JPS61167902A - Lens made of organic resin - Google Patents

Abstract

PURPOSE:To make an edge thin by making the radius of curvature of the reverse surface of a lens larger than the original radius of curvature at the outer peripheral side of a point on the lens where it is larger than prism diopter and making the coefficient of primary differentiation of the sectional curve of the reverse surface near the point on the lens continuous. CONSTITUTION:The thickness of the edge is decreased by aspherical surface working which makes the radius of curvature of the reverse surface at the outer peripheral side of a phase where a person who wears the lens begins to feel bleeding because of chromatic aberrations, and the number of prisms is decreased to improve the chromatic aberrations. Chromatic aberrations appear in a spectacle lens at (0.2 X Abbe number) prism diopter and in a lens having a 40 Abbe number at (0.2X40)=8 prism diopter, and the person who wear the lens feels chromatic aberrations at 20mm distance from the optical axis with -2D lenses and at about 13.3mm distance with -6D lenses. Therefore, >=(0.3 XAbbe number) prism diopter is preferable. Consequently, the edge is made extremely thin as to a lens with minus power.

Description

[Detailed description of the invention] 〔Technical field〕 This technology relates to plastic eye-continuation lenses.

[Prior art]

As a conventional technology, a glass lens as shown in Fig. 1 is used.
This lens is commercialized under the trade name "Skyline". This lens has a thinner edge thickness by providing an inflection point on the cross-sectional curve of the back surface at a distance of 15 to 20 Wn from the center. Although it is effective in making the lens thinner, (1) it creates a spiral ring on the lens near the point of inflection, which is unsightly for others to see, and (2) aberrations increase rapidly from near the point of inflection. There were problems such as a narrowing of the clear visual field and discomfort for the wearer.

〔the purpose〕

An object of the present invention is to provide a lens with a thin edge that is completely invisible from the outside and does not make the wearer feel that their field of vision is narrow.

Another object of the present invention is to improve image blur due to chromatic aberration in a lens having a relatively small Abbe number.

〔overview〕

The present invention improves chromatic aberration by reducing the edge thickness and reducing the number of prisms by aspherical processing that increases the radius of curvature of the back surface on the outer circumferential side from the area where the wearer starts to feel blurring due to chromatic aberration. Featured @
Furthermore, in order to reduce the edge thickness, the edge is made thinner by providing an inflection point in the cross-sectional curve of the back surface within 5 SS at most from the outer periphery of the lens.

〔Example〕

The present invention will be described below with reference to examples. When using a spectacle lens, chromatic aberration is perceived as (α2×Atsube's number) prism diopter. (Modern glasses
780.April issue) For example, for a lens with an Atsube number of 40, (0,2X40) = 8 prism diopters, and for a -4D lens, it is 20WI# from the optical axis, -6D.
It is the same for lenses of (15, 3111 around)
Regarding this value, the inventors conducted a wear test to confirm how the color blur is perceived, and as a result, the following was found.

(0,2X Atsube'#) If you look at the point on the lens of the prism diopter, you may notice some color blurring.

■ However, if you use them as regular glasses (when looking sideways, don't follow them with your eyes only, turn your face in that direction),
In terms of chromatic aberration, I found that there is no problem even with a prism diopter (0.5 x 7 tube number).Therefore, if you use a prism diopter (0.2X tube number) or less, the color will completely blur. However, in order to increase the effective diameter of the clear vision area of the lens, it is desirable that the diameter is about the same as the prism diopter (o, 3 X Abbe's number).

FIG. 2 was created based on such data. The lens in Figure 2 has a power of -6D1 and an Atsbe number of 4.
The 02 point, which is 0, is at (o, s x 40 ) = 12 prism diopters, and on the lens, it is 20 Ml1. The @ point R, which is the angled point, is the tip of the edge of a conventional spherical lens, and the point q is the point where the tangent line drawn at OF is the edge, and QR is the amount of the edge that has become distorted due to the present invention. 〇Figure 3 shows the frequency - 10D1 Atsbe's number 4
With a lens of
The point is the point where 0' is taken on the extension of P2O, and a circle whose radius is 0'P' intersects the edge, and Ql ml is the amount of the thinned edge. As another method, it is also possible to make the edges curved by using an oval shape on the outer periphery from point P or P'. Point T within 5 attacks from
By providing an inflection point, it is possible to further reduce the thickness by the amount of SQ. The distance from the outer circumference to T is 5-
If this is the case, it is not preferable because it will remain clearly as a boundary in some parts even after being processed into glasses. Conventionally, this method of thinning involves cutting the edges after beading at retail stores, but in the present invention, this type of processing is done from the beginning, so it is very difficult for retailers to do so. Pleased.

The above-mentioned lens of the present invention is difficult to deal with in terms of cost compared to conventional glass lenses, but it is possible to deal with organic resin by aspherically processing the glass mold or mold in advance. 〇 Edge thickness comparison (lens diameter 70φ, refractive index 1.6) ) (However, the above table does not include the bending process at the outer periphery 5106) ■ By applying this method to lenses with a low Abe number, not only will the edges become thinner, but the prism will be Most of the problems can be eliminated by reducing the amount.

■By adding an inflection point to the outer periphery of the lens and rounding it, it becomes possible to process the edges even thinner0.Although all of the above explanations have been made with spherical lenses in mind, the same applies to astigmatic lenses as well. It is something.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a conventional type lens with a thin edge. 2 to 4 are schematic cross-sectional views of lenses processed to have a thin rim according to the present invention. 1... Lens front surface 2... Lens back surface 3... Above the edge of the lens Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. In an organic resin lens for eyeglasses, at least (0.2
x Abbe number) Prism diopter Preferably (0.
3 x Abbe number) The radius of curvature of the back surface is larger than the original radius of curvature on the outer peripheral side from a point on the lens larger than the prism diopter, and the first derivative of the cross-sectional curve of the back surface in the vicinity of the point is continuous. An organic resin lens characterized by: 2. Within 5 mm at most from the outer periphery of the lens,
The organic resin lens according to claim 1, wherein the cross-sectional curve of the back surface has an inflection point. 3. The organic resin lens according to claim 1, wherein a lens having an Abbe number of 45 or less is used. 4. The organic resin lens according to claim 2, wherein a lens having an Abbe number of 45 or less is used.