Ultra-thin optical module

Abstract

The application discloses an ultrathin optical module, which comprises a display image source, an imaging prism unit one, an imaging prism unit two, an imaging lens unit three, a film system unit, a quarter-wave plate and a semi-transparent semi-reflective film. Light emitted by the display image source is reflected for the first time by a first surface of the imaging prism unit two, reaches a second surface of the imaging prism unit two for the second time, then reaches a third surface of the imaging prism unit two and is reflected for the third time by the film system unit, then sequentially transmits through the second surface of the imaging prism unit two, the quarter-wave plate and the imaging lens unit three to reach the semi-transparent semi-reflective film, is reflected for the fourth time by the semi-transparent semi-reflective film, then sequentially transmits through the imaging lens unit three, the quarter-wave plate, the imaging prism unit two, the film system unit, the imaging prism unit one to reach the human eye imaging, and the focal length is reasonably arranged. The application realizes a large visual field angle, light and thin, and excellent image quality.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of optical imaging technology, and particularly relates to an ultrathin optical module. BACKGROUND

[0002] In recent years, the augmented reality (AR) technology has been applied in intelligent wearable devices and developed rapidly. With the application of AR products in augmented reality becoming more and more widespread, the corresponding technology is also developing continuously, and the AR products are getting more and more attention from people, and are expected to replace the next generation of mobile terminals. The core component of the augmented reality technology is an optical module, and the field of view (FOV), thickness and display effect of the optical module will directly determine the quality of the intelligent wearable device. In particular, it is a key to restrict the development of the AR technology to achieve large FOV and thin thickness while still having excellent image quality.

[0003] At present, in the AR scheme, the Birdbath scheme can present a better image quality, and has a thickness of 18mm-20mm, which is difficult to meet the daily wearing needs of people. The light waveguide scheme of thin thickness has not yet matured, and cannot provide a better imaging effect and a larger FOV, and has a more serious color deviation and light efficiency problem. The folded light path scheme with a thickness between the two and a good imaging effect has been proposed, but due to the limitation of the material, the color difference performance is poor, which becomes a bottleneck problem of the scheme. SUMMARY

[0004] The purpose of the present application is to solve the above problems, and to provide an ultrathin optical module, which realizes a large field of view and thin thickness while having excellent image quality.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] The application provides an ultrathin optical module, which comprises a display image source, an imaging prism unit one, an imaging prism unit two, an imaging lens unit three, a film system unit, a quarter-wave plate and a semi-transmissive and semi-reflective film, light emitted by the display image source is reflected for the first time by a first surface of the imaging prism unit two, reaches a second surface of the imaging prism unit two for the second time, then reaches a third surface of the imaging prism unit two and is reflected for the third time by the film system unit, then passes through the second surface of the imaging prism unit two, the imaging lens unit three and the semi-transmissive and semi-reflective film in sequence, is reflected for the fourth time by the semi-transmissive and semi-reflective film, then passes through the imaging lens unit three, the imaging prism unit two, the film system unit and the imaging prism unit one in sequence and reaches a human eye for imaging, the quarter-wave plate is located between the imaging prism unit two and the imaging lens unit three or between the film system unit and the imaging prism unit two, and the focal length f1 of the imaging lens unit three satisfies 10mm < f1 < 30mm, and the focal length f of the ultrathin optical module satisfies 10mm < f < 22mm.

[0007] Preferably, the film system unit comprises a first absorbing polarizer and a reflective polarizer, the reflective polarizer is arranged close to the imaging prism unit two, and the first absorbing polarizer is arranged close to the imaging prism unit one.

[0008] Preferably, the slow axis of the quarter-wave plate is at an angle of 45°±1° with the reflection axis of the reflective polarizer, and the reflection axis of the reflective polarizer is parallel to the absorption axis of the first absorbing polarizer.

[0009] Preferably, the side of the display image source close to the imaging prism unit two is further provided with a second absorbing polarizer, and the thickness of the second absorbing polarizer is 10μm-300μm.

