JP2011075985A - Variable focal length lens system and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure miniaturization, and to make variable power higher, regarding a variable focal length lens system and an imaging apparatus. <P>SOLUTION: The variable focal length lens system has a positive, negative, positive, negative and positive five-group configuration. In the case of changing the positional state of the lenses from a wide-angle end state to a telephoto end state, the first lens group G1, the fourth lens group G4 and the fifth lens group G5 move in an optical axis direction, the second lens group G2 moves toward an image side, the third lens group G3 moves toward an object side, the first lens group is located closer to the object side at the telephoto end state than at the wide-angle end state, and an aperture diaphragm S moves together with the third lens group. The variable focal length lens system satisfies a conditional expression: (1) 0.4<f1/ft<0.6; and a conditional expression (2) 0.15<Δ1/ft<0.45; where f1 denotes the focal length of the first lens group, ft denotes the focal length of the entire lens system in the telephoto end state, and Δ1 denotes the moving amount of the first lens group from the wide-angle end state to the telephoto end state. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a variable focal length lens system and an imaging apparatus. More specifically, the present invention relates to a technical field of a variable focal length lens system and an imaging apparatus that are used in a video camera, a digital still camera, and the like, have an angle of view in a wide-angle end state exceeding 74 degrees, and a zoom ratio exceeding 30 times.

  Conventionally, as a recording means in a camera, a subject image formed on the surface of an image sensor is photoelectrically converted by an image sensor using a photoelectric converter such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS). A method is known in which the light amount of a subject image is converted into an electrical output by an element and recorded.

  With recent advances in microfabrication technology, the central processing unit (CPU) has been increased in speed and the storage medium has been highly integrated so that large-capacity image data that could not be handled before can be processed at high speed. It has become. In addition, the light receiving element is also highly integrated and miniaturized, and higher integration enables recording at a higher spatial frequency, and the miniaturization allows the entire camera to be miniaturized.

  However, there has been a problem that due to the high integration and miniaturization described above, the light receiving area of each photoelectric conversion element (light receiving element) is narrowed, and the influence of noise increases with a decrease in electrical output. Therefore, in order to reduce the influence of such noise, there is one in which the amount of light reaching the light receiving element is increased by increasing the aperture ratio of the optical system. In addition, there is a type in which a minute lens element called a microlens array is disposed immediately before a light receiving element.

  The microlens array restricts the exit pupil position of the lens system instead of guiding the light beam reaching between adjacent elements onto the light receiving element. As the exit pupil position of the lens system approaches the light receiving element, the angle formed with the optical axis of the chief ray that reaches the light receiving element increases, so the off-axis light flux toward the screen periphery forms a large angle with respect to the optical axis. As a result, the necessary amount of light does not reach the light receiving element, resulting in insufficient light amount.

  In recent years, user needs have been diversified as digital cameras have become popular.

  In particular, a camera equipped with a zoom lens (variable focal length lens system) that is small but has a high zoom ratio is desired.

  As a type representing a configuration of a variable focal length lens system having a high zoom ratio, a four-group configuration of positive, negative, positive and positive has been conventionally used.

  A variable focal length lens system having positive, negative, positive and positive four-group configuration includes a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. The fourth lens group having positive refractive power is arranged in order from the object side to the image side.

  For example, a variable focal length lens system described in Patent Document 1 is known as such a positive, negative, positive, and positive four-group variable focal length lens system.

  In general, as the number of movable lens groups increases, the degree of freedom in selecting the trajectory for each lens group to move during zooming from the wide-angle end state to the telephoto end state increases. It is known that it can be done.

  As variable focal length lens systems that realize such high zooming and high performance, for example, variable focal length lens systems described in Patent Literature 2 and Patent Literature 3 are known.

  In the variable focal length lens systems described in Patent Document 2 and Patent Document 3, a fifth lens group fixed in the optical axis direction is disposed on the image side of a variable focal length lens system having a positive, negative, positive four-group configuration. It has been configured.

  As another variable focal length lens system having a five-group configuration, for example, a variable focal length lens system having a positive / negative / positive / negative five-group configuration described in Patent Document 4 is known.

  A variable focal length lens system having a positive, negative, positive and negative five-group configuration includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. The fourth lens group having negative refractive power and the fifth lens group having positive refractive power are arranged in order from the object side to the image side.

  In the variable focal length lens system described in Patent Document 4, when the lens position changes from the wide-angle end state to the telephoto end state, the first lens group and the third lens group move to the object side. The second lens group once moves to the image side and then moves to the object side, the fourth lens group is fixed in the optical axis direction, and the fifth lens group moves in the optical axis direction.

JP 2006-189598 A JP 2007-79194 A JP 2007-292994 A JP 2007-264174 A

  However, in a variable focal length lens system having a positive, negative, positive, positive four-group configuration as described in Patent Document 1, it is difficult to achieve a sufficient size reduction when attempting to secure a zoom ratio exceeding 20 times. .

  That is, in the variable focal length lens system, it is possible to increase the zoom ratio without increasing the total optical length by increasing the refractive power of each lens group, but if the refractive power of each lens group is increased, Variations in various aberrations that occur when the focal length changes cannot be corrected. Accordingly, if a high zoom ratio is secured by increasing the refractive power of each lens group, a predetermined optical performance cannot be obtained. As a result, a predetermined optical performance is obtained while ensuring a high zoom ratio. For this reason, it becomes difficult to avoid an increase in size.

  On the other hand, when the variable focal length lens system is composed of five groups and the number of movable lens groups is increased, the degree of freedom of selection increases in the locus of each lens group during zooming. The fluctuation can be corrected satisfactorily, and high zooming and miniaturization can be achieved.

