CN113341563A

CN113341563A - Head-mounted display

Info

Publication number: CN113341563A
Application number: CN202010099984.9A
Authority: CN
Inventors: 邱奕荣; 石维国; 黄士挺; 李彦贤
Original assignee: Hongxing Technology Co ltd; Acer Inc
Current assignee: Hongxing Technology Co ltd; Acer Inc
Priority date: 2020-02-18
Filing date: 2020-02-18
Publication date: 2021-09-03

Abstract

The invention provides a head-mounted display. The head-mounted display includes two display units disposed in front of both eyes of a user, respectively. Each display unit includes a display device, a fresnel lens, and a plurality of moth-eye structures. The fresnel lens is disposed between the display device and one of the eyes of the user. A plurality of moth-eye structures are located on at least one surface between the display device and one of the eyes of the user.

Description

Head-mounted display

Technical Field

The present disclosure relates to displays, and particularly to a head-mounted display.

Background

The head mounted display generally employs a form of an eye mask, a helmet, or the like to dispose the display device in front of the eyes of the user, and projects image light output from the display device into the eyes of the user through a lens element. In order to reduce the size and weight of the head-mounted display, the conventional head-mounted display uses a fresnel lens as a light guiding element, but a serious stray light problem is caused.

Fig. 1 is a partial schematic view of a conventional head-mounted display 1. Referring to fig. 1, image light B output from the display device 10 tends to be reflected by the surface S11B of the fresnel lens 11 on the way toward the eye E of the user, thereby forming stray light S. Furthermore, the display device 10 may reflect stray light S and make the stray light problem more complicated/severe. In addition, when the image light B output from the display device 10 is incident on the release surface S110B of the fresnel lens structure 110, stray light S is formed deviating from the designed light path. All of the above causes deterioration of the image quality of the head mounted display 1. Therefore, how to improve the stray light while reducing the size and weight of the head-mounted display becomes one of the problems that researchers want to solve.

Disclosure of Invention

The invention provides a head-mounted display which has good display quality.

According to an embodiment of the present invention, a head-mounted display includes two display units disposed in front of both eyes of a user, respectively. Each display unit includes a display device, a fresnel lens, and a plurality of moth-eye structures. The fresnel lens is disposed between the display device and one of the eyes of the user. A plurality of moth-eye structures are located on at least one surface between the display device and one of the eyes of the user.

In an embodiment according to the present invention, the fresnel lens structure of the fresnel lens and the plurality of moth-eye structures are respectively located on opposite surfaces of the fresnel lens.

In an embodiment according to the invention, the plurality of moth-eye structures are located on a fresnel lens structure of a fresnel lens.

In an embodiment according to the present invention, each of the plurality of moth eye structures has an aspect ratio greater than 1.

In an embodiment according to the present invention, a pitch of the plurality of moth eye structures is less than or equal to 750 nm.

In an embodiment according to the present invention, a plurality of moth-eye structures are located on the display device and the fresnel lens.

In an embodiment of the invention, the fresnel lens structure of the fresnel lens includes a plurality of light guide surfaces and a plurality of mold release surfaces respectively connecting two adjacent light guide surfaces, and the mold release surfaces are anti-reflection surfaces.

In an embodiment according to the present invention, each of the plurality of mold-releasing surfaces is an atomizing surface, or each of the plurality of mold-releasing surfaces has at least one roughened structure having a level difference of more than 0.1 μm.

In an embodiment according to the present invention, each of the two display units further includes a light absorbing layer disposed on each of the plurality of mold release surfaces.

In an embodiment according to the present invention, each of the two display units includes a plurality of fresnel lenses, and the plurality of fresnel lenses are sequentially disposed between the display apparatus and one of the eyes of the user.

Based on the above, since the graded equivalent refractive index provided by the moth-eye structure contributes to reducing the reflectance, providing a plurality of moth-eye structures on at least one surface between the display device and one of the eyes of the user contributes to reducing the interface reflection in the head-mounted display, thereby effectively improving the stray light problem. Therefore, the head-mounted display of the embodiment of the invention can have good display quality.

In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanied with figures are described in detail below.

