Numerical Analysis of Wavefront Reconstruction under Conditions of High-Intensity Atmospheric Turbulence
- PDF / 1,032,623 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 45 Downloads / 173 Views
TICS OF STOCHASTICALLY-HETEROGENEOUS MEDIA
Numerical Analysis of Wavefront Reconstruction under Conditions of High-Intensity Atmospheric Turbulence V. V. Lavrinova, * and L. N. Lavrinovaa, ** a
V.E. Zuev Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, Tomsk, 634055 Russia *e-mail: [email protected] **e-mail: [email protected] Received June 3, 2019; revised December 3, 2019; accepted December 20, 2019
Abstract—The optical radiation wavefront distorted by turbulence is reconstructed based on the Hartmann method by approximating the wave function by Zernike polynomials according to estimates of local tilts. The reconstruction is analyzed for high-intensity turbulent distortions. Relying on results of statistical analysis of information on phase distortions of radiation by a hartmannogram formed in the plane of the receiving device, a method is suggested which allows one to reduce the residual reconstruction error caused by the presence of high-intensity phase fluctuations in the wavefront distribution. Keywords: Shack–Hartmann wavefront sensor, turbulent distortions of optical radiation DOI: 10.1134/S1024856020040077
INTRODUCTION The turbulent atmosphere has a large number of spatial inhomogeneities and is characterized by a wide range of spatial scales of fluctuating refractive indices. Their fluctuations lead to phase fluctuations of the optical radiation, which significantly affect the operation of optoelectronic systems. Phase fluctuations, in turn, are a source of radiation intensity fluctuations in the recording plane [1]. The intensity of radiation phase fluctuations caused by turbulence is characterized by the Fried parameter introduced for numerical estimation of the level of distortions in the radiation wavefront propagating in the atmosphere [1], in particular, for estimating the “astronomical seeing” [2–4] where typical values of the Fried parameter for visual optical radiation are determined. Visually, the influence of high-intensity atmospheric turbulence on optical radiation in a Shack– Hartmann wavefront sensor (WFS) is reflected in the fact that images in the focal plane of the microlens array become weakly illuminated or not illuminated at all; moreover, the illumination intensity of the same images varies from frame to frame by analogy with the flickering effect in images of focal spots as the optical radiation propagates along a horizontal path [5]. Work [5] was devoted to adaptive optical correction; in that work, a Maksutov–Cassegrain telescope was used as an optical receiver for wavefront measurements with a Shack–Hartmann sensor. The image of an individual hartmannogram was characterized by
central screening caused by constructional features of the telescope; visualization of a series of hartmannograms was accompanied by flickering focal spot images. For this reason, coordinates of centroids were determined by the averaged hartmannogram with the centering algorithm using the threshold intensity value. The sum of pixel values in the region of the focal spot was compared with
Data Loading...
