Patent Description:
The disclosure relates to an optical apparatus, and in particular, to an optical waveguide apparatus and a display including the optical waveguide apparatus.

A diffractive waveguide involves a method based on the principle of optical diffraction in which a diffraction phenomenon occurs after a light passes through slit-like microstructures, such that a direction of the light is changed. However, in a diffractive optical framework, optical efficiency is the biggest issue. Due to the diffraction element, much energy is lost because zero-order light is not re-used. In a diffractive waveguide system, properties including the cycle, the material, and the shape of the optical microstructures all influence the progression direction, the progression angle, and efficiency of the light. Therefore, how to design high-efficiency optical microstructures and maintain manufacturing feasibility is one of the issues to overcome in the field of diffractive waveguides. In some related art, the loss in optical energy is reduced by changing the optical microstructures. However, according to such method, it is difficult to effectively control the quality of the optical microstructures in production. Therefore, the issue of low light transmission efficiency is still present in the diffractive waveguides currently available.

The information disclosed in the "Description of Related Art" section is only intended for enhancing understanding of the background of the invention and therefore it may contain information that does not form the related art already known to a person of ordinary skill in the art. The disclosure in the "Description of Related Art" section does not mean that one or more problems to be solved by one or more embodiments of the invention were acknowledged by a person of ordinary skill in the art.

<CIT> presents display engines for use with optical waveguides. A display engine includes light emitting elements, an optical subsystem to produce a single collimated beam of light from the light emitted by the light emitting elements, one or more image producing MEMS mirrors, one or more image reprojecting MEMS mirrors, and a controller. One of the image producing MEMS mirror(s) is positioned to reflect the single beam of light produced by the optical subsystem. The controller controls the image producing MEMS mirror(s) and the image reprojecting MEMS mirror(s). The image reprojecting MEMS mirror(s) is/are controlled and is/are positioned relative to the image producing MEMS mirror(s) and relative to input-coupler(s) of optical waveguide(s) so that a pupil corresponding to a scanned image that the image producing MEMS mirror(s) project onto one of the image reprojecting MEMS mirror(s), is reprojected by the image reprojecting MEMS mirror(s) onto the input-coupler(s) of the optical waveguide(s) and thereby coupled into the optical waveguide(s).

<CIT> presents systems and methods for selectively incoupling light having different wavelengths into one of a plurality of waveguides. The systems comprise a switching device comprising switchable reflective elements that can be configured to redirect incoming light towards an incoupling element associated with one of a plurality of waveguides.

<CIT> presents a projection display arranged to display an image to an observer use waveguide techniques to generate a display defining a large exit pupil at the point of the observer and a large field of view, whilst using a small image-providing light source device. The projection display uses two parallel waveguides made from a light transmissive material. One waveguide stretches the horizontal pupil of the final display and the other waveguide stretches the vertical pupil of the final display and acts as a combiner through which the observer views an outside world scene and the image overlaid on the scene. In a colour display, each primary colour is transmitted within a separate channel R, G, B.

<CIT> provides a waveguide display having a compact projection light engine and a diffractive waveguide. The diffractive waveguide includes input diffraction gratings with rolled k-vectors. The projection light engine provides collimating light to a projected exit pupil external to the diffractive waveguide. The projection light engine components include a light (or illuminating) source, microdisplay, lenticular screen, doublet, polarizing beam splitter (PBS), cleanup polarizer, fold mirror, curved reflector and quarter waveplate.

<CIT> presents an image displaying apparatus that includes an image production apparatus, a first light conduction section and a second light conduction section. The first light conduction section includes a first light conduction plate which propagates part of incident light thereto by total reflection in the inside thereof and emits the propagated light, and a reflection type volume hologram diffraction grating disposed on the first light conduction plate. The second light conduction section includes a second light conduction plate, a first deflection section and a second deflection section.

<CIT> presents an optical device including a light-transmitting substrate having an input aperture, an output aperture, at least two major surfaces and edges, an optical element for coupling light waves into the substrate by total internal reflection, at least one partially reflecting surface located between the two major surfaces of the light-transmitting substrate for partially reflecting light waves out of the substrate, a first transparent plate, having at least two major surfaces, one of the major surfaces of the transparent plate being optically attached to a major surface of the light-transmitting substrate defining an interface plane, and a beam-splitting coating applied at the interface plane between the substrate and the transparent plate. The light waves coupled inside the light-transmitting substrate are partially reflected from the interface plane and partially pass therethrough.

