AU2021105348A4

AU2021105348A4 - Lens type light-emitting diode (led) blackboard light

Info

Publication number: AU2021105348A4
Application number: AU2021105348A
Authority: AU
Inventors: Yandan Lin; Li Zhou
Original assignee: Fudan University; Guanghua Lingang Engineering Application Technology Research and Development Shanghai Co Ltd
Current assignee: Fudan University; Guanghua Lingang Engineering Application Technology Research and Development Shanghai Co Ltd
Priority date: 2021-08-12
Filing date: 2021-08-12
Publication date: 2021-10-14
Anticipated expiration: 2029-08-12

Abstract

OF THE DISCLOSURE The present disclosure belongs to the field of lighting technology, and specifically relates to a light-emitting diode (LED) blackboard light. The lens type LED blackboard light structurally comprises a light shell, LED light beads, a printed circuit board (PCB), an optical lens and a plastic surface cover, wherein the LED light beads, the PCB, the optical lens and the plastic surface cover form an optical module placed and fixed in a groove in the light shell; and the optical lens is in a long strip shape and is formed by incident surfaces, a light-exiting surface and two different side surface internal total reflection surfaces. According to the lens type LED blackboard light provided by the present disclosure, aiming at the position characteristics of a blackboard and the light, a secondary light distribution design is carried out on an LED through the optical lens, and the lens adopts a multi-free-form-surface lens form, fully collects energy emitted by an LED light source through refraction and total internal reflection ways, re-distributes and projects onto a blackboard surface, so that lighting effects on condensed light and polarized light are achieved, the utilization ratio of optical energy is greatly improved, and meanwhile, higher uniformity on the blackboard surface is maintained. The blackboard light is simple in structure and has higher practicability. ABSTRACT DRAWING - Fig 1 17961985_1 (GHMatters) P116977.AU 1/4 100 30 10 &;>,20 FIG I 20 FIG

Description

1/4

100

10 &;>,20 FIG I

20

FIG LENS TYPE LIGHT-EMITTING DIODE (LED) BLACKBOARD LIGHT TECHNICAL FIELD

[01] The present disclosure belongs to the field of lighting technology, and specifically relates to a light-emitting diode (LED) blackboard light.

BACKGROUNDART

[02] Blackboard is the most commonly used prop in ordinary teaching activities and exhibition activities. The blackboard does not emit light, and needs to reflect the light emitted by the environment and the light and then is perceived by human eyes. The application environments of the blackboard are various, and when the ambient light is poor, a blackboard light is needed for compensation. Therefore, the optical design of the blackboard light directly affects the uniformity of the blackboard and further affects the observation of human eyes.

[031 A fluorescent light is used in a traditional blackboard light as an illumination mode, the illumination has the defects that the efficiency is low, the illumination of the blackboard is not uniform, the illumination of the lower half portion of the blackboard is obviously low, glare is serious, mercury is contained and the like, and at present, the fluorescent light is gradually phased out. LEDs, as solid-state lighting sources, gradually occupy most of the lighting market and have great advantages compared with fluorescent lights. The blackboard light using an LED light source has huge optical design space compared with a fluorescent tube, and is mainly in a reflection type and in a lens type at present. The lens type blackboard light is relatively huge in structure, high in reflector processing requirement integrally, low in integral optical efficiency and the like. Disclosed is a blackboard light with two reflectors in CN200710049769, a whole light body comprises two fluorescent lights and two parabolic reflectors, the illustrating angles of the light source are different, and certain angles are formed by the two reflectors and the blackboard respectively to be responsible for lighting different areas of the blackboard. The optical scheme of the lens type blackboard light is not mature, the lens type blackboard light mostly appears in a wall washer light form, the special situation of blackboard lighting is not satisfied, and secondary optical design with huge design improvement space is realized by adopting a lens.

SUMMARY

[04] The present disclosure aims to provide a lens type light-emitting diode (LED) blackboard light which is high in uniformity, low in glare, high in energy efficiency and compact in structure.

