MechEng3 and I have been discussing the pro's and cons of various laser projectors, and we've come upon something that doesn't exactly make sense to either one of us. So this is a call to Specwhore, Yaddatrance, Marconi, and anyone else that has experience with full color control... (Note that this whole excercise is more to understand the theory of operation than to get it hooked up right - MechEng3's projector already works just fine!)
MechEng3 is running the EasyLase USB controller and Laser Design Studio software from JMLasers.com. (And let me say right now that I'm insanely envious of his compact, *portable* whitelight projector! I can't wait to see it at SELEM this summer!) Anyway, as best as we can tell, the color output on the EasyLase controller is TTL, which I assume to mean +5 volts for blanking and 0 volts for on. All three of MechEng3's lasers are solid state, and they all support TTL blanking.
Now, the Alphalite XC Pro controller (and software) from LaserIllusions.com also supports TTL color control. But while I haven't yet received my Alphalite, I've spoken with several other Alphalite owners and they all say the same thing - namely that you only get 8 colors with the Alphalite: White, Black, Red, Green, Blue, Yellow, Pink, and Blue-green.
However, MechEng3 is able to get a full range of colors, from oranges and various shades of yellow, to yellow-greens, violet, purple, light blue, etc...
I'm wondering how this is possible... Does the Easylase unit use some form of pulse-width modulation to emulate analog color control? (IE: vary the duty cycle at extremely high frequency to simulate varying intensity?) Because if it is doing this, it's got to be running at least an order of magnitude faster than the galvos or otherwise you'd end up with dashed lines instead of smooth traces, right? And just what is the frequency limit for TTL modulation on a DPSS laser anyway?
I always thought that true RGB color control was accomplished with an *analog* color output signal from the controller that either went to the *analog* intensity control of each laser, or to the input of an AOM/PCAOM to control intensity.
So, can anyone shed some light on this issue for us?
Adam