Lensless ghost imaging has attracted much interest in recent years due to its profound physics and potential applications. In this paper we report studies of the robust properties of the lensless ghost imaging system with a pseudo-thermal light source in a strongly scattering medium. The effects of the positions of the strong medium on the ghost imaging are investigated. In the lensless ghost imaging system, a pseudo-thermal light is split into two correlated beams by a beam splitter. One beam goes to a charge-coupled detector camera, labeled as CCD2. The other beam goes to an object and then is collected in another charge-coupled detector camera, labeled as CCD1, which serves as a bucket detector. When the strong medium, a pane of ground glass disk, is placed between the object and CCD1, the bucket detector, the quality of ghost imaging is barely affected and a good image could still be obtained. The quality of the ghost imaging can also be maintained, even when the ground glass is rotating, which is the strongest scattering medium so far. However, when the strongly scattering medium is present in the optical path from the light source to CCD2 or the object, the lensless ghost imaging system hardly retrieves the image of the object. A theoretical analysis in terms of the second-order correlation function is also provided.

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Single-pixel imaging has become a topic of intense interest amongst theoreticians and experimentalists in recent years, and is still attracting great attention due to its potential applications in biomedical imaging, remote sensing, defence monitoring, etc. Two main fields should be involved in single-pixel imaging scheme: single-pixel camera and computational quantum imaging, which are proposed in the year 2006 and 2008, respectively. Although these two single-pixel imaging schemes belong to different research fields, they are nearly identical in the realization setup and using the similar image recovering algorithm. The single-pixel camera scheme is mainly based on compressive sensing algorithms, which can recover the image with about 30 percent measurements of its total pixels (raster scan method), but need the prior knowledge of the image. While the computational quantum imaging method usually recovers the image by using the second-order correlation function, which is computational fast but need more measurements to retrieve a high quality image. Thus, both the methods mentioned above are time consuming. In this paper, a single-pixel imaging scheme based on Walsh-Hadamard transform is proposed and is demonstrated both theoretically and experimentally. The retrieving times of different algorithms are discussed and compared with each other. An image of 10241024 pixels can be acquired around 1 second with our method while it will take 8 seconds by using TVAL3 algorithm on the general computer in our numerical simulation experiment. It is also experimentally demonstrated that the nature targets from 500 meters to 5000 meters away are acquired, with pixels of 128128 and in the waveband of 350-900 nm, and the speed of the imaging frame rate is achieved at 0.5 frame per second. The differences and commons between single-pixel imaging and computational quantum imaging are also discussed in this article. It is found that the Walsh-Hadamard transform we proposed is stable and can be sufficiently saving the imaging time of the single-pixel imaging schemes while maintaining a high imaging quality. Moreover, the single-pixel remote imaging scheme can be used in other wave band such as infrared and micro wave imaging, or will be useful in the case when the array detector technique is difficult to meet the requirements such as the sensitivity or the volume. And our scheme proposed here can make the single-pixel imaging technique step further toward its real applications.

Quantum imaging is such an technique that the total light intensity transmitted through or reflected by an object is collected by a bucket detector, which generally is a photodiode with a collection lens in front and with no spatial resolution, and an image of the object can be retrieved through the assistance of another spatially correlated reference beam which does not interact with the object. In this paper, Quantum imaging scheme is investigated, instead of using the conventional linear detector, and a single photon detector working in a photon-counting mode is used as a bucket detector, which is the most sensitive detector in the present. It is experimentally demonstrated that quantum imaging illuminating by pseudo-thermal light can be retrieved through using the single-photon detector working in the photon-counting mode, and the averaged power received by the bucket detector is only 2 femto-Watt. It is also experimentally and theoretically demonstrated that the image of the cooperative target can be recovered through the wake scattering medium, which cannot be realized by the classical imaging method. Furthermore, it is found that the wake scattering medium has the potential application in reducing the size of the collection lens of the bucket detector, in other words, enlarging the field of view. Besides, quantum imaging recovered by correlation of intensity fluctuations and compressive sensing algorithm are compared, and the most effective ways to retrieve the image are discussed. The scheme of our experiment which is different from the traditional ways, offers a novel method to make the quantum imaging technique step further toward its applications in wake light imaging or remote sensing.