Optical waveguide system and projection equipment

Abstract

The utility model belongs to the technical field of optical waveguides, and discloses an optical waveguide system and projection equipment. According to the optical waveguide system, red light, green light and blue light are coupled into the three layers of HPDLC gratings respectively, red light, green light and blue light are coupled out of the three layers of HPDLC gratings respectively, switching of the diffraction state and the transparent state of the three layers of HPDLC gratings is controlled through a time sequence, only one layer of grating is in the diffraction state each time, stray light formed by crosstalk can be effectively avoided, and meanwhile the effect of persistence of human eyes can be utilized, so that the stability of the optical waveguide system is improved. And image superposition is carried out, so that a user can see colored and continuous images.

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. Firstly, the relatively large volume of micro-projectors is particularly prominent in the space-constrained in-vehicle environment, not only occupying valuable storage space but also potentially affecting the driver's line of sight and operational convenience. Secondly, the highly dependent projection effect on projection distance and the smoothness of the optical path makes it difficult to maintain a stable display effect in the complex and changing in-vehicle environment. Once the projection optical 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 additional shading measures are required, which is difficult to achieve in the 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, mutual diffraction of the RGB three-color gratings occurs. 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 Utility Model

[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 the 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 waveguide, a first input coupling grating, a second input coupling grating, a third input coupling grating, a first output coupling grating, a second output coupling grating, a third input coupling grating, and a controller; the waveguide covers the input coupling region and the output coupling region; the first input coupling grating, the second input coupling grating, and the third input coupling grating are all located in the input coupling region, and the first output coupling grating, the second output coupling grating, and the third input coupling grating are all located in the output coupling region, and they are all stacked on the surface or inside of the waveguide; the first input coupling grating is used for coupling in red light, the second input coupling grating is used for coupling in green light, the third input coupling grating is used for coupling in blue light, the first output coupling grating is used for coupling out red light, the second output coupling grating is used for coupling out green light, and the third input coupling grating is used for coupling out blue light; the first input coupling grating, the second input coupling grating, the third input coupling grating, the first output coupling grating, the second output coupling grating, and the third input coupling grating are all HPDLC gratings capable of switching between a diffractive state and a transparent state; the controller is used for timing control of the state switching of the HPDLC gratings. After each switching, only one of the first input coupling grating, the second input coupling grating, and the third input coupling grating is in the diffractive state, and only one of the first output coupling grating, the second output coupling grating, and the third input coupling grating is in the diffractive state.

[0009] This solution uses three layers of HPDLC gratings to couple in red, green, and blue light respectively, and also uses three layers of HPDLC gratings to couple out red, green, and blue light respectively. By controlling the switching between the diffractive state and the transparent state of the three layers of HPDLC gratings in sequence, only one grating is in the diffractive state at a time, which can effectively avoid crosstalk and form stray light. At the same time, the persistence of vision effect of the human eye can be utilized for image superposition, enabling the user to see a colorful and continuous image. During use, the first coupling grating, the second coupling grating, and the third coupling grating take turns being in the diffractive state. The first coupling grating diffracts the red light emitted by the collimation system, the second coupling grating diffracts the green light emitted by the collimation system, and the third coupling grating diffracts the blue light emitted by the collimation system, so that the red, green, and blue light are coupled into the waveguide in turn; the waveguide totally reflects the coupled red, green, and blue light, enabling them to continue to propagate forward to the output grating; the first output grating, the second output grating, and the third coupling grating take turns being in the diffractive state. The first output grating diffracts the red light transmitted by the waveguide, the second output grating diffracts the green light transmitted by the waveguide, and the third output grating diffracts the blue light transmitted by the waveguide, so that the red, green, and blue light are coupled out of the waveguide in turn.

[0010] Preferably, the first output grating, the second output grating, and the third coupling grating are all divided into multiple sub-gratings; the optical waveguide system preferably includes an eye tracker, which is used to collect and feedback the human eye position information to the controller; the controller controls the state switching of the sub-gratings corresponding to the human eye position in sequence according to the human eye position information feedback by the eye tracker, and controls the other sub-gratings to always be in the transparent state. Thus, it can be realized that when viewing at different positions in the eyebox, the brightness received by the user is the energy coupled out once, twice, or multiple times, with high light efficiency utilization, and the energy coupled out to the human eye at different positions is basically the same, and the brightness uniformity of the eyebox is also improved.

[0011] Preferably, the optical waveguide system has a turning area, and its structure correspondingly includes a first turning grating, a second turning grating, and a third turning grating. The first turning grating, the second turning grating, and the third turning grating are all located in the turning area, and they are all stacked on the surface or inside of the waveguide; the first turning grating is used to change the propagation direction of red light in the waveguide, the second turning grating is used to change the propagation direction of green light in the waveguide, and the third turning grating is used to change the propagation direction of blue light in the waveguide; the first turning grating, the second turning grating, and the third turning grating are all HPDLC gratings capable of switching between the diffractive state and the transparent state; after the controller controls the state switching of the HPDLC grating each time, only one of the first turning grating, the second turning grating, and the third turning grating is in the diffractive state. Thus, it can not only effectively avoid crosstalk and form stray light, utilize the persistence of vision effect to enable the user to see a colorful and continuous image, but also realize two-dimensional pupil dilation to ensure the viewing experience.

[0012] For the solution with a turning area, the first turning grating, the second turning grating, the third turning grating, the first output grating, the second output grating, and the third input grating are preferably divided into multiple sub-gratings; the optical waveguide system preferably includes an eye tracker for collecting and feeding back the human eye position information to the controller; the controller controls the state switching of the sub-gratings corresponding to the human eye position in sequence according to the human eye position information fed back by the eye tracker, and controls the other sub-gratings to be always in a transparent state. Thus, it can be realized that the brightness received by the user when viewing at different positions in the eye box is the energy that has been turned once, twice, or multiple times and output once, twice, or multiple times, with high light efficiency utilization, and the energy output to the human eye at different positions is basically the same, and the brightness uniformity in the eye box is also improved.

[0013] 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 waveguide, which can prevent the waveguide, output grating, etc. from being contaminated with dust.

[0014] 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 output 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 output energy, which can balance the brightness and improve the brightness uniformity in the eye box range.

[0015] An angle selection film is preferably provided on the dust-proof plate. The angle selection film is used to selectively transmit the output light and limit the transmission of stray light.

[0016] The period Λ of the first input grating 11 and the period Λ of the first output grating 12 satisfy: Λ 11 = Λ 12 , the period Λ of the second input grating 21 and the period Λ of the second output grating 22 satisfy: Λ 21 = Λ 22 , the period Λ of the third input grating 31 and the period Λ of the third output grating 32 satisfy: Λ 31 = Λ 32 , which helps to prevent dispersion.

[0017] In a second aspect, a projection device is proposed. The projection device includes a micro display source, a collimation system, and the above-mentioned optical waveguide system. 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 input area 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, red light, green light, and blue light are respectively coupled into by three layers of HPDLC gratings and respectively coupled out by three layers of HPDLC gratings. By controlling the switching of the diffraction state and the transparent state of the three layers of HPDLC gratings in sequence, only one layer of grating is in the diffraction state each time, which can effectively avoid crosstalk from forming stray light. At the same time, the visual persistence effect of the human eye can also be utilized for image superposition, enabling users to see colorful and continuous images.

[0019] The microdisplay source is selected from any one of the DLP optical engine module, LCOS optical engine module, LBS optical engine module, and OLED display module. The projection device can specifically be a vehicle-mounted projection device.

[0020] This solution has the following beneficial effects compared with the prior art: This solution uses three layers of HPDLC gratings to respectively couple in red light, green light, and blue light, and uses three layers of HPDLC gratings to respectively couple out red light, green light, and blue light. By controlling the switching of the diffraction state and the transparent state of the three layers of HPDLC gratings in sequence, only one layer of grating is in the diffraction state each time, which can effectively avoid crosstalk from forming stray light. At the same time, the visual persistence effect of the human eye can also be utilized for image superposition, enabling users to see colorful and continuous images. Description of the Drawings

[0021] The drawings are only for illustrative purposes and should not be construed as limitations to this solution; for better illustration of this solution, some components in the drawings will 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 the projection device (first timing).

