Multifocal diffractive lens

Abstract

Provided is a multifocal diffractive lens capable of efficiently using light. A multifocal diffractive lens (100) has a diffractive grating (1c), a negative order light (L2) generates a focal point (f2) for far vision, a 0th order light (L1) generates a focal point (f1) more proximal than far vision, the number of focal points is 2 or more, and the focal point position (fc) for far vision in a multicolor performance evaluation is disposed proximally with respect to the focal point position (fs) for far vision in a monochromatic performance evaluation.

Description

Technical Field

[0001] This invention relates to a multifocal diffractive lens, primarily used in intraocular lenses. Background Technology

[0002] Conventional multifocal diffractive lenses typically use the 0th order light (refracted light) as the focal point for distance vision and the +1st order light (diffracted light) as the focal point for near or intermediate vision. As an example of a multifocal diffractive lens of a different type, a multifocal ophthalmic lens is disclosed that uses the +1st order light (diffracted light) as the focal point for distance vision to reduce chromatic aberration (see Patent Document 1). Furthermore, as another example of a multifocal diffractive lens, a trifocal lens is disclosed that uses the 0th order light (refracted light) as the focal point for intermediate vision, the +1st order light (diffracted light) as the focal point for near vision, and the -1st order light (diffracted light) as the focal point for distance vision (see Patent Document 2). Additionally, as an ophthalmic lens, a lens having negative diffraction capability to increase the width of chromatic aberration is disclosed (see Patent Document 3).

[0003] In ISO 11979-2, which relates to experimental methods for the optical properties of intraocular lenses, a monochromatic light source with a wavelength of 546±10 nm is used to measure refractive power or MTF (modulation transfer function), and the specifications of the intraocular lens are determined by evaluating its monochromatic performance. Here, in Patent Document 1, as described regarding chromatic aberration, the focus is on evaluating the multicolor (white) performance of a multifocal lens. However, in the multifocal lens of Patent Document 1, if the inconsistency between the focal position of monochromatic performance and the focal position of multicolor performance is not considered when performing a general optical design for an intraocular lens with monochromatic performance of 546±10 nm according to ISO 11979-2, the focal position will shift between monochromatic and multicolor performance. In conventional multifocal diffractive lenses, the focal position for distance vision in multicolor performance evaluation is often located on the far side compared to the focal position for distance vision in monochromatic performance evaluation. In this case, the light allocated for distance vision is focused on the retina and from the retina to the inner side, which cannot use the light efficiently and may cause deviations in the actual performance of the lens according to the specifications of the intraocular lens.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2018 / 100459

[0007] Patent Document 2: International Publication No. 2019 / 020435

[0008] Patent document 3: Japanese Patent Application Publication No. 59-224818. Summary of the Invention

[0009] The present invention was made in view of the problems in the above-mentioned background art, and its object is to provide a multifocal diffraction lens that can use light efficiently.

[0010] To achieve the above objectives, the multifocal diffraction lens of the present invention has a diffraction grating, a negative-order light generating a focal point for distance viewing, a 0th-order light generating a focal point closer to the distance, a focal number of 2 or more, and the focal point position for distance viewing in multicolor performance evaluation is positioned closer to the focal point position for distance viewing relative to the focal point position for distance viewing in monochromatic performance evaluation.

[0011] In the aforementioned multifocal diffractive lens, the multifocal lens with the far focal point in the multicolor performance evaluation positioned closer to the eye than the far focal point in the monochromatic performance evaluation is used. Thus, in the visible light range, the far focal point is positioned closer to the intraocular lens (multifocal diffractive lens) than the retina, enabling it to focus on objects in limited positions and use light efficiently.

[0012] According to a specific aspect of the present invention, in the aforementioned multifocal diffraction lens, positive-order light further generates a focal point closer to the target than the 0th-order light, with the number of focal points being 3 or more. In this case, imaging of object distances at 3 or more stages is possible.

[0013] According to another aspect of the invention, the diffraction grating has a shape that incorporates a kinoform profile. In this case, by utilizing the combination of kinoform profiles, a multifocal diffraction lens can be designed with a diffraction grating shape that generates a focal point for distance vision with negative order light, a focal point for nearer vision with 0th order light, and a focal point for even closer vision with positive order light.

[0014] According to another aspect of the invention, a correction term for the refractive index of the medium is added to the profile of the Keno lens. In this case, when using a multifocal diffractive lens intraocularly, it is envisioned that, when disposed in a liquid, the sag height of the Keno lens can be corrected using the correction term for the refractive index of the medium.

[0015] According to another aspect of the invention, a pupillary magnification correction term is added to the profile of the Kern lens. Simulations were conducted using two methods in the design value: altering the curvature and adding a refractive power, and adding a diffraction power using a diffraction grating. The results showed that even when the desired added power values ​​were the same but the resulting power values ​​differed, the pupillary magnification correction term could be used to match the power obtained from the refracted light.

[0016] According to another aspect of the invention, a trifocal diffraction lens is provided, which adds a third focal point in addition to the two focal points generated by the bifocal diffraction lens. The proximal addition power of the trifocal diffraction lens is twice that of the bifocal diffraction lens, and the number of diffraction fringes is the same.

[0017] According to another aspect of the invention, a quadfocal diffraction lens is provided, which adds two more focal points in addition to the two focal points generated by the bifocal diffraction lens. The proximal addition power of the quadfocal diffraction lens is three times that of the bifocal diffraction lens, and the number of diffraction fringes is the same.

[0018] According to another aspect of the invention, a diffraction grating has a shape combining two Keino lens profiles, and a height that is half the height of the diffraction grating with both Keino lens profiles. The light is distributed to generate negative-order light with a focal point farther from the 0th-order light and positive-order light with a focal point closer to the 0th-order light, wherein the numerical values ​​of the orders of the negative-order light and the positive-order light are equal. In this case, the variation in the height of each of the synthesized diffraction gratings is uniform, enabling the light distribution ratios to the negative-order light and the positive-order light to be almost identical.

[0019] According to another aspect of the invention, the diffraction grating has a shape combining two Keino lens profiles with different grating heights. The light is distributed to generate negative-order light that focuses at a point farther from the 0th-order light and positive-order light that focuses at a point closer to the 0th-order light, with the order values ​​of the negative and positive light being different. In this case, the order of the diffracted light that generates the focal point increases, allowing for a greater focus adjustment.

[0020] According to another aspect of the invention, the peaks and valleys in the diffraction grating have flat regions. In this case, light that could potentially be directed to the focal position of a higher-order light that is not intended to be flattened can be directed to the focal position of a lower-order light.

[0021] According to another aspect of the present invention, the multifocal diffractive lens is formed of a normally dispersive optical material, the refractive index of the material at a wavelength of 546 nm is 1.45 or more and 1.56 or less, and the degree between each focal point is set to 0.75D or more.

[0022] According to another aspect of the invention, a pair of optical surfaces are provided, one optical surface having a diffraction grating and the other optical surface having a toric shape. In this case, the other optical surface has a toric shape, thereby enabling it to be used as a multifocal diffractive lens for astigmatism correction. Attached Figure Description

[0023] Figure 1A This is a plan view illustrating the multifocal diffractive lens of the first embodiment. Figure 1B This is a side view illustrating a multifocal diffractive lens. Figure 1CThis is a schematic diagram illustrating an example of the use of a multifocal diffractive lens.

[0024] Figure 2A This diagram illustrates the relationship between the refracted light and the focal point of the diffracted light in a multifocal diffractive lens. Figure 2B This is a diagram illustrating the relationship between the focal point of monochromatic performance and the focal point of polychromatic performance.

[0025] Figure 3A This is a diagram illustrating the shape of the diffraction grating of the multifocal diffraction lens in Embodiment 1. Figure 3B This is a graph illustrating the light intensity when the multifocal diffractive lens of Example 1 is assembled. Figure 3C This is a diagram illustrating the MTF of the multifocal diffractive lens of Example 1. Figure 3D This is a diagram illustrating the shape of the diffraction grating of the multifocal diffraction lens in Comparative Example 1. Figure 3E This is a graph illustrating the light intensity when the multifocal diffractive lens of Comparative Example 1 is assembled. Figure 3F This is a graph illustrating the MTF of the multifocal diffractive lens in Comparative Example 1.

