JP2013105142A - Zoom lens and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens which achieves a high variable power ratio of 20 times or more and is reduced in size, and in which various aberrations are satisfactorily corrected, and to provide an imaging apparatus using the same.SOLUTION: The zoom lens includes, in order from an object side, a first lens group Gr1 having a positive refractive power, a second lens group Gr2 having a negative refractive power, a third lens group Gr3 having a positive refractive power, a fourth lens group Gr4 having a negative refractive power, and a fifth lens group Gr5 having a positive refractive power, and varies power by changing the distances between the above lens groups. When varying power, each of the first lens group Gr1 to the fourth lens group Gr4 moves. The fifth lens group Gr5 is a lens group which does not move in varying power and in focusing. The zoom lens satisfies the following conditional expression: (1) 6.5<|f1/f2|<15.0, where f1 is the focal length of the first lens group, and f2 is the focal length of the second lens group.

Description

  The present invention relates to a zoom lens that includes a plurality of lens groups and performs zooming by changing an interval in the optical axis direction of the lens groups, and an imaging apparatus including the zoom lens.

  In recent years, digital still cameras and video cameras using solid-state imaging devices such as CCD (Charged Coupled Device) type image sensors or CMOS (Complementary Metal Oxide Semiconductor) type image sensors have become more compact and highly variable, such as being smaller and thinner. There is an increasing demand for zoom lenses that can achieve double magnification.

  As a zoom lens having a high zoom ratio, a zoom lens having a positive / negative / positive four-group configuration is generally well known. Patent Documents 1 and 2 disclose such a zoom lens having a positive / negative / positive-positive four-group configuration. It is disclosed.

  However, in response to the above-described demand, the zoom lens disclosed in Patent Document 1 has a zoom ratio as small as 6 to 7, while the zoom lens disclosed in Patent Document 2 has a zoom ratio of 9 to 9. Although 12 times larger than that of Patent Document 1, there is a problem that the total length at the telephoto end is increased. When the total length is large, it is a disadvantageous condition for making the lens barrel compact when the lens is retracted, particularly for making it thin. In addition, since the final lens group is movable at the time of zooming, if the overall length is shortened, the captured image is easily affected by dust and scratches on the final lens group when the distance between the final lens group and the solid-state imaging device is reduced. There is also a problem. From these facts, it can be said that a zoom lens having a positive / negative / positive four-group configuration is not suitable for achieving both compactness and high zoom ratio.

  On the other hand, the first group is positive, the second group is negative, the third group is positive, and the fourth group is positive, and the fourth group has a negative refractive power between the third group and the fourth group. Patent Documents 3 and 4 disclose zoom lenses that achieve a high zoom ratio and optical performance by adding a movable lens group and fixing the final group, while achieving the same number of movable groups as the four groups. Such a zoom lens having a positive, negative, positive, and positive 5-group configuration has been developed.

JP 2008-146016 A JP 2011-28238 JP JP 2008-304708 A JP 2009-282429 A

  In the zoom lenses disclosed in Patent Documents 3 and 4, since the final lens group is fixed at the time of zooming, the influence of dust and scratches described above is suppressed, and the zoom ratio is 11 to 15 times. Compared with the zoom lenses disclosed in Patent Documents 1 and 2, a high zoom ratio is obtained. However, in recent years, there is a fact that further higher zooming is required while maintaining compactness.

  The present invention has been made in view of such a problem. For example, a zoom lens that achieves a high zoom ratio of 20 times or more, is compact, and has various aberrations corrected satisfactorily. And it aims at providing the imaging device using the same.

The zoom lens according to claim 1, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power; In a zoom lens that includes a fourth lens group having a negative refractive power and a fifth lens group having a positive refractive power, and performs zooming by changing the interval between the lens groups,
Each of the lens groups from the first lens group to the fourth lens group moves during zooming, and the fifth lens group is a lens group that does not move during zooming or focusing. The following conditional expressions are satisfied.
6.5 <| f1 / f2 | <15.0 (1)
However,
f1: Focal length of the first lens group f2: Focal length of the second lens group

  The basic configuration of the present invention for obtaining a zoom lens having both a small size and a high zoom ratio, in which aberrations are well corrected, is a first lens group having a positive refractive power and a negative refractive power in order from the object side. A second lens group having positive refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having positive refractive power. With this configuration, there are two negative lens groups, so the refractive power configuration in the entire lens system becomes symmetrical, and various aberrations corrected by symmetrical shapes such as distortion, coma, and lateral chromatic aberration are corrected. It becomes possible to correct effectively. Further, since the fourth lens group has a negative refractive power, compared to the conventional positive / negative positive / positive configuration, an effect of negative jumping (separating the light beam from the optical axis) by the fourth lens group is added. As a result, off-axis rays passing through the first to third lens groups on the object side pass more near the optical axis, thereby enabling downsizing.

  The fifth lens group is the lens group closest to the solid-state image sensor. If the fifth lens group is configured to move during zooming and focusing, the distance from the solid-state image sensor approaches and the captured image becomes the fifth lens group. There is a risk of being susceptible to the effects of garbage and scratches. In particular, in a miniaturized zoom lens, since the distance between the final lens and the solid-state image sensor is closer, the tendency is prominent. Therefore, in the present invention, the distance between the final lens and the solid-state imaging device is fixed by fixing the fifth lens group without moving in the optical axis direction, thereby suppressing the influence of dust and scratches. it can. In addition, since the solid-state imaging device can be sealed with the fifth lens group and the lens barrel, it is possible to prevent dust and other dust from being mixed and adhering to the solid-state imaging device.

