Collimating lens and collimating lens design method

Abstract

The present invention discloses a collimating lens and a collimating lens design method. The collimating lens is a rotationally symmetrical structure, the center of the light source is set on the rotational symmetry axis of the lens, and includes a total internal reflection free-form surface group, a low-angle free-form surface group and a high-angle free-form surface group. The low-angle incident light beam emitted by the light source is refracted by the low-angle free-form surface group and then collimated and emitted; the high-angle incident light beam emitted by the light source is refracted by the high-angle free-form surface group and then collimated and emitted to compensate for the light output of the collimating lens. The present application compensates for the light output of the total internal reflection part in the collimating lens by constructing free-form surfaces corresponding to high and low-angle incident light beams, so that when the high and low-angle parts and the total internal reflection part of the light reach the target illumination area, the light spot is complete and uniform. At the same time, by constructing free-form surfaces corresponding to high and low-angle incident light beams, the overall lens has more degrees of freedom and good optical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of lenses, and in particular to a collimating lens and a collimating lens design method. Background Art

[0002] There are many collimating lenses on the market, including spherical and aspherical ones. Usually, a lens group consisting of multiple lenses is used to collimate the light spot, which is not only complex in structure but also inefficient. In recent years, the use of free-form surface lenses can reduce the number of lenses to a certain extent compared to ordinary lenses, but the commonly used free-form surface lenses usually have only one or two free-form surfaces, with low degrees of freedom, and cannot achieve good optical effects.

[0003] At present, researchers have successfully designed a variety of free-form surface collimating lenses based on LED light sources. There are mainly two types, one is the total internal reflection (TIR) ​​collimating lens, and the other is the transmission collimating lens. However, these free-form surface collimating lenses have only one or two free-form surfaces, and their optical performance is relatively limited. For example, since the LED light source is a Lambertian light source with a large divergence angle, when the LED passes through the above-mentioned collimating lens, the light intensity distribution is approximately Gaussian, and most of the energy is concentrated in the center of the irradiated area, resulting in obvious glare. Therefore, a collimating lens that can reasonably distribute and regulate the light is needed. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a collimating lens and a design method thereof. The collimating lens is a fully free-form surface collimating lens. By increasing the degree of freedom, the controllability of the lens during design is improved, and the lens can reasonably distribute and control the light. The lens has good collimation performance, and can effectively improve uniformity and avoid glare. According to simulation, the divergence angle is only 1.8° at 50% of the maximum luminous intensity, and the uniformity of the light spot reaches 98.4%.

[0005] According to one aspect of the present invention, a collimating lens is provided. The collimating lens is a rotationally symmetrical structure. The center of the light source is arranged on the rotationally symmetrical axis of the lens. All surfaces of the collimating lens are free-form surfaces, including

[0006] A low-angle free-form surface group is configured to refract an incident light beam emitted by the light source and having an angle with the optical axis of the light source ranging from 0° to a first angle, and then collimate the incident light beam to emit the light beam;

[0007] A high-angle free-form surface group, configured to collimate and emit an incident light beam emitted by the light source at an angle of 90° to the optical axis of the light source after refraction, wherein the second angle is greater than the first angle;

[0008] The total internal reflection free-form surface group is configured to refract an incident light beam emitted by a light source and having an angle with the optical axis of the light source from a first angle to a second angle, and then collimate and emit the incident light beam.

[0009] The present application constructs free-form surfaces corresponding to high and low angle incident light beams, thereby compensating for the light output of the total internal reflection part in the collimating lens, so that when the high and low angle parts and the total internal reflection part of the light reach the target illumination area, the light spot is complete and uniform. At the same time, the present application constructs free-form surfaces corresponding to high and low angle incident light beams, so that the collimating lens has an additional 4 free-form surfaces, and all the surfaces of the collimating lens of the present application are free-form surfaces, which can effectively improve the controllability of the collimating lens during design, and improve the collimation and light output uniformity of the designed collimating lens through the design of each free-form surface, and avoid the problem of glare in the designed collimating lens, so that the overall lens has good optical properties. According to experiments, the light spot uniformity of the collimating lens can reach 98.4%, and the divergence angles can reach 3° and 1.8° respectively at 10% and 50% of the maximum luminous intensity. At present, not many indicators can be achieved, indicating that the collimating lens has a good collimating effect.

[0010] In some embodiments, the low-angle free-form surface group includes a second incident surface and a second exit surface. The low-angle incident light beam emitted by the light source enters the lens through the second incident surface and is refracted by the second exit surface before being collimated and emitted. The first angle is 30°.

[0011] Therefore, by setting the low-angle free-form surface group in this way, an incident light beam emitted by a light source and located near the optical axis can be refracted by the collimating lens and then collimated and emitted.

[0012] In some embodiments, the total internal reflection free-form surface group includes a first incident surface, a second reflective surface, and a first exit curved surface. The incident light beam emitted by the light source enters the lens through the first incident surface and is refracted by the second reflective surface, and then collimated and emitted from the first exit curved surface.