The embodiments of the invention provide an optical waveguide apparatus that effectively enhances light beam transmission efficiency of the optical waveguide apparatus and reduces optical energy loss caused in a light beam output by a projection apparatus to the optical waveguide apparatus to enhance a brightness of an image displayed by a display including the optical waveguide apparatus and meanwhile effectively maintain a resolution of the image. Moreover, a color temperature of the light beam output by the optical waveguide apparatus is substantially consistent with a color temperature of a light beam output by the projection apparatus.

Other purposes and advantages of the embodiments of the invention may be further understood according to the technical features disclosed herein.

To achieve one, part, or all of the foregoing purposes or other purposes, an embodiment of the invention provides an optical waveguide apparatus including an optical waveguide element and an optical recycling element. The optical waveguide element includes a first surface and a second surface opposite to the first surface. The first surface or the second surface includes an optical structure. An incident light enters the optical waveguide element via the first surface and is transmitted to the second surface. The optical recycling element is disposed on the second surface of the optical waveguide element. The incident light is transmitted to the optical recycling element via the second surface. The optical recycling element changes a transmission direction of the incident light to generate a recycled light. The recycled light enters the optical waveguide element via the second surface and is transmitted to the first surface. The incident light and the recycled light are transmitted in the optical waveguide element.

In some embodiments the optical structure may be disposed on the first surface of the optical waveguide element.

Preferably, the incident light enters the optical waveguide element by refractive diffraction via the first surface.

Preferably, the recycled light is transmitted to the first surface via the second surface and undergoes reflective diffraction at the optical structure to be transmitted in the optical waveguide element.

In some embodiments the optical structure may be disposed on the second surface of the optical waveguide element.

Preferably, the incident light is transmitted to the second surface via the first surface and undergoes reflective diffraction at the optical structure to be transmitted in the optical waveguide element.

Preferably, the recycled light enters the optical waveguide element by refractive diffraction via the second surface.

In some embodiments the optical recycling element may be selected from one of a reflection mirror, a band pass filter, a dichroic mirror, a diffraction element, and a planar optical element.

In some embodiments the optical recycling element comprises an optical film layer.

Preferably, the optical film layer may be disposed on a surface of the optical structure.

Preferably, the optical waveguide element may comprise one single waveguide plate.

Preferably, the first surface and the second surface are two opposite surfaces of the one single waveguide plate.

In some embodiments the optical waveguide element comprises a first waveguide plate and a second waveguide plate.

Preferably, the first waveguide plate and the second waveguide plate each comprise the optical structure.

Preferably, the first waveguide plate and the second waveguide plate are arranged in parallel along a light transmission direction.

Preferably, the first surface is a surface where the first waveguide plate receives the incident light, and the second surface is a surface where the second waveguide plate faces the optical recycling element.

In some embodiments the optical waveguide element may comprises a first waveguide plate, a second waveguide plate, and a third waveguide plate.

Preferably, the first waveguide plate, the second waveguide plate, and the third waveguide plate each comprises the optical structure.

Preferably, the first waveguide plate, the second waveguide plate, and the third waveguide plate are arranged in parallel along a light transmission direction, the first surface is a surface where the first waveguide plate receives the incident light, and the second surface is a surface where the third waveguide plate faces the optical recycling element.

In some embodiments the incident light comprises a first color light, a second color light, and a third color light.

Preferably, the first color light is transmitted in the first waveguide plate, the second color light is transmitted in the second waveguide plate, and the third color light is transmitted in the third waveguide plate.

In some embodiments the optical recycling element may be further disposed between the first waveguide plate and the second waveguide plate and between the second waveguide plate and the third waveguide plate.

In some embodiments, the optical waveguide apparatus may further comprise a protective element disposed on a side of the second surface of the optical waveguide element.

Preferably, the optical recycling element is disposed between the optical waveguide element and the protective element.

In some embodiments the first surface may comprise the optical structure.

Preferably, the incident light may enter the optical waveguide element via the first surface and may be transmitted to the second surface.

Preferably, the optical recycling element may be integrally formed on the second surface of the optical waveguide element, wherein the optical recycling element is a diffraction element.

