Method for determining progressive addition lens

Abstract

A method for specifying a progressive addition lens, the method comprising: a determination step for determining the degree of necessity for the size of a clear field of view region for a subject wearing a progressive addition lens; and a design selection step for selecting the design of the progressive addition lens in which the clear field-of-view region is expanded in the depth direction by reducing the lower addition degree of the middle region of the progressive zone of the progressive addition lens when it is determined that the clear field-of-view region of the subject needs to be expanded in the depth direction.

Description

Technical Field

[0001] The present invention relates to a method for determining an aspheric progressive addition lens. Background Art

[0002] In Patent Documents 1 and 2, an aspheric progressive addition lens is disclosed, which adds transmitted astigmatism to the far vision area, the near vision area, and the near vision area and the intermediate area of the intermediate area. In the near vision area and the intermediate area where transmitted astigmatism is added, after subtracting the refractive power for astigmatism correction, the portion where the amount of the refractive power in the horizontal direction is greater than the amount of the refractive power in the vertical direction (or the amount of the refractive power in the vertical direction is greater than the amount of the refractive power in the horizontal direction).

[0003] In addition, in Patent Document 3, an ophthalmic prescription assisting device is disclosed, which includes: an acquisition unit that acquires first distribution data and second distribution data, the first distribution data being measurement data of a subject's eye based on a wavefront sensor and related to the distribution of the refractive error of the subject's eye, and the second distribution data being the refractive power distribution of an ophthalmic lens for correcting the refractive error of the subject's eye and being measurement data of a part of the measurement data related to the refractive power distribution of the ophthalmic lens measured by a lensometer; an arithmetic unit that obtains third distribution data related to the distribution of the refractive error considering the correction of the ophthalmic lens based on the first distribution data and the second distribution data acquired by the acquisition unit.

[0004] In addition, in Patent Document 4, a method for determining a person's visual behavior is disclosed, which is characterized by including a step of recording the head movement of a person during the execution of a visual task, and further including a step of recording at least one eye movement of the person during the execution of the visual task, a step of determining the relative orientation of the eye with respect to the head at different time points, and a step of determining the amount of time the eye remains in each orientation.

[0005] In addition, in Non-Patent Document 1, it is disclosed that by optimizing vision within a standard arm length range, the comfort for the wearer is increased. As a means to achieve this purpose, a method for evaluating a clear vision area in an orthogonal coordinate system is disclosed in Patent Document 5, and a method for adjusting a near addition curve according to an individual is disclosed in Patent Document 6.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: International Publication No. 2020 / 067522

[0009] Patent Document 2: International Publication No. 2020 / 067523

[0010] Patent Document 3: Japanese Patent No. 6708955

[0011] Patent Document 4: Japanese Patent No. 4659027

[0012] Patent Document 5: Japanese Patent No. 6920287

[0013] Patent Document 6: Japanese Patent No. 6991135

[0014] Non - Patent Literature

[0015] Non - Patent Literature 1: Varilux X series, retrieved on March 9, Reiwa 5, Internet

[0016] <URL:https: / / www.essilor.sa / en / products / varilux - x - series> Summary of the Invention

[0017] Technical Problem to be Solved by the Invention

[0018] An object of an embodiment of the present invention is to provide a technique for determining a progressive multifocal lens that can be worn more comfortably for a subject who needs to expand the clear vision area in the depth direction.

[0019] Technical Solution for Solving the Technical Problem

[0020] A method for determining a progressive multifocal lens according to the first aspect of the present invention includes: a determination step of determining the necessity of the size of the clear vision area for a subject wearing a progressive multifocal lens; a design selection step of, when it is determined that the subject needs to expand the clear vision area in the depth direction, selecting a design of a progressive multifocal lens in which the addition power in the middle zone of the progressive zone of the progressive multifocal lens is reduced to expand the clear vision area in the depth direction.

[0021] According to the second aspect of the present invention, in the determination step of the method for determining a progressive multifocal lens according to the first aspect, based on the change in the eye gaze movement of the subject when the subject repeatedly makes near - distance observations and far - distance observations, the necessity of the size of the clear vision area is determined.

[0022] According to the third aspect of the present invention, in the determination step of the method for determining a progressive multifocal lens according to the first aspect, based on the sensitivity of the subject to aberration, the necessity of the size of the clear vision area is determined.

[0023] Fourth aspect of the present invention: According to the method for determining an aspheric progressive addition lens as described in the first aspect above, in the determination step, based on the movement trend of the object during the task, the necessity of the size of the clear vision area is determined. The task includes the actions of the subject holding, visually confirming, and moving an object capable of acquiring position information.

[0024] Fifth aspect of the present invention: According to the method for determining an aspheric progressive addition lens as described in the first aspect above, in the design selection step, a design with a reduced addition power is selected such that when the eyes of the subject are set as the origin, the vertical direction is set as the Y-axis, and the depth direction is set as the Z-axis, the position of Y = -210 mm and Z = 850 mm becomes the clear vision area.

[0025] Sixth aspect of the present invention: According to the method for determining an aspheric progressive addition lens as described in the first aspect above, in the design selection step, instead of increasing the astigmatism amount of the aspheric progressive addition lens on the principal meridian, a design of an aspheric progressive addition lens with a clear vision area expanded in the depth direction is selected.

[0026] Seventh aspect of the present invention: According to the method for determining an aspheric progressive addition lens as described in the first aspect above, in the design selection step, a design of an aspheric progressive addition lens with a clear vision area expanded in the depth direction and the left-right direction by reducing the addition power is selected.

[0027] Eighth aspect of the present invention: According to the method for determining an aspheric progressive addition lens as described in the first aspect above, when it is determined in the determination step that the subject needs to expand the clear vision area in the left-right direction, in the design selection step, a design of an aspheric progressive addition lens with a clear vision area expanded in the left-right direction is selected by smoothing the power distribution of the aspheric progressive addition lens in the left-right direction and reducing the left-right coma aberration around the principal meridian of the aspheric progressive addition lens.

[0028] Ninth aspect of the present invention: According to the method for determining an aspheric progressive addition lens as described in the eighth aspect above, in the determination step, based on the left-right coma aberration amount of the eyes of the subject, the necessity of the size of the clear vision area is determined.

[0029] Tenth aspect of the present invention: According to the method for determining an aspheric progressive addition lens as described in the eighth aspect above, the width of the smoothing filter used to smooth the power distribution in the left-right direction is greater than the narrowest width among the widths between the peaks of the left-right coma aberration on both sides of the principal meridian of the aspheric progressive addition lens before smoothing.

[0030] According to the eleventh aspect of the present invention, in the determination method of the progressive multifocal lens according to the eighth aspect described above, in the design selection step, instead of increasing the astigmatism amount of the progressive multifocal lens on the principal meridian, a design of a progressive multifocal lens with a clear vision area expanded in the left-right direction is selected.

[0031] According to the twelfth aspect of the present invention, in the determination method of the progressive multifocal lens according to the eighth aspect described above, in the design selection step, when it is determined that the subject needs to expand the clear vision area in the left-right direction, a design of a progressive multifocal lens with the addition curve of the principal meridian unchanged and the clear vision area expanded in the left-right direction is selected.

