Visible and infrared light image-taking optical system

A visible and infrared light image-taking optical system comprising:

• a first color separation optical system for separating object light incident on an image-taking optical system into object light in a visible light region and object light in an infrared light region;
• a visible light optical system for forming an object image on an image pickup surface of a visible light image-taking device which performs imaging with object light in a visible light region separated by the first color separation optical system;
• and
• an infrared light optical system for forming an object image on an image pickup surface of an infrared light image-taking device which performs imaging with object light in an infrared light region separated by the first color separation optical system, wherein
• the infrared light optical system includes a second color separation optical system different from the first color separation optical system and optically coupled to the first color separation optical system, the second color separation optical system decomposing the object light in an infrared light region received from said first color separation optical system into object lights in a plurality of different infrared wavelength regions and the infrared light image-taking device includes a plurality of image pickup elements for taking an object image formed by each object light for each object light in each infrared wavelength region decomposed by the second color separation optical system, and
• said second color separation optical system of the infrared light optical system includes dichroic filters reflecting only object light in part of wavelength regions in the infrared light region and transmitting object light in other wavelength regions in the infrared light region so as to decompose the object light in the infrared region into object lights in a plurality of different infrared wavelength regions.