| 摘要 |
PURPOSE:To make it possible to effectively measure the absolute temperature by providing a reference ultrared ray source on a middle focal plane of an optical system. CONSTITUTION:There are arranged in an optical system two middle focal planes Z1 and Z2 on which the image of an object 9 is to be formed. A reference ultrared ray source 10 is disposed in the vicinity of the boundary of fields of view on the plane Z1. An X direction scanning mirror 3 is vibrated at a slightly larger angle than the desired field of view, and the ultrared ray from the source 10 enters a detector 1 at the beginning and end of each scanning operation when the repeated scanning operations are performed by the scanning mirror 3. As a result, by clamping the detected signals from the detector 1 with the level during the time period for which the reference ultrared ray enters the detector 1, the detected signals correspond to the absolute temperature so that this temperature can be measured. |
