I'm trying to project a very thin line at a low angle over some surface defects (peaks and troughs). The scale is ~20mm square, but the defects can be sub-mm (0.2 - 1.0mm).
I am currently using a line generated by a laser pointer. The $4 laser diodes work well enough, but the line spreads out due to the low angle and poor focus(?).
Are there any better / safer alternatives, such as some LEDs + lens that could also focus the light into a line?
I'm new to engineering and optics so any advice would be much appreciated.