JP5906998B2 - Variable focal length lens system and imaging apparatus - Google Patents

Description

  The present disclosure relates to a variable focal length lens system suitable for a digital video camera or a digital still camera, and an imaging apparatus using such a variable focal length lens system. In particular, it is suitable for a variable focal length lens system in which the angle of view at the wide-angle end state includes about 24 to 36 mm in terms of 35 mm and the zoom ratio is about 4 to 7 times.

As a recording means in a camera, a subject image is formed on an image sensor surface using a photoelectric conversion element such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS), and the amount of light of the subject image is electrically converted by each photoelectric conversion element. There is known a method of recording after converting to a typical output.

  On the other hand, with the recent advancement of 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 possible. In addition, the photoelectric conversion elements are also highly integrated and miniaturized, and the high integration enables recording at higher spatial frequencies, and the miniaturization has reduced the size of the entire camera.

  However, due to the high integration and miniaturization described above, there has been a problem that the light receiving area of each photoelectric conversion element is narrowed, and the influence of noise increases with a decrease in electrical output. In order to prevent this, the amount of light reaching the photoelectric conversion element is increased by increasing the aperture ratio of the optical system. In addition, a minute lens element (so-called microlens array) is disposed immediately before each element. This microlens array restricts the exit pupil position of the lens system instead of guiding the light beam reaching between adjacent elements onto the element. When the exit pupil position of the lens system approaches the photoelectric conversion element, that is, when the angle formed by the principal ray that reaches the photoelectric conversion element becomes larger than the optical axis, the off-axis light flux toward the screen periphery forms a large angle with respect to the optical axis. As a result, the light does not reach the photoelectric conversion element, resulting in insufficient light quantity.

  In general, a zoom lens in which the angle of view in the wide-angle end state where the focal length is the shortest includes a range of about 24 mm to 35 mm in terms of 35 mm, and the angle of view in the telephoto end state where the focal length is the longest is more than 50 mm. Is called a standard zoom lens. As this standard zoom lens, a positive / negative / positive / positive 4 group zoom lens and a positive / negative / positive / negative positive 5 group zoom lens have been widely used.

  A positive / negative / positive / positive 4 group 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, and a third lens group having a positive refractive power; In this configuration, a fourth lens group having a positive refractive power is disposed (see Patent Documents 1 to 4). A positive / negative / positive / negative / positive 5 group 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, and a third lens group having a positive refractive power; This is a configuration in which a fourth lens group having a negative refractive power and a fifth lens group having a positive refractive power are arranged (see Patent Documents 5 to 7).

  A positive / negative / negative positive / positive five-group zoom lens is also known (see Patent Document 8). This positive / negative / negative / positive / positive five-group 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, and a third lens group having a negative refractive power. The fourth lens group having a positive refractive power and the fifth lens group having a positive refractive power are arranged.

JP 2004-258229 A JP 2002-323656 A JP 2003-241092 A JP 2007-114432 A JP 2004-212611 A JP 2009-155891 A JP 2010-237453 A Japanese Patent Laid-Open No. 11-64732

  In recent years, as the number of pixels has increased, there has been a problem that image blur due to camera shake or the like that occurs during shutter release tends to be noticeable. Accordingly, it is known that a lens system with little image deterioration is used for image blur correction even if some lenses constituting the lens system are shifted in a direction substantially perpendicular to the optical axis. Specifically, image blur is generated by shifting the lens, and image blur caused by camera blur or the like is canceled. As an invention related to this, for example, a zoom lens described in Japanese Patent Application Laid-Open No. 2004-212611 is known. In the zoom lens described in Patent Document 5, the lens in the vicinity of the aperture stop is shifted. In this case, since the passing ranges of the on-axis light beam and the off-axis light beam overlap, generation of coma aberration generated at the time of image shift occurs. It was difficult to correct. On the other hand, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-258229), in a positive / negative / positive / positive four-group zoom lens, a part of the fourth lens group which is the final lens group away from the aperture stop is substantially set on the optical axis. There has been proposed an optical system in which deterioration in optical performance caused during image shift is reduced by shifting in the vertical direction.

  However, when an image shift lens is disposed in the final lens group away from the stop, the lens diameter becomes substantially the same as the diagonal length of the screen, and driving the lens becomes difficult as the diagonal length of the screen increases. In addition, in the interchangeable lens camera, a mount for connecting the body and the lens is interposed, which restricts the diameter and position of the final lens group. For this reason, there are very few concrete proposals of the type which arrange | positions the lens for image shift to the last lens group. In the zoom lens described in Patent Document 1, the lens configuration of the fourth lens group is not appropriate.

  An object of the present disclosure is to provide a variable focal length lens system and an imaging apparatus capable of image shift while suppressing a decrease in optical performance.

A variable focal length lens system according to the present disclosure 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, and a third lens group having a negative refractive power. A fourth lens group having a positive refractive power and a fifth lens group having a positive refractive power are disposed, and an aperture stop is disposed on the image side of the third lens group. When the lens position state 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 changes, The first to fifth lens groups move so that the distance between the third lens group and the fourth lens group decreases and the distance between the fourth lens group and the fifth lens group decreases. The second lens group has a cemented lens, and the fifth lens group is arranged in order from the object side on the image side with respect to the first sub-lens group composed of a biconvex positive lens and the first sub-lens group. The second sub-lens group consisting of a negative lens with a concave surface facing the object side and a biconvex positive lens, and shifting the first sub-lens group in a direction perpendicular to the optical axis, Image shift is possible, and the following conditional expression is satisfied.
0.6 <Da / fw <0.9 (1)
-0.3 <fw / R23 <-0.05 (7)
However,
Da: Distance along the optical axis from the aperture stop in the wide-angle end state to the lens surface closest to the object side of the first sub lens unit
fw: focal length of the entire lens system in the wide-angle end state
R23: The radius of curvature of the object-side lens surface of the cemented lens in the second lens group .

  An imaging apparatus according to the present disclosure includes a variable focal length lens system and an imaging element that outputs an imaging signal corresponding to an optical image formed by the variable focal length lens system, and the variable focal length lens system according to the present disclosure. This is constituted by a variable focal length lens system.

  In the variable focal length lens system or the imaging apparatus according to the present disclosure, the fifth lens group includes a first sub lens group and a second sub lens group, and the first sub lens group is arranged in a direction perpendicular to the optical axis. Image shifting is performed by shifting.

  According to the variable focal length lens system or the imaging apparatus of the present disclosure, since the lens group that performs image shift is optimized, the image shift can be performed while suppressing a decrease in optical performance.

