The laser is an integrated part of many weapon systems, such as laser guided bombs, laser guided missiles and laser
beam-riding missiles. These systems pose a significant threat to military assets on the modern battlefield. The lasers
used in beam-riding missiles are particularly hard to detect as they typically use relatively low power lasers. Beamriders
are also particularly difficult to defeat as current countermeasure systems have not been optimized against this threat.
Some recent field trails conducted in the United Arab Emirates desert have demonstrated poor performance of both laser
beam-riding systems and the LWRs designed to detect them. The aim of this research is to build a complete evaluation
tool capable of assessing all the phases of an engagement of a main battle tank or armoured fighting vehicle with a laser
based guided weapon. To this end a software model has been produced using Matlab & Simulink. This complete model
has been verified using lab based experimentation and by comparison to the result of the mentioned field trials. This
project will enable both the evaluation and design of any generic laser warning receiver or missile seeker and specific
systems if various parameters are known. Moreover, this model will be used as a guide to the development of reliable
countermeasures for laser beam-riding missiles.
The manoeuvreist doctrine requires that commanders have the freedom to move around the battlespace to locations where they can best influence the outcome. To achieve this, commanders must be secure in the knowledge that they can do so undetected. Infrared (IR) sensors, with ever increasing sensitivity, are now well established in the land environment, IR signature management is therefore becoming evermore necessary for battlefield equipment. High-fidelity thermal signature models are available but require high levels of operator expertise, detailed input data, and they are time consuming to run. A simple, easy to use thermal signature model would provide a ready alternative to the more exacting complex models. Whilst not attempting to replace the high-fidelity models for the detailed analysis of thermal signatures, a simple model would have utility as a first filter of trials data and the initial testing of signature reduction concepts. A single temperature difference model of a Main Battle Tank (MBT), incorporating the emissive and reflective components of its thermal signature, is presented. This model is used as the input into a Minimum Resolvable Temperature Difference (MRTD) model for a generic thermal imaging tank sight which is used to predict the detection ranges of the MBT. The reduction in detection range afforded by emissivity variations is calculated and demonstrates the potential benefits and difficulties of this signature management procedure.
The diffuse and specular reflections of four representative scatterable anti-personnel landmines have been measured in the UV, visible and IR regions of the electromagnetic spectrum. These results are presented here and are compared to potential backgrounds in which such anti-personnel mines are likely to be sown.
The purpose of this work is to compare thin films of vanadium dioxide (VO2) produced via a sol-gel process and a reactive sputtering technique. The sol-gel process used was based on vanadium oxide triisopropoxide precursor. This was converted to soli n dried ethanol by adding water, and the substrates were then dip coated with a controlled draw method in an inert atmosphere. After drying this was followed by a final reduction stage in a low oxygen partial pressure atmosphere. The reactive sputtering technique used carefully controlled deposition rates from a vanadium metal target in argon/oxygen atmosphere to ensure correct stoichiometry. The films were deposited on silicon substrates and were tested optically and electrically above the below the transition temperature. Results of transmission and reflectivity in the IR region of the spectrum, and electrical conductivity are presented. The results show that the sol-gel technique provides a viable alternative method to sputtering for the production of thin films of vanadium dioxide.
Vanadium dioxide undergoes a semiconductor to metal phase transition at approximately 68 degrees C which is accompanied by a marked change in material conductivity and an associated change in optical properties. In order to fabricate devices, which utilize this change of optical property in the IR region of the spectrum, the design engineer requires reliable optical data. High quality vanadium dioxide films have been produced by a reactive magnetron sputtering technique from a vanadium target in an atmosphere of controlled oxygen content. A UHV system was used to ensure very low impurity level sin the deposited films. Quartz crystal monitoring allowed rigorous and reproducible control of film stoichiometry. Various thickness layers of vanadium dioxide were deposited on high optical quality IR transmitting substrates. The optical properties of these films have been determined in both the semiconducting and metallic states. Measurements were made of transmission and specular reflectance using various spectrophotometers. From these measurements n and k and absorption coefficient values were evaluated. These result are reported and compared with the previously published values given for bulk vanadium dioxide. These comparisons show excellent agreement and hence confirm the films are monocrystalline in nature as indicated by x-ray diffraction results.
An IR reflective optical modulator has been fabricated. This has been achieved by coating a thick film resistor network with a thin film of vanadium dioxide via a reactive sputtering process. Vanadium dioxide undergoes a semiconductor to metal phase transition at approximately 68 degrees C, therefore to switch the reflective optical modulator the thick film resistors in the network are driven electrically. As the resistors heat up to beyond the transition temperature, the vanadium dioxide undergoes its transition from a transparent semiconductor state to a highly reflective metallic state. Provided the thick film heater network, underneath the vanadium dioxide, is non- reflective, then a significant change in reflectivity is observed upon undergoing the transition, and hence the modulation of reflected IR radiation is achieved. The useful waveband of operation of the device encompasses the region 2-25 micrometers , this is primarily limited by the transparency of the semiconductor state of the vanadium dioxide. Correct stoichiometry of the thin film of vanadium dioxide is critical in producing good modulation depth in the reflective mode. Several devices have been fabricated and tested. They show a reflectivity increase of approximately 13:1 upon switching. The devices to date have demonstrated switch on speeds of 0.1 s and switch off speeds of 0.2 s. This has been achieved without any form of substrate temperature control apart from that produced by the electrical drive. Very slight changes in the stoichiometry of the vanadium dioxide thin film can greatly increase the temperature range and hysteresis of the semiconductor to metal phase transition. This has been utilized to allow partial phase transitions to occur, yielding partial increases in reflectivity, and hence the ability to generate grey levels in the reflected IR radiation.