| 摘要 |
PURPOSE:To focus to the infinite point by providing a two-dimensional image detector, a light source and a focus control two-dimensional detector in a plane and a flat plate window on a substance side to control then so as to condense light to the focus control two-dimensional detector. CONSTITUTION:Infrared rays are transmitted through an optical system 2 and a part of them is reflected by a flat plate window 1 and then transmitted through the optical system 2 again. An image reflected by the flat plate window 1 makes a mirror image which is symmetrical to an optical axis, and when a focus control two-dimensional detector 5 is provided in a symmetrical position to a light source 4, infrared rays emitted from the light source 4 is focused in vicinity about the focus control two-dimensional detector 5 to form an image on the focus control two-dimensional detector 5. A processing circuit 6 gives a quantity of focus control to a focus control mechanism control device 7 to control a focus control mechanism 8. This operation is always performed, thereby being able to allow the focus position of the optical system 2 to coincide with the location of a two-dimensional picture detector 3 under any change of the ambient temperature. |
