KR20120051994A - Compact optical system - Google Patents

Abstract

PURPOSE: A micro imaging optical system is provided to minimize chromatic spherical aberrations, thereby improving resolution and reducing manufacturing costs. CONSTITUTION: A first lens(L1) protruded toward an object side has positive refractive power. A second lens(L2) depressed toward the object side has positive refractive power. A third lens(L3) depressed toward the object side has negative refractive power. A fourth lens(L4) protruded toward the upper part from a paraxial side with a meniscus shape has negative refractive power. A fifth lens(L5) depressed toward the upper side has positive refractive power.

Description

Compact Optical System

The present invention relates to an ultra-compact imaging optical system, and more specifically, an aperture is disposed in front, and is sequentially composed of five lenses having positive, positive, negative, negative, and positive refractive power, and also improves resolution and slims down. And a microscopic imaging optical system that can be mounted on a portable terminal by being light in weight.

Recently, as the usage of portable terminals such as mobile communication terminals, PDAs (Personal Digital Assistants), smart phones, etc. is increased and services are diversified, various types of additional functions in addition to the basic communication functions are being installed in the portable terminals. .

Among them, a camera module is essentially mounted in the mobile terminal for image capturing, transmission, and video call, and various services are provided to the user by using image data photographed through the camera module.

In particular, as the portable terminal itself has become smaller and lighter in weight, it has been required to reduce the size, weight, and cost of an optical system composed of a lens group mounted on a camera module, and to use a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS). As the pixel size of the image sensor consisting of) gradually decreases, high resolution and high quality optical systems are required.

As described above, in order to maintain a high resolution of the optical system, it is preferable to use a plurality of lenses and to configure the optical system using glass lenses having high light transmittance and high refractive index. The same optical system design has a problem that it is difficult to satisfy the conditions of miniaturization and cost reduction.

Therefore, the optical system mounted on the mobile terminal should use a plastic lens that is easy to mold and reduce the number of lenses possible in order to reduce the size and manufacturing cost. It is difficult to satisfy the optical performance with the design of, and the design freedom of the optical system is lowered due to the reduction in the number of lenses.

In order to solve this problem, the conventional optical system adopts an optical system in which a glass lens and a plastic lens are mixed to improve the performance of the optical system and correct aberration, but it is difficult to correct aberration and difficult to apply aspherical surface. It is difficult to design an optical system with a short length due to the phase optical design. In addition, it is difficult to reduce the manufacturing cost and light weight by using a glass lens.

Accordingly, an object of the present invention is to configure all five lenses of aspherical plastic lenses and the third lens of the flint plastic lenses, thereby minimizing spherical aberration and chromatic aberration, improving resolution, miniaturization, light weight and manufacturing. It is to provide a compact imaging optical system that can reduce the cost.

In order to achieve the above object, the microscopic imaging optical system according to the present invention has a positive refractive power, a first lens having a convex shape on the object side, a positive refractive power, a second lens having a concave shape on the object side, and a negative refractive power. A third lens concave toward the object side, a fourth lens having a negative refractive power and a meniscus shape convex toward the image side on the paraxial axis, and a fifth lens having a positive refractive power and concave toward the image side; .

The optical system satisfies the following conditional expression with respect to the optical axis direction dimension.

[Condition Expression] TL / F <1.5

Here, TL: distance from the object-side surface of the first lens to the image surface

F: effective focal length of the whole optical system

The optical system satisfies the following conditional expression with respect to the optical axis direction dimension.

Conditional Expression 0.4 <F1 / F <1.2

Here, F1: effective focal length of the first lens

F: effective focal length of the whole optical system

The optical system satisfies the following conditional expression regarding the Abbe's number of the second lens and the third lens.

Conditional Expression | Vd2-Vd3 | <35

Where Vd2 is the Abbe's number of the second lens

Vd3: Abbe's number of the third lens

In addition, both surfaces of the first to fifth lenses are composed of aspherical surfaces.

