Highly efficient backlight for head mounted display devices

Abstract

The method and system relates generally to information displays, and more particularly to a system and method for a backlight assembly for information displays that provides improved efficiency. The backlight assembly may include a light guide that is sized and dimensioned to illuminate only a portion of a display imaged or focused by an optical element system. The backlight assembly may include a light source, such as one or more laser diodes, that directs a light beam into the light guide where it reflects by total internal reflection. The light guide may include a number of light extraction features configured to diffuse the light toward a display panel, such as a liquid crystal display (LCD) panel.

Description

[Technical field]

[0001] This disclosure relates generally to backlights for displays and, in at least some implementations, to backlights used in close-eye or head-mounted displays. [Background technology]

[0002] A backlit information display, such as a liquid crystal display ("LCD"), comprises several components. Two of these components are a display matrix, which intercepts light at a highly granular sub-pixel level to create the displayed image, and a light source or backlight. The light source is typically positioned behind the display matrix and illuminates the image to be displayed. For color displays, the backlight typically emits broad spectrum light, i.e., white light.

[0003] Traditionally, the light source used in backlit displays has often been one or more cold cathode fluorescent lamps ("CCFLs"). Physically, CCFLs look somewhat like miniature versions of the fluorescent light tubes used in commercial office buildings. However, CCFLs produce light in a different manner than those commercial fluorescent lamps. More recently, the use of CCFLs has given way to the use of one or more light emitting diodes ("LEDs") as the light source in information displays. Currently, LED technology is the most common backlight type for LCD displays.

[0004] Backlights can generally be classified into two types: edge-type backlights, which provide light to a display panel through the side of the display panel, and direct-type backlights, which provide light to a display panel through the bottom surface of the display panel. Edge-type backlights have a light source for generating light and a light guide panel or panels for controlling the propagation direction of the light. The light source is placed on one side of the light guide panel, which guides the light transmitted from the light source to the display panel. Depending on the shape of the light beam generated by the light source, the light source can be classified into, for example, a point light source, a linear light source, and an area light source.

[0005] Close-eye display technology can be used to present information and images to a user as part of a virtual reality ("VR") or augmented reality ("AR") system. Such close-eye displays can be incorporated into a head-mounted display ("HMD") device or headset. HMDs can take many forms, including helmets, visors, goggles, masks, glasses, and other heads or eyewear. In some embodiments, virtual reality and augmented reality systems have additional components, including a controller or computer that generates image information to operate the virtual reality or augmented reality environment. Such environments can be for a single user or for multiple users. HMDs in virtual reality and augmented reality systems can use a single information display or multiple information displays to present images to a user. Although these close-eye information displays can be adapted for direct viewing, they are often coupled to one or more lenses in the HMD. Such lenses can enhance the virtual reality or augmented reality experience. Summary of the Invention

[0006] One general aspect of the disclosure includes a display device. The display device may include a display panel having a front surface and a rear surface. The device also includes an optical subsystem positioned in front of the display panel, the optical subsystem configured to focus light received from a portion of the front surface of the display panel onto a user's eye, the portion of the front surface of the display panel being smaller than the entire front surface of the display panel. The device also includes a backlight assembly positioned behind the display panel to provide light to the display panel. The backlight assembly may have a light guide including a non-rectangular front surface, a non-rectangular rear surface opposite the front surface, and a peripheral side surface extending between the front surface and the rear surface, the front surface having a surface area sized and dimensioned to approximate the portion of the display panel from which light is received and focused by the optical subsystem. The device also includes a light source positioned adjacent to the outer peripheral side surface of the light guide, the light source operable to emit light into the light guide in a first direction parallel to the front surface of the light guide, the light guide receiving the light from the light source in the first direction and directing the light from the front surface of the light guide in a second direction toward the display panel.

