JP5140768B1 - Progressive multifocal lens, progressive multifocal lens design method, progressive multifocal lens processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an eye-friendly progressive multifocal lens at low cost.
SOLUTION: The left and right set of progressive multifocal lenses (1L, 1R), one can enroll frequency at the lower end 12 of the progressive corridor length of the progressive zone 10 is at L ₀ is located at [delta] ₀ , A non-adjustable lens in which the distance from the upper end 11 to the lower end of the progressive zone is x and the prism power at an arbitrary distance x = x ₁ is P _0, and the other is a progressive zone with the length of the progressive zone L ₁ The adjustment power lens has an addition power at the lower end of the belt of δ ₁ and a prism power of P ₁ at an arbitrary distance x = x ₁ , and the progressive belt of the adjustment lens has δ ₁ > δ ₀ and When L ₁ > L ₀ is satisfied, and the addition power at the position of x = L ₀ is δ ₀ , and the non-adjustment side lens and the adjustment side lens satisfy x ≦ L ₀ , the prism at x = x ₁ flop _of, at x = _{x 1,} assuming that L 1 = _{L 0,} and a δ ₁ = δ ₀ | difference frequency _| P 0 -P ₁ The difference of rhythm frequency is less than or equal to.

Description

  The present invention relates to a progressive multifocal lens for bifocal glasses, a design method thereof, and a processing method.

  When correcting visual acuity with glasses, the correction degree is sometimes called “degree” as a custom. As is well known, this “degree” is an index indicating the refractive power of a lens, and the degree of refraction of an object image 1 m ahead so as to move 10 mm (1 cm) is 1 prism diopter or 1 It is called a prism diopter (hereinafter referred to as diopter), and the magnitude of this diopter is expressed by the magnitude of the value. In the following description, unless otherwise specified, “frequency” represents the strength of the refractive power of a lens in units of diopters.

  When prescribing spectacle lenses for hyperopia, presbyopia, or myopia, the lens is treated as a spherical lens whose surface is a part of a spherical surface. That is, in these lenses, the focal point is on the central axis of a circle on which a part of the spherical surface is projected, and the power coincides with the reciprocal 1 / f of the focal length f of the spherical lens. The unit symbol of the frequency is expressed as “D”, “Dptr” or the like (hereinafter “D”) using diopter as a word source. In addition, a minus sign “−” is added to the power for a myopic lens, and a plus sign “+” is added to a lens for hyperopia or presbyopia. For example, if it is a 1-degree hyperopia or presbyopia lens, it is described as + 1.00D, and if it is a 2.25-degree lens for myopia, it is described as -2.25D.

  By the way, the glasses include well-known bifocal glasses. Recent lenses for bifocal glasses have continuously changed from a distance dioptric power that matches the visual acuity when looking far away to a single lens to a near power that matches the visual acuity when looking at nearby objects. A progressive multifocal lens provided with a progressive zone that is an area is the mainstream.

  FIG. 1 is a diagram showing an outline of a progressive multifocal lens. In FIG. 1, the vertical direction is defined in a state where a person wearing glasses stands upright. FIG. 1A is a plan view of the lens, showing each region having a different frequency on one lens, and FIG. 1B shows a position x and a frequency D in the aa cross section in FIG. Shows the relationship.

  As illustrated in FIG. 1A, the glasses lens including the progressive multifocal lens 1 has a circular planar shape before being processed to be fitted into the frame, and the person wearing the glasses is in front. The center position (pupil center) of the pupil when viewing is taken as the center (hereinafter referred to as eye point) 2 of the circle, and this is the optical axis of the lens 1. And there exists the distance part 3 set to the distance power for seeing a distance far above the eye point 2. Then, there is a progressive zone 10 in a region up to a predetermined length L with the eye point 2 as the upper end.

As shown in FIG. 1B, the progressive zone 10 is designed so that the power is gradually added from the distance power Sf at the upper end 11 and becomes the maximum near power Sn at the lower end 12. ing. The difference between the distance power Sf and the near power Sn, that is, the power difference between the upper end 11 and the lower end 12 of the progressive zone 10 is the addition power δ ₀ .

  In the example shown here, the relationship between the distance x downward from the upper end 11 of the progressive zone 10 and the addition power δ (x) changes linearly. That is, δ (x) is a linear function of x. Of course, the relationship between the distance x from the upper end 11 of the progressive zone 10 and the addition power δ (x) at the position x is, for example, a quadratic function so that the change in addition power increases as it goes downward. It can be designed appropriately. In addition, depending on the lens manufacturer, the relationship between x and the addition power δ (x) may be defined by a predetermined function or a predetermined correspondence relationship.

  Non-Patent Documents 1 and 2 below describe the relationship between visual acuity and spectacle lenses. In addition, basic techniques related to bifocal glasses and progressive multifocal lenses are described, for example, in Non-Patent Documents 3 and 4 below. In addition, specific prescriptions regarding far and near glasses are described in Non-Patent Document 5 below.

HOYA Corporation, “Talk of Eyes and Glasses”, [online], [Search January 17, 2012], Internet <URL: http://www.vc.hoya.co.jp/learn/eyes2.html > HOYA Corporation, “Types of Glasses Lenses”, [online], [Search January 17, 2012], Internet <URL: http://www.vc.hoya.co.jp/learn/kind.html> Tokyo / Suginami-ku Nishi-Ogikubo Eyeglass Store Optic Rainbow “Glasses for Perspective”, [online], [Search January 16, 2012], Internet <URL: http://www.opt-rainbow.com/lens_ruishin .html> Tokyo, Suginami-ku, Nishi-Ogikubo Eyeglass Store Optic Rainbow "A progressive power lens for both perspective", [online], [Search January 16, 2012], Internet <URL: http: //www.opt-rainbow. com / lens_ruishin.html> Eye Care System Co., Ltd., “Case 1 of bifocal glasses (non-viewing)”, [online], [Search on February 13, 2012], Internet <URL: http: //www.eye- care.co.jp/society_folder/case_folder/cases9.html ＞

  In a progressive multifocal lens, the addition power is set to be the same for the left and right lenses. However, when the distance dioptric powers of the left and right lenses are greatly different, the near dioptric power obtained by adding the addition power to the distance dioptric power is also greatly different between the left and right lenses. In the progressive zone, the frequency gradually increases, and in this progressive zone, the same effect as that in which a prism that refracts light in the vertical direction is separately arranged is exhibited. Therefore, the effect as a prism in which the position of the image moves up and down with respect to the optical axis becomes remarkable at the lower end of the progressive zone. Therefore, if the dioptric power differs greatly between the left and right, as a result, there is a large difference in the position of the object viewed through the lens at the lower end of the progressive zone, and the image of the object passing through the left and right lenses at the lower end of the glasses frame. The lower end will be missing.

  For example, if there is a difference of 1.00D at the lower end of the progressive zone of the left and right lenses, the height position of the object ahead of 1 m is different by 1 cm. If a horizontally written document 30 cm ahead is seen, it will be 3 mm different, and if it is a small character, one line may be shifted.

  Of course, human beings perform information processing in the brain so that the difference between the positions of the objects is different between the left and right eyes when the image of the object is formed on the retina. In other words, only information from one eye is used. For this reason, humans are hardly aware of the difference in the positions of objects seen by the left and right eyes. However, in practice, even though different images are formed between the left and right eyes, the shape and position of the left and right images are aligned forcibly, so the prism effect has a left-right difference. When glasses are used regularly, it is natural that fatigue accumulates in organs involved in vision. In addition, there is a high possibility that various somatic symptoms called “eye strain” resulting from eye fatigue will appear, which is undesirable for health.

