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Träfflista för sökning "L773:1094 4087 ;pers:(Owner Petersen Mette)"

Sökning: L773:1094 4087 > Owner Petersen Mette

  • Resultat 1-7 av 7
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1.
  • Beckers, Jacques M., et al. (författare)
  • Very high-resolution spectroscopy for extremely large telescopes using pupil slicing and adaptive optics
  • 2007
  • Ingår i: Optics Express. - 1094-4087. ; 15:5, s. 1983-1994
  • Tidskriftsartikel (refereegranskat)abstract
    • Under seeing limited conditions very high resolution spectroscopy becomes very difficult for extremely large telescopes (ELTs). Using adaptive optics (AO) the stellar image size decreases proportional with the telescope diameter. This makes the spectrograph optics and hence its resolution independent of the telescope diameter. However AO for use with ELTs at visible wavelengths require deformable mirrors with many elements. Those are not likely to be available for quite some time. We propose to use the pupil slicing technique to create a number of sub-pupils each of which having its own deformable mirror. The images from all subpupils are combined incoherently with a diameter corresponding to the diffraction limit of the sub-pupil. The technique is referred to as "Pupil Slicing Adaptive Optics" or PSAO. (c) 2007 Optical Society of America.
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2.
  • Fan, Chengyu, et al. (författare)
  • High-order laser guide star performance for the Euro50 telescope
  • 2005
  • Ingår i: Optics Express. - 1094-4087. ; 13:5, s. 1377-1383
  • Tidskriftsartikel (refereegranskat)abstract
    • High-order laser guide star performance for the Euro50 telescope is analyzed. Focus anisoplanatism residual errors using multiple LGSs are obtained by numerical simulations. Results calculated for annual mean conditions at the La Palma site show that, considering only focus anisoplanatism, it will be possible to obtain a Strehl ratio of 0.72 similar to 0.82 at 2.2 mum using 13 LGSs. A Strehl ratio of 0.60 similar to 0.70 can be obtained at 1.25 mum using 21 LGSs. The dependence of wavefront measurement error on pulsed laser power is also investigated. The variance of the measurement error is lower than 0.2 rad(2) when the laser power is larger than 14 W.
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3.
  • KNUTSSON, PER, et al. (författare)
  • Correction of static and non-common path aberrations in an adaptive optics system using inherent calibration data
  • 2021
  • Ingår i: Optics Express. - 1094-4087. ; 29:3, s. 3406-3414
  • Tidskriftsartikel (refereegranskat)abstract
    • For low-order adaptive optics systems, a method that is able to correct for system aberrations in the final focal plane is presented. The paper presents a novel figure of merit, corresponding to the integrated non-normalized tip-tilt-free optical transfer function. The inherent singular value decomposition modal content of the interaction matrix is used to optimize this figure of merit. The method has proven to be stable and robust, providing a simple mean to facilitate diffraction limited imaging in an experimental setup for ophthalmic applications.
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4.
  • Knutsson, Per, et al. (författare)
  • Emulation of dual-conjugate adaptive optics on an 8-m class telescope
  • 2003
  • Ingår i: Optics Express. - 1094-4087. ; 11:18, s. 2231-2237
  • Tidskriftsartikel (refereegranskat)abstract
    • In this article we present a downscaled laboratory setup emulating five natural guide stars, a layered static atmosphere and a 7.5-m aperture telescope equipped with dual-conjugate adaptive optics at a wavelength of 2.2 mum. Three reconstruction alternatives were evaluated; conventional adaptive optics, field-averaged conventional adaptive optics and dual-conjugate adaptive optics. The results were compared with Zemax-simulations of the setup. The expected increase of the size of the isoplanatic patch, using dual-conjugate adaptive optics, was confirmed. (C) 2003 Optical Society of America.
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5.
  • Knutsson, Per, et al. (författare)
  • Extended object wavefront sensing based on the correlation spectrum phase
  • 2005
  • Ingår i: Optics Express. - 1094-4087. ; 13:23, s. 9527-9536
