Optics Communications 411 (2018) 70–79 Contents lists available at ScienceDirect Optics Communications journal homepage: www.elsevier.com/locate/optcom Study the effects of varying interference upon the optical properties of turbid samples using NIR spatial light modulation Oren Shaul a, 1 , Michal Fanrazi-Kahana a, b, 1 , Omri Meitav a , Gad A. Pinhasi c , David Abookasis a, * a Department of Electrical and Electronics Engineering, Ariel University, Ariel 40700, Israel b Department of Physics, Ariel University, Ariel 40700, Israel c Department of Chemical Engineering and Biotechnology, Ariel University, Ariel 40700, Israel article info Keywords: Near-infrared (NIR) Spatial light modulation Absorption and scattering properties Interference Complex refractive index abstract Optical properties of biological tissues are valuable diagnostic parameters which can provide necessary information regarding tissue state during disease pathogenesis and therapy. However, different sources of interference, such as temperature changes may modify these properties, introducing confounding factors and artifacts to data, consequently skewing their interpretation and misinforming clinical decision-making. In the current study, we apply spatial light modulation, a type of diffuse reflectance hyperspectral imaging technique, to monitor the variation in optical properties of highly scattering turbid media in the presence varying levels of the following sources of interference: scattering concentration, temperature, and pressure. Spatial near-infrared (NIR) light modulation is a wide-field, non-contact emerging optical imaging platform capable of separating the effects of tissue scattering from those of absorption, thereby accurately estimating both parameters. With this technique, periodic NIR illumination patterns at alternately low and high spatial frequencies, at six discrete wavelengths between 690 to 970 nm, were sequentially projected upon the medium while a CCD camera collects the diffusely reflected light. Data analysis based assumptions is then performed off-line to recover the medium’s optical properties. We conducted a series of experiments demonstrating the changes in absorption and reduced scattering coefficients of commercially available fresh milk and chicken breast tissue under different interference conditions. In addition, information on the refractive index was study under increased pressure. This work demonstrates the utility of NIR spatial light modulation to detect varying sources of interference upon the optical properties of biological samples. © 2017 Elsevier B.V. All rights reserved. 1. Introduction Over the last forty years, great efforts have been made to determine two fundamental optical parameters: the absorption and scattering coefficients of turbid media [1–3]. In the medical field, the optical properties of biological tissue can be used to understand pathological processes or metabolic states of clinical specimens [4–6]. Specifically, the absorption coefficient may be calculated using the Beer–Lambert law to determine the concentrations of individual tissue components such as hemoglobin, lipids, water and other compounds [7,8]. The scattering coefficient, on the other hand, can provide information regarding the macroscopic tissue structural (size, density, distribution, etc.) [9,10]. The quantification of these two parameters is also important to: (1) quantitatively understand the propagation and distribution of light * Corresponding author. E-mail address: davida@ariel.ac.il (D. Abookasis). 1 These authors contributed equally to this manuscript. within a biological medium[11,12], and (2) determine the excitation and emission distribution in fluorescence diagnostics [13–15]. One should bear in mind that simultaneous quantification of light absorption and scattering is difficult because the two phenomena are not easily sep- arable. Accordingly, arsenals of optical system configurations, together with a range of mathematical light propagation models have arisen to determine tissue optical properties in the visible and near-infrared (NIR) regions. This range of systems can be divided into three main categories: continuous wave, time-resolved, and frequency domain modalities [4, 16,17]. Among recently reported approaches is spatially modulated illumination, known also as modulated imaging [18], which works in the spatial frequency domain, in contrary to other methods. With this technique, periodic illumination patterns at multiple wavelengths and spatial frequencies are projected onto the object’s surface to separately https://doi.org/10.1016/j.optcom.2017.10.067 Received 24 September 2017; Received in revised form 24 October 2017; Accepted 26 October 2017 0030-4018/© 2017 Elsevier B.V. All rights reserved.