[0010] Preferably, the transmission axis of the second absorbing polarizer is the long side of the display image source, the angle between the slow axis of the quarter-wave plate and the horizontal direction is 45°, the transmission axis of the reflective polarizer is the vertical direction, and the long side of the display image source is the left-right direction when the display image source is worn by a human body.

[0011] Preferably, the display image source is used for emitting 45° linearly polarized light, and the film system unit is used for reflecting the 45° linearly polarized light and transmitting-45° linearly polarized light.

[0012] Preferably, the angle between the display image source and the horizontal direction is 3°-45°, the angle between the surface of the imaging prism unit one close to the film system unit and the horizontal direction is 10°-60°, and the angle between the first surface and the third surface of the imaging prism unit two is 10°-60°.

[0013] Preferably, the ultrathin optical module further satisfies the following conditions:

[0014] 1.5 < n1 < 1.9, 1.5 < n2 < 1.9, 1.5 < n3 < 1.8;

[0015] 20 < Vd1 < 65, 30 < Vd2 < 65, 30 < Vd3 < 65;

[0016] wherein n1, n2, n3 are the refractive index of the first imaging prism unit, the second imaging prism unit, and the third imaging lens unit, respectively, and Vd1, Vd2, Vd3 are the Abbe number of the first imaging prism unit, the second imaging prism unit, and the third imaging lens unit, respectively.

[0017] Preferably, the ultra-thin optical module further satisfies the following conditions:

[0018] 0.5 < d1 < 5.0, 1 < d2 < 5.0, 0.5 < d3 < 3.5;

[0019] 0.15 < D1< 2.0, 0<D2< 1.0, 0.05 <D3 < 2.0;

[0020] wherein d1, d2, d3 are the thickness of the first imaging prism unit, the second imaging prism unit, and the third imaging lens unit, respectively, D1 is the air gap between the second imaging prism unit and the display image source, D2 is the air gap between the second imaging prism unit and the first imaging prism unit, and D3 is the air gap between the third imaging lens unit and the second imaging prism unit, in units of mm.

[0021] Preferably, the radius of curvature C1 of the mirror surface on the third imaging lens unit close to the human eye side satisfies: 200 < C1, and the radius of curvature C2 of the mirror surface away from the human eye side satisfies: 30 < |C2| < 80, in units of mm.

[0022] Preferably, the ultra-thin optical module further comprises a fourth imaging lens unit, which is located between the second imaging prism unit and the display image source, and the fourth imaging lens unit comprises at least one lens, the radius of curvature C3 of the mirror surface on the fourth imaging lens unit close to the second imaging prism unit satisfies: 20 < |C3| < 90, and the radius of curvature C4 of the mirror surface close to the display image source satisfies: 20 < |C4| < 90, in units of mm.

[0023] Preferably, the third imaging lens unit comprises a first lens, and the first lens is a curved mirror.

[0024] Preferably, the mirror surface of each lens is one of a diffractive surface, a spherical surface, an aspherical surface, a free-form surface, a Fresnel surface, and a plane.

[0025] Preferably, the thickness of the membrane unit is 10 μm to 300 μm, the thickness of the quarter-wave plate is 10 μm to 300 μm, and the thickness of the semi-transparent and semi-reflective membrane is 30 μm to 500 μm.

[0026] Preferably, both imaging prism unit one and imaging prism unit two are triangular prisms.

[0027] Preferably, the display image source is one of OLED display, LCOS display, Microled display, DLP display, or LBS display.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] This invention proposes a Cupcake four-fold optical path scheme, which utilizes the principles of light refraction, reflection, and polarization to achieve a shorter optical path through folded optical elements. By rationally setting optical parameters, it achieves a large field of view (FOV) (above 60°) while also exhibiting better performance in terms of thinness and image quality. Compared to the existing Cupcake three-reflection scheme, it further reduces the overall thickness by more than half from the traditional Birdbath scheme's 18mm-20mm, reducing module weight and achieving excellent image quality while maintaining a large field of view. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the ultra-thin optical module of the present invention;

