JP2006113363A - Zoom lens and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the image forming performance of a compact zoom lens which is suitably used for equipment using a mega-pixel solid-state image pickup element and whose variable power ratio is about 3. <P>SOLUTION: The zoom lens 1 includes a 1st lens group 10 having positive refractive power, whose position in an optical axis direction is always fixed in the case of variable power and focusing; a 2nd lens group 20 having negative refractive power; a 3rd lens group 30 having positive refractive power; and a 4th lens group 40 having positive refractive power in order from an object side along an optical axis O. In the zoom lens 1, at least the 2nd lens group 20 and the 4th lens group 40 are moved in the optical axis O direction so as to perform the variable power and at least the 4th lens group 40 is moved in the optical axis O direction so as to perform the focusing. The 1st lens group 10 includes a prism 13 as a catoptric element for bending an optical path and at least one plastic lens. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a zoom lens and an imaging apparatus equipped with the zoom lens.

  In recent years, in devices such as small digital still cameras and video cameras equipped with small imaging units equipped with solid-state imaging devices such as CCD (Charge Coupled Devices) type image sensors or CMOS (Complementary Metal-Oxide Semiconductor) type image sensors. As the number of pixels of a solid-state image sensor increases, there is an increasing demand for a zoom lens having higher imaging performance. Further, further miniaturization is demanded for the zoom lens of the small imaging device.

As a small zoom lens for a small image pickup device, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive refractive power. Some zoom lenses are made thin in the thickness direction by arranging a prism that bends the optical path in the first lens group and includes a fourth lens group (see, for example, Patent Document 1).
JP 2000-131610 A

  However, the conventional zoom lens as disclosed in Patent Document 1 has a long total length compared to its focal length, and if many of the lenses constituting the zoom lens are made of a glass material, the weight becomes heavy. As a result, the impact resistance is also lowered, so that it is unsuitable for use in, for example, a small-sized imaging device mounted on a mobile phone or a portable information terminal.

  The present invention has been made in view of the above problems, and has a high imaging performance suitable for use in devices such as a digital still camera and a video camera using a high-pixel solid-state imaging device, and has a zoom ratio of 3 An object of the present invention is to provide a zoom lens that is about twice as small and an image pickup apparatus equipped with this zoom lens.

In order to solve the above-mentioned problem, the invention described in claim 1
In order from the object side along the optical axis,
A first lens group having a positive refractive power and whose position in the optical axis direction 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,
At least the second lens group and the fourth lens group are moved in the optical axis direction for zooming, and at least the fourth lens group is moved in the optical axis direction for focusing.
The first lens group is a zoom lens including a reflective optical element for bending an optical path and at least one plastic lens.

The invention according to claim 2 is the zoom lens according to claim 1,
The first lens group, in order from the object side along the optical axis,
A first lens having a negative refractive power;
The reflective optical element;
A second lens having a positive refractive power,
The first lens and the second lens are plastic lenses,
25 <νd11 <35 (1)
45 <νd12 <60 (2)
(Where νd11 is the Abbe number of the d-line of the first lens, νd12 is the Abbe number of the d-line of the second lens)
It is characterized by satisfying.

The invention according to claim 3 is the zoom lens according to claim 1 or 2,
The reflective optical element comprises a prism that bends the optical path,
The prism is formed of a plastic material.

According to a fourth aspect of the present invention, in the zoom lens according to any one of the first to third aspects,
The third lens group includes only one lens having a positive refractive power, and the position in the optical axis direction is always fixed during zooming or focusing.

The invention according to claim 5 is the zoom lens according to any one of claims 1 to 4,
The lens located closest to the image side on the optical axis of the fourth lens group has an aspheric meniscus shape with a concave surface facing the image side on the optical axis, and is formed of a plastic material. To do.

A sixth aspect of the present invention is the zoom lens according to any one of the first to fifth aspects,
A fifth lens group is provided on the image side on the optical axis of the fourth lens group,
The fifth lens group is composed of one plastic lens.

The invention described in claim 7
A zoom lens according to any one of claims 1 to 6;
An image pickup apparatus comprising: an image pickup device that picks up light incident through the zoom lens.

