JP4958732B2 - Flicker correction device - Google Patents

Description

  The present invention relates to an image pickup apparatus using an image pickup element affected by flicker, for example, a flicker correction apparatus for correcting flicker in a camcorder.

  Fluorescent lamps that do not include an inverter or the like use a commercial power supply, and thus blink repeatedly at a period of 1/100 seconds in the case of 50 Hz in the Kanto region and 1/120 seconds in the case of 60 Hz in the Kansai region. Consider a case where a camcorder is photographed under such a light source.

  NTSC has 30 frames per second and 60 fields. When shooting is performed at this cycle, even if the accumulation time of the image sensor is constant, a bright field and a dark field are periodically generated as shown in FIGS. , It will be very difficult to see as a video. Such a phenomenon is called flicker.

Various techniques for correcting the flicker have been proposed. For example, there is a technique proposed in Patent Document 1.
JP 2002-152604 A

  In the flicker correction apparatus, when flicker detection is performed for flicker correction, if flicker is erroneously detected, flicker correction is performed on an image that does not need to be corrected.

  In the technique described in Patent Document 1, the shutter speed is fixed to 1/100 as a flicker correction method.

  Originally, AE requires an adjustment range of the shutter speed, but with this technique, it is fixed, so it can only be covered by other means such as an aperture and gain, and the degree of freedom of exposure control is reduced.

  In addition to these, various flicker correction techniques using gain and flicker correction techniques depending on the image sensor have been proposed. However, if these flicker correction techniques are mistakenly applied to normal images, the image quality may be deteriorated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a flicker correction apparatus that can reduce false detection of flicker and suppress the restriction of shutter speed and the deterioration of image quality due to false detection of flicker.

To achieve the above object, the flicker correction device of the present invention, there is provided a flicker correction device for correcting a flicker of the light source in the imaging apparatus, and flicker detection means, and flicker correction means, in the shooting mode, or unstable comprising a state determining means for determining whether a stable state, and control means for controlling said flicker detection means and the flicker correction means, said state determining means, at least one of the imaging control of AE and AF are performed During the determination, the control unit determines that the state is unstable. When the state determination unit determines that the state is unstable, the control unit does not detect the flicker in the flicker detection unit. When the stable state is determined, the flicker detection unit detects the flicker, and the flicker detection unit detects the flicker. And characterized in that said flicker correction means when you are done correcting the flicker.

  According to the flicker correction apparatus of the present invention, it is possible to reduce false detection of flicker, and to suppress shutter speed restriction and image quality deterioration due to false detection of flicker.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram of an imaging system of a camcorder (imaging device) on which a flicker correction device according to an embodiment of the present invention is mounted.

  In the figure, a camcorder 100 includes a lens 101, an aperture 102 for adjusting an exposure amount, a lens / aperture / shutter controller 103, an image sensor (solid-state image sensor) 104, a CDS / AGC / A / D 105, a TG 106, and a flicker detector. 107 and a flicker correction unit 108.

  The camcorder 100 also includes a signal processing unit 109, an image input / output control unit 110, a recording medium 111, an imaging switch 112, a gyro sensor 113, and a system control unit 114 that controls each of the above units (each unit). A panel / video output unit 115 is connected to the image input / output control unit 110.

  Next, the operation of the camcorder 100 configured as described above will be described.

  The light incident on the lens 101 is adjusted to an appropriate exposure by the lens / aperture / shutter controller 103 and is photoelectrically converted by the image sensor 104. The video signal photoelectrically converted by the image sensor 104 is subjected to noise removal, gain control, and A / D conversion by a CDS / AGC / A / D 105.

  Next, various kinds of image processing are performed by the signal processing unit 109. Next, the image input / output control unit 110 records an image on the recording medium 111. The recording medium 111 may be a DV tape, a DVD disk, a memory card, or the like. Also, the image output from the image input / output control unit 110 is converted into a signal suitable for a liquid crystal panel or video output by the panel / video output unit 115.

