Method for evaluating ophthalmic lens and device for evaluating ophthalmic lens

Abstract

This method for evaluating an ophthalmic lens is a method for, in the ophthalmic lens provided with a functional region having a base region in which prescribed refractive power of a wearer is achieved, and a plurality of defocus regions having refractive power different from the prescribed refractive power, measuring the center of the defocus region, wherein, when a procedure for measuring a local power average in the range of a diameter Φ centered on a position P in plan view while changing the value of the diameter Φ is repeatedly performed while the position P is being changed, the position P when the local power average changes most abruptly with respect to the change of the diameter Φ between a value corresponding to the refractive power of the defocus and a value corresponding to the refractive power of the base region is set as the center of the defocus region.

Description

Method for evaluating ophthalmic lens and apparatus for evaluating ophthalmic lens , ,

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[0006] , ,

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[0001] The present invention relates to a method for evaluating an ophthalmic lens and an apparatus for evaluating an ophthalmic lens.

[0002] For evaluating optical elements such as lenses, there are surface measurement and transmission measurement. The former is useful for understanding the quality of each front and rear surface, and the latter is useful for managing the quality as a lens. A typical example of transmission measurement is wavefront measurement using an interferometer or the like. Wavefront measurement can directly acquire wavefront information including aberrations up to higher orders, but can only be applied to lenses that are nearly aberration-free. As a method applicable to lenses with large aberrations, there is diopter distribution measurement in which a large number of minute light beams are passed through to examine the wavefront curvature of the minute light beams. The drawback of diopter distribution measurement is that wavefront information can only be acquired as a local curvature distribution.

[0003] In the case of ophthalmic lenses such as spectacle lenses and contact lenses, when viewed as a whole lens, it has a structure in which so-called aberrations such as astigmatism correction and addition are intentionally added, and when viewed in terms of a light beam unit with a diameter of about 4 mm passing through the pupil, the aberrations of interest are directly related to the wavefront curvature of spherical diopter error and coma aberration. Therefore, diopter distribution measurement is often used. For example, in the apparatus described in Patent Document 1, the local diopter per minute light beam with a diameter of 0.5 mm is measured.

[0004] Also, the diopter distribution and the curvature distribution of the wavefront are used to confirm the magnitude of the diopter and curvature at the point of interest and the variation of the diopter and curvature within a certain range. For example, Patent Document 2 discloses a method for quantifying the amount of variation.

[0005] Japanese Unexamined Patent Application Publication No. 2004-205438, Japanese Unexamined Patent Application Publication No. 2017-227572

[0006] In recent years, spectacle lenses (also referred to as myopia progression-inhibiting lenses, etc.) that exhibit an effect of suppressing myopia progression or reducing hyperopia have a functional region in which a region (also referred to as a base region) with a prescribed diopter and a region (also referred to as a defocus region) that gives a high contrast at a point different from the imaging position according to the prescribed diopter are discretely distributed within the range of a light beam with a diameter of about 4 mm passing through the pupil, and it is a system including ultra-high-order aberrations.

[0007] In evaluating lenses that suppress myopia progression, it is crucial to accurately measure the center, diameter, and pitch of the defocused area. However, there is a problem in that the boundaries of the defocused area cannot be properly identified from the local power distribution. This problem will be discussed in detail later.

[0008] One embodiment of the present invention aims to provide a technology that can accurately measure the center of a defocused region from local frequencies.

[0009] A first aspect of the present invention is an ophthalmic lens having a functional region having a base region that realizes the wearer's prescribed refractive power and a plurality of defocus regions having refractive powers different from the prescribed refractive power, wherein the method for measuring the center of the defocus region is defined as the center of the defocus region when the position P is changed most abruptly with respect to the change in diameter Φ, by repeatedly performing the procedure of measuring the local power average in a range of diameter Φ centered on position P in a planar view, while changing the value of the diameter Φ, and the local power average changes most abruptly with respect to the change in diameter Φ from a value corresponding to the refractive power of the defocus region to a value corresponding to the refractive power of the base region.

[0010] A second aspect of the present invention is an evaluation method for an ophthalmic lens according to the first aspect, wherein the minute light beam diameter φ when measuring the local power average is set to 5% or more of the shortest adjacent distance in the defocus region.

