High performance infrared lens used in aerospace optical remote sensing systems have great benefit in resource exploration, pollution monitoring etc. However the high technical threshold of manufacture, the production and launch cost due to the heavy infrared optical materials, and the long period of alignment have restricted its use especially for civil and commercial aerospace. Here we present a realization of aerospace infrared lens for mass production. An unique opto-mechanical structure design has been implemented in order to meet the requirements of the mass production of space infrared lens. Some high effective, low cost processing technology are used both for optical and mechanical parts. The produced lenses have the biggest diameter of 300mm and the best RMS of λ/50(λ=632.8nm). A smart alignment based on an online device with lens alignment and image quality measurement reduces the period from 30 days to 7 days. With the well assembled infrared lens, the space camera has a system wavefront of 0.1λRMS (λ=3.39μm) and the MTF of 0.38(@25lp/mm).
In order to realize the observation ability of a space camera with the field of view angle greater than 120 degrees and the imaging spectrum covering 350nm~ 12500nm, the design and verification of a scanning system with large field of view and multichannel were carried out. Firstly, according to the performance indicators of the camera, the structure form of the overall scanning and imaging system was determined. Two motors were used to drive the telescope system and the half-angle mirror to rotate in the same phase respectively, and by imaging with four refractive relay optical systems in different spectral bands, the camera could achieve a wide field of view imaging covering the ultraviolet to long wavelength infrared spectral range. Secondly, based on the scanning form, the optical parameters and the system structure were designed in detail. Finally, the system was alignment, and the performance of the system were measured in experiment. The wavefront aberration of each field of view in the telescope system was better than 0.047λ (λ= 632.8nm). The scan following accuracy of the half-angle mirror was better than 10″, with a deviation of 0.01mm from the scanning axis position of the telescope system. All field of view MTFavg of the four channels were better than 0.42, meeting the indicator requirements. The results show that the design of this scanning system with large field of view and multichannel is reasonable and feasible, and has important reference value for the development of related systems.
The extraction of polarization features is the key to the further application of remote sensors. For conventional remote sensing, the evaluation method of polarization characteristics is polarization sensitivity, which needs to be obtained through polarization testing. For polarization remote sensing, it is necessary to obtain the polarization characteristics of the instrument through polarization calibration. Polarization correction requires not only the measurement of the polarization characteristics of the target, but also the calibration of the polarization characteristics of the instrument, and the ultimate goal is to eliminate the polarization response of the instrument. Therefore, it is necessary to carry out research on polarization feature extraction and correction technology. This paper mainly discusses the difficulties and technical approaches of current polarization feature extraction and correction, analyzes the key technologies and related progress, and provides important reference value for further improving the quantitative acquisition of target information.
To realize the fast, high-quality alignment of off-axis reflective system, a computer-aided alignment method based on high-precision extraction of optical axis and high- precision restoration of surface shape of off-axis mirror was proposed. The optical axes of the mirrors are derived by means of a zero-position compensation detection path of the off-axis mirrors, and accuracy is better than 6", realize more rapid and accurate system initial alignment. There propose a surface shape data conversion algorithm, combined with Code V, it can realize the high-precision restoration of measured surface shape data of off-axis mirror in simulation, accurately calculate and separate the influence of shape error and position misalignment on system quality, and realize the fast and high precision alignment of off-axis reflective system. This method is applied to the practical alignment of one off-axis TMA system, wave aberration RMS≤0.084λ(λ=632.8nm) after initial alignment of the system. After only once calculation and alignment, full field RMS≤0.055λ. The experiment results demonstrate that this method is feasible.
In the field of aerospace remote sensing, the errors of optical element surface shape and position misalignment are often mixed together in the off-axis reflection system, which directly affects the accuracy of simulation analysis of computer aided alignment , and reduces the quality and efficiency of the optical system alignment. In order to solve this problem, there propose a surface shape data conversion algorithm, which can convert and process the surface shape data of optical elements. Combined with Code V, we can calculate and remove the influence of the surface shape error on the image quality of the system, and achieve optical alignment of off-axis reflection system fast with high precision. Verified analysis, the accuracy of this algorithm is higher than the traditional inversion Zernike polynomial fitting method, and reduction accuracy is better than 90%. In addition, the surface shape data conversion algorithm can also achieve restore of non-circular optical elements (such as ellipse, rectangle, shading and other arbitrary shapes) in the optical simulation software with high precision, which can provide more accurate results for optical system with high precision and rapid.
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