A planar optical waveguide based on two-dimensional grating

Abstract

The present invention discloses a planar optical waveguide based on a two-dimensional grating, which belongs to the field of augmented reality technology. The present invention includes an optical waveguide transmission mechanism and a grating working mechanism; the optical waveguide transmission mechanism is a transparent parallel waveguide; the grating working mechanism is composed of a two-dimensional grating with a fixed period and an angle of 60°; the two-dimensional grating is protruding or recessed on the upper surface of the parallel waveguide. The image of the micro-projector can be incident on the optical waveguide in any area of ​​the grating working mechanism, and the human eye can view the output image in any area of ​​the grating working mechanism; the present invention can achieve coupling, pupil expansion and decoupling of the micro-projector image through a two-dimensional grating, effectively reducing the optical installation accuracy of the optical waveguide and the micro-projector and expanding the visible area of ​​the optical waveguide, effectively realizing low-cost manufacturing of augmented reality display devices. The present invention has a simple structure, is easy to mass-produce and process, and has flexible usage forms, and has high application value.

Description

Technical Field

[0001] The present invention relates to the technical field of augmented reality, and in particular to a planar optical waveguide based on a two-dimensional grating. Background Art

[0002] Augmented reality (AR) seamlessly integrates real-world and virtual world information. It simulates physical information, previously difficult to experience within a specific time and space in the real world, and then superimposes it on the real world through computer simulation. This virtual information is then applied to the real world and perceived by human senses, resulting in a sensory experience beyond reality. The real environment and virtual objects are superimposed on the same screen or space in real time and simultaneously exist.

[0003] Augmented reality technology not only has a wide range of applications in application fields similar to virtual reality technology, such as the research and development of cutting-edge weapons and aircraft, visualization of data models, virtual training, entertainment and art, but also because of its ability to enhance the display output of the real environment, it has more obvious advantages than virtual reality technology in medical research and anatomical training, precision instrument manufacturing and maintenance, military aircraft navigation, engineering design and remote robot control.

[0004] In order to realize an optically transmissive augmented reality display solution, some people have designed free-form surface prism elements, which use a refracting and reflecting light path plus a compensating prism to realize optically transmissive augmented reality display. However, due to the need for free-form surface prisms to achieve curvature, the thickness of the optical system of this solution cannot be made very thin while achieving a good visual experience, which limits the further thinning of eyewear-type augmented reality displays.

[0005] Other designs use planar waveguides, leveraging total internal reflection of light within the planar waveguide element to transmit the projector's output beam. Multiple reflective surfaces or gratings are then used to intercept the transmitted beam to expand the optical system's exit pupil, effectively reducing the thickness of the optical components. However, existing planar waveguide designs typically require separate design and processing for the image coupling, pupil expansion, and output, making manufacturing difficult and costly. Furthermore, the waveguide's display area is limited, resulting in limited flexibility. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention provides a planar optical waveguide based on a two-dimensional grating that integrates coupling, pupil expansion, and outcoupling. The optical waveguide of the present invention is easy to process and flexible and convenient to use.

[0007] The technical solution of the present invention is:

[0008] A planar optical waveguide based on a two-dimensional grating comprises an optical waveguide transmission mechanism and a grating operating mechanism; the optical waveguide transmission mechanism is a transparent parallel waveguide; the grating operating mechanism is composed of a two-dimensional grating with a fixed period and an angle of 60°; the two-dimensional grating protrudes or is recessed from the upper surface of the parallel waveguide.

[0009] The parallel waveguide is a flat plate structure made of an optical material transparent to visible light, and the upper and lower surfaces of the parallel waveguide are parallel.

[0010] When the present invention is in use, light emitted by the microprojector passes through any area of ​​the grating working mechanism and is diffracted by the two-dimensional grating to produce multiple orders of light directions that enter the optical waveguide. Within the optical waveguide transmission mechanism, this light is then transmitted outward through total internal reflection. Each time the light passes through the grating working mechanism, it is diffracted again. Some light is diffracted and coupled out of the optical waveguide into the human eye, while other light is diffracted into multiple orders of directions and continues to be transmitted within the optical waveguide. Ultimately, light is coupled out of the entire grating working mechanism area, allowing the human eye to observe a complete and continuous image throughout the entire grating working mechanism area.

