OverviewA laser projector is a device which uses a pair of rapidly oscillating mirrors to control the direction of a laser beam. The scanning of the mirrors combined with the modulation of the laser beam allows for the production of:•Vector images/animations•Visual effects

Department of Electrical and Computer Engineering

Fig. 3 Sample vector image

Fig. 1 Block diagram of components

VECTOR LASER PROJECTORVECTOR LASER PROJECTOR

CMPE 490 DESIGN PROJECT 2010WCMPE 490 DESIGN PROJECT 2010W Josh Ibach-MacKeenMichael IveyJosh Ibach-MacKeenMichael Ivey

Design and OperationThe laser projector employs a pair of galvanometers that take an analog input voltage to control the modulation of small mirrors, allowing for control of the laser beam in the X and Y axes. Each galvanometer takes a differential input of + 5 V.

To control these galvanometers, a pair of XY coordinates is converted to an analog signal and transmitted over a pair of 10-bit Digital to Analog Converters (DACs) on the Atmel AT91EB55 Microcontroller. Each signal is passed through a noise filter to remove any unwanted noise before being passed on to the galvanometers. Since each DAC is only capable of a range of 0-2.5 V, these signals are correspondingly amplified in order to make full use of the projection angle of the galvanometers. This amplification process also produces the differential output signals needed to drive the galvanometers.

The laser is modulated by a transistor switch which is connected to a GPIO pin on the Atmel board.

Image PropertiesThe laser projector uses a custom software interpreter which translates images and animations complying to the International Laser Display Association’s (ILDA) standard file format to a form displayable by the laser. The projector is capable of drawing a maximum of 1024X1024 distinct points, and the “refresh rate” as such is entirely dependent on the number of points being drawn in an image. The projector is capable of emitting at a maximum viewing angle of 20o, but for complex images a smaller viewing angle such as 10o is required for improved image accuracy.

Fig. 2 Laser projector component boards

+X Amp+X Amp

-X Amp-X Amp

+Y Amp+Y Amp

-Y Amp-Y Amp

Laser moduleLaser module

Laser BJTLaser BJT

Atmel AT91EB55Atmel AT91EB55 Low-Pass Filter

Low-Pass Filter

Ga

lvo

YG

alv

o Y

Galvo YGalvo Y

Galvo Y Amp/Driver

Galvo Y Amp/Driver

Galvo PSU

Galvo PSU

Low-Pass Filter

Low-Pass Filter

Ga

lvo

Y

Am

p/D

rive

r

Ga

lvo

Y

Am

p/D

rive

r

BJT SwitchBJT Switch

Laser BeamLaser Beam