Two-dimensional synchronous stray light detection and correction method for imaging spectrometers

Stray light is primarily induced by internal reflections and scattering from off-axis radiation, surface scratches or particulate contamination on optical elements, and imperfections in diffraction gratings. It produces nonphysical distortions in measured spectra and radiometric quantities and is therefore a major contributor to the measurement uncertainty of imaging spectrometers. Because an imaging spectrometer simultaneously records two-dimensional responses, namely the spectral and spatial dimensions, both dimensions should be characterized and corrected in a consistent manner. In current practice, however, spectral domain and spatial domain stray light are often measured and corrected separately using different instruments and methodologies. This not only increases experimental complexity and testing workload, but more critically, the two calibrations are frequently performed using different targets and different radiance levels. The resulting mismatch in response magnitude between the spectral and spatial domains can undermine the accuracy and physical validity of the derived two-dimensional correction coefficients. To address this issue, this study proposes a two-dimensional synchronous stray light detection and joint correction method for imaging spectrometers and develops a dedicated synchronous measurement platform. Under a single experimental configuration, the same target is measured at the same response level to acquire both spectral and spatial stray light responses. A two-dimensional stray light correction matrix is then constructed and applied for pixel level joint correction. In parallel, optical mechanical stray light simulations are performed using a stray light analysis tool to verify the consistency of the underlying mechanisms and to cross-validate the experimental results. The measurements yield stray light coefficients of 0.02% in the spectral dimension and 0.05% in the spatial dimension, and the spatial domain result is consistent in order of magnitude with the two-dimensional simulation outcome of 0.013%, demonstrating the effectiveness of the proposed synchronous detection approach. After applying the spatial domain correction, the stray light coefficient is reduced to 0.012%, representing an improvement by a factor of 4.5 compared with the pre-correction level, which further confirms the effectiveness of the proposed two-dimensional synchronous stray light correction method.