Digital Holography Research Articles

3D-printed compact snap-shot lensless birefringence microscope based on digital on-axis holography

Birefringence, an inherent optical characteristic in anisotropic materials arising from structural anisotropy of materials or mechanical stress, plays a major role in understanding the microscopic structures of anisotropic materials and has been widely studied in biology and medicine. To achieve birefringence imaging of dynamic objects, various snap-shot quantitative birefringence imaging techniques relying on lenses have been developed, which are bulky and restricted to laboratory settings. In this paper, we present a 3D printed single-shot lens-free polarization holographic microscope based on digital on-axis holography, in which a birefringent beam-displacer is introduced in a conventional lens-free imaging system to realize a spatial multiplexing polarization hologram recording. Based on our proposed reconstruction algorithm, quantitative polarization holographic images and birefringence parameter distributions of dynamic samples can be retrieved simultaneously. The relevant experimental results demonstrated the feasibility of our proposed polarization imaging system, which exhibits higher stability and greater immunity to mechanical vibration and air fluctuation, and it has the potential for imaging dynamic specimens, especially in resource-limited environments.

Recent breakthroughs in digital holography, 2D/3D imaging, and holographic optical elements: introduction

The Optica Digital Holography and Three-Dimensional Imaging Topical Meeting (DH) 2024 in Paestum, Italy. brought together a vibrant hub for global experts to showcase cutting-edge research and industry pioneers to discuss the latest developments in digital holography (DH) and 3D imaging techniques. This meeting's impact is further amplified by a dedicated feature issue across three prestigious Optica journals: Applied Optics, Journal of the Optical Society of America A, and Biomedical Optics Express. This introduction summarizes the diverse and high-quality contributions, highlighting key advancements and applications that are shaping the future of DH and imaging.

Realtime particulate matter and bacteria analysis of peritoneal dialysis fluid using digital inline holography.

Realtime particulate matter and bacteria analysis of peritoneal dialysis fluid using digital inline holography.

Enlarged measurement range with noise suppression hyperspectral digital holography using a mode-locked femtosecond frequency comb

Enlarged measurement range with noise suppression hyperspectral digital holography using a mode-locked femtosecond frequency comb

High-resolution digital holography using dual-wavelength coupled phase retrieval

High-resolution digital holography using dual-wavelength coupled phase retrieval

Recent breakthroughs in digital holography, 2D/3D imaging, and holographic optical elements: introduction

The Optica Digital Holography and Three-Dimensional Imaging Topical Meeting (DH) 2024 in Paestum, Italy, brought together a vibrant hub for global experts to showcase cutting-edge research and industry pioneers to discuss the latest developments in digital holography (DH) and 3D imaging techniques. This meeting’s impact is further amplified by a dedicated feature issue across three prestigious Optica journals: Applied Optics, Journal of the Optical Society of America A, and Biomedical Optics Express. This introduction summarizes the diverse and high-quality contributions, highlighting key advancements and applications that are shaping the future of DH and imaging.

Recent breakthroughs in digital holography, 2D/3D imaging, and holographic optical elements: introduction

The Optica Digital Holography and Three-Dimensional Imaging Topical Meeting (DH) 2024 in Paestum, Italy, brought together a vibrant hub for global experts to showcase cutting-edge research and industry pioneers to discuss the latest developments in digital holography (DH) and 3D imaging techniques. This meeting’s impact is further amplified by a dedicated feature issue across three prestigious Optica journals: Applied Optics, Journal of the Optical Society of America A, and Biomedical Optics Express. This introduction summarizes the diverse and high-quality contributions, highlighting key advancements and applications that are shaping the future of DH and imaging.

