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Fan J.,Soochow University of China | Fan J.,Key Laboratory of Modern Optical Technology of Jiangsu Province | Zhou J.,Soochow University of China | Zhou J.,Key Laboratory of Modern Optical Technology of Jiangsu Province | And 2 more authors.
Zhongguo Jiguang/Chinese Journal of Lasers | Year: 2010

A combined method based on improved principal component analysis(PCA) and integer wavelet transform is proposed for hyperspectral image compression. PCA can effectively reduce the spectral correlation of hyperspectral image and integer wavelet transform by using lift scheme is widely used for spatial decorrelation. The code speed dramatically decreases when the spatial size becomes large. The hyperspectral images are partitioned into several blocks with same size and each block is encoded by PCA and integer wavelet transform independently. A non-linear model is setup to estimate the optimal retained number of principal component(PC) at any compression ratio. When the optimized compression methods are using on the hyperspectral images of the AVIRIS instrument and our developing hyperspectral imager, the compression effects is competitive and it runs fast comparing with common PCA followed by integer wavelet transform. This method is also easily completed on the hardware. Source


Yuan Y.,Soochow University of China | Yuan Y.,Key Laboratory of Modern Optical Technology of Jiangsu Province | Hu J.,Soochow University of China | Hu J.,Key Laboratory of Modern Optical Technology of Jiangsu Province | And 2 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

The design principles of three familiar compensators are introduced. They are null lens compensator, offner compensator and reflective mirror compensator. Base on the three different theories, three different kinds of compensators for the testing of F/3 hyperbolic mirror are designed. The initial parameters of every compensator are analyzed in detail. The residual wavefront error, RMS radius of the spot diagrams and the tolerance of the three compensators are presented respectively. Due to the residual wavefront error consisted in these compensators themselves, higher order aspheric terms will be introduced into the hyperbolic mirror when using these compensators to test the mirror during the process of the fabrication. These higher order aspheric terms will influence the image quality of R-C system which primary mirror is this hyperbolic mirror. The simulation of this influence is analyzed in this paper. The residual wavefront error of the three final designs are all less than λ/30. The RMS radii of the spot diagrams are all less than 0.48μm. © 2010 Copyright SPIE - The International Society for Optical Engineering. Source


Zhou Y.,Soochow University of China | Zhou Y.,Key Laboratory of Modern Optical Technology of Jiangsu Province | Shen W.,Soochow University of China | Shen W.,Key Laboratory of Modern Optical Technology of Jiangsu Province | And 4 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

Star camera is a kind of sensitive attitude sensors used for navigation of space vehicles. In order to use it on aircrafts in daytime, the conceptual design and the principle of airborne daytime infrared star cameras are introduced in this paper, as there is enough number of stars in near infrared band to be used as reference of a star camera for calculating attitude. Through analyzing the atmospheric scattering background light intensity for different altitudes, observing angles, and solar angles with Modtran software, and considering IR FPA (infrared focal plane array) performance, shot noise and the required star magnitude for daytime star trackers and sensors, the optical system parameters, i.e. FOV (field of view), clear aperture diameter and effective focal length, are determined according to the required SNR (signal to noise ratio). © 2010 Copyright SPIE - The International Society for Optical Engineering. Source


Fan J.,Soochow University of China | Fan J.,Key Laboratory of Modern Optical Technology of Jiangsu Province | Zhou J.,Soochow University of China | Zhou J.,Key Laboratory of Modern Optical Technology of Jiangsu Province | And 4 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

The huge data volume of hyperspectral image challenges its transportation and store. It is necessary to find an effective method to compress the hyperspectral image. Through analysis and comparison of current various algorithms, a mixed compression algorithm based on prediction, integer wavelet transform and embedded zero-tree wavelet (EZW) is proposed in this paper. We adopt a high-powered Digital Signal Processor (DSP) of TMS320DM642 to realize the proposed algorithm. Through modifying the mixed algorithm and optimizing its algorithmic language, the processing efficiency of the program was significantly improved, compared the non-optimized one. Our experiment show that the mixed algorithm based on DSP runs much faster than the algorithm on personal computer. The proposed method can achieve the nearly real-time compression with excellent image quality and compression performance. © 2010 SPIE. Source


Han L.,Soochow University of China | Han L.,Key Laboratory of Modern Optical Technology of Jiangsu Province | Zhao Z.,Soochow University of China | Zhao Z.,Key Laboratory of Modern Optical Technology of Jiangsu Province | And 6 more authors.
Guangxue Xuebao/Acta Optica Sinica | Year: 2016

There is a race to develop spaceborne high-resolution video cameras since Skysat-1 is launched successfully. To reduce manufacture cost and adapt to small satellite platform, it is urgent to design and develop a long focal length optical system with small volume, light weight, easy implementation and imageable for two-dimensional field of view. The full field of view coaxial three-mirror anastigmat (CTMA) appropriate for two-dimensional field of view imaging is studied. The problems of its inherent secondary obscuration and imaging plane extraction difficulty are solved. The conditions of eliminating the secondary obscuration and the relationship between the total length of the system and the tertiary mirror relay imaging magnification are presented based on paraxial geometry optics. Then the reasonable tertiary mirror relay imaging magnification and other parameters are discussed and obtained. A flat mirror near its exit pupil can be used to deflect the image plane without obscuration. The flat mirror group is used to fold optical path and the total length of the system is decreased. The method and the result for determining the initial structural parameters are presented. The optimized optical system without secondary obscuration is designed, whose effective focal length (EFL), field of view and F number are 10 m, 1.1°×1°, 14.3, respectively. The total length of the system is 1/8 of EFL. Its imaging quality is near diffraction limit. © 2016, Chinese Lasers Press. All right reserved. Source

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