Condensing and collecting optical system using an ellipsoidal reflector

Abstract

An off-axis optical system for collecting and condensing electromagnetic radiation utilizes an ellipsoidal reflector or a portion thereof configured so that the effects of magnification and optical aberrations (caused by the off-axis arrangement and an aspherical source envelope) are minimized. This is accomplished by the utilization of a specially designed ellipsoidal reflector having primary and secondary focal points along the major axis of the reflector or an effective reflecting portion thereof defined as that portion which is both illuminated by the source and subtended by the acceptance cone of the target. In the preferred embodiment, a single ellipsoidal reflector is configured with its major axis both non coincident with its geometric optical axis and with the optical axis of the target at an angle greater than zero degrees so as to reduce substantially the distance at which a focused image is formed and to achieve an average magnification near unity thereby maintaining the brightness of the source at the target. The radiant flux at the location of the target can be increased by incorporating a retro-reflector of toroidal or spherical design. In a second embodiment, the components forming the optical system of the present invention are arranged in a self-contained nautilus-shaped housing wherein the inner surface of the housing preferably comprises a reflector encompassing the retro-reflector, an effective ellipsoidal reflecting portion and a window through which the image is projected onto the target. In a third embodiment, the present invention utilizes a compound ellipsoidal reflector configuration having two ellipsoidal reflecting surfaces arranged so as to have a common focus, at which point a radiation source is located. In this embodiment, two targets located at the remaining foci of the respective reflectors are illuminated with a high flux density.