  However, in the variable focal length lens systems described in Patent Document 2 and Patent Document 3, the fifth lens group is arranged as a fixed group on the image side of the positive, negative, positive and positive four-group configuration, and the four-group configuration. However, since the movable lens group is not increased, it is difficult to achieve both higher zooming and smaller size.

  Further, in the variable focal length lens system described in Patent Document 4, the total lens length in the telephoto end state is not sufficiently shortened. It becomes difficult to plan.

  Accordingly, an object of the variable focal length lens system and the imaging apparatus of the present invention is to overcome the above-described problems and to achieve high zooming while ensuring miniaturization.

In order to solve the above-described problem, the variable focal length lens system 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, and a negative lens group. A fourth lens group having a refractive power of 5 and a fifth lens group having a positive refractive power are arranged in order from the object side to the image side, and the position of the lens changes from the wide-angle end state to the telephoto end state. Further, the distance between the first lens group and the second lens group is increased, the distance between the second lens group and the third lens group is decreased, and the third lens group and the fourth lens group are And the first lens group, the fourth lens group, and the fifth lens group move in the optical axis direction so that the distance between the fourth lens group and the fifth lens group changes. , The second lens group moves to the image side, the third lens group moves to the object side, The first lens group is located closer to the object side in the telephoto end state than in the wide-angle end state, and the aperture stop moves integrally with the third lens group, and satisfies the following conditional expressions (1) and (2) It is what you do.
(1) 0.4 <f1 / ft <0.6
(2) 0.15 <Δ1 / ft <0.45
However,
f1: Focal length ft of the first lens group ft: focal length Δ1 of the entire lens system in the telephoto end state Δ1: a moving amount of the first lens group from the wide-angle end state to the telephoto end state.

  Therefore, in the variable focal length lens system, the appropriate refractive power of the first lens group is ensured and the amount of movement of the first lens group is reduced.

In the variable focal length lens system described above, it is preferable that the following conditional expression (3) is satisfied.
(3) 0.8 <Lt / ft <1.1
However,
Lt: The total length in the telephoto end state.

  When the variable focal length lens system satisfies the conditional expression (3), an appropriate moving distance from the wide-angle end to the telephoto end of each group is ensured, and the occurrence of aberration is suppressed.

In the variable focal length lens system described above, it is desirable that the following conditional expression (4) is satisfied.
(4) −2.5 <f4 / (fw · ft) ^1/2 <−1.3
However,
f4: focal length of the fourth lens group fw: the focal length of the entire lens system in the wide-angle end state.

  When the variable focal length lens system satisfies the conditional expression (4), it is possible to secure an appropriate refractive power of the fourth lens group and to correct the off-axis aberration satisfactorily.

  In the variable focal length lens system described above, the first lens group is positioned on the image side of the cemented lens formed by cementing a negative lens positioned on the object side and a positive lens positioned on the image side. It is desirable that the lens is composed of a positive lens.

  By configuring the first lens group as described above, generation of spherical aberration and chromatic aberration is suppressed.

  In the variable focal length lens system described above, the second lens group includes a cemented lens formed by cementing a biconcave negative lens located on the object side and a biconvex positive lens located on the image side; It is desirable that the lens is composed of a meniscus negative lens located on the object side of the cemented lens and having a concave surface facing the image side.

  By configuring the second lens group as described above, occurrence of off-axis aberration is suppressed.

  In the variable focal length lens system described above, the third lens group includes a cemented lens formed by cementing a biconvex positive lens located on the object side and a biconcave negative lens located on the image side; It is desirable that the lens is constituted by a positive lens located on the image side of the cemented lens.

  By configuring the third lens group as described above, fluctuations in spherical aberration are suppressed.

  In the above-mentioned variable focal length lens system, it is desirable that the fourth lens group is composed of a biconcave negative lens.

  By configuring the fourth lens group as described above, fluctuations in spherical aberration are suppressed.

  In the variable focal length lens system described above, the fifth lens group includes a biconvex positive lens located on the object side and a meniscus negative lens located on the image side and having a concave surface facing the object side. It is desirable that the lens is constituted by a cemented lens.

  By configuring the fifth lens group as described above, aberration variations caused by the shooting distance are suppressed.

In order to solve the above-described problem, the imaging apparatus includes a variable focal length lens system and an imaging element that converts an optical image formed by the variable focal length lens system into an electrical signal, and the variable focal length lens system Are 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 negative refractive power, and a positive refractive power. Are arranged in order from the object side to the image side, and when the lens position changes from the wide-angle end state to the telephoto end state, the first lens group and the second lens group 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 increases, and the fourth lens group and the fourth lens group increase. The first lens so that the distance from the five lens groups changes. And the fourth lens group and the fifth lens group move in the optical axis direction, the second lens group moves to the image side, the third lens group moves to the object side, and the first lens group It is located on the object side in the telephoto end state compared to the wide-angle end state, and the aperture stop moves integrally with the third lens group so that the following conditional expressions (1) and (2) are satisfied. is there.
(1) 0.4 <f1 / ft <0.6
(2) 0.15 <Δ1 / ft <0.45
However,
f1: Focal length ft of the first lens group ft: focal length Δ1 of the entire lens system in the telephoto end state Δ1: a moving amount of the first lens group from the wide-angle end state to the telephoto end state.

  Therefore, in the imaging apparatus, an appropriate refractive power of the first lens group is ensured and the movement amount of the first lens group is reduced.

The variable focal length lens system of 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, and a fourth lens having a negative refractive power. The first lens group is formed when a lens group and a fifth lens group having a positive refractive power are arranged in order from the object side to the image side, and the position of the lens changes from the wide-angle end state to the telephoto end state. 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 increases, The first lens group, the fourth lens group, and the fifth lens group move in the optical axis direction so that the distance between the fourth lens group and the fifth lens group changes, and the second lens group The third lens group moves to the object side, and the first lens group moves to the wide-angle end. Located closer to the object side at the telephoto end state as compared to the state, the aperture stop moves together with the third lens group satisfies the following conditional expressions (1) and (2).
(1) 0.4 <f1 / ft <0.6
(2) 0.15 <Δ1 / ft <0.45
However,
f1: Focal length ft of the first lens group ft: focal length Δ1 of the entire lens system in the telephoto end state Δ1: a moving amount of the first lens group from the wide-angle end state to the telephoto end state.

  Therefore, high zooming can be achieved while ensuring miniaturization.

In the invention described in claim 2, the following conditional expression (3) is satisfied.
(3) 0.8 <Lt / ft <1.1
However,
Lt: The total length in the telephoto end state.

  Accordingly, it is possible to achieve high zooming and miniaturization, and it is possible to improve performance by suppressing the occurrence of aberration.

In the invention described in claim 3, the following conditional expression (4) is satisfied.
(4) −2.5 <f4 / (fw · ft) ^1/2 <−1.3
However,
f4: focal length of the fourth lens group fw: the focal length of the entire lens system in the wide-angle end state.

  Therefore, high performance and downsizing can be achieved by good correction of off-axis aberrations.

  In the invention described in claim 4, the first lens group includes a cemented lens formed by cementing a negative lens positioned on the object side and a positive lens positioned on the image side, and an image side of the cemented lens. And a positive lens located at the center.

  Therefore, it is possible to suppress the occurrence of spherical aberration and chromatic aberration when high zooming is achieved.

  In the invention described in claim 5, the second lens group is a cemented lens formed by cementing a biconcave negative lens located on the object side and a biconvex positive lens located on the image side. And a meniscus negative lens located on the object side of the cemented lens and having a concave surface facing the image side.

  Therefore, off-axis aberrations that occur during zooming can be reduced.

  In the invention described in claim 6, the third lens group is a cemented lens formed by cementing a biconvex positive lens positioned on the object side and a biconcave negative lens positioned on the image side. And a positive lens located on the image side of the cemented lens.

  Therefore, it is possible to satisfactorily correct the variation in spherical aberration that occurs during zooming.

  In the invention described in claim 7, the fourth lens group is constituted by a biconcave negative lens.

  Accordingly, it is possible to reduce the variation in spherical aberration that occurs during zooming.

  In the invention described in claim 8, the fifth lens group includes a biconvex positive lens located on the object side and a meniscus negative lens located on the image side and having a concave surface facing the object side. It is constituted by a cemented lens formed by cementing.

  Accordingly, it is possible to suppress aberration fluctuations caused by the shooting distance.

The imaging apparatus of the present invention includes a variable focal length lens system and an imaging element that converts an optical image formed by the variable focal length lens system into an electrical signal, and the variable focal length lens system has a positive refractive power. A first lens group having a negative refractive power, a third lens group having a positive refractive power, a fourth lens group having a negative refractive power, and a fifth lens group having a positive refractive power; Are arranged in order from the object side to the image side, and when the lens position changes 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 increases, and the distance between the fourth lens group and the fifth lens group increases. The first lens group and the fourth lens group and the front The fifth lens group moves in the optical axis direction, the second lens group moves to the image side, the third lens group moves to the object side, and the first lens group is at the telephoto end compared to the wide-angle end state. In the state, it is located on the object side, the aperture stop moves integrally with the third lens group, and the following conditional expressions (1) and (2) are satisfied.
(1) 0.4 <f1 / ft <0.6
(2) 0.15 <Δ1 / ft <0.45
However,
f1: Focal length ft of the first lens group ft: focal length Δ1 of the entire lens system in the telephoto end state Δ1: a moving amount of the first lens group from the wide-angle end state to the telephoto end state.

  Therefore, high zooming can be achieved while ensuring miniaturization.

  The best mode for carrying out the variable focal length lens system and the imaging apparatus of the present invention will be described below.

[Configuration of variable focal length lens system]
The variable focal length lens system of 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, and a fourth lens having a negative refractive power. A lens group and a fifth lens group having a positive refractive power are arranged in order from the object side to the image side.

  In the variable focal length lens system of the present invention, when the position of the lens changes 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 The distance between the lens group and the third lens group decreases, the distance between the third lens group and the fourth lens group increases, and the distance between the fourth lens group and the fifth lens group changes. .

  Furthermore, in the variable focal length lens system of the present invention, when the lens position changes from the wide-angle end state to the telephoto end state, the first lens group, the fourth lens group, and the fifth lens group are in the optical axis direction. The second lens group moves to the image side, and the third lens group moves to the object side.

  Furthermore, in the variable focal length lens system according to the present invention, the first lens group is positioned closer to the object side in the telephoto end state than in the wide-angle end state, and the aperture stop moves integrally with the third lens group.

In addition, the variable focal length lens system of the present invention satisfies the following conditional expressions (1) and (2).
(1) 0.4 <f1 / ft <0.6
(2) 0.15 <Δ1 / ft <0.45
However,
f1: Focal length ft of the first lens group ft: focal length Δ1 of the entire lens system in the telephoto end state Δ1: a moving amount of the first lens group from the wide-angle end state to the telephoto end state.

  Conditional expression (1) defines the focal length of the first lens group in the telephoto end state.

  If the upper limit of conditional expression (1) is exceeded, the refractive power of the first lens group becomes too weak, and it is necessary to increase the moving distance from the wide-angle end to the telephoto end in order to obtain a high zoom ratio. Miniaturization becomes difficult.

