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Technology for subsea imaging

January 5, 2022

Nearly three quarters of the Earth’s surface is covered with water and more than 80% of it is unexplored[1]. That’s a lot of Earth that we don’t know about. What are science and technology doing to address this?

Underwater image transmission

Obtaining high-quality images and video from below the waves is crucial to understanding more about the marine environment. But there are challenges involved, beyond just the obvious requirement to keep camera electronics dry!

Most cameras for use underwater are mounted on or contained with remotely operated vehicles (ROVs) which are usually attached by a tether to a surface vessel, allowing power and control to be delivered and image data to be transmitted. While some ROVs are operated cable-free, or even autonomously (the options for transmitting wireless data are explained in more detail in our blog, The Internet of Underwater Things) this often means relying on expensive or inconsistent technology.

Transmitting images along the long cables lengths involved, requires specialist technology. Camera processor boards can be used to process image signals at the point of capture and convert data into a format more suitable for transmitting along long cables. One such technology is High-Definition Visually Lossless CODEC (HD-VLC™), developed by Semtech, which can transmit high-definition still images and video along coax cables of up to 700m, even when slip rings are used. Active Silicon manufactures boards and cameras which incorporate this technology and are ideal for such long-reach image capture.

Managing light conditions

Light is subject to reflection and diffraction when light waves hit the surface of water. Water also absorbs light – in particular, red light, which is why a clear sea appears blue. Beneath the water, further scattering occurs as the light hits particles such as microorganisms and sediment. All this means that the ocean environment is devoid of light below about 1km. Capturing subsea images will usually require additional artificial lighting, adding cost and complexity to underwater exploration. Lighting will also add weight to a ROV and make it more power-hungry, thereby reducing the time of each voyage.

To make the most of limited light, sensors for underwater cameras must be carefully selected. Sony provide a variety of sensors which are developed specifically for low light conditions, such as their Starvis range. These leverage back-illuminated pixel technology in CMOS image sensors and deliver high picture quality in the visible-light and near-infrared light regions.

Handling pressure

For every 10m dived, pressure increases by 1 atmosphere – that’s 101,325 pascals, or newtons of force per square metre, or put simply, the equivalent of an additional 6.66kg of weight for every 10m of depth.  Equipment designed for subsea operation must be built, housed and rigorously tested to withstand immense pressure.

Applications for ROVs

Exploration of the deep sea has become a primary use for ROVs as innovations in technology have enabled them to operate at even greater depths. Payloads on underwater vehicles now include a huge range of scientific instruments to monitor water purity, changes in temperature, salinity, pH and evidence of other chemicals. Autofocus-zoom cameras and advanced processor boards mean that incredibly high-quality and detailed images can be captured in real-time to paint an even clearer picture of the state of our seas and the wildlife sustained within them.

But not all ROVs are discovering the unknown. Many are deployed on maintenance missions, monitoring the condition of offshore installations or huge ships. Just like other industrial inspection applications, scientists are working on making these ROVs even smarter by adding AI to enable examinations and even repairs to be conducted autonomously.

ROV technology from Active Silicon

Active Silicon has a range of autofocus-zoom block cameras designed and built for circumstances when high-resolution imaging is critical but the operating environment is challenging. Harrier cameras include options to transmit high resolution 8MP 4K video, compact models with powerful 40x zoom, and global shutter variations.

One of our Scandinavian customers is currently using our image technology in their subsea electronics for intelligent imaging and video streaming. This global player has been delighted with the high-quality image data and robust hardware that our Harrier range offers.

Furthermore, our custom design skills enable the customization of any of our products to make them ideal for subsea applications and scientific research. Contact us to see how we can advance your exploratory investigations or underwater inspection requirements.

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[1] https://www.nationalgeographic.org/encyclopedia/ocean/