Research On Designing Method Of Fixed Correctors In A Conformal Optical System

The domes of traditional seekers are always designed to be hemi-spherical orpart of hemi spherical. The dome designed in the shape of hemi-spherical induceslittle amounts of fixed aberrations when the imaging system looking at differentfield of regard (FOR), this meets the demand of optical design, but generates big airresistance and goes against the seekers performance. Because the conformal dome isdesigned in the shape of streamline with high air dynamic performance, the airresistance has been minimized, high temperature and radiation have been reduced,life time has been extended, field of fire has been increased. The combatperformance has been improved greatly. But when the imaging system looking atdifferent field of regard, conformal dome induces large amounts of varyingaberrations and reduces imaging quality. So the aberrations must be corrected.This paper started from the view of ray tracing. Firstly, by reshaping the innersurface of conformal dome, the diverged light beam that refracted from conformaldome turned into parallel ones to some extend to correct aberrations, and to be thefirst order corrector. Secondly, by using Wassermann-Wolf theory, according to raytracing method, Wassermann-Wolf equations are solved, and continuous asphereswere designed to correct the main aberrations induced by conformal domes,spherical aberration, coma and astigmatism. Thirdly, diffractive elements are used,according to the chromatic dispersion special characteristic of diffractive elementsto correct residual aberration and to be the third order corrector. Lastly, according tothe residual fixed aberrations of the conformal optical system, a reflectiveCassegrain system was used to correction the residual aberrations.The design result showed that, this method effectively reduces the aberrationsinduced by conformal domes, the modulation transfer functions of different FORhave all reached diffractive limits. This method not only corrects aberrations, butalso reduces weight, simplifies structure and increases stability of the conformaloptical system.