Waveguide display system capable of being watched freely and expanding multi-angle information

Abstract

The invention discloses a multi-angle information expansion waveguide display system capable of being watched freely, which comprises an image source (1), an optical waveguide (2), an in-coupling optical element (3) and an out-coupling optical element (4), and is characterized in that light emitted by the image source (1) enters the optical waveguide (2) through the in-coupling optical element (3) and is subjected to total reflection propagation in the optical waveguide (2); light is guided out of the optical waveguide (2) after being modulated by the out-coupling optical element (4) and enters a human eye (5), the waveguide display system has at least one characteristic that the optical waveguide (2) is of a non-flat plate structure capable of adding a deflection angle for light and the out-coupling optical element (4) is of a regional aperiodic structure, incident light is totally reflected to different regions of a waveguide out-coupling range for many times, and the incident light is reflected to the human eye (5). Therefore, the information which can be received by the human eyes is expanded, the problem of imaging blurring caused by incomplete information acquired by the human eyes during far-field watching can be relieved, and the imaging quality of the optical waveguide display system is improved.

Description

Technical Field

[0001] The present invention relates to the field of waveguide display technology, and in particular to a waveguide display system with multi-angle information expansion that can be viewed freely. Background Art

[0002] Optical waveguide display technology is often used in AR and HUD to replicate and expand micro-image sources. It has the advantages of being thin and light and having good ambient light transmittance. It is one of the best alternatives for replacing mobile phones to realize a new generation of portable display terminals in the future, and as a transparent display to promote virtual fusion reality display technology. At present, optical waveguide display technology mainly uses parallel geometric optical elements, periodic diffractive optical elements or other diffractive optical elements with consistent angle deflection performance to couple out the light multiple times to the incident light to apply a deflection effect, so that it meets the total reflection condition and is transmitted in the optical waveguide. Then, the light is coupled out multiple times through parallel geometric optical elements, periodic diffractive optical elements or other diffractive optical elements with consistent angle deflection performance, so as to achieve the effect of replicating the image source and expanding the eye box. However, in this case, the emitted image sources are parallel to each other. When multiple replica images enter the human eye, they will overlap into non-overlapping images, causing image blur, which hinders the improvement of the image quality of optical waveguide display technology. In order to solve the above-mentioned problems, the distance between the replica images is currently mainly expanded by thickening the optical waveguide, so as to avoid multiple replica images from entering the human eye as much as possible and avoid overlapping imaging. However, on the one hand, this method increases the mass and volume of the system, which is not conducive to the lightweight display system. On the other hand, when the image source has a certain divergence angle, this method cannot guarantee that all imaging information can enter the eye after the observation distance reaches a certain value, which affects the reception of display information. Summary of the invention

[0003] The present invention aims to provide a waveguide display system with multi-angle information expansion that can be viewed freely. In this system, light is coupled out at different angles at different positions by designing the surface morphology of an optical waveguide as an additional deflection angle for light, or by using an outcoupling optical element with a gradually increasing, gradually decreasing or periodically changing outcoupling angle, thereby achieving two beneficial effects: 1. The change in outcoupling angle is conducive to preventing imaging ghosting caused by light entering the eye multiple times after outcoupling, so that the human eye can see a clear image when focusing to any position. When the waveguide system disclosed in the present invention is used for three-dimensional display, the feature of being able to focus arbitrarily is conducive to the human eye observing multi-depth images; 2. The change in outcoupling angle enables the human eye to receive outgoing light from different angles at different positions within a distance behind the outcoupling element, thereby expanding the information that the human eye can receive, alleviating the problem of blurred imaging caused by incomplete information obtained by the human eye during far-field viewing, and improving the imaging quality of the optical waveguide display system.

[0004] To achieve the above object, the present invention proposes a waveguide display system with multi-angle information expansion for free viewing, including an image source, an optical waveguide, an input coupling optical element, and an output coupling optical element. The light emitted by the image source enters the optical waveguide through the input coupling optical element, undergoes total internal reflection propagation inside the optical waveguide, and after being modulated by the output coupling optical element, is exported from the optical waveguide and enters the human eye. Its characteristics are as follows: Among them, the waveguide display system has at least one of the characteristics that the optical waveguide can be a non-flat structure that can add a deflection angle to light, and the output coupling optical element is a regionally non-uniform structure. The incident light undergoes total internal reflection multiple times to different regions within the output coupling range of the waveguide and is coupled out at different angles. At this time, the human eye moves freely within a certain distance after the waveguide output coupling element, and different positions can receive outgoing light from different angles.

[0005] The image source can be a two-dimensional image source or a three-dimensional image source.

[0006] The two-dimensional image source is one of LCOS, LED array, and OLED.

[0007] The three-dimensional image source is one of a holographic image source and a light field image source.

[0008] The optical waveguide can be one of a flat structure, a wedge structure, or a curved structure.

[0009] When the optical waveguide is one of a wedge structure or a curved structure, when light is transmitted inside the optical waveguide, it can add a deflection angle to the light, so that when the light undergoes total internal reflection and is transmitted to different spatial positions in the output coupling region, it is coupled out at different angles. At this time, the human eye moves freely within a certain distance after the waveguide output coupling element, and different positions can receive outgoing light from different angles, obtaining more complete image source information while avoiding image blurring.

[0010] The input coupling optical element is one of a geometric optical element and a diffractive optical element.

[0011] The output coupling optical element is one of a geometric optical element and a diffractive optical element.

[0012] When the optical waveguide is a flat structure, the input coupling optical element of the waveguide display system has at least one of the characteristics of a regionally non-periodic spatial distribution, and the property of the output coupling optical element 4 has a regionally non-periodic spatial distribution, so that when the light undergoes total internal reflection and is transmitted to different spatial positions in the output coupling region, it is coupled out at different angles. At this time, the human eye moves freely within a certain distance after the waveguide output coupling element, and different positions can receive outgoing light from different angles, obtaining more complete image source information while avoiding image blurring.

[0013] The input coupling optical element is a uniformly distributed structure or a regionally non-uniform structure.

[0014] The out-coupling optical element is a regionally non-uniform structure. The out-coupling optical element inside the region is a uniform structure, and the optical properties are different between different regions. When light propagates to the out-coupling optical element, the out-coupling optical element will cause the out-coupling angle of the light to gradually increase, gradually decrease, or change periodically.

[0015] Further, starting from any viewpoint within a cycle interval, the local tilt angle α of the bottom surface position where the light contacts next after total reflection 0 and the change amount Δθ of the out-coupling angle between this viewpoint and the viewpoint of the next out-coupling grating 0 satisfy: |2α 0 +Δθ 0 |≥Δθ, and Δθ can be obtained from the following formula:

[0016]

[0017] d i = 2W s tanθt total

[0018]

[0019] where, θ total is the total reflection angle of the optical waveguide under the minimum incident light, n is the refractive index of the optical waveguide, d i is the minimum distance between adjacent out-coupling viewpoints at the out-coupling surface of the optical waveguide, W s is the thickness of the thinnest part of the optical waveguide, d is the distance between the pupil and the optical waveguide, W is the size of the pupil, and Δθ is the angle of deviation between adjacent orders when the primary order is exactly completely separated for the pupil at a distance of d.

[0020] Beneficial effects: By using at least one of the methods of designing the surface topography of the optical waveguide to add a deflection angle to the light and using an out-coupling optical element with an out-coupling angle that gradually increases, gradually decreases, or changes periodically, the present invention makes the light be out-coupled at different angles at different positions, achieving two beneficial effects: 1. The change in the out-coupling angle is beneficial to preventing the imaging ghosting caused by the light entering the eye multiple times after out-coupling, enabling the human eye to see a clear image when focusing at any position. When the waveguide system disclosed in the present invention is used for three-dimensional display, the feature of being able to focus arbitrarily is beneficial for the human eye to observe multi-depth images; 2. The change in the out-coupling angle enables the human eye to receive out-coupled light from different angles at different positions within a certain distance after the out-coupling element, expanding the information that the human eye can receive, and can alleviate the problem of imaging blurring caused by incomplete information obtained by the human eye during far-field viewing, improving the imaging quality of the optical waveguide display system. The present invention has important application value for realizing a far-field freely viewable optical waveguide imaging system. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of a waveguide display system with free-viewing and multi-angle information expansion according to the present invention;

