According to the need of high resolution and VIS/IR composite image, the task requirements and the necessity of spectrum selection were given. based on the analysis of the imaging mode, the design route of VIS/IR composite imaging using off-axis linear field of optical system is determined. According to the aberration auto-balance optimization of optical design software, the two channel aberrations were initially balanced. The aspheric surfaces were introduced to correct residual aberration, and the compact requirement of the composite optical system is realized. An example of the design was given, The technical indicators: The VIS channel optical system focal length is 7800mm,F number is 11.73,field of view is 2.2°×0.2°,the operating wave band is 400~900nm, the modulation transfer function of the pan-spectral is above 0.30 all over the field of view at the Nyquist frequency of 71.4lp/mm, the modulation transfer function of the multi-spectral is above 0.80 all over the field of view at the Nyquist frequency of 18lp/mm. The IR channel optical system focal length is 2500mm,F number is 3.76,field of view is 3°×0.2°,the operating wave band is 3~5μm, the modulation transfer function of the system is above 0.32 all over the field of view at the Nyquist frequency of 33lp/mm. The system can achieved the resolution 0.45m/3m at 500km orbital altitude.
Compared with conventional optical satellites, ZY-3(03) has its outstanding advantage in the combination of camera stereo observation and laser altimeter to directly obtain elevation control points, which can provide high-precision data for real three-dimensional China construction, geographic national conditions monitoring, farmland protection, geological disaster prevention, etc. In order to meet the demand of laser altimeter that the divergence angle is less than 0.1mrad, a laser beam expanding system is developed. The optical system with Galileo structure is composed of a negative lens group and a positive lens. Through the adjustment of the lens spacing and centering adjustment, the installation and adjustment of the beam expanding system under normal pressure is completed, and the wave-front error, defocusing and magnification are tested. In order to meet the conditions of vacuum use, vacuum presets are performed by adjusting the spacing between the front and rear lens groups. The vacuum divergence test of the transmitting system is carried out together with the laser. The measured divergence angle of the transmitting system is 0.084mrad, which meet the system design requirements. Subsequently, a mechanical environment test and a thermal vacuum environment test are carried out. The divergence angles before and after the tests, during the high and low temperature conditions are stable and are all less than 0.1mrad.
Aiming at the characteristics of the large format aerial measuring camera with larger field, lower distortion and telecentric beam path, a new optical system with field of 75° and lower distortion was designed in this paper. The optical system selects inverted telephoto as the initial structure instead of symmetric structure. The optical system is all sphere and has the advantages of compactness ,long back working distance and easy to fabrication and alignment. The result shows that the focal length is 135mm,with the relative aperture of 5.2 and the field of 75°,meanwhile , the modulation transfer function(MTF)is higher than 0.3 at the 100lp/mm,the distortion is lower than 0.01%,the biggest angle of incidence on image surface is smaller than 20°. This optical system can be used for the large format aerial measuring camera.
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