JP2006209100A - Zoom lens and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small sized zoom lens which is very useful for digital cameras or video cameras using a solid state imaging element with high pixel resolution, having high focusing characteristics and a variable power ratio of 5-7, as well as an imaging apparatus using the same. <P>SOLUTION: The zoom lens includes first lens unit G1 exhibiting a positive refractive power, second lens unit G2 exhibiting a negative refractive power, third lens unit G3 exhibiting a positive refractive power, fourth lens unit G4 exhibiting a positive refractive power, fifth lens unit G5 exhibiting a negative refractive power, wherein the first through fifth lens units are arranged along optical axis X in this order from an object side of the zoom lens. The second lens unit G2 is structured of a negative lens L4, a negative lens L5 and a positive lens L6, along the optical axis X in this order from an object side. Thus, the off-axial chromatic aberration in the entire zooming range can be effectively corrected. Further, when the variable power ratio is relatively high, the negative refractive power of the second lens unit G2 is shared by the two negative lenses L4 and L5, and thereby any aberration in the entire zoom lens system is effectively corrected, in particular, distortion and lateral chromatic aberration in the wide angle end can be satisfactorily corrected. In this case, at least one surface among the second lens unit G2 should be preferably an aspheric surface for the above effective correction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a zoom lens and an imaging apparatus for forming an optical image on a solid-state imaging device such as a CCD type image sensor or a CMOS type image sensor.

  2. Description of the Related Art In recent years, in a small-sized digital camera or video camera equipped with a small-sized image pickup unit equipped with a solid-state image pickup device such as a CCD (Charge Coupled Devices) type image sensor or a CMOS (Complementary Metal-Oxide Semiconductor) type image sensor, As the number of pixels increases, there is an increasing demand for zoom lenses that have higher imaging performance and higher magnification. Further, further miniaturization is required for the zoom lens of the small-sized imaging device.

As a small zoom lens for a small imaging device, for example, as disclosed in Patent Document 1, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive refractive power. The third lens group and a fourth lens group having a positive refractive power, and a prism that bends the optical path in the first lens group is arranged to reduce the thickness of the zoom lens in the thickness direction.
JP 2000-131610 A

  However, the zoom lens disclosed in Patent Document 1 has a zoom ratio as small as about 3 times, and its total length is long with respect to its focal length. On the other hand, there is a demand for a zoom lens for a compact image pickup apparatus that is more compact and has a high zoom ratio.

  The present invention has been made in view of the above-described problems, and has high imaging performance suitable for, for example, a digital camera or a video camera using a high-pixel solid-state imaging device, and a zoom ratio of 5 to 7 times. An object of the present invention is to provide a zoom lens of a small size and an imaging device using the same.

The zoom lens according to claim 1,
In order from the object side along the optical axis,
A first lens group having a positive refractive power and whose position on the optical axis is always fixed during zooming and focusing;
A second lens group having negative refractive power;
A third lens group having positive refractive power;
A fourth lens group having a positive refractive power;
A fifth lens group having negative refractive power,
Zooming is performed by moving at least the second lens group, the fourth lens group, and the fifth lens group;
The first lens group includes a reflective optical element having an action of bending a light path by reflecting a light beam,
The second lens group is configured in the order of one negative lens, one negative lens, and one positive lens from the object side along the optical axis.
The fourth lens group includes at least two positive lenses.

  According to the zoom lens of claim 1, from the object side along the optical axis, the first lens group having a positive refractive power, the second lens group having a negative refractive power, and a positive refractive power. By arranging the third lens group having the fourth lens group having a positive refractive power and the fifth lens group having a negative refractive power in this order, it is possible to achieve both high zooming and miniaturization. Can do. In addition, by configuring the second lens group in the order of one negative lens, one negative lens, and one positive lens from the object side along the optical axis, off-axis chromatic aberration in the entire zooming range is achieved. By effectively sharing the negative refracting power of the second lens group, which can be effectively corrected and increased with high magnification, between the two negative lenses, various aberrations of the entire zoom lens system can be corrected satisfactorily. It is possible to satisfactorily correct distortion and lateral chromatic aberration at the edge. In order to enhance the above effect, it is desirable that the second lens group has at least one aspherical shape. In addition, by forming the fourth lens group having a relatively large refractive power in the lens group including two positive lenses, it is possible to suppress the occurrence of spherical aberration, coma aberration, and field curvature.

  The zoom lens according to claim 2 is characterized in that, in the invention according to claim 1, the following conditional expression is satisfied.

ｆ１：前記第１レンズ群の焦点距離
ｆｗ：前記ズームレンズの広角端での焦点距離
ｆＴ：前記ズームレンズの望遠端での焦点距離

f1: Focal length fw of the first lens group fw: Focal length at the wide-angle end of the zoom lens fT: Focal length at the telephoto end of the zoom lens

  Conditional expression (1) is an expression for appropriately setting the focal length of the first lens group. By exceeding the lower limit, the refractive power of the first lens group does not become too strong, and the occurrence of aberration in the first lens group can be suppressed. Moreover, by being below the upper limit value, it is possible to appropriately ensure the positive refractive power of the first lens group, and it is possible to shorten the overall length of the zoom lens. In addition, the range of the following formula is more desirable.

