JP2008065347A - Zoom lens and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rear focus type zoom lens capable of miniaturizing the overall lens system by making a prism more compact, without impairing the optical performance. <P>SOLUTION: The zoom lens is constituted of a first lens group GR1 through a fifth lens group GR5 having positive, negative, positive, positive, and negative refractive powers, in this order starting from the object side, and is so configured as to perform zooming by moving a second lens group GR2 and a fourth lens group GR4. The first lens group GR1 has a front side lens group having a negative refractive power, an optical member that bends the optical path, and a rear side lens group having a positive refractive power, in this order starting from the object side, and the rear-side lens group comprises one lens both faces of which are convex. When the imaging magnification of the fifth lens group GR5 with the subject distance being located at infinity is β5, condition 1.0<β5<1.9 is satisfied in all regions of magnification. <P>COPYRIGHT: (C)2008,JPO&INPIT

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 ratio of about 3 to 5 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 further miniaturization is required for these small-sized imaging devices. 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. As such a rear focus 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, It has a fourth lens group having a positive refractive power, a fifth lens group having a negative refractive power, zooming is performed by moving the second and fourth lens groups, and focusing is performed by moving the fourth lens group. A five-group zoom lens configured to do is known. For example, with such a configuration, the focal lengths of the third lens group and the fifth lens group are f3 and f5, respectively, the imaging magnification of the fifth lens group when the subject distance is infinite distance is β5, and the second lens group. There is a zoom lens satisfying the following expressions (1) to (3), where f2 is the focal length and fw and ft are the focal lengths of the entire system at the wide-angle end and the telephoto end, respectively (for example, patents) Reference 1).

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. For example, 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 group having a positive refractive power And a first lens unit having a negative refractive power in order from the object side, the first lens unit having a four-unit lens configuration in which zooming is performed by moving the second and fourth lens units, There has been a zoom lens having a prism that bends the optical path and a second lens that is a single lens having positive refractive power (see, for example, Patent Document 2).
Japanese Patent No. 3015192 (paragraph numbers [0014] to [0037], FIG. 1) Japanese Unexamined Patent Publication No. 2000-131610 (paragraph numbers [0010] to [0027], FIG. 1)

  By the way, in a zoom lens having an optical system in which the optical path is bent using a prism, it is possible to further reduce the size and thickness by reducing the size of the prism. However, in the zoom lens disclosed in Patent Document 2, if the diameter and thickness of the lens included in the first lens group are further reduced, the optical performance is deteriorated, so that it is difficult to further downsize the prism. There was a problem.

  The present invention has been made in view of such a problem, and provides a rear focus type zoom lens capable of reducing the size of the entire lens system by further downsizing the prism without impairing optical performance. With the goal.

  Another object of the present invention is to provide an imaging apparatus using a rear focus type zoom lens that can reduce the size of the prism system and the entire lens system without impairing optical performance. is there.

In the present invention, in order to solve the above problems, 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, Zoom lens comprising a fourth lens group having a refractive power of 5 and a fifth lens group having a negative refractive power, and performing zooming by moving the second lens group and the fourth lens group The first lens group includes, in order from the object side, a front lens group having a negative refractive power, an optical member that bends an optical path, and a rear lens group having a positive refractive power, and the rear lens group includes: When the image forming magnification of the fifth lens group having a convex surface on both sides and a subject distance of infinity is β5 , 1.0 <β5 < Specially satisfying the condition of 1.9 The zoom lens according to is provided.

Such a zoom lens includes five lens groups each having positive, negative, positive, positive, and negative refractive power in order from the object side, and performs zooming by moving the second and fourth lens groups. It is possible. The first lens group includes a front lens group having a negative refractive power from the object side, an optical member that bends the optical path, and a rear lens group having a positive refractive power, so that the second lens group when zooming is performed. The moving direction of the fourth lens group is the optical axis direction of the rear lens group of the first lens group . The first lens group 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. The group is composed of one lens whose both surfaces are convex. Further, the imaging magnification β5 of the fifth lens group with the subject distance at infinity is configured to satisfy the condition of 1.0 <β5 <1.9 in all zooming regions.

