Wireless Underwater Camera That Doesn’t Require Batteries
MIT researchers have created a battery-free and wireless underwater camera that could be used for a variety of purposes, including climate prediction. “We are missing data from more than 95 percent of the ocean,” said the researcher. This technology, according to Associate Professor Fadel Adib, may help us develop more accurate climate models and gain a better understanding of how climate change affects the marine environment. Photographer: Adam Glanzman
A brand new underwater camera could help researchers discover previously unexplored areas of the ocean, trace the source of pollution, or monitor the effects of climate change.
Experts estimate that more than 95 percent of the Earth’s oceans have never been discovered. This means we’ve seen less of our planet’s ocean than the far side of the moon or the surface of Mars.
One of the formidable obstacles impeding widespread ocean exploration is the high cost of maintaining electricity for an underwater camera over an extended period of time. To accomplish this task, it is currently necessary to either attach it to a research vessel or dispatch a spacecraft on a regular basis to replenish its batteries.
MIT engineers have taken an important step toward finding a solution to this problem by developing a high-performance camera that does not require batteries and can operate wirelessly underwater. Its energy efficiency is nearly 100,000 times higher than that of other underwater cameras. Even in low-light conditions, such as those found underwater, the device can take color photographs and wirelessly transmit image data.
One of the many features that distinguishes this self-driving camera from other similar devices is that it is powered by sound waves. This is accomplished by converting the mechanical energy carried by sound waves as they travel through water into the electrical energy required to power its imaging and communications equipment. Following image data recording and encoding, the camera uses sound waves to communicate the data to a receiver capable of recreating the image.
Waleed Akbar and Fadel Adib
Because the camera does not require a power supply, it can operate indefinitely until it needs to be retrieved. This would allow scientists to explore previously unexplored areas of the ocean in search of new species. It could also be used to photograph ocean pollution or to monitor the well-being and development of fish raised in aquaculture farms.
“From a purely personal standpoint, one of the most fascinating applications of this camera is in the context of climate monitoring. We are working on climate models, but data for more than 95 percent of the ocean is currently unavailable. “This technology could help us build more accurate climate models and better understand how climate change affects the underwater world,” says Fadel Adib, the system’s senior author. “[T]his technology could aid in the development of more accurate climate models and a better understanding of how climate change affects the underwater world.” He is an associate professor in the Department of Electrical Engineering and Computer Science, in addition to being the director of the Signal Kinetics group at the MIT Media Lab.
Along with Adib, the paper’s co-lead authors are Sayed Saad Afzal, Waleed Akbar, and Osvy Rodriguez, all of whom are research assistants in the Signal Kinetics group, as well as Union Ha, a research scientist, and Mario DoumetDocument and Reza Ghaffarivardavagh, both of whom have previously worked in the group. The research paper was published today, September 26, 2022, in the peer-reviewed journal Nature Communications.
Disposing of one’s batteries
The scientists needed a device that could gather energy underwater on its own while only requiring a negligible amount of electricity in order to build a camera that could function independently for extended periods of time.
The energy is collected using piezoelectric transducers that are attached to the camera’s exterior in various locations. When a mechanical force is applied to piezoelectric materials, the piezoelectric materials generate an electric signal. When the transducers are struck by a sound wave as it travels through the water, they begin to vibrate, converting the mechanical energy they contain into electrical energy.
These sound waves could have come from a variety of sources, including a nearby ship or marine life. The harvested energy is stored in the camera until it has accumulated enough to power the electrical components that take photographs and transmit data.
To keep the power consumption as low as possible, the developers used commercially available ultra-low-power image sensors. These sensors, on the other hand, can only record images in grayscale. They also needed to create a low-power flash because the vast majority of underwater habitats lack any form of illumination.
“We were attempting to use as little hardware as possible, which introduced new constraints on how to build the system, communicate information, and perform image reconstruction. Adib goes on to say that solving this problem required a lot of creativity on his part.
They were able to solve both problems at the same time by using red, green, and blue LEDs. When an image is captured, the camera first illuminates the subject with a red LED before using image sensors to capture the image. The procedure is repeated with blue and green LEDs, respectively.
According to Akbar’s explanation, even though the image appears to be black and white, the red, green, and blue colored light is reflected in the white section of each photograph. After the image data are joined in post-processing to create the composite image, the color image can be rebuilt from the three source images.
When we were younger and taking art classes, we were taught that any color could be created by combining three primary hues. The color visuals we see on our computers are subject to the same set of rules. He claims that color images can be created using only the three channels represented by the colors red, green, and blue.
Information transmission via sound
Underwater backscatter is a technique used to send image data to a receiver in the form of bits (1s and 0s) one at a time. The image data is encoded as bits after it has been recorded. The sound waves are carried through the water by the receiver to the camera, which acts as a mirror to reflect the waves back to the receiver. The camera will either turn its mirror into an absorber to prevent the wave from reflecting to the receiver, or it will reflect the wave to the receiver.
When a signal is reflected from the camera, it is picked up by a hydrophone near the transmitter. If it receives a signal, it is considered a bit 1, and if it does not receive a signal, it is considered a bit 0. This binary information is used by the system during the reconstruction and post-processing of the image.
“This entire process consumes five orders of magnitude less power than standard underwater communications systems,” Afzal claims. “Since it only takes a single switch to switch the gadget from a non-reflective to a reflective state,” he continues, “it only takes a single switch.”
The camera was tested in a variety of submerged scenarios by the researchers. One of the experiments involved taking color photographs of plastic bottles floating in a pond in New Hampshire. They were also able to take photographs of an African starfish that were so clear that the minuscule tubercles that ran along its limbs were clearly visible. The device was also successful in tracking the progress of the aquatic plant Aponogeton ulvaceus over a week in a dark environment.
Since the engineers have successfully demonstrated a functional prototype, the next step will be to improve the device so that it can be used in more realistic conditions. They hope to expand the camera’s memory so that it can take real-time photos, stream images, and even record video while submerged in water.
Another goal is to increase the camera’s field of view. They were able to successfully send data from a distance of 40 meters (130 feet) from the receiver, but increasing that range would allow the camera to be used in more underwater situations.
“This will open up a lot of wonderful prospects for study both in low-power Internet of Things devices as well as underwater monitoring and research,” says Haitham Al-Hassanieh.He is an assistant professor of electrical and computer engineering at the University of Illinois in Urbana-Champaign, but he played no role in this study.
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