Slip the black "I-glasses" over your head and you get the feeling you're looking at a huge PC or television screen. What you're really viewing are two tiny monitors, so close to your eyes that your brain fuses their images into one.

Resembling a virtual-reality helmet, the product plugs into your PC or VCR and provides sound as well as sights. It's designed for people who are visually impaired or want a large display--that is, the illusion of one. It can also be used for watching movies in a dentist's chair.

The manufacturer, I-O Display Systems, claims it seems like an 80-inch screen, though to me it looked more like 35 inches.

For visually disabled users, the I-glasses' images are much clearer than what they see on a standard monitor. The problem is, the headset's viewing angles cannot adjust for people who already wear glasses.

I asked a legally blind user to test the I-glasses. He said the screen looked good, but the constant pressure against his glasses was unbearable for more than a few minutes at a time.

The monitors themselves cannot be tilted up or down for a good viewing angle. There is only a thin elastic band to adjust for a tighter or looser fit.

Another handicap is low resolution. The maximum emulation, 640 pixels by 480 pixels, works fine for DVD movies but is no good for prolonged word processing. I found myself squinting until I increased the text size to at least 16 points.

Of the people I recruited, about 20 percent complained of headaches within a few minutes. I got them, too, while running a simulation that gave the illusion of motion. I turned my head as I would in a virtual-reality helmet, but the glasses did not respond to my head-turning--only to keyboard and mouse inputs. This apparently confused my brain and left me dizzy for hours.

Later I ran the same simulation without moving my head and fared much better. Other users felt nausea while simply using a Web browser.

Besides disabled users, security-conscious users are a possible market for the I-glasses. If you need to work on a sensitive document on an airplane for instance, you can put on the I-glasses, boot up and work without fear of seatmates watching.

The I-glasses come in several models, from an inexpensive consumer version up to the scientific and technical set. The high-end model delivers true 3-D by using two graphics cards.

In general, I had fewer problems out of the box with the the consumer-oriented I-glasses. They were easy to plug into a VCR with standard cables. Every sound in a movie was audible in stereo, even background noises that might be missed in a theater. The I-glasses transported me right into the action. They also were fine for playing console video games with standard video cables.

In sum, this product might sound like rose-colored glasses for certain users, but until resolution for computer uses improves, it's mainly just a novelty.

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I-GLASSES: HEAD-MOUNTED DISPLAY SYSTEM

Telephone: 1-800-339-5287

Web address: www.i-glasses.com

Price: $799 for professional model, $499 for consumer model

Report card grade: B -

PROS:

+ Creates illusion of a large-screen monitor

+ Completely secure viewing

CONS:

- Displays at low resolution on PCs

- Fitting problems for users who wear glasses

REAL-LIFE REQUIREMENTS:

Free serial port on personal computer, plus special video board for high-end product. Works also with Silicon Graphics workstation.