Three-color micro-projection optical system

Abstract

The utility model discloses a three-color micro-projection optical system, the three-color micro-projection optical system is provided with an object side and an image side which are correspondingly arranged along an optical axis direction, the three-color micro-projection optical system comprises a diaphragm, a lens group and a color combination prism assembly which are sequentially arranged from the object side to the image side; the color combination prism assembly comprises a color combination prism, a red light-emitting chip, a green light-emitting chip and a blue light-emitting chip; the focal length of the three-color micro projection optical system is f, 5.9 mlt; flt; the thickness is 6.4 mm; the distance from the diaphragm to the image surface is the total optical length TTL and TTLlt of the three-color micro-projection optical system; and the thickness is 10.2 mm. By means of the arrangement, in the environment temperature range of 20-60 DEG C, the optical system does not defocus during working, the MTF full frequency is higher than 0.5, the total length of the optical system can be controlled within 10.2 mm, and the working performance is more stable.

Description

Technical Field

[0001] This utility model relates to the field of micro-projection technology, and in particular to a three-color micro-projection optical system. Background Technology

[0002] Currently, with the continuous advancement of technology and the gradual rise of interactive devices such as Augmented Reality (AR), the application scope of projection optical systems is becoming increasingly wide. AR devices project virtual images onto the human eye through near-eye display devices, allowing users to simultaneously receive information from both the real and virtual worlds, resulting in a super-sensory visual experience. Traditional projection solutions include active light-emitting display sources based on Liquid Crystal Display (LCD) and Organic Light Emitting Diode (OLED) screens, and passive light-emitting display sources based on Liquid Crystal On Silicon (LCOS) and Digital Light Processing (DLP) screens. These solutions are generally large and heavy, resulting in poor user comfort during extended wear. Therefore, Micro LED screens, as a new type of high-brightness, miniaturized light-emitting display source device, offer a more lightweight, portable, and comfortable wearing experience, making them more popular among users.

[0003] However, the projection optical systems currently on the market still cannot meet the requirements of large field of view and lightweight design. MicroLED microdisplays are mainly single red (R), single green (G), and single blue (B). The monochrome projection optical systems they are adapted to need to be improved to provide users with a color augmented reality display effect that is closer to the real world. Existing MicroLED color solutions are large in size and have low light efficiency, which leads to poor near-eye display effect. Utility Model Content

[0004] The main purpose of this invention is to propose a three-color micro-projection optical system, which aims to solve the problems of large size, low luminous efficiency, and poor near-eye display effect of existing MicroLED color schemes.

[0005] To achieve the above objectives, the present invention proposes a three-color micro-projection optical system, which has an object side and an image side arranged correspondingly along the optical axis. The three-color micro-projection optical system includes an aperture, a lens group, and a color combining prism assembly arranged sequentially from the object side to the image side.

[0006] The lens group includes a first lens with a positive optical power, a second lens with a positive optical power, a third lens with a negative optical power, a fourth lens with a positive optical power, and a fifth lens with a positive optical power. The first lens is a glass aspherical lens, and the second lens, the third lens, the fourth lens, and the fifth lens are all plastic aspherical lenses. The dichroic prism is made of glass;

[0007] The dichroic prism assembly includes a dichroic prism, a red light-emitting chip, a green light-emitting chip, and a blue light-emitting chip. The dichroic prism has three mirror surfaces facing different directions, and the red light-emitting chip, the green light-emitting chip, and the blue light-emitting chip are respectively arranged opposite to the three mirror surfaces;

[0008] The focal length of the three-color micro-projection optical system is f, where 5.9 mm < f < 6.4 mm;

[0009] The distance from the aperture stop to the image plane is the total optical length TTL of the three-color micro-projection optical system, and TTL < 10.2 mm.

[0010] In one embodiment, the object side surface of the first lens is convex, the image side surface is concave, and the refractive index of the first lens is n1, where 1.75 < n1 < 1.9;

[0011] The object side surface of the second lens is convex, the image side surface is concave, and the refractive index of the second lens is n2, where 1.5 < n2 < 1.6;

[0012] The object side surface of the third lens is concave, the image side surface is concave, and the refractive index of the third lens is n3, where 1.6 < n3 < 1.7;

[0013] The object side surface of the fourth lens is concave, the image side surface is convex, and the refractive index of the fourth lens is n4, where 1.6 < n4 < 1.7;

[0014] The object side surface of the fifth lens is convex, the image side surface is concave, and the refractive index of the fifth lens is n5, where 1.5 < n5 < 1.6;

[0015] The refractive index of the dichroic prism is n6, where 1.5 < n6 < 1.58.

