WO2022085873A1

WO2022085873A1 - Thin, wide viewing angle, near-eye display device, and method for same

Info

Publication number: WO2022085873A1
Application number: PCT/KR2021/002099
Authority: WO
Inventors: 방기승; 조영진; 이병호
Original assignee: 서울대학교산학협력단
Priority date: 2020-10-21
Filing date: 2021-02-19
Publication date: 2022-04-28

Abstract

Disclosed are a thin, wide viewing angle, near-eye display device, and a method for same. The display device comprises: a display panel that outputs light; a folding part which forms an optical path using a plurality of polarizing elements; a fresnel lens array in which fresnel lenses are disposed at set intervals; and a fresnel collector which is formed of a fresnel structure and forms an eye box at a set distance.

Description

Thin wide viewing angle near-eye display device and method therefor

An embodiment of the present invention relates to a near-eye display device having a wide field of view (FOV) and having a thin thickness, such as in the form of glasses, and a method therefor.

By combining a wearable display with real-time posture tracking technology to provide a screen as if the user is in a virtual space, the user can feel a lively experience as if they are in a virtual space. This is called Virtual Reality (VR). In addition, if implemented using a see-through display, users can experience the virtual world mixed with the real world. This is called Augmented Reality (AR).

The reason most VR devices on the market have a heavy headset-type structure is because of the large volume occupied by a simple optical system using one lens. Since the display must be positioned at a distance from the lens to the focal length of the lens, even a well-designed optical system requires an empty space of 5cm.

SUMMARY An object of the present invention is to provide a display apparatus and method capable of providing a wide viewing angle as well as being implemented as a device in the form of glasses by reducing a volume.

In order to achieve the above technical object, an example of a display device according to an embodiment of the present invention, a display panel for outputting light; a folding unit for forming an optical path using a plurality of polarizing elements; Fresnel lens array in which Fresnel lenses are arranged; and a Fresnel light collecting device formed in a Fresnel structure to form an eye box at a predetermined distance.

In order to achieve the above technical problem, an example of a display method according to an embodiment of the present invention includes the steps of outputting light using a display panel; forming an optical path over a predetermined distance by repeatedly reflecting light over a predetermined number of times using a plurality of polarizing elements; Floating an image of a display panel over a predetermined distance using a Fresnel lens array in which a plurality of Fresnel lenses are arranged; and forming an eye box at a predetermined distance by refracting light in an eye box direction using a Fresnel light collecting device formed in a Fresnel structure.

According to an embodiment of the present invention, it is possible to make a VR device in the form of glasses instead of the existing headset by securing a wide viewing angle while significantly reducing the volume of the optical system. In addition, a transparent augmented reality (AR) device can be implemented in a size as small as the shape of glasses.

1 is a view showing the configuration of an example of a near-eye display device according to an embodiment of the present invention;

2 is a view showing an example of a detailed configuration of a folding unit according to an embodiment of the present invention;

3 is a view showing the configuration of another embodiment of a display device according to an embodiment of the present invention;

4 is a view showing an example of a prototype of a display device according to an embodiment of the present invention;

5 is an enlarged view showing a layer structure of an optical system of a display device according to an embodiment of the present invention;

6 and 7 are diagrams illustrating an example of an image display experiment result using a display device according to an embodiment of the present invention.

Hereinafter, a near-eye display apparatus and method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating a configuration of an example of a near-eye display apparatus according to an embodiment of the present invention.

Referring to FIG. 1 , the display apparatus 100 includes a display panel 110 , a folding unit 120 , a Fresnel lens array 130 , and a Fresnel light collecting device 140 . Although the present embodiment shows the display device 100 for one eye 150 of the user for convenience of explanation, the display device 100 is in the form of glasses for outputting images to both eyes as shown in FIG. 4 or It can be manufactured in various forms, such as a VR device that can be worn on the head.

The display panel 110 may be implemented with various types of conventional panels, such as a liquid crystal display (LCD) or a light emitting diode (LED). In another embodiment, the display panel 110 may be implemented as a transparent panel as shown in FIG. 3 . The display panel may output an image for virtual reality or augmented reality.

