Step 2: The driver
To make a proper driver for the laser diode, etch the PCB and solder the components as shown in the diagram.
Some people only connects the LD with a resistor in series, but that driver is a better (but more expensive) way to use a laser diode.
The LM371 varies the voltage the LD uses (i cutted the top because it didnt overheat, i think i does not affect the way it works), the two 10ohm resistors in parallel set the maximum voltage and current the Laser Diode will get, the pot allows adjustment of output current, The 1N4001 diode protects the LD from a negative input as battery placed wrong, but LM317 can't deliver neative voltages, so maybe it is not necessary, and the capacitor protects laser diode from immediate power supply especially when switching on.
This driver is a mixture of what i have seen arround, so, if something should not go there, please tell me.