Proceedings PaperPhase Imaging In Scanning Optical Microscopes
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The confocal scanning optical microscope (CSOM) has the major advantages of a very short depth of focus, transverse definition, and image contrast that are better than with a standard microscope. The depth resolution of these microscopes is of the order of a wavelength. However, if it is necessary to carry out thickness measurements of films a small fraction of a wavelength thick, or profile steps with this order of height change, phase measurement techniques become a useful tool. Our aims have therefore been to incorporate within-CSOM phase contrast techniques and differential techniques for quantitative measurement of the position of edges, edge slope, and the thickness of thin films. In conventional microscopes this is most widely accomplished with Zernike phase contrast systems or by using Nomarski differential interference contrast (DIC). In CSOMs, heterodyne interference techniques have been used. This paper will describe two methods of phase imaging that we have been investigating, phase contrast and differential interference contrast. Most of the experiments were initially carried out on a single pinhole mechanically-scanned CSOM. Our recent goal has been to test our initial concepts on the real-time scanning optical microscope (RSOM). This microscope uses a Nipkow disk with 200,000 pinholes to dramatically increase the scan speed.