Scanlab RTC6 PCIe Board - Customer-Specific Calibration; Supplemental Information about Calibration

RTC6 boards
Doc. Rev. 1.0.21 en-US
8 Advanced Functions for Scan Head Control and Laser Control
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Customer-Specific Calibration
Automatic self-calibration is midpoint centered, that
is, the Image Field center remains stable.
If an alternative is preferred (for example, 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 Home-In
positions determined by auto_cal( Command = 0 ) can
be read out by get_hi_pos. From this, compensating
gain values and offset values can be calculated and
set by set_hi. The drift compensation set in this way
is effective immediately.
Notes
• get_hi_pos returns the last measured Home-In
positions. These are the stored Home-In reference
values immediately after
– auto_cal( Command = 0 )
– initialization by load_program_file
• After set_hi, a correction of the current position
occurs at jump speed.
• Gain and offset correction factors can also be set
by set_hi for systems without Home-In sensors.
• After auto_cal( Command = 3 ) the
galvanometer scanners are in exactly the same
position as before the command.
Supplemental Information about Calibration
• The accuracy of fit of the set drift compensation
can decrease with increasing time. Therefore,
calibration should be repeated after appropriate
time intervals. The shorter the time interval
between individual calibrations, the higher the
attained long-term repeatability. Time intervals
are typically in the range of minutes. Events such
as workpiece changes or line feeds are ideal
opportunities for conducting a new calibration.
• The accuracy of fit of the calibration, and the
thereby attained long-term repeatability, are
further enhanced by steady environmental and
load conditions.
• The measurement routine determines the Home-
In positions by several measurements. If
deviations between the individual measurements
are too large (maximum – minimum > 96 bits),
the measurement routine aborts and an error 2 is
returned. In this case, no reference values are
stored for the affected axis ( Command = 0 ) and
the gain and offset factors remain unchanged
with ( Command = 1 )
(1)
. Then get_hi_pos returns 0
instead of the faulty values.
• An error within an individual measurement cycle
can be caused by a brief mechanical or electrical
disturbance. If significant spreading occurs
within an individual measurement cycle, we
recommend the following:
– either a further measurement cycle is
immediately conducted or
– the error is initially ignored while using the
current gain values and offset values until new
correction values are determined by the next
(successful) measurement cycle.
Significant spreading across several measurement
cycles might indicate a defect in the internal
sensor system or another part of the scan system.
But because continuous (mechanical or electrical)
external disturbances or contamination can also
impair automatic self-calibration, the scan system
and its environment should in such cases be
appropriately inspected to assess overall
functionality.
• Certain hardware error states (for example, signal
faulty or not found) get permanently stored.
After correcting the error, you must call auto_cal
with Command = 0 or 4 to clear the error state.
Until this time, correction with Command = 1 or 3 is
not possible.
(1) ( Command = 0 ) always sets gain = 1.0 and offset = 0.