ece542-2 - ECE542-2 Digital Image Processing 2- Digital...

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1 ECE542-2 Digital Image Processing 2- Digital image Fundamentals Digital image Fundamentals Dr. Z. Aliyazicioglu Cal Poly Pomona Electrical & Computer Engineering 1 Cal Poly Pomona Electrical & Computer Engineering Office 9-143 Elements of Visual Perception Human analysis play a central role in choice of image processing techniques based on visual judgments. Learning the physical limitation of human vision Structure of Human Eye Eye is nearly a sphere Average diameter is 20 mm Three membranes enclose the eye The Cornea and Sclera ECE542-2 2 Cal Poly Pomona The Choroid The Retina
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2 Structure of Human Eye The Choroid Contains network of blood vessels that serve nutrition to eye. The choroid coat reduce the amount of extraneous light entering the eye Its exterior extreme is divided into the ciliary body and the iris. The lens is made up of concentric layer of fibrous cells. contains 60 to 70% water, about 6% fat and more protein It is colored by slightly yellow pigmentation. Absorbs approximately 8% of the visible light spectrum. ECE542-2 3 Cal Poly Pomona Higher absorption at shorter wavelength. Infrared and ultraviolet light can damage the eye Structure of Human Eye The retina Lines inside of the wall’s entire posterior portion When eye is properly focused, light from on object outside the eye is imaged on the retina Two classes of receptors Cones 6 to 7 million cones in each eye Located central portion of the retina called the fovea Each one connected its oven nerve end Rods 70 to 150 million are distributed over the retina ECE542-2 4 Cal Poly Pomona Several rods are connected to a single nerve Gives overall picture of the field of view. Not involved in color vision
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3 Image Formation in the Eye The distance between the center of the lens and the retina (called the focal length) varies between 17 mm and 14 mm The observer is looking at a tree 15 meter high at the 100 m. The height of object in the retinal image is Retinal image is reflected primarily in the area of the fovea 15 17 2.25 100 m hm m m m m  ECE542-2 5 Cal Poly Pomona Brightness Adaptation and Discrimination In the figure, Subjective brightness is logarithmic function of the light intensity. The long solid curve represents the range of intensities to which the visual system can adopt. Visual system can not operate over such a range simultaneously. It accomplished this large variation by changing overall sensitivity (called ECE542-2 6 Cal Poly Pomona brightness adaptation) The total range of distinct intensity levels it can be discriminate simultaneously is rather small when compared with total adaptation range
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4 Brightness Adaptation and Discrimination Example of simultaneous contrast. All the inner squares have the same intensity, but they appear progressively darker as the background becomes lighter ECE542-2 7 Cal Poly Pomona Brightness Adaptation and Discrimination
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This note was uploaded on 10/24/2010 for the course ECE 542 taught by Professor Zeki during the Spring '10 term at Cal Poly Pomona.

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ece542-2 - ECE542-2 Digital Image Processing 2- Digital...

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