Method for designing lens surface of progressive power lens

Abstract

To provide a method for designing the lens surface of a progressive refractive power lens in which the difference of visibility due to the difference of the axial direction of aberration is considered when designing the lens surface of the progressive refractive power lens.SOLUTION: A method for designing a lens surface of a progressive addition lens, the method including acquiring an optical performance of a design simulation value by repeatedly executing a ray tracing simulation while changing a shape of the lens surface so as to approach an optical performance of a design target value with respect to evaluation points distributed on the lens surface of the progressive addition lens, and determining a shape of a progressive surface by optimization calculation, the method including: A correction value for reflecting the weight of visibility with an angle in the axial direction of an aberration component as a parameter on the size of the aberration component is acquired, and the acquired correction value is applied to a design target value or a function used for a ray tracing method to calculate a design simulation value in optimization calculation.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a method for designing the lens surface of a progressive-power lens, which involves repeatedly performing ray tracing simulations for evaluation points distributed on the lens surface of the progressive-power lens to approach the optical performance of a design target value, obtaining the optical performance of a design simulation value, and determining the optical performance of the design simulation value through optimization calculations. [Background technology]

[0002] The design of a progressive addition lens surface using optimization calculations is generally performed as follows. First, data on the optical performance of the design target value is set for evaluation points distributed on the lens surface. Meanwhile, progressive sag values ​​(lens surface shape) at the evaluation points are set. The progressive sag value is discrete point cloud data that constitutes the progressive surface to be combined with the toric surface, and is a value with a directionality perpendicular to the plane on which the evaluation points exist and parallel to the lens optical axis. The progressive surface is created using this discrete point cloud data through interpolation processing such as spline interpolation. In optimization calculations, the initial progressive sag value can be any value. It can be all 0.0, or if there is a progressive surface with a known shape that approximates the optical performance of the design target value, that value can be set. The optimization calculation performs ray tracing each time the progressive sag value is slightly changed to obtain the optical performance of the design simulation value. The progressive sag value is modified to minimize the error between the optical performance of the obtained design simulation value and the optical performance of the design target value, and a progressive sag value with optical performance of the design simulation value that approximates the optical performance of the design target value is obtained. Designing the lens surface of a progressive-power lens by performing optimization calculations in this manner is well known, and is disclosed in Patent Document 1, for example.

[0003] Progressive addition lenses are designed to connect the distance and near vision zones via a progressive zone, resulting in significant astigmatism on the lens surface. Astigmatism is a component equivalent to astigmatism imparted to the eye by external factors; in other words, the astigmatism component is nothing but astigmatism. Unlike the astigmatism power imparted to the eye as a prescription due to external factors, the astigmatism component of a progressive addition lens does not have an axis of aberration (astigmatism axis) in a specific direction; instead, the axial direction is not constant, and therefore it may have all types of axes (i.e., astigmatism axes) for straight astigmatism, inverse astigmatism, and oblique astigmatism. In other words, when designing the lens surface of a progressive addition lens, it should be affected by astigmatism in addition to astigmatism imparted to the eye by such external factors. However, the conventional design methods described above have not given much consideration to the axial direction of this astigmatism. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4033344 Paragraph 0003 [Non-Patent Document 1] Author: Hidenaga Kobashi, Kazutaka Kamiya, Kimiya Shimizu, Takushi Kawamorita, Hiroshi Uozato, Paper title: "Effect of axis orientation on visual performance in astigmatic eyes", Publication name: "Journal of Cataract & Refract Surgery", Published June 22, 2012, Volume 38, Issue 8, P.1352~1359 [Non-patent document 2] FW Campbell, JJ Kulikowski, J. Levinson, paper title: "The effect of orientation on the visual resolution of gratings", publication name: "The Journal of Physiology", published November 1, 1966, vol. 187, no. 2, P.427~436 Summary of the Invention [Problem to be solved by the invention]

[0005] However, clinical findings have shown that even with the same amount of astigmatism, for example, between aberration on the parallel axis and aberration on the oblique axis (rectilinear astigmatism and oblique astigmatism when astigmatism is considered as astigmatism), aberration on the parallel axis results in better vision. In other words, with progressive power lenses, differences in the axial direction of the aberration result in differences in ease of vision (reduction of blur) that do not appear in measurements. Non-Patent Document 1 is a prior art document that mentions that the wearer's sense of blur differs depending on the axis direction even with the same amount of astigmatism. Non-Patent Document 1 describes the visual characteristics of lenses with astigmatism as follows: No aberration >> Parallel axis aberration = Vertical axis aberration >> Oblique axis aberration Furthermore, Patent Document 2 discloses that the visual characteristics for an axis change sinusoidally. "Varying sinusoidally" means that the visibility (reduction of blur) at a mapping point changes continuously depending on the phase of the aberration axis. Although the ease of vision (reduction of blur) differs depending on the axis of aberration, this has not been reflected in the design of the lens surface of progressive addition lenses. [Means for solving the problem]

