Microlens array polarization recycling optics for illumination optics

Abstract

Systems and methods for providing a polarization recycling structure for use in applications such as display systems comprising liquid crystal display assemblies. The polarization recycling structure may include a first space-varying polarizer spaced apart from a second space-varying polarizer. The first space-varying polarizer may include a lens array that receives light from a light source, focuses light of a first polarization state, and passes light of a second polarization state. The second space-varying polarizer receives light from the first space-varying polarizer, passes the focused light of the first polarization state, and converts light of the second polarization state to the first polarization state, thereby providing only light of the first polarization state at the output of the polarization recycling structure. The polarization recycling structure improves the efficiency of the illumination subsystem, thereby reducing power consumption, cost, and space requirements, and providing other advantages.

Description

[Technical Field]

[0001] The present disclosure relates generally to display systems, and more particularly to polarizers for display systems. [Background technology]

[0002] The demand for enhanced display performance has increased with the growth of smartphones, tablets, wearable devices, high-definition televisions, and other electronic devices. The growing popularity of virtual reality and augmented reality systems, particularly those using head-mounted displays, has further fueled this demand. Virtual reality systems typically completely surround the wearer's eyes and replace the actual field of view (or actual reality) in front of the wearer with a "virtual" reality, while augmented reality systems typically provide a semi-transparent or transparent overlay of one or more screens in front of the wearer's eyes so that the actual field of view is augmented with additional information. In many virtual reality and augmented reality systems, the movement of the wearer of such a head-mounted display can be tracked in various ways, for example, via sensors within and / or external to the head-mounted display, to enable the images shown to reflect the user's movement.

[0003] There is an increasing demand for displays that have improved performance while also being smaller or larger in size, consuming less power, and generating less heat than currently available displays. Thus, there is a need for improved display panels and improved techniques for making and using display panels. Summary of the Invention

[0004] The polarization recycling structure includes a first space-changing polarizer configured to receive incident light from a light source, the first space-changing polarizer forming a lens array including a plurality of lens elements each focusing light of a first polarization state, the first space-changing polarizer further configured to pass incident light having a second polarization state orthogonal to the first polarization state without such light being focused by the lens elements of the lens array; and a second space-changing polarizer spaced apart from the first space-changing polarizer and positioned to receive light from the first space-changing polarizer. and a second space-changing polarizer, wherein the second space-changing polarizer has an array of linear polarizer regions configured to pass light having the first polarization state, each of the linear polarizer regions in the array sized and dimensioned to receive focused light of the first polarization state from a respective one of the lens elements of the lens array of the first space-changing polarizer, and the second space-changing polarizer further has a polarization conversion region surrounding the linear polarizer region and converting light having the second polarization state to light having the first polarization state. Each of the first space-changing polarizer and the second space-changing polarizer includes a multi-twist retarder. The lens array of the first space-changing polarizer may include a microlens array diffraction pattern in the multi-twist retarder. The polarization conversion region may include a phase retarder. The polarization conversion region may include a quarter-wave retarder. The second space-changing polarizer may be positioned in a focal plane of the lens elements of the lens array of the first space-changing polarizer. Each of the linear polarizer regions may have a maximum dimension that is less than 100 microns, and each of the linear polarizer regions may be separated from each other linear polarizer region by at least 0.5 millimeters. The linear polarizer regions may cumulatively comprise a surface area that is less than 5 percent of the surface area of ​​the polarization conversion region.

