Patent Description:
The invention relates to an optical system, and particularly to a near-eye optical system.

The history of near-eye optical systems such as Head/Helmet-mounted displays (HMDs) may date back to the <NUM> when the U. military used a projection apparatus to project images or text information on display components into users' eyes.

In recent years, with the development of micro-display components, i.e., the growing trend of higher resolution, smaller size, and less power consumption, and the development of cloud technologies, i.e., a large amount of information can be downloaded from the cloud anytime and anywhere, the trouble of carrying a huge database around is avoided. The near-eye optical systems have been developed into a portable display device. In addition to the military field, they have also been developed in other related fields such as industrial production, simulation training, 3D display, medical services, sports, and video games to occupy an important position.

If the near-eye optical systems can provide a large field of view, the users can see a larger image with eyes. When an image beam is transmitted using a waveguide, the field of view is mainly affected by materials and a form factor of the waveguide, so the field of view provided by the conventional waveguide is limited and cannot meet requirements.

The information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Further, the information disclosed in the Background section does not mean that one or more problems to be resolved by one or more embodiments of the invention was acknowledged by a person of ordinary skill in the art.

<CIT> provides a planar waveguide binocular optical display device with a saw-toothed sandwich structure. The planar waveguide binocular optical display device comprises an image display light source, a collimating lens group, a coupling input surface, a planar waveguide substrate, a saw-toothed groove structure and a one-half light-split structure, wherein the image display light source is used for emitting display light waves for displaying a required image; a collimating lens is used for collimating the light waves of the light source; the coupling input surface is used for coupling the collimated light waves into a planar waveguide; the planar waveguide substrate is used for carrying out total reflection diffusion on the coupled light waves; the saw-toothed groove structure is used for expanding a view field and outputting the coupled light waves to the substrate; and the one-half light-split structure is used for uniformly distributing rays and improving the brightness uniformity of the image.

<CIT> presents a waveguide suitable in form factor and weight for use in a heads-up display or similar wearable display and a method of manufacturing the waveguide are disclosed. The waveguide comprises a waveguide body of light-weight, optically transparent solid material, such as plastic, with a series of micro structures embedded in the waveguide body at a top surface of the waveguide body. A first set of the micro structures near one end of the waveguide body serves to couple light into the waveguide, whereby a portion of the coupled light propagates subject to total internal reflection toward a second set of micro structures that reflects a portion of the propagated light out of the waveguide at a bottom surface of the waveguide body. The waveguide can deliver an image provided by an input light source to a human eye (or other detector) situated near the bottom surface of the waveguide body. In particular, the source image can be focused at infinity so that it appears in focus as viewed by the eye at the output of the waveguide. Methods for simple and inexpensive mass production of the waveguide are also disclosed.

<CIT> presents an apparatus that includes a waveguide comprising a front surface, a back surface and an embedded structure between the front surface and the back surface. A reflective array is formed by at least part of the embedded structure. The reflective array includes a plurality of wedges, each wedge having a primary facet, a secondary facet, and a plateau facet wherein at least one of the plurality of primary facets is at least partially reflective.

<CIT> relates to a light guide plate used for a head mounted display or the like that is mounted on a person's head for use, and a virtual image display apparatus incorporating the same.

The invention provides a near-eye optical system which can effectively expand the range of a field of view and have high optical efficiency and high image uniformity.

A near-eye optical system is configured to receive an image beam. The near-eye optical system includes a first optical waveguide, configured to expand the image beam in a first direction, and including a first surface, a second surface, a plurality of first reflecting slopes, and a plurality of second reflecting slopes. The first surface includes a first light-entering area. The second surface is opposite the first surface. The second surface includes a concave area aligned with the first light-entering area, the concave area including a flat bottom surface, and a first inclined sidewall and a second inclined sidewall opposite each other. The first reflecting slopes are disposed on the second surface, and the second reflecting slopes are disposed on the second surface. The first reflecting slopes, the concave area, and the plurality of second reflecting slopes are sequentially arranged along the first direction, and the first inclined sidewall, the flat bottom surface, and the second inclined sidewall are sequentially arranged along the first direction.

In some embodiments, at least one of the flat bottom surface, the first inclined sidewall, the second inclined sidewall, the plurality of first reflecting slopes and the plurality of second reflecting slopes may be a reflecting plane.

