Patent ID: 7724445
Filing Date: 2010-05-25
Classification: G02B

Abstract:
1. A bifocal imaging optical system comprising: a first group for wide angle imaging, which includes one lens and has a positive refractive power; a first group for telephoto imaging, which includes one or two lenses and has a positive refractive power as a whole; and a second group including one lens and having a positive refractive power, the second group being commonly used with both of the first group for wide angle imaging and the first group for telephoto imaging, wherein each of the first group for wide angle imaging, the first group for telephoto imaging and the second group has at least one aspherical surface, the first group for a wide angle and the first group for a telephoto are selectively used so as to switch an overall focal length of the bifocal imaging optical system between two focal lengths, wherein when a wide-angle imaging operation is performed, the first group for wide angle imaging and the second group are arranged on an optical axis sequentially from an object side of the bifocal imaging optical system, and when a telephoto imaging operation is performed, the first group for telephoto imaging and the second group are arranged on the optical axis sequentially from the object side, and the bifocal imaging optical system satisfies conditional expressions: wherein fw is an overall focal length of the bifocal imaging optical system in a wide-angle side, f f f