JP4758134B2 - Compact zoom photographing optical system and electronic image pickup apparatus using the same - Google Patents

Description

  The present invention relates to a compact zoom imaging optical system that realizes shortening of the overall length and reduction in diameter by devising an optical system portion, and an imaging apparatus using the same.

  In recent years, cameras equipped with a photographing optical system having an electronic image pickup device such as a digital camera have been reduced in size and increased in pixels. There is also an increasing demand for mobile phones equipped with such cameras. Accordingly, there is a demand for downsizing and high performance of the photographing optical system used in these cameras. In such a photographing optical system, a combination of optical elements is devised in order to shorten the overall length of the optical system and reduce the outer diameter of the lens. (See Patent Documents 1, 2, 3, 4, 5 and 6)

As a general configuration, there is a two-group configuration including a first lens group having negative power and a second lens group having positive power (see, for example, Patent Document 1), which has negative power. A three-group configuration comprising a first lens group, a second lens group having a positive power and a third lens group having a positive power (see, for example, Patent Document 2), a first lens group having a negative power and a positive power A three-group configuration comprising a second lens group having power and a third lens group having negative power (see, for example, Patent Document 3 or 4), a first lens group having negative power and a second lens having positive power There is a four-group configuration (for example, see Patent Document 5 or 6) in which a field lens group having a positive power is arranged based on a three-group configuration including a lens group and a third lens group having a negative power.
JP-A-4-242709 Japanese Patent Laid-Open No. 9-21950 JP-A-5-93866 JP 2004-294910 A JP-A-9-179026 JP-A-11-109230

  For example, the zoom lens described in Patent Document 1 employs a two-group configuration including a first lens group having negative power and a second lens group having positive power, and the zoom ratio is about 3 times. The total length of the optical system is relatively small, 10.3 times the maximum photographed image height. However, the number of lenses in each group is large, and the total length of the lens barrel when retracted is long. Further, in order to further reduce the overall length of the optical system, it is necessary to reduce the power of the first lens group, so that the entrance pupil position further enters the image plane side and the diameter of the first lens group becomes thicker. End up. Therefore, the lens frame that houses the optical system becomes large. As a result, the volume increases even if the optical system can be miniaturized.

  The zoom lens described in Patent Document 2 employs a three-group configuration including a first lens group having negative power, a second lens group having positive power, and a third lens group having positive power. . However, similarly to the configuration described in Patent Document 1, although the zoom ratio is about 3 times, the total length of the optical system is about 20 times the maximum photographed image height, and it is difficult to reduce the size.

  In the zoom lens described in Patent Document 3 and the bifocal lens described in Patent Document 4, a first lens group having negative power, a second lens group having positive power, and a third lens group having negative power, A three-group configuration consisting of However, compared to the configuration described in Patent Document 2, the third lens group can have a relatively strong zooming action, so that the overall length of the optical system and the lens outer diameter can be reduced. Is very effective. However, in the configuration described in Patent Document 3, the total length of the optical system is as small as 4.2 times the maximum photographed image height and the zoom ratio is 2.7 times. The incident angle of the imaging light ray with respect to the line is 30 ° or more at the maximum, and when the electronic image pickup device is used, the beam kick due to shading becomes too large, and a good image cannot be obtained. In the configuration described in Patent Document 4, the total length of the optical system is as small as 6.5 times the maximum photographed image height, but the zoom ratio is 2.3 times, and is the most at the wide-angle end and the telephoto end. In the bifocal system that is only designed to obtain good performance, performance in the intermediate focal length range is not guaranteed.

  In the variable power optical system described in Patent Document 5 and the video photographing optical system described in Patent Document 6, a first lens group having a negative power, a second lens group having a positive power, and a first lens group having a negative power. A four-group configuration in which a field lens group having a positive power is arranged based on a three-group configuration consisting of three lens groups is adopted. However, the half angle of view at the wide-angle end is 28 ° or less, and the angle of view is so narrow that wide-field photography cannot be performed.

  The present invention has been made in view of the above-described problems of the prior art. The object of the present invention is to achieve a wide angle of view while ensuring an appropriate zoom ratio and to provide shading. It is an object of the present invention to provide a compact zoom imaging optical system that can obtain a good image with less influence and can achieve downsizing of the total length of the optical system, the total length when the lens barrel is retracted, and the lens diameter.

In order to achieve the above object, a photographic optical system according to the present invention includes, in order from the object side, a first lens group having a negative power, a second lens group having a positive power, and a first lens group having a negative power. Three lens groups, and when zooming from the wide-angle end to the telephoto end, the second lens group moves to the object side so that the distance between the first lens group and the second lens group decreases, The third lens group moves so that the distance between the second lens group and the third lens group changes, and only one negative lens among the lenses constituting the first lens group is provided. second lens group comprises at least one positive lens and one negative lens, and the following conditional expressions (1), by satisfying the (2), (3), (4) and (9) Features .
4.0 ≦ W_L / (tan ω × FL) ≦ 12.0 (1)
1.7 ≦ | ΔD12 | / (tan ω × FL) ≦ 4.6 (2)
52.0 ≦ PAνd (3)
0.45 ≦ D23W / (tan ω × FL) ≦ 3.0 (4)
75.0 ≦ Pνd (9)
However,
W_L: Total length of the optical system at the wide-angle end
ω: Half angle of view in any state
FL: Focal length of the entire system in the above arbitrary state
Derutadi12: variation of distance between the first lens group and the second lens group upon zooming from the wide-angle end to the telephoto end
PAνd: Abbe number of positive lens in the second lens group
D23W: Distance between the second lens group and the third lens group at the wide-angle end
Pνd: Abbe number of at least one positive lens among the positive lenses in the second lens group .

Moreover, it is preferable that the photographing optical system according to the present invention satisfies the following conditional expression (5).
0.38 ≦ (f2 / fw) × (tan ω × FL / fw) ≦ 0.95
... (5)
However,
f2: focal length of the second lens group
fw: Total focal length at the wide-angle end.

The imaging optical system according to the present invention preferably satisfies the following conditional expression (6) .
2.7 ≦ W_L / fw ≦ 10.0 (6)
However,
fw: Total focal length at the wide-angle end
It is.

In order to achieve the above object, a photographic optical system according to the present invention includes, in order from the object side, a first lens group having a negative power, a second lens group having a positive power, and a negative power. A third lens group, and when zooming from the wide-angle end to the telephoto end, the second lens group moves toward the object side so that the distance between the first lens group and the second lens group decreases. The third lens group moves so that the distance between the second lens group and the third lens group changes, and only one negative lens among the lenses constituting the first lens group, The second lens group includes one negative lens and at least one positive lens, and satisfies the following conditional expressions (1), (2), (3), (7), and (9). It is characterized by that .
4.0 ≦ W_L / (tan ω × FL) ≦ 12.0 (1)
1.7 ≦ | ΔD12 | / (tan ω × FL) ≦ 4.6 (2)
52.0 ≦ PAνd (3)
3.7 ≦ | ΔD12 / ΔD23 | (7)
75.0 ≦ Pνd (9)
However,
W_L: Total length of the optical system at the wide-angle end
ω: Half angle of view in any state
FL: Focal length of the entire system in the above arbitrary state
Derutadi12: variation of distance between the first lens group and the second lens group upon zooming from the wide-angle end to the telephoto end
PAνd: Abbe number of positive lens in the second lens group
Derutadi23: variation of distance between the second lens group and the third lens group upon zooming from the wide-angle end to the telephoto end
Pνd: at least one positive lens among the positive lenses in the second lens group
Abbe's number .

In the photographing optical system according to the present invention, it is preferable that the first lens group includes two lenses, a negative lens and a positive lens, in order from the object side, and satisfies the following conditional expression (8).
0.6 ≦ G1Σd / (tan ω × FL) ≦ 1.3 (8)
However,
G1shigumad: the total thickness <br/> of the first lens group.

Moreover, it is preferable that the photographic optical system according to the present invention satisfies the following conditional expression (10).
45.0 ≦ Pνd−Nνd (10)
However,
Enunyud: the Abbe number of the negative lens in the second lens group.

  In the photographing optical system according to the present invention, it is preferable that the third lens group includes two or less lenses.

  In the photographic optical system according to the present invention, the first lens group includes two negative lenses and a positive lens in order from the object side, and the second lens group includes a positive lens, a negative lens, and a positive lens in order from the object side. Preferably, the third lens group is composed of three lenses or two lenses, a positive lens and a negative lens, and the third lens group is composed of one negative lens.

  In the photographing optical system according to the present invention, when the first lens group is in the state between the wide-angle end and the telephoto end during zooming, the length from the lens surface closest to the object side of the first lens group to the imaging surface is long. It is preferable to be movable so that the length can be minimized.

The imaging optical system according to the present invention, at the wide angle end, the following conditional expression (11-1), (11-2), (11-3) and more preferably satisfies the.
7.0% ≦ | DTW_ × 1.0 |
... (11-1)
3.5% ≦ || DTW_ × 0.7 | ≦ 15.0%
(11-2)
7.0% ≦ || DTW_ × 1.0 | ≦ 25.0%
... (11-3)
| ΔDTW | ≦ 15.0%
(11-4) However,
DTW_ × 0.7: at infinity,% distortion length at the position of the wide-angle end up photographing image height × 0.7 Display
DTW_ × 1.0: at infinity,% distortion length at the position of × 1.0 at the wide angle end up photographing image height displayed
ΔDTW: DTW_ × 0.7−DTW_ × 1.0
And
Y'0: Paraxial imaging height
Y ′: When the actual imaging height is assumed,
Distortion amount = (Y′−Y′0) / Y′0 × 100 (%)
It is.

  In the photographing optical system according to the present invention, it is preferable to perform focusing by moving the third lens group in the optical axis direction.

Moreover, it is preferable that the photographic optical system according to the present invention satisfies the following conditional expression (12).
0.53 ≦ tan ω × FL / fw (12)
However,
fw: the focal length of the entire system at the wide-angle end .

In order to achieve the above object, a photographic optical system according to the present invention includes, in order from the object side, a first lens group having a negative power, a second lens group having a positive power, and a negative power. a third lens group having made, moving from the wide-angle end when zooming to the telephoto end, the second lens group toward the object side so that the distance is reduced between the second lens group and the third lens group The third lens group moves so that the distance between the second lens group and the third lens group changes, and only one negative lens among the lenses constituting the first lens group, The second lens group includes one negative lens and at least one positive lens, and satisfies the following conditional expression .
4.0 ≦ W_L / (tan ω × FL) ≦ 12.0 (1)
1.7 ≦ | ΔD12 | / (tan ω × FL) ≦ 4.6 (2)
52.0 ≦ PAνd (3)
75.0 ≦ Pνd (9)
However,
W_L: Total length of the optical system at the wide-angle end
ω: Half angle of view in any state
FL: Focal length of the entire system in the above arbitrary state
Derutadi12: variation of distance between the first lens group and the second lens group upon zooming from the wide-angle end to the telephoto end
PAνd: Abbe number of positive lens in the second lens group
Pνd: Abbe number of at least one positive lens among the positive lenses in the second lens group
It is.

  Alternatively, it is preferable that the third lens group includes four groups in which a fourth lens group having a positive power on the image side and fixed even during zooming is disposed.

  In order to achieve the above object, an imaging apparatus according to the present invention includes any one of the imaging optical systems and an imaging element disposed on the image side of the imaging optical system.