[0032] According to the twelfth aspect of the present invention, in the determination method of the progressive multifocal lens according to any one of the first to twelfth aspects described above, when it is determined in the determination step that the subject does not need to expand the clear vision area, in the design selection step, the basic design of the progressive multifocal lens is selected.

[0033] Advantages of the Invention

[0034] According to an embodiment of the present invention, it is possible to determine a progressive multifocal lens that can be worn more comfortably for a subject who needs to expand the clear vision area in the depth direction. Brief Description of the Drawings

[0035] Figure 1A FIG. is an example of a clear vision area when a subject wearing a progressive multifocal lens observes closely, and is an example of a clear vision area in a state without eye aberration.

[0036] Figure 1B FIG. is an example of a clear vision area when a subject wearing a progressive multifocal lens observes closely, and is an example of a clear vision area in a state where the eye has a trefoil aberration (Z[-3, 3]) in the left-right direction.

[0037] Figure 2 FIG. is an example of a clear vision area when a subject wearing a progressive multifocal lens with the basic design and depth expansion design of the first embodiment of the present invention (+2D addition power) observes an object on the principal meridian.

[0038] Figure 3 FIG. is a flowchart showing an example of the determination method of the progressive multifocal lens of the first embodiment of the present invention.

[0039] Figure 4 FIG. is a schematic diagram for explaining the eye movement task of the first embodiment of the present invention.

[0040] Figure 5It is a diagram showing an example of the original image and multiple blurred images of the first embodiment of the present invention.

[0041] Figure 6 It is an example of a spot image formed by the aberration added to the blurred image in the first embodiment of the present invention.

[0042] Figure 7 It is a diagram showing an example of the addition power curve of a progressive multifocal lens (add power +2D) with a basic design and a depth expansion design in the first embodiment of the present invention.

[0043] Figure 8A It is a left-right direction power distribution diagram of the near vision area of a progressive multifocal lens (for left eye) with a basic design and a left-right expansion design in the first embodiment of the present invention.

[0044] Figure 8B It is Figure 8A the gradient distribution diagram.

[0045] Figure 9A It is a left-right direction power distribution diagram of the near vision area of a progressive multifocal lens (for left eye) with a basic design and a depth expansion design in the first embodiment of the present invention.

[0046] Figure 9B It is Figure 9A the gradient distribution diagram.

[0047] Figure 10 It is a diagram showing the power distribution (Power), astigmatism distribution (As), and left-right direction third-order aberration distribution (HOA, Higher Order Aberration) of the basic design of a progressive multifocal lens according to an embodiment of the present invention.

[0048] Figure 11 It is a diagram showing the power distribution (Power), astigmatism distribution (As), and left-right direction third-order aberration distribution (HOA, Higher Order Aberration) of a design that smooths only the power distribution of a progressive multifocal lens in the left-right direction according to an embodiment of the present invention.

[0049] Figure 12 It is a diagram showing the power distribution (Power), astigmatism distribution (As), and left-right direction third-order aberration distribution (HOA, Higher Order Aberration) of a design that reduces the addition power in the middle area of the progressive zone of a progressive multifocal lens according to an embodiment of the present invention.

[0050] Figure 13AThis is a diagram showing the clear vision area when a subject wearing a progressive multifocal lens with the basic design of the present invention conducts a near vision observation. The left side is a diagram of the state where the eye has no aberration, and the right side is a diagram of the state where the eye has a trefoil aberration of 0.1 μm in the rightward direction.

[0051] Figure 13B This is a diagram showing the clear vision area when a subject wearing a progressive multifocal lens with the left and right expansion design of the present invention conducts a near vision observation. The left side is a diagram of the state where the eye has no aberration, and the right side is a diagram of the state where the eye has a trefoil aberration of 0.1 μm in the rightward direction.

[0052] Figure 13C This is a diagram showing the clear vision area when a subject wearing a progressive multifocal lens with the depth expansion design of the present invention conducts a near vision observation. The left side is a diagram of the state where the eye has no aberration, and the right side is a diagram of the state where the eye has a trefoil aberration of 0.1 μm in the rightward direction.

[0053] Figure 14A This is a diagram showing an example of a bimodal light spot (left in the figure) and a blurred image (right in the figure) formed by folding the light spot.

[0054] Figure 14B This is a diagram showing an example of a unimodal light spot (left in the figure) and a blurred image (right in the figure) formed by folding the light spot. Detailed implementation mode

[0055] <Insights obtained by the inventor>

[0056] First, the insights obtained by the inventor will be described. Figure 1A And Figure 1B This is a diagram showing an example of the area where a subject wearing a progressive multifocal lens can at least distinguish the direction of a Landolt ring target with a visual acuity of 0.7 or the area where the edge of a Landolt ring target with a visual acuity of 0.3 can be clearly recognized during a near vision observation (hereinafter referred to as the clear vision area). In Figure 1A And Figure 1B Taking the left eye L of the subject as a reference, the vertical axis represents the front-back direction, and the horizontal axis represents the left-right direction. In addition, the area surrounded by the dotted line is the clear vision area of the left eye L, and the area surrounded by the solid line is the clear vision area of the right eye R. The overlapping range of the two becomes the clear vision area of both eyes. Hereinafter, in this specification, unless otherwise specified, the "clear vision area" refers to the clear vision area of both eyes. Figure 1A This is a diagram showing the clear vision area in the state where the eye has no aberration, Figure 1B This is a diagram showing an example of the clear vision area in the state where the eye has a trefoil aberration (Z[-3,3]) with a third-order aberration in the left-right direction. As Figure 1BAs can be seen, when the eye has clover aberration, the clear visual field regions on the left and right are shifted, and the clear visual field regions of both eyes are narrowed. Since the aberration of the eye varies due to individual differences or the environment, in a state where the clear visual field region is narrowed, it is possible that the subject cannot comfortably wear progressive multifocal lenses.

[0057] In addition, Figure 2 FIG. is a diagram showing an example of the clear visual field region when a subject wearing a progressive multifocal lens (add power +2D) observes an object on the principal meridian. In Figure 2 the left eye of the subject is set as the origin (0, 0), the up-down direction is set as the Y-axis, and the depth direction is set as the Z-axis. Figure 2 The region surrounded by the dashed line in FIG. represents the clear visual field region when wearing a progressive multifocal lens of the basic design. In the optical design of the progressive multifocal lens, the upper, middle, and lower segments of the polar coordinate system with the center of rotation of the eyeball as the origin are respectively assigned to the far, middle, and near vision zones, and the definition of the object distance is also defined by the polar coordinate system. On the other hand, in human spatial perception, in the orthogonal coordinate system based on the front of the face, the height and depth are more often felt. In addition, in terms of the skeleton, the movement of rotating up and down around the shoulder and moving in the depth direction by extending and flexing the arm is a movement based on the polar coordinate system, and the alignment of the posture and the switching of the half body are movements in the depth direction of the orthogonal coordinate system, performing a complex movement that mixes the two. Subjects who are used to progressive multifocals or have adaptability perceive in the polar coordinate system with the classical center of rotation of the eyeball as the origin and tend to perform rotational movements based on a fixed shoulder. On the other hand, subjects who are not used to progressive multifocals or have low adaptability perceive in the orthogonal coordinate system and tend to move while moving the shoulder back and forth.

[0058] The movement range of the former is equivalent to the sleeve length of the body size, which is called the arm length, the range from the shoulder to the little finger of the arm, and the average is known to be about 740 mm. The movement range of the latter is equivalent to the length of the kimono length of the body size, which is called the half arm span, the range from the spine to the middle finger of the horizontally extended arm, and the average is known to be about 850 mm. Although they are collectively referred to as the "arm reach range", depending on the subject, there are cases where only the narrow arm length is followed, and there are also cases where the range of moving the shoulder back and forth and the range of finger extension need to be considered. Therefore, it is preferable to determine in which coordinate system the subject perceives and moves, and perform corresponding designs and selections. In addition, it is found that for most subjects who are not used to progressive multifocals or have low adaptability, for the region where the entire distance farther than the specified distance can be seen, the optical property recognition and adaptability progress relatively quickly, but for the middle to near region where the visible range is limited both on the near side and the far side, the property recognition and adaptability development are significantly slower.

[0059] Specifically, for example, when the subject grasps an object at shoulder height for visual confirmation, the subject may not be able to comfortably wear the progressive multifocal lens in a state where the object will deviate from the clear visual field area if it is too close or too far, such as before and after grasping the object at a height of Y=-210 mm, which is equivalent to the subject's shoulder height. Currently, among the dissatisfactions listed by the subjects, there are many contents related to the difficulty of observation in the range from medium distance to close distance such as holding a slightly separated object in the hand for observation, and in actions where the posture becomes unstable (for example, in real life, it is difficult to observe when just holding a newspaper in the hand, etc.).

[0060] The inventors of the present invention have conducted in-depth research on the above-mentioned problems. As a result, there are subjects who are not troubled even when the clear visual field area is narrowed, and on the other hand, there are subjects who cannot comfortably wear progressive multifocal lenses even if the clear visual field area is not narrowed. Therefore, the following method has been found: the index of what degree of clear visual field area the subject needs (i.e., whether the size of the clear visual field area of ​​the basic design of the progressive multifocal lens is sufficient, whether it is better to expand in the left and right direction, or whether it is better to expand in the depth direction) is determined as the necessary degree of the size of the clear visual field area. For example, for subjects determined to need to expand the clear visual field area in the depth direction, the design of the progressive multifocal lens in which the clear visual field area is expanded in the depth direction is selected by reducing the lower addition power of the middle zone of the progressive band of the progressive multifocal lens. In addition, for example, the following method has been found: for subjects determined to need to expand the clear visual field area in the left and right directions, the design of the progressive multifocal lens in which the clear visual field area is expanded in the left and right directions is selected by smoothing the power distribution of the progressive multifocal lens in the left and right directions, reducing the third-order aberration in the left and right directions around the main meridian of the progressive multifocal lens, and expanding the clear visual field area in the left and right directions. It should be noted that there are multiple methods (parameters) for determining the necessary degree of the size of the clear visual field area, which will be described in detail later. According to this method, for a subject who needs to expand the clear visual field area in the depth direction or the left and right direction, a progressive multifocal lens that can be worn more comfortably can be determined with minimal risk (i.e., maintaining the basic design of the progressive multifocal lens as much as possible).

[0061] It should be noted that, in this specification, the basic design of a progressive multifocal lens refers to the design of a lens temporarily selected (or worn) by a subject, or the design of a lens temporarily recommended by a seller, etc., which becomes the basic design of the progressive multifocal lens for the subject.

[0062] In addition, the third-order aberrations (including trefoil aberration and coma) of the progressive multifocal lens are generated in the vicinity of the near vision area in a manner surrounding the principal meridian (in the direction toward the principal meridian). When it is more than 0.1 μm larger than the position where the absolute value of the third-order aberration in the left-right direction near the principal meridian is the smallest, the subject feels difficulty in performing near vision observation (for example, the direction of the Landolt ring target with a visual acuity of 0.7 is unclear, or the edge of the Landolt ring target with a visual acuity of 0.3 is not clear). Therefore, in this specification, the clear vision area can also be renamed as the area that is more than 0.1 μm larger than the position where the absolute value of the third-order aberration in the left-right direction near the principal meridian is the smallest.

[0063] In addition, in this specification, the "front-back direction" represents the direction of the radial vector R in the polar coordinate system, and the "depth direction" represents the Z direction in the XYZ orthogonal coordinate system (X is the left-right direction, and Y is the up-down direction).

[0064] [Details of the Embodiment of the Present Invention]

[0065] Next, an embodiment of the present invention will be described with reference to the accompanying drawings. It should be noted that the present invention is not limited to these examples, and as indicated by the claims, it is intended to include all changes within the meaning equivalent to the claims and the scope.

[0066] [The First Embodiment of the Present Invention]

[0067] (1) Method for Determining Eyeglass Lenses

[0068] First, the method for determining the progressive multifocal lens of the present embodiment will be described. Figure 3 is a flowchart showing an example of the method for determining the progressive multifocal lens of the present embodiment. As Figure 3 shown, the method for determining the progressive multifocal lens of the present embodiment, for example, has a clear vision area necessity determination step S101 and a design selection step S102. In the present embodiment, the following cases will be described: selecting a design that expands the clear vision area in the depth direction (depth expansion design), a design that expands the clear vision area in the left-right direction (left-right expansion design), or any design in the basic design, and determining a progressive multifocal lens more suitable for the subject.

[0069] (Clear Vision Area Necessity Determination Step S101)

[0070] The clear vision area necessity determination step S101 is a step for determining the necessity of the size of the clear vision area for a subject wearing a progressive multifocal lens (applied with the basic design). There are multiple methods (parameters) for determining the necessity of the size of the clear vision area. Hereinafter, an example will be described.

[0071] In the necessary degree determination step S101 of the clear vision area, for example, the necessary degree of the size of the clear vision area may also be determined based on the amount of third-order aberration in the left-right direction of the subject's eyes. As Figure 1B shown, when the eyes have third-order aberration (clover aberration), the clear vision area becomes narrower. Therefore, it can also be determined that a subject with a large amount of third-order aberration in the left-right direction of the eyes (absolute value of the left-right difference), for example, 0.1 μm or more, needs to expand the clear vision area in the left-right direction. In addition, when the subject has dry eyes or the like, the clover aberration of the eyes tends to increase. Therefore, for example, the measured value of the amount of third-order aberration can be adjusted in consideration of the subject's constitution. In addition, in order to measure the amount of third-order aberration of the subject's eyes, a known technique such as a wavefront sensor can be used.

[0072] However, the amount of third-order aberration of the eyes varies greatly depending on the subject's state and the surrounding environment. Therefore, it is preferable to also consider other parameters to determine the necessary degree of the size of the clear vision area. Hereinafter, other parameters for determining the necessary degree of the size of the clear vision area will be described.

[0073] In the necessary degree determination step S101 of the clear vision area, for example, the necessary degree of the size of the clear vision area may also be determined based on the change in the subject's eye movement when the subject repeatedly performs near-distance observation and far-distance observation. Figure 4 is a schematic diagram illustrating a task (hereinafter referred to as the eye movement task) for determining the necessary degree of the size of the clear vision area based on the change in the subject's eye movement. As Figure 4 shown, in the eye movement task, the subject 10 repeatedly (for example, alternately) visually confirms the near target 20 arranged at a near distance (for example, viewing distance dS = 40 cm) and the far target 30 arranged at a far distance (for example, viewing distance dL = 3 m). As the near target 20 and the far target 30, for example, a Landolt ring target image with a visual acuity of 0.7 displayed on a display terminal such as a tablet computer can be used.

