Over the last decade, polarimetric imaging technologies have undergone significant advancements that have led to the development of small, low-power polarimetric cameras capable of meeting current airborne ISR mission requirements. In this paper, we describe the design and development of a compact, real-time, infrared imaging polarimeter, provide preliminary results demonstrating the enhanced contrast possible with such a system, and discuss ways in which this technology can be integrated with existing manned and unmanned airborne platforms.
Previously, we have investigated the use of Long-Wave Infra-Red (LWIR) polarimetric imaging for the detection of
surface swimmers in a maritime environment. While better contrast and longer range are expected with Mid-Wave
Infra-Red (MWIR) polarimetric imaging, the cost of such a system is higher than a polarimetric imager operating in the
LWIR due to the advent of higher-performance micro-bolometer imaging arrays. The actual performance of a MWIR
polarimetric imager to detect a person in the water is presented. A comparative analysis of system cost between MWIR
and LWIR systems is also discussed.
Previously, we have investigated the use of Long-Wave Infra-Red (LWIR) polarimetric imaging for the detection of surface swimmers in a maritime environment. While better contrast and longer range are expected with Mid-Wave Infra-Red (MWIR) polarimetric imaging, the cost of such a system is higher than a polarimetric imager operating in the LWIR due to the advent of higher-performance micro-bolometer imaging arrays. The actual performance of a MWIR polarimetric imager to detect a person in the water is presented. A comparative analysis of system cost between MWIR and LWIR systems is also discussed.
Data from a recent "first-look" at using Long Wave InfraRed Imaging Polarimetry (LWIR-IP) to detect surface swimmers is presented and discussed. A significant increase in detection SNR over conventional IR imaging techniques was discovered. The physical phenomena that produces the increased SNR is discussed along with data that shows range effects and their degradation on the SNR. Most significantly, a method to classify the detected object using the same dataset is discussed. Augmenting current swimmer detection systems using this technique will likely significantly decrease the false alarm rates of the system, thus saving manpower resources and preserving force readiness.
Data from a recent “first-look” at using Long Wave InfraRed Imaging Polarimetry (LWIR-IP) to detect surface swimmers is presented and discussed. A significant increase in detection SNR over conventional IR imaging techniques was discovered. The physical phenomena that produces the increased SNR is discussed along with data that shows range effects and their degradation on the SNR. Most significantly, a method to classify the detected object using the same dataset is discussed. Augmenting current swimmer detection systems using this technique will likely significantly decrease the false alarm rates of the system, thus saving manpower resources and preserving force readiness.
A Pulse Coupled Neural Network (PCNN) has been developed in order to segment image data to reduce the amount of downstream processing. This paper discusses the results of applying the PCNN algorithm to data generated by various sensor platforms. The PCNN algorithm was applied to data generated by a Long Wave Infrared Imaging Polarimeter. The PCNN correctly identified the concealed vehicles and the disturbed earth and rejected 96% of the remaining pixels because they had no information content. Next, the results of applying the PCNN algorithm to noisy infrared seeker data are presented. The PCNN correctly idnetified the target even though the background was quite noisy. Finally, the PCNN algorith was applied to images containing solar glint. It correctly passed only 3& of the pixels to the downstream target/glint decision algorithm. To obtain maximum data throughput, the PCNN can be implemented in hardware.
Adaptive optics systems are used to maintain an optical system at its optimum performance through real time corrections of a wavefront. Deformable mirrors have traditionally been relatively large, expensive devices, suitable for systems such as large telescopes. The objective of the present work is to expand the range of systems that can employ adaptive optics by developing a small, low-cost MEMS deformable mirror. This deformable mirror uses a continuous membrane and has 61 actuators arranged in to approximate a circular pattern. Each actuator has an associated spring suspension, allowing it to push as well as pull on the membrane, producing locally convex or concave curvature. The folded springs are positioned so as to maximize the lateral stability. Maximum actuator displacement is six microns at less than 200 volts. The actuator resonant frequency, is greater than 10 kHz, allowing high-frequency updates of the mirror shape. To operate at high speed, the device must be sealed in a low-pressure environment. Each microactuator uses a vertical comb drive to achieve large travel at a reasonable voltage. The continuous membranes are made of silicon or silicon nitride. Both the actuator and membrane are fabricated with bulk micromachine process technologies. The design targets laser based communication specifications and medical imaging applications.
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