What do you guys think?
https://www.youtube.com/attribution_link?a=gDruvJDNWp4&u=%2Fwatch%3Fv%3DCC9kGOlxlHs%26feature%3Dshare
Certainly a simple answer to the variable focus problem.
I wonder:
-Should it have a guide that insures that it does not mis-align the lens as you move it up and down, making the beam non-parallel to the bed. Beam parallelism is hard to recognize and creates lower power and angled edge cuts.
-How do you create positive pressure to keep the lens clean using air assist.
-Can you add a laser indicator? If you do will the focus point of the pointer change as you raise and lower the lens assy.
-Using this would allow you to simply exchange lenses with differing focal lengths. Maybe put lenses in cartridges.
-Also easier to clean lenses
I would personally not use this, for all the same reasons as @donkjr mentioned. I prefer the tube within a tube method to make the focus adjustable.
Someone on this or the FB forum was working on one that adjusts using a small DVD stepper and rack and pinon, that did solve some of these problems. I finally decided to use a movable table once I found out that “its not nice to mess with the optics” :).
I think @HP_Persson has something similar to this in his laser?
my conviction is its better to adjust the object (30x20max) to the K40 focal lens than the opposite. if one day I do my own version of the K40, I would introduce the object from the front, raise it up to a ceiling (focal lens height), remove the ceiling board of the ray path (witch could have also another function, like becoming a top cover).
fixed focal design have also plenty of advantages, cheap, easy to match webcam image of the object(material) with virtual design…