With the development of optoelectronic imaging technology, remote sensing optical system gradually develops towards super large imaging field of view in order to obtain target characteristic information in a wider space. Concentric multiscale system is a new type of large field of view optical system. At present, most of the schemes studied are multiscale system based on concentric spherical lens. Due to the limitation of optical materials, this optical system is generally only used in visible and near infrared optical bands, and is difficult to be applied in long-wave infrared band. Starting from the structure principle of concentric multi-scale system and considering the application of long-wave infrared band, this paper proposes to use spherical reflector instead of concentric spherical lens to construct a retracted multi-scale system based on spherical reflector. The system can achieve all the features of multi-scale system and can be applied in the infrared band. According to the construction principle of the system and the design idea of off-axis deviation field, a multi-scale system based on spherical reflector is designed. The main parameters of the single channel of the system are: the focal length is 72mm, the system F#=2, the working band is 8-12um, and the imaging field of view is 20°×0.1°. The imaging quality of the system is close to the diffraction limit in the full field of view, and the distortion of the full field of view is less than 5%. The circular field of view imaging of 360°×0.1° can be achieved by extending the spherical reflector and multi-channel splicing.
Nanosatellites usually refer to satellites with mass less than 10 kg and practical functions. With the development of high and new technology and the promotion of demand, nanosatellites play an important role in scientific research, national defense, commercial and other fields with the advantages of small size, low power consumption, short development cycle, formation networking and low cost to complete many complex space tasks. High resolution remote sensing is one of the important applications of microsatellites, because of its small size, it requires more for optical payload. According to the structural form of RC system, this paper presents a compact coaxial four reflection catadioptric system based on the structural form of RC system. The final optical system design results are as follows: the focal length is 192.2mm, the pupil diameter is 136mm (the effective pupil diameter is 105mm), the working band is 500-900nm, the imaging field of view is 4.5°, and the total optical length is 58mm. The analysis shows that the transfer function of the optical system is higher than 0.45 at 100lp / mm, the distortion of the whole market is less than 0.12%, and the relative illuminance of the whole field of view is higher than 96%. It is proved that the optical system has good imaging quality in the full field of view, and the system has good compactness to meet the load requirements of micro nanosatellite.
In order to improve the stability of the secondary mirror mounting structure and reduce the influence of the position change of the secondary mirror on the imaging quality of the camera, the secondary mirror support structure was studied. Aiming at the problems of traditional secondary mirror support, a new type of secondary mirror bracket is proposed in this paper. The finite element analysis results show that under the same obstruction ratio, the torsional stiffness, the stiffness along the optical axis and the thermodynamic properties of the new secondary mirror bracket are similar to the secondary mirror traditional support structure, but the weight of the new s bracket is only 15.2% of the traditional support structure. The new bracket solves the shortcomings of the traditional secondary mirror support structure, such as high cost, long period and heavy weight, and is easy to assemble. It has been successfully applied in the all-day star orientation instrument.
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