Laser head patterns
I was back in Austin for Thanksgiving last week. While hanging out in the room where my dad tutors his students, undoubtedly chatting with him about what on earth I’ll do next year, I started playing with his laser pointers. He has two, one of which has multiple heads that you can screw on to get different pointer shapes (like this one). There are heads for an arrow, a circle, a line, and a cross, in addition to the normal pointer. The heads look like basically like a piece of glass in a metal frame, and I wondered: What are the patterns on the glass that produce these different pointer shapes?
Miraculously, I also happened to notice that my dad now has a little microscope! So I plunked the laser pointer heads underneath it, to try to see what they look like.
And I can’t say that I understood what I saw. For the line-shaped pointer, I saw lots of lines etched in the glass, seemingly in parallel:
But with the arrow-shaped pointer head, I saw something very weird:
…No little arrows all over, but rather, a pixelated etching of wavy lines! All I can imagine is that this is something like one of those Magic Eye pictures where an image appears when everything lines up just right.
Does anyone know how this works?