[05] According to the lens type LED blackboard light designed by the present disclosure, aiming at the position characteristics of a blackboard and a light, an array of LED light beads is subjected to secondary light distribution design through an optical lens, the optical lens adopts a multi-free-form-surface lens form, light emitted by the array of LED light beads are completely collected and redistributed through an optical system in a refraction and total reflection mode, and the light is projected to the blackboard surface, so that the lighting effect of condensed light and polarized light is

17961985_1 (GHMatters) P116977.AU realized, the utilization rate of light energy is greatly improved, and meanwhile, higher uniformity on the blackboard surface is maintained.

[061 The lens type LED blackboard light designed by the present disclosure structurally comprises a light shell, LED light beads, a printed circuit board (PCB), an optical lens and a plastic surface cover, wherein the LED light beads, the PCB, the optical lens and the plastic surface cover form an optical module of the LED blackboard light, a groove is formed in the light shell, and the optical module is placed and fixed in the groove.

[071 In the optical module, the LED light beads are welded to the PCB and distributed in an array mode; the optical lens is installed above the array of LED light beads, and the LED light beads are located below the geometric center of the optical lens; and the plastic surface cover is installed at an opening of the light shell and used for sealing the whole optical system.

[081 In the lens type LED blackboard light, the array of LED light beads and the PCB form an LED light source board module, the array of LED light beads (namely, a plurality of LED light beads) is arranged at the same intervals (namely, linearly and uniformly arranged) in the length direction of the light source board module, and the intervals can be adjusted according to different application scene requirements. Linear uniform arrangement is beneficial to transverse uniformity of illumination of the blackboard light on the blackboard, and dazzling caused by direct observation of the light by human eyes can be avoided. The LED light source board module is obliquely placed relative to the blackboard surface and slightly faces the lower portion of the blackboard, so that the lower half portion of the blackboard obtains more energy, and the difficulty of optical design can be properly reduced.

[09] In the lens type LED blackboard light, the optical lens is in a long strip shape and is composed of the following curved surfaces: incident surfaces, a light-exiting surface and two different side surface internal total reflection surfaces, wherein the incident surfaces comprise a front incident surface and side surface incident surfaces to form a groove shape, the array of LED light beads is located in the groove, and light-exiting surfaces of the LED light beads directly opposite to the front incident surface; the side surface incident surfaces and the light-exiting surface are basic planes, and the front incident surface and the side surface internal total reflection surfaces are free-form surfaces. The whole optical lens extends in the longitudinal direction of the blackboard, light emitted by the array of LED light beads is limited by the lens, all the emitted light is limited within a specific angle range, that is, in the longitudinal direction vertical to the blackboard, the light is finally limited to the face where the blackboard is located, and certain uniformity is achieved; and in the transverse direction of the blackboard, light transmission is not limited, and diffusion distribution of the light in the transverse direction of the blackboard is facilitated.

[10] In the lens type LED blackboard light, the light emitted from the array of LED light beads is divided into three paths, andfinally concentrated high-uniformity distribution is formed on the plane where the blackboard is located. The first path is realized through the front incident surface of the optical lens, the front incident surface is a free-form surface, the light emitted from a light source is directly refracted to the

17961985_1 (GHMatters) P116977.AU light-exiting surface through the front incident surface and finally emitted to the blackboard, uniform illumination in the longitudinal direction is realized, and in the light path, the optical lens mainly controls the light distribution of the light in the longitudinal direction of the blackboard. The second path and the third path are achieved through the two different side surface internal total reflection surfaces and the side surface incident surfaces respectively, light emitted from the LED light beads is refracted to the side surface internal total reflection surface on the corresponding side from one side surface incident surface, is refracted to an outer light-exiting surface through inner side total reflection and finally is emitted to the blackboard, and a longitudinal distribution cut-off line of the light on the blackboard is limited; and in the same way, the array of LED light beads is refracted to the other corresponding side surface internal total reflection surface through the other side surface incident surface and finally emitted to the blackboard to form another longitudinal distribution cut-off line, and therefore light constraint in the direction vertical to the blackboard is achieved. The three parts of light are projected to the blackboard surface through the outer light-exiting surface, are respectively irradiated to different positions in the longitudinal direction of the blackboard and are mutually overlapped, so that the illumination of the blackboard in the longitudinal direction is uniform.

