# US 12,111,446 B2 · Optical imaging system comprising four lenses of - -+-, +-+-, +++- or -++- refractive powers, image capturing unit and electronic device

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- Number: US 12,111,446 B2
- Document ID: US12111446B2
- Status: Granted
- Kind: B2
- Application number: 18/238,204
- Filed: 2023-08-25
- Published: 2023-12-14
- Granted: 2024-10-08
- Earliest claimed: 2019-03-22
- Assignees: Largan Precision Co., Ltd.
- Applicants: Largan Precision Co., Ltd.
- Inventors: Yu Jui Lin; Hsin-Hsuan Huang
- Web page: https://patentgrep.com/patent/US12111446B2

## CPC

- G02B 13/004: {having four lenses}
- G02B 9/34: having four components only
- G02B 13/18: with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration {(G02B13/002 takes precedence)}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An optical imaging system includes four lens elements which are, in order from an object side to an image side: a first lens element, a second lens element, a third lens element and a fourth lens element. Each of the four lens elements of the optical imaging system has an object-side surface facing toward the object side and an image-side surface facing toward the image side. The object-side surface of the first lens element is concave in a paraxial region thereof, and the image-side surface of the first lens element is convex in a paraxial region thereof. The object-side surface of the fourth lens element is convex in a paraxial region thereof, the image-side surface of the fourth lens element is concave in a paraxial region thereof, and the image-side surface of the fourth lens element has at least one convex shape in an off-axis region thereof.

## Claims

### Claim 1

An optical imaging system comprising four lens elements, the four lens elements being, in order from an object side to an image side, a first lens element, a second lens element, a third lens element and a fourth lens element; each of the four lens elements having an object-side surface facing toward the object side and an image-side surface facing toward the image side;
wherein the image-side surface of the first lens element is convex in a paraxial region thereof, the fourth lens element has negative refractive power, an absolute value of a focal length of the first lens element is larger than an absolute value of a focal length of the third lens element, an axial distance between the first lens element and the second lens element is larger than a central thickness of the second lens element, and an absolute value of a curvature radius of the image-side surface of the second lens element is larger than an absolute value of a curvature radius of the image-side surface of the first lens element;
wherein a focal length of the optical imaging system is f, a focal length of the fourth lens element is f4, a curvature radius of the object-side surface of the third lens element is R5, a curvature radius of the image-side surface of the third lens element is R6, a central thickness of the third lens element is CT3, a central thickness of the fourth lens element is CT4, and the following conditions are satisfied:
−0.44≤f/f4<0;
0.99≤(R5+R6)/(R5−R6)<3.0; and
CT4<CT3.

### Claim 2 (depends on 1)

The optical imaging system of claim 1, wherein the object-side surface of the second lens element is concave in a paraxial region thereof, the image-side surface of the second lens element is convex in a paraxial region thereof, the third lens element has positive refractive power, the image-side surface of the third lens element is convex in a paraxial region thereof, the object-side surface of the fourth lens element is convex in a paraxial region thereof, and the image-side surface of the fourth lens element is concave in a paraxial region thereof and has at least one inflection point.

### Claim 3 (depends on 1)

The optical imaging system of claim 1, wherein a central thickness of the first lens element is CT1, the central thickness of the second lens element is CT2, the central thickness of the third lens element is CT3, the central thickness of the fourth lens element is CT4, and the following condition is satisfied:
0.20<(CT1+CT2+CT4)/CT3<2.0.

### Claim 4 (depends on 1)

The optical imaging system of claim 1, wherein an entrance pupil diameter of the optical imaging system is EPD, the axial distance between the first lens element and the second lens element is T12, and the following condition is satisfied:
1.0<EPD/T12≤2.60.

### Claim 5 (depends on 1)

The optical imaging system of claim 1, wherein the object-side surface of the second lens element has at least one inflection point.

### Claim 6 (depends on 1)

The optical imaging system of claim 1, wherein the central thickness of the second lens element is CT2, the central thickness of the third lens element is CT3, and the following condition is satisfied:
0.20<CT2/CT3<0.60.

### Claim 7 (depends on 1)

The optical imaging system of claim 1, wherein there is an air gap in a paraxial region between each of all adjacent lens elements of the optical imaging system;
wherein a central thickness of the first lens element is CT1, the central thickness of the third lens element is CT3, and the following condition is satisfied:
CT1<CT3.

