Optics: measuring and testing – Angle measuring or angular axial alignment – Apex of angle at observing or detecting station
Patent
1997-09-04
1999-03-02
Buczinski, Stephen C.
Optics: measuring and testing
Angle measuring or angular axial alignment
Apex of angle at observing or detecting station
3561415, 250342, G01B 1126, G01J 502
Patent
active
058778551
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an arrangement for the detection of targets, comprising a detector unit rotatable about an at least substantially vertical search axis, provided with a detector and focusing means for the focusing onto the detector of radiation, such as infrared radiation emitted or reflected by targets, further comprising a point target extractor, operating on a row of two-dimensional image matrices X.sub.1, X.sub.2, . . . generated by the detector and representing the surroundings of the arrangement, for generating a predetection for each point target detected in one of the image matrices X.sub.1, X.sub.2, . . .
2. Discussion of the Background
An arrangement of this type is known for example from EP-B- 0.205.794. The aim of the point target extractor is to reduce the number of false alarms generated by a detector unit. Without a point target extractor, a detector unit will generally generate thousands of false alarms per revolution. If the point target extractor possesses all features known in the art, this number can be reduced to only a few false alarms per revolution. This, however, still renders the arrangement unfit for the autonomous and automatic operation of a weapon system.
SUMMARY OF THE INVENTION
The number of false alarms can be reduced by requiring a predetection to be observed during a number of consecutive revolutions. This has the drawback that valuable reaction time is lost. The arrangement according to the invention obviates this drawback and is characterized in that the detector unit is designed to generate, per revolution, at least two image matrices and in that a combination circuit has been provided to generate a detection if, for the at least two image matrices, predetections are generated for corresponding matrix elements.
A first embodiment of the arrangement according to the invention is characterized in that the detector unit comprises a first detector for the generation, per revolution, of an image matrix X.sub.i and a second detector for the generation, per revolution, of an image matrix Y.sub.i, the elevation directions and angles of aperture of both detectors at least substantially corresponding and in that the combination circuit generates a detection if at least two predetections for corresponding matrix elements in the row X.sub.i, Y.sub.i, X.sub.i+1, Y.sub.i+1, . . . of image matrices are generated in succession.
In this respect it is of advantage if both detectors, despite the fact that their elevation directions and opening angles correspond, yet observe a potential target in different ways. A favourable embodiment is therefore characterized in that the spectral response of the first detector differs from that of the second detector. Taking account of the spectral windows in the atmosphere, a special embodiment is characterized in that the spectral sensitivity of the first detector exhibits a maximum in the 3-5 micrometer range and the second detector in the 8-12 micrometer range.
A further favourable embodiment makes use of the fact that false alarms, particularly those caused by for instance sunlight reflected by the sea surface, exhibit a preference for certain polarization directions and is characterized in that the first detector and the second detector comprise a polarizer each. A special embodiment is then characterized in that at least one polarizer is provided with adjusting means for orientating the polarizer such that the number of prealarms is minimized.
A still further embodiment of the invention serves a useful purpose if false alarms are generated by nearby objects, such as birds. It is characterized in that the first and the second detector are positioned side by side to generate a parallax difference for at least nearby targets thus causing the point target extractors to generate prealarms for non-identical matrix elements, which will subsequently not be combined to a detection by the combination circuit.
According to a further inventive embodiment of the invention it is possibl
REFERENCES:
patent: 2830487 (1958-04-01), Griffith
patent: 3687556 (1972-08-01), Price et al.
patent: 5000564 (1991-03-01), Ake
patent: 5026153 (1991-06-01), Suzuki et al.
Buczinski Stephen C.
Hollandse Signaalapparaten B.V.
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