Image display device and image display method

Abstract

An image display device is disclosed that is capable of presenting to a viewer a high-quality lustrous video on a display screen with best screen brightness by increasing visual contrast and avoiding loss of true black elements without widening a dynamic range of a picture signal. The image display device is provided with a liquid crystal display portion, a display control portion, a backlight, a backlight control portion and an average brightness detecting portion and detects brightness of the light source in accordance with the average brightness of a picture signal to be displayed. It is further provided with a peak detecting portion and corrects the control of the backlight control portion in accordance with a detected peak value of a picture.

1 . A liquid crystal display device for controlling brightness of a light source in accordance with average brightness of a picture input to the display device, comprising a peak detector for detecting a degree of peak level of a given input picture and a brightness control for increasing the brightness of the light source as the given input picture has a larger detected degree of peak level.  
   
   
       2 . A liquid crystal display device as defined in  claim 1 , wherein, in a case when the average brightness of the picture input to the display device is not more than a specified value, the brightness control increases the brightness of the light source as the given input picture has a larger detected degree of peak level.  
   
   
       3 . A liquid crystal display device for controlling brightness of a light source in accordance with average brightness of a picture input to the display device, comprising a peak detector for detecting a degree of peak level of a given input picture and a brightness control for decreasing the brightness of the light source as the given input picture has a smaller detected degree of peak level.  
   
   
       4 . A liquid crystal display device as defined in  claim 3 , wherein, in a case when the average brightness of the picture input to the display device is not more than a specified value, the brightness control decreases the brightness of the light source as the given input picture has a smaller detected degree of peak level.  
   
   
       5 . A liquid crystal display device as defined in  claim 2 , wherein the device prevents the brightness of the light source from increasing as the picture input to the device has a larger average brightness.  
   
   
       6 . A liquid crystal display device for controlling brightness of a light source in accordance with average brightness of a picture input to the display device, comprising a peak detector for detecting a degree of peak level of a given input picture and a brightness control for correcting a control characteristic of the brightness of the light source in relation to the average brightness so as to increase the brightness of the light source as the given input picture has a larger degree of detected peak level.  
   
   
       7 . A liquid crystal display device as defined in  claim 6 , wherein, in a case when the average brightness is not more than a specified value, the brightness control corrects a control characteristic of the brightness of the light source in relation to the average brightness so as to increase the brightness of the light source as the given input picture has a larger degree of detected peak level.  
   
   
       8 . A liquid crystal display device for controlling brightness of a light source in accordance with average brightness of a picture input to the display device, comprising a peak detector for detecting a degree of peak level of a given input picture and a brightness control for correcting a control characteristic of the brightness of the light source in relation to the average brightness so as to decrease the brightness of the light source as the given input picture has a smaller degree of detected peak level.  
   
   
       9 . A liquid crystal display device as defined in  claim 8 , wherein, in a case when the average brightness is not more than a specified value, the brightness control corrects a control characteristic of the brightness of the light source in relation to the average brightness so as to decrease the brightness of the light source as the given input picture has a smaller degree of detected peak level.  
   
   
       10 . A liquid crystal display device as defined in  claim 6 , wherein the device further prevents the brightness of the light source from increasing as the picture input to the device has a larger average brightness.  
   
   
       11 . A liquid crystal display device as defined in  claim 1 , wherein the device decides the degree of peak level of the given input picture as being large in a case when the given input picture contains n or more pixels each being larger than a level m (where n and m are preset values).  
   
   
       12 . A liquid crystal display device as defined in  claim 1 , wherein the device detects a case that the given input picture contains na or more pixels each being larger than a level ma (where na and ma are preset values) and a case that the given input picture contains nb or more pixels each being larger than a level mb (where nb and mb are preset values) and decides a degree of peak level.  
   
   
       13 . A liquid crystal display device as defined in  claim 1 , wherein the device has at least three combinations of threshold level mx and threshold number nx for detecting a case that the given input picture contains nx or more pixels each being larger than a level mx (where nx and mx are preset values) and decides the degree of peak level based on results of comparison of the combinations.  
   
   
       14 . A liquid crystal display device as defined in  claim 1 , wherein the device detects a maximum level within the given input picture, compares the maximum level with a level p (where p is a preset value) and decides the degree of peak level as being large when the maximum level is larger than the level p.  
   
   
       15 . A liquid crystal display device as defined in  claim 1 , wherein the device detects a maximum level within the given input picture, compares the maximum level with a level pa and a level pb respectively (where pa and pb are preset values) and decides the degree of peak level.  
   
   
       16 . A liquid crystal display device as defined in  claim 1 , wherein the device detects a maximum level within the given input picture, compares the maximum level with at least three levels px (where px is a preset value) and decides the degree of peak level based on results of the respective comparison.  
   
   
       17 . A liquid crystal display device as defined in  claim 2 , wherein the device has a first threshold value ra (where ra is a preset value) being smaller than the specified value and controls the light source to have a fixed value of brightness in a case when the average brightness is smaller than the first threshold value ra.  
   
   
       18 . A liquid crystal display device as defined in  claim 2 , wherein the device has a second threshold value rb (where rb is a preset value) being larger than the specified value and controls the light source to have a fixed value of brightness in a case when the average brightness is larger than the second threshold value rb.  
   
   
       19 . A display control method for controlling brightness of a light source in accordance with average brightness of a picture input to the display device, comprising steps of detecting a degree of peak level of a given input picture; and increasing the brightness of the light source as the given input picture has a larger degree of peak level.  
   
   
       20 . A display control method for controlling brightness of a light source in accordance with average brightness of a picture input to a display, comprising steps of detecting a degree of peak level of a given input picture; and decreasing the brightness of the light source as the input picture has a smaller degree of peak level.  
   
   
       21 . A display control method for controlling brightness of a light source in accordance with average brightness of a picture input to a display, comprising steps of detecting a degree of peak level of a given input picture; and correcting a control characteristic of the light source in relation to the average brightness of the picture input to the device so as to increase the brightness of the light source as the given input picture has a larger degree of peak level.  
   
   
       22 . A display control method for controlling brightness of a light source in accordance with average brightness of a picture input to a display, comprising steps of detecting a degree of peak level of a given input picture; and correcting a control characteristic of the light source in relation to the average brightness so as to decrease the brightness of the light source as the given input picture has a smaller degree of peak level.