Patent Application
20140240207
1. Technical Field
This disclosure relates generally to displays, and more particularly to lighted displays.
2. Background Art
“Intelligent” portable electronic devices, such as smart phones, tablet computers, and the like, are becoming increasingly powerful computational tools. Moreover, these devices are becoming more prevalent in today's society. For example, not too long ago a mobile telephone was a simplistic device with a twelve-key keypad that only made telephone calls. Today, “smart” phones, tablet computers, personal digital assistants, and other portable electronic devices not only make telephone calls, but also manage address books, maintain calendars, play music and videos, display pictures, and surf the web.
As the capabilities of these electronic devices have progressed, so too have their user interfaces. Prior art physical keypads having a limited number of keys have given way to high resolution displays that sometimes serve as touch-sensitive user interfaces. As users have grown accustomed to using touch-sensitive displays to input data rather than physical keyboards, manufacturers have been incorporating larger and larger displays into their portable electronic devices. These larger displays, by nature, consume large amounts of power. Most of the displays are “backlit” in that they include a lighting source to project light through the display so as to make the display visible to a user in low-light environments.
It would be advantageous to have a display that is high resolution but that uses less power than prior art displays.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present disclosure.
Before describing in detail embodiments that are in accordance with the present disclosure, it should be observed that the embodiments reside primarily in combinations of method steps and apparatus components related to a low power display and methods of operating the same. Any process descriptions or blocks in flow charts should be understood as representing modules, segments, or portions of code, which include one or more executable instructions for implementing specific logical functions or steps in the process. Alternate implementations are included, and it will be clear that functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved. Accordingly, the apparatus components and method steps have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.
It will be appreciated that embodiments of the disclosure described herein may be comprised of one or more conventional processors and unique stored program instructions that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of operating a display as described herein. The non-processor circuits may include, but are not limited to, a radio receiver, a radio transmitter, signal drivers, clock circuits, power source circuits, and user input devices. As such, these functions may be interpreted as steps of a method to perform display operation. Alternatively, some or all functions could be implemented by a state machine that has no stored program instructions, or in one or more application specific integrated circuits (ASICs), in which each function or some combinations of certain of the functions are implemented as custom logic. Of course, a combination of the two approaches could be used. Thus, methods and means for these functions have been described herein. Further, it is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and ICs with minimal experimentation.
Embodiments of the disclosure are now described in detail. Referring to the drawings, like numbers indicate like parts throughout the views. As used in the description herein and throughout the claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise: the meaning of “a,” “an,” and “the” includes plural reference, the meaning of “in” includes “in” and “on.” Relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, reference designators shown herein in parenthesis indicate components shown in a figure other than the one in discussion. For example, talking about a device (10) while discussing figure A would refer to an element, 10, shown in figure other than figure A.
Embodiments of the invention provide a display having a light guide and light sources mounted on the sides of the light guide. A reflector is disposed on one side of the light guide. The light guide receives light from the light sources and delivers it to the reflector. The reflector reflects light back through the light guide to a user.
The first side of the light guide, in one embodiment, includes a plurality of convex protuberances that span the first side. The convex protuberances are configured to direct light received from the light sources to the reflector in a uniform manner. In contrast to prior art designs, embodiments of the disclosure orienting the convex protuberances toward the reflector advantageously result in a more uniformly lit overall display as perceived by a user.
In one embodiment, the other side of the light guide is configured with one or more light extractors. The light extractors receive light from the light sources and redirect it through the convex protuberances. Accordingly, the light extractors work to “catch” light that might be lost out of the second side of the light guide and to redirect that light to the reflector. One or more diffusers and/or brightness enhancement films can be disposed adjacent to the light guide on a side opposite the reflector as well to further enhance the uniformity of light being reflected from the reflector.
In one embodiment, a method of controlling a display backlighting system is configured to provide local dimming along a display to save power. The local dimming function cab be applied any of spatially, temporally, or combinations thereof. With temporal dimming, individual lights of the light sources can be controlled based upon the content of image that is being displayed on the display. The temporal dimming can be varied on a frame-by-frame basis. With spatial dimming, a single frame can be divided into several subsections. Individual lights can be turned ON and OFF within a single frame to control brightness, contrast, and definition of the image in addition to saving power. Where light sources are disposed on two sides of the light guide, subsections of the light sources can be actuated a section at a time to give rise to temporal dimming. The intensity of light being produced by the subsections of the light sources can be varied by varying a voltage or current being delivered to individual lights so that the two sides have different light intensities to achieve spatial dimming
Embodiments of the disclosure provide additional advantages over prior art designs. For example, when the display becomes large in a prior art mobile device, contrast problems arise. Most prior art displays employ a backlight that is continually ON and spans the entirety of the display. To create “black” colors, a LCD or other switchable layer attempts to block out the light being emitted by the backlight. This blocking is not entirely effective, which results in black areas looking grey. Accordingly, overall contrast is reduced. By using embodiments of the disclosure, independently actuating and/or dimming individual lights results in “blacker” blacks and “whiter” whites, thereby increasing contrast. Additionally, power consumption is reduced because the backlighting system is not continually ON.