[0006] In order to solve the above problems, Means 1 is a method for designing the lens surface of a progressive-power lens, which involves repeatedly performing ray tracing simulations while changing the shape of the lens surface for evaluation points distributed on the lens surface of the progressive-power lens so as to bring the optical performance of the lens surface closer to a design target value, thereby obtaining the optical performance of a design simulation value, and then determining the shape of the progressive surface by optimization calculation such that the optical performance of the design simulation value approximates the optical performance of the design target value, and the method obtains an axial direction of an aberration component having an angle in the range of 0 to 180 degrees for each evaluation point, obtains a correction value such that the weight of visibility or difficulty in visibility, using the angle of the axial direction of the aberration component as a parameter, is reflected in the magnitude of the aberration component, and applies the obtained correction value to at least one of the design target value and a function used in the ray tracing method to calculate the design simulation value in the optimization calculation. By using such correction values ​​in the optimization calculations for the design target values ​​and / or the function used in the ray tracing method, it is possible to obtain design simulation values ​​that reflect the weighting of the ease or difficulty of vision based on differences in axial direction. This design makes it possible to provide a progressive-power lens that reflects the user's actual vision.

[0007] The "evaluation points" are a number of points that serve as standards for measuring the optical performance and shape of the lens surface of a progressive addition lens, and are arranged on the lens surface at an arbitrary density and as evenly spaced as possible. The "design target value" is the target value when performing optimization calculations. It is the coordinates of the evaluation points on the lens XY plane perpendicular to the lens optical axis, and the optical performance at each evaluation point, for example, M and J according to Jackson's Cross Cylinder (JCC). 00 ,J 45 The JCC is expressed by the following formula 3 in relation to the S power, C power, and astigmatism axis.

[0008]

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[0009] The design target values ​​may be the measured values ​​(optical performance) of an existing progressive power lens that has already been designed, or may be values ​​obtained by a separate simulation. Also, the designer may use the optical performance values ​​appropriately corrected based on these values ​​to achieve the ideal optical performance. Also, M, J 00 ,J 45 may be replaced by S, C, or AX. The "design simulation value" is a value used together with the design target value in the calculation to minimize the objective function through optimization calculation. 00 ,J 45 It can be identified by. The ray tracing method is a method for simulating the optical performance at any coordinate (evaluation point) on the lens plane. Ray tracing calculations are performed by simulation using a computer. An "optimization calculation" is a calculation performed to determine the shape of a progressive surface that provides a design simulation value for optical performance close to the optical performance of the design target value. To determine the progressive sag value that minimizes the objective function, the optical characteristics of the lens surface shape (for example, the progressive sag value) are obtained by gradually changing it using ray tracing, and calculations are repeated to determine the changed lens surface shape that minimizes the objective function. The optimization calculation is performed by simulation using a computer device. Specific methods used for the optimization calculation include well-established, well-known methods such as the damped least squares method (DLS) and genetic algorithms.

[0010] The "axis of an aberration component" refers to three types of axes: the parallel axis, the vertical axis, and the oblique axis. Astigmatism is equivalent to the astigmatism component, as mentioned above. Therefore, among the axes of the aberration components, the parallel axis is the axis of straight astigmatism, the vertical axis is the axis of reverse astigmatism, and the oblique axis is the axis of oblique astigmatism. The parallel axis is in the 0-degree or 180-degree direction, the vertical axis is in the 90-degree direction, and the oblique axis is any other direction. In other words, it is assumed that the oblique axis may be in a direction other than 45 degrees or 135 degrees. For example, it is advisable to distinguish and weight aberrations in the oblique axis direction from aberrations in other directions. When the "weight" is a correction value that is reflected in the magnitude of the aberration component, for example, multiplying the weight by the original value is common and easy to calculate, but the weight may be reflected in the magnitude of the aberration component using any of the four arithmetic operations of addition, subtraction, multiplication, and division. Furthermore, a nonlinear weight other than the four arithmetic operations or an exponential weight may be applied. Exponential functions are also included as part of the nonlinear weight. The reason why it is called "weight of visibility or difficulty with the axial angle of the aberration component as a parameter" is that the actual visibility or difficulty differs depending on the axial angle even when there is an aberration component. For example, when there is aberration in the diagonal axis, it becomes significantly more difficult to see compared to when there is aberration in the parallel or vertical axis. As in the above-mentioned Non-Patent Document 1, visibility as a measure is No aberration >> Parallel axis aberration = Vertical axis aberration >> Oblique axis aberration This tends to be the case. Therefore, when there is an aberration component, the oblique axis is the least visible, and the aberration of the parallel axis = the vertical axis is the most visible. For this reason, it is good to change the weight depending on the axis direction. For example, when weighting visibility, it is good to give the diagonal axis the least weight and the aberration of the parallel axis and the vertical axis the most weight. When weighting visibility, the opposite method is used.

