KR101933088B1 - Lens optical system and photographing apparatus having the same - Google Patents

Abstract

A lens optical system and a photographing apparatus including the same are disclosed.
The disclosed lens optical system includes a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having positive refractive power, the first lens group having a negative refractive power, A first lens disposed on the most object side in the group and having a meniscus shape and having a positive refractive power, and a second lens disposed on the uppermost side in the first lens group and having a meniscus shape and having a negative refractive power, .

Description

TECHNICAL FIELD [0001] The present invention relates to a lens optical system and a photographing apparatus including the lens optical system.

The exemplary embodiment relates to a lens optical system configured to perform focusing with an inner focus method and perform focusing at a high speed, and a photographing apparatus including the lens optical system.

In recent years, there has been a demand for miniaturization of a photographing apparatus, a power saving function, and the like, and it is required to downsize a photographing apparatus using a solid-state image pickup device such as a CCD (Charge-Coupled Devices) type image sensor or CMOS (Complementary Metal-Oxide Semiconductor) type image sensor have. Such photographing apparatuses include a digital still camera, a video camera, and an interchangeable lens camera. Still further, a photographing apparatus using a solid-state image sensing device is suitable for miniaturization, and recently it has been applied to a small information terminal including a cellular phone. Users have a demand for high performance such as high resolution and wide angle. In addition, as the consumer's expertise in cameras continues to increase, there is an increasing demand for short-focus lenses such as wide-angle lenses and telephoto lenses.

When the number of lenses of the focusing lens group is large, the focusing speed of the focusing lens group is slow, and the size of the actuator for driving the focusing lens group is large, thereby inhibiting the miniaturization of the photographing apparatus can do.
As a prior art document, there is Japanese Patent Application Laid-Open No. 2242690.

Various embodiments provide a lens optical system capable of performing high-speed auto focusing.

Various embodiments provide a photographing apparatus capable of performing high-speed auto focusing.

A lens optical system according to an exemplary embodiment includes: a first lens group having negative refractive power; A second lens group that performs focusing and has a positive refractive power; And a third lens group having positive refractive power, wherein the first lens group comprises a first lens which is disposed on the most object side in the first lens group, has a meniscus shape and has a positive refractive power, And a second lens having a meniscus shape and having a negative refractive power, wherein the first lens group and the third lens group are fixed at the time of focusing, and have a half angle of view of 45 degrees or more.

The object side surface of the lens located closest to the object side in the second lens group may have a convex shape toward the object side.

The lens optical system can satisfy the following expression.

<Expression>

Here, R _front is the radius of curvature of the object-side surface of the most object-side lens in the second lens group, and f represents the total focal length of the lens optical system at the infinite object distance.

The lens optical system can satisfy the following expression.

<Expression>

Here, f _{1 st} is the focal length of the first lens, and f is the total focal length of the lens optical system at the infinite object distance.

The lens optical system can satisfy the following expression.

<Expression>

Here, f _AF is the focal length of the second lens group, and f _G3 is the focal length of the third lens group.

The third lens group may further include a diaphragm.

The first lens group may further include at least two lenses between the first lens and the second lens, and the lens positioned third from the object side in the first lens group may be an aspherical lens.

The lens optical system can satisfy the following expression.

<Expression>

Here, D represents the radius of the aspherical lens included in the first lens group, and y represents the half diagonal length of the image sensor used in the lens optical system.

The focal length of the lens optical system may be smaller than the rear focal length.

A third lens of meniscus shape and a fourth lens of meniscus shape may be further disposed between the first lens and the second lens.

The first lens, the second lens, the third lens, and the fourth lens may each have a meniscus shape convex toward the object side.

The third lens may have a negative refractive power and the fourth lens may have a negative refractive power.

The second lens group may include two or three lenses.

The second lens group may include a fifth lens having a positive refractive power, a sixth lens having a positive refractive power, and a seventh lens having a positive refractive power.

The fifth lens and the sixth lens may be joined.

The lens optical system may have a half angle of view ranging from 45 to 60 degrees.

An image pickup apparatus according to an exemplary embodiment includes a lens optical system and an image sensor that receives light imaged by the lens optical system,

Wherein the lens optical system includes a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having positive refractive power, the first lens group performing focusing, A first lens disposed on the most object side in the group and having a meniscus shape and having a positive refractive power, and a second lens disposed on the uppermost side in the first lens group and having a meniscus shape and having a negative refractive power, The first lens group and the third lens group are fixed when focusing, and have a half angle of view of 45 degrees or more.

The lens optical system according to the exemplary embodiment adopts the inner focus method, and can be miniaturized. In addition, the lens optical system according to the exemplary embodiment has a small number of focusing lens groups to enable high-speed focusing. Further, the exemplary embodiment can provide a retro-focus type lens optical system having a wide angle.

