JP2009047903A - Zoom lens and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens having a variable power ratio of ≥18, a viewing angle of ≥70° and superior imaging performance, and to provide an imaging apparatus. <P>SOLUTION: The zoom lens has five-group constitution of positive, negative, positive, positive and positive groups, upon varying the power, a fifth group GR5 is fixed, and the groups 1 to 4 are moved so as to increase the space between the first group (GR1) and the second group (GR2), to reduce the space between the second group and the third group (GR3), to vary a space between the third group and the fourth group (GR4) and the space between the fourth group and the fifth group. The second group at the telephoto end comes closer to the image side than that at a wide angle end, and the zoom lens satisfies the conditional expressions (1) to (7) where (1): 0.47<f1/ft<0.74, (2): 1.28<¾f2/fw¾<2.29, (3): 3.03<f3/fw<5.29, (4): 0.31<f4/ft<0.68, (5): 0.11<f5/ft<1.6, (6): 0.87<¾zl¾/√(fw×ft)<1.9, (7): 0.15<¾z2¾/√(fw×ft)<0.79, where fw denotes the focal length of the system at the wide-angle end, ft denotes the focal length of the entire system at the telephoto end, fi denotes the focal length of GRi, and zi denotes the moving amount of GRi between the wide angle end and the telephoto end. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a novel zoom lens and an imaging apparatus. Specifically, it is suitable for a photographic optical system of a digital input / output device such as a digital still camera or a digital video camera. Particularly, it has a compact and excellent imaging with a zoom ratio of 18 times or more and a field angle of 70 ° or more at a wide angle end state. The present invention relates to a zoom lens having performance and an imaging apparatus using the same.

  In recent years, imaging apparatuses using individual imaging elements such as digital still cameras are becoming popular. With the widespread use of such digital still cameras, there is a need for higher image quality. Especially in digital still cameras with a large number of pixels, shooting with excellent imaging performance corresponding to individual image sensors with a large number of pixels. There is a need for industrial lenses, particularly zoom lenses. In addition, there are strong demands for wide angle, high zoom ratio, and miniaturization, and high performance zoom lenses are required.

  As such a zoom lens, Patent Documents 1 to 3 propose a zoom lens with a high zoom ratio as well as miniaturization and widening of the lens system.

JP 2007-3554 A JP 2006-184413 A JP 2002-98893 A

  By the way, widening and high zooming are proposed in Patent Document 1, but the moving amount of each group at the time of zooming, particularly the moving amount of the first lens group is large, and a lens barrel structure is required for miniaturization. Therefore, it is difficult to improve the performance of the imaging apparatus.

  Further, Patent Document 2 proposes a high zoom ratio but does not widen the angle.

  Further, Patent Document 3 proposes widening of the angle, but the zoom ratio is about 10 and high zoom ratio is not achieved.

  Accordingly, in the present invention, a zoom lens having an excellent zooming performance with a zoom ratio of 18 times or more and an angle of view of 70 ° or more in a wide-angle end state and an imaging apparatus using the zoom lens are provided. Is an issue.

A zoom lens according to an embodiment of the present invention includes, in order from the object side, 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, A fourth lens group having a refractive power of 5 and a fifth lens group having a positive refractive power, and during zooming from the wide-angle end state to the telephoto end state, between the first lens group and the second lens group The distance increases, the distance between the second lens group and the third lens group decreases, the distance between the third lens group and the fourth lens group changes, and the fourth lens group and the fifth lens group The fifth lens group is fixed at the time of zooming, and the position of the second lens group in the telephoto end state is closer to the image side than the position of the second lens group in the wide-angle end state. Conditional expressions (1), (2), (3), (4), (5), (6), and (7) are satisfied.
(1) 0.47 <f1 / ft <0.74
(2) 1.28 <| f2 / fw | <2.29
(3) 3.03 <f3 / fw <5.29
(4) 0.31 <f4 / ft <0.68
(5) 0.11 <f5 / ft <1.6
(6) 0.87 <| z1 | / √ (fw · ft) <1.9
(7) 0.15 <| z2 | / √ (fw · ft) <0.79
However,
fw: focal length of the entire system in the wide-angle end state ft: focal length of the entire system in the telephoto end state f1: focal length f2 of the first lens group: focal length f3 of the second lens group: focal length f4 of the third lens group : Focal length f5 of the fourth lens group: focal length z1 of the fifth lens group: movement amount z1 of the first lens group during zooming from the wide-angle end to the telephoto end: during zooming from the wide-angle end to the telephoto end The amount of movement of the second lens group.

  An imaging apparatus according to an embodiment of the present invention includes the zoom lens according to the embodiment of the present invention described above and an imaging element that converts an optical image formed by the zoom lens into an electrical signal. .

  According to the present invention, it is possible to provide a compact zoom lens having a zoom ratio of 18 times or more and an angle of view of 70 ° or more in the wide-angle end state and having excellent imaging performance, and an imaging apparatus using the zoom lens.

  The best mode for carrying out the zoom lens and the imaging apparatus of the present invention will be described below with reference to the drawings.

  First, the zoom lens of the present invention will be described.

The zoom lens according to the present invention has, in order from the object side, 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 positive refractive power. The fourth lens group has a fifth lens group having a positive refractive power, and the distance between the first lens group and the second lens group increases upon zooming from the wide-angle end state to the telephoto end state, The distance between the second lens group and the third lens group decreases, the distance between the third lens group and the fourth lens group changes, and the distance between the fourth lens group and the fifth lens group. Changes, the fifth lens group is fixed during zooming, the position of the second lens group in the telephoto end state is closer to the image side than the position of the second lens group in the wide-angle end state, and the following conditional expression (1 ), (2), (3), (4), (5), (6), and (7).
(1) 0.47 <f1 / ft <0.74
(2) 1.28 <| f2 / fw | <2.29
(3) 3.03 <f3 / fw <5.29
(4) 0.31 <f4 / ft <0.68
(5) 0.11 <f5 / ft <1.6
(6) 0.87 <| z1 | / √ (fw · ft) <1.9
(7) 0.15 <| z2 | / √ (fw · ft) <0.79
However,
fw: focal length of the entire system in the wide-angle end state ft: focal length of the entire system in the telephoto end state f1: focal length f2 of the first lens group: focal length f3 of the second lens group: focal length f4 of the third lens group : Focal length f5 of the fourth lens group: focal length z1 of the fifth lens group: movement amount z1 of the first lens group during zooming from the wide-angle end to the telephoto end: during zooming from the wide-angle end to the telephoto end The amount of movement of the second lens group.

