CN115166891A - Mini-LED backlight module based on total internal reflection free-form surface - Google Patents
Mini-LED backlight module based on total internal reflection free-form surface Download PDFInfo
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
- G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
- G02B6/0033—Means for improving the coupling-out of light from the light guide
- G02B6/0035—Means for improving the coupling-out of light from the light guide provided on the surface of the light guide or in the bulk of it
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
- G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
- G02B6/0033—Means for improving the coupling-out of light from the light guide
- G02B6/0035—Means for improving the coupling-out of light from the light guide provided on the surface of the light guide or in the bulk of it
- G02B6/0036—2-D arrangement of prisms, protrusions, indentations or roughened surfaces
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
- G02F1/1336—Illuminating devices
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
- G02F1/1336—Illuminating devices
- G02F1/133602—Direct backlight
- G02F1/133603—Direct backlight with LEDs
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- Optics & Photonics (AREA)
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Abstract
The invention discloses a Mini-LED backlight module based on a total internal reflection free-form surface, which comprises a backlight unit and a diffusion film, wherein the backlight unit and the diffusion film are arranged from bottom to top. The backlight unit is composed of a plurality of Mini-LED light sources, a Mini-LED base and a dimming unit consisting of a free-form surface light guide plate. The bottom of the free-form surface light guide plate is cylindrical, and a conical free-form surface with reflection and transmission functions is arranged right above the bottom cylinder, so that part of light rays emitted by the Mini-LED are horizontally transmitted on the light guide plate, and part of the light rays are upwards collimated and transmitted to emit light through the prismatic annular transmission microstructures. The lower surface is provided with a step-type light coupling-out microstructure, and light rays horizontally transmitted in the light guide plate are collimated and emitted upwards after passing through the structure. The invention converts the light emitted by the Mini-LED light source into a large-area uniform and soft surface light source through the free-form surface light guide plate capable of collimating the light, omits a prism film, can reduce the thickness of the module, and has the advantages of higher light-emitting brightness, low power consumption and regional dimming.
Description
Technical Field
The invention relates to the technical field of display, in particular to a Mini-LED backlight module based on a total internal reflection free-form surface.
Background
The Liquid Crystal Display (LCD) technology is a passive light-emitting technology, has the traditional advantages of low production cost, low power consumption, long service life and the like, endows the LCD technology with durable vitality in the market, and mainly comprises a backlight module and liquid crystal. Low contrast is an inherent obstacle to HDR display of LCDs, and local dimming techniques are used to achieve a high dynamic range of a picture. Advances in semiconductor technology have LED to a continual reduction in the size of LEDs, which has provided many possibilities for advances in display technology. The Mini-LED is used as a new generation of LED chip technology, has a chip size of about 50-300 μm, is smaller and generates less heat compared with the traditional LED, and can be used for an LCD backlight module.
The LCD technology is classified into a direct type and a lateral type. The direct type light source is arranged at the bottom of the backlight module, and the side type light source is arranged at the side surface. Direct-lit versus edge-lit backlights have natural advantages in terms of the number of partitions. However, the direct type backlight requires a certain light mixing distance for achieving good illumination uniformity, which limits the overall thinness of the LCD display, contrary to the current trend. In addition, the direct-type backlight usually needs a large number of LED lamp beads, and the circuit and design thereof are complex and have high cost and the power consumption of the whole display is huge.
Disclosure of Invention
Accordingly, an object of the present invention is to provide a Mini-LED backlight module based on total internal reflection free-form surface, which solves the problem of excessive power consumption cost of the conventional direct-type backlight module, and reduces the thickness of the backlight module.
Which comprises a backlight unit and a diffusion film arranged from bottom to top. The backlight unit is composed of a plurality of Mini-LED light sources, a Mini-LED base and a dimming unit consisting of a free-form surface light guide plate. The bottom of the free-form surface light guide plate is cylindrical, and a conical free-form surface with reflection and transmission functions is arranged right above the bottom cylinder, so that part of light rays emitted by the Mini-LED are horizontally transmitted on the light guide plate, and part of the light rays are upwards collimated and transmitted to emit light through the prismatic annular transmission microstructures. The lower surface is provided with a step-shaped light coupling-out microstructure, and light rays horizontally transmitted in the light guide plate are collimated and emitted upwards after passing through the structure. The invention converts the light emitted by the Mini-LED light source into a large-area uniform and soft surface light source through the free-form surface light guide plate capable of collimating the light, omits a prism film, can reduce the thickness of the module, and has the advantages of higher light-emitting brightness, low power consumption and regional dimming.