The folding unit 120 extends the length of the transmission path of the light output from the display panel 110 beyond the physical thickness d of the folding unit 120 to reduce the thickness of the display device 100 . It is composed of a polarizing element. The light output from the display panel 110 is reflected several times within the folding unit 120 to increase the optical travel distance. An example of the detailed configuration of the folding unit 120 is shown in FIG. 2 .

The Fresnel lens array 130 is composed of a plurality of cells in which the Fresnel lens is present. That is, the Fresnel lens array 130 has a structure in which a plurality of Fresnel lenses are arranged. All of the Fresnel lenses may be arranged at the same interval, or all or some of the Fresnel lenses may be arranged at different intervals. The size of each cell of the Fresnel lens array 130 may be all the same or all or part of the size may be different from each other. In addition, all of the Fresnel lenses of each cell constituting the Fresnel lens array 130 may have the same shape, or some or all of them may be implemented in different shapes.

The Fresnel lens of each cell of the Fresnel lens array 130 has the effect that the image output from the display panel 110 appears at a distance (eg, 2m or more or infinity distance) at a distance (that is, floating) ) can contribute to making In order to implement a short focal length or a large refraction angle, a general optical element should have a very thick curved shape, but the Fresnel lens array 130 may implement a short focal length or a large refraction angle with a thin thickness. That is, when using the Fresnel lens array 130 compared to using a single lens, the focal length can be shortened, thereby reducing the volume of the display device 100 . Since the Fresnel lens array 130 can be implemented in a very thin and flat structure, it can be implemented in close contact with the folding unit 120 .

The Fresnel light collecting device 140 serves to collect the light output from the Fresnel lens array 130 toward the user's eyes. The viewing angle can be amplified through the Fresnel lens array 130 and the Fresnel light collecting device 140 , and an eye box can be formed with an appropriate eye relief. Here, the eye box refers to an area in which a projected image can be maintained clearly. The Fresnel light collecting device 140 may be implemented as a Fresnel lens or as a Fresnel prism array. A Fresnel prism array is a structure in which very small prisms (ie, micro prisms) are arranged.

In general, for a single lens, a VR optical system performs a floating function that floats the image of a display panel at a long distance and a light collection function that collects light toward the user's eyes at the same time. It is possible for one lens to simultaneously perform both functions when the focal length is long, but when the focal length is short and the f-number is small, it is difficult to satisfy both the floating function and the condensing function with one lens. In order to design a single lens that satisfies both functions, the complexity of the system increases, such as the thickness of the lens must be thick or the need for multiple layers, which makes it impossible to compose the optical system compactly. will fall out If the condensing function is not secured among the two functions, the viewing angle cannot be secured, and if the floating function is not secured, severe optical aberration occurs.

Accordingly, the present embodiment achieves the floating function and the light collecting function through the combination of the Fresnel lens array 130 and the Fresnel light collecting device 140 . For example, the Fresnel lens array 130 mainly focuses on the floating function to optimize the Fresnel lens structure of each cell, and the Fresnel light collecting device 140 mainly focuses on the light collecting function to focus on the Fresnel lens structure or The prism structure is optimized. Therefore, it is possible to implement a floating function and a light collecting function through the combination of the Fresnel lens array 130 and the Fresnel light collecting device 140, so that it is possible to implement an optical system having a wide viewing angle and little distortion while having a very thin form factor. According to an embodiment, various conventional methods for optimizing the structure of each Fresnel lens for a desired floating function and a desired light collecting function may be applied to the present embodiment.

