Micro display light engine and projector

Abstract

The present invention discloses a micro-display light engine, comprising a micro-LED panel, a coolant, a thin lens, a metal frame, a connecting column, and a projection lens; the micro-LED panel comprises a substrate, a plurality of micro-LED crystals for pixel light emission, a glass plate, a metal bracket, a sealing frame, a heat sink, a filler, and a transparent thermally conductive adhesive. The present invention also discloses single-engine, dual-engine, and triple-engine full-color projectors. The present invention has the remarkable advantages of being relatively simple to manufacture, capable of initial commercialization, having excellent heat dissipation and thermal stability, and having a high contrast and color gamut. This lays a certain foundation for the actual commercialization of new micro-LED micro-display projection technology.

Description

Technical Field

[0001] The present invention relates to the field of projection technology, and in particular to a micro-display light engine and a projector for optically magnifying and displaying a micro-display device. Background Art

[0002] Micro-LEDs are the most anticipated next-generation display technology, serving dual functions as illumination and pixel luminescence. In some specific products, such as LCD TVs, mini / micro-LEDs are used as backlights. In wearable applications like VR (virtual reality), AR (augmented reality), and MR (mixed reality), micro-LEDs are used as pixel luminescent devices, demonstrating their powerful and comprehensive technological advantages. In practical applications within the projection display industry, numerous patented technologies and imaginative technological explorations have emerged, such as Chinese patent publications CN110687742A, CN113242415A, CN110687741A, CN216718895U, and CN109976079A. Although many of these patents have been deemed insufficiently innovative or withdrawn, they demonstrate that micro-LED technology has already garnered widespread attention.

[0003] Currently, micro-LED display panels, as applied to the traditional projection industry, still face a long road to commercialization, achieving basic requirements such as full-color display, brightness exceeding 1000 lumens, and a contrast ratio greater than 50:1 within the same frame. In addition to the immaturity of micro-LED manufacturing technologies such as substrate stripping, bonding, mass transfer, and high-power active drivers, higher-power panels (due to the need for the highest possible brightness) are relatively scarce, while thermal stability and color consistency remain challenging. However, this hasn't dampened research and development enthusiasm and anticipation for the next generation of micro-display technology.

[0004] The current prototype of micro-LED projection display technology is still in the exploratory stage in terms of research and development direction. Specific technical approaches, including the use of color-based panels, three-primary-color panels with RGB light combination, and whether to create a one-to-one micro-lens matrix in front of the light-emitting pixels, remain largely unresolved and lack a consensus. This is fundamentally due to the lack of a practical implementation method. This is not only due to the current production challenges faced by the micro-LED panel industry itself, but also to communication barriers within the supply chain caused by inferring the technical requirements of micro-LED panels based on projector performance specifications. Furthermore, the projection industry faces practical challenges such as price-performance trade-offs, projector optics, and thermal design. These broad and practical issues make the development and commercialization of micro-LED projection products extremely challenging. However, the implementation of specific technical solutions can significantly contribute to the mass production of future micro-LED projection products.

[0005] According to the "IHS Markit Micro-LED Display Technology and Market Report" published by IHS Markit, a well-known industry analysis agency, it is predicted that the production and sales of micro-LED panels will mature and explode in 2024. This represents the maturity of the above-mentioned technologies, significant cost reductions and huge release of production capacity. Therefore, the time to develop micro-LED projection products with practical value is urgent. Summary of the Invention

[0006] The purpose of this invention is to advance and resolve specific technical challenges encountered in the commercialization of micro-LED projection displays, thereby moving micro-LED projection displays one step closer to commercialization. This invention provides a novel micro-display light engine that utilizes micro-LED pixels for light emission and projection amplification. This invention boasts relatively simple fabrication, initial commercialization, excellent heat dissipation, thermal stability, and high contrast and color gamut. This technology lays a foundation for the commercialization of novel micro-LED micro-display projection technology.

[0007] To achieve the above objectives, the present invention provides a micro display light engine, including a micro-LED panel, a coolant, a thin lens, a metal frame, a connecting column and a projection lens.

[0008] The micro-LED panel includes a substrate, a number of micro-LED chips that emit light in pixels, a glass plate, a metal bracket, a sealing frame, a heat sink, a filling glue and a transparent thermal conductive glue.

[0009] The sealing frame is in the shape of a square tube, and the length and width of the cross-section of the sealing frame are equal to the length and width of the glass plate; the incident surfaces of the substrate, sealing frame and glass plate are sequentially attached to each other; located between the substrate, sealing frame and glass plate, a plurality of the micro-LED grains are provided on the substrate, as well as a driving circuit for addressing the plurality of the micro-LED grains one by one; the electrodes of the plurality of the micro-LED grains are bonded to the driving circuit provided on the substrate; the electrodes of the plurality of the micro-LED grains are a flip-chip structure.

[0010] The length of the sealing frame is 6 μm-10 μm greater than the height of the top surfaces of the plurality of micro-LED dies above the substrate surface.

[0011] The luminous colors of some of the micro-LED chips are single primary colors, dual primary colors, or three primary colors.

[0012] The metal frame is tubular, and one end of the metal frame is in contact with the exit surface of the glass plate, and the other end is connected to the thin lens to form a closed cavity; the closed cavity is filled with the coolant; the glass plate, the coolant and the thin lens constitute a liquid lens.

[0013] The metal bracket covers the substrate, sealing frame, glass plate and one end of the metal frame, and the substrate is mounted on the inner surface of the metal bracket; the filling glue is filled between the metal frame, the glass plate and the metal bracket; the radiator is mounted on the back of the metal bracket.

