JP2004318105A - Zoom lens device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens device suitable for a digital camera equipped with a zoom lens system which is bright even in the longest focal distance state though a zoom ratio is large, and whose length in an optical axis direction in housing is very short. <P>SOLUTION: The zoom lens device is equipped with the zoom lens system and an imaging device for converting an optical image formed by the zoom lens system into electric image data in order from an object side. Then, the zoom lens system is constituted of a 1st group having negative power, a 2nd group having positive power and a 3rd group having positive power in order from the object side. The 1st group is constituted of two or three lens elements including a negative meniscus lens turning its convex surface toward the object side nearest to the object side and a positive meniscus lens turning its convex surface toward the object side nearest to an image side, the 2nd group is constituted of a positive lens, a negative lens and a positive lens in order from the object side, and the 3rd group is a single positive lens and moves on an optical axis for the purpose of focusing. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a CCD (Charge Coupled Device) and a CMOS sensor (Complementary
The present invention relates to a zoom lens device having an image pickup device for converting an optical image formed on a light receiving surface such as a metal-oxide semiconductor (complementary metal oxide semiconductor sensor) into an electric signal, and in particular, a small zoom lens having a zoom lens system. Equipment related.

2. Description of the Related Art In recent years, a digital camera that converts an optical image into an electric signal by using an imaging device such as a CCD or a CMOS sensor instead of a silver halide film, digitizes the data, and records or transfers the digital image has become popular. In such digital cameras, CCD and CMOS sensors having high pixels such as 2 million pixels and 3 million pixels have recently been provided at relatively low cost.
The demand for a high-performance zoom lens device equipped with a high-pixel image sensor has been greatly increased. Among these zoom lens devices, in particular, a compact zoom lens device equipped with a zoom lens system capable of zooming without deteriorating image quality has been desired.

In recent years, with the improvement of image processing capability of semiconductor devices and the like, personal computers, mobile computers, mobile phones, and personal digital assistants (PDAs) have been developed.
ce) and the like, a zoom lens device is built in or externally attached, which has spurred demand for a high-performance zoom lens device.

As a zoom lens system used in such a zoom lens device, a number of so-called minus-lead zoom lens systems have been proposed in which the group arranged closest to the object side has negative power. The minus lead zoom lens system has features such as easy widening of the angle and easy securing of a lens back necessary for insertion of an optical low-pass filter.

As a minus lead zoom lens system, there is a zoom lens system conventionally proposed as a photographing lens system of a camera for a silver halide film. However, in these zoom lens systems, in particular, the exit pupil position of the lens system in the shortest focal length state is relatively close to the image plane,
In particular, there is a problem that the pupil of the microlens provided corresponding to each pixel of the image sensor having a high number of pixels does not match, and a sufficient amount of peripheral light cannot be secured. In addition, since the exit pupil position fluctuates greatly at the time of zooming, there is also a problem that it is difficult to set the pupil of the micro lens. Also,
In the first place, the required optical performance such as spatial frequency characteristics is completely different between the silver halide film and the imaging device, and thus sufficient optical performance required for the imaging device cannot be secured. Therefore, there is a need to develop a dedicated zoom lens system optimized for a zoom lens device having an image sensor.

As a minus lead zoom lens system for a zoom lens device having an imaging device, for example, US Pat. No. 5,745,301 discloses a two-component zoom composed of a first group of negative power and a second group of positive power. A lens system is disclosed.

Japanese Patent Application Laid-Open No. 1-191820 discloses a first group of negative power, a second group of positive power, and a third group of positive power.
A three-component zoom lens system for a video camera comprising a group is disclosed.

Japanese Patent Application Laid-Open No. 1-216310 discloses a first group of negative power, a second group of positive power, and a third group of negative power.
There is disclosed a zoom lens system for a video camera having a four-component configuration including a group and a fourth group having a positive power.

Further, Japanese Patent Application Laid-Open No. Hei 9-79026 discloses a zoom lens for an electronic still camera having a four-component configuration including a first group of negative power, a second group of positive power, a third group of negative power, and a fourth group of positive power. A system is disclosed.

U.S. Pat.No. 5,745,301

JP-A 1-191820 JP-A 1-216310 JP-A-9-79026

However, the above-mentioned U.S. Patent No. 5,745,301, JP-A-1-191820 or JP-A-1-21631
The zoom lens system disclosed in No. 0 has a problem that the zoom ratio is about twice and the zoom ratio is small.