It is explanatory drawing which showed the refractive power arrangement | positioning of each lens group in the variable focal length lens system which concerns on one embodiment of this indication with the mode of the movement of each lens group in the case of zooming. 1 is a lens cross-sectional view illustrating a first configuration example of a variable focal length lens system according to an embodiment of the present disclosure and corresponding to Numerical Example 1. FIG. FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, distortion and lateral aberration in the wide-angle end state at an object distance of infinity of the variable focal length lens system corresponding to Numerical Example 1. FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, distortion and lateral aberration in the first intermediate focal length state at an infinite object distance of the variable focal length lens system corresponding to Numerical Example 1. FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, distortion and lateral aberration in the second intermediate focal length state at an object distance of infinity of the variable focal length lens system corresponding to Numerical Example 1. FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, distortion and lateral aberration in the telephoto end state at an object distance of infinity of the variable focal length lens system corresponding to Numerical Example 1. FIG. 6 is an aberration diagram showing lateral aberration at the time of image blur correction in the wide-angle end state at an infinite object distance of the variable focal length lens system corresponding to Numerical Example 1. FIG. 6 is an aberration diagram showing lateral aberration when correcting image blur in the first intermediate focal length state at an infinite object distance of the variable focal length lens system corresponding to Numerical Example 1. FIG. 6 is an aberration diagram showing lateral aberration at the time of image blur correction in the second intermediate focal length state at an object distance of infinity of the variable focal length lens system corresponding to Numerical Example 1. FIG. 6 is an aberration diagram showing lateral aberration when correcting image blur in the telephoto end state at an object distance of infinity of the variable focal length lens system corresponding to Numerical Example 1. 2 is a lens cross-sectional view illustrating a second configuration example of a variable focal length lens system and corresponding to Numerical Example 2. FIG. FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, distortion and lateral aberration in the wide-angle end state at an object distance of infinity of the variable focal length lens system corresponding to Numerical Example 2. FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral aberration in the first intermediate focal length state at an infinite object distance of the variable focal length lens system corresponding to Numerical Example 2. FIG. 9 is an aberration diagram showing spherical aberration, astigmatism, distortion and lateral aberration in the second intermediate focal length state at an object distance of infinity of the variable focal length lens system corresponding to Numerical Example 2. FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, distortion and lateral aberration in the telephoto end state at an object distance of infinity of the variable focal length lens system corresponding to Numerical Example 2. FIG. 10 is an aberration diagram showing lateral aberration when correcting image blur in the wide-angle end state at an infinite object distance with the variable focal length lens system corresponding to Numerical Example 2. FIG. 10 is an aberration diagram showing lateral aberration at the time of image blur correction in a first intermediate focal length state at an infinite object distance of the variable focal length lens system corresponding to Numerical Example 2. FIG. 10 is an aberration diagram showing lateral aberration at the time of image blur correction in a second intermediate focal length state at an infinite object distance in the variable focal length lens system corresponding to Numerical Example 2. FIG. 12 is an aberration diagram showing lateral aberration when correcting image blur in the telephoto end state at an object distance of infinity of the variable focal length lens system corresponding to Numerical Example 2. FIG. 7 is a lens cross-sectional view illustrating a third configuration example of a variable focal length lens system and corresponding to Numerical Example 3; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, distortion and lateral aberration in the wide-angle end state at an object distance of infinity of the variable focal length lens system corresponding to Numerical Example 3. FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, distortion and lateral aberration in the first intermediate focal length state at an infinite object distance of the variable focal length lens system corresponding to Numerical Example 3. FIG. 11 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral aberration in the second intermediate focal length state at an object distance of infinity of the variable focal length lens system corresponding to Numerical Example 3. FIG. 9 is an aberration diagram showing spherical aberration, astigmatism, distortion and lateral aberration in the telephoto end state at an object distance of infinity of the variable focal length lens system corresponding to Numerical Example 3. FIG. 10 is an aberration diagram showing lateral aberration during image blur correction in the wide-angle end state at an object distance of infinity of the variable focal length lens system corresponding to Numerical Example 3. FIG. 10 is an aberration diagram showing lateral aberration at the time of image blur correction in the first intermediate focal length state at an infinite object distance of the variable focal length lens system corresponding to Numerical Example 3. FIG. 10 is an aberration diagram showing lateral aberration during image blur correction in a second intermediate focal length state at an infinite object distance of the variable focal length lens system corresponding to Numerical Example 3. FIG. 11 is an aberration diagram showing lateral aberration when correcting image blur in the telephoto end state at an object distance of infinity of the variable focal length lens system corresponding to Numerical Example 3. It is a block diagram which shows the example of 1 structure of an imaging device.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The description will be given in the following order.
1. 1. Basic configuration of lens 2. Functions of each lens group 3. Explanation of conditional expressions 4. Desirable configuration of each lens group 5. Application example to imaging device Numerical example of lens 7. Other embodiments

[1. Basic lens configuration]
FIG. 2 illustrates a first configuration example of a variable focal length lens system according to an embodiment of the present disclosure. This configuration example corresponds to the lens configuration of Numerical Example 1 described later. Note that FIG. 2 corresponds to the lens arrangement at the wide-angle end and when focusing on infinity. Similarly, FIG. 11 and FIG. 20 show cross-sectional configurations of second and third configuration examples corresponding to lens configurations of numerical examples 2 and 3 described later. 2, 11, and 20, the symbol Simg indicates an image plane. D5, D10, D12, and D18 indicate the surface intervals of the portions that change with zooming. Bf represents the back focus (distance from the final lens surface to the image plane Simg). Z1 represents an optical axis.

  The variable focal length lens system according to the present embodiment includes, in order from the object side along the optical axis Z1, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, Substantially five lens groups in which a third lens group G3 having a negative refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a positive refractive power are arranged. It consists of

  The fifth lens group G5 includes a first sub lens group GA and a second sub lens group GB arranged on the image side of the first sub lens group GA. The first sub lens group GA is an anti-vibration lens group, and image shift is possible by shifting in a direction substantially perpendicular to the optical axis Z1.

  The aperture stop S is disposed closer to the image side than the third lens group G3. In the variable focal length lens systems 1 to 3 according to the first to third configuration examples, an aperture stop S is disposed between the third lens group G3 and the fourth lens group G4.