[0016] In one embodiment, the radius of the aperture stop is d0, where 1.5 mm < d0 < 2.5 mm, and the distance from the aperture stop to the first lens is L0, and L0 < 1.5 mm;

[0017] The semi-aperture of the first lens is d1, where 1.5 mm < d1 < 2.5 mm, and the core thickness of the first lens is L1, where 0.45 mm < L1 < 1 mm;

[0018] The semi-aperture of the second lens is d2, where 1.5 mm < d2 < 2 mm, and the core thickness of the second lens is L2, where 0.4 mm < L2 < 0.7 mm;

[0019] The semi-aperture of the third lens is d3, where 1.3 mm < d3 < 1.6 mm, and the core thickness of the third lens is L3, where 0.4 mm < L3 < 0.6 mm;

[0020] The semi-aperture of the fourth lens is d4, where 1.4 mm < d4 < 1.65 mm, and the core thickness of the fourth lens is L4, where 0.5 mm < L4 < 0.7 mm;

[0021] The semi-aperture of the fifth lens is d5, where 1.6 mm < d5 < 1.85 mm, and the core thickness of the fifth lens is L5, where 0.8 mm < L5 < 1.1 mm.

[0022] In one embodiment, the three-color micro-projection optical system satisfies: 0.45 < f / TTL < 0.7.

[0023] In one embodiment, the three-color micro-projection optical system satisfies: f / epd > 1.53; 0.48 < L f / TTL < 0.58;

[0024] where epd is the clear aperture of the aperture stop, and L f is the distance from the image side of the fifth lens to the image plane.

[0025] In one embodiment, the back focal length variation of the three-color micro-projection optical system is Δft, the back focal length variation of the first lens is Δf1, the back focal length variation of the second lens is Δf2, the back focal length variation of the third lens is Δf3, the back focal length variation of the fourth lens is Δf4, and the back focal length variation of the fifth lens is Δf5. The three-color micro-projection optical system satisfies the following conditions:

[0026] Δft = Δf1 + Δf2 + Δf3 + Δf4 + Δf5 < 7 μm.

[0027] In one embodiment, the dichroic prism is a cube dichroic prism, and the side length of the cube dichroic prism is d6, where 3.9 mm < d6 < 5.1 mm.

[0028] In one embodiment, blue band-pass filter films and red band-pass filter films are respectively provided on two diagonal sections of the cube dichroic prism;

[0029] The green light-emitting chip is located on the optical axis, and the red light-emitting chip and the blue light-emitting chip are located on opposite sides of the optical axis, so that the light emitted by the red light-emitting chip and the blue light-emitting chip can be reflected by the blue light bandpass filter and the red light bandpass filter, respectively, and then directed to the image side of the fifth lens.

[0030] In one embodiment, the blue light bandpass filter has a transmittance of T in the 400–580 nm wavelength range. B1 The transmittance in the 580–700 nm band is T B2 , among which, T B1 >95%, and T B2 <5%;

[0031] The red light bandpass filter has a transmittance of T in the 400–480 nm wavelength range. R1 The transmittance in the 480–700 nm band is T R2 , among which, T R1 <5%, and T R2 >95%.

[0032] In one embodiment, the diagonal length of the effective display area of ​​the red light-emitting chip is D1, 2.8 mm. <D1<3.4mm;

[0033] The diagonal length of the effective display area of ​​the green light-emitting chip is D2, 2.8mm. <D2<3.4mm;

[0034] The effective display area of ​​the blue light-emitting chip has a diagonal length of D3, which is 2.8mm. <D3<3.4mm。

[0035] The technical solution provided by this utility model employs a red, green, and blue light-emitting chip, combined with a color-combining prism (X-cube) to form a full-color display. This allows for the structural design of AR glasses within a small optical system size. Through the rational setting of the materials and surface shapes of the five lenses, the back focus of the optical system shifts towards the object side when the temperature of the positive lens increases, and towards the image side when the temperature of the negative lens increases. This ensures that the optical system remains focused within an ambient temperature range of 20℃ to 60℃, maintains an MTF (Mean Transmission Frequency) above 0.5 across the entire frequency range, and keeps the total length of the optical system within 10.2mm. It achieves high imaging quality in a small size, which is beneficial for the thinning and lightening of AR glasses displays and provides excellent near-eye display performance. Therefore, the three-color micro-projection optical system provided by this application offers excellent full-color imaging performance while maintaining a compact structure, excellent tolerances, and virtually no thermal defocusing when the ambient temperature changes, resulting in more stable performance. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0037] Figure 1 A three-dimensional schematic diagram of an embodiment of the three-color micro-projection optical system provided by this utility model;

[0038] Figure 2 for Figure 1 A schematic diagram of the optical path of the three-color micro-projection optical system in the image;

[0039] Figure 3 for Figure 1 A schematic diagram of the three-color micro-projection optical system described above imaging a red MTF at 20°C;

[0040] Figure 4 for Figure 1 A schematic diagram of the three-color micro-projection optical system described above imaging a green MTF at 20°C;

[0041] Figure 5 for Figure 1 A schematic diagram of the blue MTF image formed by the three-color micro-projection optical system described above at 20°C;

[0042] Figure 6 for Figure 1 A schematic diagram of the three-color micro-projection optical system described above imaging a red MTF at 60°C;