Further, the zoom lens system disclosed in Japanese Patent Application Laid-Open No. 9-179026 has a zoom ratio of about three times, but has a problem that the F-number in the longest focal length state is as large as 7 and is not a bright zoom lens system. there were.

Further, each zoom lens system requires a large number of lens elements, and has a problem that it lacks compactness, particularly compactness in the optical axis direction when stored (when retracted).

SUMMARY OF THE INVENTION It is an object of the present invention to provide a zoom lens device including a zoom lens system having a sufficiently short length in the optical axis when stored, despite a large zoom ratio.

A further object of the present invention is to provide a zoom lens device including a zoom lens system that is bright even in the longest focal length state and has a sufficiently small length in the optical axis direction when housed.

In order to solve the above problem, a zoom lens device according to claim 1 includes, in order from an object side, a zoom lens system, and an image sensor that converts an optical image formed by the zoom lens system into electrical image data. Wherein the zoom lens system includes, in order from the object side, a first unit having negative power, a second unit having positive power, and a third unit having positive power. And the first group includes a negative meniscus lens having a convex surface facing the object side disposed closest to the object side and a positive meniscus lens having a convex surface facing the object side disposed closest to the image side. Alternatively, the second group includes three lens elements, a positive lens, a negative lens, and a positive lens, in order from the object side, and the third group includes a single positive lens. There is a change in the object distance Characterized in that it moves along the optical axis for Kashingu adjustment.

Another aspect of the present invention is a digital camera including the zoom lens device. In the past, the term digital camera used to refer exclusively to those that record optical still images, but those that can simultaneously handle moving pictures and digital video cameras for home use have also been proposed, and at present there is no particular distinction between them. It is getting better. Therefore, the term digital camera used in this specification refers to a digital still camera, a digital movie camera, a web camera (
An open or private camera connected to a network that can transmit and receive images regardless of whether it is connected directly to the network or via a device having an information processing function such as a personal computer. And cameras connected to the optical device, and includes an image pickup device having an image pickup device that converts an optical image formed on a light receiving surface into an electric signal.

Another aspect of the present invention is a portable information device including the zoom lens device. Here, the portable information device is a mobile phone terminal or a PDA (Personal Digital Assistan
It means a small and portable information device terminal for personal use such as t).

As described above, according to the zoom lens device of the present invention, there is provided a zoom lens device including a zoom lens system having a sufficiently small length in the optical axis direction when housed, despite a large zoom ratio. can do.

Further, according to the zoom lens device of the present invention, it is possible to provide a zoom lens device including a zoom lens system which is bright even in the longest focal length state and has a sufficiently small length in the optical axis direction when housed.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

An image pickup apparatus according to an embodiment of the present invention includes, for example, as shown in FIG.
In order, the zoom lens system and TL that form an optical image of the object to be variable in magnification, an optical low-pass filter LPF, and an image sensor SR that converts the optical image formed by the zoom lens system TL into an electric signal, It is composed of An imaging device is a digital camera; a video camera; a personal computer, a mobile computer, a mobile phone, and a personal digital assistant (PDA).
Assistance) is a main component of a camera built in or externally attached to the camera.

The optical low-pass filter LPF has a specific cutoff frequency for adjusting the spatial frequency characteristics of the taking lens system and eliminating color moiré generated in the image sensor. The optical low-pass filter according to the embodiment is a birefringent low-pass filter formed by laminating a birefringent material such as quartz whose crystal axis is adjusted in a predetermined direction, a wave plate that changes the plane of polarization, and the like. Note that, as the optical low-pass filter, a phase-type low-pass filter or the like that achieves the required optical cutoff frequency characteristic by the diffraction effect may be employed.

The image sensor SR is composed of a CCD having a plurality of pixels, and converts an optical image formed by a zoom lens system into a CCD.
Convert to an electric signal with CD. The signal generated by the image sensor SR is subjected to predetermined digital image processing and image compression processing as required, and is recorded as digital video signals in a memory (semiconductor memory, optical disk, etc.). The signal is transmitted to another device through the device or converted into an infrared signal. Note that instead of a CCD, a CMOS sensor (Complementary M
etal-oxide Semiconductor) may be used.

