Multifocal diffractive lenses

Abstract

The present invention provides a multifocal diffraction lens capable of efficiently using light. A multifocal diffraction lens 100 has a diffraction grating 1c. Minus-order light L2 generates a focal point f2 for distant vision, zero-order light L1 generates a focal point f1 that is closer than that for distant vision, the number of focal points is two or more, and a focal position fc for distant vision in multicolor performance evaluation is disposed closer than a focal position fs for distant vision in single color performance evaluation.

Description

[Technical Field]

[0001] The present invention relates to a multifocal diffractive lens that is primarily applied to intraocular lenses. [Background technology]

[0002] Conventional multifocal diffractive lenses often use zero-order light (refracted light) as a focal point for distance vision and +1st-order light (diffracted light) as a focal point for near or intermediate vision. As an example of a different type of multifocal diffractive lens, a multifocal ophthalmic lens has been disclosed in which +1st-order light (diffracted light) is used as a focal point for distance vision to reduce chromatic aberration (see Patent Document 1). Another example of a multifocal diffractive lens has been disclosed in which zero-order light (refracted light) is used as a focal point for intermediate vision, +1st-order light (diffracted light) is used as a focal point for near vision, and −1st-order light (diffracted light) is used as a focal point for distance vision (see Patent Document 2). Furthermore, an ophthalmic lens with negative diffractive power to increase the range of chromatic aberration has been disclosed (see Patent Document 3).

[0003] ISO 11979-2, which describes testing methods for the optical properties of intraocular lenses, stipulates that refractive power, MTF (Modular Transfer Function), and the like are measured using a monochromatic light source with a wavelength of 546±10 nm, and the specifications of the intraocular lens are determined by these monochromatic performance evaluations. Here, as Patent Document 1 describes chromatic aberration, attention is being paid to evaluating the polychromatic (white) performance of multifocal lenses. However, the multifocal lens of Patent Document 1 does not take into account the difference between the focal position for monochromatic performance and the focal position for polychromatic performance. Therefore, when a typical optical design of an intraocular lens for monochromatic performance at a wavelength of 546±10 nm according to ISO 11979-2 is performed, the focal position shifts between the monochromatic performance and the polychromatic performance. In conventional multifocal diffractive lenses, the focal position for distance vision in a multicolor performance evaluation is often located on the far side compared to the focal position for distance vision in a monochromatic performance evaluation.In such cases, the light distributed for distance vision is concentrated on the retina and behind the retina, making it impossible to use the light efficiently, and there is a risk of a discrepancy between the actual performance of the intraocular lens and its specifications. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 100459 [Patent Document 2] International Publication No. 2019 / 020435 [Patent Document 3] Japanese Patent Publication No. 59-224818 Summary of the Invention

[0005] The present invention has been made in consideration of the problems of the background art described above, and has as its object to provide a multifocal diffractive lens that can use light efficiently.

[0006] In order to achieve the above object, the multifocal diffractive lens of the present invention has a diffraction grating, in which negative order light generates a focus for distance vision, zero order light generates a focus closer to the distance vision, the number of foci is two or more, and the focus position for distance vision in the multicolor performance evaluation is located closer to the focus position for distance vision in the monochromatic performance evaluation.

[0007] In the above-mentioned multifocal diffractive lens, the distance vision focus in the multicolor performance evaluation is positioned closer to the eye than the distance vision focus in the monochromatic performance evaluation, so that in the visible light range the distance vision focus is positioned closer to the intraocular lens (multifocal diffractive lens) than to the retina, making it possible to focus on objects at a finite position and allowing light to be used efficiently.

[0008] According to a specific aspect of the present invention, in the above-mentioned multifocal diffractive lens, the positive order light generates a focus closer to the zeroth order light, and the number of focuses is three or more. In this case, imaging is possible for three or more object distances.

[0009] According to another aspect of the present invention, the diffraction grating has a shape that combines kinoform profiles. In this case, by combining the kinoform profiles, it is possible to efficiently design a multifocal diffractive lens having a diffraction grating shape in which minus order light generates a focus for far vision, zero order light generates a focus closer than far vision, and plus order light generates an additional focus closer than the zero order light.

[0010] According to yet another aspect of the present invention, a correction term for the refractive index of the medium is added to the kinoform profile. In this case, when the multifocal diffractive lens is used in the eye, the kinoform sag height can be corrected by the correction term for the refractive index of the medium, assuming that the lens is placed in a liquid.

[0011] According to yet another aspect of the present invention, a correction term for pupil dilation is added to the kinoform profile. Even if simulations using two methods, one for adding refractive light power by changing the curvature and the other for adding diffracted light power using a diffraction grating, result in different power values ​​despite the same desired power values ​​being added, the correction term for pupil dilation can be used to match the power obtained by refracting light.

[0012] According to yet another aspect of the present invention, there is provided a trifocal diffractive lens that adds one more focus to the two foci produced by a bifocal diffractive lens, wherein the near addition power of the trifocal diffractive lens is twice that of the bifocal diffractive lens, but the number of diffraction fringes is the same.

[0013] According to yet another aspect of the present invention, a quadrifocal diffractive lens is provided that adds two more foci to the two foci generated by a bifocal diffractive lens, and the near addition power of the quadrifocal diffractive lens is three times that of the bifocal diffractive lens, but the number of diffraction fringes is the same.

[0014] According to yet another aspect of the present invention, the diffraction grating has a shape obtained by combining two types of kinoform profiles, has a height half the diffraction grating height of the two types of kinoform profiles, and distributes light into minus-order light that generates a focus farther than the zeroth-order light and plus-order light that generates a focus nearer than the zeroth-order light, the numerical values ​​of the orders of the minus-order light and the plus-order light being equal. In this case, the amount of change in the height of each diffraction grating after combination is equal, and it is possible to make the light distribution ratio of the minus-order light to the plus-order light approximately equal.

[0015] According to yet another aspect of the present invention, the diffraction grating has a shape that combines two types of kinoform profiles, the diffraction grating heights of the two types of kinoform profiles are different, and the light is distributed into minus order light that generates a focus farther than the zeroth order light and plus order light that generates a focus nearer than the zeroth order light, and the numerical values ​​of the orders of the minus order light and the plus order light are different. In this case, the number of diffracted order light that generates a focus increases, and the focus adjustment amount can be increased.

[0016] According to yet another aspect of the present invention, the peaks and valleys of the diffraction grating have flat regions, so that light that may be distributed to unintended focal positions of higher-order light when the peaks and valleys are not flattened can be distributed to focal positions of lower-order light.

[0017] According to yet another aspect of the present invention, the multifocal diffractive lens is formed of an optical material with normal dispersion, the refractive index of the material at a wavelength of 546 nm is 1.45 or more and 1.56 or less, and the power setting between each focus is 0.75D or more.

