阅读说明：本技术 基于朗伯型led光源的分区域匀光照明的菲涅尔透镜设计方法 (Design method of partitioned uniform light illumination Fresnel lens based on Lambert type LED light source ) 是由 张云翠 魏以婧 谢蓄芬 潘妲 于 2020-05-08 设计创作，主要内容包括：本发明公开了一种基于朗伯型LED光源的分区域匀光照明的菲涅尔透镜设计方法,根据光学扩展量守恒定律计算不同区域的边缘光线偏折角度,确定不同区域的焦距,进而确定分区域匀光照明的菲涅尔透镜面型。本发明适用于LED朗伯发光或类朗伯发光的聚光照明场合；通过对具有朗伯出光的LED经过分区域汇聚使得接收的光线更加均匀化,解决各种因LED光源配光不均而造成的菲涅尔透镜会聚后光斑能量分布不均的问题,可提高使用透镜进行聚光的LED照明系统的均匀性；同时本发明通过改变各区域菲涅尔透镜焦距的方法进行设计,大幅度提高设计效率。(The invention discloses a design method of a Fresnel lens for zoned uniform light illumination based on a Lambert type LED light source, which is characterized in that edge light deflection angles of different zones are calculated according to an optical expansion conservation law, focal lengths of the different zones are determined, and further a surface type of the Fresnel lens for zoned uniform light illumination is determined. The LED spotlight is suitable for the LED Lambert luminous or similar Lambert luminous spotlight occasions; the LEDs with Lambert light emitting are subjected to regional convergence to enable received light to be more uniform, so that the problem of uneven light spot energy distribution of converged Fresnel lenses caused by uneven light distribution of LED light sources is solved, and the uniformity of an LED illumination system using the lenses for light condensation can be improved; meanwhile, the design is carried out by changing the focal length of the Fresnel lens in each area, so that the design efficiency is greatly improved.)

1. A design method of a Fresnel lens for partitioned uniform illumination based on a Lambertian LED light source is characterized by comprising the following steps:

s1: determining the size of the Fresnel lens for the partitioned uniform light illumination, wherein the size comprises the maximum caliber size, the ring distance and the thickness parameter; determining the LED light source and analyzing the data of the light source, wherein the data comprises parameters of luminous flux, light intensity and wattage, and parameters of a receiving surface, including size, position, absorption or scattering characteristics and material parameters;

s2: dividing the Fresnel lens with the light homogenizing illumination in the divided areas into a plurality of areas, wherein the central area is located at the central position, the first area is connected with the central area, the second area is connected with the first area, the third area is connected with the second area, the fourth area is connected with the third area, the fifth area is connected with the fourth area, and so on, and all the areas are diffused outwards from the center in sequence; dividing the size of each region according to the precision, wherein the precision comprises the following steps: equal light-emitting angle, equal radius;

s3: through the law of conservation of optical expansion and the design requirement of surface dodging, the relationship between the emergent angle and the divergence angle theta-theta' of the light source is calculated as follows:

wherein theta is the half angle of light source emergence, theta' is the half angle of light ray divergence, E is the illumination of the emergent surface when the light ray reaches the emergent surface, the unit is lx, L is the distance from the image surface to the surface of the Fresnel lens, and I₀The unit is cd, i' is the light intensity of the incident surface of the light source in a solid angle in a given direction;

s4: calculating an image point formula (2) of each area according to the relation between the emergent angle and the divergence angle theta-theta', namely an edge ray angle relation formula (1), and further calculating a focal length formula (3) of each area according to an object image relation formula;

wherein l is the object distance, l 'is the image distance, R is the radius of the lens, f' is the focal length, and R is the radius of the irradiation spot of the receiving surface;

s5: and determining the surface type of the Fresnel lens for the regional uniform light illumination according to the precision and the focal length of each region.

