Source Hologram Research Articles

Адаптивный алгоритм локализации шумовых подводных источников в мелководных акваториях

An adaptive noise-resistant algorithm for holographic processing of hydroacoustic signals is presented, which provides restoration of the distance and radial velocity of underwater noise sources in shallow waters in the absence of information about the characteristics of the propagation medium. The algorithm is based on the measured values of the source hologram. The results of numerical simulation are presented. An analysis of the stability of the algorithm for estimating the source parameters with respect to intense internal waves that determine the horizontal refraction of sound field modes is performed.

Structure of interferogram and hologram of non-moving source in presence of shallow water internal waves

The results of holographic signal processing of the oceanographic experiment SWARM-95 on the coast of New Jersey are presented in the paper. The used acoustic signals were obtained on stationary acoustic track (non-moving airgun source) in the presence of shallow water intensive internal waves (IIW). The IIW led to significant 3D acoustic effects [Badiey et al., JASA 117(2), 613–625]. Within framework of holographic signal processing [Pereselkov and Kuz’kin, JASA 151(2), 666–676] the source interferogram (sound intensity distributions in frequency-time coordinates) is analyzed by two-dimensional Fourier transform (2D-FT). The result of the 2D-FT is called the Fourier hologram (source hologram). In result of holographic signal processing, the two separated sets of spectral spots are obtained in hologram domain. The first set of spectral spots corresponds to sound field in nonperturbed waveguide (without of IIW). The second set of spectral spots in hologram corresponds to hydrodynamic field perturbation by IIW. This structure of the hologram allows the reconstruction of interferogram of nonperturbed field for waveguide in the absence of IIW. The error in the reconstruction of the nonperturbed interferogram is estimated. [Work supported by grant from the Russian Science Foundation 23-61-10024.]

Broadband sound source hologram formation and application in oceanic waveguides

The physical and mathematical basics of holographic interferometry of broadband signal processing in oceanic waveguides are presented. The application of holographic processing for localization of low-noise sources is considered.

Low-frequency holographic signal processing for moving sources separation in shallow water waveguide

The results of numerical modeling of the interferometric signal processing for broadband sources (200–300 Hz) moving in shallow water waveguide is presented in the paper. Each source creates in receiver point a stable interference pattern of the intensity distribution (interferogram) in the frequency-time domain. The 2D Fourier Transformation (2D-FT) is applied to analyze the superposition of several interferograms of the sources moving in waveguide. 2D-FT of interferogram—hologram is superposition of the holograms of the sources moving in waveguide. The source hologram allows to coherently accumulate the sound intensity of the source interferogram in a relatively small area as focal spots. The sources can be separated when the sources holograms spots are not overlapped and thus can be filtered. The information about each source is in separated hologram. So, separated hologram allows to estimate source range, its velocity and direction (S. Pereselkov and V. Kuz’kin, JASA 151(2), 666–676). Within numerical experiment the separation of three noise sources with different intensities moving in different directions with different velocities is considered.The error of estimation of parameters of each source is used as a criterion of resolving efficiency of proposed method. [This study was supported by RFBR 19-29-06075, МК-4846.2022.4.]

Acoustic holography for calibration of ultrasound sources and in situ fields in therapeutic ultrasound

Therapeutic ultrasound sources, which are typically piezoelectric transducers, are intended to deliver known acoustic pressures to targeted tissue sites. Each transducer vibrates in a unique way and radiates a corresponding 3D ultrasound field. Accordingly, transducer vibrations should be known accurately in order to characterize the pressures delivered to the patient. Acoustic holography is a technique that relies on hydrophone measurements to reconstruct a source hologram that characterizes transducer vibrations [Sapozhnikov et al., JASA, 138(3), 1515–1532 (2015)]. In this way, a hologram is a signature of each transducer that can be monitored over time for quality assurance. Using holography-defined source boundary conditions, numerical forward projection of the ultrasound field based on the nonlinear wave equation can be used to accurately predict in situ temperatures and pressures in heterogeneous media for treatment planning. As such, acoustic holography goes beyond simple hydrophone scans and is uniquely suited to meet clinical needs for quantifying therapeutic ultrasound fields. In this paper, several examples of acoustic holography implementation are presented, including the characterization of single-element and multi-element flat and spherically curved sources working in linear and nonlinear regimes and in continuous and pulsed modes. [Work supported by NIH 1R01EB025187, R01EB007643, and R21CA219793; RFBR 17-02-00261 and 17-54-33034.]

