Zoom lens and imaging apparatus

Patent metadata

Field	Value
Publication number	US-12379573-B2
Application number	US-202117344866-A
Country	US
Kind code	B2
Filing date	Jun 10, 2021
Priority date	Aug 24, 2017
Publication date	Aug 5, 2025
Grant date	Aug 5, 2025

Abstract

The zoom lens consists of, in order from the object side, a first lens group that has a negative refractive power; a second lens group that has a positive refractive power; a third lens group that has a negative refractive power; and a fourth lens group that has a positive refractive power. During zooming, in each lens group, distances between the adjacent groups in the direction of the optical axis are changed. The first lens group consists of, in order from the object side, a first lens having a negative refractive power, a second lens having a negative refractive power, and a third lens having a positive refractive power. The third lens group consists of a negative lens. During focusing, only the third lens group moves along the optical axis. The zoom lens satisfies predetermined conditional expressions.

First claim

What is claimed is:

1. A zoom lens comprising, in consecutive order from a position closest to an object side:
a first lens group that has a negative refractive power;
a second lens group that has a positive refractive power; and
a third lens group that has a negative refractive power,
wherein during zooming, distances between adjacent groups of the first lens group, the second lens group, and the third lens group in a direction of an optical axis are changed,
wherein the third lens group consists of a biconcave lens,
wherein the first lens group includes a first lens having a negative refractive power at a position closest to the object side,
wherein the first lens group includes a positive meniscus lens having a shape convex toward the object side at a position closest to an image side,
wherein the second lens group includes a biconvex lens at a position closest to the image side,
wherein the zoom lens includes exactly one cemented lens, and
wherein assuming that
a refractive index of the first lens is Nd1,
an Abbe number of the first lens is νd1,
a focal length of the zoom lens during focusing on an object at infinity at a wide-angle end is fw,
a focal length of the third lens group is f3,
Conditional Expressions (1-1) and (3-1) are satisfied
1.75< Nd 1−0.0037×ν d 1<2  (1-1)

−0.5< fw/f 3<−0.2  (3-1).

2. The zoom lens according to claim 1 ,
wherein the second lens group has a stop and a cemented lens comprising at least one positive lens and at least one negative lens on the image side of the stop.

3. A zoom lens comprising, in order consecutive from a position closest to an object side:
a first lens group that has a negative refractive power;
a second lens group that has a positive refractive power; and
a third lens group that has a negative refractive power; and,
wherein during zooming, distances between adjacent groups of the first lens group, the second lens group, and the third lens group in a direction of an optical axis are changed,
wherein the third lens group consists of a negative lens having a shape concave toward the object side,
wherein the first lens group includes a first lens as a negative meniscus lens having a shape convex toward the object side at a position closest to the object side,
wherein the second lens group includes a biconvex lens at a position closest to the image side,
wherein the zoom lens includes exactly one cemented lens, and
wherein assuming that
a refractive index of the first lens is Nd1,
an Abbe number of the first lens is νd1,
a focal length of the zoom lens during focusing on an object at infinity at a wide-angle end is fw,
a focal length of the third lens group is f3,
Conditional Expressions (1-1) and (3-2) are satisfied
1.75< Nd 1−0.0037×ν d 1<2  (1-1)

−0.5< fw/f 3≤−0.27  (3-2).

4. The zoom lens according to claim 3 ,
wherein the second lens group has a stop and a cemented lens comprising at least one positive lens and at least one negative lens on the image side of the stop.

5. An imaging apparatus comprising the zoom lens according to claim 1 .

6. An imaging apparatus comprising the zoom lens according to claim 3 .

7. The zoom lens according to claim 1 ,
wherein the zoom lens includes exactly five negative lenses.

8. The zoom lens according to claim 1 ,
wherein during focusing, only the third lens group moves along the optical axis.

9. The zoom lens according to claim 3 ,
wherein the zoom lens includes exactly five negative lenses.

10. The zoom lens according to claim 3 ,
wherein during focusing, only the third lens group moves along the optical axis.

Assignees

• Fujifilm Corp

Inventors

• Nagami Ryosuke

Classifications

• H04N23/55

  Optical parts specially adapted for electronic image sensors; Mounting thereof · CPC title

• G02B13/009

  having zoom function · CPC title

• G02B15/144511 Primary

  arranged -+-+ · CPC title

• G02B15/142 Primary

  having two groups only · CPC title

• G02B15/177

  having a negative front lens or group of lenses · CPC title