2. The design method of a Fresnel lens for split-area dodging illumination based on a Lambertian LED light source as claimed in claim 1, wherein each area is composed of a part of a common Fresnel lens, and each area is obtained by: the Fresnel lens with different focal lengths is merged with the central area to form a circular Fresnel lens, the Fresnel lens with different focal lengths is merged with the first area and the central area to form a circular Fresnel lens, the Fresnel lens with different focal lengths is merged with the second area and the first area and the central area to form a circular Fresnel lens, each circular area is obtained, and finally the combined lens with multiple concentric circles is formed in a seamless mode.

3. The design method of the Fresnel lens for the area-divided dodging illumination based on the Lambertian LED light source as claimed in claims 1 and 2, wherein the inner surface of each area is a surface close to the light source and the outer surface is a surface close to the receiving surface, the outer surface of each area is a continuous irregular sawtooth small prism with an equal circular arc, namely the central part of the outer surface of each area is a circular arc lens, and the rest part is an irregular sawtooth lens; different circular radians are selected according to different focal lengths of the areas.

Technical Field

The invention relates to a non-imaging technology of optical design, in particular to a design method of a partitioned uniform light illumination Fresnel lens based on a Lambert type LED light source.

Background

The LED is a near-light emitting device for converting electric energy into light energy, has a series of advantages of small volume, low power consumption, high lighting effect, environmental protection and the like, and is widely applied to the aspects of lamp illumination, liquid crystal backlight and the like. However, as the illumination requirements of the illumination backlight application places are increased, the uniformity requirements are also higher and higher. Compared with the traditional lens, the Fresnel lens has the advantages of large area, light weight, low price, portability, easy carrying and the like, and is an optical device with wide application. For example, navigation lighting, illumination optics, etc., fresnel lens can be better the output of calibration light, reduces optical device's use for optical module is convenient simple easily dispels the heat. Compared with the past, the requirement that the Fresnel lens only focuses light or corrects the angle range of the light has been raised, and uniform light focusing becomes an important research and development of a new era.

Disclosure of Invention

The invention aims to provide a design method of a Fresnel lens for regional uniform illumination aiming at the problems of single focusing, insufficient uniform illumination and the like of the traditional Fresnel lens on the market; according to the method, a part of common Fresnel lenses with different focal lengths are combined together to form a partitioned dodging Fresnel lens consisting of a plurality of concentric arcs, so that emergent rays can be homogenized.

In order to achieve the above purpose, the present invention provides a design method of a fresnel lens with partitioned uniform light illumination based on a lambertian LED light source, wherein the method comprises:

s1: determining the size of the Fresnel lens for the partitioned uniform light illumination, wherein the size comprises the maximum caliber size, the ring distance and the thickness parameter; determining the LED light source and analyzing the data of the light source, wherein the data comprises parameters of luminous flux, light intensity and wattage, and parameters of a receiving surface, including size, position, absorption or scattering characteristics and material parameters;

s2: dividing the Fresnel lens with the light homogenizing illumination in the divided areas into a plurality of areas, wherein the central area is located at the central position, the first area is connected with the central area, the second area is connected with the first area, the third area is connected with the second area, the fourth area is connected with the third area, the fifth area is connected with the fourth area, and so on, and all the areas are diffused outwards from the center in sequence; dividing the size of each region according to the precision, wherein the precision comprises the following steps: equal light-emitting angle, equal radius;

s3: through the law of conservation of optical expansion and the design requirement of surface dodging, the relationship between the emergent angle and the divergence angle theta-theta' of the light source is calculated as follows:

wherein theta is the half angle of light source emergence, theta' is the half angle of light ray divergence, E is the illumination of the emergent surface when the light ray reaches the emergent surface, the unit is lx, L is the distance from the image surface to the surface of the Fresnel lens, and I₀The unit is cd, i' is the light intensity of the incident surface of the light source in a solid angle in a given direction;

s4: calculating an image point formula (2) of each area according to the relation between the emergent angle and the divergence angle theta-theta', namely an edge ray angle relation formula (1), and further calculating a focal length formula (3) of each area according to an object image relation formula;

wherein l is the object distance, l 'is the image distance, R is the radius of the lens, f' is the focal length, and R is the radius of the irradiation spot of the receiving surface;

s5: and determining the surface type of the Fresnel lens for the regional uniform light illumination according to the precision and the focal length of each region.

