scholarly journals Generating Bessel beams with broad depth-of-field by using phase-only acoustic holograms

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Sergio Jiménez-Gambín ◽  
Noé Jiménez ◽  
José M. Benlloch ◽  
Francisco Camarena
Keyword(s):  
Field Distribution ◽  
Focal Length ◽  
Bessel Beam ◽  
Transverse Field ◽  
High Order ◽  
Depth Of Field ◽  
Uniform Field ◽  
Axial Distribution ◽  
Bessel Beams ◽  
Wide Range

AbstractWe report zero-th and high-order acoustic Bessel beams with broad depth-of-field generated using acoustic holograms. While the transverse field distribution of Bessel beams generated using traditional passive methods is correctly described by a Bessel function, these methods present a common drawback: the axial distribution of the field is not constant, as required for ideal Bessel beams. In this work, we experimentally, numerically and theoretically report acoustic truncated Bessel beams of flat-intensity along their axis in the ultrasound regime using phase-only holograms. In particular, the beams present a uniform field distribution showing an elongated focal length of about 40 wavelengths, while the transverse width of the beam remains smaller than 0.7 wavelengths. The proposed acoustic holograms were compared with 3D-printed fraxicons, a blazed version of axicons. The performance of both phase-only holograms and fraxicons is studied and we found that both lenses produce Bessel beams in a wide range of frequencies. In addition, high-order Bessel beam were generated. We report first order Bessel beams that show a clear phase dislocation along their axis and a vortex with single topological charge. The proposed method may have potential applications in ultrasonic imaging, biomedical ultrasound and particle manipulation applications using passive lenses.

scholarly journals Depth-of-Field-Extended Plenoptic Camera Based on Tunable Multi-Focus Liquid-Crystal Microlens Array

Sensors ◽  
2020 ◽  
Vol 20 (15) ◽  
pp. 4142 ◽  
Author(s):  
Mingce Chen ◽  
Wenda He ◽  
Dong Wei ◽  
Chai Hu ◽  
Jiashuo Shi ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Radiation Power ◽  
Focal Length ◽  
Microlens Array ◽  
Oxide Semiconductor ◽  
Depth Of Field ◽  
Digital Refocusing ◽  
Wide Range ◽  
Cmos Sensor ◽  
Plenoptic Camera

Plenoptic cameras have received a wide range of research interest because it can record the 4D plenoptic function or radiance including the radiation power and ray direction. One of its important applications is digital refocusing, which can obtain 2D images focused at different depths. To achieve digital refocusing in a wide range, a large depth of field (DOF) is needed, but there are fundamental optical limitations to this. In this paper, we proposed a plenoptic camera with an extended DOF by integrating a main lens, a tunable multi-focus liquid-crystal microlens array (TMF-LCMLA), and a complementary metal oxide semiconductor (CMOS) sensor together. The TMF-LCMLA was fabricated by traditional photolithography and standard microelectronic techniques, and its optical characteristics including interference patterns, focal lengths, and point spread functions (PSFs) were experimentally analyzed. Experiments demonstrated that the proposed plenoptic camera has a wider range of digital refocusing compared to the plenoptic camera based on a conventional liquid-crystal microlens array (LCMLA) with only one corresponding focal length at a certain voltage, which is equivalent to the extension of DOF. In addition, it also has a 2D/3D switchable function, which is not available with conventional plenoptic cameras.

Producing Deep Depth of Field and Depth-Independent Resolution in Nde with Limited Diffraction Beams

1993 ◽  
Vol 15 (2) ◽  
pp. 134-149 ◽  
Author(s):  
Jian-yu Lu ◽  
James F. Greenleaf
Keyword(s):  
Nondestructive Evaluation ◽  
Gaussian Beam ◽  
Focal Length ◽  
Bessel Beam ◽  
Lateral Resolution ◽  
Depth Of Field ◽  
Finite Aperture ◽  
Deep Depth ◽  
Pulse Echo ◽  
Focused Gaussian Beam

