RTC
®
5 PC Interface Board
Rev. 1.9 e
7 Basic Functions for Scan Head and Laser Control
126
7.3.5 Output Values to the Scan
System
Calculations
X and Y coordinate values specified in vector and arc
commands will be converted by the RTC
®
5 (while
taking into account the Z axis coordinates if
necessary) into output values for the scan system’s
galvanometer scanners. Specified Z coordinate values
will be (while taking into account the X and Y coor-
dinate values) initially converted into a focal length
value and finally into an output value for the scan
system’s Z axis.
During calculation of output values based on the
specified coordinate values, the following corrections
(in the listed order, if previously configured) will be
taken into account after successful microvector-
ization:
• If a wobbel motion was enabled via set_wobbel
or set_wobbel_mode, then the X and Y coordi-
nates will be transformed in accordance with the
current wobbel vector (see page 167)
(1)
.
• If a Processing-on-the-fly correction was enabled
via set_fly_x, set_fly_y, set_fly_rot or
set_fly_x_pos, set_fly_y_pos, set_fly_rot_pos,
then it will be applied to the X and Y coordinates
(see page 177)
(2)
.
• If a coordinate transformation was defined for
aligning the scan system to the image field (see
set_matrix, set_offset, set_scale, set_angle and
corresponding list commands), then it will be
applied to the X and Y coordinates (see
page 161).
• Additionally, set_offset_xyz or
set_offset_xyz_list as well as set_defocus or
set_defocus_list can be used for defining an
offset to the Z coordinate or the calculated focal
length, which will then appropriately affect the Z
output value (see page 171).
• Coordinate values exceeding the real image field
range (into the virtual image field range, see
page 120) will be clipped to the edge of the 20-
bit real image field range.
• Correction tables assigned via select_cor_table
or select_cor_table_list will result in 2D or 3D
image field correction (see page 120).
• If automatic self-calibration was enabled via
auto_cal (see page 199), then a compensating
“Gain” and “Offset” will be taken into account
when calculating output values (gain and offset
correction can also be specified via set_hi, see
page 201).
Overflowing output values will, if necessary, be
clipped to the edge of the maximum possible range
of values.
Value Ranges
For all axes of the scan system, the output values are
(unlike with the RTC
®
4) 20-bit signed numbers (i.e.
digital values between – 524288 and +524287).
Therefore, the RTC
®
5 converts (by multiplying by 16)
image field coordinates for the Z axis specified as
16-bit signed numbers (between –32768 and
+32767) and image field coordinates for the X and Y
axes specified as 16-bit signed numbers in RTC
®
4
compatibility mode into 20-bit output values.
However – even in RTC
®
4 compatibility mode – the
RTC
®
5 does not change 20-bit values returned by the
scan system (directly or via the XY2-100 converter).
If the scan system is controlled in conjunction with an
XY2-100 converter, then the converter converts (by
eliminating the four least significant bits) the RTC
®
5’s
20-bit output values into 16-bit unsigned numbers
(i.e. into digital values between 0 and 65535) for all
axes of the scan system (such control values are
outputted by the RTC
®
4). 16-bit values returned by
the scan system are converted into 20-bit values (by
extension with four null bits).
Clock Overruns
The 10 µs clock period might not always suffice for
calculating all data required by the computation-
intensive jump, mark and arc commands if several of
the available command options are utilized simulta-
neously – e.g. simultaneous control of two scan
systems, wobbel motion, Processing-on-the-fly for
two axes (correction via McBSP interface), automatic
laser control, para vectors, data recording, variable
polygon delay (scanner delay possibly 0), short list
commands (e.g. for polylines), certain control
commands during list execution.
This overrun situation can be internally detected and
counted. You can appropriately test your application
by using get_overrun to count the number of
overruns. Such overruns result in one or several
(1) only for marking commands (mark and arc), not for jump
commands or goto_xy and goto_xyz
(2) only for marking commands (mark and arc) and jump
commands, not for goto_xy and goto_xyz
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