order to achieve the desired end result, it is often
necessary to control the focus of the engraving laser
beam(s) during the engraving process. Examples of this
would include the following:
focus control, defined as a rapid change compared of the
order of a few roll rotations or less, where an
cell is made up of several hits each at potentially
different focus position to give the desired cell shape
focus control, defined as a less rapid change compared
of the order of a few roll rotations or more, where the
focus of the engraving beam(s) is changed for each pass
engraving to maintain sharp focus for each strata.
Passive or Dynamic focus control can be enhanced by
measurement of the engraved result to provide feedback
to correct the subsequent focus changes. When focus
control feedback is applied to an engraving such as a
Laminar engraving, it may be necessary to re-stratify
the subsequent data for optimum results.
detection of optimum focus of engraving beam(s) can be
automated to eliminate manual trial and error techniques
and/or to provide feedback. This can be achieved in a
number of ways including spectrometry of the plume,
depth scanning, microscopy etc.