This application is a very cheap solution for displaying text messages on a solid or semi-opaque surface by using a laser beam. The main goal was to verify the possibility to build a simple and cheap display for displaying large text.
The basic idea was to use only one light source (a laser beam) and mirrors to scan the display surface.
So, the main parts used to build the display are:
- a laser diode from a key-chain pointer
- a cassette player motor
- an ingenious “head” with mirrors
- a PIC17F877 board with the associated circuitry
- a power supply
The head is an octagonal prism, with a small mirror on each lateral face. Each mirror is mounted with different angles, giving different reflection angles for the laser beam.
The basics of this design is similar with television principles: the laser beam is reflected by the mirrors placed on each face of the octagonal head creating a raster. This raster is modulated by turning on/off the laser beam. The Microcontroller board receives one pulse per rotation from the rotational speed sensor and calculates very precisely the moment for turning on/off the beam.
There is a RTC (real time clock) and a temperature sensor block which is optional. The purpose of this block is to provide the corresponding data to the microcontroller for displaying. But, because the main goal was to test the possibility to build the display, I didn’t assembled the optional components.
For more detail: Mechanically scanned laser display using PIC17F877