  Conversely, if the lower limit of conditional expression (1) is not reached, the refractive power of the first lens group becomes too strong, so that it is possible to reduce the size, but aberration occurs in the first lens group. This makes it easier to correct aberrations occurring in the first lens group after the second lens group.

  Therefore, when the variable focal length lens system satisfies the conditional expression (1), it is possible to achieve high zooming and miniaturization, and to suppress the occurrence of aberrations in the first lens group, thereby achieving high performance. Can do.

  Conditional expression (2) defines the amount of movement of the first lens unit from the wide-angle end state to the telephoto end state.

  If the upper limit of conditional expression (2) is exceeded, the amount of movement of the first lens group becomes large and the amount of movement of the entire lens system becomes large, making it difficult to reduce the size.

  On the other hand, if the lower limit of conditional expression (2) is not reached, aberrations are likely to occur when the refractive power of the first lens unit is increased in order to achieve high zooming, and the characteristics deteriorate. .

  Therefore, when the variable focal length lens system satisfies the conditional expression (2), it is possible to achieve a high zoom ratio and a small size, and to suppress the occurrence of aberrations and to improve performance.

  In the variable focal length lens system according to the present invention, the fifth lens group moves so as to compensate for the variation of the image plane position accompanying the movement of each lens group, and the aperture stop is disposed in the vicinity of the third lens group. Has been.

  Since the variable focal length lens system of the present invention is configured as described above, the angle of view in the wide-angle end state is 75 to 95 degrees, the zoom ratio is 30 to 40 times, and the F-number in the wide-angle end state is 2. A value of about .8 can be secured.

  Therefore, high zooming can be achieved while ensuring miniaturization. In addition, the lens barrel structure can be simplified.

In the variable focal length lens system according to an embodiment of the present invention, it is preferable that the following conditional expression (3) is satisfied.
(3) 0.8 <Lt / ft <1.1
However,
Lt: The total length in the telephoto end state.

  Conditional expression (3) defines the relationship between the total length and the focal length in the telephoto end state.

  If the upper limit of conditional expression (3) is exceeded, the overall length becomes long and it becomes impossible to reduce the size.

  On the contrary, if the lower limit of conditional expression (3) is not reached, the moving distance from the wide-angle end to the telephoto end of each group becomes too small, so that the refractive power of each group is strengthened in order to achieve high zooming. As a result, aberrations are likely to occur.

  Therefore, when the variable focal length lens system satisfies the conditional expression (3), it is possible to achieve high zooming and miniaturization, and to suppress the generation of aberrations, thereby achieving high performance.

In the variable focal length lens system according to an embodiment of the present invention, it is preferable that the following conditional expression (4) is satisfied.
(4) −2.5 <f4 / (fw · ft) ^1/2 <−1.3
However,
f4: focal length of the fourth lens group fw: the focal length of the entire lens system in the wide-angle end state.

  Conditional expression (4) defines the focal length of the fourth lens group.

  If the upper limit of conditional expression (4) is exceeded, the refractive power of the fourth lens group becomes too weak, making it difficult to correct off-axis aberrations, and increasing the size of the optical system.

  Conversely, if the lower limit of conditional expression (4) is not reached, the refractive power of the fourth lens group becomes too strong, making it difficult to balance off-axis aberrations generated in other lens groups. .

  Therefore, when the variable focal length lens system satisfies the conditional expression (4), high performance and small size can be achieved by good correction of off-axis aberrations.

  In the variable focal length lens system according to an embodiment of the present invention, the first lens group includes a cemented lens formed by cementing a negative lens positioned on the object side and a positive lens positioned on the image side, and the cemented lens. It is desirable that the lens is constituted by a positive lens located on the image side of the lens.

  By configuring the first lens group as described above, it is possible to suppress the occurrence of spherical aberration and chromatic aberration when high zooming is achieved.

  In the variable focal length lens system according to an embodiment of the present invention, the second lens group includes a biconcave negative lens located on the object side and a biconvex positive lens located on the image side. It is desirable that the lens is composed of a cemented lens that is cemented and a meniscus negative lens that is located on the object side of the cemented lens and has a concave surface facing the image side.

  By configuring the second lens group as described above, off-axis aberrations that occur during zooming can be reduced.

  Furthermore, in the variable focal length lens system according to an embodiment of the present invention, the third lens group includes a biconvex positive lens located on the object side and a biconcave negative lens located on the image side. It is desirable that the cemented lens is formed by a cemented lens and a positive lens positioned on the image side of the cemented lens, and the most object-side surface is formed as an aspherical surface.

  By configuring the third lens group as described above, it is possible to satisfactorily correct the variation in spherical aberration that occurs during zooming.

  Furthermore, in the variable focal length lens system according to an embodiment of the present invention, it is desirable that the fourth lens group is constituted by a biconcave negative lens and the object side surface is formed as an aspherical surface.

  By configuring the fourth lens group as described above, it is possible to reduce the variation in spherical aberration that occurs during zooming.

  In addition, in the variable focal length lens system according to an embodiment of the present invention, the fifth lens group is a biconvex positive lens positioned on the object side and a concave surface facing the object side positioned on the image side. It is desirable to form a cemented lens formed by cementing a meniscus negative lens.

  By configuring the fifth lens group as described above and moving it in the optical axis direction, it is possible to suppress aberration fluctuations that occur due to the shooting distance.

  In the variable focal length lens system of the present invention, one lens group or a part of one lens group out of the first lens group to the fifth lens group is moved (shifted) in a direction substantially perpendicular to the optical axis. Thus, it is possible to shift the image. In this way, the lens group or a part of the lens group is moved in a direction substantially perpendicular to the optical axis to detect image blur, the drive system that shifts each lens group, and the shift amount to the drive system based on the output of the detection system. In combination with a control system that provides the variable focal length lens system, the variable focal length lens system can also function as an anti-vibration optical system.

