KR101067630B1 - Photographic lens optical system - Google Patents

Abstract

Disclosed is a lens optical system. The disclosed lens optical system includes first to fourth lenses having positive, negative, positive, and negative refractive powers sequentially arranged in an image sensor direction from a subject. The first lens may be convex toward the subject, and both surfaces of the second lens may be concave. The third lens may be convex toward the image sensor, and at least one of the entrance surface and the exit surface of the fourth lens may be aspherical. The focal length of the first lens (f ₁₎ and the focal length of the third lens (f ₃₎ may satisfy the expression _{0.5 <f 1 / f 3 <} 1.5.

Description

Photography lens optical system

The present invention relates to an optical device, and more particularly, to a lens optical system employed in a camera.

Recently, the spread of cameras (hereinafter referred to as cameras) using solid-state imaging devices such as charge coupled devices (CCDs) and complementary metal oxide semiconductor image sensors (CMOS image sensors) is rapidly expanding. have.

In order to increase the resolution of a camera, the pixel integration degree of a solid-state image sensor is increasing. In addition, through the improvement of the performance of the lens optical system built in the camera, the compact and lightweight of the camera is also in progress.

In general, the lens optical system of a small camera uses a large number of lenses including at least one glass lens to secure its performance. If the lens optics include many lenses, they may be helpful for aberration correction. However, as many lenses are used, it may be difficult to make the lens optical system smaller and lighter, that is, the camera compact and lighter, and manufacturing and product costs may be high. In particular, glass lenses not only have high manufacturing cost but also make it difficult to miniaturize the lens optical system due to molding constraints.

SUMMARY OF THE INVENTION The present invention has been made in an effort to improve the above-described problems of the related art, and to provide a lens optical system capable of obtaining a small size, light weight, and high resolution.

In order to achieve the above object, an embodiment of the present invention includes a first lens, a second lens, a third lens, and a fourth lens sequentially arranged from the subject side between a subject and an image sensor on which the image of the subject is formed. The first lens has a positive refractive power and is convex toward the subject, the second lens has a negative refractive power, and both surfaces are concave, and the third lens has a positive refractive power and the image sensor. It is convex to the side, the fourth lens has a negative refractive power, and at least one of the incident surface and the exit surface of the fourth lens provides a lens optical system, characterized in that the aspherical surface.

The lens optical system preferably satisfies at least one of Equations 1 and 2 below.

&Quot; (1) &quot;

0.5 <f ₁ / f ₃ <1.5

Where f ₁ Is a focal length of the first lens, f ₃ Is the focal length of the third lens.

<Equation 2>

2 <| r ₄ / r ₅ | <7

Here, r ₄ is the radius of curvature of the incident surface of the second lens, r ₅ is the radius of curvature of the exit surface of the second lens.

The incident surface and the exit surface of the fourth lens may each have a plurality of inflection points.

An entrance surface and an exit surface of at least one of the first to third lenses may be aspherical.

The second to fourth lenses may be aberration correcting lenses.

An aperture may be further disposed between the first lens and the second lens.

Infrared blocking means may be further provided between the subject and the image sensor.

The infrared blocking means may be provided between the fourth lens and the image sensor.

The first to fourth lenses may be plastic lenses.

According to an embodiment of the present invention, it is possible to implement a lens optical system that can be compact, lightweight and high resolution.

More specifically, the lens optical system according to the embodiment of the present invention includes first to fourth lenses having positive, negative, positive, and negative refractive powers that are sequentially arranged in the direction of an image sensor in a subject. And at least one of two. Such lens optical system may be advantageous in miniaturization / light weight and high performance of a camera.

In particular, when the incident surface and the exit surface of the fourth lens are aspherical surfaces having a plurality of inflection points, various aberrations can be easily corrected through the fourth lens, and vignetting is performed by reducing the emission angle of chief ray. Vignetting can also be prevented.

In addition, by manufacturing the first to fourth lenses made of plastic and assembling both surfaces (incident surface and exit surface) of each lens, it is possible to implement a compact and excellent lens optical system at a lower cost than when using a glass lens. have.

