CN115629438A

CN115629438A - Optical waveguide device and near-to-eye display device

Info

Publication number: CN115629438A
Application number: CN202211093834.2A
Authority: CN
Inventors: 顾志远; 赵鑫; 郑昱
Original assignee: Journey Technology Ltd
Current assignee: Journey Technology Ltd
Priority date: 2022-09-08
Filing date: 2022-09-08
Publication date: 2023-01-20

Abstract

The invention discloses an optical waveguide device and a near-eye display device. The two sub-waveguides are similar in structure and each includes a substrate and an outcoupling reverse surface. The two sub-waveguides are arranged to overlap at the thickness interface. The coupling-out reverse surfaces are embedded in the corresponding substrates at a first inclination angle theta in parallel with each other at a preset interval along the length direction of the substrates. And the preset distance is equal to the product of the sum of the thicknesses of the first substrate and the second substrate and cot theta. When light passes through the discontinuity of the two partial reflectors, the structure can effectively reduce the phenomenon that the same path of light penetrates through the same coupling-out reflecting surface for multiple times, thereby improving the uniformity. And the problem of discontinuous exit pupil is also avoided by splicing the two layers of waveguides.

Description

Optical waveguide device and near-to-eye display device

Technical Field

The embodiment of the invention relates to the optical technology, in particular to an optical waveguide device and a near-eye display device.

Background

A head-mounted display for augmented reality adopts near-to-eye display technology, can let people when looking over the surrounding environment, watch the virtual image that is showing, and the virtual image stack can build more lifelike experience on the real world of user perception, and the user sense of immersion is stronger.

The array waveguide augmented reality display system is divided into an imaging part (a projection light machine) and a waveguide sheet, wherein the imaging part is responsible for imaging an image displayed on a screen to infinity, namely outputting parallel light, and the waveguide sheet is responsible for transversely transmitting the parallel light output by the imaging part through the array waveguide and irradiating the parallel light into pupils of people from the front of eyes, so that the feeling of a virtual display screen is presented in a space in front of a lens.

However, since the array partial mirrors are mainly used as the coupling-out structures in the array optical waveguide, when light passes through the break between the two partial mirrors, there are multiple transmission and multiple reflection phenomena, which causes a decrease in the brightness uniformity of the displayed virtual image.

Disclosure of Invention

The embodiment of the invention provides an optical waveguide device and a near-eye display device, which are used for improving the brightness uniformity of a displayed virtual image.

An embodiment of the present invention provides an optical waveguide device, including:

a first sub-waveguide including a first substrate having a first parallel surface and a second parallel surface, and a plurality of first coupling-out reflection surfaces embedded between the first parallel surface and the second parallel surface at a first inclination angle θ in parallel with each other at a predetermined interval along a length direction of the first substrate;

a second sub-waveguide including a second substrate having a third parallel surface and a fourth parallel surface, and a plurality of second coupling-out reflection surfaces embedded between the third parallel surface and the fourth parallel surface at the first inclination angle θ in parallel with each other at the preset interval along a length direction of the second substrate;

wherein the second parallel surface is disposed in overlapping relation with the third parallel surface;

the first coupling-out reflecting surfaces and the second coupling-out reflecting surfaces are in one-to-one correspondence, and the preset distance is equal to the product of the sum of the thicknesses of the first substrate and the second substrate and cot theta.

In one embodiment, the second parallel surface is separated from the third parallel surface by air.

In one embodiment, the second parallel surface and the third parallel surface are arranged by gluing, and a total reflection film is arranged on the gluing surface.

In one embodiment, the first substrate has the same thickness as the second substrate.

In one embodiment, the method further comprises the following steps:

and the prism comprises an incident surface and an emergent surface, the emergent surface is positioned to be arranged close to one end of the first sub-waveguide and one end of the second sub-waveguide, and the incident surface is perpendicular to the optical axis of the main light ray.

In one embodiment, the first inclination angle θ is 45 degrees.

In one embodiment, the number of the first coupling-out reflecting surfaces and the second coupling-out reflecting surfaces is 5-8.

Based on the same inventive concept, an embodiment of the present invention provides a near-eye display device, including a display unit and an optical waveguide device as described in any of the above embodiments;

the image light emitted by the display unit enters the first sub-waveguide and the second sub-waveguide respectively to expand the pupil and is coupled out to human eyes.

