共查询到19条相似文献，搜索用时 93 毫秒
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本文以ＣＣＤ图象为技术背景，指出ＣＣＤ图象噪声主要将以与信号有关的泊松噪声形式存在。根据图象形成的模型及图象统计特性，提出了最大似然法，最大后验概率法及最大复原方法，针对ＭＡＰ法提出了具体算法和参数估计方法，并提出应用图象分割法来提高计算机复原速度，节省存储空间。 相似文献
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分析了１８００ ～１９９５ 年的日长年均值（ △ Ｌ Ｏ Ｄ Ｙ） 观测资料表明：日长（ △ Ｌ Ｏ Ｄ Ｙ） 的十年波动明显大于观测噪声水平。用小波变换方法分析了△ Ｌ Ｏ Ｄ Ｙ 观测资料, 表明△ Ｌ Ｏ Ｄ Ｙ 的十年尺度的周期为６０ａ （ 年） 和３０ａ（ 年） , 所对应的振幅为１ ｍｓ 和０ ．５ｍｓ 左右。文中采用国际地球自转服务中心提供的（ Ｅ Ｏ Ｐ Ｃ０４９７ 的日长（ △ Ｌ Ｏ Ｄ Ｃ０４９７） 序列以及由美国国家环境预测中心和美国国家大气研究中心（ Ｎ Ｃ Ｅ Ｐ／ Ｎ Ｃ Ａ Ｒ） 利用全球气象资料归算的大气角动量（ Ａ Ａ Ｍ） 序列进行低通滤波分析, 日长和大气角动量在十年尺度上的波动不一致, 大气角动量只影响到日长短于年际以上时间尺度的变化。文中用理论近似来计算核幔电磁耦合力矩的轴向分量, 它与天文观测△ Ｌ Ｏ Ｄ 资料推出的力矩量级相当, 核幔电磁耦合假说可作为△ Ｌ Ｏ Ｄ 的十年尺度波动的可能机制 相似文献
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在人造卫星观测的ＣＣＤ图象记录中，为方便图象保存，查阅及图象处理，将图象记录中的相关信息插入记录的图象中是十分重要的。ＹＴＩ－Ａ视频时码插入器正是为此应用而设计。本仪器内有一个可自动与后面板输入秒同步到１μｓ的数字钟。记录日期包括年月日，时刻记录精度为１０μｓ，望远镜指向（Ａ，ｈ）的记录精度为１″。这些信息全部以二种格式被插入记录的图象中可供图象处理时查阅和快速读出。文中叙述了仪器原理及应用 相似文献
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在人造卫星观测的ＣＣＤ，图象记录中，为方便图象保存，查阅及图象处理，将图象记录中的相关信息插入记录的图象中是十分重要的，ＹＴＩ－Ａ视频时码插入器正是为此应用而设计，本仪器内有一个可自动与后面板输入秒同步到１μｓ的数字钟。记录日期包括年月日，时刻记录精度为１０μｓ，望远镜指向（Ａ，ｈ）的记录精度为１″，这些信息全部以二种格式被插入记录的图象中可供图象处理查阅和快速读出，文中叙述了原理及应用。 相似文献
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给出了１９９７年４月１５日至１７日在北京天台用２．１６ｍ望远镜卡焦光谱仪观测获得的６颗激变变星（ＡＢ Ｂｏｏ,ＵＸ ＵＭａ,Ｔ ＣｒＢ,ＡＨ Ｈｅｒ,Ｚ Ｃａｍ和Ｖ４２６ Ｏｐｈ）及３颗相关天体（ＵＭａ３,ＥＧ ＵＭａ和Ｌｅｏ３）的ＣＣＤ光谱,并同时拍摄了５颗晚型星（３Ｄｒａ,ｖ Ｖｉｒ,ψＬｅｏ,３４Ｂｏｏ和３６Ｃｏｍ）的ＣＣＤ光谱,作为晚型星参考谱,测量了观测样本星的Ｈα和近红外ＣａⅡ的三重 相似文献
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王海民 《中国天文和天体物理学报》1994,(3)
１９９１年７月１１日日食期间，在大熊湖天文台进行了白光观测．图象是用６５ｃｍ反射系统和ＯＳＬ的ＣＣＤ获得的．月亮边缘始终包含在视场之中，从模糊的月亮边缘轮廓推得了一维的视宁度点扩散函数（ＰＳＦ），其中包含了望远镜引起的畸变。当天的ＰＳＦ的宽度介于０．８到１．３弧秒之间。假设存在圆柱对称性，则可得到二维的ＰＳＦ。然后，运用视宁度函数，对所观测的白光像消卷积。复原方法将观测到的ｒｍｓ反衬值由５％增强到１８％；亮桥可能亮于正常的光球强度；暗的半影纤维可能暗到正常光球的５０％；而亮纤维可能达到正常光球值。 相似文献
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在１９９２年３月３１日至４月２日期间，我们利用云南天文台１ｍ望远镜２号ＣＣＤ和缩焦装置，对环星系ＮＧＣ４７３６进行了Ⅴ和Ⅰ波段深曝光观测。在经过Ｒｉｃｈａｒｄｓｏｎ－Ｌｕｃｙ图象复原以及自适应滤波两种方法处理后，发现仅仅在Ⅴ波段图象上，其核区存在一个直径约为１０″的环状结构。 相似文献
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《天文和天体物理学研究(英文版)》2014,(8)
In order to implement an observing strategy,image degradation that occurs during optical observation of space debris is ineluctable and has distinct characteristics. Image restoration is presented as a way to remove the influence of degradation in CCD images of space debris,based on assumed PSF models with the same FWHM as images of the object. In the process of image restoration,the maximum entropy method is adopted. The results of reduction using observed raw CCD images indicate that the precision in estimating positions of objects is improved and the effects of degradation are reduced. Improving the astrometry of space debris using image restoration is effective and feasible. 相似文献
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《Chinese Astronomy and Astrophysics》2013,37(1):97-106