In some embodiments the optical waveguide element may comprise another optical structure, and the incident light and the recycled light are transmitted to a projection target via the other optical structure.

To achieve one, part, or all of the foregoing purposes or other purposes, an embodiment of the invention provides a display for projecting an image light beam to a projection target, and the display includes a projection apparatus and an optical waveguide apparatus. The projection apparatus projects an incident light, and the incident light is the image light beam. The optical waveguide apparatus includes an optical waveguide element and an optical recycling element. The optical waveguide element includes a first surface and a second surface opposite to the first surface. The first surface or the second surface includes an optical structure. An incident light enters the optical waveguide element via the first surface and is transmitted to the second surface. The optical recycling element is disposed on the second surface of the optical waveguide element. The incident light is transmitted to the optical recycling element via the second surface. The optical recycling element changes a transmission direction of the incident light to generate a recycled light. The recycled light enters the optical waveguide element via the second surface and is transmitted to the first surface. The incident light and the recycled light are transmitted in the optical waveguide element and are transmitted to the projection target.

Accordingly, the embodiments of the invention at least exhibit one of the advantages or effects below. The optical waveguide apparatus of the embodiments of the invention includes the optical recycling element and effectively enhances light beam transmission efficiency of the optical waveguide apparatus and reduces optical energy loss caused in a light beam output by the projection apparatus to the optical waveguide apparatus to enhance a brightness of an image displayed by the display including the optical waveguide apparatus and meanwhile effectively maintain a resolution of the image. Moreover, a color temperature of the light beam output by the optical waveguide apparatus is substantially consistent with a color temperature of a light beam output by the projection apparatus.

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 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. The use of "including," "comprising," or "having" and variations thereof herein is meant to encompass the items listed thereafter 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 schematic diagram illustrating an optical structure according to an embodiment of the invention. Referring to <FIG>, in the embodiment, as an incident light L1 enters an optical structure <NUM>, diffraction effect of light occurs. Therefore, when the incident light L1 passes through a light-transmissive microstructure region, a reflective diffracted light L2 and a refractive diffracted light L3 are generated. In the embodiment, the diffracted light L2 and the diffracted light L3 are first-order diffracted lights.

<FIG> is a schematic diagram illustrating an optical waveguide apparatus according to an embodiment of the invention. Referring to <FIG>, an optical waveguide apparatus <NUM> of the embodiment includes an optical waveguide element <NUM> and an optical recycling element <NUM>. The optical waveguide element <NUM> includes a first surface S1 and a second surface S2. The second surface S2 is opposite to the first surface S1 and includes the optical structure <NUM>. The optical recycling element <NUM> is disposed on a side of the second surface S2 of the optical waveguide element <NUM>.

In the embodiment, the incident light L1 enters the optical waveguide element <NUM> via the first surface S1. The incident light L1 is transmitted to the optical structure <NUM> of the second surface S2 to generate the reflective diffracted light L2. The incident light L1 is transmitted to the optical recycling element <NUM> via the optical structure <NUM> of the second surface S2. The optical recycling element <NUM> changes a transmission direction of the incident light L1 to generate a recycled light L4. In the embodiment, the recycled light L4 is, for example, a zero-order diffracted light that is generated after the incident light L1 passes through the optical structure <NUM> and is reflected by the optical recycling element <NUM> and then enters the optical waveguide element <NUM> again. In an embodiment, the recycled light L4 is a first-order or high-order diffracted light. The recycled light L4 enters the optical waveguide element <NUM> via the optical structure <NUM> of the second surface S2 and is transmitted to the first surface S1. When the recycled light L4 passes through the light-transmissive microstructure region, a refractive diffracted light L5 is generated. The diffracted light L2 is a portion of the incident light L1 and is transmitted in the optical waveguide element <NUM>. The diffracted light L5 is a portion of the recycled light L4 and is transmitted in the optical waveguide element <NUM>.

The incident light L1 is reflected by the optical recycling element <NUM> due to the optical structure <NUM> and enters the optical waveguide element <NUM> again via the optical structure <NUM> to be transmitted in the optical waveguide element <NUM>. Therefore, light utilization efficiency of the optical waveguide element <NUM> can be enhanced.

