APPARATUS FOR MODULATING THE OPTICAL PERMEABILITY OF AN OPTICAL PATH

摘要

A device for modulating light in which a modulating element (1) mounted on a spring element (3) is caused to vibrate in the path (2) of a light beam by an element (4) of piezo- electric material which together with the spring element (3) is clamped between two terminal members (5). An A.C. voltage generator (9) is. connected across the terminal member (5) to energize the element (4) of piezo-electric material, the magnitude of vibration being proportional to the magnitude of the A.C. voltage. A variable D.C. voltage is superimposed on the A.C. voltage in order to adjust the zero or rest position of the modulating element (1) with respect to the light beam (2). The modulating element (1) may be an opaque element or a filter. If a filter is used it may be zones of different permeabilities. The application is to gas analysis instruments.