In addition, the first to fifth lenses are composed of plastic lenses.

In addition, the third lens is composed of a flint-based lens.

Accordingly, according to the structure of the present invention, the present invention consists of all five lenses composed of aspherical plastic lenses, and the third lens is composed of a flint-based plastic lens, thereby minimizing spherical aberration and chromatic aberration, thereby improving resolution and optical system. It has the effect of miniaturization, weight reduction and manufacturing cost reduction.

1 is a lens configuration showing the lens arrangement of the optical system for a camera according to the first embodiment of the present invention
2 is a diagram illustrating an MTF graph according to a first embodiment of the present invention;
3A to 3C are diagrams showing spherical aberration, astigmatism, and distortion aberration of the optical system shown in Table 1, Table 2, and FIG. 1, respectively.
4 is a lens diagram illustrating a lens arrangement of an optical system for a camera according to a second exemplary embodiment of the present invention.
5 is a diagram illustrating an MTF graph according to a second embodiment of the present invention.
6A to 6C are diagrams illustrating spherical aberration, astigmatism, and distortion aberration of the optical system shown in Tables 3, 4, and 4, respectively.
7 is a lens diagram illustrating a lens arrangement of an optical system for a camera according to a third exemplary embodiment of the present invention.
8 is a diagram illustrating an MTF graph according to a third embodiment of the present invention.
9A to 9C are diagrams showing spherical aberration, astigmatism, and distortion aberration of the optical system shown in Tables 5, 6, and 7, respectively.
10 is a lens configuration diagram showing the lens arrangement of the optical system for a camera according to the fourth embodiment of the present invention.
11 illustrates an MTF graph according to a fourth embodiment of the present invention.
12A to 12C are diagrams showing spherical aberration, astigmatism, and distortion aberration of the optical system shown in Table 7, Table 8, and 10, respectively.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the present specification and claims should not be construed as being limited to the common or dictionary meanings, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that it can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

1 is a lens configuration diagram showing a lens arrangement of an optical system for a camera according to a first embodiment of the present invention. As shown in FIG. 1, the microscopic optical system according to the present invention has positive refractive power in order from an object side. , A first lens L1 convex toward the object side, a second lens L2 having a positive refractive power and concave toward the object side, a third lens L3 having a negative refractive power and concave toward the object side and a negative And a fourth lens L4 having a meniscus shape that is convex upward on the paraxial axis and a fifth lens L5 that has positive refractive power and is concave upward on the paraxial axis. An opening diaphragm 1 (effective diameter) may be installed in front of the.

In addition, between the fifth lens L5 and the image surface 14, an optical filter OF including an infrared filter or a cover glass coated with an infrared filter for blocking excessive infrared rays in the light passing through the optical system is provided. Can be.

The ultra-small imaging optical system according to the present invention places the diaphragm 1 in front of the first lens L1 so as to easily secure the amount of light, and at the same time, the light that can be introduced through the first lens L1 can be blocked as much as possible. By making it possible, it is possible to configure an ultra-compact optical system while using five lenses.

In addition, the third lens (L3) by applying a plastic lens of the flint series to minimize the spherical aberration and chromatic aberration to satisfy a high level of resolution.

On the other hand, the first lens (L1) to the fifth lens (L5) can be made to correct the various aberration by forming the refractive surface of each lens as an aspherical surface, it is possible to improve the design freedom of the lens.

Accordingly, the optical system for a camera of the present invention includes the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5, respectively. , The negative and positive refractive power is arranged and the refractive surface of each lens is an aspherical surface which is easy to mold, thereby improving the resolution of the optical system, and improving the astigmatism and distortion characteristics, while simultaneously setting the aperture 1 to the front of the first lens. In order to reduce the size of the first lens (L1) it is possible to form a compact optical system.

The operation and effect of the following Conditional Expressions 1 to 3 under the optical system of the present invention having such a configuration will be described in detail.

