Improving the Uniformity of a Color-Mixing Miniature Image Projector

Abstract

The light projection system may include a discrete light source matrix for emitting light corresponding to an image. The system may also include a waveguide formed from a transparent material, the waveguide having a coupling-in interface for coupling light corresponding to the image into the waveguide and a coupling-out interface for coupling the image out of the waveguide. The system may include an internal partial reflection surface and one or more partial lenses for improving the color uniformity of the light projection system.

Description

Technical Field

[0001] The present invention relates to an optical system, and more particularly, to a novel technique for improving the color mixing uniformity for a discrete light source matrix small image projector.

Background Art

[0002] Due to the consumer demand for the improvement of the human-computer interface, there is an increasing interest in near-eye displays widely known as high-quality head-mounted displays (HMDs) or smart glasses. These devices can provide virtual reality (VR) or augmented reality (AR) experiences and improve the way users interact with digital content and the surrounding environment.

[0003] When using an HMD, consumers seek better image quality, immersive experiences, and greater comfort. Consumers expect a display that is high-resolution, vividly colored, and minimally distorted, creating a realistic and enjoyable viewing experience. Additionally, since users often wear these devices for long periods, comfort is also a crucial factor. Consumers desire a lightweight and sophisticated design that is not overly intrusive when worn in various scenarios and is more convenient. Moreover, by miniaturizing the device, portability is improved, making it easier to carry and use in various environments. Therefore, there is an increasing demand for higher-performance yet smaller and compact HMDs.

[0004] The small image projector is a very important component of a head-mounted display (HMD) because it has a significant impact on the performance and form factor of the HMD. One of the prevalent types of small image projectors is the discrete light source matrix projector. This uses individual colors (e.g., RGB) and attempts to blend them to achieve the desired color spectrum. However, conventionally, discrete light source matrix projectors have not achieved optimal color mixing and / or have required a relatively large size to properly mix the individual colors before generating the output light. As a result, there is a need to maximize visual quality with optimal color mixing while minimizing the size and weight of the small image projector. SUMMARY OF THE INVENTION

[0005] In this disclosure, a technique for improving color mixing in a small image projector system while keeping its size relatively small is disclosed.

[0006] The light projection system may include a discrete light source matrix for emitting light corresponding to an image. The system may also include a waveguide formed from a transparent material, the waveguide having a coupling-in interface for coupling light corresponding to the image into the waveguide and a coupling-out interface for coupling the image out of the waveguide. The system may include an internal partial reflection surface and one or more partial lenses for improving the color uniformity of the light projection system.

[0007] This approach achieves an improvement in color mixing while keeping the system size relatively small. This can be advantageous in applications where space constraints or small system design are important factors.

[0008] The accompanying drawings, which are incorporated herein and form a part hereof, illustrate various exemplary systems, methods, etc. of embodiments of aspects of the present invention. It is understood that the element boundaries shown in the figures (e.g., boxes, groups of boxes, or other shapes) represent an example of the boundaries. As will be appreciated by those skilled in the art, one element may be designed as multiple elements, or multiple elements may be designed as one element. An element shown as an internal component of another element may be implemented as an external component, and vice versa. Further, the elements may not be drawn to an exact scale.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0010] According to certain embodiments of the present invention, there are provided a light projection system and an optical system for achieving optical aperture expansion, for example, for the purpose of a near-eye display (which may be a virtual reality or augmented reality display) widely known as a head-mounted display (HMD) or smart glasses. Consumer demand for better and more comfortable human-computer interfaces is driving demand for better image quality and smaller devices.

[0011] Small image projectors are extremely important components of head-mounted displays because they have a significant impact on the performance and form factor of head-mounted displays. One of the prevalent types of small image projectors is the discrete light source matrix projector. This uses individual colors (e.g., RGB) and attempts to blend them to achieve the desired color spectrum. However, conventionally, discrete light source matrix projectors have not achieved optimal color mixing and / or have required a relatively large size to properly mix the individual colors before generating the output light.

[0012] In one embodiment, color mixing is improved by inserting a waveguide between the discrete light source matrix and the output of the small image projector. The waveguide receives the individual colors (e.g., RGB) emitted by separate light-emitting elements (e.g., LEDs) and guides the individual colors along its length. At the end face of the waveguide, the mixed and blended colors are combined to produce a visually uniform output.