Fig. 1 shows a lens optical system according to the first numerical example and shows a focusing operation.
FIG. 2 is an aberration diagram of the infinite object distance of the lens optical system shown in FIG. 1; FIG.
Fig. 3 shows aberration diagrams when the lens optical system shown in Fig. 1 has a magnification of (-1/30).
Fig. 4 shows a lens optical system according to the second numerical example and shows a focusing operation.
FIG. 5 is an aberration diagram of the infinite object distance of the lens optical system shown in FIG. 4;
Fig. 6 shows aberration diagrams when the lens optical system shown in Fig. 4 has a magnification of (-1/30).
Fig. 7 shows a lens optical system according to the third numerical example and shows a focusing operation.
FIG. 8 is an aberration diagram of the infinite object distance of the lens optical system shown in FIG. 7; FIG.
Fig. 9 shows aberration diagrams when the lens optical system shown in Fig. 7 has a magnification of (-1/30).
10 schematically shows a photographing apparatus according to an exemplary embodiment.

Hereinafter, a lens optical system according to an exemplary embodiment and a photographing apparatus including the same will be described in detail with reference to the accompanying drawings.

Fig. 1 shows a lens optical system 100-1 according to an exemplary embodiment of the present invention. 1 shows a lens optical system at an infinite object distance and a lower magnification (-1/30) at the top in FIG. 1, and shows the focusing operation of the lens optical system 100-1.

The lens optical system 100-1 is arranged in order from the object side O to the image side I and includes a first lens group G11 having a negative refractive power, A second lens group G21, and a third lens group G31 having a positive refractive power.

Hereinafter, the image side I indicates a direction in which an image plane IMG is formed, and the object side O indicates a direction in which a subject exists. The "object side surface" of the lens means a lens surface on the side where the subject is located with respect to the optical axis OA, for example, and the " And the right side in the figure can be indicated by the lens surface on the side having the right side. The upper surface IMG may be, for example, an image pickup element surface or an image sensor surface. The image sensor may include, for example, a sensor such as a CMOS, a complementary metal oxide semiconductor, or a charge coupled device (CCD). The image sensor is not limited to this, and may be, for example, an element for converting an image of an object into an electrical image signal.

The first lens group G11 may include a first lens L1, a second lens L21, a third lens L31 and a fourth lens L41 arranged in order from the object side to the image side. The first lens L1 may be disposed on the most object side in the first lens group G11 and the fourth lens L4 may be disposed on the most image side within the first lens group G11. The first lens L11 has a meniscus shape and can have a positive refractive power. The second lens L21 may have, for example, a meniscus shape. The second lens L21 may have negative refractive power, for example. The third lens L31 may have, for example, a meniscus shape. The third lens L31 may have negative refractive power, for example. The fourth lens L41 has a meniscus shape and can have a negative refractive power.

The first through fourth lenses L11, L21, L31, and L41 may each have a meniscus shape convex toward the object side.

The lens optical system according to various embodiments may perform focusing by a contrast auto focusing method that reads an image at high speed from an imaging sensor and performs focusing using the sharpness of the edge of the image .

For example, a mirrorless camera can use contrast auto focus.

The contrast auto focus method must continuously acquire an image while the focusing lens group performs fine movement. Therefore, a driving source for moving the focusing lens group is required. For example, as the driving source, a driving source that performs a minute rotational motion discontinuously, such as a stepping motor, can be used. Such a driving source generally transfers a focusing lens group when the torque is weak and the focusing lens group is heavy. When the focusing lens group is heavy, the focusing lens group is moved using a high gear ratio to reduce the number of driving sources , Noise may be generated due to generation of a contact sound between the gears. Therefore, it is preferable that the focusing lens group is light in order to perform focusing by the contrast auto focusing method. In the lens optical system according to various embodiments, for example, the second lens group G21 used as the focusing lens group may include two or three lenses.

In the exemplary embodiment, the lens optical system may be configured as a retro-focus type, and the resolution change may be reduced in accordance with the movement of the focusing lens group. In the retrofocus type, the back focal length (BFL) may be larger than the effective focal length (EFL). In the retro-focus type lens optical system, the first lens group G11 can have a negative refractive power. The first lens group G11 may include lenses having a plurality of negative refractive powers.

The lens optical system according to the exemplary embodiment can realize a wide angle with a half field of view of 45 degrees or more. For example, the lens optical system according to the exemplary embodiment may have a half angle of view ranging from 45 degrees to 60 degrees. The lens optical system according to the exemplary embodiment has a lightening focusing lens group including two or three lenses so as to realize high-speed auto focusing (AF), and includes a first lens group G11, It is possible to adopt an inner focus method in which the third lens group G31 is fixed at the time of focusing.

