26 July 1993 Recognition threshold for defocussed characters by the visual system
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Proceedings Volume 1983, 16th Congress of the International Commission for Optics: Optics as a Key to High Technology; 19834D (1993) https://doi.org/10.1117/12.2308576
Event: 16th Congress of the International Commission for Optics: Optics as a Key to High Technology, 1993, Budapest, Hungary
Abstract
In this paper we show how contrast (C) affects the recognition of defocussed objects. In order to do this we try to determine the maximum distance at which a subject with an induced refraction of -5.5 D can recognize a character (letters of the alphabet). Our results show that when C=1 the recognition threshold distance is such that the relation between the letter's pseudoimage (n) and the circle of confusion ( 0 corresponding to any point of the letter at this distance is at least i R- =2. When the contrast decreases, this decrease can be compensated by placing the letter closer to the subject. This behavior is linear until C=0.1. For C<0.1 the recognition threshold distance begins to increase again. This change in behavior can be explained by the variation of the depth of field with contrast showing that it is possible to recognize a defocussed letter from a longer distance without increase really the tolerance to defocus.
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C. Illueca, C. Illueca, } "Recognition threshold for defocussed characters by the visual system", Proc. SPIE 1983, 16th Congress of the International Commission for Optics: Optics as a Key to High Technology, 19834D (26 July 1993); doi: 10.1117/12.2308576; https://doi.org/10.1117/12.2308576
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