[0018] According to yet another aspect of the present invention, there is provided a pair of optical surfaces, one of which has a diffraction grating and the other of which has a toric shape. In this case, the other of the optical surfaces has a toric shape, making it possible to provide a multifocal diffractive lens for correcting astigmatism. [Brief explanation of the drawings]

[0019] [Figure 1]Figure 1A is a plan view illustrating the multifocal diffractive lens of the first embodiment, Figure 1B is a side view illustrating the multifocal diffractive lens, and Figure 1C is a conceptual diagram illustrating an example of use of the multifocal diffractive lens. [Figure 2] FIG. 2A is a diagram illustrating the relationship between the focal points of refracted light and diffracted light in a multifocal diffractive lens, and FIG. 2B is a diagram illustrating the relationship between the focal points of monochromatic performance and the focal points of polychromatic performance. [Figure 3] Figure 3A is a diagram explaining the diffraction grating shape of the multifocal diffractive lens of Example 1, Figure 3B is a diagram explaining the light intensity when the multifocal diffractive lens of Example 1 is incorporated, Figure 3C is a diagram explaining the MTF of the multifocal diffractive lens of Example 1, Figure 3D is a diagram explaining the diffraction grating shape of the multifocal diffractive lens of Comparative Example 1, Figure 3E is a diagram explaining the light intensity when the multifocal diffractive lens of Comparative Example 1 is incorporated, and Figure 3F is a diagram explaining the MTF of the multifocal diffractive lens of Comparative Example 1. [Figure 4] 4A to 4E are diagrams illustrating the MTF of the multifocal diffractive lens of Example 2. [Figure 5] 5A to 5F are diagrams illustrating the MTF of another multifocal diffractive lens of Example 2. [Figure 6] Figures 6A to 6F are figures explaining the diffraction grating shape of the multifocal diffractive lens of Example 3 of the second embodiment, Figures 6G to 6I are figures explaining the diffraction grating shape of the multifocal diffractive lens of Comparison Example 2, and Figures 6J to 6L are figures explaining the diffraction grating shape of the multifocal diffractive lens of a modified example of Example 3. [Figure 7] Figures 7A and 7B are diagrams explaining the diffraction grating shape of the multifocal diffractive lens of Example 4 of the third embodiment, Figure 7C is a diagram explaining the light intensity of the multifocal diffractive lens of Example 4, and Figure 7D is a diagram explaining the MTF of the multifocal diffractive lens of Example 4. [Figure 8] Figures 8A and 8B are diagrams explaining the diffraction grating shape of the multifocal diffractive lens of Comparative Example 3, Figure 8C is a diagram explaining the light intensity of the multifocal diffractive lens of Comparative Example 3, and Figure 8D is a diagram explaining the MTF of the multifocal diffractive lens of Comparative Example 3. [Figure 9]Figure 9A is a diagram explaining the diffraction grating shape of the multifocal diffractive lens of Example 5, Figure 9B is a diagram explaining the light intensity of the lens of Example 5 when the pupil diameter is φ3mm, Figure 9C is a diagram explaining the MTF of the lens of Example 5 when the pupil diameter is φ3mm, Figure 9D is a diagram explaining the diffraction grating shape of the multifocal diffractive lens of Comparative Example 4, Figure 9E is a diagram explaining the light intensity of the lens of Comparative Example 4 when the pupil diameter is φ3mm, and Figure 9F is a diagram explaining the MTF of the lens of Comparative Example 4 when the pupil diameter is φ3mm. [Figure 10] Figure 10A is a diagram explaining the light intensity of the lens in Example 5 when the pupil diameter is φ5mm, Figure 10B is a diagram explaining the MTF of the lens in Example 5 when the pupil diameter is φ5mm, Figure 10C is a diagram explaining the light intensity of the lens in Comparative Example 4 when the pupil diameter is φ5mm, and Figure 10D is a diagram explaining the MTF of the lens in Comparative Example 4 when the pupil diameter is φ5mm. [Figure 11] FIG. 11A is a diagram illustrating the MTF of the multifocal diffractive lens of Example 6, and FIGS. 11B and 11C are diagrams illustrating the MTF of the multifocal diffractive lens of the existing lens. [Figure 12] Figure 12A is a diagram explaining the light intensity of a quadrifocal lens with different values ​​of the coefficient α of the kinoform profile in a modified example of Example 3 shown in Figure 6L, and Figure 12B is a diagram explaining the MTF of the above quadrifocal lens with different values ​​of the coefficient α. [Figure 13] Figure 13A is a bottom view of a multifocal diffractive lens of the fourth embodiment, Figure 13B is a conceptual side view parallel to the weak meridian of the multifocal diffractive lens, Figure 13C is a conceptual side view parallel to the strong meridian of the multifocal diffractive lens, and Figure 13D is a diagram showing an example of the change in the angular direction of the edge thickness as viewed from the center of the lens body. [Figure 14] FIG. 14A is an enlarged view of a toric mark provided on the multifocal diffractive lens shown in FIG. 13A, and FIG. 14B is a cross-sectional view of the toric mark. DETAILED DESCRIPTION OF THE INVENTION

[0020] [First embodiment] A multifocal diffractive lens 100 according to a first embodiment of the present invention will be described below with reference to Fig. 1 etc. Fig. 1A is a plan view of the multifocal diffractive lens 100, Fig. 1B is a side view of the multifocal diffractive lens 100, and Fig. 1C is a conceptual diagram illustrating an example of use of the multifocal diffractive lens 100.

[0021] The multifocal diffractive lens 100 shown in FIGS. 1A and 1B is used as an intraocular lens and includes a lens body 100a that functions as a substitute for the crystalline lens 2a within an eyeball 200 shown in FIG. 1C, and two haptics 100b that support the lens body 100a within the eyeball 200. The lens body 100a and haptics 100b are integrally formed. The lens body 100a has a first optical surface 1a, which is the front surface, and a second optical surface 1b, which is the rear surface opposite the first optical surface 1a. In the illustrated example, the lens body 100a is a biconvex lens, but one side may be concave or flat depending on the lens characteristics. The haptics 100b have curved protrusions that protrude from the outer periphery of the lens body 100a. The lens body 100a and haptics 100b may be formed separately. As shown in Figure 1C, when using the multifocal diffractive lens 100, only the contents of the lens 2a are removed, leaving the surrounding capsule-like membrane (lens capsule), and the multifocal diffractive lens 100 is placed inside this capsule and fixed in place.

[0022] The multifocal diffractive lens 100 is made of a flexible soft material such as a thermoplastic resin, a non-thermoplastic resin, an inorganic amorphous substance, etc. The multifocal diffractive lens 100 is made of a normal dispersion optical material, and the refractive index of the material at a wavelength of 546 nm is 1.45 or more and 1.56 or less, and it is desirable that the power setting between each focus is 0.75D or more.

[0023] The multifocal diffractive lens 100 combines a refractive lens structure with a diffraction grating 1c, and has the diffraction grating 1c on the first optical surface 1a or the second optical surface 1b of the lens body 100a. In the example shown, the first optical surface 1a, which is one of the optical surfaces, has the diffraction grating 1c, and the other optical surface, the second optical surface 1b, has a spherical or aspherical surface. In the multifocal diffractive lens 100, minus-order light generates a focus for far vision, and zero-order light generates a focus on the near side of the far vision, the number of foci is two or more, and the focus position for far vision in the polychromatic performance evaluation is located closer to the near side than the focus position for far vision in the monochromatic performance evaluation. When we say that 0th order light (refracted light) produces a focus closer to the eye than distance vision, we mean that the 0th order light produced by light from a specific object passing through a lens is focused closer to the eye than, for example, -1st order light produced by light from the same object passing through a lens. When considered from the retina's perspective, -1st order light enables distance vision better than 0th order light.

[0024] FIG. 2A illustrates the relationship between the focal points of refracted light and diffracted light in the multifocal diffractive lens 100, and FIG. 2B illustrates the relationship between the focal points of monochromatic performance and the focal points of polychromatic performance. In the example of FIG. 2A, the power of the zeroth-order light (refracted light) L1 in the multifocal diffractive lens 100 is +20D. When the focal point f1 of the zeroth-order light is taken as the reference, the negative-order light (e.g., −1st-order light L2) generates a focal point f2 on the far side, and the positive-order light (e.g., +1st-order light L3) generates a focal point f3 on the near side. FIG. 2A shows the infinity focus of the multifocal diffractive lens 100, and the image formation position on the retina 2b is set based on the focal position of the negative-order light located at the farthest side. For the zeroth-order light, the positive-order light, and negative-order light other than the reference, images of objects located at the corresponding object distances can be formed on the retina 2b. Here, the object distance refers to the distance from infinity to each object located discretely closer to the multifocal diffractive lens 100.

