中国开放科研知识云: 检索

The state of the art for liquid crystal adaptive optics in astronomical applications (EI CONFERENCE) 会议论文
2012 International Conference on Optoelectronics and Microelectronics, ICOM 2012, August 23, 2012 - August 25, 2012, Changchun, China
Hu L.; Xuan L.; Cao Z.; Mu Q.; Peng Z.; Liu Y.; Yao L.; Yang C.; Lu X.; Xia D. L. M.

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In this paper we summarize the researches of liquid crystal (LC) adaptive optics(AO) in astronomical applications. Dual frequency and nematic LC materials were reported to be used in astronomical observations. However nematic LC with its simple producing and driving method and multi-gray-level is promising in the application. We have investigated the nematic LC AO system and promoted its application for nearly ten years. Here we reported our newest nematic LC AO system with bandwidth result of 3dB is 54.4 Hz 0dB bandwidth is 79.1Hz. 2012 IEEE.

Multi-focus image fusion algorithm based on adaptive PCNN and wavelet transform (EI CONFERENCE) 会议论文
International Symposium on Photoelectronic Detection and Imaging 2011: Advances in Imaging Detectors and Applications, May 24, 2011 - May 26, 2011, Beijing, China
Wu Z.-G.; Wang M.-J.; Han G.-L.

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Being an efficient method of information fusion image fusion has been used in many fields such as machine vision medical diagnosis military applications and remote sensing.In this paper Pulse Coupled Neural Network (PCNN) is introduced in this research field for its interesting properties in image processing including segmentation target recognition et al. and a novel algorithm based on PCNN and Wavelet Transform for Multi-focus image fusion is proposed. First the two original images are decomposed by wavelet transform. Then based on the PCNN a fusion rule in the Wavelet domain is given. This algorithm uses the wavelet coefficient in each frequency domain as the linking strength so that its value can be chosen adaptively. Wavelet coefficients map to the range of image gray-scale. The output threshold function attenuates to minimum gray over time. Then all pixels of image get the ignition. So the output of PCNN in each iteration time is ignition wavelet coefficients of threshold strength in different time. At this moment the sequences of ignition of wavelet coefficients represent ignition timing of each neuron. The ignition timing of PCNN in each neuron is mapped to corresponding image gray-scale range which is a picture of ignition timing mapping. Then it can judge the targets in the neuron are obvious features or not obvious. The fusion coefficients are decided by the compare-selection operator with the firing time gradient maps and the fusion image is reconstructed by wavelet inverse transform. Furthermore by this algorithm the threshold adjusting constant is estimated by appointed iteration number. Furthermore In order to sufficient reflect order of the firing time the threshold adjusting constant is estimated by appointed iteration number. So after the iteration achieved each of the wavelet coefficient is activated. In order to verify the effectiveness of proposed rules the experiments upon Multi-focus image are done. Moreover comparative results of evaluating fusion quality are listed. The experimental results show that the method can effectively enhance the edge details and improve the spatial resolution of the image. 2011 SPIE.

P2-2: The synthesis of graphite nanocrystals on carbon fiber surface (EI CONFERENCE) 会议论文
23rd International Vacuum Nanoelectronics Conference, IVNC 2010, July 26, 2010 - July 30, 2010, Palo Alto, CA, United states
Wang W.; Zeng L.; Liang J.

收藏 | 浏览/下载：10/0 | 提交时间：2013/03/25

Graphite nanosheets were synthesized on carbon fibers by floating catalyst method with the pretreatment of carbon fibers. Its width and height were 50 nm and 600 nm respectly. graphite nanosheets synthesized on carbon fibers may have potential applications in field emission. 2010 IEEE.

Level 0 and level 1 data processing for a type of hyper-spectral imager (EI CONFERENCE) 会议论文
2009 International Conference on Optical Instruments and Technology, OIT 2009, October 19, 2009 - October 21, 2009, Shanghai, China
Li X.; Yan C.