  In addition, by arranging an aperture stop in the vicinity of the third lens group, the off-axis light beam passes in the vicinity of the optical axis, so that the off-axis generated when the third lens group is shifted in a direction substantially perpendicular to the optical axis. It is possible to suppress fluctuations in aberration.

  Furthermore, in the variable focal length lens system of the present invention, a low-pass filter for preventing the generation of moire fringes is arranged on the image side of the lens system, or an infrared absorption filter is arranged according to the spectral sensitivity characteristics of the light receiving element. It is also possible.

  In addition, higher optical performance can be ensured by forming a plurality of aspheric surfaces in the optical system of the variable focal length lens system.

[Numerical Examples of Variable Focal Length Lens System]
Hereinafter, specific embodiments of the variable focal length lens system of the present invention and numerical examples in which specific numerical values are applied to the embodiments will be described with reference to the drawings and tables.

  The meanings of symbols shown in the following tables and explanations are as shown below.

  “ASP” for the surface number (r) indicates that the surface is aspherical. “BF” indicates back focus. “K” represents a conic constant (conic constant), and “A4”, “A6”, “A8”, and “A10” represent fourth-order, sixth-order, eighth-order, and tenth-order aspherical coefficients, respectively.

  The refractive index is a value with respect to the d-line (λ = 587.6 nm), and the curvature radius of “∞” indicates that the surface is a plane.

  Some lenses used in each numerical example have an aspheric lens surface. In the aspherical shape, “x” is the distance (sag amount) from the apex of the lens surface in the optical axis direction, “y” is the height (image height) in the direction perpendicular to the optical axis, and “c” is the apex of the lens. , Paraxial curvature (reciprocal of radius of curvature), “K” for conic constant (conic constant), “A4”, “A6”, “A8”, “A10” for 4th, 6th, 8th, 10th respectively. Is defined by Equation 1 below.

  FIG. 1 shows refractive power distribution in each embodiment of the variable focal length lens system of the present invention.

  The variable focal length lens system includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, and a negative refractive power. And a fifth lens group G5 having a positive refractive power are arranged in order from the object side to the image side.

  In the variable focal length lens system, when the lens position changes from the wide-angle end state to the telephoto end state, the distance between the first lens group G1 and the second lens group G2 increases, and the second lens group G2 and the third lens group G3. The distance between the lens group G3 decreases, the distance between the third lens group G3 and the fourth lens group G4 increases, and the distance between the fourth lens group G4 and the fifth lens group G5 changes. At this time, the first lens group G1 once moves to the image side and then to the object side, the second lens group G2 moves to the image side, the third lens group G3 moves to the object side, and the fourth lens group. G4 moves in the optical axis direction, and the fifth lens group G5 once moves to the object side and then moves to the image side. The fifth lens group G5 moves so as to correct the fluctuation of the image plane position accompanying the movement of each lens group, and moves toward the object side when focusing on a short distance. The aperture stop is disposed in the vicinity of the third lens group G3 on the object side and moves integrally with the third lens group G3.

<First Embodiment>
FIG. 2 shows a lens configuration of the variable focal length lens system 1 according to the first embodiment of the present invention, and the variable focal length lens system 1 has twelve lenses.

  The first lens group G1 includes a cemented lens formed by cementing a meniscus negative lens L1 having a convex surface facing the object side and a biconvex positive lens L2, and a meniscus positive lens having a convex surface facing the object side. L3 is arranged in order from the object side to the image side.

  The second lens group G2 includes a negative lens L4 having a concave surface directed toward the image side, and a cemented lens formed by cementing a biconcave negative lens L5 and a biconvex positive lens L6 in order from the object side to the image side. Arranged and configured.

  The third lens group G3 includes a cemented lens formed by cementing a meniscus positive lens L7 having a convex surface toward the object side and a meniscus negative lens L8 having a concave surface toward the image side, and a biconvex positive lens. L9 is arranged in order from the object side to the image side.

  The fourth lens group G4 includes a biconcave negative lens L10.

  The fifth lens group G5 includes a cemented lens in which a biconvex positive lens L11 and a meniscus negative lens L12 having a concave surface directed toward the object side are cemented.

  The aperture stop S is disposed on the object side of the third lens group and moves integrally with the third lens group.

  A filter FL is disposed between the fifth lens group G5 and the image plane IMG.

  Table 1 shows lens data of Numerical Example 1 in which specific numerical values are applied to the variable focal length lens system 1 according to the first embodiment.

  In the variable focal length lens system 1, both surfaces (surface number 6, surface number 7) of the negative lens L4 of the second lens group G2, the image side surface (surface number 10) of the positive lens L6 of the second lens group G2, The object side surface (surface number 12) of the positive lens L7 of the third lens group G3, the object side surface (surface number 17) of the negative lens L10 of the fourth lens group G4, and the object of the positive lens L11 of the fifth lens group G5 The side surface (surface number 19) is aspherical. The second-order, sixth-order, eighth-order, and tenth-order aspheric coefficients A4, A6, A8, and A10 of Numerical Example 1 are shown in Table 2 together with the conic constant K.

In Table 2 and each table showing an aspherical coefficient, which will be described later, “E-i” represents an exponential expression having a base of 10, that is, “10 ⁻ⁱ ”. For example, “0.12345E-05” “Represents“ 0.12345 × 10 ⁻⁵ ”.

