Technology for subsea imaging

March 23, 2023

Cutting-edge imaging is enabling more accurate data collection and analysis in fields such as scientific research, climate monitoring and subsea inspection. Many projects can now be conducted by remote-controlled or even autonomous vehicles, allowing deeper submersion for longer periods of time. Some marine research vessels are even left to operate for weeks at a time, capturing images and video for viewing at a later date. However, other applications require data immediately, such as inspection technologies, where a fault in an underwater structure must be identified and remedied as soon as possible.

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 under water are mounted on or contained within remotely operated vehicles (ROVs) which are often attached by a tether to a surface vessel, allowing power and control to be delivered and image data to be transmitted. Others may be operated cable-free; you can read more about the options for transmitting wireless data in our blog, The Internet of Underwater Things.

The video output required will vary according to each application, but MIPI CSI-2, IP Ethernet and SDI outputs are most commonly requested. Our Harrier autofocus-zoom cameras offer a range of outputs along with a choice of zoom options, size and weight specifications.

If long cables lengths or tethers are involved, specialist technology is required. 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, including more delicate components such as battery packs. Our partner company, Steatite Batteries, has developed a pressure tolerant Lithium Sulfur (Li-S) battery pack tested to depths of 6km. This was for a project with the National Oceanography Centre and the battery is currently in use in the NCO’s Autosub Long Range autonomous vehicle, Boaty McBoatface

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 50x 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.

Another innovator in Canada are designing our Harrier 10x AF-Zoom IP/HDMI Camera into their underwater ROVs. This will allow them to continue delivering commercial-grade subsea imaging solutions to maritime, research and aquaculture customers globally.

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