CN101201444A - Imaging lens group - Google Patents

Abstract

The present invention relates to an imaging lens assembly, and more particularly, to a miniaturized imaging lens assembly for a camera phone. The imaging lens group consists of three lenses with refractive power, and sequentially comprises the following components from an object side to an image side: a first lens element with positive refractive power having a convex front surface and a concave rear surface, and an aspheric surface disposed on the front surface; a plastic second lens with negative refractive power, wherein the front surface of the plastic second lens is a concave surface, the rear surface of the plastic second lens is a convex surface, and the front surface and the rear surface of the plastic second lens are both provided with aspheric surfaces; a plastic third lens with positive refractive power, wherein the front surface of the plastic third lens is a convex surface, the rear surface of the plastic third lens is a concave surface, and the front surface and the rear surface of the plastic third lens are both provided with aspheric surfaces; wherein the diaphragm of the imaging lens group is arranged between the first lens and the second lens; in the imaging lens group, the focal length of the first lens is f1, the focal length of the whole imaging lens group is f, and the two satisfy the following relational expression: the lens structure and the arrangement mode of the invention can effectively reduce the volume of the lens group and reduce the sensitivity of the imaging lens group, and can obtain higher resolution at the same time when f/f1 is less than 0.9.

Description

Imaging lens group

technical field

The invention relates to an imaging lens group, in particular to a miniaturized imaging lens group applied to a camera phone.

Background technique

In recent years, with the rise of mobile phone cameras, the demand for miniaturized photographic lenses has increased day by day, and the photosensitive components of general photographic lenses are only CMOS or CCD. With the gradual development of high-resolution photographic lenses, the requirements for image quality are also increasing.

Common mobile phone lenses mostly adopt a three-element lens structure. The lens structure consists of a first lens with positive refractive power, a second lens with negative refractive power, and a positive refractive power lens from the object side to the image side. The third lens constitutes the so-called Triplet type. In order to correct aberrations, a pre-aperture is generally used, but the configuration of the pre-aperture will increase the stray light, and the sensitivity of the imaging lens group will also be greater.

Contents of the invention

In order to obtain good image quality and effectively reduce the sensitivity of the imaging lens group, the purpose of the present invention is to provide a brand-new imaging lens group composed of three lenses. In order to achieve the above purpose, the adopted technical solution is:

An imaging lens group is composed of three lenses with refractive power, from the object side to the image side in order:

A first lens with positive refractive power, the front surface is convex, the back surface is concave, and the front surface is provided with an aspheric surface;

A plastic second lens with negative refractive power, the front surface is concave and the rear surface is convex, and both the front surface and the rear surface are provided with aspheric surfaces;

A plastic third lens with positive refractive power, the front surface is convex and the rear surface is concave, and both the front surface and the rear surface are provided with aspheric surfaces;

Wherein, the aperture of the above-mentioned imaging lens group is arranged between the first lens and the second lens for controlling the brightness of the imaging lens group.

In the imaging lens group of the present invention, the first lens with positive refractive power has a convex front surface and a concave rear surface, and the second lens with negative refractive power has a concave front surface and a convex rear surface, and has The third lens with positive refractive power has a convex front surface and a concave rear surface. By adopting the configuration of the present invention, the aberration of the imaging lens group can be effectively corrected, thereby obtaining good imaging quality.

Adopting the first lens with positive refractive power according to the present invention, and placing the diaphragm near the object side of the imaging lens group will make the exit pupil (Exit Pupil) of the imaging lens group far away from the imaging surface, so the light will be close to the imaging surface. The vertical incidence is incident on the photosensitive component, that is, the Telecentric feature on the image side. This feature is extremely important for the light-sensing ability of today’s solid-state photosensitive components. It can improve the sensitivity of the photosensitive component and reduce the vignetting of the imaging lens group. possibility. However, setting an inflection point on the third lens will more effectively suppress the angle at which the off-axis field of view light is incident on the photosensitive component. In addition, in the wide-angle imaging lens group, it is particularly necessary to correct distortion (Distortion) and magnification chromatic aberration (Chromatic Aberration of Magnification). The method is to place the aperture at the balance of the system's optical refractive power, and the imaging of the present invention The aperture is placed between the first lens and the second lens in the lens group, the purpose of which is to balance the characteristics of Telecentric and wide viewing angle. In addition, the position of the aperture will effectively reduce the bending angle of the light on each lens, so the sensitivity of the imaging lens group can be reduced.