[0007] Implementations may include one or more of the following features: The front surface of the light guide may be circular in shape. The front surface of the light guide may have a polygonal shape having five or more sides. The light source may include a plurality of laser diodes, each emitting a different color of light. The outer peripheral side surface of the light guide may be polished to cause total internal reflection of the light emitted by the light source. The outer peripheral side surface of the light guide may be coated with or surrounded by a mirror element to cause total internal reflection of the light emitted by the light source. The display device may comprise a pattern of light extraction features positioned on the front surface of the light guide to diffuse light from the light guide towards the display panel. The pattern of light extraction features may have a density that increases radially from the outer peripheral side surface of the light guide towards the center of the front surface. The light source may include a laser diode that emits a laser beam that reflects inside the light guide multiple times by total internal reflection, and the pattern of light extraction features may be defined such that the density of light extraction features is relatively lower proximate a determined path that the laser beam will travel within the light guide before the first n reflections, where n is an integer less than or equal to 10. The light source may include a laser diode that emits a laser beam that reflects inside the light guide by total internal reflection, and the pattern of light extraction features may include a first pattern multiplexed with a second pattern, where for the first pattern the density of light extraction features increases radially from the outer peripheral side surface toward a center of the front surface of the light guide, and for the second pattern the density of light extraction features is relatively lower proximate a determined path that the laser beam will travel within the light guide before the first n reflections, where n is an integer. The backlight assembly may further include a reflective surface positioned proximate the rear surface of the light guide. The backlight assembly may further include a light diffusing film positioned between the front surface of the light guide and the rear surface of the display panel.The light source may be coupled to the light guide by an optically clear adhesive. The light source may include a laser diode, and the backlight assembly may further include a lens positioned in front of the laser diode, and the lens may include a collimating lens or a diffusing lens. The light source may include a plurality of light emitting diodes (LEDs) spaced around the periphery of the outer periphery side surface of the light guide. The LEDs may be carried on a flexible circuit board that extends around at least a portion of the outer periphery side surface of the light guide. The LEDs may be carried on a rigid circuit board that extends around at least a portion of the outer periphery side surface of the light guide. Implementations of the described techniques may include hardware, methods or processes, or computer software on a computer-accessible medium.

[0008] One general aspect includes a head mounted display device. The head mounted display device comprises a first display device and a second display device. Each of the first display device and the second display device may have a display panel having a front surface and a rear surface. The device may also have an optics subsystem positioned in front of the display panel, the optics subsystem configured to focus light received from a portion of the front surface of the display panel onto a user's eye, the portion of the front surface of the display panel being smaller than the entire front surface of the display panel. The device also has a backlight assembly positioned behind the display panel to provide light to the display panel. The backlight assembly may include a light guide that may include a non-rectangular front surface, a non-rectangular rear surface opposite the front surface, and a peripheral side surface that extends between the front surface and the rear surface. The device may also include a laser diode positioned adjacent the outer peripheral side surface of the light guide, the laser diode operable to emit light into the light guide in a first direction parallel to the front surface of the light guide, the light guide receiving the light from the diode in the first direction, where the light reflects inside the light guide by total internal reflection. The device may also include a pattern of light extraction features positioned on the front surface of the light guide to diffuse light from the light guide towards the display panel. Other embodiments of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the method.

[0009] Implementations may include one or more of the following features: the light guide may be circular in shape; the laser diodes may include three laser diodes, each of the three laser diodes emitting a different color of light.

[0010] One general aspect includes a display device. The display device includes a display panel having a front surface and a rear surface. The device also includes an optical subsystem positioned in front of the display panel, the optical subsystem configured to focus light received from a portion of the front surface of the display panel onto a user's eye, the portion of the front surface of the display panel being smaller than the entire front surface of the display panel. The device also includes a backlight assembly positioned behind the display panel to provide light to the display panel. The backlight assembly may have a light guide that may include a non-rectangular front surface, a non-rectangular rear surface opposite the front surface, and a peripheral side surface that extends between the front surface and the rear surface. The device may also include a laser diode positioned adjacent the outer peripheral side surface of the light guide, the laser diode operable to emit light into the light guide in a first direction parallel to the front surface of the light guide, the light guide receiving the light from the diode in the first direction, where the light reflects inside the light guide by total internal reflection. The device also includes a pattern of light extraction features positioned on the front surface of the light guide to diffuse light from the light guide towards the display panel. [Brief description of the drawings]

[0011] 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 drawn shapes of these elements are not necessarily intended to convey any information regarding the actual shape of those particular elements, but may only be selected for ease of recognition in the drawings.

[0012] [Figure 1] A diagram of an example of a head-mounted display device with dual display panels according to one exemplary implementation.

[0013] [Diagram 2] FIG. 2 is a top cross-sectional view of a head mounted display device according to one non-limiting exemplary implementation.

[0014] [Diagram 3] FIG. 2 is another cross-sectional view of a head mounted display device according to one non-limiting exemplary implementation.

[0015] [Figure 4] FIG. 2 is an exploded perspective view of a display device according to one non-limiting exemplary implementation.