  According to the first aspect of the present invention, the plastic lens can be easily formed into an aspherical shape by including at least one plastic lens in the first lens group. High imaging performance can be obtained by the spherical aberration correction effect. In particular, distortion at the wide angle end can be effectively corrected. Second, plastic lenses molded by injection molding are more productive and less costly than glass lenses molded by polishing, so the zoom lens can be produced at lower costs. It is more suitable for mass production. Third, among the lenses constituting the zoom lens, the lens of the first lens group having a relatively large lens diameter and volume is made of a plastic material, so that the zoom lens can be reduced in weight, and the lens can be made resistant to it. The impact property can be improved, and a zoom lens suitable for an imaging apparatus such as a portable device can be obtained. Fourth, since the first lens group includes a reflective optical element that bends the optical path, there is a possibility that a lens closer to the object side than the reflective optical element may interfere with a lens closer to the image side than the reflective optical element. By forming at least one lens from a plastic lens, it becomes easy to process the lens into a shape that prevents interference between the lenses, and interference between the lenses due to optical path bending can be prevented.

  According to the second aspect of the present invention, reflection is achieved by configuring the negative first lens, the reflective optical element for bending the optical path, and the positive second lens from the object side on the optical axis. The diameter of the light beam incident on the optical element can be reduced, and therefore the reflective optical element can be reduced in size. Further, the first lens satisfies the formula (1) and the second lens satisfies the formula (2), so that chromatic aberration generated in the first lens group can be corrected.

  According to the third aspect of the present invention, the zoom lens can be reduced in weight by forming the prism for bending the optical path from a plastic material, the impact resistance is improved by the reduction in the weight, and the imaging device such as a portable device. The zoom lens can be suitable for mounting on a zoom lens.

  According to the fourth aspect of the present invention, the third lens group is constituted by only one positive lens, and the position in the optical axis direction is always fixed at the time of zooming and focusing. The driving unit can be simplified, and the imaging apparatus can be reduced in size and weight. The positive lens in the third lens group is preferably a plastic lens.

  According to the fifth aspect of the present invention, the most image side surface of the fourth lens group is an aspherical meniscus shape with the concave surface facing the image side, so that field curvature and distortion are effectively reduced. It can be corrected. Further, it is desirable that the most image side lens in the fourth lens group is a plastic lens.

  According to the sixth aspect of the present invention, the fifth lens group comprising only one positive lens having an aspherical shape and having a fixed position in the optical axis direction upon zooming is provided on the image side of the fourth lens group. By disposing, it is possible to effectively correct curvature of field, and to obtain a good image side telecentric characteristic. Furthermore, it is desirable that the lenses constituting the fifth lens group have a positive refractive power.

  According to the seventh aspect of the present invention, a small and lightweight imaging device can be obtained by mounting the zoom lens according to any one of the first to sixth aspects.

  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.

  The “image side telecentric characteristics” in this specification will be described. 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. The image side telecentric means that the principal ray is incident on 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 is possible to correct the image-side telecentric dissatisfaction amount by appropriately arranging the microlens array on the imaging surface of the solid-state imaging device. It is common to use a substantially image side telecentric imaging lens that is incident at an angle of about 30 °. At this time, in order to obtain good light receiving sensitivity and image quality over the entire screen, it has a substantially image side telecentric characteristic that the chief ray incident angle on the imaging surface uniformly increases with respect to the image height. desirable. Therefore, in this specification, “good image side telecentric characteristics” means that the incident angle of the principal ray at the outermost periphery of the imaging surface is about 20 ° or less.

  Further, in this specification, “plastic lens, lens formed from plastic material” and similar terms are molded from a material in which a plastic material is a base material and small-diameter particles are dispersed in the plastic material. In addition, a lens having a plastic volume ratio of half or more is included, and a case where a coating process is performed on the surface for the purpose of preventing reflection or improving surface hardness is also included. The same applies to a reflective optical element formed from a plastic material.

  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. A unit 106, an image sensor 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 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 controls the drive of the optical system 101 in zooming, focusing (movement of the second lens group 20 and the fourth lens group 40 described later), exposure, and the like under the control of the control unit 104. The timing generator 106 outputs a timing signal for analog signal output. The image sensor 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, zooming, focusing, exposure, and the like of the optical system 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, 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 along the optical axis O from the object side (subject side) to the image plane IMG side, a first lens group 10 having a positive refractive power, a second lens group 20 having a negative refractive power, and an aperture. A diaphragm D, a third lens group 30 having a positive refractive power, a fourth lens group 40 having a positive refractive power, a fifth lens group 50 having a positive refractive power, and a cover glass 61 are configured. The The image plane IMG is a light receiving surface of the solid-state image sensor 102. In addition, it is good also as a structure provided with a low-pass filter, an infrared cut filter, etc. in the front | former stage of the cover glass 61. FIG.

