CN113741011A

CN113741011A - Micro-distance optical lens

Info

Publication number: CN113741011A
Application number: CN202111090048.2A
Authority: CN
Inventors: 陈志建; 宋亮; 葛杰; 金兑映
Original assignee: Liaoning Zhonglan Photoelectric Technology Co Ltd
Current assignee: Liaoning Zhonglan Photoelectric Technology Co Ltd
Priority date: 2021-09-17
Filing date: 2021-09-17
Publication date: 2021-12-03

Abstract

The invention relates to the technical field of optical lenses, in particular to a macro optical lens, which comprises a first lens, a second lens and a third lens, wherein the first lens, the second lens and the third lens are sequentially arranged from an object side to an image surface along an optical axis; the first lens has positive refractive power, the object side surface is a convex surface, and the image side surface is a concave surface; the second lens has negative refractive power, and the object side surface of the second lens is a concave surface; the third lens element with positive refractive power has a convex object-side surface, and the image-side surface of the third lens element at least comprises an inflection point; the diaphragm is placed on the object side or between the first lens and the second lens; the macro optical lens satisfies the following conditional expression: TTL/IH is less than 1.45, tan (HFOV) is more than or equal to 1, wherein TTL is the optical total length of the optical lens; IH is the half image height of the lens group; the HFOV is half of the maximum field angle of the optical lens. The invention adopts the three-piece lens group, greatly saves the production cost, ensures the miniaturization of the lens while ensuring the high performance of the lens under the short object distance, and has smaller optical distortion and higher illumination.

Description

Micro-distance optical lens

Technical Field

The invention relates to the technical field of optical lenses, in particular to a macro optical lens.

Background

In recent years, with the rapid development of portable electronic devices, there are not only higher and higher requirements for photographing, but also more requirements in other photographing fields, such as macro photography. However, most of the photographic lenses are designed mainly for the conventional focal length, and the problems of distortion and reduced resolving power occur when the object distance is short, and in addition, the development trend of the current electronic products is light, thin, short and small, so the miniaturized photographic lens suitable for the multi-focal length is just the mainstream in the current market.

Disclosure of Invention

In view of the above-mentioned drawbacks and deficiencies of the prior art, the present invention provides a macro optical lens suitable for a mobile phone or an ultra-thin video camera device with a certain size requirement. The optical lens can keep good imaging quality at infinite distance and 5cm object distance under the condition of small volume.

In order to achieve the purpose, the invention adopts the main technical scheme that:

the invention provides a macro optical lens, which comprises a first lens, a second lens and a third lens which are sequentially arranged from an object side to an image surface along an optical axis; the first lens has positive refractive power, the object side surface is a convex surface, and the image side surface is a concave surface; the second lens has negative refractive power, and the object side surface of the second lens is a concave surface; the third lens element with positive refractive power has a convex object-side surface, and the image-side surface of the third lens element at least comprises an inflection point; the diaphragm is placed on the object side or between the first lens and the second lens; the macro optical lens satisfies the following conditional expression: TTL/IH < 1.4; wherein, TTL is the optical total length of the optical lens; IH is the half image height of the lens group; tan (HFOV) is not less than 1; the HFOV is a half of the maximum field angle of the optical lens.

Further, the first lens satisfies the following relation: 0.4< R1/F <0.5, 0.45< | F1/F2| < 1; wherein, R1 is the curvature radius of the object side surface of the first lens, and F is the focal length of the optical lens; f1 is the focal length of the first lens, and F2 is the focal length of the second lens.

Further, the optical lens satisfies the following relation: 0< | R2/R3| < 4; wherein R2 is a radius of curvature of an image-side surface of the first lens element, and R3 is a radius of curvature of an object-side surface of the second lens element.

Further, the optical lens satisfies the following relation: 0.75< CT2/CT1<0.85, 0.35< CT2/CT3< 0.75; wherein CT1 is the central thickness of the first lens element, CT2 is the central thickness of the second lens element, and CT3 is the central thickness of the third lens element.

Further, the optical lens satisfies the following relation: 0.45< (T12+ T23)/Σ CT < 0.55; wherein T12 is an axial distance between the image-side surface of the first lens element and the object-side surface of the second lens element, T23 is an axial distance between the image-side surface of the second lens element and the object-side surface of the third lens element, Σ CT is a total axial thickness of all lens elements in the optical lens assembly.

