PhotographyLaser projector: Getting something done!
So the search for a swivel bearing began. I trashed some small (normal) motors I had lying around with the intention to use their axis and bearing. After opening up all motors I had, I collected the useful parts. To my surprise, some motors had bearings that were in some kind of suspensions:
These allowed the axis to be moved in any direction, i.e. X and Y angular movement! I cut out the bearing plate of the motor in the 2nd picture and put the mirror on it, on a 45 degrees angle, like this:
With this setup, the X movement will be twice as large as the Y movement. Then I dug up a pair of nice small bass speakers:
...and a stable steel enclosure. The speakers happened to be Monacor SP-60/8s. I looked up the specs on them (after all, I'm a speaker cabinet builder) and found out they have a maximum linear displacement of 2 mm. This would allow approximately 15 and 7.5 degrees of tilt of the mirror, if I'd attach the speaker coils some 8 mm below the bearing. At 10 meters, the projection would be about 6 meters wide and 3 meters high. Pretty large. The hardened steel axis was trimmed to a usable length, and the mirror bearing plate was put on an adjustable support:
...which mounts to the side of the case. Because this was only a test, the speakers were not mounted and their cones not cut up yet. If this whole thing failed, I would't have ruined two good speakers. The mirror axis was then attached to the dust caps of the speakers with two plastic strips and a little hot melt glue.
...and then...I stumbled upon 2 identical
Hard disk pickup assemblies
Most harddisk pickup systems use moving coils, much like loudspeakers. What's so special about these two? These are from harddisks used in servers of age. In those days (we're talking 1995 here) harddisk designers had to come up with ideas to increase the speed of the head pickup in order to reduce seek time. These two harddisks featured a quadrature optical feedback system in the form of a balanced double light shaft and a glass encoder plate. I didn't count the number of steps on the encoder glass, but I estimate 256 full quadrature steps. What does this mean? It means the pickup can be positioned in one of 1024 linear angular positions over its swing range. Perfect for positioning two mirrors X and Y!
... and this is where it ends. Although I spent a lot of time in this project, and were eager to get results, it's now sitting on the shelf gathering dust. As of this writing, I haven't worked on it for more than 2 years and I seriously doubt it'll ever be finished at all. The reason: I ran into a very nice deal for very cheap (USD 1.50) diode laser modules, salvageable from obsolete devices, and easily tweakable to output 5 mW. I bought 20 of them. 16 of those are going to be used in the laser display project.
© Joris van den Heuvel, Fuzzcraft.com