JP2007233163A - Zoom lens and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact high-variable-power zoom lens suitably used for a digital still camera or the like using an imaging device such as a CCD or a CMOS, and to provide an imaging apparatus. <P>SOLUTION: The zoom lens includes a second lens group 20, a fourth lens group 40 and a fifth lens group 50 moved on different loci in zooming, and the second lens group 20, the fourth lens group 40 and the fifth lens group 50 have refractive power of different signs. It includes the fourth lens group 40 and the fifth lens group 50 moved in the same direction upon focusing. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a zoom lens and an imaging apparatus, and more particularly to a zoom lens and an imaging apparatus used for a digital still camera or the like using a solid-state imaging device such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal-Oxide Semiconductor).

Conventionally, a zoom lens suitable for a digital camera using a solid-state imaging device such as a CCD or a CMOS has been considered. In recent years, a high zoom ratio zoom lens having a zoom ratio of 5 times or more has been considered (see, for example, Patent Document 1).
JP 2003-202500 A

  However, in the example of Patent Document 1, even a large zoom ratio is about 6 times, and further higher zoom and compactness are desired.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a zoom lens and an image pickup apparatus that are highly variable and compact and that are suitable for use in a digital still camera using an image pickup element such as a CCD or CMOS.

In order to solve the above problem, the zoom lens according to claim 1 is provided by:
It has three or more lens groups that are moved along different tracks during zooming.
The lens group moved along different trajectories during zooming includes a first focusing lens group and a second focusing lens group that have different refractive powers and are moved in the same direction during focusing.

The invention according to claim 2 is the zoom lens according to claim 1,
The first focusing lens group has a positive refractive power,
The second focusing lens group has negative refractive power;
The first focusing lens group and the second focusing lens group are:
1.0 <XA (XAmax) (1)
1.0 <XB (XAmax) (2)
0.5 <XA (XAmax) / XB (XAmax) <2 (3)
However,
| Ra / Fno |: absolute value of a value obtained by dividing the moving amount Ra of the imaging position when the first focusing lens group is slightly moved at an arbitrary zoom position by Fno at the zoom position,
| Rb / Fno |: When the movement amount Rb of the imaging position when the second focusing lens group is slightly moved at an arbitrary zoom position is the absolute value of the value divided by Fno at the zoom position ,
XA = | Ra / Fno |,
XB = | Rb / Fno |,
XA (XAmax): The maximum value of the XA value in the entire zoom range,
XB (XAmax): XB value at the zoom position where the XA value is maximum,
It satisfies the following conditions.

The invention according to claim 2 is the zoom lens according to claim 1 or 2,
From the object side,
A first lens group having a positive refractive power fixed during zooming;
A second lens group having negative refractive power that moves during zooming;
A third lens group having positive refractive power fixed during zooming;
The first focusing lens group having a positive refractive power that moves during zooming;
The second focusing lens group having a negative refractive power that moves during zooming, and
One or both of the first focusing lens group and the second focusing lens group are moved during focusing, and both are moved at least during fine adjustment of focusing.

According to a fourth aspect of the present invention, in the zoom lens according to any one of the first to third aspects,
The moving ratio of the first focusing lens group and the second focusing lens group may be changed between rough adjustment and fine adjustment of the focusing.

The invention according to claim 5 is the zoom lens according to any one of claims 1 to 4,
The first focusing lens group or the second focusing lens group is moved during the coarse adjustment of the focusing,
The first focusing lens group and the second focusing lens group are moved during fine adjustment of the focusing.

A sixth aspect of the present invention is the zoom lens according to any one of the first to fifth aspects,
The moving ratio of the first focusing lens group and the second focusing lens group during focusing can be changed based on the zoom position.

The invention according to claim 7 is the zoom lens according to any one of claims 1 to 6,
The first focusing lens group and the second focusing lens group are always moved at the same speed during focusing.

The imaging device of the invention according to claim 8 is,
A zoom lens according to any one of claims 1 to 7;
And an image pickup device for picking up an image of light incident through the zoom lens.

