Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Reexamination Certificate
1991-07-02
2001-02-27
Hellner, Mark (Department: 3662)
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
C356S004010
Reexamination Certificate
active
06194723
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of protection of optoelectronic search and tracking equipment, for example passive imaging equipment using infrared detectors (from a single detector to detector arrays, or “mosaic”) or camera tube detectors, from an illumination, in particular a laser illumination from a target.
Devices using a laser source are generally intended for range-finding or fire control, or for countermeasures purposes. They are most often coupled with an acquisition and angular tracking system, of radar or optoelectronic nature, so that a fire envelope can be defined from the data acquired by this equipment (elevation and azimuth angular coordinates g and s, derivatives g′ and s′, and range and range rate data r and r′).
2. Description of the Prior Art
These means are mounted indifferently aboard the “hunter”—airplane or missile—or the target. The target itself may have engaged a fire-control sequence or countermeasures against the attacking hunter in order to deceive its fire-control system: the hunter is then exposed to a laser illumination from the target it is tracking by means of its optoelectronic means. This illumination has detrimental consequences on its optoelectronic equipment when the hostile laser illumination wavelength is within the spectral bandwidth of the equipment, and this may result in:
dazzling the photodetectors possibly up to the point where they are destroyed;
a risk of jamming depending on the operating mode of the illuminator;
a catadioptric, or “cat's eye”, effect: when the passive tracking equipment is accurately pointed at the laser illuminator carrier, it sends back in its direction identification elements which make it easily detectable. The hunter may also, through its equivalent laser signature—revealing its orientation with respect to the laser beam—provide the characteristics of its own fire-control system.
SUMMARY OF THE INVENTION
An object of the present invention is a method destined to protect optoelectronic equipment from a laser illumination in order to eliminate the detrimental consequences of such an illumination, and also the “cat's eye” effect exhibited by the equipment when the illumination is within its field of view.
Another object of the present invention is a system for implementing this method.
In order to attain these goals, the method of protection from a laser illumination for a search or tracking passive optoelectronic equipment whose object plane of the optical system of the equipment is scanned by a photosensitive sensor implementing an azimuth-elevation scanning, consists in:
detecting the time when the impact of the laser illumination enters the field of view of the optoelectronic equipment;
determining the time when the sensor of the optoelectronic equipment coincides spatially with the impact of the laser illumination within the field of view;
blocking, at the time previously determined, the sensor for a duration at least equal to the dwell time of the sensor in front of the laser impact; and
position-tracking the laser illumination impact.
REFERENCES:
patent: 4197006 (1980-04-01), Maillet
Cojan Yves
Fertala Rémy
"Thomson-CSF"
Hellner Mark
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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