ellert@convex.UUCP (04/09/88)
I know of two laser surplus dealers that sell various laser related stuff (power supplies, scanners, mirrors, power meters, etc. (addresses below). Both sell General Scanning Z170 scanners for $100 to $200 the pair (probably used, but in good condition). These scanners are small (about the volume of a cigarette pack, but "squattyer") with a shaft extending out of one end. The rotation of the shaft is slight (~ 10 degrees) requiring fairly long scanner-to-ceiling distance, the dual coils of low impedance and requiring a fairly high current signal, and the 3db point is somewhere around 300 Hz or so (a carefully designed high pass filter may help this some - taking care not to crisp the windings ...). There are probably some very troublesome mechanical resonances in these things as well (maybe a notch filter is in order here). But the price isn't too much. Small, low mass, very thin (~0.1 mm) front surface mirrors are available from Edmund Scientific (ask for the heavy-duty catalog). Some sort of low mass but still adjustable collar (setscrew maybe?) should probably be used to mount the mirror to the scanner shaft as opposed to gluing the mirror directly to the shaft. Good luck! Let us know what you find out/how it works out. Meredith Instruments POB 1724 Glendale AZ 85311 (a little cheaper) M. J. Neal Company 6672 Mallard Ct. Orient OH 43146 leigh
oliver@cup.portal.com (04/11/88)
Are there text or publications that go into detail about laser scanning systems???? Circuitry..Computers..etc.... Oliver@cup.portal.com
rusty@cadnetix.COM (Rusty) (04/12/88)
In article <61700002@convex> ellert@convex.UUCP writes: > >I know of .... Well, I've got a strange thing I need: some sort of transducer to bounce a laser beam off of (in order to modulate it digitally). But, before you think, 'Oh, that's easy", try the desired features on for size: want to modulate at as high a rate as possible. (150mHz would be great, but I'll settle for 500kHz, and 100kHz might work ok) digital modulation (two states: laser on, laser off) to be effected by passing laser through what amounts to a (very thin) slit (ok, I'll give it away - I plan to pass the laser beam through a telescope), so beam deflection need not be too huge. budget is very important. (I am self-funded - i.e. broke - for this project) Any ideas? Could i use an ultrasonic transducer in some way? What is the highest useable freq for an Ultrasonic xducer? what is its bandwidth? how about taking the cover off of a crystal and frequency modulating the crystal (very slightly, i realize)? The speed of liquid crystals is too slow, i think. Anything else like LC I could use? (Power is only in the 2-5 mW range at the moment) -- Rusty Carruth N7IKQ DOMAIN: rusty@cadnetix.com Cadnetix Corp. UUCP: cadnetix!rusty 5775 Flatiron Pkwy. {uunet,boulder,nbires}!cadnetix!rusty Boulder, CO 80301 (303) 444-8075
joel@mit-amt.MEDIA.MIT.EDU (joel s. kollin) (04/14/88)
In article <2335@cadnetix.COM> rusty@cadnetix.COM (Rusty) writes: >Well, I've got a strange thing I need: some sort of transducer >to bounce a laser beam off of (in order to modulate it digitally). > want to modulate at as high a rate as possible. (150mHz would >be great, but I'll settle for 500kHz, and 100kHz might work ok) OA> > digital modulation (two states: laser on, laser off) to be effected by >passing laser through what amounts to a (very thin) slit (ok, I'll >give it away - I plan to pass the laser beam through a telescope), >so beam deflection need not be too huge. You can use an acousto-optic modulator to deflect the laser beam and/or turn it off and on rapidly. Try Crystal Tech in Palo Alto. Other companies and electro-optics technology can be found in optics buyers guides (Photonics or Laser Focus). I hope you're not thinking of laser tv. It's been done. Also, putting the modulated beam though a telescope will change the deflection angle. >how about taking the cover off of a crystal and frequency modulating >the crystal (very slightly, i realize)? OA Maybe. Sounds like it's worth a shot to me. If it works you should write about it. >The speed of liquid crystals is too slow, i think. Anything else >like LC I could use? (Power is only in the 2-5 mW range at the moment) Doubtful. Why bother when you're using coherent light? Acousto-optics can modulate laser light up to 3 GHz. joel
oliver@cup.portal.com (04/14/88)
Well to abtain that speed you need BUCKS!! The only way to get modulation at that speed commercialy is with an Acoustic Optic (AO).. This uses a crystal vibrated to create a standing wave from the input beam. This can effectivly be pulsed at 500khz (I am not quite shure on the fig.) One drawback is that this method waste power.... What is your Application? I might be able to help you more if I knew what it was.... Oliver@cup.portal.com Laser Fantasy
ellert@convex.UUCP (04/15/88)
There is something called an A-O modulator (probably acoustic-optical) that when properly driven will deflect the beam a few degrees. The device consists of a crystal of some presumably exotic material which is driven by a high frequency oscillator/amplifier. The beam is directed *through* the crystal and logic or video signals input to the high frequency driver cause the crystal to refract the beam differently causing it to deflect a little. The only one I have seen used a 40 mHz (!) driver, was physically very small (2 or 3 cubic inches), used a LOT of power (got real hot during operation), and was capable of modulation well into the video range, although the deflection was a mere 7 mm @ 1 meter. At this distance, the beam can be moved past a hole or slit for digital modulation or across a variable gradient filter for sorta analog output. These are available from Meredith Instruments for $100 or so. There are some laser head/modulator assemblies floating around the surplus market that were removed from large FAX equipment. The assembly includes an AC HV laser power supply, a 1.5 mW precision multi-stepped-capillary bore He-Ne laser tube (current modulates better than straight bore...), intensity feedback, and a modulator board. All that is missing is a +/- 15 vdc power supply to run the modulator. Seems like both analog and digital response was good out past 80 kHz. I have seen these at flea markets and some surplus catalogs for around $150. The only really CHEAP laser modulator I am aware of (and it probably does not work) is a polorization rotator... Saw this at the International Science Fair in 1971: The beam from a high spectral purity, polarized laser is sent down the air core of a long (6 feet) coil wound with a single layer of small wire with a polarizing filter on the output end. The high-current modulation signal was applied to the coil, thereby rotating the polarization of the beam. This rotation caused a beam of varing intensity to exit the polarization filter on the end. I have not seen this actually operate, however the project did win it's regional competition back when there was a relatively higher level of technology demonstrated by high school students - so maybe it does work a little. Probably only a few percent modulation, though. leigh (214) 952-0598 (214) 492-5794
oliver@cup.portal.com (04/18/88)
AO's do not bend the light....They create a Standing Wave and split the beam...Yes they do use a LOT of power but if fast switching is what your after this is the ticket..... What is the number for Merith Instruments?? I am intersted what quality AO's are avaible for $100..The ones we use in our head cost us around $1500 a piece!!! Oliver@cup.portal.com
jbm@eos.UUCP (Jeffrey Mulligan) (04/19/88)
From article <4584@cup.portal.com>, by oliver@cup.portal.com: > AO's do not bend the light....They create a Standing Wave and split the > beam...Yes they do use a LOT of power but if fast switching is what your after > this is the ticket..... You might be able to deflect the beam by frequency modulating the RF exciter. The angles of the secondary beams are certainly a function of the frequency. > What is the number for Merith Instruments?? > I am intersted what quality AO's are avaible for $100..The ones we use in our > head cost us around $1500 a piece!!! Does this cost include RF source and/or amplifiers? -- Jeff Mulligan (jbm@ames-aurora.arpa) NASA/Ames Research Ctr., Mail Stop 239-3, Moffet Field CA, 94035 (415) 694-5150