  According to the present invention, an appropriate zoom ratio can be ensured, a wide angle of view can be achieved, a good image quality, a reduction in the total length of the optical system or the retractable length, and a reduction in the lens outer diameter can be achieved. Thus, a compact zoom photographing optical system that can be used and an image pickup apparatus using the same can be obtained.

The photographing optical system according to the present invention includes, in order from the object side, a first lens group having negative power, a second lens group having positive power, and a third lens group having negative power . Furthermore, when zooming to the telephoto end from the wide-angle end, the second lens unit moves toward the object side so that the distance is reduced between the first lens group and the second lens group, the third lens group and the second The lens unit and the third lens unit are configured to move so as to change .
With this configuration, the height of the incident light is kept low while shortening the overall length of the optical system, the incident angle on the imaging surface is made smaller than the normal to the imaging surface, and imaging is performed when an electronic imaging device is used. The influence of shading by elements can be reduced. Further, the third lens group having a negative power is disposed with a space from the second lens group, and is movable with respect to the second lens group at the time of zooming. It can have a variable power action. As a result, the outer diameter of the first lens unit can be kept small while shortening the entire system even when a zoom ratio exceeding 2.5 times is secured, and the half angle of view at the wide angle end is 28 °. A basic configuration that achieves the above (that is, conditional expression (12) “0.53 ≦ tan ω × FL / fw”, where fw is the focal length of the entire system at the wide-angle end) can be adopted.

In the photographing optical system of the present invention, the following conditional expression (1) is satisfied.
4.0 ≦ W_L / (tan ω × FL) ≦ 12.0 (1)
However,
W_L: From the lens surface closest to the object side of the first lens group at the wide-angle end to the imaging surface
Length to
ω : Half angle of view in any state
FL: The focal length of the entire system in the arbitrary state.
Conditional expression (1) is a condition for shortening the overall length of the optical system, maintaining the light beam exit angle toward the imaging plane at an appropriate value , and obtaining a good image. If the lower limit of conditional expression (1) is not reached, the total length of the optical system becomes too short, so that the incident angle of the light beam emitted from the optical system and directed to the imaging plane is suppressed to a small value with respect to the imaging plane normal. However, even if a reduction in size can be achieved, a good image cannot be obtained due to the influence of shading. If the upper limit of conditional expression (1) is exceeded, the total length of the optical system becomes too long, and it becomes impossible to achieve downsizing.

Moreover, the following conditional expression (2) is satisfied.
1.7 ≦ | ΔD12 | / (tan ω × FL) ≦ 4.6 (2)
However,
ΔD12: the first lens group and the second lens group at the time of zooming from the wide angle end to the telephoto end
Change in interval
ω : Half angle of view in any state
FL: The focal length of the entire system in the arbitrary state.
By satisfying the conditional expression (2), there is no need to increase the power of the first lens group and the second lens group or increase the zooming action of the third lens group, and the overall length of the optical system can be shortened. A zoom ratio exceeding 2.5 times can be secured without impeding realization, and good performance can be obtained while shortening the overall length of the optical system. In order to obtain a zoom ratio of 2.5 or more in a state where the lower limit of conditional expression (2) is not reached, the power of the first lens group and the second lens group are increased, or the zoom ratio of the third lens group is increased. It is necessary to enhance the action. When the powers of the first lens group and the second lens group are increased, since the powers are too strong to obtain a required zoom ratio, good performance due to zooming cannot be obtained. When the zooming action of the third lens group is enhanced, if the number of lenses in the third lens group is two or less, aberration fluctuation due to zooming cannot be suppressed, and as a result, the thickness of the lenses constituting the third lens group And the total distance between the lenses increases, making it impossible to shorten the entire length of the entire optical system or shorten the total length of the lens frame when retracted. If the upper limit of the conditional expression (2) is exceeded, it is easy to obtain a high zoom ratio, but it becomes difficult to shorten the total length of the optical system, and further, for example, an aperture that moves integrally with the second lens group is used as the second lens. For example, when the lens is disposed on the object side of the group, the entrance pupil enters the image plane side too much from the most object side surface of the first lens group. As a result, the outer diameter of the first lens group required for off-axis rays to pass through the center of the entrance pupil becomes large, and the lens diameter cannot be reduced.

  Here, by adopting a configuration in which only one negative lens among the lenses constituting the first lens group is adopted, the total thickness of the first lens group is shortened, and the total length of the entire optical system or when the lens is retracted. The total length of the lens frame can be shortened, and the first lens outer diameter can be reduced.

In addition, the second lens group has a positive lens and a negative lens. In addition, the following conditional expression (3) is satisfied.
52.0 ≦ PAνd (3)
However,
PAνd: Abbe number of the positive lens in the second lens group (in the case of multiple lenses, all positive lenses)
It is.
By satisfying the conditional expression (3), the axial chromatic aberration and the lateral chromatic aberration at the time of zooming can be effectively corrected even when the number of second lens units is small, and the zooming ratio is 2.5. Even if it is twice or more, good performance can be obtained in the entire region. When there are a plurality of positive lenses in the second lens group, it is preferable that all of them satisfy the conditional expression (3).

  With the above-described configuration, the zoom ratio is 2.5 times or more and the half angle of view at the wide-angle end is 28 ° or more. Good performance can be obtained while realizing a reduction in diameter.

  Further, by arranging a positive power lens group on the image side from the third lens group, the light beam diverged by the third lens group having negative power is made to be parallel to the optical axis, and the influence of shading is reduced. It is also possible to take measures. However, considering the shortening of the total length of the optical system or the retracted length of the lens frame, in order from the object side, a lens group having a negative power, a lens group having a positive power, and a lens group having a negative power. In order from the group or the object side, it is desirable to form four groups of a lens group having a negative power, a lens group having a positive power, a lens group having a negative power, and a lens group having a positive power.

In addition, the said conditional expression (1) and (2) is 5.5 <= W_L / (tan (omega) * FL) <= 10.5 ... (1 ')
2.2 ≦ | ΔD12 | / (tan ω × FL) ≦ 4.6 (2 ′)
If this condition is satisfied, the above effect can be further enhanced.

Moreover, it is desirable to satisfy the following conditional expression (4).
0.45 ≦ D23W / (tan ω × FL) ≦ 3.0 (4)
However,
D23W: The third lens from the most image-side lens surface of the second lens unit at the wide-angle end.
Length of the lens group to the most object side lens surface
ω : Half angle of view in any state
FL: The focal length of the entire system in the arbitrary state.
By satisfying the conditional expression (4), it is possible to obtain a good aberration correction effect and a zooming action by the third lens group even if the third lens group has a small number of lenses of two or less. If the lower limit of conditional expression (4) is not reached, it will be difficult to correct aberrations at the wide-angle end, and it will be difficult to ensure a half field angle of 28 ° or more at the wide-angle end. In addition, it becomes difficult to secure the amount of movement of the third lens group with respect to the second lens group, and it becomes difficult to maintain performance at the middle or at the telephoto end. If the upper limit of the conditional expression (4) is exceeded, when the angle of the light beam emitted from the third lens group is made small as a shading countermeasure, the power of the third lens group becomes too weak, and a zooming effect is obtained. As a result, it becomes difficult to shorten the overall length of the optical system.
The conditional expression (4) is
0.7 ≦ D23W / (tan ω × FL) ≦ 2.5 (4 ′)
If the conditional expression is satisfied, the above effect can be further enhanced .

Moreover, it is desirable that the following conditional expression (5) is satisfied.
0.38 ≦ (f2 / fw) × (tan ω × FL / fw) ≦ 0.95
... (5)
However,
f2: focal length of the second lens unit
fw: Total focal length at the wide-angle end
ω : Half angle of view in any state
FL: The focal length of the entire system in the arbitrary state.
By satisfying the conditional expression (5), it is possible to obtain a small and good performance while ensuring a zoom ratio and a half angle of view of 28 ° or more at the wide angle end. If the lower limit of conditional expression (5) is not reached, the second lens group having a large zooming effect can be obtained when a zoom ratio of 2.5 or more is maintained while maintaining the performance in the entire zooming region. Since it is necessary to make the power weaker, it becomes difficult to secure a half field angle of 28 ° or more at the wide angle end and a good performance. If the upper limit of conditional expression (5) is exceeded, the power of the second lens group will become weak, and a zoom ratio of 2.5 or more and 28 ° at the wide-angle end while maintaining the performance in the entire zoom area. to ensure a more half angle, it is necessary to largely move the second lens group. Therefore, it is necessary to take a large space for the second lens group to move, and the total length of the optical system tends to be long.
The conditional expression (5) is
0.45 ≦ (f2 / fw) × (tan ω × FL / fw) ≦ 0.85
... (5 ')
If this conditional expression is satisfied, the performance can be kept better.

Moreover, it is desirable to satisfy the following conditional expression (6).
2.7 ≦ W_L / fw ≦ 10.0 (6)
However,
W_L: Length from the lens surface closest to the object side to the imaging surface of the first lens unit at the wide-angle end
fw: Total focal length at the wide-angle end.
By satisfying the conditional expression (6), it is possible to obtain a good image with a wide angle of view, a shortened total length of the optical system, and an incident angle of the light beam on the imaging plane with respect to the imaging plane normal. It can be maintained at an appropriate angle. If the lower limit of conditional expression (6) is not reached, the incident angle of the light beam on the imaging plane with respect to the imaging plane normal becomes too large when a half angle of view of 28 ° or more is to be secured at the wide-angle end. As a result, a good image cannot be obtained. If the upper limit of conditional expression (6) is exceeded, when attempting to ensure a half angle of view of 28 ° or more at the wide-angle end, the total length of the optical system at the wide-angle end becomes too long, and thus miniaturization cannot be achieved.

Moreover, it is desirable to satisfy the following conditional expression (7).
3.7 ≦ | ΔD12 / ΔD23 | (7)
However,
ΔD12: Amount of change in the distance between the first lens unit and the second lens unit upon zooming from the wide-angle end to the telephoto end
ΔD23: an amount of change in the distance between the second lens group and the third lens group upon zooming from the wide-angle end to the telephoto end.
By satisfying the conditional expression (7), it is possible to ensure good performance in the entire zooming area even if the third lens group is configured with a small number of two or less. If the lower limit of conditional expression (7) is not reached, the positional fluctuation of the third lens group with respect to the second lens group becomes too large. Therefore, if the number of the third lens group is two or less, aberrations are maintained well over the entire zooming region. Becomes difficult. Although the performance variation due to zooming can be suppressed by using three or more third lens groups, the total thickness of the third lens group is increased, and the total length of the optical system or the retracted length of the lens frame is increased. Shortening becomes difficult.

  Furthermore, it is desirable that the first lens group is composed of two lenses of a negative lens and a positive lens in order from the object side. With this configuration, even when the zoom ratio exceeds 2.5, fluctuations due to the change in axial chromatic aberration and lateral chromatic aberration can be satisfactorily secured with a small number of lenses.

At this time, it is desirable to satisfy the following conditional expression (8).
0.6 ≦ G1Σd / (tan ω × FL) ≦ 1.3 (8)
However,
G1Σd: From the most object-side lens surface to the most image-side lens surface of the first lens unit
Length in
ω : Half angle of view in any state
FL: The focal length of the entire system in the arbitrary state.
By satisfying conditional expression (8), it is possible to satisfactorily ensure aberration fluctuations while shortening the overall length of the optical system. If the lower limit of conditional expression (8) is not reached, the degree of freedom for correcting aberrations, that is, the lens thickness and the radius of curvature are limited, so when the zoom ratio exceeds 2.5 times, It is difficult to ensure a good off-axis aberration over the entire zooming region. When the upper limit of conditional expression (8) is exceeded, it becomes difficult to shorten the total length of the optical system or the total length of the lens barrel when retracted. Further, the lens outer diameter of the first lens group becomes large, and miniaturization cannot be achieved.