[0026] Figures 4A-4E This is a diagram illustrating the MTF of the multifocal diffractive lens in Example 2.

[0027] Figures 5A-5F This is a diagram illustrating the MTF of another multifocal diffractive lens in Example 2.

[0028] Figures 6A-6F This is a diagram illustrating the shape of the diffraction grating of the multifocal diffraction lens in Embodiment 3 of the second embodiment. Figures 6G-6I This is a diagram illustrating the shape of the diffraction grating of the multifocal diffraction lens in Comparative Example 2. Figures 6J~6L This is a diagram illustrating the shape of the diffraction grating of the multifocal diffraction lens in a modified example of Embodiment 3.

[0029] Figure 7A and 7B This is a diagram illustrating the shape of the diffraction grating of the multifocal diffraction lens in Embodiment 4 of the third embodiment. Figure 7C This is a diagram illustrating the light intensity of the multifocal diffraction lens in Example 4. Figure 7D This is a diagram illustrating the MTF of the multifocal diffractive lens in Example 4.

[0030] Figure 8A and Figure 8B This is a diagram illustrating the shape of the diffraction grating of the multifocal diffraction lens in Comparative Example 3. Figure 8C This is a graph illustrating the light intensity of the multifocal diffraction lens in Comparative Example 3. Figure 8D This is a graph illustrating the MTF of the multifocal diffractive lens in Comparative Example 3.

[0031] Figure 9AThis is a diagram illustrating the shape of the diffraction grating of the multifocal diffraction lens in Example 5. Figure 9B This is a graph showing the light intensity of the lens when the pupil diameter is φ3mm in Example 5. Figure 9C This is a graph illustrating the MTF of the lens in Example 5 when the pupil diameter is φ3mm. Figure 9D This is a diagram illustrating the shape of the diffraction grating of the multifocal diffraction lens in Comparative Example 4. Figure 9E This is a graph illustrating the light intensity of the lens when the pupil diameter is φ3mm in Comparative Example 4. Figure 9F This is a graph of the MTF of the lens when the pupil diameter is φ3mm in Comparative Example 4.

[0032] Figure 10A This is a graph illustrating the light intensity of the lens when the pupil diameter is φ5mm in Example 5. Figure 10B This is a graph illustrating the MTF of the lens when the pupil diameter is φ5mm in Example 5. Figure 10C This is a graph illustrating the light intensity of the lens when the pupil diameter is φ5mm in Comparative Example 4. Figure 10D This is a graph illustrating the MTF of the lens when the pupil diameter is φ5mm in Comparative Example 4.

[0033] Figure 11A This is a diagram illustrating the MTF of the multifocal diffractive lens in Example 6. Figure 11B and 11C This is a diagram illustrating the MTF of a multifocal diffractive lens in the context of existing lenses.

[0034] Figure 12A This means that in Figure 6L The graph shows the light intensity of four-focal lenses with different values ​​of the coefficient α for the Kern lens profile in the modified examples of Embodiment 3. Figure 12B This is a graph illustrating the MTF of the aforementioned quadfocal lenses with different values ​​of coefficient α.

[0035] Figure 13A This is a bottom view of the multifocal diffractive lens according to the fourth embodiment. Figure 13B It is a schematic side view parallel to the weak principal meridian of the multifocal diffraction lens. Figure 13C It is a schematic side view parallel to the strong principal meridian of the multifocal diffractive lens. Figure 13D This is a diagram showing an example of the variation in the end thickness in the angular direction as observed from the center of the lens body.

[0036] Figure 14A It is set in Figure 13A An enlarged view of the toric surface markings on the multifocal diffractive lens shown. Figure 14B It is a cross-sectional view of the complex surface. Detailed Implementation

[0037] [First Implementation Method]

[0038] Hereinafter, the multifocal diffraction lens 100 of the first embodiment of the present invention will be described with reference to FIG1 and the like. Figure 1A This is a plan view of the multifocal diffractive lens 100. Figure 1B This is a side view of the multifocal diffraction lens 100. Figure 1C This is a schematic diagram illustrating an example of the use of the multifocal diffraction lens 100.

[0039] Figure 1A and 1B The multifocal diffractive lens 100 shown is used as an intraocular lens, having the ability to... Figure 1C The illustrated image shows a lens body 100a that functions as a lens 2a within the eyeball 200, and two support portions 100b that support the lens body 100a within the eyeball 200. The lens body 100a and the support portions 100b are integrally formed. The lens body 100a has a first optical surface 1a as its anterior surface and a second optical surface 1b as its posterior surface opposite to the first optical surface 1a. In the illustrated example, the lens body 100a is a biconvex lens; however, depending on the lens characteristics, one side may be concave or planar. The support portions 100b have curved protrusions extending from the outer periphery of the lens body 100a. Alternatively, the lens body 100a and the support portions 100b may also be formed separately. Figure 1C As shown, when using the multifocal diffraction lens 100, only the interior of the lens 2a is removed, leaving the surrounding capsule-shaped membrane (lens capsule), and the multifocal diffraction lens 100 is placed in and fixed in this capsule.

[0040] The multifocal diffractive lens 100 is formed of a flexible, soft material, such as thermoplastic resin, non-thermoplastic resin, or inorganic amorphous material. The multifocal diffractive lens 100 is formed of a normally dispersive optical material with a refractive index of 1.45 to 1.56 at a wavelength of 546 nm. In this case, the power between each focal point is preferably set to 0.75D or higher.

[0041] The multifocal diffractive lens 100 combines a refractive lens structure with a diffraction grating 1c. The diffraction grating 1c is located on either the first optical surface 1a or the second optical surface 1b of the lens body 100a. In the illustrated example, the first optical surface 1a, as one optical surface, has the diffraction grating 1c, and the second optical surface 1b, as another optical surface, has a spherical or aspherical surface. For the multifocal diffractive lens 100, negative-order light generates a focal point for distance vision, and 0th-order light generates a focal point closer to the distance. The number of focal points is two or more. The focal point position for distance vision in multicolor performance evaluation is positioned closer to the distance than the focal point position for distance vision in monochromatic performance evaluation. The 0th-order light (refracted light) generating a focal point closer to the distance means that 0th-order light produced by the lens from a specific object is focused closer than, for example, -1th-order light produced by the lens from the same object. Considering the retina as a reference, -1th-order light is better at achieving distance vision than 0th-order light.

[0042] Figure 2A This is a diagram illustrating the relationship between the focal points of refracted and diffracted light in a multifocal diffractive lens 100. Figure 2B This is a diagram illustrating the relationship between the focal points of monochromatic performance and polychromatic performance. Figure 2A In the example, when the degree of the 0th order light (refracted light) L1 is +20D and the focal point f1 of the 0th order light is taken as a reference, the negative order light (e.g., the -1st order light L2) generates the far-side focal point f2, and the positive order light (e.g., the +1st order light L3) generates the near-side focal point f3. Figure 2A The infinity focal point of the multifocal diffraction lens 100 is shown, and the imaging position on the retina 2b is set based on the focal position of the negative order light located at the farthest side. Imaging on the retina 2b is possible for objects located at the corresponding object distances, including 0th order light, positive order light, and negative order light beyond the reference. Here, object distance means the distance from infinity to the discretely distributed objects near the multifocal diffraction lens 100.

