Patent Publication Number: US-2007114354-A1

Title: System and method for adjusting brightness of rear seat entertainment monitor of vehicle in conjunction with open angle of monitor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims priority of Korean Application No. 10-2005-0097921, filed on Oct. 18, 2005, with the Korean Intellectual Property Office, the disclosure of which is fully incorporated herein by reference.  
     FIELD OF THE INVENTION  
      The present invention relates generally to rear seat entertainment systems and, more particularly, to systems and methods for improving the brightness of images on a rear seat entertainment monitor as seen from different viewing angles.  
     BACKGROUND OF THE INVENTION  
      Traditionally, Liquid Crystal Displays (LCDs) offer a limited viewing angle. Depending on the viewer&#39;s location, the displayed screen state can vary considerably; looking at the display panel from the sides, top, or bottom often results in tremendous color distortions or loss of brightness. An illustration of various viewing angles and a table of their corresponding brightness are shown in FIG. I and  FIG. 5 , respectively.  
      Referring to  FIG. 1 , when the monitor is viewed at a 90° angle, the displayed screen state is at its optimal; in other words, a brightness value of 300 cd/m 2  set in the monitor would yield a displayed screen state with a brightness value of 300 cd/m 2  as measured from Eye 3 &#39;s perspective. However, at a viewing angle of 120°, the brightness value of the displayed screen state as measured from Eye 4  drops to 200 cd/m 2  and the displayed screen state is noticeably darker. This phenomenon grows increasingly worse as the viewing angle deviates increasingly further from 90°, e.g. when the monitor is viewed at six o&#39;clock (a viewing angle of 0°) and twelve o&#39;clock (a viewing angle of 180°). In the context of a vehicular entertainment system, the problem is even greater due to the relative confinement of the rear-seat passengers to their seating positions, making it difficult for multiple passengers to simultaneously view the images in their optimal or near-optimal state.  
      As such, there is a need in the art for systems and methods that can correct the brightness of an LCD panel at wider viewing angles.  
     SUMMARY OF THE INVENTION  
      The present invention provides systems and methods for adjusting the brightness of a Rear Seat Entertainment (RSE) monitor in an automotive vehicle based on the open angle of the monitor.  
      In some embodiments of the present invention, a system for adjusting brightness of a rear seat entertainment monitor of a vehicle based on the open angle of the monitor includes a monitor open angle input unit, a control unit, an image processing unit and a Liquid Crystal Display (LCD) panel unit. The monitor open angle input unit outputs a gearing amount, which corresponds to the current open angle of the rear seat entertainment monitor of the vehicle. The control unit receives this gearing amount from the monitor open angle input unit and uses it to calculate the current open angle of the monitor, and outputs a control signal required to set parameter values for an output screen image based on the monitor&#39;s calculated open angle. In response to the control signal output from the control unit, the image processing unit outputs a screen image of the monitor using the corrected parameter values for the output screen image. The LCD panel unit then projects the image, which has been output through the image processing unit, onto a screen.  
      In some embodiments of the present invention, the method of adjusting brightness of a rear seat entertainment monitor of a vehicle based on the open angle of the monitor comprises: a) receiving from a control unit a gearing amount corresponding to an open angle of the monitor; b) calculating a current open angle of the monitor using the received gearing amount; setting parameter values for an output screen image corresponding to the current open angle after the open angle of the monitor has been calculated; c) projecting the screen image from an image processing unit onto a Liquid Crystal Display (LCD) panel unit; d) adjusting brightness of a backlight of the LCD panel unit using the parameter values set by the control unit; and e) completing adjustment of the screen brightness of the monitor. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      For a better understanding of the nature and objects of the present invention, reference should be made to the following detailed description with the accompanying drawings, in which:  
       FIG. 1  illustrates various viewing angles of a typical LCD monitor;  
       FIG. 2  illustrates a block diagram of the system of the present invention;  
       FIG. 3  illustrates the mechanism by which the open angle of the monitor is determined;  FIG. 3A  illustrates the open state of the monitor of the system according to the present invention;  FIG. 3B  is a close-up view of portion “O” according to an embodiment of the present invention;  
       FIG. 4  is a flow diagram outlining the steps of the method of the present invention;  
       FIG. 5  is a comparison of the measured brightness of a conventional monitor and the measured brightness of a monitor corrected by the system according to an embodiment of the present invention;  FIG. 5A  is a table of brightness values of a conventional monitor and  FIG. 5B  is a table of brightness values of a monitor corrected by the system according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Herein below, a preferred embodiment of the present invention will be described with reference to the accompanying drawings.  