  When the zoom lens 1 is zoomed and focused from the wide-angle end to the telephoto end, the positions of the first lens group 10, the third lens group 30, the fifth lens group 50, and the aperture stop D on the optical axis O are unchanged. The second lens group 20 and the fourth lens group 40 move on the optical axis O. Specifically, in zooming from the wide-angle end to the telephoto end, the second lens group 20 moves so that the distance between the first lens group 10 and the second lens group 20 increases, and the third lens group 30 and the third lens group 30 The fourth lens group 40 moves so that the distance from the four lens group 40 is narrowed, and at least the fourth lens group 40 moves along the optical axis O in focusing.

  The first lens group 10 includes, in order from the object side to the image plane IMG side along the optical axis O, a negative lens 11 as a plastic first lens having both surfaces aspherical and negative refractive power, and reflects light rays. Thus, a prism 13 as a reflective optical element that has an action of bending an optical path by 90 ° and is formed of plastic, and a positive lens 12 as a second lens made of plastic having both surfaces aspherical and positive refractive power are provided. Configured. In order from the object side to the image plane IMG side along the optical axis O, the negative lens 11 has surfaces S1 and S2, the prism 13 has surfaces S3, (reflection) surfaces S4 and S5, and the positive lens 12 has It has surfaces S6 and S7.

  The second lens group 20 includes, in order along the optical axis O from the object side to the image surface IMG side, a plastic negative lens 21 whose both surfaces are aspherical, and a cemented lens of the negative lens 22 and the positive lens 23. Configured. In order from the object side to the image plane IMG side along the optical axis O, the negative lens 21 has surfaces S8 and S9, and the negative lens 22 and the positive lens 23 have surfaces S10 to S12.

  The third lens group 30 is configured to include only a positive lens 31 that is located in the vicinity of the image side on the optical axis O of the aperture stop D and the object side on the optical axis O is aspherical. In order from the object side to the image plane IMG side along the optical axis O, the aperture stop D has a surface S13, and the positive lens 31 has surfaces S14 and S15.

  The fourth lens group 40 includes, in order from the object side to the image plane IMG side along the optical axis O, a cemented lens in which a positive lens 41 and a negative lens 42 are cemented, and an aspheric shape on the image side in the optical axis O direction. And a plastic meniscus lens 43 having a concave surface (surface S20). In order from the object side to the image plane IMG side along the optical axis O, the positive lens 41 and the negative lens 42 have surfaces S16 to S18, and the meniscus lens 43 has surfaces S19 and S20.

  The fifth lens group 50 includes only a plastic positive lens 51 having both aspherical surfaces on both sides. The positive lens 51 has surfaces S21 and S22 in order along the optical axis O from the object side to the image plane IMG side. The cover glass 61 has surfaces S23 and S24 in order along the optical axis O from the object side to the image plane IMG side.

The shape of each aspheric surface of the lens is as follows. In an orthogonal coordinate system in which the vertex of the surface is the origin and the optical axis direction is the X axis, the vertex curvature is C, the conic constant is K, and the aspheric coefficients are A4, A6, A8, A10. , A12 are expressed by the following equation (3).

The first lens group 10 satisfies the following expressions (1) and (2).
25 <νd11 <35 (1)
45 <νd12 <60 (2)
Where νd11 is the Abbe number of the negative lens 11 at the d-line, and νd12 is the Abbe number of the positive lens 12 at the d-line. Expression (1) is an expression that defines the Abbe number of the negative lens 11 at the d-line. Expression (2) is an expression that defines the Abbe number of the positive lens 12 at the d-line.

