JPH03213821A - Both-surface aspherical lens - Google Patents

Abstract

PURPOSE:To improve the outward appearance and performance by forming an aspherical surface which decreases in the difference in curvature between the peripheral parts on the front and rear surface sides by varying the curvature at the peripheral parts while maintaining specific degrees. CONSTITUTION:The aspherical surface is formed which decreases in the difference in curvature between the peripheral parts on the sides of the front surface 1 and rear surface 3 by varying the curvature while maintaining the specific degrees at the peripheral parts on the sides of the front surface 1 and rear surface 3. For example, a minus lens is therefore larger in curvature at the peripheral part of the front surface 1 than at the peripheral part of the rear surface 3 and small in edge thickness. A plus lens, on the other hand, is small in curvature at the peripheral part of the front surface 1 and large at the peripheral part of the rear surface 3, so the lens has rising section and becomes flat on the whole, so that the quantity of forward projection of the lens becomes small. Consequently, the outward appearance is improved, respective aberrations which can not be removed by the front aspherical surface can be corrected by the rear aspherical surface, and the optical performance of the lens can be improved.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a 1a mirror lens, and in particular, both the front and rear surfaces are aspherical to reduce both the protrusion of the lens and the thickness of the edge. The present invention relates to a double-sided aspherical lens that can improve not only its appearance but also its optical performance.

(Prior art) Conventionally, in eyeglass lenses, the optical performance of the peripheral part away from the center has been lower than the optical performance of the central part of the lens. Various lenses with aspherical surfaces have been proposed for the purpose of achieving thinness (e.g.,
56093).

The aspherical lens disclosed in this publication has a central protruding area and a thinner peripheral area in order to soften the forward protrusion of a convex lens (plus lens), which has a large curvature on the front surface, especially for hyperopia. The lens material is made of high refractive index, low dispersion glass, and the H-efficiency part of the field of view on the outer surface side of the lens is made to have an approximate curvature V at the apex, which is less than the diameter. An aspherical lens that is formed into an aspherical surface with a large radius of curvature, its outer periphery is formed into a curved surface that smoothly connects to the aspherical surface, and the rear surface of the lens is formed into an aspherical surface with a radius of curvature larger than the approximate radius of curvature at the apex. It is.

The aspherical surface of this lens means that there is no clear boundary between the convex lens part at the center of the front side and the peripheral part, and the thickness of the peripheral part can be made thinner than that of the lens. It is said to be able to eliminate aberrations.

On the other hand, for eyeglass lenses with spherical surfaces or for astigmatism, many companies have prepared lenses with predetermined power and directionality so that they can quickly respond to demand, but in the case of double-sided aspherical single-focus lenses, Because these lenses have desired optical properties through a combination of aspheric surfaces on both sides, they are difficult to keep in stock except for a few.

(Problem to be Solved by the Invention) However, the asphericization of the conventional lens described above is a boundary line based on the difference between the radius of curvature of the H-effect field suppressing area and the radius of curvature of the surrounding area in the conventional plus lens for high hyperopia. The aspheric surface was designed with the main focus on eliminating the unsightly appearance, and increasing the effective diameter of the field of view while maintaining a sense of unity in appearance.As a result, the above-mentioned Even if the problems with appearance can be solved, the optical performance,
It has not been possible to improve two or more optical performances, mainly astigmatism and power, and furthermore distortion.

-111 Spherical lenses and lenses for astigmatism can be easily manufactured by polishing in a laboratory, but when they are aspheric on both sides, a special polishing device with NC control is required, so it is difficult to manufacture these types of lenses. This in itself is expensive, unsuitable for keeping on hand, and it takes time to add it after receiving an order, which is a bottleneck for its widespread use.

In view of this, the present invention achieves thinning of not only plus lenses but also minus lenses by reducing the protrusion and edge thickness of the lens while improving the optical performance of the lens.
The object of this invention is to provide a double-sided aspherical lens that has excellent appearance and performance as a lens for spectacles, can be immediately supplied in response to demand, and can be obtained at low cost.

