Method for evaluating ophthalmic lens and device for evaluating ophthalmic lens

Abstract

Provided is a method for measuring the diameter of a defocus region in an ophthalmic lens provided with a functional region having a base region for achieving prescribed refractive power of a wearer and a plurality of defocus regions having refractive power different from the prescribed refractive power, the method comprising: a step (a) for determining the center of the defocus region to be measured in plan view; a step (b) for measuring the local power average in a range from the center of the defocus region to the diameter Φ while changing the value of the diameter Φ; and a step (c) for estimating, as the diameter of the defocus region, the value of the diameter Φ when the local power average takes an intermediate value between the refractive power of the defocus region and the refractive power of the base region.

Description

Method for Evaluating Ophthalmic Lens and Ophthalmic Lens Evaluation Apparatus

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

[0002] For the evaluation of 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 of the lens. A typical example of transmission measurement is wavefront measurement using an interferometer or the like. Wavefront measurement can directly acquire wavefront information including higher-order aberrations, but it 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 quantities directly corresponding 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 for confirming the magnitude of the diopter and curvature at a point of interest and the fluctuation of the diopter and curvature within a certain range. For example, Patent Document 2 discloses a method for quantifying the amount of fluctuation.

[0005] JP-A-2004-205438 JP-A-2017-227572

[0006] In recent years, spectacle lenses (also referred to as myopia progression inhibitory 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 scattered 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 technique that can accurately measure the diameter 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, and a method for measuring the diameter of the defocus region, comprising: (a) determining the center of the defocus region to be measured in a planar view; (b) measuring the local power average in the range of diameter Φ from the center of the defocus region by changing the value of the diameter Φ; and (c) estimating the value of the diameter Φ when the local power average takes the midpoint between the refractive power of the defocus region and the refractive power of the base region as the diameter of the defocus region.

[0010] A second aspect of the present invention is the method for evaluating an ophthalmic lens according to the first aspect, wherein in step (b), 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 ophthalmic lens evaluation method according to the second aspect, wherein in step (c), the correction coefficient k = (Φ - φ) / Φ, and the value of the diameter Φ when the local power average takes the value obtained by multiplying the intermediate value by the correction coefficient k is estimated to be the diameter of the defocus region.

[0012] A fourth aspect of the present invention is an ophthalmic lens evaluation method according to the first aspect, wherein in step (a), the procedure of measuring the local power average in a range of diameter Φ centered on position P while changing the value of the diameter Φ is repeated while changing position P, and 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, is defined as the center of the defocused region.

[0013] A fifth aspect of the present invention is an ophthalmic lens evaluation method according to the first aspect, further comprising the steps of: (d) measuring the local power of the defocus region and its surrounding area to be measured; and (e) estimating the diameter of the defocus region by considering the position where the local power takes an extreme value as the boundary of the defocus region, wherein it is determined whether to perform steps (a) to (c) or steps (d) to (e) depending on the arrangement of the defocus region.

[0014] A sixth aspect of the present invention is a method for evaluating an ophthalmic lens as described in the fifth aspect, wherein steps (a) to (c) are performed when the distance between the centers of adjacent defocus regions is less than or equal to a predetermined value, and steps (d) to (e) are performed when the distance is greater than the predetermined value.

[0015] A seventh aspect of the present invention is an ophthalmic lens evaluation device for 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 diameter of the defocus region, comprising: a measuring unit that determines the center of the defocus region to be measured in a planar view, and measures the local power average within a range of diameter Φ from the center of the defocus region by changing the value of the diameter Φ; and a calculation unit that estimates the value of the diameter Φ when the local power average takes an intermediate value between the refractive power of the defocus region and the refractive power of the base region as the diameter of the defocus region.

[0016] According to one embodiment of the present invention, the diameter of the defocused region can be accurately measured from the local frequency.

