CN100541258C - Imaging optics - Google Patents

Abstract

The invention discloses an optical lens group for imaging, which consists of two plastic lenses with refractive power, and comprises an object side and an image side, wherein a first lens with positive refractive power is firstly configured, the front surface and the rear surface of the first lens are both convex surfaces, the refractive index N1 of the first lens meets the relation of 1.6 & gt N1 & gt 1.5, the focal length of the first lens is f1, the focal length of the system is f, the front surface and the rear surface of the first lens meet the relation of f/f1 & gt 2.0, the front surface and the rear surface of the first lens are both aspheric surfaces, a second lens with negative refractive power is arranged behind the first lens, the front surface of the second lens is a concave surface, the rear surface of the second lens is a convex surface, the refractive index N2 & gt 1.55 of the second lens is an aspheric surface, and a diaphragm is arranged in front of the first lens and used for controlling the brightness of the; by means of the lens structure, arrangement and lens configuration, the size of the lens group can be effectively reduced, and higher resolution can be obtained at the same time.

Description

Imaging optics

technical field

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

Background technique

In recent years, with the rise of camera phones, the thickness of photographic lenses has gradually shrunk, and the photosensitive components of general digital cameras are nothing more than CMOS or CCD. Due to the advancement of semiconductor process technology, the pixel size of photosensitive components has changed from the early 7.4um has been reduced to the current 1.75um, which makes the demand for miniaturized photographic lenses more ardent.

The current mobile phone lens, in order to consider the correction of aberration, mostly adopts three lens structures, the most common of which is the positive and negative triplet type. However, when the height of the lens is reduced from 5mm to 3mm, the volume of the imaging system is reduced, making the It becomes difficult to place the three lenses in this space, and the thickness of the lenses must also be reduced, so that the material uniformity of the lenses produced by plastic injection molding is poor.

In view of this, the present invention is proposed.

Contents of the invention

In order to solve the problem of miniaturization of the optical system, the present invention provides an optical mirror group composed of two lenses, the gist of which is as follows:

An optical lens group for imaging, consisting of two plastic lenses with refractive power, from the object side to the image side, firstly a first lens with positive refractive power, its front and rear surfaces are convex, and its front surface , the rear surface are all aspherical, and the 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 aspheric. An aperture is arranged in the optical lens group for imaging, which is located in front of the first lens, and is used to control the brightness of the optical system, and can effectively reduce the incident angle of light on the photosensitive component.

In the optical lens group for imaging, the first lens with positive refractive power has a refractive index of N1, and the second lens with negative refractive power has a refractive index of N2, and the two satisfy the following relationship:

1.6>N1>1.5

N2>1.55

Then the optical lens group for imaging can obtain effective refractive power. Further, the refractive index N1 of the first lens and the refractive index N2 of the second lens need to satisfy the following relationship:

N1>1.54

N2<1.65

In the optical lens group for imaging, the refractive power of the system is mainly provided by the first lens, and the function of the second lens with negative refractive power is to balance and correct various aberrations generated by the system, but if its refractive index exceeds this The upper limit value will increase the height of the system. Therefore, through the proper configuration of the refractive index of the above-mentioned lenses, the imaging optical lens group will achieve a balance in the correction of refractive power and aberration.

In the optical lens group for imaging, the focal length of the first lens with positive refractive power is f1, the focal length of the second lens with negative refractive power is f2, and the focal length of the system is f, which satisfy the following relationship:

f/f1>2.0

|f/f2|<1.0

Increasing the refractive power of the positive first lens can shorten the height of the optical lens group, and can effectively reduce the incident angle of light on the photosensitive component, while the second lens with negative refractive power comes from the front surface, and its The function is to correct the aberration produced by the system, but if the refractive power is too large, the incident angle of the light on the photosensitive element will not be easily compressed. At the same time, the aspheric surface on the rear surface will be too strong, making it difficult to manufacture. Considering the suppression of high-order aberrations and the optical lens group for imaging to produce sufficient back focus, the focal length f1 of the first lens and the focal length f of the system must satisfy the following relationship:

f/f1<2.5

In order to effectively correct the chromatic aberration generated by the system, to control the Abbe Number V1 of the first lens and the Abbe Number V2 of the second lens, the following relationship must be satisfied:

V1>50

V2<40

In order to effectively reduce the angle of light incident on the photosensitive component, the curvature radius R1 of the front surface of the first lens and the curvature radius R2 of the rear surface of the first lens must satisfy the following relationship:

1.4<(R1+R2)/(R1-R2)<1.55

With the configuration of the front aperture and the strong positive refractive power provided by the rear surface of the first lens, the exit pupil (Exit Pupil) of the imaging optical lens group will be far away from the imaging surface. Therefore, after the light leaves the rear surface of the second lens, It will be incident on the photosensitive component in a manner close to vertical incidence, which is the Telecentric characteristic of the image side. This feature is extremely important for the photosensitive ability of the current solid-state photosensitive component, which will increase the photosensitive sensitivity of the photosensitive component and reduce system generation. Possibility of dark corners. The above relationship is called the shape factor of the lens. When its value is lower than the lower limit, R2 becomes relatively small, which will cause excessive aberration in the system and is difficult to control. On the other hand, when its value is higher than the upper limit When the value of R2 becomes relatively large, the refractive power of the rear surface of the first lens becomes smaller, so that the aperture must be moved forward to reduce the angle of light incident on the photosensitive component, and this will be consistent with the miniaturization of the optical lens group for imaging Goals contradicted.

In addition, the trend of miniaturization of optical lens groups for imaging and the need for the system to cover a wide range of viewing angles make the focal length very short. In this case, the radius of curvature of the lens and the size of the lens become very small. The method of grinding will be difficult to manufacture the above-mentioned lenses. Therefore, both the first lens and the second lens are made of plastic materials, and the lenses are made by injection molding, which can produce high-precision lenses at a relatively low cost; and in each An aspherical surface is set on the mirror surface, and the aspheric surface can be easily made into a shape other than a spherical surface, and more control variables are obtained to reduce aberrations, thereby reducing the number of lenses used.

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings.

Description of drawings

Fig. 1 schematic diagram of the optical system of the first embodiment;

The aberration curve diagram of the first embodiment of Fig. 2;

The schematic diagram of the optical system of the second embodiment of Fig. 3;

The aberration curve diagram of the second embodiment of Fig. 4;

【surface】

Table 1 first embodiment structural data;

Table 2 first embodiment aspherical data;

Table 3 second embodiment structural data;

Table 4 second embodiment aspherical data;

The numerical data of table 5 correlation equation of the present invention;

[Description of main component symbols]

Aperture 10, first lens 20, front surface 21, rear surface 22, second lens 30, front surface 31, rear surface 32, infrared filter filter 40, photosensitive component 50, first lens refractive index N1, second The refractive index of the lens N2, the focal length of the first lens f1, the focal length of the second lens f2, the focal length of the imaging optical lens system f, the dispersion coefficient of the first lens V1 (Abbe number), the dispersion coefficient of the second lens V2 (Abbe number), the first Radius of curvature R1 of the front surface of the lens, radius of curvature R2 of the rear surface of the first lens

Detailed ways

Please refer to FIG. 1 for the first embodiment of the present invention, and please refer to FIG. 2 for the aberration curve of the first embodiment. The main structure of the first embodiment is: an optical lens group for imaging, which is composed of two plastic lenses with refractive power, and a first lens 20 with positive refractive power is sequentially arranged from the object side to the image side, and its front surface 21 and rear surface 22 are all convex, and its front surface 20, rear surface 21 are all aspherical, a second lens 31 with negative refractive power, its front surface 31 is concave, rear surface 32 is convex, and its front Both the surface 20 and the rear surface 21 are aspherical, and an IR cut filter (IR Cut Filter) 40 is arranged between the second lens 30 and the photosensitive element 50, which does not affect the focal length of the system. An aperture 10 is arranged in the optical lens group for imaging, which is located in front of the first lens 20, and is used to control the brightness of the optical system;

In the optical lens group for imaging, the first lens 20 with positive refractive power has a refractive index N1=1.543, and the second lens 30 with negative refractive power has a refractive index N2=1.583;

The focal length of the first lens 20 with positive refractive power is f1, the focal length of the second lens 30 with negative refractive power is f2, and the focal length of the system is f. The relationship is: f/f1=2.21, |f/f2|=0.81 ;

The dispersion coefficient (Abbe Number) V1=60.3 of the first lens 20, the dispersion coefficient (Abbe Number) V2=30.2 of the second lens 30;

The radius of curvature R1 of the front surface 21 of the first lens 20 and the radius of curvature R2 of the rear surface 22 of the first lens 20 are related by:

(R1+R2)/(R1-R2)=1.451;

The radius of curvature R1 of the front surface 21 of the first lens 20 = 2.18647 mm;

Both the first lens 20 and the second lens 30 are made of plastic material, and the lenses are made by injection molding, and an aspheric surface is arranged on each mirror surface. The equation of the aspheric surface 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 , ...: 4th order, 6th order, ... aspheric coefficients.

The detailed structural data of the first embodiment are shown in Table 1, and the aspheric data are shown in Table 2.

Please refer to FIG. 3 for the second embodiment of the present invention, and please refer to FIG. 4 for the aberration curve of the second embodiment. The main structure of the second embodiment is: an optical lens group for imaging, which is composed of two plastic lenses with refractive power, and a first lens 20 with positive refractive power is sequentially arranged from the object side to the image side, and its front surface 21 and rear surface 22 are all convex, and its front surface 20, rear surface 21 are all aspherical, a second lens 30 with negative refractive power, its front surface 31 is concave, rear surface 32 is convex, and its front Both the surface 20 and the rear surface 21 are aspherical, and an IR cut filter (IR Cut Filter) 40 is arranged between the second lens 30 and the photosensitive element 50, which does not affect the focal length of the system. An aperture 10 is arranged in the optical lens group for imaging, which is located in front of the first lens 20, and is used to control the brightness of the optical system;

In the optical lens group for imaging, the first lens 20 with positive refractive power has a refractive index N1=1.543, and the second lens 30 with negative refractive power has a refractive index N2=1.583;

The focal length of the first lens 20 with positive refractive power is f1, the focal length of the second lens 30 with negative refractive power is f2, and the focal length of the system is f. The relationship is: f/f1=2.34, |f/f2|=0.95 ;

The dispersion coefficient (Abbe Number) V1=60.3 of the first lens 20, the dispersion coefficient (Abbe Number) V2=30.2 of the second lens 30;

The radius of curvature R1 of the front surface 21 of the first lens 20 and the radius of curvature R2 of the rear surface 22 of the first lens 20 are related by:

(R1+R2)/(R1-R2)=1.466;

The radius of curvature R1 of the front surface 21 of the first lens 20 = 1.78647mm;

Both the first lens 20 and the second lens 30 are made of plastic material, and the lens is made by injection molding, and an aspheric surface is arranged on each mirror surface, and the expression of the aspheric surface curve equation is the same as that of the first embodiment;

The detailed structure data of the second embodiment is shown in Table 3, and the aspheric surface data is shown in Table 4.

It is stated in advance that Tables 1 to 4 show the different numerical changes of the embodiments of the optical lens group for imaging. However, the numerical changes of the various embodiments of the present invention are all experimental results. Even if different numerical values are used, the products of the same structure are still the same. Should belong to the protection category 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 optical lens group for imaging of the present invention can effectively reduce the volume of the lens group through the lens structure, arrangement and lens configuration, and can obtain higher resolution at the same time.

Table 1

table 3

table 5

Claims (2)

1. imaging optical frames group, it is characterized in that: this imaging constitutes with the glass lens of optical frames group by two tool refracting powers, by the thing side to the picture side, be in regular turn:

First lens of the positive refracting power of tool, its front surface, rear surface are all convex surface, its refractive index N1 satisfies the relation of 1.6＞N1＞1.5, its focal length is f1, and system's focal length is f, and both satisfy the relation of 2.5＞f/f1＞2.0, and its front surface, rear surface are aspheric surface, in addition, the radius-of-curvature on the forward and backward surface of these first lens is respectively R1 and R2, and both satisfy 1.4＜(R1+R2)/(R1-R2)＜1.55 relation;

Second lens of the negative refracting power of tool, its front surface is a concave surface, the rear surface is a convex surface, its refractive index N2＞1.55, its focal length is f2, and system's focal length is f, and both satisfy | the relation of f/f2|＜1.0, and its front surface, rear surface all are aspheric surface;

Before image optics is first lens, be provided with an aperture, be used to control the brightness of optical system.

2. imaging optical frames group according to claim 1 is characterized in that: the front surface radius of curvature R 1＜4.0mm of first lens.

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