Image forming optical system and electronic image pickup apparatus using the same

CROSS-REFERENCE TO RELATED APPLICATION

The present application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2010-68921 filed on Mar. 24, 2010; the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image forming optical system, particularly an image forming optical system which has a high zooming ratio and a superior image forming performance while being of a slim type which is suitable for an electronic image pickup optical system, and an electronic image pickup apparatus having such image forming optical system.

2. Description of the Related Art

A digital camera has reached a level of being used practically, regarding making large the number of pixels (high image quality), and small-sizing and slimming. Also from a function point of view and a market point of view, a digital camera has substituted a silver salt 35 mm film camera. Therefore, a high zooming ratio and further increase in the number of pixels with the same small-size and slimness, have been sought strongly as a next trend of evolution.

A so-called positive-lead type with four or more lens groups has hitherto been used generally, as it is more effective for high zooming. However, most of the optical systems of the positive-lead type have a telephoto ratio exceeding one, and cannot be said to be of sufficiently small size.

For making an optical system of positive-lead type small, shortening of an overall length at a telephoto end is necessary. However, when the overall length of an optical system is shortened at the telephoto end, a negative curvature of field is developed. Therefore, the image forming performance is not satisfactory.

For achieving both of the small-sizing and the correction of the curvature of field, introducing a convex lens having a lower refractive index in a second lens group of the optical system of the positive-lead type is a conceivable means.

For instance, in a first embodiment of Japanese Patent Application Laid-open Publication No. 2008-203453, an arrangement is such that a refractive index of a convex lens is the smallest among all lenses in a second lens group.

Moreover, for example, in Japanese Patent Application Laid-open Publication No. 2009-9121, an arrangement is such that a positive lens having the smallest refractive index is arranged as a lens in a second lens group.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, an image forming optical system includes in order from an object side

a first lens group having a positive refractive power,

a second lens group having a negative refractive power

a third lens group having a positive refractive power, and

a fourth lens group having a positive refractive power, and

a refractive index for a d-line of a positive single lens having the largest refractive power among all lenses in the second lens group, is the smallest of a refracting index of lenses in the second lens group.

According to a second aspect of the present invention, an electronic image pickup apparatus includes

an image forming optical system according to the first aspect of the present invention, and

a photoelectric conversion element, and

the image forming optical system forms an image on the photoelectric conversion element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A, FIG. 1B, and FIG. 1C are cross-sectional views along an optical axis showing an optical arrangement at the time of infinite object point focusing of a zoom lens according to a first embodiment of the present invention, where, FIG. 1A shows a state at a wide angle end, FIG. 1B shows an intermediate state, and FIG. 1C shows a state at a telephoto end;

FIG. 2A, FIG. 2B, and FIG. 2C are diagrams showing a spherical aberration, an astigmatism, a distortion, and a chromatic aberration of magnification at the time of infinite object point focusing of the zoom lens according to the first embodiment, where, FIG. 2A shows a state at the wide angle end, FIG. 2B shows an intermediate state, and FIG. 2C shows a state at the telephoto end;

FIG. 3A, FIG. 3B, and FIG. 3C are lens cross-sectional views at the time of infinite object point focusing of a zoom lens according to a second embodiment of the present invention, where, FIG. 3A shows a state at a wide angle end, FIG. 3B shows an intermediate state, and FIG. 3C shows a state at a telephoto end;

FIG. 4A, FIG. 4B, and FIG. 4C are diagrams showing a spherical aberration, an astigmatism, a distortion, and a chromatic aberration of magnification at the time of infinite object point focusing of the zoom lens according to the second embodiment, where, FIG. 4A shows a state at the wide angle end, FIG. 4B shows an intermediate state, and FIG. 4C shows a state at the telephoto end;

FIG. 5A, FIG. 5B, and FIG. 5C are lens cross-sectional views at the time of infinite object point focusing of a zoom lens according to a third embodiment of the present invention, where, FIG. 5A shows a state at a wide angle end, FIG. 5B shows an intermediate state, and FIG. 5C shows a state at a telephoto end;

FIG. 6A, FIG. 6B, and FIG. 6C are diagrams showing a spherical aberration, an astigmatism, a distortion, and a chromatic aberration of magnification at the time of infinite object point focusing of the zoom lens according to the third embodiment, where, FIG. 6A shows a state at the wide angle end, FIG. 6B shows an intermediate state, and FIG. 6C shows a state at the telephoto end;

FIG. 7A, FIG. 7B, and FIG. 7C are lens cross-sectional views at the time of infinite object point focusing of a zoom lens according to a fourth embodiment of the present invention, where, FIG. 7A shows a state at a wide angle end, FIG. 7B shows an intermediate state, and FIG. 7C shows a state at a telephoto end;

FIG. 8A, FIG. 8B, and FIG. 8C are diagrams showing a spherical aberration, an astigmatism, a distortion, and a chromatic aberration of magnification at the time of infinite object point focusing of the zoom lens according to the fourth embodiment, where, FIG. 8A shows a state at the wide angle end, FIG. 8B shows an intermediate state, and FIG. 8C shows a state at the telephoto end;

FIG. 9A, FIG. 9B, and FIG. 9C are lens cross-sectional views at the time of infinite object point focusing of a zoom lens according to a fifth embodiment of the present invention, where, FIG. 9A shows a state at a wide angle end, FIG. 9B shows an intermediate state, and FIG. 9C shows a state at a telephoto end;

FIG. 10A, FIG. 10B, and FIG. 10C are diagrams showing a spherical aberration, an astigmatism, a distortion, and a chromatic aberration of magnification at the time of infinite object point focusing of the zoom lens according to the fifth embodiment, where, FIG. 10A shows a state at the wide angle end, FIG. 10B shows an intermediate state, and FIG. 10C shows a state at the telephoto end;

FIG. 11 is a front perspective view showing an appearance of a digital camera 40 in which, an image forming optical system according to the present invention is incorporated;

FIG. 12 is a rear perspective view of the digital camera 40;

FIG. 13 is a cross-sectional view showing an optical arrangement of the digital camera 40;

FIG. 14 is a front perspective view of a state in which, a cover of a personal computer 300 which is an example of an information processing apparatus in which, the image forming optical system of the present invention is built-in as an objective optical system, is opened;

FIG. 15 is a cross-sectional view of a photographic optical system 303 of the personal computer 300;

FIG. 16 is a side view of the personal computer 300; and

FIG. 17A, FIG. 17B, and FIG. 17C are diagrams showing a mobile telephone which is an example of the information processing apparatus in which, the image forming optical system of the present invention is built-in as a photographic optical system, where, FIG. 17A is a front view of a mobile telephone 400, FIG. 17B is a side view of the mobile telephone 400, and FIG. 17C is a cross-sectional view of a photographic optical system 405.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments in which, an image forming optical system according to the present invention is applied to a zoom lens, will be described below by referring to the accompanying diagrams. However, the present invention is not restricted to the embodiment described below. Prior to the description of the embodiments, an action and an effect of the image forming optical system of the present invention will be described below.

The image forming optical system according to the present invention includes in order from an object side

a first lens group having a positive refractive power,

a second lens group having a negative refractive power,

a third lens group having a positive refractive power, and

a fourth lens group having a positive refractive power, and

a refractive index for a d-line of a positive single lens having the largest refractive power among all lenses in the second lens group, is the smallest of a refractive index of lenses in the second lens group.

