Imaging system

Abstract

 A thermal cueing device is used to control a targetting system. The thermal cueing device has a thermal imager (2) and object identifying means (3) for identifying "hot spots" in the image produced thereby. A head-up display (5) displays, in association with a view of the scene represented by said image, a marker, including an identifying symbol, positioned so as to indicate the location of each object in the scene. A key pad (9) is provided to enable an operator to indicate the selection of an object according to its identifying symbol, and directing means (8, 12) direct the second thermal imager (14), of higher magnification, forming part of the targetting pad (13), according to the image coordinates for the selected object. The second thermal imager produces an enlarged image of the selected object, and permits a guidance system to lock on to this image.

Description

[0001] This invention relates to an imaging system and to a weapon targetting system including such an imaging system.

[0002] An example of one type of imaging system with which the invention is concerned is a thermal cueing system for use in military aircraft. In such a system, a thermal imaging device is directed forward of the aircraft and any high intensity "hot spots" in the image which exhibit temporal and spatial consistency are detected. An image consisting of, for example, arrows indicating the positions of the "hot spots" detected is superimposed in the pilot's field of view on a head-up display (HUD) or on a head-down display (HDD). The pilot must then select a target, perhaps from among several indicated by the arrows, and direct the aim of a weapons system which includes a second imaging device until the centre of the image produced by the second imaging device coincides with the selected target. The weapons system may then be caused to "lock on" to the target, the weapons system being steered so that the selected image remains centred in its field of view.

[0003] This is particularly applicable to laser guided ordnance, where laser guided bombs or missiles either seek out a laser spot on the ground directed at the target by a weapons system, or follow such a laser beam. The aircraft must carry equipment capable of tracking a ground target and firing a laser accurately pointed at the target. Such equipment is typically referred to as a "targetting pod".

[0004] A problem with such systems is that there is an appreciable delay while the pilot directs the targetting pod towards the target selected by the thermal cueing system.

[0005] The present invention provides an imaging system having first and second imaging devices and comprising:
object identifying means for identifying in the image produced by the first imaging device portions of the image having defined image characteristics, said portions representing objects of possible interest, and for determining the image coordinates for each such object;
display means for displaying in association with a view of the scene represented by said image a marker, including an identifying symbol, positioned so as to indicate the location of each object in the scene;
selection means whereby an operator may indicate the selection of an object according to its identifying symbol; and
means for directing the second imaging device according to the image coordinates for the selected object, whereby the second imaging device produces an image of the selected object.

[0006] The first imaging device is preferably a thermal imaging device, while the object identifying means may comprise means for identifying portions of the image above a predetermined intensity which have a predetermined temporal and spatial stability. The display means may comprise an aircraft head-up display or an aircraft head-down display.

[0007] The identifying symbol for each object may be a number, and the selection means may comprise a keypad whose keys are individually marked with the identifying symbols, which may be numbers.

[0008] The second imaging device may be a thermal imaging device or a video camera sensitive to visible or near infra-red light. The second imaging device may have a field of view substantially smaller than that of the first imaging device. The second imaging device may comprise means for directing the line of sight thereof in accordance with the position in the image produced thereby of a selected image feature, whereby the position of said feature in the image may be stabilised.

[0009] The invention also provides a weapon targetting system, comprising an imaging system according to the invention, and means for aiming a weapon in accordance with the direction of line of sight of the second imaging device.

[0010] Reference is made to the drawings, in which:

Figure 1 shows in diagrammatic form an imaging system in accordance with the invention; and

Figure 2 is a diagrammatic representation of a typical scene as viewed through the head-up display of the system as shown in Figure 1.

[0011] Referring to Figure 1, the imaging system comprises an infra-red sensor 1 consisting of a thermal imager 2 and a thermal cuer 3, which receives a video signal from the thermal imager and which detects those pixels in the thermal image which exceed a predetermined intensity and which are positionally stable and which reappear in a predetermined number of successive frames, and therefore have the required temporal stability. The thermal cuer 3 determines the coordinates for each group of pixels conforming with the predetermined requirements and feeds these to a labelling circuit 4 which adds to each set of coordinates an identity "tag" or identifying number. The signal from the thermal imager is also passed to a head-up display 5 via a graphics mixer 6. The head-up display is arranged to superimpose in the line of sight of the pilot looking forward from the aircraft at least some of the features of the thermal image, and for this reason the thermal imager is arranged to have a field of view substantially identical to that seen by the pilot.

