JP4849514B2 - Variable magnification optical system and imaging apparatus using the same - Google Patents

Description

  The present invention relates to a variable magnification optical system and an imaging apparatus using the same, and in particular, a compact variable magnification optical system and an electronic apparatus (for example, a digital camera, a video camera, a digital camera) including the compact variable magnification optical system. Video unit, personal computer, mobile computer, mobile phone, portable information terminal, etc.).

  In recent years, personal digital assistants and mobile phones called PDAs have exploded in popularity, and built-in compact digital cameras and digital video units using CCD (Charge Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor) sensors as image sensors. Things are also increasing. Recently, an image sensor having a relatively small size and a high pixel (megapixel) has been developed, and a small and high-performance optical system has been required.

Conventionally, as one of small optical systems, there are those disclosed in Patent Document 1 and Patent Document 2. These are variable-magnification optical systems having a three-group three-element configuration that is positive / negative. Moreover, as a negative leading compact variable power optical system, the one of Patent Document 3 can be cited. Further, examples of the variable magnification optical system having a three-group three-element configuration of negative positive and negative are those of Patent Document 4 and Patent Document 5.
JP 2002-55278 A JP 2003-177314 A Japanese Patent Application Laid-Open No. 2004-226691 JP-A-3-260611 JP 2004-133058 A

  However, the devices described in Patent Document 1 and Patent Document 2 are small variable power optical systems for electronic devices having an image sensor height of about 1.3 mm, and the correction of off-axis aberration is insufficient, and the optical performance is VGA (imaging). The number of pixels of the element is as low as about 300,000), and aberrations due to asymmetry of the power arrangement in the optical system are likely to occur. Further, the one described in Patent Document 3 is a variable magnification optical system corresponding to an ultra-small image pickup device having an image pickup device height of about 1 mm, and the third lens group is constituted by a positive refractive power lens or a negative refractive power lens. However, the optical performance is as low as VGA (the number of pixels of the image sensor is about 300,000), and aberration due to asymmetry of the power arrangement in the optical system is likely to occur. Alternatively, the third lens group is close to the image side, which is disadvantageous for miniaturization. Patent Document 4 describes a variable power optical system for a silver salt camera, which has an optical performance as high as SXGA (the number of pixels is about 1 million), but has a short back focus and a third lens group. Tends to be large, and has the disadvantage of being disadvantageous for miniaturization. Although the thing of patent document 5 is negative / positive / negative 3 group structure, since the 2nd lens group is comprised by the cemented lens of the positive lens and the negative lens, there exists a fault to which an optical system becomes large. Further, this prior art has an image sensor height of about 1.6 mm, and its optical performance is as low as VGA (the number of pixels of the image sensor is about 300,000), which is not high performance.

  The present invention has been made in view of such a situation in the prior art, and an object of the present invention is to provide a small, high-performance variable magnification optical system having a small number of components, and an electronic apparatus including the same. is there.

The variable magnification optical system of the present invention that achieves the above object comprises, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a negative refractive power. A zooming optical system for zooming by moving at least the second lens group and the third lens group to change the interval between the groups,
The negative first lens group is composed of one negative lens,
The positive second lens group includes one positive lens,
The negative third lens group is composed of one negative lens,
The negative lens of the third lens group has a negative meniscus shape with the concave surface facing the image plane side;
The refractive powers of the first lens group and the second lens group satisfy the following conditional expressions (3) and (3-2) ′.
1.8 <| f ₁ | / f ₂ <6.5 (3)
1.9 <| f ₁ (t) | / f ₂ ≦ 2.37 (3-2) ′
Where f ₁ is the focal length of the first lens group,
f ₂ is the focal length of the second lens group,
f ₁ (t) is the focal length at the telephoto end of the first lens group,
It is.

  The reason why the above configuration is adopted in the present invention and the function and effect thereof will be described below.

  Since the optical system mounted on electronic equipment is equipped with an image sensor and filters on the image side, a relatively long back focus is required, and as an advantageous optical system there is a negative leading retrofocus configuration. Is optimal.

  In the present invention, a negative refracting power is arranged in the first lens group, which is advantageous for widening the angle and obtaining a relatively long back focus. In addition, by configuring each group with one lens, the total length of the optical system when retracted can be further shortened. Further, since the second lens group having the main power of the optical system is a lens having a strong positive refractive power, it is possible to satisfactorily correct various aberrations of the negative action generated in the negative lens of the first lens group. In addition, by configuring the third lens group with a single lens having negative refractive power, various aberrations that cannot be corrected with the positive lens of the second lens group, particularly various off-axis aberrations, can be corrected well. Yes. When the third lens group is composed of one positive lens, a positive lens and a negative lens are required in the second lens group for aberration correction, and the second lens group becomes larger, leading to an increase in the size of the entire optical system. It is not preferable. Furthermore, in the present invention, the negative lens shape of the third lens group is a negative meniscus shape with the concave surface facing the image plane side, so that the principal point position is set further rearward so that the third lens group is appropriately positioned from the image plane. The third lens unit can be made compact, and a back focus that can be equipped with filters and an image sensor is secured.

  In the above variable magnification optical system of the present invention, it is desirable that the shaping factor of the negative lens in the third lens group satisfies the following conditional expression (1).

In the above variable magnification optical system of the present invention, it is desirable that the shaping factor of the negative lens in the third lens group satisfies the following conditional expression (1).
1.0 <(r ₆ + r ₇ ) / (r ₆ −r ₇ ) <2.0 (1)
Here, r ₆ and r ₇ are axial curvature radii of the object side surface and the image side surface of the negative lens of the third lens group, respectively.

In the present invention, the lens shape of the negative refractive power constituting the third lens group is a negative meniscus shape with the concave surface facing the image surface side, and the shaping factor of the lens is set to satisfy the conditional expression (1). Thus, it is possible to satisfactorily correct off-axis aberrations, particularly field curvature aberration and coma aberration. Exceeding the upper limit of 2.0 of conditional expression (1) is not preferable because the amount of aberration generated at r ₇ that is the side surface of the image surface is large and off-axis aberrations, particularly field curvature aberrations, are difficult to correct. When the lower limit of 1.0 is exceeded, the negative refractive power of the third lens group becomes weak, and various aberrations cannot be corrected by the third lens group.

  Furthermore, in the present invention, by setting the shaping factor of the negative lens of the third lens group within the following conditional expression (1-2), various off-axis aberrations, particularly field curvature aberration and coma aberration are made better. Is possible and preferable.

1.0 <(r ₆ + r ₇ ) / (r ₆ −r ₇ ) <1.6 (1-2)
It is desirable that the total lens length satisfies the following conditional expression (2).

1.9 <TL _w / f _w <3.1 (2)
Where TL _w is the total lens length at the wide-angle end (distance from the first surface to the image plane),
f _w is the focal length of the entire system at the wide-angle end,
It is.

  If the lower limit of 1.9 of conditional expression (2) is exceeded, it will be difficult to ensure back focus, and space for arranging the image sensor unit and filters will not be available. If the upper limit of 3.1 is exceeded, it is advantageous for ensuring the performance, but the optical system becomes too large and a small optical system cannot be provided, which is not preferable.

  Further, it is desirable that the refractive powers of the first lens group and the second lens group satisfy the following conditional expression (3).

1.8 <| f ₁ | / f ₂ <6.5 (3)
Where f ₁ is the focal length of the first lens group,
f ₂ is the focal length of the second lens group,
It is.

  If the upper limit of 6.5 of conditional expression (3) is exceeded, the refractive power of the second lens group becomes strong, which is advantageous for downsizing the entire variable magnification optical system, but aberrations occur in the second lens group. The amount increases, which is not preferable for aberration correction. In particular, correction of coma aberration becomes difficult, and high image quality performance cannot be secured. If the lower limit of 1.8 is exceeded, the refractive power of the second lens group becomes weak, and various aberrations occurring in the first lens group cannot be corrected well, which is not preferable. In particular, it becomes difficult to correct the curvature of field, which is an off-axis aberration, and it becomes impossible to ensure high image quality performance.

  Further, in the present invention, the refractive power of the first lens group and the second lens group is set within the following conditional expression (3-2), so that spherical aberration and off-axis field curvature aberration at the telephoto end are improved. This can be corrected and is preferable.

1.9 <| f ₁ (t) | / f ₂ <2.8 (3-2)
Where f ₁ (t) is the focal length at the telephoto end of the first lens group,
f ₂ is the focal length of the second lens group,
It is.

  Moreover, it is desirable that the negative lens constituting the third lens group satisfies the following conditional expression (4).

0.4 <r ₇ / f _w <1.0 (4)
Where r ₇ is the on-axis radius of curvature of the image side surface of the negative lens in the third lens group,
f _w is the focal length of the entire system at the wide-angle end,
It is.

  If the lower limit of 0.4 of conditional expression (4) is exceeded, the amount of coma aberration generated on the image side surface of the negative lens in the third lens group will increase, causing a deterioration in the performance of the peripheral portion. Exceeding the upper limit of 1.0 is not preferable because negative component aberration on the surface becomes too small to correct positive component spherical aberration generated in other lens elements.

  Moreover, it is desirable that the following conditional expression (5) is satisfied.

0.4 <(G23L) / Y ′ <1.1 (5)
Where Y ′ is the maximum image height (half the diagonal length of the effective imaging area),
G23L is the total thickness on the optical axis of the lenses constituting the second lens group and the third lens group,
It is.

  If the upper limit of 1.1 of conditional expression (5) is exceeded, the total length of the second lens group will increase, contributing to an increase in the overall size of the optical system. If the value exceeds the lower limit of 0.4, it is advantageous for downsizing, but it is not desirable in terms of processing and assembly because the lens becomes thinner and more easily damaged with respect to its diameter.

  Further, it is desirable that the negative lens of the first lens group is a refractive power variable optical element.

  In the present invention, the negative refractive power lens that is the first lens group is a variable refractive power lens, so that the amount of negative action aberration in the first lens group is controlled, and various aberrations in the entire zoom range are improved. It is corrected. On the wide-angle side, the negative refracting power of the first lens group is weakened to bear the magnification effect of the optical system, and at the same time, distortion that becomes negative at wide-angle is corrected well. On the telephoto side, the negative refracting power of the first lens group is strengthened to bear the zooming effect of the optical system, and at the same time, spherical aberration that becomes negative during telephoto is corrected well.

  When a variable power optical element is used for the negative lens of the first lens group, it is desirable that the variable power optical element satisfies the following conditional expression.

0.07 <| φ ₁ | <0.27 (6)
Here, φ ₁ is the refractive power of the refractive power variable optical element.

  When the upper limit of 0.27 in conditional expression (6) is exceeded, the refractive power of the variable refractive power optical element becomes too strong, making it difficult to correct off-axis aberrations, particularly distortion at the wide-angle end. On the other hand, if the lower limit of 0.07 is exceeded, the overall length becomes too long and the size is increased.

