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Abstract

An apparatus is provided for magnifying the image of distant objects which has the unique feature that, unlike the Galilean telescope, the magnification is largely determined by how far the eye is located from the apparatus. Furthermore, unlike the Loupe, objects to be viewed can be at any arbitrarily large distance from the apparatus. In addition, the apparatus does not require positioning of the eye at the exit pupil of the instrument; it does not require centering of the eye on the optic axis of the instrument; and it does not require refocusing for different object distances. Still, it provides erect, non-inverted images to the viewer. The includes a positive optical element defining an optic axis for the apparatus and having a positive focal length for converging an incoming bundle of rays of electromagnetic radiation. Also included is a negative optical element aligned with the optic axis and separated from said positive optical element by a distance d1, with the negative optical means having a negative focal length that is substantially equal in magnitude to the focal length of the positive optical means and having a focal point on the optic axis. The purpose of the negative optical element is for receiving the incoming bundle of rays of electromagnetic radiation from the positive optical element, and the condition is imposed on the positive and negative optical elements that their focal lengths be greater in magnitude than their separation d1. The apparatus further includes a housing for holding the positive and negative optical elements. Several embodiments are described which have folded optics for viewing objects to the rear which are particularly useful in vehicles.

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