JP4866120B2 - Zoom lens and imaging apparatus having the same - Google Patents

Description

  The invention of the present application relates to a zoom lens and an electronic image pickup apparatus using the same, and can be used for, for example, a video camera or a digital camera.

  Digital cameras that shoot subjects using solid-state image sensors such as CCDs and CMOSs instead of silver halide films have become widespread. In recent years, a small and thin type of such a digital camera has been favored. Of the size of the camera, the thickness direction depends mainly on the size of the optical system, so the configuration of the optical system becomes important to achieve a reduction in thickness. Recently, a so-called collapsible lens barrel is generally used in which an optical system is protruded from the camera body during photographing and the optical system is accommodated in the camera body when being carried. Therefore, in the case of a zoom lens, the configuration of the lens group considering the size when retracted is extremely important.

  On the other hand, the zoom ratio of a compact type digital camera is generally about three times, but a camera having a higher zoom ratio than that has been demanded.

  As a prior art that configures such a high zoom ratio zoom, as disclosed in the following documents (see Patent Document 1 and Patent Document 2), a positive first lens group and a negative second lens from the object side are disclosed. A type having a group, a positive third lens group, and a positive fourth lens group is known.

JP-A-4-171411

JP-A-2005-62228

  However, these prior examples have the following problems. In Patent Document 1, the third lens group is arranged in the order of a positive lens, a negative lens, a positive lens, and a negative lens from the object side, but the total thickness of the third lens group is large and a retractable structure. But miniaturization has not been achieved. In addition, since two meniscus negative lenses are arranged, the configuration is such that the diverging action of the negative lens cannot be utilized effectively, which is disadvantageous in terms of performance.

  Further, Example 4 in Patent Document 2 has the same configuration as described above, but has not been able to achieve miniaturization in the same manner. Further, since the third lens and the fourth lens are cemented, the degree of freedom of power is reduced, and the principal point position is difficult to move. Further, there is no consideration for the collapse, the number of lenses is large, and the thickness of each lens group tends to be large.

  The invention of the present application has been made in view of such a problem, and an object of the invention is to provide a zoom lens that is advantageous for downsizing while having a configuration advantageous for increasing the zoom ratio by devising the third lens group. Is to provide.

  Another object of the present invention is to provide a zoom lens that can easily increase the zoom ratio while reducing the overall length during use and maintaining the optical performance by devising the third lens group.

  A further object of the present invention is to provide a zoom lens with a shortened overall length at the wide-angle end.

  A further object of the present invention is to provide a zoom lens that reduces the number of lenses and is easy to reduce the thickness when retracted.

  It is another object of the present invention to provide an imaging apparatus including these zoom lenses.

The zoom lens according to the inventions of the present application to solve the above problems, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, positive refractive power a third lens group having made a fourth lens group having positive refractive power, said first lens group, a second lens group, said third lens group and said fourth lens group, A zoom lens that moves in the direction of the optical axis so as to change the air gap between each lens group and performs zooming from the wide-angle end to the telephoto end, and at the telephoto end with respect to the wide-angle end The distance between the first lens group and the second lens group is increased, and the distance between the second lens group and the third lens group is decreased. The third lens group includes four lenses in order from the object side: a first lens that is a positive lens, a second lens that is a negative lens, a third lens that is a positive lens, and a fourth lens that is a negative lens. The second lens in the third lens group is joined to at least one of the first lens or the third lens on the optical axis, and the third lens and the fourth lens in the third lens group An air gap is sandwiched between the two so as to satisfy the following conditional expression .
-1.5 <fg3L123 / fg3L4 <-0.8
Here, fg3L123 is the combined focal length of the first, second and third lenses of the third lens group, and fg3L4 is the focal length of the fourth lens of the third lens group.
In the inventions of the zoom lens of the present patent application, before Symbol the second lens in the third lens group, preferably at least one of the lens of the fourth lens is a biconcave lens.
In the present application the inventions of the zoom lens, before SL located in the first lens group is an object side at the telephoto end than at the wide angle end, the third lens group is preferably located on the object side .
In the present application the inventions of the zoom lens, before Symbol first lens group, the second lens group, preferably constituted by the one of the fourth lens group, respectively, or two lenses.

In the inventions of the zoom lens of the present patent application, before Symbol object side surface of the second lens of the third lens group, preferably the bonding surface of the respective positive lenses the image side surface meet next.
In the present application the inventions of the zoom lens, preferably to satisfy the following condition.
0.3 <Ih / fg3 <1.2
Here, Ih is the maximum image height, and fg3 is the focal length of the third lens group.
In the present application the inventions of the zoom lens, preferably to satisfy the following condition.
2 <fg1 / fg3 <7
Here, fg1 is the focal length of the first lens group, and fg3 is the focal length of the third lens group.

In the present application the inventions of the zoom lens, preferably to satisfy the following condition.
−1.5 <fg2 / fg3 <−0.5
Here, fg2 is the focal length of the second lens group, and fg3 is the focal length of the third lens group.
In the present application the inventions of the zoom lens, preferably to satisfy the following condition.
0.1 <fg3 / fg4 <0.85
Here, fg3 is the focal length of the third lens group, and fg4 is the focal length of the fourth lens group.
In the present application the inventions of the zoom lens, preferably to satisfy the following condition.
1.2 <β2T / β2W <5
Where β2T is the lateral magnification at the telephoto end of the second lens group, and β2W is the lateral magnification at the wide-angle end of the second lens group.
In the present application the inventions of the zoom lens, preferably to satisfy the following condition.
1.5 <β3T / β3W <5
However, β3T is a lateral magnification at the telephoto end of the third lens group, and β3W is a lateral magnification at the wide-angle end of the third lens group.

In the present application the inventions of the zoom lens, preferably to satisfy the following condition.
0.1 <Dg1 / D <2.0
However, Dg1 is a moving distance from the wide-angle end to the telephoto end of the first lens group, and D is a total value of axial distances from the entrance surface to the exit surface for each lens group.
In the present application the inventions of the zoom lens, preferably to satisfy the following condition.
0.1 <Dg3 / D <2.0
However, Dg3 is a moving distance from the wide-angle end to the telephoto end of the third lens group, and D is a total value of axial distances from the entrance surface to the exit surface for each lens group.
In the present application the inventions of the zoom lens, preferably to satisfy the following condition.
−1.25 <(rg3L1f + rg3L1r) / (rg3L1f−rg3L1r) <− 0.15
Here, rg3L1f is the radius of curvature of the object side surface of the first lens of the third lens group, and rg3L1r is the radius of curvature of the image side surface of the first lens of the third lens group.

In the present application the inventions of the zoom lens, preferably to satisfy the following condition.
−0.8 <(rg3L4f + rg3L4r) / (rg3L4f−rg3L4r) <1.5
Here, rg3L4f is the radius of curvature of the object side surface of the fourth lens of the third lens group, and rg3L4r is the radius of curvature of the image side surface of the fourth lens of the third lens group.
In the present application the inventions of the zoom lens, the second lens group negative lens from the object side, preferably constituted by only two positive lenses.
In the present application the inventions of the zoom lens preferably comprises an aperture stop disposed between the front SL and the second lens group and the third lens group.
Further, the object in the application of the inventions of the zoom lens, the front Symbol third lens group positioned closer to the object side at the telephoto end than at the wide angle end, stop the brightness at the telephoto end than at the wide angle end It is preferably located on the side.
In the present application the inventions of the zoom lens, it is preferable to satisfy the expression below.
3.5 <fT / fW
Here, fT is the focal length of the entire zoom lens system at the telephoto end, and fW is the focal length of the entire zoom lens system at the wide angle end.