[0016] [Diagram 5] 1 is a cross-sectional side view of a display device according to one non-limiting exemplary implementation.

[0017] [Figure 6] FIG. 2 is a top view of a backlight assembly including a light guide and a light source according to one non-limiting exemplary implementation.

[0018] [Figure 7A]FIG. 2 is a top view of a backlight assembly including a light guide including a first pattern of light extraction features according to one non-limiting exemplary implementation.

[0019] [Figure 7B] FIG. 13 is a top view of a backlight assembly including a light guide including a second pattern of light extraction features according to one non-limiting exemplary implementation.

[0020] [Figure 7C] FIG. 13 is a top view of a backlight assembly including a light guide including a third pattern of light extraction features according to one non-limiting exemplary implementation.

[0021] [Figure 8] 1 is a top view of a backlight assembly according to one non-limiting exemplary implementation, the backlight assembly including a light guide and two light sources, the light sources including laser diodes.

[0022] [Figure 9] 1 is a top view of a backlight assembly including a light guide, a light source, and a diffusing lens according to one non-limiting exemplary implementation.

[0023] [Figure 10] FIG. 2 is a top view of a backlight assembly according to one non-limiting exemplary implementation, including a light guide and a light source, the light source including multiple LEDs mounted on a flexible circuit board that surrounds the periphery of the light guide.

[0024] [Figure 11] FIG. 2 is a top view of a backlight assembly according to one non-limiting exemplary implementation, including a light guide and a light source, the light source including a plurality of LEDs mounted on a rigid circuit board that surrounds the periphery of the light guide.

[0025] [Figure 12] FIG. 2 is a diagram of a cylindrically shaped block of material that may be used to form multiple light guides, according to one non-limiting exemplary implementation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] 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 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 the implementations.

[0027] Unless the context requires otherwise, throughout this specification and the claims which follow, the term "comprising" is synonymous with "comprising" and is inclusive or open-ended (i.e., does not exclude additional unrecited elements or method actions).

[0028] 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.

[0029] 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 in its sense including "and / or" unless the context clearly dictates otherwise.

[0030] The headings and abstracts of the disclosure provided herein are for convenience only and do not interpret the scope or meaning of the implementations.

[0031] One or more implementations of the present disclosure are directed to a display for an electronic device, such as a head-mounted display device. The method and system relate generally to information displays, and more specifically to a system and method for a backlight assembly for information displays that provides significantly improved efficiency. The backlight assembly may include a light guide that is sized and dimensioned to illuminate only a portion of a display panel that is actually imaged or focused by an optical element system. The backlight assembly may include a light source, such as one or more laser diodes (e.g., red, green, and blue laser diodes), that direct a beam of light into the light guide where it reflects by total internal reflection. The light guide may include a plurality of light extraction features or homogenizers configured to diffuse the light toward a display panel, such as a liquid crystal display (LCD) panel.

[0032] Liquid crystal displays (LCDs) are a common example of non-emissive displays that require a separate light source, referred to as a backlight unit or assembly. Backlight assemblies provide such displays with uniform and bright light with appropriate color characteristics. Backlight technology has become more important in recent years due to the advent of edge-lit light-emitting diode (LED) backlights, which allow displays to be much thinner than previous displays while at the same time reducing power consumption. It is important to make the backlight assembly as efficient as possible to meet energy regulations or other requirements. As discussed further below, the present disclosure improves the performance of the backlight assembly by providing a backlight assembly that illuminates only a portion of the display panel that is imaged by the optical elements and thus viewed by the user's eyes, resulting in a highly efficient backlight compared to existing technologies.

[0033] 1 illustrates a non-limiting example of an electronic device in the form of a head-mounted display device 100, which can be optionally 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 his or her head, secured via one or more straps 101, and receives displayed information of a simulated environment, different from a real physical environment, from the computing system in each eye via displays 102a and 102b supported by a support structure 116 of the HMD device, which functions 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 programs (not shown) running on the computing system. The user is further capable of moving around the real physical environment in this example, 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 allow the user to further interact with the simulated environment. An HMD device may include one or more user interfaces 104 and 106 that enable a user to provide input to the HMD device 100 or to a computing system coupled to the HMD device. As the user moves location and / or changes orientation of the 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).Once the tracked position of the HMD device 100 is known, corresponding information is transmitted to the 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 the displays 102a and 102b.

