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《天文研究与技术》2017,(3)
消除综合孔径望远镜子孔径之间的相对光程差是实现高分辨率干涉成像的前提条件,条纹检测法是一种检测相对光程差的有效办法。因子孔径的空间位置排布使干涉条纹具有一定的方向性,若不能精确获知干涉条纹的角度,则无法沿条纹的法线方向行采样,进而无法根据对比度变化曲线的最大值获得子孔径之间的最小光程差位置。提出了一种基于傅里叶变换和图像二值化阈值遍历的获得干涉条纹角度的方法,首先介绍了算法的基本原理,其次通过对条纹角度为43°的仿真数据进行算法验证得到的角度为43.007 8°,与理论值的误差为0.018%,证实了方法的可行性。最后对比了未旋转相机和旋转相机两种情况下的条纹对比度变化曲线,可知通过旋转相机使条纹转至相机靶面纵轴方向再进行采样的办法,更有利于精确得到相对光程差的最小位置。 相似文献
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为检测云南天文台１．２ｍ望远镜光学成像质量,在多种光学检测方法中,我们结合实际情况,详细地讨论了两种方案的可能性。并用美国ＺＥＭＡＸ光学设计软件设计了所需的光学辅助元件。第一种方案,将全口径分割成直径为３００ｍｍ的子孔径后,利用哈特曼传感器对每个子孔径的最后成像波面进行探测,得到波前畸变量。最后将所得到的子孔径波面合成得到全口径波面,进而分析系统成像质量。第二种方案采用补偿干涉法,利用设计的补偿器补偿主镜的法线象差,得到干涉条纹,再由干涉条纹分析得到主镜面形差。这两种方法都实现微机实时采样与处理,能以较快速度计算出最后结果。最后,我们讨论了检测过程中误差来源及精度分析。在实验条件满足的情况下,整个系统的测试精度优于λ／１０。 相似文献
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激光导引星波前倾斜测量问题是限制自适应光学技术在天文领域广泛应用的关键问题之一。测量并改正激光上行到达角起伏是解决这一问题的有效方法。提出一种基于统计平均算法而不依赖自然导引星和辅助望远镜的测量方法,可以有效地测量出激光上行到达角起伏。利用具有子孔径阵列的哈特曼波前传感器对激光信标进行探测,选择部分子孔径进行倾斜量的统计平均以获得激光上行到达角起伏。仿真了统计平均算法的误差随子孔径数量的变化关系。结果表明,最小算法误差相对于望远镜全口径倾斜误差的下降比例与大气相干长度无关,而与望远镜口径有关。望远镜口径越大,算法误差相对于全口径倾斜误差下降越多。当望远镜口径为10 m时,最小算法误差下降为望远镜全口径倾斜误差的33%。 相似文献
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闭合相位法是实现长基线恒星光干涉高分辨成像的重要技术手段之一,获得精确的闭合相位信息是进行光干涉图像重构的先决条件.提出一种基于精密光程差调制的时域干涉信号闭合相位检测方法,在3路干涉臂上进行非冗余精密光程调制,并通过多次干涉测量结合数据拟合的方法消除光程差调制中存在的正弦误差,使得光程调制的精度达到20 nm以内.引入高速探测器件提升时域干涉信号的采样频率,对探测器上获得的时域干涉信号进行傅立叶变换处理,获得3路干涉臂精确的闭合相位信息.室内实验结果表明,基于精密光程调制的时域信号闭合相位计算精度可以达到1/50波长以内. 相似文献
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主动光学—新一代大望远镜的关键技术 总被引：7，自引：0，他引：7
对主动光学技术在现代天文光学望远镜中的作用和工作原理作了较全面的介绍和评化,结合作者近十年的工作对薄镜面主动光学技术和拼接镜面主动光学技术的各个关键部分,如波前检测,波前拟合,校正力的确定,共焦和共同的检测作了较详细且深入的讨论和评述,也介绍了我国目前正在研制的同时采用薄镜面主动光学和拼接镜面主动光学技术的大天区面积多目标光纤光镜望远镜的主动光学系统。 相似文献
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主动光学─新一代大望远镜的关键技术 总被引：1，自引：0，他引：1
对主动光学技术在现代天文光学望远镜中的作用和工作原理作了较全面的介绍和评论。结合作者近十年的工作对薄镜面主动光学技术和拼接镜面主动光学技术的各个关键部分,如波前检测、波前拟合、校正力的确定、共焦和共面的检测作了较详细且深入的讨论和评述．也介绍了我国目前正在研制的同时采用薄镜面主动光学和拼接镜面主动光学技术的大天区面积多目标光纤光谱望远镜的主动光学系统。 相似文献
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《天文学报》2017,(4)
在恒星干涉仪中,高速倾斜镜(Fast-steering mirror,FSM)因分辨率高、响应频率快等特点被广泛应用于校正大气湍流、仪器内部振动等引起的波前倾斜.一方面,针对倾斜镜本身在加工、装调中引入的镜面与触动器偏转轴不共面等误差进行系统分析,通过数值方法研究了上述因素在倾斜镜工作时产生的附加光程差(Optical Path Difference,OPD),并讨论了该光程差对恒星干涉仪条纹跟踪精度的影响;另一方面,两臂光束之间的平行度误差是造成干涉条纹可见度损失的主要因素之一,通过分析大气扰动引起的波前倾斜对条纹可见度的影响,提出了一种基于单一阵列探测器、简单高效的星光平行度实时校正方案,并结合室内实验论证了该方案的可行性.实验结果表明:经高速倾斜镜校正后的星光方向平行度初步满足了恒星干涉仪系统对波前倾斜的需求. 相似文献
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N. A. Bharmal † D. F. Buscher C. A. Haniff 《Monthly notices of the Royal Astronomical Society》2005,360(4):1325-1332
A new method of wavefront sensing that uses a pair of equally defocused images to derive the wavefront aberrations is presented. Unlike in conventional curvature-sensing systems, the sensor works in a near-focus regime where the transport of intensity equation is not valid, and, unlike in phase-diversity methods, a non-iterative algorithm is used to infer the wavefront aberrations. The sensor designs outlined only require a small number of detector pixels: two designs with five and nine pixels per plane are analysed, and the nine-element sensor (NES) is shown to have a competitive measurement sensitivity compared with existing low-order astronomical wavefront sensors. The NES is thus well suited to applications such as adaptive optics for the individual telescopes in an optical interferometer array. 相似文献
