Nonimaging Optics

Appendix E PERFECT OFF-AXIS IMAGING

E.1 INTRODUCTION

Let us consider a conventional axially symmetric lens system acting as a concentrator for a source at infinity (size ±β). The edge-ray theorem, when applied to this case, states that in order to obtain an ideal imaging concentrator, it must focus perfectly (i.e., on a single image point) the rays impinging on the entry aperture of the system forming an angle +β with the optical axis.¹ The impossibility of such perfect imaging of an off-axis point in three dimensions (3D) by an axially symmetric optical system was the subject of a theorem proven in the late 1970s (Welford and Winston, 1979). It was restricted to optical systems with homogeneous media separated by a finite number of optical ...