JPH0216890B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an artificial eye lens, and particularly to a bifocal artificial eye lens. The term artificial eye lens refers to an artificial eye lens that is used either on the eye or placed inside the eye. Specifically, one type of artificial eye lens is a contact lens that is used in contact with the eye to assist the function of the actual crystalline lens, and the other type is a contact lens that is inserted into the eyeball and is used in place of the crystalline lens. There is an implant lens that can be used for this purpose.

[Prior Art] Various prior applications have been made regarding contact lenses, including bifocal contact lenses. Bifocal lenses generally have a constant optical power for distant objects and a different optical power, typically larger (more incremental), for closer objects;
The summed power for near objects is referred to as the "near summation" value, usually expressed in units of diopters. Bifocal action is usually achieved through the use of different refractive index materials and/or different curvatures for different parts of the lens. The result is that the required different optical powers are provided in each section, often referred to as the far and near sections. Therefore, the user sees distant objects through the light transmitted through the far section of the lens, and sees closer objects through the light transmitted through the near section of the lens. Furthermore, it has also been proposed to effectively utilize the chromatic aberration of the eye and to form far and near zones that transmit light of various wavelengths (US Pat. No. 3,339,997). especially,
The various parts of the lens constituting the far and near zones are made of individually colored filter material.

The advantage of this US patent proposal is that the same curvature can be used for the far and near areas, so that the difference in effective optical power is given by the different wavelengths transmitted. However, the amount of optical power difference that can be achieved in this way is limited. In practice, "near add" values of up to about 1 diopter can be provided by appropriate color selection, and theoretically larger values can be provided by using purple for the near zone and red for the far zone. Although this is possible, there are practical problems in that the colors are darker and the amount of light that reaches the eye is less. Moreover, such lenses still require separate parts forming the near and far zones.

Implants or ocular lenses are designed to be placed into the eye by an ophthalmologist after removal of the crystalline lens for pathological conditions such as cataracts. However, whereas the crystalline lens, which is the eye's ability to focus on objects at various distances, can be deformed for accommodation by the ciliary muscles, implanted lenses are rigid and ciliary. Not connected to body muscles. Eyes treated in this way will have better vision than before, but
This lack of accommodation is similar to the condition known as presbyopia, which occurs when the lens hardens after middle age.

[Problems to be Solved by the Invention] Conventional bifocal lenses have separate far and near areas on the lens, which causes inconvenience for the wearer of the bifocal lenses in terms of visual performance. .

SUMMARY OF THE INVENTION An object of the present invention is to provide an artificial eye lens that does not require a far section and a near section to eliminate the above-mentioned inconveniences.

Means for Solving the Problems According to the invention, the object is to provide a lens with a base refractive power that may be zero, such that light from one of a distant object and a near object can be focused on the retina. , a diffraction means formed on the lens and having an additional diffraction power such that light from the other of a distant object and a near object can be focused on the retina. Achieved by lenses.

[Function] In the artificial eye lens of the present invention, the lens has a basic refraction of zero such that light from one of a distant object and a near object can be focused on the retina, and Diffractive means are formed on the aforementioned lens and have an additional diffractive power such that light from the other of the distant and near objects can be focused onto the retina. The above-mentioned diffraction means inherently has a wavelength selection effect, so when the artificial eye lens of the present invention is worn, light of a certain wavelength from a nearby object is diffracted by the diffraction means and falls on the retina. The light of other wavelengths from nearby objects is not diffracted and is focused at a position behind the retina, and the light of other wavelengths has an extremely disadvantageous effect on seeing nearby objects. Also, light of a certain wavelength from a distant object is diffracted by the diffraction means and focused at a position between the lens and the retina, and light of other wavelengths from a distant object is Light is focused on the retina without being diffracted by diffraction means, and light of one wavelength from a distant object is seen as light of another wavelength that is focused on the retina. There is no significant disadvantageous effect. Therefore, even if the artificial eye lens of the present invention is provided with diffraction means over the entire area of the lens having basic refractive power, it is possible to see both distant objects and near objects, and it is different from conventional bifocal lenses. There is no need to separately provide a far zone and a near zone on the lens, which can significantly improve the visual inconvenience experienced by conventional bifocal lens wearers.

