Microdisplays: The next big market?
05/01/1999
Microdisplays are the tiniest of the flat panel displays - typically under around 2 in. diagonal. Today, they are used in multimedia front projectors, virtual display headsets for wearable computers and immersive simulations, and in viewfinders for camcorders. The number of products could expand dramatically in the next few years, powered by a host of new microdisplay technologies.
Transmissive liquid-crystal displays (LCDs) are fabricated using a high temperature polysilicon (HTPS) process that allows high pixel densities and fabrication of some off-screen driver electronics - all on the same substrate. Many industry analysts view HTPS as a mature technology with limited prospects for dramatic improvements. While current technology can pack 519,000 pixels (SVGA - 800 ? 600) into a 1.3-in. diagonal package, the display is expensive, over $300, and is not very light efficient.
Nipping at the heels of HTPS is a variety of technologies that could well emerge as formidable competitors. These include low temperature polysilicon (LTPS), microelectromechanical systems (MEMS), liquid crystal-on-silicon (LCOS), several emissive technologies, and even scanned optical systems that use lasers or LEDs. Although it is still early in the development cycle, many microdisplay technologies are emerging so fast that they are sure to garner a lot of attention in the next few years.
Attractive aspects
One feature of microdisplays is their potential for lower cost. A LCOS SVGA 0.5-in. diagonal microdisplay is projected to cost less than $50 in volume production. That means they will find their way into bring-to-the-eye type viewfinders, headsets, and viewing devices that are held 8-10 in. from the eye. They can also be used in projection products to lower the cost of front projectors and rear-screen systems for HDTV or computer monitors.
Perhaps the most compelling aspect of microdisplays is the promise of greater functional integration. Common to many microdisplay concepts is the use of CMOS backplanes upon which a light modulating or emitting layer is placed. These backplanes already contain display control circuitry, but could eventually include interface electronics, application specific circuits, and microprocessors. A display could be added on top of this highly integrated logic component to create a real system-on-a-chip concept.
Microdisplays leverage mature semiconductor and/or mature LCD fabrication processes. For instance, with a LCOS microdisplay, the backplane is made in a semiconductor fab, while the liquid crystal layer and packaging is done in an LCD fab. Three emissive technologies also use a silicon backplane upon which light emitting materials - vacuum fluorescent, electroluminescent, and organic polymers - are deposited. It is a whole new electronics category.
New opportunities
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Chuck McLaughlin, principal researcher at McLaughlin & Associates, Menlo Park, CA, sees a number of opportunities for microdisplay-based products, some of which haven't yet been developed. McLaughlin sees a stunning $4 billion opportunity awaiting microdisplays in the year 2000 (see figure).
In the portable computer category, Sony Electronics, Park Ridge, NJ, is already offering an SVGA headset for use as a computer peripheral. Plug in the headset to a laptop on the airplane, turn off the direct-view display, and work on sensitive information with privacy. Or use the same headset to plug into a portable DVD player to view a movie.
For cell phones, wireless bandwidths will be in place within the year to easily enable web browsing or video on some GSM network. Four-line text displays will give way to much higher resolution microdisplays. An SVGA microdisplay can be packaged as a small eyepiece on a cell phone to produce a virtual image that looks like a desktop monitor hovering a foot or two away from the eye.
The seeds for microdisplay-based handheld companions are already being sown. 3Com, Santa Clara, CA, recently des cribed a future Palm Pilot product that interfaces to the web, but "clips" web site content for presentation on its limited resolution display. With a microdisplay, clipping is not needed.
Huge opportunities also exist in rear-screen televisions and computer monitors. Digital TVs today are expensive - a CRT-based rear-projection HDTV costs over $6000, while a plasma-display panel costs over $10,000. Microdisplays could change this. HDTVs using LCOS technology are now planned for introduction within a year for $2000-$3000, a price that that could open the flood gates for HDTV adoption.
Similar technology is also in the works for computer monitors in the 22-in. to 30-in. size range using the wide 16:9 aspect ratio. This would allow the simultaneous presentation of a TV program plus one to two pages of a word processing or web document. It would be only 300-mm deep and retail for $1000-$2000. Some prototypes are impressive.
Stanford Resources, San Jose, CA, analyst David Mentley is cautiously optimistic about the microdisplay component market. Mentley predicts growth to about $300 million in 2000, although he admits this does not take into account new product categories that could emerge. "The competition in microdisplays is fierce, and I am not sure how they can make a lot of money selling $30 microdisplays. Vendors who add optics, electronics, light sources, and packaging will do better."
Bold execution required
Undoubtedly, the key to success in microdisplays is execution. Suppliers must prove they can develop the manufacturing processes and infrastructure needed to realize these bold goals.
Some companies are building their own fabrication facilities and ramping up toward production. For example, Three-Five Systems, Tempe, AZ, now has capacity in place to make 400,000 microdisplays/month. Others, like Colorado Microdisplay, Boulder CO, are leveraging existing manufacturing facilities and teaming with Planar Systems, Beaverton, OR, to ramp up an existing LCD fab for microdisplay production.
Alternative technologies are not sitting still either. Perhaps the most successful upstart so far is the reflective digital micromirror device (DMD) technology developed by Texas Instruments, Dallas, TX. DMD-based front projection pro ducts are very popular in the ultraportable category (under 10 pounds) and dominate the market for high-brightness, large venue applications. XGA DMD devices are in production now with SXGA slated for next year.
The emergence of LTPS is also expected to have an impact on microdisplays. By using lasers, the processing temperature is lowered enough to allow traditional large-diagonal glass substrates to be used. While most development work is focused on direct-view displays, high density microdisplays are expected in a 2-3-in. size range, such as the continuous grain silicon process under development by Sharp, Osaka, Japan. This size is well suited to high-brightness applications because of the improved light coupling efficiency compared to smaller microdisplays.
This year should be a critical year for many microdisplay technologies. New capacity will come on line, new products will be introduced, and other factors will begin to converge that could spur demand for these tiny displays. This year will also see testing for manufacturability of these displays, and their promise for higher performance at lower cost.