[0005] The display includes a light source; a polarization recycling structure, a first space-changing polarizer configured to receive incident light from the light source, the first space-changing polarizer forming a lens array including a plurality of lens elements each focusing light of a first polarization state, the first space-changing polarizer further configured to pass incident light having a second polarization state orthogonal to the first polarization state without such light being focused by the lens elements of the lens array; and a second space-changing polarizer spaced apart from the first space-changing polarizer and positioned to receive light from the first space-changing polarizer, the second space-changing polarizer focusing the first polarization state. The polarization recycling structure may be summarized as comprising: an array of linear polarizer regions configured to pass light having a polarization state, each of the linear polarizer regions in the array sized and dimensioned to receive focused light of the first polarization state from a respective one of the lens elements of the lens array of the first space-varying polarizer; and a second space-varying polarizer surrounding the linear polarizer regions and further including a polarization conversion region that converts light having the second polarization state to light having the first polarization state; and a non-emissive display assembly positioned to receive the light of the first polarization state from the second space-varying polarizer. The non-emissive display assembly may include a liquid crystal display assembly. The light source may include an array of light-emitting diodes. The display may be a display of a head-mounted display device, a television, a laptop computer, a smartphone, a tablet computer, a computer monitor, or a wearable electronic device. Each of the first space-varying polarizer and the second space-varying polarizer may include a multi-twist retarder. The lens array of the first space-varying polarizer may include a microlens array diffraction pattern in a multi-twist retarder. The polarization conversion region may include a phase retarder. The polarization conversion region may include a quarter-wave retarder. The second space-varying polarizer may be positioned in a focal plane of the lens elements of the lens array of the first space-varying polarizer.Each of the linear polarizer regions may have a largest dimension that is less than 100 microns. Each of the linear polarizer regions may be separated from each other linear polarizer region by at least 0.5 millimeters.

[0006] The polarization recycling structure includes a first multi-twist retarder forming a lens array including a plurality of lens elements, each of which focuses light of a first polarization state and passes light of a second polarization state orthogonal to the first polarization state without focusing such light, and a second multi-twist retarder positioned in a focal plane of the lens elements of the lens array of the first multi-twist retarder, the second multi-twist retarder passing light having the first polarization state. and a second multi-twist retarder, the second multi-twist retarder further comprising a polarization conversion region surrounding the linear polarizer region and configured to convert light having the second polarization state to light having the first polarization state, wherein each of the linear polarizer regions in the array is sized and dimensioned to receive focused light of the first polarization state from a respective one of the lens elements of the lens array of the first multi-twist retarder. [Brief explanation of the drawings]

[0007] In the drawings, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes and angles of various elements are not necessarily drawn to scale, and some of these elements may be arbitrarily enlarged and positioned to improve the readability of the drawings. Furthermore, the particular shapes of the elements as drawn are not necessarily intended to convey any information regarding the actual shape of the particular elements, but may have been selected solely for ease of recognition in the drawings.

[0008] [Figure 1]1 is an example of a head-mounted display device with dual display panels according to one illustrated implementation.

[0009] [Figure 2] 1 is an example of a laptop with a display panel according to one illustrative implementation.

[0010] [Figure 3] 1 is an example of a smartphone with a display panel according to one non-limiting illustrative implementation.

[0011] [Figure 4] FIG. 2 is a cross-sectional view of a display panel with a backlight assembly and polarization recycling structure according to one non-limiting illustrative implementation.

[0012] [Figure 5] 5 is a simplified cross-sectional view of the polarization recycling structure shown in FIG. 4 according to one non-limiting illustrative implementation.

[0013] [Figure 6A] FIG. 1B is a front view of a first space-varying polarizer of a polarization recycling structure providing a microlens array, according to one non-limiting illustrative implementation.

[0014] [Figure 6B] FIG. 10 is a front view of a second space-varying polarizer of a polarization recycling structure that provides an array of linear polarizer regions surrounded by polarization converting regions, according to one non-limiting illustrated implementation. DETAILED DESCRIPTION OF THE INVENTION

[0015] In the following description, certain specific details are set forth to provide a thorough understanding of various disclosed implementations. However, those skilled in the art will recognize that these implementations may be practiced without one or more of these specific details, or with other methods, components, materials, etc. In other instances, well-known structures associated with computer systems, server computers, and / or communication networks have not been shown or described in detail to avoid unnecessarily obscuring the description of these implementations.

[0016] Unless the context requires otherwise, throughout this specification and the claims that follow, the term "comprising" is synonymous with "including" and is inclusive or open-ended (i.e., does not exclude additional, unrecited elements or method actions).

[0017] References throughout this specification to "one implementation" or "an implementation" mean that a particular feature, structure, or characteristic described in connection with that implementation is included in at least one implementation. Thus, the appearances of the phrase "in one implementation" or "in an implementation" in various places throughout this specification are not necessarily all referring to the same implementation. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more implementations.

