JP2899296B2 - Manufacturing method of multifocal phase plate - Google Patents

Description

The present invention relates to a method for manufacturing a multifocal optical lens using the phenomenon of simultaneous visual field in which two clear images are given to the eye at a time. And a method of manufacturing a multifocal optical lens that produces an arbitrary relative brightness between a plurality of images.

BACKGROUND OF THE INVENTION The design of bifocal glasses utilizes the principle of alternating fields of view. That is, the eye will alternately look between adjacent lenses of two different focal powers. This method has been unsuccessful in contact lenses because the contact lenses tend to move with the eyes. To solve this problem, many bifocal contact lenses are nowadays used which utilize the phenomenon of simultaneous field of view, in which two clear images are provided to the eye at a time. This is the case, for example, in US Pat. No. 3,033, DeCarle.
This is achieved by using a central lens, smaller in diameter than the pupil of the eye, surrounded by annular lenses of different power, as disclosed in US Pat. No. 7,425. This is effective only when the relative brightness of the two images is constant. Unfortunately, in this lens design, the relative brightness of the image provided by the two concentric lenses varies with each other, since the eye usually changes its pupil diameter.

More recent bifocal lens configurations include U.S. Pat.Nos. 4,210,391, 4,338,005, and 4,340,28.
As disclosed in No. 3, there is an apparatus using a region phase plate. In such a bifocal lens, two different diffraction focal powers can be obtained by the diffraction effect. However, these focus lenses use polycentric rings smaller in diameter than the pupil of the eye, so when the pupil of the eye opens and closes, only a small number of rings are involved, and the relative brightness of the two images is the same. Remains.

However, even if these lenses can maintain a constant relative lightness ratio of the images between different focal points irrespective of the incoming pupil size, this constant value is not always satisfactory. For example, FIG. 1 shows a bifocal region phase plate with a blaze according to U.S. Pat. No. 4,340,283 of the present inventor. In this case, when the design wavelength is .lambda. Plate area radius r
(K) is given by the equation r (k) = (k × λ × d) ^1/2 . In this case, the two image brightnesses are equal, ie, 1: 1
Is the ratio of Because the odd-numbered area focal power Fo is
1 / d, while the even-numbered area focus power Fe is 0
The even-numbered region has no blaze so as to be equal to, and the odd-numbered region blaze has a half wavelength (λ / 2).
Because it is chosen to change linearly to a depth equal to This is based on the inventor's U.S. patent which features 1 / d = Fo-Fe. However, if one considers FIG. 2 which is a blazed area phase plate with a blazed depth of only a quarter wavelength and is easier to manufacture than the lens of FIG. 1, the image brightness is equal. As such, the use of this lens as an ophthalmic bifocal lens is limited.

SUMMARY OF THE INVENTION A multifocal phase plate according to the present invention comprises a plurality of annular concentric regions spaced according to:

r (k) = (constant × k) ^1/2 where r (k) represents a region radius and k represents a region number. The present invention aims to realize such a multifocal phase plate,
The present invention provides a method for manufacturing the same, wherein the maximum change amount of the optical path length determined by {phase plate thickness / (n-1)} over the entire phase plate is substantially larger than half of the design wavelength. ,
Alternatively, it is characterized by being substantially small.

That is, the present invention provides: (a) selecting a design wavelength λ and a refractive index n, and (b) an expression {r (k) = (constant × k) ^1/2 } (where r
(K): radius of a plurality of annular concentric regions at predetermined intervals according to a region radius, k: region number), (c) two or more focal points of the design wavelength are determined, and (d) each of the phase plates A distribution of different thicknesses in the radial direction representing the thickness of the phase plate is determined so that the thickness of the annular region changes in the same manner in the radial direction. (E) The region number k is an odd number even though it is constant but small. (F) defining the image brightness at the two or more defined focal points, and (g) defining the image brightness as Steps (e) and (f) until equal at two or more defined focal points
(H) manufacturing the multifocal phase plate by using a material having a refractive index n so as to have a thickness distribution such that image brightness at the two or more defined focal points is equal. In the method, the thickness of the phase plate / (n−
1) The maximum change amount of the optical path length determined by｝ is substantially larger or smaller than half of the design wavelength.

Preferably, the design wavelength is in the visible light band,
As the material having the refractive index n, a material having optical refraction characteristics is desirable.

The multifocal phase plate manufactured according to the present invention can be sufficiently used as a contact lens or an intraocular lens.

The multifocal phase plate having such a configuration is composed of a main body having a plurality of concentric annular regions separated by a predetermined distance so as to generate diffraction power. Phase-shifting means are provided which provide a substantially constant phase shift in the optical path length across the.

The multifocal phase plate in the embodiment of the present invention uses the main body means including the optical refraction material. As the phase shift means, impurities buried in the main body means to obtain a desired phase shift, or
It may be constituted by a cutting portion of the main body means. The phase shifting means may occupy all the alternating regions.

The invention features the use of phase shifting means that are adjusted to exhibit equal image brightness at each focal point of the body means. The phase shift steps are adjusted to produce three focal points with equal image brightness at each focal point of the body means. In the preferred embodiment, the phase shift is adjusted so that the lens preferentially focuses some wavelengths of light. Preferably, the phase shift steps are adjusted to reduce the maximum depth of any step or blaze.

The multifocal phase plate uses a repetitive step as its shape, so that a constant phase shift occurs in an optical path length that traverses substantially the entire region in which the step is incorporated. The phase plate is designed to act as a multifocal lens in the visible light range. In such an embodiment of the present invention, the main body means of the phase plate is configured as a contact lens or a camera lens.

In a multifocal lens, it is necessary to disperse the incident light between various focal points. At this time, it is important to deepen various image brightnesses at which the intensity at each focus is almost equal. The present invention utilizes that a multifocal lens using the configuration of a diffractive lens has a region radius substantially represented by the equation r (k) = (constant × k) ^1/2 . That is, the annular regions are spaced so as to form an integer number of half-wave phase shifts. In these cases, the lens can be completely analyzed simply by looking at a small number of regions that form a repeating pattern for the entire lens.
For example, in FIGS. 1 and 2, only the first two regions (ie, region 1 and region 2) need to be examined.

First, we start by considering the phase plate of a single focus lens. Consider a flat lens with a focal power of 0 divided into concentric half-wavelength regions shown in FIG. Now, a step of a half wavelength is cut into the odd-numbered region, and the light transmitted through these odd-numbered regions is shifted by exactly a half wavelength to form the bifocal power shown in FIG. It was written by RWWood in 1941 from McMillian, New York, in his book "Physic Optics."
al Optics) "(pp. 37-40, p. 217 and p. 218). He used this technique,
The classic Rayleigh zone plate was only brightened, taking into account half-wave phase shifts.

With reference to FIG. 5, the analysis of the single focus phase plate is continued. Fig. 5 shows a diopter +1.0 single focus lens constructed in the usual way by cutting the blaze to a depth of one wavelength. This blaze is cut at an angle different from the flat step cut. Is embedded. According to RW Wood's method, to phase shift light passing through odd-numbered areas,
Each odd-numbered region can be cut into a half-wave step (broken line in FIG. 5). The result is the bifocal phase plate of FIG. However, considering the consideration of phase shift steps that are not half-wave is of some value, or can be applied to half-wave phase plates, this analysis has some uniqueness and unexpected consequences of consideration of this phase-shift step. It shows the results.

Returning to the lens of FIG. 2 where the image brightness at diopter 0.0 is brighter than at diopter +1.0. At diopter 0.0, the phase change of light passing through the region is caused only by the blaze. In diopter 1.0, the phase change of light passing through the region is caused by a half wavelength in addition to the phase shift due to the blaze. First, considering the focus at diopter 0.0 and the fact that region 1 has a quarter-wave blaze depth, the amplitude vector z1 (0) for light passing through this region is 90 degrees. Return (a quarter wavelength in the negative direction). Next, since the area 2 has no blaze, the amplitude vector z2 (0) for light passing through this area is not phase-shifted at all. Eventually, the phase angle a (0) between the two resulting amplitude vectors is diopter
It becomes 135 degrees while exhibiting the image brightness B ₀ ² at the focus of 0.0. At the focus of diopter 1.0, the amplitude vector z1 (1) for light passing through region 1 is rotated by 90 degrees. On the other hand, the amplitude vector z2 (1) for the light passing through the area 2 is rotated by 180 degrees. The phase angle a (1) between the two resulting amplitude vectors is then the image brightness B at the focus of diopter 1.0.
It becomes 45 degrees while showing ₁ ² . This is all shown in FIG. 7a, where the image brightness is calculated as the vector sum of the resulting amplitude vectors z1, z2. Since two regions are considered, it is convenient to set the value to 1/2 for the entire arc length of the small amplitude vector passing through each region. Therefore, at the focal point of diopter 0.0, the resulting light amplitude vector z1 (0) of light passing through region 1 is z1
(0) = 2 ^1/2 / π. Similarly, z2 (0) = 1/2, the phase angle a (0) between the vectors z1 (0) and z2 (0) is a (0) = 135 degrees, and the resulting lightness is B ₀ ² =
Given in 0.77. For the same reason, at the focus of diopter 1.0, z1 (1) = ^21/2 / π, z2 (1) = 1 / π, a
(1) = 45 degrees, B ₁ ² = 0.10.

