JP3759874B2 - Progressive multifocal lens - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a progressive multifocal lens having an excellent visual function.
[0002]
[Prior art]
In general, a progressive multifocal lens has an area called “distance part” for viewing a distance, an area called “intermediate part” for viewing an intermediate distance, and a near area called “near part”. An area exists. In addition, the intermediate distance here refers to a distance from about 50 cm to 2 m, and a distance farther than this is called a far distance and a near distance is called a near distance. However, sometimes far means only infinity, and near means 30 cm to 33 cm, and there is no definite definition. Since a progressive multifocal lens originally does not have a clear boundary line that can be seen from the outside, there is no inconvenience in actual wearing even if these definitions are not fixed.
[0003]
However, when designing, manufacturing, inspecting, and even framing a lens, some precisely defined points are required on the lens. Among these points, the most commonly used distance measuring position F, the near power measuring position N, and the position E through which the line of sight passes when the lens wearer looks in front (in this specification). , Including the fitting point, hereinafter referred to as the eye point position), and is normally displayed on the lens surface as optical layout information of the lens in an unprocessed state.
[0004]
Determining the positions of the distance power measurement position F and the near power measurement position N is indispensable for the verification of the standards defined by ISO and JIS, and the eye point position E is used when the lens is framed. It may be used to determine the vertical direction or the horizontal direction, or may be used in accordance with the geometric center point G.
[0005]
In addition to this, for example, the measurement position Q of the prism refractive power of the lens is essential to know the optical information of these lenses.
[0006]
In addition, although the starting position and the ending position of the progressive change are positions that show important lens information, there is no display obligation on the lens surface, and it is often difficult to specify by actual measurement.
[0007]
Further, the distance power measurement position F and the near power measurement position N are shifted upward and downward by a distance (about 2 to 4 mm) corresponding to the radius of the lens meter opening from the starting position and end position of the progressive change. Often located.
[0008]
As an inevitable defect existing in progressive multifocal lenses, the presence of astigmatism can be cited. The cause of this astigmatism is the presence of the addition power (Di) defined as the surface refractive power difference at the two points of the distance power measurement position F and the near power measurement position N. More specifically, the torsion (distortion) of the curved surface generated by the curvature change of the lens surface from the distance power measurement position F to the near power measurement position N generates astigmatism. Therefore, in order to reduce astigmatism, it is sufficient to reduce the addition value or increase the distance between the distance power measurement position F and the near power measurement position N (strictly, if the rate of change of the surface refractive power is decreased). It will be good). However, since the addition value is an additional refractive power necessary for near vision, if the value is reduced, the original purpose of the progressive multifocal lens cannot be achieved. Further, in order to increase the distance between the distance power measurement position F and the near power measurement position N, if the near power measurement position N is lowered without changing the distance power measurement position F, the line of sight is greatly lowered in near vision. It is inconvenient to turn to.
[0009]
As an attempt to improve wearing comfort by minimizing the uncomfortable feeling caused by astigmatism, Japanese Patent Application Laid-Open No. 62-10617 reduces astigmatism at the expense of distant visual field and emphasizes intermediate vision and near vision. Progressive multifocal lenses have been proposed. In the proposed progressive multifocal lens, the progressive zone length is set to 20 mm or more.
[0010]
[Problems to be solved by the invention]
However, in order to make the progressive multifocal lens easier to use, a problem arises when the addition power (Di) increases in view of the need for a progressive addition lens with a larger addition power (Di) with age. You must also consider these measures.
[0011]
In other words, wearers with a relatively small degree of addition (Di) are relatively young and have a vigorous visual life, which requires a stable visual field (dynamic visual field) when the head and line of sight are moved greatly. A wearer with a relatively high degree (Di) is relatively old and has a quiet visual life, and is required to have a stable visual field (static visual field) when the head and line of sight are not moved too much. Therefore, the design itself, that is, the astigmatism on the progressive multifocal lens, its axial direction, the average power (spherical power + 1/2 of the astigmatic power), and the prism refractive power of the lens, depending on the addition (Di) value. It is desirable to change the distribution of horizontal and vertical components to meet the above requirements.
[0012]
The progressive multifocal lens disclosed in Japanese Patent Laid-Open No. 62-10617 has been designed with an emphasis on intermediate vision and near vision, so that the distance bright vision area with surface astigmatism of 0.50 diopter or less is used. Since the width of the body is only 30 mm or less, there remains a problem that “the sense of constriction of the visual field” is likely to work strongly when the wearer unconsciously sees the distance.