Further, according to the present invention, an artificial eye in the form of a contact lens or an implanted lens has a bifocal effect that can have a focusing effect on the diffracted incident light portion and does not have a focusing effect on the non-diffracted incident light portion. lenses may be provided.

This diffractive power is equal to the refractive power of a lens and can extend over a specific wavelength range or several wavelength ranges, so as to selectively focus light within one wavelength range or several wavelength ranges. . Light of other wavelengths can pass through the hologram without being deflected by it. The diffractive power can be less than 100% efficient such that a portion of the incident light of the appropriate wavelength is diffracted and the remainder of the incident light of this wavelength is not deflected by diffraction. This artificial eye lens is
can have some diffractive power for all or most of the visible spectrum, but only about 20
Efficiency can range from % to 40%.

The artificial eye lens according to the present invention can have a focusing effect on the diffracted incident light portion and does not have a focusing effect on the non-diffracted incident light portion.
In this way the lens can have a bifocal effect, for example. Diffractive power can be added to or subtracted from the base optical power of this artificial eye lens. Thus, according to preferred features of the artificial eye lens according to the invention, the shape of the lens;
It is possible to have a base optical power for distant objects given by the curvature and material and a larger different optical power for near objects through the diffractive power, especially with transmission holograms. The hologram can be provided over the entire range of the artificial eye lens or the range used as the field of view, thus obviating the need to distinguish between near and far areas in a bifocal lens.

In principle, the difference in refractive power given by the diffractive power would normally be added to the basic refractive power, but
It can be any number of diopters desired. In practice, the refractive power of a transmission hologram ranges from 0 to +
Preferably up to about 4 diopters, giving a near additive value of up to 4 diopters.

Holograms may be formed within the layers of the artificial eye lens. On the other hand, the hologram can also actually be formed in or on the bulk material of the artificial eye lens as a surface deformation.

In the case of contact lenses, the hologram may be formed within a surface layer of a photographic material such as dichromate gelatin, such a layer typically being present on the surface of the lens remote from the eye in use. On the other hand, the hologram can actually be formed within the material body of the contact. In general, hologram formation within the surface layer is more suitable for rigid contact lenses;
On the other hand, hologram formation within the bulk material is suitable for either soft or hard contact lenses.

In the case of implanted lenses, the hologram can be formed actually within the material of the lens, or it may be formed within a layer of photographic material such as dichromate gelatin; such layers are usually It exists between the internal parts.

The aforementioned holograms are optically generated by illuminating an artificial eye lens with active and reference beams matching the required refractive power of the hologram obtained from a laser at several positions providing an effective point source of light. obtain. Such a beam produces interference fringes because the purge difference between this active beam and the reference beam is equal to the required refractive power of the resulting hologram. In practice, the reference beam is collimated, ie it can effectively originate from infinite positions.
The refractive power of the hologram is therefore equal to the divergence of the active light beam. Alternatively, active and reference beams can be used, each originating from a finite distance location that provides the necessary purge difference. The positions of generation of these beams can be generated optically rather than practically, and the holographic lens can be better adapted to the requirements of the eye and aberrations can be introduced in a planned manner. The effective field of view of the holographic e-lens can be modified by the shape and depth of the interference fringes.
The total field of the hologram can be made sufficiently wide to also include the fovea of the retina, or the active and reference beams can be deliberately shifted to provide an off-axis field of view for the hologram. In the case of contact lenses, it is desirable that the lens be shaped or ballasted to properly position such off-axis vision. In the case of implanted lenses, it is desirable to shape or mark the lenses for easy insertion in order to properly position these off-axis fields.

