L3+Notes

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

This preview shows page 1. Sign up to view the full content.

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
This is the end of the preview. Sign up to access the rest of the document.

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....
View Full Document

## 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.

Ask a homework question - tutors are online