Digital camera

• US 20060221192A1
• Filed: 10/25/2005
• Published: 10/05/2006
• Est. Priority Date: 03/31/2005
• Status: Active Grant

• Current Assignee: Monument Peak Ventures, LLC (Dominion Harbor Enterprises, LLC)
• Original Assignee: Eastman Kodak Company
• Inventors: Nakajima, Kenichi, Sakurai, Junzou
• Granted Patent: US 7,636,109 B2
• Time in Patent Office: Days
• US Class Current: 348/207.990
• CPC Class Codes: H04N 23/71 Circuitry for evaluating the brightness variation
• CPC Class Codes: H04N 23/745 Detection of flicker frequency or suppression of flicker wherein the flicker is caused by illumination, e.g. due to fluorescent tube illumination or pulsed LED illumination
• CPC Class Codes: H04N 23/88 for colour balance, e.g. white-balance circuits or colour temperature control

Abstract

A digital camera capable of accurately detecting flicker even while a video image is displayed on a display device is provided. In a digital camera, a video image is displayed on a display device ₄₀ serving as a viewfinder for photographing based on a display video signal supplied from a CMOS image sensor ₁₂₀ while image data based on a recording video signal supplied from the CMOS image sensor ₁₂₀ is recorded in a recording unit _50. The digital camera detects flicker based on a video signal supplied from a group of pixel circuits which do not supply the display video signal among the group of pixel circuits forming the CMOS image sensor 120.

Claims

1. A digital camera including an XY addressing image sensor having a first group of pixel circuits and a second group of pixel circuits, for displaying on a display device a video image based on a display video signal output from the first group of pixel circuits, and recording in a recording device image data based on a recording video signal output from the first and second groups of pixel circuits, comprising:

a flicker detection circuit for detecting flicker of a light source illuminating an object based on a flicker detection video signal output from the second group of pixel circuits while the first group of pixel circuits output the display video signal;

wherein

a first vertical synchronization signal utilized when the first group of pixel circuits output the display video signal and a second vertical synchronization signal utilized when the second group of pixel circuits output the flicker detection video signal are mutually asynchronous, and a cycle of the second vertical synchronization signal is determined in accordance with a cycle of fluctuation in luminance level of a light source assumed as the light source of the object.

2. A digital camera according to claim 1, wherein the XY addressing image sensor includes

a first vertical scanning circuit for controlling output of a video signal from the first group of pixel circuits,

a second vertical scanning circuit for controlling output of a video signal from the second group of pixel circuits, and

a horizontal scanning circuit for outputting the video signals output from the first and second vertical scanning circuits from different output terminals.

3. A digital camera according to claim 2, wherein

the cycle of the second vertical synchronization signal is determined individually for a light source having a different cycle of fluctuation in luminance level, and

the second vertical scanning circuit controls output of the video signal from the second group of pixel circuits by successively switching the cycle of the second vertical synchronization signal in accordance with the determined cycle.

4. A digital camera according to claim 2, wherein

the cycle of the second vertical synchronization signal is determined individually for a light source having a different cycle of fluctuation in luminance level,

the second vertical scanning circuit controls so that, for each determined second vertical synchronization signal, the pixel circuits individually outputs the video signal in the determined cycle,

the horizontal scanning circuit has output terminals each provided corresponding to each determined second vertical synchronization signal, and outputs the video signal output through the second vertical scanning circuit from the output terminals each provided corresponding to each second vertical synchronization signal.

5. A digital camera according to claim 1, wherein:

a display exposure period for the display video signal output from the first group of pixel circuits and a flicker detection exposure period for the flicker detection video signal output from the second group of pixel circuits are different from each other, and the flicker detection exposure period is a period determined in accordance with the cycle of fluctuation in luminance level of the light source assumed as the light source of the object.

6. A digital camera according to claim 1, wherein:

a display gain for the display video signal output from the first group of pixel circuits and a flicker detection gain for the flicker detection video signal output from the second group of pixel circuits are different from each other, and the flicker detection gain exceeds the display gain.

7. A digital camera according to claim 1, further comprising

a light source estimation circuit for estimating the light source illuminating the object by checking which of a plurality of light source regions predefined on a color difference plane includes a color difference component of the video signal, and

an adjustment circuit for adjusting white balance of each video signal output from the first and second groups of pixel circuits in accordance with the estimated light source, wherein

the light source estimation circuit changes the light source region based on a result of flicker detection performed by the flicker detection circuit.