LIGHTING APPARATUS AND CONTROL METHOD THEREOF

• US 20130265348A1
• Filed: 03/14/2013
• Published: 10/10/2013
• Est. Priority Date: 04/06/2012
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Onogi, Makoto
• Granted Patent: US 9,123,281 B2
• Time in Patent Office: Days
• US Class Current: 345/691
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• 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
• CPC Class Codes: G09G 5/10 Intensity circuits
• CPC Class Codes: Y02B 20/40 Control techniques providing energy savings, e.g. smart controller or presence detection

Abstract

A lighting apparatus for an image display apparatus is provided with: a plurality of light sources corresponding to a plurality of areas of a screen; and a control unit configured to control a duty ratio of a turn-on period and a turn-off period of each light source according to an image signal to be inputted, by carrying out pulse width modulation control on the turn-on periods of time and the turn-off periods of time of the plurality of light sources. In cases where the duty ratio of each light source is controlled according to the image signal to be inputted, the control unit regulates turn-on start timing of each light source in such a manner that a variation in the number of light sources which are turned on at the same time to be suppressed.

Claims

1. A lighting apparatus for an image display apparatus comprising:

a plurality of light sources corresponding to a plurality of areas of a screen; and

a control unit configured to control a duty ratio of a turn-on period and a turn-off period of each light source by carrying out pulse width modulation control on the turn-on periods and the turn-off periods of said plurality of light sources according to an image signal to be inputted;

wherein in cases where the duty ratio of each light source is controlled according to the image signal to be inputted, said control unit adjusts turn-on start timing of each light source in such a manner that a variation in the number of light sources which are turned on at the same time to be suppressed.

2. The lighting apparatus as set forth in claim 1, wherein

said control unit groups said plurality of light sources in such a manner that light sources with their duty ratios being mutually equal to one another or with a difference between their duty ratios being within a threshold value belong to a same group, and adjusts the turn-on start timing of each light source in such a manner that the turn-on start timings of the light sources belonging to the same group are apart from one another.

3. The lighting apparatus as set forth in claim 2, wherein

said control unit adjusts the turn-on start timings of the individual light sources by assigning a plurality of turn-on start timings set in advance to the individual light sources, respectively, and assigns the turn-on start timings preferentially from a group of light sources with large duty ratios in such a manner that the turn-on start timings of the light sources belonging to the same group are apart from one another.

4. The lighting apparatus as set forth in claim 1, wherein

in cases where there is a certain light source in which at least a part of a turn-on period for which a turn-on start timing has been adjusted, and at least a part of a one previous turn-on period preceding said turn-on period overlap with each other because of adjustment of the turn-on start timing of each light source, said control unit replaces the turn-on start timing of said certain light source with a turn-on start timing of a light source in which its duty ratio is equal to that of said certain light source or in which a difference between its duty ratio and the duty ratio of said certain light source is within a threshold value.

5. The lighting apparatus as set forth in claim 1, wherein

said control unit controls the duty ratio of each light source according to an amount of brightness characteristic of an image corresponding to each area of said screen.

6. A control method of a lighting apparatus for an image display apparatus which is provided with a plurality of light sources corresponding to a plurality of areas of a screen, said method comprising:

a step of inputting an image signal; and

a control step of controlling a duty ratio of a turn-on period and a turn-off period of each light source by carrying out pulse width modulation control on the turn-on periods and the turn-off periods of said plurality of light sources according to an image signal inputted;

wherein in said control step, in cases where the duty ratio of each light source is controlled according to the image signal inputted, turn-on start timing of each light source is adjusted in such a manner that a variation in the number of light sources which are turned on at the same time to be suppressed.

7. The control method of a lighting apparatus as set forth in claim 6, wherein

in said control step, said plurality of light sources are grouped in such a manner that light sources with their duty ratios being mutually equal to one another or with a difference between their duty ratios being within a threshold value belong to a same group, and turn-on start timing of each light source is adjusted in such a manner that the turn-on start timings of the light sources belonging to the same group are apart from one another.

8. The control method of a lighting apparatus as set forth in claim 7, wherein

in said control step, the turn-on start timings of the individual light sources are adjusted by assigning a plurality of turn-on start timings set in advance to the individual light sources, respectively, and the turn-on start timings are assigned preferentially from a group of light sources with large duty ratios in such a manner that the turn-on start timings of the light sources belonging to the same group are apart from one another.

9. The control method of a lighting apparatus as set forth in claim 6, wherein

in said control step, in cases where there is a certain light source in which at least a part of a turn-on period for which a turn-on start timing has been adjusted, and at least a part of a one previous turn-on period preceding said turn-on period overlap with each other because of adjustment of the turn-on start timing of each light source, the turn-on start timing of said certain light source is replaced with a turn-on start timing of a light source in which its duty ratio is equal to that of said certain light source or in which a difference between its duty ratio and the duty ratio of said certain light source is within a threshold value.

10. The control method of a lighting apparatus as set forth in claim 6, wherein

in said control step, the duty ratio of each light source is controlled according to an amount of brightness characteristic of an image corresponding to each area of said screen.