This means that it has more than one optic axis.

The optic axis of a crystal is a direction rather than a single line.

This effect is known as dispersion of the optic axes.

This plane contains the chief ray, but does not contain the optic axis.

By convention, the optic axis of the system is taken as the z-axis.

The closer an object is, the more our optic axes converge to intersect each other.

A crystal with only one optic axis is called a uniaxial crystal.

Some solid materials under specific conditions can demonstrate double refractions and optic axes.

In minerals that have far-off-center optic axes, only one part of the above sequence may be seen.

In a normal eye it is in the direction of the optic axis that objects are most distinctly seen.

Each lens core was split along the optic axis with forceps (Fig.

Dispersion of the optic axes is relatively strong.

In brief, a 4 mm trephine was used to extract the core of the lens around the optic axis.

The susceptibility of the optic axis, called a director, to an electric or magnetic field produces the potential for an optical switch.

Kröhnkite is biaxial negative, which reveals that the mineral has two optic axes.

Crystals are classified according to the number of optic axes (uniaxial, biaxial) they have.

Non-crystalline materials have no double refraction and thus, no optic axis.

How can this ray travel perpendicular to the optic axis and escape DR?

Kochite is biaxial, meaning it has two optic axes (lines of symmetry).

Optically, this mineral is biaxial negative, meaning that it contains two optic axes.

It images a point source into a line along the optic axis, or transforms a laser beam into a ring.

For this reason, moissanite jewels are cut along the optic axis of the crystal to minimize birefringent effects.

Cymrite, being monoclinic is anisotropic with two optic axes.

We'll consider one such plane wave component, propagating at angle θ with respect to the optic axis.

Those sections are most useful which are perpendicular to an optic axis, and consequently remain dark on rotation.