[0074] In a state where the subject can clearly visually recognize a myopic target, when the subject's line of sight moves little (for example, equivalent to the situation of reading a book in real life), the size of the clear vision area is not much of a problem. However, for example, when the subject's line of sight moves significantly from a state of visually recognizing a hyperopic target to a myopic target (for example, equivalent to the situation of moving the line of sight from watching a TV to a book in front in real life), if the clear vision area is narrow, there are subjects who feel it difficult to focus on the myopic target. Specifically, subjects who are not used to using progressive multifocal lenses and use various locations on the lens (i.e., large deviations in head movement amount and convergence amount) when visually confirming the myopic target, subjects with a long time (response time) to clearly visually confirm the myopic target, etc. fit the description. Therefore, for a line-of-sight movement task, for example, it can also be determined that subjects with large deviations in head movement amount and convergence amount (especially large deviations when transitioning from far-distance observation to near-distance observation) need to expand the clear vision area in the left-right direction. Additionally, it can also be that for a line-of-sight movement task, for example, when transitioning from far-distance observation to near-distance observation, subjects determined to have a long (or large deviation) time (response time) to clearly visually confirm the myopic target need to expand the clear vision area in the left-right direction (or depth direction). Additionally, it can also be that for a line-of-sight movement task, for example, subjects determined to have a large difference in response time when transitioning from far-distance observation to near-distance observation and when transitioning from near-distance observation to far-distance observation need to expand the clear vision area in the depth direction. Furthermore, in the line-of-sight movement task, when measuring the subject's head movement amount and convergence amount, for example, the head and eyes of the subject can be photographed using a camera equipped in a display device that displays a myopic target, and the head movement amount and convergence amount can be measured through image recognition.

[0075] In addition, in the clear vision area necessity determination step S101, for example, the necessity of the size of the clear vision area can also be determined based on the sensitivity of the subject to aberration. In the design selection step S102 described later, when selecting a design of a progressive multifocal lens with an expanded clear vision area in the left-right direction or depth direction, the amount of astigmatism on the principal meridian increases compared to the basic design. That is, as the price for expanding the clear vision area in the left-right direction or depth direction, the quality (image quality) on the principal meridian decreases compared to the basic design. Therefore, for subjects who can sensitively feel the increase in the amount of astigmatism on the principal meridian, there are progressive multifocal lenses of the basic design that they can wear comfortably without expanding the clear vision area in the left-right direction or depth direction. On the other hand, for subjects who do not feel the increase in the amount of astigmatism on the principal meridian, there are progressive multifocal lenses with a left-right expansion design or a depth expansion design that they can wear comfortably.

[0076] An example of a method for measuring the sensitivity of a subject to aberration is described. To measure the sensitivity to aberration, for example, a plurality of blurred images (two blurred images in this embodiment) obtained by changing the amount of aberration (preferably, only this amount) to be added to a specified original image can be used. Figure 5 An example of the original image and a plurality of blurred images is shown. In Figure 5 the blurred image 40A obtained by adding a specified amount of aberration to the original image 40 and the blurred image 40B obtained by increasing the amount of aberration to be added as compared with the blurred image 40A are shown.

[0077] Figure 6 An example of a spot image formed by the aberration added to the blurred image is shown. In Figure 6 a spot image trailing in the lower left of the paper surface is shown. The blurred image to which the aberration forming such a spot image is added is faintly visible in the lower left. In other words, due to the added aberration, the spatial frequency characteristics in the lower left direction are significantly (characteristically) reduced. In this specification, the characteristic direction of the reduction in the spatial frequency characteristics caused by the added aberration is referred to as the direction of the aberration.

[0078] Preferably, the directions of the aberrations added to the plurality of blurred images (for example, the blurred image 40A and the blurred image 40B) are substantially the same. Thereby, it is easy for the subject to compare the appearances of the plurality of blurred images. It should be noted that in this specification, the so-called substantially the same direction of the aberration includes not only the case where the directions are exactly the same but also the case where there is a slight difference of ±15 degrees or less in the directions of the aberrations. In addition, the direction of the aberration means the direction of the component having the largest absolute value among all the coefficients of all the blurred images when the aberrations added to the blurred images simultaneously displayed are respectively expanded by Zernike polynomials.

[0079] It should be noted that when selecting the aberration to be added to the original image 40, for example, it can be arbitrarily selected from the aberrations generated by a standard progressive multifocal lens.

[0080] After preparing a plurality of blurred images, the sensitivity of the subject to aberration can be measured by simultaneously presenting the plurality of blurred images to the subject and comparing the appearances to obtain the subjective response of the subject. Specifically, for example, simultaneously presenting as Figure 5The blurred images 40A and 40B shown are visually inspected to select which one (or "unknown") of the blurred images 40A and 40B is clearer to view (hereinafter referred to as the aberration sensitivity task). Then, if the blurred image 40A with a small amount of added aberration (i.e., correct) is selected, it can be determined that the sensitivity to blur is high, and if the blurred image 40B with a large amount of added aberration (i.e., incorrect) is selected, it can be determined that the sensitivity to blur is low. Note that in this specification, presenting multiple blurred images simultaneously means presenting multiple blurred images in a state where multiple blurred images can exist within the subject's field of view for visual recognition, and the timing of the start or end of the presentation of each blurred image is not limited (for example, the timing of the start or end of the presentation can be offset between the blurred image 40A and the blurred image 40B).

[0081] However, in the case where the sensitivity to blur is determined by a single subjective response, for example, there may be cases where, even if the appearance difference (disparity) is not actually known, the blurred image with a small amount of aberration may be occasionally selected. Therefore, in the present embodiment, it is preferable to further prepare multiple similar blurred images similar to the multiple blurred images, present the multiple similar blurred images to the subject simultaneously, that is, present multiple similar blurred images in which the amount of added aberration (preferably, only the amount of this aberration) varies, compare the appearances, and obtain the subjective response of the subject multiple times to measure the stability of the subjective response. Note that the similar blurred images are, for example, images obtained by rotating the blurred image by an arbitrary angle or images obtained by magnifying or reducing the blurred image at an arbitrary magnification.

[0082] For a subject who has a high sensitivity to blur as determined by performing the above-described aberration sensitivity task, it can also be determined that there is no need to expand the clear vision area in the left-right direction and the depth direction (or, the possibility that the disadvantages of selecting the left-right expansion design or the depth expansion design exceed the advantages is high). In addition, for a subject who has a low sensitivity to blur as determined, it can also be determined that there is a need to expand the clear vision area in the left-right direction or the depth direction (or, the possibility that the advantages of selecting the left-right expansion design or the depth expansion design exceed the disadvantages is high).

[0083] In addition, when performing the aberration sensitivity task multiple times, for stable and correct subjects, it is determined that they have a high sensitivity to blur, and in the design selection process S102, a design with low aberration can be selected. In addition, for stable and incorrect subjects, it can be determined that they have a high sensitivity to blur but prefer a state with large aberration. In the design selection process S102, a design with the aberration preferred by the subject can be selected. In addition, for subjects with few unclear responses regarding correct or incorrect answers and unstable responses, it can be determined that they have a low sensitivity to blur but do not consciously recognize it as low sensitivity. In the design selection process S102, a balanced design of a low-aberration design and a design that improves other aspects (for example, a design that expands the clear vision area in the left-right direction) can be selected. In addition, for subjects with many unclear responses, it can be determined that they have a low sensitivity to blur, and a design that improves in trade-off with aberration (for example, a design that expands the clear vision area in the left-right direction) can be selected.

