This project is a laser deflection unit which can be controlled with two stepper.
Is is used to teach students how to work with microcontrollers.
There exist also a disc with a 4-quadrant photodiode.
In the git repository there is also a code which controls the laser deflection unit so that it always points to the photodiodes.
Here I uploaded only the important files for the deflection unit because this is the part the most people can use for other projects.
The full project can be found in: https://github.com/MrPerfekt/Maya
2 Stepper Motors: 28BYJ-48 (the cheapest one you can get)
2 Light barriers: RPI-579N1 (optional) (http://at.rs-online.com/web/p/gabel-lichtschranke/7003996/)
If you buy the cheapest laser diode, it will fit. ;)