Optical system

The authors of the patent

G02B13/002 - Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface

The owners of the patent US9429736:

Samsung Electro-Mechanics Co Ltd

 

The present invention relates to an optical system.
An optical system of the present invention includes, sequentially from an object side, a first lens having a positive refractive power and an object-side surface convex toward the object side; a second lens having a negative refractive power; a third lens having a negative refractive power; a fourth lens having a positive refractive power, a fifth lens having a negative refractive power and an image-side surface convex toward an image side; and a sixth lens having a negative refractive power and an image-side surface concave toward the image side.

 

 

CROSS-REFERENCE TO RELATED APPLICATIONS
Claim and incorporate by reference domestic priority application and foreign priority application as follows:
CROSS REFERENCE TO RELATED APPLICATION
This application claims the benefit under 35 U.S.C. Section 119 of Korean Patent Application Serial Nos. 10-2012-0099876 and 10-2013-0072836, entitled filed Sep. 10, 2012 and Jun. 25, 2013, which are hereby incorporated by reference in their entirety into this application.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical system, and more particularly, to an optical system that consists of six lenses.
2. Description of the Related Art
In general, mobile communication means such as mobile communication terminals, PDA, and smartphones become to have various additional functions in addition to basic communication functions along with their increased use and diversification of services provided through communication technology.
In particular, camera modules mounted to the mobile communication means are in increasing demand as various convergence devices for high definition video shooting, automatic focus adjustment, and QR code recognition in addition to simple photo shooting using a single focus.
Further, as the size of the camera modules is gradually reduced, higher resolution is required, and manufacturing costs of the camera modules are gradually reduced along with price cuts of the mobile communication devices.
In order to reduce the unit price of the camera module, first, it is most preferred to reduce manufacturing costs of lens groups constituting an optical system embedded in the camera module. However, in order to satisfy the above-mentioned conditions on improvement of resolution, the optical system should be constituted by applying a glass lens having high optical performance, but it is impossible to reduce the manufacturing costs of the camera module by using several sheets of expensive glass lenses.
Further, when employing a plurality of glass lenses to overcome the resolution problem, it is impossible to reduce a weight of the optical system.
RELATED ART DOCUMENT
Patent Document
Patent Document 1: Korean Patent Laid-open Publication No. 2011-24872
SUMMARY OF THE INVENTION
Therefore, the present invention has been invented in order to overcome the above-described disadvantages and problems raised in a conventional mobile camera optical system and it is, therefore, an object of the present invention to provide an optical system that can implement high resolution and reduce manufacturing costs by configuring an optical system using six aspherical plastic lenses.
In accordance with one aspect of the present invention to achieve the object, there is provided an optical system including, sequentially from an object side: a first lens having a positive refractive power and an object-side surface convex toward the object side; a second lens having a negative refractive power, a third lens having a negative refractive power; a fourth lens having a positive refractive power; a fifth lens having a negative refractive power and an image-side surface convex toward an image side; and a sixth lens having a negative refractive power and an image-side surface concave toward the image side.
Further, the optical system satisfies the following Conditional Expression with respect to conditions on chromatic aberration correction.
|V3−V2|<41  Conditional Expression 1
Here, V3 is an Abbe number of the third lens, and V2 is an Abbe number of the second lens.
Further, the optical system satisfies the following Conditional Expression with respect to conditions on design of the optical system.
TTL/F<1.5  Conditional Expression 2
Here, TTL is a distance from the first lens to an image plane, and F is a focal length of the entire optical system.
Further, the optical system satisfies the following Conditional Expression with respect to conditions on miniaturization according to the focal length ratio of the optical system.
1<|F6/F|<6  Conditional Expression 3
Here, F6 is a focal length of the sixth lens, and F is a focal length of the entire optical system.
Further, the optical system satisfies the following Conditional Expression with respect to conditions on miniaturization according to the radius of curvature of the lenses of the optical system.
0<(R7+R10)/(R7−R10)<1.3  Conditional Expression 4
Here, R7 is a radius of curvature of an object-side surface of the fourth lens, and R10 is a radius of curvature of the upper surface of the fifth lens.
Further, the optical system satisfies the following Conditional Expression with respect to conditions on aberration correction of the optical system.
|R7/F|<5  Conditional Expression 5
Here, R7 is a radius of curvature of the object-side surface of the fourth lens, and F is a focal length of the entire optical system.
Further, the optical system satisfies the following Conditional Expression with respect to conditions on chromatic aberration correction of the optical system.
|Nd2−Nd5|<0.11  Conditional Expression 6
Here, Nd2 is a refractive index of the second lens at d-line wavelength (587.6 nm), and Nd5 is a refractive index of the fifth lens at d-line wavelength (587.6 nm).
Further, the optical system satisfies the following Conditional Expression with respect to conditions on spherical aberration correction of the optical system.
F3/F<−5  Conditional Expression 7
