Backlight apparatus, backlight controlling method and liquid crystal display apparatus

• US 9,099,045 B2
• Filed: 01/23/2008
• Issued: 08/04/2015
• Est. Priority Date: 01/24/2007
• Status: Expired due to Fees

• Current Assignee: Thomson Licensing (Vantiva SA)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Ueda, Mitsunori, Morimoto, Tadashi, Mizuta, Minoru
• Primary Examiner(s): Nguyen, Chanh
• Assistant Examiner(s): Kirkpatrick, John
• Application Number:
  US12/011,039
• Publication Number:
  US 20080174544A1
• Time in Patent Office: 2,750 Days
• Field of Search: 345/88, 345/102, 345/211
• US Class Current: 1/1
• CPC Class Codes: G09G 2310/0232 Special driving of display border areas
• CPC Class Codes: G09G 2310/0237 Switching ON and OFF the backlight within one frame
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• 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 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix

Abstract

Disclosed herein is a backlight apparatus for controlling a backlight wherein light emitting devices for emitting light of red, green and blue and a switching device for switching on or off light emission of the light emitting devices are provided for each of a plurality of divisional regions formed by division of a lighting region such that the light emission luminance can be varied for each of the regions, the backlight apparatus including: light emission luminance control means; current value storage means; and current control means.

Claims

1. A backlight apparatus for controlling a backlight wherein light emitting devices (LEDs) for emitting light of a plurality of colors and a switching device for switching on or off light emission of said light emitting devices are provided for divisional regions formed by division of a lighting region such that a light emission luminance can be varied for the divisional regions, said backlight apparatus comprising:

light emission luminance control means for varying a pulse width of a pulse signal to be supplied to a switching device in a first of the divisional regions to control the light emission luminance of the light emitted by a plurality of LEDs of the first divisional region, the plurality of LEDs being configured to emit light of the plurality of colors;

current value storage means for storing, for the first divisional region, current values of currents to be supplied to the plurality of LEDs, the current values being determined such that a whiteness and the light emission luminance of the light emitted by the plurality of LEDs become equal to predetermined values; and

current control means for controlling a power supplying means for supplying the currents to the plurality of LEDs so that the currents become equal to the current values stored in said current value storage means,

wherein the switching device is configured to switch the plurality of LEDs in response to a same signal, the same signal being the pulse signal,

wherein the plurality of LEDs includes a first LED configured to emit light of a first color and a second LED configured to emit light of a second color,

wherein the light emission luminance control means is configured to adjust the light emission luminance of the light emitted by the plurality of LEDs from a first luminance value to a second luminance value by controlling the switching device to adjust a same rate at which the plurality of LEDs switch on and off from a first same rate value to a second same rate value, the first luminance value having a corresponding first chromaticity and the second luminance value having a corresponding second chromaticity, and

wherein the current control means is configured to control chromaticity from the first luminance value to the second luminance value by providing current values to the first LED and the second LED that are different for at least one of the first chromaticity or the second chromaticity.

2. The backlight apparatus according to claim 1, further comprising a current value determination section for determining the current values based on the whiteness and the light emission luminance of the light emitted by the plurality of LEDs.

3. The backlight apparatus according to claim 2, wherein the current values of the currents to be supplied to the plurality of LEDs are first current values, wherein the plurality of LEDs are a first plurality of LEDs, and wherein:

the current value storage means is also for storing second current values of currents to be supplied to a second plurality of LEDs in a second of the divisional regions, and

the current value determination section is configured to determine the second current values by;

calculating coefficients relating light emission luminance of the second divisional region to the light emission luminance of the first divisional region,

determining the second current values such that a whiteness of light emitted by the second plurality of LEDs becomes equal to a predetermined value, and

adjusting the second current values based on the coefficients such that the light emission luminance of the light emitted by the second plurality of LEDs becomes equal to the light emission luminance of the light emitted by the first plurality of LEDs.

4. The backlight apparatus according to claim 1, wherein the plurality of LEDs comprises an LED configured to emit light of a red color, an LED configured to emit light of a blue color, and an LED configured to emit light of a green color.

5. The backlight apparatus according to claim 1, wherein:

the switching device in the first divisional region comprises a switch for controlling the light emission luminance of the light emitted by the plurality of LEDs of the first divisional region, and

the pulse signal is supplied to the switch.

6. The backlight apparatus according to claim 1, wherein the switching device in the first divisional region comprises a plurality of switches.

7. The backlight apparatus according to claim 1, wherein the switching device includes a single switch to which the plurality of LEDs are coupled, the plurality of LEDs being configured to emit light of the plurality of colors.