[0011] In addition, in the means 2, the optical performance distribution is obtained using the optical performance of the design simulation value calculated by applying the correction value. This allows the visual appearance of an actual progressive power lens to be visually reflected, allowing workers to easily evaluate the design state of the progressive power lens by visual inspection.Specific examples of optical performance distribution include an average power distribution chart and an astigmatism distribution chart.The former is a diagram that graphically represents the M (S power + 1 / 2C power) of the evaluation point using contour lines, and the latter is a diagram that graphically represents the C power of the evaluation point using contour lines.The astigmatism distribution chart may be, for example, two-dimensional or three-dimensional. In addition, in means 3, the optical performance distribution of the design simulation value calculated by applying the correction value is designed to be an optical performance distribution that is close to the optical performance distribution of the design target value to which the correction value is not applied. By designing the optical performance of the design simulation values ​​after correction so that it approaches the optical performance of the design target values ​​without correction, it is possible to obtain an optical performance distribution of the design simulation values ​​that reflects the design concept of the original design target values. For example, if the original design target values ​​are optical performance in which the optical performance on the ear side and the nasal side is symmetrical, it is possible to approach the design simulation values ​​after correction so that the optical performance on the ear side and the nasal side is symmetrical, while taking into account the difference in appearance due to the difference in the axial direction of the aberration.

[0012] In addition, in means 4, the weight is set using the angle of the axis of the aberration component as a parameter, and is set to be maximum or minimum when the axial direction of the aberration component is 45 degrees or 135 degrees, and conversely to be minimum or maximum when the axial direction is 0 degrees or 90 degrees. In this way, setting the maximum and minimum weights at angles of 45 degrees or 135 degrees and angles of 0 degrees or 90 degrees will conform to the characteristics of visibility or visibility. The function of visibility and axis angle direction specifically shows the characteristics of a cosine curve in which a sine wave, as shown in Figure 15, is shifted by π / 2 in radians. Figure 115 shows 180 degrees (π), which is the wavelength of a periodic function of a cosine curve with a period of 2π. Generally, as shown in Figure 15, when there is an aberration component, the characteristic is that the oblique axis is the least visible, and the aberration of the parallel axis = the vertical axis is the most visible. Therefore, when weighting visibility, it is best to give the oblique axis the smallest weight, and the aberration of the parallel axis and the vertical axis the largest weight. When weighting visibility, the opposite method is used. It is possible to have the aberration of the parallel axis = the vertical axis, but it is also possible to weight either the aberration of the parallel axis or the vertical axis differently from the other. In addition, in means 5, the weight is set to be maximum or minimum when the axial angle of the aberration component is 0 degrees, 90 degrees or 180 degrees, and conversely to be minimum or maximum when the axial angle of the aberration component is other than 0 degrees, 90 degrees or 180 degrees. Such a setting may be in accordance with the characteristics of visibility or low visibility.

[0013] In addition, in the means 6, the weight is set to w, and the weight is expressed by the following equation or an equation equivalent to the following equation, with a, b, ω, and α as coefficients. This equation is a general formula for the weight w. a, b, and (ωAX + α) are determined so that the equation holds for any suitable weight (numerical value). The coefficient ω multiplied by the axial angle is generally a parameter that changes the angular phase as an angular frequency, but in the present invention, it is used to maximize (or minimize) the axial angle of astigmatism when it is 0 degrees or 180 degrees, and minimize (or maximize) other oblique axes. The coefficient α added to the axial angle is a parameter that determines the phase at the initial position of the sine wave, but in the present invention, it is a parameter used to fine-tune the peak position of the cosine curve (the peak position of visibility or difficulty). Since equivalent equations will yield the same solution, the weight w may be expressed in other equivalent formats.

[0014]

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[0015] Furthermore, in the means 7, when the weight is set to w, it is expressed by the following formula or a formula equivalent to the following formula. This is a more specific expression of the general formula for weight w in Means 6, and is a formula that assigns a weight that is maximum when the angle of the axial direction of the aberration component is 0 degrees or 180 degrees, and minimum when the axial direction of the aberration component is 45 degrees or 135 degrees. In other words, this is a suitable formula for assigning a weight using visibility as a measure. Since equivalent formulas will yield the same solution, the weight w may be expressed in other equivalent formats.