In an image forming optical system of a positive-lead type, a Petzval's sum is susceptible to become negative, and correction of curvature of field is insufficient. Furthermore, when the overall length is shortened, since there is an increase in a negative refractive power of the second lens group in particular, the correction of the curvature of field becomes even more difficult. Therefore, by decreasing the refractive index of the positive single lens in the second lens group, it is possible to make the Petzval's sum small, and to reduce a zoom fluctuation of the curvature of field.

Moreover, by letting a front and a rear of a convex lens to be an air interface, it becomes easy to impart a refractive power to the convex lens. Therefore, it is possible to make Petzval's sum small, and the correction of the curvature of field becomes possible. Furthermore, introducing an aspheric surface also becomes easy. Therefore, since it is possible to correct favorably various off-axis aberrations, it is preferable.

Moreover, according to the present invention, it is desirable that the second lens group includes at least one concave lens having a small thickness at a center than a thickness at a center of the positive single lens.

By disposing the concave lens having a smaller thickness at the center than the thickness at the center of the positive single lens, it is possible to improve a degree of freedom of a shape of the concave lens. As a result, the refractive power of the second lens group can be increased easily, and it is possible to dispose a position of an entrance pupil on the object side. In other words, it is possible to suppress a height of light rays incident on the first lens group, and to raise the refractive power of the first lens group.

Therefore, since the correction of negative curvature of field becomes possible as well as the shortening of the overall length becomes easy, it is preferable. Furthermore, it is possible to reduce a change in a spherical aberration and a coma aberration at a telephoto end, and an astigmatism at a wide angle end which occurs at this time, by securing an optical path length of the positive single lens (the convex lens) appropriately, and it is preferable.

According to the present invention, it is desirable that the positive single lens having the largest refractive power among all lenses in the second lens group is positioned nearest to an image-plane side in the second lens group.

By disposing the convex lens in the second lens group nearest to the image-plane side, it is possible to dispose a position of a principal point of the second lens group at the object side. As a result, since it is possible to dispose the position of the entrance pupil on the object side, reducing a front-cell (front-lens) diameter of the lens is possible while maintaining a favorable optical performance.

Moreover, according to the present invention, it is desirable that the positive single lens having the largest refractive power among all lenses in the second lens group satisfies the following conditional expressions.

1.45≦nd p≦1.75 (1)
10≦ν dp≦35 (2)

where,

nd p denotes the refractive index for d-line (wavelength λ=587.6 nm) of the positive single lens in the second lens group,

ν dp denotes Abbe's number (n dp−1)/(n Fp−n Cp) for d-line (wavelength λ=587.6 nm) of the positive single lens in the second lens group, and

n dp, n Cp, and n Fp denote refractive indices for the d-line, a C-line, and an F-line respectively of the positive single lens.

Conditional expression (1) regulates a condition for a refractive index of the convex lens in the second lens group.

Conditional expression (2) regulates a condition for Abbe's number of the convex lens in the second lens group.

By satisfying conditional expression (1), it is possible to reduce Petzval's sum in the second lens group. In other words, even when the refractive power of the second lens group increases, it is possible to suppress to minimum, the change in the curvature of field at the time of zooming, and the shortening of the overall length is possible.

When a lower limit value in conditional expression (1) is surpassed, since there is no glass material that exists actually, the desired optical system cannot be achieved.

When an upper limit value in conditional expression (1) is surpassed, the correction of the field of curvature is insufficient.

Furthermore, by satisfying conditional expression (2), it is possible to correct a chromatic aberration of the second lens group favorably upon having achieved the correction of the curvature of field of the second lens group.

When a lower limit value in conditional expression (2) is surpassed, the correction of chromatic aberration is insufficient.

When an upper limit value in conditional expression (2) is surpassed, the correction of chromatic aberration is excessive.

In other words, by satisfying conditional expressions (1) and (2) simultaneously, it is possible to achieve a zooming optical system with a short overall length, in which, the chromatic aberration is corrected favorably.

Moreover, it is preferable that the positive single lens having the largest refractive power among all lenses in the second lens group satisfies conditional expression (1-1) instead of conditional expression (1).

1.60≦nd p≦1.75 (1-1)

Furthermore, it is more preferable that the positive single lens having the largest refractive power among all lenses in the second lens group satisfies conditional expression (1-2) instead of conditional expression (1).

1.60≦nd p≦1.70 (1-2)

Moreover, it is preferable that the positive single lens having the largest refractive power among all lenses in the second lens group satisfies conditional expression (2-1) instead of conditional expression (2).

10≦ν dp≦30 (2-1)

Furthermore, it is more preferable that the positive single lens having the largest refractive power among all lenses in the second lens group satisfies conditional expression (2-2) instead of conditional expression (2).

15≦ν dp≦25 (2-2)

Accordingly, it is possible to achieve effectively, a zoom lens having a short overall length in which, the chromatic aberration has been corrected favorably.

According to a preferable aspect of the present invention, it is desirable that the positive single lens having the largest refractive power among all lenses in the second lens group satisfies the following conditional expression.

0.6≦θ gF≦0.75 (3)

where,

θ gF denotes a partial dispersion ratio of the positive single lens in the second lens group, and θ gF=(ng−nF)/(nF−nC),

where,

ng denotes a refractive index for a g-line (wavelength λ=435.84 nm) of the positive single lens, nF denotes a refractive index for the F-line (wavelength λ=486.13 nm) of the positive single lens, and nC denotes a refractive index for the C-line (wavelength λ=656.27 nm) of the positive single lens.

Conditional expression (3) regulates a conditional for partial dispersion ratio of the positive single lens in the second lens group.

By satisfying conditional expression (3), shortening of the overall length while correcting a secondary spectrum sufficiently is possible. When a lower limit in conditional expression (3) is surpassed, the correction of the secondary spectrum is insufficient. When an upper limit in conditional expression (3) is surpassed, there is an excessive correction of the secondary spectrum.

where,

fp denotes a focal length of the positive single lens in the second lens group,

fw denotes a focal length of the overall optical system at a wide angle end, and

ft denotes a focal length of the overall optical system at a telephoto end.

Conditional expression (4) regulates a condition for the refractive power of the positive single lens in the second lens group.

By satisfying the conditional expression (4), it is possible to make the refractive power of the positive single lens in the second lens group strong. In other words, it is possible to reduce Petzval's sum for the second lens group, and it is possible to reduce the curvature of field of the overall optical system.

When a lower limit in conditional expression (4) is surpassed, the refractive power of the positive single lens increases excessively, and the correction of curvature of field is excessive.

When an upper limit in conditional expression (4) is surpassed, the refractive power of the positive single lens becomes excessively small, and the correction of curvature of field is insufficient.

Moreover, it is preferable that the positive single lens having the largest refractive power among all lenses in the second lens group satisfies conditional expression (4-1) instead of conditional expression (4).

0.40≦fp/(fw·ft)^1/2≦0.90 (4-1)

Furthermore, it is more preferable that the positive single lens having the largest refractive power among all lenses in the second lens group satisfies conditional expression (4-2) instead of conditional expression (4).

0.45≦fp/(fw·ft)^1/2≦0.85 (4-2)

Accordingly, it is possible to achieve a zoom lens having a short overall length in which, the curvature of field can be corrected effectively.

- where,
- R1 denotes a radius of curvature of a surface nearest to the object side of the positive single lens in the second lens group, and
- R2 denotes a radius of curvature of a surface nearest to an image side of the positive single lens in the second lens group.

By letting the positive single lens in the second lens group to have a meniscus shape which is convex toward the object side, it is possible to dispose a principal point of the second lens group further on the object side. Accordingly, it is easy to carry out substantial zooming by a small amount of movement, and to reduce the size of the optical system while maintaining a favorable performance.