Conditional expression (1) defines the ratio of the focal lengths of the first lens group and the second lens group. When the value of conditional expression (1) exceeds the lower limit value, the focal length of the first lens group is long and the focal length of the second lens group is short, so that the first lens group and the first lens at the wide-angle end are short. The combined focal length of the two lens groups is shortened, and as a result, the focal length of the entire system at the wide-angle end is shortened, so that a wide angle can be achieved. In addition, since the second lens group has an appropriate negative refractive power, the focal length variation when the second lens group moves during zooming becomes large, and high zooming is possible. On the other hand, when the value of the conditional expression (1) is less than the upper limit value, the curvature of field and the lateral chromatic aberration due to the first lens group at the telephoto end caused by the first lens group having excessive refractive power. The increase can be suppressed. It is more desirable to satisfy the following conditional expression.
6.5 <| f1 / f2 | <10.0 (1) ′

The zoom lens according to claim 2 is characterized in that, in the invention according to claim 1, the following conditional expression is satisfied.
3.0 <f5 / fW <6.5 (2)
However,
f5: focal length of the fifth lens group fW: focal length of the entire system at the wide angle end

Conditional expression (2) defines the ratio of the focal length of the entire system at the wide-angle end to the fifth lens group. Since the value of the conditional expression (2) is less than the upper limit value, the fifth lens group has an appropriate positive refractive power. Therefore, the off-axis springed up by the fourth lens group having a negative refractive power. Since the angle of the light beam can be relaxed, the chief ray incident angle (the angle formed between the chief ray and the optical axis) of the light beam that forms an image on the periphery of the imaging surface of the solid-state image sensor can be kept small, ensuring so-called telecentric characteristics. can do. Further, since the distance between the fourth lens group and the fifth lens group at the wide-angle end can be reduced, the overall length can be shortened. On the other hand, when the value of the conditional expression (2) exceeds the lower limit value, it is possible to prevent telephotoness due to an increase in the focal length at the wide-angle end, thereby enabling widening of the angle. It is more desirable to satisfy the following conditional expression.
3.5 <f5 / fW <6.5 (2) ′

A zoom lens according to a third aspect of the present invention is the zoom lens according to the first or second aspect, wherein the image blur on the image plane is corrected by moving the third lens group in a direction perpendicular to the optical axis. It is characterized by satisfying the following conditional expression.
2.5 <(1-m3T) · m45T <4.5 (3)
However,
m3T: lateral magnification at the telephoto end of the third lens group m45T: combined lateral magnification at the telephoto end of the fourth lens group and the fifth lens group

  Correction of image blur on the image plane is so-called camera shake correction. Conditional expression (3) represents the ratio of the amount of movement of the axial ray on the image plane when the third lens unit moves by a unit amount in the direction orthogonal to the optical axis. Therefore, when the value of conditional expression (3) is less than the upper limit value, it is possible to perform camera shake correction while suppressing the movement amount of the third lens group. On the other hand, when the value of conditional expression (3) exceeds the lower limit, it is possible to suppress the occurrence of aberration due to the increase in the refractive power of the third lens group.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the third lens group includes, in order from the object side, a positive P1 lens, a positive P2 lens, and a negative N1 lens. The P2 lens and the N1 lens are cemented, and satisfy the following conditional expression.
0.3 <nN1-nP2 <0.6 (4)
However,
nN1: Refractive index with respect to d-line of the N1 lens nP2: Refractive index with respect to d-line of the P2 lens

  The third lens group includes, in order from the object side, a positive P1 lens, a positive P2 lens, a negative N1 lens, and a positive P3 lens. Of these, the P2 lens and the N1 lens are cemented. . The third lens group has a large contribution to spherical aberration and coma aberration, and in order to correct these well, in the past, a positive / negative positive triplet configuration, a positive single lens and a pair of positive / negative cemented lenses, etc. Often, three lenses were used. However, in a zoom lens having a high zoom ratio, the three lenses do not have sufficient correction power for aberrations, and there is a risk that many off-axis aberrations such as coma will occur. Therefore, in the present invention, by adding another positive single lens to the image side of the positive single lens and one pair of positive and negative cemented lenses, generation of off-axis aberration is suppressed, and good optical performance is obtained. ing.

  Conditional expression (4) defines the difference in refractive index between the N1 lens and the P2 lens. When the value of conditional expression (4) exceeds the lower limit value, a combination of a negative lens having a high refractive index and a positive lens having a low refractive index becomes a combination, and spherical aberration and coma aberration that could not be corrected by the P1 lens are effectively reduced. It can be corrected. On the other hand, when the value of conditional expression (4) is lower than the upper limit value, the lens can be configured with an easily available glass material.

The zoom lens according to claim 5 is the invention according to any one of claims 1 to 4, wherein the first lens group includes a cemented lens including one negative lens and one positive lens. The following conditional expression is satisfied.
0.3 <n1N-n1P <0.6 (5)
However,
n1N: refractive index with respect to d-line of the negative lens in the cemented lens of the first lens group n1P: refractive index with respect to d-line of the positive lens in the cemented lens of the first lens group

  The first lens group includes a cemented lens including one negative lens and one positive lens in order from the object side. Conditional expression (5) defines the difference in refractive index between the negative lens and the positive lens of the cemented lens. When the cemented surface of the cemented lens is convex on the object side and the value of conditional expression (5) exceeds the lower limit value, the cemented surface becomes a divergent surface having negative refractive power, and the spherical aberration at the telephoto end is effective. Can be corrected automatically. On the other hand, when the value of conditional expression (5) is less than the upper limit value, the lens can be made of an easily available glass material.

  Further, by arranging a positive lens on the image side of the cemented lens, it is possible to share the refractive power due to the positive refractive surface of the cemented lens, so that excessive refractive power due to the positive refractive surface of the cemented lens can be reduced. Occurrence of coma aberration and the like due to this can be suppressed. Therefore, it is desirable to arrange a positive lens on the image side of the cemented lens.

  A zoom lens according to a sixth aspect of the present invention is the zoom lens according to any one of the first to fifth aspects, wherein the second lens group includes, in order from the object side, a negative lens having a concave surface facing the image side, and an image side. It is composed of a negative lens having a concave surface and a positive lens having a convex surface facing the object side.

