KR20120042127A - Photographic lens optical system - Google Patents

Abstract

PURPOSE: A photographing lens optical system is provided to induce light weight and high performance of a camera. CONSTITUTION: A first lens(I), a second lens(II), and a third lens(III) are arranged between image sensors. The first lens has positive refraction index and the entrance face thereof is swollen to a subject. The second lens has negative refraction index and is swollen to the image sensor. The third lens has negative refraction index and at least one of incidence side and emitting side thereof and has a plurality of points of inflection.

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, cameras using solid-state imaging devices such as charge coupled devices (CCDs) and complementary metal oxide semiconductor image sensors (CMOS image sensors) are 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 at least four lenses in order to secure its performance. For example, in the case of a lens optical system used for a high-pixel (ex, 3 million pixels) camera phone, four lenses are mainstream. If the lens optical system includes a large number of lenses, it may be helpful for aberration correction and view angle enlargement, but it may be difficult to make the lens optical system smaller and lighter, that is, the camera compact and lightweight, and the manufacturing and product costs may be high. Therefore, considering only securing the function, it is difficult to use a large number of lenses.

The technical problem to be achieved by the present invention is to improve the problems of the prior art described above, and to provide a lens optical system having an excellent performance while being advantageous in miniaturization and light weight.

In order to achieve the above object, an embodiment of the present invention comprises a first lens, a second lens and a third lens sequentially arranged from the side of the subject between the subject and the image sensor that the image of the subject is formed, The first lens has positive refractive power and has an incident surface convex toward the subject, the second lens has negative refractive power and convex toward the image sensor, and the third lens has negative A lens optical system having refractive power and at least one of its entrance face and exit face has a plurality of inflection points.

The lens optical system may satisfy at least one of Equations 1 and 2 below.

&Quot; (1) "

1.0 <L / f1 <2.0

Where L is the total length of the lens optical system (ie, the full length), and f1 is the focal length of the first lens.

<Equation 2>

1.0 <f / f1 <1.5

Here, f is the focal length of the entire lens optical system, f1 is the focal length of the first lens.

The exit surface of the first lens may be convex toward the image sensor.

The exit surface of the first lens may be concave with respect to the image sensor.

The second lens may be a meniscus lens.

At least one of the first and second lenses may be an aspherical lens.

At least one of the entrance surface and the exit surface of at least one of the first and second lenses may be aspherical.

Each of the entrance and exit surfaces of the third lens may have two inflection points.

The center portion of the incident surface of the third lens may be convex toward the subject and concave toward the edge.

The central portion of the exit surface of the third lens may be concave with respect to the image sensor and may be convex toward the edge.

The second and third lenses may be aberration correcting lenses.

An aperture may be disposed between the subject and the first lens.

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

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

At least one of the first to third lenses may be a plastic lens.

It is possible to implement a lens optical system that can achieve a small size, light weight, high performance and high resolution.

More specifically, the lens optical system according to the embodiment of the present invention includes first to third lenses having positive (+), negative (-), and negative (-) refractive powers sequentially arranged in the direction of the image sensor in the subject. And at least one of Equations 1 and 2 described above. Such a lens optical system can have a relatively short overall length and can easily (goodly) correct various aberrations, which can be advantageous for miniaturization / light weight and high performance of a camera.

1 is a cross-sectional view showing the arrangement of main components of the lens optical system according to the first embodiment of the present invention.
2 is a cross-sectional view showing the arrangement of main components of the lens optical system according to the second embodiment of the present invention.
3 is a cross-sectional view showing the arrangement of main components of the lens optical system according to the third embodiment of the present invention.
4 is an aberration diagram showing longitudinal spherical aberration, image curvature and distortion of the lens optical system according to the first embodiment of the present invention.
5 is an aberration diagram showing longitudinal spherical aberration, image curvature, and distortion of the lens optical system according to the second exemplary embodiment of the present invention.
6 is an aberration diagram showing longitudinal spherical aberration, image curvature, and distortion of the lens optical system according to the third exemplary embodiment of the present invention.
Explanation of symbols on the main parts of the drawings
I: First lens II: Second lens
III: Third Lens IV: Infrared Blocking Means
OBJ: Subject S1: Aperture
IMG: Image Sensor

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 (or similar) components throughout the description.

1 to 3 show a lens optical system according to the first to third embodiments of the present invention, respectively.

