Television – Camera – system and detail – Combined image signal generator and general image signal...
Patent
1997-05-19
2000-06-06
Garber, Wendy
Television
Camera, system and detail
Combined image signal generator and general image signal...
348250, H04N 964
Patent
active
060725273
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a dark shading correction circuit for use in a television camera or a video camera, the circuit intended for canceling a dark shading signal component contained in a video signal outputted from a charge coupled device (referred to as a CCD hereinafter) which is a solid-state image pickup device, thereby effecting a dark shading correction on the video signal.
BACKGROUND ART
Even in a state in which no incident light is incident on a CCD of a television camera or a video camera, or in a state in which the lens aperture is completely stopped down, it is sometimes the case where a video signal generated as if a faint light were incident on the video signal is outputted. This signal component that is unnecessary in itself is generated mainly due to a dark current of a driving circuit and the like provided inside the CCD, and it is so called the dark shading signal component. As a circuit for executing the dark shading correction by removing this dark shading signal component, there has been provided a dark shading correction circuit.
FIG. 5 is a block diagram showing a construction of a television camera provided with a prior art dark shading correction circuit 500, and the television camera provided with the dark shading correction circuit will be described with reference to the accompanying drawings.
In FIG. 5, a CCD 1, which is a solid-state image pickup device, converts pickup light that is incident via a taking lens (not shown) of the television camera into an electric signal in synchronization with a vertical synchronizing signal VD and a horizontal synchronizing signal HD, and outputs the signal to a preamplifier 2. The preamplifier 2 takes out, for example, RGB video signals of three colors R (Red), G (Green) and B (Blue) in the case of a three-plate type camera by sampling the electric signal outputted from the CCD 1 at a predetermined sampling frequency in synchronization with the vertical synchronizing signal VD and the horizontal synchronizing signal HD and thereafter amplifies the signal to output the video signal after the amplification to an adder 5. In the following signal processing, the signals are processed individually by the three colors R, G and B.
The dark shading correction circuit 500 comprises a sawtooth wave signal generator 3, an amplitude adjuster 4 and the adder 5. The sawtooth wave signal generator 3 is reset in response to the vertical synchronizing signal VD to generate a sawtooth wave signal having the opposite polarity in order to cancel the above-mentioned dark shading signal component, and output the signal to the amplitude adjuster 4. The amplitude adjuster 4 comprises, for example, a pre-set resistor element. By manually changing the resistance value of the pre-set resistor element, the amplitude of the inputted sawtooth wave signal is adjusted, and the sawtooth wave signal after the amplitude adjustment is outputted as a correction sawtooth wave signal. The adder 5 adds the video signal inputted from the preamplifier 2 to the correction sawtooth wave signal inputted from the amplitude adjuster 4 thereby cancelling the dark shading signal component, and outputs the video signal after the correction to a video signal processing circuit 13. The video signal processing circuit 13 executes a gamma processing and a matrix signal processing for conversion of the signal into, for example, an NTSC signal, and outputs the processed video signal to a magnetic recording and reproducing apparatus 14 for recording the signal on, for example, a magnetic tape.
When adjusting the pre-set resistor element of the amplitude adjuster 4, an operator performs adjustments by rotating an adjustment portion of the pre-set resistor element using a screwdriver so that the signal component of the video signal becomes substantially zero while monitoring the video signal outputted from the adder 5 by means of, for example, a CRT display monitor with the lens aperture of the television camera stopped down completely, i.e., so that the dark shading si
REFERENCES:
patent: 5105276 (1992-04-01), Schrock
patent: 5272536 (1993-12-01), Sudo et al.
patent: 5376966 (1994-12-01), Takase
patent: 5512947 (1996-04-01), Sawachi et al.
patent: 5757440 (1998-05-01), Mangelsdorf
Garber Wendy
Matsushita Electric - Industrial Co., Ltd.
Wilson Jacqueline
LandOfFree
Dark shading correction circuit does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Dark shading correction circuit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dark shading correction circuit will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2217920