<FIG> is a schematic diagram illustrating an optical waveguide apparatus according to another embodiment of the invention. Referring to <FIG>, an optical waveguide apparatus <NUM> of the embodiment is similar to the optical waveguide apparatus <NUM> of <FIG>, and a difference between the two lies in, for example, including the optical structure <NUM> on the first surface S1.

In the embodiment, the incident light L1 enters the optical waveguide element <NUM> via the first surface S1, and a refractive diffracted light L3 is generated at the optical structure <NUM>. The incident light L1 is transmitted to the optical recycling element <NUM> via the second surface S2. The optical recycling element <NUM> changes a transmission direction of the incident light L1 to generate a recycled light L4. In the embodiment, the recycled light L4 is, for example, a zero-order diffracted light that is generated after the incident light L1 passes through the optical structure <NUM> and is reflected by the optical recycling element <NUM> and then enters the optical waveguide element <NUM> again. In an embodiment, the recycled light L4 is a first-order or high-order diffracted light. The recycled light L4 enters the optical waveguide element <NUM> via the second surface S2. The recycled light L4 is transmitted to the first surface S1 to generate a reflective diffracted light L6 at the optical structure <NUM>. In other words, when the recycled light L4 passes through the light-transmissive microstructure region, the reflective diffracted light L6 is generated. The diffracted light L3 is a portion of the incident light L1 and is transmitted in the optical waveguide element <NUM>. The diffracted light L6 is a portion of the recycled light L4 and is transmitted in the optical waveguide element <NUM>.

In the embodiments of <FIG>, the optical recycling element <NUM> is, for example, an optical element having a reflection function, such as a reflection mirror, a band pass filter, and a dichroic mirror. In an embodiment, the optical recycling element <NUM> may also be an optical film layer, a diffraction element, or a planar optical element.

<FIG> is a schematic diagram illustrating an optical waveguide apparatus according to another embodiment of the invention. Referring to <FIG> and <FIG>, an optical waveguide apparatus <NUM> of the embodiment is similar to the optical waveguide apparatus <NUM> of <FIG>, and a difference between the two lies in, for example, that an optical recycling element <NUM> of the embodiment is, for example, an optical film layer. The optical recycling element <NUM> is formed by coating a reflective material on the surface of the optical structure <NUM> and is configured to reflect the diffracted light transmitted from the optical waveguide element <NUM>, such that the diffracted light enters the optical waveguide element <NUM> again. Thereby, light utilization efficiency of the optical waveguide element <NUM> can be enhanced.

<FIG> is a schematic diagram illustrating an optical waveguide apparatus according to another embodiment of the invention. Referring to <FIG> and <FIG>, an optical waveguide apparatus <NUM> of the embodiment is similar to the optical waveguide apparatus <NUM> of <FIG>, and a difference between the two lies in, for example, that an optical recycling element <NUM> of the embodiment is, for example, a diffraction element having a reflection function. The diffraction element may include another optical structure different from the optical structure <NUM> or includes a grating structure. The optical recycling element <NUM> is disposed on a side of the second surface S2 of the optical waveguide element <NUM> to reflect the diffracted light transmitted from the optical structure <NUM>, such that the diffracted light enters the optical waveguide element <NUM> again. Thereby, light utilization efficiency of the optical waveguide element <NUM> can be enhanced.

<FIG> is a schematic diagram illustrating an optical waveguide apparatus according to another embodiment of the invention. Referring to <FIG> and <FIG>, an optical waveguide apparatus <NUM> of the embodiment is similar to the optical waveguide apparatus <NUM> of <FIG>, and a difference between the two lies in, for example, that an optical recycling element <NUM> of the embodiment is, for example, a planar optical element. The planar optical element is, for example, a liquid crystal lens, a Fresnel lens, or is an optical element including a metasurface. The optical recycling element <NUM> is disposed on a side of the second surface S2 of the optical waveguide element <NUM> to reflect the diffracted light, such that the diffracted light enters the optical waveguide element <NUM> again. Thereby, light utilization efficiency of the optical waveguide element <NUM> can be enhanced.

In the embodiments of <FIG>, the optical waveguide element <NUM> includes one single waveguide plate, but the invention is not limited hereto. In an embodiment, the optical waveguide element may also include a plurality of waveguide plates.

