Television – Camera – system and detail – With single image scanning device supplying plural color...
Reexamination Certificate
2000-05-12
2004-10-26
Garber, Wendy R. (Department: 2612)
Television
Camera, system and detail
With single image scanning device supplying plural color...
C348S280000, C348S312000, C250S208100
Reexamination Certificate
active
06809764
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a solid-state electronic image sensing device with high subsampling efficiency and a method of reading a video signal out of the same. More particularly, the present invention relates to a solid-state electronic image sensing device of the type including a plurality of photosensitive cells arranged in a row and a column direction, vertical transfer paths adjoining the photosensitive cells in the row direction and in which vertical transfer electrodes are formed, and transfer gates for transferring signal charges accumulated in the photosensitive cells to the vertical transfer paths, and a method of reading a video signal out of the same.
2. Description of the Background Art
In a digital still camera, for example, including a CCD (Charge Coupled Device) image sensor or similar solid-state electronic image sensing device, image data with high quality should only be produced for being recorded in a recording medium. When the digital still camera is operated in an AE (Automatic Exposure) or an AF (Automatic Focus) photometry mode or in a shoot mode, it is not necessary to display a subject to be picked up on a monitor in the form of high quality image data.
So long as the image sensing device has a relatively small number of pixels, e.g., about 640×480 pixels, it may be driven by a conventional drive system without regard to the operation mode of the camera, i.e., the AE or AF photometry mode, the shoot mode or a mode for recording of a video signal representative of a subject in a recording medium. Today, the digital still camera with the image sensing device implements image quality comparable with one achievable with a silver halide photosensitive type of film. The number of pixels of such a camera is further increasing to meet an increasing demand for higher image quality.
The increasing number of pixels of a solid-state image sensing device, however, brings about a problem that when the device is driven by the same system at all times, signal processing for AE, AF and display of an image on a monitor cannot be rapidly completed within a preselected period of time. This prevents image data representative of a subject to be rapidly recorded in a recording medium, so that the operator of the camera is apt to miss a chance to release the shutter.
To cope with the increasing number of pixels, Japanese Patent Publication No. 6148/1985 discloses a high resolution, reliable image pickup system needing no additional optics and therefore obviating the deterioration of dimensional specification and yield at the production stage (Prior Art Document 1 hereinafter). The image pickup system of Prior Art Document 1 includes a four-phase drive, frame transfer type solid-state image sensing device. Specifically, a potential well is formed beneath a particular electrode in each field so as to pick up an object and read an image signal representative of the subject. As a result, a four field, one frame image is formed. At the same time, the duration of signal storage is controlled in accordance with a difference between the valid areas of transfer electrodes.
Japanese Patent No. 2660592 proposes a high-definition still camera with a monitoring capability that allows the operator to set a view angle while watching a subject and release the shutter of the camera at any desired time (Prior Art Document 2 hereinafter). The camera is therefore capable of dealing with a still picture in the same manner as a moving picture, e.g., a moving picture recorded by a Video Cassette Recorder).
Japanese Patent No. 2660594, like Prior Art Document 2, discloses an electronic still camera capable of reading out a signal on a four-field basis (Prior Art Document 3 hereinafter). The camera of Prior Art Document 3 executes, after exposure, read-out of stored needless signal charges during a single field scanning period and then reads out pixel signals by field scanning so as to obviate smear components. Further, after reading out the needless charges, the camera resumes scanning a field not shifted and sequentially reads out pixel signals field by field. This is successful to uniform the influence of dark current on the field-by-field pixel signals. Consequently, there can be obviated flicker ascribable to, e.g., irregularity in field-by-field luminance at the time of reproduction.
Further, Japanese Patent No. 2721603 teaches a solid-state image sensing device and a method of driving it (Prior Art Document 4 hereinafter). Generally, when a solid-state image sensing device and a monitor for displaying a scene being picked up are noticeably different in vertical resolution, vertical flicker, for example, appears on the monitor and degrades motion resolution while extending a processing time. The loss of power is another problem to arise in such a situation. The image sensor disclosed in Prior Art Document 4 reads, at the time of monitoring, charges out of only two kinds of photoelectric transduction elements alternately and reads a single frame over a 2V period so as to enhance motion resolution and obviate vertical jitter. At the time of reproduction, the device of Prior Art document 4 reads charges out of only one kind of photoelectric transduction elements and sets up the same saturation charge as in a still picture shoot mode, thereby making it needless to boost a drive voltage. This solves the power loss problem.
As stated above, a procedure for reading signal charges out of a solid-state electronic image sensing device has recently been devised in various ways in order to subsample or otherwise deal with signal charges in a manner matching with AE, AF or monitoring of a subject.
The system disclosed in Prior Art Document 1, however, has the following problems left unsolved because it effects four-phase drive at all times. Specifically, when color filters are arranged in a so-called Bayer pattern for color image pickup, the four-phase drive fails to cause all of three primary colors R (red), G (green) and B (blue) to appear in a single field. Subsampling effected in this condition would prevent a color image from being adequately displayed. In addition, the drive system is limited to four-phase drive, as mentioned above.
The devices of Prior Art Documents 2 and 3 each read out signal charges out of a great number of pixels in four consecutive fields constituting a single frame. To monitor a scene to pick up, use is made of one-half of the resulting image data, i.e., two fields of image data. However, neither Prior Art Document 2 nor 3 is practicable without resorting to a period of time corresponding to four fields in actually reading out the image data for monitoring. More specifically, during AE or AF photometry requiring rapid processing , the same period of time as during usual read-out is necessary. Prior Art Documents 2 and 3 therefore make no contribution to rapid processing.
The device of Prior Art Document 4 executes subsampling by reading out signal charges of two fields and discarding signal charges of the other two fields. The maximum degree of sampling available with Prior Art 4 is therefore one-fourth, limiting the signal reading rate.
As stated above, while various schemes have been proposed to subsample a video signal to be output from a solid-state image sensing device for realizing rapid signal processing, it is difficult to increase the degree of subsampling therewith.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a solid-state electronic image sensing device capable of increasing the degree of subsampling more than the conventional devices, and a method of reading a video signal thereoutof.
In accordance with the present invention, a solid-state electronic image sensing device includes a plurality of photosensitive cells arranged in a row direction and a column direction. Vertical transfer paths adjoin the photosensitive cells arranged in the row direction and having vertical transfer electrodes formed thereon. Transfer gates each intervene between one photosens
Misawa Takeshi
Oda Kazuya
Birch & Stewart Kolasch & Birch, LLP
Garber Wendy R.
Villecco John M
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