The zoom lens according to the present invention includes five lens groups each having positive, negative, positive, positive, and negative refractive power in order from the object side, and performs zooming by moving the second and fourth lens groups. Further, the first lens group includes a front lens group having a negative refractive power from the object side, an optical member that bends the optical path, and a rear lens group having a positive refractive power. The moving direction of the second and fourth lens groups when performing is the optical axis direction of the rear lens group of the first lens group, and the lens system is thinned. Further, the imaging magnification β5 of the fifth lens group at an infinite subject distance is configured to satisfy the condition of 1.0 <β5 <1.9 in all zooming regions. While maintaining the optical performance, the optical member of the first lens group can be further miniaturized and the entire lens system can be thinned. Further, the first lens group 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 configuring the side lens group with a single lens having both convex surfaces, a higher zoom magnification can be obtained without changing the overall length of the lens system.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a lens configuration example of a zoom lens according to an embodiment of the present invention.
In FIG. 1, as an example, a configuration example of a zoom lens used as an imaging lens of an imaging apparatus such as a digital still camera is shown. In this zoom lens, 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 group GR3 having a positive refractive power. A fourth lens group GR4 having a positive refractive power and a fifth lens group GR5 having a negative refractive power are disposed. Further, an iris IR for adjusting the amount of light is disposed on the image plane IMG side of the third lens group GR3, and a filter including a low-pass filter such as an infrared cut filter is further disposed on the image plane IMG side of the fifth lens group GR5. The FL and the cover glass CG of the image sensor are disposed. The image plane IMG is a light receiving surface of an image sensor such as a CCD (Charge Coupled Devices).

  This zoom lens is configured to perform zooming by moving the second lens group GR2 and the fourth lens group GR4. When zooming from the short focal length end to the long focal length end, the second lens group is moved from the object side to the image plane IMG side, and the fourth lens group is moved from the image plane IMG side to the object side. Further, this zoom lens employs a so-called rear focus system, and focusing can be performed by moving the fourth lens group GR4 or the fifth lens group GR5.

  Further, the first lens group GR1 includes, in order from the object side, a single lens L1 having a negative refractive power, a prism P1 for bending the optical path, and a single lens L2 having a positive refractive power. ing. Therefore, the moving direction of the lens that moves during zooming and 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 lens L2. In the present embodiment, the lens L1 is configured by a meniscus lens that is convex toward the object side, and both lens surfaces of the lens L2 are configured as convex shapes.

  The second lens group GR2 includes three lenses L3, L4, and L5 in order from the object side, and a lens surface between the lens L4 and the lens L5 is cemented. The third lens group GR3 is composed of a single lens L6. The fourth lens group GR4 is composed of two lenses L7 and L8, and the lens surface between the lens L7 and the lens L8 is cemented. The fifth lens group GR5 includes two lenses L9 and L10, and a lens surface between the lens L9 and the lens L10 is cemented.

Here, the outline | summary of this invention is demonstrated using 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. In addition, zooming is performed by moving the second lens group GR2 and the fourth lens group GR4. 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 configuring the first lens group in this way, 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. It can be kept constant regardless of zooming, focusing, or power on / off.

  In the present embodiment, as an example, one lens L1 and L2 are provided as the front lens group and the rear lens group of the first lens group GR1, respectively, and the prism P1 is provided as an optical member that bends the optical path. Yes.

Further, the zoom lens of the present invention is further configured to satisfy the condition of the following expression (4).
1.0 <β5 <1.9 (4)
However, the imaging magnification of the fifth lens group GR5 when the distance to the object is infinity is β5. When the imaging magnification β5 is designed so as to exceed the lower limit as in the condition of the equation (4), it is possible to shorten the focal length of the object side lens. As a result, the overall length of the lens system can be shortened, and the effective diameter of the lens of the first lens group GR1 can be reduced, and an optical member (prism P1 in FIG. 1) that bends the optical path accordingly. Since the size can be reduced, the depth of the lens system is further reduced.

  On the other hand, when the imaging magnification β5 is below the lower limit of the expression (4), it is difficult to reduce the effective diameter of the front lens group (the lens L1 in FIG. 1) of the first lens group GR1. If the imaging magnification β5 exceeds the upper limit of the expression (4), it is impossible to sufficiently correct spherical aberration when the F-number is designed to be small, and the exit pupil becomes the image plane IMG. Since the angle of the light incident on the image sensor deviates greatly from the vertical, shading or the like occurs and the imaging performance deteriorates.