[0022] Figure 2 It is a schematic diagram of parameter comparison of a waveguide display system with free-viewing and multi-angle information expansion according to the present invention

[0023] Figure 3 It is a schematic structural diagram of a waveguide display system with free-viewing and multi-angle information expansion provided in Embodiment 1 of the present invention;

[0024] Figure 4 It is a schematic structural diagram of a waveguide display system with free-viewing and multi-angle information expansion provided in Embodiment 2 of the present invention;

[0025] Figure 5 It is a schematic structural diagram of a waveguide display system with free-viewing and multi-angle information expansion provided in Embodiment 3 of the present invention;

[0026] In the figure: 1, image source, 2, optical waveguide, 3, input coupling optical element, 4, output coupling optical element, 5, human eye, 6, optical waveguide, 7, image source, 8, uniform transmissive polarization volume holographic grating, 9, optical waveguide with a flat structure, 10, non-periodic transmissive polarization volume holographic grating, 11, collimated color image source, 12, prism, 13, full-color non-periodic transmissive polarization volume holographic grating, Detailed implementation manners

[0027] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0028] Embodiment 1

[0029] As Figure 2 shown, the present invention proposes a waveguide display system with free-viewing and multi-angle information expansion. The display system includes: an image source 7, an optical waveguide 6, an input coupling optical element 3, and an output coupling optical element 8. The light emitted by the image source 7 enters the optical waveguide 6 through the input coupling optical element 3, undergoes total internal reflection propagation inside the optical waveguide 6, and the light is modulated by the output coupling optical element 8 and then exported from the optical waveguide 6 and enters the human eye 5.

[0030] Specifically, the shape of the optical waveguide 6 can be one of a flat structure, a wedge structure, or a curved structure. In this embodiment, the optical waveguide 6 is a wedge-shaped structure that is inclined with respect to the surface away from the image source.

[0031] Specifically, the image source 7 has a certain divergence angle. For the convenience of explanation, the relevant outgoing image sources with divergence angles are simplified into three angles: -1st order, 0th order, and 1st order. The sum of the information of the image sources at these three angles is the complete information of the image source.

[0032] Specifically, the out-coupling optical element 8 is one of a geometric optical element and a diffractive optical element. In Embodiment 1, a polarization volume holographic grating is used, which is attached to one side of the optical waveguide surface close to the image source and has a certain distance from the in-coupling optical element.

[0033] Specifically, the polarization volume holographic grating 8 has a periodic structure. As Figure 2 shown, the polarization volume holographic grating 8 is a polarization volume holographic grating with consistent diffraction performance. For the convenience of explanation, in the figure, this polarization volume holographic grating is conceptually divided into three regions: A, B, and C. In practical applications, the performance of these three regions is exactly the same.

[0034] Specifically, the diffraction angle of the out-coupling optical element 8 should be such that the light can be deflected to a propagation direction with an angle less than the critical angle of the optical waveguide. In Embodiment 1, this polarization volume holographic grating 8 can exactly vertically couple out the 0th order light in Region B. The 1st order and -1st order lights experience a similar reverse process.