[0018] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. It should also be noted that the term "or" is generally utilized to include "and / or" in its meaning unless the context clearly dictates otherwise.

[0019] The headings and abstract of the disclosure provided herein are for convenience only and do not interpret the scope or meaning of the implementations.

[0020] Many direct-view flat-panel displays and projection displays use unpolarized light sources, such as ambient light, CCFL lamps, light-emitting diodes, or other types of light sources. However, many display systems, such as those utilizing liquid crystal (LC) materials, including LC displays (LC) or LC-on-silicon (LCoS) microdisplays, may require light to be polarized to operate properly. Conventional polarizers are available that only allow light with the desired polarization to pass, but they are inefficient because undesired light is typically absorbed or reflected in a different direction. These types of polarizers can have efficiencies of less than 50%, which is particularly undesirable in applications where power consumption, size, heat generation, or cost are important factors. Another approach recycles undesired polarized light by repeatedly reflecting it and then receiving it again, so that at least some of the light has the correct polarization. While this technique offers relatively high efficiency (e.g., 50%-75%) compared to reflective or absorptive polarizers, a large portion of the light from a randomly polarized light source is still lost.

[0021] One or more implementations of the present disclosure are directed to polarization recycling structures for use in a variety of applications, including displays for electronic devices such as head-mounted display devices, laptop computers, tablet computers, televisions, smartphones, wearable computers, computer monitors, etc. Non-limiting examples of electronic devices that may include such displays are shown in Figures 1-3. As discussed further below, the present disclosure improves the performance of display systems (e.g., LCD, LCoS) or other types of components by providing a polarization recycling structure that receives unpolarized light or 45-degree polarized light and efficiently provides polarized light for use in various applications, such as display systems.

[0022] 1 illustrates a non-limiting example of an electronic device in the form of a head-mounted display device 100, which may be coupled to a video-rendering computing system via a wired or wireless connection to provide a virtual reality display to a human user. In operation, a user wears the HMD device 100 on their head, secured via one or more straps 101, and receives displayed information of a simulated environment, different from the actual physical environment, from the computing system in each eye via displays 102a and 102b supported by the HMD device's support structure 104, the computing system acting as an image-rendering system that supplies images of the simulated environment to the HMD device for display to the user, such as images generated by a game program (not shown) and / or other software program (not shown) running on the computing system. The user, in this example, is further capable of moving around the actual physical environment and may further have one or more I / O (“input / output”) devices, such as a handheld controller communicatively coupled to the computing system via a wired or wireless connection, that enable the user to further interact with the simulated environment. As the user moves location and / or changes orientation of HMD device 100, the position of the HMD device may be tracked, for example, to enable a corresponding portion of the simulated environment to be displayed to the user on the HMD device, and the controller may further employ similar techniques for use in tracking the position of the controller (and optionally, to use that information to assist in determining and / or verifying the position of the HMD device). After the tracked position of HMD device 100 is known, the corresponding information is transmitted to a computing system, which uses this tracked position information to generate one or more subsequent images of the simulated environment for display to the user via displays 102a and 102b.

[0023] 2 shows an exemplary electronic device in the form of a laptop computer 200 having an upper housing 202 and a lower housing 204 coupled together via a hinge 206 that allows the housings to rotate relative to one another. The lower housing 204 includes a keyboard 208 and may include other structures (e.g., a touchpad, various ports). The upper housing 202 includes a display panel 210 that can be used to display content to a user.

[0024] 3 illustrates an exemplary electronic device in the form of a smartphone 300. The smartphone 300 includes a housing 302 that includes a display panel 304 and a number of input components 306 (e.g., buttons). In at least some implementations, the display panel 304 may be, for example, a touchscreen display.

[0025] More generally, the displays of the present disclosure may be implemented in any type of electronic device, such as the devices shown in FIGS. 1-3 or other devices, including music players, augmented reality devices, gaming devices, navigation units, vehicle displays, wearable devices, kiosks, or other types of devices with one or more displays.

