Acoustic eye that works in the murk

时间:2019-03-07 08:12:01166网络整理admin

By Charles Seife A CAMERA that lets divers see through the murkiest of waters is being developed by a subsidiary of the aerospace company Lockheed Martin. It uses ultrasound rather than light to produce still or moving images of its surroundings even when divers can’t see their hand in front of their face. Its inventors say it would be ideal for underwater mine clearance and similar tasks. Just as we see an object by detecting the light waves reflected from it, acoustic cameras “see” an object underwater by bouncing sound waves off it. Conventional sonar, which uses ordinary sound waves to work out the direction and distance to an object, can only achieve very low resolution. The new acoustic camera—dubbed Sonocam—uses ultrasound, and can make out details on the surface of any object in its sights. This will be useful in shallow, muddy waters when a diver is looking for something like a mine or a crashed aircraft’s recorders. “With light, there’s no useful range, because the waters tend to be very murky,” says Tim White, an engineer at the Sanders company of Nashua, New Hampshire, a division of Lockheed Martin. “With sonars, you don’t get the resolution.” White and his colleagues plan to make their acoustic camera small enough for a diver to hold in his or her hands. They have tested components operating at two ultrasonic frequencies: 1 megahertz gives a coarse picture up to a range of about 50 metres, while 3 megahertz gives a fine picture—with a resolution of about 1 centimetre—at distances up to 10 metres. Michael Buckingham, a physicist at the Scripps Institution of Oceanography in La Jolla, California, believes a hand-held acoustic camera would be useful. “There are a number of applications out there,” he says. “The optical visibility can be almost zero,