This paper reports an advanced Czerny-Turner optical structure which is used for the application in imaging spectrometers. To obtain the excellent imaging quality, a cylindrical lens with a wedge angle is used between the focusing mirror and the imaging plane to remove astigmatism in broadband. It makes the advanced optical system presents high resolution over the full bandwidth and decreases the cost. An example of the imaging spectrometer in the waveband of 260nm~520nm has been designed to prove our theory. It yields the excellent modulation transfer functions (MTF) of all fields of view which are more than 0.75 over the broadband under the required Nyquist frequency (20lp/mm).
Remote sensing instrument must be calibrated the optics reflectance of the instrument in vacuum conditions before lauched. To obtain the spectral reflectivity of less than 200 millimeter diameter optical element in vacuum, the reflectance of test system is constructed. The reflectivity of the test system is consisted of a light source, the Seya-Namioka vacuum visible monochromator, the sample room as the main structural and electronic system components. It describes how the optical systems and electronic are designed. The monochromator worked band is from 400nm to 780nm, spectral resolution is 0.5nm. Dual optical compensation method is used to eliminate the source of time drift, improve the measurement accuracy with phase-locked weak signal amplification method. The system used a lock-in amplifier according to the technique using the principle of coherent detection of the modulated optical signal which is multiplied with the reference signal processed, by using the optical integrator the signal will be smoothed sended to A / D converter. To ensure the precision measurement deteced, the phase-sensitive detector function can be adjustable. The output value is not more than 10mV before each measurement, so it can be ensured that the stability of the measured radiation spectrum is less than 1 percent. The reflectivity of the test system results is shown that the wavelength accuracy is 0.1nm, and the wavelength repeatability is 0.05nm, it can achievehigh-precision measurement of optical components under vacuum body.
A near-far ultraviolet imaging spectrometer with high resolution is developed，which can be applied to the upper atmosphere observation in 115nm-295nm. The application demands of the corresponding remote sensing are analyzed. Because the imaging spectrum technology has been rarely utilized for the ionosphere observation in our country, we study some foreign advanced loads to apply the standard to our design. According to the analysis, the optical system of the imaging spectrometer is designed. The system includes an off-axis parabolic mirror as the telescope and Czerny-Turner structure as the imaging spectrum system. The photon counting detector is adopted to satisfy the observation for that the radiation is weak in near-far ultraviolet waveband. The receiving surface of the detector should be coated by different photocathode for better quantum efficiency in the near and far ultraviolet wavebands. The traditional Czerny-Turner system is not suit for the broadband imaging spectrometer because aberrations in the structure can’t be corrected homogeneously. The geometric analysis and 1st order differential calculation method are introduced to improve disadvantages based on the aberration theory. We designed an example for the advanced imaging spectrometer. The results demonstrate that the modulation transfer function (MTF) in total field of view and the waveband is more than 0.6. The design has high spatial resolution and high spectral resolution. It certificates that the design theory can be applied to the near-far ultraviolet imaging spectrometer especial for upper atmosphere observation.