This study presents the specific rule governing the image configurations of an extended source for micro lensing of the two body gravitational lens system developed by Chang and Refsdal (1979). Various topological situations of a source are considered in relation to the regions bounded by the so-called critical curves.

ABSTRACT
I. INTRODUCTION
II. THE NORMALIZED LENS EQUATION
III. CLASSIFICATION OF THE GRAVITATIONAL LENS MODEL(γ-PARAMETER)
IV. THE NUMBER OF IMAGES
V. THE NORMALIZED UNITS
VI. DISCUSSION
REFERENCE

• CHANG KYONGAE(Department of Physics and Optical Engineering Chongju University)