Optimum Environmental Conditions And Automatic Self-Calibration; Process Monitoring; Software Monitoring; Optical Process Monitoring - Scanlab hurrySCAN 10 Installation & Operation Manual

6.2 Optimum Environmental
Conditions and Automatic
Self-Calibration
Long-term repeatability is very important in many
scan head applications, e.g. for rapid prototyping in
which the processing operation can span several
hours. For such laser applications, the long-term drift
and temperature drift of the scan head's galvano-
meter scanners, which manifest as a shift (offset drift)
and increase or decrease in the size (gain drift) of the
working image field, can exceed the allowable
tolerances.
In such applications, it's helpful to start up the appli-
cation only after the scanners have reached their
operating temperature. In addition, the magnitudes
of environmental fluctuations (e.g. operating
temperature changes to which the scan head is
exposed) should be kept as small as possible and the
scan head preferably operated with a constant load.
For higher long-term repeatability requirements,
SCANLAB scan heads can be (optionally for apertures
≥
10 mm) equipped with an additional internal
sensor system for automatic self-calibration. This
reference system provides the RTC
the ability to automatically calibrate the galvano-
meter scanner position detectors at any desired time.
During calibration, the scan head automatically seeks
several reference positions within the scannable area
that are defined by the internal sensor system. The
seek values are determined and compared with fixed
reference values. From the resulting deviations, offset
and gain compensation factors are calculated.
These compensation factors are immediately made
available for use in all future positioning tasks.
The calibration routine can be initiated via a simple
®
RTC command (please refer to the RTC
details). The laser should be switched off during the
calibration procedure and no other commands are
transferred to the scan head until the calibration is
completed. The entire calibration procedure takes
place in about 5 seconds.
Thus, the effects of gain and offset drift can be reli-
ably compensated and positioning accuracy is main-
tainable over long periods of time. Remaining long-
term drift effects are the same order of magnitude as
short-term repeatability.
®
hurrySCAN 10, digital, 1064 nm, f = 254 mm
Rev. 2.6 e
6 Optimizing the Application

6.3 Process Monitoring

The scan head provides internal protective mecha-
nisms for monitoring
• the operating temperature
(also see
on page
In addition, the user has various possibilities for
monitoring the scan process as described in the
following.

Software Monitoring

For monitoring via software the scan head provides a
status signal with informations about the current
scan head operational state.

Optical Process Monitoring

For camera-based observation of the scan head's
working field SCANLAB offers a camera adapter. The
camera adapter can be mounted between the scan
head's beam entrance and the laser flange. Then the
camera adapter's dichroitic beam splitter decouples
® light reflected from the illuminated workpiece and
software with
arriving the scan head's beam entrance via the scan
objective and the scan mirrors. The light is decoupled
from the beam path and then directed to the camera.
Please contact SCANLAB for further information (see
page
®
manual for
chapter 2.3, "Internal Protective Functions",
11).
32).
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