[0014] The light-emitting surface of the glass plate is formed into a first black matrix in an area outside the light-emitting angle θ selected by the micro-LED dies.

[0015] The incident surface of the glass plate is formed into a second black matrix in an area outside the light output angle θ selected by the micro-LED chips.

[0016] The incident surface of the glass plate is provided with the transparent thermally conductive adhesive in the area opposite to the several micro-LED crystals, and the top surfaces of the several micro-LED crystals, the transparent thermally conductive adhesive and the incident surface of the glass plate are sequentially bonded; the thickness of the transparent thermally conductive adhesive is 10 μm.

[0017] The projection lens includes a lens outer barrel, and an incident lens group, an intermediate lens group, and an exit lens group installed in the lens outer barrel and arranged in sequence according to the direction of light travel; the incident lens group, the intermediate lens group, and the exit lens group each include at least one lens; the metal bracket is connected to the lens outer barrel via the connecting column; the number of the connecting columns is at least greater than or equal to three.

[0018] The Fno of the liquid lens and the projection lens after being combined is ≤1.2.

[0019] Preferably, the glass plate is made of optical crystal.

[0020] Optionally, the incident lens group includes a first lens and a second lens arranged in sequence along the direction of light travel; the number of lenses in the intermediate lens group is one; and the exit lens group includes a fourth lens and a fifth lens arranged in sequence along the direction of light travel.

[0021] Preferably, the thin lens is concave-convex, with the convex surface facing the glass plate; the convex surface and the concave surface of the thin lens are free-form surfaces, aspherical surfaces, spherical surfaces, or a combination of any two.

[0022] The thickness of the thin lens is uniform or unequal from the center to the edge.

[0023] The light-transmitting surface of the concave thin lens has a shape such that when the angles at which light is emitted by several of the micro-LED chips are greater than the angle limit imposed by the Fno value, light with an angle greater than the Fno value limit is totally reflected at the concave surface.

[0024] Optionally, the absolute value of the difference in refractive index between the coolant and the thin lens is ≤0.2; the absolute value of the difference in refractive index between the coolant and the glass plate is ≤0.3.

[0025] Optionally, the filling glue is silicone rubber.

[0026] Optionally, the transparent thermally conductive adhesive is optical grade silicone.

[0027] A single-engine full-color projector includes the micro-display light engine, wherein the number of the micro-display light engine is one, and the light-emitting colors of the micro-LED crystal grains included in the micro-display light engine are three primary colors.

[0028] A dual-engine full-color projector includes the aforementioned micro-display light engine. There are two micro-display light engines. When the light emission color of the multiple micro-LED crystals included in the first micro-display light engine is a single primary color, the light emission color of the multiple micro-LED crystals included in the second micro-display light engine is dual primary colors, and the two primary colors of the second micro-display light engine do not include the color emitted by the first micro-display light engine. The two micro-display light engines are arranged at an angle a or arranged in parallel, where the angle a is ≤14°.

[0029] When two micro-display light engines are arranged in parallel, the two micro-display light engines are arranged off-axis with respect to each other; the off-axis distance of the first micro-display light engine toward the second micro-display light engine is d, and the off-axis distance of the second micro-display light engine toward the first micro-display light engine is e; let the optical axis of the first micro-LED panel included in the first micro-display light engine be L51, the optical axis of the second micro-LED panel included in the second micro-display light engine be L55, the distance between the optical axis L51 and the optical axis L55 be c, and the projection magnification of the two micro-display light engines be β, then c = β(d + e).

[0030] A three-engine full-color projector includes the micro-display light engine described above. The number of the micro-display light engines is three, and the light-emitting color of the micro-LED crystal grains included in each micro-display light engine is one of the three primary colors.

[0031] The first micro-display light engine and the middle micro-display light engine are arranged at an angle of b / 2, and the third micro-display light engine and the middle micro-display light engine are arranged at an angle of b / 2, wherein the angle b is ≤ 28°.

[0032] Alternatively, three micro-display light engines are arranged in parallel, and in the two micro-display light engines on both sides: the off-axis distance of the first micro-display light engine toward the middle micro-display light engine is g, and the off-axis distance of the third micro-display light engine toward the middle micro-display light engine is k; let the optical axis of the first micro-LED panel included in the first micro-display light engine be L61, the optical axis of the second micro-LED panel included in the middle micro-display light engine be L62, the distance between the optical axis L61 and the optical axis L62 be f, the projection magnification of the two micro-display light engines is β, then f=βg; let the optical axis of the third micro-LED panel included in the third micro-display light engine be L63, the distance between the optical axis L63 and the optical axis L62 is j, the projection magnification of the two micro-display light engines is β, then j=βk.

[0033] The beneficial effects of the present invention are as follows:

[0034] 1. The present invention is based on the original intention of making a small Fno lens (Fno≤1.2). The coolant, transparent thermal conductive glue, glass plate, etc. are used to effectively dissipate heat from the micro-LED crystals and form a liquid lens. The liquid lens can significantly reduce the impact of stray light on the contrast of the projected image due to the small Fno of the projection lens. At the same time, the present invention makes a black matrix on the incident and exit surfaces of the glass plate to ensure that the micro-display light engine has a higher contrast and reduces stray light as much as possible. These innovative means have made a solid step forward in micro-LED micro-display projection technology. The present invention has the remarkable characteristics of being relatively simple to manufacture, being able to achieve preliminary (i.e., under current realistic conditions such as not very high resolution) productization, excellent heat dissipation and good thermal stability.

