Design method of LED lens for generating uniform collimated illumination

Abstract

The invention belongs to the technical field of optical lenses, and particularly relates to a design method of an LED lens for generating uniform collimation illumination. Comprising a primary refracting surface S1, a secondary refracting surface S2, a cylindrical surface S3 and a plane S4, and S1 and S2 are free-form surfaces; the primary refracting surface S1 is responsible for uniformly irradiating light emitted by an LED on the secondary refracting surface S2, then the light is converted into collimated light through the secondary refracting surface S2, and the cylindrical surface S3 and the plane S4 are responsible for connecting the surfaces S1 and S2; when the lens is manufactured, section data of the surface S1 are obtained through calculation according to the refraction law and optical expansion amount conservation, and then section data of the surface S2 are obtained through calculation according to the section data of the surface S1; the lens carries out secondary light distribution on LED emergent light, non-uniform divergent light is converted into uniform collimated light, energy distribution of a light source and the light emergent direction are considered, and the defect that a traditional single lens only considers the energy distribution of the light source or the light emergent direction is overcome; the uniformity of irradiation light spots can reach more than 80%, and meanwhile, the energy utilization rate of the LED can reach more than 85.51%.

Description

Technical Field

[0001] The invention belongs to the technical field of optical lenses, and in particular relates to a design method for producing a uniformly collimated LED lens. Background Art

[0002] Compared with other light sources, LED has the advantages of low energy consumption, high efficiency in energy conversion and durability. However, the light intensity distribution of most LED lamps is Lambert distribution, which has poor irradiation effect and chaotic direction of emitted light. LED needs to be distributed for the second time to improve energy utilization efficiency. The existing technology for designing a single LED lens mainly focuses on two aspects: one is that it only considers the uniformity of the ideal special irradiation spot without considering the consistency of the direction of the light after the lens distribution. This type of design does not specifically analyze and deal with the problem of light direction; therefore, although the target surface can achieve an ideal uniform irradiation spot at an optimal position, when the target surface is not in the optimal position, the uniformity of the irradiation spot and the shape and size of the spot will change. For example, the peanut lens, which has been widely used, can form a spot on the target surface after the light emitted by the light source is distributed for the second time by the peanut lens. Rectangular uniform light spot, but when the target surface is not in the best position, the uniformity of the light spot formed on the target surface will inevitably decrease, and the size and shape of the light spot will also change to varying degrees; secondly, only the consistency of the direction after the lens light distribution is considered, but the uniformity of the irradiated light spot is not considered; in this type of design, the size and shape of the light spot will not change when the target surface is in any position perpendicular to the optical axis, but the uniformity of the irradiated light spot is not considered, such as Fresnel lens and TIR collimating lens; both LED lens design methods do not use a single lens to simultaneously achieve the uniformity of the irradiated light spot after light distribution and the consistency of the direction of the light, and both have their own advantages and limitations; if the advantages of the two are combined when the light source is secondary distributed, taking into account the directionality of the light and the uniformity of the irradiated light spot, it can not only improve the energy utilization rate of the light source but also increase the scope of application, which has certain practical significance. Summary of the invention

[0003] The purpose of the present invention is to make up for the fact that the traditional single free-form surface lens cannot take into account both the uniformity of the irradiated light spot and the consistency of the light direction for the secondary light distribution of the light source, and to provide a design method for an LED lens for producing uniform collimated illumination, aiming to obtain uniform and collimated parallel light.