      The present invention provides a system, shown in  FIG. 2 , that adjusts the brightness of an RSE monitor in conjunction with the open angle of the monitor. In preferred embodiments of the present invention, the system includes a monitor open angle input unit  10 , a control unit  20 , an image processing unit  30  and a Liquid Crystal Display (LCD) panel unit  40 .  
      The monitor open angle input unit  10  outputs a gearing amount which corresponds to the current open angle a of the RSE monitor  100 , as illustrated in  FIG. 3A . The control unit  20  calculates the current open angle of the monitor using the gearing amount received from the monitor open angle input unit  10 , and then outputs a control signal required to set parameter values for an output screen image, corresponding to the calculated current monitor open angle. The image processing unit  30  outputs the screen image of the monitor using corrected parameter values for the output screen image, in response to the control signal output from the control unit  20 . The LCD panel unit  40  projects the image output from the image processing unit  30  onto the screen.  
      In the system illustrated in  FIG. 2 , the values of various parameters of the output screen image of the monitor corresponding to the open angle of the monitor, e.g. brightness, contrast, hue, gamma and color saturation of a monitor screen image, and a voltage value for the backlighting intensity of the LCD panel unit, are stored in the control unit  20  in the form of a map table  25 .  
      Further, the image processing unit  30  includes a brightness adjustment register unit  31  for adjusting brightness, a contrast adjustment register unit  32  for adjusting contrast, a hue adjustment register unit  33  for adjusting hue, a gamma adjustment register unit  34  for adjusting gamma, a saturation adjustment register unit  35  for adjusting color saturation, and a Direct Current (DC) inverter circuit unit  36  for adjusting a voltage value for the backlighting intensity of the LCD panel unit. As previously mentioned, the brightness, contrast, hue, gamma and color saturation are parameter values for the output screen image of the monitor.  
      Further, a backlight lamp unit  50  is provided in the LCD panel unit  40  to adjust the brightness of the LCD panel.  
      Further, the monitor open angle input unit  10  is manufactured to have a gear-hinge structure to output the number of clicks by which a gear has been rotated according to the current open angle of the monitor.  
      As shown in  FIG. 3B , the control unit  20  determines the number of clicks by which a gear  7  is rotated in the direction of an arrow from a reference point A to thereby determine the current open angle of the monitor. In other words, the control unit  20  receives the number of clicks of the gear, i.e. gearing amount, corresponding to the open angle of the monitor and calculates the open angle of the monitor using the number of clicks by which the gear is rotated from the reference point.  
      In preferred embodiments of the present invention, the monitor open angle input unit  10  comprises a rotatable gear-hinge structure, designated as portion “O” in  FIG. 3A . As shown in  FIG. 3B , a preferred embodiment of the gear-hinge structure comprises 8 teeth A to H on the basis of reference point A and is rotatable at an angle of 45° per tooth. However, alternate configurations of the gear-hinge structure, e.g. different number of teeth at different intervals with different gear amount per turn of the structure, can be used to achieve the object of the present invention. These features constitute the mechanism by which the open angle of the monitor is determined. The open angle of the monitor can be determined based on the gear amount, i.e. number of clicks of the gear, of the gear-hinge structure from a reference point. For example, using the monitor&#39;s closed position as the reference point, if the number of gear clicks is equal to  36  and the gear rotates five teeth from the reference point, then the current open angle of the monitor is determined to approximate 50°. In this manner, the current open angle of the monitor a between the cover  2  of the monitor and a monitor screen  4  can be determined based on the number of gear clicks from a reference point.  
