[第2讲几何光学和眼睛1.pptVIP

第一章 几何光学(参见书第一章内容) Geometrical Optics Geo＝“几何” Ray Optics Basics Postulates (基本假设) of Ray Optics Light travels in form of rays An optical medium is characterized by the refractive index ntime it takes light to travel distance d: d/c = nd/cvacoptical path: nd An inhomogeneous optical medium: n(r) r=(x,y,z)time taken by the light to travel from A to B is proportional to optical path length Fermat‘s Principle:optical rays travel between two points A, B on the path where the optical path length is an extremumin most cases a minimumlight travels the path of shortest time homogeneous medium: light travels on straight lines Optical path description Suppose we have known Snell’s law already, in a stepped index stack, we have Optical path equation The second derivative will be: Example: gradient index fiber For the index of a fiber as (in radial direction 径向) Solution Oscillation period Gradient index Natural index gradient Index above the sea Mirage 海市蜃楼 Gradient index Artificial gradient index Gradient index fiber Intense laser resulted index gradient Self-focusing, Self-defocusing Thermal lensing Geometric optics of rainbow Geometric optics of rainbow 变分值为极大和常数情况 maximum or constant 费马原理推导折射定律（cont’d) 费马原理评述 Why You Dont Believe Fermats Principle —Laurence Hecht The principle you take as a basis for your proof, to wit(智慧，智者), that nature always acts by the shortest and simplest path, is only a moral principle, not a physical one—it is not and can not be the cause of any effect in nature. This same principle must make nature irresolute(无决断的 ), not knowing which way to go when it makes a ray of light pass from a less dense to a more dense medium. …… …… －－－－by Clerselier, an expert in optics and leading spokesman, on Aug. 31, 1936 Summary of this section： Geometrical Optics (Matrix expressions) Paraxial Approximation Ray matrices and ray vectors Matrices for various optical components The Lens Maker’s Formula Why matrix? 实际光学系统常常含有多个光学元件； 对于多个光学元件，