An Analysis of Fundamental Factors Governing the Limitations in Detection of Images

摘要

Different basic factors which determine the ultimate detection limit in imaging are analyzed from a probabilistic viewpoint by considering the stochastic nature of radiation and of the attenuation and absorption processes, as well as the randomness inherent to energy conversion. It is shown mathematically that, in the case of ideal coherent radiation, deterioration of the coherence occurs when one introduces in the quanta flux fluctuations resulting from attenuation processes such as absorption and reflection. The image detector is considered as a matrix with n x m resolution elements with the information output of each element as a random variable. The standard deviation of the matrix output (temporal and spatial), as functions of the conversion yield is derived for coherent as well as ordinary light as input and related to the detection limit. The foregoing considerations are interpreted for the limits in astronomical image detection and a process is explained which allows the evaluation and reproduction of astronomical image recordings to obtain information where the threshold is governed by the statistics in the number of events of the detector output. Images obtained by this opto-electronic image processing, show information which otherwise cannot be recognized reliably by direct visual examination. Typical results are presented. (Author)