Design method of high-efficiency LED fiber illumination coupler based on free-form surface

Abstract

The application provides a design method of a high-efficiency LED optical fiber illumination coupler based on free-form surfaces, which is used for designing an LED optical fiber illumination coupler composed of a lens assembly and a reflector to converge light of an LED light source to an optical fiber incident end, and comprises the following steps: step 1, establishing an optical plane, and dividing the light emitted by the LED light source into small-angle light and large-angle light; step 2, iteratively calculating surface data of a first free-form surface according to the edge ray theory and the geometric optics law; step 3, iteratively calculating surface data of a second free-form surface according to the edge ray theory and the geometric optics law; step 4, rotating a first free-form curve generatrix to obtain the lens assembly; step 5, iteratively calculating surface data of a third free-form surface according to the edge ray theory and the geometric optics law; step 6, rotating a third free-form curve generatrix to obtain the reflector; and step 7, combining the assemblies to obtain the LED optical fiber illumination coupler.

Description

Technical Field

[0001] This invention belongs to the technical field of LED fiber optic lighting couplers, and specifically relates to a design method for a high-efficiency LED fiber optic lighting coupler based on a freeform surface. Background Technology

[0002] LED fiber optic lighting systems achieve photoelectric separation and are widely used in lighting scenarios in special environments, such as endoscopic lighting, and lighting in environments with salt spray, mold, water vapor, and mines. LED light sources are Lambertian emitters with a emission angle range of 0° to 180°. Optical fibers transmit light based on the principle of total internal reflection and have a specific numerical aperture. Therefore, optical fibers have a maximum angle of incidence. Light entering the fiber's incident end face must have an angle less than this maximum angle (generally less than 30°) for the light to propagate within the fiber; otherwise, it will exit from the side of the fiber as stray light. The function of the LED fiber optic lighting coupler is to couple as much light emitted from the LED as possible into the fiber's incident end face and achieve total internal reflection within the fiber.

[0003] There are three existing LED fiber optic lighting couplers: 1. Direct coupling of a single LED to the incident end face of the optical fiber; 2. Coupling of a single LED and a lens group to the optical fiber; 3. Coupling of multiple LEDs and a lens group to the optical fiber.

[0004] CN 109893085A discloses a scheme for direct coupling of a single LED with the incident end face of an optical fiber, realizing a small-sized and highly reliable handheld fundus camera. However, due to the direct coupling between the LED and the incident end face of the optical fiber, most of the light cannot be well coupled with the optical fiber, resulting in low system luminous efficiency and a lot of heat generated.

[0005] CN 208569112U discloses a scheme for coupling a single LED and a lens group with an optical fiber. First, the light emitted by the single LED is collimated by a collimating lens, and then the light is focused onto the incident end face of the optical fiber by a converging lens. However, it is difficult to collimate the large-angle light emitted by the LED through the lens, and too many lenses will also reduce the optical efficiency of the system.

[0006] CN 211011180U discloses a scheme for coupling a single LED and a lens group with an optical fiber. The scheme first collimates the light from the single LED using a TIR lens, and then focuses the light onto the incident end face of the optical fiber using a converging lens. Although this scheme collects LED light at a large angle, the combination of TIR and lens results in a large system size, which is not conducive to the miniaturization of the system. At the same time, the converging of the single lens has spherical aberration, which will form a blur spot near the focal point, resulting in low optical efficiency of the system.

[0007] CN 208459632U ​​discloses a scheme for coupling multiple LED light sources with a lens group. Since the converging lens needs to converge the light emitted by multiple LEDs, the system has a large size. At the same time, the system has low optical efficiency because it cannot collect the light from the LEDs at large angles.

[0008] Therefore, there is an urgent need for an optical solution with high coupling efficiency and compact system structure in the technology of LED light source couplers. Summary of the Invention

[0009] This invention is made to solve the above-mentioned problems, and aims to provide a design method for a high-efficiency LED fiber optic lighting coupler based on a freeform surface.

