A sensor generally used for infrared imaging. It consists of two chambers separated by a thin, blackened membrane. An infrared image is formed on the membrane by a lens or mirror and produces temperature differences on the membrane. A second chamber contains oil vapor that condenses on the membrane in various thicknesses. Visible light reflected from the film gives an indication of its thickness and results in interference colors at different portions of the infrared image. The time it takes for the image to form may vary from fractions of a second to a minute, depending on the temperature of the objects to be viewed.