KR101708895B1 - Telephoto single focal point lens system and photographing apparatus having the same - Google Patents

Abstract

A telephoto short-focal lens system and a photographing apparatus including the same are disclosed.
The telephoto short focal length lens system disclosed in the present invention is a telephoto short focal length lens system in which at least one lens group is arranged between an object side and an imaging element. The telephoto short focal length lens system includes a lens having a convex meniscus shape on the object side A lens group; A front lens group disposed on an object side of the focusing lens group and having a positive refractive power; And a rear lens group disposed on the upper side of the focusing lens group and having a positive refractive power.

Description

TECHNICAL FIELD [0001] The present invention relates to a telephoto short focal point lens system and a photographing apparatus including the telephoto single focal point lens system.

An exemplary embodiment relates to a telephoto short focal lens system capable of focusing at high speed and reducing manufacturing cost.

In recent years, there has been a demand for miniaturization and a power saving function of a photographing apparatus, and a photographing apparatus using a solid-state image pickup device such as a CCD (Charge Coupled Devices) type image sensor or a CMOS (Complementary Metal-Oxide Semiconductor) . 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 lens systems.

However, in the case of a telephoto lens system, the number of lenses is increased, which makes miniaturization difficult. In addition, lens processing is becoming increasingly difficult for aberration correction such as spherical aberration and curvature of field.

The exemplary embodiment provides a telephoto short focal length lens system capable of focusing at high speed and reducing manufacturing cost.

An exemplary embodiment provides an imaging apparatus including a telephoto short focal lens system capable of focusing at high speed and reducing manufacturing cost.

An exemplary embodiment is a telephoto short focal lens system in which at least one lens group is arranged between an object side and an imaging element,

A focusing lens group including a lens having a convex meniscus shape on the object side, the focusing lens group comprising:

A front lens group disposed on an object side of the focusing lens group and having a positive refractive power; And

And a rear lens group disposed on the upper side of the focusing lens group and having a positive refractive power,

Wherein the front group comprises, in order from the object side, a first lens having positive refractive power, a second lens having negative refractive power, and a third lens having negative refractive power,

The upper surface of the second lens is concave, the object side surface of the third lens is concave,

And the front group and rear group can be fixed at the time of focusing.

The second lens of the above-mentioned group may include at least one aspherical surface.

The lens on the uppermost side of the rear group may be a double concave lens.

The telephoto short-focal length lens system can satisfy the following expression.

<Expression>

0.8? B _f + Y / f? 1.2

Where b _f is the focal length, Y is the half-diagonal length of the imaging element, and f is the total effective focal length at infinity.

The telephoto short-focal length lens system can satisfy the following expression.

<Expression>

0.0? T? ₂ / f? _1? 0.15

Here, t ₂ is the distance from the image side of the first lens to the object side of the second lens, and f 1 _st represents the focal length of the first lens.

The telephoto short-focal length lens system can satisfy the following expression.

<Expression>

-0.6? Bf / f _last ? -0.1

Here, b _f represents the focal length, and f _last represents the focal length of the lens at the uppermost position of the rear group.

A diaphragm may be provided in the front group or on the object side of the focusing lens group.

The lenses disposed on the object side of the diaphragm may have a positive refractive power as a whole.

A diaphragm may be provided between the second lens and the third lens or between the entire group and the focusing lens group.

The lens between the second lens and the diaphragm may be both spherical lenses.

The focusing lens group may have a negative refractive power.

The focal length of the telephoto short-focal lens system at an infinite distance may be larger than the rear focal length.

The angle of view of the telescopic short-focal lens system may range from 40 to 60 degrees.

The whole group may further include a fourth lens having a double convex and a fifth lens having a double convex.

The focusing lens group may be composed of one sixth lens.

The rear group may include a seventh lens having a double convex lens and an eighth lens having a double concave lens.

The telephoto short-focal length lens system can satisfy the following expression.

<Expression>

1.85? N1? 1.95

Here, n1 represents the refractive index of the first lens.

The imaging device according to the exemplary embodiment includes an imaging element that receives light imaged by the telephoto short focal lens system and the telephoto short focal lens system,

Wherein the focusing lens group includes a lens having a convex meniscus shape on the object side, a front lens group disposed on the object side of the focusing lens group and having a positive refractive power, , A rear group having a positive refractive power,

Wherein the front lens group includes, in order from the object side, a first lens having positive refractive power, a second lens having negative refractive power, and a third lens having negative refractive power, wherein an upper surface of the second lens is concave, The object side surface of the third lens is concave, and the front group and rear group can be fixed at the time of focusing.