[0013] Conventionally, all else being equal, the longer the waveguide, the better the color mixing. The longer the waveguide, the better the color mixing and thus the better the image quality. However, as the waveguide gets longer, the overall size of the system also increases.

[0014] In one embodiment, color mixing is improved and the required length of the waveguide is shortened by inserting a partially reflective interface into the waveguide. This approach utilizes the reflection characteristics of the interface to improve the interaction between the lights of different colors within the waveguide. When light encounters the partially reflective interface, a portion of the light is reflected back into the waveguide while the remainder continues to propagate through the waveguide. By strategically placing this interface within the waveguide, the reflected light can be returned into the waveguide and further interact with other colors. Introducing the partially reflective interface can increase the optical path length for the light within the waveguide and effectively extend the mixing distance. As a result, color mixing is improved even within a shorter physical length of the waveguide.

[0015] The reflection characteristics of the interface (e.g., reflectance and transmittance) can be carefully adjusted to achieve the desired level of color mixing. The optimal design parameters of the partially reflective interface (e.g., material properties and positioning within the waveguide) can be determined by optimization based on simulation or experimentation.

[0016] This approach effectively shortens the required length of the waveguide while still achieving effective color mixing. This can be advantageous in applications where space constraints or small system design are important factors.

[0017] In another embodiment, the use of a partial lens at the entrance of the waveguide of the projector improves the performance of waveguide color mixing. By covering a part of the light input region of the waveguide with the partial lens, light rays emitted from different regions of the individual color projectors can be guided into the waveguide at slightly different angles. This can help improve the mixing of colors within the waveguide.

[0018] At the entrance of the waveguide between the discrete light source matrix and the waveguide, a partial lens (or lenses) that covers, for example, 50% of the light input region of the waveguide may be arranged. The partial lens can have a curved shape or specific surface features that change the directivity of the light rays. The partial lens (or lenses) redirects the light rays emitted from the covered part of the light input region of the waveguide. These redirected light rays enter the waveguide at slightly different angles compared to the light rays that enter the waveguide directly without passing through the partial lens. By introducing the light rays into the waveguide at different angles, the interaction and color mixing within the waveguide are improved. Changing the angles enables more efficient overlap and interaction of the light waves, improving color blending and mixing.

[0019] By using partial lens(es), the coupling of light from a color sequential projector to a waveguide is optimized, and the efficiency of color mixing at a shorter length is improved. This helps to distribute light from different regions of the projector across the entire waveguide, promoting better integration of colors.

[0020] In certain embodiments of the present invention, an optical system is provided for achieving optical aperture expansion for the purpose of a head-up display, most preferably a near-eye display (which may be a virtual reality display or an augmented reality display).

[0021] FIG. 1 shows a typical embodiment of a near-eye display device according to the teachings of an embodiment of the present invention, generally designated 100, using a light guiding optical element (LOE) 1. In the near-eye display 100, which uses a small image projector (or "POD") 130 optically coupled to incident an image within the LOE 1, the image light is confined in one dimension by total internal reflection at a set of planar outer surfaces ("major surfaces"). The near-eye display device 100 is presented here merely as an example, and the technology of the present invention disclosed herein is not limited to such devices, devices using partially reflective facets, etc.

[0022] The optical aperture expansion of the light from the POD 130 is achieved within the LOE 1 by one or more arrangements for gradually redirecting the image illumination, typically using a set of partially reflective surfaces (also referred to as "facets" in the same sense) that are parallel to each other and inclined obliquely with respect to the propagation direction of the image light. Each successive facet deflects a portion of the image light in the deflection direction. In a one-dimensional aperture expansion, the facets also couple out the image light towards the user's eye. Optionally, as shown here, a two-dimensional aperture expansion is achieved by gradually redirecting the image illumination (which is also confined / guided by total internal reflection) within the LOE 1 using a first set of facets within the region 116 of the LOE 1. The deflected image illumination then proceeds into a second substrate region 118 of the LOE 1 (which can be implemented as an adjacent separate substrate or as an extension of a single substrate), where a coupling-out arrangement (e.g., a further set of partially reflective facets) gradually couples out a portion of the image illumination towards the observer's eye located within a region defined as the eye movement box (EMB), thereby achieving the second dimension of the optical aperture expansion. A similar function can be obtained using diffractive optical elements (DOEs) for redirecting and / or coupling out the image illumination within one or both of the regions 116 and 118. In the following text and figures, the focus is on refractive optical elements embedded rather than diffractive optical elements, but the invention is equally applicable to near-eye displays based on diffractive or refractive embedded elements.

