Introduction to optical design

   It is well known that the spread of light follows three basic laws: that light travels in a straight line in a straight line.Independent of the light propagation law, that is, two beams of light in the spread of each other when they met on the way, according to their own way to continue to spread, and when two beams of light together in the same point in the point of the light energy is a simple addition;Law of reflection and refraction law of that light travels encountered in smooth interface of two different medium, part of the reflection refraction, another part of the transmission of reflected light and refracted light direction is determined by the law of reflection and refraction law respectively.
   Based on the basic laws of light propagation, the path of transmission in optical systems can be calculated.This process is called light tracing, which is a must for designing optical systems.
   The advent and application of electronic computers has greatly promoted the work of optical design.Optical automatic design based on the system of aberration, the influence of various structure parameters and modification of aberration correction effect of all parameters, reduce various aberrations at the same time, so can give full play to each structure parameter of aberration correction action, not only speed up the design speed, and improve the design quality.     
   In optical automatic design, it is necessary to construct a convenient for computer for evaluating image quality and can reflect the design system of the evaluation function, to guide the computer to modify structure parameters.In general, the evaluation function is composed of the weighted image difference of the second power, which is a function of the parameter of the system structure.Every modification structure parameters (called an iteration) can cause the change of the evaluation function value, if lower, said less aberration, improve image quality.
   The change of structure parameter should be constrained to ensure that the boundary conditions are satisfied.So, the so-called optical automatic design, that is, on the premise of meet the boundary conditions, after several iterations, automatically by a computer to find a set of structural parameters, make its evaluation function is minimum.Now a lot of mathematical methods used in optical automatic design, is more effective for everyone have damped least square method, adopted by the orthonormalization method and adaptive method, etc