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J. E. Oti V. F. Canales M. P. Cagigal 《Monthly notices of the Royal Astronomical Society》2005,360(4):1448-1454
We describe a novel concept for high-resolution wavefront sensing based on the optical differentiation wavefront sensor (OD). It keeps the advantages of high resolution, adjustable dynamic range, ability to work with polychromatic sources and, in addition, it achieves good performance in wavefront reconstruction when the field is perturbed by scintillation. Moreover, this new concept can be used as multi-object wavefront sensor in multiconjugate adaptive optics systems. It is able to provide high resolution and high sampling operation, which is of great interest for the projected extreme adaptive optics systems for large telescopes. 相似文献
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R. Ragazzoni M. Tordi E. Diolaiti D. Kirkman 《Monthly notices of the Royal Astronomical Society》2001,327(3):949-954
An innovative concept of wavefront sensing for Rayleigh beacons is introduced along with an example of a possible wavefront sensor. This new approach does not require the gating technique to limit the useful range of the laser source and therefore looks simpler to implement than previous Rayleigh concepts, and may additionally allow more efficient use of the photons emitted by the Rayleigh beacon. Our technique is based upon an optical element in the focal plane area whose section does not change for the conjugation of different ranges from the telescope aperture, hence the name z -invariant. The wavefront sensor shown here is an example of this new class. It is a compact pupil-plane wavefront sensor and as such allows for a layer-oriented configuration. It is shown that its sensitivity, while higher than usual gating approaches, is far from the possible limits leading us to speculate that other z -invariant wavefront sensors can reach much larger efficiencies. 相似文献
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Roberto Ragazzoni Stephan Kellner Wolfgang Gaessler Emiliano Diolaiti Jacopo Farinato 《Monthly notices of the Royal Astronomical Society》2006,368(4):1796-1802
We introduce a novel concept to sense the wavefront for adaptive optics purposes in astronomy using a conventional laser beacon. The concept we describe involves treating the light scattered in the mesospheric sodium layer as if it comes from multiple rings located at infinity. Such a concept resembles an inverse Bessel beam and is particularly suitable for multi-conjugated adaptive optics on extremely large telescopes. In fact, as the sensing process uses light apparently coming from infinity, some problems linked to the finite distance and vertical extent of the guide source are solved. Since such a technique is able to sense a wavefront solely in the radial direction, we propose furthermore a novel wavefront sensor by combining the inverse Bessel beam approach with the recently introduced z -invariant technique for a pseudo-infinite guide star sensor. 相似文献
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Active or adaptive optics often require the ability to characterize wavefront aberrations using natural extended sources.