[0023] The overall device may be implemented separately for each eye and, preferably, each POD 130 and LOE 1 is supported relative to the user's head in a state where it functions for the corresponding eye of the user. In one particularly preferred option as shown here, the support arrangement is a face-mounted lens set having a lens 112 to which the POD 130 and LOE 1 are operably connected (e.g., prescription lenses, sunglasses, etc., colloquially referred to as "glasses" in this specification), and a frame having side portions 120 for supporting the device relative to the user's ears. Other forms of support arrangements may be used, including, for example, without limitation, a headband, a visor, or a device suspended from a helmet.

[0024] The near-eye display 100 may include various additional components, typically including a controller 122 for driving the POD 130, typically using power from a small onboard battery (not shown) or some other suitable power source. The controller 122 may include all of the electronic components (e.g., at least one processor or processing circuit) necessary to drive an image projector.

[0025] Figure 2 is a simplified schematic plan view of a typical POD130. The illustrated elements of the POD130 are not shown to scale. As described above, the near-eye display 100 uses a small image projector or POD130 that is optically coupled to direct an image into the LOE1. In an embodiment of the present application, the POD130 includes a discrete light source matrix 132. A discrete light source matrix refers to a configuration in which individual light sources are arranged in a grid or matrix pattern. Each light source within the matrix emits light independently and can be controlled individually. In one example, a discrete light source matrix refers to a projection system that utilizes an array of individual light sources (e.g., light-emitting diodes (LEDs) or laser diodes arranged in a matrix configuration). Each light source corresponds to a specific color channel and is typically red (R), green (G), and blue (B) in the case of RGB color reproduction, as shown in FIG. 2. By controlling the intensity of each individual light source within the matrix, different colors and intensities can be achieved. This enables accurate color control and can create a wide range of colors and color combinations.

[0026] An example of such a small image projector 130 that includes a discrete light source matrix 132 is an LCoS system that incorporates LEDs (e.g., RGB) as light sources. In this particular LCoS system, the optical path begins with an array 132 of high-brightness LEDs that function as primary light sources.

[0027] In the illustrated embodiment of FIG. 2, the POD130 also includes a waveguide 90, which will be described in more detail below with reference to FIG. 7A. By inserting the waveguide 90 in front of the discrete light source matrix 132, color mixing is improved. The waveguide 90 may receive individual colors (e.g., RGB) (e.g., emitted by separate light-emitting elements (e.g., LEDs) of the discrete light source matrix 132) and guide the individual colors along its length.

[0028] The LCD (Liquid Crystal Display) panel itself may consist of a surface having an array of small filters. Each filter corresponds to a pixel or sub-pixel in the final image. The modulation element of the LCD panel is a layer of liquid crystal material LCD134 disposed between crossed polarizers.

[0029] When the LEDs of the discrete light source matrix 132 emit light, it reaches the LCD panel 134 through the waveguide 90. The liquid crystal layer selectively controls the amount of transmitted light. By adjusting the orientation of the liquid crystal molecules, the polarizer absorbs the light, enabling precise control of the intensity and color of light for each pixel.

[0030] The modulated light from the LCD panel 134 then passes through the projection lens system 136, and the light forming the final projected image is focused and projected. The lens system 136 can collimate the light by refracting the diverging light rays to be parallel and focusing them at infinity. The lens system 136 can also provide any necessary optical correction to ensure a sharp and accurate projection. In the illustrated embodiment of FIG. 2, the POD 130 also includes a transparent (e.g., glass) spacer 138 between the LCD panel 134 and the lens system 136.

[0031] The POD 130 may correspond to projectors other than LCDs, and / or the discrete light source matrix 132 may correspond to other types of microdisplays. For example, many LCoS & DLP projectors use color sequential technology. These alternative systems may be defined as discrete light source matrix systems and may also benefit from the techniques disclosed herein.