The CCD field of view of the Near Earth Object Survey Telescope (NEOST) is 1.94°xl.94°. As a wide-field telescope, the focusing based on a single star will lead to an uneven distribution of PSF (Point Spread Function) on the CCD image due to the field curvature. The features of the PSF distribution on the CCD image are studied. By fitting the relation between the defocusing and the FWHM (Full Width at Half Maximum) of PSF, the curved focal surface is simulated and therefore the best imaging plane is determined. Hereby, a focusing method based on the optimum imaging plane determined by judging the histogram of FWHM is proposed. 相似文献
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The effectiveness of equal power spectrum filtering in image restoration is analyzed via digital simulation. We start with a gray-scale map of concentric rings with different grey values. To obtain a dirty image, the original image is first transformed via a linear space-invariant system. Then, white noise is mixed into the image. The equal power spectrum filter is then used for the image restoration. The signal to noise ratio (SNR) and a defined steepness of the steps, together with the visual impression, are accepted to characterize the performance of the image restoration. It is concluded that a satisfactory restoration can be realized when the SNR > 15. When SNR < 5, the image is completely un-restorable. The effect of system's transfer function on image restoration is also discussed. The effectiveness of the presented model of equal power spectrum filter is confirmed by applying it to the restoration of an actual astronomical image. Finally, a typical application of the equal power spectrum filter is given. 相似文献
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Wei Duan Qian Song Ming-Zhi Wei Zhao-Wang Zhao Wei Wang Yu-Heng Zhang Zhi-Wei Feng 《天文和天体物理学研究(英文版)》2021,(1)
As the areas of CCD detectors and CCD mosaics have become larger and larger,the number of readout channels in astronomical cameras has increased accordingly to keep the image readout time within an acceptable range.For the large area cameras or the mosaic cameras,the analog Correlated Double Sampling(aCDS)circuit used in traditional astronomical cameras for suppressing readout noise is difficult to integrate into the camera controllers within the constraints of the space and energy consumption.Recently,digital CDS(dCDS)technology has been developed to solve this problem,which also offers novel analysis and noise suppression methods.In this study,a mathematical model is presented to conveniently analyze the frequency characteristic of a dCDS circuit,which is then simulated by a numerical method for investigating the noise suppression capability with different sampling weights.Importantly,using this model,the extreme point with lowest readout noise can be predicted for a certain dCDS model;and for a specific CCD readout frequency,readout noise can be suppressed by selecting the proper dCDS model.A testing system is then constructed for validating the efficiency of the proposed method. 相似文献