  By the way, the zoom lens according to the present invention is configured so as to satisfy the above-described conditions, so that when moving from the short focal length end to the long focal length end, the moving direction of each moving lens group is changed. It can be unidirectional. Specifically, by moving the second lens group GR2 from the object side to the image plane IMG side and moving the fourth lens group GR4 from the image plane IMG side to the object side, the short focal length end to the long focal length end Zooming can be performed. In the zoom lens described above, the stroke of the second lens group GR2 can be relatively reduced by relatively increasing the change in the zoom ratio due to the movement of the fourth lens group GR4.

  In the zoom lens of the present invention that satisfies the above conditions, focusing can be performed by moving the second lens group GR2 or the fourth lens group GR4. However, the focusing is performed by moving the second lens group GR2. By doing so, the stroke of the lens is reduced, and the overall length of the lens system can be shortened.

  In a conventional zoom lens having a five-group lens system, when zooming gradually from the short focal length end to the long focal length end, the fourth lens group is first moved in the object side direction, and the moving direction is changed along the way. In general, it is reversed and moved to the image plane IMG side. Thus, when the fourth lens group GR4 has an inflection point during zooming, the second lens group is in the vicinity of the inflection point. There is a problem that focusing by GR2 becomes impossible. Such a problem does not occur in the zoom lens of the present invention, and focusing by movement of the second lens group GR2 is possible.

  In addition to the zooming stroke, the lens movement space needs to be determined in consideration of the focusing stroke, but at this time, the long focal length end is more important than the focusing at the short focal length end. Focusing at requires a larger stroke. In the case of the present invention, the second lens group GR2 is positioned closest to the object side at the short focal length end where the stroke required for focusing is small, and is positioned closest to the image plane IMG at the long focal length end where a large stroke is required. To do. Accordingly, the stroke of the second lens group GR2 necessary on the object side for focusing is reduced, and at the long focal length end, the position is between the moving second lens group GR2 and the fourth lens group GR4. Therefore, the influence of the stroke required for focusing on the entire length of the lens system is reduced. As a result, the overall length of the lens system can be further shortened. Furthermore, as described above, in the zoom lens according to the present invention, the stroke of the second lens group GR2 during zooming is reduced, so that the effect of shortening the overall length of the lens system is great.

In order to perform lens driving during zooming and focusing as described above, the following formula (5) is satisfied between the strokes of the second lens group GR2 and the fourth lens group GR4. It is desirable to do.
0.5 <| dZ2 / dZ4 | <1.2 (5)
However, the stroke from the short focal length end to the long focal length end of the second lens group GR2 is dZ2, and the stroke from the short focal length end to the long focal length end of the fourth lens group GR4 when the subject distance is infinity is dZ4. And Here, if the value falls below the lower limit value of the above formula (5), it is necessary to increase the effective diameter of the fourth lens group GR4, and the thickness of the entire lens system increases. If the upper limit value of Expression (5) is exceeded, it is necessary to increase the effective diameters of the first lens group GR1 and the second lens group GR2, and similarly the thickness of the entire lens system increases.

The zoom lens according to the present invention is preferably configured to further satisfy the following expression (6) that defines the ratio of the focal lengths of the third lens group GR3 and the fifth lens group GR5.
| F5 / f3 |> 2.1 (6)
However, the focal length of the third lens group GR3 is f3, and the focal length of the fifth lens group GR5 is f5. Here, if the refractive power of the fifth lens group GR5 becomes too strong below the lower limit value of the expression (6), the negative Petzval sum increases and it becomes difficult to correct field curvature. .

Further, as described above, the first lens group GR1 includes the front lens group having negative refractive power, the optical member that bends the optical path, and the rear lens group having positive refractive power. Among them, the lens L1 is constituted by a meniscus lens having a convex shape toward the object side, and both lens surfaces of the lens L2 are constituted by convex shapes, thereby reducing the effective diameter of the lens L1 and the prism. P1 can be further downsized. In such a configuration, it is desirable that the lens L1 is further configured to satisfy the following expressions (7) and (8).
neL1> 1.8 (7)
νeL1 <30 (8)
However, the refractive index of the lens L1 with respect to the e-line is neL1, and the Abbe number based on the e-line of the lens L1 is νeL1. Here, by satisfying the condition of Expression (7), it is possible to easily perform spherical aberration correction in the first lens group GR1. Further, by satisfying the condition of Expression (8), it is possible to easily perform chromatic aberration correction in the first lens group GR1.

Next, specific numerical examples of the zoom lens having the configuration shown in FIG. 1 will be described.
Table 1 shows the numerical values of the first embodiment. Table 2 shows values of the focal length f, the F number (FNo.), And the half angle of view ω at each focal position in the first embodiment. Further, Table 3 shows the aspherical coefficients of the surfaces configured as aspherical surfaces in the first embodiment.

  In Table 1 (the same applies to Tables 2 and 3 described later), the surface numbers S1 to S24 are the light incident surfaces on the central axes of the lenses L1 to L10, the prism P1, the iris IR, the filter FL, and the cover glass CG. The emission surface is shown in order from the object side. For example, S1 indicates a lens surface on the object side of the lens L1, and S2 indicates a lens surface on the image plane IMG side. S3 indicates the object side surface of the prism P1, and S4 indicates the image side IMG side surface. For the cemented lens, the cemented surface of each lens is indicated by the same surface number. For example, S10 indicates a cemented surface between the lens L4 and the lens L5.

  R represents the curvature of each surface, d represents the distance between the surfaces, ne represents the refractive index with respect to the e-line, and νe represents the Abbe number based on the e-line. In the field of curvature R, the surface indicated by (ASP) after the numerical value indicates that the surface is constituted by an aspheric surface. 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. Further, the distance d between the surfaces that move during zooming and focusing is shown in the order of short focal length end, intermediate focal length, and long focal length end during zooming.

  In the first embodiment, both surfaces (S5 and S6) of the lens L2, the object-side surface (S12) of the lens L6, and the object-side surface (S15) of the lens L7 are each formed of an aspheric surface. ing. The shape of the aspherical surface is represented by the following formula (9).

  Here, the distance in the optical axis direction from the vertex of each lens surface is x, the radius of curvature of the lens at the vertex is r, and the conic constant is κ. Further, the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients are C4, C6, C8, and C10, respectively, and in Table 3 (the same applies to Tables 6 and 9 described later), The value is shown. Further, “E” in Table 3 (the same applies to Tables 6 and 9 described later) means an exponential expression with 10 as the base.

  As in the first embodiment, at least one lens surface of the lenses included in the first lens group GR1 is aspherical so that distortion is corrected and the effective diameter of the lens L1 is reduced. Thus, the prism P1 can be downsized. In the fifth lens group GR5, the cemented surface (S19) of the lens L9 and the lens L10 has a convex shape on the object side, so that chromatic aberration is corrected and the fifth lens against lens performance deterioration. The sensitivity of the group GR5 can be reduced. By using a cemented lens, it is possible to reduce the amount of image plane tilt and coma caused by decentration within 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.
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. In addition, the solid line indicates the spherical aberration at the e line (wavelength 546.1 nm), the broken line indicates the g line (wavelength 435.8 nm), and the alternate long and short dash line indicates the spherical aberration at the C line (656.3 nm). 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. 5 to 10 described later.)
Next, a second embodiment will be described. Table 4 shows the numerical values of the second embodiment. Table 5 shows 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. Further, Table 6 shows the aspherical coefficients of the surfaces that are aspherical in the second embodiment.

  In the second embodiment, both surfaces (S5 and S6) of the lens L2, both surfaces (S12 and S13) of the lens L6, and the object side surface (S15) of the lens L7 are each constituted by an aspheric surface.

  In the second embodiment described above, similarly to the first embodiment, both surfaces (S5 and S6) of the lens L2 of the first lens group GR1 are aspherical, so that distortion is corrected, The prism P1 is downsized. The cemented surface (S19) of the cemented lens (lens L9 and L10) used in the fifth lens group GR5 has a convex shape on the object side, and chromatic aberration is corrected.

  5 to 7 are graphs showing various aberrations at the short focal length end, the intermediate focal length, and the long focal length end, respectively. In each figure, (A) shows spherical aberration, (B) shows astigmatism, and (C) shows distortion.

  Next, a third embodiment will be described. Table 7 shows the numerical values of the third example. Table 8 shows values of the focal length f, the F number (FNo.), And the half angle of view ω at each focal position in the third embodiment. Further, Table 9 shows the aspherical coefficients of the surfaces that are aspherical in the third embodiment.

  In the third embodiment, both surfaces (S5 and S6) of the lens L2, both surfaces (S12 and S13) of the lens L6, and the object side surface (S15) of the lens L7 are each formed of an aspheric surface.

  In the third embodiment described above, as in the first embodiment, both surfaces (S5 and S6) of the lens L2 of the first lens group GR1 are aspherical, distortion is corrected, and the prism P1 is formed. It is downsized. The cemented surface (S19) of the cemented lens (lens L9 and L10) used in the fifth lens group GR5 has a convex shape on the object side, and chromatic aberration is corrected.

