Browsing by Subject "Imaging systems"

Now showing 1 - 20 of 30

Open Access
2-D triangular mesh-based mosaicking for object tracking in the presence of occlusion
(SPIE, 1997) Toklu, C.; Tekalp, A. M.; Erdem, A. Tanju
In this paper, we describe a method for temporal tracking of video objects in video clips. We employ a 2D triangular mesh to represent each video object, which allows us to describe the motion of the object by the displacements of the node points of the mesh, and to describe any intensity variations by the contrast and brightness parameters estimated for each node point. Using the temporal history of the node point locations, we continue tracking the nodes of the 2D mesh even when they become invisible because of self-occlusion or occlusion by another object. Uncovered parts of the object in the subsequent frames of the sequence are detected by means of an active contour which contains a novel shape preserving energy term. The proposed shape preserving energy term is found to be successful in tracking the boundary of an object in video sequences with complex backgrounds. By adding new nodes or updating the 2D triangular mesh we incrementally append the uncovered parts of the object detected during the tracking process to the one of the objects to generate a static mosaic of the object. Also, by texture mapping the covered pixels into the current frame of the video clip we can generate a dynamic mosaic of the object. The proposed mosaicing technique is more general than those reported in the literature because it allows for local motion and out-of-plane rotations of the object that results in self-occlusions. Experimental results demonstrate the successful tracking of the objects with deformable boundaries in the presence of occlusion.
Open Access
Cepstrum based feature extraction method for fungus detection
(SPIE, 2011) Yorulmaz, Onur; Pearson, T.C.; Çetin, A. Enis
In this paper, a method for detection of popcorn kernels infected by a fungus is developed using image processing. The method is based on two dimensional (2D) mel and Mellin-cepstrum computation from popcorn kernel images. Cepstral features that were extracted from popcorn images are classified using Support Vector Machines (SVM). Experimental results show that high recognition rates of up to 93.93% can be achieved for both damaged and healthy popcorn kernels using 2D mel-cepstrum. The success rate for healthy popcorn kernels was found to be 97.41% and the recognition rate for damaged kernels was found to be 89.43%. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
Open Access
Compression of images in CFA format
(IEEE, 2006) Cüce, Halil İbrahim; Çetin, A. Enis; Davey, M. K.
In this paper, images in Color Filter Array (CFA) format are compressed without converting them to full-RGB color images. Green pixels are extracted from the CFA image data and placed in a rectangular array, and compressed using a transform based method without estimating the corresponding luminance values. In addition, two sets of color difference (or chrominance) coefficients are obtained corresponding to the red and blue pixels of the CFA data and they are also compressed using a transform based method. The proposed method produces better PSNR values compared to the standard approach of bilinear interpolation followed by compression.
Open Access
Degrees of freedom of optical systems and signals with applications to sampling and system simulation
(Optical Society of America, 2013) Oktem F.S.; Özaktaş, Haldun M.
We study the degrees of freedom of optical systems and signals based on space-frequency (phase space) analysis. At the heart of this study is the relationship of the linear canonical transform domains to the space-frequency plane. Based on this relationship, we discuss how to explicitly quantify the degrees of freedom of first-order optical systems with multiple apertures, and give conditions for lossless transfer. Moreover, we focus on the degrees of freedom of signals in relation to the space-frequency support and provide a sub-Nyquist sampling approach to represent signals with arbitrary space-frequency support. Implications for simulating optical systems are also discussed. © 2013 Optical Society of America.
Open Access
Detection of microcalcifications in mammograms using nonlinear subband decomposition and outlier labeling
(SPIE, 1997-02) Gürcan, M. Nafi; Yardımcı, Yasemin C.; Çetin, A. Enis; Ansari, R.
Computer-aided diagnosis will be an important feature of the next generation picture archiving and communication systems. In this paper, computer-aided detection of microcalcifications in mammograms using a nonlinear subband decomposition and outlier labeling is examined. The mammogram image is first decomposed into subimages using a nonlinear subband decomposition filter bank. A suitably identified subimage is divided into overlapping square regions in which skewness and kurtosis as measures of the asymmetry and impulsiveness of the distribution are estimated. A region with high positive skewness and kurtosis is marked as a region of interest. Finally, an outlier labeling method is used to find the locations of microcalcifications in these regions. Simulation studies are presented.
Open Access
Enhancement of images corrupted with signal dependent noise: Application to ultrasonic imaging
(1993-11) Kutay, M. Alper; Karaman, Mustafa; Bozdağı, Gözde
An adaptive filter for smoothing images corrupted by signal dependent noise is presented. The filter is mainly developed for speckle suppression in medical B-scan ultrasonic imaging. The filter is based on mean filtering of the image using appropriately shaped and sized local kernels. Each filtering kernel, fitting to the local homogeneous region, is obtained through local statistics based region growing. Performance of the proposed scheme have been tested on a B-scan image of a standard tissue-mimicking ultrasound resolution phantom. The results indicate that the filter effectively reduces the speckle while preserving the resolvable details. The performance figures obtained through computer simulations on the phantom image are presented in a comparative way with some existing speckle iippression schemes.
Open Access
Fast and accurate algorithms for quadratic phase integrals in optics and signal processing
(SPIE, 2011) Koç, A.; Özaktaş, Haldun M.; Hesselink L.
The class of two-dimensional non-separable linear canonical transforms is the most general family of linear canonical transforms, which are important in both signal/image processing and optics. Application areas include noise filtering, image encryption, design and analysis of ABCD systems, etc. To facilitate these applications, one need to obtain a digital computation method and a fast algorithm to calculate the input-output relationships of these transforms. We derive an algorithm of NlogN time, N being the space-bandwidth product. The algorithm controls the space-bandwidth products, to achieve information theoretically sufficient, but not redundant, sampling required for the reconstruction of the underlying continuous functions. © 2011 SPIE.
Open Access
Feature issue of digital holography and 3D imaging (DH) introduction
(Optical Society of America (OSA), 2014-07) Hayasaki, Y.; Zhou, C.; Popescu, G.; Onural, Levent
The OSA Topical Meeting "Digital Holography and 3D Imaging (DH)," was held in Seattle, Washington, July 13-17, 2014. Feature issues based on the DH meeting series have been released by Applied Optics (AO) since 2007. This year Optics Express (OE) and AO jointly decided to have one such feature issue in each journal. The DH meeting will continue in the future, as expected, and the next meeting is scheduled to be held on 24-28 May 2015, in Shanghai Institute of Optics and Fine Mechanics, Shanghai, China. © 2014 Optical Society of America
Open Access
Fractional free space, fractional lenses, and fractional imaging systems
(OSA - The Optical Society, 2003) Sümbül, U.; Özaktaş, Haldun M.
Continuum extensions of common dual pairs of operators are presented and consolidated, based on the fractional Fourier transform. In particular, the fractional chirp multiplication, fractional chirp convolution, and fractional scaling operators are defined and expressed in terms of their common nonfractional special cases, revealing precisely how they are interpolations of their conventional counterparts. Optical realizations of these operators are possible with use of common physical components. These three operators can be interpreted as fractional lenses, fractional free space, and fractional imaging systems, respectively. Any optical system consisting of an arbitrary concatenation of sections of free space and thin lenses can be interpreted as a fractional imaging system with spherical reference surfaces. As a special case, a system departing from the classical single-lens imaging condition can be interpreted as a fractional imaging system. © 2003 Optical Society of America.
Open Access
Holographic 3DTV research within the European 3DTV project
(Optical Society of America, 2008) Onural, Levent
A European project on 3DTV has been functional since September 2004. Holographic displays for 3DTV and signal processing issues associated with diffraction and holography are among research interests. The research has already generated interesting results.
Open Access
Integral imaging using phase-only LCoS spatial light modulators as Fresnel lenslet arrays
(Optical Society of Amercia, 2011-10-27) Ÿontem, A. O.; Onural, L.
We present a digital integral imaging system. A Fresnel lenslet array pattern is written on a phase-only LCoS spatial light modulator device (SLM) to replace the regular analog lenslet array in a conventional integral imaging system. We theoretically analyze the capture part of the proposed system based on Fresnel wave propagation formulation. Because of pixelation and quantization of the lenslet array pattern, higher diffraction orders and multiple focal points emerge. Because of the multiple focal planes introduced by the discrete lenslets, multiple image planes are observed. The use of discrete lenslet arrays also causes some other artifacts on the recorded elemental images. The results reduce to those available in the literature when the effects introduced by the discrete nature of the lenslets are omitted. We performed simulations of the capture part. It is possible to obtain the elemental images with an acceptable visual quality. We also constructed an optical integral imaging system with both capture and display parts using the proposed discrete Fresnel lenslet array written on a SLM. Optical results when self-luminous objects, such as an LED array, are used indicate that the proposed system yields satisfactory results.
Open Access
Kadastral haritalarin görüntü işleme teknikleri kullanilarak vektörizasyonu
(IEEE, 2011-04) Balkoca, A.; Yergök, Ahsen İkbal; Yücekaya, S.
This study aims vectorizing cadastral maps by using image processing techniques. Firstly, landing marks on cadastral maps are found by Moore Neighbor Tracing method then the connections are extracted and connecting lines are found. The system extracted about 80%-90% of the components that user should manually draw which is discussed in Section 4. © 2011 IEEE.
Open Access
Key frame selection from MPEG video data
(SPIE, 1997-02) Gerek, Ömer. N.; Altunbaşak, Y.