[0043] Figure 7 for Figure 1 A schematic diagram of the three-color micro-projection optical system described above imaging a green MTF at 60℃;

[0044] Figure 8 for Figure 1 A schematic diagram of the blue MTF image formed by the three-color micro-projection optical system described above at 60°C;

[0045] Figure 9 for Figure 1 A schematic diagram of the field area of ​​an embodiment of the three-color micro-projection optical system in China;

[0046] Figure 10 for Figure 1 A schematic diagram illustrating the distortion behavior of an embodiment of the three-color micro-projection optical system in China;

[0047] Figure 11 for Figure 1 A dot diagram of an embodiment of the three-color micro-projection optical system;

[0048] Figure 12 for Figure 1 A schematic diagram of the relative illumination of an embodiment of the three-color micro-projection optical system.

[0049] Explanation of icon numbers:

[0050] 1000. Three-color micro-projection optical system; 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Fifth lens; 6. Color combining prism assembly; 61. Color combining prism; 62. Red light-emitting chip; 63. Green light-emitting chip; 64. Blue light-emitting chip; 65. Blue light bandpass filter; 66. Red light bandpass filter.

[0051] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0052] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0053] It should be noted that if the embodiments of this utility model involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0054] Furthermore, if the embodiments of this utility model involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0055] Currently, the projection optical systems available on the market still cannot meet the requirements of large field of view and lightweight. Micro LED micro displays mainly consist of single red (R), single green (G), and single blue (B). The monochromatic projection optical systems adapted to them need to be enhanced in providing users with a color augmented reality display effect closer to the real world. The existing Micro LED color schemes are large in volume and low in light efficiency, resulting in poor near-eye display effects.

[0056] To solve the above problems, the present utility model provides a three-color micro projection optical system 100. Figure 1 and Figure 2 is a specific embodiment of the three-color micro projection optical system 100 provided by the present utility model.

[0057] Please refer to Figure 1 and Figure 2 , the three-color micro projection optical system 100 has an object side and an image side arranged corresponding to each other along the optical axis direction. The three-color micro projection optical system 100 includes an aperture stop, a lens group, and a color combining prism assembly 6 arranged in sequence from the object side to the image side. The lens group includes a first lens 1 with a positive optical power, a second lens 2 with a positive optical power, a third lens 3 with a negative optical power, a fourth lens 4 with a positive optical power, and a fifth lens 5 with a positive optical power. The first lens 1 is a glass aspherical lens, and the second lens 2, the third lens 3, the fourth lens 4, and the fifth lens 5 are all plastic aspherical lenses. The color combining prism 61 is made of glass. The color combining prism assembly 6 includes a color combining prism 61, a red light-emitting chip 62, a green light-emitting chip 63, and a blue light-emitting chip 64. The color combining prism 61 has three mirror surfaces facing different directions, and the red light-emitting chip 62, the green light-emitting chip 63, and the blue light-emitting chip 64 are respectively arranged opposite to the three mirror surfaces. The focal length of the three-color micro projection optical system 100 is f, and 5.9 mm < f < 6.4 mm. The distance from the aperture stop to the image plane is the optical total length TTL of the three-color micro projection optical system 100, and TTL < 10.2 mm.

[0058] The technical solution provided by this utility model employs a red light-emitting chip 62, a green light-emitting chip 63, and a blue light-emitting chip 64 to form a full-color display through a color-combining prism 61 (X-cube). This allows for the structural design of AR glasses within a small optical system size. Through the rational setting of the materials and surface shapes of the five lenses, the back focus of the optical system shifts towards the object side when the temperature of the positive lens increases, and shifts towards the image side when the temperature of the negative lens increases. This ensures that the optical system remains focused within an ambient temperature range of 20℃ to 60℃, maintains a full-frequency MTF above 0.5, and keeps the total length of the optical system within 10.2mm. This small size and high imaging quality contribute to the thinning and lightening of the AR glasses display solution, and provides excellent near-eye display performance. Therefore, the three-color micro-projection optical system provided by this application offers excellent full-color imaging performance, a compact structure, excellent tolerances, and virtually no thermal defocusing when the ambient temperature changes, resulting in more stable operation.

[0059] Furthermore, the three-color micro-projection optical system 100 is composed of five lenses and a color-combining prism assembly 6. The first lens 1 is a glass aspherical lens, which minimizes or eliminates the influence of temperature. The second lens 2, the third lens 3, the fourth lens 4, and the fifth lens 5 are all plastic aspherical lenses. This arrangement of five lenses allows for mutual compensation of thermal defocusing effects caused by thermal deformation of the optical system, ensuring that the overall image quality of the lens remains unaffected. Consequently, the three-color micro-projection optical system 100 exhibits virtually no thermal defocusing even when ambient temperature changes, and the color image quality of the optical system remains at a high level. The problem of thermal defocusing is significantly improved, providing high stability to the three-color micro-projection optical system 100 and enhancing the user experience.