  According to the first aspect of the present invention, even if three or more lens units moved during zooming have a high refractive power, the movement of the imaging position due to the movement of the first and second focusing lens units. Cancel each other, and it is possible to finely adjust the imaging position, and an image sensor position with a small pixel pitch can be placed in the focal depth range with a sufficient margin. For this reason, the zoom lens can be made highly compact and compact. In addition, it is possible not to provide the first and second focusing lens groups separately from the three or more lens groups that move during zooming.

  According to the second aspect of the present invention, sufficient focusing accuracy can be secured by moving the first and second focusing lens groups according to the conditions of the expressions (1) and (2), and the focusing control can be easily performed. In addition, the refractive power of the moving first and second focusing lens groups can be increased, and the entire zoom lens can be made compact. Further, according to the condition of Expression (3), the amount of cancellation of the imaging position movement due to the movement of the first and second focusing lens groups in focusing can be increased, and focusing control can be simplified.

  According to the third aspect of the present invention, the first and second focusing lens groups can be not provided separately from the lens group such as the second lens group that moves during zooming. Furthermore, the change in the angle of view and the performance deterioration caused by focusing can be reduced.

  According to the fourth aspect of the invention, the time required for focusing can be shortened.

  According to the fifth aspect of the present invention, it is possible to perform smoothing, high speed, and high precision focusing.

  According to the sixth aspect of the invention, smooth, high-speed, and high-precision focusing is possible over the entire zoom range.

  According to the seventh aspect of the invention, focusing control can be simplified.

  According to the invention described in claim 8, a small imaging device can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the scope of the invention is not limited to the examples described.

  With reference to FIG.1 and FIG.2, the apparatus structure of this Embodiment is demonstrated. FIG. 1 shows an internal configuration of the digital still camera 100 of the present embodiment.

  As shown in FIG. 1, a digital still camera 100 as an imaging apparatus includes an optical system 101, a solid-state imaging device 102, an A / D conversion unit 103, a control unit 104, an optical system driving unit 105, and timing generation. Unit 106, image sensor drive unit 107, image memory 108, image processing unit 109, image compression unit 110, image recording unit 111, display unit 112, and operation unit 113. .

  The optical system 101 is an optical system including a zoom lens 1 described later, and receives light from a subject. The solid-state imaging device 102 is an imaging device such as a CCD or CMOS, and 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 digital still camera 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 from the ROM and expanded in the RAM, and various types of programs in cooperation with the CPU. Execute the process.

  The optical system drive unit 105 is controlled by the control unit 104 to change magnification (movement of a second lens group 20, a fourth lens group 40, and a fifth lens group 50, which will be described later), and focus (a fourth lens group 40, which will be described later). And the movement of the fifth lens group 50), exposure, etc., the optical system 101 is driven and controlled. The timing generator 106 outputs a timing signal for analog signal output. The image sensor drive unit 107 performs scanning drive control 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 an SD (Secure Digital) memory card, a memory stick, or an xD picture card set in a slot (not shown).

  The display unit 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 includes a release button, various modes, and various operation keys for setting values, and outputs information input by the user to the control unit 104.

  Here, the operation of the digital still camera 100 will be described. In subject photographing, subject monitoring (through image display) and image photographing execution are performed. In the monitoring, an image of the subject obtained through the optical system 101 is formed on the light receiving surface of the solid-state image sensor 102. A solid-state imaging device 102 disposed behind the imaging optical axis of the optical system 101 is scanned and driven by a timing generation unit 106 and an imaging device driving unit 107, and serves as a photoelectric conversion output corresponding to an optical image formed at regular intervals. Output analog 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 and the video signal is generated and output to the display unit 112.

  The display unit 112 functions as an electronic viewfinder in monitoring, and displays captured images in real time. In this state, scaling, focusing, exposure, and the like of the optical system 101 are set as needed based on an operation input via the user operation unit 113.

  In such a monitoring state, when the user depresses the release button of the operation unit 113 at a timing at which still image shooting is desired, still image data is shot. At the timing when the release button is pressed, 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 on a recording medium by the image recording unit 111.

  FIG. 2 shows a configuration of the zoom lens 1 included in the optical system 101. The zoom lens 1 includes, in order from the object side (subject side) to the image plane IMG side along the optical axis O1, a first lens group 10 having a positive refractive power, a second lens group 20 having a negative refractive power, and an aperture. A stop D1, a third lens group 30 having a positive refractive power, a fourth lens group 40 having a positive refractive power as a first focusing lens group, and a fifth lens having a negative refractive power as a second focusing lens group A group 50, a sixth lens group 60 having a positive refractive power, and a low-pass filter 71 are included. The image plane IMG is a light receiving surface of the solid-state image sensor 102. Instead of the low-pass filter 71, a configuration including an infrared cut filter, or a configuration including a glass filter or the like may be used.