  The second lens group includes, in order from the object side, a negative lens having a concave surface facing the image side, a negative lens having a concave surface facing the image side, and a positive lens having a convex surface facing the object side. By arranging two negative lenses with a concave surface facing the image side closer to the object side than the positive lens, light rays incident at a large angle from the first lens group having a large diameter are quickly relaxed, and field curvature and distortion are effective. Can be corrected automatically. Furthermore, by arranging the positive lens with the convex surface facing the object side closer to the image side than the two negative lenses, it is possible to effectively correct lateral chromatic aberration at the wide-angle end and axial chromatic aberration at the telephoto end. I can do it. In addition, since the air space between the negative lens and the positive lens in the second lens group is often extremely narrow and is susceptible to the optical performance due to lens manufacturing errors, it is desirable to join them.

A zoom lens according to a seventh aspect of the invention is characterized in that, in the invention according to any one of the first to sixth aspects, the following conditional expression is satisfied.
3.0 <(D1 + D2) / fW <6.0 (6)
However,
D1: Thickness on the optical axis of the first lens group D2: Thickness on the optical axis of the second lens group fW: Focal length of the entire system at the wide angle end

  Conditional expression (6) defines the ratio of the sum of the thicknesses on the optical axis of the first lens group and the second lens group and the focal length at the wide angle end. Zoom lenses that are required to be small and thin are generally retracted when the lens is not in use, and are made thinner than when photographing. The air space between the lens groups can be reduced by retracting, but the thickness of the lens group on the optical axis cannot be reduced by storage. Therefore, by setting the value of conditional expression (6) below the upper limit value, the thickness of the first lens group and the second lens group on the optical axis can be reduced, and it is possible to make the system compact when retracted. Become. On the other hand, by making the value of the conditional expression (6) exceed the lower limit value, it is possible to prevent the first lens group and the second lens group from being excessively thinned, and to provide an edge thickness (lens peripheral portion necessary for lens performance). (Thickness) can be secured.

  A zoom lens according to an eighth aspect of the present invention is the zoom lens according to any one of the first to seventh aspects, wherein the fifth lens group is a single lens.

  Since the fifth lens group is close to the image plane, the light beam passing through the fifth lens group becomes thin, and the generation amount of spherical aberration and coma aberration can be kept relatively small. Therefore, it is desirable that the fifth lens group is composed of a single lens in order to achieve cost reduction and downsizing of the optical system.

  The zoom lens according to a ninth aspect is the invention according to any one of the first to eighth aspects, wherein the fourth lens group is a single lens.

  Since the fourth lens group is close to the image plane next to the fifth lens group, the light beam passing through the fourth lens group becomes thin, and the generation amount of spherical aberration and coma aberration can be suppressed to be relatively small. Therefore, it is desirable to configure the fourth lens group with a single lens in order to achieve cost reduction and downsizing of the optical system.

  A zoom lens according to a tenth aspect is characterized in that, in the invention according to any one of the first to ninth aspects, the zoom lens performs focusing by moving the fourth lens group.

  By focusing with the fourth lens group, it is possible to form a clear image up to an object at a short distance without causing an increase in the total optical length or an increase in the front lens diameter due to the extension of the lens group.

  A zoom lens according to an eleventh aspect is characterized in that, in the invention according to any one of the first to tenth aspects, the lens has substantially no refractive power. That is, even when a dummy lens having substantially no power is added to the configuration of claim 1, it is within the scope of application of the present invention.

A zoom lens according to a twelfth aspect is characterized in that, in the invention according to any one of the first to eleventh aspects, a zoom ratio is 20 times or more.
An imaging apparatus according to a thirteenth aspect includes the zoom lens according to any one of the first to twelfth aspects, and an imaging element that photoelectrically converts an image formed on an imaging surface by the zoom lens. .

  According to the present invention, for example, it is possible to provide a zoom lens that achieves a high zoom ratio of, for example, a zoom ratio of 20 times or more, is compact, and has various aberrations corrected well, and an imaging device using the zoom lens. it can.

It is the perspective view (a) seen from the front upper side of the digital camera carrying the imaging device concerning this Embodiment, and the perspective view (b) seen from the back lower side. It is a block diagram of the imaging device which has the zoom lens concerning this Embodiment. 3 is a cross-sectional view of the zoom lens of Example 1. FIG. FIG. 6 is an aberration diagram (spherical aberration, astigmatism, distortion) of the zoom lens of Example 1; 6 is a cross-sectional view of a zoom lens according to Example 2. FIG. FIG. 6 is an aberration diagram (spherical aberration, astigmatism, distortion) of the zoom lens of Example 2. 6 is a cross-sectional view of a zoom lens of Example 3. FIG. FIG. 6 is an aberration diagram (spherical aberration, astigmatism, distortion) of the zoom lens of Example 3;

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view (a) viewed from the front upper side and a perspective view (b) viewed from the lower rear side of the digital camera which is an example of the imaging apparatus according to the present embodiment. FIG. 1 is a block diagram of an imaging apparatus having a zoom lens according to an embodiment.

  1A, a digital camera DC includes a retractable lens barrel 80 that includes a zoom lens 101 and retracts with respect to a camera body 81, a finder window 82, a release button 83, and a flash light emitting unit 84. , A strap attaching portion 87, a USB terminal 88, and a lens cover 89. When the lens cover 89 is opened, a switch (not shown) is turned on, and the lens barrel 80 is extended forward to enter a shooting state. On the other hand, when the lens cover 89 is closed after shooting is finished, the switch (not shown) is turned off. The lens barrel 80 is operated to retract. The configuration for retracting the lens barrel 80 is well known and will not be described in detail below.