[0060] It should be noted that in this invention, the red light-emitting chip 62 can be a red micro LED chip (R Micro LED chip), the green light-emitting chip 63 can be a green micro LED chip (G Micro LED chip), and the blue light-emitting chip 64 can be a blue micro LED chip (B Micro LED chip). The color-combining prism 61 is preferably a cross-shaped dichroic color-combining prism (X-cube), which can combine the light emitted by the three monochromatic Micro LED chips (red, green, and blue) into a single beam of full-color light.

[0061] It should be noted that in an embodiment of the present invention, the focal length f of the three-color micro-projection optical system 100 can be set to 5.9, 5.95, 6.0, 6.05, 6.1, 6.15, 6.2, 6.25, 6.3, 6.35, 6.4, 6.45, etc., or set to other data, and the present invention does not limit this.

[0062] Furthermore, in the present invention, the object side surface of the first lens 1 is convex, the image side surface is concave, and the refractive index of the first lens 1 is n1, where 1.75 < n1 < 1.9; the object side surface of the second lens 2 is convex, the image side surface is concave, and the refractive index of the second lens 2 is n2, where 1.5 < n2 < 1.6; the object side surface of the third lens 3 is concave, the image side surface is concave, and the refractive index of the third lens 3 is n3, where 1.6 < n3 < 1.7; the object side surface of the fourth lens 4 is concave, the image side surface is convex, and the refractive index of the fourth lens 4 is n4, where 1.6 < n4 < 1.7; the object side surface of the fifth lens 5 is convex, the image side surface is concave, and the refractive index of the fifth lens 5 is n5, where 1.5 < n5 < 1.6; the refractive index of the color-combining prism 61 is n6, where 1.5 < n6 < 1.58. Specifically, through a reasonable combination structure among the five lenses, the three-color micro-projection optical system 100 can still work stably when the environmental temperature changes drastically, with almost no thermal defocus, and can maintain high full-color imaging quality.

[0063] It should be noted that please refer to Figure 1 and Figure 2 , when the lens surface bends to the left, the lens surface type is expressed as +, and when the lens surface bends to the right, the lens surface type is expressed as -, and the 10 surface types of the five lenses from the object side to the image side of the present invention are +, +, +, +, -, +, -, -, +, + respectively.

[0064] This utility model does not limit the refractive index of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, or the color-combining prism 61. It is understood that, in one embodiment of this utility model, the refractive index n1 of the first lens 1 can be set to 1.75, 1.8, 1.85, 1.9, etc.; the refractive index n2 of the second lens 2 can be set to 1.50, 1.51, 1.52, 1.53, 1.54, 1.55, 1.56, 1.57, 1.58, 1.59, 1.6, etc.; and the refractive index n3 of the third lens 3 can be set to 1.6, 1.62, 1.64, 1.66, 1.68, 1.7, etc. The refractive index n4 of the fourth lens 4 can be set to 1.6, 1.62, 1.64, 1.66, 1.68, 1.7, etc.; the refractive index n5 of the fifth lens 5 can be set to 1.5, 1.51, 1.52, 1.53, 1.54, 1.55, 1.56, 1.57, 1.58, 1.59, 1.6, etc.; and the refractive index n6 of the color-combining prism 61 can be set to 1.5, 1.51, 1.52, 1.53, 1.54, 1.55, 1.56, 1.57, 1.58, etc. Of course, in other embodiments of this utility model, the refractive indices of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, and the color-combining prism 61 can also be set to other values, and this utility model does not impose any limitations on this.

[0065] Further, the radius of the aperture is d0, where 1.5 mm < d0 < 2.5 mm, and the distance from the aperture to the first lens 1 is L0, where L0 < 1.5 mm; the semi-aperture of the first lens 1 is d1, where 1.5 mm < d1 < 2.5 mm, and the core thickness of the first lens 1 is L1, where 0.45 mm < L1 < 1 mm; the semi-aperture of the second lens 2 is d2, where 1.5 mm < d2 < 2 mm, and the core thickness of the second lens 2 is L2, where 0.4 mm < L2 < 0.7 mm; the semi-aperture of the third lens 3 is d3, where 1.3 mm < d3 < 1.6 mm, the core thickness of the third lens 3 is L3, where 0.4 mm < L3 < 0.6 mm; the semi-aperture of the fourth lens 4 is d4, where 1.4 mm < d4 < 1.65 mm, the core thickness of the fourth lens 4 is L4, where 0.5 mm < L4 < 0.7 mm; the semi-aperture of the fifth lens 5 is d5, where 1.6 mm < d5 < 1.85 mm, the core thickness of the fifth lens 5 is L5, where 0.8 mm < L5 < 1.1 mm. This embodiment is a preferred embodiment. By the mutual combination of different lenses and the reasonable distribution of their aperture radii and core thicknesses, the entire optical system can better match the diffractive optical waveguide, thereby reducing the loss of light propagation, improving the coupling efficiency, and enhancing the imaging quality.