[0035] 2. The single-engine full-color projector of the present invention has a very simple structural feature, can achieve preliminary productization, and can experience the significant advantages of high color gamut, high contrast and high efficiency brought by advanced micro-LED micro-display technology.

[0036] 3. The dual-engine and triple-engine full-color projectors of the present invention, in addition to having a simple structure, can improve the brightness of micro-LEDs applied to projection products under current technical conditions and significantly reduce the difficulty of manufacturing micro-LED panels. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 Schematic diagram of the structure of an embodiment of the present invention;

[0039] Figure 2 Schematic diagram of the arrangement of the black matrix of the glass plate of the present invention;

[0040] Figure 3 It is a partial enlarged schematic diagram of the present invention;

[0041] Figure 4 A schematic diagram of two micro-display light engines of the present invention arranged at an angle a;

[0042] Figure 5 A schematic diagram of two micro-display light engines of the present invention arranged in parallel;

[0043] Figure 6 A schematic diagram of three micro-display light engines of the present invention arranged at an angle b;

[0044] Figure 7 A schematic diagram of three micro-display light engines of the present invention arranged in parallel;

[0045] Figure 8 Schematic diagram of micro-LED die and microlens;

[0046] Figure 9 It is a schematic diagram of the prior art;

[0047] Figure 10 Schematic diagram of the prior art. DETAILED DESCRIPTION

[0048] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below with reference to the accompanying drawings. The description in this part is only exemplary and explanatory and should not have any limiting effect on the scope of protection of the present invention.

[0049] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0050] It should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" and the like indicate positions or locations based on the positions shown in the accompanying drawings, or the positions or locations in which the inventive product is typically placed when in use. These terms are intended solely to facilitate and simplify the description of the present invention and are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third," etc., are used solely to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0051] Furthermore, terms such as "horizontal," "vertical," and "overhanging" do not necessarily imply that a component must be absolutely horizontal or overhanging, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it can be slightly tilted.

[0052] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0053] Although achieving full-color micro-LEDs still faces certain technical challenges, one of which is the difficulty of simultaneously growing efficient R (red), G (green), and B (blue) micro-LED crystals ["chip particles," "chip particles," "luminescent (sub-pixels," etc., hereinafter referred to]] on the same substrate material due to material growth process and technology limitations. Therefore, researchers have adopted a different approach by transferring large quantities of R, G, and B micro-LED crystals onto the same structural substrate (currently silicon or glass-based), or by using short-wavelength (such as ultraviolet or blue light) micro-LED crystals to excite long-wavelength phosphors or quantum dot materials to achieve RGB full-color display. These solutions have achieved certain implementation results and are continuously developing and maturing. For example, wearable products such as pixel-emitting micro-LED children's watches have achieved initial mass production, laying a preliminary foundation for the commercialization of micro-LED projection and creating conditions for the successful implementation of the present invention.

[0054] Each micro-LED die emits light in a cosine-like pattern (or Lambertian pattern). Therefore, projection lenses require a very large numerical aperture (Fno) to efficiently utilize and project light. However, lenses with large numerical apertures inevitably produce low-contrast images. Therefore, ensuring high contrast in projected images is a fundamental requirement for product practicality.

[0055] People have used lenses (microlens arrays) and other methods to improve the light emission (or light extraction) efficiency of direct-view micro-LED chips, and have achieved certain results. Therefore, people believe that using lenses and other methods to reduce the light emission angle of micro-LED chips can reduce the difficulty of designing and manufacturing projection lenses, or make projection lenses easier (or cheaper) to implement in theory. This has led to the emergence of some prototype patent technologies, such as Chinese patent publications CN109716174A, CN114846364A, CN112802403A, and CN112802404A, all of which attempt to change the light emission angle of micro-LED chips, that is, to shape the light emission of micro-LED chips according to the required indicators. Figure 8-9 As shown, a plurality of pixel-emitting micro-LED crystals 11' are fabricated on a substrate 1'. Each of the micro-LED crystals 11' corresponds to a light-collecting micro-lens 2'. Accordingly, a plurality of the micro-lenses 2' form a micro-lens array. In theory, this can significantly increase the Fno value of the projection lens 3'. Figure 8As shown, three random light rays L1', L2' and L3' are emitted from the micro-LED die 11'. When the light rays L1'-L3' enter and exit the microlens 2', the angles of the light rays have been refracted and changed (that is, the so-called light shaping in the industry).

[0056] The same method is then applied to the optical system of the R, G, and B three-piece micro-LED light-emitting pixel panel. Figure 10 As shown, several red micro-LED dies 211' are fabricated on the R substrate 21', with each die 211' corresponding to a microlens 22'. Several green micro-LED dies 231' are fabricated on the G substrate 23', with each die 231' corresponding to a microlens 24'. Several blue micro-LED dies 251' are fabricated on the B substrate 25', with each die 251' corresponding to a microlens 26'. The light is then combined by an X-prism 27' and projected through a projection lens 28'. Figure 10 The technology shown is not only for increasing the Fno value of the projection lens 28 ′, but firstly for adapting to the very demanding aperture function limitation of the X-prism 27 ′ (or other light combining devices based on dichroic optical film technology).