The reference and active light beams illuminate the artificial eye lens from the front or from behind, taking into account the refractive power or introducing compensation if necessary. Thus, a lens can be immersed in a liquid to produce a hologram.

In the case of contact lenses, if the active and reference beams are directed from behind, the refractive power of the rear surface must be taken into account or a compensation introduced. To effectively remove the refractive power of the contact lens surface during hologram generation, the lens can be immersed in a liquid whose refractive index matches that of the lens material.

In the case of implanted lenses, allowances must be made or compensations introduced for the optical power of the medium in which the implanted lenses function. To effectively remove the refractive power of the implanted lens surface during hologram generation, the lens can be immersed in a fluid whose ratio matches the aqueous humor and vitreous.

On the other hand, the artificial eye lens can also have a surface relief hologram, which can be generated mechanically, for example by using a suitable molding surface during its molding process.

The artificial eye lens according to the invention can be of any curvature (i.e. spherical, aspheric, toric) and of any shape (i.e. prismed or non-prismatic) to meet specific requirements. can. In the case of contact lenses, they can be of the scleral or corneal type.

The bulk material of artificial eye lenses can be colored.

Although the present invention may be used to correct hyperopic vision by providing an advantageous bifocal contact lens or to correct malaccommodative vision by providing an advantageous bifocal implant lens, it has further applications. can also be found. For example, a contact lens with diffractive power, especially a transmission hologram, according to the invention may be used to correct visual defects other than hyperopic eyes, such as intraocular macular aberrations, or to improve normal vision by reducing chromatic aberrations. can be used to Similarly, implanted lenses with diffractive power can be used to correct vision defects other than accommodative deficiencies, such as intraocular malocclusions.
Alternatively, it can be used to reduce chromatic aberration.

Furthermore, the hologram is advantageously applied over the entire area of the artificial eye lens, or over the entire field of view of use, but, if necessary, it can also be applied only to desired parts within this area. Furthermore, if necessary, a single artificial eye lens can be equipped with a plurality of separately generated holograms, which can be effectively superimposed, each with a desired diffraction profile for each wavelength range, for example. It can also be empowered and adapted to specific situations.

Now, for a more detailed understanding of the present invention,
Explanations will be added with reference to the attached drawings.

EXAMPLE FIG. 1 shows a posterior surface 2 of curvature and shape that effectively conforms to the cornea and/or sclera of a user in a well-known manner.
an artificial eye lens in the form of a contact lens 1, having a front surface 3 whose curvature and shape, in relation to the curvature and shape of this rear surface 2 and the refractive index of the lens material, provide appropriate assistance and correction of hyperopia of the user; Shown schematically. This lens is constructed to meet the specific requirements of the user, the front surface 3 can be of any curvature, i.e. spherical or toric, and the lens 1
It will be appreciated that the can be of any shape, with or without prisms. For this purpose, it suffices to consider the lens 1 as providing a basic refractive power adapted to the user's farsightedness. Therefore, light from a distant object F is focused on a position R on the retina 5 by the lens 1 together with the crystalline lens 4 of the user. The user can then look and focus on the distant object F.

However, since the user's eyesight is presbyopic, the basic lens 1 and crystalline lens 4 adapted for farsightedness do not have sufficient refractive power to focus light from a nearby object N onto the retina. Light from such a nearby object N will be focused at a position R' posteriorly distant from the retina 5, as shown by the dashed line. To overcome this, the lens 1 has a transmission hologram, shown schematically at 6. This hologram gives the lens 1 a diffractive power equal to the refractive power of the lens, so that the diffracted light from the nearby object N is transmitted by the hologram 6 (combined with the basic refractive power of the lens 1 and the crystalline lens 4). It focuses on the retina 5. Therefore, the user
Using the light diffracted by the hologram 6, a nearby object N can be viewed and focused.