In some embodiments, all may be reflecting planes.

In some embodiments, the first optical waveguide may further comprise a plurality of first reflecting surfaces disposed on the second surface.

In some embodiments, the plurality of first reflecting surfaces and the plurality of first reflecting slopes may be alternately arranged in the first direction.

In some embodiments, a plurality of second reflecting surfaces may be disposed on the second surface.

In some embodiments, the plurality of second reflecting slopes and the plurality of second reflecting surfaces may be alternately arranged in the first direction.

In some embodiments, after the image beam enters the first optical waveguide through the first light-entering area, the image beam may be reflected by the flat bottom surface to form a first part of the image beam and may leave the first optical waveguide through the first surface.

In some embodiments, the image beam may be reflected by the first inclined sidewall to form a second part of the image beam which may be reflected by the plurality of first reflecting surfaces and may be reflected by the plurality of first reflecting slopes and may leave the first optical waveguide through the first surface.

In some embodiments, the image beam may be reflected by the second inclined sidewall to form a third part of the image beam which may be reflected by the plurality of second reflecting surfaces and is may be reflected by the plurality of second reflecting slopes and leaves the first optical waveguide through the first surface.

In some embodiments, the near-eye optical system may further comprise a second optical waveguide.

In some embodiments, the second optical waveguide may be configured to expand the image beam in a second direction.

In some embodiments, the first surface may be disposed between the second optical waveguide and the second surface.

In some embodiments, a polarizing beam splitting surface may be obliquely configured in the second optical waveguide.

In some embodiments, a quarter waveplate may be disposed between the second optical waveguide and the first surface.

In some embodiments, after entering the second optical waveguide, the image beam may sequentially penetrate the polarizing beam splitting surface and the quarter waveplate to be transmitted to the first light-entering area of the first optical waveguide.

In some embodiments, the image beam leaving the first optical waveguide from the first surface may sequentially penetrate the quarter waveplate, may enter the second optical waveguide, and may be reflected by the polarizing beam splitting surface, causing the image beam to be transmitted towards the second direction in the second optical waveguide.

In some embodiments, inclination angles of the plurality of first reflecting surfaces and the plurality of second reflecting surfaces relative to the first surface may be greater than <NUM> degrees.

In some embodiments, the first inclined sidewall may be in mirror symmetry with the second inclined sidewall.

In some embodiments, the plurality of first reflecting slopes may be in mirror symmetry with the plurality of second reflecting slopes.

In some embodiments, the plurality of first reflecting surfaces may be in mirror symmetry with the plurality of second reflecting surfaces.

In some embodiments, the flat bottom surface may be a light transmission surface.

In some embodiments, first inclined sidewall, the second inclined sidewall, the plurality of first reflecting slopes, and the plurality of second reflecting slopes may be all reflecting planes.

In some embodiments, the first optical waveguide may further comprise a plurality of first transmission surfaces disposed on the second surface.

In some embodiments, the plurality of first reflecting slopes and the plurality of first transmission surfaces may be alternately arranged in the first direction.

In some embodiments, a plurality of second transmission surfaces may be disposed on the second surface.

In some embodiments, the plurality of second transmission surfaces and the plurality of second reflecting slopes may be alternately arranged in the first direction.

In some embodiments, after the image beam enters the first optical waveguide through the first light-entering area, the image beam may penetrate the flat bottom surface to form a first part of the image beam to leave the first optical waveguide, the image beam may be reflected by the first inclined sidewall to form a second part of the image beam which may penetrate the plurality of first transmission surfaces and may be reflected by the plurality of first reflecting slopes to leave the first optical waveguide.

In some embodiments, the image beam may be reflected by the second inclined sidewall to form a third part of the image beam which may penetrate the plurality of second transmission surfaces and may be reflected by the plurality of second reflecting slopes to leave the first optical waveguide.

In some embodiments, the near-eye optical system may further comprise a second optical waveguide, which may be configured to expand the image beam in a second direction.

In some embodiments, the second optical waveguide may have a second light-entering area on a surface facing the second surface.

In some embodiments, the second light-entering area may be configured to receive the image beam from the second surface.

In some embodiments, the near-eye optical system may further comprise a compensating waveguide configured on the second surface.

In some embodiments, the plurality of first transmission surfaces, the plurality of first reflecting slopes, the plurality of second transmission surfaces, and the plurality of second reflecting slopes may form a plurality of prism surface structures.

In some embodiments, a surface of the compensating waveguide facing the first optical waveguide may have a surface structure complementary to the concave area and the plurality of prism surface structures.

In some embodiments, the plurality of first transmission surfaces may be in mirror symmetry with the plurality of second transmission surfaces.

In some embodiments, a distance between the plurality of first reflecting slopes and the first surface may gradually increase along the first direction.

In some embodiments, a distance between the plurality of second reflecting slopes and the first surface may gradually decrease along the first direction.

In some embodiments, inclination angles of the first inclined sidewall, the second inclined sidewall, the plurality of first reflecting slopes, and the plurality of second reflecting slopes relative to the first surface may be all equal.

In the near-eye optical system according to embodiments of the invention, the first optical waveguide adopts a concave area including a flat bottom surface, and a first inclined sidewall and a second inclined sidewall opposite each other to divide the image beam into three parts. In this way, the range of a field of view can be expanded in two opposite directions, and the near-eye system has high optical efficiency and high image uniformity.

Other objectives, features and advantages of the present invention will be further understood from the further technological features disclosed by the embodiments of the present invention wherein there are shown and described preferred embodiments of this invention, simply by way of illustration of modes best suited to carry out the invention.

In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as "top," "bottom," "front," "back," etc., is used with reference to the orientation of the Figure(s) being described. The components of the present invention can be positioned in a number of different orientations. As such, the directional terminology is used for purposes of illustration and is in no way limiting. On the other hand, the drawings are only schematic and the sizes of components may be exaggerated for clarity. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. Unless limited otherwise, the terms "connected," "coupled," and "mounted" and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. Similarly, the terms "facing," "faces" and variations thereof herein are used broadly and encompass direct and indirect facing, and "adjacent to" and variations thereof herein are used broadly and encompass directly and indirectly "adjacent to". Therefore, the description of "A" component facing "B" component herein may contain the situations that "A" component directly faces "B" component or one or more additional components are between "A" component and "B" component. Also, the description of "A" component "adjacent to" "B" component herein may contain the situations that "A" component is directly "adjacent to" "B" component or one or more additional components are between "A" component and "B" component. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive.

<FIG> and <FIG> are schematic cross-sectional views of a near-eye optical system in two different directions according to an embodiment of the invention. Referring to <FIG> and <FIG>, the near-eye optical system <NUM> in this embodiment is configured to receive an image beam <NUM> which, for example, is emitted by a projector <NUM>. The projector <NUM> is, for example, a pico projector. The near-eye optical system <NUM> includes a first optical waveguide <NUM>, configured to expand the image beam <NUM> in a first direction D1. The first optical waveguide <NUM> includes a first surface <NUM>, a second surface <NUM>, a plurality of first reflecting slopes <NUM>, and a plurality of second reflecting slopes <NUM>. The slope is an inclined surface. The first surface <NUM> includes a first light-entering area A1. The second surface <NUM> is opposite the first surface <NUM>. The second surface <NUM> includes a concave area <NUM> aligned with and corresponding to the first light-entering area A1. The concave area <NUM> includes a flat bottom surface <NUM>, and a first inclined sidewall <NUM> and a second inclined sidewall <NUM> opposite each other. The first reflecting slopes <NUM> are disposed on the second surface <NUM>, and the second reflecting slopes <NUM> are disposed on the second surface <NUM>. In the embodiment, the first reflecting slopes <NUM>, the concave area <NUM>, and the second reflecting slopes <NUM> are sequentially arranged along the first direction D1, and the first inclined sidewall <NUM>, the flat bottom surface <NUM>, and the second inclined sidewall <NUM> are sequentially arranged along the first direction D1. It should be further noted that along a forward direction and an opposite direction of the first direction D1, the first reflecting slopes <NUM> and the second reflecting slopes <NUM> are centered around the concave area <NUM>.