(Means for Solving the Problem) Aiming to solve the problems of the above-mentioned prior art, the present invention provides a lens whose front and rear surfaces are aspherical. It is characterized by an aspherical surface that has a different curvature while maintaining a predetermined power, so that the difference in curvature between the front and rear peripheral parts is small.In the case of a minus lens, the front peripheral part The curvature of the front side is larger than the curvature of the concentric area, and the curvature of the rear side peripheral area is smaller than the curvature of the concentric area.In the case of a plus lens, the curvature of the front side peripheral area is The reason is that the lens is made of an aspherical surface whose curvature is smaller than the curvature of the rear surface side and larger than the curvature of the concentric region.Also, the lens has a structure in which the first and second lens bodies are bonded together, and each lens body has a curvature of Each bonding surface is formed into a spherical surface, and the opposite surface is formed into an aspherical surface, so that both surfaces are made aspherical by the combination of the aspherical surfaces of both lens bodies.

(Function) By creating an aspherical surface with different curvatures while maintaining a predetermined power at the front and rear peripheral parts, the difference in curvature between the front and rear peripheral parts is reduced, making it possible to create a minus lens. In the case of , the curvature of the front periphery is larger than the curvature of the rear periphery, and the edge thickness of the lens on the periphery is smaller, and in the case of a plus lens, the curvature of the front periphery is smaller, Since it becomes larger at the periphery of the rear surface, the cross section becomes upright, and the overall shape becomes flat, so that the amount of forward protrusion of the lens becomes small.

Additionally, if you prepare first and second lens bodies with the negative surface aspherical, you can select and combine these first and second lens bodies and bond them together with their spherical sides. A single focus lens with aspherical surfaces on both sides can be obtained. Therefore, preparations can be made in advance in preparation for receiving an order, which can significantly shorten the finishing period and reduce the price.Furthermore, since the strength is strengthened by bonding, thin lenses can be made in advance. The offer will be available on 01.

(Example) The present invention will be described below with reference to embodiments shown in the drawings.

Figure 1 shows the cross section of each half of the minus lens of the first embodiment, and Figure 2 shows the half cross section of the plus lens. In each figure, the solid line shows the shape of a conventional spherical lens, and the dotted line shows the shape of a conventional spherical lens. Examples of aspherical shapes according to the present invention are shown in an overlapping manner.

In the minus lens shown in FIG. 1, at the front surface 1, the central region including the axis of symmetry 2 of the lens is an arcuate surface corresponding to a base curve having a required radius of curvature R1, similar to the cross section of a conventional spherical lens. , the lens is an aspherical surface whose radius of curvature R2 gradually becomes smaller (the curvature gradually increases) toward the periphery of the lens, and on the rear surface 3, the radius of curvature R3 at the periphery gradually becomes smaller than the radius of curvature R4 at the central region. It is considered to be an aspherical surface that increases in size (curvature gradually decreases).

An example of the specific amount of change is as follows.

Specific example of the amount of change in curvature of a minus lens (a) This is an example in which a lens material with a refractive index of 1.50 is applied to a lens with an m1 power of 16D, a lens diameter of 75■■, and a base curve of 1.0D. .

(m-1).

In Table 1, r is the distance from the axis of symmetry 2, and ΔC
ΔC is the front 1. The amount of change in curvature at 1° on the rear surface 3 is shown.

/ Table 1 (b) This is an example applied to a high refractive index lens having the same prescription as the lens in (a) above, except that a lens material with a refractive index of 1.60 was used.

The curvature C1 of the front surface 1 in the axis of symmetry 2 of the lens is 1, 6
7 (m-1), and the curvature C of the rear surface 3 is 11.67 (m
').

Therefore, as an eyeglass lens that maintains the necessary power, the edge thickness T of the lens periphery can be reduced while keeping the deobiliations D t and D 2 at Dl-D2, and the protrusion from the frame that is characteristic of minus lenses when worn in a frame can be reduced. The appearance can be greatly improved by reducing the amount of water.

In the plus lens shown in Fig. 2, the central region including the symmetry axis 2 of the lens at the front surface 1 is the same as a conventional spherical lens, and the radius of curvature R5 gradually increases (the curvature gradually decreases) toward the periphery. The rear surface 3 is an aspheric surface in which the radius of curvature R6 becomes smaller (larger curvature) at the periphery, and the shape is such that there is no large difference in wall thickness overall.

