Optical waveguide system and projection device

Abstract

The utility model discloses an optical waveguide system and a projection device, and the optical waveguide system is provided with a coupling-in region and a coupling-out region, and comprises a first waveguide, a second waveguide, a first coupling-in grating, a second coupling-in grating, a first coupling-out grating and a second coupling-out grating. The first waveguide and the second waveguide cover the coupling-in region and the coupling-out region, and are stacked and arranged at an interval; the first coupling-in grating and the second coupling-in grating are both located in the coupling-in area, the first coupling-in grating is stacked on the surface of the first waveguide or in the first waveguide, and the second coupling-in grating is stacked on the surface of the second waveguide or in the second waveguide; the first coupling-out grating and the second coupling-out grating are both located in the coupling-out area, the first coupling-out grating is stacked on the surface of the first waveguide or in the first waveguide, and the second coupling-out grating is stacked on the surface of the second waveguide or in the second waveguide; the first coupling-in grating is used for coupling in red light and blue light, the first waveguide is used for transmitting the red light and the blue light, and the first coupling-out grating is used for coupling out the red light and the blue light; the second coupling-in grating is used for coupling in green light, the second waveguide is used for transmitting the green light, and the second coupling-out grating is used for coupling out the green light.

Description

Technical Field

[0001] This solution belongs to the technical field of optical waveguides, and specifically relates to an optical waveguide system and a projection device. Background Art

[0002] In the rapidly developing automotive industry, in-vehicle entertainment systems, as a crucial part of enhancing the driving and passenger experience, are undergoing unprecedented changes and innovations. With the increasing demand of consumers for high-quality and diversified entertainment, in-vehicle projection devices, as a new bridge connecting the in-vehicle space and visual enjoyment, are becoming increasingly important. Currently, the main in-vehicle projection devices on the market are micro-projector solutions, LCD liquid crystal display solutions, and head-up display (HUD) solutions. However, it is often difficult for them to achieve a perfect balance among high performance, portability, and user experience, which has become the main bottleneck restricting their further popularization and development.

[0003] Micro-projectors have been widely used in fields such as home theaters and business presentations due to their excellent image quality and clarity. However, when this technology is transplanted into the in-vehicle environment, its inherent defects emerge one by one. First of all, the relatively large volume of micro-projectors is particularly prominent in the in-vehicle space where every inch of space counts. It not only occupies valuable storage space but may also affect the driver's line of sight and operational convenience. Secondly, the projection effect highly depends on the projection distance and the smoothness of the light path, making it difficult to maintain a stable display effect in the complex and changeable in-vehicle environment. Once the projection light path is blocked, such as the movement of passengers or objects, it will cause the picture to be interrupted or distorted, seriously affecting the viewing experience. In addition, the complex optical system design and high manufacturing cost of micro-projectors also limit their popularization and application in mid- to low-end vehicle models.

[0004] Compared with micro-projectors, the LCD liquid crystal display solution has achieved significant optimization in terms of volume, and its thin, light, and portable characteristics highly fit the in-vehicle environment. However, this advantage has not been fully translated into an improvement in user experience. Problems such as uneven brightness and insufficient color saturation of the LCD screen's light source characteristics can easily cause visual fatigue and dizziness after long-term viewing, which is undoubtedly a negative factor that cannot be ignored for passengers who need to drive or ride for a long time. In addition, the display effect of the LCD screen is greatly reduced in a strong light environment and requires additional shading measures, which is difficult to achieve in an open in-vehicle environment.

[0005] The HUD solution can effectively guide the image light into the driver's line of sight through waveguide technology, enabling the driver to view vehicle information or navigation instructions without lowering their head. At the same time, it reduces light loss and distortion, which helps to improve the clarity and brightness of the image, and the display effect is not affected by ambient light, enhancing the driver's visual experience. However, when the waveguide is coupled out, there will be mutual diffraction of the RGB three-color gratings. The grating has angular selectivity, and the coupling-out angles of the same-color light on different gratings are inconsistent, resulting in a large amount of stray light and the phenomenon of RGB three-color light crosstalk. Summary of the Invention

[0006] This solution aims to overcome at least one defect in the prior art and provides an optical waveguide system for solving the problem of RGB three-color light crosstalk.

