JP2014202806A5 - - Google Patents

Description

Zoom lens and imaging apparatus having the same

  The present invention relates to a zoom lens and an image pickup apparatus having the same. For example, an image pickup apparatus using a solid-state image pickup device such as a video camera, an electronic still camera, a broadcast camera, a surveillance camera, or a camera using a silver salt film. It is suitable for an imaging device.

  In recent years, an imaging optical system used in an imaging apparatus using a solid-state imaging device has a short overall lens length, is compact (small), and has a high zoom ratio (high zoom ratio), a wide angle of view, and a high angle. There is a demand for a zoom lens with high resolution. As a zoom lens that meets these requirements, a positive lead type zoom lens in which a lens group having a positive refractive power is disposed on the object side is known. A zoom lens composed of five lens groups as a whole is known as a positive lead type zoom lens (Patent Documents 1 and 2).

  In Patent Document 1, in a zoom lens having a five-group configuration including a first lens group to a fifth lens group having positive, negative, positive, positive, and positive refractive power in order from the object side to the image side, Zooming is performed with the fourth lens group, and focusing is performed with the fourth lens group. In Patent Document 2, a second lens in a zoom lens having a five-group configuration including first to fifth lens groups having positive, negative, positive, positive, positive, or negative refractive power in order from the object side to the image side. Zooming is performed by the group and the fourth lens group, and focusing is performed by the fourth lens group.

  In Patent Documents 1 and 2, a so-called rear focus type five-group zoom lens that performs zooming by moving the second lens group, corrects image plane variation accompanying zooming in the fourth lens group, and performs focusing. Is disclosed. In general, a rear focus type zoom lens has a smaller effective diameter of the first lens group than a zoom lens that moves the first lens group to perform focusing, and the entire lens system can be easily downsized. Further, close-up photography, particularly close-up photography is facilitated. Further, since the small and light lens group is moved, the driving force of the lens group is small, and quick focusing is possible.

JP 2008-134334 A JP 2007-328306 A

  In recent years, a zoom lens used in an imaging apparatus is strongly demanded to have a high zoom ratio, a wide angle of view, and a small lens system as the imaging apparatus is downsized. In general, in a zoom lens, in order to reduce the size of the entire system while ensuring a predetermined zoom ratio, the number of lenses may be reduced while increasing the refractive power of each lens group constituting the zoom lens. However, in such a zoom lens, as the refractive power of each lens surface increases, the lens thickness increases, the effect of shortening the lens system becomes insufficient, and the occurrence of various aberrations increases. Good correction becomes difficult.

  In a positive lead type zoom lens, it is important to set each element of the zoom lens appropriately in order to reduce the size of the entire system and to obtain high optical performance over the entire zoom range while ensuring a high zoom ratio. come. For example, it is important to appropriately set the zoom type (the number of lens groups and the refractive power of each lens group), the movement trajectory associated with zooming of each lens group, and the variable magnification load and lens configuration of each lens group. come. If these configurations are not appropriate, the entire system becomes large when a high zoom ratio is achieved, and variations in various aberrations associated with zooming increase, resulting in high optical performance over the entire zoom range and the entire screen. It becomes very difficult.

  An object of the present invention is to provide a zoom lens having a high zoom ratio, a wide angle of view, a small front lens effective diameter, and a good optical performance over the entire zoom range from the wide-angle end to the telephoto end, and an image pickup apparatus having the same. .

The zoom lens according to the present invention includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, arranged in order from the object side to the image side. A fourth lens group having a refractive power and a fifth lens group having a positive or negative refractive power, and during zooming, the first lens group is stationary, and the second lens group and the fourth lens group move; In zoom lenses where the distance between adjacent lens groups changes,
The first lens group includes a negative lens G1n , a positive lens, a positive lens, and a positive lens arranged in order from the object side to the image side.
The focal length of the first lens group is f1, the focal length of the third lens group is f3, the radius of curvature of the object-side lens surface of the negative lens G1n is Ra, and the curvature of the lens surface of the negative lens G1n is on the image side. When the radius is Rb,
1.8 <f1 / f3 <3.0
−0.2 <(Ra + Rb) / (Ra−Rb) <1.1
It satisfies the following conditional expression.

  According to the present invention, it is possible to obtain a zoom lens that can easily obtain high optical performance over the entire zoom range while being small in size and having a high zoom ratio.

Cross-sectional view of a lens according to Example 1 of the present invention Aberration diagrams of the zoom lens of Example 1 of the present invention Lateral aberration diagram of the zoom lens according to Example 1 of the present invention after a 0.3 degree image position change Lens sectional drawing of Example 2 of the present invention Aberration diagrams of the zoom lens according to the second embodiment of the present invention. Lateral aberration diagram of the zoom lens according to Example 2 of the present invention after changing the image position by 0.3 degrees Lens sectional view of Example 3 of the present invention Aberration diagram of zoom lens of Embodiment 3 of the present invention Lateral aberration diagram of the zoom lens according to Example 3 of the present invention after a 0.3 degree image position change Lens sectional view of Example 4 of the present invention Aberration diagram of zoom lens of Embodiment 4 of the present invention Lateral aberration diagram of the zoom lens according to Example 4 of the present invention after changing the image position by 0.3 degrees Schematic diagram of main parts of an imaging apparatus of the present invention Schematic diagram of main parts of an imaging apparatus of the present invention

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The zoom lens according to the present invention includes a first lens group having a positive refractive power (optical power = reciprocal of focal length), a second lens group having a negative refractive power, and a positive lens arranged in order from the object side to the image side. The third lens group has a refractive power, the fourth lens group has a positive refractive power, and the fifth lens group has a positive or negative refractive power. During zooming, the first lens group does not move, the second lens group and the fourth lens group move, and the interval between adjacent lens groups changes.