  Further, in FIG. 1B, the digital camera DC includes a finder eyepiece 91 and red and green display lamps that display AF and AE information to the photographer by light emission or blinking when the release button 83 is pressed. 92, a zoom button 93 for zooming up and down according to the operation of the photographer, a menu / set button 95 for various settings, a four-way switch 96 as a selection button, an image, other character information, and the like. A monitor LCD 112 to be displayed, a playback button 97 for playing back an image shot on the monitor LCD 112, a display button 98 for selecting display and deletion of an image displayed on the monitor LCD 112 and other character information, and a shot and recorded image Erasing button 99, tripod hole 71, and battery / card cover 72 that can be freely opened and closed. The photographer can display various menus on the monitor LCD 112 with the menu / set button 95, select with the selection button 96, and confirm the setting with the menu / set button 95. Inside the battery / card cover 72, a battery for supplying power to the digital camera DC and a card-type removable memory for recording captured images are loaded.

  Further, as shown in FIG. 2, the imaging apparatus 100 mounted on the digital camera DC includes a zoom lens 101, a solid-state imaging device 102, an A / D conversion unit 103, a control unit 104, and an optical system driving unit 105. The timing generation unit 106, the image sensor driving unit 107, the image memory 108, the image processing unit 109, the image compression unit 110, the image recording unit 111, the monitor LCD 112, and the above-mentioned description with reference to FIG. And an operation unit 113 including a button group.

The zoom lens 101 has a function of forming a subject image on the imaging surface of the solid-state imaging device 102. As will be described in detail later, the zoom lens 101 according to the present embodiment has, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive refractive power. The zoom lens includes a third lens group, a fourth lens group having a negative refractive power, and a fifth lens group having a positive refractive power, and performs zooming by changing the interval between the lens groups. Each lens group from the first lens group to the fourth lens group moves during zooming, and the fifth lens group does not move during zooming or focusing. And satisfies the following conditional expression.
6.5 <| f1 / f2 | <15.0 (1)
However,
f1: Focal length of the first lens group f2: Focal length of the second lens group

  The solid-state image sensor 102 is an image sensor such as a CCD or CMOS, and includes an RGB color filter. The solid-state image sensor 102 photoelectrically converts incident light for each of R, G, and B and outputs an analog signal thereof. The A / D conversion unit 103 converts an analog signal into digital image data.

  The control unit 104 controls each unit of the imaging device 100. The control unit 104 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory), and various programs read out from the ROM and expanded in the RAM, and various in cooperation with the CPU. Execute the process.

  The optical system driving unit 105 controls the zoom lens 101 in zooming, focusing, exposure, and the like under the control of the control unit 104. The timing generator 106 outputs a timing signal for analog signal output. The image sensor driving unit 107 controls driving of the solid-state image sensor 102.

  The image memory 108 stores image data so as to be readable and writable. The image processing unit 109 performs various image processes on the image data. The image compression unit 110 compresses captured image data by a compression method such as JPEG (Joint Photographic Experts Group). The image recording unit 111 records image data on a recording medium such as a memory card set in a slot (not shown).

  The monitor LCD 112 is a color liquid crystal panel or the like, and displays image data after shooting, a through image before shooting, various operation screens, and the like. The operation unit 113 outputs information input by the user to the control unit 104 via the button group described above with reference to FIG.

  Here, the operation of the imaging apparatus 100 will be described. In subject photographing, subject monitoring (through image display) and image photographing execution are performed. In monitoring, an image of the subject obtained through the zoom lens 101 is formed on the light receiving surface (imaging surface) of the solid-state image sensor 102. An analog as a photoelectric conversion output corresponding to a light image that is driven by a timing generation unit 106 and an image sensor driving unit 107 and is imaged at regular intervals, and is driven by a solid-state image sensor 102 disposed behind the photographing optical axis of the zoom lens 101. Output the signal for one screen.

  The analog signal is appropriately gain-adjusted for each primary color component of RGB, and then converted into digital data by the A / D conversion unit 103. The digital data is subjected to color process processing including pixel interpolation processing and γ correction processing by the image processing unit 109 to generate a luminance signal Y and color difference signals Cb, Cr (image data) as digital values, and the image memory. 108, the signal is periodically read out, the video signal is generated, and output to the monitor LCD 112. Note that the control unit 104, which is also a white balance adjustment unit, adjusts the white balance of the captured image.

  The monitor LCD 112 functions as an electronic viewfinder in monitoring, and displays captured images almost in real time. In this state, zooming, focusing, exposure, and the like of the zoom lens 101 are set by driving the optical system driving unit 105 based on input from the photographer via the operation unit 113 as needed.

  In such a monitoring state, when the user operates the release button 83 at a timing at which still image shooting is desired, still image data is shot. In response to the operation of the release button 83, one frame of image data stored in the image memory 108 is read out and compressed by the image compression unit 110. The compressed image data is recorded in the removable memory by the image recording unit 111.

  In addition, when a switch (not shown) is turned off by closing the lens cover 89, the lens barrel 80 including the zoom lens 101 is driven so that the distance between the lens groups becomes narrow, and a retracting operation is performed. . At this time, if the third lens group and the fourth lens group having a smaller diameter than the first and second lens groups are configured to be retracted from the optical path, the total length after the collapsing becomes shorter.

  Note that the description in the above embodiment and each example is an example of a preferable zoom lens and imaging apparatus according to the present invention, and the present invention is not limited to this. The imaging apparatus can also be installed in a video camera.

(Example)
Next, examples suitable for the above-described embodiment will be described. However, the present invention is not limited to the following examples.
f: Focal length of the entire zoom lens system Fno: F number 2Y: Diagonal length of the imaging surface of the solid-state imaging device R: Radius of curvature D: Spacing on the axial surface Nd: Refractive index of lens material with respect to d-line νd: Abbe number of lens material

  In each embodiment, the surface described with “*” after each surface number is a surface having an aspheric shape, and the shape of the aspheric surface has the vertex of the surface as the origin and the X axis in the optical axis direction. The height in the direction perpendicular to the optical axis is h and is expressed by the following “Equation 2”.