[0007] To solve the above technical problems, the following technical solutions are adopted:

[0008] In a first aspect, an optical waveguide system is proposed. The optical waveguide system has an input coupling region and an output coupling region, and its structure includes a first waveguide, a second waveguide, a first input coupling grating, a second input coupling grating, a first output coupling grating, and a second output coupling grating; both the first waveguide and the second waveguide cover the input coupling region and the output coupling region, and they are stacked and spaced apart; the first input coupling grating and the second input coupling grating are both located in the input coupling region, the first input coupling grating is stacked on the surface or inside of the first waveguide, and the second input coupling grating is stacked on the surface or inside of the second waveguide; the first output coupling grating and the second output coupling grating are both located in the output coupling region, the first output coupling grating is stacked on the surface or inside of the first waveguide, and the second output coupling grating is stacked on the surface or inside of the second waveguide; the first input coupling grating is used to couple red light and blue light into the first waveguide, the first waveguide is used to propagate red light and blue light to the first output coupling grating, and the first output coupling grating is used to couple out red light and blue light; the second input coupling grating is used to couple green light into the second waveguide, the second waveguide is used to propagate green light to the second output coupling grating, and the second output coupling grating is used to couple out green light.

[0009] This solution uses a first waveguide, a first coupling grating, and a second output grating to transmit red and blue light with a large wavelength difference. At the same time, a second waveguide, a second coupling grating, and a second output grating are used to separately transmit green light with a small wavelength difference from the red and blue light wavelengths, which can greatly weaken or even avoid the crosstalk problem caused by different wavelengths of light being coupled out at different angles at different output gratings. During use, the first coupling grating diffracts the red and blue light emitted by the collimation system, coupling them into the first waveguide; the first waveguide totally reflects the red and blue light coupled into by the first coupling grating, allowing them to continue to propagate forward to the first output grating; the first output grating diffracts the red and blue light transmitted by the first waveguide, generating a zero-order light and a first-order light, where the zero-order light continues to undergo total reflection and the first-order light is coupled out of the first waveguide. The second coupling grating diffracts the green light emitted by the collimation system, coupling them into the second waveguide; the second waveguide totally reflects the green light coupled into by the second coupling grating, allowing them to continue to propagate forward to the second output grating; the second output grating diffracts the green light transmitted by the second waveguide, generating a zero-order light and a first-order light, where the zero-order light continues to undergo total reflection and the first-order light is coupled out of the second waveguide.

[0010] The optical waveguide system is preferably configured with a dust-proof plate that at least covers the output area and is stacked on the light-emitting side of the first waveguide and the second waveguide, which can prevent the waveguide, output grating, etc. from being contaminated with dust.

[0011] An attenuation film is preferably stacked on the dust-proof plate. The attenuation of the light energy by the attenuation film decreases monotonically in space, and its attenuation efficiency is consistent with the attenuation efficiency of the coupled-out energy, and the attenuation direction is opposite to the propagation direction of the light in the waveguide. The attenuation of the light energy by the attenuation film is superimposed on the attenuation of the coupled-out energy, which can balance the brightness and improve the brightness uniformity in the eye box range.

[0012] An angle selection film is preferably stacked on the dust-proof plate. The angle selection film is used to selectively transmit the coupled-out light and limit the transmission of stray light.

[0013] The period Λ of the first coupling grating 11 and the period Λ of the first output grating 12 preferably satisfy: Λ 11 = Λ 12 , and the period Λ of the second coupling grating 21 and the period Λ of the second output grating 22 preferably satisfy: Λ 21 = Λ 22 , which helps to prevent dispersion.

[0014] The distance d between the first waveguide and the second waveguide preferably satisfies: d ≥ 0.002 mm, so as to ensure that the red and blue light can undergo total reflection propagation in the first waveguide.

[0015] The thickness h1 of the first waveguide preferably satisfies: 1.5 mm ≤ h1 ≤ 6 mm, and the thickness h2 of the second waveguide preferably satisfies: 1.5 mm ≤ h2 ≤ 6 mm, so as to ensure the volume of the projection device and the stability of the planar waveguide.

[0016] The exit pupil distance D of the optical waveguide system preferably satisfies: 500 mm ≤ D ≤ 800 mm, so as to ensure the user viewing experience, especially in the case of an in-vehicle projection device.

[0017] In a second aspect, a projection device is provided. The projection device includes a microdisplay source, a collimation system, and the above-mentioned optical waveguide system. The microdisplay source, the collimation system, and the optical waveguide system are arranged in sequence, and the light emitted from the microdisplay source enters the coupling region of the optical waveguide system after being collimated by the collimation system.