[0010] This invention provides a design method for a high-efficiency LED fiber optic lighting coupler based on a freeform surface. The method involves designing an LED fiber optic lighting coupler composed of a lens assembly and a reflector, which focuses light emitted from an LED light source onto the incident end of an optical fiber. The method comprises the following steps:

[0011] Step 1: Establish an xyz coordinate system and take the xy plane as the optical plane. In the first quadrant of the optical plane, the LED light source is located at the origin O, and the optical axis is the x-axis. Divide the light emitted by the LED light source into small-angle light and large-angle light. The straight line containing the centerline of the incident end of the optical fiber coincides with the optical axis. The center of the LED light source is located on the optical axis.

[0012] Step 2: Based on the small-angle rays of the LED light source, using the laws of geometric optics and the theory of edge rays, calculate the surface data points of the first freeform surface of the lens assembly in the first quadrant of the optical plane through iterative calculation. Fit the data points to obtain the generatrix of the first freeform surface, and then draw the first straight line perpendicular to the y-axis through the starting point of the generatrix of the first freeform surface.

[0013] Step 3: Based on the collimated light rays from the first freeform surface, using the laws of geometric optics and the theory of edge rays, calculate the surface data points of the second freeform surface of the lens assembly in the first quadrant of the optical plane through an iterative calculation method, and fit the data points to obtain the generatrix of the second freeform surface. Then, draw a second straight line perpendicular to the y-axis through the starting point of the generatrix of the second freeform surface.

[0014] Step 4: Rotate the closed area formed by the first freeform surface generatrix, the second freeform surface generatrix, the y-axis, the first straight line, and the second straight line 360° around the optical axis to obtain the overall structure of the lens assembly. The lens assembly focuses the small-angle light from the LED light source to the incident end of the optical fiber.

[0015] Step 5: Based on the large-angle rays of the LED light source, using the laws of geometric optics and the theory of edge rays, calculate the surface data points of the third freeform surface of the reflector in the first quadrant of the optical plane through iterative calculation, and fit the data points to obtain the generatrix of the third freeform surface;

[0016] Step 6: Rotate the third freeform surface generatrix 360° around the line containing the optical axis to obtain the overall structure of the reflector. The reflector reflects the large-angle light from the LED light source to the incident end of the optical fiber.

[0017] Step 7: Combine the lens assembly and reflector to obtain an LED fiber optic lighting coupler, wherein the divergence angle of the LED light source is θ, the angle of the small-angle light is θ1, the angle of the large-angle light is θ2, and θ = θ1 + θ2.

[0018] The design method for a high-efficiency LED fiber optic lighting coupler based on a freeform surface provided by this invention may also have the following feature: step 2 includes the following sub-steps:

[0019] Step 2-1: In the design of the first freeform surface, the light rays will be collimated. In the xy plane, θ1 is divided into H equal parts, where H is a positive integer. Let the starting point coordinates of the first freeform surface be P0(Px0,Py0). The small-angle light rays from the LED light source are divided into H+1 rays, and the light OP... i The angle between (i = 0, 1, 2…H) and the x-axis is The unit vector of each ray is The light rays exiting the first freeform surface are a set of collimated rays P that are approximately parallel to the optical axis. i R i (i = 0, 1…H), its unit vector is The refractive index of air is n0, and the refractive index of the lens material is n1. Based on the laws of geometric optics and the theory of edge rays, we obtain formula (1) as follows:

[0020]

[0021] In formula (1), K 1i The constant to be determined is calculated as the unit vector of the normal to each point of the first freeform surface in the optical plane.

[0022] Step 2-2, based on geometric relationships, With OP i The following relationship must be satisfied:

[0023]

[0024] In formula (2), λ1 is a constant, which satisfies the following according to the iterative calculation method:

[0025]

[0026] By combining formulas (2) and (3), the surface shape data point P of the first freeform surface in the first quadrant of the optical plane is obtained. i (Px i ,Py i (i = 0, 1, 2…H), the first free surface generatrix is ​​obtained by fitting the data points;

[0027] Steps 2-3: Draw a first straight line perpendicular to the y-axis through the starting point P0(Px0,Py0) of the first freeform surface generatrix, intersecting the y-axis at point P. 0y (0, Py0), thus obtaining the first straight line P. 0y P0.