Further, the optical lens satisfies the following relation: 0.8< DT2/DT3< 1.1; DT2 is the maximum effective radius of the image side surface of the first lens, and DT3 is the maximum effective radius of the object side surface of the second lens.

Further, the optical lens satisfies the following relation: 0.8< SL/TTL < 1; wherein, SL is the distance between the diaphragm and the imaging surface of the optical lens on the optical axis, and TTL is the total optical length of the optical lens.

Further, the optical lens satisfies the following relation: F/EPD is less than or equal to 2.5; wherein, F is the focal length of the optical lens, and EPD is the entrance pupil diameter of the optical lens.

Further, the optical lens further includes an optical filter for correcting color deviation, and a protective glass for protecting the photosensitive element located on the image plane; the optical filter is placed behind the third lens, and the protective glass is placed behind the optical filter.

Further, the surfaces of the first lens, the second lens and the third lens are aspheric surfaces, and the aspheric coefficients satisfy the following equation: z is cy²/[1+{1－(1+k)c²y²}^+1/2]+A₄y⁴+A₆y⁶+A₈y⁸+A₁₀y¹⁰+A₁₂y¹²+A₁₄y¹⁴+A₁₆y¹⁶+A₁₈y¹⁸+A₂₀y²⁰(ii) a Wherein Z is aspheric sagittal height, c is aspheric paraxial curvature, y is lens caliber, k is cone coefficient, A₄Is a 4-order aspheric coefficient, A₆Is a 6-degree aspheric surface coefficient, A₈Is an 8 th order aspheric surface coefficient, A₁₀Is a 10 th order aspheric surface coefficient, A₁₂Is a 12 th order aspheric surface coefficient, A₁₄Is a 14 th order aspheric coefficient, A₁₆Is a 16 th order aspheric coefficient, A₁₈Is an 18 th order aspheric coefficient, A₂₀Is a 20-degree aspheric coefficient.

The invention has the beneficial effects that: according to the macro optical lens, the three-lens-group is adopted, so that the production cost is greatly saved, the optical lens is specially optimized for macro shooting, the miniaturization of the lens can be guaranteed while the high performance of the lens under the condition of short object distance is guaranteed, the optical distortion of the lens is small, and the illumination is high.

Drawings

Fig. 1 shows a schematic structural diagram of an optical lens according to embodiment 1 of the present invention;

fig. 2A, 2B, and 2C show an on-axis astigmatism graph, a distortion graph, and a modulation transfer function graph, respectively, of the optical lens of embodiment 1;

fig. 3 shows a schematic structural diagram of an optical lens according to embodiment 2 of the present invention;

fig. 4A, 4B, and 4C show an on-axis astigmatism graph, a distortion graph, and a modulation transfer function graph, respectively, of the optical lens of example 2;

fig. 5 shows a schematic structural diagram of an optical lens according to embodiment 3 of the present invention;

fig. 6A, 6B, and 6C show an on-axis astigmatism graph, a distortion graph, and a modulation transfer function graph, respectively, of the optical lens of example 3;

fig. 7 shows a schematic structural diagram of an optical lens according to embodiment 4 of the present invention;

fig. 8A, 8B, and 8C show an on-axis astigmatism graph, a distortion graph, and a modulation transfer function graph, respectively, of the optical lens of example 4.

In the figure: 1. a first lens; 2. a second lens; 3. a third lens; 4. a diaphragm; 5. an optical filter; 6. and (4) protecting the glass.

Detailed Description

For the purpose of better explaining the present invention and to facilitate understanding, the present invention will be described in detail by way of specific embodiments with reference to the accompanying drawings.

The invention provides a macro optical lens. The optical lens has a first lens 1, a second lens 2, and a third lens 3 arranged in this order from an object side to an image plane along an optical axis. The first lens element 1 has positive refractive power, and has a convex object-side surface and a concave image-side surface. The second lens element 2 has negative refractive power and a concave object-side surface. The third lens element 3 with positive refractive power has a convex object-side surface and at least one inflection point on the image-side surface. A diaphragm 4 is also included and the diaphragm 4 is placed on the object side or behind the first lens.

In the present embodiment, the macro optical lens satisfies the following conditional expression:

TTL/IH<1.45

wherein, TTL is the total optical length from the object-side surface of the optical lens to the image plane, and IH is the half-image height of the lens group. Under the condition, the miniaturization of the lens module is ensured on the basis of meeting the large image surface of the optical lens, and the optical lens module can be suitable for portable electronic equipment with strict requirements on thickness and size.