  A zoom lens according to a third aspect of the invention is characterized in that, in the invention according to the first or second aspect, the following conditional expression is satisfied.

ｆ２：前記第２レンズ群の焦点距離
ｆｗ：前記ズームレンズの広角端での焦点距離
ｆＴ：前記ズームレンズの望遠端での焦点距離

f2: focal length of the second lens group fw: focal length at the wide-angle end of the zoom lens fT: focal length at the telephoto end of the zoom lens

  Conditional expression (2) is an expression for appropriately setting the focal length of the second lens group. By exceeding the lower limit value, the negative refractive power of the second lens group can be appropriately maintained, and the amount of movement of the second lens group can be reduced to obtain a desired zoom ratio. The overall length of the lens can be shortened. Further, by being below the upper limit value, the negative refractive power of the second lens group does not become too large, and the occurrence of aberration in the second lens group can be suppressed. In addition, the range of the following formula is more desirable.

A zoom lens according to a fourth aspect of the invention is characterized in that, in the invention according to any one of the first to third aspects, the following conditional expression is satisfied.
n _2p > 1.80 (3)
ν _2P <26.0 (4)
n _2p : Refractive index ν _2P of the positive lens of the second lens group at the d-line: Abbe number of the positive lens of the second lens group at the d-line

Conditional expression (3) sets the refractive index of the positive lens of the second lens group more appropriately, and conditional expression (4) sets the Abbe number of the positive lens of the second lens group more appropriately. It is for setting. If the value n _2p exceeds the lower limit in the conditional expression (3) and the value ν _2P falls below the upper limit in the conditional expression (4), on-axis and off-axis chromatic aberrations in the entire zooming range are effectively reduced. It can be corrected. The following range is desirable.
n _2p > 1.85 (3 ′)
ν _2P <23.0 (4 ')

  According to a fifth aspect of the present invention, in the zoom lens according to any one of the first to fourth aspects, the position of the third lens group on the optical axis is always fixed during zooming and focusing. Features.

  According to the zoom lens of claim 5, the position of the third lens group in the optical axis direction is always fixed at the time of zooming and focusing, so that the lens driving mechanism of, for example, an imaging apparatus equipped with such a zoom lens is mounted. Can be simplified.

  A zoom lens according to a sixth aspect is the invention according to any one of the first to fifth aspects, wherein the third lens group has an aperture stop on the object side or the image side on the optical axis, and has at least one surface. It is characterized by comprising only one positive lens having an aspherical shape.

  According to the zoom lens of claim 6, the aperture stop is disposed close to the third lens group, and the third lens group is constituted by a single lens having at least one aspherical shape, Spherical aberration, coma aberration, and field curvature can be effectively corrected while securing a moving space for the second lens group and the fourth lens group. Also, by arranging the aperture stop on the object side of the third lens group, the entrance pupil position can be brought closer to the object side on the optical axis, and the most object side on the optical axis of the first lens group. This is more desirable because the diameter of the lens and the reflective optical element can be reduced, and thus the thickness of the imaging device in the thickness direction can be reduced.

  According to a seventh aspect of the present invention, in the zoom lens according to any one of the first to sixth aspects, the fourth lens group includes a positive lens, a negative lens, and a positive lens in this order from the object side. And

  According to the zoom lens according to claim 7, a so-called triplet type in which the fourth lens group having a relatively strong imaging action among the lens groups is arranged in order of the positive lens, the negative lens, and the positive lens from the object side. Thus, spherical aberration, coma aberration, and field curvature can be effectively corrected.

  A zoom lens according to an eighth aspect of the present invention is the zoom lens according to any of the first to seventh aspects, wherein the fourth lens group includes a cemented lens in which a positive lens and a negative lens are cemented.

  According to the zoom lens of the eighth aspect, by including the cemented lens in which the positive lens and the negative lens are cemented, one lens element constituting the fourth lens group is reduced, and the position of each lens is related to the cemented lens. There is no need to make adjustments, and manufacturing is facilitated, so that high mass productivity can be obtained.

  A zoom lens according to a ninth aspect is the invention according to any one of the first to eighth aspects, wherein the fifth lens group includes only one negative lens.

  According to the zoom lens of claim 9, by configuring the fifth lens group with a single lens having a negative refractive power, it is possible to effectively suppress spherical aberration while securing a moving space of the fourth lens group. Further, by having a negative refractive power, the Petzval sum of the entire zoom lens system is reduced, and the curvature of field can be corrected well.

  A zoom lens according to a tenth aspect is the invention according to any one of the first to ninth aspects, wherein focusing is performed by moving the fourth lens group or the fifth lens group in an optical axis direction. Features.

  By moving any one of the fourth lens group and the fifth lens group for focusing, the lens driving mechanism and the driving algorithm at the time of focusing can be simplified.

  The zoom lens according to claim 11 performs focusing by moving the fourth lens group and the fifth lens group in the direction of the optical axis in the invention according to any one of claims 1 to 9. Features.

  If the focal position change with respect to the movement amount in the optical axis direction of either one of the fourth lens group and the fifth lens group, or both lens groups is large, focusing is possible with a small movement amount. While there is an advantage, it is necessary to move the moving group (referred to as a moving lens group) with high precision in order to focus accurately. Depending on the actuator that moves the moving group, it may be difficult to move a minute amount. In such a case, if the fourth and fifth lens groups are moved together during focusing, By doing so, it is possible to reduce the focal position change with respect to the movement amount in the optical axis direction. In addition, the movement amounts of the fourth lens group and the fifth lens group do not need to be completely matched, and an optimum movement amount is determined and moved in consideration of aberration performance when focusing on a close object. May be.

  A zoom lens according to a twelfth aspect is the invention according to any one of the first to eleventh aspects, wherein the zoom lens includes the first lens group, the second lens group, the third lens group, and the fourth lens group. It is characterized by having a five-group configuration of a lens group and the fifth lens group.

  According to the zoom lens of the twelfth aspect, the zoom lens having a five-group configuration can provide a zoom lens having a small number of lenses and a low cost and a short overall length.

  A zoom lens according to a thirteenth aspect is the invention according to any one of the first to eleventh aspects, wherein the zoom lens includes the first lens group, the second lens group, the third lens group, and the fourth lens group. It has a six-group configuration including a lens group, the fifth lens group, and the sixth lens group.

  With the zoom lens having a six-group configuration, it is possible to correct aberrations satisfactorily while ensuring good image-side telecentric characteristics, and to obtain a zoom lens having a short overall length at low cost. Further, by fixing the most image side sixth lens group on the optical axis, the sealing member of the image sensor and the image sensor surface can be covered, so that it is possible to suppress the adhesion of dust and the like to them. This is more desirable.

  According to a fourteenth aspect of the present invention, in the zoom lens according to the thirteenth aspect, the sixth lens group has a positive refractive power and has at least one aspherical shape.

  According to the zoom lens of claim 14, by arranging the sixth lens group having a positive refractive power in addition to the fifth lens group having a negative refractive power, the refractive powers of both lens groups are increased. Accordingly, various aberrations of the entire zoom lens system can be effectively corrected while ensuring good image-side telecentric characteristics. Further, by having at least one aspherical shape, it is possible to effectively correct curvature of field and distortion while ensuring good image-side telecentric characteristics at a high angle of view.

  An imaging apparatus according to a fifteenth aspect includes the zoom lens according to any one of the first to fourteenth aspects and an imaging element.

  According to the present invention, for example, a compact zoom lens having a high imaging performance and a zoom ratio of about 5 to 7 times suitable for a digital camera or a video camera using a high-pixel solid-state imaging device, and the like The used imaging device can be provided.

  With reference to FIG.1 and FIG.2, the imaging device 100 carrying the zoom lens concerning embodiment of this invention is demonstrated. FIG. 1 is a block diagram of the imaging apparatus 100.

  As illustrated in FIG. 1, the imaging apparatus 100 includes a zoom lens 101, a solid-state imaging device 102, an A / D conversion unit 103, a control unit 104, an optical system driving unit 105, a timing generation unit 106, and imaging. An element driving unit 107, an image memory 108, an image processing unit 109, an image compression unit 110, an image recording unit 111, a display unit 112, and an operation unit 113 are configured.

  The zoom lens 101 has a function of forming a subject image on the imaging surface of the solid-state imaging device 102. The solid-state image sensor 102 is an image sensor 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 imaging device 100. The control unit 104 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory), and various programs read out from the ROM and expanded in the RAM, and various in cooperation with the CPU. Execute the process.

  The optical system driving unit 105 controls the zoom lens 101 in zooming, focusing (movement of a second lens group G2, a fourth lens group G4, and a fifth lens group G5 described later), exposure, and the like under the control of the control unit 104. Is 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 a memory 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 imaging apparatus 100 will be described. In subject photographing, subject monitoring (through image display) and image photographing execution are performed. In monitoring, an image of a subject obtained through the zoom lens 101 is formed on the light receiving surface of the solid-state image sensor 102. A solid-state imaging device 102 disposed behind the photographing optical axis of the zoom lens 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, zooming, focusing, exposure, and the like of the zoom lens 101 are set by driving the optical system driving unit 105 based on an operation input through the operation unit 113 by the user.

  In such a monitoring state, still image data is photographed when the user operates the release button of the operation unit 113 at the timing at which still image photographing is desired. In response to the operation of the release button, 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.

  Note that the description in each of the above embodiments and examples is an example of a preferable zoom lens and imaging apparatus according to the present invention, and the present invention is not limited to this.