The telephoto short-focal lens system according to the exemplary embodiment lightly configures the focusing lens group to enable high-speed focusing. Further, the telephoto short-focal length lens system can realize a compact and bright lens. The embodiments of the present invention can provide a small-sized and inexpensive short-focus lens system capable of ensuring high image quality by effectively controlling aberration generated when a bright lens is realized. In addition, the telephoto short focal length lens system according to the exemplary embodiment can provide a telephoto type lens system having a standard angle of view.

Fig. 1 shows a telephoto short focal lens system according to the first numerical example.
Fig. 2 is a schematic diagram of the telephoto short focal length lens system shown in Fig.
Fig. 3 shows a telephoto short focal length lens system according to the second numerical embodiment.
Fig. 4 shows an aberration diagram of the telescopic short focal lens system shown in Fig.
Fig. 5 shows a telephoto short focal lens system according to the third numerical example.
FIG. 6 shows an aberration diagram of the telephoto short focal length lens system shown in FIG. 5; FIG.
7 shows a telephoto short focal lens system according to the fourth numerical example.
Fig. 8 shows an aberration diagram of the telephoto short focal length lens system shown in Fig. 7;
9 schematically shows a photographing apparatus according to an exemplary embodiment.

Hereinafter, a telescopic short-focal lens system according to an exemplary embodiment and a photographing apparatus including the telephoto short-focal length lens system will be described in detail with reference to the accompanying drawings.

Figure 1 illustrates a telephoto short focal lens system 100 in accordance with an exemplary embodiment of the present invention.

The telephoto short focal length lens system 100 includes a focusing lens group FG for performing focusing, a front lens group FLG disposed on the object side O of the focusing lens group FG and having a positive refractive power, (RLG) disposed on the image side I of the group FG and having a positive refractive power.

The focusing lens group FG may include a single lens. For example, each of the lenses may have a convex meniscus shape on the object side (O).

The front lens group FLG is arranged in order from the object side O to the image side I and includes a first lens L1 having a positive refractive power, a second lens L2 having a negative refractive power, 3 lens L3.

The object side surface of the first lens L1 can be convex. For example, the first lens L1 may be a meniscus lens or a biconvex lens. The upper surface of the second lens L2 may be concave. For example, the second lens L2 may be a meniscus lens. The object side surface of the third lens L3 may be concave. For example, the third lens L3 may be a bi-concave lens.

The fourth lens L4 and the fifth lens L5 may be further provided on the upper side I of the third lens L3. The object side surface of the fourth lens L4 can be convex. For example, the fourth lens L4 may be a biconvex lens. The object side surface of the fifth lens L5 can be convex. For example, the fifth lens L5 may have a convex surface on the object side and a flat surface on the image side. Alternatively, the fifth lens L5 may be a biconvex lens. The third lens L3 and the fourth lens L4 may be joined together.

On the other hand, a diaphragm ST may be provided in the front lens group FLG or on the object side O of the focusing lens group FG. For example, a diaphragm ST may be provided between the second lens L2 and the third lens L3 or between the front group FLG and the focusing lens group FG.

The lenses disposed on the object side O of the diaphragm ST may have a positive refractive power as a whole. For example, when the diaphragm ST is disposed between the second lens L2 and the third lens L3, the first lens L1 and the second lens L2 may have a positive refractive power as a whole. When the diaphragm ST is disposed between the front group FLG and the focusing lens group FG, the lenses included in the front group FLG may have a positive refractive power as a whole.

On the other hand, the lens between the second lens L2 and the diaphragm ST may be a spherical lens. For example, when the diaphragm ST is disposed between the front group FLG and the focusing lens group FG, the lenses included in the front group FLG may all be spherical lenses.

The focusing lens group FG may include, for example, a sixth lens L6. The sixth lens L6 may be, for example, a convex meniscus lens on the object side. The focusing lens group FG may have a negative refractive power. The focusing lens group FG is composed of a single lens and is made lightweight, so that focusing can be performed at a high speed. In addition, the drive device for driving the focusing can be downsized, and the entire image pickup device can be downsized. When focusing, the whole group (FLG) and rear group (RLG) can be fixed.