<FIG> is a schematic diagram illustrating an optical waveguide apparatus according to another embodiment of the invention. Referring to <FIG> and <FIG>, an optical waveguide apparatus <NUM> of the embodiment is similar to the optical waveguide apparatus <NUM> of <FIG>, and a difference between the two lies in, for example, that an optical waveguide element <NUM> of the embodiment includes a first waveguide plate <NUM> and a second waveguide plate <NUM>. The first waveguide plate <NUM> and the second waveguide plate <NUM> are arranged in parallel along a transmission direction Z of the incident light L1. The first waveguide plate <NUM> and the second waveguide plate <NUM> each include the optical structure <NUM>. In the embodiment, the first surface S1 is the surface where the first waveguide plate <NUM> receives the incident light L1, and the second surface S2 is the surface where the second waveguide plate <NUM> faces the optical recycling element <NUM>. The optical recycling element <NUM> is disposed on a side of the second surface S2 of the second waveguide plate <NUM> to reflect the diffracted light, such that the diffracted light enters the first waveguide plate <NUM> and the second waveguide plate <NUM> again. Thereby, light utilization efficiency of the optical waveguide element <NUM> can be enhanced.

<FIG> is a schematic diagram illustrating an optical waveguide apparatus according to another embodiment of the invention. Referring to <FIG> and <FIG>, an optical waveguide apparatus <NUM> of the embodiment is similar to the optical waveguide apparatus <NUM> of <FIG>, and a difference between the two lies in, for example, that an optical waveguide element <NUM> of the embodiment includes a first waveguide plate <NUM>, a second waveguide plate <NUM>, and a third waveguide plate <NUM>, and an optical recycling element <NUM> is an optical film layer disposed on the second surface S2 of the optical waveguide element <NUM>. The first waveguide plate <NUM>, the second waveguide plate <NUM>, and the third waveguide plate <NUM> are arranged in parallel along the transmission direction Z of the incident light L1. The first waveguide plate <NUM>, the second waveguide plate <NUM>, and the third waveguide plate <NUM> each include the optical structure <NUM>. In the embodiment, the first surface S1 is the surface where the first waveguide plate <NUM> receives the incident light L1, and the second surface S2 is the surface where the third waveguide plate <NUM> faces the optical recycling element <NUM>.

In the embodiment, the incident light L1 includes a first color light, a second color light, and a third color light. The first color light is transmitted in the first waveguide plate <NUM>, the second color light is transmitted in the second waveguide plate <NUM>, and the third color light is transmitted in the third waveguide plate <NUM>. In an embodiment, the first waveguide plate <NUM>, the second waveguide plate <NUM>, and the third waveguide plate <NUM> are dichroic elements or polarizers (not illustrated) but are not limited hereto. The first color light, the second color light, and the third color light may be controlled to be transmitted respectively in the first waveguide plate <NUM>, the second waveguide plate <NUM>, and the third waveguide plate <NUM>.

In the embodiment, the first waveguide plate <NUM>, the second waveguide plate <NUM>, and the third waveguide plate <NUM> are, for example, respectively a blue light waveguide plate, a green light waveguide plate, and a red light waveguide plate, and the first color light, the second color light, and the third color light are, for example, respectively a blue light, a green light, and a red light. The incident light L1 enters the optical waveguide element <NUM> via the first surface S1 and sequentially passes through the blue light waveguide plate, the green light waveguide plate, and the red light waveguide plate. Therefore, the blue light of the incident light L1 has the highest output efficiency, and the red light has the lowest output efficiency. At this time, there is a case of a slightly high color temperature. However, when the recycled light L4 enters the optical waveguide element <NUM> via the second surface S2, it sequentially passes through the red light waveguide plate, the green light waveguide plate, and the blue light waveguide plate. Therefore, the blue light of the recycled light L4 has the lowest output efficiency, and the red light has the highest output efficiency.

Accordingly, in the optical waveguide apparatus <NUM> of the embodiment, the recycled light L4 is reflected back to the optical waveguide element <NUM> by the optical recycling element <NUM> to compensate for the lower output efficiency of the red light of the incident light L1, and thereby the color temperature of the light output by the optical waveguide element <NUM> is more uniform.