The present invention has been made under the above-described background, and an object thereof is to provide a progressive multifocal lens having an excellent field of view.
[0013]
[Means for Solving the Problems]
As means for solving the above-mentioned problem, the first means is:
A progressive multifocal lens in which a distance power measurement position F, a near power measurement position N, and an eye point position (field position) E through which a line of sight passes when a lens wearer is viewed from the front are preset. When the additional surface refractive power at the near power measurement position N with respect to the distance power measurement position F is taken as the addition power (Di), the lens has an addition power (Di) of at least 0.75 diopters to 3.00 diopters. When the width of a region where the value of astigmatism along the horizontal cross-sectional curve passing through the near power measurement position N is X diopters is W (Di, X) mm, the addition power ( In the relationship between two types of lenses A and B, where Di) is indicated by Da diopter and Db diopter, respectively.
When the addition (Di) is Da> Db,
W (Da, X)> W (Db, X · Db / Da)
(However, X = 1.00 diopter.)
This is a progressive multifocal lens characterized by satisfying the above relationship.
The second means is
In the progressive multifocal lens according to the first means,
When a single curve passing through the three points of the distance power measurement position F, the eye point position E, and the near power measurement position N is a main gaze line, the distance power at an arbitrary point P on the main gaze line The progressive multifocal lens is characterized in that a deviation amount H toward the horizontal nose side with respect to the measurement position F is expressed by H = K · Dp / Di.
(Where K is an arbitrary constant satisfying 1.0 ≦ K ≦ 4.0, Dp is the additional surface refractive power at point P, and Di is the addition)
The third means is
In the progressive multifocal lens according to the first or second means,
An arbitrary point P on the main gazing line is a progressive multifocal lens having two different main curvatures except for the distance power measurement position F and the near power measurement position N.
Furthermore, as other means,
It is a progressive multifocal lens in which a distance power measurement position F, a near power measurement position N, and an eye point position E through which a line of sight passes when the lens wearer is viewed from the front are preset. When the additional surface refracting power at the near power measurement position N with respect to the measurement position F is an addition power (Di), the lens has the following conditions (a) to (e): It is a focus lens.
(A) The additional surface refractive power at the eye point position E is not less than 30% and not more than 50% of the addition (Di).
(B) The lens does not have a symmetry axis that bisects the entire surface of the lens, and the right-eye lens and the left-eye lens have different refractive surfaces.
(C) The lens is used for the left eye for the right eye and the eye point position E is shifted to the nasal side from the position of the distance power measurement position F so as to correspond to the vergence effect of the near eye. The utility power measurement position N is further shifted to the nose side than the eye point position E.
(D) The distance power measurement position F is deviated 10 mm to 17 mm above the eye point position E, and the near power measurement position N is deviated 14 mm to 21 mm below the eye point position E.
(E) When the distance power measurement position F on the lens is the center and the horizontal side is set to a reference direction of 0 °, a substantially fan-shaped region extending from the 30 ° direction to the 150 ° direction is defined as the distance clear vision region, The amount of astigmatism in the far vision range is 0.50 diopters or less regardless of the addition (Di) value.
As another means,
In the progressive multifocal lens according to the other means,
The change in the optical situation along the horizontal cross-sectional curve intersecting with the arbitrary point P on the main gaze line is that the main gaze line is not displaced in the horizontal direction with reference to the distance power measurement position F. In the part, it is left-right mirror-symmetric with respect to the point P, and in the part where the main gaze line is deviated to the nose side with respect to the distance power measurement position F, the change from the point P to the nose side is more in the ear side. It is a progressive multifocal lens characterized by being more intense than the changes leading to.
[0014]
[Action]
According to the above-described means, it is possible to obtain a progressive multifocal lens having an excellent field of view. At the same time, it is possible to adopt a design that emphasizes intermediate vision and near vision. Hereinafter, the operation of the above means will be described in detail.
[0015]
In the progressive multifocal lens according to the first means described above, in view of the fact that a progressive lens having a larger addition power (Di) is required with aging, problems that occur when the addition power (Di) increases. Considered measures for.
