Facsimile and static presentation processing – Facsimile – Recording apparatus
Patent
1986-08-25
1987-12-01
Rubinson, Gene Z.
Facsimile and static presentation processing
Facsimile
Recording apparatus
35821329, 35821327, H04N 514
Patent
active
047108177
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a solid state image sensor and more particularly to a solid state image sensor of the type in which an electrical signal obtained by photoelectric conversion is directly converted into a digital signal, so that light information obtained from all picture elements is derived as digital signal.
BACKGROUND ART
It is well known that degradation of S/N ratio can be reduced largely by transmitting and processing various signals in the form of digital signal. From this point of view, even in the case of an image sensor, attempts have been made to convert a video signal into a digital signal in a stage as early as possible so that various processings of digital signals are carried out in the succeeding stages.
In a prior art image sensor, however, even in a case that a signal obtained by photoelectric conversion is converted into a digital signal in an earlier stage, various analog information obtained from picture elements of a solid stage image sensor element is once derived from the elements as time sequential analog information, and then the analog information is converted into a digital signal through an analog-to-digital (A/D) converter. That is, as shown in FIG. 1A, an analog signal derived from an image pickup tube 2A is applied through a buffer amplifier 4A to an A/D converter 6A to obtain a digital signal. Alternatively, as shown in FIG. 1B, a signal derived from a solid state image sensor element 2B is applied through a buffer amplifier 4B to an A/D converter 6B to obtain a digital signal.
Video signals are processed in various manners, so that the processing as shown in FIG. 1A or 1B in which the video signal is processed after the signal is converted into the digital signal has a merit, but with the processing as shown in FIG. 1A or 1B, the processing of an analog signal in an image pickup element prior to the A/D conversion is carried out in a conventional manner and the problems there are left unsolved. As a result, there is a disadvantage that a high quality image cannot be picked up, since an S/N ratio cannot be improved to a satisfactory degree due to superposition of various noise.
DISCLOSURE OF THE INVENTION
In view of the above, one of the objects of the present invention is to provide a solid state image sensor in which an electrical signal obtained by photoelectric conversion at each picture element is directly derived in the form of a digital signal and then the digital signal is directly served for processing.
In order to acheive the above object, a solid state image sensor comprises:
a plurality of light receiving means arranged in the form of at least one dimension and each for delivering a pulse signal representative of the number of photons incident to each light receiving means;
a plurality of counting and holding means, each connected to a corresponding one of the light receiving means and for counting the pulse signals and for holding a count value as a video output;
means for resetting the count value of each of the plurality of counting and holding means to its initial state at a predetermined interval; and
scanning means for sequentially reading out the count value from each of the counting and holding means.
Here, the solid state image sensor may comprise means for correcting the count value in accordance with a peak value or a time duration of the pulse signal, when photons are incident to the light receiving means simultaneously or within a short period of time.
Pulse signal correction means may be disposed between the light receiving means and the counting and holding means and for correcting the pulse signal from the light receiving means to a signal having a pulse width which is suitable for the counting by the counting and holding means.
Each of the plurality of light receiving means may include an avalanche photodiode or a micro-channel plate.
The plurality of light receiving means may be arranged in the form of two-dimension so that two-dimensional video information is obtained from the plurality of light receiving
REFERENCES:
patent: 4592029 (1986-05-01), Altmann
patent: 4638354 (1987-01-01), Denimal
patent: 4639781 (1987-01-01), Rucci
Barber, S., "Photon Counting with Avalanche Photodiodes", Electronic Engineering, May 1984, pp. 63-70.
Kamiya, T., "Possibility of Optical Devices", Approach to Optical Computers, IV-4, pp. 90-94, Mar. 1983.
Nippon Hoso Kyokai
Rubinson Gene Z.
Schroeder L. C.
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