In this embodiment, the refraction-based Fresnel optical elements 130 and 140 are more capable of realizing a full-color display than diffraction-based elements such as SRG (Surface Relief Grating), HOE (Holographic Optical Element), and PBP (Pancharanam Berry Phase). It is advantageous. A diffraction-based element has a very large chromatic aberration when a lens is formed because the diffraction angle is proportional to the wavelength of light. In order to overcome this and realize a full-color display, multiple diffraction crystals must be multiplexed, and three laser light sources with very thin spectral characteristics must be used for each color, which greatly increases the complexity of the system. However, the Fresnel optical elements 130 and 140 are refractive-based elements and have very small chromatic aberration compared to the diffraction-based elements. Since the chromatic aberration of the refraction-based device depends on the refractive index change characteristic with respect to the wavelength of the medium, the degree of change is very small in the visible light region, so that only one device can constitute a full-color display. The Fresnel optical elements 130 and 140 are more advantageous than the diffraction-based elements in realizing a compact system.

Since all the

optical elements

120 , 130 , and 140 of the present embodiment can be implemented in a thin structure, there is little thickness required for the optical system other than a predetermined physical distance d for forming the optical path of the folding unit 120 . In addition, since all optical elements can be designed in a flat structure, they can be implemented in the form of flat glasses as shown in FIG. 4 .

2 is a diagram illustrating an example of a detailed configuration of a folding unit according to an embodiment of the present invention.

Referring to FIG. 2 , the folding unit 120 includes a circular polarizer 200 , a beam splitter 210 , a wave plate 220 , and a polarization beam splitter. ) (230). The beam splitter 210 and the polarization beam splitter 230 are spaced apart by a predetermined distance to form an optical path.

The circularly polarized light unit 200 converts incident light into circularly polarized light. For example, the circularly polarized light unit 200 converts light (unpolarized light) emitted from the display panel 110 into circularly polarized light and outputs the converted light.

The beam splitter 210 transmits a portion of the incident light and reflects the rest. For example, the beam splitter 210 may reflect 50% of incident light and transmit 50% of the incident light. In this case, 50% of the circularly polarized light emitted from the circularly polarized part 200 passes through the beam splitter 210 . The transmittance of the beam splitter 210 may be variously modified according to an embodiment.

The wave plate 220 forms an optical path difference of a predetermined wavelength to the incident light. For example, the wave plate 220 may be implemented as a QWP (Quarter Wave Plate) that forms an optical path difference of 1/4λ. In this case, the wave plate 220 outputs linearly polarized light obtained by shifting the circularly polarized light emitted from the beam splitter 210 by a phase of 1/4λ.

The polarization beam splitter 230 transmits polarized light in a predefined direction. For example, the polarization beam splitter 230 may transmit p-polarized light or transmit s-polarized light. For example, when the polarization beam splitter 230 is implemented to transmit p-polarized light, the polarization beam splitter may reflect 100% of incident light, not p-polarized light, and transmit 100% of the p-polarized light.

For example, a case in which the polarization beam splitter 230 transmits p-polarized light and the wave plate 220 is implemented as QWP will be described. Circularly polarized light emitted from the circular polarizer 200 passes through the beam splitter 210 and is incident on the wave plate 220 , and the wave plate 220 outputs linearly polarized light having a phase shift of 1/4λ. Since the linearly polarized light emitted from the wave plate 220 is not p-polarized, it is reflected toward the wave plate 220 by the polarization beam splitter. The reflected linearly polarized light is directed toward the beam splitter 210 after a phase shift of 1/4λ occurs again while passing through the wave plate 220 . The beam splitter 210 reflects the light emitted from the wave plate 220 back to the wave plate 220 . The beam splitter 210 may reflect 50% of the light emitted from the wave plate 200 . The light reflected back to the wave plate 220 by the beam splitter 210 has a phase shift of 1/4λ again by the wave plate 220, and as a result, the linearly polarized light transmitted through the wave plate 220 is p - It becomes polarized. Accordingly, the linearly polarized light (ie, p-polarized light) emitted from the wave plate 220 passes through the polarization beam splitter 230 and is incident on the next optical element. When the beam splitter 210 reflects 50% of the incident light, the energy of the p-polarized light finally output from the polarization beam splitter 230 is 25% compared to the light initially incident on the folding unit 120 . .