[0012] The signal from the labelling circuit is passed to a symbol generator 7 which generates a graphics display signal which is passed to the graphics mixer 6 so as to add to the thermal image displayed in the head-up display arrows indicating possible targets identified by the thermal cuer together with numbers identifying the different targets. The symbol from the labelling circuit is also passed to a selection and conversion circuit 8 which is arranged to receive a key number from a key pad 9 operable by the pilot to select one of the numbered targets. The selection and conversion circuit 8 responds to the selected key number to select the required coordinates for the object and to convert those coordinates to a pointing angle.

[0013] A flip-flop 10 also receives a signal from the key pad when a key is pressed and in response sends a signal to a switch 11 which causes the pointing angle signal from the selection and conversion circuit 8 to be passed to a pointing control 12 in a targetting pod 13.

[0014] The targetting pod includes a second thermal imager 14 having a substantially narrower field of view than the thermal imager 2. The thermal imager 14 is gimbal mounted with gimbal motors controlled by signals from the pointing control and with positional feed-back signals returned to the pointing control 12. The targetting pod also contains a targetting laser (not shown).

[0015] The video signal produced by the thermal imager 14 is passed to a tracking control circuit 15 which serves to lock the thermal imager 14 onto the target presented when the initial positioning signal is received from the selection and conversion circuit 8. When the tracking circuit is locked onto the target, a pointing angle demand signal is sent by the tracking circuit via the switch 11, a reset signal also being sent by the tracking circuit 15 to the flip-flop 10 which in turn resets the switch 11.

[0016] Figure 2 illustrates diagrammatically a view as seen in the head-up display showing three targets identified by the thermal cuer 3 and indicated by numbers 1, 2 and 3 and by arrows pointing to the identified targets. To select a target, the pilot has merely to depress the appropriate key of the key pad. When the targetting pod is locked onto the selected target, the pilot is now presented with a stabilised high magnification image of the potential target, and can decide from this whether the potential target is an actual target before committing ordnance. If the pilot decides that the potential target is not valid, then he has the ability to select another target by depressing the appropriate key on the key pad. The process then repeats itself.

Claims

1. An imaging system having first and second imaging devices and comprising:
object identifying means for identifying in the image produced by the first imaging device portions of the image having defined image characteristics, said portions representing objects of possible interest, and for determining the image coordinates for each such object;
display means for displaying in association with a view of the scene represented by said image a marker, including an identifying symbol, positioned so as to indicate the location of each object in the scene;
selection means whereby an operator may indicate the selection of an object according to its identifying symbol; and
means for directing the second imaging device according to the image coordinates for the selected object, whereby the second imaging device produces an image of the selected object.

2. An imaging system according to Claim 1, wherein the first imaging device is a thermal imaging device.

3. An imaging system according to Claim 2, wherein the object identifying means comprises means for identifying portions of the image above a predetermined intensity which have a predetermined temporal and spatial stability.

4. An imaging system according to Claim 1, 2 or 3, wherein the display means comprises and aircraft head-up display.

5. An imaging system according to any preceding claim, wherein the identifying symbol is a number.

6. An imaging system according to any preceding claim, wherein the selection means comprises a key pad whose keys whose keys are individually marked with the identifying symbols.

7. An imaging system according to any preceding claim, wherein the second imaging device is a thermal imaging device.

8. An imaging system according to any of Claims 1 to 6, wherein the second imaging device is a video camera sensitive to visible or near infra-red light.

9. An imaging system according to Claim 7 or 8, wherein the second imaging device has a field of view substantially narrower than the first imaging device.

10. An imaging system according to any preceding claim, wherein the second imaging device comprises means for directing the line of sight thereof in accordance with the position in the image produced thereby of a selected image feature, whereby the position of said feature in the image may be stabilised.

11. An weapon targetting system, comprising an imaging system according to any preceding claim, and means for aiming a weapon in accordance with the direction of line of sight of the second imaging device.

12. A weapon targetting system according to Claim 11, wherein the means for aiming comprises a laser directed in accordance with the direction of line of sight of the second imaging device, the weapon ordnance being adapted to follow the path of the laser beam to the target.

Drawing