Since laser spirograph is not intended to be precise optical instrument, any available reflective material may be used as a mirror.
I know some folks have experimented with regular glass round mirrors, dental mirrors, hard drive plates and built decent working devices.
CD/DVD media may be used as mirror too but because of data tracks CD acts like diffraction grate and splits bright laser beam into few weak beams.
|DVD as a mirror. It may work as a temporary solution.|
The major drawback of regular mirror is that front side of the glass partially reflects light and that forms second ghost image. Only way to get crisp and clear image is using front surface mirror.
|How regular glass mirror and front surface mirror reflect light.|
Front surface mirrors are available on ebay and in numerous online scientific stores, also they can be salvaged from old optic hardware such as laser printers, copier, fax machine, scanner, bar code reader etc. and at least, it can be made at home workshop.
|It's possible to make own front surface mirrors.|
I've developed easy method of making front surface mirror from regular acrylic mirror sheet which should be available in Home depot or any plastic store.
Big advantage of acrylic material is that it can be easily shaped with hand tools as shown in my article about mirror balancing.
There's no strict rule how to set three mirrors for laser spirograph but I distinguish two optical configurations: parallel and square.
In parallel optical setup motors are situated along parallel lines.
I use double sided sticky tape to attach motor to base, and when beam alignment is done I secure motor on place with hot glue.
Alignment procedure is simple; start one motors at the time and aim beam that it stays within area of next mirror at maximum deflection angle.
As a spacer for laser module I use piece of scrap wood. Laser is secured with hot glue.
|Laser beam alignment may take a while.|
|After final alignment mirrors and laser module have been glued to base plate.|
|Motorized mirrors and laser module are installed inside box.|
In square optical setup, motors form three sides of the square so overall design is more compact.
In my opinion it's more advanced approach; shorter distance between reflective surfaces allow bigger tilt angle for mirrors and that results in bigger size of pattern being shown.
|Another way to situate mirrors for laser spirograph.|
|Motorized first surface mirrors. Closer view.|
|Laser spirograph is completed. Mirrors, laser module and controller are installed and wired.|
To set optimal mirror's tilt and simplify alignment I use improvised holding fixture for mirrors.
|Quick-made jig helps with mirror's alignment.|