[0066] Further, the focal length of the three-color micro-projection optical system 100 is f, and the total optical length of the three-color micro-projection optical system 100 is TTL, where 0.45 < f / TTL < 0.7. With such a setting, when the focal length f of the three-color micro-projection optical system 100 and the total optical length TTL of the three-color micro-projection optical system 100 satisfy the above relationship, the structure of the three-color micro-projection optical system 100 can be made more compact.

[0067] The clear aperture of the aperture is epd, and the focal length of the three-color micro-projection optical system 100 is f, where f / epd > 1.53. f / epd is the aperture coefficient. A larger aperture coefficient can provide a deeper depth of field in the VR glasses, enabling the user to see a clear image in a wider range, rather than just in the area near the focus. This helps to enhance the user's immersion, as the user can move their head and line of sight more freely in the virtual environment without immediately encountering the problem of image blurring.

[0068] The distance from the image side of the fifth lens 5 to the image plane is Lf, and the total optical length of the three-color micro-projection optical system 100 is TTL, where 0.48 < Lf / TTL < 0.58. Thus, when the distance from the image side of the fifth lens 5 to the image plane and the total optical length TTL of the three-color micro-projection optical system 100 satisfy the above relationship, sufficient installation space for the color-combining prism assembly 6 can be ensured.

[0069] Further, to ensure that the thermal defocusing effects caused by thermal deformation can be compensated for each other among the multiple plastic lenses of the three-color micro-projection optical system 100 during the change of the ambient temperature, so that the overall imaging quality of the three-color micro-projection optical system 100 is not affected. In the embodiment of the present invention, the back focal change amount of the three-color micro-projection optical system 100 is Δft, the back focal change amount of the first lens 1 is Δf1, the back focal change amount of the second lens 2 is Δf2, the back focal change amount of the third lens 3 is Δf3, the back focal change amount of the fourth lens 4 is Δf4, and the back focal change amount of the fifth lens 5 is Δf5. The three-color micro-projection optical system 100 satisfies the following condition: Δft = Δf1 + Δf2 + Δf3 + Δf4 + Δf5 < 7um.

[0070] It should be noted that, in this embodiment, the second lens 2, the third lens 3, and the fourth lens 4 are positive lenses. When the ambient temperature rises, the back focal change amounts of the second lens 2, the third lens 3, and the fourth lens 4 are in the direction of the object side of the three-color micro-projection optical system 100; the fourth lens 4 is a negative lens. When the ambient temperature rises, the back focal change amount of the fourth lens 4 is in the direction of the image side of the three-color micro-projection optical system 100.

[0071] It is worth mentioning that, in the present invention, the surface shapes of the multiple lenses of the three-color micro-projection optical system 100 should satisfy the following formula:

[0072]

[0073] It should be noted that the first expression is the same as the standard surface shape, and the second is the summation of the normalized coordinate power series; αi is the aspherical coefficient, expressed in optical system units, so the normalized radial coordinate ρ is used.

[0074] The color-combining prism 61 is a cube color-combining prism 61, and the side length of the cube color-combining prism 61 is d6, where 3.9mm < d6 < 5.1mm. Specifically, the side length d6 of the cube color-combining prism 61 can be 3.9mm, 4.2mm, 4.5mm, 4.8mm, 5.1mm, etc. The side length d6 of the cube color-combining prism 61 within the above range can not only have appropriate color-combining accuracy and uniformity, but also reduce chromatic dispersion and improve the accuracy of color synthesis.

[0075] Furthermore, the two diagonal facets of the cubic color-combining prism 61 are respectively provided with a blue light bandpass filter 65 and a red light bandpass filter 66. The blue light bandpass filter 65 can reflect the blue light emitted by the blue light-emitting chip 64 and transmit the green light emitted by the green light-emitting chip 63; the red light bandpass filter 66 can reflect the red light emitted by the red light-emitting chip 62 and transmit the green light emitted by the green light-emitting chip 63. The green light-emitting chip 63 is located on the optical axis, and the red light-emitting chip 62 and the blue light-emitting chip 64 are located on opposite sides of the optical axis, so that the light emitted by the red light-emitting chip 62 and the blue light-emitting chip 64 can be reflected by the red light bandpass filter 66 and the blue light bandpass filter 65 respectively and then directed towards the image side of the fifth lens 5. For details, please refer to [link to specific documentation]. Figure 1 and Figure 2 In one embodiment of this utility model, the light emitted by the blue Micro LED chip located above the color-combining prism 61 is reflected by the blue light bandpass filter 65 and then directed towards the image side of the fifth lens 5; the light emitted by the red Micro LED chip located below the color-combining prism 61 is reflected by the blue light bandpass filter 65 and then directed towards the image side of the fifth lens 5; the light emitted by the green Micro LED chip located on the side of the color-combining prism 61 away from the fifth lens 5 can pass through the red light bandpass filter 66 and the blue light bandpass filter 65 and then directed towards the image side of the fifth lens 5.