[Condition 1] TL / F <1.5

Here, TL: distance from the object-side surface of the first lens to the image surface,

F: Effective focal length of the whole optical system.

Conditional Expression 1 is a condition for defining the full length of the entire optical system.

 [Condition 2] 0.4 <F1 / F <1.2

Where F1 is the effective focal length of the first lens,

F: Effective focal length of the whole optical system.

Conditional Expression 2 defines the optical axis direction dimension of the entire optical system and is a condition for miniaturization of the optical system.

That is, if the deviation from the lower limit of Condition 2, the optical power of the first lens is too large to correct the spherical aberration. If the deviation from the upper limit of the Conditional Expression 2 may be advantageous in terms of correction of the spherical aberration, the optical axis direction of the optical system may be advantageous. As the overall length becomes longer, it is contrary to the viewpoint of miniaturization, which is a technical feature of the ultra-small imaging optical system mainly employed in portable terminals.

[Condition 3] | Vd2-Vd3 | <35

Where Vd2 is the Abbe's number of the second lens,

Vd3: Abbe's number of the third lens.

Conditional Expression 3 is a condition for chromatic aberration of the optical system. When the upper limit of the conditional expression 3 is out of the range, the focusing position for each wavelength becomes different, and a phenomenon in which the color of the captured image is blurred occurs.

Hereinafter, the optical system of the present invention will be described in more detail through specific numerical examples.

As described above, the first to fourth embodiments below have a first lens L1 having a positive refractive power in order from the object side, a convex form on the object side, a positive refractive power, and a concave shape on the object side. The second lens L2 having a negative refractive power and concave toward the object side, the fourth lens L4 having a negative refractive power and having a meniscus shape convex upward on the paraxial axis, positive It includes a fifth lens (L5) having a refractive power of the concave toward the image, and the aperture stop 1 is provided in front of the first lens (L1). In addition, an optical filter OF including an infrared filter or a cover glass coated with an infrared filter is provided between the fifth lens L5 and the image surface 14.

On the other hand, the aspherical surface used in each following example is obtained from well-known Formula (1).

Where Z is the distance from the vertex of the lens to the optical axis direction

Y: Distance in the direction perpendicular to the optical axis

c: Inverse of the radius of curvature r at the vertex of the lens

K: conic constant

A, B, C, D, E, F: Aspherical Coefficient

First Example

Table 1 below shows numerical examples according to the first embodiment of the present invention.

In addition, Figure 1 is a lens configuration showing the lens arrangement of the scientific system for the camera according to the first embodiment of the present invention, Figure 2 is a view showing an MTF graph according to the first embodiment of the present invention, Figure 3a to Figure 3c is a diagram showing spherical aberration, astigmatism, and distortion aberration of the optical system shown in Table 1, Table 2, and FIG. 1, respectively.

In addition, MTF (Modulation Transfer Function) graph is a graph showing the resolution of the optical system. AXIS represents the resolution measured at the center of the camera sensor, and the closer to 1.0 Field, the resolution measured at the outside of the sensor. In addition, the MTF graph may have curvature values, aspherical values, and apertures of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5. It can be changed depending on the thickness and position of the.

In the case of the first embodiment, the distance TL from the object-side surface 2 to the image surface of the first lens L1 is 6.428 mm, and the effective focal length F of the entire optical system is 4.850 mm. In addition, all of the first to fifth lenses L1 to L5 are made of plastic lenses.

Bending Radius (R) Thickness or distance (t) Refractive index (n) Abbe's (v) Remarks One ∞ 0.0300 2 3.0936 0.6000 1.54 56 First Lens 3 -6.1111 0.1858 4 -8.2614 0.4000 1.54 56second lens 5 -2.9080 0.1000 6 -2.9832 0.6000 1.61 26third lens 7 39.3832 0.8644 8 -1.3027 0.6000 1.54 56 Fourth Lens 9 -1.5149 0.1000 10 2.1218 1.3000 1.54 56th Fifth Lens 11 1.7900 0.4428 12 ∞ 0.3000 1.52 64 Optical Filter 13 ∞ 0.9061

In addition, the values of the aspherical coefficients of the first embodiment according to Equation 1 are shown in Table 2 below.