Furthermore, the second lens group includes one negative lens and at least one positive lens. In addition, at least one of the positive lenses satisfies the following conditional expression (9). Is desirable.
75.0 ≦ Pνd (9)
However,
Pνd: Abbe number of the positive lens in the second lens group (in the case of multiple lenses, any one positive lens)
It is.
By configuring the second lens group having a large zooming action in this way, it is possible to keep good fluctuations in axial chromatic aberration due to zooming.

At this time, it is desirable to satisfy the following conditional expression (10).
45.0 ≦ Pνd−Nνd (10)
However,
Pνd: Abbe number of the positive lens in the second lens group (in the case of multiple lenses, any one positive lens)
Nvd: Abbe number of the negative lens in the second lens group.
By satisfying the conditional expression (10), it is possible to satisfactorily ensure the variation of longitudinal chromatic aberration due to zooming and further improve the performance.

Further, in order from the object side, the first lens group is a positive lens and two negative lenses, the second lens group is a positive lens, a negative lens, three positive lenses or a positive lens, two negative lenses, and a third lens. The group is preferably composed of only one negative lens.
With this configuration, the total thickness of each lens group can be reduced, and better performance can be ensured while further shortening the overall length of the lens frame when retracted. In addition, the second lens group can be composed of two lenses, a positive lens and a negative lens, in order from the object side by making the most object side surface and the most image side surface an aspherical surface. Furthermore, the total length of the lens barrel when retracted can be further shortened. Further, a configuration in which a lens group having power is not arranged on the image plane side from the third lens group, that is, a first lens group having negative power, a second lens group having positive power, and a third lens having negative power. By using only three lens groups, the total length of the optical system or the total length when the lens barrel is retracted can be further shortened.

Furthermore, it is desirable that the first lens group is movable so that the total length of the optical system is the shortest in the state between the wide-angle end and the telephoto end during zooming.
With such a configuration, it is possible to increase the amount of change in the distance due to zooming from the first lens group to the second lens group, and to efficiently correct aberrations in the first lens group and the second lens group. Can be done. In other words, the first lens group can be effectively provided with the field curvature correction effect in the intermediate magnification range, and the overall length of the optical system can be further shortened in view of its performance.

Moreover, it is desirable to satisfy the following conditional expression (11-1).
7.0% ≦ | DTW_ × 1.0 | (11-1)
However,
DTW_ × 1.0:% display of the distortion aberration of length at the position of the maximum photographed image height at the wide angle end at × 1.0 at the time of focusing on infinity.
If the above-described conditional expression (11-1) is satisfied, that is, if a configuration is adopted in which distortion is generated to some extent, the burden on the first lens group for correcting distortion, particularly at the wide-angle end, can be reduced. Therefore, the degree of freedom of aberration correction in the first lens group in which distortion occurs most at the wide angle end can be greatly increased. As a result, the total thickness of the first lens group can be reduced, and the total length of the optical system or the total length of the lens frame when retracted can be further shortened.

It should be noted that a good image can be obtained by correcting the distortion of the photographed image using electrical processing after photographing. In that case, it is desirable to satisfy the following conditional expressions (11-2), (11-3), and (11-4).
3.5% ≦ | DTW_ × 0.7 | ≦ 15.0% (11-2)
7.0% ≦ | DTW_ × 1.0 | ≦ 25.0% (11-3)
| ΔDTW | ≦ 15.0% (11-4)
However,
DTW_ × 0.7: × 0.7 of the maximum captured image height at the wide-angle end when focusing on infinity
Of distortion in length at the position of
DTW_ × 1.0: × 1.0 of the maximum photographed image height at the wide angle end when focusing on infinity
Of distortion in length at the position of
ΔDTW: DTW_ × 0.7−DTW_ × 1.0
It is.
In the above conditional expressions (11-2) and (11-3), if the lower limit of each of the conditional expressions (11-2) and (11-3) is exceeded, that is, if the amount of distortion is too small, the burden on the lens system for correcting distortion becomes large. Therefore, it is difficult to reduce the total thickness of the first lens unit. Further, if distortion aberration correction is performed by electrical processing of an image exceeding the respective upper limits in the conditional expressions (11-2) and (11-3), the resolution is remarkably lowered, and a good image cannot be obtained. In order to prevent the resolution from being lowered due to electrical correction, it is desirable to satisfy the conditional expression (11-4).

Furthermore, it is desirable to perform focusing by moving the third lens group in the optical axis direction.
Since the third lens group can be reduced in diameter by the configuration of the optical system in the present invention, the third lens group can be reduced in size and weight. Therefore, if focusing is performed by moving the third lens group, it is easy to reduce the size of the drive actuator and the size of the lens frame can be reduced.

  At this time, by further satisfying the conditional expression (4), it is possible to appropriately secure the distance from the second lens group to the third lens group, and to sufficiently secure a driving allowance for focusing due to manufacturing variations. be able to. Further, by satisfying the conditional expression (7), it is possible to suppress aberration fluctuations due to focusing, and it is possible to ensure good performance even at a close distance.

The imaging apparatus according to the present invention has a single positive-power field lens that is fixed even at the time of zooming in the vicinity of the image sensor without arranging a low-pass filter, and the object side of the package of the image sensor It is good also as a structure sealed with a field lens and a frame.
By adopting such a configuration, it is possible to set the incident angle to the imaging surface by the field lens to an appropriate angle while shortening the overall length of the optical system, and to prevent image deterioration due to shading. Can do. In addition, although an image pickup device such as a CCD is generally provided with a cover glass, it is close to the image formation surface, so that even if it is dusty, it is reflected in the image when dust is attached. In order to prevent this, the structure is generally sealed with a low-pass filter. In the present invention, by replacing the low-pass filter with a lens having a field lens effect, it is possible to take measures against dust and to reduce the effective light beam diameter, that is, to reduce the effective light beam in each lens group. Thus, the optical system can be downsized.

In the photographic optical system of the present invention configured as described above, if the field lens is arranged as the fourth lens group on the image side from the third lens group, the effect of downsizing the optical system can be further enhanced. Furthermore, here
0.6 ≦ DL / (tan ω × FL) ≦ 1.5 (13)
However,
DL: Distance from the object side surface of the field lens to the imaging surface
ω : Half angle of view in any state
FL: When configured so as to satisfy the focal length of the entire system in the arbitrary state, it is possible to effectively eliminate dust reflection while reducing the size.

Hereinafter, the present invention will be described in detail based on illustrated embodiments. In addition, Example 2 is a reference example.

In the following embodiments, RDY is the radius of curvature of each lens surface, THI is the thickness or spacing of each lens, Nd is the refractive index of each lens at the d-line, Vd is the Abbe number of each lens at the d-line, K is a conical coefficient, A ₄ , A ₆ , A ₈ , and A ₁₀ are aspherical coefficients, f is the focal length of the entire system, Fno is the F number, 2ω is the full angle of view, and D1, D2, and D3 are variable intervals, respectively. ing.
Each aspheric shape is expressed by the following equation using each aspheric coefficient. However, the coordinate in the optical axis direction is Z, and the coordinate in the direction perpendicular to the optical axis is Y.
Z = (Y ² / r) / [1+ {1− (1 + K) · (Y / r) ² } ^1/2 ]
+ A ₄ Y ⁴ + A ₆ Y ⁶ + A ₈ Y ⁸ + A ₁₀ Y ¹⁰
In addition, among the aspheric coefficients, for example, the value of A _{4 in} the aspheric surface 2 of Example 1, −4.95666e-4, can be displayed as −4.95666 × 10 ^−4, but in this numerical data, All are displayed in the former format.
Further, in the data according to the conditional expression of the present invention in each of the following examples, each data is calculated as tan ω × FL = IH (maximum photographed image height at the wide angle end).

  FIG. 1 is a diagram illustrating the configuration of the photographing optical system according to the present embodiment, where (a) shows a state at the wide-angle end, (b) shows an intermediate state, and (c) shows a state at the telephoto end. FIG. 2 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom lens according to the present embodiment is focused on an object point at infinity, (a) is a wide angle end, (b). (C) shows the state at the telephoto end.

As shown in FIGS. 1A to 1C, the photographing optical system of the present embodiment includes a first lens group G ₁ having a negative power, an aperture stop S, and a second lens having a positive power. and the group G _2, the third lens group G ₃ having a negative power, and a filter LPF such as an optical low-pass filter is constituted by a cover glass CG of an electronic image sensor such as a CCD. Note that the CCD shows only its image plane.

The first lens group G ₁ includes a negative meniscus lens L ₁₁ having an aspheric image side surface and a convex surface facing the object side, and a positive meniscus lens L ₁₂ having a convex surface facing the object side. The second lens group G ₂ includes, in order from the object side, a cemented lens including a biconvex positive lens L ₂₁ and a negative meniscus lens L ₂₂ having a convex surface facing the image side, and both surfaces are aspherical and have a convex surface facing the image side. It is composed of a positive meniscus lens L ₂₃ has. The third lens group G _3, the surface on the object side is constituted by only a biconcave negative lens L ₃₁ which is a non-spherical surface.

In the thus configured imaging optical system of this embodiment, on the optical axis Lc During zooming from the wide angle end to the telephoto end, the first lens group G ₁ to the back object side after moving to the image side The second lens group G ₂ moves so as to approach the first lens group G ₁ , and the third lens group G ₃ moves toward the object side.

  Next, numerical data of lenses constituting the photographing optical system according to the present example are shown.

Surface RDY THI Nd Vd
1 227.039 1.000 1.80610 40.92
2 * 4.449 0.983
3 6.357 1.900 1.78470 26.29
4 20.328 D1
5 (Aperture) ∞ 0.000
6 4.254 2.300 1.49700 81.54
7 -5.098 0.700 1.90366 31.31
8 -9.394 0.255
9 * -4.810 1.636 1.51633 64.14
10 * -4.129 D2
11 * -10.807 1.000 1.69350 53.21
12 49.892 D3
13 ∞ 0.860 1.53996 59.45
14 ∞ 0.270
15 ∞ 0.500 1.51633 64.14
16 ∞ 0.690
17 (Imaging surface) ∞
*: Aspherical surface

Aspherical coefficient surface RDY K A ₄ A ₆ A ₈ A ₁₀
2 4.449 0.0000 -4.9566e-4 -5.5162e-5 2.5320e-6 -2.2245e-7
9 -4.810 0.0000 -9.2682e-4 4.1323e-4 1.6390e-5 0
10 -4.129 0.0000 2.4314e-4 3.1309e-4 2.2427e-5 4.9752e-7
11 -10.807 -0.9470 2.4674e-6 9.4532e-5 1.0943e-5 -5.3118e-7

Zoom data
Wide angle end Medium telephoto end f 6.421 10.987 18.623
Fno 3.175 4.221 5.877
2ω (°) 62.3 36.6 21.8
D1 9.598 4.011 0.495
D2 4.742 4.168 3.877
D3 2.007 5.736 11.223

Each data related to the conditional expression is
Conditional expression (1): W_L / (tan ω × FL) = 7.90
Conditional expression (2): | ΔD12 | / (tan ω × FL) = 2.53
Conditional expression (3): PAνd = 81.54 (lens L ₂₁ )
PAνd = 64.14 (lens L ₂₃ )
Conditional expression (4): D23W / (tan ω × FL) = 1.32
Conditional expression (5): (f2 / fw) × (tan ω × FL / fw) = 0.64
Conditional expression (6): W_L / fw = 4.43
Conditional expression (7): | ΔD12 / ΔD23 | = 10.58
Conditional expression (8): G1Σd / (tan ω × FL) = 1.08
Conditional expression (9): Pνd = 81.54 (lens L ₂₁ )
Pνd = 64.14 (lens L ₂₃ )
Conditional expression (10): Pνd−Nνd = 50.23 (lens L ₂₁ )
Pνd−Nνd = 32.83 (lens L ₂₃ )
Conditional expression (11-1): | DTW_ × 1.0 | = 7.25
Conditional expression (11-2): | DTW_ × 0.7 | = 3.81
Conditional expression (11-3): | DTW_ × 1.0 | = 7.25
Conditional expression (11-4): | ΔDTW | = 3.44
Conditional expression (12): tan ω × FL / fw = 0.56
It is.