[0028] The design method for a high-efficiency LED fiber optic lighting coupler based on a freeform surface provided by this invention may also have the following feature: step 3 includes the following sub-steps:

[0029] Step 3-1: In the design of the second freeform surface, the light rays will be converged to the center point R of the incident end of the optical fiber. Let the starting point coordinates of the second freeform surface be T0(Tx0,Ty0). According to the laws of geometric optics and the theory of edge rays, we obtain formula (4):

[0030]

[0031] In formula (4), K 2i The constant to be determined is calculated as the unit vector of the normal to each point of the second freeform surface in the optical plane.

[0032] Step 3-2, based on geometric relationships, and The following relationship must be satisfied:

[0033]

[0034] In formula (5), λ2 is a constant, which satisfies the following according to the iterative calculation method:

[0035]

[0036] By combining formulas (5) and (6), the surface shape data point T of the second freeform surface in the first quadrant of the optical plane is obtained. i (Tx i ,Ty i (i = 0, 1, 2…H+1), the data points are fitted to obtain the second free surface generatrix;

[0037] Step 3-3: Draw a second straight line perpendicular to the y-axis through the starting point T0(Tx0,Ty0) of the second freeform surface generatrix, and intersect the y-axis at T. 0y (0,Ty0) yields the second straight line T. 0y T0.

[0038] In the design method of a high-efficiency LED fiber optic lighting coupler based on a freeform surface provided by this invention, the following feature can also be included: According to edge ray theory and geometric optics laws, the starting points of the first and second freeform surface generatrices ensure that the outgoing light rays after collimation and convergence by the lens assembly at small angles match the numerical aperture of the optical fiber. The outgoing light rays undergo total emission after entering the optical fiber. The starting points P0(Px0, Py0) and T0(Tx0, Ty0) of the first freeform surface generatrices satisfy the following relationship:

[0039]

[0040]

[0041] In formula (8), θ max The numerical aperture of an optical fiber is NA = n0sinθ, which is the angle between the light and the optical axis at the point of total internal reflection. max .

[0042] The design method for a high-efficiency LED fiber optic lighting coupler based on a freeform surface provided by this invention may also have the following feature: step 5 includes the following sub-steps:

[0043] Step 5-1: In the design of the third freeform surface, light rays are first refracted through the first straight line P. 0y P0 and the second straight line T 0y After reflection from the third freeform surface, the light rays converge at the center point R of the incident end of the optical fiber. In the xy-plane, θ2 is divided into H equal parts, where H is a positive integer. Let the starting point coordinates of the third freeform surface be Q0(Qx0, Qy0). Points Q0, T0, and R are on a straight line. The light ray OQ... i The angle between (i = 0, 1, 2…H) and the y-axis is With the second straight line T0T 0y The intersection point is D i (Dx i Given a group (Ty0)(i=0,1,2…H), according to the laws of geometrical optics, it satisfies:

[0044]

[0045] Its unit vector is According to the laws of geometric optics:

[0046]

[0047] In formula (10), K 3i The constant to be determined is calculated as the unit vector of the normal to each point of the third freeform surface in the optical plane.

[0048] Step 5-2, based on geometric relationships, and Satisfy the following relationship:

[0049]

[0050] In formula (11), λ3 is a constant, which satisfies the following according to the iterative calculation method:

[0051]

[0052] By combining formulas (11) and (12), the surface shape data point Q of the third freeform surface in the first quadrant of the optical plane is obtained. i (Qx i Qy i (i = 0, 1, 2…H), the data points are fitted to obtain the third free surface generatrix.