[0084] In addition, as a result of further investigation by the present inventor, it has been found that subjects do not judge the visibility of an image only by the simple magnitudes of blur (or the amount of aberration causing blur) and MTF (Modulation Transfer Function). Specific examples are as follows Figure 14A and Figure 14B shown. In Figure 14A and Figure 14B , a blurred image with blur (also called a convolution spot) corresponding to the spot shown on the left side of the figure is shown on the right side of the figure. Figure 14A The spot shown in Figure 14B has a smaller degree of spot expansion (i.e., a smaller sum of squares of the aberration amount) compared to the spot shown in Figure 14B , but has bimodality. On the other hand, the spot shown in Figure 14A and Figure 14B has a slightly larger degree of spot expansion but is unimodal. When the blurred images shown in Figure 14A are presented to a specific group and a question of comparing the appearance is posed, Figure 14BThe blurred images therein are relatively preferred. It is considered that this is because there are few subjects who like bimodal blur. Therefore, in the aberration sensitivity task, it is also possible to compare a blurred image obtained by convolving a spot with a slightly smaller aberration amount but having multimodality (including bimodality equivalent to astigmatism + spherical aberration of the eye, trimodality equivalent to trefoil aberration + spherical aberration of the eye, and quadrimodality equivalent to higher-order aberration of the eye) with a blurred image obtained by convolving a spot with a slightly larger aberration amount but having unimodality. A subject who prefers the blurred image obtained by convolving a unimodal point is determined to have a high sensitivity to blur. The so-called "high sensitivity to blur" here means that compared with being sensitive to the size of the aberration, it is more sensitive to whether the aberration correction is correctly performed.

[0085] In the aberration sensitivity task, it is also possible to score according to whether the subjective response of the subject is consistent with the average support in the group, and determine the sensitivity of the subject to blur based on this score. The average support can use the statistical value when a question is previously asked to a certain group, or can be estimated by machine learning or the like. Specifically, for example, in the question of comparing the blurred images on the left and right, when there are more subjects who prefer the blurred image on the left (high support rate), for a subject who answers that the image on the left is preferred, it is set as +1 point or the like as being consistent with the average support in the group, and for a subject who answers that the image on the right is preferred, it is set as -1 point or the like as being inconsistent with the average support in the group. Then, the total score and the subtotal of each question tendency are statistically calculated. For example, when it is above a specified score (threshold), it is determined that the sensitivity to blur is high, and when it is less than the specified score (threshold), it is determined that the sensitivity to blur is low. That is to say, it is also possible to determine the sensitivity of the subject to blur based on the size relationship between the score and a previously determined threshold. By scoring in this way, it is possible to determine not only considering the simple size of the aberration amount and MTF, but also considering the subject's preference for blur (the tendency and degree of blur that the subject can allow). In addition, since it is easy to understand the characteristics of the subject, it is easy to conduct consultations when determining spectacle lenses.

[0086] In addition, in the necessary degree determination process S101 of the clear vision area, for example, a task (hereinafter referred to as the object movement task) including actions such as holding an object (such as a smartphone) capable of acquiring position information equipped with a gyro sensor (angular velocity sensor), etc. in the hand, visually confirming, and moving it can also be performed. Based on the movement trend of the object during the object movement task, the necessary degree of the size of the clear vision area is determined. Specifically, it can be that while the subject clearly visually confirms the object, the object is moved while keeping the viewing distance constant or in a way that changes the viewing distance. For a subject who can move the object smoothly in the field, it is determined that there is no need to expand the clear vision area in the depth direction. On the other hand, for a subject who cannot move the object smoothly in the field, it can be determined that there is a need to expand the clear vision area in the depth direction.

[0087] In addition, it can also be analyzed whether the movement of the object is performed by rotation and radial movement centered on the arm and eyes, or by up-and-down and horizontal movements in the orthogonal coordinate system including forward and backward movements of the shoulders and face. If it is the former, it is determined that there is no need to expand the clear vision area in the depth direction, and if it is the latter, it is determined that there is a need.

[0088] In addition, in the determination of the smoothness of the movement of the object, it can also be determined based on the time, line of sight, ups and downs of the head and shoulders, etc. from the state of never holding the object to starting the object movement task, holding the object, and until the initial visual confirmation. In particular, for a subject whose forward and backward postures when reaching for and returning to the object move significantly, since the position of the line of sight movement on the lens is likely to change correspondingly, there is a tendency to be difficult to perform depth perception, and it is preferably determined that there is a need to expand the clear vision area in the depth direction.

[0089] It should be noted that sensors other than the gyro sensor can also be used to measure the movement trend. For example, an object embedded with an IC chip can also be moved and measured using electromagnetic waves from the outside. In addition, an object without a structure for measurement can be used, and optical ranging can be used for measurement from the outside.

[0090] In addition, in the necessary degree determination process S101 of the clear vision area, for example, the necessary degree of the size of the clear vision area can also be determined considering the lifestyle of the subject such as the subject's occupation and interests. For example, for a subject in a profession where there are many situations of performing a certain action in a state where the posture is fixed within the range of the arm movement distance or slightly away from this distance, it can also be determined that there is a need to expand the clear vision area in the depth direction.

[0091] In addition, it is also possible to combine the above various parameters to determine the necessity of the size of the clear vision area. For example, in the clear vision area necessity determination step S101, it is also possible to determine the necessity of the size of the clear vision area based on at least one (preferably two, more preferably three, and further preferably four) of the third-order aberration amount in the left-right direction of the subject's eyes, the change in the subject's eye movement when the subject repeatedly performs near-distance observation and far-distance observation, the sensitivity of the subject to aberration, and the change in the movement of the object when performing an object movement task.

[0092] Among the above methods (parameters) for determining the necessity of the size of the clear vision area, the method based on the third-order aberration amount in the left-right direction of the subject's eyes, the method based on the change in the subject's eye movement when the subject repeatedly performs near-distance observation and far-distance observation, and the method based on the sensitivity of the subject to aberration are suitable for determining whether it is necessary to expand the clear vision area in the left-right direction. In addition, the method based on the change in the subject's eye movement when the subject repeatedly performs near-distance observation and far-distance observation and the method based on the change in the movement of the object when performing an object movement task are suitable for determining whether it is necessary to expand the clear vision area in the depth direction. Therefore, in the clear vision area necessity determination step S101, for example, it is also possible to judge, based on the determination result of one method, the result of prior consultation with the subject, etc., whether the possibility that the subject needs to expand the clear vision area in the left-right direction or the depth direction is high, and determine whether to adopt other methods.

[0093] (Design selection step S102)

[0094] In the design selection step S102, for example, when it is determined in the clear vision area necessity determination step S101 that the subject needs to expand the clear vision area in the depth direction, select the design of a progressive multifocal lens in which the clear vision area is expanded in the depth direction by reducing the addition power of the intermediate zone of the progressive band of the progressive multifocal lens. Thereby, it is possible to determine a progressive multifocal lens that can be worn more comfortably for a subject who needs to expand the clear vision area in the depth direction. It should be noted that in the design selection step S102, for example, it is also possible to select a lens suitable for the subject's design from among a plurality of pre-prepared customized lenses.

[0095] A more specific description is given of the design of a progressive multifocal lens (depth expansion design) that expands the clear vision area in the depth direction towards the front. For an average-sized subject, the shoulder is at a position 210 mm below the eye level. When the shoulder is extended and the arm is stretched horizontally, the middle fingertip reaches 850 mm. Therefore, it is preferred that this position becomes the clear vision area. This assumes that when an average-sized subject picks up an object, the moment of eye contact with the object is within the range of the clear vision area. That is, in the depth expansion design, as shown by the area enclosed by the solid line in Figure 2 , it is preferred that the position of Y = -210 mm and Z = 850 mm becomes the clear vision area. In this state, when the clear vision area is defined in a rectangular coordinate system along the body axis or a polar coordinate system with the shoulder as the reference, in the depth direction or the front-back direction of this coordinate system, the clear vision area extends to the distance of stretching the arm, so the subject can more easily perceive their own clear vision area and can wear the progressive multifocal lens more comfortably. It should be noted that in this specification, expanding the clear vision area in the depth direction means expanding to the distance of stretching the arm (Z = 850 mm) or the vertical range that can be seen to infinity (especially expanding downward). That is, this means not expanding the physical quantity of the lens design, but expanding the length along the depth vector (eye reference or horizontal reference) of the subject.

[0096] In addition, it is preferred that when an average-sized subject stretches the arm horizontally forward, the fingertip of the little finger is at a position 740 mm, and this position also becomes the clear vision area. This assumes that when an average-sized subject picks up an object, it is within the range of the clear vision area until the object is firmly grasped and held.

[0097] The conditions for taking the position of Y = -210 mm and Z = 850 mm as the clear vision area are described. If the distance from the lens to the center of rotation of the eyeball is 27 mm, then the position on the lens corresponding to the viewing angle tanθ = -210 / 850 is 27 mm × tanθ = -6.67 mm, that is, the position -6.67 mm away from the fitting point. Therefore, the additional power at this position considering astigmatism (additional power - absolute value of astigmatism / 2) is less than the refractive power conversion value of the distance to the position of Y = -210 mm and Z = 850 mm, which is 1000 / √(210 2 +850 2 ) = 1.14 D.

[0098] Figure 7 is an example of the additional power curve of progressive multifocal lenses (additional power +2 D) showing the basic design and the depth expansion design. In Figure 7In this figure, the horizontal axis represents the vertical position where the fitting point of the lens is set to 0, and the vertical axis represents the add power considering astigmatism (add power - absolute value of astigmatism / 2). As Figure 7 shown, in the depth expansion design, compared with the basic design, the add power in the middle area of the progressive zone (for example, the periphery at Y = -6.67 mm) is reduced. Thereby, the add power considering astigmatism (add power - absolute value of astigmatism / 2) at the position of Y = -6.67 mm can be made less than 1.14 D, as Figure 2 shown, the position of Y = -210 mm and Z = 850 mm can be made into a clear vision area. In addition, in the case of a progressive multifocal lens with an add power less than +2 D, it is preferable to reduce the add power in the middle area of the progressive zone so that the add power considering astigmatism (add power - absolute value of astigmatism / 2) at the position of Y = -6.67 mm is 1.14×(add power / 2). Thereby, for example, Figure 2 shown, the boundary on the lower end side of the clear vision area is close to the lower end of the right shoulder, so that the range where infinity can be seen can be further expanded.

[0099] As described above, by reducing the add power in the middle area of the progressive zone of the progressive multifocal lens, there is an advantage of expanding the clear vision area in the depth direction. On the other hand, compared with the basic design, there is also a disadvantage that the amount of astigmatism on the principal meridian increases. Therefore, in the design selection process S102, instead of increasing the amount of astigmatism on the principal meridian of the progressive multifocal lens, a design of the progressive multifocal lens with an expanded clear vision area in the depth direction can also be selected.

[0100] In addition, as described above, by reducing the add power in the middle area of the progressive zone of the progressive multifocal lens, the lateral coma aberration in the vicinity of the principal meridian of the progressive multifocal lens can be slightly reduced, and the clear vision area can be expanded not only in the depth direction but also in the lateral direction. Therefore, in the design selection process S102, by reducing the add power in the middle area of the progressive zone of the progressive multifocal lens, a design of the progressive multifocal lens with an expanded clear vision area in the depth direction and the lateral direction can be selected. It should be noted that when it is determined that the subject needs to expand the clear vision area in the lateral direction more than in the depth direction, it is preferable to select a lateral expansion design with a greater effect of expanding the clear vision area in the lateral direction.

[0101] In the design selection process S102, for example, when it is determined in the clear vision area necessity determination process S101 that the subject needs to expand the clear vision area in the left and right directions, a design of a progressive multifocal lens can be selected in which the power distribution of the progressive multifocal lens is smoothed in the left and right directions to reduce the third-order aberration in the left and right directions around the principal meridians of the progressive multifocal lens, and the clear vision area is expanded in the left and right directions. Thus, it is possible to determine a progressive multifocal lens that can be worn more comfortably for a subject who needs to expand the clear vision area in the left and right directions.

[0102] A more specific description will be given of the design of a progressive multifocal lens in which the clear vision area is expanded in the left and right directions (left-right expansion design). Figure 8A is a left-right direction power distribution diagram of the near vision area of a progressive multifocal lens (for the left eye), Figure 8B is Figure 8A the gradient distribution diagram. In addition, the sum value of the coma aberration and the trefoil aberration in the 0-degree direction is in a proportional relationship with this gradient distribution. As Figure 8A shown, with respect to the basic design (dashed line), in the left-right expansion design (solid line), by applying a smoothing filter (such as a Gaussian filter) in the left and right directions, the power distribution around the principal meridian P is smoothed. It should be noted that when the power of the principal meridian is reduced due to smoothing, by shifting the reduction amount in the concave direction, the power of the principal meridian can be adjusted to be the same as (or at the same level as) the basic design. As Figure 8B shown, by smoothing the power distribution in the left and right directions, the third-order aberration distribution in the left and right directions also becomes gentle, so the clear vision area (for example, the area where the third-order aberration amount around the principal meridian P is within ±0.1 μm) expands in the left and right directions. By selecting such a left-right expansion design, for a subject who needs to expand the clear vision area in the left and right directions, it is possible to determine a progressive multifocal lens that can be worn more comfortably with a minimum risk (that is, maintaining the basic design of the progressive multifocal lens as much as possible).

[0103] In addition, as described above, it is explained that there is also an effect of expanding the clear vision area in the left and right directions in the depth expansion design. Figure 9A is a left-right direction power distribution diagram of the near vision area of a progressive multifocal lens (for the left eye), Figure 9B is Figure 9A the gradient distribution diagram. In addition, the sum value of the coma aberration and the trefoil aberration in the 0-degree direction is in a proportional relationship with this gradient distribution. As Figure 9AAs shown, relative to the basic design (dashed line), in the depth-expanded design (solid line), the diopter distribution around the principal meridian P is also smoothed. In addition, when the diopter of the principal meridian is reduced due to smoothing, by shifting the reduction amount in the direction of the recess, the diopter of the principal meridian can be adjusted to be the same as (or at the same level as) the basic design. As Figure 9B shown, in the depth-expanded design, the diopter distribution is also smoothed in the left-right direction, and the coma aberration distribution in the left-right direction also becomes gentle. Therefore, the clear vision area (for example, the area where the coma aberration amount around the principal meridian P is within ±0.1 μm) is enlarged in the left-right direction.

