共查询到19条相似文献，搜索用时 78 毫秒
1.
为测量天线副面并联调整机构的相对位姿,研究了一种基于单目视觉的位姿测量系统.采用光源照射固定于动平台上的合作目标,结合滤光片等控制手段,利用单目相机采集非共面特征点的图像,获得高对比度的准理想图像.经过图像处理和平方加权质心法,提取出特征点的图像坐标,使用EPnP (Efficient Perspective-n-Point)算法进行位姿解算,最终可以得到并联调整机构的相对位姿测量方法.最后通过实验进行了精度验证,结果表明平移精度为0.1 mm,旋转精度为0.05°,满足了实验要求,为并联机构的位姿检测提供了可行性思路. 相似文献
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《天文研究与技术》2016,(4)
观测目标的亮度越小,杂散光对其的影响越大。在光谱观测中,由于谱线线心的剩余能量较小,所以杂散光对光谱观测的影响显著。在用抚仙湖1 m太阳望远镜多波段光谱仪进行光谱观测时发现,CaⅡ光谱图像在855.6 nm吸收线右侧的亮度有肉眼可见的明显下降,针对此现象分析产生光谱图像色散方向上亮度左右差异的原因,结合杂散光的理论用实验的方法找出杂散光的来源及传输路径。分析结果表明,产生此种现象是由于狭缝的次极大衍射光照亮成像镜后反射到CCD,形成一个弧形的杂散光亮斑,强度约为光谱图像平均光子数的20.9%,对CaⅡ通道的光谱图像产生了严重的影响。对分析的结果进行了理论验证。利用遮挡杂散光传输路径与图像处理两种抑制杂散光的方法对其进行消除,使CaⅡ通道杂散光恢复到正常水平。 相似文献
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自1987年以来,云台库特摄谱仪改装使用了CCD相机,将可测波段扩展到红外。本文经实测证认了适用于扩展后的7000—11700埃的Fe-Ar比较光源的标准光谱谱线表。并精确测定了仪器改装后的光栅转角计算公式,还讨论了仪器综合效率、光栅定位精度、滤光片的使用等问题。 相似文献
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《天文研究与技术》2015,(4)
针对低信噪比条件下光谱抽取精度较低的问题,对输入二维光谱图像进行预处理,提出了一种在Wigner时频域加权滤波的方法进行光纤光谱信号降噪,改善低信噪比的光谱数据质量。针对传统低通滤波不能滤除通带内混叠噪声的缺陷,采用Wigner变换获取光谱信号高集中度的时频分布。先构建带通滤波器滤除较分散的明显噪声分量,再针对通带部分设计加权滤波器,根据信号的先验信噪比进行非线性处理,最后利用Wigner变换的边缘特性重构有效信号。实验部分采用大天区面积多目标光纤光谱望远镜(the Large Sky Area Multi-Object Fiber Spectroscopic Telescope,LAMOST)系统的仿真和实测数据验证算法的有效性。 相似文献
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本文把简并中微子天体作为透明天体来讨论,从测地线方程的解出发,求得位于天体内、外的光源所发出的光线轨迹。进一步导出了由于透明天体的引力透镜作用所带来的对光强分布的影响——放大率K的表示式。并在简并中微子天体的度规下具体计算了放大率K和红移,计算的结果表明,当光源在某些位置上时,向某些方向发出的光,由于引力透镜作用其亮度可增强为原来的数百倍。本文最后提出,部分类星体可能是存在于简并中微子星团中的星系核。 相似文献
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为了满足1.2 m望远镜天文成像系统对科学目标的观测,设计了一个基于STM32控制的可调恒温滤光片转轮盒。转轮盒内有3个转轮,在各自电机驱动下可配合转动,实现最多15个滤光片的自动切换。为确保滤光片的稳定工作波长,转轮盒内置基于PID温控算法的保温系统,以保持转轮盒内部在设定的温度。上位机可通过串口与电控盒进行指令通信,并由电控盒直接驱动转轮电机及加热保温。整个系统结构紧凑,电控安全性好,单片机程序功能完备。最后测试证明该转轮盒在低温-25℃时能正常工作,在恒温模式下能使温度保持在目标温度±1℃以内,长时间工作时性能稳定,切换一次滤光片的用时在10 s以内。 相似文献
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在单轴晶体光轴任意取向的情形下应用惠更斯原理导出了双折射滤光片产生位相差的精确公式,结合几种熟知的特殊情形进行了简要讨论,给出完全一致的相关结果,揭示该普遍公式的正确性.针对光轴标定误差小的晶片,对普遍公式进行相应的近似,进一步分析了晶片定轴误差对宽视场双折射滤光器视场的影响,说明引入适当的光轴定向微扰误差可以增大滤光器某一方位角处的视场. 相似文献
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随着数字技术的发展，数字信号处理芯片的速度越来越快，这为高速数字滤波的实时实现提供了可能。简要阐述了数字滤波的原理，并对两种数字滤波的实现方法进行了分析；给出了数字滤波较模拟滤波的优势；介绍了数字滤波在射电天文测量中的各种应用。 相似文献
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Robert West Benjamin Knowles Sebastien Charnoz Matthew Hedman Alfred McEwen Carolyn Porco Henry Throop 《Planetary and Space Science》2010,58(11):1475-1488
We describe in-flight calibration of the Cassini Imaging Science Sub-system narrow- and wide-angle cameras using data from 2004 to 2009. We report on the photometric performance of the cameras including the use of polarization filters, point spread functions over a dynamic range greater than 107, gain and loss of hot pixels, changes in flat fields, and an analysis of charge transfer efficiency. Hot pixel behavior is more complicated than can be understood by a process of activation by cosmic ray damage and deactivation by annealing. Point spread function (PSF) analysis revealed a ghost feature associated with the narrow-angle camera Green filter. More generally, the observed PSFs do not fall off with distance as rapidly as expected if diffraction were the primary contributor. Stray light produces significant signal far from the center of the PSF. Our photometric analysis made use of calibrated spectra from eighteen stars and the spectral shape of the satellite Enceladus. The analysis revealed a shutter offset that differed from pre-launch calibration. It affects the shortest exposures. Star photometry results are reproducible to a few percent in most filters. No degradation in charge transfer efficiency has been detected although uncertainties are large. The results of this work have been digitally archived and incorporated into our calibration software CISSCAL available online. 相似文献