As will be explained later, this hologram 6 uses wavelength selection criteria (i.e., light within a specific wavelength range or several wavelength ranges is diffracted, while light at other wavelengths is transmitted through the hologram without being deflected). or may operate on an amplitude selection basis (i.e. a portion of the incident light of any wavelength or amplitude is diffracted;
The remainder may be transmitted undeflected by the hologram), or a combination of wavelength selection criteria and amplitude selection criteria (i.e. the hologram 6 is transmitted over a specific wavelength range or several wavelength ranges). However, only a portion of the incident light within these wavelength ranges is diffracted, and the rest of the incident light within these wavelength ranges and light at other wavelengths are deflected by the hologram. It may also be possible to operate on the basis of

It will be appreciated that light from a nearby object N, undeflected and transmitted through the hologram 6, will be focused at a position R' behind the retina. However, since position R' is remote from the retina, the image of the near object N seen by the user as light diffracted by the hologram 6 is not significantly disadvantageously affected by the undiffracted light. Conversely, when the user is looking at a distant object F, the light emitted from it and diffracted by the hologram 6 is directed to a position R'' that is forwardly separated from the retina 5 (base lens 1 and Therefore, when the user is looking at a distant object F, the focal image is the light that is not diffracted by the hologram 6, that is, the light that has passed through the hologram without being deflected. Since the position R'' is remote from the retina, this distant image is not affected too disadvantageously by the diffracted light of the hologram 6.

It will be appreciated that the hologram 6 must act in such a way as to provide a reasonable balance between the brightness of the distant object F seen as undiffracted light and the brightness of the near object N seen as diffracted light. Good morning.

It will therefore be understood that the lens 1 containing the hologram 6 provides a bifocal effect. The hologram 6 is constituted by a holographic lens having a diffractive power in addition to the basic refractive power given by the shape, curvature and material of the lens 1. In principle, there is no particular limit to the additional refractive power that can be provided by the hologram 6, but preferably it has a refractive power of up to about 4 diopters, giving a near additive value of 0 to +4 diopters.

As shown schematically in FIG. 2, the contact lens 1 can have on its front surface 3 a surface layer 7 of a photographic material, for example dichromated gelatin, and a hologram 6 formed in this surface layer 7. can be done. Since in use the front surface 3 is far from the eye, direct contact between the layer 7 and the eye can be avoided. This formation of holograms in the surface layer is particularly suitable for rigid contact lenses. On the other hand, however, the hologram 6 may actually be formed within the material of the lens 1, if this material is suitable for hologram formation using an intense light source. Inside the material (or surface relief of the material as explained later)
Hologram formation is suitable for hard and soft contact lenses.

The hologram is optically generated by active and reference beams, e.g. from a laser, effectively directed at the contact lens from a conjugate point source positioned to provide the necessary refractive power within the resulting hologram. be able to. These beams, and preferably laser beams, interfere with the photosensitive material either in the surface layer or in the bulk of the contact lens. These interference fringes give bright and dark areas, and the bright areas are absorbed by the material causing a change in its refractive index and/or absorption, forming a hologram. Because of the formation and width of these fringes, some of the light transmitted through the contact lens during use is diffracted as if the hologram were an additional lens.
The refractive power of this additional lens is determined by the two interfering light sources, in particular by the purgency difference between them. If, for example, the reference beam is made collimated, ie effectively emanating from a point source at infinite position, it will have zero divergence. If the active light flux is a finite distance from the contact lens, e.g.
If it emanates from a point source positioned at 330mm,
It has an emittance of 3 diopters. The refractive power of the holographic lens is 3 between the two ray bundles.
It is given by the purgeency difference in diopters. On the other hand, the active and reference beams emanating from a point source each positioned at a finite distance from the contact lens can be used as long as the purgeency difference between them is equal to the refractive power of the required holographic lens, i.e., in bifocal terminology, the required " can be used as long as it is equal to the "near-add" value.
It will be appreciated that the positions of occurrence of the active and reference beams may be generated optically rather than practically, ie by the use of mirrors or their equivalents.
Furthermore, aberrations can be systematically introduced to make the holographic lens better suited to the needs of the eye. These aberrations may be regular, as in the case of spherical aberration, coma, astigmatism, etc., or irregular to match the actual eye of a particular user.

