Optical Scanning Holography Research Articles

Asymmetric Optical Scanning Holography Encryption with Elgamal Algorithm

This paper proposes an asymmetric scanning holography cryptosystem based on the Elgamal algorithm. The method encodes images with sine and cosine holograms. Subsequently, each hologram is divided into a signed bit matrix and an unsigned hologram matrix, both encrypted using the sender’s private key and the receiver’s public key. The resulting ciphertext matrices are then transmitted to the receiver. Upon receipt, the receiver decrypts the ciphertext matrices using their private key and the sender’s public key. We employ an asymmetric single-image encryption method for key management and dispatch for securing imaging and transmission. Furthermore, we conducted a sensitivity analysis of the encryption system. The image encryption metrics, including histograms of holograms, adjacent pixel correlation, image correlation, the peak signal-to-noise ratio, and the structural similarity index, were also examined. The results demonstrate the security and stability of the proposed method.

Hybrid Optical Scanning Holography for Automatic Three-Dimensional Reconstruction of Brain Tumors from MRI using Active Contours

Hybrid Optical Scanning Holography for Automatic Three-Dimensional Reconstruction of Brain Tumors from MRI using Active Contours

Computational Optical Scanning Holography

Holographic techniques are indispensable tools for modern optical engineering. Over the past two decades, research about incoherent digital holography has continued to attract attention. Optical scanning holography (OSH) can obtain incoherent holograms using single-pixel detection and structured illumination with Fresnel zone patterns (FZPs). Particularly by changing the size of a detector, OSH can also obtain holograms under coherently illuminated conditions. Since 1979, OSH has continuously evolved. According to the evolution of semiconductor technology, spatial light modulators (SLMs) come to be useful for various imaging fields. By using SLM techniques for OSH, the practicality of OSH is improved. These SLM-based OSH methods are termed computational OSH (COSH). In this review, the configurations, recording and reconstruction methods, and proposed applications of COSH are reviewed.

Non-Cascaded and Crosstalk-Free Multi-Image Encryption Based on Optical Scanning Holography Using 2D Orthogonal Compressive Sensing.

We propose a non-cascaded and crosstalk-free multi-image encryption method based on optical scanning holography and 2D orthogonal compressive sensing. This approach enables the simultaneous recording and encryption of multiple plaintext images without mechanical scanning, while allows for independent retrieval of each image with exceptional quality and no crosstalk. Two features would bring about more substantial security and privacy. The one is that, by employing a sequence of pre-designed structural patterns as encryption keys at the pupil, multiple samplings can be achieved and ultimately the holographic cyphertext can be obtained. These patterns are generated using a measurement matrix processed with the generalized orthogonal one. As a result, one can accomplish the differentiation of images prior to the recording and thus neither need to pretreat the pending images nor to suppress the out-of-focus noise in the decrypted image. The other one is that, the non-cascaded architecture ensures that different plaintexts do not share sub-keys. Meanwhile, compared to 1D orthogonal compressive sensing, the 2D counterpart makes the proposed method to synchronously deal with multiple images of more complexity, while acquire significantly high-quality decrypted images and far greater encryption capacity. Further, the regularities of conversion between 1D and 2D orthogonal compressive sensing are identified, which may be instructive when to manufacture a practical multi-image cryptosystem or a single-pixel imaging equipment. A more general method or concept named synthesis pupil encoding is advanced. It may provide an effective way to combine multiple encryption methods together into a non-cascaded one. Our method possesses nonlinearity and it is also promising in multi-image asymmetric or public key cryptosystem as well as multi-user multiplexing.

Autofocus by Lissajous scanning in time reversal optical scanning holography

Autofocus by Lissajous scanning in time reversal optical scanning holography

Comparison of adaptive optical scanning holography based on new evaluation methods

Adaptive Optical Scanning Holography (AOSH) represents a powerful technique that employs an adaptive approach to selectively omit certain lines within holograms, guided by the utilization of Normalized-Mean-Error (NME) as a predictive measure. This approach effectively diminishes scanning time and conserves the storage space required for data preservation. However, there exists alternative methods superior to NME in terms of evaluating the model’s efficacy. This paper introduces two novel methods, namely Normalized-Root-Mean-Square-Error (NRMSE) and Normalized-Mean-Square-Error (NMSE), into the AOSH system, leading to the development of NRMSE-AOSH and NMSE-AOSH. These new systems aim to further minimize duration of holographic recording. Through a comparative analysis of hologram lines between the two newly proposed AOSH systems and the original AOSH, we demonstrate that both NRMSE-AOSH and NMSE-AOSH effectively reduce the number of hologram lines while maintaining the hologram’s informational content. Among the three methods, our two new methods exhibit better performance compared with the original method.

