Originally shared by Alex Krause
This guy has a nifty little laser rotary setup with a video of it in action sorry for this being a link to Facebook but it’s not available anywhere but his personal page https://m.facebook.com/story.php?story_fbid=392550817793565&id=100011159491105
That is an interesting way to go about things. Food for thought 
Nice concept! Will be difficult to implement for other items than pens (due to height/focus adjustment challenges as well as weight considerations), but definitely takes care of the linear to rotary translation without any difficult calculations!..