  Therefore, the zoom lens of the present invention has a compact and excellent imaging performance with a zoom ratio of 18 times or more and an angle of view of 70 ° or more at the wide angle end state.

  Conditional expression (1) represents an appropriate range of the focal length of the first lens group. If the lower limit of conditional expression (1) is not reached, the focal length of the first lens group will be shortened. For this reason, it becomes difficult to sufficiently correct spherical aberration, axial chromatic aberration, and the like. On the other hand, if the upper limit value of conditional expression (1) is exceeded, the function of the first lens group becomes weak. For this reason, it becomes difficult to achieve high zooming.

  It should be noted that when 0.55 <f1 / ft <0.65, the aberration amount can be suppressed more satisfactorily.

  Conditional expression (2) represents an appropriate range of the focal length of the second lens group. If the lower limit of conditional expression (2) is not reached, the focal length of the second lens group will be shortened. For this reason, it becomes difficult to sufficiently correct spherical aberration, coma aberration, and the like. On the other hand, if the upper limit value of conditional expression (2) is exceeded, the focal length of the second lens group becomes longer. This undesirably increases the effective diameter of the first lens group.

  In addition, when 1.61 <| f2 / fw | <1.96, the aberration amount can be further suppressed.

  Conditional expression (3) indicates an appropriate range of the focal length of the third lens group. If the lower limit value of conditional expression (3) is not reached, the focal length of the third lens group becomes shorter. For this reason, it becomes difficult to sufficiently correct spherical aberration, coma aberration, and the like. On the other hand, if the upper limit value of conditional expression (3) is exceeded, the function of the third lens group becomes weak. For this reason, it becomes difficult to achieve high zooming.

  Note that when 3.78 <f3 / fw <4.54, the aberration amount can be suppressed more satisfactorily.

  Conditional expression (4) shows an appropriate range of the focal length of the fourth lens group. If the lower limit of conditional expression (4) is not reached, the focal length of the fourth lens group will be shortened. For this reason, it becomes difficult to sufficiently correct spherical aberration, astigmatism, and the like. On the other hand, if the upper limit value of conditional expression (4) is exceeded, the function of the fourth lens group becomes weak. For this reason, it becomes difficult to satisfactorily correct variations in various aberrations during zooming.

  It should be noted that when 0.43 <f4 / ft <0.56, the aberration amount can be suppressed more satisfactorily.

  Conditional expression (5) represents an appropriate range of the focal length of the fifth lens group. If the lower limit of conditional expression (5) is not reached, the focal length of the fifth lens group will be shortened. For this reason, it becomes difficult to sufficiently correct spherical aberration, astigmatism, and the like. On the other hand, if the upper limit of conditional expression (5) is exceeded, the function of the fifth lens group becomes weak. For this reason, it becomes difficult to satisfactorily correct variations in various aberrations during zooming. Furthermore, the effect of causing light rays to enter the image plane substantially perpendicularly is reduced.

  If 0.6 <f5 / ft <1.1, the amount of aberration can be suppressed more satisfactorily.

  Conditional expression (6) shows an appropriate range of the relative position with respect to the image plane of the first lens group accompanying zooming. By reducing the amount of relative movement with respect to the image plane of the first lens group during zooming, the lens barrel is combined with a structure (a plurality of cylinders with different diameters are combined so that each cylinder can slide). In this case, the number of collapsible steps is reduced and the lens barrel structure can be simplified. If the lower limit value of conditional expression (6) is not reached, the change in the air gap between the first lens group and the second lens group becomes small. For this reason, it is difficult to achieve a high zoom ratio, and further, it becomes difficult to secure the peripheral light amount on the wide angle end side accompanying the widening of the angle. If the upper limit value of conditional expression (6) is exceeded, the change in the air gap between the first lens group and the second lens group becomes excessive. This leads to an increase in the overall length of the zoom lens, making it impossible to simplify the lens barrel structure.

  It is more preferable that 1.21 <| z1 | / √ (fw · ft) <1.56.

  Conditional expression (7) represents an appropriate range of the relative position with respect to the image plane of the second lens group accompanying zooming. By making the relative movement amount of the second lens group relative to the image plane in an appropriate range during zooming, high zooming is realized along with widening of the angle. If the lower limit value of conditional expression (7) is not reached, the change in the air gap between the first lens group and the second lens group becomes small. For this reason, it is difficult to achieve a high zoom ratio, and further, it becomes difficult to secure the peripheral light amount on the wide angle end side accompanying the widening of the angle. If the upper limit value of conditional expression (7) is exceeded, the change in the air gap between the first lens group and the second lens group becomes excessive. This leads to an increase in the overall length of the zoom lens, making it impossible to simplify the lens barrel structure.

  It is further preferable that 0.22 <| z2 | / √ (fw · ft) <0.51.

  By configuring so that the position of the second lens group in the telephoto end state is closer to the image side than the position of the second lens group in the wide-angle end state, the distance between the first lens group and the second lens group at the telephoto end is set. Even when the air interval is the same, the position of the first lens group can be made more image side, that is, the total lens length at the telephoto end can be shortened, and when a retractable lens barrel is adopted, The amount of projection of the lens barrel from the camera body at the telephoto end can be reduced.

