Harmonic diffraction-based myopia prevention and control lens design method

Abstract

The invention discloses a method for designing a myopia prevention and control lens based on harmonic diffraction. Relates to the technical field of eye vision optics, in particular to the technical field of a myopia prevention and control lens design method based on harmonic diffraction. According to the method, a harmonic diffractive optical lens chromatic aberration correction method and a harmonic diffractive optical lens diffraction efficiency calculation method when shielding is considered are firstly designed, chromatic aberration is effectively eliminated, the diffraction efficiency is evaluated, and then influences of chromatic aberration correction and shielding error manufacturing are balanced by designing a balance optimization model. The method comprises the following steps: designing a diffractive optical element on the refraction surface of a myopia prevention and control lens to obtain a refractive and diffractive optical lens; modulating the harmonic number # imgabs0 # of the refractive and diffractive optical lens to obtain a harmonic diffractive optical lens; designing a chromatic aberration correction method of the harmonic diffractive optical lens; harmonic diffractive optical lenses are designed that take into account additional refractive power and diffraction efficiency at the time of manufacturing shields.

Description

Technical Field

[0001] The present invention relates to the technical field of ophthalmic optics, and in particular to the technical field of a method for designing a lens for myopia prevention and control based on harmonic diffraction. Background Art

[0002] With the increasing prevalence of myopia in adolescents in recent years, the prevention and control of myopia through optical methods has become a new research hotspot. Myopia is primarily caused by improper eye use, which stretches the retina. Myopia prevention glasses—which can modulate light, directing some light in front of the retina, thereby stretching the retina toward normal development—are currently a research hotspot.

[0003] However, current myopia prevention and control lenses are limited to refractive designs, which restricts their further development. First, the main reason for the dispersion of glasses is that the medium has different refractive indices for light of different wavelengths. Dispersion will lead to a decrease in image clarity, especially in low-refractive-index materials. When light passes through the lens, light of different wavelengths will be deflected to varying degrees due to the difference in refractive index, resulting in blurred images or color distortion; secondly, the thickness of the lens will also affect the degree of dispersion and aberration. Since myopia prevention and control lenses are usually thicker, this makes the dispersion more significant; secondly, how to further reduce the thickness of myopia prevention and control glasses and provide excellent achromatic effects has always been the focus of this field; finally, limited by the low degrees of freedom of refractive lenses, the refractive design cannot develop further. A new design method with high degrees of freedom has become the key to the development of myopia prevention and control glasses.

[0004] Diffractive optical elements, due to their superior optical performance, can further reduce lens thickness and eliminate the effects of refractive lens dispersion (a key issue in large lens design). Their high degree of freedom in designing diffractive optical elements promises to bring new vitality to the design of myopia prevention and control lenses. However, the small periodic radius of diffractive lenses with high optical power presents challenges in the manufacture of large-diameter lenses (compared to the size of another commonly discussed element in optometry, intraocular lenses), leading to significant manufacturing occlusion errors, a problem not encountered in other diffractive optical element designs. Furthermore, when attempting to reduce the periodic radius by increasing the harmonic number, balancing dispersion correction with the size of the periodic radius is crucial for the application of diffractive myopia prevention and control lenses. Summary of the Invention

[0005] In response to the aforementioned problems of excessive manufacturing occlusion errors in existing refractive and diffractive optical elements, and the difficulty in balancing dispersion and manufacturing occlusion errors in harmonic diffractive optical elements, the present invention proposes a method for designing myopia prevention and control lenses based on harmonic diffraction. First, a method for correcting chromatic aberration of harmonic diffractive optical lenses and a method for calculating the diffraction efficiency of harmonic diffractive optical lenses considering occlusion are designed to effectively eliminate chromatic aberration and evaluate diffraction efficiency. Then, a balanced optimization model is designed to balance the effects of chromatic aberration correction and manufacturing occlusion errors.

