Patent ID: 7292395

Claim:
A dual-focus switchable lens comprising: in order from an object side of the dual-focus switchable lens, a first lens group having a negative refractive power, the first lens group comprising a first lens having a negative refractive power and a second lens having a positive refractive power in order from the object side, at least one of the first and second lenses being an aspherical lens; a second lens group having a positive refractive power, the second lens group comprising a cemented lens and a single lens having an aspherical surface and having a negative refractive power in order from the object side; a third lens group having a positive refractive power, the third lens group comprising a positive lens, wherein two focal points of the dual-focus switchable lens is switched by moving the second lens group while maintaining the first and third lens groups substantially stationary, and the dual-focus switchable lens satisfies conditional expressions (1) to (6): 22<( W w +W t )/2<34 (1) 2 <|f 5 |/f w (2) 4.5 <T L /Y IM <6.5 (3) 1.75 ≦f t /f w ≦3.0 (4) 2.3 ≦FNO w ≦3.5 (5) 16.0≦ν 1 −ν 2 (6) wherein W w represents a half angle-of-view in a wide-angle position of the dual-focus switchable lens; W t represents a half angle-of-view in a telephoto position of the dual-focus switchable lens; f w represents a focal length of the dual-focus switchable lens in the wide-angle position; f t represents a focal length of the dual-focus switchable lens in the telephoto position f 5 represents a focal length of the single lens in the second lens group; T L represents a maximum length of the dual-focus switchable lens; Y IM represents an image height FNO w represents F number in the wide-angle position; ν 1 represents Abbe number of the first lens; and ν 2 represents Abbe number of the second lens.