In one embodiment, the display unit comprises a micro organic light emitting diode display, a micro light emitting diode display, or a liquid crystal display.

In one embodiment, the near-eye display device comprises a virtual reality display device or an augmented reality display device.

The optical waveguide device and the near-eye display device provided by the embodiment of the invention comprise two sub waveguides. The two sub-waveguides are similar in structure and each includes a substrate and an outcoupling reverse surface. The two sub-waveguides are arranged to overlap at the thickness interface. The coupling-out reverse surfaces are embedded in the corresponding substrates at a first inclination angle theta in parallel with each other at a preset interval along the length direction of the substrates. And the preset distance is equal to the product of the sum of the thickness of the first substrate and the thickness of the second substrate and cot theta. When light passes through the discontinuity of the two partial reflectors, the structure can effectively reduce the phenomenon that the same path of light penetrates through the same coupling-out reflecting surface for multiple times, thereby improving the uniformity. And moreover, by splicing the two layers of waveguides, the problem of discontinuous exit pupil is also avoided.

Drawings

FIG. 1 is a schematic diagram of a conventional arrayed optical waveguide structure;

FIG. 2 is a schematic structural diagram of an optical waveguide device according to an embodiment of the present invention;

fig. 3 is a schematic top view structure diagram of a near-eye display device according to an embodiment of the present invention;

figure 4 is a schematic diagram of exit pupil expansion principles provided by an embodiment of the present invention;

FIG. 5 is a schematic diagram of an exit pupil of an arrayed reflective waveguide at different positions as the exit pupil expands according to an embodiment of the present invention;

figure 6 is a schematic diagram of the propagation paths of three exit pupils in a waveguide provided by an embodiment of the present invention;

fig. 7 is a schematic top view structure diagram of an optical waveguide device according to an embodiment of the present invention.

Description of the main element reference numerals

10. An optical waveguide device; 11. a first sub-waveguide; 111. a first parallel surface; 113. a second parallel surface; 115. a first outcoupling reflective surface; 12. a second sub-waveguide; 121. a third parallel surface; 123. a fourth parallel surface; 125. a second outcoupling reflective surface; 13. a prism; 131. an incident surface; 133. an exit surface; 20. a display unit.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. It should be noted that the terms "upper", "lower", "left", "right", and the like used in the description of the embodiments of the present invention are used in the angle shown in the drawings, and should not be construed as limiting the embodiments of the present invention. In addition, in this context, it is also to be understood that when an element is referred to as being "on" or "under" another element, it can be directly formed on "or" under "the other element or be indirectly formed on" or "under" the other element through an intermediate element. The terms "first," "second," and the like, are used for descriptive purposes only and are not intended to denote any order, quantity, or importance, but rather are used to distinguish one element from another. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

Referring to fig. 1, a schematic diagram of an array optical waveguide structure provided in the conventional technical solution includes a coupling-in structure and a coupling-out structure. The incoupling structure is usually a prism, and is mainly used to couple the light emitted from the light engine into the waveguide for total reflection transmission. The outcoupling structure is usually an array of partially reflecting mirrors, which are mainly used to couple light out of the optical waveguide and to complete the pupil expansion.

When the structure is used for displaying a virtual image, the problem of nonuniform brightness exists due to the structure, and the bright and dark changes are obvious in the pupil expanding direction.

Referring to fig. 2, in order to improve the brightness uniformity, an embodiment of the invention provides an optical waveguide device 10. The optical waveguide device 10 includes a first sub-waveguide 11 and a second sub-waveguide 12. The first sub-waveguide 11 comprises a first substrate having a first parallel surface 111 and a second parallel surface 113 and a plurality of first out-coupling reflecting surfaces 115. A plurality of first coupling-out reflecting surfaces 115 are embedded between the first parallel surface 111 and the second parallel surface 113 at a first inclination angle θ in parallel with each other at a predetermined interval along a length direction of the first substrate. The second sub-waveguide 12 comprises a second substrate having a third 121 and a fourth 123 parallel surface and a plurality of second outcoupling reflective surfaces 125. A plurality of second coupling-out reflecting surfaces 125 are embedded between the third parallel surface 121 and the fourth parallel surface 123 at the first inclination angle θ in parallel with each other along the length direction of the second substrate at the preset interval. Wherein the second parallel surface 113 is disposed to overlap the third parallel surface 121. The first coupling-out reflecting surfaces 115 and the second coupling-out reflecting surfaces 125 are in one-to-one correspondence, and the preset distance is equal to the product of the sum of the thicknesses of the first and second substrates and cot θ.

