INFRARED OPTICAL SYSTEM X6/X2 PERISCOPE TELESCOPE

摘要

ABSTRACTINFRARED OPTICAL SYSTEMA forward looking infrared optical system comprises arefractor telescope in combination with a powered window andfold mirror arrangement. The arrangement comprises a poweredwindow element with concentric spherical refractive surfaceshaving their common centre of curvature on the common opticalaxis where the latter is folded by the reflective surface of themirror element. Because the window element is powered itintroduces significant spherical aberration and some colouraberration to the system. However, the telescope providescompensation for such aberrations by being non-afocal andnon-diffraction limited. This is achieved by the objectivesystem of the telescope being telephoto and formed of first andsecond elements of which the first element is positively poweredand the second element is negatively powered and colourcorrective. The refractive surfaces of the second element areeach spherical whereas at least one refractive surface of thefirst element is aspheric. The second element is made of amaterial having a lower refractive index than that of the firstelement.