KR20180123849A - Lens optical system and photographing apparatus having the same - Google Patents

Abstract

Disclosed are a lens optical system capable of fast autofocusing, and a photographing apparatus including the same. The lens optical system comprises: a first lens group including at least two meniscus lenses having a positive refractive power and having a negative refractive power; a second lens group performing focusing and having a negative refractive power; and a third lens unit having a positive refractive power, wherein the first lens group and the third lens group are fixed when focusing, an F number is 1.8 or less, a half angle of view is 30 degrees or more, and a focal length may be longer than a back focal length.

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 lens optics and telephoto lens optics.

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.

An exemplary embodiment provides a lens optic capable of fast autofocusing.

An exemplary embodiment provides a photographing apparatus capable of quick auto focusing.

A lens optical system according to an exemplary embodiment includes: a first lens group including at least two meniscus lenses having positive refractive power and having a negative refractive power; A second lens group that performs focusing and has a negative refractive power; And a third lens group having a positive refractive power, wherein the first lens group and the third lens group are fixed at the time of focusing, has an F number of 1.8 or less, has a half angle of view of 30 degrees or more, It is longer than the focal length.

The first lens group may include an aspherical lens after the second lens from the object side.

The first lens group or the third lens group may include a diaphragm.

The lens optical system can satisfy the following expression.

<Expression>

Here, L _stop is the distance from the diaphragm to the upper surface, and BFL is the distance from the image side of the uppermost lens of the third lens group to the upper surface at the infinite object distance.

The lens optical system can satisfy the following expression.

<Expression>

Where D _last is the diameter of the most image side lens of the third lens group and Y is the anti-diagonal size of the image element.

The lens optical system can satisfy the following expression.

<Expression>

Here, L is the distance from the object-side surface of the most object-side lens of the lens optical system to the image surface, and f is the focal length of the entire lens optical system at the infinite object distance.

The lens optical system may further include a driver for tilting the first lens group and de-centering the third lens group.

The second lens group may include at least one aspherical lens.

The first lens group may include a first lens and a second lens in meniscus form convex to the object side in order from the object side.

And the second lens group may be composed of only one lens.

And one lens of the second lens group may have a negative refractive power.

And the second lens group may include a meniscus lens convex on the object side or a double concave lens.

The first lens group may include a cemented lens at the uppermost side in the first lens group.

The cemented lens may include a biconvex lens and a meniscus lens.

The lens optics may have a half angle of view in the range of 30-50 degrees.

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

A first lens group having at least two meniscus lenses having positive refractive power and having positive refractive power, a second lens group having negative refractive power, and a third lens having positive refractive power, A first lens group and a third lens group are fixed at the time of focusing, an F number of 1.8 or less, a half angle of view of 30 degrees or more, and a focal length is longer than a focal length.

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 provides a bright lens system having an F number of 1.8 or less, and the number of focusing lens groups is made small to enable high-speed focusing. Further, the exemplary embodiment can provide a telephoto 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 shows a lateral aberration diagram of the infinite object distance of the lens optical system shown in Fig. 1. Fig.
Fig. 3 shows a lens optical system according to the second numerical embodiment, and shows a focusing operation.
Fig. 4 shows a lateral aberration diagram of the infinite object distance of the lens optical system shown in Fig. 3;
Fig. 5 shows a lens optical system according to the third numerical example and shows a focusing operation.
Fig. 6 shows a lateral aberration diagram of the infinite object distance of the lens optical system shown in Fig. 5;
Fig. 7 shows aberration diagrams when the first lens unit of the lens optical system according to the first aberration example is tilted by (+) 5 minutes.
8 shows aberration diagrams when the first lens group of the lens optical system according to the first aberration example is not tilted.
FIG. 9 shows aberration diagrams when the first lens unit of the lens optical system according to the first aberration example is tilted (-) for 5 minutes.
10 shows aberration diagrams when the third lens unit of the lens optical system according to the first aberration example is decentered by (+) 0.05 mm.
11 shows aberration diagrams when the third lens group of the lens optical system according to the first aberration example is not decentered.
12 shows aberration diagrams when the third lens unit of the lens optical system according to the first aberration example is (-) 0.05 mm decentered.
13 schematically shows a photographing apparatus according to an exemplary embodiment.

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. It should be understood, however, that this invention is not intended to be limited to the particular embodiments described herein but includes various modifications, equivalents, and / or alternatives of the embodiments of this document . In connection with the description of the drawings, like reference numerals may be used for similar components.

In this document, the expressions " having, " " having, " " comprising, " or &Quot;, and does not exclude the presence of additional features.

In this document, the expressions "A or B," "at least one of A or / and B," or "one or more of A and / or B," etc. may include all possible combinations of the listed items . For example, "A or B," "at least one of A and B," or "at least one of A or B" includes (1) at least one A, (2) Or (3) at least one A and at least one B all together.

As used herein, the terms "first," "second," "first," or "second," and the like may denote various components, regardless of their order and / or importance, But is used to distinguish it from other components and does not limit the components. For example, the first user equipment and the second user equipment may represent different user equipment, regardless of order or importance. For example, without departing from the scope of the rights described in this document, the first component may be named as the second component, and similarly the second component may be named as the first component.

(Or functionally or communicatively) coupled with / to "another component (eg, a second component), or a component (eg, a second component) Quot; connected to ", it is to be understood that any such element may be directly connected to the other element or may be connected through another element (e.g., a third element). On the other hand, when it is mentioned that a component (e.g., a first component) is " directly connected " or " directly connected " to another component (e.g., a second component) It can be understood that there is no other component (e.g., a third component) between other components.

As used herein, the phrase " configured to " (or set) to be " configured according to circumstances may include, for example, having the capacity to, To be designed to, "" adapted to, "" made to, "or" capable of ". The term " configured to (or set up) " may not necessarily mean " specifically designed to " in hardware. Instead, in some situations, the expression " configured to " may mean that the device can " do " with other devices or components.

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 positive refractive power, A second lens group G21, and a third lens group G31 having a positive refractive power. And the second lens group G21 can perform focusing.

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 refers to, for example, the lens surface on the side where the subject is on the basis of the optical axis OA and the " And the right side in the drawing can be shown as the lens surface on the side having the upper surface. 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 meniscus lens L11 and a second meniscus lens L21 on the most object side O, for example. The first meniscus lens L11 may have a negative refractive power and the second meniscus lens L21 may have a negative refractive power. The first meniscus lens L11 and the second meniscus lens L21 can adjust the angle of view. The first lens group G11 includes at least one aspherical lens to correct the astigmatism and the surface curvature. A meniscus lens can be employed as an aspherical lens so as to be advantageous for forming an aspheric lens. Further, the first lens group may include an aspherical lens after the second lens from the object side so as not to increase the size of the aspherical lens. For example, in the first lens group G11, the second meniscus lens L21 may be composed of an aspherical lens rather than the first meniscus lens L11.

The first lens group G11 includes a third lens L31, a fourth lens L41, a fifth lens L51, a sixth lens L61, a seventh lens L71, an eighth lens L81, And a ninth lens L91. The third lens L31 may be a biconvex lens. The fourth lens L41 may have a negative refractive power. The fifth lens L51 and the sixth lens L61 may be joined together. The eighth lens L81 and the ninth lens L91 may be joined. However, such a lens configuration is merely an example and can be variously configured.

The lens optical system according to the exemplary embodiment can arrange the lenses in a double-gauss type so as to realize stable optical performance. For example, as shown in FIG. 1, the first lens group G11 may have a double-gauss shape. The double gauss type may be, for example, symmetrical arrangement of the refracting power of the lens, or a shape of a part of the lens may be symmetrical. For example, the upper surface of the fourth lens L41 may be concave, and the object side surface of the fifth lens L51 may be concave. The generation of aberration in the first lens group G11 can be reduced by configuring the first lens group G11 as a double Gauss type.

Further, the diaphragm ST is provided between the first lens group G11 and the second lens group G21 for performing focusing, thereby effectively correcting the distortion aberration. For example, the diaphragm ST may be provided on the most image side I of the first lens group G11. 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. In the second numerical embodiment, the diaphragm ST may be provided between the lenses included in the first lens group G12. In the third numerical embodiment, a stop ST may be provided in the third lens group G33. It is also possible that the diaphragm ST is provided between the lenses included in the third lens group. The diameter of each lens group can be determined according to the position of the stop ST.

When the diaphragm ST is positioned in the fixed lens group, the structure of the diaphragm mechanism becomes easy. Generally, in a lens optical system having a wide angle of view, a retrofocus type in which the back focal distance is larger than the focal length of the lens optical system is designed. However, the various embodiments of the present invention can be applied to mirrorless cameras, and because the flange back distance, which is the distance from the mount face to the image plane of the mirrorless camera, is relatively short compared to the DSLR, And a telephoto type so as to satisfy the mechanical limit of the flange back distance.

The second lens group G21 may include one or two lenses. The second lens group G21 is constituted by a small number of lenses and can perform high-speed focusing. For example, the second lens group G21 may be composed of only one tenth lens L101. For example, the tenth lens L101 may have a negative refractive power. In focusing, the first lens group G11 and the third lens group G31 can be fixed.

Since the first lens group G11 has a positive refractive power, the aperture of the lens of the second lens group G21 can be made small and high-speed auto focusing can be achieved. Also, by focusing the first lens group G11 and the third lens group G31 during focusing to reduce the weight of the moving lens group, high-speed auto focusing can be achieved. Further, when the first lens group G11 and the third lens group G31 are fixed, the sealing operation of the lens optical system is easy, which can be advantageous for dust prevention and spinning.

On the other hand, in order to secure a wide angle of view, a lens located on the object side (O) of the first lens group G11 may have a negative refractive power. To this end, a first meniscus lens L11 and a second meniscus lens L21 having a negative refractive power may be disposed on the object side of the first lens group G11.

The lens optical system according to various embodiments may be constructed by a contrast auto focusing method in which an image is read at a high speed from an image sensor and a focusing is performed using an edge sharpness of an image Focusing can be performed. 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.

Therefore, in the lens optical system according to various embodiments, the focusing lens group is composed of only one lens or two lenses so that high-speed auto focusing can be performed.

When a focusing lens group is composed of only one lens, a variety of aberrations occur. Therefore, an aspherical lens may be employed to correct the aberration. However, due to the physical limitations of the large-diameter lens optical system, the size of the aspherical lens used here must be increased, resulting in an increase in manufacturing cost and an increase in the product weight. To minimize this problem, the refractive power of each lens can be adjusted.

The third lens group G31 may include a plurality of lenses. For example, the third lens group G31 may include an eleventh lens L111, a twelfth lens L121, a thirteenth lens L131, and a fourteenth lens L141. The eleventh lens L111 may have a positive refractive power, and the twelfth lens L121 may have a positive refractive power. The thirteenth lens L131 may have a negative refractive power, and the fourteenth lens L141 may have a positive refractive power. The eleventh lens L111 and the twelfth lens L121 may be joined. The thirteenth lens L131 and the fourteenth lens L141 may be joined.

The lens optical system according to the exemplary embodiment may have a half angle of view of at least 30 degrees. For example, the lens optics according to the exemplary embodiment may have a half angle of view in the range of 30-50 degrees.

On the other hand, since the mirrorless camera does not need a mirror, it can have a relatively shorter back focal length (BFL) than a general DSLR camera. The posterior focal length represents the distance from the image plane to the image plane of the lens on the most image side. The lens optical system according to the exemplary embodiment may be configured as a telephoto type. The telephoto type may have a back focal length (BFL) smaller than an effective focal length (EFL).

Since there is no mirror box in the mirrorless camera, there is a margin for a flange-back distance relatively to the lens optical system for DSLR, so that the upper surface of the fourteenth lens L141 on the most image side of the lens system is concave Shape so as to serve as a field flattener. The lens on the most image side in the large diameter lens system is constituted by a one-side concave lens and acts as a field flattener, so that the curvature of the image surface can be easily corrected.

The lens optical system according to the exemplary embodiment includes a focusing lens group having a half angle of view of 30 degrees or more and lightweight so as to enable high-speed auto focusing, and is configured as a telephoto type considering a short flange- .

 According to various embodiments, at least one optical element OD1 may be provided between the fourteenth lens L141 and the image 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. 3 shows a lens optical system 100-2 according to the second numerical example. The lens optical system 100-2 includes a first lens group G12 having a positive refractive power, a second lens group G22 performing focusing with a negative refractive power, and a third lens group G32 having a positive refractive power . The first lens group G12 may include a first meniscus lens L12 and a second meniscus lens L22 on the most object side O side. The first meniscus lens L12 may have a negative refractive power and the second meniscus lens L22 may have a negative refractive power.

The first lens group G12 includes a third lens L32, a fourth lens L42, a fifth lens L52, a sixth lens L62, a seventh lens L72, an eighth lens L82, And a ninth lens L92. The third lens L32 may be a biconvex lens. The fifth lens L52 and the sixth lens L62 may be joined together. The eighth lens L82 and the ninth lens L92 can be joined. A diaphragm ST may be provided between the seventh lens L72 and the eighth lens L82.

The second lens group G22 may include a tenth lens L102 having a negative refractive power. The third lens group G32 may include an eleventh lens L112, a twelfth lens L122, a thirteenth lens L132, and a fourteenth lens L142. The eleventh lens L112 and the twelfth lens L122 may be bonded together and the thirteenth lens L132 and the fourteenth lens L142 may be bonded together. An optical element OD2 may be provided between the fourteenth lens L142 and the image surface IMG.

Fig. 5 shows a lens optical system 100-3 according to the third numerical example. The lens optical system 100-3 includes a first lens group G13 having a positive refractive power, a second lens group G23 performing focusing with a negative refractive power, and a third lens group G33 having a positive refractive power . The first lens group G13 may include a first meniscus lens L13 and a second meniscus lens L23 on the most object side O side. The first meniscus lens L13 may have a negative refractive power and the second meniscus lens L23 may have a negative refractive power.

The first lens group G13 includes a third lens L33, a fourth lens L43, a fifth lens L53, a sixth lens L63, a seventh lens L73, and an eighth lens L83. . &Lt; / RTI &gt; The third lens L33 may be a lens whose object side is flat and whose upper side is convex. The fourth lens L43 and the fifth lens L53 may be joined. The seventh lens L72 and the eighth lens L82 may be joined.

And the second lens group G23 may include a ninth lens L92 having a negative refractive power. The ninth lens L92 may be a bi-concave lens. The third lens group G33 may include a tenth lens L103, an eleventh lens L113, and a twelfth lens L123. A diaphragm ST may be provided between the eleventh lens L113 and the twelfth lens L123. The tenth lens L103 and the eleventh lens L113 may be joined together. An optical element OD3 may be provided between the twelfth lens L123 and the image surface IMG.

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, L is the distance to the _stop aperture from the upper surface, BFL is the distance to the upper surface (image plane) (IMG) from the image-side surface of the third lens image side lens of the infinite object distance.

Equation 1 is a condition for determining the aperture position in the lens optical system. The size of the object side lens or the image side lens of the lens optical system may have an appropriate range depending on the aperture position. If (BFL / L _stop ) is smaller than the lower limit value in Equation 1, the aperture position is closer to the object side (O), and in this case, the aperture of the upper lens becomes larger. (BFL / L _stop ) is larger than the upper limit value, the position of the diaphragm becomes closer to the upper side, and the diameter of the object side lens becomes larger. In the interchangeable lens system, there is a limitation on the diameter of the last lens on the image side. For example, the diameter of the most image side lens can be limited by the mount surface of the lens optical system and the structure of the camera body. When the equation 1 is satisfied, the diameter limitation of the interchangeable lens system can be satisfied.

The lens optical system according to the exemplary embodiment can satisfy the following expression.

<식 2>

<Formula 2>

Where D _last is the diameter of the most image side lens of the third lens group and Y is the anti-diagonal size of the image element.

Equation 2 limits the aperture size of the lens located on the most image side of the lens optical system. (D _last / Y) is larger than the upper limit of Equation 2, unintentional light shielding may occur due to the internal structure of the camera body. If (D _last / Y) is smaller than the lower limit value of Equation 2, The angle of incidence of the light ray is increased, and the peripheral light quantity ratio may be lowered. In addition, since a principal ray incident on an edge of the image sensor is shielded, it may be difficult to achieve a desired angle of view.

The lens optical system according to the exemplary embodiment can satisfy the following expression.

<식 3>

<Formula 3>

Here, L is the distance from the object side to the image plane of the most object-side lens of the lens optical system, and f is the focal length of the entire lens optical system at the infinite object distance.

(L / f) is smaller than the lower limit value of Equation (3), the lens optical system becomes smaller in size and it becomes difficult to secure the optical performance. When (L / f) The size of the lens optical system may be reduced.

On the other hand, when the lens is tilted or decentered, the resolving power may change. The tilt and decenter sensitivities are the ratios of the change in resolving power according to the degree of tilt or decenter, respectively. In the lens optical system according to various embodiments, the first lens group has a large tilt sensitivity, and in this case, it is advantageous to correct the resolution to increase the yield. That is, the first lens unit can easily correct the resolution by adjusting the tilt. FIGS. 7, 8 and 9 show aberration changes due to the tilt adjustment of the first lens group. FIG. 7 shows a case where the first lens group is tilted by (+) 5 minutes, FIG. 8 shows a case where the first lens group is not tilted, and FIG. Minute tilted state.

The third lens groups G31, G32, and G33 can correct the resolving power through decentering adjustment. Figs. 10, 11, and 12 show changes in aberration caused by decentering adjustment of the third lens group G31 in the first numerical example. Fig. 10 shows the aberration when the third lens group G31 is decentered by (+) 0.05 mm. Fig. 11 shows the aberration when the third lens group G31 is not decentered, 12 shows the aberration when the third lens group G31 is (-) 0.05 mm decentered.

 In order to correct the resolution as described above, a driving unit D for tilting the first lens group and decentering the third lens group may be further provided.

The lens optical system according to the exemplary embodiment may have an F number of 1.8 or less. When the F number is small, the aberration can be relatively large. Therefore, an aspherical surface may be used to correct the aberration. The first lens group G11 includes at least one aspherical lens to correct astigmatism and distortion. Further, the second lens group G21 includes an aspheric lens, and an aberration correction effect can be obtained together with autofocusing.

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 4>

<Formula 4>

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. Also, the third 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 optical 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 imaging element surface or an imaging element 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 = 24.601 mm, Fno / 1.440, HFOV = 42.975 DEG

Lens face R Dn Nd Vd H-Ape Note Object infinity D0 One 44.449 2.400 1.839450 42.72 23.19 First lens group:
fixing 2 20.724 4.364 3 * 14.889 2.500 1.518253 64.06 4* 10.852 9.151 5 36.049 6.930 1.916948 35.25 6 -621.464 0.100 7 89.878 2.500 1.498450 81.61 8 24.550 8.075 9 -23.469 3.310 1.916948 35.25 10 -21.996 2.500 1.855048 23.78 11 -32.188 0.100 12 -719.200 5.090 1.916948 35.25 13 -43.973 0.100 14 56.822 8.420 1.732338 54.67 15 -30.443 2.500 1.768567 26.61 16 -113.799 1.400 17 (ST) infinity D1 13.50 18 * 600,000 2.100 1.855042 23.77 Second lens group: Focusing 19 * 36.772 D2 20 63.421 3.580 1.916948 35.25 Third lens group:
fixing 21 255.637 6.940 1.438098 95.1 22 -29.364 1.196 23 -211.593 2.400 1.652218 33.84 24 44.121 4.440 1.732247 54.04 25 * 1000,000 D3 16.67 26 infinity 2.500 1.518719 64.2 Optical element 27 infinity D4 Image infinity D5

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

Aspherical coefficient 3 4 18 19 25 K -1.398036 -1.757313 -20.000000 4.982366 20.000000 A -4.044405E-05 1.202771E-05 1.786160E-05 1.015133E-05 1.191131E-05 B 4.860121E-08 -1.308960E-07 -9.628640E-08 -1.082647E-07 -7.469545E-09 C 3.197242E-11 5.146203E-10 5.270900E-10 2.549497E-10 5.019409E-11 D -2.194424E-13 -1.145484E-12 -1.923329E-12 -4.559877E-13 -1.254609E-13 E 2.209605E-16 9.236532E-16 3.262026E-15 -3.971376E-15 1.669450E-16

D1, D2, D3, D4, and D4 for the infinite object distance in the first embodiment, the object distance in which the magnification m is (-1/30), and TL = D5), focal length (f), MAG, F number, and half angle of view. Here, OAL represents the distance on the optical axis from the object side to the image plane of the object-side lens, and MAG represents the magnification. " in air " indicates the distance from the image side of the most image side lens of the lens optical system to the image plane (image pickup element) when there is no optical element. That is, " in air " can represent the focal length in the absence of an optical element.

Item Infinite object distance MAG = -1 / 30 D0 infinity 724.494205 D1 2.175017 3.028670 D2 10.571983 9.718330 D3 17.657000 17.657000 D4 1.020398 1.049026 D5 -0.020398 -0.049026 in Air 20.303124 20.303124 f 24.601068 EFL / MAG 0.033329 HFOV 42.975 42.099 Fno 1.440 1.465 OAL 114.000000 114.000000

Figure 2 shows a ray fan for an infinite object distance for a first numerical embodiment. Here, the dotted line represents the C-line, the solid line represents the d-line, and the one dotted line represents the transverse aberration for the F-line. The C-line shows a wavelength of 656.2700 nm, the d-line shows 587.5600 nm, and the F-line shows a wavelength of 486.1300 nm.

The transverse aberration shows the aberrations for the Zango (Tangential) and Sagittal (Sagittal) surfaces.

&Lt; Second Numerical Embodiment >

Fig. 3 shows the lens optical system 100-2 according to the second numerical example, and the following is the design data of the second numerical example.

f = 23.543 mm, Fno / 1.439552, HFOV = 44.980416 [deg.]

Lens face R Dn Nd Vd H-Ape Note Object infinity D0 One 39.864 2.000 1.552063 75.5 20.47 First lens group:
fixing 2 15.801 1.924 3 * 19.722 2.000 1.519779 52.15 4* 16.979 6.876 5 75.094 4.088 1.910483 31.31 6 -129.215 1.592 7 -45.014 2.000 1.438098 95.1 8 -55.156 2.322 9 -34.126 2.215 1.886217 40.14 10 -32.445 2.000 1.607181 38.01 11 -80.568 0.100 12 224.157 3.743 1.916948 35.25 13 -53.988 1.140 14 (ST) infinity 1.959 11.35 15 72.035 4.856 1.732338 54.67 16 -30.787 2.000 1.812631 25.46 17 -54.212 D1 18 * -252.613 2.000 1.855048 23.78 Second lens group: Focusing 19 * 31.381 D2 20 113.202 9.477 1.732338 54.67 Third lens group: Fixed 21 -28.310 2.000 1.855048 23.78 22 -36.581 0.642 23 157.681 4.190 1.699798 55.46 24 -258.598 2.776 1.732247 54.04 25 * -102.750 D3 20.35 26 infinity 2.500 1.518719 64.2 Optical element 27 infinity D4 IMG infinity 0.000

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

Aspheric lens 3 4 18 19 25 K 0.498923 -2.336901 -10.000000 1.954425 10.000000 A 1.264890E-05 7.575094E-05 1.525996E-05 1.261913E-05 7.701576E-06 B 6.265619E-08 2.440239E-08 -7.045790E-08 -6.901293E-08 -1.761721E-08 C -1.823923E-10 1.266908E-10 4.579810E-11 -1.126714E-10 5.589991E-11 D -1.148910E-13 -2.152989E-12 8.531216E-13 3.219041E-13 -1.137686E-13 E -4.659399E-16 3.846477E-15 -2.356194E-15 2.969885E-15 8.815425E-17

D1, D2, D3, D4, and D5, and the focal lengths of the infinite object distance and magnification m in the case of the object distance of (-1/30) (f), magnification (MAG), F number, and half angle of view.

Item Infinite object distance MAG = -1 / 30 D0 infinity 702.052711 D1 0.100000 0.975138 D2 8.000000 7.124862 D3 17.500000 17.500000 D4 0.999855 0.999855 in Air 20.145979 20.145979 f 23.542619 MAG 0.033333 HFOV 44.980416 43.528815 Fno 1.439552 1.471797 OAL 90.999855 90.999855

4 shows a ray fan for an infinite object distance for a second numerical embodiment.

&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 = 23.4 mm, Fno / 1.440078, HFOV = 45.73 DEG

Lens face Radius Thick Glass Glass H-Ape Note Object infinity D0 One 120.266 4.000 732338.5467 732338.5467 32.12 First lens group:
fixing 2 25.985 8.102 3 * 35.909 4.000 498450.8161 498450.8161 4* 29.724 7.378 5 infinity 5.261 855048.2378 855048.2378 6 -87.574 6.000 7 -36.110 9.157 732338.5467 732338.5467 8 -26.444 2.370 910483.3131 910483.3131 9 -47.340 0.100 10 infinity 6.866 916948.3525 916948.3525 11 -62.817 0.100 12 52.480 2.000 910483.3131 910483.3131 13 71.944 5.076 916948.3525 916948.3525 14 infinity D1 15 * -919.696 2.000 855048.2378 855048.2378 Second lens group: Focusing 16 * 37.277 D2 17 27.574 5.926 732338.5467 732338.5467 Third lens group: Fixed 18 -341.836 2.000 855048.2378 855048.2378 19 59.781 2.000 20 (ST) infinity 11.781 11.70 21 31.611 4.719 438098.951 438098.951 22 * -95.046 D3 14.70 23 infinity 2.500 518719.642 518719.642 Optical element 24 infinity D4 IMG infinity 0.000

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

Aspherical coefficient 3 4 15 16 22 K -0.079645 -0.650225 -20.00000 -0.889817 10.840882 A -1.237731E-06 2.060930E-06 3.543765E-06 4.989924E-06 2.399107E-05 B -3.444505E-08 -5.177569E-08 -3.523152E-08 -4.273039E-08 7.691342E-08 C 3.546869E-11 5.431993E-11 1.236278E-10 1.546462E-10 -6.678067E-10 D 6.187811E-14 8.410513E-14 -2.235934E-13 -3.364173E-13 3.522899E-12 E -8.434479E-17 -1.599035E-16 1.637221E-16 3.342523E-16 -6.290108E-15

D1, D2, D3, and D4, focal length f (f), and focal length f (f) of the object distance of the infinite object distance and magnification MAG ), Magnification (MAG), F number, and half angle of view.

Item Infinite object distance MAG = -1 / 30 D0 infinity 690.674417 D1 1.500000 2.367842 D2 12.165000 11.297158 D3 18.999616 18.999616 D4 1.000000 1.000000 in Air 21.645740 21.645740 f 23.400063 MAG 0.033333 HFOV 45.726892 44.051294 Fno 1.440078 1.442318 OAL 125.000616 125.000616

Fig. 6 shows a ray fan for an infinite object distance for a third numerical example.

As described above, the lens optical system according to the embodiment of the present invention can realize a telephoto type lens optical system having a half angle of view of about 30 degrees or more and an effective focal length that is longer 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 3, respectively.

Example 1 Example 2 Example 3 BFL 20.303 20.146 21.646 L _Stop 54.56 59 39 D _Last 33.35 40.71 29.41 Y 21.7 21.7 21.7 L 114 91 125 f 24.601 23.543 23.4

식 (1)

Equation (1) 0.372 0.341 0.555

Equation (2) 1.537 1.876 1.355

Equation (3) 4.634 3.865 5.342

13 shows a photographing apparatus having a lens optical system 100 according to an exemplary embodiment. As the lens optical system 100, the lens optical systems 100-1, 100-2, and 100-3 described with reference to FIGS. 1, 3, and 5 can be applied. The imaging device may include an imaging element 112 that receives light imaged by the lens optics 100. In addition, a display unit 115 for displaying a subject image may be provided. The photographing apparatus may employ, for example, a contrast auto focus detection system or a phase difference auto focus detection system. The photographing apparatus can be applied to, for example, a mirrorless camera or a DSLR.

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. Further, the lens optical system according to the exemplary embodiment can provide a bright lens system having an F number of 1.8 or less.

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 (16)

A first lens group including at least two meniscus lenses having positive refractive power and negative refractive power;
A second lens group that performs focusing and has a negative refractive power; And
And a third lens unit having a positive refractive power,
The first lens group and the third lens group are fixed at the time of focusing,
A lens optical system having an F number of 1.8 or less, a half angle of view of 30 degrees or more, and a focal length longer than a posterior focal length. The method according to claim 1,
Wherein the first lens group includes an aspherical lens after the second lens from the object side. The method according to claim 1,
Wherein the first lens group or the third lens group includes a diaphragm. The method according to claim 1,
A lens optical system satisfying the following expression.
<Expression>

Here, L _stop is the distance from the diaphragm to the upper surface, and BFL is the distance from the image side of the uppermost lens of the third lens group to the upper surface at the infinite object distance. The method according to claim 1,
A lens optical system satisfying the following expression.
<Expression>

Where D _last is the diameter of the most image side lens of the third lens group and Y is the anti-diagonal size of the image element. The method according to claim 1,
A lens optical system satisfying the following expression.
<Expression>

Here, L is the distance from the object-side surface of the most object-side lens of the lens optical system to the image surface, and f is the focal length of the entire lens optical system at the infinite object distance. The method according to claim 1,
And a driving unit for tilting the first lens group and de-centering the third lens group. The method according to claim 1,
And the second lens group includes at least one aspherical lens. The method according to claim 1,
Wherein the first lens group includes a first lens and a second lens in meniscus shape convex toward the object side in order from the object side. The method according to claim 1,
Wherein the second lens group is composed of only one lens. 11. The method of claim 10,
And one lens of the second lens group has a negative refractive power. 11. The method of claim 10,
Wherein the second lens group includes a meniscus lens convex on its object side or a concave lens. The method according to claim 1,
Wherein the first lens group includes a cemented lens at the uppermost side in the first lens group. 13. The method of claim 12,
Wherein the cemented lens comprises a biconvex lens and a meniscus lens. The method according to claim 1,
Wherein the lens optical system has a half angle of view in the range of 30-50 degrees. A lens optical system according to any one of claims 1 to 15; And
And an image sensor for receiving the light image formed by the lens optical system.

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