Synrad Firestar f series User Manual

technical reference
36
Synrad Firestar f-Series operator’s manual
Controlling laser power
The Controlling laser power section includes subsections:
■ Control signals
■ Operating modes
Control signals
Much of the information provided in this section describes the use of a SYNRAD UC-2000 Universal La-
ser Controller to provide PWM Command signals to the f-Series laser. If using an alternate method of laser
control, thoroughly review this section, Controlling laser power, as well as the following section, User I/O
connections, for an understanding of the signal requirements necessary to control Firestar lasers. For more
information about the UC-2000, please consult the UC-2000 Laser Controller Operator’s Manual.
Tickle pulse
Tickle pulses pre-ionize the laser gas to just below the lasing threshold so that a further increase in pulse
width adds enough energy to the plasma to cause laser emission. Tickle pulses cause the laser to respond
predictably and almost instantaneously to PWM Command signals, even when there is considerable delay
(laser o time) between applied Command signals. All Firestar f-Series lasers incorporate a built-in tickle
generator, freeing customers from the need to supply tickle pulses between lasing commands.
Internal circuitry monitors the incoming PWM signal and determines the amount of time the laser was
on (lasing) during the last 200 microsecond (µs) interval. If the laser’s on time was greater than the preset
tickle value, then no tickle pulse is generated because the PWM signal was sucient to maintain a plasma
state. If no PWM signal was applied during the 200-µs measurement period (or was shorter than the preset
tickle value), internal circuitry generates a tickle pulse such that the laser always receives a pre-set amount
of RF drive averaged over any 200-µs interval.
Warning
serious
personal
injury
Because of phase dierences, external tickle pulses may combine with
the internally-generated tickle signal causing the Lase LED to icker
during the transition from tickle to lasing. Laser output may occur if
the Lase LED ickers.
Pulse Width Modulation (PWM)
Pulse Width Modulation, or PWM, controls laser power by varying the duty cycle of Firestar’s RF ampli-
ers, which in turn control the time-averaged RF power applied to the laser. Typically, laser output follows
the PWM input with a rise and fall time constant of ~150 µs; however, the laser cannot precisely follow
PWM input signals if the “On” pulse is less than 150 µs in duration. At a constant 50% duty cycle, f-Series
lasers typically reach 90–100% of full optical output when operated at a frequency of 3 kHz.
The percentage of optical output increases as duty cycle increases (at a constant PWM frequency) or as
PWM frequency decreases (at a constant duty cycle). Figure 3-3 on the following page shows representa-
tive f-Series optical output waveforms at two dierent duty cycles and frequencies.

Synrad Firestar f series Specifications

General

Brand	Synrad
Model	Firestar f series
Category	Measuring Instruments
Language	English