Preferably, each of the regions is formed by a part of a common fresnel lens, and each region is obtained by: the Fresnel lens with different focal lengths is merged with the central area to form a circular Fresnel lens, the Fresnel lens with different focal lengths is merged with the first area and the central area to form a circular Fresnel lens, the Fresnel lens with different focal lengths is merged with the second area and the first area and the central area to form a circular Fresnel lens, each circular area is obtained, and finally the combined lens with multiple concentric circles is formed in a seamless mode.

Preferably, the inner surface of each region is a surface close to the light source, the outer surface of each region is a surface close to the receiving surface, and the outer surface of each region is a continuous small irregular sawtooth prism with an equal circular arc, that is, the central part of the outer surface of each region is a circular arc lens, and the rest part is an irregular sawtooth lens; different circular radians are selected according to different focal lengths of the areas.

The invention has the beneficial effects that: the design method disclosed by the invention has the advantages that the cost is greatly saved on the material, the structure is compact and simple, and the preparation, the production and the processing are easy; different from the traditional single-focal-length Fresnel lens, the Fresnel lens in each area of the partitioned uniform light Fresnel lens has different focal lengths, belongs to a multi-focal Fresnel lens and can enhance the uniformity of light ray emergence; however, the traditional multi-focal-length Fresnel lens is different from other multi-focal-length Fresnel lenses in that the traditional multi-focal-length Fresnel lens carries out light homogenizing design on parallel light such as sunlight, the light homogenizing of the regional light homogenizing Fresnel lens is innovatively carried out according to the light emitting light energy distribution characteristics of an LED light source, the light homogenizing performance of an LED illumination optical system is improved, meanwhile, a plurality of regions are designed as independent Fresnel lenses, the focal length of each region is determined through calculation, the surface type of the Fresnel lens is determined by using a method for changing the focal length, the radius of each region of the Fresnel lens is prevented from being recalculated, and the design efficiency is improved.

Drawings

FIG. 1 is a schematic diagram of a zone principle of a Fresnel lens with zone uniform illumination;

FIG. 2 is a schematic diagram of Fresnel lens ray exit;

FIG. 3 is a diagram of a central region model of a Fresnel lens with light uniformizing illumination in different regions;

FIG. 4 is a diagram of a first region model of a Fresnel lens with uniform illumination in different regions;

FIG. 5 is a diagram of a second area model of a Fresnel lens with uniform illumination in different areas;

FIG. 6 is a third area model diagram of a Fresnel lens with uniform illumination in different areas;

FIG. 7 is a diagram of a fourth area model of a Fresnel lens with uniform illumination in different areas;

FIG. 8 is a diagram of a fifth area model of a Fresnel lens with uniform illumination in different areas;

FIG. 9 is a graph of irradiance distribution for a conventional Fresnel lens;

FIG. 10 is a distribution diagram of irradiance of a zoned uniform Fresnel lens;

fig. 11 is a schematic diagram of the design method of the fresnel lens based on the partitioned area dodging illumination of the LED.

Detailed Description

As shown in fig. 1, the invention provides a design method of a fresnel lens for realizing uniform illumination of an LED, wherein 1 is an LED light source, and 2 is a lens; fig. 1 shows the relationship between the exit angle and the divergence angle of the fresnel lens, i.e. the exit angle and the divergence angle θ - θ', according to the optical relationship:

I·Ω＝φ (1)

I＝I₀·cosθ (2)

wherein, I is the light intensity of the point light source S reaching the emergent face in a given direction solid angle, and the unit is cd; e is the illumination of the light reaching the exit surface, and the unit is 1 x; a is the area of the emergent surface, and the unit is square meter; omega is the solid angle in a given direction, theta is the ray emergence half angle, theta 'is the ray divergence half angle, phi is the luminous flux of the light source reaching the emergence surface in the solid angle in the given direction, L is the object distance, L' is the image distance, R is the radius of the lens, R is the radius of the illumination spot of the receiving surface, and L is the distance from the image surface to the surface of the fresnel lens.