The lens optical system according to the exemplary embodiment may have a short focal length to be suitable for a mirrorless camera. The back focal distance may represent the distance from the object side of the last lens of the lens optics to the image sensor. Since the mirrorless camera does not need a mirror, it is not necessary to secure a space for installing the mirror, so that the focal length may be short.

The first lens L11 on the object side of the first lens group G11 may have a positive refractive power. Since the first lens L11 has a positive refractive power and the light flux is converged, the diameter of the lens in which the first lens L11 is located later can be reduced. Further, the first to fourth lenses L11, L21, L31, and L41 of the first lens group have a meniscus shape to reduce coma aberration, and a lens having a positive refractive power and a lens having a negative refractive power The chromatic aberration in the first lens unit can be effectively corrected.

The second lens group G21 includes two or three lenses, and may have a positive refractive power. In the second lens group G21, the object side surface of the fifth lens L51 located closest to the object side in the second lens group may have a convex shape toward the object side. For example, the fifth lens L51 may be a biconvex lens. A sixth lens L61 and a seventh lens L71 may be further provided on the upper side of the fifth lens L51. The sixth lens L61 may have, for example, an upper surface concave toward the image side. For example, the sixth lens L61 may be a bi-concave lens. The seventh lens L71 may have a meniscus shape convex toward the object side, for example. For example, the fifth lens L51 and the sixth lens L61 may be joined. The second lens group G21 may include at least one aspherical lens. For example, the seventh lens L71 of the second lens group G21 may be an aspherical lens.

The third lens group G31 may include a plurality of lenses. The third lens group G31 may include, for example, an eighth lens L81, a ninth lens L91, and a tenth lens L101. The eighth lens L81 may have a negative refractive power and the ninth lens L91 may have a positive refractive power. The eighth lens L81 may have a convex meniscus shape toward the object side. The ninth lens L91 may be a biconvex lens. The tenth lens L101 may have a convex meniscus shape upward. The eighth lens L81, the ninth lens L91, and the tenth lens L101 may be triple-bonded. An eleventh lens L111, a twelfth lens L121, a thirteenth lens L131, and a fourteenth lens L141 may be further provided on the image side of the tenth lens L101. The tenth lens L101 may have negative refractive power. The tenth lens L101 may be a double concave lens. The eleventh lens L111 may have a positive refractive power. The eleventh lens L11 may be a biconvex lens. The twelfth lens L121 may have negative refractive power. The twelfth lens L12 may be a double concave lens. The thirteenth lens L131 may have a positive refractive power. The thirteenth lens L131 may be a biconvex lens. For example, the twelfth lens L121 and the thirteenth lens L131 may be joined.

The third lens group G31 may include at least one aspherical lens. For example, the twelfth lens L121 of the third lens group G23 may be an aspheric lens.

The third lens group G31 may include a diaphragm ST. The stop ST is for adjusting the diameter of the light beam, and may include, for example, an aperture stop, a variable stop, or a stop in the form of a mask. A stop ST may be provided between the lenses included in the third lens group G31. For example, a stop ST may be provided between the ninth lens L91 and the tenth lens L101. The diameter of each lens group can be determined according to the position of the stop ST. For example, in the interchangeable lens system, since there is a limitation on the diameter of the last lens on the image side, if the aperture stop is located in the third lens unit to satisfy the above condition, the diameter of the third lens unit becomes small, have.

According to various embodiments, at least one optical element OD1 may be provided between the thirteenth lens L131 and the upper surface IMG. The optical element OD1 may comprise at least one of, for example, a broadband pass filter, or a cover glass. For example, when a broadband pass filter is provided as an optical element, it may include a broadband coating that transmits light having a wavelength in the range of 400-1000 nm. The broadband pass filter can pass both visible light and infrared light, for example. Alternatively, the optical element OD1 may comprise a visible light transmission filter. However, it is also possible that a lens optical system is constructed without an optical element.

Fig. 4 shows a lens optical system 100-2 according to the second numerical example. The lens optical system 100-2 may include a first lens group G12 having a negative refractive power, a second lens group G22 having a positive refractive power, and a third lens group G32 having a positive refractive power. The first lens group G12 may include a first lens L12, a second lens L22, a third lens L32, and a fourth lens L42. The first lens L12 may have a positive refractive power. The first lens L12, the second lens L22, the third lens L32 and the fourth lens L42 may have meniscus shapes convex toward the object side O respectively.

The second lens group G22 may include a fifth lens L52, a sixth lens L62, and a seventh lens L72. The fifth lens L52 may have a positive refractive power. The fifth lens L52 may include a convex object side surface 9 toward the object side O. [ The fifth lens L52 may be, for example, a biconvex lens. The sixth lens L62 may have a meniscus shape convex toward the image side I. The seventh lens L72 may have a meniscus shape convex toward the image side I. The third lens group G32 includes an eighth lens L82, a ninth lens L92, a tenth lens L102, an eleventh lens L112, a twelfth lens L122, and a thirteenth lens L132. . &Lt; / RTI &gt; The eighth lens L82, the ninth lens L92, and the tenth lens L102 may be triple-bonded. A diaphragm ST may be provided between the ninth lens L92 and the tenth lens L102.