However,
Ai: i-order aspheric coefficient R: radius of curvature K: conic constant

Example 1
Table 1 shows lens data of Example 1. In the following (including the lens data in the table), a power of 10 (for example, 2.5 × 10 ⁻⁰² ) is expressed using E (for example, 2.5E-02). 3A and 3B are cross-sectional views of the zoom lens of Example 1. FIG. 3A shows a wide-angle end state, FIG. 3B shows an intermediate state, and FIG. 3C shows a telephoto end state. In the drawing, Gr1 is a first lens group having a positive refractive power, and includes a first lens L1, a second lens L2, and a third lens L3. The first lens L1 that is one negative lens and the second lens L2 that is one positive lens are cemented, and the cemented surface is convex on the object side. Gr2 is a second lens group having a negative refractive power, a fourth lens L4 that is a negative lens having a concave surface facing the image side, and a fifth lens L5 that is a negative lens having a concave surface facing the image side. The sixth lens L6 is a positive lens having a convex surface directed toward the object side. The fifth lens L5 and the sixth lens L6 are cemented, and the cemented surface is convex on the object side. Gr3 is a third lens group having positive refractive power, and includes a seventh lens L7 (positive P1 lens), an eighth lens L8 (positive P2 lens), and a ninth lens L9 (negative N1 lens). It consists of a tenth lens L10 (positive P3 lens). The eighth lens L8 and the ninth lens L9 are cemented, and the cemented surface is convex on the image side. Gr4 is a fourth lens group having negative refractive power, and is composed of only the eleventh lens L11. Further, Gr5 is a fifth lens group having a positive refractive power, and includes only the twelfth lens L12. S denotes an aperture stop provided on the object side of the seventh lens L7, and I denotes an imaging surface. F1 and F2 are parallel flat plates assuming an optical low-pass filter, an IR cut filter, a seal glass of a solid-state image sensor, and the like.

[Table 1]
Example 1
f = 4.12-21.15-109.59
Fno = 3.13-4.92-6.08
Zoom ratio = 26.60

Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 52.962 1.500 1.90370 31.3 15.76
2 33.783 4.660 1.48750 70.4 15.02
3 277.200 0.200 14.75
4 38.131 3.650 1.48750 70.4 14.15
5 405.000 d1 13.95
6 2670.000 0.800 1.91080 35.3 8.31
7 8.945 5.010 6.42
8 -18.905 0.710 1.48750 70.4 6.17
9 12.787 2.310 1.92290 20.9 6.14
10 54.300 d2 6.00
11 (Aperture) ∞ 0.620 3.24
12 * 17.308 2.620 1.69350 53.2 3.42
13 * -24.699 0.380 3.50
14 11.681 3.010 1.48750 70.4 3.45
15 -27.710 2.500 1.90370 31.3 3.16
16 10.822 0.740 2.94
17 24.500 1.650 1.49700 81.6 3.01
18 -13.511 d3 3.05
19 * 5576.445 1.100 1.54470 56.2 2.95
20 * 9.522 d4 2.90
21 * 61.735 3.500 1.54470 56.2 4.70
22 * -10.581 1.057 4.69
23 ∞ 0.300 1.52310 54.5 4.50
24 ∞ 3.830 4.47
25 ∞ 0.500 1.51680 64.2 4.06
26 ∞ 0.370 4.03

Aspheric coefficient

Surface 12 Surface 20
K = 0.00000E + 00 K = 0.00000E + 00
A4 = -0.56600E-04 A4 = -0.23368E-03
A6 = -0.31016E-04 A6 = 0.22004E-03
A8 = 0.49703E-05 A8 = -0.30770E-04
A10 = -0.38910E-06 A10 = 0.16520E-05
A12 = 0.11034E-07

Side 13 Side 21
K = 0.00000E + 00 K = 0.00000E + 00
A4 = 0.22903E-04 A4 = 0.30477E-03
A6 = -0.33741E-04 A6 = 0.10647E-04
A8 = 0.53349E-05 A8 = -0.11281E-06
A10 = -0.41097E-06 A10 = 0.10753E-08
A12 = 0.11520E-07

19th page 22nd page
K = 0.00000E + 00 K = 0.00000E + 00
A4 = -0.39392E-03 A4 = 0.55143E-03
A6 = 0.15875E-03 A6 = -0.36835E-06
A8 = -0.21849E-04 A8 = 0.29881E-06
A10 = 0.11547E-05 A10 = -0.35562E-08

Focal length of each position, F number, angle of view (°), diagonal length of imaging surface, distance between groups

f Fno angle of view 2Y d1 d2 d3 d4
4.12 3.13 86.6 6.453 0.788 38.373 2.103 2.935
21.15 4.92 20.8 7.98 24.438 12.528 6.708 8.963
109.59 6.08 4.1 7.957 45.936 1.107 11.046 10.584

Lens group data

Lens group Start surface Focal length (mm)
1 1 69.03
2 6 -8.68
3 11 13.43
4 19 -17.51
5 21 16.87

  FIG. 4 is an aberration diagram of Example 1 (spherical aberration, astigmatism, distortion). Here, FIG. 4A is an aberration diagram at the wide-angle end. FIG. 4B is an aberration diagram in the middle. FIG. 4C is an aberration diagram at the telephoto end. Here, in the spherical aberration diagram, the dotted line represents the amount of spherical aberration with respect to the g line, and the solid line represents the amount of spherical aberration with respect to the d line. In the astigmatism diagram, the solid line S represents the sagittal plane, and the dotted line M represents the meridional plane (the same applies hereinafter).

  In the zoom lens of Example 1, the first lens group Gr1, the second lens group Gr2, the third lens group Gr3, and the fourth lens group Gr4 move along the optical axis direction during zooming from the wide-angle end to the telephoto end. However, zooming can be performed by changing the interval between the lens groups. The fifth lens group Gr5 is fixed during zooming. Further, by moving only the fourth lens group Gr4 in the optical axis direction, focusing from infinity to a finite distance can be performed. It is assumed that the seventh lens L7 is a glass mold lens, the eleventh lens L11 and the twelfth lens L12 are plastic lenses, and the other lenses are polished lenses made of a glass material. The eleventh lens L11 and the twelfth lens L12 are lenses arranged relatively on the image side, and since the light flux passing through the lens is also thin, the influence on the optical performance due to temperature change is small, so a plastic lens is used. By doing so, the cost can be reduced. Moreover, since the plastic lens by injection molding can easily manufacture an aspherical lens, each aspherical lens can effectively correct each aberration such as field curvature and distortion.