  Therefore, even in a progressive multifocal lens in which the left and right distance dioptric powers differ greatly, it is necessary to prevent the prism effect caused by the left and right lenses and to correctly align the position of an object to be viewed through the progressive zone. Of course, even if a lens having such characteristics can be actually designed, the manufacturing process becomes complicated if the surface shape of the lens becomes extremely complicated. Moreover, if a lens having a complicated shape is designed each time according to the visual acuity of each user, the time and cost required for the design increase.

  Therefore, an object of the present invention is to provide a progressive multifocal lens that is easy to manufacture and is easy on the eyes, a design method for the progressive multifocal lens, and a processing method for the lens.

The present invention for achieving the above object is a set of left and right progressive multifocal lenses corresponding to left and right eyes,
The left and right lenses have a progressive zone in which the addition power gradually increases downward with the optical axis position as the upper end, the left and right lenses as non-adjustment side lenses, and the other lens as adjustment side lenses,
The unregulated side lens is the length of the progressive zone is L _0, with increasing input power at the lower end of the corridor is [delta] _0, the distance the lower end as the lower limit, downward from the upper end of the corridor And x is a prism power resulting from the prism effect at an arbitrary distance x = x ₁ , and P ₀ is
The adjustment side lens has a length of the progressive zone L ₁ , an addition power at the lower end of the progressive zone is δ ₁ , and a distance from the upper end of the progressive zone to the lower side with the lower end as a lower limit x Let P _{1 be} the prism power resulting from the prism effect at an arbitrary distance x = x ₁ ,
The progressive zone of the adjustment side lens satisfies δ ₁ > δ ₀ and L ₁ > L ₀ , and the addition power at the position of x = L ₀ is δ ₀ ,
When the non-adjustment side lens and the adjustment side lens satisfy x ≦ L ₀ , the prism power difference | P ₀ −P ₁ | at x = x ₁ is L ₁ = L ₀ and δ ₁ = δ Is less than or equal to the difference in prism power at x = x ₁ assuming _zero .
It is a progressive multifocal lens characterized by this.

It is more preferable that the non-adjustment side lens and the adjustment side lens are progressive multifocal lenses in which the difference in prism power | P ₀ −P ₁ | is minimum at the position where x = L _0. .

Further, the scope of the present invention includes a design method for the progressive multifocal lens.
The distance spherical equivalents of the left and right lenses expressed by the length of the progressive zone L ₀ and the power in units of prism diopters are Sf _L and Sf _R , respectively, and the addition powers of the left and right lenses are both δ. _{In addition} to executing an initial value setting step for setting an initial value to ₀ ,
The initial value is the following three formulas Sf _L × Sf _R > 0
| Sf _L -Sf _R |> 0
(Sf _L + δ ₀ ) × (Sf _R + δ ₀ ) ≧ 0
If all are satisfied,
Based on the sign of the Sf _L and Sf _R , which is the same sign, the sign of the value of the calculation formula Sf _L -Sf _R , the calculation formula (Sf _L + δ ₀ ), and the sign of (Sf _R + δ ₀ ) An adjustment-side lens determination step that defines either the left or right lens as the adjustment-side lens and the other lens as the non-adjustment-side lens;
The progressive zone length of the adjustment lens is extended from L ₀ to L ₁ , the addition power is increased from δ ₀ to δ ₁ , and the power corresponding to the prism effect in the vertical direction in the progressive zone is Progressive band correction that adjusts L ₁ and δ ₁ so as to approximate the prism power of the adjustment-side lens and the non-adjustment-side lens with respect to the prism power of the left and right lenses based on the initial value. Steps,
Of the initial values corresponding to the adjustment side lens, the resetting step of changing the L ₀ and the δ ₀ to the L ₁ and the δ ₁ adjusted by the progressive zone correction step, respectively,
This is a method of designing a progressive-band multifocal lens characterized by

In the adjustment side lens determination step,
Sf _L > 0 and Sf _R > 0 and Sf _L + δ ₀ > 0 and Sf _R + δ ₀ > 0, or Sf _L <0 and Sf _R <0 and Sf _L + δ ₀ > 0 and Sf _R + δ ₀ > 0. In this case, among the left and right lenses, the lens corresponding to the smaller value of each of the distance powers Sf _L and Sf _R is used as the adjustment side lens.
When Sf _L <0 and Sf _R <0 and Sf _L + δ ₀ <0 and Sf _R + δ ₀ <0 , the absolute values of the distance powers Sf _L and Sf _R of the left and right lenses are small. The lens corresponding to the direction is the adjustment side lens,
In the progressive zone correction step, in each progressive zone of the adjustment side lens and the non-adjustment side lens, a progressive zone multifocal lens that approximates the prism power at a distance L ₀ from the upper end downward. It can also be a design method.

In the progressive zone correction step,
The relationship between the distance x from the upper end of the progressive zone in the non-adjustment side lens and the adjustment side lens and the addition power δ (x) is expressed by the following functions δ (x) = fa (x) and δ, respectively. (X) = fb (x)
As well as
The relationship between the distance x and the prism power P (x) in the non-adjustment side lens and the adjustment side lens is expressed by the following functions P (x) = ga (x) and P (x) = gb (x)
Stipulated in
When (Sf _L + δ ₀ ) × (Sf _R + δ ₀ )> 0,
δ ₀ = fa (L ₀ ) = fb (L ₀ )
δ ₁ = fb (L ₁ ),
ga (L ₀ ) = gb (L ₀ )
By calculating the L ₁ and the δ ₁ so as to satisfy all of the following conditions, the distance L ₀ from the upper end to the lower side in each progressive zone of the adjustment side lens and the non-adjustment side lens is calculated. A progressive multifocal lens design method that matches the prism power at the position can also be adopted.

Further, in the progressive zone correction step, for a lens having a progressive zone where the progressive zone length is L and the addition power at the lower end of the progressive zone is δ, the formula δ (x) = fa (x) ,
Sf _L > 0, Sf _R > 0, Sf _L + δ ₀ > 0, Sf _R + δ ₀ > 0
If all of the above are satisfied, within the region of the progressive zone,
δ (x)> 0
In the area that satisfies
δ (x) = {(Sf + δ) x / L} −Sf
And a function represented by
Sf _L <0, Sf _R <0, Sf _L + δ ₀ > 0, Sf _R + δ ₀ > 0
If all of the above are satisfied, within the region of the progressive zone,
δ (x)> 0, x> 0
In the area that satisfies
δ (x) = {(Sf + δ) L / x} −Sf
A progressive-band multifocal lens design method that defines a function represented by

Or, (Sf _L + δ ₀ ) × (Sf _R + δ ₀ ) = 0
If it is,
In the adjustment side lens determination step, a lens corresponding to an expression having a value of 0 among the expression (Sf _L + δ ₀ ) and the expression (Sf _R + δ ₀ ) is set as the adjustment side lens,
In the progressive zone correction step, the progressive zone multifocal lens design method of adjusting the L ₁ and the δ ₁ so that the prism powers of the adjustment side lens and the non-adjustment side lens are approximated at the upper end of the progression zone It can also be.

In the design method of any of the progressive zone multifocal lenses described above, when at least one of the addition power and the progressive zone length can be set only with a jump value, or a specified value in which a numerical range is restricted,
In the resetting step, it is possible to adopt a specified value that is closest to the one that can be set only with a specified value out of the δ ₁ and the L ₁ adjusted in the progressive zone correcting step.

