The present invention comprises a first lens group (G1) having a positive refractive power and a rear group (GR) having a plurality of lens groups, the first lens group and the rear group being arranged side by side on the optical axis in order from an object side, wherein: when the magnification is varied from a wide-angle end to a telephoto end, the distance between the first lens group (G1) and the rear group (GR) changes; distances between the plurality of lens groups constituting the rear group (GR) change from each other; the rear group (GR) has, in order from the object side, a first focusing lens group (GF1) having a negative refractive power and a second focusing lens group (GF2) having a negative refractive power; both the first and second focusing lens groups move toward an image side on the optical axis when focusing from infinity to a short distance position; and the following conditional expression is satisfied.

0.000<(MWF1/MTF1)/(MWF2/MTF2)<0.500

where

MWF1, which is an amount of movement of the first focusing lens group when focusing from infinity to a short distance position in the wide-angle end state, MTF1, which is an amount of movement of the first focusing lens group when focusing from infinity to a short distance position in the telephoto end state,

MWF2, which is an amount of movement of the second focusing lens group when focusing from infinity to a short distance position in the wide-angle end state, and

MTF2, which is an amount of movement of the second focusing lens group when focusing from infinity to a short distance position in the telephoto end state, are all set such that the movement toward the image side is positive.

The present invention comprises a first lens group (G1) having a positive refractive power and a rear group (GR) having a plurality of lens groups, the first lens group and the rear group being arranged side by side on the optical axis in order from an object side, wherein: when the magnification is varied from a wide-angle end to a telephoto end, the distance between the first lens group (G1) and the rear group (GR) changes; distances between the plurality of lens groups constituting the rear group (GR) change from each other; the rear group (GR) has, in order from the object side, a first focusing lens group (GF1) having a negative refractive power and a second focusing lens group (GF2) having a negative refractive power; both the first and second focusing lens groups move toward an image side on the optical axis when focusing from infinity to a short distance position; and the following conditional expression is satisfied.

0.000<(MWF1/MTF1)/(MWF2/MTF2)<0.500

where

MWF1, which is an amount of movement of the first focusing lens group when focusing from infinity to a short distance position in the wide-angle end state, MTF1, which is an amount of movement of the first focusing lens group when focusing from infinity to a short distance position in the telephoto end state,

MWF2, which is an amount of movement of the second focusing lens group when focusing from infinity to a short distance position in the wide-angle end state, and

MTF2, which is an amount of movement of the second focusing lens group when focusing from infinity to a short distance position in the telephoto end state, are all set such that the movement toward the image side is positive.

An endoscope magnification optical system includes, in order starting from an object side, a first lens group having positive power, a second lens group having positive power, and a third lens group including at least a meniscus lens with a concave surface facing the object side and a positive lens, and the endoscope magnification optical system is configured to magnify an optical image by moving at least the second lens group in an optical axis direction with respect to the first lens group, which is a fixed lens group, while a distance from a lens surface located the closest to the object of the first lens group to an image plane is kept constant.

An endoscope magnification optical system includes, in order starting from an object side, a first lens group having positive power, a second lens group having positive power, and a third lens group including at least a meniscus lens with a concave surface facing the object side and a positive lens, and the endoscope magnification optical system is configured to magnify an optical image by moving at least the second lens group in an optical axis direction with respect to the first lens group, which is a fixed lens group, while a distance from a lens surface located the closest to the object of the first lens group to an image plane is kept constant.

A variable magnification optical system (ZL) comprises a preceding lens group (GA) having negative refractive power and a succeeding lens group (GB) having positive refractive power, which are arranged in order from the object side along an optical axis. The succeeding lens group (GB) has a focusing group (GF) and an image-side group (GC) disposed closer to the image side than the focusing group (GF), the focusing group (GF) moves to the image side along the optical axis from focusing on an object at infinity to focusing on a close-distance object, and the following conditional expression is satisfied.

1.80<fF/fBaw

FNow<3.40 where fF is the focal length of the focusing group (GF), fBaw is the focal length in the wide-angle end state of an image-side lens group (GBa) composed of lenses disposed on the image side from the focusing group (GF), and FNow is the F-number of the variable magnification optical system (ZL) in the wide-angle end state.

A variable magnification optical system (ZL) comprises a preceding lens group (GA) having negative refractive power and a succeeding lens group (GB) having positive refractive power, which are arranged in order from the object side along an optical axis. The succeeding lens group (GB) has a focusing group (GF) and an image-side group (GC) disposed closer to the image side than the focusing group (GF), the focusing group (GF) moves to the image side along the optical axis from focusing on an object at infinity to focusing on a close-distance object, and the following conditional expression is satisfied.

1.80<fF/fBaw

FNow<3.40 where fF is the focal length of the focusing group (GF), fBaw is the focal length in the wide-angle end state of an image-side lens group (GBa) composed of lenses disposed on the image side from the focusing group (GF), and FNow is the F-number of the variable magnification optical system (ZL) in the wide-angle end state.

A lens assembly includes a first lens group, a second lens group, and a third lens group, all of which are arranged in order from a first side to a second side along an optical axis. The first lens group is with positive refractive power. The second lens group is with positive refractive power. The third lens group is with positive refractive power. The first lens group is fixed, the second lens group can move along the optical axis, and the third lens group can move along the optical axis, so that the lens assembly is zoomed from a wide-angle end to a telephoto end to change an effective focal length.

A lens assembly includes a first lens group, a second lens group, and a third lens group, all of which are arranged in order from a first side to a second side along an optical axis. The first lens group is with positive refractive power. The second lens group is with positive refractive power. The third lens group is with positive refractive power. The first lens group is fixed, the second lens group can move along the optical axis, and the third lens group can move along the optical axis, so that the lens assembly is zoomed from a wide-angle end to a telephoto end to change an effective focal length.

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 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.