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

Augmented Reality (AR) is mainly composed of two main components: a projection device and an optical waveguide. The optical waveguide is currently divided into a geometric optical waveguide and a diffractive optical waveguide. Among them, the geometric optical waveguide is further divided into a mirror array type and a microstructure type. The geometric optical waveguide of the mirror array-type uses a plurality of coatings with different transmissive and reflective rates to achieve a uniform light output. However, its manufacturing process is quite complicated, and the requirements for the coatings with the transmissive and reflective rates of and a parallel degree between the coatings are extremely high and difficult to mass produce. The geometric optical waveguide of the microstructure type has a micro-prism array on an upper surface of a light output area so the uniform light output can be achieved after beams hit the micro-structures. Therefore, its manufacturing process is much simpler compared with the mirror array type and easier to mass produce.

However, for the geometric optical waveguide of the microstructure type, during an optical waveguide conduction of an emitted light from a display device, because the light incident at different angles are not all output at expected light output areas, a displayed image may show an uneven light distribution. Consequently, as a part of the light cannot enter human eyes, visible dark lines will be seen on the displayed image.

For example, incident light that enter the optical waveguide at different angles will go through different numbers of total reflections in a designed transmission path before being transmitted to user eyes. Among them, the incident light undergone fewer total reflections need to be output earlier to be received by the eyes. Conversely, the incident light undergone more total reflections need to be output later. However, in practical applications, the incident light undergone fewer total reflections is not designed to be output earlier. Instead, the incident light that has undergone more total reflections is designed to be output earlier. Consequently, the waste of energy affects the energy incident on the eyes of the user. In addition, the above-mentioned light output problem also causes obvious bright and dark stripes on the image received by the eyes, resulting in a poor user experience.

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 were acknowledged by a person of ordinary skill in the art. <CIT> relates to a lightguide that includes: a coupling structure having a light-receiving surface to receive a light beam from a display element; and a light guide plate which includes a first light-guiding layer having a prism surface that is disposed so as to partially transmit the light beam entering from the coupling structure and propagating therein, and which includes a second light-guiding layer covering the prism surface, the light guide plate having an outgoing surface via which the light beam having been transmitted through the prism surface is allowed to exit. A refractive index of the coupling structure is different from a refractive index of the light guide plate. <CIT> relates to a light guide plate that is configured to allow light output from a display element to be propagated therein and to allow at least a part of the light propagated therein to be reflected by a plurality of reflective structures. The plurality of reflective structures each include a reflective surface inclining with respect to a light output surface. The guide plate includes a first transparent member; a second transparent member; and a third transparent member provided between the first transparent member and the second transparent member. The plurality of reflective structures are provided at positions in contact with the third transparent member. <CIT> relates to a lightguide that includes: a coupling structure having a light receiving surface receiving light from a display element; and a light guide plate having a light receiving section at which light from the coupling structure enters, the light guide plate including a plurality of reflecting sections arranged so as to reflect light entering from the light receiving section and traveling through an inside of the light guide plate mainly in a first direction, the light guide plate being configured such that the light reflected by the plurality of reflecting sections outgoes from an exit surface, wherein each of the plurality of reflecting sections has a reflecting surface which is oblique to the exit surface, and when seen in a normal direction of the exit surface, the area ratio per unit area of the oblique reflecting surface varies depending on a distance from the light receiving section.

The invention provides a near-eye optical system, which can provide a favorable light output effect.

An embodiment of the invention provides a near-eye optical system for receiving an image beam, which includes a first optical waveguide and a second optical waveguide. The first optical waveguide is configured to expand an image beam in a first direction, and includes a first surface, a second surface and a plurality of first reflective inclined surfaces. The first surface has a first light incident area. The second surface is opposite to the first surface. The first reflective inclined surfaces are disposed on the first surface, located at one side of the first light incident surface, and arranged along the first direction. The first surface is sequentially divided into the first light incident area and a plurality of first optical areas along the first direction. A line number density of the first reflective inclined surfaces in the first optical area closest to the first light incident area in the first direction is less than a line number density of the first reflective inclined surfaces in the first optical area furthest from the first light incident area in the first direction. The second optical waveguide is configured to expand the image beam in a second direction. The first direction is vertical to the second direction.

Another embodiment of the invention provides a near-eye optical system for receiving an image beam. The near-eye optical system includes an optical waveguide configured to expand the image beam in a direction. The optical waveguide includes a near-eye surface and a structure surface. The structure surface includes a light incident area and is opposite to the near-eye surface. The light incident area is located in a transmission path of the image beam. A plurality of reflective inclined surfaces are disposed on the structure surface and located at one side of the light incident surface and arranged along the direction. The structure surface is sequentially divided into the light incident area and a plurality of optical areas along the direction. A line number density of the reflective inclined surfaces in the optical area closest to the light incident area in the direction is less than a line number density of the reflective inclined surfaces in the optical area furthest from the light incident area in the direction.

The first surface may called structured surface. The second surface may be called near eye surface.

In some of the embodiments, the line number density of the first reflective inclined surfaces in the first optical area closest to the first light incident area may be a constant value.

In some of the embodiments, the line number density of the first reflective inclined surfaces in the first optical area furthest from the first light incident area may be a constant value.

In some of the embodiments, the line number densities of the first reflective inclined surfaces in at least one first optical area between the first optical area closest to the first light incident area and the first optical area furthest from the first light incident area may show non-increasing and non-decreasing oscillation distributions.

In some of the embodiments, two partial beams of the image beam reflected by any adjacent two of the first reflective inclined surfaces may at least partially overlap with each other in a viewing angle range formed in an eye of a user.

In some of the embodiments, a width of each of the first reflective inclined surfaces in the first direction may be less than or equal to a pitch from the first reflective inclined surface to the next first reflective inclined surface in the first direction.

In some of the embodiments, the pitch may be less than or equal to a pupil diameter of the eye.

In some of the embodiments, the pupil diameter may be greater than or equal to <NUM> millimeter and less than or equal to <NUM> millimeter.

In some of the embodiments, the line number density of the first reflective inclined surfaces may increase from being closer to the first light incident area to being farther from the first light incident area in the first direction.

In some of the embodiments, the first optical waveguide may further comprise a second beam splitting inclined surface, disposed on the first light incident area, and/or may be configured to transmit the image beam from the first light incident area towards the first optical areas.

In some of the embodiments, the second optical waveguide may further comprise a third surface, facing the second surface.

In some of the embodiments, the second optical waveguide may further comprise a fourth surface, having a second light incident area, and opposite to the third surface.

In some of the embodiments, the second light incident area may be located in a transmission path of the image beam from the second surface.

In some of the embodiments, the second optical waveguide may further comprise a plurality of third reflective inclined surfaces, disposed on the fourth surface, located at one side of the second light incident surface, and arranged along the second direction.

In some of the embodiments, the fourth surface may be sequentially divided into the second light incident area and a plurality of second optical areas along the second direction.

In some of the embodiments, a line number density of the third reflective inclined surfaces in the second optical area closest to the second light incident area in the second direction may be less than a line number density of the third reflective inclined surfaces in the second optical area furthest from the second light incident area in the second direction.

In some of the embodiments, the second optical waveguide may further comprise a fourth reflective inclined surface, disposed on the second light incident area, and configured to transmit the image beam from the second light incident area towards the second optical areas.

In some of the embodiments, the line number density of the third reflective inclined surfaces in the second optical area closest to the second light incident area may be a constant value.

In some of the embodiments, the line number density of the third reflective inclined surfaces in the second optical area furthest from the second light incident area may be a constant value.

In some of the embodiments, the line number densities of the third reflective inclined surfaces in at least one second optical area between the second optical area closest to the second light incident area and the second optical area furthest from the second light incident area show non-increasing and non-decreasing oscillation distributions.

In some of the embodiments, two partial beams of the image beam reflected by any adjacent two of the third reflective inclined surfaces may at least partially overlap with each other in a viewing angle range formed in an eye of a user.

In some of the embodiments, a width of each of the third reflective inclined surfaces in the second direction may be less than or equal to a pitch from the third reflective inclined surface to the next third reflective inclined surface in the second direction.

In some of the embodiments, the pitch may be less than or equal to a pupil diameter of the eye, and the pupil diameter is greater than or equal to <NUM> millimeter and less than or equal to <NUM> millimeter.

In some of the embodiments, the line number density of the third reflective inclined surfaces may increase from being closer to the second light incident area to being farther from the second light incident area in the second direction.

In some of the embodiments, the near-eye optical system may further comprise a projection device, configured to emit the image beam.