[11] Moreover, periodic microarrays are additionally arranged on the light-exiting surface of the optical lens and are called as microstructures, so that the uniformity of illumination on the blackboard surface is further improved. The microstructures are periodically arranged optical microcomponents relative to the whole optical surface. The simplest microstructures are formed by intercepting spheres, the radius of curvature of the sphere and the height of a protruding optical surface are used for representing the microcomponents, and the periodic rule is represented by periodically arranged parameters, namely the transverse and longitudinal intervals of the same microcomponents. The microstructures change the light distribution in a small range, and has the effect of enabling light to be more randomly distributed on the blackboard in the original light distribution under the basic effect of the whole optical system, has a certain effect on improving the uniformity and dispersion, and can also prevent human eyes from directly observing the light to cause strong dazzling feeling.

[12] According to the lens type blackboard light, the free-form surface lens is adopted for achieving secondary optical design. Compared with a blackboard light in a reflection form, the blackboard light adopting the free-form surface lens as the optical design has the advantages that on one hand, more energy can be uniformly projected on the blackboard surface; and on the other side, on the premise of without needing more structural bodies, glare can be effectively prevented by means of optical components, and the structural size is small. Compared with an existing lens type blackboard light, the LED blackboard light is simpler and lighter in structural size, and through the special secondary optical design of the lens and the microstructure design of the light-exiting surface, the uniformity is improved, and glare is reduced.

[131 In the optical lens, the free-form surface design is obtained by calculating and solving a partial differential equation through a light flux mapping method. Through the light flux mapping method, the corresponding relation between an angle and a target

17961985_1 (GHMatters) P116977.AU point is determined according to the angle and the position of light emitted from different angles to obtain geometric parameters of the free-form surfaces, and the partial differential equation is solved according to the geometric relation obtained through the light flux mapping method to obtain the surface types of the free-form surfaces.

[14] The process of solving the partial differential equation to obtain the surface types of the free-form surfaces is as follows: the corresponding relation 0=F(R) of the known light flux mapping method -R, 0 is an included angle between the light and a design reference axis during design, R is the position where the design light falls on an irradiated target surface through an optical system, and 0and R are defined and set in advance. When the lighting effect does not meet the requirement, the distribution of the irradiated surface is checked according to the light tracing of a model so as to define the improvement direction, then the design is carried out by adjusting the corresponding relation 0=F(R), and the light distribution is adjusted.

[15] When 01 corresponds to Ri, 02 corresponds to R2, ... and the like, 0-R of each design light meets the corresponding relation 0=F(R).

[16] A partial differential equation method of a single free-form surface, as shown in FIG. 6, comprises the following steps: setting R to be a position on a target surface, x and y to be positions of points required to be solved on the free-form surface, iNto be an incident angle of design light, and out to be the final emergent angle of the design light;

[17] emitting the light from the LED, refracting the light through a point (x, y) on the free-form surface of the optical lens and then through the refraction of the plane to reach the light-exiting surface; setting the distance from the LED to the center of the bottom of the optical lens to be do, the center thickness from the bottom of the optical lens to the top of the optical lens to be di, and the distance from the top of the optical lens to the target surface to be d2, wherein ai is an included angle between the tangent direction of the curved surface and the reference axis, a2 and bi are shown as alternate interior angles in light path diagrams and are included angles between the refracted light and the reference axis, and a2 is equal to bi; and n is the refractive index of the optical lens and is determined by the lens material.

[181 From the LED to the target surface, the expression of R is as follows:

[19] R=x tan0in+(do+di-x)tanbi+d2tan0out (1)

[201 The relation of y and x is satisfied according to the geometric relation:

[21] y=x tanOin (2)

[221 Derivation is carried out on equation (2) Oin, it needs to be noted that x is also a function of Oin, so that the partial derivative of x on Oin must be considered in the equation, so that the same processing is carried out with y, and the equation can be obtained:

- -d x tan + (3)

[23] do, dain (COS a,Y

dy dx

[241 In the equation, two unknown terms d in and dGhl are included, so

17961985 1 (GHMatters) P116977.AU that further simplified is needed.

