X-ray or gamma ray systems or devices – Electronic circuit – With display or signaling
Patent
1993-03-17
1995-07-18
Dzierzynski, Paul M.
X-ray or gamma ray systems or devices
Electronic circuit
With display or signaling
378 62, 36441313, H05G 164
Patent
active
054349028
ABSTRACT:
Compensating for vignetting (loss of brightness at the edge of an image) is achieved by electronically multiplying the pixel-values of the vignetted image by a gain characteristic so as to obtain an unperturbed image. A gain characteristic pertaining to a particular vignetting effect is formed by a set of correction factors for all pixels. These correction factors are obtained from the image of an object having a spatially homogeneous brightness distribution. Various gain characteristics can be stored so that vignetting is compensated for even when the adjustments of the imaging system are varied. When, in order to improve spatial resolution, the image formed on the output screen of an image intensifier in an x-ray examination apparatus is split into two sub-images which are subsequently recombined, the vignetting effects in either of the sub-images are inevitably different due to the use of a beam splitter. The vignetting is decomposed into vignetting effects in a horizontal and in a vertical direction in the recombined image. Correction for vignetting is achieved by multiplying decomposition factors pertaining to horizontal and to vertical vignetting.
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patent: 4969172 (1990-11-01), Marinus
Bruce David Vernon
Dzierzynski Paul M.
Slobod Jack D.
U.S. Philips Corporation
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