In that case, the sphere surface behaves as a concave spherical mirror with the required curvature for retroreflection. In the paraxial approximation, this effect can be achieved with lowest divergence with a single transparent sphere when the refractive index of the material is exactly one plus the refractive index n i of the medium from which the radiation is incident (n i is around 1 for air). These two types have similar optical properties.Ī large relatively thin retroreflector can be formed by combining many small corner reflectors, using the standard hexagonal tiling.Ĭat's eye Eyeshine from retroreflectors of the transparent sphere type is clearly visible in this cat's eyesĪnother common type of retroreflector consists of refracting optical elements with a reflective surface, arranged so that the focal surface of the refractive element coincides with the reflective surface, typically a transparent sphere and (optionally) a spherical mirror. The second form uses mutually perpendicular flat mirrors bracketing an air space. In this structure, the reflection is achieved either by total internal reflection or silvering of the outer cube surfaces. In the more common form, the corner is literally the truncated corner of a cube of transparent material such as conventional optical glass. Therefore, as the ray reflects first from side x then side y and finally from side z the ray direction goes from to to to and it leaves the corner with all three components of its direction exactly reversed.Ĭorner reflectors occur in two varieties. When the ray reflects from the first side, say x, the ray's x-component, a, is reversed to − a, while the y- and z-components are unchanged. The three corresponding normal vectors of the corner's sides form a basis ( x, y, z) in which to represent the direction of an arbitrary incoming ray. A set of three mutually perpendicular reflective surfaces, placed to form the internal corner of a cube, work as a retroreflector.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |