Thanks for the welcome.
Quick question: how do I upload an avatar image for my profile?
Anyway..... I got into laser display back in late 2003. I was very surprised how connected to audio the whole thing is. A guy I know wanted me to help him design a show for Akron's First Night 2004 New Year's Celebration. He had some rather expensive proprietary laser projection gear.
I had already been doing a lot of graphics programming in Linux, working directly with the RAM on the video card (aka The Linux Frame Buffer). Using that to work with color vector art was no big deal.
Once I created enough material to make a show, I used his proprietary laser DAC card to play the show and recorded the individual outputs of the DAC onto a modified ADAT machine! As you might guess, the channels were X, Y, red, green, and blue. The ADAT machine needed to be modified so that it was DC coupled. The decoupling capacitors on the inputs and the outputs needed to be shorted. That way the ADAT could record and reproduce audio-like signals with DC offsets.
Once I saw that I could use an ADAT machine to produce laser signals, I knew I could write my own application to do all of this in software and use a common multi-channel sound card as the output device. When I started on the project in 2004, Dolby 7.1 computer devices had not really taken off yet. I could get stereo, 4 channel, then 6 channel and finally 8 channel PCI cards. Then came 6 channel USB and finally 8 channel USB.
The idea is the same with a computer sound device. First you need to tap the DAC outputs before they go through the decoupling caps. Those signals are all positive voltage with a constant DC offset. So a single stage op-amp needs to be added externally to add a regulated negative voltage to correct for the positive offset and to boost the gain a bit for laser projection devices.
If you google "LaserBoy DAC" you will see that there are kits out there that do this and a lot of home brew boards as well.
The software I wrote and the related technology of modifying the sound care are free and open source and the software is under GNU GPL.
First it only ran in Linux, but sometime in 2006 someone clued me in to libSDL. So now it can be compiled and run in just about any OS that is supported by libSDL; Linux, Windows, Mac-OSX and others. It comes with all of the source code in C++ and a compiled executable for Windows.
It allows you to open files of the type ild (ILDA: International Laser Display Association), DXF (generic CAD), formatted plain ASCII text tables and wave, all as sources of color vector art. You can also open bitmap files as color maps or masks or into the background of the display area for tracing. It also lets you draw individual vectors, place objects by math, move, scale, rotate and apply pre-defined functions to create animations.
Whatever you create can be saved as ild, DXF, txt, bitmap and WAVE! The wave is what you play from any wave player in any OS that supports multi-channel waves. That is what drives the sound card to produce the signals that are the laser show!
James.