In some of the embodiments, the image beam from the projection device may enter the first optical waveguide via the first light incident area.

In some of the embodiments, the optical waveguide may further comprise a light incident area-reflective inclined surface, disposed on the light incident area, and configured to transmit the image beam from the light incident area towards the optical areas.

In some of the embodiments, the line number density of the reflective inclined surfaces in the optical area closest to the light incident area may be a constant value, and/or the line number density of the reflective inclined surfaces in the optical area furthest from the light incident area may be a constant value.

In some of the embodiments, the line number densities of the reflective inclined surfaces may show a non-increasing and non-decreasing oscillation distribution in at least one optical area between the optical area closest to the light incident area and the optical area furthest from the light incident area.

In some of the embodiments, two partial beams of the image beam reflected by any adjacent two of the reflective inclined surfaces may at least partially overlap with each other in a viewing angle range formed in an eye of a user.

In some of the embodiments, a width of each of the reflective inclined surfaces in the direction may be less than or equal to a pitch from the reflective inclined surface to the next reflective inclined surface in the direction, and/or the pitch may be less than or equal to a pupil diameter of the eye, and the pupil diameter is greater than or equal to <NUM> millimeter and less than or equal to <NUM> millimeter.

In some of the embodiments, the line number density of the reflective inclined surfaces may increase from being closer to the light incident area to being farther from the light incident area in the direction.

In some of the embodiments, the near-eye optical system may further comprise a projection device, configured to emit the image beam, wherein the image beam from the projection device may enter the optical waveguide via the light incident area.

In some of the embodiments, the near-eye optical system may further comprise a first optical waveguide, located in a transmission path of the image beam and disposed between the projection device and the optical waveguide.

Based on the above, the near-eye optical system of the invention has a plurality of reflective inclined surfaces, and a line number density of the reflective inclined surfaces in the optical areas closest to the light incident area in the direction is less than a line number density of the reflective inclined surfaces in the optical areas furthest from the light incident area in the direction. As a result, the near-eye optical system can make light incident at different angles on the eye more uniformly, reduce the occurrence of bright and dark stripes, and provide good experience for the user.

Other objectives, features and advantages of the invention will be further understood from the further technological features disclosed by the embodiments of the 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> is a 3D view of the near-eye optical system from a perspective angle according to an embodiment of the invention. <FIG> is a 3D view of the near-eye optical system from another perspective angle according to an embodiment of the invention. Referring to <FIG> together, a near-eye optical system <NUM> of the present embodiment includes a first optical waveguide <NUM> and a second optical waveguide <NUM>. A projection device (as shown by <FIG>) emits an image beam towards a first surface <NUM>, and the image beam is expanded in a Y direction by the first optical waveguide <NUM> and transmitted to the second optical waveguide <NUM>. The second optical waveguide <NUM> expands the image beam in an X direction, and causes the image beam to go through at least one total reflection in the second optical waveguide <NUM> to be reflected by a third reflective inclined surface <NUM> and incident on an eye E of a user. The first surface <NUM> includes a first beam splitting inclined surface <NUM>, a second beam splitting inclined surface <NUM>, a plurality of protruding micro-structures <NUM> and a plurality of protruding microstructures <NUM>. The protruding microstructures <NUM> have a plurality of second reflective inclined surfaces <NUM>, and the protruding microstructures <NUM> have a plurality of first reflective inclined surfaces <NUM>. The first beam splitting inclined surface <NUM> and the second beam splitting inclined surface <NUM> are configured to receive the image beam and guide the image beam to the second reflective inclined surfaces <NUM> and the first reflective inclined surfaces <NUM>.

The following content will describe how the image beam is guided to the first reflective inclined surfaces <NUM>. The Y direction is an arrangement direction of the first reflective inclined surfaces <NUM> of <FIG> or an extending direction of each of the third reflective inclined surfaces <NUM> of <FIG>, and the X direction is an extending direction of each of the first reflective inclined surfaces <NUM> of <FIG> or an arrangement direction of the third reflective inclined surfaces <NUM> of <FIG>. A Z direction is a direction of a third surface <NUM> of the second optical waveguide <NUM> of <FIG> facing towards the first surface <NUM> of the first optical waveguide <NUM>, and the X direction and the Y direction are perpendicular to each other. The first direction is vertical to the second direction.