[0018] This solution uses the optical waveguide system proposed in the first aspect to transmit the image light beams emitted by the microdisplay source and the collimation system. Among them, the red light and the blue light are transmitted by the first waveguide, the first coupling grating, and the second output coupling grating, and the green light is separately transmitted by the second waveguide, the second coupling grating, and the second output coupling grating, which can greatly reduce or even avoid the crosstalk problem caused by the different angles of output coupling of light with different wavelengths at different output coupling gratings.

[0019] The microdisplay source is preferably any one of a DLP optical engine module, an LCOS optical engine module, an LBS optical engine module, and an OLED display module. The projection device may specifically be an in-vehicle projection device.

[0020] This solution has the following beneficial effects compared with the prior art: This solution uses the first waveguide, the first coupling grating, and the second output coupling grating to transmit the red light and the blue light with a large wavelength difference, and at the same time uses the second waveguide, the second coupling grating, and the second output coupling grating to separately transmit the green light with a small wavelength difference from the red and blue lights, which can greatly reduce or even avoid the crosstalk problem caused by the different angles of output coupling of light with different wavelengths at different output coupling gratings. Description of the Drawings

[0021] The drawings are only for illustrative purposes and should not be construed as limitations on this solution; for better illustration of this solution, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the dimensions of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0022] Figure 1 It is a schematic diagram of the structure and optical path of a projection device.

[0023] Figure 2 It is a schematic diagram of the structure and optical path of another projection device.

[0024] Figure 3 It is a diagram showing the relationship between energy and position.

[0025] Description of reference numerals: Microdisplay source 100, collimation system 200, optical waveguide system 300, light coupling-in region 301, light coupling-out region 302, first waveguide 311, first light coupling-in grating 312, first light coupling-out grating 313, second waveguide 321, second light coupling-in grating 322, second light coupling-out grating 323, dust-proof plate 331, attenuation film 332, angle selection film 333. Detailed implementation manners

[0026] To enable those skilled in the art to better understand this solution, the following further elaborates on this solution with specific embodiments.

[0027] Figures 1-2 Schematically shows a possible projection device. The projection device includes a microdisplay source 100, a collimation system 200, and an optical waveguide system 300, which are arranged in sequence.

[0028] The microdisplay source 100, as an image output module, is a core component in various projection display systems such as in-vehicle head-up display (HUD) and augmented reality head-up display (AR-HUD). It is responsible for generating high-quality image information and emitting image light beams, which are then projected into the line of sight of a user (such as a driver or a passenger) through an optical system composed of the collimation system 200 and the optical waveguide system 300, providing an intuitive and rich information display and interaction experience. Specifically, the microdisplay source 100 can be a DLP (Digital Light Processing) optical engine module, an LCOS (Liquid Crystal on Silicon) optical engine module, an LBS (Laser Beam Scanning) optical engine module, an OLED (Organic Light-Emitting Diode) display module, etc.

[0029] The collimation system 200 collimates the image light beams from the microdisplay source 100 so that the image light beams can be emitted as parallel light to the optical waveguide system 300. Specifically, the collimation system 200 can be composed of one, two, or multiple (three or more) lenses, and the surface type of the lenses can be planar, spherical, aspherical, freeform surface, etc. This solution does not particularly limit the number and surface type of the lenses.

[0030] The optical waveguide system 300 has an input coupling region 301 and an output coupling region 302. The light rays emitted from the microdisplay source 100 enter the input coupling region 301 of the optical waveguide system 300 after being collimated by the collimation system 200, are coupled in, propagated, and coupled out through the optical waveguide system 300, and finally are emitted from the output coupling region 302 of the optical waveguide system 300 to the human eye. Specifically, the optical waveguide system 300 includes a first waveguide 311, a second waveguide 321, a first input coupling grating 312, a second input coupling grating 322, a first output coupling grating 313, and a second output coupling grating 323. They are all layered structures with two opposite surfaces, namely a first surface and a second surface. The first waveguide 311 and the second waveguide 321 both cover the input coupling region 301 and the output coupling region 302, and they are stacked and arranged at a distance. The first input coupling grating 312 and the second input coupling grating 322 are both located in the input coupling region 301. The first input coupling grating 312 is stacked on the surface or inside the first waveguide 311. Specifically, it can be arranged on the first surface of the first waveguide 311, or on the second surface of the first waveguide 311, or between the first surface and the second surface of the first waveguide 311. The second input coupling grating 322 is stacked on the surface or inside the second waveguide 321. Specifically, it can be arranged on the first surface of the second waveguide 321, or on the second surface of the second waveguide 321, or between the first surface and the second surface of the second waveguide 321. The first output coupling grating 313 and the second output coupling grating 323 are both located in the output coupling region 302. The first output coupling grating 313 is stacked on the surface or inside the first waveguide 311. Specifically, it can be arranged on the first surface of the first waveguide 311, or on the second surface of the first waveguide 311, or between the first surface and the second surface of the first waveguide 311. The second output coupling grating 323 is stacked on the surface or inside the second waveguide 321. Specifically, it can be arranged on the first surface of the second waveguide 321, or on the second surface of the second waveguide 321, or between the first surface and the second surface of the second waveguide 321.