Spatially divided two-step phase-shifting method for computational optical scanning holography

Computational optical scanning holography (COSH) is one of the single-pixel incoherent digital holographic techniques; therefore, three-dimensional fluorescent objects can be measured as a digital hologram with a single-pixel detector. However, due to the requirement of a phase-shifting method to remove unnecessary components from holograms, the number of measurements of COSH is larger than the number of pixels. To reduce the number of measurements, the spatially divided phase-shifting method has been proposed. Similar to the parallel four-step phase-shifting digital holography, the spatially divided phase-shifting method can obtain four phase-shifted holograms simultaneously. However, the spatially divided phase-shifting method has a problem in that the spatial resolution is lower than the original COSH. In this paper, a spatially divided two-step phase-shifting method is proposed to improve spatial resolution. The numerical evaluation results indicate the feasibility of the proposed method. In addition, the proposed method is applied to microscopy for proof of principle experiment. The experimental results indicate the proposed method improves the image quality compared with the conventional spatially divided four-step phase shifting method.

Quantitative phase imaging based on motionless optical scanning holography.

Optical scanning holography (OSH) can be applied to 3D fluorescent imaging. However, the optical setup for OSH is complicated due to the requirement of a phase shifter, a 2D mechanical scanner, and an interferometer. Although motionless optical scanning holography (MOSH) can overcome the problem, quantitative phase imaging (QPI) has not yet been realized because MOSH can only obtain incoherent holograms. If QPI in MOSH is realized, MOSH can be applied to various applications. In this Letter, MOSH-based QPI (MOSH-QPI) is proposed. In addition, a simple description of a coherent mode of OSH is presented. In the proof-of-principle experiment, the spatially divided phase-shifting technique is applied to reduce the number of measurements. The feasibility of MOSH-QPI is confirmed by measuring a phase distribution of a microlens array. MOSH-QPI is also applied to measure practical samples, and its results are compared with the experimental results of the conventional one using a Mach-Zehnder interferometer.

Single recording without heterodyning in optical scanning holography

We have built a system for off-axis optical scanning holography (OSH) and for the first time experimentally demonstrated the recording of a hologram without heterodyning or a spatial light modulator for temporal frequency shifting. To solve the problem of phase fluctuation, a phase monitoring module is included in the system. Single sideband filtering together with phase compensation is performed for the reconstruction without the zeroth-order light and the twin image. Properties and practical issues in the coherent-mode and incoherent-mode of off-axis OSH are also discussed.

Suppressing defocus noise with U-net in optical scanning holography

Suppressing defocus noise with U-net in optical scanning holography

Polarization imaging by use of optical scanning holography

Polarization imaging by use of optical scanning holography

Roadmap of incoherent digital holography

This roadmap article focuses on spatially incoherent digital holography (IDH). Representative IDH methods such as optical scanning holography (OSH), Fresnel incoherent correlation holography (FINCH), coded aperture correlation holography (COACH), IDH with a Fresnel zone aperture, and IDH with an interferometer along with a state-of-the-art optical device are introduced as modern IDH methods. We describe these IDH techniques with applications of three-dimensional (3D) imagers, 3D thermography, and 3D microscopy.

Three-dimensional imaging by interferenceless optical scanning holography

Optical scanning holography (OSH) can perform high quality, speckle-free three-dimensional (3D) holographic imaging. However, conventional OSH system contains an interferometer, which is sensitive to environmental disturbances. Here, we develop an interferenceless OSH (IOSH) system to overcome this issue. In IOSH, the interferometer is replaced by a digital micro device (DMD) together with a projection module. The Fresnel zone plates are directly displayed on the DMD and projected to the object target. The high frame-rate DMD can serve as both the display device and the scanning device, and thus the system can be compact, robust, and low cost. We have studied the system performance by analyzing the 3D complex point spread function. The ability of 3D imaging by IOSH has also been demonstrated experimentally.

Deep-learning based reconstruction in optical scanning holography

Optical scanning holography (OSH) can be used to record holograms of large three-dimensional (3-D) objects, based on a two-dimensional (2-D) optical scan. For semi-transparent objects, diffraction waves from all the sections can be recorded in the hologram. Numerical reconstruction of a 3-D volumetric image from an optical scanned hologram is a difficult task. The main problems are the intensive computational load, and the heavy blurring of each reconstructed section with the defocused noise from other sections. In this paper, we propose a deep-learning network for high quality image reconstruction from the optical scanned holograms. Within the framework, a U-net structure is adopted to learn the mapping between a collection of holograms, and their reconstructed volumetric images. We use a two-pupil optical heterodyne scanning system to obtain the training data where a five-fold cross validation method is used to prevent from overfitting and produce enough images in the dataset. The deep-learning based OSH can eliminate the defocus noise and generate high quality reconstruction results from an unknown hologram. Our proposed method is significantly faster than conventional OSH reconstruction algorithms, and hence suitable for processing large holograms that are captured by OSH. The feasibility of our approach is demonstrated with numerical simulations and optical experiments. The deep-learning reconstruction method proposed in the present paper is also applicable to other digital holograms obtained from conventional digital holographic systems.

