JP2008170874A - Zoom lens and imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact-sized zoom lens which is suitable for a photographing optical system of digital input/output equipment such as digital still cameras and digital video cameras and has an about 10-times variable magnification ratio, and also provide an imaging device using the zoom lens. <P>SOLUTION: The zoom lens 1 comprises a plurality of lens groups GR1, GR2, GR3, GR4 and GR5, and its variable magnification is performed by changing spacings between the groups. In addition, the last lens group (the fifth lens group GR5), which is arranged at the nearest position to an image side, is fixed in the optical axis direction when variable magnification is made and has a refractory power-variable optical element L14 whose refractory power varies when the variable magnification is made. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a novel zoom lens and an imaging apparatus. Specifically, the present invention relates to a compact zoom lens having a high zoom ratio suitable for a photographing optical system of a digital input / output device such as a digital still camera or a digital video camera, and an imaging apparatus using the zoom lens.

  In recent years, an imaging apparatus using a solid-state imaging device such as a digital still camera has been spreading. With the widespread use of such digital still cameras, there is a need for higher image quality. Especially in digital still cameras with a large number of pixels, imaging with excellent imaging performance corresponding to a solid-state imaging device with a large number of pixels. There is a need for industrial lenses, particularly zoom lenses. In addition, there is a strong demand for miniaturization and a high zoom ratio, and there is a demand for a compact zoom lens with a large zoom ratio.

  In order to achieve miniaturization, an optical system is bent by inserting a prism between lenses to reduce the size in the direction of the incident optical axis. For example, in the optical system described in Patent Document 1, there is proposed a zoom lens that is downsized in the direction of the incident optical axis by bending the optical axis using a prism in a positive, negative, positive, four-group zoom configuration. .

  On the other hand, a method for optically correcting image blurring of a captured image caused by vibration of the imaging device such as camera shake by moving some optical elements in the lens group perpendicularly to the optical axis is proposed. Has been. For example, Patent Document 2 discloses a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, a fourth lens group having a positive refractive power, and a negative lens group. A zoom lens that corrects camera shake by moving a positive lens in the fifth lens group in a direction perpendicular to the optical axis has been proposed.

JP-A-8-248318 JP 2006-71993 A

  However, in the zoom lens described in Patent Document 1, the front lens diameter and the reflecting member are large, and the size reduction is not sufficient. In the zoom lens described in Patent Document 2, the zooming ratio is small because the zooming action of the lens group moving on the optical axis is small. Further, in the zoom lens described in Patent Document 2, the lens arranged closest to the image side is used as a blur correction lens, and the movement of the blur correction lens that moves in the direction perpendicular to the optical axis at the telephoto end as the zoom ratio increases. The amount increases, and the size of the optical system increases in the radial direction. This is because the optical axis is bent to reduce the size in the direction of the incident optical axis, so-called thinning, while increasing the diameter at the drive portion of the vibration reduction lens, and eventually hindering thinning. Become.

  The present invention has been made in view of the above-described problems, and is a compact zoom lens having a high zoom ratio of about 10 times suitable for a photographing optical system of a digital input / output device such as a digital still camera or a digital video camera. It is an object to provide an imaging apparatus using a zoom lens.

  A zoom lens according to an embodiment of the present invention is a zoom lens that includes a plurality of lens groups and performs zooming by changing a group interval, and is a final lens group disposed on the most image side among the plurality of lens groups. However, it is fixed in the optical axis direction at the time of zooming and has a refractive power variable optical element, and the refractive power of the refractive power variable optical element changes at the time of zooming.

  An imaging apparatus according to an embodiment of the present invention includes a zoom lens and an imaging element that converts an optical image formed by the zoom lens into an electrical signal, and the zoom lens includes a plurality of lens groups. A zoom lens that performs zooming by changing the group interval, and the final lens group arranged closest to the image side among the plurality of lens groups is fixed in the optical axis direction at the time of zooming and has a variable refractive power An optical element is included, and the refractive power of the variable refractive power optical element changes upon zooming.

  In this invention, it can comprise compactly and achieves the high zoom ratio of about 10 times.

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

  First, the zoom lens will be described.

  The zoom lens according to the present invention is a zoom lens that includes a plurality of lens groups and performs zooming by changing a group interval, and the final lens group arranged closest to the image side among the plurality of lens groups is at the time of zooming. In addition to being fixed in the optical axis direction, it has a refractive power variable optical element, and the refractive power of the variable refractive power optical element changes upon zooming.

