JP5971251B2 - Imaging device - Google Patents

Description

The present invention relates to an image pickup apparatus including a Zumuren's for the imaging device to the projection surface is curved, in particular, to an image pickup apparatus having a zoom lens consisting of three lens groups.

  Conventionally, as a zoom lens and an imaging apparatus corresponding to an imaging element having a curved projection surface, there is one disclosed in Example 4 of Patent Document 1 below.

  However, the zoom lens disclosed in Patent Document 1 has a low zoom ratio of about 2, and it is difficult to say that the zoom lens satisfies sufficient specifications.

JP 2006-184873 A

It is an object of the present invention to provide an imaging apparatus including a zoom lens having a high zoom ratio of at least 3 and further excellent correction of various aberrations.

An imaging apparatus according to the present invention is an imaging apparatus having a zoom lens for forming a subject image on a projection surface, and an imaging element in which the projection surface is curved in an arbitrary cross section toward the periphery of the screen. The zoom lens includes, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. At the time of zooming from the end to the telephoto end, the distance between the lens groups is changed to satisfy the following conditional expressions (1) , (2) , (4), and (5) .
2.44 ≦ f2 / fW <3.0 (1)
0.3 <f2 / fT ≦ 0.61 (2)
3.9 <| P′W × RIW | <7.0 (4)
1.0 <| P′T × RIT | <1.5 (5)
Where f2: focal length of the second lens group fW: focal length of the entire system at the wide angle end fT: focal length of the entire system at the telephoto end
P′W = Σ [(h _jw / h _1w ) × (1 / r _j )
× {(1 / n _j ) − (1 / n _{j + 1} )}] (j = 1, 2, 3,...)
h _jw : Paraxial axial ray height on the lens j-th surface at the wide-angle end
(H _jw = h _{1w on} the first lens surface )
r _j : radius of curvature of lens j-th surface
n _j : Refractive index of the medium on the object side from the lens j-th surface
n _{j + 1} : refractive index of the medium on the image side from the lens j-th surface
RIW: radius of curvature of projection surface at wide-angle end when object distance is infinity
P′T = Σ [(h _jt / h _1t ) × (1 / r _j )
× {(1 / n _j ) − (1 / n _{j + 1} )}] (j = 1, 2, 3,...)
h _jt : Paraxial axial ray height on the lens j-th surface at the telephoto end
(H _jt = h _{1t on} the first lens surface )
RIT: radius of curvature of projection surface at telephoto end when object distance is infinity

  A projection surface such as an imaging surface of the imaging element is curved to be a concave surface or a convex surface. Thus, since the projection surface is curved to be a concave surface or a convex surface, it is possible to achieve both downsizing and high performance of the imaging apparatus. More specifically, when the projection surface is curved at the periphery, for example, to the zoom lens side (concave surface), the chief ray incident angle of the light beam incident on the projection surface becomes relatively small, and so-called telecentric characteristic correction is performed. Become advantageous. When the projection surface is curved and approaches the zoom lens near the periphery, the chief ray incident angle of the light beam incident on the projection surface is smaller than when the projection surface is flat. Even if the characteristics are not sufficiently corrected, the aperture efficiency does not decrease and the occurrence of shading can be suppressed. In addition, distortion and coma can be easily corrected, and the imaging apparatus can be downsized. Furthermore, the projection surface is preferably curved into a spherical shape. When the projection surface is curved in this way, both the long side direction and the short side direction of the screen are curved in the same way, and can be matched to the field curvature of the zoom lens, improving the performance of the entire screen. It becomes possible to make it. Further, since it is not necessary to sufficiently correct the curvature of field on the zoom lens side, it is not necessary to reduce the Petzval sum, and the degree of freedom in selecting a glass material is increased, so that chromatic aberration can be corrected well.

Since the zoom lens according to the present invention has a configuration close to a so-called retrofocus type, it is possible to ensure a long back focus compared to the focal length, and it is easy to arrange filters and cover glasses. Since the negative lens group is at the head, the front lens diameter can be relatively small even at a wide angle of view. If the lower limit of conditional expressions (1) and (2) is exceeded, the refractive power of the second lens group will not be too strong, and the aberration generated here will be too great, or the optical performance change due to manufacturing errors in this group will change. It doesn't get too big. On the other hand, by falling below the upper limits of both conditional expressions (1) and (2), the refractive power of the second lens group does not become too weak, and the optical system becomes large in order to ensure the amount of movement necessary for zooming. Can be prevented.
Further, if it is within the range of the conditional expression (4), the difference between the curvature of field at the wide angle end and the amount of curvature of the projection surface can be kept small, and good optical performance can be maintained.
Further, if it is within the range of the conditional expression (5), the difference between the curvature of field at the telephoto end and the amount of curvature of the projection surface can be kept small, and good optical performance can be maintained.