[0006] The method comprises the following steps: S1. Designing a diffractive optical element on the refractive surface of the myopia prevention and control lens to obtain a refractive-diffractive optical lens; S2, harmonic number of modulated refractive optical lens , and obtain a harmonic diffraction optical lens; S3, based on harmonics Calculating the periodic radius of a harmonic diffraction optical lens , additional optical power , true cycle width and step height ; S4, perform chromatic aberration correction of the harmonic diffraction optical lens, and calculate the chromatic aberration of the corrected harmonic diffraction optical lens ; S5. Overcome the influence of occlusion error in manufacturing additional focal length on diffraction efficiency and calculate the true diffraction efficiency of harmonic diffraction optical lenses ; S6. Design a balanced optimization model to balance the chromatic aberration and true diffraction efficiency of the harmonic diffraction optical lens: S61, performing chromatic aberration correction of a harmonic diffraction optical lens; S62, calculation , and judging whether the actual diffraction efficiency of the harmonic diffraction optical lens tends to be stable after the processing of step S61, if it tends to be stable, then ending the balance and obtaining a myopia prevention and control lens based on harmonic diffraction; Otherwise, the harmonic diffraction design parameters are adjusted and steps S61-S62 are repeated.

[0007] Furthermore, the corrected chromatic aberration of the harmonic diffraction optical lens ,pass: Calculate, where represents the chromatic aberration of the corrected harmonic diffraction optical lens, The period radius of the harmonic diffraction optical lens is The optical focal length, represents the diffraction order of the harmonic diffraction optical lens, It represents the difference between the wavelength of light C and light F of the harmonic diffraction optical lens. represents the central wavelength of the harmonic diffraction optical lens, Represents the harmonic diffraction optical lens diffraction rings, Represents the period radius of the harmonic diffraction optical lens.

[0008] Furthermore, the actual diffraction efficiency of the harmonic diffraction optical lens is ,pass: Calculate, where represents the Sigmoid function, Indicates the central wavelength of the harmonic diffraction optical lens The actual wavelength The ratio of represents the image distance of the harmonic diffraction optical lens, Indicates the blocking width of the harmonic diffraction optical lens.

[0009] Furthermore, the periodic radius of the harmonic diffraction optical lens is pass: Obtain, among which, Represents the focal length of the diffractive optical element.

[0010] Furthermore, the additional optical power of the harmonic diffraction optical lens is obtained by: get.

[0011] Furthermore, the real period width of the harmonic diffraction optical lens is determined by: get.

[0012] Furthermore, the step height of the harmonic diffraction optical lens is determined by: Obtain, among which, represents the refractive index of the diffractive optical lens material, Represents the ambient refractive index.

[0013] Furthermore, the harmonic diffraction design parameters include: harmonic number and additional optical power.

[0014] The beneficial effects of the method of the invention are: (1) The method described in the present invention applies harmonic diffraction optical lenses to the design and manufacture of myopia prevention and control lenses for the first time, breaking the technical barrier that myopia prevention and control lenses are limited to refractive designs, and providing a feasible, high-performance new future solution for the design of myopia prevention and control lenses.

[0015] (2) The method for correcting chromatic aberration of the harmonic diffraction optical lens and the method for adjusting the periodic radius of the harmonic diffraction optical lens designed by the present invention can correct chromatic aberration by adjusting the harmonic number. Compared with the refractive diffraction optical lens, the method of the present invention can adjust the periodic radius while correcting the chromatic aberration, thereby reducing the manufacturing occlusion error.

[0016] (3) The method described in the present invention designs a method for calculating the real diffraction efficiency, chromatic aberration correction method, period radius calculation method, additional optical power calculation method, period width calculation method and step height calculation method of a harmonic diffraction optical lens, providing a complete processable achromatic core correction area and an optical design method for a defocus area that meets process feasibility for manufacturing a myopia prevention and control lens based on harmonic diffraction.