[0053] In the design method of a high-efficiency LED fiber optic lighting coupler based on a freeform surface provided by this invention, the following feature can also be included: According to edge ray theory and geometric optics laws, the starting point position of the third freeform surface generatrix ensures that the outgoing ray after large-angle light rays are reflected by the reflector matches the numerical aperture of the optical fiber. The outgoing ray undergoes total emission after entering the optical fiber. The starting point Q of the third freeform surface generatrix... H (Qx H Qy H )satisfy:

[0054]

[0055] The role and effect of invention

[0056] The design method of a high-efficiency LED fiber optic lighting coupler based on freeform surfaces according to the present invention can simultaneously converge and utilize large-angle and small-angle light rays from the LED light source through the designed lens assembly and reflector, thus improving light energy utilization and reducing heat dissipation difficulty; because the outgoing light is matched with the numerical aperture of the optical fiber based on the edge ray principle, the designed LED fiber optic lighting coupler can be applied to thin-diameter optical fibers, improving coupling efficiency; and the LED fiber optic lighting coupler designed by the present invention can achieve light collimation and convergence through three freeform surfaces, resulting in a compact system structure. Attached Figure Description

[0057] Figure 1 This is a flowchart illustrating a design method for a high-efficiency LED fiber optic lighting coupler based on a freeform surface, as described in an embodiment of the present invention.

[0058] Figure 2 This is a surface view of the LED fiber optic lighting coupler in the first quadrant of the optical plane according to an embodiment of the present invention;

[0059] Figure 3 This is a schematic diagram of the design of the first freeform surface in an embodiment of the present invention;

[0060] Figure 4 This is a schematic diagram of the design of the second free-form surface in an embodiment of the present invention;

[0061] Figure 5 This is a schematic diagram of the lens assembly in an embodiment of the present invention;

[0062] Figure 6 This is a schematic diagram of the design of the third freeform surface in an embodiment of the present invention;

[0063] Figure 7 This is a schematic diagram of the reflector structure in an embodiment of the present invention;

[0064] Figure 8 This is a schematic diagram of the overall structure of the LED fiber optic lighting coupler in an embodiment of the present invention;

[0065] Figure 9 This is a schematic diagram of the LED fiber optic lighting coupler converging LED light from an embodiment of the present invention. Detailed Implementation

[0066] To make the technical means and effects of the present invention easy to understand, the present invention will be specifically described below in conjunction with embodiments and accompanying drawings.

[0067] <Example>

[0068] Figure 1 This is a flowchart illustrating a design method for a high-efficiency LED fiber optic lighting coupler based on a freeform surface, as described in an embodiment of the present invention.

[0069] like Figure 1 As shown in this embodiment, a design method for a high-efficiency LED fiber optic lighting coupler based on a freeform surface is presented. This method is used to design an LED fiber optic lighting coupler composed of a lens assembly and a reflector. The LED fiber optic lighting coupler is used to focus the light emitted by an LED light source onto the incident end of an optical fiber. The method includes the following steps:

[0070] Figure 2This is a surface view of the LED fiber optic lighting coupler in the first quadrant of the optical plane according to an embodiment of the present invention.

[0071] like Figure 2 As shown, in step 1, an xyz coordinate system is established, and the xy plane is taken as the optical plane. In the first quadrant of the optical plane, the LED light source 1 is located at the origin O, and the optical axis is the x-axis. The light emitted by the LED light source 1 is divided into small-angle light and large-angle light. The straight line containing the centerline of the incident end 2 of the optical fiber coincides with the optical axis. The center point of the incident end 2 of the optical fiber is R, with coordinates (Rx, 0). The center of the LED light source 1 is located on the optical axis. The divergence angle of the LED light source 1 is θ. The angle of the small-angle light is θ1, and the angle of the large-angle light is θ2. θ = θ1 + θ2.

[0072] Figure 3 This is a schematic diagram of the design of the first freeform surface in an embodiment of the present invention.

[0073] like Figure 3 As shown, in step 2, based on the small-angle light rays of the LED light source 1, the geometric optics law and edge ray theory are used to calculate the surface data points of the first freeform surface 31 of the lens assembly in the first quadrant of the optical plane through iterative calculation. The data points are fitted to obtain the first freeform surface generatrix 32, and then a first straight line perpendicular to the y-axis is drawn through the starting point of the first freeform surface generatrix 32.