  In the zoom lens according to an embodiment of the present invention, the second lens group includes a negative lens, a negative lens, a positive lens, and a concave on the object side, which are located in order from the object side and have a convex surface facing the object side. It is desirable that the negative lens is made up of four negative lenses, and at least one of the negative lenses is an aspherical lens.

  By including an aspherical surface in the second lens group, it is possible to satisfactorily correct field curvature that occurs in the second lens group. Further, by correcting the aberration generated when the refractive power of the second lens group is increased with an aspherical surface, the amount of movement of the first lens group and the second lens group associated with high zooming can be reduced.

  When obtaining a predetermined zoom ratio while reducing the movement amount of the first lens group and the second lens group, it is difficult to weaken the refractive power of the first lens group and the second lens group. In particular, in the positive / negative / positive / positive / positive five-group zoom lens of the present invention, there is only one lens group having negative refractive power, and the second lens group is responsible for most of the zooming action. The amount of movement necessary to obtain a predetermined zoom ratio is reduced, and the total lens length can be shortened. The use of an aspheric lens is effective in achieving both miniaturization and high zoom ratio, and various aberrations that occur when the refractive power of the second lens group is increased are corrected by introducing an aspheric surface. can do.

  In the second lens group, the off-axis light beam passes away from the optical axis in the wide-angle end state, and the on-axis light beam passes in the expanded state in the telephoto end state. As the refractive power of the second lens group is increased, the off-axis light beam passes away from the optical axis in the wide-angle end state, so that there is a problem that coma occurs and the image surface is likely to be under. Accordingly, the image side surface of the concave meniscus lens closest to the object side of the second lens group where the position where the off-axis light beam passes most changes between the wide-angle end and the telephoto end is an aspherical surface, and the refractive power decreases as the distance from the optical axis increases. By adopting such an aspherical shape, coma aberration and curvature of field that occur with a change in the angle of view can be favorably corrected in the wide-angle end state. In particular, a further effect can be exerted by abruptly increasing the amount of the aspheric surface from the position where the light beam passes near the wide-angle end (approximately 50% of the effective diameter outside the axis).

In the zoom lens according to an embodiment of the present invention, the first lens group includes one or two cemented lenses of a negative lens and a positive lens that are positioned in order from the object side, and a convex surface facing the object side. It is desirable to have one positive meniscus lens and satisfy the following conditional expression (8).
(8) νabe> 53
However,
νabe: The average value of the Abbe number with respect to the d-line (λ (wavelength) = 587.6 nm (nanometer)) of a positive meniscus lens having a convex surface facing the object side in the first lens group.

  With such a configuration, the amount of axial chromatic aberration in the telephoto end state can be satisfactorily suppressed. If the lower limit of conditional expression (8) is not reached, the amount of axial chromatic aberration in the telephoto end state increases, which is not preferable.

  Specific embodiments of the zoom lens according to the present invention will be described below.

  In each embodiment, the lens surface includes an aspheric surface. The aspherical shape is defined by the following equation (1).

Here, “Z” is the distance in the optical axis direction when the height from the optical axis between the tangential plane and the aspheric surface at the aspheric vertex is “H”, and “C” is the curvature (1 / r) of the aspheric vertex. , “K” represents a conic constant, and “A2i” represents a 2i-th aspherical coefficient.

  FIG. 1 shows a lens configuration of a zoom lens 1 according to a first embodiment of the present invention. The zoom lens 1 includes, in order from the object side, a first lens group GR1 having a positive refractive power, a second lens group GR2 having a negative refractive power, a third lens group GR3 having a positive refractive power, A fourth lens group GR4 having a refractive power of 5 and a fifth lens group GR5 having a positive refractive power are arranged. An iris IR for adjusting the amount of light is disposed on the object side of the third lens group GR3, and a filter FL including an infrared cut filter and a low-pass filter is further disposed on the image plane IMG side of the fifth lens group GR5. Has been placed. The image plane IMG is, for example, a light receiving surface of an image sensor such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS).

  When zooming from the wide-angle end state to the telephoto end state, the air gap between the first lens group GR1 and the second lens group GR2 increases, and the distance between the second lens group GR2 and the third lens group GR3 increases. So that the air gap between the third lens group GR3 and the fourth lens group GR4 changes, and the air gap between the fourth lens group GR4 and the fifth lens group GR5 changes. The first lens group GR1 and the third lens group GR3 move in the object side direction. Further, when zooming from the wide-angle end state to the telephoto end state, the second lens group GR2 in the telephoto end state is positioned on the image plane side with respect to the position of the second lens group GR2 in the wide-angle end state. The lens group GR2 moves so as to draw a convex locus on the image side. During zooming, the fourth lens group GR4 moves so as to draw a convex locus on the object side, and further, the fourth lens group GR4 is moved in the object side direction to perform focusing from a long distance to a short distance. The fifth lens group GR5 is fixed during zooming.

  The first lens group GR1 includes, in order from the object side, a cemented lens of a negative meniscus lens L1 having a convex surface facing the object side and a biconvex positive lens L2, and a positive meniscus lens L3 having a convex surface facing the object side. It consists of. The second lens group GR2 includes, in order from the object side, a negative meniscus lens L4 having a convex surface directed toward the object side, a cemented lens of a biconcave negative lens L5 and a biconvex positive lens L6, and an image side. And a negative meniscus lens L7 having a convex surface. The third lens group GR3 includes a biconvex positive lens L8 positioned in order from the object side, a negative meniscus lens L9 having a convex surface facing the object side, and a biconvex positive lens L10. The fourth lens group GR4 includes a cemented lens of a biconvex positive lens L11 and a negative meniscus lens L12, which are sequentially positioned from the object side. The fifth lens group GR5 includes a positive meniscus lens L13 having a convex surface directed toward the object side.