[0017] (4) The balanced optimization model designed by the method described in the present invention can rationally design the structure of the myopia prevention and control lens, balance the effects of chromatic aberration correction and manufacturing error occlusion, and can manufacture high-precision and high-performance diffraction myopia prevention and control lenses. The method described in the present invention is versatile and can provide a new research direction for the diffraction myopia prevention and control route. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The wavefront diagram of the diffractive optical lens of the present invention; Figure 2 This is a schematic diagram of the shielding effect produced by the diffractive optical lens of the present invention; Figure 3 This is a schematic diagram of the relationship between the additional focal power and diffraction efficiency of the downward-refractive diffractive optical lens considering the occlusion effect when the diffraction order is 1 according to the present invention, wherein the abscissa represents the additional focal power and the ordinate represents the diffraction efficiency; Figure 4 This is a flow chart of the balance optimization model of the present invention; Figure 5 Schematic diagram of the overall outline of the harmonic diffraction optical lens of the present invention; Figure 6 Schematic diagram of the modeling results of the harmonic diffraction optical lens in the ZEMAX model of the present invention; Figure 7 Schematic diagram of the defocusing effect of the harmonic diffraction optical lens of the present invention; Figure 8 Schematic diagram of imaging quality results of the correction area and the defocused area according to the present invention, wherein the abscissa represents the spatial frequency and the ordinate represents the modulation transfer function; Figure 9 This is a schematic diagram of the surface profile of the correction area measured by the step profiler of the present invention, wherein the abscissa represents the periodic radius and the ordinate represents the sagittal height; Figure 10 Schematic diagram of the surface profile of the defocused area measured by the step profiler of the present invention, wherein the abscissa represents the periodic radius and the ordinate represents the sagittal height; Figure 11 The present invention Figure 9A three-dimensional information graph of the measurement area, where the horizontal axis represents the length of the measurement area, the vertical axis represents the width of the measurement area, and the color legend represents the surface measurement accuracy at different positions. The value 0 represents the absence of manufacturing accuracy error. The Label represents the name of the measurement data, the Value represents the value of the measurement data, and the Units represents the unit of the measurement data. Figure 12 The present invention Figure 11 The cross-sectional view in the X-axis direction of the three-dimensional information diagram, where the abscissa represents the period radius and the ordinate represents the manufacturing error measurement value; Figure 13 The present invention Figure 11 A cross-sectional view in the Y-axis direction of the three-dimensional information diagram, where the abscissa represents the period radius and the ordinate represents the manufacturing error measurement value; Figure 14 The present invention Figure 10 A three-dimensional information graph of the measurement area, where the horizontal axis represents the length of the measurement area, the vertical axis represents the width of the measurement area, and the color legend represents the surface measurement accuracy at different positions. The value 0 represents the absence of manufacturing accuracy error. The Label represents the name of the measurement data, the Value represents the value of the measurement data, and the Units represents the unit of the measurement data. Figure 15 The present invention Figure 13 The cross-sectional view in the X-axis direction of the three-dimensional information diagram, where the abscissa represents the period radius and the ordinate represents the manufacturing error measurement value; Figure 16 The present invention Figure 13 A cross-sectional view in the Y-axis direction of the three-dimensional information diagram, where the abscissa represents the period radius and the ordinate represents the manufacturing error measurement value; Figure 17 This is a schematic diagram of the harmonic diffraction myopia prevention and control lens manufactured according to the present invention; Figure 18 This is a schematic diagram of the focal power measurement results of the present invention; Figure 19 This is a schematic diagram of the structure of the measurement system of the present invention; Figure 20 This is a comparison chart of diffraction efficiency at different wavelengths according to the present invention. DETAILED DESCRIPTION

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0020] Example 1 This embodiment provides a method for designing a myopia prevention and control lens based on harmonic diffraction, the method comprising the following steps: Step 1: Design a diffractive optical element on the refractive surface of the myopia prevention and control lens to obtain a refractive diffractive optical lens.

[0021] Step 2: Modulate the harmonics of the refractive-diffractive optical lens , and a harmonic diffraction optical lens is obtained.

[0022] Example 2 This embodiment is a further limitation of Example 1, and further illustrates that the refractive-diffractive optical lens cannot be directly applied to the current myopia prevention and control design.

[0023] Diffractive optical elements are widely used in optical systems such as visual systems. In addition to their arbitrary phase distribution, their special dispersion characteristics are also one of the reasons for their widespread application.

[0024] For a refractive optical lens, its Abbe number can be expressed as: (1) in, represents the ambient refractive index, The image distance of the refractive optical lens is expressed as The wavelength of time, Indicates that the environment The refractive index at and They represent the wavelengths of the refractive optical lens at F light (short wavelength) and C light (long wavelength), and Respectively indicate the environment and The refractive index at .

