CN100547446C - Photography Optical System - Google Patents

Abstract

A photographic optical system comprises three lens elements with refractive power, in order 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 photographic optical system is arranged between the first lens and the second lens; in the photographing optical system, the focal length of the first lens is f1, the focal length of the second lens is f2, and the focal length of the entire photographing optical system is f, which satisfies the following relation: f/f1 is greater than 0.95, f/f2 is greater than 0.34, so that the lens structure and arrangement can effectively reduce the volume of the lens group, reduce the sensitivity of the optical system and obtain higher resolution at the same time.

Description

Photography Optical System

technical field

The invention relates to an optical system, in particular to a miniaturized photographic optical system 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 nothing more than CMOS or CCD. Due to the advancement of semiconductor process technology, the pixel area of photosensitive components Shrinking, miniaturized photographic lenses are gradually developing towards the field of high-resolution images, so the requirements for image quality are also increasing.

Common mobile phone lenses usually use a three-element lens structure. From the object side to the image side, they are a first lens with positive refractive power, a second lens with negative refractive power, and a third lens with positive refractive power. Three lenses, constitute the so-called Triplet type. In order to correct aberrations, the form of a front aperture is generally used, but the configuration of the front aperture will increase the stray light, and the sensitivity of the optical system is also greater.

Contents of the invention

In order to obtain good image quality and effectively reduce the sensitivity of the optical system, the present invention provides a brand-new optical system composed of three lenses, the gist of which is as follows:

A photographic optical system, 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, 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 photographic optical system is arranged between the first lens and the second lens for controlling the brightness of the optical system;

In the photographic optical system of the present invention, the refractive power of the system is mainly provided by the first lens with positive refractive power, the function of the second lens with negative refractive power is mainly to correct chromatic aberration, and the third lens functions as a correction lens, and its function is Balance and correct various aberrations generated by the system.

In the photographic optical system 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. With the above configuration, the imaging quality can be effectively improved.

With the strong positive refractive power provided by the first lens, and placing the aperture close to the object side of the optical system, the exit pupil (Exit Pupil) of the photographic optical system will be far away from the imaging surface. Incident on the photosensitive component, this is the Telecentric characteristic of the image side. This characteristic is extremely important for the light-sensing ability of the current solid-state photosensitive component. It will increase the sensitivity of the photosensitive component and reduce the possibility of vignetting in the optical system. The third lens is provided with an inflection point, which will more effectively suppress the angle at which light from the off-axis field of view is incident on the photosensitive component. In addition, in the wide-angle optical system, it is particularly necessary to correct the distortion (Distortion) and the chromatic aberration of magnification (Chromatic Aberration of Magnification). The method is to place the aperture at the balance of the optical refractive power of the system. The system places the aperture between the first lens and the second lens, the purpose of which is to achieve a balance between the characteristics of Telecentric and wide field of view. Furthermore, the aforesaid position of the aperture will effectively reduce the bending angle of the light on each lens, thus reducing the sensitivity of the optical system.

With the trend of miniaturization of camera phone lenses and the need for the system to cover a wide range of viewing angles, the focal length of the optical system becomes very short. In this case, the radius of curvature of the lens and the size of the lens become very small, traditionally The method of glass grinding will be difficult to manufacture the above-mentioned lenses. Therefore, using plastic material on the lens and making the lens by injection molding can produce high-precision lenses at a relatively low cost; and set an aspheric surface on the mirror surface , the aspherical surface can be easily made into a shape other than a 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 optical system can be effectively reduced.

In the photographic optical system of the present invention, the dispersion coefficient (Abbe number) of the second lens is V2, and it satisfies the following relationship:

V2<40

V2 satisfying this relationship can effectively correct the chromatic aberration generated by the system and improve the resolution of the photographic optical system.

Further, it is ideal to make the Abbe number V2 of the second lens satisfy the following relationship:

V2<28

Furthermore, it is more ideal to make the Abbe number V2 of the second lens satisfy the following relationship:

V2<25.

In the photographic optical system 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, which satisfy the following relationship:

V1>50

V3>50;

V1 and V3 satisfying this relationship can effectively correct the chromatic aberration generated by the system. Further, it is ideal to make the Abbe number V1 of the first lens satisfy the following relationship:

V1>58.

In the photographic optical system of the present invention, the refractive index of the second lens is N2, which satisfies the following relationship:

N2<1.65

If the refractive index of the second lens is higher than the above upper limit, it is not easy to find a suitable optical plastic material to match the optical system.

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

f/f1>0.95.

The above relationship can provide sufficient refractive power of the optical system, and can shorten the total length of the optical system. Furthermore, it is more ideal to make f/f1 satisfy the following relationship:

f/f1>1.2

Furthermore, it is more ideal to make f/f1 satisfy the following relationship:

f/f1>1.25.

In the photographic optical system of the present invention, the focal length of the second lens is f2, and the focal length of the overall photographic optical system is f, both of which satisfy the following relationship:

|f/f2|＞0.34

|f/f2|<0.9;

If |f/f2| is smaller than the above lower limit, the chromatic aberration of the photographic optical system will be difficult to correct, and if |f/f2| The goal of miniaturization of the photographic optical system is contrary.

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

f/f3＜0.25

The third lens acts as a correction lens, and its function is to balance and correct various aberrations generated by the system. If f/f3 is greater than the above upper limit, the back focal length (Back Focal Length) of the photographic optical system will be too short.

In the photographic optical system 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<R1/R2<0.5

When R1/R2 is lower than the above-mentioned lower limit, the astigmatism (Astigmatism) produced by the photographic optical system will be difficult to correct. On the other hand, when R1/R2 is higher than the above-mentioned upper limit, the spherical aberration in the photographic optical system will (Sphericalaberration) correction is more difficult. It is ideal if R1/R2 satisfies the following relationship:

0.1<R1/R2<0.2.

In the photographic optical system 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 relationship:

ANG32＜-30[deg]

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

In the photographic optical system of the present invention, the mirror height at the effective diameter position of the rear surface of the third lens is SAG32, which satisfies the following relationship:

SAG32＜-0.2[mm]

The direction of the mirror height is defined as: "When the peripheral effective diameter height faces the image side, it is defined as positive; when the effective diameter height faces the object side, it is defined as negative." When the height of the mirror surface satisfies the above relationship, it can effectively reduce the angle at which light enters the photosensitive component and enhance the ability of the system to correct off-axis aberrations.

In the photographic optical system 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 distance between the effective diameter positions of the front surface and the rear surface of the lens projected on the optical axis". If the peripheral thickness satisfies the above relationship, the height of the overall optical system can be reduced, and the image quality can be effectively improved.

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

T23＞0.2[mm]

The aforementioned relationship can effectively correct the off-axis aberration of the optical system. Furthermore, it is more ideal to make T23 satisfy the following relationship:

T23＞0.38[mm]

In the photographic optical system of the present invention, an inflection point is provided on the rear surface of the first lens, so that the image quality can be effectively improved.

In the photographic optical system of the present invention, the subject of the photographic optical system is imaged on the electronic photosensitive component, and the total length of the photographic optical system is TL, and the imaging height of the photographic optical system is ImgH, satisfying the following relationship:

TL/ImgH<2.05

The above relationship can maintain the characteristics of miniaturization of the photographic optical system.

The beneficial effects of the present invention are: the present invention is a photographic optical system, whereby the lens structure and arrangement can effectively reduce the volume of the lens group, reduce the sensitivity of the optical system, and obtain higher resolution at the same time.

Description of drawings

Figure 1 is a schematic diagram of the optical system of Embodiment 1.

Fig. 2 is an aberration curve diagram of Embodiment 1.

Fig. 3 is a schematic diagram of the optical system of Embodiment 2.

Fig. 4 is the aberration curve diagram of the second embodiment.

First lens 10, front surface 11, rear surface 12, second lens 20, front surface 21, rear surface 22, third lens 30, front surface 31, rear surface 32, aperture 40 of photographic optical system, infrared ray filter Light sheet (IR Filter) 50, photosensitive component protection glass (Sensor Cover Glass) 60, imaging surface 70.

Abbe number V1 of the first lens

Abbe number V2 of the second lens

Abbe number V3 of the third lens

Refractive index N2 of the second lens

The focal length of the first lens f1

The focal length of the second lens f2

The focal length of the third lens is f3

Overall photographic optical system focal length f

The radius of curvature R1 of the front surface of the first lens

The radius of curvature R2 of the rear surface of the first lens

The mirror angle ANG32 of the effective diameter position of the rear surface of the third lens

The height of the effective diameter position of the rear surface of the third lens SAG32

Mirror pitch T23 between the second lens and the third lens

Central thickness CT2 of the second lens

Peripheral thickness ET1 of the first lens

Total length TL of photographic optical system

The imaging height of the photographic optical system ImgH

Detailed ways

Example 1

Please refer to FIG. 1 for Embodiment 1 of the present invention, and please refer to FIG. 2 for the aberration curve of Embodiment 1. The main structure of the photographic optical system in Example 1 is composed of three lenses with refractive power, and the order from the object side to the image side is as follows:

A first lens 10 with positive refractive power has a convex front surface 11 and a concave rear surface 12 made of plastic. curved point;

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;

Furthermore, it is a third lens 30 with positive refractive power, its front surface 31 is convex, its rear surface 32 is concave, its material is plastic, its front surface 31, rear surface 32 are all aspherical, and the third lens 30 Set with inflection point;

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

It also includes an infrared filter filter 50 (IR Filter), placed behind the third lens 30, which 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 described aspheric curve is 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 , ...: 4th order, 6th order, ... aspheric coefficients.

In the photographic optical system of embodiment 1, 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=55.8.

In the imaging optical system of Example 1, the refractive index of the second lens is N2, and its relationship is: N2=1.606.

In the photographic optical system of embodiment 1, 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 photographic optical system is f, its relationship is: f/f1= 1.26, |f/f2|=0.36, f/f3=0.15.

In the imaging optical system of Embodiment 1, the radius of curvature of the front surface of the first lens is R1, and the radius of curvature of the rear surface of the first lens is R2, and the relationship is: R1/R2=0.13.

In the imaging optical system of Embodiment 1, the mirror angle at the effective diameter position of the rear surface of the third lens is ANG32, and the relationship is: ANG32=-34.1 [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, and when the peripheral effective radial angle is inclined to the object side, it is defined as negative."

In the imaging optical system of Example 1, the height of the effective diameter of the rear surface of the third lens is SAG32, and the relationship is: SAG32=-0.25 [mm].

The direction of the effective diameter height is defined as: "When the peripheral effective diameter height faces the image side, it is defined as positive; the effective diameter height faces the object side, then it is defined as negative."

In the photographic optical system of Embodiment 1, 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=0.400[ mm], CT2 = 0.400 [mm], T23 = 0.403 [mm].

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

In the photographic optical system of embodiment 1, the total length of the photographic optical system is TL, and the imaging height of the photographic optical system is ImgH, and the relationship is: TL/ImgH=1.94.

The detailed structural data of Example 1 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

Please refer to FIG. 3 for Example 2 of the present invention, and please refer to FIG. 4 for the aberration curve of Example 2. The main structure of the photographic optical system in Example 2 is composed of three lenses with refractive power, and the order from the object side to the image side is as follows:

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;

Furthermore, it is a third lens 30 with positive refractive power, its front surface 31 is convex, its rear surface 32 is concave, its material is plastic, its front surface 31, rear surface 32 are all aspherical, and the third lens 30 Set with inflection point;

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

It also includes an infrared filter filter 50 (IR Filter), placed behind the third lens 30, which 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 aspheric curve of embodiment 2 is the same as that of embodiment 1.

In the photographic optical system of embodiment 2, the Abbe Number of the first lens is V1, the Abbe Number of the second lens is V2, and the Abbe Number of the third lens is V3, and its relationship is: V1=60.3, V2=23.4 , V3=55.8.

In the photographic optical system of Embodiment 2, the refractive index of the second lens is N2, and its relationship is: N2=1.632.

In the photographic optical system of embodiment 2, 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 photographic optical system is f, and its relationship is: f/f1=1.22 , |f/f2|=0.44, f/f3=0.24.

In the photographing optical system of Embodiment 2, the radius of curvature of the front surface of the first lens is R1, and the radius of curvature of the rear surface of the first lens is R2, and the relationship is: R1/R2=0.27.

In the photographic optical system of Embodiment 2, the mirror angle at the effective diameter position of the rear surface of the third lens is ANG32, and its relationship is: ANG32=-39.6[deg.].

The definition of the direction of the mirror angle ANG32 is the same as that of the first embodiment.

In the photographic optical system of Embodiment 2, the height of the effective diameter of the rear surface of the third lens is SAG32, and the relationship is: SAG32=-0.14 [mm].

The direction definition of the effective diameter height SAG32 is the same as that of the first embodiment.

In the photographing optical system of embodiment 2, 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 relation is: ET1=0.359 [mm ], CT2 = 0.350 [mm], T23 = 0.070 [mm].

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

In the photographic optical system of embodiment 2, the total length of the photographic optical system is TL, and the imaging height of the photographic optical system is ImgH, and the relationship is: TL/ImgH=2.03.

The detailed structural data of Example 2 are shown in Table 3, and the aspheric surface data are shown in Table 4, where the units of radius of curvature, thickness and focal length are mm, and HFOV is defined as half of the maximum viewing angle. It is stated in advance here that Table 1 to Table 4 show the different numerical changes of the photographic optical system embodiments, but the numerical changes of the various embodiments of the present invention are all experimental results. 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.

To sum up, the present invention is a photographic optical system, whereby the lens structure and arrangement can effectively reduce the volume of the lens group, reduce the sensitivity of the optical system, and obtain higher resolution at the same time. Therefore, the present invention has not been seen in various publications before the filing date, nor has it been publicly used, so the present invention should be novel and inventive.

(Example 1)

f (focal length) = 4.05mm, Fno = 2.8, HFOV (half angle of view) = 33.0deg.

Table 1

Aspheric Coefficient aspheric coefficient

Table 2

(Example 2)

f (focal length) = 2.89mm, Fno = 2.8, HFOV (half angle of view) = 31.7deg.

table 3

Aspheric Coefficient aspheric coefficient

Table 4

table 5

Claims (1)

1. A photographic optical system consisting of three lenses with refractive power, the photographic optical system from the object side to the image side in order: a) a plastic first lens with positive refractive power, the front surface is convex, the rear surface is concave, and the front surface and the rear surface are provided with aspheric surfaces; b) a plastic second lens with negative refractive power, the front surface is concave, the rear surface is convex, and both the front surface and the rear surface are provided with aspheric surfaces; c) a plastic third lens with positive refractive power, the front surface is convex, the rear surface is concave, and both the front surface and the rear surface are provided with aspheric surfaces, and the third lens is provided with an inflection point; and d) An aperture is also provided between the first lens and the second lens for controlling the brightness of the optical system; In the photographic optical system, the focal length of the first lens is f1, the focal length of the second lens is f2, and the focal length of the overall photographic optical system is f, satisfying the following relationship: f/f1>0.95 |f/f2|＞0.34 In the photographic optical system, the dispersion coefficient of the second lens is V2, which satisfies the following relationship: V2<28 In the photographic optical system, the radius of curvature of the front surface of the first lens is R1, and the radius of curvature of the rear surface of the first lens is R2, both of which satisfy the following relationship: 0<R1/R2<0.5 It is characterized in that, the focal length of the third lens is f3, the focal length of the overall photographic optical system is f, and both satisfy the following relationship: f/f3<0.25.

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