The present invention also extends to a processing method of a progressive multifocal lens designed by any one of the methods described above.
When fitted to a spectacle frame, as the vertical position of the upper end of the corridor at the left and right lenses are aligned, the lens of the upper and lower cutting Then both the Adjustment side of the lens, the length of the progressive zone the As the initial value L ₀ , the lower end side is cut in the middle of the progressive zone,
This is a processing method of a progressive multifocal lens characterized by this.

  According to the progressive multifocal lens of the present invention, it is possible to reduce the difference between the vertical positions of the images generated in the left and right lenses due to the prism effect in the progressive zone, and to provide bifocal glasses that are extremely easy on the eyes. Moreover, since it is easy to manufacture, it can be expected to provide bifocal glasses that are easy on the eyes without increasing costs.

It is explanatory drawing about the schematic structure of a progressive multifocal lens, and the frequency of a progressive zone. It is the schematic for demonstrating the prism effect in the progressive zone of a progressive multifocal lens. It is a figure for demonstrating the design method of the progressive multifocal lens which concerns on 1st Example of this invention. It is a figure which shows the positional relationship of the progressive multifocal lens designed by the method based on the 1st Example of this invention, and a spectacles frame. It is a figure which shows the optical characteristic of the progressive multifocal lens designed by the method based on the 2nd Example of this invention, and has shown the relationship between the position in a progressive zone, and prism power. It is a figure which shows the optical characteristic of the progressive multifocal lens designed by the method based on the 3rd Example of this invention, and has shown the relationship between the position in a progressive zone, and prism power.

=== Basic Concept of the Invention ===
FIG. 2 is a diagram showing an outline of the prism effect in the progressive multifocal lens. 2A is a plan view of the lens, and FIG. 2B is a relation 21 between the distance x from the upper end 11 of the progressive zone 11 and the power D corresponding to the addition power δ in the section aa in FIG. An example of the relationship 22 between the distance x and P (x) is shown. In the following description, when the left and right lenses 1 are distinguished, the left and right lenses are denoted by 1L and 1R, respectively. For the sake of simplicity, the relationship between the distance x from the upper end 11 of the progressive zone 10 and the addition power δ (x) at that position is as shown in FIG. It is assumed that it is expressed by a linear function.

If the relationship between the distance x and δ (x) is a linear function, the progressive zone length is L ₀ and the addition power at the lower end 12 of the progressive zone 10 is δ as shown in FIG. _0, the lower end 12 of the progressive zone 10, the distance x = _{L 0.} Therefore, the relationship between x and the addition power δ (x) at that position is indicated by a straight line 21 indicated by a solid line in FIG.

In addition, the relationship between the position x and the refractive power (hereinafter referred to as prism power) P (x) generated by the vertical prism effect at the position x can be obtained based on the well-known Prentice equation. it can. That is, when the power at the distance x from the lens optical axis (here, the eye point) 2 is D, the prism power P (x) is
P (x) = D · x (Formula 1)
It is represented by

Next, the prism frequency P (x) at the lower end x = L ₀ of the progressive zone 10 is considered. Here, in order to explain the concept of the present invention more simply, the relationship between the distance x and the prism power P (x) is approximated by a straight line as shown by the dotted line in FIG. A calculation formula is obtained in which D in the above formula is the sum of the distance power Sf and the addition power δ ₀ and the prism power P (L ₀ ) at the lower end thereof. A general approximation formula can be used for this calculation formula. For example, in Non-Patent Document _{5, P (L 0) =} (Sf + δ 0/2) adopts a formula corresponding to L _0, in the following, with priority is given to ease of description, the present inventors The following approximate expression P (L ₀ ) = (Sf + δ ₀ ) L ₀ (Equation 2)
(However, the unit of L ₀ is cm). Then, the prism frequencies at the upper end 11 and the lower end 12 of the progressive zone 10 are interpolated with a straight line.

Note that even if the relationship between the position x and the prism power P (x) is different from Equation 2 or even if the relationship is not a linear function, the added value of the distance power Sf and the addition power δ ₀ Is larger, and the progressive zone length L is longer. It is known that the concept, the action, the effect, etc. of the present invention are not changed even when Equation 2 is replaced with another equation.

Here, consider a case where the distance powers of the left and right lenses (1L, 1R) are different. Assuming that the distance dioptric powers of the left and right lenses (1L, 1R) are Sf _L and Sf _R , respectively, it is conventionally assumed that the progressive zone length L and the addition power δ are the same for both eyes. At the lower end 12 of the progressive zone 10, δ in Equation 2 becomes the same δ ₀ for the left and right lenses (1L, 1R). If the absolute value of the difference between the prism powers of both eyes is ΔP, then ΔP is
ΔP = | (Sf _L −Sf _R ) L ₀ |
It becomes.

Therefore, as the progressive zone 10 is longer and the difference in the distance power (Sf _L , Sf _R ) between the left and right lenses (1L, 1R) is larger, the prisms in the left and right lenses (1L, 1R) at the lower end of the progressive zone 12 are larger. The frequency difference ΔP increases. Certainly, if the addition power is changed by the left and right lenses (1L, 1R) and the prism power at the lower end 12 of the progressive zone 10 is made to coincide, the vertical position of the object seen at the lower end of the progressive zone 10 will be the same on the left and right. However, in this case, the position where the initial addition power δ ₀ is different between the left and right lenses (1L, 1R).

As a specific example, the initial addition power δ ₀ of both the left and right lenses (1L, 1R) is + 1.50D, the initial progressive zone length is L ₀ = 10.00 mm (1.00 cm), and Sf _L = When the left and right lenses (1L, 1R) are manufactured under the prescription of + 2.00D and Sf _R = + 3.00D, the near powers Sn _L and Sn _R of the left and right lenses (1L, 1R) are respectively Sn _L = + 3.50, Sn _R = + 4.50. Then, the right and left lenses (1L, 1R) a prism effect at the lower end 12 of the progressive zone 10 in _{P L} ([delta]), if the _{P R} ([delta]), these _{P L (δ), P R} (δ) has the formula 2 can be obtained by substituting δ ₀ = 1.50D and L = 10.00 mm, and P _L (δ) = + 3.50D and P _R (δ) = + 4.50D. Therefore, in the glasses finally produced based on the above prescription, the image seen at the lower end of the frame with the right eye is lost with the left eye.

Therefore, for the left lens 1L, in order to align with the prism power of the right lens 1R, the addition power of the left lens is set to +2.50, and the near power of the left and right lenses (1L, 1R) are both set to +4.50. To do. Thereby, also for the left lens 1L, the prism power at the point of the progressive zone length L = 10.00 mm downward from the upper end 11 of the progressive zone 12 becomes + 4.50D, which is equal to the right lens 1R. However, in the prescription, since the addition power δ ₀ is +2.00 D, in the left lens 1L, the position x (δ) where the initial addition power δ ₀ = + 2.00 D is at the lower end 12 of the initial progressive zone 10. Will move upward from the position (x = L). Therefore, when the left and right eyeballs are rotated downward in order to see a nearby object, the left lens 1L has an excessive power at the lower end 12 of the progressive zone 10, and there is still a health problem.

<Technology>
As described above, when the distance dioptric powers of the left and right lenses (1L, 1R) are different, the left lens (1L, 1R) tries to equalize the prism power at the lower end of the progressive zone 12 with one lens (1L or 1R). When the addition power of () is increased, the position at which the prescribed addition power δ ₀ is obtained in one of the lenses (1R or 1L) is shifted from the initial position of the progressive zone lower end 12 (x = L ₀ ).

