SYMBOL LASER PROJECTION DISPLAY (LPD):

A MINIATURE, HIGH RESOLUTION PROJECTION ENGINE

INTRODUCTION

In recent years, mobile devices such as PDAs, cell phones and

laptops have become smaller and more powerful, while the end

user markets for such products have become increasingly

ubiquitous. However, the human interface elements (e.g. displays

and keypads) are posing limitations on the ability of OEMs to

continue to reduce the size of these devices. Symbol's laser

projection display (LPD) technology can resolve this issue for the

display element by providing a very small, power efficient display

engine which produces full color, high quality images.

The LPD technology is analogous in function to cathode ray tube

(CRT) technology, with the replacement of the CRT electron beams

with three visible laser beams. The LPD image is created via two

orthogonally moving mirrors, one of which is a high speed micro-

machined mirror. Unlike a CRT, however, LPD can be projected in

free space on any light diffusing surface at any distance, and does

not require a vacuum tube and phosphor screen.

Figures 1 and 2 shows an actual sample of the LPD opto-mechanical

engine, in comparison to a typical clamshell-style cell phone:

LPD SYSTEM ARCHITECTURE

Symbol employed a holistic approach to the design of the LPD

system, which resulted in a high performance, manufacturable

projection device. The first generation embodiment of LPD is a full

color projection engine that can project a high quality image on

virtually any surface. The LPD engine is comprised of a red laser

(635 nm), a blue laser (440 nm) and a green laser (532 nm). The

combination of these three primary colors allows the LPD engine

to render any color accurately within a wide color gamut. The red

and blue lasers are semiconductor diodes, which are small in size

and operate at low power. Both red and blue laser diodes are

available commercially and their output intensity can be directly

modulated by changing the drive current at high speed. Since there

are no commercially available green semiconductor lasers, the LPD

engine uses a frequency doubled, diode pumped solid-state (DPSS)

green laser. In this DPSS laser, an 808 nm semiconductor laser

pumps a Nd:YVO4 crystal, which emits 1064 nm radiation.

The infrared cavity contains a KTP second harmonic generating

(SHG) crystal, which doubles the infrared laser frequency.

June 2006

Figure 2. Symbol LPD - Optomechanical (Front View)

WHITE PAPER

Figure 1. Symbol LPD - Optomechanical (Top View)

Symbol Technologies has developed a micro laser projection display (LPD) engine, which employs red, green, and blue lasers to produce full

color, XGA resolution images and HD quality video. Since lasers are small, power efficient light sources, the device is miniature (4.3 cubic

inches) and can be battery operated (5 watts average power consumption). The projected image is always in focus regardless of the distance

between the projector and the display surface. The LPD device produces images with 24 bit color depth within an unparalleled color gamut.