| 摘要 |
PURPOSE:To enable an observer to recognize images by consisting an optical device of heating elements which heat a core layer so as to generate a change in the refractive index thereof and a light source for conducting light to the optical element, then heating the core layer to the extent of avoiding boiling the core layer. CONSTITUTION:A heating resistor 4b is electrically heated, and the heat thereof is transmitted via a clad layer 2 to a core layer 1 to form a heated region 6. The core layer 1 is heated to the extent of avoiding boiling the core layer. If a material of which the refractive index changes negative with a change in temp. is selected as the layer 1, a thermal gradient index region is formed in the heating region 6 in the layer 1. As a result, the course of the light, which arrives at the region 6, of light 7, is disturbed and therefore the total reflection condition is broken. At least a part of the light arriving at the region 6 passes the layer 3 without propagating in the core layer any longer and emerges to the outside of the optical element as exit light 8. If very small spot-like heating resistors are disposed in the shape of a dot matrix, an observer is able to recognize characters and images from the shape that the point sets in the heating region form. |
