Television – Camera – system and detail – Still and motion modes of operation
Reexamination Certificate
1996-06-24
2003-02-11
Moe, Aung S. (Department: 2612)
Television
Camera, system and detail
Still and motion modes of operation
C348S322000, C348S323000
Reexamination Certificate
active
06519000
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image pickup apparatus equipped with an image sensing device such as a CCD (charge coupled device) with an interline structure, having the capability of individually reading all pixels.
2. Description of the Related Art
A CCD image sensor of the interline type is widely used as an image sensing device in a video camera. This type of CCD is composed of: an array of photoelectric conversion elements (pixels) for generating an electric charge in response to incident light; vertical transfer blocks (VCCDs) for reading the charges accumulated in the respective pixels and transferring the charges in a vertical direction; and a horizontal transfer block (HCCD) for transferring in a horizontal direction the charges received from the vertical transfer blocks.
FIG. 14
is a layout of pixels
101
and a vertical transfer block
102
disposed on a CCD chip of the interline type. As shown in
FIG. 14
, the vertical transfer block
102
includes a plurality of transfer gate electrodes
103
wherein two transfer gate electrodes
103
are disposed at a position corresponding to each pixel
101
. One of the two transfer gate electrodes
103
is formed at a position more closely adjacent to the corresponding pixel
101
. When a charge transfer pulse is applied to the transfer gate electrodes
103
, a charge is transferred into the vertical transfer block
102
via the transfer gate electrode
103
closer to the pixel
101
.
The conventional interline-type CCD is designed for use in a video camera for taking a moving picture. For that purpose, an image signal is output basically according to the field-reading scheme in which all pixels
101
are read during each field period and the charges read from two pixels located at adjacent positions along the vertical direction are added together before being output. The combination of pixels to be added together is varied in an interlaced fashion between even-numbered fields and odd-numbered fields. That is, in even-numbered fields, the upper two pixels of the four pixels
101
shown in
FIG. 14
are added together and the lower two pixels are also added together wherein the addition is performed in the vertical transfer block
102
. In odd-numbered fields, on the other hand, the two pixels in the middle of the four pixels
101
shown in
FIG. 14
are added together. However, the vertical resolution of this type of CCD is one-half that of a CCD of the frame-reading type in which pixel charges are directly output without being added. Thus, the conventional interline-type CCD cannot provide a high resolution required to take a still picture.
To solve the above problem, an interline-type CCD having the capability of individually reading all pixels
101
each field period and producing one frame of image signal from non-added pixel values within one field period has been proposed.
FIG. 13
is a layout of pixels
101
and a vertical transfer block
102
disposed on a CCD chip. In this CCD, as shown in
FIG. 13
, transfer gate electrodes
103
are disposed in a vertical transfer block
102
so that three transfer gate electrodes are located at a position corresponding to each pixel. This arrangement makes it possible to read full frame data during one field period without a reduction in the vertical resolution due to the addition of charges performed in the vertical transfer block
102
.
However, if a CCD of the type shown in
FIG. 13
is employed in an image pickup apparatus, although it becomes possible to separately read charges from all pixels
101
during one field period, the three-transfer-gate structure of the vertical transfer block
102
makes it impossible to add two pixels along the vertical direction which is possible in the case of the CCD shown in FIG.
14
. This means that, in the image pickup apparatus with the CCD having the full frame reading capability, such as that shown in
FIG. 13
, it is impossible to directly obtain a field signal of a moving picture.
Therefore, in the image pickup apparatus of the above-described type, after reading a frame signal from the CCD, it is required to add pixel values along the vertical direction for all pixel values so that a field signal of a moving picture can be produced from the frame signal.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an image pickup apparatus equipped with an interline-type image-sensing device, having the capability of individually reading all pixels thereby directly obtaining a field signal of a moving picture.
According to an aspect of the present invention, there is provided an image pickup apparatus, equipped with an interline-type image-sensing device, the image-sensing device including: a plurality of photoelectric conversion elements; a vertical transfer block for transferring the charges received from the photoelectric conversion elements along one direction, the vertical transfer block including transfer electrodes disposed in such a manner that at least three transfer electrodes are disposed for each photoelectric conversion element; and a horizontal transfer block for transferring the charges received from the vertical transfer block along a direction crossing the above-described one direction; wherein the charges read from the photoelectric conversion elements on a plurality of lines located at adjacent positions along the above-described one direction of the image-sensing device are successively transferred through the vertical transfer block so that the charges read from the photoelectric conversion elements on the plurality of lines located at adjacent positions along the above-described one direction of the image-sensing device are added together in the horizontal transfer block thereby outputting the added pixel signal.
According to another aspect of the present invention, the image pickup apparatus further includes mode switching means for switching the driving mode of the image-sensing device, the mode switching means being adapted to switch the driving mode so that the image-sensing device is driven either in a still picture mode or in a moving picture mode, wherein in the still picture mode one frame data is output during one field period, the frame data being produced on the basis of the charges read from the photoelectric conversion elements in which no addition is performed between the charges read from two photoelectric conversion elements located at adjacent positions along the above-described one direction, while in the moving picture mode, field data is output, the field data being produced on the basis of the charges read from the photoelectric conversion elements in which the charges read from two photoelectric conversion elements located at adjacent positions along the above-described one direction are added together.
According to still another aspect of the invention, the above-described moving picture mode comprises at least either:
a normal moving picture mode in which the addition operation of adding the charges read from two photoelectric conversion elements located at adjacent positions along the above-described one direction is performed once during each horizontal blanking period thereby outputting one field data during one field period; or
a high-speed moving picture mode in which the addition operation of adding the charges read from two photoelectric conversion elements located at adjacent positions along the above-described one direction is performed twice during each horizontal blanking period thereby outputting one field data during a half field period.
According to a further aspect of the invention, in the moving picture mode, the addition of the charge between two photoelectric conversion elements is performed in such a manner that the combination of two photoelectric conversion elements is interlaced between odd-numbered fields and even-numbered fields.
According to another aspect of the invention, the driving pulse for driving the horizontal transfer block has an amplitude corresponding to the number of photoe
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Moe Aung S.
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