FIG. 1 is a lens configuration diagram illustrating a configuration of a zoom lens system according to the first embodiment. The zoom lens system includes, in order from the object side, a negative meniscus first lens L1 having a convex surface facing the object side.
A first group Gr1 including a negative meniscus second lens L2 having a convex surface facing the object side and a positive meniscus third lens L3 having a convex surface facing the object side, and an aperture ST, having the convex surface facing the object side. The second group Gr2 includes a positive meniscus fourth lens L4, a biconcave fifth lens L5, and a biconvex sixth lens L6, and a positive meniscus seventh lens having a convex surface facing the object side. A third unit Gr3 including only the lens L7. During zooming from the shortest focal length state to the longest focal length state, the first group Gr1 moves while drawing a locus of a U-turn convex to the image side, the second group Gr2 moves monotonously to the object side, and the third group Gr2. Gr3 moves while drawing a convex trajectory toward the object side. In focusing from an infinity in-focus condition to a finite object in-focus condition, the seventh lens L7 is independently moved to the object side.

FIG. 2 is a lens configuration diagram illustrating a configuration of a zoom lens system according to a second embodiment. The zoom lens system includes, in order from the object side, a first group Gr1 including a negative meniscus first lens L1 having a convex surface facing the object side and a positive meniscus second lens L2 having a convex surface facing the object side. Aperture ST,
A second lens unit Gr2 including a positive meniscus third lens L3 having a convex surface facing the object side, a biconcave fourth lens L4, and a biconvex fifth lens L5, and a positive meniscus having a convex surface facing the object side And a third group Gr3 including only a sixth lens having a shape. During zooming from the shortest focal length state to the longest focal length state, the first group Gr1 moves while drawing a locus of a U-turn convex on the image side, and the second group Gr2
Moves monotonously to the object side, and the third lens unit Gr3 moves to the image side. In focusing from an infinity in-focus condition to a finite object in-focus condition, the sixth lens L6 is independently moved to the object side.

The zoom lens system of each embodiment includes, in order from the object side, a first unit having negative power, a second unit having positive power, and a third unit having positive power. One group is
It is composed of two or three lens elements including a negative meniscus lens having a convex surface facing the object side disposed closest to the object side and a positive meniscus lens having a convex surface facing the object side disposed closest to the image side. The second group includes, in order from the object side, a positive lens, a negative lens, and a positive lens. It is difficult to reduce the number of units in the first lens group when trying to reduce the size while maintaining optical performance. Therefore, the number of sheets can be reduced by forming the second lens unit with a simple configuration of positive, negative, and positive triplets. In particular, by forming the second lens unit with three positive, negative, positive lenses, it is possible to satisfactorily correct axial spherical aberration.

The third unit is a positive single lens, and is configured to move on the optical axis for focusing adjustment according to a change in object distance. It is desirable that the third lens group disposed closest to the image side be the focus group, so that the lens element with a small load on the drive system can be focused.

  Further, it is desirable that the zoom lens system according to each of the embodiments satisfies the following conditional expression (1).

0.6 <Tsum / fw <2.6 (1)
However,
Tsum: Sum of the thicknesses of all the lens elements included in the zoom lens system,
fw: focal length of the zoom lens system in the shortest focal length state,
It is.

Conditional expression (1) defines the sum of the thicknesses of all the lens elements included in the zoom lens system. The size in the optical axis direction of the zoom lens system when retracted is the largest factor that roughly determines the size in the thickness direction of a digital camera or a portable information device. The size in the optical axis direction at the time of collapsing cannot be physically smaller than the sum of the thicknesses of the lens elements. Therefore, if Tsum cannot be reduced, a compact zoom lens system cannot be achieved when retracted. Conditional expression (1) is exactly a conditional expression that defines the thickness when retracted. If the lower limit of the conditional expression is exceeded, it becomes difficult to physically configure the optical system. On the other hand, when the value exceeds the upper limit, the thickness of the lens becomes too large, which exceeds the limit allowed in digital cameras and portable information devices. It is to be noted that conditional expression (4) is more effective when it is set in the following range.

Tsum / fw <2.2 (1) '
Tsum / fw <2.0 (1) ''
Each lens group constituting the first and second embodiments described above is constituted only by a refraction type lens which deflects an incident light beam by refraction, but is not limited to this. For example, each lens group may be composed of a diffractive lens that deflects an incident light beam by diffraction, a hybrid refraction / diffraction lens that deflects an incident light beam by a combination of a diffraction action and a refraction action, or the like.

Further, a reflecting member that bends the incident optical axis may be added by appropriately adjusting the air gap existing in each lens group or between the lens groups. Bending the incident optical axis is preferable because the degree of freedom of arrangement of the optical system can be improved and the thickness of the optical device in the direction of the incident optical axis can be reduced.

