摘要 :
Integrity performance is a confidence level which reflects the correctness of navigation information. The positioning accuracy and availability would be improved when user combines the GPS navigation information with that of Galil...
展开
Integrity performance is a confidence level which reflects the correctness of navigation information. The positioning accuracy and availability would be improved when user combines the GPS navigation information with that of Galileo and COMPASS systems. For local users, it is important to make full use of the whole integrity information of the three constellations. Based on the analysis of critical characters of multi-constellation navigation satellite system, considering the critical parameters of RAIM algorithm, missed detection probability is given using the information of satellite failure probability, missed detection probability and integrity risk, horizontal protection level (HPL) and vertical protection level (VPL) are analyzed both in theory and mathematical simulation. Results show that the receiver autonomous integrity monitoring performance based on multi-constellation navigation satellite system is much better than that based on a single constellation system. Both the missed detection probability and protection levels are improved. The availability of RAIM algorithm is enhanced.
收起
摘要 :
Integrity performance is a confidence level which reflects the correctness of navigation information. The positioning accuracy and availability would be improved when user combines the GPS navigation information with that of Galil...
展开
Integrity performance is a confidence level which reflects the correctness of navigation information. The positioning accuracy and availability would be improved when user combines the GPS navigation information with that of Galileo and COMPASS systems. For local users, it is important to make full use of the whole integrity information of the three constellations. Based on the analysis of critical characters of multi-constellation navigation satellite system, considering the critical parameters of RAIM algorithm, missed detection probability is given using the information of satellite failure probability, missed detection probability and integrity risk, horizontal protection level (HPL) and vertical protection level (VPL) are analyzed both in theory and mathematical simulation. Results show that the receiver autonomous integrity monitoring performance based on multi-constellation navigation satellite system is much better than that based on a single constellation system. Both the missed detection probability and protection levels are improved. The availability of RAIM algorithm is enhanced.
收起
摘要 :
Wavefront coding is a technology which combination of the optical design and digital image processing. By inserting a phase mask closed to the pupil plane of the continuous zoom optical system, the wavefront of the system is re-mo...
展开
Wavefront coding is a technology which combination of the optical design and digital image processing. By inserting a phase mask closed to the pupil plane of the continuous zoom optical system, the wavefront of the system is re-modulated. And the depth of focus is extended consequently. In reality the idea is same as the athermalization theory of infrared optical system. In this paper, an uncooled infrared continuous zoom optical system with effective focal as 38mm- 19mm, F number as 1.2, operating wavelength varying from 8um to 12um was designed. A cubic phase mask was used at the pupil plane to re-modulate the wavefront. Then the performance of the infrared continuous zoom system was simulated with CODEV as the environment temperature varying from -40 ℃ to 60 ℃. MTF curve of the optical system with phase mask are compared with the traditional before using phase mask. Decode the image of the coding system, and the result show that wavefront coding technology can make the system not sensitive to thermal defocus, and then realize the athermal design of the infrared optical system.
收起
摘要 :
The dual-camera coded aperture snapshot spectral imager(DC-CASSI) includes the coded aperture snapshot spectral imager(CASSI) and panchromatic imager. CASSI can obtain the three-dimensional spectral image information of the target...
展开
The dual-camera coded aperture snapshot spectral imager(DC-CASSI) includes the coded aperture snapshot spectral imager(CASSI) and panchromatic imager. CASSI can obtain the three-dimensional spectral image information of the target in a single coding within a single integral time, but it is difficult to achieve high-quality reconstruction of spectral image in a single coding. Therefore, the panchromatic image acquired by the panchromatic imager should be fused with it to obtain high-quality multispectral reconstruction images. Based on the imaging characteristics of DC-CASSI, a multispectral and panchromatic image fusion algorithm based on Non-subsampled Shearlets Transform (NSST) and improved Pulse Coupled Neural Network(PCNN) is proposed. The fusion experimental results show that compared with other traditional fusion algorithms, the proposed fusion algorithm can be well applied to DC-CASSI and maximum improving the spatial resolution of multispectral coded image while preserving spectral characteristics of the multispectral coded image.
收起
摘要 :
The dual-camera coded aperture snapshot spectral imager(DC-CASSI) includes the coded aperture snapshot spectral imager(CASSI) and panchromatic imager. CASSI can obtain the three-dimensional spectral image information of the target...
展开
The dual-camera coded aperture snapshot spectral imager(DC-CASSI) includes the coded aperture snapshot spectral imager(CASSI) and panchromatic imager. CASSI can obtain the three-dimensional spectral image information of the target in a single coding within a single integral time, but it is difficult to achieve high-quality reconstruction of spectral image in a single coding. Therefore, the panchromatic image acquired by the panchromatic imager should be fused with it to obtain high-quality multispectral reconstruction images. Based on the imaging characteristics of DC-CASSI, a multispectral and panchromatic image fusion algorithm based on Non-subsampled Shearlets Transform (NSST) and improved Pulse Coupled Neural Network(PCNN) is proposed. The fusion experimental results show that compared with other traditional fusion algorithms, the proposed fusion algorithm can be well applied to DC-CASSI and maximum improving the spatial resolution of multispectral coded image while preserving spectral characteristics of the multispectral coded image.
收起
摘要 :
Based on a 640×512 cooled staring focal plane array(FPA) detector, pixel size 15μm×15μm. a long focal length mid-wavelength infrared optical system was designed. In this paper, the working wavelength is 3μm~5μm, the temperat...
展开
Based on a 640×512 cooled staring focal plane array(FPA) detector, pixel size 15μm×15μm. a long focal length mid-wavelength infrared optical system was designed. In this paper, the working wavelength is 3μm~5μm, the temperature range is -30℃～+50℃. this system can realize 1000mm focal length, the F-number is 4, the full field of view is 0.70°. satisfy 100% cold shield efficiency. A re-imaging refractive system was adopted in this designed optical system consists of a main objective group and a projection group. First of all. the structural selection and the initial parameter calculation were introduced. Secondly, on the basis of variety of the temperature, a focusing len was presented in this system to adjust to produce a clear image. Last but not the least, to improve image quality and environment adaptability, the analysis of temperature change and ghost image were described particularly. The design results prove that at the spatial frequency of 33 lp/mm, the axis MTF of the optical system is greater than 0.35, the system can offer a high resolution and excellent images, and it has the advantages of good adaptability, simple structure, easy to adjust, and high transmittance.
收起
摘要 :
Based on a 640x512 cooled staring focal plane array(FPA) detector, pixel size 15μm×15μm, a long focal length mid-wavelength infrared optical system was designed. In this paper, the working wavelength is 3μm ~5μm, the temperat...
展开
Based on a 640x512 cooled staring focal plane array(FPA) detector, pixel size 15μm×15μm, a long focal length mid-wavelength infrared optical system was designed. In this paper, the working wavelength is 3μm ~5μm, the temperature range is -30°C~+50°C, this system can realize 1000mm focal length, the F-number is 4, the full field of view is 0.70°, satisfy 100% cold shield efficiency. A re-imaging refractive system was adopted in this designed optical system consists of a main objective group and a projection group. First of all, the structural selection and the initial parameter calculation were introduced. Secondly, on the basis of variety of the temperature, a focusing len was presented in this system to adjust to produce a clear image. Last but not the least, to improve image quality and environment adaptability, the analysis of temperature change and ghost image were described particularly. The design results prove that at the spatial frequency of 33 lp/mm, the axis MTF of the optical system is greater than 0.35, the system can offer a high resolution and excellent images, and it has the advantages of good adaptability, simple structure, easy to adjust, and high transmittance.
收起
摘要 :
Based on a 640x512 cooled staring focal plane array(FPA) detector, pixel size 15μm×15μm, a long focal length mid-wavelength infrared optical system was designed. In this paper, the working wavelength is 3μm ~5μm, the temperat...
展开
Based on a 640x512 cooled staring focal plane array(FPA) detector, pixel size 15μm×15μm, a long focal length mid-wavelength infrared optical system was designed. In this paper, the working wavelength is 3μm ~5μm, the temperature range is -30°C~+50°C, this system can realize 1000mm focal length, the F-number is 4, the full field of view is 0.70°, satisfy 100% cold shield efficiency. A re-imaging refractive system was adopted in this designed optical system consists of a main objective group and a projection group. First of all, the structural selection and the initial parameter calculation were introduced. Secondly, on the basis of variety of the temperature, a focusing len was presented in this system to adjust to produce a clear image. Last but not the least, to improve image quality and environment adaptability, the analysis of temperature change and ghost image were described particularly. The design results prove that at the spatial frequency of 33 lp/mm, the axis MTF of the optical system is greater than 0.35, the system can offer a high resolution and excellent images, and it has the advantages of good adaptability, simple structure, easy to adjust, and high transmittance.
收起
摘要 :
Binary optics can be used to increase optical performances, decrease size and weight, and decrease systems costs in numerous applications. By means of hybrid diffractive-refractive, a switch-zoom optical system of catadioptric lar...
展开
Binary optics can be used to increase optical performances, decrease size and weight, and decrease systems costs in numerous applications. By means of hybrid diffractive-refractive, a switch-zoom optical system of catadioptric large aperture ground-based photoelectric detection is designed. The characteristic of the system is that it is a compact optical system without moving parts which can get two focal lengths. And the quality of image approaches the diffraction limited. Ritchey-Chretien (R-C) mirror and a field lens are common for long-focus system and short-focus system. Two refract groups transmitting optical system are used for zooming, In order to satisfy the demand of energy regulation, it is designed afocal beam between field lens and later refract optical system. Filter and variable density plate are placed in it to guarantee the imaging quality. The focal length is 3750mm and F number is 7.5 for the long-focus system, and the focal length is 1850mm and F number is 3.75 for the short-focus system. Former part and later lens of the system are both perfect imaging. They can be fabricated and detected independently. So the design demand can be satisfied better and the imaging quality can be improved.
收起
摘要 :
Binary optics can be used to increase optical performances, decrease size and weight, and decrease systems costs in numerous applications. By means of hybrid diffractive-refractive, a switch-zoom optical system of catadioptric lar...
展开
Binary optics can be used to increase optical performances, decrease size and weight, and decrease systems costs in numerous applications. By means of hybrid diffractive-refractive, a switch-zoom optical system of catadioptric large aperture ground-based photoelectric detection is designed. The characteristic of the system is that it is a compact optical system without moving parts which can get two focal lengths. And the quality of image approaches the diffraction limited. Ritchey-Chretien (R-C) mirror and a field lens are common for long-focus system and short-focus system. Two refract groups transmitting optical system are used for zooming, In order to satisfy the demand of energy regulation, it is designed afocal beam between field lens and later refract optical system. Filter and variable density plate are placed in it to guarantee the imaging quality. The focal length is 3750mm and F number is 7.5 for the long-focus system, and the focal length is 1850mm and F number is 3.75 for the short-focus system. Former part and later lens of the system are both perfect imaging. They can be fabricated and detected independently. So the design demand can be satisfied better and the imaging quality can be improved.
收起
原文获取