A method for phase modulation of an achromatic liquid crystal holographic lens

Abstract

The application discloses a phase modulation method of an achromatic liquid crystal holographic lens, and belongs to the technical field of holographic optics. The method realizes the synchronous focusing of red, green and blue light by regulating the spatial orientation distribution of liquid crystal molecules and constructing a multi-wavelength phase modulation model. Specifically, the deflection angle of the liquid crystal molecules is calculated according to the wavelength of the incident light and the position of the lens to form a refractive index gradient distribution; the holographic phase distribution is generated based on the molecular orientation to make different wavelengths of light focus on the same focal point; and the phase intensity coefficient is dynamically optimized, and the finite element simulation is iteratively adjusted to control the focal point light intensity deviation of the three wavelengths. The application eliminates the chromatic aberration phenomenon of the traditional lens, realizes the confocal plane focusing of different wavelengths of light within a certain focal length range, and improves the focal point intensity consistency. The prepared ultrathin liquid crystal lens has low thickness, significantly improves the light focusing efficiency, and is suitable for high-precision imaging systems and display devices.

Description

Technical Field

[0001] The present invention relates to the technical field of holographic optics, and in particular to a phase modulation method of an achromatic liquid crystal holographic lens. Background Art

[0002] In an optical system, incident light of different wavelengths produces different phase differences when passing through an optical medium, which is called chromatic aberration. This chromatic aberration phenomenon can significantly reduce the image quality, causing the focal length and focal intensity of light to be different after passing through the lens, making it impossible to focus on the same focal plane, and the focal length gradually decreases with increasing wavelength. This phenomenon seriously affects the convenience of daily life and the accuracy of scientific research, and has therefore attracted widespread attention from scientific researchers. Traditional achromatic lenses have limited performance and have failed to solve this problem well. Achromatic waveplate lenses are designed with surfaces of varying thicknesses and angles based on the characteristics of different light, compensating for differences in refractive index, so that light of different wavelengths can achieve uniform focal length and focal intensity after passing through the lens, effectively solving the chromatic aberration problem.

[0003] In early research, to address the chromatic aberration caused by light of different wavelengths, the initial approach employed a composite lens composed of two concave and convex lenses cemented together from different materials. However, the thickness of this doublet lens limited its application. Subsequently, researchers further attempted to combine two refractive lenses with different dispersion characteristics to create an achromatic refractive lens. However, this composite lens structure was relatively heavy and had a high F-value, limiting its ease of use and optical efficiency. Subsequent research focused on developing a new type of achromatic metasurface lens. This lens uses a metasurface structure to manipulate the amplitude, phase, and polarization state of electromagnetic waves, allowing light of different wavelengths to be focused at a similar focal position after passing through the lens. Unlike traditional composite lenses, this type of lens is a single optical element with a thin, lightweight micro-nanostructure design. It can be manufactured through processes such as nano-thermal embossing, UV-curing embossing, and microcontact printing, effectively reducing its size and thickness, achieving both lightweight and low F-value characteristics. Aieta et al. realized a metasurface by using dispersion phase compensation, which increased the diffraction efficiency of three different wavelengths of light tested to 9.8%, 10.3%, and 12.6%, respectively; Zhao et al. used metasurfaces to control the behavior of different light waves to produce achromatic geometric phases, increasing the corresponding diffraction efficiency of three test wavelengths to over 25%; Wang et al. designed, fabricated, and characterized a cylindrical diffraction lens that can transmit the entire visible wavelength range (450 The achromatic metasurface lens effectively focuses light from wavelengths from 100 nm to 700 nm onto a single line, improving the average optical efficiency of the three tested wavelengths by 24.9%, 23.0%, and 21.5%, respectively. The performance of the achromatic metasurface lens significantly outperforms previously reported achromatic lenses.