[0011] As a preferred solution, the refractive index of the parallel waveguide is 1.4-2.2 and the thickness is 0.3-2.5 mm. The refractive index of optical materials currently on the market is generally within this range. Theoretically, the larger the refractive index of the parallel waveguide in the present invention, the better.

[0012] As a preferred solution, the period of the two-dimensional grating is 200 to 700 nm.

[0013] As a preferred solution, the two-dimensional grating is cylindrical or prism-shaped with a rhombus bottom surface. Of course, the two-dimensional grating can also be in other feasible shapes.

[0014] As a preferred solution, the diameter or side length of the two-dimensional grating is 50 to 650 nm, and the height or depth is 80 to 650 nm.

[0015] As a preferred solution, a fixed coupling-in point is provided on the grating operating mechanism. To address the problem of weakening light transmission intensity within the optical waveguide after the two-dimensional grating couples light out, which in turn causes the brightness of the final image to gradually decrease in the direction of light transmission, the depth of the two-dimensional grating is controlled by region, thereby controlling the uniformity of the light coupling-out intensity within each region. To facilitate control of intensity uniformity, a fixed coupling-in point is provided on the grating operating mechanism. Of course, if uniformity requirements are not stringent, depth modulation can be omitted and coupling can be performed at any position, meaning that a dedicated coupling-in point is not necessary.

[0016] Furthermore, the coupling-in point has a diameter or side length of 200 to 650 nm, and a height or depth of 200 to 650 nm.

[0017] As a preferred solution, the diameter or side length of the coupling-in point is greater than the diameter or side length of each coupling-out point located at its periphery, and the height or depth is greater than the height or depth of each coupling-out point located at its periphery.

[0018] Furthermore, the farther the out-coupling point is from the in-coupling point, the larger its diameter or side length.

[0019] As a preferred solution, the farther the out-coupling point is from the in-coupling point, the greater its height or depth.

[0020] The depth and shape of the two-dimensional grating are modulated to ensure better uniformity of the light outcoupling intensity in each area.

[0021] The beneficial effects of the present invention are:

[0022] 1. The optical waveguide transmission mechanism is a transparent parallel waveguide, and the grating operating mechanism is a two-dimensional grating with a fixed period and a 60° angle. The micro-projector image can enter the optical waveguide from any area of ​​the grating operating mechanism, and the human eye can view the output image from any area of ​​the grating operating mechanism.

[0023] 2. The present invention can achieve the coupling, pupil expansion and decoupling of the micro-projector image through a two-dimensional grating, effectively reducing the optical installation accuracy of the light guide and the micro-projector and expanding the visible area of ​​the light guide, effectively realizing the low-cost manufacturing of the augmented reality display device.

[0024] 3. The depth and shape of the parallel waveguide surface can be modulated by grating according to the area, thereby improving the uniformity of the light outcoupling intensity in each area.

[0025] 4. The present invention has a simple structure, is easy to mass-produce and process, and is flexible in use, thus having high industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 A schematic structural diagram of a planar optical waveguide based on a two-dimensional grating according to the present invention;

[0028] Figure 2 Schematic diagram of a cylindrical two-dimensional grating in the present invention;

[0029] Figure 3 This is a schematic diagram of the principle of light transmission in an optical waveguide when using the present invention;

[0030] Figure 4 This is a schematic diagram of the grating working mechanism divided into different areas in the present invention;

[0031] Figure 5 Schematic diagram of another structure of a planar optical waveguide based on a two-dimensional grating according to the present invention;

[0032] Figure 6 Schematic diagram of a two-dimensional grating (shape: a prism with a rhombus bottom surface) in the present invention;

[0033] Figure 7 Schematic diagram of the two-dimensional grating in the present invention being an elliptical cylinder;

[0034] Figure 8 Schematic diagram of a two-dimensional grating (shape: a prism with a double rhombus bottom surface) in the present invention;

[0035] Figure 9 Schematic diagram of the two-dimensional grating in the present invention being a triangular prism. DETAILED DESCRIPTION

[0036] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below with reference to specific diagrams and examples.

