A review on recent near infrared spectroscopic measurement setups and their challenges

Despite near infrared spectroscopy (NIRS) has been studied as an alternative measurement approach in various applications, NIRS measurement setup that used in most of studies is ambiguous. Thus, this study aims to review the measurement setup of different near infrared spectroscopic (NIRS) acquisition modes with respect to different types of instrumentation and samples, and to classify them systematically. The relationship among different reported acquisition modes was analysed. Different reported acquisition modes were classified based on the position of instruments in acquiring near infrared signals. A detailed analysis is provided to highlight the distinction of different NIRS acquisition modes. The challenges of existing measurement setups have been discussed. Interaction and diffuse reflection are the same because both measure diffuse signals that reflected from the inner parts of a sample. Finding shows that future NIRS investigation should address the concerns that related to the acquisition modes, unwanted signals, and measurement parameters.