Drawings

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

FIG. 1 is a partial schematic view of a prior art head mounted display;

FIG. 2 is a schematic diagram of a head mounted display according to a first embodiment of the present invention;

FIG. 3 is a partial schematic view of a plurality of moth eye structures of FIG. 2;

FIGS. 4A-4H are respective partial schematic views of other embodiments of the Fresnel lens of FIG. 2;

fig. 5 to 8 are schematic views of head-mounted displays according to second to fifth embodiments of the present invention, respectively.

Detailed Description

Directional phrases used herein include, for example: "upper", "lower", "front", "rear", "left", "right", etc., refer only to the orientation of the figures. Accordingly, the directional terminology is used for purposes of illustration and is in no way limiting. In the drawings, which illustrate general features of methods, structures, and/or materials used in certain embodiments. These drawings, however, should not be construed as defining or limiting the scope or nature encompassed by these embodiments. For example, the relative sizes, thicknesses, and locations of various layers, regions, or structures may be reduced or exaggerated for clarity.

In the embodiments, the same or similar elements will be denoted by the same or similar reference numerals, and the detailed description thereof will be omitted. Furthermore, features from different embodiments may be combined without conflict and simple equivalent changes and modifications made in the present specification or claims may still fall within the scope of the present invention. In addition, the terms "first", "second", and the like in the description or the claims are only used for naming discrete (discrete) elements or distinguishing different embodiments or ranges, and are not used for limiting the upper limit or the lower limit of the number of elements, nor for limiting the manufacturing order or the arrangement order of the elements.

FIG. 2 is a schematic diagram of a head mounted display according to a first embodiment of the present invention. Referring to fig. 2, the head-mounted display 2 includes two display units 20 respectively disposed in front of two eyes (a left eye EL and a right eye ER) of a user. Each display unit 20 includes a display device 200, a fresnel lens 201, and a plurality of moth-eye structures 202.

The display device 200 is adapted to provide image light B with image information, e.g. grey scale, color, etc. For example, the display device 200 may be a liquid crystal display, but is not limited thereto.

The fresnel lens 201 is disposed between the display apparatus 200 and the user's left eye EL (or right eye ER), and the fresnel lens 201 is adapted to guide the image light B output by the display apparatus 200 into the user's left eye EL (or right eye ER). The fresnel lens 201 has a fresnel lens structure 2010, and the fresnel lens structure 2010 includes a plurality of light guide surfaces S2010A and a plurality of release surfaces S2010B respectively connecting adjacent two light guide surfaces S2010A. When the fresnel lens structure 2010 is a convex lens, the release surface S2010B is closer to the center of the fresnel lens structure 2010 than the corresponding light guiding surface S2010A. Conversely, when the fresnel lens structure 2010 is a concave lens, the release surface S2010B may be farther from the center of the fresnel lens structure 2010 than the corresponding light guiding surface S2010A. Fig. 2 schematically illustrates an architecture of the fresnel lens structure 2010 as a convex lens.

A plurality of moth eye structures 202 are located on at least one surface between the display device 200 and one of the eyes of the user. For example, the plurality of moth-eye structures 202 may be located on the inner surface SI (surface facing the display device 200) or the outer surface SO (surface facing the user) of the fresnel lens 201. Further, the setting surface of the fresnel lens structure 2010 of the fresnel lens 201 may be the inner surface SI or the outer surface SO of the fresnel lens 201. Fig. 2 schematically illustrates that the fresnel lens structure 2010 and the plurality of moth-eye structures 202 are respectively located on opposite surfaces of the fresnel lens 201, wherein the fresnel lens structure 2010 is located on an outer surface SO of the fresnel lens 201, and the plurality of moth-eye structures 202 are located on an inner surface SI of the fresnel lens 201. By disposing the moth-eye structures 202 on the inner surface SI of the fresnel lens 201, damage (e.g., scratch) and contamination (e.g., dust or fingerprint) to the moth-eye structures 202 caused by human or environmental factors can be avoided, which helps to prolong the service life of the head-mounted display 2. However, the arrangement surfaces of the plurality of moth-eye structures 202 and the relative arrangement relationship between the plurality of moth-eye structures 202 and the fresnel lens structure 2010 are not limited to those shown in fig. 2. For example, the fresnel lens structure 2010 may be located on the inner surface SI of the fresnel lens 201, and the plurality of moth-eye structures 202 may be located on the outer surface SO of the fresnel lens 201. Alternatively, the plurality of moth eye structures 202 may also be located on at least one of the other surfaces between the display device 200 and one of the eyes of the user.

