This application is directed to a lens assembly configured to focus light on a sensor array of an optical device. The lens assembly comprises one or more optical lenses and an electrochromic layer positioned between the one or more optical lenses and the sensor array. The electrochromic layer has one or more optical properties that are responsive to voltage applied to the layer, including a first optical property related to optical transmissivity. The first optical property includes a first state, responsive to a first applied voltage, in which the layer is substantially opaque to a predefined band of IR wavelengths. The first optical property also includes a second state, responsive to a second applied voltage distinct from the first applied voltage, in which the layer is substantially transparent to the predefined band of IR wavelengths and visible wavelengths.