[0031] Figure 2 This is the MTF diagram of Embodiment 1 of the ultrathin optical module of the present invention;

[0032] Figure 3 This is a dot diagram of Embodiment 1 of the ultrathin optical module of the present invention;

[0033] Figure 4 This is the MTF diagram of Embodiment 2 of the ultrathin optical module of the present invention;

[0034] Figure 5 This is a dot diagram of Embodiment 2 of the ultrathin optical module of the present invention;

[0035] Figure 6 This is the MTF diagram of embodiment 3 of the ultrathin optical module of the present invention;

[0036] Figure 7 This is a dot diagram of embodiment 3 of the ultrathin optical module of the present invention;

[0037] Figure 8 This is the MTF diagram of embodiment 4 of the ultrathin optical module of the present invention;

[0038] Figure 9 This is a dot diagram of embodiment 4 of the ultra-thin optical module of the present invention.

[0039] Description of reference numerals: 1. display image source; 2. first imaging prism unit; 3. second imaging prism unit; 4. third imaging lens unit; 5. film system unit; 6. quarter-wave plate; 7. semi-transmissive and semi-reflective film; 8. absorptive polarizer; eye, human eye. Detailed implementation manners

[0040] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0041] It should be noted that unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field of the present application. The terms used in the specification of the present application herein are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0042] As Figure 1 shown, a thin optical module includes a display image source 1, a first imaging prism unit 2, a second imaging prism unit 3, a third imaging lens unit 4, a film system unit 5, a quarter-wave plate 6, and a semi-transmissive and semi-reflective film 7. The light emitted by the display image source 1 is first reflected by the first surface of the second imaging prism unit 3, then reaches the second surface of the second imaging prism unit 3 for a second reflection, and then reaches the third surface of the second imaging prism unit 3 and is reflected by the film system unit 5 for a third reflection, and then sequentially passes through the second surface of the second imaging prism unit 3, the third imaging lens unit 4 to reach the semi-transmissive and semi-reflective film 7. After being reflected by the semi-transmissive and semi-reflective film 7 for a fourth reflection, it then sequentially passes through the third imaging lens unit 4, the second imaging prism unit 3, the film system unit 5, the first imaging prism unit 2 to reach the human eye for imaging. The quarter-wave plate 6 is located between the second imaging prism unit 3 and the third imaging lens unit 4, or between the film system unit 5 and the second imaging prism unit 3, and the focal length f1 of the third imaging lens unit 4 satisfies: 10 mm < f1 < 30 mm, and the focal length f of the thin optical module satisfies: 10 mm < f < 22 mm.

[0043] For ease of understanding, the direction in which the human eye looks straight ahead is regarded as the horizontal direction, and the specific orientation can also be adjusted. Then the relative positions of the angles mentioned below can all be deflected as a whole.

[0044] The image source 1 provides the image. The film unit 5 is located between the imaging prism unit 2 3 and the imaging lens unit 3 4. The quarter-wave plate 6 can be located between the imaging prism unit 2 3 and the imaging lens unit 3 4, or between the film unit 5 and the imaging prism unit 2 3, depending on actual needs. The semi-transparent and semi-reflective film 7 is located on the side of the imaging lens unit 3 4 facing away from the human eye. The first surface of the imaging prism unit 2 3 is the surface close to the image source 1, the second surface is the surface of the imaging prism unit 2 3 away from the human eye, and the third surface is the attachment surface of the film unit 5.

[0045] Imaging prism unit 1 (2) includes a prism and is located between imaging prism unit 2 (3) and the human eye. The prism can be made of plastic or glass. The film unit can be attached to the imaging prism or coated onto it. Imaging prism unit 2 (3) also includes a prism, which can be made of plastic or glass. Similarly, the film unit can be attached to or coated onto the prism. This film unit functions as a polarizing and reflecting light. Therefore, it can be composed of, but is not limited to, the following film materials: absorptive polarizers, quarter-wave plates, reflective polarizers, etc., and can be arbitrarily combined.