[0043] In this embodiment, the following structure will be described: The multifocal diffraction lens 100 is a bifocal diffraction lens that utilizes 0th-order light L1 and -1st-order light L2. In the multifocal diffraction lens 100, 0th-order light L1 generates a focal point f1 for near vision, and -1st-order light L2 generates a focal point f2 for distance vision. In the multifocal diffraction lens 100, the distance F from the multifocal diffraction lens 100 to the retina 2b is used as a standard value for the focal position for distance vision. That is, in this embodiment, the focal position of -1st-order light L2 corresponds to distance F. Furthermore, the focal length of -1st-order light L2 can be varied by setting or designing the diffraction structure that generates the focal point for distance vision, in accordance with the distance F.

[0044] like Figure 2BAs shown, in the multifocal diffractive lens 100, as described above, the focal position fc for distance viewing in the multicolor performance evaluation is positioned closer to the focal position fs for distance viewing in the monochromatic performance evaluation. That is, the focal position fc for distance viewing in the multicolor performance evaluation is moved closer to the focal position fs for distance viewing in the monochromatic performance evaluation.

[0045] In the multifocal diffractive lens 100, the focal point for multicolor performance evaluation is positioned near the eye. Therefore, in the visible light range, the focal point is positioned closer to the retina 2b than the intraocular lens 100, enabling focused illumination of objects in limited positions and efficient light utilization. The configuration of the distal focal point position is based on the phenomenon in intraocular lenses where spherical aberration is retained near the eye. This will be explained in detail below. In intraocular lenses, with low correction where spherical aberration is retained near the eye, light is focused onto the retina and the area in front of the retina. This limits the range of aberrations retained within the eye, allowing the aberrations to be utilized at the focal point. To efficiently utilize light, intraocular lenses are often selected with low correction to retain spherical aberration near the eye. This is a phenomenon observed in monochromatic performance, but it is also considered the same when considering multicolor performance. Compared to monochromatic lenses, intraocular lenses are used in practice in a multi-color manner. Preferably, the focal position is set at a reference position with monochromatic performance, and in both monochromatic and multi-color performances, the focal position for distance vision is configured to be closer to the intraocular lens than the retina. That is, as with the multifocal diffractive lens 100 of this embodiment, it is preferable that the focal position of the multi-color performance is moved closer to the retina than the focal position of the monochromatic performance.

[0046] Furthermore, chromatic aberration is considered in multi-color performance. Regarding the chromatic aberration of refracted light, the blue focus, which is shorter than 546 nm, forms near the focal point, while the red focus, which is longer than 546 nm, forms far the focal point. Therefore, the blue, green, and red focal points are formed sequentially from the near side. Moreover, in positive-order diffracted light, the red, green, and blue focal points are formed sequentially from the near side, while in negative-order diffracted light, the blue, green, and red focal points are formed sequentially from the near side. That is, regarding the chromatic aberration produced by diffracted light, in positive-order light it is the opposite of the refracted light, while in negative-order light it is the same direction as the refracted light. Furthermore, it is known that in multifocal diffractive lenses, the chromatic aberration produced by diffracted light compensates for the chromatic aberration produced by refracted light. Therefore, in a typical diffractive lens, the blue focal point, which is shorter than 546 nm, is more often formed far from the green focal point, which is near the designed wavelength of 546 nm. That is, a typical diffractive lens exhibits the opposite chromatic aberration to a typical refractive lens, forming red, green, and blue focal points sequentially from the near side. In the distance focal point of the multifocal diffractive lens 100 of this embodiment, even though it is a diffractive lens, it forms a blue focal point near the near side relative to the green focal point, thus forming blue, green, and red focal points sequentially from the near side.

[0047] In the multifocal diffractive lens 100, to shift the focal position for evaluating polychromatic performance relative to the focal position for evaluating monochromatic performance, the principle that the intensity of refracted and diffracted light varies with wavelength in polychromatic performance is utilized. Using the intensity of a monochromatic light source at 546 nm as a reference, in refracted light, the intensity decreases on the shorter wavelength side and increases on the longer wavelength side, but the change is small. Conversely, in diffracted light, the intensity increases on the shorter wavelength side and decreases on the longer wavelength side. Specifically, for diffracted light of order -1 (distant light), the intensity of the shorter wavelength (blue) side, which is closer to 546 nm, increases, and as a polychromatic performance characteristic, it shifts closer to the wavelength. On the other hand, for refracted light of order 0 (near light), the intensity of the longer wavelength (red) side, which is farther from 546 nm, increases, and as a polychromatic performance characteristic, it shifts farther to the wavelength. By placing negative-order light (diffracted light) at the far focal point and placing zero-order light (refracted light) at the focal point closer to the far focal point, the wavelength range of increased light intensity in polychromatic performance is concentrated between the negative-order light (diffracted light) and the zero-order light (refracted light) in monochromatic performance. Therefore, the far focal point in polychromatic performance evaluation is placed closer to the far focal point compared to monochromatic performance.

[0048] The optical surfaces of the multifocal diffractive lens 100 will be described below. In the multifocal diffractive lens 100, the refractive lens structure consists of… Figure 2A The hypothetical reference surface 1d of order 0 shown can be either spherical or aspherical. Furthermore, reference surface 1d uses the aspherical profile described below. Here, the aspherical coefficient of order x can also be set to 0. Additionally, a conic constant k and a fourth-order aspherical coefficient A4 can be used, and furthermore, a sixth-order aspherical coefficient A6 or an eighth-order aspherical coefficient A8 can also be used.

[0049]

[0050] Here,

[0051] z(s): Sag height

[0052] r: Distance from the optical axis (radius)

[0053] R: Radius of curvature

[0054] k: quadratic constant

[0055] A4: Fourth-order aspheric coefficient

[0056] A6: 6th order aspherical coefficient

[0057] A8: 8th order aspherical coefficient

[0058] Furthermore, the diffraction grating 1c has a shape designed using the profile of a Kernos lens. That is, the diffraction grating 1c has a diffraction pattern based on the profile of a Kernos lens, with the thickness or height difference of the Kernos lens and the spacing or pitch of the rings appropriately adjusted relative to an imaginary reference plane 1d of order 0. In the illustrated example, diffraction patterns for order 0 and order 1 light are shown, with each ring of the Kernos lens having a concave surface on the lens body 100a side relative to the reference plane 1d.

[0059] When calculating the diffraction grating height h(r) for diffraction grating 1c, the parameters were modified using the Keino lens profile formula described in the following reference (specifically, n). A The formulas for (λ0) and M) are used. In the Kern lens profile formula, correction terms for the medium refractive index and pupil magnification are added. Specifically, the medium refractive index n in the formula... A This is a correction term intended for liquid configuration; the pupillary magnification M is a correction term used to match the diopter obtained from refracted light. Furthermore, in the original formula, it is assumed that the medium used for air configuration has a refractive index of 1.0. Also, in the formula, r is the distance from the optical axis (radius), m is the diffraction fringe (m = 0, 1, 2, ...), n... L λ is the material refractive index, λ0 is the design wavelength, α is the coefficient used to adjust the sag height s(r) of the Kern lens, and P is the additional diffraction power.

[0060] Reference: Dale A. Buralli, G. Michael Morris, and John R. Rogers., "Optical performance of holographic kinoforms", Applied Optics, vol. 28, No. 5, 976 (1989)

[0061]

[0062]

[0063] κ=-n L 2 (λ0)

[0064]

[0065] →m=m(r)-MOD{m(r),m order}

[0066]

[0067]

[0068] By varying the height of the diffraction grating using the coefficient α in the above formula, the distribution of light to any two focal points is altered. That is, the order of light obtained changes by changing the height of the diffraction grating. For example, α = 0 results in 0th order light, α = 1 results in +1st order light, and α = 0.5 results in both 0th and +1st order light. Furthermore, α = -1 results in -1st order light, α = -2 results in -2nd order light, and α = -1.5 results in both -1st and -2nd order light. The number of diffraction fringes is determined by the diffraction addition degree. Here, as an example, when determining the focal length f, a pupil magnification M = 1.13 is considered. Simulations using two methods—changing the curvature and adding refracted light degree, and adding diffracted light degree using a diffraction grating—result in different final diffraction values, even though both methods aim to add the same degree. Since the diffraction increment is approximately equal to the refracted diffraction increment divided by 1.13, a correction term of M is added to ensure consistency between the two. On the actual pupil surface, considering that the diffraction grating fringe spacing is M = 1.13 times, resulting in a diffraction increment of 1 / 1.13 times, this becomes a formula that considers a diffraction increment of 1.13 times on the lens surface. Alternatively, M = 1 can be used instead of M = 1.

