NIR Optics and Measurement Methods

Abstract

What type of components does a NIR spectrometer consist of? How do these parts determine the performance of the instruments? The measurement targets of NIR spectroscopy span a wide variety from transparent liquids to opaque solid samples, and as described in Chap. 8, the NIR spectrometers are characterized by a wide variety of device specifications and shapes. Consequently, what are the criteria for choosing a spectrometer? In the first half of this chapter (9.1), the basics of the optics that comprise the NIR spectrometer, such as the light source, spectroscopic element, and detector, are explained. This will allow the reader to understand the specifications, that control the functions of the spectrometer. Next, in the latter half of this chapter (9.2), the measurement method is explained for each sample form, namely liquid, solid, and paste. The most characteristic feature of NIR spectroscopy is the use of diffuse reflected light, and the “interactance” method, which is a unique application. It can be inferred that diffuse reflectance method contributes to the expansion of the range of sample forms that are measurable by NIR spectroscopy.