[0013] Therefore, by setting the total internal reflection free-form surface group in this way, the incident light beam emitted by the light source can be refracted inside the collimating lens and then emitted in a collimated manner.

[0014] In some embodiments, the position where the incident light beam emitted by the light source is reflected onto the first exit curved surface gradually moves away from the second exit curved surface from the intersection position of the first exit curved surface and the second exit curved surface as the angle between the incident light beam and the optical axis of the light source decreases. Thus, by such a design, the light beam refracted by the total internal reflection part of the collimating lens can be made more uniform, thereby improving the uniformity of the light spot.

[0015] In some embodiments, the high-angle free-form surface group includes a third incident surface and a first reflective surface. The high-angle incident light beam emitted by the light source enters the lens through the third incident surface and is refracted by the first reflective surface, and then collimated and emitted from the first exit surface and / or the second exit surface to compensate for the light output of the collimating lens. The second angle is 60°.

[0016] Therefore, by setting a high-angle free-form surface group, the incident light beam emitted by the light source at an angle close to 90° can be utilized to compensate for the light output of the collimating lens, thereby effectively improving the optical efficiency of the collimating lens.

[0017] In some embodiments, the curvature of the second incident curved surface can be designed to be a negative value along the light transmission direction, and can be configured to allow the light beam to be refracted by the second incident curved surface and then emitted in parallel. Thus, the second incident curved surface can be designed to be concave, so that the light beam is concentrated toward the center, the uniformity of the light spot is improved, the LED chip is prevented from imaging, and the light output collimation performance is improved.

[0018] According to another aspect of the present invention, a collimating lens design method is provided, the steps comprising:

[0019] Set initial values ​​based on design requirements and lens size, calculate discrete points on the total internal reflection free-form surface and fit them into a curve;

[0020] Construct the incident surface curve and the exit surface curve of the low-angle incident light beam;

[0021] Constructing an incident surface curve and a reflection surface curve of a high-angle incident light beam according to the light output of the total internal reflection free curve and the light output of the exit surface curve of the low-angle incident light beam;

[0022] A half-section curve of the collimating lens is obtained according to the total internal reflection free-form surface curve, the incident surface curve and the exit surface curve of the low-angle incident light beam, and the incident surface curve and the reflection surface curve of the high-angle incident light beam;

[0023] Construct a 3D model of the collimating lens based on the half-section curve.

[0024] The collimating lens design method of the present application firstly performs calculation design on the free-form surface of the total internal reflection part of the collimating lens, and then designs the free-form surfaces of the high-angle and low-angle parts to supplement the light output of the total internal reflection part, so that the designed collimating lens can have high collimation performance and high light spot uniformity, thereby improving the lighting effect of the collimating lens.

[0025] In some embodiments, a method for calculating discrete points on a total internal reflection free-form surface includes:

[0026] According to Snell's law, we can get the coordinate expression and tangent slope expression of the point where the incident light beam passes through each free-form surface line.

[0027] According to the law of conservation of energy, the Pythagorean theorem, and the coordinate expressions of the points on each free-form surface line through which the incident light beam passes and the expressions of the slopes of the tangent lines, the coordinate expressions of the points on each free-form surface line through which the next incident light beam passes are obtained;

[0028] The discrete points on the free-curve line of total internal reflection are obtained according to the coordinate expressions of the points on each free-curve line through which the incident light beam passes and the coordinate expressions of the points on each free-curve line through which the next incident light beam passes.

[0029] Therefore, the corresponding discrete points on the total internal reflection free-form surface line can be calculated by the calculation method, so as to construct the free-form curve profiles of the total internal reflection part of the collimating lens.

[0030] In some embodiments, the low-angle incident light beam and / or the incident surface curve and the exit surface curve are constructed by trial and error. Thus, the incident surface curve and the exit surface curve corresponding to the low-angle incident light beam can be constructed by this method to supplement the light output of the low-angle part of the total internal reflection part of the collimating lens.

[0031] In some embodiments, the steps further include:

[0032] Perform optical simulation on the 3D model of the collimating lens;

[0033] The initial values ​​are adjusted according to the simulation results to obtain an initial 3D model.

[0034] Therefore, the constructed 3D model can be simulated and analyzed through optical simulation, and the initial value can be adjusted to optimize the collimation and uniformity of the output light to obtain an optimized initial 3D model.

[0035] In some embodiments, the steps further include:

[0036] The initial 3D model is optimized using the normal vector correction method and result comparison method;

[0037] Perform high and low angle light compensation on the initial 3D model.