[0034] 2 illustrates a top cross-sectional view of a head-mounted display device 200 according to one non-limiting exemplary implementation. The head-mounted display device 200 includes a rigid housing or body 202 that holds a left optical system 204a and a right optical system 204b. The left optical system 204a includes a display device 206a for providing an image to a user's left eye 212a. Similarly, the right optical system 204b includes a display device 206b for providing an image to a user's right eye 212b. The left optical system 204a and the right optical system 204b may be similar or identical to one another. Thus, the discussion below with reference to the optical system 204a may apply equally to both optical systems 204a and 204b.

[0035] The optical system 204a provides an image to an exit pupil 214a, which is a location in front of the body 202 where a user's left eye 212a would be positioned when wearing the head mounted display device 200. The optical system 204a includes a display 206a and an optics subsystem 208a. The optics subsystem 208a focuses and magnifies light from the display device 206a and may also correct for one or more types of optical errors such as distortion, aberrations, etc. The optics subsystem 208a directs image light to the exit pupil 214a for presentation to the user's left eye 212a.

[0036] When a user wears the head mounted display device 200, the user's nose is positioned between the two optical subsystems 204a and 204b. Each of the display systems 206a and 206b may include a rectangular (e.g., square) display panel or matrix, such as an LCD panel. As discussed further below with reference to FIG. 4, each of the display systems 206a and 206b may include a backlight assembly configured to provide light to only a portion of the display panel that is actually imaged or focused by the optical subsystem 208a. In this manner, pixels of the display panel that are not imaged by the optical subsystem 208a are not provided with light from the backlight, thereby reducing the amount of light that needs to be generated by the backlight, thereby significantly improving the efficiency of the backlight.

[0037] FIG. 3 illustrates an exemplary backlit LCD display 300 with a backlight assembly in a head-mounted display configuration, such as in a virtual reality or augmented reality headset. FIG. 3 illustrates a backlight assembly 302 that emits light 303 that passes through an LCD panel 304, thereby displaying a viewable image. A diffusion layer (not shown) may also be provided to produce a more uniform light. The light 305 that exits the LCD panel 304 then passes through an optics subsystem or lens assembly 208, which may include one or more lenses. In certain embodiments, the lenses in the optics subsystem 208 may be conventional spherical, aspheric, Fresnel, or any other type of imaging lens. The optics subsystem 208 may have a single type of lens surface or may be a combination of multiple lens types. In some implementations, the optics subsystem 208 may have a pancake configuration, which may comprise a polarization-based reflective or refractive optical system. In this case, the optics subsystem 208 may comprise an assembly of optical elements configured to direct the light 307 from the LCD 304 towards the user's eye 212 using on-axis optical bending based at least in part on the polarization of the light. The optics subsystem 208 may include various optical elements other than lenses. For example, the optics subsystem 208 may include at least one polarizing beam splitter and a substrate including a twisted liquid crystal element. The twisted liquid crystal element may be configured to change the phase of the light within the optics subsystem 208. The light 307 exits the optics subsystem 208 directed towards the user's eye 212. In some embodiments, the light 307 creates an eyebox of approximately 10 millimeters (e.g., 5 mm to 25 mm, etc.). One skilled in the art will appreciate that FIG. 3 is intended to illustrate the general flow of light between the components shown in some embodiments, rather than the physical design or layout of the HMD system.

[0038] In certain embodiments, a head mounted display is designed to be viewed by both the left and right eyes of a user. This may be accomplished using separate left and right LCD displays, as shown in Figures 1 and 2, or may be accomplished using a single LCD display. Similarly, a virtual reality or augmented reality headset may include a single optics subsystem, or it may use separate left and right optics subsystems 208a and 208b, as shown in Figure 2.

[0039] FIG. 4 is an exploded perspective view of an exemplary display device 400 according to one or more implementations of the present disclosure. The display device 400 includes a display system 406 and an optical system 404 including an optics subsystem 412. The display system 406 includes a circular light guide 408 of a backlight assembly and a rectangular display panel 410, such as an LCD panel. For purposes of illustration, other components of the backlight assembly are not shown in FIG. 4. In operation, the backlight light guide 408 receives light and emits the received light toward a user's eye 212 in a direction indicated by an arrow 430. The display panel 410 is positioned between the light guide 408 and the optics subsystem 412 and controls the amount of light passing from the light guide on a pixel-by-pixel basis via suitable control circuitry. Light passing through the display panel 410 is focused onto the user's eye 212 by the optics subsystem 412.