[0025] For the refractive part of the myopia prevention and control lens, the refractive index at short wavelength is greater than that at long wavelength, which means that the refractive index at F light is greater than that at C light, so the Abbe number of the refractive part of the myopia prevention and control lens is Is positive. For a diffraction optical lens, its Abbe number can be expressed as: (2) in, 、 and Represent the wavelengths of the diffraction optical lens at D, F, and C light, respectively.

[0026] In the FDC light band (‌F, D, and C light waves‌ are three specific wavelengths defined by the Fraunhofer Institute in Germany for chromatic aberration analysis and optical system design. The specific wavelengths are as follows:‌‌F light‌: 486.1 nm (hydrogen blue light), D light‌: 587.6 nm (helium yellow light), C light‌: 656.3 nm (hydrogen red light), these rays are often used to evaluate the dispersion performance of lenses), the Abbe number of the diffraction optical lens It is negative. In summary, the diffraction optical lens (element) has a negative Abbe number, and the refractive optical lens has a positive Abbe number. The diffraction optical element is combined with the refractive optical lens, and a diffraction optical element is designed on the refractive surface of the myopia prevention and control lens. At this time, the diffraction part can correct the chromatic aberration of the refractive part.

[0027] First, for a refractive optical lens, its optical power at any wavelength can be expressed as: (3) in, and Respectively represent the curvature radius of the front and rear surfaces of the refractive optical lens, and denote the refractive indices of the refractive optical lens and the environment, respectively, Indicates the actual wavelength of the refracting optical lens.

[0028] The chromatic aberration of a refractive optical lens in the FDC band can be calculated using the difference in optical power between F light and C light, which can be expressed as: (4) in, represents the ambient Abbe number, represents the central wavelength of the refractive optical lens, The periodic radius of the refractive optical lens is The optical power of a refracting optical lens.

[0029] For diffraction optical lenses, the chromatic aberration in the FDC band can also be calculated using the difference in optical power between F light and C light, expressed as: (5) in, represents the additional optical power of the diffractive optical lens, represents the diffraction order of the diffraction optical lens, It represents the difference between the wavelength of C light and the wavelength of F light of the diffraction optical lens. , Indicates the actual wavelength of the diffraction optical lens, The image distance of the diffraction lens is The additional optical power, Indicates the central wavelength of a diffractive optical lens.

[0030] For a diffractive optical lens, its overall chromatic aberration can be corrected by formula (6), where: Represents the chromatic aberration of the corrected diffractive optical lens.

[0031] (6) According to formula (6), by adjusting the additional optical power of the refractive-diffractive optical lens, the chromatic aberration can be completely corrected. However, at the same time, the additional optical power is related to the periodic radius, and the size of the periodic radius will cause manufacturing occlusion errors.

[0032] like Figure 1 As shown, Figure 1 The wavefront diagram of the diffractive optical lens is shown, where 、 and Represents the 1st, 2nd and diffraction periods (zones), represents the focal length of the diffractive optical element; Figure 1 In the optical path analysis, we can get the expression of light passing through different diffraction rings in the refractive diffraction optical lens, specifically: (7) in, Represents the diffractive optical lens The period radius of the diffraction rings, represents the actual wavelength of the diffractive optical lens, represents the image distance of the diffractive optical lens, Represents the refractive index of the diffractive optical lens material.

[0033] when , the items with very small values can be ignored, so The calculation formula is shown in formula (8): (8) in, According to formula (8), the period radius of the diffraction ring presents a periodic distribution. It can be found that when different optical powers are added (optical power is the inverse of the focal length), the period radius and period width will produce different changes, and the period radius width will decrease as the added optical power increases.

[0034] like Figure 2As shown in the figure, in the manufacturing process of single-point diamond, whether it is direct turning or turning mold, manufacturing obstruction will occur on the refractive diffractive optical lens. The diffraction efficiency of the refractive diffractive optical lens will decrease due to the obstruction effect during the single-point diamond processing process. Too small a period width will bring greater manufacturing shadow obstruction. For the edge period with a small period width, its diffraction efficiency will be seriously reduced. Therefore, planning a reasonable period width has also become an important criterion in the manufacturing process of refractive diffractive optical lenses.