[0016]
In other words, wearers with a relatively small degree of addition (Di) are relatively young and have a vigorous visual life, which requires a stable visual field (dynamic visual field) when the head and line of sight are moved greatly. A wearer with a relatively high degree (Di) is relatively old and has a quiet visual life, and is required to have a stable visual field (static visual field) when the head and line of sight are not moved too much. Therefore, the design itself, that is, the astigmatism on the progressive multifocal lens, its axial direction, the average power (spherical power + 1/2 of the astigmatic power), and the prism refractive power of the lens, depending on the addition (Di) value. It is desirable to change the distribution of horizontal and vertical components to meet the above requirements.
[0017]
In addition, as a result of the wearing test performed independently, there is almost no correlation between the limit astigmatism amount of the clear vision region and the addition power (Di) in near vision, and it is within about 0.75 to 1.00 diopters. It has been found that astigmatism can be clearly seen. Therefore, if the design is the same for any value of addition (Di) as in the prior art, when the addition (Di) increases, the near vision range cannot be avoided. As the addition (Di) increases, the above-mentioned tendency can be alleviated by changing to a design in which the width W of astigmatism within about 1.00 diopter is increased as the near vision range.
[0018]
In summary, for example, the addition (Di) has a range of 0.25 diopter to 5.00 diopter, at least 0.75 diopter to 3.00 diopter, and the horizontal direction passing through the near power measurement position N. When the width of the region where the value of astigmatism along the cross-sectional curve is X diopter or less is W (Di, X) mm,
In the relationship between the two types of lenses A and B, the addition power (Di) is indicated by Da diopter and Db diopter, respectively.
When the addition power (Di) is Da> Db,
W (Da, X)> W (Db, X · Db / Da)
(However, X = 1.00 diopter.)
As a result, when the addition (Di) increases, the tendency for the near vision range to become narrower can be alleviated.
[0019]
However, when the addition (Di) increases, reducing the astigmatism in the near-field region increases the near-side astigmatism, so that the static field of view is more stable but the dynamic field of view is not. It becomes stable. That is, if a progressive multifocal lens having a relatively small addition is designed to stabilize the dynamic field of view, and the above method is applied to a progressive multifocal lens having a relatively large addition, a relatively large addition can be obtained. As a result, the static field of view of the progressive multifocal lens is stabilized, and the above-mentioned requirements are satisfied at the same time.
[0020]
In the second means, in order to make the progressive multifocal lens according to the first means easier to use, the distance power measurement position F, the eye point position E, and the near power measurement position N are three points. Is assumed to be the main gaze line in the sense that the gaze passing frequency is highest when gazing, and the position of the distance power measurement position F at any point P on this main gaze line is The deviation amount H to the horizontal nose as a reference is
K is an arbitrary constant satisfying 1.0 ≦ K ≦ 4.0,
The additional surface power at point P is Dp,
When the addition level is Di,
H = K ・ Dp / Di
The position of the main line of sight on the lens is defined as
[0021]
The reason why the additional surface refractive power is increased along the main line of sight is to see a target at a closer distance, and viewing a target at a closer distance means that the lines of sight of the left and right eyes are more nasal. Therefore, in order to cope with this, it is necessary to increase the amount of deviation of the main gaze to the nasal side. Therefore, the amount of deviation H at any point P on the main line of sight is proportional to the value obtained by dividing the additional surface power Dp at point P by Di. The reason why the arbitrary constant K is given a width is that the line of sight is refracted when passing through the lens because of the prism action due to the horizontal component of the transmission refractive power of the lens at the position of the deviation amount H. This is because K is small when the transmission refractive power is negative, and K is large when it is positive. When the transmission refractive power is 0, a value of about K = 2.5 is desirable.
[0022]
In the third means, in order to make the progressive multifocal lens according to the first or second means easier to use, an arbitrary point P on the main gaze line is a distance power measurement position F and a near power measurement position N. Except that the two main curvatures have different portions.
[0023]
The optical conditions that have been used so far include astigmatism on the progressive multifocal lens, its axial direction, average power (spherical power + 1/2 of astigmatic power), and horizontal component of the prism refractive power of the lens. And vertical component distribution. These have been treated mainly as the state of the progressive multifocal lens surface for ease of explanation. That is, astigmatism is the surface astigmatism of the progressive surface, the average power is the surface average power of the progressive surface, and the prism refractive power is the difference between the normal direction of the progressive surface and the back surface. It was a value calculated relatively simply from the above.