The rear group RLG may include, for example, a seventh lens L7 and an eighth lens L8. The seventh lens L7 may be a lens whose object side O is convex. The seventh lens L7 may be, for example, a biconvex lens. The eighth lens L8 may be a lens whose upper side I is concave. The eighth lens L8 may be, for example, a double concave lens.

The telephoto short focal length lens system according to the exemplary embodiment makes it possible to perform focusing at high speed by reducing the weight of the focusing lens group. In the present embodiment, for example, contrast auto-focus for focusing while moving a small distance can be realized at the time of capturing a moving image. In this case, for example, a stepping motor may be used as the driving source of the focusing lens group. Such a stepping motor may not be suitable for moving a heavy lens group because the torque of the driving source is small. Therefore, it is preferable that the focusing lens group is made lightweight so that the load on the driving source is small. In this embodiment, the focusing lens group may be composed of a single lens. When focusing is performed with a single lens, an aberration may occur, and an aspheric lens may be employed to correct such aberration.

However, in the case of the large-diameter lens system, the diameter of the aspherical lens becomes large, which increases the manufacturing cost and increases the product weight. To reduce this problem, it is necessary to appropriately distribute the refractive power of each lens.

The telescopic short focal length lens system according to the embodiment of the present invention may have a large diameter characteristic. In the case of a large-diameter lens system, the diameter of the most object-side lens becomes large. When the lens having such a large diameter is constituted by an aspheric lens, the lens unit cost may be increased. .

On the other hand, in order to correct the astigmatism, the second lens L2 may have at least one aspherical surface. Here, the aperture of the second lens can be reduced by causing the first lens (L1) to have a positive refractive power so that the light incident on the second lens converges. If the diameter of the second lens is small, manufacturing cost can be reduced even when the second lens is made of an aspherical lens. Further, the telephoto short-focal lens system according to the embodiment of the present invention can be employed in a photographing apparatus without a mirror. In this case, since there is room in the flange-back of the lens system for SLR (Single Lens Reflex) in a mirror-free photographing apparatus, it can serve as a field flattener by employing a double concave lens as the upper lens. have. The lens on the uppermost side of the large lens system is composed of a double concave lens and acts as a field flattener, so that the curvature of the image can be easily corrected.

The lens system according to the embodiment of the present invention arranges the lenses in a double-gauss type so as to realize stable optical performance. For example, as shown in FIG. 1, the whole group (FLG) may have a double-gauss type. In a double gauss type, generation of aberrations in the entire group (FLG) can be reduced. Alternatively, the number of lenses on both sides of the diaphragm can be made equal to each other, thereby making it easy to correct distortion aberrations and the like. For example, an iris is provided between the front group FLG and the focusing lens group FG to effectively correct the distortion aberration.

Further, when the second lens is composed of an aspherical lens, the spherical aberration in the front group FLG can be easily corrected.

On the other hand, the telephoto short focal length lens system according to the exemplary embodiment can satisfy the following expression.

0.8? (B _f + Y) / f? 1.2 (1)

Where b _f is the focal length, Y is the half-diagonal length of the imaging element, and f is the total effective focal length at infinity.

The telephoto short-focal length lens system according to the embodiment of the present invention may have a standard angle of view having a half angle of view (angle of view in the range of 40 to 60 degrees) in the range of 20 to 30 degrees. Also, the effective focal length at an infinite distance may be a telephoto type that is longer than a back focal length (BFL). In the telephoto type, if the effective focal length is excessively larger than the after focal distance, the lens system may have a telephoto angle of view rather than a standard angle of view. Conversely, if the effective focal length is shorter than the rear focal length, it becomes a wide-angle lens. In this embodiment, when Equation (1) is satisfied, the effective focal length can be made larger than the rear focal length while having a normal view angle.

The telephoto short focal length lens system according to the exemplary embodiment can satisfy the following expression.

0.0? T? ₂ / f? _1? 0.15 <Formula 2>

Here, t ₂ is the distance from the image side of the first lens to the object side of the second lens, and f 1 _st represents the focal length of the first lens. That is, t ₂ may indicate the distance between the first lens and the second lens.

When the formula (2) is satisfied, the distance between the first lens and the second lens can be adjusted to reduce the diameter of the second lens, which is an aspherical lens, thereby reducing the lens processing cost. Further, the spherical aberration correction in the front group FLG and the astigmatism correction of the entire lens system can be performed through the second lens of the aspherical surface. At this time, by reducing the diameter of the second lens by increasing the refractivity (focal length) of the first lens and by increasing the distance between the first lens and the second lens, it is possible to perform aberration correction inexpensively and effectively.