In a specific aspect or aspect of the present invention, the following conditional expression (3) is satisfied in the imaging apparatus .
−12 <RIT / L <−7 (3)
Where RIT: radius of curvature of projection surface at the telephoto end when the object distance is infinite L: maximum image height
(However, the image height here is the length of the arc along the curved projection surface.)

  If the value of conditional expression (3) is less than the upper limit, the curvature of the projection surface becomes small, and overcorrection of the curvature of field can be prevented. In addition, it is possible to prevent the final surface of the zoom lens and the surface to be projected from being too close, and to ensure a sufficient air space for inserting an infrared (IR) cut filter or the like. Beyond the lower limit, the curvature of the projection surface becomes large, and it is possible to prevent the telecentric characteristics and the correction of the curvature of field in the zoom lens from increasing.

In still another aspect of the present invention, the imaging device satisfies the following conditional expression (6).
−0.15 <L / EW <−0.07 (6)
L: Maximum image height EW: Exit pupil position at the wide-angle end (based on the projection surface on the optical axis)

  If it is within the range of conditional expression (6), the incident angle of the image light on the projection surface can be kept moderate by appropriately separating the exit pupil position from the projection surface while suppressing an increase in the total lens length. In addition, problems such as shading and color misregistration can be suppressed.

  In still another aspect of the present invention, the third lens group includes one positive lens, and focusing is performed by moving the third lens group. The third lens group is located relatively close to the image plane, the light beam passing therethrough is relatively thin, and good optical performance can be realized even if it is composed of one positive lens. Further, since the third lens group is composed of one lens, it is lightweight, and it is possible to suppress the load on the actuator to a minimum by moving the third lens group during focusing.

  In a specific aspect of the present invention, in the imaging device, the amount of curvature of the projection surface is changed according to the focal length of the zoom lens. Strictly speaking, in the case of a zoom lens, since the value of the curvature of field at each focal length is different, better optical performance can be obtained by changing the amount of curvature of the projection surface for each focal length. .

  In another aspect of the present invention, the amount of curvature of the projection surface is changed according to the focusing distance of the zoom lens. Strictly speaking, in the case of a zoom lens, since the value of the field curvature at each focusing distance is different, better optical performance can be obtained by changing the amount of curvature of the projection surface for each focusing distance. .

It is a figure explaining the camera module of one Embodiment of this invention. It is a block diagram explaining the imaging device incorporating the camera module of FIG. It is a block diagram explaining a portable communication terminal provided with an imaging device. 3 is a cross-sectional view of the zoom lens of Example 1. FIG. 5A, 5B, and 5C are diagrams illustrating the lens arrangement of the zoom lens at the wide-angle end, the intermediate position, and the telephoto end. 6A to 6C are aberration diagrams at the wide-angle end of the zoom lens of Example 1. FIGS. 6D to 6F are aberration diagrams at an intermediate position of the zoom lens of Example 1. FIGS. FIG. 3 is an aberration diagram at a telephoto end of the zoom lens in Example 1; 6 is a cross-sectional view of a zoom lens according to Example 2. FIG. 8A, 8B, and 8C are diagrams illustrating the lens arrangement of the zoom lens at the wide-angle end, the intermediate position, and the telephoto end. 9A to 9C are aberration diagrams at the wide-angle end of the zoom lens of Example 2, and FIGS. 9D to 9F are aberration diagrams at an intermediate position of the zoom lens of Example 2, and FIGS. FIG. 6 is an aberration diagram at a telephoto end of a zoom lens according to Example 2; 6 is a cross-sectional view of a zoom lens of Example 3. FIG. 11A to 11C are aberration diagrams at the wide-angle end of the zoom lens of Example 3, FIGS. 11D to 11F are aberration diagrams at an intermediate position of the zoom lens of Example 3, and FIGS. FIG. 6 is an aberration diagram at a telephoto end of a zoom lens according to Example 3; 6 is a cross-sectional view of a zoom lens according to Example 4. FIG. 13A to 13C are aberration diagrams at the wide-angle end of the zoom lens of Example 4. FIGS. 13D to 13F are aberration diagrams at an intermediate position of the zoom lens of Example 4. FIGS. 13G to 13I are FIG. 10 is an aberration diagram at a telephoto end of a zoom lens in Example 4; 6 is a cross-sectional view of a zoom lens according to Example 5. FIG. FIGS. 15A to 15C are aberration diagrams at the wide-angle end of the zoom lens of Example 5, FIGS. 15D to 15F are aberration diagrams at an intermediate position of the zoom lens of Example 5, and FIGS. FIG. 10 is an aberration diagram at a telephoto end of a zoom lens according to Example 5; FIGS. 16A to 16C are aberration diagrams at the wide-angle end of the zoom lens of Example 5, FIGS. 16D to 16F are aberration diagrams at an intermediate position of the zoom lens of Example 5, and FIGS. FIG. 10 is an aberration diagram at a telephoto end of a zoom lens according to Example 5;

