Scientists make underwater revolution, teach drones to see seafloor clearly
Technology from Chinese scientists could unlock the secrets of the ocean (photo: Edward Jenner)
Underwater drones will be able to see the ocean floor more clearly without powerful computers. Scientists have created an acoustic lens that eliminates sonar signal distortion. The new technology could make underwater exploration significantly cheaper, BGR reports.
Why underwater drones see a blurry image
Satellites have now mapped 100 percent of the seafloor, but only at a resolution of about 1.6 kilometers.
Shipborne multibeam sonars can provide detail down to 15 to 50 meters at great depths.
Scientists believe autonomous underwater drones can bring measuring equipment closer to the seafloor, but this creates another obstacle. To protect the equipment and reduce hydrodynamic drag, sonar transducers are placed behind a curved fairing.
The dome's curved shape distorts the wavefront, causing the sound beam to spread and lose power.
Modern electronic beam-correction systems require significant amounts of energy and computing power, which is critical for autonomous devices.
How a new silicone lens works
Chinese scientists calculated the distortion pattern and created a physical lens that corrects the sound wave before it passes through the fairing, similar to how an optical system optimized images for the Hubble Space Telescope.
The lens has several distinctive features:
Material: The lens consists of concentric silicone rings.
Tungsten additives: Each ring contains a different proportion of tungsten microparticles, which changes how fast sound travels through the material.
Customization: The holographic lens can be individually manufactured to match the shape of the dome on a specific underwater vehicle model.
Test results, prospects
Laboratory tests showed the lens narrows the sonar beam from more than 65 degrees to 16–30 degrees.
During field tests on the Jiulong River, the drone detected a submerged plastic sphere at about 1.8 meters deep. Without the lens, the echo signal was completely lost amid environmental reflections, while the new technology reduced interference by 11.98 decibels.
Scientists believe the technology could make it possible to study in detail more than 100,000 underwater mountains taller than 1,000 meters, of which less than 0.1 percent have been studied so far.
The next stage of the research is to test the lens in real seawater.
