Research On Opticalal Systeme Of Large Aperture Spaceborne Spectrometer

Since its birth,spaceborne imaging spectrometer has been widely used in agriculture,military,marine monitoring and other fields.At the same time,it puts forward higher requirements for its optical system,such as large field of view,large aperture,multi-channel,light and miniaturization.Among them,the reflective optical system is easy to achieve light and miniaturization,large aperture.Therefore,the spaceborne imaging spectrometer has been widely concerned in the optical system.Combined with the urgent needs of the development of optical system of spaceborne imaging spectrometer,the following research is carried out in this paper:(1)The basic theory of optical system of large aperture spaceborne imaging spectrometer is studied,and the overall scheme of the system is proposed.In order to meet the requirements of large field of view and high resolution,the off-axis three mirror system is used as the remote module of the spectrometer.When the spectrograph is divided by grating or prism,the system is difficult to achieve miniaturization and has high energy loss.Therefore,the spectroscopic system of the spectrometer adopts the scheme of first field of view and then narrow band color splitter.(2)Aiming at the problem of light occlusion in the process of off-axis system optimization,an optimization method of eliminating occlusion is proposed.Considering the task requirements of the satellite platform for the miniaturization of the optical system,an optimization method of miniaturization is proposed.According to the above two methods,a macro language program is written,and an exit pupil size of 643 mm based on off-axis three mirror structure is designed by using the macro language program.The optical system of spaceborne imaging spectrometer,which has four channels,no occlusion,envelope volume of 99 mm × 260 mm × 433.155 mm in X × Y× Z direction,the optical transmission coefficients of each channel of the system are greater than 0.3.(3)Because the system has the characteristics of multi-channel and common optical elements,and each channel has different sensitivity to the tolerance of common optical elements,the tolerance analysis scheme of the system is put forward,which is as follows: the most sensitive channel to the tolerance of common optical elements in the system is firstly analyzed,and the tolerance values of common optical elements are the same when the other channels are analyzed.The tolerance of each channel of the system is analyzed by using the above scheme,and the tolerance range which can meet the system performance index is given,so as to provide some guidance for the system installation and adjustment.(4)Zygo,4D interferometer and compensator are used to detect the surface of each optical element in the system.According to the structural characteristics of aspherical surface in the off-axis system and the angle between the optical axis of the optical element,a scheme of adjusting the off-axis system with compensation positioning tooling is proposed.By using the above scheme and related instruments,the prototype of the spaceborne imaging spectrometer was installed and tested.The test results show that: in the full field of view of13.4°× 5°,the RMS value of each field of view is less than 0.1723λ,the PV value is less than 0.8984λ,the weight of the whole machine is only 14.428 kg,and the actual imaging quality of each channel is excellent.