      The method of adjusting the brightness of a rear seat entertainment monitor in conjunction with the open angle of the monitor according to an embodiment of the present invention, using the system having the above construction, is described with reference to the flowchart of  FIG. 4  based on  FIG. 2 .  
      As shown in  FIG. 4 , the control unit  20  receives a gearing amount, i.e. the number of clicks by which the gear is rotated, corresponding to the current open angle of the monitor from the monitor open angle input unit  10  at step S 10 , and then calculates the current open angle of the monitor at step S 20 . In the above operation, the calculation of the current open angle of the monitor is performed using the number of clicks by which the gear is rotated from the reference point, as described above with reference to  FIGS. 3A and 3B .  
      After the current open angle of the monitor has been calculated at step S 20 , the control unit  20  sets parameter values for an output screen image corresponding to the current open angle of the monitor, e.g. brightness, contrast, hue, gamma, and color saturation required for outputting the screen image of the monitor, and a voltage value required for adjusting the backlighting intensity of the LCD panel unit, using the stored map table at step S 30 .  
      In some embodiments of the present invention, the control unit  20  is a Micom means that adjusts various parameters, e.g. brightness, contrast, chroma, hue, gamma and saturation, of the LCD. It should be noted that alternative means capable of serving the above function can be used to achieve the object of the present invention. The Micom means comprise a memory wherein map table  25  is stored. The map table  25  contains data in the form of a table containing parameter values, e.g. brightness, contrast, chroma, hue, gamma, and saturation, etc. according to various open angles. To adjust the brightness of the screen image outputted on the LCD panel, the control unit  20  comprises a processor that can access data from the map table and thus retrieve the appropriate signals for brightness, contrast, chroma, hue, gamma, and saturation given the open angel of the monitor. The control unit  20  then transmits these signals to the appropriate registers in the image processing unit  30 . Likewise, an appropriate voltage value signal of the backlight lamp unit is selected based on the open angle of the monitor and transmitted to the DC inverter circuit of the image processing unit  30 , thereby altering or correcting the brightness of the screen image as outputted on the LCD panel.  
      In summary, after respective parameter values have been set at step S 30 , correction control signals for respective parameter values outputted from the control unit  20  are inputted to the image processing unit  30 , thereby directing the correction of the respective parameter values. After respective parameter values have been corrected, the image processing unit  30  projects a screen image, in which the respective parameter values have been corrected, onto the LCD panel unit  40 , and adjusts the backlighting brightness of the backlight lamp unit  50  in the LCD panel unit  40 . In this manner, the screen image brightness of the monitor is adjusted based on the open angle of the monitor at steps S 40  and S 50 .  
      A demonstration of the extent to which the brightness of the screen images can be adjusted at various viewing angles is provided in  FIG. 5 . As shown therein, significant improvement in brightness is achieved for viewing angles ranging from 0 to 30° and from 150 to 180° as compared with the image brightness of conventional monitor. These results are based on the fact that the brightness of the monitor is optimal at 318 cd/m 2  when the open angle of the monitor is 90°.  
      As is apparent from the foregoing, there is an advantage in a system and method for adjusting the brightness of the RSE monitor of a vehicle in conjunction with the open angle of the monitor of the present invention, in that it can provide a bright image even at a non-perpendicular viewing angle. Thus, the present invention saves users from the inconvenience of having to adjust the open angle of the monitor each time, thereby effectively extending the useful viewing range of the monitor.  
      While the present invention has been described with reference to the particular illustrative embodiments, it is not to be limited to the foregoing embodiments. Those skilled in the art will appreciate that changes or modifications to the embodiments can be made without departing from the scope and spirit of the present invention.