[0069] In the multifocal diffractive lens 100 described above, the multifocal lens with the distance focal point in the multicolor performance evaluation positioned closer to the eye than the distance focal point in the monochromatic performance evaluation is used. Therefore, in the visible light range, the distance focal point is positioned closer to the retina 2b than the multifocal diffractive lens 100, which serves as an intraocular lens. This allows for focusing on objects in limited positions and efficient use of light. Consequently, when performing general optical design of an intraocular lens at a wavelength of 546 nm (monochromatic performance) according to ISO 11979-2, the risk of hyperopia in white light source environments (multicolor performance) can be avoided.

[0070] [Example 1]

[0071] <MTF Simulation with Bifocal Diffractive Lens + 1.5D (Comparison of Example 1 and Comparative Example 1)>

[0072] In Example 1, the following situation will be explained: With regard to bifocal diffractive lenses, when the 0th order light generates the focal point for near vision and the -1st order light generates the focal point for far vision, light can be used efficiently in multicolor performance evaluation.

[0073] In Example 1, the MTF simulation of the multifocal diffraction lens 100 was performed as follows (and the same applies to subsequent examples). For the multicolor performance evaluation, used to assess the optical performance of white light, represented by sunlight, simulations were conducted using five wavelengths within the visible light region of 380nm to 780nm: 430nm, 490nm, 546nm, 590nm, and 650nm. Furthermore, these wavelength selections are only one example used to represent white light. The MTF count was compared at 50 per mm. On the other hand, the monochromatic performance evaluation was performed using a monochromatic light source with a wavelength of 546 ± 10nm according to ISO 11979-2:2014, Annex C (MTF); therefore, a simulation using a wavelength of 546nm was conducted.

[0074] In Example 1, a bifocal diffractive lens with a distal +20D and a near +21.5D lens was used for comparison. In Example 1, the 0th order light generated the focal point for near vision, and the -1st order light generated the focal point for distance vision. In Comparative Example 1, the 0th order light generated the focal point for distance vision, and the +1st order light generated the focal point for near vision. Figure 3A This diagram illustrates the shape of the diffraction grating added in -1.5D and 0D in Example 1. Figure 3B This is a graph illustrating the light intensity at +21.5D (near side) refraction and -1.5D (far side) diffraction in Example 1. Figure 3C This is a diagram illustrating the MTF of +21.5D refraction and -1.5D diffraction in Example 1. Figure 3D This is a diagram illustrating the shapes of the diffraction gratings added to 0D and +1.5D in Comparative Example 1. Figure 3E This is a graph illustrating the light intensity of refraction +20D (far side) and diffraction +1.5D (near side) in Comparative Example 1. Figure 3F This is a graph illustrating the MTF of refraction +20D and diffraction +1.5D in Comparative Example 1. Furthermore, in Figure 3A and 3D In the diagram, the negative side of the diffraction grating depth (diffraction grating height) shows the lens body 100a side of the multifocal diffraction lens 100 (the same applies in other embodiments).

[0075] like Figure 3C As shown, in the MTF results of Example 1, the far-side focal position of the multicolor performance shifts towards the near side relative to the far-side focal position of the monochromatic performance. In contrast, as... Figure 3F As shown, in the MTF results of Comparative Example 1, the far-side focal position of the multicolor performance shifts further away than the far-side focal position of the monochromatic performance. This can be achieved by... Figure 3B and 3EThe intensity results in the polychromatic performance are shown to illustrate this. Diffracted light passing through a diffraction grating designed at a wavelength of 546 nm exhibits the following characteristics: the intensity increases on the shorter wavelength side compared to the design wavelength, and the intensity decreases on the longer wavelength side compared to the design wavelength. In contrast, there is virtually no change in the intensity of the refracted light. Figure 3B In the light intensity results of Example 1 shown, there exists a short-wavelength region where the light intensity increases closer to the focal position than at the far focal position, and a long-wavelength region where the light intensity is equal further away than at the focal position than at the near focal position, both existing at the far focal position and the near focal position. In contrast, in Figure 3E In the light intensity results of Comparative Example 1 shown, there exists a short-wavelength region where the light intensity is equal closer to the far-focus position than at the near-focus position, and a long-wavelength region where the light intensity decreases further away than at the near-focus position, between the far-focus and near-focus positions. Based on the distribution of these light intensity results, Example 1 teaches that the wavelength regions with increased light intensity are concentrated between the far-focus and near-focus positions, thereby shifting the far-focus position of the multicolor performance closer to the near-focus position relative to the far-focus position of the monochromatic performance in the MTF results.

[0076] As in Example 1, a multifocal lens with the focal point in the multicolor performance evaluation positioned near the eye compared to the focal point in the monochromatic performance evaluation is used. Thus, in the visible light range, the focal point is positioned closer to the intraocular lens (multifocal diffraction lens) than the retina, enabling efficient use of light.

[0077] [Example 2]

[0078] Simulation of changes in refractive index and interfocal angle

[0079] In Example 2, the following situation will be explained: among lens materials with a refractive index n in the range of 1.45 to 1.56 at a wavelength of 546 nm, it is preferable to set the interfocal diopter to 0.75D or higher.

[0080] like Figures 4A-4E As shown, in a lens material with a refractive index n = 1.52 at a wavelength of 546 nm, a bifocal diffraction lens was used to simulate and compare the monochromatic and polychromatic performance at the far-side focal position when the added power A was varied to -0.6D, -0.75D, -1.5D, -2.0D, and -3.0D, with the addition power A varying to -0.6D, -0.75D, -1.5D, -2.0D, and -3.0D. The results are as follows: Figure 4A As shown, when the degree A = -0.6D is added, the far focal position of the polychromatic performance shifts further away from the far focal position of the monochromatic performance. However, as... Figures 4B-4EAs shown, when additional degrees are added, the far-side focal position of the multicolor performance shifts closer to the near-side focal position relative to the far-side focal position of the monochromatic performance. Therefore, it can be confirmed that in the diffraction grating shape of this embodiment, by setting the degree difference between each focal point to 0.75D or more, the effects of the invention can be obtained.

[0081] Next, as Figure 5A and Figure 5B As shown, simulations were performed on a bifocal diffraction lens with a refractive index n = 1.52 at a wavelength of 546 nm. The lens produced a far-side +26D from -1st-order light (with a power A = -0.75D) and a near-side +26.75D from 0th-order light. Simulations were also performed on a bifocal diffraction lens with a far-side +6D from -1st-order light (with a power A = -0.75D) and a near-side +6.75D from 0th-order light. This confirmed that, regardless of the far-side power, the far-side focal position of the multicolor performance shifts closer to the near-side focal position compared to the monochromatic performance. Based on this result, the same effect of the invention can be obtained even when the far-side power setting is changed.

[0082] In addition, such as Figures 5C-5F As shown, simulations were performed on bifocal diffraction lenses generating a far focal length of +20D from -1st-order light (with a power of A = -0.75D) and a near focal length of +20.75D from 0th-order light, and on bifocal diffraction lenses generating a far focal length of +20D from -1st-order light (with a power of A = -1.5D) and a near focal length of +21.5D from 0th-order light, respectively, for lens materials with a refractive index n = 1.45 at a wavelength of 546 nm and lens materials with a refractive index n = 1.56 at a wavelength of 546 nm. This confirmed that, under what conditions, the far focal position of the polychromatic performance shifts towards the near focal position relative to the far focal position of the monochromatic performance. Based on this result, it can be confirmed that the same effect of the invention can be obtained even with lens materials whose refractive index at a wavelength of 546 nm is in the range of 1.45 ≤ n ≤ 1.56.

