Don's Laser Things: K40 Optical Model & Alignment Tools
Solved Part 4 – Observation of light rays | Chegg.com
x700 #4 test on slanted bed: laser depth of cut vs. lens orientation - YouTube
2.5" Premium Focus Lens w/holder fits Trotec Speedy 300 and more models. Less detailed graphics engraving but more efficient for large area laser engraving.