JP4496460B2 - Zoom lens and imaging device - Google Patents

Description

  The present invention relates to a compact zoom lens having a high variable magnification, which is suitable as a photographing optical system for digital input / output devices such as a digital still camera and a digital video camera, and an imaging apparatus using such a zoom lens.

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

  Therefore, in order to realize a zoom lens with high zoom ratio, various aberrations that occur during zooming can be easily corrected by making the lens group multi-component and appropriately changing the distance between the lens groups. Attempts have been made to achieve scaling.

  For example, in the optical system described in Patent Document 1, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive refractive power. A zoom lens is proposed that includes a fourth lens group having, a fifth lens group having negative refractive power, and a sixth lens group having positive refractive power.

  On the other hand, an attempt has been made to further reduce the size of the optical axis by bending the optical axis by inserting a prism between the lenses. . For example, in the optical system described in Patent Document 2, a proposal has been made to reduce the size in the optical axis direction by bending the optical axis using a prism in a zoom lens having a positive, negative, positive four-group configuration.

JP 2000-89112 A

JP-A-8-248318

  However, in the optical system described in Patent Document 1, the fifth lens group and the sixth lens group are fixed, so that the optical system is substantially composed of five components. It is not possible to exhibit sufficient performance to cope with it.

  Moreover, in the optical system described in Patent Document 2, the front lens and the reflecting member (prism) are large, and the size reduction is not sufficiently performed.

  In view of the above problems, it is an object of the present invention to provide a compact and highly variable zoom lens used for a video camera, a digital still camera, and the like, and an imaging apparatus using such a zoom lens.

In order to solve the above-described problem, the zoom lens according to the present invention has a first lens group having a positive refractive power and fixed during zooming, a second lens group having a negative refractive power, and a positive refractive power. A third lens group, a fourth lens group having a positive refractive power, a fifth lens group having a negative refractive power, and a sixth lens group, and the optical axis is bent into the first lens group. look including a reflecting member for the object-side lens unit from the reflecting member in the first lens group, the focal length of the object-side lens unit from the reflecting member in the first lens group and fa, the fw at the wide-angle end As the focal length of the entire lens system, conditional expression (1) 2.0 <| fa / fw | <5.0 is satisfied .

Therefore, in the zoom lens of the present invention, the image can be enlarged at a stretch by the fifth lens group and the sixth lens group. Further, it is possible to reduce the size of the front lens and the reflecting member while properly correcting the distortion, and to reduce the size.

  Furthermore, an imaging apparatus according to the present invention includes the zoom lens and an imaging element that converts an optical image formed by the zoom lens into an electrical signal.

  Therefore, the imaging apparatus of the present invention can be configured in a small size.

The zoom lens according to the present invention includes a plurality of groups, and performs zooming by changing a group interval. The zoom lens has a positive refractive power, a first lens group fixed during zooming, and a negative refractive power. The second lens group includes a third lens group having a positive refractive power, a fourth lens group having a positive refractive power, a fifth lens group having a negative refractive power, and a sixth lens group. the saw including a reflecting member for bending the optical axis in the first lens group, the lens group on the object side of the reflecting member in the first lens unit, the object side of the reflecting member of the first lens group fa Conditional expression (1) 2.0 <| fa / fw | <5.0 is satisfied, where fo is the focal length of the lens group, fw is the focal length of the entire lens system at the wide angle end .

In addition, the imaging apparatus of the present invention includes a zoom lens that includes a plurality of groups and performs zooming by changing a group interval, and an imaging element that converts an optical image formed by the zoom lens into an electrical signal. The zoom lens includes a first lens group having a positive refractive power and fixed during zooming, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. And a fourth lens group having a positive refractive power, a fifth lens group having a negative refractive power, and a sixth lens group, and a reflecting member for bending the optical axis in the first lens group only contains the object-side lens unit from the reflecting member in the first lens group, the focal length of the object-side lens unit from the reflecting member in the first lens group and fa, the entire lens system at the wide-angle end to fw Satisfies the conditional expression (1) 2.0 <| fa / fw | <5.0 Characterized in that it.

  Accordingly, in the present invention, since the optical axis is bent by the reflecting member provided in the first lens group, the size in the optical axis direction, so-called thickness, can be reduced, and a so-called thin imaging device is obtained. Can do.

