scholarly journals A Simplified Model for Optical Systems with Random Phase Screens

Sensors ◽  
2021 ◽  
Vol 21 (17) ◽  
pp. 5811
Author(s):  
Malchiel Haskel ◽  
Adrian Stern
Keyword(s):  
Optical System ◽  
Light Propagation ◽  
Random Phase ◽  
Biological Tissues ◽  
Complete Separation ◽  
Optical Systems ◽  
Scattering Media ◽  
The Individual ◽  
Phase Screens ◽  
Si Effect

A first-order optical system with arbitrary multiple masks placed at arbitrary positions is the basic scheme of various optical systems. Generally, masks in optical systems have a non-shift invariant (SI) effect; thus, the individual effect of each mask on the output cannot be entirely separated. The goal of this paper is to develop a technique where complete separation might be achieved in the common case of random phase screens (RPSs) as masks. RPSs are commonly used to model light propagation through the atmosphere or through biological tissues. We demonstrate the utility of the technique on an optical system with multiple RPSs that model random scattering media.

scholarly journals Fast 3D movement of a laser focusing spot behind scattering media by utilizing optical memory effect and optical conjugate planes

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Vinh Tran ◽  
Sujit K. Sahoo ◽  
Cuong Dang
Keyword(s):  
Memory Effect ◽  
Light Propagation ◽  
Optical Memory ◽  
Biological Tissues ◽  
Frame Rate ◽  
Optimization Process ◽  
Turbid Media ◽  
Scattering Media ◽  
Focus Spot ◽  
Wavefront Shaping

AbstractControlling light propagation intentionally through turbid media such as ground glass or biological tissue has been demonstrated for many useful applications. Due to random scattering effect, one of the important goals is to draw a desired shape behind turbid media with a swift and precise method. Feedback wavefront shaping method which is known as a very effective approach to focus the light, is restricted by slow optimization process for obtaining multiple spots. Here we propose a technique to implement feedback wavefront shaping with optical memory effect and optical 4f system to speedy move focus spot and form shapes in 3D space behind scattering media. Starting with only one optimization process to achieve a focusing spot, the advantages of the optical configuration and full digital control allow us to move the focus spot with high quality at the speed of SLM frame rate. Multiple focusing spots can be achieved simultaneously by combining multiple phase patterns on a single SLM. By inheriting the phase patterns in the initial focusing process, we can enhance the intensity of the focusing spot at the edge of memory effect in with 50% reduction in optimization time. With a new focusing spot, we have two partially overlapped memory effect regions, expanding our 3D scanning range. With fast wavefront shaping devices, our proposed technique could potentially find appealing applications with biological tissues.

scholarly journals Distortion matrix concept for deep optical imaging in scattering media

2020 ◽  
Vol 6 (30) ◽  
pp. eaay7170 ◽  
Author(s):  
Amaury Badon ◽  
Victor Barolle ◽  
Kristina Irsch ◽  
A. Claude Boccara ◽  
Mathias Fink ◽  
...  
Keyword(s):  
Optical Imaging ◽  
Multiple Scattering ◽  
Adaptive Optics ◽  
Light Propagation ◽  
Biological Tissues ◽  
Image Resolution ◽  
Scattering Media ◽  
Dynamic Correction ◽  
Value Decomposition ◽  
Distortion Matrix

In optical imaging, light propagation is affected by the inhomogeneities of the medium. Sample-induced aberrations and multiple scattering can strongly degrade the image resolution and contrast. On the basis of a dynamic correction of the incident and/or reflected wavefronts, adaptive optics has been used to compensate for those aberrations. However, it only applies to spatially invariant aberrations or to thin aberrating layers. Here, we propose a global and noninvasive approach based on the distortion matrix concept. This matrix basically connects any focusing point of the image with the distorted part of its wavefront in reflection. A singular value decomposition of the distortion matrix allows to correct for high-order aberrations and forward multiple scattering over multiple isoplanatic modes. Proof-of-concept experiments are performed through biological tissues including a turbid cornea. We demonstrate a Strehl ratio enhancement up to 2500 and recover a diffraction-limited resolution until a depth of 10 scattering mean free paths.

Atomic Resolution in Crystal Aperture Stem

1990 ◽  
Vol 48 (1) ◽  
pp. 236-237
Author(s):  
J T Fourie
Keyword(s):  
Optical System ◽  
Spherical Aberration ◽  
Three Dimensional ◽  
Transmission Function ◽  
Optical Systems ◽  
Bragg Angle ◽  
Electron Optical System ◽  
Intimate Contact ◽  
Diffraction Effects ◽  
Design Aspect

The attempts at improvement of electron optical systems to date, have largely been directed towards the design aspect of magnetic lenses and towards the establishment of ideal lens combinations. In the present work the emphasis has been placed on the utilization of a unique three-dimensional crystal objective aperture within a standard electron optical system with the aim to reduce the spherical aberration without introducing diffraction effects. A brief summary of this work together with a description of results obtained recently, will be given.The concept of utilizing a crystal as aperture in an electron optical system was introduced by Fourie who employed a {111} crystal foil as a collector aperture, by mounting the sample directly on top of the foil and in intimate contact with the foil. In the present work the sample was mounted on the bottom of the foil so that the crystal would function as an objective or probe forming aperture. The transmission function of such a crystal aperture depends on the thickness, t, and the orientation of the foil. The expression for calculating the transmission function was derived by Hashimoto, Howie and Whelan on the basis of the electron equivalent of the Borrmann anomalous absorption effect in crystals. In Fig. 1 the functions for a g220 diffraction vector and t = 0.53 and 1.0 μm are shown. Here n= Θ‒ΘB, where Θ is the angle between the incident ray and the (hkl) planes, and ΘB is the Bragg angle.