[0037] like Figure 1 、 Figure 2 As shown, the planar optical waveguide based on the two-dimensional grating of the present invention includes an optical waveguide transmission mechanism 1 and a grating operating mechanism 2.

[0038] The optical waveguide transmission mechanism 1 is a transparent parallel waveguide, which is a flat plate structure made of an optical material transparent to visible light. The upper and lower surfaces of the parallel waveguide are parallel, the thickness of the parallel waveguide is 0.3 to 2.5 mm, and the refractive index of the waveguide material is 1.4 to 2.2. Figure 2 The grating working mechanism 2 is composed of a two-dimensional grating with a fixed period and an angle of 60°. The grating period T ranges from 200 to 700 nm. The grating can be modulated in depth and shape according to the region on the waveguide surface. Figure 2 The shape of the two-dimensional grating is cylindrical. The two-dimensional grating can also be other shapes, such as Figure 6 、 Figure 7 、 Figure 8 、 Figure 9 shown.

[0039] Reference Figure 3After the light of the image of the micro-projector 3 is irradiated on any area a of the grating working area, the light is diffracted by the grating to produce four diffraction orders b, c, d, and e, which are transmitted in four directions in the optical waveguide respectively. The angle between these four beams of light and the waveguide interface in the optical waveguide is greater than the Brewster angle required for total reflection, ensuring that the light is transmitted losslessly in the waveguide transmission part. When the light beams b, c, d, and e are irradiated on the grating working area again, part of the light beam will enter the diffraction coupling waveguide respectively, and the remaining light beam will be diffracted by the two-dimensional grating into three orders again and continue to be transmitted by total reflection in the optical waveguide. For example, the light beam b will be diffracted into light beams f, g, and h and continue to be transmitted in the optical waveguide. This cycle will eventually allow light to be coupled out in the entire grating working area, so that the human eye 4 can see a complete and continuous image at any position.

[0040] Figure 1 The two-dimensional grating protrudes from the upper surface of the parallel waveguide. Figure 5 The planar optical waveguide based on the two-dimensional grating of the present invention can also be recessed in the upper surface of the parallel waveguide.

[0041] Example 1

[0042] like Figure 1 、 Figure 2 As shown, the planar optical waveguide based on the two-dimensional grating of the present invention includes an optical waveguide transmission mechanism 1 and a grating operating mechanism 2.

[0043] In this embodiment, the optical waveguide transmission mechanism 1 is a parallel plate glass with a thickness of 0.5 mm and a refractive index of 1.5.

[0044] A cylindrical two-dimensional grating with an angle of 60°, a period T of 360nm, a diameter R of 100nm, and a depth of 150nm is machined on the surface of parallel flat glass (optical waveguide) to form a grating working mechanism 2.

[0045] The optical waveguide was divided into 30 regions, A to E in the longitudinal direction and 1 to 6 in the transverse direction. The micro-projector image was projected into the optical waveguide from region C5. The image intensity was measured in the remaining regions and normalized. The measurement results are shown in Table 1.

[0046] Table 1 Image intensity test results of Example 1

[0047] 1 2 3 4 5 6 A 0.5 0.6 0.7 0.8 0.7 0.8 B 0.6 0.65 0.75 1 0.8 1 C 0.65 0.7 0.8 0.9 Incoupling 0.9 D 0.6 0.65 0.75 1 0.8 1 E 0.5 0.6 0.7 0.8 0.7 0.8

[0048] Example 2

[0049] like Figure 1 、 Figure 2 As shown, the planar optical waveguide based on the two-dimensional grating of the present invention includes an optical waveguide transmission mechanism 1 and a grating operating mechanism 2.