  As a result, the whole can be made compact, and a high zoom ratio of about 10 times is achieved. That is, the refractive power of the refractive power variable optical element included in the final lens group generates a zooming action that cannot be performed only by movement of the plurality of lens groups on the optical axis, thereby enabling a high zooming ratio. . Furthermore, zooming in the final lens group has little effect on optical performance, and there is little aberration fluctuation due to zooming.

  Therefore, by adding a group including a refractive power variable optical element to the image side of a known zoom lens whose performance is sufficiently evaluated, it becomes possible to increase only the zoom ratio while maintaining the existing performance. Thus, it is possible to easily obtain a zoom lens with a high zoom ratio by utilizing the already acquired technical assets (lens design).

  As the refractive power variable optical element, for example, an element utilizing an electrocapillary phenomenon (electrowetting phenomenon) is applicable. For example, it is configured such that two conductive or polar liquids having different refractive powers and not mixed with each other are sealed in a sealed container, and a voltage can be applied between the liquids. There is a configuration in which the radius of curvature of the interface between two liquids is changed to change the direction of refraction of light passing across the interface between the two liquids.

In the zoom lens according to the embodiment of the present invention, it is preferable that the following conditional expression (1) is satisfied.
(1) 1.0 <βet / βew <2.0
However,
βew: lateral magnification at the wide-angle end of the final lens group βet: lateral magnification at the telephoto end of the final lens group.

  Conditional expression (1) defines the ratio between the lateral magnification at the wide-angle end and the lateral magnification at the telephoto end of the final lens group. If the lower limit of conditional expression (1) is not reached, the zooming action in the final lens group is lost and it is difficult to increase the magnification. When the upper limit value of conditional expression (1) is exceeded, it becomes difficult to correct peripheral coma and lateral chromatic aberration. In addition, when the aperture that defines the F number is disposed closer to the object side than the final lens group, the F number at the telephoto end becomes too large (dark) when the upper limit of conditional expression (1) is exceeded.

  In the zoom lens according to the embodiment of the present invention, the most object side lens group among the plurality of lens groups is fixed in position during zooming, and is a reflecting member for bending the optical axis by approximately 90 degrees. It is desirable to have This makes it possible to reduce the size in the direction of the incident optical axis, that is, to reduce the thickness.

  In addition, when using a prism for the reflection member for bending an optical axis, it is desirable to use a glass material with a high refractive index. This makes it possible to reduce the size of the reflecting member, which is advantageous for reducing the size of the entire zoom lens.

In the zoom lens according to an embodiment of the present invention, the final lens group includes a shift lens group that shifts an image by moving in a direction substantially orthogonal to the optical axis, and the refractive power variable optical element is the It is desirable that the lens is disposed on the image side from the shift lens group and satisfies the following conditional expression (2).
(2) 1.0 <bbT / bbW <2.0
However,
bbW: Lateral magnification at the wide-angle end of the lens unit located on the image side of the shift lens unit
bbT: The lateral magnification at the telephoto end of the lens unit located on the image side from the shift lens unit.

  Thereby, the influence on the optical performance due to the shift of the shift lens group can be reduced. In addition, the shift amount of the shift lens group can be reduced, thereby reducing the outer diameter of the drive unit for shifting the shift lens group, contributing to downsizing. In particular, when a reflecting member for bending the optical axis approximately 90 degrees is provided, it is possible to reduce the size in the direction of the incident optical axis, that is, to reduce the thickness, but in such a configuration, when the shift amount of the shift lens group increases, The size in the direction of the incident optical axis is increased, which is contrary to the reduction in thickness. Therefore, particularly in an optical system including a reflecting member, the effect of this embodiment is great.

  When the shift lens group is shifted in the direction perpendicular to the optical axis to correct image shift due to camera shake, generally, the shift amount of the shift lens group increases as the magnification ratio increases. However, when the magnification is changed on the image side of the shift lens group, the change in the magnification does not affect the shift amount of the shift lens group, and only the magnification on the object side of the shift lens group is shifted by the shift lens group. Affect the amount. Therefore, as in the present embodiment, by disposing the refractive power variable optical element on the image side from the shift lens group, the shift amount of the shift lens group can be reduced for the variable magnification.

  Conditional expression (2) defines the ratio between the lateral magnification at the wide-angle end and the lateral magnification at the telephoto end of the lens group located on the image side of the shift lens group. By satisfying conditional expression (2), the shift amount of the shift lens group for correcting the image blur can be reduced at the telephoto end where the image blur amount is large, and the drive device for shifting the shift lens group Can be miniaturized.

