Scanlab RTC 4 - YAG Modes

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 page 52. 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 set_laser_timing (see
page 108). 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 set_firstpulse_killer or
set_firstpulse_killer_list (see page 105).
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 figure 17 on page 36).
•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 µs 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 figure 23 on page 52. To set the
output signal, use the command write_da_1 or
write_da_1_list.
Alternatively, the lamp current can be controlled digi-
tally via the 8-bit digital output port on the
LASER EXTENSION connector (figure 24 on page 53).
The commands for setting the 8-bit port are
write_8bit_port and write_8bit_port_list.
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 set_laser_timing
(see page 108).
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.