# US 9,435,985 B2 · Optical imaging system, image capturing unit and electronic device

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- Number: US 9,435,985 B2
- Document ID: US9435985B2
- Status: Granted
- Kind: B2
- Application number: 14/671,580
- Filed: 2015-03-27
- Published: 2016-07-21
- Granted: 2016-09-06
- Earliest claimed: 2015-01-16
- Assignees: Largan Precision Co., Ltd.
- Applicants: LARGAN Precision Co., Ltd.
- Inventors: Lin-Yao Liao; Wei-Yu Chen
- Web page: https://patentgrep.com/patent/US9435985B2

## CPC

- G02B 13/0045: {having five or more lenses}
- G02B 9/60: having five components only
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An optical imaging system includes, in order from an object side to an image side, a first lens element, a second lens element, a third lens element, a fourth lens element and a fifth lens element. The first lens element with refractive power has an object-side surface being convex in a paraxial region. The second lens element with positive refractive power has an image-side surface being convex in a paraxial region. The third lens element with negative refractive power has an object-side surface being concave in a paraxial region. The fourth lens element with positive refractive power has an object-side surface being concave and an image-side surface being convex in a paraxial region. The fifth lens element with negative refractive power has an image-side surface being concave in a paraxial region, wherein the image-side surface thereof has at least one convex shape in an off-axis region.

## Claims

### Claim 1

An optical imaging system comprising, in order from an object side to an image side:
a first lens element having an object-side surface being convex in a paraxial region thereof;
a second lens element with positive refractive power having an image-side surface being convex in a paraxial region thereof, wherein at least one of an object-side surface and the image-side surface of the second lens element is aspheric;
a third lens element with negative refractive power having an object-side surface being concave in a paraxial region thereof, wherein at least one of the object-side surface and an image-side surface of the third lens element is aspheric;
a fourth lens element with positive refractive power having an object-side surface being concave in a paraxial region thereof and an image-side surface being convex in a paraxial region thereof, wherein at least one of the object-side surface and the image-side surface of the fourth lens element is aspheric; and
a fifth lens element with negative refractive power having an image-side surface being concave in a paraxial region thereof, wherein the image-side surface of the fifth lens element has at least one convex shape in an off-axis region thereof, and both of an object-side surface and the image-side surface of the fifth lens element are aspheric;
wherein the optical imaging system has a total of five lens elements, the fourth lens element has the largest central thickness among the first lens element, the second lens element, the third lens element, the fourth lens element and the fifth lens element;
wherein an axial distance between the first lens element and the second lens element is T12, a central thickness of the second lens element is CT2, a central thickness of the fourth lens element is CT4, a central thickness of the fifth lens element is CT5, 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 focal length of the first lens element is f1, a focal length of the second lens element is f2, and the following conditions are satisfied:
1.05<T12/CT2;
1.30<CT4/CT5;
(R5+R6)/(R5−R6)<−0.25; and
|f2/f1|<0.80.

### Claim 2 (depends on 1)

The optical imaging system of claim 1, wherein the object-side surface of the fifth lens element is convex in a paraxial region thereof.

### Claim 3 (depends on 2)

The optical imaging system of claim 2, wherein the focal length of the first lens element is f1, the focal length of the second lens element is f2, and the following condition is satisfied:
|f2/f1|<0.40.

### Claim 4 (depends on 2)

The optical imaging system of claim 2, wherein the curvature radius of the object-side surface of the third lens element is R5, the curvature radius of the image-side surface of the third lens element is R6, and the following condition is satisfied:
−2.0<(R5+R6)/(R5−R6)<−0.50.

### Claim 5 (depends on 2)

The optical imaging system of claim 2, wherein the 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, an axial distance between the third lens element and the fourth lens element is T34, an axial distance between the fourth lens element and the fifth lens element is T45, and the following condition is satisfied:
0.90<T12/(T23+T34+T45)<2.0.

### Claim 6 (depends on 1)

The optical imaging system of claim 1, wherein a projection on an optical axis from a position of a maximum effective radius of the image-side surface of the third lens element is closer to the object side than a vertex of the image-side surface of the third lens element on the optical axis.

### Claim 7 (depends on 6)

The optical imaging system of claim 6, wherein the projection of the position of the maximum effective radius of the image-side surface of the third lens element on the optical axis is closer to the image side than an intersection of the object-side surface of the third lens element and the optical axis.