[0011] A third aspect of the present invention is an evaluation method for an ophthalmic lens as described in the first aspect, wherein the local power of the defocus region and its vicinity is measured, the centroid G of the region where the absolute value of the local power is greater than or equal to a certain value is found, and the vicinity of the centroid G is defined as the range in which the position P is changed.

[0012] A fourth aspect of the present invention is an evaluation method for an ophthalmic lens as described in the first aspect, comprising measuring the local power in the defocus region and its vicinity, finding the centroid G of the region where the absolute value of the local power is greater than or equal to a certain value, finding a point A among the points near the centroid G where the bias of the local power within a predetermined range is minimized, and defining the vicinity of point A as the range in which the position P is changed.

[0013] A fifth aspect of the present invention is an ophthalmic lens having a functional region having a base region that realizes the wearer's prescribed refractive power and a plurality of defocus regions having refractive powers different from the prescribed refractive power, and an ophthalmic lens evaluation device having a device for measuring the center of the defocus region, comprising: a measurement unit that repeatedly performs a procedure of measuring the local power average in a range of diameter Φ centered on position P in a planar view, while changing the value of the diameter Φ, while changing position P; and a calculation unit that sets the position P at which the local power average changes most sharply with respect to the change in diameter Φ, from a value corresponding to the refractive power of the defocus region to a value corresponding to the refractive power of the base region, as the center of the defocus region.

[0014] According to one embodiment of the present invention, the center of the defocused region can be accurately measured from the local frequency.

[0015] Figure 1 is an example of the shape diagram (top of page) and local power distribution diagram (bottom of page) around the defocused area in a myopia progression suppression lens. Figure 2 is another example of the shape diagram (top of page) and local power distribution diagram (bottom of page) around the defocused area in a myopia progression suppression lens. Figure 3 is another example of the shape diagram (top of page) and local power distribution diagram (bottom of page) around the defocused area in a myopia progression suppression lens. Figure 4 is a schematic plan view of the object-side surface of the spectacle lens to be evaluated in the first embodiment of the present invention. Figure 5 is a graph showing the relationship between the local power average and the diameter Φ of the circular range when the center of the circular range for measuring the local power average coincides with the center of the defocused area. Figure 6 is a graph showing the relationship between the local power average and the diameter Φ of the circular range when the center of the circular range and the center of the defocused area 14 are misaligned. Figure 7 is the shape diagram (top of page) and local power distribution diagram (bottom of page) around the defocused area in Sample 1 of the embodiment. Figure 8 shows the shape diagram (top of the page) and the local frequency distribution diagram (bottom of the page) of the defocus region in Sample 2 of the embodiment.

[0016] <Inventor's Findings> First, we will explain the problem of not being able to properly distinguish the boundary of the defocus region from the local power distribution. In this specification, local power refers to the average spherical power within the range of a minute luminous beam. Figure 1 is an example of the shape diagram (top of the page) and local power distribution diagram (bottom of the page) of the area around the defocus region in a myopia progression suppression lens. For details on the myopia progression suppression lens, see, for example, U.S. Patent Publication No. 2017 / 0131567. Here, we show an example in which a convex region (defocus region) with a defocus power of 3.5D and a diameter of 1 mm is provided on a surface with a prescription power of 0D. The graph in the upper right of Figure 1 is a cross-sectional view of the sag amount in the x direction (lateral direction) passing through the center, and the graph in the lower right is a cross-sectional view of the local power in the x direction (lateral direction) passing through the center. In this specification, defocus power refers to the difference (average spherical power) between the refractive power of the defocus region (also called segment power) and the refractive power of the part other than the defocus region (e.g., the base region).

[0017] As shown in Figure 1, the local power is measured as negative around the boundary of the defocused area. This is because the boundary of the defocused area is considered to be concave (V-shaped) from a microscopic perspective. Therefore, the area within the defocused area that is measured to have the original power of 3.5D is considered to have a diameter of only about 0.7 mm. Consequently, it is not possible to calculate the center or diameter of the defocused area by finding the boundary and approximating it as a circle. Figure 2 shows another example of the shape diagram (top of the page) and local power distribution diagram (bottom of the page) around the defocused area in a myopia progression suppression lens. Conventionally, methods such as finding an area where the power value is above a certain value and using its centroid as the center are often employed, but if the defocused area is subjected to a grinding surface process or if the measurement noise is large, the centroid may be shifted as shown in Figure 2.

