Double-sided directional free-form surface light beam regulation and control device suitable for double light sources and design method thereof

Abstract

The invention discloses a double-sided directional free-form surface light beam regulation and control device suitable for double light sources and a design method thereof, and belongs to the field of non-imaging optical and free-form surface optical design. The device comprises a light source module, a first free-form surface, a second free-form surface, a first target surface and a second target surface. The light source module comprises two different types of light sources, namely a laser light source and an LED light source, located on the two sides of the lens. The two light sources can work independently. And the first free-form surface and the second free-form surface form an integral double-sided free-form surface lens structure which is used for realizing directional light beam regulation and control on the two light sources. The shapes of the two free-form surfaces are independently designed through a bidirectional iteration geometrical optical algorithm, so that the system meets the energy conservation and refraction laws in two light source modes, and compatibility and direction selective regulation and control of different space coherence light sources are achieved. The dual-function integration of laser beam shaping and LED illumination can be realized in a single lens, and the laser beam shaping and LED illumination lens has the advantages of high luminous efficiency, compact structure and high adaptability.

Description

Technical Field

[0001] This invention relates to the fields of non-imaging optics and freeform surface optics design, specifically to a dual-light source dual-directional freeform surface beam control device and its design method, which can achieve direction-selective beam shaping and illuminance control according to the type of incident light source (Gaussian distributed laser or divergent LED). Background Technology

[0002] Freeform surface optics has become an important research direction in the fields of optical design and precision manufacturing in recent years. It achieves precise control of light propagation path through asymmetric and non-rotational surface design, playing an important role in fields such as lighting, display, imaging and laser processing.

[0003] Traditional freeform surface illumination lenses typically achieve energy redistribution based on the principle of geometric optics mapping, thereby obtaining a preset illuminance distribution under a single incident light field. However, most of these systems are designed for a single light source type and a fixed light incident direction, lacking compatibility with different light source distribution characteristics. Therefore, it is difficult to achieve efficient light energy utilization and directional switchable illumination control in multi-mode optical systems.

[0004] Existing freeform surface lighting systems are mostly limited to creating a prescribed illuminance distribution only along the direction of light propagation for the same type of light source (such as LEDs or two lasers). When the characteristics of the light sources on the left and right sides differ significantly—for example, one side is a quasi-Gaussian distributed laser source and the other side is a wide-angle diverging LED source—traditional freeform surface systems cannot simultaneously achieve beam shaping and illuminance homogenization within the same lens structure. Furthermore, laser sources possess high spatial coherence, narrow divergence angle, and high energy density, while LED sources exhibit low coherence and a wide-angle distribution. The significant differences in energy density, divergence angle, and luminous flux between the two place higher demands on the design of freeform surface shapes.

[0005] Therefore, there is an urgent need for a new freeform surface design and device structure that can independently and directionally selectively control the beams of two different types of light sources, laser and LED, within the same lens, and achieve adaptive matching of the light field and control of energy distribution in bidirectional working mode to meet the needs of applications such as intelligent lighting, laser processing, micro-projection and optical communication. Summary of the Invention

[0006] This invention addresses the technical problem of existing freeform surface lighting systems, which can only adapt to a single light source and cannot simultaneously achieve laser beam shaping and LED illuminance uniformity. It proposes a dual-sided directional freeform surface beam control device suitable for dual light sources. This device integrates two sets of freeform surfaces within a single lens and utilizes geometric optics mapping and bidirectional iterative optimization methods to ensure that light sources with different optical properties on both sides can form a preset light field distribution when operating independently, thus achieving the dual functions of laser beam shaping and LED lighting. This invention can automatically respond to different light sources according to the incident direction, achieving direction-dependent and light source-adaptive light field control.

[0007] This invention proposes a direction-selective, dual-light-source, double-sided directional freeform surface beam control device, comprising a light source module, a first freeform surface, a second freeform surface, a first target surface, and a second target surface. The first and second freeform surfaces together constitute an integral double-sided freeform surface lens structure. The light emitted by the light source module includes two different types of light sources located on both sides of the lens: a laser light source and an LED light source, and the relative positions of the light sources and the lens surface are fixed. When the light is incident from a first direction, the light emitted by the light source module is refracted sequentially by the first and second freeform surfaces, forming a preset first beam distribution on the first target surface. When the light is incident from a second direction, the light emitted by the light source module is refracted sequentially by the second and first freeform surfaces, forming a second preset beam distribution on the second target surface.

[0008] Preferably, the laser source outputs a Gaussian intensity distribution, and the LED source outputs a Lambertian divergent light field; the laser source and the LED source can be lit independently. When the laser source is used, the freeform lens shapes the laser beam to achieve a first preset beam distribution. When the LED source is lit, the freeform lens redistributes the energy of the LED divergent light field to achieve a second preset beam distribution.

[0009] Preferably, both the first freeform surface and the second freeform surface are defined using B-spline form:

[0010] Define U={u0,…,u m} is a non-decreasing increasing sequence of real numbers, i.e., u i ≤u i+1 (i=0,1,…,m), where u i The nodes are called nodes, U is called the node vector, and m is the number of nodes; the p-th order B-spline basis function N of the i-th node. i,p (u) is defined as:

[0011]

[0012] The p-order B-spline curve is defined as:

[0013]

[0014] Where { P i Let} be the control point defined at node i, C(u) be the coordinates of the surface point, a, b be the range of values ​​for the node, and n be the number of control points; the B-spline surface uses a bidirectional control point mesh and two node vectors, constructed by the product of two univariate B-spline functions:

[0015] .

[0016] Preferably, when the light source is placed on the left side of the first freeform surface, the light propagates from left to right, and the light beam defined by the parameter coordinates u(u,v) intersects the first target surface at coordinates x1(x1,y1) after refraction by the two surfaces; when the light source is placed on the right side of the second freeform surface, the light propagates from right to left, and the light beam defined by the parameter coordinates u(u,v) intersects the second target surface at coordinates x2(x2,y2) after refraction by the two surfaces; under the two illumination modes, the light refracted by the freeform surface travels from the light source coordinate u to the target surface intersection coordinate x, forming a light mapping relationship M. k (u;S1,S2): u→x, k=1,2 represent the illumination modes corresponding to the light source being placed at the left and right ends of the lens, respectively, where M k S1 is the mapping function from the light source coordinates u to the target point coordinates x, and S2 is the surface characterization function of the first freeform surface and the second freeform surface, respectively; the illuminance I1(x1,y1) of the first target surface and the illuminance I2(x2,y2) of the second target surface satisfy the following energy conservation relationship:

[0017]

[0018] Among them, DM k The Jacobian matrix represents the mapping relationship of light rays, det represents the determinant of the matrix, I0 is the illuminance distribution of the preset light source, and the illuminance I1(x1,y1) of the first target surface and the illuminance I2(x2,y2) of the second target surface have independently definable geometric shapes and illuminance distributions on the first target surface and the second target surface.

[0019] This invention also provides a design method for a dual-light source, two-sided directional freeform surface beam control device, comprising the following steps:

[0020] First, an optical model is established, including a light source, two freeform surfaces, and a target surface. The position, direction, and illuminance distribution of the light source, as well as the preset illuminance distributions of the first and second target surfaces, are set, and the initial geometry of the first and second freeform surfaces is determined.

[0021] Then, a two-stage optimization is performed:

[0022] In the first stage of optimization, the optical surface of the current first freeform surface is fixed, and a second freeform surface is designed to control the laser beam illuminance distribution to the preset illuminance distribution of the first target surface. The calculated point cloud of the second freeform surface is then fitted into a B-spline form.

[0023] In the second stage of optimization, the optical surface of the current second freeform surface is fixed, and the first freeform surface is designed to control the LED illuminance distribution to the preset illuminance distribution of the first target surface. The calculated point cloud of the first freeform surface is then fitted into a B-spline form.

[0024] Repeat the above two-stage alternating optimization until the illuminance error functions in both directions converge to the preset threshold simultaneously. After the iteration, a combination of freeform surfaces that satisfies the bidirectional lighting conditions is obtained.

[0025] Preferably, the illuminance error function formula is as follows:

[0026]

[0027] Where L represents the illuminance error function, I1 sim and I2 sim dA1 and dA2 represent the simulated illuminance distributions on the first target surface and the second target surface, respectively; I1 and I2 represent the micro-areas of the first target surface and the second target surface, respectively; and I1 and I2 represent the preset illuminance distributions on the first target surface and the second target surface, respectively.

[0028] Preferably, both optical surfaces of the double-sided freeform lens are freeform surfaces and do not have any rotational or translational symmetry characteristics.

[0029] Preferably, the refractive index of each region of the freeform lens is the same, and the medium surrounding the freeform lens is a homogeneous medium with a refractive index different from that of the lens.

[0030] The beneficial effects of this invention compared to the prior art are:

[0031] This invention achieves integrated bidirectional beam shaping functionality, realizing independent beam shaping functions for both forward and reverse directions and for two different light sources in a single lens, i.e., two illumination modes in a single lens, thus improving system integration.

[0032] This invention achieves a strict match between the illuminance of the outgoing target surface and the preset illuminance distribution through geometric optics iterative optimization, enabling complex lighting functions to be realized from both sides downwards, thus fulfilling highly demanding lighting requirements.

[0033] The dual-sided directional freeform surface beam control device for laser and LED light sources involved in this invention has strong scalability and can further broaden the application scenarios of light source types such as laser light sources, VCSEL light sources, and two different light sources used in two lighting modes. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of a double-sided directional freeform surface beam control device applicable to laser and LED light sources according to the present invention;

[0035] Figure 2 This is a schematic diagram illustrating the working principle of the freeform surface lens of the present invention.

[0036] Figure 3 This is a schematic diagram illustrating the ray tracing principle of the freeform surface lens of this invention;

[0037] Figure 4 The diagram shows the elevation distribution of the first and second freeform surfaces in the embodiment.

[0038] Figure 5 The Gaussian curvature distribution diagrams for the first and second freeform surfaces in this embodiment are shown.

[0039] Figure 6 This is a model diagram of the double-sided oriented freeform lens in the embodiment;

[0040] Figure 7 This is a simulated illuminance distribution diagram of the first and second target surfaces of the present invention;

[0041] Wherein, 1 is the light source module, 2 is the first freeform surface, 3 is the second freeform surface, 4 is the first target surface, and 5 is the second target surface. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings and specific examples. However, the scope of protection of the present invention is not limited to the following embodiments.

[0043] like Figure 1 and Figure 2 As shown, the present invention provides a direction-selective double-sided directional freeform surface beam control device, comprising a light source module 1, a first freeform surface 2, a second freeform surface 3, a first target surface 4, and a second target surface 5. The first freeform surface 2 and the second freeform surface 3 together constitute an integral double-sided freeform surface lens structure; the light source module 1 can be arranged on both sides of the lens according to different illumination directions, and the relative positions of the light source and the lens surface are fixed. See [reference needed]. Figure 1When light is incident from the first direction, the light emitted by the light source module 1 is refracted sequentially by the first freeform surface 2 and the second freeform surface 3, forming a preset first beam distribution on the first target surface 4. When light is incident from the second direction (i.e., the other side of the lens), the light emitted by the light source module 1 is refracted sequentially by the second freeform surface 3 and the first freeform surface 2, forming a second preset beam distribution on the second target surface 5. The two illumination modes do not interfere with each other, and the light in each direction satisfies Snell's law and the energy conservation condition. See [link to relevant documentation]. Figure 2 The double-sided freeform lens of this invention can be made of high-transmittance glass or optical polymer materials, with a wavelength range of 400nm–700nm in the visible light spectrum. It can be manufactured using processes such as single-stage molding, double-sided ultra-precision polishing, or injection molding. The refractive index is the same in all regions of the freeform lens, and the surrounding medium is air. The freeform lens serves simultaneously as a shaping lens after both LED and laser light sources, i.e., a secondary lens.

[0044] In embodiments of the present invention, both the first freeform surface 2 and the second freeform surface 3 are defined using B-spline form. Define U = {u0, …, u0} m} is a non-decreasing increasing sequence of real numbers, i.e., u i ≤ u i+1 (i = 0, 1, …,m), where u i The nodes are called nodes, U is called the node vector, and m is the number of nodes. The p-th (p+1)th order B-spline basis function N at the i-th node... i,p (u) is defined as:

[0045]

[0046] The p-order B-spline curve is defined as:

[0047]

[0048] Where { P i Let} represent the control point defined at node i, C(u) be the coordinates of the surface point, a and b be the range of values ​​for the node, and n be the number of control points. Correspondingly, a B-spline surface can be constructed using a bidirectional control point mesh and two node vectors, by multiplying two univariate B-spline functions:

[0049]

[0050] The first freeform surface is characterized as the parametric surface S1(x,y), and the second freeform surface is characterized as the parametric surface S2(x,y).