In order to achieve the purpose, the invention specifically adopts the following technical scheme:
the utility model provides a Mini-LED backlight unit based on total internal reflection free-form surface which characterized in that: comprises a backlight unit and a diffusion film arranged from bottom to top; the backlight unit is composed of a plurality of Mini-LEDs, a Mini-LED base and a dimming unit consisting of a free-form surface light guide plate; the bottom of the free-form surface light guide plate is cylindrical, and a conical free-form surface with reflection and transmission functions is arranged right above the bottom cylinder, so that part of light rays emitted by the Mini-LED are horizontally transmitted in the light guide plate, and part of the light rays are upwards collimated and transmitted to emit light through the prismatic annular transmission microstructures; the lower surface of the free-form surface light guide plate is provided with a step type light coupling-out microstructure, so that light rays horizontally transmitted in the light guide plate are collimated and emitted upwards after passing through the structure.
Furthermore, a cylinder at the bottom of the free-form surface light guide plate is embedded with a cylindrical seat stand in the Mini-LED base; the Mini-LED is positioned at the right center of the cylindrical seat stand, and the distance between the light emitting surface of the Mini-LED and the bottom of the free-form surface light guide plate is a calculated fixed value; the conical total internal reflection free-form surface in the free-form surface light guide plate is positioned right above the Mini-LED, and the height of the free-form surface is equal to the total height of the stepped light coupling-out microstructure; the luminous intensity rule of the Mini-LED accords with Lambert distribution or other symmetrical luminous intensity distribution, and the luminous surface faces the free-form surface light guide plate.
The Mini-LED base of the single regional dimming unit has the shape of a cylindrical seat stand, a single direct type Mini-LED light source is embedded in the center of the cylindrical seat stand, and a cylinder at the bottom of the free-form surface light guide plate is matched with the cylindrical seat stand of the base.
Further, the conical free-form surface is used for enabling the coupled light to horizontally collimate and propagate in the free-form surface light guide plate; the stepped light coupling-out microstructure is provided with a stepped inclined surface and is used for collimating horizontally transmitted light and emitting light upwards, and uniform light emission is realized by matching the step height of each stage with the light intensity distribution of the light source.
Further, a coordinate system is established by taking the center of the Mini-LED light-emitting surface as an origin, and the coordinates (x) of discrete points of a section curve of the section of the conical free-form surface i ,y i ) The following relationship is satisfied:
in the formula, theta i The angle theta between the light emitted by the Mini-LED and the horizontal plane max The maximum value of the luminous half angle is shown, N is the total number of the segments, N is the refractive index of the free-form surface light guide plate material, and R is the distance between the bottom surface of the free-form surface light guide plate and the Mini-LED light-emitting surface.
Further, a coordinate system is established by taking the center of the light emitting surface of the Mini-LED as an origin, and the coordinates (x) of discrete points of a tangent plane curve of the prismatic annular transmission microstructure are i ,y i ) The following relationship is satisfied:
in the formula, theta i The angle theta between the light emitted by the Mini-LED and the horizontal plane max The maximum value of the luminous half angle is shown, N is the total number of the segments, N is the refractive index of the free-form surface light guide plate material, and R is the distance between the bottom surface of the free-form surface light guide plate and the Mini-LED light-emitting surface.
Furthermore, the lower surface of the free-form surface light guide plate is provided with a stepped light coupling-out microstructure which is divided into N sections, each section is provided with a 45-degree inclined surface, a section of small platform is arranged in front of each section of inclined surface, the width of each section of small platform is kept equal, and light rays which are transmitted through horizontal collimation of the total internal reflection of the conical free-form surface in the free-form surface light guide plate are vertically collimated upwards to emit light after the total internal reflection of the 45-degree inclined surface.