Point spread function of incoherent digital holography based on spiral phase modulation

Fresnel incoherent correlation holography (FINCH) has attracted much attention because it is able to record the holograms of three-dimensional (3D) samples under incoherent illumination with just a charge coupled device (CCD) and spatial light modulator (SLM). The FINCH technology achieves the splitting and phase shifting of the incident beam by loading a phase mask on an SLM. Three holograms, whose phase factors are different from each other, are recorded sequentially by a CCD. After the three holograms are superposed in the computer, the zero order image and a twin image are eliminated, and a complex hologram is obtained. The 3D properties of the object are revealed when the complex hologram is reconstructed in the computer. Spiral phase filters (SPFs) are commonly used to produce optical vortices, which can enhance and recognize image edges. In this paper, the spiral phase modulated FINCH system illuminated by Xenon lamp is built, in which the phase-only SLM is space-division multiplexed by a helical lens (superposed by an SPF and a lens) and a conventional lens. The mathematical model of spiral phase modulated FINCH system is established based on wave optics theory. The specific forms of the point spread function (PSF) and the reconstruction distance of the system are given for the first time. Experiments are conducted by using a small aperture with a diameter of 20 nm as a point source, the point source hologram recorded by CCD and the reconstructed image are consistent with the simulated ones. When the system is used for imaging resolution target and unstained onion cells, the edge contrast enhancement effects are obtained without the loss of resolution. The results show that the spiral phase modulated FINCH system can not only improve the edge contrast of the amplitude object, but also extract the edge information or recognition of the phase objects. This method has an important application prospect in the quantitative imaging of phase objects such as in real-time monitoring cell division and deformation of living cells.

Characterization of an electromagnetic lithotripter using transient acoustic holography

Shock wave lithotripters radiate high intensity pulses that are focused on a kidney stone. High pressure, short rise time, and path-dependent nonlinearity make characterization in water and extrapolation to tissue difficult. Here acoustic holography is applied for the first time to characterize a lithotripter. Acoustic holography is a method to determine the distribution of acoustic pressure on the surface of the source ("source hologram"). The electromagnetic lithotripter characterized in this effort is a commercial model (Dornier Compact S, Dornier MedTech GmbH, Wessling, Germany) with 6.5 mm focal width. A broadband hydrophone (HGL-0200, sensitive diameter 200 µm, Onda Corp., Sunnyvale, CA) was used to sequentially measure the field over a set of points in a plane in front of the source. Following the previously developed transient holography approach, the recorded pressure field was numerically back-propagated to the source surface and then used for nonlinear forward propagation to predict waveforms in different points in the focal region. Pressure signals predicted from the source hologram coincide well with the waveforms measured by a fiber optic hydrophone. Moreover, the method provides an accurate boundary condition from which the field in tissue can be simulated. [Work supported by RSF 14-15-00665 and NIH R21EB016118, R01EB007643, and DK043881.]

Fast compression of computer-generated holographic images based on a GPU-accelerated skip-dimension vector quantization method

A method for fast and low bit-rate compression of digital holograms based on a new vector quantization (VQ) method known as the skip-dimension VQ (SDVQ) is proposed. Briefly, a complex hologram is converted into a real off-axis hologram, and partitioned into a set of image vectors. The image vectors are passed into a graphic processing unit (GPU), and compressed through SDVQ into a set of code indices considerably smaller in data size than the source hologram. Experimental evaluation reveals that our scheme is capable of compressing a digital hologram to a compression ratio of over 500 times, in approximately 20-22 ms.

59.3: Fast Hologram Pattern Generation by Removing Concentric Redundancy

AbstractWe propose a fast hologram pattern generation framework by removing concentric redundancy of point source hologram. We minimized repeated or redundant calculations in point hologram generation and accumulation process, and results shows that proposed method is over 1400 times faster than analytic method.

Study on the inside source hologram reconstruction algorithm based on discrete Fourier transform

The inside source hologram reconstruction algorithm based on discrete Fourier transform was investigated in detail, and how to calculate the contribution of whole spherical hologram to the reconstructed image of atoms was demonstrated in this algorithm, which was previously regarded to be capable of calculating only half of the spherical hologram. Using the sampling theorem in this issue, we are able to examine such essential factors as the sampling rate of the hologram, domain and resolution of reconstructed image.

Thermality in de Sitter spacetime and holography

Assuming the existence of a $dS/CFT$ correspondence we study the holograms of sources moving along geodesics in the bulk by calculating the one point functions they induce in the boundary theory. In analogy with a similar study of uniformly accelerated sources in $AdS$ spacetime, we argue that comoving geodesic observers correspond to a coordinate system on the boundary in which the one point function is {\it constant}. For $dS_3$ we show that the conformal transformations on the boundary which achieve this - when continued suitably to Lorentzian signature - induce nontrivial Bogoliubov transformations between modes, leading to a thermal spectrum. This may be regarded as a holographic signature of thermality detected by bulk geodesic observers.

Using microwave holography and microstrip antenna for 3D mouse investigation

A dynamic technique for establishing a three dimensional (3D) mouse is possible by combining holography with a microstrip antenna in order to enter 3D data into a computer. The idea depends on two techniques, the first generates a point source hologram from a dipole antenna. Secondly a receiving microstrip antenna will be attached to operator's hand. A practical system for this purpose is constructed and performances are evaluated theoretically and tested experimentally. Scanning time is improved by replacing the antenna element with an array to achieve reasonable or real time results in editing 3D images. A simulation model is developed to create similar holograms. Experimental and simulation results give excellent agreement.

Holographic decoding of three-dimensional objects

A holographic method for coding and decoding three-dimensional information is described. The coded object in an extended source hologram is decoded by means of a ‘key’ hologram. The reconstructions of a decoded, three-dimensional object scene are shown and discussed.

A holographic information decoding method

The compensation of an extended source hologram is achieved by a second hologram negative.