  Further, it is desirable to perform focusing by moving the negative lens of the first lens group.

  It is preferable to move the negative first lens, which is the first lens group, to perform focusing so that aberration variation with respect to a change in distance is small.

  When a variable refractive power optical element is used for the negative lens of the first lens group, focusing can be performed by changing the refractive power of the variable refractive power optical element. In this case, a moving group mechanism at the time of focusing becomes unnecessary, and a simple lens frame configuration is possible.

  The present invention includes an imaging apparatus including any of the above variable magnification optical systems and an image sensor disposed on the image side of the variable magnification optical system. With such a configuration, the same effect as that of the above-described variable magnification optical system can be obtained.

  According to the present invention described above, a compact and high-performance variable magnification optical system having a small number of components and an electronic device equipped with the same can be obtained.

  Examples 1 to 5 of the variable magnification optical system of the present invention will be described below. FIGS. 1 to 5 show lens cross-sectional views of the wide-angle end (a), the intermediate state (b), and the telephoto end (c) when focusing on an object point at infinity in Examples 1 to 5, respectively. In the figure, the first lens group is G1, the aperture stop is S, the second lens group is G2, the third lens group is G3, and a parallel plate constituting a low-pass filter or the like with a wavelength range limiting coat that limits infrared light. Is denoted by F and the image plane is denoted by I.

  Examples 1 to 5 are variable magnification optical systems for electronic equipment having an image pickup element height of about 2.3 mm. All of these examples are, in order from the object side, a negative refractive power lens having a concave surface directed to the image plane side, an aperture, and both Consists of a convex positive refracting lens and a negative refracting meniscus lens with the concave surface facing the image side, and zooming is performed by moving the second lens group G2 and the third lens group G3 to change the distance between each group. ing.

  The first negative lens constituting the first lens group G1 of Examples 1, 2, and 5 is composed of a liquid crystal lens (refractive power variable element) whose refractive power changes with zooming.

  Further, it is assumed that the distortion aberration of the third embodiment is corrected by image processing after receiving light by the electronic image sensor.

  The first negative lens constituting the first lens group G1 of Example 4 is composed of a variable shape lens (refractive power variable element) whose shape changes with zooming.

  As shown in FIG. 1, the variable magnification optical system of Example 1 includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, The zoom lens includes a third lens group G3 having negative refractive power. When zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, and the second lens group G2 is an aperture stop S. The third lens group G3 moves to the object side while increasing the distance from the second lens group G2.

  In order from the object side, the first lens group G1 is composed of a negative meniscus lens having a convex surface directed toward the object side, and its refractive index increases upon zooming from the wide-angle end to the telephoto end. The second lens group G2 is composed of a biconvex positive lens, and the third lens group G3 is composed of a negative meniscus lens having a convex surface facing the object side. The aspherical surfaces are five surfaces including both surfaces of the negative meniscus lens of the first lens group G1, both surfaces of the biconvex positive lens of the second lens group G2, and the image side surface of the negative meniscus lens of the third lens group G3. Used for.

  As shown in FIG. 2, the variable magnification optical system of Example 2 includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, The zoom lens includes a third lens group G3 having negative refractive power. When zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, and the second lens group G2 is an aperture stop S. The third lens group G3 moves to the object side while increasing the distance from the second lens group G2.

  In order from the object side, the first lens group G1 is composed of a negative meniscus lens having a convex surface directed toward the object side, and its refractive index increases upon zooming from the wide-angle end to the telephoto end. The second lens group G2 is composed of a biconvex positive lens, and the third lens group G3 is composed of a negative meniscus lens having a convex surface facing the object side. The aspherical surfaces are five surfaces including both surfaces of the negative meniscus lens of the first lens group G1, both surfaces of the biconvex positive lens of the second lens group G2, and the image side surface of the negative meniscus lens of the third lens group G3. Used for.

  As shown in FIG. 3, the variable magnification optical system of Example 3 includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, The zoom lens includes a third lens group G3 having negative refractive power. When zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, and the second lens group G2 is an aperture stop S. The third lens group G3 moves toward the object side, and the third lens group G3 moves toward the object side while once reducing the distance from the second lens group G2.

  In order from the object side, the first lens group G1 is composed of a negative meniscus lens having a convex surface facing the object side, the second lens group G2 is composed of a biconvex positive lens, and the third lens group G3 is convex on the object side. It consists of a negative meniscus lens. The aspherical surfaces are five surfaces including both surfaces of the negative meniscus lens of the first lens group G1, both surfaces of the biconvex positive lens of the second lens group G2, and the image side surface of the negative meniscus lens of the third lens group G3. Used for.

  As shown in FIG. 4, the zoom optical system of Example 4 includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, The zoom lens includes a third lens group G3 having negative refractive power. When zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, and the second lens group G2 is an aperture stop S. The third lens group G3 moves to the object side while increasing the distance from the second lens group G2.

  In order from the object side, the first lens group G1 is composed of a negative meniscus lens having a convex surface directed toward the object side. The radius of curvature of the second surface decreases upon zooming from the wide-angle end to the telephoto end. The distance between the surface and the second surface is also reduced. The second lens group G2 is composed of a biconvex positive lens, and the third lens group G3 is composed of a negative meniscus lens having a convex surface facing the object side. The aspherical surfaces are five surfaces including both surfaces of the negative meniscus lens of the first lens group G1, both surfaces of the biconvex positive lens of the second lens group G2, and the image side surface of the negative meniscus lens of the third lens group G3. Used for.

