The Navigation and Terrain Camera of Tianwen-1 Mars Rover is mainly used for the guidance, navigation and control of the Mars rover, and it will also be used for scientific research works.Due to the complexity of the working environment of the Mars rover, its optical imaging system is easily affected by stray light, which forms stray light radiation on the image plane, thus reducing the imaging quality and affecting the accuracy of navigation. In this paper, the variation of irradiance of image plane with incident angle in camera field of view is studied, and the irradiance distribution of each lens surface is compared and analyzed. Combined with the principle of bidirectional reflectance distribution function (BRDF), the reason of irradiance variation law is analyzed. Referring to the results of the irradiance distribution analysis, it can avoid the influence of the stray light in the specific direction on the normal imaging of the camera in the actual detection process. The imaging quality and aberration of the optical system are analyzed and evaluated by combining the spot diagram, MTF curve and Seidel coefficient, and the results meet the needs of practical application. Then the imaging quality change of the optical system in the range of -110℃~60℃ are analyzed. Finally, the tolerance of the whole system is analyzed.
Performances of a novel solar extreme ultraviolet (EUV) slitless imaging spectrometer in a stigmatic design are presented with an aberration-correcting flat-field holographic concave grating (HCG). The instrument is based on a conventional off-axis Maksutov telescope with aberration-corrected holographic rulings on the secondary optic. These rulings with varied line-space enable stigmatic imaging in diffracted light with a minimum number of optical elements, thereby maintaining a high system efficiency. The novel design has improved temporal resolution prominently by throwing away the slit and no scanning, either spatially or spectrally, permitting EUV spectroscopy with a high time cadence in observation of the full solar disk. In this approach all data are taken simultaneously over the whole field of view, and hence no confusion of temporal evolution with spatial or spectral variation. ZEMAX software is used to obtain the final parameters of spectrometer through global optimization and multiple configuration. The slitless imaging spectrometer possesses imaging detectors at three orders of flat-field HCG, which provides cotemporal imaging and spectroscopy with high spatial resolving element (1.8arcsec/pixel) and spectral resolving element (60mÅ/pixel) for a narrowband at 304 Å and a wide field of view (36arcmin). The performance of the resulting optical design are evaluated, and the imaging quality obtained here is excellent which can be inferred from the root-mean-square spot diagram.
It has been challenging for medium wave infrared (MWIR) optical imaging system to work in a large temperature range and stationary effective focal length, on account of the thermal effect of optical elements and machinery. Performances of a MWIR space remote sensor in an advanced passive thermal-free design are presented with a fronting R-C system and a rear spherical lens group. A general analytical expression for eliminating thermal defocus and chromatic aberration is obtained, and it is demonstrated that these defocus and aberrations are minimized when this MWIR space remote sensor is operated at a broadband (3um to 5um) and large temperature range (-40°C to 40°C). The ZEMAX software is used to obtain the final parameters of space remote sensor by global optimization, which realize 100% cold shield efficiency. The MWIR space remote sensor has a focal length of 2150mm, F number of 3.58, full field of view of angle of 0.4°×0.4°and pixel size of 15μm. This optical system provides a high ground sample distance (GSD) of 251m and wide single landscape width (SLW) of 251km×251km in geosynchronous orbit. The imaging quality of the space optical remote sensor is almost diffraction limited which can be inferred from metrics such as root-mean-square spot diagram, MTF, wavefront function etc.
In the field of space optical, the application of advanced optical instruments for related target detection and identification has become an advanced technology in modern optics. In order to complete the task of search in wide field of view and detailed investigation in small field of view, it is inevitable to use the structure of the zoom system to achieve a better observation for important targets. The innovation of this paper lies in using the zoom optical system in space detection, which achieve firstly military needs of searched target in the large field of view and recognized target in the small field of view. At the same time, this paper also completes firstly the design of variable focus optical detection system in the range of hemisphere space, the zoom optical system is working in the range of visible and infrared wavelengths, the perspective angle reaches 360 ° and the zoom ratio of the visible system is up to 15. The visible system has a zoom range of 60~900 mm, a detection band of 0.48~0.70μm, and a F-number of 2.0 to 5.0. The infrared system has a zoom range of 150 ~ 900mm, a detection band of 8~12μm, and a F-number of 1.2 to 3.0. The MTF of the visible zoom system is above 0.4 at spatial frequency of 45 lp / mm, and the infrared zoom system is above 0.4 at spatial frequency of 11 lp / mm. The design results show that the system has a good image quality.
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