The telephoto short focal length lens system according to the exemplary embodiment can satisfy the following expression.

-0.6 < / = bf / f _last &lt; = - 0.1 &lt;

Here, b _f represents the focal length, and f _last represents the focal length of the lens at the uppermost position of the rear group. The back focal distance represents the distance from the image side of the eighth lens L8 on the most upper side to the image surface Img.

The distance from the upper surface of the eighth lens to the image surface Img can be made shorter than the focal length of the eighth lens L8 which operates as a field flattener when the formula 3 is satisfied, It is possible to increase the effect of correcting the curvature of the image surface. When the eighth lens is located too close to the image surface, it is difficult to use the lens interchangeable camera product. Therefore, it is possible to easily correct the image surface curvature when (bf / f _last ) .

The telephoto short focal length lens system according to the exemplary embodiment can satisfy the following expression.

1.85? N1? 1.95 <Formula 4>

Here, n1 represents the refractive index of the first lens. This condition is a condition for correcting the curvature of the surface of the optical system. The higher the refractive index

When the first lens is formed of a high-refraction material satisfying Formula 4, the curvature of the image surface can be easily corrected. For example, in a large-diameter optical system with a small F / #, the depth of focus is small and it is difficult to correct the curvature of the surface. Using a high refractive index material under the condition of Equation 4 makes it easy to correct the curvature of the surface, and thus a high performance lens system can be manufactured.

On the other hand, when the second lens has a negative refractive power, the lenses on the upper side of the second lens diverge with rays after the second lens can have a larger diameter. Therefore, the lens between the diaphragm in the second lens, which is a section in which the ray is diverging, does not use an aspherical surface, thereby reducing the cost of the product.

Next, definition of an aspherical surface used in a telephoto short focal length lens system according to an embodiment of the present invention 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 =

In the embodiment of the present invention, a telephoto short-focal lens system can be implemented through various embodiments according to the following design. Hereinafter, the total effective focal length f is expressed in mm, the half angle of view (HFOV) is expressed in degrees, and * indicates an aspheric surface. F denotes the F number, D0 denotes the distance from the object to the object side surface of the first lens, and D1, D2, D3 and D4 denote the variable interval between the lenses.

At least one filter (P) may be provided on the uppermost side (I) of each embodiment. The filter P 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 an imaging lens without a filter. The image of the subject 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.

In each embodiment, the lens surface numbers S1, S2, S3 ... Sn (n is a natural number) 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 of the lens group for convenience.

&Lt; First Numerical Embodiment >

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

f = 51.054 mm, F / 1.46, HFOV = 23.0 DEG

Lens face Radius of curvature Lens thickness or spacing Refractive index Abe number Object inf. D0 S1 89.068 5.6 1.91082 35.25 S2 292.82 16.465 S3 * 258.807 2.5 1.58313 59.46 S4 * 36.508 5.769 S5 (ST) inf. 4.563 S6 -32.142 2.2 1.64769 33.84 S7 32.142 14 1.72916 54.67 S8 -39.819 0.1 S9 51.914 5.9 1.91082 35.25 S10 inf. D1 S11 * 70.41 1.3 1.60710 26.63 S12 * 26.082 D2 S13 * 60.631 9.5 1.75501 51.16 S14 * -43.573 3.997 S15 -694.408 1.5 1.63980 34.57 S16 44.098 D3 S17 inf. 2 1.51680 64.20 S18 inf. D4 Img inf. 0

The following shows the variable spacing between infinite distance and near distance in the first numerical example.

No. Object (D0) S10 (D1) S12 (D2) S16 (D3) S18 (D4) Infinite distance
(m = 0) inf. 1.5 15.15962 31.28230 1.01018 Nearest street
(m = -1 / 8) 397.37746 9.17822 7.48140 31.28230 1.07340

In Table 2, m represents the magnification.

The following shows the aspherical surface coefficients in the first numerical example.