<FIG> is a schematic diagram illustrating an optical waveguide apparatus according to another embodiment of the invention. Referring to <FIG>, an optical waveguide apparatus <NUM> of the embodiment is similar to the optical waveguide apparatus <NUM> of <FIG>, and a difference between the two lies in, for example, that the optical recycling element <NUM> includes a plurality of optical film layers <NUM>, <NUM>, <NUM>. The optical film layers <NUM>, <NUM>, <NUM> are, for example, the optical recycling element <NUM>. The optical film layer <NUM> is disposed between the first waveguide plate <NUM> and the second waveguide plate <NUM>. The optical film layer <NUM> is disposed between the second waveguide plate <NUM> and the third waveguide plate <NUM>. The optical film layer <NUM> is disposed on the second surface S2 of the optical waveguide element <NUM>.

<FIG> is a schematic diagram illustrating an optical waveguide apparatus according to another embodiment of the invention. Referring to <FIG>, an optical waveguide apparatus <NUM> of the embodiment is similar to the optical waveguide apparatus <NUM> of <FIG>, and a difference between the two lies in, for example, that the optical waveguide apparatus <NUM> further includes a protective element <NUM>, and an optical recycling element <NUM> is disposed between the optical waveguide element <NUM> and the protective element <NUM>. The protective element <NUM> is disposed on a side of the second surface S2 of the optical waveguide element <NUM>. In an embodiment, the protective element <NUM> is, for example, a cover glass. In other words, in the case that the optical waveguide element <NUM> includes the cover glass, the optical recycling element <NUM> may also be disposed between the optical waveguide element <NUM> and the cover glass.

<FIG> is a schematic diagram illustrating an optical waveguide apparatus according to still another embodiment of the invention. Referring to <FIG>, an optical waveguide apparatus <NUM> of the embodiment includes an optical waveguide element <NUM> and an optical recycling element <NUM>. The optical waveguide element <NUM> includes a first surface S1 and a second surface S2. The second surface S2 is opposite to the first surface S1, and the first surface S1 includes an optical structure <NUM>. The optical recycling element <NUM> is disposed on the second surface S2 of the optical waveguide element <NUM>. Specifically, the optical recycling element <NUM> is integrally formed on the second surface S2 of the optical waveguide element <NUM>. An incident light L1 is reflected due to the optical recycling element <NUM> and enters the optical waveguide element <NUM> again to be transmitted in the optical waveguide element <NUM>. Therefore, light utilization efficiency of the optical waveguide element <NUM> can be enhanced.

<FIG> is a schematic diagram illustrating a display according to another embodiment of the invention. Referring to <FIG>, a display <NUM> of the embodiment includes a projection apparatus <NUM> and an optical waveguide apparatus <NUM>. The projection apparatus <NUM> includes a light valve element to project an incident light L1. Specifically, the incident light L1 is an image light beam. The light valve element is, for example, a reflective or transmissive spatial light modulator. The reflective spatial light modulator includes, for example, a reflective liquid crystal on silicon (LCOS) or a digital micro-mirror device (DMD). The transmissive spatial light modulator includes, for example, a transparent liquid crystal panel. The optical waveguide apparatus <NUM> includes an optical waveguide element <NUM> and an optical recycling element <NUM>. The optical waveguide element <NUM> includes a first surface S1 and a second surface S2. The second surface S2 is opposite to the first surface S1 and includes an optical structure <NUM>. The optical recycling element <NUM> is disposed on a side of the second surface S2 of the optical waveguide element <NUM>.

In the embodiment, the incident light L1 enters the optical waveguide element <NUM> via the first surface S1. The incident light L1 is transmitted to the optical structure <NUM> of the second surface S2 to generate a reflective diffracted light L2. The incident light L1 is transmitted to the optical recycling element <NUM> via the optical structure <NUM> of the second surface S2. The optical recycling element <NUM> changes a transmission direction of the incident light L1 to generate a recycled light L4. In the embodiment, the recycled light L4 is, for example, a zero-order diffracted light that is generated after the incident light L1 passes through the optical structure <NUM> and is reflected by the optical recycling element <NUM> and then enters the optical waveguide element <NUM> again. In an embodiment, the recycled light L4 is a first-order or high-order diffracted light. The recycled light L4 enters the optical waveguide element <NUM> via the optical structure <NUM> of the second surface S2 and is transmitted to the first surface S1. When the recycled light L4 passes through the light-transmissive microstructure region, a refractive diffracted light L5 is generated. The diffracted light L2 is a portion of the incident light L1 and is transmitted in the optical waveguide element <NUM>. The diffracted light L5 is a portion of the recycled light L4 and is transmitted in the optical waveguide element <NUM>.