Another advantage involves the “Z-stackup.” The Z-stackup refers to the vertical height from the front surface of a display to the rear surface of the display. With prior art displays, a backlighting element must be placed across the major face of the display, which makes the overall height thicker. This increased Z-dimension stackup height results in a thicker overall electronic device. By using a light guide configured in accordance with one or more embodiments of the disclosure, a thinner display results. Moreover, by disposing the convex protuberances toward the reflector, no loss of contrast control results despite the light guide being substantially thinner than in prior art designs. The use of individually controllable zones or subportions of the light sources further allows the Z-stackup to become even thinner. What's more, light guides configured in accordance with embodiments of the disclosure work to prevent light diffusion across zones or subsections of the display to further enhance contrast control.
Turning first to
While light gets blocked when a pixel is in the second state, due to the physical limitations of the liquid crystal media the light is not completely blocked. Consequently, shapes 103,104 that are supposed to appear black appear to be washed out or grey. Accordingly, the contrast between the shapes 103,104 and other colors, such as the white background 110, is poor. Moreover, since the backlight is always ON, the display becomes the most power hungry component in the prior art electronic device 100. Where the prior art electronic device 100 is a mobile phone, for example, the relatively large amounts of power consumed by the prior art display 101 result in lesser performance, reduced talk time, and quicker battery depletion.
The prior art electronic device 100 of
Turning now to
A user 210 is holding the electronic device 200. The operating system environment, which is configured as executable code operating on one or more processors or control circuits of the electronic device 200, has associated therewith various applications or “apps.” Examples of such applications shown in
The display 201 of the electronic device 200 is configured in accordance with one or more embodiments of the disclosure. In one embodiment, the display 201 includes a light guide that defines a first major face, a second major face, and one or more edge surfaces. One or more light sources are disposed along the one or more edge surfaces to deliver light to the light guide through the one or more edge surfaces. A diffuser is disposed adjacent to the first major face and a reflector is disposed adjacent to the second major face. In one embodiment, the first major face is substantially planar and defines a plurality of light extractors to receive the light from the one or more light sources and redirect the light toward the reflector. In one embodiment, the second major face defines a plurality of convex protuberances extending from the second major face toward the reflector and spanning a major dimension of the second major face, each convex protuberance to direct the light from the light guide to the reflector.
By using the display 201 configured in this fashion, light elements of the light sources can be selectively turned OFF and ON. Further, the voltage or current applied to the light elements can be varied so as to selectively alter the amount of light being presented by each light element. Accordingly, there is no need to keep a large backlight continually ON as was the case in the prior art electronic device (100). This results in reduced power consumption. The reduced power consumption occurs despite the fact that the display 201 of
Turning now to
As shown in the schematic block diagram 300, a control circuit 301 is operable with the display 201, which is touch-sensitive in this illustrative embodiment. The control circuit 301, which may be a microprocessor, programmable logic, application specific integrated circuit device, or other similar device, is capable of executing program instructions, such as those that will be described with reference to the methods discussed below. The program instructions may be stored either in the control circuit 301 or in a memory 302 or other computer readable medium operable with the control circuit 301. The memory 302 can also store executable code corresponding to the various applications 303 that are operable on the electronic device (200), such as those described above with reference to
Coupled to, and operable with, the controller is the display 201. The explanatory display 201 of
In the illustrative embodiment of
Beneath the fascia layer 310 is the capacitive touch sensor layer 311. The capacitive touch sensor layer 311, which can be constructed by depositing small capacitive plate electrodes on a transparent substrate, is configured to detect the presence of an object, such as a user's finger or stylus, near to or touching the display 201. Circuitry operable with or disposed within the control circuit 301 is configured to detect a change in the capacitance of a particular plate combination on the capacitive touch sensor layer 311. The capacitive touch sensor layer 311 may be used in a general mode, for instance to detect the general proximate position of an object relative to the touch sensitive display. The capacitive touch sensor layer 311 may also be used in a specific mode, where a particular capacitor plate pair may be detected to detect the precise location of an object along length and width of the touch sensitive display. Note that the capacitive touch sensor layer 311 is a particular implementation of an electromagnetic field sensor, and other types of electromagnetic field sensors, such as a magnetic field sensor, can replace the capacitive field sensor.
