the development of digital computers, lens optimization was a hand-calculation task using trigonometric and logarithmic tables to plot 2-D cuts through the multi-dimensional space. Computerized ray tracing allows the performance of a lens to be modelled quickly, so that the design space can be searched rapidly. This allows design concepts to be rapidly refined. Popular optical design software includes Zemax's OpticStudio, Synopsys's Code V, and Lambda Research's OSLO. In most cases the designer must first choose a viable design for the optical system, and then numerical modelling is used to refine it. The designer ensures that designs optimized by the computer meet all requirements, and makes adjustments or restarts the process when they do not. See also Optical engineering Fabrication and testing (optical components) Ray transfer matrix analysis Photographic lens design Stray light References Notes Bibliography Smith, Warren J., Modern Lens Design, McGraw-Hill, Inc., 1992, Kingslake, Rudolph, Lens Design Fundamentals, Academic Press, 1978 Shannon, Robert R., The Art and Science of Optical Design, Cambridge University Press, 1997. External links The GNU Optical design and simulation library Geometrical optics Glass chemistry Glass engineering and science Lenses Physical optics