Optically active materials and articles and systems in which they may be used
The inventors of the present application developed novel optically active materials, methods, and articles. One embodiment of the present application is an optically active article, comprising: an infrared-reflecting material positioned adjacent to an optically active substrate such that the infrared-reflecting material forms a pattern that can be read by an infrared sensor when the optically active substrate is illuminated by an infrared light source. Another embodiment of the present application relates to a method of manufacturing an optically active article, comprising: obtaining an optically active sheeting; and positioning an infrared-reflecting material on the optically active sheeting to form a pattern. The optically active article may be, for example, a license plate.
1. An optically active article, comprising:
an infrared-reflecting material positioned adjacent to an optically active substrate such that the infrared-reflecting material forms a pattern that can be read by an infrared sensor when the optically active article is illuminated by an infrared light source;
wherein the infrared-reflecting material is transparent to visible light, and wherein the optically active substrate is at least one of reflective or retroreflective.
2. The optically active article of claim 1 , wherein the retroreflective substrate includes prismatic sheeting or beaded sheeting.
3. The optically active article of claim 1 , wherein the infrared-reflecting material is a multilayer optical film.
4. The optically active article of claim 1 , further comprising an underlying pattern that is visible in the visible light spectrum through the optically active substrate.
5. The optically active article of claim 1 , wherein the pattern includes at least one of machine readable information, graphics, images, alphanumeric characters, bar codes, or other indicia.
6. The optically active article of claim 1 , wherein the visibility of the pattern differs based on the angle at which the optically active article is viewed.
7. The optically active article of claim 1 , wherein the article is a signage selected from a group consisting essentially of a license plate, a validation sticker, a usage permit, an identification label, or a tag.