Imaging device according to the present invention includes at least one of the zoom lens of the present application, it is arranged on the image side of the zoom lens, and it comprises an imaging device for converting an image formed by the zoom lens into an electric signal It is characterized by .

  By configuring as in the invention of the present application, it is possible to obtain a zoom lens and an imaging apparatus that are small and have a high zoom ratio.

  Prior to the description of the embodiments of the present invention, the operation and effect of the present invention will be described.

For securing the zooming ratio in the present invention, in order the positive first lens group from the object side, a negative second lens group, a positive third lens group, the configuration composed of the positive fourth lens group employed ing.

  In this configuration, increasing the power of the third lens group having a large zooming effect is effective for downsizing. Therefore, in order to prevent the performance from deteriorating, it is necessary to make it easy to suppress the aberration generation amount in the third lens group even if the power is increased.

Therefore, in the present application inventions, a first lens of a positive lens of the third lens group in order from the object side, a second lens of a negative lens, a third lens of a positive lens, is constituted by four fourth lens of a negative lens . Thereby , even if the power of the third lens group is increased, the convergence and diverging actions are alternately arranged, so that aberration can be effectively corrected and high performance can be achieved. Further, it becomes possible to effectively exhibit the zooming action of the third lens group by moving the principal point on the object side at the same time.

  As the zoom ratio increases, the problem of chromatic aberration increases. Therefore, it is preferable to provide a cemented lens also in the third lens group. However, here, when the fourth lens closest to the image side among the negative lenses in the third lens group is cemented with the adjacent positive lens, the object side surface of the negative lens depends on the radius of curvature of the image side surface of the positive lens. And will not be able to get enough negative power.

Therefore, the ability to the main points from the object side is constituted of a telephoto type configuration in the third lens group is less likely to take is lowered. Therefore, in the present application inventions, and the object side surface or the image side surface of the second lens is a negative lens of the third lens group and the bonding surface with the adjacent positive lens. This makes it easy to obtain a zoom ratio by smooth principal point movement, which is advantageous for shortening the overall length.

  In addition, the occurrence of chromatic aberration when the zoom ratio is increased can be reduced, and high performance can be achieved. Further, by joining the second lens and the positive lens in the third lens group, the configuration length in the optical axis direction of the third lens group can be reduced, and a reduction in thickness can be achieved.

Further, the principal point to the object toward, the zoom lens of the present invention constitutes an air spacing interposed useless between the third lens and the fourth lens of the third lens group. This ensures that secure the zoom ratio, it is easy to shorten the total length when used.
In the zoom lens according to the present invention, the first, second, and third combined focal lengths of the third lens group and the focal length of the fourth lens satisfy the following conditional expression.
-1.5 <fg3L123 / fg3L4 <-0.8
Here, fg3L123 is the combined focal length of the first, second and third lenses of the third lens group, and fg3L4 is the focal length of the fourth lens of the third lens group.
If the upper limit of the conditional expression is not exceeded, the power of the fourth lens can be maintained, the telephoto effect in the third lens group can be ensured, and the principal point interval with the second lens group can be reduced, resulting in a smaller and higher size. This is advantageous for changing the zoom ratio. Alternatively, it is advantageous to suppress the power of the first, second, and third lens combining system from becoming too strong, and to suppress the occurrence of higher-order aberrations.
On the other hand, if it does not fall below the lower limit, the power of the fourth lens can be suppressed, and coma aberration and distortion can be prevented from being overcorrected. Alternatively, it is advantageous for securing the power of the synthesis system of the first, second, and third lenses to shorten the overall length.

Further, Oite the Zumuren's of the present invention, when composed of a first lens by bonding a third lens, respectively, it is possible to reduce the thickness at more lens housing.

Meanwhile, in order from the object side as described above, positive, negative, positive, in the positive type zoom lens comprising a power, a positive lens power of the stronger the power of the third lens group in the third lens group strong It becomes. Therefore, the configuration of the negative lens in the third lens group is important for correcting aberrations.

  Here, when the negative lens is formed in a meniscus shape, the power of one surface becomes extremely strong and high-order aberrations are generated, so that the aberrations cannot be effectively corrected in a balanced manner.

  Further, since the curvature is large (the absolute value of the radius of curvature is small), the protrusion of the lens surface at a position away from the optical axis is large, the negative lens is large in the thickness direction, and the configuration length of the third lens group It becomes difficult to make small.

Therefore, in the present application inventions of the zoom lens, before Symbol the second lens in the third lens group, it is preferable to constitute at least one of the lens of the fourth lens at biconcave lens. Accordingly, it is possible to share the function of negative refractive power on both surfaces of the negative lens to suppress the generation of higher-order aberrations, to suppress the enlargement of the negative lens, and to satisfy both the miniaturization and the high performance at the same time . Further, in the zoom lens according to the present invention, if the fourth lens of the third lens group is a biconcave negative lens and the object side of the biconcave negative lens is configured to have an air gap, the fourth lens Negative power can be secured without using a surface with strong curvature, and the telephoto type configuration in the third lens group can make the principal point closer to the object, ensuring a zoom ratio and shortening the overall length during use. This is advantageous for further miniaturization and ensuring optical performance . It is more preferable that the conditions in the present invention and discussed later in relation to the invention also satisfies at the same time.

Further, Oite herein the inventions of the zoom lens, the first lens group at the telephoto end is located closer to the object side than at the wide angle end, if so the third lens unit is located on the object side, the The balance between the contribution of the second lens group and the third lens group to the zooming and the aberration can be improved. Therefore, it is preferable for increasing the zoom ratio that the first lens group and the third lens group are moved as described above to cause the third lens group to actively wait for the zooming load.

  In order to shorten the total length at the wide-angle end, it is preferable to make the first lens group move as described above and to ensure the focal length at the telephoto end.

In the zoom lens of the present invention, it is preferable to limit the number of lenses and shorten the total length when retracted.

Specifically, in the present application inventions of the zoom lens, the first lens group, the second lens group, by constituting the fourth lens group at one or two lenses each thin when it collapsed And the lens diameter can be reduced.

  Furthermore, it is preferable that the first lens group is composed of two lenses, a positive lens and a negative lens, in consideration of chromatic aberration. The second lens group is preferably composed of two lenses, a positive lens and a negative lens, in consideration of chromatic aberration. The fourth lens group may have a small power burden. Therefore, it is preferable that the fourth lens group is composed of a single positive lens in order to reduce the size when the lens is retracted.

  In addition, it is preferable that the movement of the fourth lens group corrects minute aberration fluctuations (astigmatism fluctuations and coma aberration fluctuations) and adjusts the exit pupil, which reduces the burden of lens driving.

  The image pickup apparatus of the present invention is preferably an image pickup apparatus provided with an image pickup element that is disposed on the image side of the zoom lens of the present invention and that converts an image formed by the zoom lens into an electric signal. In addition, the imaging apparatus may include a configuration that will be described later.

  In general, such an image pickup device is liable to have an effect on light quantity shortage and color reproduction when the incident angle of incident light increases. Therefore, as in the zoom lens of the invention of the present application, it is preferable that the emitted light beam is configured to have a positive, negative, positive, and positive lens group configuration in order from the object side so that the emitted light beam approaches the optical axis.

  Next, an embodiment of an imaging apparatus according to the invention of the present application will be described in detail with reference to the drawings.

Example 1
FIG. 1 is a cross-sectional view along the optical axis showing the optical configuration of a zoom lens according to Example 1 of the present invention. (a) is a diagram showing the state at the wide-angle end, (a ′), (b), (b ′) are in the middle state from the wide-angle end to the telephoto end, and (c) is a diagram showing the state at the telephoto end. The focal length increases in the order of (a), (a ′), (b), (b ′), and (c).