  FIG. 3 is a diagram illustrating the configuration of the zoom lens according to the present embodiment, where (a) shows a state at the wide-angle end, (b) shows an intermediate state, and (c) shows a state at the telephoto end. 4A and 4B are aberration diagrams illustrating spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom lens according to the present exemplary embodiment is focused on an object point at infinity. FIG. 4A is a wide-angle end, and FIG. In the middle, (c) shows the state at the telephoto end.

As shown in FIGS. 3A to 3C, the photographing optical system of the present embodiment includes a first lens group G ₁ having a negative power, an aperture stop S, and a second lens having a positive power. and the group G _2, the third lens group G ₃ having a negative power, and a filter LPF such as an optical low-pass filter is constituted by a cover glass CG of an electronic image sensor such as a CCD. Note that the CCD shows only its image plane.

The first lens group G ₁ includes a negative meniscus lens L ₁₁ having a convex surface facing the object side, and a positive meniscus lens L ₁₂ having an aspheric surface on the image side and a convex surface facing the object side. The second lens group G ₂ includes a cemented lens including a biconvex positive lens L ₂₁ and a biconcave negative lens L _{22 in} order from the object side, and a positive meniscus lens L ₂₃ having both aspheric surfaces and a convex surface facing the image side. It is comprised by. The third lens group G _3, the surface on the object side and a positive meniscus lens L ₃₁ with a convex surface facing the located image side aspherical, is constituted by a cemented lens consisting of order of double-concave negative lens L _32.

In the thus configured imaging optical system of this embodiment, on the optical axis Lc During zooming from the wide angle end to the telephoto end, the first lens group G ₁ to the back object side after moving to the image side The second lens group G ₂ moves so as to approach the first lens group G ₁ , and the third lens group G ₃ moves toward the object side.

  Next, numerical data of lenses constituting the photographing optical system according to the present example are shown.

Surface RDY THI Nd Vd
1 57.730 0.600 1.83481 42.71
2 4.622 1.111
3 8.641 1.500 1.80518 25.42
4 * 39.110 D1
5 (Aperture) ∞ 0.000
6 3.458 1.500 1.52249 59.84
7 -8.009 0.550 1.78470 26.29
8 161.908 0.216
9 * -8.729 2.169 1.58313 59.38
10 * -4.823 D2
11 * -7.616 1.500 1.80518 25.42
12 -6.745 0.800 1.71700 47.92
13 29.092 D3
14 ∞ 0.860 1.53996 59.45
15 ∞ 0.270
16 ∞ 0.500 1.51633 64.14
17 ∞ 0.670
18 (imaging plane) ∞
*: Aspherical surface

Aspherical coefficient surface RDY K A ₄ A ₆ A ₈ A ₁₀
4 39.110 0.0000 -5.9530e-4 -2.9044e-5 1.3306e-6 -1.3015e-7
9 -8.729 0.0000 -3.3861e-3 3.7892e-4 3.7139e-5 0
10 -4.823 0.0000 2.3875e-3 3.1323e-4 7.1820e-5 -2.8424e-6
11 -7.616 -4.6840 -1.3270e-3 -9.3731e-5 5.0609e-6 0

Zoom data
Wide-angle end Intermediate telephoto end f 6.319 10.979 18.769
Fno 3.382 4.414 6.386
2ω (°) 62.3 36.2 21.5
D1 9.251 3.116 0.237
D2 3.962 4.130 3.859
D3 1.167 3.494 8.484

The data related to the above conditional expressions is
Conditional expression (1): W_L / (tan ω × FL) = 7.40
Conditional expression (2): | ΔD12 | / (tan ω × FL) = 2.50
Conditional expression (3): PAνd = 59.84 (lens L ₂₁ )
PAνd = 59.38 (lens L ₂₃ )
Conditional expression (4): D23W / (tan ω × FL) = 1.10
Conditional expression (5): (f2 / fw) × (tan ω × FL / fw) = 0.60
Conditional expression (6): W_L / fw = 4.21
Conditional expression (7): | ΔD12 / ΔD23 | = 87.51
Conditional expression (8): G1Σd / (tan ω × FL) = 0.89
Conditional expression (9): Pνd = 59.84 (lens L ₂₁ )
Pνd = 59.38 (lens L ₂₃ )
Conditional expression (10): Pνd−Nνd = 33.55 (lens L ₂₁ )
Pνd−Nνd = 33.09 (lens L ₂₃ )
Conditional expression (11-1): | DTW_ × 1.0 | = 5.7
Conditional expression (11-2): | DTW_ × 0.7 | = 3.43
Conditional expression (11-3): | DTW_ × 1.0 | = 5.7
Conditional expression (11-4): | ΔDTW | = 2.27
Conditional expression (12): tan ω × FL / fw = 0.57
It is.

  FIG. 5 is a diagram illustrating the configuration of the photographing optical system according to the present embodiment, in which (a) shows a state at the wide-angle end, (b) shows an intermediate state, and (c) shows a state at the telephoto end. FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, distortion, and chromatic aberration of magnification when the zoom lens according to this example is focused on an object point at infinity, (a) is a wide angle end, (b). (C) shows the state at the telephoto end.

As shown in FIGS. 5A to 5C, the photographing optical system of the present embodiment includes a first lens group G ₁ having a negative power, an aperture stop S, and a second lens having a positive power. and the group G _2, the third lens group G ₃ having a negative power, and a filter LPF such as an optical low-pass filter is constituted by a cover glass CG of an electronic image sensor such as a CCD. Note that the CCD shows only its image plane.

The first lens group G ₁ includes a negative meniscus lens L ₁₁ having an aspheric image side surface and a convex surface facing the object side, and a positive meniscus lens L ₁₂ having a convex surface facing the object side. The second lens group G ₂ is composed of a cemented lens including a biconvex positive lens L ₂₁ whose surface on the object side is aspheric in order from the object side, and a negative meniscus lens L ₂₂ having a convex surface facing the image side. Yes. The third lens group G _3, the surface on the object side is constituted by only the negative meniscus lens L ₃₁ with a convex surface facing the located image side aspherical surface.

In the thus configured imaging optical system of this embodiment, on the optical axis Lc During zooming from the wide angle end to the telephoto end, the first lens group G ₁ to the back object side after moving to the image side The second lens group G ₂ moves so as to approach the first lens group G ₁ , and the third lens group G ₃ moves toward the object side.

  Next, numerical data of lenses constituting the photographing optical system according to the present example are shown.

Surface RDY THI Nd Vd
1 -1509.343 1.000 1.80610 40.92
2 * 4.505 0.814
3 6.136 1.900 1.75520 27.51
4 23.672 D1
5 (Aperture) ∞ 0.000
6 * 5.020 2.300 1.49700 81.54
7 -4.305 0.700 1.90366 31.31
8 -6.592 D2
9 * -3.141 1.000 1.69350 53.21
10 -4.676 D3
11 ∞ 0.860 1.53996 59.45
12 ∞ 0.270
13 ∞ 0.500 1.51633 64.14
14 ∞ 0.680
15 (Imaging surface) ∞
*: Aspherical surface

Aspherical coefficient surface RDY K A ₄ A ₆ A ₈ A ₁₀
2 4.505 0.0000 -4.1673e-4 -4.5309e-5 2.0852e-6 -1.9520e-7
6 5.020 0.0000 -7.8656e-4 -9.4142e-5 1.0613e-5 -3.0000e-7
9 -3.141 -0.9738 -4.2198e-3 -1.5162e-4 -6.3744e-5 5.7360e-6

Zoom data
Wide angle end Medium telephoto end f 6.464 10.398 18.420
Fno 3.325 4.069 5.623
2ω (°) 63.1 38.7 22.0
D1 11.236 4.782 0.225
D2 5.859 5.907 5.871
D3 2.143 4.576 9.755

The data related to the above conditional expressions is
Conditional expression (1): W_L / (tan ω × FL) = 8.13
Conditional expression (2): | ΔD12 | / (tan ω × FL) = 3.06
Conditional expression (3): PAνd = 81.54
Conditional expression (4): D23W / (tan ω × FL) = 1.63
Conditional expression (5): (f2 / fw) × (tan ω × FL / fw) = 0.64
Conditional expression (6): W_L / fw = 4.53
Conditional expression (7): | ΔD12 / ΔD23 | = 11.01.00
Conditional expression (8): G1Σd / (tan ω × FL) = 1.03
Conditional expression (9): Pνd = 81.54
Conditional expression (10): Pνd−Nνd = 50.23
Conditional expression (11-1): | DTW_ × 1.0 | = 9.22
Conditional expression (11-2): | DTW_ × 0.7 | = 4.62
Conditional expression (11-3): | DTW_ × 1.0 | = 9.22
Conditional expression (11-4): | ΔDTW | = 4.6
Conditional expression (12): tan ω × FL / fw = 0.56
It is.

  FIG. 7 is a diagram illustrating the configuration of the photographing optical system according to the present embodiment, where (a) shows a state at the wide-angle end, (b) shows an intermediate state, and (c) shows a state at the telephoto end. FIG. 8 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom lens according to the present embodiment is focused on an object point at infinity, (a) is a wide angle end, (b). (C) shows the state at the telephoto end.

As shown in FIGS. 7A to 7C, the photographing optical system of the present embodiment includes a first lens group G ₁ having a negative power, an aperture stop S, and a second lens having a positive power. and the group G _2, the third lens group G ₃ having a negative power, and a filter LPF such as an optical low-pass filter is constituted by a cover glass CG of an electronic image sensor such as a CCD. Note that the CCD shows only its image plane.

The first lens group G ₁ includes a negative meniscus lens L ₁₁ having a convex surface directed toward the object side, and a biconvex positive lens L ₁₂ having an aspheric surface on the image side. The second lens group G ₂ includes, in order from the object side, a cemented lens including a biconvex positive lens L ₂₁ and a negative meniscus lens L ₂₂ having a convex surface facing the image side, and both surfaces are aspherical and have a convex surface facing the image side. It is composed of a positive meniscus lens L ₂₃ has. The third lens group G _3, the surface on the object side is constituted by only a biconcave negative lens L ₃₁ which is a non-spherical surface.

In the thus configured imaging optical system of this embodiment, on the optical axis Lc During zooming from the wide angle end to the telephoto end, the first lens group G ₁ to the back object side after moving to the image side The second lens group G ₂ moves so as to approach the first lens group G ₁ , and the third lens group G ₃ moves toward the object side.

  Next, numerical data of lenses constituting the photographing optical system according to the present example are shown.