### Claim 8 (depends on 1)

The optical imaging system of claim 1, wherein the object-side surface of the second lens element has at least one concave shape in an off-axis region thereof.

### Claim 9 (depends on 1)

The optical imaging system of claim 1, wherein a focal length of the third lens element is f3, a focal length of the fourth lens element is f4, a focal length of the fifth lens element is f5, and the following condition is satisfied:
3.0<|f3/f4|+|f4/f5|+|f5/f3|<3.6.

### Claim 10 (depends on 1)

The optical imaging system of claim 1, wherein a central thickness of the first lens element is CT1, a 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:
1.35<CT4/(CT1+CT3)<2.5.

### Claim 11 (depends on 1)

The optical imaging system of claim 1, wherein a curvature radius of the object-side surface of the fourth lens element is R7, a focal length of the fifth lens element is f5, and the following condition is satisfied:
1.85<R7/f5.

### Claim 12 (depends on 1)

The optical imaging system of claim 1, wherein half of a maximal field of view of the optical imaging system is HFOV, and the following condition is satisfied:
0.85<tan(HFOV)<1.50.

### Claim 13 (depends on 1)

The optical imaging system of claim 1, wherein an Abbe number of the first lens element is V1, an Abbe number of the fifth lens element is V5, and the following condition is satisfied:
V1−V5<10.

### Claim 14 (depends on 1)

The optical imaging system of claim 1, wherein the axial distance between the first lens element and the second lens element is T12, the central thickness of the second lens element is CT2, and the following condition is satisfied:
1.15<T12/CT2<3.5.

### Claim 15 (depends on 1)

The optical imaging system of claim 1, wherein the first lens element has positive refractive power, and the first lens element has an image-side surface being concave in a paraxial region thereof.

### Claim 16 (depends on 13)

The optical imaging system of claim 13, wherein a focal length of the optical imaging system is f, the curvature radius of the object-side surface of the third lens element is R5, the curvature radius of the image-side surface of the third lens element is R6, and the following condition is satisfied:
0.85<(f/R6)−(f/R5)<2.0.

### Claim 17 (depends on 13)

The optical imaging system of claim 13, wherein the 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, an axial distance between the third lens element and the fourth lens element is T34, an axial distance between the fourth lens element and the fifth lens element is T45, and T12 is larger than T23, T34, or T45, and the following condition is satisfied:
8.0<T12/T34<25.0.

### Claim 18 (depends on 1)

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

### Claim 19 (depends on 18)

An electronic device, comprising:
the image capturing unit of claim 18.

### Claim 20

An optical imaging system comprising, in order from an object side to an image side:
a first lens element having an object-side surface being convex in a paraxial region thereof;
a second lens element with positive refractive power having an image-side surface being convex in a paraxial region thereof, wherein at least one of an object-side surface and the image-side surface of the second lens element is aspheric;
a third lens element with negative refractive power having an object-side surface being concave in a paraxial region thereof, wherein at least one of the object-side surface and an image-side surface of the third lens element is aspheric;
a fourth lens element with positive refractive power having an object-side surface being concave in a paraxial region thereof and an image-side surface being convex in a paraxial region thereof, wherein at least one of the object-side surface and the image-side surface of the fourth lens element is aspheric; and
a fifth lens element with negative refractive power having an image-side surface being concave in a paraxial region thereof, wherein the image-side surface of the fifth lens element has at least one convex shape in an off-axis region thereof, and both of an object-side surface and the image-side surface of the fifth lens element are aspheric;
wherein the optical imaging system has a total of five lens elements, an absolute value of a focal length of the third lens element is smaller than an absolute value of a focal length of the first lens element;
wherein an axial distance between the first lens element and the second lens element is T12, a central thickness of the second lens element is CT2, a central thickness of the fourth lens element is CT4, a central thickness of the fifth lens element is CT5, 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 focal length of the first lens element is f1, a focal length of the second lens element is f2, and the following conditions are satisfied:
1.05<T12/CT2;
1.30<CT4/CT5;
(R5+R6)/(R5−R6)<−0.25; and
|f2/f1|<0.80.