Lens face S3 S4 S11 S12 S13 S14 K 0.0 0.0 -1.0 0.0 -1.0 -1.0 A 2.800271e-5 3.794746e-5 -2.615944e-5 -2.64089e-5 1.032626e-6 3.726441e-6 B -1.112542e-7 -8.131049e-8 7.986998e-8 6.315456e-8 -5.446275e-10 -1.002132e-8 C 2.40426e-10 1.456721e-10 -1.784626e-10 -1.298645e-10 1.539119e-12 6.184733e-11 D -2.375052e-13 8.920152e-14 2.413631e-13 9.856495e-14 -4.577296e-14 -2.497023e-13 E -1.413996e-16 1.706501e-16 5.172875e-16 F -1.926959e-19 -4.276458e-19

Fig. 2 shows a ray fan for the first numerical example. Fig. 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 a telephoto short-focal length lens system according to the second numerical example, and the following shows design data of the second numerical example.

f = 51.031 mm, F / 1.44, HFOV = 23.0 DEG

Lens face Radius of curvature Lens thickness or spacing Refractive index Abe number Object inf. D0 S1 78.809 6.25 1.88300 40.80 S2 inf. 9.273 S3 * 29.196 3 1.69350 53.20 S4 * 15.444 10.919 S5 -37.747 2.2 1.72825 28.32 S6 37.747 11.36 1.77250 49.62 S7 -48.326 0.1 S8 80.446 8.22 1.88300 40.80 S9 -80.446 One S10 (ST) inf. D1 S11 * 51.588 1.5 1.68893 31.16 S12 * 28.176 D2 S13 * 72.622 9.5 1.69678 55.46 S14 * -46.336 9.576 S15 -222.233 1.5 1.64769 33.84 S16 52.944 D3 S17 inf. 2 1.51680 64.20 S18 inf. D4 Img inf. D5

The following shows the variable spacing between infinite distance and near distance in the second numerical example.

No. Object (D0) S10 (D1) S12 (D2) S16 (D3) S18 (D4) Img (D5) Infinite distance
(m = 0) inf. 1.49027 16.44026 18.5 1.01958 -0.00373 Nearest street
(m = -1 / 8) 397.37604 11.76005 7.48140 18.5 1.06844 -0.00352

The following is the aspherical surface coefficient in the second numerical example.

Lens face S3 S4 S11 S12 S13 S14 K -1.0 -1.0 -1.0 -1.0 -1.0 -1.0 A -7.189652e-5 -7.078040e-5 -1.006543e-5 -5.894184e-6 1.059151e-6 2.045255e-6 B 1.932686e-7 2.579044e-7 1.569416e-008 1.431663e-008 -5.687210e-9 -6.185010e-9 C -3.693794e-10 -5.472632e-10 -2.346265e-11 -1.506092e-11 2.582543e-11 2.636926e-011 D 3.250228e-013 5.512509e-13 1.916261e-014 3.690204e-15 -6.218297e-14 -6.325093e-14 E -9.924396e-18 6.581346e-17 6.696173e-17

&Lt; Third Numerical Embodiment >

Fig. 5 shows a telephoto short-focal lens system according to the third numerical example, and the following shows design data of the third numerical example.

f = 51.058 mm, F / 1.44, HFOV = 23.0 DEG

Lens face Radius of curvature Lens thickness or spacing Refractive index Abe number Object inf. D0 S1 258.269 6.25 1.90366 31.31 S2 -258.269 5.904 S3 * 19.533 3 1.71300 53.94 S4 * 14.153 14.742 S5 -39.527 2.2 1.72825 28.32 S6 39.527 11.67 1.77250 49.62 S7 -49.547 0.1 S8 81.239 7.5 1.83481 42.72 S9 -81.239 One S10 (ST) inf. D1 S11 * 19.66 1.5 1.88202 37.22 S12 * 14.922 D2 S13 * 76.709 9.5 1.69680 55.46 S14 * -47.094 10.402 S15 -81.239 1.5 1.64769 33.84 S16 81.239 D3 S17 inf. 2 1.51680 64.20 S18 inf. D4 Img inf. 0

The following shows the variable spacing between infinite distance and near distance in the third numerical example.

No. Object (D0) S10 (D1) S12 (D2) S16 (D3) S18 (D4) Infinite distance
m = 0 inf. 1.49947 14.91843 18.5 1.0341 Nearest street
m = -1 / 8 397.74259 9.96729 6.45060 18.5 1.0341

The following is an aspherical surface coefficient in the third numerical example.