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Gaussian phase-speed filters are widely used in time-distance helioseismology to select specific wave packets whose travel
times are then measured at the solar surface. This filtering increases the signal-to-noise (S/N) ratio of the temporal cross-covariances
that are fitted to derive the travel times. The central phase speeds of these Gaussian filters are prescribed by a solar model;
their widths are typically chosen empirically. No systematic study has been published on the effect of this filter width on
the S/N ratio of the travel times. Such an analysis requires the ability to generate both noise and signal travel-time perturbations,
this is now possible due to the recent introduction of a noise model and Born-approximation sensitivity kernels. These kernels
allow for a derivation of travel-time perturbations as functions of a given sound-speed perturbation and are dependent on
the phase-speed filters applied to the data, unlike simpler kernels. In this paper, we show that there is indeed an optimum
value of the filter width that results in a maximum S/N ratio for the travel-time maps. Narrower filters exclude too much
signal to produce useful travel-time perturbation maps, while broader filters are not selective enough. 相似文献
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T. D. Padalia 《Astrophysics and Space Science》1987,129(2):413-414
Intrinsic light variations inB andV filters have been found on the three observed light curves of RW Ceti. 相似文献
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Photoelectric light curves of the eclipsing binary RZ Cas are presented forB andV filters. The light curves are analysed for light and geometrical elements, starting with a previously suggested preliminary method. The approximate results thus obtained are then optimised through the Wilson-Devinney computer programs. 相似文献
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D. Herranz M. López-Caniego J. L. Sanz J. González-Nuevo 《Monthly notices of the Royal Astronomical Society》2009,394(1):510-520
In this work we address the problem of simultaneous multifrequency detection of extragalactic point sources in the maps of the cosmic microwave background. We apply a new linear filtering technique, the 'matched matrix filters', that incorporates full spatial information, including the cross-correlation among channels, without making any a priori assumption about the spectral behaviour of the sources. A substantial reduction of the background is achieved thanks to the optimal combination of filtered maps. We describe the new technique in detail and apply it to the detection of radio sources and estimation of their parameters in realistic all-sky Planck simulations at 30, 44, 70 and 100 GHz. Then, we compare the results with the single-frequency approach based on the standard matched filter, in terms of reliability, completeness and flux accuracy of the resulting point source catalogues. The new filters outperform the standard matched filters for all these indexes at 30, 44 and 70 GHz, whereas at 100 GHz both kinds of filters have a similar performance. We find a notable increment of the number of true detections for a fixed reliability level. In particular, for a 95 per cent reliability we practically double the number of detections at 30, 44 and 70 GHz. 相似文献
