| 摘要 |
An infrared radiation detecting system comprises a detector element 13A forming part of a detector 13 incorporating a cold shield 14 and an optical system 12, 15, for imaging infrared radiation from a field of view O onto a real image surface 19 spaced from the detector element 13A and relaying the image I from the surface 19 to the detector element 13A is provided with a graticule 20 having markings which are reflective to infrared radiation emitted by the detector 13. Graticule 20 is located at the image surface 19 so that the graticule markings are imaged onto the detector element 13A in superimposition with the infrared radiation from the field of view O. |