[0057] Obviously, see Figure 9 As shown, the above technology hopes to significantly compress the light output angle of a Lambertian-emitting micro-LED die, such as die 11', through a single lens, such as microlens 2', for example, from 90° on one side (Fno is about 0.5) to 12° on one side (Fno is about 2.4), which is unrealistic. At the same time, a microlens array composed of several microlenses needs to achieve a one-to-one correspondence (optical coaxiality) with the optical centers of several micro-LED dies. This beautiful idea is subject to uncertainty, especially after a large number of transfers and re-bonding, it is almost impossible to achieve. Furthermore, the effectiveness of the compression shaping of the light output angle of the micro-LED die by a single lens depends on the ratio of the light-transmitting area of ​​the single lens to the top light-emitting area of ​​the micro-LED die, which is constrained by several engineering conditions such as the size of the micro-LED die and the spacing between the die. If the ratio of the light-transmitting area of ​​a single lens to the top emitting area of ​​the micro-LED die approaches 1, then the single lens cannot change the light emission angle of the micro-LED die (unless light extraction efficiency is significantly sacrificed), meaning the compression shaping effect approaches zero. If R&D is blindly pursued for these uncertain goals, the final R&D results are predictable.

[0058] Compared to various existing prototype patented technologies that may be uncertain in implementation, the present invention is based on the original intention of producing a small Fno lens (Fno ≤ 1.2). Through the coolant 21, transparent thermal adhesive 17 and glass plate 12, it completes the heat dissipation of the micro-LED die 11 and forms a liquid lens. It also ensures that the contrast of the projected image affected by stray light due to the projection lens's too small Fno is properly resolved, making micro-LED micro-display projection technology a solid step forward.

[0059] Example 1:

[0060] like Figure 1-3 As shown, a micro display light engine provided by this embodiment includes a micro-LED panel, a coolant 21, a thin lens 22, a metal frame 23, a connecting column 24 and a projection lens.

[0061] The micro-LED panel includes a substrate 1, several micro-LED chips 11 for pixel light emission, a glass plate 12, a metal bracket 13, a sealing frame 14, a heat sink 15, a filler 16, and a transparent thermal conductive adhesive 17. With current technology, color consistency (tolerance for each primary color wavelength <2nm) is not yet too stringent, but there are solutions to correct brightness consistency.

[0062] The sealing frame 14 is in the shape of a square tube, and the length and width of its cross section are equal to those of the glass plate 12. The sealing frame 14 is preferably (but not limited to) made of the same material as the glass plate 12. It is also preferred (but not limited to) that the substrate 1, glass plate 12, and sealing frame 14 are all made of sapphire glass to achieve excellent thermal conductivity and eliminate the risk of failure due to thermal expansion and contraction. The incident surfaces of the substrate 1, the sealing frame 14 and the glass plate 12 are sequentially attached; a plurality of the micro-LED grains 11 are provided on the substrate 1 between the substrate 1, the sealing frame 14 and the glass plate 12, as well as a driving circuit for addressing the plurality of micro-LED grains 11 one by one (a low-temperature polysilicon TFT active driving circuit is manufactured on the substrate 1. These technologies are very mature in China, such as BOE and Huaxing Optoelectronics, and abroad, such as AUO and Samsung. They are not shown in the figure and will not be described in detail); the electrodes of the plurality of the micro-LED grains 11 are bonded to the driving circuit provided on the substrate 1, and the electrodes of the plurality of the micro-LED grains 11 are a flip-chip structure (not shown in the figure).

[0063] The length of the sealing frame 14 (referring to the length of the square tube) is 6μm-10μm greater than the height of the top surfaces of the micro-LED dies 11 above the surface of the substrate 1. After the micro-LED dies 11 are transferred in large quantities to the receiving substrate (substrate 1) and bonded, their tops are uneven. This is partly due to the thickness tolerance of the micro-LED dies 11 themselves, and partly due to height differences during bonding. Therefore, the length of the sealing frame 14 is very important. Otherwise, the heat dissipation effect of the glass plate 12 and transparent thermally conductive adhesive 17 on the micro-LED dies 11 will be significantly reduced.

[0064] The luminous colors of some of the micro-LED crystals are single primary color, dual primary color, or three primary colors. The difficulty of manufacturing micro-LED panels is from low to high, from single primary color to dual primary color to three primary colors. Three primary colors are full-color display. As mentioned above, by making R, G, B micro-LED crystals 11 on the same substrate 1, or using short-wave (such as ultraviolet or blue light) micro-LED crystals 11 to excite long-wave phosphors or quantum dot materials to achieve RGB full-color display. Under current technical conditions, wavelength excitation technology still has many problems.

[0065] The metal frame 23 is tubular, with one end of the metal frame 23 contacting the light-emitting surface of the glass plate 12 and the other end connected to the thin lens 22 to form a sealed cavity. The sealed cavity is filled with the coolant 21. The glass plate 12, the coolant 21, and the thin lens 22 form a liquid lens. Preferably, the inner wall of the metal frame 23 is black to absorb stray light, and the outer wall may optionally include a heat-expanding structure to dissipate heat from the coolant 21.

[0066] The metal bracket 13 covers the substrate 1, sealing frame 14, glass plate 12, and one end of the metal frame 23. The substrate 1 is mounted on the inner surface of the metal bracket 13. The gap between the metal frame 23, the glass plate 12, and the metal bracket 13 is filled with the filler 16. The filler further strengthens and divides the forces acting on the metal frame 23, the substrate 1, and the glass plate 12, thereby concentrating the forces acting on the micro-LED panel on the metal bracket 13 as much as possible. The heat sink 15 is mounted on the back of the metal bracket 13. The heat sink 15 is preferably, but not limited to, a straight rib profile heat sink.

[0067] See also Figure 2 and Figure 3 The emitting surface of the glass plate 12 is in the area outside the light emitting angle θ selected by the micro-LED crystal grains 11 ( Figure 3The area outside the middle light L1 and L2) is made into a first black matrix 121; the light output angle θ is a specific value, and the angle corresponding to the Fno is used as a reference design value, but the value of the light output angle θ does not mean that it is equal to the limit value of Fno [arcsin(0.5 / Fno)]. Light with a light output angle of the micro-LED chip 11 greater than the angle corresponding to Fno [arcsin(0.5 / Fno)] cannot be used by the light engine, so it is blocked as much as possible to reduce stray light. When the Fno = 1.2, light of about > 24.6° can no longer be used. However, the micro-LED chip 11 is not an absolute point light source, so the selection of the specific value of θ is often an empirical reflection during the design. Light with a light output angle of the micro-LED chip 11 greater than θ is blocked by the first black matrix 121 as much as possible to ensure the contrast of the projected image. The specific size of the first black matrix 121 is mainly related to the size of the micro-LED die 11 , the thickness of the transparent thermal conductive adhesive 17 , the selection of θ, and the thickness of the glass plate 12 .

[0068] The manufacturing process for the first black matrix 121 is very mature, similar to the BM (Black Matrix) manufacturing process for LCDs. This BM process is more than sufficient for the production of the first black matrix 121 of the present invention, as the BM line width is already very mature and stable under current technical conditions (≤3μm). However, micro-LED panels used for projection currently do not require such a fine structure (≤3μm). Furthermore, considering the mutual non-interference between the first black matrix 121 (organic material + toner) and the coolant 21, the fabrication of a transparent protective film on the surface of the first black matrix 121 is a common sense issue and will not be further elaborated.

[0069] Accordingly, a second black matrix 122 is fabricated on the incident surface of the glass plate 12 in areas outside the selected light emission angle θ of the micro-LED dies 11. The specific dimensions of the second black matrix 122 are primarily dependent on the size of the micro-LED dies 11, the value of θ, and the thickness of the transparent thermally conductive adhesive 17.

[0070] The arrangement of the first black matrix 121 and the second black matrix 122 is also helpful in further improving the depth of field of the projection lens.

[0071] The incident surface of the glass plate 12 is coated with transparent thermally conductive adhesive 17 in the area opposite the micro-LED die 11. The top surfaces of the micro-LED die 11, the transparent thermally conductive adhesive 17, and the incident surface of the glass plate 12 are sequentially bonded. The transparent thermally conductive adhesive 17 has a thickness of 10 μm. Preferably, the transparent thermally conductive adhesive 17 is optical-grade silicone to provide good thermal conductivity, sufficient light resistance, excellent interfacial filling elasticity, and good transmittance. The production process of the transparent thermally conductive adhesive 17 is similar to that of the first black matrix 121 and the second black matrix 122.

[0072] The projection lens includes a lens outer barrel 34, and an incident lens group 31, an intermediate lens group 32, and an exit lens group 33 installed in the lens outer barrel 34 and arranged in sequence according to the direction of light travel; the incident lens group 31, the intermediate lens group 32, and the exit lens group 33 each contain at least one lens; the metal bracket 13 is connected to the lens outer barrel 34 via the connecting column 24; the number of the connecting columns 24 is at least greater than or equal to three.

[0073] The Fno of the liquid lens and the projection lens after being combined is ≤1.2.

[0074] In this embodiment, the micro-LED panel is selected (but not limited to) a panel of about 2.6 inches (improved from the full-color micro-LED panel manufacturing process of the latest smart watch) as the pixel light source of the present invention, with a resolution of 480*RGB*272. Each (group) of light-emitting pixels includes three directly emitting sub-pixel grains of R, G, and B, and the three sub-pixels are arranged in a (but not limited to) "pin" shape; the size of each light-emitting sub-pixel is about 12μm*12μm; to ensure the smooth production of the substrate 1, the center distance of each group of light-emitting pixels is 0.12 mm. In this embodiment, the spatial frequency MTF of the projection lens takes a value of 5 Lp / mm, and the design target value can easily be >65% throughout the range. When Fno = 1.2, many indicators such as depth of field, aberration, and distortion are relatively excellent; the number of lenses in the incident lens group 31 of the projection lens is two, which are the first lens 311 (positive lens) and the second lens 312 (negative lens) in sequence according to the light traveling direction. The incident lens group 31 undertakes the main chromatic aberration correction; the number of lenses in the intermediate lens group 32 is one, which contributes the main magnification; the number of lenses in the exit lens group 33 is two, which are the fourth lens 331 (negative lens) and the fifth lens 332 (positive lens) in sequence according to the light traveling direction. The substrate 1 is formed with the drive circuit of the micro-LED grains 11 and the electrodes for bonding with the micro-LED grains 11 after a series of process flows such as thin film deposition, photoresist coating, exposure, development, etching, and photoresist stripping on sapphire glass. Of course, it also includes contact pads (Pad) for other peripheral circuits, as well as the wiring structure for the inflow and outflow of large currents, etc., which will not be elaborated here.

[0075] The thin lens 22 is preferably (but not limited to) a concave-convex type, and the convex surface faces the glass plate 12; the convex surface and the concave surface of the thin lens 22 are one of a free-form surface, an aspherical surface, or a spherical surface, or a combination of any two. In this embodiment, both the convex surface and the concave surface of the thin lens 22 are free-form surfaces, and the thickness is unequal from the center to the edge, but the offset value is relatively very, very small, and is basically close to equal thickness to ensure the best accuracy during injection molding.