[0032] In the illustrated embodiment of FIG. 2, the POD 130 includes an internal partial reflection surface 45 and a partial lens 97, as will be described in detail below.

[0033] FIG. 2A shows a typical waveguide 10 that can form part of the POD 130, similar to the waveguide 90 of FIG. 2. The waveguide 10 may be formed from a transparent material and may have at least two major outer surfaces 12, 14 for supporting the propagation of light along the length of the waveguide 10. The waveguide 10 also has a coupling-in interface 16 for coupling an image into the waveguide 10. In the example of FIG. 2A, the waveguide 10 has a square cross-section of 2×2 mm as an example.

[0034] In the illustrated embodiment of FIG. 2A, the discrete light source matrix 132 of the POD 130 of FIG. 2 corresponds to a quad 2×2 LED array. As an example, the entrance size to the waveguide is 2×2 mm and each individual led is 1×1 mm. Light from the array 132 is introduced into the waveguide 10 through the coupling-in interface 16 and follows the illustrated coupling-in pattern in the order of GB:RG (first column: green, blue; second column: red, green).

[0035] FIG. 2C shows the color distribution detected at the end 18 of the waveguide 10 as a function of the length of the waveguide 10. For illustrative purposes (where color cannot be reproduced here), the colors are shown as shades. The increase in color uniformity corresponds to an increase in achromaticity at the end 18 of the waveguide 10, while the increase in contrast corresponds to an increase in chromaticity at the end 18.

[0036] As can be seen from FIG. 2C, the length of the waveguide 10 along the general direction in which the light travels plays a role in the color mixing process. When the waveguide 10 is long (5 mm), there are more opportunities for the individual colors to interact and mix with each other than when the waveguide 10 is short (2.5 mm), resulting in a more uniform and blended output. When the waveguide 10 is even longer (10 mm), there are even more opportunities for the individual colors to interact and mix with each other than when the waveguide 10 is short (2.5 mm and 5 mm), resulting in a more uniform and blended output.

[0037] FIG. 2B shows a typical waveguide 20 similar to waveguide 10, except that it includes an internal partial reflection surface or interface 25 that extends along the length of waveguide 20 (the general direction in which light travels). In the illustrated embodiment of FIG. 2B, interface 25 is arranged as a plane that is oblique to the square cross-section (the cross-section perpendicular to the length) of waveguide 20. In the illustrated embodiment, interface 25 is arranged to obliquely cross two G (green) LEDs.

[0038] The surface 25 may be coated with a partial reflection coating. In this embodiment, a reflection coating is assumed such that surface 25 reflects 50% of the light incident thereon for all wavelengths and all angles. As an example, this can be achieved by forming waveguide 20 using two prisms each having a triangular cross-section and the length of waveguide 20. The interface surfaces of one or both of the prisms may be coated with a partial reflection coating. Then, the two prisms may be adhered to each other such that the interface between the two prisms corresponds to the internal partial reflection surface 25.

[0039] FIG. 2C shows the color distribution detected at the end 18 of waveguide 20 that includes the internal partial reflection surface 25 as a function of the length of waveguide 20. As can be seen from FIG. 2C, the presence of the partial reflection surface 25 in waveguide 20 improves color mixing from waveguide 10 to waveguide 20.

[0040] An ideal coating having the same reflectivity for all wavelengths and angles may be difficult to achieve. However, mixing can also be improved by using a layer of a high refractive index adhesive on the surface 25. This can potentially be achieved, for example, by forming the waveguide 20 using two prisms each having a triangular cross-section and the length of the waveguide 20, as described above. The two prisms may be adhered to each other using a high refractive index adhesive such that the interface between the two prisms corresponds to the internal partial reflection surface 25. An example of a high refractive index adhesive or adhesive is an epoxy-based adhesive containing high refractive index particles or additives. These additives are typically fine particles of a material having a high refractive index (for example, titanium dioxide (TiO2) or barium titanate (BaTiO3)). When mixed with the epoxy adhesive, its refractive index increases and becomes higher than that of the surface of the prism.