The material body of the contact lens can be colored.

The effective field of view of the holographic e-lens can be changed depending on the shape and depth of the interference fringes. Only a small angle is required to give good vision to the fovea, but this is not on the axis of the cornea and crystalline lens. The field of view increases its area. That is, by either making it sufficiently wide or, for shaped or ballasted contact lenses, rather by deliberately shifting the active and reference beams to provide an off-axis field of view for the hologram. Must encompass the fossa.

The active and reference beams can be directed from the front to the contact lens, as schematically shown in FIG. 10 and 11 in the figure show these ray bundles. In this case, the refractive power of the front surface of the contact lens does not adversely affect the production of the hologram, and the vergence difference between the beam bundles is maintained.

The active and reference beams can also be directed selectively from behind the contact lens. However, in this case it is necessary to take into account the refractive power of the rear surface or to introduce compensation. In order to effectively remove the refractive power of the contact lens surface during hologram generation, the contact lens 1 is
As shown schematically in FIG. 4, it can be immersed in a liquid 8 whose refractive index matches that of the contact lens material. This liquid is supplied to a bath vessel 9 of such dimensions and shape as to hold the immersed contact lens 1 in a fixed position and to which the active and reference beams are directed (as shown schematically at 10 and 11).
can be accommodated. On the other hand, the contact lens may be suspended in a liquid.

It is desirable that the hologram 6 be provided over the entire area of the lens 1 or at least over the entire area used as the field of view, thereby eliminating the need to distinguish between near and far areas.

Although specifically discussed in the discussion of bifocals by way of example, contact lenses with diffractive power may have other applications, such as for correcting vision defects other than presbyopia. Additionally, contact lenses with diffractive power could be used to reduce chromatic aberration during emmetropia, for example for athletes or soldiers (emmetropes are generally
diopters of vertical chromatic aberration).

Figure 5 is similar to Figure 1, but this one is inserted into the eyeball instead of the crystalline lens (in addition to the contact lens in Figure 1, which assists the crystalline lens).
1 schematically shows an artificial eye lens in the form of an implanted lens;

Therefore, FIG. 5 shows the user's hyperopia in relation to the posterior surface 2' of constant curvature and shape, the curvature and shape of this posterior surface 2', the refractive index of the lens material, and the refractive index of the aqueous humor and vitreous. An implanted lens 1' is shown with an anterior surface 3' of a predetermined curvature and shape that provides the proper assistance and correction of the lens. This lens 1' is tailored to meet the specific requirements of the user, so that the front surface 3' and the rear surface 2' can have any curvature, i.e. spherical or toric, and the lens 1 It will be appreciated that ' can be of any shape, ie without or with prisms. For this purpose, it is sufficient to consider lens 1' to provide a basic refractive power suitable for the distance vision of the user. Therefore, light from a distant object F combines with the user's cornea 4' and is focused by the implanted lens 1' at a position R on the retina 5'. The user can then look at the distant object F and focus on it.

However, since the user's visual acuity lacks accommodation, the basic lens 1' and cornea 4' adjusted for hyperopia have insufficient refractive power to focus light from a nearby object N onto the retina. It is. As shown by the dashed line, light from a nearby object N hits the retina 5'
It will focus at a position R' spaced backward from the point R'.
To overcome this, the implanted lens 1' provides a lens with a diffractive power equal to the refractive power of the lens 6'
It has a transmission hologram schematically shown in , in which the diffracted light from a nearby object N is reflected by the hologram 6' (combined with the fundamental forces of the implanted lens 1' and the cornea 4') onto the retina 5'. Try to stay focused. In this way, the user can use the force diffracted by the hologram 6 to view and focus on the nearby object N.

