Spatially varying polarizer for display backlight

Abstract

Systems and methods for providing a display for an electronic device including a liquid crystal display panel assembly, a backlight assembly having a light source, and a spatially varying polarizer providing a phase delay that varies as a function of a propagation length from the light source. The display may also include a linear polarizer and other optical components that improve the efficiency of the backlight assembly, thereby reducing power consumption, cost, space requirements and providing other advantages.

Description

Technical Field

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

[0002] With the growth of smartphones, tablets, wearable devices, high-definition televisions, and other electronic devices, the demand for displays with enhanced capabilities is also increasing. Virtual reality and augmented reality systems, particularly those using head-mounted displays, have further increased this demand. Virtual reality systems typically completely encase the wearer's eyes and replace the actual view (or actual reality) in front of the wearer with a "virtual" reality; while augmented reality systems typically provide a translucent or transparent covering of one or more screens in front of the wearer's eyes, thereby augmenting the actual view 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 (e.g., by sensors in and / or external to the head-mounted display) so that the displayed image can reflect the user's movement.

[0003] There is an increasing need for displays that have improved performance while also being smaller or larger in size, consuming less power and generating less heat relative to what is currently available. Therefore, a need exists for improved display panels and improved techniques for making and using display panels. Summary of the invention

[0004] The display can be summarized as including: a non-emissive display panel assembly; a backlight assembly including a light source; and a spatially varying polarizer located between the non-emissive display panel assembly and the backlight assembly, the spatially varying polarizer having a polarization that varies spatially as a function of a propagation length from the light source. The spatially varying polarizer may include a multi-twisted retarder. The spatially varying polarizer may provide no retardation at a near end near the light source and provide a quarter-wavelength retardation at a far end opposite the near end. The retardation of the spatially varying polarizer may vary linearly or nonlinearly between a near end near the light source and a far end opposite the near end.

[0005] The display may also include a linear polarizer positioned between the spatially varying polarizer and the non-emissive display panel assembly. The linear polarizer may include a dual brightness enhancing film (DBEF).

[0006] The display may also include a control circuit operably coupled to the spatially varying polarizer, the control circuit being operable to selectively adjust the delay provided by the spatially varying polarizer. The backlight assembly may include a light guide having light scattering characteristics. The backlight assembly may include a light guide that does not include any light scattering characteristics. The backlight assembly may include a wedge-shaped light guide. The non-emissive display panel assembly may include a liquid crystal display panel assembly. The light source may include an array of light emitting diodes.

[0007] The display can be summarized as including: a non-emissive display panel assembly; a backlight assembly including a light guide and a light source providing light to the edge of the light guide; a reflective polarizer located between the non-emissive display panel assembly and the light guide; and a spatially variable polarizer located between the reflective polarizer and the light guide, the spatially variable polarizer having a polarization that varies spatially as a function of the propagation length from the light source. The spatially variable polarizer may include a multi-twisted retarder. The reflective polarizer may include a dual brightness enhancement film (DBEF). The spatially variable polarizer may provide no delay at the proximal end near the light source and provide a quarter-wavelength delay at the distal end opposite the proximal end. The light guide may include light scattering features. The light guide may not include any light scattering features. 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 smart phone, a tablet computer, a computer monitor, or a wearable electronic device. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In the drawings, the same reference numerals represent similar elements or actions. The sizes and relative positions of the elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not necessarily drawn to scale, and some of these elements may be arbitrarily enlarged and positioned to improve the readability of the drawings. In addition, the particular shapes of the elements shown in the drawings are not necessarily intended to convey any information about the actual shape of the particular element, and may be selected only for ease of identification in the drawings.

[0009] Figure 1 is an example of a head mounted display device including dual display panels according to an exemplary embodiment.

[0010] Figure 2 is an example of a laptop computer including a display panel according to an exemplary embodiment.

[0011] Figure 3 is an example of a smart phone including a display panel according to one non-limiting exemplary embodiment.

[0012] Figure 4 is a cross-sectional view of a display panel including a backlight assembly with a spatially varying polarizer according to one non-limiting exemplary embodiment.

[0013] Figure 5 is a detailed cross-sectional view of a display panel according to one non-limiting exemplary embodiment.

[0014] Figure 6 is a graph illustrating an example of phase retardation for a spatially varying polarizer as a function of propagation length from a light source according to one non-limiting exemplary embodiment.

[0015] Figure 7 is a plan view of a spatially varying polarizer according to a non-limiting exemplary embodiment showing that the phase retardation for the spatially varying polarizer varies as a function of propagation length from a light source from no retardation (linear) at the edge close to the light source to a quarter wavelength retardation (circular) at the edge far from the light source. DETAILED DESCRIPTION

[0016] In the following description, certain specific details are set forth in order to provide a thorough understanding of the various disclosed embodiments. However, one skilled in the relevant art will recognize that the embodiments may be practiced without one or more of these specific details, or with other methods, components, materials, etc. In other cases, well-known structures associated with computer systems, server computers, and / or communication networks are not shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

[0017] Throughout the specification and the appended claims, the word "comprising" is synonymous with "including" and is inclusive or open-ended (ie, does not exclude other unrecited elements or methodological acts) unless the context requires otherwise.

[0018] Throughout this specification, reference to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0019] 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 employed in its sense including "and / or" unless the context clearly dictates otherwise.

[0020] The titles and abstracts of the disclosure provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.

[0021] One or more embodiments of the present disclosure relate to displays for electronic devices, such as head mounted display devices, laptop computers, tablet computers, televisions, smart phones, wearable computers, computer monitors, etc. Figures 1 to 3 Non-limiting examples of electronic devices that may include such displays are shown in FIG.

[0022] Liquid crystal display (LCD) is a common example of a non-emissive display that requires an independent light source (referred to as a backlight unit or assembly). The backlight assembly provides uniform and bright light with appropriate color characteristics for such a display. Recently, backlight technology has become more important due to the emergence of edge-lit light emitting diode (LED) backlights, which make displays thinner than previous displays while also reducing power consumption. In order to meet energy regulations or meet other requirements, it is important to make the backlight assembly as efficient as possible. As discussed further below, the present disclosure improves the performance of the backlight assembly by providing a spatially varying polarizer, which provides a phase delay that varies as a function of the propagation length of the light source away from the backlight assembly.

[0023] Figure 1A non-limiting example of an electronic device in the form of a head mounted display device 100 is shown, wherein the head mounted display device 100 can be connected to a video rendering computing system via a wired or wireless connection to provide virtual reality imaging to a human user. In operation, the user wears the HMD device 100 secured by one or more straps 101 on their head, and receives displayed information of a simulated environment different from the actual physical environment from the computing system at each eye through displays 102a and 102b supported by a support structure 104 of the HMD device, the computing system acting as an image rendering system that provides an image of the simulated environment to the HMD device for display to the user, the image being, for example, an image generated by a game program (not shown) and / or other software program (not shown) running on the computing system. In this example, the user is also able to move around the actual physical environment, and may also have one or more I / O ("input / output") devices, such as a handheld controller communicatively connected to the computing system via a wired or wireless connection, for allowing the user to further interact with the simulated environment. As the user moves the position of the HMD device 100 and / or changes the orientation of the HMD device 100, the position of the HMD device can be tracked to allow the corresponding portion of the simulated environment to be displayed to the user on the HMD device, and the controller can also employ similar techniques to track the position of the controller (and optionally use this information to help determine and / or verify the position of the HMD device). After knowing the tracked position of the HMD device 100, the corresponding information is sent to the computing system, which uses the tracked position information to generate one or more subsequent images of the simulated environment for display to the user via displays 102a and 102b.

[0024] Figure 2 An exemplary electronic device in the form of a laptop computer 200 is shown having an upper housing 202 and a lower housing 204 coupled together by a hinge 206 that allows the housings to rotate relative to each other. 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.

[0025] Figure 3 An exemplary electronic device is shown in the form of a smartphone 300. Smartphone 300 includes a housing 302 including a display panel 304 and a plurality of input components 306 (eg, buttons). In at least some embodiments, display panel 304 may be, for example, a touch screen display.