[0040] The light guide 408 includes a front surface 414, a rear surface (not shown), and a peripheral side surface 416 connecting the front surface to the rear surface. Similarly, the display panel 410 includes a front surface 418, a rear surface (not shown), and a peripheral side surface 420 connecting the front surface to the rear surface. The optics subsystem 412 includes a front surface 422, a rear surface (not shown), and a peripheral side surface 424 connecting the front surface to the rear surface.

[0041] The display panel 410 includes a central portion 426 (indicated by the dashed circle in FIG. 4) that is imaged or focused by the optics subsystem 412, and a peripheral region 428 that is not imaged or focused by the optics subsystem 412. The specific size and shape of the central portion or region 426 of the display panel 410 will depend on the specific design and configuration of the optics subsystem 412. As shown, the central portion 426 may be circular in shape. In at least some implementations, the central portion may have a different shape.

[0042] In the embodiment shown, at least the front surface 414 of the light guide 408 has a surface area sized and dimensioned to approximate (e.g., within 5 percent, within 20 percent) the size of the portion 426 of the display panel 410 from which light is received and focused by the optics subsystem 412. In this example, the front surface 414 has a circular shape. In other implementations, the front surface 414 of the light guide 408 can have the shape of a polygon with five or more sides (e.g., a pentagon, hexagon, octagon, irregularly shaped polygon) while still approximating the portion 426 of the display panel 410 imaged by the optics subsystem 412 compared to a light guide having approximately the same shape as the LCD panel 410.

[0043] 5 is a cross-sectional side view of a display device 500 in accordance with one or more embodiments of the present disclosure. The display device 500 includes a display panel 504, such as an LCD panel. The display device 500 further includes a backlight assembly including a light guide 502 having a front surface 510, a rear surface 512, and a peripheral side surface 514 extending between the front and rear surfaces. As discussed above, the light guide 502 may be sized and dimensioned to provide light to the display panel 504 substantially only in an area imaged by the focusing optical elements (e.g., optical element subsystem 208 or 412). In at least some implementations, the backlight assembly further includes a reflective or specular layer or surface 506 positioned proximate to or coated on the rear surface 512 of the light guide 502, and may include one or more optical film layers 508 (e.g., a diffusive layer) positioned between the light guide 502 and the display panel 504.

[0044] The light source 518 may be positioned adjacent to the outer circumferential side surface 514. In at least some implementations, the light source 518 may be coupled to the outer circumferential side surface 514 by an optically clear adhesive 520 (e.g., epoxy) or other suitable coupler. As discussed further below, the light source 518 may be one or more laser light sources (e.g., red, green, and blue semiconductor laser diodes) that emit a beam 522 of light having particular dimensions (e.g., 1 mm to 5 mm by 1 mm to 5 mm square, Gaussian, etc.) in a first direction toward the center 516 of the light guide 502. The light source 518 may comprise multiple laser sources, each emitting light having a different color (e.g., red, green, blue). The light source 518 may comprise one or more other light sources or optional lenses that provide light to the light guide 502. In at least some implementations, the light source 518 may include multiple LEDs (e.g., white LEDs) that surround at least a portion of the outer circumferential side surface 514 of the light guide 502.

[0045] As light beam 522 propagates through light guide 502 in a first direction (horizontally as shown in FIG. 5), the light guide functions to direct the light in a second direction, indicated by arrow 524 (upward as shown in FIG. 5), through the display panel 504. The backlight may be operable to distribute the light at least somewhat uniformly across the pixels of the display panel that are within the area or portion imaged by the focusing optics as discussed above.

[0046] The light guide 502 may be constructed from a clear glass material, a clear plastic material (e.g., polymethyl methacrylate (PMMA), polycarbonate (PC)), or any other suitable material. The optional optical film layer or stack 508 may include a diffusing layer that promotes uniform distribution of light from the light guide 502 across the pixels of the display panel 504. The optical film layer 508 may additionally or alternatively include one or more other layers, such as a reflective polarizing layer or a brightness enhancement film (BEF) layer, etc.

