INFRARED ZOOM LENS AND INFRARED CAMERA

摘要

An infrared zoom lens reduced in size and manufacturable at low cost while maintaining the brightness of image and its related techniques are provided. The infrared zoom lens (1a) comprises first to third lens groups (G1 to G3) made of zinc sulphide. The first lens group (G1) is composed of one or two lenses, and has a positive refracting power. The second lens group (G2) is composed of one or two lenses, and has a negative refracting power. The third lens group (G3) is composed of two or more lenses. The whole lens groups have a positive refracting power. The infrared zoom lens comprises, as the final lens on the image plane side, a positive meniscus lens with its convex surface facing an object. During zooming, the second lens group (G2) is moved along the optical axis. At least one lens surface of the first to third lens groups (G1 to G3) is a refracting one. At least one lens surface of the first and third lens groups (G1, G3) is an aspherical one.