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.
