GB2623046A

GB2623046A - Guided weapons system and tracking and guiding a weapon

Info

Publication number: GB2623046A
Application number: GB8039092.5A
Authority: GB
Inventors: Robert Barron Donald
Original assignee: EMI Ltd
Current assignee: EMI Ltd
Priority date: 1980-01-08
Filing date: 1980-12-09
Publication date: 2024-04-03

Abstract

A projectile 1 carries a thermal or infrared (IR0 beacon B which is tracked using an infrared imager 3. The imager scans an image of a scene including the beacon and a target 2 in raster fashion having e.g. three fields per sequence. To image the target 2 when the intensity of the beacon tends to obscure the target, the beacon is imaged only once every three fields. This is achieved by interposing a filter arrangement 34 between the beacon and the IR detectors 31 to pass the beacon image to the detectors once every three fields and to pass the target image to the detectors in the other two fields. Alternatively, the beacon is switched on in only one field in every three fields and the filter arrangement operates in that one field to pass only the beacon image to the detectors 31.

Description

GUIDED WEAPONS SYSTEM AND

-TRACKING AND GUIDING A WEAPON

The present invention relates to a guided weapons system, and to a system for tracking and guiding the weapon.

In a previous proposal for tracking and guiding a projectile, Such as a guided missile, the thermal radiation produced by the missile propellant, or by a thermal beacon arranged on the missile, is detected by a static-split detector and signals derived from the static split to guide the missile to its target.-An optical arrangement associated with the static-split: detector is used to view the missile and the target, the missile being controlled to stay on the line of sight to the target.

A later proposal is to track the missile using a thermal imaging device, which also views the target to obtain signals representing the deviatien of the missile from a desired path to the target ant. to use thosd signals to guide the missile. In this proposal a thermal beacon is arranged on the missile. However, the energy emitted from the beacon is intense and at* short range it could completely obscure the target.

According to_one aspect of the invention, there is provided a system for tracking, and producing guidance signals for, a projectile carrying a beacon producing thermal radiation, the system including: a detector arrangement sensitive to thermal radiation to produce electrical signals; scanning means arranged to cause the detector arrangement * to scan through a thermal image of a scene (which may include * images of the beacon and a target) according to a preset scanning pattern so that the said signals form a representation * of the sbene, the pattern comprising a repeating sequence of a plurality of fields; means arranged to cause the detectors of the detec oe arrangement to -receive-radiation from the beacon In one field of each sequence and to cause the detectors to receive radiation 10 from the scene but substantially excluding radiation from the * beacon in at least one other field of each sequence; and means arranged to compare the positions, in each sequence, of the beacon and the target to produce guidance signals for the projectile.

According to another aspect, there is provided a guided weapons system comprising a projectile including a guidance arrangement and carrying a beacon for producing thermal radiation, -a detector arrangement sensitive to thermal radiation to 20 produce electrical signals; scanning means arranged to cause the detector arrangement to scan through a thermal -Image of a scene (which may include images of the beacon and a * target) according to e preset scanning pattern so that the said signals form a representation of the scene, the pattern comprising a repeating sequence of a plPrality of fielde; weans arranged to, cause' the detectors of the detector arrangement to receive radiation from the beacon in one field of each sequence and to cause the detectors to receive radiation froth the scene but substantially excluding radiation from the beacon in at least one other field of each sequence; means arranged to compare the positions, in each sequence, of the beacon and the target to produce guidance signals for the projectile, and a data link arranged to transmit at least the guidance 10 signals to the guidanee arrangement of the projectile.

In one embodiment of the invention the causing means comprises meanS atranged to sequentially filter the radiation received by the deteCtor arrangement to allow radiation from the beacon'to pass to the -detectors inane field of each sequence and to allow radiation 'from the scene, but substantially excluding radiation from the beacon, to pass to the detectors in at; least one other field of each sequence.