[0025] In this embodiment, the multifocal diffractive lens 100 is a bifocal diffractive lens, and a configuration will be described in which 0th-order light L1 and −1st-order light L2 are used. In the multifocal diffractive lens 100, the 0th-order light L1 generates a focal point f1 for near vision, and the −1st-order light L2 generates a focal point f2 for far vision. In the multifocal diffractive lens 100, the distance F from the multifocal diffractive lens 100 to the retina 2b is set as the standard value for the focal position for far vision. That is, in this embodiment, the focal position of the −1st-order light L2 corresponds to the distance F. Note that the focal length of the −1st-order light L2 can be changed according to the distance F by setting or designing a diffractive structure that generates a focal point for far vision.

[0026] 2B, as described above, the multifocal diffractive lens 100 has a focal position fc for distance vision in the polychromatic performance evaluation located closer to the near side than the focal position fs for distance vision in the monochromatic performance evaluation. In other words, the focal position fc for distance vision in the polychromatic performance evaluation is shifted closer to the near side than the focal position fs for distance vision in the monochromatic performance evaluation.

[0027] In the multifocal diffractive lens 100, by positioning the distance vision focus in polychromatic performance evaluation on the near side, the distance vision focus in the visible light range is positioned closer to the multifocal diffractive lens 100 (an intraocular lens) than the retina 2b, making it possible to focus on objects at a finite location, thereby enabling efficient use of light. The positioning of the distance focus position is based on the phenomenon of intraocular lenses leaving spherical aberration on the near side. This is explained in detail below. In an intraocular lens, when spherical aberration is low-corrected and remains on the near side, light is focused on the retina and in front of the retina. By leaving a range of aberration within the eye, the aberration can be used for focusing. To efficiently use light, intraocular lenses are often selected to have low-correction spherical aberration that remains on the near side. While this is an issue in monochromatic performance, it is believed to be similar when considering polychromatic performance. Intraocular lenses are actually used in polychromatic lenses rather than monochromatic lenses, and while the focal position is set to the reference position for monochromatic lenses, it is desirable that the focal position for distance vision be positioned closer to the intraocular lens than to the retina for both monochromatic and polychromatic lenses. In other words, it is desirable that the focal position for polychromatic lenses be shifted to the near side compared to the focal position for monochromatic lenses, as in the multifocal diffractive lens 100 of this embodiment.

[0028] In addition, chromatic aberration is considered when considering multi-color performance. The chromatic aberration of refracted light is such that the blue focus, which is shorter than 546 nm, is formed on the near side, and the red focus, which is longer than 546 nm, is formed on the far side, resulting in blue, green, and red foci formed in that order from the near side. Furthermore, for positive-order diffracted light, red, green, and blue foci are formed in that order from the near side, while for negative-order diffracted light, blue, green, and red foci are formed in that order from the near side. In other words, with regard to chromatic aberration caused by diffracted light, positive-order light exhibits chromatic aberration in the opposite direction to that of refracted light, while negative-order light exhibits chromatic aberration in the same direction as that of refracted light. It is known that multifocal diffractive lenses compensate for chromatic aberration caused by refracted light with chromatic aberration caused by diffracted light. Therefore, with typical diffractive lenses, a blue focus, which is shorter than 546 nm in wavelength, is often formed on the far side of the green focus, which is near the design wavelength of 546 nm. In other words, a typical diffractive lens has the opposite chromatic aberration to a normal refractive lens, and red, green, and blue foci are formed in order from the near side. At the distance vision focus of the multifocal diffractive lens 100 of this embodiment, even though it is a diffractive lens, a blue focus is formed on the near side of the green focus, so blue, green, and red foci are formed in order from the near side.

[0029] In the multifocal diffractive lens 100, the distance vision focal position in the polychromatic performance evaluation is shifted relative to the distance vision focal position in the monochromatic performance evaluation by utilizing the fact that the light intensity of refracted light and diffracted light in polychromatic performance varies depending on wavelength. When the light intensity of a monochromatic light source at 546 nm is used as a reference, the light intensity of refracted light decreases on the short wavelength side, while the intensity of the long wavelength side increases, but the amount of change is small. In contrast, the light intensity of diffracted light increases on the short wavelength side, while the intensity of the long wavelength side decreases. Specifically, for -1st-order diffracted light (light for distance vision), the light intensity of the short wavelength (blue) side located closer than 546 nm increases, resulting in a shift in polychromatic performance toward the near side. Meanwhile, for 0th-order refracted light (light for near vision), the light intensity of the long wavelength (red) side located farther than 546 nm increases, resulting in a shift in polychromatic performance toward the far side. By placing minus order light (diffracted light) at the far vision focus and zero order light (refracted light) at a focus closer to the far vision focus, in polychromatic performance, the wavelength range with increased light intensity is concentrated between the minus order light (diffracted light) and zero order light (refracted light) in monochromatic performance, so the far vision focus in polychromatic performance evaluation is placed closer to the far vision focus in monochromatic performance.

[0030] The optical surfaces of the multifocal diffractive lens 100 will be described below. In the multifocal diffractive lens 100, the refractive lens structure is represented by a zero-order virtual reference surface 1d shown in FIG. 2A, and has a spherical or aspherical surface. The reference surface 1d uses the following aspherical profile formula. Here, the x-order aspherical coefficient may be set to 0. Also, the conic constant k and the fourth-order aspherical coefficient A4 may be used, and further, the sixth-order aspherical coefficient A6 or the eighth-order aspherical coefficient A8 may be used. TIFF0007772708000001.tif31158 where, z(s): sag height r: distance from the optical axis (radius) R: radius of curvature k: Conic constant A4: 4th order aspheric coefficients A6: 6th order aspheric coefficients A8: 8th order aspheric coefficient

[0031] Furthermore, the diffraction grating 1c has a shape designed by a kinoform profile. That is, the diffraction grating 1c has a diffraction pattern based on the kinoform profile, and the thickness or step of the kinoform and the interval or pitch of the annular zones are appropriately adjusted with respect to a virtual zeroth-order reference plane 1d. The illustrated example shows the diffraction patterns of zeroth-order and first-order light, and each annular zone of the kinoform has a concave surface facing the lens body 100a with respect to the reference plane 1d.

[0032] To calculate the grating height h(r) for the grating 1c, the parameters (specifically, n A (λ0) and M) were changed. In the kinoform profile equation, correction terms for the refractive index of the medium and the pupil dilation rate were added. Specifically, the refractive index of the medium n A is a correction term for the purpose of placement in liquid, and pupil dilation factor M is a correction term to match the power obtained by refracted light. In the original formula, the refractive index of air is 1.0, assuming placement in air. In the formula, r is the distance (radius) from the optical axis, m is the diffraction fringe (m=0, 1, 2, ...), and n L is the refractive index of the material, λ0 is the design wavelength, α is a coefficient for adjusting the kinoform sag height s(r), and P is the diffracted optical power to be added. Reference: Dale A. Buralli, G. Michael Morris, and John R. Rogers., "Optical performance of holographic kinoforms", Applied Optics, vol.28, No.5, 976 (1989) TIFF0007772708000002.tif87134

[0033] The distribution of light to any two foci is changed by varying the diffraction grating height using the coefficient α in the above equation. In other words, changing the diffraction grating height changes the resulting order. For example, when α = 0, the result is 0th order light, when α = 1, the result is +1st order light, and when α = 0.5, the result is 0th and +1st order light. Also, when α = -1, the result is -1st order light, when α = -2, the result is -2nd order light, and when α = -1.5, the result is -1st and -2nd order light. The number of diffraction fringes is determined by the diffraction power. Here, as an example, when determining the focal length f, a pupil dilation factor M = 1.13 was taken into consideration. Simulations were performed using two methods for designing the lens: adding refracted light power by changing the curvature and adding diffracted light power using a diffraction grating. The resulting power values ​​were different, even though the desired power values ​​were the same. Because the added power of diffracted light is approximately equal to the added power of refracted light / 1.13, a correction term M was added to match the two. At the actual pupil plane, the diffraction power is considered to be 1 / 1.13 due to the diffraction grating fringe pitch being M=1.13, and this formula assumes that the diffraction power is multiplied by 1.13 at the lens surface. Note that it is not necessary to take M=1.13 into consideration, and M=1 may also be used.