[0018] Therefore, one possible method is to consider the location where the local frequency takes an extreme value (the location indicated by the arrow in the lower right of Figure 1) as the (virtual) boundary of the defocused region, and then estimate the center and diameter of the defocused region by performing a circular approximation on it. Hereafter, in this specification, the method of estimating the center and diameter of the defocused region from the local frequency extreme values ​​as described above will be called the "extreme value method".

[0019] However, the extreme value method has a significant drawback. Figure 3 shows another example of the shape diagram (top of the page) and local power distribution diagram (bottom of the page) around the defocus area in a myopia progression control lens. As shown in Figure 3, when multiple defocus areas are located close together, depending on the pitch of the defocus areas, the extreme value may be located midway between two defocus areas (the position indicated by the arrow in the lower right of Figure 3). In such cases, the estimated center of the defocus area may be shifted, potentially preventing accurate evaluation.

[0020] The inventor diligently researched the problems described above. He then discovered a new algorithm that takes into account the continuity with the center of the defocus region by using the integration of local frequencies. First, we will explain the case where the small beam diameter φ used when measuring local frequencies is sufficiently small, and the local frequency distribution is given as a continuous function.

[0021] Let w(x,y) be the unknown wavefront at coordinate (x,y) on the lens. Assume that the coordinate (x,y) is a continuous value, and that the local frequency s(x,y) can be expressed as the second derivative of the wavefront, as shown in the following equation.

[0022]

[0023] Here, the local frequency mean s (overline) in a circular range of diameter Φ and radius u can be expressed by the following formula.

[0024]

[0025] According to Green's theorem, the surface integral of the second derivative of x above can be replaced with a line integral. The same applies to the second derivative of y. Therefore, the local frequency mean s (overline) can be expressed by the following formula.

[0026]

[0027] From the integration range of the above formula, it can be seen that the local mean power s (overline) is determined solely by the gradient along the circumference. In other words, for a lens with a defocus region on a surface of prescription power (base power) 0D, if the entire circumference is the base region, the local mean power is zero, and if the entire circumference is the defocus region, the local mean power is equal to the segment power. Therefore, if the circumference is the boundary of the defocus region, the local mean power will be the intermediate value between the refractive power of the defocus region (segment power) and the refractive power of the base region (base power).

[0028] If the boundary of the defocused region is known, the center and diameter of the defocused region can be estimated. Hereafter, in this specification, the method of estimating the center and diameter of the defocused region from the local frequency mean will be called the "mean circle range method".

[0029] [Details of Embodiments of the Invention] Next, one embodiment of the present invention will be described below with reference to the drawings. However, the present invention is not limited to these examples and is intended to include all modifications within the meaning and scope equivalent to the claims as shown in the claims.

[0030] The spectacle lenses described herein have an object-facing surface and an eye-facing surface. The "object-facing surface" is the surface that faces the object when the spectacle lenses are worn by the wearer, and the "eye-facing surface" is the opposite surface, that is, the surface that faces the eye when the spectacle lenses are worn by the wearer. This relationship also applies to the lens substrate that forms the basis of the spectacle lenses. In other words, the lens substrate also has an object-facing surface and an eye-facing surface.

[0031] In this specification, the eye point is, for example, the position through which the line of sight passes when the wearer is looking straight ahead while wearing eyeglasses, and this example will be given hereafter. The eye point may also be the position through which the line of sight passes when the wearer views an object close to the wearer (so to speak, when viewing at close range), i.e., the near-seeing eye point. In one embodiment of the present invention, an example is given in which the geometric center of the eyeglass lens before it is fitted into the frame coincides with the eye point, coincides with the prism reference point, and coincides with the lens center. The position of the eye point can be determined by referring to a remark chart or centration chart issued by the lens manufacturer.

[0032] In this specification, the defocus power may be any of the following, or equivalent: (1) The difference in transmitted refractive power between the base region and the defocus region under lens mounting or measurement system conditions. (2) The value obtained by multiplying the difference in curvature between the base region and the defocus region by the influence of refractive power and the influence of the angle of incidence. (3) An alternative value using the height of the defocus region relative to the base region (especially the boundary between the defocus region and the base region). (4) The deviation of the point where the optical indicators (MTF, spot intensity, etc.) are best for the light beam passing through the base region and the light beam passing through the defocus region, respectively. Furthermore, the defocus power is not limited to the mean spherical power, but may also be treated as the power in a specific direction or the power in the direction of maximum or minimum.

[0033] <First Embodiment of the Invention> (1) Eyeglass Lens First, the eyeglass lens to be evaluated in this embodiment will be briefly described. Figure 4 is a schematic plan view of the object-side surface of the eyeglass lens 10 to be evaluated in this embodiment. As shown in Figure 4, the eyeglass lens 10 is a myopia progression suppression lens that has a myopia progression suppression effect, and comprises a central clear region 11, a functional region 12, and a peripheral clear region 15.

[0034] The central clear region 11 is the region that realizes the wearer's prescribed refractive power and includes the eye point of the spectacle lens 10. In this embodiment, the case in which the center of the central clear region 11 coincides with the eye point of the spectacle lens 10 is illustrated. The central clear region 11 is, for example, a transparent portion having a smooth surface shape, and is the region that causes the light beam incident from the object-side surface to exit from the eye-side surface, enter the wearer's pupil, and converge onto the retina.

[0035] The central clear area 11 allows for the realization of the prescribed power (spherical power, astigmatism power, astigmatism axis, etc.). This spherical power may be the power to be corrected when looking straight ahead (distance from infinity to about 1 m) (distance vision power), or it may be the power to be corrected when looking at intermediate objects (distance from about 1 m to 40 cm) or near objects (distance from about 40 cm to 10 cm).

[0036] Furthermore, the central clear area 11 does not have any configurations (for example, convex or concave areas) intended to produce a myopia progression suppression effect or a hyperopia reduction effect (hereinafter also referred to as myopia progression suppression effect, etc.).

[0037] The central clear region 11 of this embodiment (and the base region 13 and peripheral clear region 15 within the functional region 12, which will be described later) functions as a so-called single-focus lens. Its surface shape is not particularly limited, but in this embodiment, the case in which the central clear region 11 is spherical is given as an example.

[0038] The functional region 12 is an annular region that surrounds the central clear region 11 and has a portion with a refractive power different from the wearer's prescribed refractive power. In this embodiment, the functional region 12 has multiple defocus regions 14 (also called convex regions) arranged in an island-like manner (i.e., spaced apart from each other) as portions with a refractive power different from the wearer's prescribed refractive power. The multiple defocus regions 14 are, for example, independently and discretely arranged such that the center of each defocus region 14 is the vertex of an equilateral triangle. In the functional region 12, the portion other than the defocus regions 14 is a base region 13 that performs the same function as the central clear region 11. The functional region 12 is, for example, a region that causes a light beam incident from the object-side surface to exit from the eye-side surface, while preventing at least a portion of the light beam incident in the wearer's pupil from converging on the retina. As a result, the spectacle lens 10 of this embodiment exhibits a myopia progression suppression effect. In this specification, "planar view" refers to the view from the normal of the eye point on the outer surface (object-side surface or eyeball-side surface) of the spectacle lens 10, unless otherwise specified. The present invention will also be effective when the configuration is applied to a planar view from an arbitrary point on the lens, such as the normal of the point to be evaluated, instead of a planar view from the normal of the eye point. Furthermore, the myopia progression suppression effect or hyperopia progression suppression effect is achieved by the light-gathering effect of the defocus area 14 in the functional area 12 toward the outside of the retina and / or the contrast reduction effect on the retina.

[0039] Multiple defocus regions 14 may be formed on at least one of the object-side surface or the eye-side surface of the spectacle lens 10. Alternatively, they may be formed embedded between the object-side surface and the eye-side surface (inside the lens). In this embodiment, an example is given in which multiple defocus regions 14 are provided only on the object-side surface of the spectacle lens 10. The surface shape of the defocus region 14 is not particularly limited, but in this embodiment, a spherical shape (circular shape in plan view) will be described. It is preferable that the multiple defocus regions 14 within the functional region 12 satisfy either or both of the following (1) and (2): (1) In order for the lens as a whole to exert a sufficient myopia progression suppression effect, they collectively occupy 20% or more of the area of ​​the functional region 12. (2) In order for the light-gathering effect of each defocus region 14 to be fully exerted, the centers (or vertices) of each defocus region 14 are separated by 0.2 mm or more. In particular, if the defocus region 14 is spherical, it is preferable that either or both of the following (i) and (ii) are satisfied. (i) The number of defocus areas 14 is 18 or more. (ii) The number of defocus areas 14 is 5000 or less. Furthermore, if the defocus areas 14 are arranged in a concentric circle pattern with respect to a point on the lens, it is preferable that either or both of the following conditions (iii) and (iv) are met: (iii) The number of defocus areas 14 is 2 or more rings. (iv) The number of defocus areas 14 is 50 or less rings.