[0026] More generally, the displays of the present disclosure may be implemented in any type of electronic device, such as Figures 1 to 3The device shown or other devices, the other device including a music player, a gaming device, a navigation unit, a vehicle display, a wearable device, a self-service terminal, or other types of devices that include one or more displays.

[0027] Figure 4 4 shows a cross-sectional side view of an exemplary liquid crystal display (LCD) 400 according to one or more embodiments of the present disclosure. The display 400 can be implemented as any type of electronic device, such as Figure 1 , Figure 2 and Figure 3 The devices 100, 200 and 300 are shown in FIG.

[0028] The display 400 includes a plurality of stacked layers, each of which is substantially similar in shape (e.g., rectangular). The display 400 may include a backlight assembly 402 that receives light 403 from a light source 404 that is substantially located near 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 component layers), other light management layers (e.g., optical films 408), and a linear or reflective polarizer 410 (e.g., a dual brightness enhancement film (DBEF)).

[0029] The display 400 also includes an optical retarding layer in the form of a spatially varying polarizer (SVP) 412 that varies the optical properties of the optical signal as a function of the propagation length (e.g., Figure 4 As discussed further below, spatially varying polarizer 412 is used to increase the efficiency and uniformity of light source 404 by increasing the amount of light that is passed upward (as shown) to LCD panel 406.

[0030] When optical film 408 is present, optical film 408 can be formed as part of backlight assembly 402, or can be formed separately. Spatially varying polarizer 412 can be located above optical film 408 and below reflective polarizer 410, as shown. In other embodiments, display 400 can include spatially varying polarizer 412, but may not include separate linear polarizer 410. It should be understood that Figure 4 The configuration shown in is merely illustrative, and other configurations that may include different arrangements of the same layers, fewer layers or more layers, or different layers are contemplated. As non-limiting examples, spatially varying polarizer 412 may be located between one or more optical films 408, between an optical film and backlight assembly 402, within backlight assembly 402, and the like.

[0031] Figure 5A more detailed cross-sectional view of an exemplary display 500 that can implement features of the present disclosure is shown. The display 500 can be implemented as any type of electronic device, such as in Figure 1 , Figure 2 and Figure 3 The devices 100, 200 and 300 shown in FIG. Figure 4 The display 400 is similar or identical to the display 400 .

[0032] Display 500 includes a backlight assembly including a light guide prism or light guide plate (LGP) 502 and a reflector 504 that can be used to generate a backlight 506. In operation, the backlight 506 travels outward (upward as shown) and through display pixel structures in display layer 507, where the backlight 506 illuminates an image generated by the display pixels for viewing by a user 508 in direction 510. Display layer 507 can be provided in a plastic or metal structure to form a display module mounted in a housing of an electronic device. Display layer 507 can form a liquid crystal display panel or can be used to form other types of displays.

[0033] In the example shown, the display layer 507 includes a liquid crystal layer 512 located between display layers 514 and 516, which can be located between a lower polarizer layer 518 and an upper polarizer layer 520. Layers 514 and 516 can be formed by transparent substrate layers, such as transparent layers of plastic or glass. Layers 514 and 516 can include, for example, a color filter layer or a thin film transistor layer. Color filter elements, transistors, conductive traces, or other structures can be formed on the substrates of layers 514 and 516 to form a color filter layer and / or a thin film transistor layer. In at least some embodiments, layers 514 or 516 or other layers may include touch sensor electrodes for implementing the touch screen function of the display 500. As a non-limiting example, layer 516 may include such a thin film transistor layer, which includes a transistor and an array of display pixel electrodes for applying an electric field to the liquid crystal layer 512. In this example, layer 514 can be such a color filter layer, which includes an array of color filter elements for providing the display 500 with the ability to display color images. In other embodiments, layer 514 may be a thin-film transistor layer and layer 516 may be a color filter layer.