In addition, since the image can be enlarged at a stretch by the fifth lens group and the sixth lens group, the first lens group including the reflecting member can be configured in a small size, and the zoom lens can be reduced in size, and thus imaged. The device can be miniaturized. Further, it is possible to reduce the size of the front lens and the reflecting member while properly correcting the distortion, and to reduce the size.

According to the second and eighth aspects of the present invention, since the light amount adjusting member inserted in the optical path is fixed during zooming, the zoom lens can be further reduced in size. That is, in a light amount adjusting member, for example, a shutter that also serves as an aperture or a diaphragm, a mechanism for moving the aperture blade and the shutter blade is necessary to adjust the amount of light passing through. Increases in size. In order to move such a large lens during zooming, it is necessary to secure a movable region for that purpose, which is an obstacle to miniaturization of the zoom lens. Therefore, the zoom lens can be reduced in size by fixing such a light amount adjusting member during zooming.

In the invention described in claim 3 and claim 9 , since the third lens group is fixed during zooming, the light amount adjusting member that is fixed during zooming may be disposed close to the third lens group. it can.

In the inventions described in claims 4 to 6 and 10 to 12 , the fifth lens group includes f5 as a focal length of the fifth lens group and fw as a whole lens system at a wide angle end. Since the conditional expression (2) 0.8 <| f5 / fw | <6.0 is satisfied, the size can be reduced while satisfactorily correcting coma and lateral chromatic aberration.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.

  As shown in FIGS. 1, 5, 9, and 13, the zoom lens of the present invention includes a first lens group GR1 having a positive refractive power and fixed during zooming, and a second lens group having a negative refractive power. GR2, a third lens group GR3 having a positive refractive power, a fourth lens group GR4 having a positive refractive power, a fifth lens group GR5 having a negative refractive power, and a sixth lens group GR6 The first lens group GR1 includes a reflecting member G2 for bending the optical axis. The refractive power of the sixth lens group GR6 may be positive or negative.

  By including the reflecting member G2 for bending the optical axis in the first lens group GR1, the size in the optical axis direction can be reduced. Further, since the image can be enlarged by the fifth lens group GR5 and the sixth lens group GR6, the size of the first lens group, in particular, the front lens G1 and the reflecting member G2 can be reduced evenly. Can be obtained.

  By fixing the light amount adjusting member IR during zooming, the zoom lens can be reduced in size. That is, in a light amount adjusting member, for example, a shutter that also serves as a diaphragm or a diaphragm, a mechanism for moving the diaphragm blade and the shutter blade is necessary to adjust the amount of light passing through. Increases in size. In order to move such a large lens during zooming, it is necessary to secure a movable region for that purpose, which is an obstacle to miniaturization of the zoom lens. Therefore, the zoom lens can be reduced in size by fixing such a light amount adjusting member during zooming.

  Here, the light amount adjusting member is not limited to the above-described diaphragm or shutter. What can adjust the light quantity which reaches | attains an imaging surface, for example, an ND filter, a liquid crystal light control element, etc. are equivalent to the light quantity adjustment member here. In the case of an ND filter, a state with a large amount of light and a small amount of light can be selected by inserting / removing an ND filter having a predetermined density in the optical path. As a result, it is possible to perform almost stepless light amount adjustment.

  The third lens group GR3 described above is also preferably fixed during zooming. As a result, the light quantity adjusting member IR that is fixed during zooming is disposed in the vicinity of the third lens group GR3, for example, in the vicinity of the image plane side of the third lens group GR3, thereby making it possible to reduce the size of the zoom lens.

  In the zoom lens of the present invention, the focal length of the lens group G1 closer to the object side than the reflecting member G2 in the first lens group GR1, and the focal length of the lens group G1 closer to the object side than the reflecting member G2 in the first lens group GR1. , Fw is preferably the focal length of the entire lens system at the wide angle end, and the following conditional expression (1) is preferably satisfied.

(1) 2.0 <| fa / fw | <5.0
Conditional expression (1) defines the focal length of the lens group G1 on the object side of the reflecting member G2 in the first lens group GR1. If the lower limit of conditional expression (1) is not reached, it will be difficult to correct distortion, and if the upper limit of conditional expression (1) is exceeded, the power of the first lens group GR1 will become weak, so that a desired zoom ratio can be obtained. In this case, the front ball (G1) and the reflecting member G2 must be enlarged, which makes it difficult to reduce the size.

