| 摘要 |
PURPOSE:To improve condensing efficiency by disposing a plane diffraction grating on an imaging luminous flux of an incident slit and disposing an exit slit on the circumference which is centered at the rotating center of said slit and has the radius corresponding to the distance from said center up to the imaging position of a zero order diffracted image. CONSTITUTION:The luminous flux incident from an incident slit 1 is reflected by an imaging spherical mirror 2 and is irradiated to a plane reflecting diffraction grating 3. The diffracted light dispersed by the grating 3 is imaged on a circumference 6 and monochromatic light is taken out via an exit slit 4. Since the slit 1 is positioned on an optical axis 5, the diffracted light has substantially no astigmatism and since the slit 4 is positioned on the circumference 6, the curvature of field owing to the rotation of the grating 3 is eliminated by which the condensing efficiency is improved. |