  If the lower limit value of conditional expression (2) is not reached, the shift amount of the shift lens group becomes large, making it difficult to reduce the size and thickness. If the upper limit value of conditional expression (2) is exceeded, it will be difficult to correct aberrations during shifting of the shift lens group.

  In the zoom lens according to an embodiment of the present invention, the plurality of lens groups includes a reflecting member arranged in order from the object side and configured to bend the optical axis by approximately 90 degrees, and has a positive refractive power. A first lens group whose position is fixed during zooming, a second lens group having negative refractive power and moving along the optical axis during zooming, and a position having positive refractive power during zooming A third lens group having a fixed refractive power, a fourth lens group that has positive refractive power and moves in the optical axis direction to correct a change in the position of the image plane upon zooming, and performs focusing. It is desirable that the fifth lens group (final lens group) has a refractive power and its position is fixed at the time of zooming. As a result, the size can be further reduced.

  The first lens group includes a reflecting member for bending the optical axis by 90 degrees, and by fixing the position, the first lens group can be reduced in the depth direction, that is, in the optical axis direction incident on the zoom lens. Become. More preferably, it is possible to reduce the space for bending the optical axis by disposing a negative lens on the object side of the reflecting member, or by configuring the reflecting member with a prism, and suitable for downsizing in the depth direction. It becomes.

  By using the first lens group and the third lens group as positive lens groups, and moving the negative second lens group along the optical axis during zooming, the zoom lens structure is small but suitable for high zooming. .

  By making the fifth lens group a negative lens group, the combined focal length from the first lens group to the fourth lens group can be shortened, and the configuration is suitable for downsizing the entire length, that is, downsizing in the height direction. Become.

  Furthermore, in the zoom lens having such a configuration, when the shift lens group that corrects image blur is arranged in the fifth lens group that is fixed in the optical axis direction, the driving mechanism for shifting and the optical axis of the movable lens group are arranged. Interference with the drive mechanism for movement in the direction can be avoided, and the configuration is preferable for downsizing in the depth direction.

  In the five-group zoom lens having such a configuration, when the refractive power variable optical element is disposed in the fifth lens group, the focal length is increased without increasing the movement amount of the second lens group and the fourth lens group as the moving lens group. Since the zoom lens can be changed, the zoom lens has a high zoom ratio without increasing its size in the entire length, that is, in the height direction (when the optical axis is bent up or down by a reflecting member that bends the optical axis by 90 °). It becomes possible. In addition, an increase in the shift amount of the shift lens group at the time of high zooming can be reduced, and the configuration is suitable for downsizing in the depth direction (when a reflecting member that bends the optical axis by 90 ° is provided).

  Further, since the fifth lens group having the refractive power variable optical element is a lens group fixed in the optical axis direction, a drive mechanism for moving the movable lens group in the optical axis direction and a mechanism for varying the refractive power; This is a preferable configuration for downsizing in the depth direction.

  In the zoom lens according to the embodiment of the present invention, focusing during short-distance shooting may be performed by changing the refractive power of the refractive power variable optical element. As a result, power consumption for driving the focusing lens can be reduced.

  In the zoom lens according to an embodiment of the present invention, it is more preferable to use an ND filter or a liquid crystal light control element instead of changing the aperture diameter for adjusting the light amount.

  In the zoom lens according to the embodiment of the present invention, it is desirable to correct a color shift generated at the time of camera shake correction by electrical signal processing. As a result, the lens load related to correction of chromatic aberration is reduced, the number of lenses can be reduced, and lens design is facilitated.

  Next, specific embodiments of the zoom lens 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.

  In each embodiment, an aspherical surface is introduced, and the aspherical shape is defined by the following equation (1).

Here, “Z” is the distance in the optical axis direction when the height from the optical axis between the tangential plane and the spherical surface at the apex of the aspheric surface is “H” (= √ (X ² + Y ² )), and “C” is non- It is assumed that the curvature of the spherical vertex (1 / r), “K” represents the conic constant, and “A2i” represents the second i-th aspherical coefficient.

  FIG. 1 is a diagram showing a lens configuration of a zoom lens 1 according to the first embodiment of the present invention. In FIG. 1, the upper stage shows the position on the optical axis of each lens group at the wide-angle end, and the lower stage at the telephoto end.

  The zoom lens 1 includes, in order from the object side, a first lens group GR1 having a positive refractive power, a second lens group GR2 having a negative refractive power, a third lens group GR3 having a positive refractive power, and a positive refractive power. And a fourth lens group GR4 having negative refractive power and a fifth lens group GR5 having negative refractive power are arranged.