  The aperture 102 also has a role of a shutter that adjusts the exposure time during still image shooting. In the case of still image shooting, the aperture 102 is closed by closing the aperture 102 after the image sensor 104 starts accumulating charges. Will be determined.

  Although detailed control will be described later, the flicker detection timing is measured by the system control unit 114, the flicker detection unit 107 performs flicker detection, and the flicker correction unit 108 performs flicker correction.

(Flicker detection timing)
FIG. 2 is a state transition diagram when detecting flicker in the camcorder of FIG.

  When the camcorder 100 is turned on, a state in which no shooting is performed, such as a preparation period until shooting and an image browsing mode, are collectively referred to as a non-shooting mode 201.

  In the situation where shooting is possible and actual shooting recording is performed, and shooting recording is not performed, but recording is possible at any time, including situations where the captured image is displayed on the liquid crystal display device etc. in real time The shooting mode 204 is assumed.

  The shooting mode 204 includes an unstable state 202 and a stable state 203 described later. A state in which flicker detection is not performed is defined as an unstable state 202. A state where flicker detection is performed is a stable state 203. The resource 205 is an imaging control system and an external sensor system, and the resource 206 is a flicker detection system.

  When the power of the camcorder 100 is turned on, the non-photographing mode 201 is entered. Here, when preparations such as OS activation are completed, the mode transitions to the shooting mode 204. In the shooting mode 204, the state is initially shifted to the unstable state 202.

  In the unstable state 202, the imaging control system and external sensor system of the resource 205 are monitored. While imaging control is being performed, specifically, while AE, AWB, AF, ZOOM (zoom), etc. are operating, images are not stable, flicker detection is difficult, and false detection may occur. Flicker detection is not performed.

  Similarly, in the following state detected by the external sensor system, flicker detection is not performed because the image is not stable and flicker detection is difficult. Specifically, the following states are a state where the image is moving, a state where the camcorder is shaken by the gyro, and a state where the pan is panned.

  While the imaging control system and the external sensor system of the resource 205 are moving, the unstable state 202 is maintained. If the imaging control system and the external sensor system of the resource 205 do not operate for a certain period, the transition to the stable state 203 is made.

  In the stable state 203, flicker is detected with reference to information on the flicker detection system of the resource 206. A known method is used as the flicker detection method, and an example will be described later.

  At the same time, the imaging control system and the external sensor system of the resource 205 are monitored, and the instantaneous imaging control and the camcorder 100 shake are ignored, and the stable state 203 is maintained.

  However, if imaging control is performed for a certain period of time or if the camcorder 100 moves, the state transitions from the stable state 203 to the unstable state 2102.

(Flicker detection method)
A known method is used for flicker detection. An example is shown below.

  FIG. 3 is a diagram illustrating an example of flicker.

  The sine wave in the graph represents a state in which the fluorescent lamp is lit with a commercial power supply of 50 Hz. Fluorescent lamps are lit at both AC + and-, and as a result, are lit 100 times per second.

  The NTSC-compatible camcorder 100 has 60 fields per second, the accumulation time of the image sensor 104 is also 1/60 seconds, the sine wave peak is assumed to be 1, and 1 period 1/50 seconds is 2π. The accumulation amount of the image sensor 104 is as shown in FIG.

  In this way, a bright field and a dark field are repeated at a cycle of 20 Hz by recording a light source of 100 Hz (light source of alternating current + -100 times) and 60 fields.

  In order to detect this, the integrated value of the screen brightness is stored around the past 10 frames, the sum of the 20 Hz bandpass filter is stored for 3 fields, and the difference between the integrated values of these 3 fields is constant. If it is above, it is determined that flicker has occurred.

(Flicker correction method)
A known method is also used for flicker correction. An example is shown below.

  FIG. 5 is a diagram illustrating an example of flicker correction.

  Similar to FIG. 3, the sine wave represents the lighting of the fluorescent lamp. Here, if the shutter speed of each field is set to 1/100 second, the accumulation amount becomes the same in every field as shown in FIG.

