fullspeceng wrote:There are two ways to control laser power:
1) Adjust the pulse width -> limitation to on/off time
2) Adjust the current power supply -> reaction time limited
Statement number 2 seems correct (Power is controlled by the 0-5V or PWM pin). Let's assume we have placed 2 volts on the analog control pin. When we take the TTL control pin to the laser ON state, a typical 40W tube will produce about 6-10 Watts. If we raise the voltage from 2 volts to 3 volts the output will rise to about 20W. The problem with the present DC tube and power supply is the fact that the turn-on point is not very reliable. It doesn't start at 0 and cleanly rise to 40W. It starts at about 8 W with a very noisy output and rises to about 35W maximum. I don't see how you could make an accurate 8 bit power control using this analog input pin.
Statement number 1 doesn't make sense to me. Assume we have the analog pin at 3 volts to get the 20W. If we take the TTL control pin ON to fire the laser for 1 millisecond, we will get 20W for 1 ms. If we turn it on for 500us, we will get 20W for 500us.
The power density was the same in both cases. If the laser mirror were sweeping this beam at 1 meter per second, then the 1 ms pulse would make a line that is 1mm long and the 500us pulse would make a line .5mm long. The burn depth of these two lines would be identical because they both received the same watts/sec.
Using the above example (20W, 1M/S mirror speed, 1ms pulse, producing a 1mm line)
If I wanted that 1mm line to be EXACTLY 255 times deeper I have the following choices:
1. I could hit it 255 times with the same power (or)
2. I could drop the mirror sweep speed by 1/255 and fire the laser for 255 ms. (or)
3. Raise the 20W laser to 5100W.
That is why I proposed the multiple pass software. I could do it myself with CorelDraw, but imagine this process. Tell Corel to only show you the parts of the image with gray depth = 255. Process to laser.
Tell Corel to only show you the parts of the image with gray depth = 255 and 254. Process to laser.
etc. etc.
Since there could be errors after multiple indexing of the Y axis, I would prefer to do all the 255 passes on the present Y position before indexing forward to process the next line.