Disclosed are methods and apparatus for altering the phase and/or amplitude
of an optical beam within an inspection system using one or more spatial
light modulator(s) (SLMs). In one embodiment, an apparatus for optically
inspecting a sample with an optical beam is disclosed. The apparatus
includes a beam generator for directing an incident optical beam onto the
sample whereby at least a first portion of the incident optical beam is
directed from the sample as an output beam and a detector positioned to
receive at least a portion of the output beam. The detector is also
operable to generate an output signal based on the output beam. The
apparatus further includes one or more imaging optics for directing the
output beam to the detector and a programmable spatial light modulator
(SLM) positioned within an optical path of the incident or output beam.
The SLM is configurable to adjust a phase and/or amplitude profile of the
incident beam or the output beam. The apparatus also has a control system
operable to configure the SLM to alter the phase and/or amplitude profile
of the incident beam or the output beam. For example, the SLM may be
configured to alter the illumination profile of the incident beam to
achieve different inspection modes. In another example, the SLM may be
configured to alter the phase and/or amplitude profile of the output beam
so as to substantially eliminate aberrations produced by the imaging
optics. In other embodiments, the apparatus may include two or more SLM's
which are configurable to alter the phase and/or amplitude profile of both
the incident beam and the output beam.