  As shown in FIG. 5, the variable magnification optical system of Example 5 includes, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a negative refractive power. The aperture stop is provided on the object-side surface of the biconvex positive lens constituting the second lens group G2. When zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 is moved to the object side, and the third lens group G3 is spaced from the second lens group G2. Move to the object side while spreading.

  In order from the object side, the first lens group G1 is composed of a negative meniscus lens having a convex surface directed toward the object side, and its refractive index increases upon zooming from the wide-angle end to the telephoto end. The second lens group G2 is composed of a biconvex positive lens, and the third lens group G3 is composed of a negative meniscus lens having a convex surface facing the object side. The aspherical surfaces are five surfaces including both surfaces of the negative meniscus lens of the first lens group G1, both surfaces of the biconvex positive lens of the second lens group G2, and the image side surface of the negative meniscus lens of the third lens group G3. Used for.

Hereinafter, numerical data of each embodiment described above, but the symbols are outside the above, f is the focal length, F _NO is the F-number, FIY image height, omega half field angle, WE denotes a wide angle end, ST Is an intermediate state, TE is a telephoto end, r ₁ , r _2, are curvature radii of lens surfaces, d ₁ , d _2, are intervals between the lens surfaces, n _d1 , n _d2, are d lines of each lens Refractive index, ν _d1 , ν _d2 ... Is the Abbe number of each lens. The aspherical shape is represented by the following formula, where x is an optical axis with the light traveling direction being positive, and y is a direction orthogonal to the optical axis.

x = (y ² / r) / [1+ {1- (K + 1) (y / r) ² } ^1/2 ]
+ A ₂ y ² + A ₄ y ⁴ + A ₆ y ⁶ + A ₈ y ⁸
Here, r is a paraxial radius of curvature, K is a conical coefficient, and A ₂ , A ₄ , A ₆ , and A ₈ are second-order, fourth-order, sixth-order, and eighth-order aspheric coefficients, respectively.

  In the numerical data of the following examples, the value indicating the length is the length in mm.

Example 1
r ₁ = 26.751 (aspherical surface) d ₁ = 0.50 n _d1 = (variable) ν _d1 = (variable)
r ₂ = 3.372 (aspherical surface) d ₂ = (variable)
r ₃ = ∞ (aperture) d ₃ = 0.29
r ₄ = 2.017 (aspherical surface) d ₄ = 0.88 n _d2 = 1.74716 ν _d2 = 52.76
r ₅ = -5.122 (aspherical surface) d ₅ = (variable)
r ₆ = 9.395 d ₆ = 0.54 n _d3 = 1.84700 ν _d3 = 24.00
r ₇ = 1.928 (aspherical surface) d ₇ = (variable)
r ₈ = ∞ d ₈ = 0.50 n _d4 = 1.51633 ν _d4 = 64.14
r ₉ = ∞ d ₉ = 0.50
r ₁₀ = ∞ (image plane)
Aspheric coefficient 1st surface K = 0
A ₄ = -3.7730 × 10 ^-3
A ₆ = 2.3022 × 10 ^-3
A ₈ = -1.9976 × 10 ^-4
Second side K = 0
A ₄ = 5.2428 × 10 ^-4
A ₆ = 3.6118 × 10 ^-3
A ₈ = 4.9284 × 10 ^-4
4th surface K = -1.0229
A ₄ = 6.2154 × 10 ^-3
A ₆ = -5.1160 × 10 ^-3
A ₈ = 0.0000
Fifth side K = 0
A ₄ = 4.3196 × 10 ^-3
A ₆ = -7.9105 × 10 ^-3
A ₈ = 2.3019 × 10 ^-3
Surface 7 K = -0.4034
A ₄ = 3.6964 × 10 ^-2
A ₆ = 4.3544 × 10 ^-2
A ₈ = -1.6171 × 10 ^-2
Zoom data (∞)
WE ST TE
f (mm) 3.60 5.10 7.20
F _NO 2.80 3.81 4.57
FIY (mm) 2.25 2.25 2.25
d ₂ 3.51 1.98 0.89
d ₅ 0.11 0.20 0.37
d ₇ 2.70 4.14 5.06
n ₁ 1.48000 1.75306 1.82000
ν ₁ 56.5 53.3 52.5
f ₁ -8.09 -5.17 -4.75
φ ₁ -0.12 -0.19 -0.21.

Example 2
r ₁ = 9.065 (aspherical surface) d ₁ = 0.50 n _d1 = (variable) ν _d1 = (variable)
r ₂ = 2.565 (aspherical surface) d ₂ = (variable)
r ₃ = ∞ (aperture) d ₃ = 0.23
r ₄ = 2.009 (aspherical surface) d ₄ = 0.82 n _d2 = 1.73792 ν _d2 = 53.77
r ₅ = -5.289 (aspherical surface) d ₅ = (variable)
r ₆ = 27.324 d ₆ = 0.61 n _d3 = 1.84700 ν _d3 = 24.00
r ₇ = 2.261 (aspherical surface) d ₇ = (variable)
r ₈ = ∞ d ₈ = 0.50 n _d4 = 1.51633 ν _d4 = 64.14
r ₉ = ∞ d ₉ = 0.50
r ₁₀ = ∞ (image plane)
Aspheric coefficient 1st surface K = 0
A ₄ = -1.1146 × 10 ^-2
A ₆ = 3.4522 × 10 ^-3
A ₈ = -3.0779 × 10 ^-4
Second side K = 0
A ₄ = -1.1417 × 10 ^-2
A ₆ = 6.1065 × 10 ^-3
A ₈ = -4.6860 × 10 ^-5
4th surface K = -0.9282
A ₄ = 7.7959 × 10 ^-3
A ₆ = -4.9582 × 10 ^-3
A ₈ = 0.0000
Fifth side K = 0
A ₄ = 6.7293 × 10 ^-3
A ₆ = -9.2563 × 10 ^-3
A ₈ = 2.7121 × 10 ^-3
Surface 7 K = 0.5015
A ₄ = 3.0181 × 10 ^-2
A ₆ = 4.3227 × 10 ^-2
A ₈ = -1.4779 × 10 ^-2
Zoom data (∞)
WE ST TE
f (mm) 3.60 5.10 7.20
F _NO 2.80 3.75 4.49
FIY (mm) 2.25 2.25 2.25
d ₂ 3.69 2.24 1.15
d ₅ 0.23 0.30 0.45
d ₇ 2.71 4.10 5.04
n ₁ 1.52000 1.73616 1.78000
ν ₁ 50.5 49.6 49.5
f ₁ -7.07 -5.02 -4.75
φ ₁ -0.14 -0.20 -0.21.