In the present embodiment, half of the maximum field angle of the macro optical lens HFOV satisfies the following condition:

tan(HFOV)≥1

the lens satisfying the above conditions can control the full field angle of the imaging lens, and can make the light beam in the object space form high-quality imaging on the imaging surface.

In the present embodiment, the first lens object-side curvature radius R1 of the macro optical lens and the focal length F of the macro optical lens satisfy the following condition:

0.4<R1/F<0.5

the camera lens that satisfies above-mentioned condition can ensure that the ratio of the effective focal length of the radius of curvature of the object side of first lens and optical imaging camera lens is in certain extent, has both guaranteed that first lens provides sufficient bending force, also satisfies the demand of minor caliber simultaneously to be favorable to later stage machine-shaping.

In an embodiment, the focal length F1 of the first lens and the focal length F2 of the second lens of the macro optical lens satisfy the following condition:

0.45<|F1/F2|<1

the lens meeting the above conditions can adjust the focal length ratio of the first lens and the second lens, and reduce the aberration of the optical system.

In this embodiment, the image-side surface curvature radius R2 of the first lens element and the object-side surface curvature radius R3 of the second lens element of the macro optical lens satisfy the following conditions:

0<|R2/R3|<4

the lens meeting the conditions can effectively balance the surface type of the first lens and the second lens, can control the light convergence capacity of the lens, can correct the influence of aberration on the lens, and improves the performance of the lens.

In the present embodiment, the center thickness CT1 of the first lens element, the center thickness CT2 of the second lens element and the center thickness CT3 of the third lens element on the optical axis of the macro optical lens satisfy the following conditions:

0.75<CT2/CT1<0.85

0.35<CT2/CT3<0.75

the thickness proportion that satisfies the camera lens of above-mentioned condition can effectual control lens group both can promote the imaging quality, also can avoid too high because of the lens sensitivity that the thickness leads to is favorable to processing and the shaping of lens group.

In this embodiment, an axial distance T12 between the image side surface of the first lens element and the object side surface of the second lens element, an axial distance T23 between the image side surface of the second lens element and the object side surface of the third lens element, and an axial thickness sum Σ CT of all the lens elements satisfy the following condition:

0.45<(T12+T23)/ΣCT<0.55

the lens meeting the conditions can reduce the total thickness of the lens, and reasonably control the position and the thickness of the lens, so that the space application of the optical system is more efficient.

In the present embodiment, the maximum effective radius DT2 of the image-side surface of the first lens and the maximum effective radius DT3 of the object-side surface of the second lens of the macro optical lens satisfy the following conditions:

0.8<DT2/DT3<1.1

the lens satisfying the above conditions is advantageous for maintaining the effective diameter of the lens, satisfying the large field angle, and correcting the distortion and spherical aberration of the optical system.

In the present embodiment, the distance SL from the macro optical lens stop to the imaging plane on the optical axis and the total optical length TTL of the lens satisfy the following conditions:

0.8<SL/TTL<1

the lens meeting the conditions is beneficial to enlarging the relative aperture of the lens, improving the light incoming quantity of the optical system and keeping the high illumination of the edge of the lens.

In the present embodiment, the focal length F and the entrance pupil diameter EPD of the macro optical lens satisfy the following conditions:

F/EPD≤2.5

after the lens meets the conditions, the size of the aperture of the optical system can be ensured, the imaging quality of the image space photosensitive chip is improved, and the influence of dark current on imaging is reduced.

In the present embodiment, the macro optical lens has at least one inflection point on the image-side surface of the third lens. The lens meeting the conditions can be beneficial to the uniform distribution of light rays on the third lens, the brightness of the edge and the center of an image plane is ensured, and in addition, the further compression of the optical total length is facilitated.

In the present embodiment, the diaphragm 4 may be provided at an appropriate position as needed. For example, the diaphragm 4 may be disposed on the object side, or placed between the first lens 1 and the second lens 2. Optionally, the above optical lens may further include a filter 5 for correcting color deviation and a protective glass 6 for protecting a photosensitive element located on an image forming surface.