  The third lens group GR3 or a part of the lenses in the third lens group GR3 may be moved in a direction perpendicular to the optical axis to correct image blur caused by camera shake or the like. Is possible.

  Table 1 shows lens data of Numerical Example 1 in which specific numerical values are applied to the zoom lens 1 according to the first embodiment. In the following tables, “i (= 1, 2, 3,...)” Indicates the order of each optical surface from the object side, and “ri” indicates the curvature of the i-th lens surface from the object side. Radius, “di” is the surface spacing on the optical axis between the i-th surface and the (i + 1) -th surface from the object side, [ni] is the refractive index with respect to the d-line of the i-th surface from the object side, and “νi” Is the Abbe number for the d-line on the i-th surface from the object side, “f” is the focal length of the entire lens system, “Fno” is the open F value, and “ω” is the half angle of view. Further, “INF” for “ri” indicates that the surface is a plane, and “variable” for “di” indicates that the space between the surfaces is variable.

  In the zoom lens 1, when zooming from the wide-angle end state to the telephoto end state, the distance d5 between the first lens group GR1 and the second lens group GR2, the second lens group GR2 and the third lens group GR3 (iris IR ), The distance d19 between the third lens group GR3 and the fourth lens group GR4, and the distance d22 between the fourth lens group GR4 and the fifth lens group GR5 are changed. Therefore, the values in the wide-angle end state (f (focal length) = 5.15), the intermediate focal length state (f = 22.43), and the telephoto end state (f = 97.97) of each interval in the numerical value example 1. Is shown in Table 2.

In the zoom lens 1, the image side surface r7 of the negative meniscus lens L4 of the second lens group GR2, the object side surface r14 of the positive lens L8 of the third lens group Gr3, the object side surface r20 of the biconvex lens L11 of the fourth lens group GR4 and the fifth lens group GR4. The object side surface r23 of the positive meniscus lens L13 in the lens group GR5 is formed of an aspherical surface. Table 3 shows the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients A4, A6, A8, and A10 of each surface in Numerical Example 1. In Table 3 and the following tables showing aspheric surfaces, “E-i” represents an exponential expression with a base of 10, that is, “10- ⁱ ”. For example, “0.12345E-05” represents “ 0.12345 × 10 ⁻⁵ ”.

  Table 4 shows values corresponding to the conditional expressions (1) to (8) in Numerical Example 1 together with the focal length “f”, the F number “Fno”, and the half angle of view “ω”.

  2 to 4 show aberration diagrams of spherical aberration, astigmatism, and distortion at the wide-angle end (FIG. 2), the standard (FIG. 3), and the telephoto end (FIG. 4) of Numerical Example 1. FIG. Values for the d-line are shown, and spherical aberration also shows values for the C-line (wavelength = 656.3 nm, broken line) and the g-line (wavelength = 435.8 nm, one-dot chain line). In the astigmatism diagram, the solid line indicates the value on the sagittal image plane, and the broken line indicates the value on the meridional image plane.

  FIG. 5 shows the lens configuration of the zoom lens 2 according to the second embodiment of the present invention. The zoom lens 2 includes, in order from the object side, a first lens group GR1 having a positive refractive power, a second lens group GR2 having a negative refractive power, a third lens group GR3 having a positive refractive power, A fourth lens group GR4 having a refractive power of 5 and a fifth lens group GR5 having a positive refractive power are arranged. An iris IR for adjusting the amount of light is disposed on the object side of the third lens group GR3, and a filter FL including an infrared cut filter and a low-pass filter is further disposed on the image plane IMG side of the fifth lens group GR5. Has been placed. The image surface IMG is, for example, a light receiving surface of an image sensor such as a CCD or CMOS.

  When zooming from the wide-angle end state to the telephoto end state, the air gap between the first lens group GR1 and the second lens group GR2 increases, and the distance between the second lens group GR2 and the third lens group GR3 increases. So that the air gap between the third lens group GR3 and the fourth lens group GR4 changes, and the air gap between the fourth lens group GR4 and the fifth lens group GR5 changes. The first lens group GR1 and the third lens group GR3 move in the object side direction. Further, when zooming from the wide-angle end state to the telephoto end state, the second lens group GR2 in the telephoto end state is positioned on the image plane side with respect to the position of the second lens group GR2 in the wide-angle end state. The lens group GR2 moves so as to draw a convex locus on the image side. During zooming, the fourth lens group GR4 moves so as to draw a convex locus on the object side, and further, the fourth lens group GR4 is moved in the object side direction to perform focusing from a long distance to a short distance. The fifth lens group GR5 is fixed during zooming.

  The first lens group GR1 includes, in order from the object side, a cemented lens of a negative meniscus lens L1 having a convex surface facing the object side and a biconvex positive lens L2, and a positive meniscus lens L3 having a convex surface facing the object side. It consists of. The second lens group GR2 includes, in order from the object side, a negative meniscus lens L4 having a convex surface directed toward the object side, a cemented lens of a biconcave negative lens L5 and a biconvex positive lens L6, and an image side. And a negative meniscus lens L7 having a convex surface. The third lens group GR3 includes a positive meniscus lens L8 having a convex surface facing the object side, a negative meniscus lens L9 having a convex surface facing the object side, and a biconvex positive lens L10, which are sequentially positioned from the object side. . The fourth lens group GR4 includes a cemented lens of a biconvex positive lens L11 and a negative meniscus lens L12, which are sequentially positioned from the object side. The fifth lens group GR5 includes a positive meniscus lens L13 having a convex surface directed toward the object side.

  The third lens group GR3 or a part of the lenses in the third lens group GR3 may be moved in a direction perpendicular to the optical axis to correct image blur caused by camera shake or the like. Is possible.

  Table 5 shows lens data of a numerical example 2 in which specific numerical values are applied to the zoom lens 2 according to the second embodiment.

