JP4496743B2 - Zoom lens and imaging device - Google Patents

Description

  The present invention relates to a zoom lens and an image pickup apparatus using the zoom lens as an image pickup lens, and in particular, realizes a magnification of about 4 to 6 times suitable for a small image pickup apparatus such as a digital still camera or a home video camera. The present invention relates to a possible rear focus zoom lens and an image pickup apparatus using the zoom lens.

  In recent years, digital still cameras and digital video cameras have been widely used for home use, but for these small-sized imaging devices, further miniaturization that places importance on portability is required. For this reason, miniaturization by shortening the overall length and depth is also demanded for photographing lenses mounted on them, particularly zoom lenses. Further, for such a photographing lens, particularly for a digital still camera, there is a demand for an improvement in lens performance as well as a reduction in size in response to an increase in the number of pixels of an image sensor.

  For example, a so-called rear focus type zoom lens that performs focusing by moving a lens group other than the first lens group arranged closest to the object side relatively easily reduces the size of the entire lens system and reduces the number of pixels. It is known that imaging performance suitable for many solid-state imaging devices can be obtained. Also, recently, the optical path from the first lens group to the image plane is bent halfway to shorten the front-rear length when it is incorporated in an imaging device, and the movable direction of the lens during zooming is set to the vertical direction. It has been considered to eliminate the protrusions of the lens during shooting.

Conventionally, as such a zoom lens, the first lens group is composed of a negative lens group and a positive lens group in order from the object side, and among these, the positive lens group includes at least a negative lens, a positive lens, and a positive lens in order from the object side. The distance between the most object side surface of the first lens group and the most image side surface is D1, and the distance between the negative lens group and the positive lens group of the first lens group is D1A. Then, there was a zoom lens configured to satisfy the following expression (1) (for example, see Patent Document 1).
1.2 <D1 / D1A <1.7 (1)
In this zoom lens, by disposing the negative lens group on the object side of the first lens group, it is possible to widen the angle while keeping the entire lens diameter small, and as a result, between the negative lens group and the positive lens group. It is possible to secure a space for bending the optical axis by arranging a prism or the like.

As a similar zoom lens, 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 positive refractive power The fourth lens group has a four-group lens structure in which zooming is performed by moving the second and fourth lens groups, and the first lens group has a negative refractive power in order from the object side. There has been a zoom lens having a first lens of a lens, a prism that bends an optical path, and a second lens that is a single lens having a positive refractive power (see, for example, Patent Document 2).
Japanese Patent Laid-Open No. 9-138347 (paragraph numbers [0013] to [0021], FIG. 1) Japanese Unexamined Patent Publication No. 2000-131610 (paragraph numbers [0010] to [0027], FIG. 1)

  However, the zoom lenses disclosed in the above patent documents have a problem that the number of lenses is large, and for these, further reduction in the overall length of the lens system and reduction in manufacturing costs are required. It was.

  In particular, when attempting to achieve higher magnification and smaller size for such a zoom lens, the variation in aberrations at the time of focusing increases, and the entire object distance system from an infinite object to a near object is wide. There is a problem that it is difficult to maintain both high optical performance and downsizing the entire lens system.

  The present invention has been made in view of such points, and a zoom lens having a rear focus type zooming ratio of about 4 to 6 times capable of downsizing the entire lens system without impairing optical performance. The purpose is to provide.

  Another object of the present invention is to provide an imaging apparatus using a rear focus type zoom lens having a zoom ratio of about 4 to 6 times, which can downsize the entire lens system without impairing optical performance. It is to be.

In the present invention, in order to solve the above-described problem, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a positive refractive power and an optical aperture are arranged in order from the object side. the third lens group has, fourth lens group having positive refractive power, and a fifth lens group having negative refractive power, upon zooming from the wide-angle end to the telephoto end, the image the second lens group from the object side The fourth lens group moves so as to correct the movement of the image plane during zooming, and the first lens group, the third lens group, and the fifth lens group do not move. In the zoom lens configured as described above, the first lens group includes, in order from the object side, one front lens having a negative refractive power, an optical member that bends the optical path, and a rear lens group having a positive refractive power. , Subject distance The imaging magnification of the second lens group at infinity when the? 2t,
| Β2t | <0.95
And the focal length of the entire lens at the wide angle end is fw, and the focal lengths of the second lens group, the third lens group, the fourth lens group, and the fifth lens group are f2, f3, f4, and When f5
0.8 <| f2 / fw | <1.5
1.5 <| f5 / f3 | <2.8
0.5 <f3 / f4 <1.2
A zoom lens that satisfies the following conditions is provided.

