Lecture 14 Royal Institute of Technology（皇家理工学院的讲座14）.pdfVIP

Lecture 14 Point Spread Function (PSF), Modulation Transfer Function (MTF), Signal-to-noise Ratio (SNR), Contrast-to-noise Ratio (CNR), and Receiver Operating Curves (ROC) Point Spread Function (PSF) • Recollect that Image restoration refers to the removal or minimization of known degradations in an image • This includes deblurring of images degraded by the limitations of the sensor or its environment, noise filtering, and correction of geometric distortions or non-linearities due to sensors. Point Spread Function (PSF) • The figure below shows a typical situation in an imaging system: Point Spread Function (PSF) • The image of a point source is blurred and degraded due to noise by an imaging system. • If the imaging system is linear, the image of an object can be expressed as: where (x,y) is the additive noise function,f () is the object, g(x,y) is the image, and h(x,y;) is the Point Spread Function (PSF). The “;” is used to distinguish the input and output pairs of coordinates in this case. Point Spread Function (PSF) • A typical image restoration problem, give the formulation in the previous slide is of the form: Find an estimate off (a,b) given The Point Spread Function, The blurred image, and, The statistical properties of the noise and/or the factors affecting the noise contribution. PSF • The point spread function (PSF) describes the imaging system response to a point input, and is analogous to the impulse response. • A point input, represented as a single pixel in the “ideal” image, will be reproduced as something other than a single pixel in the “real” image. PSF A “Point Source” PSF • T