  1A, 1B, 1C, and 1D respectively show the wide angle end (short focal length end), the intermediate zoom position 1, the intermediate zoom position 2, and the telephoto end of the zoom lens according to the first embodiment of the present invention. It is lens sectional drawing in an end (long focal length end). 2A, 2B, 2C, and 2D are aberration diagrams at the wide-angle end, the intermediate zoom position 1, the intermediate zoom position 2, and the telephoto end of the zoom lens according to the first embodiment, respectively.

  FIGS. 3A and 3B are lateral aberration diagrams after a 0.3 degree image position change (after image stabilization) at the wide-angle end and the telephoto end of the zoom lens of Example 1, respectively. Example 1 is a zoom lens having a zoom ratio of 13.57 and an aperture ratio (F number) of 1.80 to 2.80. The intermediate zoom position 1 and the intermediate zoom position 2 are as shown in numerical examples described later.

  4A, 4B, 4C, and 4D are lens cross-sectional views at the wide-angle end, the intermediate zoom position 1, the intermediate zoom position 2, and the telephoto end of the zoom lens according to Embodiment 2 of the present invention, respectively. is there. FIGS. 5A, 5B, 5C, and 5D are aberration diagrams at the wide-angle end, the intermediate zoom position 1, the intermediate zoom position 2, and the telephoto end, respectively, of the zoom lens according to the second exemplary embodiment. 6A and 6B are lateral aberration diagrams after a 0.3 degree image position change at the wide-angle end and the telephoto end of the zoom lens of Example 2, respectively. Example 2 is a zoom lens having a zoom ratio of 13.79 and an aperture ratio of 1.80 to 2.88.

  7A, 7B, 7C, and 7D are lens cross-sectional views at the wide-angle end, the intermediate zoom position 1, the intermediate zoom position 2, and the telephoto end of the zoom lens according to Embodiment 3 of the present invention, respectively. is there. FIGS. 8A, 8B, 8C, and 8D are aberration diagrams at the wide-angle end, the intermediate zoom position 1, the intermediate zoom position 2, and the telephoto end, respectively, of the zoom lens according to the third exemplary embodiment. FIGS. 9A and 9B are lateral aberration diagrams after a 0.3 degree image position change at the wide-angle end and the telephoto end of the zoom lens of Example 3, respectively. Example 3 is a zoom lens having a zoom ratio of 11.99 and an aperture ratio of 1.80 to 2.88.

  FIGS. 10A, 10 </ b> B, 10 </ b> C, and 10 </ b> D are lens cross-sectional views at the wide angle end, the intermediate zoom position 1, the intermediate zoom position 2, and the telephoto end, respectively, of the zoom lens according to the fourth exemplary embodiment of the present invention. is there. FIGS. 11A, 11B, 11C, and 11D are aberration diagrams at the wide-angle end, the intermediate zoom position 1, the intermediate zoom position 2, and the telephoto end, respectively, of the zoom lens according to the fourth exemplary embodiment. 12A and 12B are lateral aberration diagrams after a 0.3 degree image position change at the wide-angle end and the telephoto end of the zoom lens of Example 4, respectively. Example 4 is a zoom lens having a zoom ratio of 11.83 and an aperture ratio of 1.80 to 2.88. 13 and 14 are schematic views of the main part of the imaging apparatus of the present invention.

  The zoom lens of the present invention is used for an imaging apparatus such as a digital camera, a video camera, a silver salt film camera, or the like. In the lens cross-sectional view, the left is the front (object side, enlargement side) and the right is the rear (image side, reduction side). In the lens cross-sectional view, i indicates the order of the lens groups from the object side to the image side, and Li is the i-th lens group.

  Next, features of the zoom lens of each embodiment will be described. In the lens cross-sectional views of the respective embodiments, L1 is a first lens group having a positive refractive power, L2 is a second lens group having a negative refractive power, L3 is a third lens group having a positive refractive power, and L4 is a positive refraction. The fourth lens unit L5 is a fifth lens unit having a positive or negative refractive power. SP is an F-number determining member (hereinafter also referred to as “aperture stop”) that acts as an aperture stop that determines (limits) an open F-number (Fno) light beam, and is positioned on the object side of the third lens unit L3. Yes.

  G is an optical block corresponding to an optical filter, a face plate, a quartz low-pass filter, an infrared cut filter, or the like. IP is an image plane, and when used as an imaging optical system for a video camera or a digital still camera, an imaging plane of an imaging element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor is placed. Further, when used as a photographing optical system for a silver salt film camera, a photosensitive surface corresponding to the film surface is provided.

  Among the aberration diagrams, in the spherical aberration diagram, the solid line is the d line, and the two-dot chain line is the g line. In the astigmatism diagram, the dotted line is the meridional image plane, and the solid line is the sagittal image plane. Lateral chromatic aberration is represented by the g-line. In the lateral aberration diagram, hgt is the image height, the solid line is the meridional section of the d line, and the dotted line is the lateral aberration of the sagittal section of the d line. Fno is an F number, and ω is a half angle of view (degrees). The half angle of view ω is a value based on the ray tracing value. In the lens cross-sectional view, arrows indicate the movement trajectory of each lens unit during zooming from the wide-angle end to the telephoto end. During zooming, the second lens unit L2 and the fourth lens unit L4 move.

  At this time, the distance between the first lens unit and the second lens unit becomes wider at the telephoto end than at the wide angle end. Further, the distance between the second lens unit L2 and the third lens unit L3 is narrowed.

  In each of the following embodiments, the wide-angle end and the telephoto end refer to zoom positions when the zoom lens unit is positioned at both ends of the range in which the zoom lens unit can be moved on the optical axis due to the mechanism. In each embodiment, zooming is performed by moving the second lens unit L2 to the image side as indicated by an arrow during zooming from the wide-angle end to the telephoto end. The fourth lens unit L4 is moved along a convex locus toward the object side to correct the image plane variation accompanying the zooming.

  In addition, a rear focus type that performs focusing by moving the fourth lens unit L4 on the optical axis is employed. A solid curve 4a and a dotted curve 4b relating to the fourth lens unit L4 are movement trajectories for correcting image plane fluctuations accompanying zooming when focusing on infinity and a short distance, respectively. Thus, by making the fourth lens unit L4 a convex locus toward the object side, the space between the third lens unit L3 and the fourth lens unit L4 can be effectively used, and the total lens length (from the first lens surface to the image surface) Effective distance reduction.

Further, when focusing from infinity to a short distance at the telephoto end, the fourth lens unit L4 is moved forward as indicated by an arrow 4c. The first partial group is moved so as to have a component in the direction perpendicular to the optical axis, and the imaging position is moved in the direction perpendicular to the optical axis. That is, image blur correction (anti-vibration due to camera shake) is performed. The aperture stop SP does not move during zooming.

The fifth lens unit L5 includes a first partial group having a negative refractive power and a second partial group having a positive refractive power. Then, the image stabilization group constituted by one of the first partial group and the second partial group moves in a direction having a component perpendicular to the optical axis to correct image blur. Specifically, the fifth lens unit L5 includes, in order from the object side to the image side, a negative first subgroup of refractive power to correct the image blur by moving in a direction having a component in a direction perpendicular to the optical axis And a second partial group having a positive refractive power.

The present invention includes first to fourth lens units L1 to L4 and a fifth lens unit L5 having positive, negative, positive, and positive refractive powers in order from the object side to the image side in order to ensure a high zoom ratio. doing. Then, the second and fourth lens units L2 and L4 are moved during zooming. This achieves a zoom lens with a high zoom ratio and a compact zoom lens system. During zooming , the third lens unit L3 and the fifth lens unit L5 do not move. In order to reduce the size and weight of the correction lens group for image blur correction, a first partial group having a negative refractive power is provided in the fifth lens group L5. As a result, the entire lens system can be downsized while having an image blur correction function.

In each embodiment, the first lens unit L1 includes a negative lens G1n , a positive lens, a positive lens, and a positive lens arranged in order from the object side to the image side. The focal length of the first lens unit L1 is f1, and the focal length of the third lens unit L3 is f3. The radius of curvature of the object side lens surface of the negative lens G1n is Ra, and the radius of curvature of the image side lens surface of the negative lens G1n is Rb. At this time,
1.8 <f1 / f3 <3.0 (1)
−0.2 <(Ra + Rb) / (Ra−Rb) <1.1 (2)
The following conditional expression is satisfied.

  In the zoom lens according to each embodiment, in order to ensure a high zoom ratio and correct various aberrations, the first lens unit L1 to L1 having positive, negative, positive, and positive refractive powers in order from the object side to the image side. The fourth lens unit L4 includes a fourth lens unit L4 and a fifth lens unit L5 having a positive or negative refractive power.

  By keeping the first lens unit L1 stationary during zooming, high positional accuracy is maintained, and changes in the overall lens length (distance from the first lens surface L1 to the image plane) during zooming are eliminated. Also, the number of movable lens groups is reduced during zooming to simplify the mechanical parts. The simplification of the mechanical parts can reduce the generation of dust and the like, and it becomes easy to configure a zoom lens that maintains high optical performance and an imaging device using the same. Further, when an accessory such as a converter lens is attached, it is easy to ensure mechanical strength.

  During zooming, the second lens unit L2 and the fourth lens unit L4 are moved to reduce the number of movable lens units, thereby reducing the size of the entire lens system and simplifying the configuration. In the first lens unit L1, the off-axis light beam passes through a position away from the optical axis. Further, the total lens length and the lens diameter are greatly affected by the configuration of the first lens unit L1. For this reason, it is important to appropriately set the lens configuration of the first lens unit L1 in order to reduce the size of the entire system.

  Therefore, in each embodiment, the first lens unit L1 is composed of one negative lens and three positive lenses in order from the object side to the image side. And the curvature radius of the lens surface of each positive lens is made into an appropriate range, and the increase in the effective diameter of the front lens is suppressed as much as possible. By configuring the first lens unit L1 in this way, the lens units subsequent to the second lens unit L2 have excellent curvature of field and lateral chromatic aberration on the wide-angle side without imposing much burden on wide-angle viewing. Spherical aberration and coma are corrected well on the telephoto side.

  Conditional expression (1) defines the ratio of the focal lengths of the first lens unit L1 and the third lens unit L3. When the focal length of the third lens unit L3 is reduced beyond the upper limit of conditional expression (1), it is advantageous for downsizing the entire system, but it is possible to satisfactorily suppress spherical aberration and coma on the wide angle side. It becomes difficult. If the lower limit of conditional expression (1) is exceeded and the focal length of the first lens unit L1 becomes small, more axial chromatic aberration and spherical aberration will occur than in the first lens unit L1, making it difficult to correct these various aberrations.

  Conditional expression (2) defines the shape factor of the negative lens G1n of the first lens unit L1. When the upper limit of conditional expression (2) is exceeded, it becomes difficult to move the image side principal point of the first lens unit L1 to the image side, and the effective diameter of the front lens becomes large. When the lower limit of conditional expression (2) is exceeded, the concave curvature of the lens surface on the object side becomes too large, and many high-order aberrations occur. For this reason, when downsizing the entire system, it is difficult to correct this higher-order aberration, which is not preferable.