This paper describes a method for selecting key frames by using a number of parameters extracted from the MPEG video stream. The parameters are directly extracted from the compressed video stream without decompression. A combination of these parameters are then used in a rule based decision system. The computational complexity for extracting the parameters and for key frame decision rule is very small. As a results, the overall operation is very quickly performed and this makes our algorithm handy for practical purposes. The experimental results show that this method can select the distinctive frames of video streams successfully.
Open Access
Man-made object classification in SAR images using 2-D cepstrum
(IEEE, 2009-05) Eryildirim, A.; Çetin, A. Enis
In this paper, a novel descriptive feature parameter extraction method from Synthetic Aperture Radar (SAR) images is proposed. The new method is based on the two-dimensional (2-D) real cepstrum. This novel 2-D cepstrum method is compared with principal component analysis (PCA) method by testing over the MSTAR image database. The extracted features are classified using Support Vector Machine (SVM). We demonstrate that discrimination of natural background (clutter) and man-made objects (metal objects) in SAR imagery is possible using the 2-D cepstrum feature parameters. In addition, the computational cost of the cepstrum method is lower than the PCA method. Experimental results are presented. ©2009 IEEE.
Open Access
Mel-cepstral methods for image feature extraction
(IEEE, 2010) Çakır, Serdar; Çetin, A. Enis
A feature extraction method based on two-dimensional (2D) mel-cepstrum is introduced. The concept of one-dimensional (1D) mel-cepstrum which is widely used in speech recognition is extended to 2D in this article. Feature matrices resulting from the 2D mel-cepstrum, Fourier LDA, 2D PCA and original image matrices are converted to feature vectors and individually applied to a Support Vector Machine (SVM) classification engine for comparison. The AR face database, ORL database, Yale database and FRGC version 2 database are used in experimental studies, which indicate that recognition rates obtained by the 2D mel-cepstrum method is superior to the recognition rates obtained using Fourier LDA, 2D PCA and ordinary image matrix based face recognition. This indicates that 2D mel-cepstral analysis can be used in image feature extraction problems. © 2010 IEEE.
Open Access
Microwave imaging of three-dimensional conducting objects using the newton minimization approach
(IEEE, 2013) Etminan, A.; Gürel, Levent
In this work, we present a framework to detect the shape of unknown perfect electric conducting objects by using inverse scattering and microwave imaging. The initialguess object, which evolves to achieve the target, is modeled by triangles such that vertices of the triangles are the unknowns of our problem.
Open Access
Object rigidity and reflectivity identification based on motion analysis
(IEEE, 2010) Zang, D.; Schrater P.R.; Doerschner, Katja
Rigidity and reflectivity are important properties of objects, identifying these properties is a fundamental problem for many computer vision applications like motion and tracking. In this paper, we extend our previous work to propose a motion analysis based approach for detecting the object's rigidity and reflectivity. This approach consists of two steps. The first step aims to identify object rigidity based on motion estimation and optic flow matching. The second step is to classify specular rigid and diffuse rigid objects using structure from motion and Procrustes analysis. We show how rigid bodies can be detected without knowing any prior motion information by using a mutual information based matching method. In addition, we use a statistic way to set thresholds for rigidity classification. Presented results demonstrate that our approach can efficiently classify the rigidity and reflectivity of an object. © 2010 IEEE.
Open Access
Processing of optically-captured digital holograms for three-dimensional display
(2009-04) Naughton, T.J.; Kreis, T.; Onural, Levent; Ferraro, P.; Depeursinge, C.; Emery, Y.; Hennelly, B. M.; Kujawiñska, M.
In digital holography, holograms are usually optically captured and then two-dimensional slices of the reconstruction volume are reconstructed by computer and displayed on a two-dimensional display. When the recording is of a three-dimensional scene then such two-dimensional display becomes restrictive. We outline our progress on capturing larger ranges of perspectives of three-dimensional scenes, and our progress on four approaches to better visualise this three-dimensional information encoded in the digital holograms. The research has been performed within a European Commission funded research project dedicated the capture, processing, transmission, and display of real-world 3D and 4D scenes using digital holography. © 2009 SPIE.
Open Access
Rate-distortion based piecewise planar 3D scene geometry representation
(IEEE, 2006) Imre, E.; Alatan, A.A.; Güdükbay, Uğur
This paper proposes a novel 3D piecewise planar reconstruction algorithm, to build a 3D scene representation that minimizes the intensity error between a particular frame and its prediction. 3D scene geometry is exploited to remove the visual redundancy between frame pairs for any predictive coding scheme. This approach associates the rate increase with the quality of representation, and is shown to be rate-distortion efficient by the experiments. © 2007 IEEE.
Open Access
Real-time fringe pattern generation with high quality
(OSA, 2009) Kang, Hoonjong; Yaraş, Fahri; Onural, Levent; Yoshikawa, H.
A hologram computation procedure and its GPU implementation are presented. The procedure is based on partitioning. Each segment has an approximate but simpler frequency domain representation. Quality of the results is comparable to Fresnel holograms.