  In the variable focal length lens system 1, upon zooming between the wide-angle end state and the telephoto end state, the surface distance D5 between the first lens group G1 and the second lens group G2, the second lens group G2, and the aperture stop S The surface distance D10 between the third lens group G3 and the fourth lens group G4, the surface distance D18 between the fourth lens group G4 and the fifth lens group G5, and the fifth lens group G5 and the filter FL. The inter-surface distance D21 changes. Table 3 shows the distance between each surface and the variable distance in the wide-angle end state, the intermediate focal length state, and the telephoto end state in Numerical Example 1 together with the F number, the angle of view, the image height, and the total lens length.

  Table 4 shows the start surface and focal length of each group in Numerical Example 1.

  FIGS. 3 to 8 show aberration diagrams of the numerical example 1 in the infinitely focused state, in which FIGS. 3 and 4 are in a wide-angle end state, FIGS. 5 and 6 are in an intermediate focal length state, and FIGS. The aberration diagram in a telephoto end state is shown.

  3 to 8, in the astigmatism diagrams, the solid line indicates the value on the sagittal image plane, the broken line indicates the value on the meridional image plane, and in the lateral aberration diagrams, A indicates the angle of view and y indicates the image height.

  From each aberration diagram, it is clear that Numerical Example 1 has excellent imaging performance with various aberrations corrected well.

<Second Embodiment>
FIG. 9 shows a lens configuration of the variable focal length lens system 2 according to the second embodiment of the present invention, and the variable focal length lens system 2 has 13 lenses. The first lens group G1 includes a cemented lens formed by cementing a meniscus negative lens L1 having a convex surface facing the object side and a biconvex positive lens L2, and a meniscus positive lens having a convex surface facing the object side. L3 is arranged in order from the object side to the image side.

  The second lens group G2 includes a negative lens L4 having a concave surface facing the image side, a cemented lens formed by cementing a biconcave negative lens L5 and a biconvex positive lens L6, and a convex surface facing the image side. The positive meniscus lens L7 is arranged in order from the object side to the image side.

  In the third lens group G3, a cemented lens in which a biconvex positive lens L8 and a biconcave negative lens L9 are cemented, and a biconvex positive lens L10 are sequentially arranged from the object side to the image side. Configured.

  The fourth lens group G4 includes a meniscus negative lens L11 having a concave surface directed toward the object side.

  The fifth lens group G5 includes a cemented lens in which a biconvex positive lens L12 and a meniscus negative lens L13 having a concave surface directed toward the object side are cemented.

  The aperture stop S is disposed on the object side of the third lens group and moves integrally with the third lens group.

  A filter FL is disposed between the fifth lens group G5 and the image plane IMG.

  Table 5 shows lens data of Numerical Example 2 in which specific numerical values are applied to the variable focal length lens system 2 according to the second embodiment.

  In the variable focal length lens system 2, both surfaces (surface number 6, surface number 7) of the negative lens L4 of the second lens group G2, the image side surface (surface number 12) of the positive lens L7 of the second lens group G2, The object side surface (surface number 14) of the positive lens L8 of the third lens group G3, the object side surface (surface number 19) of the negative lens L11 of the fourth lens group G4, and the object of the positive lens L12 of the fifth lens group G5 The side surface (surface number 21) is formed as an aspherical surface. Table 6 shows the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients A4, A6, A8, and A10 of the aspheric surface in Numerical Example 2 together with the conic constant K.

  In the variable focal length lens system 2, upon zooming between the wide-angle end state and the telephoto end state, the surface distance D5 between the first lens group G1 and the second lens group G2, the second lens group G2, and the aperture stop S The surface distance D12 between the third lens group G3 and the fourth lens group G4, the surface distance D20 between the fourth lens group G4 and the fifth lens group G5, and the fifth lens group G5 and the filter FL. The inter-surface distance D23 changes. Table 7 shows the distance between each surface and the variable distance in the wide-angle end state, the intermediate focal length state, and the telephoto end state in Numerical Example 2 together with the F number, the angle of view, the image height, and the total lens length.

  Table 8 shows the start surface and focal length of each group in Numerical Example 2.

  FIGS. 10 to 15 show aberration diagrams of the numerical example 2 in the infinite focus state. FIGS. 10 and 11 are the wide-angle end state, FIGS. 12 and 13 are the intermediate focal length states, and FIGS. The aberration diagram in a telephoto end state is shown.

  10 to 15, in the astigmatism diagrams, the solid line indicates the value on the sagittal image plane, the broken line indicates the value on the meridional image plane, and in the lateral aberration diagrams, A indicates the angle of view and y indicates the image height.

  From each aberration diagram, it is clear that Numerical Example 2 has excellent imaging performance with various aberrations corrected well.

[Values of conditional expression for variable focal length lens system]
Table 9 shows values of the conditional expressions (1) to (4) in the variable focal length lens system 1 and the variable focal length lens system 2.

  As can be seen from Table 9, the variable focal length lens system 1 and the variable focal length lens system 2 satisfy the conditional expressions (1) to (4).

[Configuration of imaging apparatus equipped with variable focal length lens system]
Hereinafter, an imaging apparatus of the present invention provided with a variable focal length lens system will be described.

  The imaging apparatus of the present invention is an apparatus that includes a variable focal length lens system and an imaging element that converts an optical image formed by the variable focal length lens system into an electrical signal.

  In the imaging apparatus of the present invention, the variable focal length lens system 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, and a negative refractive power. And a fifth lens group having a positive refractive power are arranged in order from the object side to the image side.

  In the imaging apparatus of the present invention, when the variable focal length lens system changes the position of the lens 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 increases, and the fourth lens group and the fifth lens group The interval changes.

  Further, according to the imaging apparatus of the present invention, the first lens group, the fourth lens group, and the fifth lens group are changed when the variable focal length lens system changes the lens position state from the wide-angle end state to the telephoto end state. Moves in the optical axis direction, the second lens group moves toward the image side, and the third lens group moves toward the object side.