When a lower limit in conditional expression (5) is surpassed and decreases, correction of a coma aberration and a spherical aberration at the telephoto end and an astigmatism at the wide angle end which occur at a surface nearest to the object side of the positive single lens (convex lens) becomes difficult. Therefore it is not desirable that the lower limit in conditional expression (5) is surpassed.

When an upper limit in conditional expression (5) is surpassed and increases, it is not possible to draw the position of the principal point of the second lens group toward the object, and small-sizing becomes difficult.

An electronic image pickup apparatus according to the present invention includes

the image forming optical system described above, and

a photoelectric conversion element, and

the image forming optical system forms an image on the photoelectric conversion element.

Accordingly, it is possible to achieve an electronic image pickup apparatus having a small size and a high zooming ratio.

Exemplary embodiments of the image forming optical system and the electronic image pickup apparatus according to the present invention will be described below in detail.

A zoom lens according to a first embodiment of the present invention will be described below. FIG. 1A, FIG. 1B, and FIG. 1C are cross-sectional views along an optical axis showing an optical arrangement at the time of infinite object point focusing of the zoom lens according to the first embodiment of the present invention, where, FIG. 1A shows a state at a wide angle end, FIG. 1B shows an intermediate state, and FIG. 1C shows a state at a telephoto end.

FIG. 2A, FIG. 2B, and FIG. 2C are diagrams showing a spherical aberration (SA), an astigmatism (AS), a distortion (DT), and a chromatic aberration of magnification (CC) at the time of infinite object point focusing of the zoom lens according to the first embodiment, where, FIG. 2A shows a state at the wide angle end, FIG. 2B shows an intermediate state, and FIG. 2C shows a state at the telephoto end. Moreover, FIY denotes an image height. Symbols in aberration diagrams are same for all the embodiments which will be described later.

The zoom lens of the first embodiment, as shown in FIG. 1A, FIG. 1B, and FIG. 1C, includes in order from an object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power. In all the embodiments which will be described below, in the lens cross-sectional views, CG denotes a cover glass, and I denotes an in image pickup surface of an electronic image pickup element.

The zoom lens according to the first embodiment has a zooming ratio of 7.0 times from the wide angle end to the telephoto end, and an overall length of an optical system is maximum at the telephoto end, which is 40.1 mm.

The first lens group G1, includes in order from an object side, a cemented lens of a negative meniscus lens L1 having a convex surface directed toward the object side and a positive meniscus lens L2 having a convex surface directed toward the object side, and has a positive refractive power as a whole.

The second lens group G2, includes in order from the object side, a negative meniscus lens L3 having a convex surface directed toward the object side, a biconcave negative lens L4, and a positive meniscus lens L5 having a convex surface directed toward the object side, and has a negative refractive power as a whole.

The positive meniscus lens L5 is made of a medium having the smallest refractive index among all the lenses in the second lens group G2, and corrects Petzval's sum for the overall zoom lens favorably.

The third lens group G3, includes in order from the object side, a biconvex positive lens L6, and a cemented lens of a positive meniscus lens L7 having a convex surface directed toward the object side and a negative meniscus lens L8 having a convex surface directed toward the object side, and has a positive refractive power as a whole.

The fourth lens group G4 includes one lens which is a biconvex positive lens L9.

While taking a picture at an object point which is near, focusing is to be carried out by moving the fourth lens group G4 in an optical axial direction.

At the time of zooming from the wide angle end to the telephoto end, the first lens group G1 moves toward the object side. The second lens group G2 moves toward an image side. The third lens group G3 moves toward the object side. The fourth lens group G4, after moving toward the object side, moves toward the image side.

An aspheric surface is provided to six surfaces namely, a surface on the image side of the positive meniscus lens L2 in the first lens group G1, both surfaces of the positive meniscus lens L5 in the second lens group G2, both surfaces of the biconvex positive lens L6 in the third lens group G3, and a surface on the object side of the biconvex positive lens L9 in the fourth lens group G4.

Next, a zoom lens according to a second embodiment of the present invention will be described below. FIG. 3A, FIG. 3B, and FIG. 3C are cross-sectional views along an optical axis showing an optical arrangement at the time of infinite object point focusing of the zoom lens according to the second embodiment of the present invention, where, FIG. 3A shows a state at a wide angle end, FIG. 3B shows an intermediate state, and FIG. 3C shows a state at a telephoto end.

FIG. 4A, FIG. 4B, and FIG. 4C are diagrams showing a spherical aberration (SA), an astigmatism (AS), a distortion (DT), and a chromatic aberration of magnification (CC) at the time of infinite object point focusing of the zoom lens according to the second embodiment, where, FIG. 4A shows a state at a wide angle end, FIG. 4B shows an intermediate state, and FIG. 4C shows a state at the telephoto end.

The zoom lens of the second embodiment, as shown in FIG. 3A, FIG. 3B, and FIG. 3C, includes in order from an object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power.

The zoom lens according to the second embodiment has a zooming ratio of 9.6 times from the wide angle end to the telephoto end, and an overall length of an optical system is maximum at the telephoto end, which is 48.0 mm.

The first lens group G1, includes in order from an object side, a cemented lens of a negative meniscus lens L1 having a convex surface directed toward the object side, a positive meniscus lens L2 having a convex surface directed toward the object side, and a biconvex lens L3, and has a positive refractive power as a whole.

The positive meniscus lens L2 is made of an energy-curable resin having an anomalous dispersibility. Accordingly, the chromatic aberration of magnification, particularly, the chromatic aberration of magnification due to a secondary spectrum, at the telephoto end is corrected favorably without increasing a thickness of the first lens group G1.

The second lens group G2, includes in order from the object side, a negative meniscus lens L4 having a convex surface directed toward the object side, a biconcave negative lens L5, and a positive meniscus lens L6 having a convex surface directed toward the object side, and has a negative refractive power as a whole.

The positive meniscus lens L6 is made of a medium having the smallest refractive index among all the lenses in the second lens group G2, and corrects Petzval's sum for the overall zoom lens favorably.

The third lens group G3, includes in order from the object side, a biconvex positive lens L7, and a cemented lens of a positive meniscus lens L8 having a convex surface directed toward the object side and a negative meniscus lens L9 having a convex surface directed toward the object side, and has a positive refractive power as a whole.

The fourth lens group G4 includes one lens which is a biconvex positive lens L10.

While taking a picture at an object point which is near, focusing is to be carried out by moving the fourth lens group G4 in an optical axial direction.

An aspheric surface is provided to seven surfaces namely, a surface on the image side of the biconvex lens L3 in the first lens group G1, a surface on the image side of the biconcave negative lens L5, and a surface on the object side of the positive meniscus lens L6 in the second lens group G2, both surfaces of the biconvex positive lens L7 in the third lens group G3, and both surfaces of the biconvex positive lens L10 in the fourth lens group G4.

Next, a zoom lens according to a third embodiment of the present invention will be described below. FIG. 5A, FIG. 5B, and FIG. 5C are cross-sectional views along an optical axis showing an optical arrangement at the time of infinite object point focusing of the zoom lens according to the third embodiment of the present invention, where, FIG. 5A shows a state at a wide angle end, FIG. 5B shows an intermediate state, and FIG. 5C shows a state at a telephoto end.

FIG. 6A, FIG. 6B, and FIG. 6C are diagrams showing a spherical aberration (SA), an astigmatism (AS), a distortion (DT), and a chromatic aberration of magnification (CC) at the time of infinite object point focusing of the zoom lens according to the third embodiment, where, FIG. 6A shows a state at the wide angle end, FIG. 6B shows an intermediate state, and FIG. 6C shows a state at the telephoto end.