  By doing this, flicker can be corrected. However, since the shutter speed is limited to 1/100 second, only an aperture and a gain can be used for automatic exposure, and exposure control can be limited.

  In the embodiment of the present invention, the system control unit 114 functions as a state determination unit that determines that the unstable state 202 has transitioned to the stable state 203 in the photographing mode.

  Further, the system control unit 114 causes the flicker detection unit 107 to detect flicker and also causes the flicker correction unit 108 to detect flicker when the state determination unit determines that the state has changed from the unstable state 202 to the stable state 203. It functions as a control means for performing correction.

  In addition, the system control unit 114 functions as a first information acquisition unit that acquires information from the imaging control system of the resource 205 and a second information acquisition unit that acquires information from the external sensor system.

  Then, based on the information from the first and second information acquisition means, the state determination means determines that the state has transitioned from the unstable state 202 to the stable state 203.

  The image sensor 104 is an element that can be stored and read almost simultaneously in frame units or field units including the CCD, and the flicker detection means is based on the integrated value of luminance of the captured image and the past integrated value in frame or field units. Perform flicker detection.

  The flicker correction unit performs flicker correction by setting the shutter speed for imaging to an integral multiple of 1/100 second.

  The image sensor 104 is an element that can store and read in units of lines including CMOS, and the flicker detection means detects flicker from the integrated value of luminance of the captured image and the past integrated value in units of line. The flicker correction means controls the gain for each line and performs flicker correction.

  Note that flicker may occur even with a light source other than a fluorescent lamp (such as an LED light source), and the present invention is applicable to a light source other than a fluorescent lamp.

1 is a block diagram of an imaging system of a camcorder on which a flicker correction apparatus according to an embodiment of the present invention is mounted. FIG. 2 is a state transition diagram when flicker is detected in the camcorder of FIG. 1. It is a figure which shows an example of a flicker. It is a figure which shows the integrated value of the flicker of FIG. It is a figure which shows an example of flicker correction. It is a figure which shows the integrated value of the flicker correction | amendment of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Camcorder 104 Image pick-up element 107 Flicker detection part 108 Flicker correction part 113 Gyro sensor 114 System control part 202 Unstable state 203 Stable state 204 Shooting mode 205,206 Resource

Claims (6)

A flicker correction device for correcting a flicker of the light source in the imaging apparatus,
Flicker detection means;
Flicker correction means;
In shooting mode, thereby determining whether an unstable state or a stable state,
Control means for controlling the flicker detection means and the flicker correction means,
The state determination means determines that the unstable state while at least one of the imaging control of AE and AF is being performed,
The control means does not detect the flicker in the flicker detection means when the state determination means determines the unstable state, and the flicker when the state determination means determines the stable state. A flicker correction apparatus characterized by causing the detection means to detect the flicker and causing the flicker correction means to correct the flicker when the flicker is detected by the flicker detection means . The control means does not detect the flicker in the flicker detection means when the state determination means determines the unstable state, and the state determination means makes a transition from the unstable state to the stable state. The flicker correction apparatus according to claim 1, wherein the flicker detection unit causes the flicker detection unit to detect the flicker. The solid-state imaging device mounted on the imaging device is an element capable of accumulating and reading almost simultaneously in units of frames or fields including a CCD, and the flicker detection means is a luminance of captured images in units of frames or fields. flicker correction device according to claim 1 or 2 integral value of the past of the integrated value and performs detection of the flicker. The flicker correction means, flicker correction device according to claim 3, characterized in that said by an integral multiple of 1/100 second shutter speed for imaging of the imaging apparatus corrects the flicker. The solid-state imaging device mounted on the imaging apparatus is an element that can store and read in units of lines including CMOS, and the flicker detection unit includes an integrated value of luminance and past integrated values of captured images in units of lines. flicker correction device according to claim 1 or 2, characterized in that the flicker detected. The flicker correction means, the solids to control the gain for each line of the image pickup device, the flicker correction device according to claim 5, characterized in that the correction of the flickers.

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