![]() The new volumetric-display technique was reported in Nature on Wednesday. The same principle enables a visual trick often seen on the Fourth of July, when the glowing head of a sparkler appears to trace golden outlines as one moves it through the night air. This phenomenon is known as persistence of vision. Thanks to its high speed-the particle can zip vertically at almost nine meters per second and horizontally at nearly four-the glowing dot fools the human eye into perceiving a continuous image. “We illuminate that levitated particle using RGB LEDs-red, green, blue-so we can control the color of the scattering light,” Hirayama says. ![]() These speakers emit patterns of sound waves in the ultrasonic range-too high for the human ear to pick up-which sets up vibrations in the air that manipulate a plastic sphere slightly smaller than a sesame seed.Īs the bead flies around in programmed patterns, the researchers project changing colors onto it. It looks like a 10-centimeter box with open sides and a top and bottom that consist of arrays of tiny speakers (512 in all). Hirayama and his colleagues produced their own floating images with a system they call a multimodal acoustic trap display (MATD). ![]() “I like the Star Wars thing,” says study co-author Ryuji Hirayama, a research fellow at the University of Sussex in England. Picture it like the message R2-D2 carries from Princess Leia in a very famous film. This type of display is called volumetric: Unlike holographic technology, it can create an image without requiring a screen, and it can be viewed from all sides. Credit: Eimontas Jankauskis University of Sussex Fast-moving dot can trick the human eye into seeing a figure eight or a smiley face. Some researchers believe this improvement could lead to applications such as mixing or sorting grains of powder, performing small chemical reactions in isolation, contributing to novel 3-D printing methods-or creating displays that would be visible from any angle. The technology has gained greater capabilities in the past decade, allowing acoustic systems to push and pull small particles around like sonic tractor beams. Since the 1940s, scientists have toyed with the concept of acoustic levitation, the use of soundwave vibrations to trap tiny objects in midair. Researchers have harnessed acoustic waves to produce levitating three-dimensional images, create a sensation of touch and even supply a soundtrack. Multiple passive sonar devices may allow for triangulation of a sound source.To move visual technology into the future, sometimes it helps to make a little noise. Passive sonar cannot measure the range of an object unless it is used in conjunction with other passive listening devices. Rather, it only detects sound waves coming towards it. Unlike active sonar, passive sonar does not emit its own signal, which is an advantage for military vessels that do not want to be found or for scientific missions that concentrate on quietly “listening” to the ocean. Passive sonar systems are used primarily to detect noise from marine objects (such as submarines or ships) and marine animals like whales. ![]() By determining the time between the emission of the sound pulse and its reception, the transducer can determine the range and orientation of the object. If the transducer is equipped with the ability to receive signals, it measures the strength of the signal. If an object is in the path of the sound pulse, the sound bounces off the object and returns an “echo” to the sonar transducer. Active SonarĪctive sonar transducers emit an acoustic signal or pulse of sound into the water. There are two types of sonar-active and passive. NOAA scientists primarily use sonar to develop nautical charts, locate underwater hazards to navigation, search for and map objects on the seafloor such as shipwrecks, and map the seafloor itself. Sonar, short for Sound Navigation and Ranging, is helpful for exploring and mapping the ocean because sound waves travel farther in the water than do radar and light waves. ![]()
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