Abstract:
Backlighting lamps in an LCD are extinguished when they are in regions beyond the area of the demanded image produced by an associated LCD cell matrix that overlays the lamps. In some cases the size of the demanded image may be reduced according to a user-input energy savings mode and then lamps beyond the image region are extinguished. Energy savings are realized.

Description:
I. FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to establishing backlighting in a liquid crystal display (LCD). 
       II. BACKGROUND OF THE INVENTION 
       [0002]    Some LCDs use backlighting in which the brightness of the backlight is varied according to ambient light levels in an effort to reduce energy consumption. For example the backlighting intensity can be reduced when the ambient light levels are low, because darker rooms require less backlighting than brighter rooms. 
       SUMMARY OF THE INVENTION 
       [0003]    As recognized herein, in addition to the energy savings that may be achieved using the method mentioned above, additional energy savings may be further achieved according to present principles. 
         [0004]    Accordingly, a liquid crystal display (LCD) includes elongated co-planar lamps and a matrix of LCD cells juxtaposed with the lamps. The lamps provide backlighting for the matrix. Control circuitry controls the matrix to present a demanded image. The demanded image covers an image area, and the control circuitry maintains lamps outside the image area deenergized independently of ambient light conditions. 
         [0005]    The lamps may be oriented vertically or horizontally. In example embodiments the control circuitry establishes an intensity of illumination for lamps within the image area based at least in part on ambient light conditions. In some implementations the control circuitry scales the image area in response to user input representing a desired energy use such that which lamps that are maintained deenergized are defined at least in part using the user input. In some examples the control circuitry includes a microprocessor and/or a display driver circuit. 
         [0006]    In another aspect, a method includes providing backlighting lamps in an LCD, and extinguishing a subset of backlighting lamps in response to a determination that the subset of backlighting lamps is in regions beyond an area of a demanded image produced by an associated LCD cell matrix that overlays the lamps. 
         [0007]    In another aspect, an apparatus has a TV tuner, control circuitry receiving a demanded image from the TV tuner, and a liquid crustal display (LCD) coupled to the control circuitry to present the demanded image. The control circuitry establishes a backlighting of the LCD in response to an area encompassed by the demanded image when displayed on the LCD. 
         [0008]    The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a schematic diagram of one embodiment of a liquid crystal display (LCD) implemented in a TV environment; 
           [0010]      FIG. 2  is a schematic diagram showing internal components of the TV shown in  FIG. 1 ; 
           [0011]      FIGS. 3 and 4  are schematic plan views of two embodiments of the backlighting lamps, illustrating some lamps deenergized when they lay outside the area of the demanded image; 
           [0012]      FIG. 5  is a schematic plan view of the LCD showing various user-defined demanded image area sizes; and 
           [0013]      FIGS. 6 and 7  are flow charts showing logic that may be used in accordance with present principles. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0014]    Referring initially to  FIG. 1 , an LCD  10  in accordance with present principles is shown embodied in one intended environment, namely, a TV  12  with TV tuner  14 , display driver circuit  16  for driving the LCD  10 , computer readable storage medium  18  such as disk-based or solid storage, and a microprocessor  20  accessing the medium  18  in accordance with logic set forth herein. The microprocessor  20  may control the display driver circuit  16  as appropriate to present the demanded image using the LCD  10 , in which case the microprocessor  20  with display driver circuit  16  establish control circuitry. In other implementations the microprocessor  20 /display driver circuitry  16  functionalities may be implemented by a single device. 
         [0015]    The TV  12  may include inputs other than the TV tuner  14 , e.g., the TV may receive video input from an optical disk player, a wide area computer network, etc. The LCD  10  may be used in other applications requiring video presentation, such as portable computers/portable communication devices, etc. 
         [0016]      FIG. 2  shows that the LCD  10  may include a planar array  22  of backlight lamps as discussed further below. The array  22  provides backlighting for a matrix  24  of LCD cells that are controlled by the control circuitry to provide, in combination with the backlighting, a demanded image. Without limitation, the lamps in the array  22  can be light emitting diode (LED) lamps, hot cathode fluorescent (HCFL) lamps, and cold cathode fluorescent (CCFL) lamps. 
         [0017]    Typically, a diffuser assembly  26  may be interposed between the backlighting array  22  and matrix  24  to diffuse backlight from the lamps onto the cells of the matrix. The components  22 ,  24 ,  26  typically establish three planes of components. A power source  28  is also typically provided to provide illumination power to the LCD  10  under control of the control circuitry. 