Note that while the capacitive touch sensor layer 311 and the fascia layer 310 are shown as separate layers in
Beneath the capacitive touch sensor layer 311 are, optionally, one or more layers of brightness enhancement film 312. Brightness enhancement films 312 are polymer film sheets that include an imprinted prismatic surface pattern to diffuse light. It has been said that the prismatic surface pattern, when viewed closely, resembles a series of triangles or gear teeth extending distally from the surface of the sheet. Each of these prisms redirects light passing out of the display 201 toward the viewer. Without the brightness enhancement film 312, some of the light emitted by the display 201 may not be available to the viewer due to the fact that the angle at which the light exits the display 201 is above or below a viewer's field of view. The brightness enhancement film 312 works to collimate the light toward the user's field of view. Such brightness enhancement films 312 are available from 3M Corporation, for example.
It should be noted that the brightness enhancement film 312 can comprise one or more layers of film. For example, in one embodiment, the brightness enhancement film 312 can comprise two layers of film, or alternatively can comprise a dual brightness enhancement film. A second layer of film can provide a reflective sheet to recycle any light that fails to intersect a prism of the primary layer at the appropriate angle for collimation. Where multiple layers are use, light either passes through the prisms to the user's field of view or else “bounces” between the reflector 317 until it reaches a prism of the primary layer at the proper angle. A single sheet of brightness enhancement film 312 can increase brightness of the display by as much as 605, while two sheets disposed orthogonally relative to each other can provide up to a 120% increase in brightness. As will be appreciated by those of ordinary skill in the art having the benefit of this disclosure, the use of the brightness enhancement film 312 allows the light sources 315,316 to decrease the amount of power consumed to deliver a specified amount of display brightness.
Beneath the optional brightness enhancement film 312, in one embodiment, is a diffuser 313. The diffuser 313, in one embodiment, is a layer that diffuses, spreads, or scatters received light to soften the same. The diffuser 313 can be constructed from glass or plastic.
Disposed beneath the diffuser 313 is a light guide 314. Details of the light guide 314 will be explained in more detail with reference to
Disposed adjacent to the light guide 314 are one or more light sources 315,316. In the illustrative embodiment of
Beneath the light guide 314 is the reflector 317. In one embodiment, the reflector 317 is configured to reflect light delivered to the reflector 317 by the plurality of convex protuberances extending from the light guide 314 toward the reflector 317. The reflector 317 can then return the light to the light guide 314. The reflector 317 can be disposed adjacent the light guide 314 and can be manufactured from a reflective material such as polyethylene terephthalate in one embodiment.
As described above, the second brightness enhancement film layer 422 includes an imprinted prismatic surface pattern to diffuse light. Illustrating by example, in one embodiment the brightness enhancement film layers 412,422 each comprise a prismatic structure disposed along the surface thereof. The prismatic surface pattern of the second brightness enhancement film layer 422 collimates received light toward the user's field of view. The first brightness enhancement film layer 412, having another prismatic structure oriented substantially orthogonally relative to the prismatic structure of the second brightness enhancement film layer 422, provides a reflective function to recycle any light that fails to intersect a prismatic structure of the primary layer at the appropriate angle for collimation.
The diffuser 313 is disposed below the brightness enhancement film layers 412,422. In this illustrative embodiment, the brightness enhancement film layers 412,422 are disposed adjacent to the diffuser 313 on a side of the diffuser 313 that is opposite, i.e., facing away from, the reflector 317. The two brightness enhancement film layers 412,422 are configured in one embodiment to diffuse the light passing from the light guide 314 through the diffuser 313.
The light guide 314 is disposed beneath the diffuser 313. Turning briefly to
As shown in
The second major face 502 defines a plurality of convex protuberances 507 extending from the second major face 502 and spanning a major dimension 508 of the second major face 502. As will be shown below in the discussion of
The cross section of each of the plurality of convex protuberances 507 can take a variety of shapes. For example, convex protuberances 517 define a portioned disc cross section. Convex protuberances 527 define a frustoconical cross section. Convex protuberances 537 define a triangular cross section. These shapes of cross sections are illustrative only. Other cross section shapes will be obvious to those of ordinary skill in the art having the benefit of this disclosure.