[0046] Imaging lens unit 3 4 is a lens group with aberration correction function. The lens group can be made of glass or plastic. Its surface shape includes, but is not limited to, the following types: diffractive surface lens, spherical lens, aspherical lens, freeform surface lens, Fresnel lens, flat plate lens, etc. Aspherical lens is preferred. If imaging lens unit 3 4 is a curved mirror, a semi-transparent and semi-reflective coating is provided on the outer side of the curved mirror (the side away from imaging prism unit 2 3). The semi-transparent and semi-reflective coating can be achieved by coating or by applying a film.

[0047] In one embodiment, the film unit 5 includes a first absorptive polarizer and a reflective polarizer. The reflective polarizer is disposed near the imaging prism unit 2, and the first absorptive polarizer is disposed near the imaging prism unit 1. Preferably, the reflective polarizer is attached to the imaging prism unit 2, and the first absorptive polarizer is attached to the imaging prism unit 1.

[0048] In one embodiment, the slow axis of the quarter-wave plate 6 is at an angle of 45° ± 1° to the reflection axis of the reflective polarizer, and the reflection axis of the reflective polarizer is parallel to the absorption axis of the first absorptive polarizer.

[0049] To ensure proper imaging, the reflective polarizer and the quarter-wave plate 6 have a specific angular relationship. The slow axis of the quarter-wave plate 6 needs to be attached at a 45° angle to the reflection axis of the reflective polarizer, with a tolerance of ±1 degree. This ensures that linearly polarized light is converted into standard circularly polarized light. The reflection axis of the reflective polarizer and the absorption axis of the first absorptive polarizer must be parallel to eliminate ghosting.

[0050] In one embodiment, a second absorptive polarizer 8 is provided on the side of the image source 1 near the imaging prism unit 2 3, and the thickness of the second absorptive polarizer 8 is 10μm~300μm.

[0051] If the second absorptive polarizer 8 is too thin, problems such as unstable optical performance, poor polarization effect, and inability to form a suitable shape will occur. It will also be more susceptible to external environmental influences, such as mechanical damage and chemical corrosion, thereby reducing its durability. On the other hand, if the second absorptive polarizer 8 is too thick, it will increase reflectivity, leading to increased light loss. It will also affect its polarization effect, resulting in poor optical performance and the risk of ghosting.

[0052] In one embodiment, the transmission axis of the second absorptive polarizer 8 is the long side of the image source 1, the slow axis of the quarter-wave plate 6 is at an angle of 45° with the horizontal direction, the transmission axis of the reflective polarizer is the vertical direction, and the long side of the image source 1 is the left-right direction when the human body wears it.

[0053] Among them, the slow axis of quarter-wave plate 6 is parallel to the horizontal direction (e.g. Figure 1 The angle between the lower surface of the imaging prism unit 2 (which is a horizontal plane) and the horizontal plane is 45°. This means that as viewed by the human eye, a 45° clockwise or counter-clockwise rotation is acceptable. The transmission axis of the reflective polarizer (PBS) is vertical, and the long side of the image source 1 corresponds to the left-right direction when worn by the human body (i.e.,...). Figure 1 (The direction perpendicular to the paper). Note that the relative position of the angle can be rotated as a whole.

[0054] In one embodiment, the image source 1 is used to emit 45° linearly polarized light, and the film unit 5 is used to reflect 45° linearly polarized light and transmit -45° linearly polarized light.

[0055] In one embodiment, the angle between the image source 1 and the horizontal direction is 3° to 45°, the angle between the surface of the imaging prism unit 1 near the film unit 5 and the horizontal direction is 10° to 60°, and the angle between the first and third surfaces of the imaging prism unit 2 is 10° to 60°. This facilitates four-fold folding, thereby ensuring a small size and better image quality.