  For example, in each of the above embodiments and examples, an example of a digital still camera has been described as an image pickup apparatus equipped with a zoom lens. However, the present invention is not limited to this, and a video camera or a mobile phone with an image pickup function is described. It may be a device such as a portable terminal having at least an imaging function, 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. 2, an example of a mobile phone 300 on which the imaging apparatus 100 is mounted will be described. FIG. 2 is a block diagram showing an internal configuration of the mobile phone 300.

  As shown in FIG. 2, the mobile phone 300 has a control unit (CPU) 310 that performs overall control of each unit and executes a program corresponding to each process, and an operation unit 320 that inputs a number and the like using keys. A display unit 330 that displays captured images in addition to predetermined data, a wireless communication unit 340 for realizing various information communication with an external server or the like via the antenna 341, and the imaging apparatus 100. A storage unit (ROM) 360 that stores necessary data such as a system program, various processing programs, and a terminal ID of the mobile phone 100; various processing programs and data executed by the control unit 310; Alternatively, the imaging apparatus 100 includes a temporary storage unit (RAM) 370 that is used as a work area for temporarily storing imaging data and the like. There.

  Note that the control unit 104 of the imaging apparatus 100 and the control unit 310 of the mobile phone 300 are communicably connected. In such a case, the functions of the display unit 112 and the operation unit 113 shown in FIG. However, the operation of the imaging apparatus 100 itself is basically the same. More specifically, an external connection terminal (not shown) of the imaging device 100 is connected to the control unit 310 of the mobile phone 300, and a release signal is transmitted from the mobile phone 300 side to the imaging device 100 side and obtained by imaging. Image signals such as luminance signals and color difference signals are output from the imaging apparatus 100 side to the control unit 310 side. Such an image signal can be stored in the storage unit 360 or displayed on the display unit 330 by the control system of the mobile phone 300, and further transmitted to the outside as video information via the wireless communication unit 340. .

  In addition, an image pickup apparatus equipped with a zoom lens is arranged with a control unit and an image processing unit arranged on a substrate, and is coupled to a separate unit having a display unit and an operation unit by a connector or the like. You may comprise as a camera module on the assumption that it is used.

Examples of the zoom lens that can be used in the imaging apparatus 100 of FIG. 1 will be described below, but the present invention is not limited to this. Symbols used in each example are as follows.
f: Focal length r of the entire zoom lens system r: radius of curvature d: axial top surface spacing nd: refractive index νd of lens material with respect to d-line: Abbe number of lens material

  In each embodiment, the shape of the aspherical surface is expressed by the following formula, where the vertex of the surface is the origin, the X axis is taken in the optical axis direction, and the height in the direction perpendicular to the optical axis is h.

In the following (including the lens data in the table), a power of 10 (for example, 2.5 × 10 ⁻⁰² ) is expressed using E (for example, 2.5E-02).

Example 1
[specification]
Focal length: f = 6.40 mm to 16.50 mm to 42.60 mm
Angle of view: 2ω = 63.4 ° to 24.4 ° to 9.5 °

  Table 1 shows lens data of the zoom lens according to the first example. FIG. 3 is a cross-sectional view of the zoom lens according to the first example. FIG. 4 is an aberration diagram of spherical aberration, astigmatism, and distortion of the zoom lens according to the first example. Here, FIG. 4A is an aberration diagram at a focal length of 6.40 mm. FIG. 4B is an aberration diagram when the focal length is 16.50 mm. FIG. 4C is an aberration diagram when the focal length is 42.60 mm.

  The zoom lens of Example 1 includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, and a first lens having a positive refractive power in order from the object side along the optical axis X. 3 lens group G3, 4th lens group G4 of positive refractive power, 5th lens group G5 of negative refractive power, 6th lens group G6 of positive refractive power, and at the time of zooming from the wide angle end to the telephoto end The positions of the first lens group G1, the third lens group G3, the sixth lens group G6, and the aperture stop S on the optical axis are unchanged, and the first lens group G1 is changed during zooming from the wide angle end to the telephoto end. The second lens group G2 moves so that the distance between the second lens group G2 and the fourth lens group G4 moves so that the distance between the third lens group G3 and the fourth lens group G4 decreases, and the fifth lens The fifth lens group G5 is moved so that the distance between the group G5 and the sixth lens group G6 is widened. At least the fourth lens group G4 or the fifth lens group G5 move on the optical axis. Although focusing can be performed by moving any of the moving groups, the second lens group G2 has a large change in focal length with respect to the amount of movement in the optical axis direction. It is not preferable to move the second lens group G2 because the variation in the angle of view is conspicuous. Further, since the fourth lens group G4 and the fifth lens group G5 have a large focal position change with respect to the movement amount in the optical axis direction, there is an advantage that focusing is possible with a small movement amount. On the other hand, it is necessary to move the moving group with high accuracy in order to achieve accurate focusing. Depending on the actuator that moves the moving group, a small amount of movement may be difficult. In such a case, the fourth lens group G4 and the fifth lens group G5 are moved together during focusing. By doing so, the focal position change with respect to the movement amount in the optical axis direction can be reduced. Further, the movement amounts of the fourth lens group G4 and the fifth lens group G5 do not need to be completely matched, and the optimum movement amount is determined and moved in consideration of the aberration performance at the time of focusing on a short distance object. May be. Although not shown, when the mechanical shutter is changed from the wide-angle end to the telephoto end, a mechanism for moving the mechanical shutter is not necessary by arranging the mechanical shutter in the vicinity of the aperture stop S whose position on the optical axis is unchanged. Therefore, the thickness of the imaging device in the thickness direction can be reduced.