Limited diffraction beams, such as Durnin's J0 Bessel beam, are a class of nonspreading solutions to the isotropic/homogeneous scalar wave equation. These beams can be approximately produced with finite aperture and energy over a deep depth of field. In this paper, we report the application of a broadband J0 Bessel beam to nondestructive evaluation (NDE) of materials. Pulse-echo images of a stainless steel block phantom were obtained with both the Jo Bessel beam and a conventional focused Gaussian beam. Results show that uniformly high resolutions were obtained with the J0 Bessel beam over a large distance. In addition, the lateral resolution of the J0 Bessel beam is almost independent of the speed of sound of the materials inspected. In contrast, the lateral resolution of images obtained with the conventional focused Gaussian beam changes dramatically with the distance and the focal length of the beam in water is greatly reduced by the steel block. Therefore, limited diffraction beams could be useful for nondestructive evaluation of materials of different speeds of sound. Restoration of pulse-echo images obtained with these beams could be simplified.

scholarly journals Imaging with extended depth of field by means of the peacock eye optical element

2017 ◽  
Vol 9 (4) ◽  
pp. 128 ◽  
Author(s):  
Walter Torres ◽  
John F. Barrera ◽  
Rodrigo Henao ◽  
Zbigniew Jaroszewicz ◽  
Karol Kakarenko ◽  
...  
Keyword(s):  
Focal Length ◽  
Random Phase ◽  
Focal Depth ◽  
Optical Element ◽  
Depth Of Field ◽  
Depth Of Focus ◽  
Extended Depth Of Focus ◽  
Wide Range ◽  
Extended Depth Of Field ◽  
Imaging Properties

The paper presents imaging properties of the peacock eye optical element. Its abilities for imaging with extended depth of field is illustrated experimentally in monochromatic as well as polychromatic light. According to the obtained results the element makes possible to maintain the acceptable resolution, contrast and brightness of the output images for a wide range of defocusing. Full Text: PDF ReferencesJ. Ares, R. Flores, S. Bara, and Z. Jaroszewicz, "Presbyopia Compensation with a Quartic Axicon", Optom. Vis. Sci. 82, 107 (2005). CrossRef G.-m. Dai, "Optical surface optimization for the correction of presbyopia", Appl. Opt. 45, 4184 (2006). CrossRef Z. Liu, A. Flores, M. R. Wang, and J. J. Yang, "Diffractive infrared lens with extended depth of focus", Opt. Eng. 46, 018002 (1-9) (2007). CrossRef E. E. Garcia-Guerrero, E. R. Mendez, H. M. Escamilla, T. A. Leskova, and A. A. Maradudin, "Design and fabrication of random phase diffusers for extending the depth of focus", Opt. Express 15, 910 (2007). CrossRef J. Lin, J. Liu, J. Ye, and S. Liu, "Design of microlenses with long focal depth based on the general focal length function", J. Opt. Soc. Am. A 24, 1747 (2007). CrossRef N. Davidson, A. A. Friesem, and E. Hasman, "Holographic axilens: high resolution and long focal depth", Opt. Lett. 16, 523 (1991). CrossRef A. Kołodziejczyk, S. Bara, Z. Jaroszewicz, and M. Sypek, "The Light Sword Optical Element?a New Diffraction Structure with Extended Depth of Focus", J. Mod. Opt. 37, 1283 (1990). CrossRef K. Petelczyc, S. Bará, A. Ciro Lopez, Z. Jaroszewicz, K. Kakarenko, A. Kolodziejczyk, and M. Sypek, "Imaging properties of the light sword optical element used as a contact lens in a presbyopic eye model", Opt. Express 19, 25602 (2011). CrossRef K. Kakarenko, I. Ducin, K. Grabowiecki, Z. Jaroszewicz, A. Kolodziejczyk, A. Mira-Agudelo, K. Petelczyc, A. Składowska, M. Sypek, "Assessment of imaging with extended depth-of-field by means of the light sword lens in terms of visual acuity scale", Biomed Opt Express 6, 1738 (2015). CrossRef Z. Jaroszewicz, A. Kołodziejczyk, D. Mouriz, and J. Sochacki, "Generalized Zone Plates Focusing Light into Arbitrary Line Segments", J. Mod. Opt. 40, 601 (1993). CrossRef L. A. Romero, M. S. Millían, Z. Jaroszewicz, A. Kolodziejczyk, "Double peacock eye optical element for extended focal depth imaging with ophthalmic applications", J. Biomed. Opt. 17 046013 (2012). CrossRef