[0031] The first waveguide 311 and the second waveguide 321 can be collectively referred to as waveguides, which are used to realize the back-and-forth reflection propagation of light beams. The waveguide usually has a total reflection critical angle θ c , and for the light rays with the absolute value of the incident angle exceeding the total reflection critical angle θ c , when they irradiate on the first surface or the second surface of the waveguide in the waveguide, they can be completely reflected back by the first surface or the second surface of the waveguide, and thus propagate along the extension direction of the waveguide in the form of back-and-forth reflection in the waveguide. The first waveguide 311 and the second waveguide 321 can both be selected as planar waveguides.

[0032] The first input coupling grating 312 and the second input coupling grating 322 can be collectively referred to as input coupling gratings, which are used to realize the coupling in of light beams. When the light rays are emitted to the optical waveguide system 300, the absolute value of their incident angle is usually less than the total reflection critical angle θ of the waveguidec It cannot propagate back and forth in the waveguide. The coupling grating can diffract light and change its incident angle, so that the absolute value of the incident angle of the light exceeds the total reflection critical angle θ of the waveguide. c Therefore, it can propagate back and forth in the waveguide, thereby realizing the coupling of the light beam. Both the first coupling grating 312 and the second coupling grating 322 can be volume holographic gratings.

[0033] The first output grating 313 and the second output grating 323 can be collectively referred to as the output grating, which is used to realize the output of the light beam. When the light propagates back and forth in the waveguide, the absolute value of its incident angle exceeds the total reflection critical angle θ of the waveguide. c When it irradiates the surface of the waveguide in the waveguide, it will be reflected back into the waveguide and cannot be emitted out of the waveguide. The output grating can diffract light and change its incident angle, so that the absolute value of the incident angle of the light is less than the total reflection critical angle θ of the waveguide. c Therefore, it can be emitted out of the waveguide, thereby realizing the output of the light beam. Both the first output grating 313 and the second output grating 323 can be volume holographic gratings.

[0034] The first waveguide 311, the first coupling grating 312 and the first output grating 313 are used to realize the transmission of red light and blue light. The second waveguide 321, the second coupling grating 322 and the second output grating 323 are used to realize the transmission of green light. Specifically, the first coupling grating 312 is used to couple red light and blue light into the first waveguide 311. The first waveguide 311 is used to propagate red light and blue light to the first output grating 313. The first output grating 313 is used to output red light and blue light. The second coupling grating 322 is used to couple green light into the second waveguide 321. The second waveguide 321 is used to propagate green light to the second output grating 323. The second output grating 323 is used to output green light.

[0035] When red light, green light and blue light are output in the same waveguide, due to the small wavelength difference between green light and red light and blue light, red light will not only be output by the red light output grating, but also by the green light output grating. Green light will not only be output by the green light output grating, but also by the red light output grating and the blue light output grating. Blue light will not only be output by the blue light output grating, but also by the green light output grating. Coupled with the angular selectivity of the output grating, the output angles of red light in the red light output grating and the green light output grating are inconsistent. The output angles of green light in the green light output grating, the red light output grating and the blue light output grating are inconsistent. The output angles of blue light in the blue light output grating and the green light output grating are inconsistent, resulting in a large amount of stray light and causing crosstalk. The wavelength difference between red light and blue light is large, about 150 nm, and the crosstalk is small. Transmitting green light alone by the second waveguide 321, the second coupling grating 322 and the second output grating 323 can greatly reduce or even avoid the crosstalk problem.