[0016]

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[0017] In addition, in the eighth means, the weight is set to take a maximum or minimum value between 1.1 and 2.0. These are specific values ​​that are appropriate for the weights, because if the weights are too large, they will not match the actual astigmatism of the progressive lens. A more suitable value is a maximum or minimum value of 1.5 to 1.8, which reflects the actual vision due to the difference in aberration of the parallel axis and the oblique axis. The maximum or minimum value is determined by the aberration of the parallel axis and the oblique axis according to the prescription. Figure 16 is a graph showing the difference in visual acuity (perception) between aberrations along the parallel axis and aberrations along the oblique axis, as disclosed in the above-mentioned Non-Patent Document 1. The horizontal axis represents astigmatism, and the vertical axis represents logarithmic visual acuity (logMAR value). The open bars represent aberrations along the parallel axis, and the filled bars represent aberrations along the oblique axis. The graph shows the average logarithmic visual acuity obtained by having multiple subjects visually view the optotype. In other words, when there is aberration along the parallel axis, vision is generally 0.1 to 0.25 better than when there is aberration along the oblique axis. In addition, it is known from the following paper, for example, that there is a linear correlation between the logarithmic visual acuity decline and the astigmatism power (astigmatism). “Author: Tavazzi S, Vlasak N, Zeri F, Title: “Effects of Lens-Induced Astigmatism at Near and Far Distances”, Publishing magazine: “Clinical Optometry”, Publication date: 6 May 2023, Volume 15, P.105-P.117” Therefore, for example, when considering 0.2, an intermediate value between 0.1 and 0.3, the astigmatism change rate corresponding to a logarithmic visual acuity of 0.2 is approximately 1.8. From this, the weight given to the astigmatism C of the mapping point before correction can be set to 1.8 as the maximum or minimum value, and the astigmatism C' of the mapping point after correction can be calculated as C' = 1.8C. Here, let's set a+bcos(4AX)=1.8 to find a and b. In this case, the solution is a=1.4 and b=-0.4, so a maximum weight of 1.8 and a minimum weight of 1.0 will be assigned. The weight will vary to some extent depending on the difference in visual acuity (how it appears); if the difference in visual acuity (how it appears) is 0.1, the weight will be around 1.1, and if the difference in visual acuity (how it appears) is 0.25, the weight will be around 2.0. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a progressive power lens that is designed to reflect the user's actual vision. [Brief explanation of the drawings]

[0019] [Figure 1] 10A and 10B are an average power distribution diagram and an astigmatism distribution diagram of a design A that is not weighted and is used to explain an embodiment of the present invention. [Figure 2] In the explanation of the same example, the average power distribution diagram and astigmatism distribution diagram are given weights reflecting the actual vision as in design A. [Figure 3] 10 is a comparative graph of cross-sectional aberrations for the conventional evaluation of design A and the new evaluation of design A in the same example, with the horizontal axis representing the distance from the center and the vertical axis representing the amount of astigmatism. [Figure 4] 10A and 10B are a mean power distribution chart and an astigmatism distribution chart of the design target value of design A′ in Example 1. [Figure 5] 10A and 10B are a mean power distribution diagram and an astigmatism distribution diagram created based on the optical characteristics obtained by optimization calculation of design A′ in Example 1. [Figure 6] 6 is a comparison graph of cross-sectional aberrations, showing the comparison graph of FIG. 3 plus the new evaluation of design A' of FIG. 5. [Figure 7] 10A and 10B are an average power distribution diagram and an astigmatism distribution diagram created based on the optical characteristics obtained by optimization calculation of design A' in Example 1-2. [Figure 8] The characteristics of the thick line in the comparison graph in Figure 6 are compared with the cross-sectional aberration of Design A' in Figure 7, which is a new evaluation. [Figure 9]This is a graph that uses a sine curve to explain how the weight of equation 9 changes depending on the angle of the axial direction of the aberration component. [Figure 10] 10A and 10B are a mean power distribution diagram and an astigmatism distribution diagram created based on the optical characteristics obtained by optimization calculation of design A' in Example 1-3. [Figure 11] A comparison graph of cross-sectional aberrations of the characteristics of the thick line in the comparison graph of Figure 8, with the new evaluation of design A' in Figure 10. [Figure 12] 10A and 10B are a mean power distribution diagram and an astigmatism distribution diagram created based on the optical characteristics obtained by optimization calculation of design A′ in Example 2. [Figure 13] A comparison graph of cross-sectional aberrations of the characteristics of the thick line in the comparison graph of Figure 8 compared to the new evaluation of design A' in Figure 12. [Figure 14] FIG. 10 is an explanatory diagram illustrating the cross-sectional direction of a comparison graph of cross-sectional aberration. [Figure 15] A graph showing 180 degrees (π), which is the wavelength of a periodic function of a cosine curve, as a characteristic obtained based on the results of a visual characteristic test conducted on a certain number of subjects. [Figure 16] A graph showing the difference in visual acuity (appearance) between aberrations along the parallel axis and aberrations along the diagonal axis. DETAILED DESCRIPTION OF THE INVENTION

