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Enhanced Contrast Holographic Interferometry

IP.com Disclosure Number: IPCOM000038767D
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Crawforth, L: AUTHOR [+3]

Abstract

To enhance fringe contrast requires considering the polarization of all beams present. In making the original hologram, the polarizations of the object and reference beams are parallel, a condition for interference. In typical interference holography, no change of object polarization is made at playback. The present method consists of rotating the polarization of the object beam by 90 degrees at playback before impinging on the recorded hologram. At this point, there are no interference fringes seen, since the two polarizations are orthogonal. We next pass the light emerging from the hologram through a second polarizer at 45 degrees to the vertical, and again obtain interference fringes.

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Enhanced Contrast Holographic Interferometry

To enhance fringe contrast requires considering the polarization of all beams present. In making the original hologram, the polarizations of the object and reference beams are parallel, a condition for interference. In typical interference holography, no change of object polarization is made at playback. The present method consists of rotating the polarization of the object beam by 90 degrees at playback before impinging on the recorded hologram. At this point, there are no interference fringes seen, since the two polarizations are orthogonal. We next pass the light emerging from the hologram through a second polarizer at 45 degrees to the vertical, and again obtain interference fringes. When this same polarizer is now rotated to -45 degrees vertical, the interference pattern is seen to have shifted 180 degrees, and light and dark interference fringes have reversed order. Subtraction of these two fringe patterns effectively cancels the background illumination while considerably enhancing the fringe contrast. Inline realtime set up with procedure is as follows: The original hologram is processed, with polarizations of the object and reference beams being linearly polarized and parallel at 45 degrees to vertical. At playback, the polarization of the object beam is rotated through 90 degrees before reaching the hologram. The light emerging from the hologram, a combination of the original object with that of the deformed o...