Surface RDY THI Nd Vd
1 73.661 1.000 1.88300 40.76
2 5.028 1.169
3 11.374 1.900 1.79491 25.63
4 * -150.535 D1
5 (Aperture) ∞ 0.000
6 4.830 2.300 1.49700 81.54
7 -6.741 0.700 1.90366 31.31
8 -15.751 0.347
9 * -6.192 1.953 1.49700 81.54
10 * -4.358 D2
11 * -17.517 1.000 1.52542 55.78
12 14.588 D3
13 ∞ 0.860 1.53996 59.45
14 ∞ 0.270
15 ∞ 0.500 1.51633 64.14
16 ∞ 0.700
17 (Imaging surface) ∞
*: Aspherical surface

Aspherical coefficient surface RDY K A ₄ A ₆ A ₈ A ₁₀
4 -150.535 0.0000 -5.3086e-4 -3.2502e-5 2.0814e-6 -1.2613e-7
9 -6.192 0.0000 -1.4389e-3 9.2876e-5 1.9238e-5 0
10 -4.358 0.0000 1.7222e-3 1.0830e-4 1.1592e-5 3.9738e-7
11 -17.517 -3.4344 1.6615e-4 -1.5432e-4 2.3481e-5 -2.2777e-6

Zoom data
Wide angle end Medium telephoto end f 6.456 10.964 18.550
Fno 3.164 4.322 5.816
2ω (°) 61.0 36.7 21.9
D1 10.658 5.129 0.441
D2 5.941 4.441 4.483
D3 1.574 6.635 11.599

The data related to the above conditional expressions is
Conditional expression (1): W_L / (tan ω × FL) = 8.58
Conditional expression (2): | ΔD12 | / (tan ω × FL) = 2.84
Conditional expression (3): PAνd = 81.54 (lens L ₂₁ )
PAνd = 81.54 (lens L ₂₃ )
Conditional expression (4): D23W / (tan ω × FL) = 1.65
Conditional expression (5): (f2 / fw) × (tan ω × FL / fw) = 0.72
Conditional expression (6): W_L / fw = 4.78
Conditional expression (7): | ΔD12 / ΔD23 | = 7.00
Conditional expression (8): G1Σd / (tan ω × FL) = 1.13
Conditional expression (9): Pνd = 81.54 (lens L ₂₁ )
Pνd = 81.54 (lens L ₂₃ )
Conditional expression (10): Pνd−Nνd = 50.23 (lens L ₂₁ )
Pνd−Nνd = 50.23 (lens L ₂₃ )
Conditional expression (11-1): | DTW_ × 1.0 | = 5.32
Conditional expression (11-2): | DTW_ × 0.7 | = 3.5
Conditional expression (11-3): | DTW_ × 1.0 | = 5.32
Conditional expression (11-4): | ΔDTW | = 1.82
Conditional expression (12): tan ω × FL / fw = 0.56
It is.

  FIG. 9 is a diagram illustrating the configuration of the photographing optical system according to the present embodiment, where (a) shows a state at the wide-angle end, (b) shows an intermediate state, and (c) shows a state at the telephoto end. FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, distortion aberration, and chromatic aberration of magnification when the zoom lens according to the present embodiment is focused on an object point at infinity, (a) is a wide angle end, (b). (C) shows the state at the telephoto end.

As shown in FIGS. 9A to 9C, the photographing optical system of the present embodiment includes a first lens group G ₁ having a negative power, an aperture stop S, and a second lens having a positive power. and the group G _2, the third lens group G ₃ having a negative power, and a filter LPF such as an optical low-pass filter is constituted by a cover glass CG of an electronic image sensor such as a CCD. Note that the CCD shows only its image plane.

The first lens group G ₁ includes a negative meniscus lens L ₁₁ having a convex surface facing the object side, and a positive meniscus lens L ₁₂ having an aspheric surface on the image side and a convex surface facing the object side. The positive meniscus lens L ₂₁ is a high refractive index lens having a refractive index of 2.0 or more. The second lens group G ₂ includes a cemented lens including a biconvex positive lens L ₂₁ and a biconcave negative lens L _{22 in} order from the object side, and a positive meniscus lens L ₂₃ having both aspheric surfaces and a convex surface facing the image side. It is comprised by. The third lens group G _3, the surface on the object side is constituted by only the negative meniscus lens L ₃₁ with a convex surface facing the located image side aspherical surface.

In the thus configured imaging optical system of this embodiment, on the optical axis Lc During zooming from the wide angle end to the telephoto end, the first lens group G ₁ to the back object side after moving to the image side The second lens group G ₂ moves so as to approach the first lens group G ₁ , and the third lens group G ₃ moves toward the object side.

  Next, numerical data of lenses constituting the photographing optical system according to the present example are shown.

Surface RDY THI Nd Vd
1 77.437 1.000 1.83400 37.16
2 5.478 1.372
3 9.585 1.700 2.00170 20.60
4 * 19.862 D1
5 (Aperture) ∞ 0.000
6 3.916 2.300 1.49700 81.54
7 -7.139 0.700 1.59270 35.31
8 45.016 0.792
9 * -12.798 1.424 1.49700 81.54
10 * -7.946 D2
11 * -9.048 1.000 1.69350 53.21
12 -16.344 D3
13 ∞ 0.860 1.53996 59.45
14 ∞ 0.270
15 ∞ 0.500 1.51633 64.14
16 ∞ 0.710
17 (Imaging surface) ∞
*: Aspherical surface

Aspherical coefficient surface RDY K A ₄ A ₆ A ₈ A ₁₀
4 19.862 0.0000 -2.1914e-4 -1.4058e-5 596192e-7 -2.7906e-8
9 -12.798 0.0000 -4.1691e-3 -6.6339e-5 5.1839e-5 0
10 -7.946 0.0000 1.1644e-4 2.1552e-4 2.1585e-5 5.5954e-6
11 -9.048 -25.9881 -4.4825e-3 6.5559e-4 -7.7810e-5 4.9252e-6

Zoom data
Wide-angle end Medium telephoto end f 6.452 10.915 18.491
Fno 3.377 4.178 5.544
2ω (°) 64.1 37.4 22.1
D1 12.786 5.123 0.583
D2 4.161 4.741 5.582
D3 2.984 5.301 9.240

The data related to the above conditional expressions is
Conditional expression (1): W_L / (tan ω × FL) = 9.04
Conditional expression (2): | ΔD12 | / (tan ω × FL) = 3.39
Conditional expression (3): PAνd = 81.54 (lens L ₂₁ )
PAνd = 81.54 (lens L ₂₃ )
Conditional expression (4): D23W / (tan ω × FL) = 1.16
Conditional expression (5): (f2 / fw) × (tan ω × FL / fw) = 0.74
Conditional expression (6): W_L / fw = 0.05
Conditional expression (7): | ΔD12 / ΔD23 | = 8.59
Conditional expression (8): G1Σd / (tan ω × FL) = 1.13
Conditional expression (9): Pνd = 81.54 (lens L ₂₁ )
Pνd = 81.54 (lens L ₂₃ )
Conditional expression (10): Pνd−Nνd = 46.23 (lens L ₂₁ )
Pνd−Nνd = 46.23 (lens L ₂₃ )
Conditional expression (11-1): | DTW_ × 1.0 | = 10.92
Conditional expression (11-2): | DTW_ × 0.7 | = 5.35
Conditional expression (11-3): | DTW_ × 1.0 | = 10.92
Conditional expression (11-4): | ΔDTW | = 5.57
Conditional expression (12): tan ω × FL / fw = 0.56
It is.

  FIG. 11 is a diagram illustrating the configuration of the photographing optical system according to the present embodiment, where (a) shows a state at the wide-angle end, (b) shows an intermediate state, and (c) shows a state at the telephoto end. FIG. 12 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration when the zoom lens according to the present embodiment is focused on an object point at infinity, (a) is a wide angle end, (b). (C) shows the state at the telephoto end.

As shown in FIGS. 11A to 11C, the photographing optical system of the present embodiment includes a first lens group G ₁ having a negative power, an aperture stop S, and a second lens having a positive power. and the group G _2, the third lens group G ₃ having a negative power, and a filter LPF such as an optical low-pass filter is constituted by a cover glass CG of an electronic image sensor such as a CCD. Note that the CCD shows only its image plane.

The first lens group G ₁ is composed of a biconcave negative lens L ₁₁ and a biconvex positive lens L ₁₂ having an aspheric image side surface. The second lens group G ₂ includes, in order from the object side, a biconvex positive lens L ₂₁ having an aspheric surface on the object side, a biconcave negative lens L _22, and an aspheric surface on the image side, in the vicinity of the optical axis. and a cemented lens and the positive lens L ₂₃ of double-convex shape, consists in. The third lens group G _3, the surface on the object side is constituted by only the negative meniscus lens L ₃₁ with a convex surface facing the located image side aspherical surface. The non-spherical surface of the second lens group G ₂ of the positive lens L _23, the diverging action to the periphery portion from the center of the lens is formed to be strong.

In the thus configured imaging optical system of this embodiment, on the optical axis Lc During zooming from the wide angle end to the telephoto end, the first lens group G ₁ to the back object side after moving to the image side The second lens group G ₂ moves so as to approach the first lens group G ₁ , and the third lens group G ₃ moves toward the object side.

  Next, numerical data of lenses constituting the photographing optical system according to the present example are shown.

Surface RDY THI Nd Vd
1 -33.263 1.000 1.88300 40.76
2 5.599 1.045
3 14.498 1.900 1.79491 25.63
4 * -33.379 D1
5 (Aperture) ∞ 0.000
6 * 4.252 2.300 1.58913 61.14
7 -11.529 0.700 1.90366 31.31
8 19.276 2.400 1.49700 81.54
9 * -17.629 D2
10 * -11.470 1.000 1.69350 53.21
11 -27.549 D3
12 ∞ 0.860 1.53996 59.45
13 ∞ 0.270
14 ∞ 0.500 1.51633 64.14
15 ∞ 0.680
15 (Imaging surface) ∞
*: Aspherical surface

Aspherical coefficient surface RDY K A ₄ A ₆ A ₈ A ₁₀
4 -33.379 0.0000 -4.9940e-4 -2.5928e-5 1.7005e-6 -1.0924e-7
6 4.252 0.0000 -2.9274e-4 9.8595e-6 5.8581e-7 0
9 -17.629 0.0000 3.4083e-3 3.1904e-4 -3.6228e-5 7.8849e-6
10 -11.470 -9.0000 -8.7688e-4 1.2335e-4 -3.0872e-5 2.5343e-6

Zoom data
Wide angle end Medium telephoto end f 6.421 10.981 18.472
Fno 3.069 4.032 5.436
2ω (°) 64.4 37.2 22.1
D1 10.672 4.621 0.610
D2 5.505 5.064 6.622
D3 1.936 5.938 9.405

The data related to the above conditional expressions is
Conditional expression (1): W_L / (tan ω × FL) = 8.55
Conditional expression (2): | ΔD12 | / (tan ω × FL) = 2.79
Conditional expression (3): PAνd = 61.14 (lens L ₂₁ )
PAνd = 81.54 (lens L ₂₃ )
Conditional expression (4): D23W / (tan ω × FL) = 1.53
Conditional expression (5): (f2 / fw) × (tan ω × FL / fw) = 0.74
Conditional expression (6): W_L / fw = 4.79
Conditional expression (7): | ΔD12 / ΔD23 | = 9.06
Conditional expression (8): G1Σd / (tan ω × FL) = 1.10
Conditional expression (9): Pνd = 61.14 (lens L ₂₁ )
Pνd = 81.54 (lens L ₂₃ )
Conditional expression (10): Pνd−Nνd = 29.83 (lens L ₂₁ )
Pνd−Nνd = 50.23 (lens L ₂₃ )
Conditional expression (11-1): | DTW_ × 1.0 | = 10.98
Conditional expression (11-2): | DTW_ × 0.7 | = 5.6
Conditional expression (11-3): | DTW_ × 1.0 | = 10.98
Conditional expression (11-4): | ΔDTW | = 5.38
Conditional expression (12): tan ω × FL / fw = 0.56
It is.