[0035] The calculation method of the diffraction efficiency of the refractive optical lens without considering the manufacturing occlusion is: (9) in, represents the Sigmoid function, represents the phase delay of the diffractive optical lens, Indicates the central wavelength of the diffractive optical lens The actual wavelength The ratio of Indicates the diffraction order of the diffractive optical lens; The calculation method of the diffraction efficiency of the refractive optical lens considering manufacturing occlusion is: (10) in, represents the occlusion width (effect), Usually considered to be 20um, Represents the period width of the diffractive optical lens.

[0036] The period width of the diffractive optical lens is calculated by formula (11): (11) in, represents the actual wavelength of the diffractive optical lens, The image distance of the diffractive lens is expressed as The additional optical power of Since the additional optical power will affect the period width in the refractive diffractive optical lens, the diffraction efficiency of the refractive diffractive optical lens is calculated by formula (12) considering the influence of the additional optical power and processing shading error: (12) like Figure 3 As shown, when the diffraction order is 1, the greater the additional focal length, the lower the diffraction efficiency. This is because the greater the additional focal length, The smaller ( = equal to the inverse of the additional optical power), from formula (8), we can know that The smaller the The smaller the period radius If it is too small, it will cause occlusion errors in the manufacture of the refractive-diffractive optical lens. Therefore, when using the refractive-diffractive optical lens to correct chromatic aberration, it is also necessary to consider the manufacturing occlusion errors caused by the reduction of the periodic radius.

[0037] Example 3 This embodiment further limits Embodiments 1 and 2.

[0038] According to Example 2, although the refractive diffraction optical lens has excellent performance, it cannot be applied to the current myopia prevention and control design due to the challenges it faces. For this reason, the design of harmonic diffraction optics is introduced. The harmonic diffraction optical lens achieves imaging characteristics different from those of the traditional diffraction optical lens by improving the diffraction phase (modulating the harmonic number M). The optical path difference between adjacent rings of the harmonic diffraction optical lens is different from the diffraction optical lens, which is 1 wavelength apart, but an integer M times the wavelength (M is the harmonic diffraction number, referred to as the harmonic number). That is, at this time, the first The difference between the diffraction rings and the central ring is not , but . That is, in the harmonic diffraction optical lens, formula (7) can be transformed into formula (13), where, represents the central wavelength of the harmonic diffraction optical lens, Express the image distance of the harmonic diffraction optical lens: (13) For the harmonic diffraction optical lens, the present invention has the following designs: The method for obtaining the periodic radius is designed as follows: (14), obtain the period radius of the harmonic diffraction optical lens ; The method for obtaining the additional optical power is designed as follows: (15), obtain the additional optical power of the harmonic diffraction optical lens ,in, represents the diffraction order of the harmonic diffraction optical lens; The phase delay of the traditional single focus refractive diffraction optical lens is 1 wavelength, and the harmonic diffraction optical lens is M times, the phase delay is also transformed into M wavelengths, so the method for obtaining the step height of the harmonic diffraction optical lens is designed as follows: (16), obtain the step height of the harmonic diffraction optical lens ,in, Indicates the actual wavelength of the harmonic diffraction optical lens; The ideal (not considering manufacturing occlusion) diffraction efficiency of the harmonic diffraction optical lens is designed to be obtained by: (17), obtain the ideal diffraction efficiency of the harmonic diffraction optical lens ,in, Indicates the central wavelength of the harmonic diffraction optical lens The actual wavelength The ratio of The chromatic aberration correction method of the harmonic diffraction optical lens is designed as follows: (18) is corrected, where represents the chromatic aberration of the corrected harmonic diffraction optical lens, The period radius of the harmonic diffraction optical lens is The optical focal length, It represents the difference between the wavelength of light C and light F of the harmonic diffraction optical lens. represents the central wavelength of the harmonic diffraction optical lens; the method for obtaining the real period width (considering the additional focal length and manufacturing occlusion) of the harmonic diffraction optical lens is designed as follows: (19), the real period width of the harmonic diffraction optical lens is obtained ; A higher additional focal length will result in a smaller true period width of the harmonic diffraction optical lens. A smaller true period width will increase the manufacturing occlusion range, thereby affecting the diffraction efficiency of the harmonic diffraction optical lens. The method for obtaining the true (when considering additional focal length and manufacturing occlusion) diffraction efficiency of the harmonic diffraction optical lens is designed as follows: (20) Obtain the true diffraction efficiency of the harmonic diffraction optical lens ; According to the above design content of harmonic diffraction optical lens, when M is adjusted to a larger value (harmonic diffraction focal length), While the design remains the same, a larger periodic radius and smaller manufacturing occlusion errors can be achieved, resulting in higher diffraction efficiency. However, the present inventors have also discovered that while the use of harmonic diffractive optical lenses can increase the periodic radius and thus improve manufacturing feasibility, the relatively high harmonic number used also results in excessive chromatic aberration correction (leading to overcorrection). Therefore, the model selection should be comprehensively balanced between chromatic aberration correction, manufacturing performance, and processing feasibility.