[0020] A method for designing the lens surface of a progressive power lens according to an embodiment of the present invention will now be described. 1. Design target values The design target values ​​are the coordinates of the evaluation points on the lens XY plane perpendicular to the lens optical axis, and the M and J values ​​at each evaluation point according to JCC. 00 ,J 45 In the following Example 1, a correction process is performed in which a predetermined weight w is given to the C frequency of the design target value. The weight w will be explained in detail in "4. Calculation of Correction Value" below. The design target value indicates the optical performance at the evaluation point, and since the design target value has a nonlinear relationship with the lens surface shape of the progressive addition lens, it is unclear what kind of lens surface shape will show optical performance that approximates the design target value. Therefore, the progressive sag at the evaluation point is changed little by little, and the following ray tracing simulation is performed each time, to find the optical performance of the design simulation value at each evaluation point.

[0021] 2. Ray tracing simulation In this embodiment The ray tracing method is performed when the progressive sag value of the evaluation point is changed through simulation by a calculation computer (not shown), and the optical performance of the design simulation value is obtained. In the ray tracing method, calculations are performed using a ray tracing function. Ray tracing functions are prepared depending on the purpose (for evaluating parallel light, for evaluating light normal to the back surface, for evaluating transmitted light). In this embodiment, a ray tracing function for evaluating transmitted light is used. Processing methods using ray tracing functions are well known, so the following will only provide an overview of them. 1) The vertex of the lens surface is set as the origin, and the coordinates of the object point in the virtual three-dimensional space are defined. 2) Define the coordinates of the center of rotation of the eyeball (Ex, Ey) in the virtual three-dimensional space. 3) Calculate the angle of incidence of the chief ray that emanates from the object point coordinates and passes through the lens evaluation point (Xn, Yn) and the eyeball rotation center point (Ex, Ey). 4) Consider the pair of secondary rays surrounding the principal ray, and find the intersection of the secondary rays. Then calculate the reciprocal of the visual distance from the rear surface of the lens to the intersection as the power. 5) Repeat the above calculations for the angle of the secondary ray from 0 to 360 degrees in 1-degree steps, and find the most positive and most negative powers, as well as the angle at the most positive power. Most accurate power (the most positive power) ... S power Most negative power (the most negative power)... S+C power Angle at most correct degree … AX and C power is calculated as the most negative power - the most positive power. In Example 2 below, a correction process is performed in which a predetermined weight w is assigned to the C power obtained at this stage. In "3. Regarding optimization calculations" below, the C power data is calculated using a numerical value to which the weight w is assigned. The weight w will be explained in detail in "4. Regarding calculation of correction values" below.

[0022] 3. Optimization calculation An optimization calculation is performed by a calculation computer (not shown) using the optical performance of the design target value and the optical performance of the design simulation value. In the method of this embodiment, the progressive sag value of the evaluation point is changed little by little, ray tracing is performed while changing the value, and an objective function is set to calculate and sum the squared difference between the optical characteristic data of the obtained design simulation value and the optical characteristic data of the design target value, and an optimization calculation is performed to determine the progressive sag value. In this embodiment, the damped least squares method is used as the optimization method. Since the damped least squares method is well known, only an outline of it will be described below. In the damped least squares method, the following equation (4) expressed as a vector is used as the general formula for the objective function. In equation (4), the linear system is set as Ax=b. A is an m×n matrix, x is the progressive sag vector, and b is the optical performance vector of the design target value. m is the M, J at the evaluation point. 00 ,J 45 is the optical characteristic data, and n is the progressive sag data at the evaluation point. λ in Equation 4 is a damping factor specific to the damped least squares method, and is a non-negative coefficient for controlling the regularization term. The normal equation of equation 5 is derived by solving the partial differential calculation of ∂J / ∂x=0 for the objective function, and the progressive sag value x is calculated using equation 6 based on equation 5. The progressive sag value x is changed little by little and calculations are performed, and if a preset convergence criterion is met at a certain stage, the progressive sag value x at that stage is the final value. If the convergence criterion is not met, λ is adjusted and the progressive sag value x is calculated again based on equation 6 until the condition is met. LU decomposition is used to calculate equation 6. By performing the ray tracing simulation in step 2 for the final solution of the progressive sag value x, the optical characteristics of the S power, C power, and AX at each evaluation point are determined. Based on these optical characteristics at the evaluation points, an average power distribution chart and an astigmatism distribution chart are created to evaluate the design.