The object side and image side surfaces of the first lens 1, the second lens 2 and the third lens 3 are aspheric, wherein the aspheric coefficients satisfy the following equation:

Z＝cy²/[1+{1－(1+k)c²y²}^+1/2]+A₄y⁴+A₆y⁶+A₈y⁸+A₁₀y¹⁰+A₁₂y¹²+A₁₄y¹⁴+A₁₆y¹⁶+A₁₈y¹⁸+A₂₀y²⁰

wherein Z is aspheric sagittal height, c is aspheric paraxial curvature, y is lens caliber, k is cone coefficient, A₄Is a 4-order aspheric coefficient, A₆Is a 6-degree aspheric surface coefficient, A₈Is an 8 th order aspheric surface coefficient, A₁₀Is a 10 th order aspheric surface coefficient, A₁₂Is a 12 th order aspheric surface coefficient, A₁₄Is a 14 th order aspheric coefficient, A₁₆Is a 16 th order aspheric coefficient, A₁₈Is an 18 th order aspheric coefficient, A₂₀Is a 20-degree aspheric coefficient.

Example 1:

reference is now made to fig. 1, which is a block diagram illustrating a macro optical lens according to embodiment 1 of the present application.

As shown in fig. 1, a macro optical lens according to an exemplary embodiment of the present application, in order from an object side to an image side along an optical axis, includes: the lens includes a diaphragm, a first lens having positive refractive power, a second lens having negative refractive power, a third lens having positive refractive power, an optical filter, and a cover glass. The filter has an object side and an image side. The protective glass is used for protecting the photosensitive element. The incident light passes through each lens surface in sequence and is finally imaged on an imaging surface.

Table one (a) shows the surface type, radius of curvature, thickness, and material of each lens of the optical lens of example 1. Wherein the unit of the radius of curvature and the thickness are both millimeters (mm). Inf/50 refers to the object distance, which is understood to mean the distance of the object from the optical system, which is suitable for infinity or 5 cm.

The design parameters of the lens assembly of the present embodiment refer to the following table:

watch 1 (a)

Watch 1 (b)

Surface number

1

2

3

4

5

6

k

-1.56E+00

-9.86E+01

1.08E+00

-2.07E+01

-7.76E+00

-9.78E-01

A₄

1.09E-01

1.81E-01

-3.29E+00

-5.91E+00

1.27E-01

-4.47E-01

A₆

2.62E+01

5.32E+01

2.16E+00

5.52E+01

-3.15E+00

-3.18E-01

A₈

-1.20E+03

-2.70E+03

1.02E+03

-4.19E+02

1.01E+01

1.06E+00

A₁₀

3.12E+04

6.76E+04

-2.73E+04

2.21E+03

-1.84E+01

-8.38E-01

A₁₂

-4.98E+05

-9.88E+05

3.69E+05

-7.28E+03

2.07E+01

-3.83E-01

A₁₄

4.94E+06

8.61E+06

-2.95E+06

1.26E+04

-1.42E+01

1.16E+00

A₁₆

-2.95E+07

-4.35E+07

1.40E+07

-3.77E+03

5.71E+00

-8.65E-01

A₁₈

9.76E+07

1.15E+08

-3.62E+07

-1.99E+04

-1.22E+00

2.90E-01

A₂₀

-1.37E+08

-1.19E+08

3.93E+07

2.08E+04

1.03E-01

-3.71E-02

In this embodiment, specific parameters of the optical lens are shown in the following table:

watch 1 (c)

According to the table one (a), the table one (b) and fig. 1, the lens shape and the lens attributes of the embodiment 1 are clearly shown, which indicates that the embodiment 1 is a macro optical lens capable of realizing miniaturization.

As shown clearly from the data in table (c) and the astigmatism curve in fig. 2A, after the lens meets the above requirements, the maximum difference between the astigmatism S line and the astigmatism T line of the lens is about 0.04mm, which indicates that the lens has a better astigmatism improving capability.

It is clearly shown from the data in table (c) and the distortion curve in fig. 2B that the maximum distortion value of the lens is less than 1% after the lens meets the above requirements, which indicates that the lens has a good capability of improving distortion.

As shown clearly from the data in table one (C) and the modulation transfer function curve in fig. 2C, the Modulation Transfer Function (MTF) at the test frequency (110lp/mm) of the lens at the object distance of 5cm is greater than 0.4 at both the on-axis point and the off-axis point, which indicates that the lens still has higher performance at the shorter object distance.

It is explained from the above information that embodiment 1 of the macro lens has the characteristics of miniaturization of the lens, small distortion of the lens, and taking of a clear image.

