KR20120094730A - Photographic lens optical system - Google Patents

Abstract

PURPOSE: A photography lens optical system is provided to obtain high performance and high resolution and to easily revise all kinds of aberrations through a fifth lens. CONSTITUTION: A first lens(I), a second lens(II), a third lens(III), a fourth lens(IV), and a fifth lens(V) are successively arranged between an object and an image sensor(IMG) from the object side. The first lens has a positive refraction index and has convex double sides. The second lens has a negative refraction index and has a meniscus shape which is convex toward the object side. The third lens has the positive refraction index. The fourth lens has the positive refraction index. The fifth lens has the negative refraction index. An incidence surface and an emitting surface of the fifth lens are formed into an aspherical surface.

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, miniaturization and weight reduction of the camera are also progressing through the performance improvement of the lens optical system built into the camera.

In general, the lens optical system of a small camera uses a large number (6-7 sheets) of lenses including at least one glass lens to secure its performance. When the lens optical system includes many lenses, it may be difficult to reduce the size and weight of the lens optical system, and the manufacturing cost 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 that is advantageous in miniaturization and weight reduction, and has high performance and high resolution.

In order to achieve the above object, an embodiment of the present invention provides a first lens, a second lens, a third lens, a fourth lens, and a first 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. 5, wherein the first lens has positive refractive power and double-sided convex, the second lens has negative refractive power, and has a meniscus shape convex toward the subject, and the third lens has a third refractive index. The lens has negative refractive power, the fourth lens has positive refractive power, has a meniscus shape convex toward the image sensor, and the fifth lens has negative refractive power. A lens optical system is characterized in that at least one of the entrance face and the exit face is an aspherical surface.

The lens optical system may satisfy at least one of Equations 1 to 4 below.

&Quot; (1) "

0.5 <f1 / TL <1.0

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

&Quot; (2) &quot;

0.4 <R1 / f <0.6

Here, R1 is the radius of curvature of the incident surface of the first lens, f is the focal length of the entire lens optical system.

&Quot; (3) &quot;

30 <Vd1-Vd2 <35

Here, Vd1 is the Abbe's number of the first lens, and Vd2 is the Abbe's number of the second lens.

&Quot; (4) &quot;

0.2 <BL / TL <0.4

Here, BL is a distance from the exit surface of the fifth lens to the image sensor, and TL is the total length of the lens optical system (ie, the full length).

The third lens may have a convex shape toward the subject in the vicinity of an optical axis.

The incident surface and the exit surface of the third lens may be convex toward the subject in the vicinity of the optical axis and concave toward the edge.

At least one of the first to fourth lenses may be an aspherical lens.

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

At least one of the entrance face and the exit face of the fifth lens may have a plurality of inflection points.

The incident surface of the fifth lens may not have an inflection point, and the emission surface of the fifth lens may have two inflection points.

The incident surface of the fifth lens may be concave with respect to the subject, and the center portion of the emission surface of the fifth lens may be concave with respect to the image sensor and may be convex toward the edge.

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

The center portion of the incident surface of the fifth lens may be convex toward the subject and concave toward the edge, and the center portion of the exit surface of the fifth lens may be concave with respect to the image sensor and convex toward the edge.

The second, third, fourth and fifth 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 fifth lens and the image sensor.

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

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

More specifically, the lens optical system according to the embodiment of the present invention has the refractive power of positive (+), negative (-), negative (-), positive (+), and negative (-) sequentially arranged in the direction of the image sensor in the subject. It includes a first to fifth lens having a, may satisfy at least one of the above-described equations (1) to (4). Such a lens optical system can easily (goodly) correct various aberrations and have a relatively short overall length, which can be advantageous for high performance and miniaturization of a camera.

In particular, when at least one of the incident surface and the exit surface of the fifth lens is an aspherical surface having a plurality of inflection points, various aberrations can be easily corrected through the fifth lens, and the emission angle of chief ray can be adjusted. Vignetting can also be prevented by making it small.

In addition, since the first to fifth lenses are made of plastic, and both surfaces (incident surface and exit surface) of each lens are composed of aspherical surfaces, the lens optical system is more compact and superior in performance than a glass lens. Can be implemented.

