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Microdisplays: Coming Soon to an Eye Near You?

Photonics Spectra
Sep 2008
Texting, global positioning and streaming video on your portable device’s tiny screen could soon seem very old school compared with having that information projected directly onto your eye.

Melinda Rose, Web Editor, photonics.com

Imagine strolling past a restaurant and having its menu hover translucently in your field of vision, or getting a call from friends and having a GPS-like map appear in front of you as a guide to their exact location. These types of “augmented reality” scenarios could be closer than you might think, because the basic technology is already being developed for handheld devices, and specialized optics needed to guide the images to your eye is in the works right now at Microvision Inc. of Redmond, Wash.

TWMicrodisplay_Fig-1_directions.jpg

Figure 1. Microvision is working to incorporate its PicoP display engine into eyewear that would project directly onto the eye the GPS and other images that normally are viewed on tiny mobile device screens. Model ©2007 Patrick Bennett, composition ©2008 Microvision.


The company’s pico projector display engine, called the PicoP, comprises a microelectromechanical systems scanner; red, green and blue laser light sources; optics to guide the laser beams; and drive electronics to process data signals and to synchronize the color mix and placement of individual pixels.

The tiny scanning mirror is about the size of the head of a pin, with the entire device being “about the size of an Andes thin-mint chocolate,” said Ben Averch, product manager of eyewear display. “Our focus as a business is to take this engine and embed it into iPod-size devices or as a projector into a cell phone.”

The single scanning mirror is designed to scan both horizontally and vertically so that a single beam of light can be precisely steered side to side and up and down at very high speeds – 30 million pixels a second – to project a complete video image. Because the brain can’t follow something moving that fast, the projected video being rendered line by line appears to move as smoothly as video on a traditional screen, Averch said.

Rather than the LEDs favored by some of its competitors, the company uses lasers as its light source because they provide a brighter image, Averch said. Brightness is important if the projected image is to be seen on a sunny day.

Microvision and other companies developing mobile projectors, such as 3M and Texas Instruments, are counting on consumers to be tired of watching videos, especially full-length movies, on tiny cell phone or iPod screens and to appreciate the ability to project – and share with friends – large still or video images from such portable media players onto a wall, a ceiling, a school locker or even an item of clothing.

The company has been exhibiting its PicoP handheld accessory device, dubbed the SHOW, at display conferences such as the 2008 International Consumer Electronics Show and this month’s Society for Information Display (SID) mobile displays conference in San Diego. The palm-size, battery-operated SHOW connects to mobile devices via video-out ports, where it can be used to project vivid, full-color, high-resolution images that can range in size from 12 to 100 in. The projected image has an infinite focus, so “whether it’s 12 inches or 6 feet away, it self-focuses,” Averch said. The SHOW is designed to have at least two hours of play time per charge, and Microvision expects it to enter the marketplace by the end of the third or in the fourth quarter, said Matt Nichols, director of communications.

The company is currently working with partners such as Motorola to embed the PicoP into handheld devices such as cell phones; volume production of such embedded devices is expected in 2009, Nichols said.

The wearable pico projector

In addition to creating the handheld SHOW projector and embedding the PicoP into other devices, the company is also working to create eyewear that incorporates the technology. Instead of being projected onto a surface, the image would be projected onto the wearer’s eye.

The eyewear would connect either via wire or wirelessly to the user’s mobile device for social networking, entertainment and other applications. Text of a keynote address could be streamed in real time to a public speaker, for example – like having a personal, invisible teleprompter. Or blueprints could appear for firefighters trying to search a burning building.

The main challenge to adapting the projector for eyewear is the specialized optics required to trap the laser beam and direct it to the wearer’s eye, Averch said. The beam travels inside the optical material, which steers it directly onto the eye, creating the illusion that the image the wearer is seeing is hovering in space in front of him and that it is visible only to himself.

The PicoP optics was redesigned over the past year to create the much larger field of view required in a wearable device. Averch said that one of the design challenges was making sure that each viewing angle is delivered with uniform brightness.

Microvision introduced its wide-angle PicoP at the SID conference in 2007, where it presented a tabletop version of the technology that proved its optical feasibility. The company has been working since to create a handheld device featuring the technology and to incorporate the projector into a wearable prototype, such as a helmet-mounted display, under two contracts from the US Air Force.

TWMicrodisplay_Fig2_show_projection.jpg
Figure 2. Shown is a prototype of the palm-size, battery-powered SHOW projector, which connects to devices such as iPods to project bright, full-color, always-in-focus, high-resolution images that can range in size from 12 to 100 in. Image courtesy of Microvision.


The Air Force requires a high-brightness, lightweight, wearable device with a large field of view for use by advance forces, or scouts, who often spend a long time in hostile conditions carrying a lot of heavy gear. The Air Force is looking to replace with the wearable PicoP some of the items troops carry that contain display screens.

Concept demonstrators will be sent to the military by the end of the year. The design of the optics must be simplified before it can be manufactured at high volumes or head into the retail market, Averch said.

While the military is concerned primarily with the device’s performance, the consumer marketplace demands something else entirely.

For mobile device eyewear marketed to the public, “We’re primarily concerned with fashion and ergonomics,” Averch said. “People aren’t going to wear these things unless they look cool and are comfortable.” He envisions partnerships with style trendsetters such as Dolce & Gabbana to make the eyewear itself attractive and fashionable.

Because the PicoP engine is only 7 mm thick and weighs only a few grams, “We don’t expect it to be dramatically heavier than a regular pair of frames.”

The eyewear’s power consumption also will be very efficient, he said, because “We only need to draw the image where it needs to augment your view.” Lasers that turn on to draw “Incoming call from Gramma,” for example, won’t take up the same viewing space or use the same amount of power as when drawing moving video.

With Bluetooth technology and speech-to-text functions, it could be possible someday to both receive and send text messages without even touching your phone.

“Over 2 trillion text messages were sent last year. We’re positioning the eyewear as a new way to deliver text messages so you don’t have to pull your phone out to interact,” Averch said.

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