         [0018]    In  FIG. 3 , details of an example array  22  of backlighting lamps  30  are shown. In the example shown in  FIG. 3 , the lamps  30  are elongated and oriented vertically when the display is positioned upright as shown in  FIG. 1 . The lamps  30  typically can be parallel to each other as shown. 
         [0019]    In the example shown in  FIG. 3 , the overall dimension available for display of demanded images on the LCD  10  is 16×9, whereas the demanded image encompasses a 4:3 aspect ratio area defined by the dimensions “a” and “b” that is less than the available display area of the LCD  10 . Lamps  30  that are beyond the area of the demanded image, in this case, lamps  30  that are beyond the boundaries of the dimension “a”, are maintained deenergized, while lamps  30  within the dimension “a” are energized to enable presentation of the demanded image. The deenergization of lamps  30  beyond the area of the demanded image is maintained regardless of whatever backlight dimming may be implemented within the dimension “a” to account for ambient light and/or demanded image pixel brightness. Thus, it is to be understood that present principles may be used to deenergize lamps  30  beyond the dimension “a” in conjunction with backlight control of lamps  30  within the dimension “a” to enhance energy savings. 
         [0020]      FIG. 4  shows an alternate array  22   a  of backlight lamps  32  that are horizontally oriented when the LCD is upright. In all other essential respects the arrays  22 ,  22   a  of  FIGS. 3 and 4  are identical; thus, for example, when the overall dimension available for display of demanded images on the LCD  10  is 16×9 and the demanded image in a demanded image area defined by the dimensions “c” and “d” is in letterbox format, lamps  32  that do not underlie the area of the demanded image, i.e., lamps  32  beyond the dimension “d”, are maintained deenergized. 
         [0021]    In addition to automatically deenergizing the lamps beyond an otherwise unmodified demanded image area, the control circuitry may scale the size of the demanded image in response to, e.g., user input. For example, a user interface maybe presented in a “setup” mode on the LCD that requests the user to select a desired energy savings mode. The mode may be established by numeric input, e.g., “save 80%”, or the user may be presented a menu of a limited number of options, e.g., “100%”, “50%”, “16%”. This latter implementation is illustrated in  FIG. 5 , in which the demanded image area is scaled down to a 16% image area  34  in response to the user effectively selecting “use ⅙ of the total available backlight power”. When the user selects “50%” the demanded image area is confined to area  36 , while the full available screen—area  38 —is used to present the demanded image in response to a “100%” selection. Backlighting lamps outside the selected area are maintained deenergized. 
         [0022]    The above principles may be embodied by logic executable by the present control circuitry and illustrated in  FIGS. 6 and 7 . At block  40  in  FIG. 6 , a demanded image is received. Moving to block  42 , the area of the demanded image is compared to the total area that may be backlit, and at block  44  lamps in regions that do not underlie the area of the demanded image are maintained deenergized. 
         [0023]    In contrast, for the case in which image size can be scaled per user input and backlighting lamps deenergized accordingly, at block  46  in  FIG. 7  a user interface may be presented to the user as described above to enable the user to select an energy savings mode. In essence, the user selects an image size, with smaller image sizes translating to lower energy use. The video scalar (and thus the size of the area occupied on screen by the demanded image) is adjusted according to the user input at block  48 . Proceeding to block  50 , LCD backlighting lamps that lie beyond the re-sized demanded image area are maintained deenergized. 
         [0024]    Accordingly, it may now be appreciated that the speed of the addressable back light is not important for the power saving feature. The user may select the level of power savings required in some example embodiments, and the actively back lit area of the display is varied accordingly. In such embodiments the video scalar is also controlled so that the video content is scaled appropriately to match the area of the actively controlled back light area. 
         [0025]    In some embodiments, recognizing that, as explained above, the demanded image area may not encompass the full screen area available for image presentation, the location of the demanded image on screen may be moved slightly from time to time, either randomly or in accordance with a time schedule. For instance, the demanded image in  FIG. 3  may periodically be shifted one or a few pixels left or right, while the demanded image in  FIG. 4  may be shifted one or a few pixels up or down. It may be appreciated that which lamps are energized and deenergized likewise change as necessary to backlight the current area of the demanded image while maintaining lamps deenergized that lie outside the current area of the demanded image. 
         [0026]    While the particular DYNAMICALLY ESTABLISHED BACKLIGHT FOR ENERGY CONSERVATION IN LCD is herein shown and described in detail, it is to be understood that the subject matter which is encompassed by the present invention is limited only by the claims.