11.1 Introduction: Present-Day Trends in Imaging
Imaging has always been the primary goal of informational optics. The whole history of optics is, without any exaggeration, a history of creating and perfecting imaging devices. Starting more than 2000 years ago from ancient magnifying glasses, optics has been evolving with ever increasing speed from Galileo's telescope and van Leeuwenhoek's microscope, through mastering new types of radiations and sensors, to the modern wide variety of imaging methods and devices of which most significant are holography, methods of computed tomography, adaptive optics, synthetic aperture and coded aperture imaging, and digital holography. The main characteristic feature of this latest stage of the evolution of optics is integration of physical optics with digital computers. With this, informational optics is reaching its maturity. It is becoming digital and imaging is becoming computational.
The following qualities make digital computational imaging an ultimate solution for imaging:
â¢ Processing versatility. Digital computers integrated into optical information processing and imaging systems enable them to perform not only element wise and integral signal transformations such as spatial Fourier analysis, signal convolution, and correlation, which are characteristic for analog optics, but any operations needed. This eliminates the major limitation of optical information processing and makes optical information processing integrated with digital signal processing almost almighty.
â¢ Flexibility and adaptability. No hardware modifications are necessary to reprogram digital computers for solving different tasks. With the same hardware, one can build an arbitrary problem solver by simply selecting or designing an appropriate code for the computer. This feature makes digital computers also an ideal vehicle for processing optical signals adaptively since, with the help of computers, they can easily be adapted to varying signals, tasks, and end-user requirements.
â¢ Universal digital form of the data. Acquiring and processing quantitative information carried by optical signals and connecting optical systems to other informational systems and networks is most natural when data are handled in a digital form. In the same way that in economics money is a general equivalent, digital signals are the general equivalent in information handling. Thanks to its universal nature, the digital signal is an ideal means for integrating different informational systems.