[0056] In one embodiment, the ultrathin optical module also satisfies the following condition:

[0057] 1.5 <n1<1.9,1.5<n2<1.9,1.5<n3<1.8;

[0058] 20 <Vd1<65,30<Vd2<65,30<Vd3<65;

[0059] Where, n1, n2, and n3 are the refractive indices of the first imaging prism unit 2, the second imaging prism unit 3, and the third imaging lens unit 4 respectively, and Vd1, Vd2, and Vd3 are the Abbe numbers of the first imaging prism unit 2, the second imaging prism unit 3, and the third imaging lens unit 4 respectively.

[0060] In one embodiment, the ultra-thin optical module further satisfies the following conditions:

[0061] 0.5 < d1 < 5.0, 1 < d2 < 5.0, 0.5 < d3 < 3.5;

[0062] 0.15 < D1 < 2.0, 0 < D2 < 1.0, 0.05 < D3 < 2.0;

[0063] Where, d1, d2, and d3 are the thicknesses of the first imaging prism unit 2, the second imaging prism unit 3, and the third imaging lens unit 4 respectively, D1 is the air gap between the second imaging prism unit 3 and the display image source 1, D2 is the air gap between the second imaging prism unit 3 and the first imaging prism unit 2, and D3 is the air gap between the third imaging lens unit 4 and the second imaging prism unit 3, with the unit of mm.

[0064] In one embodiment, the radius of curvature C1 of the mirror surface on the side of the third imaging lens unit 4 close to the human eye satisfies: 200 < C1, and the radius of curvature C2 of the mirror surface far from the human eye satisfies: 30 < |C2| < 80, with the unit of mm.

[0065] In one embodiment, the ultra-thin optical module further includes a fourth imaging lens unit. The fourth imaging lens unit is located between the second imaging prism unit 3 and the display image source 1, and the fourth imaging lens unit includes at least one lens. The radius of curvature C3 of the mirror surface on the side of the fourth imaging lens unit close to the second imaging prism unit 3 satisfies: 20 < |C3| < 90, and the radius of curvature C4 of the mirror surface close to the display image source 1 satisfies: 20 < |C4| < 90, with the unit of mm.

[0066] In one embodiment, the third imaging lens unit 4 includes a first lens, and the first lens is a curved mirror.

[0067] In one embodiment, the mirror surface of each lens is one of a diffractive surface, a spherical surface, an aspherical surface, a freeform surface, a Fresnel surface, and a planar surface.

[0068] In one embodiment, the thickness of the film system unit 5 is 10 μm to 300 μm, the thickness of the quarter-wave plate 6 is 10 μm to 300 μm, and the thickness of the semi-transmissive semi-reflective film 7 is 30 μm to 500 μm.

[0069] In this context, excessively thin film units can lead to: 1. Difficulty in forming, increased fragility and deformation, thus affecting polarization effects; 2. Decreased durability: the material is more easily damaged due to its fragility, making it prone to wear and scratches. Excessive thickness, on the other hand, degrades optical performance: transmittance and polarization rate decrease, affecting its application in optical devices and increasing the likelihood of ghosting. A quarter-wave plate (6) is an optical device used to adjust the polarization state and change the phase of light. If too thin, it cannot be formed and is prone to brittleness; if too thick, it will produce ghosting. For semi-transparent and semi-reflective films (7), when using vapor deposition, if too thin, vapor deposition is impossible and thickness uniformity cannot be guaranteed; if too thick, there is a risk of film peeling off. Both excessively thin and excessively thick films make it difficult to guarantee imaging effects and stability.

[0070] In one embodiment, both imaging prism unit 2 and imaging prism unit 3 are triangular prisms. The specific shapes can be adjusted according to actual needs.

[0071] In one embodiment, the display image source 1 is one of an OLED display, an LCOS display, a Microled display, a DLP display, and an LBS display. The display image source 1 includes, but is not limited to, the above-mentioned devices, and is preferably an OLED display.

