KR20160076341A - Lens optical system - Google Patents

Abstract

A lens optical system is disclosed. The lens optical system of the present invention includes a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged from the object side to the sensor side between an object and a sensor that forms an image of the object, Wherein the object side of the first lens is convex to the object side and the second lens has a negative refractive power and the object side surface of the second lens is at least flat in the vicinity of the optical axis, Wherein the fourth lens has a convex meniscus shape on the sensor side, the fourth lens has a negative refractive power, the sensor side surface of the fourth lens is concave toward the sensor side, has at least one inflection point, satisfies the following conditional expression do.
<Conditional expression>
1.0 < f2 / f | < 3.0
Here, f2 represents the focal length of the second lens, and f represents the focal length of the lens optical system.

Description

Lens optical system

The present invention relates to a lens optical system, and more particularly, to a lens optical system that can be mounted on a camera module for image capture.

The camera module for imaging includes a lens optical system including at least one lens and an image sensor that receives light that has passed through the lens optical system and converts the light into an electric signal. Solid-state image sensors such as a charge coupled device (CCD) or a complimentary metal oxide semiconductor image sensor (CMOS image sensor) are widely used as image sensors.

Recent camera modules are widely employed in electronic devices such as smart phones, tablet computers, and lab-top computers. Such an electronic device tends to be miniaturized and thinned in order to improve convenience and aesthetics of the user. In addition, the conventional camera device is also gradually becoming smaller and thinner. Accordingly, a camera module mounted on such an electronic device is also required to be miniaturized, and a form having a small thickness is required.

In recent camera modules, a lens having a wide angle of view is required so that more information can be photographed by one shot. However, it is difficult to design a lens that has a wide angle of view and can be used in combination with a high-resolution image sensor and has excellent optical performance such as aberration and distortion.

Therefore, it is required to develop a high-performance lens optical system that can be used in combination with a high-resolution image sensor with a small size and a wide angle of view.

An object of the present invention is to provide a high-performance lens optical system that can be used in combination with a high-resolution image sensor with a small size and a wide angle of view.

A lens optical system according to the present invention for solving the above-mentioned problems is characterized by comprising a first lens, a second lens, a third lens, and a fourth lens arranged sequentially from the object side to the sensor side between an object and a sensor, Wherein the first lens has a positive refractive power, the object side of the first lens is convex to the object side, the second lens has a negative refractive power, and the object side of the second lens has at least a plane Wherein the third lens has a positive refractive power and has a convex meniscus shape toward the sensor side, the fourth lens has a negative refractive power, and the sensor side surface of the fourth lens is concave toward the sensor side and has at least one inflection point And satisfies the following conditional expression.

<Conditional expression>

1.0 < f2 / f | < 3.0

Here, f2 represents the focal length of the second lens, and f represents the focal length of the lens optical system.

In one embodiment of the present invention, the sensor side surface of the first lens is convex to the sensor side, and the sensor side surface of the second lens is concave toward the sensor side.

In an embodiment of the present invention, the object side surface of the fourth lens is convex from the object side to the object side near the optical axis, and may have at least one inflection point.

In one embodiment of the present invention, the object side of the second lens may be planar in the effective plane.

In one embodiment of the present invention, the object side of the second lens may be planar.

In one embodiment of the present invention, all surfaces except the object side of the second lens may be aspherical.

In one embodiment of the present invention, the imaging apparatus may further include a diaphragm located between the object side surfaces of the first lens.

In one embodiment of the present invention, the following conditional expression can be further satisfied.

<Conditional expression>

0.75 < SL / TTL < 1.25

SL denotes a distance on the optical axis between the diaphragm and the sensor, and TTL denotes a distance on the optical axis between the object side surface of the first lens and the sensor.

In one embodiment of the present invention, the following conditional expression can be further satisfied.

<Conditional expression>

1.0 <tan (?) / F <4.0

Here,? Represents the angle of view of the lens optical system, and f represents the focal length of the lens optical system.

In one embodiment of the present invention, the following conditional expression can be further satisfied.

<Conditional expression>

50 < (V3 + V4) / 2 < 60

Here, V3 represents Abbe number of the third lens, and V4 represents Abbe number of the fourth lens.