[0004] The present invention provides a design method for an LED lens for generating uniform collimated illumination, and the specific steps are as follows: (1) In a rectangular coordinate system, with the position of the LED as the origin, a circular plane is placed in front of the LED, and the free-form surface S1 is located between the LED and the target plane. When the light emitted by the LED passes through the free-form surface After refraction, the target plane can be evenly illuminated, thus a free-form surface can be established. Mathematical model of (2) Establish the relationship between the coordinates of the circular plane and the light source's angle of incidence: The illumination of the circular plane is (constant), ideally, the light source (LED) is The luminous flux emitted by the solid angle corresponding to the cone angle corresponds to the luminous flux on the circular plane The luminous flux received within a circle of radius; (3) Establish a mathematical model of the cross-sectional curve of the free-form surface S1; (4) Solve the coordinate data set of the cross-sectional curve of the free-form surface S1; write a code in the mathematical software MATLAB to solve the surface according to the cross-sectional mathematical model of the free-form surface S1 The cross-sectional abscissa data set With the vertical coordinate data set And the data set of the angle between the direction vector of the light and the horizontal direction after the light passes through the free surface S1 once ; (5) The secondary refractive surface S2 is designed with a microstructure on the circular plane of the first part, and the cross-sectional curve data coordinates of the surface S2 are iteratively solved using the data obtained in the first part, so that the light can be collimated after being refracted by S2; (6) Based on the law of refraction, the coordinate data set of surface S1 obtained in step (5), the angle data set of the light after the first refraction, and the light after the second refraction of surface S2 are all collimated, and the direction vectors are , and then we can get the surface The iterative formula for the section curve coordinates is: (7) Set the number of loops and the number of iterations in each loop: According to the iteration formula in the previous step, as the number of iterations increases, and The deviation will become larger and larger. If the number of cycles is too low, the refractive surface S2 obtained will lead to poor final effect. Therefore, a tolerance step size needs to be set during the iteration process. ,when When , the initial coordinates of the cross-section curve of surface S2 are reset in the next iteration to start a new cycle; (8) After obtaining the cross-sectional curve data coordinates of the primary refractive surface S1 and the secondary refractive surface S2, the cross-sectional curves of the connecting surfaces S3 and S4 are obtained; the cross-sectional curves of the primary refractive surface S1, the secondary refractive surface S2, and the connecting surfaces S3 and S4 are connected end to end to obtain the coordinate data of the complete lens cross-sectional curve; then, the lens cross-sectional curve data coordinates are imported into Solidworks software to establish a lens part model; (9) The lens parts are imported into the relational tracing program Tracepro for ray tracing. The lens surface is optimized based on the simulation results to improve the uniformity of the irradiation and the accuracy of the light direction. Finally, an LED lens for producing uniform collimated lighting is obtained.

[0005] The invention has good collimation, and the light spot sizes generated on the target receiving surface at different distances are consistent. After the LED light source is light-distributed by the lens, the direction of the light emitted is consistent.

[0006] Compared with the existing design method of free-form surface lenses, the present invention utilizes a double free-form surface and the second free-form surface utilizes a microstructure design method. The designed single lens takes into account both the directionality of light and the uniformity of the irradiated light spot, making up for the deficiency that most single lenses in the prior art can only control one effect. The present invention has good lighting effect, good collimation, compact structure, simple design method, and is suitable for LED point light sources and other types of point light sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 (a) and (b) are schematic diagrams for explaining the method for solving the primary refractive surface S1 and the secondary refractive surface S2 according to the present invention, respectively; Figure 2 is a perspective view of the free-form surface lens of the present invention; Figure 3 (a)-(c) are respectively a side view (a), a bottom view (b), and a top view (c) of the free-form surface lens of the present invention; Figure 4 This is a light path diagram after the light source is subjected to secondary light distribution in the present invention; Figure 5 (a)-(c) are the irradiation distribution diagrams, profile curve diagrams and full-color diagrams at different distances of the present invention. DETAILED DESCRIPTION

[0008] The present invention will be described in more detail below with reference to embodiments and drawings.

[0009] Step 1: Primary refraction surface The specific steps of design are as follows: like Figure 1 (a) In a rectangular coordinate system, with the position of the LED as the origin, a circular plane is placed in front of the LED, and the free-form surface S1 is located between the LED and the target plane. When the light emitted by the LED is refracted by the free-form surface S1, it can be evenly illuminated on the target plane. Thus, a mathematical model of the free-form surface S1 can be established. The specific process is as follows: (1) Set the initial conditions: the position of the LED is the origin, and the optical axis of the LED is Axis, Freeform Surface and The axis intersection point is ( ,, the radius of the circular plane is And the distance from the LED is , that is, the circular plane and The intersection of the axes is , LED and free-form surface The refractive index of the area between (Refractive index of air is 1), free-form surface The refractive index of the area between the circular plane is , ; (2) Establish the relationship between the coordinates of the circular plane and the light source's angle of incidence: The illumination of the circular plane is (constant), ideally, the light source (LED) is The luminous flux emitted by the solid angle corresponding to the cone angle corresponds to the luminous flux on the circular plane The luminous flux received within a circle of radius, the light intensity distribution of the LED is , according to the conservation of optical etendue: (1) From formula (1), we can get (2) (3) Establish the cross-sectional mathematical model of the free-form surface S1; LED emits any The unit direction vector of the light ray at the angle is:

[0010] And the intersection point with the free surface S1 is , is the straight-line distance between the intersection point and the light source. Combining the results of the previous step, we can get the distance of the light through the surface The unit direction vector of the ray emitted after refraction is:

[0011] in

[0012] According to the law of refraction, the cross-sectional curve derivative of the free-form surface S1 can be obtained as: (3) Substitution , combined with formula (1), (2), and (3), we can get: (4) Formula (4) is the mathematical model of the cross-sectional curve of the free-form surface S1; (4) Solve the coordinate data set of the cross-sectional curve of the free-form surface S1; write a code in the mathematical software MATLAB to calculate the cross-sectional coordinate data set of the free-form surface S1 according to the cross-sectional mathematical model of the free-form surface S1 With the vertical coordinate data set .

[0013] Step 2: Design of secondary refractive surface S2. The specific steps are as follows: like Figure 1 (b), the secondary refractive surface S2 is designed with a microstructure on the circular plane of the first part, and the cross-sectional curve data coordinates of the incident surface S2 are iteratively solved using the data obtained in the first part, so that the light can be collimated after being refracted by S2. The specific process is as follows.

[0014] (1) Data preparation: Based on the coordinate data set of the free-form surface S1 obtained in the first part The light exit angle can be obtained Dataset And the refraction angle data set after the light is refracted successively , all the obtained data sets have the same number and the elements correspond one to one; (2) Establish the iterative solution formula for the secondary refractive surface S2: The coordinates of the points are The data coordinates of this point correspond to the first The coordinates of the first element should be the same as those of the free-form surface S1. The coordinate points are on the same straight line, so the horizontal and vertical coordinates of the point should satisfy; (5) At this time, the corresponding unit direction vector of the light after one refraction is:

[0015] The unit direction vectors of the light after secondary refraction by surface S2 are:

[0016] Based on the law of refraction, the unit normal vector of the refractive surface S2 at this point is: (6) Combining formulas (5) and (6), we can get the secondary refraction surface Iterative solution formula for the cross-sectional curve: (7) (8) (3) Set the number of loops and the number of iterations in each loop: According to the iterative formulas (7) and (8), perform iterative solution. As the number of iterations increases, and The deviation will become larger and larger; if the number of cycles is too low, the secondary refraction surface This will result in poor final results; therefore, a tolerance step size needs to be set during the iteration process. ,when When the iteration is completed, the data that has been iterated is saved, and the initial coordinates of the cross-section curve of the secondary refraction S2 surface are reset in the next iteration, and a new cycle is performed; the sum of the number of iterations in all cycles is equal to the number of elements in any data set; (4) Solve the coordinate data set of the cross-sectional curve of the secondary refractive surface S2; write a code in the mathematical software MATLAB to solve the cross-sectional horizontal coordinate data set of surface S2 according to the cross-sectional iteration formula of the free-form surface S2 With the vertical coordinate data set ; (5) Based on the coordinate data of the free-form surface S1 and the secondary refractive surface S2, the cross-sectional curve of the connecting surfaces S3 and S4 is obtained.

[0017] Step 3: Import the lens cross-section curve data coordinates obtained from steps 1 and 2 into Solidworks software to create the lens part.

[0018] Step 4: Import the obtained lens parts into the ray tracing program Tracepro. The specific steps of simulation verification are as follows: (1) Import the lens part, set the surface property of the part to Default (lens) and the material property to SCHOTT (BASF10), and its refractive index is 1.6541; (2) Set the light source to a Lambert body light source and the number of traced rays to 1,000,000; (3) Set multiple target receiving surfaces of the same size but at different distances from the light source. The simulation result sampling points are 128*128, the resolution is 50, and the receiving surface property is Default (Perfect absorber). (4) Perform ray tracing on the model and analyze and verify the simulation results.

