A decline in imaging quality will occur when the sampling data of ghost imaging is recorded by binarization. Based on the Otsu binarization, a method named Otsu binary ghost imaging (OBGI) is proposed to enhance imaging quality. Both theoretical and experimental results show that, with an appropriate threshold value, OBGI can enhance imaging quality significantly when compared with ordinary binary ghost imaging, even providing better imaging quality than that of traditional ghost imaging. It is also shown the method is more applicable under the conditions of low-light level and with a complicated object.
In an imaging system, resolution and signal-to-noise ratio (SNR) are two important indexes to characterize imaging quality. Ghost imaging is a novel imaging method whose imaging resolution and SNR are affected by the speckle size. In this paper, the relation between speckle size and resolution as well as that between speckle size and SNR in the GI system is analyzed in detail. It is shown that the critical resolution, resolvable minimum-separation between two adjacent objects, is approximately equal to the speckle size (speckle diameter). There exists an optimum SNR when the speckle size is larger than the object size. Based on our conclusion, we propose a scheme to enhance the critical resolution of the GI system by using a vortex beam, and the enhancement ability under different topological charges is clearly presented, which can be quantized by a simple formula.
The influence of uneven temperature distribution on imaging quality of computational ghost imaging (CGI) in the underwater environment is investigated experimentally. It is shown that as the water temperature increases, imaging quality presents a trend from deterioration to improvement. The results can be explained by the changes of the temperature difference between the upper and lower layers of underwater environment and laser spot travelling through the underwater environment. Moreover, the effect from different positions of the underwater environment with the same water temperature on CGI is also discussed.
In a free space optical communication (FSOC) system, atmospheric turbulence will increase the bit error ratio (BER) and impair FSOC link reliability. Since computational temporal ghost imaging (CTGI) has anti-interference, we present an FSOC system over atmospheric turbulence based on CTGI. The simulation results show that the BER performance of CTGI is better than on–off keying under different atmospheric turbulence regimes. To improve the performance of the CTGI scheme, the influence of the number of transmission samples and code length is analyzed. It is shown that BER performance improves with the increment of the number of samples, while code length has no impact. This scheme provides an idea for reliable communication over atmospheric turbulence and an important reference for improving wireless optical communication in an extreme environment.
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