现代光学设计外文翻译

现代光学设计外文翻译内容摘要：

efficient as regards puting time, but requires careful design of the merit function. Still another type of merit function uses the variance of the wavefront to define the defect items. The merit function used in the various David Grey programs is of this type, and is certainly one of the best of the mercially available merit functions in producing a good balance of the aberrations. Characteristics which do not relate to image quality can also be controlled by the lens design program. Specific construction parameters, such as radii, thicknesses, spaces, and the like, as well as focal length, working distance, magnification, numerical aperture, required clear apertures, etc., can be controlled. Some programs include such items in the merit function along with the image defects. There are two drawbacks which somewhat offset the neat simplicity of this approach. One is that if the firstorder characteristics which are targeted are not initially close to the target values, the program may correct the image aberrations without controlling these firstorder characteristic。 the result may be , for example, a wellcorrected lens with the wrong focal length or numerical aperture. The program often finds this to be a local optimum and is unable to move away from it. The other drawback is that the inclusion of these items in the merit function has the effect of slowing the process of improving the image quality. An alternative approach is to use a system of constraints outside the merit function. Note also that many of these items can be controlled by features which are included in almost all programs, namely anglesolves and heightsolves. These algebraically solve for a radius or space to produce a desired ray slope or height. In any case, the merit function is a summation of suitably weighted defect items which, it is hoped, describes in a single number the worth of the system. The smaller the value of the merit function, the better the lens. The numerical value of the merit depends on the construction of the optical system。 it is a function of the construction parameters which are designated as variables. Without getting into the details of the mathematics involved, we can realize that the merit function is an ndimensional space, where n is the number of the variable constructional parameters in the optical system. The task of the design program is to find a location in this space(.,a lens prescription or a solution vector) which minimizes the size of the merit function. In general, for a lens of reasonable plexity there will be many such locations in a typical merit function space. The automatic design program will simply drive the lens design to the nearest minimum in the merit function. optimization The lens design program typically operates this way: Each variable parameter is changed(one at a time) by a small increment whose size is chosen as a promise between a large value(to get good numerical accuracy) and a small value (to get the local differential). The change produced in every item in the merit function is calculated. The result is a matrix of the partial derivatives of the defect items with respect to the parameters. Since there are usually many more defect items than variable parameters,。