[0035] Next, the propagation process of the light is further explained. Assume that the divergence angle of the light source 7 is not large, and the deflection angles added by the grating to the lights of the three orders are the same. Therefore, the angle between the lights of the three orders during out-coupling is the same as that during in-coupling. Since the light is added a deflection angle each time it passes through the inclined side of the optical waveguide 7, there will also be an angular offset when the lights of the same order are out-coupled at different positions. Assume that the diffraction angle of Region A is deflected by an angle θ to the left relative to Region B. Similarly, Region C has a deflection angle of θ degrees to the right relative to Region B. This means that when the light is out-coupled in Region A, the light of the same order will have a deflection angle of θ relative to that in Region B. Assume the observation regions A and B. Taking the 0th order as an example, when the human eye 5 is at a certain distance from the out-coupling grating, the 0th order light that originally had the opportunity to enter the human eye at position ① in Region A no longer enters the human eye at position ①, while the 1st order light in Region A and the 0th order and -1st order lights in Region B can enter the human eye at position ① simultaneously, forming a complete image. Similarly, the human eye at position ② can receive a complete image composed of the -1st order light in Region B, the 1st order and 0th order lights in Region C, while avoiding the interference of the 1st order and 0th order lights in Region B and the -1st order light in Region C.

[0036] Embodiment 2

[0037] The difference from the above-mentioned Embodiment 1 is that, as Figure 3 shown, in this Embodiment 2, the optical waveguide 9 is of a flat structure, and when light propagates in the optical waveguide 9, the propagation direction thereof will not gradually deviate.

[0038] Specifically, the image source 7 has a certain divergence angle.

[0039] Specifically, the input coupling optical element 3 is one of a geometric optical element and a diffractive optical element. In this Embodiment 1, a transmissive polarization volume holographic grating attached to one side of the optical waveguide 9 close to the image source 7 and facing the image source 7 is used as the input coupling optical element. When the light emitted from the image source 7 passes through the transmissive polarization volume holographic grating 3, high-efficiency Bragg diffraction occurs, resulting in the deflection of its propagation direction. In order to enable the deflected light to propagate inside the optical waveguide 9, the diffraction angle of the polarization volume holographic grating 3 should exceed the critical angle of the optical waveguide 9.

[0040] Specifically, the output coupling optical element 10 is one of a geometric optical element and a diffractive optical element. In this Embodiment 2, a polarization volume holographic grating attached to one side of the optical waveguide 9 close to the image source 7 and having a certain distance from the input coupling optical element is used as the output coupling optical element.

[0041] Specifically, the polarization volume holographic grating 10 has a non-periodic structure. As Figure 3 shown, the polarization volume holographic grating 10 is composed of a plurality of periodic regions with continuously offset diffraction angles. Each periodic region is a uniform ordinary polarization volume holographic grating, which can perform high-efficiency Bragg diffraction on the incident light, causing it to leave the optical waveguide and propagate in the air, thereby entering the human eye. Between different regions, the diffraction angles of the polarization volume holographic grating are offset to a certain extent, which will cause the output angles of the incident light at the same angle when coupled out in different regions to change.

[0042] Next, the propagation process of light is further explained. For the convenience of explanation, the outgoing image source with a divergence angle is simplified into three angles of -1 level, 0 level, and 1 level. The sum of the information of the image sources at the three angles is the complete information of the image source. The output grating 10 has three regions A, B, and C with a uniform period. The diffraction angle of region B is opposite to that of the input grating 7. Therefore, the 0-level light perpendicular to the input waveguide will be output perpendicularly in region B, and the -1-level and 1-level lights will undergo the same reverse process when passing through the output coupling grating. Assuming that the divergence angle of the light source is not large, the deflection angles added by the grating to the lights of the three orders are the same. Therefore, the angle between the lights of the three orders during output is the same as that during input. The diffraction angle of region A is deflected to the left by an angle θ relative to region B. Similarly, region C has a deflection angle of θ degrees to the right relative to region B. This means that when the light is output in region A, the light of the same order will have a deflection angle of θ relative to that in region B. Assuming observation regions A and B, taking the 0 level as an example, when the human eye 5 is at a certain distance from the output coupling grating, the 0-level light in region A that originally had the opportunity to enter the human eye at position ① no longer enters the human eye at position ①, while the 1-level light in region A, the 0-level and -1-level lights in region B can enter the human eye at position ① simultaneously, forming a complete image. Similarly, the human eye at position ② can receive a complete image composed of the -1-level light in region B, the 1-level and 0-level lights in region C, while avoiding the interference of the 1-level and 0-level lights in region B and the -1-level light in region C.