With the trend of lens miniaturization for digital portable devices and the need for the system to cover a wide range of viewing angles, the focal length of the imaging lens group becomes very short. In this case, the radius of curvature of the lens and the size of the lens become small , it will be difficult to manufacture the above-mentioned lenses with the traditional glass grinding method. Therefore, the lens is made of plastic material and injection molding can be used to produce high-precision lenses at a relatively low cost; and set on the mirror surface Aspherical surface, aspheric surface can be easily made into shapes other than spherical surface, and more control variables can be obtained to reduce aberrations, thereby reducing the number of lenses used, so the total length of the imaging lens group can be effectively reduced.

In the imaging lens group of the present invention, the dispersion coefficient (Abbe number) of the second lens is V2, and it satisfies following relation:

V2<40.

The above relationship can effectively correct the chromatic aberration generated by the system and improve the resolving power of the imaging lens group. Preferably, the dispersion coefficient (Abbe number) V2 of the second lens satisfies the following relationship:

V2<28.

In the imaging lens group of the present invention, the dispersion coefficient (Abbe number) of the first lens is V1, and the dispersion coefficient (Abbe number) of the third lens is V3, and the two satisfy the following relationship:

V1>50

V3>50;

The above relationship can effectively correct the chromatic aberration produced by the system. Preferably, the dispersion coefficient (Abbenumber) V1 of the first lens satisfies the following relationship:

V1>60.

In the imaging lens group of the present invention, the refractive index of the first lens is N1, and the refractive index of the second lens is N2, and both satisfy the following relationship:

N1<1.6

N2<1.65;

If the refractive indices of the first lens and the second lens are higher than the upper limit of the above relationship, it is not easy to find a suitable optical plastic material to match the imaging lens group.

In the imaging lens group of the present invention, the focal length of the first lens is f1, and the focal length of the overall imaging lens group is f, both of which satisfy the following relationship:

f/f1<0.9

Applying the above relationship can provide enough refractive power of the imaging lens group, and can effectively reduce the aberration produced by the imaging lens group. Preferably, f/f1 satisfies the following relationship:

f/f1＜0.85

More preferably, f/f1 satisfies the following relationship:

f/f1<0.7.

In the imaging lens group of the present invention, the focal length of the second lens is f2, and the focal length of the overall imaging lens group is f, and both satisfy the following relationship:

0.3<|f/f2|<0.9

If |f/f2| is less than the lower limit value of the above relational expression, the chromatic aberration of the imaging lens group will be difficult to correct; if |f/f2| is greater than the upper limit value of the above relational expression, the total length of the imaging lens group will be too long , which is contrary to the goal of miniaturization of the imaging lens group.

In the imaging lens group of the present invention, the focal length of the third lens is f3, and the focal length of the overall imaging lens group is f, both of which satisfy the following relationship:

f/f3>0.8

The third lens has a positive refractive power, and its function is to distribute the required refractive power of the imaging lens group. If f/f3 is less than the lower limit of the above relationship, the back focal length (Back Focal Length) of the imaging lens group will be too long.

In the imaging lens group of the present invention, the radius of curvature of the front surface of the first lens is R1, the radius of curvature of the rear surface of the first lens is R2, and both satisfy the following relationship:

0.1<R1/R2<0.8

On the one hand, when R1/R2 is lower than the lower limit value of the above relationship, the astigmatism (Astigmatism) produced by the imaging lens group will be difficult to correct; on the other hand, when R1/R2 is higher than the upper limit value of the above relationship, for the imaging lens The correction of spherical aberration (Spherical Aberration) in the group is more difficult. Preferably, R1/R2 satisfies the following relationship:

0.25<R1/R2<0.35.

In the imaging lens group of the present invention, the radius of curvature of the front surface of the second lens is R3, and the radius of curvature of the rear surface of the second lens is R4, both of which satisfy the following relationship:

0.45<R3/R4<0.6

On the one hand, when R3/R4 is lower than the lower limit of the above relationship, R3 becomes relatively small, which will make the total height of the imaging lens group too large; on the other hand, when R3/R4 is higher than the upper limit of the above relationship When , R3 becomes relatively large, and the chromatic aberration produced by the imaging lens group will be difficult to correct.

In the imaging lens group of the present invention, the radius of curvature of the front surface of the third lens is R5, and the radius of curvature of the rear surface of the third lens is R6, and both satisfy the following relationship:

0.45<R5/R6<0.6

The above relationship will be beneficial to correct the higher-order aberrations of the imaging lens group.

In the imaging lens group of the present invention, the radius of curvature of the front surface of the first lens is R1, which satisfies the following relationship:

R1＜2[mm]

The above relationship can enable the first lens to obtain sufficient refractive power, so that the total length of the imaging lens group can be shortened.

In the imaging lens group of the present invention, the mirror angle at the effective diameter position of the rear surface of the third lens is ANG32, which satisfies the following relational expression:

ANG32＜-10[deg]

The direction of the mirror angle is defined as "when the mirror angle at the peripheral effective diameter position is inclined to the image side, it is defined as positive, and when the mirror angle at the peripheral effective diameter position is inclined to the object side, it is defined as negative."

The above relationship can effectively reduce the angle at which light is incident on the photosensitive component, and enhance the ability of the imaging lens group to correct off-axis aberrations.

In the imaging lens group of the present invention, the central thickness of the second lens is CT2, and the peripheral thickness of the first lens is ET1, satisfying the following relationship:

CT2＜0.4[mm]

ET1<0.4[mm];

Peripheral thickness is defined as the length projected on the optical axis from the distance between the effective diameter positions of the front surface and the back surface of the lens. The above relationship can reduce the height of the overall imaging lens group, and can effectively improve the image quality. When considering the good uniformity of plastic injection molded lenses, the central thickness CT2 of the second lens must satisfy the following relationship:

CT2 > 0.25 [mm].

In the imaging lens group of the present invention, the mirror distance between the second lens and the third lens is T23, which satisfies the following relationship:

T23＜0.1[mm]

The aforementioned relationship can reduce the total length of the overall imaging lens group.

In the imaging lens group of the present invention, the subject of the imaging lens group is imaged on the electronic photosensitive component, and the total length of the imaging lens group is TL, and the imaging height of the imaging lens group is ImgH, which satisfies the following relationship:

TL/ImgH<2.5

The above relationship can maintain the characteristics of miniaturization of the imaging lens group.

An imaging lens group described in the present invention has the following advantages:

1. Applying the lens structure and arrangement of the imaging lens group of the product of the present invention can effectively reduce the volume of the lens group, reduce the sensitivity of the imaging lens group, and obtain higher resolution at the same time;

2. The product of the present invention has industrial applicability, not only improves the existing imaging lens group, but also has additional functions that the existing imaging lens group does not have.

Description of drawings

Fig. 1 is the schematic diagram of the imaging lens group of embodiment 1;

Fig. 2 is the aberration curve diagram of embodiment 1;

Fig. 3 is the schematic diagram of the imaging lens group of embodiment 2;

FIG. 4 is an aberration curve diagram of Example 2. FIG.

Detailed ways

Example 1

As shown in FIG. 1 , the aberration curve of this embodiment is shown in FIG. 2 . The imaging lens group is mainly composed of three lenses with refractive power, from the object side to the image side in order:

A first lens 10 with positive refractive power, the front surface 11 is convex, the rear surface 12 is concave, the material is plastic, and the front surface 11 and the rear surface 12 are aspherical;

A second lens 20 with negative refractive power, the front surface 21 is concave, the rear surface 22 is convex, the material is plastic, and the front surface 21 and the rear surface 22 are aspherical;

Also have a third lens 30 with positive refractive power, its front surface 31 is a convex surface, and its rear surface 32 is a concave surface. have an inflection point;

An aperture 40 of the imaging lens group, located between the first lens 10 and the second lens 20, is used to control the brightness of the imaging lens group;

Also includes an infrared filter filter 50 (IR Filter), placed behind the third lens 30, it does not affect the focal length of the system;

It also includes a photosensitive component protection glass 60 (Sensor Cover Glass), placed behind the infrared filter filter 50, which does not affect the focal length of the system;

An imaging surface 70 is placed behind the protective glass 60 of the photosensitive component.

