Using the refractive index modulation in liquid crystals by an externally applied electric field, we show that a polymer dispersed liquid crystal (PDLC) can be used in a Fabry-Perot etalon to produce a tunable optical filter for use in the visible region. Voltage applied to the film changes the refractive index and the optical length of the cavity, converting the system into an interference filter with a variable frequency bandwidth. We demonstrate further that the wavelength can be tuned over 150 nm using less than 20 V of power.