Liquid crystal display apparatus with control of LCD and backlight corresponding to an image

• US 7,595,784 B2
• Filed: 02/09/2005
• Issued: 09/29/2009
• Est. Priority Date: 02/09/2004
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Original Assignee: Hitachi Displays Limited (Japan Display Incorporated)
• Inventors: Yamamoto, Tsunenori, Konno, Akitoyo, Wakagi, Masatoshi, Inuzuka, Tatsuki, Hiyama, Ikuo, Kajita, Daisuke
• Primary Examiner(s): Mengistu; Amare
• Assistant Examiner(s): LAM, VINH TANG
• Application Number:
  US11/053,256
• Publication Number:
  US 20050231457A1
• Time in Patent Office: 1,693 Days
• Field of Search: 345/38, 345/47, 345/48, 345/63, 345/77, 345/87, 345/90, 345/102, 345/104, 345/206, 345/207, 345/211, 345/690
• US Class Current: 345/102
• CPC Class Codes: G02F 1/133601 for spatial active dimming
• CPC Class Codes: G09G 2300/0491 Use of a bi-refringent liquid crystal, optically controlled bi-refringence [OCB] with bend and splay states, or electrically controlled bi-refringence [ECB] for controlling the color
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/0257 Reduction of after-image effects
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0653 Controlling or limiting the speed of brightness adjustment of the illumination source
• CPC Class Codes: G09G 2320/103 Detection of image changes, e.g. determination of an index representative of the image change
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources

Abstract

The liquid crystal display apparatus includes a liquid crystal display, a backlight unit for emitting rays of light of three or more colors, the ray of each color being controlled, and applying these rays of light onto the liquid crystal display. A controller is further provided for controlling a change of display data of each color of the liquid crystal display and an emitted light quantity of each color of the backlight unit at a time, based on a video signal being inputted for displaying the corresponding image and an output signal sent from an ambient light sensor for sensing ambient light.

Claims

1. A liquid crystal display apparatus comprising:

a liquid crystal display composed of a pair of substrates, a liquid crystal layer laid between said pair of substrates, a plurality of electrode groups for applying an electric field onto said liquid crystal layer, and a plurality of active elements being connected with said electrode groups and having a plurality of sub-pixel structures;

a backlight unit arranged for controllable light emission of a plurality of colors, for applying a ray of light of each color onto said liquid crystal display;

a controller for controlling a change of display data of each color on said liquid crystal display and a quantity of each color ray of light emitted from said backlight unit, based on an output signal sent from a backlight sensor for sensing light emission of said backlight unit and a video signal of each color being inputted for displaying the corresponding image on said liquid crystal display; and

a subtitle detecting circuit for detecting a subtitle displayed on the liquid crystal display;

wherein said controller determines a conversion maximum gray scale point MAX in accordance with a result of an analysis of a video signal of each color to be inputted for displaying onto said liquid crystal display, changes said display data so as to convert said inputted video signal at the MAX into a signal at a gray scale in which a liquid crystal transmittance becomes maximum, and lowers a backlight luminance output into a luminance level indicated by the MAX in said input and output characteristic;

wherein no conversion of a 0 gray scale signal of each color in said inputted video signal is executed with respect to the color with the highest MAX and the conversion of said 0 gray scale signal of the remaining colors is executed so as to make the 0 gray scale of each color equal to a 0 gray scale luminance level at which the MAX becomes the highest; and

wherein if the subtitle is detected, said conversion maximum gray scale point MAX is determined on an analyzed result of a video signal excepting a signal portion corresponding with said detected subtitle.

2. A liquid crystal display apparatus according to claim 1, wherein said backlight unit is composed of light-emitting diodes of three primary colors and the light emission of said backlight unit is controlled through the effect of pulse width modulation.

3. A liquid crystal display apparatus according to claim 1, wherein said display data changed for being outputted to said liquid crystal display uses portions of a gradation characteristic of said liquid crystal display.

4. A liquid crystal display apparatus according to claim 1, wherein said conversion maximum gray scale point MAX has a restricted inter-frame variation, and a convertible quantity if no scene change occurs is smaller than the convertible quantity if any scene change occurs.

5. A liquid crystal display apparatus according to claim 1, wherein said controller determines said conversion maximum gray scale point MAX in accordance with an image signal of each color imputed to be displayed on the liquid crystal display, an output signals from an optical sensor for sensing light emission of the backlight, and an output signals from an ambient light sensor.

6. A liquid crystal display apparatus comprising:

a liquid crystal display composed of a pair of substrates, a liquid crystal layer laid between said substrates, a plurality of electrode groups for applying an electric field onto said liquid crystal layer, and a plurality of active elements being connected

a controller for controlling a change of display data of each color on said liquid crystal display and a quantity of each color ray of light emitted from said backlight unit, based on an output signal sent from a backlight sensor for sensing light emission of said backlight unit and a video signal of each color being inputted for displaying the corresponding image on said liquid crystal display; and

a subtitle detecting circuit for detecting a subtitle displayed on the liquid crystal display;

wherein said controller determines a conversion maximum gray scale point MAX in accordance with an analyzed result of a video signal of each color to be inputted for displaying onto said liquid crystal display, changes said display data so as to convert said inputted video signal at the MAX into a signal at a gray scale in which a liquid crystal transmittance becomes maximum, and lowers a backlight luminance output into a luminance level indicated by the MAX in said input and output characteristic;

wherein no conversion of a 0 gray scale signal of each color in said inputted video signal is executed with respect to the color with the highest MAX and the conversion of said 0 gray scale signal of the remaining colors is executed so as to make the 0 gray scale of each color equal to a 0 gray scale luminance level at which the MAX becomes the highest; and

wherein, for a data signal representing the subtitle included in an inputted video signal, for the color with the lowest MAX of the colors, said data signal representing the subtitle is not converted, and for the remaining colors, said data signal is converted so as to make the maximum gray scale of each color equal to the maximum luminance level of the color with the lowest MAX.

7. A liquid crystal display apparatus according to claim 6, wherein said controller determines said conversion maximum gray scale point MAX in accordance with an image signal of each color imputed to be displayed on the liquid crystal display, an output signals from an optical sensor for sensing light emission of the backlight, and an output signals from an ambient light sensor.

8. A liquid crystal display apparatus according to claim 6, wherein said backlight unit is composed of light-emitting diodes of three primary colors and the light emission of said backlight unit is controlled through the effect of pulse width modulation.

9. A liquid crystal display apparatus according to claim 6, wherein said display data changed for being outputted to said liquid crystal display uses portions of a gradation characteristic of said liquid crystal display.

10. A liquid crystal display apparatus according to claim 6, further comprising a subtitle detecting circuit for detecting a subtitle displayed on the liquid crystal display, wherein if the subtitle is detected, said conversion maximum gray scale point MAX is determined on an analyzed result of a video signal excepting a signal portion corresponding with said detected subtitle.

11. A liquid crystal display apparatus according to claim 6, wherein said conversion maximum gray scale point MAX has a restricted inter-frame variation, and a convertible quantity if no scene change occurs is smaller than the convertible quantity if any scene change occurs.