For the electronics geeks.....modulation

[Bradfo69]

O.k., here's the newbie educational question for today.

Analog and TTL modulation. I basically understand the difference (I think) but, don't always understand what the "range" represents and how it affects me as a purchasing decision.

Say for example, you look at an ad for a laser and, they make reference to analog modulation 0-10kHz. Another ad might say analog modulation 0-20kHz. So... what's the difference? (besides "10k" smartass...!you knew you were thinking it!)

Same with TTL, I've seen 20k and 30k in TTL as well.

Why do I want one or the other or, better put, what does 10k versus 20k versus 30k give you?

Thanks! (And yes, I "googled it" first.)

[Jimboy3625]

I might be totally off here but I think that it refers to the rate at which the laser responds to the modulation signal. So a laser with an analog 20K modulation would respond slower than a laser with an analog 30K modulation, same for TTL.

Basically how many times does the laser scan for changes in the modulation signal per a given amount of time. The more times it scans for a change in the signal in a given time the faster it can react to that change.

Can anyone corroborate this?

Jim

[mixedgas]

1/30,000 works out to .00003335 or so seconds. In reality few graphics or beam effects ever need to change color every point, in fact you would be just fine if you were so slow as to change just every 3 or even 5 points, because of hidden points inserted into the scanned effect by software to allow for the physics of the galvo, ie undershoot and overshoot.

So a 10K pps minimum modulation is fine. In fact a 6K pps is probably fine. In reality few DPSS greens will change that fast. Its marketing speak. Direct diodes will easily hit 100 Khz with cheap drivers, so you only see specs on DPSS greens and dpss (473 nm ) blues.

Steve

[dnar]

As the modulation signal (analog) is just an audio signal in effect, the difference between 10k and 30k is that you hear more cymbals at 30k

Only joking, partially.

I do wonder how the modulation speed is measured, is it the -3dB point?

[Bradfo69]

@ Steve, Thanks P'fessor! (God I love this forum. )

Cymbals? At 30k, that was Steve Perry near the end of Journey tours! Only dogs and flying mammals could hear him!

[taggalucci]

And to add to the above (as I'm not sure that the difference between analogue and TTL has been covered)...

Analogue will allow a varying level to be applied to the signal whereas TTL is binary on or off. TTL is therefore undesirable for wide palette colour as there's only 8 colour combinations in TTL modulated RGB.

There is pulse width modulation of TTL which could emulate an analogue signal, but I wouldn't go there. Go analogue.

[dnar]

And to add to the above (as I'm not sure that the difference between analogue and TTL has been covered)...

Analogue will allow a varying level to be applied to the signal whereas TTL is binary on or off. TTL is therefore undesirable for wide palette colour as there's only 8 colour combinations in TTL modulated RGB.

There is pulse width modulation of TTL which could emulate an analogue signal, but I wouldn't go there. Go analogue.

TTL. Ah binary. There are only 10 types of people in this world. Those that understand binary, and those that don't.

[lasersmith23]

taggalucci brought up a great point. If you want basic colors, TTL will do the job. Later on, though, you will kick yourself for not paying a little more to have a wider color palette in the millions+ of colors. Also, the faster the modulation, the more capable your system will perform for raster graphics (if wanted) without the tails and other artifacts caused from slower modulation lasers. The faster the laser array, the more professional the system (image quality-wise).

[flecom]

Its marketing speak.

Accepted Answer

[Bradfo69]

I understood the basic difference between TTL vs. analog and, usually always look for analog although, my beam table is TTL which really I believe, is preferred since you're not color mixing and you're running full power on or off.

Analog vs TTL is really just a difference in the driver correct? The head is pretty much the head regardless, correct?