Fig. 7 shows a lens optical system 100-3 according to the third numerical example. The lens optical system 100-3 may include a first lens group G13 having a negative refractive power, a second lens group G23 having a positive refractive power, and a third lens group G33 having a positive refractive power. The first lens group G13 may include a first lens L13, a second lens L23, a third lens L33, and a fourth lens L43. The first lens L13 may have a positive refractive power. The first lens L13, the second lens L23, the third lens L33 and the fourth lens L43 may have meniscus shapes convex toward the object side O, respectively.

The second lens group G23 may include a fifth lens L53, a sixth lens L63, and a seventh lens L73. The fifth lens L53 may have a positive refractive power. The fifth lens L53 may include a convex object side surface 9 toward the object side O. [ The sixth lens L63 may have a meniscus shape convex toward the image side I. The seventh lens L73 may have a meniscus shape convex toward the image side I. The third lens group G33 includes an eighth lens L83, a ninth lens L93, a tenth lens L103, an eleventh lens L113, a twelfth lens L123, and a thirteenth lens L133. . &Lt; / RTI &gt; The eighth lens L83, the ninth lens L93, and the tenth lens L103 may be triple-bonded. A diaphragm ST may be provided between the ninth lens L93 and the tenth lens L103.

The lens optical system according to various embodiments can satisfy the following expression. The following equations will be described with reference to Fig. 1, but can also be applied to a lens optical system according to another embodiment.

<식 1>

<Formula 1>

Here, R _front is the radius of curvature of the object side surface of the lens closest to the object side of the second lens group, and f indicates the entire focal length of the lens optical system at the infinite object distance.

When the second lens group G21 has a positive refractive power, it is advantageous for the aberration correction or the like that the object side surface of the lens closest to the object side of the second lens group G21 has a convex shape toward the object side. When the curvature of the object side surface of the lens closest to the object side of the second lens group G21 satisfies the equation (1), aberration correction can be facilitated. The curvature of the object side surface of the most object side lens (fifth lens) L51 of the second lens group G21 becomes very small when the radius R _front / f is smaller than the lower limit value of the equation (1) L51 are too short, the performance variation due to the lens assembly may become large. (R _front / f) is larger than the upper limit value of Equation (1), the focal length of the fifth lens L51 may become long and the amount of focusing movement may become too large. Equation 1 is also a condition regarding the weight of the focusing lens group. The fifth lens may have a positive refractive power so that the focusing lens group has a positive refractive power and the fifth lens may be composed of a biconvex lens. When the fifth lens is composed of a biconvex lens, there may be a limit in reducing the center thickness of the fifth lens. When the expression (1) is satisfied, it is easy to process the fifth lens, and the amount of focusing movement can be reduced. (R _front / f) exceeds the upper limit value of Equation (1), the thickness of the fifth lens (L51) becomes thick, so that the entire weight of the second lens group becomes heavy. If the weight of the second lens group is heavy, it may be difficult to perform focusing quickly.

The lens optical system according to various embodiments can satisfy the following expression.

<식 2>

<Formula 2>

Here, f _{1 st} is the focal length of the first lens, and f is the total focal length of the lens optical system at the infinite object distance.

(f _1st / f) is more than the upper limit value of the expression 1, the first lens group (G11) a first lens (L11) focal length (f _1st) is too long, generally the first lens group (G11) of the As the diameter increases, miniaturization of the lens optical system may become difficult. (f _1st / f) is smaller than the lower limit value of the equation (1), the focal length (f _{1 st} ) of the first lens G 11 becomes too short so that the sensitivity of the lens becomes large and the total refractive power of the first lens group becomes small, Making it difficult to make the optical system a wide angle.

The lens optical system according to various embodiments can satisfy the following expression.

<식 3>

<Formula 3>

Here, f _AF is the focal length of the second lens group, and f _G3 is the focal length of the third lens group.

Equation 3 defines the focal length ratio between the second lens group G21 and the third lens group G31. (f _AF / f _G3 ) When the formula (3) is satisfied, the lenses constituting the third lens group of the second lens group have refractive powers of similar magnitudes, and the sensitivity can be reduced. In order to reduce the amount of movement of the second lens group, which is the focusing lens group, it is advantageous to reduce the focal length of the second lens group. However, if the focal length of the second lens group is too small, the sensitivity becomes large, .

 According to various embodiments, the first lens group G11 may include at least one aspherical lens. For example, in the first lens group G11, the third lens from the object side may be an aspherical lens. The aspheric lens can effectively correct the astigmatism and distortion aberration of the lens optical system. The smaller the diameter of the aspherical lens is, the more the lens manufacturing cost can be reduced. However, in order to enhance the aberration correction effect, a lens having a larger diameter is advantageous. Therefore, by constructing the third lens L31 of the first lens group G11 with an aspherical lens, both the manufacturing cost of the aspherical lens and the aberration correction can be satisfied. Alternatively, the fourth lens L41 may be an aspherical lens.

The lens optical system according to various embodiments can satisfy the following expression.

<식 4>

<Formula 4>

Here, D represents the radius of the aspherical lens included in the first lens group, and y represents the half diagonal length of the image sensor used in the lens optical system.

(D / y) satisfies the expression (4), the manufacturing cost of the aspherical lens of the first lens group can be reduced and the aberration can be corrected effectively. (D / y) is smaller than the lower limit value of the equation (4), the production cost of the aspherical lens is reduced, but the aberration correction may become difficult. The manufacturing cost of the lens can be increased.

On the other hand, if the weight of the second lens group G21 is reduced, high-speed auto focusing can be performed, so that the number of lenses constituting the second lens group is reduced as much as possible. However, if the number of lenses is too small, it is difficult to correct aberrations. Accordingly, the second lens group includes a two- or three-lens system, performs autofocusing at high speed, minimizes changes in aberration caused by focusing, and has stable resolution performance regardless of the object distance.

It is also preferable that a third lens group having a positive refractive power is provided for correcting the residual aberrations not corrected by the first lens group and the second lens group.

The definition of the aspheric surface used in the lens optical system according to the exemplary embodiment is as follows.

The aspheric surface shape can be expressed by the following equation with the optical axis direction as the z-axis and the direction perpendicular to the optical axis direction as the y-axis, with the traveling direction of the light beam as a normal. Where Z is the distance from the apex of the lens in the direction of the optical axis, Y is the distance in the direction perpendicular to the optical axis, K is the conic constant, A, B, C, D, E, F. (1 / R) of the radius of curvature at the apex of the lens, respectively.

<식 5>

&Lt; EMI ID =

For example, the third lens of the first lens group may be an aspherical lens. The second lens group may include at least one aspherical lens.

At least one optical element OD1, OD2, and OD3 may be provided on the uppermost side I in the drawings. The optical elements OD1 (OD2) and OD3 may include at least one of, for example, a low pass filter, an IR-cut filter, and a cover glass. However, it is also possible to construct a lens system without an optical filter. The image of the object can be incident on the image plane (IMG) through the lenses. The upper surface IMG may be, for example, an image pickup element surface or an image sensor surface. The imaging device may comprise, for example, a CCD or CMOS.

In the present invention, the lens optical system can be implemented by numerical embodiments according to various designs as follows. Hereinafter, the total effective focal length f is expressed in mm units, the half angle of view (HFOV) is expressed in degrees, * denotes an aspherical surface, and Fno denotes an F number. In the following description, object denotes an object, R denotes a radius of curvature, Dn denotes a thickness of a lens or an air gap between a lens and a lens, in mm units. Nd denotes a refractive index, Vd denotes an Abbe number, Ape represents the radius of the lens.

In each numerical embodiment, the lens surface numbers (1, 2, 3,... N) are sequentially aligned from the object side (O) to the image side (I). In the drawing, the lens surface number is written only for the object side surface of the lens closest to the object side of each lens group and the upper side surface of the lens at the uppermost side for convenience.

&Lt; First Numerical Embodiment >

Fig. 1 shows a lens optical system 100-1 according to the first numerical example, and the following shows design data of the first numerical example.

f = 14.537 mm, Fno / 2.87, HFOV = 57.031 DEG

Lens face R Dn Nd Vd H-Ape Note object infinity D0 One 110.229 5.900 1.69680 55.46 First lens group:
fixing 2 192.497 0.100 3 61.219 2.320 1.80610 33.27 4 20.952 3.373 5 * 63.395 2.650 1.805000 40.9 18.04 6 * 22.996 5.200 15.21 7 37.480 1.400 1.49700 81.61 8 13.779 D1 9 23.816 4.200 1.84666 23.78 Second lens group: Focusing 10 -91.888 1.100 1.92286 20.88 11 444.168 0.100 12 * 200,000 2.000 1.877950 37.3 13 * 178.331 D2 14 88.870 0.900 1.71736 29.50 The third lens group
fixing 15 9.878 7.550 1.60342 38.01 16 -10.975 0.900 1.84666 23.78 17 -18.434 0.129 ST infinity 2.963 19 -59.894 0.900 1.56384 60.83 20 30.341 0.860 21 * 17.909 6.610 1.588530 60.37 22 * -12.535 0.100 23 -18.801 0.900 1.782000 37.1 24 14.403 7.650 1.49700 81.61 25 -40.628 D3 26 infinity 2.500 1.51680 64.20 Optical element 27 infinity D4 IMG infinity D5

Table 2 shows the aspherical surface coefficients in the first embodiment.