  When the zoom lens 1 performs zooming and focusing between the wide-angle end and the telephoto end, the first lens group 10, the third lens group 30, the sixth lens group 60, and the aperture stop D1 are on the optical axis O1. The position is unchanged. During zooming, the second lens group 20, the fourth lens group 40, and the fifth lens group 50 are moved on the optical axis O <b> 1 via the optical system driving unit 105 under the control of the control unit 104. Further, during focusing, the fourth lens group 40 and the fifth lens group 50 are moved to positions on the optical axis O <b> 1 via the optical system driving unit 105 under the control of the control unit 104.

  The first lens group 10 includes, in order along the optical axis O1 from the object side to the image plane IMG side of the solid-state image sensor 102, a negative lens 11 having a concave surface directed to the image side, a parallel plate prism 12, and a double-sided convex shape. Positive lens 13 and a double-sided convex positive lens 14. In order from the object side to the image plane IMG side along the optical axis O1, the negative lens 11 has surfaces S1 and S2, the prism 12 has surfaces S3 and S4, and the positive lens 13 has surfaces S5 and S6. The positive lens 14 has surfaces S7 and S8.

  The second lens group 20 includes, in order from the object side to the image plane IMG side, along the optical axis O1, a double-sided concave negative lens 21, a double-sided concave negative lens 22, and a positive lens 23 having a convex surface facing the object side. And a lens. In order from the object side to the image plane IMG side along the optical axis O1, the negative lens 21 has surfaces S9 and S10, and the negative lens 22 and the positive lens 23 have surfaces S11 to S13.

  The third lens group 30 includes only a meniscus positive lens 31 that is positioned in the vicinity of the image side on the optical axis O1 of the aperture stop D1 and has a concave surface facing the image side. In order from the object side to the image plane IMG side along the optical axis O1, the aperture stop D1 has a surface S14, and the positive lens 31 has surfaces S15 and S16.

  The fourth lens group 40 includes, in order from the object side to the image plane IMG side, along the optical axis O1, a cemented lens in which a double-sided positive lens 41 and a meniscus negative lens 42 having a concave surface facing the object side are cemented. And a double-sided convex positive lens 43. In order from the object side to the image plane IMG side along the optical axis O1, the positive lens 41 and the negative lens 42 have surfaces S17 to S19, and the positive lens 43 has surfaces S20 and S21.

  The fifth lens group 50 includes only a negative lens 51 having a concave surface facing the image side. The negative lens 51 has surfaces S22 and S23 in order along the optical axis O1 from the object side to the image plane IMG side.

  The sixth lens group 60 includes only a positive lens 61 having a convex surface facing the image side. The positive lens 61 has surfaces S24 and S25 in order along the optical axis O1 from the object side to the image plane IMG side.

  The low-pass filter 71 has surfaces S26 and S27 in order along the optical axis O1 from the object side to the image plane IMG side.

  Next, the movement operation of the lens group of the zoom lens 1 through the optical system driving unit 105 under the control of the control unit 104 will be described.

  In general, it is effective to increase the number of lens units that move during zooming and to increase the refractive power of these lens units in order to make compact zoom lenses with high zoom ratios. . On the other hand, in order to reduce the number of movable lens groups among all the lens groups constituting the zoom lens in order to achieve a simpler structure, one of the lens groups that move during zooming is used. It is effective to perform focusing for moving the lens group.

  However, in this case, if the refractive power of each movable lens group is increased in order to reduce the size of the zoom lens, even if the focusing movable lens group is moved by a small amount, image formation is possible. The position tends to move greatly. As a recent trend, the number of pixels of the image sensor is increasing, and accordingly, the pixel pitch is reduced and the depth of focus is reduced. For this reason, as described above, in a situation where the imaging movement greatly occurs even when the movable lens group for focusing is slightly moved, a situation occurs in which the position of the imaging element cannot be within the focal depth range. That is, there is a possibility that focusing cannot be performed.

