Critical resolution in ghost imaging system with pseudo-thermal light

The resolution limit, which characterizes the resolution power of an optical imaging system, is defined as the resolvable minimum-separation between two points. In classical optical imaging, the resolution limit is given by the Rayleigh diffraction limit. In this paper, we propose a concept of critical resolution, which is used to describe the minimum separation of two adjacent objects that an imaging system can resolve. The critical resolution of pseudo-thermal ghost imaging (PGI) system is analyzed. To quantify the critical resolution, we develop a mathematical formula from which one can evaluate whether a prescribed object can be resolved in a PGI system. The evolution process from critical resolution to resolution limit is presented when the object size towards to zero. The results show that the resolution limit of PGI system is 1.98 times the speckle size. Our results can not only promote the development of GI technology, but also provide theoretical guidance for the design of GI system.