[0047] The light guide 502 may include a number of light extraction features 526, also referred to as homogenizer protrusions or depressions, which facilitate projecting light from within the light guide 502 upward toward the display panel 504, as indicated by arrow 524. In the embodiment shown, the light extraction features 526 are positioned on the top or front surface 510 of the light guide 502, although in other embodiments, the light extraction features may alternatively or additionally be positioned on the bottom or rear surface 512 of the light guide. Additionally, although the light extraction features are shown as protruding protrusions, in at least some implementations, some or all of the light extraction features may instead comprise depressions in the surface of the light guide 502. Additionally, in at least some implementations, the light guide 502 may include a variety of thicknesses, with or without light extraction features on the top surface, bottom surface, or both.

[0048] FIG. 6 is a top view of the circular light guide 502 and light source 518 also shown in FIG. 5. As shown, the light source 518 (e.g., three laser diodes) emits a beam 522a into the light guide 502, which reflects by total internal reflection from the outer circumferential side surface 514 of the light guide. The first reflected beam is labeled as beam 522b and the second reflected beam is labeled as beam 522c. The light from the light source 518 subsequently reflects many times within the light guide 502 resulting in substantially uniform light across the front surface 510 of the light guide, where the light is extracted by the light extraction features 526 (FIG. 5). As shown, the light source 518 is positioned and oriented to introduce the beam 522a into the light guide 502 at an angle such that the first N reflected beams form a "star-shaped" pattern resulting in a more uniform distribution of light within the light guide.

[0049] 7A is a top view of a light guide 700 of a backlight assembly including a first pattern of light extraction features 706 on a front or top surface 702 of the light guide. In this example, the density of light extraction features 706 increases from the outer peripheral side surface 704 of the light guide 700 towards the center 708 of the light guide. In this way, more light is extracted from the center 708 of the light guide 700 than from the peripheral regions, which is advantageous since a user's attention is typically directed toward the more central part of the display panel.

[0050] 7B is a top view of a light guide 710 of a backlight assembly including a second pattern of light extraction features 716. In this example, a laser diode source 711 is provided that emits a beam 720 into the light guide 710 that reflects from the outer circumferential side surface 712 by total internal reflection in a star-shaped pattern within the light guide. In this embodiment, the second pattern of light extraction features 716 is defined such that the density of light extraction features is relatively lower proximate to a determined path that the laser beam 720 travels within the light guide 710 before the first N reflections, where N is an integer less than or equal to 10 (e.g., 3, 5, 7, 10). In this example, four beam paths and three reflections are shown, and the light extraction features 716 are not positioned on the known paths of the first four beam paths or the three reflections. Because the beam of light is most intense during its first few passes, keeping the light extraction features away from such passes prevents large amounts of light from being extracted along the first few passes, which could otherwise reduce the uniformity of the backlight.

[0051] 7C is a top view of a light guide 730 of a backlight assembly including a third pattern of light extraction features 736. In this example, a laser diode source 740 is provided that emits a beam 742 into the light guide 730 that reflects from the outer peripheral side surface 732 by total internal reflection within the light guide. In this embodiment, the third pattern comprises a first pattern (shown in FIG. 7A) multiplexed with a second pattern (shown in FIG. 7B) to result in a higher density of light extraction features 736 toward the center 738 of the light guide 730, while having a lower density of light extraction features proximate the first N passes or reflections of the light beam where the beam is relatively brighter than subsequent passes.

[0052] 8 is a top view of a backlight assembly 800 including a light guide 802 and two light sources 808 and 810, the light sources including laser diodes. Although this is not required, the light sources 808 and 810 are positioned on opposite sides of the light guide 802. The light source 808 emits a beam 809 that reflects from a peripheral side surface 806 by total internal reflection within the light guide 802 below the light guide front surface 804. Similarly, the light source 810 emits a beam 811 that reflects from a peripheral side surface 806 by total internal reflection within the light guide 802 below the light guide front surface 804. Although two light sources 808 and 810 are shown, it will be understood that in other implementations more than two light sources may be provided.

[0053] 9 is a top view of a backlight assembly 900 including a light guide 902 having a top surface 904, a bottom surface (not shown), and a peripheral side surface 906. The backlight assembly 900 further includes a light source 908 in the form of one or more laser diodes, as discussed above. In this illustrated embodiment, a diffusing lens 910 (e.g., a cylindrical lens) is provided to distribute the light 912 over a wide angle within the light guide 902. As a non-limiting example, the diffusing lens 910 may be operable to spread the light 912 in a direction parallel to the top or front surface 904 of the light guide 902 at angles of 30 degrees, 60 degrees, 120 degrees, etc. from the light source 908. In at least some implementations, instead of a diffusing lens, the lens 910 may comprise a collimating lens or one or more other types of lenses.