  Therefore, the present inventor changed the way of thinking and doubted the structure of a conventional progressive multifocal lens in which the progressive zone length is the same for the left and right lenses (1L, 1R) and the design concept of the lens itself. Also, the common sense that the left and right lenses (1L, 1R) have the same add power was discarded. Then, starting from this concept change, if the addition power is increased and the progressive zone 10 is lengthened, the position that becomes the addition power as originally prescribed exists in the middle of the progressive zone 10. I realized that the prism power at this position can be increased. That is, if the progressive zone 10 of one of the left and right lenses (1L or 1R) is extended, the position of the addition power according to the original prescription is substantially matched between the left and right lenses (1L, 1R), and at that position. It has been found that the prism power difference ΔP is smaller than the initial difference.

  If the design is made so that the lower end 12 of the initial progressive zone 10 is fitted into the spectacle frame, the difference in the position of the image seen at the lower end of the spectacle frame is reduced, and the burden on the eyes is reduced. I came up with a technical idea. That is, the lens on the side where the progressive zone 10 is extended is not used up to the lower end 12 of the progressive zone 10, but the middle part is used as a part that is actually fitted into the spectacle frame. The present invention has been conceived as a result of intensive studies based on such changes in ideas and knowledge. Below, some design methods of the progressive multifocal lens which concern on one Embodiment of this invention are mentioned as an Example of this invention, and the said technical thought is demonstrated more concretely.

=== First Embodiment ===
First, a basic example is given as the first example. In the first embodiment, as shown in FIG. 1, the addition power at the lower end 12 of the progressive zone 10 is δ ₀ , and the distance x from the upper end 11 and the addition power δ (x) at that distance are When the progression zone length is L ₀ , the addition power δ ₀ and the relationship between x and δ (x) is the following linear function:
δ (x) = δ ₀ x / L ₀ (Equation 3)
It is assumed that it is set to be.

In the following, the addition power is increased from the initial addition power δ ₀ to δ ₁ for _one of the left and right lenses (1L, 1R), and the progressive zone length based on the original prescription is used. The initial length is set to L ₀ , and the progressive zone length L ₀ is changed to be extended to L ₁ . Then, the lens on the side where the addition power and the progressive zone length are changed is set as the adjustment-side lens, and the distance power of the adjustment-side lens is set as Sfb. Also, let the near-use frequency be Snb.

On the other hand, the lens (1R or 1L) that does not change the initial prescription of the progressive zone length and addition power is referred to as a non-adjustment lens, and the distance power and near power of the non-adjustment lens are Let them be Sfa and Sna, respectively. As a matter of course, the progressive zone length and the addition power of the non-adjustment side lens are L ₀ and δ ₀ , respectively. When the distance x from the upper end 11 of the progressive zone 10 becomes the initial progressive zone length L ₀ , the addition power is the initial δ ₀ and the prism power is the same for both the adjustment side lens and the non-adjustment side lens. L ₁ and δ ₁ are obtained so that

First, in order to obtain L ₁ , the condition that the adjustment-side lens and the non-adjustment-side lens have the same prism power at the position where the initial addition power δ ₀ is applied is applied to Equation 2 above. Thereby,
P (δ ₀ ) = (Sfa + δ ₀ ) L ₀ = (Sfb + δ ₀ ) L ₁ (Formula 4)
And
L ₁ = (Sfa + δ ₀ ) L ₀ / (Sfb + δ ₀ ) (Formula 5)
It becomes. Next, in the adjustment side lens, the relationship between the addition power δ in the progressive zone and its position x is as follows. In the above equation 3, δ ₀ becomes δ ₁ and L ₀ becomes L ₁ .
δ (x) = L ₀ = δ ₁ x / L ₁
And substituting L ₁ obtained by the above equation 5 into this equation,
δ ₁ = δ ₀ L ₁ / L ₀ (Expression 6)
It becomes.

Of course, from Equation 5 and Equation 6,
δ ₁ = δ ₀ L ₁ / L ₀ = δ ₀ (Sfa + δ ₀ ) L ₀ / L ₀ (Sfb + δ ₀ )
= Δ ₀ (Sfa + δ ₀ ) / L ₀ (Sfb + δ ₀ ) (Expression 7)
L ₁ = δ ₁ L ₀ / δ ₀ (Expression 8)
Then, L ₁ can be obtained after obtaining δ ₁ .

Here, some examples of the adjustment side lens and the non-adjustment side lens will be considered according to the combination of the signs of the distance power (Sfa, Sfb) and the near power (Sna, Snb). In the present invention, it is assumed that the combination of symbols is the same for the adjustment side lens and the non-adjustment side lens. As the combination conditions of the codes, the following (1) to (3) are conceivable when the distance power is Sf and the near power is Sn, regardless of whether the lens is on the adjustment side or the non-adjustment side.
(1) Sf> 0, Sn = Sf + δ ₀ > 0
(2) Sf <0, Sn = Sf + δ ₀ <0
(3) Sf <0, Sn = Sf + δ ₀ > 0
In the above technical idea, it is necessary that L ₁ > L ₀ and δ ₁ > δ ₀ . Thus, L1 obtained from Equation 5 or [delta] ₁ obtained by the formula 7, is, in order to satisfy these conditions, the equation 5 or equation 7,
(Sfa + δ ₀ ) / (Sfb + δ ₀ )> 1
Is a condition. And in the case of condition (1),
Sfa + δ ₀ > 0, Sfb + δ ₀ > 0
Therefore, the lens with the smaller distance power among the left and right lenses is the adjustment side lens. In the case of condition (2),
Sfa + δ ₀ <0, Sfb + δ ₀ <0
Therefore, the lens on the adjustment side is the one with the smaller absolute value of the distance power among the left and right lenses. And in the case of condition (3),
Sfa + δ ₀ > 0, Sfb + δ ₀ > 0
Therefore, as in the condition (1), the lens with the smaller distance power is the adjustment side lens.

  In addition, below, the specific prescription example corresponding to the case of the said conditions (1)-(3) is given, and the correctness of the said Formulas 5-8 is demonstrated.

<Specific example of condition (1)>
Table 1 shows specific initial formulation examples corresponding to the condition (1).

As shown in Table 1, here, the distance power Sf and the near power Sn are made to correspond to the left and right lenses (1L, 1R), respectively, and are set to Sf _L , Sf _R , Sn _L , Sn _R , respectively. . The initial addition power and progressive zone length are the same on the left and right, and are δ ₀ and L ₀ , respectively. In Table 1 and the following tables, the progressive zone length and the position unit are mm. Further, in each of the following embodiments including the first embodiment, the well-known “distance astigmatism power” and “astigmatism axis degree” are reflected in the narrowly-defined distance vision power when the astigmatism is not corrected. A value called “distance spherical power” (or “distance spherical equivalent”), which is an index of refractive index when regarded as a spherical lens, is called “distance power”. Accordingly, hereinafter, “distance power” is synonymous with “distance spherical power”. Further, the near power is also synonymous with “near spherical power” which is a value obtained by adding the addition power δ ₀ to “far spherical power”.

Table 2 shows the characteristics of the lenses designed based on Table 1.

In Table 2, the addition power gradually increasing in the region from the upper end 11 to the lower end 12 of the progressive zone 10 is set as δ, and the prism power at a certain addition power δ is determined for each of the left and right lenses (1L, 1R). P _L (δ) and P _R (δ) are used. The distances from the upper end 11 of the progressive zone 10 are x _L (δ) and x _R (δ).