  When the zoom lens 2 changes magnification from the wide-angle end state to the telephoto end state, the distance d5 between the first lens group GR1 and the second lens group GR2, the second lens group GR2 and the third lens group GR3 (iris IR ), The distance d19 between the third lens group GR3 and the fourth lens group GR4, and the distance d22 between the fourth lens group GR4 and the fifth lens group GR5 are changed. Therefore, Table 6 shows the values in the wide-angle end state (f = 5.15), the intermediate focal length state (f = 22.44), and the telephoto end state (f = 97.82) for each interval in Numerical Example 2. Show.

  In the zoom lens 2, the image side surface r7 of the negative meniscus lens L4 of the second lens group GR2, both surfaces r14 and r15 of the positive lens L8 of the third lens group Gr3, the object side surface r20 of the biconvex lens L11 of the fourth lens group GR4, Both surfaces r23 and r24 of the positive meniscus lens L13 of the five lens group GR5 are aspherical. Table 7 shows the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients A4, A6, A8, and A10 of each surface in Numerical Example 2.

  Table 8 shows values corresponding to the conditional expressions (1) to (8) in Numerical Example 2 together with the focal length “f”, the F number “Fno”, and the half angle of view “ω”.

  6 to 8 show respective aberration diagrams of spherical aberration, astigmatism and distortion at the wide angle end (FIG. 6), the standard (FIG. 7) and the telephoto end (FIG. 8) of Numerical Example 2. Values for the d-line are shown, and for spherical aberration, values for the C-line (dashed line) and g-line (dashed line) are also shown. In the astigmatism diagram, the solid line indicates the value on the sagittal image plane, and the broken line indicates the value on the meridional image plane.

  FIG. 9 shows a lens configuration of the zoom lens 3 according to the third embodiment of the present invention. The zoom lens 3 includes, in order from the object side, a first lens group GR1 having a positive refractive power, a second lens group GR2 having a negative refractive power, a third lens group GR3 having a positive refractive power, A fourth lens group GR4 having a refractive power of 5 and a fifth lens group GR5 having a positive refractive power are arranged. An iris IR for adjusting the amount of light is disposed on the object side of the third lens group GR3, and a filter FL including an infrared cut filter and a low-pass filter is further disposed on the image plane IMG side of the fifth lens group GR5. Has been placed. The image surface IMG is, for example, a light receiving surface of an image sensor such as a CCD or CMOS.

  When zooming from the wide-angle end state to the telephoto end state, the air gap between the first lens group GR1 and the second lens group GR2 increases, and the distance between the second lens group GR2 and the third lens group GR3 increases. So that the air gap between the third lens group GR3 and the fourth lens group GR4 changes, and the air gap between the fourth lens group GR4 and the fifth lens group GR5 changes. The first lens group GR1 and the third lens group GR3 move in the object side direction. Further, when zooming from the wide-angle end state to the telephoto end state, the second lens group GR2 in the telephoto end state is positioned on the image plane side with respect to the position of the second lens group GR2 in the wide-angle end state. The lens group GR2 moves so as to draw a convex locus on the image side. During zooming, the fourth lens group GR4 moves so as to draw a convex locus on the object side, and further, the fourth lens group GR4 is moved in the object side direction to perform focusing from a long distance to a short distance. The fifth lens group GR5 is fixed during zooming.

  The first lens group GR1 includes, in order from the object side, a cemented lens of a negative meniscus lens L1 having a convex surface facing the object side and a biconvex positive lens L2, and a positive meniscus lens L3 having a convex surface facing the object side. And L4. The second lens group GR2 includes, in order from the object side, a negative meniscus lens L5 having a convex surface facing the object side, a biconcave negative lens L6, a biconvex positive lens L7, and a convex surface on the image side. And a negative meniscus lens L8. The third lens group GR3 includes, in order from the object side, a biconvex positive lens L9, a negative meniscus lens L10 having a convex surface facing the object side, and a positive meniscus lens L11 having a convex surface facing the object side. . The fourth lens group GR4 includes a cemented lens of a biconvex positive lens L12 and a biconcave negative lens L13, which are sequentially arranged from the object side. The fifth lens group GR5 includes a positive meniscus lens L14 having a convex surface directed toward the object side.

  The third lens group GR3 or a part of the third lens group GR3 may be moved in a direction perpendicular to the optical axis to correct image blur caused by camera shake or the like. Is possible.

  Table 9 shows lens data of a numerical example 3 in which specific numerical values are applied to the zoom lens 3 according to the third embodiment.

  When zooming from the wide-angle end state to the telephoto end state in the zoom lens 3, the distance d7 between the first lens group GR1 and the second lens group GR2, the second lens group GR2 and the third lens group GR3 (iris IR ), The distance d22 between the third lens group GR3 and the fourth lens group GR4, and the distance d25 between the fourth lens group GR4 and the fifth lens group GR5 are changed. Therefore, Table 10 shows values in the wide-angle end state (f = 5.15), the intermediate focal length state (f = 22.36), and the telephoto end state (f = 96.90) for each interval in Numerical Example 3. Show.

  In the zoom lens 3, the image side surface r9 of the negative meniscus lens L5 of the second lens group GR2, the double-sided surfaces r17 and r18 of the biconvex lens L9 of the third lens group GR3, and the object side surface r23 of the biconvex lens L12 of the fourth lens group GR4 are not. It consists of a spherical surface. Table 11 shows the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients A4, A6, A8, and A10 of the surfaces in Numerical Example 3.

  Table 12 shows values corresponding to the conditional expressions (1) to (8) in Numerical Example 3 together with the focal length “f”, the F number “Fno”, and the half angle of view “ω”.

  10 to 12 show aberration diagrams of spherical aberration, astigmatism, and distortion at the wide angle end (FIG. 10), the standard (FIG. 11), and the telephoto end (FIG. 12) of Numerical Example 3. Values for the d-line are shown, and for spherical aberration, values for the C-line (dashed line) and g-line (dashed line) are also shown. In the astigmatism diagram, the solid line indicates the value on the sagittal image plane, and the broken line indicates the value on the meridional image plane.

