Development of an Infrared Microscope for Three-dimensional Structural Study on Small Oritented Specimens

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For the three-dimensional structural study on small oriented specimens, such as, fine single crystals, single domains of polycrystalline specimens and elongated polymer films, an infrared microscope has been newly developed. In stead of the Cassegr ain condenser, an IR condenser consisting of a rotary stage and an ellipsoidal mirror was designed for oblique transmission measurement. With this condenser, most of the incident radiation can be utilized for the oblique transmission measurement. The efficiency is several times higher than the measurement using an Cassegr ain condenser. Furthermore, any incident direction can be selected, which is quite convenient for the measurement where the orientation change of specimens is very difficult, for example, the measurement at a low temperature using a cryostat.For micro FTIR spectroscopy, prevention of the saturation of MCT detectors is important. For the adjustment of the incident radiation intensity, IR interference filters were employed. Contrary to usual adjustment using a slit or wiregauze, interference filters pass the IR radiation of desired frequency range. So the IR spectra can be taken with IR radiation of high intensity, which makes SN ratio high.Wire grids for electron microscopes were also adopted for holding specimens. Through the mesh, the incident radiation directly impinges the specimen, which greatly reduces stray light.