Research on the Etalon Effect in Dispersive Hyperspectral VNIR Imagers Using Back-Illuminated CCDs

Abstract

Dispersive hyperspectral visible and near-infrared (VNIR) imagers using back-illuminated (BI) charge-coupled devices (CCDs) suffer from interference fringes in the near-infrared band, known as the etalon effect. This effect causes a signal modulation which can become increasingly serious (±25% or more) when the spectral resolution gets higher than 5 nm, bringing huge difficulties for subsequent processing and quantitative applications of the hyperspectral data. A mathematical model to describe the fringe pattern is established by taking both the system parameters and the interference principle of multilayer thin films into account. Then, the model is used to simulate the distribution of interference fringes as a function of wavelength, and the simulated results are verified with the measured data from a VNIR grating-based hyperspectral imager. It turns out that the model is able to describe the interference fringes accurately. In addition, quantitative analysis of the influence of related factors on interference fringes is carried out, and a single-layer model is introduced for comparison, providing the theoretical foundation for the subsequent correction of interference fringes. This paper provides an important reference for the design and application of dispersive hyperspectral VNIR imagers using BI-CCDs.