[0040] The peripheral clear area 15 is an annular region that provides the wearer's prescribed refractive power and surrounds the functional area 12. In this embodiment, the peripheral clear area 15 performs the same function as the central clear area 11. Furthermore, since the peripheral clear area 15 is provided along the outer circumference of the spectacle lens 10 so as to surround the functional area 12, peripheral vision is easily ensured.

[0041] Various commonly used lens substrates can be used as the lens substrate constituting the eyeglass lens 10. The lens substrate may be, for example, a plastic lens substrate or a glass lens substrate. The glass lens substrate may be, for example, a lens substrate made of inorganic glass. As a lens substrate, a plastic lens substrate is preferred from the viewpoint of being lightweight and less prone to breakage. Examples of plastic lens substrates include styrene resins such as (meth)acrylic resin, polycarbonate resin, allyl resin, allyl carbonate resin such as diethylene glycol bisallyl carbonate resin (CR-39), vinyl resin, polyester resin, polyether resin, urethane resin obtained by the reaction of an isocyanate compound with a hydroxyl compound such as diethylene glycol, thiourethane resin obtained by the reaction of an isocyanate compound with a polythiol compound, and cured products (generally called transparent resins) obtained by curing a curable composition containing a (thio)epoxy compound having one or more disulfide bonds in the molecule. The curable composition may also be called a polymerizable composition. As the lens substrate, an undyed one (colorless lens) or a dyed one (dyed lens) may be used. The thickness of the lens substrate is not particularly limited, but for example, the thickness (center thickness) may be about 1 to 30 mm. The refractive index of the lens substrate may be, for example, about 1.60 to 1.75. However, the refractive index of the lens substrate is not limited to this range, and may be within this range or outside of it. In this specification, refractive index refers to the refractive index for light with a wavelength of 500 nm.

[0042] (2) Evaluation method for ophthalmic lenses Next, the evaluation method for ophthalmic lenses of this embodiment will be described. In this embodiment, the case in which the center of the defocus region 14 of the spectacle lens 10 is determined by the average circle range method described above will be described. Accurately determining the center of the defocus region 14 is important when evaluating lenses that suppress myopia progression, etc.

[0043] FIG. 5 is a graph showing the relationship between the local diopter average and the diameter Φ of the circular range when the center of the circular range for measuring the local diopter average coincides with the center of the defocus region 14. As shown in FIG. 5, the local diopter average changes steeply around the value of the diameter Φ corresponding to the diameter (1.0 mm) of the defocus region 14. In this case, the value of the diameter Φ when the local diopter average takes the intermediate value (1.75 D, the dotted line in the graph) between the segment diopter and the base diopter can be estimated as the diameter of the defocus region 14.

[0044] However, when the center of the circular range does not coincide with the center of the defocus region 14, an intermediate value between the segment diopter and the base diopter can be obtained even for a circular range diameter that is independent of the diameter of the defocus region 14. FIG. 6 is a graph showing the relationship between the local diopter average and the diameter Φ of the circular range when the center of the circular range is shifted from the center of the defocus region 14. As shown in FIG. 6, when the center of the circular range is shifted from the center of the defocus region 14, the range of values that are neither the segment diopter nor the base diopter becomes wider compared to FIG. 5.

[0045] Therefore, when the procedure of measuring the local diopter average in the range of the diameter Φ centered on the position P by changing the value of the diameter Φ is repeated by changing the position P, the position P at which the local diopter average changes most steeply with respect to the change in the diameter Φ from the value corresponding to the refractive power (segment diopter) of the defocus region 14 to the value corresponding to the refractive power (base diopter) of the base region 13 can be said to be the center of the defocus region 14. Thereby, it becomes possible to accurately determine the center of the defocus region 14.