1 to 3, 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 and a third lens III are provided. The first lens I may have a positive refractive power, and its incident surface 1 * may be convex toward the object OBJ. The emission surface 2 * of the first lens I may be convex or concave toward the image sensor IMG side. 1 and 3, the exit surface 2 * of the first lens I is convex toward the image sensor IMG, and in the embodiment of FIG. 2, the exit surface 2 * of the first lens I is convex. ) Is concave with respect to the image sensor IMG. Accordingly, the first lens I may be a biconvex lens (FIGS. 1 and 3) or a meniscus lens convex toward the object OBJ (FIG. 2). The second lens II may be a meniscus lens having a negative refractive power and convex toward the image sensor IMG side. At least one of the first and second lenses I and II may be an aspherical lens. In other words, at least one of the entrance surfaces 1 * and 3 * and the exit surfaces 2 * and 4 * of at least one of the first and second lenses I and II may be aspheric. For example, the incident surfaces 1 * and 3 * and the exit surfaces 2 * and 4 * of each of the first and second lenses I and II may be aspherical. The third lens III may have negative refractive power, and at least one of the entrance surface 5 * and the exit surface 6 * of the third lens III may be an aspherical surface having a plurality of inflection points. have. For example, each of the incident surface 5 * and the exit surface 6 * of the third lens III may have two inflection points. In this case, the center of the incident surface 5 * of the third lens III may be convex toward the object OBJ and its periphery may be concave, and the center of the exit surface 6 * may be relative to the image sensor IMG. It may be concave and its periphery may be convex. The first lens I may have a strong positive refractive power, and the second and third lenses II and III may function as an aberration correcting lens.

The diaphragm S1 and the infrared ray blocking unit IV may be further provided. The aperture S1 may be provided between the subject OBJ and the first lens I. That is, the aperture S1 may be provided at the object OBJ side of the first lens I. FIG. The infrared ray blocking means IV may be provided between the third lens III and the image sensor IMG. The infrared blocking means IV may be an infrared blocking filter. The positions of the diaphragm S1 and the infrared ray blocking means IV are exemplary, and their positions may vary.

It is preferable that the lens optical system according to the embodiments of the present invention having the above-described configuration satisfies at least one of the following Equations 1 and 2.

&Quot; (1) &quot;

1.0 <L / f1 <2.0

Where L is the total length of the lens optical system (ie, the full length), and f1 is the focal length of the first lens (I).

Equation 1 shows the conditions for compacting the lens optical system. When L / f1 is equal to or greater than the upper limit (2.0) in Equation 1, it is advantageous to compact the lens optical system, but various aberrations such as spherical aberration may increase. On the other hand, when L / f1 is lower than the lower limit value (1.0), it is advantageous for aberration correction, but since the overall length of the lens optical system becomes long, compactness may become difficult.

<Equation 2>

1.0 <f / f1 <1.5

Here, f is the focal length of the entire lens optical system, f1 is the focal length of the first lens (I).

Equation 2 is a condition for determining the refractive power of the first lens I, and is related to the correction of the spherical aberration and the compactness of the lens optical system. When f / f1 in Equation 2 is higher than the upper limit (1.5), it is advantageous to compact the lens optical system, but correction of spherical aberration may be difficult. On the other hand, when f / f1 in Equation 2 is lower than the lower limit value (1.0), the correction of spherical aberration becomes easy, but it may be difficult to compact the lens optical system.

When the conditions of Equations 1 and 2 are satisfied, a short electric field can be secured while maintaining various aberrations such as spherical aberration in a good state, thereby achieving a compact and excellent lens optical system.

In the first to third embodiments of the present invention described above, the values of Equations 1 and 2 are as shown in Tables 1 and 2 below. In Table 1 and Table 2, the units of the L, f1 and f values are mm.

division L f1 Equation 1
(1.0 <L / f1 <2.0) First embodiment 3.250 2.052 1.583 Second embodiment 3.250 2.066 1.573 Third embodiment 3.210 1.968 1.631

division f f1 Equation 2
(1.0 <f / f1 <1.5) First embodiment 2.760 2.052 1.345 Second embodiment 2.796 2.066 1.353 Third embodiment 2.740 1.968 1.392

Referring to Tables 1 and 2, it can be seen that the lens optical systems of the first to third 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 third lenses (I? III) can be made of plastic, considering its shape and dimensions. That is, all of the first to third lenses I? III may be plastic lenses. In the case of a glass lens, it is difficult to miniaturize the lens optical system due to not only a high manufacturing cost but also constraints on the molding, but in this embodiment, all of the first to third lenses I to III may be made of plastic. Various benefits can be achieved accordingly. However, the material of the first to third lenses I? III is not limited to the plastic herein. If necessary, at least one of the first to third lenses I? III may be made of glass.

