Simulation Of Holograms Research Articles

Simulation of digital lensless holographic microscopy holograms: a physics-image processing approach.

This work presents a method for simulating digital lensless holographic microscopy (DLHM) holograms using a physics-based image processing approach. While DLHM has gained significant attention in biology, biomedicine, and environmental monitoring, the current modeling of DLHM holograms has been limited, hindering potential applications, including learning-based solutions and generative model training. In this study, the DLHM propagation process is decomposed into the diffraction of a complex-valued spherical wavefront and the non-homogeneous magnification of the diffracted field that encodes the sample information, which accelerates and enhances the hologram simulation. The proposed model is validated by comparing simulated and experimental holograms of standard test targets under diverse imaging conditions. Comparative analyses are conducted against other DLHM hologram modeling methods, including direct Rayleigh-Sommerfeld diffraction, its convolutional implementation, and the Fresnel-Bluestein formalism. The proposed model is shown to outperform these methods in overall similarity to experimental recordings across a wide range of imaging conditions while maintaining computational efficiency. This DLHM hologram modeling approach provides researchers with a powerful tool for simulating trustable holograms. The model can be publicly accessed through the open-access repository https://github.com/mloper23/DLHM-model.

A spatial phase-shifting method for real-space wave reconstruction of off-axis electron holograms

The Fourier transform with a side-band filter is the well-established method for reconstructing off-axis fringe-type holograms due to its ease of implementation and fast processing. However, this method works in reciprocal space and requires inversion of a side-band sub-region, which can degrade the spatial resolution of reconstructed wave compared to the original hologram. We present a new method, the spatial phase-shifting (SPS) method, for real-space wave reconstruction of off-axis electron holograms. We describe the working principles of the SPS method in analogy to the temporal phase-shifting method. We conducted both hologram simulations and experiments to evaluate its applicability and effectiveness. We compared the wave reconstruction results of the SPS and the conventional Fourier transform method, highlighting the advantages of the newly proposed SPS method. Our results demonstrate that the proposed SPS method is particularly effective for real-space wave reconstruction of small-sized hologram, providing an alternative approach to off-axis type holography wave reconstruction.

Evaporating droplet hologram simulation for digital in-line holography setup with divergent beam

Generalized Lorenz-Mie theory (GLMT) for a multilayered sphere is used to simulate holograms produced by evaporating spherical droplets with refractive index gradient in the surrounding air/vapor mixture. Simulated holograms provide a physical interpretation of experimental holograms produced by evaporating Diethyl Ether droplets with diameter in the order of 50 μm and recorded in a digital in-line holography configuration with a divergent beam. Refractive index gradients in the surrounding medium lead to a modification of the center part of the droplet holograms, where the first fringe is unusually bright. GLMT simulations reproduce this modification well, assuming an exponential decay of the refractive index from the droplet surface to infinity. The diverging beam effect is also considered. In both evaporating and nonevaporating cases, an equivalence is found between Gaussian beam and plane wave illuminations, simply based on a magnification ratio to be applied to the droplets' parameters.

Digital holography simulations and experiments to quantify the accuracy of 3D particle location and 2D sizing using a proposed hybrid method

The accuracy of digital in-line holography to detect particle position and size within a 3D domain is evaluated with particular focus placed on detection of nonspherical particles. Dimensionless models are proposed for simulation of holograms from single particles, and these models are used to evaluate the uncertainty of existing particle detection methods. From the lessons learned, a new hybrid method is proposed. This method features automatic determination of optimum thresholds, and simulations indicate improved accuracy compared to alternative methods. To validate this, experiments are performed using quasi-stationary, 3D particle fields with imposed translations. For the spherical particles considered in experiments, the proposed hybrid method resolves mean particle concentration and size to within 4% of the actual value, while the standard deviation of particle depth is less than two particle diameters. Initial experimental results for nonspherical particles reveal similar performance.

디지털 입자 홀로그래피에서 입자의 초점면 결정에 관한 연구

The correlation coefficient method, which was proposed by our research group, is applied to digital particle holography to locate the focal plane of particles. It uses the fact that the correlation coefficient is maximum at the focal plane. The factors influencing this method are discussed with a numerical simulation of holograms. For real holograms, the Wiener filter was proposed to process both recorded holograms and reconstructed images. The application results using the dot array target showed that the Wiener filter is a very effective tool for processing holography-related images. The effects of the dot size and the object distance on the errors in the determination of the focal plane by the correlation coefficient method were investigated by using the calibration target.

Application of the correlation coefficient method for determination of the focal plane to digital particle holography

The correlation coefficient (CC) method, which was proposed by our research group, is applied to digital particle holography to locate the focal plane of particles. It uses the fact that the CC is maximum at the focal plane. The factors influencing this method are discussed with a numerical simulation of holograms. For real holograms, the Wiener filter was proposed to process both recorded holograms and reconstructed images. The application results using the dot array target showed that the Wiener filter is a very effective tool for processing holography-related images. The effects of the dot size and the object distance on the errors in the determination of the focal plane by the CC method were investigated by using the calibration target.

Evaluation of high‐precision phase‐shifting electron holography by using hologram simulation

AbstractIn phase‐shifting electron holography, Fresnel diffraction at an electron biprism introduces distortions to the amplitude and phase of the electron waves, which cause phase errors in the reconstructed phase images. To reduce the phase errors, two correction methods have been proposed, termed Fresnel corrections. In order to evaluate the phase‐shifting electron holography with Fresnel corrections, we faithfully simulated holograms by considering the influence of Fresnel diffraction, the quantum noise and the electron wave coherency, and then compared the phase images reconstructed from corrected and uncorrected holograms. We found that the phase error due to Fresnel diffraction was reduced to 1/20 by using Fresnel corrections, and that the phase measurement precision reached 2π/410 rad. We are able to observe the weak electric field due to positive charges corresponding to five electrons. Copyright © 2003 John Wiley & Sons, Ltd.

Precise Evaluation of Charging Effect on SiO<SUB>2</SUB> Particles by Simulation of Holograms

The charging effect due to the electron irradiation in spherical SiO 2 particles of 250nm in diameter has been analyzed by electron holography. Electron holograms of a charged SiO 2 particle on the side surface of the carbon film were simulated taking into account the electric shielding effect due to the carbon film. In order to compare the observed hologram and the simulated holograms quantitatively, the residual index between the observed and simulated images was evaluated. Through the quantitative analysis taking into account the shielding effect with the limited side surface area of the carbon film, the amount of the charge was evaluated to be 3.38 x 10 -17 C for the current density of incident electron beam at 0.24 A/m 2 without an objective aperture.

Hologram simulation for off-axis electron holography

Hologram simulation for electron holography using an electron biprism is described. An electron hologram is superimposed by Fresnel fringes originating from the electron biprism, which affects both the amplitude and the phase of the object wave and the reference wave. In this simulation, we consider the effects of Fresnel diffraction as well as the electron-wave phase shift due to the electromagnetic field produced by the specimen. We also take into account the phase shift due to the inner potential of the specimen, the amplitude modulation due to the absorption of the incident electrons by the specimen, reference-wave distortion caused by the electromagnetic fields, coherency of the electron wave, and quantum noise of the detected electrons. Simulated and experimentally obtained holograms and reconstructed images are compared for the cases of a charged latex spherical particle and a single magnetic-domain spherical particle placed on a carbon film.

True 3D Computer Modeling: Sculpture of Numerical Abstraction

True 3D Computer Modeling: Sculpture of Numerical Abstraction