Example 2:

reference is now made to fig. 3, which is a block diagram illustrating a macro optical lens according to embodiment 2 of the present application.

As shown in fig. 3, a macro optical lens according to an exemplary embodiment of the present application, in order from an object side to an image side along an optical axis, includes: the lens includes a diaphragm, a first lens having positive refractive power, a second lens having negative refractive power, a third lens having positive refractive power, an optical filter, and a cover glass. The filter has an object side and an image side. The protective glass is used for protecting the photosensitive element. The incident light passes through each lens surface in sequence and is finally imaged on an imaging surface.

Table two (a) shows the surface type, radius of curvature, thickness, and material of each lens of the optical lens of example 2. Wherein the unit of the radius of curvature and the thickness are both millimeters (mm).

In this embodiment, the specific design parameters refer to the following table:

watch two (a)

Watch two (b)

Surface number

1

2

3

4

5

6

k

-1.65E+00

-9.83E+01

-1.28E+00

-2.08E+01

-7.97E+00

-6.97E-01

A₄

-2.19E-01

2.54E-02

-3.27E+00

-5.40E+00

3.35E-02

-5.09E-01

A₆

5.70E+01

7.05E+01

-1.81E+00

4.75E+01

-2.83E+00

-2.98E-01

A₈

-2.52E+03

-3.92E+03

1.30E+03

-3.59E+02

9.00E+00

1.07E+00

A₁₀

6.34E+04

1.10E+05

-3.81E+04

1.90E+03

-1.66E+01

-9.63E-01

A₁₂

-9.61E+05

-1.81E+06

5.70E+05

-6.58E+03

1.97E+01

-2.49E-01

A₁₄

8.91E+06

1.81E+07

-5.04E+06

1.46E+04

-1.47E+01

1.18E+00

A₁₆

-4.93E+07

-1.07E+08

2.63E+07

-2.15E+04

6.63E+00

-9.71E-01

A₁₈

1.49E+08

3.43E+08

-7.49E+07

2.70E+04

-1.63E+00

3.53E-01

A₂₀

-1.87E+08

-4.58E+08

8.94E+07

-2.43E+04

1.68E-01

-4.89E-02

In this embodiment, the specific parameters of the lens are shown in the following table:

watch two (c)

According to the second table (a), the second table (b) and fig. 3, the lens shape and the properties of the lens in embodiment 2 are clearly shown, which means that embodiment 2 is a macro optical lens capable of realizing miniaturization.

As shown clearly from the data in table two (c) and the astigmatism curve in fig. 4A, after the lens meets the above requirements, the maximum difference between the astigmatism S line and the astigmatism T line of the lens is about 0.03mm, which indicates that the lens has a better astigmatism improving capability.

It is clearly shown from the data in table two (c) and the distortion curve in fig. 4B that the maximum distortion value of the lens is less than 1% after the lens meets the above requirements, which indicates that the lens has a good capability of improving distortion.

As shown clearly from the data in table two (C) and the modulation transfer function curve in fig. 4C, the Modulation Transfer Function (MTF) at the test frequency (110lp/mm) of the lens at the object distance of 5cm is greater than 0.38 at both the on-axis point and the off-axis point, which indicates that the lens still has higher performance at the shorter object distance.

It is explained from the above information that embodiment 2 of the macro lens has the characteristics of miniaturization of the lens, small distortion of the lens, and taking of a clear image.

Example 3:

reference is now made to fig. 5, which is a block diagram illustrating a macro optical lens according to embodiment 3 of the present application.

As shown in fig. 5, the macro optical lens according to the exemplary embodiment of the present application, in order from an object side to an image side along an optical axis, includes: the lens includes a first lens having a positive refractive power, a diaphragm, a second lens having a negative refractive power, a third lens having a positive refractive power, an optical filter, and a cover glass. The filter has an object side and an image side. The protective glass is used for protecting the photosensitive element. The incident light passes through each lens surface in sequence and is finally imaged on an imaging surface.