Furthermore, the height of each section of inclined plane of the stepped light coupling-out microstructure corresponds to the luminous intensity rule of the Mini-LED, so that the luminous flux of the light collimated upwards after passing through each section of inclined plane is kept consistent, and the uniform illumination of the light emitting surface is realized; establishing a coordinate system by taking the center of the light emitting surface of the Mini-LED as an origin, wherein the height of each level of inclined plane is defined by the following relational expression:
in the formula, H i Is the height of the i-th step slope, a i Is the light-emitting half angle corresponding to the i-th segment, b i Is the transmission angle F of the light corresponding to the i-th section after the light is incident on the free-form surface light guide plate i Is the point coordinate of the ith segment of light ray when the total internal reflection of the free-form surface occurs, theta' i Is the horizontal reflection ray of the ith segment and is at F i Angle of tangent to point, xp i The horizontal distance, XP, of the illuminating surface irradiated on the free-form surface light guide plate corresponding to the infinitesimal da of the lighting half-angle of the ith section i Scanning the projection distance of the illumination surface on the free-form surface in the horizontal direction for the light-emitting half-angle infinitesimal da, YS i The projection distance of the illumination surface on the free-form surface in the vertical direction of the section, yf, is scanned by the luminous half-angle infinitesimal da i Is a pointF i R is the distance from the bottom surface of the free-form surface light guide plate to the Mini-LED light-emitting surface, a max At maximum luminous half angle, yf max Is the maximum ordinate of the curve, yf min Is the minimum ordinate of the curve; yf max And yf min The value of (d) is determined by a conic free-form curve; the final objective is to find the recursive relationship between Hi +1 and Hi, thereby determining the size of each stage H while achieving better uniformity of light extraction.
Furthermore, the backlight unit is divided into a plurality of regional dimming units, each regional dimming unit comprises a single Mini-LED light source, a Mini-LED base and a free-form surface light guide plate, and the splicing seams of the adjacent regional dimming units are between 0.2mm and 2 mm; each dimming unit individually controls the light emitting brightness of the area by controlling the power of the Mini-LED.
Further, the free-form surface light guide plate is prepared by using an injection molding or PDMS imprinting method.
The injection molding method comprises the following steps: the male and female mold inserts of the mechanical mold are prepared through the procedures of numerical control machining (CNC), electric spark machining (EDM), wire cutting and the like and respectively correspond to the front surface and the back surface of the free-form surface light guide plate. And (3) putting the mould into an injection molding machine, melting the raw material master batch, injecting the melted raw material master batch into the mould, and molding to obtain the designed free-form surface light guide plate in batches. The PDMS imprinting method comprises the following steps: preparing a mold on a silicon wafer through photoetching and etching, casting a mixture of a PDMS prepolymer and a curing agent thereof on the surface of the mold, impressing PDMS, heating and curing or ultraviolet curing for a certain time, and peeling the PDMS from the surface of the mold, thereby obtaining the free-form surface light guide plate with a conical free-form surface microstructure and a bottom stepped light coupling microstructure. And assembling the Mini-LED, the Mini-LED base and the free-form surface light guide plate to form a dimming unit. Then, the dimming units are spliced to form a backlight unit, and finally, the backlight unit and the diffusion film are assembled.
Compared with the prior art, the invention and the optimized scheme thereof have the following beneficial effects:
a tapered free-form surface light guide plate is designed, the path of light emitted by a Mini-LED is adjusted, the light emitting area of the Mini-LD can be increased under the condition of the same quantity, the quantity of lamp beads is reduced, the quantity of circuits is further reduced, and the power consumption is greatly reduced.
Through the control of the conical free-form surface and the stepped light coupling-out microstructure, the emergent angle of light can be effectively reduced, the brightness is further improved, and meanwhile, a prism film can be omitted, so that the thickness of the module is reduced. In addition, the power of the Mini-LED in the dimming unit is controlled, so that the function of regional dimming can be realized, the contrast of the brightness of a picture is greatly improved, and the high dynamic range of the image is realized.
Drawings
Fig. 1 is a schematic structural diagram of a total internal reflection free-form surface Mini-LED backlight module according to an embodiment of the present invention.
Fig. 2 is a schematic structural view of a free-form surface light guide plate array of a backlight unit according to an embodiment of the invention.
Fig. 3 is a schematic structural diagram of a Mini-LED base array of a backlight unit according to an embodiment of the invention.
Fig. 4 is a schematic cross-sectional view of a free-form surface light guide plate according to an embodiment of the invention.
FIG. 5 and FIG. 6 are schematic views of the ray paths of the Mini-LED according to the embodiment of the present invention
FIG. 7 is a schematic diagram of a tapered total internal reflection free form surface design concept according to an embodiment of the present invention.