In such a zoom lens, in order from the object side, first to fifth lens groups having positive, negative, positive, positive and negative refractive powers are provided, respectively, and the third lens group includes an optical aperture. Is arranged, and during zooming from the wide-angle end to the telephoto end, the second lens group moves from the object side to the image plane side, and the fourth lens group moves to correct the movement of the image plane accompanying zooming, Further, the first lens group, the third lens group, and the fifth lens group are configured not to move. When the first lens group includes, in order from the object side, one front lens having a negative refractive power, an optical member that bends the optical path, and a rear lens group having a positive refractive power, zooming is performed. The moving direction of the second lens group and the fourth lens group is the optical axis direction of the rear lens group of the first lens group. Further, with respect to the imaging magnification β2t of the second lens group at an object distance of infinity, the condition | β2t | <0.95 is satisfied, and the focal length of the entire lens at the wide angle end is fw, and the second lens When the focal lengths of the lens group, the third lens group, the fourth lens group, and the fifth lens group are f2, f3, f4, and f5, respectively, 0.8 <| f2 / fw | <1.5, 1.5 <| F5 / f3 | <2.8 and 0.5 <f3 / f4 <1.2 are satisfied to satisfy each condition, so that the zoom ratio is increased and the optical system is excellent even when the lens system is downsized. The performance can be maintained.

In the zoom lens of the present invention, the first lens group includes, in order from the object side, one front lens having negative refractive power, an optical member that bends the optical path, and a rear lens group having positive refractive power. Thus, the moving direction of the second lens group and the fourth lens group during zooming is the optical axis direction of the rear lens group of the first lens group, so that the lens system is thinned. In addition to this, for the imaging magnification β2t of the second lens group at an object distance of infinity, the condition | β2t | <0.95 is satisfied, and the focal length of the entire lens at the wide angle end is fw, When the focal lengths of the second lens group, the third lens group, the fourth lens group, and the fifth lens group are f2, f3, f4, and f5, respectively, 0.8 <| f2 / fw | <1.5, By satisfying the conditions of 1.5 <| f5 / f3 | <2.8 and 0.5 <f3 / f4 <1.2, a change of about 4 to 6 times is maintained while maintaining good optical performance. The magnification can be obtained and the lens system can be miniaturized.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a sectional view showing the structure of a zoom lens according to the first embodiment of the present invention.
In the zoom lens shown in FIG. 1, in order from the object side to the image plane IMG side, a first lens group GR1 having a positive refractive power, a second lens group GR2 having a negative refractive power, and a third lens having a positive refractive power. A lens group GR3, a fourth lens group GR4 having a positive refractive power, and a fifth lens group GR5 having a negative refractive power are arranged. An iris IR for adjusting the amount of light is disposed on the image plane IMG side of the third lens group GR3. Further, a filter FL made of a low-pass filter such as an infrared cut filter and a cover glass CG of the image sensor are arranged further on the image plane IMG side of the fifth lens group GR5. The image plane IMG is a light receiving surface of an image sensor such as a CCD (Charge Coupled Devices).

  In this zoom lens, during zooming from the wide-angle end to the telephoto end, the second lens group GR2 moves from the object side to the image plane IMG side, and the fourth lens group GR4 corrects the movement of the image plane accompanying zooming. It is the composition which moves as follows. In zooming, the first lens group GR1, the third lens group GR3, and the fifth lens group GR5 do not move.

  Further, the first lens group GR1 includes, in order from the object side, a lens L1 having a negative refractive power, a prism P1 for bending the optical path, and lenses L2 and L3 disposed on the rear side. The lenses L2 and L3 have a positive refractive power as a whole. With such a configuration, the moving direction of the lens that moves during zooming or focusing is different from the optical axis direction of the lens L1 closest to the object side, and is the optical axis direction of the lenses L2 and L3. In this embodiment, the lens L2 is constituted by a convex meniscus lens having a convex surface facing the image plane IMG, and the lens L3 is constituted by a convex lens having a convex surface facing the object side.

