Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Conference Object Citation - WoS: 2Citation - Scopus: 2Çok Bakışlı 3b Geriçatımın Polarizasyon Görüntüleme Kullanımıyla İyileştirilmesi(Institute of Electrical and Electronics Engineers Inc., 2014) Ozan, Şükrü; Gümüştekin, ŞevketPerformance of stereo imaging methods, which are used to find depth information of a scene, can be adversely affected by surface reflection properties of subjects in the scene and possible change in relative camera and light source positions. In this study a catadioptric multiview imaging system, which is constructed by using planar mirrors, is proposed. Stereo matching problems which are caused by the specular reflections in the scene are highlighted and it is shown that those problems can be significantly alleviated by using polarization images.Conference Object Yapısal Aydınlatma Kullanarak Yüzeylerin Geometrik ve Yansıtıcılık Özelliklerinin Geri Çatımı(Institute of Electrical and Electronics Engineers Inc., 2015) Ozan, Şükrü; Gümüştekin, ŞevketIt is not possible to perform a robust and dense surface reconstruction for plain colored surfaces which have insufficient surface features, and for surfaces which have specularity effect because of the material nature by using traditional stereo imaging methods. The proposed surface scanner system in this work makes it possible to get a robust and dense surface reconstruction even for plain colored and/or semi glossy surfaces. Reflection properties of the surface material are also reconstructed to some extent by using the information gathered after scanning process. Moreover, the experimental results are shown.Conference Object Citation - Scopus: 3Sahne Aydınlatmasında Kullanılan Işık Kaynağının Renklilik Değerlerinin Tek İmge Kullanılarak Kestirimi(IEEE, 2011) Ozan, Şükrü; Gümüştekin, ŞevketIn this study, main goal is to estimate scene illuminant chromaticity values for each of the three color channels (red, green, blue). It is found that analysis of the pixel values, which are expressed by dichromatic reflection and inverse-intensity chromaticity space definitions, with appropriate statistical methods gives aproximate values for light source chromaticity within an acceptable error range. Single image of a scene is sufficient for calculations. We saw that chromaticity values of light sources with different colors can be approximately calculated. © 2011 IEEE.Conference Object Ölçülmüş Çydf Verilerinin Lafortune Modeli ile Etkin Gösterimi(IEEE, 2010) Ozan, Şükrü; Gümüştekin, ŞevketThe bi-directional reflectance distribution function (BRDF) describes the appearance of a material by its interaction with light. In this study, Lafortune BRDF model is fitted to densely sampled measured BRDF data by using Levenberg - Marquardt Algorithm. The obtained results are visualised by a physically based ray tracing software and the proposed method is analysed. ©2010 IEEE.Article Citation - WoS: 11Citation - Scopus: 11Calibration of Double Stripe 3d Laser Scanner Systems Using Planarity and Orthogonality Constraints(Elsevier Ltd., 2014) Ozan, Şükrü; Gümüştekin, ŞevketIn this study, 3D scanning systems that utilize a pair of laser stripes are studied. Three types of scanning systems are implemented to scan environments, rough surfaces of near planar objects and small 3D objects. These scanners make use of double laser stripes to minimize the undesired effect of occlusions. Calibration of these scanning systems is crucially important for the alignment of 3D points which are reconstructed from different stripes. In this paper, the main focus is on the calibration problem, following a treatment on the pre-processing of stripe projections using dynamic programming and localization of 2D image points with sub-pixel accuracy. The 3D points corresponding to laser stripes are used in an optimization procedure that imposes geometrical constraints such as coplanarities and orthogonalities. It is shown that, calibration procedure proposed here, significantly improves the alignment of 3D points scanned using two laser stripes.Conference Object Citation - Scopus: 2Çift Çizgisel Lazerli Bir 3b Ortam Tarayıcısının Kablibrasyonu(Institute of Electrical and Electronics Engineers Inc., 2012) Ozan, Şükrü; Gümüştekin, Şevket3B lazer tarayıcılar yüzey geometrisinin yakalanması için yaygın olarak kullanılan sistemlerdir. Geleneksel lazer tarayıcı sistemler bir adet lazer ışık kaynağına sahiptir. Bu çalışmada iki adet lazer ışık kaynağına sahip bir 3B lazer tarayıcı ele alınmıştır. Bu tarayıcı özellikle sahnelerdeki örtme etkisinin en küçüklenebilmesini sağlamaktadır. Ancak birden fazla lazer kaynağına sahip lazer tarayıcılar için kalibrasyon önemli bir problem olmaktadır. Çalışmamızda bu sistemlerde karşılaşılan kalibrasyon problemi tanımlanmıştır. Bu problemin çözümü için taranan sahnelerdeki dikgenlik, eş-düzlemsellik bilgileri kullanılmıştır.Article Citation - WoS: 2Citation - Scopus: 2Enhancing Stereo Matching Performance by Colour Normalisation and Specularity Removal(Institution of Engineering and Technology, 2011) Ozan, Şükrü; Gümüştekin, ŞevketA method to enhance the performance of stereo matching is presented. The position of the specular light reflection on an object surface varies due to the change in the position of the camera, light source, object or all combined. Additionally, there may be situations exhibiting a colour shift owing to a change in the light source chromaticity or camera white balance settings. These variations cause misleading results when stereo matching algorithms are applied. In this reported work, a single-image-based statistical method is used to normalise source images. This process effectively eliminates non-saturated specularities regardless of their positions on the object. The effect of specularity removal is tested on stereo image pairs. © 2011 The Institution of Engineering and Technology.Conference Object Citation - WoS: 1Citation - Scopus: 2A Case Study on Logging Visual Activities: Chess Game(Springer Verlag, 2006) Ozan, Şükrü; Gümüştekin, ŞevketAutomatically recognizing and analyzing visual activities in complex environments is a challenging and open-ended problem. In this study this task is performed in a chess game scenario where the rules, actions and the environment are well defined. The purpose here is to detect and observe a FIDE (Fédération International des Ėchecs) compatible chess board, generating a log file of the moves made by human players. A series of basic image processing operations have been applied to perform the desired task. The first step of automatically detecting a chess board is followed by locating the positions of the pieces. After the initial setup is established every move made by a player is automatically detected and verified. Intel® Open Source Computer Vision Library (OpenCV) is used in the current software implementation.