[0004] Subsequent studies have shown that liquid crystal holographic lenses have significant potential in achromatic properties, comparable to or even surpassing metasurface lenses. Its advantages are lower loss, higher light focusing efficiency, simple preparation process, low cost and ultra-thin structure (1.3±0.1 μm ), which can help achieve confocal focusing and uniform light intensity distribution of light of different wavelengths after passing through the lens from multiple dimensions. Therefore, the core issue of achromatic holographic lens design is to simultaneously optimize the confocal focusing and uniform light intensity distribution of light of different wavelengths after passing through the lens to achieve better achromatic effect. Summary of the Invention

[0005] The technical problem to be solved by this invention is to improve the achromatic ability and light focusing efficiency of existing achromatic lenses, improve the low production efficiency caused by micro-nanostructures, eliminate chromatic aberration caused by the different focal lengths of light beams of different wavelengths, and enhance the imaging quality of optical systems. This invention proposes a phase modulation method for an achromatic liquid crystal holographic lens to improve the response efficiency at different wavelengths. Through the optimized design of the liquid crystal lens phase, a more efficient chromatic aberration correction mechanism with adjustable focus is achieved.

[0006] In order to solve the above problems, the technical solution adopted by the present invention is:

[0007] The present invention uses orientable liquid crystal rod-shaped molecular materials to produce an achromatic holographic lens. Each position on the surface of the achromatic holographic lens is composed of liquid crystal rod-shaped molecules with different deflection angles and different refractive index distributions. This can solve the problem of focal length decreasing with increasing wavelength, thereby eliminating the phase difference (i.e., chromatic aberration) caused by different wavelengths of light.

[0008] When the incident light passes through the lens surface, due to the difference in its incident position, the present invention is based on the incident light beam on the lens surface, that is, x Axis and z The position coordinates on the axis are calculated in reverse according to formula (1) to calculate the deflection angle of the optical axis of the liquid crystal rod-shaped molecules at different positions on the lens. α By using this method, the optical axis orientation distribution of liquid crystal rod-shaped molecules under any wavelength and focal length can be designed according to the wavelength and focal length of the incident light. The deflection angle of the liquid crystal molecule optical axis must satisfy the following relationship:

[0009] (1);

[0010] in, α The optical axis of the liquid crystal rod molecules is on the surface of the lens ( xz plane), the wavelength of the incident light beam is , n =1,2,3 correspond to blue, green and red wavelengths respectively,f is the focal length of the target where the light is focused, x , z Represents the liquid crystal rod-like molecules on the lens surface ( xz The position coordinates on the plane.

[0011] Furthermore, the phase of the light wave is not only affected by the wavelength of the light wave, but also closely related to its irradiation position on the liquid crystal holographic lens. The present invention needs to design the phase distribution at each position of the liquid crystal holographic lens according to the wavelength of the incident light. Specifically, the position of the light wave on the lens can be determined by its x , z The coordinates are determined, so the phase at different positions of the lens can be calculated by formula (2). Therefore, precise control can be achieved by adjusting the phase of the light beam corresponding to the lens, and light of different wavelengths can be focused to one focal position. Therefore, the liquid crystal holographic lens is xz The phase at each position on the plane satisfies the following relationship:

[0012] (2).

[0013] In order to eliminate the chromatic aberration caused by wavelength difference, the present invention uses formula (3) to correct the phase at different positions of the lens. Through this formula, light beams of different wavelengths can achieve the same light intensity at the focal position. Unified, so that the focus points converge on the same focal plane, thus significantly improving the focusing efficiency of the lens. The light intensity at the improved focal position E , the phase of the focused light Phase with liquid crystal holographic lens ( xz plane) satisfies the following relationship:

[0014] (3);

[0015] (4);

[0016] in is the wavelength of incident light The phase weight coefficient, ( x , y ) represents the light in xy The coordinates of the focal point of the plane, is the single wavelength phase generated in step 2, i is an imaginary unit;

[0017] Finite element simulation is used to calculate the light intensity of blue, green and red wavelengths at the focus. 、 、 ,Adjustment Make the three-wavelength focal light intensity close to the same.

[0018] Based on the above-mentioned liquid crystal holographic lens phase modulation model, a finite element simulation model of the liquid crystal holographic lens is established in COMSOL software. The specific steps include:

[0019] Step 1: First, set the blue, green, and red wavelength parameters to 486nm, 587nm, and 656nm respectively.

[0020] Step 2: Set the liquid crystal material parameters and boundary conditions, mainly setting the refractive index of the liquid crystal material and , dielectric anisotropy coefficient , elastic constant K 11 , K 22 , K 33 wait, K 11 , K 22 , K 33 The boundary conditions on both sides of the lens are set as periodic boundary conditions or perfectly matched layer absorption boundaries.