The zoom lens of the third embodiment, as shown in FIG. 5A, FIG. 5B, and FIG. 5C, includes in order from an object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power.

The zoom lens according to the third embodiment has a zooming ratio of 9.6 times from the wide angle end to the telephoto end, and an overall length of an optical system is maximum at the telephoto end, which is 47.5 mm.

The first lens group G1, includes in order from an object side, a cemented lens of a negative meniscus lens L1 having a convex surface directed toward the object side and a biconvex positive lens L2, and has a positive refractive power as a whole.

The fourth lens group G4 includes one lens which is a biconvex positive lens L9.

While taking a picture at an object point which is near, focusing is to be carried out by moving the fourth lens group G4 in an optical axial direction.

At the time of zooming from the wide angle, end to the telephoto end, the first lens group G1 moves toward the object side. The second lens group G2 moves toward an image side. The third lens group G3 moves toward the object side. The forth lens group G4, after moving toward the object side, moves toward the image side.

An aspheric surface is provided to seven surfaces namely, a surface on the image side of the biconvex positive lens L2 in the first lens group G1, a surface on the image side of the biconcave negative lens L4 and a surface on the object side of the positive meniscus lens L5 in the second lens group G2, both surfaces of the biconvex positive lens L6 in the third lens group G3, and both surfaces of the biconvex positive lens L9 in the fourth lens group G4.

Next, a zoom lens according to a fourth embodiment of the present invention will be described below. FIG. 7A, FIG. 7B, and FIG. 7C are cross-sectional views along an optical axis showing an optical arrangement at the time of infinite object point focusing of the zoom lens according to the fourth embodiment of the present invention, where, FIG. 7A shows a state at a wide angle end, FIG. 7B shows an intermediate state, and FIG. 7C shows a state at a telephoto end.

FIG. 8A, FIG. 8B, an FIG. 8C are diagrams showing a spherical aberration (SA), an astigmatism (AS), a distortion (DT), and a chromatic aberration of magnification (CC) at the time of infinite object point focusing of the zoom lens according to the fourth embodiment, where, FIG. 8A shows a state at the wide angle end, FIG. 8B shows an intermediate state, and FIG. 8C shows a state at the telephoto end.

The zoom lens of the fourth embodiment, as shown in FIG. 7A, FIG. 7B, and FIG. 7C, includes in order from an object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power.

The zoom lens according to the fourth embodiment has a zooming ratio of 9.6 times from the wide angle end to the telephoto end, and an overall length of an optical system is maximum at the telephoto end, which is 41.2 mm.

The first lens group G1, includes in order from an object side, a cemented lens of a negative meniscus lens L1 having a convex surface directed toward the object side, a positive meniscus lens L2 having a convex surface directed toward the object side, and a biconvex positive lens L3, and has a positive refractive power as a whole.

The second lens group G2, includes in order from the object side, a negative meniscus lens L4 having a convex surface directed toward the object side, a cemented lens of a positive meniscus lens L5 having a concave surface directed toward the object side and a biconcave negative lens L6, and a positive meniscus lens L7 having a convex surface directed toward the object side, and has a negative refractive power as a whole.

The positive meniscus lens L5 is made of an energy-curable resin having an anomalous dispersibility. Accordingly, the chromatic aberration of magnification, particularly, the chromatic aberration of magnification due to a secondary spectrum, at the telephoto end is corrected favorably without increasing a thickness of the second lens group G2.

The positive meniscus lens L7 is made of a medium having the smallest refractive index among all the lenses in the second lens group G2, and corrects Petzval's sum for the overall zoom lens favorably.

The third lens group G3, includes in order from the object side, a biconvex positive lens L8, a cemented lens of a positive meniscus lens L9 having a convex surface directed toward the object side and a negative meniscus lens L10 having a convex surface directed toward the object side, and has a positive refractive power as a whole.

The fourth lens group G4 includes one lens which is a positive meniscus lens L11 having a convex surface directed toward the object side.

While taking a picture at an object point which is near, focusing is to be carried out by moving the fourth lens group G4 in an optical axial direction.

An aspheric surface is provided to 10 surfaces namely, both surfaces of the biconvex positive lens L3 in the first lens group G1, a surface on the object side of the positive meniscus lens L5, a surface on an image side of the biconcave negative lens L6, and a surface on the object side of the positive meniscus lens L7 in the second lens group G2, both surfaces of the biconvex positive lens L8 and a surface on the object side of the positive meniscus lens L9 in the third lens group G3, and both surfaces of the biconvex positive lens L11 in the fourth lens group G4.

Next, a zoom lens according to a fifth embodiment of the present invention will be described below. FIG. 9A, FIG. 9B, and FIG. 9C are cross-sectional views along an optical axis showing an optical arrangement at the time of infinite object point focusing of the zoom lens according to the fifth embodiment of the present invention, where, FIG. 9A shows a state at a wide angle end, FIG. 9B shows an intermediate state, and FIG. 9C shows a state at a telephoto end.

FIG. 10A, FIG. 10B, and FIG. 10C are diagrams showing a spherical aberration (SA), an astigmatism (AS), a distortion (DT), and a chromatic aberration of magnification (CC) at the time of infinite object point focusing of the zoom lens according to the fifth embodiment, where, FIG. 10A shows a state at the wide angle end, FIG. 10B shows an intermediate state, and FIG. 10C shows a state at the telephoto end.

The zoom lens of the fifth embodiment, as shown in FIG. 9A, FIG. 9B, and FIG. 9C, includes in order from an object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power.

The zoom lens according to the fifth embodiment has a zooming ratio of 14.4 times from the wide angle end to the telephoto end, and an overall length of an optical system is maximum at the telephoto end, which is 58.0 mm.

The positive meniscus lens L6 is made of a medium having the lower refractive index among all the lenses in the second lens group G2, and corrects Petzval's sum for the overall zoom lens favorably.

The fourth lens group G4 includes one lens which is a biconvex positive lens L10.

While taking a picture at an object point which is near, focusing is to be carried out by moving the fourth lens group G4 in an optical axial direction.

An aspheric surface is provided to eight surfaces namely, a surface on an image side of the positive meniscus lens L3 in the first lens group G1, a surface on the object side of the biconcave negative lens L5 and a surface on the object side of the positive meniscus lens L6 in the second lens group G2, both surfaces of the biconvex positive lens L7 and a surface on the object side of the positive meniscus lens L8 in the third lens group G3, and both surfaces of the biconvex positive lens L10 in the fourth lens group G4.

Numerical data of each embodiment described above is shown below. In each of the numerical data, each of r1, r2, denotes radius of curvature of each lens surface, each of d1, d2, . . . denotes a distance between two lenses, each of nd1, nd2, . . . denotes a refractive index of each lens for a d-line, and each of νd1, νd2, . . . denotes an Abbe constant for each lens. F_NOdenotes an F number, f denotes a focal length of the entire zoom lens system. Further, * denotes an aspheric data, ER denotes an effective radius, S denotes an aperture stop, WE denotes a wide angle end, ST denotes an intermediate state, TE denotes a telephoto end.

When z is let to be an optical axis with a direction of traveling of light as a positive (direction), and y is let to be in a direction orthogonal to the optical axis, a shape of the aspheric surface is described by the following expression.

x=(y²/r)/[1+{1−(K+1)(y/r)²}^1/2]+A4y⁴+A6y⁶+A8y⁸+A10y¹⁰+A12y¹²

where, r denotes a paraxial radius of curvature, K denotes a conical coefficient, A4, A6, A8, A10, and A₁₂denote aspherical surface coefficients of a fourth order, a sixth order, an eight order, a tenth order, and a twelfth order respectively. Moreover, in the aspherical surface coefficients, ‘e−n’ (where, n is an integral number) indicates ‘10⁻ⁿ’.

