Synchronization - Scanlab RTC 5 PC Interface Board Installation And Operation Manual

Synchronization

Figure 43 on page 116 shows the timing diagram for
scan-head and laser control in Sky Writing mode 1.
The timing diagram for Sky Writing mode 2 and 3 is
similar, but here the scanner perform no reverse
motion in the run-in and run-out phases.
The Timelag, Nprev, Npost and LaserOnShift param-
eters are specifiable for the commands
set_sky_writing_para and
corresponding list commands:
• The Nprev parameter is a whole number in units
of 10 µs and defines the duration of the run-in:
– Run-in duration / µs = 20 · Nprev (mode 1)
– Run-in duration / µs = 10 · Nprev (mode 2, 3)
• The Npost parameter is a whole number in units
of 10 µs and defines the duration of the run-out:
– Run-out duration / µs = 20 · Npost (mode 1)
– Run-out duration / µs = 10 · Npost (mode 2, 3)
• The parameters Timelag (whole number in units
of 1 µs) and LaserOnShift (whole number in
units of 0.5 µs) define the delay of the
"laser active" laser control signals' switch-on and
switch-off time points relative to the set starting
position and set ending position:
– Delay of switch-on time point relative to the set
starting position / µs
= Timelag - 0.5 · LaserOnShift
– Delay of switch-off time point relative to the set
ending position / µs
= Timelag
For LaserOnShift = 0, the "laser active" laser
control signals will be switched on/off with a delay of
Timelag relative to the set starting position and to
the set ending position. By setting the parameter
Timelag to the actual tracking error (and the param-
eters Nprev and Npost to sufficiently large values),
you'll ensure that the "laser active" laser control
signals will switch on/off precisely at the endpoints of
the desired vector, that the tracking error becomes
constant even before the vector's startpoint is
reached, and that the vector executes right up to its
endpoint with constant marking speed and therefore
also with a constant tracking error.
The Parameter LaserOnShift allows adjustment of
the "laser active" laser control signals' switch-on time
point. Positive values delay switching on of the laser
control signals. Negative values result in an earlier
switch-on of the laser control signals, but no earlier
than the beginning of the run-in phase (an additional
delay such as a negative LaserOn delay – see
®
RTC 5 PC Interface Board
Rev. 1.9 e
7 Basic Functions for Scan Head and Laser Control
set_sky_writing and the
set_laser_delays – is not possible). Negative values
can be used (for example in the YAG modes, where a
FirstPulseKiller signal and a positive Q-Switch delay
may be previously set) for shifting the "laser active"
laser control signals' switch-on time point so far
forward (even to within the run-in phase) that the
first laser pulse coincides with the target start
position.
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