[0034] During operation of the display 500, control circuitry 522 operably coupled to layer 516 (which in this example includes a thin film transistor layer) may be used to generate information to be displayed on the display. The control circuitry 522 may include various circuits and components, such as a display driver circuit, a flexible circuit board, various conductive traces and connectors, etc., to drive the transistors of layer 516.

[0035] The backlight assembly may include a light guide prism or light guide plate 502, which may be formed of a transparent material such as glass or plastic. The light guide prism 502 may be rectangular in shape or may have a wedge shape that is thicker toward a light source 524 and tapers in a direction away from the light source. During operation, the light source 524 generates light 526 that is directed into an edge of the light guide prism 502. The light source 524 may be any suitable light source, such as an array of light emitting diodes (LEDs), disposed along an edge of the light guide prism to couple light into the light guide prism.

[0036] Light 526 emitted from light source 524 can be coupled to the edge surface of light guide prism 502 and can be distributed throughout the prism by total internal reflection. In at least some embodiments, light guide prism 502 can include light scattering features 528, which can be referred to as dots, pits, or protrusions, for example. Light scattering features 528 can be located on the upper surface or the lower surface of light guide prism 502.

[0037] In other embodiments, the light-guiding prism 502 may not include any light-scattering features 528; this may allow for more efficient use of the light source 524, since light-scattering features reduce efficiency and result in loss of polarization control. In such embodiments, the light 526 may be provided to the light-guiding prism 502 at relatively wide angles (e.g., ±40°, ±20°), and the spatially varying polarizer 532 may be tuned to provide uniform backlighting over the entire length of the display 500, as discussed further below.

[0038] Light 526 that is scattered upward (as shown) from the light-guiding prism 502 can be used as a backlight 506 for the display 500. The downward scattered light 526 can be reflected back in an upward direction by the reflector 504, which can be formed of any suitable reflective material, such as white plastic or other reflective material.

[0039] To improve the performance of the backlight assembly, embodiments of the present disclosure include one or more optical films 530, spatially varying polarizers 532, or reflective polarizers 534 (eg, DBEF).

[0040] The optical film layers 530 may include one or more diffusive layers (eg, diffuser films) to reduce hot spots, compensation films to enhance off-axis viewing, or other types of films (eg, prismatic films to collimate the backlight 506).

[0041] The spatially varying polarizer 532 can be located between the reflective polarizer 534 and the optical film 530. More generally, the spatially varying polarizer 532 can be located anywhere between the reflective polarizer 534 and the light guiding prism 502.

[0042] In at least some embodiments, display 500 includes spatially varying polarizer 532 and does not include linear reflective polarizer 534. In such embodiments, spatially varying polarizer 532 can be adjusted to selectively allow light to pass therethrough in a manner that transmits light uniformly without significant loss. For example, the spatially varying polarizer can provide linear polarization at the near end, where the spatially varying polarizer gradually changes retardation to provide circular polarization (e.g., λ / 4 retardation) at the far end.

[0043] The spatially varying polarizer 532 may include a wave retarder formed of a birefringent material. Birefringence is the property of a material having a refractive index that depends on the polarization and propagation direction of the light. The wave retarder changes the polarization state or phase of light propagating through the wave retarder. The wave retarder may have a slow axis (or extraordinary axis) and a fast axis (ordinary axis). When polarized light travels through the wave retarder, light along the fast axis travels faster than light along the slow axis.

[0044] As described above, spatially varying polarizer 532 can provide a phase delay that is proportional to the distance from light source 524 (e.g., Figure 5 This varies as a function of the propagation length (L) of the light guide prism 502 (shown from left to right), which allows for a more uniform and efficient distribution of light from the light guide prism 502 to the display layer 507. Figure 6 is a diagram showing a spatially variable polarizer for the present disclosure (for example, respectively Figure 4 and Figure 5 6 is a graph 600 of a non-limiting example of phase retardation as a function of propagation length for the spatially varying polarizers 412 and 532 shown in FIG. 6 . In this example, the spatially varying polarizer provides no retardation at the proximal end near a light source (e.g., light source 524), and increases the retardation linearly to provide a retardation of λ / 4 at the distal end of the spatially varying polarizer away from the light source. Specifically, in the illustrated example, the retardation of the spatially varying polarizer is 0λ at ​​0L, (1 / 4)L is (1 / 16)λ, (1 / 2)L is (1 / 8)λ, (3 / 4)L is (3 / 16)λ, and (1 / 4)λ at L. Figure 7 A top view 700 of the spatially varying polarizer 532 is shown, illustrating that the phase retardation of the spatially varying polarizer varies as a function of propagation length away from the light source 524 from no retardation (linear) at the left edge near the light source (as shown) to a quarter wavelength retardation (circular) at the right edge away from the light source.

