MIT scientists invent revolutionary underwater camera

By Stephen Beech via SWNS

A battery-free, wireless, underwater camera has been invented that is around 100,000 times more energy-efficient than others.

Scientists at the Massachusetts Institute of Technology (MIT) say the radical new device could help explore unknown regions of the ocean, track pollution, or even monitor the effects of climate change.

It is estimated that more than 95 percent of Earth’s oceans have never been observed - which means we have seen less of our planet’s ocean than we have the far side of the moon or the surface of Mars.

The high cost of powering an underwater camera for a long time, by tethering it to a research vessel or sending a ship to recharge its batteries, is a challenge preventing widespread undersea exploration.

The researchers have taken a major step to overcome the problem by developing a battery-free, wireless underwater camera that they say is about 100,000 times more energy-efficient than other undersea cameras.

The device takes color photos, even in dark underwater environments, and transmits image data wirelessly through the water.

The autonomous camera is powered by sound.

Engineers explained that it converts mechanical energy from sound waves traveling through water into electrical energy that powers its imaging and communications equipment.

After capturing and encoding image data, the camera also uses sound waves to transmit data to a receiver that reconstructs the image.

Because it doesn’t need a power source, scientists say it could run for weeks on end before retrieval, enabling researchers to search remote parts of the ocean for new species.

They say It could also be used to capture images of ocean pollution or monitor the health and growth of fish raised in aquaculture farms.

Study senior author Professor Fadel Adib, of MIT, said: “One of the most exciting applications of this camera for me personally is in the context of climate monitoring.

"We are building climate models, but we are missing data from over 95 percent of the ocean.

"This technology could help us build more accurate climate models and better understand how climate change impacts the underwater world."

To build a camera that could operate autonomously for long periods, researchers needed a device that could harvest energy underwater on its own while consuming very little power.

The camera acquires energy using transducers made from piezoelectric materials that are placed around its exterior.

Adib explained that piezoelectric materials produce an electric signal when a mechanical force is applied to them.

When a sound wave traveling through the water hits the transducers, they vibrate and convert that mechanical energy into electrical energy.

Those sound waves could come from any source, such as a passing ship or marine life. The camera stores harvested energy until it has built up enough to power the electronics that take photos and communicate data.

To keep power consumption as low as possible, the researchers used off-the-shelf, ultra-low-power imaging sensors.

But those sensors only capture grayscale images. And since most underwater environments lack a light source, they needed to develop a low-power flash, too.

Adib said: “We were trying to minimize the hardware as much as possible, and that creates new constraints on how to build the system, send information, and perform image reconstruction.

"It took a fair amount of creativity to figure out how to do this."

They solved both problems simultaneously using red, green, and blue LEDs.

When the camera captures an image, it shines a red LED and then uses image sensors to take the photo. It repeats the same process with green and blue LEDs.

Even though the image looks black and white, the team explained that the red, green, and blue colored light is reflected in the white part of each photo.

When the image data are combined in post-processing, the color image can be reconstructed.

Co-lead author Waleed Akbar said: “When we were kids in art class, we were taught that we could make all colors using three basic colors.

"The same rules follow for color images we see on our computers. We just need red, green, and blue - these three channels - to construct color images."

Once image data are captured, they are encoded as bits (1s and 0s) and sent to a receiver one bit at a time using a process called underwater backscatter.

The receiver transmits sound waves through the water to the camera, which acts as a mirror to reflect those waves. The camera either reflects a wave back to the receiver or changes its mirror to an absorber so that it does not reflect back.

A hydrophone next to the transmitter senses if a signal is reflected back from the camera. If it receives a signal, that is a bit-1, and if there is no signal, that is a bit-0. The system uses this binary information to reconstruct and post-process the image.

Co-lead author Saad Afzal added: "This whole process, since it just requires a single switch to convert the device from a non-reflective state to a reflective state, consumes five orders of magnitude less power than typical underwater communications systems."

The researchers tested the camera in several underwater environments. In one, they captured color images of plastic bottles floating in a New Hampshire pond.

They were also able to take such high-quality photos of an African starfish that tiny tubercles along its arms were clearly visible.

The device was also effective at repeatedly imaging the underwater plant Aponogeton ulvaceus in a dark environment over the course of a week to monitor its growth.

Now that they have demonstrated a working prototype, the researchers plan to enhance the device so it is practical for deployment in real-world settings.

They also want to increase the camera’s memory so it could capture photos in real-time, stream images, or even shoot underwater video.

They also want to extend the camera’s range. They successfully transmitted data 40 meters from the receiver, but pushing that range wider would enable the camera to be used in more underwater settings.

The findings were published in the journal Nature Communications.