This study designed a large aperture infrared diffraction system that utilizes Schupmann's achromatic theory to achieve wavelength tunable high-resolution imaging. The impact of stitching error on imaging quality was analyzed based on geometric optics, and simulation analysis was conducted on stitching error based on wavefront aberration. The results indicate that the system has reached the diffraction limit of imaging quality in the design band, and both wavefront aberration and distortion are within acceptable ranges. Splicing error analysis shows that translation error has a significant impact on imaging quality, while edge mismatch error and tilt error have a smaller impact. This system has the characteristics of lightweight and low cost, and is suitable for various space observation tasks.
A new lightweight infrared multi-spectral camera is developed. The camera is designed for near-space remote sensing. The camera is 13.6kg, and the angle resolution is 0.4mrad. It includes a middle wave (MW) channel (3.7μm~4.8μm) and a long wave (LW) channel (8μm~12μm). The optical system adopts a refract system, a dichroic beam-splitter is utilized to separate LM from MW. The MW/LW channel focus is 62.5mm, and the optical field of view is 14.36°×10.87°. The two channels all have five spectral bands. Filter wheel assemblies are used to split the in-coming MW and LW radiant flux into 5 spectral bands. The detectors of the two channel all have 640×512 pixels, and the pixel size is 25μm. The working temperature of MW detector is 80K, and LW detector is 60K. The two channels could image simultaneously. This camera has been tested in the low temperature and low pressure environmental test chambers. It also passes the random vibration tests. The camera has got 5 flights missions, and each mission is about 3~4 hours. Lots of good quality images are obtained during the flying missions.
Ocean remote sensing satellites have the advantages of long-distance, non-contact observation with large field of view, all-day, all-weather and real-time imaging, and have become an important means of global marine environment monitoring. The development of marine remote sensing in my country is going through a leap from "following" - "running side by side" - "leading". Quantitative application is the characteristic of marine satellite data application. In order to obtain the corresponding relationship between the input radiation and output of the remote sensing camera, and use it for quantitative inversion of the radiation information of the remote sensing target, the radiation calibration of the remote sensing camera is required. In this paper, starting from the high quantitative calibration index requirements of the new generation of ocean water color and water temperature scanner payload, a set of on-board radiation calibration device is designed and developed to realize the full spectrum, full aperture and full optical path high-precision calibration of the payload. The accuracy of the on-board radiation calibration device: the black body emissivity is 0.98, the measurement and temperature control accuracy is better than 0.05K, the temperature stability is better than 0.05K/30min, and the temperature uniformity is better than 0.2K.
The infrared multi-spectral camera on near-space vehicle had the characteristics of high spatial resolution, high time resolution. A new dual-channel infrared multi-spectral remote sensing camera was developed. It included a middle wave (MW) channel (3.7μm~4.8μm) and a long wave (LW) channel (8μμm~12.5μm). The optical system adopted a refract system, a dichroic beam-splitter was utilized to separate LM form MW. The MW and LW channel all had five spectral bands , and filter wheel assemblies were used to split the in-coming MW and LW radiant flux into 5 spectral bands. The optical system aperture was 45mm, and the focal of the two infrared channels were 62.5m. The full field modulation transfer function (MTF) of MW channel was over 0.67, and the MTF of LW was over 0.329. The focal of MW and LW channel had 640×512 pixels, and the pixel size was 25μm. Because of the high integrated design, the total weight of the camera was 18.5kg. The camera would be used to monitor the fire and the forest fires and marine pollution on a airship.
KEYWORDS: Black bodies, Body temperature, Calibration, Temperature metrology, Resistance, Control systems, Satellites, Platinum, Infrared radiation, Cameras
This article elaborates on the working principle of the on-board blackbody calibration system, through the high-performance design and accurate index accuracy of the key indicators of high and low large-aperture surface blackbody (effective emission surface normal emissivity, temperature stability, temperature uniformity) Effective control, so as to obtain high and low temperature blackbody normal emissivity 0.98, temperature stability ≤ ± 0.15K/30min, temperature uniformity ±0.25K high-performance calibration indicators. By adding different thermal control measures to the high temperature black body and the low temperature black body, the temperature stability of the working temperature control interval required by each can be obtained. Among them, the temperature of the high-temperature black body is realized by applying a heat sheet with a reasonable cloth, while the temperature of the low-temperature black body is lower than the ambient temperature in the camera, and the temperature compensation is realized by installing a heat sink in the cold space, and then attaching the heating sheet to the heat pipe. For both high temperature blackbody and low temperature blackbody, precision platinum resistance thermometers are used to accurately monitor their temperature in real time. By reasonably arranging the position of the platinum resistance and the platinum resistance test line, the blackbody temperature measurement accuracy can be controlled within ±0.05°C. In the end, the high-stability large-aperture blackbody calibration system through the comprehensive work of various structural components, thermal control components and the main optical system to obtain the high-precision infrared temperature calibration requirements required by the load, which provides for subsequent model development. Successful engineering experience.
Because of the high specific stiffness, the excellent thermal conductivity and thermal stability, silicon carbide (SiC) material is widely used as the material of optical reflecting mirror. The hardness of SiC is 22.2±2.2 GPa. It is difficult to be machined. A new robot flexible-belt grinding system was developed. It consists of a robot grinding system, a stress monitoring system and a clamping platform. The robot has a 6-axis manipulator. The robotic arm maximum travel range is more than 3m. Several grinding experiments were carried out, and the optimum grinding parameters for SiC were obtained. The line speed of flexible-belt is 10m/s, the feeding speed of the robot is 5mm/s. A Φ1.55m SiC mirror was grinded, and the entire processing cycle is 40 days. The processing efficiency is increased by 90%. After the polishing and coating process, the mirror surface was measured by a interferometer. The surface root mean square(RMS) is 0.0157 λ(λ=632.8nm).
Liquid crystal tunable filter utilizes the electrically controlled birefringence effect of liquid crystal material to achieve rapid tuning of the central wavelength of the transmission spectrum. In this paper, we propose a fan Solc liquid crystal tunable filter with 8-stage structure, and the thickness of the nematic liquid crystal material in each liquid crystal cell is 3 μm. We compile a program according to Jones matrix calculation method to simulate and analyze the 8-stage Solc liquid crystal tunable filter. It can be clearly derived from the simulation results that this liquid crystal tunable filter can freely tune the center wavelength of the transmitted light in the spectral range of 400 nm to 800 nm. When the transmission peaks of the liquid crystal tunable filter are at 450 nm, 540 nm, 630 nm, and 750 nm, the full width at half maximum of the transmission spectrum are 45 nm, 54 nm, 63 nm, and 75 nm, respectively. What’s more, when the thickness of the liquid crystal material decreases from 10 μm to 6μm, the free spectral range of the 8-stage Solc liquid crystal tunable filter increases. We also performed a simulation experiment on 4, 8, 12 and 16-stage fan Solc liquid crystal tunable filters.The thickness of the liquid crystal material in these Solc-type liquid crystal tunable filters is still 3 μm. As the the number of stages of liquid crystal tunable filters increases, the full width at half maximum decreases gradually and is approximately inversely proportional.
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