Fig. 8 is a schematic diagram illustrating a design principle of a prismatic-annular transmission microstructure according to an embodiment of the present invention.
Fig. 9 is a schematic diagram illustrating a design principle of a stepped light-outcoupling microstructure according to an embodiment of the present invention.
Fig. 10 is a simulation diagram of the illumination simulation result according to the embodiment of the present invention.
Fig. 11 is a simulation diagram of the illumination simulation result after the partial partitioned light sources are turned off according to the embodiment of the invention.
Fig. 12 is a schematic diagram of a splicing shape of another example of the dimming unit according to the embodiment of the invention.
In the figure: 1-Mini-LED base array; 2-a free-form surface light guide plate array; 3-a diffusion membrane; 11-Mini-LED base; 112-Mini-LED; 113-cylindrical seat stand; 21-a free-form surface light guide plate; 211-stepped light outcoupling microstructures; 212-tapered total internal reflection free-form surface; 213-bottom cylinder; 2121-edge annular transmission microstructure.
Detailed Description
In order to make the features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail as follows:
it should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
Referring to fig. 1, an embodiment of the invention provides a Mini-LED backlight module based on a total internal reflection free-form surface, which includes a backlight unit composed of a Mini-LED base array 1 and a free-form surface light guide plate array 2, and a diffusion film 3, which are sequentially arranged from bottom to top. The light rays with small emergent angles emitted by the backlight unit are further optimized through the diffusion film 3, and are converted into uniform and soft surface light sources to provide backlight sources for the liquid crystal display panel.
Referring to fig. 2, in the present embodiment, the entire backlight unit is formed by splicing a plurality of free-form-surface light guide plates 21.
Referring to fig. 3, in this embodiment, the Mini-LED base 11 has a cylindrical base 113 for positioning a single free-form surface light guide plate, and a Mini-LED 112 is placed in the center.
Referring to fig. 4, in the present embodiment, a structure composed of a stepped light-outcoupling microstructure 211, a tapered total internal reflection free-form surface 212, and a bottom cylinder 213 is disposed above the Mini-LED mount of each free-form surface light guide plate.
Referring to fig. 5, the conical total internal reflection free-form surface 212 has prismatic annular transmissive microstructures 2121.
Preferably, in this embodiment, the bottom cylinder of the free-form surface light guide plate is fitted to the cylindrical base 113 in the Mini-LED base. The Mini-LED is positioned at the right center of the cylindrical seat platform 113, and the distance between the light emitting surface of the Mini-LED and the bottom of the free-form surface light guide plate is a calculated fixed value. The conical total internal reflection free-form surface in the free-form surface light guide plate is positioned right above the Mini-LED, and the height of the free-form surface is equal to the total height of the stepped light-coupling-out microstructure.
Preferably, in this embodiment, the preparation method adopts a PDMS imprinting method, and includes the following steps: preparing a mold on a silicon wafer through photoetching and etching, casting a mixture of a PDMS prepolymer and a curing agent thereof on the surface of the mold, impressing PDMS, heating and curing or ultraviolet curing for a certain time, and peeling the PDMS from the surface of the mold, thereby obtaining the free-form surface light guide plate with a conical free-form surface microstructure and a bottom stepped light coupling microstructure. And assembling the Mini-LED, the Mini-LED base and the free-form surface light guide plate to form a dimming unit. Then, the dimming units are spliced to form a backlight unit, and finally, the backlight unit and the diffusion film are assembled.
The invention is further illustrated by the following specific examples.
Example 1 was carried out:
referring to fig. 2, in the present embodiment, the backlight unit is formed by splicing 9 partitions, that is, nine single free-form-surface light guide plates 21, a gap between the free-form-surface light guide plates is less than 0.3mm, and brightness of the free-form-surface light guide plates of different partitions is controlled by controlling power of Mini-LEDs, so that a function of regional dimming is realized, and contrast of a display image is improved.
In this embodiment, the free-form surface light guide plate is made of PMMA plastic, the transparent material has a refractive index n of 1.4936, the Mini-LED base is made of common black plastic, and the maximum half angle of light emission of the Mini-LED is 60 °.