In this embodiment, materials of the first optical waveguide <NUM> and the second optical waveguide <NUM> may be plastic or glass, and their refractive indexes may be the same or different. The first optical waveguide <NUM> and the second optical waveguide <NUM> may be bonded by an optical adhesive. For allowing the image beam to go through the total reflection in the first optical waveguide <NUM> and the second optical waveguide <NUM>, the refractive indexes of the first optical waveguide <NUM> and the second optical waveguide <NUM> are more preferably to be greater than refractive indexes of the optical glue and air.

<FIG> is a side view of a part of the near-eye optical system according to an embodiment of the invention. <FIG> is a cross sectional view of a first optical waveguide according to an embodiment of the invention. <FIG> illustrates an image beam I perpendicularly incident on the first surface <NUM>. However, the image beam I should be in a light cone shape with different incident angles, and a projection device <NUM> can project the image beam I. Further, <FIG> illustrates a part of the first optical waveguide <NUM>, in which a ratio between a dimension of the first reflective inclined surface <NUM> (e.g., a width L or a height of the first reflective inclined surface <NUM>) and a dimension of the first optical waveguide <NUM> are adjusted for convenience of explanation.

Referring to <FIG> together, specifically, the near-eye optical system <NUM> according to an embodiment of the invention is used to receive the image beam I. The near-eye optical system <NUM> further includes the projection device <NUM> for emitting the image beam I, wherein the image beam I from the projection device <NUM> enters the first optical waveguide <NUM> via a first light incident area E1. The first optical waveguide <NUM> is configured to expand the image beam I in a first direction (e.g., the Y direction), and the first optical waveguide <NUM> includes the first surface <NUM>, a second surface <NUM> and the first reflective inclined surfaces <NUM> of the protruding microstructures <NUM>. The first surface <NUM> has the first light incident area E1. The second surface <NUM> is opposite to the first surface <NUM>. The first reflective inclined surfaces <NUM> are disposed on the first surface <NUM>, and the first reflective inclined surfaces <NUM> are arranged along the first direction. In addition, the first surface <NUM> is sequentially divided into the first light incident area E1 and a plurality of first optical areas along the first direction (e.g., first optical areas O1 and O1' illustrated in <FIG>, and the first optical areas O1, O1' and O1" illustrated in <FIG>).

In this embodiment, the first reflective inclined surfaces <NUM> are surfaces of the protruding microstructures <NUM> on the first surface <NUM>. In other embodiments, the first reflective inclined surfaces <NUM> may also surfaces of a plurality of micro-depressed surfaces on the first surface <NUM>, but not limited thereto.

Furthermore, in this embodiment, the first optical waveguide <NUM> further includes the second beam splitting inclined surface <NUM>, which is disposed on the first light incident area E1, and configured to transmit the image beam I from the first light incident area E1 towards the first optical areas O1, O1' and O1". Further, for allowing the image light beam I to be transmitted to the second optical waveguide <NUM>, the first reflective inclined surface <NUM> is coated with a reflective layer or a partly-transmissive and partly-reflective layer. Alternatively, the first surface <NUM> and the first reflective inclined surface <NUM> are coated with a reflective layer or a partly-transmissive and partly-reflective layer. The second beam splitting inclined surface <NUM> is formed by the partly-transmissive and partly-reflective layer embedded in the first optical waveguide <NUM>.

In addition, for allowing the image beam I at different angles to be evenly incident on the eye E so that the user has a good experience, the first reflective inclined surfaces <NUM> of the invention may have different pitches P in the different first optical areas O1, O1' and O1". Specifically, a line number density of the first reflective inclined surfaces <NUM> (representing multiple prism columns) in the first optical area O1 closest to the first light incident area E1 in the first direction is less than a line number density of the first reflective inclined surfaces <NUM> in the first optical area O1' furthest from the first light incident area E1 in the first direction. It is worth noting that, a plane area is provided between the adjacent first reflective inclined surfaces <NUM> in the first direction (Y), and a plane area is provided between the adjacent third reflective inclined surfaces <NUM> in the second direction (X). Besides, the first direction is vertical to the second direction.