EXAMPLE 1

Unit mm

Surface data

Surface no.
r
d
nd
νd
ER

Object plane
∞
∞

1
12.2051
0.7000
1.94595
17.98
7.522

2
9.9298
3.5162
1.62263
58.16
7.020

3*
20365.6694
Variable

6.800

4
54.0994
0.7500
1.88300
40.76
5.122

5
4.8062
2.1000

3.655

6
−22.6962
0.6000
1.69350
53.21
3.800

7*
9.5974
0.2000

3.429

8*
6.4751
1.2654
1.62980
19.20
3.447

9
39.0927
Variable

3.400

10(S)
∞
−0.3000

1.900

11*
4.9906
1.5000
1.51633
64.14
1.948

12*
−11.7157
0.1000

1.875

13
3.9602
1.2035
1.69350
53.21
1.773

14
126.7199
0.4000
1.90366
31.31
1.545

15
2.9820
Variable

1.563

16*
10.8265
1.4500
1.53110
55.91
4.002

17
72.3763
Variable

4.000

18
∞
0.3000
1.51633
64.14
4.110

19
∞
0.5000

4.115

20
∞
0.6790
1.51633
64.14
4.127

Image plane
∞

(Light receiving

surface)

Aspherical surface data

3rd surface

κ = 0.000

A4 = 4.02872e−05, A6 = −1.74846e−07, A8 = 2.73292e−09,

A10 = −2.09410e−11

7th surface

κ = 0.124

A4 = −3.96733e−04, A6 = 2.25803e−05, A8 = −7.63555e−07

8th surface

κ = −0.937

A4 = −1.98542e−04, A6 = 1.13819e−05, A8 = −3.41417e−07

11th surface

κ = 0.000

A4 = −7.61090e−04, A6 = 9.17926e−05

12th surface

κ = −10.084

A4 = −9.59804e−05, A6 = 1.36092e−04, A8 = −1.30419e−05,

A10 = 2.46559e−06

16th surface

κ = 0.000

A4 = −6.17458e−05, A6 = 1.59931e−05, A8 = −3.32680e−07

Various data

Zoom ratio 6.978

Wide
Intermediate
Telephoto

angle end
state
end

Focal length
5.509
14.478
38.437

Fno.
3.737
4.762
5.203

Angle of field 2ω
0.000
0.000
0.000

Image height
3.830
3.830
3.830

BF
3.574
9.276
5.846

Total lens length
36.264
36.355
40.075

Object distance
∞
∞
∞

d3
0.248
4.332
9.731

d9
12.452
4.649
0.800

d15
6.505
4.613
10.214

d17
2.367
7.915
4.535

WE (extremely
ST (extremely
TE (extremely

close)
close)
close)

Object distance
∞
∞
200.00

d3
1.218
6.839
0.248

d9
7.927
2.729
12.452

d15
8.209
7.000
6.116

d17
4.005
8.288
2.756

Wide
Intermediate
Telephoto

angle end
state
end

Radius of aperture stop
1.900
1.900
1.900

Entrance pupil position
11.286
21.329
51.783

Exit pupil position
−12.143
−8.511
−22.449

Front side principal
14.864
24.022
38.005

point position

Back side principal
−5.329
−14.145
−38.154

point position

Lens
Initial surface
Focal length

L1
1
−66.210

L2
2
15.955

L3
4
−6.017

L4
6
−9.653

L5
8
12.140

L6
11
6.992

L7
13
5.871

L8
14
−3.385

Zoom lens data

Group
Initial surface
Group focal length

G1
1
21.822

G2
4
−5.217

G3
10
8.751

G4
16
23.776

Group
Group structure length

G1
4.216

G2
4.915

G3
3.403

G4
1.450

Group
Front side principal point position

G1
−0.257

G2
0.615

G3
−2.979

G4
−0.165

Group
Back side principal point position

G1
−2.777

G2
−3.165

G3
−3.922

G4
−1.105

EXAMPLE 2

Unit mm

Surface data

Surface no.
r
d
nd
νd
ER

Object plane
∞
∞

1
14.0382
0.6899
1.94595
17.98
7.673

2
10.6023
0.3665
1.63387
23.38
7.074

3
11.5697
2.8624
1.67790
55.34
7.048

4*
−75793.8403
Variable

6.800

5
93.9163
0.6363
1.88300
40.76
5.233

6
5.1552
2.1734

3.862

7
−41.1036
0.6274
1.74320
49.34
3.800

8*
8.9549
0.4048

3.631

9*
6.7108
1.1933
1.62980
19.20
3.662

10
54.8892
Variable

3.600

11(S)
∞
−0.3500

2.110

12*
5.5910
1.1695
1.51633
64.14
2.122

13*
−13.7671
0.1000

2.121

14
4.4565
1.4788
1.67790
50.72
2.066

15
15.3688
0.3944
2.00330
28.27
1.807

16
3.3863
Variable

1.650

17*
12.2879
2.0078
1.49700
81.54
4.221

18*
−595.0683
Variable

4.237

19
∞
0.3000
1.51633
64.14
4.150

20
∞
0.5000

4.146

21
∞
0.5000
1.51633
64.14
4.137

22
∞
0.5010

4.132

Image plane
∞

(Light receiving

surface)

Aspherical surface data

4th surface

κ = 0.000

A4 = 2.05540e−05, A6 = 1.98219e−09, A8 = −1.16761e−09,

A10 = 1.19838e−11

8th surface

κ = 1.028

A4 = −1.31693e−03, A6 = 3.93380e−05, A8 = −1.05662e−06

9th surface

κ = −1.206

A4 = −7.82471e−04, A6 = 4.29259e−05, A8 = −7.87816e−07

12th surface

κ = 0.000

A4 = −7.35163e−04, A6 = 2.89169e−05

13th surface

κ = 0.000

A4 = 2.35783e−04, A6 = 3.97826e−05, A8 = −2.48480e−06,

A10 = 4.25092e−07

17th surface

κ = 0.000

A4 = −1.26342e−04, A6 = 2.85270e−06, A8 = −3.03124e−07

18th surface

κ = −4.196

A4 = −7.68705e−06, A6 = −2.95930e−06, A8 = −1.99269e−07

Various data

Zoom ratio 9.630

Wide
Intermediate
Telephoto

angle end
state
end

Focal length
5.410
16.790
52.100

Fno.
3.918
5.239
6.027

Angle of field 2ω
0.000
0.000
0.000

Image height
3.830
3.830
3.830

BF
4.615
11.296
6.552

Total lens length
41.703
42.740
47.723

Object distance
∞
∞
∞

d4
0.361
5.729
11.848

d10
15.968
5.820
0.800

d16
7.004
6.140
14.768

d18
3.086
9.769
5.005

WE (extremely
ST (extremely
TE (extremely

close)
close)
close)

