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One of the key tasks of a laser systems field service engineer is to determine where and
why an optical system is not performing to specification or why it has failed prematurely.
On most occasions, the field service engineer is faced with a completely failed optical
system and is left to isolate how and where the failure occurred and if the rest of the
system was affected, if at all. Failure modes are the manner whereby the failure itself is
observed. Generally speaking, an "optical failure mode" describes the way in which the
optical failure happens and its impact on an entire optical system. Optical failure modes
of diffractive optical beam shapers must be determined according to each components
performance standards as identified through its design and testing. Optical performance
standards must be quantified if they are to be upheld. Quantifiable performance standards
are more precise than qualitative standards, but each have a role in determining overall
performance. If an optical designer or engineer is incapable of specifying precisely, the
optical / functional performance they want from the diffractive optical beam shaper, then
it is difficult, if not near impossible, to make a field service and maintenance engineer
responsible for maintaining optical performance or to identify the possible different
failure modes and mechanisms. Performance can be a function of the placement of optics
due to routine maintenance or general wear and tear, but there needs to be established
means of identifying both circumstances. Diffractive optical element failure mechanisms
are straightforward; defined simply as the physical, chemical or other processes that led
to the failure of the diffractive optical element itself. This paper outlines schematically
the various (Highest Ranked) failure modes and mechanisms encountered by a standard
industrial diffractive optical beam shaper operating at 355 nm in an industrial
environment. Furthermore, an overview of field data including optical lifetime averages,
metrological image data of failed optical elements and methods to prevent premature
failure will be shared.
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