Reflective beam splitting objective

摘要

A reflecting beam splitting objective employing only three mirrors obtains a high reflective efficiency. In one embodiment, the objective contains a small intercepting mirror between primary and secondary mirrors of a Cassegrain mirror arrangement. The position of the intercepting mirror is determined so that the mirror receives an input beam and directs that beam onto a first portion of the secondary mirror without vignetting the beam when it is reflected from the secondary mirror to a first portion of the primary mirror or by cutting off part of the image transmitted from the second portion of the secondary mirror to a focus behind the primary mirror. The objective may use all energy that is input into the objective to image a sample. The objective has demonstrated particular utility in the field of infrared spectroscopy of small samples.