Example 3
r ₁ = 170.653 (aspherical surface) d ₁ = 0.50 n _d1 = 1.52542 ν _d1 = 55.78
r ₂ = 2.807 (aspherical surface) d ₂ = (variable)
r ₃ = ∞ (aperture) d ₃ = 0.00
r ₄ = 1.898 (aspherical surface) d ₄ = 1.14 n _d2 = 1.58313 ν _d2 = 59.38
r ₅ = -2.872 (aspherical surface) d ₅ = (variable)
r ₆ = 32.126 d ₆ = 0.50 n _d3 = 1.60687 ν _d3 = 27.03
r ₇ = 1.973 (aspherical surface) d ₇ = (variable)
r ₈ = ∞ d ₈ = 0.50 n _d4 = 1.51633 ν _d4 = 64.14
r ₉ = ∞ d ₉ = 0.50
r ₁₀ = ∞ (image plane)
Aspheric coefficient 1st surface K = 0
A ₄ = -4.4751 × 10 ^-2
A ₆ = 4.4143 × 10 ^-3
A ₈ = 7.0371 × 10 ^-4
Second side K = 0
A ₄ = -5.4025 × 10 ^-2
A ₆ = 5.0229 × 10 ^-3
A ₈ = 1.9408 × 10 ^-3
4th surface K = -1.2270
A ₄ = 9.7027 × 10 ^-3
A ₆ = 1.4144 × 10 ^-2
A ₈ = 0.0000
Fifth side K = 0
A ₄ = 6.5584 × 10 ^-2
A ₆ = -4.0609 × 10 ^-3
A ₈ = 5.2558 × 10 ^-3
Surface 7 K = 2.0411
A ₄ = -8.5633 × 10 ^-2
A ₆ = 3.0959 × 10 ^-2
A ₈ = -2.9048 × 10 ^-2
Zoom data (∞)
WE ST TE
f (mm) 3.60 6.22 7.20
F _NO 2.80 3.86 4.18
ω (°) 34.80 19.46 17.37
d ₂ 3.17 1.36 0.88
d ₅ 0.21 0.11 0.15
d ₇ 2.98 4.89 5.33.

Example 4
r ₁ = 10.687 (aspherical surface) d ₁ = (variable) n _d1 = 1.70269 ν _d1 = 49.62
r ₂ = (variable) (aspherical surface) d ₂ = (variable)
r ₃ = ∞ (aperture) d ₃ = 0.26
r ₄ = 2.058 (aspherical surface) d ₄ = 0.81 n _d2 = 1.74100 ν _d2 = 52.64
r ₅ = -5.559 (aspherical surface) d ₅ = (variable)
r ₆ = 11.123 d ₆ = 0.82 n _d3 = 1.84666 ν _d3 = 23.78
r ₇ = 1.942 (aspherical surface) d ₇ = (variable)
r ₈ = ∞ d ₈ = 0.50 n _d4 = 1.51633 ν _d4 = 64.14
r ₉ = ∞ d ₉ = 0.50
r ₁₀ = ∞ (image plane)
Aspheric coefficient 1st surface K = 0
A ₄ = -1.4506 × 10 ^-2
A ₆ = 3.3139 × 10 ^-3
A ₈ = -2.1979 × 10 ^-4
Second side K = 0
A ₄ = (variable)
A ₆ = (variable)
A ₈ = (variable)
4th surface K = -1.0654
A ₄ = 5.6061 × 10 ^-3
A ₆ = -4.2360 × 10 ^-3
A ₈ = 0.0000
Fifth side K = 0
A ₄ = 6.5699 × 10 ^-3
A ₆ = -8.6317 × 10 ^-3
A ₈ = 2.3784 × 10 ^-3
Surface 7 K = 0.0590
A ₄ = 2.6397 × 10 ^-2
A ₆ = 4.3305 × 10 ^-2
A ₈ = -1.5416 × 10 ^-2
Zoom data (∞)
WE ST TE
f (mm) 3.60 5.10 7.20
F _NO 2.76 4.13 5.05
FIY (mm) 2.25 2.25 2.25
d ₁ 0.76 0.52 0.50
d ₂ 3.73 2.15 1.05
d ₅ 0.15 0.23 0.41
d ₇ 1.98 3.72 4.65
r ₂ 4.503 2.792 2.560
A ₄ (2nd surface) -1.6051 × 10 ^-2 -1.7286 × 10 ^-2 -1.8638 × 10 ^-2
A ₆ (2nd surface) 5.6250 × 10 ^-3 5.5014 × 10 ^-3 7.2142 × 10 ^-3
A ₈ (2nd surface) -2.8595 × 10 ^-4 -1.8522 × 10 ^-4 -1.2779 × 10 ^-3
f ₁ -11.67 -5.53 -4.92.
φ ₁ -0.09 -0.18 -0.20

