Scanlab RTC 5 PC Interface Board - 8.11.4 Calibration During an Application; Automatic Self-Calibration; Customer-Specific Calibration

RTC
®
5 PC Interface Board
Rev. 1.9 e
8 Advanced Functions for Scan Head and Laser Control
201
innovators for industry
8.11.4 Calibration During an Applica-
tion
Automatic Self-Calibration
Automatic self-calibration of the scan system during
an application can be executed with
auto_cal(
Command = 1). Here, a measurement
routine is started for determining the current Home-
In positions. From the resulting deviation compared
to the previously (with
Command = 0) stored reference
value, the RTC
®
5 calculates and sets gain and offset
values – separately for the X and Y axis. This resulting
drift compensation setting has immediate effect on
the current output positions and all subsequent ones.
It remains in effect until auto_cal(
Command = 1) is
called again or until drift compensation is shut off
with auto_cal(
Command = 2) (whereby the settings
Gain = 1.0 and Offset = 0 take effect).
Notes
• In principle, after auto_cal(
Command = 0, 1 and
2), the galvanometer scanners will be in the same
position as before the command. However, a
newly calculated or set drift compensation might
lead to correction of the position.
• After a reset or initialization (via
load_program_file), automatic drift compen-
sation is switched off – as with auto_cal (
Command
= 2). Nevertheless, previously determined
reference values remain available.
• The calibration routine started with
auto_cal(
Command = 1) typically lasts 1-2 seconds
(depending on the magnitude of the drift). But if
auto_cal(
Command = 1) isn’t preceded by
auto_cal(
Command = 0 or 4), then an automatic
ASC hardware check will be performed, which
can extend the command’s execution time by a
few seconds.
Customer-Specific Calibration
Automatic self-calibration is midpoint centered, so
that the image field’s center remains stable. If an
alternative is preferred (e.g. if the left edge should
remain stable, size is irrelevant), then the calibration
can also be externally calculated and set. For such a
customer-specific calibration, the get_hi_pos
command can be used to query the Home-In position
that was detected and stored in the DLL with
auto_cal(
Command = 0, 1 or 3). The drift can be deter-
mined via repeated calls of the commands
auto_cal(
Command = 3) and get_hi_pos. From this,
compensating gain and offset factors can be calcu-
lated and then set via set_hi. The resulting drift
compensation setting has effect immediately on the
current output position and all subsequent ones.
Notes
• get_hi_pos returns the current (last determined)
Home-In positions. Directly after
auto_cal(
Command = 0), these are also the last
determined and stored Home-In reference values.
Directly after initialization (init_rtc5_dll),
get_hi_pos returns the reference values from the
EEPROM (also see get_hi_pos command
description).
•After set_hi, a correction of the current position
might occur at jump speed.
• Gain and offset correction factors can also be set
via set_hi for systems without Home-In sensors.
•After auto_cal(
Command = 3), the galvanometer
scanners will be in exactly the same position as
before the command.