You’re quite right, John ... they are pricey, ‘though It’s encouraging to see better prices on ebay

My post was really just for technical information.

For what you are are doing [with the wire shadow and very small displacements], I don’t think you need worry about laser lines anyway: Unless I am very much mistaken, you could use any collimated light-source that filled the area of the sensor.

As for laser spot quality ... the classic solution is to use ‘Spatial Filtering’ ... but that’s another potentially costly and bulky solution to a problem that might not exist.

My impression is that this project is all about leveraging the precision of mass-market sensors with ingenious software.

MichaelG.