DE4243200C1 - Land vehicle friend-foe identification device - Google Patents

Abstract

The device responds to a masked infrared marking which is only visible to friendly observers. The object carries large format heated image elements with a low degree of thermal emission. The heating elements are controlled so that the apparent temp. of the image elements corresp. to the true temp. of the vehicle surface surrounding the markings so that the markings are not visible to a normal thermal imaging device An infrared laser on the observation side , esp. a CO2 pulse laser, is used to illuminate the object. An infrared camera, whose image field is coupled to the alignment of the laser, can be synchronised with the laser to generate a standing image, from which an epsilon-image pattern can be read if present.

Description

The invention relates to a device for friend-foe identification of land driving testify according to the preamble of claim 1.

Such a device is known from EP 0 127 088 A2, in which Reference encrypted interrogation signals in an active intelligent system recorded and returned with active encrypted response signals. Such known systems are "cooperative" and "active". This means that the Inquirer reveals himself through his action and both his friend-enemy Status, just like his position reveals.

The reliable friend-foe identifier under combat conditions (IFF Identi fication Friend Foe) is a well-known but not yet satisfactorily resolved Problem. A recent example is the Gulf War, in which the 25th US soldiers were killed in attacks from their own ranks.

As is known, a so-called cooperative IFF system has been introduced in airspace, which is based on sending and answering encrypted  Radio signals based. The querying observer reveals himself through this action, but in case of doubt he will use the system to create a To avoid endangering his compatriots.

For land vehicles, IFF has been radio-based for various reasons not proven. The main problems here are insufficient reliability liquidity, for example in the identification of hidden and camouflaged Objects or when assigning multiple response signals from one Direction. For the identification of vehicles with ground-to-ground or aerial So ground contacts are looking for an alternative method, which is the special conditions of the objects, the natural background basic, the landscape formation and the weapon ranges considered and provides sufficient spatial resolution and separation ability.

One tool that seems interesting in this context is the Thermal imaging technology. The observation is therefore purely passive, i. H. The opponent does not notice that he is being viewed or recognized. Of course, it provides a warmth Imager itself - if introduced - a very useful BIFF system (Battlefield-IFF) because the IR signatures of different vehicle types sometimes clearly differentiate and therefore easy to identify day and night are. Experience has shown, however, that the sole use IR vision technology under real environmental conditions and in critical Situations not enough. An additional object is required Make a mark.

It is known, for example, to use foils or coatings with a lower marking Heat emission, so-called "thermal tapes" or "low emissive paints"  to use. Because normal vehicle paintwork or camouflage coatings always a high degree of heat emission of typically 85 to 95% areas with low emissions (ε <50%) stand out significantly the environment. Become simple geometric patterns, stripes, book Letters and similar symbols applied, these can easily in the heat image device can be recognized. A disadvantage, however, is that the opponent immediately recognizes these signs and of course as welcome Visual aids and ideal targeting will use while its own not particularly marked for him, but at least are normally camouflaged and are therefore relatively well protected. Even if every day If other patterns for identification are agreed upon, this gravie Do not let the detrimental disadvantage be eliminated, since it is fundamental for friend and foe the same information is available. The use of IR signatures with The help of thermal tapes and similar materials therefore only has one some effect if the opponent is not or only to a limited extent has thermal imaging equipment. On the other hand, they are comparable on both sides IR visual aids are available, the use of IR-significant markie is available diametrically opposed to the demand for effective camouflage and is therefore inevitable.

Similar problems also exist with other devices which in have been proposed in this context and in some form are based on the use of actively radiating IR light sources. So it is obvious to build a cooperative BIFF based on lasers and thus part of the aftermath associated with the propagation of radio waves avoid parts. However, here, too, would be from both sides significant light signals a relatively high discovery  represent risk that is not with the particularly important on the ground Tolerates element of camouflage and deception.

The present invention is based on the object of a device create which of the recognition of own objects of a battlefield serves without the effect of the imported camouflage and the usual camouflage possibilities to impair. The marked objects should be friend-side be easily and reliably identifiable, but possible for the opponent stay camouflaged, d. H. not or only under much less favorable conditions being visible.