The task becomes especially challenging when dealing with widely extended sources such as the solar granulation. We propose
a new approach based on the processing of oppositely defocused images. This method, which is a generalization of a technique
known as curvature sensing, derives the wavefront curvature from the difference between two oppositely defocused images and
determines the second momenta of the point spread function. The proposed method measures the wavefront aberration from the
images themselves, requires little computational resources, is fast enough to be used in a real-time adaptive optics system
and is particularly adapted to random patterns such as solar granulation or spot penumbras whose morphology evolves during
the observation. We envision the application of the method to real-time seeing compensation in solar astronomical telescopes,
and to the correction of optical system aberrations in remote sensing instrumentation. This effort is directed towards building
a curvature sensor for the real-time applications. 相似文献
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A. R. Bayanna B. Kumar R. E. Louis P. Venkatakrishnan S. K. Mathew 《Journal of Astrophysics and Astronomy》2008,29(1-2):353-357
A low-order Adaptive Optics (AO) system is being developed at the Udaipur Solar Observatory and we present in this paper the status of the project, which includes the image stabilization system and calibration of wavefront sensor and deformable mirror. The image stabilization system comprises of a piezo driven tip-tilt mirror, a high speed camera (955 fps), a frame grabber system for sensing the overall tilt and a Linux based Intel Pentium 4 control computer with Red Hat Linux OS. The system operates under PID control. In the closed loop, an rms image motion of 0.1–0.2 arcsec was observed with the improvement factor varying from 10–20 depending on the external conditions. Error rejection bandwidth of the system at 0 dB is 80–100 Hz. In addition to that, we report the on-going efforts in the calibration of lenslet array and deformable mirror for sensing and correcting the local tilt of the wavefront. 相似文献
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Mei Rong Hu Zhong-wen Xu Teng Sun Chang-sheng 《Chinese Astronomy and Astrophysics》2018,42(3):475-486
In stellar interferometers, the fast-steering mirror (FSM) is widely utilized to correct the wavefront tilt caused by the atmospheric turbulence and internal instrumental vibration, because of its high resolution and fast response frequency. In this study, the non-coplanar error between the FSM and the actuator deflection axis introduced by the manufacturing, assembly, and adjustment is analyzed systematically. Via a numerical method, the additional optical path difference (OPD) caused by the above factors is studied, and its effect on the fringe tracking accuracy of a stellar interferometer is also discussed. On the other hand, the starlight parallelism between the beams of two arms is one of the main factors for the loss of fringe visibility. By analyzing the influence of wavefront tilt caused by the atmospheric turbulence on fringe visibility, a simple and efficient real-time correction scheme of starlight parallelism is proposed based on a single array detector. The feasibility of this scheme is demonstrated by a laboratory experiment. The results show that after the correction of fast-steering mirror, the starlight parallelism meets preliminarily the requirement of a stellar interferometer on the wavefront tilt. 相似文献
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T. Butterley R. W. Wilson M. Sarazin 《Monthly notices of the Royal Astronomical Society》2006,369(2):835-845
Slope Detection and Ranging (SLODAR) is a technique for the measurement of the vertical profile of atmospheric optical turbulence strength. Its main applications are astronomical site characterization and real-time optimization of imaging with adaptive optical correction. The turbulence profile is recovered from the cross-covariance of the slope of the optical phase aberration for a double star source, measured at the telescope with a wavefront sensor (WFS). Here, we determine the theoretical response of a SLODAR system based on a Shack–Hartmann WFS to a thin turbulent layer at a given altitude, and also as a function of the spatial power spectral index of the optical phase aberrations. Recovery of the turbulence profile via fitting of these theoretical response functions is explored. The limiting resolution in altitude of the instrument and the statistical uncertainty of the measured profiles are discussed. We examine the measurement of the total integrated turbulence strength (the seeing) from the WFS data and, by subtraction, the fractional contribution from all turbulence above the maximum altitude for direct sensing of the instrument. We take into account the effects of noise in the measurement of wavefront slopes from centroids and the form of the spatial structure function of the atmospheric optical aberrations. 相似文献
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Ren Rutten Maarten Blanken Richard McDermid Thomas Gregory Paul Jolley Tim Morris Richard Myers Johan Pragt Ton Schoenmaker Remko Stuik Gordon Talbot 《New Astronomy Reviews》2006,49(10-12):632
The scientific exploitation of adaptive optics (AO) with natural guide stars is severely constrained by the limited presence of bright guide stars for wavefront sensing. Use of a laser beam as an alternative means to provide a source for wavefront sensing has the potential of drastically improving the sky coverage for AO. For this reason at the 4.2-m William Herschel Telescope a project was started to develop a Rayleigh laser beacon to work together with the existing NAOMI adaptive optics instrumentation and the OASIS integral field spectrograph. This paper presents the rationale for this development, highlights some of the technical aspects, and gives some expected performance measures. 相似文献
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《天文和天体物理学研究(英文版)》2015,(5)
The wavefront measuring range and recovery precision of a curvature sensor can be improved by an intensity compensation algorithm. However, in a focal system with a fast f-number, especially a telescope with a large field of view, the accuracy of this algorithm cannot meet the requirements. A theoretical analysis of the corrected intensity compensation algorithm in a focal system with a fast f-number is first introduced and afterwards the mathematical equations used in this algorithm are expressed.The corrected result is then verified through simulation. The method used by such a simulation can be described as follows. First, the curvature signal from a focal system with a fast f-number is simulated by Monte Carlo ray tracing; then the wavefront result is calculated by the inner loop of the FFT wavefront recovery algorithm and the outer loop of the intensity compensation algorithm. Upon comparing the intensity compensation algorithm of an ideal system with the corrected intensity compensation algorithm, we reveal that the recovered precision of the curvature sensor can be greatly improved by the corrected intensity compensation algorithm. 相似文献