RTC
®
5 PC Interface Board
Rev. 1.9 e
7 Basic Functions for Scan Head and Laser Control
133
• The command set_laser_control (Bit #0) can be
used to specify whether a Q-Switch pulse
(LASER1) should execute to completion or be cut
off when it has not yet fully executed when the
LASERON signal is switched off (see figure 49 on
page 134). This cannot be specified for standby
signals; if applicable, these will be cut off.
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
®
5 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 423).
Differences Between the YAG Modes
The four YAG laser modes only differ in the relative
start time of the first Q-Switch pulse with reference
to the FirstPulseKiller signal (also see the timing
diagrams in figure 49 on page 134).
•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.
•In YAG mode 5 the time interval can be specified
via set_qswitch_delay or
set_qswitch_delay_list. YAG modes 1-3 are
special cases of YAG mode 5 with:
– Q-Switch delay = 0 (YAG mode 1)
– Q-Switch delay = Length of the FirstPulseKiller
signal (YAG mode 2)
– Q-Switch delay = 10 µs (YAG mode 3)
The set_laser_mode command, however, merely
preselects the Q-Switch delays. In YAG modes 1-3,
too, the Q-Switch delay can therefore be subse-
quently changed via set_qswitch_delay or
set_qswitch_delay_list. For YAG mode 2, each
set_firstpulse_killer or set_firstpulse_killer_list
command results in a corresponding adjustment of
the Q-Switch delay, too.
Lamp Current (Laser Power)
To control the lamp current of a YAG laser, the 12-bit
analog output ports, ANALOG OUT1 or
ANALOG OUT2 can be used. They are available via the
15-pin D-SUB laser connector – see figure 10 on
page 46. To set the output signal, use the control
command write_da_x or the short list command
write_da_x_list.
Alternatively, the lamp current can be controlled digi-
tally via the 8-bit digital output port on the
EXTENSION 2 connector (figure 17 on page 50). The
commands for setting the 8-bit port are
write_8bit_port and write_8bit_port_list (also refer
to "EXTENSION 2 Connector", page 50, for details).
When the lamp current is changed, continued
execution of the list can, if required, be halted via the
long_delay command until a stable laser power level
has been achieved.
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