[0021] Step 3: According to the liquid crystal molecule deflection angle obtained above, Frank-Oseen The elastic continuum equation calculates the pointing vector of the optical axis of the liquid crystal molecules, and then converts the pointing vector into a spatially varying refractive index tensor.

[0022] Step 4: Perform optical diffraction analysis of the liquid crystal holographic lens and divide the liquid crystal layer (the constructed liquid crystal lens) into a large number of high-resolution grids (the grid size is set to ≤ λ / 10, about 50 nm ), and then use the Maxwell equation solver to solve the light field distribution of the parallel light wave focused by the liquid crystal holographic lens.

[0023] The optimization goal is to optimize the light intensity deviation of the three wavelengths of blue, green and red at the focus to ≤5%. =486nm, =587nm, = Dynamic adjustment at 656nm ; Output The phase weight coefficient combination.

[0024] The specific iterative simulation process to determine the optimal coefficient combination is as follows: first calculate the distance difference between the blue, green and red focal points. If the distance difference is too large (for example, the focus distance difference is greater than the threshold 1), μm), so that the light intensity deviation is greater than 5%, according to the size and direction of the deviation, the coefficient corresponding to the above light intensity formula is automatically adjusted , then use the adjusted new coefficient combination to conduct simulation tests again, compare the deviations of the blue, green, and red focus intensities, and repeat the above process until the focus points of the three colors are close enough, that is, the blue, green, and red light intensities are almost the same at the same position, and end the iterative simulation.

[0025] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0026] The achromatic liquid crystal holographic lens provided by the present invention can achieve the unification of the focusing focal length and focal light intensity of light of different wavelengths. That is, it can make light of different wavelengths focus at the same distance and have the same focal length after passing through the lens, eliminating the phase difference (i.e., chromatic aberration) caused by different wavelengths, making the focal intensity of the three wavelengths almost the same, further improving the focal length efficiency of light, and providing a technical reference for those skilled in the art when designing achromatic lenses. The simulation design method of the present invention can also reduce experimental losses, making the lens thinner at a lower cost, easier to manufacture, and having extremely high economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the achromatic liquid crystal holographic lens proposed in the present invention;

[0028] Figure 2 These are front views of light focusing simulations before optimization of the present invention; (a) is a front view of blue light focusing simulations before optimization of the present invention; (b) is a front view of green light focusing simulations before optimization of the present invention; (c) is a front view of red light focusing simulations before optimization of the present invention;

[0029] Figure 3 : These are simulated top views of light focusing before optimization of the present invention; (a) is a simulated top view of blue light focusing before optimization of the present invention; (b) is a simulated top view of green light focusing before optimization of the present invention; (c) is a simulated top view of red light focusing before optimization of the present invention;

[0030] Figure 4 This is the distribution diagram of the energy curve of red, green and blue light at the focus of the lens before optimization of the present invention;

[0031] Figure 5 The figures are front-view effect diagrams of the optimized light focusing simulation of the present invention; (a) is the front-view effect diagram of the optimized blue light focusing simulation of the present invention; (b) is the front-view effect diagram of the optimized green light focusing simulation of the present invention; (c) is the front-view effect diagram of the optimized red light focusing simulation of the present invention;

[0032] Figure 6Optimized top views of light focusing according to the present invention; (a) is an optimized top view of blue light focusing according to the present invention; (b) is an optimized top view of green light focusing according to the present invention; (c) is an optimized top view of red light focusing according to the present invention;

[0033] Figure 7 This is the distribution diagram of the focused energy curve of the red, green and blue light at the focus of the lens after optimization of the present invention. DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0035] The present invention adopts the liquid crystal rod-shaped molecular material made of Figure 1 The achromatic metasurface waveplate crystal lens shown is composed of several crystals with different angles and refractive indices. It can solve the problem of focal length decreasing with increasing wavelength, thereby eliminating the phase difference (i.e. chromatic aberration) caused by different wavelengths of light.

[0036] This invention uses the interference of two circularly polarized light beams—a collimated beam and a divergent beam—to produce color fringes. When the coherent light sources have the same frequency, a constant phase difference, and consistent vibration directions, interference occurs, creating color fringes. Each wavelength component in the color fringes has a different focal length after passing through the lens, resulting in a phase difference (i.e., chromatic aberration).