Hereinafter, a lens optical system according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. Like numbers refer to like elements throughout.

1 to 4 show a lens optical system according to the first to fourth embodiments of the present invention, respectively.

1 to 4, the lens optical system according to the exemplary embodiments of the present invention is sequentially arranged from the subject OBJ between the subject OBJ and the image sensor IMG that forms an image of the subject OBJ. A first lens I, a second lens II, a third lens III and a fourth lens IV are provided. The first lens I may be a meniscus lens which has a positive refractive power and is convex toward the object OBJ. The second lens II may be a lens having negative refractive power, and both surfaces thereof (that is, the incident surface 4 * and the exit surface 5 *) are concave. The third lens III may be a meniscus lens having positive refractive power and convex toward the image sensor IMG side. At least one of the entrance surfaces 1 *, 4 *, and 6 * and the emission surfaces 2 *, 5 *, and 7 * of the first to third lenses I to III may be aspherical. For example, the incident surfaces 1 *, 4 *, 6 * and the exit surfaces 2 *, 5 *, 7 * of each of the first to third lenses I to III may be aspherical. The fourth lens IV may have negative refractive power, and at least one of the entrance surface 8 * and the exit surface 9 * of the fourth lens IV may be aspherical. For example, each of the incident surface 8 * and the exit surface 9 * of the fourth lens IV may be an aspherical surface having a plurality of inflection points. Here, the number of inflection points is a curve (hereinafter referred to as a first curve) corresponding to the incident surface 8 * of the cross-sectional view of the fourth lens IV of FIGS. 1 to 4 and a curve corresponding to the exit surface 9 * ( Hereinafter, the number of inflection points in the second curve). That is, a plurality of inflection points may be provided in each of the first curve and the second curve. The second to fourth lenses II to IV can function as aberration correcting lenses.

An aperture S1 may be provided between the first lens I and the second lens II. In addition, an infrared ray blocking unit V may be provided between the fourth lens IV and the image sensor IMG. The infrared blocking means V may be an infrared blocking filter. The infrared ray blocking unit V may be provided between the subject OBJ and the fourth lens IV.

And the lens optical system according to the embodiments of the present invention having the above configuration preferably satisfies at least one of the following equations (1) and (2).

0.5 <f ₁ / f ₃ <1.5

Where f ₁ Is the focal length of the first lens I, f ₃ Is the focal length of the third lens III.

Equation 1 relates to the distribution of refractive power of lenses having positive (+) refractive power, that is, the first and third lenses I and III, and represents a condition for reducing spherical aberration of the entire lens optical system. When f ₁ / f ₃ is equal to or larger than the upper limit (1.5) in Equation 1, it is advantageous for compacting the lens optical system, but spherical aberration may increase. On the other hand, when f ₁ / f ₃ is lower than or equal to the lower limit (0.5), spherical aberration correction is advantageous, but since the overall length of the lens optical system becomes long, it may be difficult to compact.

2 <| r ₄ / r ₅ | <7

Where r ₄ Is the radius of curvature of the incident surface 4 * of the second lens II, r ₅ Is the radius of curvature of the exit surface 5 * of the second lens II.

Equation 2 shows a condition for determining the refractive power of the second lens (II) having negative refractive power. When using the second lens II that satisfies Equation 2, that is, has a relatively strong negative refractive power, chromatic aberration correction through the second lens II may be easy.

In the above first to fourth embodiments of the present invention, the values of Equations 1 and 2 are as shown in Tables 1 and 2 below.

division f ₁ f ₃ Equation 1
(0.5 <f ₁ / f ₃ <1.5) First embodiment 2.563 2.219 1.155 Second embodiment 2.608 1.8845 1.384 Third embodiment 2.128 2.1416 0.994 Fourth embodiment 2.084 2.2245 0.937

division r ₄ r ₅ Equation 2
(2 <| r ₄ / r ₅ | <7) First embodiment -12.618 3.828 3.296 Second embodiment -16.950 3.206 5.288 Third embodiment -17.818 2.862 6.225 Fourth embodiment -7.207 3.566 2.021

Referring to Tables 1 and 2, it can be seen that the lens optical systems of the first to fourth embodiments satisfy Equations 1 and 2.