As shown in fig. 3, in the present embodiment, the Mini-LED chassis 11 has a cylindrical pedestal 113 at the center for positioning the single free-form surface light guide plate. A Mini-LED 112 is arranged in the center of the cylinder, and the size is 0.1mm multiplied by 0.1mm. The distance between the light emitting surface of the Mini-LED and the bottom of the free-form surface light guide plate is 0.3mm.
As shown in fig. 4, in this example, the monolithic free-form-surface light guide plate has one stepped light-outcoupling microstructure 211, a tapered total internal reflection free-form surface 212, and a bottom cylinder 213. The radius of the bottom surface of the bottom cylinder 213 matches the cylindrical pedestal 113 in the Mini-LED base 11. During assembly, the bottom cylinder 213 of the free-form surface light guide plate is inserted into the cylindrical seat 113 of the base, so as to fix a single free-form surface light guide plate. The tapered tir free-form surface 212 is used to allow the coupled-in light to propagate horizontally collimated within the free-form surface light guide plate, and the light propagation path is shown in fig. 5. The stepped light coupling-out microstructure 211 has a stepped slope, and can collimate and emit light in a vertical direction, and the light is uniformly emitted by matching the step height of each step with the light intensity distribution of the light source, and the specific light path is as shown in fig. 6.
As shown in fig. 5, in this example, the tapered tir free form surface 212 surface has transmitted-light microstructures 2121. Part of light rays transmit from the light-emitting microstructure to make up for the problem of insufficient light rays. The design principle of the prismatic-annular transmission microstructure is shown in fig. 8, and each section of transmission surface is matched with a corresponding light-emitting half angle, so that the part of light is collimated and transmitted to emit light. Establishing a coordinate system by taking the center of the Mini-LED light-emitting surface as an origin, calculating discrete point coordinates (xi, yi) of a sectioning surface of each section of the transmission curved surface by using an iterative calculation method, and importing modeling software to obtain a model of the edge-ring-shaped transmission microstructure, wherein the specific calculation formula is as follows:
in the formula, theta i Angle theta between light emitted from Mini-LED and horizontal plane max The maximum value of the half angle of the light emission, and N is the total number of segmentsN is the refractive index of the free-form surface light guide plate material, and R is the distance between the bottom surface of the free-form surface light guide plate and the Mini-LED light-emitting surface. In this example, the refractive index n of the light guide plate material is 1.4936, and the maximum light emission half angle θ max The value of (1) is 60 degrees, the value of the number of segments N is 3000, and the distance R between the bottom surface of the free-form surface light guide plate and the Mini-LED light-emitting surface is 0.3mm.
As shown in fig. 7, the light emitted from the Mini-LED is coupled in through the bottom surface, passes through the tapered total internal reflection free-form surface 212, and then is horizontally collimated and transmitted inside the free-form surface light guide plate. A coordinate system is established by taking the Mini-LED light-emitting surface center as an original point, and the coordinates (xi, yi) of discrete points of a free-form surface cutting plane are obtained by iterative calculation, wherein the calculation formula is as follows:
in the formula, theta i The angle theta between the light emitted by the Mini-LED and the horizontal plane max The maximum value of the luminous half angle is shown, N is the total number of the segments, N is the refractive index of the free-form surface light guide plate material, and R is the distance between the bottom surface of the free-form surface light guide plate and the Mini-LED light-emitting surface.
In this example, the maximum radius of the conical tir free-form surface 212 is 1.37mm and the radius of the cylindrical bottom surface is 1.37mm, which is calculated by substituting numerical values into the equation. The thickness of the free-form surface of the single free-form surface light guide plate is 0.9mm, and therefore, the height of the stepped light-coupling microstructure is also 0.9mm. As can be seen from the above, the maximum thickness of the single-piece free-form-surface light guide plate in this example is 1.2mm.
