Originally Posted by
Pangolin
Hard to say what's the cause -- whether it is purely visual (i.e. in your mind), or the fault of that which is driving the laser, or the laser diode driver. Nothing would be surprising...
If you scope the input to the laser diode driver and it's nice and square, then you could look at laser output using a photodiode and see if that it equally as square.
But there sure are a lot of crappy laser diode drivers out there...
Thanks Bill, done that already, which leads me to know that it is the signal conditioning being presented to the projector's ILDA input connector. An the surge is measurable with a laser power meter, it's not in my mind. The initial "brightness surge" does not occur with the projector laser diode outputs when driven by an EtherDream2 or FB3QS, (and these and my outputs are perfectly square as seen on a scope), only when driven by a perfectly square, TTL derived blanking signals whose peek voltage is adjusted via a TL084 opamp to be at or below the respective diode's near max voltage. I noted these two DAC's max RGB ON voltages, having been adjusted for proper blanking with LSX and QS respectively, and my circuit is replicating these full ON voltages.
Maybe the difference is that I'm not conditioning the RGB diode blanking singles to swing between near turn-on threshold and near max. on, just 0v to near max. I don't see how this could make a difference, though, could it? I should add I'm only trying to turn each color ON or OFF where ON is near but not at full intensity.
I'll take a closer look at the EtherDream2 and FB3QS blanking signals.
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Everything depends on everything else