Theory and Applications of Diffuse Reflectance Spectroscopy

Abstract

At present there are at least 100 papers in the literature in which the diffuse reflectance method is used without question to obtain approximate absorption spectra of solids in the visible and near UV, or in which attempts are made to overcome the recognized limitations of the method, namely, that diffuse reflectance spectra are not always identical to transmission spectra. Some of the theories proposed to account for the difference will be discussed, those which purportedly permit one to compute absorption coefficients from diffuse reflectance data: the Kubelka-Munk dilution model, Johnson's plate model, and the Melamed model.

Quantitative diffuse reflectance spectroscopy of large powders: the Melamed model revisited

“…(17) to the value x: It turns out that both the original and the corrected Melamed model are most sensitive to this value, which can only be estimated upon fitting the model to the data for nonhomogeneous, nonspherical particles. This sensitivity has been noticed previously: Companion 5 ducibility of average packing conditions in powdered specimens. Figure 8 shows that the model is much less sensitive to the refractive index value than to the xu value.…”

“…respect to both Johnson 3 and Melamed models has previously been made by Companion. 5 The original and corrected Melamed models converge in the limit of very high kd to the same value [Eqs. (16), (17)]:…”

“…4 A review of the literature built on the Melamed model revealed that warnings about numerous typographical errors encountered in the original paper' have been voiced previously. 5 ' 6 These errors include the final analytical expression for the absolute diffuse reflectance R, given by Melamed [Ref. 1,Eq.…”

“…A great deal of confusion exists even in ascertaining whether a given author has used the erroneous formula 7 for R, or the typographically correct one. 5 In our own effort to obtain quantitative optical absorption coefficient spectra of large size powders using diffuse reflectance IR Fourier transform spectroscopy (DRIFTS) we thoroughly re-examined the Melamed model due to its direct applicability to the interpretation of compensated (i.e., relative) spectra in terms of the optical properties of powders. In addition to the numerous, but easily corrigible typographical errors, we found several physical inconsistencies of the model.…”

Evaluation of the human placenta optical scattering properties using continuous wave and frequency-domain diffuse reflectance spectroscopy

“…The most common method to assess oxygenation is using optical methodologies, which largely rely on diffuse reflectance spectroscopy (DRS). [8][9][10] Typically, for this purpose, light in the near-infrared (NIR) range (700 to 900 nm) of wavelengths is directed to a tissue in close proximity to the circulation. Given that NIR can penetrate tissue without substantial attenuation by normal components, such as adipose tissue and water, light can diffuse into the tissue from a source and backscattered light can be detected with optical methods.…”