RTC
®
4 PC Interface Board
Rev. 1.3 e
4 Principle Of Operation
34
innovators for industry
YAG Modes
With the commands
set_laser_mode(1)
,
set_laser_mode(2)
or
set_laser_mode(3)
one can
choose between three different YAG laser control
modes. In all three YAG modes, the RTC
®
4 supplies
the following signals:
• a LASERON signal
• a
Q-Switch signal
with variable pulse width and
frequency (LASER1)
• a programmable
FirstPulseKiller signal
(LASER2)
The signals are available via the 9-pin D-SUB
laser connector – see
. The LASER1 and
LASER2 signals are additionally available at the LASER
EXTENSION connector.
Q-Switch Signal
The Q-Switch signal is available for control of the
laser’s Q switch. The Q-Switch period and pulse width
are set with the command
. Note that
half
of the output period must
be specified. The parameter
pulse_width2
(for the
LASER2 signal) has no effect in the YAG modes.
FirstPulseKiller Signal
The FirstPulseKiller signal is available for reduction of
the laser pulse power at the beginning of a pulse
train. The initial pulses of a pulse train often have a
higher energy than the following pulses. These
intensity variations are to be avoided in most laser
marking applications. Therefore the laser should be
equipped with a FirstPulseKiller device that reduces
the power of the first laser pulses.
The RTC
®
4 provides a control signal for the
FirstPulseKiller (TTL level). The FirstPulseKiller signal is
started together with the LASERON signal. While the
FirstPulseKiller signal is active, the energy of the
pulses should be reduced adequately.
The length of the FirstPulseKiller signal is set with the
command
or
.
Differences Between YAG Modes 1 - 3
The three YAG laser modes only differ in the relative
start time of the first Q-Switch pulse (also see the
timing diagrams in
• In
YAG Mode 1
the first Q-Switch pulse starts at
the
beginning
of the FirstPulseKiller signal.
• In
YAG Mode 2
the first Q-Switch pulse starts at
the
end
of the FirstPulseKiller signal. This mode is
provided for certain YAG laser types.
• In
YAG Mode 3
the first Q-Switch pulse starts
10
µ
s after the beginning of the FirstPulseKiller
signal.
Lamp Current (Laser Power)
To control the lamp current of a YAG laser, the analog
output signal ANALOG OUT1 (10-bit signal) can be
used. This signal is available via the 9-pin D-SUB laser
connector – see
. To set the
output signal, use the command
or
Alternatively, the lamp current can be controlled digi-
tally via the 8-bit digital output port on the
LASER EXTENSION connector (
).
The commands for setting the 8-bit port are
Please refer to
"Laser Extension Connector", page 53
,
for details.
• Please note that the actual Q-Switch period
and the pulse width depend on the time base
specified via the command
The time base can be set to 1 MHz or 8 MHz.
In general, it is recommended to set the time base to
8 MHz (command
set_laser_timing(..,..,..,1)
).
A time base of 1 MHz should only be chosen if
necessary.
