Radiant energy – Photocells; circuits and apparatus – With circuit for evaluating a web – strand – strip – or sheet
Reexamination Certificate
2001-03-26
2004-01-06
Nguyen, Tu T. (Department: 2877)
Radiant energy
Photocells; circuits and apparatus
With circuit for evaluating a web, strand, strip, or sheet
Reexamination Certificate
active
06674089
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates in general to the detection of trip-wires and in particular to the detection of trip-wires using optical techniques.
The reliable detection of trip-wires has been a problem that has plagued the military research community for some time. Military and law enforcement agencies currently do not have an effective way of detecting simple trip-wires. This problem is exacerbated during combat situations in which meticulous inspection of one's pathway is often not possible. Civilian law enforcement groups, such as the Drug Enforcement Agency (DEA), have reported an increase in so-called “booby-trapped” incidences involving their agents. It is often the case that when an illegal crop is identified, DEA personnel are placed at great risk during the secure phase of an operation in which booby-traps are searched out and disarmed.
A similar problem involves the detection and early warning of power-lines and hanging cables during certain helicopter missions. A particularly troublesome situation encountered by military pilots involves urban night missions in which the probability of a helicopter coming in contact with a power cable or wire is greatly increased.
The state of the art involving the detection of suspended wires and cables can be broken into two classifications, i.e., natural/ambient or active illumination schemes. Both methods are actually adaptations of a much broader application and consequently do not function very effectively. The natural illumination method (favored among most robotic scientists since it is the simplest to implement) involves applying various pattern recognition algorithms (PRAs) to transmitted video imagery from visible cameras mounted on a robot. The PRAs are designed to key in on and identify any “fine-line” structures that are present in the video scene. Unfortunately, this approach must overcome two fundamental problems. First, naturally illuminated 2-D video scenes do not convey the type of information necessary for PRAs to accurately distinguish between common straight edges (e.g., a sharp edge of a tabletop) and suspended wires. As a result, the false-alarm rate is often very high for all but the most simple of scenes. Second, by their very nature, trip-wires are designed to blend into their backgrounds and thus often do not exhibit the necessary contrast needed for PRAs to “key on”.
Active illumination methods (sometimes termed 3-D laser imaging/Doppler) use a pulsed laser to illuminate an extended target by optically scanning out a 2-D area using a particular scan. Coincident sensors are then used to record the position and time delay in the scattered signal. A pseudo image is generated that gives rough dimensions and distance to the illuminated object. Such systems are currently deployed and undergoing evaluation on various military helicopters. These systems are both extremely complex and expensive to deploy. Furthermore, this technique is only effective in identifying targets that have reasonably large extended areas and are inefficient in identifying objects that possess small geometric cross-sections, such as hanging wires or cables.
Both active and passive techniques as outlined above are deficient in their approaches because they cue on features that are not entirely unique to the target of interest, i.e., trip-wires and/or cables.
REFERENCES:
patent: 4902126 (1990-02-01), Koechner
patent: 5594232 (1997-01-01), Giordano
patent: 6064759 (2000-05-01), Buckley et al.
RSTA for Small Roveers in Urban Warfare, Stuart Young, Pete Budulas, Philip Emmerman, Mike Scanlon, Nassy Srour, Dave Hillis, Phil David, Pete Fisher, Steve Vinci, Art Harrison, Kris Gurton, Sam Crow and Mark Wellman.
Clohan, Jr. Paul S.
Nguyen Tu T.
Randolph William
The United States of America as represented by the Secretary of
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