Referring to <FIG>, in this embodiment, the line number density of the first reflective inclined surfaces <NUM> in the first optical area O1 closest to the first light incident area E1 is a constant value (i.e., the pitch between the first reflective inclined surfaces <NUM> is a fixed value), and the line number density of the first reflective inclined surfaces <NUM> in the first optical area O1' furthest from the first light incident area E1 is a constant value. For example, in <FIG>, the pitch P between the first reflective inclined surfaces <NUM> in the first optical areas O1 is <NUM> millimeter, and the pitch P between the first reflective inclined surfaces <NUM> in the first optical areas O1' is <NUM> millimeter. However, the invention is not limited thereto. The line number density and the pitch P of the first reflective inclined surfaces <NUM> should be determined according to design requirements.

Further, in an embodiment, for example, at least one first optical area O1" is provided between the first optical area O1 closest to the first light incident area E1 and the first optical area O1' furthest from the first light incident area E1, and the line number densities of the first reflective inclined surfaces <NUM> in the at least one first optical area O1" show a non-increasing and non-decreasing oscillation distribution. For example, in <FIG>, the pitches P of the at least one first optical area O1" are sequentially <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> millimeter in a direction from the first optical area O1 towards the first optical area O1'. However, the invention is not limited thereto. The line number density and the pitch P of the first reflective inclined surfaces <NUM> in the at least one first optical area O1" should be determined according to design requirements.

In this embodiment, a width L of each of the first reflective inclined surfaces <NUM> in the first direction is less than or equal to the pitch P from the first reflective inclined surface <NUM> to the next first reflective inclined surface <NUM> in the first direction. The pitch P is less than or equal to a pupil diameter of the eye E, and the pupil diameter is greater than or equal to <NUM> millimeter and less than or equal to <NUM> millimeter.

In an embodiment, the line number density of the first reflective inclined surfaces <NUM> increases from being closer to the first light incident area E1 to being farther from the first light incident area E1 in the first direction. It is worth noting that, the first light incident area E1 does not have the structure of the first reflective inclined surface <NUM>.

<FIG> is an example of using Bézier curve to simulate a line density of reflective inclined surfaces in the embodiment of the invention. <FIG> is another example of using Bézier curve to simulate a line density of reflective inclined surfaces in the embodiment of the invention. <FIG> is an example of optimizing a line density of reflective inclined surfaces in the embodiment of the invention. In <FIG>, the horizontal axis indicates position in units of millimeter, and the vertical axis indicates line density in units of the number per millimeter. The smaller the value of the position, the closer to the light incident area; and the larger the value of the position, the farther from the light incident area. <FIG> represent that the characteristics of the reflective inclined surfaces of the first optical waveguide and the reflective inclined surfaces of the second optical waveguide. The first optical waveguide is mentioned in following description as example.

Referring to <FIG> together, a distribution curve of the line density may be designed according to Bézier curve for the first reflective inclined surface <NUM> of the embodiment of the invention. However, a better method should be designed in accordance with the imaging effect, such as <FIG>.

Referring to <FIG>, first of all, the first reflective inclined surface <NUM> closest to the first light incident area E1 is used as a starting point. The next first reflective inclined surface <NUM> is disposed with a starting pitch P of <NUM> millimeter, for example, and whether an imaging image will show bright and dark stripes is then calculated. If not, at least one first reflective inclined surface <NUM> is disposed again at the starting pitch P, and the number of the at least one first reflective inclined surfaces <NUM> is counted until the imaging image shows bright and dark stripes. If yes, another stating pitch P is set (e.g., <NUM> millimeter), the next first reflective inclined surface <NUM> is disposed at said another starting pitch P, and whether the imaging image will show bright and dark stripes is calculated. Then, the above steps are repeated to calculate the number of the first reflective inclined surfaces <NUM>, and so and so forth. The line density of the first reflective inclined surfaces <NUM> of this embodiment is shown in <FIG>. In the first optical area O1, the line density of the first reflective inclined surfaces <NUM> is <NUM> per millimeter. In the first optical area O1', the line density of the first reflective inclined surfaces <NUM> is <NUM> per millimeter. Furthermore, the line number densities of the first reflective inclined surfaces <NUM> in the first optical area O1" show a non-increasing and non-decreasing oscillation distribution.

Based on the above, in the near-eye optical system <NUM> of the invention, by providing different line number densities or different pitches of the first reflective inclined surfaces <NUM> among the different first optical areas O1, O1' and O1" and making the width L of the first reflective inclined surface <NUM> less than or equal to the pitch P, the near-eye optical system <NUM> can make light incident at different angles on the eye E more uniformly, reduce the occurrence of bright and dark stripes, and provide good experience for the user.

