1. A method for measuring linewidths in selected subregions of a microminiature element, such subregion including features exhibiting two contrasting optical properties, said element also including at least two reference subregions each exhibiting uniformly a different one of said two optical properties, said method comprising the steps of directing light from a source at each of said reference subregions, generating normalized reference signals derived from light obtained directly from said source and from light that impinged upon said reference subregions, directing light from said source at a selected subregion, generating a normalized subregion signal derived from light obtained directly from said source and from light that impinged upon said selected subregion, processing said normalized reference signals and said normalized subregion signal to generate a signal representative of one of said optical properties of said selected subregion, and processing said last-mentioned signal in accordance with a predetermined relationship to generate a signal representative of a specific linewidth in said selected subregion.