Thermal ghost imaging with averaged speckle patterns

Abstract

We present theoretical and experimental results showing that a thermal ghost imaging system can produce images of high quality even when it uses detectors so slow that they respond only to intensity-averaged (that is, "blurred") speckle patterns, as long as the collected signal variation is predominantly caused by the random fluctuation of the incident speckle field rather than other noise sources. In our experimental study, we show that the quality of the ghost image is not degraded when as many as 25 speckle patterns are averaged together for each measurement. This surprising result comes from the fact that the averaging of speckle patterns leads to a decrease in the contrast but not in the kurtosis, and the image quality of a ghost imaging system is dependent on the kurtosis rather than the contrast ratio of the illuminating field. These results suggest that a broad class of imaging systems based on the use of speckle techniques can be implemented even using detectors that respond slowly on the time scale of the fluctuating speckle pattern.

Influence of detector response speed on the contrast-to-noise ratio of reflective ghost imaging

“…With the model introduced by Chan et al [16,17] and Brida et al [15], an analysis of image quality of transmissive ghost imaging with averaged speckle patterns was presented by Zerom et al [18]. Here we discuss the CNR of RGI following this model.…”

“…The ghost image of the object can be reconstructed by correlating the bucket signal with the intensity distribution of the incident speckle pattern projected onto the object, averaging over many measurements. The second-order correlation of RGI can be expressed as [16][17][18] …”

“…It is well known that a slow response detector used in conventional imager based on speckles would produce blurred images of object. However, in performing transmissive ghost imaging with intensity-averaged (or blurred) speckle patterns, Brida et al [15] and Zerom et al [18] showed that the image quality of transmissive ghost imaging can remain high, even though the response speed of detectors is much slower than the correlation time of the illuminating speckle field, as long as the fluctuation of the detected signal is mainly caused by the illuminating speckle field rather than noise of the detection system. This result implies that using slow detectors for true thermal light GI is possible.…”

“…Some important factors which influence the image quality of GI have been considered, such as illumination levels, the number of speckles transmitted through the mask in the object channel, the number of spatio-temporal modes detected by the reference detector, and the response speed of detector [15][16][17][18]. It is well known that a slow response detector used in conventional imager based on speckles would produce blurred images of object.…”

Compressive microscopic imaging with “positive–negative” light modulation

“…The first demonstration of ghost imaging (GI) [1,2] utilized biphoton pairs which were produced by spontaneous parametric down conversion in a nonlinear crystal, hence the phenomenon was interpreted as the result of quantum entanglement of the photon pairs [3]. Subsequently, further theoretical and experimental work showed that GI is also achievable with pseudo-thermal [4][5][6][7][8][9][10] as well as true thermal light [11,12] and can be explained with a classical statistical model [13,14].…”