[0023] Figure 2 It is a schematic diagram of the structure and optical path of the projection device (second timing).

[0024] Figure 3 It is a schematic diagram of the structure and optical path of the projection device (third timing).

[0025] Figure 4 It is a schematic diagram of the structure and optical path of the eye-tracking projection device (first timing).

[0026] Figure 5 It is a schematic diagram of the structure and optical path of the eye-tracking projection device (second timing).

[0027] Figure 6 It is a schematic diagram of the structure and optical path of the eye-tracking projection device (third timing).

[0028] Figure 7It is a schematic diagram of the structure and optical path of a two-dimensional pupil expansion projection device (first timing).

[0029] Figure 8 It is a schematic diagram of the structure and optical path of a two-dimensional pupil expansion eye tracking projection device (first timing).

[0030] Figure 9 It is a relationship diagram of energy and position.

[0031] Explanation of reference numerals: Microdisplay source 100, collimation system 200, optical waveguide system 300, coupling-in region 301, coupling-out region 302, turning region 303, waveguide 310, first coupling grating 321, second coupling grating 322, third coupling grating 323, first coupling-out grating 331, second coupling-out grating 332, third coupling-out grating 333, first turning grating 341, second turning grating 342, third turning grating 343, dust-proof plate 351, attenuation film 352, angle selection film 353. Detailed implementation manners

[0032] To enable those skilled in the art to better understand this solution, the following further elaborates on this solution in conjunction with specific embodiments.

[0033] Figures 1 to 8 It schematically shows a possible projection device. The projection device includes a microdisplay source 100, a collimation system 200, and an optical waveguide 310 system 300, and the microdisplay source 100, the collimation system 200, and the optical waveguide 310 system 300 are arranged in sequence.

[0034] 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 the user (such as the driver or passenger) through the optical system composed of the collimation system 200 and the optical waveguide 310 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.

[0035] The collimation system 200 collimates the image light beam from the microdisplay source 100, enabling the image light beam to be emitted as parallel light to the optical waveguide 310 system 300. Specifically, the collimation system 200 can be composed of one, two, or multiple (three or more) lenses. The surface type of the lens can be planar, spherical, aspherical, freeform surface, etc. This solution does not make special limitations on the number and surface type of the lenses.

[0036] The optical waveguide 310 system 300 has an input coupling region 301 and an output coupling region 302. The light emitted from the microdisplay source 100 enters the input coupling region 301 of the optical waveguide 310 system 300 after being collimated by the collimation system 200, is coupled in, propagated, and coupled out by the optical waveguide 310 system 300, and finally exits from the output coupling region 302 of the optical waveguide 310 system 300 to the human eye. Specifically, the optical waveguide 310 system 300 includes a waveguide 310, a first input coupling grating 321, a second input coupling grating 322, a third input coupling grating 323, a first output coupling grating 331, a second output coupling grating 332, a third input coupling grating 323, and a controller. Among them, the waveguide 310, the first input coupling grating 321, the second input coupling grating 322, the third input coupling grating 323, the first output coupling grating 331, the second output coupling grating 332, and the third input coupling grating 323 are all layered structures with two opposite surfaces, namely the first surface and the second surface. The waveguide 310 covers the input coupling region 301 and the output coupling region 302. The first input coupling grating 321, the second input coupling grating 322, and the third input coupling grating 323 are all located in the input coupling region 301. The first output coupling grating 331, the second output coupling grating 332, and the third input coupling grating 323 are all located in the output coupling region 302. The first input coupling grating 321, the second input coupling grating 322, the third input coupling grating 323, the first output coupling grating 331, the second output coupling grating 332, and the third input coupling grating 323 are all stacked on the surface or inside of the waveguide 310. Specifically, they can be arranged on the first surface of the waveguide 310, or on the second surface of the waveguide 310, or between the first surface and the second surface of the waveguide 310.

[0037] The waveguide 310 is used to realize the back-and-forth reflection propagation of the light beam. The waveguide 310 usually has a total reflection critical angle θ c , and for the light with the absolute value of the incident angle exceeding the total reflection critical angle θ c , when it irradiates on the first surface or the second surface of the waveguide 310 in the waveguide 310, it can be completely reflected back by the first surface or the second surface of the waveguide 310, and thus propagates along the extension direction of the waveguide 310 in the form of back-and-forth reflection in the waveguide 310.