[0037] The present invention provides a liquid crystal phase modulation method for an achromatic holographic lens, which is based on the wavelength of the incident light and the position coordinates when the incident light is irradiated on the lens surface ( x , z ) Reversely calculate the deflection angle of the optical axis of the liquid crystal rod-shaped molecules at different positions on the lens to achieve the focusing of light of any wavelength at the focal length position of the lens. The formula is as follows:

[0038] (1);

[0039] in, α The optical axis of the liquid crystal rod molecules is on the surface of the lens ( xz plane), the wavelength of the incident light beam is , n =1,2,3 correspond to blue, green and red wavelengths respectively, f is the focal length of the target where the light is focused, x , z Represents the liquid crystal rod-like molecules on the lens surface ( xz The position coordinates on the plane.

[0040] In this embodiment, the phase distribution that the liquid crystal holographic lens needs to satisfy under incident light of three different wavelengths: blue, green, and red is designed. The wavelengths of the incident light are: =486nm, =587nm, =656nm.

[0041] Due to the difference in wavelengths of the three types of light, the medium responds differently to light of different wavelengths, causing the focal length of the lens to decrease as the wavelength of the incident light increases. The specific focusing effects of incident light of three different wavelengths, blue, green, and red, are as follows: Figure 2 As shown. Among them, from Figure 2 As can be seen in (a), the wavelength is 486 nm The incident light (blue light) has the largest focal length after passing through the lens, and the wavelength is 656 nm The focal length of the incident light (red light) is the smallest, such as Figure 2 As shown in (c). Moreover, the focal points of the blue, green and red light waves are not on the same focal plane. At this time, the parameters of the liquid crystal holographic lens are: thickness of 1.3±0.1 μm ; focal length 80–100 μm Focal diameter ratio F #=1.

[0042] Furthermore, in Figure 3 From the focal plane view shown in (b), we can see that at a wavelength of 587 nm The focal spot diameter at the green wavelength is 1.43 um , the focusing effect is good, while the blue and red wavelengths are not focused at the focal point of the designed liquid crystal holographic lens, e.g. Figure 3 (a) and Figure 3 As shown in (c).

[0043] Furthermore, if Figure 4 As shown in the energy distribution curves of the blue, green, and red light focuses, the existence of dispersion causes different wavelengths of light to have different focal intensities at the same focal plane, resulting in serious deviations in the focal points of different light, which reduces the light control efficiency of the liquid crystal holographic lens.

[0044] Furthermore, the phase of the light wave depends not only on the wavelength of the light wave, but also on the position of the light wave on the lens. x Axis and z The coordinates of the axis are determined, so the phases of different light waves can be calculated using relevant formulas. Therefore, the phase of the light wave can be precisely controlled by adjusting the position of the light beam on the lens. The phases of different light waves satisfy the following relationship:

[0045] (2);

[0046] in, is the liquid crystal phase at different positions of the lens.

[0047] In order to effectively eliminate the dispersion phenomenon caused by the difference in light wavelength, the present invention introduces formula (3) to accurately correct the phase at different positions of the liquid crystal holographic lens. With the help of this formula, the phase of red, green and blue light can be unified and coordinated, and the focus points can be accurately converged on the same focal plane, thereby significantly improving the focusing efficiency and accuracy of the lens. The improved light focusing intensity E , the phase of the focused light Phase with liquid crystal holographic lens The relationship satisfies the following conditions:

[0048] (3);

[0049] (4);

[0050] in, E is the energy of light focused after passing through the liquid crystal holographic lens, and the variables and represent the coordinates of the focal point of the light. According to the changes of x, y, The calculated phase of the focused light is a coefficient used to adjust the phase intensity of the liquid crystal holographic lens corresponding to different incident light wavelengths. This coefficient is a constant value and can be dynamically adjusted according to the simulation results.

[0051] optimization The steps are:

[0052] Based on the above-mentioned liquid crystal holographic lens phase modulation model, a finite element simulation model of the liquid crystal holographic lens is established in COMSOL software. The specific steps include:

[0053] Step 1: First, set the blue, green, and red wavelength parameters to 486 nm 、587 nm 、656 nm .

[0054] Step 2: Set the liquid crystal material parameters and boundary conditions, mainly setting the refractive index of the liquid crystal material and , dielectric anisotropy coefficient , elastic constant K 11 , K 22 , K 33 etc.; the boundary conditions on both sides of the lens are set as periodic boundary conditions or perfectly matched layer absorption boundaries.

