Computational Ghost Imaging System Research Articles

Optical image authentication and encryption scheme with computational ghost imaging

Most of the previous image encryption schemes overlook certifying the source of the encrypted images, thus the receiver may be misled by messages coming from unauthorized users or wrong sources. To simultaneously accomplish image encryption and source authentication of the encrypted images, an optical image authentication and encryption scheme is proposed by integrating computational ghost imaging (CGI) with quick response (QR) code. Firstly, the plaintext image is converted into a QR code and encrypted by a scrambling-diffusion structure. Then, the authentication image is enciphered by a CGI system and a diffusion structure. The intermediate resulting images are marked and embedded into the random matrices to withstand the differential attack. Moreover, the source of the encrypted images can be identified by the reconstructed authentication image and the nonlinear correlation coefficient (NCC) result. The authentication is considered successful if a sharp peak appears in the center of the NCC result. Numerical simulations show that the proposed scheme can not only withstand different attacks, but also avoid being misled by misinformation during the decryption process.

Detection Model and Correction Method for Quadrant Detector-Based Computational Ghost Imaging System

Detection Model and Correction Method for Quadrant Detector-Based Computational Ghost Imaging System

A crosstalk-free multiple-image encryption scheme based on computational ghost imaging with binarized detection

Crosstalk noise is a main problem limiting the performance of multiple-image encryption (MIE) scheme. In this work, we proposed a crosstalk-free MIE scheme based on computational ghost imaging (CGI) with binarized detection. In the encryption process, the plaintext images are encrypted into intensity sequences by the CGI system and quantified into two levels to obtain binary ciphertext sequences, which does not cause severe degradation in decrypted image quality compared to traditional CGI. Then, for the binary ciphertext sequences, we can combine them into a decimal grayscale ciphertext. To enhance security, a pixel bit layer scrambling (PBLS) algorithm is designed to scramble the grayscale ciphertext to obtain the final ciphertext. In the decryption process, anyone of the plaintext images can be decrypted without being affected by other plaintext images after performing inverse PBLS algorithm on the ciphertext and extracting the binary ciphertext sequence. The effectiveness, robustness, encryption capacity and security of the proposed scheme are demonstrated by numerical simulations and theoretical analysis.

Reconstruction method of computational ghost imaging under atmospheric turbulence based on deep learning

Ghost imaging, as an emerging imaging method, has great advantages in harsh environment with its off-object imaging characteristics. In this paper, we use a turbulence model based compressive sensing computational ghost imaging system to simulate atmospheric turbulence, analyze the effects of various factors on the imaging results, and recover the images under extreme turbulence conditions using conditional generation adversarial network, which can finally recover the images well. The simulation results show that the image reconstruction method proposed in this paper can recover the image well under the condition of very low sampling rate (1.56%).

Optical steganography with RVNCA-based keys for 3D object

Traditional 3D image steganography is cumbersome and difficult owing to the special structure of 3D image, imposing a practical limit for its applications. Herein, we propose a 3D image steganography scheme utilizing computational ghost imaging (CGI). Furthermore, triple keys are introduced in the steganography to increase the difficulty of being cracked greatly. With the help of backward ray tracing (BRT) technology, the element image array (EIA) of the 3D object is obtained as the target of ghost imaging. For encryption, we utilize restricted vertical neighborhood cellular automata (RVNCA) to encode random masks of the CGI system as the key, which greatly improves the security of the steganography scheme and facilitates the management and transmission of the key. Finally, we reconstruct the decrypted image optically and obtain a full color and full parallax 3D image through the display device.

High-Quality Computational Ghost Imaging with a Conditional GAN

In this study, we demonstrated a framework for improving the image quality of computational ghost imaging (CGI) that used a conditional generative adversarial network (cGAN). With a set of low-quality images from a CGI system and their corresponding ground-truth counterparts, a cGAN was trained that could generate high-quality images from new low-quality images. The results showed that compared with the traditional method based on compressed sensing, this method greatly improved the image quality when the sampling ratio was low.