  FIG. 1 shows the refractive power arrangement of each lens group along with the movement of each lens group during zooming. When the lens position changes from the wide-angle end state (W) where the focal length is the shortest to the telephoto end state (T) where the focal length is the longest, the distance D5 between the first lens group G1 and the second lens group G2 is The distance D10 between the second lens group G2 and the third lens group G3 is increased, the distance D12 between the third lens group G3 and the fourth lens group G4 is decreased, and the fourth lens group G4 and the fifth lens are increased. All lens groups are moved so that the distance D18 from the group G5 decreases.

[2. Functions of each lens group]
Next, the function of each lens group will be described. In the variable focal length lens system according to the present embodiment, the first lens group G1 and the second lens group G2 are arranged close to each other in the wide-angle end state, so that the off-axis light beam incident on the first lens group G1 It approaches the optical axis Z1. As a result, the lens diameter can be reduced. At the same time, when the lens position state changes from the wide-angle end state toward the telephoto end state, the axis passing through the first lens group G1 is increased by increasing the distance D5 between the first lens group G1 and the second lens group G2. The outer luminous flux is separated from the optical axis Z1. In the present embodiment, this change in height is used to satisfactorily correct off-axis aberration fluctuations associated with changes in lens position.

  Since the second lens group G2 and the third lens group G3 have negative refracting power, the off-axis light beam incident on the first lens group G1 is brought closer to the optical axis by being arranged close to some extent in the wide-angle end state. . When the lens position state changes from the wide-angle end state to the telephoto end state, the combined refractive power of the two lens groups is changed by changing the distance between the second lens group G2 and the third lens group G3. Thereby, the combined refractive power from the first lens group G1 to the third lens group G3 can be effectively changed.

  In the fourth lens group G4, the light beam diverged by the third lens group G3 is incident, so that an axial aberration is likely to occur, and is mainly responsible for correcting the axial aberration. Although the fifth lens group G5 has a role of forming an image of the light beam, in the present embodiment, in order to shorten the total lens length, the first lens group G5 is disposed on the object side and has a positive refractive power. The sub lens group GA and a second sub lens group GB which is disposed on the image side and has negative refractive power are configured.

Based on the above configuration, in the present embodiment, focusing on the following conditions [A] and [B], the first sub-lens group GA is shifted in a direction substantially perpendicular to the optical axis Z1. It suppresses the degradation of optical performance that occurs.
[A] Set an appropriate distance between the aperture stop S and the first sub-lens group GA. [B] Set an appropriate lateral magnification of the second sub-lens group GB.

  Conventionally, proposals have been made regarding zoom lenses in which the final lens group is shifted in a direction substantially perpendicular to the optical axis Z1. However, as described above, when the distance from the image plane is shortened, the diameter of the shift lens group is increased. Alternatively, in the interchangeable lens camera, the mount portion and the mechanical mechanism portion that drives the shift lens group interfere with each other. Therefore, in the present embodiment, by setting the second sub lens group GB to have a negative refractive power, the combined focal length of the first lens group G1 to the first sub lens group GA is positively small, that is, Strong positive refractive power. As a result, attention was paid to the fact that the lens diameter of the first sub-lens group GA can be reduced, and at the same time, the back focus of the entire lens system can be extended to reduce interference at the mount portion. In particular, the distance between the aperture stop S and the shift lens group is important for satisfactorily correcting fluctuations in coma aberration during image shift. Certainly, the longer the distance is, the more the axial aberration and the off-axis aberration can be corrected independently, but the lens diameter of the shift lens group increases. Also, it causes interference with the mount part. For this reason, the above condition [A] is focused.

The second sub-lens group GB has a function of enlarging an image formed by the first lens group G1 to the first sub-lens group GA. When the lateral magnification of the first sub lens group GA is βA and the lateral magnification of the second sub lens group GB is βB, the blur correction coefficient BA of the first sub lens group GA is
BA = (1-βA) · βB
Can be expressed as

  For this reason, when the lateral magnification βB of the second sub lens group GB becomes smaller (closer to 1), the blur correction coefficient becomes smaller, and the first sub lens group GA required for shifting the image by a predetermined amount is reduced. Increases the amount of movement. As a result, the performance change at the time of image shift becomes large.

Under the above conditions, the focus sensitivity of the first sub-lens group GA (change rate of the image plane position when moved in the optical axis direction by a minute amount) ΔB is ΔB = (1−βA ² ) · βB ²
Can be expressed as

  The first sub-lens group GA moves in a direction perpendicular to the optical axis Z1. However, since the positional deviation in the optical axis direction that occurs during driving is recorded as a focal deviation, it is important to set the focus sensitivity appropriately. It is. In the present embodiment, since the lateral magnification βB of the second sub-lens group GB is larger than 1, when the numerical value increases, the focus sensitivity ΔB increases in proportion to the square. For this reason, it is important to appropriately set the lateral magnification of the second sub lens group GB, and attention is paid to the above condition [B].

[3. Explanation of conditional expression]
Next, conditional expressions satisfied by the variable focal length lens system according to the present embodiment will be described.

The variable focal length lens system according to the present embodiment satisfies the following conditional expression (1).
0.6 <Da / fw <0.9 (1)
However,
Da: distance along the optical axis Z1 from the aperture stop S in the wide-angle end state to the lens surface closest to the object side of the first sub-lens group GA (see FIG. 2)
And

  Conditional expression (1) is a conditional expression that numerically limits the above condition [A]. If the lower limit value of conditional expression (1) is not reached, the off-axis light beam passing through the first sub-lens group GA approaches the optical axis, so that the change in off-axis aberration that occurs during image shift cannot be corrected well. . On the contrary, when the upper limit value of conditional expression (1) is exceeded, the off-axis light beam passing through the first sub-lens group GA and the second sub-lens group GB is separated from the optical axis Z1. As a result, the rear lens diameter is increased, and the light beam is blocked at the lens mount portion.

Note that it is desirable to reduce the weight of the first sub lens group GA in order to reduce the size of the lens barrel by reducing the lens driving mechanism during camera shake correction. In this case, it is desirable that the upper limit value of the conditional expression (1) is 0.85 as in the following conditional expression (1A) ′. In order to correct the change in off-axis aberration more favorably, it is preferable to set the lower limit value as in the following conditional expression (1B) ′. Furthermore, it is more preferable to set as the following conditional expression (1) ''.
0.6 <Da / fw <0.85 (1A) ′
0.7 <Da / fw <0.9 (1B) '
0.7 <Da / fw <0.85 (1) ''

It is desirable that the variable focal length lens system according to the present embodiment also satisfies the following conditional expression (2).
1.2 <β5B <1.7 (2)
However,
fw: focal length of the entire lens system in the wide-angle end state β5B: lateral magnification in the wide-angle end state of the second sub-lens group GB.