[0051] like Figure 3As shown, the system's central optical axis is set along the z-direction, with the first freeform surface 2 located on the left and the second freeform surface 3 on the right. When the light source is placed to the left of the first freeform surface 2, the light propagates from left to right. The light beam, defined by the parameter coordinates u(u,v), intersects the first target surface at coordinates x1(x1,y1) after refraction by the two surfaces. When the light source is placed to the right of the second freeform surface 3, the light propagates from right to left. The light beam, defined by the parameter coordinates u(u,v), intersects the second target surface at coordinates x2(x2,y2) after refraction by the two surfaces. In both illumination modes, the light refracted by the freeform surfaces travels from the light source coordinate u to the target surface intersection point x, forming a light mapping relationship M. k (u;S1,S2): u→x, k=1,2 represent the lighting patterns corresponding to the light source being placed at the left and right ends, respectively, where M k S1 is the mapping function from the light source coordinates u to the target point coordinates x, and S2 is the surface characterization function of the first and second freeform surfaces, respectively. The illuminance I1(x1, y1) of the first target surface and the illuminance I2(x2, y2) of the second target surface satisfy the following energy conservation relationship:

[0052]

[0053] Among them, DM k The Jacobian matrix represents the mapping relationship of light rays, det represents the determinant of the matrix, and I0 is the illuminance distribution of the preset light source.

[0054] The specific design steps for the aforementioned direction-selective double-sided directional freeform surface illumination lens are as follows:

[0055] Step 1: Establish an optical model including a light source, two freeform surfaces, and a target surface. Set up the optical path structure of the double-sided freeform lens. Both optical surfaces of the freeform lens are freeform surfaces, without any rotational or translational symmetry characteristics. The lens has two illumination modes corresponding to a laser light source and an LED light source placed at preset positions on both sides of the freeform surface. After refraction by the freeform surface, target illuminance distributions adapted to different light sources are obtained on the first and second target surfaces. Perform freeform surface design based on the initial design parameters.

[0056] The freeform lens can control the luminous energy distribution of both the laser and LED light sources, where the laser source is a collimated Gaussian beam with a cross-sectional illuminance distribution as follows:

[0057]

[0058] Where E0 is the light intensity at the center point and r0 is the waist radius of the Gaussian beam.

[0059] The LED light source emits light in a Lambertian distribution, and its illuminance distribution on a plane with a projection distance of z0 is as follows:

[0060]

[0061] Step 2: Set the position, direction, and illuminance distribution of the light source, as well as the preset illuminance distribution of the first and second target surfaces: Establish a global rectangular coordinate system xyz with the center of the freeform lens as the origin, set the lens thickness t, the positions of the light source on the left and right sides z1 and z2, and the positions of the first and second target surfaces z t1 and z t2 The preset illumination distributions I1(x,y) and I2(x,y) of the first and second target surfaces are set, and the preset lens material and its refractive index are set.

[0062] Step 3, set the initial optical surface S (0) 1 and S (0) 2. Use a sphere or a known freeform surface as the initial geometry. Traverse the light rays emitted from the light source under both lighting modes to obtain the initial ray mapping relationship M. (0) k (u; S (0) 1,S (0) 2): k = 1, 2.

[0063] Step 4, First stage optimization (forward): Fix the S of the current first freeform surface 2 (n) 1. Design a second freeform surface 3 to control the laser beam illuminance distribution I0(u, v) to the preset illuminance distribution I1(x1, y1) on the first target surface. Calculate the deviation of the incident light distribution on the second freeform surface 3 from the illuminance on the target surface using ray tracing, based on the ray mapping relationship and the energy conservation equation:

[0064]

[0065] Adjust the local curvature and normal vector direction of the second free surface (3) to make its output illuminance distribution approximate the target I1(x, y). The following energy conservation relationship must be satisfied:

[0066]

[0067] The calculated point cloud of the second free surface is fitted into a B-spline form.

[0068] Step 5, Second Stage Optimization (Reverse): Fix the S of the current second freeform surface 3 (n) 2. Design the first freeform surface 2 to realize the LED illuminance distribution. The illuminance distribution I2(x2, y2) of the first target surface is controlled by ray tracing. The deviation of the incident light distribution on the first freeform surface (2) from the illuminance of the target surface is calculated by ray tracing. The illuminance is determined by ray mapping relationship and energy conservation equation.

[0069]

[0070] Adjust the local curvature and normal vector direction of the first freeform surface (2) so that its output illuminance distribution approximates the target I2(x, y). The following energy conservation relationship must be satisfied:

[0071]

[0072] The calculated point cloud of the first freeform surface is fitted into a B-spline form.