[0083] Based on the above results, it can be confirmed that among lens materials with a refractive index n in the range of 1.45 to 1.56 at a wavelength of 546 nm, it is preferable to set the interfocal diopter to 0.75D or higher.

[0084] [Second Implementation]

[0085] The multifocal diffraction lens of the second embodiment will now be described. Furthermore, the multifocal diffraction lens of the second embodiment is a modification of the multifocal diffraction lens of the first embodiment; matters not specifically described are the same as in the first embodiment.

[0086] In this embodiment, in the multifocal diffraction lens 100, positive-order light further generates a focal point closer to the near side than the 0th-order light, with the number of focal points being 3 or more. Therefore, imaging of object distances at 3 or more stages is possible. The multifocal diffraction lens 100 is a trifocal diffraction lens that adds one more focal point in addition to the two focal points generated by the bifocal diffraction lens. The near-side power addition is twice that of the bifocal diffraction lens, and the number of diffraction fringes is the same. That is, the near-side power addition of the trifocal diffraction lens, which adds a focal point closer to the near side, is twice that of the bifocal diffraction lens. The trifocal diffraction lens, which adds one more focal point in addition to the two focal points generated by the bifocal diffraction lens, synthesizes two different Cairns lens profiles with different power additions.

[0087] In the multifocal diffraction lens 100, in the case of a trifocal diffraction lens, the diffraction grating is a combination of two Cairnal lens profiles, having a height that is half the height of the diffraction grating of the two Cairnal lens profiles (e.g., described later). Figure 6C The diffraction grating depth D shown is used to distribute light into negative-order light that generates a focal point farther from the 0th-order light and positive-order light that generates a focal point closer to the 0th-order light, with the order values ​​of the negative and positive light being equal. Therefore, the variation in the height of each diffraction grating after synthesis is uniform, enabling the light distribution ratio for the negative and positive orders to be almost identical.

[0088] For the multifocal diffractive lens 100, in the case of a trifocal diffractive lens, for example, the 0th order light generates the focal point for viewing at midpoint, the -1st order light generates the focal point for viewing at a distance, and the +1st order light generates the focal point for viewing at near distance.

[0089] Furthermore, the multifocal diffraction lens 100 can also be a quadfocal diffraction lens that adds two more focal points in addition to the two focal points generated by the bifocal diffraction lens. The proximal power addition of the quadfocal diffraction lens is three times that of the bifocal diffraction lens, and the number of diffraction fringes can also be the same. That is, the proximal power addition of the quadfocal diffraction lens with the added focal points is three times that of the bifocal diffraction lens. The quadfocal diffraction lens, which adds two more focal points in addition to the two focal points generated by the bifocal diffraction lens, synthesizes two different Cairns lens profiles with different power additions.

[0090] For the multifocal diffraction lens 100, in the case of a fourfocal diffraction lens, the diffraction grating heights of the two Cairn lens profiles are different. The light is distributed to generate negative-order light at a focal point farther from the 0th order and positive-order light at a focal point closer to the 0th order. The order values ​​of the negative and positive light are different. Therefore, the order of the diffracted light at the focal point increases, allowing for a larger focal adjustment. In this case, the two order values ​​are not equal; for example, this means four focal points of order -1, 0, +1, and +2.

[0091] [Example 3]

[0092] <Comparison of trifocal diffractive lenses with the same diffraction grating shape and those with +1.5D and +3D diffraction grating shapes (previous Kanon lenses)>

[0093] In Example 3, the added power when synthesizing two Cairn lens profiles in a trifocal diffractive lens is explained.

[0094] In the multifocal diffraction lens 100, two different Keno lens profiles with different diopters are synthesized, thus creating a trifocal diffraction lens. Figure 6C This diagram illustrates the diffraction grating shape design selected at the maximum (max) level in Example 3, showing that... Figure 6A The +1.5D added diffraction grating shape shown is... Figure 6B The diffraction grating shape with -1.5D added is shown as a synthesized diffraction grating shape. Figure 6F This diagram illustrates the minimum (min) selected diffraction grating shape design in Example 3, showing that... Figure 6D The +1.5D added diffraction grating shape shown is... Figure 6E The diffraction grating shape with a -1.5D addition shown is the synthesized diffraction grating shape. Furthermore, in the maximum selection of diffraction grating shape design, the darkest option is chosen, and in the minimum selection, the lightest option is chosen. Figure 6I This diagram illustrates the general diffraction grating shape design in Comparative Example 2, showing that... Figure 6G The +1.5D added diffraction grating shape shown is... Figure 6H The diffraction grating shape with the addition of +3.0D shown was synthesized into a diffraction grating shape.

[0095] like Figure 6C , 6FAs shown in 6I, it can be said that with the same addition power setting for the trifocal diffraction lens, the number of diffraction fringes in this embodiment is reduced, resulting in a diffraction grating shape that is easier to manufacture. Furthermore, the diffraction grating height (diffraction grating depth D) of the trifocal diffraction lens is half the height of the diffraction grating in both Keino lens profiles. At this point, it is possible to generate negative-order light that is the far-side focal point compared to the 0th-order light and positive-order light that is the near-side focal point compared to the 0th-order light, with both order values ​​being equal. For example, when α = 1.0, it becomes a trifocal diffraction lens with -1st, 0th, and +1st orders. Furthermore, when α = 2.0, the diffracted light becomes relatively stronger than the 0th-order light, resulting in four focal points with -2nd, -1st, +1st, and +2nd orders. Furthermore, regarding the height of the diffraction grating here, the result of adjusting the distribution of light to the three focal points is that α = 1.3 in the diffraction grating shape of this embodiment, and α = 0.6 in a general diffraction grating shape, but this is just one example.

[0096] Furthermore, as a variation of Example 3, it is also possible to add diffraction gratings with different heights for two different Keno lens profiles. Specifically, by setting the coefficient α to different values, a four-focal lens is created. Figure 6L This diagram illustrates the minimally selected diffraction grating shape design in a variation of Example 3, showing that... Figure 6J The diffraction grating shapes added for +1.0D and +2.0D shown are similar to... Figure 6K The diffraction grating shape with a -1.0D addition shown is a synthesized diffraction grating shape. While the setting of the coefficient α is not limited, it is preferable that when one Kernok lens profile is xα, the other Kernok lens profile is preferably 2xα. In this case, negative-order light, which is the focal point on the far side compared to the 0th-order light, and positive-order light, which is the focal point on the near side compared to the 0th-order light, can be generated, and the order values ​​of the two are not equal. For example, when the Kernok lens profiles with addition powers of -1.0D and +1.0D are set to α = 1.0 and α = 2.0 respectively, a four-focal lens of -1st, 0th, +1st, and +2nd orders is formed. By setting α = 2.0 on the +1.0D side, the diffracted light is relatively stronger on the positive-order side, and in addition to the +1st-order light, the +2nd-order light is also efficiently extracted. In a typical diffraction grating shape, the number of diffraction fringes increases with the number of focal points. However, in the diffraction grating shape of this embodiment, the number of focal points can be increased without increasing the number of diffraction fringes. Furthermore, α is set to 1.0 and α = 2.0 in the two Cairn lens profiles; however, this is just one example, and the light intensity ratio of each focal point can be adjusted according to the setting of the coefficient α.

[0097] The following describes an example of setting the coefficient α. This is a variation of Example 3. Figure 6LIn the following section, the following explanation is given regarding quadfocal lenses: For quadfocal lenses with the added power of -1.0D and +1.0D lens profiles set to α=1.0 and α=2.0 respectively, the profiles are changed to α=1.3 and α=2.0.

[0098] Figure 12A This means that in Figure 6L The graph shows the light intensity of the aforementioned quadfocal lenses with different values ​​of the coefficient α for the Kern lens profile in the modified example of Embodiment 3. Figure 12B This is a graph illustrating the MTF of the aforementioned quadfocal lenses with different values ​​of coefficient α.