  FIG. 13 is a diagram illustrating the configuration of the photographing optical system according to the present embodiment, where (a) shows a state at the wide-angle end, (b) shows an intermediate state, and (c) shows a state at the telephoto end. FIG. 14 is an aberration diagram showing spherical aberration, astigmatism, distortion, and chromatic aberration of magnification when the zoom lens according to this example is focused on an object point at infinity, (a) is a wide angle end, (b). (C) shows the state at the telephoto end.

As shown in FIGS. 13A to 13C, the photographing optical system of the present embodiment includes a first lens group G ₁ having a negative power, an aperture stop S, and a second lens having a positive power. a group G _2, the third lens group G ₃ having a negative power, and a filter LPF such as an optical low-pass filter, is constituted by a cover glass CG of an electronic image sensor such as a CCD. Note that the CCD shows only its image plane.

The first lens group G ₁ includes a negative meniscus lens L ₁₁ having a convex surface facing the object side, and a positive meniscus lens L ₁₂ having an aspheric surface on the image side and a convex surface facing the object side. The second lens group G ₂ includes, in order from the object side, a biconvex positive lens L ₂₁ having an aspheric surface on the object side, a biconcave negative lens L _22, and a biconvex positive lens L ₂₃ having an aspheric surface on the image side. Are constituted by a cemented lens. The third lens group G _3, the surface on the object side is constituted by only a biconcave negative lens L ₃₁ which is a non-spherical surface.

In the thus configured imaging optical system of this embodiment, on the optical axis Lc During zooming from the wide angle end to the telephoto end, the first lens group G ₁ to the back object side after moving to the image side The second lens group G ₂ moves so as to approach the first lens group G ₁ , and the third lens group G ₃ moves toward the object side.

  Next, numerical data of lenses constituting the photographing optical system according to the present example are shown.

Surface RDY THI Nd Vd
1 40.542 1.000 1.88300 40.76
2 4.735 1.204
3 9.223 1.900 1.79491 25.63
4 * 68.819 D1
5 (Aperture) ∞ 0.000
6 * 10.713 2.300 1.60738 56.81
7 -18.391 0.700 1.80518 25.42
8 28.012 2.263 1.49700 81.54
9 * -4.673 D2
10 * -5.423 1.000 1.51633 64.14
11 471.117 D3
12 ∞ 0.860 1.53996 59.45
13 ∞ 0.270
14 ∞ 0.500 1.51633 64.14
15 ∞ 0.680
16 (imaging plane) ∞
*: Aspherical surface

Aspherical coefficient surface RDY K A ₄ A ₆ A ₈ A ₁₀
4 68.819 0.0000 -6.4913e-4 -1.9359e-5 3.0300e-7 -6.0365e-8
6 10.713 0.0000 -1.8351e-3 -4.6465e-5 -9.0296e-6 0
9 -4.673 0.0000 3.1401e-4 9.6298e-6 -6.4092e-6 4.6545e-7
10 -5.423 -12.3438 -9.5794e-3 1.0572e-3 -1.0738e-4 3.8669e-6

Zoom data
Wide-angle end Intermediate telephoto end f 6.378 10.937 18.684
Fno 3.027 4.043 5.885
2ω (°) 61.5 36.5 21.7
D1 9.870 3.902 0.725
D2 7.294 6.919 6.287
D3 0.463 3.559 9.344

The data related to the above conditional expressions is
Conditional expression (1): W_L / (tan ω × FL) = 8.42
Conditional expression (2): | ΔD12 | / (tan ω × FL) = 2.54
Conditional expression (3): PAνd = 56.81 (lens L ₂₁ )
PAνd = 81.54 (lens L ₂₃ )
Conditional expression (4): D23W / (tan ω × FL) = 2.03
Conditional expression (5): (f2 / fw) × (tan ω × FL / fw) = 0.70
Conditional expression (6): W_L / fw = 4.75
Conditional expression (7): | ΔD12 / ΔD23 | = 9.14
Conditional expression (8): G1Σd / (tan ω × FL) = 1.14
Conditional expression (9): Pνd = 56.81 (lens L ₂₁ )
Pνd = 81.54 (lens L ₂₃ )
Conditional expression (10): Pνd−Nνd = 31.39 (lens L ₂₁ )
Pνd−Nνd = 56.12 (lens L ₂₃ )
Conditional expression (11-1): | DTW_ × 1.0 | = 5.11
Conditional expression (11-2): | DTW_ × 0.7 | = 3.1
Conditional expression (11-3): | DTW_ × 1.0 | = 5.11
Conditional expression (11-4): | ΔDTW | = 2.01
Conditional expression (12): tan ω × FL / fw = 0.56
It is.

  FIG. 15 is a diagram illustrating the configuration of the photographing optical system according to the present embodiment, where (a) shows a state at the wide-angle end, (b) shows an intermediate state, and (c) shows a state at the telephoto end. FIG. 16 is an aberration diagram showing spherical aberration, astigmatism, distortion, and chromatic aberration of magnification when the zoom lens according to this example is focused on an object point at infinity, (a) is a wide angle end, (b). (C) shows the state at the telephoto end.

As shown in FIGS. 15A to 15C, the imaging optical system of the present embodiment includes a first lens group G ₁ having a negative power, an aperture stop S, and a second lens having a positive power. and the group G _2, the third lens group G ₃ having a negative power, and a filter LPF such as an optical low-pass filter is constituted by a cover glass CG of an electronic image sensor such as a CCD. Note that the CCD shows only its image plane.

The first lens group G ₁ includes a biconcave negative lens L ₁₁ having an aspherical surface on the image side and a positive meniscus lens L ₁₂ having a convex surface on the object side. The second lens group G ₂ includes, in order from the object side, a biconvex positive lens L ₂₁ having an aspheric surface on the object side, a biconcave negative lens L _22, and an aspheric surface on the image side, in the vicinity of the optical axis. and a cemented lens and the positive lens L ₂₃ of double-convex shape, consists in. The third lens group G _3, the surface on the object side is constituted by only the negative meniscus lens L ₃₁ with a convex surface facing the located image side aspherical surface. The non-spherical surface of the second lens group G ₂ of the positive lens L _23, the diverging action to the periphery portion from the center of the lens is formed to be strong.

In the thus configured imaging optical system of this embodiment, on the optical axis Lc During zooming from the wide angle end to the telephoto end, the first lens group G ₁ to the back object side after moving to the image side The second lens group G ₂ moves so as to approach the first lens group G ₁ , and the third lens group G ₃ moves toward the object side.

  Next, numerical data of lenses constituting the photographing optical system according to the present example are shown.

Surface RDY THI Nd Vd
1 -32.124 1.000 1.80610 40.92
2 * 5.093 1.276
3 9.074 1.900 1.80518 25.42
4 101.120 D1
5 (Aperture) ∞ 0.000
6 * 4.169 2.300 1.58913 61.14
7 -8.891 0.700 1.90366 31.31
8 25.399 2.400 1.49700 81.54
9 * -20.234 D2
10 * -20.714 1.000 1.69350 53.21
11 -128.281 D3
12 ∞ 0.860 1.53996 59.45
13 ∞ 0.270
14 ∞ 0.500 1.51633 64.14
15 ∞ 0.690
16 (imaging plane) ∞
*: Aspherical surface

Aspherical coefficient surface RDY K A ₄ A ₆ A ₈ A ₁₀
2 5.093 0.0000 -6.9963e-4 -3.8289e-5 1.6845e-6 -9.9045e-8
6 4.169 0.0000 -1.8911e-4 2.5782e-5 -2.6040e-7 0
9 -20.234 0.0000 3.7473e-3 3.9515e-4 -5.7133e-5 1.3231e-5
10 -20.714 -8.6949 -2.3460e-4 7.2885e-5 -1.8393e-5 1.7472e-6

Zoom data
Wide angle end Medium telephoto end f 6.421 10.973 18.471
Fno 3.302 4.327 5.852
2ω (°) 63.8 37.0 22.1
D1 10.803 4.592 0.550
D2 5.397 4.411 5.324
D3 1.987 6.555 10.921

The data related to the above conditional expressions is
Conditional expression (1): W_L / (tan ω × FL) = 8.63
Conditional expression (2): | ΔD12 | / (tan ω × FL) = 2.85
Conditional expression (3): PAνd = 61.14 (lens L ₂₁ )
PAνd = 81.54 (lens L ₂₃ )
Conditional expression (4): D23W / (tan ω × FL) = 1.50
Conditional expression (5): (f2 / fw) × (tan ω × FL / fw) = 0.76
Conditional expression (6): W_L / fw = 4.84
Conditional expression (7): | ΔD12 / ΔD23 | = 146.43
Conditional expression (8): G1Σd / (tan ω × FL) = 1.16
Conditional expression (9): Pνd = 61.14 (lens L ₂₁ )
Pνd = 81.54 (lens L ₂₃ )
Conditional expression (10): Pνd−Nνd = 29.83 (lens L ₂₁ )
Pνd−Nνd = 50.23 (lens L ₂₃ )
Conditional expression (11-1): | DTW_ × 1.0 | = 10
Conditional expression (11-2): | DTW_ × 0.7 | = 4.59
Conditional expression (11-3): | DTW_ × 1.0 | = 10
Conditional expression (11-4): | ΔDTW | = 5.41
Conditional expression (12): tan ω × FL / fw = 0.56
It is.

  FIG. 17 is a diagram illustrating the configuration of the photographing optical system according to the present embodiment, where (a) shows a state at the wide-angle end, (b) shows an intermediate state, and (c) shows a state at the telephoto end. FIG. 18 is an aberration diagram showing spherical aberration, astigmatism, distortion, and chromatic aberration of magnification when the zoom lens according to this example is focused on an object point at infinity, (a) is a wide angle end, (b). (C) shows the state at the telephoto end.

As shown in FIGS. 17A to 17C, the photographing optical system of the present embodiment includes a first lens group G ₁ having a negative power, an aperture stop S, and a second lens having a positive power. and the group G _2, the third lens group G ₃ having a negative power, a fourth lens group G ₄ having a positive power is composed of a, a cover glass CG of an electronic image sensor such as a CCD. Note that the CCD shows only its image plane.

The first lens group G ₁ is composed of a biconcave negative lens L ₁₁ and a biconvex positive lens L ₁₂ having an aspheric image side surface. The second lens group G ₂ includes, in order from the object side, a biconvex positive lens L ₂₁ having an aspheric surface on the object side, a biconcave negative lens L _22, and an aspheric surface on the image side, in the vicinity of the optical axis. and a cemented lens and the positive lens L ₂₃ of double-convex shape, consists in. The third lens group G _3, the surface on the object side is constituted by only a biconcave negative lens L ₃₁ which is a non-spherical surface. The fourth lens group G ₄ includes only a convex flat lens L ₄₁ having a convex surface directed toward the object side. The convex flat lens L ₄₁ used in this example is a molded lens made of plastic.

