Geometric Optics

Abstract

The ability to model the propagation of light is a vital element of understanding any display technology. Whether it is a liquid crystal display backlight or a digital cinema projector, the principles of optical propagation still apply. For the majority of applications, a simple geometric optical model will suffice and allow the system to be carefully defined. Ray tracing is the most fundamental property of geometric optics. By defining a ray and its direction, its path can be traced through the system using fundamental physical rules. This chapter covers the concept of ray tracing for simple lenses including the derivation of the lensmaker’s equation and the paraxial approximation. This is then analyzed further to define the basic set of aberrations which characterize imperfections in an optical system. Rays can then be traced through boundaries to build up the theory of reflections and transmission. This leads to the concept of total internal reflection, which is a powerful technique often used in displays to control the flow of optical energy within a system. The basic principles are explored from Fresnel reflection through to total internal reflection, and a simple display application is identified to illustrate the power of these applications. Finally, the properties of reflections are also used to define the function of antireflection coatings and optical enhancement cavity structures. A simple on-axis theory is presented to analyze the basic function of these optical strictures based on the principles of geometric optics.