Patent ID: 6829102
Filing Date: 2004-12-07
Classification: G02B

Abstract:
A zoom lens comprising: a first group of lenses having negative focal length, a second group of lenses having positive focal length, and a third group of lenses having the positive focal length in order from an object side, the second group of lenses moving monotonically from an image side to the object side and the first group of lenses moves so as to correct shift in a position of an image surface, which is attended with a change in magnification, when the magnification is changed from an end of short focus to the end of long focus,wherein the first group of lenses has at least two lenses and an air lens formed between the two lenses, both sides of the air lens are an aspheric surface, and the first group of lenses satisfies the following conditional expressions: no>1.50 andni>1.60 where no indicates a refractive index to d line of the lens arranged on the object side of the air lens and ni indicates a refractive index to the d line of the lens arranged on the image side of the air lens.