In the thus configured imaging optical system of this embodiment, on the optical axis Lc During zooming from the wide angle end to the telephoto end, the first lens group G ₁ to the back object side after moving to the image side The second lens group G ₂ moves so as to approach the first lens group G ₁ , and the third lens group G ₃ moves toward the object side.

  Next, numerical data of lenses constituting the photographing optical system according to the present example are shown.

Surface RDY THI Nd Vd
1 -47.518 1.000 1.88300 40.76
2 5.169 1.376
3 23.251 1.900 1.79491 25.63
4 * -20.455 D1
5 (Aperture) ∞ 0.000
6 * 4.172 2.300 1.58913 61.14
7 -13.092 0.700 1.90366 31.31
8 13.883 2.400 1.49700 81.54
9 * -17.320 D2
10 * -24.216 1.000 1.69350 53.21
11 26.122 D3
12 20.000 1.200 1.52542 55.78
13 ∞ 0.400
14 ∞ 0.500 1.51633 64.14
15 ∞ 0.690
16 (imaging plane) ∞
*: Aspherical surface

Aspherical coefficient surface RDY K A ₄ A ₆ A ₈ A ₁₀
4 -20.455 0.0000 -5.6343e-4 -3.2087e-5 2.2662e-6 -1.4938e-7
6 4.172 0.0000 -3.0725e-4 5.3126e-6 5.8987e-7 0
9 -17.320 0.0000 3.6809e-3 4.1838e-4 -6.7426e-5 1.2679e-5
10 -24.216 -9.3274 -1.9976e-4 3.4609e-5 -1.4306e-5 1.5505e-6

Zoom data
Wide angle end Medium telephoto end f 6.388 11.022 18.400
Fno 3.160 4.326 5.800
2ω (°) 63.1 36.5 21.9
D1 10.078 4.714 0.612
D2 5.349 5.022 7.310
D3 1.946 6.164 8.572

The data related to the above conditional expressions is
Conditional expression (1): W_L / (tan ω × FL) = 8.57
Conditional expression (2): | ΔD12 | / (tan ω × FL) = 2.63
Conditional expression (3): PAνd = 61.14 (lens L ₂₁ )
PAνd = 81.54 (lens L ₂₃ )
Conditional expression (4): D23W / (tan ω × FL) = 1.49
Conditional expression (5): (f2 / fw) × (tan ω × FL / fw) = 0.78
Conditional expression (6): W_L / fw = 4.90
Conditional expression (7): | ΔD12 / ΔD23 | = 4.83
Conditional expression (8): G1Σd / (tan ω × FL) = 1.19
Conditional expression (9): Pνd = 61.14 (lens L ₂₁ )
Pνd = 81.54 (lens L ₂₃ )
Conditional expression (10): Pνd−Nνd = 29.83 (lens L ₂₁ )
Pνd−Nνd = 50.23 (lens L ₂₃ )
Conditional expression (11-1): | DTW_ × 1.0 | = 8.17
Conditional expression (11-2): | DTW_ × 0.7 | = 4.27
Conditional expression (11-3): | DTW_ × 1.0 | = 8.17
Conditional expression (11-4): | ΔDTW | = 3.9
Conditional expression (12): tan ω × FL / fw = 0.57
It is.

Further, as shown in FIG. 19, in this embodiment, a convex flat lens L ₄₁ , a CCD cover glass CG, and a CCD as an electronic imaging device are arranged in order from the object side on the image side of the third lens group. ing. The CCD cover glass CG and the CCD, which is an electronic image sensor, are attached to the support frame 11 to constitute the image sensor package 1. The image pickup device package 1 is attached to a holding member 2 that is a part of a member constituting the image pickup apparatus together with the convex flat lens L ₄₁ , and is sealed between the two. In the present embodiment, by adopting such a configuration, dust such as dust can be prevented from adhering to the surface of the CCD cover glass CG. At this time, the data related to the conditional expression (13) is
Conditional expression (13): DL / (tan ω × FL) = 0.78
It is.

  The photographing optical system according to the present invention as described above can be used for a photographing apparatus, particularly a digital camera or a video camera, which performs photographing by causing an image sensor such as a CCD to receive an object image formed by the optical system. The specific example is illustrated below.

  20, FIG. 21, and FIG. 22 show conceptual diagrams of a configuration in which the photographing optical system according to the present invention is incorporated in the photographing optical system 41 of the digital camera. 20 is a front perspective view showing the appearance of the digital camera 40, FIG. 21 is a rear front view thereof, and FIG. 22 is a schematic perspective plan view showing the configuration of the digital camera 40. However, FIGS. 20 and 22 show the photographic optical system 41 when it is not retracted.

  In this example, the digital camera 40 includes a photographing optical system 41 disposed on the photographing optical path 42, a finder optical system 43 disposed on the finder optical path 44, a shutter 45, a flash 46, a liquid crystal display monitor 47, a focal point. A distance change button 61, a setting change switch 62, and the like are provided. Further, when the photographing optical system 41 is retracted, the cover 60 is slid to cover the photographing optical system 41 and the finder optical system 43.

  When the cover 60 is opened and the digital camera 40 is set to the photographing state, the photographing optical system 41 is in the non-collapsed state shown in FIG. In this state, when the shutter 45 disposed on the upper part of the digital camera 40 is pressed, photographing is performed through the photographing optical system 41, for example, the photographing optical system according to the first embodiment of the present invention. The object image formed by the photographing optical system 41 is formed on the image formation surface of the CCD 49 through the low-pass filter LF with IR cut coating and the cover glass CG. The object image received by the CCD 49 is displayed as an electronic image on the liquid crystal display monitor 47 provided on the back of the camera via the processing means 51. Further, by connecting the recording means 52 to the processing means 51, it is also possible to record a photographed electronic image. The recording means 52 may be provided separately from the processing means 51, or may be configured to perform recording and writing electronically using a floppy (registered trademark) disk, memory card, MO, or the like. Further, instead of the CCD 49, a silver salt film may be arranged to constitute a silver salt camera.

  Further, a finder objective optical system 53 is disposed on the finder optical path 44. The finder objective optical system 53 includes a plurality of lens groups (three groups in the figure) and two prisms, and the focal length changes in conjunction with the photographing optical system 41. The object image formed by the finder optical system 53 is formed on the field frame 57 of the erecting prism 55 that is an image erecting member. Behind the erecting prism 55, an eyepiece optical system 59 for guiding the erect image to the observer eyeball E is disposed. A cover member 50 is disposed on the exit side of the eyepiece optical system 59.

  In the digital camera 40 configured in this manner, the photographing optical system 41 has high performance, small size, and can be retracted, so that good performance can be ensured and downsizing can be realized.

  The present invention may have the following configurations in addition to the configurations described in the claims.

(1) In an imaging apparatus including, in order from the object side, a photographing optical system having a first lens group having negative power, a second lens group having positive power, and a third lens group having negative power ,
When zooming from the wide-angle end to the telephoto end, the second lens group moves to the object side so that the distance between the first lens group and the second lens group is reduced, and the third lens group is the first lens group. Move so that the distance between the second lens group and the third lens group changes,
Of the lenses constituting the first lens group, there is only one negative lens, and the second lens group has at least one positive lens and at least one negative lens,
And the imaging device characterized by satisfying the following conditional expressions.
4.0 ≦ W_L / IH ≦ 12.0
1.7 ≦ | ΔD12 | /IH≦4.6
52.0 ≤ PAνd
However,
W_L: Total length of the optical system at the wide-angle end
IH: Maximum image height
ΔD12: Amount of change in the distance between the first lens unit and the second lens unit upon zooming from the wide-angle end to the telephoto end
PAνd: Abbe number of the positive lens in the second lens group (in the case of multiple lenses, all positive lenses)
It is.

(2) The imaging apparatus according to (1), further satisfying the following conditional expression:
0.45 ≦ D23W / IH ≦ 3.0
However,
D23W: Distance between the second lens group and the third lens group at the wide-angle end.

(3) The imaging apparatus according to (1) or (2), further satisfying the following conditional expression:
0.38 ≦ (f2 / fw) × (IH / fw) ≦ 0.95
However,
f2: focal length of the second lens unit
fw: Total focal length at the wide-angle end.

(4) The imaging apparatus according to any one of (1) to (3), further satisfying the following conditional expression:
2.7 ≦ W_L / fw ≦ 10.0
However,
fw: Total focal length at the wide-angle end.

(5) The imaging apparatus according to any one of (1) to (4), further satisfying the following conditional expression:
3.7 ≦ | ΔD12 / ΔD23 |
However,
ΔD23: an amount of change in the distance between the second lens unit and the third lens unit upon zooming from the wide-angle end to the telephoto end.

(6) The first lens group includes two lenses, a negative lens and a positive lens, in order from the object side, and satisfies the following conditional expression: (1) to (5) Imaging device.
0.6 ≦ G1Σd / IH ≦ 1.3
However,
G1Σd: the total thickness of the first lens group.

(7) The second lens group includes one negative lens and at least one positive lens, and at least one of the positive lenses satisfies the following conditional expression: The imaging device according to any one of (6) to (6).
75.0 ≦ Pνd
However,
Pνd: Abbe number of the positive lens in the second lens group (in the case of multiple lenses, any one positive lens)
It is.

(8) The imaging apparatus according to (7), further satisfying the following conditional expression:
45.0 ≦ Pνd−Nνd
However,
Nvd: Abbe number of the negative lens in the second lens group.

(9) The imaging apparatus according to any one of (1) to (8), wherein the third lens group includes two or less lenses.

(10) The first lens group includes, in order from the object side, two lenses, a negative lens and a positive lens,
The second lens group includes, in order from the object side, three positive lenses, negative lenses, and positive lenses or positive lenses and two negative lenses.
The imaging apparatus according to any one of (1) to (9), wherein the third lens group includes one negative lens.

(11) In the above (1) to (10), the first lens group is movable between the wide-angle end and the telephoto end at the time of zooming so that the total length of the optical system becomes the shortest. The imaging device according to any one of the above.

(12) The imaging apparatus according to any one of (1) to (11), wherein the following conditional expression is further satisfied at the wide-angle end.
7.0% ≦ | DTW_ × 1.0 |
3.5% ≦ || DTW_ × 0.7 | ≦ 15.0%
7.0% ≦ || DTW_ × 1.0 | ≦ 25.0%
| ΔDTW | ≦ 15.0%
However,
DTW_ × 0.7: × 0.7 of the maximum captured image height at the wide-angle end when focusing on infinity
Of distortion in length at the position of
DTW_ × 1.0: × 1.0 of the maximum photographed image height at the wide angle end when focusing on infinity
Of distortion in length at the position of
ΔDTW: DTW_ × 0.7−DTW_ × 1.0
And
Y′0: paraxial imaging height,
Y ′: When the actual imaging height is assumed,
Distortion amount = (Y′−Y′0) / Y′0 × 100 (%)
It is.

(13) The imaging apparatus according to any one of (1) to (12), wherein focusing is performed by moving the third lens group in the optical axis direction.

(14) The imaging apparatus according to any one of (1) to (13), further satisfying the following conditional expression:
0.53 ≤ IH / fw
However,
fw: Total focal length at the wide-angle end.

(15) The imaging device according to any one of (1) to (14), including only the first lens group, the second lens group, and the third lens group.

(16) Any one of (1) to (14) above, wherein a fourth lens group having a positive power and fixed even during zooming is disposed on the image side of the third lens group. The imaging apparatus according to item 1.

(17) The imaging apparatus according to (16) above,
An image sensor disposed on the image side of the imaging optical system,
An image pickup apparatus, wherein an object side of the image pickup element is sealed by a most image side surface of the fourth lens group and a lens frame of the image pickup apparatus.