On the other hand, in the lens optical system according to the embodiments of the present invention having the above-described configuration, the first to fourth lenses (I to IV) can be made of plastic, considering its shape and dimensions. That is, all of the first to fourth lenses I to IV may be plastic lenses. In the case of the glass lens, the manufacturing cost is high and it is difficult to miniaturize the lens optical system due to molding constraints. However, since the first to fourth lenses I to IV can all be made of plastic, You can benefit.

Hereinafter, the first to fourth embodiments of the present invention will be described in detail with reference to the lens data and the accompanying drawings.

Tables 3 to 6 show curvature radii, lens thicknesses, or distances between lenses, refractive indices, and Abbe constants, and the like, for respective lenses of the lens optical system of FIGS. 1 to 4, respectively. In Tables 3 to 6, r is the radius of curvature, d is the lens thickness or lens spacing, or the distance between adjacent components, N _d is the refractive index of the lens measured using the d-line, and V _d is the Abbe constant. It is shown. In lens surface numbers of Tables 3 to 6, * indicates that the lens surface is aspheric. And the unit of r value and d value is mm.

First embodiment if r d N _d V _d I One* 1.372 0.576 1.54 56.0 2* 57.274 0.100 S1 infinity 0.100 Ⅱ 4* -12.618 0.300 1.63 23.00 5 * 3.828 0.496 Ⅲ 6 * -1.648 0.815 1.54 56.0 7 * -0.820 0.183 Ⅳ 8* 12.394 0.453 1.53 55.70 9 * 1.240 0.300 Ⅴ 10 infinity 0.300 1.51 64.1 11 0.820 IMG infinity

Second embodiment if r d N _d V _d I One* 1.363 0.556 1.54 56.0 2* 57.459 0.100 S1 infinity 0.100 Ⅱ 4* -16.950 0.310 1.63 23.00 5 * 3.206 0.496 Ⅲ 6 * -1.864 0.840 1.54 56.0 7 * -0.755 0.195 Ⅳ 8* 11.334 0.400 1.53 55.70 9 * 1.062 0.300 Ⅴ 10 infinity 0.300 1.51 64.1 11 0.810 IMG infinity

Third embodiment if r d N _d V _d I One* 1.095 0.453 1.53 55.70 2* 26.669 0.050 S1 infinity 0.100 Ⅱ 4* -17.818 0.300 1.63 23.00 5 * 2.862 0.336 Ⅲ 6 * -1.085 0.582 1.53 55.70 7 * -0.660 0.100 Ⅳ 8* 1.924 0.349 1.53 55.70 9 * 0.803 0.300 Ⅴ 10 infinity 0.300 1.51 64.1 11 0.680 IMG infinity

Fourth embodiment if r d N _d V _d I One* 1.075 0.461 1.54 56.0 2* 27.478 0.050 S1 infinity 0.100 Ⅱ 4* -7.207 0.300 1.63 23.00 5 * 3.566 0.336 Ⅲ 6 * -1.095 0.579 1.54 56.0 7 * -0.674 0.100 Ⅳ 8* 1.784 0.344 1.53 55.70 9 * 0.792 0.300 Ⅴ 10 infinity 0.300 1.51 64.1 11 0.680 IMG infinity

On the other hand, the aperture ratio Fno and the focal length f of the lens optical system according to the first to fourth embodiments of the present invention respectively corresponding to FIGS. 1 to 4 are shown in Table 7 below.

division Fno Focal Length (f) [mm] First embodiment 2.6 3.549 Second embodiment 2.6 3.474 Third embodiment 2.8 2.787 Fourth embodiment 2.8 3.600

In addition, in the lens optical system according to the first to fourth embodiments of the present invention, the aspherical surface of each lens satisfies the aspherical equation (3).

Where x is the distance from the vertex of the lens in the optical axis direction, y is the distance in the direction perpendicular to the optical axis, c 'is the inverse of the radius of curvature at the vertex of the lens (= 1 / r), and K is Conic constants A, B, C, D, E, F, G, H and J represent aspherical coefficients, respectively.

Tables 8 to 11 show aspherical surface coefficients of aspherical surfaces in the lens system according to the first to fourth embodiments corresponding to FIGS. 1 to 4, respectively. That is, Tables 8 to 11 show the incidence planes (1 *, 4 *, 6 *, 8 *) and exit planes (2 *, 5 *, 7 *, 9 *) of each lens of Tables 3 to 6, respectively. Aspheric coefficient is shown.

One* 2* 4* 5 * 6 * 7 * 8* 9 * K 0.062 5345.686 -666.071 11.054 1.349 -2.613 -9000.000 -10.410 A -0.003 0.0474 0.1086 0.1746 0.0038 -0.1681 -0.0991 -0.1065 B 0.0515 -0.0674 -0.2278 -0.1150 -0.1934 0.0356 0.0433 0.0388 C -0.2072 -0.0562 0.1092 -0.0930 0.4785 0.0085 -0.0036 -0.0121 D 0.4222 0.0663 -0.4563 0.1034 -0.5988 -0.0625 -0.0004 0.0018 E -0.2703 -0.2648 0.5450 0.5026 0.3665 0.0740 -4.1138 × 10 ^-5 2.2031 × 10 ^-5 F -0.3430 - -0.4528 -0.5566 0.6434 -0.0210 -7.6971 × 10 ^-6 -1.4365 × 10 ^-5 G 0.2250 - 0.5360 -0.2709 -0.3279 0.0124 6.0034 × 10 ^-6 -9.3755 × 10 ^-7 H 0.6037 - - 0.3783 -0.5421 0.0062 2.5293 × 10 ^-6 -6.3720 × 10 ^-8 J -0.6542 - - 0.0053 0.2588 -0.0088 -5.8830 × 10 ^-7 5.5263 × 10 ^-8

One* 2* 4* 5 * 6 * 7 * 8* 9 * K 0.1052 5602.4729 -767.7106 7.4454 1.6843 -2.7288 -6048.5788 -9.1296 A 0.0044 0.0493 0.0815 0.1341 -0.0297 -0.2031 -0.0833 -0.1008 B 0.0619 -0.0690 -0.2541 -0.1126 -0.1571 0.0579 0.0406 0.0377 C -0.2082 -0.0320 0.1483 -0.0143 0.4549 0.0073 -0.0044 -0.0114 D 0.4361 0.0394 -0.5393 -0.1201 -0.6077 -0.0775 -0.0004 0.0017 E -0.3302 -0.3227 0.5107 0.5438 0.2641 0.0675 -2.5530 × 10 ^-5 1.4047 × 10 ^-5 F -0.2897 - -0.4528 -0.6760 0.5491 -0.0201 -5.2594 × 10 ^-6 -1.0000 × 10 ^-5 G 0.2917 - 0.5360 0.0724 -0.1549 0.0159 7.1701 × 10 ^-6 -6.1373 × 10 ^-7 H 0.6132 - - 0.3783 -0.4164 0.0083 2.4186 × 10 ^-6 -1.4607 × 10 ^-7 J -0.8269 - - 0.0053 -0.1623 -0.0125 -8.2985 × 10 ^-7 -6.1195 × 10 ^-8

One* 2* 4* 5 * 6 * 7 * 8* 9 * K 0.0375 962.9598 194.6632 -2.6962 1.0173 -2.0541 -49.6161 -7.5713 A 0.0129 0.0302 0.1237 0.3305 0.1728 -0.3279 -0.2227 -0.2494 B 0.1141 -0.3795 -1.1900 -0.3027 -0.5155 0.1724 0.1183 0.1478 C -0.9774 -1.2164 1.6306 -0.4485 2.4758 -0.1184 -0.0060 -0.0698 D 3.0935 1.5312 -8.3939 1.4341 -3.9445 -0.6579 -0.0013 0.0124 E -4.5355 -4.8180 4.4175 3.0873 7.3613 1.3173 -0.0022 0.0014 F -6.5779 4.4165 × 10 ^-8 6.3481 -11.6480 9.3371 -0.0875 -0.0015 0.0002 G 8.2965 6.4618 × 10 ^-9 16.5931 4.7867 0.8776 0.7240 -0.0002 -0.0002 H 25.6572 4.4677 × 10 ^-8 - 4.7297 -26.1182 0.2642 0.0002 -0.0001 J -66.8534 2.7172 × 10 ^-8 - -18.9090 -59.7434 -1.8685 3.0063 × 10 ^-5 1.5881 × 10 ^-5