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

Tables 3 to 5 show curvature radii, lens thicknesses, or distances between lenses, refractive indexes, and Abbe constants, respectively, for the lenses constituting the lens optical system of FIGS. 1 to 3, respectively. In Tables 3 to 5, 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, V _d is the Abbe constant It is shown. In lens surface numbers of Tables 3 to 5, * 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 S1 infinity I
One* 1.2187 0.4282 1.53 55.7 2* -9.4479 0.4500 Ⅱ 3 * -0.7000 0.3144 1.63 23.4 4* -1.0087 0.4374 Ⅲ 5 * 1.3594 0.5000 1.53 55.7 6 * 1.1755 0.4000 Ⅳ 7 infinity 0.3000 1.51 64.1 8 0.4208 IMG infinity -0.0008

Second embodiment if R D N _d V _d S1 infinity I
One* 1.100 0.4327 1.53 55.7 2* 479.4135 0.3935 Ⅱ 3 * -0.8137 0.3300 1.63 23.4 4* -1.2219 0.4704 Ⅲ 5 * 1.3835 0.5099 1.53 55.7 6 * 1.2030 0.2500 Ⅳ 7 infinity 0.3000 1.51 64.1 8 0.5657 IMG infinity -0.0022

Third embodiment if R D N _d V _d S1 infinity -0.0404 I
One* 1.0905 0.4851 1.53 55.7 2* -23.8985 0.3812 Ⅱ 3 * -0.6979 0.3246 1.63 23.4 4* -1.0340 0.3810 Ⅲ 5 * 1.8156 0.5773 1.53 55.7 6 * 1.6092 0.2500 Ⅳ 7 infinity 0.3000 1.51 64.1 8 0.5460 IMG infinity 0.0060

Meanwhile, the aperture ratios (Fno), the focal lengths (f), and the overall length (L) of the lens optical system according to the first to third embodiments of the present invention, respectively, corresponding to FIGS. 1 to 3 are shown in Table 6 below. .

division Fno Focal Length (f) [mm] Overall length (L) [mm] First embodiment 2.8 2.760 3.250 Second embodiment 2.8 2.796 3.250 Third embodiment 2.75 2.740 3.210

In addition, in the lens optical system according to the first to third embodiments of the present invention, the aspherical surface of each lens satisfies the aspherical equation of Equation 3 below.

&Quot; (3) &quot;

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 For conic constants, A, B, C, D and E represent aspherical coefficients.

Tables 7 to 9 show aspherical surface coefficients of the aspherical surface in the lens system according to the first to third embodiments corresponding to FIGS. 1 to 3, respectively. That is, Tables 7 to 9 show aspherical surface coefficients of the incident surfaces 1 *, 3 *, 5 * and the exit surfaces 2 *, 4 *, 6 * of each lens of Tables 3-5, respectively.

Cotton (Figure 1) K A B C D E One* -0.3084 -0.0964 -0.3818 -0.1633 1.0483 -13.6967 2* -94.3263 -0.3590 -0.3344 -0.6157 0.7692 -5.6630 3 * -3.3885 -1.1559 2.8575 1.2104 -6.9872 3.9241 4* -4.7338 -0.6765 2.1470 -1.2717 2.8890 -2.7180 5 * -11.8793 -0.3008 0.2176 -0.0377 -0.0459 -0.0041 6 * -7.7185 -0.2395 0.1527 -0.0744 0.0103 0.0031

Cotton (Figure 2) K A B C D E One* -0.1985 -0.0585 -0.3534 -0.2730 1.8583 -12.7228 2* 0.0000 -0.3256 -0.6278 -0.0198 -1.2581 -1.3029 3 * -3.9947 -1.2394 1.7489 2.5064 -0.9066 -9.3327 4* -4.7197 -0.6531 1.6951 -0.8306 2.7649 -0.8721 5 * -9.1765 -0.3983 0.2184 -0.0097 -0.0422 -0.0033 6 * -5.1414 -0.3260 0.2176 -0.1268 0.0367 -0.0025