[0074] Step 2 includes the following sub-steps:

[0075] Step 2-1: In the design of the first freeform surface 31, the light rays will be collimated. In the xy plane, θ1 is divided into H equal parts, where H is a positive integer. Let the starting point coordinates of the first freeform surface be P0(Px0,Py0). The light rays emitted by the LED light source 1 at a small angle are divided into H+1 rays, and the light ray OP... i The angle between (i = 0, 1, 2…H) and the x-axis is The unit vector of each ray is The light rays exiting the first freeform surface 31 are a set of collimated rays P that are approximately parallel to the optical axis. i R i (i = 0, 1…H), its unit vector is The refractive index of air is n0, and the refractive index of the lens material is n1. Based on the laws of geometric optics and the theory of edge rays, we obtain formula (1) as follows:

[0076]

[0077] In formula (1), K 1i As an undetermined constant, the calculated value is the unit vector of the normal to each point on the first freeform surface 31 within the optical plane.

[0078] Step 2-2, based on geometric relationships, With OP i The following relationship must be satisfied:

[0079]

[0080] In formula (2), λ1 is a constant, which satisfies the following according to the iterative calculation method:

[0081]

[0082] By combining formulas (2) and (3), the surface shape data point P of the first freeform surface 31 in the first quadrant of the optical plane is obtained. i (Px i ,Py i (i = 0, 1, 2…H), the data points are fitted to obtain the generatrix 32 of the first free curve;

[0083] Steps 2-3: Draw a first straight line perpendicular to the y-axis through the starting point P0(Px0,Py0) of the first freeform surface 31, intersecting the y-axis at point P. 0y (0, Py0), thus obtaining the first straight line P. 0y P0.

[0084] Figure 4 This is a schematic diagram of the design of the second free surface in an embodiment of the present invention.

[0085] like Figure 4 As shown, in step 3, based on the collimated light rays of the first freeform surface 31, the geometric optics law and edge ray theory are used to calculate the surface data points of the second freeform surface 33 of the lens assembly in the first quadrant of the optical plane through an iterative calculation method, and the data points are fitted to obtain the generatrix 34 of the second freeform surface. Then, a second straight line perpendicular to the y-axis is drawn through the starting point of the generatrix 34 of the second freeform surface.

[0086] Step 3 includes the following sub-steps:

[0087] Step 3-1: In the design of the second freeform surface 33, the light rays will be focused to the center point R of the incident end 2 of the optical fiber. Let the starting point coordinates of the second freeform surface 33 be T0(Tx0,Ty0). According to the laws of geometric optics and the theory of edge rays, we obtain formula (4):

[0088]

[0089] In formula (4), K 2i As an undetermined constant, the calculated value is the unit vector of the normal to each point of the second freeform surface 33 in the optical plane.

[0090] Step 3-2, based on geometric relationships, and The following relationship must be satisfied:

[0091]

[0092] In formula (5), λ2 is a constant, which satisfies the following according to the iterative calculation method:

[0093]

[0094] By combining formulas (5) and (6), the surface shape data points T of the second freeform surface 33 in the first quadrant of the optical plane are obtained. i (Tx i ,Ty i (i = 0, 1, 2…H+1), the data points are fitted to obtain the second free surface generatrix 34;

[0095] Step 3-3: Draw a second straight line perpendicular to the y-axis through the starting point T0(Tx0,Ty0) of the second freeform surface generatrix 34, and intersect the y-axis at T. 0y (0,Ty0) yields the second straight line T. 0y T0.

[0096] According to edge ray theory and geometric optics laws, the starting positions of the first freeform surface generatrix 32 and the second freeform surface generatrix 34 ensure that the outgoing ray after collimation and convergence by the lens assembly matches the numerical aperture of the optical fiber. The outgoing ray undergoes total emission after entering the optical fiber. The starting point P0(Px0,Py0) of the first freeform surface generatrix 32 and the starting point T0(Tx0,Ty0) of the first freeform surface generatrix 34 satisfy the following:

[0097]

[0098]

[0099] In formula (8), θ max The numerical aperture of an optical fiber is NA = n0sinθ, which is the angle between the light and the optical axis at the point of total internal reflection. max .