  The first lens group GR1 includes, in order from the object side, a first lens L1 having a negative refractive power, a prism L2 as a reflecting member for bending the optical axis by 90 degrees, and a third lens L3 having a positive refractive power. The fourth lens L4 has a positive refractive power and both surfaces are aspherical, and the position on the optical axis is fixed during zooming. Bending the optical axis by 90 degrees with the prism L2 enables efficient downsizing in the incident optical axis direction. The second lens group GR2 includes, in order from the object side, a fifth lens L5 having negative refractive power, a cemented lens of the negative lens L6 and positive lens L7, and an eighth lens L8 having negative refractive power. During zooming from the wide-angle end to the telephoto end, it moves on the optical axis from the object side to the image side. The third lens group GR3 is composed of a positive lens L9 having both aspheric surfaces. The position on the optical axis is fixed during zooming. The fourth lens group GR4 includes a cemented lens of a positive lens L10 and a negative lens L11 each having an aspheric object side surface. The fourth lens group GR4 moves on the optical axis during zooming, and changes in image plane position during zooming. Correction and focusing during close-up shooting. The fifth lens group GR5 is hermetically sealed by a negative lens L12, which is positioned in order from the object side, a positive lens L13 that is a shift lens group for correcting image blur by moving perpendicularly to the optical axis direction, and a transparent parallel plate. The shape of the boundary refracting surface VS of two kinds of liquids with different refractive indexes filled in the liquid chamber is constituted by a liquid type refractive power variable optical element L14 that changes by applying a voltage. At the wide-angle end, the boundary refracting surface VS of the liquid is shaped to have a convex surface facing the object side, and at the time of zooming, the shape of the boundary refracting surface VS is continuously changed by controlling the applied voltage. The telephoto end has a concave surface facing the object side. That is, the refractive power of the liquid type variable refractive power optical element L14 has a positive refractive power at the wide-angle end and a negative refractive power at the telephoto end. Contribute. An iris IR for adjusting the amount of light is disposed on the image plane IMG side of the third lens group GR3, and a filter including an infrared cut filter and a low-pass filter is further disposed on the image plane IMG side of the fifth lens group GR5. FL is arranged. The image plane IMG is a light receiving surface of an image sensor such as a CCD (Charge Coupled Devices).

  Table 1 shows lens data of Numerical Example 1 in which specific numerical values are applied to the zoom lens 1 according to the first embodiment. In Table 1 and other lens data tables, “si” indicates the surface number of the i-th surface counted from the object side, and “ri” represents the radius of curvature of the i-th surface counted from the object side. "Di" indicates the axial upper surface distance between the i-th surface and the (i + 1) -th surface counted from the object side, and "ni" indicates the d-line of the i-th surface counted from the object side. The refractive index with respect to (wavelength 587.6 nm) is indicated, and “νi” indicates the Abbe number with respect to the d-line of the i-th surface counted from the object side. “INF” for “ri” indicates that the surface is a plane, “ASP” for “ri” indicates that the surface is an aspheric surface, and “variable” for “ri” indicates that the surface is aspheric. The curvature of the surface is variable, and “variable” for “di” indicates that the surface interval is a variable interval.

  During zooming from the wide-angle end to the telephoto end, the distance d8 between the first lens group GR1 and the second lens group GR2, the distance d15 between the second lens group GR2 and the third lens group GR3, the third lens The distance d18 between the group GR3 (aperture stop IR) and the fourth lens group GR4 and the distance d21 between the fourth lens group GR4 and the fifth lens group GR5 are changed. Accordingly, the values in the wide-angle end state (f = 5.00), the intermediate focal length state (f = 15.83), and the telephoto end state (f = 47.41) of the intervals in Numerical Example 1 are used as the focal length. Table 2 shows “f”, F number “Fno”, and half angle of view “ω (degrees)”. Note that the change in the distance between the front and rear of the boundary refracting surface VS of the refractive power variable optical element L14 is replaced with the radius of curvature (r28) of the boundary refracting surface VS.

Both surfaces (r7, r8) of the positive lens L4, both surfaces (r16, r17) of the positive lens L9, and the object side surface (r19) of the positive lens L10 are aspherical. Therefore, Table 3 shows the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients A4, A6, A8, and A10 of each surface in Numerical Example 1 together with the conic constant ε. In Table 3 and the following table showing aspherical coefficients, “E-i” represents an exponential expression with a base of 10, that is, “10- ⁱ ”. For example, “0.12345E-05” represents “ 0.12345 × 10 ⁻⁵ ”.