[0026] 4 illustrates a cross-sectional side view of an exemplary liquid crystal display (LCD) 400 according to one or more embodiments of the present disclosure. Display 400 may be implemented in any type of electronic device, such as device 100 of FIG. 1, device 200 of FIG. 2, and device 300 of FIG. 3. Furthermore, it should be understood that implementations of the present disclosure may be used with other types of displays (e.g., LCoS) or in any other application where it is desired to efficiently obtain polarized light from unpolarized (randomly polarized) light.

[0027] The display 400 includes multiple stacked layers, each of which may be generally similar in shape (e.g., rectangular). The display 400 may include a backlight assembly 402 that receives light 403 from a light source 404 positioned substantially adjacent an edge of the backlight assembly 402. The display 400 also includes a display module that includes an LCD panel 406 or other display layers (e.g., any non-emissive display assembly layers), other light processing layers such as optical films 408, and polarization recycling optical elements or structures 410. As discussed further below, the polarization recycling structures 410 are operable to receive unpolarized light and efficiently output linearly polarized light for use by the LCD panel 406. The optical film layers 408 may include one or more diffusive layers (e.g., diffusion films) to reduce hot spots, compensation films to improve off-axis viewing, or other types of films (e.g., prismatic films to collimate the backlight 402).

[0028] It should be understood that the configuration shown in FIG. 4 is merely exemplary and that other configurations are contemplated which may include the same layers arranged differently, fewer or more layers, or different layers.

[0029] 5 shows a simplified cross-sectional side view of an example polarization recycling structure 500 that may implement features of the present disclosure. The polarization recycling structure 500 may be implemented in any type of electronic device, such as device 100 of FIG. 1, device 200 of FIG. 2, and device 300 of FIG. 3, and may be similar to or identical to polarization recycling structure 410 of FIG. 4.

[0030] The polarization recycling structure 500 comprises a first space-varying polarizer 502 spaced apart from a second space-varying polarizer 504. The polarizers 502 and 504 may be separated using, for example, a suitable transparent spacer element or layer (not shown). A simplified plan view of the first space-varying polarizer 502 is shown in FIG. 6A , and a simplified plan view of the second space-varying polarizer 504 is shown in FIG. 6B . As discussed further below, each of the first space-varying polarizer 502 and the second space-varying polarizer 504 may be formed from a multi-twist retarder (MTR) material. In operation, the polarization recycling structure 500 is operable to receive randomly polarized light 506 from a light source (e.g., an LED) and provide polarized light 508 of a first polarization state to a component, such as a liquid crystal component of a display, as discussed above.

[0031] The first space-varying polarizer 502 is configured to receive randomly polarized incident light 506. As shown in FIGS. 5 and 6A, the first space-varying polarizer 502 may provide a diffraction pattern forming a lens array (e.g., a 2D microlens array) including a plurality of lens elements 510, each of which focuses light 512 of a first polarization state. The first space-varying polarizer 502 is further configured to pass incident light 514 (shown by dashed lines in FIG. 5) having a second polarization state orthogonal to the first polarization state without such light being focused by the lens elements 510 of the lens array. In other words, the first space-varying polarizer 502 may be polarization-sensitive in the sense that it focuses light of the first polarization state through the lens elements and passes light of the second polarization state without substantial alteration.

[0032] The second space-changing polarizer 504 may be spaced apart from the first space-changing polarizer and positioned to receive light 512 and 514 from the first space-changing polarizer 502. As an example, the second space-changing polarizer 504 may be positioned at or proximate to the focal plane of the lens elements 510 of the first space-changing polarizer. As shown in FIGS. 5 and 6B , the second space-changing polarizer 504 includes an array of linear polarizer regions 516 configured to pass focused light 512 having a first polarization state. As shown, each of the linear polarizer regions 516 in the array may be sized and dimensioned to receive focused light 512 of the first polarization state from a respective one of the lens elements 510 of the lens array of the first space-changing polarizer 502.

[0033] The second space-varying polarizer 504 further comprises a polarization conversion region 518 that surrounds the linear polarizer region 516 and converts light 514 having the second polarization state to light having the first polarization state. As an example, the polarization conversion region 518 may include a phase retarder, such as a quarter-wave retarder. Thus, the light 508 exiting the polarization recycling structure 500 is light of the first polarization state required by one or more downstream components, such as a liquid crystal assembly of a display system (e.g., LCD, LCoS).

[0034] Each of the linear polarizer regions 516 may have a maximum dimension 520 ( FIG. 5 ) that is less than or equal to 100 microns (e.g., 20 microns, 50 microns, 80 microns), and each of the linear polarizer regions may be separated from each other linear polarizer region by a distance 522, which in some implementations may be at least 0.5 millimeters (e.g., 0.5 millimeters, 1 millimeter, 2 millimeters). In at least some implementations, the linear polarizer regions 516 cumulatively comprise a surface area that is less than or equal to 5 percent (e.g., 0.5 percent, 1 percent, 3 percent) of the surface area of ​​the polarization conversion region 518. The linear polarizer regions 516 may have any suitable surface area shape (e.g., circular, rectangular).

[0035] As an overview of the operation of the polarization recycling structure 500, incident light 506 includes light of both orthogonal first and second polarization states. A portion of the light 506 having the first polarization state is focused by the lens element 510 of the first space-change polarizer 502, passes through the linear polarizer region 516 of the second space-change polarizer 504, and exits the polarization recycling structure 500 as light 508 having the first polarization state. A portion of the light 506 having the second polarization state passes through the first space-change polarizer 502 without being focused by the lens element 510 (see light 514), is converted to the first polarization state by the polarization conversion region 518 of the second space-change polarizer 504, and also exits the polarization recycling structure 500 as light 508 having the first polarization state. In this way, all of the light 506 incident on the polarization recycling structure 500 is provided at the output as light 508 of the first polarization state, except for light 514 of the second polarization state that is blocked by the linear polarizer region 516 of the second space-variant polarizer 504. However, because the area of ​​the linear polarizer region can be small relative to the total area of ​​the space-variant polarizer 504, which primarily includes the polarization conversion region 518, only a small fraction (e.g., 1 percent, 5 percent) of the light 506 is lost. Therefore, the polarization recycling structure 500 may advantageously provide polarized light from unpolarized light with very high efficiency (e.g., greater than 90 percent, greater than 95 percent).

[0036] As discussed above, one or both of the first space-varying polarizer 502 and the second space-varying polarizer 504 of the polarization recycling structure 500 may include a wave retarder formed from a birefringent material. Birefringence is a property of a material that has a refractive index that depends on the polarization and direction of propagation of the light. A wave retarder alters the polarization state or phase of light traveling through it. The wave retarder may have a slow axis (or extraordinary axis) and a fast axis (or ordinary axis). When polarized light travels through the wave retarder, light along the fast axis travels more quickly than light along the slow axis.

[0037] In at least some implementations, the space-varying polarizers 502 and 504 may be formed from multi-twist retarders (MTRs), which are waveplate-like retardation films that provide precise and customized levels of broadband, narrowband, or multiband retardation in a single thin film. More specifically, MTRs comprise two or more twisted liquid crystal (LC) layers on a single substrate and with a single alignment layer. Subsequent LC layers are directly aligned by the previous layer, thereby enabling simple fabrication and achieving automatic layer alignment, resulting in a monolithic film with a continuously varying optical axis.

[0038] The various implementations described above can be combined to provide further implementations. These and other modifications can be made to the implementations in light of the above detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific implementations disclosed in the specification and claims, but should be construed to include all possible implementations along with the full range of equivalents to which such claims are entitled. Accordingly, the claims are not limited by this disclosure.

Claims

1. a first space-varying polarizer configured to receive incident light from a light source, the first space-varying polarizer forming a lens array including a plurality of lens elements each focusing light of a first polarization state, the first space-varying polarizer further configured to pass incident light having a second polarization state orthogonal to the first polarization state without such light being focused by the lens elements of the lens array; a second space-changing polarizer spaced apart from the first space-changing polarizer and positioned to receive light from the first space-changing polarizer, the second space-changing polarizer having an array of linear polarizer regions configured to pass light having the first polarization state, each of the linear polarizer regions in the array sized and dimensioned to receive focused light of the first polarization state from a respective one of the lens elements of the lens array of the first space-changing polarizer, the second space-changing polarizer further having a polarization conversion region surrounding the linear polarizer regions and converting light having the second polarization state to light having the first polarization state; A polarization recycling structure comprising:

2. The polarization recycling structure of claim 1 , wherein the first space-varying polarizer and the second space-varying polarizer each comprise a multi-twist retarder.

3. 3. The polarization recycling structure of claim 1, wherein the lens array of the first space-varying polarizer comprises a microlens array diffractive pattern in a multi-twist retarder.

4. The polarization recycling structure of claim 1 , wherein the polarization converting region comprises a phase retarder.

5. The polarization recycling structure of claim 1 , wherein the polarization converting region comprises a half-wave retarder.

6. The polarization recycling structure of claim 1 , wherein the second space-varying polarizer is positioned in a focal plane of the lens elements of the lens array of the first space-varying polarizer.

7. 7. The polarization recycling structure of claim 1, wherein each of the linear polarizer regions has a largest dimension that is less than 100 microns, and each of the linear polarizer regions is separated from each other linear polarizer region by at least 0.5 millimeters.

8. 8. The polarization recycling structure of claim 1, wherein the linear polarizer regions cumulatively comprise a surface area that is less than 5 percent of the surface area of ​​the polarization converting region.

9. A light source and 1. A polarization recycling structure comprising: a first space-varying polarizer configured to receive incident light from the light source, the first space-varying polarizer forming a lens array including a plurality of lens elements each focusing light of a first polarization state, the first space-varying polarizer further configured to pass incident light having a second polarization state orthogonal to the first polarization state without such light being focused by the lens elements of the lens array; a second space-changing polarizer spaced apart from the first space-changing polarizer and positioned to receive light from the first space-changing polarizer, the second space-changing polarizer including an array of linear polarizer regions configured to pass light having the first polarization state, each of the linear polarizer regions in the array being sized and dimensioned to receive focused light of the first polarization state from a respective one of the lens elements of the lens array of the first space-changing polarizer, the second space-changing polarizer further including a polarization conversion region surrounding the linear polarizer regions and converting light having the second polarization state to light having the first polarization state; a polarization recycling structure having a non-emissive display assembly positioned to receive light of the first polarization state from the second space-varying polarizer; and A display comprising:

10. The display of claim 9 , wherein the non-emissive display assembly comprises a liquid crystal display assembly.

11. 11. A display as claimed in claim 9 or 10, wherein the light source comprises an array of light emitting diodes.

12. 12. The display of claim 9, wherein the display is a display of a head-mounted display device, a television, a laptop computer, a smartphone, a tablet computer, a computer monitor, or a wearable electronic device.

13. 13. The display of claim 9, wherein the first space-varying polarizer and the second space-varying polarizer each comprise a multi-twist retarder.

14. 14. The display of claim 9, wherein the lens array of the first space-varying polarizer comprises a microlens array diffractive pattern in a multi-twist retarder.

15. 15. A display according to any one of claims 9 to 14, wherein the polarization converting region comprises a phase retarder.

16. 16. A display according to any one of claims 9 to 15, wherein the polarization converting region comprises a half-wave retarder.

17. 17. A display according to any one of claims 9 to 16, wherein the second space-varying polarizer is positioned in a focal plane of the lens elements of the lens array of the first space-varying polarizer.

18. 18. A display according to any one of claims 9 to 17, wherein each of the linear polariser regions has a largest dimension that is less than 100 microns.

19. 19. A display according to any one of claims 9 to 18, wherein each of the linear polariser regions is spaced apart from each other linear polariser region by at least 0.5 millimetres.

20. a first multi-twist retarder forming a lens array including a plurality of lens elements, each of which focuses light of a first polarization state and passes light of a second polarization state orthogonal to the first polarization state without focusing such light; a second multi-twist retarder positioned in a focal plane of the lens elements of the lens array of the first multi-twist retarder, the second multi-twist retarder having an array of linear polarizer regions configured to pass light having the first polarization state, each of the linear polarizer regions in the array being sized and dimensioned to receive focused light of the first polarization state from a respective one of the lens elements of the lens array of the first multi-twist retarder, the second multi-twist retarder further having a polarization conversion region surrounding the linear polarizer regions and converting light having the second polarization state to light having the first polarization state; A polarization recycling structure comprising:

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