Scattering medium-robust computational ghost imaging with random superimposed-speckle patterns

Illumination patterns of a ghost imaging (GI) system disturb when passing through a scattering medium. Within limits, the larger the speckle size, the stronger the anti-interference ability of illumination pattern to scattering medium, but the lower the imaging resolution. Computational ghost imaging (CGI) system has the advantage of flexible design of illumination patterns. We analyze and demonstrate that using random superimposed-speckle patterns as the illumination pattern of CGI system (RSCGI) can enhance the anti-interference ability of illumination pattern to scattering medium without reducing the imaging resolution when intensity fluctuation correlation reconstruction algorithm is used. Experimental results show that the contrast-to-noise ratio (CNR) and imaging resolution are obviously improved.

Three-dimensional computational ghost imaging using a dynamic virtual projection unit generated by Risley prisms.

Computational ghost imaging (CGI) using stereo vision is able to achieve three-dimensional (3D) imaging by using multiple projection units or multiple bucket detectors which are separated spatially. We present a compact 3D CGI system that consists of Risley prisms, a stationary projection unit and a bucket detector. By rotating double prisms to various angles, speckle patterns appear to be projected by a dynamic virtual projection unit at different positions and multi-view ghost images are obtained for 3D imaging. In the process of reconstruction, a convolutional neural network (CNN) for super-resolution (SR) is adopted to enhance the angular resolution of reconstructed images. Moreover, an optimized 3D CNN is implemented for disparity estimation and 3D reconstruction. The experimental results validate the effectiveness of the method and indicate that the compact system with flexibility has potential in applications such as navigation and detection.

Analysis of the allowable maximum amplitude of random jitter in computational ghost imaging.

The imaging blur caused by the relative motion between an imaging system and an imaging target can be eliminated by a compensation operation based on the motion law, although it is invalid when the movement is random. In this paper, the influence of the random jitter on imaging resolution is investigated quantitatively in a computational ghost imaging system, and the maximum of random-jitter amplitude that the system can allow is analyzed. The numerical and experimental results verify our conclusion, and the error between the experiment and simulation is less than 12%. The main reason for the error is the disturbance of experimental noise. By using ghost imaging algorithms to reduce the corresponding impact, this error can be further reduced to 6%.

High-performance scanning-mode polarization based computational ghost imaging (SPCGI).

Computational ghost imaging (CGI) uses preset patterns and single-pixel detection, breaking through the traditional form of point-to-point imaging. In this paper, based on the Monte Carlo model, a reflective polarization based CGI (PCGI) system has been proposed and constructed under the foggy environments. And the imaging performances of the PCGI at different optical distances have been investigated and analyzed quantitatively. When the targets and the background have a small difference in reflectivity, the difference of polarization characteristics between the targets and the background can help the CGI to remove the interference of scattering light and improve the imaging contrast. Besides, in order to further improve imaging efficiency, a scanning-mode polarization based CGI (SPCGI) has also been proposed, in which the combination of polarization characteristics and the scanning-mode plays an important role to improve the CGI's imaging efficiency and imaging quality.

An encryption method based on computational ghost imaging with chaotic mapping and DNA encoding

An encryption method based on computational ghost imaging (CGI) with chaotic mapping and DNA encoding is proposed. To reduce the amount of keys in the CGI-based encryption system, the chaotic mapping algorithm is used to generate the random sequence as the speckle measurement matrix of CGI system. The measurement data of the bucket detector is subjected to block and DNA operations, which introduce the nonlinear characteristics in the encryption process. The problem of linear vulnerability of the encryption system has been greatly improved. Numerical simulation results show that, compared with the traditional CGI-based encryption method, the proposed method greatly reduces the amount of keys, increases the key space and enhances the security of the system.

High performance optical image hiding based on computational ghost imaging with BCH error correction coding technique

The conventional image hiding scheme based on computational ghost imaging (CGI) has low-quality reconstructed watermark and unsatisfied security. In this paper, a high performance optical image hiding scheme is proposed to cope with these issues. The watermark is first read as a binary number sequence and processed by exclusive-OR operation with a random number sequence that generated by chaotic system. Thereafter, the result is coded with Bose-Chaudhuri-Hocquenghem error correction code and encrypted by the CGI system. Finally, the obtained cyphertext is quantified into two levels and hidden in the host image. Differing from other watermarking schemes, binary images, grayscale images and color images can be used as watermarks to be reconstructed losslessly, and a series of simulation results illustrate the feasibility and effectiveness of the proposed scheme.

25,000 fps Computational Ghost Imaging with Ultrafast Structured Illumination

Computational ghost imaging, as an alternative photoelectric imaging technology, uses a single-pixel detector with no spatial resolution to capture information and reconstruct the image of a scene. Due to its essentially temporal measurement manner, improving the image frame rate is always a major concern in the research of computational ghost imaging technology. By taking advantage of the fast switching time of LED, an LED array was developed to provide a structured illumination light source in our work, which significantly improves the structured illumination rate in the computational ghost imaging system. The design of the LED array driver circuit presented in this work makes full use of the LED switching time and achieves a pattern displaying rate of 12.5 MHz. Continuous images with 32 × 32 pixel resolution are reconstructed at a frame rate of 25,000 fps, which is approximately 500 times faster than what a universally used digital micromirror device can achieve. The LED array presented in this work can potentially be applied to other techniques requiring high-speed structured illumination, such as fringe 3D profiling and array-based LIFI.

A Remote Security Computational Ghost Imaging Method Based on Quantum Key Distribution Technology

Computational ghost imaging (CGI) is a method of acquiring object information by measuring light field intensity, which would be used to achieve imaging in a complicated environment. The main issue to be addressed in CGI technology is how to achieve rapid and high-quality imaging while assuring the secure transmission of detection data in practical distant imaging applications. In order to address the mentioned issues, this paper proposes a remote secure CGI method based on quantum communication technology. Using the quantum key distribution (QKD) network, the CGI system can be reconstructed while solving the problem of information security transmission between the detector and the reconstructed computing device. By exploring the influence of different random measurement matrices on the quality of image reconstruction, it is found that the randomness of the numerical sequence constituting the matrix is positively correlated with the imaging quality. Based on this discovery, a new type of quantum cryptography measurement matrix is constructed using quantum cryptography with good randomness. In addition, through further orthogonalization and normalization of the matrix, the matrix has both good randomness and orthogonality, and high-quality imaging results can be obtained at a low sampling rate. The feasibility and effectiveness of the method are verified by simulation imaging experiments. Compared with the traditional GI system, the method proposed in this paper has higher transmission security and high-quality imaging under this premise, which provides a new idea for the practical development of CGI technology.

Generalized forgery attack to optical encryption systems

In previous works, the attacking methods to optical encryption systems are mainly investigated from the aspect of cryptanalysis. An alternative forgery attack is proposed recently for an encrypted computational ghost imaging (CGI) system by confusing the receiver with forged keys and fake decrypted images. But the limitation is that it only works for binary single-pixel intensity values. We propose a different forgery attacking algorithm that works for grayscale single-pixel intensity values in a general CGI system. In addition, we transfer the concept of forgery attack to the well-known double random phase encoding (DRPE) system and propose a corresponding iterative attacking algorithm. Furthermore, we propose several metrics to evaluate the imperceptibility level of the forged keys. We prove that a forgery attack can be implemented not only in a particular situation but also for general optical encryption systems.

Underwater compressive computational ghost imaging with wavelet enhancement.

We propose a compressive Hadamard computational ghost imaging (CGI) method to restore clear images of objects in the underwater environment. We construct an underwater CGI system model and develop a total variation regularization prior-based compressed-sensing algorithm for the CGI image reconstruction. We design a wavelet enhancement algorithm to further denoise and enhance the quality of the CGI image. We build an experimental setup and implement a series of experiments. The effectiveness and advantages of the proposed method are experimentally investigated. The results show that the proposed method can achieve clear imaging for underwater objects with a sub-Nyquist sampling ratio. The proposed method is helpful for improving the image quality of the underwater CGI.