[0024]
However, since an actual lens is put in a spectacle frame and worn in a forward tilted state of about 5 ° to 10 ° at a position of about 12 mm in front of the eye, actually, the angle at which the line of sight intersects with the lens and at that position It is obvious that the thickness (strictly speaking, the optical path length of the line of sight within the lens) is related, so the above astigmatism is the transmission astigmatism, the average power is the transmission average power, and the prism Refractive power is included in the technical scope of the present invention even if it is regarded as a value to be calculated from the deflection angle of the line of sight (only the expression of addition, particularly “additional surface refractive power”, Because it is the definition of.) Therefore, the description of the main gaze line does not necessarily refer to the “line without surface astigmatism (= navel meridian)” that is often used in the past, but the fact that there is no surface astigmatism is not necessarily in the actual use situation. This is because it is not an essential requirement of the present invention because it is not the best state.
[0025]
According to the study by the present inventors, the distribution of the area of the “distance portion”, “intermediate portion”, and “near portion” in a general progressive multifocal lens can be clearly distinguished. Although there are some differences depending on the type of lens, the “distance part” is the widest. This is because it corresponds to the extremely high frequency of far vision in daily life. Further, the sensitivity of the human eye to astigmatism is the most sensitive in far vision, and a tendency to become dull as it shifts from intermediate vision to near vision.
[0026]
Even if we look at the results of our own wearing tests, it is necessary that the clear vision area in far vision is astigmatism within about 0.50 diopters, but in the near vision, it is about 0.75 to 1. It has been found that astigmatism within 00 diopters can be clearly seen. Therefore, it is determined that it is not reasonable to simply compare the widths of the clear vision areas with a certain astigmatism value. Furthermore, it is a psychological burden for humans to narrow the far field of view. This is not just a question of “convenient or inconvenient”, but the psychological pressure of “feeling of constriction of the visual field” causes the wearer to avoid the glasses.
[0027]
In view of such a situation, in the progressive multifocal lens according to the other means described above, the far vision range is substantially fan-shaped and widens from the 30 ° direction to the 150 ° direction with respect to the position of F, and spreads wide. The astigmatism in this clear distance vision range was 0.50 diopters or less regardless of the value of addition (Di). The reason why the limit value was determined regardless of the value of the addition power (Di) was that, as a result of the wearing test conducted independently, there was almost no correlation between the limit astigmatism amount in the clear vision region in far vision and the addition power (Di). It was because it was not recognized.
[0028]
In addition, the reason why the shape of the far vision area is defined as “a substantially fan-shaped area having a widening at the end” as described above is to prevent the wearer from having a “feeling of narrowing of the visual field”.
Further, in order to make the eye point position E through which the line of sight passes suitable for viewing an intermediate distance when the wearer of the progressive multifocal lens according to other means performs a front view, an addition at the eye point position E is added. The surface refractive power was 30% or more and 50% or less of the addition (Di). This is because, by many wearing tests, the change in surface refractive power from the distance power measurement position E to the near power measurement position N becomes severe at less than 30%, and the astigmatism on the side of the intermediate field is sufficiently reduced. This is because it has been found that if the distance exceeds 50%, it is not possible to ensure a sufficient distance vision range.
[0029]
In addition, the progressive multifocal lens according to other means has a sufficiently reduced astigmatism as compared with a normal progressive multifocal lens, so the side is used widely. There is a need for good vision. Therefore, there is a symmetry axis that bisects the entire surface of the lens, and so-called “left-right symmetric design” that rotates 5 ° to 10 ° during frame insertion is not preferable because it does not consider binocular vision at the side. Therefore, the right-eye lens and the left-eye lens have different surfaces, so-called “left-right separate design” is positioned as the optimum.
[0030]
Furthermore, the horizontal arrangement of the three points of the distance power measurement position F, the eye point position E, and the near power measurement position N corresponds to the eye converging effect for the right eye and the left eye. Therefore, the position of the eye point position E is shifted to the nose side from the position of the distance power measurement position F, and the position of the near power measurement position N is further to the nose side than the position of the eye point position E. It must be deviated.
[0031]
Further, as the arrangement of these three points in the vertical direction, the position of the distance power measurement position F is preferably 10 mm to 17 mm, more preferably 12 mm to 15 mm higher than the position of the eye point position E by many wearing tests. The distance power measurement position N and the distance power measurement position N are preferably shifted from the eye point position E by 14 mm to 21 mm, more preferably 16 mm to 19 mm. It has been found that the distance from the position N is sufficient to reduce the change in refractive power, and at the same time, it is an optimum compatible range for a reasonable line-of-sight movement to the two near and far regions.