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.
5 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.
6 is aberration diagrams showing longitudinal spherical aberration, image curvature, and distortion of the lens optical system according to the second exemplary embodiment of the present invention.
7 is aberration diagrams showing longitudinal spherical aberration, image curvature and distortion of the lens optical system according to the third exemplary embodiment of the present invention.
8 is aberration diagrams showing longitudinal spherical aberration, image curvature, and distortion of the lens optical system according to the fourth exemplary embodiment of the present invention.
Description of the Related Art [0002]
I: First lens II: Second lens
III: Third Lens IV: Fourth Lens
Ⅴ: fifth lens Ⅵ: 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 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, a fourth lens IV and a fifth lens V are provided. The first lens I may be a lens having positive refractive power and having both surfaces (that is, the incident surface 2 * and the exit surface 3 *) convex. The second lens II may be a meniscus lens having a negative refractive power and convex toward the object OBJ. The third lens III may have negative refractive power. The third lens III is generally convex toward the image sensor IMG, but may have a somewhat convex shape toward the subject OBJ near the optical axis. In other words, the incident surface 6 * and the exit surface 7 * of the third lens III may be convex toward the subject OBJ in the vicinity of the optical axis (that is, at the center) and concave toward the edge. The fourth lens IV may be a meniscus lens having positive refractive power and convex toward the image sensor IMG. At least one of the first to fourth lenses I? IV may be an aspheric lens. In other words, the entrance surfaces 2 *, 4 *, 6 *, 8 * and the exit surfaces 3 *, 5 *, 7 *, 9 * of at least one of the first to fourth lenses I? IV. At least one of may be aspherical. For example, the entrance surfaces 2 *, 4 *, 6 *, 8 * and the exit surfaces 3 *, 5 *, 7 *, 9 * of each of the first to fourth lenses I? IV are both aspherical. Can be. The fifth lens V may have negative refractive power, and at least one of the incident surface 10 * and the exit surface 11 * of the fifth lens V may be aspherical. At least one of the incident surface 10 * and the exit surface 11 * of the fifth lens V may be an aspherical surface having a plurality of inflection points. 1 and 4, the incident surface 10 * of the fifth lens V does not have an inflection point, and the emission surface 11 * has two inflection points. In this case, the incident surface 10 * of the fifth lens V may be concave with respect to the subject OBJ, and the center portion of the exit surface 11 * is concave with respect to the image sensor IMG and convex toward the edge. Can be done. 2 and 3, each of the incident surface 10 * and the exit surface 11 * of the fifth lens V has two inflection points. In this case, the center portion of the incident surface 10 * of the fifth lens V may be convex toward the subject OBJ and may be concave toward the edge, and the center portion of the exit surface 11 * may be with respect to the image sensor IMG. It can be concave and convex to the edge. The first lens I may have a strong positive refractive power, and the second to fifth lenses II, III, IV, and V may function as an aberration correcting lens.

Aperture S1 and infrared ray blocking means VI 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 VI may be provided between the fifth lens V and the image sensor IMG. The infrared blocking means VI may be an infrared blocking filter. The positions of the diaphragm S1 and the infrared ray blocking means VI 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 to 4.

&Quot; (1) &quot;

0.5 <f1 / TL <1.0

Here, f1 is the focal length of the first lens I, and TL is the total length of the lens optical system (ie, the full length). The overall length (ie, full length) TL of the lens optical system refers to the distance from the incident surface 2 * of the first lens I to the image sensor IMG.

Equation 1 shows the conditions for compacting the lens optical system. Equation 1 also relates to the correction of spherical aberration of the lens optical system. When f1 / TL is greater than or equal to the upper limit (1.0) 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 f1 / TL is lower than or equal to the lower limit (0.5), the aberration correction is advantageous, but since the total length of the lens optical system becomes long, compactness may become difficult. When the condition of Equation 1 is satisfied, the lens optical system can be made compact while maintaining the spherical aberration in a good state.

&Quot; (2) &quot;

0.4 <R1 / f <0.6

Here, R1 is the radius of curvature of the incident surface 2 * of the first lens I, and f is the focal length of the entire lens optical system.

Equation 2 shows a condition for reducing spherical aberration of the lens optical system. Equation 2 also relates to the compactness of the lens optical system. When R1 / f is greater than or equal to the upper limit value (0.6) in Equation 2, spherical aberration may be large, although it is advantageous to compact the lens optical system. On the other hand, when R1 / f is less than or equal to the lower limit (0.4), spherical aberration correction is advantageous, but since the overall length of the lens optical system becomes long, compactness may become difficult.

