Digital camera with analog and digital clamp circuit

Details Digital camera with analog and digital clamp circuit Digital camera with analog and digital clamp circuit

2000-09-14

2001-11-27

Garber, Wendy R. (Department: 2612)

Television

Camera, system and detail

Combined image signal generator and general image signal...

C348S243000

Reexamination Certificate

active

06323900

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to digital cameras, and more particularly to a digital camera adapted to process analogically and digitally an image signal from a CCD using a mosaic-type color filter or a stripe-type color filter, for example, so as to clamp a black level.
2. Description of the Prior Art
There is disclosed one example of a conventional digital video camera of this kind by Japanese Provisional Patent Publication (Kokai) H4-192677 [H04N 5/15, 5/92] laid open to public inspection dated Jul. 10, 1992. This prior art discloses that an analog video signal is analog-clamped and thereafter A/D-converted into a digital signal for being subjected to digital clamping, thereby providing effective utilization of a dynamic range during A/D conversion and keeping constant a quantization level as a tip level of a synchronization signal.
With such conventional techniques, however, there is a fear that noises superposed onto the analog video signal due to analog clamping might have an effect upon digital clamping. Nevertheless, the same publication does not disclose a solving method therefor at all.
SUMMARY OF THE INVENTION
Therefore, a principle object of the invention is to provide a digital camera capable of clamping a digital signal in an appropriate manner.
According to the invention, a digital camera comprises a CCD imager for outputting line signals, each of the line signals being clamped in an analog clamp area of the CCD imager by an analog clamp means and then converted into a digital signal, the digital signal being digital-clamped in a digital clamp area by a digital clamp means, the digital video camera characterized in that: the analog clamp area is set such that both horizontal ends of the analog clamp area are positioned at the outside of the digital clamp area.
The analog clamp means clamps each line signal outputted from the CCD imager in the analog clamp area, while the digital clamp means clamps the digital signal in the digital clamp area. Here, the analog clamp area is set such that the both horizontal ends thereof are positioned at the outside of the digital clamp area. That is, the analog clamp area is set such that it covers the digital clamp area at least with respect to a horizontal direction, or set at a different area from the digital clamp area. By doing so, even if there occurs noise at the both horizontal ends when each line signal is clamped by the analog clamp means, there is no possibility that the noise influences on the processing by the digital clamp means.
According to the present invention, the both horizontal ends of the analog clamp area are arranged so as to be positioned at the outside of the digital clamp area, so that it is possible to appropriately clamp the CCD output.
The above described object, other objects, features and advantages of this invention will be more apparent from the following description on examples with reference to the accompanying drawings.


REFERENCES:
patent: 4652927 (1987-03-01), Hashimoto
patent: 4740828 (1988-04-01), Kinoshita
patent: 4910599 (1990-03-01), Hashimoto
patent: 5448306 (1995-09-01), Koyama
patent: 5612739 (1997-03-01), Maki et al.
patent: 5642162 (1997-06-01), Maki et al.
patent: 5717457 (1998-02-01), Morimoto
patent: 5717459 (1998-02-01), Maki et al.
patent: 6157407 (2000-12-01), Kobayashi
patent: 62-67969 (1987-03-01), None
patent: 4-207475 (1992-07-01), None
patent: 4-192677 (1992-10-01), None

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