The equation of the aforementioned aspheric curve is expressed as follows:

X(Y)＝(Y ² /R)/(1+sqrt(1-(1+k)*(Y/R) ² ))+A ₄ *Y ₄ +A ₆ *Y ⁶ +...

in:

X: the cross-sectional distance of the lens

Y: the height of the point on the aspheric curve from the optical axis

k: cone coefficient

A ₄ , A ₆ , . . . : aspheric coefficients of 4th order, 6th order, . . .

In the present embodiment imaging lens group, the dispersion coefficient (Abbe Number) of the first lens is V1, the dispersion coefficient of the second lens is V2, and the dispersion coefficient of the 3rd lens is V3, and its relation is: V1=60.3, V2=26.6 , V3=60.3.

In the imaging lens group of this embodiment, the refractive index of the first lens is N1, and the refractive index of the second lens is N2, and their relationship is: N1=1.543, N2=1.606.

In the imaging lens group of this embodiment, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, and the focal length of the overall imaging lens group is f, and its relationship is: f/f1=0.79 , |f/f2|=0.74, f/f3=1.07.

In the imaging lens group of this embodiment, the radius of curvature of the front surface of the first lens is R1, the radius of curvature of the rear surface of the first lens is R2, the radius of curvature of the front surface of the second lens is R3, and the radius of curvature of the rear surface of the second lens is R4, the radius of curvature of the front surface of the third lens is R5, the radius of curvature of the rear surface of the third lens is R6, and the relationship is: R1/R2=0.31, R3/R4=0.52, R5/R6=0.54.

In the imaging lens group of this embodiment, the radius of curvature of the front surface of the first lens is R1, and the relationship is: R1=1.50464 [mm].

In the imaging lens group of this embodiment, the mirror angle at the effective diameter position of the rear surface of the third lens is ANG32, and its relationship is: ANG32=-11.8 [deg.].

The direction of the mirror angle is defined as: when the peripheral effective radial angle is inclined to the image side, it is defined as positive; when the peripheral effective radial angle is inclined to the object side, it is defined as negative.

In the imaging lens group of the present embodiment, the peripheral thickness of the first lens is ET1, the central thickness of the second lens is CT2, and the mirror distance between the second lens and the third lens is T23, and its relationship is: ET1=0.387 [mm ], CT2 = 0.392 [mm], T23 = 0.096 [mm].

Peripheral thickness is defined as the length projected on the optical axis from the distance between the effective diameter positions of the front surface and the rear surface of the lens.

In the imaging lens group of this embodiment, the total length of the imaging lens group is TL, and the imaging height of the imaging lens group is ImgH, and the relationship is: TL/ImgH=2.37.

The detailed structural data of this embodiment are shown in Table 1, and the aspheric surface data are shown in Table 2, where the units of the radius of curvature, thickness and focal length are mm, and HFOV is defined as half of the maximum viewing angle.

Example 2

As shown in FIG. 3 , the aberration curve of this embodiment is shown in FIG. 4 . The imaging lens group is mainly composed of three lenses with refractive power, from the object side to the image side in order:

A first lens 10 with positive refractive power, the front surface 11 is convex, the rear surface 12 is concave, the material is plastic, and the front surface 11 and the rear surface 12 are aspherical;

A second lens 20 with negative refractive power, the front surface 21 is concave, the rear surface 22 is convex, the material is plastic, and the front surface 21 and the rear surface 22 are aspherical;

Also have a third lens 30 with positive refractive power, its front surface 31 is a convex surface, and its rear surface 32 is a concave surface. have an inflection point;

An aperture 40 of the imaging lens group, located between the first lens 10 and the second lens 20, is used to control the brightness of the imaging lens group;

Also includes an infrared filter filter 50 (IR Filter), placed behind the third lens 30, it does not affect the focal length of the system;

It also includes a photosensitive component protection glass 60 (Sensor Cover Glass), placed behind the infrared filter filter 50, which does not affect the focal length of the system;

An imaging surface 70 is placed behind the protective glass 60 of the photosensitive component.

