Apodizing filter system useful for reducing spot size in optical measurements and other applications

An apparatus for measuring a sample, including:

• a source which emits radiation;
• means for focusing radiation from the source into a sampling beam to the sample;
• means for detecting radiation of the sampling beam that has been modified by a portion of the sample, said portion defining a measurement spot;
• and
• means for apodizing radiation that is from the source, wherein said detecting means detects radiation that has been apodized by the apodizing means, to reduce size of the measurement spot.

A radiation imaging system with improved resolution, comprising:

• means for focusing radiation from an object surface to a focal surface;
• an apodizer positioned in a radiation path between the object surface and the focal surface, said apodizer having a two dimensional pattern of alternating high transmittance areas and substantially opaque areas, said pattern having a locally averaged transmittance function that is an apodizing function;
• and
• a filter in the radiation path following the apodizer, said filter blocking scattered radiation that is generated by, or passed by, the apodizer;
• wherein radiation transmitted through the apodizer and the filter along said radiation path comprises image radiation, said image radiation having a diffraction point spread function;
• wherein the apodizer reduces tails of the point spread function relative to that of a clear, unapodized aperture.

A method for measuring ellipsometric parameters of a sample, including the steps of:

• focusing polarized broadband radiation from a source into a sampling beam directed at the sample;
• separating into wavelength components radiation of the sampling beam that has been modified by a portion of the sample, said portion defining a measurement spot;
• detecting the wavelength components to provide outputs;
• and
• determining from the outputs changes of polarized state caused by the sample;
• and
• apodizing radiation that is from the source, wherein said detecting step detects radiation that has been apodized in the apodizing step, to reduce size of the measurement spot.

An apparatus for measuring ellipsometric parameters of a sample, including the steps of:

• means for focusing polarized broadband radiation from a source into a sampling beam directed at the sample;
• means for separating into wavelength components radiation of the sampling beam that has been modified by a portion of the sample, said portion defining a measurement spot;
• a detector detecting the wavelength components to determine changes of polarized state caused by the sample;
• and
• an apodizer that apodizes radiation that is from the source and that is detected by the detector to reduce size of the measurement spot.