[0099] like Figure 12A As shown, it can be confirmed that when comparing the light intensity peaks at each focal position, the light intensity peak of the near focal point (+2nd order light) increases by the amount by which the light intensity peak of the intermediate focal point (0th order light) decreases or disappears. By changing the setting of the coefficient α, the light distribution ratio for each focal position can be adjusted. Furthermore, as... Figure 12B As shown, the MTF results also show the same results as the light intensity. Furthermore, here, the setting of the coefficient α for the Keno lens profile with a power of +1.0D has been changed; however, the setting of the coefficient α for the Keno lens profile with a power of -1.0D can also be changed, or both can be changed, and the power added can also be changed.

[0100] [Third Implementation Method]

[0101] The multifocal diffraction lens of the third embodiment will now be described. Furthermore, the multifocal diffraction lens of the third embodiment is a modification of the multifocal diffraction lenses of the first and second embodiments; matters not specifically described are the same as those in the first embodiment, etc.

[0102] In this embodiment, the peak-valley portion 300 in the diffraction grating of the multifocal diffraction lens 100 has a flat region 3c (see below). Figure 7A and 7B Therefore, it is possible to direct light from the focal position of a non-intended high-order light to the focal position of a low-order light without flattening the peak-valley region 300. Furthermore, having a flat region 3c implies limitations on peak height and valley depth, including not only straight shapes but also inclined or arcuate shapes, etc.

[0103] [Example 4]

[0104] Flattening of peaks and valleys in a trifocal diffraction lens

[0105] In Example 4, a trifocal diffraction lens in which a flat region 3c is provided in the peak-valley portion 300 of the diffraction grating shape of the multifocal diffraction lens 100 is described.

[0106] Compared to Figure 7A The -1.5D, 0D, and +1.5D values ​​shown are added to... Figure 6C The peaks and valleys 300 (referred to collectively as peaks 3a and valleys 3b) in the 1.97 μm height of the trifocal diffraction lens were flattened with a limit of 0.4 μm, which would become 20% of the height of the diffraction grating. Figure 7B The peak 3a and valley 3b shown are compared. Figure 7B As shown, the peak-valley portion 300 of the diffraction grating shape in Example 4 has a flat region 3c. Figure 7C This is an explanation Figure 7A The diffraction lens before planarization and Figure 7B The graph shown is a diagram of the light intensity after the diffraction lens has been flattened. Figure 7D This is an explanation Figure 7A The diffraction lens before planarization and Figure 7B The MTF of the planarized diffractive lens is shown in the figure.

[0107] like Figure 7C As shown, it can be confirmed that when comparing the peak light intensity at each focal position, the peak light intensity at the central focal point (0th order light) significantly increases by the amount of decrease in the peak light intensity of the ±2nd order light, and the total amount of light concentrated within any focal range also increases from 1.96 × 10⁻⁶. 6 (V / m) 2 The height becomes 2.32 × 10 6 (V / m) 2 It became 1.18 times. Furthermore, such as... Figure 7D As shown, the MTF results also show the same results as the light intensity. Furthermore, all peaks and valleys 300 have been flattened here, but only a portion of the peaks and valleys 300 can be flattened, and the aforementioned 20% flattening ratio can be adjusted.

[0108] Furthermore, for Comparative Example 3, 0D, +1.5D, and +3D were added. Figure 6I The typical trifocal diffraction lens shown can synthesize a portion of the diffraction grating shape, with a +1.5D addition and a -1.5D addition having the same diffraction fringe spacing. Figure 8A This is a diagram illustrating the shape of a portion of the diffraction grating before synthesis. Figure 8B This is a diagram illustrating the shape of a portion of the synthesized diffraction grating. Figure 8C This is an explanation Figure 8A The part shown is a diffraction lens before synthesis and Figure 8B The image shown is a partial graph of the light intensity of the synthesized diffraction lens. Figure 8D This is an explanation Figure 8A The part shown is a diffraction lens before synthesis and Figure 8BThe image shown is a partial MTF plot of the synthesized diffractive lens. Figure 8C As shown, it can be confirmed that in Comparative Example 3, the peak light intensity of the intermediate focal point (+1st order light) and the distance focal point (0th order light) increased by the amount of decrease in the peak light intensity of the near focal point (+2nd order light), and the total amount of light focused into any focal range also increased from 2.10 × 10⁻⁶. 6 (V / m) 2 The height becomes 2.24 × 10 6 (V / m) 2 It becomes 1.06 times. Furthermore, such as... Figure 8D As shown, the MTF results also show the same results as the light intensity. Therefore, compared to Comparative Example 3, in Example 4, the increase in the total amount of light concentrated within any focal range is much greater, which greatly enables the light that could potentially be distributed to the focal position of a higher-order light that is not intended to be distributed to the focal position of a lower-order light.

[0109] [Example 5]

[0110] <Comparison with planarization and previous processing methods of Kino lenses>

[0111] In Example 5, the machining process R during the cutting of the diffraction grating shape of the multifocal diffraction lens 100 will be described.

[0112] In the Figure 7B When machining the diffraction grating-shaped mold of Embodiment 4 shown, due to the cutting of the valley 3b (refer to...) Figure 7A Because the machining radius (R) is given, the following situation may occur: the shape of the diffraction grating collapses, and the optical performance cannot be as shown in the simulation results. In Example 5, the change in simulation results is shown for a +3D added trifocal lens machined with a cutting tool tip radius (R) of 0.3 mm. Figure 9A This illustrates the shape of the diffraction grating in Example 5 (and...). Figure 7B (Same) diagram, Figure 9B This is a graph illustrating the light intensity of the lens when the pupil diameter is φ3mm in Example 5. Figure 9C This is a graph illustrating the MTF of the lens in Example 5 when the pupil diameter is φ3mm. Furthermore, Figure 10A This is a graph illustrating the light intensity of the lens when the pupil diameter is φ5mm in Example 5. Figure 10B This is a diagram illustrating the MTF of the lens when the pupil diameter is φ5mm in Example 5. Figure 9D This illustrates the shape of the diffraction grating in Comparative Example 4 (and...). Figure 8B (Same) diagram, Figure 9E This is a graph illustrating the light intensity of the lens when the pupil diameter is φ3mm in Comparative Example 4. Figure 9F This is a graph illustrating the MTF of the lens when the pupil diameter is φ3mm in Comparative Example 4. Furthermore, Figure 10C This is a graph illustrating the light intensity of the lens when the pupil diameter is φ5mm in Comparative Example 4. Figure 10D This is a graph illustrating the MTF of the lens when the pupil diameter is φ5mm in Comparative Example 4.

[0113] like Figure 9A As shown, in the diffraction grating shape of this embodiment, the design value and the processing value are almost identical. In contrast, as... Figure 9D As shown, in typical diffraction grating shapes, deviations occur between the designed and manufactured values, particularly noticeable towards the outer periphery where the deviation increases. Furthermore, in typical diffraction grating shapes, the manufactured values ​​show a decrease in grating height compared to the designed values. This results in an increased distribution of light to the distant focal point (0th order light) and a decreased distribution of light to the near focal point (+2nd order light). This... Figure 9E , 9F The simulation results of light intensity and MTF shown in 10C and 10D also confirm this, and in particular, it can be confirmed that the larger the pupil diameter, the more significant the effect; for a near focus with a pupil diameter of φ5mm, it has disappeared. In Example 5, the results with a cutting tool tip R of 0.3mm are shown; however, by reducing the cutting tool tip R, this tendency is reduced. However, in this case, it is shown that the cutting tool is prone to defects, and the cutting tool has poor durability. Thus, it can be said that the diffraction grating shape of this embodiment is a shape that is easy to machine. Furthermore, the sharp part is easily affected by cutting resistance, and shape collapse is prone to occur; however, it is also shown that this can be improved by flattening all the peaks and valleys, reducing shape collapse during machining.