  FIG. 1 is a cross-sectional view illustrating a camera module including a zoom lens according to an embodiment of the present invention.

  The camera module 50 includes a zoom lens 10 that forms a subject image, an image sensor 51 that detects a subject image formed by the zoom lens 10, a support body 52 that supports the image sensor 51 in a curved state, and the support. A wiring board 54 that holds the body 52 from behind and has wiring and the like, and a lens barrel portion 55 that holds the zoom lens 10 and has an opening OP through which a light beam from the object side enters. The camera module 50 is used by being incorporated in an imaging device to be described later.

  The zoom lens 10 includes, in order from the object side, a first lens group GR1, an aperture stop S, a second lens group GR2, and a third lens group GR3. Each lens group GR1-GR3 can consist of a single or several lens.

  The image sensor 51 is a sensor chip made of a solid-state image sensor, that is, an integrated circuit. The imaging element 51 has a photoelectric conversion unit 51a as a light receiving unit, and a drive circuit 51b is incidentally formed around the photoelectric conversion unit 51a.

  The support body 52 has a role of maintaining and fixing the imaging element 51 in a concave shape that is symmetrically recessed around the optical axis AX. Thereby, the projection surface IM provided in the photoelectric conversion unit 51a of the image sensor 51 is in a curved state (specifically, tilted toward the zoom lens 10 so as to be directed to the central optical axis AX in an arbitrary cross section including the optical axis AX). Is a spherical concave surface. The support 52 incorporates a curvature adjustment actuator 52a that incorporates a mechanism that expands or contracts according to a drive signal, such as a piezo element, and uses the curvature amount (specifically, curvature) of the projection surface IM as a reference. The state can be increased or decreased to a desired level. In addition, you may arrange | position the image surface conversion element of Unexamined-Japanese-Patent No. 2010-109096 on the photoelectric conversion part 51a of the image pick-up element 51 which has a flat image pick-up surface. In this case, the first surface curved in the concave of the image plane conversion element made of a fiber bundle or the like becomes the projection surface IM.

  The wiring board 54 has a role of aligning and fixing the imaging element 51 to other members (for example, the lens barrel portion 55) via the support body 52. The wiring board 54 includes a rigid main body portion 54a that supports the support body 52 on one surface side, and a flexible printed circuit board 54b that has one end connected to the other surface side of the main body portion 54a. The main body portion 54a is connected to the drive circuit 51b via the bonding wire W on the one surface side, and is connected to the flexible printed board 54b on the other surface side. A parallel flat plate F is disposed and fixed on the zoom lens 10 side of the wiring board 54 so as to cover the image sensor 51 by a holder member (not shown).

  The flexible printed circuit board 54b connects the main body portion 54a and an external circuit (not shown) (for example, a control circuit included in a host device on which the camera module 50 is mounted), and the image sensor 51 and the bending adjustment actuator 52a are connected from the external circuit. It is possible to receive a voltage and a signal for driving and to output a detection signal to the external circuit.

  The lens barrel 55 houses and holds the zoom lens 10. The lens barrel portion 55 enables operations such as zooming and focusing of the zoom lens 10 by moving a specific lens group among the lens groups GR1 to GR3 constituting the zoom lens 10 along the optical axis AX. Drive mechanism 55a.

  With reference to FIG. 2, an imaging apparatus 100 incorporating the camera module 50 of FIG. 1 will be described.

