Artificial test eyes have been developed for a multimodal ophthalmic imaging platform. The test eyes can be used for alignment of different imaging modalities and for fluorescence channel performance testing. Different scattering and absorption characteristics can be realized in the artificial retina.
IR decoys can be an effective countermeasure against IR guided anti ship missiles. However, it's not so easy to determine how the decoys should be deployed to get maximum effectiveness. A limitation of trials is that results are obtained for the specific trial condition only. Software tools have been developed to solve these problems. One solution uses recorded IR imagery from a decoy deployment trial, while the other solution generates IR imagery and is thus independent of trials. In the first solution, a combination of hardware and software is used that allows recording of a scene with an infrared camera, and simulating a missile seeker. A pre-processing algorithm corrects the recorded images before they are fed into the seeker algorithm of the simulated missile. To perform this correction the pre-processing uses the speed, distance to the target and field of view of the IR camera as fixed parameters and the speed and starting distance of the simulated missile as variable parameters. Modtran and the Navy Aerosol Model are used to calculate the atmospheric transmission effects in the pre-processing. The second solution generates artificial IR images that are subsequently fed into the seeker algorithm. This solution also allows variation of those parameters that are fixed when recorded IR imagery is used. Examples are among others: the signature of the target ship, the orientation, size and speed of the target ship, the type of decoy, the timing of the decoy sequence, atmospheric conditions etc. With these tools the effectiveness of decoy deployment in various scenarios can be evaluated.
This paper describes the development and implementation of a low cost
camera system that uses polarisation features of visible light for
faster area reduction. The camera system will be mounted on a
mechanical minefield area reduction asset, namely an AT mine roller of
The HALO Trust. The automatic detection system will give an audible
alarm in order to stop the AT mine roller before the rollers detonate a mine.
This paper gives a comparison of two vehicle-mounted infrared
systems for landmine detection. The first system is a down-ward looking standard infrared camera using processing methods developed within the EU project LOTUS. The second system is using a forward-looking polarimetric infrared camera. Feature-based classification is used for this system. With these systems data have been acquired simultaneously of different test lanes from a moving platform. The performance of each system is evaluated using a leave-one-out method. On the training set the polarimetric infrared system performs better especially for low false alarm rates. On the independent evaluation set the differences are much smaller. On the ferruginous soil test lane the down-ward looking system performs better at certain points whereas on the grass test lane the forward-looking system performs better at certain points.
Polarimetric scattering models are developed to predict the detectability of surface-laid landmines. A specular polarimetric model works well only under the condition that there is either no sunlight or the sun is not close to the specular reflection direction. Moreover, this model does not give insight why certain man-made objects like landmines give a higher polarimetric signature than natural background. By introducing a polarimetric bidirectional reflectance distribution function (BRDF) the specular model is extended. This new model gives a better prediction of the polarimetric signature and gives a close match to the measurements of landmines with different casings as well as the sand background. The model parameters indicate that the landmines have a lower surface roughness and a higher refractive index, which is the reason why these objects are detectable from the background based on their polarimetric signature.
A specular model has been used to predict the passive polarimetric infrared (IR) signature of surface-laid landmines. The signature depends on the temperature of the landmine and the sky radiance. The temperature of the landmine is measured using a thermocouple. The signature itself is measured using a polarimetric IR camera setup. The predictions are fit to the measurements using the refractive index as an optimization parameter. The obtained refractive indices of each landmine type are consistent, but for the PMN landmine much lower than determined in a previous indoor experiment. Throughout the measurement day, the average landmine polarimetric signature was higher than the average background signature. Moreover the polarimetric signature appears to be a more robust indicator of the shape of the landmine's top surface than the normal IR signature. A simulator of passive polarimetric imagery is also being developed. That work is based on a physical model for both the thermal and radiometric processes, and it includes a finite-element solution for the heat transfer problem, ray tracing to describe the incident sunlight and the effects of shadowing, and analytical models for the Mueller matrices of rough dielectric surfaces. Preliminary results from that model show substantial qualitative agreement with measured images.
The advent of low-observable (stealth) ships, of which the new Air Defense and Command Frigate (LCF) is an example, must be followed by an increased interest in signature control during operations. Taking full operational advantage of the stealth character of low-observable ships requires on-board signature control. At all times, the ship's visibility for expected threats must be known. This paper presents an active infrared-signature control system, that will be used on board the LCF. The system is the first step towards a full signature management system, which takes into account all systems affecting the signature during operations. Such a system should not only consider electro- optical signatures, but all relevant signatures: radar, acoustic, magnetic, etc.