[0038] Therefore, the free-form surface of the total internal reflection part in the initial 3D model can be optimized through this method step, the slight deviation of the normal vector of the fitted free-form surface of the total internal reflection part due to software calculation can be reduced, and the high and low light in the initial 3D model can be compensated, thereby completing the overall optimization of the collimating lens and obtaining a complete optical lens structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the overall structure of a collimating lens according to one embodiment of the present invention;

[0040] Figure 2 for Figure 1 Ray tracing diagrams of a high-angle incident light beam and a low-angle incident light beam of an implementation method;

[0041] Figure 3 for Figure 1 Normalized irradiance image of the collimating lens at 40m far field of the embodiment;

[0042] Figure 4 for Figure 1 Normalized irradiance distribution curves of the collimating lens in the horizontal and vertical directions of the embodiment;

[0043] Figure 5 for Figure 1 Angular distribution curve of radiation intensity of the collimating lens of the embodiment;

[0044] Figure 6 A flow chart of a collimating lens design method according to an embodiment of the present invention;

[0045] Figure 7 for Figure 6 A flowchart of a method for calculating discrete points on a free-form surface with total internal reflection;

[0046] Figure 8 Schematic diagram of the iterative relationship for calculating discrete points on a free-form surface with total internal reflection;

[0047] Fig. 9 is a schematic diagram of a half-section curve of a collimating lens;

[0048] Explanation of the accompanying drawings: 1. Second incident curved surface; 2. First incident curved surface; 3. Third incident curved surface; 4. First reflection curved surface; 5. Second reflection curved surface; 6. Second exit curved surface; 7. First exit curved surface; 8. First connecting curved surface; 9. Second connecting curved surface. DETAILED DESCRIPTION

[0049] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0050] Embodiment 1

[0051] Figure 1 and Figure 2 The structural diagram of a collimating lens according to one embodiment of the present invention is schematically shown.

[0052] According to one aspect of the present invention, a collimating lens is provided, referring to Figure 1The collimating lens is a rotationally symmetrical structure, the center of the light source is arranged on the rotationally symmetrical axis of the lens, and includes a first free-form surface, a second free-form surface, an inner side surface and an outer side surface.

[0053] The first free-form surface is used to collimate the light beam, and includes a second exit curved surface 6 located in the middle of the first free-form surface and a first exit curved surface 7 surrounding the second exit curved surface 6. In this embodiment, the direction of the collimated emission is the same as the direction of the optical axis of the light source. The optical axis is a line passing through the center of the collimating lens, and the direction is from the second incident curved surface (1) to the second exit curved surface (6). The target illumination area is a plane perpendicular to the light emitted by the collimating lens.

[0054] The second free-curved surface is arranged opposite to the first free-curved surface, and the second free-curved surface includes a second incident curved surface 1. The low-angle incident light beam emitted by the light source is refracted to the second exit curved surface 6 through the second incident curved surface 1. The second incident curved surface 1 and the second exit curved surface 6 constitute a low-angle free-curved surface group of the collimating lens.

[0055] The inner side surface is connected to the second free-curved surface and forms a receiving cavity for arranging the light source with the second free-curved surface, and the outer side surface is connected to the first free-curved surface and the inner side surface;

[0056] The inner side surface includes a first incident curved surface 2 close to the second free curved surface and a third incident curved surface 3 close to the outer side surface, and the outer side surface includes a second reflective curved surface 5 close to the first exit curved surface 7 and a first reflective curved surface 4 close to the inner side surface;

[0057] Thus, one end of the first incident curved surface 2 is connected to the second incident curved surface 1, the other end of the first incident curved surface 2 is connected to the third incident curved surface 3, the other end of the third incident curved surface 3 is connected to the first reflective curved surface 4, the other end of the first reflective curved surface 4 is connected to the second reflective curved surface 5, the other end of the second reflective curved surface 5 is connected to the first exit curved surface 7, and the first exit curved surface 7 is surrounded by the outside of the second exit curved surface 6 to form a collimating lens;

[0058] The incident light beam emitted by the light source is refracted by the first incident curved surface 2 to the second reflective curved surface 5, and is reflected by the second reflective curved surface 5 to the first exit curved surface 7. The first incident curved surface 2, the second reflective curved surface 5 and the first exit curved surface 7 constitute a total internal reflection free-form curved surface group of the collimating lens.

[0059] The high-angle incident light beam emitted by the light source is refracted by the third incident curved surface 3 to the first reflective curved surface 4, and is reflected by the first reflective curved surface 4 to the first exit curved surface 7 and / or the second exit curved surface 6 to compensate for the light output. The third incident curved surface 3 and the first reflective curved surface 4 constitute a high-angle free-form surface group of the collimating lens.

[0060] The light output compensation here should be understood as improving the utilization rate of the high-angle light of the light source, reducing the light loss of the high-angle part of the light source, and setting the position of the light output point according to the light output conditions of the first output curved surface 7 and the second output curved surface 6, so as to make the light spot of the collimating lens more uniform and complete.

[0061] The low-angle incident beam and high-angle incident beam mentioned here are named according to the angle between the beam emitted by the light source and the optical axis of the light source. Figure 2 , the light beam in the middle of the figure is a low-angle incident light beam, while the light beams at the two ends of the figure are high-angle incident light beams. Specifically, low angle means that the angle between the light axis of the light source is between 0° and 30°, while high angle means that the angle between the light axis of the light source is between 60° and 90°.

[0062] It can be seen that in this lens, the light source is arranged in the accommodating cavity, is divided into three light beams, is incident on the collimating lens, and is refracted and emitted from the first free-form surface of the collimating lens in a collimated manner. Figure 2 For a low-angle incident light beam located near the optical axis of the light source, it is refracted into the collimating lens from the second incident curved surface 1, and then refracted by the second exit curved surface 6 before exiting the collimating lens.

[0063] In some embodiments, the curvature of the second incident curved surface 1 is designed to be a negative value along the light transmission direction, so that the low-angle incident light beam is concentrated toward the center of the collimating lens after being refracted by the second incident curved surface 1. The curvature of the second incident curved surface 1 is designed to be a negative value along the light transmission direction, that is, the second incident curved surface 1 is set to be concave toward the direction of the accommodating cavity, and because the second incident curved surface 1 is set to make the low-angle incident light beam passing through the second incident curved surface 1 be concentrated toward the center of the lens, the second exit curved surface 6 needs to be similarly set to be concave toward the direction of the accommodating cavity, so that the low-angle incident light beam concentrated after being refracted by the second incident curved surface 1 can be collimated and emitted out of the lens.

[0064] For an incident light beam that is neither within the high angle range nor within the low angle range, it is refracted from the first incident curved surface 2 on the inner side into the interior of the collimating lens, and after being reflected by the second reflective curved surface 5, it is emitted from the collimating lens at the first exit curved surface 7. This part is the total internal reflection part of the collimating lens, which mainly includes the first incident curved surface 2, the second reflective curved surface 5 and the first exit curved surface 7, so that most of the light beams emitted by the light source are output through the total internal reflection part of the collimating lens. Specifically, the position of the incident light beam emitted by the light source reflected on the first exit curved surface 7 gradually moves away from the second exit curved surface 6 from the intersection position of the first exit curved surface 7 and the second exit curved surface 6 as the angle of the incident light beam decreases, and the first exit curved surface 7 bends upward and outward from the edge of the second exit curved surface 6, so that the overall first free-form surface forms a concave shape, so that the light beam refracted by the total internal reflection part in the collimating lens can be more uniform, and the uniformity of the light spot is higher.

[0065] For a high-angle incident light beam whose angle with the optical axis of the light source is close to 90°, it is refracted into the collimating lens from the third incident curved surface 3 on the inner side, and after being reflected by the first reflective curved surface 4, it is used as a supplement to the light output of the first exit curved surface 7 and the second exit curved surface 6, and is emitted from the collimating lens on the first exit curved surface 7 and / or the second exit curved surface 6. This part is the high-angle incident light beam part, which, like the low-angle incident light beam part, compensates for the light output of the total internal reflection part. The high-angle incident light beam and the low-angle incident light beam are distributed to assist the light output of the total internal reflection part, so that the overall collimating lens can obtain a better light spot effect, as shown in reference Figure 2 In the ray tracing of the high-angle incident light beam, the high-angle incident light beam can be emitted at the junction of the first exit curved surface 7 and the second exit curved surface 6 after refraction, so that the light output of the collimating lens is more uniform.

[0066] In addition to the seven free-curved surfaces of the first exit curved surface 7, the second exit curved surface 6, the first incident curved surface 2, the second incident curved surface 1, the third incident curved surface 3, the first reflection curved surface 4 and the second reflection curved surface 5, the overall collimating lens also has a first connecting curved surface 8 connected between the third incident curved surface 3 and the first reflection curved surface 4 as a connecting surface between the curved surfaces, and a second connecting curved surface 9 connected between the first exit curved surface 7 and the second reflection curved surface 5 as a connecting surface between the curved surfaces, so that the curved surfaces of the overall collimating lens are completely connected.

[0067] The present application constructs free-form surfaces corresponding to high and low angle incident light beams, thereby compensating for the light output of the total internal reflection part in the collimating lens, so that when the high and low angle parts and the total internal reflection part of the light reach the target illumination area, the light spot is complete and uniform. At the same time, since the collimating lens of the present application is constructed with 7 free-form surfaces, the overall lens has more degrees of freedom and good optical performance.