[0038] The first input grating 321, the second input grating 322, and the third input grating 323 can be collectively referred to as input gratings, which are used to achieve the coupling of light beams. When light is emitted into the optical waveguide 310 system 300, the absolute value of its incident angle is usually less than the total reflection critical angle θ of the waveguide 310 c , and it cannot propagate back and forth in the waveguide 310. The input 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 310 c , so that it can propagate back and forth in the waveguide 310, thereby achieving the coupling of the light beam. Among them, the first input grating 321 is used to couple red light, the second input grating 322 is used to couple green light, and the third input grating 323 is used to couple blue light.

[0039] The first output grating 331, the second output grating 332, and the third output grating 333 can be collectively referred to as output gratings, which are used to achieve the output of light beams. When light propagates back and forth in the waveguide 310, the absolute value of its incident angle exceeds the total reflection critical angle θ of the waveguide 310 c , when it irradiates the surface of the waveguide 310 in the waveguide 310, it will be reflected back into the waveguide 310 and cannot be emitted outside the waveguide 310. 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 310 c , so that it can be emitted outside the waveguide 310, thereby achieving the output of the light beam. Among them, the first output grating 331 is used to output red light, the second output grating 332 is used to output green light, and the third input grating 323 is used to output blue light.

[0040] The first input grating 321, the second input grating 322, the third input grating 323, the first output grating 331, the second output grating 332, and the third input grating 323 are all HPDLC gratings. The HPDLC (Holographic polymer-dispersed liquid crystal) grating is a grating structure formed by using the holographic grating interference exposure method to regularly and periodically distribute the polymer and liquid crystal in the polymer-dispersed liquid crystal material. It can realize the switching between the diffractive state and the transparent state under the action of an external electric field. When the voltage is turned off, the HPDLC grating is in the diffractive state. At this time, the liquid crystal molecules are arranged periodically in the polymer matrix to form a grating structure, which diffracts the incident light. This diffraction effect enables light to be coupled into or out of the waveguide 310. When the voltage is turned on, the HPDLC grating is in the transparent state. At this time, the liquid crystal molecules are rearranged under the action of the electric field and tend to be parallel (or perpendicular, depending on the liquid crystal type) to the electric field direction, so that the grating structure becomes uniform, weakening the diffraction effect, and light can pass through almost unobstructed.

[0041] The controller is used for timing control of the state switching of the HPDLC grating. After each switching, only one of the first input grating 321, the second input grating 322, and the third input grating 323 is in the diffractive state, and only one of the first output grating 331, the second output grating 332, and the third input grating 323 is in the diffractive state. When red light, green light, and blue light are coupled out in the same waveguide 310, due to the small wavelength difference between green light and red light and blue light, red light will not only be coupled out by the red light output grating, but also by the green light output grating. Green light will not only be coupled out 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 coupled out 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, and 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. By timing control of the switching between the diffractive state and the transparent state of the three-layer grating (diffracting red, green, and blue light respectively), only one layer of the grating is in the diffractive state each time, which can effectively avoid the formation of crosstalk and stray light. At the same time, the persistence of vision effect of the human eye can also be utilized for image superposition, enabling the user to see a colorful and continuous image.

[0042] During use, the first input grating 321, the second input grating 322, and the third input grating 323 take turns to be in the diffractive state. The first input grating 321 diffracts the red light emitted by the collimating system 200, the second input grating 322 diffracts the green light emitted by the collimating system 200, and the third input grating 323 diffracts the blue light emitted by the collimating system 200, so that red light, green light, and blue light are alternately coupled into the waveguide 310; the waveguide 310 totally reflects the coupled red light, green light, and blue light, enabling them to continue to propagate forward to the output grating; the first output grating 331, the second output grating 332, and the third input grating 323 take turns to be in the diffractive state. The first output grating 331 diffracts the red light transmitted by the waveguide 310, the second output grating 332 diffracts the green light transmitted by the waveguide 310, and the third output grating 333 diffracts the blue light transmitted by the waveguide 310, so that red light, green light, and blue light are alternately coupled out of the waveguide 310.

