As Photonics Advances, Safety and Security Progress

HANK HOGAN, CONTRIBUTING EDITOR, hank.hogan@photonics.com

In safety and security, the fundamental drive is to collect as much data as possible. That arises from the nature of the problem, said Benjamin Pflaum, CEO of ABUS Security-Center GmbH & Co. KG, an Affing, Germany-based company that makes alarm and video surveillance systems. “Your burglar or any other offender, they don’t have patterns that you can put into analytics up front. We cannot predict what part of the information we will need.”

Video surveillance cameras, like the one in this cutaway view, are increasing in resolution, which improves safety and security but strains networks and storage. Photo courtesy of ABUS Security-Center.

Collecting that information is getting easier, thanks to photonics advances. Consider, for example, protecting a house, building or fence perimeter. Here, improvements arise from innovations in sources and detectors. On the source side, LEDs can rapidly cycle on or off, something not possible with the high intensity discharge lighting that is currently used outdoors. Combined with a presence sensor and networking, this makes it possible to have lighting travel with a car or person, saving energy while still providing security and safety.

Adding such capabilities to indoor lighting enables the spotting of activity in rooms for which there should be none. “We see some of that being implemented in corporate offices, where security is a concern,” said John Casadonte, vertical marketing manager for lighting at Cree Inc. of Durham, N.C. The company makes LED lighting, controls and other equipment.

LEDs offer advantages over traditional outdoor lighting, such as the ability to rapidly cycle on and off. Photo courtesy of Cree.

On the camera front, resolutions are moving to the multi-megapixel, high-definition range. Having many such cameras churning out mountains of largely routine video could overburden network, storage and analysis systems. But, since in security nothing can be safely discarded in advance, Pflaum predicted the data load will continue to grow.

There’s also the expanding use of nonvisible wavelengths. For example, ABUS has systems where an infrared detector will pick up a heat signal and then direct a visible camera in the proper direction.

Such systems make use of thermal infrared, which has a wavelength of about 10 µm. Objects emit thermal IR in a characteristic manner, making it possible to detect and distinguish people from an animal, a wall or a tree. Doing so at long range requires cooling the detector; this raises the system price significantly, according to Emmanuel Bercier, product line manager at ULIS, based in Veurey-Voroize, France, which makes microbolometers (uncooled infrared sensors) that are used in automobiles to warn drivers of unseen hazards. They also provide security for solar arrays and other installations where distances are less than a kilometer.

Low-cost thermal IR imagers can improve the safety and security of cars by revealing otherwise invisible objects, as shown in this visible image (a) compared to an IR image; (b) A pedestrian crossing a street is highlighted in the IR image. Photo courtesy of ULIS.

“In that case, the uncooled microbolometer is enough. Depending on the application, this technology can be 10 or 100 times cheaper than the cooled technology,” Bercier said.

The maximum resolution of infrared sensors is much less than that of visible imagers for several reasons. A major one is the wavelength of the light, which translates into a greater than 10 times larger pixel size of thermal IR, as compared to visible sensors. Over time, today’s 17- to 25-µm IR detector pixels will shrink to 10 to 12 µm, and resolutions will go up from a current maximum of 1024 × 768 pixels to perhaps 1280 × 1024, Bercier said.

ULIS is a subsidiary of Sofradir. Based in Palaiseau, France, Sofradir makes thermal, mid- and short-wave IR detectors. The latter capture light of wavelengths from about 1 to just under 2 µm. That spectrum offers a way to see without being seen, since the illumination is invisible to people. Short-wave IR (SWIR) is part of the security solution.

“The main requirement of the market is to be able to see better and to better identify the threats and the environment,” said Claire Valentin, Sofradir director of marketing. “To do that, the SWIR is coupled with a thermal or visible imager.”

As is the case with long-wave IR, the SWIR pixel size is dropping. Five years ago, it stood at 30 µm, whereas today it is 15 µm, she said, adding that in the future this should drop to 10 µm or less, at least for indium gallium arsenide detectors.

Another detector material — silicon — dominates visible imagers and can even capture the near IR, from about 0.8 to 1.2 µm. The near-IR quantum efficiency of such sensors and the ability to work in low light conditions can be upped significantly using a technology from SiOnyx LLC of Beverly, Mass. The company’s process roughens the surface and increases the near-IR light absorption, said Jim Carey, principal scientist. This treated silicon can be used in night vision, allowing imaging systems to handle low- and bright-light conditions. It also can be used in other security applications, such as biometric identification; using the iris, the eye is illuminated and the resulting image captured.

Lightning-fast reaction: The camera in Opel’s eye-tracking system scans the driver’s eyes more than 50 times per second to instantaneously adjust the headlamp beam. Photo courtesy of GM.

The best way to do this is not to use visible light. “In order to remove the effect of pigmentation, the preferred wavelength is 850 nm, which is in the near-infrared,” Carey said.

Advances in photonics are contributing to safety and security in other ways, too. For example, more than 30,000 people die annually on American roads, at times because drivers can’t see. The industry wants to effectively abolish part of the problem.

“The goal is to make driving at night like driving in daylight,” said Shannen Borngesser, engineering group manager for exterior lighting at GM. The Detroit-based automaker is making progress toward that goal, thanks to cameras and LEDs. The former allow the automatic identification of oncoming cars. The latter then creates a custom shadow pattern, allowing vehicles to drive with high beam headlights always on without blinding oncoming traffic. The system is currently found in Europe and will soon be available elsewhere, pending regulatory approval. Borngesser has had personal successful experience with the technology.

Other advances that are further out in time involve the use of lasers to provide illumination that changes based upon road or weather conditions. For instance, algorithms may adjust the pattern so that less glare arises from raindrops. Or a camera, possibly an infrared one, may locate a deer or bicyclist and direct the illuminating beam to the otherwise invisible potential hazard.

The rest of the road remains brightly illuminated. Photo courtesy of GM.

Being able to rapidly change the LED or laser-projection pattern allows another possibility: illumination that tracks what the driver is looking at. Drivers shift their gaze about, now looking at a point on the road and then glancing at something in the car before moving back to another location on the highway. This approach demands cameras that provide fast, accurate and reliable information about a driver’s eyes, as well as sophisticated software and control schemes.

“The hardest part is coming up with an algorithm to filter eye movement so the lights aren’t bouncing all over the place,” Borngesser said. She added that the technology has been demonstrated, but it will be at least several years before it becomes commercially available.

Other photonics-related innovations are improving safety and security by taking to the air. A case in point comes from Colorado’s Mesa County, where the sheriff’s office uses cameras carried by unmanned aerial vehicles (drones) to quickly and accurately capture three-dimensional details about a crime or accident scene. This capability benefits the public via the completeness of the data and the speed of the process.

“We can photo and recreate a traffic accident at an intersection in about 15 or 20 minutes instead of you sitting there in traffic for a couple hours while they measure everything,” said Ben Miller, unmanned aircraft program director for the Mesa County Sheriff’s Office.

Another example of airborne imaging comes from Persistent Surveillance Systems. The Xenia, Ohio-based firm puts a 192-MP, three-color camera on a small plane. During flight, the camera images large swaths of real estate. The video data travels down a 600-Mb per second link and is stored in a custom disk array of up to 400-TB capacity. The optics are set so that individuals appear as a single pixel — large enough for tracking and forensic purposes, but otherwise not personally identifiable. When a police report comes in, company analysts can examine the images to determine what people at the scene did.

Airborne imagers, such as on this drone used by the Mesa County, Colo., Sheriff’s Office, can speed up accident scene capture, and improve safety and security in other ways. Photo courtesy of Mesa County Sheriff’s Office.

Sometimes the crime is current, in which case so, too, is the expected response. “Once we see people fleeing the scene, our job is to catch up to them in real time,” said Ross McNutt, company president.

At other times, all that is known is that a crime occurred. An example: A body may be found in an alley. Analysts will then look back through the images and try to solve the crime. According to McNutt, this process has been successful, starting with nothing more than a report of a body and a single shell casing of a known caliber. These aerial examples face regulatory challenges, however. Drones, at the moment, are restricted in where they can fly and who can fly them, which is one reason why Persistent Surveillance Systems uses manned aircraft.

There also are privacy concerns. A drone on the way to an accident scene may fly over houses of innocent people and wide area surveillance could capture private activity. Procedures are in place to address these and other issues, such as the elimination of personally identifiable information and strict data retention policies. However, in a legal proceeding, defendants may want every possible bit of imaging; this could become a complicating factor.

Today, airborne imaging for safety applications is not widely used. Over time, though, the situation could change. As for the overall future of these varied security and safety applications, every part of the spectrum may eventually be used, either for illumination or detection. Imager resolution will continue to climb.

These trends arise from the far-reaching nature of what activities have to be detected and identified. As ABUS’s Pflaum said, “We have to cover a fairly broad range of possible behavior.”

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