[0073] Step 6: Repeat the above two steps alternately to optimize until the illuminance error function in both directions is satisfied. Simultaneously converges to the preset threshold:

[0074]

[0075] Among them, I1 sim and I2 sim dA1 and dA2 represent the simulated illuminance distributions on the first target surface and the second target surface, respectively; I1 and I2 represent the micro-areas of the first target surface and the second target surface, respectively; and I1 and I2 represent the preset illuminance distributions on the first target surface and the second target surface, respectively.

[0076] After the iteration, a combination of freeform surfaces that satisfy the bidirectional illumination condition is obtained.

[0077] Example: A double-sided directional freeform surface lens is used as follows Figure 1 The structure shown has the lens center located at the origin of the global coordinate system, and the lens thickness is 20mm. In illumination mode 1, the laser source is located to the left of the lens at z1=-40mm, and the first target surface is located to the right of the lens at z1=-40mm. t1 =60mm; In illumination mode 2, the LED light source is located on the right side of the lens, z2=40mm, and the second target surface is located on the left side of the lens, z t2 =-100mm; the preset illuminance of the first target surface is a uniformly distributed triangular region, and the preset illuminance of the second target surface is a uniformly distributed trapezoidal region; the preset lens material is polymethyl methacrylate (PMMA), with a refractive index of 1.4894 at a wavelength of 550nm.

[0078] The initial freeform surface is characterized as a standard surface, and its sagitta is represented by the following equation:

[0079]

[0080] The initial surface coefficients of the first freeform surface are C1 = 1 / R1 = -1 / 70, k = 0; the initial surface coefficients of the second freeform surface are C2 = 1 / R2 = 1 / 70, k = 0. Steps 4-6 above are performed iteratively to obtain the final freeform surface lens. The elevation distributions of the first and second freeform surfaces are shown in [reference needed]. Figure 4 For the Gaussian curvature distributions of the first and second freeform surfaces, please refer to [reference needed]. Figure 5 ; Figure 4 Figure 5 The surface shapes and Gaussian curvatures of the first and second freeform surfaces shown indicate that the lens has complex asymmetric surface features. The lens structure model was obtained by modeling the designed double freeform surfaces in CAD software. (See attached image for lens structure model). Figure 6 Compared to conventional lenses, the lens implemented in this invention has a more complex surface structure. The freeform lens model is subjected to non-sequential Monte Carlo ray tracing in optical software for illumination modes 1 and 2, respectively, to obtain simulated illuminance distributions on the first and second target surfaces. See [link to relevant documentation]. Figure 7 Simulation results show that the lens achieves different illuminance distribution controls for laser and LED light sources, demonstrating the ability of a single lens to independently control beams for different light sources. The illuminance diagram clearly shows that the proposed dual-sided directional freeform surface illumination device effectively achieves two illumination modes. When the corresponding light sources are placed on opposite sides of the lens, two different predetermined illumination spots are achieved on the first and second target surfaces, respectively.

[0081] As can be seen from the embodiments, the dual-sided directional freeform surface beam control device proposed in this invention, suitable for dual light sources, can achieve direction-selective beam shaping and illuminance control in a single optical element. Moreover, the lens surface is continuously smooth and easy to optically process. It has the advantages of compact structure, high light efficiency, and strong scalability, which verifies the feasibility and application potential of this invention.

Claims

1. A dual-light source, double-sided directional freeform surface beam control device, characterized in that, The system includes a light source module (1), a first freeform surface (2), a second freeform surface (3), a first target surface (4), and a second target surface (5). The first freeform surface (2) and the second freeform surface (3) together form an integral double-sided freeform surface lens structure. The light emitted by the light source module (1) includes two different types of light sources located on both sides of the lens: a laser light source (L1) and an LED light source (L2), and the relative positions of the light source and the lens surface are fixed. When the light is incident from the first direction, the light emitted by the light source module (1) is refracted sequentially by the first freeform surface (2) and the second freeform surface (3) to form a preset first beam distribution on the first target surface (4). When the light is incident from the second direction, the light emitted by the light source module (1) is refracted sequentially by the second freeform surface (3) and the first freeform surface (2) to form a second preset beam distribution on the second target surface (5).

2. The dual-light source, dual-directional freeform surface beam control device according to claim 1, characterized in that, The laser source (L1) outputs a Gaussian light intensity distribution, and the LED source (L2) outputs a Lambertian divergent light field. The laser source (L1) and the LED source (L2) can be lit independently. When the laser source (L1) is used, the freeform lens shapes the laser beam to form a first preset beam distribution. When the LED source (L2) is lit, the freeform lens redistributes the energy of the LED divergent light field to form a second preset beam distribution.

