Underwater video cameras of a proposed type (and, optionally, their light sources) would not be housed in pressure vessels. Conventional underwater cameras and their light sources are housed in pods that keep the contents dry and maintain interior pressures of about 1 atmosphere (0.1 MPa). Pods strong enough to withstand the pressures at great ocean depths are bulky, heavy, and expensive. Elimination of the pods would make it possible to build camera/light-source units that would be significantly smaller, lighter, and less expensive. The depth ratings of the proposed camera/light source units would be essentially unlimited because the strengths of their housings would no longer be an issue.
A camera according to the proposal would contain an active-pixel image sensor and readout circuits, all in the form of a single silicon-based complementary metal oxide/semiconductor (CMOS) integrated- circuit chip. As long as none of the circuitry and none of the electrical leads were exposed to seawater, which is electrically conductive, silicon integrated- circuit chips could withstand the hydrostatic pressure of even the deepest ocean. The pressure would change the semiconductor band gap by only a slight amount — not enough to degrade imaging performance significantly.Electrical contact with seawater would be prevented by potting the integratedcircuit chip in a transparent plastic case. The electrical leads for supplying power to the chip and extracting the video signal would also be potted, though not necessarily in the same transparent plastic. The hydrostatic pressure would tend to compress the plastic case and the chip equally on all sides; there would be no need for great strength because there would be no need to hold back high pressure on one side against low pressure on the other side. A light source suitable for use with the camera could consist of light-emitting diodes (LEDs). Like integrated-circuit chips, LEDs can withstand very large hydrostatic pressures.
If power-supply regulators or filter capacitors were needed, these could be attached in chip form directly onto the back of, and potted with, the imager chip. Because CMOS imagers dissipate little power, the potting would not result in overheating. To minimize the cost of the camera, a fixed lens could be fabricated as part of the plastic case. For improved optical performance at greater cost, an adjustable glass achromatic lens would be mounted in a reservoir that would be filled with transparent oil and subject to the full hydrostatic pressure, and the reservoir would be mounted on the case to position the lens in front of the image sensor. The lens would by adjusted for focus by use of a motor inside the reservoir (oil-filled motors already exist).
This work was done by Thomas Cunningham of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free online at www.techbriefs.com/tsp under the Electronics/Computers category. NPO-30774
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Deep-Sea Video Cameras Without Pressure Housings
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Overview
The document titled "Technical Support Package for Deep-Sea Video Cameras Without Pressure Housings" from NASA's Jet Propulsion Laboratory outlines advancements in underwater camera technology, specifically focusing on an Active Pixel Sensor (APS)-based camera designed for deep-sea operations. Traditional video cameras are not suitable for extreme underwater pressures, as they require protective pressure housings to maintain functionality. These housings are heavy, expensive, and limit the camera's application in deep-sea research.
The APS technology represents a significant breakthrough, allowing cameras to operate at depths where pressures can exceed 1200 atmospheres (approximately 17,000 lbs. per square inch). This innovation eliminates the need for bulky pressure pods, drastically reducing the weight, mass, and cost associated with underwater imaging systems. The APS utilizes complementary metal-oxide-semiconductor (CMOS) technology, which integrates both the imager chip and the necessary support electronics onto a single chip. This integration minimizes the need for additional electronic components, making the camera more compact and efficient.
The document emphasizes the challenges of deep-sea exploration, noting that the ocean floor remains less explored than outer space due to the difficulties in deploying research personnel and robotic vehicles to extreme depths. The increasing pressure with depth, combined with the absorption of light by water, complicates imaging efforts beyond 100 meters. Therefore, effective underwater cameras and illumination sources are essential for capturing high-quality images in these environments.
The APS-based camera is poised to enhance existing undersea research missions and enable new applications, such as undersea sensor networks and micro-robots. By providing a reliable imaging solution that can withstand the harsh conditions of the deep sea, this technology opens up new possibilities for scientific exploration and data collection.
In summary, the document presents a comprehensive overview of the development and potential impact of APS technology in deep-sea video cameras, highlighting its advantages over traditional systems and its role in advancing underwater research capabilities. This innovation not only addresses the limitations of existing technologies but also paves the way for future explorations of the ocean's depths.
