A double freeform surface lens and its design method

Abstract

This invention discloses a double freeform surface lens and its design method. The inner and outer surface contour curves of the double freeform surface lens are both composed of multiple curve segments, each corresponding to a unit emission angle of an extended light source. These segments are smoothly connected and share a common tangent. The method includes: determining the maximum emission angle of the extended light source and dividing it equally to obtain the unit emission angle; constructing multiple circular arc curves with the center height of the inner and outer surfaces of the lens as the starting point and the unit emission angle as the step size; connecting the beginning and end of the multiple circular arc curves on the inner and outer surfaces to obtain the inner and outer surface contour curves of the double freeform surface lens; and optimizing the inner and outer surface contour curves to obtain the double freeform surface lens. By using this invention, high uniformity and high luminous efficiency can be obtained on the target plane when the ratio of lens height to light source diameter is less than 1.2. This invention can be widely applied in the field of optical device design.

Description

Technical Field

[0001] This invention relates to the field of optical device design, and more particularly to a double freeform surface lens and its design method. Background Technology

[0002] LEDs are widely used due to their numerous advantages, including long lifespan, low energy consumption, high luminous efficacy, and environmental friendliness. Because LEDs emit light with an approximate Lambertian distribution, we need to re-distribute the light emitted by the packaged LED within an optical system. This redistribution aims to distribute the approximately Lambertian beam onto the target illumination area to meet people's lighting needs. Most design methods approximate the light source as an ideal point source for light distribution design. However, the high-power LEDs constantly being updated in the market today are not ideal point sources. Therefore, the light distribution design methods used for point sources are clearly not directly applicable to extended light sources with non-negligible light emission sizes.

[0003] Currently, the design approach for extended light source illumination systems is less effective for ultra-compact optical systems (e.g., H / D < 2, where H is the center height of the lens and D is the diameter of the extended light source), and cannot meet the application requirements. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a double freeform surface lens and its design method, which achieves high uniformity and high luminous efficiency on the target plane when the ratio of lens height to light source diameter is less than 1.2 (H / D<1.2).

[0005] The first technical solution adopted in this invention is: a double freeform surface lens, wherein the inner surface contour curve and the outer surface contour curve of the double freeform surface lens are both composed of multiple curve segments, each curve segment corresponds to the unit emission angle of the extended light source, and each curve segment is smoothly connected and has a common tangent.

[0006] The second technical solution adopted in this invention is: a design method for a double freeform surface lens, comprising:

[0007] Determine the maximum emission angle of the extended light source and divide it equally to obtain the unit emission angle;

[0008] Using the center height of the inner and outer surfaces of the lens as the starting point and the unit emission angle as the step size, construct multiple circular arc curves;

[0009] By connecting the beginning and end of the multiple arc curves on the inner and outer surfaces respectively, the inner and outer surface contour curves of the double freeform surface lens are obtained.

[0010] The inner and outer surface contour curves are optimized to obtain a double freeform surface lens.

[0011] Furthermore, the step of optimizing the inner and outer surface contour curves to obtain the double freeform lens specifically includes:

[0012] Define an evaluation function, setting luminous efficacy and uniformity as adjustment targets;

[0013] The multiple circular arcs in the inner and outer surface contour curves are optimized respectively, and the evaluation function value of the optimized contour curve is calculated.

[0014] If the evaluation function value meets the preset threshold, a double freeform lens is obtained.

[0015] Furthermore, the step of optimizing the multiple arc curves in the inner and outer surface contour curves and calculating the evaluation function value of the optimized contour curve specifically includes:

[0016] By changing the radius of curvature of each arc segment in the inner and outer surface contour curves, a new contour curve is formed.

[0017] The radius of the first arc segment of the inner surface profile curve is smaller than the radius of the first arc segment of the outer surface profile curve.

[0018] The parameters of the new profile curve are transferred to the optical simulation software, where a model is created and ray tracing is performed to calculate the evaluation function value of the new profile curve.

[0019] This optimization process allows for the design of lenses with arbitrary height ratios and emission angles by optimizing each arc segment.

[0020] Furthermore, the evaluation function formula is expressed as follows:

[0021]

[0022] In the above formula, C1, C2, and C3 represent the relevant weights, Ф1 represents the luminous flux of the target plane, Ф2 represents the total luminous flux emitted by the light source, RSD represents the performance measure of light distribution uniformity, RSD1 represents the overall light distribution uniformity of the target plane, and RSD2 represents the light distribution uniformity of the edge 1 / 3 area of ​​the target plane.

[0023] Furthermore, the RSD function formula is expressed as follows:

[0024]

[0025] In the above formula, Np represents the total number of sampling points within the effective analysis region on the target plane, and E s (i) represents the simulated irradiance level at the checkpoint in the target area, and E0(i) represents the average irradiance within the analysis area.

[0026] The beneficial effects of this invention are: This invention utilizes an optimization algorithm to directly optimize the contour curves of the inner and outer surfaces of the lens, achieving high uniformity and luminous efficiency on a specified target plane even with a reduced ratio of lens height to light source size. Compared to traditional extended light source lens design methods, this invention does not require complex iterative point coordinate calculations or multiple manual optimizations via negative feedback. Attached Figure Description

[0027] Figure 1 This is a flowchart of the steps of a double freeform surface lens design method according to the present invention;

[0028] Figure 2 This is a schematic diagram of the design of a double freeform surface lens according to the present invention;

[0029] Figure 3 This is a schematic diagram of the lens model after multiple optimizations in a specific embodiment of the present invention. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art.

[0031] The present invention provides a double freeform surface lens, wherein the inner surface contour curve and the outer surface contour curve of the double freeform surface lens are both composed of multiple curve segments, each curve segment corresponds to the unit emission angle of the extended light source, and each curve segment is smoothly connected and has a common tangent.

[0032] Specifically, the contour curves of both the inner and outer surfaces are obtained by rotating free curves designed under two-dimensional conditions. The lens can achieve a uniform illumination distribution with clear edges on the target plane under the condition that H / D < 1.2.

[0033] Each unit's emission angle corresponds to a short free curve, which can be an arc, a B-spline curve, or a Bézier curve with different radii of curvature. The connection points of each free curve have the same tangent to ensure a smooth connection.

[0034] Reference Figure 1 A design method for a double freeform surface lens, comprising:

[0035] S1. Determine the maximum emission angle θ of the extended light source. max Divide the maximum emission angle into N equal parts to obtain the unit emission angle;

[0036] Δθ=θ max / N

[0037] In the above formula, Δθ represents the unit emission angle.

[0038] S2. Determine the central heights of the inner and outer surfaces of the lens, where the central height of the inner surface is less than that of the outer surface

[0039] S3. Starting from the central heights of the inner and outer surfaces of the lens and using the unit emission angle Δθ as the step size, construct multiple arc curves;

[0040] Specifically, starting from (0, H), connect the N arcs end to end to form the outer surface contour curve. Determine the height h of the inner surface of the lens, where h < H. According to the design method of the outer surface contour curve of the lens, starting from (0, h), connect the N arcs end to end to form the inner surface contour curve.

[0041] As Figure 2 shown:

[0042] The outer surface contour curve A0A n = AOA n + A1A2 + … A n-1 A n ;

[0043] The inner surface contour curve B0B n = BOB n + B1B2 + … B n-1 B n .

[0044] S4. Connect the multiple arc curves of the inner and outer surfaces end to end respectively to obtain the inner and outer surface contour curves of the double free-form surface lens;

[0045] S5. Optimize the inner and outer surface contour curves to obtain the double free-form surface lens.

[0046] S5.1. Define the evaluation function f and set the luminous efficiency and uniformity as the adjustment targets;

[0047] Specifically, the value of f varies between 0 and 1. The smaller f is, the higher the luminous efficiency and uniformity.

[0048] The formula of the evaluation function is expressed as follows:

[0049]

[0050] In the above formula, C1, C2, and C3 represent relevant weights, Ф1 represents the luminous flux of the target plane, Ф2 represents the total luminous flux emitted by the light source, RSD represents the performance metric of the light distribution uniformity, RSD1 represents the overall light distribution uniformity of the target plane, and RSD2 represents the light distribution uniformity of the 1 / 3 area at the edge of the target plane.

[0051] This evaluation function simultaneously constrains both illumination uniformity and luminous efficacy. In terms of evaluating the uniformity of light distribution, it controls the overall uniformity while enhancing the uniformity of edge illuminance, ensuring that the light spot obtained on the target plane has high illuminance, high uniformity, and clear edges.

[0052] The RSD function formula is expressed as follows:

[0053]

[0054] In the above formula, Np represents the total number of sampling points within the effective analysis region on the target plane, and E s (i) represents the simulated irradiance level at the checkpoint in the target area, and E0(i) represents the average irradiance within the analysis area.

[0055] The smaller the RSD value, the more uniform the lighting performance.

[0056] S5.2 Optimize the multiple arc curves in the inner and outer surface contour curves respectively and calculate the evaluation function value of the optimized contour curves;

[0057] S5.2.1 Change the radius of curvature of each arc segment in the inner and outer surface contour curves to form a new contour curve;

[0058] Specifically, one of the following algorithms—genetic algorithm, simulated annealing algorithm, and particle swarm optimization algorithm—is selected to arbitrarily change each small segment of the curve that makes up the inner and outer surface contours of the lens.

[0059] S5.2.2 The radius of the first arc of the inner surface profile curve is smaller than the radius of the first arc of the outer surface profile curve;

[0060] S5.2.3 Transfer the parameters of the new profile curve to the optical simulation software, model and perform ray tracing in the optical simulation software, and calculate the evaluation function value of the new profile curve.

[0061] Specifically, the parameters of the two free curves are transmitted to the optical simulation software through DDE technology. The model is then created and ray tracing is performed in the optical simulation software. The simulation results are then transmitted to the data analysis software through DDE technology for data analysis. Based on the evaluation function value of the new profile curve, it is determined whether the free curve meets the requirements.

[0062] S5.3. If the evaluation function value meets the preset threshold, the double freeform lens is obtained.

[0063] Specifically, repeat the optimization process until the requirements are met. Figure 3 This is the lens model that meets the requirements after multiple optimizations.

[0064] When the method of this invention is simulated in optical line software, the double surface of the lens can be automatically optimized, providing a new method for lighting optics design for researchers who are not good at mathematics or optics.

[0065] The lens profile curve of this invention has a high degree of freedom, and a profile curve that meets the requirements can be found quickly.

[0066] The design method of this invention utilizes the interaction between software to directly model in the light analysis software, avoiding the errors caused by third-party software modeling. This method has good efficiency and versatility in the standard lighting design of extended LED light sources in three-dimensional rotationally symmetric geometry.

[0067] A device:

[0068] At least one processor;

[0069] At least one memory for storing at least one program;

[0070] When the at least one program is executed by the at least one processor, the at least one processor implements the design method of a double freeform lens as described above.

[0071] The content of the above method embodiments is applicable to the device embodiments. The specific functions implemented by the device embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0072] A storage medium storing processor-executable instructions, characterized in that: the processor-executable instructions, when executed by the processor, are used to implement a design method for a double freeform lens as described above.

[0073] The content of the above method embodiments is applicable to this storage medium embodiment. The specific functions implemented in this storage medium embodiment are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those achieved in the above method embodiments.

[0074] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A biaxial freeform lens, characterized by: The inner surface profile curve and the outer surface profile curve of the double free-form lens are composed of multiple curves, each curve corresponding to a unit light emitting angle of the extended light source, and the curves are smoothly connected and have a common tangent; The design method of the double free-form lens is as follows: Determining a maximum emission angle of an extended light source Divided into Parts, get unit emission angle ; The calculation formula of the unit light emitting angle is as follows: Taking the center height of the inner and outer surfaces of the lens as the starting point and the unit light emitting angle as the step size, a plurality of circular arc curves are constructed; The first and last of the plurality of circular arc curves of the inner and outer surfaces are connected to obtain the inner and outer surface profile curves of the double free-form lens; The inner and outer surface profile curves are optimized to obtain the double free-form lens; The step of optimizing the inner and outer surface profile curves to obtain the double free-form lens specifically includes: Defining an evaluation function and setting light efficiency and uniformity as the adjustment target; The plurality of circular arc curves in the inner and outer surface profile curves are respectively optimized, and the evaluation function value of the optimized profile curve is calculated; It is judged that the evaluation function value meets the preset threshold value to obtain the double free-form lens; The step of optimizing the plurality of circular arc curves in the inner and outer surface profile curves and calculating the evaluation function value of the optimized profile curve specifically includes: Changing the radius of curvature of each circular arc in the inner and outer surface profile curves to form a new profile curve; The first circular arc radius of the inner surface profile curve is smaller than the first circular arc radius of the outer surface profile curve; The parameters of the new profile curve are transmitted to the optical simulation software, the profile curve is modeled in the optical simulation software, and the light ray tracing is performed to calculate the evaluation function value of the new profile curve; The evaluation function formula is as follows: In the above formula, C 1、 C 2、 C 3 represents the correlation weight, Φ1 represents the light flux of the target plane, Φ2 represents the total light flux emitted by the light source, and RSD represents the performance measure of light distribution uniformity, RSD 1 represents the light distribution uniformity of the whole target plane, RSD 2 represents the light distribution uniformity of the 1 / 3 area of the edge of the target plane.

2. The biconic aspherical lens according to claim 1, wherein The RSD function formula is as follows: In the above formulae, Np represents the total number of sampling points within the effective analysis region on the target plane, represents the simulated irradiance level of the checkpoint on the target region, represents the average value of the irradiance within the analysis region.

Images