[0054] 10 is a top view of a backlight assembly 1000 including a light guide 1002 with a peripheral side surface 1004, as discussed above. In this embodiment, the backlight assembly 1000 includes a plurality of LEDs 1010 (e.g., white LEDs) mounted on a flexible circuit board 1008 that surrounds the peripheral side surface 1004 of the light guide 1002. Each of the LEDs 1010 is positioned to direct light 1012 toward a center 1006 of the light guide 1002. In at least some implementations, a flexible circuit board may be provided that carries the LEDs, the flexible circuit board surrounding less than the entire peripheral side surface 1004 of the light guide 1002.

[0055] FIG. 11 is a top view of a backlight assembly 1100 including a light guide 1102 with a peripheral side surface 1104. In this embodiment, the peripheral side surface 1104 is octagonal in shape, although it will be understood that other regular or irregular polygonal shapes may alternatively be used. The backlight assembly 1100 includes a plurality of LEDs 1110 (e.g., white LEDs) mounted on respective rigid circuit boards 1108, each adjacent one side of the peripheral side surface 1104 of the light guide 1102. Each of the LEDs 1110 is positioned to direct light 1112 toward a center 1106 of the light guide 1102, as discussed above with reference to other embodiments. In at least some implementations, one or more rigid circuit boards carrying the LEDs may be provided, the rigid circuit boards surrounding less than the entire peripheral side surface 1104 of the light guide 1102.

[0056] FIG. 12 illustrates a cylindrical block of material 1200 that can be used to form a plurality of individual light guides 1204, such as any of the light guides discussed herein. Although a cylindrical shape is illustrated as an example, in other implementations, other shapes may be used (e.g., a block of material having a polygonal cross section). As discussed above, the block 1200 can be constructed from a transparent glass material or a transparent plastic material (e.g., polymethylmethacrylate (PMMA), polycarbonate (PC)), or other suitable materials for light guides. In at least some implementations, the exterior surface 1202 of the block 1200 can be processed to promote total internal reflection of light within the resulting light guide. As an example, the exterior surface 1202 can be polished so that it is a smooth surface, or it can be coated or lapped with a reflective or mirror layer. Once processed, the block 1200 can be cut into a plurality of wafers 1204 that can be used as light guides of the present disclosure. An exemplary resulting light guide 1206 is shown, which, as discussed above, includes a top or front surface 1208, a bottom or back surface 1210, and an outer circumferential side surface 1212. Additionally or alternatively, the outer circumferential surface 1212 of the individual light guides 1206 may be processed (e.g., polished, mirror-finished) after the block 1200 is cut to provide a surface that promotes total internal reflection of the light beam inside the light guide 1206.

[0057] Those skilled in the art will recognize that many of the methods or algorithms described herein may utilize additional operations, omit some operations, and / or perform operations in a different order than specified. The various implementations described above may also be combined to provide further implementations. These and other changes may 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 rather to include all possible implementations along with the full scope of equivalents that are covered by such claims. Thus, the claims are not limited by this disclosure.

Claims

1. A display panel having a front surface and a rear surface; an optical subsystem positioned in front of the display panel, the optical subsystem configured to focus light received from a portion of the front surface of the display panel onto a user's eye, the portion of the front surface of the display panel being smaller than the entire front surface of the display panel; and a backlight assembly positioned behind the display panel to provide light to the display panel, the backlight assembly comprising: a light guide including a non-rectangular front surface, a non-rectangular rear surface opposite the front surface, and a peripheral side surface extending between the front and rear surfaces, the front surface having a surface area sized and dimensioned to approximate the portion of the display panel from which light is received and focused by the optics subsystem; and a light source positioned adjacent the outer circumferential side surface of the light guide, the light source operable to emit light into the light guide in a first direction parallel to the front surface of the light guide, the light guide receiving the light from the light source in the first direction and directing the light from the front surface of the light guide in a second direction toward the display panel; having Display device.

2. The display device of claim 1 , wherein the front surface of the light guide is circular in shape.

3. 10. The display device of claim 1, wherein the front surface of the light guide has the shape of a polygon having five or more sides.

4. 4. A display device according to claim 1, wherein the light source comprises a plurality of laser diodes, each emitting light of a different colour.

5. 4. The display device of claim 1, wherein the outer peripheral side surface of the light guide is polished to cause total internal reflection of the light emitted by the light source.