Object distance
∞
∞
200.00

d4
3.167
9.543
0.361

d10
9.727
3.118
15.968

d16
5.639
6.026
6.688

d18
6.718
10.383
3.402

Wide
Intermediate
Telephoto

angle end
state
end

Radius of aperture stop
2.110
2.110
2.110

Entrance pupil position
11.025
24.759
63.277

Exit pupil position
−13.630
−11.767
−47.759

Front side principal
14.831
29.326
65.397

point position

Back side principal
−4.909
−16.290
−51.581

point position

Lens
Initial surface
Focal length

L1
1
−50.746

L2
2
174.408

L3
3
17.065

L4
5
−6.198

L5
7
−9.841

L6
9
12.025

L7
12
7.863

L8
14
8.778

Zoom lens data

Group
Initial surface
Group focal length

G1
1
23.617

G2
5
−5.624

G3
11
10.468

G4
17
24.251

Group
Group structure length

G1
3.919

G2
5.035

G3
2.793

G4
2.008

Group
Front side principal point position

G1
−0.194

G2
0.398

G3
−3.786

G4
0.027

Group
Back side principal point position

G1
−2.475

G2
−3.674

G3
−3.917

G4
−1.316

EXAMPLE 3

Unit mm

Surface data

Surface no.
r
d
nd
νd
ER

Object plane
∞
∞

1
14.2782
0.6502
1.94595
17.98
7.587

2
11.2423
3.0229
1.67790
55.34
7.074

3*
−73816.9294
Variable

6.800

4
82.6376
0.6393
1.88300
40.76
5.220

5
5.1180
2.1872

3.853

6
−38.9398
0.5643
1.74320
49.34
3.800

7*
9.3716
0.3633

3.644

8*
6.6523
1.2348
1.62980
19.20
3.672

9
48.8218
Variable

3.600

10 (S)
∞
−0.3500

2.100

11*
5.6770
1.5000
1.51633
64.14
2.109

12*
−13.6326
0.1000

2.110

13
4.3843
1.4155
1.67790
50.72
2.055

14
13.8824
0.3961
2.00330
28.27
1.808

15
3.3901
Variable

1.650

16*
13.8743
1.6000
1.49700
81.54
4.078

17*
−908.1765
Variable

4.186

18
∞
0.3000
1.51633
64.14
4.120

19
∞
0.5000

4.117

20
∞
0.5000
1.51633
64.14
4.111

21
∞
0.5040

4.107

Image plane
∞

(Light

receiving

surface)

Aspherical surface data

3rd surface

κ = 0.000

A4 = 2.14759e−05, A6 = 2.21108e−08, A8 = −1.31981e−09,

A10 = 1.18716e−11

7th surface

κ = 1.861

A4 = −1.49755e−03, A6 = 3.72890e−05, A8 = −9.74767e−07

8th surface

κ = −1.680

A4 = −6.84639e−04, A6 = 4.18018e−05, A8 = −5.50154e−07

11th surface

κ = 0.000

A4 = −7.39357e−04, A6 = 2.58199e−05

12th surface

κ = 0.000

A4 = 2.67649e−04, A6 = −5.51889e−06, A8 = 1.17249e−05,

A10 = −1.05257e−06

16th surface

κ = 0.000

A4 = −6.64758e−04, A6 = 3.07346e−05, A8 = −2.37901e−06

17th surface

κ = 0.000

A4 = −5.81441e−04, A6 = 2.07326e−05, A8 = −1.99372e−06

Various data

Zoom ratio 9.630

Wide
Intermediate
Telephoto

angle end
state
end

Focal length
5.410
16.789
52.098

Fno.
3.954
5.381
6.271

Angle of field 2ω
0.000
0.000
0.000

Image height
3.830
3.830
3.830

BF
4.664
11.555
6.559

Total lens length
41.377
42.321
47.253

Object distance
∞
∞
∞

d3
0.251
5.387
11.468

d9
16.156
5.931
0.800

d15
6.983
6.124
15.104

d17
3.132
10.028
5.015

WE (extremely
ST (extremely
TE (extremely

close)
close)
close)

Object distance
∞
∞
200.00

d3
2.904
9.214
0.251

d9
9.872
3.209
16.156

d15
5.668
6.027
6.621

d17
6.902
10.714
3.494

Wide
Intermediate
Telephoto

angle end
state
end

Radius of aperture stop
2.100
2.100
2.100

Entrance pupil position
10.630
23.210
58.524

Exit pupil position
−12.833
−11.157
−41.469

Front side principal
14.367
27.589
54.108

point position

Back side principal
−4.906
−16.290
−51.582

point position

Lens
Initial surface
Focal length

L1
1
−62.390

L2
2
16.582

L3
4
−6.203

L4
6
−10.113

L5
8
12.092

L6
11
7.973

L7
13
8.916

L8
14
−4.557

Zoom lens data

Group
Initial surface
Group focal length

G1
1
23.286

G2
4
−5.678

G3
10
10.338

G4
16
27.512

Group
Group structure length

G1
3.673

G2
4.989

G3
3.062

G4
1.600

Group
Front side principal point position

G1
−0.185

G2
0.407

G3
−3.630

G4
0.016

Group
Back side principal point position

G1
−2.317

G2
−3.608

G3
−3.936

G4
−1.053

EXAMPLE 4

Unit mm

Surface data

Surface no.
r
d
nd
νd
ER

Object plane
∞
∞

1
12.9837
0.6300
1.94595
17.98
6.615

2
10.3471
0.1500
1.63494
23.22
6.055

3*
10.7059
2.4395
1.61881
63.85
6.030

4*
−171.0581
Variable

5.650

5
329136.3206
0.4500
2.00330
28.27
4.589

6
6.1657
1.4211

3.678

7*
−42.8104
0.4804
1.63494
23.22
3.684

8
−10.8625
0.5000
1.77377
47.18
3.675

9*
7.6760
0.2000

3.482

10*
6.1392
1.3000
1.62980
19.20
3.504

11
324.1097
Variable

3.450

12 (S)
∞
−0.2000

1.850

13*
5.5846
1.4000
1.58313
59.38
1.882

14*
−14.0167
0.0446

1.861

15*
3.7068
2.3942
1.51633
64.14
1.821

16
279.7276
0.3523
2.00330
28.27
1.399

17
2.9742
Variable

1.302

18*
8.7590
1.9227
1.58313
59.38
4.702

19*
46280.0000
Variable

4.709

20
∞
0.3000
1.51633
64.14
4.366

21
∞
0.5000

4.336

22
∞
0.5000
1.51633
64.14
4.259

23
∞
0.4970

4.209

Image plane
∞

(Light

receiving

surface)

Aspherical surface data

3rd surface

κ = 0.000

A4 = 6.87586e−06, A6 = −5.39937e−07

4th surface

κ = −1.000

A4 = 3.00789e−05, A6 = −1.93704e−08, A8 = −2.09144e−10

7th surface

κ = 0.000

A4 = −2.17420e−04, A6 = −8.46972e−06, A8 = 5.72783e−09

9th surface

κ = 0.000

A4 = −4.16070e−04, A6 = −4.08445e−05

10th surface

κ = 0.000

A4 = −6.81102e−04, A6 = −4.38347e−05

13th surface

κ = −0.178

A4 = 8.10235e−04, A6 = 1.47070e−04, A8 = 6.97154e−06,

A10 = 2.84551e−06

14th surface

κ = −3.249

A4 = 1.68031e−03, A6 = 1.16330e−04, A8 = 3.00974e−05,

A10 = 5.06249e−07

15th surface

κ = −0.163

A4 = 3.91452e−04, A6 = −1.93288e−04, A8 = 7.80962e−05,

A10 = −1.12898e−05

18th surface

κ = 0.000

A4 = −5.13572e−04, A6 = 1.23209e−05, A8 = −2.56619e−07

19th surface

κ = 0.000

A4 = −5.42480e−04, A6 = 3.34890e−06

Various data

Zoom ratio 9.599

Wide
Intermediate
Telephoto

angle end
state
end

Focal length
5.169
16.800
49.611

Fno.
3.910
5.612
6.262

Angle of field 2ω
0.000
0.000
0.000

Image height
3.830
3.830
3.830

BF
3.093
9.557
3.190

Total lens length
34.082
36.780
40.980

Object distance
∞
∞
∞

d4
0.243
5.168
11.494

d11
12.519
4.120
0.696

d17
4.742
4.450
12.114

d19
1.568
8.002
1.665

WE (extremely
ST (extremely
TE (extremely

close)
close)
close)