Here, F3 is a focal length of the third lens, and F is a focal length of the entire optical system.
And the first to sixth lenses may be plastic lenses, and both surfaces of the first to sixth lenses may be aspherical surfaces.
Further, an optical filter, which is formed of a cover glass coated with an infrared cut filter for blocking excessive infrared rays included in light introduced from the outside, may be further included between the sixth lens and the image plane.
BRIEF DESCRIPTION OF DRAWINGS
These and/or other aspects and advantages of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a configuration diagram showing lens arrangement of an optical system in accordance with a first embodiment of the present invention;
FIG. 2 is an MTF graph of the optical system shown in FIG. 1;
FIG. 3 is a diagram of aberration of the optical system shown in Table 1 and FIG. 1;
FIG. 4 is a configuration diagram showing lens arrangement of an optical system for cameras in accordance with a second embodiment of the present invention;
FIG. 5 is an MTF graph of the optical system shown in FIG. 4;
FIG. 6 is a diagram of aberration of the optical system shown in Table 3 and FIG. 4;
FIG. 7 is a configuration diagram showing lens arrangement of an optical system for cameras in accordance with a third embodiment of the present invention;
FIG. 8 is an MTF graph of the optical system shown in FIG. 7;
FIG. 9 is a diagram of aberration of the optical system shown in Table 5 and FIG. 7;
FIG. 10 is a configuration diagram showing lens arrangement of an optical system for cameras in accordance with a fourth embodiment of the present invention;
FIG. 11 is an MTF graph of the optical system shown in FIG. 10; and
FIG. 12 is a diagram of aberration of the optical system shown in Table 7 and FIG. 10.
DETAILED DESCRIPTION OF THE PREFERABLE EMBODIMENTS
A matter regarding to an operation effect including a technical configuration for an object of an optical system in accordance with the present invention to achieve the object will be clearly appreciated through the following detailed description with reference to the accompanying drawings illustrating preferable embodiments of the present invention.
However, in the following lens configuration diagram of each embodiment, the thickness, size, and shape of lenses may be somewhat exaggerated for detailed description of the present invention. Particularly, the shape of a spherical surface or an aspherical surface shown in the lens configuration diagram is shown as an example and not limited thereto.
First, FIG. 1 is a lens configuration diagram showing an embodiment of an optical system in accordance with the present invention. As shown, an optical system of the present embodiment includes a first lens L1 having a positive refractive power, a second lens L2 having a negative refractive power, a third lens L3 having a negative refractive power, a fourth lens L4 having a positive refractive power, a fifth lens L5 having a negative refractive power, and a sixth lens L6 having a negative refractive power.
At this time, the first lens L1 may have a shape in which an object-side surface is convex toward an object side, the fifth lens L5 may have a shape in which an image-side surface is convex toward an image side, and the sixth lens L6 may have a shape in which an image-side surface is concave toward the image side.
Further, an optical filter OF, which is formed of an infrared filter for blocking excessive infrared rays included in light passing through the optical system or a cover glass coated with the infrared filter, may be provided between the sixth lens L6 and an image plane 15.
Further, in the optical system of the present invention, all of the first to sixth lenses L1 to L6 may be plastic lenses, and one or both surfaces of the first to sixth lenses L1 to L6 may be aspherical surfaces.
The reason for forming at least one surface of the lenses, which constitute the optical system in accordance with the present invention, as an aspherical surface is to improve the degree of freedom in design for facilitating correction of aberration including chromatic aberration and mitigating manufacturing tolerances. Further, the reason for forming all of the first to sixth lens L1 to L6 with plastic lenses is to configure an optical system that can be used in mobile devices by achieving a light weight even though the optical system consists of a plurality of lenses due to characteristics of the optical system having easiness in manufacture of aspherical surfaces compared to glass lenses and mainly mounted to the mobile devices.
Meanwhile, as mentioned above, the optical system of the present invention can perform aberration correction and achieve miniaturization while using a plurality of lenses by the following Conditional Expressions 1 and 2. Conditional Expressions and operational effects will be described below.
|V3−V2|<41  Conditional Expression 1
Here, V3 is an Abbe number of the third lens L3, and V2 is an Abbe number of the second lens L2.
Conditional Expression 1 is a condition on chromatic aberration correction of the optical system. It is possible to facilitate chromatic aberration correction by maintaining a difference in the Abbe number between the third lens L3 and the second lens L2 at less than a predetermined value. At this time, it is possible to minimize chromatic aberration when satisfying Conditional Expression 1, and the chromatic aberration may occur when deviating from an upper limit of Conditional Expression 1.
TTL/F<1.5  Conditional Expression 2
Here, TTL is a distance from the first lens L1 to the image plane 15, and F is a focal length of the entire optical system.
Conditional Expression 2, which is a condition on miniaturization according to the focal length ratio of the optical system, is a conditional expression on the ratio of the distance from the first lens L1 to the upper surface to the focal length of the entire optical system. At this time, when deviating from an upper limit of Conditional Expression 2, it is difficult to manufacture a compact optical system that satisfies a predetermined viewing angle required for mobile cameras.
1<|F6/F|<6  Conditional Expression 3
Here, F6 is a focal length of the sixth lens L6, and F is a focal length of the entire optical system.
Conditional Expression 3, which is a condition on miniaturization according to the focal length ratio of the optical system, is a conditional expression on the ratio of the focal length of the sixth lens L6 to the focal length of the entire optical system. At this time, when deviating from an upper limit of Conditional Expression 3, it is difficult to satisfy the condition of miniaturization since a refractive power of the entire optical system is reduced, and when deviating from a lower limit of Conditional Expression 3, it is difficult to correct a distortion due to deviation from telecentric characteristics.
0<(R7+R10)/(R7−R10)<1.3  Conditional Expression 4
Here, R7 is a radius of curvature of an object-side surface of the fourth lens LA, and R10 is a radius of curvature of the upper surface of the fifth lens L5.
Conditional Expression 4, which is a condition on miniaturization according to the radius of curvature of the lenses of the optical system, is a conditional expression on the ratio of the sum and the difference of the radius of the curvature of the fourth lens L4 and the fifth lens L5. At this time, when deviating from an upper limit of Conditional Expression 4, it is difficult to achieve miniaturization and sensitivity of the lens is increased since an effective diameter of the lens is increased, and when deviating from a lower limit of Conditional Expression 4, it is impossible to obtain high resolution of the optical system.
|R7/F|<5  Conditional Expression 5
Here, R7 is a radius of curvature of an object-side surface of the fourth lens L4, and F is a focal length of the entire optical system.
Conditional Expression 5, which is a condition on aberration correction of the optical system, is a conditional expression on the ratio of the radius of curvature of the object-side surface of the fourth lens L4 to the focal length of the entire optical system. At this time, when deviating from an upper limit of Conditional Expression 5, it is difficult to implement high resolution due to a difficulty in the aberration correction of the optical system.
|Nd2−Nd5|<0.11  Conditional Expression 6
Here. Nd2 is a refractive index of the second lens L2 at d-line wavelength (587.6 nm), and Nd5 is a refractive index of the fifth lens L5 at d-line wavelength (587.6 nm).
Conditional Expression 6, which is a condition on chromatic aberration correction of the optical system, is a conditional expression on the difference in the refractive index at d-line wavelength (587.6 nm) between the second lens L2 and the fifth lens L5. At this time, when satisfying the condition of Conditional Expression 6, it is possible to implement high resolution of the optical system and minimize chromatic aberration.
F3/F<−5  Conditional Expression 7
Here, F3 is a focal length of the third lens L3, and F is a focal length of the entire optical system.
Conditional Expression 7, which is a condition on aspherical aberration correction of the optical system, is a conditional expression on the ratio of the focal length of the third lens L3 to the focal length of the entire optical system. At this time, when deviating from an upper limit of Conditional Expression 7, it is difficult to implement high resolution of the optical system due to a difficulty in the aspherical aberration correction.
Hereinafter, a compact wide-angle optical system in accordance with the present invention will be described in detail with reference to specific numerical embodiments.
As described above, all of the following first to fourth embodiments include a first lens L1 having a positive refractive power and an object-side surface convex toward an object side; a second lens L2 having a negative refractive power; a third lens L3 having a negative refractive power; a fourth lens L4 having a positive refractive power; a fifth lens L5 having a positive refractive power and an image-side surface toward an image side; and a sixth lens L6 having a negative refractive power and an image-side surface concave toward the image side, and an optical filter OF, which is formed of an infrared filter or a cover glass coated with the infrared filter, is provided between the sixth lens L6 and an image plane 15.
Further, the first to sixth lenses L1 to L6 are formed of plastic lenses whose both surfaces are aspherical surfaces.
Meanwhile, an aspherical surface used in each of the following embodiments is obtained from known Equation 1, and E and a number following the E used in a Conic constant K and aspherical coefficients A, B, C, D, E, and F represent a 10's power. For example, E+02 represents 102, and E-02 represents 10−2.
Z = cY 2 1 + 1 - ( 1 + K ) c 2 Y 2 + AY 4 + BY 6 + CY 8 + DY 10 + EY 12 + FY 14 + [ Equation 1 ]
Here, Z: distance from vertex of lens in the direction of optical axis
    • Y: distance in the direction perpendicular to optical axis
    • c: reciprocal of radius of curvature (R) at vertex of lens
    • K: Conic constant
    • A, B, C, D, E, F: aspherical coefficients
First Embodiment
The following Table 1 shows numerical examples according to the first embodiment of the present invention.
Further, FIG. 1 is a configuration diagram showing lens arrangement of an optical system in accordance with the first embodiment of the present invention, FIG. 2 is an MTF graph of the optical system shown in FIG. 1, and FIG. 3 is a diagram of aberration of the optical system shown in Table 1 and FIG. 1.
In the first embodiment, an effective focal length F of the entire optical system is 4.09 mm, and a distance TTL from the first lens L1 to the image plane 15 is 5.0 mm. Further, all of the first to sixth lenses L1 to L6 are aspherical plastic lenses.
Further, in the first embodiment, a focal length F6 of the sixth lens L6 is −5.98 mm, a refractive index of the second lens L2 at d-line wavelength (587.6 nm) is 1.6322, a refractive index of the fifth lens L5 at d-line wavelength (587.6 nm) is 1.6349, and a focal length F3 of the third lens 13 is −100 mm.
TABLE 1
        Abbe  
Surface Radius of Thickness Refractive Number
No. Curvature (R) (mm) Index (n) (v) Remarks
 
*1 1.5260 0.368 1.546 56.1 First lens
*2 40.7516 0.103
*3 3.3040 0.265 1.639 23.4 Second lens
*4 1.6417 0.346
*5 60.4625 0.396 1.546 56.1 Third lens
*6 28.6383 0.280
*7 −11.4963 0.452 1.546 56.1 Fourth lens
*8 −1.8821 0.200
*9 −1.0947 0.366 1.641 24.0 Fifth lens
*10 −1.4527 0.389
*11 3.6227 0.867 1.546 56.1 Sixth lens
*12 1.5733 0.261
13 0.300 1.519 64.2 Optical filter
14 0.397

In Table 1, the sign * in front of the surface No. represents an aspherical surface. In the first embodiment, both surfaces of the first to sixth lenses L1 to L6 are aspherical surfaces.
Further, values of aspherical coefficients of the first embodiment by Equation 1 are as in the following Table 2.
TABLE 2
Sur- Y            
face di-
No. ameter K A B C D E
 
1 1.526 0.274 −0.009 0.005 −0.006 −0.003 0.041
2 40.752 0.000 −0.066 0.281 −0.512 0.530 −0.243
3 3.304 0.000 −0.155 0.485 −0.794 0.716 −0.297
4 1.642 0.126 −0.113 0.384 −0.517 0.422 −0.130
5 60.463 −6.264 −0.123 0.105 −0.067 −0.041 0.000
6 60.463 −0.264 −0.123 0.105 −0.067 −0.041 0.000
7 −11.496 0.000 −0.155 0.019 −0.149 0.320 −0.205
8 −1.882 0.000 0.012 0.003 −0.090 0.137 −0.050
9 −1.095 −3.056 0.037 −0.033 −0.013 0.047 −0.044
10 −1.453 −2.403 0.020 −0.015 0.014 −0.001 −0.006
11 3.623 0.961 −0.205 0.095 −0.025 0.003 0.000
12 1.573 −5.499 −0.070 0.026 −0.006 0.001 0.000

Second Embodiment
The following Table 3 shows numerical examples according to the second embodiment of the present invention.
Further, FIG. 4 is a configuration diagram showing lens arrangement of an optical system for cameras in accordance with the second embodiment of the present invention, FIG. 5 is an MTF graph of the optical system shown in FIG. 4, and FIG. 6 is a diagram of aberration of the optical system shown in Table 3 and FIG. 4.
In the second embodiment, an effective focal length F of the entire optical system is 4.08 mm, and a distance TTL from the first lens L1 to the image plane 15 is 4.98 mm. Further, all of the first to sixth lenses L1 to L6 are aspherical plastic lenses.
Further, in the second embodiment, a focal length of the sixth lens L6 is −4.45 mm, a refractive index of the second lens L2 at d-line wavelength (587.6 nm) is 1.6322, a refractive index of the fifth lens L5 at d-line wavelength (587.6 nm) is 1.6349, and a focal length F3 of the third lens L3 is −100 mm.
TABLE 3
Surface Radius of Thickness Refractive Abbe  
No. Curvature (R) (mm) Index (n) Number Remarks
 
*1 1.5579 0.524 1.546 56.1 First lens
*2 52.8207 0.100
*3 4.1293 0.265 1.639 23.4 Second lens
*4 1.8117 0.328
*5 31.2499 0.468 1.546 56.1 Third lens
*6 19.7761 0.152
*7 −18.8115 0.468 1.546 56.1 Fourth lens
*8 −1.8607 0.200
*9 −1.1485 0.374 1.641 24.0 Fifth lens
*10 −1.4518 0.379
*11 5.3377 0.810 1.546 56.1 Sixth lens
*12 1.5809 0.230
13 0.300 1.519 64.2 Optical filter
14 0.3972

In Table 3, the sign * in front of the surface No. represents an aspherical surface. In the second embodiment, both surfaces of the first to sixth lenses L1 to L6 are aspherical surfaces.
Further, values of aspherical coefficients of the second embodiment by Equation 1 are as in the following Table 4.
TABLE 4
Sur- Y            
face di-            
No. ameter K A B C D E
 
1 1.558 0.264 −0.008 0.002 −0.011 −0.010 0.034
2 52.821 0.000 −0.073 0.265 −0.513 0.524 −0.260
3 4.129 0.000 −0.170 0.477 −0.793 0.732 −0.309
4 1.812 −0.359 −0.120 0.376 −0.514 0.400 −0.143
5 31.250 −6.264 −0.122 0.081 −0.053 −0.049 0.000
6 19.776 1.931 −0.196 0.015 0.026 −0.059 0.000
7 −18.811 0.000 −0.193 −0.005 −0.143 0.320 −0.207
8 −1.861 0.000 0.008 −0.005 −0.090 0.137 −0.050
9 −1.148 −3.133 0.031 −0.035 −0.013 0.047 −0.044
10 −1.452 −2.700 0.010 −0.015 0.015 −0.001 −0.006
11 5.338 2.421 −0.214 0.094 −0.024 0.003 0.000
12 1.581 −6.412 −0.070 0.025 −0.006 0.001 0.000

Third Embodiment
The following Table 5 shows numerical examples according to the third embodiment of the present invention.
Further, FIG. 7 is a configuration diagram showing lens arrangement of an optical system for cameras in accordance with the third embodiment of the present invention, FIG. 8 is an MTF graph of the optical system shown in FIG. 7, and FIG. 9 is a diagram of aberration of the optical system shown in Table 5 and FIG. 7.
In the third embodiment, an effective focal length F of the entire optical system is 4.25 mm, and a distance TTL from the first lens L1 to the image plane 15 is 5.15 mm. Further, all of the first to sixth lenses L1 to L6 are aspherical plastic lenses.
Further, in the third embodiment, a focal length of the sixth lens L6 is −4.80 mm, a refractive index of the second lens L2 at d-line wavelength (587.6 nm) is 1.6322, a refractive index of the fifth lens L5 at d-line wavelength (587.6 nm) is 1.5255, and a focal length F3 of the third lens L3 is −100 mm.
TABLE 5
        Abbe  
Surface Radius of Thickness Refractive Number
No. Curvature (R) (mm) Index (n) (v) Remarks
 
*1 1.622 0.522 1.545 58.6 First lens
*2 14.1321 0.100
*3 4.2747 0.325 1.639 23.4 Second lens
*4 1.9509 0.323
*5 9.000 0.460 1.553 64.4 Third lens
*6 7.6039 0.120
*7 14.4977 0.480 1.544 54.4 Fourth lens
*8 −2.6646 0.301
*9 −1.2720 0.363 1.525 53.4 Fifth lens
*10 −1.6007 0.116
*11 7.4492 1.046 1.543 65.1 Sixth lens
*12 1.8403 0.228
13 0.300 1.519 64.2 Optical filter
14 0.436

In Table 5, the sign * in front of the surface No. represents an aspherical surface. In the third embodiment, both surfaces of the first to sixth lenses L1 to L6 are aspherical surfaces.
Further, values of aspherical coefficients of the third embodiment by Equation 1 are as in the following Table 6.
TABLE 6
Surface No. Y diameter K A B C D E
 
1 1.622 0.348 −0.010 0.006 −0.015 0.012 0.006
2 14.132 0.000 −0.154 0.403 −0.611 0.529 −0.213
3 4.275 0.000 −0.268 0.601 −0.818 0.611 −0.204
4 1.951 0.984 −0.194 0.403 −0.467 0.262 −0.041
5 9.000 −6.264 −0.147 0.104 −0.054 −0.072 0.000
6 7.604 1.931 −0.234 0.007 0.044 −0.042 0.000
7 14.498 0.000 −0.170 −0.006 −0.150 0.386 −0.249
8 −2.665 0.000 −0.012 −0.005 −0.090 0.137 −0.050
9 −1.272 −5.056 −0.017 −0.021 −0.013 0.047 −0.044
10 −1.601 −5.435 −0.075 0.038 0.011 −0.008 −0.004
11 7.449 −109.275 −0.219 0.096 −0.021 0.002 0.000
12 1.840 −7.257 −0.064 0.022 −0.006 0.001 0.000

Fourth Embodiment
The following Table 7 shows numerical examples according to the fourth embodiment of the present invention.
Further, FIG. 10 is a configuration diagram showing lens arrangement of an optical system for cameras in accordance with the fourth embodiment of the present invention, FIG. 11 is an MTF graph of the optical system shown in FIG. 10, and FIG. 12 is a diagram of aberration of the optical system shown in Table 7 and FIG. 10.
In the fourth embodiment, an effective focal length F of the entire optical system is 4.07 mm, and a distance TTL from the first lens L1 to the image plane 15 is 5.01 mm. Further, all of the first to sixth lenses L1 to L6 are aspherical plastic lenses.
Further, in the fourth embodiment, a focal length of the sixth lens L6 is −23.26 mm, a refractive index of the second lens L2 at d-line wavelength (587.6 nm) is 1.6322, a refractive index of the fifth lens L5 at d-line wavelength (587.6 nm) is 1.6349, and a focal length F3 of the third lens L3 is −24.42 mm.
TABLE 7
        Abbe  
Surface Radius of Thickness Refractive Number
No. Curvature (R) (mm) Index (n) (v) Remarks
 
*1 1.5876 0.546 1.546 56.1 First lens
*2 28.2697 0.100
*3 3.2326 0.282 1.639 23.4 Second lens
*4 1.6274 0.305
*5 7.0777 0.280 1.546 56.1 Third lens
*6 4.5532 0.120
*7 12.4861 0.463 1.546 56.1 Fourth lens
*8 −3.8661 0.320
*9 −1.1565 0.360 1.641 24.0 Fifth lens
*10 −1.4830 0.102
*11 2.4612 1.029 1.546 56.1 Sixth lens
*12 1.7573 0.223
13 0.300 1.519 64.2 Optical filter
14 0.573

In Table 7, the sign * in front of the surface No. represents an aspherical surface. In the fourth embodiment, both surfaces of the first to sixth lenses L1 to L6 are aspherical surfaces.
Further, values of aspherical coefficients of the fourth embodiment by Equation 1 are as in the following Table 8.
TABLE 8
Sur- Y            
face di-
No. ameter K A B C D E
 
1 1.588 0.209 −0.013 0.000 −0.029 0.005 0.017
2 28.270 0.000 −0.160 0.378 −0.622 0.533 −0.223
3 3.233 0.000 −0.288 0.607 −0.814 0.620 −0.191
4 1.627 0.567 −0.208 0.386 −0.436 0.251 −0.022
5 7.078 −6.264 −0.087 0.064 −0.071 −0.032 0.000
6 4.553 1.931 −0.081 −0.007 0.018 −0.030 0.000
7 12.486 0.000 −0.068 −0.002 −0.162 0.375 −0.254
8 −3.866 0.000 −0.004 −0.001 −0.090 0.137 −0.050
9 −1.156 −5.285 0.011 −0.008 −0.013 0.047 −0.044
10 −1.483 −5.840 −0.066 0.045 0.010 −0.009 −0.004
11 2.461 −6.322 −0.180 0.082 −0.021 0.003 0.000
12 1.757 −4.217 −0.079 0.026 −0.006 0.001 0.000

Meanwhile, values of Conditional Expressions for the first to fourth embodiments are as in the following Table 9.
  TABLE 9
 
  Embodiment Embodiment   Embodiment
  1 2 Embodiment 3 4
 
 
Conditional 32.6 32.6 41.0 32.6
expression 1
Conditional 1.22 1.22 1.2 1.23
expression 2
Conditional −1.46 −1.09 −1.12 −5.71
expression 3
Conditional 1.29 1.17 0.80 0.79
expression 4
Conditional −2.81 −4.61 3.40 3.06
expression 5
Conditional −0.0028 −0.0028 0.1066 −0.0028
expression 6
Conditional −24.52 −24.60 −23.51 −5.99
expression 7

As described above, the optical system in accordance with the present invention can improve aberration correction efficiency and reduce manufacturing costs by forming six lenses with aspherical plastic lenses and implement high resolution by minimizing chromatic aberration.
Further, the present invention can manufacture a high resolution optical system by configuring the first and fourth lenses of the six lenses constituting the optical system to have a positive refractive power and thus reducing an aberration value.
As described above, although the preferable embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that substitutions. modifications and variations may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.


1. An optical system consisting of, sequentially from an object side:
a first lens having a positive refractive power and an object-side surface convex toward the object side;
a second lens having a negative refractive power;
a third lens having a negative refractive power;
a fourth lens having a positive refractive power;
a fifth lens having a negative refractive power and an image-side surface convex toward an image side; and
a six lens having a negative refractive power and an image-side surface concave toward the image side.
2. The optical system according to claim 1, wherein the optical system satisfies the following Conditional Expression with respect to conditions on chromatic aberration correction:

|V3−V2|<41,  Conditional Expression
where V3 is an Abbe number of the third lens, and V2 is an Abbe number of the second lens.
3. The optical system according to claim 1, wherein the optical system satisfies the following Conditional Expression with respect to conditions on design of the optical system:

TTL/F<1.5,  Conditional Expression
where TTL is a distance from the first lens to an image plane, and F is a focal length of the entire optical system.
4. The optical system according to claim 1, wherein the optical system satisfies the following Conditional Expression with respect to conditions on miniaturization according to the focal length ratio of the optical system:

1<|F6/F|<6,  Conditional Expression
where F6 is a focal length of the sixth lens, and F is a focal length of the entire optical system.
5. The optical system according to claim 1, wherein the optical system satisfies the following Conditional Expression with respect to conditions on miniaturization according to the radius of curvature of the lenses of the optical system:

0<(R7+R10)/(R7−R10)<1.3,  Conditional Expression
where R7 is a radius of curvature of an object-side surface of the fourth lens, and R10 is a radius of curvature of an image-side surface of the fifth lens.
6. The optical system according to claim 1, wherein the optical system satisfies the following Conditional Expression with respect to conditions of aberration correction of the optical system:

|R7/F|<5,  Conditional Expression
where R7 is a radius of curvature of the object-side surface of the fourth lens, and F is a focal length of the entire optical system.
7. The optical system according to claim 1, wherein the optical system satisfies the following Conditional Expression with respect to conditions on chromatic aberration correction of the optical system:

|Nd2−Nd5|<0.11,  Conditional Expression
where Nd2 is a refractive index of the second lens at d-line wavelength (587.6 nm), and Nd5 is a refractive index of the fifth lens at d-line wavelength (587.6 nm).
8. The optical system according to claim 1, wherein the optical system satisfies the following Conditional Expression with respect to conditions on spherical aberration correction of the optical system:

F3/F<−5,  Conditional Expression
where F3 is a focal length of the third lens, and F is a focal length of the entire optical system.
9. The optical system according to claim 1, wherein the first to sixth lenses are plastic lenses.
10. The optical system according to claim 1, wherein both surfaces of the first to sixth lenses are aspherical surfaces.
11. The optical system according to claim 1, further comprising:
an optical filter provided between the six lens and an image plane and formed of a cover glass coated with an infrared cut filter for blocking excessive infrared rays included in light introduced from the outside.

 

 

Patent trol of patentswamp
Similar patents
an optical lens system includes, in order from an object side to an image side, a first lens element, a second lens element, a third lens element and a fourth lens element. the first lens element with positive refractive power has an object-side surface being convex in a paraxial region thereof. the second lens element has negative refractive power. the third lens element with positive refractive power has an image-side surface being convex in a paraxial region thereof, wherein both of the surfaces thereof are aspheric. the fourth lens element with negative refractive power has an image-side surface being concave in a paraxial region thereof, wherein the image-side surface of the fourth lens element has at least one convex shape in an off-axis region thereof, and both of the surfaces thereof are aspheric. the optical lens system has a total of four lens elements with refractive power.
a projection zoom lens in which a magnification change operation is performed by moving three to four lens groups as moving groups, wherein a first lens group, which is a lens group on the most-magnification side, substantially consists of a moving group having a negative refractive power; a lens group on the most-reduction side is composed of a moving group having a positive refractive power; and the first lens group which is the lens group the most-magnification side substantially consists of two lenses. in this case, conditional formula below is satisfied, where fw is the focal length of the entire system at the wide angle end and fm is the focal length of the lens group on the most-magnification side:
−3.5<fm/fw<−1.0  .
this achieves miniaturization and cost reduction, and corrects various aberrations satisfactorily.
an imaging lens is formed from six lenses, including a negative first lens having a concave surface toward the object side, a positive second lens, a negative third lens, a negative fourth lens of a meniscus shape with a concave surface toward the object side, a fifth lens, and a sixth lens having a concave surface toward the image side. the surface toward the image side thereof has an aspherical shape having at least one inflection point thereon, provided in this order from the object side.
Optical system // US9423593
there is provided a first lens having a refractive power, an object-side surface thereof being convex toward an object; a second lens having positive refractive power; a third lens having negative refractive power; a fourth lens having positive refractive power; and a fifth lens having negative refractive power. the optical system satisfies the condition:
t34/t23>8.0
    • where t23 is a distance between the second and third lenses, and t34 is a distance between the third and fourth lenses.
an imaging lens includes: a first lens group; a stop; a positive second lens group; and a negative third lens group which is fixed while focusing, in order from the object side. the first lens group includes at least one positive lens, at least one cemented lens, and a negative meniscus lens having a concave surface toward the image side, in order from the object side. the second lens group includes a cemented lens formed by a biconcave lens and a biconvex lens and a biconvex lens, in order from the object side. the third lens group includes a negative meniscus lens having a convex surface toward the object side, a biconcave lens, and a biconvex lens, in order from the object side. the first lens group, the stop, and the second lens group move integrally along the optical axis to focus from an infinite to a finite distance.
an optical imaging lens includes: a first, second, third and fourth lens element, the first lens element having an object-side surface with a convex portion in a vicinity of the optical axis, the second lens element having an object-side surface with a convex portion in a vicinity of the optical axis, and an image-side surface with a concave portion in a vicinity of its periphery, the third lens element having an image-side surface with a convex portion in a vicinity of the optical axis, the fourth lens element having an image-side surface with a concave portion in a vicinity of the optical axis, wherein the optical imaging lens set does not include any lens element with refractive power other than said first, second, third and fourth lens elements.
a finder optical system includes, in the order from a display device side to an eye point side, a first lens group to increase a light beam height of a light beam bundle incident from a display device side and to emit the light beam bundle to the eye point side, and a second lens group having an image formation action.
arrayed imaging systems include an array of detectors formed with a common base and a first array of layered optical elements, each one of the layered optical elements being optically connected with a detector in the array of detectors.
the magnification of the variable magnification finder is switchable, and the finder includes a positive lens group, a negative lens group, and an eyepiece lens group in this order from an object side in a high magnification state. the positive lens group is retracted from an optical path of the variable magnification finder to the outside of the optical path and the negative lens group moves toward the object side when magnification is changed from the high magnification state to a low magnification state. the following conditional formula is satisfied when the focal length of the negative lens group is fn:
−15 mm
a photographing lens system includes, in order from an object side to an image side, a first lens element, a second lens element, a third lens element, a fourth lens element and a fifth lens element. the first lens element with refractive power has a convex object-side surface. the second lens element has refractive power. the third lens element with refractive power has a convex object-side surface and a concave image-side surface. the fourth lens element with refractive power has an object-side surface and an image-side surface being both aspheric. the fifth lens element with refractive power has a concave image-side surface, wherein an object-side surface and the image-side surface thereof are aspheric, and the image-side surface of the fifth lens element has at least one convex shape in an off-axial region thereof. the photographing lens system has a total of five lens elements with refractive power.
To top