Fig. 3 is a partial schematic view of a plurality of moth eye structures 202 in fig. 2. Referring to fig. 3, the moth-eye structure 202 is a nano-scale pillar structure, and a width W (or a diameter) of the moth-eye structure 202 decreases in a direction X away from the installation surface S202 of the plurality of moth-eye structures 202. Here, the disposing surface S202 of the plurality of moth eye structures 202 may be any one surface between the display device 200 and one of the eyes of the user in fig. 2.

Since the width W of the moth-eye structure 202 decreases in the direction X, in the cross section CS parallel to the setting surface S202, the area occupied by air increases with an increase in the distance DT between the cross section CS and the setting surface S202, and the area occupied by the plurality of moth-eye structures 202 decreases with an increase in the distance DT. Since the refractive index of air is smaller than that of the moth-eye structure 202, the equivalent refractive index at which the cross section CS is located decreases with increasing distance DT. That is, the equivalent refractive index decreases along the direction X.

According to the reflectivity formula, the larger the difference between the refractive indices of the two media, the higher the reflectivity at the interface of the two media. Therefore, disposing the moth-eye structure 202 providing a graded equivalent refractive index at the interface of two media having a large difference in refractive index helps to reduce the reflectance (interface reflection) at the interface. For example, a plurality of moth-eye structures 202 may be disposed on at least one surface between the display device 200 and one of the eyes of the user (any one surface having an interface reflection problem) to reduce the interface reflection in the head-mounted display 2, thereby effectively improving the stray light problem.

In fig. 2, the plurality of moth-eye structures 202 are located on the inner surface SI of the fresnel lens 201, and therefore contribute to reducing stray light generated by interface reflection occurring on the inner surface SI of the fresnel lens 201. Furthermore, reducing stray light formed at the inner surface SI of the fresnel lens 201 also helps to ameliorate the ghost problem, since stray light formed at the inner surface SI of the fresnel lens 201 (i.e., light reflected by the inner surface of the fresnel lens 201) passes toward the display device 200 and is then reflected by the display device 200, making the stray light problem more complicated/severe (e.g., forming ghost images). Therefore, the head mounted display 2 can have good display quality.

The variation rate of the equivalent refractive index at the locations of the moth-eye structures 202 can be designed from the depth D and the width W of each of the moth-eye structures 202. When the aspect ratio (the ratio of the depth D to the width W) of each of the plurality of moth-eye structures 202 is larger than 1, the equivalent refractive index does not vary too sharply, and an effect of gradual change of the equivalent refractive index can be achieved.

In addition, the pitch P of the moth-eye structures 202 may be designed according to the wavelength range used by the head-mounted display 2. When the wavelength range is limited to visible light, the pitch P of the plurality of moth-eye structures 202 is, for example, less than or equal to 750 nm.

The head-mounted display 2 may further include other elements or film layers according to different requirements. For example, the head-mounted display 2 may further include at least one anti-reflection layer (not shown) to further reduce interface reflection in the head-mounted display 2. The at least one anti-reflective layer may be disposed on at least one surface between the display device 200 and one of the eyes of the user, for example, on a surface of the display device 200 facing the fresnel lens 201, to reduce interface reflection at the surface. However, the disposing surface of the at least one anti-reflection layer is not limited thereto. The following embodiments may further provide the at least one anti-reflection layer according to requirements, which will not be repeated below.

In addition, since light incident on the release surface S2010B also forms stray light and affects image quality (for example, forms image smear), the multiple release surfaces S2010B of the fresnel lens structure 2010 may be further designed as anti-reflection surfaces to reduce directivity of stray light and reduce light intensity of stray light transmitted to the eyes of a user, thereby effectively improving problems such as image smear.

Fig. 4A to 4H are partial schematic views of other embodiments of the fresnel lens 201 in fig. 2. As shown in fig. 4A to 4G, the shape of the release surface S2010B can be changed by changing the mold for manufacturing the fresnel lens 201, for example, the smooth release surface S2010B shown in fig. 2 is changed to the non-smooth (bumpy) release surface S2010B shown in fig. 4A to 4G, so as to achieve the anti-reflection effect. Alternatively, as shown in fig. 4H, each of the two display units 20 (refer to fig. 2) may further include a light absorbing layer 203 disposed on each of the plurality of mold release surfaces S2010B, and light transmitted to the mold release surface S2010B is absorbed by the light absorbing layer 203 to achieve an antireflection effect.