In a further -embodiment, the causing means comprises means arranged to stop the... emissionof the radiation of the beacon from the projectile during the said other field of each

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sequence. This is preferably achieved by deactivating the beacon during the-said other field. In a preferred form of, . this embodiment the causing Means further Comprises means arranged to sequentially filter the radiation received by the detector arrangement to allow substantially only radiation from the beacon to pass to the detectors during he Saia one field of each sequence. -3-.

Preferably each sequence comprises three' fields and the * detectors receive radiation from the beacon in' onlyone field In every three fields.

For a better understanding of the invention, reference will now be made, by way of example to the accompanying drawing, in which: Figure 1 is a schematic diagram of a system for tracking and guiding a projectile, end Figure. 2 is a bloelcdiagram of a detail of artedif cation of the systeM of Figure 1.

It is desired to automatically guide a missile 1 to a target 2. The system shown in Figure 1 comprises a thermal imager 3 for viewing the scene including the missile 1 and the target 2, the missile carrying a beacon B to facilitate tracking. However, at short range, the intensity of the beacon may completely obscure the target.

The imager comprises an arrangement of thermal ( nfrared) detectors 31 and a scanning mechanism-32 which causes an image, of the scene fotmed hy an optical arrangement 33 to be scanned over the detectors according to a preset scanning pattern. In order to at least reduce the obscuring of the target by the -beacon, a filter arrangement 34 'is provided between the scene I " and the detector arrangement 31 e.g. between the mechanisth 32 u and the arrangement 51 to sequentially filter the radiation synchronously with the operation of the scanning mechanism 32.

In this example, the mechanism 32 produces three interlaced fields in each frame of the scanning pattern, and in one of-the fields radiation in a frequency band ranging from above the highest beacon frequency down to a frequency below the lowest, beacon frequency is allowed by the filter arrangement to pass to the detectors, whilst in the other two fields radiation in that band is substantially blocked.' Preferably in the said one field a long wave band-pass filter is used to pass the beacon radiation to the detector arrangement, and a short wave * band-pass filter is used in the other twd fields' to. pass the target_ image. The filter arrangement: accordingly preferably includes a rotating disc comprising the long wave band-pass filter and the short wave band-pass filter, the disc being rotated by a,drive meehanism synchronously with the operation of the scanning mechanism. Thus in the said one field, tracking of the projectile is achieved, whilst in the other two fields imaging of the target is achieved.

Yet another possibility is available Should the frequencies of the beacon radiation be within the frequency band of the target, as would-occur.with a carbon dioxide laser at 10.6 microns and thermal imaging by the arrangement 31 in the 0-12 microns atmospheric window. By synchronisinga clock on the missile controlling the-missile beacon with the Operation of the scanning-mechanism 32 in the ground equipment, the beacon may be extinguished during-the imaging fields, thus eliminating the need to introduces beacon band stop filter (or short wave band-pass filter) in these fields: The filter arrangement is operated however to introduce a beacon-band pass filter when the beacon is Actuated in the beacon imaging field sc'that-in that field only radiation from the beacon passes to the detector arrangement 31. For this purpose the missile includes a,synchronising arrangement as shown in Figure 2. A sYnchronising circuit 20 receives via the data link 39 synchronising signals derived from the scanning mechanism 32 and fed to the data link as indicated by dotted line 40 in Figure A. The circuit 20 synchronises a clock 21 with the scanning mechanism so that the energisation of the beacon is controlled by a switch 30 to

_deactivate it.during the imaging-fields.

The detector arrangement 31 produces a video signal, representing the scene which is fed to a display deviee 35 and an auto-lock-tbllow system (A.L.F.). The display device displays an image of the scene. It includes a touch panel 36 which in conjunction with a designator-37 (e.g. a so-called light-pen) actuates a target designator circuit 38 to feed to the A.L.F. System signals representing the position of the desired target 2 in the image of the scene. In known manner, the A.La.,system compares the position of the beacon in the image of the--scene.. with the position of the target.to produce guidance signals for the missile. These guidance signals are transmitted to-a-guidance arrangement on the missile via a data link 39 which may be-for example a radio link, an optical fibre link, or a wire link.