  Furthermore, in the imaging apparatus of the present invention, the variable focal length lens system is such that the first lens group is positioned on the object side in the telephoto end state compared to the wide-angle end state, and the aperture stop moves integrally with the third lens group. .

In addition, in the imaging apparatus of the present invention, the variable focal length lens system satisfies the following conditional expressions (1) and (2).
(1) 0.4 <f1 / ft <0.6
(2) 0.15 <Δ1 / ft <0.45
However,
f1: Focal length ft of the first lens group ft: focal length Δ1 of the entire lens system in the telephoto end state Δ1: a moving amount of the first lens group from the wide-angle end state to the telephoto end state.

  Conditional expression (1) defines the focal length of the first lens group in the telephoto end state.

  If the upper limit of conditional expression (1) is exceeded, the refractive power of the first lens group becomes too weak, and it is necessary to increase the moving distance from the wide-angle end to the telephoto end in order to obtain a high zoom ratio. Miniaturization becomes difficult.

  Conversely, if the lower limit of conditional expression (1) is not reached, the refractive power of the first lens group becomes too strong, so that it is possible to reduce the size, but aberration occurs in the first lens group. This makes it easier to correct aberrations occurring in the first lens group after the second lens group.

  Therefore, when the variable focal length lens system satisfies the conditional expression (1), it is possible to achieve high zooming and miniaturization, and to suppress the occurrence of aberrations in the first lens group, thereby achieving high performance. Can do.

  Conditional expression (2) defines the amount of movement of the first lens unit from the wide-angle end state to the telephoto end state.

  If the upper limit of conditional expression (2) is exceeded, the amount of movement of the first lens group becomes large and the amount of movement of the entire lens system becomes large, making it difficult to reduce the size.

  On the other hand, if the lower limit of conditional expression (2) is not reached, aberrations are likely to occur when the refractive power of the first lens unit is increased in order to achieve high zooming, and the characteristics deteriorate. .

  Therefore, when the variable focal length lens system satisfies the conditional expression (2), it is possible to achieve a high zoom ratio and a small size, and to suppress the occurrence of aberrations and to improve performance.

  In the imaging apparatus of the present invention, in the variable focal length lens system, the fifth lens group moves so as to compensate for the variation of the image plane position accompanying the movement of each lens group, and the aperture stop is the third lens group. It is arranged in the vicinity.

  In the imaging apparatus of the present invention, the variable focal length lens system is configured as described above, so that the angle of view in the wide-angle end state is 75 degrees to 95 degrees, the zoom ratio is 30 to 40 times, and in the wide-angle end state. An F number of about 2.8 can be secured.

  Therefore, high zooming can be achieved while ensuring miniaturization. In addition, the lens barrel structure can be simplified.

[One Embodiment of Imaging Device]
FIG. 16 is a block diagram of a digital still camera according to an embodiment of the imaging apparatus of the present invention.

  An imaging apparatus (digital still camera) 100 performs a camera block 10 that performs an imaging function, a camera signal processing unit 20 that performs signal processing such as analog-digital conversion of a captured image signal, and recording and reproduction processing of the image signal. And an image processing unit 30. The imaging apparatus 100 also includes an LCD (Liquid Crystal Display) 40 that displays captured images and the like, an R / W (reader / writer) 50 that writes and reads image signals to and from the memory card 1000, and imaging. And a CPU (Central Processing Unit) 60 for controlling the entire apparatus. Furthermore, the imaging apparatus 100 includes an input unit 70 including various switches and the like on which a user performs a required operation, and a lens drive control unit 80 that controls driving of lenses arranged in the camera block 10.

  The camera block 10 includes an optical system including a variable focal length lens system 11 (variable focal length lens systems 1 and 2 to which the present invention is applied), a CCD (Charge Coupled Device), a CMOS (Complementary Metal-Oxide Semiconductor), and the like. It is comprised with the image pick-up element 12 grade | etc.,.

  The camera signal processing unit 20 performs various types of signal processing such as conversion of the 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 LCD 40 has a function of displaying various data such as an operation state of the user's input unit 70 and a photographed image.

  The R / W 50 writes the image data encoded by the image processing unit 30 to the memory card 1000 and reads the image data recorded on the memory card 1000.

  The CPU 60 functions as a control processing unit that controls each circuit block provided in the imaging apparatus 100, 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 a user to the CPU 60.

  The lens drive control unit 80 controls a motor (not shown) that drives each lens of the variable focal length lens system 11 based on a control signal from the CPU 60.

  The memory card 1000 is a semiconductor memory that can be attached to and detached from a slot connected to the R / W 50, for example.

  Hereinafter, an operation in the imaging apparatus 100 will be described.

  In a shooting standby state, under the control of the CPU 60, an image signal shot 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 variable focal length lens system 11 is controlled based on the control of the lens drive control unit 80. The predetermined lens is moved.

  When a shutter (not shown) of the camera block 10 is operated 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. Converted to data format digital data. The converted data is output to the R / W 50 and written to the memory card 1000.

  The focusing is performed by the lens drive control unit 80 based on a control signal from the CPU 60, for example, when the shutter release button of the input unit 50 is half pressed or when the shutter release button is fully pressed for recording (photographing). This is performed by moving a predetermined lens of the variable focal length lens system 11.

  When reproducing the image data recorded on the memory card 1000, predetermined image data is read from the memory card 1000 by the R / W 50 in accordance with an operation on the input unit 70, and decompressed and decoded by the image processing unit 30. After the processing is performed, the reproduction image signal is output to the LCD 40 and the reproduction image is displayed.