[0023]

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[0024]

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[0025]

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[0026] 4. Calculation of correction values In the above sections "1. Design Target Values" and "2. Ray Tracing Simulation," we mentioned that a correction process is performed to assign a predetermined weight w to the C power. Here, we will explain the weight w assigned to the C power. This weight w is a correction value that reflects the weight of visibility, with the axial angle of the aberration component as a parameter, on the magnitude of the aberration component. Equation 7 is a formula for calculating the weight w. Equation 8 is a formula for expressing the C power (C') after the weight w is applied to the C power and correction processing is performed. In this embodiment, the weight for visibility is set to a maximum of 1.8, and if the axis of astigmatism in each evaluation value is the parallel axis or the vertical axis, a weight of 1.8 is applied, and if it is the oblique axis, a weight of 1.0 is applied. The calculation computer performs calculations using C' to which the weight w corrected in "1. Regarding design target values" in Example 1 and in "2. Regarding ray tracing simulation" in Example 2 is applied.

[0027]

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[0028]

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[0029] 5. Specific Examples Below, we will explain examples designed using the method of the above embodiment. A progressive-power lens with design A to which weight w is not applied is designed, and average power distribution charts and astigmatism distribution charts are created and evaluated for examples 1 and 2 in which weight w is applied to design A as a comparative example. Figure 1 shows the average power distribution and astigmatism distribution for design A, a conventional design in which weighting w is not applied (i.e., the axial direction of astigmatism is not taken into consideration). The design concept of design A is to ensure symmetrical optical performance on the ear and nasal sides. (However, the entire progressive surface is rotated by -0.15 radians to provide an inset.) However, if we correct the C power for such design A using equations 6 and 7 to create an average power distribution diagram and an astigmatism distribution diagram, we get Figure 2. In other words, Figure 2 is an average power distribution diagram and an astigmatism distribution diagram in which the optical characteristics of design A have been weighted to reflect actual vision. Here, the average power distribution diagrams and astigmatism distribution diagrams of Figures 1 and 2 are evaluated; the former is referred to as the "conventional evaluation of design A," and the latter as the "new evaluation of design A." Here, the "new evaluation" refers to a design in which weights for ease of vision or difficulty of vision are assigned, with the axial angle of the aberration component used as a parameter, in order to reflect actual vision. The "conventional evaluation" refers to a design that was evaluated without taking such weights into account. Figure 3 is a comparative graph of cross-sectional aberrations comparing the cross-sectional aberrations for the conventional design A evaluation and the new design A evaluation, with the horizontal axis representing the distance from the center and the vertical axis representing the amount of astigmatism. As shown in Figure 14, the cross-sectional direction was a direction tilted by -0.15 radians from the horizontal cross section at Y=14.0 mm. This cross-sectional direction is also the same for the comparative graphs of cross-sectional aberrations in the following examples. In the comparative graph of cross-sectional aberrations in Figure 3, the conventional design A evaluation is shown with a dashed line, and the new design A evaluation is shown with a solid line.

[0030] As can be seen from Figure 3, in the new evaluation of Design A, which reflects actual vision, the symmetry of optical performance on the ear side and nasal side is broken in both the average power distribution diagram and the astigmatism distribution diagram, and it is clear that the shape of Design A does not fulfill the original design concept (symmetrical optical performance on the ear side and nasal side). In the new evaluation of Design A, the C power on the nasal side has increased in the astigmatism distribution diagram, and because the C power is 1.4 times greater on average, the overall amount of aberration also increases. Furthermore, because the average power is S + C / 2, this is also affected by the C power and is evaluated as having broken symmetry on the ear side and nasal side. Therefore, designing to aim for design A', which takes into consideration the axial direction of astigmatism (i.e., gives weight w), which indicates optical characteristics in which the optical performance on the ear side and the nasal side is symmetrical, as shown in Figure 1 of design A, will be in line with the original design concept of design A. In the following, designs A' with different methods of assigning weight w will be referred to as Examples 1 and 2, and the average power distribution diagram and astigmatism distribution diagram based on the optical performance obtained in accordance with the above embodiment will be evaluated.

