[OPTICAL REVIEW Vol. 8, No. 4 (2001) 287-293]

The Double Monochromator Geometric Theory and Compensation of Aberrations

Elena SOKOLOVA* and Sandra MOGO

Universidade da Beira Interior Dep. Física Covilhã;, Portugal

(Received January 29, 2001; Accepted April 26, 2001)

The light path function for the double monochromator is constructed, and the formulas of account of the members of its expanding in ascending power series adequate for the defocusing and the first order astigmatism aberrations are found. On the basis of results of the minimisation of obtained expressions the opportunity of construction of a double monochromator so that the second monochromator fractionally compensates aberrations of the first one is analysed. It is also noticed, that in the scheme of the double monochromator under certain conditions compensation of an astigmatism of the second order is automatically carried out. It allows to use a deviation angle of the scheme for more complete compensation of other aberrations and to develop double monochromators with the improved performances.

Key words : diffraction grating, aberration, monochromator