Moreover, the image beam I may be in the light cone shape with different incident angles, and the projection device <NUM> can project the image beam I. Also, in this embodiment, two partial beams of the image beam I reflected by any adjacent two of the first reflective inclined surfaces <NUM> at least partially overlap with each other in a viewing angle range formed in the eye E of the user. Therefore, the imaging effect of the image beam I on the eye E is better so the image beam I can be uniformly imaged on the eye E. In other words, the light uniformity of the image beam I on the eye E may be increased, and light or dark stripes generated on the eye E may be reduced.

<FIG> is a partial enlarged view of the second optical waveguide of <FIG> at the third reflective inclined surface. Referring to <FIG> and <FIG> together, in this embodiment, the second optical waveguide <NUM> of the near-eye optical system <NUM> is configured to expand the image beam I in the second direction (e.g., the X direction). The second optical waveguide <NUM> includes the third surface <NUM>, a fourth surface <NUM> and the third reflective inclined surfaces <NUM> formed on the fourth surface <NUM>.

<FIG> is a cross sectional view of a second optical waveguide of <FIG>. In this embodiment, the fourth surface <NUM> has a second light incident area E2, the fourth surface <NUM> is a structure surface, for example. The second light incident area E2 is located in a transmission path of the image beam I from the second surface <NUM>. The third surface <NUM> faces the second surface <NUM> and is opposite to the fourth surface <NUM>. The third surface <NUM> is near-eye surface, for example. The third reflective inclined surfaces <NUM> are disposed on the fourth surface <NUM>, located at another side of the second light incident surface E2, and arranged along the second direction (X). The fourth surface <NUM> is sequentially divided into the second light incident area (light incident area) E2 and a plurality of second optical areas (optical area) O2, O2' and O2" along the second direction. The second light incident area E2 is located between the third surface (near-eye surface) <NUM> and the protruding structure <NUM>.

In this embodiment, the second optical waveguide <NUM> further includes a fourth reflective inclined surface <NUM>, which is disposed on the second light incident area E2 and configured to transmit the image beam I from the second light incident area E2 towards the second optical areas <NUM>, O2' and O2". For example, the fourth reflective inclined surface <NUM> is a light incident area-reflective inclined surface. The fourth reflective inclined surface <NUM> is a surface of a protruding structure <NUM> at one side of the fourth surface <NUM>. Furthermore, for allowing the image light beam I to be transmitted from the second light incident area E2 to the second optical areas O2, O2' and O2", the fourth reflective inclined surface <NUM> may be coated with a reflective layer. For allowing the image beam I to be transmitted to the eye E, the third reflective inclined surface <NUM> of the second optical waveguide <NUM> may be coated with a reflective layer, or the entire third reflective inclined surface <NUM> may also be coated with a reflective layer. In this way, the near-eye optical system <NUM> may be a VR (Virtual Reality) system. In an embodiment, the third reflective inclined surface <NUM> of the second optical waveguide <NUM> may be coated with a partly-transmissive and partly-reflective layer, or the fourth surface <NUM> and the third reflective inclined surface <NUM> may both be coated with a partly-transmissive and partly-reflective layer. In this way, the near-eye optical system <NUM> may be an AR (Augmented Reality) system, in which an ambient beam may be incident on the second optical waveguide <NUM> from the fourth surface <NUM> of the second optical waveguide <NUM>, and then be transmitted to the human eye from the third surface <NUM>.

In this embodiment, a line number density of the third reflective inclined surfaces <NUM> in the second optical area O2 closest to the second light incident area E2 in the second direction is less than a line number density of the third reflective inclined surfaces <NUM> in the second optical area O2' furthest from the second light incident area E2 in the second direction.

In an embodiment, the line number density of the third reflective inclined surfaces <NUM> in the second optical area O2 closest to the second light incident area E2 is a constant value, and the line number density of the third reflective inclined surfaces <NUM> in the second optical area O2' furthest from the second light incident area E2 is a constant value.

In this embodiment, the line number densities of the third reflective inclined surfaces <NUM> in at least one second optical area O2" between the second optical area O2 closest to the second light incident area E2 and the second optical area O2' furthest from the second light incident area E2 show a non-increasing and non-decreasing oscillation distribution.

