L3+Notes - and exposure times • Astronomical examples...

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Barrett - CS450 Winter 2011 Lecture 3 Acquisition Devices Objectives : To understand Signal and Image Acquisition and related concepts. Aperture • What is a point measurement? Why can’t we make point measurements? • How does the area over which we are integrating affect resolution? • How is the aperture of a camera physically controlled? • How do lenses allow physically larger apertures with effectively smaller ones? - They collect/magnify the light, physically, through the (larger) lens, and focus it on the sensor. The lens essentially becomes the physically (collecting) aperture. Sensor & Noise • Converts light to chemical/electrical response • Noise: What is it and what affects it? (dark room, short exposure vs. daylight, longer exp.) • SNR: What is it? ( μ / σ ) How to measure? Flat field, pixel with ROI over varying light levels
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Unformatted text preview: and exposure times. • Astronomical examples, CIDs and long integration times. • Do you like high SNR or low SNR? What happens when σ gets larger than μ ? (Noise greater than Signal) • Where does noise come from? Lights. Fans. 60 Hz. Notch filters. • How do you decrease noise? (Turn up the lights, larger aperture, longer integration.) How do you increase noise (dark, fast exp.) Cameras and Linearity • Explain what is meant by a “linear” system (not Ax + B) • Describe Superposition Gain and Offset • Show examples in Photoshop (with “Curves.”) • Ax + B (Which is Gain? Which is offset?) • What does this have to do with the brightness and contrast knobs on your TV? • Gain = Constrast/Slope; Offset = Brightness/y-intercept Transfer Function • Example: Point-spread function • Characterize System....
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This note was uploaded on 03/02/2012 for the course C S 450 taught by Professor Morse,b during the Winter '08 term at BYU.

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