Lens face S3 S4 S11 S12 S13 S14 K -1.0 -1.0 -1.0 -1.0 -1.0 -1.0 A -2.786513e-5 -2.196281e-5 -8.121009e-5 -8.595209e-5 3.639360e-6 2.803754e-6 B -5.452657e-8 -7.568641e-8 2.473183e-7 2.909580e-7 -1.605320e-8 -1.325979e-8 C 1.710336e-10 3.056263e-10 -4.461522e-10 -5.434427e-10 6.108839e-11 4.711960e-11 D -1.558703e-13 -3.313110e-13 3.554712e-13 4.181461e-13 -1.149497e-13 -8.720721e-14 E -4.416554e-17 8.602491e-17 6.699328e-17

&Lt; Fourth Numerical Embodiment >

Fig. 7 shows a telephoto short-focal length lens system according to the fourth numerical example, and the following shows design data of the fourth numerical example.

f = 51.058 mm, F / 1.44, HFOV = 23.0 DEG

Lens face Radius of curvature Lens thickness or spacing Refractive index Abe number Object inf. D0 S1 258.269 6.25 1.90366 31.31 S2 -258.269 5.904 S3 * 19.533 3 1.71300 53.94 S4 * 14.153 9.447 S5 (ST) inf. 5.295 S6 -39.527 2.2 1.72825 28.32 S7 39.527 11.67 1.77250 49.62 S8 -49.547 0.1 S9 81.239 7.5 1.83481 42.72 S10 -81.239 One S11 inf. D1 S12 * 19.66 1.5 1.88202 37.22 S13 * 14.922 D2 S14 * 76.709 9.5 1.69680 55.46 S15 * -47.094 10.402 S16 -81.239 1.5 1.64769 33.84 S17 81.239 D3 S18 inf. 2 1.51680 64.20 S19 inf. D4 Img inf. 0

The following shows the variable spacing between infinite distance and near distance in the fourth numerical example.

No. Object (D0) thi s10 (D1) thi s12 (D2) thi s16 (D3) thi s18 (D4) m = 0 inf. 1.49947 14.91843 18.5 1.0341 m = -1 / 8 397.74259 9.96729 6.45060 18.5 1.0341

The following is the aspherical surface coefficient in the fourth numerical example.

Lens face S3 S4 S11 S12 S13 S14 K -1.0 -1.0 -1.0 -1.0 -1.0 -1.0 A -2.786513e-5 -2.196281e-5 -8.121009e-5 -8.595209e-5 3.639360e-6 2.803754e-6 B -5.452657e-8 -7.568641e-8 2.473183e-7 2.909580e-7 -1.605320e-8 -1.325979e-8 C 1.710336e-10 3.056263e-10 -4.461522e-10 -5.434427e-10 6.108839e-11 4.711960e-11 D -1.558703e-13 -3.313110e-13 3.554712e-13 4.181461e-13 -1.149497e-13 -8.720721e-14 E -4.416554e-17 8.602491e-17 6.699328e-17

As described above, the telescopic short focal length lens system according to the embodiment of the present invention can realize a telephoto type lens system having a half angle of view in the range of about 20 to 30 degrees and an effective focal length longer than the rear focal length. Further, the telephoto short-focal length lens system can be configured such that the focusing lens group is lightened and the manufacturing cost is not high so as to realize high-speed auto focusing (AF) with a small F number.

Next, it is shown that the first to fourth numerical embodiments above satisfy the above-mentioned formulas 1 to 3, respectively.

expression Example 1 Example 2 Example 3 Example 4 b _f 33.611 20.838 20.853 20.853 Y 21.7 21.7 21.7 21.7 f 51.054 51.031 51.058 51.058 t ₂ 16.465 9.273 5.904 5.904 f _{One st} 138.718 89.251 143.727 143.727 f _last -64.758 -65.874 -125.429 -125.429 Equation (1) 1.083 0.834 0.833 0.833 Equation (2) 0.119 0.104 0.041 0.041 Equation (3) -0.519 -0.316 -0.166 -0.166 (4) 1.85? N1? 1.95 1.91082 1.88300 1.90366 1.90366

9 shows a photographing apparatus having a telephoto short-focal length lens system 100 according to an exemplary embodiment. The telephoto short focal length lens system 100 is substantially the same as that described with reference to Figs. 1, 3, 5 and 7. The photographing apparatus includes an imaging element 112 that receives the light imaged by the telephoto short-focal length lens system 100. The photographing apparatus may include a recording means 113 recording information corresponding to the photoelectrically-converted object from the imaging element 112, and a finder 114 for observing a subject image. In addition, a display unit 115 for displaying a subject image may be provided. Here, an example in which the viewfinder 114 and the display unit 115 are separately provided is shown, but only the display unit can be provided without a viewfinder. The photographing apparatus shown in FIG. 9 is only an example, and the present invention is not limited thereto, but can be applied to various optical apparatuses other than a camera. Thus, by applying the telephoto short-focal lens system according to the exemplary embodiment to a photographing apparatus such as a digital camera, it is possible to realize an optical apparatus capable of fast auto focusing.