  Conditional expression (2) is a conditional expression that numerically limits the above condition [B]. When the lower limit value of conditional expression (2) is not reached, the blur correction coefficient of the first sub-lens group GA becomes small, and the performance change that occurs when the first sub-lens group GA is shifted is satisfactorily suppressed. Will not be able to. On the contrary, if the upper limit value of conditional expression (2) is exceeded, the stopping accuracy in the optical axis direction increases, and as a result, a focus shift occurs during photographing and a blurred image is recorded.

In order to obtain better optical performance, it is preferable to set the numerical range of the conditional expression (2) as the following conditional expression (2) ′, more preferably (2) ″.
1.2 <β5B <1.6 (2) ′
1.2 <β5B <1.5 (2) ''

In the present embodiment, in order to simplify the drive mechanism that shifts the first sub-lens group GA in a direction substantially perpendicular to the optical axis Z1, it is desirable that the sub-lens group GA is composed of one lens block. . Here, “one lens block” is a single lens or a cemented lens of a convex lens and a concave lens. At the same time, it is desirable to satisfy the following conditional expression (3) in order to suppress the performance change that occurs during the shift.
−0.4 <(R5A + R5B) / (R5A−R5B) <0 (3)
However,
R5A: radius of curvature of the lens surface closest to the object side of the first sub lens group GA R5B: radius of curvature of the lens surface closest to the image side of the first sub lens group GA.

  Conditional expression (3) is a conditional expression that prescribes the shape of the first sub-lens group GA. If the value is below the lower limit, coma aberration fluctuations that occur during shifting increase, and performance at the periphery of the screen during image shifting. Will drop significantly. On the other hand, when the value exceeds the upper limit value, the off-axis light beam passing through the second sub-lens group GB moves away from the optical axis, and as a result, a large amount of coma occurs at the periphery of the screen in the wide-angle end state. End up.

In order to obtain better optical performance, it is preferable to set the numerical range of the conditional expression (3) as the following conditional expression (3) ′.
−0.3 <(R5A + R5B) / (R5A−R5B) <0 (3) ′

In the present embodiment, it is desirable to satisfy the following conditional expression (4) for further miniaturization.
-0.25 <fw / f14w <0.15 (4)
However,
f14w: The combined focal length of the first to fourth lens groups in the wide-angle end state.

  Conditional expression (4) is a conditional expression that defines the combined focal length of the first to fourth lens units in the wide-angle end state. If the upper limit value of conditional expression (4) is exceeded, off-axis light beams that pass through the first lens group G1 and the second lens group G2 are separated from the optical axis Z1 in the wide-angle end state. The generated coma aberration cannot be corrected satisfactorily. On the other hand, if the lower limit value of conditional expression (4) is not reached, the total lens length in the wide-angle end state becomes large, and the lens system cannot be sufficiently miniaturized.

In order to obtain better optical performance, it is preferable to set the numerical range of the conditional expression (4) as the following conditional expression (4) ′, more preferably (4) ″.
−0.25 <fw / f14w <0.1 (4) ′
-0.25 <fw / f14w <0.05 (4) ''

In the present embodiment, it is desirable to satisfy the following conditional expression (5) in order to balance the reduction in size and performance of the first sub lens group GA.
0.2 <Da / Db <0.35 (5)
However,
Db: distance along the optical axis Z1 from the aperture stop S to the image plane Simg in the wide-angle end state (see FIG. 2)
And

  Conditional expression (5) is a conditional expression that defines where the first sub lens group GA is located between the aperture stop S and the image plane position. When the upper limit value of conditional expression (5) is exceeded, the first sub lens group GA is located on the image side. For this reason, the off-axis light beam passing through the first sub-lens group GA is separated from the optical axis Z1, and as a result, the first sub-lens group GA cannot be sufficiently reduced in size. Conversely, when the lower limit value of conditional expression (5) is not reached, the off-axis light beam passing through the first sub lens group GA approaches the optical axis Z1. As a result, it becomes difficult to independently correct the on-axis aberration and the off-axis aberration, and it becomes difficult to sufficiently improve the optical performance in the peripheral portion of the screen.

In order to achieve higher performance, it is preferable to set the numerical range of the conditional expression (5) as the following conditional expression (5A) ′ or (5B) ′.
0.2 <Da / Db <0.3 (5A) '
Or
0.25 <Da / Db <0.35 (5B) ′

Furthermore, it is more preferable to set as the following conditional expression (5) ″.
0.25 <Da / Db <0.3 (5) ''

By the way, in the present embodiment, the second lens group G2 that has conventionally been constituted by one lens group is divided into two lens groups (second lens group G2 and third lens group G3). By utilizing this separation and moving the third lens group G3 at the time of focusing at a short distance, it is possible to compensate for variations in the image plane position due to the subject. In particular, in order to reduce the lens diameter of the first lens group G1 and to form the third lens group G3 with one lens, it is desirable to satisfy the following conditional expression (6).
−0.7 <fw / f12w <−0.35 (6)
However,
f12w: The combined focal length of the first lens group G1 and the second lens group G2 in the wide-angle end state.

  Conditional expression (6) is a conditional expression that defines the combined focal length of the first lens group G1 and the second lens group G2 in the wide-angle end state. If the upper limit value of conditional expression (6) is exceeded, the off-axis light beam incident on the first lens group G1 in the wide-angle end state moves away from the optical axis Z1, and the lens diameter increases. In addition, since the refractive power of the third lens group G3 increases positively and negatively in order to ensure a predetermined back focus, the positive spherical aberration generated in the third lens group G3 can be favorably corrected regardless of the zoom position. It will be difficult. If the lower limit value of conditional expression (6) is not reached, the amount of movement of the third lens group G3 becomes very large at the time of focusing at a short distance, so that the first lens group G1 and the aperture stop S are The interval of will spread. As a result, the lens diameter of the first lens group G1 is increased, and a large amount of coma occurs at the periphery of the screen.

In order to achieve higher performance, it is preferable to set the numerical range of the conditional expression (6) as the following conditional expression (6A) ′ or (6B) ′.
−0.7 <fw / f12w <−0.4 (6A) ′
Or
−0.6 <fw / f12w <−0.35 (6B) ′

Furthermore, it is more preferable to set as the following conditional expression (6) ″.
-0.6 <fw / f12w <-0.4 (6) ''

  In the present embodiment, in order to achieve both size reduction and high performance, the second lens group G2 includes, in order from the object side, a negative lens L21 having a concave surface directed toward the image side, and a junction between the negative lens and the positive lens. It is desirable that the lens L22 be configured. In particular, in the present embodiment, the negative lens L21 disposed on the object side mainly corrects curvature of field, and the cemented lens L22 disposed on the image side mainly corrects spherical aberration. The correction function is separated. As a result, it can be configured with a small number of lenses, and high performance can be achieved. Furthermore, the negative lens L21 disposed closest to the object side of the second lens group G2 is an aspherical lens, so that it is possible to satisfactorily correct coma variation due to a change in the angle of view in the wide-angle end state. It is.

In order to better correct the curvature of field in the wide-angle end state and improve the performance, it is desirable to satisfy the following conditional expression (7).
-0.3 <fw / R23 <-0.05 (7)
However,
R23: The radius of curvature of the object-side lens surface of the cemented lens L22 in the second lens group G2.

  Conditional expression (7) defines the shape of the cemented lens L22 in G2. If the lower limit value of conditional expression (7) is not reached, it will be difficult to sufficiently correct the curvature of field in the wide-angle end state. On the contrary, when the upper limit value of conditional expression (7) is exceeded, the off-axis light beam passing through the first lens group G1 is further away from the optical axis Z1, and the coma aberration generated at the periphery of the screen cannot be corrected sufficiently. High performance cannot be achieved.

In order to further improve the performance, it is preferable to set the numerical range of the conditional expression (7) as the following conditional expression (7A) ′ or (7B) ′.
−0.3 <fw / R23 <−0.1 (7A) ′
Or
−0.25 <fw / R23 <−0.05 (7B) ′

Furthermore, it is more preferable to set as the following conditional expression (7) ″.
-0.25 <fw / R23 <-0.1 (7) ''

  As described above, according to the present embodiment, since the lens group that performs image shift is optimized, image shift can be performed while suppressing a decrease in optical performance. In particular, an optimum image shift is possible for a lens having an angle of view of about 70 to 80 degrees at the wide-angle end state, a zoom ratio of about 5 times, and an F value of about F2.8 to 4 at the wide-angle end state.

[4. Desirable configuration of each lens group]
In the present embodiment, in order to achieve both high optical performance and downsizing, it is desirable to configure each lens group as follows.

  In the present embodiment, in order to achieve higher performance, the first lens group G1 is arranged in order from the object side, a cemented lens L11 including a negative lens and a positive lens, and one positive lens arranged on the image side. It is desirable that the lens L12 be configured. In the first lens group G1, particularly in the telephoto end state, the axial light beam is incident with a wide light beam diameter, and therefore, negative spherical aberration is likely to occur. In addition, since off-axis light flux is incident away from the optical axis, off-axis aberration is likely to occur. In the present embodiment, the negative spherical aberration and the longitudinal chromatic aberration are favorably corrected by disposing the cemented lens L11 of the negative lens and the positive lens on the most object side of the first lens group G1. The single positive lens L12 arranged on the image side of the cemented lens L11 mainly corrects the coma variation due to the change in the angle of view, and the function of each lens is clarified. Performance can be realized. In order to further improve the performance, it is desirable that the cemented lens L11 in the first lens group G1 is composed of two lenses, which are a negative lens and a positive lens.

  The third lens group G3 is disposed in the vicinity of the aperture stop S and mainly corrects spherical aberration. In addition, it is desirable that the third lens group G3 moves so as to compensate for variations in image plane position due to changes in the subject distance. In particular, in order to increase the speed of the autofocus operation, it is desirable that the third lens group G3 is composed of one negative lens L3 to be aspherical.

  The fourth lens group G4 is preferably composed of a biconvex positive lens L41 and a cemented lens L42 composed of a biconvex positive lens and a biconcave negative lens. In the present embodiment, in order to shorten the total lens length, the negative lens is disposed on the most image side of the fourth lens group G4. At the same time, in order to correct negative spherical aberration, it is desirable that the positive lens L41 disposed on the object side be an aspherical surface.

  In order to better suppress the occurrence of chromatic aberration, it is desirable to use a glass material with high anomalous dispersion for the first lens group G1. In particular, among the lenses constituting the first lens group G1, the positive lens in the cemented lens L11 is made of a glass material having high anomalous dispersion, so that the secondary dispersion generated at the center of the screen in the telephoto end state is corrected well. can do. In order to satisfactorily correct chromatic aberration in the wide-angle end state, it is desirable to use a glass material having high anomalous dispersion in the fourth lens group G4 and the fifth lens group G5.

  It is of course possible to arrange a low-pass filter on the image side of the lens system in order to prevent the occurrence of moire fringes or an infrared cut filter according to the spectral sensitivity characteristics of the light receiving element.

[5. Application example to imaging device]
FIG. 29 shows a configuration example of the imaging apparatus 100 to which the variable focal length lens system according to the present embodiment is applied. The imaging device 100 is, for example, a digital still camera, and includes a camera block 10, a camera signal processing unit 20, an image processing unit 30, an LCD (Liquid Crystal Display) 40, and an R / W (reader / writer) 50. , A CPU (Central Processing Unit) 60, an input unit 70, and a lens drive control unit 80 .

  The camera block 10 has an imaging function, and includes an optical system including a lens system 11 (for example, the variable focal length lens system 1 shown in FIG. 2) as an imaging lens, a CCD (Charge Coupled Devices), and a CMOS (Complementary). And an imaging device 12 such as a metal oxide semiconductor. The imaging element 12 outputs an imaging signal (image signal) corresponding to the optical image by converting the optical image formed by the lens system 11 into an electrical signal.

  The camera signal processing unit 20 performs various signal processing such as analog-digital conversion, noise removal, image quality correction, and conversion to luminance / color difference signals on the image signal output from the image sensor 12.

  The image processing unit 30 performs recording and reproduction processing of an image signal, and 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. It has become.

  The LCD 40 has a function of displaying various data such as an operation state of the user input unit 70 and a photographed image. The R / W 50 performs writing of the image data encoded by the image processing unit 30 to the memory card 1000 and reading of the image data recorded on the memory card 1000. 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.

  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 various switches that are operated by a user, and includes, for example, a shutter release button for performing a shutter operation, a selection switch for selecting an operation mode, and the like. An instruction input signal corresponding to the above is output to the CPU 60. The lens drive control unit 80 controls driving of the lenses arranged in the camera block 10 and controls a motor (not shown) that drives each lens of the lens system 11 based on a control signal from the CPU 60. It has become.

  Although not shown, the imaging apparatus 100 includes a shake detection unit that detects a shake of the apparatus due to a camera shake.

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. For example, when an instruction input signal for zooming or focusing is input from the input unit 70, the CPU 60 outputs a control signal to the lens drive control unit 80, and the lens system 11 is controlled based on the control of the lens drive control unit 80. The predetermined lens moves.

  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 digital data in data format. The converted data is output to the R / W 50 and written to the memory card 1000.

Note that 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 70 is half-pressed or when it is fully pressed for recording (photographing). This is performed by moving a predetermined lens of the 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 response to 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.

  Further, the CPU 60 operates the lens drive control unit 80 based on a signal output from a shake detection unit (not shown), and moves the anti-vibration lens group in a direction substantially perpendicular to the optical axis Z1 according to the shake amount. .

  In the above-described embodiment, an example in which the imaging device is applied to a digital still camera has been described. However, the application range of the imaging device is not limited to a digital still camera, and other various electronic devices can be used as imaging devices. You may make it make it 100 specific object. For example, various other electronic devices such as an interchangeable lens camera, a digital video camera, a mobile phone incorporating a digital video camera, and a PDA (Personal Digital Assistant) are specifically targeted for the imaging apparatus 100. May be.

<6. Numerical Examples of Lens>
Next, specific numerical examples of the variable focal length lens system according to the present embodiment will be described.
In addition, the meanings of symbols shown in the following tables and descriptions are as shown below. “Surface number” indicates the number of the i-th surface that is numbered sequentially so as to increase toward the image side, with the surface of the component closest to the object side being the first. The “curvature radius” indicates a value (mm) of the paraxial curvature radius of the i-th surface. “Surface spacing” indicates the distance (mm) on the optical axis between the i-th surface and the (i + 1) -th surface. “Refractive index” indicates the value of the refractive index at the d-line (wavelength 587.6 nm) of the material of the optical element having the i-th surface. “Abbe number” indicates the value of the Abbe number in the d-line of the material of the optical element having the i-th surface. Bf represents the back focus (distance from the final lens surface to the image plane Simg).

The portion where the value of “curvature radius” is 0 indicates a flat surface or a diaphragm surface. The surface with “*” in the surface number is an aspherical surface. The aspherical shape is a shape represented by the following equation. In the aspheric coefficient data, the symbol “E” indicates that the next numerical value is a “power exponent” with a base of 10, and the numerical value represented by an exponential function with the base 10 is “E”. Indicates that the number before “is multiplied. For example, “1.0E-05” indicates “1.0 × 10 ⁻⁵ ”.

(Aspherical formula)
^{x = cy 2 / (1+ (} 1- (1 + k) c 2 y 2) 1/2) + Ay 4 + By 6 + ...

  Where y is the height from the optical axis Z1, x is the amount of sag, c is the curvature, k is the conic constant, and A, B,.

(Configuration common to each numerical example)
The variable focal length lens systems 1 to 3 according to the following numerical examples all have a first lens group G1 having a positive refractive power and a negative refractive power in order from the object side along the optical axis Z1. The second lens group G2, the third lens group G3 having negative refractive power, the fourth lens group G4 having positive refractive power, and the fifth lens group G5 having positive refractive power are disposed. The lens is substantially composed of five lens groups. The fifth lens group G5 includes, in order from the object side, a first sub lens group GA and a second sub lens group GB. Image shifting is possible by shifting the first sub-lens group GA in a direction substantially perpendicular to the optical axis Z1.

  The first lens group G1, in order from the object side, is a cemented lens L11 including a negative meniscus lens having a convex surface facing the object side and a positive lens having a convex surface facing the object side, and a meniscus shape having a convex surface facing the object side. It comprises a positive lens L12. The second lens group G2 includes, in order from the object side, a meniscus negative lens L21 having a convex surface directed toward the object side, and a negative cemented lens L22 including a biconcave negative lens and a biconvex positive lens. ing. The third lens group G3 includes a meniscus negative lens L3 having a concave surface directed toward the object side. The fourth lens group G4 includes a biconvex positive lens L41 and a cemented lens L42 including a biconvex lens and a biconcave lens. The fifth lens group G5 includes a biconvex positive lens L51, a meniscus negative lens L52 having a concave surface directed toward the object side, and a biconvex positive lens L53. The first sub lens group GA is composed of a positive lens L51, and the second sub lens group GB is composed of a negative lens L52 and a positive lens L53. The aperture stop S is disposed between the third lens group G3 and the fourth lens group G4, and moves integrally with the fourth lens group G4 when the lens position state changes.

[Numerical Example 1]
[Table 1] to [Table 3] show specific lens data corresponding to the variable focal length lens system 1 according to the first configuration example shown in FIG. In particular, [Table 1] shows the basic lens data, and [Table 2] shows data related to the aspherical surface. [Table 3] shows other data. In the variable focal length lens system 1 according to Numerical Example 1, since the first to fifth lens groups move with zooming, the value of the surface interval before and after each lens group is variable. . The data of this variable surface interval is shown in [Table 3]. [Table 3] also shows the focal length, half angle of view, and F number of the entire system in each zoom range.

  In Numerical Example 1, the ninth surface, the fourteenth surface, the fifteenth surface, the twenty-second surface, the twenty-third surface, and the twenty-fourth surface are aspherical surfaces.

  [Table 4] shows the shift amount of the first sub lens group GA at the time of image blur correction of 0.5 degrees.

  [Table 5] shows values related to the above conditional expressions. As can be seen from [Table 5], the variable focal length lens system 1 according to Numerical Example 1 satisfies the values of the conditional expressions.

  The aberration performance of the variable focal length lens system 1 according to Numerical Example 1 is shown in FIGS. Each aberration is the one when focusing on infinity. 3 and 7 show aberrations at the wide-angle end. 4 and 8 show aberrations at the first intermediate focal length. 5 and 9 show aberrations at the second intermediate focal length. 6 and 10 show aberrations at the telephoto end.

  3 to 6 show spherical aberration, astigmatism, distortion (distortion aberration), and lateral aberration as aberration diagrams. 7 to 10 show lateral aberrations at the time of image blur correction. Each of these aberration diagrams shows aberrations with the d-line (587.6 nm) as a reference wavelength. In the astigmatism diagram, the solid line indicates the sagittal direction, and the broken line indicates the meridional direction. In the lateral aberration diagram, A represents the angle of view, and y represents the image height.

  As can be seen from the above aberration diagrams, it is clear that various aberrations are well corrected and have excellent imaging performance.

[Numerical Example 2]
[Table 6] - [Table 8] show specific lens data corresponding to the variable focal length lens system 2 according to the second configuration example shown in FIG. 11. In particular, [Table 6] shows the basic lens data, and [Table 7] shows data related to the aspherical surface. [Table 8] shows other data. In the variable focal length lens system 2 according to Numerical Example 2, since the first to fifth lens groups move with zooming, the value of the surface interval before and after each lens group is variable. . The data of this variable surface interval is shown in [Table 8]. [Table 8] also shows the focal length, half angle of view, and F number of the entire system in each zoom range.

  In Numerical Example 2, the sixth surface, the eleventh surface, the twelfth surface, the nineteenth surface, the twentieth surface, and the twenty-second surface are aspherical surfaces.

  [Table 9] shows the shift amount of the first sub lens group GA at the time of image blur correction of 0.5 degrees.

  [Table 10] shows values related to the above conditional expressions. As can be seen from [Table 10], the variable focal length lens system 2 according to Numerical Example 2 satisfies the values of the conditional expressions.

  The aberration performance of the variable focal length lens system 2 according to Numerical Example 2 is shown in FIGS. Each aberration is the one when focusing on infinity. 12 and 16 show aberrations at the wide-angle end. 13 and 17 show aberrations at the first intermediate focal length. 14 and 18 show aberrations at the second intermediate focal length. 15 and 19 show aberrations at the telephoto end.

  12 to 15 show spherical aberration, astigmatism, distortion (distortion aberration), and lateral aberration as aberration diagrams. 16 to 19 show lateral aberrations at the time of image blur correction. Each of these aberration diagrams shows aberrations with the d-line (587.6 nm) as a reference wavelength. In the astigmatism diagram, the solid line indicates the sagittal direction, and the broken line indicates the meridional direction. In the lateral aberration diagram, A represents the angle of view, and y represents the image height.

  As can be seen from the above aberration diagrams, it is clear that various aberrations are well corrected and have excellent imaging performance.

[Numerical Example 3]
[Table 11] to [Table 13] show specific lens data corresponding to the variable focal length lens system 3 according to the third configuration example shown in FIG. 20. In particular, [Table 11] shows the basic lens data, and [Table 12] shows data related to the aspherical surface. [Table 13] shows other data. In the variable focal length lens system 3 according to Numerical Example 3, each of the first to fifth lens groups moves with zooming, so that the value of the surface interval before and after each lens group is variable. . The variable surface spacing data is shown in [Table 13]. [Table 11] also shows the focal length, half angle of view, and F number of the entire system in each zoom range.

  In Numerical Example 3, the ninth surface, the fourteenth surface, the fifteenth surface, the twenty-second surface, the twenty-third surface, and the twenty-fourth surface are aspherical surfaces.

  [Table 14] shows the shift amount of the first sub lens group GA at the time of image blur correction of 0.5 degrees.

  [Table 15] shows values related to each conditional expression described above. As can be seen from [Table 15], the variable focal length lens system 3 according to Numerical Example 3 satisfies the values of the conditional expressions.

  The aberration performance of the variable focal length lens system 3 according to Numerical Example 3 is shown in FIGS. Each aberration is the one when focusing on infinity. 21 and 25 show aberrations at the wide angle end. 22 and 26 show aberrations at the first intermediate focal length. 23 and 27 show aberrations at the second intermediate focal length. 24 and 28 show aberrations at the telephoto end.

  FIGS. 21 to 24 show spherical aberration, astigmatism, distortion (distortion aberration), and lateral aberration as aberration diagrams. 25 to 28 show lateral aberrations at the time of image blur correction. Each of these aberration diagrams shows aberrations with the d-line (587.6 nm) as a reference wavelength. In the astigmatism diagram, the solid line indicates the sagittal direction, and the broken line indicates the meridional direction. In the lateral aberration diagram, A represents the angle of view, and y represents the image height.

  As can be seen from the above aberration diagrams, it is clear that various aberrations are well corrected and have excellent imaging performance.

<7. Other Embodiments>
The technology according to the present disclosure is not limited to the description of the above-described embodiments and examples, and various modifications can be made.
For example, the shapes and numerical values of the respective parts shown in the numerical examples are merely examples of embodiments for carrying out the present technology, and the technical scope of the present technology is interpreted in a limited manner by these. There should be no such thing.

  In the above-described embodiments and examples, the configuration including substantially five lens groups has been described. However, the configuration may further include a lens having substantially no refractive power.