Example 5
r ₁ = 11.019 (aspherical surface) d ₁ = 0.50 n _d1 = (variable) ν _d1 = (variable)
r ₂ = 2.614 (aspherical surface) d ₂ = (variable)
r ₃ = 1.950 (aspherical surface) d ₃ = 0.85 n _d2 = 1.76225 ν _d2 = 51.25
(Aperture)
r ₄ = -4.595 (aspherical surface) d ₄ = (variable)
r ₅ = 55.017 d ₅ = 0.50 n _d3 = 1.84700 ν _d3 = 24.00
r ₆ = 2.126 (aspherical surface) d ₆ = (variable)
r ₇ = ∞ d ₇ = 0.50 n _d4 = 1.51633 ν _d4 = 64.14
r ₈ = ∞ d ₈ = 0.50
r ₉ = ∞ (image plane)
Aspheric coefficient 1st surface K = 0
A ₄ = -1.0007 × 10 ^-2
A ₆ = 4.2473 × 10 ^-3
A ₈ = -4.6301 × 10 ^-4
Second side K = 0
A ₄ = -6.9714 × 10 ^-3
A ₆ = 7.8294 × 10 ^-3
A ₈ = -1.1709 × 10 ^-5
Third side K = -0.9283
A ₄ = 7.1066 × 10 ^-3
A ₆ = -5.2297 × 10 ^-3
A ₈ = 0.0000
4th surface K = 0
A ₄ = 6.7535 × 10 ^-3
A ₆ = -9.2607 × 10 ^-3
A ₈ = 3.2086 × 10 ^-3
6th surface K = 0.4987
A ₄ = 3.0255 × 10 ^-2
A ₆ = 5.5872 × 10 ^-2
A ₈ = -2.4416 × 10 ^-2
Zoom data (∞)
WE ST TE
f (mm) 3.60 5.10 7.20
F _NO 2.80 3.78 4.63
FIY (mm) 2.25 2.25 2.25
d ₂ 3.46 2.12 1.09
d ₄ 0.19 0.26 0.43
d ₆ 2.70 3.97 4.83
n ₁ 1.52000 1.71358 1.78000
ν ₁ 50.5 49.6 49.5
f ₁ -6.73 -4.92 -4.51
φ ₁ -0.15 -0.20 -0.22.

  Aberration diagrams at the time of focusing on an object point at infinity in Examples 1 to 5 are shown in FIGS. In these aberration diagrams, (a) is a wide angle end, (b) is an intermediate state, (c) is a spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration at a telephoto end ( CC). In each aberration diagram, “FIY” represents the image height, and “ω” represents the half angle of view.

The values of conditional expressions (1) to (6) and values of f ₁ in Examples 1 to 5 are as follows.

Conditional Example Example 1 Example 2 Example 3 Example 4 Example 5
(1) 1.52 1.18 1.13 1.42 1.08
(2) 2.65 2.72 2.64 2.64 2.56
(3) Wide angle end 3.95 3.41 2.35 5.50 3.53
Telephoto end 2.32 2.29 2.32 2.37
(3-2) 2.32 2.29 2.35 2.32 2.37
(4) 0.54 0.63 0.55 0.54 0.59
(5) 0.63 0.63 0.73 0.72 0.60
(6) Wide angle end -0.12 -0.14 -0.09 -0.15
Telephoto end -0.21 -0.21 -0.20 -0.22
f ₁ Wide angle end -8.09 -7.07 -11.67 -6.73
Telephoto end -4.75 -4.75 -4.92 -4.51
.

  An example of an electronic photographing apparatus, particularly a digital camera, a video camera, and an information processing apparatus, which forms an object image with the variable magnification optical system according to the present invention as described above and receives the image on an image sensor such as a CCD. It can be used for personal computers, telephones, especially mobile phones that are convenient to carry. The embodiment is illustrated below.

  FIGS. 11 to 13 are conceptual diagrams of a configuration in which the variable magnification optical system according to the present invention is incorporated in a photographing optical system 41 of a digital camera. 11 is a front perspective view showing the appearance of the digital camera 40, FIG. 12 is a rear front view thereof, and FIG. 13 is a schematic perspective plan view showing the configuration of the digital camera 40. However, in FIGS. 11 and 13, the photographing optical system 41 is not retracted. In this example, the digital camera 40 includes a photographing optical system 41 having a photographing optical path 42, a finder optical system 43 having a finder optical path 44, a shutter button 45, a flash 46, a liquid crystal display monitor 47, a focal length change button 61, When the photographing optical system 41 is retracted, including the setting change switch 62, the photographing optical system 41, the finder optical system 43, and the flash 46 are covered with the cover 60 by sliding the cover 60. When the cover 60 is opened and the camera 40 is set to the photographing state, the photographing optical system 41 is brought into the non-collapsed state of FIG. 13, and when the shutter button 45 disposed on the upper part of the camera 40 is pressed, the photographing is performed in conjunction therewith. Photographing is performed through the optical system 41, for example, the variable magnification optical system of the first embodiment. An object image formed by the photographing optical system 41 is formed on the image pickup surface of the CCD 49 through a low-pass filter with IR cut coating and a cover glass F. 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, the processing means 51 is connected to a recording means 52 so that a photographed electronic image can be recorded. The recording means 52 may be provided separately from the processing means 51, or may be configured to perform recording / writing electronically using a floppy disk, memory card, MO, or the like. Further, it may be configured as a silver salt camera in which a silver salt film is arranged in place of the CCD 49.

