Resolution In Correlated Imaging With Thermal Light

Correlated imaging, which is also named coincidence imaging or ghost imaging, is a completely new theory of imaging deriving from quantum theory. The peculiar characters arising from correlated imaging have become one of the central topics in quantum optics in recent years. Usual correlated imaging is a technique which allows one to perform coherent imaging with incoherent light by exploiting the spatial correlation. Each of the correlated beams is sent through a distinct linear optical system, traditionally called the test system and the reference system. An object is placed in the test system and then the information about the object is recreated nonlocally from the spatial correlation function between the test and reference system in a nonlocal fashion by means of the second-order correlation measurement. Initially, the possibility of performing correlated imaging was ascribed to the presence of spatial entanglement between the two systems. It was claimed that quantum entanglement was a crucial prerequisite for achieving ghost imaging. Lately this view has been challenged from both theoretical and experimental aspects. It has been shown that classical correlation can play the same or similar role as quantum entanglement. A thermal or quasi-thermal source can exhibit such classical correlation. So we can realize correlated imaging with thermal or quasi-thermal light. Correlated imaging using classical thermal light provides us with an experimental basis for its application in other areas, such as quantum eraser, quantum cryptography, quantum holography, phase-conjugate mirror and so on.In this thesis, the resolution and noise in correlated imaging with thermal light are studied in detail. We obtain the analytical expression of resolution in third-order correlated imaging with thermal light, and find that the resolution of third-order correlated imaging can be decomposed into the product of the resolution of second-order correlated imaging and a modulation function. It is found that the resolution of third-order correlated imaging is much better than that of second-order correlated imaging. Through the analysis of the point spread function which describes the resolution of third-order correlated imaging, we find that the resolution of two ghost images can be modulated each other. The noise in correlated imaging is calculated, and it is proved that the noise amplitude of third-order correlated imaging with thermal light is the same with that of second-order correlated imaging. It is indicated that the noise can be reduced by repeated measurements, the signal-noise rate can be enhanced, and the quality of the images can be improved.The thesis consists of five chapters. The first chapter is aimed to briefly review the developing history and main achievements of correlated imaging. In the second chapter, we introduce the basic theories of correlated imaging, including linear optics transfer systems and its impulse response functions. In the third chapter, second-order and third-order correlated imaging with thermal light are introduced. In the fourth chapter, we investigate the resolution in second-order and third-order correlated imaging with thermal light, and discuss the noise caused by the classically random fluctuations of the thermal source. We shall conclude this thesis with conclusions and outlook in the last chapter.