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Engineers at the Massachusetts Institute of Technology have built a battery-free wireless underwater camera that can help scientists explore unknown areas of the ocean, track pollution or monitor the effects of climate change.

Engineers at the Massachusetts Institute of Technology have built a wireless, battery-free underwater camera that collects energy on its own while consuming very little power, according to a new paper published in the journal Nature Communications.

The system can take color photographs of long-range underwater objects-even in dark environments-and transmit data wirelessly to monitor the underwater environment in real time, helping to discover new rare species or monitor ocean currents, pollution or commercial and military operations.

We already have a variety of underwater image shooting methods for battery-free wireless underwater cameras, but according to the researchers, "most oceans and marine life have not been observed. This is because most of the existing underwater image shooting methods need to be connected to ships, underwater drones or power plants for power and communications."

Methods that do not use network sharing must contain battery power, which limits their life. Although in principle it is possible to collect energy from waves, underwater currents and even sunlight, adding the necessary equipment can lead to heavier and more expensive underwater cameras.

As a result, the MIT team set out to develop a solution for battery-free wireless imaging. The design goal is to minimize the amount of hardware required. They also want to keep power consumption to a minimum, so they use cheap off-the-shelf imaging sensors.

But this sensor only produces grayscale images. The team also needs to develop a low-power flash because most underwater environments don't have much natural light.

An overview of the working principle of the underwater backscatter imaging system has proved that the solutions to these two challenges combine red, green and blue LED. The camera uses a red LED for in-situ lighting, captures the image with its sensor, and then repeats the process using green and blue LED.

According to the author, the image may look black and white, but the light from the three colors from LED is reflected to the white part of each image. Therefore, the full color image can be reconstructed in the post-processing process.

"when we were young in art class, the teacher taught us that we could use three basic colors to make all colors," said co-author Fadel Adib. "for the color images we see on the computer, follow the same rule: we only need red, green and blue channels to build color images."

After the image data is encoded into bits, the sensor relies on piezoelectric acoustic backscattering for ultra-low power communication, rather than the battery. Instead of generating its own acoustic signals (such as sonar), this method relies on modulating the reflection of incident underwater sound to transmit one data at a time.

The data is picked up by a remote receiver capable of restoring the modulation mode, and then the binary information is used to reconstruct the image. The researchers estimate that their underwater cameras are about 100000 times more energy efficient than similar cameras and can run for weeks.

Of course, the team built a proof-of-concept prototype and conducted some tests to prove that their approach was effective. For example, they took images of pollution (in the form of plastic bottles) at Cather Pond (Keser Pond) in southeastern New Hampshire and African starfish (Protoist Linckley) in a "controlled environment with external lighting". The latter image has enough resolution to capture various nodules on the five arms of the starfish.

Using sample images obtained from underwater backscatter imaging, the team was also able to use their underwater wireless cameras to monitor the growth of aquatic plants (Aponogeton ulvaceus) in a few days and to detect and locate visual tags commonly used for underwater tracking and robot operations. The camera achieves high detection rate and high positioning accuracy, with a distance of about 3.5 meters (about 11 feet and a half). The researchers believe that a longer detection range can be achieved by using higher resolution sensors. Distance is also a factor in the camera's energy collection and communication capabilities, according to tests conducted in Charles River in eastern Massachusetts. As expected, both key capabilities decrease as distance decreases, although the camera successfully transmits data 40 meters (131 feet) from the receiver.

In short, "the cordless, cheap and fully integrated nature of our approach makes it an ideal method for large-scale marine deployment," the authors write. Expanding their methods requires more complex and efficient transducers, as well as higher-power underwater acoustic transmission. People can also use the existing buoy mesh network on the ocean surface or underwater robot networks such as Argo buoys to provide remote power for energy collection cameras.

"personally, one of the most exciting applications of this camera is in the context of climate monitoring," Adib said. "We are building climate models, but we lack data from more than 95 per cent of the oceans. This technology can help us build more accurate climate models and better understand how climate change affects the undersea world.

The information provided in this article is for general guidance and information purposes only, and the content of this article should not be regarded as investment, business, legal or tax advice under any circumstances. This article comes from the official account of Wechat: new Research (ID:chuxinyanjiu), author: JENNIFER OUELLETTE, Source: Medium, compiled by Liu Tangshi

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