Cotton number K A B C D E F 2 0.0000 -0.02822 -0.00994 -0.04085 0.03700 -0.03006 0.00000 3 23.73738 -0.02721 -0.01740 -0.02963 0.02315 -0.01008 0.00000 4 40.70522 -0.01323 -0.00182 -0.02699 0.02413 -0.00212 0.00000 5 -1.07459 -0.01217 0.00501 -0.01753 0.01957 -0.00542 0.00000 6 0.00000 0.02344 -0.01890 0.00950 0.00489 -0.00207 0.00000 7 0.00000 0.03488 -0.02557 0.00889 -0.00246 0.00009 0.00000 8 -6.00677 -0.09968 0.05251 -0.02136 0.00871 -0.00180 0.00000 9 -0.59250 -0.02760 0.04271 -0.01665 0.00635 -0.00068 0.00000 10 -10.41333 -0.06277 0.02468 -0.00608 0.00067 -0.00003 0.00000 11 -4.21491 -0.05498 0.01578 -0.00323 0.00032 -0.00001 0.00000

2nd Example

Table 3 below shows a numerical example according to the second embodiment of the present invention.

In addition, Figure 4 is a lens configuration showing the lens arrangement of the scientific system for the camera according to the second embodiment of the present invention, Figure 5 is a view showing an MTF graph according to a second embodiment of the present invention, Figure 6a to Figure 6C is a diagram showing spherical aberration, astigmatism, and distortion aberration of the optical system shown in Tables 3, 4, and 4, respectively.

In the case of the second embodiment, the distance TL from the object-side surface 2 to the image surface of the first lens L1 is 6.351 mm, and the effective focal length F of the entire optical system is 4.870 mm. In addition, all of the first to fifth lenses L1 to L5 are made of plastic lenses.

Cotton number Bending Radius (R) Thickness or distance (t) Refractive index (n) Abbe's (v) Remarks One ∞ 0.0300 2 3.1730 0.5800 1.53 56 First lens 3 -5.6189 0.1745 4 -7.4955 0.4300 1.53 56 Second lens 5 -2.7765 0.1000 6 -2.8791 0.6900 1.61 26 Third lens 7 100.0000 0.8194 8 -1.1564 0.5000 1.53 56 Fourth lens 9 -1.3426 0.1000 10 2.0955 1.2000 1.53 56 Fifth lens 11 1.7494 0.4429 12 ∞ 0.3000 1.52 64 Optical filter 13 ∞ 0.9856

In addition, the values of the aspherical coefficients of the second embodiment according to Equation 1 are shown in Table 4 below.

Cotton number K A B C D E F 2 0.0000 -0.03485 -0.01410 -0.04194 0.03307 -0.02831 0.00000 3 20.39808 -0.03979 -0.01167 -0.03009 0.02358 -0.00917 0.00000 4 38.23877 -0.01858 0.00700 -0.02253 0.02207 -0.00015 0.00000 5 -0.77818 -0.01395 0.00042 -0.01320 0.01869 -0.00745 0.00000 6 0.00000 0.01577 -0.01694 0.01191 0.00705 -0.00547 0.00000 7 0.00000 0.02642 -0.02130 0.01129 -0.00433 0.00055 0.00000 8 -5.2759 -0.12433 0.05327 -0.02070 0.00891 -0.00060 0.00000 9 -0.64456 -0.01657 0.03580 -0.01690 0.00810 -0.00063 0.00000 10 -12.18704 -0.07067 0.02744 -0.00738 0.00085 -0.00005 0.00000 11 -5.27211 -0.05280 0.01522 -0.00341 0.00038 -0.00002 0.00000

The third Example

Table 5 below shows a numerical example according to the third embodiment of the present invention.

