On January 26, 2022 6:32:09 AM UTC, "David Lanzendörfer" leviathan@libresilicon.com wrote:
Hi What about just buying a new cheap Chinese laser diode and a photo diode and then putting a mirror onto the lense carrier, which reflects the laser diode beam back to the photo diode next to the laser diode?
dc32 used 2 and got a phase differential which increased accuracy. actually, it was infrared but you get the idea. source is somewhere, uses an ATTINY. mirror not needed, works with any reflective surface.
i saw well over a year ago some maker actually used a DVD sensor (taken from a DVD player) which did 2D phase differential, when it produces a circle instead of an oval the 4 readings in 4 quadrants are equal and you have focus.
the nice thing is, if the oval is squashed one way you are too close, squashed the other way is too far.
l.