The solid angle is defined as:

from the integral determinations:

A＝πR²(4)

thus:

Ω＝2πsinθdθ (5)

and because:

φ＝E·A (6)

equation (7) can be derived from equations (1) through (6):

the formula can be arranged to obtain:

πI₀sin²θ＝Eπ·R²(8)

the calculation formula for obtaining the spot radius R of the irradiation surface is as follows:

r can be determined by the distance L from the image plane to the fresnel lens and the image distance L':

then the relation between the exit angle theta' after being deflected by the Fresnel lens and the exit angle theta of the light source is obtained as

As shown in fig. 2, the focal length formula derivation process for the sub-region is as follows:

the objective relation formula of the Fresnel lens is as follows:

according to the geometric relationship and the angle formula, the following results are obtained:

can also be expressed as

In combination with the above formula, the focal length can be calculated as:

wherein, R is calculated by combining the formula (9) and is substituted into the formula (15), and the focal lengths of different areas can be obtained.

As shown in fig. 3 to 8, the design example described in the method of the present invention includes six regions, but is not limited to six regions, so as to achieve uniform illumination, solve the problem that light is not uniform enough due to focusing or emission of light, and the lens is not limited to the above-mentioned specific embodiment, but can be extended to any solution that can implement a uniform light device.

The method provides a region division method and a region light focal length calculation method aiming at the LED light source with Lambert light distribution so as to determine the Fresnel lens surface type, and the method improves the illumination uniformity of a receiving surface. The Fresnel lens comprises a plurality of areas, wherein the center area is located at the center, the first area is connected with the center area, the second area is connected with the first area, the third area is connected with the second area, the fourth area is connected with the third area, the fifth area is connected with the fourth area, and so on, all the areas diffuse outwards from the center in sequence, all the areas are integrated on one lens plane, and the focal lengths of all the areas are different. The acquisition mode of each region is as follows: the central area is the most complete Fresnel lens, the first area is a union set of Fresnel lenses with different focal lengths and the central area, the second area is a union set of Fresnel lenses with different focal lengths and a union set of the first area and the central area, and the third area is a union set of Fresnel lenses with different focal lengths and a union set of the second area, the first area and the central area, so that the area of each ring is obtained.

Each region is a part of a common Fresnel lens, the part is an annular belt of the common Fresnel lens, the inner surface of each region is a surface close to a light source, the outer surface of each region is a surface close to a receiving surface, the outer surface of each region is a small irregular sawtooth prism with continuous equal circular arcs, the center part of the lens of each region is an arc lens, the rest part of the lens is a sawtooth lens, the small irregular sawtooth prism is that the focal length of each region lens is different, so the small sawtooth prisms are also different, and different circular radians are selected according to different focal lengths of each region.

The region division mode is divided according to the space light ray division mode and the processing level, and can also be adjusted according to the design accuracy requirement. And the focal length of the Fresnel lens in each area is determined according to the light emitting characteristics of the LED light source and the position and the size of the image surface.

The equal radius or the equal light-emitting angle belongs to the precision division of light source incidence, the purpose of obtaining the focal length is to standardize the light emission after the light passes through the lens, the light emission can be standardized by adjusting the focal length of the lens, and the surface shape of the lens can be obtained by obtaining the focal length of the lens.