  If it is within the range of conditional expression (1) and conditional expression (2), a new lens is added to the first lens group L1 and the third lens group L3 in order to increase the radius of curvature of the lens surface of each lens surface. This is unnecessary, and the number of lenses in each lens group can be reduced. As a result, it becomes easy to reduce the size of the entire system and to obtain high optical performance.

  By configuring as described above, it is possible to easily obtain a zoom lens in which various aberrations such as spherical aberration, coma and curvature of field are well corrected, a high zoom ratio and a wide angle of view, and a small lens system as a whole. It is done.

In each embodiment, it is preferable to satisfy one or more of the following conditional expressions. Nd3i the refractive index of the positive lens of the material included in the third lens unit L3, Nyudi3i the Abbe number, the relative partial dispersion and ShitagF3i. The focal length of the entire system at the wide-angle end is fW, and the focal length of the entire system at the telephoto end is fT. The third lens unit L3 has an aperture stop SP that does not move during zooming on the object side, the total lens length at the wide-angle end is TDW, and the air conversion distance from the aperture stop SP to the image plane (when a parallel plane plate such as a filter is removed) Is a DSP.

  The amount of movement of the second lens unit L2 on the optical axis in zooming from the wide-angle end to the telephoto end is m2. The moving amount m2 refers to the difference between the position on the optical axis of the second lens unit L2 at the wide-angle end and the position on the optical axis of the second lens unit L2 at the telephoto end. The sign of the amount of movement m2 is positive when the second lens unit L2 is positioned closer to the image side at the telephoto end than at the wide angle end.

The lateral magnification of the image stabilizing group at the telephoto end is βa, and the lateral magnification of the optical system located on the image side from the image stabilizing group at the telephoto end is βb (when the lens unit is not on the image side from the image stabilizing group , the lateral magnification βb = 1. And). Let the focal length of the negative lens G1n be f1n. At this time, the third lens unit L3 includes a positive lens G31 that satisfies at least one of conditional expressions (3), (4), and (10). The zoom lens as a whole preferably satisfies one or more of the following conditional expressions.

1.54 <nd3i <2.00 (3)
55 <νd3i <100 (4)
1.0 <f3 / √ (fW × fT) <3.0 (5)
0.2 <DSP / TDW <0.7 (6)
1.5 <| m2 | / √ (fW × fT) <3.0 (7)
0.4 <| (1-βa) × βb | <1.5 (8)
0.8 <| f1n | / f1 <2.0 (9)
−0.00162 × νd3i + 0.642 <θgF3i (10)
Next, the technical meaning of each conditional expression will be described.

Conditional expressions (3), (4), and (10) define the material of at least one positive lens among the one or more positive lenses constituting the third lens unit L3. Note that the Abbe number νd and the partial dispersion ratio θgF are Nd, NF, NC, and Ng when the refractive indices of the Fraunhofer d-line, F-line, C-line, and g-line are Nd, NF, NC, and Ng.
νd = (Nd−1) / (NF−NC)
θgF = (Ng−NF) / (NF−NC)
Defined by

In each example, the third lens unit L3 has a positive lens made of a material that satisfies the conditional expressions (3) and (4) at the same time, so that primary achromaticity and secondary spectrum can be corrected well. ing. In each embodiment, the positive lens G31 satisfies the conditional expressions (3), (4), and (10).

Condition (3) defines the positive lens G3 refractive index of the first material of the third lens unit L3. If the upper limit of conditional expression (3) is exceeded, the existing optical glass tends to have a higher specific gravity as the refractive index is higher, so it is difficult to reduce the weight of the entire system. If the lower limit of conditional expression (3) is exceeded and the refractive index of the material of the positive lens G31 becomes too small, the curvature of the lens surface of the positive lens G31 must be increased. In this case, a low order aberration coefficient is greatly generated, and in particular, coma becomes large, which is not preferable.

  Conditional expression (4) defines the Abbe number of the positive lens G31 of the third lens unit L3. Conditional expression (4) is a condition for mainly suppressing axial chromatic aberration. If the lower limit of conditional expression (4) is exceeded, fluctuations in axial chromatic aberration will increase during zooming, and increasing the zoom ratio will undesirably cause a large amount of chromatic aberration on the telephoto side. More preferably, it is desirable that the positive lens G31 of the third lens unit L3 satisfies all the conditional expressions (3), (4), and (10) at the same time. When all of the conditional expressions (3), (4), and (10) are satisfied at the same time, it becomes easy to correct primary achromaticity and secondary spectrum well, and further increase the zoom ratio.

  Conditional expression (5) defines the refractive power of the third lens unit L3. Conditional expression (5) is a condition for widening the angle of view while satisfactorily correcting mainly spherical aberration and coma. If the refractive power of the third lens unit L3 is reduced beyond the upper limit of the conditional expression (5), it is advantageous for shortening the total lens length. However, when the zoom ratio is increased, the variation in field curvature during zooming is increased. Increases, and it is difficult to correct this. If the refractive power of the third lens unit L3 is increased beyond the lower limit of the conditional expression (5), it is advantageous for widening the angle of view, but spherical aberration and coma increase on the wide angle side. It is difficult to correct this aberration, which is not preferable.

  Conditional expression (6) defines the position of the aperture stop SP at the wide-angle end. If the upper limit of conditional expression (6) is exceeded, the change in the distance from the optical axis of the peripheral light beam incident on the periphery of the screen of the lens group on the image side from the aperture stop SP becomes large, so that the aberration of the peripheral light beam can be corrected well. It is not preferable because the number of lenses is increased or an aspherical surface is used. Exceeding the lower limit of conditional expression (6) is not preferable because the off-axis light beam of the first lens unit L1 moves away from the optical axis on the telephoto end side and the radial direction of the first lens unit L1 increases.

  Conditional expression (7) defines the amount of movement of the second lens unit L2 during zooming. Conditional expression (7) is mainly for reducing the size of the entire lens system. When the upper limit of conditional expression (7) is exceeded, the amount of movement of the second lens unit L2 becomes too large, and the effect of shortening the total lens length at the wide angle end is reduced, and the radial direction of the first lens unit L1 is increased. Come. When the lower limit of conditional expression (7) is exceeded, the amount of movement of the second lens unit L2 becomes too small, and it is necessary to increase the refractive power of the second lens unit L2 in order to obtain a predetermined zoom ratio.

  Then, the fluctuation of the field curvature increases during zooming, and it becomes difficult to correct the field curvature well over the entire zoom range.

Conditional expression (8) is the final lens group. The image shift sensitivity of the first partial group constituting the fifth lens group L5 is defined. Here, the image shift sensitivity TS is the shift amount ΔL in the vertical direction of the shift group when the shift group moving in the direction perpendicular to the optical axis is moved in the direction perpendicular to the optical axis, and at that time Ratio of movement amount ΔI of the imaging position on the image plane TS = ΔI / ΔL
It is.

Exceeding the upper limit of conditional expression (8), if the image shifts greatly with respect to the minute movement of the first subgroup , high drive control is required and the mechanism becomes complicated, which is not preferable. When the lower limit of conditional expression (8) is exceeded, the amount of movement required to shift the image of the first subgroup by a predetermined amount increases, making it difficult to reduce the size of the entire system. Further, it is not good because aberration variation increases when the first partial group is shifted in order to shift the image by a predetermined amount. In order to reduce the size and weight of the first partial group for image blur correction, it is desirable that the first partial group is composed of one component (single lens or cemented lens).

  Conditional expression (9) defines the focal length of the negative lens G1n of the first lens unit L1 by the focal length of the first lens unit L1. If the upper limit of conditional expression (9) is exceeded and the focal length of the negative lens G1n increases, it becomes difficult to move the image-side principal point of the first lens unit L1 to the image side. Moreover, it becomes difficult to correct chromatic aberration. If the lower limit of conditional expression (9) is exceeded and the focal length of the negative lens G1n becomes small, the curvature of field becomes large at the wide-angle end, making it difficult to correct the curvature of field, resulting in a high zoom ratio and downsizing of the entire system. It becomes difficult. In addition, it is possible to prevent the lower ray of the off-axis light beam from being insufficiently corrected on the telephoto side, and at the same time, it is difficult to correct chromatic aberration.

  More preferably, the numerical ranges of the conditional expressions (1) to (9) are set as follows.

1.85 <f1 / f3 <2.70 (1a)
0.2 <(Ra + Rb) / (Ra−Rb) ≦ 1.0 (2a)
1.54 <nd3i <1.8 (3a)
55 <νd3i <80 (4a)
1.1 <f3 / √ (fW × fT) <2.0 (5a)
0.2 <DSP / TDW <0.5 (6a)
1.7 <| m2 | / √ (fW × fT) <2.5 (7a)
0.4 <| (1-βa) × βb | <0.8 (8a)
0.8 <| f1n | / f1 <1.5 (9a)
By satisfying conditional expression (1a), it becomes easy to suppress fluctuations in coma and field curvature during zooming. By satisfying conditional expression (2a), it becomes easy to satisfactorily correct spherical aberration and coma on the telephoto side while reducing the effective diameter of the front lens. By satisfying conditional expression (3a), it is easy to increase the zoom ratio and reduce the size of the entire system. By satisfying conditional expression (4a), it is possible to satisfactorily correct spherical aberration and coma, while reducing the need to add a new lens to the third lens unit L3, and facilitating downsizing of the entire system. .

When the conditional expression (5a) is satisfied, the refractive power of the third lens unit L3 becomes appropriate, and correction of coma aberration becomes easy while achieving a high zoom ratio. By satisfying conditional expression (6a), the position of the aperture stop becomes more appropriate, and it becomes easy to reduce the effective diameter of the front lens while widening the angle of view. By satisfying conditional expression (7a), the amount of movement of the second lens unit L2 during zooming becomes more appropriate, and a high zoom ratio and downsizing of the entire system are facilitated. By satisfying conditional expression (8a), the shift sensitivity of the first subgroup that performs image displacement becomes more appropriate, and image displacement is facilitated while maintaining high imaging performance.

  By satisfying conditional expression (9a), it becomes easy to shorten the total lens length while favorably correcting spherical aberration on the telephoto side. Preferably, the numerical ranges of conditional expressions (1a) to (9a) are set as follows.

1.9 <f1 / f3 <2.5 (1b)
0.4 <(Ra + Rb) / (Ra−Rb) ≦ 1.0 (2b)
1.55 <nd3i <1.70 (3b)
60 <νd3i <80 (4b)
1.2 <f3 / √ (fW × fT) <1.8 (5b)
0.3 <DSP / TDW <0.4 (6b)
1.8 <| m2 | / √ (fW × fT) <2.4 (7b)
0.5 <| (1-βa) × βb | <0.7 (8b)
0.9 <| f1n | / f1 <1.5 (9b)
In the zoom lens of each embodiment, a wide angle of view is achieved by increasing the refractive power of the first lens unit L1 and the second lens unit L2 to some extent. Also. The distance between the first lens unit L1 and the aperture stop SP is reduced to reduce the effective diameter of the front lens. As a result, the effective lens diameter of the first lens unit L1 is reduced. Further, the distance from the aperture stop SP to the image plane IP is reduced by increasing the refractive power of the third lens unit L3 to some extent. This shortens the total lens length.

  In the zoom lens of each embodiment, the second lens unit L2 is moved to the image side from the wide-angle end toward the telephoto end, and the distance between the first lens unit L1 and the second lens unit L2 is widened at the telephoto end rather than the wide-angle end. The zooming effect is obtained. The fourth lens unit L4 is moved to the object side to focus from infinity to a short distance.

  With the configuration as described above, the overall lens length is shortened at the wide-angle end and the telephoto end, and a high zoom ratio is achieved. In each embodiment, it is desirable that the third lens unit L1 has at least one aspheric surface. In order to obtain a bright zoom lens with a relatively small F number at the wide-angle end, the third lens unit L3 should have a simple lens configuration, and it is desirable to provide an aspherical surface. In Examples 1 to 3, the aberration generated from the positive lens G31 is kept low by making at least one lens surface of the positive lens G31 of the third lens unit L3 an aspherical surface.

  That is, the aberration caused by the aspherical surface is opposite to the aberration generated from the reference spherical surface of the positive lens G31, thereby balancing the aberration caused by the reference spherical surface and the aberration caused by the aspherical surface. In addition, when the third lens unit L3 is configured by a single positive lens G31, it is easy to simplify the lens configuration and reduce the size of the entire system.

  In Examples 1 to 4, by using an aspheric lens for the third lens unit L3, spherical aberration, coma, and the like are favorably corrected on the wide angle side while ensuring a predetermined brightness. In Examples 3 and 4, the optical performance is further improved by employing an aspheric lens for the second lens unit L2. In particular, the field curvature is corrected well on the wide angle side. In Example 3, aberration is favorably corrected using an aspherical lens in which the negative refractive power is weakened from the center to the periphery in the negative lens closest to the object side in the second lens unit L2.

In each embodiment, one component ( first partial group ) on the object side of the fifth lens unit L5 is moved so as to have a component perpendicular to the optical axis. Thus, the shake of the captured image when the entire optical system vibrates (tilts) is corrected. However, camera shake correction may be performed by moving an arbitrary lens group in a direction perpendicular to the optical axis.

  Next, an embodiment of a camcorder (video camera) using the zoom lens of the present invention as a photographing optical system will be described with reference to FIG. 13 and an embodiment of a digital still camera with reference to FIG. In FIG. 13, reference numeral 10 denotes a camera body, and 11 denotes a photographing optical system configured by any one zoom lens described in the first to fourth embodiments. Reference numeral 12 denotes a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor that receives a subject image formed by the photographing optical system 11 and is built in the camera body.

  Reference numeral 13 is a finder for observing a subject image formed on the solid-state image sensor 12, which includes a liquid crystal display panel or the like. In FIG. 14, reference numeral 20 denotes a camera body, and reference numeral 21 denotes a photographing optical system constituted by any one zoom lens described in the first to fourth embodiments. Reference numeral 22 denotes a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor that receives a subject image formed by the photographing optical system 21 and is built in the camera body. In addition, the zoom lens of each embodiment can also be used as a projection optical system for a projection apparatus (projector).

The imaging apparatus of the present invention preferably includes any one of the zoom lenses described above and a circuit that electrically corrects distortion and / or lateral chromatic aberration. In this way, if the lens configuration is such that distortion can be allowed when the zoom lens is configured, the number of zoom lenses can be easily reduced or reduced in size. In addition, by electrically correcting the chromatic aberration of magnification, it is possible to reduce the color blur of the captured image and to improve the resolution.

Next, numerical examples 1 to 4 corresponding to the first to fourth embodiments of the present invention will be described. In the numerical examples, i indicates the order of the surface from the object. ri is the radius of curvature of the i-th surface in order from the object side, di is the lens thickness and air spacing between the i-th and i + 1-th in order from the object side, and ndi and νdi are the i-th optical in order from the object side. The refractive index and Abbe number of the material of the member. The two surfaces closest to the image side are glass materials such as face plates.

  The aspherical shape is the X axis in the optical axis direction, the H axis in the direction perpendicular to the optical axis, the light traveling direction is positive, R is the paraxial radius of curvature, K is the conic constant, and A4, A6, A8, and A10 are aspherical surfaces. When using coefficients

It is expressed by the following formula. * Means a surface having an aspherical shape. “E−x” means 10 ^−x . BF is a back focus, and is represented by an air conversion length from the final lens surface to the image plane. Table 1 shows the lens data of each numerical example and the calculation results of the conditional expressions based thereon.

[Numerical Example 1]
Unit mm

Surface data surface number rd nd νd
1 -344.066 1.50 1.84666 23.8
2 50.245 4.07 1.60311 60.6
3 -164.337 0.20
4 49.901 2.95 1.80 400 46.6
5 -700.592 0.17
6 26.799 2.05 1.77250 49.6
7 48.404 (variable)
8 115.929 0.70 1.88300 40.8
9 8.374 2.63
10 -13.413 0.60 1.80000 29.8
11 14.604 1.50
12 -15.366 0.60 1.88300 40.8
13 -34.927 0.20
14 40.719 2.03 1.92286 18.9
15 -18.683 (variable)
16 (Aperture) ∞ 1.20
17 * 16.419 3.45 1.55332 71.7
18 * -21.931 (variable)
19 12.803 0.60 1.84666 23.8
20 6.466 2.13 1.63854 55.4
21 -64.684 (variable)
22 * 35.578 1.02 1.83481 42.7
23 -46.779 0.50 1.64769 33.8
24 5.419 3.47
25 10.055 3.23 1.51633 64.1
26 -9.717 3.00
27 ∞ 1.00 1.51633 64.1
28 ∞ 1.00
Image plane ∞

Aspheric data 17th surface
K = -6.51338e-001 A 4 = -8.42369e-005 A 6 = -2.73669e-008
A 8 = -1.56859e-008 A10 = 3.10785e-010

18th page
K = -4.76736e + 000 A 4 = -4.65862e-005 A 6 = -1.49561e-007

22nd page
K = 3.24617e + 001 A 4 = -2.09482e-004

Various data Zoom ratio 13.57

Focal length 3.64 11.01 22.91 49.32
F number 1.80 2.38 2.62 2.80
Half angle of view (degrees) 36.60 11.55 5.61 2.61
Image height 2.70 2.25 2.25 2.25
Total lens length 75.25 75.25 75.25 75.25
BF 4.66 4.66 4.66 4.66

d 7 0.70 14.78 20.61 24.98
d15 25.88 11.80 5.97 1.60
d18 8.17 5.31 4.38 6.78
d21 1.04 3.90 4.83 2.43

Zoom lens group data group Start surface Focal length
1 1 36.16
2 8 -6.70
3 16 17.53
4 19 22.81
5 22 20.93

[Numerical Example 2]
Unit mm

Surface data surface number rd nd νd
1 -119.285 1.50 1.90366 31.3
2 42.832 0.95
3 59.781 4.01 1.60311 60.6
4 -102.751 0.15
5 39.872 4.22 1.71300 53.9
6 -188.813 0.15
7 33.362 2.56 1.69680 55.5
8 93.777 (variable)
9 -2382.167 0.70 2.00 100 29.1
10 8.456 2.14
11 -100.789 0.60 1.91082 35.3
12 16.952 1.74
13 -15.765 0.60 1.60060 41.4
14 -136.190 0.10
15 30.045 1.97 2.00272 19.3
16 -26.332 (variable)
17 (Aperture) ∞ 1.20
18 * 10.244 3.02 1.59201 67.0
19 * -92.682 (variable)
20 9.567 0.50 1.84666 23.8
21 4.692 2.57 1.63854 55.4
22 -111.246 (variable)
23 35.328 0.70 1.55332 71.7
24 * 5.925 2.22
25 14.027 1.85 1.48749 70.2
26 -10.516 0.50 1.95906 17.5
27 -18.317 2.00
28 ∞ 1.00 1.51633 64.1
29 ∞ 1.00
Image plane ∞

Aspheric data 18th surface
K = 5.98255e-001 A 4 = -1.21465e-004 A 6 = -7.94578e-007
A 8 = 3.78495e-008 A10 = -3.95509e-010

19th page
K = -6.81901e + 002 A 4 = -4.56027e-006 A 6 = 3.68274e-006

24th page
K = -4.64351e-001 A 4 = 6.19195e-004

Various data Zoom ratio 13.79

Focal length 3.50 11.39 19.59 48.28
F number 1.80 2.45 2.46 2.88
Half angle of view (degrees) 36.59 11.17 6.55 2.67
Image height 2.60 2.25 2.25 2.25
Total lens length 74.51 74.51 74.51 74.51
BF 3.66 3.66 3.66 3.66

d 8 0.70 17.70 22.80 29.03
d16 29.93 12.93 7.83 1.60
d19 4.79 3.06 2.69 4.86
d22 1.48 3.22 3.58 1.41

Zoom lens group data group Start surface Focal length
1 1 38.51
2 9 -8.26
3 17 15.75
4 20 19.84
5 23 -37.98

[Numerical Example 3]
Unit mm

Surface data surface number rd nd νd
1 ∞ 1.50 1.84666 23.8
2 41.344 1.80
3 94.752 3.03 1.48749 70.2
4 -126.575 0.15
5 46.422 2.80 1.69680 55.5
6 297.361 0.15
7 37.804 3.27 1.83481 42.7
8 1147.293 (variable)
9 -124.873 0.60 1.85135 40.1
10 * 7.294 2.81
11 -16.328 0.60 1.80 400 46.6
12 47.325 0.20
13 19.795 1.81 1.92286 18.9
14 -76.231 (variable)
15 (Aperture) ∞ 1.20
16 * 20.125 3.33 1.55332 71.7
17 * -24.740 (variable)
18 23.545 0.60 1.84666 23.8
19 9.952 2.14 1.63854 55.4
20 -25.683 (variable)
21 * 45.164 1.16 1.88300 40.8
22 -52.263 0.60 1.67270 32.1
23 6.244 1.82
24 7.565 3.50 1.69680 55.5
25 -428.888 3.30
26 ∞ 1.00 1.51633 64.1
27 ∞ 1.00
Image plane ∞

Aspheric data 10th surface
K = -1.10126e-001 A 4 = -1.61117e-005

16th page
K = -2.63299e + 000 A 4 = 2.93548e-006 A 6 = -3.06369e-009
A 8 = 1.93110e-008 A10 = -2.66803e-010

17th page
K = -5.96116e + 000 A 4 = 1.08153e-005 A 6 = 6.08640e-007

21st page
K = -7.26973e + 001 A 4 = 1.08789e-004

Various data Zoom ratio 11.99

Focal length 3.81 15.73 27.56 45.70
F number 1.80 2.48 2.69 2.88
Half angle of view (degrees) 34.31 10.80 6.21 3.76
Image height 2.60 3.00 3.00 3.00
Total lens length 79.68 79.68 79.68 79.68
BF 4.96 4.96 4.96 4.96

d 8 0.70 18.05 23.28 28.24
d14 29.14 8.95 4.35 1.60
d17 8.69 5.93 3.95 4.69
d20 3.14 8.74 10.09 7.14

Zoom lens group data group Start surface Focal length
1 1 39.66
2 9 -7.87
3 15 20.60
4 18 25.40
5 21 42.15

