An attachment optical system includes a first converter optical system attachable to an object side of an imaging optical system, and a second converter optical system attachable to an image side of the imaging optical system. The first converter optical system includes a dome-shaped cover and at least one positive lens. A predetermined condition is satisfied.

A zoom lens, a camera module, and a mobile terminal. The zoom lens includes a first lens group with negative focal power, a second lens group with positive focal power, and a third lens group with negative focal power that are sequentially arranged from an object side to an image side. The first lens group is a fixed lens group. The second lens group is a zoom lens group and slides along an optical axis on an image side of the first lens group. The third lens group is a compensation lens group and slides along the optical axis on an image side of the second lens group. In addition, the zoom lens may further include a fixed fourth lens group located on an image side of the third lens group.

A zoom optical system according to an embodiment of the present invention includes a first lens group, a second lens group, a third lens group, and a fourth lens group which are sequentially arranged in a direction from a subject side to an image side, wherein the second lens group and the third lens group are movable, and an effective focal length (EFL) in a telephoto mode is defined by an expression below.

[00001]$11.5<\frac{{\mathrm{EFL}}_{\mathrm{tele}}}{H_{\mathrm{imageD}}}<12.5$

Here, EFL.sub.tele is the EFL of the zoom optical system in the telephoto mode, and tele H.sub.imageD is a half value of a diagonal length of a pixel area of an image sensor.

A zoom lens includes a first lens unit having negative refractive power, a second lens unit having positive refractive power, an intermediate unit including one or more lens units, and a final lens unit having positive refractive power disposed closest to the image side. The first lens unit includes negative lenses G1, G2 and G3 disposed in this order from an object side to an image side. The final lens unit includes at least one negative lens and a positive lens disposed closest to the image side. The zoom lens satisfies predetermined inequalities.

A zoom lens includes, in order from an object side to an image side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a rear unit including one or more lens units. Distances between adjacent lens units change during zooming. The first lens unit includes a negative lens made of resin. The rear unit includes a positive lens made of resin. A predetermined condition is satisfied.

A zoom optical system according to an embodiment of the present invention comprises a first lens group, a second lens group, a third lens group, and a fourth lens group which are successively arranged from an object side to an image side, wherein the first lens group to the fourth lens group each comprise two lenses, wherein the second lens group and the third lens group are movable, and wherein the telephoto effective focal length (EFL) is defined by the mathematical expression below:

[00001]$9.0<\frac{{\mathrm{EFL}}_{\mathrm{tele}}}{H_{\mathrm{imageD}}}<9.5$ where, EFL.sub.tele refers to the effective focal length of the zoom optical system in the telephoto, and H.sub.imageD refers to a value of half a diagonal length of an image sensor pixel area.

An optical system (LS) has an aperture stop (S), and a positive lens (L4) disposed closer to the object side than the aperture stop (S). The positive lens (L4) satisfies the following conditional expressions.

−0.010<ndP1−(2.015−0.0068×νdP1)

50.00<νdP1<65.00

0.545<θgFP1

−0.010<θgFP1−(0.6418−0.00168×νdP1)

where ndP1 is the refractive index to the d line of the positive lens, νdP1 is the Abbe number with respect to the d line of the positive lens, and θgFP1 is the partial dispersion ratio of the positive lens.

An optical system (LS) Includes lenses (L22,L23) satisfying the following conditional expressions,
νdLZ<35.0, and
0.702<θgFLZ+(0.00316×νdLZ),
where νdLZ: Abbe number of the lens with reference to d-line, and θgFLZ: a partial dispersion ratio of the lens, wherein θgFLZ is defined by the following expression,
θgFLZ−(ngLZ−nFLZ)/(nFLZ−nCLZ). wherein a refractive index of the lens with reference to g-line is ngLZ, a refractive index of the lens with reference to F-line is nFLZ, and a refractive index of the lens with reference to C-line is nCLZ.

The variable magnification optical system consists of a front group, a middle group, and a rear group, in order from an object side. The front group consists of two or fewer lens groups and has a negative refractive power. The middle group includes only one lens group that has a positive refractive power as a lens group. The rear group consists of three or less lens groups. An aperture stop is disposed between a lens surface closest to an image side in the front group and a lens surface closest to the object side in the rear group. The front group includes at least three negative lenses and at least one positive lens. A negative meniscus lens convex toward the object side is disposed closest to the object side in the front group. The variable magnification optical system satisfies predetermined conditional expressions.

A zoom optical system according to an embodiment of the present invention comprises a first lens group, a second lens group, a third lens group, and a fourth lens group which are sequentially arranged in a direction from a subject side to an image side, wherein each of the first lens group to the fourth lens group includes at least two lenses, the second lens group and the third lens group are movable, and an effective focal length (EFL) in a wide angle mode is defined by an expression below.

[00001]$5.5<\frac{{\mathrm{EFL}}_{\mathrm{wide}}}{H_{\mathrm{image}D}}<6.5.$

Here, EFL.sub.wide is the EFL of the zoom optical system in the wide angle mode, and H.sub.imageD is a half value of a diagonal length of a pixel area of an image sensor.