Zemax EE Software and Programming - Dissertation Example

? Chapter 4 Details on Zemax EE Software and Programming 4 Introduction This dissertation aims to use Zemax software to understand the light pathsthrough ray tracing for various light shapes and samples with different geometries made from glass, polymeric materials, and Al metal. Optical design parameters are modeled based on the data obtained to achieve optimum collection of solar radiation. Aside from investigating properties such as reflection coefficient, absorption coefficient, temperature variation, and thermal conductivity, additional theoretical estimations are made. An example is the determination of focal length, exposed effective areas, and light collection and concentration for all components. A number of designs are evaluated to examine the effect of different geometrical shapes of light pipes for refraction studies and light cups for reflection studies. Zemax software is used for a large part of this study. Therefore, this chapter details the basics of Zemax software for optical design and ray tracing. Software programs for lens design and optical studies have been of immense utility in the field of optics. Their advent has substantially simplified and enhanced our understanding of optical design and analysis. As stated by Winston, Minano, and Benitez (2005), The design of imaging optical systems is a classic ?eld of research that has achieved a high level of development. There are on the market optical design programs that permit the numerical optimization of the design parameters, allowing us to obtain results that were unattainable with the analytical tools used before the development of computers (p. 219). Software programs are based on a number of optical principles, such as geometrical optics and ray tracing that function according to the basic laws of optics. The following sections discuss these basic principles along with an introduction to Zemax software that is used in this study. 4.2. Ray Tracing Programs and Geometrical Optics The basic tool required in designing any imaging or non-imaging optical system is geometrical optics (Winston, Minano, & Benitez, 2005). Geometrical optics is based on the universal laws of reflection, refraction, and transmission of light. The incident light on a reflective surface and the reflected light from that surface always make equal angles to the normal, and they lie on the same plane. In case of transmitted light, the direction of the refracted and transmitted ray changes according to Snell’s law of refraction, according to which the sine of the angle between the incident ray and the normal is in constant ratio with the sine of the angle between the refracted ray and the normal, with all three being coplanar (Winston, Minano, & Benitez). Based on these universal laws of light, the behavior of a light ray in any optical system can be predicted. Simple optical systems can be predicted manually, but complex ones require sophisticated computer programs that can easily predict the behavior of light through computerized ray tracing. Even the analysis and design of solar concentrators requires such a program. Ray tracing is the process of constructing or following the paths of light rays through an optical system consisting of refracting and reflecting surfaces (Winston, Minano, & Benitez, 2005). For instance, the transmission of a specific concentrator can be determined through ray tracing as follows: N rays enter a concentrator’s aperture at a ? angle of incidence at the entry aperture of the concentrator, as shown in Figure 4.1. Fig. 4.1: Ray tracing of the rays transmitted through a concentrator to determine transmission (Winston, Minano, & Benitez, 2005). After the rays are traced through the optical system, N’ rays appear from the concentrator’s exit aperture. The dimensions of the exit aperture are determined based on the required concentration ratio of the system. The remaining N and N’ rays are lost through various processes such as ray scattering. The transmission power of the system for a different angle of incidence ? can then be calculated as N’/N. Reflection and refraction laws are taken in vector form to perform ray tracing for the geometrical optics of a system. Figure 4.2 shows the vector formulation for both reflection and refraction. Fig. 4.2: Vector formulation for reflection (left) and refraction (right), where n, r, r’ and r” are all unit vectors (Winston, Minano, & Benitez, 2005). In these vector formulations, r, r’, r”, and n are respective unit vectors along the incident, refracted, reflected rays and the normal pointing into the surface of the material. The vector equation for the law of reflection can thus be written as r” = r – 2 (n*r) n In case of refraction, the vector equation can be written as n’ r’ ? n = n r ? n where n and n’ are the refractive indices of the media on the refractive surface’s either side. This equation replaces the actual equation: n’ sin I’=n sin I where I’ and I are the angle of refraction and angle of incidence, respectively. The preferred form of the vector formulation of refraction for the purpose of ray tracing is given as follows: n’ r’ = n r + (n’ r’. n – n r. n) n Another concept that is important in the design of concentrators is total internal reflection. When a ray traveling from a medium with n refractive index enters a medium with n’ refractive index that is lesser than the refractive index n of the first medium (n’ Read More