  FIG. 13 shows the lens configuration of a zoom lens 4 according to the fourth embodiment of the present invention. The zoom lens 4 includes, in order from the object side, a first lens group GR1 having a positive refractive power, a second lens group GR2 having a negative refractive power, a third lens group GR3 having a positive refractive power, A fourth lens group GR4 having a refractive power of 5 and a fifth lens group GR5 having a positive refractive power are arranged. An iris IR for adjusting the amount of light is disposed on the object side of the third lens group GR3, and a filter FL including an infrared cut filter and a low-pass filter is further disposed on the image plane IMG side of the fifth lens group GR5. Has been placed. The image surface IMG is, for example, a light receiving surface of an image sensor such as a CCD or CMOS.

  When zooming from the wide-angle end state to the telephoto end state, the air gap between the first lens group GR1 and the second lens group GR2 increases, and the distance between the second lens group GR2 and the third lens group GR3 increases. So that the air gap between the third lens group GR3 and the fourth lens group GR4 changes, and the air gap between the fourth lens group GR4 and the fifth lens group GR5 changes. The first lens group GR1 and the third lens group GR3 move in the object side direction. Further, when zooming from the wide-angle end state to the telephoto end state, the second lens group GR2 in the telephoto end state is positioned on the image plane side with respect to the position of the second lens group GR2 in the wide-angle end state. The lens group GR2 moves so as to draw a convex locus on the image side. During zooming, the fourth lens group GR4 moves so as to draw a convex locus on the object side, and further, the fourth lens group GR4 is moved in the object side direction to perform focusing from a long distance to a short distance. The fifth lens group GR5 is fixed during zooming.

  The first lens group GR1 includes, in order from the object side, a cemented lens of a negative meniscus lens L1 having a convex surface facing the object side and a biconvex positive lens L2, and a positive meniscus lens L3 having a convex surface facing the object side. And L4. The second lens group GR2 includes, in order from the object side, a negative meniscus lens L5 having a convex surface facing the object side, a biconcave negative lens L6, a biconvex positive lens L7, and a convex surface on the image side. And a negative meniscus lens L8. The third lens group GR3 includes, in order from the object side, a biconvex positive lens L9, a negative meniscus lens L10 having a convex surface facing the object side, and a positive meniscus lens L11 having a convex surface facing the object side. . The fourth lens group GR4 includes a cemented lens of a biconvex positive lens L12 and a biconcave negative lens L13, which are sequentially arranged from the object side. The fifth lens group GR5 includes a positive meniscus lens L14 having a convex surface directed toward the object side.

  The third lens group GR3 or a part of the lenses in the third lens group GR3 may be moved in a direction perpendicular to the optical axis to correct image blur caused by camera shake or the like. Is possible.

  Table 13 shows lens data of a numerical example 4 in which specific numerical values are applied to the zoom lens 4 according to the fourth embodiment.

  When zooming from the wide-angle end state to the telephoto end state in the zoom lens 4, the distance d7 between the first lens group GR1 and the second lens group GR2, the second lens group GR2 and the third lens group GR3 (iris IR ), The distance d22 between the third lens group GR3 and the fourth lens group GR4, and the distance d25 between the fourth lens group GR4 and the fifth lens group GR5 are changed. Therefore, Table 14 shows values in the wide-angle end state (f = 5.15), the intermediate focal length state (f = 22.36), and the telephoto end state (f = 96.91) for each interval in Numerical Example 4. Show.

  In the zoom lens 4, the image side surface r9 of the negative meniscus lens L5 of the second lens group GR2, the double-sided surfaces r17 and r18 of the biconvex lens L9 of the third lens group GR3, and the object side surface r23 of the biconvex lens L12 of the fourth lens group GR4 are not. It consists of a spherical surface. Table 15 shows the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients A4, A6, A8, and A10 of the surfaces in Numerical Example 4.

  Table 16 shows values corresponding to the conditional expressions (1) to (8) in Numerical Example 4 together with the focal length “f”, the F number “Fno”, and the half angle of view “ω”.

  FIGS. 14 to 16 show aberration diagrams of spherical aberration, astigmatism, and distortion at the wide-angle end (FIG. 14), the standard (FIG. 15), and the telephoto end (FIG. 16) of Numerical Example 4. Values for the d-line are shown, and for spherical aberration, values for the C-line (dashed line) and g-line (dashed line) are also shown. In the astigmatism diagram, the solid line indicates the value on the sagittal image plane, and the broken line indicates the value on the meridional image plane.

  Next, the imaging apparatus of the present invention will be described.

An imaging apparatus according to the present invention includes a zoom lens and an image sensor that converts an optical image formed by the zoom lens into an electrical signal. The zoom lens has a first refractive power in order from the object side. A lens group, a second lens group having a negative refractive power, a third lens group having a positive refractive power, a fourth lens group having a positive refractive power, and a fifth lens group having a positive refractive power, During zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, The distance between the third lens group and the fourth lens group changes, the distance between the fourth lens group and the fifth lens group changes, and the fifth lens group is fixed at the time of zooming, and is in the telephoto end state. The position of the second lens group at the position closer to the image side than the position of the second lens group at the wide-angle end state Ri, the following conditional expressions (1), (2), (3), (4), (5), (6), and satisfies (7).
(1) 0.47 <f1 / ft <0.74
(2) 1.28 <| f2 / fw | <2.29
(3) 3.03 <f3 / fw <5.29
(4) 0.31 <f4 / ft <0.68
(5) 0.11 <f5 / ft <1.6
(6) 0.87 <| z1 | / √ (fw · ft) <1.9
(7) 0.15 <| z2 | / √ (fw · ft) <0.79
However,
fw: focal length of the entire system in the wide-angle end state ft: focal length of the entire system in the telephoto end state f1: focal length f2 of the first lens group: focal length f3 of the second lens group: focal length f4 of the third lens group : Focal length f5 of the fourth lens group: focal length z1 of the fifth lens group: movement amount z1 of the first lens group during zooming from the wide-angle end to the telephoto end: during zooming from the wide-angle end to the telephoto end The amount of movement of the second lens group.

