Patent ID: 7747550
Filing Date: 2010-06-29
Classification: G02B,G06F

Abstract:
1. A system for designing a free form reflector, the system comprising: a user input interface; a free form reflector design unit installed in a computer, comprising: a nonuniform rational basis splines (NURBS) algorithm generating module configured for generating an NURBS algorithm according to data received by the user input interface and for describing a free form surface by performing the NURBS algorithm; a merit evaluation function constructing module configured for constructing a merit evaluation function for calculating the difference between a desired illuminance distribution and a current distribution generated by a receiver; wherein the merit evaluation function is described as the following equation: wherein: Wij is the weight value of each bin; Eij, and Eij′ are the calculated illuminance value and the desired illuminance value of the bin with the serial number (i and j), respectively; wherein Eij′ is replaced with a constant value E 0 in the merit evaluation function, if the uniform illuminance distribution is required on the receiver; a differential evolution (DE) algorithm generating module configured for generating an DE algorithm for use in determining an optimum free form surface; wherein the step of generating the DE algorithm comprises the steps of: (i) randomly generating a gene of an initial chromosome in a population between a maximum value and a minimum value; wherein the gene of the initial chromosome in the population is generated by utilizing the following equation: X(0)=(X (ii) calculating a gene of a parent chromosome by utilizing the following equation: wherein: r 1 and r 2 are two random integers in [1, N]; λ and β are two parameters; M is the number of variables; and V j is the jth gene of the ith parent chromosome; (iii) calculating a gene of a child chromosome by utilizing the following equation: wherein: CR is the crossover probability, which is depicted as CRε[0,1]; randij is a random float point number between 0 and 1; and Rndi is a random integer between 1 and M; (iv) comparing a merit evaluation function value of the child chromosome with a merit evaluation function value of the initial chromosome, and replacing the initial chromosome with the child chromosome in the population if the merit evaluation function value of the child chromosome is smaller than the merit evaluation function value of the initial chromosome; (v) generating a best chromosome in the next generation of the population by choosing the next chromosome for updating and repeating from step (ii) to the step (iv) until the entire population has been processed; and (vi) repeating step (i) to step (v) until a desired minimum merit evaluation function value has been achieved or until the evolution has attained the maximum iteration times; and a free form surface building module configured for building an optimum free form surface according to the NURBS algorithm, the merit evaluation function, and the DE algorithm; and a free form reflector output unit.