Image display apparatus, display unit driver and image display method for the same

• US 20050057486A1
• Filed: 07/20/2004
• Published: 03/17/2005
• Est. Priority Date: 08/27/2003
• Status: Active Grant

• Current Assignee: Maxell, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Sakamoto, Hirofumi, Aoki, Hiroshi, Hasegawa, Ryo, Takata, Haruki, Tsuru, Yasutaka
• Granted Patent: US 7,333,081 B2
• Time in Patent Office: Days
• US Class Current: 345/102
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/2092 Details of a display terminals using a flat panel, the details relating to the control arrangement of the display terminal and to the interfaces thereto suitable for both CRT and flat panel G09G5/003; specific for a CRT G09G1/165
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 5/04 using circuits for interfacing with colour displays
• CPC Class Codes: H04N 9/3155 for controlling the light source light source control per se H05B35/00 – H05B47/00; control of an illumination source for displays in general G09G3/3406

Abstract

An object of the present invention is to provide an image display technology with which high contrast can be stably obtained. In order to achieve the above object, the present invention changes the gain of a digital luminance signal by feeding back information on maximum and average luminance levels of the luminance signal, adjusts image contrast, and in accordance with the average luminance level detected from the feedback system, controls the illuminance of the backlight applied to a display unit. The control increases the illuminance of the backlight when the detected average luminance level is higher than the upper-limit value of a previously set reference range, and reduces the illuminance when the detected average luminance level is lower than the lower-limit value of the reference range.

Claims

1. A display unit driver for an image display apparatus for displaying an image on a display unit in accordance with a digital video signal, said driver comprising:

a first controller for feedback-controlling a gain of a digital luminance signal; and

a second controller, in accordance with an average luminance level of the digital luminance signal controlled by said first controller, for controlling an illuminance of backlight applied to a screen of the display unit.

2. A display unit driver for an image display apparatus for displaying an image on a display unit in accordance with a digital video signal, said driver comprising:

a first controller for feedback-controlling a gain of a digital luminance signal; and

a second controller for controlling, in accordance with an average luminance level of the digital luminance signal controlled by said first controller, an illuminance of backlight applied to a screen of the display unit;

wherein said second controller increases the illuminance of the backlight when the average luminance level is higher than an upper-limit value of a previously set reference range, and reduces the illuminance of the backlight when the average luminance level is lower than a lower-limit value of the reference range.

3. A display unit driver for an image display apparatus for displaying an image on a display unit in accordance with a digital video signal, said driver comprising:

a first control system that adjusts video contrast by feeding back information on a maximum luminance level of a digital luminance signal and information on an average luminance level of the digital luminance signal, and changing a gain thereof; and

a second control system for performing control to ensure that when the average luminance level is higher than an upper-limit value of a previously set reference range, an illuminance of backlight applied to a screen of the display unit is increased, and that when the average luminance level is lower than a lower-limit value of the reference range, the illuminance is reduced.

4. A display unit driver for an image display apparatus for displaying an image on a display unit in accordance with a digital video signal, said driver comprising:

a first control system for adjusting image contrast of the display unit by identifying a corresponding luminance region of a maximum luminance level, and a corresponding luminance region of an average luminance level, of an A/D-conversion-obtained digital luminance signal during a required period, feeding back information on both identified luminance regions, and changing a gain of the luminance signal;

a second control system for performing control to ensure that when the average luminance level is higher than an upper-limit value of a previously set reference range, an illuminance of backlight applied to a screen of the display unit is increased, and that when the average luminance level is lower than a lower-limit value of the reference range, the illuminance is reduced; and

a third control system for performing color image correction of the display unit by modifying a gain of a chrominance signal in accordance with information on both the identified luminance regions.

5. The display unit driver according to claim 4, wherein said second control system is a feed-forward control system.

6. A display unit driver for an image display apparatus for displaying an image on a display unit in accordance with a digital video signal, said driver comprising:

a luminance level detector for detecting a maximum luminance level, and an average luminance level, of an A/D-conversion-obtained digital luminance signal during a required period;

a first microcomputer for identifying a corresponding luminance region of the maximum luminance level and a corresponding luminance region of the average luminance level, and controlling a gain of the luminance signal in accordance with information on both the identified luminance regions;

a backlight controller for controlling an illuminance of backlight applied to a screen of the display unit; and

a second microcomputer for controlling said backlight controller, in accordance with the luminance region information of the average luminance level sent from said first microcomputer, so as to ensure that when the average luminance level is higher than an upper-limit value of a previously set reference range, the illuminance of the backlight is increased, and that when the average luminance level is lower than a lower-limit value of the reference range, the illuminance is reduced;

wherein said luminance level detector and said first microcomputer constitute a feedback control system to control a gain of the luminance signal and adjust image contrast, and said second microcomputer and said backlight controller constitute a feed-forward control system linked to the feedback control system, and thus perform backlight control.