[0031] A-1. Example 1 In Example 1, a design target value for conventional evaluation is created using the reciprocal of the weight w in "1. Regarding the design target value" in the above embodiment, and a design A' is created by performing an optimization calculation without giving the weight w to the C power in "2. Regarding the ray tracing simulation" (i.e., by a well-known ray tracing simulation). In other words, in Example 1, in anticipation of the weight w being multiplied, the design target value is the optical performance multiplied by the reciprocal of the weight w (1 / w) in a conventional ray tracing simulation. Taking the weight w as the inverse means multiplying the C power of design A by the inverse (1 / w) in equation 7 and replacing it with C'. As a result, the design target value of design A' is modified so that when AX = 45 degrees, 135 degrees of oblique astigmatism in the conventional evaluation, the conventional C power is 1.0 / 1.8 times, and when AX = 0 degrees, 90 degrees of straight and inverted astigmatism, the conventional C power (1.0 times) is obtained. Figure 4 shows the average power distribution and astigmatism distribution of this design target value of design A'. This is none other than the characteristics of the new evaluation of design A, shown by the solid line in Figure 3. Fig. 5 shows an average power distribution chart and an astigmatism distribution chart created based on the design target values ​​of this design A', based on optical characteristics obtained by well-known ray tracing simulations and optimization calculations. Fig. 6 also shows a comparison graph of cross-sectional aberrations, in which the new design A' evaluation of Example 1 is shown with a thick solid line in addition to the conventional design A evaluation and new design A evaluation. Fig. 6 reveals that the new design A' evaluation has improved symmetry compared to the conventional design A evaluation and new design A evaluation of Fig. 3 above.

[0032] A-2. Example 1-2 Example 1-2 is a modification of the "design target value of the conventional evaluation using the reciprocal of the weight of the new evaluation" in Example 1. In Example 1, the C power of the conventional evaluation of design A was corrected to the C power multiplied by the reciprocal of Equation 6 as the design target value, but in Example 1-2, the design target value is corrected by performing the following processing. (1) The S, C, and AX of the conventional evaluation of Design A are once evaluated as M and J by JCC. 00 ,J 45 Convert to. (2) Next, J 00 and J 45 Multiply the inverse of the formula for number 7 only, M, J 00 ',J 45 'Let's say. (3) Convert the values ​​back to S, C, and AX to obtain S', C', and AX'. (4) Replace S', C', AX' with S, C, AX. The design target value of Example 1 does not include any change in the S power, whereas in Example 1-2, a change is also made to the S power. FIG. 7 shows an average power distribution chart and an astigmatism distribution chart created based on the design target value of such design A', based on the optical characteristics obtained by well-known ray tracing simulation and optimization calculation. 8 shows a comparison graph of cross-sectional aberrations in which the new design A' evaluation of Example 1-2 is indicated by a thick solid line instead of the new design A' evaluation of Example 1-2 in FIG. 6. As can be seen from FIG. 8, the position of the maximum aberration (most negative value) in Example 1-2 has shifted to the periphery of the lens compared to Example 1, and is closer to the theoretical new evaluation value of the target data (FIG. 1). The improvement in symmetry is almost the same as in Example 1.

[0033] A-3. Regarding Examples 1-3 In Example 1-3, the "design target value of the conventional evaluation, which is the reciprocal of the weight of the new evaluation" in Example 1 is also modified. In Example 1-3, the reciprocal (1 / w') of the following equation (9) is used instead of the reciprocal (1 / w) of equation (7) in Example 1-2. The characteristics of the weight w' in this equation are as shown in the graph in FIG.

[0034]

number

[0035] In the formula (7), the C power was 1.4 times the conventional power on average, but in the formula (9), it was 1.0 times the conventional power on average. Example 1-3 was designed with the idea that by making the total amount of aberration in the lens uniform compared to the conventional evaluation, the aberration distribution would be improved in the optimization calculation. Fig. 10 shows an average power distribution diagram and an astigmatism distribution diagram created based on the design target values ​​of this design A', based on optical characteristics obtained by well-known ray tracing simulation and optimization calculation. Fig. 11 also shows a comparative graph of cross-sectional aberrations, in which the new evaluation of design A' of example 1-3 is shown with a thick solid line instead of the new evaluation of design A' of example 1-2 in Fig. 6. The results of Fig. 11 show that, among the examples used this time, the new evaluation (design that reflects actual vision) showed the greatest improvement in symmetry.

[0036] B. Example 2 In Example 2, design A' was created by using the design target values ​​from the conventional evaluation in "1. Regarding design target values" in the above embodiment, and performing optimization calculations using the C power with weight w in "2. Regarding ray tracing simulation." In "2. Ray tracing simulation", the value of C power calculated by the ray tracing method is corrected by applying the formulas 6 and 7. Fig. 12 shows an average power distribution chart and an astigmatism distribution chart created based on the optical characteristics obtained by a correction ray tracing simulation and optimization calculation using a C power corrected according to this design concept. As a comparison diagram of cross-sectional aberration corresponding to Fig. 5, Fig. 13 shows a comparison graph of cross-sectional aberration in which the new design A' evaluation of Example 2 is indicated by a thick solid line in addition to the conventional design A evaluation and the new design A evaluation. Example 2 did not achieve as great an improvement in symmetry as Example 1.