  The second lens group GR2 includes three lenses L4, L5, and L6 in order from the object side, and a lens surface between the lens L5 and the lens L6 is cemented. The third lens group GR3 is composed of a single lens L7. The fourth lens group GR4 is composed of two lenses L8 and L9, and the lens surface between the lens L8 and the lens L9 is cemented. The fifth lens group GR5 includes two lenses L10 and L11, and a lens surface between the lens L10 and the lens L11 is cemented.

Here, items common to the following embodiments will be described with reference to FIG.
As shown in FIG. 1, the zoom lens according to the present invention has a five-group configuration including a first lens group GR1 to a fifth lens group GR5 each having positive, negative, positive, positive, and negative refractive powers in order from the object side. The third lens group GR3 includes an iris IR, and at the time of zooming from the wide-angle end to the telephoto end, at least the second lens group GR2 moves from the object side to the image plane IMG side, and the fourth lens group GR4 performs zooming. It moves so as to correct the accompanying movement of the image plane, and at this time, the first lens group GR1, the third lens group GR3, and the fifth lens group GR5 are configured not to move. The first lens group GR1 includes, in order from the object side, a front lens group having a negative refractive power, an optical member that bends the optical path, and a rear lens group having a positive refractive power. By adopting such a configuration for the first lens group GR1, the moving direction of the lens that moves during zooming and focusing is the optical axis direction of the rear lens group, so that the depth of the lens system is reduced and the depth is reduced. Can be kept constant regardless of zooming, focusing, or power on / off.

  In the example of FIG. 1, a lens L1 is provided as the front lens group of the first lens group GR1, a prism P1 is provided as an optical member for bending the optical path, and two lenses L2 and L3 are provided as the rear lens group. It has been.

The zoom lens of the present invention is further configured to satisfy the condition of the following expression (2) when the imaging magnification of the second lens group GR2 at an infinite subject distance is β2t. .
| Β2t | <0.95 (2)
By satisfying the condition of the formula (2), it is possible to reduce the size of the lens system and increase the magnification while maintaining good optical performance.

The zoom lens according to the present invention is configured to further satisfy the conditions of the following expressions (3) to (5) with respect to the focal lengths of the second lens group GR2 to the fifth lens group GR5 and the entire lens system. It is desirable.
0.8 <| f2 / fw | <1.5 (3)
1.5 <| f5 / f3 | <2.8 (4)
0.5 <f3 / f4 <1.2 (5)
However, the focal length of the entire lens system at the wide-angle end is fw, and the focal lengths of the second lens group GR2, the third lens group GR3, the fourth lens group GR4, and the fifth lens group GR5 are f2, f3, f4, and f5, respectively. And

  The above equation (3) is a condition that defines the ratio between the focal length f2 of the second lens group GR2 and the focal length fw of the entire lens system at the wide-angle end. If the value of this ratio falls below the lower limit of the expression (3) and the focal length f2 of the second lens group GR2 becomes shorter, the Petzval sum becomes larger on the underside, making it difficult to correct aberrations such as image plane tilt. On the contrary, if the ratio value exceeds the upper limit value of the expression (3) and the focal length f2 becomes longer, the moving amount of the second lens group GR2 during zooming increases, and the effective diameter of the front lens increases. The overall length and thickness of the lens system will increase.

  Further, the expression (4) mainly shortens the length of the lens system after the third lens group GR3 under the condition that defines the ratio of the focal lengths f3 and f5 of the third lens group GR3 and the fifth lens group GR5. However, this is for obtaining good optical performance. If the value of this ratio falls below the lower limit value of Expression (4) and the refractive power of the fifth lens group GR5 becomes too strong, the negative Petzval sum increases and it becomes difficult to correct field curvature. On the other hand, if the ratio value exceeds the upper limit value of Expression (4) and the refractive power of the fifth lens group GR5 becomes too weak, it is difficult to sufficiently shorten the overall length of the lens system.