  In order to achieve compactness in the zoom lens 1 of the present embodiment, zooming is performed by moving the second lens group 20, the fourth lens group 40, and the fifth lens group 50 as three lens groups. Furthermore, even when each of the second lens group 20, the fourth lens group 40, and the fifth lens group 50 has a strong refractive power, the focusing is performed as two lens groups having refractive powers having different signs. This is performed by moving the fourth lens group 40 and the fifth lens group 50. The movement of the fourth lens group 40 and the fifth lens group 50 during the focusing cancels the movement of the imaging position due to the movement so that fine imaging position adjustment is possible, and the solid-state imaging device 102 with a small pixel pitch can be adjusted. Even when used, the position of the solid-state image sensor 102 can be set within a focal depth range with a sufficient margin.

  In addition, the zoom lens 1 having a high zoom ratio according to the present embodiment moves in order from the object side to the image plane IMG side in order from the first lens group 10 having a positive refractive power fixed during zooming. A second lens group 20 having a negative refractive power, a third lens group 30 having a positive refractive power fixed during zooming, and a fourth lens group 40 having a positive refractive power moving during zooming, The fifth lens group 50 has a negative refractive power that moves during zooming. In such a configuration, when focusing is performed by moving the fourth lens group 40 or the fifth lens group 50, it is not necessary to provide the focusing movable lens group separately from the zooming movable lens group. In addition, this configuration is advantageous in that the change in the angle of view and the performance deterioration caused by focusing can be reduced.

  However, when focusing is performed by moving only one of the fourth lens group 40 and the fifth lens group 50 in the zoom lens 1, the refractive power of the fourth lens group 40 or the fifth lens group 50 tends to be strong. In addition, even when the fourth lens group 40 or the fifth lens group 50 is moved by a slight amount, a situation occurs in which the imaging position moves greatly and the image sensor position cannot be within the focal depth range. . That is, focusing cannot be performed. Therefore, focusing is performed by movement of the fourth lens group 40 having positive refractive power and the fifth lens group 50 having negative refractive power in the same direction. As a result, the imaging position movement caused by the movement of the fourth lens group 40 and the fifth lens group 50 can be canceled out to make fine adjustment of the imaging position, and even when the solid-state imaging device 102 having a small pixel pitch is used. The solid-state image sensor 102 can be placed with a sufficient margin within the focal depth range.

  In the zoom lens 1, as described above, when focusing is performed by moving only one of the fourth lens group 40 and the fifth lens group 50, the amount of movement of the imaging position increases. For this reason, using this, in the present embodiment, the fourth lens group 40 or the fifth lens group 50 is moved during coarse adjustment of focusing. Further, the fourth lens group 40 and the fifth lens group 50 are moved only during fine adjustment of focusing. According to such a configuration, it is possible to reduce the time required for focusing.

  Alternatively, the ratio of the moving speeds of the two lens groups (the fourth lens group 40 and the fifth lens group 50) that move during focusing can be changed between the coarse adjustment and the fine adjustment for focusing, thereby further smoothing and increasing the speed. High-precision focusing can be realized.

  Further, the amount of movement of the image forming position accompanying the movement of the lens group during focusing, and the depth of focus vary depending on the zoom position. Therefore, in the present embodiment, the moving ratio of the fourth lens group 40 and the fifth lens group 50 that move during focusing is changed according to the zoom position. This enables smooth, high-speed and high-precision focusing throughout the entire zoom range.

  Or conversely, when the fourth lens group 40 and the fifth lens group 50 are always moved at the same speed during focusing, there is an advantage that the control is simplified.

Next, conditional expressions satisfied by the zoom lens 1 will be described. The following formulas (1), (2), and (3) are formulas for realizing a compact zoom lens while effectively using the focusing method in the present embodiment and enabling high-precision focusing. .
1.0 <XA (XAmax) (1)
1.0 <XB (XAmax) (2)
0.5 <XA (XAmax) / XB (XAmax) <2 (3)
However,
| Ra / Fno |: Absolute value of a value obtained by dividing the moving amount Ra of the imaging position when the fourth lens group 40 is slightly moved at an arbitrary zoom position by Fno (aperture value) at the zoom position.
| Rb / Fno |: When the movement amount Rb of the imaging position when the fifth lens group 50 is slightly moved at an arbitrary zoom position is an absolute value obtained by dividing by Fno at the zoom position.
XA = | Ra / Fno |,
XB = | Rb / Fno |,
XA (XAmax): The maximum value of the XA value in the entire zoom range,
XB (XAmax): XB value at the zoom position where the XA value is maximum,
And

