Free-form surface single-focus hyperopia correction lens and design method

Abstract

The present application belongs to the field of ophthalmology, and proposes a free-form single-focus hyperopia correction lens and a design method. First, the radial distance from the edge point of the hyperopia correction lens in each direction to the center of the pupil is calculated; then, based on the monocular hypercyclic surface prescription and surface design parameters, the diopter value of the hyperopia correction lens in each direction is used to calculate the sagittal difference between the outer surface and the inner surface of the hyperopia correction lens in each direction, and the maximum sagittal difference is found from the sagittal difference. The minimum center thickness of the hyperopia correction lens is equal to the maximum sagittal difference plus the minimum edge thickness; the radial distance in each direction of the frame is added with the cutting margin, and the edge thickness before cutting in each direction is verified. If the minimum value of the edge thickness in each direction is greater than or equal to the set value, the center thickness remains unchanged; otherwise, the edge thickness here is set to the set value, and then the center thickness is recalculated in combination with the sagittal of the outer surface and the inner surface here. The center thickness and edge thickness of the lens of the present application are significantly reduced, and have a better light and thin effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of ophthalmology, and in particular relates to a lens for vision correction and a design method thereof. Background Art

[0002] To reduce the center thickness and weight of hyperopic lenses, custom-made, shrink lenses with a minimum edge thickness of 0.5mm before trimming are often used. A free-form surface is used on the inner surface of the lens. The center thickness is calculated based on the wearer's prescription, frame data, and lens profile data. This shrink lens matches the frame shape and significantly reduces the center thickness compared to mold-cast lenses with an edge thickness of no less than 1.1mm and a fixed diameter of 65mm or 70mm. However, the edge thickness of these custom-made shrink lenses for internal astigmatism is calculated using a diameter that includes the maximum radial dimension of the frame and the trimming allowance, located on the base curve cross-section of the inner surface. Based on the relationship between surface sag, center thickness, and edge thickness, the calculated center thickness is significantly greater when the base curve is located farther from the maximum radial dimension of the frame. This results in an excessively thick edge thickness in the finished lens after trimming, thus failing to achieve optimal lens thinning. This increases the lens weight and compromises wearer comfort. Summary of the Invention

[0003] In order to solve the problems raised in the above background technology, the technical solution of the present invention is:

[0004] A method for designing a free-form surface single-focus hyperopia correction lens, wherein the hyperopia correction lens is a positive lens with an astigmatism correction surface on the inner surface, the inner surface is located on the eye side, and the outer surface is arranged opposite to the inner surface; the outer surface is spherical or aspherical, and the inner surface is a toroidal surface. The design method comprises the following steps:

[0005] St1. First, calculate the radial distance from each edge of the hyperopia correction lens to the pupil center based on the individual pupillary distance, pupil height, selected frame coordinates, and nose bridge width data in the prescription.

[0006] St2. Based on the monocular toric prescription and face shape design parameters, calculate the sagittal difference between the outer and inner surfaces of the hyperopia correction lens in each direction using the diopter values of the hyperopia correction lens in each direction. From these sagittal differences, find the maximum sagittal difference. The minimum center thickness of the hyperopia correction lens is equal to the maximum sagittal difference plus the minimum edge thickness. Add the trimming allowance to the radial distance in each direction of the frame and calculate the edge thickness in each direction before trimming. If the minimum edge thickness in each direction is greater than or equal to the set value, the center thickness remains unchanged. Otherwise, set the edge thickness at the set value and recalculate the center thickness based on the sagittal difference between the outer and inner surfaces at that location.

[0007] St3, use the center thickness obtained by the above method as a parameter to customize the edge grinding of the hyperopia lens in the laboratory.

[0008] Preferably, the frame coordinate data in St1 includes: the shape, size and nose bridge width data of the inner frame; obtained by scanning the frame or by pre-stored frame coordinate data; the frame coordinate data is the polar coordinate data of the edge point of the inner frame of the frame (ρ i ,θ i ), i = 1°, 2°, ..., 360°; ρ represents the distance from the edge point of the inner frame of the frame to the polar coordinate pole, θ represents the angle of the ray connecting the edge point of the inner frame of the frame to the pole relative to the polar axis; the position of the polar coordinate pole is related to the accuracy of the placement of the frame, and the pole position is set at the geometric center of the inner frame of the frame, that is, the intersection of the half-height and half-width lines of the inner frame of the frame.

[0009] More specifically, the steps of calculating the radial distances from the edge points of the hyperopia correction lens in each direction to the pupil center in St1 include:

[0010] St1.1, the polar coordinate data of the inner edge point of the selected eyeglass frame (ρ i ,θ i ), i=1°, 2°, ..., 360°, converted into rectangular coordinate data (X i ,Y i ), i=1,2,…,360, where X i Indicates the horizontal coordinate value of the edge point, Y i Indicates the vertical coordinate value of the edge point. The conversion formula is as follows:

[0011] X i =ρ i cosθ i ,i=1°,2°,…,360° (1)

[0012] Y i =ρ i sinθ i ,i=1°,2°,…,360° (2)

[0013] St1.2, based on the left eye independent pupil distance LPD or right eye independent pupil distance RPD, pupil height PH, and the nose bridge width DBL of the selected frame, calculate the position of the pupil center point on the frame rectangular coordinate system (X0, Y0) using the following formula:

[0014] Y0=min(Y i )+PH,i=1,2,…,360 (3)

[0015] Left eye:

[0016] Right eye:

[0017] Where, min(Y i ) means finding the minimum value from all Y coordinate data of the edge points of the frame, max(X i ) means to find the maximum value from all X coordinate data of the edge points of the frame, min(X i ) means finding the minimum value from all X coordinate data of the edge points of the frame;

[0018] St1.3, calculate the radial distance ρ from the edge of the frame in each direction to the pupil center i ;

[0019] According to the pupil center coordinates (X0, Y0), the pupil center position is translated to the coordinate origin, and the frame edge point coordinates become (N xi , N yi ), i = 1, 2, ..., 360; find the radial distance ρ from the edge of the frame to the center of the pupil in each direction i , i=1,2,…,360, the calculation formula is as follows:

[0020] N xi =X i -X0, i=1,2,…,360(6)

[0021] N yi =Y i -Y0, i=1,2,…,360(7)

[0022]

[0023] In more detail, St2 determines the center thickness of the hyperopia corrective lens including the following steps:

[0024] St2.1, rewrite the wearer's sphero-cylindrical prescription into a negative internal diffuse lens prescription. After the conversion, the outer surface of the lens is spherical or aspherical, and the inner surface is designed as a toroidal surface;

[0025] St2.2, based on the negative inner diffuser prescription and the inner surface shape design requirements, determine the inner surface refractive power F in all directions of the circumference. i ; Based on the negative inner dispersion prescription and the refractive index of the lens, calculate the radius of curvature R1 of the outer surface of the lens;

[0026] St2.3, the radial distance ρ from the edge of the frame to the pupil center obtained according to St1.3 i , the outer surface spherical radius R1 and the refractive power F of the inner surface in all directions obtained by St2.2 i , and the surface shape data of the inner surface, calculate the outer surface sagittal height S1 of the edge points of the frame in all directionsi and inner surface height S2 i According to the relationship between the inner and outer surface sagitta, edge thickness and center thickness, from S1 i -S2 i Find the maximum value in , plus the minimum edge thickness e min , which is the minimum center thickness t of the hyperopia correction lens min ;

[0027] t min =max(S1 i -S2 i )+e min , i=1,2,…,360

[0028] St2.4, radial distance ρ in all directions at the edge of the lens i Add the cutting allowance r0 and calculate the edge thickness e before cutting i Is it greater than or equal to the set value e0? If not, the center thickness needs to be increased to meet e i The minimum value is equal to e0; increase the radial distance from the edge of the lens to the center of the pupil to ρ i +r0, recalculate the sagitta of the inner and outer surfaces and Then, the edge thickness e is calculated based on the relationship between the inner and outer surface sagittal heights, edge thickness and center thickness. i , and find the minimum value; if the minimum value at this time is greater than or equal to e0, the minimum center thickness t min unchanged; if the minimum value is less than e0, set the edge thickness in this direction (set as m direction) to e0 and calculate the new center thickness of the lens The calculation formula is as follows:

[0029]

[0030] From e i Find the minimum value. If the minimum value is greater than or equal to the set value e0, the minimum center thickness t min unchanged; if the minimum value is less than the set value e0, let i=m at that location, then the new center thickness The calculation formula is as follows:

[0031]

[0032] St3, use the minimum center thickness t obtained in St2 min or The center thickness of the hyperopia correction lens is used for custom edge grinding of the hyperopia lens.

[0033] The preferred r0≤1.2mm, 0.5mm≤e min≤0.8mm, 0.3mm≤e0≤0.6mm.

[0034] Using the lenses obtained in this application, the radial dimensions of the frame, with the pupil center as the origin, are used as the criterion for calculating edge thickness. The sagittal heights of the inner and outer surfaces are calculated using the actual diopter values in each direction of the lens. The sagittal height difference that produces the minimum edge thickness is then determined, ultimately yielding the minimum center thickness. Compared to comparable, custom-made, shrink-lens lenses, the lenses of this invention exhibit significantly reduced center and edge thicknesses, achieving maximum lens thickness reduction while meeting the minimum edge thickness requirement for hyperopia correction lenses. Similarly, the volume and weight of the lenses are also significantly reduced compared to existing shrink-lens lenses, resulting in an optimally lightweight, thin, and aesthetically pleasing finished lens, enhancing wearer comfort.

[0035] The method for designing a free-form surface monofocal custom-made astigmatic lens for hyperopia correction can accurately locate the minimum edge thickness of the lens when the wearer's monocular independent pupil distance, nose bridge width, frame data, prescription, and facial shape parameters are determined to meet process requirements, and then determine the minimum center thickness of the lens, so that the finished lens has the optimal lightness, beauty, and thinness effect.