  Expression (5) is a condition relating to the refractive power of the third lens group GR3 and the fourth lens group GR4, in order to shorten the length of the lens system after the third lens group GR3 while maintaining the optical performance. belongs to. If the ratio of the focal lengths f3 and f4 of each lens group is less than the lower limit of the expression (5) and the refractive power of the third lens group GR3 becomes too strong, it is advantageous for shortening the overall length of the lens system, but spherical aberration And it becomes difficult to correct coma aberration well. In addition, it is difficult to ensure the back focus. On the contrary, if the ratio value exceeds the upper limit value of the expression (5) and the refractive power of the third lens group GR3 becomes too weak, the Petzval sum in the entire lens system becomes large on the under side, and the image surface is tilted. growing. Further, the shortening of the lens system becomes insufficient, the back focus becomes too long, the effective diameter of the fourth lens group GR4 becomes large, the lens becomes heavy, and smooth focusing becomes impossible.

  Therefore, by configuring so as to satisfy the conditions of the above expressions (3) and (4), the Petzval sum at the wide-angle end can be corrected well, and the overall length of the lens system can be shortened. Further, by configuring so as to further satisfy the condition of Expression (5), it becomes possible to satisfactorily correct spherical aberration and coma and further shorten the overall length of the lens system.

  Further, in the zoom lens of the present invention, in addition to satisfying the conditions of the above expressions (3) to (5), the rear lens group of the first lens group GR1 is arranged in order from the object side to the image plane IMG. It is desirable to comprise a convex meniscus lens having a convex surface on the side and a convex lens having a convex surface on the object side. With such a configuration, it is possible to satisfactorily correct spherical aberration and Petzval sum in the entire zooming region from the wide-angle end to the telephoto end.

  In the zoom lens according to the present invention, it is preferable that at least one of the lenses included in the first lens group GR1 is an aspherical surface. With such a configuration, it is possible to favorably correct curvature of field and spherical aberration in the long focal length range.

Next, specific numerical examples of the zoom lens according to the present invention will be described.
Table 1 shows numerical values of the lens system in the first example. Table 2 shows the focal length f, F number (FNo.), Half angle of view ω at each focal position in the first embodiment, and the lens interval at each focal position. Further, Table 3 shows the aspherical coefficients of the surfaces configured as aspherical surfaces in the first embodiment.

なお、表１（後述する表４も同様）において、面番号Ｓ１〜Ｓ２６は、レンズＬ１〜Ｌ１１、プリズムＰ１、アイリスＩＲ、フィルタＦＬおよびカバーガラスＣＧの中心軸における光の入射面および出射面を、物体側から順に示している。例えば、面番号Ｓ１はレンズＬ１の物体側のレンズ面を示し、面番号Ｓ２はその像面ＩＭＧ側のレンズ面を示している。また、面番号Ｓ３はプリズムＰ１の物体側の面を示し、面番号Ｓ４はその像面ＩＭＧ側の面を示している。また、接合レンズについては、各レンズの接合面を同一の面番号で示している。例えば、面番号Ｓ１２はレンズＬ５とレンズＬ６との接合面を示している。

In Table 1 (the same applies to Table 4 described later), the surface numbers S1 to S26 indicate the light incident surface and the light exit surface on the central axes of the lenses L1 to L11, the prism P1, the iris IR, the filter FL, and the cover glass CG. They are shown in order from the object side. For example, the surface number S1 indicates the lens surface on the object side of the lens L1, and the surface number S2 indicates the lens surface on the image plane IMG side. The surface number S3 indicates the object side surface of the prism P1, and the surface number S4 indicates the image surface IMG side surface. For the cemented lens, the cemented surface of each lens is indicated by the same surface number. For example, the surface number S12 indicates the cemented surface between the lens L5 and the lens L6.

  R represents the curvature of each surface, d represents the distance between the surfaces, Nd represents the refractive index with respect to the d-line (wavelength 587.6 nm), and νd represents the Abbe number based on the d-line. A distance d indicates a distance between the surface and a surface adjacent to the image plane IMG side. For example, the value of the distance d described in the field of the surface number S1 indicates the thickness between the object side and the image surface IMG side of the lens L1.

  In Table 2 (the same applies to Table 5 described later), the focal length f, the F number (FNo.), The half angle of view ω, and the lens interval are set to the short focal length end and intermediate focal length during zooming. , In the order of the long focal length end. In this table, the lens interval indicates a distance from a surface in parentheses to a surface adjacent to the image plane IMG side.