[0100] Figure 5 This is a schematic diagram of the lens assembly in an embodiment of the present invention.

[0101] like Figure 4 and Figure 5As shown, in step 4, the closed area formed by the first freeform surface generatrix 32, the second freeform surface generatrix 34, the y-axis, the first straight line, and the second straight line is rotated 360° around the optical axis to obtain the overall structure of the lens assembly 3. The lens assembly 3 focuses the small-angle light from the LED light source to the incident end 2 of the optical fiber.

[0102] Figure 6 This is a schematic diagram of the design of the third free surface in an embodiment of the present invention.

[0103] like Figure 6 As shown, in step 5, based on the large-angle rays of the LED light source 1, the edge ray theory and geometric optics laws are used to calculate the surface data points of the third freeform surface 41 in the first quadrant of the optical plane through iterative calculation, and the data points are fitted to obtain the generatrix 42 of the third freeform surface.

[0104] Step 5 includes the following sub-steps:

[0105] Step 5-1: In the design of the third freeform surface 41, the light ray is first refracted through the first straight line P. 0y P0 and the second straight line T 0y After reflection by the third freeform surface 41, the light rays converge at the center point R of the incident end 2 of the optical fiber. In the xy plane, θ2 is divided into H equal parts, where H is a positive integer. Let the starting point coordinates of the third freeform surface 41 be Q0(Qx0,Qy0). Points Q0, T0, and R are on a straight line. The light ray OQ i The angle between (i = 0, 1, 2…H) and the y-axis is With the straight line T0T 0y The intersection point is D i (Dx i Given a group (Ty0)(i=0,1,2…H), according to the laws of geometrical optics, it satisfies:

[0106]

[0107] Its unit vector is According to the laws of geometric optics:

[0108]

[0109] In formula (11), K 3i As an undetermined constant, the calculated value is the unit vector of the normal to each point on the third freeform surface 41 within the optical plane.

[0110] Step 5-2, based on geometric relationships, and Satisfy the following relationship:

[0111]

[0112] In formula (11), λ3 is a constant, which satisfies the following according to the iterative calculation method:

[0113]

[0114] By combining formulas (11) and (12), the surface shape data point Q of the third freeform surface 41 in the first quadrant of the optical plane is obtained. i (Qx i Qy i (i = 0, 1, 2…H), the data points are fitted to obtain the third free surface generatrix 42.

[0115] According to edge ray theory and geometric optics laws, the starting point of the third freeform surface generatrix 42 ensures that the outgoing ray after large-angle rays are reflected by the reflector matches the numerical aperture of the optical fiber. The outgoing ray undergoes total emission upon entering the optical fiber. The starting point Q of the third freeform surface generatrix 42... H (Qx H Qy H )satisfy:

[0116]

[0117] Figure 7 This is a schematic diagram of the reflector in an embodiment of the present invention.

[0118] like Figure 6 and Figure 7 As shown, in step 6, the third freeform surface generatrix 42 of the third freeform surface 41 is rotated 360° around the x-axis to obtain the overall structure of the reflector 4. The thickness of the reflector 4 can be determined according to the application requirements and processing level.

[0119] Figure 8 This is a schematic diagram of the overall structure of the LED fiber optic lighting coupler in an embodiment of the present invention.

[0120] like Figure 8 As shown, in step 7, the lens assembly 3 and the reflector 4 are combined to obtain an LED fiber optic lighting coupler, with the reflector 4 located outside the lens assembly 3.

[0121] Figure 9 This is a schematic diagram of the LED fiber optic lighting coupler converging LED light from an embodiment of the present invention.

[0122] like Figure 9 As shown, the small-angle light from the LED light source 1 is collimated by the first freeform surface 31 and then converged by the second freeform surface 33 to the incident end 2 of the optical fiber. The large-angle light from the LED light source 1 is reflected by the third freeform surface 41 and converged to the incident end 2 of the optical fiber.