[0043] The energy of the light passing through the output grating is divided into two parts. One part is the first-order light. The absolute value of the incident angle of this part of the light does not satisfy the total reflection condition. When it reaches the surface of the waveguide 310, it exits the waveguide 310 in the form of parallel light to the eyebox area outside the waveguide 310. The other part is the zero-order light. The absolute value of the incident angle of this part of the light satisfies the total reflection condition. After reaching the surface of the waveguide 310, it continues to propagate in the waveguide 310 in the form of total reflection until it passes through the output grating again and is divided into two parts again, and this cycle continues until it no longer passes through the output grating. Each time light is output, pupil expansion can be achieved once, increasing the area of the viewable 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 the viewing positions A1 to A5 decreases step by step. 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 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.

[0044] The first output grating 331, the second output grating 332, and the third input grating 323 can all be divided into multiple sub-gratings. Each sub-grating corresponds to one, two, or multiple pupil expansions. At the same time, an eye tracker (not shown) is configured to collect and feedback the human eye position information to the controller, so that the controller can, according to the human eye position information feedback by the eye tracker, control the state switching of the sub-grating corresponding to the human eye position in sequence, and control the other sub-gratings to always be in a transparent state. For example Figures 4 to 6 , when the human eye is located at the viewing position A2, the eye tracker can collect and feedback the human eye position information to the controller. The controller will, according to this human eye position information, control the state switching of the sub-grating G2 in sequence, and control the other sub-gratings to always be in a transparent state. This can achieve that the brightness received by the user when viewing at different positions of the eyebox is the energy output once, twice, or multiple times (to be compatible with the eye tracking error, each sub-grating can be set to correspond to 3 to 5 pupil expansions to ensure that the human eye can receive the image. In this case, there may be a situation where the output is 3 to 5 times). The light efficiency utilization rate is high, and the energy output to the human eye at different positions is basically the same, and the brightness uniformity of the eyebox is also improved.

[0045] The optical waveguide 310 system 300 can also be equipped with a turning area 303, such as Figure 7As shown. Correspondingly, the optical waveguide 310 system 300 further includes a first turning grating 341, a second turning grating 342, and a third turning grating 343. The first turning grating 341, the second turning grating 342, and the third turning grating 343 are also layered structures with two opposite surfaces, namely a first surface and a second surface respectively. The first turning grating 341, the second turning grating 342, and the third turning grating 343 are all located in the turning area 303, and they are stacked on the surface or inside of the waveguide 310. Specifically, they can be arranged on the first surface of the waveguide 310, or on the second surface of the waveguide 310, or between the first surface and the second surface of the waveguide 310.

[0046] The first turning grating 341, the second turning grating 342, and the third turning grating 343 can be collectively referred to as turning gratings, which are used to achieve the turning of light beams. After the light is coupled into the waveguide 310, it will reflect back and forth in one direction in the waveguide 310. When it is coupled out by the coupling-out grating and the pupil expansion is realized, it also performs multiple pupil expansions in the same direction, and only one-dimensional pupil expansion can be achieved. It is difficult for the coupled-out light to fill the eye box with requirements for both horizontal and vertical dimensions. The turning grating can change the propagation direction of the light in the waveguide 310 before the light enters the coupling-out area 302 and amplify the light beam range, so as to achieve the turning of the light beam. After the turning, it is coupled out by the coupling-out grating multiple times to realize two-dimensional pupil expansion. Among them, the first turning grating 341 is used to change the propagation direction of the red light in the waveguide 310, the second turning grating 342 is used to change the propagation direction of the green light in the waveguide 310, and the third turning grating 343 is used to change the propagation direction of the blue light in the waveguide 310.