Comparison of Deterministic and Linear Cosine Spatial Filtering of Transmission Electron Micrographs

1972 ◽  
Vol 30 ◽  
pp. 596-597
Author(s):  
David A. Ansley
Keyword(s):  
Spherical Aberration ◽  
Focal Length ◽  
Chromatic Aberration ◽  
Spatial Filter ◽  
Operating Conditions ◽  
Objective Lens ◽  
List Type ◽  
Spatial Filters ◽  
Transmission Electron ◽  
Wide Range

The coherence of the electron flux of a transmission electron microscope (TEM) limits the direct application of deconvolution techniques which have been used successfully on unmanned spacecraft programs. The theory assumes noncoherent illumination. Deconvolution of a TEM micrograph will, therefore, in general produce spurious detail rather than improved resolution.A primary goal of our research is to study the performance of several types of linear spatial filters as a function of specimen contrast, phase, and coherence. We have, therefore, developed a one-dimensional analysis and plotting program to simulate a wide 'range of operating conditions of the TEM, including adjustment of the:(1) Specimen amplitude, phase, and separation(2) Illumination wavelength, half-angle, and tilt(3) Objective lens focal length and aperture width(4) Spherical aberration, defocus, and chromatic aberration focus shift(5) Detector gamma, additive, and multiplicative noise constants(6) Type of spatial filter: linear cosine, linear sine, or deterministic

Ultrahigh resolution optical coherence elastography using a Bessel beam for extended depth of field

2016 ◽  
Author(s):  
Andrea Curatolo ◽  
Martin Villiger ◽  
Dirk Lorenser ◽  
Philip Wijesinghe ◽  
Alexander Fritz ◽  
...  
Keyword(s):  
Bessel Beam ◽  
Depth Of Field ◽  
Optical Coherence ◽  
Ultrahigh Resolution ◽  
Extended Depth Of Field

A Calculation Method of Magnetic Anomaly Field Distribution of Ellipsoid with Arbitrary Posture

2021 ◽  
Author(s):  
Song-tong Han ◽  
Bo Zhang ◽  
Xiao-li Rong ◽  
Lei-xiang Bian ◽  
Guo-kai Zhang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Finite Element ◽  
Magnetic Anomaly ◽  
Field Distribution ◽  
Calculation Method ◽  
Gravity Potential ◽  
Anomaly Field ◽  
Finite Element Software ◽  
Wide Range ◽  
Distribution Equation

The ellipsoidal magnetization model has a wide range of application scenarios. For example, in aviation magnetic field prospecting, mineral prospecting, seabed prospecting, and UXO (unexploded ordnance) detection. However, because the existing ellipsoid magnetization formula is relatively complicated, the detection model is usually replaced by a dipole. Such a model increases the error probability and poses a significant challenge for subsequent imaging and pattern recognition. Based on the distribution of ellipsoid gravity potential and magnetic potential, the magnetic anomaly field distribution equation generated by the ellipsoid is deduced by changing the aspect ratio, making the ellipsoid equivalent to a sphere. The result of formula derivation shows that the two magnetic anomaly fields are consistent. This paper uses COMSOL finite element software to model UXO, ellipsoids, and spheres and analyzes magnetic anomalies. The conclusion shows that the ellipsoid model can completely replace the UXO model when the error range of 1nT is satisfied. Finally, we established two sets of ellipsoids and calculated the magnetic anomalous field distributions on different planes using deduction formulas and finite element software. We compared the experimental results and found that the relative error of the two sets of data was within [Formula: see text]‰. Error analysis found that the error distribution is standardized and conforms to the normal distribution. The above mathematical analysis and finite element simulation prove that the calculation method is simple and reliable and provides a magnetic field distribution equation for subsequent UXO inversion.