[0076] The surface shape of the light-passing surface of the concave surface of the thin lens 22 is such that when the angles of the light rays emitted by several of the micro-LED grains 11 are greater than the limitation of the light ray angle by the Fno value, the light rays greater than the limitation angle of the Fno value are totally reflected at the concave surface. Here, it needs to be specifically noted that as described above, the micro-LED grains 11 are not absolute point light sources, and for the light rays with an emission angle greater than the corresponding angle of the Fno value, in practice, it is not said that all of them can absolutely achieve total reflection. This is also a reasonable selection problem of the chief ray and the off-axis ray in engineering experience, which will not be elaborated here.

[0077] The absolute value of the difference in refractive index between the coolant 21 and the thin lens 22 is ≤ 0.2; the absolute value of the difference in refractive index between the coolant 21 and the glass plate 12 is ≤ 0.3. Selecting appropriate refractive index matching can effectively reduce Fresnel reflections at various interfaces, improve light transmission efficiency, and reduce stray light.

[0078] Since the micro-LED panel driving circuit uses LTPS TFT technology, after being projected and enlarged to 100 inches, a series of process defects such as screen distortion, mosaics, bright and dark lines, and uneven brightness still exist under the current technical conditions of grain screening and driving circuits. The total driving power consumption of this embodiment is close to 100W, and each group of pixels is about 0.61mW, of which the R sub-pixel is about 0.15mW, the G sub-pixel is about 0.24mW, and the B sub-pixel is about 0.22mW. The remaining approximately 20W of power is consumed by the driving circuit. The micro-display light engine can output a luminous flux of about >800 lumens, and the same frame (ANSI, American Standards Association) that is, eight white / eight black contrast is as high as 600:1, the color gamut is as high as 95% (NTSC), and the sequential field contrast (full white / full black) is close to infinity. These are all very The projected image demonstrates outstanding performance compared to domestic LCD or DLP projectors, including superior contrast, color gamut, depth, smearing, ghosting, and high-speed motion images, such as the jittering of stopwatch characters. The temperature rise of each die, particularly those in the central region of the micro-LED panel, is controlled to <3°C-4°C compared to the heat sink 15 and coolant 21. This demonstrates superior heat dissipation, even at Joule heat output of approximately 70W and within a 2.6-inch area. With technological advancements, brightness and resolution will continue to improve, while issues such as screen distortion, pixelation, bright and dark lines, and uneven brightness will be addressed.

[0079] Example 2

[0080] This embodiment provides a single-engine full-color projector, including the micro-display light engine described in the first embodiment. The number of the micro-display light engine is one, and the micro-LED chips 11 included in the micro-display light engine emit light of three primary colors.

[0081] The single-engine projector of this embodiment has a very simple structural feature, can achieve preliminary productization, and can experience the significant advantages of high color gamut, high contrast and high efficiency brought by advanced micro-LED micro-display technology.

[0082] Embodiment three:

[0083] See also Figure 4As shown, this embodiment provides a dual-engine full-color projector, including the micro-display light engine described in Example 1. There are two micro-display light engines. When the micro-LED dies 11 included in the first micro-display light engine 341 emit a single primary color, the micro-LED dies 11 included in the second micro-display light engine 342 emit dual primary colors. The two primary colors of the second micro-display light engine 342 do not include the color emitted by the first micro-display light engine 341. The two micro-display light engines 341 and 342 are arranged at an angle a. The angle a is ≤ 14°.

[0084] As mentioned above, the dual-engine method can improve the output brightness of the projector and reduce the difficulty of producing micro-LED panels. Defects such as screen distortion, mosaics, bright and dark lines, and uneven brightness can be alleviated to a certain extent, and it has a certain cost-effectiveness.

[0085] But it is not Figure 4 The layout shown can achieve practical image projection. However, necessary electronic keystone correction is required (the driver circuit needs to change the addressing start and end positions of each row of grains) so that the two micro-display light engines 341 and 342 can both project rectangular images of the same size. Through necessary mechanical position adjustment, the output images of the two micro-display light engines 341 and 342 can be perfectly overlapped to produce a full-color image.

[0086] Angle a is a value selected based on the actual application scenario and depends on the projection ratio of the micro-display light engine. For example, if angle a needs to be greater than 14° for the output images of the two micro-display light engines 341 and 342 to overlap, then the depth of field index of the projection lens is difficult to design and produce, and thus it is basically impractical.

[0087] Embodiment four:

[0088] See also Figure 5 As shown, the difference between Example 4 and Example 3 is that: the two micro-display light engines 341 and 342 are arranged in parallel, and the two micro-display light engines 341 and 342 are arranged off-axis with respect to each other; the off-axis distance of the first micro-display light engine 341 toward the second micro-display light engine 342 is d, and the off-axis distance of the second micro-display light engine 342 toward the first micro-display light engine 341 is e; let the optical axis of the first micro-LED panel 131 included in the first micro-display light engine 341 be L51, the optical axis of the second micro-LED panel 132 included in the second micro-display light engine 342 be L55, the distance between the optical axis L51 and the optical axis L55 be c, and the projection magnification of the two micro-display light engines 341 and 342 be β, then c=β(d+e).

