Abstract: A set of interlocking elements capable of being joined together to form a corner piece of a puzzle game that constitutes a three-dimensional pictorial representation of a structure. In one embodiment, the set of interlocking elements comprises a first element that can be folded into a corner configuration. A second generally planar element interlocks through a dovetail-type joint with the first element to maintain the first element in a folded, corner-like configuration. The first and the second elements are provided with image-bearing surfaces that constitute individual pictorial entities contributing to a complete representation of the structure. When the first and the second elements are interlocked, the image-bearing surfaces unite visually to provide image continuity over the exposed surface of the corner piece. In a second embodiment, the set of interlocking element includes three discrete planar elements that unite through male/female joints into a T-shaped configuration.

Abstract: The apparatus described basically includes a vessel (10) which has a horizontal transparent window (11) and contains an index liquid (12). An optical fiber (13) is mounted in this vessel perpendicular to the window (11). Light (14) is launched and focused by a condenser (15) onto fiber (13). The light cone of aperture angle (2.beta.) due to the guided and leaky modes is eliminated using an annular mirror (16) that reflects the remaining portion of the aperture light cone (2.alpha.) escaping laterally from the fiber. This light reflected by the mirror (16) is focused by an annular condenser (18) and reflected onto a detector (20) by a flat mirror (19) with a hole in the center. Measuring the amount of light received by the detector (20) allows the refractive index of the fiber to be determined.

Abstract: An optical coupling device wherein at least two light conductors are coupled through the intermediary of a transparent block in the shape of a half-ellipsoid on whose foci converge the end sections of the two light conductors. A light beam emerging from one conductor is reflected and transforms itself into a beam converging on the end of the second conductor. A slot permits the introduction of a liquid-crystal attenuating device connected to an alternating voltage source.