[0068] For the performance of the collimating lens of this application, a simulation model is established by importing the solid model of the collimating lens into TracePro. The lens material is PMMA, and its refractive index is 1.49386. The incident light is a 1mm×1mm plane Lamber light source, the wavelength is set to 0.46μm, and the number of rays is 1 million. The receiving surface (target illumination area surface) is a square screen, 40m away from the light source, which is used to check the light distribution in the far field. The Monte Carlo trajectory tracking algorithm can be used to simulate the transmission path of light, and the results are shown in Figure 2. Figures 3 to 5 shown. Figure 3 This is a normalized irradiance diagram. The white dashed lines in the horizontal and vertical directions mark the center lines in the two directions respectively, and the intersection of the two dashed lines is on the optical axis. The central area formed by the intersection of the four white solid lines represents the area of ​​the uniform spot, which is about 0.4×0.4m 2 . It corresponds to Figure 4 Normalized irradiance distribution curves in horizontal and vertical directions for the area marked by the black dashed line. Uniformity is defined as:

[0069]

[0070] where σ E is the irradiance standard deviation, is the average irradiance, Figure 4 The solid line in the middle is the normalized irradiance distribution curve in the vertical direction, and the dotted line is the normalized irradiance distribution curve in the horizontal direction. The two are approximately overlapped in this figure, and the uniformity of the marked area in the horizontal and vertical directions is calculated to be 98.4%. Compared with the ordinary Gaussian spot, the spot uniformity is improved. Figure 5 The collimating lens of the present application, taking into account the divergence angles at 10% and 50% of the maximum luminous intensity, has corresponding θ values ​​of 3° and 1.8°, respectively, indicating that the collimating lens of the present application has an excellent collimating effect.

[0071] Embodiment 2

[0072] Figure 6 The flow of a collimating lens design method in one embodiment of the present invention is schematically illustrated.

[0073] According to another aspect of the present invention, a collimating lens design method is provided, referring to Figure 1 , the steps include:

[0074] Step S1: setting initial values ​​based on design requirements and lens size, calculating discrete points on the total internal reflection free-form surface and fitting them into a curve.

[0075] In step S1, the design requirements and the size and material of the lens need to be determined first. Due to the differences in design requirements, lens size, target spot position, etc., the design of each free-form surface of the lens itself will also be different.

[0076] The collimating lens of the present application mainly uses the free-form surface of the total internal reflection part as the light output, so the curve of this part is designed first. Figure 7 , when calculating the discrete points on the total internal reflection free-form surface, it can be achieved by the following steps:

[0077] Step S11: according to Snell's law, the coordinate expression and tangent slope expression of the point where the incident light beam passes through each free-form surface line are obtained;

[0078] Step S12: Calculate the coordinate expression of the point on each free-form surface line that the next incident light beam passes through according to the law of conservation of energy, the Pythagorean theorem, and the coordinate expression of the point on each free-form surface line that the incident light beam passes through and the tangent slope expression;

[0079] Step S13: Obtain discrete points on the total internal reflection free-curve line based on the coordinate expression of the points on each free-curve line that the incident light beam passes through and the coordinate expression of the points on each free-curve line that the next incident light beam passes through.

[0080] Therefore, the calculation method can be used to calculate the discrete points on each free-form curve line of the corresponding total internal reflection, so as to construct the free-form curve profiles of the total internal reflection part of the collimating lens.

[0081] Specifically, the collimating lens of one embodiment of the present application is taken as an example to illustrate the specific design calculation of step S11 to step S13:

[0082] Reference Figure 8 , construct a two-dimensional rectangular coordinate system, construct the first incident surface line, the second reflection surface line and the first exit surface line on the two-dimensional rectangular coordinate system, and set the light source at the origin. Take a beam of light as an example. The light beam enters the lens through point C on the first incident surface line, and then refracts to point D on the second reflection surface line. After reflection, it intersects with point E on the first exit surface line, and finally reaches the target illumination area vertically. Its focus is S, and the Y axis is the optical axis, which is perpendicular to the target illumination area. According to Snell's law, the following formula is obtained:

[0083]

[0084]

[0085]

[0086] in, is the incident light, To project light, For reflected light, is transmitted light, is the normal vector of point C, is the tangent vector at point C, is the normal vector of point D, is the tangent vector at point D, is the normal vector of point E, is the tangent vector at point E.

[0087] From formulas (2), (3) and (4), we can get:

[0088]

[0089]

[0090]

[0091] The coordinates of points C, D, E, and S are defined as (x c ,y c )、(x d ,y d )、(x e ,y e )、(x s ,y s ). According to equations (5), (6) and (7), the normal vector It can be represented by the following coordinates:

[0092]

[0093]

[0094]

[0095] Where R1, R2, and R3 are:

[0096]

[0097]

[0098]

[0099] Here R1, R2, and R3 have no physical meaning and are only used to simplify the formula. Then we can get the slope K of the tangent line passing through points C, D, and E. c , K d , K e :

[0100]

[0101]

[0102]

[0103] Reference for derivation of iteration relations Figure 8 The first incident curved line, the second reflected curved line, the first exit curved line, and any two adjacent points on the target illumination area are defined as C n , C n+1 , D n , D n+1 、E n 、E n+1 , S n , S n+1 The coordinates are (x cn ,y cn )、(x cn+1 ,y cn+1 )、(x dn ,y dn )、(x dn+1 ,y dn+1 )、(x en ,y en )、(x en+1 ,y en+1 )、(x sn ,y sn )、(x sn+1 ,y sn+1 ). From equations (14), (15) and (16), we can get n , D n 、E n The tangent line equation is:

[0104] yy cn =K cn (xx cn ) (17)

[0105] yy dn =K dn (xx dn ) (18)

[0106] yy en =K en (xx en ) (19)

[0107] where λ n yes and the x-axis, Δλ is and The angle between them, K cn , K dn , K en It passes through point Cn , D n 、E n The slope of the tangent line. When Δλ is small enough, the straight line OC n+1 and through point C n The focus of the tangent line is at point C n+1 Approximately coincide. Therefore, point C n+1 The coordinate equation is:

[0108]

[0109] y cn+1 =tan(λ n +Δλ)·x cn+1 (twenty one)

[0110] Wherein formula (21) is also OC n+1 The linear equation of .