[0043] Specifically, the periodically varying polarization volume holographic grating 10 can be prepared by means of micro-nano structure alignment or pixelated exposure alignment.

[0044] Embodiment 3

[0045] As Figure 4 shown, the difference from the above Embodiment 1 is that in this Embodiment 3, the optical waveguide 9 is a flat structure; the difference from the above Embodiment 2 is that the input coupling optical element 12 is a geometric optical element insensitive to wavelength.

[0046] Specifically, the image source 11 is collimated, and all the lights are parallel to each other.

[0047] Specifically, the image source 11 is a color image source, which is composed of three colors of red, green, and blue in this Embodiment 3.

[0048] Specifically, in this Embodiment 3, a prism on the side facing away from the image source 11 and opposite to the image source 11 is used as the input coupling optical element 12, and the three-color lights emitted by the image source 11 are reflected with high efficiency and achromatically when passing through the prism 12. In order to enable the deflected light to propagate inside the optical waveguide, the reflection angle of the prism 12 should exceed the critical angle of the optical waveguide 9.

[0049] Specifically, the out-coupling optical element 13 is one of a geometric optical element and a diffractive optical element. In this Embodiment 2, a polarization volume holographic grating is used, which is attached to one side of the optical waveguide surface close to the image source 11 and has a certain distance from the in-coupling optical element 12 in the horizontal direction. The polarization volume holographic grating is composed of a red layer that can respond to red light and a green layer that can respond to blue and green light. For simplicity, it is represented by a single block in the figure.

[0050] Specifically, the gratings of each block will cause a certain angle between the propagation directions of the three-color light coupled out. Between different regions, there is a certain shift in the diffraction angle of the polarization volume holographic grating, which will cause the emergence angle of the incident light at the same angle to change when coupled out in different regions.

[0051] Next, the propagation process of the light will be further explained. For the convenience of explanation, the information of the image source 11 is simplified into three parts: red light, green light, and blue light. The sum of the information of the three-color image sources is the complete information of the image source. The out-coupling grating 13 has three regions A, B, and C with consistent color performance. Among them, the diffraction angle of the B region for green light can just vertically couple out the green light. Since the blue light and the red light have different diffraction angles when passing through the out-coupling grating, their propagation directions form an angle with the green light when coupled out. Therefore, the angle between the three-color light when coupled out is determined by the double-layer polarization volume holographic grating. The diffraction angle of the A region for the three-color light deflects θ degrees to the left relative to the B region. Similarly, the color angle of the C region for the three-color light deflects θ degrees to the right relative to the B region. This means that when the light is coupled out in the A region, the light of the same color will have a θ-degree deflection relative to that in the B region. Assuming observation regions A and B, taking the 0th order as an example, when the human eye 5 is at a certain distance from the out-coupling grating, the green light that originally had the opportunity to enter the human eye at position ① in the A region no longer enters the human eye at position ①, while the blue light in the A region and the green and red lights in the B region can enter the human eye at position ① simultaneously, forming a complete image. Similarly, the human eye at position ② can receive a complete image composed of the blue light in region B, the green and red lights in region C, while avoiding the interference of the green and blue lights in region B and the red light in region C.

[0052] Specifically, the full-color periodically varying polarization volume holographic grating 13 can be prepared by means of micro-nano structure alignment or pixelated exposure alignment.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this invention belongs. The terms used in the specification of this invention herein are only for the purpose of describing specific embodiments and are not intended to limit the invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0054] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patent of the present invention. For those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A waveguide display system with multi-angle information expansion that can be viewed freely, characterized in that: The invention comprises an image source (1), an optical waveguide (2), an in-coupling optical element (3) and an out-coupling optical element (4). The light emitted by the image source (1) enters the optical waveguide (2) through the in-coupling optical element (3), is totally reflected and propagates inside the optical waveguide (2), and is modulated by the out-coupling optical element (4) and then guided out of the optical waveguide (2) to enter a human eye (5). The invention is characterized in that: the waveguide display system has at least one of the following characteristics: the optical waveguide (2) is a non-flat structure capable of adding a deflection angle to the light, and the out-coupling optical element (4) is a regional non-uniform structure. The incident light is totally reflected multiple times to different regions of the waveguide out-coupling range and is coupled out at different angles. At this time, the human eye (5) can move freely within a certain distance after the waveguide out of the coupling element, and different positions can receive outgoing light from different angles.