  In the zoom lens of the present invention, the fifth lens group GR5 satisfies the conditional expression (2), where f5 is the focal length of the fifth lens group GR5 and fw is the focal length of the entire lens system at the wide angle end. It is preferable to do.

(2) 0.8 <| f5 / fw | <6.0
Conditional expression (2) defines the focal length of the fifth lens group GR5. If the lower limit of conditional expression (2) is not reached, it will be difficult to correct peripheral coma and lateral chromatic aberration, and high mounting accuracy will be required. If the upper limit of conditional expression (2) is exceeded, the power of the fifth lens group GR5 will weaken, making it difficult to reduce the size.

  When a prism is used for the reflecting member G2 disposed to bend the optical axis in the first lens group GR1, a material having a high refractive index, for example, a glass material having a refractive index of 1.8 or more is used. preferable.

  Next, each embodiment of the zoom lens of the present invention shown in FIGS. 1, 5, 9, and 13 will be described, and Tables 1 to 13 and FIGS. 2 to 4, FIGS. 6 to 8, and FIG. FIG. 12 to FIG. 12 and FIG. 14 to FIG. 16 show numerical examples according to the respective embodiments. FIG. 1 is a diagram showing the lens configuration of a zoom lens according to a first embodiment of the present invention. In the first embodiment, 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 A fourth lens group GR4 having a negative refractive power, a fifth lens group GR5 having a negative refractive power, and a sixth lens group GR6 having a positive refractive power. The first lens group GR1 includes a negative lens G1. And a right-angle prism G2 for bending the optical axis by 90 ° and a positive lens G3 having aspheric surfaces on both sides. The second lens group GR2 includes a negative lens G4, a cemented lens of a negative lens G5 and a positive lens G6, and a negative lens G7. The third lens group GR3 includes a positive lens G8 having aspheric surfaces on both sides. The fourth lens group GR4 includes a cemented lens of a positive lens G9 and a negative lens G10. The fifth lens group GR5 includes a cemented lens of a negative lens G11 and a positive lens G12. The sixth lens group GR6 includes a positive lens G13 having aspheric surfaces on both sides. In addition, a diaphragm IR is disposed close to the image plane side of the third lens group GR3, and a low-pass filter LPF is disposed between the sixth lens group GR6 and the imaging surface IMG.

  During zooming, the first lens group GR1, the third lens group GR3, and the fifth lens group GR5 are fixed, and the second lens group GR2, the fourth lens group GR4, and the sixth lens group GR6 are movable. For example, when the focal length state changes from the wide-angle end to the telephoto end, the first lens group GR1, the third lens group GR3, and the fifth lens group GR5 are fixed (the change of the fixed lens group is shown in FIG. Indicated by broken line arrows (the same applies to FIGS. 5, 9 and 13 below), the second lens group GR2, the fourth lens group GR4 and the sixth lens group GR6 are optical axes as indicated by solid line arrows in FIG. Move up.

  Table 1 shows values in Numerical Example 1 of the zoom lens according to the first embodiment. In this specification, “si” is the i-th surface from the object side, “di” is the axial upper surface distance between the i-th and i + 1-th surfaces from the object side, and “ni” is from the object side. “vi” represents the refractive index of the medium having the i-th surface at the d-line, and “vi” represents the Abbe number of the medium having the i-th surface from the object side. “INFINITY” indicates that the surface is a plane, and “ASP” indicates that the surface is an aspherical surface.

  In the zoom lens according to the first embodiment, during zooming, the axial upper surface distance (air distance) d6 between the first lens group GR1 and the second lens group GR2, the second lens group GR2, and the third lens group GR3. The axial upper surface distance (air interval) d13 between the aperture stop IR and the fourth lens group GR4, the axial upper surface interval (air interval) d16, and between the fourth lens group GR4 and the fifth lens group GR5. Axis upper surface interval (air interval) d19, an axial upper surface interval (air interval) d22 between the fifth lens group GR5 and the sixth lens group GR6, and an axial upper surface interval between the sixth lens group GR6 and the low pass filter LPF ( The air interval d24 changes. Therefore, Table 2 shows the above-described axial upper surface spacing (air spacing) at the wide-angle end, the intermediate focal position, and the telephoto end, together with the F number FNO and the half angle of view ω. Note that f is the focal length of the entire lens system.

