Ammunition and explosives – Smoke generating
Reexamination Certificate
2001-09-27
2002-11-26
Nelson, Peter A. (Department: 3641)
Ammunition and explosives
Smoke generating
C102S336000, C102S505000
Reexamination Certificate
active
06484640
ABSTRACT:
The subject of the present invention is a process for the production of a screen smoke one-sidedly transparent in the infrared spectral range, whereby scattered particles of suitable size introduced into an aerosol are impinged against by means of infrared radiation so that there is given a strongly marked forwards scattering on the scattered particles. The aerosol itself consist of known screen smoke strongly absorbing in the visible range.
In the case of military deployment and also in the case of police deployment against barricaded prepetrators, is of considrable advantage when, for a short time, ones own change of position cannot be observed by the opponents. Since today an observation takes place not only in the visible range but also via IR and radar technology, in the past smoke-producing mixtures have been developed to a large extent which are brought as thrown bodies between ones own position and that of the opponent and there produce a local wall of smoke which slowly breaks up in the air or is driven away by the wind or are burnt in so-called smoke pots, whereupon the smoke cloud produced is spread out with the wind between ones own position and the position of the opponents (cf. EP 0 106 334 A2, DE 43 37 071 C1, DE 40 30 430 C1). Although such smoke screens give a very good protection not only in the visual but also in the infrared spectral range, they have the disadvantage that during the time in which the smoke is impenetrable (usually about 20-60 seconds), not only the smoke producer but also the opponent can change the position so that for a subsequent use not only the opponent must again ascertain his own position but one must oneself again also ascertain the position of the opponent. The smoke producer would, therefore, have a considerable tactical advantage when, during the effective phase of the artifical smoke, he could admittedly camouflage his own actions but, at the same time, could also follow the actions of the opponent and react thereon.
Therefore, the task forming the basis of the invention is to develop a one-sidedly transparent screen smoke.
The known screen smokes usually consist of aerosols of solid and liquid particles, whereby the size of the individual particles lie in the order of magnitude of the wavelength of the radiation to be weakened so that they are suitable for a scattering and absorption of the light.
From U.S. Pat. No. 5,682,010 is known a one-sided camouflage action in the visual range in the case of which such a mist cloud containing an absorbing aerosol is simultaneously produced with an aerosol cloud of particles which do not absorb the light but merely scatter, whereby the absorbing cloud in closer to ones own position and the scattering cloud to that of the opponent. In this way, the light coming from the opponent is less weakened than the light from ones own object observable by the opponent so that, in all, a residual light can be observed sufficient for the ascertainment of the opponent's position. Insofar as both mist clouds mix with one another, the effects for both sides are the same so that the above advantage is lost. It is a disadvantage of this device that the simultaneous production of the two mist clouds at definite intervals from one another and to the discharge and target is difficult and, due to different local wind influences, the mist clouds are also additionally displaced against one another. Therefore, this manner of procedure is not suitable for practical use.
According to DE 196 01 506 A1, a one-sidedly permeable sight barrier is thereby achieved in that one brings to shining a per se transparent artificial mist, consisting of aerosol particles or gases, by radiation with electromagnetic radiation of appropriate wavelength (fluorescence, Raman scattering, diffuse reflection). Since this lighting up is an isotropic effect, i.e. also takes place on the side of the mist producer, a pulsed radiation source is used, the impulse frequency of which is adapted to the period of time of the emission effects.
By means of a closure, the detector of the mist user is shut off during the radiation time go that only electromagnetic radiation is detected in the radiation pauses. The radiation frequency is typically so high that the opponent sees a continuously emitting mist cloud. In order to prevent countermeasures of the opponent, the impulse sequence of the radiation source is modulated by an algorithm not known to the opponent. The disadvantages of this process are, on the one hand, the devices necessary for the laborious, expensive and susceptible exciting and detection process and, on the other hand, the toxicologically hazardous fluorescing substances in the mist cloud necessary for the radiation excitation.
Because of the discussed disadvantages (function of the one-sided vision barrier only in the case of ideal wind conditions not occurring in practice; requirement of a laborious and expensive detection process or presence of toxicologically hazardous substances in the aerosol cloud), neither of the two processes have hitherto been used in practice.
The invention solves the above-described problems in that there is produced a smoke one-sidedly transparent in the infrared spectral range with the features of the main claim. The solution is promoted by the means described in the subsidiary claims.
The producer of this smoke can carry out the detection of the opponent during the effective phase by means of suitable electronic sids (IR camera), whereas the sight not only in the visual but also in the infrared spectral range is removed from the opponent by irradiation of the LOS (line of sight).
The present invention uses a per se known smoke, impenetrable in the visual spectral range (&lgr;=380 nm-780 nm) but transparent in the infrared spectral range (&lgr;=780 nm-14.0 &mgr;m), from an aerosol with particle size of 0.1-5 &mgr;m which contains additionally produced scattered particles of a size of 10 to 100 &mgr;m. This two-component smoke is irradiated with an IR radiation source from the side of the smoke producer.
In
FIG. 1
is to be seen a schematic illustration of the configuration. For both sides, the visual spectral range is covered by the first smoke component
6
. The irradiation with electromagnetic waves in the IR range, which is made available either by a high capacity lamp with appropriate filters or by means of a pyrotechnic radiator
2
, brings about, in the case of the second smoke component, the produced scattered particles
5
, a characteristic forwards scattering
7
of the IR radiation in the direction of the opponent
9
, whereas the scattering back portion of the IR radiation remains negligibly small.
The so resultant irradiation in the direction of the opponent
9
prevents the observation of the smoke producer
1
by means of an IR camera (typical detection wavelengths: 8.0-14.0 &mgr;m), whereas with the IR camera of the smoke producer
3
, the observation of the opponent
9
is possible without problems.
In order to make clear the physical effects of the scattering of the IR radiation on the produced scattered particles
5
or the aerosol particles of the smoke components
6
covering in the visual spectral region, there were calculated radiation diagrams according to Mie's scattered light theory. In contradistinction to the Rayleigh scattering, in the case of knowledge of the optical and geometric properties of the scattered particles (complex refractive index m (&lgr;); size parameter (x), this theory offers exact solutions for isotropic spheroidal scattered particles on any desired size.
Since most observation apparatus work in the wave-length range of 8.0-14.0 &mgr;m, as reference wavelength there was chosen &lgr;=10.0 &mgr;m.
As example for the size-adapted scattering centres, there is used a spheroidal-shaped quartz particle with a radius of r=20 &mgr;m, whereby there is given the size parameter x of 12.57. The wavelength-dependent complex refractive index amounts to m(&lgr;)=2.67-0.05 i for &lgr;=10 &mgr;m. The quartz particle is pr
Dochnahl Axel
Koch Ernst-Christian
Schneider Josef
Foley & Lardner
Nelson Peter A.
Pepete GmbH
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