As shown in Table 2, when the lenses (1L, 1R) are designed based on the initial prescription shown in Table 1, the left and right lenses (1L, 1R) are both lower end x _L (δ ) = X _R (δ) = 10 mm and the addition power δ = + 2.0. However, since there is a difference between the left and right distance powers Sf _L and Sf _R , the left and right near powers Sn _L and Sn _{R result} in a difference. Accordingly, at the lower end x _L (δ) = x _R (δ) = 10 mm of the progressive zone where the initial addition power δ ₀ = + 2.0, the prism power P _R (δ) = + 4.00D of the right lens. On the other hand, in the left lens, P _L (δ) = + 5.00 D, and the prism power difference ΔP differs by 1.00 D on the left and right. Since the progressive zone 10 has a positive frequency throughout, the progressive zone 10 exhibits a prism effect based on the upper side. Therefore, at the lower end 12 of the progressive zone 10, the image of the right eye with a small near vision frequency is missing. Therefore, the prism power at the lower end 12 of the progressive zone 10 is matched between the left and right lenses using the above formulas 5 and 6. Here, the right lens having a small distance power is the adjustment side lens.

Table 3 shows the final formulation example.

Table 4 shows the characteristics in the progressive zone based on the final prescription.

As shown in Table 4, both the left and right lenses (1L, 1R) have an addition power δ = + 2.00 at the position of x (δ) = 10.00 mm which is the lower end 12 of the initial progressive zone 10, The prism power at the position is the same as P _R (δ) = P _L (δ) = + 5.00. That is, the left and right lenses (1L, 1R) have the same prism power with the same addition power at the lower end 12 of the progressive zone 10. In addition, each setting value shown in Table 3 and the numerical value shown in Table 4 can be calculated | required, for example using the general spreadsheet software installed in the general purpose personal computer. That is, the various setting values shown in Table 1 may be input as initial values to the spreadsheet software that is being activated, and the initial values may be substituted into Equations 5 to 8 for calculation.

FIG. 3 shows optical characteristics of the progressive zone 10 in the lenses (1L, 1R) designed based on the first embodiment. FIG. 3A is a graph of the optical characteristics shown in Table 2. The relationship between the distance x from the upper end 11 of the progressive zone 10 and the power D in each of the left and right lenses (1L, 1R). (21a, 21b) and the relationship (22a, 22b) between x and the prism power P (x) are shown. In the lenses manufactured according to the original prescription, the progressive zone lengths of the left and right lenses (1L, 1R) are both L ₀ , and the addition power is δ _0, which is the same for the left and right lenses (1L, 1R). The left and right lens (1L, 1R) prism powers (P _R (δ), P _L (δ)) at the lower end 12 of the progressive zone 10 are the distance powers (Sf _L , A difference ΔP occurs according to the difference of Sf _R ).

FIG. 3B is a graph showing the optical characteristics shown in Table 4. Here, the right lens 1R is redesigned based on the first embodiment. Then, with respect to the graph shown in (A), a relationship 23 between x and D and a relationship 24 between x and P (x) in the right lens 1R are shown. As shown, extending the progressive band of the right lens 1R to L _1, and increases the power addition in [delta] _1. As a result, the slope of the straight line 22b indicating the relationship between the initial x and P (x) changes, and the prism power P (x) of the left and right lenses at x = L ₀ which is the lower end 12 of the initial progressive zone 10. And the addition frequency at that time also matches the original δ ₀ .

  In addition, when producing glasses using the lenses (1L, 1R) manufactured based on the prescription shown in Table 3, the left and right lenses (1L, 1R) are moved to the lower end 12 position of the initial progressive zone 10. What is necessary is just to process as what is used. That is, the lower end 12 of the initial progressive zone 10 may be designed as the lower end position of the spectacle frame. FIG. 4 illustrates a method for processing the lenses (1L, 1R) designed based on the first embodiment. In this figure, the positional relationship between the left and right lenses (1L, 1R) and the frame 30 when the eyeglass frame 30 is viewed from the front is shown.

The frame 30 and the left and right lenses (1L) are arranged so that the lower ends 31 of the left and right frame frames (30L, 30R) corresponding to the left and right lenses (1L, 1R) substantially coincide with the lower end position of the initial progressive zone 10a. , 1R) and are arranged, for the right lens 1R, and the length of the progressive zone 10b is extended to L _1, also be extended below the lower end initial position of the progressive corridor 10b Cutting is performed at the lower end position of the progressive zone 10a of the left lens 1a, that is, at the same lower end position as the initial progressive zone. Accordingly, when the left and right lenses (1L, 1R) are fitted into the left and right frame frames (30L, 30R), the addition power and the prism power at the lower end position 31 of the left and right frame frames (30L, 30R) match. In addition, image omission due to the difference in prism power is eliminated. In the middle of the progressive zone (10a, 10b), the left and right prism powers (P _R (δ), P _L (δ)) at the same addition power δ gradually approximate toward the lower end 31. , The eyeglasses for both perspective and nearer.

<Specific example of condition (2)>
Next, specific formulation examples corresponding to the above condition (2) are shown in Table 5 below.

Table 6 below shows characteristics of lenses designed based on Table 5.

Table 7 below shows the final formulation example in the condition (2).

Table 8 shows the characteristics of the lens designed based on the final prescription.

As shown in Table 8, both the left and right lenses (1L, 1R) are at the position of x (δ) = 10.00 mm which is the lower end 12 of the initial progressive zone 10, and the initial addition power shown in Table 5 is used. δ = + 2.00, and the prism power at that position is the same as P _R (δ) = P _L (δ) = + 5.00.

<Specific example of condition (3)>
A specific example of the condition (3) is also shown. The prescription contents are illustrated in Table 9 below.

Table 10 below shows characteristics of lenses designed based on Table 5.

Table 11 below shows the final formulation example in the condition (3).

Table 12 shows the characteristics of the lens designed based on the final prescription.

As shown in Table 12, both the left and right lenses (1L, 1R) are at the position of x (δ) = 10.00 mm which is the lower end 12 of the initial progressive zone 10, and the initial addition power shown in Table 9 is used. δ = + 3.00, and the prism power at that position is the same as P _R (δ) = P _L (δ) = + 2.50.

<When Sf + δ ₀ = 0>
By the way, in the above conditions (1) to (3), when the near power is 0, that is,
Sf + δ ₀ = 0
When the condition is applied to the above formula 5 or 7, the L ₁ and δ ₁ become 0 or ∞. In such a case, it is realistic to design as originally prescribed. Further, the progressive zone length in an actual progressive multifocal lens is about 10 mm to 18 mm. In the above formula 5, when the value of Sfb + δ ₀ becomes small, the progressive zone length becomes extremely long, and even if the design is possible, the design is possible. It is virtually impossible to actually manufacture lenses based on Therefore, the above equation 5, when the progressive zone length L ₁ becomes impossible fabrication length would specify the longest corridor length can be produced. In any case, when there is a difference in the distance dioptric power of the left and right lenses, by increasing the addition power and progressive zone length of one lens from the values specified in the original prescription, at the lower end of the progressive zone By approximating the left-right difference of the prism power, the vertical position of the image viewed at the lower end of the progressive zone is not greatly deviated, and it is possible to provide bifocal glasses that are easy on the eyes.