[25] According to a Snell refraction formula, the light satisfies the following equation in the optical system:

sin (- a1+ in= nxsin 1 -al +bl) (4)

[261 2 2

[27] According to the definition of curved surface inclination angles, the point (x,y) satisfies the following equation: dy = tan al (5)

[281 dx

[29] According to the equation (4) and the equation (5), the following equation can be obtained: dy sin Oin -n sin bl (6)

[30] dx cos 0 i-ncosb1

[311 Through simultaneous establishment of the equation (3) and the equation (6), the following relation of x and Oin is finally obtained: cos 81P1 -ncos bl X dX = dX dy - 11ki -"fl'1fl bI (cs 0 (7) d78n dy din

[32] m e nsin bl )<itanl

[33] Through simultaneous establishment, the differential equation about x and Oin is finally obtained. The partial differential equation is solved generally through a computer, and Oin=Oand x=do are known to be initial solutions of the partial differential equation. The physical significance of the differential equation is that the unique coordinate of the free-form surface is uniquely determined by knowing the light source angle and the target illumination condition of a designer, namely the corresponding relation, and a series of coordinate points on the free-form surface can be obtained by solving the partial differential equation. And then the coordinate points are connected into a curve to form an initial model for simulation, the corresponding relation 0=F(R) is directionally adjusted according to a simulation result, and a new model is obtained through solving for simulation. Similar to a partial differential equation of refraction, the solution of the reflected part is also operated similarly.

BRIEF DESCRIPTION OF THE DRAWINGS

[341 FIG.1 is a stereoscopic exploded view of a lens type light-emitting diode (LED) blackboard light in the present disclosure.

[35] FIG. 2 is a light path diagram of the lens type LED blackboard light in the present disclosure.

[361 FIG. 3 is a diagram of an LED light source board.

[37] FIG. 4 is a schematic diagram of a light flux mapping method designed for blackboard light lens design.

[38] FIG. 5 is a light path diagram of a free-form surface lens.

[391 FIG. 6 is a schematic diagram for solving points on the free-form surfaces through partial differential.

17961985 1 (GHMatters) P116977.AU

[401 FIG. 7 is a complete surface type of the LED lens.

[41] Reference signs in drawings: 10, LED light source board; 20, optical lens; 30, light shell; 100, LED blackboard light; 200, blackboard surface; 21, front incident surface of optical lens; 22, side surface internal total reflection surface of optical lens; 23, side surface internal total reflection surface of optical lens; and 24, outer light-exiting surface of optical lens.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[42] FIG. 1 is a stereoscopic exploded view of a lens type light-emitting diode (LED) blackboard light 100 in the present disclosure. An LED light source board 10 is arranged on a light shell 30 and is inclined relative to a blackboard, and a lens is arranged on the LED light source board. As shown in FIG. 2, the lens 20 adopts a multi-free-form-surface lens form, and the energy emitted by the light source is collected, redistributed and projected onto the blackboard surface 200 by means of refraction and internal total reflection. As shown in FIG. 3, by adjusting the arrangement distance D of the LED on the light source board 10, the uniformity of the blackboard in the transverse direction can be enhanced, and the emergent light flux can also be controlled.

[43] The surface types of the free-form surfaces of the lens are obtained through a light flux mapping method and a partial differential equation method. As shown in FIG. 4, according to the light flux mapping method, the corresponding relation between the angle and the target point is determined according to the angle and the position of the light emitted from different angles. As shown in FIG. 6, according to the partial differential equation method, the geometric relation obtained by the light flux mapping method is solved through the partial differential equation solution to obtain the surface types, and the following is theoretical analysis of the partial differential equation: the preset corresponding relation 0=F(R) of the known light flux mapping method 0-R, 01 corresponds to RI, and 02 corresponds to R2.