  2 to 4 show aberration diagrams of spherical aberration, astigmatism, and distortion of Numerical Example 1. FIG. 2 is in the wide-angle end state, FIG. 3 is in the intermediate focal length state, and FIG. 4 is in the telephoto end state. Each aberration diagram is shown in FIG. In the spherical aberration in each of the aberration diagrams of FIGS. 2 to 4, the solid line indicates the value for the d line, the broken line indicates the value for the C line (wavelength 656.3 nm), and the alternate long and short dash line indicates the value for the g line (wavelength 435.8 nm). The values for the d-line are shown in the point aberration diagram and the distortion diagram. In the graph showing astigmatism, the solid line indicates the value on the sagittal image plane, and the broken line indicates the value on the meridional image plane.

  It is clear that Numerical Example 1 has excellent imaging performance from each aberration diagram.

  FIG. 5 is a diagram showing a lens configuration of the zoom lens 2 according to the second embodiment of the present invention. In FIG. 2, the upper stage shows the position on the optical axis of each lens group at the wide-angle end, and the lower stage at the telephoto end.

  The zoom lens 2 includes, in order from the object side, a first lens group GR1 having a positive refractive power, a second lens group GR2 having a negative refractive power, a third lens group GR3 having a positive refractive power, and a positive refractive power. And a fourth lens group GR4 having negative refractive power and a fifth lens group GR5 having negative refractive power are arranged.

  The first lens group GR1 includes a first lens L1 having a negative refractive power, which is positioned in order from the object side, a prism L2 as a reflecting member for bending the optical axis by 90 degrees, and a positive refractive power that has both surfaces non-reflective. It consists of a third lens L3 composed of a spherical surface, and its position on the optical axis is fixed during zooming. Efficient downsizing in the direction of the incident optical axis is performed by bending the optical axis by 90 degrees with a prism. The second lens group GR2 includes a fourth lens L4 having a negative refractive power, a cemented lens of a negative lens L5 and a positive lens L6, and a seventh lens L7 having a negative refractive power, which are sequentially arranged from the object side. During zooming from the wide-angle end to the telephoto end, it moves on the optical axis from the object side to the image side. The third lens group GR3 is composed of a positive lens L8 having both aspheric surfaces, and the position on the optical axis is fixed during zooming. The fourth lens group GR4 is composed of a cemented lens of a positive lens L9 and a negative lens L10 each having an aspheric object side surface. The fourth lens group GR4 moves on the optical axis during zooming to change the image plane position during zooming. Performs correction and focusing during close-up shooting. The fifth lens group GR5 is hermetically sealed by a negative lens L11 positioned in order from the object side, a positive lens L12 that is a shift lens group for correcting image blur by moving perpendicularly to the optical axis direction, and a transparent parallel plate. The shape of the boundary refracting surface VS of two types of liquids with different refractive indexes filled in the liquid chamber is constituted by a liquid type refractive power variable optical element L13 that changes when a voltage is applied. At the wide-angle end, the boundary refracting surface VS of the liquid is shaped to have a convex surface facing the object side, and at the time of zooming, the shape of the boundary refracting surface VS is continuously changed by controlling the applied voltage. The telephoto end has a concave surface facing the object side. That is, the refractive power of the liquid type variable refractive power optical element L13 has a positive refractive power at the wide-angle end and a negative refractive power at the telephoto end. Contribute. An iris IR for adjusting the amount of light is disposed on the image plane IMG side of the third lens group GR3, and a filter including an infrared cut filter and a low-pass filter is further disposed on the image plane IMG side of the fifth lens group GR5. FL is arranged. The image plane IMG is a light receiving surface of an image sensor such as a CCD.

  Table 4 shows lens data of Numerical Example 2 in which specific numerical values are applied to the zoom lens 2 according to the second embodiment.

  During zooming from the wide-angle end to the telephoto end, the distance d6 between the first lens group GR1 and the second lens group GR2, the distance d13 between the second lens group GR2 and the third lens group GR3, the third lens The distance d16 between the group GR3 (aperture stop IR) and the fourth lens group GR4 and the distance d19 between the fourth lens group GR4 and the fifth lens group GR5 are changed. Therefore, the values in the wide-angle end state (f = 6.10), the intermediate focal length state (f = 15.70), and the telephoto end state (f = 40.60) of the intervals in Numerical Example 2 are used as the focal length. Table 5 shows “f”, F number “Fno”, and half angle of view “ω (degrees)”. Note that the change in the distance between the front and rear of the boundary refractive surface VS of the refractive power variable optical element L13 is replaced with the radius of curvature (r26) of the boundary refractive surface VS.