Table three (a) shows the surface type, radius of curvature, thickness, and material of each lens of the optical lens of example 3. Wherein the unit of the radius of curvature and the thickness are both millimeters (mm).

watch III (a)

Watch III (b)

Surface number

1

2

3

4

5

6

k

-2.05E+00

-9.86E+01

-1.22E+00

-2.12E+01

-8.17E+00

-7.16E-01

A₄

4.11E-01

5.65E-01

-1.69E+00

-4.95E+00

-5.70E-01

-1.16E+00

A₆

1.55E+00

-2.96E+01

-4.71E+01

2.85E+01

-1.42E+00

3.19E-01

A₈

-4.99E+01

1.27E+03

2.54E+03

-1.02E+02

5.61E+00

2.80E+00

A₁₀

8.07E+02

-3.42E+04

-7.20E+04

-6.94E+02

-4.37E+00

-8.49E+00

A₁₂

-7.86E+03

5.50E+05

1.21E+06

1.23E+04

-6.10E+00

1.31E+01

A₁₄

4.61E+04

-5.41E+06

-1.24E+07

-7.61E+04

1.49E+01

-1.20E+01

A₁₆

-1.60E+05

3.17E+07

7.57E+07

2.51E+05

-1.25E+01

6.49E+00

A₁₈

3.01E+05

-1.02E+08

-2.53E+08

-4.28E+05

4.90E+00

-1.92E+00

A₂₀

-2.36E+05

1.38E+08

3.53E+08

2.92E+05

-7.59E-01

2.37E-01

watch III (c)

From table three (a), table three (b) and fig. 5, the lens shape and each attribute of the lens in embodiment 3 are clearly shown, which indicates that embodiment 3 is a macro optical lens capable of realizing miniaturization.

As clearly shown from the data in table three (c) and the description of the astigmatism curves in fig. 6A, after the lens meets the above requirements, the maximum difference between the astigmatism S line and the astigmatism T line of the lens is about 0.03mm, which indicates that the lens has a good ability to improve astigmatism.

It is clearly shown from the data in table three (c) and the distortion curve in fig. 6B that the maximum distortion value of the lens is less than 1% after the lens meets the above requirements, which indicates that the lens has a good capability of improving distortion.

As shown more clearly in table three (C) and the modulation transfer function curve in fig. 6C, the Modulation Transfer Function (MTF) of the test frequency (110lp/mm) is greater than 0.5 at 5cm object distance, which indicates that the lens still has higher performance at shorter object distance.

It is explained from the above information that embodiment 3 of the macro lens has the characteristics of miniaturization of the lens, small distortion of the lens, and taking of a clear image.

Example 4:

reference is now made to fig. 7, which is a block diagram illustrating a macro optical lens according to embodiment 4 of the present application.

As shown in fig. 7, a macro optical lens according to an exemplary embodiment of the present application, in order from an object side to an image side along an optical axis, includes: the lens includes a first lens having a positive refractive power, a diaphragm, a second lens having a negative refractive power, a third lens having a positive refractive power, an optical filter, and a cover glass. The filter has an object side and an image side. The protective glass is used for protecting the photosensitive element. The incident light passes through each lens surface in sequence and is finally imaged on an imaging surface.

Table four (a) shows the surface type, radius of curvature, thickness, and material of each lens of the optical lens of example 4. Wherein the unit of the radius of curvature and the thickness are both millimeters (mm).

watch four (a)

Watch four (b)

Surface number

1

2

3

4

5

6

k

-1.99E+00

-9.86E+01

-1.10E+00

-2.07E+01

-8.24E+00

-7.20E-01

A₄

4.66E-01

6.38E-01

-1.87E+00

-5.11E+00

-5.26E-01

-1.20E+00

A₆

-1.25E+00

-3.48E+01

-3.41E+01

3.29E+01

-1.60E+00

6.84E-01

A₈

1.59E+01

1.52E+03

1.99E+03

-1.80E+02

5.96E+00

1.17E+00

A₁₀

-1.24E+02

-4.12E+04

-5.72E+04

1.40E+02

-5.26E+00

-4.40E+00

A₁₂

4.88E+02

6.72E+05

9.52E+05

6.74E+03

-3.97E+00

6.76E+00

A₁₄

-1.51E+03

-6.68E+06

-9.62E+06

-5.35E+04

1.20E+01

-5.95E+00

A₁₆

7.12E+03

3.97E+07

5.80E+07

1.95E+05

-1.03E+01

3.06E+00

A₁₈

-2.87E+04

-1.29E+08

-1.90E+08

-3.53E+05

4.11E+00

-8.50E-01

A₂₀

4.26E+04

1.77E+08

2.58E+08

2.49E+05

-6.41E-01

9.90E-02

watch four (c)

According to table four (a), table four (b) and fig. 7, the lens shape and each attribute of the lens in embodiment 4 are clearly shown, which indicates that embodiment 4 is a macro optical lens capable of realizing miniaturization.

