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13 May 2008 Lidar for obstacle detection during helicopter landing
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Helicopter pilots in military and civilian operations need visual assistance for safe flight and landing under adverse conditions, especially during white-out condition or brown-out condition, in which it is difficult for a pilot to see obstacles or ground through snow or dust generated by the helicopter's rotorwash. There have been intensive efforts to develop a sensor that can detect obstacles or ground inside aerosols in recent years. LIDAR can use the gating function of timing discrimination to suppress the effect of scattering from aerosols, it can generally "see" farther than passive sensors such as human eyes and cameras inside aerosols. The challenge of using a LIDAR under aerosol conditions is not only the requirement of high laser power for penetrating aerosols, but also the requirement of high detection dynamic range and the suppression of aerosol scattering in front of a LIDAR. Neptec's Obscurant Penetrating Autosynchronous LIDAR (OPAL) uses an autosynchronized optical design, which utilizes a triangulation relationship to control the amount of return beam accepted by the TOF (time-of-flight) receiver as a function of target range. The design also maintains this property during high-speed optical scanning. As a result, OPAL can suppress the return signals from nearby aerosol scattering and, at the same time, have a sensitivity and dynamic range to detect obstacles or ground inside aerosol. Neptec has conducted experiments to study the effect of atmospheric aerosol scattering on LIDAR, FLIR and human vision by using a propagation and aerosol evaluation corridor. Neptec has also carried out flight tests of a prototype of OPAL on a NRC Bell 412 helicopter. In this paper, the concept of the OPAL that is uniquely designed to penetrate aerosols will be described and its applications in helicopter landing will be discussed.
© (2008) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
X. Zhu, P. Church, and M. Labrie "Lidar for obstacle detection during helicopter landing", Proc. SPIE 6950, Laser Radar Technology and Applications XIII, 69500T (13 May 2008);

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