Holographic image subtraction by recording in Fourier plane and space filtration with thin light beam
Abstract
A simple holographic method of image subtraction is proposed which ensures a sufficiently high brightness of the difference image without one of phase shifters. Its gist is double exposure of the Fourier hologram on which the two images were recorded with a small relative transverse shift, followed by the illumination with a thin laser beam for space filtration and subsequent optical Fourier transformation of the reconstructed field. The method is based on the theory of a diffusely illuminated transparency and the interference pattern of coherent light in the Fourier plane. The method was tested experimentally on a piece of chalk whose surface microrelief had been altered mechanically during the time between two successive exposures. Measurements with a standard optical gauge revealed formation of the difference image with insignificant background noise but rather appreciable speckle noise, the latter limiting the resolution to only 0.05 mm unless reduced by further filtration with a laser beam of oblong cross section.
- Publication:
-
USSR Rept Phys Math JPRS UPM
- Pub Date:
- April 1984
- Bibcode:
- 1984RpPhM.......19K
- Keywords:
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- Holographic Subtraction;
- Image Enhancement;
- Image Reconstruction;
- Laser Interferometry;
- Spatial Filtering;
- Fourier Transformation;
- Holographic Interferometry;
- Light Beams;
- Instrumentation and Photography