The diffracted light L2 and the diffracted light L5 are transmitted in total reflection in the optical waveguide element <NUM> to a position of the first surface S1 at which another optical structure <NUM> is disposed. The diffracted light L2 and the diffracted light L5 pass through the optical waveguide element <NUM> via the optical structure <NUM> and are transmitted to a projection target <NUM>. The projection target <NUM> is, for example, a human eye or a light beam receiver (e.g., a camera or an optical sensor) but is not limited hereto.

It is noted that, in an embodiment, the optical recycling element <NUM> and the second surface S2 are disposed in parallel to each other so that a brightness of an image is enhanced without lowering a resolution of the image. In contrast, in a case where the optical recycling element <NUM> and the second surface S2 are not disposed in parallel to each other, if the optical recycling element <NUM> is rotated by an angle (e.g., <NUM>°) along a first-axis direction (X) or the optical recycling element <NUM> is rotated by an angle (e.g., <NUM>°) along a second-axis direction (Y) such that an included angle is present between the optical recycling element <NUM> and the second surface S2, the image is offset and the resolution is thus lowered.

<FIG> is a schematic diagram illustrating a display according to another embodiment of the invention. Referring to <FIG>, a display <NUM> of the embodiment is similar to the display <NUM> of <FIG>, and a difference between the two lies in, for example, that the other optical structure <NUM> of the embodiment is disposed on the second surface S2 of the optical waveguide element <NUM>. The diffracted light L2 and the diffracted light L5 are transmitted in total reflection in the optical waveguide element <NUM> to the position of the optical structure <NUM> of the second surface S2. The diffracted light L2 and the diffracted light L5 pass through the optical waveguide element <NUM> via the optical structure <NUM> and are transmitted to a projection target <NUM>. The projection target <NUM> is, for example, a human eye or a light beam receiver (e.g., a CCD (charge-coupled device), a CMOS (complementary metal-oxide semiconductor), etc.) but is not limited hereto. Through the arrangement of the optical structure <NUM>, the diffracted light L2 and the diffracted light L5 are transmitted out of the optical waveguide element <NUM> and are transmitted to the projection target <NUM>. It is noted that the invention does not limit that the diffracted light beam has to leave the optical waveguide element <NUM> via the first surface S1 if the optical structure <NUM> is disposed on the first surface S1. It is also possible that the diffracted light beam may leave the optical waveguide element <NUM> via the second surface S2, which shall depend on the manufacturer's design of the light travel paths.

Claim 1:
An optical waveguide apparatus comprising:
an optical waveguide element (<NUM>) comprising:
a first surface (S1); and
a second surface (S2) opposite to the first surface (S1), wherein the first surface (S1) or the second surface (S2) comprises an optical structure (<NUM>, <NUM>) configured to diffract an incident light (L1), and wherein the incident light (L1) enters the optical waveguide element (<NUM>) via the first surface (S1) and is transmitted to the second surface (S2); and
characterized in that the optical waveguide apparatus further comprising:
an optical recycling element (<NUM>) disposed on the second surface (S2) of the optical waveguide element (<NUM>);
wherein a zero-order diffracted light and a reflective diffracted light (L2) transmitted in the optical waveguide element (<NUM>) are generated by the incident light (L1) passing through the optical structure (<NUM>), or the zero-order diffracted light and a refractive diffracted light (L3) transmitted in the optical waveguide element (<NUM>) are generated by the incident light (L1) passing through the optical structure (<NUM>), the incident light (L1) is transmitted to the optical recycling element (<NUM>) via the optical structure (<NUM>) and the second surface (S2), and the optical recycling element (<NUM>) is configured to reflect the zero-order diffracted light to form a recycled light (L4), the recycled light (L4) enters the optical waveguide element (<NUM>) via the second surface (S2) and is transmitted to the first surface (S1), and the recycled light (L4) is transmitted in the optical waveguide element (<NUM>), wherein the recycled light (L4) is a first-order or high-order diffracted light.