RTC6 boards
Doc. Rev. 1.0.21 en-US
7 Basic Functions for Scan Head Control and Laser Control
139
• Elliptical arcs can also be marked by circular
Arc Commands (for example, arc_abs) if an
appropriate coordinate transformation (for
example, scaling that differs in the
x direction/y direction) has been specified by
set_matrix. Here, though, the effective
mark speed varies along the arc, see also the note
on page 227.
This contrasts with mark_ellipse_abs and
mark_ellipse_rel, where in 10 µs intervals the
step length gets adjusted for the ellipse’s shape at
the current position such that the arc is marked
with a (largely) constant mark speed.
For very large eccentricities and also at high
mark speeds, however, such stepwise ellipse
approximation by a 10 µs clock can produce
numerical inaccuracies in the end point regions of
the large half-axis. Consequently, the effective
mark speed there might not be precisely constant
(for example, an eccentricity of
a
/
b
= 2 and 100
Microsteps per circumference would produce a
speed deviation of approx. 3.7%). However, the
outputted point always lies exactly on the ellipse.
Moreover, as closed equations do not exist for
calculating an ellipse arc length, the step length
of the finally-marked Microstep is generally
shorter and the mark speed correspondingly
lower than specified. Nevertheless, the end
position is always exact.
Likewise, Sky Writing might produce run-in/run-
out irregularities at the large half-axis. Users
themselves must ensure that the parameter
values used are consistent with the required
precision.
[*]Para[*] Commands
• para_jump_abs
• para_jump_abs_3d
• para_jump_rel
• para_jump_rel_3d
• para_laser_on_pulses_list (special case)
• para_mark_abs
• para_mark_abs_3d
• para_mark_rel
• para_mark_rel_3d
• timed_para_jump_abs
• timed_para_jump_abs_3d
• timed_para_jump_rel
• timed_para_jump_rel_3d
• t
imed_para_mark_abs
• timed_para_mark_abs_3d
• timed_para_mark_rel
• timed_para_mark_rel_3d
If
the “vector-controlled laser control” is activated,
these commands simultaneously vary a signal
parameter linearly along the mark or jump vector, see
Section ”Vector-Defined Laser Control”, page 206.
[*]para_mark[*] commands generally do not take
Sky Writing into account.
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