As noted above in connection with hologram 6 of FIG. 1, and as will be explained in more detail below, hologram 6' may be based on wavelength selection criteria, amplitude selection criteria, or a combination of both. It can work.

It will be appreciated that light that does not undergo diffraction passes through the hologram 6' without being deflected. nearby object N
Such light from is focused at a position R′ behind the retina. However, since position R' is remote from the retina, the undiffracted light does not significantly disadvantage the user in viewing the nearby object N as diffracted light. Conversely, when the user is looking at a distant object F, the light transmitted therefrom and diffracted by the hologram 6' is directed to a position R'' that is forwardly separated from the retina 5', as shown by the broken line.
(combined with the action of the implanted lens 1' and cornea 4')
Connect your focus. Therefore, when the user is looking at a distant object F, he is focusing on the undiffracted light, and since the position R'' is far from the retina, he is focusing on the diffracted light in order to see far away. It does not function at a huge disadvantage.

Furthermore, there must be a reasonable balance between the brightness of the distant object F seen as undiffracted light and the brightness of the near object N seen as diffracted light.

It will therefore be understood that the implanted lens 1' combined with the hologram 6' gives a bifocal effect and that this hologram constitutes a holographic lens with a diffractive power that adds to the basic optical power of the lens 1'. . In principle, there is no particular limit to the additional refractive power that can be provided by this hologram 6';
Preferably, it has a power that provides a near addition value of up to approximately 4 diopters, that is, from 0 to +4 diopters.

As shown schematically in FIG. 6, the implanted lens 1' can have a layer 7' of photographic material, for example dichromate gelatin, within its dimensions, and the hologram 6' ’ can be formed within.

On the other hand, however, the hologram 6' can actually be formed in the bulk material of the implanted lens 1', if it is suitable, or, as will be pointed out later, by a surface relief of the material. The bulk material of the implanted lens can be colored.

Holograms can be generated optically, for example by active and reference beams from a laser. These ray bundles are arranged in essentially the same manner as previously described in connection with the contact lenses of FIGS. Effectively directed from a point source to the implanted lens. These light beams, in particular laser beams, interfere within the photosensitive material, either within the layer 7' or in the bulk material of the implanted lens 1'.

If the active and reference beams are deliberately deflected to provide an off-axis field of view for the hologram, the implanted lens should have a suitable shape to allow for proper orientation and easy surgical implantation. It is preferable to add a mark.

Implanted lens 1' for the hologram formation procedure
In order to effectively reduce the refractive power of the surface of the seventh
As shown schematically in the figure, the implanted lens 1' includes:
It can be immersed in a liquid 8' whose refractive index matches that of the aqueous humor and vitreous body. The liquid is placed in a bath container 9' having a support (not shown) for supporting the immersed implanted lens 1' in a fixed position.
The active and reference beams are directed to it (schematically indicated at 10' and 11').

The movable operating modes of the hologram 6 or 6' will now be explained in more detail with reference to FIG. 8, which shows graphically the efficiency versus wavelength.

Curve 100 represents the normal human visual response extending from the so-called blue end of the visible spectrum to the red end.

Block 20 represents an ideal transmission hologram of the selected wavelength with 100% efficiency. In this way, the hologram diffracts all light rays over a selected reference range in the visible spectrum, but has no effect on light rays outside the selected wavelength range that pass through the hologram undeflected. do not have. Holograms, for example, operate in a wavelength range extending between about one-fifth and about one-fourth of the visible spectrum, i.e., wavelengths of approximately 30 to 40 nanometers located along the green portion of the visible spectrum. can affect the area. In the figure, block 20 is shown as having vertical sides that provide a specific wavelength cutoff between 100% diffraction and zero diffraction. Such a cutoff is probably impossible to achieve in practice, and changing the wavelength will usually result in a decrease in the diffraction index.

