JP2006227516A5 - - Google Patents

Claims (10)

In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, and a distance between the lens groups. In zoom lenses that change the magnification by changing
The first lens group is composed of one negative lens and one positive lens in order from the object side,
The second lens group is composed of two positive lenses and one negative lens in order from the object side.
The zoom lens, wherein the third lens group is composed of one positive lens, and the third lens group satisfies the following conditional expression.
0.5 <(R1-R2) / (R1 + R2) <0.95
However, R1 is the curvature radius on the object side optical axis of the positive lens of the third lens group, and R2 is the curvature radius on the image side optical axis of the positive lens of the third lens group. The first lens group includes, in order from the object side, a negative meniscus lens having a convex surface directed toward the object side and a positive lens.
The second lens group is composed of one positive lens in order from the object side, and a cemented lens of a biconvex lens and a biconcave lens,
The zoom lens according to claim 1, wherein the third lens group includes one positive meniscus lens.   An image surface side surface of the negative meniscus lens having a convex surface facing the object side of the first lens group and an image surface side surface of the positive meniscus lens of the third lens group are aspherical surfaces. The zoom lens according to claim 2. The zoom lens according to claim 2 or 3, wherein the biconvex lens of the cemented lens in the second lens group satisfies the following conditional expression.
| (R3 + R4) / (R3-R4) | <0.1
Where R3 is the radius of curvature on the object side optical axis of the biconvex lens of the cemented lens in the second lens group, and R4 is the image side surface of the biconvex lens of the cemented lens in the second lens group. The radius of curvature on the optical axis.   5. The zoom lens according to claim 2, wherein the absolute values of the curvatures of both surfaces of the biconvex lens of the cemented lens in the second lens group are equal.   The zoom lens according to claim 1, wherein the positive lens of the third lens group is formed of a plastic lens. The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
D2 / D1 <1.5
However, D1 is the thickness on the optical axis of the lens closest to the object side of the first lens group, and D2 is the air space on the optical axis of the first lens and the second lens of the first lens group.   The zoom lens according to any one of claims 1 to 7, wherein both surfaces of a positive lens closest to the object side in the second lens group are aspherical surfaces.   9. The zoom lens according to claim 1, further comprising a stop that moves integrally with the second lens group on the object side of a positive lens closest to the object side in the second lens group. 10.   An electronic apparatus using the zoom lens according to claim 1.