Selective imaging of sound sources in air using phase-calibrated multiwavelength digital holographic reconstructions

Olsson, Erik

doi:10.1117/1.2752826

Cited by 7 publications

(6 citation statements)

References 24 publications

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“…This result was obtained from simulations and verified experimentally in Ref. 4. The discussion above was for a single point source only.…”

Section: ͑4͒supporting

confidence: 73%

“…In Ref. 4, it was shown how this property can be used in order to make selective imaging of sound sources. The phase of the reconstructed complex amplitude at a position corresponding to a sound source, with the phase response compensated for, equals zero, independent of the wavelength of the sound field.…”

Section: Numerical Propagation Of Sound Wavesmentioning

confidence: 99%

“…That property can be used to perform selective imaging of sound sources, with improved spatial resolution and a low image noise level, using multiple wavelengths. 4 Those factors are of importance in optoacoustic imaging ͑OA͒, 5 which in recent years has become a promising technique for the detection of breast cancer at the early stage. 6 In this paper, the two-dimensional ͑2-D͒ selective imaging described in Ref.…”

Section: Introductionmentioning

confidence: 99%

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Three-dimensional selective imaging of sound sources

Olsson

Forsberg

2009

Opt. Eng

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A technique for 3-D selective imaging of sound sources is described analytically and demonstrated experimentally. Onedimensional recordings of the acoustic field is measured using laser vibrometry. By applying digital holographic and tomographic algorithms to the acquired 1-D data, the full 3-D complex amplitude is reconstructed. The use of multiple frequencies in the spectral content of the acoustic field gives a number of advantages: higher spatial resolution, less noise in the reconstructed image, less sensitivity to noise in the measurements, and the possibility to perform selective imaging. Theory for all three steps-the measurement of sound using light, numerical propagation of waves, and finally the tomographic reconstruction in the process are given. In the experiment, the positions of three ultrasound sources are accurately determined and two different types of transducers are distinguished from each other. This multiwavelength technique could show to be a useful addition to optoacoustic imaging.

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“…This result was obtained from simulations and verified experimentally in Ref. 4. The discussion above was for a single point source only.…”

Section: ͑4͒supporting

confidence: 73%

Section: Numerical Propagation Of Sound Wavesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Three-dimensional selective imaging of sound sources

Olsson

Forsberg

2009

Opt. Eng

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“…Therefore care needs to be taken to interpret any stress values calculated using the method. This 'line integration' issue is discussed in detail in [19], [20] and may be essentially eliminated when performing computer tomography, as shown by Olsson & Forsberg [14].…”

Section: Theoretical Backgroundmentioning

confidence: 99%

High sensitivity non-contact method for dynamic quantification of elastic waves and strains in transparent media

Malkin¹,

Robert²

2014

Measurement

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This paper presents time resolved quantitative evaluation of elastic stress waves in solid media by utilising an adaptation of the well-established laser Doppler vibrometry method. We show that the introduction of elastic stress waves in a transparent medium gives rise to detectable and quantifiable changes in the refractive index, which is proportional to stress. The method is tested for mechanical excitation at frequencies from 10 to 25kHz in an acrylic bar. This refractometric quantification can measure internal strains as low as 1x10 -11 . Additionally, finite element analysis is conducted to gauge the validity of the results. In the presented work an acrylic bar is used, this method however should be applicable to any transparent solid. Theoretical backgroundThe refractive index, n, of a medium is defined as;With c 0 : velocity of light in a vacuum and v: the velocity of light in the medium. The refractive index of a medium is influenced by stress, density and temperature of the host medium [7][8]. If we consider a simple adiabatic (no change in system temperature), isochoric (no change in system volume) event in a solid domain where there is a change in stress, this will result in a corresponding change in n. Solids will exhibit either a positive or negative linear relationship between n and stress. Monitoring the change in n (refractometry) can therefore be used to monitor stresses within solids. Probing dynamic events with traditional refractometry where n changes at frequencies in the kHz range is, as yet, not possible. What can be probed however, using Laser Doppler interferometry, is the variation in velocity, v, of light in the medium and therefore allowing stress to be estimated. The principle of the measurement technique is elegantly described by Nakamura et al.[11] and is reported here in Figure 1. Monochromatic laser light is directed through a region of the medium, of length a, in which the stress fluctuates. The laser exits the region and if reflected from a rigid wall, back through the region and into the interferometer. This modulated path length, Δa, appears identical to a physical displacement of the reflective rigid wall.(2)The output signal from a laser Doppler vibrometer (LDV) is the velocity of the apparent displacement of the rigid wall, as shown in [12].Where f: frequency of stress fluctuation and, v LDV : velocity from LDV, which is integrated with respect to time to give the apparent displacement, Δa, as shown in Eq 2. Most refracto-vibrometry is primarily based on using the method for either air or water pressure measurement [13][14][15][16][17], with some preliminary work conducted into stresses in solids by Zipser et. al. [18]. The principle of measurement however holds for any medium, not just air. Therefore we developed an experimental procedure that enables the quantitative investigation of elastic waves propagating in a solid.An empirical relation between the longitudinal strain, ε, of a block of polymethyl methacrylate (PMMA), and n, from Nazarov et al [10], is show...

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“…Olsson & Tatar note that "any quantitative data obtained when measuring 3D sound fields using laser vibrometry must be viewed with some scepticism" due to the line integration problem when using a point source. In 2007, however, Olsson showed that the method could be used to measure the pressure magnitude correctly by using a correction factor [27]. While the results were accurate, Olsson's method did not lend itself to simple measurement of sound fields, requiring considerable technical expertise.…”

Section: Theory Of Refracto-vibrometrymentioning

confidence: 99%

A simple method for quantitative imaging of 2D acoustic fields using refracto-vibrometry

Malkin

Todd

Robert

2014

Journal of Sound and Vibration

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This paper presents a simple 2D method for rapid time resolved quantitative imaging of acoustic waves using refracto-vibrometry. We present the theoretical background, the experimental method and reconstructions of acoustic reflection and interference. We investigate the applicability of the method, in particular the effect of sound radiator geometry. Finite element and experimental reconstructions of the sound fields are analysed. The spatial limitations and accuracy of the method are presented and discussed.

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Selective imaging of sound sources in air using phase-calibrated multiwavelength digital holographic reconstructions

Cited by 7 publications

References 24 publications

Three-dimensional selective imaging of sound sources

Three-dimensional selective imaging of sound sources

High sensitivity non-contact method for dynamic quantification of elastic waves and strains in transparent media

A simple method for quantitative imaging of 2D acoustic fields using refracto-vibrometry

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