平面回折格子単色計の光学的性質

抄録

The optical properties of plane grating monochromators such as of Ebert and Czerny-Turner type are examined by the method of geometrical optics. The grating equation and the expression for the focal plane are derived, and by using them the expressions of image form are given. Further the optical system that minimizes the wavelength impurity is discussed and such residual aberrations as coma and astigmatism are examined. In any monochromator the focal plane depends. upon the grating position and the off-axial amount of collimator. In Ebert type monochromator with a circular-arc shaped entrance slit the image form is circular-arc only in a symmetric arrangement and elliptic in other arrangements, and the light through a circular-arc shaped exit slit is free from the wavelength error, and even if the slit is long, the image will be not so much blurred by residual aberrations. Therefore it is advisable to use a long circular-arc slits if the system is of Ebert type. In Ebert or Czerny-Turner type monochromator with a straight entrance slit the image form is parabolic. In Czerny-Turner type both the image form and focal plane are affected by its non-concentric quantity.