Method could lead to smaller active/passive IR cameras

Used in civilian and military applications, the cameras often fall into one of two types: active, which use an invisible IR source to illuminate the scene, usually in the near or short-wavelength IR; and passive, which detect the thermal radiation given off by a warm object, typically in the mid- or long-wavelength IR, without the need for any illumination.

Until now, dual-mode active and passive IR cameras needed either two different IR detectors or complex controllable filters to accommodate the different wavelengths and then required additional signal processing to reconstruct a single image from the two modes. 

However, Northwestern University’s Center for Quantum Devices claims to have found a way to integrate active and passive IR imaging capability into a single chip. According to Northwestern, this opens the way to lighter and simpler dual-mode active/passive cameras with lower power dissipation.

A paper about the findings, ‘Active and passive infrared imager based on short-wave and mid-wave type-II superlattice dual-band detectors’, was published on 1 January in the journal Optic Letters. The work was led by Manijeh Razeghi, Walter P Murphy professor of electrical engineering and computer science in Northwestern’s McCormick School of Engineering and Applied Science.