=== Application Example of the First Embodiment ===
In the design method of the first embodiment, a contradiction arises from Equations 5 and 7. Therefore, it is not assumed that Sf + δ ₀ = Sn = 0, that is, the frequency at the lower end 12 of the progressive zone 10 is 0. It was. However, this is because the addition power of the left and right lenses and the prism power are intended to match at the lower end 12 of the initial progressive zone 10, and the prism powers of the left and right lenses are approximated without matching exactly. Since it is obvious that it is quite easy to see only by adding only Sf + δ ₀ = 0, the addition power may be increased or decreased.

In the initial prescription, when one of the left and right lenses is Sf + δ ₀ = Sn = 0, and the other lens is Sf <0 and Sn = Sf + δ ₀ <0, the prism at the lower end of the progressive zone 12 Instead of giving up on approximating the power, it is also conceivable to reduce the left-right difference in the prism power over the entire progression zone 10. Specific examples are given below.

Table 13 shows the initial prescription contents in the application example.

Table 14 shows the characteristics of the lenses designed based on Table 13.

As shown in Table 13, the left lens has Sn = Sf _L + δ ₀ = 0, and the right lens has Sf _R = −3.00 D and Sf _R + δ ₀ = −1.00 D. . From the upper end to the lower end of the progressive zone, the difference in prism power between the left and right lenses is uniformly 1.00D.
Next, the progressive zone length L of the left lens is extended from the initial 10.00 mm to 15.00 mm, and the addition power δ is corrected to increase from 2.00D to 3.00D.

Table 15 shows the prescription content after correction.

Table 16 shows the characteristics of the lens designed based on Table 15.

  As shown in Table 16, at the lower end 12 of the progressive zone 10, the difference in prism power between the left and right lenses is 1.00 D, which is the same as the original, but at the upper end 11, the prism power is the same, and toward the lower end 12. The difference gradually approaches the initial 1.00D. That is, the difference in prism power between the left and right lenses (1L, 1R) over the entire area of the progressive zone 10 is more approximate than the original, and instead of allowing one of the lenses to lack an image at the lower end 12 of the progressive zone. In addition, the difference in the prism power gradually increases from the upper end 11 to the lower end 12 of the progressive zone 10, and it is much easier to see than there is a certain difference in the entire area of the progressive zone 10.

=== About the relationship between the position in the progressive zone and the prism power ===
In the first embodiment, the addition powers δ (x) of the left and right lenses (1L, 1R) match according to the distance x from the eye point 2, and the prism power P (x) is the initial progressive zone 10 The left and right lenses (1L, 1R) coincide at the lower end 12 of the lens. However, in the middle of the progressive zone 10, although the difference in the prism power P (x) between the left and right lenses (1L, 1R) gradually decreases, the vertical positions are different. This is because the relationship between the position x and δ in the progressive zone 10 is a simple linear function. Therefore, in the following, the relationship between the position x and the prism power P (x) in the progressive zone 10 of the left and right lenses (1L, 1R) is more approximate than in the first embodiment, depending on the relationship between the δ and the position x. Examples that can be made are listed as second and third examples corresponding to the above conditions (1) and (2), respectively.

=== Second Embodiment ===
<Relationship between position in the progressive zone and prism power>
Based on the prescription example shown in Table 1, the design method according to the second embodiment will be described. In the second embodiment, when the length in the progressive zone 10 is L ₀ and the addition power at the lower end is δ ₀ , the addition power δ in the middle of the progressive belt 10 and the position x ( x (δ) = (Sf + δ) L ₀ / (Sf + δ ₀ ) (Equation 9)
It is said. That is, when Equation 9 is transformed with δ as a function δ (x) of x,
δ (x) = {(Sf + δ ₀ ) x / L ₀ } −Sf (Equation 10)
It is said. In addition, in the relationship between the addition power δ and the position x in the progressive zone 10 shown in Expression 9 and Expression 10, the addition power (δ, δ (x)) is a negative value on the upper end 11 side of the progression band 10. However, in actuality, since the addition power (δ, δ (x)) is not set to a negative value, from the upper end 11 of the progressive zone 10 to a position where the addition power is δ = 0 to a position x (δ). May be set so as to satisfy δ ≧ 0 by adopting the above Equation 4.

<Lens design>
As described above, the basic concept of the present invention is to extend the progressive zone length of the adjusting lens from the original prescription and increase the addition power, thereby changing the addition power at the lower end 12 of the initial progressive belt 10 to the left and right. The prism powers of the left and right lenses (10L, 10R) are approximated while matching with the other lenses (10L, 10R). Therefore, in the second embodiment, the initial prescription is the same as that shown in Table 1, and the above formula 2 is adopted as the relationship between the position in the prescription progressive zone 10 and the prism power, and the formula 2 An example is given in which the progressive zone length L ₁ and the addition power δ _{1 of} the adjustment-side lens are obtained based on the above equation 10.

First, Table 17 shows optical characteristics of the lens before correction in the second example.

As shown in Table 17, the relationship between δ and x follows Formula 9 above. Next, in the same manner as in the first embodiment, when the formula 5 derived from the formula 2 is applied as it is to determine the progressive zone length L ₁ of the adjustment lens,
L ₁ = (Sfa + δ ₀ ) L ₀ / (Sfb + δ ₀ ) (Formula 5)
It becomes. And for the adjustment side lens, Equation 10 is
δ (x) = {(Sfb + δ ₁ ) x / L ₁ } −Sfb (Formula 11)
Thus, L ₁ in Expression 5 is substituted into Expression 11. Further, since Expression 11 is δ (x) = δ ₀ when x = L ₀ , the addition power δ ₁ of the adjustment side lens is
δ ₁ = (Sfa−Sfb) + δ ₀ (Equation 12)
It becomes. Here, since Sfa> 0 and Sfb> 0 and δ ₁ > δ ₀ , the smaller distance power of the left and right lenses becomes the adjustment side lens, and the addition power δ _{1 of the} adjustment side lens Is a value obtained by adding the initial addition power δ ₀ to the difference in distance power between the left and right lenses. In other words, δ ₁ is set so that the near powers of the left and right lenses are matched.

Therefore, in the first example, the contents of the prescription described in Table 1 above are finally as shown in Table 18 below according to the above Formula 5 and Formula 11.

Table 19 shows the optical characteristics of lenses designed based on the prescription in Table 18.

Here, based on Table 19, the relationship between the position x and the prism power P (x) in the left and right lenses (1L, 1R) will be verified. That is, Table 19 shows the relationship between the position x (δ) and the prism power P (δ) with respect to the addition power δ in the middle of the progressive zone 10, and this is the relationship between the position x (δ) and the prism power P (δ). Try to fix it. Figure 5 is obtained by the relationship between the prism power P (x) at position x and its location in the graph, FIG. 5 (A) the relationship between the x _R and P _{R (x)} in the right lens 1R (B) is a graph obtained by adding the relationship between x _L and P _L (x) in the left lens 1L to the graph shown in (A). As shown in (A), the relationship between x _R and P _R (x) is indicated by a black circle “●”, and the locus of this black circle is a straight line.

In (B), the relationship between x _L and P _L (x) in the left lens 1L is indicated by a white circle “◯”. And this white circle corresponds with the locus | trajectory of the black circle shown to (A). That is, it was confirmed that the left and right lenses (1L, 1R) have the same prism power P (x) at the same position x.

  As described above, in the first embodiment, the left and right lenses (1L, 1R) have the same addition power δ (x) at the same position x in the progressive zone 10, whereas in the second embodiment, The positions x at which the left and right lenses (1L, 1R) have the same prism power P (x) coincide. Therefore, the height of the image in the vertical direction is aligned with the left and right lenses over the progressive zone, and if the lens designed based on this second embodiment is used, it is possible to make the glasses for both perspective and perspective more gentle to the eyes. it can.

=== Third embodiment ===
<Relationship between position in the progressive zone and prism power>
Similar to the second embodiment, the third embodiment is a design method for approximating the height of the image in the vertical direction with the left and right lenses (1L, 1R) over the progressive zone 10. The difference from the first embodiment is that the distance power and the distance power on the left and right are negative values. Here, the design method according to the third embodiment will be described using the prescription shown in Table 5 as an example.

In the third embodiment, when the length in the progression zone 10 is L ₀ and the addition power at the lower end is δ ₀ , the addition power δ in the middle of the progression zone 10 and the position x ( x (δ) = (Sf + δ ₀ ) / (Sf + δ) L ₀ (Equation 13)
It is said. That is, when Equation 13 is transformed with δ as a function δ (x) of x,
δ (x) = (Sf + δ ₀ ) / xL ₀ −Sf (Expression 14)
It is said. Also in the third embodiment, as shown in Expression 12 and Expression 13, when the position near the upper end 11 of the progressive zone 10, that is, when the value of the position x is small, δ (x) becomes a negative value. When x = 0, δ is infinite. Therefore, in the case of the third embodiment as well, from the upper end 11 of the progressive zone 10 to the position x where the addition power is δ (x) = 0, the above equation 4 is used, and so on. What is necessary is just to set a relationship suitably.

<Lens design>
As a third embodiment, a specific example is given in which the progressive zone length L ₁ and the addition power δ _{1 of} the adjustment side lens are obtained based on the above-described Expression 2 and Expression 13 above.
First, Table 20 shows optical characteristics of the lens before correction in the third example.

As shown in Table 20, the relationship between δ and x follows Formula 12 above. Next, in the same manner as in the second embodiment, when obtaining the progressive zone length L ₁ of the directly applicable to adjust the lens to the formula 5 derived from the above equation 2,
L ₁ = (Sfa + δ ₀ ) L ₀ / (Sfb + δ ₀ ) (Formula 5)
It becomes. And for the adjustment side lens, Equation 14 is
δ (x) = (Sfb + δ ₁ ) / xL ₁ −Sfb (Equation 15)
Thus, L ₁ in Expression 5 is substituted into Expression 15. In addition, since Expression 15 is δ (x) = δ ₀ when x = L ₀ , the addition power δ ₁ of the adjustment side lens is
δ ₁ = {(Sfa + δ ₀ ) ² / (Sfa + δ ₀ )} − Sfb (Expression 16)
It becomes. Here, since Sfa <0, Sfa + δ ₀ <0, Sfb <0, Sfb + δ ₀ <0, δ ₁ > δ _0, it is far away from the left and right lenses (1L, 1R) from Equation 5. The lens with the smaller absolute value is the adjustment side lens.

From the above, in the third example, the contents of the prescription in Table 5 above are finally as shown in Table 21 below according to the above Formula 5 and Formula 16.

Table 22 shows optical characteristics of lenses designed based on the prescription in Table 21.

  Next, based on Table 22, it will be verified whether or not the prism power P (x) at the same position x in the progressive zone 10 matches between the left and right lenses (1L, 1R). FIG. 6 shows the relationship between x and P (x) for the left and right lenses (1L, 1R). In FIG. 6, the entire relationship between x (δ) and P (δ) in the left and right lenses (1L, 1R) shown in Table 22 is a scatter diagram, and all points are accurately plotted on one curve. It was confirmed that the same prism power P (x) is obtained at the same position x in the progressive zone 10. Therefore, if the lens designed based on the method of the second embodiment is used, even the near / far glasses for nearsighted people can be used for both near and near glasses.

=== Other Embodiments ===
<About the calculation formula>
In each of the above embodiments, the relationship between the distance x from the upper end 11 in the progressive zone 10 and the prism power P (x) at the position of the distance x is defined by Equation 2. In addition, the position x (δ) at a certain addition power δ in the middle of the progressive zone 10 is defined by Equation 3, Equation 9, Equation 13, and the like. Each of these formulas is a formula employed for simply explaining the concept of the present invention. For example, the relationship between δ and x (δ) is considered to be different depending on the lens manufacturer, and there are various approximate and theoretical formulas for the relationship between δ and P (δ) or x and P (x).

  However, the essence of the present invention is not in these equations. In the present invention, when there is a difference in the distance power between the left and right lenses (1L, 1R), one lens is used as the adjustment side lens, and the length of the progressive zone is made longer than that of the other non-adjustment side lens. The addition power at the lower end of the progressive zone is to be larger than the value of the non-adjustment side lens. Then, by increasing the length of the progressive zone and the addition power, the addition power at the lower end of the progressive zone in the non-adjustment side lens and the lower end position of the progressive zone of the non-adjustment side lens in the middle of the progression zone in the adjustment side lens And the power of the prisms of the left and right lenses at the position are approximated.

<Left and right lens design>
In each of the above embodiments, the pair of left and right lenses are provided with progressive bands based on the same rule. That is, the relationship between the position x and the addition power δ is the same for the left and right lenses. Of course, as in the application example of the first embodiment, when the near power of one lens is 0 in the initial prescription, for the lens, the relationship between x and the addition power in the progressive zone is as follows: It is also possible in principle to adopt Formula 3 as in the first embodiment and to design the other lens based on Formula 10 or Formula 14 in the second or third embodiment.

<About design and prescription>
In each of the above embodiments, when making spectacles using a lens designed based on the method of each embodiment, the design values are adopted as they are for prescription. However, general spectacle lenses are off-the-shelf products, and set values such as distance power, addition power, and progressive zone length are skip values. Moreover, the numerical range which can be set is also limited.

  For example, the progressive zone length is in 1 mm increments, and the addition power is in 0.25 D increments. Further, there is an upper limit value (about 18 mm) for the progressive zone length, and the lower limit and the upper limit are usually defined in the set value itself for the distance power, the near power, and the addition power. That is, it can be said that an actual spectacle lens prescription is an “instruction document” for designating an optimum lens from a wide variety of ready-made lenses. Therefore, the addition power and progress after change described in the final prescription (Table 3, Table 7, Table 11, Table 15, Table 18, Table 21) obtained by the design method according to each of the above-described embodiments. The band length is a design value to the last. In other words, it is an ideal value, and in an actual prescription, a prescription is made so as to select a lens having a set value that is closest to the ideal value.

  In any case, regardless of whether the distance diopter, addition power, progressive zone length, etc. are jump values, the various set values obtained by the design method of the present invention are special lenses with complex surface shapes. This is not a value for specially manufacturing the lens, but a value for specifying a conventional lens. If the relationship between the addition power δ and its position x (δ) in the progressive zone is known in advance, an optimal lens design may be performed based on the relationship. In other words, the lens manufacturer can be provided with a pair of bifocal glasses that are easier on the eyes than before simply by specifying a prescription. Moreover, an off-the-shelf lens can be used as it is without designating special numerical values. Therefore, the user can obtain bifocal glasses that are easier to see than ever and are easier to see than conventional ones at a conventional price.

  The present invention can be applied to lenses for bifocal glasses.