[0114] (other)

[0115] [Example 6]

[0116] <MTF measurement results of the prototype and existing lens in this embodiment>

[0117] In Example 6, the one with Figure 9A The multifocal diffraction lens with the diffraction grating shape shown was compared with existing lenses to verify the effectiveness of near-side shift of the distance focal point in multicolor performance evaluation.

[0118] The MTF (monochromatic performance and multicolor performance) measurements of the lens in Example 6 were performed as follows. A halogen lamp was used as the light source for white light evaluation. For monochromatic light evaluation, an interference filter was used to extract 546 nm from the halogen lamp light source.

[0119] Figures 11A-11CThe results of MTF measurements are shown for a prototype with a negative-order focal length (FOF) of this embodiment, a conventional lens A with a 0-order focal length (FOF), and a conventional lens B with a positive-order focal length (FOF). Specifically, Figure 11A This is a graph illustrating the defocus MTF measurement results of this sample (distance focal point = -1st order light, intermediate focal point = 0th order light). Figure 11B The results are the defocus MTF measurements of existing lens A (distance focal point = 0th order light, central focal point = +1st order light). Figure 11C This is the defocus MTF measurement result of existing lens B (distance focal point = +1 order light, intermediate focal point = +2 order light). For example... Figure 11A As shown, for this prototype with a negative-order light at the distance focal point and a zero-order light at the mid-view focal point, the distance focal point in the multicolor performance evaluation is positioned closer to the light source than the distance focal point in the monochromatic performance evaluation. In contrast, as... Figure 11B and 11C As shown, for existing lens A, where the distance focal point is a 0th-order light and the mid-view focal point is a positive-order light, and for existing lens B, where both the distance focal point and the mid-view focal point are positive-order light, the distance focal point in the multicolor performance evaluation is positioned further away than the distance focal point in the monochromatic performance evaluation, and the same trend was observed in both simulation results and physical verification results. This suggests that the prototype of this embodiment can efficiently utilize light in white light.

[0120] [Fourth Implementation Method]

[0121] The multifocal diffraction lens of the fourth embodiment will now be described. Furthermore, the multifocal diffraction lens of the fourth embodiment is a modification of the multifocal diffraction lenses of the first to third embodiments; matters not specifically described are the same as those in the first embodiment, etc.

[0122] Figure 13A This is a bottom view of the multifocal diffraction lens 100 according to the fourth embodiment. Figure 13B This is a schematic side view parallel to the weak principal meridian L1 of the multifocal diffraction lens 100. Figure 13C This is a schematic side view parallel to the strong principal meridian L2 of the multifocal diffraction lens 100. Furthermore, in Figure 13B and 13C In order to make the explanation easier to understand, the following is shown: Figure 13A A schematic diagram of a multifocal diffractive lens 100 with the support portion 100b removed.

[0123] like Figures 13A-13CAs shown, in the multifocal diffractive lens 100 of this embodiment, the first optical surface 1a, which is an optical surface, has a diffraction grating, and the second optical surface 1b, which is another optical surface, has a tortuous surface shape (torsional surface). Regarding the first optical surface 1a, since it is the same as in the first embodiment, the description is omitted.

[0124] In the multifocal diffractive lens 100, by utilizing the toric surface of the second optical surface 1b, a difference in refractive power is generated in the meridian directions of the weak principal meridian L1 and the strong principal meridian L2, which are orthogonal to each other on the surface. This difference can be used to correct astigmatism. In the toric surface, the meridian with the greater refractive power is the strong principal meridian L2, and the meridian with the less refractive power is the weak principal meridian L1.

[0125] The cross-sectional shape of the second optical surface 1b of the multifocal diffractive lens 100 in any meridional direction (angle θ) is expressed by a formula including the following.

[0126]

[0127] Here, c is the paraxial curvature of the multifocal diffraction lens 100 preceding the toric surface specified in the second term, r is the distance from the optical axis OA of the multifocal diffraction lens 100, and k is a conic constant about the plane of rotational symmetry of the optical axis OA in the multifocal diffraction lens 100 preceding the toric surface. The symbols c, r, and k are common to the meridional direction on the second optical surface 1b. Furthermore, A(θ) and B(θ) are parameters expressed as functions of the angle dependent on the meridional direction, given by the following equation.

[0128] A(θ)=a 2x cos 2 θ+a 2y sin 2 θ

[0129] B(θ)=a 4x cos 4 θ+a 2x2y cos 2 θsin 2 θ+a 4y sin 4 θ

[0130] like Figure 13AAs shown, a toric surface mark MA is formed on the lens body 100a of the multifocal diffraction lens 100. This toric surface mark MA is a mark indicating the astigmatic axis. Specifically, near the outer edge of the toric surface (second optical surface 1b) of the lens body 100a, a pair of toric surface marks MA are arranged such that the optical axis OA of the lens body 100a is positioned opposite each other. An imaginary line connecting the pair of toric surface marks MA represents the first axis of the lens body 100a (e.g., the weak principal meridian L1), and a line passing through the optical axis OA of the lens body 100a and orthogonal to the first axis represents the second axis (e.g., the strong principal meridian L2). By utilizing the toric surface mark MA, after the multifocal diffraction lens 100 is inserted into the patient's eyeball, the position of the multifocal diffraction lens 100 can be adjusted so that the astigmatic axis of the patient's cornea (the strong principal meridian axis of the cornea) is aligned with the toric surface axis (the weak principal meridian axis of the lens) of the multifocal diffraction lens 100.

[0131] As in Figure 14A As shown in the enlarged view, in the top view of the second optical surface 1b, the toric surface mark MA has a rectangular shape with rounded corners. Regarding the shape of the toric surface mark MA, the radial length of the lens body 100a differs from its circumferential length. Specifically, the toric surface mark MA has a long side in the radial direction and a short side in the circumferential direction. The toric surface mark MA is composed of a pair of straight sections AL1, whose long side is parallel to the weak principal meridian L1 at its edge 4a, and a curved section AL2, whose short side is a parabola connecting the pair of straight sections AL1. By making the toric surface mark MA have the above-described shape, even when only one end of the toric surface mark MA can be visually confirmed during the alignment of the astigmatic axis after the insertion of the multifocal diffraction lens 100, the direction of the astigmatic axis can be determined based on the shape of the edge 4a. Figure 14B As shown, the complex surface mark MA has a recess 1e in the cross-section along the optical axis OA. The recess 1e has a bottom surface 4b and an inclined surface 4c that connects to the bottom surface 4b from the edge 4a. Furthermore, the shape of the complex surface mark MA can also be an ellipse, an oblong, a rectangle, or a polygon with a long side and a short side. In addition, the edge 4a can also be chamfered, and the bottom surface 4b or the inclined surface 4c can also be curved.

[0132] like Figures 13A-13C As shown, the multifocal diffractive lens 100 has a planarization portion 100d with a substantially fixed end thickness formed at the end 100c of the lens body 100a. The planarization portion 100d is formed to include an end 100c that overlaps with the strong principal meridian L2 when viewed from the lens center (optical axis OA). Specifically, the strong principal meridian L2 and... Figure 13AThe X-axis overlaps as shown. In this embodiment, a pair of planarization portions 100d are provided at the end 100c of the toric surface (second optical surface 1b) of the lens body 100a, facing each other with respect to the optical axis OA of the lens body 100a. Furthermore, the shape of the planarization portions 100d is set to be approximately linearly symmetrical with respect to the X-axis, i.e., the strong principal meridian L2. Alternatively, the planarization portions 100d may be formed from a gently sloping surface or a curved surface. In this case, at the end 100c of the lens body 100a, the curvature near the strong principal meridian L2 corresponding to the planarization portions 100d is smaller than the curvature near the weak principal meridian L1.

[0133] In the planarization section 100d, the end thickness at a position with a radius r from the center of the lens is set as e(r). By appropriately determining the end thickness e(r), the range of the angle φ in which the planarization section 100d is formed, as observed from the center of the lens in the top view of the second optical surface 1b, and the radial width L of the planarization section 100d in the lens body 100a are determined. Since the toric surface of the second optical surface 1b is defined as described in the aforementioned formula, when the end thickness e(r) is determined, the intersection line of the toric surface of the second optical surface 1b and the plane of the planarization section 100d is determined.