  According to the present embodiment, by providing the first lens group 10 with the plastic negative lens 11 and the positive lens 12, first, the plastic lens can be easily formed into an aspheric shape. High imaging performance can be obtained by the spherical aberration correction effect. In particular, distortion at the wide angle end can be effectively corrected. Secondly, the plastic lens molded by injection molding has better productivity and lower cost than the glass lens molded by polishing, so the zoom lens 1 can be produced at low cost. Furthermore, it is suitable for mass production. Third, among the lenses constituting the zoom lens 1, the lens of the first lens group 10 having a relatively large lens diameter and volume is formed of a plastic material, so that the zoom lens 1 can be reduced in weight, and Thereby, the impact resistance can be improved, and the zoom lens 1 suitable for mounting on the portable digital still camera 100 can be obtained.

  Fourth, since the first lens group 10 includes a prism 13 as a reflective optical element that bends the optical path, the negative lens 11 on the object side of the prism 13 and the positive lens 12 on the image side of the prism 13 interfere with each other. However, if the negative lens 11 and the positive lens 12 are made of plastic lenses, it becomes easy to process the lens in a shape that prevents the interference between the lenses. Can be prevented. Although the first lens group 10 includes the plastic negative lens 11 and the positive lens 12, the first lens group 10 is not limited to this, and the first lens group includes at least one plastic lens. Also good.

  Further, by configuring the first lens group 10 with the negative lens 11, the prism 13, and the positive lens 12 in order from the object side on the optical axis O, the diameter of the light beam incident on the prism 13 can be reduced. Therefore, the prism 13 can be reduced in size. Further, when the negative lens 11 satisfies Expression (1) and the positive lens 12 satisfies Expression (2), chromatic aberration generated in the first lens group 10 can be corrected.

  Further, by forming the prism 13 for bending the optical path from a plastic material, the zoom lens 1 can be reduced in weight, the impact resistance can be improved due to the reduction in weight, and it is suitable for mounting on the portable digital still camera 100. The zoom lens 1 can be obtained.

  Further, the third lens group 30 is composed of only one positive lens 31, and the position in the direction of the optical axis O is always fixed at the time of zooming and focusing, so that the optical system driving unit 105 of the digital still camera 100 is fixed. The digital still camera 100 can be reduced in size and weight. Furthermore, since the positive lens 31 is a plastic lens, the digital still camera 100 can be further reduced in size and weight.

  Further, by making the most image-side surface S20 of the fourth lens group 40 into an aspheric meniscus shape with the concave surface facing the image side, it is possible to effectively correct curvature of field and distortion. Further, the lens (meniscus lens 43) on the most image side (image plane IMG side) of the fourth lens group 40 is not limited to a plastic lens, but is made of plastic as in the present embodiment. A lens is desirable.

  In addition, by disposing a fifth lens group 50 consisting of only one plastic lens having an aspherical shape, the position in the optical axis O direction is fixed at the time of zooming, on the image side of the fourth lens group 40, The curvature of field can be corrected effectively, and a good image side telecentric characteristic can be easily obtained. Further, since the fifth lens group 50 includes the positive lens 51 having a positive refractive power, the field curvature can be corrected more effectively, and a better image side telecentric characteristic can be easily obtained.

  In addition, a small and lightweight 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: curvature at the surface Si (i: number) of the optical element, di: distance [mm] (the thickness of the optical element on the optical axis O or its gap length), ndi: di portion Is the refractive index at the d-line, νdi: Abbe number of the di portion. Further, di is an interval between the surfaces Si and S (i + 1) on the optical axis O.

  In Table 1 (b), the first surface S1, the second surface S2, the sixth surface S6, the seventh surface S7, the eighth surface S8, the ninth surface S9, the fourteenth surface S14, the twentieth surface S20, Each aspheric coefficient of the 21st surface S21 and the 22nd surface S22 indicates each coefficient of the above equation (3). In Table 1 (c), the values of the lengths d7, d12, d15, and d20 when the focal length f of the zoom lens 1 is changed to 6.30 mm, 10.60 mm, and 17.90 mm are shown. In addition, the field angles of the zoom lens 1 corresponding to the focal lengths f = 6.30 mm, 10.60 mm, and 17.90 mm are the field angles 2ω = 63.0 °, 38.0 °, and 23.0 °, respectively.

Table 2 shows the values of νd11 and νd12 in the zoom lens 1 of the present embodiment.

  As shown in Table 2, the values of νd11 and νd12 in the zoom lens 1 of the present example satisfy the above formulas (1) and (2) in order.

