CN103018885B - Imaging lens - Google Patents

Abstract

The present invention provides a kind of imaging lens, and it includes the most successively: first lens with positive light coke, second lens with negative power and an imaging surface；These first lens include a first surface and a second surface, and these second lens include one the 3rd surface and one the 4th surface；Described imaging lens meets following condition: FB/TTL > 0.23；G1R1/F1>1.93；X/Y>0.27；X/T<0.89；G2R1/F2<G2R2/F2<G1R2/F2；Wherein, FB is the 4th surface and imaging surface beeline along optical axis direction, TTL is the overall length of imaging lens, X is the curved surface transverse height on the 4th surface, and Y is the curved surface longitudinally height on the 4th surface, and T is second lens thickness on optical axis, G2R1 is the radius of curvature on the 3rd surface, G2R2 is the radius of curvature on the 4th surface, and G1R2 is the radius of curvature of second surface, and F2 is the focal length of the second lens.

Description

imaging lens

technical field

The invention relates to an imaging technology, in particular to an imaging lens.

Background technique

In order to increase the pixel size from VGA to 1.3M while keeping the product price competitive, the size of the CMOS image sensor must also be maintained. For example, the original image sensor size of VGA is 1/6", its resolution is 640x480, and the pixel size (Pixel Size) is 3.6μm. In order to maintain a close product price, 1.3M will use an image sensor with a size of 1/6.4", its resolution is 1280x960, and the pixel size will be reduced to 1.75μm. This is because the same wafer (Wafer) The number of dies that can be cut out remains close, so the cost of CMOS image sensors will not increase due to the increase in pixels.

However, under the premise that the pixel size is reduced to 1.75 μm, the imaging quality of the required lens design will need to be improved with the reduction of the pixel size in order to meet the needs of users; the items for improving the lens quality will include: 1) high resolution , 2) Low distortion, 3) Long back convex, the long back convex is to make the last lens of the designed lens away from the image sensor, so as to avoid the scratches and stains on the last lens from being imaged on the image sensor.

Contents of the invention

In view of this, it is necessary to provide an imaging lens with high resolution, low chromatic aberration and long back convexity.

An imaging lens, which comprises sequentially from the object side to the image side: a first lens with positive refractive power, a second lens with negative refractive power and an imaging surface; the first lens includes a first surface and A second surface, the second lens includes a third surface and a fourth surface; the imaging lens satisfies the following conditions: FB/TTL>0.23; G1R1/F1>1.93; X/Y>0.27; X/T< 0.89; G2R1/F2<G2R2/F2<G1R2/F2; where, FB is the shortest distance between the fourth surface and the imaging surface along the optical axis, TTL is the total length of the imaging lens, X is the lateral height of the fourth surface, Y is the longitudinal height of the curved surface of the fourth surface, T is the thickness of the second lens on the optical axis, G1R1 is the radius of curvature of the first surface, G2R1 is the radius of curvature of the third surface, G2R2 is the radius of curvature of the fourth surface, G1R2 is the radius of curvature of the second surface, F1 is the focal length of the first lens, and F2 is the focal length of the second lens. The surfaces of the first lens G1 and the second lens G2 are both aspherical, and satisfy the surface formula of aspheric surfaces:

$\mathrm{<span\; class="notranslate">\; Z</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; ch</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; c</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&Sigma;A</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}}$

Among them, X is the displacement value from the optical axis at a position of height h along the optical axis, and the surface vertex is used as a reference. A fixed number, A _i is the second aspheric coefficient of i.

In the imaging lens provided by the present invention, the conditional formula FB/TTL>0.23 ensures that the imaging lens has a long back convex; the conditional formula G1R1/F1>1.93 makes the first lens have a smaller optical power, thereby reducing the The off-center sensitivity of the imaging lens; the conditional formula X/Y>0.27 and G1R2/F1<G3R2/F3<0 ensures that the focal power distribution of the imaging lens is appropriate and has a good aberration correction effect; the conditional formula X/T< 0.89, to ensure that the second lens is easy to injection mold, so that the plastic injected from the single side gate can easily reach the opposite side. A lens system that satisfies the above conditions can also ensure better imaging quality in the case of a long back convexity and a wide viewing angle.

Description of drawings

FIG. 1 is a schematic structural diagram of an imaging lens provided by the present invention.

FIG. 2 is a characteristic curve diagram of spherical aberration of the imaging lens provided by the first embodiment of the present invention.

FIG. 3 is a field curvature characteristic curve diagram of the imaging lens provided by the first embodiment of the present invention.

FIG. 4 is a graph showing distortion characteristics of the imaging lens provided by the first embodiment of the present invention.

FIG. 5 is a characteristic curve diagram of the modulation transfer function of the imaging lens provided by the first embodiment of the present invention.

FIG. 6 is a characteristic curve diagram of spherical aberration of the imaging lens provided by the second embodiment of the present invention.

FIG. 7 is a graph of field curvature characteristics of the imaging lens provided by the second embodiment of the present invention.

FIG. 8 is a graph showing distortion characteristics of the imaging lens provided by the second embodiment of the present invention.

FIG. 9 is a characteristic curve diagram of the modulation transfer function of the imaging lens provided by the second embodiment of the present invention.

Description of main component symbols

Imaging lens 100

First lens G1

Second lens G2

first surface 11

second surface 12

third surface 13

fourth surface 14

Aperture 20

Filter 40

front surface 42

rear surface 44

Imaging Surface 101

The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings.

detailed description

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

Please refer to Fig. 1, a kind of imaging lens 100 provided by the present invention, it comprises in sequence from object side to image side: a first lens G1 with positive refractive power, a second lens G2 with positive refractive power and an imaging Surface 101. The first lens G1 includes a first surface 11 protruding toward the object side and a second surface 12 protruding toward the image side. The second lens G2 includes a third surface 13 concave toward the object side and a fourth surface 14 convex toward the image side.

The imaging lens further includes a diaphragm 20 and a filter 40 , the diaphragm 20 is located on the object side of the first surface 11 , and the filter 40 is located between the fourth surface 14 and the imaging surface 101 . The aperture 20 is used to control the light flux passing through the first lens G1. The filter 40 is used to filter out infrared rays in the light passing through the second lens G2, and includes a front surface 42 facing the object side and a rear surface 44 facing the image side.

In this embodiment, light enters the diaphragm 20 from the object side, and is imaged on the imaging surface 60 after passing through the first lens G1 , the second lens G2 , and the filter 40 in sequence. It can be understood that an imaging system can be formed by disposing an image sensor (not shown), such as a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS), on the imaging surface 60 .

The imaging lens 100 satisfies the following conditional formula:

(1) FB/TTL>0.23;

(2) G1R1/F1>1.93;

(3)X/Y>0.27;

(4)X/T<0.89;

(5) G2R1/F2<G2R2/F2<G1R2/F2;

Wherein, FB is the shortest distance between the fourth surface 14 and the imaging surface 60 along the optical axis, TTL is the total length of the imaging lens 100, X is the horizontal height of the curved surface of the fourth surface 14, and Y is the longitudinal height of the curved surface of the fourth surface 14 , T is the thickness of the second lens G2 on the optical axis, G1R1 is the radius of curvature of the third surface 11, G2R1 is the radius of curvature of the third surface 13, G2R2 is the radius of curvature of the fourth surface 14, G1R2 is the radius of curvature of the second surface 12 The radius of curvature, F1 is the focal length of the first lens G1, and F2 is the focal length of the second lens G2.

In the conditional formula of imaging lens 100 provided by the present invention, conditional formula (1) ensures that imaging lens 100 has a long back convex; conditional formula (2) makes the first lens G1 have a smaller optical power, thereby reducing The off-center sensitivity of the imaging lens 100 is ensured; Conditional expressions (3) and (5) ensure that the focal power distribution of the imaging lens 100 is appropriate and have a good aberration correction effect; Conditional expressions (4) ensure that the second lens G2 Easy to injection molding, so that the plastic injected from a single side gate can easily reach the opposite side.

The imaging lens 100 may further satisfy the following conditional formula:

(6) G1R2/F2<0.31;

(7) G2R1/F2<0.19;

(8) G2R2/F2<0.25;

The conditional expressions (6), (7) and (8) further ensure the imaging quality of the imaging lens 100 .

The imaging lens 100 may further satisfy the following conditional formula:

(9) Vd1>53

(10) Vd2<33;

Wherein, Vd1 is the Abbe number of the first lens G1, and Vd2 is the Abbe number of the second lens G2. The conditional expressions (9) and (10) enable the chromatic aberration of the imaging lens 100 to be better eliminated.

Wherein, the surfaces of the first lens G1 and the second lens G2 are both aspheric surfaces, and satisfy the surface formula of aspheric surfaces:

$\mathrm{<span\; class="notranslate">\; Z</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; ch</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; c</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&Sigma;A</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}}$

Among them, Z is the displacement value from the optical axis at the position of height h along the optical axis, taking the surface vertex as a reference, c is the reciprocal of the radius of curvature, h is the distance between the point on the aspheric curve and the optical axis, and k is the cone Fixed number (Coin Constant), A _i is i-th order Aspherical Coefficient.

By substituting the data in Table 1, Table 2, and Table 3 (please refer to the following) into the above expressions, the aspherical shape of each lens surface in the imaging lens 100 of the first embodiment of the present invention can be obtained. In addition, by substituting the data in Table 4, Table 5, and Table 6 into the above expressions, the aspherical shape of each lens surface in the imaging lens 100 of the second embodiment of the present invention can be known.

The optical surfaces arranged in order from the object end to the image end are respectively listed in the following tables, where it is agreed that F/No is the aperture number of the imaging lens 100, 2ω is the field angle of the imaging lens 100, and R is the optical angle of each lens. The radius of curvature of the surface, D is the on-axis distance from the corresponding optical surface to the next optical surface (the length of the optical axis cut by the two optical surfaces), Nd is the refractive index of the corresponding lens group to d light (wavelength is 587 nanometers) , Vd is the Abbe number (Abbe number) of d light in the corresponding lens group, and k is the quadric surface coefficient.

first embodiment

Each optical component of the imaging lens 100 provided by the first embodiment of the present invention satisfies the conditions in Table 1 and Table 2.

Table 1

optical surface face shape R(mm) D(mm) Nd Vd Aperture 20 flat gigantic 0.01 -- -- first surface 11 Aspherical 2.80 1.21 1.53 56.0 second surface 12 Aspherical -0.81 0.58 -- -- third surface 13 Aspherical -0.34 0.43 1.58 31.0 fourth surface 14 Aspherical -0.57 0.10 -- -- front surface 41 flat gigantic 0.55 1.52 58.6 rear surface 42 flat gigantic 0.43 -- -- Imaging surface 101 flat gigantic -- -- --

Table 2

table 3

F(mm) F/No 2ω 2.20 2.79 64.77°

In this embodiment, FB/TTL=0.327; G1R1/F1=2.12; X/Y=0.39; X/T=0.79; G2R1/F2=0.07; G2R2/F2=0.13; G1R2/F2=0.18.

The spherical aberration, curvature of field, distortion, and MTF of the imaging lens 100 provided in this embodiment are shown in FIGS. 2 to 5 respectively. Specifically, the six curves shown in Figure 2 are for F-line (wavelength of 486.1 nanometers (nm)), d-line (wavelength of 587.6nm), C-line (wavelength of 656.3nm), e-line (wavelength of 546.1nm ), g-line (wavelength of 435.8nm), h-line (wavelength of 404.7nm) and the observed aberration value curve. From the three curves, it can be seen that the aberration value generated by the imaging lens 100 of the first embodiment to visible light (with a wavelength range between 400nm and 700nm) is controlled within the range of -0.2 mm to 0.2 mm. As shown in FIG. 3 , curves T and S are characteristic curves of tangential field curvature and characteristic curves of sagittal field curvature respectively. It can be seen from FIG. 3 that the meridional field curvature and sagittal field curvature of the imaging lens 100 are controlled within the range of -0.20 mm to 0 mm. Further, the curve shown in FIG. 4 is the distortion characteristic curve of the imaging lens 100 . It can be seen from FIG. 4 that the optical distortion of the imaging lens 100 is controlled within the range of 0-2.00%. As shown in Figure 5, under the condition of 1/2 frequency (Nyquist frequency) (1/2 frequency (half frequency) of the present embodiment is 180lp/mm), the MTF>40% of the central field of view (as shown in the curve mc ), the MTF of the 0.8 field of view>30% (as shown by the curve mp), and the MTF of the other fields between the central field of view and the 0.8 field of view are between 30% and 40% (as shown by the curve mt Show).

second embodiment

Each optical component of the imaging lens 100 provided by the second embodiment of the present invention satisfies the conditions in Table 4, Table 5, and Table 6.

Table 4

optical surface face shape R(mm) D(mm) Nd Vd Aperture 20 flat gigantic 0.02 -- -- first surface 11 Aspherical 2.66 1.22 1.53 56.0 second surface 12 Aspherical -0.80 0.55 -- -- third surface 13 Aspherical -0.34 0.42 1.58 31.0 fourth surface 14 Aspherical -0.59 0.10 -- -- front surface 41 flat gigantic 0.55 1.52 58.6 rear surface 42 flat gigantic 0.45 -- -- Imaging surface 101 flat gigantic -- -- --

table 5

Table 6

F(mm) F/No 2ω 2.21 2.79 64.74°

In this embodiment, FB/TTL=0.333; G1R1/F1=2.03; X/Y=0.37; X/T=0.78; G2R1/F2=0.09; G2R2/F2=0.15; G1R2/F2=0.21.

The spherical aberration, curvature of field, distortion, and MTF of the imaging lens 100 provided in this embodiment are shown in FIGS. 6 to 9 respectively. Specifically, the six curves shown in Figure 6 are for F-line (wavelength of 486.1 nanometers (nm)), d-line (wavelength of 587.6nm), C-line (wavelength of 656.3nm), e-line (wavelength of 546.1nm ), g-line (wavelength of 435.8nm), h-line (wavelength of 404.7nm) and the observed aberration value curve. From the three curves, it can be seen that the aberration value generated by the imaging lens 100 of the first embodiment to visible light (with a wavelength range between 400nm and 700nm) is controlled within the range of -0.2 mm to 0.2 mm. As shown in FIG. 7 , curves T and S are characteristic curves of tangential field curvature and characteristic curves of sagittal field curvature respectively. It can be seen from FIG. 7 that the meridional field curvature and sagittal field curvature of the imaging lens 100 are controlled within the range of -0.20 mm to 0 mm. Further, the curve shown in FIG. 8 is the distortion characteristic curve of the imaging lens 100. It can be seen from FIG. 8 that the optical distortion of the imaging lens 100 is controlled within the range of -1.00%˜1.00%. As shown in Figure 9, under the condition of 1/2 frequency (Nyquist frequency) (1/2 frequency (half frequency) of the present embodiment is 180lp/mm), the MTF>40% of the central field of view (as shown in the curve mc ), the MTF of the 0.8 field of view>30% (as shown by the curve mp), and the MTF of the other fields between the central field of view and the 0.8 field of view are between 30% and 40% (as shown by the curve mt Show).

In the imaging lens provided by the present invention, the conditional formula FB/TTL>0.23 ensures that the imaging lens has a long back convex; the conditional formula G1R1/F1>1.93 makes the first lens have a smaller optical power, thereby reducing the The off-center sensitivity of the imaging lens; the conditional formula X/Y>0.27 and G1R2/F1<G3R2/F3<0 ensures that the focal power distribution of the imaging lens is appropriate and has a good aberration correction effect; the conditional formula X/T< 0.89, to ensure that the second lens is easy to injection mold, so that the plastic injected from the single side gate can easily reach the opposite side. A lens system that satisfies the above conditions can also ensure better imaging quality in the case of a long back convexity and a wide viewing angle.

In addition, those skilled in the art can also make other changes within the spirit of the present invention. Of course, these changes made according to the spirit of the present invention should be included in the scope of protection claimed by the present invention.

Claims (6)

1. an imaging lens, it includes the most successively: one to have positive light burnt First lens of degree, second lens with negative power and an imaging surface；This is years old One lens include a first surface and a second surface, and these second lens include one the 3rd surface And one the 4th surface；Described imaging lens meets following condition:

FB/TTL>0.23；

G1R1/F1>1.93；

X/Y>0.27；

X/T<0.89；

G2R1/F2<G2R2/F2<G1R2/F2；

Wherein, FB is the 4th surface and imaging surface beeline along optical axis direction, TTL For the overall length of imaging lens, X is the curved surface transverse height on the 4th surface, and Y is the 4th surface Curved surface longitudinally height, T is second lens thickness on optical axis, and G1R1 is first surface Radius of curvature, G2R1 is the radius of curvature on the 3rd surface, and G2R2 is the song on the 4th surface Rate radius, G1R2 is the radius of curvature of second surface, and F1 is the focal length of the first lens, F2 Being the focal length of the second lens, the surface of described first lens G1 and the second lens G2 is non- Sphere, and meet the face type formula of aspheric surface:

$Z=\frac{{\mathrm{ch}}^2}{1+\sqrt{1-(k+1)c^2{h}^2}}+{\mathrm{\&Sigma;A}}_i{h}^i$

Wherein, Z be along optical axis direction height for h position with surface vertices make with reference to away from The shift value of optical axis, c is the inverse of radius of curvature, and h is the point in aspheric curve and optical axis Distance, k is circular cone fixed number, A_iTake second place asphericity coefficient for i.

2. imaging lens as claimed in claim 1, it is characterised in that: described first eyeglass Following condition is also met with the second eyeglass:

G1R2/F2<0.31；

G2R1/F2<0.19；

G2R2/F2<0.25。

3. imaging lens as claimed in claim 1, it is characterised in that: described first eyeglass Following condition is also met with the second eyeglass:

Vd1>53

Vd2<33；

Wherein, Vd1 is the Abbe number of the first lens, and Vd2 is the Abbe number of the second lens.

4. imaging lens as claimed in claim 1, it is characterised in that: described first surface Protruding towards thing side, described second surface protrudes towards image side, and described 3rd surface is towards thing Caving in side, described 4th surface is protruded towards image side.

5. imaging lens as claimed in claim 1, it is characterised in that: described imaging lens Also including that a diaphragm, described diaphragm are positioned at the thing side of first surface, described diaphragm is used for controlling Luminous flux by the first lens.

6. imaging lens as claimed in claim 1, it is characterised in that: described imaging lens Also include an optical filter, described optical filter between the 4th surface and imaging surface, described filter Mating plate is for filtering the Infrared in the light of the second lens.