In this paper, the generation mechanism of stray light is analyzed for a visible and near infrared imaging spectrometer with a spectral range of 400nm to 900nm. The optical mechanical model of the instrument was established and its stray light level was simulated. Based on the notch method, A stray light measuring device is built. The veiling glare index of the imaging spectrometer is measured to be 0.84%. The uncertainty of measurement is assessed by GUM method, and the influence of uncertainty components on the measurement results is analyzed. When the confidence probability of the measuring device is 95.45%, the measurement uncertainty of veiling glare index is 0.15%. Finally, a comparison and analysis are made between the simulated values of the veiling glare index and the actual measured values. This work provides technical support for the development of high resolution imaging spectrometer.
The grating imaging spectrometer has the characteristics of good linearity, wide dispersion range and is widely used in the field of remote sensing. Distortions (including smile and keystone) are one of the important parameters of the grating imaging spectrometer, which directly affects the quality of the image and spectral information obtained by the imaging spectrometer. In order to get the requirements of two kinds of distortions in the design process of the grating imaging spectrometer, the effect of the smile and keystone on the target detection is simulated and analyzed respectively. Based on the spectral response function with the Gaussian, the change of the spectral signal acquired by the grating imaging spectrometer with the amount of the different smile is calculated by combining with the spectral data of the atmospheric in the visible and near-infrared (0.4~1μm). The results show that the amount of smile should be no more than 1nm, 0.6nm and 0.2nm respectively when the spectral resolutions of the imaging spectrometer are 20nm, 10nm and 5nm. With the assumption that the spatial response function is the rectangle function, the effect of the different keystone on spectral signal acquisition of the imaging spectrometer is simulated by using the hyperspectral data. The results indicate that the offset of the keystone should be controlled within 0.04d (d is the pixel width).
A measurement system for diffraction efficiency of convex gratings is designed. The measurement system mainly
includes four components as a light source, a front system, a dispersing system that contains a convex grating, and a
detector. Based on the definition and measuring principle of diffraction efficiency, the optical scheme of the
measurement system is analyzed and the design result is given. Then, in order to validate the feasibility of the designed
system, the measurement system is set up and the diffraction efficiency of a convex grating with the aperture of 35 mm,
the curvature-radius of 72mm, the blazed angle of 6.4°, the grating period of 2.5μm and the working waveband of
400nm-900nm is tested. Based on GUM (Guide to the Expression of Uncertainty in Measurement), the uncertainties
in the measuring results are evaluated. The measured diffraction efficiency data are compared to the theoretical ones,
which are calculated based on the grating groove parameters got by an atomic force microscope and Rigorous Couple
Wave Analysis, and the reliability of the measurement system is illustrated. Finally, the measurement performance of the
system is analyzed and tested. The results show that, the testing accuracy, the testing stability and the testing
repeatability are 2.5%, 0.085% and 3.5% , respectively.