Preventing forgery attacks in computational ghost imaging or disabling ghost imaging in a "spatiotemporal" scattering medium with weighted multiplicative signals.

The ghost imaging (GI) approach is an intriguing and promising image acquisition technique that can transmit high-quality image information in a scattering environment. In this paper, we focus on two concerns recently emerged in the GI modality: one is the vulnerability to forgery attacks in GI-based optical encryption [Opt. Lett.45, 3917 (2020)OPLEDP0146-959210.1364/OL.392424], and the other is the potential threat of GI to personal privacy regarding non-invasive imaging [Opt. Express28, 17232 (2020)OPEXFF1094-408710.1364/OE.391788]. The core idea is to recommend introducing weighted multiplicative signals [Opt. Express27, 36505 (2019)OPEXFF1094-408710.1364/OE.27.036505] into the computational GI system, whether on the transmitting end or the receiving end. At the transmitting end, the random multiplicative signal can be used as an additional key that can reduce the possibility of forgery attacks, thereby increasing image transmission security. On the receiving end, the introduction of a random multiplicative signal to a spatial scattering medium makes it a "spatiotemporal" scattering medium, whose transmittance changes with time. Further, the spatiotemporal scattering medium can disable direct imaging and GI at the same time with low cost, thereby having great potential in privacy protection in daily lives.

Non-imaging target recognition algorithm based on projection matrix and image Euclidean distance by computational ghost imaging

With the development of target recognition technology, people pay more and more attention to target recognition. This paper proposed a non-imaging target recognition technology based on projection matrix and image Euclidean distance by computational ghost imaging. The main features of spatial sample images are extracted by principal component analysis. The projection matrix of eigenspace is used as the modulation matrix in computational ghost imaging algorithm to reduce data redundancy. And by calculating the image Euclidean distance, the correlation of pixels is taken into full consideration in spatial position, so as to improve the accuracy of traditional target recognition algorithms. In this paper, the target recognition is realized by directly using the detector observations of the computational ghost imaging system based on the eigenspace projection matrix and the calculation of the image Euclidean distance. The algorithm not only has better recognition performance without reconstructing the image.

A blind watermarking scheme based on computational ghost imaging in wavelet domain

A secure, robust, and blind watermarking method based on computational ghost imaging (CGI) in the discrete wavelet transform domain is proposed. In this method, an original watermark is firstly encrypted by the CGI system with chaotic key, then the sequences of the ciphertext are quantified into two levels and hidden in the wavelet coefficients of a host image. The quantization on the ciphertext compresses the amount of data to be hidden but does not induce serious deterioration in the retrieved image comparing with the conventional CGI. Simulation results show that the decrypted watermark is still distinguishable and can be authenticated with the nonlinear correlation coefficient. The embedded data can be blindly extracted with no help of the original host image. The chaotic key acts as both the encryption and the embedding key, which guarantee the security of the watermarking scheme.

High-quality underwater computational ghost imaging with shaped Lorentz sources

We show that the quality of the underwater imaging can be effectively improved by utilizing the computational ghost imaging (CGI) scheme with shaped Lorentz sources. The formula for the point-spread function in the underwater CGI system with a shaped Lorentz source is derived theoretically, and numerical examples are given to see how the CGI quality can be affected by the oceanic turbulence, including the rate of dissipation of mean-square temperature, the rate of dissipation of turbulent kinetic energy per unit mass of fluid, and the relative strength of temperature salinity fluctuations, as well as the modulation factor of the shaped Lorentz source. In addition, the relative mean square error is applied to quantitatively evaluate the quality of the recovered images in our underwater CGI system. Compared with the widely used Gaussian source, our results show that the long-distance underwater CGI quality can be greatly enhanced by properly adjusting the modulation factor of the shaped Lorentz source, owing to its almost non-diffracting property. Therefore, our proposed method may be useful for the real application in the long-distance underwater imaging.