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Hyper-spectral imaging (HSI) is a kind of optical remote sensor that can simultaneously obtain spatial and spectral information of ground targets. We are now designing a data processing system for a type of space-borne push-broom HSI then it performs radiometric and spectral calibration based on the ground calibration results and onboard calibration collection. The detailed algorithms for bad pixel replacement which has 128 spectral channels covering the spectral range from 400nm to 2500nm. With its large amount of spectral channels radiometric and spectral calibration were presented. After processing the HSI collects large volume of spectral imaging data need to be efficiently and accurately processed and calibrated. In this paper the digital numbers downlinked from the spacecraft can be converted into at-sensor absolute spectral radiance of ground targets the detailed Level 0 and Level 1 data processing steps for the HSI were presented. The Level 0 processing refers to a set of tasks performed on the data downlinked from the spacecraft thus providing accurate quantified spectral imaging data for various applications. 2009 SPIE. including decoding to extract science data separating the science data into files corresponding to different tasks (e.g. ground imaging dark imaging and onboard calibration) checking data integrity and instrument settings data format conversion and Level 0 files creation. The Level 1 processing performs several steps on Level 0 data. Firstly it corrects the image artifacts (mostly the SWIR smear effect) subtracts the dark background and performs the bad pixel replacement according to the prelaunch measurement

Analysis of laser jamming to satellite-based detector (EI CONFERENCE) 会议论文
International Symposium on Photoelectronic Detection and Imaging 2009: Laser Sensing and Imaging, June 17, 2009 - June 19, 2009, Beijing, China
Wang S.-W.; Guo L.-H.; Guo R.-H.

收藏 | 浏览/下载：16/0 | 提交时间：2013/03/25

The reconnaissance satellite communication satellite and navigation satellite used in the military applications have played more and more important role in the advanced technique wars and already become the significant support and aid system for military actions. With the development of all kinds of satellites anti-satellite laser weapons emerge as the times require. The experiments and analyses of laser disturbing CCD (charge coupled detector) in near ground have been studied by many research groups but their results are not suitable to the case that using laser disturbs the satellite-based detector. Because the distance between the satellite-based detector and the ground is very large it is difficult to damage it directly. However the optical receive system of satellite detector has large optical gain so laser disturbing satellite detector is possible. In order to determine its feasibility the theoretical analyses and experimental study are carried out in the paper. Firstly the influence factors of laser disturbing satellite detector are analyzed in detail which including laser power density on the surface of the detector after long distance transmission and laser power density threshold for disturbing etc. These factors are not only induced by the satellite orbit but dependence on the following parameters: laser average power in the ground laser beam quality tracing and aiming precision and atmospheric transmission. A calculation model is developed by considering all factors which then the power density entering into the detector can be calculated. Secondly the laser disturbing experiment is performed by using LD (laser diode) with the wavelength 808 nm disturbing CCD 5 kilometer away which the disturbing threshold value is obtained as 3.5510-4mW/cm2 that coincides with other researcher's results. Finally using the theoretical model the energy density of laser on the photosensitive surface of MSTI-3 satellite detector is estimated as about 100mW/cm2 which is largely exceed the disturbing threshold and therefore verify the feasibility of using this kind of laser disturbing the satellite-based detector. According to the results. using the similar laser power density absolutely saturate the requirements to laser disturbing satellite-based detector. If considering the peak power of pulsed laser even decrease laser average power it is also possible to damage the detector. This result will provide the reliable evidences to evaluate the effect of laser disturbing satellite-based detector. 2009 SPIE.

Research on long focal length On-axis TMA system for high-resolution remote sensing (EI CONFERENCE) 会议论文
3rd International Symposium on Advanced Optical Manufacturing and Testing Technologies, AOMATT 2007: Advanced Optical Manufacturing Technologies, July 8, 2007 - July 12, 2007, Chengdu, China
Zhong X.; Zhang L.; Jin G.

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TMA (Three Mirror Anastigmatic) is popular to the design of space-based optical system. This paper describes the characteristics of the on-axis TMA optical system. An on-axis TMA system with 13m focal length is designed and analyzed. To solve the initial configuration parameters Cassagrain structure is confirmed firstly and then the tertiary mirror. Based on initial configuration parameters automatic optimization is executed in ZEMAX program and design result with excellent image quality is acquired which shows the procedure we choosed with good advantage of computer processing. As the distortion of the design reaches 1% its influences on TDICCD brushing camera are discussed. The source of distortion is analyzed and correcting methods are considered. Zero focal power corrector is chosen to correct the distortion and the corrected distortion is less than 0.02%. The research on on-axis TMA system in this paper makes a foundation for farther high-resolution remote sensing applications.

Integrated mach-zehnder micro-interferometer for gas trace remote sensing (EI CONFERENCE) 会议论文
ICO20: Remote Sensing and Infrared Devices and Systems, August 21, 2005 - August 26, 2005, Changchun, China
Chiarini M.; Bentini G. G.; Bianconi M.; Cerutti A.; Pennestri G.; Wang P.; She L.; Mazzoldi P.; Sada C.

