Presentation04 - Computer Vision Lecture#4 Hossam...

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Computer Vision Lecture #4 Hossam Abdelmunim 1 & Aly A. Farag 2 1 Computer & Systems Engineering Department, Ain Shams University, Cairo, Egypt 2 Electerical and Computer Engineering Department, University of Louisville, Louisville, KY, USA ECE619/645 – Spring 2011
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Image Formation
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Overview • Pinhole camera • Refraction of light • Thin-lens equation • Optical power and accommodation • Image irradiance and scene radiance • Human eye • Geometry of perspective imaging
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Lens-less Imaging Systems - Pinhole Optics Projects images – without lens – with infinite depth of field Smaller the pinhole – better the focus – less the light energy from any single point Good for tracking solar eclipses
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Pinhole Camera (Cont…) Distant Objects are Smaller
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Pinhole Camera (Cont…) Bigger Hole-More Blurred Images
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Diffraction Two disadvantages to pinhole systems – Low light collecting power – diffraction Diffraction Light bends as it passes by the edge of a narrow aperture Human vision at high light levels, pupil (aperture) is small and blurring is due to diffraction – at low light levels, pupil is open and blurring is due to lens imperfections
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Diffraction and pinhole optics
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Lenses Collect More Lights • With a lens, diverging rays from a scene point are converged back to an image point
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Refraction: Snell’s law
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Lens Equation
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Thin Lens relates the distance between the scene point being viewed and the lens to the distance between the lens and the point’s image (where the rays from that point are brought into focus by the lens) Let M be a point being viewed, p is the distance of M from the lens along the optical axis. The thin lens focuses all the rays from M onto the same point, the image point m at distance q from the lens.
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Thin Lens Equation m can be determined by intersecting two known rays
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This note was uploaded on 01/12/2012 for the course ECE 618 taught by Professor Amini during the Spring '08 term at University of Louisville.

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Presentation04 - Computer Vision Lecture#4 Hossam...

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