  In the first embodiment, both surfaces s5 and s6 of the positive lens G3 of the first lens group GR1, both surfaces s14 and s15 of the positive lens G8 constituting the third lens group GR3, and the positive lens constituting the sixth lens group GR6. Both sides s23 and s24 of G13 are aspherical. Therefore, Table 3 shows the conic constant ε and the fourth, sixth, eighth and tenth aspherical coefficients A, B, C and D of the above-mentioned surfaces in Numerical Example 1.

  In this specification, the shape of the aspherical surface is expressed by the following equation (1).

However,
x: distance in the optical axis direction from the apex of the lens surface,
y: height in the direction perpendicular to the optical axis c: paraxial curvature at the lens apex,
ε: conic constant,
A ⁱ : i-th aspheric coefficient

  FIG. 2 shows each spherical aberration, astigmatism, and distortion in the numerical example 1 at the wide-angle end, FIG. 3 at the intermediate focal position between the wide-angle end and the telephoto end, and FIG. 4 at the telephoto end. . In the spherical aberration, the vertical axis indicates the ratio of the open F value, the horizontal axis indicates the defocus, the solid line indicates the d-line, the broken line indicates the C-line, and the alternate long and short dash line indicates the spherical aberration, and the astigmatism indicates the vertical aberration. The axis represents the image height, the horizontal axis represents the focus, the solid line represents the sagittal image plane, and the broken line represents the meridional image plane. For the distortion aberration, the vertical axis represents the image height and the horizontal axis represents the percentage.

  As apparent from Tables 1 to 3 and the aberration diagrams, the zoom lens of Numerical Example 1 satisfies the conditional expressions (1) and (2), and each aberration is balanced. It is well corrected.

  FIG. 5 is a diagram showing a lens configuration of a second embodiment of the zoom lens according to the present invention. In the second embodiment, 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 A fourth lens group GR4 having a negative refractive power, a fifth lens group GR5 having a negative refractive power, and a sixth lens group GR6 having a negative refractive power. The first lens group GR1 includes a negative lens G1. And a right-angle prism G2 for bending the optical axis by 90 ° and a positive lens G3 having aspheric surfaces on both sides. The second lens group GR2 includes a negative lens G4, a cemented lens of a negative lens G5 and a positive lens G6, and a negative lens G7. The third lens group GR3 includes a positive lens G8 having aspheric surfaces on both sides. The fourth lens group GR4 includes a cemented lens of a positive lens G9 having an aspheric surface on the object side and a negative lens G10. The fifth lens group GR5 includes a cemented lens of a negative lens G11 and a positive lens G12. The sixth lens group GR6 includes a cemented lens of a negative lens G13 and a positive lens G14. In addition, a diaphragm IR is disposed close to the image plane side of the third lens group GR3, and a low-pass filter LPF is disposed between the sixth lens group GR6 and the imaging surface IMG.

  During zooming, the first lens group GR1 and the third lens group GR3 are fixed, and the second lens group GR2, the fourth lens group GR4, the fifth lens group GR5, and the sixth lens group GR6 are movable. For example, when the focal length state changes from the wide-angle end to the telephoto end, the first lens group GR1 and the third lens group GR35 are fixed, and the second lens group GR2, the fourth lens group GR4, and the fifth lens group GR5 are fixed. The sixth lens group GR6 moves on the optical axis as indicated by solid arrows in FIG.

  Table 4 shows values in Numerical Example 2 of the zoom lens according to the second embodiment.

  In the zoom lens according to the second embodiment, during zooming, the axial upper surface distance (air distance) d6 between the first lens group GR1 and the second lens group GR2, the second lens group GR2, and the third lens group GR3. The axial upper surface distance (air interval) d13 between the aperture stop IR and the fourth lens group GR4, the axial upper surface interval (air interval) d16, and between the fourth lens group GR4 and the fifth lens group GR5. Axis upper surface interval (air interval) d19, an axial upper surface interval (air interval) d22 between the fifth lens group GR5 and the sixth lens group GR6, and an axial upper surface interval between the sixth lens group GR6 and the low pass filter LPF ( The air interval d25 changes. Therefore, Table 5 shows the above-mentioned axis top surface spacing (air spacing) at the wide angle end, the intermediate focal position, and the telephoto end, together with the F number FNO and the half angle of view ω. Note that f is the focal length of the entire lens system.