In the embodiment, the first optical waveguide <NUM> further includes a plurality of first reflecting surfaces <NUM> and a plurality of second reflecting surfaces <NUM>. The first reflecting surfaces <NUM> are disposed on the second surface <NUM>, wherein the first reflecting surfaces <NUM> and the first reflecting slopes <NUM> are alternately arranged in the first direction D1. The second reflecting surfaces <NUM> are disposed on the second surface <NUM>, wherein the second reflecting slopes <NUM> and the second reflecting surfaces <NUM> are alternately arranged in the first direction D1. In the embodiment, the flat bottom surface <NUM>, the first inclined sidewall <NUM>, the second inclined sidewall <NUM>, the first reflecting slopes <NUM>, the second reflecting slopes <NUM>, the first reflecting surfaces <NUM>, and the second reflecting surfaces <NUM> are all reflecting planes (reflecting surfaces), which may be coated with a reflecting layer, such as a metal reflecting layer.

In the embodiment, after the image beam <NUM> enters the first optical waveguide <NUM> through the first light-entering area A1, the image beam <NUM> is reflected by the flat bottom surface <NUM> to form a first part 112a of the image beam <NUM> and leaves the first optical waveguide <NUM> through the first surface <NUM>. The image beam <NUM> is reflected by the first inclined sidewall <NUM> to form a second part 112b of the image beam <NUM> which is reflected by the first reflecting surfaces <NUM> and is reflected by the first reflecting slopes <NUM> and leaves the first optical waveguide <NUM> through the first surface <NUM>. The image beam <NUM> is reflected by the second inclined sidewall <NUM> to form a third part 112c of the image beam <NUM> which is reflected by the second reflecting surfaces <NUM> and is reflected by the second reflecting slopes <NUM> and leaves the first optical waveguide <NUM> through the first surface <NUM>.

In the embodiment, the near-eye optical system <NUM> further includes a second optical waveguide <NUM>, a polarizing beam splitting surface <NUM>, and a quarter waveplate <NUM>. The second optical waveguide <NUM> is configured to expand the image beam <NUM> in a second direction D2. In the embodiment, the second direction D2 is perpendicular to the first direction D1. When a user wears the near-eye optical system <NUM>, the first direction D1 is, for example, a horizontal direction, and the second direction D2 is, for example, a vertical direction (gravity direction). However, in other embodiments, it is also possible that the first direction D1 is the vertical direction and the second direction D2 is the horizontal direction. In the embodiment, the first surface <NUM> is configured between the second optical waveguide <NUM> and the second surface <NUM>.

Referring to <FIG>, the polarizing beam splitting surface <NUM> is obliquely configured in the second optical waveguide <NUM>, and the quarter waveplate <NUM> configured between the second optical waveguide <NUM> and the first surface <NUM>. After the image beam <NUM> from the projector <NUM> enters the second optical waveguide <NUM>, it sequentially penetrates the polarizing beam splitting surface <NUM> and the quarter waveplate <NUM> to be transmitted to the first light-entering area A1 of the first optical waveguide <NUM>. Next, as described above, after passing through the above path, the first part 112a, the second part 112b, and the third part 112c of the image beam <NUM> leave the first optical waveguide <NUM> from the first surface <NUM>. The image beam <NUM> leaving the first optical waveguide <NUM> from the first surface <NUM> sequentially penetrates the quarter waveplate <NUM>, enters the second optical waveguide <NUM>, and is reflected by the polarizing beam splitting surface <NUM>, causing the image beam <NUM> to be transmitted towards the second direction D2 in the second optical waveguide <NUM>. In the embodiment, the image beam <NUM> from the projector <NUM> is, for example, a P-polarizing beam or a non-polarizing beam for the polarizing beam splitting surface <NUM>; therefore, the image beam <NUM> penetrating the polarizing beam splitting surface <NUM> is a P-polarizing beam. Then, the image beam <NUM> enters the first optical waveguide <NUM> after passing through the quarter waveplate <NUM>, and through reflection and transmittance inside the first optical waveguide <NUM>, the image beam <NUM> leaving the first optical waveguide <NUM> from the first surface <NUM> may be converted to an S-polarizing beam after penetrating the quarter waveplate <NUM>, which may be reflected by the polarizing beam splitting surface <NUM>, causing the image beam <NUM> to be transmitted towards the second direction D2 in the second optical waveguide <NUM>.