[0111] According to the law of conservation of energy:

[0112]

[0113] Where φ is the energy distribution angle of the receiving surface, and E is the illumination received by the receiving surface. When n = 1, equation (22) can be written as:

[0114]

[0115] Where ω is a coefficient used to adjust the convergence. Further,

[0116]

[0117]

[0118]

[0119]

[0120] When Δλ is small enough, the straight line OE n+1 and through point E n The intersection of the tangent line and point E n+1 Approximately coincide. Combining (19) and (27), point E n+1 The coordinate equation is:

[0121]

[0122]

[0123] When Δλ is small enough, D n D n+1 Approximately a straight line, define D n Dn+1 The distance is f. According to the Pythagorean theorem, we can get:

[0124] (y dn+1 -y dn ) 2 +(x dn+1 -x dn ) 2 =f 2 (30)

[0125] Combining (18) and (30), point D n+1 The coordinates can be written as:

[0126]

[0127]

[0128] Visible D n+1 The coordinates of are related to f. In order to control the growth rate of the first incident surface line, the second reflected surface line, and the first exit surface line, two equations are added:

[0129] Y=(K cn -K cn+1 ) 2 +(K dn -K dn+1 ) 2 +(K en -K en+1 ) 2 (33)

[0130] f m =f0+mΔf (34)

[0131] where f m D for different m n D n+1 The distance, m is a non-negative integer. f0 and Δf are f m Initial value and step size. Define f0 = Δf = 0.01, at different f m Calculate a series of Y values, what we need is the minimum value of Y. This way we can get point D n+1 At this point, the iterative algorithm for the discrete points of the free-form surface of the total internal reflection part is completed, and point C can be calculated n+1 , D n+1 、E n+1 To obtain a first incident curved line, a second reflected curved line, and a first exit curved line.

[0132] Step S2: constructing an incident surface curve and an exit surface curve of a low-angle incident light beam.

[0133] In step S2, when constructing the incident surface curve and the exit surface curve of the low-angle incident light beam, they are mainly constructed by trial and error. The trial and error method is mainly to optimize the lens model through optical simulation based on experience by experienced optical engineers to meet the design requirements. The addition of the incident surface curve and the exit surface curve of the low-angle incident light beam can compensate for the light output of the free curve of the total internal reflection part and improve the uniformity of the light spot. When constructing the incident surface curve of the low-angle incident light beam, the curvature of the incident surface can be designed to be a negative value along the light transmission direction, so that the light beam is concentrated to the center of the lens, uniform lighting is achieved, the LED chip is placed for imaging, and the lens is collimated to emit light.

[0134] Taking the collimating lens in the first embodiment of the present application as an example, the second incident curved surface 1 is the incident surface of the low-angle incident light beam, and the second exit curved surface 6 is the exit surface of the low-angle incident light beam. The curvature of the second incident curved surface 1 is designed to be a negative value along the light transmission direction to concentrate the light toward the center and compensate for the light output of the low-angle part.

[0135] Step S3: constructing the incident surface curve and the reflection surface curve of the high-angle incident light beam according to the light output of the total internal reflection free curve and the light output of the exit surface curve of the low-angle incident light beam.

[0136] In step S3, when constructing the incident surface curve and the reflection surface curve of the high-angle incident light beam, they are mainly constructed by trial and error. The addition of the incident surface curve and the reflection surface curve of the high-angle incident light beam can compensate the light output of the free curve of the total internal reflection part after the high-angle incident light beam in the light source is refracted, thereby improving the uniformity of the light spot. During the construction, it is also necessary to perform 2D ray tracing on the obtained free curve profile, and appropriately increase and adjust the control points on the curve to make the light output approximately collimated.

[0137] Taking the collimating lens in Example 1 of the present application as an example, the third incident surface 3 is the incident surface of the high-angle incident light beam, and the first reflection surface 4 is the reflection surface of the high-angle incident light beam. Specifically, the third incident surface 3 is arranged at a position close to the outer side surface of the collimating lens, and the first reflection surface 4 is arranged at a position close to the inner side surface. During construction, it is also necessary to perform 2D ray tracing on the obtained free curve profile, and appropriately increase and adjust the control points on the curve to make the light output approximately collimated.