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The realisation process and the preliminary tests on the performances of an integrated Mach-Zehnder Interferometer on LiNbO3 (Lithium Niobate) substrate is presented. The microsystem has been obtained by using medium mass Ion Implantation on X-cut Lithium Niobate crystals. The interferometer is formed by integrated optical channel waveguides: the phase shift between the two optical paths has been obtained 1mm 2 cross section and weights a few grams. The power consumption is in the milliwatt range. In the present work results obtained in the spectral window (0.4m-1.1m) will be presented. The performance of the device without moving parts evaluated on standard radiation sources by applying a suitable electric field. The whole device is 60mm long demonstrates that a spectral resolution better than 0.3nm can be obtained on 400nm spectral windows. The Micro-interferometer has been tested in laboratory with a calibrated cell containing NO2 gas and has demonstrated sensitivity in the ppb range if suitable optical paths are used. Its reduced dimensions and weights make these micro-systems ideal for a wide range of applications has a 0.57times spanning from Space Technology Earth observation for Environment monitoring to Safety and Security applications.

Research on the nonuniformity correction of linear TDI CCD remote camera (EI CONFERENCE) 会议论文
Advanced Materials and Devices for Sensing and Imaging II, November 8, 2004 - November 10, 2004, Beijing, China
Ya-xia L.; Zhi-hang H.

收藏 | 浏览/下载：13/0 | 提交时间：2013/03/25

Many applications such as industrial inspection and overhead reconnaissance benefit from line scanning architectures where time delay integration (TDI) significantly improves sensitivity[5]. Images with linear response have become the backbone of the imaging industry. But each pixel of the TDI CCD has unique light sensitivity characteristics. Because these characteristics and the lens of the optical system affect camera's linearization and its performance they must be removed through calibration. The process by which a CCD image is calibrated is known as nonuniformity correction. This paper discusses several methods of nonuniformity correction[2]. The first is one-point correction technique which requires only one calibration point. This approach is to shift each curve toward the nominal curve by subtracting the offset from or adding the offset to the average. The second is two-point correction technique which requires two calibration points. Each point is rotated and aligned so that all the detectors have the same response under the same radiance. The third is multipoint correction. It is recommended that more calibration points be implemented at appropriate regions of the response curve. Depend on the linear photoelectric response of the TDI CCD we use two-point calibration and the standard deviations for the images are given before and after the correction.

Packaging technology of polymer/Si arrayed waveguide grating and their environmental stability (EI CONFERENCE) 会议论文
2005 6th International Conference on Electronics Packaging Technology, August 30, 2005 - September 2, 2005, Dameisha, Shenzhen, China
Zhang D.; Wang F.; Zhang Y.; Zhang X.; Deng W.; Shulin E.

收藏 | 浏览/下载：26/0 | 提交时间：2013/03/25

Future optical communication systems will use more of the exceptional high bandwidth of optical fiber. Wavelength division multiplexing (WDM) systems are well suited to transport terabits of information via the fiber[1]. Multiplexers/ demultiplexers (MUX/DEMUX) are essential components for dense WDM systems. Several different kinds of multiplexer types have been developed in the past: (a) interference filters (b) fiber gratings and (c) planar lightwave circuit (PLC) MUX/DEMUXers[2 3]. The planar fabrication process of the last mentioned PLCs allows the realization of high performance filters with a large number of wavelength channels. Further an integration with other optical elements seems to be possible. Arrayed waveguide gratings (AWG) are a special kind of PLC-MUX/DEMUXers which are very attractive components for WDM systems because of their great flexibility in filter design[4 5]. Basically an AWG is an optical spectrograph built in planar waveguide technique. Typically AWGs works in a high grating order (50-250). For AWG multiplexer applications in communications systems a precise wavelength controllability and wavelength stability with long term is demanded. Recently a polymeric (especially fluorinated polymer with low optical absorption loss in the infrared region) AWG has attracted much attention because of its easy fabrication low cost possibility and a potential of integration with other polymer devices[6]. Standard AWGs however show a change of center wavelength with temperature. A method to prevent this temperature drift is to package the AWG together with a temperature controller in order to tune and fix the desired filter-wavelength. In this paper a 32-channel AWG was fabricated using a cross-linkable fluorinated poly (ether ether ketone) (FPEEK) its package technology and environmental stability were also discussed. 2005 IEEE.

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