In this paper we report studies on imaging through a defocusing gradient-index rod. We have obtained analytic expressions for the third-order aberration of this system and compared it with the total aberration obtained by numerical ray tracing. Our studies show that the rod length can be critically optimized for low aberrations depending on the numerical aperture requirement. Further, a value of the fourth-order grading parameter exists for which the aberration can be reduced to a minimum for fixed values of other parameters.
© 1983 Optical Society of AmericaPDF Article