The substrate material of the first sub-waveguide 11 and the second sub-waveguide 12 in the present embodiment may be a transparent glass material or a transparent resin material.

It should be noted that the outcoupling reflective surfaces (beam splitters) shown in the drawings are only schematic and are not limiting to the embodiments of the present invention, and the number of beam splitters may be designed according to practical situations in practical implementation, and in one embodiment, the number of the first outcoupling reflective surfaces 115 and the number of the second outcoupling reflective surfaces 125 are 5-8. In addition, the forming process of the coupling-out reflecting surfaces is not limited, for example, a plurality of parallelogram structures can be manufactured first, the two side surfaces of the parallelogram are plated with the semi-transparent half-returning film to form the beam splitter, and then the beam splitter and the semi-transparent half-returning film are attached together to form the coupling-out reflecting surfaces.

The structure of the optical waveguide device 10 in the present embodiment is formed by stacking two sub-waveguides. It can be understood that a conventional waveguide is split into two at its thickness interface. The first out-coupling reflecting surface 115 and the second out-coupling reflecting surface 125 may be partially reflecting mirrors. The first plurality of outcoupling reflective surfaces 115 makes an angle θ with the second parallel surface 113. The plurality of second coupling-out reflecting surfaces 125 and the fourth parallel surface 123 form an angle θ. It is understood that the angular range of the first inclination angle θ is not limited, and optionally, the first inclination angle θ is 45 degrees. Further, the sum of the first inclination angle theta and the critical angle of total reflection is in the range of 60-120 deg. This arrangement can further prevent the generation of stray light.

The preset distance is equal to the product of the sum of the thicknesses of the first substrate and the second substrate and the cot theta, so that the coupling-out reflecting surfaces of the single sub-waveguides are not spliced seamlessly, but the coupling-out reflecting surfaces formed by superposition are spliced seamlessly. In one embodiment, the first substrate and the second substrate have different thicknesses. In another embodiment, the first substrate has the same thickness as the second substrate.

The working principle of the optical waveguide device 10 provided in the present embodiment is as follows:

in use, the optical waveguide device 10 provided in the present embodiment is placed in a near-eye display apparatus, as shown in fig. 3, which includes a display unit 20 in addition to the optical waveguide device 10 described above.

The display unit 20 may include an image source and a collimating optical system. Image light emitted by an image source is output through collimation of the collimation optical system, enters the upper layer of sub-waveguide and the lower layer of sub-waveguide, is totally reflected respectively, and then is subjected to exit pupil expansion through the array partial reflector, wherein the exit pupil expansion principle is shown in figure 4. Fig. 4 (a) shows the change in the entrance pupil after the incident light enters the waveguide sheet. When an incident light enters the waveguide, the incident angle of the incident light must satisfy the total reflection condition, and the aperture size of the incident light needs to fill the entrance pupil of the waveguide.

The incident light beam enters the waveguide and starts total reflection transmission, and the entrance pupil is copied every time the incident light beam is totally reflected twice, as shown in the copy pupil 1 and the copy pupil 2 in fig. 4 (a), the copy pupils of the entrance pupil after being totally reflected twice and four times respectively are copied, and the light beam after being totally reflected can be equivalently regarded as the light beam emitted by the copy pupil after the position is changed. Thus, when a partially reflecting mirror is provided in the waveguide, all light rays from the replicated pupil will be reflected out of the waveguide, and the coupled-out pupil we call the exit pupil, as shown in figure 4 (b). When the partial reflecting mirror is provided with a plurality of partial reflecting mirrors, namely, when the partial reflecting mirror is arranged in an array, the reflecting mirror can reflect more light rays for copying the pupil, and the exit pupil expansion is finished.