In one embodiment of the present invention, the following conditional expression can be further satisfied.

<Conditional expression>

30deg <CRA <35deg

Here, CRA

In one embodiment of the present invention, the following conditional expression can be further satisfied.

<Conditional expression>

2.0 <TTL / BFL <4.0

Here, TTL represents the distance on the optical axis between the object side surface of the first lens and the sensor, and BFL represents the distance on the optical axis between the sensor side surface of the fourth lens and the sensor.

The lens optical system according to an embodiment of the present invention is a high performance lens optical system that can be used in combination with a high resolution image sensor while being small and having wide angle of view.

The lens optical system according to an embodiment of the present invention is advantageous in that the entire length of the lens optical system is short because the distance between the sensor side surface of the last lens and the sensor is relatively short and the camera module can be miniaturized as a result.

One embodiment of the present invention is advantageous in that the spherical aberration and the coma aberration are maintained at a certain level or less while the angle of view is wider than the focal length of the lens optical system.

1 is a lens configuration diagram of a lens optical system of a first embodiment according to an embodiment of the present invention.
2 is a lens configuration diagram of a lens optical system of a second embodiment according to an embodiment of the present invention.
3 is a lens configuration diagram of a lens optical system according to the third embodiment of the present invention.
4 is a lens configuration diagram of a lens optical system of a fourth embodiment according to an embodiment of the present invention.
Fig. 5 sequentially shows spherical aberration, astigmatism, and distortion aberration of the lens optical system of the first embodiment shown in Fig.
Fig. 6 sequentially shows spherical aberration, astigmatism, and distortion aberration of the lens optical system of the second embodiment shown in Fig.
Fig. 7 sequentially shows spherical aberration, astigmatism, and distortion aberration of the lens optical system of the third embodiment shown in Fig.
Fig. 8 sequentially shows spherical aberration, astigmatism, and distortion aberration of the lens optical system of the fourth embodiment shown in Fig.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, if it is judged that it is possible to make the gist of the present invention obscure by adding a detailed description of a technique or configuration already known in the field, it is omitted from the detailed description. In addition, terms used in the present specification are terms used to appropriately express embodiments of the present invention, which may vary depending on the person or custom in the field. Therefore, the definitions of these terms should be based on the contents throughout this specification.

Hereinafter, a lens optical system according to an embodiment of the present invention will be described with reference to FIGS. 1 to 5 attached hereto.

1 to 4 are lens configuration diagrams for a lens optical system according to the first to fourth embodiments of the present invention, respectively.

1 to 4, a lens optical system according to embodiments of the present invention includes a first lens L1, a second lens L2, and a third lens L3 between an object corresponding to a subject of a lens optical system and a sensor IS, (L2), a third lens (L3), and a fourth lens (L4). The first through fourth lenses L1, L2, L3, and L4 are sequentially arranged from the object side to the sensor side.

Each lens has opposite surfaces facing each other. In one lens, the surface facing the object side corresponds to the incident surface, which is the surface through which the light enters the lens. Further, in one lens, the surface facing the sensor corresponds to the exit surface, which is the surface from which the light is emitted from the lens. In the present specification, the object side surface of the n-th lens and the incident surface are denoted by Sn1, and the sensor side surface and the emitting surface are denoted by Sn2. Therefore, the object side surface and the incident surface of the first lens L1 are denoted by S11, and the sensor side surface and the emitting surface are denoted by S12. The object side surface and incident surface of the second lens L2 are represented by S21, and the sensor side surface and the emitting surface are represented by S22. The object side surface and incident surface of the third lens L3 are represented by S31, and the sensor side surface and the emitting surface are represented by S32. The object side surface and incident surface of the fourth lens L4 are represented by S41, and the sensor side surface and the emitting surface are represented by S42.

The first lens L1 has a positive refractive power. In the first lens L1, S11 is convex toward the object side, and S12 is convex toward the sensor side. S11 and S12 may all be aspherical. The first lens L1 may be formed of a plastic material.

