I'd like to share my latest project, a scanning laser microscope with you.
Some words concerning the principle: The pinciple is quite simple. The laser beam is focused on the object and the reflective light is being measured with a photodiode (in my case a BPW34). To focus right the current through the focusing coil is varied. The position of the object is changed by two Speakers, which are driven with different voltages. The speaker-membrane is moving and therefore the object-table, which is connected with the membrane is moving too. With this way of moving head you can reach movements down to µm.
A Commercial cd-rom-drive is ideal for our purpose. It combines everything we need, a laser-Diode, a lens with variable Focus and a photodiode. In my case I've changed the build in photo Diode with a lot of Pins against a single BPW34 with just two Output-Pins. Older cd-drives are suitable for the laser microscope because they aren't so miniaturized like modern drives. I use a cd-rom-drive instead of a DVD- or bluray-drive, because in the early days of this technology the pins have been larger and more separated than in modern drives...
You'll have to find out the two Pins for the vertical coil and the laserdiode. If you replace the built-in photodiode against a larger model you'll have no problems with soldering.
The laser-Diode needs a constant current, about 80mA. This can be easily realized with a LM317 and some resistors.