### Claim 8 (depends on 1)

The optical imaging system of claim 1, wherein a vertical distance between a critical point on the object-side surface of the first lens element and an optical axis is Yc11, a vertical distance between a critical point on the image-side surface of the fourth lens element and the optical axis is Yc42, and the following condition is satisfied:
0.15<Yc11/Yc42<1.50.

### Claim 9 (depends on 1)

The optical imaging system of claim 1, wherein the absolute value of the focal length of the first lens element is larger than an absolute value of a focal length of the second lens element.

### Claim 10 (depends on 1)

An image capturing unit, comprising:
the optical imaging system of claim 1; and
an image sensor disposed on an image surface of the optical imaging system.

### Claim 11 (depends on 10)

An electronic device, comprising:
the image capturing unit of claim 10.

### Claim 12

An optical imaging system comprising four lens elements, the four lens elements being, in order from an object side to an image side, a first lens element, a second lens element, a third lens element and a fourth lens element; each of the four lens elements having an object-side surface facing toward the object side and an image-side surface facing toward the image side;
wherein the image-side surface of the first lens element is convex in a paraxial region thereof, the fourth lens element has negative refractive power, an absolute value of a focal length of the first lens element is larger than an absolute value of a focal length of the second lens element, the absolute value of the focal length of the first lens element is larger than an absolute value of a focal length of the third lens element, an Abbe number of the first lens element is larger than an Abbe number of the third lens element;
wherein a focal length of the optical imaging system is f, a focal length of the fourth lens element is f4, a curvature radius of the object-side surface of the third lens element is R5, a curvature radius of the image-side surface of the third lens element is R6, a central thickness of the second lens element is CT2, a central thickness of the third lens element is CT3, a central thickness of the fourth lens element is CT4, and the following conditions are satisfied:
−0.44≤f/f4<0;
0.99≤(R5+R6)/(R5−R6)<3.0;
0.20<CT2/CT3<0.60; and
CT4<CT3.

### Claim 13 (depends on 12)

The optical imaging system of claim 12, wherein the object-side surface of the second lens element is concave in a paraxial region thereof, the image-side surface of the second lens element is convex in a paraxial region thereof, the third lens element has positive refractive power, the image-side surface of the third lens element is convex in a paraxial region thereof, the object-side surface of the fourth lens element is convex in a paraxial region thereof and has at least one inflection point, and the image-side surface of the fourth lens element is concave in a paraxial region thereof.

### Claim 14 (depends on 12)

The optical imaging system of claim 12, wherein the image-side surface of the fourth lens element has at least one inflection point;
wherein a central thickness of the first lens element is CT1, the central thickness of the third lens element is CT3, and the following condition is satisfied:
CT1<CT3.

### Claim 15 (depends on 12)

The optical imaging system of claim 12, wherein a central thickness of the first lens element is CT1, the central thickness of the second lens element is CT2, the central thickness of the third lens element is CT3, the central thickness of the fourth lens element is CT4, an axial distance between the first lens element and the second lens element is T12, an axial distance between the second lens element and the third lens element is T23, and the following conditions are satisfied:
0.20<(CT1+CT2+CT4)/CT3<2.0; and
T23<T12.

### Claim 16 (depends on 12)

The optical imaging system of claim 12, wherein an entrance pupil diameter of the optical imaging system is EPD, an axial distance between the first lens element and the second lens element is T12, and the following condition is satisfied:
1.0<EPD/T12≤2.60.

### Claim 17 (depends on 12)

The optical imaging system of claim 12, wherein the object-side surface of the first lens element has at least one critical point in an off-axis region thereof.

### Claim 18 (depends on 12)

The optical imaging system of claim 12, wherein there is an air gap in a paraxial region between each of all adjacent lens elements of the optical imaging system;
wherein an axial distance between the first lens element and the second lens element is T12, an axial distance between the third lens element and the fourth lens element is T34, and the following condition is satisfied:
T34<T12.

### Claim 19 (depends on 12)

The optical imaging system of claim 12, wherein an axial distance between the first lens element and the second lens element is larger than the central thickness of the second lens element.

### Claim 20 (depends on 12)

The optical imaging system of claim 12, wherein an absolute value of a curvature radius of the object-side surface of the first lens element is larger than an absolute value of a curvature radius of the image-side surface of the fourth lens element.