[0104] Preferably, the width of the smoothing filter for smoothing the diopter distribution of the progressive multifocal lens in the left-right direction is greater than the narrowest width among the widths between the peaks of the coma aberrations on both sides in the left-right direction located on the principal meridian in the progressive multifocal lens before smoothing. Thereby, the coma aberration can be effectively reduced.

[0105] As described above, by smoothing only the diopter distribution of the progressive multifocal lens in the left-right direction, it has the advantages of reducing the coma aberration in the left-right direction around the principal meridian of the progressive multifocal lens and enlarging the clear vision area in the left-right direction. On the other hand, compared with the basic design, there is also the disadvantage that the astigmatism amount on the principal meridian increases. Therefore, in the design selection step S102, it is also possible to select the design of the progressive multifocal lens with the clear vision area enlarged in the left-right direction instead of the increase in the astigmatism amount on the principal meridian of the progressive multifocal lens.

[0106] When it is determined that the subject needs to enlarge the clear vision area in the left-right direction, in the design selection step S102, it is preferable to select the design of the progressive multifocal lens that does not change the add-curve of the principal meridian and enlarges the clear vision area in the left-right direction only by smoothing the diopter distribution in the left-right direction. Thereby, the increase in the aberration in the up-down direction can be reduced, the basic design of the progressive multifocal lens can be maintained as much as possible, and the clear vision area can be enlarged in the left-right direction.

[0107] In addition, in the clear vision area necessity determination step S101, when it is determined that the subject does not need to enlarge the clear vision area in the left-right direction and the depth direction (or the possibility that the disadvantages of selecting the left-right expansion design and the depth expansion design exceed the advantages is high), it is also possible not to select the left-right expansion design and the depth expansion design, but to select the basic design of the progressive multifocal lens. Thereby, it is possible to provide a progressive multifocal lens with the quality (image quality) on the principal meridian optimized for subjects who do not need to enlarge the clear vision area in the left-right direction and the depth direction.

[0108] By applying the method described above to multiple subjects, a design of a progressive multifocal lens suitable for the needs of each subject can be provided.

[0109] <Other Embodiments of the Present Invention>

[0110] As described above, specific embodiments of the present invention have been described, but the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist thereof.

[0111] For example, in the above embodiment, a method for determining a progressive multifocal lens has been described, but the present invention can also be used as a method for determining the degree of necessity of the size of a clear vision area. In this case, it is also possible to perform only the clear vision area necessity determination step S101 and omit the design selection step S102.

[0112] In addition, for example, in the above embodiment, a case of selecting any one of the left-right expansion design, the depth expansion design, or the basic design has been described, but the left-right expansion design and the depth expansion design are not limited to one, and it is also possible to select from a plurality of variations (for example, the size of the clear vision area in the left-right direction is different).

[0113] In addition, for example, in the above embodiment, a design selection corresponding to the third-order aberration of the eyeball has been described, but in addition to this, it is also possible to perform design selection according to (or considering) the degree of fixation deviation and the degree of deviation between the line of sight and the visual axis of the eye. This is because the horizontal third-order aberration component is added or subtracted from the measured ocular aberration according to the degree of the above deviation. In addition, in addition to the degree of the above deviation, factors eccentric in the horizontal direction from the standard model in design or measurement also become factors for changing the third-order aberration amount, and thus are preferably used for the judgment of design selection.

[0114] Examples

[0115] Next, examples of the present invention will be described. These examples are an example of the present invention, and the present invention is not limited to these examples.

[0116] (Clear Vision Area Necessity Determination Step S101)

[0117] In this embodiment, the above-described line-of-sight movement task is performed, and the degree of necessity of the size of the clear vision area is determined based on the progress of the subject's line-of-sight movement. Specifically, as Figure 4As shown, a near target 20 (a Landolt ring chart image with a visual acuity of 0.7 displayed on a smartphone) is arranged at a position 30 degrees below the subject 10 and at a viewing distance dS = 40 cm, and a far target 30 (a Landolt ring chart image with a visual acuity of 0.7 displayed on a tablet terminal) is arranged in front of the subject 10 at a viewing distance dL = 3 m. Then, the near target 20 and the far target 30 are alternately displayed a total of 30 times, and the subject 10 is visually confirmed and asked to answer the opening direction of the Landolt ring chart image.

[0118] In this embodiment, when the deviation of the head movement amount and the convergence amount of the subject during the eye movement task is large, or when the response time is long (or the deviation is large), it is determined that the subject needs to expand the clear vision area in the left - right direction. In addition, although the deviation of the head movement amount and the convergence amount is small, when there is a large difference between the response time from far - distance observation to near - distance observation and the response time from near - distance observation to far - distance observation, it is determined that the subject needs to expand the clear vision area in the depth direction. Then, when neither of the above situations is met, it is determined that the subject does not need to expand the clear vision area in the left - right direction and the depth direction.

[0119] The above determination is made based on the correlation with the ability to observe clearly through the observable points on the lens. However, depending on the subject, there are cases where the head moves back and forth due to habits or customs regardless of whether progressive multifocal lenses are worn. It is also possible to ask in advance to deal with such situations and take them into account in the determination. In the case of a subject with a habit of moving the head back and forth, in order to mitigate the influence of the amount of distance movement and the shaking of the line of sight caused by head movement, there are also many cases where a depth - expansion design is preferred. It should be noted that since it is often impossible to determine the appropriate design only through simple head movement, it is preferred to make a judgment based on multiple information and multiple tasks.

[0120] (Design selection process S102)

[0121] Figure 10 It is a diagram showing the power distribution (Power), astigmatism distribution (As), and higher - order aberration distribution in the left - right direction (HOA, Higher Order Aberration) of the basic design of a progressive multifocal lens. In this embodiment, when it is determined that the subject does not need to expand the clear vision area in the left - right direction and the depth direction, this basic design is selected. In addition, Figure 11This is a diagram showing the power distribution (Power), astigmatism distribution (As), and the third-order aberration distribution in the left-right direction (HOA, Higher Order Aberration) of a design that smooths the power distribution of the progressive multifocal lens only in the left-right direction. In this embodiment, when it is determined that the subject needs to expand the clear vision area in the left-right direction, this design (left-right expansion design) is selected. Additionally, Figure 12 This is a diagram showing the power distribution (Power), astigmatism distribution (As), and the third-order aberration distribution in the left-right direction (HOA, Higher Order Aberration) of a design that reduces the addition power in the middle zone of the progressive band of the progressive multifocal lens. In this embodiment, when it is determined that the subject needs to expand the clear vision area in the depth direction, this design (depth expansion design) is selected. Additionally, Figures 10 to 12 The third-order aberration distribution shown represents the sum of the squares of the 0-degree component of coma aberration and the 0-degree component of trefoil aberration.

[0122] As Figure 10 and Figure 11 shown, it was confirmed that in the left-right expansion design, compared with the basic design, instead of a slight increase in the astigmatism amount on the principal meridian, the third-order aberration amount in the left-right direction around the principal meridian decreased. Additionally, as Figure 10 and Figure 12 shown, it was confirmed that in the depth expansion design, compared with the basic design, instead of a slight increase in the astigmatism amount on the principal meridian, the third-order aberration amount in the left-right direction around the principal meridian slightly decreased.

[0123] Figure 13A This is a diagram showing the clear vision area (the area in the direction of the Landolt ring target with at least a clear vision of 0.7, or the area where the edge of the Landolt ring target with a vision of 0.3 is clearly visible) when a subject wearing a progressive multifocal lens with the basic design observes at a near distance. The left side is a diagram of the state of the eye without aberration, and the right side is a diagram of the state of the eye with 0.1 μm of trefoil aberration in the right direction. Figure 13B This is a diagram showing the clear vision area when a subject wearing a progressive multifocal lens with the left-right expansion design observes at a near distance. The left side is a diagram of the state of the eye without aberration, and the right side is a diagram of the state of the eye with 0.1 μm of trefoil aberration in the right direction. Figure 13C This is a diagram showing the clear vision area when a subject wearing a progressive multifocal lens with the depth expansion design observes at a near distance. The left side is a diagram of the state of the eye without aberration, and the right side is a diagram of the state of the eye with 0.1 μm of trefoil aberration in the right direction. In Figures 13A to 13CIn this case, with the left eye of the subject as the reference, the vertical axis represents the front-back direction, and the horizontal axis represents the left-right direction. Additionally, the area surrounded by the dashed line is the clear visual field area of the left eye, the area surrounded by the solid line is the clear visual field area of the right eye, and the overlapping range of the two becomes the clear visual field area of both eyes.

[0124] As Figure 13A and Figure 13B shown, it was confirmed that in the left-right expansion design, compared with the basic design, the clear visual field area was enlarged in the left-right direction. The same was confirmed when the subject's eyes had trefoil aberration. Additionally, it was confirmed that when the subject's eyes had trefoil aberration, the magnification effect of the clear visual field area based on the left-right expansion design became more significant. Additionally, as Figure 13A and Figure 13C shown, it was confirmed that in the depth expansion design, compared with the basic design, the clear visual field area was also enlarged in the left-right direction.

[0125] As described in the first embodiment, in order for the position of the middle fingertip when the subject extends the shoulder and horizontally extends the arm ( Figure 2 the position where Y = -210 mm and Z = 850 mm in

[0126] ) to be in the clear visual field area, it is only necessary that the addition power considering astigmatism (addition power - absolute value of astigmatism / 2) at the position on the lens -6.67 mm from the fitting point is less than 1.14 D. In the basic design of this embodiment, the addition power considering astigmatism is 1.211 D, which does not meet the above condition. On the other hand, in the depth expansion design of this embodiment, the addition power considering astigmatism is 1.135 D, and it was confirmed that the above condition is met. That is, in the depth expansion design, it was confirmed that the position where Y = -210 mm and Z = 850 mm becomes the clear visual field area.

[0127] In addition, in this specification, the clear vision area is estimated based on the add power and the astigmatism amount. However, the following method can also be used: multiplying the Optical Transfer Function (OTF) or the Modulation Transfer Function (MTF) by the Contrast Sensitivity Function (CSF) of the visual system as a weight function, and integrating the result within a specific bandwidth of spatial frequencies. In the above calculation, the lens can be considered alone, or physiological factors such as the eye aberration, the eye axis, and the visual axis of the eye can be considered. In addition, the degree of blur perception can also be reflected in the threshold value.

[0128] Description of Reference Numerals

[0129] 10: Subject

[0130] 20: Near target

[0131] 30: Far target

[0132] 40: Original image

[0133] 40A, 40B: Blurred images

[0134] S101: Process for determining the necessity of the clear vision area

[0135] S102: Design selection process

Claims

1. A method for determining a progressive multifocal lens, characterized in that: have: A determination step for determining the necessary size of the clear visual field area for subjects wearing progressive multifocal lenses; The design selection process is to select a progressive multifocal lens design that expands the clear visual field area in the depth direction by reducing the lower addition power of the middle zone of the progressive zone of the progressive multifocal lens when it is determined that the subject needs to expand the clear visual field area in the depth direction.

2. The method for determining a progressive addition lens according to claim 1, characterized in that: In the determination step, the necessary degree of the size of the clear visual field area is determined based on the transition of the line of sight of the subject when the subject is repeatedly subjected to close-up observation and long-distance observation.

3. The method for determining a progressive addition lens according to claim 1, characterized in that: In the determination step, the necessary degree of the size of the clear visual field area is determined based on the subject's sensitivity to aberrations.

4. The method for determining a progressive addition lens according to claim 1, characterized in that: In the determination step, the necessary degree of the size of the clear visual field area is determined based on the movement transition of the object when performing a task, wherein the task includes the subject holding, visually confirming, and moving an object capable of acquiring position information.

5. The method for determining a progressive addition lens according to claim 1, characterized in that: In the design selection process, a design that reduces the lower added light intensity is selected so that when the subject's eyes are set as the origin, the up and down direction is set as the Y axis, and the depth direction is set as the Z axis, the position of Y=-210mm and Z=850mm becomes a clear field of vision.

6. The method for determining a progressive addition lens according to claim 1, characterized in that: In the design selection step, instead of increasing the astigmatism amount of the progressive addition lens on the principal meridian, a design of the progressive addition lens that expands the clear visual field area in the depth direction is selected.

7. The method for determining a progressive addition lens according to claim 1, characterized in that: In the design selection step, a design of a progressive addition lens is selected in which the clear visual field area is expanded in the depth direction and the left-right direction by reducing the lower addition power.

8. The method for determining a progressive addition lens according to claim 1, characterized in that: If it is determined in the determination step that the subject needs to expand the clear visual field area in the left-right direction, in the design selection step, a design of a progressive addition lens is selected that expands the clear visual field area in the left-right direction by smoothing the power distribution of the progressive addition lens in the left-right direction and reducing the third-order aberration in the left-right direction around the main meridian of the progressive addition lens.

9. The method for determining a progressive addition lens according to claim 8, characterized in that: In the determination step, the necessary degree of the size of the clear visual field area is determined based on the amount of third-order aberration in the left-right direction of the eye of the subject.

10. The method for determining a progressive addition lens according to claim 8, characterized in that: The width of the smoothing filter for smoothing the power distribution in the left-right direction is larger than the narrowest width among the widths between the peaks of the third-order aberration located on both sides of the principal meridian in the left-right direction in the progressive addition lens before smoothing.

11. The method for determining a progressive addition lens according to claim 8, characterized in that: In the design selection step, instead of increasing the amount of astigmatism of the progressive addition lens on the principal meridian, a design of a progressive addition lens that expands a clear visual field area in the left and right directions is selected.

12. The method for determining a progressive addition lens according to claim 8, characterized in that: In the design selection process, when it is determined that the subject needs to expand the clear visual field area in the left and right directions, a progressive multifocal lens design that does not change the lower addition curve of the main meridian but expands the clear visual field area in the left and right directions is selected.

13. The method for determining a progressive addition lens according to any one of claims 1 to 12, characterized in that: If it is determined in the determination step that the subject does not need to expand the clear visual field area, a basic design of a progressive addition lens is selected in the design selection step.

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