[0047] The first turning grating 341, the second turning grating 342, and the third turning grating 343 are also HPDLC gratings. Correspondingly, the controller is also used for the timing control of the state switching of the first turning grating 341, the second turning grating 342, and the third turning grating 343. After each switching, only one of the first turning grating 341, the second turning grating 342, and the third turning grating 343 is in the diffractive state. During use, the first turning grating 341, the second turning grating 342, and the third turning grating 343 take turns to be in the diffractive state. The first turning grating 341 diffracts the red light transmitted by the waveguide 310, the second turning grating 342 diffracts the green light transmitted by the waveguide 310, and the third turning grating 343 diffracts the blue light transmitted by the waveguide 310, so that the red light, green light, and blue light propagating in the waveguide 310 turn and propagate to the coupling-out grating in turn, and finally are coupled out of the waveguide 310 by the coupling-out grating in turn.

[0048] For the solution where the optical waveguide 310 system 300 has an input coupling region 301, a turning region 303, and an output coupling region 302, the first turning grating 341, the second turning grating 342, the third turning grating 343, the first output coupling grating 331, the second output coupling grating 332, and the third input coupling grating 323 can all be divided into multiple sub-gratings. Each sub-grating corresponds to one, two, or multiple pupil expansions. Meanwhile, an eye tracker (not shown) is configured to collect and feedback the human eye position information to the controller, so that the controller can, according to the human eye position information feedback by the eye tracker, control the state switching of the sub-grating corresponding to the human eye position in sequence, and control other sub-gratings to always be in a transparent state. For example Figure 8 , when the human eye is located at the viewing position A22 (the position corresponding to the sub-grating G22), the eye tracker can collect and feedback the human eye position information to the controller. The controller will, according to this human eye position information, control the state switching of the sub-gratings G2 and G22 in sequence, and control other sub-gratings to always be in a transparent state. This can achieve that when viewing at different positions in the eye box, the brightness received by the user is the energy that has been turned once, twice, or multiple times and output coupled once, twice, or multiple times (to be compatible with the eye tracking error, each sub-grating can be set to correspond to 3 - 5 pupil expansions to ensure that the human eye can receive the image. At this time, there may be a situation where it is turned 3 - 5 times and output coupled 3 - 5 times). The light efficiency utilization rate is high, and the energy output coupled to the human eye at different positions is basically the same, and the brightness uniformity of the eye box is also improved.

[0049] As Figures 1 to 6 shown, the optical waveguide 310 system 300 can also be configured with a dust-proof plate 351. The dust-proof plate 351 covers at least the output coupling region 302 and is stacked on the light output side of the waveguide 310 to prevent the waveguide 310, the output coupling grating, etc. from being contaminated with dust. An attenuation film 352 can be configured on the dust-proof plate 351, or an angle selection film 353 can be configured, or both the attenuation film 352 and the angle selection film 353 can be configured simultaneously (as Figures 1 to 3 ), to screen the light output coupled by the output coupling grating. After being screened, the output coupled light enters the human eye. The dust-proof plate 351 is also a layered structure with two opposite surfaces, namely the first surface and the second surface. The attenuation film 352 and the angle selection film 353 can be stacked on the first surface of the dust-proof plate 351, or can be stacked on the second surface of the dust-proof plate 351; for the solution of simultaneously configuring the attenuation film 352 and the angle selection film 353, the attenuation film 352 and the angle selection film 353 can be respectively stacked on the two surfaces of the dust-proof plate 351, or can be jointly stacked on one surface of the dust-proof plate 351.

[0050] The attenuation of the attenuation film 352 to the light energy decreases monotonically in space, and its attenuation efficiency is consistent with the attenuation efficiency of the output coupled energy, and the attenuation direction is opposite to the propagation direction of the light in the waveguide 310, as Figure 9As shown in the figure, when the two are superimposed, the brightness at each position of the eyebox can be made to be W0 = W1 - W2, thereby achieving brightness balance and improving the brightness uniformity within the eyebox range.

[0051] The angle selection film 353 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 introduced 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 351, and the stray light often has a certain incident angle with the dust-proof plate 351. By adding the angle selection film 353 on the dust-proof plate 351, the light that is close to perpendicularly incident on the dust-proof plate 351 is selected to pass through, and the light that is incident on the dust-proof plate 351 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.

