Non-invasive determination of optical properties of scattering media

Weng, Cuncheng

doi:10.1051/epjap/2010057

Cited by 2 publications

(4 citation statements)

References 24 publications

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“…Additionally, the phase spectrum of the modulated light intensity signal is irregular due to random scatterings of the modulated light inside the solution, resulting in the inability to measure the ultrasound-induced phase shift. Consequently, for the value of B g less than 1, the modulated light intensity varies periodically at the ultrasonic frequency and its signal is a sinusoidal signal of frequency Ω, which confirms equation (19).…”

Section: Methodssupporting

confidence: 67%

“…The tank was filled with a mixed solution consisting of 2.0 ml intralipid injection (C 14-24 , Zhejiang Kanglaite Pharmaceutical) and 300 ml distilled water, which offered a reduced scattering coefficient of about 0. 2 mm −1 , a scattering coefficient of about 2.0 mm −1 and a free path length of about 0.5 mm [19]. The intralipid mainly consists of soybean oil, lecithin and glycerol.…”

Section: Methodsmentioning

confidence: 99%

“…From equation (19), the modulated light intensity varies periodically at the ultrasonic frequency and its signal is a sinusoidal signal of frequency Ω for the value of B g less than 1. In this experiment, the value of kΔnl was about 0.29 (6.28 × 1.33 × 3 × 7.3 × 10 −9 /6.3 × 10 −7 = 0.29) by calculation based on the above experimental conditions: λ = 630 nm, n 0 = 1.33, Δn = 7.3 × 10 −6 , l = 3.0 mm.…”

Section: Methodsmentioning

confidence: 99%

“…Fourier transform of the modulated light intensity signal in figure 5 is showed in figure 6. Form figures 5 and 6, the modulated light intensity varies periodically at the ultrasonic frequency and its signal is a sinusoidal signal of frequency 1.7 MHz for the driving signal with the amplitude of 5 V, as shown in equation (19). Additionally, the phase spectrum of the modulated light intensity signal is irregular due to random scatterings of the modulated light inside the solution, resulting in the inability to measure the ultrasound-induced phase shift.…”

Section: Methodsmentioning

confidence: 99%

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Correlations between the optical phase modulation and the optical frequency and phase shifts in ultrasound-modulated optical tomography

Weng

2024

Phys. Scr.

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IIn ultrasound-modulated optical tomography, ultrasound causes the phase of incident light to vary periodically with ultrasound. The periodic variation in phase is known as phase modulation. The phase modulation causes the modulated light intensity to vary periodically with the ultrasound, which is called ultrasonic modulation of light. As is well known, incident light is shifted in frequency and phase by ultrasound in acousto-optic effect, and the tomography is based on the effect. However, the correlations between the phase modulation and the frequency and phase shifts in the ultrasonic modulation of light have been ignored. In this paper, the correlations are investigated theoretically and experimentally in detail. Studies reveal that the modulated light is phase-modulated by the frequency and phase shifts, and the frequency shift is the fundamental cause for the ultrasonic modulation of light. Studies show that the frequency shift, rather than the phase shift, causes the modulated light intensity to vary periodically with the ultrasound. Additionally, the modulated light intensity signal is composed of cosine signals with frequencies Ω, 2Ω, 3Ω, etc, and the amplitude of the cosine signals depends on the amplitude of the phase modulation. Then, the modulated light intensity signal contains relatively more cosine signals with high frequency as the amplitude of the phase modulation increases. At last, for the ultrasound with lower power, the amplitude ratio of cosine signals with frequencies of 2Ω and Ω increases as the scattering coefficient of turbid media increases. Studies find that both the frequency-shifted light and the amplitude ratio can be used to image turbid media.

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Section: Methodssupporting

confidence: 67%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Correlations between the optical phase modulation and the optical frequency and phase shifts in ultrasound-modulated optical tomography

Weng

2024

Phys. Scr.

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State-of-the art of acousto-optic sensing and imaging of turbid media

2012

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Acousto-optic (AO) is an emerging hybrid technique for measuring optical contrast in turbid media using coherent light and ultrasound (US). A turbid object is illuminated with a coherent light source leading to speckle formation in the remitted light. With the use of US, a small volume is selected,which is commonly referred to as the "tagging" volume. This volume acts as a source of modulated light, where modulation might involve phase and intensity change. The tagging volume is created by focusing ultrasound for good lateral resolution; the axial resolution is accomplished by making either the US frequency, amplitude, or phase time-dependent. Typical resolutions are in the order of 1 mm. We will concentrate on the progress in the field since 2003. Different schemes will be discussed to detect the modulated photons based on speckle detection, heterodyne detection, photorefractive crystal (PRC) assisted detection, and spectral hole burning (SHB) as well as Fabry-Perot interferometers. The SHB and Fabry-Perot interferometer techniques are insensitive to speckle decorrelation and therefore suitable for in vivo imaging. However, heterodyne and PRC methods also have potential for in vivo measurements. Besides measuring optical properties such as scattering and absorption, AO can be applied in fluorescence and elastography applications.

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Non-invasive determination of optical properties of scattering media

Cited by 2 publications

References 24 publications

Correlations between the optical phase modulation and the optical frequency and phase shifts in ultrasound-modulated optical tomography

Correlations between the optical phase modulation and the optical frequency and phase shifts in ultrasound-modulated optical tomography

State-of-the art of acousto-optic sensing and imaging of turbid media

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