8. A backlight controlling method wherein light emitting devices (LEDs) for emitting light of a plurality of colors and a switching device for switching on or off light emission of said light emitting devices are provided for divisional regions formed by division of a lighting region such that a light emission luminance can be varied for the divisional regions, said backlight controlling method comprising acts of:

varying a pulse width of a pulse signal to be supplied to a switching device in a first of the divisional regions to control the light emission luminance of the light emitted by a plurality of LEDs of the first divisional region, the plurality of LEDs being configured to emit light of the plurality of colors;

controlling a power supplying section supplying currents to the plurality of LEDs so that the currents become equal to stored current values with which a whiteness and the light emission luminance of the light emitted by the plurality of LEDs become equal to predetermined values,

wherein the switching device switches the plurality of LEDs in response to a same signal, the same signal being the pulse signal,

wherein the plurality of LEDs includes a first LED configured to emit light of a first color and a second LED configured to emit light of a second color,

wherein the method further comprises adjusting the light emission luminance of the light emitted by the plurality of LEDs from a first luminance value to a second luminance value by controlling the switching device to adjust a same rate at which the plurality of LEDs switch on and off from a first same rate value to a second same rate value, the first luminance value having a corresponding first chromaticity and the second luminance value having a corresponding second chromaticity, and

wherein the current values to the first LED and the second LED are different for at least one of the first chromaticity or the second chromaticity.

9. The backlight controlling method according to claim 8, wherein

the current values of the currents to be supplied to the plurality of LEDs are first current values, wherein the plurality of LEDs are a first plurality of LEDs, and wherein:

the method further comprises determining second current values of currents to be supplied to a second plurality of LEDs in a second of the divisional regions by;

calculating coefficients relating light emission luminance of the second divisional region to the light emission luminance of the first divisional region,

determining the second current values such that a whiteness of light emitted by the second plurality of LEDs becomes equal to a predetermined value, and

adjusting the second current values based on the coefficients such that the light emission luminance of the light emitted by the second plurality of LEDs becomes equal to the light emission luminance of the light emitted by the first plurality of LEDs.

10. The backlight controlling method according to claim 8, wherein

the plurality of LEDs comprises an LED configured to emit light of a red color, an LED configured to emit light of a blue color, and an LED configured to emit light of a green color.

11. The backlight controlling method according to claim 8, wherein:

the switching device in the first divisional region comprises a plurality of switches.

12. The backlight controlling method according to claim 8, wherein:

the switching device in the first divisional region comprises a first switch for controlling light emission luminance of light emitted by the first LED, and a second switch for controlling light emission luminance of light emitted by the second LED, and

the pulse signal is supplied to the first and second switches.

13. The backlight controlling method according to claim 8, further comprising adjusting the whiteness of the light emitted by the plurality of LEDs by adjusting values of the currents supplied to the plurality of LEDs while switching the plurality of LEDs on and off at the same rate.

14. A liquid crystal display apparatus, comprising:

a backlight wherein light emitting devices (LEDs) configured to emit light of a plurality of colors and a switching device for switching on or off light emission of said light emitting devices are provided for divisional regions formed by division of a lighting region such that a light emission luminance can be varied for the divisional regions;

light emission luminance control means for varying a pulse width of a pulse signal to be supplied to a switching device in a first of the divisional regions to control the light emission luminance of the light emitted by a plurality of LEDs of the first divisional region, the plurality of LEDs being configured to emit light of the plurality of colors;

current value storage means for storing, for the first divisional region, current values of currents to be supplied to the plurality of LEDs, the current values being determined such that a whiteness and the light emission luminance of the light emitted by the plurality of LEDs become equal to predetermined values; and

current control means for controlling a power supplying means for supplying the currents to be supplied to the plurality of LEDs so that the currents become equal to the current values stored in said current value storage means,

wherein the switching device is configured to switch the plurality of LEDs in response to a same signal, the same signal being the pulse signal,

wherein the plurality of LEDs includes a first LED configured to emit light of a first color and a second LED configured to emit light of a second color,

wherein the light emission luminance control means is configured to adjust the light emission luminance of the light emitted by the plurality of LEDs from a first luminance value to a second luminance value by controlling the switching device to adjust a same rate at which the plurality of LEDs switch on and off from a first same rate value to a second same rate value, the first luminance value having a corresponding first chromaticity and the second luminance value having a corresponding second chromaticity, and

wherein the current control means is configured to control chromaticity from the first luminance value to the second luminance value by providing current values to the first LED and the second LED that are different for at least one of the first chromaticity or the second chromaticity.