Advancements in Digital Holography for Crystalline Material Characterization: A Review (Invited)

AbstractAs an interferometric imaging method, digital holography has shown its unique potential in many fields, especially in the mature and diverse fields of crystallography. Compared to early microscopy imaging and X‐ray diffraction approach, this technique captures and accurately reproduces the three‐dimensional information of the crystal in real time. It offers advantages such as fast imaging, nondestructive testing, and optimized data processing. This review discusses the progress of digital holography in crystallography, covering crystallization, mineral imaging, and microstructure analysis of two‐dimensional materials. The reconstruction of copper sulfate pentahydrate and sodium chloride crystallization serves as an example to demonstrate its powerful ability. Particular emphasis is placed on the advancement of optical instruments and the development of image reconstruction approaches. Regarding the solutions to problems such as dataset processing and field of view limitations, this paper summarizes the research results of combining digital holography with deep learning algorithm models and the free field of view method. In addition, the operating principle of the technology is expounded and the future development direction is also prospected.

Portable Filter-Free Lens-Free Incoherent Digital Holography System

A portable incoherent digital holography system without a polarization filter or a refractive lens was developed. Phase-shifted self-interference incoherent holograms of light diffracted from an object were generated without attenuation due to a polarization filter using two polarization-sensitive phase-only spatial light modulators (TPP-SLMs). The number of optical elements in filter-free lens-free incoherent digital holography was reduced to make the system compact and portable. Experiments were conducted using the developed digital holography system set on a tripod stand and objects illuminated by a light-emitting diode.

Event-driven neuromorphic holography for dynamic particle imaging.

Digital holography has emerged as a powerful tool for investigating dynamic particle behaviors in the spatiotemporal domain. However, the performance of this technique is fundamentally limited by the system's space-time bandwidth, leading to a trade-off between accuracy and speed. This study presents a novel, to the best of our knowledge, approach integrating event-driven neuromorphic imaging with digital holography for dynamic particle imaging. Through comprehensive analysis of synthetic and real-world experiments, we demonstrate that the proposed method significantly improves data efficiency and hologram contrast by over tenfold. This technique, termed "neuromorphic holography," offers promising applications for efficient dynamic particle imaging.

Super-resolution reconstruction of off-axis digital holography based on Real-ESRGAN

Super-resolution reconstruction of off-axis digital holography based on Real-ESRGAN

Particle positioning and characterization using wavefront curvature with a convolutional neural network in digital holography

Accurately and simultaneously determining the axial position, radius, and refractive index of spherical particles remains challenging in digital holography (DH). Applications such as fluid dynamics, fuel droplet evaporation, and aerosol characterization often require low-numerical-aperture (NA) optical setups to capture a broad field of view. However, the reduced number of interference fringes hinders accurate parameter estimation using conventional holographic interference pattern analysis. To address this limitation, we present a method that employs a one-dimensional convolutional neural network trained on wavefront curvature profiles along the optical axis. This approach enables the accurate and simultaneous determination of all three parameters for low- and high-NA systems. In a low-NA (0.02) setup, our method achieves accuracies of 0.3%, 2.0%, and 7.0% for radius, axial position, and refractive index estimation, respectively, outperforming conventional methods. Experimental validation confirmed the effectiveness of our approach, enhancing the capabilities of DH for particle characterization across diverse applications requiring any NA setup.

High-Fidelity Infrared Imaging Technique of Crystal Growth based on U-shaped Residual Network Digital Holography with Attention Module

High-Fidelity Infrared Imaging Technique of Crystal Growth based on U-shaped Residual Network Digital Holography with Attention Module

Fourier-inspired single-pixel holography.

Fourier-inspired single-pixel holography (FISH) is an effective digital holography (DH) approach that utilizes a single-pixel detector instead of a conventional camera to capture light field information. FISH combines the Fourier single-pixel imaging and off-axis holography technique, allowing one to acquire useful information directly, rather than recording the hologram in the spatial domain and filtering unwanted terms in the Fourier domain. Furthermore, we employ a deep learning technique to jointly optimize the sampling mask and the imaging enhancement model, to achieve high-quality results at a low sampling ratio. Both simulations and experimental results demonstrate the effectiveness of FISH in single-pixel phase imaging. FISH combines the strengths of single-pixel imaging (SPI) and DH, potentially expanding DH's applications to specialized spectral bands and low-light environments while equipping SPI with capabilities for phase detection and coherent gating.

Unsupervised cross talk suppression for self-interference digital holography.

