sephail.net - Laser POV Projector

Introduction

The goal of this project was to expand upon the extremely popular LED persistence of vision (POV) devices that have become a staple of introductory electronic kits. By using the same POV concept as the LED-based kits, we can construct a laser projector for a significantly lower price than any commercially available unit.

Theory

While browsing around a warehouse full of surplus optical and electronic equipment, I came across a neat little 8-sided polygon laser scanner module. It was one of those parts that you stumble upon and just have to find a use for (I'm sure you know how it is). Presumably, the module was originally designed for a bar code scanner, but upon contacting the manufacturer (Toshiba), they were unable to provide me with any information beyond the response, "yes, we have a record that we made that device." No data sheets or other specifications of any kind were available. After a little tinkering, I discovered that the built-in stepper motor controller circuitry outputs its pulses onto one of the control lines available from the motor interface cable and precisely controls the rotational speed of the motor -- both great features to have for a projector device. Unfortunately, only a limited number of the motors were available at the time and they are currently out of production. I don't have any pointers as to where to obtain such a device, either. Fortunately, every other component of the projector is widely available and can generally be ordered without too much hassle.

This laser POV projector works by utilizing the laser scanner motor assembly to create the horizontal scan and a first-surface mirror mounted to a high-power speaker driver to create the vertical sweep. The speaker driver + mirror combination acts in the same way as the galvos used in the significantly-more-expensive commercial laser projectors. The components (including the laser) are mounted so that the beam reflects off of the scanner motor, onto the vertical sweep mirror, and finally onto the projection surface. All of the components are controlled by a microcontroller (ATtiny2313) to create a virtual dot matrix display on which text or graphics may be displayed.