One* 2* 4* 5 * 6 * 7 * 8* 9 * K 0.0592 2631.3883 -16.5007 -1.1984 1.1143 -2.0566 -38.4305 -7.0314 A 0.0172 0.0253 0.1269 0.3379 0.1801 -0.3264 -0.2248 -0.2471 B 0.1074 -0.3969 -1.1801 -0.2974 -0.4831 0.1785 0.1136 0.1442 C -0.9332 -1.0938 1.3531 -0.5349 2.3195 -0.1176 -0.0083 -0.0686 D 3.2364 0.1124 -8.4108 1.0575 -4.3548 -0.6794 -0.0005 0.0122 E -4.5047 -4.8180 4.4175 3.9244 7.0145 1.2730 -0.0016 0.0011 F -7.3849 - 6.3481 -11.6480 10.1701 -0.1562 -0.0013 0.0002 G 6.6211 - 16.5931 4.7867 0.8776 0.6609 -0.0002 -0.0002 H 29.3889 - - 4.7297 -26.1182 0.2981 0.0002 -0.0001 J -66.8534 - - -18.9090 -59.7434 -1.5922 3.4166 × 10 ^-5 1.3711 × 10 ^-5

5A to 5C show the longitudinal spherical aberration and the astigmatic field curvature of the lens optical system according to the first embodiment of the present invention (Fig. 1), that is, the lens optical system having the numerical values shown in Table 3, respectively. And aberration showing distortion.

FIG. 5A shows spherical aberration of the lens optical system for light of various wavelengths, and FIG. 5B shows top surface curvature, that is, tangential field curvature (T1 to T5) and spherical phase, of the lens optical system for light of various wavelengths. Sagittal field curvatures S1 to S5 are shown. The wavelengths of light used to obtain the results of FIGS. 5A and 5B were 435.8343 nm, 486.1327 nm, 546.0740 nm, 587.5618 nm, and 656.2725 nm. On the other hand, the wavelength of the light used to obtain the data in FIG. 5C was 546.0740 nm.

6A to 6C show longitudinal spherical aberration, image curvature and distortion of the lens optical system according to the second embodiment of the present invention (FIG. 2), that is, the lens optical system having the numerical values shown in Table 4. FIG.

7A to 7C show longitudinal spherical aberration, image curvature and distortion of the lens optical system according to the third embodiment of the present invention (FIG. 3), that is, the lens optical system having the numerical values shown in Table 5. FIG.

8A to 8C show longitudinal spherical aberration, image curvature, and distortion of the lens optical system according to the fourth embodiment of the present invention (FIG. 4), that is, the lens optical system having the numerical values shown in Table 6. FIG.

As described above, the lens optical system according to the exemplary embodiments of the present invention has positive, negative, positive, and negative values which are sequentially arranged in the direction of the image sensor IMG from the subject OBJ. The first to fourth lenses (I to IV) having a refractive power of the) may be included, and at least one of Equations 1 and 2 described above may be satisfied. Such lens optical system may be advantageous in miniaturization / light weight and high performance of a camera. Therefore, it is possible to implement a lens optical system that can obtain a small, lightweight and high resolution.

Particularly, in the lens optical system according to the exemplary embodiment of the present invention, when the incident surface 8 * and the exit surface 9 * of the fourth lens IV are aspherical surfaces having a plurality of inflection points, the fourth lens IV may be various types. The aberration can be easily corrected, and vignetting can be prevented by reducing the emission angle of chief ray.

In addition, since the first to fourth lenses I to IV are made of plastic and both surfaces (incident surface and exit surface) of each of the lenses I to IV are aspherical surfaces, it is compact at a lower cost than using a glass lens. It is possible to implement a lens optical system with excellent performance.