[0041] FIG. 2B discloses a partial reflection surface 25 arranged along the diagonal of the square cross-section of the waveguide 20, but other embodiments with different geometric shapes of the surface and cross-section are also conceivable. For example, similar results can also be obtained in the case of a tapered waveguide where the size cross-section of the surface of the exit end 18 is different from that of the inlet end 16.

[0042] FIGS. 3A, 3B, and 3C show a similar configuration except that the waveguides 30 of the POD 130 have a rectangular cross-section. In this embodiment, the discrete light source matrix 132 of the POD 130 includes LEDs in a 3×2 array in the BGR:RGB format, as shown in FIG. 3A. The cross-section is, by way of example, 3×2 mm. In FIG. 3B, the waveguide 40 includes a partial reflection surface 45 (similar to the surface 25) arranged along the diagonal of the central G LED. The inner surface 45 divides the rectangular cross-section into two equal trapezoids. FIG. 3C shows the effect of the internal partial reflection surface 45. As can be seen from FIG. 3C, color mixing is improved along with the length of the waveguides 30, 40, and importantly, color mixing is improved by the inclusion of the internal partial reflection surface 45 within the waveguide 40.

[0043] Figures 4A and 4B show the same principle applied to a waveguide having a circular cross-section to improve color mixing. Waveguides with square and rectangular cross-sections are more commonly used, but circular waveguides have their own uses and advantages in certain scenarios.

[0044] In FIGS. 4A and 4B, a discrete light source matrix 132 in the form of a quad array of LEDs is introduced to irradiate light onto the input surface 16 of the waveguide 50 (a waveguide with a circular cross-section). The circular cross-section may be set such that the circle exactly surrounds the quad array. For example, if the side of the square is 1 mm, the diameter Φ of the circle is

[0045]

Number

[0046] In addition to the partial reflection surface described above, a partial lens can be used to improve the color mixing performance of the POD130. The partial lens corresponds to a portion smaller than the coupling-in interface 16 of the waveguide or the entire input surface. For example, the partial lens may correspond to 25% - 75% of the area of the coupling-in interface 16.

[0047] FIG. 5A shows a waveguide 70 having a configuration similar to that of waveguide 10 of FIG. 2A, except that the waveguide 70 includes a partial lens 77 at a coupling-in interface 16 (the optical inlet of the waveguide 70). In the illustrated embodiment of FIG. 5A, the discrete light source matrix 132 of FIG. 2 corresponds to a quad 2×2 LED array. Light from the discrete light source matrix 132 is introduced into the waveguide 70 through the coupling-in interface 16 and forms a coupling-in pattern in the order of GB:RG (first column: green, blue; second column: red, green), similar to FIG. 2A. However, the embodiment of FIG. 5A includes a partial lens 77.

[0048] In the illustrated embodiment, the lens 77 has an annular cross-section that overlaps 50% of the area of the coupling-in interface 16 of the waveguide 70. The diameter of the outer circle is the same as the width / height of the coupling-in interface 16 (the width / height of the quad LED array), and the diameter of the inner circle (the part without the lens 77) is about 0.6 of the overall width / height. Thus, the lens 77 covers 50% of the area of the coupling-in interface 16.

[0049] The lens 77 splits the light irradiated by the discrete light source matrix 132 such that 50% of the light is refracted by the lens and the center comes to a position opposite to the light not refracted by the lens, thereby improving the mixing. Such a 50% split can be achieved by a lens having an annular cross-section as shown in FIG. 5B, by a lens having a cross-section overlapping the inner circle (having an area of 50%) as shown by the partially filled area in FIG. 5C, or by a partially filled square as shown in FIG. 5D.

[0050] FIG. 5E shows an annular 50% partial lens, and FIG. 5F shows a square 50% partial lens for a cylindrical waveguide. These partial lenses may be partial cylindrical lenses whose flat surfaces are arranged with respect to the coupling-in interface 16 of the waveguide.

[0051] Using partial lenses contributes to color mixing in the same way as the internal partial surfaces, as described above. FIG. 5G shows the color distribution detected at the end 18 of the waveguide 70 including the partial lens 77 as a function of the length of the waveguide 70, compared to the waveguide 10. As can be seen from FIG. 5G, the presence of the partial lens 77 in the waveguide 70 improves color mixing from the waveguide 10 to the waveguide 70.