[0036] The method for designing a free-form surface single-focus astigmatism lens for hyperopia correction is described. The minimum edge thickness of the free-form surface lens obtained according to this method appears at or near the maximum radius position of the frame centered on the pupil, indicating that the radius of the frame centered on the pupil is the main factor affecting the calculation of the center thickness, followed by the refractive power in various directions of the inner and outer surfaces of the lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is the shape diagram of the left eye frame of the glasses;

[0038] Figure 2 A schematic diagram of the relative positions of the human eye data and the frame;

[0039] Figure 3 This is an optical "cross" diagram of the conversion of the spherocylinder prescription in Example 1 into a negative inner dispersion prescription;

[0040] Figure 4 Schematic diagram comparing the edge thickness of the finished lens of the present invention and the comparative lens in Example 1;

[0041] Figure 5 Schematic diagram of the minimum edge thickness position of the lens of the present invention and the comparative lens in Example 1;

[0042] Figure 6 This is the shape diagram of the right eye frame of the glasses;

[0043] Figure 7Schematic diagram comparing the edge thickness of the lens of the present invention and the comparative lens after edge cutting in Example 2;

[0044] Figure 8 Schematic diagram of the minimum edge thickness position of the lens of the present invention and the comparison lens in Example 2. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present invention are described clearly and completely below.

[0046] Example 1

[0047] A wearer's left eye has a sphero-cylindrical prescription of S+4.00D and C-2.00D, with the cylinder direction at 90° vertical. The wearer's left eye has an independent pupil distance (LPD) of 33mm, a nose bridge width (DBL) of 18mm, and a pupil height (PH) of 22mm. Polar coordinate data for edge points of the selected frame type are shown in Table 1. A free-form surface monofocal hyperopia correction lens for hyperopia correction is designed according to the method of the present invention. The lens center thickness is required to meet a minimum edge thickness of 0.5mm after trimming, and the edge thickness after adding a 1mm trimming allowance to the radial distance in all directions of the lens is greater than or equal to 0.3mm. If the latter condition is not met, the center thickness can be appropriately increased to achieve a minimum edge thickness of 0.3mm.

[0048] The design steps include:

[0049] St1, calculate the radial distance ρ from the edge points of the hyperopia correction lens in each direction to the pupil center i ;

[0050] St1.1, the polar coordinate data (ρ i ,θ i ), i=1°, 2°, ..., 360°, converted into rectangular coordinate data (X i , Y i ), i = 1, 2, ..., 360; where ρ represents the distance from the edge point of the frame to the polar coordinate pole, and θ represents the angle of the ray connecting the edge point to the pole relative to the polar axis; in the embodiment, the pole is located at the geometric center of the frame by default; X i Indicates the horizontal coordinate value of the edge point, Y i Indicates the vertical coordinate value of the edge point. The conversion formula is as follows:

[0051] X i =ρ i cosθ i , i=1°,2°,…,360°

[0052] Y i =ρ i sinθi , i=1°,2°,…,360°

[0053] Draw a frame diagram based on the above rectangular coordinate data, such as Figure 1 As shown, the position of X=0, Y=0 in the figure is the origin of the rectangular coordinate system;

[0054] St1.2, based on the left eye independent pupil distance LPD, pupil height PH, and the nose bridge width DBL of the selected frame, the position of the pupil center point of the frame in the rectangular coordinate system (X0, Y0) is calculated as follows:

[0055] Y0=min(Y i )+PH=-21.24+22=0.76mm,i=1,2,…,360

[0056] Left eye:

[0057] Where, min(Y i ) means finding the minimum value from all Y coordinate data of the edge points of the frame, man(X i ) means finding the maximum value from all X coordinate data of the edge points of the frame; Figure 2 This is a schematic diagram of human eye data and frame position;

[0058] St1.3, calculate the radial distance ρ from the edge of the frame in each direction to the pupil center i . Calculate the rectangular coordinates (N) of the edge of the frame using the pupil center (X0, Y0) as the coordinate origin. xi , N yi ), and then calculate the radial distance ρ from the edge of the frame to the center of the pupil in each direction i , i=1,2,…,360, the calculation formula is as follows:

[0059] N xi =X i -X0, i=1,2,…,360

[0060] N yi =Y i -Y0, i=1,2,…,360

[0061]

[0062] Among them, N xi Indicates the horizontal coordinate value of the edge point of the frame after coordinate translation; N yi Indicates the vertical coordinate value of the edge point of the frame after coordinate translation.

[0063] To facilitate subsequent comparison, the radial distance ρ i Find the maximum value ρ inmax :

[0064] ρ max =max(ρ i )=29.76mm,i=1,2,…,360

[0065] ρ max Add the cutting margin r0 (=1mm) and the maximum radius r before cutting the lens max :

[0066] r max =ρ max +1=30.76mm

[0067] St2, determine the center thickness t of the hyperopia correction lens min ;

[0068] St2.1, rewrite the wearer's spherical cylindrical lens prescription into a negative internal dispersion lens prescription; after conversion, the outer surface of the lens is designed to be spherical, with a refractive power of +5.00DS; the inner surface is a toroidal surface, with a base curve axially 180°, a high-order aspheric curve shape, and a refractive power of -1.00DC, and an orthogonal curve axially 90°, a parabola shape, and a refractive power of -3.00DC. The converted negative internal dispersion lens prescription is:

[0069]

[0070] The above conversion is represented by an optical "cross" diagram, such as Figure 3 , the left side of the equal sign in the figure is the original sphero-cylindrical lens prescription, and the right side is the lens prescription in the form of negative internal dispersion;

[0071] St2.2, calculate the refractive power F of the inner surface of the hyperopia correction lens in all circumferential directions i And the spherical radius R1 of the outer surface of the lens.

