On Tue, Dec 20, 2005 at 08:12:06AM -0800, Neil Baylis wrote:
> You don't need to mount the laser on the shaft of the stepping motor.
> All you need is a tiny mirror mounted on the end of the shaft at 45
> degrees. Point the laser into it, i.e. along the axis of the motor,
> and it will scan the beam through 360 degrees if you want. This will
> also work with a clock movement, even a very small one. The mirror
> only needs to be big enough to intercept the laser. This lets you use
> any laser.

As someone else mentioned I'll need a front-silvered mirror for that. I
thought of this option initially, and decided against it as the mirror
would eventually get dusty. Cleaning is problimatic as it's high up on a
ceiling and would requier special training. 

I wonder though... Is there such a thing as a "pseudo-half-silvered"
mirror? Make one that applys the silver to a glass carrier and then
applies a very thin protective film to the silver. While there still
would be two reflections present they could be very close to each other,
making the resulting beam be for all practical purposes a single beam.

> Meredith instruments is a source of good quality modules. You can get
> one with a built in collimating lens, and a good long lifetime.

Good resource! Their 650nm 3.5mW is cheap too, only $20. At 3.5mW it's
about the brightness I want, as described below...

> Be careful with safety issues if the beam is moving slowly.

Well I plan to use a very *low-powered* laser. One that is (relatively)
eye-safe. Most laser pointers are such that if you look at one, even
star at one, you are only temporarily blinded. That level of safety is
exactly what I want. 3.5mW might just give that to me... :)

-- 
pete@petertodd.ca http://www.petertodd.ca
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