(Example 2)
Table 2 shows lens data of Example 2. 5A and 5B are cross-sectional views of the zoom lens of Example 2, where FIG. 5A illustrates a wide-angle end state, FIG. 5B illustrates an intermediate state, and FIG. 5C illustrates a telephoto end state. In the drawing, Gr1 is a first lens group having a positive refractive power, and includes a first lens L1, a second lens L2, and a third lens L3. The first lens L1 that is one negative lens and the second lens L2 that is one positive lens are cemented, and the cemented surface is convex on the object side. Gr2 is a second lens group having a negative refractive power, a fourth lens L4 that is a negative lens having a concave surface facing the image side, and a fifth lens L5 that is a negative lens having a concave surface facing the image side. The sixth lens L6 is a positive lens having a convex surface directed toward the object side. The fifth lens L5 and the sixth lens L6 are cemented, and the cemented surface is convex on the object side. Gr3 is a third lens group having positive refractive power, and includes a seventh lens L7 (positive P1 lens), an eighth lens L8 (positive P2 lens), and a ninth lens L9 (negative N1 lens). It consists of a tenth lens L10 (positive P3 lens). The eighth lens L8 and the ninth lens L9 are cemented, and the cemented surface is convex on the image side. Gr4 is a fourth lens group having negative refractive power, and is composed of only the eleventh lens L11. Further, Gr5 is a fifth lens group having a positive refractive power, and includes only the twelfth lens L12. S denotes an aperture stop provided between the seventh lens L7 and the eighth lens L8, and I denotes an imaging surface. F1 and F2 are parallel flat plates assuming an optical low-pass filter, an IR cut filter, a seal glass of a solid-state image sensor, and the like.

[Table 2]
Example 2
f = 4.42-20.02-91.49
Fno = 2.98-4.70-5.90
Zoom ratio = 20.68

Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 66.346 1.500 1.84670 23.8 17.03
2 36.513 5.475 1.48750 70.4 15.52
3 -1712.538 0.200 14.42
4 31.663 3.286 1.72920 54.7 14.10
5 88.075 d1 13.83
6 109.014 0.800 1.83480 42.7 8.76
7 8.130 4.997 6.42
8 -15.470 0.710 1.51740 52.2 6.27
9 14.184 2.279 1.92290 20.9 6.22
10 81.744 d2 6.10
11 14.851 1.913 1.53170 48.8 3.71
12 -32.613 0.792 3.55
13 (Aperture) ∞ -0.150 3.29
14 10.354 2.510 1.48750 70.4 3.28
15 -14.193 2.000 1.83400 37.4 3.10
16 15.229 0.615 2.97
17 * 25.131 2.500 1.58310 59.5 3.01
18 -14.290 d3 3.05
19 * 25.569 1.009 1.60700 27.0 2.89
20 * 7.318 d4 2.81
21 * -818.962 3.000 1.53050 55.7 4.42
22 * -11.123 1.409 4.48
23 ∞ 0.500 1.52310 54.5 4.27
24 ∞ 3.630 4.24
25 ∞ 0.500 1.51680 64.2 3.90
26 ∞ 0.380 3.87

Aspheric coefficient

17th 21st
K = 0.00000E + 00 K = 0.00000E + 00
A4 = -0.13295E-03 A4 = 0.25995E-03
A6 = -0.27921E-05 A6 = 0.22159E-04
A8 = 0.51186E-06 A8 = -0.44387E-06
A10 = -0.25239E-07 A10 = 0.24853E-08

19th page 22nd page
K = 0.00000E + 00 K = 0.00000E + 00
A4 = -0.52548E-03 A4 = 0.11650E-03
A6 = 0.63402E-04 A6 = 0.15982E-04
A8 = -0.13611E-04 A8 = 0.43958E-07
A10 = 0.82709E-06 A10 = -0.54674E-08

20th page
K = 0.00000E + 00
A4 = -0.19220E-03
A6 = 0.70141E-04
A8 = -0.15100E-04
A10 = 0.93019E-06

Focal length of each position, F number, angle of view (°), diagonal length of imaging surface, distance between groups

f Fno angle of view 2Y d1 d2 d3 d4
4.42 2.98 82.9 6.7 0.991 37.000 2.925 3.027
20.02 4.70 22.1 7.666 17.370 12.838 5.823 10.027
91.49 5.90 4.9 7.663 33.305 0.870 9.725 11.855

Lens group data

Lens group Start surface Focal length (mm)
1 1 55.14
2 6 -8.43
3 11 12.91
4 19 -17.25
5 21 21.23

  FIG. 6 is an aberration diagram of Example 2 (spherical aberration, astigmatism, distortion). Here, FIG. 6A is an aberration diagram at the wide-angle end. FIG. 6B is an aberration diagram in the middle. FIG. 6C is an aberration diagram at the telephoto end.

  In the zoom lens of Example 2, the first lens group Gr1, the second lens group Gr2, the third lens group Gr3, and the fourth lens group Gr4 move along the optical axis direction during zooming from the wide-angle end to the telephoto end. However, zooming can be performed by changing the interval between the lens groups. The fifth lens group Gr5 is fixed during zooming. Further, by moving only the fourth lens group Gr4 in the optical axis direction, focusing from infinity to a finite distance can be performed. It is assumed that the tenth lens L10 is a glass mold lens, the eleventh lens L11 and the twelfth lens L12 are plastic lenses, and the other lenses are polished lenses made of a glass material.

