| 摘要 |
PROBLEM TO BE SOLVED: To provide a diffractive optical element capable of easily and accurately measuring the grating direction and grating period of diffraction grating having various cross-sectional shapes. SOLUTION: The diffractive optical element 1 is provided with an index 3 linearly extended along the grating direction of the diffraction grating and consisting of a deformed part selected from a projected or recessed shape of which a cross section vertical to the grating direction is different from the surface shape of a diffraction grating forming face 1b, a plane shape and a shape having a level difference part. |
