35mm-Size Display Has VGA Resolution

Nicholas Baran

It may not be long before you can wear a head-mounted display that's about the size of a 35mm slide yet sports 640- by 480-pixel VGA resolution. The technology behind the so-called Smart Slide from Kopin (Taunton, MA) is the ability to place active-matrix display circuitry on a single-crystal silicon wafer. The top layer of the silicon wafer, which contains the pixel array and integrated circuitry, is lifted and transferred to glass, leaving a transparent IC.

According to Dr. John Fan, Kopin's president and CEO, one of the major advantages of placing the display circuitry directly on silicon is that standard IC-fabrication techniques and facilities can be used rather than the specialized equipment used for the typical (and expensive) "silicon-grown-on-glass" LC D-fabrication method.

The limitation of this technique is the size of the silicon wafer. Although silicon wafers are available in sizes of up to 12 inches, it is more economical to use projection, since this technique allows a pixel resolution of 2000 lines per inch or even better, Fan says. "There are many ways to enlarge an image from a small display," he says. Therefore, the company is focusing on miniaturized displays and on projection systems that project the image from the Smart Slide to a larger screen.

Fan says that the Pocket Pro compact projection system, Kopin's first commercial product, will be available for $1500 in "a few months" and that once mass production starts, the price will drop steeply.

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Illustration: Kopin's Smart Slide imaging device consists of a thin-film, transparent IC containing the active matrix, the drive circuitry and other logic, and the liquid crystal, which is sandwiched between two glass panels.