[0072] The following detailed description is provided through specific embodiments. In each embodiment, imaging prism unit one is prism one, imaging prism unit two is prism two, display image source 1 is display screen, reflecting mirror is curved mirror, and imaging lens unit four is lens four. Figure 1 The shape of the curved mirror is for illustrative purposes only and is not intended to limit the specific shape. Any surface of this ultrathin optical module that is aspherical adopts an even-order aspherical surface shape and satisfies the following aspherical formula:

[0073] ;

[0074] Where z is the sagitta, Y is the center height of the lens, k is the conic coefficient, and C is the curvature. Let N be the aspheric coefficient of the i-th order, and N be a positive integer.

[0075] Example 1:

[0076] The total length of the ultrathin optical module in this embodiment is 9mm, demonstrating a feasible four-reflection design. Specifically, a 110μm second absorptive polarizer 8 is attached to the image source 1, the film unit 5 has a thickness of 150μm, the quarter-wave plate 6 has a thickness of 30μm, and the semi-transparent and semi-reflective film 7 has a thickness of 50μm. The curved mirror in this embodiment is an easily fabricated hyperboloid lens. Specific optical parameters are shown in Tables 1 and 2.

[0077] Table 1

[0078]

[0079] Table 2

[0080]

[0081] Based on the above data, such as Figure 2 , 3 As shown, the MTF is greater than 0.2 at 10 lp / mm. Because this optical module is a visual optics system, and considering the angular resolution of the human eye, this MTF value ensures that the human eye receives a very clear and sharp image, effectively guaranteeing a comfortable wearing experience. The biggest advantage of this solution is that it can compress the overall length, with a total length of less than or equal to 9mm. Both the dot plot and the MTF value meet the requirements of human visual resolution.

[0082] Example 2:

[0083] The total length of the ultrathin optical module in this embodiment is 9mm, demonstrating a feasible four-reflection design. Specifically, an 80μm second absorptive polarizer 8 is attached to the image source 1, the film unit 5 has a thickness of 120μm, the quarter-wave plate 6 has a thickness of 60μm, and the semi-transparent and semi-reflective film 7 has a thickness of 70μm. The curved mirror in this embodiment is an easily fabricated plano-convex lens. Specific optical parameters are shown in Tables 3 and 4.

[0084] Table 3

[0085]

[0086] Table 4

[0087]

[0088] Based on the above data, such as Figure 4 , 5 As shown, the MTF is greater than 0.2 at 10 lp / mm. Because this optical module is a visual optics system, and considering the angular resolution of the human eye, this MTF value ensures that the human eye receives a very clear and sharp image, effectively guaranteeing a comfortable wearing experience. The biggest advantage of this solution is that it can compress the overall length, with a total length of less than or equal to 9mm. Both the dot plot and the MTF value meet the requirements of human visual resolution.

[0089] Example 3:

[0090] This embodiment of the ultra-thin optical module has a total length of 9mm, demonstrating a feasible four-fold reflection design. Specifically, a 100μm second absorptive polarizer 8 is attached to the image source 1, the film unit 5 has a thickness of 140μm, the quarter-wave plate 6 has a thickness of 60μm, and the semi-transparent and semi-reflective film 7 has a thickness of 60μm. In this embodiment, the mirror surface near the imaging prism unit 2 3 has only fourth and sixth order terms, making it an easily fabricated hyperboloid lens. It also demonstrates the possibility of adding a lens between the imaging prism unit 2 3 and the image source 1. Specific optical parameters are shown in Tables 5 and 6.

[0091] Table 5

[0092]

[0093] Table 6

[0094]

[0095] Based on the above data, such as Figure 6 , 7 As shown, the MTF is greater than 0.2 at 10 lp / mm. Because this optical module is a visual optics system, and considering the angular resolution of the human eye, this MTF value ensures that the human eye receives a very clear and sharp image, effectively guaranteeing a comfortable wearing experience. The biggest advantage of this solution is that it can compress the overall length, with a total length of less than or equal to 9mm. Both the dot plot and the MTF value meet the requirements of human visual resolution.