Hereinafter, the configuration of the zoom lens embodying the present invention will be described more specifically with reference to construction data, aberration diagrams, and the like. In addition, the following Examples 1 and 2 are the first to the first
Lens configuration diagrams respectively corresponding to the second embodiment and representing the first and second embodiments
(Figures 1 and 2 http://www.ipdl.jpo-miti.go.jp/Tokujitu/tjitemdrw.ipdl?N0000=231&N05
00 = 1E_N /; >>=;=>: 6 /// & N0001 = 148 & N0552 = 9 & N0553 = 000012) shows the corresponding lens configurations of Examples 1 and 2.

In the construction data of each embodiment, ri (i = 1, 2, 3, ...) is the radius of curvature of the i-th surface counted from the object side, di (i = 1, 2, 3, ...) Indicates the i-th axial distance from the object side, and Ni (i = 1,2,3, ...) and νi (i = 1,2,3, ...) The refractive index (Nd) and Abbe number (νd) of the i-th optical element counted for the d-line are shown. In the construction data, the axial top surface interval (variable interval) that changes during zooming is from the shortest focal length state (short focal length end) [W] to the middle (intermediate focal length state) [M] to the longest focal length state (long). Focal length end) [T]
Is the axial air spacing between each lens group. The focal length f and the F-number FNO of the entire system corresponding to each focal length state [W], [M], [T] are also shown.

A surface with * added to the radius of curvature ri indicates a surface constituted by an aspheric surface, and is defined by the following formula (AS) representing the surface shape of the aspheric surface. The aspherical surface data of each example is shown together with other data.

Z (h) = r- (r ^ 2-ε ・ h ^ 2) ^ 1/2 + (A4 ・ h ^ 4 + A6 ・ h ^ 6 + A8 ・ h ^ 8 + ...) (AS)
r: radius of paraxial curvature of aspheric surface
ε: elliptic coefficient,
Ai: the i-th aspherical coefficient of the aspherical surface,

<Example 1>
f = 4.6-9.0-13.2 mm
FNo. = 2.48-3.19-4.00
[Curvature radius] [Shaft upper surface interval] [Refractive index (Nd)] [Abbe number]
r1 * = 17.532
d1 = 1.000 N1 = 1.83130 ν1 = 41.7
r2 = 6.828
d2 = 2.710
r3 = 23.417
d3 = 1.000 N2 = 1.52510 ν2 = 56.38
r4 * = 6.095
d4 = 1.967
r5 = 11.146
d5 = 2.110 N3 = 1.84666 ν3 = 23.78
r6 = 26.577
d6 = 16.386-4.389-1.000
r7 = ∞
d7 = 0.600
r8 = 6.850
d8 = 1.863 N4 = 1.82879 ν4 = 41.94
r7 = 45.202
d9 = 1.547
r8 = -13.689
d10 = 1.000 N5 = 1.70405 ν5 = 26.37
r9 = 6.002
d11 = 0.100
r12 * = 6.111
d12 = 1.988 N6 = 1.52510 ν6 = 56.38
r13 * = -8.632
d13 = 5.514-10.734-17.333
r14 = 10.647
d14 = 1.445 N7 = 1.52510 ν7 = 56.38
r15 = 32.538
d15 = 2.271-2.578-1.207
r16 = ∞
d16 = 2.500 N8 = 1.51633 ν8 = 64.14
r17 = ∞

[Aspheric coefficient]
r4
ε = 1.0000E + 00
A4 = -6.7060E-04
A6 = -1.7530E-05
A8 = 4.5843E-07
A10 = -2.0557E-08

