GB2318939A - Infra-red identification device - Google Patents

Abstract

An observer in a helicopter 1 track a fugitive 2 and police 4, 5 using a infra-red camera. In order to distinguish the people, each policeman eg 5 eases a infra-red beacon in his helmet which emits a distinctive pulse pattern and which can be seen by the observer via the IR camera. The beacon may use a plurality of IREDs, whose output may be collimated by a lens. Application to other persons, objects or fixed locations is mentioned.

Description

Identification Devices This invention relates to devices used to identify persons or objects viewed by means of an apparatus capable of detecting radiation other than visible light.

There are both civil and military circumstances during which persons or objects are viewed by means of detection of non-visible radiation. Cameras and other recording devices sensitive to radiation in the infra-red region of the electromagnetic spectrum are used by, for example, police and law enforcement authorities for the detection and tracking of suspects travelling by foot or of vehicles, both at night and under other unfavourable visible light conditions.

Often such cameras are mounted in aircraft for ease of movement, and the camera operator is normally able to communicate with search personnel on the ground by means of two-way radio.

In a situation where such an airborne (or otherwise distant) infra-red observer needs to co-ordinate a search for a target he has sighted, it is a significant disadvantage that he is unable to distinguish between the infra-red images of individual members of a search team. The transmission of directional instructions to individual searchers, who may themselves be operating under conditions of negligible or zero visibility, is thus inefficient, increasing the opportunity for the target to move or otherwise escape detection. A similar argument also applies to the co-ordination of other groups of individuals operating under conditions of restricted visibility, for example fire rescue personnel working in smoke-filled buildings or other enclosures. Likewise the guiding of personnel to a predetermined location or object under conditions of impaired visibility presents a similar difficulty.

According to the present invention there is provided a portable, lightweight, pulsing electromagnetic radiation source, with a self-contained or separate energy supply, capable of being finnly secured to the clothing or headwear of a member of a search team (or other person, object or location), and providing, by means of regular or otherwise pulses of radiation, a distinctive and recognisable radiation signature for the individual, object or location so equipped which is visible to a distant observer using radiation detection equipment.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying figures, in which: Figure 1 illustrates a typical search directed by a distant infra-red observer; Figure 2 illustrates a typical conformation for such an identifying unit; Figure 3 illustrates an astable multivibrator electronic circuit; and Figure 4 describes a block diagram of a typical electronic driving system.

Referring to Figure 1, a distant observer (1) is aware ofthe position of the infrared signal emitted by a target (2), and also of the positions of the infra-red signals of the searchers (3) with whom he is in communication. The searchers are to be guided in the direction (4) of the target by instruction from the observer. The logistical task of the observer is made more efficient by the ability to identify a particular searcher (5), by means of an attached pulsing infra-red source, visible above that individual's background infra-red output. It will be appreciated that the search for a target so described is given by way of an example; other similar situations requiring observer co-ordination of a number of persons or objects will be seen to be within the spirit of the invention.

A diagrammatic view of the infra-red pulse generator is given in Figure 2, where a printed circuit board (6) is provided with a battery of direct current cells (7), providing an energy source for an electronic control module (8), and subsequently for a radiation emitting transducer (9). In the case where the user carries a separate energy source, a connection by wire or other means to the printed circuit board would be provided. To facilitate attachment to the clothing or headgear of the user, a hole (10) or clip or other convenient fastening device is provided in the printed circuit board. Figure 2 is given by way of an example; extensions in the form of the provision of a plurality of radiation emitting transducers, or of one or more radiation emitting transducers being sited at some further distance from the printed circuit board by means of connecting wires, optical fibres, or other suitable devices, will be seen to be within the spirit of the invention.

Figure 3 illustrates an astable multivibrator circuit diagram, where the symbols represent electronic components in the way usual for those skilled in the art. By means of an applied d.c. potential difference at (11) from the aforementioned battery of cells (7) or separate energy source, a sequence of electrical pulses is obtained at (12), which are used, through a suitable conditioning circuit, for energising the radiation output transducer. Such a pulse generation circuit is illustrated only as an example; those skilled in the art will clearly appreciate that other suitable circuits, together with integrated circuit and other implementations of such circuits, are widely known. Suitable choices of the resistive and capacitative elements in the circuit given in Figure 3, or of other elements in analogous circuits, will produce output pulses of differing durations and frequencies; this facilitates the use of a plurality of pulse generation units, each operating with characteristically differing patterns of radiation pulsation, to be used by the observer to distinguish between a number of searchers or other objects.

A block diagram of the typical control circuit required is given in Figure 4. A switch unit (13) controls a pulse generator (14) (such as that illustrated in Figure 3), which, through a transducer driver (15), controls an output transducer (16).

The switch allows the user to turn the radiation output of the unit off in situations where such enhanced detectability would be disadvantageous, and also to choose between a selection of output pulsation patterns, including a continuous, nonpulsing output. Although the illustrated embodiment of the invention refers specifically to an infra-red pulse generator, preferably with a radiation emitting diode as the output transducer, it will be appreciated by those versed in the art that a suitable choice of radiation output transducer will generate a signal visible to an observer suitably equipped with a detector operating in any frequency band of the electromagnetic spectrum.

Claims (1)

1. Claims

   1. A portable, lightweight, pulsing electromagnetic radiation source, with a self-contained or separate energy supply, capable of being firmly secured to the clothing or headwear of a member of a search team (or other person, object or location), and providing, by means of regular or otherwise pulses of radiation, a distinctive and recognisable radiation signature for the individual, object or location so equipped which is visible to a distant observer using radiation detection equipment.

   2. A portable, pulsing radiation source, as claimed in Claim 1, provided with a means of electronically controlling the pulsation frequency, whether regular or otherwise, and the duration of radiation pulses, whether fixed or variable.

   3. A portable, pulsing radiation source, as claimed in Claims 1 and 2, wherein the radiation transducer is a radiation emitting diode, and the radiation so produced has a frequency recognised by those skilled in the art as falling within the infra-red part of the electromagnetic spectrum.

   4. A portable, pulsing radiation source, as claimed in Claims 1,2, and 3, provided with a radiation emitting transducer sited remotely from the control circuitry, and connected to the same by electrically conductive wires, optical fibres, or other suitable means.

   4. A portable, pulsing radiation source, as claimed in Claims 1,2, 3 and 4, provided with a plurality of radiation emitting transducers.

   6. A portable, pulsing radiation source, as claimed in Claims 1, 2, 3, 4 and 5, wherein the radiation emitted is collimated by means of a directional lens or other device.

   7. An identification device substantially as herein described with reference to the accompanying drawings.