[0076] In one embodiment of this application, the blue light bandpass filter 65 has a transmittance of TB1 in the 400–580 nm wavelength range and a transmittance of TB2 in the 580–700 nm wavelength range, wherein TB1 > 95% and TB2 < 5%; the red light bandpass filter 66 has a transmittance of TR1 in the 400–480 nm wavelength range and a transmittance of TR2 in the 480–700 nm wavelength range, wherein TR1 < 5% and TR2 > 95%. In an optical system, stray light may interfere with imaging quality or affect the accuracy of the optical signal. The blue light bandpass filter 65 allows 95% of light in the 400–580 nm wavelength band to pass through and 95% of light in the 580–700 nm wavelength band (red light) to be reflected, thus separating blue light from other light. The red light bandpass filter 66 allows 95% of light in the 480–700 nm wavelength band to pass through and 95% of light in the 400–480 nm wavelength band (blue light) to be reflected, thus separating red light from other light. In the color-combining prism 61, the blue light bandpass filter 65 has a higher transmittance in the 400-580nm wavelength range and a lower transmittance in the 580-700nm wavelength range, which better reflects red light incident on the blue light bandpass filter 65 while transmitting blue and green light. Similarly, the red light bandpass filter 66 has a lower transmittance in the 400-480nm wavelength range and a higher transmittance in the 480-700nm wavelength range, which better reflects blue light incident on the red light bandpass filter 66 while transmitting red and green light. For details, please refer to [link to relevant documentation]. Figure 1 and Figure 2 The light emitted by the blue Micro LED chip located above the color-combining prism 61, after being reflected by the red bandpass filter 66, is 95% directed towards the image side of the fifth lens 5. The light emitted by the red Micro LED chip located below the color-combining prism 61, after being reflected by the blue bandpass filter 65, is 95% directed towards the image side of the fifth lens 5. The light emitted by the green Micro LED chip located on the side of the color-combining prism 61 away from the fifth lens 5 can pass through both the red and blue bandpass filters 66 and reach the image side of the fifth lens 5 with 95% efficiency. This results in a better imaging effect.

[0077] To improve the color combination accuracy after the light passes through the color combining prism 61, that is, the light from different chips can reach each preset position after passing through the color combining prism 61, thereby avoiding ghosting or blurred imaging, the distances from the red light-emitting chip 62, the green light-emitting chip 63, and the blue light-emitting chip 64 to the image side surface of the fifth lens 5 are different respectively. Or, the distances from the red light-emitting chip 62, the green light-emitting chip 63, and the blue light-emitting chip 64 to the surface opposite to the color combining prism 61 are different respectively. Or, the relative positions of the effective display areas of the red light-emitting chip 62, the green light-emitting chip 63, and the blue light-emitting chip 64 with respect to the surface opposite to the color combining prism 61 are different, so that the light emitted by each light-emitting chip can be combined into a beam of light. Please refer to Figure 1 , the effective display area of the upper blue Micro LED chip is set to be biased to the right with respect to the upper surface of the color combining prism 61, the effective display area of the upper red Micro LED chip is set to be biased to the left with respect to the lower surface of the color combining prism 61, and the effective display area of the right green Micro LED chip is set to be biased upward with respect to the surface of the color combining prism 61, so that the light emitted by each light-emitting chip can be combined into a beam of light. In other specific embodiments, automatic assembly AA can be used, and through real-time imaging analysis and precise control, precise alignment and assembly between optical components can be achieved, greatly improving the assembly accuracy and making the imaging quality of the optical system excellent.

[0078] Furthermore, the diagonal length of the effective display area of the red light-emitting chip 62 is D1, where 2.8 mm < D1 < 3.4 mm; the diagonal length of the effective display area of the green light-emitting chip 63 is D2, where 2.8 mm < D2 < 3.4 mm; the diagonal length of the effective display area of the blue light-emitting chip 64 is D3, where 2.8 mm < D3 < 3.4 mm. The effective display areas of the above dimensions can have better cooperation with the color combining prism 61, thereby further improving the imaging quality.

[0079] Based on the above content, the three-color micro-projection optical system provided by the present invention has an optical total length less than 10.2 mm. It uses R (red), G (green), and B (blue) three single-color Micro LED chips for color combination through an X-cube. Since the three chips are separately assembled with five lenses and the X-cube through AA, the imaging quality of the optical system is excellent. It can achieve that within the range of ambient temperature from 20 °C to 60 °C, the lens does not lose focus during operation, and the MTF is higher than 0.5 in the full-frequency state. The optical engine based on this optical system is used for AR glasses and has a good resolution effect. Under normal use temperature, the optical engine almost has no thermal defocus. In addition, because the size of the optical engine is smaller than the current industry situation, this optical engine is beneficial to the structural design and final assembly of AR glasses. And due to the small size of the optical engine, the AR glasses are thinner and lighter, and the user experience is more excellent.