As shown in fig. 9, each step height H of the stepped light-outcoupling microstructure 211 matches the light intensity distribution of the light source. Establishing a coordinate system by taking the center of the light emitting surface of the Mini-LED as an origin, and obtaining a relation formula between the heights of each level through iterative calculation under the condition that the total height is fixed to be 0.9mm, wherein the specific iterative calculation formula is as follows:
in the formula, H i Is the height of the i-th step slope, a i Is the half angle of light emission corresponding to the i-th segment, bi is the transmission angle of the light incident on the light guide plate i Is the point coordinate of the i-th segment of light ray when the total internal reflection of the free-form surface occurs, theta i Is the horizontal reflection ray of the ith segment and is at F i Angle of tangent to point, xp i The horizontal distance, XP, of the illuminating surface irradiated on the free-form surface light guide plate corresponding to the infinitesimal da of the lighting half-angle of the ith section i Scanning the projection distance of the illumination surface on the free-form surface in the horizontal direction for the light-emitting half-angle infinitesimal da, YS i The projection distance of the illumination surface on the free-form surface in the vertical direction of the section, yf, is scanned by the luminous half-angle infinitesimal da i Is the ordinate of the point Fi, R is the distance from the bottom surface of the free-form surface light guide plate to the Mini-LED light emitting surface, a max At maximum luminous half angle, yf max Is the maximum ordinate, yf, of the curve min The smallest ordinate of the curve. yf max And yf min Is determined by a tapered free-form curve. In the present example, yf is known from the above calculation of the free-form surface max Is 1.5mm, yf min 0.6mm, and their difference, i.e., the longitudinal height of the free-form surface, is 0.9mm. H can be obtained after the calculation is finished i+1 And H i The size of each stage H is determined by the recurrence relation between the two stages H. In this example, H due to the stepped light outcoupling microstructure i Too many are not listed here.
In this embodiment, the calculated parameters of the free-form surface light guide plate and the Mini-LED chassis are modeled by solidworks and then are combined into a 3 × 3 array, i.e., the backlight unit is obtained. The backlight unit in this embodiment has a size of 42mm × 42mm × 1.5mm, and the monolithic dimming unit has a size of 14mm × 14mm × 1.5mm. After the diffusion film 3 is added on the backlight unit, a complete designed backlight module can be formed.
In this embodiment, in order to verify the light emitting effect of the embodiment of the present invention, illumination simulation analysis is performed on the Mini-LED backlight module based on the total internal reflection free-form surface through optical simulation software lighttools, and the result is shown in fig. 10. After the light source of part of the area is turned off, the design module is simulated, and the simulation diagram is shown in fig. 11. The result shows that the embodiment of the invention has good dimming performance.
Further, as shown in fig. 12, the shape of the light modulation unit in the invention includes, but is not limited to, a square, and other shapes such as a regular hexagon, a regular triangle, and a regular octagon are all variants of the invention.
The foregoing is directed to preferred embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. However, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope of the technical solution of the present invention.
The present invention is not limited to the above preferred embodiments, and all other various types of Mini-LED backlight modules based on tir free-form surfaces can be obtained by anyone who can use the present invention.
Claims (9)
1. The utility model provides a Mini-LED backlight unit based on total internal reflection free-form surface which characterized in that: comprises a backlight unit and a diffusion film arranged from bottom to top; the backlight unit is composed of a plurality of Mini-LEDs, a Mini-LED base and a dimming unit consisting of a free-form surface light guide plate; the bottom of the free-form surface light guide plate is cylindrical, and a conical free-form surface with reflection and transmission functions is arranged right above the bottom cylinder, so that part of light rays emitted by the Mini-LED are horizontally transmitted in the light guide plate, and part of the light rays are upwards collimated and transmitted to emit light through the prismatic annular transmission microstructures; the lower surface of the free-form surface light guide plate is provided with a step type light coupling-out microstructure, so that light rays horizontally transmitted in the light guide plate are collimated and emitted upwards after passing through the structure.
2. The Mini-LED backlight module based on the total internal reflection free-form surface of claim 1, wherein: the bottom cylinder of the free-form surface light guide plate is embedded with a cylindrical seat stand in the Mini-LED base; the Mini-LED is positioned at the right center of the cylindrical seat stand, and the distance between the light emitting surface of the Mini-LED and the bottom of the free-form surface light guide plate is a calculated fixed value; the conical total internal reflection free-form surface in the free-form surface light guide plate is positioned right above the Mini-LED, and the height of the free-form surface is equal to the total height of the stepped light coupling-out microstructure; the luminous intensity rule of the Mini-LED accords with Lambert distribution or other symmetrical luminous intensity distribution, and the luminous surface faces the free-form surface light guide plate.
3. The Mini-LED backlight module based on the total internal reflection free-form surface of claim 1, wherein: the conical free-form surface is used for enabling the coupled light to horizontally collimate and propagate in the free-form surface light guide plate; the stepped light coupling-out microstructure is provided with a stepped inclined surface and is used for collimating horizontally transmitted light and emitting light upwards, and uniform light emission is realized by matching the step height of each stage with the light intensity distribution of the light source.
