Blur Identification Based on Higher Order Spectral Nulls

The identification of the point spread function (PSF) from the degraded image data constitutes an important first step in image restoration that is known as blur identification. Though a number of blur identification algorithms have been developed in recent years, two of the earlier methods based on the power spectrum and power cepstrum remain popular, because they are easy to implement and have proved to be effective in practical situations. Both methods are limited to PSF\u27s which exhibit spectral nulls, such as due to defocused lens and linear motion blur. Another limitation of these methods is the degradation of their performance in the presence of observation noise. The central slice of the power bispectrum has been employed as an alternative to the power spectrum which can suppress the effects of additive Gaussian noise. In this paper, we utilize the bicepstrum for the identification of linear motion and defocus blurs. We present simulation results where the performance of the blur identification methods based on the spectrum, the cepstrum, the bispectrum and the bicepstrum is compared for different blur sizes and signal-to-noise ratio levels

Blur identification and restoration of images of coronary microvessel

The objective of this research was to identify the blur characteristics of the blurred images of the rat coronary microvessel, and the information of the blur characteristics was used to restore the blurred images. The blur characteristics were analyzed by using the image power cepstrum. The Wiener filter was implemented to restore the images. There were two types of point spread functions proposed and studied for the restoration. They were: defocus blur PSF and motion blur PSF. The images were transferred from HP A900 system to an AVS workstation. The images were processed and manipulated by the AVS, and showed significant improvement in quality. Blur characteristics which were similar to the motion blur were found in all the images. The motion blur PSF did not show much effectiveness in the restoration process. No defocus blur or motion blur characteristics appeared on the cepstrum of the microvessel images, suggesting that the strobe technique was capable of acquiring stationary coronary microvessel images

Development of image restoration techniques

Image denoising and image deblurring are studied as part of the thesis. In deblurring, blind deconvolution is investigated. Out of the several classes of blind deconvolution techniques, Non parametric Methods based on Image Constraints are studied at greater depth. A new algorithm based on the Iterative Blind Deconvolution(IBD) technique is developed. The algorithm makes use of spatial domain constraints of non-negativity and support. The Fourier-domain constraint may be described as constraining the product of the Fourier spectra of the image f and the Fourier spectra of the point spread function h to be equal to the convolution spectrum. Within each iteration, the algorithm switches between spatial domain and frequency domain and imposes known constraints on each. The convergence of the original IBD can be accelerated by limiting high magnitude values in frequency domain of both estimated image and point spread function. The new algorithm converges within less than 25 iterations where as the original IBD took nearly 500 iterations. Inclusion of the support constraint in the spatial domain improves quality of the restored image. Also, sum of the spatial domain values of the point spread function should be made equal to one at the end of each iteration, for preventing the loss of image intensity. PSNR values calculated for restored images show signi¯cant improvement in image quality. A PSNR of 17.8dB is obtained for the improved scheme where as it is 14.3dB for the original IBD. A new stopping criteria based on standard deviation of the image power for last k iterations is de¯ned for stopping the algorithm when it converges. In denoising, an edge retrieval technique is developed which preserves the image details along with e®ectively removing impulse noise. Noisy pixels are detected in the ¯rst phase and in the next phase those pixel values are replaced with an estimate of the actual value. For dealing with the wrong classi¯cation of edge pixels as noisy pixels, an edge retrieval technique based on pixel-wise MAD is de¯ned. This scheme retrieves the pixels which are wrongly classi¯ed as noise. The algorithm gives high PSNR values as well as very good detail preservation

Motion deblurring for optical character recognition

Master'sMASTER OF SCIENC

Blind Restoration of Motion Blurred Barcode Images using Ridgelet Transform and Radial Basis Function Neural Network

The aim of any image restoration techniques is recovering the original image from a degraded observation. One of the most common degradation phenomena in images is motion blur. In case of blind image restoration accurate estimation of motion blur parameters is required for deblurring of such images. This paper proposed a novel technique for estimating the parameters of motion blur using ridgelet transform. Initially, the energy of ridgelet coefficients is used to estimate the blur angle and then blur length is estimated using a radial biases function neural network. This work is tested on different barcode images with varying parameters of blur. The simulation results show that the proposed method improves the restoration performance

Dimensionality reduction for hyperspectral data

This thesis is about dimensionality reduction for hyperspectral data. Special emphasis is given to dimensionality reduction techniques known as kernel eigenmap methods and manifold learning algorithms. Kernel eigenmap methods require a nearest neighbor or a radius parameter be set. A new algorithm that does not require these neighborhood parameters is given. Most kernel eigenmap methods use the eigenvectors of the kernel as coordinates for the data. An algorithm that uses the frame potential along with subspace frames to create nonorthogonal coordinates is given. The algorithms are demonstrated on hyperspectral data. The last two chapters include analysis of representation systems for LIDAR data and motion blur estimation, respectively

Motion blur invariant for estimating motion parameters of medical ultrasound images

High-quality medical ultrasound imaging is definitely concerning motion blur, while medical image analysis requires motionless and accurate data acquired by sonographers. The main idea of this paper is to establish some motion blur invariant in both frequency and moment domain to estimate the motion parameters of ultrasound images. We propose a discrete model of point spread function of motion blur convolution based on the Dirac delta function to simplify the analysis of motion invariant in frequency and moment domain. This model paves the way for estimating the motion angle and length in terms of the proposed invariant features. In this research, the performance of the proposed schemes is compared with other state-of-the-art existing methods of image deblurring. The experimental study performs using fetal phantom images and clinical fetal ultrasound images as well as breast scans. Moreover, to validate the accuracy of the proposed experimental framework, we apply two image quality assessment methods as no-reference and full-reference to show the robustness of the proposed algorithms compared to the well-known approaches