Scallop Imaging Security Cameras Give New Meaning to All-Seeing
With only two eyes apiece, spanning a mere 180-degree field of view, humans have an innately limited understanding of what it means to see. Some insects have compound eyes with hundreds or thousands of facets that can form a nearly 360-degree picture of the world around them. The shells of many scallop species are rimmed by 100 or more brilliant blue eyes; a scallop can’t actually see much (since it doesn’t even have a brain), but its eyes can detect motion from any direction, warning it when to clam up.
Inspired in part by the scallop, engineers at Tenebraex—a small Boston company that makes optical equipment for the military—are unveiling a new type of surveillance camera today that combines images from five separate image sensors, each equivalent to the camera in a typical cell phone. Each camera has a roughly 40-degree field of view, and when stitched together, the five video feeds span a full 180 degrees, giving security personnel a comprehensive real-time view of a scene without the distortion created by traditional fisheye lenses, and without the delays created by remote-control pan-and-tilt cameras. Tenebraex’s engineers call the device the Digital Window, and it’s the debut product for Scallop Imaging, a new Tenebraex subsidiary that hopes to sell its technology to camera makers and system integrators in the security industry.
“Using multiple, lost-cost imaging sensors allows you to do things you couldn’t do otherwise,” says Peter Jones, president of Tenebraex. “They’re small enough and cheap enough that you can put them anyplace where you want situational awareness, without having to install a big eyeball with a motor turning it back and forth.” That could be a big advantage in locations where purse-snatchers and other wrongdoers have learned to look for remote-controlled cameras and strike when they’re pointed away. “There’s no motion to catch your eye, because the sensors are looking everywhere at once,” says Jones.
The Digital Window device is so small it will fit into a hole in the wall the same size as a light switch or power socket. It’s powered by the same Ethernet cable that connects it to a building’s surveillance system.
The Digital Window is only the latest in a eclectic series of vision-related technologies from Tenebraex. The company’s first product was a honeycomb-like screen that fits over the lenses of military-grade binoculars and rifle sights to keep out glare and prevent reflections that might give away a user’s position. (Reflections off optical devices are a more serious problem in wartime than you might think: a glint from Moshe Dayan’s binoculars during the 1941 Allied invasion of Syria showed a Vichy French soldier where to shoot, costing the future Israeli general and politician his left eye.) Using a similar type of screen, Tenebraex licenses filters to Philips Lighting that make vehicle headlights look black, red, or blue when they’re turned off. The company also makes a full-color night vision system, as well as a system called EyePilot that helps color-blind people distinguish different colors on a computer display.
Jones says the impetus for Digital Window originally sprang from a request from the Department of Defense, which wanted to add a large bulletproof window to the door of the M2/M3 Bradley Fighting Vehicle. The window would give soldiers about to exit the vehicle a better look at what awaited them. But it would also create a huge reflection, so some kind of camouflaging system was needed.
In the end, the project was dropped. “But what they really wanted to do in the Bradley was to make that door, in effect, transparent,” says Jones. “It doesn’t really matter how you get there—you just want an undistorted view. That was the genesis of the idea; it got us thinking about using multiple, low-cost sensors on the outside of the vehicle and having a display inside.”
Digital Window is the first instantiation of that idea—it’s just built for stationary installation as part of a security system, rather than the outside of a moving vehicle. (Not coincidentally, however, Scallop is investigating automotive applications of the technology, including distortion-free backup cameras for the rear ends of trucks, vans, and SUVs.)
In a way, Digital Window is the video equivalent of the low-budget panoramic and gigapixel imaging techniques that are becoming popular among amateur digital photographers (a subject I covered in a column last summer). The key to making a decent panorama or gigapixel image is to control the exposure across multiple images; but in practice, this is so difficult that most gigapixel hobbyists use specialized photo editing software to achieve smooth tones across a stitched-together composite.
Ellen Cargill, the director of product development for Scallop, says that the biggest challenge in putting together the Digital Window system was figuring out how to do the same thing for the frames in video images, 15 times a second.
“These inexpensive imaging modules have a fair amount of manufacturing tolerance, and if you just looked at what you get from five separate cameras, they would never match in exposure in color tint,” Cargill says. “When you butt them up against each other, it becomes painfully obvious. So we don’t just plug them together and start rolling—there is a lot going on to make the five images look seamless and matching.”
Another key element of the Scallop Imaging system is the so-called “downsampling” that occurs inside the wall-socket-sized box holding the cameras and their electronics. The cameras collect more information than can actually be transmitted over Ethernet cables at standard video rates. So in addition to stitching together and smoothing the images, the device reduces the resolution of the overall image to a size that can be transmitted at 15 frames per second.
That saves enough bandwidth, Jones says, to allow the device to send a full, 7-megapixel still photo of the 180-degree panorama every second or two. It also gives the camera operator the ability to “zoom in” on—or rather, request the full-resolution video stream for—a selected portion of the overall panorama. And if recognizing someone’s face is important, the periodic 7-megapixel still image provides plenty of resolution, providing that the person isn’t too far away.
Jones says there are a couple of other commercially available systems that provide views of 180 degrees or greater without a pan-and-tilt camera—one using an extremely wide-angle lens that points up toward the sky, giving security personnel a view all the way around the rim, the other using a system of precisely curved mirrors. But both are “insanely expensive” compared to the Scallop Imaging technology, he says. “We are doubly disruptive,” Jones says. “You get high capacity in a package that’s far cheaper and easier to deal with.”
Jones can’t yet say exactly how much the Digital Window system will cost, since the company is still looking for a manufacturing partner who can help fund the final stages of product development and bring the system to market. (Jones says he expects to strike a deal early in 2009.) But a Digital Window unit will definitely cost far less than a pan-and-tilt camera, says Jones, and about the same as one of the140-degree-field-of-view fisheye-lens cameras used in many static security applications. “And for that, you’re getting a smaller package, a much higher resolution, and a full 180-degree field of view without distortion,” he says.
Trending on Xconomy
By posting a comment, you agree to our terms and conditions.