3. The dual-light source, dual-directional freeform surface beam control device according to claim 2, characterized in that, Both the first free surface (2) and the second free surface (3) are defined in B-spline form: Define U={u0,…,u m } is a non-decreasing increasing sequence of real numbers, i.e., u i ≤u i+1 (i=0,1,…,m), where u i The nodes are called nodes, U is called the node vector, and m is the number of nodes; the p-th order B-spline basis function N of the i-th node. i,p (u) is defined as: The p-order B-spline curve is defined as: Where {P i Let} be the control point defined at node i, C(u) be the coordinates of the surface point, a, b be the range of values ​​for the node, and n be the number of control points; the B-spline surface uses a bidirectional control point mesh and two node vectors, constructed by the product of two univariate B-spline functions: 。 4. The dual-light source, dual-directional freeform surface beam control device according to claim 3, characterized in that, When the light source is placed to the left of the first freeform surface (2), the light propagates from left to right. The light beam defined by the parameter coordinate u(u,v) intersects the first target surface at coordinate x1(x1,y1) after being refracted by the two surfaces. When the light source is placed to the right of the second freeform surface (3), the light propagates from right to left. The light beam defined by the parameter coordinate u(u,v) intersects the second target surface at coordinate x2(x2,y2) after being refracted by the two surfaces. In both lighting modes, the light refracted by the freeform surface starts from the light source coordinate u and ends at the target surface at coordinate x, forming a light mapping relationship M. k (u;S1,S2): u→x, k=1,2 represent the illumination modes corresponding to the light source being placed at the left and right ends of the lens, respectively, where M k S1 is the mapping function from the light source coordinates u to the target point coordinates x, and S2 is the surface characterization function of the first and second freeform surfaces, respectively; the illuminance I1(x1,y1) of the first target surface and the illuminance I2(x2,y2) of the second target surface satisfy the following energy conservation relationship: Among them, DM k The Jacobian matrix represents the mapping relationship of light rays, det represents the determinant of the matrix, I0 is the illuminance distribution of the preset light source, and the illuminance I1(x1,y1) of the first target surface and the illuminance I2(x2,y2) of the second target surface have independently definable geometric shapes and illuminance distributions on the first target surface (4) and the second target surface (5).

5. A design method for a dual-source, two-sided directional freeform surface beam control device as described in any one of claims 1-4, characterized in that, Includes the following steps: First, an optical model is established, including a light source, two freeform surfaces and a target surface. The position and direction of the light source, the illuminance distribution of the light source, and the preset illuminance distribution of the first and second target surfaces are set. The initial geometry of the first freeform surface (2) and the second freeform surface (3) is also set. Then, a two-stage optimization is performed: In the first stage of optimization, the optical surface of the current first freeform surface (2) is fixed, and a second freeform surface (3) is designed to realize the control of the laser beam illuminance distribution to the preset illuminance distribution of the first target surface. The calculated point cloud of the second freeform surface is fitted into a B-spline form. In the second stage of optimization, the optical surface of the current second freeform surface (3) is fixed, and the first freeform surface (2) is designed to realize the control of the LED illuminance distribution to the preset illuminance distribution of the first target surface. The calculated point cloud of the first freeform surface is fitted into a B-spline form. Repeat the above two-stage alternating optimization until the illuminance error functions in both directions converge to the preset threshold simultaneously. After the iteration, a combination of freeform surfaces that satisfies the bidirectional lighting conditions is obtained.

6. The design method of a dual-light source, dual-sided directional freeform surface beam control device according to claim 5, characterized in that, Both optical surfaces of the double-sided freeform lens are freeform surfaces and do not have any rotational or translational symmetry properties.

7. The design method of a dual-light source, dual-sided directional freeform surface beam control device according to claim 6, characterized in that, The formula for the illuminance error function is as follows: Where L represents the illuminance error function, I1 sim and I2 sim dA1 and dA2 represent the simulated illuminance distributions on the first target surface and the second target surface, respectively; I1 and I2 represent the micro-areas of the first target surface and the second target surface, respectively; and I1 and I2 represent the preset illuminance distributions on the first target surface and the second target surface, respectively.

8. The design method of a dual-light source, dual-sided directional freeform surface beam control device according to claim 7, characterized in that, The freeform lens has the same refractive index in all regions, and the medium surrounding the freeform lens is a homogeneous medium with a refractive index different from that of the lens.

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