[0039] Example 4 This embodiment further limits Embodiments 1 to 3.

[0040] like Figure 4 As shown, this embodiment designs a balanced optimization model, comprehensively considering the correction of chromatic aberration and manufacturing occlusion error, and corrects the chromatic aberration of the harmonic diffraction optical lens while maintaining a stable diffraction efficiency after considering the occlusion effect.

[0041] S41, using a chromatic aberration correction method for a harmonic diffraction optical lens (Formula (18)) to correct the chromatic aberration of the harmonic diffraction optical lens; S42. Use formula (20) to calculate the actual diffraction efficiency of the harmonic diffraction optical lens considering the additional focal length and manufacturing occlusion , and judge whether its real diffraction efficiency tends to be stable. If at this time, the real diffraction efficiency tends to be stable, then the balance is ended, and a myopia prevention and control lens based on harmonic diffraction is obtained; Otherwise, adjust the harmonic diffraction design parameters (increase the harmonic number or reduce the additional optical power), re-enter the balance optimization model, and repeat steps S41-S42.

[0042] Example 5 This embodiment further limits Embodiments 1 to 4.

[0043] This embodiment conducts simulation experiments in a ZEMAX model to verify the performance of the method of the present invention.

[0044] The design objectives of the simulation experiment in this embodiment are: the additional focal length of the core correction area is designed to be -5D, the focal length of the through-focus area is -3D, the aperture of the optical zone is 35mm, the overall aperture is 70mm, the material is E48R (refractive index: 1.531, Abbe number: 56), and the human eye model adopts the Atchison model. The Atchison human eye data is shown in Table 1, where X represents the myopic focal length of the human eye: Table 1

[0045] Under the premise of comprehensively considering the design and manufacturing challenges of the above embodiments 1 to 6, the core correction area parameter design adopts Figure 4 In the balance optimization model shown, the curvature radius of the front and rear surfaces is calculated based on the influence of the lens-to-eye distance. The design parameters used in this example are shown in Table 2: Table 2

[0046] The parameters of the harmonic diffraction optical lens obtained by the balance optimization model in this embodiment are shown in Table 3: Table 3

[0047] The defocused area uses the same refractive substrate as the correction area (the conic coefficient of the refractive substrate and the aspheric parameters are obtained through ZEMAX optimization). The optical focal length and harmonic number of the diffraction obtained at this time are shown in Table 3.

[0048] The main viewing area of the harmonic diffraction optical lens used in this embodiment is at 0-4mm, 6-8mm, 10-12mm, and 14-16mm in radius. The defocus area is at 4-6mm, 8-10mm, 12-14mm, and 16-17.5mm in radius. The overall outline is as follows: Figure 5 shown.