  Further, a finder objective optical system 53 is disposed on the finder optical path 44. The finder objective optical system 53 is composed of a plurality of lens groups (three groups in the figure) and two prisms, and is composed of a zoom optical system in which the focal length changes in conjunction with the variable magnification optical system of the photographing optical system 41. The object image formed by the finder objective optical system 53 is formed on the field frame 57 of the erecting prism 55 which 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 a high performance and a small size and can be retracted, so that a high performance and a small size can be realized.

  Next, a personal computer which is an example of an information processing apparatus in which the variable magnification optical system according to the present invention is built as an objective optical system is shown in FIGS. 14 is a front perspective view with the cover of the personal computer 300 opened, FIG. 15 is a sectional view of the photographing optical system 303 of the personal computer 300, and FIG. 16 is a side view of the state of FIG. As shown in FIGS. 14 to 16, the personal computer 300 includes a keyboard 301 for a writer to input information from the outside, information processing means and recording means (not shown), and a monitor for displaying information to the operator. 302 and a photographing optical system 303 for photographing the operator himself and surrounding images. Here, the monitor 302 may be a transmissive liquid crystal display element that is illuminated from the back by a backlight (not shown), a reflective liquid crystal display element that reflects and displays light from the front, a CRT display, or the like. Further, in the drawing, the photographing optical system 303 is built in the upper right of the monitor 302. However, the imaging optical system 303 is not limited to the place, and may be anywhere around the monitor 302 or the keyboard 301.

  The photographing optical system 303 has an objective lens 112 made up of a variable magnification optical system (abbreviated in the drawing) according to the present invention and an image sensor chip 162 that receives an image on a photographing optical path 304. These are built in the personal computer 300.

  Here, an optical low-pass filter F is additionally attached on the image sensor chip 162 to be integrally formed as an image pickup unit 160, and can be fitted and attached to the rear end of the lens frame 113 of the objective lens 112 with one touch. Therefore, the center alignment of the objective lens 112 and the image sensor chip 162 and the adjustment of the surface interval are unnecessary, and the assembly is simple. A cover glass 114 for protecting the objective lens 112 is disposed at the tip of the lens frame 113. The driving mechanism for the variable magnification optical system in the lens frame 113 is not shown.

  The object image received by the image sensor chip 162 is input to the processing means of the personal computer 300 via the terminal 166 and displayed on the monitor 302 as an electronic image. FIG. A rendered image 305 is shown. The image 305 can also be displayed on the personal computer of the communication partner from a remote location via the processing means, the Internet, or the telephone.

  Next, FIG. 17 shows a telephone which is an example of an information processing apparatus in which the variable magnification optical system according to the present invention is incorporated as a photographing optical system, particularly a portable telephone which is convenient to carry. 17A is a front view of the mobile phone 400, FIG. 17B is a side view, and FIG. 17C is a cross-sectional view of the photographing optical system 405. As illustrated in FIGS. 17A to 17C, the mobile phone 400 includes a microphone unit 401 that inputs an operator's voice as information, a speaker unit 402 that outputs a voice of a call partner, and an operator who receives information. An input dial 403 for inputting information, a monitor 404 for displaying information such as a photographed image and a telephone number of the operator and the other party, a photographing optical system 405, an antenna 406 for transmitting and receiving communication radio waves, and an image And processing means (not shown) for processing information, communication information, input signals, and the like. Here, the monitor 404 is a liquid crystal display element. In the drawing, the arrangement positions of the respective components are not particularly limited to these. The photographing optical system 405 includes an objective lens 112 made up of a variable magnification optical system (abbreviated in the drawing) according to the present invention disposed on a photographing optical path 407, and an image sensor chip 162 that receives an object image. These are built in the mobile phone 400.

  Here, an optical low-pass filter F is additionally attached on the image sensor chip 162 to be integrally formed as an image pickup unit 160, and can be fitted and attached to the rear end of the lens frame 113 of the objective lens 112 with one touch. Therefore, the center alignment of the objective lens 112 and the image sensor chip 162 and the adjustment of the surface interval are unnecessary, and the assembly is simple. A cover glass 114 for protecting the objective lens 112 is disposed at the tip of the lens frame 113. The driving mechanism for the variable magnification optical system in the lens frame 113 is not shown.

  The object image received by the imaging element chip 162 is input to the processing means (not shown) via the terminal 166 and displayed as an electronic image on the monitor 404, the monitor of the communication partner, or both. . Further, when transmitting an image to a communication partner, the processing means includes a signal processing function for converting information of an object image received by the image sensor chip 162 into a signal that can be transmitted.

  In each embodiment, if a filter such as a low-pass filter is omitted, the camera thickness when retracted can be made thinner.

  According to the embodiment of the present invention, a variable magnification optical system that is small and secures high image quality performance of SXGA (the number of pixels is about 1 million), and a small image quality of SXGA (the number of pixels is about 1 million). It is possible to provide an electronic device equipped with a variable magnification optical system that ensures performance.