An example of the specific amount of change is as follows.

Specific example of the amount of change in curvature of a plus lens (c) Using a lens material with a curvature of 1.50, the power is +3D, the lens diameter is 75■■, and the base curve is 4.0D
This is an example of application to a lens.

The curvature C1 of the front surface 1 in the axis of symmetry 2 of the lens is 2.0
(m-1), and the curvature c of the rear surface 3 is 8.0 (m-').

Table 3 (d) is an example applied to a high refractive index lens having the same prescription as the lens in (C) above, except that a lens material with a refractive index of 1.60 was used.

The curvature C□ of the front surface 1 in the axis of symmetry 2 of the lens is 6,67
(m-1), the curvature C of the rear surface 3 is 1.67 (m-1)
It is.

Figures 3 (^) to (F) show the amount of astigmatism depending on the viewing angle when the lens is worn, and the viewing distance is infinite ('').
, 1 ms 0. M1 for each case of 3m
The results are shown below. The vertical axis shows the angle of field of view (unit: [degrees]) with respect to the optical center of the lens, and the horizontal axis shows astigmatism.

Figure 3 (A) shows the lens of Example (a), Figure 3 (B) shows the lens of Example (b), and Figure 3 (C) shows the same prescription (power: 13D, base curve). 1.0D) of a conventional lens (both front and rear surfaces are spherical).

In addition, Fig. 3 (D) shows the lens of specific example (e), Fig. 3 (E) shows the lens of specific example (d), and Fig. 3 (1') is the same as these (e) and (d). The case of a conventional lens (both front and rear surfaces are spherical) with prescription (power +3D, base curve 4.0D) is shown.

In both cases, astigmatism is reduced compared to the conventional ones, and in particular, astigmatism when looking at a distance of 1 meter is reduced in the philtrum. According to the present invention, by adjusting the transition of the chemotaxis of the curvature, it is possible to minimize astigmatism when viewing short distances depending on the usage, or to minimize astigmatism when viewing long distances. Adjustments can be made to minimize aberrations.

Further, by adopting the above configuration, it is possible to satisfactorily correct not only astigmatism but also distortion. In other words, by making the front surface 1 aspheric, each of the above aberrations can be removed to some extent, but by making the rear surface 3 aspheric, the portions that cannot be corrected by making the front surface 1 aspheric alone can be corrected by changing the edge thickness T of the lens or toward the front. This can be achieved while reducing the amount of protrusion, and 2f! I! Optimization of the above optical performance can be achieved.

FIG. 4 shows a cross section of a second embodiment, in which a double-sided aspherical lens is formed by laminating a first lens body 1A and a second lens body IB. be.

Bonding surfaces of the first and second lens bodies IA and IB 4.
5 are each formed into a spherical surface, and the opposite surfaces thereof are formed into an aspherical surface 6 (front surface) and 7 (rear surface), respectively.

These lens bodies IA and IB are molded using plastic. As the material, for example, a material with a refractive index of 1.55 consisting of diaryl phthalate 609o and allyl diglycol carbonate 4096 is used, and the center thickness is t! is said to be about 0.5 dragon.

The first and second lens bodies IA and I formed in this way
After applying a 1% cyanoacrylate primer to the bonding surface 4.5 consisting of the spherical surface of B, for example, a butyl acrylate film (approximately 0.2 m + * thickness) is interposed as the adhesive 8, as shown in Figure 6. They are placed in a mold 9 and pressure molded, or integrated by vacuum compression molding. In addition, as the adhesive 8, UV-based, epoxy-based, or cyanoacrylic-based adhesives can be used, and all of them are highly transparent, and the bonding surfaces 4 and 5 are entirely blued. Ru.

When the double-sided aspherical lens is a negative lens,
At least one of the first and second lens bodies IA and IB
The center thickness t2 of each lens element is 0.7 mm or less,
When the lens is a plus lens, the peripheral thickness t3 of at least one lens element is 0.7- or less.