  In the above-described embodiment, an example in which the imaging device is applied to a digital still camera has been shown. However, the application range of the imaging device is not limited to a digital still camera, and a digital video camera and a camera are incorporated. It can be widely applied as a camera unit of a digital input / output device such as a mobile phone or a PDA (Personal Digital Assistant) incorporating a camera.

  The shapes and numerical values of the respective parts shown in the above-described embodiments are merely examples of embodiments for carrying out the present invention, and the technical scope of the present invention is interpreted in a limited manner by these. There should be no.

It is a figure which shows refractive power distribution in each embodiment of the variable focal length lens system of this invention. It is a figure which shows the lens structure of 1st Embodiment of this invention variable focal-length lens system. FIG. 4 to FIG. 8 show aberration diagrams of numerical examples in which specific numerical values are applied to the first embodiment, and this figure shows spherical aberration, astigmatism, and distortion in the wide-angle end state. . It is a figure which shows the lateral aberration in a wide angle end state. It is a figure which shows the spherical aberration, the astigmatism, and the distortion aberration in the intermediate focal length state. It is a figure which shows the lateral aberration in an intermediate | middle focal distance state. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a telephoto end state. It is a figure which shows the lateral aberration in a telephoto end state. It is a figure which shows the lens structure of 2nd Embodiment of this invention variable focal-length lens system. FIGS. 11 to 15 show aberration diagrams of numerical examples in which specific numerical values are applied to the second embodiment, and FIG. 11 is a diagram showing spherical aberration, astigmatism, and distortion in the wide-angle end state. . It is a figure which shows the lateral aberration in a wide angle end state. It is a figure which shows the spherical aberration, the astigmatism, and the distortion aberration in the intermediate focal length state. It is a figure which shows the lateral aberration in an intermediate | middle focal distance state. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a telephoto end state. It is a figure which shows the lateral aberration in a telephoto end state. It is a block diagram which shows one Embodiment of this invention imaging device.

  DESCRIPTION OF SYMBOLS 1 ... Variable focal length lens system, 2 ... Variable focal length lens system, G1 ... 1st lens group, G2 ... 2nd lens group, G3 ... 3rd lens group, G4 ... 4th lens group, G5 ... 5th lens group DESCRIPTION OF SYMBOLS 100 ... Imaging device 11 ... Variable focal length lens system 12 ... Imaging device

Claims (9)

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 negative refractive power, and a positive refractive power The fifth lens group is arranged in order from the object side to the image side,
When the lens position changes 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 distance between the second lens group and the third lens group. Decreases, the distance between the third lens group and the fourth lens group increases, and the distance between the fourth lens group and the fifth lens group changes. 4 lens group and the fifth lens group move in the optical axis direction, the second lens group moves to the image side, the third lens group moves to the object side,
The first lens group is located closer to the object side in the telephoto end state than in the wide-angle end state,
The aperture stop moves together with the third lens group,
A variable focal length lens system that satisfies the following conditional expressions (1) and (2).
(1) 0.4 <f1 / ft <0.6
(2) 0.15 <Δ1 / ft <0.45
However,
f1: Focal length ft of the first lens group ft: focal length Δ1 of the entire lens system in the telephoto end state Δ1: a moving amount of the first lens group from the wide-angle end state to the telephoto end state. The variable focal length lens system according to claim 1, wherein the following conditional expression (3) is satisfied.
(3) 0.8 <Lt / ft <1.1
However,
Lt: The total length in the telephoto end state. The variable focal length lens system according to claim 1, wherein the following conditional expression (4) is satisfied.
(4) −2.5 <f4 / (fw · ft) ^1/2 <−1.3
However,
f4: focal length of the fourth lens group fw: the focal length of the entire lens system in the wide-angle end state. The first lens group includes a cemented lens formed by cementing a negative lens positioned on the object side and a positive lens positioned on the image side, and a positive lens positioned on the image side of the cemented lens. The variable focal length lens system described in 1. The second lens group includes a cemented lens formed by cementing a biconcave negative lens positioned on the object side and a biconvex positive lens positioned on the image side, and an image positioned on the object side of the cemented lens. The variable focal length lens system according to claim 1, comprising: a negative meniscus lens having a concave surface directed toward the side. The third lens group includes a cemented lens formed by cementing a biconvex positive lens positioned on the object side and a biconcave negative lens positioned on the image side, and a positive lens positioned on the image side of the cemented lens. The variable focal length lens system according to claim 1, comprising a lens. The variable focal length lens system according to claim 1, wherein the fourth lens group is configured by a biconcave negative lens. The fifth lens group includes a cemented lens formed by cementing a biconvex positive lens located on the object side and a meniscus negative lens located on the image side and having a concave surface facing the object side. The variable focal length lens system described in 1. A variable focal length lens system and an image sensor that converts an optical image formed by the variable focal length lens system into an electrical signal;
The variable focal length lens system 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, a fourth lens group having a negative refractive power, and a positive refractive power The fifth lens group is arranged in order from the object side to the image side,
When the lens position changes 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 distance between the second lens group and the third lens group. Decreases, the distance between the third lens group and the fourth lens group increases, and the distance between the fourth lens group and the fifth lens group changes. 4 lens group and the fifth lens group move in the optical axis direction, the second lens group moves to the image side, the third lens group moves to the object side,
The first lens group is located closer to the object side in the telephoto end state than in the wide-angle end state,
The aperture stop moves together with the third lens group,
An imaging device that satisfies the following conditional expressions (1) and (2).
(1) 0.4 <f1 / ft <0.6
(2) 0.15 <Δ1 / ft <0.45
However,
f1: Focal length ft of the first lens group ft: focal length Δ1 of the entire lens system in the telephoto end state Δ1: a moving amount of the first lens group from the wide-angle end state to the telephoto end state.

Images