T takes squinting and guesswork to make out the
details of postage-stamp-size snapshots displayed on cellphones and
digital cameras. But researchers are working on pocket-size
projectors so that one day people will be able to see a
high-resolution slide show right out of a camera, a cellphone or an
In the future, the miniprojectors may also be attached to DVD
players, so people can watch a movie with a TV-quality picture on a
Most standard digital projectors are bulky. Even the trimmest
video projectors used for office presentations have the dimensions
and the weight of a telephone book. But prototypes of a new
generation of miniprojectors, including ones only slightly thicker
than a credit card, have been developed, some based on
light-emitting diodes, others on lasers.
"There will probably be two or three different technologies for
miniprojectors that will coexist," said V. Michael Bove Jr., who has
developed a prototype. Dr. Bove is director of the consumer
electronics research project at the Media Lab at M.I.T.
"The important point is that whatever the technology, there are
going to be significant differences from present office video
projectors and projector TV's," he said.
For example, future miniprojectors designed to be embedded in
other devices may be used to cast images like control panels or maps
onto a car dashboard.
"They are going to radically alter the way we work with
projectors when you can download a map onto a phone and point the
projector at a surface to get a higher-resolution image," Dr. Bove
There are still problems to solve before inexpensive
miniprojectors the size of sugar cubes roll off the assembly line.
"It's going to take a while to make the projector design efficient,"
he said. Power consumption is an important issue since in many cases
the projector would draw power from the cellphone or whatever device
it is coupled to.
At present, Dr. Bove said, projection TV's and video projectors
can use hundreds of watts of electricity, but only a couple of watts
at most will be available when they are powered by batteries in
Because of the challenges, Dr. Bove predicted that before the
projectors are fully miniaturized, the earliest versions would
appear as attachments to laptops. "There's more room and power on a
laptop," he said. "Eventually, though, they will find their way into
Electric Research Laboratories in Cambridge, Mass., Ramesh
Raskar leads a group that has demonstrated a pocket-size projector
meant one day to attach to cellphones, digital cameras or
Lumileds Lighting, a company based in San Jose, Calif., that
makes extremely bright light-emitting diodes, has also developed a
prototype for a compact projector. Steve Paolini, director of
business development, said it was meant not for big-screen displays
in meeting rooms, but for personal uses. "Our initial goal was a
screen the size of a piece of paper," he said, "with the size and
brightness of a laptop screen."
The Lumileds projector is not for sale; it was built, Mr. Paolini
said, to demonstrate the power of light-emitting diodes. "But
there's no technical reason why pocket projectors can't be built
now," he said. "It's a market issue."
Lasers rather than L.E.D.'s are the basis for a hand-held
projector in development at Light Blue Optics, a company in
Cambridge, England. "We want a device that you can download films
to, press a button and see a huge screen projection," said Adrian
Cable, director of the company.
The large projections are produced holographically. "These are
not the three-dimensional holographic projections of Princess Leia
in 'Star Wars,' " Dr. Cable said, but instead two-dimensional ones
produced by an optical process different from standard projection.
Dr. Cable, who has a doctorate in holographic optics from
Cambridge, said the basics of projecting video holographically have
been known for 20 years. In it, light is forced to propagate not in
straight lines but through small gaps that force it to diffract.
Precise control of this diffraction can produce holographic
"Historically, images projected holographically have tended to be
grainy and poor in quality," Dr. Cable said. And even when the
images were acceptable, the computational problems involved in
calculating the holograms were time-consuming. "It used to take 20
minutes to calculate the hologram for one video frame," he said.
But the Cambridge group's work has resulted in improvements in
image quality and processing speed, he said. "It's much simpler to
form an image holographically," he said. "You need smaller and fewer
lenses, leading to a smaller projector."
At Mitsubishi Electric, Dr. Raskar and his group have developed
several methods to demonstrate how people will interact with
projector images in the future. For example, they have developed a
method to stabilize the projected image so that once it is fixed on
a wall it will not move with subsequent hand movement. Then they
developed a way to click and drag items within the projected image
from one place to another, using a game of tick-tack-toe projected
on a wall as an example.
"Now you can actually interact with the projected contents," he
said. "You point where the piece is, and then drag it to where you
want it to go."
Mr. Paolini of Lumileds also thinks that game playing is in the
miniprojectors' future. When he took one of the prototypes home, he
said, his son started playing with it on his bed, aiming it at the
"Think of it," Mr. Paolini said. "You can play games on the