Patent Application
20080185976
The present invention relates to displays, and more particularly, to a system and method of controlling a display backlight.
Backlights are used in transmissive displays, such as liquid crystal displays (LCDs), to enhance user visibility of the display under various conditions by illuminating the display. Although the overall structure and configuration may vary, a typical backlight includes a plurality of light sources that are placed behind the display. The light sources, when appropriately energized, emit light and illuminate the display. Various types of light source backlights have been developed and used. For example, incandescent light, electroluminescent (EL) light, cold cathode fluorescent lamp (CCFL), hot cathode fluorescent lamp (HCFL), and light emitting diode (LED) backlights, just to name a few, have been developed and used.
In some instances, it may be desirable to operate a display, and more specifically the display backlight, in a reduced power operational mode. For example, depending on the end-use of the display, it may be desirable to operate the display in a reduced power mode for various off-nominal operating conditions, for thermal management purposes, and/or for battery management purposes. Backlights are typically designed to produce substantially uniform luminance for the entire display region. Thus, even when the display is operated in a reduced power mode, each of the light sources may be energized, albeit at a reduced power level, even though the entire display may not be needed during the reduced power mode. This can potentially exacerbate the condition and/or purpose for being in the reduced power operational mode.
Hence, there is a need for a system and method of controlling display backlights that, when the need arises to operate the display in a reduced power mode, the backlight does not potentially exacerbate the condition and/or purpose for being in the reduced power operational mode. The present invention addresses at least this need.
In one embodiment, and by way of example only, a backlight system for a display includes a plurality of light sources and a backlight controller. Each light source is coupled to be selectively energized and deenergized and is operable, upon being energized to emit light and illuminate a portion of the display. The backlight controller is configured to determine if reduced power operation is desired and, if so, to selectively deenergize selected ones of the light sources and selectively energize selected other ones of the light sources.
In another exemplary embodiment, a display system includes a display, a backlight, and a backlight controller. The display includes a display region in which an image may be selectively rendered. The backlight is spaced apart from the display region and includes a plurality of light sources. Each light source is coupled to be selectively energized and deenergized and operable, upon being energized, to emit light. The backlight controller is coupled to the backlight and is configured to determine if reduced power operation is desired, energize each light source in a manner that at least substantially uniformly backlights the display region if reduced power operation is not desired, and selectively deenergize selected ones of the light sources and selectively energize selected other ones of the light sources in a manner that selectively backlights only selected sections of the display region if reduced power operation is desired.
In yet another exemplary embodiment, a method of controlling backlight luminance of a display that includes a display region in which an image may be selectively rendered includes determining if operation in a reduced power mode is desired. If operation in the reduced power mode is not desired, the display region is at least substantially uniformly backlit. If operation in the reduced power mode is desired, only selected sections of the display region are selectively backlit.
The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.
The backlight 104 is coupled to the display 102, and includes a plurality of light sources 108, and a diffuser 112. The light sources 108 are each coupled to a substrate 114, which is spaced apart from the display 102 to form a backlight cavity 116 therebetween. The light sources 108 are each configured, upon being energized, to emit light toward the display 102. The light sources 108 are preferably implemented using a plurality of white LEDs. It will be appreciated, however, that the light sources 108 could be implemented using a plurality of color LEDs, incandescent lights, electroluminescent (EL) lights, cold cathode fluorescent lamps, or hot cathode fluorescent lamps, just to name a few.
No matter how the light sources 108 are each implemented, the light rays that are emitted from the light sources 108 optically mix in the backlight cavity 116 and enter the diffuser 112. The diffuser 112, as is generally known, statistically redirects the optically mixed light rays from the backlight cavity 116 and preferably distributes the mixed light rays toward the display 102 with substantial uniformity.
The display device 100, as noted above, may be used as an avionics display. An avionics display, as is generally known, is used to render a plurality of images representative of various types of data and/or aircraft status for display to a pilot. These data and/or status may vary, and may include, for example, aircraft speed, aircraft altitude, aircraft attitude, and aircraft heading, just to name a few. Thus, the display 102 may be configured to render a plurality of images, each in different sections of the display region 106. For example, in the embodiment depicted in
Before proceeding further, it is noted that the display 102 may be configured to render the plurality of images in the display region 104 using any one of numerous processes now known or developed in the future. A description of these processes is not needed to fully describe or enable the invention encompassed in the accompanying claims. As such, no further description of the processes will be provided herein.
