year to more than three million in 2013.
Sanju Khatri, principal analyst for sig-nage/projection at iSuppli, said tiny displays have been a major obstacle, preventing smart phones and small laptops frombecoming primary platforms for computing and Internet access.
“The growth potential for embedded
pico projectors will be limited during the
next few years due to challenges in areas
including power consumption, size and
manufacturing,” she said. “As these issues
are resolved, pico projectors will appear in
many more mobile electronics devices.”
That might make microprojectors the
hot accessory, possibly as soon as this
Christmas. The upside: You could soon
project bigger versions of the photos or
videos from mobile devices onto virtually
any surface without having to download
them first. The downside: There may be
no escaping a slide show of Uncle Phil’s
two weeks in Branson, Mo.
Self-contained pico projectors now areabout the size of a garage-door opener, butthe trend is to embed them into portablethings, such as a cell phone, an MP3player or a digital camera.
Pico projectors with laser light sourcesare expected on the market sometime thisyear as consumers demand smaller devices. Diode manufacturers have beenbusy building diodes that lase at shorterand shorter wavelengths because theshorter the wavelength, the less powerthey use and the brighter the image is tothe human eye.
“We are still planning to begin initialshipments of SHOWWX later this summer,” said Matt Nichols, director of communications for the Redmond, Wash.-based Microvision. SHOWWX is ahandheld pico projector driven by thelaser-based PicoP display engine. (Formore information on projection technology, see “Microdisplays: Coming Soon toan Eye Near You?” September 2008, p.68, and, in this issue, “Flat Screens GoDeep – and More,” p. 56.)
High-power red laser diodes emitting at660 nm are standard in devices such asrecordable DVD players, but that wavelength appears relatively dark to thehuman eye, making the diodes ill-suitedfor compact projectors equipped withRGB lasers.
Mitsubishi Electric said it solved that
problem with its new red series – diodes
that emit at 638 nm – which provide the
brightness needed for pico projectors.
The company introduced the red diodes
at Laser World of Photonics in Munich in
June, saying they appear much brighter
than 660 nm or even the commonly used
645-nm diodes at the same output power.
Blue (450 to 480 nm) diodes showed upabout 15 years ago and are used now inBlu-ray disc players. In January at Photonics West 2009, Osram Opto Semiconductors GmbH of Regensburg, Germany,announced a blue laser with a wavelengthof 450 nm and an output of 50 mW that itsaid is the smallest in its class.
It ain’t easy beamin’ green
One hurdle that laser makers have hadto overcome is with the green wavelength,which stretches from 520 to 570 nm, with532 considered optimal for displays.
Green lasers have been achievedthrough frequency conversion of infraredlasers but have been unable to directlyemit green light. Recently, engineers havebeen inching closer to pure green emittersby producing wavelengths in the blue-green spectrum.
In February, researchers at Rohm Co.Ltd. in Kyoto, Japan, said they had pusheda gallium nitride (GaN) diode to thelongest recorded wavelength yet produced,499.8 nm, but said their technique is notsuitable for mass production. Later thatmonth, Osram Opto Semiconductors Inc.,Sunnyvale, Calif., published a paper inApplied Physics Letters describing anelectrically pumped 500-nm-emittingdiode based on its blue technology. InMay, in an Applied Physics Express paper,Nichia Corp. of Tokushima, Japan, said ithad created a 515-nm device. (At presstime, Osram Opto announced it achieved adirect-emitting green indium GaN laser at515 nm.)
Then in July, Sumitomo Electric Industries Ltd. of Osaka, Japan, announced thatit had created the first direct-emitting greenlaser at 531 nm. The company said it overcame a problem with GaN semiconductors(used commercially for blue LEDs), inwhich the material’s luminance efficiencyrapidly declines as the wavelength increases, by developing a GaN crystal thatinhibits the efficiency drop. The result wasroom-temperature pulse operation of alaser diode emitting in the pure-greenregion at 531 nm. Sumitomo has appliedfor 60 patents on the technology.
Spectralus Corp. of Santa Clara, Calif.,is reporting this month at the Eurodisplay2009 conference on its developments ingreen laser efficiency. In June, it announced a milestone in shrinking greenlasers: an eight-pin butterfly package forits 100-mW green laser. It also said thatthe lasers demonstrated 30 percent optical-to-optical (808- into 532-nm wavelength)conversion efficiency levels.
The company said in a statement that itis preparing a mass-production packagetailored for pico and embedded projectorsfor the fourth quarter of 2009.
Microvision signed a supply deal withCorning Inc. of Rochester, N. Y., in Mayfor its G-1000 synthetic green lasers andan agreement with Osram Opto for its blueand green lasers, to ensure an ample supply of diodes as it prepares to begin commercial production of the SHOWWX.
Nichols said he expects quantities to bein the thousands for the remainder of thisyear, constrained more by supply than by
Microvision’spico projector, the SHOWWX.
Courtesy of Microvision Inc.
A green laser emits from an oscillator. Courtesy ofSumitomo Electric Industries Ltd.