A spatial filter is an optical device used to spatially filter and clean up beams produced by various light sources. A non-ideal light source does not typically produce an output beam with a perfectly uniform intensity distribution. A spatial filter acts similarly to a low-pass filter, removing high spatial frequencies from the optical beam—typically associated with the geometry of the light source or noise introduced by various factors—and thereby producing a cleaner and more uniform beam.
Spatial filters are essential and widely used components in optical setups and play an important role in optical measurement techniques such as interferometry, holography, and microscopy.
