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

"You hear a lot about 3D graphics," he continues. "Most high-end games have them. It means perspective and light shading. You can rotate them, get motion parallax and mono eye views. That's good enough in computer-aided design, but if you're looking at mammograms, aerial imagery and other complex images, that's where you have to use stereo 3D. By viewing it stereoscopically, they get depth cues. It's more realistic and you're making full use of your senses."

The fundamental principle is triangulation. By taking photographs from at least two different locations, so-called "lines of sight" can be developed from each camera to points on the object. These lines of sight are mathematically intersected to produce the three-dimensional coordinates of the points of interest.

The objective of a stereoscopic display is to present a left-eye image solely to that eye and right-eye image only to the right eye, which allows the human visual system to merge the two images and produce stereopsis. Planar, for example, does this with what it calls StereoMirror™ technology. The StereoMirror™ monitor consists of two active matrix LCD (AMLCD) units oriented at a 110-degree angle. A passive beamsplitter mirror bisects the angle formed between the two monitors. One side of the mirror has a reflective coating, and the side has an antireflective coating which minimizes secondary reflections.

LCD displays operate based on the ability of liquid crystal material to modulate plane-polarized light. In this unit, the polarized light emitted from the top monitor is rotated 90 degrees from that of the bottom monitor. The image from the lower monitor is seen through the mirror. When stereo pair images from the two monitors are viewed through crossed-polarizing glasses the user only sees the left-eye image with the eyepiece having the 0-degree oriented polarized while the right-eye image is seen with the eyepiece having the 90-degree polarizer. The result is a single, fused stereoscopic image.

Stereopsis in Health Care

3D imaging now is being used in a number of clinical trials. At Emory University in Atlanta, Ga., researchers are conducting a trial comparing stereo 3D to standard 2D diagnoses in breast cancer. The physicians will examine 2,000 patients and compare 3D and 2D images.



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