2. The waveguide display system with multi-angle information expansion capable of being viewed freely according to claim 1, characterized in that: The image source (1) is a two-dimensional image source or a three-dimensional image source.

3. The waveguide display system with multi-angle information expansion capable of being viewed freely according to claim 2, characterized in that: The two-dimensional image source is one of LCOS, LED array and OLED; The three-dimensional image source is one of a holographic image source and a light field image source; The optical waveguide (2) is one of a flat plate structure, a wedge-shaped structure or a curved structure.

4. The waveguide display system with multi-angle information expansion capable of being viewed freely according to claim 3, characterized in that: When the optical waveguide (2) is a wedge-shaped structure or a curved structure, when light is transmitted in the optical waveguide, a deflection angle can be added to the light, so that the light is coupled out at different angles when it is transmitted to different spatial positions of the outcoupling region through total reflection. At this time, the human eye (5) can move freely within a certain distance after the waveguide exits the coupling element, and different positions can receive outgoing light from different angles, thereby avoiding image blur and obtaining more complete image source information.

5. The waveguide display system with multi-angle information expansion capable of being viewed freely according to claim 1, characterized in that: The in-coupling optical element (3) is one of a geometric optical element and a diffractive optical element.

6. The waveguide display system with multi-angle information expansion capable of being viewed freely according to claim 1, characterized in that: The outcoupling optical element (4) is one of a geometric optical element and a diffractive optical element.

7. The waveguide display system with multi-angle information expansion capable of being viewed freely according to claim 4, characterized in that: When the optical waveguide (2) is a flat plate structure, the waveguide display system has an in-coupling optical element (3) having a regional non-periodic spatial distribution, and the property of the out-coupling optical element (4) has at least one characteristic of the regional non-periodic spatial distribution, so that when the light is transmitted to different spatial positions of the out-coupling region through total reflection, it is coupled out at different angles. At this time, the human eye (5) can move freely within a distance after the waveguide exits the coupling element, and different positions can receive outgoing light from different angles, thereby avoiding imaging blur and obtaining more complete image source information.

8. The waveguide display system with multi-angle information expansion capable of being viewed freely according to claim 7, characterized in that: The in-coupling optical element (3) is a uniformly distributed structure or a regionally non-uniform structure.

9. The waveguide display system with multi-angle information expansion capable of being viewed freely according to claim 8, characterized in that: The out-coupling optical element (4) is a regional non-uniform structure, the out-coupling optical element inside the region is a uniform structure, the optical properties of different regions are different, and when light propagates to the out-coupling optical element (4), the out-coupling optical element will cause the out-coupling angle of the light to gradually increase, gradually decrease, or change periodically.

10. The waveguide display system with multi-angle information expansion capable of being viewed freely according to claim 1, characterized in that: Starting from any viewpoint within a period, the local tilt angle α0 of the bottom surface position that the light contacts next time after total reflection and the outcoupling angle change Δθ0 between the viewpoint and the viewpoint of the next outcoupling grating satisfy: |2α0+Δθ0|≥Δθ, Δθ can be obtained from the following formula: d i =2W s tanθ total Among them, θ total is the total reflection angle of the optical waveguide under the minimum incident light, n is the refractive index of the optical waveguide, d i is the minimum distance between adjacent exit viewpoints on the exit surface of the light waveguide, W s is the thickness of the optical waveguide at its thinnest point, d is the distance between the pupil and the optical waveguide, W is the size of the pupil, and Δθ is the angle of displacement of adjacent orders when the main orders are just completely separated for the pupil at a distance d.

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