A slit imaging system using two concave mirrors.

摘要

Configurations of optical systems using two concave mirrors to image an off-axis slit are used advantageously in monochromators or spectrographs in which the coma produced by one mirror is cancelled by that produced by the other mirror. However, such systems produce a curved line image of a straight line slit. This curvature is substantially removed in a two concave mirror optical system in which the off-axis angle and the separation 2L between the mirrors are chosen so that the principal ray OP1 from the center of the line object to the first mirror and the principal ray P2I from the second mirror to the center of the line image are both substantially perpendicular to an axis of symmetry of the optical system which passes through the centers of curvature C1, C2 of the two concave mirrors. The image line is then curved in a plane normal to the image plane and appears substantially straight in the image plane.