[0036] During use, the first coupling grating 312 diffracts the red light and blue light emitted by the collimation system 200, and couples them into the first waveguide 311; the first waveguide 311 totally reflects the red light and blue light coupled by the first coupling grating 312, so that they continue to propagate forward to the first coupling-out grating 313; the first coupling-out grating 313 diffracts the red light and blue light transmitted by the first waveguide 311 to generate zero-order light and first-order light, where the zero-order light continues to undergo total reflection, and the first-order light is coupled out of the first waveguide 311. The second coupling grating 322 diffracts the green light emitted by the collimation system 200, and couples them into the second waveguide 321; the second waveguide 321 totally reflects the green light coupled by the second coupling grating 322, so that they continue to propagate forward to the second coupling-out grating 323; the second coupling-out grating 323 diffracts the green light transmitted by the second waveguide 321 to generate zero-order light and first-order light, where the zero-order light continues to undergo total reflection, and the first-order light is coupled out of the second waveguide 321.

[0037] The period of the coupling grating is kept consistent with the period of the coupling-out grating, which helps to prevent dispersion. Specifically, the period Λ of the first coupling grating 312 11 is the same as the period Λ of the first coupling-out grating 313 12 satisfies: Λ 11 = Λ 12 , and the period Λ of the second coupling grating 322 21 is the same as the period Λ of the second coupling-out grating 323 22 satisfies: Λ 21 = Λ 22 .

[0038] The distance d between the first waveguide 311 and the second waveguide 321 satisfies: d ≥ 0.002 mm, so as to ensure that the red light and blue light can undergo total reflection propagation in the first waveguide 311.

[0039] The thickness of the waveguide monolayer is in the range of 1.5 - 6 mm, so as to ensure the volume of the projection device and the stability of the planar waveguide. Specifically, the thickness h1 of the first waveguide 311 satisfies: 1.5 mm ≤ h1 ≤ 6 mm, and the thickness h2 of the second waveguide 321 satisfies: 1.5 mm ≤ h2 ≤ 6 mm.

[0040] The optical waveguide system 300 may also be configured with a dust-proof plate 331. The dust-proof plate 331 covers at least the light output area 302 and is stacked on the light output side of the first waveguide 311 and the second waveguide 321 to prevent the waveguides, output gratings, etc. from being contaminated with dust. An attenuation film 332 may be configured on the dust-proof plate 331, or an angle selection film 333 may be configured, or both the attenuation film 332 and the angle selection film 333 may be configured simultaneously to screen the light output by the output grating, and the output light enters the human eye after screening. The dust-proof plate 331 is also a layered structure with two opposite surfaces, namely the first surface and the second surface. The attenuation film 332 and the angle selection film 333 may be stacked on the first surface of the dust-proof plate 331, or may be stacked on the second surface of the dust-proof plate 331; for the solution with both the attenuation film 332 and the angle selection film 333 configured, the attenuation film 332 and the angle selection film 333 may be respectively stacked on the two surfaces of the dust-proof plate 331, or may be jointly stacked on one surface of the dust-proof plate 331.

[0041] The attenuation film 332 is used to balance the brightness at each position of the eyebox. The energy of the light passing through the output grating is divided into two parts. One part is the first-order light, and the absolute value of the incident angle of this part of the light does not satisfy the total reflection condition. When it reaches the waveguide surface, it exits the waveguide in the form of parallel light to the eyebox area outside the waveguide. The other part is the zero-order light, and the absolute value of the incident angle of this part of the light satisfies the total reflection condition. After reaching the waveguide surface, it continues to propagate in the waveguide in the form of total reflection until it passes through the output grating again and is divided into two parts again, and this process continues until it no longer passes through the output grating. Each time the output light can achieve pupil expansion, increasing the area of the visible region. According to the law of conservation of energy, it can be inferred that the energy output each time is decreasing, and the light energy that can be seen at viewing positions A1 - A5 decreases gradually. Therefore, the larger the pupil expansion, the lower the edge energy, and the worse the brightness uniformity at each position of the eyebox. For the user's viewing experience, the eyebox needs to meet certain size requirements. For example, the horizontal size of the eyebox in a vehicle-mounted display system is usually greater than 100 mm, and the vertical size is usually greater than 40 mm. In other words, multiple pupil expansions are inevitable. The attenuation of the attenuation film 332 to the light energy decreases monotonically in space, and its attenuation efficiency is consistent with the attenuation efficiency of the output energy. The attenuation direction is opposite to the propagation direction of the light in the waveguide, as Figure 3 shown. The superposition of the two can make the brightness at each position of the eyebox be W0 = W1 - W2, thus achieving brightness balance and improving the brightness uniformity in the eyebox range.