[0072] In this example, the diopter on the inner surface of the lens from the base curve to the orthogonal arc is designed to change continuously, and the absolute value of the diopter in each direction is expressed by the polar diameter r of an ellipse under polar coordinates. i Indicates that the length of the minor axis of the ellipse is the absolute value of the base arc diopter (-1.00DC) (i.e. a = 1), the length of the major axis of the ellipse is the absolute value of the orthogonal arc diopter (-3.00DC) (i.e. b = 3), the minor axis direction of the ellipse is in the diopter direction of the base arc (γ = 90°), and the distance r from each point on the ellipse to the pole is i (Polar diameter) represents the absolute value of the diopter in each direction. After adding the minus sign, the diopter F in each direction of the inner surface of the lens is obtained. i , the calculation formula is as follows:

[0073]

[0074] Substituting the parameters into

[0075] The outer spherical radius R1 is calculated from the outer spherical power (F1 = +5.00DS) and the refractive index of the lens material (n = 1.56) using the following formula:

[0076]

[0077] St2.3, determine the minimum center thickness t of the hyperopia correction lens min ; According to St1.3, the radial distance ρ from the edge of the frame to the center of the pupil i , the outer surface spherical radius R1 and the refractive power F of the inner surface in all directions obtained by St2.2 i , and the surface shape data of the inner surface, calculate the outer surface sagittal height S1 of the edge points of the frame in all directions i and inner surface height S2 i According to the relationship between the inner and outer surface sagitta, edge thickness and center thickness, from S1 i -S2 i Find the maximum value in , plus the minimum edge thickness e min (=0.5mm), which is the minimum center thickness t of the hyperopia correction lens min ; Here, it can also be understood as from S2 i -S1 i Find the minimum value, plus the minimum center thickness t min , which is the minimum edge thickness e min (=0.5mm);

[0078] The calculation formula of the outer surface sagitta is:

[0079]

[0080] The calculation formula of the inner surface sagittal height is:

[0081]

[0082] Where k is the cone coefficient, a j is the high-order aspheric coefficient. In this example, k = 0, a2 = 5.20e-07, a3 = -5e-11, and the other coefficients are 0. i is the vertex curvature of the curve in each direction of the circumference, c i =1 / R i , R i The calculation formula is as follows:

[0083]

[0084] Where, F iThe refractive power in each direction of the inner surface of the lens obtained by St2.2.

[0085] According to the relationship between the sagittal height of the inner and outer surfaces of the lens, the edge thickness and the center thickness, from S1 i -S2 i Find the maximum value in , plus the minimum edge thickness e min , which is the minimum center thickness t of the hyperopia correction lens min , the calculation formula is as follows:

[0086] t min =max(S1 i -S2 i )+e min , i=1,2,…,360

[0087] According to calculation, S1 i -S2 i The maximum value occurs on the frame with radial dimension ρ max , i = 161, and

[0088] max(S1 i -S2 i )=2.46mm

[0089] Add e min value (=0.5mm), that is, the minimum edge thickness e min Appears on the frame with a radial dimension of ρ max The position of

[0090] t min =max(S1 i -S2 i )+0.5=2.46+0.5=2.96mm

[0091] St2.4, radial distance ρ in all directions at the edge of the lens i Add the cutting allowance r0 (=1mm) and calculate the edge thickness e before cutting. i Is it greater than or equal to the set value e0 (= 0.3mm)? If not, increase the center thickness to meet e i The minimum value is equal to 0.3mm. Increase the radial distance from the edge of the lens to the center of the pupil to ρ i +1, recalculate the sagitta of the inner and outer surfaces and Then, the edge thickness e is calculated based on the relationship between the inner and outer surface sagittal heights, edge thickness and center thickness. i , and find the minimum value; if e i The minimum value is greater than or equal to 0.3mm, and the minimum center thickness t min unchanged; if ei The minimum value is less than 0.3mm, and the e i The edge thickness of the position with the minimum value (i=m) is set to 0.3mm, and the new center thickness of the lens is calculated The calculation formula is as follows:

[0092] The calculation formula of the outer surface sagitta is:

[0093]

[0094] The calculation formula of the inner surface sagittal height is:

[0095]

[0096] The edge thickness calculation formula is:

[0097]

[0098] From e i Find the minimum value. If the minimum value is greater than or equal to the set value e0, the minimum center thickness t min If the minimum value is less than the set value e0, then let i=m at that location, and the new center thickness is The calculation formula is as follows:

[0099]

[0100] In this embodiment, e i The minimum value of is 0.37mm, which is greater than e0 (=0.3mm), so the minimum center thickness remains unchanged, t min =2.96mm.

[0101] In order to illustrate the thinning effect of this patent, based on the same prescription, frame and face shape data, a comparison is made with the garage-customized shrink lens whose radial dimensions used to calculate the center thickness mentioned in the "Background Technology" include the maximum radial dimensions of the frame and the cutting edge allowance.

[0102] Because the human eye data and the frame data are the same, the maximum radius of the customized shrink lens of the garage is the same as the maximum radius r before cutting edge of the present invention. max Same, so the lens diameter D = 2 × r max =2*30.76=61.52mm.

[0103] Because the prescription and surface shape data are the same as those used in the present invention, the sagittal height S1 corresponding to the outer surface sphere is calculated. * When, from St2.2, we know that R1 is 112mm; and r max =30.76mm, then:

[0104]

[0105] Set the minimum edge thickness e at the base curve of the inner surface of the lens min is 0.5mm, and then according to the diopter F of the base curve b And the lens refractive index n get the vertex curvature radius r of the high-order aspheric curve of the inner surface base curve b , calculate the sag S corresponding to the base arc b * According to the relationship between lens sagittal height, edge thickness and center thickness, the center thickness of the hyperopic lens is t * =S1 * +e min -S b * , the specific calculation is as follows:

[0106]

[0107]

[0108] Where c is the vertex curvature, c = 1 / r b =1 / 560; r is the radial distance of the lens, where r = r max =30.76mm; k is the cone coefficient, a i In this example, k = 0, a2 = 5.20e-07, a3 = -5e-11, and the remaining coefficients are 0.

[0109] t * =S1 * +e min -S b * =3.54mm

[0110] Compared with the lens of the present invention, the difference in center thickness of the reduced lens is:

[0111] t * -t min =0.58mm

[0112] It can be seen from this that the hyperopia correction lens designed by the present invention has a center thickness reduced by 0.58mm compared to a reduced lens with a diameter of 61.52mm and a minimum edge thickness of 0.5mm at the base curve of the inner surface of the lens before cutting. The reduction ratio is 16.38%, further reducing the center thickness.

[0113] Figure 4This is a diagram of the finished lens with the center of the pupil as the origin. The edge thicknesses of the two lenses are marked at intervals of 30° on the diagram. The value inside the frame is the edge thickness of the lens of the present invention, and the value outside the frame is the edge thickness of the reduced lens used for comparison. The marked area is the position where the edge thickness is the smallest on the finished lens. The upper and lower sides of the dimension lines are the edge thickness values of the reduced lens and the lens of the present invention, respectively. It can be seen intuitively from the diagram that the edge thickness of the lens of the present invention is much smaller than that of the comparison lens. In addition, due to the reduction in center thickness, the volume and weight of the lens of the present invention will be greatly reduced compared to the original hyperopia correction lens, greatly increasing the comfort of the wearer. It should be noted that since the frame type and face shape data selected for the two lenses are exactly the same, only the center thickness is different. Therefore, the difference in edge thickness of the two lenses is equal to the difference in center thickness. The difference change shown in the diagram is caused by data rounding error.

[0114] Figure 5 The minimum edge thickness e of the shrinking lens of the present invention and the comparison lens in Example 1 when calculating the center thickness is shown. min As can be seen from the figure, the e min At the maximum radial dimension position of the frame, that is, ρ max The contrast of the shrink lens is min It is on the circle with diameter D corresponding to the base curve of the inner surface of the lens, D = 2×r max =2×(ρ max +1). When the base curve of the inner surface is exactly at the maximum radial dimension position of the frame ρ max When the radial dimension of the present invention is smaller than that of the shrink lens by only a cutting margin, the smaller radial dimension brings a smaller sagittal height difference between the inner and outer surfaces of the lens, and the final center thickness and edge thickness will also be smaller, but the difference between the two will not be too much; However, when the distance between the base curve position of the inner surface and the maximum radial dimension position of the frame is ρ max Farther away, for example Figure 5 The base arc position is shown at 90°, with the maximum radial dimension ρ max In the 161° direction (i=161), the center thickness and edge thickness are affected not only by the radial dimension but also by the variation of the sagittal height caused by the different diopters in each direction. In this case, the difference between the results of the two methods is quite large. In this example, the circle corresponding to the base curve is at a greater radial distance from the frame. If the minimum edge thickness e is determined on this circle with a diameter D, min (=0.5mm), according to the characteristics of hyperopia glasses with thick center and thin edges, the minimum edge thickness of the frame where the base curve is located after cutting will increase more than 0.5mm. Figure 4 It can be seen that the increase from 0.5 to 2.91 is nearly five times, and the minimum edge thickness of the frame is at ρ maxThe best way is to use the radial dimension of the frame with the pupil center as the origin as the condition for calculating the edge thickness, and calculate the sagitta of the inner and outer surfaces with the actual diopter value in each direction of the lens, and find the sagitta difference that produces the minimum edge thickness, and finally get the minimum center thickness t min The present invention is designed and calculated based on this idea, so that the minimum edge thickness of the finished lens is equal to the minimum value that can be achieved in the process, so that the finished lens has the best lightness, beauty and thinness effect.

[0115] Example 2

[0116] A wearer's sphero-cylindrical prescription is S+3.50D, C-1.50D, with a cylindrical direction at a 160° oblique angle. The wearer's right eye has an independent pupil distance (LPD) of 34mm, a nose bridge width (DBL) of 18mm, and a pupil height (PH) of 22mm. The polar coordinates of the inner edge points of the selected frame type are shown in Table 2. A free-form surface monofocal hyperopia correction lens for hyperopia correction is designed according to the method of the present invention. The requirements are that the center thickness of the lens satisfies a minimum edge thickness of 0.5mm after trimming, and the edge thickness of the lens in all radial directions, after adding a 1mm trimming allowance, is greater than or equal to 0.3mm. If the latter condition is not met, the center thickness can be appropriately increased to achieve a minimum edge thickness of 0.3mm.

[0117] The design steps include:

[0118] St1, calculate the radial distance ρ from the edge points of the hyperopia correction lens in each direction to the pupil center i ;

[0119] St1.1, the polar coordinate data (ρ i ,θ i ), i=1°, 2°, ..., 360°, converted into rectangular coordinate data (X i , Y i ), i=1,2,…,360; the conversion formula is as follows:

[0120] X i =ρ i cosθ i , i=1°,2°,…,360°

[0121] Y i =ρ i sinθ i , i=1°,2°,…,360°

[0122] Draw a frame diagram based on the above rectangular coordinate data, such as Figure 5As shown;

[0123] St1.2, based on the right eye independent pupil distance (RPD) and pupil height (PH) in the prescription, and the nose bridge width (DBL) of the selected frame, calculate the position of the pupil center point (X0, Y0) in the frame's rectangular coordinate system. The calculation formula is as follows:

[0124] Y0=min(Y i )+PH=-21.23+22=0.77mm,i=1,2,…,360

[0125] Right eye:

[0126] Where, min(X i ) means finding the minimum value from all X coordinate data of the edge points of the frame; Figure 2 This is a schematic diagram of human eye data and frame position;

[0127] St1.3, calculate the radial distance ρ from the edge of the frame in each direction to the pupil center i ; This part of the method is the same as Example 1;

[0128] Also, to facilitate subsequent comparison, the radial distance ρ i Find the maximum value ρ in max :

[0129] ρ max =max(ρ i )=28.94mm,i=1,2,…,360

[0130] ρ max Add the cutting margin r0 (=1mm) and the maximum radius r before cutting the lens max :

[0131] r max =ρ max +1=29.94mm

[0132] St2, determine the minimum center thickness t of the hyperopia correction lens min ;

[0133] St2.1, rewrite the wearer's spherical cylindrical lens prescription into a negative internal dispersion lens prescription; after conversion, the outer surface of the lens is designed to be spherical, with a refractive power of +4.00DS; the inner surface is a toroidal surface, with a base curve axial angle of 70°, a high-order aspheric curve shape, and a refractive power of -1.00DC; the orthogonal arc axial angle of 160°, a parabola shape, and a refractive power of -2.00DC. The converted negative internal dispersion lens prescription is:

[0134]

[0135] St2.2, calculate the refractive power F of the inner surface of the hyperopia correction lens in all circumferential directions i and the spherical radius R1 of the outer surface of the lens;

[0136] The method for determining the diopter in each direction of the inner surface of the lens is the same as in Example 1. The absolute value of the diopter in each direction is expressed by the polar diameter r of the ellipse under the polar coordinates. i The length of the minor axis of the ellipse is the absolute value of the base arc diopter (-0.5DC) (i.e. a = 0.5), the length of the major axis of the ellipse is the absolute value of the orthogonal arc diopter (-2.00DC) (i.e. b = 3), the minor axis of the ellipse is in the diopter direction of the base arc (γ = 160°), and the distance r from each point on the ellipse to the pole is i (Polar diameter) represents the absolute value of the diopter in each direction. After adding the minus sign, the diopter F in each direction of the inner surface of the lens is obtained. i , the calculation formula is as follows:

[0137]

[0138] Substituting the parameters into

[0139] The outer spherical radius R1 is calculated from the outer spherical power (F1 = +4.00DS) and the refractive index of the lens material (n = 1.56) as follows:

[0140]

[0141] St2.3, determine the minimum center thickness t of the hyperopia correction lens min The method is the same as in Example 1, and the calculation is as follows:

[0142] The calculation formula of the outer surface sagitta is:

[0143]

[0144] The calculation formula of the inner surface sagittal height is:

[0145]

[0146] Where, k = 0, a2 = 5.20e-07, a3 = -5e-11, and the remaining coefficients are 0. i =1 / R i , R i The calculation formula is as follows:

[0147]

[0148] According to the relationship between the sagittal height of the inner and outer surfaces of the lens, the edge thickness and the center thickness, from S1 i -S2i Find the maximum value among them and add the minimum edge thickness 0.5mm to get the minimum center thickness t of the hyperopia correction lens. min , the calculation formula is as follows:

[0149] t min =max(S1 i -S2 i )+0.5, i=1,2,…,360

[0150] According to calculation, S1 i -S2 i The maximum value occurs on the frame with radial dimension ρ max position, i = 22, and

[0151] max(S1 i -S2 i )=2.00mm, so t min =2.50mm

[0152] St2.4, radial distance ρ in all directions at the edge of the lens i Add the cutting allowance r0 (=1mm) and calculate the edge thickness e before cutting. i Is it greater than or equal to 0.3mm? If not, the center thickness needs to be increased to meet e i The minimum value is equal to 0.3mm. The method is the same as in Example 1, and the calculation formula is as follows:

[0153] The calculation formula of the outer surface sagitta is:

[0154]

[0155] The calculation formula of inner surface sagitta is:

[0156]

[0157] The edge thickness calculation formula is:

[0158]

[0159] In this embodiment, e i The minimum value is 0.39mm. If it is greater than 0.3mm, the minimum center thickness remains unchanged. min =2.50mm.