[0017] 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 graph showing the average local power in the range of diameter Φ from the center of the defocused area shown in Figure 1, measured by changing the value of diameter Φ. Figure 5 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 6 is a flowchart of the evaluation method for an ophthalmic lens in the first embodiment of the present invention. Figure 7 is a graph showing the relationship between the average local power and the diameter Φ of the circular range when the center of the circular range is offset from the center of the defocused area. Figure 8 shows a plan view (left side of the page), a cross-sectional view (center of the page), and a magnified view (right side of the page) of the weighting function when the minute light beam diameter φ is sufficiently small. Figure 9 shows a plan view (left side of the page), a cross-sectional view (center of the page), and a magnified view (right side of the page) of the weighting function when the minute light beam diameter φ is 0.2 mm. Figure 10 is a graph of the local power average of the defocus region (diameter 1 mm) shown in Figure 1, measured under the condition that the minute light beam diameter φ is 0.2 mm. Figure 11 is a flowchart of the evaluation method for an ophthalmic lens according to the second embodiment of the present invention. Figure 12 is a graph showing the local power values ​​when the minute light beam diameter φ is changed. Figure 13 shows the shape diagram (top of the page) and local power distribution diagram (bottom of the page) of the area around the defocus region in sample 1 of the example. Figure 14 shows the shape diagram (top of page) and local frequency distribution diagram (bottom of page) around the defocused area in Sample 2 of the Example. Figure 15 shows the shape diagram (top of page) and local frequency distribution diagram (bottom of page) around the defocused area in Sample 3 of the Example.

[0018] <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).

[0019] 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.

[0020] 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".

[0021] 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.

[0022] 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.

[0023] 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.

[0024]

[0025] Here, the local frequency mean s (overline) in a circular range of diameter Φ and radius u can be expressed by the following formula.

[0026]

[0027] 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.

[0028]

[0029] 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).

[0030] Figure 4 is a graph showing the local frequency mean within the range of diameter Φ from the center of the defocus region shown in Figure 1, measured while varying the value of diameter Φ. In this case, the diameter Φ value at which the local frequency mean takes the midpoint between the segment frequency and the base frequency (1.75D, the dotted line on the graph) can be estimated as the diameter of the defocus region. Hereafter, in this specification, the method of estimating the center and diameter of the defocus region from the local frequency mean as described above will be called the "mean circle range method".

[0031] [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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] <First Embodiment of the Invention> (1) Eyeglass Lens First, the eyeglass lens to be evaluated in this embodiment will be briefly described. Figure 5 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 5, 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.

[0036] 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.

[0037] 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).

[0038] 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.).

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] As the lens substrate constituting the spectacle lens 10, various commonly used lens substrates can be used. 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. From the viewpoints of light weight and difficulty in cracking, a plastic lens substrate is preferable as the lens substrate. Examples of the plastic lens substrate include styrene resins such as (meth)acrylic resins, polycarbonate resins, allyl resins, allyl carbonate resins such as diethylene glycol bisallyl carbonate resin (CR-39), vinyl resins, polyester resins, polyether resins, urethane resins obtained by reacting an isocyanate compound with a hydroxy compound such as diethylene glycol, thiourethane resins obtained by reacting an isocyanate compound with a polythiol compound, and cured products of a curable composition containing a (thio)epoxy compound having one or more disulfide bonds in the molecule (generally called a transparent resin). The curable composition may also be referred to as a polymerizable composition. As the lens substrate, an undyed one (colorless lens) may be used, or a dyed one (dyed lens) may be used. The thickness of the lens substrate is not particularly limited, but for example, the thickness (central thickness) may be about 1 to 30 mm. The refractive index of the lens substrate may be, for example, about 1.60 to

[0044] 1.75. However, the refractive index of the lens substrate is not limited to this range, and it may be above or below this range even within this range. In this specification, the refractive index refers to the refractive index with respect to light having a wavelength of 500 nm.

[0044] (2) Evaluation method of ophthalmic lens Next, the evaluation method of the ophthalmic lens of the present embodiment will be described. In the present embodiment, a case where the diameter of the defocus region 14 of the spectacle lens 10 is obtained by the average circle range method described above will be described. FIG. 6 is a flowchart showing the evaluation method of the ophthalmic lens of the present embodiment. As shown in FIG. 6, the evaluation method of the ophthalmic lens of the present embodiment has, for example, a center determination step S100, a local refractive power average measurement step S110, and a diameter estimation step S120.