Object distance
∞
∞
200.00

d4
1.578
8.927
0.243

d11
6.152
2.124
12.519

d17
4.297
5.097
4.489

d19
6.166
8.000
1.821

Wide
Intermediate
Telephoto

angle end
state
end

Radius of aperture stop
1.850
1.850
1.850

Entrance pupil position
9.108
19.970
57.695

Exit pupil position
−11.567
−10.760
−134.431

Front side principal
12.455
22.878
89.422

point position

Back side principal
−4.671
−16.272
−49.114

point position

Lens
Initial surface
Focal length

L1
1
−60.941

L2
2
418.237

L3
3
16.366

L4
5
−6.146

L5
7
22.792

L6
8
−5.745

L7
10
9.920

L8
13
7.033

Zoom lens data

Group
Initial surface
Group focal length

G1
1
22.060

G2
5
−5.230

G3
12
8.127

G4
18
15.023

Group
Group structure length

G1
3.219

G2
4.351

G3
3.991

G4
1.923

Group
Front side principal point position

G1
−0.074

G2
0.329

G3
−5.372

G4
−0.000

Group
Back side principal point position

G1
−2.006

G2
−2.911

G3
−4.621

G4
−1.215

EXAMPLE 5

Unit mm

Surface data

Surface no.
r
d
nd
νd
ER

Object plane
∞
∞

1
29.6438
0.8000
1.94595
17.98
9.277

2
22.7582
2.5000
1.43875
94.93
8.873

3
−919.7113
0.2000

8.648

4
18.4752
1.8420
1.58913
61.14
7.654

5*
124.5971
Variable

7.500

6
854.6114
0.6000
1.88300
40.76
5.135

7
6.2969
2.0000

4.003

8*
−15.9456
0.6000
1.86400
40.58
4.000

9
11.3216
0.1824

3.801

10*
6.3382
1.5000
1.62980
19.20
3.890

11
1859.5060
Variable

3.900

12 (S)
∞
−0.0642

2.300

13*
6.4671
1.6937
1.51633
64.14
2.404

14*
−16.3815
0.6243

2.313

15*
6.7315
1.7713
1.73310
48.91
2.217

16
29.3758
0.4546
2.00330
28.27
1.900

17
4.6579
Variable

1.949

18*
12.8433
2.1364
1.53110
55.91
4.362

19*
−8239.2978
Variable

4.400

20
∞
0.6429
1.51633
64.14
4.178

21
∞
0.5000

4.159

22
∞
0.5000
1.51633
64.14
4.136

23
∞
0.2260

4.125

Image plane
∞

(Light

receiving

surface)

Aspherical surface data

5th surface

κ = 0.000

A4 = 3.72259e−06, A6 = −2.07222e−09, A8 = −1.91172e−11,

A10 = 1.86542e−13

8th surface

κ = −62.178

A4 = −3.56643e−04, A6 = −1.18653e−07

10th surface

κ = −7.971

A4 = 1.34475e−03, A6 = −2.98368e−05, A8 = 3.63953e−07

13th surface

κ = 0.000

A4 = 5.20471e−04, A6 = 1.61643e−04, A8 = −1.21576e−05,

A10 = 2.04496e−06

14th surface

κ = 0.000

A4 = 3.34744e−03, A6 = −2.70328e−05, A8 = −4.89982e−07,

A10 = 2.93219e−06

15th surface

κ = 0.998

A4 = 1.22876e−03, A6 = −1.31583e−04, A8 = 3.18278e−06,

A10 = 4.01703e−07

18th surface

κ = 0.000

A4 = −1.78516e−04, A6 = 8.62892e−07, A8 = −5.24052e−07

19th surface

κ = 0.000

A4 = −8.59778e−05, A6 = −4.95316e−07, A8 = −5.01498e−07

Various data

Zoom ratio 14.419

Wide
Intermediate
Telephoto

angle end
state
end

Focal length
5.493
20.736
79.198

Fno.
4.335
5.452
6.059

Angle of field 2ω
0.000
0.000
0.000

Image height
3.830
3.830
3.830

BF
4.999
15.070
6.341

Total lens length
52.630
53.898
57.884

Object distance
∞
∞
∞

d5
0.287
9.221
16.333

d11
20.652
7.593
0.700

d17
9.852
5.174
17.670

d19
3.519
13.366
4.790

WE (extremely
ST (extremely
TE (extremely

close)
close)
close)

Object distance
∞
∞
200.00

d5
4.329
14.011
0.287

d11
11.733
4.550
20.652

d17
6.679
6.839
9.549

d19
9.688
12.198
3.822

Wide
Intermediate
Telephoto

angle end
state
end

Radius of aperture stop
2.300
2.300
2.300

Entrance pupil position
12.017
38.582
102.149

Exit pupil position
−24.596
−11.561
−106.938

Front side principal
16.490
43.172
125.977

point position

Back side principal
−5.267
−20.286
−78.901

point position

Lens
Initial surface
Focal length

L1
1
−109.777

L2
2
50.659

L3
4
36.584

L4
6
−7.187

L5
8
−7.586

L6
10
10.095

L7
13
9.213

L8
15
11.530

Zoom lens data

Group
Initial surface
Group focal length

G1
1
27.112

G2
6
−5.804

G3
12
12.686

G4
18
24.147

Group
Group structure length

G1
5.342

G2
4.882

G3
4.980

G4
2.136

Group
Front side principal point position

G1
1.383

G2
0.506

G3
−4.286

G4
0.002

Group
Back side principal point position

G1
−2.175

G2
−3.250

G3
−5.682

G4
−1.393

Further, numeral value of conditional expressions are shown below:

Example 1
Example 2
Example 3
Example 4
Example 5

(1) ndp
1.62980
1.62980
1.62980
1.62980
1.62980

(2) vdp
19.20
19.20
19.20
19.20
19.20

(3) θgF
0.695
0.695
0.695
0.695
0.695

(4) fp/
0.848
0.716
0.720
0.620
0.491

(fw * ft)^1/2

(5) (R1+
−1.40
−1.28
−1.32
−1.04
−1.01

R2)/

(R1 - R2)

fp
12.1402
12.0246
12.092
9.9205
10.0952

fw
5.417
5.410
5.410
5.167
5.410

ft
37.873
52.100
52.100
49.596
78.099

R1
6.4751
6.7108
6.6523
6.1392
6.3382

R2
39.0927
54.8892
48.8218
324.1097
1859.506

Thus, it is possible to use such image forming optical system of the present invention in a photographic apparatus in which an image of an object is photographed by an electronic image pickup element such as a CCD and a CMOS, particularly a digital camera and a video camera, a personal computer, a telephone, and a portable terminal which are examples of an information processing unit, particularly a portable telephone which is easy to carry. Embodiments thereof will be exemplified below.

In FIG. 11 to FIG. 13 show conceptual diagrams of structures in which the image forming optical system according to the present invention is incorporated in a photographic optical system 41 of a digital camera. FIG. 11 is a frontward perspective view showing an appearance of a digital camera 40, FIG. 12 is a rearward perspective view of the same, and FIG. 13 is a cross-sectional view showing an optical arrangement of the digital camera 40.

