Indicatrix

In`di`ca´trix

(Geom. of Three Dimensions) A certain conic section supposed to be drawn in the tangent plane to any surface, and used to determine the accidents of curvature of the surface at the point of contact. The curve is similar to the intersection of the surface with a parallel to the tangent plane and indefinitely near it. It is an ellipse when the curvature is synclastic, and an hyperbola when the curvature is anticlastic.

Indicatrix

indicatrix

[in′dik·ə‚triks] (optics) index ellipsoid

Indicatrix

in optics a vector diagram representing the dependence on direction of the characteristics of a light field (light intensity and polarization) or of the optical characteristics of the medium (indexes of refraction; reflectivity).

A particular case of the indicatrix is the scattering indicatrix, which represents the dependence of the intensity of the scattered light on the angle of scattering under the condition that the incident light is not polarized, and the optical indicatrix (in crystal optics). The optical indicatrix of an optically isotropic medium is a sphere. The indicatrix for crystals with trigonal, hexagonal, and tetragonal systems is an ellipsoid of revolution. The indicatrix for crystals with rhombic, monoclinic, and tri-clinic systems is a general ellipsoid.

The indicatrix is used when the analytical equations for the corresponding angular dependences are complex or unknown, and also for the systematization of experimental data.