[0045] (Center determination step S100) The center determination step S100 is a step of determining the center of the defocus area 14 to be measured in a plan view. Accurately obtaining the center of the defocus area 14 is important not only when evaluating a myopia progression-inhibiting lens or the like, but also when determining the diameter of the defocus area 14 by the average circle range method. This is because when the center of the circle range does not coincide with the center of the defocus area 14, even if the diameter of the circle range is not related to the diameter of the defocus area 14, an intermediate value between the segment power and the base power can be obtained. FIG. 7 is a graph showing the relationship between the local power average and the diameter Φ of the circle range when the center of the circle range is deviated from the center of the defocus area 14. As shown in FIG. 7, when the center of the circle range is deviated from the center of the defocus area 14, the range of taking values that are neither the segment power nor the base power becomes wider compared to FIG. 4.

[0046] Therefore, when the procedure of measuring the local power average in the range of the diameter Φ centered on the position P while changing the value of the diameter Φ is repeated while changing the position P, the position P at which the local power average changes most steeply with respect to the change in the diameter Φ from the value corresponding to the segment power to the value corresponding to the base power can be said to be the center of the defocus area 14. By determining the center of the defocus area 14 in this way, it becomes possible to more accurately determine the diameter of the defocus area 14 in the subsequent steps.

[0047] As described above, if the position P is changed and measurements are repeated, the amount of measurement (calculation) may become enormous. Therefore, in the center determination step S100, it is preferable to determine the center by the following procedure: (1) Find the centroid G of the region where the absolute value of the local frequency is greater than or equal to a certain value (for example, 90% or more of the absolute value of the segment frequency). If 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) Find point A among the points in the vicinity of the centroid G (for example, within 0.1 mm) where the bias of the local frequency within the diameter range of the provisional defocus region 14 is minimized. The diameter of the provisional defocus region 14 may be, for example, the smallest circumscribed circle diameter that can enclose the point where the local frequency is a constant value. (3) Among the points in the vicinity of point A (for example, within 0.1 mm), the point where the average local frequency changes most sharply when the diameter Φ of the circle range changes is set as the center of the defocus region 14. This reduces the amount of measurement (calculation) required, while allowing for a more accurate determination of the diameter of the defocused region 14 in a later step.

[0048] (Local frequency mean measurement step S110) The local frequency mean measurement step S110 is a step in which the local frequency mean of the range of diameter Φ from the center of the defocus region 14 determined in the center determination step S100 is measured by changing the value of the diameter Φ. This step yields a graph showing the relationship between the local frequency mean and the diameter Φ of the circular range, as shown in Figure 4.

[0049] (Diameter Estimation Step S120) The diameter estimation step S120 is a step in which the diameter Φ value at which the local frequency mean takes the midpoint between the refractive power (segment frequency) of the defocused region 14 and the refractive power (base frequency) of the base region 13 is estimated to be the diameter of the defocused region 14. This makes it possible to accurately determine the diameter of the defocused region 14 from the local frequency.

[0050] Here, we consider the case where the minute light beam diameter φ when measuring the local frequency average in the local frequency average measurement step S110 is not sufficiently small, for example, when the minute light beam diameter φ is 5% or more of the shortest adjacent distance between defocused regions 14 (the distance between the boundaries of adjacent defocused regions 14). If the shortest adjacent distance between defocused regions 14 is unknown, 5% or more of the shortest adjacent distance between defocused regions 14 may be replaced with 5% or more of the provisional diameter of the defocused region 14 as described above, or with 0.1 mm or more.

[0051] Figure 8 shows a plan view (left), a cross-sectional view (center), and a magnified view (right) of the weighting function when the small luminous beam diameter φ is sufficiently small. Figure 9 shows a plan view (left), a cross-sectional view (center), and a magnified view (right) of the weighting function when the small luminous beam diameter φ is 0.2 mm. The weighting function referred to here is a function obtained by convolving a filter that calculates the local frequency per small luminous beam diameter φ from an (unknown) wavefront with a function that sets the inside of a circle with a diameter of 1 to 1 and the outside to 0. The operation of calculating the local frequency average is equivalent to taking the average of the wavefront using the weighting function. As shown in Figure 8, when the small luminous beam diameter φ is sufficiently small, the weighting function is a function that takes the difference between the point immediately outside and immediately inside the point with a radius of 0.5 mm (the outer circumference of the circle). On the other hand, as shown in Figure 9, when the small luminous beam diameter φ is not sufficiently small, the weighting function means taking the difference between the value near a radius of 0.4 mm and the value near a radius of 0.6 mm. In other words, the difference between wavefronts separated by approximately the small luminous beam diameter φ on the outer circumference of the circle becomes the gradient on the circumference when calculating the local frequency average.