An evaluation tool for the effectiveness of infrared decoys against anti-ship missiles has been built. In a flexible software setup, different methods of preprocessing and detection can be chosen for the processing of recorded infrared image sequences. Since a flying missile seeker with a variable speed and variable starting distance is simulated, the recorded images, from a static camera or a camera moving at relatively low speed, are corrected before they are fed into the seeker algorithm of the simulated missile. MODTRAN and the Naval Aerosol Model are used to calculate the atmospheric transmission effects in the preprocessing. The hot spot seeker algorithm uses features such as contrast and position above or below the horizon to differentiate between ship, infrared decoys and false alarms resulting from clutter. During the simulation the track window of the seeker is visualized on the recorded images. The aim point of the missile during the flight is logged in a file to enable evaluation. With this tool the effectiveness of a recorded decoy deployment in various scenarios can be evaluated by varying the missile parameters such as distance between missile and ship when the first decoy is deployed, missile search algorithm, and missile track algorithm.
Linear polarization of Thermal InfraRed (TIR) radiation occurs whenever radiation is reflected or emitted from a smooth surface (such as the top of a landmine) and observed from a grazing angle. The background (soil and vegetation) is generally much rougher and therefore has less pronounced linear polarized radiation. This difference in polarization can be used to enhanced detection of land mines using TIR cameras. A measurement setup is constructed for measurement of polarized TIR images. This setup contains a rotating polarization filter which rotates synchronously with the frame sync of the camera. Either a Long wave InfraRed (LWIR) or a Mid Wave InfaRed (MWIR) camera can be mounted behind the rotating polarization filter. The synchronisation allows a sequence of images to be taken with a predefined constant angle of rotation between the images. Out of this image sequence three independent Stokes images are calculated, consisting of the unpolarized part, the vertical/horizontal polarizations and the two diagonal polarizations. An initial model is developed that describes the polarization due to reflection of and emission from a smooth surface. This model predicts the linear polarization for a landmine `illuminated' by a source that is either hotter or cooler than the surface of the landmine. The measurement setup is used indoors to validate the model. The measurements agree well with the model predictions.
The infrared (IR) radiation emitted or reflected in an off- normal direction from a smooth surface is partially polarized. This principle can be used for enhanced discrimination of targets from backgrounds in a marine environment. It has been shown that (man-made) targets do not demonstrate a pronounced polarization effect when observed from near normal direction whereas the sea background radiation has a certain degree of polarization in slant observation path. A measurement setup has been constructed for collecting polarized IR imagery. This setup contains a rotating polarization filter that rotates synchronously with the frame sync of the camera. Either a long wave IR (LWIR) or a mid wave IR (MWIR) camera can be mounted behind the rotating polarization filter. The synchronization allows a sequence of images to be taken with a predefined constant angle of rotation between the images. Out of this image sequence three independent Stokes images are constructed, containing the normal intensity part, the vertical/horizontal polarization and the diagonal polarization. Up to 20 full linearly polarized images can be acquired per second. Measurements are taken at the North Sea coast with this setup. The recorded images are analyzed to determine the influence of polarization on the detection of small targets in such an environment. Furthermore differences between polarization contrasts in MWIR are analyzed.
In this paper the landmine detection performance of an IR and a visual light camera both equipped with a polarization filter are compared with the detection performance of these cameras without polarization filters. Sequences of images have been recorded with a rotating polarization filter in front of the cameras.
In the framework of the Dutch government humanitarian demining project 'HOM-2000', an outdoor test facility has been realized to test, improve and develop detection equipment for land mines. This sophisticated facility, allows us to access and compare the performance of the individual and of a combination of different sensor against a variety of threats. The test facility entails six test lanes of 30 square meters each, filled with different types of soil. The groundwater level of the lanes can be regulated separately and the temperature of the soil and of the st miens is monitored. A moveable measurement platform has been realized which is completely free of electrically conducting materials. With this platform the individual or fused detection system can be moved automatically over the whole test site with an accuracy of one centimeter in every direction. Test mines and mine-like objects have been placed in the lanes. The set of test mines contains nine different types of both anti personnel and anti tank mines, low metal content and non-metal mines. To simulate the high explosives, the test mines have been filled with a silicone rubber.