Television – Camera – system and detail – Solid-state image sensor
Patent
1992-06-01
1994-11-15
Mancuso, Joseph
Television
Camera, system and detail
Solid-state image sensor
348312, H04N 314
Patent
active
053652703
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and a device for throughput compression for a videophone camera provided with a charge-transfer photosensitive array. It also relates to a corresponding image transmission system.
2. Discussion of the Background
In order to reduce the throughput of information transmitted by the cameras of moving-picture transmission systems, it is known to store the images in buffer memories, thus making it possible to dispense with the interlacing of lines so as to retain on transmission only one image out of two, or to reduce the number of images transmitted per second in the ratios 1/4 or 1/6, or else to code the images to be transmitted with codes of diverse types, with variable lengths for example. However, these techniques lead to expensive embodiments which cannot easily be carried over to videophone cameras whose cost price must reflect the average quality demanded of this type of equipment.
SUMMARY OF THE INVENTION
The aim of the invention is to alleviate the abovementioned disadvantages.
To this effect, the subject of the invention is a method of throughput compression for a videophone camera comprising an array of charge-transfer photosensitive cells as an image sensor, characterized in that it consists: interlaced even and odd lines of cells supplied by each cell of an even line into the first storage cells respectively interval T.sub.1 the electric charges contained in the first storage cells M.sub.1 into second storage cells respectively charges stored in the second cells to the electric charges supplied by each counterpart cell of an odd line the camera the duty cycles of the intervals T.sub.1, T.sub.2 and T.sub.3 relative to the scan period for the lines of the array of photosensitive cells in the inverse ratio of the timing speeds.
The subject of the invention is also a device for implementing the abovementioned method and an application of the method and of the device to the production of a system for image transmission by videophone.
The invention has the advantage of being applicable equally well to structured arrays in order to effect interline transfers as to structured arrays in order to effect interframe transfers.
It also has the other advantages of making it possible to effect a spatial filtering on the points of the image by pairwise compounding of the information contained in the lines of the charge-transfer photosensitive array and a time filtering by reducing the number of images analyzed per unit time, making it possible, for example, to go from images containing 50 frames per second under the CCIR standard to images scrolling at rates of 50; 25; 16.7; 12.5; 10 or 8.3 images per second for example. It also makes it possible to effect a space time filtering on objects or persons in motion, because the sampling effected on the points of the charge-transfer photosensitive array can be effected at a slow rate, thus making it possible to better reveal the low-frequency components of the motion. Moreover, the reduction in the timing of the control signals applied to the charge-transfer photosensitive array has the effect of increasing the integration time of the charge-transfer cells and of increasing the amplitude of the signal supplied by each cell of the array, this increasing the sensitivity of cameras equipped with the photosensitive arrays according to the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Other characteristics and advantages of the invention will emerge below with the aid of the description which follows, made in connection with the attached drawings wherein:
FIG. 1 shows an illustration of the method according to the invention,
FIG. 2 shows an array of charge-transfer photosensitive cells for a videophone camera according to the invention,
FIGS. 3 and 4 show two diagrams to illustrate an implementation of the method according to the invention,
FIGS. 5a and 5b show two timing diagrams corresponding to the functioning of the devices of FIGS. 2 and 3,
FIG. 6 shows an overall diagr
REFERENCES:
patent: 4339775 (1982-07-01), Lemke et al.
patent: 4706123 (1987-11-01), Chautemps
patent: 4831453 (1989-07-01), Takemura
patent: 4876703 (1989-10-01), Urata et al.
Buchner Georges
Eouzan Jean-Yves
Guichard Jacques
Hertaux Jean-Claude
Etat Francais represented by Le Centre National d'Etudes des
Greening Wendy R.
Mancuso Joseph
Thomson-CFS
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