  FIG. 3A shows the spherical aberration, astigmatism, and distortion of the zoom lens 1 of the present example at the focal length f = 6.30 mm. FIG. 3B shows the spherical aberration, astigmatism and distortion of the zoom lens 1 of the present embodiment at the focal length f = 10.60 mm. FIG. 3C shows the spherical aberration, astigmatism and distortion of the zoom lens 1 of the present embodiment at the focal length f = 17.00 mm. As shown in FIGS. 3A, 3B, and 3C, according to the zoom lens 1 of the present embodiment, spherical aberration, astigmatism, and distortion are excellent even when the focal length f is changed. Can be corrected.

  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, 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, a mobile phone with an image pickup 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. 4, an example of a mobile phone 200 equipped with an imaging unit 250 as an imaging device will be described. FIG. 4 shows an internal configuration of the mobile phone 200.

  As shown in FIG. 4, a 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 is used to input 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 (R) used as a work area for temporarily storing processing data or imaging data or the like by the imaging unit 250. M) and a 270.

  The image pickup unit 250 includes the zoom lens 1, the (solid) image pickup element, the lens barrel, the drive mechanism of the zoom lens 1, and the like in the above embodiment. The image pickup unit 250 itself includes a control unit and image processing. The lens unit is assumed to be connected to a control unit, an operation unit, a display unit, and the like by a connector or the like without having a unit. 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 image signals such as luminance signals and color difference signals captured by the imaging unit 250 are transmitted to the control unit 210 side via the external connection terminal. Is output. 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.

  Moreover, in the said embodiment and Example 1, although the structure which uses a prism as a reflective optical element was demonstrated, it is not limited to this, It is good also as a structure which uses other reflective optical elements, such as a mirror.

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, astigmatism, and distortion of the zoom lens 1 of Example 1 in the focal distance f = 6.30mm. FIG. 6B is a diagram illustrating spherical aberration, astigmatism, and distortion of the zoom lens 1 at a focal length f = 10.60 mm. (C) is a diagram showing spherical aberration, astigmatism and distortion of the zoom lens 1 at a focal length f = 17.90 mm. 3 is a block diagram showing an internal configuration of a mobile phone 200. FIG.

Explanation of symbols

O Optical axis 100 Digital still camera 101 Optical system 1 Zoom lens D Aperture stop 10 First lens group 11 Negative lens 13 Prism 12 Positive lens 20 Second lens group 21, 22 Negative lens 23 Positive lens 30 Third lens group 31 Positive lens 40 fourth lens group 41 positive lens 42 negative lens 43 meniscus lens 50 fifth lens group 51 positive lens 61 cover glass 102 solid-state image sensor 103 A / D converter 104 controller 105 optical system driver 106 image sensor driver 107 timing Generation 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 unit 241 Antenna 250 Imaging unit 260 Storage unit 270 Temporary storage Part

Claims (7)

In order from the object side along the optical axis,
A first lens group having a positive refractive power and whose position in the optical axis direction 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,
At least the second lens group and the fourth lens group are moved in the optical axis direction for zooming, and at least the fourth lens group is moved in the optical axis direction for focusing.
The zoom lens according to claim 1, wherein the first lens group includes a reflective optical element for bending an optical path and at least one plastic lens. The first lens group, in order from the object side along the optical axis,
A first lens having a negative refractive power;
The reflective optical element;
A second lens having a positive refractive power,
The first lens and the second lens are plastic lenses,
25 <νd11 <35 (1)
45 <νd12 <60 (2)
(Where νd11 is the Abbe number of the first lens at the d-line, νd12 is the Abbe number of the second lens at the d-line)
The zoom lens according to claim 1, wherein: The reflective optical element comprises a prism that bends the optical path,
The zoom lens according to claim 1, wherein the prism is made of a plastic material.   The third lens group comprises only one lens having a positive refractive power, and the position in the optical axis direction is always fixed during zooming or focusing. The zoom lens according to item.   The lens located closest to the image side on the optical axis of the fourth lens group has an aspheric meniscus shape with a concave surface facing the image side on the optical axis, and is formed of a plastic material. The zoom lens according to any one of claims 1 to 4. A fifth lens group is provided on the image side on the optical axis of the fourth lens group,
The zoom lens according to any one of claims 1 to 5, wherein the fifth lens group includes a single plastic lens. A zoom lens according to any one of claims 1 to 6;
An image pickup apparatus comprising: an image pickup device that picks up light incident through the zoom lens.

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