converting a regular mirror to a first surface one

[ghosttrain]

Hey, my first laser "projector" used stepper motors too
But I had ordinary mirrors. Have you by any chance measured the performance of the platters? From what I read there are several coatings on top of the aluminum which may or may not be a good thing. The aluminum layer itself sounds to be as smooth as you'd need.

[dkumpula]

Last week I made 24 FS mirrors with this method and glued them to the backside of moving heads. They work, but there is a quite noticeable loss as the beam is reflected off a bounce mirror with only 82% reflectivity.

Thankfully, SurplusShed has a deal this week on surplus Kodak FS mirrors: http://www.surplusshed.com/pages/item/l3750.html Only US$1 for 4-5/16" X 2-3/8" aluminized FS mirrors. Not quite the 3"x3" I'd like, but I'll live with 3" x 2 3/8" if they quality is higher than the homemade mirrors. Worst case, I lost $30 and I'll invest in some custom mirrors from the site Planters suggested.

I'll post the reflectivity results for these when they arrive.

-David

[ghosttrain]

Thanks for sharing your results. Er, are you talking about the other mirror you mentioned, or a hdd platter?

[dkumpula]

Just a follow-up . .

Those Surplus Shed FS bounce mirrors arrived and I just did a quick reflectivity test and they measure in at 90% on the 638nm diode I used for testing. That's not the nice 98% you'd want in a projector steering mirror, but its still better and cheaper than the 82% Do-It-Yourself approach.

Oh, and after 2 weeks after mounting those original DIY mirrors, I remeasured and they are still have 82% reflectivity. (They have been sitting indoors in a room with 80% humidity.)

I never did get all the layers of paint off of the other mirror I was trying to strip, but with a stack of the Surplus Shed mirrors sitting here, I don't have a need to keep messing with it.

-David