[0052] FIG. 6A shows a waveguide 80 having both the partial lens 77 at the coupling-in interface 16 and the partial reflective surface 25 along the waveguide 80. The results of color mixing are shown in FIG. 6B. FIG. 6B shows the color distribution without mixing by either the partial lens or the partial reflective surface (waveguide 10), compared to the color distribution by the inner surface 25 with a high refractive index (e.g., 1.7; Abbe = 30) and the 50% partial lens 77 (waveguide 80). As seen in FIG. 6B, the results over an equivalent length (e.g., 10 mm) are nearly ideally uniform and correspond to nearly pure white.

[0053] FIG. 7A shows the rectangular waveguide 90 of FIG. 2 having both the partial lens 97 at the coupling-in interface 16 and the partial reflective surface 45 along the waveguide 90. According to the same rationale as in the case of the hexagonal LED array 132 of the 3×2 RGB:BGR array, a pair of two cylindrical lenses 97 can be introduced into half of the LED region (the region of the coupling-in interface 16). They are arranged to overlap half of the BR and RB LEDs and one quarter of the GG LEDs. The lens 97 may be semi-cylindrical with a power along the horizontal direction, refracting the GG LED light towards the RB LED, or vice versa. Using a semi-cylindrical lens instead of a hemispherical lens may result in a better mixing effect. However, hemispherical lenses should also be considered as they can provide an improvement over the prior art. The exact focal length of the lens 97 may need to be varied according to the exact length of the waveguide 90. The partial semi-cylindrical lens 97 can be introduced in front of the waveguide 90 together with the internal partial reflective surface 45, as shown in FIG. 7A.

[0054] The result of color mixing is shown in FIG. 7B. FIG. 7B shows a color distribution without mixing by either a partial lens or a partial reflecting surface (waveguide 10) compared with a color distribution (waveguide 90) by an inner surface 45 of a high refractive index (e.g., 1.7; Abbe = 30) and a 50% partial lens 97 (radius of curvature 1.5 mm, conic constant zero, size H = 1 mm, W = 0.375 mm). As seen in FIG. 7B, the results over an equal length (e.g., 10 mm) are nearly ideally uniform and correspond to nearly complete white.

[0055] A typical method can be better understood with reference to the flowchart of FIG. 8. For the purpose of simplicity of explanation, the illustrated methodology is shown and described as a series of blocks, but it should be understood that the methodology is not limited by the order of the blocks. This is because some blocks may be performed in an order different from that shown and described, or simultaneously with other blocks. Further, the blocks required to implement the typical methodology may be fewer than all those shown. Further, additional methodology, alternative methodology, or both may use additional blocks not shown.

[0056] In a flowchart, a block represents a "processing block" that can be implemented by logic. A processing block may represent a method step or a device element for executing a method step. A flowchart does not depict the syntax for any particular programming language, methodology, or style (e.g., procedural, object-oriented). Rather, a flowchart shows the functional information that a person skilled in the art can use to develop the logic for executing the illustrated processing. In some examples, it is understood that program elements such as temporary variables, routine loops, etc. are not illustrated. Further, it is understood that electronic applications and software applications may include dynamic and flexible processes such that the illustrated blocks can be executed in a different order than illustrated, or the blocks can be combined or separated into multiple components. It is understood that the process can be implemented using various programming approaches such as machine language, procedural, object-oriented, or artificial intelligence techniques.

[0057] FIG. 8 shows a flowchart for a typical method 200. As shown in FIG. 8, process 200 may include providing a discrete light source matrix for emitting light corresponding to an image (block 201). Process 200 may also include providing a waveguide having a coupling-in interface for coupling light corresponding to the image into the waveguide, an internal partial reflection interface inside the waveguide, or a partial lens (s) at the input of the waveguide (block 202). Also as shown in FIG. 8, process 200 may include arranging the discrete light source matrix to optically communicate with the coupling-in interface of the waveguide (block 204).

[0058] Still further, as shown in FIG. 8, in a first embodiment, process 200 may include reflecting a first portion of the light emitted by the discrete light source matrix from the internal partial reflection interface and transmitting a second portion of the light emitted by the discrete light source matrix through the internal partial reflection interface to improve color mixing (block 206).

[0059] In the second embodiment, alone or in combination with the first embodiment, process 200 uses one or more lenses to split the light output by the discrete light source matrix such that 25% to 50% of the light is refracted by one or more lenses and centered at a position opposite to the light not refracted by one or more lenses (block 208).

[0060] In the third embodiment, alone or in combination with the first or second embodiment, the discrete light source matrix is part of a projector selected from the group having a digital light processing (DLP) projector, an LCD or LCoS (liquid crystal on silicon) projector, and an LED array.

[0061] In the fourth embodiment, alone or in combination with one or more of the first to third embodiments, the internal partial reflection interface includes a partially reflective coating and / or a high refractive index adhesive.

[0062] In the fifth embodiment, alone or in combination with one or more of the first to fourth embodiments, the waveguide is cylindrical with a circular cross-section, and the internal partial reflection interface is arranged to divide the circular cross-section.

[0063] FIG. 8 shows an example block of process 200. However, in some embodiments, process 200 may include additional blocks, fewer blocks, different blocks, or blocks in a different arrangement compared to that shown in FIG. 8. FIG. 1 shows a schematic diagram of a typical optical system for a near-eye display (NED). Additionally or alternatively, two or more blocks of process 200 may be executed in parallel. Definition

[0064] Included below are definitions of selected terms used herein. The definitions include various examples or forms of components that are within the scope of the term and can be used in embodiments. The examples are not intended to be limiting. Both the singular and plural forms of the terms can be within the scope of the definitions.

[0065] "Operable connection" or an entity being "operably connected" means a connection through which signals, physical communication, or logical communication can be sent and received. Typically, an operable connection includes a physical interface, an electrical interface, or a data interface, but note that an operable connection can include different combinations of these or other types of connections sufficient to enable operable control. For example, two entities can be operably connected by being able to transmit signals directly to each other or through one or more intermediate entities such as a processor, an operating system, logic, software, or other entities. An operable connection can be made using logical or physical communication channels.

[0066] The terms "includes" or "including", as used in the detailed description or claims, are intended to be inclusive in the same manner as the term "comprising" as interpreted when used as a transitional term in the claims. Further, the term "or", as used in the detailed description or claims (e.g., A or B), is intended to mean "A or B or both". When the applicant intends to indicate "only A or B, but not both", the term "only A or B, but not both" is used. Thus, the use of the term "or" herein is inclusive and not exclusive. See Bryan A. Garner, A Dictionary of Modern Legal Usage 624 (2d Ed. 1995).

[0067] Although exemplary systems, methods, etc. have been illustrated by way of example and described in some detail, it is not the intention of the applicant to limit the scope in such detail or in any way. Of course, for the purpose of describing the systems, methods, etc. described herein, it is not possible to describe every conceivable combination of components or methodologies. Further advantages and modifications will be readily apparent to those skilled in the art. Accordingly, the invention is not limited to the specific details, representative apparatus, and illustrative examples shown and described. Thus, this application is intended to cover alterations, modifications, and variations that fall within the scope of the appended claims. Further, the foregoing description is not intended to limit the scope of the invention. Rather, the scope of the invention is determined by the appended claims and their equivalents.

Claims

1. An optical projection system for improving the uniformity of color mixing, comprising: A discrete light source matrix for emitting light corresponding to an image; A waveguide formed of a transparent material, having a coupling-in interface for coupling the light corresponding to the image into the waveguide, and a coupling-out interface for coupling the image out of the waveguide; An internal partial reflection surface disposed within the waveguide and extending along the length of the waveguide, the internal partial reflection surface being disposed so as to obliquely cross a cross section perpendicular to the length of the waveguide; One or more partial lenses disposed between the discrete light source matrix and the coupling-in interface, the one or more partial lenses overlapping only 25% to 75% of the area of the discrete light source matrix or the area of the coupling-in interface.

2. The optical projection system according to claim 1, wherein the internal partial reflection surface is coated with a partial reflection coating or corresponds to a high refractive index material.

3. The optical projection system according to claim 1, wherein the internal partial reflection surface includes a coated surface having a reflection coating that reflects approximately 50% of the light for all wavelengths and incident angles.

4. The optical projection system according to claim 1, wherein the waveguide includes two prisms each having a triangular cross section, the two prisms are adhered to each other, and an interface between the two prisms corresponds to the internal partial reflection surface.

5. The optical projection system according to claim 1, wherein the optical projection system corresponds to a projector selected from the group consisting of a digital light processing (DLP) projector, an LCD (liquid crystal display), an LCoS (liquid crystal on silicon) projector, and an array of LEDs.

6. An optical projection system for improving the uniformity of color mixing, comprising: A discrete light source matrix for emitting light corresponding to an image; An optical waveguide formed of a transparent material, having a coupling-in interface for coupling the light corresponding to the image into the optical waveguide, and a coupling-out interface for coupling the image out of the optical waveguide; An internal partial reflection surface disposed within the optical waveguide and extending along the length of the optical waveguide, the internal partial reflection surface being disposed so as to obliquely cross a cross section perpendicular to the length of the optical waveguide. **Claim 7** The optical projection system according to claim 6, wherein the internal partial reflection surface is coated with a partial reflection coating or corresponds to a high refractive index material. **Claim 8** The optical projection system according to claim 6, wherein the internal partial reflection surface includes a coated surface having a reflection coating that reflects approximately 50% of the light for all wavelengths and angles. **Claim 9** The optical projection system according to claim 6, wherein the optical waveguide includes two prisms each having a triangular cross section, the two prisms being adhered to each other, and an interface between the two prisms corresponding to the internal partial reflection surface. **Claim 10** The optical projection system according to claim 6, wherein the optical waveguide is tapered with a varying cross-sectional size, and the internal partial reflection surface is disposed obliquely. **Claim 11** An optical projection system for improving the uniformity of color mixing, comprising: A discrete light source matrix for emitting light corresponding to an image; An optical waveguide formed of a transparent material, having a coupling-in interface for coupling the light corresponding to the image into the optical waveguide, and a coupling-out interface for coupling the image out of the optical waveguide; One or more partial lenses disposed between the discrete light source matrix and the coupling-in interface, the one or more partial lenses overlapping a) the area of the coupling-in interface or b) 25% to 75% of the output area of the discrete light source matrix, an optical projection system. Claim 12 The optical projection system according to claim 11, wherein the waveguide is cylindrical with a circular cross-section, and the internal partial reflection surface is arranged to divide the circular cross-section. Claim 13 The optical projection system according to claim 11, wherein the waveguide is cylindrical and the one or more partial lenses have an annular cross-section. Claim 14 The optical projection system according to claim 11, wherein the internal partial reflection surface is coated with a partial reflection coating and / or includes a high refractive index adhesive. Claim 15 The optical projection system according to claim 11, wherein the discrete light source matrix corresponds to a projector selected from the group consisting of a digital light processing (DLP) projector, an LCD, a liquid crystal on silicon (LCoS) projector, and an array of LEDs. Claim 16 A method for improving color uniformity of a small optical projector, comprising: Providing a discrete light source matrix for emitting light corresponding to an image; Providing a waveguide having a rectangular or circular cross-section, the waveguide having a coupling-in interface for coupling light corresponding to the image into the waveguide and an internal partial reflection interface inside the waveguide; Arranging the discrete light source matrix to be in optical communication with the coupling-in interface of the waveguide; Reflecting a first portion of the light emitted by the discrete light source matrix from the internal partial reflection interface and transmitting a second portion of the light emitted by the discrete light source matrix through the internal partial reflection interface to improve color mixing of the output of the small light projector. A method including this.

17. Using one or more lenses to split the light output by the discrete light source matrix, and causing 50% of the light to be refracted by the one or more lenses so that the center comes to a position opposite to the light not refracted by the one or more lenses. The method according to claim 16, comprising:

18. The method according to claim 16, wherein the small light projector is selected from the group consisting of a digital light processing (DLP) projector, an LCD, an LCoS (liquid crystal on silicon) projector, and an LED array.

19. The method according to claim 16, wherein the internal partial reflection interface is coated with a partial reflection coating and / or includes a high refractive index adhesive.

20. The method according to claim 16, wherein the waveguide is cylindrical with a circular cross-section, and the internal partial reflection interface is arranged to divide the circular cross-section.

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