(Example 3)
Table 3 shows lens data of Example 3. 7A and 7B are cross-sectional views of the zoom lens of Example 3. FIG. 7A shows a wide-angle end state, FIG. 7B shows an intermediate state, and FIG. 7C shows a telephoto end state. In the drawing, Gr1 is a first lens group having a positive refractive power, and includes a first lens L1, a second lens L2, and a third lens L3. The first lens L1 that is one negative lens and the second lens L2 that is one positive lens are cemented, and the cemented surface is convex on the object side. Gr2 is a second lens group having a negative refractive power, a fourth lens L4 that is a negative lens having a concave surface facing the image side, and a fifth lens L5 that is a negative lens having a concave surface facing the image side. The sixth lens L6 is a positive lens having a convex surface directed toward the object side. The fifth lens L5 and the sixth lens L6 are cemented, and the cemented surface is convex on the object side. Gr3 is a third lens group having positive refractive power, and includes a seventh lens L7 (positive P1 lens), an eighth lens L8 (positive P2 lens), and a ninth lens L9 (negative N1 lens). It consists of a tenth lens L10 (positive P3 lens). The eighth lens L8 and the ninth lens L9 are cemented, and the cemented surface is convex on the image side. Gr4 is a fourth lens group having negative refractive power, and is composed of only the eleventh lens L11. Further, Gr5 is a fifth lens group having a positive refractive power, and includes only the twelfth lens L12. S denotes an aperture stop provided on the object side of the seventh lens L7, and I denotes an imaging surface. F1 and F2 are parallel flat plates assuming an optical low-pass filter, an IR cut filter, a seal glass of a solid-state image sensor, and the like.

[Table 3]
Example 3
f = 4.16-26.19-166.30
Fno = 2.86-5.33-6.50
Zoom ratio = 40.00

Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 75.269 1.556 1.91080 35.3 17.82
2 39.509 5.384 1.49700 81.6 16.21
3 -252.462 0.689 15.37
4 34.030 3.592 1.49700 81.6 14.00
5 163.590 d1 13.79
6 90.402 0.800 1.88300 40.8 7.79
7 8.456 5.240 5.89
8 -10.504 0.700 1.77250 49.6 5.23
9 42.609 1.562 1.94590 18.0 5.35
10 -33.322 d2 5.00
11 (Aperture) ∞ 0.280 3.62
12 * 8.860 2.100 1.59200 67.0 3.96
13 * -32.501 0.300 3.93
14 10.890 1.901 1.56880 56.0 3.83
15 -26.210 1.445 1.88300 40.8 3.65
16 7.245 0.729 3.32
17 10.287 2.074 1.54070 47.2 3.44
18 -25.035 d3 3.50
19 * -13.619 1.087 2.00180 19.3 3.06
20 * -49.482 d4 3.02
21 * 100.000 3.500 1.54470 56.2 4.80
22 * -15.787 4.225 4.70
23 ∞ 0.500 1.52310 54.5 4.19
24 ∞ 2.000 4.16

Aspheric coefficient

Surface 12 Surface 20
K = 0.00000E + 00 K = 0.00000E + 00
A4 = -0.39993E-04 A4 = 0.24984E-02
A6 = -0.23314E-04 A6 = 0.18627E-04
A8 = 0.34989E-05 A8 = -0.50743E-05
A10 = -0.21587E-06 A10 = 0.11704E-06
A12 = 0.51476E-08

Side 13 Side 21
K = 0.00000E + 00 K = 0.00000E + 00
A4 = 0.14737E-03 A4 = 0.73781E-04
A6 = -0.22655E-04 A6 = 0.32694E-04
A8 = 0.37143E-05 A8 = -0.77209E-06
A10 = -0.23856E-06 A10 = 0.77872E-08
A12 = 0.59113E-08

19th page 22nd page
K = 0.00000E + 00 K = 0.00000E + 00
A4 = 0.24426E-02 A4 = -0.13247E-03
A6 = -0.16710E-04 A6 = 0.27583E-04
A8 = -0.46194E-05 A8 = -0.18995E-06
A10 = 0.16976E-06 A10 = -0.24753E-08

Focal length of each position, F number, angle of view (°), diagonal length of imaging surface, distance between groups

f Fno angle of view 2Y d1 d2 d3 d4
4.16 2.86 88.2 6.577 0.598 29.142 2.102 2.803
26.19 5.33 17.5 7.834 27.181 11.052 4.938 15.365
166.30 6.50 2.8 7.919 47.243 0.920 10.593 14.784

Lens group data

Lens group Start surface Focal length (mm)
1 1 66.01
2 6 -6.74
3 11 11.62
4 19 -19.05
5 21 25.30

  FIG. 8 is an aberration diagram of Example 3 (spherical aberration, astigmatism, distortion). Here, FIG. 8A is an aberration diagram at the wide-angle end. FIG. 8B is an aberration diagram in the middle. FIG. 8C is an aberration diagram at the telephoto end.

  In the zoom lens of Example 3, the first lens group Gr1, the second lens group Gr2, the third lens group Gr3, and the fourth lens group Gr4 move along the optical axis direction during zooming from the wide-angle end to the telephoto end. However, zooming can be performed by changing the interval between the lens groups. The fifth lens group Gr5 is fixed during zooming. Further, by moving only the fourth lens group Gr4 in the optical axis direction, focusing from infinity to a finite distance can be performed. It is assumed that the seventh lens L7 and the eleventh lens L11 are glass mold lenses, the twelfth lens L12 is a plastic lens, and the other lenses are polished lenses made of a glass material.

  Table 4 shows values of the respective examples corresponding to the respective conditional expressions.