In the embodiment, the second optical waveguide <NUM> may include a plurality of reflecting slopes <NUM> arranged in the second direction D2, which may reflect the image beam <NUM> transmitted in the second optical waveguide <NUM> to a user's eye <NUM> to image an image of the image beam <NUM> on retina of the eye <NUM> through a light-focusing effect between cornea and lens of the eye <NUM>. That is, the near-eye optical system <NUM> may form a virtual image in front of the eye <NUM>, and the second optical waveguide <NUM> is located between the eye <NUM> and the virtual image. The first direction D1 and the second direction D2 may be perpendicular to a third direction D3 which may be parallel to or approximately parallel to a straight direction of the eye <NUM>. In addition, in the embodiment, the eye <NUM> not only may see the virtual image displayed by the near-eye optical system <NUM>, but also may see surrounding scenery behind the second optical waveguide <NUM> through the second optical waveguide <NUM>. That is, an ambient beam passing through the second optical waveguide <NUM> is accepted by the eye <NUM>, so the near-eye optical system <NUM> may be used as an augmented reality display.

In the embodiment, inclination angles <NUM> and θ2 of the first reflecting surfaces and the plurality of second reflecting surfaces relative to the first surface <NUM> are all greater than <NUM> degrees. In addition, in the embodiment, the first inclined sidewall <NUM> is in mirror symmetry with the second inclined sidewall <NUM>, the first reflecting slopes <NUM> are in mirror symmetry with the second reflecting slopes <NUM>, and the first reflecting surfaces <NUM> are in mirror symmetry with the second reflecting surfaces <NUM>. The mirror symmetry takes the concave area <NUM> as a reference standard.

In the near-eye optical system <NUM> of the embodiment, its first optical waveguide <NUM> adopts a concave area <NUM> including a flat bottom surface <NUM>, and a first inclined sidewall <NUM> and a second inclined sidewall <NUM> opposite each other to divide the image beam <NUM> into three parts. In this way, the range of a field of view can be expanded in two opposite directions (i.e., in the first direction D1 and in the opposite direction of the first direction D1), the near-eye system <NUM> can improve optical efficiency and image uniformity, and the field of view is increased. In addition, in the near-eye optical system <NUM> of the embodiment, unlike ordinary waveguides that take advantage of total reflection characteristics of two opposite surfaces, in the embodiment, the image beam <NUM> directly hits a light extraction structure formed by the first reflecting surfaces <NUM> and the first reflecting slopes <NUM> and a light extraction structure formed by the second reflecting surfaces <NUM> and the second reflecting slopes <NUM> after being reflected by the first inclined sidewall <NUM> and the second inclined sidewall <NUM>, and is not propagated by total reflection in the first optical waveguide <NUM>. Therefore, the near-eye optical system of the embodiment can accurately transmit the image beam <NUM> to the eye <NUM>, and can improve optical efficiency. In addition, since the first optical waveguide <NUM> does not take advantage of total reflection characteristics of two opposite surfaces like the ordinary waveguides, during design of the light extraction structures, influences of a light extraction structure of the image beam <NUM> with a small field of view on a light extraction structure of the image beam <NUM> with a large field of view can be effectively avoided, that is, in the embodiment, light extraction structures with different fields of view may be designed separately, the image beam <NUM> may be adjusted separately some fields of view, and image uniformity may be improved accordingly. The light extraction structures are, for example, prism column structures.

Besides, in the embodiment, a width of the flat bottom surface <NUM> in the first direction D1 is less than that in the first direction D1 when the image beam <NUM> is incident on the concave area <NUM>. In addition, the sum of the inclination angle <NUM> of the first reflecting surfaces <NUM> relative to the first surface <NUM> (or the inclination angle θ2 of the second reflecting surfaces <NUM> relative to the first surface <NUM>) plus an inclination angle θ3 of the first reflecting slopes <NUM> relative to the first surface <NUM> (or an inclination angle θ4 of the second reflecting slopes <NUM> relative to the first surface <NUM>) and plus an inclination angle θ5 of the first inclined sidewall <NUM> relative to the first surface <NUM> (or an inclination angle θ6 of the second inclined sidewall <NUM> relative to the first surface <NUM>) is, for example, <NUM> degrees. Moreover, the first reflecting slopes <NUM>, the second reflecting slopes <NUM>, the first reflecting surfaces <NUM>, and the second reflecting surfaces <NUM> may be regarded as surfaces of light extraction structures protruding upwards from a datum reference plane <NUM>, wherein the datum reference plane <NUM> may be parallel to the first surface <NUM> and the second surface <NUM>, and the flat bottom surface <NUM> may be parallel to the first surface <NUM>. In the embodiment, two neighbouring light extraction structures are adjacent to each other. However, in other embodiments, a gap may exist between the two neighbouring light extraction structures, and the second surface <NUM> between two neighbouring light extraction structures connects the two light extraction structures together along the datum reference plane <NUM>.