Aspherical coefficient 5 6 12 13 21 22 K 0.391538 -0.952731 -58.835394 -63.853601 -0.478183 -0.741465 A 1.294741E-04 1.455188E-04 3.854496E-05 5.292057E-05 -8.843514E-06 4.603878E-05 B -4.620516E-07 -1.616711E-08 -4.672307E-08 -1.175961E-07 1.583978E-07 -1.152029E-07 C 1.022139E-09 -4.025521E-09 1.578082E-09 3.507457E-09 -4.698134E-10 2.865089E-09 D -2.140571E-12 1.498157E-11 -3.278302E-12 -1.557372E-11 -1.156605E-11 -4.187808E-11 E 3.117095E-15 -1.802555E-14 -1.408525E-14 2.022021E-15 1.836682E-13 3.133810E-13 F -5.194795E-19 5.813824E-22 -3.446867E-27 7.638678E-28 3.932483E-17 4.174785E-26 G -3.006030E-21 -2.109536E-33 -1.920661E-33 -1.923668E-33

D1, D2, D3, D4, and D4 for the case where the infinite object distance, the magnification (MAG) in the first embodiment, and the object distance with magnification (-1/30) D5), focal length (f), magnification (MAG), F number (Fno), and half angle of view. Here, TL is the distance from the subject to the upper surface, and represents the distance from the object to the object. TL can be used to indicate the shortest shooting distance in the lens optical system.

Item Infinite object distance MAG = -1 / 30 TL = 0.2m D0 infinity 411.570745 94.636274 D1 18.418548 18.786854 19.865161 D2 3.480179 3.111872 2.033566 D3 22.66 22.66 22.66 D4 0.448429 0.507222 0.548758 D5 0.051571 -0.007222 -0.048758 f 14.537406 MAG 0.033344 0.121511 Fno 2.867 2.872 2.875 HFOV 57.031 57.269 58.028

Fig. 2 shows a transverse aberration diagram for the first numerical example at an infinite object distance, and Fig. 3 shows a transverse aberration diagram when the magnification is (-1/30). Here, the dotted line indicates a wavelength of 656.2700 nm, the solid line indicates a wavelength of 587.5600 nm, and the one dotted line indicates a transverse aberration with respect to a wavelength of 486.1300 nm. The transverse aberrations show aberrations for the Zango (tangential) and Sagittal (top) surfaces.

&Lt; Second Numerical Embodiment >

Fig. 4 shows the lens optical system 100-2 according to the second numerical example, and the following shows design data of the second numerical example.

f = 14.479 mm, Fno / 2.87, HFOV = 56.990357 DEG

Lens face R Dn Nd Vd H-Ape Note object infinity D0 One 45.087 4.320 1.84666 23.78 First lens group: fixed 2 48.471 0.100 3 38.529 1.600 1.92286 20.88 4 18.089 3.900 5 * 26.699 3.080 1.690000 53 16.66 6 * 12.894 7.850 12.95 7 34.647 1.400 1.49700 81.61 8 17.726 D1 9 34.940 4.140 1.74077 27.76 Second lens group: Focusing 10 -32.437 1.600 1.92286 20.88 11 -36.528 0.100 12 -55.156 1.600 1.92286 20.88 13 -69.460 D2 14 74.365 2.360 1.92286 20.88 Third lens group: Fixed 15 -71.697 2.610 1.62041 60.34 16 -17.257 1.600 1.75211 25.05 17 -171.785 0.835 ST infinity 2.828 19 -60.510 1.600 1.83400 37.34 20 23.117 0.106 21 * 15,000 4.400 1.514730 63.86 22 * -22.078 0.684 23 59.394 1.600 1.84666 23.78 24 11.693 7.760 1.49700 81.61 25 -54.169 D3 26 infinity 2.500 1.51680 64.20 Optical element 27 infinity D4 IMG infinity 0.000

Table 5 shows the aspherical surface coefficients in the second embodiment.

Aspherical coefficient 5 6 21 22 K 0.995616 -0.449635 -0.557765 -0.432220 A 9.683649E-05 1.502932E-04 -2.528287E-05 2.917921E-05 B -3.239017E-07 -2.757923E-08 1.167872E-07 -5.217748E-08 C 3.001238E-10 -2.093515E-09 -3.098113E-09 4.633349E-10 D -2.888184E-13 -7.171896E-12 -1.314859E-11 -4.659356E-11 E -3.829072E-17 5.723602E-14 1.763502E-13 2.116636E-23 F 2.180179E-18 -9.501349E-17 9.868293E-27 9.866934E-27 G -6.795685E-21

Table 6 shows the relationship between the infinite object distance in the second embodiment, the object distance with magnification (MAG) of -1/30, the variable distance, focal length f, magnification MAG, , An F number (Fno), and a half angle of view. TL is the distance from the subject to the top surface, and represents the distance from the object. In Table 6, "in Air " means the distance from the image side of the most image side lens of the lens optical system to the image pickup element (upper surface) in the absence of the optical element.

