| 摘要 |
PROBLEM TO BE SOLVED: To obtain a spectroscope capable of obtaining high diffraction efficiency with small aberration regardless of wavelengths by bringing a main light beam of converging rays into incidence onto a grating plane at a point different from a point of intersection between an axis of rotation and the grating plane in a plane diffraction grating, and determining the groove shape of each region in the grating plane according to the location of rotation of the regions with the axis of rotation as a center. SOLUTION: Light from an entrance slit 1 is reflected by a concave mirror 2, converted into converging rays, and diffracted at a diffraction grating 3 to form an image at an exit slit 4. In rectangular coordinates with the origin at the point of incidence 31 of the main light beam of converging rays on the grating plane 30 of the diffraction grating 3, the x-axis intersects with the grating plane 30 at right angles, the y-axis intersects with grating grooves at right angles, and the z-axis is in parallel with the grating grooves. The diffraction grating 3 is rotated on an axis which is passed through a center of rotation 32 difference form a point of incidence 31 and which intersects the grating plane 30 at right angles to perform wavelength scanning. The angleϕthat the normal of a plane including both the optical path of incident light onto the diffraction grating 3 and the optical path of emergent diffracted light forms with the z-axis indicates the location of rotation of the diffraction rating 3. The reference location of rotation (ϕ=0) is a location of rotation at which the grating grooves intersect with incident light at right angles.
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