4. The Mini-LED backlight module based on the total internal reflection free-form surface of claim 1, wherein:
establishing a coordinate system by taking the center of the Mini-LED light-emitting surface as an origin, and obtaining the coordinates (x) of discrete points of a section curve of the section of the conical free-form surface i ,y i ) The following relationship is satisfied:
in the formula, theta i The angle theta between the light emitted by the Mini-LED and the horizontal plane max And the maximum value of the luminous half angle is obtained, N is the total number of the segments, N is the refractive index of the free-form surface light guide plate material, and R is the distance between the bottom surface of the free-form surface light guide plate and the Mini-LED light-emitting surface.
5. The Mini-LED backlight module based on the total internal reflection free-form surface of claim 1, wherein:
establishing a coordinate system by taking the center of the Mini-LED light-emitting surface as an origin, and obtaining discrete point coordinates (x) of the tangent curve of the edge-ring-shaped transmission microstructure i ,y i ) The following relationship is satisfied:
in the formula, theta i The angle theta between the light emitted by the Mini-LED and the horizontal plane max The maximum value of the luminous half angle is shown, N is the total number of the segments, N is the refractive index of the free-form surface light guide plate material, and R is the distance between the bottom surface of the free-form surface light guide plate and the Mini-LED light-emitting surface.
6. The Mini-LED backlight module based on the total internal reflection free-form surface of claim 1, wherein: the lower surface of the free-form surface light guide plate is provided with a stepped light coupling-out microstructure which is divided into N sections, each section is provided with a 45-degree inclined plane, a section of small platform is arranged in front of each section of inclined plane, the width of each section of small platform is kept equal, and light rays transmitted by horizontal collimation of the total internal reflection of the conical free-form surface in the free-form surface light guide plate are vertically collimated upwards to emit light after the total internal reflection of the 45-degree inclined plane.
7. The Mini-LED backlight module based on the total internal reflection free-form surface of claim 6, wherein:
the height of each section of inclined plane of the stepped light coupling-out microstructure corresponds to the light-emitting intensity rule of the Mini-LED, so that the luminous flux of the light which is collimated upwards after passing through each section of inclined plane is kept consistent, and the uniform illumination of the light-emitting surface is realized; establishing a coordinate system by taking the center of the light emitting surface of the Mini-LED as an origin, wherein the height of each level of inclined plane is defined by the following relational expression:
in the formula, H i Is the height of the i-th step slope, a i Is the light-emitting half angle corresponding to the i-th segment, b i Is the transmission angle F of the light corresponding to the i-th section after the light is incident on the free-form surface light guide plate i Is the point coordinate of the ith segment of light ray when the total internal reflection of the free-form surface occurs, theta' i Is the horizontal reflected light of the i-th section and is at F i Angle of tangent to point, xp i The horizontal distance, XP, of the illuminating surface irradiated on the free-form surface light guide plate corresponding to the infinitesimal da of the lighting half-angle of the ith section i Scanning the projection distance of the illumination surface on the free-form surface in the horizontal direction for the light-emitting half-angle infinitesimal da, YS i The projection distance of the illumination surface on the free-form surface in the vertical direction of the section, yf, is scanned by the luminous half-angle infinitesimal da i Is point F i R is the distance from the bottom surface of the free-form surface light guide plate to the Mini-LED light-emitting surface, a max At maximum luminous half angle, yf max Is the maximum ordinate, yf, of the curve min Is the minimum ordinate of the curve; yf max And yf min The value of (d) is determined by a conic free-form curve;the final objective is to find the recursive relationship between Hi +1 and Hi to determine the size of each stage H while achieving better uniformity of light extraction.
8. The Mini-LED backlight module based on the total internal reflection free-form surface of claim 1, wherein: the backlight unit is divided into a plurality of regional dimming units, each regional dimming unit comprises a single Mini-LED light source, a Mini-LED base and a free-form surface light guide plate, and the splicing seam of the adjacent regional dimming units is between 0.2mm and 2 mm; each dimming unit individually controls the light emitting brightness of the area by controlling the power of the Mini-LED.
9. The Mini-LED backlight module based on the total internal reflection free-form surface of claim 1, wherein: the free-form surface light guide plate is prepared by using an injection molding or PDMS imprinting method.
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