Abstract: A device, for imaging infrared radiation from a scene, includes a detector of the infrared radiation, an enclosure for keeping the detector at an operating temperature thereof, an optical system, outside the enclosure, for focusing the infrared radiation onto the detector via a window of the enclosure, and a filter. In one embodiment, the filter is positioned at an intermediate focal plane of the optical system. In another embodiment, the filter is on a surface of an optical element of the optical system and has a defocusing relationship to the detector.

Abstract: A method and apparatus for active pyrometric measurement of the temperature of a body whose emissivity varies with wavelength. The emissivity is inferred from reflectivity measured at two wavelengths in an irradiation wavelength band and extrapolated to a wavelength in an emission wavelength band. The extrapolated emissivity is used to correct a blackbody estimate of the temperature of the body in the emission wavelength band. The extrapolation, being temperature-dependent, is done iteratively. Both reflectivity and emission measurements are performed via a common optical head that is shaped, and is positioned relative to the body, so that the optical head has a sufficiently large solid angle of acceptance that the measured temperature is independent of superficial roughness of the body.

Abstract: A method of remotely measuring the temperature of a body, such as a semiconductor wafer, whose transparency varies with both wavelength and temperature and is characterized by an optical absorption edge. The body is illuminated at wavelengths on either side of the optical absorption edge. Based on the measured reflectivity at wavelengths shorter than the optical absorption edge, the direct reflectivity at wavelengths longer than the optical absorption edge is predicted and used to estimate the component of total reflectivity, at wavelengths longer than the optical absorption edge, which corresponds to propagation through the body and reflection back through the body. Light reflected from the body, measured in an "active" channel, is distinguished from light emitted passively by the body and measured in a "passive" channel. In the case of an opaque body, this allows the estimation of the emissivity of the body, and a temperature estimate based on Planck's law.