[0046] When repeatedly measuring by changing the position P as described above, the measurement amount (computation amount) may become extremely large. Therefore, it is preferable to determine the center according to the following procedure. (1) Search for the centroid G of an area where the absolute value of the local frequency is a certain value or more (for example, 90% or more of the absolute value of the segment frequency). When the segment frequency is unknown, the maximum value of the absolute value of the local frequency (excluding obvious outliers) may be used as the provisional segment frequency. (2) Among the points in the vicinity of the centroid G (for example, within 0.1 mm), when the diameter Φ of the circular range changes, the point where the average local frequency changes most steeply is set as the center of the defocus area 14. This makes it possible to accurately determine the center of the defocus area 14 while reducing the measurement amount (computation amount).

[0047] Also, it is more preferable to determine the center according to the following procedure. (1) Search for the centroid G of an area where the absolute value of the local frequency is a certain value or more (for example, 90% or more of the absolute value of the segment frequency). When the segment frequency is unknown, the maximum value of the absolute value of the local frequency (excluding obvious outliers) may be used as the provisional segment frequency. (2) Search for a point A where the bias of the local frequency in the range of the diameter of the provisional defocus area 14 is minimized among the points in the vicinity of the centroid G (for example, within 0.1 mm). The diameter of the provisional defocus area 14 may be, for example, the minimum circumscribed circle diameter that can enclose the points where the local frequency is a constant value. (3) Among the points in the vicinity of the point A (for example, within 0.1 mm), when the diameter Φ of the circular range changes, the point where the average local frequency changes most steeply is set as the center of the defocus area 14. This makes it possible to more accurately determine the center of the defocus area 14 while reducing the measurement amount (computation amount).

[0048] Furthermore, the mean circle range method of this embodiment makes it possible to accurately determine the center of the defocus region 14 even when the minute light beam diameter φ when measuring the local frequency mean is not sufficiently small. Specifically, it is possible to accurately determine the center of the defocus region 14 even when the minute light beam diameter φ is 5% or more of the shortest adjacent distance between defocus regions 14 (the distance between the boundaries of adjacent defocus regions 14). If the shortest adjacent distance between defocus regions 14 is unknown, 5% or more of the shortest adjacent distance between defocus regions 14 may be replaced with 5% or more of the provisional diameter of the defocus region 14 as described above, or with 0.1 mm or more.

[0049] (3) Apparatus for Evaluating Ophthalmic Lenses The present invention is also applicable as an apparatus for evaluating ophthalmic lenses. The apparatus for evaluating ophthalmic lenses of this embodiment is, for example, an apparatus for measuring the center of a defocused region in an ophthalmic lens having a base region that realizes the wearer's prescribed refractive power and a functional region having a plurality of defocused regions having refractive powers different from the prescribed refractive power, and comprises a measurement unit that repeatedly performs a procedure of measuring the local power average in a range of diameter Φ centered on position P in a planar view, while changing the value of the diameter Φ, while changing position P, and a calculation unit that defines the center of the defocused region as the position P at which the local power average changes most sharply with respect to the change in diameter Φ, from a value corresponding to the refractive power of the defocused region to a value corresponding to the refractive power of the base region. A known power distribution measuring device can be used as the measurement unit. The method for determining the center of the defocused region, the local power average, the diameter of the defocused region, etc., is as described in (2) Apparatus for Evaluating Ophthalmic Lenses.

[0050] <Other Embodiments of the Invention> Although embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above, and can be modified in various ways without departing from the spirit of the invention.

[0051] For example, although the above-described embodiment described the case in which eyeglass lenses were to be evaluated, the present invention is also applicable to ophthalmic lenses such as contact lenses and IOLs (intraocular lenses).

[0052] Next, embodiments of the present invention will be described. These embodiments are examples of the present invention, and the present invention is not limited to these embodiments.

[0053] Figure 7 shows the shape diagram (top of page) and the local frequency distribution diagram (bottom of page) of the defocus region of Sample 1. In Sample 1, a defocus region (center: x=0 mm, y=0 mm) with a defocus power of 3.5 D and a diameter of 1 mm is provided on a surface with a prescription power of 0 D, and a surface roughness of RMS (root mean square roughness) of 0.1 mm is added. The minute light beam diameter φ used when measuring the local frequency is 0.2 mm.

