Vision_Notes_1 - Vision Notes* Wilson S. Geisler University...

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1 Vision Notes * Wilson S. Geisler University of Texas January, 2003 * These notes are in an unfinished state; there are gaps, some missing sections and possibly some minor errors (but hopefully no major errors).
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2 I. Vision and visual systems ......................................................................................... 5 A. Some general comments ....................................................................................... 5 1. Light as a source of information. ........................................................................... 5 2. Importance of vision . ............................................................................................. 5 3. Steps in the process of vision. ................................................................................ 6 4. Biological and artificial vision systems. ................................................................. 6 B. Visual tasks and visual performance ............................................................... 7 1. Objective versus subjective tasks. .......................................................................... 8 2. Identification and estimation tasks. ...................................................................... 10 3. Measures of performance. .................................................................................... 10 4. Feedback in visual tasks. ...................................................................................... 11 5. Two-alternative forced-choice tasks. ................................................................... 12 6. N-alternative forced choice tasks. ........................................................................ 23 7. Testing physiological theories with behavioral measurements . .......................... 23 8. Classical detection and discrimination tasks. ....................................................... 23 9. Direct estimation tasks. ........................................................................................ 23 10. Partition tasks. .................................................................................................... 23 C. Physical constraints on visual processing .................................................... 23 D. Physiological constraints on visual processing ............................................ 25 E. Bayesian/Optimal Models ................................................................................. 25 1. Description of tasks. ............................................................................................. 25 2. Model of the environmental and biological constraints. ...................................... 25 3. Theory of how to complete the processing tasks with optimal efficiency. .......... 25 F. Actual-performance models .............................................................................. 25 1. Anatomy. .............................................................................................................. 25 2. Physiology. ............................................................................................................ 26 3. Behavioral performance. ....................................................................................... 26 4. Linear and nonlinear systems analysis. ................................................................. 26 II. Visual Stimuli .......................................................................................................... 27 A. Light and light sources ....................................................................................... 27 1. Visible light. .......................................................................................................... 27 2. Definition of power. .............................................................................................. 28 3. Coherent and incoherent light. .............................................................................. 28 4. Spectral power distribution. ................................................................................. 29 5. Photons. ................................................................................................................. 29 6. Randomness of light . ............................................................................................ 30 7. Spectral quantum distribution. .............................................................................. 31 8. Radiometry. ........................................................................................................... 32 9. Photometry. ........................................................................................................... 32 10. Colorimetry. ........................................................................................................ 34 B. Light, surfaces and reflectance ......................................................................... 35 1. Primary and secondary (reflected) light sources. ................................................. 35 2. Description of reflected light . ............................................................................... 35 3. Extracting the reflectance function. ...................................................................... 36 4. Extracting surface texture and region boundaries. ................................................ 38
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3 5. Extracting surface orientation and distance. ......................................................... 38 III. Image formation: geometrical optics ................................................................. 38 A. Visual scene as a collection of point sources ................................................. 39 B. Two point sources ................................................................................................ 39 C. Imaging with pin-holes ...................................................................................... 39 D. Imaging with lenses ............................................................................................ 40 1. The image and object planes. ............................................................................... 41 2. The image distance depends on the object distance. ............................................. 41 3. Lens focal length and power. ................................................................................ 41 4. Aperture size and depth-of-focus. ......................................................................... 42 E. Geometrical optics ............................................................................................... 42 1. Snell's law . ............................................................................................................ 42 2. Ray tracing. ........................................................................................................... 43 3. The cardinal points. ............................................................................................... 43 4. Monochromatic aberrations . ................................................................................. 44 5. Chromatic aberrations. .......................................................................................... 45 F. Optics of the eye ................................................................................................... 45 1. The cornea. ............................................................................................................ 46 2. The iris . ................................................................................................................. 46 3. The lens. ................................................................................................................ 47 4. Schematic eye . ...................................................................................................... 47 5. Reduced schematic eye. ........................................................................................ 47 6. Size and location of retinal images. ...................................................................... 50 7. Ocular transmittance. ............................................................................................ 50 8. Retinal illumination . ............................................................................................. 51 9. Aberrations. ........................................................................................................... 53 10. Diffraction. .......................................................................................................... 54 IV. Linear systems analysis ....................................................................................... 56 A. Constraints defining linear systems ............................................................... 56 B. Impulse-response functions and convolution ................................................ 58 1. Convolution formula for one-dimensional systems. ............................................. 59 2. Convolution formula for two-dimensional systems. ............................................. 60 3. Measuring the impulse-response function . .......................................................... 60 C. Linear weighting functions and cross correlation ........................................ 61 1. Cross-correlation formula for one-dimensional systems. ..................................... 61 2. Cross-correlation formula for two-dimensional systems. ..................................... 62 3. Measurement of the weighting function . .............................................................. 62 D. The Fourier transform ....................................................................................... 63 1. One-dimensional systems . .................................................................................... 67 2. Two-dimensional systems. .................................................................................... 72 V.
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This note was uploaded on 08/12/2008 for the course PSY 380E taught by Professor Geisler during the Fall '07 term at University of Texas at Austin.

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Vision_Notes_1 - Vision Notes* Wilson S. Geisler University...

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