  Therefore, the imaging apparatus of the present invention has a compact and excellent imaging performance with a zoom ratio of 18 times or more and an angle of view of 70 ° or more in the wide-angle end state.

  FIG. 17 shows a block diagram of a specific embodiment in which the imaging apparatus of the present invention is applied to a digital still camera.

  The digital still camera 100 includes a camera block 10 having an imaging function, a camera signal processing unit 20 that performs signal processing such as analog-digital conversion of a captured image signal, and an image processing unit 30 that performs recording and reproduction processing of the image signal. An LCD (Liquid Crystal Display) 40 for displaying captured images, an R / W (reader / writer) 50 for writing / reading to / from the memory card 51, a CPU 60 for controlling the entire apparatus, and a user An input unit 70 for operation input and a lens drive control unit 80 for controlling driving of the lenses in the camera block 10 are provided.

  The camera block 10 includes an optical system including a zoom lens 11 to which the present invention is applied, an image sensor 12 such as a CCD or CMOS, and the like. The zoom lens 11 uses the zoom lens according to the first to fourth embodiments and the numerical examples 1 to 4 and the zoom lens of the present invention which is implemented in a form other than the form shown in the present specification. I can do it. The camera signal processing unit 20 performs signal processing such as conversion of an output signal from the image sensor 12 into a digital signal, noise removal, image quality correction, and conversion into a luminance / color difference signal. The image processing unit 30 performs compression encoding / decompression decoding processing of an image signal based on a predetermined image data format, conversion processing of data specifications such as resolution, and the like.

  The memory card 51 is composed of a detachable semiconductor memory. The R / W 50 writes the image data encoded by the image processing unit 30 to the memory card 51 and reads the image data recorded on the memory card 51. The CPU 60 is a control processing unit that controls each circuit block in the digital still camera, and controls each circuit block based on an instruction input signal or the like from the input unit 70.

  The input unit 70 includes, for example, a shutter release button for performing a shutter operation, a selection switch for selecting an operation mode, and the like, and outputs an instruction input signal corresponding to an operation by the user to the CPU 60. The lens drive control unit 80 controls a motor (not shown) that drives the lens in the zoom lens 11 based on a control signal from the CPU 60.

The operation of this digital still camera will be briefly described below.
In the shooting standby state, under the control of the CPU 60, the image signal captured by the camera block 10 is output to the LCD 40 via the camera signal processing unit 20 and displayed as a camera through image. When an instruction input signal for zooming is input from the input unit 70, the CPU 60 outputs a control signal to the lens drive control unit 80, and the zoom lens 11 in the zoom lens 11 is controlled based on the control of the lens drive control unit 80. A predetermined lens is moved.

  When a shutter (not shown) of the camera block 10 is released by an instruction input signal from the input unit 70, the captured image signal is output from the camera signal processing unit 20 to the image processing unit 30 and subjected to compression encoding processing. Is converted into digital data of the data format. The converted data is output to the R / W 50 and written to the memory card 51.

  Note that focusing is performed by the lens drive control unit 80 based on a control signal from the CPU 60 when the shutter release button is half-pressed or when the shutter release button is fully pressed for recording. This is done by moving the lens.

  When reproducing the image data recorded on the memory card 51, predetermined image data is read from the memory card 51 by the R / W 50 in response to an operation by the input unit 70, and decompressed and decoded by the image processing unit 30. After the conversion processing, the reproduced image signal is output to the LCD 40. As a result, a reproduced image is displayed.

  FIG. 18 shows an external appearance (perspective view) of the digital still camera shown in FIG.

  A part of the lens barrel 21 that supports the zoom lens 11 projects forward in the approximate center of the front surface of the camera body 20. Inside the camera body 20, an image sensor 12 such as a CCD that receives a subject image formed by the zoom lens 11, a memory card 51 that records an electrical image signal output from the image sensor 12, and the like are housed. An LCD 40 is disposed on the back of the camera body 20.

  The zoom lens according to the present invention is designed to satisfy the above-described conditions, so that the camera body 20 can be further reduced in size, and can be zoomed with a zoom ratio of 18 times or more while being small. In addition, it is possible to obtain a high-quality captured image with little aberration at each focal length.

  In the above-described embodiment, the case where the imaging device of the present invention is applied to a digital still camera has been described. However, the imaging device can also be applied to other imaging devices such as a video camera.

  In addition, the shapes, structures, and numerical values in the above-described embodiments are merely examples of specific embodiments for carrying out the present invention, and the technical scope of the present invention is limitedly interpreted by these. It must not be done.