  In both formulas (1) and (2), if XA (XAmax) or XB (XAmax) exceeds the lower limit, the fourth lens group 40 and the fifth lens are used without using the focusing method in the zoom lens 1 of the present embodiment. By moving only one of the lens groups 50, sufficient focus accuracy can be ensured, and control can be simplified. However, on the other hand, the refractive power of the fourth lens group 40 or the fifth lens group 50 decreases, and the entire zoom lens 1 tends to increase.

  Further, if XA (XAmax) / XB (XAmax) exceeds the range of the expression (3), the amount of cancellation of the imaging position movement due to the movement of the fourth lens group 40 and the fifth lens group 50 in focusing becomes small. Focusing control becomes difficult.

  As described above, according to the present embodiment, even if the refractive power of the second lens group 20, the fourth lens group 40, and the fifth lens group 50 moved during zooming is high, the fourth lens group 40 moved during focusing, The fifth lens group 50 cancels the movement of the imaging position due to the movement and enables fine adjustment of the imaging position, so that the position of the solid-state imaging device 102 with a small pixel pitch has a sufficient margin within the focal depth range. Therefore, the zoom lens 1 can be made highly compact and compact. Also, the focusing movable lens group (fourth lens group 40, fifth lens group 50) is provided separately from the zooming movable lens group (second lens group 20, fourth lens group 40, fifth lens group 50). It makes it possible not to. Furthermore, the change in the angle of view and the performance deterioration caused by focusing can be reduced.

  Further, by moving the fourth lens group 40 and the fifth lens group 50 according to the conditions of the expressions (1) and (2), sufficient focusing accuracy can be ensured, focusing control can be simplified, and the lens can be moved. The refractive power of the fourth lens group 40 and the fifth lens group 50 can be increased, and the entire zoom lens 1 can be made compact. Further, the amount of cancellation of the imaging position movement due to the movement of the fourth lens group 40 and the fifth lens group 50 in the focusing can be increased by the condition of the expression (3), and the focusing control can be simplified.

  Further, the fourth lens group 40 or the fifth lens group 50 is moved during the coarse adjustment of the focusing of the zoom lens 1, and the fourth lens group 40 and the fifth lens group 50 are moved only during the fine adjustment. Time can be shortened.

  In addition, when the ratio of the moving speed of the fourth lens group 40 and the fifth lens group 50 moving during focusing is changed between the coarse adjustment and the fine adjustment of focusing, smoother, faster, and more accurate focusing is possible. It becomes.

  In addition, since the moving ratio of the fourth lens group 40 and the fifth lens group 50 that move during focusing is changed depending on the zoom position, it is possible to perform smooth, high-speed, and high-precision focusing throughout the entire zoom range.

  Further, when the fourth lens group 40 and the fifth lens group 50 are always moved at the same speed during focusing regardless of the zoom position, the focusing control can be simplified.

  In addition, a small digital still camera 100 equipped with the zoom lens 1 can be obtained.

A specific example 1 according to the above embodiment will be described. The zoom lens 1 of the present example satisfies the following Table 1.

  In Table 1 (a) above, ri: radius of curvature at the surface Si (i: number) of the optical element, di: distance [mm] (the thickness of the optical element on the optical axis O1 or its gap length), ndi: di The refractive index of the part, νdi: Abbe number of the di part. On the optical axis O1, the distance between the surfaces Sj and S (j + 1) is dj (where j is an arbitrary number of i).

In Table 1 (b), the second surface S2, the tenth surface S10, the fifteenth surface S15, the twentieth surface S20, the twenty-first surface S21, the twenty-fourth surface S24, and the twenty-fifth surface S25 are aspherical surfaces. . The shape of each aspherical surface of the lens is that the apex of the surface is the origin, the Z axis is the optical axis direction, the Y axis is the direction orthogonal to the optical axis, the paraxial radius of curvature is r, the conic constant is K, The spherical coefficient is represented by the following equation (4), with A4, A6, and A8.

  In Table 1 (c), the angle of view (2ω), Fno, lengths d8, d13, d16, d21 when the focal length f of the zoom lens 1 is changed to 6.4 mm, 16.5 mm, 42.6 mm. , D23 values are shown.

  Table 1 (d) shows values of XA (XAmax), XB (XAmax), XA (XAmax) / XB (XAmax) in the zoom lens 1 of the present embodiment.

  As shown in Table 1 (d), each value of XA (XAmax), XB (XAmax), XA (XAmax) / XB (XAmax) in the zoom lens 1 of the present embodiment is expressed by the above formula (1), Expressions (2) and (3) are satisfied.

  Specifically, XA (XAmax) = 1.42 and XB (XAmax) = 1.32, both showing large values. This indicates that the amount of movement of the imaging position is large relative to the amount of movement of the focus lens group.

In this embodiment, the ratio of the moving amount of the imaging position to the moving amount of the fourth lens group 40 and the fifth lens group 50 at the telephoto end of zoom is
(Movement amount of image forming position) / (Movement amount of fourth lens group 40) = 8.0
(Movement amount of image forming position) / (Movement amount of fifth lens group 50) = 7.4
Is calculated.

Recently, many image pickup devices having a small pixel pitch have been used as the number of pixels increases. If the allowable circle of confusion is set to 4 [μm], which is twice the pixel pitch, using the solid-state imaging device 102 with a pixel pitch of 2 [μm], using Fno 5.63 at the telephoto end in this embodiment. The depth of focus is
(Depth of focus) = 4 × 5.63 × 2 = 45 [μm]
Is calculated.

In this embodiment, when focusing is performed with only one of the fourth lens group 40 and the fifth lens group 50, the value of the movement pitch {(depth of focus) / (ratio of movement amount of the imaging position)} is ,
45/8 = 5.6 [μm] (fourth lens group 40)
Or
45 / 7.4 = 6.1 [μm] (fifth lens group 50)
Is calculated.

  Therefore, in any case, it is understood that the moving pitch of the fourth lens group 40 or the fifth lens group 50 needs to be at least about 6 μm or less in order to keep the imaging element surface within the depth of focus. Further, considering mechanical backlash and the like, the movement pitch must actually be at least half of this value, which is impossible with a general actuator such as a pulse motor.

In the case of the present embodiment, this problem is solved by moving the fourth lens group 40 and the fifth lens group 50 in the same direction during focusing. For example, in this embodiment, it is assumed that the fourth lens group 40 and the fifth lens group 50 are moved by the same amount during focusing, and the imaging position with respect to the integral movement amount of the fourth lens group 40 and the fifth lens group 50 is determined. When calculating the ratio of the movement amount of
(Moving amount of imaging position) / (Moving amount of fourth lens group 40 and fifth lens group 50) = 0.6
Is calculated. Therefore, a focus lens group moving pitch for keeping the position of the image sensor within the depth of focus is greatly roughened, and a zoom lens system that can easily focus even if a general actuator is used for the optical system drive unit 105 is realized. I understand that I can do it.

  FIG. 3A shows the spherical aberration of the zoom lens 1 of the present embodiment at a focal length f = 6.4 mm. FIG. 3B similarly shows astigmatism of the zoom lens 1. FIG. 3C similarly shows distortion aberration of the zoom lens 1. FIG. 4A shows the spherical aberration of the zoom lens 1 of the present embodiment at the focal length f = 16.5 mm. FIG. 4B shows the astigmatism of the zoom lens 1 in the same manner. FIG. 4C similarly shows distortion aberration of the zoom lens 1. FIG. 5A shows the spherical aberration of the zoom lens 1 of the present embodiment at a focal length f = 42.6 mm. FIG. 5B similarly shows astigmatism of the zoom lens 1. FIG. 5C similarly shows distortion aberration of the zoom lens 1.

  3A, FIG. 4A, and FIG. 5A show spherical aberrations at the d-line and the g-line. In the spherical aberration diagram, the vertical axis represents the axial incident height. The MAX values of the on-axis incident heights in FIGS. 3A, 4A, and 5A are 0.90 mm, 2.06 mm, and 3.78 mm, respectively. 3 (b), 4 (b), and 5 (b), non-existence on the T plane (tangential plane, meridional plane (M plane, ΔM)) and S plane (sagittal plane) in the d line. Point aberration is shown. 3C, FIG. 4C, and FIG. 5C show distortion aberration at the d-line. In the graphs of astigmatism and distortion, + Y on the vertical axis indicates the image height. As shown in FIGS. 3 to 5, according to the zoom lens 1 of the present embodiment, spherical aberration, astigmatism, and distortion can be favorably corrected even when the focal length f is changed.

  The descriptions in the above embodiment and Example 1 are examples of a suitable zoom lens and imaging apparatus according to the present invention, and the present invention is not limited to this.

  For example, in the above embodiment and Example 1, the three lens groups (the second lens group 20, the fourth lens group 40, and the fifth lens group 50) are moved during zooming. However, the present invention is not limited to this. It is not a thing. A configuration may be adopted in which four or more lenses are moved during zooming.

  Moreover, in the said embodiment and Example 1, although it was set as the structure by which the parallel lens prism 12 was included in the 1st lens group 10, it is not limited to this. Another shape may be used as long as the optical path length is an equivalent prism. For example, a right-angle prism that bends the optical axis at a right angle may be used. Further, the number and combination of the positive lens and the negative lens included in each lens group of the zoom lens are not limited to the above embodiment and the example of the first example.

  In the above embodiment and Example 1, an example of a digital still camera has been described as an imaging device equipped with a zoom lens. However, the present invention is not limited to this, and a video camera, a mobile phone with an imaging function, It is good also as apparatuses, such as a portable terminal which has an imaging function at least, such as PHS (Personal Handyphone System) and PDA (Personal Digital Assistant).

  In addition, an imaging device equipped with a zoom lens may be used as an imaging unit installed in the device. Here, with reference to FIG. 6, an example of a mobile phone 200 equipped with an imaging unit 250 as an imaging device will be described. FIG. 6 shows an internal configuration of the mobile phone 200.

  As shown in FIG. 13, the mobile phone 200 has a control unit (CPU) 210 that performs overall control of each unit and executes a program corresponding to each process, and an operation unit 220 that inputs a number and the like using keys. A display unit 230 for displaying captured images in addition to predetermined data, a wireless communication unit 240 for realizing various information communication with an external server or the like via the antenna 241, and an imaging device An imaging unit 250, a storage unit (ROM) 260 storing necessary data such as a system program and various processing programs and a terminal ID of the mobile phone 200, and various processing programs and data executed by the control unit 210; Alternatively, a temporary storage unit (used as a work area for temporarily storing processing data or imaging data or the like by the imaging unit 250) AM) and a 270.

  The imaging unit 250 includes a zoom lens 1, a (solid-state) imaging device, a lens barrel, a drive mechanism for the zoom lens 1, and the like. The imaging unit 250 itself does not have a control unit or an image processing unit. The lens unit is assumed to be coupled to a control unit, an operation unit, a display unit, and the like by a connector or the like. Specifically, in the imaging unit 250, for example, the object-side end surface of the housing in the imaging optical system is provided on the back surface of the mobile phone 200 (the main display unit of the display unit 230 is the front), and below the main display unit. Is disposed at a position corresponding to. The external connection terminal of the imaging unit 250 is connected to the control unit 210 of the mobile phone 200 and outputs an image signal such as a luminance signal or a color difference signal to the control unit 210 side. The image signal input from the imaging unit 250 is stored in the storage unit 260 or displayed on the display unit 230 by the control system of the mobile phone 200, and is further displayed as video information via the wireless communication unit 240. Sent to the outside.

  An imaging unit as an imaging device equipped with a zoom lens includes the lens unit, a control unit, an image processing unit, and the like disposed on a substrate, and includes a display unit, an operation unit, and the like using connectors. You may comprise as a camera module on the assumption that it is couple | bonded and used separately.