Cotton (Figure 3) K A B C D E One* -0.0573 -0.0587 -0.2934 -0.6039 0.8871 0.9081 2* 0.0000 -0.3422 -0.5269 -0.7545 0.0159 1.8921 3 * -3.0185 -1.3145 2.5081 2.4805 -5.4446 -9.9698 4* -3.8804 -0.6921 2.0532 -0.6868 2.2604 -2.2861 5 * -26.2229 -0.3130 0.2074 -0.0278 -0.0457 -0.0005 6 * -12.1383 -0.2194 0.1104 -0.0530 0.0090 0.0002

4 is a view showing longitudinal spherical aberration, astigmatic field curvature and distortion of a lens optical system according to a first embodiment of the present invention (ie, a lens optical system having numerical values shown in Table 3). Aberration diagram showing distortion.

Figure 4 (a) shows the spherical aberration of the lens optical system for the light of various wavelengths, (b) is the top surface curvature, that is, the tangential field curvature (T) and the sagittal surface curvature of the lens optical system field curvature) (S). (a) The wavelengths of light used for obtaining the data were 435.8343 nm, 486.1327 nm, 546.0740 nm, 587.5618 nm, and 656.2725 nm. The wavelength of the light used to obtain the data (b) and (c) was 546.0740 nm. The same applies to FIGS. 5 and 6.

5A, 5B, and 5C are longitudinal spherical aberration and image curvature of the lens optical system according to the second embodiment (Fig. 2) of the present invention, that is, the lens optical system having numerical values shown in Table 4, respectively. And aberration diagram showing distortion.

(A), (b) and (c) of FIG. 6 are longitudinal spherical aberration and image curvature of the lens optical system according to the third embodiment of the present invention (FIG. 3), that is, the lens optical system having numerical values shown in Table 5. And aberration diagram showing distortion.

As described above, the lens optical system according to the embodiments of the present invention has positive (+), negative (-), and negative (-) refractive powers sequentially arranged in the direction of the image sensor IMG from the subject OBJ. The first to third lenses I? III may be included, and at least one of Equations 1 and 2 described above may be satisfied. Such a lens optical system can include three lenses, have a short overall length, and can easily (goodly) correct various aberrations. Therefore, according to the embodiment of the present invention, it is possible to implement a lens optical system that can obtain a small size, light weight, high performance and high resolution. In addition, as mentioned above, the glass lens is manufactured by making the first to third lenses I? III from plastic and assembling at least one of both surfaces (incident surface and exit surface) of each lens. It is possible to realize a lens optical system that is compact and excellent in performance at a lower cost than using.

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 appreciated by those skilled in the art that a blocking film may be used in place of the filter as the infrared blocking means (IV). It will be appreciated that various other modifications are possible. 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.

Claims (14)

A first lens, a second lens, and a third lens 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 has positive (+) refractive power and its incident surface is convex toward the subject side,
The second lens has a negative refractive power and convex toward the image sensor.
The third lens has a negative refractive power and at least one of its incidence and exit faces has a plurality of inflection points,
Lens optical system that satisfies the following equation.
&Lt; Equation &
1.0 <L / f1 <2.0
Here, L represents the full length of the lens optical system, f1 represents the focal length of the first lens. The method of claim 1,
A lens optical system wherein the following equation holds between a focal length f of the lens optical system and a focal length f1 of the first lens.
&Lt; Equation &
1.0 <f / f1 <1.5 The method of claim 1,
The lens optical system of which the exit surface of the first lens is convex toward the image sensor. The method of claim 1,
And an exit surface of the first lens is concave with respect to the image sensor. The method of claim 1,
The second lens is a lens optical system of a meniscus lens. The method of claim 1,
At least one of the first and second lenses is an aspherical lens. The method of claim 1,
And at least one of an entrance surface and an exit surface of at least one of the first and second lenses is an aspherical surface. The method of claim 1,
The optical system of claim 3, wherein each of the entrance and exit surfaces of the third lens has two inflection points. The method of claim 1,
The center portion of the incident surface of the third lens is convex toward the subject and concave toward the edge,
The central portion of the exit surface of the third lens is concave with respect to the image sensor and convex toward the edge of the lens optical system. The method of claim 1,
And the second and third lenses are aberration correcting lenses. The method of claim 1,
The lens optical system, the aperture is disposed between the subject and the first 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 12,
The infrared blocking means is a lens optical system provided between the third lens and the image sensor. The method of claim 1,
At least one of the first to third lenses is a lens optical system.

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