The equation representation of the aspheric curve of this embodiment is the same as that of Embodiment 1.

In this imaging lens group, the dispersion coefficient (Abbe Number) of the first lens is V1, the dispersion coefficient of the second lens is V2, and the dispersion coefficient of the third lens is V3, and its relation is: V1=60.3, V2=30.2, V3 = 60.3.

In the imaging lens group, the refractive index of the first lens is N1, and the refractive index of the second lens is N2, and their relationship is: N1=1.543, N2=1.583.

In this imaging lens group, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, and the focal length of the overall imaging lens group is f, and its relationship is: f/f1=0.69, | f/f2|=0.71, f/f3=1.16.

In the imaging lens group, the radius of curvature of the front surface of the first lens is R1, the radius of curvature of the rear surface of the first lens is R2, the radius of curvature of the front surface of the second lens is R3, and the radius of curvature of the rear surface of the second lens is R4, The radius of curvature of the front surface of the third lens is R5, the radius of curvature of the rear surface of the third lens is R6, and the relationship is: R1/R2=0.29, R3/R4=0.51, R5/R6=0.53.

In the imaging lens group, the radius of curvature of the front surface of the first lens is R1, and the relationship is: R1=1.75452 [mm].

In the imaging lens group, the mirror angle at the effective diameter position of the rear surface of the third lens is ANG32, and its relationship is: ANG32=-11.7 [deg.].

The definition of the direction of the mirror angle ANG32 at the effective diameter position is the same as that of the first embodiment.

In this imaging lens group, the peripheral thickness of the first lens is ET1, the central thickness of the second lens is CT2, and the mirror spacing between the second lens and the third lens is T23, and its relation is: ET1=0.404[mm], CT2 = 0.395 [mm], T23 = 0.078 [mm].

The definition of the peripheral thickness is the same as that of Example 1.

In the imaging lens group, the total length of the imaging lens group is TL, and the imaging height of the imaging lens group is ImgH, and the relationship is: TL/ImgH=2.49.

The detailed structural data of this embodiment is shown in Table 3, and the aspheric surface data are shown in Table 4, where the units of the radius of curvature, thickness and focal length are mm, and HFOV is defined as half of the maximum viewing angle.

Tables 1 to 4 show different numerical changes of the imaging lens group embodiments. The numerical changes of the various embodiments of the present invention are obtained through experiments. Even if different numerical values are used, products with the same structure should still belong to the protection scope of the present invention. Table 5 is the numerical data corresponding to the relevant equations of the present invention for each embodiment.

Table 1

Table 2

table 3

Table 4

table 5

Claims (24)

1. imaging lens group is made of the lens of three pieces of tool refracting powers, it is characterized in that: described lens by the thing side to being followed successively by as side:

First lens of the positive refracting power of one tool, its front surface are that convex surface, rear surface are concave surface, and its front surface is provided with aspheric surface;

Plastics second lens of the negative refracting power of one tool, its front surface is that concave surface, rear surface are convex surface, and its front surface, rear surface are provided with aspheric surface;

Plastics the 3rd lens of the positive refracting power of one tool, its front surface are that convex surface, rear surface are concave surface, and its front surface, rear surface are provided with aspheric surface;

And also be provided with an aperture, and be arranged between described first lens and described second lens, be used to control the brightness of imaging lens group;

In the above-mentioned imaging lens group, the focal length of described first lens is f1, and the focal length of whole imaging lens group is f, satisfies following relational expression:

f/f1＜0.9。

2. imaging lens group according to claim 1 is characterized in that: the material of described first lens is plastics, and its rear surface is aspheric surface, also is provided with the point of inflexion on described the 3rd lens.

3. imaging lens group according to claim 2 is characterized in that: the abbe number of described second lens is V2, satisfies following relational expression:

V2＜40。

4. imaging lens group according to claim 3 is characterized in that: the abbe number of described second lens is V2, satisfies following relational expression:

V2＜28。

5. imaging lens group according to claim 2 is characterized in that: the refractive index of described first lens is N1, satisfies following relational expression:

N1＜1.6。

6. imaging lens group according to claim 5 is characterized in that: the refractive index of described second lens is N2, satisfies following relational expression:

N2＜1.65。

7. imaging lens group according to claim 3 is characterized in that: the front surface radius-of-curvature of described first lens is R1, and the rear surface radius-of-curvature of first lens is R2, and both satisfy following relational expression:

0.1＜R1/R2＜0.8。

8. imaging lens group according to claim 7 is characterized in that: the front surface radius-of-curvature of described first lens is R1, and the rear surface radius-of-curvature of first lens is R2, and both satisfy following relational expression:

0.25＜R1/R2＜0.35。

9. imaging lens group according to claim 3 is characterized in that: the front surface radius-of-curvature of described second lens is R3, and the rear surface radius-of-curvature of second lens is R4, and both satisfy following relational expression:

0.45＜R3/R4＜0.6。

10. imaging lens group according to claim 9 is characterized in that: the front surface radius-of-curvature of described the 3rd lens is R5, and the rear surface radius-of-curvature of the 3rd lens is R6, and both satisfy following relational expression:

0.45＜R5/R6＜0.6。

11. imaging lens group according to claim 3 is characterized in that: the mirror angle of the effective diameter position of described the 3rd lens rear surface is ANG32, satisfies following relational expression:

ANG32＜-10[deg.]。

12. according to right 3 described imaging lens group, it is characterized in that: the center thickness of described second lens is CT2, satisfies following relational expression:

CT2＜0.4[mm]。

13. imaging lens group according to claim 12 is characterized in that: the center thickness of described second lens is CT2, satisfies following relational expression:

CT2＞0.25[mm]。

14. imaging lens group according to claim 13 is characterized in that: the peripheral thickness of described first lens is ET1, satisfies following relational expression:

ET1＜0.4[mm]。

15. imaging lens group according to claim 14 is characterized in that: the mirror spacing between described second lens and described the 3rd lens is T23, satisfies following relational expression:

T23＜0.1[mm]。

16. imaging lens group according to claim 2 is characterized in that: the focal length of described first lens is f1, and the focal length of whole imaging lens group is f, and both satisfy following relational expression:

f/f1＜0.85。

17. imaging lens group according to claim 16 is characterized in that: the focal length of described first lens is f1, and the focal length of whole imaging lens group is f, and both satisfy following relational expression:

f/f1＜0.7。

18. imaging lens group according to claim 17 is characterized in that: the abbe number of described second lens is V2, satisfies following relational expression:

V2＜40。

19. according to right 3 described imaging lens group, it is characterized in that: the focal length of described second lens is f2, the focal length of whole imaging lens group is f, and both satisfy following relational expression:

0.3＜|f/f2|＜0.9。

20. imaging lens group according to claim 3 is characterized in that: the focal length of described the 3rd lens is f3, and whole imaging lens group focal length is f, and both satisfy following relational expression:

f/f3＞0.8。

21. imaging lens group according to claim 3 is characterized in that: the abbe number of described first lens is V1, and the abbe number of described the 3rd lens is V3, satisfies following relational expression:

V1＞50

V3＞50。

22. imaging lens group according to claim 21 is characterized in that: the abbe number of described first lens is V1, satisfies following relational expression:

V1＞60。

23. imaging lens group according to claim 7 is characterized in that: the front surface radius-of-curvature of described first lens is R1, satisfies following relational expression:

R1＜2.0[mm]。

24. imaging lens group according to claim 3 is characterized in that: the object of described imaging lens group images in the sense electronics optical assembly, and the length overall of imaging lens group is TL, and the imaging of imaging lens group highly is ImgH, and both satisfy following relational expression:

TL/ImgH＜2.5。

Images