Way back in 1988, a family trip to a planetarium with a laser show started my obsession with working with lasers. Which lead to a part time job in col lege working on high power ion lasers used for shows at the local marine li fe park. Which lead to a 20+ year career in using lasers for science and industry.
The light show business got me a first serious job as a technician at the local college. After all if you can keep a 30,000$ water cooled, 480 volt powered laser based on a six foot glass tube running on a rock tour, you mi ght just have the skills to keep scientific lasers running. After ten year s in academia, the more serious jobs arrived.
Which peaked as a field service engineer on systems ranging from UV to Far IR, pulse times as small as seven femtoseconds, and more then once tuning s ystems in the Terawatt peak power level.
So I have not forgot my humble laser show roots, and I help my best friend keep his laser show company running.
A frequent problem for him (and me) is dealing with collaboration when the other company has a green only laser projector, and he uses RGB. Green lase rs are cheap, red and blue light is actually expensive, even with blue lase r diodes being available.
While DMD based projectors have reduced the show/display industry to a shre d of its former self, when you need to light up a mountain or ski slope wi th a company logo, XY vector scanned laser projectors still can do things t hat arrays of DMD based video projectors can not.
So before some one laughs at my simple need for 5 KHz bandwidth, keep in mi nd that my idea of a small projection area is 150 feet by 450 feet on the w all of a building. With 60 watts of laser, at levels of optical flux that w ould melt a digital micromirror array.
Vector scanned mechanical graphics is not dead. In fact vector scanning of laser light is growing exponentially for laser marking, microscopy, and med ical diagnostics.
So I did not slip a digit or two on the scientific notation. We use gal vanometer scanners that have roughly a DC to 6 KHz frequency response for s mall angle steps, with a 3 mm square mirror attached. One scanner for up-do wn, and one for left-right. They are entirely analog, with complex PID loop s and capacitive position feedback sensors. The feedback loops are hand tun ed, usually having six 20 trimpots to adjust. The mirror inertia is about 0 .28 gm-cm and the shaft inertia is about 1/2 that. Not bad for something de rived from a moving iron meter movement. One could make a argument for worl d's fastest off the shelf mechanical servosystem. Disk drive arms are at be st, about 1/10th as fast as these.
The problem is, the further I move into the installation and repair of larg e systems, the less time I have to practice electronic design. So I'm getti ng forgetful in my old age.
So have a laugh when I tell you the industry standard driver for the signal lines is a differential pair of TL082s.
And yes, in theory, all the control signals for a large display fit on seve n channels of a DC coupled sound card, although only the hobbyists use thos e. The rest of us use Coldfire based dedicated vector processor cards. This gives us 16 bit 3D wireframe graphics with 64,000 possible colors. And No, Mr. Panteltje, I'm not going to give you a pair to play with after you accused me of slipping five orders of magnitude. I'm not THAT senile y et. :-)
Thanks guys for the much needed refresher course in active rectification.
The "select high" circuit is not a standard example in electronics texts, i n fact its quite rare in any on-line documents.
Again thanks for the examples....
Steve