Now, by cutting the steps in the even-numbered area,
Light passing through the even region can be phase shifted by an amount that depends on the depth of the step. The present invention makes use of any phase shifting effects and does not need to be equal to half a wavelength. 7b
The figure shows the amplitude vectors z1 and z2 of the light representing the light from the region 1 and the light from the region 2, respectively, and each focus is divided by an additional phase shift of b degrees. The resulting lightness B ₀ ^{2 at} diopter 1.0 is also shown. In FIG. 7b, if Maze the phase angle b (by increasing the depth of the step), dim image B ₁ while becomes bright, bright image B ₀ is found to be dim. There is an exact phase shift that clearly has equal image brightness. In this particular case, a phase shift of 0.157 wavelength is so, and FIG. 7c shows such a resulting lens. It should also be noted that the maximum facet depth in this lens is 0.407 wavelength deep. Typically, diffractive lenses require a phase shift of 0.5 wavelength or more. Since many manufacturing techniques (eg, ion implantation) limit the maximum amount of phase shift that can be achieved, it is advantageous to reduce the required maximum amount of phase shift. This is one of the special cases of using the phase shift step, and it is natural to select a phase shift step other than the 0.157 wavelength.

It is also of interest to consider the application of the present invention to a lens that uses a symmetrically aligned focus with respect to diopter 0.0, as described in the inventor's US Pat. No. 4,338,005. FIG. 8 shows an example of this type of lens. This particular lens is an example of a trifocal lens, each having a focus of unequal brightness. In this special case, 0.
By utilizing the phase shift step of 212 wavelengths, a trifocal lens having the same brightness as shown in FIG. 9 can be constructed.

Regarding the trifocal lens, the flat lens of power 0 shown in FIG. 3 is considered as a degenerate trifocal lens having focal points of different brightness. In fact, two of the focal points in this case
First, the brightness is 0. Nevertheless, the principles of the invention can still be applied. FIG. 10 shows the resulting trifocal lens. An important advantage of this trifocal lens is that it can be more easily manufactured because etching steps is easier than cutting blazes in many production techniques (i.e., ion reactive etching). It has a simple step structure. While RW Wood's bifocal lens is a simple step design, this is the first trifocal lens of a similarly simple design. It is clear from the above analysis that whenever a phase shift of wavelength x produces a satisfactory lens, a complementary lens can also be obtained using a phase shift of wavelength (1-x). FIG. 11 shows a complementary trifocal lens with respect to the lens shown in FIG.

So far, only monochromatic light has been considered. If the lenses of FIGS. 10 and 11 were designed for light of a specific light wavelength, for example, yellow light, the inherent chromatic aberration in the diffractive lens would be as shown in FIGS. 10 and 11. Further, a lightness distribution is generated for each of the red (R), yellow (Y), and blue (B) lights as shown. In addition to chromatic aberration at the focal point, chromatic aberration can be confirmed also in brightness. However, chromatic aberration in lightness is usually reversed in a complementary lens. This makes it possible, for example, to design compound lenses, such as the lens of FIG. 12, which can significantly reduce chromatic aberrations in brightness.

Given the inherent chromatic aberration in lens brightness utilizing diffractive power, a lens that preferentially transmits a particular selected wavelength can also be designed. For example, looking at the lens of FIG. 13, it is a trifocal lens that targets blue light at the focal point of diopter 0.0 and red light at the focal points of diopters +1.0 and −1.0. Now, a phase shift of 0.5 wavelength can be used to eliminate the focus of diopter 0.0, and there is also a bifocal lens shown in FIG. 14 that selectively focuses red light while attenuating blue light. This, of course, has benefits for aphakic and other patients who need to cut out blue light as much as possible.