The second lens L2 has a negative refracting power. In the second lens L2, S21 is at least flat in the vicinity of the optical axis, and S22 is concave toward the sensor side. S21 may be a plane in the vicinity of the optical axis as well as within the effective diameter of the optical lens system. Further, S21 may be formed as a whole plane. S22 may be formed as an aspherical surface. The second lens L2 may be formed of a plastic material.

The third lens L3 has a positive refractive power. The third lens L3 has a convex meniscus shape toward the sensor side. Specifically, in the third lens L3, S31 is concave toward the object side, and S32 is convex toward the sensor side. S31 and S32 may all be aspherical. The third lens L3 may be formed of a plastic material.

The fourth lens L4 has a negative refracting power. In the fourth lens L4, S41 is convex toward the object side in the vicinity of the optical axis, and S42 is convex toward the sensor side in the vicinity of the optical axis. S41 and S42 may all be aspherical. Specifically, S41 may include a convex portion toward the object side in the vicinity of the optical axis, and a concave portion toward the periphery of the lens in the vicinity of the optical axis. S41 may include at least one inflection point. S42 may include a concave portion toward the sensor side in the vicinity of the optical axis and a convex portion toward the periphery of the lens in the vicinity of the optical axis. S42 may include at least one inflection point.

Referring to Figs. 1 to 4, the lens optical system may include a diaphragm S.

The diaphragm S may be located on the object side of the first lens L1 or may be located across the first lens L1. Specifically, the diaphragm S may be positioned over the object side surface of the first lens L1. The diaphragm S can block a part of light and adjust the amount of light irradiated into the lens optical system.

The lens optical system may include an optical filter (OF). The optical filter OF may be positioned between the fourth lens L4 and the sensor IS. The optical filter (OF) can block light in a band other than visible light. Specifically, the optical filter (OF) can block the light in the infrared band.

The sensor IS may be an image sensor that receives the light passing through the lens and converts it into an electric signal. It is preferable that the sensor IS is located on the rear surface of the fourth lens L4 so that the light passing through the first through fourth lenses L4 is formed on the object side surface of the sensor.

The lens optical system according to the embodiments of the present invention having the above configuration can satisfy the following conditional expression.

<Conditional Expression 1>

1.0 < f2 / f | < 3.0

Here, f2 represents the focal length of the second lens L2, and f represents the focal length of the lens optical system.

Conditional expression 1 is a conditional expression for limiting the focal length of the second lens L2 with respect to the entire focal length of the lens optical system. When the focal length of the second lens L2 satisfies the above-described condition with respect to the focal length of the lens optical system, the angle of view of the lens optical system can be increased.

<Conditional expression 2>

0.75 < SL / TTL < 1.25

SL denotes a distance on the optical axis between the diaphragm S and the sensor IS and TTL denotes a distance on the optical axis between the object side surface of the first lens L1 and the sensor IS.

Conditional expression 2 is a conditional expression for limiting the position of the diaphragm in the lens optical system. When the SL / TTL is smaller than the lower limit value (0.75) in the conditional expression (2), the diaphragm is positioned on the sensor side with respect to the first lens (L1). When the SL / TTL is greater than the upper limit value (1.25) in the conditional expression (2), the diaphragm is positioned on the object side with respect to the first lens L1. As shown in Figs. 1 to 4, the SL / TTL must satisfy the above condition in the conditional expression 2 in order that the diaphragm S is placed over the object side of the first lens L1.

<Conditional expression 3>

1.0 <tan (?) / F <4.0

Here,? Represents the angle of view of the lens optical system, and f represents the focal length of the lens optical system.

Conditional expression 3 is a conditional expression that defines the angle of view in the lens optical system. If tan (&amp;thetas;) / f is smaller than the lower limit value (1.0) in conditional expression (3), the angle of view is too small to realize an optical lens system. On the other hand, if tan (?) / F is larger than the upper limit value (4.0) in conditional expression 3, the angle of view can be increased to realize a wide-angle lens optical system. However, since spherical aberration and coma aberration become large, .

<Conditional expression 4>

50 < (V3 + V4) / 2 < 60

Here, V3 represents the Abbe number of the third lens L3, and V4 represents Abbe number of the fourth lens L4.