[0052] Therefore, if the minute luminous beam diameter φ is not sufficiently small, the local frequency mean tends to be calculated as smaller by referring to the slope slightly inside the boundary of the defocused region 14. For this reason, in the diameter estimation step S120, it is preferable to set the correction coefficient k = (Φ - φ) / Φ and estimate the diameter Φ when the local frequency mean takes the value obtained by multiplying the midpoint between the segment frequency and the base frequency by the correction coefficient k as the diameter of the defocused region 14. Figure 10 is a graph of the local frequency mean of the defocused region 14 (diameter 1 mm) shown in Figure 1, measured under the condition that the minute luminous beam diameter φ is 0.2 mm. As shown in Figure 10, it can be seen that the intersection of the local frequency mean line and the midpoint × correction coefficient k line corresponds to the diameter of the defocused region 14. This makes it possible to determine the diameter of the defocused region 14 more accurately even when the minute luminous beam diameter φ is not sufficiently small.

[0053] (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 diameter 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 measuring unit that determines the center of the defocused region to be measured in a planar view, and measures the local power average within a range of diameter Φ from the center of the defocused region by changing the value of diameter Φ, and a calculation unit that estimates the diameter Φ value when the local power average takes the intermediate value between the refractive power of the defocused region and the refractive power of the base region as the diameter of the defocused region. A known power distribution measuring device can be used as the measuring 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.

[0054] <Second Embodiment of the Invention> Next, a second embodiment of the invention will be described. The same parts as in the first embodiment will be omitted from the description. Figure 11 is a flowchart of the method for evaluating an ophthalmic lens according to the second embodiment. As shown in Figure 11, the method for evaluating an ophthalmic lens according to the second embodiment includes a local power measurement step S200 and a diameter estimation step S210, in addition to the center determination step S100, local power averaging measurement step S110, and diameter estimation step S120 described in the first embodiment. For example, depending on the arrangement of the defocused area to be measured, it is determined whether to perform the center determination step S100, local power averaging measurement step S110, and diameter estimation step S120, or to perform the local power measurement step S200 and diameter estimation step S210. The local power measurement step S200 and diameter estimation step S210 are algorithms for determining the diameter of the defocused area using the extreme value method described above. In other words, the method for evaluating an ophthalmic lens according to the second embodiment is a method for determining the diameter of the defocused area by using the average circle range method and the extreme value method interchangeably.

[0055] As described above, the extreme value method may not be able to provide a correct evaluation when multiple defocus regions are located close together. Therefore, in the evaluation method for ophthalmic lenses of the second embodiment, it is preferable to perform the center determination step S100, the local power averaging measurement step S110, and the diameter estimation step S120 when the distance between the centers of adjacent defocus regions is less than or equal to a predetermined value (i.e., employing the average circle range method), and to perform the local power measurement step S200 and the diameter estimation step S210 when it is greater than the predetermined value (i.e., employing the extreme value method).

[0056] Specifically, it is preferable to use the mean circle range method when the distance between the centers of adjacent defocus regions is less than or equal to the sum of the smallest circumscribed circle radii (provisional defocus region radii) that enclose the points where the local frequency in each defocus region is constant, plus twice the minute luminous beam diameter φ. It is preferable to use the extreme value method when the distance is greater than the sum of the provisional defocus region radii plus twice the minute luminous beam diameter φ. When using the polar method under more reliable conditions, twice the minute luminous beam diameter φ may be replaced with three times the minute luminous beam diameter φ. (*Note: The extreme value method can be used when the distance between segment boundaries = base width is greater than the infinitesimal beam diameter. In narrower fields, the method fails because an extreme value occurs at a point where both boundaries are simultaneously included in the infinitesimal beam diameter. In other words, the original condition is (center distance - twice the segment radius) > infinitesimal beam diameter. However, since the segment radius is unknown before implementing the method, the smallest circumscribed circle radius that can enclose a point where the local frequency is a constant value + infinitesimal beam radius is used as the provisional segment radius, and then the condition is changed to center distance > ~.) This makes it easier to determine the diameter of the defocused region more accurately, regardless of the arrangement of the defocused region. Alternatively, the above determination can be omitted, and the extreme value method can be directly implemented. If there is only one extreme value between adjacent defocused regions in the local frequency distribution, the extreme value method can be deemed unsuitable, and the mean circle range method can be adopted.