According to the above analysis, although the array reflection waveguide can realize exit pupil expansion through the thin substrate and the array partial reflectors, there are some problems in the process, one of which is at the boundary of every two partial reflectors, which may have a problem of uneven brightness, so that human eyes may have bright and dark stripes when watching, which affects the experience effect.

Figure 5 shows the exit pupil of the reflective waveguide of the array at different positions as the exit pupil expands. The exit pupil section R0-1 indicates that the light rays emanating from the 0 th part of the entrance pupil are reflected by the partial mirror 1, R2-2 indicates that the light rays emanating from the 2 nd part of the entrance pupil are reflected by the partial mirror 2, and R4-3 indicates that the light rays emanating from the 4 th part of the entrance pupil are reflected by the partial mirror 3. The exit pupil R1-1 indicates that the light rays emerging from the 1 st part of the entrance pupil are reflected by the partial mirror 1, and R3-2 indicates that the light rays emerging from the 2 nd part of the entrance pupil are reflected by the partial mirror 3. The blue exit pupil R1-2 indicates that light rays emanating from the 1 st part of the entrance pupil are reflected by the partial mirror 2 and R3-3 indicates that light rays emanating from the 3 rd part of the entrance pupil are reflected by the partial mirror 3.

Fig. 6 shows the propagation paths of the exit pupils within the waveguides, respectively. The exit pupils R0-1 and R2-2 are the exit pupils R0-1 and R2 are the

exit pupils

0 and 2 part directly incident on the reflector and then reflected out of the waveguide, while the exit pupil R1-1 is more transmissive to the reflector 1 than to R0-1 and then reflected by the reflector 1, and the exit pupil R1-1 part contains energy equal to the energy left after the exit pupil 0 part is reflected by the reflector 1, so that R1-1 energy is less than R0-1, and a bright-dark cut-off is created, and similarly, the exit pupil R3-2 energy is less than the exit pupil R2-2. Similarly, the energy of the exit pupils R1-2 and R3-3 is weaker than that of the exit pupils R2-2 and R4-3, respectively. More intuitively, the exit pupils R0-1, R2-2 and R4-3 are equivalent to the entrance pupil and the copy pupil passing through only one reflective surface relative to the other exit pupils, and the other exit pupils pass through both reflective surfaces, so there is a difference in energy.

According to the above analysis, the problem of the brightness non-uniformity can be solved if the exit pupil and the copy pupil pass through only one reflective surface. Fig. 7 shows a corresponding way, in which there is no case where the exit pupil and the copy pupil pass through two reflecting surfaces, but since there is no seamless splicing between the array mirrors in this structure, the expanded exit pupil is discontinuous, and there is a position where the human eye cannot see an image when viewing the expanded exit pupil. We therefore propose the structure shown in fig. 2, which solves the problem of uneven brightness caused by the exit pupil and the copy pupil passing through two reflecting surfaces, and also avoids the problem of discontinuity of the exit pupil shown in fig. 7, by the combination of two layers of waveguides.

Two sub-waveguides are included in this embodiment. The two sub-waveguides are similar in structure and each includes a substrate and an outcoupling reverse surface. The two sub-waveguides are arranged to overlap at the thickness interface. The coupling-out reverse surfaces are embedded in the corresponding substrates at a first inclination angle theta in parallel with each other at a preset interval along the length direction of the substrates. And the preset distance is equal to the product of the sum of the thicknesses of the first substrate and the second substrate and cot theta. When light passes through the discontinuity of the two partial reflectors, the structure can effectively reduce the phenomenon that the same path of light penetrates through the same coupling-out reflecting surface for multiple times, thereby improving the uniformity. And moreover, by splicing the two layers of waveguides, the problem of discontinuous exit pupil is also avoided.

In one embodiment, the second parallel surface 113 is separated from the third parallel surface 121 by air. That is, it can be understood that the second parallel surface 113 is abutted against but not glued to the third parallel surface 121, and this structure can ensure that light entering the two sub-waveguides is transmitted only within their respective bases.

In one embodiment, the second parallel surface 113 and the third parallel surface 121 are arranged by being bonded together, and a total reflection film is arranged on the bonded surface. This arrangement ensures that light entering the two sub-waveguides is transmitted only within their respective bases.

