NCJ Number
178564
Date Published
February 1999
Length
24 pages
Annotation
Several working models of a handheld, battery-operated prototype of a remote concealed-weapons detector have been built and tested; this weapons detector will enable police and security personnel to detect metallic and nonmetallic weapons concealed beneath clothing in a person from beyond arm's length to a distance of about 20 feet.
Abstract
The detector transmits narrow ultrasound pulses and detects the ultrasound glints reflected off hard surfaces beneath clothing. These detectors can be used for hands-off, stand-off frisking of suspects for metallic and nonmetallic weapons. They can also be used to search for metallic and nonmetallic weapons on cooperative persons at courthouse entrances and other monitored security portals. The detector can image weapons and not just detect them, at ranges up to 15 feet, using the same ultrasound frequency of 40 kHz used by commercial rangefinders. The concealed-weapons detector operates in a way similar to that of a rangefinder, but at higher peak fluxes and pulse repetition frequencies. The detector alerts the user to concealed weapons audibly and visibly by detecting ultrasound glints above a body/clothing baseline and by compensating for changing range and attenuation. The detector locates concealed weapons within a 6-inch illuminated spot at 10 feet. The signal processor eliminates any signal from beyond the target. Figures and appended progress report from 1997