In fig. 4A, each of the plurality of release surfaces S2010B of the fresnel lens structure 2010 is an atomized surface (roughened surface). In fig. 4B to 4G, each of the plurality of release surfaces S2010B of the fresnel-lens structure 2010 has at least one roughened structure. The roughened structure may be a concave portion P1 or a convex portion P2. The shape of the concave portion P1 (or the convex portion P2) may be a circular arc or a saw-tooth shape. In addition, the height difference HL of the roughened structure is larger than 0.1 micrometer, so that stray light can be effectively diffused in a large range, and the light intensity of the stray light transmitted to eyes of a user can be effectively reduced. The height difference HL is defined as a distance between the most recessed part of the concave part P1 (or the most protruded part of the convex part P2) and the reference plane RF. The reference plane RF is the surface formed by the line connecting the highest and lowest of the release surface S2010B.

As shown in fig. 4B and 4E, each of the plurality of release surfaces S2010B of the fresnel lens structure 2010 may have two roughened structures, such as one concave portion P1 and one convex portion P2. In fig. 4B, both the concave portion P1 and the convex portion P2 have an arc shape. In fig. 4E, the concave portions P1 and the convex portions P2 are both saw-toothed.

As shown in fig. 4C and 4F, each of the plurality of release surfaces S2010B of the fresnel-lens structure 2010 may have two roughened structures, such as two recesses P1. In fig. 4C, both the concave portions P1 have an arc shape. In fig. 4F, both the recesses P1 are saw-toothed in shape.

As shown in fig. 4D and 4G, each of the plurality of release surfaces S2010B of the fresnel-lens structure 2010 may have two roughened structures, such as two convex portions P2. In fig. 4D, both of the projections P2 have an arc shape. In fig. 4G, both the projections P2 are saw-toothed.

It should be noted that the number of the roughened structures and the shapes of the roughened structures of each of the plurality of release surfaces S2010B of the fresnel lens structure 2010 may be changed as required, and are not limited to those shown in fig. 4B to 4G. In other embodiments, the release surface S2010B may have the number of roughened structures of one or more than two. Further, when the number of the roughened structures of the mold-releasing surface S2010B is two or more, the shape of the roughened structures may be a circular arc shape, a saw-toothed shape, or a combination of the two shapes. It should be noted that the release surface S2010B in the following embodiments may be modified to be an antireflection surface as described above, and will not be described again below.

Fig. 5 to 8 are schematic views of head mounted

displays

3, 4, 5, 6 according to second to fifth embodiments of the present invention, respectively. Referring to fig. 5, the main differences between the head mounted display 3 and the head mounted display 2 of fig. 2 are as follows. In the display unit 30 of the head-mounted display 3, the surface on which the fresnel lens structure 2010 is disposed is the inner surface SI of the fresnel lens 201, and the plurality of moth-eye structures 202 are located on the fresnel lens structure 2010 of the fresnel lens 201, for example, on the plurality of light guide surfaces S2010A of the fresnel lens structure 2010, but not limited thereto. For example, moth eye structures 202 may also be located on light guiding surfaces S2010A and release surfaces S2010B.

Referring to fig. 6, the main differences between the head mounted display 4 and the head mounted display 2 of fig. 2 are as follows. In the display unit 40 of the head-mounted display 4, a plurality of moth-eye structures 202 are located on the display device 200 in addition to the fresnel lens 201. Thus, interface reflections occurring at the interface of the display device 200 with air may be further reduced. Any of the embodiments of the present invention may be modified in the same manner, and will not be repeated below.

Referring to fig. 7, the main differences between the head mounted display 5 and the head mounted display 3 of fig. 5 are as follows. The display unit 50 of the head-mounted display 5 further includes an optical film 204 located between the display device 200 and the fresnel lens 201. Further, a plurality of moth-eye structures 202 are provided on the optical film 204 in addition to the fresnel lens 201. In particular, the optical film 204 may be any optical element or optical layer disposed between the display device 200 and the fresnel lens 201 as desired. By providing a plurality of moth eye structures 202 on the optical film 204, it helps to reduce interface reflection that occurs at the interface of the optical film 204 with air. Fig. 7 schematically illustrates a plurality of moth eye structures 202 on one surface of an optical film 204. However, in other embodiments, a plurality of moth eye structures 202 may be located on opposing surfaces of the optical film 204. Any of the embodiments of the present invention may be modified in the same manner, and will not be repeated below.

