I thought more of a delay before the pumping energy is high enough in the cristall bevore it emits green laser light. seriously i forgot all the details and where i read this but it was something about that dpss "turns on" slover than a diode and "turns off" with a delay too. thats why a user at PL developed the "DPSS correction circuit" to remove "tails" in scanning projections.

You may be right.. like I said, FrothyChimp is the man when it comes to DPSS stuff. What you are describing sounds like power sags and surges (instability). In a green DPSS laser, when the pulse of pump energy hits the crystal, it does take a brief instant for the power level to come up, so if that is what you're describing then yes, there is a delay. I believe however, that even though it is not at full power, green light is emitted the instant the pump beam hits the crystal. There is most likely enough power present that data communication could still take place, and like I said in my last post, these stability issues are far more of a problem than propagation delay.

Are you sure you aren't thinking of sound?

Sound as well.. In lenses and prisms, refraction occurs because the light slows down (its phase velocity decreases) slightly as it leaves the solid material and enters the air, which causes the light waves to change direction slightly..

You've got it backwards. See speed of light.

Mmm.. I'm still not too sure about that. That statement is comparing an unknown transparent material (could be solid, liquid, or gas) to a vacuum (which has unique properties when it comes to transmitting energy), whereas my statement is comparing a solid transparent material to a gaseous transparent material.

You may be correct, but I'll have to do more research later. I'm at work presently, so I'm a bit limited, and I can't remember all my high school physics ATM..

Regardless of the order of things, I still don't think that the speed change would slow or delay the transmission of light enough to prevent modulation up into the MHz range..

You are correct, cyparagon.. Here's a link that describes this in more detail. Thanks for your input!

http://www.physlink.com/Education/As...TOKEN=62018254

So, any delay would depend on the type of solid medium, and on its specific properties. It is true that DPSS lasers are more limited in terms of modulation speed than their diode counterparts, but just how much more limited I have no idea..

My own personal experience with high speed optical data transmission has always been with diodes only, and I'd imagine that has to do with what is described in the link above. That, coupled with the instability that DPSS lasers tend to display while being modulated is pretty much a deal-killer for this type of application.

How about just blanking CW lasers with a extremely rapid LCD or DLP?

There has to be a solution cause coherent has a working model. We've all seen it on youtube with that news broadcast.

That's basically exactly what AOMs (acousto-optic modulators) do. Here's a link with more info on that: http://www.rp-photonics.com/acousto_...odulators.html

If you combine an AOM with an aperture or mirror, it will modulate the beam at very high speeds. The maximum speed depends on the AOM.

AOMs are the only practical way of modulating gas lasers, but they work great with DPSS systems. Coherent doesn't even build direct modulation capability into their green DPSS systems (or any of their DPSS systems that I know of), so an AOM is the only way to do it. AOMs are superior to directly modulating DPSS lasers in general since they eliminate any instability/mode-hopping.

I definitely wouldn't be at all surprised to see MEMS technology like DLPs involved in laser TV technology somewhere..

Great... thanks! now we are a step further - we need AOM's in MHz Range for a Beamer

Aren't they scanning alreay with a MEMS X/Y Mirror? at least Microvision does...

As far as I know, the current laser TVs just combine the beams and feed the white beam to a DLP chip. Since there's no scanning needed and each of the DLP mirrors corresponds to it's own pixel, the chip acts as a PCAOM (albeit at only 60Hz or so)

Ok. then this would be another way to do it, nor?

Combining RGB(r), expanding the Beam, fire to DLP so the back reflection goes of of Beamer

Is the DLP capable of controlling color blending? I always thought that in systems using DLPs, the incoming light is color-cycled, while the DLP controls the position of the scanning beam(s).

Yeah older systems used a spinning color disk to rapidly cycle through colors, but newer systems use three DLP chips and a combining optic. So one DLP chip per color.

^Thanks! I thought that was how it works.. Is that some kind of laser chiller in your avatar?

Outsch. 3x DLP... recombining the prozessed beams with a laser could be a challenge.

Maybe... just color cycle the laser too and use just one DLP? Assuming we change the color three times per frame its just 75Hz modulating speed instead of multiple Mhz!

Yeah it actually is a water chiller I built a few years ago, although it wasn't specifically designed for cooling lasers.

Back to the scanner - getting into AOMs and such, this would be a pretty pricey project for someone to make from scratch.

I saw AOM's with driver on fleebay for 30$... mybe woth a try.

Is it possible to combine the beam first and then modulate by a AOM like a multiline Argon?

I have one of those AOMs, and the only problem with that idea is that those are coated for red HeNe wavelengths. The losses with green or blue is too high..

With a properly coated PCAOM you can combine the beams first. That would be the only practical way to build this kind of project. You wouldn't necessarily need three AOMs. One of the main functions of PCAOMs in laser show use is to control color intensity as you already know, so that would definitely be the way to go here.

Ack. can you aproximate what a proberly 650/532/473(/405) coated PCAOM would cost?

Other way could be eventually polarize the lasers and then modulate by lcd layer...

To the mirrors: What about rotating polygon mirrors

It's not the coatings that's the problem, the problem is the driver. The driver creates a wave in the crystal which changes the crystals properties at certain wavelengths, if the driver is at an incorrect frequency then it can't modulate at that wavelength.

-Adam

$1600 - 5000 new

Wow! you learn something new every day. I always just assumed that the coatings were responsible (and I still do think they matter a little in terms of losses) but given how AOMs work that makes perfect sense...

So this means you cant just use any AOM and maybe even not a for-multiline one, cause the freuquencies must fit your lasers exactly?

we should get back to the cheaper lcd blanking idea