As shown clearly from the data in table four (c) and the description of the astigmatism curves in fig. 8A, the maximum difference between the astigmatism S line and the astigmatism T line of the lens is about 0.03mm after the lens meets the above requirements, which indicates that the lens has good astigmatism improving capability.

It is clearly shown from the data in table four (c) and the distortion curve in fig. 8B that the maximum distortion value of the lens is less than 1% after the lens meets the above requirements, which indicates that the lens has a good capability of improving distortion.

As shown clearly from the data in table four (C) and the modulation transfer function curve in fig. 8C, the Modulation Transfer Function (MTF) at the test frequency (110lp/mm) is greater than 0.5 at the object distance of 5cm, which indicates that the lens still has higher performance at a shorter object distance.

It is explained from the above information that embodiment 4 of the macro lens has the characteristics of miniaturization of the lens, small distortion of the lens, and taking of a clear image.

Although embodiments of the present invention have been shown and described above, it should be understood that the above embodiments are illustrative and not restrictive, and that those skilled in the art may make changes, modifications, substitutions and alterations to the above embodiments without departing from the scope of the present invention.

Claims

1. A macro optical lens is characterized by comprising a first lens, a second lens and a third lens which are sequentially arranged from an object side to an image plane along an optical axis;

the first lens has positive refractive power, the object side surface is a convex surface, and the image side surface is a concave surface; the second lens has negative refractive power, and the object side surface of the second lens is a concave surface; the third lens element with positive refractive power has a convex object-side surface, and the image-side surface of the third lens element at least comprises an inflection point;

the diaphragm is placed on the object side or between the first lens and the second lens;

the macro optical lens satisfies the following conditional expression:

TTL/IH<1.45

wherein, TTL is the optical total length of the optical lens; IH is the half image height of the lens group;

tan(HFOV)≥1

the HFOV is a half of the maximum field angle of the optical lens.

2. The macro optical lens according to claim 1, wherein the first lens satisfies the following relation:

0.4<R1/F<0.5

0.45<|F1/F2|<1

wherein, R1 is the curvature radius of the object side surface of the first lens, and F is the focal length of the optical lens; f1 is the focal length of the first lens, and F2 is the focal length of the second lens.

3. A macro optical lens according to claim 1, characterized in that the optical lens satisfies the following relation:

0<|R2/R3|<4

wherein R2 is a radius of curvature of an image-side surface of the first lens element, and R3 is a radius of curvature of an object-side surface of the second lens element.

4. A macro optical lens according to claim 1, characterized in that the optical lens satisfies the following relation:

0.75<CT2/CT1<0.85

0.35<CT2/CT3<0.75

wherein CT1 is the central thickness of the first lens element, CT2 is the central thickness of the second lens element, and CT3 is the central thickness of the third lens element.

5. A macro optical lens according to claim 1, characterized in that the optical lens satisfies the following relation:

0.45<(T12+T23)/ΣCT<0.55

wherein T12 is an axial distance between the image-side surface of the first lens element and the object-side surface of the second lens element, T23 is an axial distance between the image-side surface of the second lens element and the object-side surface of the third lens element, Σ CT is a total axial thickness of all lens elements in the optical lens assembly.

6. A macro optical lens according to claim 1, characterized in that the optical lens satisfies the following relation:

0.8<DT2/DT3<1.1

DT2 is the maximum effective radius of the image side surface of the first lens, and DT3 is the maximum effective radius of the object side surface of the second lens.

7. A macro optical lens according to claim 1, characterized in that the optical lens satisfies the following relation:

0.8<SL/TTL<1

wherein, SL is the distance between the diaphragm and the imaging surface of the optical lens on the optical axis, and TTL is the total optical length of the optical lens.

8. A macro optical lens according to claim 1, characterized in that the optical lens satisfies the following relation:

F/EPD≤2.5

wherein, F is the focal length of the optical lens, and EPD is the entrance pupil diameter of the optical lens.

9. The macro optical lens according to claim 1, wherein the optical lens further comprises a filter for correcting color deviation, and a protective glass for protecting a photosensitive element located on an image plane; the optical filter is placed behind the third lens, and the protective glass is placed behind the optical filter.

10. The macro optical lens according to claim 1, wherein the surfaces of the first lens, the second lens and the third lens are aspheric, and the aspheric coefficients satisfy the following equation: