KR101582089B1 - Wide angle lens and imaging optical device having the same - Google Patents

Abstract

A wide-angle lens and an imaging optical apparatus having the same are disclosed.

The disclosed wide-angle lens includes a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a diaphragm and a positive refractive power arranged from the object side to the image side, The lens group includes one positive lens.

Description

[0001] The present invention relates to a wide angle lens and an imaging optical device having the same,

Field of the Invention [0002] The present invention relates to a wide-angle lens and an imaging optical apparatus having the same.

2. Description of the Related Art Recently, digital cameras and video cameras having solid-state image pickup devices such as a CCD (Charge Coupled Device) and a CMOS (Complementary Metal-Oxide Semiconductor) have been widely used. Particularly, there is an increasing demand for a lens-interchangeable single reflex camera, and an entry-level single-lens reflex camera is also emerging. On the other hand, an imaging optical apparatus such as a digital camera or a mobile phone camera using an imaging device such as a CCD or CMOS is required to be downsized, lightweight, and low in cost.

And, as the demand for cameras increases, the demand for single focus lenses such as telephoto lenses and wide angle lenses is also increasing. A so-called retrofocus type (inverted telephoto type) lens structure composed of a first lens group having a long refocusing power and a negative refracting power and a second lens group having a positive refracting power has been proposed as the wide-angle lens. In general, the retrofocus type lens is focused by the second lens group. In this case, since the variation of the ray height of the off-axis light flux incident on the lens system is large, the aberration generation amount tends to increase. Therefore, in the retrofocus type lens, a method of correcting the aberration variation at the time of focusing is needed.

The present invention provides a wide-angle lens having a long after-focus distance and improved aberration correction performance, and an imaging optical apparatus having the same.

According to an embodiment of the present invention, there is provided a zoom lens comprising a first lens group having negative refracting power, a second lens group having positive refracting power, and a third lens group having iris and positive refracting power arranged from the object side to the image side, ,

The second lens group includes one positive lens, and provides a wide-angle lens satisfying the following equation.

<Expression>

nII (p) < 1.75

Here, nII (p) represents the refractive index of the positive lens of the second lens group.

According to another embodiment of the present invention, there is provided a zoom lens comprising a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a diaphragm and a positive refractive power arranged from the object side to the image side, ,

The second lens group includes one positive lens, and provides a wide-angle lens satisfying the following equation.

<Expression>

-1.2 < fI / f < -0.6

-0.6 < fI / fIII < -0.2

Here, f represents the total focal length, fI represents the focal length of the first lens unit, and fIII represents the focal length of the third lens unit.

According to another embodiment of the present invention, the first lens group may include one positive lens and two meniscus lenses having a convex shape on the object side.

According to another embodiment of the present invention, the second lens group may further include one negative lens.

According to another embodiment of the present invention, the positive lens and the negative lens may be formed by bonding the second lens group.

According to another embodiment of the present invention, the third lens group may include a first positive lens having a positive refractive power, a cemented lens having a negative refractive power cemented with a second positive lens, and a third positive lens.

According to another embodiment of the present invention, the third lens group may include at least one aspherical surface.

According to another embodiment of the present invention, when focusing according to the object distance, the first lens group and the second lens group are moved while maintaining a constant interval between the first lens group and the second lens group, The group can be moved.

According to another embodiment of the present invention, when focusing according to the object distance, the first lens group is fixed, and the second lens group and the third lens group can be moved.

According to an embodiment of the present invention,

Wide angle lens; And an imaging sensor for receiving the image formed by the wide-angle lens,

Wherein the wide-angle lens is arranged from the object side to the image side, the first lens group having a negative refractive power, the second lens group having a positive refractive power, and the third lens group having a diaphragm and a positive refractive power,

Wherein the second lens group includes one positive lens and satisfies the following expression.

<Expression>

nII (p) < 1.75

Here, nII (p) represents the refractive index of the positive lens of the second lens group.

According to another embodiment of the present invention,

Wide angle lens; And an imaging sensor for receiving the image formed by the wide-angle lens,

Wherein the wide-angle lens is arranged from the object side to the image side, the first lens group having a negative refractive power, the second lens group having a positive refractive power, and the third lens group having a diaphragm and a positive refractive power,

Wherein the second lens group includes one positive lens and satisfies the following expression.

<Expression>

-1.2 < fI / f < -0.6

-0.6 < fI / fIII < -0.2

Here, f represents the total focal length, fI represents the focal length of the first lens unit, and fIII represents the focal length of the third lens unit.

Hereinafter, a wide-angle lens according to an embodiment of the present invention and a photographing optical apparatus having the same will be described in detail with reference to the accompanying drawings.

The wide-angle lens according to the present invention includes a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power and including a diaphragm from the object side.

Figs. 1A, 2A, 3A, 4A, and 5A show a wide-angle lens according to the first to fifth embodiments of the present invention. Referring to FIG. 1A, a wide-angle lens according to an embodiment of the present invention includes a first lens group G1, a second lens group G2, and a third lens group G3. The first lens group G1 includes one positive lens 1 and two negative lenses 2 and 3 from the object side O to ensure a sufficient focal length. The two negative lenses (2) and (3) may have a meniscus shape convex toward the object side (O). On the other hand, the negative lens 3 on the image side I of the first lens group G1 may include an aspherical surface. The negative lens 3 may be made of, for example, a hybrid lens. Figs. 1A and 3A show an example in which the negative lens 3 is fabricated with a hybrid lens.

The second lens group G2 may include one positive lens 4 as shown in Figs. 1A, 2A, 3A, and 4A. Alternatively, as shown in FIG. 5A, the second lens group G2 may include a cemented lens composed of one negative lens 14 and one positive lens 15.

The third lens group G3 includes a diaphragm ST from the object side O, a first positive lens 5 and a positive biconvex lens 16, a second positive lens 6 and 17, (7), (18), and a third positive lens (8) (19). The third lens group G3 may include at least one aspherical surface. Reference numerals 9 and 20 denote filters.

On the other hand, when focusing according to the change of the object distance, the distance between the second lens group G2 and the third lens group G3 is changed so that the distance between the first lens group G1, the second lens group G2, The entire lens group G3 can be moved. At this time, the first lens group G1 and the second lens group G2 may be moved together so that the interval between the first lens group G1 and the second lens group G2 does not change. By thus moving the first lens group G1 and the second lens group G2 together, the configuration of the moving mechanism can be simplified. For example, when the wide-angle lens shown in Figs. 1A, 2A, 3A, and 4A focuses the first lens group and the second lens group while the interval between the first lens group and the second lens group is maintained, do. In the present invention, when the third lens group G3 is moved, the diaphragm ST can be interlocked.

Alternatively, when focusing the optical lens according to another embodiment of the present invention, the first lens group G1 may be fixed, and the second lens group G2 and the third lens group G3 may be moved to perform focusing . For example, the wide-angle lens shown in FIG. 5A shows an operation in which the second lens group G2 and the third lens group G3 are moved to perform focusing.

Meanwhile, the wide-angle lens according to the embodiment of the present invention can be configured to satisfy the following expression.

nII (p) < 1.75

Here, nII (p) represents the refractive index of the positive lens of the second lens group G2.

Equation 1 shows the refractive index at the d-line (587.56 nm) of the positive lens included in the second lens group G2. When the positive lens is out of the range of the formula 1, And it is difficult to correct a variation in chromatic aberration of magnification due to focusing, so that it becomes difficult to satisfy satisfactory imaging performance.

Next, the wide-angle lens according to the present invention can be configured to satisfy the following.

-1.2 < fI / f < -0.6

-0.6 < fI / fIII < -0.2

Here, f represents the total focal length, fI represents the focal length of the first lens unit, and fIII represents the focal length of the third lens unit.

Equation (2) shows the ratio of the focal length of the first lens group to the entire focal length. When fI / f exceeds the upper limit value, it becomes difficult to correct the distortion aberration and spherical aberration, do. Conversely, when the fI / f is out of the lower limit, the wide-angle lens deviates from the retro-focus mode, making it difficult to secure the post-focus distance, and the amount of movement due to focusing increases.

Equation (3) represents the ratio of the focal length of the first lens group G1 to the focal length of the third lens group G3. When fI / fIII exceeds the upper limit value, the spherical aberration correction becomes difficult. Conversely, Out of the retro focus form, it becomes difficult to secure the post focal distance.

Next, definition of an aspherical surface included in the embodiment of the present invention is as follows.

The aspheric surface shape can be expressed by the following equation with the advancing direction of the light beam as a normal when the optical axis direction is the X axis and the direction perpendicular to the optical axis direction is the Y axis. Where x is the distance from the vertex of the lens to the optical axis direction, y is the distance in a direction perpendicular to the optical axis, K is a conic constant, A, B, C, and D are aspheric coefficients, and c represents the inverse number (1 / R) of the radius of curvature at the apex of the lens.

As described above, the aspherical lens can be suitably arranged to mass-produce a large number of lenses while lowering the manufacturing cost of the lens.