[0034] In the multifocal diffractive lens 100 described above, by using a multifocal lens in which the distance vision focus in the polychromatic performance evaluation is located closer to the near side than the distance vision focus in the monochromatic performance evaluation, the distance vision focus in the visible light range is located closer to the multifocal diffractive lens 100, which is an intraocular lens, than to the retina 2b, making it possible to focus on an object at a finite position and using light efficiently. This makes it possible to avoid the risk of hyperopia in a white light source environment (polychromatic performance) when performing general optical design of an intraocular lens at a wavelength of 546 nm (monochromatic performance) in accordance with ISO11979-2.

[0035] Example 1 <MTF Simulation of Bifocal Diffractive Lens +1.5D (Comparison between Example 1 and Comparative Example 1)> In Example 1, it is explained that for a bifocal diffractive lens, when 0th order light generates a focus for near vision and -1st order light generates a focus for far vision, light can be used efficiently in polychromatic performance evaluation.

[0036] In Example 1, an MTF simulation of the multifocal diffractive lens 100 was performed as follows (the same applies to subsequent Examples). For polychromatic performance evaluation to evaluate optical performance in white light, which is representative of sunlight, a simulation was performed using five wavelengths of 430 nm, 490 nm, 546 nm, 590 nm, and 650 nm in the visible light range of 380 nm to 780 nm. Note that these wavelength selections are merely examples for representing white light. The MTF number was compared at 50 lines / mm. Meanwhile, for monochromatic performance evaluation, ISO11979-2:2014, Annex C (MTF) requires measurement using a monochromatic light source with a wavelength of 546±10 nm, so a simulation was performed at a wavelength of 546 nm.

[0037] In Example 1, a bifocal diffractive lens with distance of +20D and near of +21.5D was compared. In Example 1, the 0th order light generates a focus for near vision, and the -1st order light generates a focus for far vision. In Comparative Example 1, the 0th order light generates a focus for far vision, and the +1st order light generates a focus for near vision. FIG. 3A is a diagram illustrating the diffraction grating shape of -1.5D and 0D addition in Example 1, FIG. 3B is a diagram illustrating the light intensity of refraction +21.5D (near) and diffraction -1.5D (far) in Example 1, and FIG. 3C is a diagram illustrating the MTF of refraction +21.5D and diffraction -1.5D in Example 1. Fig. 3D is a diagram illustrating the diffraction grating shape of 0D and +1.5D addition in Comparative Example 1, Fig. 3E is a diagram illustrating the light intensity of refraction +20D (far) and diffraction +1.5D (near) in Comparative Example 1, and Fig. 3F is a diagram illustrating the MTF of refraction +20D and diffraction +1.5D in Comparative Example 1. Note that in Figs. 3A and 3D, the minus side of the diffraction grating depth (diffraction grating height) indicates the lens body 100a side in the multifocal diffractive lens 100 (the same applies to other embodiments).

[0038] As shown in Figure 3C, in the MTF results for Example 1, the far focal position for polychromatic performance is shifted toward the near side relative to the far focal position for monochromatic performance. In contrast, as shown in Figure 3F, in the MTF results for Comparative Example 1, the far focal position for polychromatic performance is shifted toward the far side relative to the far focal position for monochromatic performance. This can be explained by the light intensity results for polychromatic performance shown in Figures 3B and 3E. Diffracted light passing through a diffraction grating designed for a wavelength of 546 nm is characterized by increased light intensity on the shorter wavelength side than the design wavelength and decreased light intensity on the longer wavelength side than the design wavelength. In contrast, there is almost no change in the light intensity of refracted light. In the light intensity results for Example 1 shown in Figure 3B, a short-wavelength region with increased light intensity nearer than the far focal position and a long-wavelength region with equivalent light intensity farther from the near focal position exist between the far focal position and the near focal position. In contrast, in the light intensity results for Comparative Example 1 shown in Figure 3E, a short-wavelength region with equivalent light intensity closer to the far focal position and a long-wavelength region with reduced light intensity farther from the near focal position are present between the far focal position and the near focal position. The distribution of these light intensity results suggests that in Example 1, the wavelength range with increased light intensity is concentrated between the far focal position and the near focal position, and therefore the far focal position of polychromatic performance is shifted toward the near side in the MTF results relative to the far focal position of monochromatic performance.

[0039] As in Example 1, by using a multifocal lens in which the distance vision focus in the multicolor performance evaluation is positioned closer to the distance vision focus in the monochromatic performance evaluation, the distance vision focus in the visible light range is positioned closer to the intraocular lens (multifocal diffractive lens) than to the retina, allowing light to be used efficiently.

[0040] Example 2 <Simulation when refractive index and interfocal power change> In Example 2, it will be explained that it is desirable to set each interfocal power to 0.75D or more for a lens material whose refractive index n at a wavelength of 546 nm is in the range of 1.45 to 1.56.

[0041] As shown in Figures 4A to 4E, a bifocal diffractive lens was used, with a lens material having a refractive index n = 1.52 at a wavelength of 546 nm. The lens generates a distance of +20D with -1st-order light (hereinafter, the added power is referred to as A) and a near focal point of (+20-A)D with 0th-order light. The distance focal positions of the monochromatic and polychromatic performances were compared by simulation when the added power A was changed to five levels: -0.6D, -0.75D, -1.5D, -2.0D, and -3.0D. As a result, as shown in Figure 4A, when the added power A = -0.6D, the distance focal position of the polychromatic performance shifted toward the far side relative to the distance focal position of the monochromatic performance. However, as shown in Figures 4B to 4E, at other added powers, the distance focal position of the polychromatic performance shifted toward the near side relative to the distance focal position of the monochromatic performance. This confirmed that in the diffraction grating shape of this embodiment, the effect of the invention can be obtained by setting the power difference between the focal points to 0.75D or more.

[0042] Next, as shown in Figures 5A and 5B, we performed simulations using a bifocal diffractive lens with a lens material refractive index n = 1.52 at a wavelength of 546 nm, generating a distance of +26D with -1st-order light (added power A = -0.75D) and a near distance of +26.75D with 0th-order light, and a bifocal diffractive lens with a distance of +6D with -1st-order light (added power A = -0.75D) and a near distance of +6.75D with 0th-order light. This confirmed that, regardless of the distance power, the distance focus position of the polychromatic performance shifts toward the near side relative to the distance focus position of the monochromatic performance. This result confirmed that the effects of the invention can be obtained even when the distance power setting is changed.

[0043] 5C-5F, simulations were performed on a bifocal diffractive lens that generates a distance of +20D using -1st-order light (added power A = -0.75D) and a near distance of +20.75D using 0th-order light, and a bifocal diffractive lens that generates a distance of +20D using -1st-order light (added power A = -1.5D) and a near distance of +21.5D using 0th-order light. The simulations were performed on a lens material with a material refractive index n = 1.45 at a wavelength of 546 nm and a lens material with a material refractive index n = 1.56 at a wavelength of 546 nm. The simulations confirmed that the far focal position of polychromatic performance shifts toward the near side relative to the far focal position of monochromatic performance under both conditions. The results confirmed that the effects of the present invention can be achieved with lens materials whose material refractive index at a wavelength of 546 nm is in the range of 1.45≦n≦1.56.