[0019] The present invention is explained by using embodiments and does not limit the present invention. Other changes that other researchers may conceive of by referring to the embodiments disclosed in the present invention should fall within the scope defined by the claims of the present invention.

Claims

1. A method for designing an LED lens for producing uniform collimated illumination; characterized in that: The specific steps are as follows: (1) In a rectangular coordinate system, with the position of the LED as the origin, a circular plane is placed in front of the LED, and the free-form surface S1 is located between the LED and the target plane. When the light emitted by the LED passes through the free-form surface After refraction, the target plane can be evenly illuminated, thus a free-form surface can be established. Mathematical model of (2) Establish the relationship between the coordinates of the circular plane and the light source's angle of incidence: The illumination of the circular plane is (constant), ideally, the light source (LED) is The luminous flux emitted by the solid angle corresponding to the cone angle corresponds to the luminous flux on the circular plane The luminous flux received within a circle of radius; (3) Establish a mathematical model of the cross-sectional curve of the free-form surface S1. Based on the law of refraction and the unit direction vector of the light emission and the unit vector of the light emission after one refraction, the mathematical model of the cross-sectional curve of the free-form surface S1 can be obtained as follows: （1） (4) Solve the coordinate data set of the cross-sectional curve of the free-form surface S1; write a code in the mathematical software MATLAB to solve the surface according to the cross-sectional mathematical model of the free-form surface S1 Cross-sectional abscissa data set With the vertical coordinate data set And the data set of the angle between the direction vector of the light and the horizontal direction after the light passes through the free surface S1 once ; (5) The secondary refractive surface S2 is designed with a microstructure on the circular plane of the first part, and the cross-sectional curve data coordinates of the surface S2 are iteratively solved using the data obtained in the first part, so that the light can be collimated after being refracted by S2; (6) Based on the law of refraction, the coordinate data set of surface S1 obtained in step (5), the angle data set of the light after the first refraction, and the light after the second refraction of surface S2 are all collimated, and the direction vectors are , and then we can get the surface The cross-sectional curve coordinate iteration formula is: （2） （3） (7) Set the number of loops and the number of iterations in each loop: According to the iteration formula in the previous step, as the number of iterations increases, and The deviation will become larger and larger. If the number of cycles is too low, the refractive surface S2 obtained will lead to poor final effect. Therefore, a tolerance step size needs to be set during the iteration process. ,when When , the initial coordinates of the cross-section curve of surface S2 are reset in the next iteration to start a new cycle; (8) After obtaining the cross-sectional curve data coordinates of the primary refractive surface S1 and the secondary refractive surface S2, the cross-sectional curves of the connecting surfaces S3 and S4 are obtained; the cross-sectional curves of the primary refractive surface S1, the secondary refractive surface S2, and the connecting surfaces S3 and S4 are connected end to end to obtain the coordinate data of the complete lens cross-sectional curve; then, the lens cross-sectional curve data coordinates are imported into Solidworks software to establish a lens part model; (9) The lens parts are imported into the relational tracing program Tracepro, and the Mote-Carlo method is used to trace the rays of light on the lens. The lens surface is optimized based on the simulation results to improve the uniformity of its irradiation and the accuracy of the light direction. Finally, an LED lens for producing uniform collimated illumination is obtained.

2. The present invention has good collimation, and the size of the light spot generated on the target receiving surface at different distances is consistent. After the LED light source is matched by the lens, the direction of the light emitted is consistent.

3. Compared with the existing design method of free-form surface lenses, the present invention utilizes double free-form surfaces and the second free-form surface utilizes a microstructure design method. The designed single lens takes into account both the directionality of light and the uniformity of the irradiation spot, making up for the deficiency that most single lenses in the prior art can only control one effect. The present invention has good lighting effect, good collimation, compact structure, simple design method, and is suitable for LED point light sources and other types of point light sources.

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