  In the first embodiment, the image plane IMG side surface (S6) of the lens L2, the image plane IMG side surface (S15) of the lens L7, the object side surface (S17) of the lens L8, and the lens L11. Each surface (S22) on the image plane IMG side is composed of an aspherical surface. The shape of the aspherical surface is expressed by the following formula (6).

ただし、非球面の深さ、すなわち各レンズ面の頂点からの光軸方向の距離をｘ、レンズ面の頂点でのレンズの曲率半径をｒ、円錐定数をκとする。また、４次、６次、８次および１０次の非球面係数をそれぞれＡ、Ｂ、ＣおよびＤとしており、表３（後述する表６でも同様）では、これらの非球面係数の値を示している。また、表３（後述する表６でも同様）中の“Ｅ”は、１０を底とする指数表現を意味している。

Here, the depth of the aspheric surface, that is, the distance in the optical axis direction from the apex of each lens surface is x, the radius of curvature of the lens at the apex of the lens surface is r, and the conic constant is κ. In addition, the fourth, sixth, eighth and tenth aspheric coefficients are A, B, C and D, respectively, and Table 3 (the same applies to Table 6 described later) shows the values of these aspheric coefficients. ing. Further, “E” in Table 3 (also in Table 6 described later) means an exponential expression with 10 as the base.

  In the first embodiment, in the rear lens group of the first lens group GR1, the lens L2 is a convex meniscus lens having a convex surface facing the image plane IMG, and the lens L3 is a convex lens having a convex surface facing the object side. (Convex meniscus lens), and spherical aberration and Petzval sum are satisfactorily corrected in the entire zooming region from the wide-angle end to the telephoto end. Further, since the surface on the image plane IMG side of the lens L2 is aspherical, distortion can be corrected, the effective diameter of the lens L1 can be reduced, and the prism P1 can be downsized. . By using a cemented lens, it is possible to reduce the amount of image plane tilt and coma caused by decentering in the lens group and to facilitate manufacturing.

2 to 4 are graphs showing various aberrations at the short focal length end, the intermediate focal length, and the long focal length end, respectively, for the first example.
Here, (A) of each figure shows spherical aberration, the vertical axis shows the ratio to the open F value, and the horizontal axis shows the focus amount. Also, (B) in each figure shows astigmatism, the vertical axis shows the image height, the horizontal axis shows the focus amount, the solid line shows the value on the sagittal image plane, and the broken line shows the value on the meridional image plane. Furthermore, (C) in each figure shows distortion, the vertical axis shows the image height, and the horizontal axis shows the ratio (%). (The same applies to FIGS. 6 to 8 described later.)
Next, a second embodiment will be described.

  FIG. 5 is a cross-sectional view showing a configuration of a zoom lens according to the second embodiment of the present invention. In the zoom lens shown in FIG. 5, the basic configuration such as the lens group configuration, the number of lenses, the position of the cemented lens and the aspherical surface is the same as that in the first embodiment.

  Table 4 shows numerical values of the lens system in the second example. Table 5 shows the values of the focal length f, the F number (FNo.) And the half angle of view ω at each focal position in the second embodiment, and the lens interval at each focal position. Further, Table 6 shows the aspherical coefficients of the surfaces constituted by aspherical surfaces in the second embodiment.

この第２の実施例では、レンズＬ２の像面ＩＭＧ側の面が非球面とされたことにより、歪曲収差が補正されるとともに、レンズＬ１の有効径を小さくし、プリズムＰ１を小型化することが可能となっている。

In the second embodiment, since the surface of the lens L2 on the image plane IMG side is aspherical, distortion is corrected, the effective diameter of the lens L1 is reduced, and the prism P1 is reduced in size. Is possible.

  6 to 8 are graphs showing various aberrations at the short focal length end, the intermediate focal length, and the long focal length end, respectively, in the second example. In each figure, (A) shows spherical aberration, (B) shows astigmatism, and (C) shows distortion.

  Here, Table 7 shows numerical values for obtaining the conditions of the above equations (4) to (8) in the first, second and third embodiments.