[0044] From the above results, it was confirmed that it is desirable to set each interfocal power to 0.75D or more for lens materials whose material refractive index n at a wavelength of 546nm is in the range of 1.45 to 1.56.

[0045] Second Embodiment The multifocal diffractive lens according to the second embodiment will be described below. Note that the multifocal diffractive lens according to the second embodiment is a modified version of the multifocal diffractive lens according to the first embodiment, and matters that are not specifically described are the same as those in the first embodiment.

[0046] In this embodiment, in the multifocal diffractive lens 100, the positive order light generates an additional focus closer to the zeroth order light, resulting in three or more foci. This enables imaging at three or more object distances. The multifocal diffractive lens 100 is a trifocal diffractive lens that adds one additional focus to the two foci generated by a bifocal diffractive lens. The near addition power of the trifocal diffractive lens is twice that of the bifocal diffractive lens, but the number of diffraction fringes is the same. In other words, the near addition power of the trifocal diffractive lens, which adds a focus nearer than the bifocal diffractive lens, is twice that of the bifocal diffractive lens. A trifocal diffractive lens that adds one additional focus to the two foci generated by a bifocal diffractive lens, is a combination of two kinoform profiles with different addition powers.

[0047] In the multifocal diffractive lens 100, in the case of a trifocal diffractive lens, the diffraction grating is a combination of two types of kinoform profiles, has a height half the diffraction grating height of the two types of kinoform profiles (for example, the diffraction grating depth D shown in FIG. 6C described later), and is distributed into minus order light that generates a focus farther than the zeroth order light and plus order light that generates a focus closer than the zeroth order light, and the numerical values ​​of the orders of the minus order light and the plus order light are equal. As a result, the change in the height of each diffraction grating after combination is equal, and the light distribution ratio to the minus order light and the plus order light can be made almost the same.

[0048] In the case of a trifocal diffractive lens, the multifocal diffractive lens 100 has, for example, a zeroth order light that generates a focus for intermediate vision, a -1st order light that generates a focus for distance vision, and a +1st order light that generates a focus for near vision.

[0049] Furthermore, the multifocal diffractive lens 100 is a quadrifocal diffractive lens that adds two more foci to the two foci generated by the bifocal diffractive lens, and the near addition power of the quadrifocal diffractive lens is three times that of the bifocal diffractive lens, and the number of diffraction fringes may be the same. In other words, the near addition power of the quadrifocal diffractive lens, which adds a focus to the near side of the bifocal diffractive lens, is three times that of the bifocal diffractive lens. A quadrifocal diffractive lens that adds two more foci to the two foci generated by the bifocal diffractive lens is a combination of two kinoform profiles with different addition powers.

[0050] In the case of the multifocal diffractive lens 100, in the case of a four-focal diffractive lens, the diffraction grating has two types of kinoform profiles with different diffraction grating heights, and the light is distributed into minus-order light that generates a focus farther than the zeroth-order light and plus-order light that generates a focus nearer than the zeroth-order light, with the numerical values ​​of the minus-order light and plus-order light being different. This increases the number of diffracted orders that generate a focus, allowing for a larger focus adjustment amount. In this case, the numerical values ​​of both orders are unequal, meaning four foci, for example, -1st order, 0th order, +1st order, and +2nd order.

[0051] Example 3 <Comparison of the diffraction grating shape with the same addition power setting of the trifocal diffractive lens with +1.5D and +3D addition diffraction grating shapes (conventional kinoform)> In Example 3, the addition power when combining two types of kinoform profiles in a trifocal diffractive lens will be described.

[0052] In the multifocal diffractive lens 100, a trifocal diffractive lens is formed by combining two kinoform profiles with different addition powers. FIG. 6C is a diagram for explaining the maximum selected diffraction grating shape design in Example 3, showing a diffraction grating shape obtained by combining the +1.5D addition diffraction grating shape shown in FIG. 6A and the -1.5D addition diffraction grating shape shown in FIG. 6B. FIG. 6F is a diagram for explaining the minimum selected diffraction grating shape design in Example 3, showing a diffraction grating shape obtained by combining the +1.5D addition diffraction grating shape shown in FIG. 6D and the -1.5D addition diffraction grating shape shown in FIG. 6E. Note that the maximum selection of the diffraction grating shape design selects the deeper one, and the minimum selection selects the shallower one. FIG. 6I is a diagram for explaining a general diffraction grating shape design in Comparative Example 2, showing a diffraction grating shape obtained by combining the +1.5D addition diffraction grating shape shown in FIG. 6G and the +3.0D addition diffraction grating shape shown in FIG. 6H.

[0053] As shown in Figures 6C, 6F, and 6I, when the addition power setting of the trifocal diffractive lens is the same, the number of diffraction fringes in this embodiment is reduced, resulting in a diffraction grating shape that is easy to fabricate. Furthermore, the diffraction grating height (diffraction grating depth D) of the trifocal diffractive lens is half the height of the diffraction grating heights of the two types of kinoform profiles. At this time, it is possible to generate negative order light, which is a focus farther than the zeroth order light, and positive order light, which is a focus closer than the zeroth order light, with the order values ​​of both light being equal. For example, when α = 1.0, the lens results in a trifocal diffractive lens with -1st order, 0th order, and +1st order. Furthermore, when α = 2.0, the diffracted light is relatively stronger than the zeroth order light, resulting in a quadruple focus with -2nd order, -1st order, +1st order, and +2nd order. Regarding the diffraction grating height, as a result of adjusting the light distribution to the three foci, α = 1.3 for the diffraction grating shape of this embodiment and α = 0.6 for a typical diffraction grating shape, but this is merely an example.

[0054] As a modification of the third embodiment, the diffraction grating heights of two kinoform profiles with different added powers may be mismatched. Specifically, a quadrifocal lens is obtained by setting the coefficient α to different values. FIG. 6L illustrates the design of the minimum selected diffraction grating shape in a modification of the third embodiment, showing a diffraction grating shape obtained by combining the +1.0D and +2.0D added diffraction grating shapes shown in FIG. 6J and the -1.0D added diffraction grating shape shown in FIG. 6K. While the setting of the coefficient α is not limited, it is preferable that when one kinoform profile is xα, the other kinoform profile is 2xα. In this case, a negative order light with a focus farther than the zeroth order light and a positive order light with a focus closer than the zeroth order light can be generated, and the order values ​​of the two lights are unequal. For example, when the kinoform profiles with addition powers of -1.0D and +1.0D are set to α = 1.0 and α = 2.0, respectively, the resulting quadrifocal lens has -1st, 0th, +1st, and +2nd orders. By setting α = 2.0 on the +1.0D side, the diffracted light on the positive order side becomes relatively stronger, allowing for efficient extraction of not only +1st order light but also +2nd order light. While a typical diffraction grating shape increases the number of diffraction fringes as the number of focal points increases, the diffraction grating shape of this embodiment is characterized by the fact that the number of focal points can be increased without increasing the number of diffraction fringes. Note that while α = 1.0 and α = 2.0 are used for the two kinoform profiles, this is merely an example, and the light intensity ratio at each focal point can be adjusted by adjusting the coefficient α.

[0055] An example of setting the coefficient α will be described below. In Fig. 6L, which is a modification of the third embodiment, the kinoform profile of the quadrifocal lens with addition powers of -1.0D and +1.0D is set to α = 1.0 and α = 2.0, respectively. A quadrifocal lens in which α = 1.3 and α = 2.0 will be described.