FIG. 2 is a diagram illustrating a lens configuration of the zoom lens according to the first embodiment of the present invention, in which the position of each optical element in the wide-angle end state is shown in the upper stage, and each optical element in the intermediate focal length (standard) state is interrupted. The position of each optical element in the telephoto end state is shown in the lower part. FIGS. 3 and 4 show various aberrations of Numerical Example 1 in which specific numerical values are applied to the zoom lens according to the first embodiment. This diagram shows spherical aberration, astigmatism and It shows distortion aberration. It shows spherical aberration, astigmatism and distortion in the intermediate focal length (standard) state. It shows spherical aberration, astigmatism, and distortion in the telephoto end state. It is a figure which shows the lens structure of the zoom lens concerning the 2nd Embodiment of this invention, The position of each optical element in a wide-angle end state is shown on the upper stage, Each optical element in an intermediate | middle focal distance (standard) state on interruption The position of each optical element in the telephoto end state is shown in the lower part. FIGS. 7 and 8 show various aberrations of Numerical Example 2 in which specific numerical values are applied to the zoom lens according to the second embodiment. This diagram shows spherical aberration, astigmatism and It shows distortion aberration. It shows spherical aberration, astigmatism and distortion in the intermediate focal length (standard) state. It shows spherical aberration, astigmatism, and distortion in the telephoto end state. It is a figure which shows the lens structure of the zoom lens concerning the 3rd Embodiment of this invention, The position of each optical element in a wide-angle end state is an upper stage, Each optical element in an intermediate | middle focal distance (standard) state is interrupted The position of each optical element in the telephoto end state is shown in the lower part. 11 and 12 show various aberrations of Numerical Example 3 in which specific numerical values are applied to the zoom lens according to the third embodiment. This diagram shows spherical aberration, astigmatism and It shows distortion aberration. It shows spherical aberration, astigmatism and distortion in the intermediate focal length (standard) state. It shows spherical aberration, astigmatism, and distortion in the telephoto end state. It is a figure which shows the lens structure of the zoom lens concerning the 4th Embodiment of this invention, The position of each optical element in a wide-angle end state is an upper stage, Each optical element in an intermediate | middle focal distance (standard) state is interrupted The position of each optical element in the telephoto end state is shown in the lower part. 15 and FIG. 16 show various aberrations of Numerical Example 4 in which specific numerical values are applied to the zoom lens according to the fourth embodiment, and FIG. 15 shows spherical aberration, astigmatism in the wide-angle end state, and FIG. It shows distortion aberration. It shows spherical aberration, astigmatism and distortion in the intermediate focal length (standard) state. It shows spherical aberration, astigmatism, and distortion in the telephoto end state. FIG. 18 shows an embodiment in which the imaging apparatus of the present invention is applied to a digital still camera together with FIG. 18, and this figure is a block diagram. It is a schematic perspective view showing an external appearance.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Zoom lens, 2 ... Zoom lens, 3 ... Zoom lens, 4 ... Zoom lens, GR1 ... 1st lens group, GR2 ... 2nd lens group, GR3 ... 3rd lens group, GR4 ... 4th lens group, GR5 ... 5th lens group, 100 ... Digital still camera, 11 ... Zoom lens, 12 ... Image sensor

Claims (4)

In order from the object side, 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, a fourth lens group having a positive refractive power, And a fifth lens group having a refractive power of 5 mm, and in zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group increases, and the second lens group and the second lens group The distance between the third lens group decreases, the distance between the third lens group and the fourth lens group changes, the distance between the fourth lens group and the fifth lens group changes, and the fifth lens group changes. The lens group is fixed during zooming, and the position of the second lens group in the telephoto end state is closer to the image side than the position of the second lens group in the wide-angle end state, and the following conditional expressions (1), (2), A zoom lens satisfying (3), (4), (5), (6), and (7).
(1) 0.47 <f1 / ft <0.74
(2) 1.28 <| f2 / fw | <2.29
(3) 3.03 <f3 / fw <5.29
(4) 0.31 <f4 / ft <0.68
(5) 0.11 <f5 / ft <1.6
(6) 0.87 <| z1 | / √ (fw · ft) <1.9
(7) 0.15 <| z2 | / √ (fw · ft) <0.79
However,
fw: focal length of the entire system in the wide-angle end state ft: focal length of the entire system in the telephoto end state f1: focal length f2 of the first lens group: focal length f3 of the second lens group: focal length f4 of the third lens group : Focal length f5 of the fourth lens group: focal length z1 of the fifth lens group: movement amount z1 of the first lens group during zooming from the wide-angle end to the telephoto end: during zooming from the wide-angle end to the telephoto end The amount of movement of the second lens group. The second lens group is composed of four lenses, a negative lens having a convex surface facing the object side, a negative lens, a positive lens, and a negative lens having a concave surface facing the object side. The zoom lens according to claim 1, wherein at least one of the lenses is an aspheric lens. The first lens group includes a cemented lens of a negative lens and a positive lens, which is positioned in order from the object side, and one or two positive meniscus lenses having a convex surface facing the object side. The zoom lens according to claim 1, wherein (8) is satisfied.
(8) νabe> 53
However,
νabe: The average value of the Abbe number with respect to the d-line (λ (wavelength) = 587.6 nm (nanometer)) of a positive meniscus lens having a convex surface facing the object side in the first lens group. An imaging apparatus comprising a zoom lens and an image sensor that converts an optical image formed by the zoom lens into an electrical signal,
The zoom lens includes, in order from the object side, 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 first lens group having a positive refractive power. A fourth lens group and a fifth lens group having a positive refractive power, and when changing magnification from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group increases. The distance between the second lens group and the third lens group decreases, the distance between the third lens group and the fourth lens group changes, and the distance between the fourth lens group and the fifth lens group changes. The fifth lens group is fixed at the time of zooming, the position of the second lens group in the telephoto end state is closer to the image side than the position of the second lens group in the wide-angle end state, and the following conditional expression (1) , (2), (3), (4), (5), (6), (7) are satisfied.
(1) 0.47 <f1 / ft <0.74
(2) 1.28 <| f2 / fw | <2.29
(3) 3.03 <f3 / fw <5.29
(4) 0.31 <f4 / ft <0.68
(5) 0.11 <f5 / ft <1.6
(6) 0.87 <| z1 | / √ (fw · ft) <1.9
(7) 0.15 <| z2 | / √ (fw · ft) <0.79
However,
fw: focal length of the entire system in the wide-angle end state ft: focal length of the entire system in the telephoto end state f1: focal length f2 of the first lens group: focal length f3 of the second lens group: focal length f4 of the third lens group : Focal length f5 of the fourth lens group: focal length z1 of the fifth lens group: movement amount z1 of the first lens group during zooming from the wide-angle end to the telephoto end: during zooming from the wide-angle end to the telephoto end The amount of movement of the second lens group.

Images