Turning now to
The backlight controller 304 is coupled to, and independently controls, each of the drivers 302, and thus independently controls which light sources 106 are energized and deenergized. More specifically, the backlight controller 304 is configured to determine if reduced power operation of the display device 100 is desired. If the backlight controller 304 determines that reduced power operation is not desired, then it preferably energizes, via the drivers 302, of each of the light sources 106. If, however, the backlight controller 304 determines that reduced power operation is desired, it selectively deenergizes, via the drivers 302, selected ones of the light sources 106 and selectively energizes, via the drivers 302, selected other ones of the light sources 106. It will be appreciated that the light sources 106 that are energized and deenergized during the reduced power operation may vary with one or more system conditions that resulted in the desire, or continued desire, for reduced power operation. For example, under some reduced power operation conditions, it may be desirable to only deenergize one or two of the light sources 106, whereas under other reduced power operation conditions it may be desirable to deenergize all but one or two of the light sources. Moreover, situations could be encountered in which the reduced power operation condition may initially result in only one or two of the light sources 106 being deenergized; however, as time goes it on may be desirable to selectively deenergize additional light sources 106. It will additionally be appreciated that the backlight controller 304 may also be configured to independently control the luminance levels of the energized light sources 106, at least during reduced power operational modes. In addition, it will be appreciated that in some embodiments the drivers 302 could be formed as an integral part of the backlight controller 304.
The backlight controller 304 is preferably responsive to one or more input signals to determine whether reduced power operation of the display device 100. In the depicted embodiment these input signals include a user input signal 306, a thermal sensor signal 308 that is representative of the thermal state of the display device 100, a signal representative of primary power supply state 310, a signal representative of backup power supply state 312, and a signal representative of the state of one or more sensor signals 314. The user input signal 306 is supplied from a user interface 316. The user interface 316 is provided so that a user can manually place the backlight controller 304 into the reduced power operation. Although the user interface 316 may be implemented using various user interface devices, it is configured, in response to user stimuli supplied thereto from a user, to selectively supply the user input signal 306 to the backlight controller 304.
The thermal sensor signal 308 is supplied either directly or indirectly from one or more thermal sensors 318 (only one depicted in
The signal representative of primary power supply state 310 is supplied either directly or indirectly from a display device primary power supply 322 and indicates, for example, whether the primary power supply 322 is operating properly, improperly, or not at all. The signal representative of backup power supply state 312 is supplied either directly or indirectly from a display device backup power supply 324 and indicates, for example, whether the backup power supply 324 is being used to supplying power to the display device 100 and, if it is, whether it is operating properly. The backup power supply 324 may be implemented as a redundant power supply that is substantially identical to the primary power supply, or it may be implemented using a battery. It will be appreciated that if the backup power supply 324 is implemented using a battery, a signal representative of battery charge status 326 may also be supplied to the backup controller 304, and the backup controller 304 may be further responsive to this signal to, for example, control which light sources 106 are energized and deenergized during operation in the reduced power operational mode, and the luminance levels associated with the energized light sources 106.
The backlight controller 304 additionally receives one or more feedback signals 318 from one or more light sensors 320 (only one depicted in
As
With the above-described configuration, the backlight controller 304, based on the above-described signals that are supplied thereto, determines if operation of the display device 100 in a reduced power mode is desired. If the backlight controller 304 determines that operation in the reduced power mode is not desired, the backlight controller 304 will energize, via the drivers 302, each of the light sources 108 to uniformly (or at least substantially uniformly) backlight the display region 106. If, however, the backlight controller determines that operation in the reduced power mode is desired, the backlight controller 304 will selectively backlight only selected sections 202 of the display region 106 by selectively deenergizing selected ones of the light sources 108 and selectively energizing selected other ones of the light sources 108. As noted above, the backlight controller 304 may additionally independently control the luminance levels of the energized light sources 106 to further reduce the power consumption by the backlight 104.
While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.