scholarly journals Vari-Focal Light Field Camera for Extended Depth of Field

Micromachines ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1453
Author(s):  
Hyun Myung Kim ◽  
Min Seok Kim ◽  
Sehui Chang ◽  
Jiseong Jeong ◽  
Hae-Gon Jeon ◽  
...  
Keyword(s):  
Light Field ◽  
High Reliability ◽  
Focal Length ◽  
Outdoor Environment ◽  
Depth Of Field ◽  
Depth Information ◽  
Single Shot ◽  
Depth Sensing ◽  
Depth Measurement ◽  
Sensing Applications

The light field camera provides a robust way to capture both spatial and angular information within a single shot. One of its important applications is in 3D depth sensing, which can extract depth information from the acquired scene. However, conventional light field cameras suffer from shallow depth of field (DoF). Here, a vari-focal light field camera (VF-LFC) with an extended DoF is newly proposed for mid-range 3D depth sensing applications. As a main lens of the system, a vari-focal lens with four different focal lengths is adopted to extend the DoF up to ~15 m. The focal length of the micro-lens array (MLA) is optimized by considering the DoF both in the image plane and in the object plane for each focal length. By dividing measurement regions with each focal length, depth estimation with high reliability is available within the entire DoF. The proposed VF-LFC is evaluated by the disparity data extracted from images with different distances. Moreover, the depth measurement in an outdoor environment demonstrates that our VF-LFC could be applied in various fields such as delivery robots, autonomous vehicles, and remote sensing drones.

scholarly journals An experimental decomposition of nonlinear forces on a surface-piercing column: Stokes-type expansions of the force harmonics

2018 ◽  
Vol 848 ◽  
pp. 42-77 ◽  
Author(s):  
L. F. Chen ◽  
J. Zang ◽  
P. H. Taylor ◽  
L. Sun ◽  
G. C. J. Morgan ◽  
...  
Keyword(s):  
High Order ◽  
Quality Data ◽  
Wave Group ◽  
Wave Loading ◽  
Harmonic Force ◽  
Wave Basin ◽  
Wide Range ◽  
Time Histories ◽  
Focused Wave ◽  
Sloping Bed

Wave loading on marine structures is the major external force to be considered in the design of such structures. The accurate prediction of the nonlinear high-order components of the wave loading has been an unresolved challenging problem. In this paper, the nonlinear harmonic components of hydrodynamic forces on a bottom-mounted vertical cylinder are investigated experimentally. A large number of experiments were conducted in the Danish Hydraulic Institute shallow water wave basin on the cylinder, both on a flat bed and a sloping bed, as part of a European collaborative research project. High-quality data sets for focused wave groups have been collected for a wide range of wave conditions. The high-order harmonic force components are separated by applying the ‘phase-inversion’ method to the measured force time histories for a crest focused wave group and the same wave group inverted. This separation method is found to work well even for locally violent nearly-breaking waves formed from bidirectional wave pairs. It is also found that the $n$th-harmonic force scales with the $n$th power of the envelope of both the linear undisturbed free-surface elevation and the linear force component in both time variation and amplitude. This allows estimation of the higher-order harmonic shapes and time histories from knowledge of the linear component alone. The experiments also show that the harmonic structure of the wave loading on the cylinder is virtually unaltered by the introduction of a sloping bed, depending only on the local wave properties at the cylinder. Furthermore, our new experimental results reveal that for certain wave cases the linear loading is actually less than 40 % of the total wave loading and the high-order harmonics contribute more than 60 % of the loading. The significance of this striking new result is that it reveals the importance of high-order nonlinear wave loading on offshore structures and means that such loading should be considered in their design.

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