[0032]
Further, in order to make the progressive multifocal lens according to the other means easier to use, the contents of the above-described “left and right separate design” can be further improved by the following technique. That is, in order to obtain good binocular vision, astigmatism on the lens through which the line of sight passes, its axial direction, average power (spherical power + 1/2 of astigmatism power), and prism refractive power of the lens It is necessary for the left and right eyes to match the horizontal and vertical components. Here, when the target to be seen is in front of the lens wearer, it is sufficient to consider the arrangement of the main gaze line and the distribution of the surface refractive power.
[0033]
However, if the target to be seen moves to the side of the lens wearer, the line of sight of one eye moves to the ear and the line of sight of the other eye moves to the nose. The optical conditions of the two are not necessarily the same. If the target to be seen is infinitely far away from the lens wearer, the left and right eye gaze angles are the same when moving from front view to side view, so the distribution of optical conditions on the lens is Left-right mirror symmetry in the horizontal direction with respect to the main gaze line (meaning a symmetrical arrangement as if a mirror was placed at the position of the main gaze line, not just “right-left symmetry”).
[0034]
This is because the above-mentioned “optical state” includes those having directivity such as the axial direction of astigmatism. ) Is desirable. On the other hand, if the target to be seen is a finite distance of the lens wearer, the lines of sight of the left and right eyes are closer to the nose side due to the convergence action of the eyes. In this state, when moving from the front view to the side view, if the distance to the target is unchanged, the angles of contact of the left and right eyes are the same. However, when moving from the front view to the side view, as is readily understood when taking a very close example as an example, the distance to the target is usually increased. If so, the vergence effect of the eyes is weakened, and the eyes of both eyes become nearly parallel.
[0035]
Therefore, if the target to be seen is at a finite distance of the lens wearer, the angle of contact between the left and right eyes when moving from the front view to the side view is different, and the line of sight moving to the ear side is the nose side Larger than the line of sight to move to. This tendency is due to the rotation of the head in side view (usually the head rotates about half of the angle from front view to side view and the eyeball rotates the rest). On the accompanying spectacle lens, it becomes more condensed and noticeable. For this reason, in order to see a finite distance, it is desirable that the portion where the main gazing line is deviated to the nose side with respect to the position of F is asymmetric in the horizontal direction.
[0036]
In progressive multifocal lenses, the distribution of optical conditions on the lens in the horizontal direction from the main line of sight changes normally, so that the optical conditions on the lens through which the left and right lines of sight pass are the same. Therefore, it is desirable that the change from the main gaze to the nose side is more severe than the change from the ear side.
[0037]
To summarize the above points:
Astigmatism change, horizontal astigmatism change, average refractive power change, change in horizontal component of prism refractive power, along a horizontal cross-sectional curve intersecting an arbitrary point P on the main gazing line At least one of the optical conditions such as the change in the vertical component of the refractive power of the prism is left-right mirror-symmetric with respect to the point P in a portion not horizontally displaced with respect to the position of the distance power measurement position F. It is desirable that the change from the point P to the nose side is more intense than the change to the ear side in the portion that is displaced to the nose side with respect to the position of the distance power measurement position F. .
[0038]
DETAILED DESCRIPTION OF THE INVENTION
Example 1
FIG. 1 is a diagram for explaining a layout of optical information of the progressive multifocal lens for the right eye according to the first embodiment. In FIG. 1, the distance power measurement position F is 14 mm above the lens geometric center O, and the near power measurement position N is 17.5 mm below the lens geometric center O and 2.5 mm inward of the nose. There is a position E through which the line of sight passes when the lens wearer looks in front at a position 1.0 mm in the horizontal nose side of the geometric center of the lens (the figure is drawn slightly exaggerated for explanation). .
[0039]
In this embodiment, the distance power is S-1.00 diopter, and the addition power is Di = + 2.00 diopter. The additional surface power at the distance power measurement position E is +0.76 diopters, which corresponds to about 38% of the addition (Di). When the distance right power measurement position F on the lens is set as the center and the horizontal right side is set to a reference direction of 0 °, a substantially fan-shaped region Df extending from the 30 ° direction to the 150 ° direction is a far vision region. Astigmatism in the region is 0.50 diopter or less.
[0040]
1 is a main gaze line, and the lens passes through three points, a distance power measurement position F, an eye point position E, and a near power measurement position N. Although divided into a “nose side portion” and an “ear side portion”, these two surface portions are asymmetric in the horizontal direction.