The conditional expression (4) is a conditional expression for limiting the optical characteristics of the material forming the third lens L3 and the fourth lens L4. (V3 + V4) / 2 in Conditional Expression 4 means the average of the Abbe numbers of the third lens L3 and the fourth lens L4. The third lens L3 and the fourth lens L4 may be made of a plastic resin material having Abbe number of 50 or more. For example, the third lens L3 and the fourth lens L4 may be made of Z-E48R having Abbe number of 55.8559 or APEL-5514ML having Abbe number of 56.0928.

In the case where the third lens L3 and the fourth lens L4 are formed of a plastic material satisfying the above conditions, manufacturing cost can be lowered compared with a glass lens having similar characteristics, The range can be increased.

<Conditional expression 5>

30deg <CRA <35deg

Here, CRA represents the maximum value of the angle at which the principal ray is incident on the sensor.

Conditional expression 5 is a conditional expression that defines the sensor incident angle of the principal ray. By limiting the CRA, it becomes possible to design a lens having a sufficiently large angle of view and a small back focus length (BFL).

<Conditional Expression 6>

2.0 <TTL / BFL <4.0

Herein, TTL denotes a distance on the optical axis between the object side surface of the first lens L1 and the sensor IS, and BFL denotes a distance on the optical axis between the sensor side surface of the fourth lens L4 and the sensor IS Represents the distance.

Conditional expression 6 is a conditional expression for limiting the total length of the lens optical system to a certain level or less. In the case of lens optics with a relatively short total length, the distance between the sensor side of the last lens and the sensor surface tends to decrease. In the lens optical system shown in Figs. 1 to 4, TTL / BFL in the conditional expression (6) is preferably close to the upper limit value (4.0). As the TTL / BFL increases in the lens optical system, the total length can be shortened.

Hereinafter, a first embodiment of the present invention will be described with reference to Figs. 1 and 5. Fig.

The following is a table relating to the optical data of the lens optical system of the first embodiment shown in Fig. The table below shows the curvature radius r of each lens constituting the lens optical system, the lens thickness and the distance d between the lenses, the refractive index N _d , the focal length f, the Abbe number V _d , Focal length, Fno, total length (TTL), and angle of view (FOV).

Component r d N _d f V _d iris ∞ -0.0300 The first lens S11 * 1.7513 0.5185 1.5465 1.7929 56.0928 S12 * -1.9915 0.0500 The second lens S21 ∞ 0.2100 1.6483 -3.1769 22.4336 S22 * 2.0596 0.2753 Third lens S31 * -1.2890 0.4475 1.5340 2.1495 55.8559 S32 * -0.6806 0.0500 The fourth lens S41 * 0.8211 0.3000 1.5340 -3.2077 55.8559 S42 * 0.4845 0.2600 Focal Length (F) 2.0902 Fno 2.4600 CRA 32.00 TTL (First lens ~ Image) 2.9213 FOV 81.40

In the above table, * indicates that the lens surface is aspherical. And the distance unit of r, d and f is mm.

The aspherical surface of the lens surface of the lens optical system of the first embodiment shown in Fig. 1 satisfies the aspherical surface equation of the following equation.

&Lt; Equation &

Where z is the distance from the apex of the lens in the direction of the optical axis and y is the distance in the direction perpendicular to the optical axis. R is the radius of curvature at the apex of the lens, and K is the conic constant. In addition, A ₂ to A ₁₂ represent aspheric coefficients.

The following is a table concerning the aspherical surface coefficients of the aspherical surface of the lens surface of the lens optical system of the first embodiment shown in Fig.

K A ₂ A ₄ A ₆ A ₈ A ₁₀ A ₁₂ S11 -0.9833 -0.0615 -1.0468 5.0643 -12.6012 0.0000 0.0000 S12 0.0000 -0.1036 0.6071 -2.8522 2.3204 0.0000 0.0000 S21 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 S22 2.3658 0.0704 -0.6023 1.0998 -1.2101 0.0000 0.0000 S31 0.9468 0.8931 -2.3925 5.0552 -3.8551 0.0000 0.0000 S32 -4.6674 -0.7543 1.9891 -4.4826 6.7720 -3.2363 0.0000 S41 -2.9573 -0.8301 0.7180 -0.3402 0.0907 -0.0099 0.0000 S42 -3.2486 -0.5007 0.4898 -0.3610 0.1702 -0.0448 0.0004

The following is a table summarizing the values of the conditional expressions 1 to 6 in the lens optical system of the first embodiment shown in Fig.

