Image Number 5 for United States Patent #5255069.
There is disclosed an interferometric system including electro-optical apparatus and method for examining and characterizing ultra fine details of various specimens such as a piece of photographic film. The method includes illuminating a specimen with a thin wide substantially pure Gaussian light beam, detecting the interfering patterns of light from the specimen, and characterizing ultra fine details of elements of the specimen by means of the detected light patterns. The apparatus includes a laser, a magnifying telescope, a multi-prism beam expander, and a linear array of photo-diodes. Signals from the photo-diodes are displayed on an optical multichannel analyzer (OMA) to provide a waveform characteristic of ultra fine elements of the specimen. Both "near-field" and "far-field" characterizations are possible and details of elements having diameters of the order of the wavelength of the light used (e.g., about 0.6 .mu.m) are detected.