[0055] Step 3: The holographic lens phase modulation model described above and Frank-Oseen The elastic continuum equation calculates the pointing vector of the optical axis of the liquid crystal molecules, and then converts the pointing vector into a spatially varying refractive index tensor.

[0056] Step 4: Perform optical diffraction analysis of the liquid crystal holographic lens and divide the liquid crystal layer (the constructed liquid crystal lens) into a large number of high-resolution grids (the grid size is set to ≤ λ / 10, about 50 nm ), and then use the Maxwell equation solver to solve the light field distribution of the parallel light wave focused by the liquid crystal holographic lens.

[0057] With the focus light intensity consistency as the optimization goal, =486 nm , 587 nm , 656 nm Dynamic adjustment Output The phase weight coefficient combination.

[0058] The specific iterative simulation process to determine the optimal coefficient combination is as follows: First, calculate the distance difference between the blue, green, and red focal points. If the distance difference is too large, making the light intensity deviation greater than 5%, automatically adjust the coefficient corresponding to the above light intensity formula according to the size and direction of the deviation. , then use the adjusted new coefficient combination, conduct simulation tests again, compare the red, green and blue focus intensity deviations, and repeat the above process until the focus points of blue, green and red are close enough, that is, the blue, green and red light intensities are almost the same at the same position, and end the iterative simulation.

[0059] Furthermore, different settings are made for the three different wavelengths of light: blue, green, and red. , respectively: 1.26, 1, 1.05.

[0060] After optimization, the focusing effect of the liquid crystal holographic lens is as follows: Figure 5 shown. Figure 5 (a), (b), and (c) show the focusing effect of three different wavelengths of blue, green, and red light at the focal length of the lens. The corresponding phase intensity of light of different wavelengths on the lens surface is optimized, so that all light rays are focused on the same focal plane.

[0061] Furthermore, if Figure 6 As shown, light of three different incident wavelengths, blue, green and red, can all exhibit similar focusing intensities at the same focusing position, effectively ensuring that light of different wavelengths can be focused at the focal length of the liquid crystal holographic lens.

[0062] Furthermore, if Figure 7 As shown in the figure, after introducing the formula to optimize the phase distribution on the surface of the liquid crystal holographic lens, the focused light intensities of the three wavelengths of blue, green and red at the focus of the lens are almost equal, and the focused light intensities of blue, green and red light are all close to 100%. The offset of the focus position is significantly reduced, and the optical efficiency and consistency of the lens for focusing blue, green and red light of different wavelengths are significantly improved.

[0063] The present invention proposes a phase modulation method based on an achromatic liquid crystal holographic lens with adjustable focal length, aiming to achieve consistency in the focusing position and light intensity of light of different wavelengths after passing through the lens, effectively eliminating the chromatic aberration problem common to traditional optical lenses and holographic lenses.

[0064] This invention effectively addresses the inherent drawbacks of traditional achromatic lenses, such as doublets, such as their heavy weight and large size. To verify the effectiveness of the proposed liquid crystal holographic lens phase modulation method, a finite element simulation model of the achromatic liquid crystal holographic lens was established, and its focusing effect was quantitatively analyzed.

[0065] Experimental results show that light of three different wavelengths, blue, green, and red, can be focused at the same distance after passing through the lens, achieving focal length consistency and effectively eliminating phase differences (i.e., chromatic aberration) caused by wavelength differences. This results in consistent focal intensities for the three wavelengths, significantly improving light focal efficiency. This invention provides an important technical reference for those skilled in the art in designing achromatic lenses. It also effectively reduces losses during the experimental process and can achieve thinner lens thickness while lowering production costs, making it easier to mass-produce and possessing significant economic value.

[0066] The above specific embodiments only express several embodiments of the present invention, and their descriptions are relatively specific and detailed, but do not constitute a limitation on the scope of protection of the present invention. It should be noted that for those skilled in the art, various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors without departing from the concept of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be within the scope of protection of the present invention. Therefore, the scope of protection of the patent of the present invention shall be based on the attached claims.