In this embodiment, a width of each of the third reflective inclined surfaces <NUM> in the second direction is less than or equal to a pitch from the third reflective inclined surface <NUM> to the next third reflective inclined surface <NUM> in the second direction. The pitch is less than or equal to a pupil diameter of the eye E, and the pupil diameter is greater than or equal to <NUM> millimeter and less than or equal to <NUM> millimeter.

Referring to <FIG> again, in the other embodiment, the near-eye optical system <NUM> comprises the second optical waveguide <NUM> and the protruding structure <NUM>. The near-eye optical system <NUM> further comprises a first optical waveguide. However, the first optical waveguide is different from the first optical waveguide <NUM> of <FIG>. The first optical waveguide of <FIG> does not have the plurality of protruding microstructures <NUM> and the plurality of protruding microstructures <NUM>. The first optical waveguide of <FIG> only transmits the image beam I into the second optical waveguide <NUM> in the transmission path of the image beam I. The first optical waveguide is located between the projection device and the second optical waveguide (optical waveguide).

In an embodiment, the line number density of the third reflective inclined surfaces <NUM> increases from being closer to the second light incident area E2 to being farther from the second light incident area E2 in the second direction.

Based on the above, in the near-eye optical system <NUM> of the invention, by providing different line number densities or different pitches of the third reflective inclined surfaces <NUM> among the different second optical areas O2, O2' and O2" and making the width of the third reflective inclined surface <NUM> less than or equal to the pitch, the near-eye optical system <NUM> can make light incident at different angles on the eye E more uniformly, reduce the occurrence of bright and dark stripes, and provide good experience for the user.

Moreover, as similar to the first reflective inclined surface <NUM> described above, two partial beams of the image beam I reflected by any adjacent two of the third reflective inclined surfaces <NUM> at least partially overlap with each other in a viewing angle range formed in the eye E of the user in this embodiment. Therefore, the imaging effect of the image beam I on the eye E is better so the image beam I can be uniformly imaged on the eye E. In other words, the light uniformity of the image beam I on the eye E may be increased, and light or dark stripes generated on the eye E may be reduced.

In addition, in the same manner as the above-mentioned design method of the first reflective inclined surfaces <NUM>, the pitch between the third reflective inclined surfaces <NUM> in the embodiment of the invention may also be designed according to the manner of <FIG>, which is not repeated herein. It is worth mentioning that both the first reflective inclined surface <NUM> and the third reflective inclined surface <NUM> are composed of a plurality of prism columns.

In summary, the near-eye optical system of the invention has a plurality of reflective inclined surfaces, and a line number density of the first reflective inclined surfaces in the first optical areas closest to the first light incident area in the first direction is less than a line number density of the first reflective inclined surfaces in the first optical areas furthest from the first light incident area in the first direction. As a result, the near-eye optical system can make light incident at different angles on the eye more uniformly, reduce the occurrence of bright and dark stripes, and provide good experience for the user. Furthermore, the designer may design the near-eye optical system according to the distribution curve of the line number density of the optimized first reflective inclined surface, so that the user experience is better.

Claim 1:
A near-eye optical system for receiving an image beam, comprising a first optical waveguide (<NUM>), configured to expand the image beam (I) in a first direction (X), and comprising:
a near-eye surface (<NUM>);
a structure surface (<NUM>) comprising a first light incident area (E2) opposite to the near-eye surface (<NUM>), wherein the first light incident area (E2) is located in a transmission path of the image beam (I); and
a plurality of first reflective inclined surfaces (<NUM>), disposed on the structure surface (<NUM>), located at one side of the first light incident surface (E2), and arranged along the first direction (X), wherein the structure surface (<NUM>) is sequentially divided into the first light incident area (E2) and a plurality of first optical areas (O2) along the first direction (X), and a line number density of the first reflective inclined surfaces (<NUM>) in one of the plurality of first optical areas (O2) closest to the first light incident area (E2) in the first direction (X) is less than a line number density of the first reflective inclined surfaces (<NUM>) in another one of the plurality of first optical areas (O2') furthest from the first light incident area (E2) in the first direction (X),
wherein the first optical waveguide (<NUM>) comprises a further reflective inclined surface (<NUM>), which is disposed on the first light incident area (E2), wherein the further reflective inclined surface (<NUM>) is a surface of a protruding structure (<NUM>) at one side of the structure surface (<NUM>).