[0049] The results of the simulation test are as follows Figure 6 、 7 As shown in 8, Figure 6 Schematic diagram showing the modeling results of the harmonic diffraction optical lens in the ZEMAX model. Figure 7 Schematic diagram showing the defocusing effect of a harmonic diffraction optical lens. Figure 8 A schematic diagram showing the imaging quality results of the correction area and the defocused area. The horizontal axis represents the spatial frequency, and the vertical axis represents the modulation transfer function. The spatial frequency describes the fineness of the details in the image, while the modulation transfer function (MTF) quantifies the imaging system's ability to transmit contrast at different spatial frequencies. The higher the MTF value, the better the system can preserve the details and contrast of the image, thereby producing clearer, sharper, and more detailed imaging results. In the field of ophthalmic optical system design, when the spatial frequency (lp / mm) is 50, if the modulation transfer function (MTF) value is greater than 0.3, it is generally believed that the human eye can receive good image quality. Figure 8 It can be seen that the harmonic diffraction optical lens achieves good imaging effects in both the correction and defocus areas.

[0050] Example 6 This embodiment further limits Embodiments 1 to 5.

[0051] This example further evaluates the diffraction efficiency of the harmonic diffraction optical lens in Example 7 (Zemax cannot analyze the diffraction efficiency).

[0052] Formula (12) and formula (20) are used to calculate the influence of the occlusion error of each ring zone by using the refractive diffraction optical lens and the harmonic diffraction optical lens respectively (since the occlusion effect mainly affects the edge ring zone, the comparison starts from the 10th ring zone). The results can be seen from Table 4: Table 4

[0053] Table 4 shows that manufacturing occlusion errors significantly impact each ring zone in a refractive diffractive lens. Harmonic diffractive lenses significantly reduce the degree to which occlusion errors reduce diffraction efficiency. Furthermore, the period radius of refractive diffractive lenses is extremely small, making them unable to support the high-precision machining requirements of a single-point diamond lathe. However, the period radius of harmonic diffractive lenses is larger, making them amenable to high-precision machining using a single-point diamond lathe.

[0054] Analysis of single point diamond lathe processing results: Figure 9 and 10 As shown, Figure 9 and 10The figure shows the relationship between the surface profiles of the correction area and the defocused area measured by the step profiler. It can be seen that there is a serrated linear structure relationship between the periodic radius and the sagittal height, indicating that the diffraction structure is well processed.

[0055] like Figures 11 to 16 Shown, showing Figure 9 and 10 The specific accuracy of the measurement area measured by white light interferometer, the RMS accuracy of the method described in the present invention reached 14.8nm and 13.5nm respectively, achieving the nanometer-level precision design goal.

[0056] like Figure 17 As shown in the figure, the appearance of the manufactured myopia prevention and control lens is shown, and the focal power of each area is measured using a focal meter. The focal power measurement results are shown in the figure. Figure 18 As shown, the focal power of the correction area (6 to 8mm and -8 to -6mm) is approximately -5.15D. It should be noted that the extra -0.15D compensates for the difference in diopter caused by the distance between the lens and the eye, thus meeting the design requirement of -5D. The defocus area (4 to 6mm and -6 to -4mm) is approximately -3.1D. The extra -0.1D also compensates for the difference in diopter caused by the distance between the lens and the eye, thus meeting the design requirement of -3D. In summary, the focal power of the correction area, the focal power of the defocus area, and the size of the focal power distribution area all meet the design requirements, achieving precise and high-performance design and processing.

[0057] pass Figure 19 The measurement system shown measures the diffraction efficiency of incident light of different wavelengths passing through the correction area. The measurement system consists of a light source, a collimating device (parallel light tube), a lens, an optical power meter receiver and an optical power meter. The incident wavelength is changed to 530nm, 554nm and 565nm. This embodiment measures the actual diffraction efficiency of the refractive diffraction optical lens (corrected for chromatic aberration by the traditional refractive diffraction chromatic aberration correction method) and the harmonic diffraction optical lens (corrected for chromatic aberration by the harmonic diffraction optical lens chromatic aberration correction method) at three wavelengths, that is, by measuring the energy at the focus, it is determined whether the system is affected by chromatic aberration (if there is chromatic aberration, it will cause the focal length to shift, resulting in a decrease in energy at the focus compared to the ideal value). The measurement results are shown in the figure below. Figure 20 As shown, the diffraction efficiency of the harmonic diffraction optical lens is stable over the entire wavelength band, achieving correction of chromatic aberration (since it is very close to the ideal value, it also proves that the influence of occlusion error has been eliminated).