&Quot; (3) &quot;

30 <Vd1-Vd2 <35

Here, Vd1 is the Abbe's number of the first lens I, and Vd2 is the Abbe's number of the second lens II. The Abbe numbers Vd1 and Vd2 are measured by using a d-line.

In Equation 3, the Abbe number Vd1 of the first lens I and the Abbe number Vd2 of the second lens II are related to the materials of the lenses I and II. Represents a condition for reducing chromatic aberration. When the condition of Equation 3 is satisfied, a correction effect of axial chromatic aberration and chromatic difference of magnification can be obtained.

&Quot; (4) &quot;

0.2 <BL / TL <0.4

Here, BL is the distance from the exit surface 11 * of the fifth lens V to the image sensor IMG, and TL is the total length of the lens optical system (ie, the full length).

Equation 4 shows the conditions for compacting the lens optical system. When the BL / TL is less than or equal to the lower limit (0.2) in Equation 4, it is advantageous to compact the lens optical system, but various aberrations such as spherical aberration can be increased. On the other hand, when the BL / TL is greater than or equal to the upper limit (0.4), it is advantageous for aberration correction, but it may be difficult to compact since the overall length of the lens optical system becomes long.

In addition, when the imaging surface is a CCD or CMOS image sensor, the angle of the light beam toward the periphery of the screen may be increased. As in the embodiment of the present invention, the exit surface 11 * of the fifth lens V may be plural. When composed of an inflection aspherical surface having an inflection point of, the maximum emission angle of chief ray can be reduced to 25 ° or less. By doing so, spherical aberration, coma aberration, and astigmatism can be corrected easily (easily), and distortion can be easily corrected.

In the above first to fourth embodiments of the present invention, the values of Equations 1 to 4 are as shown in Tables 1 to 4 below. In Table 1, Table 2 and Table 4, the units of the focal lengths f1 and f and the lengths TL and BL are mm.

division f1 TL Equation 1
(0.5 <f1 / TL <1.0) First Embodiment 3.414 5.863 0.582 Second Embodiment 3.433 5.416 0.634 Third Embodiment 3.432 5.581 0.615 Fourth Embodiment 3.411 5.864 0.582

division R1 f Equation 2
(0.4 <R1 / f <0.6) First Embodiment 2.125 4.890 0.435 Second Embodiment 2.075 4.375 0.474 Third Embodiment 2.076 4.526 0.459 Fourth Embodiment 2.120 4.890 0.434

division Vd1 Vd2 Equation 3
(30 <Vd1-Vd2 <35) First Embodiment 55.85 23.4 32.45 Second Embodiment 56.09 23.4 32.69 Third Embodiment 56.09 23.4 32.69 Fourth Embodiment 55.85 23.4 32.45

division BL TL Equation 4
(0.2 <BL / TL <0.4) First Embodiment 1.793 5.863 0.306 Second Embodiment 1.601 5.416 0.296 Third Embodiment 1.509 5.581 0.270 Fourth Embodiment 1.794 5.864 0.306

Referring to Tables 1 to 4, it can be seen that the lens optical systems of the first to fourth embodiments satisfy Equations 1 to 4.

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 fifth lenses I to V may be made of plastic in consideration of its shape and dimensions. That is, all of the first to fifth lenses I to V 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. Various benefits can be achieved accordingly. However, the material of the first to fifth lenses I? V is not limited to the plastic herein. If necessary, at least one of the first to fifth lenses I to V may be made of glass.

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 5 to 8 show curvature radii, lens thicknesses, or distances between lenses, refractive indexes, Abbe's numbers, and the like, for respective lenses of the lens optical system of FIGS. 1 to 4, respectively. In Tables 5 to 8, R is the radius of curvature, D is the lens thickness or lens spacing, or the distance between adjacent components, Nd is the refractive index of the lens measured using the d-line, Vd is d-line (d- Abbe's number of the lens is shown. In the lens surface number, * indicates that the lens surface is aspheric. And the unit of R value and D value is mm.

