Purpose
To simplify numerical analysis of ray tracing techniques in application to models of the human eye.
Methods
Recently a method that simplifies calculation of geometrical points spread function has been proposed for circularly symmetric systems (Gagnon et al., App. Opt. 2014). The method is based on Chebyshev polynomials and it is realized with the help of Matlab Chebfun toolbox - a new tool for computing with functions developed at Oxford University (www.chebfun.org). An extension of this method to 2D non-circularly symmetric systems is proposed. In this method, surfaces, rays, and refractive indices are all represented in functional forms being approximated by Chebyshev polynomials. Although generalization from one dimensional to two dimensional Chebyshev polynomials is not trivial (i.e., not all properties of 1D Chebyshev polynomials are present in their 2D representations), there are many benefits of using them including the ease of surface representation, manipulation of multiple surface designs, and the ability to represent gradient index (GRIN) type lenses. Such a representation appears to be an ideal tool for performing ray tracing in anatomically correct eye models such as the one proposed by Liou and Brenner (JOSA A, 1997).
Results
A two-dimensional Chebyshev function based ray tracing procedure for an arbitrary number of surfaces and arbitrary surface shapes has been developed. The Liou and Brenner anatomically accurate model of the human eye has been used for evaluating the method (Figure 1). Computational complexity (assessed as the CPU time) increases with the addition of each surface in a linear form indicating that the method has a great computational potential to be used for more intricate eye models in which, for example, the crystalline lens is described with multiple surfaces.
Conclusions
Performing ray tracing with Chebfun toolbox substantially simplifies calculations as it is based on object oriented programming with handle functions. Realization of the ray tracing technique in Matlab is particularly attractive among researchers for whom other ray tracing optical engineering packages such as those employed in Zemax are more cumbersome and sometimes difficult to acquire.