[0123] The role and effect of the embodiments

[0124] According to the design method of a high-efficiency LED fiber optic lighting coupler based on freeform surfaces involved in this embodiment, the large-angle and small-angle light rays from the LED light source can be converged and utilized simultaneously through the designed lens assembly and reflector, thus improving light energy utilization and reducing heat dissipation difficulty. Because the outgoing light rays are matched with the numerical aperture of the optical fiber based on the edge ray theory, the designed LED fiber optic lighting coupler can be applied to thin-diameter optical fibers, improving coupling efficiency. Furthermore, the LED fiber optic lighting coupler designed in this embodiment can complete the collimation and convergence of light rays through three freeform surfaces, resulting in a compact system structure.

[0125] The above embodiments are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention.

Claims

1. A design method for a high-efficiency LED fiber optic lighting coupler based on a freeform surface, used to design an LED fiber optic lighting coupler composed of a lens assembly and a reflector, wherein the LED fiber optic lighting coupler is used to focus light emitted from an LED light source onto the incident end of an optical fiber, characterized in that, Includes the following steps: Step 1: Establish an xyz coordinate system and take the xy plane as the optical plane. In the first quadrant of the optical plane, the LED light source is located at the origin O, and the optical axis is the x-axis. The light emitted by the LED light source is divided into small-angle light and large-angle light. The straight line of the centerline of the incident end of the optical fiber coincides with the optical axis. The center of the LED light source is located on the optical axis. Step 2: Based on the small-angle rays of the LED light source, using the laws of geometric optics and the theory of edge rays, calculate the surface data points of the first freeform surface of the lens assembly in the first quadrant of the optical plane through an iterative calculation method. Fit the data points to obtain the generatrix of the first freeform surface, and then draw a first straight line perpendicular to the y-axis through the starting point of the generatrix of the first freeform surface. Step 3: Based on the collimated light rays from the first freeform surface, using the laws of geometric optics and the theory of edge rays, calculate the surface data points of the second freeform surface of the lens assembly in the first quadrant of the optical plane through an iterative calculation method, and fit the data points to obtain the generatrix of the second freeform surface. Then, draw a second straight line perpendicular to the y-axis through the starting point of the generatrix of the second freeform surface. Step 4: Rotate the closed area formed by the first freeform surface generatrix, the second freeform surface generatrix, the y-axis, the first straight line, and the second straight line 360° around the optical axis to obtain the overall structure of the lens assembly. The lens assembly focuses the small-angle light from the LED light source to the incident end of the optical fiber. Step 5: Based on the large-angle rays of the LED light source, using the laws of geometric optics and the theory of edge rays, calculate the surface data points of the third freeform surface of the reflector in the first quadrant of the optical plane through an iterative calculation method, and fit the data points to obtain the generatrix of the third freeform surface; Step 6: Rotate the third freeform surface generatrix around the line containing the optical axis by 360° to obtain the overall structure of the reflector. The reflector reflects the large-angle light from the LED light source to the incident end of the optical fiber. Step 7: Combine the lens assembly and the reflector to obtain the LED fiber optic lighting coupler. Wherein, the divergence angle of the LED light source is θ, the angle of the small-angle ray is θ1, and the angle of the large-angle ray is θ2, where θ = θ1 + θ2. Step 2 includes the following sub-steps: Step 2-1: In the design of the first freeform surface, the light rays will be collimated. In the xy plane, θ1 is divided into H equal parts, where H is a positive integer. Let the starting point coordinates of the first freeform surface be P0(Px0, Py0). The small-angle light rays of the LED light source are divided into H+1 rays, and the light OP... i The angle between (i = 0, 1, 2…H) and the x-axis is The unit vector of each ray is The light rays emitted after passing through the first freeform surface are a set of collimated rays P that are approximately parallel to the optical axis. i R i (i = 0, 1…H), its unit vector is The refractive index of air is n0, and the refractive index of the lens material is n1. Based on the laws of geometric optics and the theory of edge rays, we obtain formula (1) as follows: In