In addition, in the embodiment, a distance from the first reflecting surface <NUM> of the light extraction structure farthest from the concave area <NUM> to the center of the concave area is less than h/tan(<NUM>*(θ5)-<NUM>°-arcsin(sin(ϕ/n)+w/<NUM>), where h is a distance from the flat bottom surface <NUM> to the datum reference plane <NUM> in the third direction D3 (i.e., in the direction perpendicular to the first surface <NUM>), ϕ is a maximum output angle in the air before the image beam <NUM> is incident on the second optical waveguide <NUM>, n is an refractive index of the material of the first optical waveguide <NUM>, and w is a width of the flat bottom surface <NUM> in the first direction D1. In an embodiment, when it is greater than the above distance, the image beam <NUM> may not be incident.

<FIG> and <FIG> are schematic cross-sectional views of a near-eye optical system in two different directions according to another embodiment of the invention. Referring to <FIG> and <FIG>, the near-eye optical system 100a of the embodiment is similar to the near-eye optical system <NUM> in <FIG> and <FIG>, and their main differences are described as follows. In the near-eye optical system 100a of the embodiment, the flat bottom surface 232a of the concave area <NUM> of the first optical waveguide 200a is a light transmission surface, and the first inclined sidewall <NUM>, the second inclined sidewall <NUM>, the first reflecting slopes <NUM>, and the second reflecting slopes <NUM> are all reflecting planes, which may be coated with a reflecting layer, such as a metal reflecting layer.

In the embodiment, the first optical waveguide 200a does not include the first reflecting surfaces <NUM> and the second reflecting surfaces <NUM>; instead, the first optical waveguide 200a includes a plurality of first transmission surfaces 224a and a plurality of second transmission surfaces 228a. The first transmission surfaces 224a are disposed on the second surface <NUM>, wherein the first reflecting slopes <NUM> and the first transmission surfaces 224a are alternately arranged in the first direction D1. The second transmission surfaces 228a are disposed on the second surface <NUM>, wherein the second transmission surfaces 228a and the second reflecting slopes <NUM> are alternately arranged in the first direction D1.

In the present disclosure, after the image beam <NUM> from the projector <NUM> enters the first optical waveguide 200a through the first light-entering area A1, the image beam <NUM> penetrates the flat bottom surface 232a to form a first part 112a of the image beam <NUM> to leave the first optical waveguide 200a, the image beam <NUM> is reflected by the first inclined sidewall <NUM> to form a second part 112b of the image beam <NUM> which penetrates the plurality of first transmission surfaces 224a and is reflected by the plurality of first reflecting slopes <NUM> to leave the first optical waveguide 200a, and the image beam <NUM> is reflected by the second inclined sidewall <NUM> to form a third part 112c of the image beam <NUM> which penetrates the plurality of second transmission surfaces 228a and is reflected by the plurality of second reflecting slopes <NUM> to leave the first optical waveguide 200a.

In the embodiment, the near-eye optical system 100a further includes a compensating waveguide <NUM> configured on the second surface <NUM>, wherein the first transmission surfaces 224a, the first reflecting slopes <NUM>, the second transmission surfaces 228a, and the second reflecting slopes <NUM> form a plurality of prism surface structures <NUM>, and a surface <NUM> of the compensating waveguide <NUM> facing the first optical waveguide 200a includes a surface structure <NUM> complementary to the concave area <NUM> and the prism surface structures <NUM>. In detail, the surface structure <NUM> of the compensating waveguide <NUM> is complementary to the surface <NUM> of the first optical waveguide 200a.

