How to build a simple electronic focus for your DIY WebCam Microscope?
Allmost all todays compact disc players have an electronic focus element composed of a small lens and two electric coils. The lens can be moved up and down by powering one of the two coils with around 1.5 volts.
Compact Disc Focus Element
The lens setup can be removed fairly easily from the rest of the CD electronics. In combination with a web cam this makes a nice microscope with electronic focus. Just glue the whole unit on top of the webcam after removing the original lens.
To control the lens movement you can power the coil through a potentiometer (low resistance, about 200 ohm). Or you may want to connect it to an arduino and control the focus of your microscope with a PWM signal.
See the movie below of the setup in action: