JP2011221554A - Zoom lens and video camera using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens that is compact and can obtain excellent aberration correction throughout an entire zoom range.SOLUTION: The zoom lens includes, in order from an object side to an imaging plane 18 side, a first lens group 11 having positive refractive power and being kept stationary relative to the imaging plane 18 at the time of zooming and also focusing, a second lens group 12 having negative refractive power and performing zooming by moving on an optical axis, a diaphragm 13 remaining stationary relative to the imaging plane 18, a third lens group 14 having positive refractive power and zooming by moving on the optical axis, a fourth lens group 15 having positive refractive power and moving on the optical axis so as to keep the imaging plane 18 varying with a movement of an object at a fixed position from a reference plane and a fifth lens group 16 remaining stationary relative to the imaging plane.

Description

  The present invention relates to a small and high-performance zoom lens used in a video camera or the like and a video camera using the same.

  In recent consumer video cameras, with the widespread use of the DV format, it is essential to achieve both compactness and high image quality. Accordingly, there is a strong demand for a zoom lens mounted thereon that has a high optical quality and a short optical total length.

  For example, Japanese Patent Laid-Open No. 9-281392 (Patent Document 1) discloses a zoom lens having a small size, high image quality, and a zoom ratio of about 10 times.

JP-A-9-281392

  The zoom lens disclosed in the above publication has a four-group configuration, the first lens group and the third lens group are fixed with respect to the image plane, and the use magnification of the fourth lens group at the wide-angle end and the telephoto end is substantially the same. It is. Therefore, a zoom ratio of about 10 times is realized only by the use magnification of the second lens group.

  However, with this configuration, there is a problem in that the amount of movement of the second lens group is large, and it is difficult to realize downsizing and to achieve good aberration correction over the entire zoom range.

  The present invention has been made in order to solve the above-described problems in the prior art, and is a zoom lens having a four-group or five-group configuration, in which the use magnifications of both the second lens group and the third lens group are equal. Providing a zoom lens that is small and that can realize good aberration correction throughout the entire zoom range by sharing the zoom ratio with the third lens group in addition to the second lens group. In addition, an object is to provide a small and high-quality video camera using the zoom lens.

  In order to achieve the above object, the first configuration of the zoom lens according to the present invention has a positive refractive power arranged in order from the object side to the image plane side, and is fixed with respect to the image plane. The first lens group, the second lens group having a negative refractive power and performing a zooming action by moving on the optical axis, a stop fixed with respect to the image plane, and a positive refractive power And a third lens group that performs a zooming action by moving on the optical axis, and an optical axis that has a negative refracting power and maintains an image plane that varies with the movement of the object at a fixed position from the reference plane. A zoom lens comprising a fourth lens group that moves upward and a fifth lens group that has a positive refractive power and is fixed with respect to the image plane, wherein the first lens group is from the object side. The second lens is composed of three lenses, which are sequentially arranged, a negative lens and two positive lenses. Is composed of three lenses, which are arranged in order from the object side, consisting of two negative lenses and a positive lens, and the third lens group and the fifth lens group include at least one positive lens and at least one positive lens. The second lens group has a use magnification of 0 when the third lens group includes the same magnification, and the third lens group has a use magnification of 1 ×. .8 or more and 1.1 or less.

  A second configuration of the zoom lens according to the present invention includes a first lens group that is arranged in order from the object side to the image plane side, has a positive refractive power, and is fixed with respect to the image plane. The second lens group having a negative refractive power and performing a zooming action by moving on the optical axis, an aperture fixed to the image plane, and having a positive refractive power on the optical axis A third lens group that performs a zooming action by moving the lens, a fourth lens group that has a negative refractive power and is fixed with respect to the image plane, and has a positive refractive power. A zoom lens having a fifth lens group that moves on the optical axis so as to keep the fluctuating image plane at a fixed position from the reference plane, wherein the first lens group is disposed in order from the object side. The second lens group is composed of three lenses including a negative lens and two positive lenses. The third lens group and the fifth lens group are configured by three lenses including two negative lenses and a positive lens that are arranged, and each of the third lens group and the fifth lens group includes at least one positive lens and at least one negative lens. And the use magnification of the second lens group when the use magnification of the third lens group includes the same magnification and the use magnification of the third lens group is the same magnification is 0.8 or more and 1.1. It is characterized by the following.

  Further, a third configuration of the zoom lens according to the present invention includes a first lens group that is arranged in order from the object side to the image plane side, has a positive refractive power, and is fixed with respect to the image plane. The second lens group having a negative refractive power and performing a zooming action by moving on the optical axis, an aperture fixed to the image plane, and having a positive refractive power on the optical axis A third lens group that performs a zooming action by moving the lens, and a third lens group that has a positive refractive power and moves on the optical axis so as to keep an image plane that varies with the movement of the object at a fixed position from the reference plane. The zoom lens includes four lens groups, and the first lens group includes three lenses including a negative lens and two positive lenses arranged in order from the object side. The lens group consists of three lenses, which are arranged in order from the object side, consisting of two negative lenses and a positive lens. The third lens group and the fourth lens group are composed of at least one positive lens and at least one negative lens, and the use magnification of the third lens group is the same magnification. And the use magnification of the second lens group when the use magnification of the third lens group is equal is 0.8 or more and 1.1 or less.

  In addition, the fourth configuration of the zoom lens according to the present invention has a positive refracting power arranged in order from the object side to the image plane side, and an image plane that varies with the movement of the object is constant from the reference plane. A first lens group that moves on the optical axis so as to maintain the position, a second lens group that has a negative refractive power and performs a zooming action by moving on the optical axis, and an image plane A zoom including a fixed stop, a third lens group having a positive refractive power and performing a zooming action by moving on the optical axis, and a fourth lens group fixed to the image plane The first lens group is composed of three lenses including a negative lens and two positive lenses arranged in order from the object side, and the second lens group is in order from the object side. Consists of three lenses, consisting of two negative and positive lenses arranged The third lens group and the fourth lens group include at least one positive lens and at least one negative lens, and the use magnification of the third lens group includes equal magnification, The use magnification of the second lens group when the use magnification of the three lens groups is equal is 0.8 or more and 1.1 or less.

  According to the first to fourth configurations of the zoom lens of the present invention, various aberrations including chromatic aberration can be favorably corrected over the entire zoom range by optimizing the shape of the lens type, the glass material, and the lens surface. Can do. In addition, when the use magnification of the third lens group includes the same magnification, and the use magnification of the second lens group when the use magnification of the third lens group is the same magnification, the use magnification of the second lens group is 0.8 or more and 1.1 or less. Can be achieved.

In the first to fourth configurations of the zoom lens according to the present invention, the usage magnification of the third lens group at the telephoto end is m3T, the usage magnification of the third lens group at the wide-angle end is m3W, and the zoom ratio is When Z is satisfied, it is preferable that the following condition (Equation 7) is satisfied.
[Equation 7]
(M3T / m3W) / Z> 0.1
According to this preferred example, further miniaturization can be achieved.

In the first to fourth configurations of the zoom lens according to the present invention, when the focal length of the third lens group is f3 and the focal length of the entire system at the wide angle end is fw, It is preferred that the conditions are satisfied.
[Equation 8]
2.5 <f3 / fw <3.5
According to this preferable example, a back focus into which a crystal filter or an IR cut filter can be inserted can be secured, and a small zoom lens can be realized.

  In the first to fourth configurations of the zoom lens according to the present invention, it is preferable that the third lens group includes two positive lenses and a negative lens. According to this preferred example, axial chromatic aberration as well as spherical aberration can be corrected well over the entire zoom range.

In the first to fourth configurations of the zoom lens of the present invention, the third lens group includes a positive lens and a negative lens, and includes at least one aspheric surface, and is in the vicinity of the optical axis. When the local curvature radius of R30 is R30 and the local curvature radius of the outer peripheral portion is R31, the following condition (Equation 9) is preferably satisfied.
[Equation 9]
1.5 <R31 / R30 <2.5
According to this preferable example, axial chromatic aberration can be corrected well together with spherical aberration.

  In the first or second configuration of the zoom lens of the present invention, it is preferable that the fourth lens group is configured by a single concave lens. According to this preferred example, a long back focus can be ensured with a simple configuration without causing large aberrations.

In the first or second configuration of the zoom lens of the present invention, when the focal length of the fourth lens group is f4 and the focal length of the entire system at the wide angle end is fw, the following (Equation 10) The zoom lens according to claim 1, wherein the condition is satisfied.
[Equation 10]
2.5 <| f4 | / fw <5.0
According to this preferable example, a back focus into which a crystal filter or an IR cut filter can be inserted can be secured, and a high-quality zoom lens can be realized.

  In the first or second configuration of the zoom lens according to the present invention, it is preferable that the fifth lens group includes two positive lenses and a negative lens. According to this preferred example, it is possible to satisfactorily correct lateral chromatic aberration as well as coma aberration over the entire zoom range.

In the first or second configuration of the zoom lens according to the present invention, the fifth lens group includes a positive lens and a negative lens, includes at least one aspheric surface, and is locally located near the optical axis. When the radius of curvature is R40 and the local radius of curvature of the outer peripheral portion is R41, the following condition (Equation 11) is preferably satisfied.
[Equation 11]
R41 / R40 <1.0
According to this preferable example, the coma aberration of the light beam inside the principal ray of the off-axis light can be corrected satisfactorily.

In the third or fourth configuration of the zoom lens according to the present invention, the lens located closest to the object side constituting the fourth lens group is a negative lens, and the most object constituting the fourth lens group. When the focal length of the negative lens located on the side is f41 and the focal length of the entire system at the wide angle end is fw, it is preferable that the following condition (Equation 12) is satisfied.
[Equation 12]
2.5 <| f41 | / fw <5.0
According to this preferable example, a back focus into which a crystal filter or an IR cut filter can be inserted can be secured, and a high-quality zoom lens can be realized.

  In addition, the configuration of the video camera according to the present invention is a video camera including a zoom lens, and the zoom lens includes any one of the first to fourth configurations of the zoom lens according to the present invention. To do. According to this configuration of the video camera, a small and high-quality video camera can be realized.

  According to the zoom lens of the present invention, in the zoom lens having the four-group or five-group configuration, the use magnifications of both the second lens group and the third lens group both include the same magnification, and the third lens is used together with the second lens group. By sharing the zoom ratio also in the lens group, it is possible to realize a small aberration and good aberration correction over the entire zoom range.

  Furthermore, according to the video camera of the present invention, since the zoom lens of the present invention is used, a small and high-quality video camera can be realized.

1 is a layout diagram illustrating a configuration of a zoom lens according to a first embodiment of the present invention. Arrangement diagram showing the configuration of the zoom lens according to the second embodiment of the present invention Arrangement diagram showing the configuration of the zoom lens according to the third embodiment of the present invention Arrangement | positioning figure which shows the structure of the zoom lens in the 4th Embodiment of this invention. Arrangement diagram showing the configuration of the zoom lens according to the fifth embodiment of the present invention Arrangement diagram showing the configuration of the video camera in the sixth embodiment of the present invention Aberration performance chart at the wide-angle end of the zoom lens according to Example 1 of the present invention Aberration performance chart at the standard position of the zoom lens of Example 1 of the present invention Aberration performance chart at the telephoto end of the zoom lens of Example 1 of the present invention Aberration performance chart at the wide-angle end of the zoom lens according to Example 2 of the present invention Aberration performance chart at the standard position of the zoom lens according to the second embodiment of the present invention Aberration performance chart at the telephoto end of the zoom lens according to Example 2 of the present invention Aberration performance chart at the wide-angle end of the zoom lens according to Example 3 of the present invention Aberration performance chart at the standard position of the zoom lens according to Example 3 of the present invention Aberration performance chart at the telephoto end of the zoom lens according to the third exemplary embodiment of the present invention Aberration performance chart at the wide-angle end of the zoom lens according to Example 4 of the present invention Aberration performance chart at standard position of zoom lens of Example 4 of the present invention Aberration performance chart at the telephoto end of the zoom lens according to Example 4 of the present invention Aberration performance chart at the wide-angle end of the zoom lens according to Example 5 of the present invention Aberration performance chart at standard position of zoom lens of Example 5 of the present invention Aberration performance chart at the telephoto end of the zoom lens according to Example 5 of the present invention

  Hereinafter, the present invention will be described more specifically using embodiments.

[First Embodiment]
FIG. 1 is a layout diagram showing the configuration of the zoom lens according to the first embodiment of the present invention. As shown in FIG. 1, the zoom lens according to the present embodiment is arranged in order from the object side (left side in FIG. 1) to the image plane 18 side (right side in FIG. 1). And a second lens group 12, a diaphragm 13, a third lens group 14, a fourth lens group 15, a fifth lens group 16, and an optical low-pass filter and a flat plate 17 equivalent to a CCD face plate. Has been.

  The first lens group 11 is composed of three lenses having a positive refractive power and arranged in order from the object side. The first lens group 11 includes a negative lens and two positive lenses. It is fixed to the surface 18. The second lens group 12 is composed of three lenses including two negative lenses and a positive lens arranged in order from the object side. The second lens group 12 has a negative refractive power as a whole and moves on the optical axis. This is a lens group that performs a zooming action. The diaphragm 13 is fixed with respect to the image plane 18. The third lens group 14 is composed of three lenses, which are arranged in order from the object side, including a first positive lens and a cemented lens of a second positive lens and a negative lens. It has a refractive power of The third lens group 14 is a lens group that performs a zooming action by moving on the optical axis. The fourth lens group 15 is constituted by a single concave lens, and is a lens group that performs focus adjustment by moving on the optical axis. In other words, the fourth lens group 15 moves on the optical axis so as to keep the image plane 18 that varies with the movement of the object at a fixed position from the reference plane. The fifth lens group 16 is composed of three lenses including two positive lenses and a negative lens arranged in order from the object side, and has a positive refractive power as a whole. It is in a specified state.

  In the zoom lens according to the present embodiment, the use magnification of the third lens group 14 includes the same magnification, and the use magnification of the second lens group 12 when the use magnification of the third lens group 14 is the same magnification is 0.8. The size is reduced by setting it to 1.1 or less.

When the magnification of the third lens group 14 at the telephoto end is m3T, the magnification of the third lens group 14 at the wide-angle end is m3W, and the zoom ratio is Z, it is desirable that the following condition (Equation 13) is satisfied. .
[Equation 13]
(M3T / m3W) / Z> 0.1
By satisfying the above condition (Equation 13), further miniaturization can be achieved.

Further, when the focal length of the third lens group 14 is f3 and the focal length of the entire system at the wide angle end is fw, it is desirable that the following condition (Equation 14) is satisfied.
[Formula 14]
2.5 <f3 / fw <3.5
The above (Equation 14) is a conditional expression regarding the power of the third lens group 14. When f3 / fw is 2.5 or less, it becomes difficult to secure a back focus into which a crystal filter, an IR cut filter, or the like can be inserted. Further, when f3 / fw is 3.5 or more, the total length becomes long, and it becomes difficult to realize a small zoom lens.

  The third lens group 14 includes two positive lenses and a negative lens, and the axial chromatic aberration is well corrected along with the spherical aberration over the entire zoom range.

  Further, the fourth lens group is composed of one negative lens, and a long back focus is secured with a simple configuration without causing large aberrations.

Further, when the focal length of the fourth lens group 15 is f4 and the focal length of the entire system at the wide angle end is fw, it is desirable that the following condition (Equation 15) is satisfied.
[Equation 15]
2.5 <| f4 | / fw <5.0
The above (Expression 15) is a conditional expression regarding the power of the fourth lens group 15. When | f4 | / fw is 2.5 or less, it is difficult to achieve good aberration correction with a single negative lens. If | f4 | / fw is 5.0 or more, it becomes difficult to secure a back focus into which a crystal filter, an IR cut filter, or the like can be inserted.

  The fifth lens group 16 is composed of two positive lenses and a negative lens, and the lateral chromatic aberration is well corrected along with coma throughout the entire zoom range.

[Second Embodiment]
FIG. 2 is a layout diagram showing a configuration of a zoom lens according to the second embodiment of the present invention. As shown in FIG. 2, the zoom lens in the present embodiment is arranged in order from the object side (left side in FIG. 2) to the image plane 28 side (right side in FIG. 2). And a second lens group 22, a diaphragm 23, a third lens group 24, a fourth lens group 25, a fifth lens group 26, an optical low-pass filter, and a flat plate 27 equivalent to a CCD face plate. Has been.

  The first lens group 21 is composed of three lenses having a positive refractive power and arranged in order from the object side. The first lens group 21 includes a negative lens and two positive lenses. It is in a fixed state with respect to the surface 28. The second lens group 22 is composed of three lenses including two negative lenses and a positive lens arranged in order from the object side, and has a negative refractive power as a whole and moves on the optical axis. This is a lens group that performs a zooming action. The diaphragm 23 is fixed with respect to the image plane 28. The third lens group 24 is composed of two lenses that are arranged in order from the object side and are composed of a cemented lens of a positive lens and a negative lens, and has a positive refractive power as a whole. The third lens group 24 is a lens group that performs a zooming action by moving on the optical axis. The fourth lens group 25 is composed of one negative lens, and is a lens group that performs focus adjustment by moving on the optical axis. That is, the fourth lens group 25 moves on the optical axis so as to keep the image plane 28 that fluctuates with the movement of the object at a fixed position from the reference plane. The fifth lens group 26 is composed of three lenses including two positive lenses and a negative lens arranged in order from the object side, and has a positive refractive power as a whole. It is in a specified state.

  As in the first embodiment, the use magnification of the third lens group 24 includes the same magnification, and the use magnification of the second lens group 22 when the use magnification of the third lens group 24 is the same magnification is 0. A size reduction is achieved by setting it to 8 or more and 1.1 or less.

  Further, as in the first embodiment, it is preferable that the conditional expressions (Equation 13) to (Equation 15) are satisfied.

Further, when the third lens group 24 includes at least one aspherical surface, the local curvature radius near the optical axis is R30, and the local curvature radius of the outer peripheral portion is R31, the following condition (Equation 16) is satisfied. It is desirable to be done.
[Equation 16]
1.5 <R31 / R30 <2.5
The above (Expression 16) is a conditional expression related to the aspherical surface of the object side surface of the lens located closest to the object side that constitutes the third lens group 24, and defines a range for satisfactorily correcting spherical aberration. . When R31 / R30 is 1.5 or less, negative spherical aberration occurs, and when R31 / R30 is 2.5 or more, overcorrection occurs and positive spherical aberration occurs.

[Third Embodiment]
FIG. 3 is a layout diagram showing a configuration of a zoom lens according to the third embodiment of the present invention. As shown in FIG. 3, the zoom lens according to the present embodiment is arranged in order from the object side (left side in FIG. 3) to the image plane 38 side (right side in FIG. 3). And a second lens group 32, a diaphragm 33, a third lens group 34, a fourth lens group 35, a fifth lens group 36, an optical low-pass filter, and a flat plate 37 equivalent to a CCD face plate. Has been.

  The first lens group 31 includes three lenses having a positive refractive power and arranged in order from the object side. The first lens group 31 includes a negative lens and two positive lenses. It is fixed to the surface 38. The second lens group 32 is composed of three lenses including two negative lenses and a positive lens arranged in order from the object side, and has a negative refractive power as a whole and moves on the optical axis. This is a lens group that performs a zooming action. The diaphragm 33 is fixed with respect to the image plane 38. The third lens group 34 is composed of two lenses composed of a cemented lens of a positive lens and a negative lens arranged in order from the object side, and has a positive refractive power as a whole. The third lens group 34 is a lens group that performs a zooming action by moving on the optical axis. The fourth lens group 35 is constituted by one negative lens and is fixed to the image plane 38. The fifth lens group 36 includes two lenses, which are a positive lens and a negative lens, arranged in order from the object side, and has a positive refractive power as a whole and moves on the optical axis. This is a lens group that performs focus adjustment. That is, the fifth lens group 36 moves on the optical axis so as to keep the image plane 38 that fluctuates due to the movement of the object at a fixed position from the reference plane.

  As in the first embodiment, the use magnification of the third lens group 34 includes the same magnification, and the use magnification of the second lens group 32 when the use magnification of the third lens group 34 is the same magnification is 0. A size reduction is achieved by setting it to 8 or more and 1.1 or less.

  Further, as in the first embodiment, it is desirable that the conditional expressions (Equation 13) to (Equation 16) are satisfied.

Further, when the fifth lens group 35 includes at least one aspheric surface, the local curvature radius near the optical axis is R40, and the local curvature radius of the outer peripheral portion is R41, the following condition (Equation 17) is satisfied. It is desirable to be done.
[Equation 17]
R41 / R40 <1.0
The above (Expression 17) is a conditional expression related to the aspherical surface of the object-side surface of the fourth lens group 35, and defines a range for satisfactorily correcting the coma aberration of the light beam inside the principal ray of off-axis light. It is. When R41 / R40 is 1.0 or more, outward frames are generated.

[Fourth Embodiment]
FIG. 4 is a layout diagram showing a configuration of a zoom lens according to the fourth embodiment of the present invention. As shown in FIG. 4, the zoom lens according to the present embodiment is arranged in order from the object side (left side in FIG. 4) to the image plane 47 side (right side in FIG. 4). And a second lens group 42, a diaphragm 43, a third lens group 44, a fourth lens group 45, an optical low-pass filter, and a flat plate 46 equivalent to a CCD face plate.

  The first lens group 41 has a positive refracting power as a whole, and includes three lenses including a negative lens and two positive lenses arranged in order from the object side. Both are fixed to the image plane 47. The second lens group 42 includes three lenses that are arranged in order from the object side and are composed of a first negative lens and a cemented lens of a second negative lens and a positive lens, and negative refraction as a whole. This lens group has a force and performs a zooming action by moving on the optical axis. The third lens group 44 is composed of two lenses that are arranged in order from the object side and are composed of a cemented lens of a positive lens and a negative lens, and has a positive refractive power as a whole. The third lens group 44 is a lens group that performs a zooming action by moving on the optical axis. The fourth lens group 45 includes a first negative lens, two positive lenses, and a second negative lens, which are arranged in order from the object side. This is a lens group that simultaneously performs movement and focus adjustment. That is, the fourth lens group 45 moves on the optical axis so as to keep the image plane 28, which fluctuates due to the movement of the object, at a constant position from the reference plane, and the image of the image caused by the magnification change caused by the movement of the second lens group 42. Move and adjust the focus at the same time.

  As in the first embodiment, the use magnification of the third lens group 44 includes the same magnification, and the use magnification of the second lens group 42 when the use magnification of the third lens group 44 is the same magnification is 0.00. A size reduction is achieved by setting it to 8 or more and 1.1 or less.

  Further, as in the first embodiment, it is desirable that the conditional expressions (Equation 13) to (Equation 17) are satisfied.

Further, when the focal length of the negative lens located closest to the object side constituting the fourth lens group 45 is f41 and the focal length of the entire system at the wide angle end is fw, the following condition (Equation 18) is satisfied. Is desirable.
[Equation 18]
2.5 <| f41 | / fw <5.0
When | f41 | / fw is 2.5 or less, it is difficult to realize a small zoom lens. If | f41 | / fw is 5.0 or more, it becomes difficult to secure a back focus into which a crystal filter, an IR cut filter, or the like can be inserted.

[Fifth Embodiment]
FIG. 5 is a layout diagram showing a configuration of a zoom lens according to the fifth embodiment of the present invention. As shown in FIG. 5, the zoom lens in the present embodiment is arranged in order from the object side (left side in FIG. 5) to the image plane 57 side (right side in FIG. 5). And a second lens group 52, a diaphragm 53, a third lens group 54, a fourth lens group 55, an optical low-pass filter, and a flat plate 56 equivalent to a CCD face plate.

  The first lens group 51 has a positive refractive power as a whole, and is composed of three lenses including a negative lens and two positive lenses arranged in order from the object side, and varies depending on the movement of the object. It moves on the optical axis so as to keep the image plane 57 at a fixed position from the reference plane. The second lens group 52 includes three lenses, which are arranged in order from the object side and are composed of a first negative lens and a cemented lens of a second negative lens and a positive lens, and negative refraction as a whole. This lens group has a force and performs a zooming action by moving on the optical axis. The third lens group 54 is composed of two lenses composed of a cemented lens of a positive lens and a negative lens arranged in order from the object side, and has a positive refractive power as a whole. It is a lens group that performs a zooming action by moving. The fourth lens group 55 includes a first negative lens, two positive lenses, and a second negative lens arranged in order from the object side, and is fixed to the image plane 57.

  As in the first embodiment, the use magnification of the third lens group 54 includes the same magnification, and the use magnification of the second lens group 52 when the use magnification of the third lens group 54 is the same magnification is 0. A size reduction is achieved by setting it to 8 or more and 1.1 or less.

  Further, as in the fourth embodiment, it is desirable that the conditional expressions (Equation 13) to (Equation 18) are satisfied.

[Sixth Embodiment]
FIG. 6 is a layout diagram showing the configuration of the video camera according to the sixth embodiment of the present invention. As shown in FIG. 6, the video camera according to the present embodiment includes the zoom lens 61, the image sensor 62, and the signal processing circuit 63 according to the first to fifth embodiments. Thereby, a small and high-quality video camera can be realized.

  Hereinafter, the present invention will be described in more detail with reference to specific examples.

Example 1
The following (Table 1) shows specific examples of the zoom lens according to the first embodiment.

上記（表１）において、ｒ（ｍｍ）はレンズの曲率半径、ｄ（ｍｍ）はレンズの肉厚又はレンズの空気間隔、ｎは各レンズのｄ線に対する屈折率、νは各レンズのｄ線に対するアッベ数をそれぞれ示している（以下の実施例２〜５についても同様である）。

In Table 1 above, r (mm) is the radius of curvature of the lens, d (mm) is the lens thickness or lens air spacing, n is the refractive index with respect to the d-line of each lens, and ν is the d-line of each lens. (The same applies to the following Examples 2 to 5).

  In addition, the following (Table 2) shows values when there is an object point at infinity as an example of an air interval variable by zooming.

上記（表２）において、標準位置は第２レンズ群と第３レンズ群の使用倍率が等倍のときの位置である。また、ｆ、Ｆ／ＮＯ、ω（゜）は、上記（表１）に示すズームレンズの広角端、標準位置、望遠端における焦点距離、Ｆナンバー、入射半画角を表している（以下の実施例２〜５についても同様である）。

In the above (Table 2), the standard position is a position when the use magnification of the second lens group and the third lens group is equal. Further, f, F / NO, and ω (°) represent the focal length, F number, and incident half angle of view at the wide-angle end, the standard position, and the telephoto end of the zoom lens shown in (Table 1) (the following). The same applies to Examples 2 to 5).

  Further, the following (Table 3) shows values when an object point is located at a position of 1.5 m as measured from the front end of the lens, as an example of an air interval variable by zooming.

上記（表３）において、ｄ６、ｄ１１、ｄ１２は上記（表２）と同じであるため、省略している。

In the above (Table 3), d6, d11, and d12 are the same as the above (Table 2), and thus are omitted.

  As can be seen from the above (Table 2) and (Table 3), the focus adjustment is performed on the short-distance object point by the fourth lens group approaching the fifth lens group.

  Table 4 below shows values related to the present example among the conditional expressions.

上記（表４）に示すように、本実施例においては、第３レンズ群の使用倍率が上記（数１３）の条件式を満足し、さらなる小型化が図られている。また、本実施例においては、第３レンズ群の焦点距離ｆ３が上記（数１４）の条件式を満足しており、水晶フィルターやＩＲカットフィルターなどを挿入することのできるバックフォーカスが確保され、かつ、小型のズームレンズが実現されている。

As shown in (Table 4) above, in this embodiment, the use magnification of the third lens group satisfies the conditional expression (Equation 13), and further miniaturization is achieved. In this embodiment, the focal length f3 of the third lens group satisfies the conditional expression (Equation 14), and a back focus in which a crystal filter or an IR cut filter can be inserted is secured. In addition, a small zoom lens has been realized.

  In the present embodiment, the third lens group is configured by three lenses that are arranged in order from the object side and that are composed of a first positive lens and a cemented lens of a second positive lens and a negative lens. Thus, a zoom lens that is small and has a spherical aberration and axial chromatic aberration corrected well over the entire zoom range has been realized.

  In the present embodiment, the fourth lens group is composed of one negative lens, and a long back focus is secured with a simple configuration.

  Further, as shown in Table 4 above, in this embodiment, the focal length f4 of the fourth lens group satisfies the conditional expression (Equation 15), and a crystal filter, an IR cut filter, or the like is inserted. A zoom lens with a high image quality and a high back focus is realized.

  In the present embodiment, the fifth lens group includes two positive lenses and a negative lens, and the chromatic aberration of magnification is well corrected along with coma throughout the entire zoom range.

  7 to 9 are aberration performance diagrams of the zoom lens shown in Table 1 above at the wide-angle end, the standard position, and the telephoto end. In each figure, (a) is a diagram of spherical aberration with respect to the d-line. Further, (b) is a diagram of astigmatism, where a solid line indicates sagittal field curvature and a broken line indicates meridional field curvature. (C) is a diagram of distortion, (d) is a diagram of axial chromatic aberration, the solid line indicates the value for the d line, the short broken line indicates the value for the F line, and the long broken line indicates the value for the C line. Yes. Further, (e) is a diagram of lateral chromatic aberration, where a short broken line indicates a value for the F line, and a long broken line indicates a value for the C line. The description of the above (a)-(e) is the same also about FIGS. 10-21.

  As can be seen from FIGS. 7 to 9, the zoom lens in the present example shows good aberration performance.

(Example 2)
The following (Table 5) shows specific examples of the zoom lens according to the second embodiment.

非球面形状は、下記（数１９）によって定義される（以下の実施例３〜５についても同様である）。

The aspherical shape is defined by the following (Equation 19) (the same applies to Examples 3 to 5 below).

但し、
ＳＡＧ：光軸からの高さがＨにおける非球面上の点の非球面頂点からの距離
Ｈ：光軸からの高さ
Ｒ：非球面頂点の曲率半径
Ｋ：円錐常数
Ｄ、Ｅ：非球面係数
下記（表６）に、本実施例におけるズームレンズの非球面形状を示す。

However,
SAG: distance from the aspherical vertex of the point on the aspherical surface at a height H from the optical axis H: height from the optical axis R: radius of curvature of the aspherical vertex K: conical constant D, E: aspherical coefficient The following (Table 6) shows the aspherical shape of the zoom lens in the present example.

また、下記（表７）に、ズーミングによって可変な空気間隔の実施例として、無限遠に物点がある場合の値を示す。

Further, the following (Table 7) shows values when there is an object point at infinity as an example of an air interval variable by zooming.

また、下記（表８）に、ズーミングによって可変な空気間隔の実施例として、レンズ先端から測って１．５ｍの位置に物点がある場合の値を示す。

Further, (Table 8) below shows values when an object point is located at a position of 1.5 m as measured from the lens front end as an example of an air interval variable by zooming.

上記（表８）において、ｄ６、ｄ１１、ｄ１２は上記（表７）と同じであるため、省略している。

In the above (Table 8), d6, d11, and d12 are the same as those in (Table 7) and are omitted.

  As can be seen from the above (Table 7) and (Table 8), the focus adjustment is performed on the short-distance object point by the fourth lens group approaching the fifth lens group.

  Table 9 below shows values related to the present example among the conditional expressions.

上記（表９）に示すように、本実施例においては、上記（数１３）、（数１４）、（数１５）の条件式を満たしている。

As shown in (Table 9) above, in this embodiment, the conditional expressions (Equation 13), (Equation 14), and (Equation 15) are satisfied.

  In the present embodiment, the object-side surface of the lens that is located closest to the object side that constitutes the third lens group is an aspherical surface, and has a local radius of curvature R30 near the optical axis and a local radius of curvature at the outer periphery. R31 has the value shown in (Table 9) above, satisfies the conditional expression (Equation 16), and corrects the spherical aberration over the entire zoom range.

  10 to 12 show aberration performance diagrams at the wide-angle end, the standard position, and the telephoto end of the zoom lens shown in Table 5 above. As can be seen from FIGS. 10 to 12, the zoom lens in the present example shows good aberration performance.

(Example 3)
Table 10 below shows specific examples of the zoom lens according to the third embodiment.

下記（表１１）に、本実施例におけるズームレンズの非球面形状を示す。

The following (Table 11) shows the aspherical shape of the zoom lens in the present example.

また、下記（表１２）に、ズーミングによって可変な空気間隔の実施例として、無限遠に物点がある場合の値を示す。

Further, the following (Table 12) shows values when there is an object point at infinity as an example of an air interval variable by zooming.

また、下記（表１３）に、ズーミングによって可変な空気間隔の実施例として、レンズ先端から測って１．５ｍの位置に物点がある場合の値を示す。

Further, (Table 13) below shows values when an object point is located at a position of 1.5 m as measured from the front end of the lens as an example of an air interval variable by zooming.

上記（表１３）において、ｄ６、ｄ１１、ｄ１２、ｄ１５は上記（表１２）と同じであるため、省略している。

In the above (Table 13), d6, d11, d12, and d15 are the same as the above (Table 12), and thus are omitted.

  As can be seen from the above (Table 12) and (Table 13), the focus adjustment is performed on the short-distance object point by the fifth lens group approaching the fourth lens group.

  Table 14 below shows values related to the present example among the conditional expressions.

上記（表１４）に示すように、本実施例においては、上記（数１３）、（数１４）、（数１５）、（数１６）の条件式を満たしている。

As shown in the above (Table 14), in this embodiment, the conditional expressions (Equation 13), (Equation 14), (Equation 15), and (Equation 16) are satisfied.

  In the present embodiment, the object-side surface of the most object-side lens constituting the fifth lens group is an aspheric surface, and the local curvature radius R40 near the optical axis and the local curvature radius R41 at the outer peripheral portion are It has the values shown in (Table 14) above, satisfies the conditional expression (Equation 17), and corrects coma aberration throughout the entire zoom range.

  FIGS. 13 to 15 show aberration performance diagrams at the wide-angle end, the standard position, and the telephoto end of the zoom lens shown in (Table 10) above. As can be seen from FIG. 13 to FIG. 15, the zoom lens in the present example shows good aberration performance.

Example 4
The following (Table 15) shows specific examples of the zoom lens according to the fourth embodiment.

下記（表１６）に、本実施例におけるズームレンズの非球面形状を示す。

The following (Table 16) shows the aspherical shape of the zoom lens in the present example.

また、下記（表１７）に、ズーミングによって可変な空気間隔の実施例として、無限遠に物点がある場合の値を示す。

Further, the following (Table 17) shows values when there is an object point at infinity as an example of an air interval variable by zooming.

また、下記（表１８）に、ズーミングによって可変な空気間隔の実施例として、レンズ先端から測って１．５ｍの位置に物点がある場合の値を示す。

Further, (Table 18) below shows values when an object point is located at a position of 1.5 m as measured from the lens front end as an example of an air interval variable by zooming.

上記（表１８）において、ｄ６、ｄ１１、ｄ１２は上記（表１７）と同じであるため、省略している。

In the above (Table 18), d6, d11, and d12 are omitted because they are the same as the above (Table 17).

  As can be seen from the above (Table 17) and (Table 18), the focus adjustment is performed on the short-distance object point by the fourth lens group approaching the third lens group.

  Table 19 below shows values related to the present example among the conditional expressions.

上記（表１９）に示すように、本実施例においては、上記（数１３）、（数１４）、（数１６）の条件式を満たしている。

As shown in the above (Table 19), in the present embodiment, the conditional expressions (Equation 13), (Equation 14), and (Equation 16) are satisfied.

  Further, in this embodiment, the focal length f41 of the concave lens located on the most object side constituting the fourth lens group satisfies the conditional expression (Equation 18), and a quartz filter, an IR cut filter, or the like is inserted. A back focus that can be achieved is ensured, and a small zoom lens is realized.

  16 to 18 show aberration performance diagrams at the wide-angle end, the standard position, and the telephoto end of the zoom lens shown in (Table 15) above. As can be seen from FIG. 16 to FIG. 18, the zoom lens in the present example shows good aberration performance.

(Example 5)
The following (Table 20) shows specific examples of the zoom lens according to the fifth embodiment.

下記（表２１）に、本実施例におけるズームレンズの非球面形状を示す。

The following (Table 21) shows the aspherical shape of the zoom lens in the present example.

また、下記（表２２）に、ズーミングによって可変な空気間隔の実施例として、無限遠に物点がある場合の値を示す。

Further, (Table 22) below shows values when there is an object point at infinity as an example of an air interval variable by zooming.

また、下記（表２３）に、ズーミングによって可変な空気間隔の実施例として、レンズ先端から測って１．５ｍの位置に物点がある場合の値を示す。

Further, (Table 23) below shows values when an object point is located at a position of 1.5 m as measured from the front end of the lens, as an example of an air interval variable by zooming.

上記（表２３）において、ｄ１１、ｄ１２、ｄ１５は上記（表２２）と同じであるため、省略している。

In the above (Table 23), d11, d12, and d15 are the same as the above (Table 22), and thus are omitted.

  As can be seen from the above (Table 22) and (Table 23), focus adjustment is performed on the short-distance object point by extending the first lens group toward the object side.

  The above (Table 24) shows values related to the present example among the conditional expressions.

上記（表２４）に示すように、本実施例においては、上記（数１３）、（数１４）、（数１６）、（数１７）の条件式を満たしている。

As shown in the above (Table 24), in this example, the conditional expressions (Equation 13), (Equation 14), (Equation 16), and (Equation 17) are satisfied.

  FIGS. 19 to 21 show aberration performance diagrams at the wide-angle end, the standard position, and the telephoto end of the zoom lens shown in (Table 20) above. As can be seen from FIGS. 19 to 21, the zoom lens in the present example shows good aberration performance.

11, 21, 31, 41, 51 First lens group 12, 22, 32, 42, 52 Second lens group 13, 23, 33, 43, 53 Aperture 14, 24, 34, 44, 54 Third lens group 15 , 25, 35, 45, 55 Fourth lens group 16, 26, 36 Fifth lens group 17, 27, 37, 46, 56 Flat plate 18, 28, 38, 47, 57 Image surface 61 Zoom lens 62 Image sensor 63 Signal Processing circuit

Claims (7)

Arranged in order from the object side to the image plane side,
A first lens group having positive refractive power and fixed with respect to the image plane;
A second lens group having a negative refractive power and performing a zooming action by moving on the optical axis;
An aperture fixed to the image plane;
A third lens group having a positive refractive power and performing a zooming action by moving on the optical axis;
A fourth lens group having negative refractive power and fixed with respect to the image plane;
A fifth lens group that has a positive refractive power and moves on the optical axis so as to keep an image plane that varies with the movement of the object at a fixed position from the reference plane,
The use magnification of the third lens group includes equal magnification, and the use magnification of the second lens group when the use magnification of the third lens group is equal magnification is 0.8 or more and 1.1 or less,
The second lens group includes three lenses that are arranged in order from the object side, including two negative lenses and a positive lens,
The magnification of the third lens group at the telephoto end is m3T, the magnification of the third lens group at the wide-angle end is m3W, the zoom ratio is Z, the focal length of the third lens group is f3, and the entire system at the wide-angle end. A zoom lens that satisfies the following conditions (Equation 1) and (Equation 2) when the focal length is fw.
[Equation 1]
(M3T / m3W) / Z> 0.1
[Equation 2]
2.5 <f3 / fw <3.5 The third lens group includes a positive lens and a negative lens, and includes at least one aspherical surface. The local curvature radius near the optical axis is R30, and the local curvature radius of the outer peripheral portion is R31. The zoom lens according to claim 1, wherein the following condition (Equation 3) is satisfied.
[Equation 3]
1.5 <R31 / R30 <2.5   The zoom lens according to claim 1, wherein the fourth lens group includes one concave lens. 2. The zoom lens according to claim 1, wherein when the focal length of the fourth lens group is f <b> 4 and the focal length of the entire system at the wide-angle end is fw, the following condition (Equation 4) is satisfied.
[Equation 4]
2.5 <| f4 | / fw <5.0   The zoom lens according to claim 1, wherein the fifth lens group includes two positive lenses and a negative lens. When the fifth lens group includes a positive lens and a negative lens, includes at least one aspherical surface, the local curvature radius near the optical axis is R40, and the local curvature radius of the outer peripheral portion is R41, The zoom lens according to claim 1, wherein the condition of (Equation 5) is satisfied.
[Equation 5]
R41 / R40 <1.0   A video camera comprising a zoom lens, wherein the zoom lens according to claim 1 is used as the zoom lens.

Images