Improvement in the article of glass with change in behavior or local progressive fototropico fotocromico and process for making glass lenses of quality oftalmica

摘要

PHOTOCHROMIC GRADIENT LENSES The invention achieves local variation, or a continuous gradation, in photochromic or phototropic properties across the face of glass lenses and lens blanks, especially those of ophthalmic quality. The lenses and lens blanks contain all those ingredients required to produce photochromic o? phototropic behavior. They are exposed to a locally variable temperature field or environment, in such manner as to, in at least one portion of the lens or lens blank cause the temperature therein to exceed the strain point but not the softening point of the glass. In other portions of the lens or lens blank the temperature is below the strain point, thus causing development of phototropic or photochromic behavior only in those portions of the lens or lens blank exposed to the temperatures above the strain point.