# On Ghost Imaging Studies for Information Optical Imaging
###### Abstract  
Since the birth of information theory, to understand, study, and optimize optical imaging systems from the information-theoretic viewpoint has been an important research subfield of optical imaging, accompanied by a series of corresponding advances. However, since the \"direct point-to-point\" image information acquisition mode of traditional optical imaging systems, which directly performs one-to-one signal mapping from the object to the detection plane, lacks a \"coding-decoding\" operation on the image information, related studies based on information theory are more meaningful in the theoretical sense, while almost acting as icing on the cake for the optimization and design of practical systems and contributing little to substantive breakthroughs in further imaging capabilities. With breakthroughs in modern light-field modulation techniques as well as ghost imaging techniques, which establish point-to-point image signal reproduction based on high-order correlation of light fields, currently, it is able to encode the image information with controllable spatiotemporal light-field fluctuations during the ghost imaging process. Combined with modern digital photoelectric detection technologies, ghost imaging systems behave more in line with the modulation-demodulation information transmission mode compared to traditional optical imaging. This puts forward imperative demands and challenges for understanding and optimizing ghost imaging systems from the viewpoint of information theory, as well as bringing more development opportunities for the research field of information optical imaging. This article will briefly review the development of information optical imaging since the birth of information theory, overview its current research status by combining with latest related progresses in ghost imaging, and discuss the potential developing tendency of this research topic. g +
Footnote †: journal: Applied Sciences  
**Citation:** [PERSON]; [PERSON] On Ghost Imaging Studies for Information Optical Imaging. _Appl. Sci._**2002**, 12, 10981.  
resolution descriptions of traditional imaging systems [3; 9; 10; 11; 12; 13; 14; 15; 16; 17], including quantitative ones, such as the \"information resolution distance\" [11; 12] based on analyzing the optical information capacity and the \"statistical resolution\" [16; 17] based on the viewpoint of statistical signal estimation, which complement the classical diffraction-limited resolution description and have been applied to analyze the resolution limit in the microscopy system [18; 19] and imaging through scattering media [20]. Generally, these studies focus on describing the resolution of image information in the two-dimensional (2-D) spatial domain. However, according to the optical Shannon formula, the information capacity of an optical system actually depends on multiple dimensions of light fields and is described as [3; 4]  
\[\mathrm{I}=N_{\mathrm{DOF}}\log_{2}(1+\mathrm{SNR}), \tag{1}\]  
where SNR is the signal-to-noise ratio of optical signals, and \(N_{\mathrm{DOF}}\) is called the optical degree of freedom (DOF), which consists of multiple-dimensional (temporal, spatial, spectral, and polarization) components [4]  
\[N_{\mathrm{DOF}}=N_{t}\cdot N_{s}\cdot N_{c}\cdot N_{\psi}. \tag{2}\]  
This dimension disagreement between resolution analysis and optical information is actually related to the imaging and detection mechanism of traditional imaging systems. Since the \"direct point-to-point\" signal mapping from the object to the detection plane is performed while current optical detectors are restricted to conduct 2-D planar intensity detection, the information of multiple dimensions (e.g., spectral, polarization, and temporal) of light is lost after the detection (essentially all degenerated into the 2-D spatial dimension).