[0042] The angle selection film 333 is used to limit stray light from entering the human eye. After passing through the collimation system 200, the light is not absolutely collimated. Only an ideal optical system can achieve absolute collimation. Therefore, some stray light will also be brought during the coupling out process. The light entering the human eye is parallel light with a small angle. The coupled out light usually perpendicularly enters the dust-proof plate 331. The stray light often has a certain incident angle with the dust-proof plate 331. By adding the angle selection film 333 on the dust-proof plate 331, the light close to perpendicularly incident on the dust-proof plate 331 is selected to pass through, and the light incident on the dust-proof plate 331 at a large angle is restricted from passing through, thereby limiting the stray light from entering the human eye. The limiting angle can be determined according to the actual design efficiency and is not restricted in this case.

[0043] This projection device can be used as a vehicle-mounted projection device. The exit pupil distance D of the optical waveguide system 300 is preferably satisfied: 500mm ≤ D ≤ 800mm to ensure the user viewing experience.

[0044] Obviously, the above-mentioned embodiments of this solution are merely examples for clearly explaining this solution, rather than limitations on the implementation manners of this solution. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of this solution shall be included within the protection scope of the claims of this solution.

Claims

1. An optical waveguide system, characterized in that: The optical waveguide system has an incoupling region and an outcoupling region, and its structure includes a first waveguide, a second waveguide, a first incoupling grating, a second incoupling grating, a first outcoupling grating and a second outcoupling grating; the first waveguide and the second waveguide both cover the incoupling region and the outcoupling region, and they are stacked and arranged at a distance; the first incoupling grating and the second incoupling grating are both located in the incoupling region, the first incoupling grating is stacked and arranged on the surface or inside of the first waveguide, and the second incoupling grating is stacked and arranged on the surface or inside of the second waveguide; the first outcoupling grating and the second outcoupling grating are both located in the outcoupling region, the first outcoupling grating is stacked and arranged on the surface or inside of the first waveguide, and the second outcoupling grating is stacked and arranged on the surface or inside of the second waveguide; The first coupling-in grating is used to couple red light and blue light into the first waveguide, and the first waveguide is used to propagate red light and blue light to the first coupling-out grating, and the first coupling-out grating is used to couple out red light and blue light; the second coupling-in grating is used to couple green light into the second waveguide, and the second waveguide is used to propagate green light to the second coupling-out grating, and the second coupling-out grating is used to couple out green light.

2. The optical waveguide system according to claim 1, characterized in that The optical waveguide system further comprises a dustproof plate, which at least covers the outcoupling region and is stacked on the light-emitting sides of the first waveguide and the second waveguide.

3. The optical waveguide system according to claim 2, characterized in that An attenuation film is stacked on the dustproof plate. The attenuation of the light energy by the attenuation film decreases monotonically in space. Its attenuation efficiency is consistent with the attenuation efficiency of the coupled-out energy, and the attenuation direction is opposite to the propagation direction of the light in the waveguide.

4. The optical waveguide system according to claim 2, characterized in that An angle selection film is stacked on the dustproof plate, and the angle selection film is used to selectively transmit the outcoupled light and limit the transmission of stray light.

5. The optical waveguide system according to any one of claims 1 to 4, characterized in that: The period of the first coupling grating is 11 and the period Λ of the first outcoupling grating 12 Satisfaction: Λ 11 =Λ 12 ; and / or The period of the second coupling grating is 21 and the period Λ of the second outcoupling grating 22 Satisfaction: Λ 21 =Λ 22 .

6. The optical waveguide system according to any one of claims 1 to 4, characterized in that: A distance d between the first waveguide and the second waveguide satisfies: d≥0.002 mm.

7. The optical waveguide system according to any one of claims 1 to 4, characterized in that: The thickness h1 of the first waveguide satisfies: 1.5 mm ≤ h1 ≤ 6 mm; and / or The thickness h2 of the second waveguide satisfies: 1.5 mm ≤ h2 ≤ 6 mm.

8. The optical waveguide system according to any one of claims 1 to 4, characterized in that: The exit pupil distance D of the optical waveguide system satisfies: 500mm≤D≤800mm.

9. A projection device, characterized in that: The projection device comprises a micro-display source, a collimation system and the optical waveguide system according to any one of claims 1 to 8, wherein the micro-display source, the collimation system and the optical waveguide system are arranged in sequence, and the light emitted by the micro-display source enters the coupling region of the optical waveguide system after being collimated by the collimation system.

10. The projection device according to claim 9, characterized in that: The micro display source is selected from any one of a DLP optical machine module, an LCOS optical machine module, an LBS optical machine module, and an OLED display module; and / or The projection device is a vehicle-mounted projection device.

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