In one embodiment, optical waveguide device 10 further includes a prism 13. The prism 13 includes an incident surface 131 and an exit surface 133, the exit surface 133 is positioned adjacent to one end of the first sub-waveguide 11 and the second sub-waveguide 12, and the incident surface 131 is perpendicular to the optical axis of the principal ray. The chief ray may be understood as a ray at a midpoint defining the field angle of the image.

In an alternative embodiment, as shown in fig. 2 and 3, the sides of the first and second substrates facing away from the coupling-out reflecting surface are convexly provided with corresponding tapers. The two corresponding tapers transition smoothly. The conical part is provided with an inclined plane which is a light incident plane. Specifically, the tapered portion may be integrally formed with the main body of the corresponding substrate, or may be an independent component attached to the corresponding sidewall of the main body of the corresponding substrate, which may be flexibly selected according to design requirements.

The prism 13 is a triangular prism, and the emergent surface of the triangular prism is attached to the incident surface of the conical part, and the emergent surface and the incident surface form a triangular structure.

Specifically, the triangular prism has an incident surface and an exit surface, and the other surfaces can be reflecting surfaces to ensure that light entering the triangular prism through the incident surface can enter the upper and lower sub-waveguides through the triangular prism.

Based on the same inventive concept, an embodiment of the present invention is a near-eye display device including a display unit 20 and the optical waveguide device 10 as described in any one of the above embodiments.

The image light emitted from the display unit 20 enters the first sub-waveguide 11 and the second sub-waveguide 12 respectively to expand the pupil and is coupled out to the human eye.

The display unit 20 may include a display and an imaging system. The display unit 20 may also comprise an illumination system when the display is a passive display source. When the display unit 20 emits a plurality of light beams which need to be polarized, the display unit 20 may further include a polarizer.

The near-eye display device in the embodiment of the present invention may be a virtual reality VR display device or an augmented reality AR display device. Specifically, when the substrate cannot transmit external light or is provided with a shading device, human eyes cannot observe external ambient light, the near-to-eye display device is a VR display device, and when the substrate has a certain transmittance to the external light, human eyes can simultaneously observe the external ambient light and light emitted by the display unit 20, the near-to-eye display device is an AR display device.

The display unit 20 is used for emitting imaging light beams, and the near-eye display device provided by the embodiment can be matched with various display units 20 for use. Alternatively, the display unit 20 includes a Micro organic light emitting diode (Micro OLED) display, a Micro light emitting diode (Micro LED) display, or a Liquid Crystal (LC) display. Further, the micro organic light emitting diode display, the micro light emitting diode display or the liquid crystal display may be all silicon-based displays. The silicon-based display takes a monocrystalline silicon wafer as a substrate, has the pixel size about 1/10 of that of the traditional display, has the advantages of low power consumption, small volume, high resolution and the like, and is very suitable for a near-to-eye display device for close-range observation.

It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. An optical waveguide device, comprising:

a second sub-waveguide including a second substrate having a third parallel surface and a fourth parallel surface and a plurality of second coupling-out reflecting surfaces embedded between the third parallel surface and the fourth parallel surface at the first inclination angle θ in parallel to each other at the preset interval along a length direction of the second substrate;

2. The optical waveguide device of claim 1 wherein the second parallel surface is separated from the third parallel surface by air.

3. The optical waveguide device according to claim 1, wherein the second parallel surface and the third parallel surface are arranged by being glued therebetween, and a total reflection film is provided on a glued surface thereof.

4. The optical waveguide device according to claim 1, wherein the thickness of the first substrate and the thickness of the second substrate are the same.

5. The optical waveguide device according to claim 1, further comprising:

6. The optical waveguide device of claim 1, wherein the first tilt angle θ is 45 degrees.

7. The optical waveguide device according to claim 1, wherein the number of the first outcoupling reflective surfaces and the second outcoupling reflective surfaces is 5 to 8.

8. A near-eye display device comprising a display unit and the optical waveguide device according to any one of claims 1 to 7;

9. A near-eye display device as claimed in claim 8 wherein the display unit comprises a micro-organic light emitting diode display, a micro-light emitting diode display or a liquid crystal display.

10. The near-eye display device of claim 8, wherein the near-eye display device comprises a virtual reality display device or an augmented reality display device.