Optical scanning holography for a three-dimensional equal scale display.

We propose an optical scanning holography (OSH) for optical reconstruction with equal scale magnification or demagnification ratio along the transverse and longitudinal directions when the magnification or demagnification ratio of the hologram is priori known. First, we review the principles of OSH. Second, we propose an equal scale OSH that encodes a 3D distribution of a 3D scene with a scanning beam pattern that is formed by the superposition of two spherical waves with the same curvature direction. The hologram recorded by the equal scale OSH reconstructs the 3D scene with equal scale magnification or demagnification along the transverse and longitudinal directions. Finally, we provide simulation and experiment results to illustrate and clarify the proposed idea.

Review of Incoherent Digital Holography: Applications to Multidimensional Incoherent Digital Holographic Microscopy and Palm-Sized Digital Holographic Recorder—Holosensor

We review advancements in incoherent digital holography (IDH) with an image sensor and its applications to multidimensional microscopy and a palm-sized hologram recorder termed “holosensor”. There are two types of representative IDH technique: IDH with a structured illumination and a single photodetector termed optical scanning holography and self-interference IDH. The latter IDH is a technique to obtain an incoherent digital hologram by modulating an incoherent light wave between an object and an image sensor. Multidimensional information such as three-dimensional space and wavelengths is simultaneously recorded without changing optical filters by introducing interferometric techniques invented in laser holography. Applications to high-speed color-multiplexed holographic fluorescence microscopy, single-shot incoherent full-color holographic microscopy with white light, and a palm-sized multidimensional incoherent hologram recorder have been developed using multidimensional IDH systems. Schematics and experimental results obtained using IDH techniques, incoherent holographic microscopy systems, and compact IDH systems are introduced.

Secure and Robust Optical Multi-Stage Medical Image Cryptosystem

Due to the rapid growth of telemedicine and healthcare services, color medical image security applications have been expanded precipitously. In this paper, an asymmetric PTFrFT (Phase Truncated Fractional Fourier Transform)-based color medical image cryptosystem is suggested. Two different phases in the fractional Fourier and output planes are provided as deciphering keys. Accordingly, the ciphering keys will not be employed for the deciphering procedure. Thus, the introduced PTFrFT algorithm comprises asymmetric ciphering and deciphering processes in contrast to the traditional optical symmetric OSH (Optical Scanning Holography) and DRPE (Double Random Phase Encoding) algorithms. One of the principal impacts of the introduced asymmetric cryptosystem is that it eliminates the one-dimensionality aspects of the related symmetric cryptosystems due to its remarkable feature of phase nonlinear truncation components. More comparisons on various color medical images are examined and analyzed to substantiate the cryptosystem efficacy. The achieved experimental outcomes ensure that the introduced cryptosystem is robust and secure. It has terrific cryptography performance compared to conventional cryptography algorithms, even in the presence of noise and severe channel attacks.

Cancelable Speaker Identification System Based on Optical-Like Encryption Algorithms

Biometric authentication is a rapidly growing trend that is gaining increasing attention in the last decades. It achieves safe access to systems using biometrics instead of the traditional passwords. The utilization of a biometric in its original format makes it usable only once. Therefore, a cancelable biometric template should be used, so that it can be replaced when it is attacked. Cancelable biometrics aims to enhance the security and privacy of biometric authentication. Digital encryption is an efficient technique to be used in order to generate cancelable biometric templates. In this paper, a highly-secure encryption algorithm is proposed to ensure secure biometric data in verification systems. The considered biometric in this paper is the speech signal. The speech signal is transformed into its spectrogram. Then, the spectrogram is encrypted using two cascaded optical encryption algorithms. The first algorithm is the Optical Scanning Holography (OSH) for its efficiency as an encryption tool. The OSH encrypted spectrogram is encrypted using Double Random Phase Encoding (DRPE) by implementing two Random Phase Masks (RPMs). After the two cascaded optical encryption algorithms, the cancelable template is obtained. The verification is implemented through correlation estimation between enrolled and test templates in their encrypted format. If the correlation value is larger than a threshold value, the user is authorized. The threshold value can be determined from the genuine and imposter correlation distribution curves as the midpoint between the two curves. The implementation of optical encryption is adopted using its software rather than the optical setup. The efficiency of the proposed cancelable biometric algorithm is illustrated by the simulation results. It can improve the biometric data security without deteriorating the recognition accuracy. Simulation results give close-to-zero values for the Equal Error Rate (EER) and close-to-one values for the Area under Receiver Operator Characteristic (AROC) curve.

Single Recording Without Heterodyning in Optical Scanning Holography

Single Recording Without Heterodyning in Optical Scanning Holography

Suppressing Defocus Noise with U-Net in Optical Scanning Holography

Suppressing Defocus Noise with U-Net in Optical Scanning Holography