Instrument for Measuring the Marginal Power of Spectacle Lenses*
Francis E. Washer · Journal of the Optical Society of America · 1955
An instrument is described that permits the measurement of meridional power at selected intervals from the center of the lens to the edge of the useful field. The viewing system simulates the rolling eye so that measurements are made under conditions closely approximating conditions of use. The instrument is capable of measuring spherical and cylindrical power with respect to the vertex sphere. A divided circle permits the measurement of distortion. Results of measurement are presented for two types of spectacle lenses of identical powers.