Conditional expression Target value The target value in the first embodiment Conditional expression 1 1.0 < f2 / f | < 3.0 | f2 / f | 1.5199 Conditional expression 2 0.75 < SL / TTL < 1.25 SL / TTL 0.9897 Conditional expression 3 1.0 <tan (?) / F <4.0 tan (?) / f 3.1634 Conditional expression 4 50 < (V3 + V4) / 2 < 60 (V3 + V4) / 2 55.8559 Conditional expression 5 30deg <CRA <35deg CRA 32.00 Conditional expression 6 2.0 <TTL / BFL <4.0 TTL / BFL 3.6066

As shown in the table, it can be seen that the objective values of the conditional expressions 1 to 6 of the lens optical system of the first embodiment are consistent with the conditional expressions 1 to 6. [

Fig. 5 sequentially shows spherical aberration, astigmatism, and distortion aberration of the lens optical system of the first embodiment shown in Fig. The wavelengths used to measure spherical aberration are 435.8 nm, 486.1 nm, 546.1 nm 587.6 nm and 656.3 nm. The wavelength measured to measure astigmatism and distortion is 546.1 nm.

Hereinafter, a second embodiment of the present invention will be described with reference to Figs. 2 and 6. Fig.

The following is a table relating to the optical data of the lens optical system of the second embodiment shown in Fig. The table below shows the curvature radius r of each lens constituting the lens optical system, the lens thickness and the distance d between the lenses, the refractive index N _d , the focal length f, the Abbe number V _d , Focal length, Fno, total length (TTL), and angle of view (FOV).

Component r d N _d f V _d iris ∞ -0.0300 The first lens S11 * 1.7424 0.5255 1.5465 1.7886 56.0928 S12 * -1.9892 0.0500 The second lens S21 ∞ 0.2100 1.6483 -3.1700 22.4336 S22 * 2.0551 0.2780 Third lens S31 * -1.2866 0.4466 1.5340 2.1306 55.8559 S32 * -0.6768 0.0500 The fourth lens S41 * 0.8282 0.3000 1.5340 -3.0897 55.8559 S42 * 0.4819 0.2600 Focal Length (F) 2.1050 Fno 2.4599 CRA 32.00 TTL (First lens ~ Image) 2.9301 FOV 81.00

In the above table, * indicates that the lens surface is aspherical. And the distance unit of r, d and f is mm.

The aspherical surface of the lens surface of the lens optical system of the second embodiment shown in Fig. 2 satisfies the aspherical surface equation of the following equation.

&Lt; Equation &

Where z is the distance from the apex of the lens in the direction of the optical axis and y is the distance in the direction perpendicular to the optical axis. R is the radius of curvature at the apex of the lens, and K is the conic constant. In addition, A ₂ to A ₁₂ represent aspheric coefficients.

The following is a table relating to aspherical surface coefficients of the aspherical surface of the lens surface of the lens optical system of the second embodiment shown in Fig.

K A ₂ A ₄ A ₆ A ₈ A ₁₀ A ₁₂ S11 -0.9448 -0.0606 -1.0440 5.0738 -12.4881 0.0000 0.0000 S12 0.0000 -0.1035 0.6080 -2.8423 2.3398 0.0000 0.0000 S21 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 S22 2.3849 0.0709 -0.6017 1.1004 -1.2104 0.0000 0.0000 S31 0.9517 0.8919 -2.3936 5.0536 -3.8546 0.0000 0.0000 S32 -4.6743 -0.7533 1.9889 -4.4840 6.7695 -3.2392 0.0000 S41 -3.1168 -0.8287 0.7189 -0.3401 0.0907 -0.0099 0.0000 S42 -3.3092 -0.4999 0.4892 -0.3608 0.1703 -0.0449 0.0004

The following is a table summarizing the values of the conditional expressions 1 to 6 in the lens optical system of the second embodiment shown in Fig.