[0050] In this embodiment, the optical waveguide transmission mechanism 1 is a parallel plate glass with a thickness of 1.9 mm and a refractive index of 1.8.

[0051] A two-dimensional prism grating with a diamond bottom surface and an angle of 60°, a period T of 450nm, a side length of 200nm, and a depth of 250nm is machined on the surface of parallel flat glass (optical waveguide) to form a grating working mechanism 2.

[0052] The optical waveguide was divided into 30 regions, A to E in the longitudinal direction and 1 to 6 in the transverse direction. The micro-projector image was projected into the optical waveguide from region C4. The image intensity was measured in the remaining regions and normalized. The measurement results are shown in Table 1.

[0053] Table 2 Image intensity test results of Example 2

[0054] 1 2 3 4 5 6 A 0.65 0.75 0.85 0.75 0.85 0.75 B 0.7 0.75 1 0.85 1 0.75 C 0.75 0.85 0.9 Incoupling 0.9 0.85 D 0.7 0.8 1 0.8 1 0.8 E 0.65 0.75 0.85 0.7 0.85 0.75

[0055] Example 3

[0056] like Figure 1 、 Figure 2 As shown, the planar optical waveguide based on the two-dimensional grating of the present invention includes an optical waveguide transmission mechanism 1 and a grating operating mechanism 2.

[0057] In this embodiment, the optical waveguide transmission mechanism 1 is a parallel plate glass with a thickness of 0.5 mm and a refractive index of 1.5.

[0058] A cylindrical two-dimensional grating with an angle of 60°, a period T of 360nm, and a diameter of 100nm is machined on the surface of parallel flat glass (optical waveguide) to form a grating working mechanism 2.

[0059] To address the problem of the weakening of the light transmission intensity in the optical waveguide after the two-dimensional grating couples the light out, which in turn causes the brightness of the final image to gradually weaken in the direction of light transmission, the depth of the two-dimensional grating is controlled by region, thereby controlling the uniformity of the light coupling intensity in each region. The optical waveguide is divided into 30 regions, A to E in the longitudinal direction and 1 to 6 in the transverse direction. The depth division of the processed two-dimensional grating cylinder is shown in Table 3.

[0060] Table 3 Depth of two-dimensional grating cylinder in Example 3 by region

[0061] 1 2 3 4 5 6 A 250nm 200nm 170nm 140nm 120nm 140nm B 200nm 170nm 140nm 120nm 100nm 120nm C 200nm 170nm 140nm 120nm 250nm 120nm D 200nm 170nm 140nm 120nm 100nm 120nm E 250nm 200nm 170nm 140nm 120nm 140nm

[0062] The micro-projector image is projected from the C5 region into the optical waveguide, and the image intensity is measured in the remaining regions and normalized. The measurement results are shown in Table 4.

[0063] Table 4 Image intensity test results of Example 3

[0064] 1 2 3 4 5 6 A 0.85 0.88 0.95 0.96 0.7 0.96 B 0.9 0.92 0.95 1 0.8 1 C 0.9 0.92 0.95 0.97 Incoupling 0.97 D 0.9 0.92 0.95 1 0.8 1 E 0.85 0.88 0.95 0.97 0.7 0.97

[0065] Example 4

[0066] like Figure 1 、 Figure 2 As shown, the planar optical waveguide based on the two-dimensional grating of the present invention includes an optical waveguide transmission mechanism 1 and a grating operating mechanism 2.

[0067] In this embodiment, the optical waveguide transmission mechanism 1 is a parallel plate glass with a thickness of 0.5 mm and a refractive index of 1.5.

[0068] A cylindrical two-dimensional grating with an angle of 60°, a period T of 360nm, and a depth of 150nm is machined on the surface of parallel flat glass (optical waveguide) to form a grating working mechanism 2.