This object is achieved in that the objects are equipped with "hidden signatures". These hidden signatures consist of areas with reduced heat emissivity £ in any agreed pattern (picture). At the same time, a temperature increase (T-picture) is generated with heating elements in the same place. A relatively simple control technique ensures that the effect of the emissivity reduction just compensates for the effect of the temperature increase, ie the heat radiation L. of the surrounding area corresponds to the radiation L _{i of} the marking area

L₀ = L _i (1)

with the result that the marking is not visible in the thermal image. Since the Heat radiation is generally given by

L = const · ⁴ · T⁴, (2)

the requirement ( 1 ) is met in that

ε₀T₀4 = ε _i T _i 4 thus T _i = (ε₀ / ε _i ) 1/4 · T₀ (3).

The temperature T _{i of} the marking surface must therefore be raised somewhat in relation to the surrounding surface in accordance with relationship ( 3 ).

The relationship ( 3 ) is not entirely correct, since if the ε value is lowered, the reflection effect inevitably increases and the overall radiation L _{i is} influenced thereby. As long as the ε _i value is not set too low, these deviations are limited. In addition, according to the invention, a further measure is used to prevent uncontrolled reflection of ambient radiation: As can be seen in Fig. 1, the surface is provided with a microprismatic structure which has retroreflective properties. In order to achieve a perfect masking of the ε-image from the enemy observer, only the radiation temperature of the surroundings in the direction of the opponent has to be determined with a simple sensor and used to correct equation (3).

The exact correction formula corresponds to the known laws of the beam physics and should therefore not be reproduced here. Likewise, poses the technical implementation of the relationships according to the state of the Technology is not a problem.

The visualization of the hidden signature in the friendly viewing device is now solved as follows: The thermal imager  is coupled with a small CO₂ laser, the radiation frequency of 10.6 µm, as is known, in the center of the heat radiation of the normal order ambient temperature. The observer sends a single pulse (approx 50 msec), the camera receives the reflected signal and synchronizes save it as a still image for a few seconds. The ε mark of the The vehicle is clearly recognizable. Because of the retroreflective upper Unlike the laser rangefinder, the area of the marking is only very low laser pulse power required.

As shown in FIG. 1, the structure of the hidden IFF signature consists of adjustable heating elements with a microprism-like surface structure. Distance and depth of the prisms are preferably about 50-100 microns. The surface can be provided with a solid, low-emissivity coating, a metal layer. The prisms are sealed with an IR-transparent top layer, which is also colored in the colors of the camouflage paint.

The micro-structure of the structure is not mandatory and only becomes practical Reasons preferred. The optical effect also exists with macroscopic Structures with dimensions in the millimeter range or larger.

Instead of the fixed reflector layer, elements with control can also be used heat emission can be used. Such elements correspond the prior art and are for example in the patent DE 36 43 692. The previous development and application This technique was based solely on camouflage against infrared reconnaissance aligned. In connection with the present invention, one results  advantageous combination of identifiability by friendly observers and multispectral camouflage against enemy reconnaissance. The be Special advantage when using controllable picture elements is that the hidden signature switched off or any (shape, size, orientation) can be changed. This is an additional safeguard against enemy Liche detection of the mark possible, or can be effective deception effects can be achieved by using the IR marker used by the opponent is simulated.

Claims (4)

1. Device for friend-enemy identification of land vehicles, characterized in that a hidden, only friend-side visible IR marking is generated by the object side

• - Large-format heatable picture elements with low heat emission are provided, and
• - That a regulation is provided with which the heating elements can be controlled so that the apparent temperature of the picture elements corresponds precisely to the true temperature of the surfaces surrounding the marking of the vehicle, so that the marking is not visible in normal thermal imaging devices, and by the observer side
• - An IR laser, especially a CO₂ pulse laser for lighting the objects and
• an IR camera is provided, the image field of which is coupled to the alignment of the laser and which can be synchronized with the laser to produce a still image from which a possibly existing ε image pattern can be read.

2. Device according to claim 1, characterized in that the picture elements with a retroreflective, in particular provided with a microprismatic surface structure are preferred, the dimensions of the prism surfaces are larger than 20 µm. 3. Device according to one of the preceding claims characterized that controllable when used on the property ε elements a temporal, directionally selective or pictorial Change in marking is achieved.   4. Device according to one of the preceding claims, characterized characterized that controllable when used on the property ε elements featured an IR marker used by the opponent is deceived.