Curve 3 for a more practical transmission hologram
Indicated by 0. This curve shows a maximum diffraction index of approximately 60% at a particular wavelength value, and the diffraction index decreases as the wavelength changes this value. In this way, 60% of the light rays of a particular wavelength value are diffracted by the hologram, while the remaining 40% are transmitted through it undeflected. The relative ratio of the diffracted light of other wavelengths to the unpolarized light changes as shown in the curve.

Line 40 represents an ideal non-wavelength selective transmission hologram, i.e. with the same diffraction index for all waves (approximately
(shown in the figure as 40%) indicates that diffraction is performed. Therefore, 40% of any wavelength of light that passes through a hologram will be diffracted, and 60% will pass through unpolarized. In reality, such holograms are extremely difficult to create.

Typically, wide-area holograms have some variation in diffraction index with wavelength. A typical example is curve 50.
Shown below. In other words, as the wavelength deviates from the wavelength value to which the value of the maximum diffraction index applies, the diffraction index decreases to either side of the maximum value. . This hologram has diffractive power over the entire visible spectrum (as shown by line 40 with an ideal non-wavelength selective hologram), but is less than 100% efficient. Therefore,
For every wavelength in the visible spectrum, some of the light rays are transmitted through the hologram and diffracted,
One remaining ray passes through undeflected.

In this way the hologram 6 or 6' is
Block 20 of the figure may act on a wavelength selection criterion, as illustrated, or line 40 may act on an amplitude selection criterion, or curve 30 may act on a wavelength selection criterion and an amplitude selection criterion. and over the entire visible spectrum with varying efficiencies, varying from about 20% to about 40% for different wavelengths, as curve 50 illustrates. will be done.

Referring again to FIGS. 1 and 5, the wavelength selection effect is such that light from an object N that is close within one or more wavelengths on which the hologram acts is focused on the retina;
On the other hand, rays of other wavelengths are focused at position R′,
It will be understood that what is meant is that there is no significant disadvantage in viewing the nearby object N. Light from a distant object F within one or more wavelength ranges on which the hologram acts is focused at a position R'', which is extremely disadvantageous for viewing the distant object F as light of other wavelengths is focused on the retina. The amplitude-selective effect means that the light of the appropriate wavelength from the nearby object N will be focused on the retina, and some will be focused at the position R'. Similarly, some light of the appropriate wavelength from a distant object F will be focused at position R', and some will be focused on the retina.
If the hologram acts on all wavelengths in the visible spectrum (less than 100% efficiency), some of the light from the nearby object N will be focused on the retina at any wavelength, and some will be focused on the retina at any wavelength, and some will be focused on the retina at any wavelength.
Some of the light from the distant object F is focused at R', and some of the light from the distant object F is focused on the retina. The combination of wavelength selection and amplitude selection Within the wavelength range, some of the light coming from a nearby object N is focused on the retina,
On the other hand, some of the other light is focused at position R' with light of wavelengths outside one or more effective wavelength ranges, and some of the light coming from a distant object F within one or more effective wavelength ranges is focused at position R''. Knot, on the other hand;
Some of the others are meant to be focused on the retina along with light of one or more wavelengths outside the effective wavelength range. In all cases, positions R' and R'' are distant from the retina, so light that is focused at these positions is not focused on the retina and is therefore seen as light that is focused on the retina. In particular, it does not have a particularly disadvantageous effect.

As mentioned above, to form a transmission hologram in order to effectively add refractive power to the basic refractive power of a basic artificial eye lens, or to give refractive power to a basic artificial eye lens that basically has no refractive power. It will be appreciated that transmission holograms can be formed. Furthermore, a transmission hologram of negative refractive power could be provided. In other words,
This is to effectively reduce the refractive power from the basic refractive power of the basic artificial eye lens. Therefore, a bifocal lens can have a base refractive power adapted to near images and a hologram to which refractive power is effectively applied in the negative direction for distant images. Furthermore, if desired, multiple separately generated holograms of different refractive powers (eg, operable for different wavelength ranges) can be incorporated into a single artificial eye lens. As explained above, the hologram is advantageously provided over the entire area of the lens or the area used as the field of view, but if desired, it can also be provided over only some areas (and Separately generated holograms can also be provided for each of the various areas, preferably overlapping).