FIG. 3 is a lens cross-sectional view of the zoom lens according to the first embodiment of the present invention at the wide-angle end (a), the intermediate state (b), and the telephoto end (c) when focusing on an object point at infinity. FIG. 3 is a lens cross-sectional view similar to FIG. 1 of the variable magnification optical system of Example 2. FIG. 4 is a lens cross-sectional view similar to FIG. 1 of the variable magnification optical system of Example 3. FIG. 6 is a lens cross-sectional view similar to FIG. 1 of the variable magnification optical system of Example 4. FIG. 6 is a lens cross-sectional view similar to FIG. 1 of the variable magnification optical system of Example 5. FIG. 6 is an aberration diagram for Example 1 upon focusing on an object point at infinity. FIG. 6 is an aberration diagram for Example 2 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 3 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 4 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 5 upon focusing on an object point at infinity. It is a front perspective view which shows the external appearance of the digital camera incorporating the variable magnification optical system by this invention. FIG. 12 is a rear perspective view of the digital camera of FIG. 11. It is sectional drawing of the digital camera of FIG. It is the front perspective view which opened the cover of the personal computer incorporating the variable magnification optical system by this invention as an objective optical system. It is sectional drawing of the imaging optical system of a personal computer. It is a side view of the state of FIG. FIG. 2 is a front view (a), a side view (b), and a sectional view (c) of the photographing optical system of a mobile phone in which the variable magnification optical system according to the present invention is incorporated as an objective optical system.

Explanation of symbols

G1 ... first lens group G2 ... second lens group G3 ... third lens group S ... aperture stop F ... parallel plate I constituting a low-pass filter, etc .... image plane E ... observer eyeball 40 ... digital camera 41 ... shooting optical system 42 ... Optical path for photographing 43 ... Viewfinder optical system 44 ... Optical path for viewfinder 45 ... Shutter button 46 ... Flash 47 ... Liquid crystal display monitor 49 ... CCD
DESCRIPTION OF SYMBOLS 50 ... Cover member 51 ... Processing means 52 ... Recording means 53 ... Finder objective optical system 55 ... Erect prism 57 ... Field frame 59 ... Eyepiece optical system 60 ... Cover 61 ... Focal length change button 62 ... Setting change switch 112 ... Objective Lens 113 ... Mirror frame 114 ... Cover glass 160 ... Imaging unit 162 ... Imaging element chip 166 ... Terminal 300 ... PC 301 ... Keyboard 302 ... Monitor 303 ... Shooting optical system 304 ... Shooting optical path 305 ... Image 400 ... Mobile phone 401 ... Microphone unit 402 ... Speaker unit 403 ... Input dial 404 ... Monitor 405 ... Shooting optical system 406 ... Antenna 407 ... Shooting optical path

Claims (10)

In order from the object side, the first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a negative refractive power, and at least the second lens group and the third lens group are moved. A variable power optical system that performs variable power by changing the distance between each group,
The negative first lens group is composed of one negative lens,
The positive second lens group includes one positive lens,
The negative third lens group is composed of one negative lens,
Ri negative meniscus der negative lens of the third lens group is a concave surface facing the image side,
Wherein the first lens group, the refractive power of the second lens group following conditional expression (3), the variable magnification optical system characterized that you satisfied (3-2) '.
1.8 <| f ₁ | / f ₂ <6.5 (3)
1.9 <| f ₁ (t) | / f ₂ ≦ 2.37 (3-2) ′
Where f ₁ is the focal length of the first lens group,
f ₂ is the focal length of the second lens group,
f ₁ (t) is the focal length at the telephoto end of the first lens group,
It is. 2. The variable magnification optical system according to claim 1, wherein a shaping factor of the negative lens of the third lens group satisfies the following conditional expression (1).
1.0 <(r ₆ + r ₇ ) / (r ₆ −r ₇ ) <2.0 (1)
Here, r ₆ and r ₇ are axial curvature radii of the object side surface and the image side surface of the negative lens of the third lens group, respectively. The variable magnification optical system according to claim 1 or 2, wherein the total lens length satisfies the following conditional expression (2).
1.9 <TL _w / f _w <3.1 (2)
Where TL _w is the total lens length at the wide-angle end (distance from the first surface to the image plane),
f _w is the focal length of the entire system at the wide-angle end,
It is. The variable magnification optical system according to any one of claims 1 to 3 , wherein the negative lens constituting the third lens group satisfies the following conditional expression (4).
0.4 <r ₇ / f _w <1.0 (4)
Where r ₇ is the on-axis radius of curvature of the image side surface of the negative lens in the third lens group,
f _w is the focal length of the entire system at the wide-angle end,
It is. The zoom lens system according to any one of claims 1 to 4 , wherein the following conditional expression (5) is satisfied.
0.4 <(G23L) / Y ′ <1.1 (5)
Where Y ′ is the maximum image height,
G23L is the total thickness on the optical axis of the lenses constituting the second lens group and the third lens group,
It is. Negative lens variable magnification optical system of any one of claims 1 to 5, characterized in that the refractive power variable optical element of the first lens group. The variable power optical system according to claim 6, wherein the refractive power variable optical element satisfies the following conditional expression.
0.07 <| φ ₁ | <0.27 (6)
Here, φ ₁ is the refractive power of the refractive power variable optical element. The variable power optical system of any one of claims 1 to 7, characterized in that to perform focusing by moving the negative lens of the first lens group. Claim 6 or 7 variable power optical system, wherein the focusing is performed by changing the refractive power of the refractive power variable optical element. An imaging apparatus comprising: the variable magnification optical system according to any one of claims 1 to 9 ; and an imaging element disposed on an image side of the variable magnification optical system.

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