Patent ID: 7494232

Claim:
A passive broadband long wave infrared radiation (LWIR) optical limiter device comprising an infrared (IR) limiting layer pair selected so that energy from visible and near infrared radiation having wavelengths in the range 3 to 5 microns activates said LWIR optical limiter and thereby prevents undesired radiation from impinging upon a radiation-sensitive detector device protected by said LWIR optical limiter device, wherein said optical limiter device comprises an IR limiting layer pair in which an external layer closer to a source of radiation comprises a material, selected from the group consisting of vanadium dioxide and vanadium sesquioxide, that can change from a semiconductor phase to a metal phase upon heating and in which an internal layer further from the source of radiation comprises chalcogenide glass material that strongly absorbs radiation except for radiation of the wavelength region to which the device is sensitive, wherein the external layer and the internal layer are adjacent to each other, and wherein said device comprises a broadband interference filter coating that transmits radiation of 7˜4 microns wavelength and reflects radiation of other wavelengths.