[0069] To address the problem of weakening light transmission intensity within the optical waveguide after the two-dimensional grating couples light out, which in turn causes the brightness of the final image to gradually weaken in the direction of light transmission, the depth of the two-dimensional grating is controlled by region, thereby controlling the uniformity of the light coupling intensity within each region. The optical waveguide is divided into 30 regions, A to E in the longitudinal direction and 1 to 6 in the transverse direction. The diameter R of the machined two-dimensional grating cylinder is divided into regions as shown in Table 3.

[0070] Table 5 Two-dimensional grating cylinder diameter R in Example 4 by region

[0071] 1 2 3 4 5 6 A 260nm 240nm 210nm 170nm 130nm 170nm B 240nm 210nm 170nm 130nm 100nm 130nm C 240nm 210nm 170nm 130nm 220nm 130nm D 240nm 210nm 170nm 130nm 100nm 130nm E 260nm 240nm 210nm 170nm 130nm 170nm

[0072] The micro-projector image is projected from area C5 into the optical waveguide, and the image intensity is measured in the remaining areas and normalized. The measurement results are shown in Table 6.

[0073] Table 6 Image intensity test results of Example 4

[0074] 1 2 3 4 5 6 A 0.82 0.88 0.91 0.94 0.94 0.94 B 0.88 0.91 0.95 1 0.96 1 C 0.88 0.91 0.93 0.96 Incoupling 0.96 D 0.88 0.91 0.93 1 0.96 1 E 0.82 0.88 0.91 0.94 0.94 0.94

[0075] This invention uses a fixed-period two-dimensional grating waveguide to achieve image incoupling, pupil expansion, and decoupling. Light from the microprojector, after passing through any area of ​​the grating's operating mechanism, is diffracted by the two-dimensional grating to produce multiple orders of light that enter the waveguide. After being transmitted through total internal reflection within the waveguide, the light is decoupled out of the waveguide, ultimately allowing the image to be visible in any area of ​​the grating's operating section. This invention boasts a simple structure, ease of mass production, and flexible application options, making it highly valuable for industrial applications.

[0076] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A planar optical waveguide based on a two-dimensional grating, characterized in that: The invention comprises an optical waveguide transmission mechanism and a grating working mechanism; the optical waveguide transmission mechanism is a transparent parallel waveguide; the grating working mechanism is composed of a two-dimensional grating with a fixed period and an angle of 60°; the two-dimensional grating is protruding or recessed on the upper surface of the parallel waveguide; the two-dimensional grating is modulated in depth and shape according to the area on the surface of the parallel waveguide.

2. The planar optical waveguide based on a two-dimensional grating according to claim 1, wherein: The parallel waveguide has a refractive index of 1.4 to 2.2 and a thickness of 0.3 to 2.5 mm.

3. The planar optical waveguide based on a two-dimensional grating according to claim 1, wherein: The period of the two-dimensional grating is 200-700 nm.

4. The planar optical waveguide based on a two-dimensional grating according to claim 1, wherein: The two-dimensional grating is cylindrical or prism-shaped with a rhombus bottom.

5. The planar optical waveguide based on a two-dimensional grating according to claim 1 or 4, characterized in that: The diameter or side length of the two-dimensional grating is 50-650 nm, and the height or depth is 80-650 nm.

6. The planar optical waveguide based on a two-dimensional grating according to claim 1, wherein: A fixed coupling point is provided on the grating operating mechanism.

7. The planar optical waveguide based on a two-dimensional grating according to claim 6, characterized in that: The diameter or side length of the coupling point is 200~650nm, and the height or depth is 200~650nm.

8. The planar optical waveguide based on a two-dimensional grating according to claim 6, characterized in that: The diameter or side length of the coupling-in point is greater than the diameter or side length of each coupling-out point located at its periphery, and the height or depth is greater than the height or depth of each coupling-out point located at its periphery.

9. The planar optical waveguide based on a two-dimensional grating according to claim 8, characterized in that: The farther the outgoing coupling point is from the incoming coupling point, the larger its diameter or side length.

10. The planar optical waveguide based on a two-dimensional grating according to claim 8, characterized in that: The farther the out-coupling point is from the in-coupling point, the greater its height or depth.

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