## Abstract

We present and apply a novel method, the scattering photoacoustic (SPA) technique, for measuring optical parameters in weakly absorbing, highly scattering suspensions. In this method, a solid absorber is in contact with a suspension sample to permit the photoacoustic detection of the sample’s light-scattering properties. We conducted measurements conducted to determine the reduced scattering coefficients of Intralipid suspensions with a concentration range of 0.1–5%, and the results are in good agreement with those achieved by other researchers. Moreover, we also illustrate the relationship between the amplitude of the SPA signal and absorption, scattering, and detection distance. Through a study of Intralipid–ink mixes, we demonstrate that the SPA technique has the ability to determine simultaneously the absorption and reduced scattering coefficients of turbid media. This new technique has low cost and is noninvasive, and it enables on-line measurements to be made.

© 2005 Optical Society of America

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### Equations (7)

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(1)
$${V}_{\text{PA}}=\frac{k}{r}\frac{\mathrm{\beta}{\nu}^{2}}{{C}_{P}}\frac{{E}_{a}}{{{R}_{a}}^{2}},$$
(2)
$${V}_{\text{SPA}}={k}^{\prime}\frac{\mathrm{\alpha}{\mathrm{\beta}}^{\prime}{{\nu}^{\prime}}^{2}}{2{{C}_{p}}^{\prime}}F,$$
(3)
$$F(r)=\frac{F}{4\mathrm{\pi}Dr}exp(-r\sqrt{{\mathrm{\mu}}_{a}/D}).$$
(4)
$${R}_{d\infty}\approx exp\left\{-\frac{7}{{[3(1+{{\mathrm{\mu}}_{s}}^{\prime}/{\mathrm{\mu}}_{a})]}^{1/2}}\right\},$$
(5)
$$\begin{array}{cc}{V}_{\text{SPA}}& =K\left\{1-exp\left[-7{\left(\frac{{\mathrm{\mu}}_{a}}{{3{\mathrm{\mu}}_{s}}^{\prime}}\right)}^{1/2}\right]\right\}{{\mathrm{\mu}}_{s}}^{\prime}\frac{1}{r}\\ \hfill & \times exp(-r\sqrt{3{\mathrm{\mu}}_{a}{{\mathrm{\mu}}_{s}}^{\prime}}),\end{array}$$
(6)
$$K=\frac{3{k}^{\prime}}{8\mathrm{\pi}}\frac{{E}_{l}\mathrm{\alpha}{\mathrm{\beta}}^{\prime}{{\nu}^{\prime}}^{2}}{{{C}_{p}}^{\prime}}.$$
(7)
$$\text{ln}(r{V}_{\text{SPA}})=-\sqrt{3{\mathrm{\mu}}_{a}{{\mathrm{\mu}}_{s}}^{\prime}}r+ln(K\lfloor 1-exp\{-7{[{\mathrm{\mu}}_{a}/(3{{\mathrm{\mu}}_{s}}^{\prime})]}^{1/2}\}\rfloor {{\mathrm{\mu}}_{s}}^{\prime}).$$