[0057] (Local frequency measurement step S200) The local frequency measurement step S200 is a step in which the local frequency of the defocused region to be measured and its surrounding area is measured. This step yields a local frequency distribution as shown in Figure 1.

[0058] (Diameter Estimation Step S210) The diameter estimation step S210 is a step in which the position where the local frequency obtained in the local frequency measurement step S200 takes an extreme value is considered to be the boundary of the defocused region, and the diameter of the defocused region is estimated. Specifically, in the cross-sectional view of the local frequency passing through the center of the defocused region to be measured (see Figure 1, lower right), the distance between the two extreme values ​​closest to the center of the defocused region can be taken as the diameter. Alternatively, the average distance between two extreme values ​​may be calculated using cross-sectional views in multiple directions and taken as the diameter.

[0059] In the extreme value method, if the minute beam diameter φ used to measure local frequencies is not sufficiently small—for example, if the minute beam diameter φ is 5% or more of the shortest adjacent distance between defocused regions—the measured value tends to be slightly larger than the actual diameter of the defocused region. In the example shown in Figure 1 (minute beam diameter φ is 0.2 mm), the distance between the two extreme values ​​is approximately 1.05 mm, compared to the actual diameter of the defocused region of 1 mm.

[0060] Figure 12 is a graph showing the local frequency values ​​when the minute luminous beam diameter φ is changed (around the boundary between two defocus regions). As shown in Figure 12, it can be seen that as the minute luminous beam diameter φ increases, the position where the extreme value is taken is shifted outward from the center of the defocus region, away from the original position of the boundary of the defocus region (positions 0.5 and 1.0 on the horizontal axis). Therefore, in the diameter estimation step S210, it is preferable to store in advance the discrepancy (boundary shift amount) between the position of the extreme value corresponding to the minute luminous beam diameter φ of the local frequency measuring device and the position of the boundary of the defocus region, and to estimate the diameter by subtracting the boundary shift amount from the distance between the two extreme values.

[0061] <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.

[0062] For example, in the above embodiment, in the center determination step S100, the center of the defocus region was set to the position P at which the local frequency mean changes most sharply with respect to the change in diameter Φ. However, the method for determining the center of the defocus region is not limited to this. Specifically, one could search for a region where the absolute value of the local frequency is greater than or equal to a certain value (for example, 90% or more of the absolute value of the segment frequency) and set its centroid as the center, or, in a cross-sectional view of the local frequency as shown in the lower right of Figure 1, the midpoint between two extreme values ​​could be set as the center of the defocus region. Alternatively, an approximate circle connecting the extreme values ​​in the extreme value method could be calculated, and its center could be set as the center of the defocus region.

[0063] Furthermore, in the second embodiment described above, we explained the case in which the average circle range method or the extreme value method is adopted depending on the arrangement of the defocus region to be measured. However, the method to be adopted may be determined by other conditions. Specifically, the method to be adopted may be determined depending on the surface condition of the functional region (e.g., surface roughness). Alternatively, the extreme value method may be adopted regardless of the conditions.

[0064] Furthermore, 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).

[0065] 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.

[0066] Figure 13 shows the shape diagram (top of the page) and the local frequency distribution diagram (bottom of the page) of the defocus region of Sample 1. In Sample 1, a 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 diameter of the minute light beam used when measuring the local power is 0.3 mm.

[0067] For Sample 1, the diameter of the defocus region was measured using the following three methods. Method 1 is a method of estimating the diameter 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 the extreme value method described in the second embodiment above. Method 3 is the mean circle range method described in the first embodiment above.

[0068] The diameter of the defocused area of ​​sample 1 measured by method 1 was 0.63 mm, the diameter of the defocused area of ​​sample 1 measured by method 2 was 1.07 mm (1.00 mm after subtracting the pre-calculated boundary displacement of 0.065 mm), and the diameter of the defocused area of ​​sample 1 measured by method 3 was 1.01 mm. From these results, it was confirmed that the diameter of the defocused area can be accurately measured from the local frequency using the extreme value method or the mean circle range method.