[0080] It should be noted that in this embodiment, the basic parameter tables of the curvatures, materials, apertures, and conic coefficients of the lenses of the three-color micro-projection optical system are shown in Table 1 as follows:

[0081] Table 1

[0082] Surface number Surface type radius of curvature thickness Material Net diameter Extension area Mechanical half diameter Conic coefficient TCE×1E-6 0 STANDARD unlimited unlimited 0.000 0.000 0.000 0.000 0.000 1 STANDARD unlimited 0.000 1.900 0.000 1.850 0.000 0.000 2 XASPHERE 5.800 0.664 D-ZLAF50 1.850 0.000 1.850 0.019 0.000 3 XASPHERE 39.800 0.118 1.799 0.000 1.850 -12.011 20.000 4 XASPHERE 4.6600 0.554 480R 1.674 0.000 1.674 0.822 0.000 5 XASPHERE 8.170 0.829 1.537 0.000 1.674 13.568 18.000 6 XASPHERE -2.153 0.421 EP-5000 1.446 0.000 1.494 -5.386 0.000 7 XASPHERE 8.223 0.333 1.494 0.000 1.494 4.310 18.000 8 XASPHERE -11.474 0.581 EP-8000 1.545 0.000 1.578 -22.109 0.000 9 XASPHERE -4.182 0.098 1.578 0.000 1.578 -7.521 18.000 10 XASPHERE 2.355 0.963 APL5014CL 1.758 0.000 1.817 -2.464 0.000 11 XASPHERE 18.562 0.625 1.817 0.000 1.817 18.392 0.000 12 STANDARD unlimited 4.410 H-K9L 1.783 0.000 1.783 0.000 0.000 13 STANDARD unlimited 0.410 1.643 0.000 1.783 0.000 0.000 14 STANDARD unlimited 0.000 1.625 0.000 1.625 0.000 0.000

[0083] Furthermore, in this embodiment, based on this framework, the optimized surface coefficients of each lens are shown in Table 2 as follows:

[0084] Table 2

[0085]

[0086]

[0087] Figure 3 This is a schematic diagram of the red MTF imaging of the three-color micro-projection optical system in this embodiment at 20°C; Figure 4 This is a schematic diagram of the green MTF imaging of the three-color micro-projection optical system in this embodiment at 20°C; Figure 5 This is a schematic diagram of the blue MTF imaging of the three-color micro-projection optical system in this embodiment at 20°C; Figure 6 This is a schematic diagram of the red MTF imaging of the three-color micro-projection optical system in this embodiment at 60°C; Figure 7 This is a schematic diagram of the green MTF imaging of the three-color micro-projection optical system in this embodiment at 60°C; Figure 8 This is a schematic diagram of the blue MTF imaging of the three-color micro-projection optical system in this embodiment at 60°C; It can be seen that Figures 3-8 as the temperature increases, the MTF of the three-color micro-projection optical system attenuates slightly, showing a trend of thermal defocus. However, at 60°C, both the MTF and the defocus remain at a high level. The corresponding opto-mechanical system of the three-color micro-projection optical system is used for AR glasses, and users can consider that there is no change in this performance.

[0088] Figure 9 This is Figure 1 a schematic diagram of the field area of an embodiment of the three-color micro-projection optical system in Figure 10 This is Figure 1 a schematic diagram of the distortion performance of an embodiment of the three-color micro-projection optical system in Figure 9 and Figure 10 It can be seen that the three-color micro-projection optical system can compress the distortion to within 2%, and for the image combination required for binocular display of AR glasses, it will not affect the final binocular image combination and display effect of the glasses.

[0089] Figure 11 This is Figure 1A dot diagram of an embodiment of the three-color micro-projection optical system; by Figure 11 It can be seen that the RMS radius is less than 1.5 pixels.

[0090] Figure 12 for Figure 1 A schematic diagram of the relative illumination of an embodiment of the three-color micro-projection optical system, provided by Figure 12 It can be seen that the three-color micro-projection optical system can maintain a relative illuminance of over 0.8 across the entire field of view, ensuring that the optical engine has high light efficiency.

[0091] The above description is only a preferred embodiment of the present utility model and does not limit the patent scope of the present utility model. All equivalent structural transformations made under the concept of the present utility model and using the contents of the present utility model specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present utility model.

Claims

1. A three-color micro-projection optical system, characterized in that, The three-color micro-projection optical system has an object side and an image side arranged corresponding to each other along the optical axis direction. The three-color micro-projection optical system includes an aperture stop, a lens group, and a color-combining prism assembly arranged in sequence from the object side to the image side; The lens group includes a first lens with a positive optical power, a second lens with a positive optical power, a third lens with a negative optical power, a fourth lens with a positive optical power, and a fifth lens with a positive optical power. The first lens is a glass aspherical lens, and the second lens, the third lens, the fourth lens, and the fifth lens are all plastic aspherical lenses. The color-combining prism is made of glass; The color-combining prism assembly includes a color-combining prism, a red light-emitting chip, a green light-emitting chip, and a blue light-emitting chip. The color-combining prism has three mirrors facing different directions, and the red light-emitting chip, the green light-emitting chip, and the blue light-emitting chip are respectively arranged opposite to the three mirrors; The focal length of the three-color micro-projection optical system is f, and 5.9 mm < f < 6.4 mm; The distance from the aperture stop to the image plane is the total optical length TTL of the three-color micro-projection optical system, and TTL < 10.2 mm.