  Both surfaces (r5, r6) of the positive lens L3, both surfaces (r14, r15) of the positive lens L8, and the object side surface (r17) of the positive lens L9 are aspherical. Therefore, Table 6 shows the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients A4, A6, A8, and A10 of each surface in Numerical Example 2 together with the conic constant ε.

  FIGS. 6 to 8 show aberration diagrams of the spherical aberration, astigmatism and distortion of Numerical Example 2, FIG. 6 is in the wide angle end state, FIG. 7 is in the intermediate focal length state, and FIG. 8 is in the telephoto end state. Each aberration diagram is shown in FIG. 6 to 8, in the spherical aberration, the solid line indicates the value with respect to the d-line, the broken line indicates the value with respect to the C-line, and the alternate long and short dash line indicates the value with respect to the g-line. Indicates the value. In the graph showing astigmatism, the solid line indicates the value on the sagittal image plane, and the broken line indicates the value on the meridional image plane.

  It is clear that Numerical Example 2 has excellent imaging performance from each aberration diagram.

  FIG. 9 is a diagram showing a lens configuration of the zoom lens 3 according to the third embodiment of the present invention. In FIG. 3, the upper stage shows the position on the optical axis of each lens group at the wide-angle end, and the lower stage at the telephoto end.

  The zoom lens 3 includes, in order from the object side, a first lens group GR1 having a positive refractive power, a second lens group GR2 having a negative refractive power, a third lens group GR3 having a positive refractive power, and a positive refractive power. And a fourth lens group GR4 having negative refractive power and a fifth lens group GR5 having negative refractive power are arranged.

  The first lens group GR1 includes a first lens L1 having a negative refractive power, which is positioned in order from the object side, a prism L2 as a reflecting member for bending the optical axis by 90 degrees, and a positive refractive power that has both surfaces non-reflective. It consists of a third lens L3 composed of a spherical surface, and its position on the optical axis is fixed during zooming. Efficient downsizing in the direction of the incident optical axis is performed by bending the optical axis by 90 degrees with a prism. The second lens group GR2 includes a fourth lens L4 having a negative refractive power, a cemented lens of a negative lens L5 and a positive lens L6, and a seventh lens L7 having a negative refractive power, which are sequentially arranged from the object side. During zooming from the wide-angle end to the telephoto end, it moves on the optical axis from the object side to the image side. The third lens group GR3 is composed of a positive lens L8 having both aspheric surfaces, and the position on the optical axis is fixed during zooming. The fourth lens group GR4 is composed of a cemented lens of a positive lens L9 and a negative lens L10 each having an aspheric object side surface. The fourth lens group GR4 moves on the optical axis during zooming to change the image plane position during zooming. Performs correction and focusing during close-up shooting. The fifth lens group GR5 is hermetically sealed by a negative lens L11 positioned in order from the object side, a positive lens L12 that is a shift lens group for correcting image blur by moving perpendicularly to the optical axis direction, and a transparent parallel plate. The boundary refracting surface VS of two types of liquids with different refractive indices filled in the liquid chamber is configured by a liquid type refractive power variable optical element L13 that changes by applying a voltage and a positive lens L14. . At the wide-angle end, the boundary refracting surface VS of the liquid is shaped to have a convex surface facing the object side, and at the time of zooming, the shape of the boundary refracting surface VS is continuously changed by controlling the applied voltage. The telephoto end has a concave surface facing the object side. That is, the refractive power of the liquid type variable refractive power optical element L13 has a positive refractive power at the wide-angle end and a negative refractive power at the telephoto end. Contribute. An iris IR for adjusting the amount of light is disposed on the image plane IMG side of the third lens group GR3, and a filter including an infrared cut filter and a low-pass filter is further disposed on the image plane IMG side of the fifth lens group GR5. FL is arranged. The image plane IMG is a light receiving surface of an image sensor such as a CCD.

  Table 7 shows lens data of Numerical Example 3 in which specific numerical values are applied to the zoom lens 3 according to the third embodiment.

  During zooming from the wide-angle end to the telephoto end, the distance d6 between the first lens group GR1 and the second lens group GR2, the distance d13 between the second lens group GR2 and the third lens group GR3, the third lens The distance d16 between the group GR3 (aperture stop IR) and the fourth lens group GR4 and the distance d19 between the fourth lens group GR4 and the fifth lens group GR5 are changed. Therefore, the values in the wide-angle end state (f = 6.10), the intermediate focal length state (f = 15.70), and the telephoto end state (f = 40.60) of each interval in Numerical Example 3 are used as the focal length. Table 8 shows “f”, F number “Fno”, and half angle of view “ω (degrees)”. Note that the change in the distance between the front and rear of the boundary refractive surface VS of the refractive power variable optical element L13 is replaced with the radius of curvature (r26) of the boundary refractive surface VS.

