Parallel rays lens for optical telephone

Abstract From the Canadian patent

In an optical telephone wherein amplitude modulated light is converted to sound by applying the modulated light to an enclosed volume of gas, wherein the volume and/or pressure of gas varies in synchronism with the instantaneous energy of the modulated light, and wherein an optical fiber is used as the transmission element, the improvement is provided by the means to more uniformly distribute the optical energy in the gas cell causing an improved and more efficient conversion of the modulated light directly into sound. The means can be provided by covering the light entering side with a positive lens and positioning the optical fiber at the focal point of the lens.