[0134] The end thickness e(r) of the planarization portion 100d is set to be thinner than the end thickness on the weak principal meridian L1 side of the lens body 100a and thicker than the end thickness when the planarization portion 100d is formed as a tortuous surface of the lens body 100a. Therefore, the end thickness on the weak principal meridian L1 side of the lens body 100a, i.e., the end thickness of the portion overlapping the Y-axis, can be the same as in conventional lens bodies. Conventionally, the end thickness in the strong principal meridian L2 direction is thinner; however, by ensuring the end thickness in the strong principal meridian L2 direction is a predetermined thickness as in this embodiment, it is possible to maintain an end thickness sufficient to prevent posterior cataracts while preventing unnecessarily thickening of the center thickness of the lens body 100a. Furthermore, since the end thickness in the strong principal meridian L2 direction is ensured to be a predetermined thickness, even if the support portion 100b is provided on the planarization portion 100d, the force of the lens body 100a being pressed against the posterior capsule of the lens by the support portion 100b can be stably obtained.

[0135] Figure 13D This is a diagram illustrating an example of the variation of the end thickness e(r) in the angular direction as viewed from the lens center of the lens body 100a. Figure 13DIn the diagram, the horizontal axis represents the angle φ (unit: °), and the vertical axis represents the sag Z of the second optical surface 1b (unit: mm). The directions of angle φ at 0° and 180° correspond to the weak principal meridian L1 of the lens body 100a, while the direction of angle φ at 90° corresponds to the strong principal meridian L2 of the lens body 100a. Furthermore, the variation in end thickness e(r) within the angle φ range of 180° to 360° is the same as the variation within the angle φ range of 0° to 180°.

[0136] exist Figure 13D In the example shown, the end thickness e(r) of the lens body 100a is approximately fixed within a range of 70° to 110° along the strong principal meridian L2 direction (angle φ = 90°). That is, a planarization portion 100d is formed within the aforementioned angular range.

[0137] Furthermore, in this embodiment, in Figure 13A In the example shown, the support portion 100b is arranged opposite to the weak principal meridian L1 and connected to the flattening portion 100d; however, the configuration of the support portion 100b can be appropriately changed.

[0138] The present invention has been described above according to embodiments; however, the present invention is not limited to the above embodiments. For example, the shape of the diffraction grating of the multifocal diffraction lens 100 can be appropriately changed within the range that satisfies the conditions of the above embodiments.

[0139] Furthermore, in the above embodiments, as long as the negative-order light generates the focal point for viewing at a distance, the 0-order light generates the focal point closer to the distance, and the focal point position for viewing at a distance in the multicolor performance evaluation is configured to be closer to the focal point position for viewing at a distance relative to the focal point position for viewing at a distance in the monochromatic performance evaluation, the order of the diffracted light that generates the focal point for viewing at near, intermediate, or far distance can be appropriately changed.

[0140] Furthermore, the multifocal diffractive lens 100 described above can be applied to various ophthalmic lenses.

[0141] Furthermore, in the above embodiment, a first optical surface 1a of a pair of optical surfaces of the multifocal diffraction lens 100 has a diffraction grating and the other second optical surface 1b has a spherical, aspherical, complex, or other structure. However, it is also possible to adopt a structure in which the first optical surface 1a has a spherical, aspherical, complex, or other structure and the second optical surface 1b has a diffraction grating.

Claims

1. A multifocal diffractive lens, wherein, It has a diffraction grating, Negative-order light generates the focal point for distant viewing, 0th-order light generates the focal point closer to the target, and positive-order light generates the focal point closer to the target than the 0th-order light. The number of focal points is 3 or more. The diffraction grating has a shape that combines two different Cairn lens profiles. The focal position for distance viewing in the multicolor performance evaluation using wavelengths of 430nm, 490nm, 546nm, 590nm, and 650nm is positioned closer to the focal position for distance viewing relative to the focal position for monochromatic performance evaluation using a wavelength of 546±10nm. The diffraction grating has a shape that combines the diffraction grating shape with positive degree addition and the diffraction grating shape with negative degree addition. The multifocal diffraction lens is a lens that adds one or more focal points in addition to the two focal points generated by the bifocal diffraction lens, and the number of diffraction fringes is the same as that of the bifocal diffraction lens.

2. The multifocal diffractive lens according to claim 1, wherein, The correction term for the refractive index of the additional medium on the profile of the Kern lens.

3. The multifocal diffractive lens according to claim 1, wherein, Add a pupil magnification correction term to the outline of the Kaino lens.

4. The multifocal diffractive lens according to claim 1, wherein, The multifocal diffractive lens is a trifocal diffractive lens that adds a third focal point in addition to the two focal points generated by the bifocal diffractive lens. The near-side addition power of the trifocal diffraction lens is twice that of the bifocal diffraction lens, and the number of diffraction fringes is the same.

5. The multifocal diffractive lens according to claim 1, wherein, The multifocal diffractive lens is a quadfocal diffractive lens that adds two more focal points in addition to the two focal points generated by the bifocal diffractive lens. The near-side addition power of the quadfocal diffraction lens is 3 times that of the bifocal diffraction lens, and the number of diffraction fringes is the same.

6. The multifocal diffractive lens according to claim 1, wherein, The height of the diffraction grating having half the height of both of the described Caino lens profiles, The light is distributed to generate a negative-order light that produces a focal point farther than the 0th-order light and a positive-order light that produces a focal point closer than the 0th-order light, wherein the order values ​​of the negative-order light and the positive-order light are equal.

7. The multifocal diffractive lens according to claim 1, wherein, The two types of Keno lens profiles have different diffraction grating heights. The light is distributed to generate a negative-order light that produces a focal point farther than the 0th-order light and a positive-order light that produces a focal point closer than the 0th-order light, wherein the order values ​​of the negative-order light and the positive-order light are different.

8. The multifocal diffractive lens according to any one of claims 1 to 7, wherein, The peaks and valleys in the diffraction grating have flat regions.

9. The multifocal diffractive lens according to any one of claims 1 to 7, wherein, It is formed of optical materials with normal dispersion, and the refractive index of the material at a wavelength of 546nm is above 1.45 and below 1.

56. The degree setting between each focal point is above 0.75D.

10. The multifocal diffractive lens according to any one of claims 1 to 7, wherein, It has a pair of optical surfaces, one of which has a diffraction grating and the other has a tortuous surface shape.

11. The multifocal diffractive lens according to any one of claims 1 to 4 and 6, wherein, The multifocal diffraction lens is a trifocal diffraction lens of order -1, 0, and +1. The diffraction grating has a shape that combines the first and second Keino lens profiles. The first Keino lens profile has a diffraction grating shape with positive diopters corresponding to the +1st order light and the 0th order light, and the second Keino lens profile has a diffraction grating shape with negative diopters corresponding to the -1st order light and the 0th order light.

12. The multifocal diffractive lens according to any one of claims 1 to 3, 5 and 7, wherein, The multifocal diffraction lens is a fourfocal diffraction lens of order -1, 0, +1, and +2. The diffraction grating has a shape that combines the first and second Keino lens profiles. The first Keino lens profile has a diffraction grating shape with positive diopters corresponding to the +1 and +2 light, and the second Keino lens profile has a diffraction grating shape with negative diopters corresponding to the -1 and 0 light.

13. The multifocal diffractive lens according to any one of claims 1 to 7, wherein, The two types of Cairn lens profiles have the same number of diffraction fringes. The number of diffraction fringes in the diffraction grating is the same as the number of diffraction fringes in the profile of the Kern lens.

14. The multifocal diffractive lens according to any one of claims 1 to 7, wherein, The height of the diffraction grating is lower than the height of the diffraction grating for both of the aforementioned Keno lens profiles.

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