For example, this technique can take the following composition.
[1]
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 negative refractive power, and a fourth lens having a positive refractive power A group and a fifth lens group having a positive refractive power, and an aperture stop is disposed closer to the image side than the third lens group,
When the lens position state 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 increases. The first to fifth lenses change so that the distance between the third lens group and the fourth lens group decreases and the distance between the fourth lens group and the fifth lens group decreases. The group moves,
The fifth lens group includes a first sub-lens group and a second sub-lens group disposed closer to the image side than the first sub-lens group.
By shifting the first sub-lens group in a direction perpendicular to the optical axis, image shift is possible,
Variable focal length lens system that satisfies the following conditional expression.
0.6 <Da / fw <0.9 (1)
However,
Da: A distance along the optical axis from the aperture stop in the wide-angle end state to the lens surface closest to the object side of the first sub lens unit.
[2]
The variable focal length lens system according to [1], wherein the following conditional expression is satisfied.
1.2 <β5B <1.7 (2)
However,
fw: focal length of the entire lens system in the wide-angle end state β5B: lateral magnification in the wide-angle end state of the second sub-lens group.
[3]
The variable focal length lens system according to [1] or [2], wherein the following conditional expression is satisfied.
−0.4 <(R5A + R5B) / (R5A−R5B) <0 (3)
However,
R5A: radius of curvature of the lens surface closest to the object side of the first sub lens group R5B: radius of curvature of the lens surface closest to the image side of the first sub lens group.
[4]
The variable focal length lens system according to [3], wherein the first sub-lens group includes one lens block.
[5]
The variable focal length lens system according to any one of [1] to [4], wherein the following conditional expression is satisfied.
-0.25 <fw / f14w <0.15 (4)
However,
f14w: The combined focal length of the first to fourth lens groups in the wide-angle end state.
[6]
The variable focal length lens system according to any one of [1] to [5], wherein the following conditional expression is satisfied.
0.2 <Da / Db <0.35 (5)
However,
Db: a distance along the optical axis from the aperture stop to the image plane in the wide-angle end state.
[7]
The variable focal length lens system according to any one of [1] to [6], wherein the following conditional expression is satisfied.
−0.7 <fw / f12w <−0.35 (6)
However,
f12w: The combined focal length of the first lens group and the second lens group in the wide-angle end state.
[8]
The variable focal length lens system according to any one of [1] to [7], wherein the second lens group includes a cemented lens and satisfies the following conditional expression:
-0.3 <fw / R23 <-0.05 (7)
However,
R23: The radius of curvature of the object-side lens surface of the cemented lens in the second lens group.
[9]
The variable focal length lens system according to any one of [1] to [8], further including a lens having substantially no refractive power.
[10]
A variable focal length lens system, and an imaging device that outputs an imaging signal corresponding to an optical image formed by the variable focal length lens system,
The variable focal length lens system 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 negative refractive power, and a fourth lens having a positive refractive power A group and a fifth lens group having a positive refractive power, and an aperture stop is disposed closer to the image side than the third lens group,
When the lens position state 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 increases. The first to fifth lenses change so that the distance between the third lens group and the fourth lens group decreases and the distance between the fourth lens group and the fifth lens group decreases. The group moves,
The fifth lens group includes a first sub-lens group and a second sub-lens group disposed closer to the image side than the first sub-lens group.
By shifting the first sub-lens group in a direction perpendicular to the optical axis, image shift is possible,
An imaging device that satisfies the following conditional expression.
0.6 <Da / fw <0.9 (1)
However,
Da: A distance along the optical axis from the aperture stop in the wide-angle end state to the lens surface closest to the object side of the first sub lens unit.
[11]
The imaging apparatus according to [10], wherein the variable focal length lens system further includes a lens having substantially no refractive power.

  G1 ... 1st lens group, G2 ... 2nd lens group, G3 ... 3rd lens group, G4 ... 4th lens group, G5 ... 5th lens group, GA ... 1st sub lens group, GB ... 2nd sub Lens group, S: Aperture stop, Simg: Image plane, Z1: Optical axis, 1, 2, 3 ... Variable focal length lens system, 10 ... Camera block, 11 ... Lens system, 12 ... Image sensor, 20 ... Camera signal processing 30: Image processing unit, 40: LCD, 50: R / W (reader / writer), 60: CPU, 70: Input unit, 80: Lens drive control unit, 100: Imaging device, 1000: Memory card.

Claims (9)

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 negative refractive power, and a fourth lens having a positive refractive power A group and a fifth lens group having a positive refractive power, and an aperture stop is disposed closer to the image side than the third lens group,
When the lens position state 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 increases. The first to fifth lenses change so that the distance between the third lens group and the fourth lens group decreases and the distance between the fourth lens group and the fifth lens group decreases. The group moves,
The second lens group includes a cemented lens;
The fifth lens group is arranged in order from the object side on the image side of the first sub-lens group composed of a biconvex positive lens and the first sub-lens group, and has a concave surface facing the object side. A second sub-lens group consisting of a negative lens and a biconvex positive lens ;
By shifting the first sub-lens group in a direction perpendicular to the optical axis, image shift is possible,
Variable focal length lens system that satisfies the following conditional expression.
0.6 <Da / fw <0.9 (1)
-0.3 <fw / R23 <-0.05 (7)
However,
Da: distance along the optical axis from the aperture stop in the wide-angle end state to the lens surface closest to the object side of the first sub-lens group
fw: focal length of the entire lens system in the wide-angle end state
R23: The radius of curvature of the object-side lens surface of the cemented lens in the second lens group . The variable focal length lens system according to claim 1, wherein the following conditional expression is satisfied.
1.2 <β5B <1.7 (2)
However ,
β5B: The lateral magnification of the second sub lens group in the wide-angle end state. The variable focal length lens system according to claim 1, wherein the following conditional expression is satisfied.
−0.4 <(R5A + R5B) / (R5A−R5B) <0 (3)
However,
R5A: radius of curvature of the lens surface closest to the object side of the first sub lens group R5B: radius of curvature of the lens surface closest to the image side of the first sub lens group. The variable focal length lens system according to any one of claims 1 to 3 , wherein the following conditional expression is satisfied.
-0.25 <fw / f14w <0.15 (4)
However,
f14w: The combined focal length of the first to fourth lens groups in the wide-angle end state. The variable focal length lens system according to any one of claims 1 to 4 , wherein the following conditional expression is satisfied.
0.2 <Da / Db <0.35 (5)
However,
Db: a distance along the optical axis from the aperture stop to the image plane in the wide-angle end state. The variable focal length lens system according to any one of claims 1 to 5 , wherein the following conditional expression is satisfied.
−0.7 <fw / f12w <−0.35 (6)
However,
f12w: The combined focal length of the first lens group and the second lens group in the wide-angle end state. The variable focal length lens system according to any one of claims 1 to 6 , further comprising a lens having substantially no refractive power. A variable focal length lens system, and an imaging device that outputs an imaging signal corresponding to an optical image formed by the variable focal length lens system,
The variable focal length lens system 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 negative refractive power, and a fourth lens having a positive refractive power A group and a fifth lens group having a positive refractive power, and an aperture stop is disposed closer to the image side than the third lens group,
When the lens position state 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 increases. The first to fifth lenses change so that the distance between the third lens group and the fourth lens group decreases and the distance between the fourth lens group and the fifth lens group decreases. The group moves,
The second lens group includes a cemented lens;
The fifth lens group is arranged in order from the object side on the image side of the first sub-lens group composed of a biconvex positive lens and the first sub-lens group, and has a concave surface facing the object side. A second sub-lens group consisting of a negative lens and a biconvex positive lens ;
By shifting the first sub-lens group in a direction perpendicular to the optical axis, image shift is possible,
An imaging device that satisfies the following conditional expression.
0.6 <Da / fw <0.9 (1)
-0.3 <fw / R23 <-0.05 (7)
However,
Da: distance along the optical axis from the aperture stop in the wide-angle end state to the lens surface closest to the object side of the first sub-lens group
fw: focal length of the entire lens system in the wide-angle end state
R23: The radius of curvature of the object-side lens surface of the cemented lens in the second lens group . The imaging apparatus according to claim 8 , wherein the variable focal length lens system further includes a lens having substantially no refractive power.

Images