Vest-pocket beamer

Dec 08, 2004
Vest-pocket beamer

The vest-pocket projector could soon become reality. It is based on a tilting micromirror that builds up the picture line by line. The designers of a laboratory prototype have managed to raise its operating speed and resolution to the point where graphics and text are clearly legible.

The future beamer is likely to be no larger than a cube of sugar. Incorporated in a cell phone, the miniature projector would always be on hand – to present PowerPoint slides to a small group of customers or for quickly consulting an online journal. It could provide useful orientation in unfamiliar towns by projecting a street map onto the wall of the nearest building. This may be fantasy, but researchers at the Fraunhofer Institute for Silicon Technology ISIT have already built a demonstrator for a device of this size. It is capable of projecting text and images at a resolution of 320 by 240 pixels. Its chief component is a tilting mirror measuring 1.5 millimeters in diameter, which can be mass-produced on a microchip. The mirror deflects a laser beam by rapidly switching its angle of orientation, building up the picture pixel by pixel.

“The special feature of this mirror is the way it is mounted,” relates Ulrich Hofmann. “It is held by two torsion springs that allow the mirror to be tipped around two axes, in order to deflect the laser beam both horizontally and vertically.” Each time the mirror is moved, the springs pull it back to its original position so quickly that the movement can be repeated, in different directions, several thousand times per second. The electronics have been speeded up to match this high switching frequency. The control circuits take mere nanoseconds to decide how the laser light must be modulated in order to display each pixel with the right brightness. To avoid projection errors, the laser diode is backed up by a duplicate. It directs its beam at the mirror, but the light is reflected back to a photodiode that senses the mirror’s angle of orientation. “If, for instance, the mirror is knocked out of position by unexpected vibrations, the backup laser notices this,” explains Hofmann. “The electronics can then respond by adapting the projection data accordingly.” This feature makes the system insensitive to most external sources of interference.

The demonstrator is still too bulky to fit inside a cell phone. “When we did our tests, the electronics had not yet been miniaturized to that extent,” the physisist says. But that is one of the researchers’ next objectives, alongside increasing the mirror’s switching speed and hence the resolution. Another problem that remains to be resolved is the light source: At present, the only available laser diodes of sufficient durability and brightness all emit red light. Here, the researchers are waiting for their colleagues to find a solution. But their system is already designed to operate with multicolor diodes.

Source: Fraunhofer-Gesellschaft

Explore further: The New York Times to cut 100 newsroom jobs

add to favorites email to friend print save as pdf

Related Stories

A prison for photons in a diamond-like photonic crystal

Sep 24, 2014

Scientists from the MESA+ Institute for Nanotechnology at the University of Twente in the Netherlands have designed a novel type of reso­nant cavity that serves as a prison for photons. The cavity confines ...

Researchers design plasmonic cavity-free nanolaser

Sep 22, 2014

(Phys.org) —A team of researchers at Imperial College in London has designed a new type of laser, one that could be made much smaller than today's models because it would be cavity-free. In their paper ...

Recommended for you

The New York Times to cut 100 newsroom jobs

17 minutes ago

The New York Times Co. says it is cutting about 100 newsroom jobs through buyouts and layoffs in an effort to trim costs and focus more on its digital efforts.

Minimally invasive surgery with hydraulic assistance

59 minutes ago

Endoscopic surgery requires great manual dexterity on the part of the operating surgeon. Future endoscopic instruments equipped with a hydraulic control system will provide added support during minimally ...

Engineering new vehicle powertrains

1 hour ago

Car engines – whether driven by gasoline, diesel, or electricity – waste an abundance of energy. Researchers are working on ways to stem this wastefulness. Ultramodern test facilities are helping them ...

Analyzing gold and steel – rapidly and precisely

2 hours ago

Optical emission spectrometers are widely used in the steel industry but the instruments currently employed are relatively large and bulky. A novel sensor makes it possible to significantly reduce their size ...

More efficient transformer materials

2 hours ago

Almost every electronic device contains a transformer. An important material used in their construction is electrical steel. Researchers have found a way to improve the performance of electrical steel and ...

DARPA technology identifies counterfeit microelectronics

3 hours ago

Advanced software and equipment to aid in the fight against counterfeit microelectronics in U.S. weapons and cybersecurity systems has been transitioned to military partners under DARPA's Integrity and Reliability ...

User comments : 0