15. The liquid crystal display apparatus according to claim 14, wherein the current values of the currents to be supplied to the plurality of LEDs are first current values, wherein the plurality of LEDs are a first plurality of LEDs, and wherein:

the current value storage means is also for storing second current values of currents to be supplied to a second plurality of LEDs in a second of the divisional regions, and

the liquid crystal display apparatus further comprises a current value determination section configured to determine the second current values by;

calculating coefficients relating light emission luminance of the second divisional region to the light emission luminance of the first divisional region,

determining the second current values such that a whiteness of light emitted by the second plurality of LEDs becomes equal to a predetermined value, and

adjusting the second current values based on the coefficients such that the light emission luminance of the light emitted by the second plurality of LEDs becomes equal to the light emission luminance of the light emitted by the first plurality of LEDs.

16. The liquid crystal display apparatus according to claim 14, wherein the plurality of LEDs comprises an LED configured to emit light of a red color, an LED configured to emit light of a blue color, and an LED configured to emit light of a green color.

17. The liquid crystal display apparatus according to claim 14, wherein:

the switching device in the first divisional region comprises a plurality of switches.

18. The liquid crystal display apparatus according to claim 14, Wherein:

the switching device in the first divisional region comprises a first switch for controlling light emission luminance of light emitted by the first LED and a second switch for controlling light emission luminance of light emitted by the second LED, and

the pulse signal is supplied to the first and second switches.

19. A backlight apparatus for controlling a backlight wherein light emitting devices (LEDs) for emitting light of a plurality of colors and a switching device for switching on or off light emission of said light emitting devices are provided for divisional regions formed by division of a lighting region such that a light emission luminance can be varied for the divisional regions, said backlight apparatus comprising:

a light emission luminance control section configured to vary a pulse width of a pulse signal to be supplied to a switching device in a first of the divisional regions to control the light emission luminance of the light emitted by a plurality of LEDs of the first divisional region, the plurality of LEDs being configured to emit light of the plurality of colors;

a current value storage section configured to store, for the first divisional region, current values of currents to be supplied to the plurality of LEDs, the current values being determined such that a whiteness and the light emission luminance of the light emitted by the plurality of LEDs become equal to predetermined values; and

a current control section configured to control a power supply section to control the currents to be supplied to the plurality of LEDs so that the currents become equal to the current values stored in said current value storage section,

wherein the switching device is configured to switch the plurality of LEDs in response to a same signal, the same signal being the pulse signal,

wherein the plurality of LEDs includes a first LED configured to emit light of a first color and a second LED configured to emit light of a second color,

wherein the light emission luminance control section is configured to adjust the light emission luminance of the light emitted by the plurality of LEDs from a first luminance value to a second luminance value by controlling the switching device to adjust a same rate at which the plurality of LEDs switch on and off from a first same rate value to a second same rate value, the first luminance value having a corresponding first chromaticity and the second luminance value having a corresponding second chromaticity, and

wherein the current control section is configured to control chromaticity from the first luminance value to the second luminance value by providing current values to the first LED and the second LED that are different for at least one of the first chromaticity or the second chromaticity.

20. The backlight apparatus according to claim 19, wherein the current values of the currents to be supplied to the plurality of LEDs are first current values, wherein the plurality of LEDs are a first plurality of LEDs, and wherein:

the current value storage section is further configured to store second current values of currents to be supplied to a second plurality of LEDs in a second of the divisional regions, and

the backlight apparatus further comprises a current value determination section configured to determine the second current values by;

calculating coefficients relating light emission luminance of the second divisional region to the light emission luminance of the first divisional region,

determining the second current values such that a whiteness of light emitted by the second plurality of LEDs becomes equal to a predetermined value, and

adjusting the second current values based on the coefficients such that the light emission luminance of the light emitted by the second plurality of LEDs becomes equal to the light emission luminance of the light emitted by the first plurality of LEDs.

21. The backlight apparatus according to claim 19, wherein:

the switching device in the first divisional region comprises a switch for controlling the light emission luminance of the light emitted by the plurality of LEDs of the first divisional region, and

the pulse signal is supplied to the switch.

22. The backlight apparatus according to claim 19, wherein the switching device in the first divisional region comprises a plurality of switches.

23. The backlight apparatus according to claim 19, wherein the current control section is further configured to adjust the whiteness of the light emitted by the plurality of LEDs by adjusting values of the currents supplied to the plurality of LEDs while the plurality of LEDs switch on and off at the same rate.