### Claim 21 (depends on 20)

The optical imaging system of claim 20, wherein the object-side surface of the fifth lens element is convex in a paraxial region thereof.

### Claim 22 (depends on 21)

The optical imaging system of claim 21, wherein the focal length of the first lens element is f1, the focal length of the second lens element is f2, and the following condition is satisfied:
|f2/f1|<0.40.

### Claim 23 (depends on 21)

The optical imaging system of claim 21, wherein the curvature radius of the object-side surface of the third lens element is R5, the curvature radius of the image-side surface of the third lens element is R6, and the following condition is satisfied:
−2.0<(R5+R6)/(R5−R6)<−0.50.

### Claim 24 (depends on 21)

The optical imaging system of claim 21, wherein the fourth lens element has the largest central thickness among the first lens element, the second lens element, the third lens element, the fourth lens element and the fifth lens element.

### Claim 25 (depends on 21)

The optical imaging system of claim 21, wherein the 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, an axial distance between the third lens element and the fourth lens element is T34, an axial distance between the fourth lens element and the fifth lens element is T45, and the following condition is satisfied:
0.90<T12/(T23+T34+T45)<2.0.

### Claim 26 (depends on 20)

The optical imaging system of claim 20, wherein a projection on an optical axis from a position of a maximum effective radius of the image-side surface of the third lens element is closer to the object side than a vertex of the image-side surface of the third lens element on the optical axis.

### Claim 27 (depends on 26)

The optical imaging system of claim 26, wherein the projection of the position of the maximum effective radius of the image-side surface of the third lens element on the optical axis is closer to the image side than an intersection of the object-side surface of the third lens element and the optical axis.

### Claim 28 (depends on 20)

The optical imaging system of claim 20, wherein the object-side surface of the second lens element has at least one concave shape in an off-axis region thereof.

### Claim 29 (depends on 20)

The optical imaging system of claim 20, wherein a focal length of the third lens element is f3, a focal length of the fourth lens element is f4, a focal length of the fifth lens element is f5, and the following condition is satisfied:
3.0<|f3/f4|+|f4/f5|+|f5/f3|<3.6.

### Claim 30 (depends on 20)

The optical imaging system of claim 20, wherein a central thickness of the first lens element is CT1, a 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:
1.35<CT4/(CT1+CT3)<2.5.

### Claim 31 (depends on 20)

The optical imaging system of claim 20, wherein a curvature radius of the object-side surface of the fourth lens element is R7, a focal length of the fifth lens element is f5, and the following condition is satisfied:
1.85<R7/f5.

### Claim 32 (depends on 20)

The optical imaging system of claim 20, wherein half of a maximal field of view of the optical imaging system is HFOV, and the following condition is satisfied:
0.85<tan(HFOV)<1.50.

### Claim 33 (depends on 20)

The optical imaging system of claim 20, wherein an Abbe number of the first lens element is V1, an Abbe number of the fifth lens element is V5, and the following condition is satisfied:
V1−V5<10.

### Claim 34 (depends on 20)

The optical imaging system of claim 20, wherein the axial distance between the first lens element and the second lens element is T12, the central thickness of the second lens element is CT2, and the following condition is satisfied:
1.15<T12/CT2<3.5.

### Claim 35 (depends on 20)

The optical imaging system of claim 20, wherein the first lens element has positive refractive power, and the first lens element has an image-side surface being concave in a paraxial region thereof.

### Claim 36 (depends on 33)

The optical imaging system of claim 33, wherein a focal length of the optical imaging system is f, the curvature radius of the object-side surface of the third lens element is R5, the curvature radius of the image-side surface of the third lens element is R6, and the following condition is satisfied:
0.85<(f/R6)−(f/R5)<2.0.

### Claim 37 (depends on 33)

The optical imaging system of claim 33, wherein the 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, an axial distance between the third lens element and the fourth lens element is T34, an axial distance between the fourth lens element and the fifth lens element is T45, and T12 is larger than T23, T34, or T45, and the following condition is satisfied:
8.0<T12/T34<25.0.

### Claim 38 (depends on 20)

An image capturing unit, comprising:
the optical imaging system of claim 20; and
an image sensor, wherein the image sensor is disposed on the image side of the optical imaging system.

### Claim 39 (depends on 38)

An electronic device, comprising:
the image capturing unit of claim 38.