In view of the foregoing, it is a primary object of the present invention to adjust the ratio of image brightness at different focal points of a diffractive multifocal lens.

It is another object of the present invention to equalize the lightness at different focal points of a diffractive multifocal lens that originally has different lightness.

It is another object of the present invention to reduce the maximum phase shift required to form a diffractive multifocal lens.

Yet another object and advantage of the present invention is to simplify the structure of certain multifocal lenses by replacing the blaze with a step.

Yet another object and advantage of the present invention is to successfully handle chromatic aberration of lightness to form a lens that selects only one wavelength.

Other objects and advantages of the present invention will become more fully apparent from the following description of preferred embodiments thereof, taken in conjunction with the accompanying drawings.

(Description of Preferred Embodiment) FIG. 15 shows an embodiment of the present invention. The illustrated multifocal phase plate is a trifocal phase plate, which has a front surface I bounded by radii r (1) to r (6).
It consists of a carrier lens or body CL divided into two concentric annular regions. In any actual lens,
The number of regions may be slightly different, with six regions being selected merely as an example. The carrier lens or body, of course, is constructed according to the basic principles involved in the design of an optical lens, with the front face I and the rear face B exhibiting a spherical, spherical cylindrical or other suitable lens design. The power P of the spherical, spherical, or aspherical surface of the carrier lens is determined according to the respective curvatures of the front surface I and the rear surface B, the center thickness CT, and the refractive index n of the carrier lens, while following the standard lens formula. Each of these parameters is determined by the use of the trifocal phase plate and the resulting material. For example, when this trifocal phase plate is used as a spectacle lens, the rear surface B is formed so as to minimize axial chromatic aberration. Standard optical materials, such as, for example, glass, plastic or other optical materials, including those used in the manufacture of eyeglasses, contact lenses, and the like, are used in the lenses of the present invention and in all of the following examples. Available for manufacturing.

In this embodiment, the alternating annular regions have a light wavelength of about 0.319 / (n-1), where n is the refractive index of the carrier lens.
Is uniformly etched to a depth of. This, of course, causes a phase shift of 0.319 wavelength of light between adjacent annular regions. The spacing between the annular regions is, of course, given by the region plate formula for r (k). In particular, the radius r (k) that determines the boundary between the annular regions is determined by r (k) = (k × λ / F) ^1/2 . Here, k = 1, 2, 3,...
An integer representing the number of the region, λ is equal to the light wavelength to be considered, and F represents the focal power. The trifocal lens in this case results in diopter PF, diopter P,
In diopter P + F, three focus powers having the same image brightness are provided.

A novel and important feature of this embodiment and all of the following embodiments is the ratio of image brightness determined by the specific depth of the step etched into the surface of the lens. The depth in this case is (b / 360) × λ / (n−
Given in 1). In this case, b = 114.84, which is determined from the following equation as shown in the above description.

z1 ² (0) + z2 ² (0) −2 · z1 (0) · z2 (0) · cos [a (0) + b] = z1 ² (1) + z2 ² (1) −2 · z1 (1) · z2 (1) .cos [a (1) + b] Needless to say, different values of b provide another embodiment of the present invention.

Another embodiment of the present invention using ion implantation is shown in FIG. Here, the region is formed by ion implantation into the surface of the carrier lens CL. Refractive index of the carrier lens by ion implantation is changed to n ¹ from n. Further, the depth of implantation is given by the formula (b / 360) × λ / (n
−n ¹ ). In this case, the blaze has a depth of 0.5 /
(N-1) wavelength, and the step is 0.319 / (n-1) in depth.
It is. Here, n is the refractive index of the carrier lens CL.
The carrier lens has front I, rear B and focal power P
It is designed to have The annular region r (k) is given by the equation r
(K) = (k × λ / F) ^1/2 here,
λ is a design wavelength. The three focal powers of this lens are P, P + F / 2 and P + F.