[Numerical Example 4]
Unit mm

Surface data surface number rd nd νd
1 -800.000 1.50 1.90366 31.3
2 39.916 0.82
3 45.540 4.51 1.60311 60.6
4 -166.248 0.15
5 37.763 3.89 1.69680 55.5
6 -808.672 0.15
7 36.152 1.96 1.69680 55.5
8 72.304 (variable)
9 -130.913 0.70 2.00 100 29.1
10 8.032 3.36
11 -16.195 0.60 1.91082 35.3
12 18.017 0.00
13 18.017 2.42 2.00178 19.3
14 * -23.343 (variable)
15 (Aperture) ∞ 1.20
16 * 14.319 2.18 1.59201 67.0
17 * -88.129 (variable)
18 11.007 0.50 1.84666 23.8
19 6.235 2.45 1.63854 55.4
20 -42.556 (variable)
21 11.433 0.70 1.55332 71.7
22 * 4.539 2.13
23 8.024 2.16 1.56384 60.7
24 -22.110 0.50 1.95906 17.5
25 -850.000 4.40
26 ∞ 1.00 1.51633 64.1
27 ∞ 1.00
Image plane ∞

Aspheric data 14th surface
K = 8.00261e-001 A 4 = -5.85355e-005 A 6 = -5.61599e-007

16th page
K = 5.69141e-001 A 4 = 1.42937e-005 A 6 = 1.76326e-006
A 8 = 1.42819e-007 A10 = -1.67455e-009

17th page
K = -8.78133e + 002 A 4 = 3.70614e-005 A 6 = 8.23852e-006

22nd page
K = -3.87586e-001 A 4 = 1.40888e-004

Various data Zoom ratio 11.83

Focal length 3.47 11.03 28.06 41.04
F number 1.80 2.45 2.77 2.88
Half angle of view (degrees) 36.85 11.53 4.58 3.14
Image height 2.60 2.25 2.25 2.25
Total lens length 75.82 75.82 75.82 75.82
BF 6.06 6.06 6.06 6.06

d 8 0.70 17.43 25.79 28.58
d14 29.58 12.85 4.49 1.70
d17 6.34 4.09 2.96 3.51
d20 1.26 3.50 4.63 4.09

Zoom lens group data group Start surface Focal length
1 1 41.70
2 9 -7.65
3 15 20.97
4 18 17.26
5 21 -97.91

L1 ... 1st lens group L2 ... 2nd lens group L3 ... 3rd lens group L4 ... 4th lens group L5 ... 5th lens group SP ... Aperture

Claims (12)

A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power, which are arranged in order from the object side to the image side. The first lens group does not move during zooming, the second lens group and the fourth lens group move, and the interval between adjacent lens groups is increased. In the changing zoom lens,
The first lens group includes a negative lens G1n , a positive lens, a positive lens, and a positive lens arranged in order from the object side to the image side.
The focal length of the first lens group is f1, the focal length of the third lens group is f3, the radius of curvature of the object-side lens surface of the negative lens G1n is Ra, and the curvature of the lens surface of the negative lens G1n is on the image side. When the radius is Rb,
1.8 <f1 / f3 <3.0
−0.2 <(Ra + Rb) / (Ra−Rb) <1.1
A zoom lens satisfying the following conditional expression: When the refractive index of the material of the positive lens included in the third lens group is nd3i and the Abbe number is νd3i, the third lens group is
1.54 <nd3i <2.00
55 <νd3i <100
The zoom lens according to claim 1 , further comprising a positive lens that satisfies the following conditional expression: When the focal length of the entire system at the wide angle end is fW and the focal length of the entire system at the telephoto end is fT,
1.0 <f3 / √ (fW × fT) <3.0
The zoom lens according to claim 1 or 2, characterized by satisfying the conditional expression. When the third lens unit has an aperture stop that does not move during zooming on the object side, the total lens length at the wide-angle end is TDW, and the air- converted distance from the aperture stop to the image plane is DSP,
0.2 <DSP / TDW <0.7
The zoom lens according to any one of claims 1 to 3, characterized by satisfying the conditional expression. When the amount of movement of the second lens group on the optical axis in zooming from the wide-angle end to the telephoto end is m2, the focal length of the entire system at the wide-angle end is fW, and the focal length of the entire system at the telephoto end is fT.
1.5 <| m2 | / √ (fW × fT) <3.0
The zoom lens according to any one of claims 1 to 4, characterized by satisfying the conditional expression. The fifth lens group includes a first subgroup having a negative refractive power and a second sub group having a positive refractive power, when the image blur compensation, one of the first subgroup or the second subgroup The anti-vibration group consisting of one moves in a direction having a component perpendicular to the optical axis,
When βa a lateral magnification of the vibration-proof group at the telephoto end, the lateral magnification at the telephoto end of the optical system located on the image side of the front Symbol vibration-proof group and beta b,
0.4 <| (1-βa) × βb | <1.5
The zoom lens according to any one of claims 1 to 5, characterized by satisfying the conditional expression. When the focal length of the negative lens G1n is f1n,
0.8 <| f1n | / f1 <2.0
The zoom lens according to any one of claims 1 to 6, characterized by satisfying the conditional expression. When the Abbe number of the material of the positive lens included in the third lens group is νd3i and the partial dispersion ratio is θgF3i, the third lens group is
−0.00162 × νd3i + 0.642 <θgF3i
The zoom lens according to any one of claims 1 to 7, characterized in that it has a positive lens that satisfies a conditional expression. The zoom lens according to any one of claims 1 to 8 the third lens group and the fifth lens group is characterized by a stationary during zooming. The zoom lens according to any one of claims 1 to 9, wherein the third lens group includes a single positive lens. The fifth lens group, disposed in order from the object side to the image side, a first subgroup having a negative refractive power and a second sub group having a positive refractive power, the first subgroup during image blur compensation There zoom lens according to any one of claims 1 to 10, characterized in that movement in a direction having a component in a direction perpendicular to the optical axis. A zoom lens according to any one of claims 1 to 11, an imaging apparatus characterized by having an image pickup device which receives an image formed by the zoom lens.