Recently, it has been found that by mixing inorganic fine particles in a plastic material, the temperature change of the plastic material can be reduced. More specifically, mixing fine particles with a transparent plastic material generally causes light scattering and lowers the transmittance, so it was difficult to use as an optical material. By making it smaller than the wavelength, it is possible to substantially prevent scattering. The refractive index of the plastic material decreases with increasing temperature, but the refractive index of inorganic particles increases with increasing temperature. Therefore, it is possible to make almost no change in the refractive index by using these temperature dependencies so as to cancel each other. Specifically, by dispersing inorganic particles having a maximum length of 20 nanometers or less in a plastic material as a base material, a plastic material with extremely low temperature dependence of the refractive index is obtained. For example, by dispersing fine particles of niobium oxide (Nb ₂ O ₅ ) in acrylic, the refractive index change due to temperature change can be reduced. In the present invention, by using a plastic material in which such inorganic particles are dispersed for the eleventh lens and the twelfth lens, it is possible to further suppress the image point position fluctuation at the time of temperature change of the entire zoom lens system. Become.

  In recent years, as a method for mounting a large number of image pickup devices at low cost, a reflow process (heating process) is performed on a substrate on which solder is previously potted while an IC chip or other electronic component and an optical element are placed on the substrate. A technique has been proposed in which an electronic component and an optical element are simultaneously mounted on a substrate by melting solder.

  In order to perform mounting using such a reflow process, it is necessary to heat the optical element to about 200 to 260 degrees together with the electronic components. However, in such a high temperature, a lens using a thermoplastic resin is thermally deformed. However, there is a problem that the optical performance deteriorates due to discoloration. As one of the methods for solving such a problem, a technology has been proposed that uses a glass mold lens having excellent heat resistance and achieves both miniaturization and optical performance in a high temperature environment. Since the cost is higher than the lens used, there is a problem that it is difficult to meet the demand for cost reduction of the imaging device.

  Therefore, by using an energy curable resin as the material of the zoom lens, the optical performance degradation when exposed to high temperatures is small compared to a lens using a thermoplastic resin such as polycarbonate or polyolefin, It is effective for the reflow process, is easier to manufacture than a glass mold lens, is inexpensive, and can achieve both low cost and mass productivity of an imaging apparatus incorporating a zoom lens. The energy curable resin refers to both a thermosetting resin and an ultraviolet curable resin. You may form the plastic lens of this invention using the above-mentioned energy curable resin.

  The present invention is not limited to the embodiments described in the specification, and other embodiments and modifications are apparent to those skilled in the art from the embodiments and ideas described in the present specification. It is. For example, even when a dummy lens having substantially no power is further provided, it is within the scope of the present invention.

71 Tripod hole 72 Card cover 80 Lens barrel 81 Camera body 82 Viewfinder window 83 Release button 84 Flash light emitting part 87 Strap attaching part 88 USB terminal 89 Lens cover 91 Viewfinder eyepiece 92 Display lamp 93 Zoom button 95 Set button 96 Four directions Switch 96 Selection button 97 Playback button 98 Display button 99 Erase button 100 Imaging device 101 Zoom lens 102 Solid-state imaging device 103 Conversion unit 104 Control unit 105 Optical system driving unit 106 Timing generation unit 107 Imaging device driving unit 108 Image memory 109 Image processing unit 110 Image compression unit 111 Image recording unit 112 Monitor LCD
113 Operation unit DC Digital camera Gr1 to Gr5 Lens group L1 to L12 Lens S Aperture stop I Imaging surfaces F1 and F2 Parallel plates

Claims (13)

In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens having a negative refractive power In a zoom lens that includes a group and a fifth lens group having a positive refractive power, and performs zooming by changing the interval between the lens groups,
Each of the lens groups from the first lens group to the fourth lens group moves during zooming, and the fifth lens group is a lens group that does not move during zooming or focusing. A zoom lens satisfying the following conditional expression:
6.5 <| f1 / f2 | <15.0 (1)
However,
f1: Focal length of the first lens group f2: Focal length of the second lens group The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
3.0 <f5 / fW <6.5 (2)
However,
f5: focal length of the fifth lens group fW: focal length of the entire system at the wide angle end The image blur on the image plane is corrected by moving the third lens group in a direction orthogonal to the optical axis, and the following conditional expression is satisfied: The zoom lens according to 1 or 2.
2.5 <(1-m3T) · m45T <4.5 (3)
However,
m3T: lateral magnification at the telephoto end of the third lens group m45T: combined lateral magnification at the telephoto end of the fourth lens group and the fifth lens group The third lens group includes, in order from the object side, a positive P1 lens, a positive P2 lens, a negative N1 lens, and a positive P3 lens. Among these, the P2 lens and the N1 lens are cemented, The zoom lens according to any one of claims 1 to 3, wherein the following conditional expression is satisfied.
0.3 <nN1-nP2 <0.6 (4)
However,
nN1: Refractive index with respect to d-line of the N1 lens nP2: Refractive index with respect to d-line of the P2 lens 5. The first lens group includes a cemented lens including one negative lens and one positive lens, and satisfies the following conditional expression: 5. Zoom lens.
0.3 <n1N-n1P <0.6 (5)
However,
n1N: refractive index with respect to d-line of the negative lens in the cemented lens of the first lens group n1P: refractive index with respect to d-line of the positive lens in the cemented lens of the first lens group   The second lens group includes, in order from the object side, a negative lens having a concave surface facing the image side, a negative lens having a concave surface facing the image side, and a positive lens having a convex surface facing the object side. The zoom lens according to any one of claims 1 to 5, characterized in that: The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
3.0 <(D1 + D2) / fW <6.0 (6)
However,
D1: Thickness on the optical axis of the first lens group D2: Thickness on the optical axis of the second lens group fW: Focal length of the entire system at the wide angle end   The zoom lens according to claim 1, wherein the fifth lens group is a single lens.   The zoom lens according to claim 1, wherein the fourth lens group is a single lens.   The zoom lens according to claim 1, wherein the zoom lens performs focusing by moving the fourth lens group.   The zoom lens according to claim 1, further comprising a lens having substantially no refractive power.   The zoom lens according to claim 1, wherein the zoom lens has a zoom ratio of 20 times or more.   An image pickup apparatus comprising: the zoom lens according to claim 1; and an image pickup device that photoelectrically converts an image formed on an image pickup surface by the zoom lens.