r12
ε = 1.0000E + 00
A4 = -4.4664E-04
A6 = 1.7277E-05
A8 = 2.2515E-06
A10 = 6.2964E-07

r13
ε = 1.0000E + 00
A4 = 6.5827E-04
A6 = -5.4681E-05
A8 = 2.7981E-05
A10 = -3.5378E-06
A12 = 2.5910E-07

r14
ε = 1.0000E + 00
A4 = -3.7480E-04
A6 = 3.8380E-05
A8 = -2.3902E-06
A10 = 5.7640E-08

<Example 2>
f = 5.8-11.4-16.7 mm
FNo. = 2.55-3.31-4.10
[Curvature radius] [Shaft upper surface interval] [Refractive index (Nd)] [Abbe number]
r1 = 86.761
d1 = 1.000 N1 = 1.75975 ν1 = 50.67
r2 * = 6.379
d2 = 2.721
r3 = 12.040
d3 = 1.936 N2 = 1.84666 ν2 = 23.78
r4 = 24.841
d4 = 18.257-5.090-1.000
r5 = ∞
d5 = 0.600
r6 = 7.714
d6 = 1.964 N3 = 1.78555 ν3 = 46.83
r7 = 67.389
d7 = 2.166
r8 = -14.995
d8 = 1.000 N4 = 1.80518 ν4 = 25.43
r9 * = 9.471
d9 = 0.722
r10 = 15.351
d10 = 2.537 N5 = 1.75450 ν5 = 51.57
r11 = -11.485
d11 = 5.143-12.942-20.477
r12 * = 9.438
d12 = 1.525 N6 = 1.52510 ν6 = 56.38
r13 * = 20.696
d13 = 3.927-3.054-1.521
r14 = ∞
d14 = 2.500 N7 = 1.51633 ν7 = 64.14
r15 = ∞

[Aspheric coefficient]
r2
ε = 1.0000E + 00
A4 = -3.1282E-04
A6 = -1.2185E-05
A8 = 4.0718E-07
A10 = -1.3528E-08

r9
ε = 1.0000E + 00
A4 = 4.0197E-04
A6 = 4.7244E-06
A8 = -8.7786E-07
A10 = 3.9925E-08

r12
ε = 1.0000E + 00
A4 = 2.0421E-04
A6 = 1.1890E-05
A8 = -7.4750E-07
A10 = 5.3768E-08

r13
ε = 1.0000E + 00
A4 = 6.5428E-04
A6 = -1.9795E-05
A8 = 8.8594E-07
A10 = 4.0482E-08

3 and 6 are aberration diagrams of Examples 1 and 2, FIGS. 3 and 4 are aberrations of Examples 1 and 2 in an infinity in-focus state, and FIGS. 9 shows respective aberrations of Examples 1 and 2 in a focused state of a close object (object distance of 40 cm). In each aberration diagram, the upper part is the shortest focal length state, the middle part is middle,
The lower row shows various aberrations in the longest focal length state (in order from the left, spherical aberration, astigmatism, distortion; Y ′:
(Image height). Further, the solid line (d) in the spherical aberration diagram, the dashed line (g) indicates the spherical aberration for the d-line and the g-line, respectively, and the dashed line (SC) indicates the sine condition, and the dashed line (DM) in the astigmatism diagram. And the solid line (D
S) represents astigmatism with respect to d-line on the meridional surface and the sagittal surface, respectively.

1 is a lens configuration diagram illustrating a first embodiment (Example 1) of the present invention. FIG. 4 is a lens configuration diagram illustrating a second embodiment (Example 2) of the present invention. Aberration diagram of the first embodiment (Example 1) of the present invention when focused on infinity Aberration diagram of the second embodiment (Example 2) of the present invention when focused on infinity Aberration diagram of the first embodiment (Example 1) of the present invention when a close object is in focus Aberration diagram of the second embodiment (Example 2) of the present invention in a state where a close object is in focus FIG. 1 is a diagram showing a schematic configuration of a zoom lens device according to the present invention.

Explanation of reference numerals

Zoom lens system (TL)
First lens group (Gr1)
Second lens group (Gr2)
Third lens group (Gr3)
4th lens group (Gr4)
Filter (LPF)
Image sensor (SR)

Claims (4)

A zoom lens device including, in order from the object side, a zoom lens system, and an imaging element that converts an optical image formed by the zoom lens system into electrical image data,
The zoom lens system includes, in order from the object side, a first group having negative power, a second group having positive power, and a third group having positive power,
The first lens unit includes two or three lenses including a negative meniscus lens having a convex surface facing the object side closest to the object side and a positive meniscus lens having a convex surface facing the object side closest to the image side. It is composed of elements,
The second group includes, in order from the object, a positive lens, a negative lens, and a positive lens.
The third lens unit is a positive single lens, and moves on the optical axis for focusing adjustment according to a change in object distance. 2. The zoom lens device according to claim 1, wherein the following conditional expression (1) is satisfied.
0.6 <Tsum / fw <2.6
However,
Tsum: Sum of the thicknesses of all the lens elements included in the zoom lens system,
fw: focal length of the zoom lens system in the shortest focal length state,
It is.   A digital camera comprising the zoom lens device according to claim 1. A portable information device comprising the zoom lens device according to claim 1.

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