この表７に示すように、上記の第１および第２の実施例は、式（２）〜（５）の各条件を満足している。また、図２〜図４、および図６〜図８の諸収差図によれば、各実施例とも短焦点距離端、中間焦点距離および長焦点距離端において、各種収差がバランスよく補正されていることがわかる。従って、４倍程度の変倍比を有する撮像装置用、特に画素数の比較的多いデジタルスチルカメラ用のズームレンズとして、好適なものが実現されている。

As shown in Table 7, the first and second examples described above satisfy the conditions of the expressions (2) to (5). 2 to 4 and FIGS. 6 to 8, the various aberrations are corrected in a balanced manner at the short focal length end, the intermediate focal length, and the long focal length end in each example. I understand that. Accordingly, a zoom lens suitable for an image pickup apparatus having a zoom ratio of about 4 times, particularly a digital still camera having a relatively large number of pixels has been realized.

Next, an example of an imaging apparatus using the zoom lens will be described. FIG. 9 is a block diagram showing a configuration example of a digital still camera in which the zoom lens of the present invention can be mounted.
The digital still camera shown in FIG. 9 has a camera block 10 that performs an imaging function, a camera signal processing unit 20 that performs signal processing such as analog-digital conversion of a captured image signal, and an image that performs recording and reproduction processing of the image signal. A processing unit 30, an LCD (Liquid Crystal Display) 40 for displaying captured images, an R / W (reader / writer) 50 for writing / reading data to / from the memory card 51, and a CPU 60 for controlling the entire apparatus , An input unit 70 for operation input by the user, and a lens drive control unit 80 for controlling driving of the lenses in the camera block 10 are provided.

  The camera block 10 includes an optical system including a zoom lens 11 to which the present invention is applied, an image sensor 12 such as a CCD, and the like. The camera signal processing unit 20 performs signal processing such as conversion of an output signal from the image sensor 12 into a digital signal, noise removal, image quality correction, and conversion into a luminance / color difference signal. The image processing unit 30 performs compression encoding / decompression decoding processing of an image signal based on a predetermined image data format, conversion processing of data specifications such as resolution, and the like.

  The memory card 51 is composed of a detachable semiconductor memory. The R / W 50 writes the image data encoded by the image processing unit 30 to the memory card 51 and reads the image data recorded on the memory card 51. The CPU 60 is a control processing unit that controls each circuit block in the digital still camera, and controls each circuit block based on an instruction input signal or the like from the input unit 70.

  The input unit 70 includes, for example, a shutter release button for performing a shutter operation, a selection switch for selecting an operation mode, and the like, and outputs an instruction input signal corresponding to an operation by a user to the CPU 60. The lens drive control unit 80 controls a motor (not shown) that drives the lens in the zoom lens 11 based on a control signal from the CPU 60.

The operation of this digital still camera will be briefly described below.
In the shooting standby state, under the control of the CPU 60, the image signal captured by the camera block 10 is output to the LCD 40 via the camera signal processing unit 20 and displayed as a camera through image. When an instruction input signal for zooming is input from the input unit 70, the CPU 60 outputs a control signal to the lens drive control unit 80, and the zoom lens 11 in the zoom lens 11 is controlled based on the control of the lens drive control unit 80. A predetermined lens is moved.

  When a shutter (not shown) of the camera block 10 is released by an instruction input signal from the input unit 70, the captured image signal is output from the camera signal processing unit 20 to the image processing unit 30 and subjected to compression encoding processing. Is converted into digital data of the data format. The converted data is output to the R / W 50 and written to the memory card 51.

  The focusing is performed by the lens drive control unit 80 based on a control signal from the CPU 60 based on a control signal from the CPU 60, for example, when the shutter release button is half-pressed or when it is fully pressed for recording. This is done by moving the lens.

  When reproducing the image data recorded on the memory card 51, predetermined image data is read from the memory card 51 by the R / W 50 in response to an operation by the input unit 70, and decompressed and decoded by the image processing unit 30. After the conversion processing, the reproduced image signal is output to the LCD 40. As a result, a reproduced image is displayed.

FIG. 10 is a cross-sectional view showing a component mounting structure in the digital still camera.
FIG. 10 shows the inside of the digital still camera when a subject is present on the left side of the drawing. The zoom lens 11 is housed in the camera housing 90, and the image sensor 12 is provided below the zoom lens 11. The LCD 40 is provided on the surface of the camera casing 90 facing the subject, and is used to adjust the angle of view during shooting.

