ABSTRACT
According to a well-known saying, a picture is worth a thousand words. In the context of this book, this statement provides an intuitive comparison between the data transfer rates of two dierent information channels: optical and acoustic. In addition, the primary information about physical objects and phenomena is oen conveyed by light. ese circumstances account for the widespread use of optical, and in particular photographic, techniques in modern experimental physics. However, optical images recorded during an experiment most oen defy immediate visual interpretation, representing rather some sort of primordial data about the spatial distribution of the parameters of an object under investigation. What is more, in general these data nowadays do not even take the form of a traditional image, but rather take the form of an array of numbers, reecting a luminosity distribution. e output data (photographic images) have to meet the requirements of the experiment to obtain the reliability and accuracy of a reconstructed set of functions of space and time, describing the state of the object that is the nal goal of each experiment. Meeting these requirements can be either possible or impossible,
depending on certain specic parameters of the measuring and recording devices. e latter devices usually come in a sequence of individual units, each one transforming the original information contained by the light. is oen results in a signicant discrepancy between the input and output images, that is, a loss of accuracy. Trying to predict the output as well as to explore the limits of the measuring and recording devices, which in addition to optical components include a variety of radio-electronic devices with built-in communication channels, automatic microphotometers, analog-to-digital converters, memory units, and so on, calls for a unied and systematic approach. at is why, for the purpose of describing and analyzing these systems, it is natural to apply well-developed methods of information theory. Indeed, information theory was designed to dene and optimize the transmission rate of the information channels as well as the capacity of information storage systems. Generally speaking, all the experimental equipment listed earlier is used to transmit, receive, transform, and record information. As was mentioned earlier, there is no essential dierence whether the information is encoded in the spatial or temporal signal structure in dierent devices. All these devices, to an equal extent, have a fundamental set of characteristics in common, the rst and foremost being linearity and stability (spatial or temporal invariance). is was explored in detail in Chapter 2, taking advantage of the almost complete similarity of the mathematical tools to extend the welldeveloped analysis and methods of communication theory to applications well beyond the original scope of this theory, such as to optical devices.
