A Camera for Near, Far, and Wide

By David H FreedmanNov 1, 1995 6:00 AM


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Your baby is smiling for the first time. Desperate to capture the moment on film, you grope for your camera--the idiot-proof one with automatic focus--and shoot. But when the prints arrive from the photo shop, the dog grinning in the background is in perfect focus, while your baby is a blur.

Frustrating, isn’t it? Focusing is the bane of amateur photographers, and autofocus cameras offer only a partial solution. The problem is fundamental to the way cameras work. Light waves bouncing off the object being photographed pass through a lens, which bends them so that they form an upside-down image. Exactly how far behind the lens this image forms depends on the distance to the object in front of the lens. That’s where focusing comes in. When the lens is moved forward or backward, the image is made to land smack on the film. Autofocus cameras basically follow the same script, adjusting the lens until the object in the center of the frame is in focus.

Narendra Ahuja, an engineer at the University of Illinois, has a different idea about how cameras in this high-tech age should operate. Ahuja has invented a camera that keeps every object in the frame in perfect focus, no matter whether it is a few inches in front of your face or on the distant horizon.

To begin with, Ahuja dispensed with film in favor of the more flexible medium of electronics. In his camera, the light coming through the lens falls on an electronic backplane, a patch of light-sensitive electronic cells, each of which generates a tiny electric voltage proportional to the brightness of the image at that spot. These voltages constitute an electronic snapshot that can be stored in a tiny memory chip and manipulated with a computer. Next came a more radical step. He tilted the camera’s backplane so that one side was closer to the lens than the other.

In a conventional camera this tilting would only create a very distorted image. On the end of the backplane closer to the lens, people in the foreground would appear in focus, and the distant mountains behind them would be blurry; while on the other end of the backplane, people would be blurry while the mountains would come through in sharp focus. That would solve our focusing problem only if the various objects in the photograph had the courtesy to line up right to left according to distance. But since Ahuja’s image is captured electronically, he has the freedom to play around with it a little.

That freedom led him to his third and even more radical step. Rather than keeping the lens fixed, he spins it so that the entire scene sweeps across the backplane. The lens starts out pointing to the left, rotates to face straight ahead, and then keeps going until it is aiming to the right. During this sweep, an image of every object is dragged across the backplane. As a result, each object, regardless of its distance, ends up at least for an instant in focus on the backplane. The computer keeps track of the myriad images that fall on the backplane and picks out the ones that are in focus by measuring which have the most contrast. Finally, the computer assembles the images into one master image in which--voilà!-- everything appears in focus.

With the spinning lens and electronically manipulated pictures, Ahuja found he could also program the camera to take panoramic pictures. The lens simply rotates as it does normally, except that it sweeps through a very large angle (up to 360 degrees). Even though the backplane is not big enough to contain the entire scene all at once, the computer simply stores every piece of the wide image and then assembles it afterward.

Ahuja is now working on a portable version of the camera to demonstrate to manufacturers who might be willing to bankroll further development. He says nothing in the design makes it inherently costly. It is a simple modification of existing equipment, he says. The only big difference is in performance.

For now, though, his invention is merely a crude laboratory curiosity--the lens is stuck onto a bulky box that spins on a motorized tripod, and its photographs are grainy and washed-out. But they are impeccably well focused.

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