Analysis of Reflectance and Transmittance Measurements on Absorbing and Scattering Small Samples Using a Modified Integrating Sphere Setup

Abstract

The aim of the present paper is to analyze reflectance and transmittance measurements on small scattering and absorbing samples. The long term goal is to perform quantitative, spectroscopic in vivo measurements of pigments in small samples of plant material. Small samples such as small leaves constitute a special experimental challenge in cases in which the sample beam has a larger cross-sectional area than the sample. The experimental errors introduced when measuring reflectance and transmittance on small absorbing and scattering samples are investigated theoretically and experimentally by using a blue polyester sample as an appropriate test sample. The experiments are performed with either a mask or a lens setup combined with a mask inserted in the sample beam. In particular, the errors introduced in the reflectance measurements can be very large and larger than 100%. It is shown that any direct illumination of the mask must be avoided. To obtain more accurate values for the reflection coefficient it is necessary to combine the mask with a focusing lens system, adjust the mask and sample very carefully, and choose the ratio between the aperture of the mask and the beam area as large as possible. In the case of transmittance measurements, it is shown that the combination of a special sample fixture and a lens system gives rise to smaller errors compared to the errors introduced by the mask alone or the mask combined with a focusing lens system.

Effect of Antioxidant and Antimicrobial Coating based on Whey Protein Nanofibrils with TiO2 Nanotubes on the Quality and Shelf Life of Chilled Meat

“…A conventional spectrophotometer equipped with an integrating sphere is often used to measure reflectance or transmittance to assess for a smooth surface, which allows the physical status of a film to be monitored [20,21]. Transmittance measurements on small samples are much more accurate than reflectance measurements [20]. Therefore, the ultraviolet spectroscopy (UV)-Vis (200–800 nm) transmission spectra of different composite films were obtained (Figure 3A).…”

“…The addition of TNPs or TNTs changed the functional properties of EFCs. First, the MC values of the films were higher than the films without them, which may result from the super-hydrophilicity of TNPs [20]. Second, the solubility in water values of the films were lower than the films without them.…”

Intensity-Value Corrections for Integrating Sphere Measurements of Solid Samples Measured behind Glass

“…Brunsting et al 30 demonstrated the experimental adaptations that are needed for both the reference and sample optical trains to accurately measure samples of small diameter and yield results with correct ratios. Jernshøj and Hassing 31 studied this problem further and showed that in order to measure small samples using a mask that there are not only light–mask interactions where the beam impinges upon the mask, but also reflections among the sample, the mask, and the port itself. In a similar manner, we have found that there are multiple reflection effects between the protective glass and the sample itself.…”

Raman Spectroscopy: A Non-Destructive and On-Site Tool for Control of Food Quality?

“…Reflection measurements performed on different kind of green plants and on different plant parts are similar and contain almost identical spectral information. The example in figure 1 shows reflection spectra from two types of leaves of a Hibiscus, rosa sinensis, namely a foliage leaf and a sepal Jernshøj & Hassing (2009). The spectra shows differences in the absolute reflection values, but are very similar with respect to spectral information.…”

“…carotenes, in the sepals than in the green leaves. A quantitative analysis of chlorophyll and carotenoid from these spectra is possible, when applying empirical models, this reflects the complex scattering and interaction processes taking place in the leaf Jernshøj & Hassing (2009);Kortüm (1969). However, due to the poorly resolved spectra, it may be impossible to discriminate between the presence of closely related molecular species, such as the antioxidants α-and β-carotene.…”