[0045] Although the illustrated example shows a spatially variable polarizer with a linearly increasing delay varying between 0 and λ / 4, it will be appreciated that a variety of other configurations may be provided. In general, a spatially variable polarizer may provide a delay that varies in any manner as a function of the propagation length from the light source, and the amount of delay may be any value (e.g., λ / 20, λ / 10, λ / 4, λ, 2λ). In addition, the amount of delay may only increase, only decrease, or increase and decrease simultaneously. The amount of delay may vary continuously, or may vary in multiple steps. The amount of delay may vary according to any type of function, including, for example, a linear function, a polynomial function, an exponential function, a step function, other types of functions, or combinations thereof.

[0046] In at least some embodiments, the spatially variable polarizer can be formed by a multi-twistretarder (MTR), which is a wave plate-like retardation film that provides precise and customized levels of broadband, narrowband or multi-band retardation in a single film. More specifically, the MTR includes two or more twisted liquid crystal (LC) layers on a single substrate and has a single alignment layer. Subsequent LC layers are directly aligned through the existing layers, allowing simple manufacturing and achieving automatic layer alignment, and thereby forming a monolithic film with a continuously varying optical axis.

[0047] Refer to Figure 5 In at least some embodiments, control circuitry 522 may be operably coupled to spatially varying polarizer 532 to selectively change the spatially dependent phase retardation of the spatially varying polarizer to any desired configuration. In such embodiments, display 500 may include additional layers, such as one or more additional thin-film transistor layers, that allow for selective control of the spatially dependent phase retardation of spatially varying polarizer 532. Control circuitry 522 may control the phase retardation at any desired rate (e.g., only once, periodically, at a rate equal to a frame rate or a fraction thereof of display 500, etc.).

[0048] The foregoing detailed description has been described various embodiments of the device and / or process by using block diagrams, schematic diagrams and examples. Where such block diagrams, schematic diagrams and examples include one or more functions and / or operations, it will be understood by those skilled in the art that each function and / or operation within such block diagrams, flow charts or examples may be implemented individually and / or collectively by various hardware, software, firmware or almost any combination thereof. In one embodiment, the subject matter may be implemented by an application specific integrated circuit (ASIC). However, it will be appreciated by those skilled in the art that the embodiments disclosed herein may be implemented in whole or in part as one or more computer programs (e.g., as one or more programs running on one or more computer systems), as one or more programs running on one or more controllers (e.g., microcontrollers), as one or more programs running on one or more processors (e.g., microprocessors), as firmware, or in fact as any combination thereof in a standard integrated circuit equivalently implemented, and it will be appreciated that designing circuits and / or writing codes for software and / or firmware will be reasonably derived by those of ordinary skill in the art based on the present disclosure.

[0049] Those skilled in the art will recognize that many of the methods or algorithms described herein may employ additional acts, may omit some acts, and / or may perform acts in a different order than specified.

[0050] Furthermore, those skilled in the art will appreciate that the mechanisms taught herein can be distributed as program products in a variety of forms, and that the exemplary embodiments apply equally regardless of the particular type of signal bearing medium used to actually perform the distribution. Examples of signal bearing media include, but are not limited to, the following: recordable media such as floppy disks, hard drives, CDROMs, digital tapes, and computer memory.