As shown in fig. 11, I is an LED light source, II is a partitioned light-homogenizing fresnel lens, and III is an irradiation region receiving surface, the fresnel lens is made of PMMA and other common materials, and the present embodiment can be designed and manufactured through the following steps:

s1: determining the size of a partitioned uniform light Fresnel lens, wherein the maximum aperture of a Fresnel lens is 120mm, the ring distance is 1mm, the thickness is 5mm, and the object distance is 100mm, namely, a light source is placed at a position 100mm away from the left side of the partitioned Fresnel lens, a receiving surface is placed at a position 500mm away from the right side of the partitioned Fresnel lens, the size of the receiving surface is 300mm multiplied by 300mm, meanwhile, a COB integrated LED light source is selected as 100W, other LED light sources can be selected as well, the size is 50mm multiplied by 50mm, and 100 ten thousand light rays are used for light ray tracing;

s2: dividing the fresnel lens with regional uniform light illumination into 6 regions, as shown in fig. 3 to 8, wherein the central region is located at the center, the first region is connected with the central region, the second region is connected with the first region, the third region is connected with the second region, the fourth region is connected with the third region, the fifth region is connected with the fourth region, and so on, each region is diffused from the center to the outside in sequence, all the regions are integrated on one lens plane, the size of each region is divided according to the precision, the embodiment is divided according to the equal-width caliber, the size of each region is divided every 10mm precision, and the obtained regions are respectively: 10mm, 20mm, 30mm, 40mm, 50mm and 60mm, thus obtaining the combined lens formed by the seamless connection of six concentric circles;

s3: the relation between the angles of the marginal rays is calculated by the law of conservation of optical expansion and the design requirement of surface dodging, as shown in a formula (11);

s4: calculating an image point formula (14) of each area according to the relation between the emergent angle and the divergence angle theta-theta', namely an edge ray angle relation formula (11), and further calculating a focal length formula (15) of each area according to an object image relation formula;

s5: and finally, the surface type of the Fresnel lens for uniform illumination can be determined, light emitted by the LED light source passes through the outer surface and then is emitted to the small sawtooth prisms of the small irregular circular arcs on the outer surface for dimming and emergent, and uniform light is emitted to improve the uniform performance of the Fresnel lens.

The common dodging Fresnel lens with the same caliber, namely the caliber is 120mm, the ring distance is 1mm, the thickness is 3mm and the object distance is 100mm is used for placing a light source at a position 100mm away from the zoned Fresnel lens to be compared, namely the two Fresnel lenses are respectively led into Tracepro optical simulation software to be simulated under the same condition, and finally the obtained irradiance distribution diagrams are compared.

Wherein, according to the specification of IEC60904-9 international standard, the uniformity of the spot energy can be expressed as:

wherein E is_maxRepresenting the maximum intensity of light on the light energy receiving surface, E_minRepresents the average value of the intensity of light incident on the light energy receiving surface. The illuminance map of the condensing system is simulated herein using the Tracepro software, recording a minimum of typically 10^-nMagnitude of order, so using averageThe value replaces the minimum value to calculate the spot uniformity, denoted as E_meanNamely:

fig. 9 and 10 are graphs comparing irradiance distribution of a common fresnel lens with irradiance of a partitioned dodging fresnel lens, and it can be seen from fig. 9 and 10 that the uniformity of light spots of the common fresnel lens is 79%, and the uniformity of light spots of the partitioned dodging fresnel lens is 84%, so that the uniformity of the light spots is improved. According to the experimental result, the optimal effect of the emergent light rays is obtained when the annular distance and the thickness of each area are consistent, and the nonuniformity of the emergent light rays can be reduced.

In this embodiment, the light may be further refined, the precision of dividing each radius of 10mm may be further refined, and the uniformity of the light may be further improved.

In summary, the invention designs the Fresnel lens for the partitioned light-homogenizing illumination based on the LED, the partitioned light-homogenizing Fresnel lens can be prepared through a casting mold and is combined with a common reflector or a designed reflector for use, so that the light emergent uniformity is further improved.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be able to cover the technical solutions and the inventive concepts of the present invention within the technical scope of the present invention.