Single-shot Digital Holography Research Articles

Dielectric Metasurface Enabled Compact, Single-Shot Digital Holography for Quantitative Phase Imaging.

Quantitative phase imaging (QPI) enables nondestructive, real-time, label-free imaging of transparent specimens and can reveal information about their fundamental properties such as cell size and morphology, mass density, particle dynamics, and cellular fluctuations. Development of high-performance and low-cost quantitative phase imaging systems is thus required in many fields, including on-site biomedical imaging and industrial inspection. Here, we propose an ultracompact, highly stable interferometer based on a single-layer dielectric metasurface for common path off-axis digital holography and experimentally demonstrate quantitative phase imaging. The interferometric imaging system leveraging an ultrathin multifunctional metasurface captures image plane holograms in a single shot and provides quantitative phase information on the test samples for extraction of its physical properties. With the benefits of planar engineering and high integrability, the proposed metasurface-based method establishes a stable miniaturized QPI system for reliable and cost-effective point-of-care devices, live cell imaging, 3D topography, and edge detection for optical computing.

Single-shot digital holography of multiple-beam Fizeau holograms for optical phase reconstruction through the focal depth of optical fibers

Multiple-beam Fizeau interference (MBFI) is characterized by its ability to represent the fine features of phase objects. Single-shot digital holographic interferometry (SSDHI) is used for numerical focusing of the recorded holograms. In this work, the two methods are gathered and employed for solving the problem of studying the thick phase objects. The problem of thick phase objects, such as optical fibers, in MBFI is the full focusing of the fiber's optical phase in one-time single shot phase map. The proposed method is designed to collect the optical phase map due to the optical fiber through the focal depth. The main idea is based on the analysis of the MBFI to several two-beam interference sets. Each two-beam interference is treated by SSDHI method to get the optical phase at different planes of focus inside the object. Then, the resultant optical phase due to the optical fiber is collected from these planes of focus. Retrieving the optical phase maps of the multiple-beam holograms through the focal depth, for the first time, is possible using the angular spectrum method. In this case, a laser source with quite long coherence length is used as a light source.The proposed method is applied on two thick samples of, single mode and graded index, optical fibers to reconstruct the resultant optical phase maps through the focal depth. The reconstructed optical phase maps are determined for the harmonics of MBFI holograms’ angular spectra. The method proves its ability to provide more accurate, numerical focusing and phase maps reconstruction. Where, MBFI analyses indicate the magnification of optical phase differences.

Adaptive constraints by morphological operations for single-shot digital holography

Digital holography provides access to quantitative measurement of the entire complex field, which is indispensable for the investigation of wave-matter interactions. The emerging iterative phase retrieval approach enables to solve the inverse imaging problem only from the given intensity measurements and physical constraints. However, enforcing imprecise constraints limits the reconstruction accuracy and convergence speed. Here, we propose an advanced iterative phase retrieval framework for single-shot in-line digital holography that incorporates adaptive constraints, which achieves optimized convergence behavior, high-fidelity and twin-image-free reconstruction. In conjunction with morphological operations which can extract the object structure while eliminating the irrelevant part such as artifacts and noise, adaptive constraints allow the support region to be accurately estimated and automatically updated at each iteration. Numerical reconstruction of complex-valued objects and the capability of noise immunity are investigated. The improved reconstruction performance of this approach is experimentally validated. Such flexible and versatile framework has promising applications in biomedicine, X-ray coherent diffractive imaging and wavefront sensing.

Single-shot digital holography separating the real and imaginary parts of a signal beam in the rhombic region of the Fourier plane

Single-shot digital holography separating the real and imaginary parts of a signal beam in the rhombic region of the Fourier plane

Image sequence encryption based on chaotic fingerprint phase mask and single-shot digital holography

Image sequence encryption based on chaotic fingerprint phase mask and single-shot digital holography

Despeckling by sparse sampling on Bernoulli process in single-shot digital holography

Despeckling by sparse sampling on Bernoulli process in single-shot digital holography

Redundant speckle elimination in digital holography with the Gauss window function

Digital Holography (DH) is a popular and practical technology for recording the complex-valued information of the object field. However, speckle, caused by the coherent light, greatly reduces the quality of the reconstructed image. In this paper, a speckle-suppression algorithm called Gauss speckle elimination mask (GSEM) that only needs a single-shot DH is proposed. This method utilizes the Gauss window function to extract the sub-holograms. Besides, the gray value compensation is proposed in this method for restoring the grayscale distribution. All sub-holograms are operated by the gray value compensation, then a new stack of sub-reconstructed images is acquired. The output compounded by this stack of sub-reconstructed images avoids the additional noise caused by the ringing effect. It could be shown in this paper that this method has a better performance in speckle-suppression while maintaining the image contrast.

Single-shot On-axis Digital Holography Reconstruction Method Based on Deep Learning

Single-shot On-axis Digital Holography Reconstruction Method Based on Deep Learning

Imaging through deep turbulence using single-shot digital holography data.

This paper uses an experimental setup consisting of phase plates and a digital-holography receiver to validate the performance of an algorithm, referred to as multi-plane iterative reconstruction (MIR), for imaging through deep turbulence. In general, deep-turbulence conditions arise from aberrations being distributed along the propagation path. The resulting phase errors then cause a multifaceted problem with multiple empirically determined limitations. To address these limitations, the MIR algorithm works by sensing and correcting for the distributed-volume phase errors using single-shot digital holography data (i.e., one speckle measurement from the coherent illumination of an optically rough extended object). As such, we first show that our distributed-volume phase errors, created using the phase plates, follow path-integrated Kolmogorov statistics for weak-to-deep turbulence strengths. We then present results from two MIR algorithm configurations: a) where we have a priori knowledge of the placement of the phase plates, so that we sense and correct in the exact locations of the phase errors, and b) where we do not have a priori knowledge of the placement of the phase plates, so that we sense and correct in two fixed planes for all phase-error combinations. Given weak-to-deep turbulence strengths, the results show that the two MIR algorithm configurations perform comparably for the four imaging scenarios tested. Such results are promising for tactical applications, where one might not have a priori knowledge of the deep-turbulence conditions.

Deep DIH: Single-Shot Digital In-Line Holography Reconstruction by Deep Learning

Digital in-line holography is commonly used to reconstruct 3D images from 2D holograms for microscopic objects. One of the technical challenges that arise in the signal processing stage is removing the twin image that is caused by the phase-conjugate wavefront from the recorded holograms. Twin image removal is typically formulated as a non-linear inverse problem due to the irreversible scattering process when generating the hologram. Recently, end-to-end deep learning-based methods have been utilized to reconstruct the object wavefront (as a surrogate for the 3D structure of the object) directly from a single-shot in-line digital hologram. However, massive data pairs are required to train deep learning models for acceptable reconstruction precision. In contrast to typical image processing problems, well-curated datasets for in-line digital holography does not exist. Also, the trained model highly influenced by the morphological properties of the object and hence can vary for different applications. Therefore, data collection can be prohibitively cumbersome in practice as a major hindrance to using deep learning for digital holography. In this paper, we proposed a novel implementation of autoencoder-based deep learning architecture for single-shot hologram reconstruction solely based on the current sample without the need for massive datasets to train the model. The simulations results demonstrate the superior performance of the proposed method compared to the state of the art single-shot compressive digital in-line hologram reconstruction method.

Imaging through distributed-volume aberrations using single-shot digital holography.

This paper explores the use of single-shot digital holography data and a novel algorithm, referred to as multiplane iterative reconstruction (MIR), for imaging through distributed-volume aberrations. Such aberrations result in a linear, shift-varying or "anisoplanatic" physical process, where multiple-look angles give rise to different point spread functions within the field of view of the imaging system. The MIR algorithm jointly computes the maximum a posteriori estimates of the anisoplanatic phase errors and the speckle-free object reflectance from the single-shot digital holography data. Using both simulations and experiments, we show that the MIR algorithm outperforms the leading multiplane image-sharpening algorithm over a wide range of anisoplanatic conditions.

Demonstration of single-shot digital holography using a Bayesian framework.

In this paper, we present experimental results for image reconstruction, with isoplanatic phase-error correction, from single-shot digital holography data. We demonstrate the utility of using a model-based iterative reconstruction (MBIR) algorithm to jointly compute the maximum a posteriori estimates of the phase errors and the real-valued object reflectance function. Specifically, we show that the MBIR algorithm is robust to noise and phase errors over a range of conditions.

Full field-of-view digital lens-free holography for weak-scattering objects based on grating modulation.

Grating-based single-shot digital lens-free holography with spatial spectral multiplexing is proposed to realize full field-of-view (FOV) imaging for weak-scattering objects. Multiple object waves are generated by a one-dimensional grating that is placed in near contact with the object to avoid the cross talk among different diffraction orders during reconstruction. A multiplexed off-axis hologram is created by interference between the object waves and reference wave and captured by an image sensor in one shot. Multiple imaging areas corresponding to the captured object waves can be simultaneously retrieved during reconstruction. A formula which guarantees full FOV imaging without cross talk or information loss is presented. The imaging experiments of a USAF resolution target are presented to demonstrate the feasibility of this method.

Ultra-short pulsed off-axis digital holography for imaging dynamic targets in highly scattering conditions.

A single-shot digital holography system using an ultra-short pulsed laser is demonstrated to be very effective in suppressing the multiple-scattering noise associated with imaging dynamic targets in highly scattering environments, such as biological tissues and fuel injection systems. A planar off-axis reference wave configuration is used to generate a fixed carrier spatial frequency in the recorded holograms in order to separate coherent signal from incoherent noise in Fourier transformed holograms. The single-shot imaging system does not require averaging between multiple shots and can capture images of transient phenomena, such as the formation of diesel fuel injection sprays, and can overcome the problem of mechanical vibrations for recording holograms in industrial and laboratory environments.

Optical Image Encryption Based on Mixed Chaotic Maps and Single-Shot Digital Holography

Random phase masks play a key role in optical image encryption schemes based on double random phase technique. In this paper, a mixed chaotic method is proposed, which can efficiently solve some weaknesses that one-dimensional (1-D) single chaotic maps encounter to generate random phase masks. Based on the chaotic random phase masks, optical image encryption and decryption are realized with a single-shot digital holographic technique. In the proposed encryption scheme, the initial value and parameters of mixed chaotic maps serve as secret keys, which is convenient for the key management and transmission. Moreover, it also possesses high resistance against statistical attack, brute-force attack, noise attack and shear attack. Simulation results and security analysis verify the validity and security of the proposed encryption scheme.

Single Shot Digital Holography Using Iterative Reconstruction with Alternating Updates of Amplitude and Phase

We present an image recovery approach to improve amplitude and phase reconstruction from single shot digital holograms, using iterative reconstruction with alternating updates. This approach allows the flexibility to apply different priors to amplitude and phase, improves phase reconstruction in image areas with low amplitudes, and does not require phase unwrapping for regularization. Phantom simulations and experimental measurements of a grating sample both demonstrate that the proposed method helps to reduce noise and resolve finer features. The improved image reconstruction from this technique will benefit the many applications of digital holography.

Single-shot digital holography for fast measuring optical properties of fibers.

We propose a fast method for measuring optical properties, e.g., the refractive index profile and birefringence, of fibers. It is based on recovering the phase distribution of light refracted by a fiber sample at the recording plane from a single-shot digital hologram. During the recovering process, an optimized approach based on the spatial carrier frequency method was utilized. The proposed approach enhances affects that arise from the limited spatial extent of the bandpass filter associated with the implementation of the spatial carrier frequency method. In contrast to the low spatial resolution of off-axis digital holograms, the method ensures the best utilization of the camera support. From the recovered phase information, the optical path difference is measured; thus, the refractive index profile, the mean refractive index, and the birefringence of isotactic polypropylene (IPP) are determined. Experimental results are given for illustration.

Single-shot multiwavelength phase unwrapping using a single reference beam and a monochromatic image sensor

We propose single-shot multiwavelength phase unwrapping using a single reference beam and a monochromatic image sensor. A single beam containing multiple wavelengths passes through a reference arm and acts as reference waves. Multiple-wavelength information is multiplexed in the space domain on the monochromatic image sensor and is separated in the spatial frequency domain by utilizing the spatial frequency difference of interference fringes at multiple wavelengths. From a single hologram, multiwavelength phase unwrapping is conducted and an unwrapped phase image is obtained. Both transmission and reflective single-shot multiwavelength digital holography systems using a monochromatic image sensor can be constructed with a simple optical setup employing the proposed technique. Single-shot multiwavelength phase unwrapping by the proposed technique is numerically simulated and experimentally demonstrated.

Three-dimensional display system using near on-axis, phase-only digital holography

We propose a method for carrying out three-dimensional (3D) display based on single-shot digital holography. The 3D display is realized from a digital hologram (DH) by displaying the complex function recovered through the constrained optimization approach on a phase-only spatial light modulator (SLM). A DH of a multiplane object is recorded in a near on-axis configuration, and the complex function corresponding to the object in the hologram plane is recovered. The recovered function is converted into a phase-only function, and it is displayed on a phase SLM. The optical reconstruction through simple diffraction from the SLM reproduced the 3D scene, and the image reconstructed at each plane has been observed.

Image/video encryption using single shot digital holography

We propose a method for image/video encryption that combines double random-phase encoding in the Fresnel domain with a single shot digital holography. In this method, a complex object field can be reconstructed with only single frame hologram based on a constrained optimization method. The system without multiple shots and Fourier lens is simple, and allows to dynamically encrypt information. We test the proposed method on a computer simulated image, a grayscale image and a video in AVI format. Also we investigate the quality of the decryption process and the performance against noise attacks. The experimental results demonstrate the performance of the method.