The oceans cover an area of more than 360 million square kilometers of the Earth’s surface of 510 million square kilometers. Despite the vast area covered by these massive flats, more than 95% of the ocean area has yet to be explored.
Underwater photography is a key to understanding marine environments and revealing their diversity. Imaging makes it possible to discover new marine species, understand the impact of climate change, global food production, and even aquaculture, the world’s fastest growing food sector.
Despite the advancement of imaging techniques in general, there is a major obstacle to underwater photography and observation. Existing cameras must be attached to either ships or drones, as they consume a lot of energy, require constant batteries to be changed, and must also be pulled out to empty their content. These are things that would make it difficult to photograph and monitor underwater.
The high cost of operating an underwater camera for an extended period, by attaching it to a research vessel or sending a ship to recharge its batteries, presents a formidable challenge preventing large-scale undersea exploration.
However, researchers at the Massachusetts Institute of Technology in the United States were able to overcome these obstacles by designing a new camera without a battery, and can transmit images wirelessly.
The scientific team led by the Lebanese researcher at the Massachusetts Institute of Technology, Fadel Adib, was able to design this camera and test it in marine environments at a low cost of no more than $100, according to what Adib said in exclusive statements to Al-Sharq.
According to a scientific paper published in the journal Nature Communications, the new camera works by harvesting sound waves. That is, it converts mechanical energy from sound waves traveling through the water into electrical energy that powers its imaging and communications equipment.
After capturing and encoding the image data, the camera also uses sound waves to transmit the data to a receiver that reconstructs the image.
Adeeb told Al-Sharq that the camera consumes about 100,000 times less energy than a mobile phone camera. It can also capture color photos even in dark underwater environments.
Because it doesn’t require an external power source, the camera can run for weeks on end before it can be retrieved, allowing scientists to search remote parts of the ocean for new species.
The camera can also be used to take pictures of ocean pollution or monitor the health and growth of fish raised in aquaculture farms.
One of the most exciting applications of this camera comes in the context of climate monitoring. When scientists build climate models, there is no data from more than 95% of the ocean.
In his interview with Al-Sharq, Adeeb explained: “This technology can help us build more accurate climate models and a better understanding of how climate change affects the underwater world.”
To design such a camera that would operate independently for long periods of time, the researchers needed a device that could harvest energy underwater on its own.
So, the researchers designed a transducer of piezoelectric materials, which are materials capable of generating electrical potential when subjected to mechanical force.
How does the wireless camera work?
In the case of the newly designed camera, when a sound wave hits the transducer, the particles of the piezoelectric material vibrate, converting that mechanical energy into electrical energy. Sound waves are generated in marine environments from many sources, such as transiting ships or marine life.
This process results in the generation of a very small amount of energy. “Here comes the big challenge. The cameras need a lot of energy to operate them,” Adeeb says. Even with the harvested energy stored inside the transformer, the amount is still very small.
So, to keep power consumption as low as possible, the researchers used imaging sensors that were specifically designed for ultra-low power use.
But those sensors only capture grayscale images. Since most underwater environments lack a light source, the researchers also needed to develop a low-power ‘flash’. “Here came the new step,” Adeeb said.
According to Adeeb, the researchers used LED lights that have red, green and blue colors. They emit light sequentially, sensors capture the image during the light emission, and the images originally captured are processed in black and white in order to save energy.
“It took a fair amount of creativity to figure out how to do this,” the Lebanese researcher added. “The red, green and blue colored light is reflected in the white part of each image. When the image data is combined in post-processing, it can be reconstructed color image.
He continued, “The camera contains an innovative transmitting sensor that reflects the energy harvesting process, then we harvest the energy from the sound, and then we load the sound itself with data and send it to the receiver.”
Once image data is captured, it is encoded in bits (1 and 0) and sent to a receiver one bit at a time using a process called underwater backscattering. The receiver transmits sound waves through the water to a camera, which acts as a mirror to reflect those waves.
Thus, the camera either reflects a wave back to the receiver or changes its mirror to absorb the wave so that it is not reflected back.
A microphone next to the transmitter senses if a signal is reflected from the camera, if it receives a signal, this is “bit 1”, and if there is no signal, then it is “bit 0”, and the system uses this binary information to rebuild and process the image.
This whole process, since it only requires one switch to switch the device from a non-reflective state to a reflective state, consumes very little power, much less than the usual underwater communication systems.
The researchers tested the camera in several underwater environments. In one, they took color photos of plastic bottles floating in a New Hampshire pond. They were also able to take high-quality images of the African starfish, so that the small tubercles along its arms were clearly visible. The device was also effective in repeatedly photographing plants that had been grown underwater in a dark environment for a week to monitor their growth.
Now that they’ve demonstrated a working prototype, the researchers plan to improve the device so that it’s practical for use in real-world settings. The researchers hope to increase the camera’s memory so it can take pictures in real time, or even shoot a video underwater.
They also want to expand the range of data transmission. According to Adib, “we succeeded in transmitting data 100 meters from the receiver after the study was published,” noting the need to improve that distance to use the camera in the real world.
In general, this camera can be used in many applications such as oceanography, marine archeology, robotics, military applications, and even during natural disasters.