[0096] Example 4:

[0097] The total length of the ultrathin optical module in this embodiment is 8.5 mm, demonstrating a feasible four-fold reflection design and the possibility of further reducing the total length. Specifically, a 90 μm second absorptive polarizer 8 is attached to the image source 1, the film unit 5 has a thickness of 130 μm, the quarter-wave plate 6 has a thickness of 40 μm, and the semi-transparent and semi-reflective film 7 has a thickness of 50 μm. In this embodiment, the mirror surface near the imaging prism unit 3 has only fourth and sixth order terms, making it an easily fabricated hyperboloid lens. Specific optical parameters are shown in Tables 7 and 8.

[0098] Table 7

[0099]

[0100] Table 8

[0101]

[0102] Based on the above data, such as Figure 8 , 9As shown, the MTF is greater than 0.1 at 10 lp / mm. Because this optical module is a visual optics system, and considering the angular resolution of the human eye, this MTF value ensures that the human eye receives a very clear and sharp image, effectively guaranteeing a comfortable wearing experience. The biggest advantage of this solution is that it can compress the overall length, with a total length of less than or equal to 8.5mm. Both the dot plot and the MTF value meet the requirements of human visual resolution.

[0103] Working principle: Image source 1 emits linearly polarized light at 45°, which undergoes a first reflection at the first surface of imaging prism unit 2 3. The first reflected light then undergoes a second reflection at the second surface of imaging prism unit 2 3, and is reflected onto the film unit 5 attached to the third surface of imaging prism unit 2. Film unit 5 has an optical path modulation function, capable of reflecting 45° linearly polarized light and transmitting -45° linearly polarized light, achieving a third reflection of the light onto the curved surface of imaging lens unit 3 4, away from the human eye. This curved surface is equipped with a semi-transparent, semi-reflective film 7 to reflect the light back to imaging prism unit 2 3. At this point, the angle of the linearly polarized light becomes -45°, allowing it to pass through film unit 5 and ultimately reach the human eye for imaging. Figure 1 As shown.

[0104] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0105] The embodiments described above are merely specific and detailed examples of the embodiments described in this application, and should not be construed as limiting the scope of the application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. An ultra-thin optical module, characterized in that: The ultra-thin optical module includes a display image source (1), a first imaging prism unit (2), a second imaging prism unit (3), a third imaging lens unit (4), a film system unit (5), a quarter-wave plate (6), and a semi-transmissive and semi-reflective film (7). The light emitted by the display image source (1) is first reflected by the first surface of the second imaging prism unit (3), then reaches the second surface of the second imaging prism unit (3) for a second reflection, and then reaches the third surface of the second imaging prism unit (3) and is reflected by the film system unit (5) for a third reflection, and then successively passes through the second surface of the second imaging prism unit (3), the third imaging lens unit (4) and reaches the semi-transmissive and semi-reflective film (7). After being reflected by the semi-transmissive and semi-reflective film (7) for a fourth reflection, it then successively passes through the third imaging lens unit (4), the second imaging prism unit (3), the film system unit (5), the first imaging prism unit (2) and reaches the human eye for imaging. The quarter-wave plate (6) is located between the second imaging prism unit (3) and the third imaging lens unit (4), or between the film system unit (5) and the second imaging prism unit (3), and the focal length f1 of the third imaging lens unit (4) satisfies: 10mm < f1 < 30mm, and the focal length f of the ultra-thin optical module satisfies: 10mm < f < 22mm; The ultra-thin optical module also satisfies the following conditions: 0.5 < d1 < 5.0, 1 < d2 < 5.0, 0.5 < d3 < 3.5; 0.15 < D1< 2.0, 0<D2< 1.0, 0.05 <D3 < 2.0; Wherein, d1, d2, and d3 are the thicknesses of the first imaging prism unit (2), the second imaging prism unit (3), and the third imaging lens unit (4) in sequence, D1 is the air gap between the second imaging prism unit (3) and the display image source (1), D2 is the air gap between the second imaging prism unit (3) and the first imaging prism unit (2), D3 is the air gap between the third imaging lens unit (4) and the second imaging prism unit (3), and the unit is mm; The radius of curvature C1 of the mirror surface on the side of the third imaging lens unit (4) close to the human eye satisfies: 200 <C1, and the radius of curvature C2 of the mirror surface far from the human eye satisfies: -80<C2≤-60, and the unit is mm.

2. The ultra-thin optical module as described in claim 1, characterized in that: The film system unit (5) includes a first absorptive polarizer and a reflective polarizer. The reflective polarizer is arranged close to the second imaging prism unit (3), and the first absorptive polarizer is arranged close to the first imaging prism unit (2).

3. The ultra-thin optical module as described in claim 2, characterized in that: The slow axis of the quarter-wave plate (6) forms an angle of 45°±1° with the reflection axis of the reflective polarizer, and the reflection axis of the reflective polarizer is parallel to the absorption axis of the first absorptive polarizer.

4. The ultra-thin optical module as described in claim 2, characterized in that: A second absorptive polarizer (8) is further provided on one side of the display image source (1) close to the second imaging prism unit (3), and the thickness of the second absorptive polarizer (8) is 10μm~300μm.

5. The ultra-thin optical module as described in claim 4, characterized in that: The transmission axis of the second absorptive polarizer (8) is the long side of the display image source (1), the slow axis of the quarter-wave plate (6) is at an angle of 45° with the horizontal direction, the transmission axis of the reflective polarizer is the vertical direction, and the long side of the display image source (1) is the left and right direction when the human body wears it.

6. The ultra-thin optical module as described in claim 1, characterized in that: The display image source (1) is used to emit 45° linearly polarized light, and the film unit (5) is used to reflect 45° linearly polarized light and transmit -45° linearly polarized light.

7. The ultra-thin optical module as described in claim 1, characterized in that: The angle between the display image source (1) and the horizontal direction is 3°~45°, the angle between the surface of the imaging prism unit one (2) near the film unit (5) and the horizontal direction is 10°~60°, and the angle between the first surface and the third surface of the imaging prism unit two (3) is 10°~60°.

8. The ultra-thin optical module as described in claim 1, characterized in that: The ultra-thin optical module also meets the following conditions: 1.5 < n1 < 1.9, 1.5 < n2 < 1.9, 1.5 < n3 < 1.8; 20 < Vd1 < 65, 30 < Vd2 < 65, 30 < Vd3 < 65; Wherein, n1, n2, and n3 are the refractive indices of the imaging prism unit 1 (2), imaging prism unit 2 (3), and imaging lens unit 3 (4) respectively, and Vd1, Vd2, and Vd3 are the Abbe numbers of the imaging prism unit 1 (2), imaging prism unit 2 (3), and imaging lens unit 3 (4) respectively.

9. The ultra-thin optical module as described in claim 1, characterized in that: The ultra-thin optical module also includes an imaging lens unit four, which is located between the imaging prism unit two (3) and the display image source (1). The imaging lens unit four includes at least one lens. The radius of curvature C3 of the mirror surface of the imaging lens unit four near the imaging prism unit two (3) satisfies: 20 < |C3| < 90, and the radius of curvature C4 of the mirror surface near the display image source (1) satisfies: 20 < |C4| < 90, in mm.

10. The ultra-thin optical module as described in claim 1, characterized in that: The imaging lens unit three (4) includes a first lens, which is a curved mirror.

11. The ultra-thin optical module as described in claim 9 or 10, characterized in that: The mirror surface of each lens is one of the following: diffraction surface, spherical surface, aspherical surface, freeform surface, Fresnel surface, or plane.

12. The ultra-thin optical module as described in claim 1, characterized in that: The thickness of the membrane unit (5) is 10 μm to 300 μm, the thickness of the quarter-wave plate (6) is 10 μm to 300 μm, and the thickness of the semi-transparent and semi-reflective membrane (7) is 30 μm to 500 μm.

13. The ultra-thin optical module as described in claim 1, characterized in that: Both the imaging prism unit one (2) and the imaging prism unit two (3) are triangular prisms.

14. The ultra-thin optical module as described in claim 1, characterized in that: The display image source (1) is one of OLED display, LCOS display, Microled display, DLP display, or LBS display.

Images