Since the light emitted from the display panel 110 is repeated three times back and forth between the beam splitter 210 and the polarization beam splitter 230 of the folding unit 120, the display panel 110 and the Fresnel lens array 130. An optical distance equivalent to three times the physical distance between them can be secured. Since the physical distance of the optical system of the display apparatus 100 can be reduced by 1/3 through the folding unit 120 , the volume of the display apparatus 100 can be reduced. Since the physical distance can be further reduced through the folding unit 120 in addition to the reduced optical distance due to the use of the Fresnel lens array 130 , the distance of the optical system of the display apparatus 100 can be implemented very short.

3 is a diagram showing the configuration of another embodiment of a display device according to an embodiment of the present invention.

Referring to FIG. 3 , the display device includes a linear polarizer 300 , a transparent screen 310 , a waveguide 320 , and a polarization-dependent optical device 330 . The polarization-dependent optical device 330 includes a salpin Fresnel lens array 130 and a Fresnel light collecting device 140 in FIG. 1 . In this embodiment, the folding unit 120 may be omitted.

The transparent screen 310 is a transparent panel implemented with a holographic diffusion plate or a polarization-dependent diffusion plate.

The waveguide 320 provides a path for the light 340 to travel from the image source to the transparent screen 310 . The structure and method of the waveguide 320 for transmitting the light 340 from the image source to the transparent screen may be variously modified.

Using the transparent screen 310, the external light 350 of the real world and the light 345 output from the transparent screen 310 are both incident to the user's eyes. That is, when the display device of the present embodiment is used, augmented reality may be provided. The external light 350 is directly incident to the user's eye, and the light 345 of the transparent screen 310 must be incident to the user's eye through a predetermined optical system salpin in FIGS. 1 and 2 .

To this end, in the present embodiment, the polarization directions of the external light 350 and the light 345 of the transparent screen are different from each other. As an embodiment, light output from the transparent screen 310 may be implemented as p-polarized light. For example, the transparent screen 310 may receive the p-polarized image light 340 through the waveguide 320 and output it. In this case, the external light 350 in the real world may be converted into s-polarized light through the linear polarizer 300 . That is, the linear polarization unit 300 converts real-world light (unpolarized light) 350 coming from the outside of the display device into s-polarized light 360 and outputs it. In another embodiment, when the output light 345 of the transparent screen 310 is s-polarized light, the linear polarizer 300 may be implemented to convert the external light 350 into p-polarized light and output it. The following embodiment will be described on the assumption that the linear polarizer 300 outputs the s-polarized light 360 .

The s-polarized light 360 emitted from the linear polarizer 300 passes through the transparent screen 310 and the waveguide 320 as it is and is incident on the polarization-dependent optical device 330 . Since the s-polarized light 360 is light incident from the real world, it is preferable to pass through the polarization-dependent optical element 330 as it is and enter the user's eyes. The polarization-dependent optical element 330 may be implemented as a p-polarization-dependent optical element so that the s-polarization 360 can pass through the polarization-dependent optical element 330 as it is. For example, both of the Fresnel lens array 130 and the Fresnel light collecting device 140 constituting the polarization-dependent optical device 330 transmit p-polarized light and cause refraction for only s-polarized light (birefringent). ) can be implemented as a material with properties. At this time, the p-polarized light 345 emitted from the transparent screen 310 is refracted by the polarization-dependent light element 330 in the salpin method shown in FIG. 1 and is incident on the user's eyes.

4 is a diagram illustrating an example of a prototype of a display device according to an embodiment of the present invention. Referring to FIG. 4 , since the volume of the optical system can be very small, the display device can be implemented in the form of thin glasses.

Since the display device of the present embodiment can be implemented with a thin thickness and light weight, portability can be greatly improved, and wearability can be improved to increase the range of a user's virtual reality utilization time and environment. In particular, if it is linked with a camera that takes an external view, the display method of the present embodiment can be used to implement mixed reality (MR), a true meaning that can be worn for a long time even in daily life.