  FIG. 2 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom lens according to Example 1 is focused at an object point at infinity. (a) is a wide angle end, (b) is a state in the middle of (b) in FIG. 1, and (c) is a view showing a state at a telephoto end.

  The zoom lens optical system of Example 1 includes, in order from the object side, a positive first lens group G11, a negative second lens group G12, an aperture stop S, a positive third lens group G13, and a positive 4th lens group G14. A plane parallel plate FL1 and a CCD light receiving surface P are disposed on the image side of the fourth lens group G14.

  In order from the object side, the first lens group G11 includes a negative meniscus lens L11 having a convex surface directed toward the object side and a positive lens L12 having biconvex surfaces, and the lenses L11 and L12 are cemented. The second lens group G12 includes a biconcave negative lens L13 having both aspheric surfaces and a positive meniscus lens L14 having a convex surface facing the object side. The third lens group G13 includes a positive meniscus lens L15 having an aspheric object side surface and a convex surface facing the object side, a negative meniscus lens L16 having a convex surface facing the object side, and a positive lens L17 having a biconvex surface having an aspheric surface on the image side. And both surfaces are composed of an aspherical biconcave negative lens L18, and the lenses L15, L16 and L17 are cemented. The fourth lens group G14 includes a biconvex positive lens L19 having an aspheric image side. The plane-parallel plate FL1 is a cover glass that protects the CCD light-receiving surface, but it may be constituted by a low-pass filter subjected to infrared cut.

  In the zoom lens optical system of Example 1, the first lens group G11 moves to the object side and the second lens group G12 once moves to the image side from the wide angle end to the telephoto end during zooming. The direction of movement is reversed near the focal length state and moves toward the object side, the third lens group G13 moves toward the object side, and the fourth lens group G14 moves once toward the object side and then moves near the intermediate focal length state. The direction is reversed to move to the image side. The intermediate focal length state is a state in which the focal length is a geometric average of the focal length of the entire zoom lens system at the wide-angle end and the focal length of the entire zoom lens system at the telephoto end.

  In Example 1, the image height (Ih) is 3.8 mm, the focal length is 6.60 to 10.20 to 16.40 to 22.69 to 31.85 mm, and Fno is 2.78 to 3. .17-3.70-4.35-5.45.

Next, numerical data of optical members constituting the optical system of Example 1 are shown.
In the numerical data of the first embodiment, R is the radius of curvature of each lens surface, D is the thickness or air spacing of each lens, Nd and Vd are the refractive index and Abbe number of each lens at the d-line, D3 , D7, D14, and D16 represent variable intervals. Fno is the F number, f is the focal length of the entire system, 2ω is the angle of view (ω is the half angle of view). The unit of R, D, and f is mm. ASP means an aspherical surface, and the aspherical surface shape takes the optical axis direction as z, the direction orthogonal to the optical axis as y, the paraxial radius of curvature as R, the conic coefficient as k, and the aspherical coefficient as A4 and A6. , A8, A10, it is expressed by the following formula.
z = (y ² / R) / [1+ {1- (1 + k) (y / R) ² } ^1/2 ]
^{+ A4y 4 + A6y 6 + A8y} 8 + A10y 10
In addition, among the aspheric coefficients, for example, 3.81503e-05 which is the value of A4 in the aspheric surface 4 of Example 1 can be displayed as 3.815033 × 10 ^−5, but in the numerical data, all of the former It is displayed in the format. These symbols are common to numerical data in the embodiments described later.

Numerical data 1
Surface number R D Nd Vd
1 17.105 0.90 1.84666 23.78
2 13.550 3.40 1.49700 81.54
3 -65.008 D3
4 -13.940 ASP 1.00 1.80610 40.92
5 5.016 ASP 1.25
6 8.993 1.80 1.92286 20.88
7 33.594 D7
8 Aperture 0.00
9 3.837 ASP 2.64 1.49700 81.54
10 197.151 0.50 1.67270 32.10
11 5.421 1.50 1.58913 61.14
12 -8.056 ASP 1.75
13 -45.923 ASP 1.00 1.69350 53.21
14 4.948 ASP D14
15 10.719 1.80 1.48749 70.41
16 -65.649 ASP D16
17 ∞ 0.53 1.51633 64.14
18 ∞ 0.60
19 ∞ (light receiving surface, image surface)

Aspheric coefficient Surface number R k
4 -13.940 -1.734
A4 A6 A8 A10
3.81503e-05 1.13065e-05 -4.06931e-07 5.57665e-09
Surface number R k
5 5.016 0.000
A4 A6 A8 A10
-8.22923e-04 -1.09424e-05 2.08584e-07 -5.80955e-08
Surface number R k
9 3.837 0.000
A4 A6 A8 A10
-1.04110e-03 -8.07966e-07 -4.43569e-06 8.64254e-08
Surface number R k
12 -8.056 0.000
A4 A6 A8 A10
4.69718e-03 -8.50261e-06 -1.73554e-05 4.19191e-06
Surface number R k
13 -45.923 -2317.509
A4 A6 A8 A10
-1.85235e-04 -9.09826e-05 -2.32982e-04 2.86280e-05
Surface number R k
14 4.948 0.000
A4 A6 A8 A10
5.23559e-04 -7.73655e-04 -1.30728e-05 9.38150e-06
Surface number R k
16 -65.649 0.000
A4 A6 A8 A10
-3.35014e-04 4.74160e-06 4.18422e-07 -1.57103e-08

Zoom data <br/> Focal length f 6.6 10.2 16.4 22.69 31.85
Fno 2.78 3.17 3.7 4.35 5.45
Angle of view 2ω 65.06 40.03 25.24 18.38 13.15

D3 1.08 4.28 7.25 8.78 9.51
D7 10.5 6.85 3.38 1.94 0.7
D14 2.8 3.84 4.94 8.01 12.64
D16 1.46 2 3.24 2.59 1.48

Example 2
FIG. 3 is a cross-sectional view along the optical axis showing the optical configuration of the zoom lens according to Embodiment 2 of the present invention. (a '), (b), (b') is a figure in the middle state from a wide angle end to a telephoto end, (c) is a figure which shows the state in a telephoto end, respectively. The focal length increases in the order of (a), (a ′), (b), (b ′), and (c).

  FIG. 4 is an aberration diagram illustrating spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom lens according to Example 2 is focused at infinity. (a) is a wide angle end, (b) is a state in the middle of FIG. 3 (b), and (c) is a view showing a state at the telephoto end.

  The zoom lens optical system of Example 2 includes, in order from the object side, a positive first lens group G21, a negative second lens group G22, an aperture stop S, a positive third lens group G23, and a positive fourth lens group. A lens group G24 is provided.

  In this zoom lens optical system, in order from the object side, the first lens group G21 includes a negative meniscus lens L21 having a convex surface directed toward the object side, and a positive lens L22 having a biconvex surface. L21 and L22 are joined. The second lens group G22 includes a biconcave negative lens L23 having both aspheric surfaces and a positive meniscus lens L24 having a convex surface directed toward the object side. The third lens group G23 has an aspherical object-side surface, a biconvex positive lens L25, a biconcave negative lens L26, a biconvex positive lens L27 whose image side surface is aspheric, and both aspherical biconcave surfaces. Negative lens L28, and the lenses L25, L26, and L27 are cemented. The fourth lens group G24 is composed of a biconvex positive lens L29. The plane-parallel plate FL1 is a cover glass that protects the CCD light-receiving surface, but it may be constituted by a low-pass filter subjected to infrared cut.

  In the zoom lens optical system, at the time of zooming, from the wide angle end to the telephoto end, the first lens group G21 moves to the object side, and the second lens group G22 once moves to the image side, and then the vicinity of the intermediate focal length state. The moving direction is reversed to move toward the object side, the third lens group G23 moves toward the object side, and the fourth lens group G24 is fixed during zooming.

  In the second embodiment, the image height is 3.8 mm, the focal length is 6.60 to 10.20 to 16.40 to 22.69 to 31.85 mm, and Fno is 2.80 to 3.23 to 3.93 to 4.54 to 5.55.

Numerical data 2
Surface number R D Nd Vd
1 15.992 0.90 1.84666 23.78
2 12.619 3.40 1.49700 81.54
3 -117.880 D3
4 -15.197 ASP 1.00 1.80610 40.92
5 4.971 ASP 1.30
6 8.781 1.80 1.92286 20.88
7 29.416 D7
8 Aperture 0.00
9 3.859 ASP 2.80 1.49700 81.54
10 -93.989 0.50 1.67270 32.10
11 6.025 1.50 1.58913 61.14
12 -8.038 ASP 1.72
13 -43.943 ASP 1.00 1.69350 53.21
14 5.308 ASP D14
15 489.427 1.80 1.48749 70.41
16 -9.935 1.50
17 ∞ 0.53 1.51633 64.14
18 ∞ 0.60
19 ∞ (light receiving surface, image surface)

Aspheric coefficient Surface number R k
4 -15.197 -2.064
A4 A6 A8 A10
1.94094e-05 1.16844e-05 -3.83705e-07 4.75767e-09
Surface number R k
5 4.971 0.000
A4 A6 A8 A10
-8.11256e-04 -8.10969e-06 3.79322e-07 -7.17961e-08
Surface number R k
9 3.859 0.000
A4 A6 A8 A10
-1.00753e-03 4.09967e-08 -4.44294e-06 9.40707e-08
Surface number R k
12 -8.038 0.000
A4 A6 A8 A10
4.69780e-03 -4.89948e-06 -1.77698e-05 4.35255e-06
Surface number R k
13 -43.943 -2092.754
A4 A6 A8 A10
-2.81666e-04 -9.50198e-05 -2.35970e-04 3.17349e-05
Surface number R k
14 5.308 0.000
A4 A6 A8 A10
8.47602e-04 -7.58376e-04 -1.96245e-05 1.18487e-05

Zoom data <br/> Focal length f 6.6 10.2 16.41 22.69 31.91
Fno 2.8 3.24 3.93 4.54 5.55
Angle of view 2ω 64.81 40.18 25.23 18.51 13.46

D3 1.1 4.33 6.92 8.55 9.45
D7 11.12 7.48 4.21 2.37 0.7
D14 2.78 4.33 6.80 8.98 12.49

Example 3
FIG. 5 is a cross-sectional view along the optical axis showing the optical configuration of the zoom lens according to Embodiment 3 of the present invention. (a) is a diagram showing the state at the wide-angle end, (a ′), (b), (b ′) are in the middle state from the wide-angle end to the telephoto end, and (c) is a diagram showing the state at the telephoto end. The focal length increases in the order of (a), (a ′), (b), (b ′), and (c).

  FIG. 6 is an aberration diagram illustrating spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom lens according to Example 1 is focused at an object point at infinity. (a) is a wide angle end, (b) is a state in the middle of FIG. 5 (b), and (c) is a view showing a state at the telephoto end.

  The zoom lens optical system of Example 3 includes, in order from the object side, a positive first lens group G31, a negative second lens group G32, an aperture stop S, a positive third lens group G33, and a positive fourth lens. Group G34 is arranged. A plane parallel plate FL1 and a CCD light receiving surface P are disposed on the image side of the fourth lens group G34.

  In the zoom lens optical system, in order from the object side, the first lens group G31 includes a negative meniscus lens L31 having a convex surface facing the object side, and a positive lens L32 having a biconvex surface, and the lenses L31 and L32. Are joined. The second lens group G32 includes a biconcave negative lens L33 having both aspheric surfaces and a positive meniscus lens L34 having a convex surface directed toward the object side. The third lens group G33 has a double-sided aspheric positive lens L35, a negative meniscus lens L36 having a convex surface facing the object side, a biconvex seventh positive lens L37, and a double-sided negative negative lens L38. The lenses L36 and L37 are cemented. The fourth lens group G34 includes a positive meniscus lens L39 having an aspheric image side and a convex surface on the object side. The plane-parallel plate FL1 is a cover glass that protects the CCD light-receiving surface, but it may be constituted by a low-pass filter subjected to infrared cut.

  In the zoom lens optical system, at the time of zooming, from the wide angle end to the telephoto end, the first lens group G31 moves to the object side, the second lens group G32 once moves to the image side, and then the vicinity of the intermediate focal length state. The direction of movement is reversed to move to the object side, the third lens group G33 is moved to the object side, the fourth lens group G34 is once moved to the object side, and the direction of movement is reversed in the vicinity of the intermediate focal length state. Configured to move sideways.

  In Example 3, the image height is 3.8 mm, the focal length is 6.58 to 10.20 to 16.41 to 22.70 to 31.96 mm, and Fno is 3.02 to 3.32 to 3.79 to 4.28 to 5.23.

Numerical data 3
Surface number RD Nd Vd
1 17.082 0.90 1.84666 23.78
2 13.655 3.40 1.49700 81.54
3 -139.714 D3
4 -17.102 ASP 1.00 1.80610 40.92
5 4.974 ASP 1.11
6 8.009 1.80 1.92286 20.88
7 22.100 D7
8 Aperture 0.00
9 4.114 ASP 1.50 1.52249 59.84
10 -78.260 ASP 0.10
11 13.279 0.50 1.66680 33.05
12 3.029 1.70 1.60311 60.64
13 -23.913 1.67
14 -27.589 ASP 0.80 1.69350 53.21
15 5.047 ASP D15
16 8.929 1.80 1.62280 57.05
17 46.438 ASP D17
18 ∞ 0.53 1.51633 64.14
19 ∞ 0.60
20 ∞ (light receiving surface, image surface)

Aspheric coefficient Surface number R k
4 -17.102 0.462
A4 A6 A8 A10
1.57936e-05 1.18959e-05 -4.27812e-07 6.30369e-09
Surface number R k
5 4.974 0.000
A4 A6 A8 A10
-7.43812e-04 -5.73906e-06 -6.46247e-07 -3.83737e-08
Surface number R k
9 4.114 0.000
A4 A6 A8 A10
-9.77640e-04 -5.31689e-05 -7.30852e-06 3.86874e-07
Surface number R k
10 -78.260 -858.800
A4 A6 A8 A10
2.33917e-04 1.30319e-05 -1.13148e-05 8.11961e-07
Surface number R k
14 -27.589 148.407
A4 A6 A8 A10
-4.59299e-03 -2.84914e-05 -3.88470e-05 1.24819e-05
Surface number R k
15 5.047 0.000
A4 A6 A8 A10
-2.18686e-03 -3.81331e-08 4.84203e-05 -4.19607e-06
Surface number R k
17 46.438 0.000
A4 A6 A8 A10
-1.43002e-04 -1.66900e-05 1.80760e-07 3.97325e-09

Zoom data <br/> Focal length f 6.58 10.2 16.41 22.7 31.96
Fno 3.02 3.32 3.79 4.28 5.23
Angle of view 2ω 65.34 40.66 25.44 18.37 13.1

D3 1.08 4.68 8.95 12.21 13.22
D7 10.06 5.62 2.76 2.19 0.7
D15 2.8 1.82 2.69 6.52 10.17
D17 1.49 3.52 4.43 2.27 1.5

Example 4
FIG. 7 is a cross-sectional view along the optical axis showing the optical configuration of a zoom lens according to Embodiment 4 of the present invention. (a) is a diagram showing the state at the wide-angle end, (a ′), (b), (b ′) are in the middle state from the wide-angle end to the telephoto end, and (c) is a diagram showing the state at the telephoto end. The focal length increases in the order of (a), (a ′), (b), (b ′), and (c).

  FIG. 8 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom lens according to Example 1 is focused at an object point at infinity. (a) is a wide angle end, (b) is a state in the middle of FIG. 7 (b), and (c) is a view showing a state at the telephoto end.

  The zoom lens optical system of Example 4 includes, in order from the object side, a positive first lens group G41, a negative second lens group G42, an aperture stop S, a positive third lens group G43, a flare stop F, and a positive 4th lens group G44. A plane parallel plate FL1 and a CCD light receiving surface P are disposed on the image side of the fourth lens group G44.

  In this zoom lens optical system, in order from the object side, the first lens group G41 includes a negative meniscus lens L41 having a convex surface facing the object side and a positive lens L42 having a biconvex surface. Are joined. The second lens group G42 includes a biconcave negative lens L43 having both aspheric surfaces and a positive meniscus lens L44 having a convex surface directed toward the object side. The third lens group G43 includes a positive lens L45 having an aspheric surface on the object side and a biconvex surface, a negative meniscus lens L46 having a convex surface facing the image side, and a positive lens L47 having an aspheric surface on the image side and a biconvex surface. Both are composed of an aspherical biconcave negative lens L48, and the lenses L45 and L46 are cemented. The fourth lens group G44 includes a ninth positive lens L49 having an aspheric surface on the image side and a convex surface on the object side. The plane-parallel plate FL1 is a cover glass that protects the CCD light-receiving surface, but it may be constituted by a low-pass filter subjected to infrared cut.

  In the zoom lens optical system, at the time of zooming, from the wide angle end to the telephoto end, the first lens group G41 moves to the object side, and the second lens group G42 once moves to the image side, and then near the intermediate focal length state. The movement direction is reversed to move to the object side, the third lens group G43 is moved to the object side, the fourth lens group G44 is once moved to the object side, and the movement direction is reversed in the vicinity of the intermediate focal length state. Configured to move to the side.

  In Example 4, the image height is 3.8 mm, the focal length is 6.58 to 10.20 to 16.41 to 22.70 to 31.96 mm, and Fno is 2.72 to 3.02 to 3.47 to 3.96 to 4.85.

Numerical data 4
Surface number RD Nd Vd
1 17.095 0.90 1.84666 23.78
2 13.518 3.40 1.49700 81.54
3 -101.177 D3
4 -16.982 ASP 1.00 1.80610 40.92
5 4.929 ASP 1.27
6 8.068 1.80 1.92286 20.88
7 21.452 D7
8 Aperture 0.00
9 4.501 ASP 2.20 1.51633 64.14
10 -9.014 0.50 1.75520 27.51
11 -292.165 0.10
12 5.626 1.54 1.64000 60.08
13 -89.546 ASP 1.28
14 -20.730 ASP 0.80 1.76200 40.10
15 4.852 ASP D15
16 10.169 1.80 1.51823 58.90
17 189.133 ASP D17
18 ∞ 0.53 1.51633 64.14
19 ∞ 0.60
20 ∞ (light receiving surface, image surface)

Aspheric coefficient Surface number R k
4 -16.982 -0.946
A4 A6 A8 A10
4.84159e-05 9.45464e-06 -4.44388e-07 6.75559e-09
Surface number R k
5 4.929 0.000
A4 A6 A8 A10
-6.13111e-04 -1.65534e-05 8.42860e-08 -7.94179e-08
Surface number R k
9 4.501 0.000
A4 A6 A8 A10
-2.91618e-04 -2.81730e-05 2.58747e-07 -1.14929e-07
Surface number R k
13 -89.546 0.000
A4 A6 A8 A10
4.46072e-04 -5.02786e-05 -1.55359e-05 7.63152e-07
Surface number R k
14 -20.730 -40.532
A4 A6 A8 A10
-5.23184e-03 -5.37771e-04 -7.03569e-05 1.52760e-05
Surface number R k
15 4.852 0.000
A4 A6 A8 A10
-8.21368e-05 -3.72623e-04 4.36786e-06 6.53299e-06
Surface number R k
17 189.133 0.000
A4 A6 A8 A10
-5.92248e-04 2.07817e-05 -1.00456e-06 1.94084e-08

Zoom data <br/> Focal length f 6.58 10.2 16.4 22.69 31.99
Fno 2.72 3.02 3.47 3.96 4.85
Angle of view 2ω 65.25 40.34 25.24 18.48 13.1

D3 1.05 4.58 8.85 11.09 12.28
D7 10.16 5.92 3.32 1.97 0.7
D15 2.8 2.06 3.71 6.49 10.81
D17 1.74 3.64 3.89 3.03 1.5

Numerical data relating to conditional expressions described later are shown below.
[Conditional Formula Calculation Table for Each Example]

  In each of the above-described embodiments, a flare stop may be disposed in addition to the brightness stop in order to cut unnecessary light such as ghost and flare. This is because the object side of the first lens group in the embodiment, between the first lens group and the second lens group, between the second lens group and the third lens group, and between the third lens group and the fourth lens group. Or any position between the fourth lens group and the image plane.

  Moreover, in order to cut the said unnecessary light, a frame may be comprised and another member may be comprised. Further, it may be printed directly on the optical system, painted, or adhered with a seal.

  The shape may be any shape such as a circle, an ellipse, a rectangle, a polygon, or a range surrounded by a function curve. Further, not only harmful light flux but also light flux such as coma flare around the screen may be cut.

  Each lens may be provided with an antireflection coating to reduce ghosts and flares. A multi-coat is desirable because it can effectively reduce ghost and flare. Moreover, you may perform an infrared cut coat on a lens surface, a cover glass, etc.

  In addition, focusing for adjusting the focus is preferably performed by moving the fourth lens group, but focusing may be performed by moving the first lens group, the second lens group, or the third lens group. Further, focusing may be performed by moving a plurality of lens groups. Further, focusing may be performed by extending the entire lens system, or focusing may be performed by extending or retracting a part of the lenses.

  Further, the reduction in brightness at the periphery of the image may be reduced by shifting the micro lens of the CCD. For example, the design of the CCD microlens may be changed in accordance with the incident angle of the light beam at each image height. Further, the amount of decrease in the peripheral portion of the image may be corrected by image processing.

  Alternatively, distortion may be intentionally generated by an optical system, and distortion may be corrected by performing electrical image processing after shooting.

  The parallel flat plate FL1 of each embodiment is a CCD cover glass. The CCD cover glass may be a low-pass filter with IR cut coating.

The present invention described above, if example embodiment, may be configured as follows. Moreover, when it is set as the structure in any one of the said invention, it is preferable to satisfy any one or more of the structures or conditional expressions shown below.

( 1 ) The zoom lens according to any one of claims 1 to 5, wherein the following conditional expression is satisfied:
0.3 <Ih / fg3 <1.2
Here, Ih is the maximum image height, and fg3 is the focal length of the third lens group.

  If the upper limit of this conditional expression is not exceeded, the power of the third lens group is prevented from becoming too strong, which is advantageous for correcting spherical aberration and coma.

  If it does not fall below the lower limit, the power of the third lens group is secured, which is advantageous for shortening the overall length. Alternatively, the power of the first or second lens group can be suppressed to suppress the aberration of the first and second lens groups, and the number of lenses can be reduced.

The following conditional expression is preferably satisfied.
0.35 <Ih / fg3 <0.7

The focal length of the third lens group should satisfy the following conditional expression.
0.3 <Ih / fg3 <1.2

( 2 ) The zoom lens according to any one of claims 1 to 6, wherein the zoom lens satisfies the following conditional expression.
2 <fg1 / fg3 <7
Here, fg1 is the focal length of the first lens group, and fg3 is the focal length of the third lens group.

  The focal lengths of the first lens group and the third lens group should satisfy this conditional expression.

  If the upper limit of this conditional expression is not exceeded, the power of the first lens group is maintained, which is advantageous for shortening the overall length. Alternatively, the power of the third lens group is prevented from becoming too strong, which is advantageous for correcting spherical aberration and coma aberration.

  On the other hand, if it does not fall below the lower limit, the power of the first lens group is suppressed, which is advantageous for correcting distortion and astigmatism. Alternatively, securing the power of the third lens group is advantageous for shortening the overall length.

(3) In FIG Murenzu according to any one of claims 1 to 7, the zoom lens or an imaging device and satisfies the following condition.
−1.5 <fg2 / fg3 <−0.5
Here, fg2 is the focal length of the second lens group, and fg3 is the focal length of the third lens group.

  The focal lengths of the second lens group and the third lens group should satisfy this conditional expression.

  If the upper limit of this conditional expression is not exceeded, suppressing the power of the third lens group is advantageous for correcting spherical aberration and coma that are likely to occur in the third lens group.

  On the other hand, if the value is not lower than the lower limit, the power of the second lens group is suppressed to correct distortion and astigmatism in addition to spherical aberration and coma that are likely to occur in the second lens group. It will be advantageous.

The following conditional expression is preferably satisfied.
−1.2 <fg2 / fg3 <−0.65

(4) In FIG Murenzu according to any one of claims 1 to 8, the zoom lens or an imaging device and satisfies the following condition.
0.1 <fg3 / fg4 <0.85
Here, fg3 is the focal length of the third lens group, and fg4 is the focal length of the fourth lens group.

  If the upper limit of this conditional expression is not exceeded, the principal point is prevented from moving too far in the direction of the fourth lens group, and the back focus is reduced, which is advantageous for shortening the overall length.

  On the other hand, if it does not fall below the lower limit, it is possible to prevent the principal point from moving too much in the direction of the third lens group, to secure the back focus, and to prevent the incident angle on the image plane such as CCD from becoming too large. Moreover, it becomes easy to maintain the aberration correction effect of the fourth lens group.

The following conditional expression is preferably satisfied.
0.2 <fg3 / fg4 <0.6

(5) In Fig Murenzu according to any one of claims 1 to 9, the zoom lens or an imaging device and satisfies the following condition.
1.2 <β2T / β2W <5
Where β2T is the lateral magnification at the telephoto end of the second lens group, and β2W is the lateral magnification at the wide-angle end of the second lens group.

The lateral magnification of the second lens group should satisfy this conditional expression.
1.2 <β2T / β2W <5.0
Where β2T is the lateral magnification at the telephoto end of the second lens group, and β2W is the lateral magnification at the wide-angle end of the second lens group.

  If the upper limit of this conditional expression is not exceeded, it is advantageous to suppress the zooming effect of the second lens unit from becoming too large and to suppress aberration fluctuations due to zooming.

  On the other hand, if it does not fall below the lower limit, the zooming effect of the second lens group can be ensured, and the movement amount of the other lens groups is suppressed, which is advantageous for shortening the overall length.

The following conditional expression is preferably satisfied.
1.35 <β2T / β2W <3

(6) In FIG Murenzu according to any one of claims 1 to 10, a zoom lens or an imaging device and satisfies the following condition.
1.5 <β3T / β3W <5
However, β3T is a lateral magnification at the telephoto end of the third lens group, and β3W is a lateral magnification at the wide-angle end of the third lens group.

  The lateral magnification of the third lens group should satisfy this conditional expression.

  If the upper limit of this conditional expression is not exceeded, it is advantageous to suppress the zooming effect of the third lens unit from becoming too large and to suppress aberration fluctuations due to zooming.

  On the other hand, if the upper limit of this conditional expression is not exceeded, it is advantageous to suppress the zooming effect of the third lens unit from becoming too large and to suppress aberration fluctuations due to zooming.

The following conditional expression is preferably satisfied.
1.8 <β3T / β3W <4

( 7 ) The zoom lens according to any one of claims 1 to 11 , wherein the zoom lens or the imaging apparatus satisfies the following conditional expression.
0.1 <Dg1 / D <2.0
However, Dg1 is a moving distance from the wide-angle end to the telephoto end of the first lens group, and D is a total value of axial distances from the entrance surface to the exit surface for each lens group.

  The moving distance of the first lens group should satisfy this conditional expression.

  If the upper limit of this conditional expression is not exceeded, the movement distance of the first lens unit is prevented from becoming too large, which is advantageous for shortening the total length of the telephoto end.

  On the other hand, if it does not fall below the lower limit, the movement distance of the first lens group is secured, the zooming effect of the second lens group arranged on the image side is prevented from becoming too large, and aberration fluctuations due to zooming are suppressed. easy. Alternatively, it is advantageous for shortening the overall length of the wide angle end.

The following conditional expression is preferably satisfied.
0.2 <Dg1 / D <1.0

( 8 ) The zoom lens according to any one of claims 1 to 12 , wherein the zoom lens or the imaging apparatus satisfies the following conditional expression.
0.1 <Dg3 / D <2.0
However, Dg3 is a moving distance from the wide-angle end to the telephoto end of the third lens group, and D is a total value of axial distances from the entrance surface to the exit surface for each lens group.

  The moving distance of the third lens group should satisfy this conditional expression.

  If the upper limit of this conditional expression is not exceeded, the moving distance of the third lens group is suppressed, which is advantageous for shortening the overall length and reducing aberration fluctuations due to zooming.

  On the other hand, if it does not fall below the lower limit, the moving distance of the third lens unit is ensured and the zooming effect of the second lens unit arranged on the object side is prevented from becoming too large, which is advantageous in reducing the overall length. Become. Alternatively, the aberration correction can be easily balanced by the second and third lens groups.

The following conditional expression is preferably satisfied.
0.2 <Dg3 / D <1.0

( 9 ) The zoom lens according to any one of claims 1 to 13 , wherein the zoom lens or the imaging apparatus satisfies the following conditional expression.
−1.25 <(rg3L1f + rg3L1r) / (rg3L1f−rg3L1r) <− 0.15
Here, rg3L1f is the radius of curvature of the object side surface of the first lens of the third lens group, and rg3L1r is the radius of curvature of the image side surface of the first lens of the third lens group.

  The radius of curvature of the first lens of the third lens group should satisfy this conditional expression.

  If the upper limit of this conditional expression is not exceeded, spherical aberration and coma aberration generated on the object side can be effectively corrected on the image side surface, which is advantageous in securing performance.

  On the other hand, if it does not fall below the lower limit, the curvature of both surfaces is prevented from becoming too close, which is advantageous for securing the lens power.

The following conditional expression is preferably satisfied.
-1.15 <(rg3L2f + rg3L2r) / (rg3L2f-rg3L2r) <2.5

The following conditional expression is preferably satisfied.
−0.5 <(rg3L2f + rg3L2r) / (rg3L2f−rg3L2r) <2

(10) In the zoom lens according to any one of claims 1 to 14, a zoom lens or an imaging device and satisfies the following condition.
−0.8 <(rg3L4f + rg3L4r) / (rg3L4f−rg3L4r) <1.5
Here, rg3L4f is the radius of curvature of the object side surface of the fourth lens of the third lens group, and rg3L4r is the radius of curvature of the image side surface of the fourth lens of the third lens group.

  The radius of curvature of the fourth lens in the third lens group should satisfy this conditional expression.

  If the upper limit of this conditional expression is not exceeded, it is possible to suppress the curvatures of both surfaces from becoming too close, to secure power, and to reduce the overall length. Alternatively, the curvature on the image side is suppressed, which is advantageous for thinning the lens in the thickness direction and reducing higher-order aberrations.

  On the other hand, if the value is not less than the lower limit, the curvature on the image side is ensured to ensure the aberration correction effect, and the curvature on the object side is suppressed, which is advantageous for reducing higher-order aberrations.

The following conditional expression is preferably satisfied.
0.4 <(rg3L3f + rg3L3r) / (rg3L3f-rg3L3r) <1.2

(11) claimed in's Murenzu according to any one of claim 1 to 15, the second lens group negative lens from the object side, a zoom lens or an imaging apparatus characterized by being composed of only two positive lenses .

  It is the number of lens elements that greatly depends on the thickness of the camera when the lens is housed. Therefore, it is better to reduce the number of lenses as much as possible. Of these, the second lens group has a large lens diameter and tends to have a large construction length, which has been an obstacle to miniaturization. Therefore, in order to correct the chromatic aberration, coma aberration, etc., the second lens group has two lenses, a negative lens and a positive lens, in order to achieve a balance between miniaturization and performance. However, if the number is reduced, it becomes difficult to control the fluctuation of the principal point position, and it becomes difficult to exhibit the zoom effect with the third lens group arranged on the image side.

  In the third lens group of the present invention, it is easy to move the principal point position in the direction of the second lens group, so this influence can be reduced. Therefore, the zooming effect can be maintained even if the second lens group is reduced to two. That is, in the third lens group of the invention of the present application, in order to efficiently achieve downsizing and high performance, it is desirable that the second lens group is composed of two lenses, a negative lens and a positive lens, from the object side.

( 12 ) The zoom lens or the imaging device according to any one of claims 1 to 16 , further comprising an aperture stop disposed between the second lens group and the third lens group.

  Disposing the aperture stop at this position to limit the diameter of the light beam is advantageous for reducing the diameter of the third lens group.

  Further, the reduction in the diameter of the third lens group is advantageous for securing the power of the third lens group and shortening the thickness direction.

( 13 ) The third lens group is located on the object side at the telephoto end with respect to the wide-angle end, and the brightness stop is located on the object side at the telephoto end with respect to the wide-angle end. The zoom lens or the imaging device according to ( 11 ).

  With such a configuration, it is advantageous to secure the moving range of the third lens group, which is advantageous for downsizing and high zoom ratio.

(14) according to claim 1 wherein (13) noise in the zoom lens or the imaging apparatus of deviation crab described, the following conditions zoom lens or an imaging device which satisfies the equation.
3.5 <fT / fW
Here, fT is the focal length of the entire zoom lens system at the telephoto end, and fW is the focal length of the entire zoom lens system at the wide angle end.

  If the lower limit of this conditional expression is not exceeded, high-magnification zoom can be achieved with optical zoom, and image quality degradation can be suppressed even when electronic zoom is used.

The following conditional expression is preferably satisfied.
4.0 <fT / fW (19-1)

The following conditional expression is preferably satisfied.
4.5 <fT / fW (19-2)

More preferably, each of the above-mentioned constituent requirements satisfies a plurality at the same time.
Further, the upper limit value and lower limit value of the conditional expression may be any one of the upper limit value and lower limit value of the further specified conditional expression.

  It is preferable that the above-described constituent requirements and conditional expressions of the inventions of the present application satisfy a plurality at the same time. Satisfying the above-mentioned constituent requirements and a plurality of conditional expressions at the same time is advantageous for downsizing, high zoom ratio, and high performance.

  The zoom lens of the invention of the present application is preferably a four-group zoom lens because it is possible to balance size reduction and performance.

  Further, either the upper limit value or the lower limit value of the conditional expression may be set as the upper limit value or lower limit value of the more limited conditional expression.

  The above-described zoom lens of the present invention can be used in various photographing apparatuses using electronic image pickup devices such as CCDs and CMOS sensors, cameras having a retractable lens barrel, and the like. The specific application example is shown below.

9 to 11 are conceptual diagrams of a configuration in which the zoom optical system according to the present invention is incorporated in a photographing optical system 41 of a digital camera. 9 is a front perspective view showing the appearance of the digital camera 40, FIG. 10 is a rear front view thereof, and FIG. 11 is a schematic perspective plan view showing the configuration of the digital camera 40. However, FIGS. 9 and 11 show a state in which the photographing optical system 41 is not retracted. In this example, the digital camera 40 includes a photographing optical system 41 having a photographing optical path 42, a finder optical system 43 having a finder optical path 44, a shutter button 45, a flash 46, a liquid crystal display monitor 47, a focal length change button 61, When the photographing optical system 41 is retracted, including the setting change switch 62, the photographing optical system 41, the finder optical system 43, and the flash 46 are covered with the cover 60 by sliding the cover 60. When the cover 60 is opened and the camera 40 is set to the photographing state, the photographing optical system 41 enters the non-collapsed state shown in FIG. 11. When the shutter button 45 disposed on the upper side of the camera 40 is pressed, the photographing is performed in conjunction therewith. Photographing is performed through the optical system 41, for example, the zoom lens of the first embodiment. An object image formed by the photographing optical system 41 is formed on the image pickup surface of the CCD 49 via a low-pass filter FL subjected to IR cut coating and a cover glass CG. The object image received by the CCD 49 is displayed as an electronic image on the liquid crystal display monitor 47 provided on the back of the camera via the processing means 51. Further, the processing means 51 is connected to a recording means 52 so that a photographed electronic image can be recorded. The recording unit 52 may be provided separately from the processing unit 51, or may be configured to perform recording and writing electronically using a floppy (registered trademark) disk, a memory card, an MO, or the like. Further, it may be configured as a silver salt camera in which a silver salt film is arranged in place of the CCD 49.

  Further, a finder objective optical system 53 is disposed on the finder optical path 44. The finder objective optical system 53 includes a plurality of lens groups and two prisms. The finder objective optical system 53 includes a zoom optical system in which the focal length changes in conjunction with the zoom lens of the photographing optical system 41. The finder objective optical system 53 is formed by the finder objective optical system 53. The object image thus formed is formed on the field frame 57 immediately before the erecting prism 55 which is a part of the image erecting member. Behind the erecting prism 55, an eyepiece optical system 59 for guiding the erect image to the observer eyeball E is disposed. A cover member 50 is disposed on the exit side of the eyepiece optical system 59.

  In the camera 40 configured in this manner, since the photographing optical system 41 is a variable magnification optical system having a high zoom ratio and good aberration, high performance can be realized, and the photographing optical system 41 can be reduced in number of optical members. Since the retractable storage is possible, it is possible to realize a reduction in size, thickness and cost.

  Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications can be made without departing from the scope of the invention.

It is sectional drawing which follows the optical axis which shows the optical structure of the zoom lens which concerns on Example 1 of invention of this application. (a) is a diagram showing the state at the wide-angle end, (a ′), (b), (b ′) are in the middle state from the wide-angle end to the telephoto end, and (c) is a diagram showing the state at the telephoto end. FIG. 4 is an aberration diagram illustrating spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom lens according to Example 1 is focused on an object point at infinity. (a) is a wide angle end, (b) is a state in the middle of FIG. 1 (b), and (c) is a view showing a state at the telephoto end. It is sectional drawing which follows the optical axis which shows the optical structure of the zoom lens which concerns on Example 2 of invention of this application. (a) is a diagram showing the state at the wide-angle end, (a ′), (b), (b ′) are in the middle state from the wide-angle end to the telephoto end, and (c) is a diagram showing the state at the telephoto end. FIGS. 3A and 3B are diagrams illustrating spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom lens according to Example 2 is focused on an object at infinity, in which FIG. 3A illustrates a wide angle end, and FIG. (C) is a diagram showing a state at the telephoto end. It is sectional drawing which follows the optical axis which shows the optical structure of the zoom lens which concerns on Example 3 of invention of this application. (a) is a diagram showing the state at the wide-angle end, (a ′), (b), (b ′) are in the middle state from the wide-angle end to the telephoto end, and (c) is a diagram showing the state at the telephoto end. It is a figure which shows the spherical aberration, the astigmatism, the distortion aberration, and the chromatic aberration of magnification at the time of infinity object point focusing of the zoom lens concerning Example 3. (a) is a wide angle end, (b) is a state in the middle of FIG. 5 (b), and (c) is a view showing a state at the telephoto end. It is sectional drawing which follows the optical axis which shows the optical structure of the zoom lens which concerns on Example 4 of invention of this application. (a) is a diagram showing the state at the wide-angle end, (a ′), (b), (b ′) are in the middle state from the wide-angle end to the telephoto end, and (c) is a diagram showing the state at the telephoto end. FIGS. 7A and 7B are diagrams illustrating spherical aberration, astigmatism, distortion, and lateral chromatic aberration at the infinity focal point of the zoom lens according to Example 4, where FIG. 7A is a wide angle end, and FIG. (C) is a diagram showing a state at the telephoto end, respectively. It is a front perspective view which shows the external appearance of the electronic camera 40 to which the zoom lens of invention of this application is applied. FIG. 10 is a rear perspective view of the digital camera 40 of FIG. 9 . FIG. 10 is a schematic perspective plan view showing the configuration of the digital camera 40 of FIG. 9 .

Explanation of symbols

S Brightness stop F Flare stop FL Parallel flat plate CG Cover glass P Imaging surface Gn1 First lens group (in Example n)
Gn2 2nd lens group Gn3 3rd lens group Gn4 4th lens group Lmn nth lens 40 in Example m Digital camera 41 Imaging optical system 42 Imaging optical path 43 Viewfinder optical system 44 Viewfinder optical path 45 Shutter button 46 Flash 47 Liquid crystal Display monitor 48 Cover glass 49 CCD
50 cover member 51 processing means 52 recording means 53 finder objective optical system 55 erecting prism 57 field frame 59 eyepiece optical system 60 cover 61 focal length change button E observer eyeball

Claims (20)

From the object side,
A first lens group having a positive refractive power;
A second lens group having negative refractive power;
A third lens group having positive refractive power;
It consists of a fourth lens group having positive refractive power,
The first lens group, the second lens group, the third lens group, and the fourth lens group move in the optical axis direction so as to change the air gap between the respective lens groups. A zoom lens that zooms from the wide-angle end to the telephoto end,
The distance between the first lens group and the second lens group at the telephoto end with respect to the wide-angle end increases.
The distance between the second lens group and the third lens group decreases,
The third lens group includes four lenses in order from the object side: a first lens that is a positive lens, a second lens that is a negative lens, a third lens that is a positive lens, and a fourth lens that is a negative lens.
They are joined on the optical axis and at least one of the third lens and the second lens in groups the first lens or the third lens,
An air gap is interposed between the third lens and the fourth lens of the third lens group;
A zoom lens satisfying the following conditional expression:
-1.5 <fg3L123 / fg3L4 <-0.8
Here, fg3L123 is the combined focal length of the first, second and third lenses of the third lens group, and fg3L4 is the focal length of the fourth lens of the third lens group.   2. The zoom lens according to claim 1, wherein at least one of the second lens and the fourth lens in the third lens group is a biconcave lens. The zoom lens according to claim 1 or 2 ,
The first lens group is located on the object side at the telephoto end with respect to the wide-angle end,
A zoom lens, wherein the third lens group is located on the object side. The first lens group, the second lens group, a zoom lens according to claim 1 to 3 Neu Zureka, characterized in that the fourth lens group is constituted by one or two lenses, respectively. 5. The zoom lens according to claim 1, wherein the object side surface and the image side surface of the second lens of the third lens group are cemented surfaces with adjacent positive lenses. 6. lens. 6. The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
0.3 <Ih / fg3 <1.2
Here, Ih is the maximum image height, and fg3 is the focal length of the third lens group. In the zoom lens according to any one of claims 1 to 6, the zoom lens and satisfies the following condition.
2 <fg1 / fg3 <7
Here, fg1 is the focal length of the first lens group, and fg3 is the focal length of the third lens group. In the zoom lens according to any one of claims 1 to 7, the zoom lens and satisfies the following condition.
−1.5 <fg2 / fg3 <−0.5
Here, fg2 is the focal length of the second lens group, and fg3 is the focal length of the third lens group. In the zoom lens according to any one of claims 1 to 8, the zoom lens and satisfies the following condition.
0.1 <fg3 / fg4 <0.85
Here, fg3 is the focal length of the third lens group, and fg4 is the focal length of the fourth lens group. In any of the zoom lens according to claim 1 to 9, the zoom lens and satisfies the following condition.
1.2 <β2T / β2W <5
Where β2T is the lateral magnification at the telephoto end of the second lens group, and β2W is the lateral magnification at the wide-angle end of the second lens group. In any of the zoom lens according to claim 1 to 10, the zoom lens and satisfies the following condition.
1.5 <β3T / β3W <5
However, β3T is a lateral magnification at the telephoto end of the third lens group, and β3W is a lateral magnification at the wide-angle end of the third lens group. In the zoom lens according to any one of claims 1 to 11, the zoom lens and satisfies the following condition.
0.1 <Dg1 / D <2.0
However, Dg1 is a moving distance from the wide-angle end to the telephoto end of the first lens group, and D is a total value of axial distances from the entrance surface to the exit surface for each lens group. In the zoom lens according to any one of claims 1 to 12, the zoom lens and satisfies the following condition.
0.1 <Dg3 / D <2.0
However, Dg3 is a moving distance from the wide-angle end to the telephoto end of the third lens group, and D is a total value of axial distances from the entrance surface to the exit surface for each lens group. In the zoom lens according to any one of claims 1 to 13, the zoom lens and satisfies the following condition.
−1.25 <(rg3L1f + rg3L1r) / (rg3L1f−rg3L1r) <− 0.15
Here, rg3L1f is the radius of curvature of the object side surface of the first lens of the third lens group, and rg3L1r is the radius of curvature of the image side surface of the first lens of the third lens group. In the zoom lens according to any one of claims 1 to 14, the zoom lens and satisfies the following condition.
−0.8 <(rg3L4f + rg3L4r) / (rg3L4f−rg3L4r) <1.5
Here, rg3L4f is the radius of curvature of the object side surface of the fourth lens of the third lens group, and rg3L4r is the radius of curvature of the image side surface of the fourth lens of the third lens group. 16. The zoom lens according to claim 1, wherein the second lens group includes only two lenses, a negative lens and a positive lens, from the object side . The zoom lens according to any one of claims 1 to 16, characterized by comprising an aperture stop disposed between the second lens group and the third lens group. The third lens group is positioned closer to the object side at the telephoto end than at the wide angle end, the aperture stop to claim 17, characterized in that located on the object side at the telephoto end than at the wide angle end The described zoom lens. In claims 1 to 18 Neu deviation crab zoom lens according zoom lens satisfies the following conditional expression.
3.5 <fT / fW
Here, fT is the focal length of the entire zoom lens system at the telephoto end, and fW is the focal length of the entire zoom lens system at the wide angle end. At least one of the zoom lens according to claim 1 to 19,
An image pickup apparatus, comprising: an image pickup device disposed on an image side of the zoom lens and converting an image formed by the zoom lens into an electric signal.

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