Since its inception, ghost imaging technology has drawn wide interest and has been reported in many application scenarios due to its advantages, including strong anti-scattering capacity, lens-free imaging, and off-object imaging. In practice, however, ghost imaging technology still struggles with a number of fundamental issues, such as reliable signal recognition and quick imaging in challenging situations. These requirements call for more sophisticated algorithms, as well as hardware design and control. In this study, we design and develop a sequence-controlled ghost imaging system on the basis of the pseudothermal light ghost imaging technology scheme, which can achieve high-quality imaging under various conditions by precisely controlling the main components of the system. Apart from the fundamental correlation imaging algorithm, this system presents three more imaging algorithms, namely, differential ghost imaging, normalized ghost imaging, and positive-negative correlation imaging. A secondary optimization scheme for the images reconstructed by the positive-negative correlation algorithm is proposed to further improve the imaging quality. For the development of ghost imaging systems for a larger range of applications and more complicated situations, we hope that our system can serve as a model.

In this paper, the sequence control capability of the ghost imaging system and the algorithm's optimization impact on the imaging quality are demonstrated through comparison tests. Figure 1 (a) is the schematic diagram of the pseudothermal light ghost imaging system. Figure 1 (b) is the GUI interface of the system, through which the operations of the system can be directly controlled, such as the position of the displacement platform, the speed of the ground glass, the sampling times, and the imaging algorithm. The synchronous control of the system and the control of the electric displacement platform are realized by the control unit while the signal acquisition is completed. In addition, the differential ghost imaging, normalized ghost imaging, as well as positive-negative correlation algorithm and its optimization algorithm, are integrated to further improve the performance of the ghost imaging system.

The system's sequence control performance is empirically demonstrated by research on the precise control of the speckle size and the sufficient sampling times for higher-quality imaging under different conditions. Comparison experiments of traditional ghost imaging, differential ghost imaging, normalized ghost imaging, and positive-negative correlation imaging and its optimized algorithm are conducted for various objects to verify the optimization effect of the system's algorithm on the imaging quality.

The system improves the imaging quality via both precise hardware control and an optimized algorithm (Fig. 1). The research shows that the speckle size of the object surface directly affects the imaging quality, and this system can accurately adjust the speckle size by controlling the relevant components to image objects of different sizes with the optimal resolution. In the experiment, two objects of different sizes are selected; the speckle size is adjusted, and the imaging with different speckle sizes is compared. The effect of the speckle size on the imaging quality and the optimal speckle sizes corresponding to different objects can be found through observations of the quality curves (Figs. 2 and 3). In addition, since traditional pseudothermal light ghost imaging requires sufficient sampling to achieve higher-quality imaging, the system generates a large amount of effective data by controlling the position of the rotating glass to satisfy this requirement (Figs. 4 and 5). Meanwhile, different imaging algorithms are combined in the system to optimize the imaging effect to a certain extent for different objects. In the comparison experiments of traditional ghost imaging with differential ghost imaging and normalized ghost imaging, the optimization effects of differential ghost imaging and normalized ghost imaging on imaging quality are confirmed. Both have a similar noise reduction effect under a large sampling times, and the optimization effect on different transmission-type objects also differs (Figs. 6 and 7). Meanwhile, noise reduction is performed again on the reconstructed images of the positive-negative correlation algorithm. It is found that the imaging noise is significantly reduced, and the value of the modulation factor is changed to avoid serious loss of some information on the object during noise reduction for optimal imaging results (Figs. 9 and 10).

Based on the principle of traditional pseudothermal light ghost imaging, we designed and developed a sequence-controlled pseudothermal light ghost imaging system, which could achieve precise control of the speckle size and quantity of sampling for ghost imaging, while combining different imaging algorithms and proposing further optimization schemes to finally improve the imaging quality for different objects.