Surface profiling with fiber-optical confocal scanning interference microscope based on the restricted scanning range

The surface profile of a specimen can be measured with a confocal scanning microscope, where the height of a point on the surface is determined from the peak position of the corresponding axial response curve. The narrow axial response curve must be a key factor in this application, because the measuring accuracy depends on the full width at half maximum of the curve. Therefore, a confocal microscope with a broad axial response curve will not be utilized as a surface-profiling tool as long as its curve is not narrowed. A fiber-optical confocal scanning interference microscope was constructed with a 4-port fiber-optic coupler, where one port of the coupler was used as the reference arm providing the reference beam. Its axial response curve was so broad that the conventional method could not be applied to it. The laser diode with the wavelength of 1.55 /spl mu/m was used as a light source, the specimen was scanned along the optical axis.