(18) The imaging device according to (17), wherein the fourth lens group includes one positive lens.

(19) The imaging apparatus according to (17), wherein a low-pass filter is disposed between the imaging optical system and the imaging element.

1 is a diagram illustrating a configuration of a zoom lens according to Example 1 of the present invention, where (a) shows a state at a wide angle end, (b) shows an intermediate state, and (c) shows a state at a telephoto end. FIG. 4A is an aberration curve diagram of the zoom lens according to Example 1 of the present invention. FIG. 5A illustrates a state at the wide-angle end, FIG. 5B illustrates an intermediate state, and FIG. FIG. 5 is a diagram illustrating a configuration of a zoom lens according to Example 2 of the present invention, where (a) shows a state at a wide angle end, (b) shows an intermediate state, and (c) shows a state at a telephoto end. FIG. 7A is an aberration curve diagram of the zoom lens according to Example 2 of the present invention, where FIG. 10A illustrates a state at the wide-angle end, FIG. 10B illustrates an intermediate state, and FIG. FIG. 6 is a diagram illustrating a configuration of a zoom lens according to Example 3 of the present invention, where (a) shows a state at a wide angle end, (b) shows an intermediate state, and (c) shows a state at a telephoto end. FIG. 7A is an aberration curve diagram of the zoom lens according to Example 3 of the present invention, where (a) shows a state at a wide angle end, (b) shows an intermediate state, and (c) shows a state at a telephoto end. FIG. 7 is a diagram illustrating a configuration of a zoom lens according to Example 4 of the present invention, where (a) shows a state at a wide angle end, (b) shows an intermediate state, and (c) shows a state at a telephoto end. FIG. 6A is an aberration curve diagram of the zoom lens according to Example 4 of the present invention, where FIG. 5A illustrates a state at the wide-angle end, FIG. 5B illustrates an intermediate state, and FIG. FIG. 10 is a diagram illustrating a configuration of a zoom lens according to Example 5 of the present invention, where (a) shows a state at a wide angle end, (b) shows an intermediate state, and (c) shows a state at a telephoto end. FIG. 7A is an aberration curve diagram of a zoom lens according to Example 5 of the present invention, where FIG. 10A illustrates a state at the wide-angle end, FIG. 10B illustrates an intermediate state, and FIG. FIG. 10 is a diagram illustrating a configuration of a zoom lens according to Example 6 of the present invention, where (a) shows a state at a wide angle end, (b) shows an intermediate state, and (c) shows a state at a telephoto end. FIG. 10A is an aberration curve diagram of a zoom lens according to Example 6 of the present invention. FIG. 10A illustrates a state at the wide-angle end (b) in the middle, and FIG. FIG. 10 is a diagram illustrating a configuration of a zoom lens according to Example 7 of the present invention, where (a) illustrates a state at a wide angle end, (b) illustrates an intermediate state, and (c) illustrates a state at a telephoto end. FIG. 9A is an aberration curve diagram of a zoom lens according to Example 7 of the present invention. FIG. 10A illustrates a state at the wide-angle end, FIG. 10B illustrates an intermediate state, and FIG. FIG. 10 is a diagram illustrating a configuration of a zoom lens according to Example 8 of the present invention, where (a) shows a state at a wide angle end, (b) shows an intermediate state, and (c) shows a state at a telephoto end. FIG. 9A is an aberration curve diagram of the zoom lens according to Example 8 of the present invention. FIG. 10A illustrates a state at the wide-angle end, FIG. 10B illustrates an intermediate state, and FIG. FIG. 10 is a diagram illustrating a configuration of a zoom lens according to Example 9 of the present invention, where (a) illustrates a state at a wide angle end, (b) illustrates an intermediate state, and (c) illustrates a state at a telephoto end. FIG. 10A is an aberration curve diagram of the zoom lens according to Example 9 of the present invention. FIG. 10A illustrates a state at the wide-angle end, FIG. 10B illustrates an intermediate state, and FIG. It is a figure which shows the specific example of a structure which seals an image pick-up element package using a 4th lens group. It is a front perspective view which shows the external appearance of the digital camera to which the optical system of this invention is applied. FIG. 21 is a rear perspective view of the digital camera of FIG. 20. FIG. 21 is a perspective plan view showing the configuration of the digital camera of FIG. 20.

Explanation of symbols

G ₁ 1st lens group G ₂ 2nd lens group G ₃ 3rd lens group G ₄ 4th lens group S Aperture LPF Filter CG Cover glass Lc Optical axis 1 Image sensor package 11 Support frame 2 Holding member 40 Digital camera 41 Imaging optical system 42 Optical path for shooting 43 Viewfinder optical system 44 Optical path for viewfinder 45 Shutter 46 Flash 47 LCD monitor 49 CCD
50 Cover member 51 Processing means 52 Recording means 53 Objective optical system for viewfinder 55 Erecting prism 57 Field frame 59 Eyepiece optical system 60 Cover 61 Focal length change button 62 Setting change switch

Claims (15)

In order from the object side, a first lens group having a negative power, a second lens group having a positive power, and a third lens group having a negative power,
When zooming from the wide-angle end to the telephoto end, the second lens group moves to the object side so that the distance between the first lens group and the second lens group is reduced, and the third lens group is the first lens group. Move so that the distance between the second lens group and the third lens group changes,
The negative lens of the first lens lens constituting the group is only one, the second lens group comprises at least one positive lens and one negative lens,
An imaging optical system characterized by satisfying the following conditional expression:
4.0 ≦ W_L / (tan ω × FL) ≦ 12.0
1.7 ≦ | ΔD12 | / (tan ω × FL) ≦ 4.6
52.0 ≤ PAνd
0.45 ≦ D23W / (tan ω × FL) ≦ 3.0
75.0 ≦ Pνd
However,
W_L: Total length of the optical system at the wide-angle end
ω: half angle of view in any state
FL: Focal length of the entire system in the above arbitrary state
Derutadi12: variation of distance between the first lens group and the second lens group upon zooming from the wide-angle end to the telephoto end
PAnyud: Abbe number of the positive lens in the second lens group
D23W: Distance between the second lens group and the third lens group at the wide-angle end
Pνd: Abbe number of at least one positive lens among the positive lenses in the second lens group . The imaging optical system according to claim 1, further satisfying the following conditional expression:
0.38 ≦ (f2 / fw) × (tan ω × FL / fw) ≦ 0.95
However,
f2: focal length of the second lens group
fw: the focal length of the entire system at the wide-angle end . The photographing optical system according to claim 1, further satisfying the following conditional expression:
2.7 ≦ W_L / fw ≦ 10.0
However ,
f w: The focal length of the entire system at the wide angle end. In order from the object side, a first lens group having a negative power, a second lens group having a positive power, and a third lens group having a negative power,
When zooming from the wide-angle end to the telephoto end, the second lens group moves to the object side so that the distance between the first lens group and the second lens group is reduced, and the third lens group is the first lens group. Move so that the distance between the second lens group and the third lens group changes,
Of the lenses constituting the first lens group, there is only one negative lens, and the second lens group comprises one negative lens and at least one positive lens,
And, it characterized by satisfaction of the following condition shooting optical system.
4.0 ≦ W_L / (tan ω × FL) ≦ 12.0
1.7 ≦ | ΔD12 | / (tan ω × FL) ≦ 4.6
52.0 ≤ PAνd
3.7 ≦ | ΔD12 / ΔD23 |
75.0 ≦ Pνd
However,
W_L: Total length of the optical system at the wide-angle end
ω: Half angle of view in any state
FL: Focal length of the entire system in the above arbitrary state
Derutadi12: variation of distance between the first lens group and the second lens group upon zooming from the wide-angle end to the telephoto end
PAνd: Abbe number of positive lens in the second lens group
Derutadi23: variation of distance between the second lens group and the third lens group upon zooming from the wide-angle end to the telephoto end
Pνd: Abbe number of at least one positive lens among the positive lenses in the second lens group . 5. The photographing optical system according to claim 1, wherein the first lens group includes two lenses of a negative lens and a positive lens in order from the object side, and satisfies the following conditional expression: .
0.6 ≦ G1Σd / (tan ω × FL) ≦ 1.3
However,
G1? D: the total thickness of the first lens group . Imaging optical system according to any one of claims 1 to 5, characterized in that further satisfying the expression below.
45.0 ≦ Pνd−Nνd
However,
Nvd: Abbe number of the negative lens in the second lens group . The photographic optical system according to claim 1 , wherein the third lens group includes two or less lenses . The first lens group includes, in order from the object side, a negative lens and a positive lens,
The second lens group includes, in order from the object side, three positive lenses, negative lenses, and positive lenses or two positive lenses and two negative lenses.
The photographic optical system according to claim 1, wherein the third lens group includes one negative lens . 9. The first lens group according to claim 1, wherein the first lens group is movable between the wide-angle end and the telephoto end during zooming so that the total length of the optical system is minimized. Shooting optical system. The photographing optical system according to claim 1 , further satisfying the following conditional expression at the wide-angle end .
7.0% ≦ | DTW_ × 1.0 |
3.5% ≦ || DTW_ × 0.7 | ≦ 15.0%
7.0% ≦ || DTW_ × 1.0 | ≦ 25.0%
| ΔDTW | ≦ 15.0%
However,
DTW_ × 0.7: % distortion aberration display at the position of the maximum image height at the wide-angle end at × 0.7 when focusing on infinity
DTW_ × 1.0: % display of distortion aberration of length at the position of the maximum captured image height at the wide-angle end of × 1.0 when focused at infinity
ΔDTW: DTW_ × 0.7−DTW_ × 1.0
And
Y'0: Paraxial imaging height
Y ′: Actual imaging height
If
Distortion amount = (Y′−Y′0) / Y′0 × 100 (%)
It is. The photographing optical system according to claim 1, wherein focusing is performed by moving the third lens group in an optical axis direction . Imaging optical system according to any one of claims 1乃optimum 1 1, characterized by further satisfying the expression below.
0.53 ≤ tan ω x FL / fw
However,
fw: the focal length of the entire system at the wide-angle end . In order from the object side, the first lens group having a negative power, a second lens group having a positive power, and a third lens group having a negative power,
When zooming from the wide-angle end to the telephoto end, the second lens group moves to the object side so that the distance between the first lens group and the second lens group is reduced, and the third lens group is the first lens group. Move so that the distance between the second lens group and the third lens group changes,
Of the lenses constituting the first lens group, there is only one negative lens, and the second lens group comprises one negative lens and at least one positive lens,
And, projection optical system Taking you and satisfies the following conditional expression.
4.0 ≦ W_L / (tan ω × FL) ≦ 12.0
1.7 ≦ | ΔD12 | / (tan ω × FL) ≦ 4.6
52.0 ≤ PAνd
75.0 ≦ Pνd
However,
W_L: Total length of the optical system at the wide-angle end
ω: Half angle of view in any state
FL: Focal length of the entire system in the above arbitrary state
Derutadi12: variation of distance between the first lens group and the second lens group upon zooming from the wide-angle end to the telephoto end
PAνd: Abbe number of positive lens in the second lens group
Pνd: Abbe number of at least one positive lens among the positive lenses in the second lens group
It is. The photographing according to any one of claims 1 to 12, wherein a fourth lens group having a positive power and fixed even during zooming is disposed on the image side of the third lens group. Optical system. An imaging optical system according to any one of 請 Motomeko 1 to 14, an imaging apparatus characterized by and an image pickup device located on the image side of the imaging optical system.