Experimental results for correlation-based wavefront sensing

Poyneer, L A; Palmer, D W; LaFortune, K N; Bauman, B

doi:10.1117/12615231

Cited by 16 publications

(17 citation statements)

References 4 publications

(5 reference statements)

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“…A previously built tracking system described in other works [11][12][13][14] and our earlier works [1][2][3][4][5] uses the standard centre of mass method to calculate the reference star's position. It is a simple method that does not require large computations but does not take into account present atmospheric conditions and specific parameters of the optical system in a particular observation session.…”

Section: Discussionmentioning

confidence: 99%

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Stars’ Centroid Determination Using PSF-Fitting Method

Suszyński

Wawryn

2015

Metrology and Measurement Systems

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This paper presents an algorithm for restoring telescope images corrupted by turbulence effects and readout noise of a telescope system in order to determine centroid positions of stars, especially the position of a reference star. A computation method employing an accurate centroid estimation algorithm reconstructing a point spread function (PSF) from the recorded astronomical images has been used. Minimisation of turbulence effects and telescope control system noise in long exposure images acquired and recorded by the ground telescope is proposed. As a solution of the distortion error a minimisation signal is dedicated to GoTo calibration procedures built in control mechanisms of the electromechanical telescope system. The proposed method has been verified in the Matlab environment for real deep sky images recorded by the ground telescope system.

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Section: Discussionmentioning

confidence: 99%

“…Many different computation methods are adopted to reduce the image distortions [7][8][9][10]. Mathematically simplest methods are based on computing the centre of mass [11] and the weighted centre of mass [12][13][14] of a star, respectively. A Gaussian pattern matching [15] is also used in the centroid detection.…”

Section: Introductionmentioning

confidence: 99%

Stars’ Centroid Determination Using PSF-Fitting Method

Suszyński

Wawryn

2015

Metrology and Measurement Systems

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“…Readout noise, background noise, photon noise and scintillation effects are dominant effects in atmospheric AO. Due to the presence of noise, mathematically simplest centroiding algorithm like Center of Gravity (CoG) method leads to large wavefront reconstruction errors [6] [7][8][9]. In this paper, we studied the performance of CoG, WCoG, IWCoG and IWC techniques.…”

Section: Figure 1 Principle Of Shack Hartmann Sensormentioning

confidence: 99%

Centroid Detection by Gaussian Pattern Matching in Adaptive Optics

Akondi¹,

Roopashree²,

Prasad³

2010

IJCA

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Shack Hartmann wavefront sensor is a two dimensional array of lenslets which is used to detect the incoming phase distorted wavefront through local tilt measurements made by recording the spot pattern near the focal plane. Wavefront reconstruction is performed in two stages -(a) image centroiding to calculate local slopes, (b) formation of the wavefront shape from local slope measurement. Centroiding accuracy contributes to most of the wavefront reconstruction error in Shack Hartmann sensor based adaptive optics system with readout and background noise. It becomes even more difficult in atmospheric adaptive optics case, where scintillation effects may also occur. In this paper we used a denoising technique based on thresholded Zernike reconstructor to minimize the effects due to readout and background noise. At low signal to noise ratio, this denoising technique can be improved further by taking the advantage of the shape of the spot. Assuming a Gaussian pattern for individual spots, it is shown that the centroiding accuracy can be improved in the presence of strong scintillations and background.

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“…However, the results obtained from this technique are not accurate in Hartmann patterns affected by noise, background illumination and spot modulating signals. In the past, several approaches have been proposed to accurately obtain the Hartmann centroids in these adverse situations, such as, the weighted centre of gravity [3], the iteratively weighted centroiding [4] and matched filter approaches [5]. These methods can obtain accurate results in presence of noise, but they are not appropriate in cases where the Hartmann pattern is affected by background illumination and/or a varying spot modulation or contrast signal [6,7].…”

Section: Introductionmentioning

confidence: 99%

Shack-Hartmann spot dislocation map determination using an optical flow method

Vargas¹,

Restrepo²,

Belenguer³

2014

Opt. Express

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We present a robust, dense, and accurate Shack-Hartmann spot dislocation map determination method based on a regularized optical flow algorithm that does not require obtaining the spot centroids. The method is capable to measure in presence of strong noise, background illumination and spot modulating signals, which are typical limiting factors of traditional centroid detection algorithms. Moreover, the proposed approach is able to face cases where some of the reference beam spots have not a corresponding one in the distorted Hartmann diagram, and it can expand the dynamic range of the Shack-Hartmann sensor unwrapping the obtained dense dislocation maps. We have tested the algorithm with both simulations and experimental data obtaining satisfactory results. A complete MATLAB package that can reproduce all the results can be downloaded from [http://goo.gl/XbZVOr].

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Experimental results for correlation-based wavefront sensing

Cited by 16 publications

References 4 publications

Stars’ Centroid Determination Using PSF-Fitting Method

Stars’ Centroid Determination Using PSF-Fitting Method

Centroid Detection by Gaussian Pattern Matching in Adaptive Optics

Shack-Hartmann spot dislocation map determination using an optical flow method

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