Optical spectrometer system having a curved reflective imaging slit body

Abstract

An optical spectrometer system that includes an optical element having a two-dimensional, curved, reflective, low emissivity slit body, or surround, in which an imaging slit is formed. The optical spectrometer system includes a detector, such as an infrared detector, for example, disposed in a cavity at a focal plane thereof, an optical system in the cavity for focusing radiation onto the detector, and an entrance pupil disposed in the cavity. The curved slit body effectively and substantially eliminates out-of-field radiation from impinging upon the slit body, and its low emissivity greatly reduces self-emission from the slit body. The reflective slit body is a low emissivity element that images the detector back upon itself and passes background energy that falls within a cone defined by the entrance pupil. By using the two-dimensional curved slit body, a relatively small detector dewar or focal plane cooler may be employed in the optical spectrometer system to cool the detector. The two-dimensional curved slit body emits less than three percent of in-field radiation and permits virtually none of the radiation derived from walls of the cavity from being imaged at the detector. The curved slit body preferably has a torroidal shape, and is formed so that central rays are normal to the slit body at all points. The curved slit body images the detector back upon itself, thus minimizing background effects. Use of the curved slit body eliminates the need to cool the slit body and walls of the cavity.