[0052] The period of the coupling-in grating is kept consistent with the period of the coupling-out grating, which helps to prevent chromatic dispersion. Specifically, the period Λ of the first coupling-in grating 321 11 is the same as the period Λ of the first coupling-out grating 331 12 satisfies: Λ 11 = Λ 12 , the period Λ of the second coupling-in grating 322 21 is the same as the period Λ of the second coupling-out grating 332 22 satisfies: Λ 21 = Λ 22 , the period Λ of the third coupling-in grating 323 31 is the same as the period Λ of the third coupling-out grating 333 32 satisfies: Λ 31 = Λ 32 .

[0053] This projection device can be used as a vehicle-mounted projection device. The exit pupil distance D of the optical waveguide 310 system 300 is preferably satisfied: 500mm ≤ D ≤ 800mm to ensure the user viewing experience.

[0054] Obviously, the above-mentioned embodiments of this solution are only examples for clearly illustrating 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 alterations can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of this solution should 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 waveguide, a first incoupling grating, a second incoupling grating, a third incoupling grating, a first outcoupling grating, a second outcoupling grating, a third incoupling grating and a controller; the waveguide covers the incoupling region and the outcoupling region; the first incoupling grating, the second incoupling grating and the third incoupling grating are all located in the incoupling region, the first outcoupling grating, the second outcoupling grating and the third incoupling grating are all located in the outcoupling region, and they are all stacked on the surface or inside of the waveguide; the first incoupling grating is used to couple in red light, the second incoupling grating is used to couple in green light, the third incoupling grating is used to couple in blue light, the first outcoupling grating is used to couple out red light, the second outcoupling grating is used to couple out green light, and the third incoupling grating is used to couple out blue light; The first coupling-in grating, the second coupling-in grating, the third coupling-in grating, the first coupling-out grating, the second coupling-out grating and the third coupling-in grating are all HPDLC gratings that can switch between a diffraction state and a transparent state; the controller is used for timing control of the state switching of the HPDLC grating, and after each switching, one and only one of the first coupling-in grating, the second coupling-in grating and the third coupling-in grating is in the diffraction state, and one and only one of the first coupling-out grating, the second coupling-out grating and the third coupling-in grating is in the diffraction state.

2. The optical waveguide system according to claim 1, characterized in that The first out-coupling grating, the second out-coupling grating and the third in-coupling grating are all divided into a plurality of sub-gratings; the optical waveguide system further comprises an eye tracker, which is used to collect and feed back information about the position of human eyes to the controller; the controller sequentially controls the state switching of the sub-grating corresponding to the position of the human eye according to the information about the position of the human eye fed back by the eye tracker, and controls the other sub-gratings to always be in a transparent state.

3. The optical waveguide system according to claim 1, characterized in that The optical waveguide system also has a turning zone, and its structure also includes a first turning grating, a second turning grating and a third turning grating. The first turning grating, the second turning grating and the third turning grating are all located in the turning zone, and they are all stacked on the surface or inside of the waveguide; the first turning grating is used to change the propagation direction of red light in the waveguide, the second turning grating is used to change the propagation direction of green light in the waveguide, and the third turning grating is used to change the propagation direction of blue light in the waveguide; the first turning grating, the second turning grating and the third turning grating are all HPDLC gratings that can switch between a diffraction state and a transparent state; each time the controller controls the HPDLC grating state to switch, one and only one of the first turning grating, the second turning grating and the third turning grating is in a diffraction state.

4. The optical waveguide system according to claim 3, characterized in that The first turning grating, the second turning grating, the third turning grating, the first out-coupling grating, the second out-coupling grating and the third in-coupling grating are all divided into a plurality of sub-gratings; the optical waveguide system further comprises an eye tracker, which is used to collect and feed back eye position information to the controller; the controller sequentially controls the state switching of the sub-grating corresponding to the eye position according to the eye position information fed back by the eye tracker, and controls the other sub-gratings to always be in a transparent state.

5. 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 output side of the waveguide.

6. The optical waveguide system according to claim 5, 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.

7. The optical waveguide system according to claim 5, 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.

8. The optical waveguide system according to any one of claims 1 to 7, 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 , the period of the second coupling grating Λ 21 and the period Λ of the second outcoupling grating 22 Satisfaction: Λ 21 =Λ 22 , the period of the third coupling grating Λ 31 and the period Λ of the third outcoupling grating 32 Satisfaction: Λ 31 =Λ 32 .

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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