  In the second embodiment, both surfaces s5 and s6 of the positive lens G3 of the first lens group GR1, both surfaces s14 and s15 of the positive lens G8 constituting the third lens group GR3, and the positive lens G9 of the fourth lens group GR4. The object-side surface s17 is an aspherical surface. Therefore, Table 6 shows the conic constant ε and the fourth, sixth, eighth, and tenth aspherical coefficients A, B, C, and D of the above surfaces in Numerical Example 2.

  FIG. 6 shows each spherical aberration, astigmatism, and distortion in the numerical example 2 at the wide-angle end, FIG. 7 at the intermediate focal position between the wide-angle end and the telephoto end, and FIG. 8 at the telephoto end. . In the spherical aberration, the vertical axis indicates the ratio of the open F value, the horizontal axis indicates the defocus, the solid line indicates the d-line, the broken line indicates the C-line, and the alternate long and short dash line indicates the spherical aberration, and the astigmatism indicates the vertical aberration. The axis represents the image height, the horizontal axis represents the focus, the solid line represents the sagittal image plane, and the broken line represents the meridional image plane. For the distortion aberration, the vertical axis represents the image height and the horizontal axis represents the percentage.

  As apparent from Tables 4 to 6 and the aberration diagrams, the zoom lens according to Numerical Example 2 satisfies the conditional expressions (1) and (2), and each aberration is balanced. It is well corrected.

  FIG. 9 is a diagram showing the lens configuration of a third embodiment of the zoom lens according to the present invention. In the third embodiment, 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 A fourth lens group GR4 having a negative refractive power, a fifth lens group GR5 having a negative refractive power, and a sixth lens group GR6 having a positive refractive power. The first lens group GR1 includes a negative lens G1. And a right-angle prism G2 for bending the optical axis by 90 ° and a positive lens G3 having aspheric surfaces on both sides. The second lens group GR2 includes a negative lens G4, a cemented lens of a negative lens G5 and a positive lens G6, and a negative lens G7. The third lens group GR3 includes a positive lens G8 having aspheric surfaces on both sides. The fourth lens group GR4 includes a cemented lens of a positive lens G9 having an aspheric surface on the object side and a negative lens G10. The fifth lens group GR5 includes a cemented lens of a negative lens G11 and a positive lens G12. The sixth lens group GR6 includes a positive lens G13 having an aspheric surface on the object side. In addition, a diaphragm IR is disposed close to the image plane side of the third lens group GR3, and a low-pass filter LPF is disposed between the sixth lens group GR6 and the imaging surface IMG.

  During zooming, the first lens group GR1, the third lens group GR3, and the fifth lens group GR5 are fixed, and the second lens group GR2, the fourth lens group GR4, and the sixth lens group GR6 are movable. For example, when the focal length state changes from the wide-angle end to the telephoto end, the first lens group GR1, the third lens group GR35, and the fifth lens group GR5 are fixed, the second lens group GR2, and the fourth lens group GR4. The sixth lens group GR6 moves on the optical axis as indicated by solid arrows in FIG. Moreover, the fourth lens group GR4 and the sixth lens group GR6 are linked to each other, that is, move the same amount in the same direction at the same time.

  Table 7 shows values in Numerical Example 3 of the zoom lens according to the third embodiment.

  In the zoom lens according to the third embodiment, during zooming, the axial upper surface distance (air distance) d6 between the first lens group GR1 and the second lens group GR2, the second lens group GR2, and the third lens group GR3. The axial upper surface distance (air interval) d13 between the aperture stop IR and the fourth lens group GR4, the axial upper surface interval (air interval) d16, and between the fourth lens group GR4 and the fifth lens group GR5. Axis upper surface interval (air interval) d19, an axial upper surface interval (air interval) d22 between the fifth lens group GR5 and the sixth lens group GR6, and an axial upper surface interval between the sixth lens group GR6 and the low pass filter LPF ( The air interval d24 changes. Therefore, Table 8 shows the above-described axial upper surface spacing (air spacing) at the wide angle end, the intermediate focal position, and the telephoto end, together with the F number FNO and the half angle of view ω. Note that f is the focal length of the entire lens system.

