Multi-transmitter aperture synthesis with Zernike based aberration correction

Abstract

Multi-transmitter aperture synthesis increases the effective aperture in coherent imaging by shifting the backscattered speckle field across a physical aperture or set of apertures. Through proper arrangement of the transmitter locations, it is possible to obtain speckle fields with overlapping regions, which allows fast computation of optical aberrations from wavefront differences. In this paper, we present a method where Zernike polynomials are used to model the aberrations and high-order aberrations are estimated without the need to do phase unwrapping of the difference fronts.

Deep-turbulence wavefront sensing using digital-holographic detection in the off-axis image plane recording geometry

“…This choice provided low percentage errors (less than 0.5%) between the continuous and discrete calculations using Eqs. (14)- (17). 38 Propagation to the image plane from the exit-pupil plane occurred via a three-step process using WaveProp and AOTools: (1) by doubling the number of N × N grid points in the exit-pupil plane with a side length of D 1 from 256 × 256 grid points to 512 × 512 grid points via zero padding; (2) numerically solving the convolution form of the Fresnel diffraction integral via 2-D FFTs; and (3) cropping out the center 256 × 256 grid points, so that f ¼ Q I D 2 1 ∕ð256λÞ (i.e., the image plane side length was equal to the exit-pupil plane side length).…”

“…In practice, digitalholographic detection allows for the estimation of the complex field in the presence of an extended noncooperative object via speckle averaging and image sharpening algorithms or the angular diversity created by using multiple transmitters and receivers. [7][8][9][10][11][12][13][14][15][16][17][18] This versatility allows for long-range imaging, 19 three-dimensional imaging, 20 laser radar, 21 and synthetic-aperture imaging. 22 In general, the applications are abundant.…”