[0056] Figure 12A is a diagram explaining the light intensity of the above-mentioned quadrifocal lens with different values ​​of the coefficient α of the kinoform profile in a modified example of Example 3 shown in Figure 6L, and Figure 12B is a diagram explaining the MTF of the above-mentioned quadrifocal lens with different values ​​of the coefficient α.

[0057] As shown in Figure 12A, comparing the light intensity peaks at each focus position, the light intensity peak at the intermediate vision focus (0th order light) decreases or disappears, while the light intensity peak at the near vision focus (+2nd order light) increases. This confirms that the light distribution ratio at each focus position can be adjusted by changing the setting of coefficient α. Furthermore, as shown in Figure 12B, the MTF results also show similar results to the light intensity. Note that while the setting of coefficient α of the kinoform profile with an addition power of +1.0 D was changed here, it is also possible to change the setting of coefficient α of the kinoform profile with an addition power of -1.0 D, or both, or the addition power may also be changed.

[0058] Third Embodiment The multifocal diffractive lens according to the third embodiment will be described below. The multifocal diffractive lens according to the third embodiment is a modified version of the multifocal diffractive lenses according to the first and second embodiments, and matters not specifically described are the same as those of the first embodiment, etc.

[0059] In this embodiment, the peak-valley portion 300 in the diffraction grating of the multifocal diffractive lens 100 has a flat region 3c (see FIGS. 7A and 7B described later). This allows light that may be distributed to an unintended focal position of a high-order light if the peak-valley portion 300 is not flattened to be distributed to a focal position of a low-order light. Note that having a flat region 3c means that the peak height and the valley depth are limited, and includes not only a linear shape but also an inclined shape, an arc shape, etc.

[0060] Example 4 <Flattening of peaks and valleys in trifocal diffractive lenses> In the fourth embodiment, a trifocal diffractive lens in which flat regions 3c are provided in the peak-valley portions 300 of the diffraction grating pattern of the multifocal diffractive lens 100 will be described.

[0061] The trifocal diffractive lens of FIG. 6C, shown in FIG. 7A, has a diffraction grating shape with a height of 1.97 μm, and the peak-valley portion 300 (collectively referring to the peaks 3a and valleys 3b) is compared with the peaks 3a and valleys 3b shown in FIG. 7B, which are flattened to a limit of 0.4 μm, which is 20% of the height of the diffraction grating shape. As shown in FIG. 7B, the diffraction grating shape of Example 4 has a flat region 3c in the peak-valley portion 300. FIG. 7C illustrates the light intensity of the diffractive lens shown in FIG. 7A before flattening and the diffractive lens shown in FIG. 7B after flattening. FIG. 7D illustrates the MTF of the diffractive lens shown in FIG. 7A before flattening and the diffractive lens shown in FIG. 7B after flattening.

[0062] As shown in Figure 7C, when comparing the light intensity peaks at each focus position, the light intensity peaks of the ±2nd order light decreased, and the light intensity peak of the intermediate focus (0th order light) increased significantly. The total amount of light collected within an arbitrary focus range was 1.96 × 10 6 (V / m) 2 to 2.32 x 10 6 (V / m) 2 It can be seen that the peak-valley luminance is increased by 1.18 times. Furthermore, as shown in FIG. 7D, the MTF results show results similar to those for the light intensity. Note that although all peaks and valleys 300 were flattened here, it is also possible to flatten only some of the peaks and valleys 300, or to adjust the rate of 20% flattening described above.

[0063] In addition, for the general trifocal diffractive lens shown in FIG. 6I with 0D, +1.5D, and +3D additions in Comparative Example 3, it is possible to synthesize a portion of the diffraction grating shape with -1.5D addition, which has the same diffraction fringe pitch as the +1.5D addition. FIG. 8A is a diagram illustrating the diffraction grating shape before partial synthesis, and FIG. 8B is a diagram illustrating the diffraction grating shape after partial synthesis. FIG. 8C is a diagram illustrating the light intensity of the diffractive lens shown in FIG. 8A before partial synthesis and the diffractive lens shown in FIG. 8B after partial synthesis. FIG. 8D is a diagram illustrating the MTF of the diffractive lens shown in FIG. 8A before partial synthesis and the diffractive lens shown in FIG. 8B after partial synthesis. As shown in FIG. 8C, in the case of Comparative Example 3, the light intensity peak of the near vision focus (+2nd order light) is reduced, and the light intensity peaks of the intermediate vision focus (+1st order light) and the far vision focus (0th order light) are increased, and the total amount of light collected within an arbitrary focal range is also 2.10 × 10 6 (V / m) 2 to 2.24 x 10 6 (V / m) 2 It can be seen that the increase is 1.06 times. Furthermore, as shown in FIG. 8D, the MTF results also show results similar to those of the light intensity. From this, Example 4 has a larger increase in the total amount of light collected within a given focal range than Comparative Example 3, and is highly effective in distributing light that may be distributed to the focal position of unintended high-order light to the focal position of low-order light.

[0064] Example 5 <Comparison of processing radius between flattened and conventional kinoform> In the fifth embodiment, the processing R during cutting of the diffraction grating shape of the multifocal diffractive lens 100 will be described.

[0065] When cutting the mold for the diffraction grating shape of Example 4 shown in Figure 7B, a processing radius is imparted to the valleys 3b (see Figure 7A), which can cause the diffraction grating shape to collapse and result in optical performance that does not match the simulation results. Example 5 shows the change in simulation results when a +3D addition trifocal lens is machined using a tool tip radius of 0.3 mm. Figure 9A is a diagram illustrating the diffraction grating shape of Example 5 (similar to Figure 7B), Figure 9B is a diagram illustrating the light intensity of the lens in Example 5 when the pupil diameter is φ3 mm, and Figure 9C is a diagram illustrating the MTF of the lens in Example 5 when the pupil diameter is φ3 mm. Furthermore, Figure 10A is a diagram illustrating the light intensity of the lens in Example 5 when the pupil diameter is φ5 mm, and Figure 10B is a diagram illustrating the MTF of the lens in Example 5 when the pupil diameter is φ5 mm. Fig. 9D is a diagram illustrating the diffraction grating shape (similar to Fig. 8B) of Comparative Example 4, Fig. 9E is a diagram illustrating the light intensity of the lens of Comparative Example 4 when the pupil diameter is φ3 mm, and Fig. 9F is a diagram illustrating the MTF of the lens of Comparative Example 4 when the pupil diameter is φ3 mm. Also, Fig. 10C is a diagram illustrating the light intensity of the lens of Comparative Example 4 when the pupil diameter is φ5 mm, and Fig. 10D is a diagram illustrating the MTF of the lens of Comparative Example 4 when the pupil diameter is φ5 mm.

[0066] As shown in Figure 9A, the design and processing values ​​of the diffraction grating shape of this embodiment are nearly identical. However, as shown in Figure 9D, a deviation between the design and processing values ​​occurs for a typical diffraction grating shape, with the deviation becoming larger toward the outer periphery. Note that for a typical diffraction grating shape, the processing value changes so that the diffraction grating height is smaller than the design value. This results in an increase in the light distribution to the far vision focus (0th-order light) and a decrease in the light distribution to the near vision focus (+2nd-order light). This is also confirmed by the light intensity and MTF simulation results shown in Figures 9E, 9F, 10C, and 10D. The effect is particularly pronounced as the pupil diameter increases, and it can be seen that the near vision focus disappears for a pupil diameter of 5 mm. While the results for Example 5 show a tool tip radius of 0.3 mm, this tendency is reduced by reducing the tool tip radius. However, in this case, tool tip breakage is likely to occur, suggesting poor tool durability. This indicates that the diffraction grating shape of this embodiment is easy to machine. Furthermore, although the sharp tip is vulnerable to cutting resistance and prone to deformation, this can be improved by flattening all peaks and valleys, suggesting that deformation during cutting can be reduced.