  The first lens group G1 includes a negative lens L1 having an aspheric shape on the image side, a prism P2 having a function of bending a light path by reflecting light, a positive lens L3, and a positive lens L4. The group G2 includes a negative lens L5 having an aspheric shape on the image side, and a cemented lens in which the negative lens L6 and the positive lens L7 are cemented. The third lens group G3 is a positive lens having an aspheric shape on the object side. It consists only of the lens L8 (however, in the present invention, the aperture stop S may be included in the third lens group G3. The same applies hereinafter), and the fourth lens group G4 is joined to the positive lens L9 and the negative lens L10. And a positive plastic lens L11 having a double-sided aspheric shape. The fifth lens group G5 is composed only of a negative lens L12. The sixth lens group G6 has a double-sided aspheric shape. Only consisting of a positive plastic lens L13 that. Between the sixth lens group G6 and the imaging surface of the solid-state imaging device IM, a low-pass filter LP having an optical surface with an infrared cut coat and a seal glass SG covering the imaging surface of the solid-state imaging device IM are arranged. ing. In this embodiment, the position of the aspheric surface is arranged as described above, but it is not necessary to limit to this.

(Example 2)
[specification]
Focal length: f = 6.30 mm to 16.30 mm to 41.90 mm
Angle of view: 2ω = 62.8 ° to 24.8 ° to 9.9 °

  Table 2 shows lens data of the zoom lens according to the second example. FIG. 5 is a cross-sectional view of the zoom lens according to Example 2, and FIG. 6 is an aberration diagram of spherical aberration, astigmatism, and distortion of the zoom lens according to Example 2. Here, FIG. 6A is an aberration diagram at a focal length of 6.30 mm. FIG. 6B is an aberration diagram when the focal length is 16.30 mm. FIG. 6C is an aberration diagram when the focal length is 41.90 mm.

  The zoom lens of Example 2 includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, and a first lens having a positive refractive power in order from the object side along the optical axis X. 3 lens group G3, 4th lens group G4 of positive refractive power, 5th lens group G5 of negative refractive power, 6th lens group G6 of positive refractive power, and at the time of zooming from the wide angle end to the telephoto end The positions of the first lens group G1, the third lens group G3, the sixth lens group G6, and the aperture stop S on the optical axis are unchanged, and the first lens group G1 is changed during zooming from the wide angle end to the telephoto end. The second lens group G2 moves so that the distance between the second lens group G2 and the fourth lens group G4 moves so that the distance between the third lens group G3 and the fourth lens group G4 decreases, and the fifth lens The fifth lens group G5 is moved so that the distance between the group G5 and the sixth lens group G6 is widened. At least the fourth lens group G4 or the fifth lens group G5 move on the optical axis. Although focusing can be performed by moving any of the moving groups, the second lens group G2 has a large change in focal length with respect to the amount of movement in the optical axis direction. It is not preferable to move the second lens group G2 because the variation in the angle of view is conspicuous. Further, since the fourth lens group G4 and the fifth lens group G5 have a large focal position change with respect to the movement amount in the optical axis direction, there is an advantage that focusing is possible with a small movement amount. On the other hand, it is necessary to move the moving group with high accuracy in order to achieve accurate focusing. Depending on the actuator that moves the moving group, a small amount of movement may be difficult. In such a case, the fourth lens group G4 and the fifth lens group G5 are moved together during focusing. By doing so, the focal position change with respect to the movement amount in the optical axis direction can be reduced. Further, the movement amounts of the fourth lens group G4 and the fifth lens group G5 do not need to be completely matched, and the optimum movement amount is determined and moved in consideration of the aberration performance at the time of focusing on a short distance object. May be. Although not shown, when the mechanical shutter is zoomed from the wide-angle end to the telephoto end, it is not necessary to have a mechanism for moving the mechanical shutter by arranging it near the aperture stop whose position on the optical axis is unchanged. Therefore, the thickness of the imaging device in the thickness direction can be reduced.

