lbg@gitpyr.UUCP (Lee B Grey, Programmer Extraordinaire) (10/04/85)
If this is not appropriate for this newsgroup, please don't yell. I'm just curious and not sure where else to go. I would assume that the laser people are too involved with discussing Neon versus Argon versus Polygon to talk about anything as frivilous as laser shows... Anyway, I was wondering if anyone could give a brief dissertation on how laser shows are done. I realize that a computer controls a mirror, but it all seems rather magical. I mean, what kind of motors are used that can move so accurately, so quickly? How often is the image redrawn? Is the laser strobed in some way? Etc. etc. etc. I hope this is something of interest, and not an annoyance. Thanks. Lee Grey
jbn@wdl1.UUCP (10/06/85)
The basic idea is to use a loudspeaker driver to move the mirror; some rigs are as simple as a small bit of mirror glued to a loudspeaker cone. But I'd like to hear more about what's commercially available. John Nagle
dan@rna.UUCP (Dan Ts'o) (10/10/85)
In article <737@wdl1.UUCP> jbn@wdl1.UUCP writes: > > The basic idea is to use a loudspeaker driver to move the mirror; >some rigs are as simple as a small bit of mirror glued to a loudspeaker >cone. But I'd like to hear more about what's commercially available. Well, that might produce interesting results, but that would not allow any kind of 2D linearity. You could never produce the pretty 3 color laser graphics animations shown at Siggraph, nor the regular oscilloscope-like displays. The real thing uses mirrors on galvanometers. Such mirrors are produced by a company in Watertown, Mass called General Scanning. They make drivers as well, although you can drive the coils with a regular stereo hifi amplifier. Two mirror are used, each one mounted on a shaft that is driven by a galvanometer. The mirror are placed one above the other, tilted and one rotated by 45 degrees. This arrangement allows one coil to control the X axis and the other to control the Y. You can drive the X axis with a waveform generator and the Y with your music to produce a laser oscilloscope. It is best to filter out the high frequencies and drive the Y mirrors with just the bass portion of the music because the eye cannot follow the high frequency stuff. The mirrors themselves have a frequency response from DC (if you use the right drivers) to about 1Khz. To represent the high frequency portion of the music, you could drive the mirror with the amplitude envelope (just like AM). I have never done this but it should work. I hope this helps. Cheers, Dan Ts'o Dept. Neurobiology Rockefeller Univ. 1230 York Ave. NY, NY 10021 212-570-7671 ...cmcl2!rna!dan rna!dan@cmcl2.arpa
fournier@Navajo.ARPA (10/14/85)
*** REPLACE THIS LINE WITH YOUR LASER BEAM *** There is a paper on computer driven laser displays in the Proceedings of Graphics Interface '82, by Ken Deaton. Graphics Interface is a Canadian Computer Graphics conference, and the Proceedings should be reasonably widely available (ask your librarian for it by name!). By the way the next one is in May '86 in Vancouver. Be there.