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper we investigate the performance of a Fourier based algorithm for fast subpixel shift determination of two mutually shifted images subjected to noise. The algorithm will be used for Shack-Hartmann based adaptive optics correction of images of an extended object subjected to dynamical atmospheric fluctuations. The performance of the algorithm is investigated both analytically and by Monte Carlo simulations. Good agreement is achieved in relation to how the precision of the shift estimate depends on image parameters such as contrast, photon counts and readout noise, as well as the dependence on sampling format, zero-padding and field of view. Compared to the conventional method for extended object wavefront sensing, a reduction of the computational cost is gained at a marginal expense of precision.
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6.
  • Thaung, Jörgen, 1965, et al. (författare)
  • Dual-conjugate adaptive optics for wide-field high-resolution retinal imaging.
  • 2009
  • Ingår i: Optics express. - 1094-4087. ; 17:6, s. 4454-67
  • Tidskriftsartikel (refereegranskat)abstract
    • We present analysis and preliminary laboratory testing of a real-time dual-conjugate adaptive optics (DCAO) instrument for ophthalmology that will enable wide-field high resolution imaging of the retina in vivo. The setup comprises five retinal guide stars (GS) and two deformable mirrors (DM), one conjugate to the pupil and one conjugate to a plane close to the retina. The DCAO instrument has a closed-loop wavefront sensing wavelength of 834 nm and an imaging wavelength of 575 nm. It incorporates an array of collimator lenses to spatially filter the light from all guide stars using one adjustable iris, and images the Hartmann patterns of multiple reference sources on a single detector. Zemax simulations were performed at 834 nm and 575 nm with the Navarro 99 and the Liou- Brennan eye models. Two correction alternatives were evaluated; conventional single conjugate AO (SCAO, using one GS and a pupil DM) and DCAO (using multiple GS and two DM). Zemax simulations at 575 nm based on the Navarro 99 eye model show that the diameter of the corrected field of view for diffraction-limited imaging (Strehl >or= 0.8) increases from 1.5 deg with SCAO to 6.5 deg using DCAO. The increase for the less stringent condition of a wavefront error of 1 rad or less (Strehl >or= 0.37) is from 3 deg with SCAO to approximately 7.4 deg using DCAO. Corresponding results for the Liou-Brennan eye model are 3.1 deg (SCAO) and 8.2 deg (DCAO) for Strehl >or= 0.8, and 4.8 deg (SCAO) and 9.6 deg (DCAO) for Strehl >or= 0.37. Potential gain in corrected field of view with DCAO is confirmed both by laboratory experiments on a model eye and by preliminary in vivo imaging of a human eye.
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7.
  • Wu, Zhiwen, et al. (författare)
  • Comparison of wavefront sensor models for simulation of adaptive optics
  • 2009
  • Ingår i: Optics Express. - 1094-4087. ; 17:22, s. 20575-20583
  • Tidskriftsartikel (refereegranskat)abstract
    • The new generation of extremely large telescopes will have adaptive optics. Due to the complexity and cost of such systems, it is important to simulate their performance before construction. Most systems planned will have Shack-Hartmann wavefront sensors. Different mathematical models are available for simulation of such wavefront sensors. The choice of wavefront sensor model strongly influences computation time and simulation accuracy. We have studied the influence of three wavefront sensor models on performance calculations for a generic, adaptive optics (AO) system designed for K-band operation of a 42 m telescope. The performance of this AO system has been investigated both for reduced wavelengths and for reduced r(0) in the K band. The telescope AO system was designed for K-band operation, that is both the subaperture size and the actuator pitch were matched to a fixed value of r(0) in the K-band. We find that under certain conditions, such as investigating limiting guide star magnitude for large Strehl-ratios, a full model based on Fraunhofer propagation to the subimages is significantly more accurate. It does however require long computation times. The shortcomings of simpler models based on either direct use of average wavefront tilt over the subapertures for actuator control, or use of the average tilt to move a precalculated point spread function in the subimages are most pronounced for studies of system limitations to operating parameter variations. In the long run, efficient parallelization techniques may be developed to overcome the problem. (C) 2009 Optical Society of America
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  • Resultat 1-7 av 7

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