  In the third embodiment, both surfaces s5 and s6 of the positive lens G3 of the first lens group GR1, both surfaces s14 and s15 of the positive lens G8 constituting the third lens group GR3, and the positive lens G9 of the fourth lens group GR4. The object-side surface s17 and the object-side surface s23 of the positive lens G13 constituting the sixth lens group GR6 are aspheric. Accordingly, Table 9 shows the conic constant ε and the fourth, sixth, eighth, and tenth aspherical coefficients A, B, C, and D of the above surfaces in Numerical Example 2.

  FIG. 10 shows the spherical aberration, astigmatism, and distortion in the numerical example 3 at the wide-angle end, FIG. 11 at the intermediate focal position between the wide-angle end and the telephoto end, and FIG. 12 at the telephoto end. . In the spherical aberration, the vertical axis indicates the ratio of the open F value, the horizontal axis indicates the defocus, the solid line indicates the d-line, the broken line indicates the C-line, and the alternate long and short dash line indicates the spherical aberration, and the astigmatism indicates the vertical aberration. The axis represents the image height, the horizontal axis represents the focus, the solid line represents the sagittal image plane, and the broken line represents the meridional image plane. For the distortion aberration, the vertical axis represents the image height and the horizontal axis represents the percentage.

  As apparent from Tables 7 to 9 and the aberration diagrams, the zoom lens according to Numerical Example 3 satisfies the conditional expressions (1) and (2), and each aberration is balanced. It is well corrected.

  FIG. 13 is a diagram showing the lens configuration of a fourth embodiment of the zoom lens according to the present invention. In the fourth embodiment, 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 A fourth lens group GR4 having a negative refractive power, a fifth lens group GR5 having a negative refractive power, and a sixth lens group GR6 having a positive refractive power. The first lens group GR1 includes a negative lens G1. And a right-angle prism G2 for bending the optical axis by 90 ° and a positive lens G3 having aspheric surfaces on both sides. The second lens group GR2 includes a negative lens G4 and a cemented lens of a negative lens G5 and a positive lens G6. The third lens group GR3 includes a positive lens G7 having aspheric surfaces on both sides. The fourth lens group GR4 includes a cemented lens of a positive lens G8 and a negative lens G9 having an aspheric surface on the object side. The fifth lens group GR5 includes a cemented lens of a negative lens G10 and a positive lens G11. The sixth lens group includes a positive lens G12. In addition, a diaphragm IR is disposed close to the image plane side of the third lens group GR3, and a low-pass filter LPF is disposed between the sixth lens group GR6 and the imaging surface IMG.

  During zooming, the first lens group GR1, the third lens group GR3, and the sixth lens group GR6 are fixed, and the second lens group GR2, the fourth lens group GR4, and the fifth lens group GR5 are movable. For example, when the focal length state changes from the wide-angle end to the telephoto end, the first lens group GR1, the third lens group GR35, and the sixth lens group GR6 are fixed, the second lens group GR2, and the fourth lens group GR4. The fifth lens group GR5 moves on the optical axis as shown by the solid line arrow in FIG.

  Table 10 shows values in Numerical Example 4 of the zoom lens according to the fourth embodiment.

  In the zoom lens according to the fourth embodiment, during zooming, the axial upper surface distance (air distance) d6 between the first lens group GR1 and the second lens group GR2, the second lens group GR2, and the third lens group GR3. The axial upper surface distance (air interval) d11 between the aperture stop IR and the fourth lens group GR4, the axial upper surface interval (air interval) d14, and between the fourth lens group GR4 and the fifth lens group GR5. The axial upper surface interval (air interval) d17 and the axial upper surface interval (air interval) d20 between the fifth lens group GR5 and the sixth lens group GR6 change. Therefore, Table 11 shows the above-mentioned axis top surface spacing (air spacing) at the wide angle end, the intermediate focal position, and the telephoto end, together with the F number FNO and the half angle of view ω. Note that f is the focal length of the entire lens system.

  In the fourth embodiment, both surfaces s5 and s6 of the positive lens G3 of the first lens group GR1, both surfaces s12 and s13 of the positive lens G7 constituting the third lens group GR3, and the positive lens G8 of the fourth lens group GR4. The object side surface s15 is formed of an aspherical surface. Therefore, Table 12 shows the conic constant ε and the fourth, sixth, eighth and tenth aspherical coefficients A, B, C and D of the above-mentioned surfaces in Numerical Example 2.

  FIG. 14 shows the spherical aberration, astigmatism, and distortion in Numerical Example 4 at the wide-angle end, FIG. 15 at the intermediate focal position between the wide-angle end and the telephoto end, and FIG. 16 at the telephoto end. . In the spherical aberration, the vertical axis indicates the ratio of the open F value, the horizontal axis indicates the defocus, the solid line indicates the d-line, the broken line indicates the C-line, and the alternate long and short dash line indicates the spherical aberration, and the astigmatism indicates the vertical aberration. The axis represents the image height, the horizontal axis represents the focus, the solid line represents the sagittal image plane, and the broken line represents the meridional image plane. For the distortion aberration, the vertical axis represents the image height and the horizontal axis represents the percentage.

  As apparent from Tables 10 to 12 and the aberration diagrams, the zoom lens according to Numerical Example 4 satisfies the conditional expressions (1) and (2), and each aberration is balanced. It is well corrected.

  Table 13 shows the values in the conditional expressions (1) and (2)) for each of the numerical examples 1 to 4.

  FIG. 17 shows Embodiment 1 of the imaging apparatus of the present invention.

  The imaging apparatus 1 includes a zoom lens 2 and includes an imaging element 3 that converts an optical image formed by the zoom lens 2 into an electrical signal. For example, an image sensor using a photoelectric conversion element such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) is applicable. The zoom lens according to the present invention can be applied to the zoom lens 2. In FIG. 17, the zoom lens according to the first embodiment shown in FIG. 1 is a single lens group other than the first lens group GR1. Simplified on the lens. Of course, not only the zoom lens according to the first embodiment, but also the zoom lens according to the second to fourth embodiments and other forms than those shown in the present specification are configured. The zoom lens of the present invention can be used.

  The electric signal formed by the image sensor 3 is sent to the control circuit 5 by the video separation circuit 4 and the video signal is sent to the video processing circuit. The signal sent to the video processing circuit is processed into a form suitable for the subsequent processing, and is subjected to various processes such as display by a display device, recording on a recording medium, and transfer by a communication means.

  For example, an operation signal from the outside such as an operation of a zoom button is input to the control circuit 5, and various processes are performed according to the operation signal. For example, when a zooming command by the zoom button is input, the driving units 9, 10, 11 are operated via the driver circuits 6, 7, 8 to set the focal length state based on the command, and the second lens group GR 2. The fourth lens group GR4 and the sixth lens group GR6 are moved to predetermined positions. Position information of the second lens group GR2, the fourth lens group GR4, and the sixth lens group GR6 obtained by the sensors 12, 13, and 14 is input to the control circuit 5, and command signals are sent to the driver circuits 6, 7, and 8. Referenced when outputting. Further, the control circuit 5 checks the focus state based on the signal sent from the video separation circuit 4 and controls, for example, the fourth lens group GR4 via the driver circuit 7 so as to obtain the optimum focus state. To do.

  The above-described imaging apparatus 1 can take various forms as specific products. For example, the present invention can be widely applied as a camera unit of a digital input / output device such as a digital still camera, a digital video camera, a mobile phone incorporating a camera, and a PDA (Personal Digital Assistant) incorporating a camera.

  It should be noted that the specific shapes, structures, and numerical values of the respective parts shown in the respective embodiments and numerical examples described above are merely examples of the implementation performed in carrying out the present invention. The technical scope of the present invention should not be construed in a limited manner.

  It can be used as a digital still camera, a digital video camera, a mobile phone with a built-in camera, a camera unit of a digital input / output device such as a PDA (Personal Digital Assistant) with a built-in camera, and a zoom lens used for these. It is.