FIG. 17 shows another embodiment of the present invention using a deposition film forming technique. Here, the area is the carrier lens CL
Is formed by forming a film of the additional material D on the surface of the substrate. The optical path through the carrier lens increases due to the film formation. In this case, a complex lens-mirror system, that is, a lens CL adhered to the mirror M is obtained. The film thickness is calculated by the formula (b / 720) × λ / (n ¹
-1). Here, n ¹ is the refractive index of the film material.

The above disclosure relates only to preferred embodiments of the invention, and numerous modifications and improvements may be made without departing from the spirit and scope of the invention as set forth in the appended claims.

[Brief description of the drawings]

FIG. 1 shows a portion of a cross-sectional view of a typical bifocal phase plate and a corresponding lightness versus focus power graph showing equal lightness at each focus (ie, B ₀ = B ₁ ). . FIG. 2 is a graph of a portion of another cross-sectional view of a bifocal phase plate and the corresponding lightness versus focus power showing the lightness inequality (ie, B ₀ ≠ B ₁ ) at each focus. Show. FIG. 3 is a cross-sectional view of a zero-power flat lens, and
4 shows a corresponding lightness versus focus power graph showing single focus at infinity (ie, diopter 0.0). FIG. 4 shows a cross-sectional view of a zero power flat lens deformed by RW wood, and a corresponding lightness vs. focus power graph showing a bifocal of equal lightness. FIG. 5 shows a portion of a cross-sectional view of a blazed lens having a single focus power, and a corresponding lightness versus focus power graph showing a single focus. Figure 6 shows RW
FIG. 6 shows a portion of a cross-sectional view of the lens of FIG. 5 deformed by wood and a corresponding lightness vs. focus power graph showing a bifocal of equal lightness. FIG. 7a is a geometric representation of the amplitude vector of light passing through the annular region of the lens of FIG. FIG. 7b is the introduction of b of the phase shift between region 1 and region 2, schematically illustrates how the brightness B ₀ ² and B ₁ ² is changed. FIG. 7c shows a cross-sectional view of a modification of the lens of FIG. 2 according to the invention in which the image brightness at each of the two focal points is equal (ie B ₀ = B ₁ = 0.36). 8 to 14 show a part of a cross-sectional view of a trifocal lens with a blaze and a step, and a corresponding graph of lightness versus focal power. FIG. 15 is a cross-sectional view of a trifocal lens in which a step is formed by ion reaction etching. FIG. 16 is a cross-sectional view of a trifocal lens in which a blazed step is formed by ion implantation. FIG. 17 is a cross-sectional view of a trifocal mirror in which a step is formed on the mirror surface by film formation. CL: Contact lens I: Front of lens B: Rear of lens CT: Central thickness of lens

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Patent 2868801 (JP, B2) Patent 2849097 (JP, B2) Japanese Patent Publication No. 1-1772 (JP, B2) US Patent 4,338,005 (US, A) US Patent 4210391 (US U.S. Pat. No. 4,340,283 (US, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 5/18 G02C 7/06

Claims (5)

(57) [Claims] 1. A method for manufacturing a multifocal phase plate, comprising: (a) selecting a design wavelength λ and a refractive index n; and (b) formula {r (k) = (constant × k) ^1/2 }. (However, r
(K): radius of a plurality of annular concentric regions at predetermined intervals according to a region radius, k: region number), (c) two or more focal points of the design wavelength are determined, and (d) each of the phase plates A distribution of different thicknesses in the radial direction representing the thickness of the phase plate is determined so that the thickness of the annular region changes in the same manner in the radial direction. (E) The region number k is an odd number even though it is constant but small. (F) defining the image brightness at the two or more defined focal points, and (g) defining the image brightness as Steps (e) and (f) until equal at two or more defined focal points
(H) manufacturing the multifocal phase plate by using a material having a refractive index n so as to have a thickness distribution such that image brightness at the two or more defined focal points is equal. In the method, the thickness of the phase plate / (n−
1) A method of manufacturing a multifocal phase plate, wherein the maximum change amount of the optical path length determined by｝ is substantially larger or smaller than half of the design wavelength. 2. The method according to claim 1, wherein the design wavelength is in a visible light band. 3. The method according to claim 1, wherein the material having the refractive index n is a material having an optical refraction characteristic. 4. The method according to claim 2, wherein the multifocal phase plate is a contact lens. 5. The method according to claim 2, wherein the multifocal phase plate is an intraocular lens.