|"I made the hardware mainly from stuff I had laying around but also from some stuff I had to buy specially for this project.|
The polygon mirror assembly is mounted vertically on the flatbed scanners sled. The flatbed scanner sled is the Vertical axis, and the polygon mirror deflecting the laser in the scanner is the horizontal axis. Each Horizontal line is scanned about 150 times before the sled moves on to the next vertical position. The laser is scanned by the mirror continually at 55 Revolutions of the mirror per second, or 333 Hz scan rate, as the mirror is hexagon shaped. The exposure pattern is produced by turning the laser on and of synced to the rotation of the mirror.
There are two microcontroller boards used. One is a digital servo speed controller for the polygon mirror motor. It just runs the motor up to the exact speed when requested, and sends a servo locked signal while the motor is at the correct speed.
The other Board is the main board, which has the current source to control the Laser, and a driver for the stepper motor. This Board is connected to the PC through an uart. The PC instructs the machine what to do. The PC can tell the main board to start the scanner and run the stepper to a specific position, and transfer data for scan lines, one line at a time. Each scan line is scanned about half a second, and then the PC tells the stepper to move on one position, and sends the data for the next scan line. During the half second, the line is exposed about 150 times."