| 摘要 |
PURPOSE:To prevent an incident infrared-ray quantity on the photodetecting surface of a detector from varying by scanning, by setting a size of a diaphragm so that a light for connecting an aperture diaphragm provided between a scanning optical part and the detector, and a point on the surface of the detector is free from eclipse by a lens frame. CONSTITUTION:An aperture diaphragm 14 is provided between a scanning mirror 2 and a detector 3, and constituted so that a light in a solid angle for seeing an aperture diaphragm 14 from a point on the photodetecting surface of the detector 3 is reflected by the scanning mirror so as to all transmits through a condensing lens 1, and is free from eclipse by a lens frame 4, etc. Accordingly, the solid angle for seeing the aperture diaphragm 4 from the detector 3 is not varied by scanning of the scanning mirror 2, and also even if there is an infrared-ray radiating distribution in the inside of an optical system, the radiation quantity of incident infrared-rays is not varied by scanning, therefore, an output of the detector 3 also becomes constant, and a scanning type optical system whose detecting performance is excellent can be constituted. |