[0089] The projection lens and liquid lens of the first micro-display light engine 341 are coaxial (L52), and the projection lens and liquid lens of the second micro-display light engine 342 are coaxial (L56). A straight line segment (length c) is connected between the center of the micro-LED panel 131 included in the first micro-display light engine 341 (on L51) and the center of the micro-LED panel 132 included in the second micro-display light engine 342 (on L55), assumed to be A (straight line segment A is not drawn in the figure). The offset of the projector is called the offset. The projection lens and liquid lens of the first micro-display light engine 341 only need to be moved as a whole along straight line segment A, or the projection lens and liquid lens of the second micro-display light engine 342 only need to be moved as a whole along straight line segment A, until the output images of the two micro-display light engines 341 and 342 overlap.

[0090] In this embodiment, when the two light engines overlap their images, electronic keystone correction is not required, so the images are not compressed and can maintain the best clarity. Compared with the third embodiment, installation and debugging are also much simpler, which can improve user usability.

[0091] Embodiment five:

[0092] See also Figure 6 As shown, this embodiment provides a three-engine full-color projector, including the micro-display light engine described in Example 1. The number of the micro-display light engines is three, and the light-emitting color of the several micro-LED grains 11 included in each micro-display light engine is one of the three primary colors.

[0093] The first micro-display light engine 343 and the middle micro-display light engine 344 are arranged at an angle b / 2, and the third micro-display light engine 345 and the middle micro-display light engine 344 are arranged at an angle b / 2, wherein the angle b≤28°.

[0094] Obviously, this embodiment is similar to the third embodiment, but it can output higher brightness while reducing the difficulty of manufacturing micro-LED panels, offering better cost-performance. It also offers substantial improvements to issues such as screen distortion, mosaics, and bright and dark lines, which are specific to single-color micro-display light engines.

[0095] Generally speaking, the three-engine approach generally includes (but is not limited to) a green micro-display light engine as the middle stage, and red and blue micro-display light engines on both sides.

[0096] Example 6:

[0097] See also Figure 7As shown, this embodiment provides a three-engine full-color projector, including the micro-display light engine described in Example 1. The number of the micro-display light engines is three, and the light-emitting color of the several micro-LED grains 11 included in each micro-display light engine is one of the three primary colors.

[0098] The three micro-display light engines 343, 344, and 345 are arranged in parallel. In the two micro-display light engines 343 and 345 on both sides, the first micro-display light engine 343 has an off-axis distance g toward the middle micro-display light engine 344, and the third micro-display light engine 345 has an off-axis distance k toward the middle micro-display light engine 344. Let the optical axis of the first micro-LED panel 133 included in the first micro-display light engine 343 be L61, and the optical axis of the micro-LED panel 133 included in the middle micro-display light engine 344 be L62. The optical axis of the second micro-LED panel 134 is L62, the distance between the optical axis L61 and the optical axis L62 is f, the projection magnification of the two micro-display light engines 343 and 344 is β, then f=βg; similarly, let the optical axis of the third micro-LED panel 135 included in the third micro-display light engine 345 be L63, the distance between the optical axis L63 and the optical axis L62 is j, the projection magnification of the two micro-display light engines 345 and 344 is β, then j=βk.

[0099] Obviously, this embodiment is similar to the fourth embodiment, but this embodiment can output higher brightness and reduce the difficulty of manufacturing the micro-LED panel, and has better cost performance and practicality.

[0100] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A micro display light engine, characterized in that: It includes a micro-LED panel, a cooling liquid (21), a thin lens (22), a metal frame (23), a connecting column (24) and a projection lens; The micro-LED panel comprises a substrate (1), a plurality of micro-LED crystals (11) for pixel light emission, a glass plate (12), a metal bracket (13), a sealing frame (14), a heat sink (15), a filling glue (16) and a transparent thermal conductive glue (17); The sealing frame (14) is in the shape of a square tube, and the length and width of the cross section of the sealing frame (14) are equal to the length and width of the glass plate (12); the incident surfaces of the substrate (1), the sealing frame (14) and the glass plate (12) are sequentially attached; a plurality of micro-LED crystals (11) and a driving circuit for addressing the plurality of micro-LED crystals (11) are provided on the substrate (1) between the substrate (1), the sealing frame (14) and the glass plate (12); the electrodes of the plurality of micro-LED crystals (11) are bonded to the driving circuit provided on the substrate (1); the electrodes of the plurality of micro-LED crystals (11) are in a flip-chip structure; The length of the sealing frame (14) is 6 μm-10 μm greater than the height of the top surfaces of the plurality of micro-LED crystals (11) above the surface of the substrate (1); The luminous colors of the micro-LED crystal grains (11) are single primary colors, dual primary colors, or three primary colors; The metal frame (23) is tubular, and one end of the metal frame (23) is in contact with the exit surface of the glass plate (12), and the other end is connected to the thin lens (22) to form a closed cavity; the closed cavity is filled with the cooling liquid (21); the glass plate (12), the cooling liquid (21) and the thin lens (22) constitute a liquid lens; The metal bracket (13) covers the substrate (1), the sealing frame (14), the glass plate (12) and one end of the metal frame (23), and the substrate (1) is mounted on the inner surface of the metal bracket (13); the filling glue (16) is filled between the metal frame (23), the glass plate (12) and the metal bracket (13); the heat sink (15) is mounted on the back of the metal bracket (13); The emission surface of the glass plate (12) is formed into a first black matrix (121) in an area outside the light emission angle θ selected by the plurality of micro-LED crystal grains (11); The incident surface of the glass plate (12) is formed into a second black matrix (122) in an area outside the light emission angle θ selected by the plurality of micro-LED crystal grains (11); The incident surface of the glass plate (12) is provided with the transparent thermal conductive adhesive (17) in a region opposite to the plurality of micro-LED crystals (11), and the top surfaces of the plurality of micro-LED crystals (11), the transparent thermal conductive adhesive (17), and the incident surface of the glass plate (12) are sequentially bonded; the thickness of the transparent thermal conductive adhesive (17) is 10 μm; The projection lens comprises a lens outer barrel (34), and an incident lens group (31), an intermediate lens group (32), and an exit lens group (33) which are installed in the lens outer barrel (34) and arranged in sequence according to the direction of light travel; the incident lens group (31), the intermediate lens group (32), and the exit lens group (33) each comprise at least one lens; the metal bracket (13) is connected to the lens outer barrel (34) via the connecting column (24); the number of the connecting columns (24) is at least greater than or equal to three; The Fno of the liquid lens and the projection lens after being combined is ≤1.