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利用计算机数值模拟的方法，对等功率谱滤波方法的图像恢复效果进行测定，原始清晰图像选用以（0，0）为圆心的台阶式灰度图，且台阶灰度值非常接近，这些清晰图像首先进行系统退化，然后加入噪声（本文选用白噪声）生成脏图，图像恢复采用等功率谱滤波器，并将信噪比简化为常数k，图像恢复效果的好坏，用恢复后图像的信噪经和台阶的陡度（台阶的下底宽减上底宽，单位为像素个数）来定量测量，并结合普通图像的恢复，进行定性的视觉观察，主要测量退化图像的信噪比对图像恢复效果的影响，结果是：当信噪比＞15：1，图像恢复效果较好，当信噪比小于该值时，图像恢复效果较差，当信噪比下降到5：1时，图像恢复效果极差，几乎无法辨认，其次是系统传递函H对图像恢复效果的影响，也进行了一些讨论，最后，通过对实际的天文图像进行恢复，验证了测量过程的合理性和结果的正确性，并列举了等功率谱波器的一个典型应用，即在同态滤波器中使用等功率谱滤波器的传递函数。 相似文献
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Eric Lantz Jean-Luc Blanchet Luca Furfaro Fabrice Devaux 《Monthly notices of the Royal Astronomical Society》2008,386(4):2262-2270
A multi-imaging strategy is proposed and experimentally tested to improve the accuracy of photon counting with an electron multiplying CCD (EMCCD), by taking into account the random nature of its on-chip gain and the possibility of multiple photodetection events on one pixel. This strategy is based on Bayesian estimation on each image, with a priori information given by the sum of the images. The method works even for images with large dynamic range, with more improvement in the low light level areas. In these areas, two thirds of the variance added by the EMCCD in a conventional imaging mode are removed, making the physical photon noise predominant in the detected image. 相似文献
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T. Sako T. Sekiguchi M. Sasaki K. Okajima F. Abe I. A. Bond J. B. Hearnshaw Y. Itow K. Kamiya P. M. Kilmartin K. Masuda Y. Matsubara Y. Muraki N. J. Rattenbury D. J. Sullivan T. Sumi P. Tristram T. Yanagisawa P. C. M. Yock 《Experimental Astronomy》2008,22(1-2):51-66
We have developed a wide-field mosaic CCD camera, MOA-cam3, mounted at the prime focus of the Microlensing Observations in Astrophysics (MOA) 1.8-m telescope. The camera consists of ten E2V CCD4482 chips, each having 2k×4k pixels, and covers a 2.2 deg2 field of view with a single exposure. The optical system is well optimized to realize uniform image quality over this wide field. The chips are constantly cooled by a cryocooler at ??80° C, at which temperature dark current noise is negligible for a typical 1–3 min exposure. The CCD output charge is converted to a 16-bit digital signal by the GenIII system (Astronomical Research Cameras Inc.) and readout is within 25 s. Readout noise of 2–3 ADU (rms) is also negligible. We prepared a wide-band red filter for an effective microlensing survey and also Bessell V, I filters for standard astronomical studies. Microlensing studies have entered into a new era, which requires more statistics, and more rapid alerts to catch exotic light curves. Our new system is a powerful tool to realize both these requirements. 相似文献
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分析了低光度天文应用时CCD器件的主要噪声源的噪声特性和三种典型CCD读出信号处理方式的噪声抑制效果;提出了天文CCD读出信号的相关多次采样(CMS)处理新方法,并分析了四次采样抑制CCD读出噪声的实验结果。 相似文献