7 is a lens configuration diagram showing a lens arrangement of a scientific system for a camera according to a third embodiment of the present invention, FIG. 8 is a view showing an MTF graph according to a third embodiment of the present invention, and FIGS. 9A to 9. 9c is a diagram showing spherical aberration, astigmatism, and distortion aberration of the optical system shown in Tables 5, 6, and 7, respectively.

In the third embodiment, the distance TL from the object-side surface 2 to the image surface of the first lens L1 is 6.332 mm, and the effective focal length F of the entire optical system is 4.869 mm. In addition, all of the first to fifth lenses L1 to L5 are made of plastic lenses.

Cotton number Bending Radius (R) Thickness or distance (t) Refractive index (n) Abbe's (v) Remarks One ∞ 0.0300 2 3.2502 0.5700 1.53 56 First lens 3 -5.6755 0.1488 4 -7.5955 0.4500 1.53 56 Second lens 5 -2.6951 0.1000 6 -2.9334 0.6000 1.61 26 Third lens 7 100.0000 0.9131 8 -1.1277 0.5000 1.53 56 Fourth lens 9 -1.3071 0.1000 10 2.1532 1.2000 1.53 56 Fifth lens 11 1.7592 0.4429 12 ∞ 0.3000 1.52 64 Optical filter 13 ∞ 0.9780

In addition, the values of the aspherical coefficients of the second embodiment according to Equation 1 are shown in Table 4 below.

Cotton number K A B C D E F 2 0.00000 -0.03718 -0.01439 -0.04173 0.03130 -0.02610 0.00000 3 19.66174 -0.04419 -0.00960 -0.02995 0.02310 -0.00924 0.00000 4 38.99464 -0.01957 0.00880 -0.02134 0.02054 -0.00134 0.00000 5 -0.60541 -0.01510 -0.00090 -0.01281 0.01879 -0.00854 0.00000 6 0.00000 0.01168 -0.01778 0.01306 0.00777 -0.00619 0.00000 7 0.00000 0.02186 -0.02092 0.01208 -0.00487 0.00060 0.00000 8 -4.89562 -0.13483 0.05348 -0.02037 0.00877 -0.00047 0.00000 9 -0.64856 -0.01376 0.03385 -0.01695 0.00850 -0.00071 0.00000 10 -12.60294 -0.06909 0.02724 -0.00783 0.00105 -0.00008 0.00000 11 -5.45385 -0.05125 0.01466 -0.00332 0.00037 -0.00002 0.00000

Fourth Example

Table 7 below shows a numerical example according to the fourth embodiment of the present invention.

10 is a lens configuration diagram showing the lens arrangement of the scientific system for the camera according to the fourth embodiment of the present invention, FIG. 11 is a view showing an MTF graph according to the fourth embodiment of the present invention, and FIGS. 12c is a diagram showing spherical aberration, astigmatism, and distortion aberration of the optical system shown in Table 7, Table 8, and FIG. 10, respectively.

In the case of the fourth embodiment, the distance TL from the object-side surface 2 to the image surface of the first lens L1 is 6.4352 mm, and the effective focal length F of the entire optical system is 4.880 mm. In addition, all of the first to fifth lenses L1 to L5 are made of plastic lenses.

Cotton number Bending Radius (R) Thickness or distance (t) Refractive index (n) Abbe's (v) Remarks One ∞ 0.0300 2 3.3216 0.5700 1.53 56 First lens 3 -5.7462 0.2080 4 -7.6813 0.4500 1.53 56 Second lens 5 -2.6406 0.1000 6 -2.5304 0.6000 1.61 26 Third lens 7 -18.0721 0.9402 8 -1.1071 0.5000 1.53 56 Fourth lens 9 -1.2848 0.1000 10 2.1076 1.2400 1.53 56 Fifth lens 11 1.7438 0.4429 12 ∞ 0.3000 1.52 64 Optical filter 13 ∞ 0.9539

In addition, the values of the aspherical coefficients of the second embodiment according to Equation 1 are shown in Table 4 below.

