ABSTRACT
Until comparatively recently, the discussion of image formation has relied on one of three models for the behavior of light. The so-called ray model uses a geometrical approach, and is satisfactory for describing the basic geometry of the formation of an image by an optical device, but it doesn’t describe the nature of the fine structure of an optical image, nor does it predict the phenomenon of diffraction. The Huyghens wave model does describe diffraction fairly well, but is difficult to use with gratings that are other than binary, i.e. ‘square’, in transmittance profile. The Maxwell electromagnetic model is capable of describing all optical phenomena except photochemical and photoelectronic effects, but the precision of its descriptions demands a level of mathematical ability well beyond the reach of most people.