  8 to 10 are graphs showing various aberrations at the short focal length end, the intermediate focal length, and the long focal length end, respectively. In each figure, (A) shows spherical aberration, (B) shows astigmatism, and (C) shows distortion.

  Here, Table 10 shows numerical values for obtaining the conditions of the above equations (4) to (8) in the first, second and third embodiments.

  As shown in Table 10, the first to third examples described above satisfy the conditions of the expressions (4) to (8). In addition, according to the various aberration diagrams of FIGS. 2 to 10, it is understood that 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. Therefore, a zoom lens suitable for an imaging apparatus having a zoom ratio of about 3 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. 11 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.
A digital still camera shown in FIG. 11 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. 12 is a cross-sectional view showing a component mounting structure in the digital still camera.
FIG. 12 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, by designing the zoom lens 11 so as to satisfy the above-described conditions, 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 various focal lengths.

  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.

It is sectional drawing which shows the lens structural example of the zoom lens which concerns on embodiment of this invention. FIG. 6 is a diagram illustrating various aberrations at a short focal length end in the first example. FIG. 5 is a diagram illustrating various aberrations at an intermediate focal length in the first example. FIG. 6 is a diagram illustrating various aberrations at a long focal length end in the first example. FIG. 12 is a diagram illustrating various aberrations at a short focal length end in the second example. FIG. 6 is a diagram illustrating various aberrations at an intermediate focal length in the second example. It is an aberration diagram at the long focal length end in the second embodiment. FIG. 10 is a diagram illustrating various aberrations at a short focal length end in the third example. FIG. 12 is a diagram illustrating various aberrations at an intermediate focal length in the third example. FIG. 12 is a diagram illustrating various aberrations at a long focal length end in the third 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 L10: Lens, P1: Prism, IR ... Iris, FL ... Filter, CG ... Cover glass, IMG ... Image plane

Claims (10)

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, a fourth lens group having a positive refractive power, and a negative A zoom lens configured to perform zooming by moving the second lens group and the fourth lens group, the fifth lens group having a refractive power of
The first lens group includes, in order from the object side, a front lens group having negative refractive power, an optical member that bends the optical path, and a rear lens group having positive refractive power,
The rear lens group is composed of one lens whose both surfaces are convex,
When the imaging magnification of the fifth lens group with an object distance of infinity is β5 ,
1.0 <β5 <1.9
A zoom lens that satisfies the following conditions.   The zoom lens is configured to perform zooming from the wide-angle side to the telephoto side by moving the second lens group from the object side to the image plane side and moving the fourth lens group from the image plane side to the object side. The zoom lens according to claim 1.   The zoom lens according to claim 2, wherein the zoom lens is configured to perform focusing by moving the second lens group. The stroke from the short focal length end to the long focal length end of the second lens group is dZ2, and the stroke from the short focal length end to the long focal length end of the fourth lens group when the subject distance is infinity is dZ4. sometimes,
0.5 <| dZ2 / dZ4 | <1.2
The zoom lens according to claim 3, further satisfying the following condition. When the focal length of the third lens group is f3 and the focal length of the fifth lens group is f5,
| F5 / f3 |> 2.1
The zoom lens according to claim 1, further satisfying the following condition.   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 fifth lens group includes a cemented lens having a cemented surface in which a surface facing the object side is a convex surface. In the first lens group,
The front lens group is composed of a single meniscus lens having a negative refractive power and having a convex shape toward the object side,
The optical member is made of a prism,
The zoom lens according to claim 1. When the refractive index for the e-line of the front lens group is neL1, and the Abbe number with respect to the e-line of the front lens group is νeL1,
neL1> 1.8
νeL1 <30
The zoom lens according to claim 8, further satisfying the following condition. 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, a fourth lens group having a positive refractive power, and a negative In an imaging apparatus using a zoom lens configured to perform zooming by moving the second lens group and the fourth lens group, the fifth lens group having a refractive power of
The first lens group includes, in order from the object side, a front lens group having negative refractive power, an optical member that bends the optical path, and a rear lens group having positive refractive power,
The rear lens group is composed of one lens whose both surfaces are convex,
When the imaging magnification of the fifth lens group with an object distance of infinity is β5 ,
1.0 <β5 <1.9
An imaging apparatus characterized by satisfying the following conditions.

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