2. The three-color micro-projection optical system as described in claim 1, characterized in that, The object side surface of the first lens is convex, and the image side surface is concave. The refractive index of the first lens is n1, and 1.75 < n1 < 1.9; The object side surface of the second lens is convex, and the image side surface is concave. The refractive index of the second lens is n2, and 1.5 < n2 < 1.6; The object side surface of the third lens is concave, and the image side surface is concave. The refractive index of the third lens is n3, and 1.6 < n3 < 1.7; The object side surface of the fourth lens is concave, and the image side surface is convex. The refractive index of the fourth lens is n4, and 1.6 < n4 < 1.7; The object side surface of the fifth lens is convex, and the image side surface is concave. The refractive index of the fifth lens is n5, and 1.5 < n5 < 1.6; The refractive index of the color-combining prism is n6, and 1.5 < n6 < 1.

58.

3. The three-color micro-projection optical system as described in claim 2, characterized in that, The radius of the aperture stop is d0, and 1.5 mm < d0 < 2.5 mm. The distance from the aperture stop to the first lens is L0, and L0 < 1.5 mm; The semi-aperture of the first lens is d1, and 1.5 mm < d1 < 2.5 mm. The core thickness of the first lens is L1, and 0.45 mm < L1 < 1 mm; The semi-aperture of the second lens is d2, and 1.5 mm < d2 < 2 mm. The core thickness of the second lens is L2, and 0.4 mm < L2 < 0.7 mm; The semi-aperture of the third lens is d3, and 1.3 mm < d3 < 1.6 mm. The core thickness of the third lens is L3, and 0.4 mm < L3 < 0.6 mm; The semi-aperture of the fourth lens is d4, and 1.4 mm < d4 < 1.65 mm. The core thickness of the fourth lens is L4, and 0.5 mm < L4 < 0.7 mm; The semi-aperture of the fifth lens is d5, and 1.6 mm < d5 < 1.85 mm. The core thickness of the fifth lens is L5, and 0.8 mm < L5 < 1.1 mm.

4. The three-color micro-projection optical system as described in claim 1, characterized in that, The three-color micro-projection optical system satisfies: 0.45 < f / TTL < 0.

7.

5. The three-color micro-projection optical system as described in claim 1, characterized in that, The three-color micro-projection optical system satisfies: f / epd > 1.53; 0.48 < L. f / TTL < 0.58; Where epd is the aperture of the aperture, L f The distance is the distance from the image-side surface of the fifth lens to the image plane.

6. The three-color micro-projection optical system as described in claim 1, characterized in that, The back focal length variation of the three-color micro-projection optical system is Δft, the back focal length variation of the first lens is Δf2, the back focal length variation of the second lens is Δf2, the back focal length variation of the third lens is Δf3, the back focal length variation of the fourth lens is Δf4, and the back focal length variation of the fifth lens is Δf5. The three-color micro-projection optical system satisfies the following conditions: △ft=△f1+△f2+△f3+△f4+△f5<7um.

7. The three-color micro-projection optical system as described in claim 1, characterized in that, The color-combining prism is a cubic color-combining prism with a side length of d6 and 3.9 mm. <d6<5.1mm。 8. The three-color micro-projection optical system as described in claim 7, characterized in that, The two diagonal facets of the cube-shaped color-combining prism are respectively provided with a blue light bandpass filter and a red light bandpass filter; The green light-emitting chip is located on the optical axis, and the red light-emitting chip and the blue light-emitting chip are located on opposite sides of the optical axis, so that the light emitted by the red light-emitting chip and the blue light-emitting chip can be reflected by the blue light bandpass filter and the red light bandpass filter, respectively, and then directed to the image side of the fifth lens.

9. The three-color micro-projection optical system as described in claim 8, characterized in that, The blue light bandpass filter has a transmittance of T in the 400–580 nm wavelength range. B1 The transmittance in the 580–700 nm band is T B2 , among which, T B1 >95%, and T B2 <5%; The red light bandpass filter has a transmittance of T in the 400–480 nm wavelength range. R1 The transmittance in the 480–700 nm band is T R2 , among which, T R1 <5%, and T R2 >95%.

10. The three-color micro-projection optical system as described in claim 1, characterized in that, The diagonal length of the effective display area of ​​the red light-emitting chip is D1, 2.8mm. <D1<3.4mm; The diagonal length of the effective display area of ​​the green light-emitting chip is D2, 2.8mm. <D2<3.4mm; The effective display area of ​​the blue light-emitting chip has a diagonal length of D3, which is 2.8mm. <D3<3.4mm。

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