technical reference
39Synrad Firestar ti-Series operator’s manual
Controlling laser power
SYNRAD’s Firestar ti-Series lasers produce an optical output pulse that is almost exactly square (see Figure
3-5), meaning that there is no leading edge overshoot and virtually no power variation across the actual
pulse. The square output pulse of the ti-Series laser coupled with its shorter rise times (~75 µs) means that
material processing is more efficient since a greater amount of laser energy is absorbed, which is especially
desirable when working with high threshold materials.
T
1
2.00 V M 200µs Ch1 1.24 V
Ch1
M3
Optical output pulse (10% duty cycle at 100 Hz)
Figure 3-5 Representative ti-Series optical output pulse
Marking/engraving operation
When the delay between the end of one PWM Command signal pulse and the beginning of the next
PWM pulse exceeds 200 microseconds (less than or equal to 5 kHz), Firestar’s on-board tickle generator
sends a tickle pulse to maintain plasma ionization in the tube. Because the on-board tickle generator can
not anticipate when the next PWM Command pulse will arrive, the tickle pulse (which typically lasts for
2–6 µs depending on the laser) can effectively merge with a PWM signal that follows closely afterwards.
When the PWM pulse that follows is short, causing the tickle pulse to become a significant fraction of the
PWM pulse duration, then the tickle pulse effectively substantially increases the length of the PWM pulse
it has merged with. For subtle marking applications on sensitive, low threshold materials this lengthened
PWM pulse may affect mark quality.
While this situation can occur when using PWM Command signal frequencies of 5 kHz and less, it is im-
portant to note that it isn’t the Command signal frequency itself that is the determining factor but rather
this behavior happens only when the off time between PWM pulses exceeds 200 microseconds.
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