Abstract
The aberrations of off-axis plane grating spectrometers with one mirror in the camera and another in the collimator are calculated by means of the plate diagram method. Spectrometers in the Z and U configurations with spherical, centred parabolic and off-axis parabolic mirrors are studied. Making use of the opportunity provided by the method, the aberrations in each system are rapidly analysed in order to make a first selection among the designs under consideration. The analytical results are compared with those obtained by ray tracing. The study shows clearly the optimal field of application of each design.