  The zoom lens of the present invention can perform zooming and focusing by bending the optical axis of light from a subject with a prism and moving a predetermined lens along the bent direction (vertical direction in the figure). It has become. Therefore, it is possible to perform shooting without projecting the zoom lens 11 from the camera housing 90, and the depth of the camera body at the time of shooting is shortened. In addition to this, the zoom lens 11 is designed so as to satisfy the above-described conditions, so that the camera housing 90 can be further thinned and downsized in the vertical direction. It is possible to obtain a high-quality captured image with a small aberration at each focal length.

  In the above embodiment, the case where the zoom lens of the present invention is applied to a digital still camera has been described. However, the present invention can also be applied to other imaging devices such as a video camera.

1 is a cross-sectional view showing a configuration of a zoom lens according to a first example of the present invention. FIG. 5 is a diagram showing various aberrations at the short focal length end for the first example. FIG. 6 is a diagram showing various aberrations at an intermediate focal length for the first example. FIG. 6 is a diagram showing various aberrations at the long focal length end for the first example. It is sectional drawing which shows the structure of the zoom lens which concerns on 2nd Example of this invention. FIG. 10 is a diagram illustrating various aberrations at the short focal length end of the second example. FIG. 6 is a diagram showing various aberrations at an intermediate focal length for the second example. It is various aberrational figures in the long focal length end about the 2nd example. It is a block diagram which shows the structural example of the digital still camera which can mount the zoom lens of this invention. It is sectional drawing which shows the attachment structure of the components in the digital still camera which concerns on embodiment of this invention.

Explanation of symbols

  GR1: First lens group, GR2: Second lens group, GR3: Third lens group, GR4: Fourth lens group, GR5: Fifth lens group, L1 to L11: Lens, P1: Prism, IR ... Iris, FL ... Filter, CG ... Cover glass, IMG ... Image plane

Claims (5)

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 provided with an optical aperture, and a positive refractive power. the fourth lens group, and a fifth lens group having negative refractive power, upon zooming from the wide-angle end to the telephoto end, with the second lens group moves from the object side to the image plane side, the fourth lens having In a zoom lens configured such that the group moves so as to correct the movement of the image plane due to zooming, and the first lens group, the third lens group, and the fifth lens group do not move,
The first lens group includes, in order from the object side, one front lens having negative refractive power, an optical member that bends the optical path, and a rear lens group having positive refractive power,
When the imaging magnification of the second lens group at an object distance of infinity is β2t,
| Β2t | <0.95
And the focal length of the entire lens at the wide angle end is fw, and the focal lengths of the second lens group, the third lens group, the fourth lens group, and the fifth lens group are f2, f3, f4, and When f5
0.8 <| f2 / fw | <1.5
1.5 <| f5 / f3 | <2.8
0.5 <f3 / f4 <1.2
A zoom lens that satisfies the following conditions. 2. The rear lens group of the first lens group includes, in order from the object side, a convex meniscus lens having a convex surface facing the image surface side and a convex lens having a convex surface facing the object side. Zoom lens. 2. The zoom lens according to claim 1, wherein at least one surface of the lenses included in the first lens group is an aspherical surface. The zoom lens according to claim 1, wherein the optical member of the first lens group includes a prism. 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 provided with an optical aperture, and a positive refractive power. the fourth lens group, and a fifth lens group having negative refractive power, upon zooming from the wide-angle end to the telephoto end, with the second lens group moves from the object side to the image plane side, the fourth lens having A zoom lens configured so that the group moves so as to correct the movement of the image plane due to zooming, and the first lens group, the third lens group, and the fifth lens group do not move is used as an imaging lens. In the imaging device
The first lens group includes, in order from the object side, one front lens having negative refractive power, an optical member that bends the optical path, and a rear lens group having positive refractive power,
When the imaging magnification of the second lens group at an object distance of infinity is β2t,
| Β2t | <0.95
And the focal length of the entire lens at the wide angle end is fw, and the focal lengths of the second lens group, the third lens group, the fourth lens group, and the fifth lens group are f2, f3, f4, and When f5
0.8 <| f2 / fw | <1.5
1.5 <| f5 / f3 | <2.8
0.5 <f3 / f4 <1.2
An imaging device characterized by satisfying each of the following conditions:

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