For example, beyond the field of virtual reality used for gaming and virtual experience within a certain range of space, it provides a work environment such as a virtual monitor in the work space in daily life, or as in the example of Pokemon-Go. Innovative visual experience in many fields, such as providing a virtual reality experience fused with the real world, enhancing user's visual information for military purposes using infrared camera information and high magnification camera information, or providing high magnification images to people with low vision can provide

In addition, when used as an augmented reality device, it provides the advantage of observing images of the real world with the naked eye without digital processing and provides a wide viewing angle comparable to that of a virtual reality device, so that users can feel a deeper sense of immersion. It is possible to implement mixed reality and augmented reality without concern.

5 is an enlarged view illustrating a layer structure of an optical system of a display device according to an embodiment of the present invention.

Referring to FIG. 5, the thickness of the folding part implemented by QWP, a beam splitter, QWP, which serves as a circular polarizer, a spacer, glass, and a polarizing beam splitter that forms a predetermined interval to form an optical path is several mm. can In addition, it is possible to implement a Fresnel lens array and a Fresnel lens in a thin and flat structure. Therefore, the display device can be implemented with a thickness of about 8.8 mm including the display panel. This embodiment is only one example to show that the thickness of the display device can be reduced, and the thickness of each element and the distance between the elements are not limited to this embodiment. For example, since the thickness of each element can be made thinner, it is also possible to implement a display device thinner than the present embodiment.

6, the left image 600 is rearranged to correspond to each cell of the Fresnel lens array of the display device to generate the right image 610, and then the right image 610 is input to the display panel of the display device . In order to implement virtual reality or augmented reality, various conventional methods for rearranging an image input to a display panel as shown in FIG. 6 may be applied to this embodiment.

Referring to FIG. 7 , when the display device outputs the right image 610 of FIG. 6 through the display panel, the user's eyes see the image 700 of a wide viewing angle as shown in FIG. 7 . Although the display device of this embodiment has a thin structure, it is possible to provide a user with a high-resolution full-color image having a viewing angle of 102 degrees * 102 degrees, and also can secure an eye box of a stable size of 8 mm * 8 mm or more.

So far, the present invention has been looked at with respect to preferred embodiments thereof. Those of ordinary skill in the art to which the present invention pertains will understand that the present invention can be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments are to be considered in an illustrative rather than a restrictive sense. The scope of the present invention is indicated in the claims rather than the foregoing description, and all differences within the scope equivalent thereto should be construed as being included in the present invention.

Claims

a display panel for outputting light;

a folding unit for forming an optical path using a plurality of polarizing elements;

a Fresnel lens array in which Fresnel lenses are arranged; and

A display device comprising: a Fresnel light collecting device formed in a Fresnel structure to form an eye box at a predetermined distance.
According to claim 1, wherein the Fresnel light collecting device,

A display device comprising a Fresnel lens or a Fresnel prism array.
According to claim 1, wherein the folding unit,

a circularly polarizing unit converting the light output from the display panel into circularly polarized light;

a beam splitter that transmits a portion of incident light and reflects a portion;

a wave plate forming an optical path difference of a predetermined wavelength; and

Including; a polarization beam splitter that transmits polarized light in a predefined direction;

The circularly polarized light passes through the beam splitter and is incident on the wave plate,

The linearly polarized light output from the wave plate is reflected or transmitted by the polarizing beam splitter according to a polarization state.
The method of claim 3, wherein the wave plate comprises:

A display device, characterized in that it is composed of a QWP (Quater Wave Plate) that forms an optical path difference of 1/4λ.
According to claim 3, The polarization beam splitter,

A display device, characterized in that it transmits p-polarized light or s-polarized light.
According to claim 1, wherein the display panel,

a transparent screen composed of a holographic diffuser or a polarization-dependent diffuser; and

and a waveguide that transmits light composed of polarized light in a first direction to the transparent screen.
outputting light using a display panel;

forming an optical path over a predetermined distance by repeatedly reflecting light over a predetermined number of times using a plurality of polarizing elements;

Floating an image of a display panel over a predetermined distance using a Fresnel lens array in which a plurality of Fresnel lenses are arranged; and

A display method comprising: forming an eye box at a predetermined distance by refracting light in an eye box direction using a Fresnel light collecting device formed in a Fresnel structure.