[0160] In order to illustrate the thinning effect of this patent, based on the same prescription, frame and face shape data, a hyperopia corrective lens mentioned in the "Background Technology" is used as an example for comparison, in which the radial dimensions used to calculate the center thickness include the maximum radial dimensions of the frame and the cutting edge allowance.

[0161] Because the human eye data and the frame data are the same, the maximum radius r of the customized shrink lens max The maximum radius r before cutting edge of the present invention max Same, so the lens diameter D = 2 × r max =2×29.94=59.88mm.

[0162] Because the prescription and surface shape data are the same as those used in the present invention, the sagittal height S1 corresponding to the outer surface sphere is calculated. * When, from St2.2, we know that R1 is 140mm; r max =29.94mm, the calculation formula is as follows:

[0163]

[0164] Set the minimum edge thickness e at the base curve of the inner surface of the lens min is 0.5mm, and then according to the diopter F of the base curve b The vertex curvature radius r of the base curve of the inner surface high-order aspheric curve is obtained by combining the lens refractive index n b , calculate the sag S corresponding to the base arc b * According to the relationship between lens sagittal height, edge thickness and center thickness, the center thickness of the hyperopic lens is t * =S1 * +e min -S b * The specific calculation is as follows:

[0165]

[0166]

[0167] Where c is the vertex curvature, c = 1 / r b =1 / 1120; r is the radial distance of the lens, where r = r max =29.94mm; k is the cone coefficient, a i In this example, k = 0, a2 = 5.20e-07, a3 = -5e-11, and the remaining coefficients are 0.

[0168] t * =S1 * +e min -S b * =2.96mm

[0169] Compared with the lens of the present invention, the difference in center thickness of the reduced lens is:

[0170] t * -tmin =2.96-2.50=0.46mm

[0171] It can be seen from this that the hyperopia correction lens designed by the present invention has a center thickness reduced by 0.46mm compared to a reduced lens with a diameter of 59.88mm and a minimum edge thickness of 0.5mm at the base curve of the inner surface of the lens before cutting. The reduction ratio is 15.54%, further reducing the center thickness.

[0172] Figure 6 This is the finished appearance of the frame with the pupil center as the origin, and the example one Figure 4 Similarly, the edge thicknesses of the finished lenses for the two designs are plotted at 30° intervals. The highlighted areas indicate the locations and sizes of the minimum edge thicknesses for the two lenses. The figure clearly shows that the edge thickness of the present invention lens is significantly smaller than that of the comparative lens. Combined with the reduced center thickness, the volume and weight of the present invention lens are significantly reduced compared to existing hyperopia correction lenses, significantly increasing wearer comfort.

[0173] Figure 7 The minimum edge thickness e of the present invention and the comparison lens in Example 2 when calculating the center thickness is shown. min As can be seen from the figure, the e min (=0.5mm) at the maximum radial dimension of the frame, i.e. ρ max At (i = 22), while the e of the contrasting shrink lens min (=0.5mm) is on the circle with diameter D corresponding to the base curve on the inner surface of the lens, D=2×r max =2×(ρ max +1), not only is there a difference in the radial size of the cutting edge margin, but also due to the different positions, the sagittal height of the inner and outer surfaces is different, resulting in the actual minimum edge thickness being at the maximum radial position of the frame determined by the present invention, that is, ρ max It can be seen that the method of the present invention can accurately determine the location of the minimum edge thickness of the lens based on the wearer's requirements such as the monocular independent pupil distance, nose bridge width, frame data, prescription, and facial parameters to meet the process requirements, and then determine the minimum center thickness of the lens, so that the finished lens has the optimal light and thin effect.

[0174] Table 1 Polar coordinate data table of the inner edge points of the selected eyeglass frame type in Example 1

[0175]

[0176]

[0177]

[0178] Table 2 Polar coordinate data table of the inner edge points of the selected eyeglass frame type in Example 2

[0179]

[0180]

[0181]