Referring to fig. 8, the main differences between the head mounted display 6 and the head mounted display 2 of fig. 2 are as follows. The display unit 60 of the head-mounted display 6 includes a plurality of fresnel lenses (e.g., the fresnel lenses 205 and 201), and the fresnel lenses (e.g., the fresnel lenses 205 and 201) are sequentially disposed between the display device 200 and one of the eyes of the user. Fig. 8 omits to show a plurality of moth-eye structures and a fresnel lens structure of each fresnel lens. However, the plurality of moth-eye structures may be disposed on at least one of a plurality of surfaces between the display device 200 and one of the eyes of the user (e.g., a surface of the display device 200 facing the fresnel lens 205, an inner surface SI of the fresnel lens 205, an outer surface SO of the fresnel lens 205, the inner surface SI of the fresnel lens 201, the outer surface SO of the fresnel lens 201, an inner surface or an outer surface of the optical film (if any)). Further, the fresnel lens structure of the fresnel lens 205 (or the fresnel lens 201) may be located on the outer surface SO or the inner surface SI of the fresnel lens 205 (or the fresnel lens 201).

In summary, since the graded equivalent refractive index provided by the moth-eye structure helps to reduce the reflectivity, the provision of a plurality of moth-eye structures on at least one surface between the display device and one of the eyes of the user helps to reduce the interface reflection in the head-mounted display, thereby effectively improving the stray light problem. Therefore, the head-mounted display of the embodiment of the invention can have good display quality. In some embodiments, an anti-reflective layer may be disposed on at least one surface between the display device and one of the user's eyes to further reduce interfacial reflections. In other embodiments, the multiple mold release surfaces of the fresnel lens structure may be designed as anti-reflection surfaces to reduce the directivity of stray light, so that the intensity of stray light transmitted to the eyes of a user is reduced. In still other embodiments, a plurality of moth eye structures may be disposed on the display device or the optical film (if any). In still other embodiments, the display unit may include a plurality of fresnel lenses, and a plurality of moth-eye structures may be disposed on at least one of the plurality of fresnel lenses.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A head-mounted display, comprising:

two display units respectively disposed in front of both eyes of a user, wherein each of the two display units includes:

a display device;

a Fresnel lens disposed between the display device and one of the eyes of a user; and

a plurality of moth eye structures on at least one surface between the display device and one of the user's eyes.

2. The head-mounted display of claim 1, wherein the Fresnel lens structure of the Fresnel lens and the plurality of moth-eye structures are located on opposite surfaces of the Fresnel lens.

3. The head-mounted display of claim 1, wherein the plurality of moth-eye structures are located on a fresnel lens structure of the fresnel lens.

4. The head-mounted display of claim 1, wherein each of the plurality of moth-eye structures has an aspect ratio greater than 1.

5. The head-mounted display of claim 1, wherein a pitch of the plurality of moth-eye structures is less than or equal to 750 nanometers.

6. The head-mounted display of claim 1, wherein the plurality of moth-eye structures are located on the display device and the Fresnel lens.

7. The head-mounted display of claim 1, wherein the Fresnel lens structure of the Fresnel lens comprises a plurality of light guide surfaces and a plurality of mold release surfaces respectively connecting two adjacent light guide surfaces, and the mold release surfaces are anti-reflection surfaces.

8. The head-mounted display of claim 7, wherein each of the plurality of release surfaces is a fogging surface, or each of the plurality of release surfaces has at least one roughened structure, and a height difference of the at least one roughened structure is greater than 0.1 μm.

9. The head-mounted display of claim 7, wherein each of the two display units further comprises:

and a light absorbing layer disposed on each of the plurality of release surfaces.

10. The head-mounted display of claim 1, wherein each of the two display units comprises a plurality of fresnel lenses, and the plurality of fresnel lenses are sequentially disposed between the display device and the one of the eyes of the user.