An electromechanical shutter has been developed which will modulate the light flux from a variety of sources in response to an electrical input at frequencies up to 100 cps. Feedback assures a linearity of 0.6% and, in addition, maintains a constant output in spite of fluctuations in source intensity.
ROLAND W. GUBISCH, "Low-Frequency Light Modulator," J. Opt. Soc. Am. 55, 409-409 (1965)