Advanced Imaging

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Advanced Imaging Magazine

Updated: July 8th, 2008 05:26 PM CDT

Stereopsis: Two Eyes, One 3D Image

Planar Systems, Inc.
Planar's StereoMirror monitor consists of two active matrix LCD (AMLCD) units oriented at a 110-degree angle and bisected by a passive beamsplitter mirror. When stereo pair images from the two monitors are viewed through crossed-polarizing the result is a single, fused stereoscopic image.
Planar Systems, Inc.
Planar's StereoMirror monitor.
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By Barry Hochfelder

The most powerful source of human depth perception is stereopsis, the response created in our visual systems by comparing the views we get from our two eyes.

Think back a few million years. A caveman is out hunting for that day's meal. So is a saber-toothed tiger. The caveman spots the animal. How close is that carnivore? Without stereopsis—and 5 percent of the population does not have it—our man probably became cat food.

Our eyes are separated by about 65mm, giving each a slightly different view. The visual system determines the relative depth of different objects in the visual scene. Another way to think of it is by remembering the View-Master® that many of us enjoyed as kids. There's a left-eye image and a right-eye image. While one of its cardboard reels holds 14 film slides there really are only seven stereoscopic images that are viewed simultaneously, one for each eye, which simulates binocular depth perception creating the 3D image.

The View-Master® is a popular toy and has earned a place in the National Toy Hall of Fame. We no longer have to worry about saber-toothed tigers, but 3D technology is saving lives by its use in health care. It is viable in radiology, giving physicians sharper resolution in, for example, mammographies and lung cancer diagnoses. It's also valuable in diabetic retinopathy and minimally invasive surgery.

There are a couple of ways to create the 3D image, says Scott Robinson, Production Marketing Manager, Stereoscopic Display at Planar Systems, Inc. (Beaverton, Ore.). "One is the View-Master® approach. You have two cameras side-by-side and click the shutters at the same time," he says. "The second way is 3D data. All the video games use it. To create stereo, you have to render a second view. Shift it over about 3 degrees so you create a left and right view. It's the way to do it in computed tomography (CT) and magnetic resonance imaging (MRI) data sets.

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