  Both surfaces (r5, r6) of the positive lens L3, both surfaces (r14, r15) of the positive lens L8, and the object side surface (r17) of the positive lens L9 are aspherical. Therefore, Table 9 shows the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients A4, A6, A8, and A10 of each surface in Numerical Example 3 together with the conic constant ε.

  FIGS. 10 to 12 show aberration diagrams of the spherical aberration, astigmatism, and distortion aberration in Numerical Example 3. FIG. 10 shows a wide-angle end state, FIG. 11 shows an intermediate focal length state, and FIG. 12 shows a telephoto end state. Each aberration diagram is shown in FIG. 10 to 12, in the spherical aberration, the solid line indicates the value with respect to the d line, the broken line indicates the value with respect to the C line, and the alternate long and short dash line indicates the values with respect to the g line. Indicates the value. In the graph showing astigmatism, the solid line indicates the value on the sagittal image plane, and the broken line indicates the value on the meridional image plane.

  It is clear that Numerical Example 3 has excellent imaging performance from each aberration diagram.

  Table 10 shows values corresponding to the conditional expressions (1) and (2) in the numerical examples 1 to 3.

  As is clear from Table 10, the zoom lenses of the numerical examples 1 to 3 satisfy the conditional expressions (1) and (2). Also, as shown in the respective aberration diagrams, In the intermediate focal length state), it can be seen that each aberration is corrected in a balanced manner at the telephoto end.

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

  The image pickup apparatus of the present invention includes a zoom lens and an image pickup element that converts an optical image formed by the zoom lens into an electrical signal. The zoom lens includes a plurality of lens groups and is changed by changing the group interval. A zoom lens that performs magnification, and a final lens group disposed closest to the image side among the plurality of lens groups is fixed in the optical axis direction at the time of zooming and has a refractive power variable optical element. The refractive power of the optical power variable optical element changes upon doubling.

  FIG. 13 is a block diagram showing a configuration example of a digital still camera in which the zoom lens according to the present invention described above can be mounted.

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

  The lens block 10 includes an optical system including a zoom lens 11 to which the present invention is applied, an imaging element 12 such as a CCD, and the like. The camera signal processing unit 20 performs signal processing such as conversion of an output signal from the image sensor 12 into a digital signal, noise removal, image quality correction, and conversion into a luminance / color difference signal. The image processing unit 30 performs compression encoding / decompression decoding processing of an image signal based on a predetermined image data format, conversion processing of data specifications such as resolution, and the like. As the zoom lens 11, the zoom lenses 1 to 3 of the present invention and numerical examples 1 to 3 of the present invention can be used, and the zoom lens 11 is implemented according to a mode other than the above-described embodiment and numerical examples. The zoom lens of the present invention can also be used.

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

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

  The operation of the digital still camera 100 will be briefly described below.

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

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

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

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

  FIG. 14 is a schematic cross-sectional view showing an example of the arrangement of parts in the digital still camera 100. FIG. 14 shows the inside of the digital still camera when a subject is present on the left side in the drawing.

  The zoom lens 11 is housed in the camera housing 90, and the image sensor 12 is provided below the zoom lens 11. The LCD 40 is provided on the surface of the camera housing 90 on the side facing the subject, and is used to adjust the angle of view at the time of shooting, to reproduce images, and to check various setting information.

  The zoom lens 11 according to the present invention bends the optical axis of light from a subject by a prism, and further moves a predetermined lens along the bent direction (vertical direction or horizontal direction in the figure) to perform zooming or focusing. It is possible to do. Therefore, it is possible to perform shooting without projecting the zoom lens 11 from the camera housing 90, and the depth of the camera body at the time of shooting is shortened. In addition to this, the zoom lens 11 is designed so as to satisfy the above-described conditions, so that the camera housing 90 can be further reduced in size and can be zoomed about 8 to 12 times while being small. In addition, it is possible to obtain high-quality captured images with little aberration at various focal lengths.

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

  In addition, the shapes and numerical values of the respective parts shown in the respective embodiments and numerical examples are merely examples of specific embodiments for carrying out the present invention, and the technology of the present invention is thereby limited. The scope should not be interpreted in a limited way.