[44] According to the partial differential equation method, physical quantities limited by a mapping relation are solved to obtain a unique solution through simultaneous refraction and reflection formulas and determination of initial conditions. However, in the blackboard light, the size of the LED cannot be ignored, the light is obliquely placed relative to the blackboard, the distance between the lower half portion of the blackboard and the blackboard light is longer than the upper half portion of the blackboard, inconvenience is brought to accurate definition of the mapping relation, and therefore an iterative optimization idea is needed in actual use, repeated calculation is carried out by setting an optimization function, and then the required surface types are obtained through iterative optimization, that is, by changing the mapping relation that 01 corresponds to Rii, 0 corresponds to R21 and the like, Rii is different from R, and R21 is different from R2.

[45] FIG. 5 is a generatrix outline of a blackboard light lens, light emitted from the light source board 10 is refracted by a front incident surface 21, reflected by a side surface internal total reflection surface 22 and a side surface internal total reflection surface 23 and finally emitted by an outer light-exiting surface 24 together, and all the

17961985_1 (GHMatters) P116977.AU free-form surfaces are solved by the partial differential equation method. According to the light tracing of each curved surface, the spatial light distribution of the three parts is basically consistent, so that the distribution of the three parts on the blackboard is mutually overlapped, light spots are softer relative to the separated mapping relation of the three parts, and the optical effect can be improved by properly adding light spots on the outer light-exiting surface for firing, finally as shown in FIG. 7.

[46] It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

[471 In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

17961985_1 (GHMatters) P116977.AU

Claims

WHAT IS CLAIMED IS:

1. A lens type light-emitting diode (LED) blackboard light, comprising a light shell, LED light beads, a printed circuit board (PCB), an optical lens and a plastic surface cover, wherein the LED light beads, the PCB, the optical lens and the plastic surface cover form an optical module of the LED blackboard light, a groove is formed in the light shell, and the optical module is placed and fixed in the groove; in the optical module, the LED light beads are welded to the PCB and distributed in an array mode; the optical lens is installed above the array of LED light beads, and the LED light beads are located below the geometric center of the optical lens; the plastic surface cover is installed at an opening of the light shell and used for sealing the whole optical system; the array of LED light beads and the PCB form an LED light source board module, and the array of LED light beads is linearly and uniformly arranged in the length direction of the light source board module; the optical lens is in a long strip shape and is composed of the following curved surfaces: incident surfaces, a light-exiting surface and two different side surface internal total reflection surfaces, wherein the incident surfaces comprise a front incident surface and side surface incident surfaces to form a groove shape, the array of LED light beads is located in the groove, and light-exiting surfaces of the LED light beads directly opposite to the front incident surface; the side surface incident surfaces and the light-exiting surface are basic planes, and the front incident surface and the side surface internal total reflection surfaces are free-form surfaces; the whole optical lens extends in the longitudinal direction of the blackboard, light emitted by the array of LED light beads is limited by the lens, all the emitted light is limited within a specific angle range, that is, in the longitudinal direction vertical to the blackboard, the light is finally limited to the face where the blackboard is located, and certain uniformity is achieved; and in the transverse direction of the blackboard, light transmission is not limited, and diffusion distribution of the light in the transverse direction of the blackboard is facilitated.

2. The lens type light-emitting diode (LED) blackboard light according to claim 1, wherein the light emitted from the array of LED light beads is divided into three paths, and finally concentrated high-uniformity distribution is formed on the plane where the blackboard is located; the first path is realized through the front incident surface of the optical lens, the light emitted from a light source is directly refracted to the light-exiting surface through the front incident surface and finally emitted to the blackboard, uniform illumination in the longitudinal direction is realized, and in the light path, the optical lens mainly controls the light distribution of the light in the longitudinal direction of the blackboard; the second path and the third path are achieved through the two different side surface internal total reflection surfaces and the side surface incident surfaces respectively, light emitted from the LED light beads is refracted to the side surface internal total reflection surface on the corresponding side from one side surface incident surface, is refracted to an outer light-exiting surface through inner side total reflection and finally is emitted to the blackboard, and a longitudinal distribution cut-off line of

