Are you sure you need to use a digicam for a 1/2" line. If you can put sensors close enough, just use a small bank of cheap light sensors.

For a digicam, I'd look into using a digicam with a parallel or USB interface. I don't know which camera protocols are available, but some are supported under Linux and are thus free.

I bought a QuickCam by Logitec hoping to do some computer vision using the micro; but it turns out that Logitec refuses to release the protocol specs for that version of digicam. Some of the earlier Logitec cameras are supported under Linux.

Let us know what you decide.
<>< Lance.