Sharp nose lens design using refractive index gradient

摘要

For infrared sensors located at the nose of a missile or aprojectile, an age-old problem occurs. A conflict betweenoptical quality and aerodynamic drag exists. A new approachfor solving this problem is being developed using gradientrefractive index, GRIN, for lens design. The equations forlens design incorporating GRIN are formulated for the specialcase of spherically symmetrical GRIN. A computer code for designing a GRIN lens and for determining aberrations hasbeen developed. A different program (LENS) calculateslens design and lens performance for the case of homogeneousrefractive index. Results of this program provide a checkon the more complex program which includes GRIN. Thecomputed program calculates the spot diagram for both meridianaland skew rays. The spot diagram, which is the intersectionof rays with the focal plane, is plotted, and the Oj-j^gand centroid location of the spot diagram are calculated.Also a cumulative energy diagram is obtained from the program.The computer code has been organized to calculate the itemsenumerated above for either a circular cone for the inside oroutside surface of the pointed lens. For homogeneousrefractive index, both cases are included in the programdiscussed in this report. However, for the GRIN case, onlythe complete program for a lens with a conical surface onthe outside is reported here. The alternate case is beingdeveloped by a thesis student.Features of the computer program include the following: useof many subroutines for clarity and for easy modification, anduse of program structure for easy integration into anoptimization code.Sample lens designs and lens performance are presented. Thecomputer code provides the tools for lens design. Considerablesadditional work is needed for selecting the best lens design.