Mark,

how are you progressing with your wood burning idea ?

I've been looking into a few things (but not the lasers !!) and
believe there's a cheap and workable solution

In this video

http://www.youtube.com/watch?v=3DXV-if-oqXn4

the diode from a DVD burner is being used to mark wood, and
fairly quickly too (I notice that so many people take these lasers
very lightly indeed. Class 3B is dangerous. One thing that surprised
me is that just about everyone sells high power lasers but very
very few sell glasses/goggles)

Over the past few weeks I've found 7 broken 16x DVD burners
in workshop and scrapdealer bins, and free. All of them have
working diodes, both the high power red writer and the lower
power IR reader

Here's a driver circuit I've been working on

http://home.clear.net.nz/pages/joecolquitt/burner_schematic.gif

I'm awaiting some laser glasses before proceeding with full-power
tests but in the meantime have sorted out the jigs and optics. I've
also designed the copying mechanism but not yet built anything.
The stepper motors from the drives will come in handy for that

In addition to the collimating lens used in the video above, and
others like it, I'll add a focussing lens to get a finer line which
would be burned more quickly

One idea I had was to find a chemical that would react to a red
or IR laser and darken, kind of like invisible ink, but so far I've
not found one. Maybe I'll try good ol' lemon juice one day

I'll keep you posted

Joe
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