Software Development For Correlated Imaging With A Weak Light CCD

Correlated imaging is a novel imaging method which make use of the intensity correlation effect of thermal light. Compared with the classical imaging method, correlated imaging has many outstanding advantages: it can image nonlocally, the resolution of imaging is not limited by Rayleigh diffraction limit and can get a higher resolution, moreover correlated imaging can realize turbulence-free image. Thermal light intensity signal detection and coincidence measurement are the most important parts of the correlated imaging system. Despite thermal light correlated imaging was first performed with a transmissive object, thermal light correlated imaging of a reflective object will be much more meaningful in future practical applications. Compared with transmitted light correlated imaging, reflected light is much weaker and imaging with a lot of noise, so it is very necessary to study the reflected light correlated imaging and develop appropriate acquisition procedures of light intensity as well as quick and efficient coincidence measurement methods.This paper is focused on the software realization of the the acquisition of light intensity and coincidence detection. We work on the theory and physics of correlated imaging, then realize the acquisition software of a weak light CCD and coincidence detection. The detailed content includes:1. Briefly overview the history of correlated imaging, then we analyze the development of coincidence detection with a CCD as the detector.2. The first-order coherence and Hanbury Brown and Twiss(HBT) correlation of thermal light are analyzed theoretically from the view of coherence of thernal light. We focuse on the correlation property of pseudo-thernal light, including the temporal and spatial correlation, which is the physical nature of correlated imaging of thermal light. Based on the HBT correlation, the transverse coherence length of pseudo-thernal light is calcutaed by using the MATLAB.3. The light intensity in the correlated imaging of a reflective object is so weak that in our study a weak light CCD is employed as the light intensity detector. After analyzations of the working principle and performance characteristics of INFINITY 3-1-M weak light CCD, a fast acquisition program of this type CCD is accomplished to meet the requirements of correlated imaging.4. The last but the most important step of a correlated imaging system is the coincidence detection of light intensity, then we get the object image in the reference path. We start with a brief introduction of coincidence detection, with particular emphasize on the Positive-Negative-Fluctuation Correlation(PNFC) protocol. Then a detail description of this protocal is made,also we study the theoretical foundation of PNFC protocol. Finally, we achieve a HBT correlation with 100% visibilities by using PNFC protocol in MATLAB software.Moreover, we achieve a correlated image of a reflective objectwith much higher visibility by using this coincidence method.