7. The display unit driver according to claim 6, said backlight controller and said second microcomputer are provided in the display unit.

8. An image display apparatus for displaying an image on a display unit in accordance with a digital video signal, said apparatus comprising:

the display unit having a display panel and a backlight generator, and displaying an image by use of the digital video signal while backlight is being applied to the display panel; and

a display unit driver for driving both the display panel and backlight generator of said display unit by detecting an average luminance level of a digital luminance signal whose gain was feedback-controlled, and controlling the backlight generator in accordance with information on the average luminance level to ensure that when the average luminance level is higher than an upper-limit value of a previously set reference range, an illuminance of the backlight applied to a screen of said display unit is increased, and that when the average luminance level is lower than a lower-limit value of the reference range, the illuminance is reduced.

9. The image display apparatus according to claim 8, wherein said display unit driver provides control to ensure that:

when the average luminance level is higher than the upper-limit value of the reference range, in a first region exceeding the upper-limit value, the illuminance of the backlight is increased as the average luminance level increases, and in a second region where the average luminance level is even higher than in the first region, an increase in the illuminance is suppressed to make the illuminance substantially constant; and

when the average luminance level is lower than the lower-limit value of the reference range, in a third region overstepping the lower-limit value, the illuminance of the backlight is reduced as the average luminance level decreases, and in a fourth region where the average luminance level is even lower than in the third region, a decrease in the illuminance is suppressed to make the illuminance substantially constant.

10. An image display apparatus for displaying an image on a display unit in accordance with a digital video signal, said apparatus comprising:

a luminance level detector for detecting a maximum luminance level, and an average luminance level, of a digital luminance signal during a required period;

a first microcomputer for identifying a first corresponding luminance region of the maximum luminance level detected, and a second corresponding luminance region of the average luminance level detected, and performing gain control of either an analog luminance signal obtained before A/D conversion, or the digital luminance signal existing after the A/D conversion, or both of the analog and digital luminance signals, in accordance with information on the identified first and second luminance regions or information on the identified second luminance region;

a backlight controller for controlling an illuminance of the backlight applied to a screen;

a second microcomputer for controlling said backlight controller, in accordance with the information on the second luminance region, sent from said first microcomputer, so as to ensure that when the average luminance level is higher than an upper-limit value of a previously set reference range, the illuminance of the backlight is increased, and that when the average luminance level is lower than a lower-limit value of the reference range, the illuminance is reduced;

a color matrix circuit for forming and transmitting digital video signals for red, green, and blue, in accordance with digital chrominance signals and the digital luminance signal; and

the display unit having a display panel and a backlight generator, and displaying an image by use of the digital video signals output from said color matrix circuit, while the backlight is being applied to the screen;

wherein said luminance level detector and said first microcomputer constitute a feedback control system to control the gains of the luminance signals and adjust video contrast of said display unit, and said second microcomputer and said backlight controller constitute a feed-forward control system linked to the feedback control system, and thus perform backlight control of said display unit.

11. An image display apparatus for displaying an image on a display unit in accordance with a digital video signal, said apparatus comprising:

a first controller for controlling an illuminance of backlight applied to a screen of the display unit, in accordance with average luminance level information on a digital luminance signal having a feedback-controlled gain; and

a second controller for identifying whether the display unit is configured to irradiate the screen with the backlight, and when the display unit is configured to irradiate the screen with the backlight, controlling said first controller to make the illuminance of the backlight controllable.

12. An image display apparatus for displaying an image on a display unit in accordance with a digital video signal, said apparatus comprising:

a first microcomputer for identifying a first corresponding luminance region of a maximum luminance level, and a second corresponding luminance region of an average luminance level, of a digital luminance signal during a required period, feeding back information on the first and second luminance regions identified or information on the second luminance region identified, and performing gain control of either an analog luminance signal obtained before A/D conversion, or a digital luminance signal obtained after the A/D conversion, or both the analog and digital luminance signals;

a backlight controller for controlling an illuminance of the backlight applied to a screen of the display unit; and

a second microcomputer for controlling said backlight controller in accordance with the information on the second luminance region, sent from said first microcomputer;

wherein, in accordance with ID information that includes type information on the display unit, either said first microcomputer or said second microcomputer or both thereof identify whether the display unit is configured to irradiate the screen with the backlight, and if identification results indicate that the display unit is configured to irradiate the screen with the backlight, said second microcomputer controls said backlight controller and thus the backlight is controlled.

13. An image display apparatus for displaying an image on a display unit in accordance with a digital video signal, said apparatus comprising:

a video amplifier for modifying, in terms of gain, either an analog luminance signal obtained before A/D conversion, or a digital luminance signal obtained after the A/D conversion, or both the analog and digital luminance signals;

a first microcomputer for feeding back information based on a luminance level of the digital luminance signal, and controlling said video amplifier;

a color corrector for color-correcting an image on the display unit by modifying a gain of a chrominance signal in accordance with the information based on the luminance level, sent from said first microcomputer;

a backlight controller for controlling an illuminance of the backlight applied to a screen of the display unit; and

a second microcomputer for controlling said backlight controller in accordance with the information on the luminance region, sent from said first microcomputer;

wherein, in accordance with ID information on the display unit, either said first microcomputer or said second microcomputer or both thereof identify whether the display unit is configured to irradiate the screen with the backlight, modify circuit setup conditions relating to either said video amplifier or said color corrector or both thereof, and make the display unit adaptable.

14. An image display method for displaying an image on a display unit in accordance with a digital video signal, said method comprising the steps of:

detecting an average luminance level of a gain-feedback-controlled digital luminance signal;

comparing the average luminance level detected, with a previously set reference range;

performing control to ensure that, as a result of the comparison, when the average luminance level is higher than an upper-limit value of the reference range, an illuminance of the backlight applied to a screen of the display unit is increased, and when the average luminance level is lower than a lower-limit value of the reference range, the illuminance is reduced;

wherein an image is displayed on the display unit in a backlight-applied state.

15. An image display method for displaying an image on a display unit in accordance with a digital video signal, said method comprising the steps of:

detecting a maximum luminance level, and an average luminance level, of a gain-feedback-controlled digital luminance signal during a required period;

identifying a first corresponding luminance region of the maximum luminance level detected, and a second corresponding luminance region of the average luminance level detected, and performing gain control on either an analog luminance signal obtained before A/D conversion, or the digital luminance signal existing after the A/D conversion, or both of the analog and digital luminance signals, in accordance with information on the first luminance region identified or information on the second luminance region identified;

comparing the detected average luminance level with a value of a previously set reference range in accordance with the information of the identified second luminance region;

performing control to ensure that, as a result of the comparison, when the detected average luminance level is higher than an upper-limit value of the reference range, an illuminance of the backlight applied to a screen of the display unit is increased, and when the detected average luminance level is lower than a lower-limit value of the reference range, the illuminance is reduced; and

forming and transmitting digital video signals for red, green, and blue, in accordance with digital chrominance signals and the gain-controlled digital luminance signal;

wherein an image is displayed in a backlight-applied state on the display unit.

16. An image display method for displaying an image on a display unit in accordance with a digital video signal, said method comprising the steps of:

identifying a first corresponding luminance region of a maximum luminance level, and a second corresponding luminance region of an average luminance level, of a digital luminance signal during a required period, feeding back information on the first and second luminance regions identified or information on the second luminance region identified, and thus performing gain control of either an analog luminance signal obtained before A/D conversion, or the digital luminance signal existing after the A/D conversion, or both of the analog and digital luminance signals;

determining whether the display unit is configured to irradiate a screen with backlight;

if the determination results indicate that the display unit is configured to irradiate the screen with backlight, comparing the average luminance level with a value of a previously set reference range in accordance with the information of the identified second luminance region; and

performing control to ensure that, as a result of the comparison, when the average luminance level is higher than an upper-limit value of the reference range, an illuminance of the backlight applied to the screen of the display unit is increased, and when the average luminance level is lower than a lower-limit value of the reference range, the illuminance is reduced;

wherein an image is displayed on the display unit in a backlight-applied state.