Optically isotropic devices

DETAILED DESCRIPTION OF THE INVENTION As indicated above, in many optical devices it is important that optical clarity and uniformity be achieved.
For example, in such uses as optical disks for information storage and lenses, optical clarity and uniformity are basic requirements of the devices.
Although glass of various compositions are frequently used in optical devices, it is sometimes necessary or desirable to use organic polymeric materials in optical devices.
In such a situation, care must be taken to insure that optical anisotropies are not introduced through either the nature of the optical polymers employed or through the processing of polymers.
Although optical anisotropies may originate with the nature of the materials employed, this problem is usually avoided by the choice of a proper material.
Thus, when a material does not have the proper optical properties while in its bulk state, other materials will be chosen.
However, it is more difficult to avoid optical anisotropies which may be introduced through the processing of the materials.
For example, in injection molding or casting processes, or in practially any other shape-forming processes, stress must be placed on the polymeric materials to force them to flow or to conform to the shape of the mold.
Such stresses are directional in nature and it had the effect of orienting the long molecules of the polymer in the direction of the applied stress.
It is believed that the observed optical birefringence in optical devices and components made of polymeric materials is due to the orientation of the molecules during the manufacturing process.
For the purposes of the present invention, such optical birefringence may be thought of as the difference in the indices of refraction of the optical device when subjected to light sources that have been polarized in different directions.
One solution to this optical anisotropic problem caused by stressing and orientation of the polymer molecular chains is to hold the devices in the mold until the internal stresses relax