Self-interference digital holography extends the application of digital holography to non-coherent imaging fields such as fluorescence and scattered light, providing a new solution, to the best of our knowledge, for wide field 3D imaging of low coherence or partially coherent signals. However, cross talk information has always been an important factor limiting the resolution of this imaging method. The suppression of cross talk information is a complex nonlinear problem, and deep learning can easily obtain its corresponding nonlinear model through data-driven methods. However, in real experiments, it is difficult to obtain such paired datasets to complete training. Here, we propose an unsupervised cross talk suppression method based on a cycle-consistent generative adversarial network (CycleGAN) for self-interference digital holography. Through the introduction of a saliency constraint, the unsupervised model, named crosstalk suppressing with unsupervised neural network (CS-UNN), can learn the mapping between two image domains without requiring paired training data while avoiding distortions of the image content. Experimental analysis has shown that this method can suppress cross talk information in reconstructed images without the need for training strategies on a large number of paired datasets, providing an effective solution for the application of the self-interference digital holography technology.

Digital Holography Interferometry for Refractive Index Characterization and Temperature Mapping of Aqueous Solutions at Supercooled Temperatures

Digital Holography Interferometry for Refractive Index Characterization and Temperature Mapping of Aqueous Solutions at Supercooled Temperatures

Robust holographic imaging for real-world applications with joint optimization

Digital inline holography offers a compact, lensless imaging solution, but its practical deployment is often hindered by the need for precise system alignment and calibration, particularly regarding propagation distance. This work presents J-Net, a robust, untrained neural network that significantly mitigates these limitations. J-Net eliminates the need for prior knowledge or calibration of the propagation distance by simultaneously reconstructing both the complex-valued object magnitude and the propagation distance from a single hologram. This inherent robustness to distance variations makes J-Net highly practical for real-world applications where precise system control is difficult or impossible. Experimental results demonstrate high-quality amplitude and phase reconstruction even under mismatched distance conditions, showcasing J-Net’s potential to enable robust deployment of holographic imaging across diverse fields.

Enhanced three-dimensional imaging with large depth of field using pre-processing in optical scanning holography

Optical scanning holography (OSH) emerges as a groundbreaking single-pixel real-time holographic recording technique, charting new territory beyond conventional digital holography. A notable challenge in OSH, as with all three-dimensional (3D) imaging methods, is the susceptibility of reconstructed images corrupted by defocus noise. The noise is an unintended result of diffraction on the focused plane from out-of-focus planes of the three-dimensional object, which can degrade image quality upon holographic reconstruction. Current methods, however, all use some algorithms to post-process holographic data to achieve the purpose of eliminating out-of-focus noise, which is difficult to meet the requirements of real-time image processing. We propose an innovative pre-processing approach in optical scanning holography that not only eliminates defocus noise but also significantly enhances image quality. Preprocessing is accomplished by the utilization of a focus-tunable lens (FTL) to refocus the optical scanning beam according to the depth of the occlusion-free object. Complex holograms are then captured without the artifacts associated with defocus through real-time holographic data pre-processing. Numerical simulations and experimental results demonstrate that our proposed method can directly obtain high-quality reconstructed images with all the 3D information being in focus simultaneously.

Orbital angular momentum coherent state beams.

Paraxial propagation through isotropic, homogeneous, linear media exhibits invariance under rotations around the propagation axis, a symmetry described by the su(2) Lie algebra. We explore a family of paraxial beams that exploit this symmetry, constructed as linear superpositions of Laguerre-Gaussian beams (LGBs), serving as optical analogs of generalized SU(2) Lie group coherent states. A single complex parameter controls a smooth transition between Laguerre-Gaussian and Hermite-Gaussian beams (HGBs), producing intermediate beams that blend the characteristics of both families. Our beams exhibit propagation-invariant properties, up to a scaling factor, a highly desirable feature for optical applications. Experimental validation via digital holography demonstrates the practical feasibility of our approach.

Learning enhanced dual-wavelength digital holography for measuring large-height complex step samples

Learning enhanced dual-wavelength digital holography for measuring large-height complex step samples