First Embodiment if R D Nd Vd S1 I
2* 2.125 0.762 1.531 55.85 3 * -11.142 0.100 Ⅱ 4* 24.739 0.347 1.632 23.4 5 * 2.997 0.598 Ⅲ 6 * 8.363 0.404 1.531 55.85 7 * 8.215 0.501 Ⅳ 8* -4.651 0.724 1.531 55.85 9 * -0.988 0.215 Ⅴ 10 * -24.701 0.419 1.531 55.85 11 * 1.192 0.500 VI 12 0.300 1.516 64.10 13 0.993 IMG infinity

Second Embodiment if R D Nd Vd S1 I
2* 2.075 0.623 1.544 56.09 3 * -17.523 0.137 Ⅱ 4* 18.482 0.244 1.632 23.4 5 * 3.294 0.397 Ⅲ 6 * 40.684 0.415 1.531 55.85 7 * 16.396 0.564 Ⅳ 8* -4.011 0.660 1.544 56.09 9 * -1.083 0.349 Ⅴ 10 * 14.198 0.426 1.531 55.85 11 * 1.245 0.393 VI 12 0.226 1.516 64.10 13 0.982 IMG infinity

Third Embodiment if R D Nd Vd S1 I
2* 2.076 0.620 1.544 56.09 3 * -17.391 0.105 Ⅱ 4* 18.555 0.421 1.632 23.4 5 * 3.268 0.439 Ⅲ 6 * 36.389 0.455 1.531 55.85 7 * 17.185 0.564 Ⅳ 8* -4.021 0.717 1.544 56.09 9 * -1.095 0.330 Ⅴ 10 * 25.981 0.421 1.531 55.85 11 * 1.275 0.393 VI 12 0.226 1.516 64.10 13 0.890 IMG infinity

Fourth Embodiment if R D Nd Vd S1 I
2* 2.120 0.754 1.531 55.85 3 * -11.246 0.107 Ⅱ 4* 24.348 0.361 1.632 23.4 5 * 3.031 0.569 Ⅲ 6 * 9.019 0.409 1.531 55.85 7 * 8.494 0.506 Ⅳ 8* -4.719 0.694 1.531 55.85 9 * -0.954 0.125 Ⅴ 10 * -10.497 0.545 1.531 55.85 11 * 1.217 0.500 VI 12 0.300 1.516 64.10 13 0.994 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 9 below. Here, the focal length f is the focal length of the entire lens optical system.

division Fno Focal Length (f) [mm] First Embodiment 2.27 4.890 Second Embodiment 2.60 4.375 Third Embodiment 2.60 4.526 Fourth Embodiment 2.27 4.890

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 (5).

<Equation 5>

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, and A, B, C, D and E represent aspherical coefficients.

Tables 10 to 13 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 10 to 13 show incident surfaces (2 *, 4 *, 6 *, 8 *, 10 *) and exit surfaces (3 *, 5 *, 7 *, 9) of each lens of Tables 5-8, respectively. *, 11 *) aspheric coefficients.

if K A B C D E 2* -0.1262 -0.0028 -0.0063 0.0036 -0.0063 -0.0011 3 * -235.7124 -0.0088 -0.0178 -0.0059 -0.0013 0.0009 4* 310.6954 -0.0027 -0.0209 0.0024 0.0009 0.0002 5 * 0.7342 -0.0211 0.0041 0.0041 -0.0061 0.0031 6 * -180.5155 -0.0455 -0.0196 -0.0023 -0.0006 -0.0003 7 * -199.5417 -0.0401 -0.0107 -0.0051 -0.0011 -0.0004 8* 8.8221 -0.0385 0.0139 -0.0005 -0.0043 0.0009 9 * -3.7485 -0.0822 0.0260 -0.0038 -2.77E-05 8.21E-05 10 * -2677.9656 -0.0475 0.0063 0.0001 1.43E-05 -4.25E-07 11 * -7.5686 -0.0468 0.0085 -0.0012 4.25E-05 4.63E-06

if K A B C D E 2* -0.1567 -0.0019 -0.0091 -0.0012 -7.58E-03 -8.01E-05 3 * -637.7645 -0.0227 -0.0214 -0.0045 -1.48E-03 -1.55E-04 4* 201.9558 -0.0184 -0.0236 0.0069 2.56E-03 1.32E-04 5 * 1.3248 -0.0156 0.0019 0.0064 -5.31E-03 3.22E-03 6 * -15303.8525 -0.0550 -0.0153 0.0041 1.27E-03 -3.99E-04 7 * -1381.9170 -0.0391 -0.0136 -0.0043 -7.06E-04 -2.99E-04 8* 7.7667 -0.0284 0.0168 -0.0047 -4.37E-03 1.70E-03 9 * -3.1643 -0.0710 0.0241 -0.0036 3.24E-05 6.13E-05 10 * -2952.6517 -0.0305 0.0053 -0.0003 -1.10E-05 9.52E-07 11 * -7.2563 -0.0343 0.0048 -0.0006 2.18E-05 -1.06E-07

