Patent ID: 7835086
Filing Date: 2010-11-16
Classification: G02B

Abstract:
1. A lens barrel comprising: a photographing optical system which introduces an object image to an imaging device; a zoom lens which is included in the photographing optical system; and a barrel which accommodates the zoom lens; wherein the zoom lens includes a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power and a fourth lens group having positive refractive power, arranged in order from the object side toward the imaging device side, the second lens group includes a first lens having a negative refractive power, a second lens having a negative refractive power whose diameter is smaller than that of the first lens, and a third lens having a positive refractive power whose diameter is smaller than that of the second lens, arranged in order from the object side toward the imaging device side, the barrel includes a lens frame to which a first inner circumference surface, a second inner circumference surface and a third inner circumference surface are formed on the same axis, the first lens, the second lens and the third lens are press-fitted at the outer circumferences thereof respectively to the first inner circumference surface, the second inner circumference surface and the third inner circumference surface so as to be accommodated in the lens frame, the first lens is formed so that both lens faces at the object side and the imaging device side shape convex toward the object side and the curvature of the lens face at the imaging device side is larger than that of the lens face at the object side, the second lens is formed so that both lens faces at the object side and the imaging device side shape concave so that the center portions of the lens faces are to become closer to each other, the third lens is formed so that a lens face at the object side shapes convex toward the object side, a ring-shaped first reference plane extending on a plane which is perpendicular to the optical axis of the first lens is formed at the periphery of the lens face at the imaging device side of the first lens, a ring-shaped second reference plane extending on a plane which is perpendicular to the optical axis of the second lens is formed at the periphery of the lens face at the object side of the second lens, a ring-shaped third reference plane extending on a plane which is perpendicular to the optical axis of the second lens is formed at the periphery of the lens face at the imaging device side of the second lens, a ring-shaped fourth reference plane extending on a plane which is perpendicular to the optical axis of the third lens is formed at the periphery of the lens face at the object side of the third lens, and positioning of the first lens, the second lens and the third lens in the optical axis direction thereof is performed in the state that the first reference plane and the second reference plane are contacted and the third reference plane and the fourth reference plane are contacted.