If provided, the clock in the missile may be controlled so that the beacon is only activated when the tracker (i.e. imager 3, ALF system display 35 and designator 38) expects to be imaging it. ThUs pewer may be conserved on the Missile. 6hoOld the tracker lose the missile, the clock would be instructed to activate the beacon. These functions may be achieved by deriving suitable control signals from the A.L.F. system and feeding them to the missile via the data link.

Claims

What we claim is:- 1. - A system for tracking, and producing guidance signals for, a projectile carrying a beacon producing thermal radiation, the. system including: a detector arrangement sensitive to thermal radiation to produce electrical signals; scanning means arranged to cause the detector arrangement to scan through a thermal image of a scene (which may include images of the beacon and a target) according to a preset scanning pattern so that the said signals form a representation of the scene, the pattern comprising a repeating sequence of a plurality of fields; means arranged to cause the detectors of the detector arrangement to receive radiation from the beacon in one field of each sequence and to cause the detectors to receive radiation from the scene but substantially excluding radiation from the beacon in at least one other field of each sequence; and means arranged to compare the positions, in each sequence, of the beacon and the target to produce guidapee signals for the projectile.
2. A system according to Claim 1, wherein the causing means comprises means arranged to sequentially filter the radiation received by the detector arrangement to allow radiation from the beacon to pass to the detectors in one field of each sequence and to allow radiation from the scene, but substantially excluding radiation from the beacon, to pass to the detectors in at least one other field of each sequence.
3. A system according to Claim 1, wherein the causing means comprises means for stopping the emission of the radiation of the other beacon from the projectile during the said other field of each sequence.
4. A system according to Claim 3, wherein the stopping means comprises means for deactuating the beacon during the said other field.
5. A System according to Claim 3 or 4 wherein the causing means further comprises means, rranged to sequentially filter the radiation received by the detector arrangement to allow substantially only radiation from the beacon to pass to the detectors during the said one field of each sequence.
6. A system according to any preceding claim, wherein the said sequence comprises three fields and the causing means causes the detectors to receive radiation only from the beacon in the said one field and only from the scene excluding the beacon in said other fields, 7, A guided weapons system comprising a projectile including a guidance-arrangement, and-carrying a beacon--for producing thermal radiation, a-detector arrangement sensitive to thermal radiation to produce electrical signals; scanning means arranged to cause the detector arrangement to scan through a thermal Image of a scene (which may include images of the beacon and a target) according to a preset scanning pattern so that the said signals form a representation of the scene, the pattern comprising a repeating sequence of a plurality of fields; -10 -means arranged to cause the detectors of the detector arrangement to receive radiation from the beacon in one field of each sequence and to cause the detectors to receive radiation from the scene but substantially excluding radiation from the beacon in at least one other field of each sequence; means arranged to compare the positions, in each sequencef of the beacon and the target to produce guidance signals for the, projectile, and * a data link arranged to transmit at least the guidance signals to the guidance arrangement of the projectile.8. A system according to Claim 6 wherein the causing means comprises means arranged to sequentially filter the radiation received by the detector arrangement to allow radiation from the beacon to pass to the detectors in one field of each sequence and to allow radiation from the scene, but substantially excluding radiation from the beacon, to pass to the detectors in at least one other field of each sequence.9. A syystem according to Claim 6 wherein the causing means comprises means for stopping the emission of the radiation of the other beacon from-the projectile during the_said other field of each -sequence 10. A-system according to Claim 8 wherein the stopping means comprises means for deactuating the beacon during the said other field.11. A system according to Claim 8 or 9 wherein the causing means further comprises means arranged to sequentially filter the radiation received by the detector arrangement to allow substantially only radiation from the beacon to pass to the detectors during the said one field of each sequence.12. A tracking and guidance system substantially as hereinbefore described with reference to Figure 1 of the drawings.13. A tracking and guidance system substantially as hereinbefore described with reference to Figure 1 and 2 of the. drawings.14. A weapons system substantially as hereinbefore described with reference to Figure 1 of the drawings.15. A weapons system substantially as hereinbefore described with reference to Figure 1 and 2 of the drawings.What we claim is:- 1. A system for tracking, and producing guidance signals for, a projectile carrying a beacon producing thermal radiation, the system including: a detector arrangement sensitive o therMal radiation to produce electrical signals; scanning means arranged to cause the detectordarrangement to scan through a thermal-image of a scene (whiCh may/include images, -of the beacon and a target) according to a preset scanning pattern' so. that the Said signals form-a representation of the scene, the pattern comprising a repeating sequence of a plurality of fields; means arranged to cause the detectors of the detector -arrangement to receive radiation from the beacon in one field of each sequence: and to cause the detectors to receive radiation from the scene but substantially excluding radiation from the beacon in* at least one other field of each sequence; andmeans arranged: to compare the positions, in each sequence,: * . . of the beacon and-the-target to produce guidance signals for the -J projectile.2. A system: according to Claim t" wherein the causing means'-_comprises means-arranged to sequentially filter the radiation received by the detector arrangement to allow radiation from the beacon to-pass to the detectors in one field of each sequence and to allow radiation from the scene, but substantially excluding radiation from the beacon, to pass to the detectors in at least one other-field of each sequence.3. A system according to Claim 1, wherein the causing means comprises means for stopping the emission of radiation from said beacon during the said other field of each sequence.4. A system according to Claim 3, wherein the stopping means comprises means for deactuating the beacon during the said other field.5. A system according to Claim 3 or 4 wherein the causing means further comprises means arranged to sequentially filter the radiation received by the detector arrangement to allow substantially only radiation from the beacon to pass to the detectors during the said one field of each sequence.6. A system according to any preceding claim, wherein the said sequence comprises three fields and the causing means causes the detectors to receive radiation only from the beacon in the said one field and only from the scene excluding the beacon in said other fields.
7. A guided weapons system comprising a projectile including a guidance arrangement and carrying a beacon for producing thermal radiation, a detector arrangement sensitive to thermal radiation to produce electrical signals; scanning means arranged to cause the detector arrangement to scan through a thermal image of a scene (which may include images of the beacon and a target) according to a preset scanning pattern so that the said signals form a representation of the scene, the pattern comprising a repeating sequence of a plurality of fields; means arranged to cause the detectors or the detector arrangement to receive radiation from the beacon in one field of each sequence and to cause the detectors to receive radiation from the scene but substantially excluding radiation from the beacon in at least one other field of each sequence; means arranged to compare the positions, in each sequence, of the beacon and the target to produce guidance signals for the projectile, and a data link arranged to transmit at least the guidance signals to the guidance arrangement of the projectile.
8. A system according to Claim 7 wherein the causing means comprises means arranged to sequentially filter the radiation received by the detector arrangement to allow radiation from the beacon to pass to the detectors in one field of each sequence and to allow radiation from the scene, but substantially excluding radiation from the beacon, to pass to the detectors in at least one other field of each sequence.
9. A system according to Claim 7 wherein the causing means comprises means for stopping the emission of radiation from said beacon from the projectile during the said other field of each sequence.
10. A system according to Claim 9 wherein the stopping means comprises means for deactuating the beacon during the said other field.
11. A system according to Claim 9 or Claim 10 wherein the causing means further comprises means arranged to sequentially "len 1m.-filter the radiation received by the detector arrangement to allow substantially only radiation from the beacon to pass to the detectors during the said one field of each sequence.
12. A tracking and guidance system substantially as hereinbefore described with reference to Figure 1 of the drawings.
13. A tracking and guidance system substantially as hereinbefore described with reference to Figure-1 and 2 of the drawings. .
14. it weapons system substantially as hereinbefore described with reference to Figure 1 of the drawings:
15. A weapons system substantially as hereinbefore described with reference to Figure 1 and 2 of the drawings.