The digital camera 40, in a case of this example, includes the photographic optical system 41 (an objective optical system for photography 48) having an optical path for photography 42, a finder optical system 43 having an optical path for finder 44, a shutter 45, a flash 46, and a liquid-crystal display monitor 47. Moreover, when the shutter 45 disposed at an upper portion of the camera 40 is pressed, in conjugation with this, a photograph is taken through the photographic optical system 41 (objective optical system for photography 48) such as the zoom lens in the first embodiment.

An object image formed by the photographic optical system 41 (photographic objective optical system 48) is formed on an image pickup surface 50 of a CCD 49. The object image photoreceived at the CCD 49 is displayed on the liquid-crystal display monitor 47 which is provided on a camera rear surface as an electronic image, via an image processing means 51. Moreover, a memory etc. is disposed in the image processing means 51, and it is possible to record the electronic image photographed. This memory may be provided separately from the image processing means 51, or may be formed by carrying out by writing by recording (recorded writing) electronically by a floppy (registered trademark) disc, memory card, or an MO etc.

Furthermore, an objective optical system for finder 53 is disposed in the optical path for finder 44. This objective optical system for finder 53 includes a cover lens 54, a first prism 10, an aperture stop 2, a second prism 20, and a lens for focusing 66. An object image is formed on an image forming surface 67 by this objective optical system for finder 53. This object image is formed in a field frame of a Porro prism which is an image erecting member equipped with a first reflecting surface 56 and a second reflecting surface 58. On a rear side of this Porro prism, an eyepiece optical system 59 which guides an image formed as an erected normal image is disposed.

By the digital camera 40 structured in such manner, it is possible to realize an optical image pickup apparatus having a zoom lens with a reduced size and thickness, in which the number of structural components is reduced.

Next, a personal computer which is an example of an information processing apparatus with a built-in image forming system as an objective optical system is shown in FIG. 14 to FIG. 16. FIG. 14 is a frontward perspective view of a personal computer 300 with its cover opened, FIG. 15 is a cross-sectional view of a photographic optical system 303 of the personal computer 300, and FIG. 16 is a side view of FIG. 14. As it is shown in FIG. 14 to FIG. 16, the personal computer 300 has a keyboard 301, an information processing means and a recording means, a monitor 302, and a photographic optical system 303.

Here, the keyboard 301 is for an operator to input information from an outside. The information processing means and the recording means are omitted in the diagram. The monitor 302 is for displaying the information to the operator. The photographic optical system 303 is for photographing an image of the operator or a surrounding. The monitor 302 may be a display such as a liquid-crystal display or a CRT display. As the liquid-crystal display, a transmission liquid-crystal display device which illuminates from a rear surface by a backlight not shown in the diagram, and a reflection liquid-crystal display device which displays by reflecting light from a front surface are available. Moreover, in the diagram, the photographic optical system 303 is built-in at a right side of the monitor 302, but without restricting to this location, the photographic optical system 303 may be anywhere around the monitor 302 and the keyboard 301.

This photographic optical system 303 has an objective optical system 100 which includes the zoom lens in the first embodiment for example, and an electronic image pickup element chip 162 which receives an image. These are built into the personal computer 300.

At a front end of a mirror frame, a cover glass 102 for protecting the objective optical system 100 is disposed.

An object image received at the electronic image pickup element chip 162 is input to a processing means of the personal computer 300 via a terminal 166. Further, the object image is displayed as an electronic image on the monitor 302. In FIG. 14, an image 305 photographed by the user is displayed as an example of the electronic image. Moreover, it is also possible to display the image 305 on a personal computer of a communication counterpart from a remote location via a processing means. For transmitting the image to the remote location, the Internet and telephone are used.

Next, a telephone which is an example of an information processing apparatus in which the image forming optical system of the present invention is built-in as a photographic optical system, particularly a portable telephone which is easy to carry is shown in FIG. 17A, FIG. 17B, and FIG. 17C. FIG. 17A is a front view of a portable telephone 400, FIG. 17B is a side view of the portable telephone 400, and FIG. 17C is a cross-sectional view of a photographic optical system 405. As shown in FIG. 17A to FIG. 17C, the portable telephone 400 includes a microphone section 401, a speaker section 402, an input dial 403, a monitor 404, the photographic optical system 405, an antenna 406, and a processing means.

Here, the microphone section 401 is for inputting a voice of the operator as information. The speaker section 402 is for outputting a voice of the communication counterpart. The input dial 403 is for the operator to input information. The monitor 404 is for displaying a photographic image of the operator himself and the communication counterpart, and information such as a telephone number. The antenna 406 is for carrying out a transmission and a reception of communication electric waves. The processing means (not shown in the diagram) is for carrying out processing of image information, communication information, and input signal etc.

Here, the monitor 404 is a liquid-crystal display device. Moreover, in the diagram, a position of disposing each structural element is not restricted in particular to a position in the diagram. This photographic optical system 405 has an objective optical system 100 which is disposed in a photographic optical path 407 and an image pickup element chip 162 which receives an object image. As the objective optical system 100, the zoom lens in the first embodiment for example, is used. These are built into the portable telephone 400.

At a front end of a mirror frame, a cover glass 102 for protecting the objective optical system 100 is disposed.

An object image received at the electronic image pickup element chip 162 is input to an image processing means which is not shown in the diagram, via a terminal 166. Further, the object image finally displayed as an electronic image on the monitor 404 or a monitor of the communication counterpart, or both. Moreover, a signal processing function is included in the processing means. In a case of transmitting an image to the communication counterpart, according to this function, information of the object image received at the electronic image pickup element chip 162 is converted to a signal which can be transmitted.

Various modifications can be made to the present invention without departing from its essence.

According to the present invention, an effect is shown that it is possible provide an image forming optical system in which the curvature of field is corrected favorably, which has been sought strictly in particular, for high zooming ratio and small-sizing, while achieving both the small-sizing and the high zooming ratio, and an electronic image pickup apparatus which includes such image forming optical system.

Number	Name	Date	Kind
4934795	Estelle	Jun 1990	A
5694253	Shibayama	Dec 1997	A
7489450	Matsumoto et al.	Feb 2009	B2
7872807	Mihara	Jan 2011	B2
20030197950	Eguchi	Oct 2003	A1
20040095653	Miyauchi	May 2004	A1
20050254138	Yoneyama	Nov 2005	A1
20080165261	Kamo	Jul 2008	A1
20090067061	Ono et al.	Mar 2009	A1
20090290216	Fujisaki	Nov 2009	A1
20100194928	Amanai	Aug 2010	A1

Number	Date	Country
08-211290	Aug 1996	JP
2003-302576	Oct 2003	JP
2003-315676	Nov 2003	JP
2008-203453	Sep 2008	JP
2009-009121	Jan 2009	JP
2009-093118	Apr 2009	JP

Image forming optical system and electronic image pickup apparatus using the same

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Term Extension

Abstract

Description

Claims

Priority Claims (1)

US Referenced Citations (11)

Foreign Referenced Citations (6)

Non-Patent Literature Citations (3)

Related Publications (1)

Entry
Schott Glass, schott—datasheet—all—us (N-SF14), May 12, 2006, Schott North American, Inc., p. 99.
Schott Glass, schott—datasheet—all—us (N-SF10), Sep. 3, 2001, Schott North American, Inc., p. 97.
Japanese Office Action, dated Dec. 4, 2013, issued in corresponding Japanese Patent Application No. 2010-068921.