Mars surface composition detector (MarSCoDe) is a scientific instrument suite onboard the Mars rover of the “Tianwen-1” mission, which uses laser-induced breakdown spectroscopy and shortwave infrared spectroscopy to detect the composition of soils and rocks at the surface of Mars. The optical head unit (OHU) is the core hardware of MarSCoDe, containing a Cassegrain telescope and other optical modules for lasers generation and signals transmission. The unit lacks thermal control resources and is located outside the rover’s cabin, which will directly face the Martian surface drastic temperature changes. We introduce the optomechanical designs that realize the lightweight and high thermal stability of the OHU optical system, especially the designs and implementations of the semiopen primary mirror based on silicon carbide and the fully closed optical bench based on carbon fiber-reinforced polymer. Meanwhile, the advantages and difficulties of silicon carbide, long carbon fiber-reinforced silicon carbide composites, and carbon fiber-reinforced polymer materials used for small and compact optomechanical systems are discussed. Subsequently, the environmental adaptability of the telescope system of OHU was studied through analytical and experimental methods, which show that it can achieve the required optical performance over a temperature range of approximately 100°C.
Coupling of scattering light in space into a single-mode fiber is a key technology in the process of developing the Laser Doppler Velocity Radar. In order to make sure that the radar can get the longest detect distance, we have discussed the method of determining the key parameters of the receiver/transmitter common-path optical system based on the singlemode fiber coupling, from the points of laser radar detect distance equation, principle of single-mode fiber coupling efficiency reach maximum, and considerations of laser transmitter. In the engineering development process of an laser Doppler velocity radar, we have designed the optical system which fulfills the requirement of detect distance bigger than 3Km, then given out simulation results of single-mode fiber coupling efficiency versus lens spherical aberration, fiber defocus and fiber tilt. The tolerance analysis result indicates that the coupling efficiency will bigger than 52% under the usual levels of optical manufacture and assembly. At last we designed specialized equipment for testing the single-mode fiber coupling efficiency of the system we developed, the results showed that after mechanical vibration and thermal experiments, the single-mode coupling efficiency is 55.9%, and in the operating temperature range of 20±3°C, the lowest coupling efficiency is 45%, which is still bigger than 35% as the system required to make sure the detect distance bigger than 3Km.
We design a kind of imaging LiDAR with sixteen channels, which consists of a fiber laser source, dual scanning galvanometers, range measurement circuits and information processing circuits etc. The image LiDAR provides sixteen range measurements for one laser shot and the distance accuracy of each channel is about 4cm. This paper provides a calibrate method to correct point cloud images captured with the multi-channel LiDAR. The method needs to construct different slanted planes to cover the imaging field, and establish precise plane equations in the known ground coordinates, then fit planes with point clouds data and calculate correction parameters of all channels through the error model. The image accuracy is better than 5cm processed by this calibration method.
Our group designed a thermal IR hyper-spectral imaging system in this paper mounted in a vacuum encapsulated cavity
with temperature controlling equipments. The spectral resolution is 80 nm; the spatial resolution is 1.0 mrad; the spectral
channels are 32. By comparing and verifying the theoretical simulated calculation and experimental results for this
system, we obtained the precise relationship between the temperature and background irradiation of optical and
mechanical structures, and found the most significant components in the optic path for improving imaging quality that
should be traded especially, also we had a conclusion that it should cool the imaging optics and structures to about 100K
if we need utilize the full dynamic range and capture high quality of imagery.
This paper introduces a skill but practical optical model of developing wide field of view push-broom hyperspectral
imager. Usually, the field of view of a push-broom hyperspectral imaging sensor is less than 30 degrees, and it can not
meet the requirement for typical earth observation mission. This paper addresses the difficulty of developing wide field
of view imaging sensor and presents an optical model of wide field of view hyperspectal imager. The optical model of
hyperspectral imager is composed of a large field of view lens, a long entrance slit, two spectrometers and two area
detector arrays and has a cross-track field of view of 60 degrees. The lens images a ground belt onto the long entrance
slit, the slit acts as a field stop and allow only light from a linear belt in the scene to enter the imager. The light passing
through the long slit is divided two equal parts using a special skill and it is separated and imaged on the area detector
arrays by the two spectrometer. The analysis shows that the wide field of view hyperspectral imager doesn't drop down
the spatial resolution.
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