[0054] For Sample 1, the center of the defocus region was measured using the following three methods. Method 1 is a method of estimating the center by considering the range in which the absolute value of the local frequency is 90% or more of the absolute value of the segment frequency as the defocus region. Method 2 is a method of estimating the center by considering the location where the local frequency takes an extremum as the boundary of the defocus region (extremum method). Method 3 is the mean circle range method described in the first embodiment above.

[0055] The center of the defocused area of ​​sample 1 measured by method 1 was x = 0.021 mm, y = 0.007 mm; the center of the defocused area of ​​sample 1 measured by method 2 was x = 0.003 mm, y = -0.003 mm; and the center of the defocused area of ​​sample 1 measured by method 3 was x = 0.003 mm, y = -0.003 mm. Therefore, it was confirmed that the mean circle range method allows for accurate measurement of the center of the defocused area from local frequencies, even when surface roughness is present.

[0056] Figure 8 shows the shape diagram (top of page) and the local frequency distribution diagram (bottom of page) of the defocus region of Sample 2. In Sample 2, three defocus regions with a defocus power of 3.5D and a diameter of 1 mm are provided on a plane with a prescription power of 0D. The distance between the boundaries of the two left defocus regions is 0.27 mm, and the distance between the boundaries of the two right defocus regions is 0.4 mm. The center of the central defocus region is at x=0 mm, y=0 mm. The diameter of the minute light beam used when measuring the local frequency is 0.3 mm.

[0057] For sample 2, the center of the central defocus region was measured using methods 1, 2, and 3 described above. As a result, the center of the defocus region of sample 2 using method 1 was x = 0.001 mm, y = 0.002 mm; the center of the defocus region of sample 2 using method 2 was x = -0.063 mm, y = -0.001 mm; and the center of the defocus region of sample 2 using method 3 was x = -0.003 mm, y = 0.000 mm. From the above, it was confirmed that by using the mean circle range method, the center of the defocus region can be accurately measured from the local frequency even when multiple defocus regions are located in close proximity.

[0058] 10 Eyeglass lens 11 Central clear area 12 Functional area 13 Base area 14 Defocus area 15 Peripheral clear area

Claims

1. An ophthalmic lens having a functional region having a base region that realizes the wearer's prescribed refractive power and a plurality of defocus regions having refractive powers different from the prescribed refractive power, wherein a method for measuring the center of the defocus region is defined as the center of the defocus region when, in plan view, the local average power in a range of diameter Φ centered on position P is measured while changing the value of the diameter Φ, and this procedure is repeated while changing position P, the local average power changes most sharply with respect to the change in diameter Φ from a value corresponding to the refractive power of the defocus region to a value corresponding to the refractive power of the base region.

2. The method for evaluating an ophthalmic lens according to claim 1, wherein the diameter of the minute light beam φ when measuring the local power average is 5% or more of the shortest adjacent distance in the defocus region.

3. A method for evaluating an ophthalmic lens according to claim 1, comprising measuring the local power in the defocus region and its vicinity, finding the centroid G of the region where the absolute value of the local power is greater than or equal to a certain value, and defining the vicinity of the centroid G as the range in which the position P is changed.

4. A method for evaluating an ophthalmic lens according to claim 1, comprising measuring the local power in the defocused region and its vicinity, finding the centroid G of the region where the absolute value of the local power is greater than or equal to a certain value, finding a point A among the points near the centroid G where the bias of the local power within a predetermined range is minimized, and defining the vicinity of point A as the range in which the position P is changed.

5. An ophthalmic lens having a functional region having a base region that realizes the wearer's prescribed refractive power and a plurality of defocus regions having refractive powers different from the prescribed refractive power, the device for measuring the center of the defocus region, comprising: a measurement unit that repeatedly performs a procedure of measuring the local power average in a range of diameter Φ centered on position P in a planar view, while changing the value of the diameter Φ, while changing position P; and a calculation unit that sets the position P at which the local power average changes most abruptly with respect to the change in diameter Φ, from a value corresponding to the refractive power of the defocus region to a value corresponding to the refractive power of the base region, as the center of the defocus region.

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