[0138] Step S4: obtaining a half-section curve of the collimating lens according to the total internal reflection free-form surface curve, the incident surface curve and the exit surface curve of the low-angle incident light beam, and the incident surface curve and the reflection surface curve of the high-angle incident light beam.

[0139] In step S4, the free curve of the total internal reflection part, the incident surface curve and the exit surface curve of the low-angle incident light beam, and the incident surface curve and the reflection surface curve of the high-angle incident light beam are combined to complete the connection.

[0140] refer to Fig. 9 Taking the collimating lens in the first embodiment of the present application as an example, the second exit curved surface 6 line is connected to the first exit curved surface line, the second incident curved surface 1 line is connected to the first incident curved surface line, the first incident curved surface line is connected to the third incident curved surface 3 line, the first reflection curved surface 4 line is connected to the second reflection curved surface line, and a first connecting curved surface 8 line is constructed between the third incident curved surface 3 line and the first reflection curved surface 4 line to connect the third incident curved surface 3 line and the first reflection curved surface 4 line, and a second connecting curved surface 9 line is constructed between the second reflection curved surface line and the first exit curved surface line to connect the second reflection curved surface line and the first exit curved surface line, thereby completing the half-profile curve of the collimating lens.

[0141] Step S5: constructing a 3D model of the collimating lens according to the half-section curve.

[0142] In step S5, when constructing the 3D model of the collimating lens according to the half-section curve, the half-section curve of the collimating lens is rotated around the central axis, thereby obtaining each free-form surface of the collimating lens and forming the 3D model of the collimating lens. Specifically, the half-section curve can be imported into the modeling software, and the corresponding function of the modeling software can be used to realize the construction of the 3D model.

[0143] Taking the collimating lens in Example 1 as an example, after the half-section curve is rotated, the first exit curve line is rotated to form the first exit curve 7, the second exit curve 6 is rotated to form the second exit curve 6, the second incident curve 1 is rotated to form the second incident curve 1, the first incident curve line is rotated to form the first incident curve 2, the third incident curve 3 is rotated to form the third incident curve 3, the first reflection curve 4 is rotated to form the first reflection curve 4, the second reflection curve is rotated to form the second reflection curve, the first connecting curve 8 is rotated to form the first connecting curve 8, and the second connecting curve 9 is rotated to form the second connecting curve 9, thereby forming an overall 3D model of the collimating lens.

[0144] In some embodiments, the steps further include:

[0145] Step S6: performing optical simulation on the collimating lens 3D model.

[0146] In step S6, a 3D model of the collimating lens may be constructed by using Creo, and then imported into TracePro for optical simulation.

[0147] Step S7: adjusting the initial value according to the simulation result to obtain an initial 3D model.

[0148] In step S7, the simulation results are judged. If the simulation results are not good enough, the initial values ​​need to be adjusted and the 3D model needs to be rebuilt; if the simulation results are acceptable, the obtained initial 3D model is further optimized.

[0149] Step S8: Optimize the initial 3D model using the normal vector correction method and the result comparison method.

[0150] In step S8, the free-form surface of the total internal reflection part of the initial 3D model is optimized until a good collimation effect is achieved. Because the curve fitting of the discrete points is achieved by ray tracing software, there may be a slight deviation from the calculated normal vector, which is then optimized to improve the collimation and uniformity of the collimating lens.

[0151] Step S9: Perform high and low angle light compensation on the initial 3D model.

[0152] In step S9, light compensation is performed on the free-form surfaces of the high-angle incident beam part and the low-angle incident beam part of the initial 3D model. Specifically, several coordinate points in the curve are selected as optimization variables, and a spot edge transition evaluation function (this function is a built-in function in the TracePro software) is established to determine whether the light intensity distribution curve is smooth. The optimization function of TracePro is used to optimize the light distribution, thereby further optimizing the collimation and uniformity of the collimating lens, and finally obtaining a complete optical lens structure.

[0153] The collimating lens design method of the present application firstly performs calculation design on the free-form surface of the total internal reflection part of the collimating lens, and then designs the free-form surfaces of the high-angle and low-angle parts to supplement the light output of the total internal reflection part, so that the designed collimating lens can have high collimation performance and high light spot uniformity, thereby improving the lighting effect of the collimating lens.

[0154] Through the collimating lens design method of the present application, the collimating lens described in Example 1 can be designed, and all of its curved surfaces are free-form surfaces, thereby effectively improving the controllability of the collimating lens during design, so as to improve the light output uniformity of the designed collimating lens and avoid the glare problem of the designed collimating lens through the design of each free-form surface, and the design method constructs free-form surfaces corresponding to high and low angle incident light beams, thereby supplementing the light output of the total internal reflection part in the collimating lens, so that when the high and low angle parts and the total internal reflection part of the two parts of light reach the target illumination area, the light spot is complete and uniform. After simulation, the light spot uniformity of the collimating lens designed by the design method can reach 98.4%, and the divergence angle can reach 3° and 1.8° respectively at 10% and 50% of the maximum luminous intensity. At present, not many can achieve this index, indicating that the collimating lens designed by the design method of the collimating lens has a good collimating effect.

