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Unformatted text preview: Final Exam ECE/CS 181b June 12, 2008 Name: This is a closed book/notes examination. Calculators and other devices with memory are not allowed. Instructions: All questions on this exam are weighted equally. To receive full credit, answer the following questions clearly and completely, providing analytical derivations when required. If the space provided is insufficient, you may use extra paper, but make sure your name and the question number is on it. For this exam, we will adopt the following conventions (READ CARE- FULLY): Boldface letters indicate points ( x ), lines ( l ), vectors ( p ) or matrices ( H ). All the quantities related to the second camera are identified by the superscript prime ( ). The notation H : A 7 A means a matrix H which maps A to A . The notation x x means that x and x are corresponding elements (points, lines, etc.) in the two image planes. 1 QUESTION 1 : Edge Detection. This question is about the Laplacian of the Gaussian operator, used in the context of edge detection: 1. Describe how you would use the LoG operator to detect edges in im- ages. Answer : Mainly two-step process. First the image is filtered with a sec- ond derivative of a gaussian (the filter is isotropic, therefore the com- putation can be performed efficiently in the frequency domain). Second the zero crossings of the output are identified as edge points. 2. Describe the LoG operator in terms of the order of the derivatives that it computes. Comment about the main advantages and disadvantages of this. Answer : LoG is a second derivative type of operator. Advantages: good localization. Disadvantages: sensitive to noise. 3. What parameter has to be tuned by the user? Answer : LoG requires to set the , that is the scale of the Gaussian blurring....
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- Fall '08