2 to 4 show a first embodiment of a zoom lens according to the present invention, and this figure is a schematic diagram showing a lens configuration. FIG. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a wide angle end. It is a figure which shows the spherical aberration, astigmatism, and a distortion aberration in the intermediate focus position of a wide angle end and a telephoto end. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a telephoto end. 6 to 8 show a second embodiment of the zoom lens of the present invention, and this figure is a schematic diagram showing the lens configuration. FIG. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a wide angle end. It is a figure which shows the spherical aberration, astigmatism, and a distortion aberration in the intermediate focus position of a wide angle end and a telephoto end. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a telephoto end. FIG. 10 to FIG. 12 show a third embodiment of the zoom lens of the present invention, and this figure is a schematic diagram showing the lens configuration. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a wide angle end. It is a figure which shows the spherical aberration, astigmatism, and a distortion aberration in the intermediate focus position of a wide angle end and a telephoto end. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a telephoto end. FIG. 14 to FIG. 16 show a fourth embodiment of the zoom lens according to the present invention, which is a schematic diagram showing the lens configuration. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a wide angle end. It is a figure which shows the spherical aberration, astigmatism, and a distortion aberration in the intermediate focus position of a wide angle end and a telephoto end. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a telephoto end. It is a block diagram of the principal part which shows embodiment of the imaging device of this invention.

Explanation of symbols

  GR1: First lens group, GR2: Second lens group, GR3: Third lens group, GR4: Fourth lens group, GR5: Fifth lens group, GR6: Sixth lens group, G1: Negative of first lens group Lens (lens group positioned on the object side with respect to the reflecting member), IR ... diaphragm (light quantity adjusting member), 1 ... imaging device, 2 ... zoom lens, 3 ... imaging device

Claims (12)

A zoom lens comprising a plurality of groups and performing zooming by changing a group interval,
A first lens group having positive refractive power and fixed during zooming, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens having positive refractive power A group, a fifth lens group having negative refractive power, and a sixth lens group,
Look including a reflecting member for bending the optical axis in the first lens group,
The zoom lens according to claim 1, wherein the lens group on the object side of the reflecting member in the first lens group satisfies the following conditional expression (1).
(1) 2.0 <| fa / fw | <5.0
However,
fa: Focal length of the lens unit on the object side of the reflecting member in the first lens unit
fw: Focal length of the entire lens system at the wide-angle end
And The zoom lens according to claim 1, wherein the light amount adjustment member inserted in the optical path is fixed during zooming. The zoom lens according to claim 2, wherein the third lens group is fixed during zooming. The zoom lens according to claim 1, wherein the fifth lens group satisfies the following conditional expression (2).
(2) 0.8 <| f5 / fw | <6.0
However,
f5: The focal length of the fifth lens group. The zoom lens according to claim 2, wherein the fifth lens group satisfies the following conditional expression (2).
(2) 0.8 <| f5 / fw | <6.0
However,
f5: The focal length of the fifth lens group. The zoom lens according to claim 3, wherein the fifth lens group satisfies the following conditional expression (2).
(2) 0.8 <| f5 / fw | <6.0
However,
f5: The focal length of the fifth lens group. An imaging apparatus comprising a zoom lens composed of a plurality of groups and performing zooming by changing a group interval, and an image sensor that converts an optical image formed by the zoom lens into an electrical signal,
The zoom lens includes a first lens group having a positive refractive power and fixed during zooming, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive refractive power. A fourth lens group having, a fifth lens group having negative refractive power, and a sixth lens group,
Look including a reflecting member for bending the optical axis in the first lens group,
An image pickup apparatus, wherein the lens group on the object side of the reflecting member in the first lens group satisfies the following conditional expression (1).
(1) 2.0 <| fa / fw | <5.0
However,
fa: Focal length of the lens unit on the object side of the reflecting member in the first lens unit
fw: Focal length of the entire lens system at the wide-angle end
And The image pickup apparatus according to claim 7 , wherein the light amount adjusting member inserted in the optical path is fixed during zooming. The imaging apparatus according to claim 8 , wherein the third lens group is fixed during zooming. The imaging apparatus according to claim 7, characterized in that the fifth lens group satisfies the following conditional expression (2).
(2) 0.8 <| f5 / fw | <6.0
However,
f5: The focal length of the fifth lens group. The imaging apparatus according to claim 8 , wherein the fifth lens group satisfies the following conditional expression (2).
(2) 0.8 <| f5 / fw | <6.0
However,
f5: The focal length of the fifth lens group. The imaging device according to claim 9 , wherein the fifth lens group satisfies the following conditional expression (2).
(2) 0.8 <| f5 / fw | <6.0
However,
f5: The focal length of the fifth lens group.

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