formula (1), K 1i The constant to be determined is the unit vector of the normal to each point of the first freeform surface in the optical plane. Step 2-2, based on geometric relationships, With OP i The following relationship must be satisfied: In formula (2), λ1 is a constant, which satisfies the following according to the iterative calculation method: By combining formulas (2) and (3), the surface shape data point P of the first freeform surface in the first quadrant of the optical plane is obtained. i (Px i ,Py i (i = 0, 1, 2…H), the first freeform surface generatrix is ​​obtained by fitting the data points; Steps 2-3: Draw the first straight line perpendicular to the y-axis through the starting point P0(Px0,Py0) of the first freeform surface generatrix, and intersect the y-axis at point P. 0y (0, Py0) is used to obtain the first straight line P. 0y P0, Step 3 includes the following sub-steps: Step 3-1: In the design of the second freeform surface, the light rays will be converged to the center point R of the incident end of the optical fiber. Let the starting point coordinates of the second freeform surface be T0(Tx0,Ty0). According to the laws of geometric optics and the theory of edge rays, we obtain formula (4): In formula (4), K 2i The constant to be determined is calculated as the unit vector of the normal to each point of the second freeform surface in the optical plane. Step 3-2, based on geometric relationships, and The following relationship must be satisfied: In formula (5), λ2 is a constant, which satisfies the following according to the iterative calculation method: By combining formulas (5) and (6), the surface shape data point T of the second freeform surface in the first quadrant of the optical plane is obtained. i (Tx i ,Ty i (i = 0, 1, 2…H+1), the data points are fitted to obtain the second freeform surface generatrix; Step 3-3: Draw the second straight line perpendicular to the y-axis through the starting point T0(Tx0,Ty0) of the second freeform surface generatrix, and intersect the y-axis at T. 0y (0,Ty0) is used to obtain the second straight line T. 0y T0, Step 5 includes the following sub-steps: Step 5-1: In the design of the third freeform surface, light rays are first refracted through the first straight line P. 0y P0 and the second straight line T 0y After reflection from the third freeform surface, the light rays converge at the center point R of the incident end of the optical fiber. In the xy plane, θ2 is divided into H equal parts, where H is a positive integer. Let the starting point coordinates of the third freeform surface be Q0(Qx0, Qy0). Points Q0, T0, and R are on a straight line. The light ray OQ... i The angle between (i = 0, 1, 2…H) and the y-axis is With the second straight line T0T 0y The intersection point is D i (Dx i According to the laws of geometric optics, the following conditions are met: (i = 0, 1, 2…H) Its unit vector is According to the laws of geometric optics: In formula (10), K 3i The constant to be determined is the unit vector of the normal to each point of the third freeform surface in the optical plane. Step 5-2, based on geometric relationships, and Satisfy the following relationship: In formula (11), λ3 is a constant, which satisfies the following according to the iterative calculation method: By combining formulas (11) and (12), the surface shape data point Q of the third freeform surface in the first quadrant of the optical plane is obtained. i (Qx i Qy i (i = 0, 1, 2…H), the data points are fitted to obtain the third free surface generatrix.

2. The design method for a high-efficiency LED fiber optic lighting coupler based on a freeform surface according to claim 1, characterized in that: in, According to edge ray theory and geometric optics laws, the starting positions of the first and second freeform surface generatrices ensure that the outgoing ray after the small-angle ray is collimated and converged by the lens assembly matches the numerical aperture of the optical fiber. The outgoing ray undergoes total emission upon entering the optical fiber. The starting points P0(Px0, Py0) of the first and second freeform surface generatrices satisfy the following relationship: In formula (8), θ max The numerical aperture NA of the optical fiber is NA = n0sinθ, which is the angle between the optical fiber and the optical axis at the point of total internal reflection. max Rx represents the x-coordinate of the center point R.

3. The design method for a high-efficiency LED fiber optic lighting coupler based on a freeform surface according to claim 2, characterized in that: in, According to edge ray theory and geometric optics laws, the starting point of the third freeform surface generatrix ensures that the outgoing ray after the large-angle ray is reflected by the reflector matches the numerical aperture of the optical fiber. The outgoing ray undergoes total emission after entering the optical fiber. The starting point Q0(Qx0, Qy0) of the third freeform surface generatrix satisfies:

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