Catoptric System Using Scheimpflug Optics

An inspection tool including:

• a first stage configured to support an object in an object plane;
• an illumination unit including an illumination source and illumination optics that are cooperatively configured to direct homogenous incident light onto the object;
• a second stage configured to support an image sensor in a final image plane, and
• a catoptric system configured to generate a magnified image on the image sensor using patterned light beams reflected from the object, the catoptric system comprising:
• a first plurality of mirrors configured and arranged in accordance with the Scheimpflug condition to collect the patterned light beams reflected from the object and to redirect the patterned light beams along a first optical axis such that the redirected light beams form an intermediate image at an intermediate image plane, wherein both the first optical axis and the intermediate image plane are oblique to the object plane;
• and
• a second plurality of mirrors configured to redirect the light beams from the first optical axis to a second optical axis that is perpendicular to the intermediate image plane such that the redirected light beams form the magnified image on the image sensor.

A method for inspecting an object disposed in an object plane, the method comprising:

• directing homogenous incident light onto the object;
• utilizing a first plurality of mirrors to collect light beams reflected from the object and to redirect the light beams along a first optical axis such that the redirected light beams form an intermediate image at an intermediate image plane, wherein both the first optical axis and the intermediate image plane are oblique to the object plane;
• utilizing a second plurality of mirrors to redirect the light beams from the first optical axis to a second optical axis that is perpendicular to the intermediate image plane such that the redirected light beams form the magnified image at a final image plane that is parallel to the intermediate image plane;
• and
• utilizing an image sensor disposed in the final image plane to capture the magnified image.