Claims

1. A design method for a free-form surface single-focus hyperopia correction lens, wherein the hyperopia correction lens is a positive lens with the astigmatism correction side on the inner surface, the inner surface is located on the eye side, and the outer surface is arranged opposite to the inner surface; the outer surface is spherical or aspherical, and the inner surface is a toroidal surface; characterized in that: The design methodology includes the following steps: St1. First, calculate the radial distance ρ from the edge point of the hyperopia correction lens in each direction to the pupil center based on the monocular independent pupil distance, pupil height, selected frame coordinate data, and nose bridge width data in the eyeglass prescription. i ; St2. Based on the monocular toric prescription and face shape design parameters, calculate the sagittal difference between the outer and inner surfaces of the hyperopia correction lens in each direction using the diopter values of the hyperopia correction lens in each direction. From these sagittal differences, find the maximum sagittal difference. The minimum center thickness of the hyperopia correction lens is equal to the maximum sagittal difference plus the minimum edge thickness. Add the trimming allowance to the radial distance in each direction of the frame and calculate the edge thickness in each direction before trimming. If the minimum edge thickness in each direction is greater than or equal to the set value, the center thickness remains unchanged. Otherwise, set the edge thickness at the set value and recalculate the center thickness based on the sagittal difference between the outer and inner surfaces at that location. Determining the center thickness of the hyperopia correction lens in St2 includes the following steps: St2.1: Rewrite the wearer's sphero-cylindrical prescription into a negative internal dispersion prescription; St2.2: Determine the refractive power F of the inner surface in all directions of the circumference based on the negative inner diffuser prescription and the inner surface shape design requirements. i ; Based on the negative inner dispersion prescription and the refractive index of the lens, calculate the radius of curvature R1 of the outer surface of the lens; St2.3: According to the radial distance ρ from the edge of the frame to the center of the pupil i , the curvature radius R1 of the outer surface, the diopter F of the inner surface in all directions i , and the surface shape data of the inner surface, calculate the outer surface sagittal height S1 of the edge points of the frame in all directions i and inner surface height S2 i According to the relationship between the inner and outer surface sagitta, edge thickness and center thickness, from S1 i -S2 i Find the maximum value in , plus the minimum edge thickness e min , which is the minimum center thickness t of the hyperopia correction lens min ; t min =max(S1 i -S2 i )+e min ,i=1,2,…,360 St2.4: Radial distance ρ in all directions at the edge of the lens i Add the cutting allowance r0 and calculate the edge thickness e before cutting i Is it greater than or equal to the set value e0? If not, the center thickness needs to be increased to meet e i The minimum value is equal to e0; increase the radial distance from the edge of the lens to the center of the pupil to ρ i +r0, recalculate the sagitta of the inner and outer surfaces and Then, the edge thickness e is calculated based on the relationship between the inner and outer surface sagittal heights, edge thickness and center thickness. i , and find the minimum value; if the minimum value at this time is greater than or equal to e0, the minimum center thickness t min unchanged; if the minimum value is less than e0, set the edge thickness in this direction to e0 and calculate the new lens center thickness The calculation formula is as follows: From e i Find the minimum value. If the minimum value is greater than or equal to the set value e0, the minimum center thickness t min unchanged; if the minimum value is less than the set value e0, let i=m at that location, then the new center thickness The calculation formula is as follows: St3, use the minimum center thickness t obtained in St2 min or The center thickness of the hyperopia correction lens is used for custom edge grinding of the hyperopia lens.

2. The method for designing a free-form surface single-focus hyperopia corrective lens according to claim 1, characterized in that: The frame coordinate data described in St1 include: the shape, size and nose bridge width data of the inner frame; obtained by scanning the frame or by pre-stored frame coordinate data; the frame coordinate data is the polar coordinate data of the edge point of the inner frame of the frame (ρ i ,θ i ), i = 1°, 2°, ..., 360°; ρ represents the distance from the edge point of the inner frame of the frame to the polar coordinate pole, θ represents the angle of the ray connecting the edge point of the inner frame of the frame to the pole relative to the polar axis; the position of the polar coordinate pole is related to the accuracy of the placement of the frame, and the pole position is set at the geometric center of the inner frame of the frame, that is, the intersection of the half-height and half-width lines of the inner frame of the frame.

3. The design method of the free-form surface single-focus hyperopia correction lens according to claim 1, characterized in that: The step of calculating the radial distance from the edge points of the hyperopia correction lens in each direction to the pupil center in St1 includes: St1.1, the polar coordinate data of the inner edge point of the selected eyeglass frame (ρ i ,θ i ), i=1°, 2°, ..., 360°, converted into rectangular coordinate data (X i , Y i ), i=1,2,…,360, where X i Indicates the horizontal coordinate value of the edge point, Y i Indicates the vertical coordinate value of the edge point. The conversion formula is as follows: X i =ρ i cosθ i ,i=1°,2°,…,360° (1) Y i =ρ i sinth i ,i=1°,2°,...,360° (2) St1.2, based on the left eye independent pupil distance LPD or right eye independent pupil distance RPD, pupil height PH, and the nose bridge width DBL of the selected frame, calculate the coordinates of the pupil center point on the frame's rectangular coordinate system (X0, Y0). The calculation formula is: Y0=min(Y i )+PH,i=1,2,…,360 (3) Left eye: Right eye: Where, min(Y i ) means finding the minimum value from all Y coordinate data of the edge points of the frame, max(X i ) means to find the maximum value from all X coordinate data of the edge points of the frame, min(X i ) means finding the minimum value from all X coordinate data of the edge points of the frame; St1.3, calculate the radial distance ρ from the edge of the frame in each direction to the pupil center i ; According to the coordinates of the pupil center point (X0, Y0), the pupil center point is translated to the coordinate origin by translation. At this time, the coordinates of the edge point of the frame become (N xi , N yi ), i = 1, 2, ..., 360; find the radial distance ρ from the edge of the frame to the center of the pupil in each direction i , i=1,2,…,360, the calculation formula is as follows: N xi =X i -X0,i=1,2,…,360 (6) N yi =Y i -Y0,i=1,2,…,360 (7) 4. The method for designing a free-form surface single-focus hyperopia corrective lens according to claim 3, wherein: r0≤1.2mm,0.5mm≤e min ≤0.8mm,0.3mm≤e0≤0.6mm。 5. A free-form surface single-focus hyperopia correction lens, characterized by: The free-form surface monofocal hyperopia correction lens is obtained by using the design method of any one of claims 1 to 4.

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