In one or more embodiments, the light guide 314 can be formed in a substantially tabular shape. In one or more embodiments, the first major face 501 and the second major face 502 can be formed in a substantially rectangular shape. In one or more embodiments, the light guide 314 can be made of a transparent resin such as an acrylic resin, polycarbonate resin, and so forth. The one or more edge surfaces 503,504 can be configured to operate as the light incident surfaces to receive light emitted from the one or more light sources 315,316. Accordingly, a respective one of the one or more edge surfaces 503,504 can be located so as to face each of the one or more light sources as shown in
As the terms are used herein, a direction orthogonal to the one or more edge surfaces 503,504 of the light guide 314 may be referred to as the X-axis direction. A longitudinal direction of the one or more edge surfaces 503,504 of the light guide 314 may be referred to as the Y-axis direction, and a direction perpendicular to the second major face 502 may be referred to as the Z-axis direction, as shown in
Turning back to
Turning now to
Turning now to
As noted above, temporal control can include altering a voltage or current applied to an individual light emitting diode to dim or actuate/deactuate one or more individual light emitting diodes 701,702,703,801,802,803. In one embodiment, this control can be based upon the content being presented on the display 201. Further, this control can occur on a frame-by-frame basis. For example, if the content being presented on the display 201 is a video being shown at a frame rate of 60 frames per second, the temporal control can occur such that the amount of light emitted by the light emitting diodes 701,702,703,801,802,803 changes sixty or more times per second.
With spatial control, the control circuit 301 is configured to apply dimming and/or lighting control to the groups 704,705,706,804,805,806. Individual groups 704,705,706,804,805,806 can be selectively actuated during an individual frame to control brightness and contrast. For example, group 704 can be OFF while groups 704,805,806 are ON, with groups 704,806 being brighter than group 805. Of course, a combination of spatial and temporal control can be used as well.
In addition to spatial and temporal actuation, in one embodiment the control circuit 301 can be configured to actuate the light emitting diodes 701,702,703,801,802,803 or groups 704,705,706,804,805,806 sequentially as well by actuating light emitting diodes 701,702,703,801,802,803 or groups 704,705,706,804,805,806 before another of the light emitting diodes 701,702,703,801,802,803 or groups 704,705,706,804,805,806 disposed adjacent to the first. For example, light emitting diode 701 can be actuated before light emitting diode 702. Similarly, group 704 can be actuated before group 705, and so forth.
In one embodiment, the groups 704,705,706,804,805,806 are arranged in pairs on opposite sides of the light guide 314. For example, groups 704,804 define one pair, while groups 705,805 define another pair, and so forth. In one embodiment, each pair is disposed on opposite sides of the light guide 314 so as to define one or more predefined zones 707,708,709.
The control circuit 301 can be configured to actuate selected pairs in a first mode by turning ON a first pair corresponding to a first predefined zone, e.g., predefined zone 707, while turning OFF a second pair corresponding to a second predefined zone, e.g., predefined zone 708. Further, the control circuit 301 can also actuate the pairs in a second mode in corresponding zones by of actuating a first member of the pair, e.g., group 704, to emit more light into a predefined zone 707 than another member of the pair, e.g., group 804. Of course, combinations of the first mode and the second mode to control the predefined zones 707,708,709 can be used as well. In one or more embodiments, the first mode and second mode control of the pairs along the predefined zones 707,708,709 can be based upon frames of content received by the control circuit 301.
Turning now to
Turning now to
The brightness and contrast of each frame 901,902,903,904 is being controlled spatially and temporally. Additionally, the brightness and contrast of each frame 901,902,903,904 is being controlled using the first mode and second mode corresponding to predefined zones as well. Illustrating this by example, in the first frame 901, spatial control can be seen in that group 704 is OFF, while group 804 is ON. Note that this is also an example of first mode zone control, as group 706 and group 806 are disposed opposite the light guide 314 relative to each other so as to define predetermined zone 709. Temporal control can be seen as individual light emitting diodes 811,812,813,814,815,810 are all being dimmed to levels that are different and distinct from levels being output by other light emitting diodes. Note that this is an example of second mode zone control, as group 807 and group 808 are disposed on opposite sides of the light guide 314 so as to define predetermined zone 809.
This all changes in frame 902 due to the changes in the content 900. In the first frame 901, in predefined zone 713, second mode zone control is occurring because group 905 is being driven to a different brightness output from group 906. In predefined zone 714, first mode zone control is occurring. Temporal control of light emitting diodes 811,812,813,814,815,810 is occurring in predetermined zone 809. Spatial control is occurring in zone 907. As shown, any of spatial control, temporal control, first mode zone control, or second mode zone control can occur, alone or in combination, on a frame-by-frame basis based upon the content 900. The control occurring in each frame 901,902,903,904 is different in
In the foregoing specification, specific embodiments of the present disclosure have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present disclosure as set forth in the claims below. Thus, while preferred embodiments of the disclosure have been illustrated and described, it is clear that the disclosure is not so limited. Numerous modifications, changes, variations, substitutions, and equivalents will occur to those skilled in the art without departing from the spirit and scope of the present disclosure as defined by the following claims. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present disclosure. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims.
