A comparison of methods has been conducted of the optical techniques of ellipso-polarimetry, and dark field microscopy to determine the resolution of the spatial variations in thickness within thin films in real time. The ellipso-polarimeter is an adaptation of normal point ellipsometric methods to accommodate assessment of spatial distribution, but unlike the traditional methods, will utilize the image as qualitative information rather than quantitative. This is achieved through the use of a coherent light source, beam expander, and collimating/focusing optics for the throughput of the system, and the use of a CCD camera to collect the two-dimensional signal for display on a video monitor. The use of the CCD camera allows the collection of data at video rates, thus observation of thickness distribution can be done in "real time", and can be stored as a digital file for archive purposes or output to a hard copy device. It is also possible to utilize image processing techniques to extract or enhance information present in the images. The dark field method is also an adaptation from traditional microscopy techniques, and utilizes oblique illumination from a coherent source with on axis optics to collect scattered light and display it as an image on a monitor. It is possible that either of these techniques could be implemented for a quality control application where a deviation in material type or from a desired thickness needs to be recognized either by a human operator or in an automated fashion under computer control, though the type of variation which is to be detected will dictate which method to utilize.
Library of Congress Subject Headings
Ellipsometry--Technique; Microscopy--Technique; Thin films
Department, Program, or Center
Chester F. Carlson Center for Imaging Science (COS)
Eubanks, Craig S., "Comparison of Ellipso-polarimetry and dark-field methods for determination of thickness variations in thin films" (1991). Thesis. Rochester Institute of Technology. Accessed from
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