Furthermore, instead of optically generating the hologram as described above, mechanical formation methods could be used. The hologram could therefore take the form of a surface relief hologram, or it could also be generated mechanically, for example during the molding of the basic artificial eye lens, thus adapting the appropriate molding surface. You can also do it. That is, one could have appropriate grooves or ridges to provide the desired relief on the lens surface to form a hologram. Additionally, a mechanically formed hologram can be made to fit within a lens by forming it in two parts and then joining them together.

Additionally, transmission holograms would be the best way to provide diffractive power to artificial eye lenses;
However, the hologram could also be provided in other ways, for example by forming a band plate in a manner analogous to a diffraction grating.

[Effects of the Invention] Even if the artificial eye lens of the present invention is provided with diffraction means over the entire area of the lens having basic refractive power,
It is now possible to see distant objects and near objects separately, and there is no need to separately provide far and near areas on the lens like in conventional bifocal lenses, and it is possible to see objects that are far away and near objects separately. This can significantly improve the inconvenience of visual movements.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the path of light passing through a bifocal contact lens according to the present invention, FIG. 2 is a schematic cross-sectional diagram of the contact lens, and FIGS.
5 is a schematic diagram illustrating the procedure for generating a hologram in a contact lens; FIG. 5 is a schematic diagram representing the path of light passing through a bifocal implanted lens according to the present invention; and FIG. FIG. 7 is a schematic cross-sectional view, and FIG. 7 is a schematic diagram illustrating the procedure for generating a hologram in an implanted lens. FIG. 8 is a graph showing response efficiency versus wavelength. 1...Contact lens, 6...Transmission hologram.

Claims (1)

[Scope of Claims] 1. A lens having a base refractive power that may be zero such that light from one of a distant object and a near object can be focused on the retina; and diffraction means having additional diffraction power for focusing light from the other nearby object onto the retina. 2. An artificial eye lens according to claim 1, wherein the diffraction means comprises a hologram. 3. The artificial eye lens according to claim 1, wherein the diffraction means has a retardation band plate. 4. The artificial eye lens according to any one of claims 1 to 3, wherein the diffraction means is provided on the surface of the lens. 5. An artificial eye lens according to any one of claims 1 to 3, wherein the diffraction means is arranged within the lens. 6. An artificial eye lens according to any one of claims 1 to 5, wherein the diffraction means are provided over the entire visually used area of the lens. 7. Artificial eye lens according to any one of claims 1 to 5, wherein the diffraction means are provided only in a part of the visually used area of the lens. 8. Said diffraction means have an efficiency of less than 100% over part or all of the visible spectrum, such that a part of the incident light of the relevant wavelengths is diffracted but the remaining incident light of said relevant wavelengths is not deflected by diffraction. 8. Artificial eye lens according to any one of claims 1 to 7, which has a diffractive power of , and can have diffractive powers of different efficiencies over different parts of the visible spectrum. 9. the lens has a basic refractive power given to the distant object by the shape, curvature and material of the lens, and the diffraction means has a positive diffractive power added to the basic refractive power; 9. The artificial eye lens according to claim 1, wherein the artificial eye lens provides a relatively large refractive power to the nearby object. 10. The artificial eye lens according to any one of claims 1 to 9, wherein the lens is a contact lens. 11. The artificial eye lens according to any one of claims 1 to 9, wherein the lens is an implanted lens. 12. The artificial eye lens of claim 2, wherein the hologram is a surface relief hologram.