Item Infinite object distance MAG = -1 / 30 TL = 0.2m D0 infinity 405.203946 98.825000 D1 18.112323 18.697289 20.158016 D2 2.560677 1.975711 0.514984 D3 21.429000 21.429000 21.429000 D4 0.500000 0.500000 0.500000 in Air 23.577209 23.577209 23.577209 f 14.479038 MAG 0.033333 0.113008 HFOV 56.990357 57.877177 60.216090

Fig. 5 shows the ray fan for the second numerical example at an infinite object distance, and Fig. 6 shows the lateral aberration when the magnification is (-1/30). Here, the dotted line represents the wavelength of 656.2700 nm, the solid line represents the wavelength of 587.5600 nm, and the one dotted line represents the transverse aberration for the wavelength of 479.9100 nm.

&Lt; Third Numerical Embodiment >

Fig. 7 shows the lens optical system 100-3 according to the third numerical example, and the following is the design data of the third numerical example.

f = 14.52 mm, Fno / 2.86, HFOV = 57.078423 DEG

Lens face R Dn Nd Vd H-Ape Note object infinity D0 One 76.649 5.120 1.62041 60.34 First lens group: fixed 2 121.089 0.100 3 45.421 2.020 1.80610 33.27 4 18.040 4.293 5 * 52.320 2.800 1.805000 40.9 16.43 6 * 20.699 5.000 13.80 7 38.559 0.950 1.49700 81.61 8 12.890 D1 9 29.903 3.020 1.69895 30.05 Second lens group: Focusing 10 149.118 2.170 1.92286 20.88 11 -400.833 0.100 12 * 94.680 2.150 1.879150 37.22 13 * 745.757 D2 14 72.644 1,000 1.72342 37.99 Third lens group: Fixed 15 10.357 7.620 1.60342 38.01 16 -11.123 0.950 1.80518 25.46 17 -20.875 0.714 ST infinity 1.700 19 133.903 0.950 1.80610 33.27 20 21.718 0.100 21 * 14.792 5.960 1.589130 61.81 22 * -14.179 0.104 23 -20.042 0.950 1.83400 37.34 24 12.658 7.600 1.49700 81.61 25 -32.085 D3 26 infinity 2.500 1.51680 64.20 Optical element 27 infinity D4 IMG infinity 0.000

Table 8 shows the aspherical surface coefficients in the third embodiment.

ASP 5 6 12 13 21 22 K 2.163229 -0.660233 -2.253919 -2884.008769 -0.422565 -0.643408 A 1.340587E-04 1.625401E-04 -5.158866E-06 -3.363777E-06 -2.832550E-06 3.888786E-05 B -4.440620E-07 1.156394E-07 -6.330578E-08 -1.106300E-07 8.230915E-08 -1.835930E-07 C 7.728644E-10 -5.599641E-09 -3.415059E-10 2.024215E-11 1.373934E-09 3.947837E-09 D -1.442911E-12 1.552847E-11 8.256376E-12 6.763863E-12 -3.705821E-11 -6.205485E-11 E 1.689860E-15 -1.136673E-14 -8.591385E-26 2.022021E-15 1.837375E-13 3.134994E-13 F 5.004316E-19 -4.474455E-27 3.933968E-17 4.211330E-26 G -3.006030E-21

Table 9 shows the infinite object distance in the third embodiment, the object distance with magnification (MAG) of -1/30, the variable distance, focal length f, magnification (MAG) for TL = , An F number (Fno), and a half angle of view. TL is the distance from the subject to the top surface, and represents the distance from the object.

 Item Infinite object distance m = -1 / 30 TL = 0.2m D0 846.082428 410.484093 95.039853 D1 19.317145 19.503721 20.494595 D2 1.926002 1.739426 0.748552 D3 25.346000 25.346000 25.346000 D4 0.500000 0.500000 0.500000 in Air 27.492125 27.492125 27.492125 f 0.016667 MAG 0.033333 0.120832 HFOV 57.078423 57.238220 58.140003

Fig. 8 shows the ray fan for the third numerical example at the infinite object distance, and Fig. 9 shows the lateral aberration when the magnification is (-1/30). Here, the dotted line represents the wavelength of 656.2700 nm, the solid line represents the wavelength of 587.5600 nm, and the one dotted line represents the transverse aberration for the wavelength of 479.9100 nm.

As described above, the lens optical system according to the embodiment of the present invention can realize a retro focus type lens system having a half angle of view of about 45 degrees or more and an effective focal length shorter than a rear focal length. In addition, the lens optical system can be configured such that the focusing lens group is lightened and the manufacturing cost is not high so that high-speed auto focusing (AF) can be realized.

Next, it is shown that the first to third numerical embodiments described above satisfy the above-mentioned formulas 1 to 4, respectively.

R _front f R _front / f Equation 1 Example 1 23.816 14.537 1.638 Example 2 34.94 14.479 2.413 Example 3 29.903 14.52 2.059 f _1st f f _1st / f Equation 2 Example 1 357.997 14.537 24.627 Example 2 481.151 14.479 33.231 Example 3 321.111 14.52 22.115 f _AF f _G3 f _AF / f _G3 Equation 3 Example 1 30.351 42.839 0.708 Example 2 27.739 66.28 0.419 Example 3 28.729 55.678 0.516 D y D / y Equation 4 Example 1 18.05 21.7 0.832 Example 2 16.67 21.7 0.768 Example 3 16.43 21.7 0.757

Fig. 9 shows a photographing apparatus having a lens optical system 100 according to an exemplary embodiment. The lens optical system 100 is substantially the same as the lens optical systems 100-1, 100-2, and 100-3 described with reference to Figs. 1, 4, and 7. The photographing apparatus may include an image sensor 112 that receives light imaged by the lens optical system 100. [ In addition, a display unit 115 for displaying a subject image may be provided. The photographing apparatus can be applied to, for example, a mirrorless camera.

The lens optical system according to the exemplary embodiment can implement miniaturization by adopting the inner focusing method in which some lenses inside the lens optical system are moved and focused. Further, by using the inner focusing method, the photographing apparatus can be conveniently carried.

The above-described embodiments are merely illustrative, and various modifications and equivalent other embodiments are possible without departing from the scope of the present invention. Therefore, the scope of the true technical protection according to the embodiment of the present invention should be determined by the technical idea of the invention described in the following claims.

G11, G12, G13: first lens group, G21, G22, G32: second lens group
G31, G32, G33: Third lens group

Claims (17)

A first lens group having negative refractive power;
A second lens group that performs focusing and has a positive refractive power; And
And a third lens group having positive refractive power,
Wherein the first lens group includes a first lens which is disposed on the most object side in the first lens group and has a meniscus shape and has a positive refractive power and a second lens which is disposed on the most image side in the first lens group, And a second lens having a positive refractive power,
When focusing, the first lens group and the third lens group are fixed,
Having a half angle of view of more than 45 degrees,
A lens optical system satisfying the following expression.
<Expression>

Here, f _{1 st} is the focal length of the first lens, and f is the total focal length of the lens optical system at the infinite object distance. The method according to claim 1,
Wherein the object side surface of the lens located closest to the object side in the second lens group has a convex shape toward the object side. 3. The method of claim 2,
A lens optical system satisfying the following expression.
<Expression>

Here, R _front is the radius of curvature of the object-side surface of the most object-side lens in the second lens group, and f represents the total focal length of the lens optical system at the infinite object distance. delete 4. The method according to any one of claims 1 to 3,
A lens optical system satisfying the following expression.
<Expression>

Here, f _AF is the focal length of the second lens group, and f _G3 is the focal length of the third lens group. 4. The method according to any one of claims 1 to 3,
And the third lens group further includes a stop. 4. The method according to any one of claims 1 to 3,
Wherein the first lens group further comprises at least two or more lenses between the first lens and the second lens, and the lens positioned third from the object side in the first lens group is an aspherical lens. 8. The method of claim 7,
A lens optical system satisfying the following expression.
<Expression>

Here, D represents the radius of the aspherical lens included in the first lens group, and y represents the half diagonal length of the image sensor used in the lens optical system. The method according to claim 1,
And the focal length of the lens optical system is smaller than the rear focal length. The method according to claim 1,
And a third lens of meniscus shape and a fourth lens of meniscus shape are further disposed between the first lens and the second lens. 11. The method of claim 10,
Wherein the first lens, the second lens, the third lens, and the fourth lens have a meniscus shape convex toward the object side, respectively. 11. The method of claim 10,
The third lens has a negative refracting power and the fourth lens has a negative refracting power. The method according to claim 1,
And the second lens group includes two or three lenses. The method according to claim 1,
The second lens group includes a fifth lens having a positive refractive power, a sixth lens having a positive refractive power, and a seventh lens having a positive refractive power. 15. The method of claim 14,
And the fifth lens and the sixth lens are bonded to each other. 4. The method according to any one of claims 1 to 3,
Wherein the lens optical system has a half angle of view ranging from 45 to 60 degrees. A lens optical system according to any one of claims 1 to 3; And
And an image sensor for receiving the light image formed by the lens optical system.

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