[0069] Figure 14 shows the shape diagram (top of the page) and the local frequency distribution diagram (bottom of the page) of the area around the defocus region of Sample 2. In Sample 2, multiple defocus regions with a defocus power of 3.5D and a diameter of 1 mm are provided on a surface with a prescription power of 0D, at a pitch (center-to-center distance) of 1.33 mm. The diameter of the minute light beam used when measuring the local frequency is 0.3 mm.

[0070] The diameter of the defocused area of ​​sample 2 was measured using methods 1, 2, and 3 described above. As a result, the diameter of the defocused area of ​​sample 2 measured by method 1 was 0.63 mm, the diameter of the defocused area of ​​sample 2 measured by method 2 was 1.33 mm (1.27 mm after subtracting the pre-calculated boundary displacement of 0.065 mm), and the diameter of the defocused area of ​​sample 2 measured by method 3 was 1.01 mm. From the above, it was confirmed that the mean circle range method can accurately measure the diameter of the defocused area from the local frequency even when multiple defocused areas are located in close proximity to each other.

[0071] Figure 15 shows the shape diagram (top of page) and the local frequency distribution diagram (bottom of page) of the defocus region of Sample 3. In Sample 3, a 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, and a surface roughness of RMS (root mean square roughness) of 0.1 mm is added. The diameter of the minute light beam φ when measuring the local power is 0.2 mm.

[0072] The diameter of the defocused region of sample 3 was measured using methods 1, 2, and 3 described above. As a result, the diameter of the defocused region of sample 3 measured by method 1 was 0.75 mm, the diameter of the defocused region of sample 3 measured by method 2 was 0.99 to 1.05 mm (after subtracting the pre-calculated boundary displacement of 0.065 mm, the diameter was 0.93 to 0.99 mm), and the diameter of the defocused region of sample 3 measured by method 3 was 1.01 mm. Note that in method 2, the extremum search was unsuccessful, and the measurement results oscillated. From the above, it was confirmed that the diameter of the defocused region can be accurately measured from the local frequency even when surface roughness is added by using the mean circle range method.

[0073] 10 Eyeglass lens 11 Central clear area 12 Functional area 13 Base area 14 Defocus area 15 Peripheral clear area S100 Center determination step S110 Local power averaging measurement step S120 Diameter estimation step S200 Local power measurement step S210 Diameter estimation step

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, the method for measuring the diameter of the defocus region, comprising: (a) determining the center of the defocus region to be measured in a planar view; (b) measuring the local power average within a range of diameter Φ from the center of the defocus region by changing the value of the diameter Φ; and (c) estimating the diameter of the defocus region as the value of the diameter Φ when the local power average takes the midpoint between the refractive power of the defocus region and the refractive power of the base region.

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

3. In step (c), the correction coefficient k = (Φ - φ) / Φ, and the value of the diameter Φ when the local power mean takes the value obtained by multiplying the intermediate value by the correction coefficient k is estimated to be the diameter of the defocus region, the method for evaluating an ophthalmic lens according to claim 2.

4. The method for evaluating an ophthalmic lens according to claim 1, wherein in step (a), the procedure of measuring the local power average in a range of diameter Φ centered on position P while changing the value of the diameter Φ is repeated while changing position P, and 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 is defined as the center of the defocused region.

5. A method for evaluating an ophthalmic lens according to claim 1, further comprising: (d) measuring the local power of the defocus region and its surrounding area to be measured; and (e) estimating the diameter of the defocus region by considering the position where the local power takes an extreme value as the boundary of the defocus region, wherein it is determined whether to perform steps (a) to (c) or steps (d) to (e) depending on the arrangement of the defocus region.

6. The method for evaluating an ophthalmic lens according to claim 5, wherein steps (a) to (c) are performed when the distance between the centers of adjacent defocus regions is less than or equal to a predetermined value, and steps (d) to (e) are performed when the distance is greater than the predetermined value.

7. 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 diameter of the defocus region, comprising: a measuring unit that determines the center of the defocus region to be measured in a planar view, and measures the local power average within a range of diameter Φ from the center of the defocus region by changing the value of the diameter Φ; and a calculation unit that estimates the value of the diameter Φ when the local power average takes the midpoint between the refractive power of the defocus region and the refractive power of the base region as the diameter of the defocus region.

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