6. 4. A display device according to claim 1, wherein the outer side surface of the light guide is coated with or surrounded by a mirror element so as to cause total internal reflection of the light emitted by the light source.

7. 4. The display device of claim 1 , further comprising a pattern of light extraction features positioned on the front surface of the light guide to diffuse light from the light guide towards the display panel.

8. 8. The display device of claim 7, wherein the pattern of light extraction features has a density that increases radially from the outer circumferential side surface toward the center of the front surface of the light guide.

9. 8. The display device of claim 7, wherein the light source includes a laser diode that emits a laser beam that reflects multiple times inside the light guide by total internal reflection, and the pattern of light extraction features is defined such that the density of light extraction features is relatively lower adjacent a determined path that the laser beam travels within the light guide before its first N reflections, where N is an integer less than or equal to 10.

10. 8. The display device of claim 7, wherein the light source comprises a laser diode emitting a laser beam that reflects inside the light guide by total internal reflection, and the pattern of light extraction features comprises a first pattern multiplexed with a second pattern, wherein for the first pattern a density of light extraction features increases radially from the outer peripheral side surface toward the center of the front surface of the light guide, and for the second pattern a density of light extraction features is relatively lower proximate a determined path that the laser beam travels within the light guide before its first N reflections, where N is an integer less than or equal to 10.

11. 4. The display device of claim 1, wherein the backlight assembly further comprises a reflective surface positioned adjacent to the rear surface of the light guide.

12. 4. The display device of claim 1, wherein the backlight assembly further comprises a light diffusing film positioned between the front surface of the light guide and the rear surface of the display panel.

13. 4. The display device of claim 1, wherein the light source is coupled to the light guide by an optically clear adhesive.

14. 4. The display device of claim 1, wherein the light source comprises a laser diode, the backlight assembly further comprising a lens positioned in front of the laser diode, the lens comprising a collimator lens or a diffusing lens.

15. 4. The display device of claim 1, wherein the light source comprises a plurality of light emitting diodes (LEDs) spaced circumferentially around the outer circumferential side surface of the light guide.

16. 16. The display device of claim 15, wherein the LEDs are carried on a flexible circuit board that extends around at least a portion of the outer circumferential side surface of the light guide.

17. 16. The display device of claim 15, wherein the LEDs are carried on a rigid circuit board that extends around at least a portion of the outer circumferential side surface of the light guide.

18. a first display device and a second display device, each of the first display device and the second display device comprising: A display panel having a front surface and a rear surface; an optical subsystem positioned in front of the display panel, the optical subsystem configured to focus light received from a portion of the front surface of the display panel onto a user's eye, the portion of the front surface of the display panel being smaller than the entire front surface of the display panel; and a backlight assembly positioned behind the display panel to provide light to the display panel, the backlight assembly comprising: a light guide including a non-rectangular front surface, a non-rectangular rear surface opposite said front surface, and a peripheral side surface extending between said front and rear surfaces; a laser diode positioned adjacent the outer circumferential side surface of the light guide, the laser diode operable to emit light into the light guide in a first direction parallel to the front surface of the light guide, the light guide receiving the light from the laser diode in the first direction, where the light reflects off an interior of the light guide by total internal reflection; and a pattern of light extraction features positioned on the front surface of the light guide to diffuse light from the light guide towards the display panel; Including, Head mounted display device.

19. 20. The head mounted display device of claim 18, wherein the light guide is circular in shape.

20. 20. A head mounted display device as claimed in claim 18 or 19, wherein the laser diodes include three laser diodes, each of the three laser diodes emitting light of a different colour.

21. A display panel having a front surface and a rear surface; an optical subsystem positioned in front of the display panel, the optical subsystem configured to focus light received from a portion of the front surface of the display panel onto a user's eye, the portion of the front surface of the display panel being smaller than the entire front surface of the display panel; and a backlight assembly positioned behind the display panel to provide light to the display panel, the backlight assembly comprising: a light guide including a non-rectangular front surface, a non-rectangular rear surface opposite said front surface, and a peripheral side surface extending between said front and rear surfaces; a laser diode positioned adjacent the outer circumferential side surface of the light guide, the laser diode operable to emit light into the light guide in a first direction parallel to the front surface of the light guide, the light guide receiving the light from the laser diode in the first direction, where the light reflects off an interior of the light guide by total internal reflection; and a pattern of light extraction features positioned on the front surface of the light guide to diffuse light from the light guide towards the display panel; having Display device.

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