The double-sided aspherical lens having the above structure was subjected to an FDA drop ball test to examine the fracture state. As a result, cracks were observed, but no fragments were scattered. On the other hand, when the same test was conducted on a conventional single-layer lens made of the same material with a center thickness of 1.2 mm, the lens was destroyed.

〔Effect of the invention〕

As explained above, according to the present invention, in the case of minus lenses, the edge thickness can be reduced, so that there is less protrusion when attached to a frame, which improves the appearance.
In addition, in the case of a plus lens, there is no extreme front bulge, and it has a uniform thickness, which is also pleasing in terms of appearance.Furthermore, each aberration that cannot be removed by the front aspheric surface is eliminated by the rear aspheric surface. Since it can be corrected,
The optical performance of the lens can be significantly improved.

In addition, the lens has a structure in which first and second lens bodies are bonded together, and the bonding surfaces of each lens body are each formed into a spherical surface,
By forming the opposite surface to be an aspherical surface and making both surfaces aspherical by combining the aspherical surfaces of both lens bodies, the first and second lens bodies can be mass-produced and stockpiled in advance; By selecting and bonding the first and second lens bodies according to the order, it is possible to provide a double-sided aspheric single focus lens that meets the order, and there is no need to use sophisticated equipment as in the past. Therefore, it can be provided to τm6 at low cost and in a short period of time. In addition, since the bonding surfaces of the first and second lens bodies are both spherical, the directionality during bonding is not restricted and can be arbitrarily selected. The combination of aspheric surfaces of the lens body can be optimally selected.

Furthermore, the center 1v of the lens is thinned < (0.7 @ 11 or less)
When molded into Il', distortion occurs in the lens, causing abnormal aberrations, but by bonding the two lenses together, the rigidity is increased, the distortions are eliminated, and the aberrations can be returned to normal.Therefore, the lens can be made thinner. It becomes possible to achieve this goal.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the case where the present invention is applied to a minus lens, Fig. 2 is an explanatory diagram showing the case where the present invention is applied to a plus lens, and Figs. 3 (^) to (P) are the inventive lens and the conventional lens. FIG. 4 is a vertical cross-sectional side view showing an embodiment of the double-sided aspherical single focus lens according to the present invention, and FIG. 5 is (A).
(B) is a side view showing the lens body before lamination, No. 6
The figure is a longitudinal side view showing an example of a bonding jig. 1...Front surface, 2...Axis of symmetry, 3...Back surface, T...
・Edge thickness, IA, IB... Lens body, 4.5... Bonding surface, 6.7... Aspherical surface, 8... Adhesive, 9...
・Type.

Claims (1)

[Claims] 1. A lens in which both the front and rear surfaces are aspheric, and the front and rear surfaces have different curvatures while maintaining a predetermined power at the peripheral portions of the front and rear surfaces. A double-sided aspherical lens characterized by having an aspherical surface that reduces the difference in curvature at each peripheral portion. 2. The double-sided aspherical lens according to claim 1, wherein the negative lens has an aspherical surface in which the curvature of the front peripheral part is larger than the curvature of the concentric region, and the curvature of the rear peripheral part is smaller than the curvature of the concentric region. Spherical lens. 3. The double-sided aspherical lens according to claim 1, wherein the positive lens has an aspherical surface in which the curvature of the front peripheral part is smaller than the curvature of the concentric region and the curvature of the rear peripheral part is larger than the curvature of the concentric region. Spherical lens. 4. The lens has a structure in which first and second lens bodies are bonded together, and the bonding surfaces of each lens body are each formed into a spherical surface, and the opposite surface is formed into an aspherical surface, so that both lens bodies are bonded together. A double-sided aspherical lens characterized in that both sides are aspherical by a combination of aspherical surfaces. 5. The refractive index of the material constituting the lens body is 1.55.
The double-sided aspherical lens according to claim 4, which has the above. 6. The double-sided aspherical lens according to claim 4 or 5, wherein when the lens is a minus lens, the center thickness of at least one of the two lens bodies is 0.7 mm or less. 7. The double-sided aspherical lens according to claim 4 or 5, wherein when it is a plus lens, the peripheral edge thickness of at least one of the two lens bodies is 0.7 mm or less.