Writing for Military Embedded Systems, Amanda Harvey notes that stringent size, weight, power and cost (SWaP-C) requirements are influencing nearly every modern military platform.
“Everything seems to be getting smaller in the U.S. military arsenal – whether it’s an unmanned aerial vehicle (UAV), an intelligence, surveillance, and reconnaissance (ISR) payload, or a handheld GPS device,” Harvey explained.
“The electronics driving these systems are also getting more powerful and as a result generate more heat and at times require more power to run – not a perfect marriage for systems that need to perform on the battlefield.”
However, there is at least one notable exception bucking the increased power-sipping trend. As Dr. Patrick R. Gill of Rambus confirms, lensless smart sensor (LSS) technology, which can potentially be integrated across a wide range of military and civilian platforms, consumes a minimal amount of power while generating a negligible heat signature.
Pioneered by Rambus scientists, LSS is roughly analogous to the way a human, animal or insect brain perceives the world: the real-time interpretation of a scene or object facilitated by inherent pattern recognition capabilities. Simply put, data leaving a human retina looks nothing like a map of light intensity, although it contains all the information required to interpret an image.
Similarly, LSS allows sensors to capture information-rich images using a low-cost phase grating. Although the raw ‘snap’ is indecipherable to the naked human eye, the sensor, which is approximately the size of pinhead, is capable of capturing all of the information in the visual world up to a certain resolution.
“LSS can be made smaller than lensed cameras. As power requirements scale with sensor area, LSS becomes an attractive option for low SWaP-C systems,” said Gill.
“One possible use for LSS in a low SWaP-C environment is inside a new generation of quad-copters, hex-copters and UAVs where the technology would be tasked with bolstering obstacle-avoiding capabilities.”
As Gill notes, a constellation of Rambus lensless sensors would total less than a gram, making optical crash avoidance possible even with the smallest of flyers.
“Small mass is often especially important when adding hardware to the periphery of a ‘copter as opposed to the center of the craft, so unloading some of the burden of optical sensing from optics to the processor makes particular sense,” he continued.
“For applications like tiny flying robots, LSS technology could potentially enable sensing in one of the smallest form factors and power budgets available.”
To be sure, lensless sensors are a natural fit for stringent SWaP-C requirements in UAVs and beyond.
“Firstly, the lack of a lens reduces both size and weight, especially at the periphery where weight matters the most,” he explained. “Secondly, LSS power requirements are minimal, especially if the downstream application can make use of a low-complexity algorithm. Recently, we’ve found a large class of lightweight but useful algorithms that operate on LSS data. These algorithms require fewer than 100 operations per pixel, meaning the energy needed to implement them is minimal compared to the energy required to capture the data.”
Meanwhile, thermal applications tend to field a reduced number of sensors, making the above-mentioned low-complexity algorithms even more power-friendly.
“A lensless smart sensor manufactured from a single thermal diffraction grating is capable of capturing intelligible signals from a larger range of incident angles – perhaps greater than 100 degrees,” he explained.
“In fact, a large field of view combined with the higher selling price of thermal imaging systems (compared to their visible-light counterparts) could mean that wide-angle thermal sensing will be one of the first commercially advantageous applications of LSS technology.”
In a broader sense, says Gill, LSS optics are easier to manufacture and mount than lenses. As compute capabilities become cheaper and sensor hubs such as the Frizz achieve near ubiquity, an increasing proportion of devices will pack the circuits to handle LSS – making the TOC for LSS lower than focusing systems.
“There are also a number of tiny light sensor + compute packages emerging where we could simply replace the focusing element with an LSS grating. Either one offers enough horsepower to execute LSS-specific computation – plus some basic computer vision tasks,” he concluded.
Interested in learning more about LSS technology? You can read “The LSS-wearables connection” here, “From lensless sensors to artificial intelligence” here and “Why insects can help us build better ‘bots” here.