if K A B C D E 2* -0.1190 -0.0012 -0.0086 -0.0013 -7.89E-03 -2.90E-04 3 * -682.5101 -0.0237 -0.0222 -0.0047 -1.38E-03 -1.09E-04 4* 202.9293 -0.0181 -0.0237 0.0067 2.43E-03 8.69E-05 5 * 1.3572 -0.0156 0.0024 0.0067 -5.19E-03 3.21E-03 6 * -10079.3928 -0.0546 -0.0165 0.0033 8.77E-04 -4.99E-04 7 * -1445.7728 -0.0398 -0.0127 -0.0039 -5.88E-04 -2.83E-04 8* 7.6941 -0.0319 0.0168 -0.0047 -4.47E-03 1.67E-03 9 * -3.3296 -0.0687 0.0239 -0.0038 -4.67E-05 3.58E-05 10 * -21014.4361 -0.0298 0.0054 -0.0003 -1.16E-05 7.75E-07 11 * -7.1659 -0.0326 0.0050 -0.0006 2.34E-05 8.28E-08

if K A B C D E 2* -0.1158 -0.0022 -0.0072 0.0039 -6.05E-03 -1.12E-03 3 * -245.2942 -0.0088 -0.0175 -0.0055 -1.28E-03 7.37E-04 4* 303.3829 -0.0015 -0.0206 0.0023 8.52E-04 1.81E-04 5 * 0.9364 -0.0195 0.0047 0.0040 -5.84E-03 3.17E-03 6 * -175.2053 -0.0505 -0.0184 -0.0013 -4.68E-04 -3.62E-04 7 * -179.1370 -0.0418 -0.0119 -0.0055 -9.71E-04 -3.25E-04 8* 8.4245 -0.0285 0.0126 -0.0016 -4.65E-03 9.33E-04 9 * -3.7405 -0.0804 0.0291 -0.0044 -2.61E-04 6.57E-05 10 * -399.3694 -0.0496 0.0054 0.0002 1.53E-05 -1.12E-06 11 * -8.3786 -0.0477 0.0091 -0.0015 5.62E-05 6.60E-06

FIG. 5 shows the longitudinal spherical aberration, the astigmatic field curvature and the distortion of the lens optical system according to the first embodiment of the present invention (ie, the lens optical system having the numerical values shown in Table 5). Aberration diagram showing distortion.

Figure 5 (a) shows the spherical aberration of the lens optical system for light of various wavelengths, (b) is the image curvature of the lens optical system, that is, tangential field curvature (T) and sagittal surface curvature (sagittal) field curvature) (S). (a) The wavelengths of light used for obtaining the data were 656.2725 nm, 587.5618 nm, 546.0740 nm, 486.1327 nm, and 435.8343 nm. The wavelength of the light used to obtain the data (b) and (c) was 546.0740 nm. The same applies to FIGS. 6 to 8.

(A), (b) and (c) of FIG. 6 are longitudinal spherical aberration and image curvature of the lens optical system according to the second embodiment of the present invention (FIG. 2), that is, the lens optical system having numerical values shown in Table 6. And aberration diagram showing distortion.

(A), (b) and (c) of FIG. 7 respectively illustrate longitudinal spherical aberration and image curvature of the lens optical system according to the third embodiment (FIG. 3) of the present invention, that is, the lens optical system having numerical values shown in Table 7. And aberration diagram showing distortion.

8A, 8B, and 8C are longitudinal spherical aberration and image curvature of the lens optical system according to the fourth embodiment (Fig. 4) of the present invention, that is, the lens optical system having numerical values shown in Table 8; And aberration diagram showing distortion.

As described above, the lens optical system according to the exemplary embodiments of the present invention includes positive, negative, negative, and positive lenses sequentially arranged in the direction of the image sensor IMG from the subject OBJ. ), The first to fifth lenses I to V having negative refractive power may be included, and at least one of Equations 1 to 4 may be satisfied. Such a lens optical system can easily (goodly) correct various aberrations and have a relatively short overall length. Therefore, according to the embodiment of the present invention, it is possible to implement a lens optical system that can obtain a small size, high performance and high resolution.

