This might work
This is my concept for laser digitizing. First get a laser displacement sensor, Ebay has all kinds fairly cheap acurate to a couple ov microns. Problem is these units have an analog output so take a look at this http://www.usdigital.com/products/epot/.
This unit will take an analog signal and convert it to quadrature or step and direction signal. this is where I have to do some research, the scanning program would have to move X and Y but only move z till the range output turns on which means the laser is in range of the part.
Any input would be nice I work in automation and I am converting a BP series1