  The first lens group G1 includes a negative lens L1, a prism P2 having a function of bending an optical path by reflecting a light beam, a positive lens L3, and a positive lens L4 having an aspheric shape on the object side. The group G2 includes a negative lens L5 having an aspheric shape on the image side, and a cemented lens in which the negative lens L6 and the positive lens L7 are cemented. The third lens group G3 is a positive lens having an aspheric shape on the object side. The fourth lens group G4 includes only a lens L8. The fourth lens group G4 includes a cemented lens in which a positive lens L9 and a negative lens L10 are cemented with each other, and a positive plastic lens L11 having a double-sided aspheric shape. The fifth lens group G5 includes: The sixth lens group G6 includes only a negative lens L12, and the sixth lens group G6 includes only a positive plastic lens L13 having a double-sided aspheric shape. Between the sixth lens group G6 and the imaging surface of the solid-state imaging device IM, a low-pass filter LP having an optical surface with an infrared cut coat and a seal glass SG covering the imaging surface of the solid-state imaging device IM are arranged. ing. In this embodiment, the position of the aspheric surface is arranged as described above, but it is not necessary to limit to this.

(Example 3)
[specification]
Focal length: f = 6.30mm-13.70mm-30.00mm
Angle of view: 2ω = 62.2 ° -28.9 ° -13.4 °

  Table 3 shows lens data of the zoom lens according to the third example. FIG. 7 is a cross-sectional view of the zoom lens according to the first example, and FIG. 8 is an aberration diagram of spherical aberration, astigmatism, and distortion of the zoom lens according to the third example. Here, FIG. 8A is an aberration diagram at a focal length of 6.30 mm. FIG. 8B is an aberration diagram when the focal length is 13.70 mm. FIG. 8C is an aberration diagram when the focal length is 30.00 mm.

  The zoom lens according to the third exemplary embodiment includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, and a first lens having a positive refractive power in order from the object side along the optical axis X. 3 lens group G3, 4th lens group G4 of positive refracting power, 5th lens group G5 of negative refracting power, and at the time of zooming from wide angle end to telephoto end, 1st lens group G1, 3rd lens group The position of G3 and the aperture stop S on the optical axis is unchanged, and the second lens group G2 is arranged so that the distance between the first lens group G1 and the second lens group G2 is widened upon zooming from the wide-angle end to the telephoto end. And the fourth lens group G4 moves so that the distance between the third lens group G3 and the fourth lens group G4 is reduced. At the time of focusing, at least the fourth lens group G4 or the fifth lens group G5 is on the optical axis. To move. Although focusing can be performed by moving any of the moving groups, the second lens group G2 has a large change in focal length with respect to the amount of movement in the optical axis direction. It is not preferable to move the second lens group G2 because the variation in the angle of view is conspicuous. Further, in this embodiment, since the negative refractive power of the fifth lens group G5 is not strong compared to the first and second embodiments having the sixth lens group G6 having a positive refractive power, the fourth lens group G4 and the fifth lens group G5. Since the focal position change with respect to the movement amount of the lens group G5 in the optical axis direction is not so large, the fourth lens group G4 or the fifth lens group G5 may be moved alone to perform focusing. Although not shown, when the mechanical shutter is zoomed from the wide-angle end to the telephoto end, it is not necessary to have a mechanism for moving the mechanical shutter by arranging it near the aperture stop whose position on the optical axis is unchanged. Therefore, the thickness of the imaging device in the thickness direction can be reduced.

  The first lens group G1 includes a negative lens L1, a prism P2 having a function of bending a light path by reflecting a light beam, and a positive lens L3 having a double-sided aspheric shape. The second lens group G2 includes a negative lens L4. And a cemented lens in which a negative lens L5 and a positive lens L6 are cemented. The third lens group G3 is composed only of a positive lens L7 having an aspheric shape on the object side, and the fourth lens group G4 is composed of an object side. The fifth lens group G5 is composed of only a negative plastic lens L11 having a double-sided aspherical shape. The positive lens L8 has an aspherical shape and a cemented lens in which the negative lens L9 and the positive lens 10 are cemented. Between the fifth lens group G5 and the imaging surface of the solid-state imaging device IM, a low-pass filter LP having an optical surface with an infrared cut coat and a seal glass SG covering the imaging surface of the solid-state imaging device IM are arranged. ing. In this embodiment, the position of the aspheric surface is arranged as described above, but it is not necessary to limit to this.

Example 4
[specification]
Focal length: f = 6.49 mm to 14.46 mm to 43.16 mm
Angle of view: 2ω = 60.6 ° -27.2 ° -9.2 °

  Table 4 shows lens data of the zoom lens according to the fourth example. FIG. 9 is a cross-sectional view of the zoom lens according to Example 4, and FIG. 10 is an aberration diagram of spherical aberration, astigmatism, and distortion of the zoom lens according to Example 4. FIG. 10A is an aberration diagram when the focal length is 6.49 mm. FIG. 10B is an aberration diagram at a focal length of 14.46 mm. FIG. 10C is an aberration diagram when the focal length is 43.16 mm.