In particular, when at least one of the entrance surface 10 * and the exit surface 11 * of the fifth lens V is an aspherical surface having a plurality of inflection points in the lens optical system according to the exemplary embodiment of the present invention, the fifth lens V Various aberrations can be easily corrected, and vignetting can be prevented by reducing the emission angle of chief ray.

In addition, the first to fifth lenses I to V are made of plastic, and both surfaces (incident surface and exit surface) of each lens I to V are aspherical, thereby using 6 to 7 glass lenses. It is possible to implement a lens optical system that is compact and excellent performance at a lower cost than the case.

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 VI. 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 (23)

A first lens, a second lens, a third lens, a fourth lens, and a fifth 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 has positive refractive power and is convex on both sides,
The second lens has a negative refractive power and has a meniscus shape in which it is convex toward the subject.
The third lens has a negative refractive power,
The fourth lens has a positive refractive power and a meniscus shape convex toward the image sensor.
The fifth lens has a negative refractive power, and at least one of its entrance and exit surfaces is an aspherical surface. The method of claim 1,
The lens optical system of the following equation holds between the focusing distance f1 of the first lens and the full length TL of the lens optical system.
&Lt; Equation &
0.5 <f1 / TL <1.0 The method according to claim 1 or 2,
The lens optical system of the following equation holds between the radius of curvature (R1) of the incident surface of the first lens and the focal length (f) of the lens optical system.
&Lt; Equation &
0.4 <R1 / f <0.6 The method according to claim 1 or 2,
The lens optical system of the following equation holds between the Abbe number (Vd1) of the first lens and the Abbe number (Vd2) of the second lens.
&Lt; Equation &
30 <Vd1-Vd2 <35 The method of claim 3, wherein
The lens optical system of the following equation holds between the Abbe number (Vd1) of the first lens and the Abbe number (Vd2) of the second lens.
&Lt; Equation &
30 <Vd1-Vd2 <35 The method according to claim 1 or 2,
The lens optical system of the following formula holds between the distance (BL) from the exit surface of the fifth lens to the image sensor and the full length (TL) of the lens optical system.
&Lt; Equation &
0.2 <BL / TL <0.4 The method of claim 3, wherein
The lens optical system of the following formula holds between the distance (BL) from the exit surface of the fifth lens to the image sensor and the full length (TL) of the lens optical system.
&Lt; Equation &
0.2 <BL / TL <0.4 The method of claim 4, wherein
The lens optical system of the following formula holds between the distance (BL) from the exit surface of the fifth lens to the image sensor and the full length (TL) of the lens optical system.
&Lt; Equation &
0.2 <BL / TL <0.4 The method of claim 5, wherein
The lens optical system of the following formula holds between the distance (BL) from the exit surface of the fifth lens to the image sensor and the full length (TL) of the lens optical system.
&Lt; Equation &
0.2 <BL / TL <0.4 The method of claim 1,
And the third lens is convex toward the subject in the vicinity of an optical axis. The method of claim 1,
The incident surface and the exit surface of the third lens are convex toward the subject side near the optical axis and concave toward the edge. The method of claim 1,
At least one of the first to fourth lenses is a lens optical system. The method of claim 1,
At least one of the incident surface and the exit surface of at least one of the first to fourth lenses of the lens optical system. The method of claim 1,
At least one of the incident surface and the exit surface of the fifth lens has a plurality of inflection points. 15. The method of claim 14,
The incident surface of the fifth lens does not have an inflection point,
The emission surface of the fifth lens has two inflection points. The method of claim 15,
The incident surface of the fifth lens is concave with respect to the subject,
And a center portion of the exit surface of the fifth lens is concave with respect to the image sensor and is convex toward the edge. 15. The method of claim 14,
The optical system of claim 5, wherein each of the entrance and exit surfaces of the fifth lens has two inflection points. The method of claim 17,
The center portion of the incident surface of the fifth lens is convex toward the subject and concave toward the edge,
And a center portion of the exit surface of the fifth lens is concave with respect to the image sensor and is convex toward the edge. The method of claim 1,
And the second, third, fourth and fifth 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. 22. The method of claim 21,
The infrared blocking means is a lens optical system provided between the fifth lens and the image sensor. The method of claim 1,
At least one of the first to fifth lenses is a lens optical system.

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