1,1L, 1R lens, 2 optical axis (eye point), 3 distance portion, 4 near portion,
10, 10a, 10b Progression zone, 11 Upper end of progression zone, 12 Lower end of progression zone,
30 glasses frame, 31L, 31R glasses frame lens frame,
31 Lower end of lens frame, L, L ₀ , L ₁ progressive zone length

Claims (9)

A pair of progressive multifocal lenses corresponding to the left and right eyes,
The left and right lenses have a progressive zone in which the addition power gradually increases downward with the optical axis position as the upper end, the left and right lenses as non-adjustment side lenses, and the other lens as adjustment side lenses,
The non-adjustment side lens has a progressive zone length L ₀ , an addition power at the lower end of the progressive zone is δ ₀ , and a lower distance from the upper end of the progressive zone, with the lower end as a lower limit. Let x be the prism power resulting from the prism effect at an arbitrary distance x = x ₁ , P ₀ ,
The adjustment side lens has a length of the progressive zone L ₁ , an addition power at the lower end of the progressive zone is δ ₁ , and a distance from the upper end of the progressive zone to the lower side with the lower end as a lower limit x Let P _{1 be} the prism power resulting from the prism effect at an arbitrary distance x = x ₁ ,
The progressive zone of the adjustment side lens satisfies δ ₁ > δ ₀ and L ₁ > L ₀ , and the addition power at the position of x = L ₀ is δ ₀ ,
When the non-adjustment side lens and the adjustment side lens satisfy x ≦ L ₀ , the prism power difference | P ₀ −P ₁ | at x = x ₁ is L ₁ = L ₀ and δ ₁ = δ Is less than or equal to the difference in prism power at x = x ₁ assuming _zero .
Progressive multifocal lens characterized by that. 2. The progressive lens according to claim 1, wherein the non-adjustment side lens and the adjustment side lens have a minimum difference in prism power | P ₀ −P ₁ | at a position where x = L _0. Multifocal lens. A progressive multifocal lens design method,
The distance spherical equivalents of the left and right lenses expressed by the length of the progressive zone L ₀ and the power in units of prism diopters are Sf _L and Sf _R , respectively, and the addition powers of the left and right lenses are both δ. _{In addition} to executing an initial value setting step for setting an initial value to ₀ ,
The initial value is the following three formulas Sf _L × Sf _R > 0
| Sf _L -Sf _R |> 0
(Sf _L + δ ₀ ) × (Sf _R + δ ₀ ) ≧ 0
If all are satisfied,
Based on the sign of the Sf _L and Sf _R , which is the same sign, the sign of the value of the calculation formula Sf _L -Sf _R , the calculation formula (Sf _L + δ ₀ ), and the sign of (Sf _R + δ ₀ ) An adjustment-side lens determination step that defines either the left or right lens as the adjustment-side lens and the other lens as the non-adjustment-side lens;
The progressive zone length of the adjustment lens is extended from L ₀ to L ₁ , the addition power is increased from δ ₀ to δ ₁ , and the power corresponding to the prism effect in the vertical direction in the progressive zone is Progressive band correction that adjusts L ₁ and δ ₁ so as to approximate the prism power of the adjustment-side lens and the non-adjustment-side lens with respect to the prism power of the left and right lenses based on the initial value. Steps,
Of the initial values corresponding to the adjustment side lens, the resetting step of changing the L ₀ and the δ ₀ to the L ₁ and the δ ₁ adjusted by the progressive zone correction step, respectively,
A method of designing a progressive-band multifocal lens, characterized in that In claim 3,
In the adjustment side lens determination step,
Sf _L > 0 and Sf _R > 0 and Sf _L + δ ₀ > 0 and Sf _R + δ ₀ > 0, or Sf _L <0 and Sf _R <0 and Sf _L + δ ₀ > 0 and Sf _R + δ ₀ > 0. In this case, among the left and right lenses, the lens corresponding to the smaller value of each of the distance powers Sf _L and Sf _R is used as the adjustment side lens.
When Sf _L <0 and Sf _R <0 and Sf _L + δ ₀ <0 and Sf _R + δ ₀ <0 , the absolute values of the distance powers Sf _L and Sf _R of the left and right lenses are small. The lens corresponding to the direction is the adjustment side lens,
In the progressive zone correction step, in the progressive zones of the adjustment side lens and the non-adjustment side lens, the prism power at a position of a distance L ₀ is approximated downward from the upper end,
A progressive-band multifocal lens design method characterized by the above. In claim 4,
In the progressive zone correction step,
The relationship between the distance x from the upper end of the progressive zone in the non-adjustment side lens and the adjustment side lens and the addition power δ (x) is expressed by the following functions δ (x) = fa (x) and δ, respectively. (X) = fb (x)
As well as
The relationship between the distance x and the prism power P (x) in the non-adjustment side lens and the adjustment side lens is expressed by the following functions P (x) = ga (x) and P (x) = gb (x)
Stipulated in
When (Sf _L + δ ₀ ) × (Sf _R + δ ₀ )> 0,
δ ₀ = fa (L ₀ ) = fb (L ₀ )
δ ₁ = fb (L ₁ ),
ga (L ₀ ) = gb (L ₀ )
By calculating the L ₁ and the δ ₁ so as to satisfy all of the following conditions, the distance L ₀ from the upper end to the lower side in each progressive zone of the adjustment side lens and the non-adjustment side lens is calculated. Match the prism power at the position,
A progressive multifocal lens design method characterized by the above. In claim 5,
In the progressive zone correction step, for a lens having a progressive zone where the progressive zone length is L and the addition power at the lower end of the progressive zone is δ, the equation δ (x) = fa (x)
Sf _L > 0, Sf _R > 0, Sf _L + δ ₀ > 0, Sf _R + δ ₀ > 0
If all of the above are satisfied, within the region of the progressive zone,
δ (x)> 0
In the area that satisfies
δ (x) = {(Sf + δ) x / L} −Sf
And a function represented by
Sf _L <0, Sf _R <0, Sf _L + δ ₀ > 0, Sf _R + δ ₀ > 0
If all of the above are satisfied, within the region of the progressive zone,
δ (x)> 0, x> 0
In the area that satisfies
δ (x) = {(Sf + δ) L / x} −Sf
Specifies the function represented by
A progressive-band multifocal lens design method characterized by the above. In claim 3,
(Sf _L + δ ₀ ) × (Sf _R + δ ₀ ) = 0
If it is,
In the adjustment side lens determination step, a lens corresponding to an expression having a value of 0 among the expression (Sf _L + δ ₀ ) and the expression (Sf _R + δ ₀ ) is set as the adjustment side lens,
In the progressive zone correction step, the L ₁ and the δ ₁ are adjusted so that the prism powers of the adjustment side lens and the non-adjustment side lens are approximated at the upper end of the progression zone.
A progressive-band multifocal lens design method characterized by the above. In any one of claims 3 to 7, when at least one of the addition power and the progressive zone length can be set only with a jump value, or a specified value in which a numerical range is restricted,
In the resetting step, among the δ ₁ and the L ₁ adjusted in the progressive zone correction step, the closest approximate value is adopted for the one that can be set only with the specified value.
A progressive-band multifocal lens design method characterized by the above. A processing method of a progressive multifocal lens designed by the method according to any one of claims 3 to 8,
When fitted to a spectacle frame, as the vertical position of the upper end of the corridor at the left and right lenses are aligned, as well as cutting the upper and lower lens, said the adjustment side of the lens, the length of the progressive zone the As the initial value L ₀ , the lower end side is cut in the middle of the progressive zone,
A progressive multifocal lens processing method characterized by the above.

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