[0037] The present embodiment and examples have the above-described configuration and thus provide the following effects. (1) In designing the lens surface of a progressive-power lens, when calculating a design simulation value by optimization calculation so as to approach the optical performance of the design target value, by performing optimization calculation by applying a correction value to at least one of the design target value and a function used in ray tracing, which is a weight that reflects the difference in the appearance of the aberration component of astigmatism in the axial direction, to the magnitude of the aberration component, it is possible to design a lens surface of a progressive-power lens that reflects the actual appearance. (2) The initial design concept (symmetrical optical performance on the ear and nose sides), which did not reflect actual vision, was designed to be reflected in design A', which reflects actual vision. Therefore, even if the optical characteristics are different, it is possible to design in accordance with the original design concept.

[0038] The above-described embodiment has been described merely as a specific embodiment for illustrating the principles and concepts of the present invention. In other words, the present invention is not limited to the above-described embodiment. The present invention can also be embodied in the following modified forms, for example. In the calculations of the above embodiment, the parameter of the weight w was determined so that the maximum weight would be 1.8 as shown in Equation 7, but the weight value can be changed as appropriate. Also, in the above, the weight was given by multiplying the aberration value of the original evaluation point, but it may also be given by other arithmetic operations, or a nonlinear weight may also be given. In the above embodiments, correction is performed to give weight to the design target value in embodiment 1, and correction is performed to give weight to the ray tracing simulation in embodiment 2. In other words, one correction process is performed on the entire calculation, but for example, correction to give weight to the design target value may also be performed in embodiment 2. In the above embodiment, visibility is used as a measure of weighting, but it is also possible to use visibility as a measure for calculation. The present invention is not limited to the configurations described in the above embodiments. The components of each embodiment and variation may be arbitrarily selected and combined. Furthermore, any component of each embodiment or variation may be arbitrarily combined with any component described in the Summary of the Invention, or any component embodying any component described in the Summary of the Invention. The present invention also intends to obtain rights to these by filing an amendment or divisional application of this application. Furthermore, the applicant intends to obtain rights to the overall design or partial design by filing a conversion application to a design application. The drawings depict the entire device in solid lines, but they also include partial designs claimed for parts of the device. For example, a partial design may be a partial design for a part of the device, or a partial design may be included for a part of the device regardless of the part. A partial design may be a part of the device, or a part of that part.

Claims

1. A method for designing a lens surface of a progressive addition lens, comprising: repeatedly performing a ray tracing simulation while changing the shape of the lens surface at evaluation points distributed on the lens surface of the progressive addition lens so as to approach the optical performance of a design target value, obtaining the optical performance of a design simulation value; and determining, by optimization calculation, the shape of the progressive addition lens such that the optical performance of the design simulation value approximates the optical performance of the design target value, a method for designing a lens surface of a progressive power lens, comprising: obtaining an axial direction of an aberration component having an angle in the range of 0 to 180 degrees for each evaluation point; obtaining a correction value that reflects a weight of visibility or difficulty in visibility, using the angle of the axial direction of the aberration component as a parameter, on the magnitude of the aberration component; and applying the obtained correction value to at least one of the design target value and a function used in ray tracing to calculate the design simulation value in optimization calculation.

2. 2. The method for designing a lens surface of a progressive power lens according to claim 1, wherein an optical performance distribution is obtained using the optical performance of the design simulation value calculated by applying the correction value.

3. 3. The method for designing a lens surface of a progressive power lens according to claim 2, wherein the optical performance distribution of the design simulation value calculated by applying the correction value is designed to be an optical performance distribution that is close to the optical performance distribution of the design target value to which the correction value is not applied.

4. 3. The method for designing a lens surface of a progressive power lens according to claim 1, wherein the weight is set to be maximum or minimum when the axial direction of the aberration component is 45 degrees or 135 degrees, and conversely to be minimum or maximum when the axial direction is 0 degrees or 90 degrees.

5. 3. The method for designing a lens surface of a progressive power lens according to claim 1, wherein the weight is set to be maximum or minimum when the axial angle of the aberration component is 0 degrees, 90 degrees or 180 degrees, and conversely to be minimum or maximum when the axial angle of the aberration component is other than 0 degrees, 90 degrees or 180 degrees.

6. 3. The method for designing a lens surface of a progressive power lens according to claim 1, wherein the weight is w and the coefficients are a, b, ω, and α, and the design method is expressed by the following formula or a formula equivalent to the following formula: [Equation 1]

7. 7. The method for designing a lens surface of a progressive power lens according to claim 6, wherein the weight is expressed by the following formula or a formula equivalent to the following formula when the weight is w: [Equation 2]

8. 8. The method for designing a lens surface of a progressive power lens according to claim 7, wherein the weight has a maximum or minimum value of 1.1 to 2.0.

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