Single-Material Waveplates for Pupil Polarization Filtering

An optical inspection system, comprising:

• one or more single-material gratings to convert a polarization of light scattered from a target from an elliptical polarization that varies spatially across a collection pupil to a linear polarization that is uniformly oriented across the collection pupil, wherein:
• the one or more single-material gratings have phase retardation that varies spatially across the collection pupil in accordance with the elliptical polarization, and
• the one or more single-material gratings comprise a two-dimensional grating;
• and
• a linear polarizer to filter out the light having the linear polarization.

An optical inspection system, comprising:

• one or more single-material gratings to convert a polarization of light scattered from a target from an elliptical polarization that varies spatially across a collection pupil to a linear polarization that is uniformly oriented across the collection pupil, wherein:
• the one or more single-material gratings have phase retardation that varies spatially across the collection pupil in accordance with the elliptical polarization,
• the one or more single-material gratings comprise a first one-dimensional grating and a second one-dimensional grating,
• the first one-dimensional grating has a uniform duty cycle and an orientation that varies spatially across the collection pupil, and
• the second one-dimensional grating has a duty cycle that varies spatially across the collection pupil and a uniform orientation;
• and
• a linear polarizer to filter out the light having the linear polarization.