Conditional expression Target value The target value in the first embodiment Conditional expression 1 1.0 < f2 / f | < 3.0 | f2 / f | 1.5059 Conditional expression 2 0.75 < SL / TTL < 1.25 SL / TTL 0.9898 Conditional expression 3 1.0 <tan (?) / F <4.0 tan (?) / f 2.9994 Conditional expression 4 50 < (V3 + V4) / 2 < 60 (V3 + V4) / 2 55.8559 Conditional expression 5 30deg <CRA <35deg CRA 32.00 Conditional expression 6 2.0 <TTL / BFL <4.0 TTL / BFL 3.6174

As shown in the table, it can be seen that the object values of the conditional expressions 1 to 6 of the lens optical system of the second embodiment are consistent with the conditional expressions 1 to 6.

Fig. 6 sequentially shows spherical aberration, astigmatism, and distortion aberration of the lens optical system of the second embodiment shown in Fig. The wavelengths used to measure spherical aberration are 435.8 nm, 486.1 nm, 546.1 nm 587.6 nm and 656.3 nm. The wavelength measured to measure astigmatism and distortion is 546.1 nm.

Hereinafter, a third embodiment of the present invention will be described with reference to Figs. 3 and 7. Fig.

The following is a table relating to the optical data of the lens optical system of the third embodiment shown in Fig. The table below shows the curvature radius r of each lens constituting the lens optical system, the lens thickness and the distance d between the lenses, the refractive index N _d , the focal length f, the Abbe number V _d , Focal length, Fno, total length (TTL), and angle of view (FOV).

Component r d N _d f V _d iris ∞ -0.1000 The first lens S11 * 1.1639 0.5434 1.5459 2.1257 56.0928 S12 * -325.6548 0.0300 The second lens S21 ∞ 0.2100 1.6467 -6.7882 22.4336 S22 * 4.3900 0.3904 Third lens S31 * -1.6356 0.7445 1.5459 1.6021 56.0928 S32 * -0.6615 0.1000 The fourth lens S41 * 74.7256 0.4002 1.5335 -1.4132 55.8559 S42 * 0.7450 0.2800 Focal Length (F) 2.6950 Fno 2.4500 CRA 32.99 TTL (First lens ~ Image) 3.3685 FOV 80.10

In the above table, * indicates that the lens surface is aspherical. And the distance unit of r, d and f is mm.

The aspherical surface of the lens surface of the lens optical system of the third embodiment shown in Fig. 3 satisfies the aspherical surface equation of the following equation.

&Lt; Equation &

Where z is the distance from the apex of the lens in the direction of the optical axis and y is the distance in the direction perpendicular to the optical axis. R is the radius of curvature at the apex of the lens, and K is the conic constant. In addition, A ₂ to A ₁₂ represent aspheric coefficients.

The following is a table concerning the aspherical surface coefficients of the aspherical surface of the lens surface of the lens optical system of the third embodiment shown in Fig.

K A ₂ A ₄ A ₆ A ₈ A ₁₀ A ₁₂ S11 -0.2276 0.0082 -0.4156 1.2662 -2.5911 0.0000 0.0000 S12 0.0000 -0.3362 -0.1419 0.3922 -1.3434 0.0000 0.0000 S21 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 S22 36.9979 0.2949 0.0196 -0.1247 0.2929 0.0000 0.0000 S31 3.9043 0.0242 -0.2828 0.7226 -0.3390 0.0000 0.0000 S32 -4.1881 -0.5316 0.8744 -1.2985 1.1911 -0.4171 0.0000 S41 100.0000 -0.3142 0.2489 -0.0867 0.0149 -0.0011 0.0000 S42 -6.7264 -0.1835 0.1328 -0.0710 0.0230 -0.0044 0.0004

The following is a table summarizing the values of the conditional expressions 1 to 6 in the lens optical system of the third embodiment shown in Fig.