It is a figure which shows the lens structure of 1st Embodiment of this invention zoom lens. FIG. 3 and FIG. 4 show aberration diagrams of Numerical Example 1 in which specific numerical values are applied to the first embodiment. This diagram shows spherical aberration, astigmatism, and distortion in the wide-angle end state. . It shows spherical aberration, astigmatism, and distortion in the intermediate focal length state. It shows spherical aberration, astigmatism, and distortion in the telephoto end state. It is a figure which shows the lens structure of 2nd Embodiment of this invention zoom lens. FIG. 7 and FIG. 8 show aberration diagrams of Numerical Example 2 in which specific numerical values are applied to the second embodiment. This diagram shows spherical aberration, astigmatism, and distortion in the wide-angle end state. . It shows spherical aberration, astigmatism, and distortion in the intermediate focal length state. It shows spherical aberration, astigmatism, and distortion in the telephoto end state. It is a figure which shows the lens structure of 3rd Embodiment of this invention zoom lens. FIG. 11 and FIG. 12 show aberration diagrams of Numerical Example 3 in which specific numerical values are applied to the third embodiment. This drawing shows spherical aberration, astigmatism, and distortion in the wide-angle end state. . It shows spherical aberration, astigmatism, and distortion in the intermediate focal length state. It shows spherical aberration, astigmatism, and distortion in the telephoto end state. 1 is a circuit block diagram of an embodiment in which the imaging apparatus of the present invention is applied to a digital still camera. It is a schematic sectional drawing which shows the example of arrangement | positioning of the components in the camera housing | casing of a digital still camera.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Zoom lens, GR1 ... 1st lens group (the most object side lens group), L2 ... Right angle prism (reflective member), GR2 ... 2nd lens group, GR3 ... 3rd lens group, GR4 ... 4th lens group, GR5: fifth lens group (final lens group), L13: positive lens (shift lens group), L14: refractive power variable optical element, 2 ... zoom lens, GR1: first lens group (lens group closest to the object side), L2 ... right angle prism (reflective member), GR2 ... second lens group, GR3 ... third lens group, GR4 ... fourth lens group, GR5 ... fifth lens group (final lens group), L12 ... positive lens (shift lens group) ), L13: Variable refractive power optical element, 3 ... Zoom lens, GR1: First lens group (most object side lens group), L2: Right angle prism (reflecting member), GR2: Second lens group, GR3: Third Lens group GR4: fourth lens group, GR5: fifth lens group (final lens group), L12: positive lens (shift lens group), L13: refractive power variable optical element, 100: digital still camera (imaging device), 11: zoom Lens, 12 ... Image sensor

Claims (6)

A zoom lens comprising a plurality of lens groups and performing zooming by changing the group interval,
The final lens group disposed on the most image side among the plurality of lens groups is fixed in the optical axis direction at the time of zooming and has a refractive power variable optical element. A zoom lens characterized by a change in refractive power. The zoom lens according to claim 1, wherein the following conditional expression (1) is satisfied.
(1) 1.0 <βet / βew <2.0
However,
βew: lateral magnification at the wide-angle end of the final lens group βet: lateral magnification at the telephoto end of the final lens group. 2. The zoom according to claim 1, wherein the lens group closest to the object among the plurality of lens groups has a reflecting member that is fixed in position during zooming and that bends the optical axis by approximately 90 degrees. lens. The final lens group has a shift lens group that shifts an image by moving in a direction substantially orthogonal to the optical axis,
The refractive power variable optical element is disposed on the image side from the shift lens group,
The zoom lens according to claim 1 or 3, wherein the following conditional expression (2) is satisfied.
(2) 1.0 <bbT / bbW <2.0
However,
bbW: Lateral magnification at the wide-angle end of the lens unit located on the image side of the shift lens unit
bbT: The lateral magnification at the telephoto end of the lens unit located on the image side from the shift lens unit. A plurality of lens groups arranged in order from the object side, including a reflecting member for bending the optical axis by approximately 90 degrees, having a positive refractive power and having a fixed position during zooming; A second lens group having negative refractive power and moving along the optical axis at the time of zooming; a third lens group having positive refractive power and whose position is fixed during zooming; and positive refractive power A fourth lens group that corrects a change in the position of the image plane during zooming by moving in the direction of the optical axis and performs focusing, and has a negative refractive power, and its position is fixed during zooming The zoom lens according to claim 4, wherein the zoom lens is a fifth lens group (final lens group). An imaging apparatus having a zoom lens and an image sensor that converts an optical image formed by the zoom lens into an electrical signal,
The zoom lens is a zoom lens that includes a plurality of lens groups and performs zooming by changing a group interval, and the final lens group disposed closest to the image side among the plurality of lens groups is light when zooming. An imaging apparatus characterized by being fixed in the axial direction and having a refractive power variable optical element, and the refractive power of the variable refractive power optical element changes upon zooming.

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