JPS601604B2 - eyeglass lenses for astigmatism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention increases the degree of freedom in determining the surface shape by making both the outer and inner surfaces of the spectacle lens for astigmatism into trick surfaces, and the degree of astigmatism outside the bag becomes the degree of astigmatism on the axis. This is an attempt to improve aberrations so that they are equal.

Conventionally, by setting either the outer or inner surface as a trick surface and appropriately setting the surface shape,
There are plans to improve aberrations, especially astigmatism, which corresponds to astigmatism.

For example, one surface is a trick surface and the other surface is a spherical surface, and astigmatism (astigmatism) in the two principal meridian directions is corrected at a reasonable off-axis angle (for eyeglass lenses, the correction angle is usually around 30 degrees due to the effective field of view, etc.). It is possible to set the surface shape of the lens so as to satisfy the condition of so-called Equal-false tigmatism, which equalizes the values of the chromaticity (power). By setting the surface shape in this way, Eq female 11 As
A lens with a correction angle that satisfies the condition of tigmatSm In the belt-shaped part, approximately the same degree of astigmatism can be obtained, but unfortunately, the value of this degree of astigmatism is not always on the axis and its vicinity, which is the normal degree of astigmatism of this lens. is not equal to the astigmatism value.

Examples of this are shown in Tables 1 and 2. Table 1,
As is clear from 2, the value of the correction angle 30o and the degree of astigmatism in its vicinity covers the weak part of the negative lens and the entire correct lens in the inner trick, and the entire negative and correct lenses in the outer trick, and The error with Yugami is particularly large. For example, in a lens with a spherical power of 5.00 diopters and an astigmatic power of 2.00 diopters with an inner trick, the difference between the astigmatism at an angle of 30o and the astigmatism on the ball is 0.260 diopters; Considering that eyeglass lenses are commercialized with astigmatism in 0.25 diopter steps, the astigmatism of this part of this lens exceeds the astigmatism of the next lens in one step, and it is clearly a poor dioptric power. I can say that.

Further, in eyeglass lenses, the refractive index and thickness of the lens are determined by constraints such as mass production, weight, shape, etc., and usually do not provide a degree of freedom for improving optical performance.

Therefore, in a lens where either the outer or inner surface is a trick surface and the other is a spherical surface, there is only one degree of freedom in determining the lens shape to satisfy a given lens power, and this degree of freedom is In order to correct the degree of astigmatism using the above equation, it is possible to satisfy the condition of Equal-ship tigmatjsm, or to equalize the degrees of astigmatism of the angles to be corrected in either principal meridian on the axis. However, in the case of any correction other than the correction that satisfies the conditions of Equal-Astigmatism,
The degree of astigmatism in the direction of the uncorrected principal meridian is distorted.

(See Tables 3 to 6) In order to improve this drawback, the present invention uses both the outer and inner surfaces as trick surfaces to have two degrees of freedom, and these two degrees of freedom reduce the degree of astigmatism of the off-axis correction angle. Correct it so that it is equal (Eq Female 1 - Ast
igmatSm conditions), and at the same time, the degree of astigmatism is corrected to be equal to the normal degree of astigmatism on the ball. That is, within the range of a lens in which the rear apex refractive power P of the lens alone is correct, the refractive index N of the lens d-lhe is 1.522 miNSI. 254, and when the larger rear vertex refractive power Dv (dioptres) including the sign of the astigmatic lens is Dv<2.75 (dioptres), the lens center thickness d is 1.6 + 0.1 Dv≦
dS2.20.1Dv, 2.75 (diopters)
When ≦Dv, the minimum edge thickness t (rib) is 0.5 (side) St
S.I. 1 (fence), and the surface refractive powers Ps and PC at two mutually orthogonal main fleas on the outer surface are .).

≦ispicy3Aijxlyi<Ps<. ≦i chapter j≦3Bi
jxlyJ2). ≦i sheep j≦3CijX1y1<RC〈
〇≦i j≦3Dii be.

Furthermore, within the range where the rear apex refractive power P of the lens alone is negative, the refractive index N of the lens at e in d-1 is set to 1.522 SNSI.
．． 524, and the center thickness d (willow) of the lens is Dv me 1 (
diopter) is 1.300.10v middSI
．． When 900.1Dv, 11 (diopters)≦Dv, 1.600.1Dv≦dS2.200.1Dv, and the surface refractive powers Ps and Pc at the mutually orthogonal principal meridians of the outer surface.
is satisfied that each coefficient in the constraint expressions '1} and (2) takes values as shown in the following table.

By correcting in this way, the off-axis correction angle (
It goes without saying that the degree of astigmatism in the two principal meridian directions of 30o) is equal and equal to the regular degree of astigmatism on the bag.
Eq female 1-AstigmatS also at other angles
This is significantly improved compared to the one corrected under the conditions of m. (See Table 7) Conditions Equations 11 and 21 express the relationship in which such correction is made using a correction angle of 30o and a target object.For example, the astigmatism power is 1 dioptre, 2 dioptre, Graphs of the case of 4 days of trees are shown in Figures 3, 4, and 5. The solid line in the figure represents a curve completely corrected at an angle of 30o, and the broken line represents the upper and lower boundary lines indicated by the ◯ and ◯ equations. That is, the object of the present invention can be sufficiently achieved even within this upper and lower boundary line including the solid line, which is a complete correction. FIG. 1 is a sectional view showing the geometrical position of the lens and the eyeball, and shows the distance between the rear apex of the lens and the center of rotation of the eye of 25 skin and the correction angle a=300 in the present invention. It is.

Also, Figure 2 is a front view of the lens, and shows the two main meridians of the astigmatic lens (n and Sagtta).
lmerjdnen). However, DH is the smaller rear vertex refractive power including the sign. Next, Table 1 mentioned above
~ Table 7 is shown.

In these tables, the refractive index of the lens is 1.523.
The center thickness d (side) of the lens is d when Dv≦-1.
= 1.6 0.1Dv, d when 1≦Dv<2.75
= 1.9 + 0.1 Dv, and when 2.75≦Dv, the minimum edge thickness was set to be on the 0.7 side. Equal
- When corrected under Astigmatism conditions Table I (
(2 diopters of astigmatism) Error with the astigmatism on the axis (inner T.C.) Object, unit Diopter Table 2 (2 diopters of astigmatism) Error with the axial astigmatism (inner T.C.)
Unit diopter - axial astigmatism and extrasheath (angle 300)
Table 3 when the astigmatism of T-yamafune ENTIALM old RIDIAN is made equal
(Astigmatism: 2 diopters) Error with on-sheath astigmatism (inward, Chapter C) Table 4 (Tongue contingency: 2 diopters) Error with on-axis astigmatism (outer surface T.C) On-axis and off-axis ( Angle 30o) SAGITTALMERID
Table 5 when the degree of astigmatism of IAN is made equal
(Random shelf summer 2 diopters) Error with axial astigmatism (inner T.C) Table 6

(Astigmatism 2 db,) Error with on-axis astigmatism (
External T. C) Example 7 of the present invention
(Astigmatism level 2 Diof.

Tory) Error with Hatakami astigmatic skin

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the geometrical positions of the lenses and the eyeball. Figure 2 is a front view of the lens, showing the two principal meridians of the astigmatic lens (Tan sac nt also I Meridian and Sagt side M
er illusion also shows n). Figures 3 to 5 show astigmatism levels of 1 diopter, 2 diopter, and 4 according to the present invention, respectively.
1 is a graphical representation of an example in diopters. Figure 'Figure 2 Figure 2 Little brother Figure 4 Figure 4

Claims (1)

[Claims] 1. In a spectacle lens for astigmatism, both the outer and inner surfaces are made up of trick surfaces, and the rear apex refractive power P of the lens alone is within the range of a positive lens, and the d-line refractive index N of the lens is within the range of a positive lens. 1
．． 522≦N≦1.524, and when the larger rear vertex refractive power Dv (dioptres) including the sign of the astigmatic lens is Dv<2.75 (dioptres), the lens center thickness d is 1.6+0.1Dv≦ d≦2.2+0.1Dv,
2.75 (diopters)≦Dv, the minimum edge thickness t (mm) is 0.5 (mm)≦t≦1.1 (mm), and the surface of the two main meridians perpendicular to each other on the outer surface The refractive powers Ps and Pc are ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ However, x: value of P y: value of degree of astigmatism (>0) Each coefficient Aij, Bij, Cij, Dij is a value as shown in the following table A spectacle lens for astigmatism that satisfies the following: ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ 2. In a spectacle lens for astigmatism, both the outer and inner surfaces are made up of trick surfaces, and the d-line refractive index N of the lens is set to 1 within the range where the rear apex refractive power P of the lens alone is negative.
．． 522≦N≦1.524, and the center thickness of the lens d(m
m) is 1.3+0.1 when the larger rear vertex refractive power Dv (dioptres) including the sign of the astigmatic lens is Dv≦-1 (dioptres) Dv≦d≦1.9+0.1
Dv, -1 (diopter) ≦ 1.6+ when Dv
0.1Dv≦d≦2.2+0.1Dv, and the surface refractive powers Ps and Pc at the two mutually orthogonal principal meridians of the outer surface are ▲There are mathematical formulas, chemical formulas, tables, etc.▼ However, the value of x: P y: Value of degree of astigmatism (>0) Each coefficient Aij, Bij, Cij, Dij takes a value as shown in the following table ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ Glasses for astigmatism characterized by satisfying the following. lens.