r691175002 wrote:The main differentiator here is the speed of the pulses vs the rise time of the laser. Naturally if you are pulsing faster than the rise time the pulses will blend together. I would argue that we are already pulsing faster than the rise time on our chinese tubes so technically we are already grayscale engraving anyways.
If you sent really fast PWM signals to the laser you would be able to set the grey level. However, a PWM signal control like that makes the laser SLOWER to respond than it already is unless you have some kind of feedback method and a very fast PID controller. Getting a good greyscale out of these tubes is going to be almost hopeless because the transients are not nice to deal with. It would be one thing if the tube had a very predictable on/off cycle and played nice, but it doesn't. The problem is that the tubes responce changes with a lot of variables and the on response is not nice... it goes to about double max power and then decays down.
I am now coming back to my original conclusions that the only way to get reliable, quick performance out of these tubes on some reasonable engraving speed is to use a beam chopper and/or an AOM or EOM which is fairly pricy and leave the tube on all the time durning an engraving and let the chopper do the work of splitting the beam into very small pwm segments