  The zoom lens according to the fourth exemplary embodiment includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, and a first lens having a positive refractive power in order from the object side along the optical axis X. 3 lens group G3, 4th lens group G4 of positive refractive power, 5th lens group G5 of negative refractive power, 6th lens group G6 of positive refractive power, and at the time of zooming from wide angle end to telephoto end The positions of the first lens group G1, the third lens group G3, the sixth lens group G6, and the aperture stop S on the optical axis are unchanged, and the first lens group G1 is changed during zooming from the wide-angle end to the telephoto end. The second lens group G2 is moved so that the distance between the second lens group G2 and the fourth lens group G4 is moved so that the distance between the third lens group G3 and the fourth lens group G4 is narrowed. The fifth lens group G5 is moved so that the distance between the group G5 and the sixth lens group G6 is widened. At least the fifth lens group G5 moves toward the image side in the optical axis direction. Although focusing can be performed by moving any moving group among all the moving groups, the second lens group G2 has a large focal length change with respect to the moving amount in the optical axis direction, so that it is photographed before and after focusing. It is not preferable to move the second lens group G2 because the variation in the angle of view is conspicuous. Further, since the fourth lens group G4 and the fifth lens group G5 have a relatively large focal position change with respect to the movement amount in the optical axis direction, there is an advantage that focusing is possible with a small movement amount. On the other hand, it is necessary to move the moving group with high accuracy in order to achieve accurate focusing. Depending on the actuator that moves the moving group, it may be difficult to move a minute amount. In such a case, the fourth lens group G4 and the fifth lens group G5 are moved together during focusing. By doing so, the focal position change with respect to the movement amount in the optical axis direction can be reduced. Further, the movement amounts of the fourth lens group G4 and the fifth lens group G5 do not need to be completely matched, and the optimum movement amount is determined and moved in consideration of the aberration performance at the time of focusing on a close object. May be. Further, when the mechanical shutter is zoomed from the wide-angle end to the telephoto end, by disposing the mechanical shutter in the vicinity of the aperture stop S where the position on the optical axis is unchanged, a mechanism for moving the mechanical shutter becomes unnecessary. The thickness in the thickness direction can be reduced.

  The first lens group G1 includes a negative lens L1, a prism P2 having a function of bending a light path by reflecting a light beam, a positive lens L3, and a positive lens L4. The second lens group G2 includes a negative lens L5 and a negative lens L5. The third lens group G3 is composed only of a positive glass mold lens L8 having an aspheric shape on the object side, and the fourth lens group G4 is negative with the positive lens L9. The fifth lens group G5 is composed only of a negative plastic lens L12 having a double-sided aspheric shape, and is composed of only a three-lens cemented lens in which a lens L10 and a positive glass mold lens L11 having an aspheric shape on the image side are cemented. The sixth lens group G6 comprises solely a positive plastic lens L13 having a double-sided aspheric shape. Further, between the sixth lens group G6 and the imaging surface of the solid-state imaging device IM, an infrared cut filter IRCF having an infrared cut coat on the optical surface and a seal glass SG covering the imaging surface of the solid-state imaging device IM are arranged. Has been. In this embodiment, the position of the aspheric surface is arranged as described above, but it is not necessary to limit to this.

  Table 5 summarizes the values of the equations (1) and (2) corresponding to the above-described embodiment.

In the above-described embodiments, the prism is used as the reflective optical element having the function of bending the optical path by reflecting the light beam. However, the present invention is not limited to this. For example, a mirror may be used. By configuring the reflective optical element with a prism, the diameter of the light beam passing through the reflective optical system is reduced, so that the prism can be reduced in size and the thickness in the thickness direction of the imaging device can be reduced. It is desirable that the prism be made of a material that satisfies the following conditional expression.
ndp> 1.7 (5)
ndp: Refractive index at the d-line of the prism

  Conditional expression (5) is an expression defining the range of the refractive index of the prism material. By exceeding the lower limit, the diameter of the light beam passing through the prism is reduced, so that the prism can be miniaturized and the thickness of the imaging device in the thickness direction can be reduced.

  In the above-described embodiment, the optical path is bent 90 degrees in the same direction as the long side direction of the image pickup device by the prism for bending the optical path, but the optical axis is bent in the same direction as the short side direction of the image pickup device. Such a design may be used. In the case of bending the optical path in the short side direction, the size of the prism can be reduced, which is convenient for downsizing the zoom lens.

  The “thickness direction of the imaging device” in this specification refers to the same direction as the optical axis direction of the incident surface in the reflective optical element of the first lens group.

  In particular, a zoom lens used in an image pickup apparatus including a solid-state image pickup device is required to be image side telecentric in order to obtain good light receiving sensitivity over the entire screen. Image-side telecentric means that the principal ray enters the imaging surface of the solid-state imaging device at an angle parallel to the optical axis at each image height. In recent years, it has become possible to correct the image-side telecentric dissatisfaction amount by appropriately arranging a microlens array on the imaging surface of a solid-state imaging device.

  In the present invention, the term “plastic lens” includes a lens having a plastic material as a base material, molded from a material in which small-diameter particles are dispersed in the plastic material, and having a plastic volume ratio of more than half, This includes the case where the surface is coated for the purpose of preventing reflection and improving surface strength.