2.

2. The micro display light engine according to claim 1, characterized in that: The glass plate (12) is made of optical crystal.

3. The micro display light engine according to claim 1, characterized in that: The incident lens group (31) comprises a first lens (311) and a second lens (312) arranged in sequence according to the direction of light travel; the number of lenses in the intermediate lens group (32) is one; and the exit lens group (33) comprises a fourth lens (331) and a fifth lens (332) arranged in sequence according to the direction of light travel.

4. The micro display light engine according to claim 1, characterized in that: The thin lens (22) is concave-convex, with the convex surface facing the glass plate (12); the convex surface and the concave surface of the thin lens (22) are free-form surfaces, aspherical surfaces, spherical surfaces, or a combination of any two thereof; The thickness of the thin lens (22) is uniform or unequal from the center to the edge; The concave light-transmitting surface of the thin lens (22) has a surface shape such that when the angle of light emitted by a plurality of the micro-LED crystal grains (11) is greater than the angle limit of the light by the Fno value, the light with an angle greater than the Fno value limit is totally reflected at the concave surface.

5. The micro display light engine according to claim 1, characterized in that: The absolute value of the difference in refractive index between the cooling liquid (21) and the thin lens (22) is ≤0.2; the absolute value of the difference in refractive index between the cooling liquid (21) and the glass plate (12) is ≤0.

3.

6. The micro display light engine according to claim 1, characterized in that: The filling rubber (16) is silicone rubber.

7. The micro display light engine according to claim 1, characterized in that: The transparent heat-conducting adhesive (17) is optical grade silicone.

8. A single-engine full-color projector, characterized in that: The micro-display light engine comprises the micro-display light engine according to any one of claims 1 to 7, wherein the number of the micro-display light engine is one, and the light-emitting colors of the plurality of micro-LED crystals (11) included in the micro-display light engine are three primary colors.

9. A dual-engine full-color projector, characterized in that: A micro-display light engine comprising the micro-display light engine according to any one of claims 1 to 7, wherein the number of the micro-display light engines is two, and when the luminous color of the plurality of micro-LED crystals (11) included in the first micro-display light engine (341) is a single primary color, the luminous color of the plurality of micro-LED crystals (11) included in the second micro-display light engine (342) is a dual primary color, and the two primary colors of the second micro-display light engine (342) do not include the color emitted by the first micro-display light engine (341); the two micro-display light engines (341, 342) are arranged at an angle a or arranged in parallel, wherein the angle a is ≤14°; When the two micro-display light engines (341, 342) are arranged in parallel, the two micro-display light engines (341, 342) are arranged off-axis with respect to each other; the off-axis distance of the first micro-display light engine (341) toward the second micro-display light engine (342) is d, and the off-axis distance of the second micro-display light engine (342) toward the first micro-display light engine (341) is e; the optical axis of the first micro-LED panel (131) included in the first micro-display light engine (341) is L51, the optical axis of the second micro-LED panel (132) included in the second micro-display light engine (342) is L55, the distance between the optical axis L51 and the optical axis L55 is c, and the projection magnification of the two micro-display light engines (341, 342) is β, then c=β(d+e).

10. A three-engine full-color projector, characterized in that: A micro-display light engine comprising the micro-display light engine according to any one of claims 1 to 7, wherein the number of the micro-display light engines is three, and the light emitting color of the plurality of micro-LED dies (11) included in each micro-display light engine is one of three primary colors; The first micro-display light engine (343) and the intermediate micro-display light engine (344) are arranged at an angle b / 2, and the third micro-display light engine (345) and the intermediate micro-display light engine (344) are arranged at an angle b / 2, wherein the angle b is ≤ 28°; Alternatively, three micro-display light engines (343, 344, 345) are arranged in parallel, and in the two micro-display light engines (343, 345) on both sides, the off-axis distance of the first micro-display light engine (343) toward the middle micro-display light engine (344) is g, and the off-axis distance of the third micro-display light engine (345) toward the middle micro-display light engine (344) is k; let the optical axis of the first micro-LED panel (133) included in the first micro-display light engine (343) be L61, the optical axis of the second micro-LED panel (134) included in the middle micro-display light engine (344) be L62, the distance between the optical axis L61 and the optical axis L62 be f, and the projection magnification of the two micro-display light engines (343, 344) be β, then f=βg; Let the optical axis of the third micro-LED panel (135) included in the third micro-display light engine (345) be L63, the distance between the optical axis L63 and the optical axis L62 be j, and the projection magnification of the two micro-display light engines (345, 344) be β, then j=βk.

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