Conditional expression Target value The target value in the first embodiment Conditional expression 1 1.0 < f2 / f | < 3.0 | f2 / f | 2.5188 Conditional expression 2 0.75 < SL / TTL < 1.25 SL / TTL 0.9703 Conditional expression 3 1.0 <tan (?) / F <4.0 tan (?) / f 2.1187 Conditional expression 4 50 < (V3 + V4) / 2 < 60 (V3 + V4) / 2 55.9743 Conditional expression 5 30deg <CRA <35deg CRA 32.99 Conditional expression 6 2.0 <TTL / BFL <4.0 TTL / BFL 5.0276

As shown in the table, it can be seen that the objective values of the conditional expressions 1 to 6 of the lens optical system of the third embodiment are consistent with the conditional expressions 1 to 6. [

Fig. 7 sequentially shows spherical aberration, astigmatism, and distortion aberration of the lens optical system of the third embodiment shown in Fig. The wavelengths used to measure spherical aberration are 435.8 nm, 486.1 nm, 546.1 nm 587.6 nm and 656.3 nm. The wavelength measured to measure astigmatism and distortion is 546.1 nm.

Hereinafter, a fourth embodiment of the present invention will be described with reference to Figs. 4 and 8. Fig.

The following is a table relating to the optical data of the lens optical system of the fourth embodiment shown in Fig. The table below shows the curvature radius r of each lens constituting the lens optical system, the lens thickness and the distance d between the lenses, the refractive index N _d , the focal length f, the Abbe number V _d , Focal length, Fno, total length (TTL), and angle of view (FOV).

Component r d N _d f V _d iris ∞ 0.0000 The first lens S11 * 1.2500 0.5472 1.5465 2.1264 56.0928 S12 * -13.9632 0.0500 The second lens S21 ∞ 0.2100 1.6483 -5.2744 22.4336 S22 * 3.4194 0.4116 Third lens S31 * -1.5154 0.7711 1.5465 1.4751 56.0928 S32 * -0.6208 0.0500 The fourth lens S41 * 6.1300 0.4000 1.5340 -1.4279 55.8559 S42 * 0.6627 0.2800 Focal Length (F) 2.8362 Fno 2.4500 CRA 32.55 TTL (First lens ~ Image) 3.5700 FOV 77.50

In the above table, * indicates that the lens surface is aspherical. And the distance unit of r, d and f is mm.

The aspherical surface of the lens surface of the lens optical system of the fourth embodiment shown in Fig. 4 satisfies the aspherical surface equation of the following equation.

&Lt; Equation &

Where z is the distance from the apex of the lens in the direction of the optical axis and y is the distance in the direction perpendicular to the optical axis. R is the radius of curvature at the apex of the lens, and K is the conic constant. In addition, A ₂ to A ₁₂ represent aspheric coefficients.

The following is a table concerning the aspherical surface coefficients of the aspherical surface of the lens surface of the lens optical system of the fourth embodiment shown in Fig.

K A ₂ A ₄ A ₆ A ₈ A ₁₀ A ₁₂ S11 -0.2891 -0.0016 -0.3551 0.9097 -1.8725 0.0000 0.0000 S12 0.0000 -0.2860 -0.1128 0.2146 -0.7885 0.0000 0.0000 S21 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 S22 18.9232 0.2281 0.0185 0.0538 -0.2309 0.0000 0.0000 S31 2.9220 0.0487 -0.0885 0.3806 0.3187 0.0000 0.0000 S32 -4.0589 -0.4527 0.7194 -1.0143 0.9665 -0.3635 0.0000 S41 -4.4608 -0.2463 0.2045 -0.0803 0.0162 -0.0014 0.0000 S42 -6.3136 -0.1615 0.1224 -0.0682 0.0239 -0.0046 0.0003

The following is a table summarizing the values of the conditional expressions 1 to 6 in the lens optical system of the fourth embodiment shown in FIG.

Conditional expression Target value The target value in the first embodiment Conditional expression 1 1.0 < f2 / f | < 3.0 | f2 / f | 1.8597 Conditional expression 2 0.75 < SL / TTL < 1.25 SL / TTL 1.0000 Conditional expression 3 1.0 <tan (?) / F <4.0 tan (?) / f 1.5919 Conditional expression 4 50 < (V3 + V4) / 2 < 60 (V3 + V4) / 2 55.9743 Conditional expression 5 30deg <CRA <35deg CRA 32.55 Conditional expression 6 2.0 <TTL / BFL <4.0 TTL / BFL 4.2000

As shown in the table, it can be seen that the object values of the conditional expressions 1 to 6 of the lens optical system of the fourth embodiment are consistent with the conditional expressions 1 to 6.

