Measurement and Analysis of Papers, Inks, and Lamination Films Using Fourier-Transform Near-Infrared Hyperspectral Imaging System
摘要
Visible and near-infrared hyperspectral imaging (HSI) has become instrumental in document examination, enabling authentication, tampering detection, and visualisation of obscured or faded samples. Utilising Si-CCD and Si-CMOS detectors operating in the 0.4–1.0 µm wavelength range, relatively inexpensive HSI systems can be constructed. On the other hand, longer-wavelength light detection requires detectors such as those made of InGaAs. In addition, HSI systems paired with spectrometers have been developed and commercialised. We adopt a near-infrared HSI system capable of detecting wavelengths from 1.0 to 2.35 µm to assess the spectral properties of various materials, including different types of paper, oil inks, and plastic cards. We evaluate the system capability to capture information that cannot be detected using conventional HSI operating in the 0.4–1.0 µm wavelength range. HSI systems are often equipped with dispersive or Fourier-transform spectrometers, each offering distinct advantages. The Fourier-transform spectrometer achieves superior light throughput compared with its dispersive counterpart, possibly increasing the instruments sensitivity for a given detector. Hence, we present measurement results obtained using a Fourier-transform HSI system.