The amount of information transmitted via a photon beam that is modulated in s equal, discrete steps from a given maximum expected number of pulses kmax and down to a given kmin is computed. The numbers of pulses refer to the counts of a photoemissive detector. The information i reaches a maximum im for a certain number s = sm for which the difference δk of the expected number of detected pulses from successive levels is about 2.7 times the rms fluctuation of the kmax level. The reliability (ratio of the information obtained in the presence of noise to the information that would be obtained without noise) of this maximum information im is about 0.8. im is very nearly a function of the single parameter . These results hold, provided that the rms fluctuation of the kmax level is not too different from that of the kmin level. For kmin = 0, maximum information is obtained with a somewhat smaller spacing δk, and its reliability is about 0.61 for kmax ≥ 20.
© 1971 Optical Society of AmericaFull Article | PDF Article
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