| 摘要 |
PROBLEM TO BE SOLVED: To match a reference pattern with a target pattern with a high degree of accuracy, by providing a spatial filter having a specific number of apertures which are line-symmetric with respect to a plurality of line segments that pass through the center of the pupil of an objective lens and that are parallel with a regular arrangement direction of the pattern and, orthogonal to each other. SOLUTION: A spatial filter 11 has more than four apertures which are line-symmetric with respect to two line segments that pass through the center of the pupil of an objective lens 12 in parallel with a regular arrangement direction of a pattern and that cross together, orthogonal to one another. Light emitted from a fiber bundle 16 is projected onto the filter 11 through an illuminating lens 17 and a half-mirror 18, and passes through one point of one of the apertures so as to serve as a secondary light source. Then, it is turned into a parallel ray beam which is irradiated onto a sample 13 by an angle ϕwith respect to an optical axis Lc by means of a lens 12. A zero-degree diffraction light beam among the diffraction light beams passes, as a normal reflection light beam, through the aperture of the filter 11 by means of the lens 12, and is led to an image plane by a focusing lens 14. |