[0041]
FIG. 2 is a diagram showing the deviation amount H at an arbitrary point P on the main gaze line, and FIG. 3 is a diagram showing the additional surface refractive power D at the arbitrary point P on the main gaze line. 2 and 3, the abscissa represents a position where a positive numerical value is above the geometric center point of the lens and a negative numerical value is a downward position. As can be seen at first glance, the shapes of the graphs in FIGS. 2 and 3 are similar, only the ordinate is different. This is because H and D have a direct proportional relationship of H = K · D / Di, where K is a constant of 2.5.
[0042]
(Example 2)
FIG. 4 is a diagram for explaining a layout of optical information of the progressive multifocal lens for the right eye according to the second embodiment. In FIG. 4, the distance power measurement position F is 14 mm above the geometric center of the lens and 1.0 mm in the horizontal ear side, and near to the position 17.5 mm below the geometric center of the lens and 1.5 mm inward on the nose side. There is a position E at which the line of sight passes when the lens wearer looks in front from the frequency measurement position N and the position of the geometric center of the lens.
[0043]
In this embodiment, the distance power measurement position F, the eye point position E, and the near power measurement position N in the first embodiment shown in FIG. 1 are all displaced by 1.0 mm toward the horizontal ear. It is an arrangement. Others are the same as the progressive multifocal lens of Example 1.
[0044]
The advantage of the lens of Example 2 over the lens of Example 1 is that the eye point position E can be made coincident with the center point on the back surface processing, and can be easily used as a prism refractive power measurement point.
[0045]
Example 3
5 and 6 are diagrams showing the astigmatism distribution of the progressive multifocal lens of Example 3. FIG. Here, FIG. 5 corresponds to the embodiment of the two progressive multifocal lenses of the addition power Da = + 1.00 diopter, and FIG. 6 shows the addition power Db = + 2.00 diopter, respectively. A solid line) indicates astigmatism contours for each 0.25 diopter, and the numerical value written beside each curve represents the amount of astigmatism (unit: diopter).
[0046]
The distance power measurement position F, the eye point position E, and the near power measurement position N shown in each of FIGS. 5 and 6 are arranged in the same manner as in the first embodiment, and are arranged in a substantially central longitudinal direction of the lens. A curved line (dotted line) is a main gazing line, and passes through three points of a distance power measurement position F, an eye point position E, and a near power measurement position N. Of the intervals between the contour lines of astigmatism drawn in each part, the main gaze line is not horizontally displaced with respect to the position of the distance power measurement position F (above the distance power measurement position F). In a portion that is mirror-symmetrical and the main line of sight is deviated to the nose side with respect to the position of the distance power measurement position F (below the distance power measurement position F), ) ”Is“ dense ”and“ ear side portion (left side) ”is“ sparse ”, and the change from the main gaze to the nose is more intense than the change to the ear. This feature is the same not only in astigmatism but also in the horizontal and vertical components of astigmatism axial direction, average refractive power, and prism refractive power.
[0047]
Further, when the width of the region where the value of astigmatism along the horizontal sectional curve passing through the near power measurement position N is X diopters or less is W (Di, X) mm, the addition (Di) is In the relationship between the two types of lenses A and B indicated by Da diopter and Db diopter respectively.
When the addition (Di) is Da> Db,
W (Da, X)> W (Db, X · Db / Da)
(However, X = 1.00 diopter)
Meet the relationship.
[0048]
Therefore, the near portion W1 in FIG. 5 is represented as W1 = W (1.00, 0.50), and the near portion W2 in FIG. 6 is represented as W2 = W (2.00, 1.00). Therefore, since the lens of FIG. 5 has twice the addition power of the lens of FIG. 6, if the lens of FIG. 5 and the lens of FIG. 6 have the same design, the lens of FIG. It should be equal to a stack of two lenses. That is, the width (W2) of the astigmatism amount 1.00 diopter in the addition Db = + 2.00 diopter is equal to the width (W1) of the astigmatism amount 0.50 diopter in the addition Da = + 1.00 diopter. Should be.
[0049]
However, when comparing the widths of two horizontal arrows passing through N in the lens of FIG. 5 and the lens of FIG. 6, W2> W1, that is, W (2.00,1.00)> W (1.00 , 0.50), and it can be seen that the design is designed to alleviate the tendency for the near vision range to narrow when the addition becomes large.