[0058] Finally, it should be noted that because the diffractive microstructure bears the majority of the refractive power, the edge thickness of the harmonic diffractive optical lens described in this invention (measured to meet the 70mm diameter of a large frame) is 4.9211mm, while the edge thickness of a traditional refractive design reaches 7.9175mm, a 37.85% reduction compared to a refractive lens. It should be noted that in the method described in this invention, the aspheric substrate design does not intentionally pursue edge thinning, indicating that the edge thickness can be further reduced with the aspheric substrate. The combination of diffraction and aspheric thinning can achieve an ultra-thin edge thickness, which is unattainable with traditional single aspheric designs.

[0059] In summary, the method described in the present invention successfully manufactured a high-precision, high-performance harmonic diffraction myopia prevention and control lens. The design results are versatile and can provide guidance for the harmonic diffraction myopia prevention and control route.

Claims

1. A method for designing a lens for myopia prevention and control based on harmonic diffraction, characterized in that: The method comprises the following steps: S1. Designing a diffractive optical element on the refractive surface of the myopia prevention and control lens to obtain a refractive-diffractive optical lens; S2, harmonic number of modulated refractive optical lens , and obtain a harmonic diffraction optical lens; S3, based on harmonics Calculating the periodic radius of a harmonic diffraction optical lens , additional optical power , true cycle width and step height ; S4, perform chromatic aberration correction of the harmonic diffraction optical lens, and calculate the chromatic aberration of the corrected harmonic diffraction optical lens ; S5. Overcome the influence of occlusion error in manufacturing additional optical power on diffraction efficiency and calculate the true diffraction efficiency of harmonic diffraction optical lenses ; S6. Design a balanced optimization model to balance the chromatic aberration and true diffraction efficiency of the harmonic diffraction optical lens: S61, performing chromatic aberration correction of a harmonic diffraction optical lens; S62, calculation , and judging whether the actual diffraction efficiency of the harmonic diffraction optical lens tends to be stable after the processing of step S61, if it tends to be stable, then ending the balance and obtaining a myopia prevention and control lens based on harmonic diffraction; Otherwise, the harmonic diffraction design parameters are adjusted and steps S61-S62 are repeated.

2. The method for designing a myopia prevention and control lens based on harmonic diffraction according to claim 1, characterized in that: The corrected chromatic aberration of the harmonic diffraction optical lens ,pass: Calculate, where represents the chromatic aberration of the corrected harmonic diffraction optical lens, The period radius of the harmonic diffraction optical lens is The optical focal length, represents the diffraction order of the harmonic diffraction optical lens, It represents the difference between the wavelength of light C and light F of the harmonic diffraction optical lens. represents the central wavelength of the harmonic diffraction optical lens, Represents the harmonic diffraction optical lens diffraction rings, Represents the period radius of the harmonic diffraction optical lens.

3. The method for designing a myopia prevention and control lens based on harmonic diffraction according to claim 2, characterized in that: The real diffraction efficiency of the harmonic diffraction optical lens ,pass: Calculate, where represents the Sigmoid function, Indicates the central wavelength of the harmonic diffraction optical lens The actual wavelength The ratio of represents the image distance of the harmonic diffraction optical lens, Indicates the blocking width of the harmonic diffraction optical lens.

4. The method for designing a myopia prevention and control lens based on harmonic diffraction according to claim 3, characterized in that: The period radius of the harmonic diffraction optical lens pass: Obtain, among which, Represents the focal length of the diffractive optical element.

5. The method for designing a myopia prevention and control lens based on harmonic diffraction according to claim 4, characterized in that: The additional optical power of the harmonic diffraction optical lens is provided by: get.

6. The method for designing a myopia prevention and control lens based on harmonic diffraction according to claim 5, characterized in that: The real period width of the harmonic diffraction optical lens is determined by: get.

7. The method for designing a myopia prevention and control lens based on harmonic diffraction according to claim 6, characterized in that: The step height of the harmonic diffraction optical lens is determined by: Obtain, among which, represents the refractive index of the diffractive optical lens material, Represents the ambient refractive index.

8. The method for designing a myopia prevention and control lens based on harmonic diffraction according to claim 7, characterized in that: The harmonic diffraction design parameters include: harmonic number and additional optical power.

Images