Next, specific lens data of various embodiments of the wide-angle lens according to the present invention will be described. Hereinafter, f denotes the focal length of the entire lens system, Fno denotes the F number, R denotes the radius of curvature, D denotes the center thickness of the lens or the distance between the lens and the lens, Nd denotes the refractive index, Vd denotes the Abbe number, ST represents the aperture.

&Lt; Embodiment 1 >

FIG. 1A shows a wide-angle lens according to the first embodiment, and the following shows design data of the first embodiment.

  f; 14.4 Fno; 2.88 2ω; 89.8 DEG

               R D Nd Vd

OBJ: INFINITY D0

S1: 34.12400 4.760000 1.65844 50.85

S2: 72.32800 0.200000

S3: 25.22700 1.600000 1.90366 31.32

S4: 11.18700 3.870000

S5: 41.77000 1.500000 1.80420 46.50

S6: 10.49500 0.250000 1.51840 52.10

S7: 10.12900 D1

     ASP:

     K: 0.000000

     A: -0.442831E-04 B: -0.180614E-06 C: -0.109554E-07 D: 0.000000E + 00

S8: 19.49000 5.800000 1.69895 30.05

S9: -69.03000 D2

ST: INFINITY 2.750000

S11: 31.45000 5.000000 1.58313 59.46

S12: -18.38700 0.150000

      ASP:

      K: 0.000000

      A: 0.153668E-03 B: 0.197344E-06 C: -0.447986E-08 D: 0.629065E-10

 S13: -163.00000 3.950000 1.80420 46.50

 S14: -10.58300 1.200000 1.75520 27.53

 S15: 23.35900 1.820000

 S16: -59.96000 3.850000 1.48749 70.44

 S17: -14.52000 D3

 S18: INFINITY 2.500000 1.51680 64.20

 S19: INFINITY 0.500000

 IMG: INFINITY

 The following is data on variable distance when focusing.

Imaging magnification 0 0.0200 0.1300 D0 INFINITY 709.80957 100.56744 D1 8.09000 8.09000 8.09000 D2 4.21000 3.99226 3.29200 D3 19.01587 19.30684 20.90689

FIG. 1B shows spherical aberration, surface curvature, and distortion aberration of the wide-angle lens according to the first embodiment of the present invention, respectively. Tangential field curvature (T) and sagittal field curvature (S) are shown for the curvature of field.

&Lt; Example 2 >

2A shows a lens system according to the second embodiment, and the following shows design data of the second embodiment.

 f; 14.4 Fno; 2.88 2ω; 89.8 DEG

               R D Nd Vd

  OBJ: INFINITY D0

  S1: 38.60000 4.650000 1.62299 58.12

  S2: 87.08000 0.200000

  S3: 23.13000 1.600000 1.90366 31.32

  S4: 10.70500 4.180000

  S5: 68.93900 1.500000 1.80420 46.50

  S6: 11.91500 D1

  S7: 22.27400 5.800000 1.67270 32.17

  S8: -34.67000 D2

  ST: INFINITY 2.750000

  S10: 28.95100 4.970000 1.58313 59.46

  S11: -15.06300 0.400000

     ASP:

     K: 0.000000

     A: 0.201524E-03 B: 0.356625E-07 C: -0.672143E-08 D: 0.118381E-09

  S12: -33.09000 3.820000 1.83481 42.72

  S13: -9.55200 1.200000 1.75520 27.53

  S14: 21.70900 1.788000

  S15: -72.81100 4.170000 1.48749 70.44

  S16: -13.70000 D3

  S17: INFINITY 2.500000 1.51680 64.20

  S18: INFINITY 0.500000

  IMG: INFINITY

Imaging magnification 0 0.0200 0.1300 D0 INFINITY 708.90070 100.00268 D1 8.77000 8.77000 8.77000 D2 4.10000 3.85053 3.29200 D3 18.83259 19.12143 20.70455

FIG. 2B shows spherical aberration, field curvature, and distortion aberration in the lens system according to the second embodiment.

&Lt; Third Embodiment >

3A shows a lens system according to the third embodiment, and the following is a design data of the third embodiment.

  f; 14.4 Fno; 2.06 2ω; 89.8 DEG

                 R D Nd Vd

  OBJ: INFINITY D0

  S1: 38.13000 5.100000 1.65844 50.85

  S2: 75.53600 0.200000

  S3: 28.18000 1.600000 1.90366 31.32

  S4: 13.32000 4.400000

  S5: 39.89500 1.500000 1.80420 46.50

  S6: 11.95500 0.300000 1.51840 52.100

  S7: 11.66400 D1

     ASP:

     K: 0.000000

     A: -0.228077E-04 B: -0.124276E-07 C: -0.431353E-08 D: 0.000000E + 00

  S8: 30.01000 6.800000 1.72825 28.32

  S9: -57.97200 D2

  ST: INFINITY 2.750000

  S11: 30.70000 5.700000 1.74330 49.33

  S12: -19.60900 0.150000

     ASP:

     K: 0.000000

     A: 0.989620E-04 B: -0.250844E-07 C: -0.421621E-08 D: 0.420641E-10

  S13: -52.28000 3.550000 1.77250 49.62

  S14: -13.45000 1.500000 1.80518 25.450

  S15: 21.23000 2.200000

  S16: -121.00000 4.440000 1.48749 70.44

  S17: -15.06300 D3

  S18: INFINITY 2.500000 1.51680 64.20

  S19: INFINITY 0.500000

  IMG: INFINITY

Imaging magnification 0 0.0200 0.1300 D0 INFINITY 706.30457 97.36432 D1 12.63000 12.63000 12.63000 D2 4.68000 4.37727 3.29200 D3 18.74382 19.03182 20.61498

3B shows spherical aberration, field curvature, and distortion aberration in the lens system according to the third embodiment.

<Example 4>

4A shows the lens system according to the fourth embodiment, and the following is a design data of the fourth embodiment.

  f; 16.3 Fno; 2.06 2ω; 82.6 DEG

                 R D Nd Vd

  OBJ: INFINITY D0

  S1: 39.27500 5.530000 1.58913 61.25

  S2: 137.00000 0.200000

  S3: 29.00000 1.800000 1.90366 31.32

  S4: 12.26900 5.030000

  S5: 197.00000 1.500000 1.48749 70.44

  S6: 12.93000 D1

  S7: 28.92000 6.600000 1.71736 29.50

  S8: -71.07800 D2

  ST: INFINITY 3.000000

  S10: 40.51000 4.800000 1.77377 47.17

  S11: -18.75700 0.260000

     ASP:

     K: 0.000000

     A: 0.676179E-04 B: -0.935940E-07 C: 0.576713E-09 D: -0.120720E-11

 S12: -30.39200 3.400000 1.71300 53.94

 S13: -13.00000 1.500000 1.76182 26.61

 S14: 22.95000 2.270000

 S15: 61.43900 5.240000 1.48749 70.44

 S16: -18.98000 D3

 S17: INFINITY 2.500000 1.51680 64.20

 S18: INFINITY 0.500000

  IMG: INFINITY

Imaging magnification 0 0.0200 0.1300 D0 INFINITY 801.33225 111.92761 D1 12.63000 12.63000 12.63000 D2 4.34000 4.04149 3.07000 D3 21.82989 22.15597 23.94809

4B shows spherical aberration, field curvature, and distortion aberration in the lens system according to the fourth embodiment.

<Fifth Embodiment>

FIG. 5A shows the lens system according to the fifth embodiment, and the following shows design data of the fifth embodiment.

 f; 14.39 Fno; 2.88 2ω; 93.9 DEG

                 R D Nd Vd

  OBJ: INFINITY D0

  S1: 46.21000 4.310000 1.75700 47.71

  S2: 113.60000 0.200000

  S3: 31.50000 1.600000 1.83481 42.73

  S4: 10.54000 3.270000

  S5: 24.64000 1.200000 1.80420 46.50

  S6: 10.00000 D1

     ASP:

     K: 0.000000

     A: -0.164527E-04 B: -0.171958E-07 C: -0.572766E-08 D: 0.000000E + 00

  S7: 39.60000 1.800000 1.80420 46.50

  S8: 8.96200 5.800000 1.64770 33.84

  S9: -48.67400 D2

  ST: INFINITY 2.750000

  S11: 27.99000 5.200000 1.51443 63.28

  S12: -13.29600 1.030000

     ASP:

     K: 0.000000

     A: 0.607166E-04 B: 0.177856E-06 C: -0.246352E-08 D: 0.267855E-10

  S13: 60.08600 4.750000 1.58913 61.25

  S14: -11.55000 1.000000 1.74950 35.04

  S15: 19.56000 1.190000

  S16: 46.25500 4.500000 1.49700 81.61

  S17: -19.36000 D3

  S18: INFINITY 2.500000 1.51680 64.20

  S19: INFINITY 0.500000

  IMG: INFINITY

Imaging magnification 0 0.0200 0.1300 D0 INFINITY 698.87419 89.82005 D1 6.65000 6.99853 8.96066 D2 4.00000 3.77991 2.56322 D3 25.90525 25.77680 25.03137

The following shows that the first to fifth embodiments of the present invention satisfy equations (1), (2) and (3).

Equation 1 Equation 2 Equation 3 First Embodiment 1.699 -0.77 -0.44 Second Embodiment 1.673 -0.77 -0.38 Third Embodiment 1.728 -0.96 -0.47 Fourth Embodiment 1.717 -0.95 -0.49 Fifth Embodiment 1.648 -0.69 -0.54

Fig. 6 shows an optical imaging apparatus having a wide-angle lens according to an embodiment of the present invention. The imaging optical apparatus includes the above-described wide-angle lens 111 and an imaging sensor 112 that receives light image-formed by the wide-angle lens 111. The imaging optical apparatus includes a recording means 113 in which information corresponding to an object photoelectrically converted from the imaging sensor 112 is recorded, and a finder 114 for observing a subject image. Further, a liquid crystal display panel 115 may be provided to display a subject image. The imaging optical apparatus shown in FIG. 6 is only an example, and the present invention is not limited thereto, but may be applied to various optical apparatuses other than a camera. As described above, by applying the wide-angle lens of the present invention to an imaging optical apparatus such as a digital camera, an optical apparatus capable of photographing a subject at a small size and at a wide angle is realized.

The present invention implements retrofocus lenses suitable for wide-angle lenses used in, for example, single-lens reflex cameras and digital cameras using 35 mm film or image sensors. The wide-angle lens according to the present invention is suitable for a wide-angle wide-angle lens having a wide-angle of view of about 80 degrees or more and a diameter ratio of about 1: 2.8. In addition, a sufficient long focal length can be ensured and used as a retrofocus type lens.

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. Accordingly, the true scope of protection of the present invention should be determined by the technical idea of the invention described in the following claims.

1A shows a wide-angle lens according to a first embodiment of the present invention.

FIG. 1B shows longitudinal spherical aberration, surface curvature, and distortion of the wide-angle lens according to the first embodiment.

2A shows a wide-angle lens according to a second embodiment of the present invention.

2B shows longitudinal spherical aberration, field curvature, and distortion of the lens optical system according to the second embodiment.

3A shows a wide-angle lens according to a third embodiment of the present invention.

3B shows longitudinal spherical aberration, field curvature, and distortion of the lens optical system according to the third embodiment.

4A shows a wide-angle lens according to a fourth embodiment of the present invention.

FIG. 4B shows longitudinal spherical aberration, field curvature, and distortion of the wide-angle lens according to the fourth embodiment.

5A shows a wide-angle lens according to a fifth embodiment of the present invention.

FIG. 5B shows longitudinal spherical aberration, field curvature, and distortion of the wide-angle lens according to the fifth embodiment.

6 schematically shows an image-forming optical apparatus according to an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

G1 ... first lens group, G2 ... second lens group

G3 ... third lens group

Claims (10)

A first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having iris and positive refractive power, arranged from the object side to the image side, In focusing according to the object distance, the first lens group and the second lens group are moved while maintaining a constant distance between the first lens group and the second lens group, the third lens group is moved, or the object distance The first lens group is fixed, the second lens group and the third lens group are moved during focusing, Wherein the second lens group includes one positive lens, and satisfies the following expression. <Expression> nII (p) < 1.75 Here, nII (p) represents the refractive index of the positive lens of the second lens group. A first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having iris and positive refractive power, arranged from the object side to the image side, In focusing according to the object distance, the first lens group and the second lens group are moved while maintaining a constant distance between the first lens group and the second lens group, the third lens group is moved, or the object distance The first lens group is fixed, the second lens group and the third lens group are moved during focusing, Wherein the second lens group includes one positive lens, and satisfies the following expression. <Expression> -1.2 < fI / f < -0.6 -0.6 < fI / fIII < -0.2 Here, f represents the total focal length, fI represents the focal length of the first lens unit, and fIII represents the focal length of the third lens unit. 3. The method according to claim 1 or 2, Wherein the first lens group includes one positive lens and two meniscus negative lenses convex toward the object side. 3. The method according to claim 1 or 2, And the second lens group further comprises one negative lens. 5. The method of claim 4, And the second lens group includes the positive lens and the negative lens joined together. 3. The method according to claim 1 or 2, The third lens group includes a first positive lens having two convex portions, a cemented lens having a second positive lens and a negative concave negative lens bonded together, and a third positive lens. 3. The method according to claim 1 or 2, And the third lens group includes at least one aspherical surface. delete delete The wide-angle lens according to claim 1 or 2; And And an imaging sensor for receiving the image formed by the wide-angle lens.

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