Claims

1. A phase modulation method for an achromatic liquid crystal holographic lens, characterized in that: The steps include: Step 1: According to the wavelength λ of the incident beam n , the target focal length f and the position coordinates (x, z) of the light beam on the lens surface, n = 1, 2, 3 correspond to the blue, green, and red wavelengths respectively, and the deflection angle α of the optical axis of the liquid crystal rod-shaped molecules is calculated by the following formula: Regulating the spatial orientation distribution of liquid crystal molecules at various positions on the lens surface based on the deflection angle α; Step 2: Based on the molecular orientation determined in step 1, the incident light wavelength λ n And position coordinates (x, z), the phase distribution of the liquid crystal holographic lens at each position in the xz plane is generated by the following formula A phase modulation model is constructed to focus light of different wavelengths to a target focal length f using a liquid crystal holographic lens. The liquid crystal holographic lens satisfies the following requirements: thickness of 1.3±0.1 μm; focal length of 80–100 μm; and focal diameter ratio F#=1. Step 3: Phase distribution generated in step 2 Energy-weighted correction is performed, and the focal light intensity E of each wavelength of red, green, and blue in the xy plane and the corresponding composite phase φ(x, y) of the three wavelengths of red, green, and blue light in the xy plane are calculated using the following formula, dynamically optimizing the phase weight coefficient of the incident light wavelength: Among them A k is the wavelength of incident light λ k The phase weight coefficient, (x,y) represents the focus coordinates of the light in the xy plane, is the single wavelength phase generated in step 2, i is the imaginary unit; Finite element simulation is used to calculate the light intensity E1, E2, and E3 of the three wavelengths of blue, green, and red at the focus, and adjust A n Make the three-wavelength focal light intensity close to the same; The phase weight coefficient optimization in step 3 specifically includes: Based on the phase modulation model, a finite element simulation model of the liquid crystal holographic lens was established in COMSOL software; With the light intensity deviation of blue, green and red wavelengths at the focus ≤ 5% as the optimization goal, A is dynamically adjusted at λ1 = 486nm, λ2 = 587nm, and λ3 = 656nm. n ; Output the phase weight coefficient A that makes E1≈E2≈E3 n combination; Among them, dynamic adjustment A n The specific steps include: Step 1: Set the incident light wavelength parameters: λ1 = 486nm, λ2 = 587nm, λ3 = 656nm; Step 2: Set the liquid crystal material parameters: ordinary light refractive index n o and the extraordinary refractive index n e , dielectric anisotropy coefficient Δε, elastic constant K 11 ,K 22 ,K 33 , corresponding to the liquid crystal molecular bending, twisting, and bending deformation modes respectively; setting boundary conditions: the boundary conditions on both sides of the lens are set to periodic boundary conditions or perfectly matched layer absorption boundaries; Step 3: Based on the liquid crystal molecule deflection angle obtained in step 1, the pointing vector of the liquid crystal molecule optical axis is calculated using the Frank-Oseen elastic continuum equation, and then the pointing vector is converted into a spatially varying refractive index tensor; Step 4: Perform optical diffraction analysis and solve the liquid crystal holographic lens. Divide the liquid crystal lens into a high-resolution grid with a grid size of less than or equal to λ / 10. Then use the Maxwell equation solver to solve the light field distribution of blue, green, and red light waves passing through the liquid crystal holographic lens. Step 5: Execute phase weight coefficient A n Iterate the simulation optimization process and output the optimal coefficient combination; the specific steps include: (a) Calculation of the current phase weight coefficient A in the finite element simulation model n The focal position and intensity of blue, green and red light E n ; (b) Calculate the distance difference between the focal points and the light intensity deviation; (c) If the focus distance difference is greater than the threshold or the light intensity deviation is greater than 5%, the phase weight coefficient A is automatically adjusted according to the deviation size and direction n ; (d) Repeat the simulation test using the adjusted new phase weight coefficient combination; (e) Repeat steps (a) to (d) until the distance difference between the three wavelength focus points is less than the threshold and the light intensity deviation is less than or equal to 5%, and then end the iteration.

2. The method according to claim 1, characterized in that The liquid crystal rod-shaped molecules described in step 1 are orientable polymer materials; the distribution of the deflection angle α causes the refractive index of the lens surface to change in a continuous gradient.

3. The method according to claim 1, characterized in that In step 2, the incident light wavelength λ n Covering the visible light band, including λ1=486nm, λ2=587nm, and λ3=656nm.

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