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Giulia Schettino Ernesto Oliva Massimo Inguscio Carlo Baffa Elisabetta Giani Andrea Tozzi Pablo Cancio Pastor 《Experimental Astronomy》2011,31(1):69-81
A spectrally filtered Optical Frequency Comb (OFC) laser is proposed as a versatile calibration source for astronomical spectrometers in the 1?C2 ??m spectral range. Such a source overcomes the limitations of current calibration lamps providing a uniform spectrum of equally spaced lines with similar intensity and extremely high long-term frequency stability. We present preliminary studies and results of a system which filters the OFC from a 100 MHz comb spacing to 16 GHz one, an adequate spacing for spectrometers with resolving power ????/???>30000. The first approach employs two Fabry-Perot cavities in series, made of dielectric coated mirrors, followed by a non-linear optical broadening system. The limitations of such a filtering process are discussed. These can be overcome by the second approach, based on filtering cavities with metallic coated mirrors. 相似文献
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Leslie Hebb Larry Petro Holland C. Ford David R. Ardila Ignacio Toledo Dante Minniti David A. Golimowski Mark Clampin 《Monthly notices of the Royal Astronomical Society》2007,379(1):63-72
We present high-cadence, high-precision multiband photometry of the young, M1Ve, debris disc star, AU Microscopii. The data were obtained in three continuum filters spanning a wavelength range from 4500 to 6600 Å, plus Hα, over 28 nights in 2005. The light curves show intrinsic stellar variability due to star-spots with an amplitude in the blue band of 0.051 mag and a period of 4.847 d. In addition, three large flares were detected in the data which all occur near the minimum brightness of the star. We remove the intrinsic stellar variability and combine the light curves of all the filters in order to search for transits by possible planetary companions orbiting in the plane of the nearly edge-on debris disc. The combined final light curve has a sampling of 0.35 min and a standard deviation of 6.8 mmag. We performed Monte Carlo simulations by adding fake transits to the observed light curve and find with 95 per cent significance that there are no Jupiter mass planets orbiting in the plane of the debris disc on circular orbits with periods, P ≤ 5 d. In addition, there are no young Neptune like planets (with radii 2.5 times smaller than the young Jupiter) on circular orbits with periods, P ≤ 3 d. 相似文献
19.
A. Robledo-Martinez R. Aliaga-Rossel I.H. Mitchell J.P. Chittenden A.E. Dangor M.G. Haines 《Astrophysics and Space Science》1997,256(1-2):491-497
An experimental technique for the detection and time-resolved characterisation of hard X-radiation from a Z-pinch is described. The detectors employed consist of combinations of plastic scintillators and photomultipliers tubes coupled through optical fiber. The scintillators were fitted with thick aluminium and lead filters and cross filtering is then used to obtain the energy of the X-rays. It was found that the X-rays can reach energies of up to 4 MeV, much higher than the applied voltage. The observed radiation intensity varied with the disruption time lag. 相似文献