Referring to <FIG>, in the embodiment, after leaving the first optical waveguide 200a through the above path, the first part 112a, the second part 112b, and the third part 112c of the image beam <NUM> are transmitted to a second light-entering area A2 on a surface <NUM> of the second optical waveguide <NUM> facing the second surface <NUM>, and enter the second optical waveguide <NUM> from the second light-entering area A2. For example, after leaving the first optical waveguide 200a, the image beam <NUM> first penetrates the compensating waveguide <NUM> and then enters the second optical waveguide <NUM> from the second light-entering area A2. That is, the second light-entering area A2 is configured to receive the image beam <NUM> from the second surface <NUM> of the first optical waveguide 200a.

In the sent embodiment, the first inclined sidewall <NUM> is in mirror symmetry with the second inclined sidewall <NUM>, the first reflecting slopes <NUM> are in mirror symmetry with the second reflecting slopes <NUM>, and the first transmission surfaces 224a are in mirror symmetry with the second transmission surfaces 228a. In the embodiment, inclination angles of the first inclined sidewall <NUM>, the second inclined sidewall <NUM>, the first reflecting slopes <NUM>, and the second reflecting slopes <NUM> relative to the first surface <NUM> are all equal.

<FIG> is a schematic cross-sectional view of a first optical waveguide and a compensating waveguide of a near-eye optical system according to yet another embodiment of the invention. Referring to <FIG>, the first optical waveguide 200b and the compensating waveguide 205b in the embodiment are similar to the first optical waveguide 200a and the compensating waveguide <NUM> in <FIG>, and their main differences are described as follows. In the first optical waveguide 200b of the embodiment, a distance H1 between the first reflecting slopes 222b and the first surface <NUM> increases along the first direction D1, and a distance H2 between the second reflecting slopes 226b and the first surface <NUM> decreases along the first direction D1. In other words, the closer to the concave area <NUM>, the greater the distances H1 and H2 from the first reflecting slopes 222b and the second reflecting slopes 226b to the first surface <NUM>, and the farther away from the concave area <NUM>, the smaller the distances. In this way, the first reflecting slopes 222b and the second reflecting slopes 226b far away from the concave area <NUM> can also receive the image beam <NUM> with enough light intensity, so brightness uniformity of the image may be effectively maintained. In addition, in the embodiment, the first reflecting surface 224b is configured between two neighbouring first reflecting slopes 222b, and the second reflecting surface 228b is configured between two neighbouring second reflecting slopes 226b. The distances H1 and H2 from the first reflecting slopes 222b and the second reflecting slopes 226b to the first surface <NUM> are values calculated based on average values.

Based on the above, in the near-eye optical system according to the embodiments of the invention, its first optical waveguide adopts a concave area including a flat bottom surface, and a first inclined sidewall and a second inclined sidewall opposite each other to divide the image beam into three parts. In this way, the range of a field of view can be expanded in two opposite directions, and the near-eye system has high optical efficiency and high image uniformity.

Claim 1:
A near-eye optical system (<NUM>), configured to receive an image beam (<NUM>), wherein the near-eye optical system (<NUM>) comprises:
a first optical waveguide (<NUM>), configured to expand the image beam (<NUM>) in a first direction (D1) and in an opposite direction of the first direction (D1), and comprising:
a first surface (<NUM>) having a first light-entering area (A1);
a second surface (<NUM>) opposite to the first surface (<NUM>), the second surface (<NUM>) having a concave area (<NUM>) aligned with the first light-entering area (A1), and the concave area (<NUM>) having a flat bottom surface (<NUM>), and a first inclined sidewall (<NUM>) and a second inclined sidewall (<NUM>) opposite to each other;
a plurality of first reflecting slopes (<NUM>) disposed on the second surface (<NUM>); and
a plurality of second reflecting slopes (<NUM>) disposed on the second surface (<NUM>), wherein the plurality of first reflecting slopes (<NUM>), the concave area (<NUM>), and the plurality of second reflecting slopes (<NUM>) are sequentially arranged along the first direction (D1), and the first inclined sidewall (<NUM>), the flat bottom surface (<NUM>), and the second inclined sidewall (<NUM>) are sequentially arranged along the first direction (D1), and
wherein the flat bottom surface (<NUM>) corresponding to the first light-entering area (A1) is located between the first inclined sidewall (<NUM>) and the second inclined sidewall (<NUM>), and configured to receive the image beam (<NUM>) and guide the image beam (<NUM>) to leave the first optical waveguide (<NUM>).