It is a figure which shows the internal structure of the digital still camera 100 of embodiment which concerns on this invention. 1 is a diagram illustrating a configuration of a zoom lens 1 included in an optical system 101. FIG. (A) is a figure which shows the spherical aberration of the zoom lens 1 of the Example in the focal distance f = 6.4mm. (B) is a figure which shows the astigmatism of the zoom lens 1 similarly. (C) is a figure which similarly shows the distortion aberration of the zoom lens 1. FIG. (A) is a figure which shows the spherical aberration of the zoom lens 1 of the Example in the focal distance f = 16.5mm. (B) is a figure which shows the astigmatism of the zoom lens 1 similarly. (C) is a figure which similarly shows the distortion aberration of the zoom lens 1. FIG. (A) is a figure which shows the spherical aberration of the zoom lens 1 of the Example in the focal distance f = 42.6mm. (B) is a figure which shows the astigmatism of the zoom lens 1 similarly. (C) is a figure which similarly shows the distortion aberration of the zoom lens 1. FIG. 3 is a block diagram showing an internal configuration of a mobile phone 200. FIG.

Explanation of symbols

O1 Optical axis 100 Digital still camera 101 Optical system 1 Zoom lens 10 First lens group 11 Negative lens 12 Prism 13 Positive lens 14 Positive lens 20 Second lens group 21 Negative lens 22 Negative lens 23 Positive lens 30 Third lens group 31 Positive Lens 40 Fourth lens group 41 Positive lens 42 Negative lens 43 Positive lens 50 Fifth lens group 51 Negative lens 60 Sixth lens group 61 Positive lens D1 Aperture stop 71 Low-pass filter 102 Solid-state imaging device 103 A / D conversion unit 104 Control unit 105 Optical system drive unit 106 Timing generation unit 107 Image sensor drive unit 108 Image memory 109 Image processing unit 110 Image compression unit 111 Image recording unit 112 Display unit 113 Operation unit 200 Mobile phone 210 Control unit 220 Operation unit 230 Display unit 240 Wireless communication 241 Antenna 250 Imaging unit Doo 260 storage unit 270 temporary storage unit

Claims (8)

It has three or more lens groups that are moved along different tracks during zooming.
The lens group moved along different trajectories during zooming includes a first focusing lens group and a second focusing lens group that have different refractive powers and are moved in the same direction during focusing. lens. The first focusing lens group has a positive refractive power,
The second focusing lens group has negative refractive power;
The first focusing lens group and the second focusing lens group are:
1.0 <XA (XAmax) (1)
1.0 <XB (XAmax) (2)
0.5 <XA (XAmax) / XB (XAmax) <2 (3)
However,
| Ra / Fno |: absolute value of a value obtained by dividing the moving amount Ra of the imaging position when the first focusing lens group is slightly moved at an arbitrary zoom position by Fno at the zoom position,
| Rb / Fno |: When the movement amount Rb of the imaging position when the second focusing lens group is slightly moved at an arbitrary zoom position is the absolute value of the value divided by Fno at the zoom position ,
XA = | Ra / Fno |,
XB = | Rb / Fno |,
XA (XAmax): The maximum value of the XA value in the entire zoom range,
XB (XAmax): XB value at the zoom position where the XA value is maximum,
The zoom lens according to claim 1, wherein the following condition is satisfied. From the object side,
A first lens group having a positive refractive power fixed during zooming;
A second lens group having negative refractive power that moves during zooming;
A third lens group having positive refractive power fixed during zooming;
The first focusing lens group having a positive refractive power that moves during zooming;
The second focusing lens group having a negative refractive power that moves during zooming, and
The first focusing lens group and the second focusing lens group are moved either or both at the time of focusing, and both are moved at least during the fine adjustment of the focusing. The zoom lens according to 2.   4. The movement ratio of the first focusing lens group and the second focusing lens group can be changed between a coarse adjustment and a fine adjustment of the focusing. 5. Zoom lens. The first focusing lens group or the second focusing lens group is moved during the coarse adjustment of the focusing,
5. The zoom lens according to claim 1, wherein the first focusing lens group and the second focusing lens group are moved during fine adjustment of the focusing. 6.   6. The zoom lens according to claim 1, wherein a moving ratio of the first focusing lens group and the second focusing lens group during focusing is changed based on a zoom position.   The zoom lens according to any one of claims 1 to 6, wherein the first focusing lens group and the second focusing lens group are always moved at the same speed during focusing. A zoom lens according to any one of claims 1 to 7;
An image pickup apparatus comprising: an image pickup device that picks up light incident through the zoom lens.

Images