# Patent

## Title
Photographic optical system

## Abstract

The present invention discloses a photographic optical system which includes a first lens (focal length f1), a second lens (focal length f2), a third lens (focal length f3), a fourth lens (focal length f4), a fifth lens (focal length f5), a sixth lens (focal length f6) and a seventh lens (focal length f7). The photographic optical system disclosed in the present invention by optimizing rationally face shape, distributing refractive power, selecting optical material, is designed as a big relative stop photographic optical system, and can provide the imaging performance in low illumination environment.

## Background
FIELD OF THE INVENTION
The present invention discloses a photographic optical system, specifically, a photography optical system of portable electronic devices.
DESCRIPTION OF RELATED ART
In recent years, with the vigorous development of mini photographic lens, the demand of mini picturing module is rising. The general camera sensor is either photosensitive coupling component or complementary metal oxide conductive component. With the progress of semiconductor manufacturing technology, the sensor pixel size is smaller. Combined with current development trend of electronic product of better function, light, thin, short and small, as a result, the mini camera with good imaging quality becomes the mainstream of current market.
In the camera sensor lens, the resolution of image gradually increases, pixel size decreases, the lens shall have high resolution and excellent optical performance, for example, wide angle of lens, imaging in high dynamic range, reducing tolerance sensitivity of the lens, etc. The existing camera lens composed of seven pieces of lens, restricted by the structure, is unable to correct further senior aberration, for example spherical aberration, so that the imaging performance is limited.
Therefore, it is necessary to provide a kind of new technology solution to overcome above disadvantage.



BRIEF DESCRIPTION OF THE DRAWINGS
Many aspects of the embodiment can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
FIG. 1 is an exemplary structural diagram of a photographic optical system of the present disclosure.
FIG. 2 is an MTF curve diagram of the photographic optical system shown in FIG. 1.
FIG. 3 is a field curvature curve diagram of the photographic optical system in FIG. 1.
FIG. 4 is a distortion curve diagram of the photographic optical system in FIG. 1.



DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT
The present invention will hereinafter be described in detail with reference to an exemplary embodiment. To make the technical problems to be solved, technical solutions and beneficial effects of present disclosure more apparent, the present disclosure is described in further detail together with the figures and the embodiment. It should be understood the specific embodiment described hereby is only to explain this disclosure, not intended to limit this disclosure.
FIG. 1 is an exemplary structural diagram of a photographic optical system of the present disclosure. The photographic optical system 1 comprises seven lenses installed coaxially and lined up from the object side to the image side in turn as follows: a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160 and a seventh lens 170. In this embodiment, 7 lenses above are plastic lenses.
The first lens 110 has a negative refractive power. Its object side surface 112 is convex and its image side surface 114 is concave. It is made of plastic. The object side surface 112 and the image side surface 114 of the first lens 110 can be spherical or aspherical.
The object side surface 122 of the second lens 120 is convex and its image side surface 124 is concave. It is made of plastic. The object side surface 122 and the image side surface 124 of the second lens 120 are even aspherical.
The object side surface 132 of the third lens 130 is convex and its image side surface 134 is convex. It is made of plastic. The object side surface 132 and the image side surface 134 of the third lens 130 are even aspherical. The image side surface of the third lens has two points of inflection and two stagnation points.
The object side surface 142 of the fourth lens 140 is convex and the image side surface 144 of the fourth lens 140 is concave. It is made of plastic. The object side surface 142 and the image side surface 144 of the fourth lens 140 are even aspherical. The object side surface of the fourth lens has one point of inflection and one stagnation point.
The object side surface 152 of the fifth lens 150 is concave and the image side surface 154 is convex. It is made of plastic material. The object side surface 152 and the image side surface 154 of the fifth lens 150 are even aspherical. The image side surface of the fifth lens has one point of inflection.
The object side surface 162 of the sixth lens 160 is concave and the image side surface 164 is convex. It is made of plastic material. The object side surface 162 and the image side surface 164 of the sixth lens 160 are even aspherical. The image side surface of the sixth lens has two points of inflection.
The object side surface 172 of the seventh lens 170 is concave and the image side surface 174 is transferred from concave to convex from optical axis to circumference. It is made of plastic. The object side surface 172 and the image side surface 174 of the seventh lens 170 are even aspherical. The object side surface 172 of the seventh lens 170 has one point of inflection and one stagnation point. The image side surface 174 of the seventh lens 170 has two points of inflection and one stagnation point.
In which, the object side surface is convex, referring to that the object side surface toward the object surface is in convex shape. The object side surface is concave, referring to that the object side surface toward the object surface is in concave shape. The image side surface is convex, referring to that the image side surface toward the image surface is in convex shape. The image side surface is concave, referring to that the image side surface toward the image surface is in concave shape.
The combination refractive power of the first lens 110 and the second lens 120 is approximate zero refractive power, can correct rationally the spherical aberration, not introduce chromatic aberration and field curvature. The fourth lens 140 and the fifth lens 150 are made of optical material with high refractive index and low abbe number, can reduce effectively chromatic aberration of the system. The seventh lens 170 is a negative refractive power lens, can reduce effectively the field curvature of the system. By optimizing rationally the surface shape of the seven lens, distributing refractive power, selecting optical material, the photographic optical system 1 has good imaging performance under low illumination.
The photographic optical system 1 also includes an aperture 100 and a glass plate 180. The aperture 100 is located between the second lens 120 and the third lens 130, can control the amount of light and the depth of field. The glass plate 180 is located at the side of the image side surface 174 of the seventh lens 170. The glass plate 180 can be a filter to filter light. Its type can be selected according to actual requirement. The image side surface 190 is the imaging side of the object, located at the side of the glass plate 180 far from the seventh lens 170.
In the photographic optical system 1 disclosed in the present invention, in order to realize the design requirement of the photographic optical system 1 on miniaturization, high sensitivity, high optical performance and wide view angle, the first lens 110, the second lens 120, the third lens 130, the fourth lens 140, the fifth lens 150, the sixth lens 160 and the seventh lens 170 of the photographic optical system 100 shall meet following conditions:
1. Focal Length:
Under the overall structure of the photographic optical system 1, the focal length of the first lens 110, the second lens 120, the third lens 130, the fourth lens 140, the fifth lens 150, the sixth lens 160 and the seventh lens 170 of the photographic optical system 1 shall meet the following conditions:

−5 mm<f1<−1 mm; 2 mm<f2<6 mm; 2 mm<f3<5 mm; −10 mm<f4<−2 mm;

−30 mm<f5<−10 mm; 1 mm<f6<5 mm; −5 mm<f7<−2 mm;

−1.5<f1/f<−0.5; 1.0<f2/f<2.5; 0.5<f3/f<1.5; −2.5<f4/f<−0.5;

−10<f5/f<−2; 0.2<f6/f<1.2; −2.5<f7/f<−0.4; where

f1: the focal length of the first lens,

f2: the focal length of the second lens,

f3: the focal length of the third lens,

f4: the focal length of the fourth lens,

f5: the focal length of the fifth lens,

f6: the focal length of the sixth lens.

f7: the focal length of the seven lens, f: the focal length of whole photography optical system.

2. Refractive Power
Under the overall structure of the photographic optical system 1, the refractive power of the first lens 110, the second lens 120, the third lens 130, the fourth lens 140, the fifth lens 150, the sixth lens 160 and the seventh lens 170 of the photographic optical system 1 shall meet the conditions:

1.50<n1<1.55; 1.50<n2<1.55; 1.50<n3<1.55; 1.60<n4<1.70;

1.60<n5<1.70; 1.50<n6<1.55; 1.50<n7<1.55; where,

n1: the refractive power of the first lens,

n2: the refractive power of the second lens,

n3: the refractive power of the third lens,

n4: the refractive power of the fourth lens,

n5: the refractive power of the fifth lens,

n6: the refractive power of the fifth lens,

n7: the refractive power of the seven lens.

3. Abbe Number
Under the overall structure of the photographic optical system 1, Abbe number of the first lens 110, the second lens 120, the third lens 130, the fourth lens 140, the fifth lens 150, the sixth lens 160 and the seventh lens 170 of the photographic optical system 1 shall meet the conditions:

40<v1<60; 40<v2<60; 40<v3<60; 15<v4<30; 15<v5<30;

40<v6<60; 40<v7<60; where,

v1: abbe number of the first lens,

v2: abbe number of the second lens,

v3: abbe number of the second lens,

v4: abbe number of the fourth lens,

v5: abbe number of the fifth lens,

v6: abbe number of the sixth lens,

v7: abbe number of the seven lens.

If the focal length, refractive power and Abbe number of the first lens 110, the second lens 120, the third lens 130, the fourth lens 140, the fifth lens 150, the sixth lens 160 and the seventh lens 170 satisfy the conditions stated above, the chromatic aberration and telocentric characteristics of the photographic optical system 1 may be degraded, and will increase the sensitivity of the photographic optical system, difficult to realize the miniaturization and wide view angle of the photographic optical system, and is not conducive to reduce cost of the photographic optical system 1.
In this embodiment, the focal length, the refractive power and Abbe number of the first lens 110, the second lens 120, the third lens 130, the fourth lens 140, the fifth lens 150, the sixth lens 160, the seventh lens 170 and the glass plate 180 of the photographic optical system 1 are respectively shown in following table:










TABLE 1







Refractive



Type
Focal length (mm)
power
Abbe number


















Photographic
3.5
—
—


optical system


The first lens
−4.591
1.5441
56.1


The second lens
4.438
1.5441
56.1


The third lens
2.517
1.5441
56.1


The fourth lens
−4.671
1.651
21.5


The fifth lens
−20.223
1.651
21.5


The sixth lens
2.321
1.5441
56.1


The seven lens
−2.105
1.5441
56.1


Glass plate
∞
1.5168
64.16734









The continuity of the object side surface and the image side surface, the radius of curvature, SAG and semi-diameter SD of the first lens 110 (P1), the second lens 120 (P2), the third lens 130 (P3), the fourth lens 140 (P4), the fifth lens 150 (P5), the sixth lens 160 (P6) and the seventh lens 170 (P7) of the photographic optical system 1 are shown in table 2:











TABLE 2







Radius of

Semi-diameter


Lens
Continuity
curvature R
SAG
SD





















P1
Aspherical
R11
94.687
SAG11
0.012
3.023



Aspherical
R12
2.4396
SAG12
0.343
2.494


P2
Even
R21
2.0113
SAG21
0.392
2.348



aspherical



Even
R22
10.8108
SAG22
0.064
2.172



aspherical


P3
Even
R31
1.4637
SAG31
0.316
1.819



aspherical



Even
R32
−18.9556
SAG32
−0.027
1.842



aspherical


P4
Even
R41
55.361
SAG41
0.022
1.812



aspherical



Even
R42
2.9002
SAG42
0.183
1.755



aspherical


P5
Even
R51
−9.3555
SAG51
−0.211
1.756



aspherical



Even
R52
−32.0195
SAG52
−0.182
2.079



aspherical


P6
Even
R61
−5.1511
SAG61
−0.200
2.782



aspherical



Even
R62
−1.063
SAG62
−0.595
3.335



aspherical


P7
Even
R71
−15.1868
SAG71
−0.342
4.539



aspherical



Even
R72
1.256
SAG72
−0.331
4.958



aspherical









where,

R11: The curvature radius of the object side surface of the first lens P1;

R12: The curvature radius of the image side surface of the first lens P1;

R21: The curvature radius of the object side surface of the second lens P2;

R22: The curvature radius of the image side surface of the second lens P2;

R31: The curvature radius of the object side surface of the third lens P3;

R32: The curvature radius of the image side surface of the third lens P3;

R41: The curvature radius of the object side surface of the fourth lens P4;

R42: The curvature radius of the image side surface of the fourth lens P4;

R51: The curvature radius of the object side surface of the fifth lens P5;

R52: The curvature radius of the image side surface of the fifth lens P5;

R61: The curvature radius of the object side surface of the sixth lens P6;

R62: The curvature radius of the image side surface of the sixth lens P6;

R71: The curvature radius of the object side surface of the seven lens P7;

R72: The curvature radius of the image side surface of the seven lens P7;

SAG11: the distance from the surface projection point of the first lens on the optical axis to the lens center of the object side surface;

SAG12: the distance from the surface projection point of the first lens on the optical axis to the lens center of the image side surface;

SAG21: the distance from the surface projection point of the second lens on the optical axis to the lens center of the object side surface;

SAG22: the distance from the surface projection point of the second lens on the optical axis to the lens center of the image side surface;

SAG31: the distance from the surface projection point of the third lens on the optical axis to the lens center of the object side surface;

SAG32: the distance from the surface projection point of the third lens on the optical axis to the lens center of the image side surface;

SAG41: the distance from the surface projection point of the fourth lens on the optical axis to the lens center of the object side surface;

SAG42: the distance from the surface projection point of the fourth lens on the optical axis to the lens center of the image side surface;

SAG51: the distance from the surface projection point of the fifth lens on the optical axis to the lens center of the object side surface;

SAG52: the distance from the surface projection point of the fifth lens on the optical axis to the lens center of the image side surface;

SAG61: the distance from the surface projection point of the sixth lens on the optical axis to the lens center of the object side surface;

SAG62: the distance from the surface projection point of the sixth lens on the optical axis to the lens center of the image side surface;

SAG71: the distance from the surface projection point of the seven lens on the optical axis to the lens center of the object side surface;

SAG72: the distance from the surface projection point of the seven lens on the optical axis to the lens center of the image side surface.

The thickness of the first lens 110 (P1), the second lens 120 (P2), the aperture 100 (ST), the third lens 130 (P3), the fourth lens 140 (P4), the fifth lens 150 (P5), the sixth lens 160 (P6), the seventh lens 170 (P7) and the glass plate 180 (Tg) of the photographic optical system 1 is shown in table 3:









TABLE 3







Thickness (mm)



















T1
0.250



T12
0.140



T2
0.500



ST
0.345



T23
−0.245



T3
0.646



T34
0.050



T4
0.250



T45
0.394



T5
0.250



T56
0.313



T6
0.663



T67
0.306



T7
0.450



Tg
0.221










Where,

T1: The thickness of the first lens;

T12: The axial distance from the image side surface of the first lens and the object side surface of the second lens;

T2: The thickness of the second lens;

ST: The axial distance from the image side surface of the second lens to the aperture;

T23: The axial distance from the aperture to the object side surface of the third lens;

T3: The thickness of the third lens;

T34: The axial distance from the image side surface of the third lens and the object side surface of the fourth lens;

T4: The thickness of the fourth lens;

T45: The axial distance from the image side surface of the fourth lens to the fifth lens;

T5: The thickness of the fifth lens;

T56: The axial distance from the fifth lens to the sixth lens;

T6: The thickness of the sixth lens;

T67: The axial distance from the sixth lens to the seventh lens;

T7: The thickness of the seventh lens.








TABLE 4







Relation table between main light angle CRA and the


image height of the photographic optical system











Biggest image height





percentage
Image height (mm)
CRA (degree)















0.1H
0.294
6.6



0.2H
0.588
13.0



0.3H
0.882
19.0



0.4H
1.176
24.3



0.5H
1.470
28.5



0.6H
1.764
31.0



0.7H
2.058
31.3



0.8H
2.352
32.1



0.9H
2.646
33.2



1.0H
2.94
32.3



max
—
33.2










In this embodiment, DFOV=78.93 degrees, HFOV=66.88 degrees, VFOV=52.59 degrees, in which: FOV is defined as the biggest view angle range of the photographic optical system, HFOV is defined as horizontal view angle, DFOV is defined as diagonal view angle, VFOV is defined as vertical view angle.
Please refer also to FIGS. 2-4, the photographic optical system 1 disclosed in the present invention has high optical performance.
In addition, in the photographic optical system 1 disclosed in the present invention, the photographic optical system 1 is designed on the basis of the optical system with large relative aperture. Total optical length is less than 5.2 mm, view angle is between 78 degree to 80 degree.
The photographic optical system 1 disclosed in the present invention has following beneficial effects:
In present invention, through optimizing surface type, distributing focal power, selecting optical material, a big relative aperture photographic optical system is designed, which can provide good imaging performance in low illumination environment. The image is clear. The combination focal power of the first lens 110 and the second lens 120 is approximate zero focal power lens, can correct rationally the spherical aberration, not introduce chromatic aberration and field curvature. The fourth lens 140 and the fifth lens 150 are made of material with high refractive index and low abbe number, can reduce effectively chromatic aberration of the system. The seventh lens 170 is negative focal power lens which can reduce effectively the field curvature of the system.
It is to be understood, however, that even though numerous characteristics and advantages of the present exemplary embodiment have been set forth in the foregoing description, together with details of the structures and functions of the embodiment, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms where the appended claims are expressed.

## Claims

1. A photographic optical system comprising, in an order from an object side to an image side:
a first lens having a negative refractive power and an object side surface thereof being convex;
a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens;
and a seventh lens having negative refractive power;
wherein the photographic optical system further meets the following conditions (1) ̃(7):


−1.5<f1/f<−0.5  (1)



1.0<f2/f<2.5  (2)



0.5<f3/f<1.5  (3)



−2.5<f4/f<−0.5  (4)



−10<f5/f<−2  (5)



0.2<f6/f<1.2  (6)



−2.5<f7/f<−0.4  (7)


where,
f1: The focal length of the first lens;
f2: The focal length of the second lens;
f3: The focal length of the third lens;
f4: The focal length of the fourth lens;
f5: The focal length of the fifth lens;
f6: The focal length of the sixth lens;
f7: The focal length of the seven lens;
f: The focal length of whole photography optical system.

2. The photographic optical system as described in claim 1 further satisfying the following conditions (8) ̃(28):


−5 mm<f1<−1 mm  (8)



1.50<n1<1.55  (9)



40<v1<60  (10)



2 mm<f2<6 mm  (11)



1.50<n2<1.55  (12)



40<v2<60  (13)



2 mm<f3<5 mm  (14)



1.50<n3<1.55  (15)



40<v3<60  (16)



−10 mm<f4<−2 mm  (17)



1.60<n4<1.70  (18)



15<v4<30  (19)



−30 mm<f5<−10 mm  (20)



1.60<n5<1.70  (21)



15<v5<30  (22)



1 mm<f6<5 mm  (23)



1.50<n6<1.55  (24)



40<v6<60  (25)



−5 mm<f7<−2 mm  (26)



1.50<n7<1.55  (27)



40<v7<60  (28)

where,
f1: The focal length of the first lens;
n1: The refractive power of the first lens;
v1: Abbe number of the first lens;
f2: The focal length of the second lens;
n2: The refractive power of the second lens;
v2: Abbe number of the second lens;
f3: The focal length of the third lens;
n3: The refractive power of the third lens;
v3: Abbe number of the third lens;
f4: The focal length of the fourth lens;
n4: The refractive power of the fourth lens;
v4: Abbe number of the fourth lens;
f5: The focal length of the fifth lens;
n5: The refractive power of the fifth lens;
v5: Abbe number of the fifth lens;
f6: The focal length of the sixth lens;
n6: The refractive power of the sixth lens;
v6: Abbe number of the sixth lens;
f7: The focal length of the seven lens;
n7: The refractive power of the seven lens;
v7: Abbe number of the seven lens.

3. The photography optical system as described in claim 2, wherein the first lens and the second lens are almost zero focal power lenses for correcting rationally the spherical aberration, and the photography optical system further meets the following condition:


f1-2>60 mm or f1-2<−50 mm  (29)

where,
f1-2: The combination focal length of the first lens and the second lens.

4. The photography optical system as described in claim 2, wherein the photographic optical system also meets the following conditions:


TTL<5.4 mm;



78°<FOV<88°;

where,
TTL: The distance from the object side surface to the imaging surface of the first lens;
FOV: The biggest view angle range of the photographical optical system.

5. The photographic optical system as described in claim 1, wherein a ratio between the focal length and the system total optical length of the photographic optical system meets the following condition:


f/TTL>0.65  (30)

where,
TTL: The distance from the object side surface to imaging surface of the first lens.

6. The photography optical system as described in claim 1, wherein the fourth lens and the fifth lens are made of material with high refractive index and low abbe number, which can correct rationally the chromatic aberration of the system, and the fourth lens meets the conditions:


1.60<n4<1.70; 15<v4<30; and

the fifth lens meets the conditions:


1.60<n5<1.70; 15<v5<30.

7. The photography optical system as described in claim 6, wherein the object side surface of the fourth lens, the image side surface of the fifth lens and the object side surface of the seventh lens have one inflection point respectively; the image side surface of the third lens, the image side surface of the sixth lens and the image side surface of the seventh lens have two inflection points respectively.

8. The photographic optical system as described in claim 1, wherein the seventh lens is a negative lens and meets the condition:


−5 mm<f7<−2 mm.

9. The photography optical system as described in claim 8, wherein the image side surface of the third lens has two stagnation points; the object side surface of the fourth lens, the object side surface and the image side surface of the seventh lens have one stagnation point respectively.

10. The photography optical system as described in claim 1, wherein the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are plastic lenses.