[0051] The various embodiments described above may be combined to provide further embodiments. These and other changes may be made to the embodiments in light of the above detailed description. Generally, in the appended claims, the terms used should not be interpreted as limiting the claims to the specific embodiments disclosed in the specification and claims, but should be interpreted as including all possible embodiments and the full range of equivalents granted by these claims. Therefore, the claims are not limited by the present disclosure.

Claims

1. Head-mounted display device, including: a first display and a second display, each of the first display and the second display comprising: Non-emissive display panel assembly; a backlight assembly including a light source; and A spatially varying polarizer is positioned between the non-emissive display panel assembly and the backlight assembly, the spatially varying polarizer having a polarization that varies spatially as a function of a propagation length from the light source.

2. The head mounted display device according to claim 1, wherein: The spatially varying polarizer includes a multi-twist retarder.

3. The head mounted display device according to claim 1, wherein: The spatially varying polarizer provides no retardation at a proximal end proximate to the light source and provides a quarter-wavelength retardation at a distal end opposite the proximal end.

4. The head mounted display device according to claim 1, wherein: The retardation of the spatially varying polarizer varies linearly or nonlinearly between a proximal end close to the light source and a distal end opposite to the proximal end.

5. The head mounted display device according to claim 1, further comprising: A linear polarizer is positioned between the spatially varying polarizer and the non-emissive display panel assembly.

6. The head mounted display device according to claim 5, wherein: The linear polarizer includes a dual brightness enhancing film (DBEF).

7. The head mounted display device according to claim 1, further comprising: A control circuit is operably coupled to the spatially varying polarizer, the control circuit being operable to selectively adjust the retardation provided by the spatially varying polarizer.

8. The head mounted display device according to claim 1, wherein: The backlight assembly includes a light guide plate having light scattering features.

9. The head mounted display device according to claim 1, wherein: The backlight assembly includes a light guide plate without any light scattering features.

10. The head mounted display device according to claim 1, wherein: The backlight assembly includes a wedge-shaped light guide plate.

11. The head mounted display device according to claim 1, wherein: The non-emissive display panel assembly includes a liquid crystal display panel assembly.

12. The head mounted display device according to claim 1, wherein: The light source comprises an array of light emitting diodes.

13. The head mounted display device according to claim 1, wherein: The retardation of the spatially varying polarizer only increases as a function of the propagation length from the light source.

14. The head mounted display device according to claim 1, wherein: The retardation of the spatially varying polarizer varies as a function of a propagation length from the light source according to at least one of a linear function, a polynomial function, an exponential function, or a step function.

15. Head-mounted display devices, including: a first display and a second display, each of the first display and the second display comprising: Non-emissive display panel assembly; A backlight assembly including a light guide plate and a light source for providing light to an edge of the light guide plate; a reflective polarizer disposed between the non-emissive display panel assembly and the light guide plate; and A spatially varying polarizer is positioned between the reflective polarizer and the light guide, the spatially varying polarizer having a polarization that varies spatially as a function of a propagation length from the light source.

16. The head mounted display device according to claim 15, wherein: The spatially varying polarizer includes a multi-twist retarder.

17. The head mounted display device according to claim 15, wherein: The reflective polarizer includes a dual brightness enhancing film (DBEF).

18. The head mounted display device according to claim 15, wherein: The spatially varying polarizer provides no retardation at a proximal end proximate to the light source and provides a quarter-wavelength retardation at a distal end opposite the proximal end.

19. The head mounted display device according to claim 15, wherein: The light guide plate includes light scattering features.

20. The head mounted display device according to claim 15, wherein: The light guide plate does not include any light scattering features.

21. The head mounted display device according to claim 15, wherein: The light source comprises an array of light emitting diodes.

22. The head mounted display device according to claim 15, wherein: The retardation of the spatially varying polarizer only increases or only decreases as a function of the propagation length from the light source.

23. The head mounted display device of claim 15, wherein: The retardation of the spatially varying polarizer increases and decreases as a function of propagation length from the light source.

24. The head mounted display device according to claim 15, wherein: The retardation of the spatially varying polarizer varies as a function of a propagation length from the light source according to at least one of a linear function, a polynomial function, an exponential function, or a step function.

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