationally symmetric with respect to an optical axis.

7. Ophthalmological optical element according to any of the preceding claims, wherein the first and second diffractive optical elements (21, 22) are each described by a phase polynomial of a second or higher order in a cross-sectional plane, wherein, with a tolerance range of ±20%, in particular ±10% and in particular ±5%, the following relationship applies between a first coefficient a1,DOE1 of the phase polynomial of the first diffractive optical element (21) and a first coefficient a1,DOE2 of the phase polynomial of the second diffractive optical element (22): a 1 , DOE 1 a 1 , DOE 1 + a 1 DOE 2 = 20 D d , where D specifies a resultant additional optical power by the first and second diffractive optical elements, d specifies a distance between the first and second diffractive optical elements and λ0 specifies a design wavelength.

8. Pair of spectacles having a frame and a first and a second spectacle lens, characterized in that the first and / or second spectacle lens is an ophthalmological optical element (1) according to any of Claims 1 to 7.

9. Head-mounted display apparatus (60) having an ophthalmological optical element (1) according to any of Claims 1 to 7, wherein the ophthalmological optical element (1) further has an input coupling optical unit (61) that, by means of the first optical substrate (10) of the ophthalmological optical element (1), is embodied to input couple an image to be displayed.

10. Computer-implemented method for designing an ophthalmological optical element (1), in particular a spectacle lens, for the purpose of the production thereof, wherein the ophthalmological optical element (1) has a first optical substrate (10), which has a positive or negative first optical power (D1); a first diffractive optical element (21), which has a second optical power (D2); and a second diffractive optical element (22), which has a third optical power (D3); wherein the first diffractive optical element (21) and the second diffractive optical element (22) have opposite optical powers; wherein the method includes the following steps: - selecting (S101) the first optical substrate (10), which has a positive or negative first optical power (D1), according to a dioptre range to be corrected; - providing (S102) the first diffractive optical element (21), which has the second optical power (D2), and the second diffractive optical element (22), which has the third optical power (D3); wherein the first and second diffractive optical elements (21, 22) are selected in such a way that an absolute value of a sum of the second optical power (D2) of the first diffractive optical element (21) and the third optical power (D3) of the second diffractive optical element (22) divided by an absolute value of a difference between the second optical power (D2) and the third optical power (D3) is less than 1 / 10, in particular less than 1 / 15 and in particular less than 1 / 20.

11. Method according to Claim 10, characterized in that the first optical substrate (10) is selected from a set of predetermined first optical substrates, wherein each of the predetermined optical substrates (10) acts as a basis for a dioptre range to be corrected, the set of predetermined first optical substrates having, in particular, at least one of the following dioptre ranges: 0...+5dpt, 0...-5dpt, +5...+8dpt and -5...-8dpt; in particular wherein a substrate of the set of predetermined first optical substrates (10) acts as a basis for a dioptre range of at least 2, in particular at least 3 and in particular at least 4 dioptres.

12. Method for producing an ophthalmological optical element (1), in particular a spectacle lens, including the steps of: - designing the ophthalmological optical element in accordance with a method according to either of Claims 10 and 11, and - producing the ophthalmological optical element (1).

13. Computer program product having program code for carrying out a method according to either of Claims 10 and 11 when the computer program product is executed on a data processing system.