[0067] 〔others〕 Example 6 <MTF measurement results of the prototype of this embodiment and existing lenses> In Example 6, a multifocal diffractive lens having the diffraction grating shape shown in FIG. 9A was compared with an existing lens to verify the effectiveness of near shift of the far vision focus in polychromatic performance evaluation.

[0068] The MTF measurement results (monochromatic performance, polychromatic performance) of the lens of Example 6 were 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.

[0069] 11A to 11C show the results of MTF measurements for a prototype of the present embodiment, whose distance focus is made up of minus-order light, existing lens A, whose distance focus is made up of zeroth-order light, and existing lens B, whose distance focus is made up of plus-order light. Specifically, FIG. 11A illustrates the through-focus MTF measurement results for the prototype (distance focus = -1st-order light, intermediate focus = 0th-order light), FIG. 11B illustrates the through-focus MTF measurement results for existing lens A (distance focus = 0th-order light, intermediate focus = +1st-order light), and FIG. 11C illustrates the through-focus MTF measurement results for existing lens B (distance focus = +1st-order light, intermediate focus = +2nd-order light). As shown in FIG. 11A, for the prototype, whose distance focus is made up of minus-order light and whose intermediate focus is made up of zeroth-order light, the distance focus in the polychromatic performance evaluation is positioned closer to the near side than the distance focus in the monochromatic performance evaluation. 11B and 11C, in the case of existing lens A, in which the far vision focus is zero-order light and the intermediate vision focus is plus-order light, and existing lens B, in which both the far vision focus and the intermediate vision focus are plus-order light, the far vision focus in the polychromatic performance evaluation is located on the far side compared to the far vision focus in the monochromatic performance evaluation, and similar trends were obtained in the simulation results and the actual confirmation results. This suggests that the prototype of this embodiment can efficiently use light in white light.

[0070] [Fourth embodiment] The multifocal diffractive lens according to the fourth embodiment will be described below. The multifocal diffractive lens according to the fourth embodiment is a modified version of the multifocal diffractive lenses according to the first to third embodiments, and matters not specifically described are the same as those of the first embodiment, etc.

[0071] Figure 13A is a bottom view of the multifocal diffractive lens 100 of the fourth embodiment, Figure 13B is a conceptual side view parallel to the weak meridian L1 of the multifocal diffractive lens 100, and Figure 13C is a conceptual side view parallel to the strong meridian L2 of the multifocal diffractive lens 100. Note that Figures 13B and 13C show conceptual views in which the support part 100b is removed from the multifocal diffractive lens 100 of Figure 13A for ease of explanation.

[0072] 13A to 13C, in the multifocal diffractive lens 100 of this embodiment, the first optical surface 1a, which is one optical surface, has a diffraction grating, and the second optical surface 1b, which is the other optical surface, has a toric shape (toric surface). The first optical surface 1a is the same as in the first embodiment, so a description thereof will be omitted.

[0073] In the multifocal diffractive lens 100, the toric surface of the second optical surface 1b creates a difference in the refractive power of the lens in the radial directions of the weakest meridian L1 and the strongest meridian L2, which are set on the surface and are perpendicular to each other, and this difference can be used to correct astigmatism. In the toric surface, the meridian in the direction of the stronger refractive power is the strongest meridian L2, and the meridian in the direction of the weakest refractive power is the weakest meridian L1.

[0074] The cross-sectional shape of the multifocal diffractive lens 100 in any meridian direction (angle θ) on the second optical surface 1b is expressed by an equation including the following equation. TIFF0007772708000003.tif24136Here, c is the paraxial curvature of the multifocal diffractive lens 100 before adding the toric surface defined by the second and subsequent terms, r is the distance from the optical axis OA of the multifocal diffractive lens 100, k is the conic constant of the surface rotationally symmetrical with respect to the optical axis OA in the multifocal diffractive lens 100 before adding the toric surface, and the symbols c, r, and k are common to the meridian direction on the second optical surface 1b. Also, A(θ) and B(θ) are parameters expressed as functions that depend on the angle in the meridian direction and are given by the following equations. TIFF0007772708000004.tif22132

[0075] As shown in FIG. 13A, a toric mark MA, which is a mark indicating the astigmatic axis, is formed on the lens body 100a of the multifocal diffractive lens 100. Specifically, a pair of toric marks MA are provided near the outer edge of the toric surface (second optical surface 1b) of the lens body 100a so as to face each other across the optical axis OA of the lens body 100a. An imaginary line connecting the pair of toric marks MA represents a first axis (e.g., the weak principal meridian L1) of the lens body 100a, and a line passing through the optical axis OA of the lens body 100a and perpendicular to the first axis represents a second axis (e.g., the strong principal meridian L2). By using the toric mark MA, after inserting the multifocal diffractive lens 100 into a patient's eyeball, the position of the multifocal diffractive lens 100 can be adjusted so that the astigmatic axis of the patient's cornea (the strong principal meridian axis) and the toric axis of the multifocal diffractive lens 100 (the weak principal meridian axis of the lens) coincide with each other.

[0076] As shown enlarged in FIG. 14A, the toric mark MA has a rectangular shape with rounded corners when viewed from above on the second optical surface 1b. The outer shape of the toric mark MA differs between its radial length and its circumferential length relative to the lens body 100a. Specifically, the toric mark MA has a long side in the radial direction of the lens body 100a and a short side in the circumferential direction. The toric mark MA has, at its edge 4a, a pair of straight line segments AL1 parallel to the weak meridian L1 as its long side, and a curved line segment AL2 connecting the pair of straight line segments AL1 by a parabola as its short side. By configuring the outer shape of the toric mark MA as described above, the direction of the astigmatic axis can be determined based on the shape of the edge 4a during astigmatic axis alignment after insertion of the multifocal diffractive lens 100, even when only one end of the toric mark MA is visible. 14B, the toric mark MA has a recess 1e in a cross section along the optical axis OA, and the recess 1e has a bottom surface 4b and an inclined surface 4c connecting the edge 4a to the bottom surface 4b. The outer shape of the toric mark MA may be a polygon having long and short sides, such as an ellipse, an oval, or a rectangle. The edge 4a may be chamfered, and the bottom surface 4b and the inclined surface 4c may have curved surfaces.

[0077] As shown in FIGS. 13A to 13C, the multifocal diffractive lens 100 has a flattened portion 100d formed at an end 100c of the lens body 100a, the end having a substantially uniform thickness. The flattened portion 100d is formed to include an end 100c that overlaps with the most intense meridian L2 when viewed from the lens center (optical axis OA). Specifically, the most intense meridian L2 overlaps with the X-axis shown in FIG. 13A. In this embodiment, a pair of flattened portions 100d are provided at the end 100c of the toric surface (second optical surface 1b) of the lens body 100a, facing each other across the optical axis OA of the lens body 100a. The shape of the flattened portions 100d is provided to be substantially symmetrical with respect to the X-axis, i.e., the most intense meridian L2. The flattened portion 100d may be formed as a gently inclined surface, a curved surface, or the like. In this case, at the end 100c of the lens body 100a, the curvature in the vicinity of the strong meridian L2 corresponding to the flattened portion 100d is smaller than the curvature in the vicinity of the weak meridian L1.

