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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.

References in periodicals archive ?
Tissot's indicatrix is based on a set of equally sized circles on curved surface of the globe.
The example of plane map of the world in an equirectangular projection with Tissot's indicatrix of distortion of radius of 500 km is presented in Figure 12.
However, the image of transformed circle should not be treated as distortion like Tissot's indicatrix but the natural form of the circle existing in modeling structure.
Let the spherical indicatrix of the principal normal vector of the curve C be denoted by [C.
2] be the tangent vector of the spherical indicatrix of the principal normal vector of the curve C and let [[bar.
We observe that the mentioned indicatrix can be a helix, so, one can ask whether this tangent spherical image is a general helix or not.
This curve is called the trinormal spherical image or trinormal indicatrix of the curve [beta] in [E.
A generalization of the Clausius-Mosotti [1] expression for dense polymeric media, taken as similar to high density solution with nonspherical optical indicatrix representation [3] due to the effect of its environment polarization, is given by
Gamma] = 1/3 + s and g = (1 - [Gamma])/[Gamma] are two structural constants of the medium where 1/3 is the value of [Gamma] corresponding to the spherical indicatrix and s is an index of nonsphericity.
To illustrate Tissot's indicatrix, ellipses are placed at the intersections of 30 [degrees] graticules in Figure 9.
One problem is that the indicatrix is frequently interpreted to be limited to the forward transformation from the globe to a map projection only.
The Tissot Indicatrix, an ellipse which describes relative directional distortion at each point, is everywhere a circle for conformal maps.

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