The telephoto short-focal length lens system according to the exemplary embodiment adopts the inner focus method and can realize miniaturization. In this embodiment, by using the inner focusing method in which some lenses in the lens system are moved by focusing rather than the front focusing method in which the lens closest to the object side of the telescopic short focal lens system performs focusing, You can carry it.

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.

FLG: All groups, FG: Focusing lens group
RLG: rear lens, L1: first lens
L2 is a second lens, L3 is a third lens,
L4: fourth lens, L5: fifth lens
L6: sixth lens, L7: seventh lens
L8: Eighth lens

Claims (19)

A telephoto short focal length lens system in which at least one lens group is arranged between an object side and an imaging element,
A focusing lens group including a lens having a convex meniscus shape on the object side, the focusing lens group comprising:
A front lens group disposed on an object side of the focusing lens group and having a positive refractive power; And
And a rear lens group disposed on the upper side of the focusing lens group and having a positive refractive power,
Wherein the front group comprises, in order from the object side, a first lens having positive refractive power, a second lens having negative refractive power, and a third lens having negative refractive power,
The upper surface of the second lens is concave, the object side surface of the third lens is concave,
When the focusing is performed, the front group and the rear group are fixed,
Wherein the lens on the uppermost side of said rear group is a bi-concave lens. The method according to claim 1,
Wherein said second lens of said all group comprises at least one aspherical surface. delete delete The method according to claim 1,
Telephoto short focal length lens system satisfying the following equation.
<Expression>
0.0? T? ₂ / f? _1? 0.15
Here, t ₂ is the distance from the image side of the first lens to the object side of the second lens, and f 1 _st represents the focal length of the first lens. The method according to claim 1,
Telephoto short focal length lens system satisfying the following equation.
<Expression>
-0.6? Bf / f _last ? -0.1
Here, b _f represents the focal length, and f _last represents the focal length of the lens at the uppermost position of the rear group. The method according to any one of claims 1, 2, 5, and 6,
A telephoto short-focal lens system having a diaphragm in the front group or the object side of the focusing lens group. 8. The method of claim 7,
And the lenses disposed on the object side of the diaphragm have a positive refractive power as a whole. The method according to any one of claims 1, 2, 5, and 6,
And a stop is provided between the second lens and the third lens or between the front group and the focusing lens group. 10. The method of claim 9,
Wherein the lens between the second lens and the diaphragm is a spherical lens. The method according to any one of claims 1, 2, 5, and 6,
Wherein the focusing lens group has a negative refractive power. The method according to any one of claims 1, 2, 5, and 6,
Wherein the telescopic short focal length lens system has a focal length greater than an after focal length at an infinite distance. The method according to any one of claims 1, 2, 5, and 6,
Wherein the telescopic short focal length lens system has an angle of view of 40-60 degrees. The method according to any one of claims 1, 2, 5, and 6,
Wherein said front group further comprises a fourth lens of double-convex and a fifth lens of double-convex. The method according to any one of claims 1, 2, 5, and 6,
Wherein the focusing lens group is composed of one sixth lens. The method according to any one of claims 1, 2, 5, and 6,
And the rear group further comprises a seventh lens having both convex on the object side of the positive lens. The method according to any one of claims 1, 2, 5, and 6,
Telephoto short focal length lens system satisfying the following equation.
<Expression>
1.85? N1? 1.95
Here, n1 represents the refractive index of the first lens. A telephoto short-focal lens system according to any one of claims 1, 2, 5, or 6; And
And an imaging element for receiving light formed by said telephoto short-focal lens system. 19. The method of claim 18,
The photographing apparatus satisfying the following expression.
<Expression>
0.8? B _f + Y / f? 1.2
Where b _f is the focal length, Y is the half-diagonal length of the imaging element, and f is the total effective focal length at infinity.

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