This work presents a newly constructed setup for laser damage assessment at FOI, Sweden. The laboratory-based system is built around a 2 kW single mode fiber laser. The design, characterisation and performance of the system will be discussed. Initial studies on various fiber-reinforced plastics are presented. The time-to-penetration of different test-coupons is compared to analytical models and the range of applicability of these simple models will be discussed. Finally, laser damage studies on a hobby UAV will be shown.
Detecting and identifying objects inside a forest edge on the other side of an open field is an important task in defence and security applications. This can be difficult to achieve with passive imaging sensors because of the partial obscuration by the foliage. High-resolution 3D imaging enables separation of hidden objects from branches and leaves and can provide data for detection, recognition, and identification of partly occluded targets. We use a photon counting lidar system with panoramic scanning to produce high quality 3D data for this task. The FOI system is built around the Princeton Lightwave Inc. (PLI) Falcon detector which is a 32×128 pixel array of InGaAs Geiger-mode avalanche photodiodes. The system operates at 1557 nm and has been designed for suitable resolution at standoff ranges of 1 to 2 km. In this paper, we investigate the detection capability when combining measurements from multiple measurement positions. A field trial has been performed where data from the same scene was collected from different sensor positions. The system was mounted on a car and moved between different positions along a road. The measurements were performed first without and then with vehicles in the target area. The distance to the forest edge varied between from approximately 1.0 to 1.5 km, and the difference of the angle of incidence was approximately 45 degrees from the outer positions along the road. To merge the data from the different positions we apply registration of the data sets using derived point clouds to transform all data into a common coordinate system. Data from the different sensor positions is analyzed by overlaying the derived point clouds from the different positions. We compare data from different viewpoints to data from only one viewpoint. The results show that the combined point clouds from multiples positions covers more of scene than from a single position. We also perform change detection using registered point clouds from the same measurement positions. In the change detection we found the changes we had introduced (vehicles and equipment).
The ability to detect optics is important for military surveillance, and allows early threat detection. Present-day optics detection systems are exploiting that focusing optics are retro-reflective. Hence, it is possible to discover threats, including riflescopes, electro-optical sensors, and magnifying optical assemblies used for weapon guidance, by illuminating them with a laser. However, the sensors have performance limitations and do not usually provide range information about the target. This work suggests a scanning optics detection system that uses a linear array of avalanche photo diodes (APD) with high sensitivity providing information about the target range and angular location. An experimental system using four pixels of a 16×1 linear APD array was constructed and tested against reference targets outdoors. The receiver assembly consisted of a micro-lens array, focusing optics, bandpass filter, and pre-amplifier circuit. The system also contained a pulsed NIR-laser, motorized pan-tilt stages for the scanning, and a calibrated scene camera to measure the background signal. It was possible to detect reference targets at over kilometre range while distinguishing the background, using dedicated signal analysis and noise reduction. The suggested scheme definitely benefit in long-range performance compared to similar techniques that use CCD/CMOS-sensors. The drawback using an APD array lies in reduced angular resolution and increased complexity of data acquisition electronics. In addition, the experimental results will be discussed in terms of a performance model, influence from turbulence effects and suggestions for future sensor improvements.
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