FIG. 8 sequentially shows spherical aberration, astigmatism, and distortion aberration of the lens optical system of the fourth embodiment shown in FIG. The wavelengths used to measure spherical aberration are 435.8 nm, 486.1 nm, 546.1 nm 587.6 nm and 656.3 nm. The wavelength measured to measure astigmatism and distortion is 546.1 nm.

The embodiments of the lens optical system of the present invention have been described above. The present invention is not limited to the above-described embodiments and the accompanying drawings, and various modifications and changes may be made by those skilled in the art to which the present invention pertains. Therefore, the scope of the present invention should be determined by the equivalents of the claims and the claims.

L1: first lens L2: second lens
L3: Third lens L4: Fourth lens
S11: Object side surface of the first lens S12: Sensor side surface of the first lens
S21: Object side of the second lens S22: Sensor side of the second lens
S31: Object side of the third lens S42: Sensor side of the fourth lens
S41: Object side of the fourth lens S42: Sensor side of the fourth lens
IS: Sensor S: Aperture
OF: optical filter

Claims (12)

A first lens, a second lens, a third lens and a fourth lens sequentially arranged from the object side to the sensor side between an object and a sensor that forms an image of the object,
Wherein the first lens has a positive refractive power, the object side surface of the first lens is convex toward the object side,
The second lens has a negative refractive power, the object side surface of the second lens is at least flat in the vicinity of the optical axis,
The third lens has a positive refractive power and has a convex meniscus shape toward the sensor side,
The fourth lens has a negative refractive power, the sensor side surface of the fourth lens is concave toward the sensor side and has at least one inflection point,
A lens optical system satisfying the following conditional expression.
<Conditional expression>
1.0 < f2 / f | < 3.0
Here, f2 represents the focal length of the second lens, and f represents the focal length of the lens optical system.
The method according to claim 1,
The sensor side surface of the first lens is convex toward the sensor side,
And the sensor side surface of the second lens is concave toward the sensor side.
The method according to claim 1,
Wherein the object side surface of the fourth lens is convex on the object side in the vicinity of the optical axis and has at least one inflection point.
The method according to claim 1,
And the object side surface of the second lens is plane within the effective diameter.
The method according to claim 1,
And the object side surface of the second lens is flat.
The method according to claim 1,
Wherein all surfaces except the object side surface of the second lens are aspherical surfaces.
The method according to claim 1,
And a diaphragm located between the object side surfaces of the first lens.
8. The method of claim 7,
A lens optical system further satisfying the following conditional expression.
<Conditional expression>
0.75 < SL / TTL < 1.25
SL denotes a distance on the optical axis between the diaphragm and the sensor, and TTL denotes a distance on the optical axis between the object side surface of the first lens and the sensor.
The method according to claim 1,
A lens optical system further satisfying the following conditional expression.
<Conditional expression>
1.0 <tan (?) / F <4.0
Here,? Represents the angle of view of the lens optical system, and f represents the focal length of the lens optical system. The method according to claim 1,
A lens optical system further satisfying the following conditional expression.
<Conditional expression>
50 < (V3 + V4) / 2 < 60
Here, V3 represents Abbe number of the third lens, and V4 represents Abbe number of the fourth lens.
The method according to claim 1,
A lens optical system further satisfying the following conditional expression.
<Conditional expression>
30deg <CRA <35deg
Here, CRA represents the maximum value of the angle at which the principal ray is incident on the sensor.
The method according to claim 1,
A lens optical system further satisfying the following conditional expression.
<Conditional expression>
2.0 <TTL / BFL <4.0
Here, TTL represents the distance on the optical axis between the object side surface of the first lens and the sensor, and BFL represents the distance on the optical axis between the sensor side surface of the fourth lens and the sensor.

Images