17961985_1 (GHMatters) P116977.AU the light on the blackboard is limited; in the same way, the array of LED light beads is refracted to the other corresponding side surface internal total reflection surface through the other side surface incident surface and finally emitted to the blackboard to form another longitudinal distribution cut-off line, and therefore light constraint in the direction vertical to the blackboard is achieved; the three parts of light are projected to a blackboard surface through the outer light-exiting surface, are respectively irradiated to different positions in the longitudinal direction of the blackboard and are mutually overlapped, so that the illumination of the blackboard in the longitudinal direction is uniform.

3. The lens type light-emitting diode (LED) blackboard light according to claim 2, wherein periodic microarrays are additionally arranged on the light-exiting surface of the optical lens and are called as microstructures, so that the uniformity of illumination on the blackboard surface is further improved; and the microstructures are periodically arranged optical microcomponents relative to the whole optical surface.

4. The lens type light-emitting diode (LED) blackboard light according to claim 1, 2 or 3, wherein in the optical lens, the free-form surface design is obtained by calculating and solving a partial differential equation through a light flux mapping method; and through the light flux mapping method, the corresponding relation between an angle and a target point is determined according to the angle and the position of light emitted from different angles to obtain geometric parameters of the free-form surfaces, and the partial differential equation is solved according to the geometric relation obtained through the light flux mapping method to obtain the surface types of the free-form surfaces.

5. The lens type light-emitting diode (LED) blackboard light according to claim 4, wherein the corresponding relation 0=F(R) of the known light flux mapping method0-R, o is an included angle between the light and a design reference axis during design, R is the position where the design light falls on an irradiated target surface through an optical system, and 0 and R are defined and set in advance; when the lighting effect does not meet the requirement, the distribution of the irradiated surface is checked according to the light tracing of a model so as to define the improvement direction, then the design is carried out by adjusting the corresponding relation 0=F(R), and the light distribution is adjusted; and when 01 corresponds to Ri, 02 corresponds to R2, ... and the like, 0-R of each design light meets the corresponding relation 0=F(R); wherein the process of solving the partial differential equation to obtain the surface types of the free-form surfaces is as follows: a partial differential equation method of a single free-form surface comprises the following steps: setting R to be a position on a target surface, x and y to be positions of points required to be solved on the free-form surface, in to be an incident angle of design light, and out to be the final emergent angle of the design light; emitting the light from the LED, refracting the light through a point (x, y) on the free-form surface of the optical lens and then through the refraction of the plane to reach the light-exiting surface; setting the distance from the LED to the center of the bottom

17961985_1 (GHMatters) P116977.AU of the optical lens to be do, the center thickness from the bottom of the optical lens to the top of the optical lens to be di, and the distance from the top of the optical lens to the target surface to be d2, wherein ai is an included angle between the tangent direction of the curved surface and the reference axis, a2 and bi are included angles between the refracted light and the reference axis, and a2 is equal to bi; n is the refractive index of the optical lens and is determined by the lens material; from the LED to the target surface, the expression of R is as follows: R=x tanin+(do+di-x)tanbi+d2tan~out (1) according to the geometric relation that y and x are satisfied, through derivation operation, and according to a Snell refraction formula, the relation that the light in the optical system is satisfied and the definition of curved surface inclination angles, the relation between x and 0 in satisfies the following differential equation: dx _dx dy si _________________in)

- ~ 0i -n , (cOsO (7)

The partial differential equation is solved through a computer, and Oin=O and x=do are known to be initial solutions of the partial differential equation, so that the partial differential equation is solved to obtain a series of coordinate points on the free-form surface; and the coordinate points are connected into a curve to form an initial model for simulation, and then according to a simulation result, the corresponding relation0=F(R) is directionally adjusted, and a new model is obtained for simulation through solving, wherein similar to a partial differential equation of refraction, the solution of the reflected part is also operated similarly.

17961985 1 (GHMatters) P116977.AU