[0078] In flattened portion 100d, the edge thickness at a position of radius r from the lens center is defined as e(r). By appropriately determining edge thickness e(r), the range of angle φ at which flattened portion 100d is formed as viewed from the lens center in a top view of second optical surface 1b and width L of flattened portion 100d in the radial direction of lens body 100a are determined. Because the toric surface of second optical surface 1b is defined by the above-mentioned formula, determining edge thickness e(r) determines the intersection line between the toric surface of second optical surface 1b and the plane of flattened portion 100d.

[0079] The edge thickness e(r) of the flattened portion 100d is set to be thinner than the edge thickness of the lens body 100a on the minor meridian L1 side and thicker than the edge thickness when the flattened portion 100d is formed as a toric surface of the lens body 100a. This allows the edge thickness of the lens body 100a on the minor meridian L1 side, i.e., the edge thickness of the portion overlapping the Y-axis, to be the same as that of a conventional lens body. Conventionally, the edge thickness in the direction of the major meridian L2 is thin. However, by ensuring a predetermined edge thickness in the direction of the major meridian L2 as in this embodiment, it is possible to prevent the center thickness of the lens body 100a from becoming unnecessarily thick while maintaining an edge thickness sufficient to maintain the secondary cataract prevention effect. Furthermore, because the edge thickness in the direction of the major meridian L2 is ensured to be a predetermined thickness, even if the flattened portion 100d is provided with haptics 100b, the force with which the lens body 100a is pressed against the posterior capsule of the crystalline lens by the haptics 100b can be stably obtained.

[0080] Fig. 13D is a diagram showing an example of change in the angular direction of the edge thickness e(r) of the lens body 100a as viewed from the lens center. In Fig. 13D, the horizontal axis represents the angle φ (unit: °), and the vertical axis represents the sag Z (unit: mm) at the second optical surface 1b. The directions where the angle φ is 0° and 180° are the directions of the minor meridian L1 of the lens body 100a, and the direction where the angle φ is 90° is the directions of the major meridian L2 of the lens body 100a. Note that the change in the edge thickness e(r) when the angle φ is in the range of 180° to 360° is the same as the change in the edge thickness e(r) when the angle φ is in the range of 0° to 180°.

[0081] 13D, the end thickness e(r) of the lens body 100a is substantially constant in the range of 70° to 110° about the direction of the greatest meridian L2 (angle φ=90°). In other words, the flattened portion 100d is formed in the above angle range.

[0082] In this embodiment, in the example shown in Figure 13A, the support portion 100b is arranged so as to face each other across the weak meridian L1 and to be connected to the flattened portion 100d, but the arrangement of the support portion 100b can be changed as appropriate.

[0083] Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments, etc. For example, the diffraction grating shape of the multifocal diffractive lens 100 can be changed as appropriate within the range that satisfies the conditions of the above embodiments.

[0084] Furthermore, in the above embodiment, if the configuration is such that the negative order light generates a focus for distance vision, the zero order light generates a focus closer than distance vision, and the focus position for distance vision in the polychromatic performance evaluation is located closer to the focus position for distance vision in the monochromatic performance evaluation, the order of diffraction light that generates a focus for near vision, intermediate vision, or distance vision can be changed as appropriate.

[0085] Furthermore, the multifocal diffractive lens 100 of the above embodiment can be applied to various ophthalmic lenses.

[0086] Furthermore, in the above embodiment, of the pair of optical surfaces of the multifocal diffractive lens 100, one of the first optical surface 1a has a diffraction grating, and the other, second optical surface 1b has a spherical, aspherical, toric surface, etc. However, the first optical surface 1a may also have a spherical, aspherical, toric surface, etc., and the second optical surface 1b may have a diffraction grating.

Claims

1. having a diffraction grating, The negative order light generates a focal point for far vision, the zeroth order light generates a focal point closer to the far vision, and the positive order light generates a focal point closer to the zeroth order light, The number of foci is 3 or more, the diffraction grating has a shape that combines two types of kinoform profiles; a focal position for distance vision in the polychromatic performance evaluation is disposed on the near side of a focal position for distance vision in the monochromatic performance evaluation; A multifocal diffractive lens in which the height of the diffraction grating is constant.

2. The multifocal diffractive lens according to claim 1 , wherein a correction term for the refractive index of the medium is added to the kinoform profile.

3. A multifocal diffractive lens according to claim 1 or 2, wherein a correction term for pupil dilation is added to the kinoform profile.

4. A trifocal diffractive lens is a lens that adds one more focus to the two focuses generated by a bifocal diffractive lens. the near addition power of the trifocal diffractive lens is double that of the bifocal diffractive lens; A multifocal diffractive lens according to any one of claims 1 to 3, wherein the number of diffraction fringes is the same.

5. A quadrifocal diffractive lens is a lens that adds two more foci to the two foci generated by a bifocal diffractive lens. the near addition power of the quadrifocal diffractive lens relative to the bifocal diffractive lens is three times that of the bifocal diffractive lens; A multifocal diffractive lens according to any one of claims 1 to 3, wherein the number of diffraction fringes is the same.

6. the diffraction grating has a shape that combines two types of kinoform profiles; having a height half the height of the diffraction grating of the two types of kinoform profiles; A multifocal diffractive lens according to any one of claims 1 to 4, wherein the light is distributed into the negative order light that generates a focus farther than the zeroth order light and the positive order light that generates a focus closer than the zeroth order light, and the numerical orders of the negative order light and the positive order light are equal.

7. the diffraction grating has a shape that combines two types of kinoform profiles; The two types of kinoform profiles have different grating heights, A multifocal diffractive lens according to any one of claims 1 to 3 and 5, wherein the light is distributed into the negative order light that generates a focus farther than the zeroth order light and the positive order light that generates a focus closer than the zeroth order light, and the numerical orders 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 of the diffraction grating have flat regions.

9. A multifocal diffractive lens according to any one of claims 1 to 8, which is formed from an optical material with normal dispersion, has a material refractive index of 1.45 or more and 1.56 or less at a wavelength of 546 nm, and has a power setting of 0.75D or more between each focus.

10. 10. A multifocal diffractive lens according to any one of claims 1 to 9, comprising a pair of optical surfaces, one of which has a diffraction grating and the other of which has a toric shape.

11. The multifocal diffractive lens according to any one of claims 1 to 10, wherein the diffraction grating has a shape that combines a diffraction grating shape with a positive power addition and a diffraction grating shape with a negative power addition.

12. A trifocal diffractive lens with -1st order, 0th order, and +1st order. A multifocal diffractive lens according to any one of claims 1 to 4 and 6, wherein the diffraction grating has a shape that is a combination of a first kinoform profile having a diffraction grating shape with positive power addition corresponding to +1st order light and the 0th order light, and a second kinoform profile having a diffraction grating shape with negative power addition corresponding to -1st order light and the 0th order light.

13. A four-focal diffractive lens with −1st order, 0th order, +1st order, and +2nd order. A multifocal diffractive lens according to any one of claims 1 to 3, 5 and 7, wherein the diffraction grating has a shape that is a combination of a first kinoform profile having a diffraction grating shape with positive power addition corresponding to +1st order light and +2nd order light, and a second kinoform profile having a diffraction grating shape with negative power addition corresponding to -1st order light and the 0th order light.

14. the diffraction grating has a shape that combines two types of kinoform profiles; the two types of kinoform profiles have the same number of diffraction fringes; A multifocal diffractive lens according to any one of claims 1 to 13, wherein the number of diffraction fringes of the diffraction grating is the same as the number of diffraction fringes of the kinoform profile.

15. the diffraction grating has a shape that combines two types of kinoform profiles; A multifocal diffractive lens according to any one of claims 1 to 14, wherein the height of the diffraction grating is lower than the heights of the diffraction gratings of the two types of kinoform profiles.

Images