scholarly journals OAM light propagation through tissue

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Netanel Biton ◽  
Judy Kupferman ◽  
Shlomi Arnon
Keyword(s):  
Light Propagation ◽  
Biological Imaging ◽  
Gaussian Beams ◽  
Medical Implants ◽  
Optical Wireless ◽  
Scattering Media ◽  
Valuable Contribution ◽  
Light Beams ◽  
First Time ◽  
Diffuse Media

AbstractA major challenge in use of the optical spectrum for communication and imaging applications is the scattering of light as it passes through diffuse media. Recent studies indicate that light beams with orbital angular momentum (OAM) can penetrate deeper through diffuse media than simple Gaussian beams. To the best knowledge of the authors, in this paper we describe for the first time an experiment examining transmission of OAM beams through biological tissue with thickness of up to a few centimeters, and for OAM modes reaching up to 20. Our results indicate that OAM beams do indeed show a higher transmittance relative to Gaussian beams, and that the greater the OAM, the higher the transmittance also up to 20, Our results extend measured results to highly multi scattering media and indicate that at 2.6 cm tissue thickness for OAM of order 20, we measure nearly 30% more power in comparison to a Gaussian beam. In addition, we develop a mathematical model describing the improved permeability. This work shows that OAM beams can be a valuable contribution to optical wireless communication (OWC) for medical implants, optical biological imaging, as well as recent innovative applications of medical diagnosis.

System of retinal visual acuity determination based on random phase screens for diagnostics of initial shapes of cataracts

2003 ◽  
Author(s):  
Alexander V. Novokhreshenov ◽  
Valery V. Bakutkin ◽  
Valery V. Tuchin ◽  
Vladimir P. Ryabukho ◽  
Irina L. Maksimova ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Random Phase ◽  
Phase Screens

scholarly journals Численное моделирование миграции фотонов в однородных и неоднородных цилиндрических фантомах

2020 ◽  
Vol 128 (6) ◽  
pp. 832
Author(s):  
А.Ю. Потлов ◽  
С.В. Фролов ◽  
С.Г. Проскурин
Keyword(s):  
Radiation Transfer ◽  
Biological Tissues ◽  
Photon Density ◽  
Radiation Transfer Equation ◽  
Scattering Media ◽  
Soft Biological Tissues ◽  
Photon Diffusion ◽  
Low Coherence ◽  
The Brain ◽  
Pulsed Irradiation

The specific features of photon diffusion of low-coherence pulsed irradiation in phantoms of soft biological tissues (blood-saturated tissues of the brain, breast, etc.) are described. The results of photon migration simulation using the Diffusion Approximation to the Radiation Transfer Equation (RTE) are compared with ones of the Monte Carlo simulations. It has been confirmed that the Photon Density Normalized Maximum (PDNM) moves towards the center of the investigated object in case of relatively uniform and strongly scattering media. In the presence of inhomogeneities, type of the PDNM motion changes drastically. Presence of an absorbing inhomogeneity in the medium directs trajectory of the PDNM motion of towards the point symmetric to the inhomogeneity relative to the geometric center of the investigated object. In case of scattering the PDNM moves toward the direction of the center of the scattering inhomogeneity.

scholarly journals An individual-based mechanical model of cell movement in heterogeneous tissues and its coarse-grained approximation

2018 ◽  
Author(s):  
R. J. Murphy ◽  
P. R. Buenzli ◽  
R. E. Baker ◽  
M. J. Simpson
Keyword(s):  
Mechanical Model ◽  
Numerical Solutions ◽  
Cell Movement ◽  
Biological Tissues ◽  
Tissue Level ◽  
Cellular Level ◽  
Coarse Grained ◽  
Mechanical Heterogeneity ◽  
Single Scale ◽  
The Individual

AbstractMechanical heterogeneity in biological tissues, in particular stiffness, can be used to distinguish between healthy and diseased states. However, it is often difficult to explore relationships between cellular-level properties and tissue-level outcomes when biological experiments are performed at a single scale only. To overcome this difficulty we develop a multi-scale mathematical model which provides a clear framework to explore these connections across biological scales. Starting with an individual-based mechanical model of cell movement, we subsequently derive a novel coarse-grained system of partial differential equations governing the evolution of the cell density due to heterogeneous cellular properties. We demonstrate that solutions of the individual-based model converge to numerical solutions of the coarse-grained model, for both slowly-varying-in-space and rapidly-varying-in-space cellular properties. Applications of the model are discussed, including determining relative cellular-level properties and an interpretation of data from a breast cancer detection experiment.

scholarly journals Beam-smoothing effect in broad-band random-phase irradiation

1993 ◽  
Vol 11 (2) ◽  
pp. 385-390 ◽  
Author(s):  
I. Matsushima ◽  
Y. Owadano ◽  
Y. Matsumoto ◽  
I. Okuda ◽  
T. Tomie ◽  
...  
Keyword(s):  
Laser Irradiation ◽  
Optical System ◽  
Random Phase ◽  
Broad Band ◽  
Laser Fusion ◽  
Phase Plate ◽  
Smoothing Effect ◽  
Broad Bandwidth ◽  
A New Technique ◽  
Focusing Lens

A new technique to achieve smooth laser irradiation profiles on laser fusion targets is evaluated numerically and experimentally. In this technique, smoothing is obtained by using a spectral dispersing optic and a random-phase plate placed in front of a focusing lens employing the broad-bandwidth of KrF lasers. Experimental results and numerical calculations agree well, verifying that this simple optical system is effective for smooth irradiation on targets.

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