1 is a block diagram of an imaging apparatus 100. FIG. 4 is a block diagram showing an internal configuration of a mobile phone 300. FIG. 1 is a cross-sectional view of a zoom lens according to Example 1. FIG. FIG. 4A is an aberration diagram of spherical aberration, astigmatism, and distortion of the zoom lens according to Example 1, FIG. 4A is an aberration diagram with a focal length of 6.40 mm, and FIG. FIG. 4C is an aberration diagram with a focal length of 42.60 mm. 6 is a cross-sectional view of a zoom lens according to Example 2. FIG. FIG. 6A is an aberration diagram of spherical aberration, astigmatism, and distortion of the zoom lens according to Example 2, FIG. 6A is an aberration diagram of a focal length of 6.30 mm, and FIG. FIG. 6C is an aberration diagram with a focal length of 41.90 mm. 7 is a cross-sectional view of a zoom lens according to Example 3. FIG. FIG. 8A is an aberration diagram of spherical aberration, astigmatism, and distortion of the zoom lens according to Example 3, FIG. 8A is an aberration diagram of a focal length of 6.30 mm, and FIG. FIG. 8C is an aberration diagram at a focal length of 30.00 mm. 6 is a cross-sectional view of a zoom lens according to Example 4; FIG. FIGS. 10A and 10B are aberration diagrams of spherical aberration, astigmatism, and distortion of the zoom lens according to Example 4, FIG. 10A is an aberration diagram with a focal length of 6.49 mm, and FIG. FIG. 10C is an aberration diagram with a focal length of 43.16 mm.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Imaging device 101 Zoom lens 102 Solid-state image sensor 103 Conversion part 104 Control part 105 Optical system drive part 106 Timing generation part 107 Image sensor drive part 108 Image memory 109 Image processing part 110 Image compression part 111 Image recording part 112 Display part 113 Operation | movement Unit 113 operation unit 300 mobile phone 310 control unit 320 operation unit 330 display unit 340 wireless communication unit 341 antenna 360 storage unit G1 to G6 lens group L1 to L13 lens LP low pass filter P2 prism S aperture stop SG seal glass IM solid-state imaging device

Claims (15)

In order from the object side along the optical axis,
A first lens group having a positive refractive power and whose position on the optical axis is always fixed during zooming and focusing;
A second lens group having negative refractive power;
A third lens group having positive refractive power;
A fourth lens group having a positive refractive power;
A fifth lens group having negative refractive power,
Zooming is performed by moving at least the second lens group, the fourth lens group, and the fifth lens group;
The first lens group includes a reflective optical element having an action of bending a light path by reflecting a light beam,
The second lens group is configured in the order of one negative lens, one negative lens, and one positive lens from the object side along the optical axis.
The zoom lens according to claim 4, wherein the fourth lens group includes at least two positive lenses. The zoom lens according to claim 1, wherein the following conditional expression is satisfied.

f1: Focal length fw of the first lens group fw: Focal length at the wide-angle end of the zoom lens fT: Focal length at the telephoto end of the zoom lens The zoom lens according to claim 1, wherein the following conditional expression is satisfied.

f2: focal length of the second lens group fw: focal length at the wide-angle end of the zoom lens fT: focal length at the telephoto end of the zoom lens The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
n _2p > 1.80 (3)
ν _2P > 26.0 (4)
n _2p : Refractive index ν _2P of the positive lens of the second lens group at the d-line: Abbe number of the positive lens of the second lens group at the d-line   5. The zoom lens according to claim 1, wherein the position of the third lens group on the optical axis is always fixed during zooming and focusing.   2. The third lens group includes an aperture stop on the object side or the image side on the optical axis, and includes only one positive lens having at least one aspherical shape. The zoom lens according to any one of?   The zoom lens according to claim 1, wherein the fourth lens group is configured in the order of a positive lens, a negative lens, and a positive lens from the object side.   The zoom lens according to claim 1, wherein the fourth lens group includes a cemented lens in which a positive lens and a negative lens are cemented.   The zoom lens according to any one of claims 1 to 8, wherein the fifth lens group includes only one negative lens.   The zoom lens according to any one of claims 1 to 9, wherein focusing is performed by moving the fourth lens group or the fifth lens group in an optical axis direction.   The zoom lens according to claim 1, wherein focusing is performed by moving the fourth lens group and the fifth lens group in an optical axis direction.   The zoom lens has a five-group configuration including the first lens group, the second lens group, the third lens group, the fourth lens group, and the fifth lens group. The zoom lens according to any one of the above.   The zoom lens has a six-group configuration including the first lens group, the second lens group, the third lens group, the fourth lens group, the fifth lens group, and the sixth lens group. The zoom lens according to claim 1.   The zoom lens according to claim 13, wherein the sixth lens group has a positive refractive power and has at least one aspherical shape. An image pickup apparatus comprising the zoom lens according to claim 1 and an image pickup device.

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