[0050]
(Example 4)
FIG. 7 is a graph showing the astigmatism distribution of the progressive multifocal lens for the right eye in Example 4. In this embodiment, the distance power is S + 1.50 diopters, the addition power is Di = + 2.00 diopters, and the curves (solid lines) are contour lines of astigmatism every 0.25 diopters. The numerical value written beside this represents the amount of astigmatism (unit: diopter).
[0051]
The distance power measurement position F is 15 mm above the geometric center O of the lens, the distance power measurement position N is 19 mm below the geometric center O of the lens and 2.5 mm inward of the nose side, and the geometric center O of the lens. There is a position E through which the line of sight passes when the lens wearer views the front in a position of 1.0 mm in the horizontal nose side. A single curve (dotted line) in the central longitudinal direction of the lens is a main gazing line, and passes through three points: a distance power measurement position F, an eye point position E, and a near power measurement position N. Below this main gazing line, there is a portion that intersects the contour line of astigmatism, and there are two different parts of the main curvature at each point along the main gazing line below the lens. I understand.
[0052]
In this embodiment, the line of sight intersects the lens for all line-of-sight directions on the assumption that the lens is framed in a spectacle frame and worn at a position of about 12 mm in front of the eye in a 7 ° forward tilt state. Considering the angle and the optical path length of the line of sight within the lens at that position, the distribution of transmission astigmatism, the distribution of transmission average power, and the distribution of the deflection angle of the line of sight are more desirable. The lens surface was set. As a result, two portions having different main curvatures at each point along the main line of sight occurred. However, only the positions of F and N are set to have the same two main curvatures for the convenience of the inspection process.
[0053]
【The invention's effect】
As described above in detail, the progressive multifocal lens according to the present invention has an excellent visual field function, little lateral image shaking, and a well-balanced visual field in the distance, near, and middle. A progressive multifocal lens having
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a layout of optical information of a progressive multifocal lens for a right eye according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating a deviation amount H at an arbitrary point P on the main gazing line of the progressive multifocal lens for the right eye according to the first embodiment of the present invention.
FIG. 3 is a diagram illustrating an additional surface refractive power D at an arbitrary point P on the main line of sight of the progressive multifocal lens for the right eye according to the first embodiment of the present invention.
FIG. 4 is a diagram for explaining a layout of optical information of a progressive multifocal lens for the right eye according to a second embodiment of the present invention.
FIG. 5 is a diagram showing an astigmatism distribution of a progressive multifocal lens for the right eye according to Example 3 of the present invention.
FIG. 6 is a diagram showing an astigmatism distribution of a progressive multifocal lens for the right eye according to Example 3 of the present invention.
7 is a graph showing astigmatism distribution of a progressive multifocal lens for the right eye according to Example 4 of the present invention. FIG.
[Explanation of symbols]
E: eye point position, F: distance power measurement position, N: near power measurement position, Df: distance clear vision area, O: geometric center of the lens.

Claims (2)

A progressive multifocal lens design method in which a distance power measurement position F, a near power measurement position N, and an eye point position (field position) E through which a line of sight passes when a lens wearer is viewed in front are preset. When the additional surface refracting power at the near power measurement position N with respect to the distance power measurement position F is taken as addition (Di), the lens has an addition (Di) of at least 0.75 diopters to 3. When the width of an area having an astigmatism value of X diopter or less along the horizontal sectional curve passing through the near power measurement position N is W (Di, X) mm In the relationship between the two types of lenses A and B, where the addition (Di) is indicated by Da diopter and Db diopter, respectively, when the addition (Di) is Da> Db,
W (Da, X)> W (Db, X · Db / Da)
Satisfying the relationship of X = 1.00 diopter,
In addition, when a single curve passing through the three points of the distance power measurement position F, the eye point position E, and the near power measurement position N is a main gaze line, an arbitrary point P on the main gaze line is A method for designing a progressive multifocal lens, characterized in that a deviation amount H toward the horizontal nose side with respect to the power measurement position F is expressed by H = K · Dp / Di. (Where K is an arbitrary constant satisfying 1.0 ≦ K ≦ 4.0, Dp is the additional surface refractive power at point P, and Di is the addition)   2. The method of designing a progressive multifocal lens according to claim 1, wherein an arbitrary point P on the main gaze line is a portion where two main curvatures are different except for a distance power measurement position F and a near power measurement position N. A method for designing a progressive multifocal lens, comprising:

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