Cotton number K A B C D E F 2 0.00000 -0.03881 -0.01583 -0.04165 0.02991 -0.02574 0.00000 3 19.75229 -0.05089 -0.00934 -0.02912 0.02332 -0.01011 0.00000 4 38.96265 -0.02180 0.01229 -0.01787 0.02047 -0.00062 0.00000 5 -0.58238 -0.01517 0.00095 -0.01110 0.02025 -0.00774 0.00000 6 0.00000 0.00918 -0.01804 0.01529 0.00928 -0.00684 0.00000 7 0.00000 0.01607 -0.02086 0.01377 -0.00572 0.00097 0.00000 8 -4.65920 -0.14586 0.05495 -0.01992 0.00828 -0.00046 0.00000 9 -0.63735 -0.01179 0.03318 -0.01647 0.00876 -0.00103 0.00000 10 -11.73911 -0.05660 0.02573 -0.00804 0.00123 -0.00009 0.00000 11 -5.31363 -0.04684 0.01409 -0.00312 0.00033 -0.00001 0.00000

In addition, the distance TL from the object-side surface 2 of the first lens L1 to the image surface according to each embodiment, the effective focal length F of the entire optical system, and the effective focal length of the first lens L1 ( F1) may be represented as shown in Table 9 below, and the calculation results using Conditional Expressions 1 to 3 may also be shown as Table 9 below.

First embodiment Second Embodiment Third embodiment Fourth Embodiment TL 6.428 6.351 6.332 6.435 F 4.850 4.870 4.869 4.880 F1 3.847 3.799 3.869 3.939 Vd2 56 56 56 56 Vd3 26 26 26 26 TL / F 1.325 1.304 1.300 1.319 F1 / F 0.793 0.780 0.795 0.807 | Vd2-Vd3 | 30 30 30 30

As shown in Table 9 above, it can be seen that the first to fourth embodiments of the present invention satisfy conditional expressions 1 to 3.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It is to be understood that various modifications and changes may be made without departing from the scope of the appended claims.

L1: first lens L2: second lens
L3: third lens L4: fourth lens
L5: fifth lens OF: optical filter
1: aperture
2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13: face number

Claims (7)

A first lens having positive refractive power and convex toward the object;
A second lens having positive refractive power and concave toward the object side;
A third lens having negative refractive power and concave toward the object side;
A fourth lens having a negative refractive power and shaped like a meniscus convex toward the image side on the paraxial axis; And
A fifth lens having positive refractive power and concave toward the image;
Miniature imaging optical system comprising a.
The method of claim 1,
The optical system,
An ultra-small imaging optical system that satisfies the following conditional expression with respect to the optical axis direction.
[Condition Expression] TL / F <1.5
Here, TL: distance from the object-side surface of the first lens to the image surface
F: effective focal length of the whole optical system
The method of claim 1,
The optical system,
An ultra-small imaging optical system that satisfies the following conditional expression with respect to the optical axis direction.
Conditional Expression 0.4 <F1 / F <1.2
Here, F1: effective focal length of the first lens
F: effective focal length of the whole optical system
The method of claim 1,
The optical system,
An ultra-small imaging optical system that satisfies the following conditional expression regarding the Abbe's number of the second lens and the third lens.
Conditional Expression | Vd2-Vd3 | <35
Where Vd2 is the Abbe's number of the second lens
Vd3: Abbe's number of the third lens
The method of claim 1,
The first to fifth lenses,
Ultra-compact optical system with both sides composed of aspherical surface.
The method of claim 1,
The first to fifth lenses,
Ultra-small imaging optics composed of plastic lenses.
The method of claim 1,
The third lens,
Ultra-compact optical system composed of flint-type lenses.

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