While many details are set forth in the foregoing description, they should be construed as illustrative of preferred embodiments, rather than to limit the scope of the invention. For example, it will be apparent to those skilled in the art that at least one of the first to fourth lenses I to IV may be manufactured from a glass material instead of plastic. It will also be appreciated that a blocking film may be used in place of the filter as the infrared blocking means (V). Therefore, the scope of the present invention should not be defined by the described embodiments, but should be determined by the technical spirit described in the claims.

1 to 4 are cross-sectional views showing the arrangement of main components of the lens optical system according to the first to fourth embodiments of the present invention, respectively.

5A to 5C are aberration diagrams showing longitudinal spherical aberration, image curvature, and distortion of the lens optical system according to the first embodiment of the present invention, respectively.

6A to 6C are aberration diagrams showing longitudinal spherical aberration, image curvature, and distortion of the lens optical system according to the second embodiment of the present invention, respectively.

7A to 7C are aberration diagrams showing longitudinal spherical aberration, image curvature, and distortion of the lens optical system according to the third embodiment of the present invention, respectively.

8A to 8C are aberration diagrams showing longitudinal spherical aberration, image curvature, and distortion of the lens optical system according to the fourth embodiment of the present invention, respectively.

Explanation of symbols on the main parts of the drawings

I: First Lens II: Second Lens

III: Third Lens IV: Fourth Lens

Ⅴ: infrared ray blocking means OBJ: subject

S1: Aperture IMG: Image Sensor

Claims (12)

A first lens, a second lens, a third lens, and a fourth lens, which are sequentially arranged from the subject side, between the subject and the image sensor on which the image of the subject is formed; The first lens is convex toward the subject with positive refractive power, The second lens is concave on both sides with a negative refractive power, The third lens has a positive refractive power and is convex toward the image sensor, The fourth lens has negative refractive power, at least one of the incident surface and the exit surface of the fourth lens is an aspherical surface, The focal length of the first lens (f ₁₎ and the focal length (f ₃₎ between the equation 0.5 <f ₁ / f ₃ <lens optical system, characterized in that 1.5 the establishment of the third lens. delete The method of claim 1, Joining the radius of curvature (r ₄₎ and the exit radius of curvature (r _5), and then the lens optical system, which equation is satisfied between a surface of the second lens surface of the second lens. &Lt; Equation & 2 <| r ₄ / r ₅ | <7 delete The method according to claim 1 or 3, The optical system of claim 4, wherein the incident surface and the exit surface of the fourth lens each have a plurality of inflection points. The method of claim 1, The optical system of claim 1, wherein the incident surface and the exit surface of at least one of the first to third lenses are aspherical surfaces. The method of claim 1, And the second to fourth lenses are aberration correcting lenses. The method of claim 1, The lens optical system, wherein the aperture is further disposed between the first lens and the second lens. The method of claim 1, Lens optical system further comprises an infrared ray blocking means between the subject and the image sensor. The method of claim 9, The infrared blocking means is a lens optical system provided between the fourth lens and the image sensor. The method of claim 1, The first to fourth lenses are lens optical systems. A first lens, a second lens, a third lens, and a fourth lens, which are sequentially arranged from the subject side, between the subject and the image sensor on which the image of the subject is formed; The first lens is convex toward the subject with positive refractive power, The second lens is concave on both sides with a negative refractive power, The third lens has a positive refractive power and is convex toward the image sensor, The fourth lens has negative refractive power, at least one of the incident surface and the exit surface of the fourth lens is an aspherical surface, An aperture is disposed between the first lens and the second lens, Lens optical system satisfying the following equations. Equation 1: 0.5 <f ₁ / f ₃ <1.5 Equation 2: 2 <| r ₄ / r ₅ | <7 In Equation 1, f ₁ and f ₃ represent the focal length of the first lens and the focal length of the third lens, respectively, and in Equation 2, r ₄ and r ₅ represent the incidence plane of the second lens, respectively. The radius of curvature and the radius of curvature of the exit surface of the second lens are shown.

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