Hacked Gadgets has a follow up to to the hard drive laser oscilloscope, here’s how to make one – “A hard drive voice coil circuit is hacked to allow it to be directly connected to a stereo output. This allows audio to move the hard drive read write head. Mirrors are positioned on the center of the platter and hinged on the side to allow a way for the laser to be moved in two axis. The read write head is connected to the hinged mirror so that they move together. And finally a laser is mounted to the hard drive pointing at the hinged mirror. Crank up the tunes and have fun!” – Link.
HOW TO – Making a hard drive laser oscilloscope