Optics and Photonics Journal, 2013, 3, 250-258 http://dx.doi.org/10.4236/opj.2013.33040 Published Online July 2013 (http://www.scirp.org/journal/opj) Recognition of Direction of New Apertures from the Elongated Speckle Images: Simulation Abdallah Mohamed Hamed Physics Department, Faculty of Science, Ain Shams University, Cairo, Egypt Email: Amhamed73@hotmail.com Received January 31, 2013; revised March 2, 2013; accepted March 9, 2013 Copyright © 2013 Abdallah Mohamed Hamed. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ABSTRACT In this paper, we present an elongated speckle images produced from diffusers using sharp elliptical apertures. The ori- entation of the elliptic aperture is recognized from the direction of the elongation in the speckle images. The aperture tilting out of the plane is investigated. Three models of elliptical apertures are considered and the corresponding speckle images are obtained. The 1st model is composed of two orthogonal ellipses or plus symbol pupil; the 2nd has four sym- metric ellipses with an angle of 45˚ between each of them or in the form of a snow flake pupil and the 3rd model looks like an airplane. Also, the autocorrelation profiles of the speckle images corresponding to the diffused airplane are ob- tained from which the average speckle size is computed. Finally, the reconstructed images of the described elliptical models and its autocorrelation images, making use of Mat lab code, are obtained. Keywords: Digital Imaging; Sharp Elliptical Apertures; Plus Symbol and Snow Flake Pupils 1. Introduction The production of elongated speckle images was ob- tained using the mechanical scanning of the static spec- kle pattern [1]. The author presented a technique of spa- tially oriented speckle-screen encoding to improve the grating encoding technique for white-light image proc- essing. Also, an artificial screen composed of small strips photographed several times on a high resolution film is designed to obtain elongation of nearly ten times the av- erage grain size of natural speckle [2]. In a recent publi- cation by the author [3], numerical elliptical apertures of small elliptic shapes are analyzed and the Fourier trans- form is operated giving the speckle images of diffusers modulated by these elliptic apertures. An approach for determining the roughness of engi- neering surfaces is resulted from the speckle elongation effect. The laser speckle pattern, arising from light scat- tered from rough surfaces that are illuminated by poly- chromatic laser light, is detected in the far-field region. The incoherent superposition of these light intensities and the angular dispersion cause the effect of speckle elongation [4,5]. This is characterized by increasing speckle widths and leads to a radial structure of the spec- kle patterns. With increasing surface roughness, the elon- gation is replaced more and more by the de-correlation of the monochromatic speckle patterns for the different wavelengths. Such effects were detected with the CCD technique and analyzed by local autocorrelation func- tions of intensity fluctuations that were calculated for different areas of the speckle patterns. Hence, the auto- correlation method is applied to process laser speckle patterns. The relation between surface roughness, speckle elongation, and correlation length of autocorrelation function can be obtained. Consequently, the measured surface roughness can be achieved [6]. An oriented pho- tographic diffuser was used to record an elongated spec- kle pattern. It is found that the contrast transfer, when gratings are imaged through the slits in the diffuser, is considerably higher compared to imaging through a cir- cular pinhole of comparable dimensions [7]. An autocor- relation algorithm for speckle size evaluation has been investigated [8-11]. The authors measured the average speckle size from the auto-covariance function of the digitized intensity speckle pattern. The spatial character- istics such as speckle size can be used to measure the roughness of surfaces [12,13]. An important remark must be taken into consideration during the recording of speckle data which states that the speckle size must be greater than the pixel size of the CCD camera in order to resolve variations in speckle intensity [14]. Recently, a Fast cal- culation method for optical diffraction on tilted plane was investigated [15]. Copyright © 2013 SciRes. OPJ