[0155] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A collimating lens, characterized in that: The collimating lens is a rotationally symmetrical structure, the center of the light source is arranged on the rotationally symmetrical axis of the lens, and all surfaces of the collimating lens are free-form surfaces, including A low-angle free-form surface group is configured to refract an incident light beam emitted by the light source and having an angle with the optical axis of the light source ranging from 0° to a first angle, and then emit the incident light beam, so as to compensate for the light output of the total internal reflection free-form surface group; A high-angle free-form surface group, configured to refract an incident light beam emitted by the light source at an angle of 90° to the optical axis of the light source and then emit the light, so as to compensate for the light output of the total internal reflection free-form surface group, wherein the second angle is greater than the first angle; A total internal reflection free-form surface group is configured to collimate and emit an incident light beam emitted by a light source at an angle from a first angle to a second angle with respect to an optical axis of the light source after refraction; The exit curved surface of the collimating lens comprises a first exit curved surface (7) and a second exit curved surface (6); a low-angle incident light beam emitted by the light source is emitted from the second exit curved surface (6); an incident light beam emitted by the light source and having an angle with the optical axis of the light source between the first angle and the second angle is collimated and emitted from the first exit curved surface (7); and a high-angle incident light beam emitted by the light source is emitted from the first exit curved surface (7) and / or the second exit curved surface (6) to compensate for the light output of the collimating lens; The low-angle free-form surface group comprises a second incident curved surface (1) and a second exit curved surface (6), the low-angle incident light beam emitted by the light source enters the lens through the second incident curved surface (1) and exits through the second exit curved surface (6), and the first angle is 30°; The total internal reflection free-form surface group comprises a first incident curved surface (2), a second reflective curved surface (5) and a first exit curved surface (7); an incident light beam emitted by a light source enters the lens through the first incident curved surface (2) and is refracted through the second reflective curved surface (5), and then collimatedly emitted from the first exit curved surface (7); The high-angle free-form surface group comprises a third incident curved surface (3) and a first reflective curved surface (4); a high-angle incident light beam emitted by a light source enters the lens through the third incident curved surface (3) and is refracted through the first reflective curved surface (4), and then is emitted from the first exit curved surface (7) and / or the second exit curved surface (6) to compensate for the light output of the collimating lens; the second angle is 60°.

2. The collimating lens according to claim 1, characterized in that: The position where the incident light beam emitted by the light source is reflected onto the first exit curved surface (7) gradually moves away from the second exit curved surface (6) from the intersection position of the first exit curved surface (7) and the second exit curved surface (6) as the angle between the incident light beam and the optical axis of the light source decreases.

3. The collimating lens according to claim 1, characterized in that: The curvature of the second incident curved surface (1) is designed to be a negative value along the light transmission direction, and is arranged so that the light beam can be refracted by the second incident curved surface (1) and then emitted in parallel.

4. A method for designing a collimating lens, characterized in that: include: Set initial values ​​based on design requirements and lens size, calculate discrete points on the total internal reflection free-form surface line and fit them into a curve; Constructing an incident surface curve and an exit surface curve of a low-angle incident light beam for compensating the light output of the total internal reflection free-form surface group; Constructing an incident surface curve and a reflection surface curve of a high-angle incident light beam for compensating the light output of the total internal reflection free-form surface group according to the light output of the total internal reflection free-form curve and the light output of the exit surface curve of the low-angle incident light beam; A half-section curve of the collimating lens is obtained according to the total internal reflection free-form surface curve, the incident surface curve and the exit surface curve of the low-angle incident light beam, and the incident surface curve and the reflection surface curve of the high-angle incident light beam; Construct a 3D model of the collimating lens based on the half-section curve; The method for calculating discrete points on a total internal reflection free-form surface comprises: According to Snell's law, we can get the coordinate expression and tangent slope expression of the point where the incident light beam passes through each free-form surface line. According to the law of conservation of energy, the Pythagorean theorem, and the coordinate expressions of the points on each free-form surface line through which the incident light beam passes and the expressions of the slopes of the tangent lines, the coordinate expressions of the points on each free-form surface line through which the next incident light beam passes are obtained; The discrete points on the free-curve line of total internal reflection are obtained according to the coordinate expressions of the points on each free-curve line through which the incident light beam passes and the coordinate expressions of the points on each free-curve line through which the next incident light beam passes.

5. The collimating lens design method according to claim 4, characterized in that: When constructing the incident surface curve and the exit surface curve of the low-angle incident light beam and / or the high-angle incident light beam, a trial-and-error method is adopted to construct and obtain the curve.

6. The collimating lens design method according to claim 4, characterized in that: The steps also include: Perform optical simulation on the 3D model of the collimating lens; The initial values ​​are adjusted according to the simulation results to obtain an initial 3D model.

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