  In addition to the camera module 50 described above, the imaging apparatus 100 includes an A / D conversion unit 102, a control unit 103, a projection surface driving unit 104, an optical system driving unit 105, a timing generation unit 106, an imaging 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 provided.

  The camera module 50 includes the zoom lens 10 and the image sensor 51 described with reference to FIG. The zoom lens 10 has a function of forming a subject image on the projection surface of the image sensor 51. The imaging device 51 has a photoelectric conversion unit 51a made of a CCD (charge coupled device) or CMOS (complementary metal oxide semiconductor), photoelectrically converts incident light for each RGB, and outputs an analog signal thereof.

  The A / D converter 102 converts the detection signal output from the image sensor 51 or an analog signal as a photoelectric conversion signal into digital image data.

  The control unit 103 controls each unit of the imaging device 100. The control unit 103 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like. Execute the process.

  The projection surface driving unit 104 operates in synchronization with the optical system driving unit 105 under the control of the control unit 103. Specifically, the projection surface drive unit 104 receives the control signal from the control unit 103 and operates the curvature adjustment actuator 52a, and the curvature of the projection surface IM according to the focal length of the zoom lens 10, that is, the zooming state. Adjust the amount. Further, the projection surface drive unit 104 operates the curve adjustment actuator 52a in response to the control signal from the control unit 103, and changes the curvature amount of the projection surface IM according to the focus distance of the zoom lens 10, that is, the focus state. Make fine adjustments.

  The optical system drive unit 105 controls the state of the zoom lens 10 by operating the drive mechanism 55a of the zoom lens 10 when performing zooming, focusing, exposure, and the like under the control of the control unit 103.

  The timing generator 106 outputs a timing signal for analog signal output. The image sensor driving unit 107 performs scanning drive control of the image sensor 51 based on the timing signal.

  The image memory 108 stores image data detected by the image sensor 51 and digitized by the A / D converter 102 so as to be readable and writable.

  The image processing unit 109 performs various types of image processing on the image data stored in the image memory 108 and the like. The image compression unit 110 compresses captured image data before and after image processing 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 and various operation keys for setting various modes, and outputs information input by the user to the control unit 103.

  Here, the operation of the imaging apparatus 100 will be described. At the time of shooting, subject monitoring (through image display) and image shooting execution are performed. In monitoring, an image of a subject obtained through the zoom lens 10 is formed on the curved projection surface IM (see FIG. 1) of the image sensor 51. The image pickup device 51 is scanned and driven by the timing generation unit 106 and the image pickup device drive unit 107, and outputs an analog signal for one screen as a photoelectric conversion output corresponding to a light image formed at regular intervals.

  This analog signal is appropriately gain-adjusted for each primary color component of RGB in a circuit attached to the image sensor 51 and then converted into digital data by the A / D converter 102. The digital data is subjected to color process processing including pixel interpolation processing and Y correction processing by the image processing unit 109 to generate a luminance signal Y and color difference signals Cb and Cr (image data) as digital values, and the image memory. 108. The digital data is periodically read out from the image processing unit 109 to generate a video signal, which is 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 10 are set by driving the optical system driving unit 105 based on an operation input performed by the user via the operation unit 113 at any time. Along with this, the amount of curvature of the projection surface IM is adjusted by the projection surface driving unit 104.

  In such a monitoring state, when the user operates the release button of the operation unit 113, still image data is captured. 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.

  The above-described imaging apparatus 100 is an example of an imaging apparatus suitable for the present invention, and the present invention is not limited to this.

  In other words, the imaging device equipped with the camera module 50 or the zoom lens 10 may be a digital still camera, a video camera, a mobile phone with an imaging function, a PHS (Personal Handyphone System), a PDA (Personal Digital Assistant), or the like. .

  In the imaging apparatus 100 described above, the camera module 50 can be attached to and detached from the control unit 103 on the main body side via a connector or the like. In particular, when the imaging apparatus 100 is an interchangeable lens camera, the camera module 50 functions as an interchangeable lens and is detachably fixed to a camera body or the like incorporating the control unit 103 or the like.

  Next, an example of a mobile phone or other mobile communication terminal 300 on which the imaging device 100 illustrated in FIG. 2 is mounted will be described with reference to FIG.

  The mobile communication terminal 300 is configured to control each unit in an integrated manner and execute a program corresponding to each process, a control unit (CPU) 310, an operation unit 320 for operating and inputting numbers and the like with keys, and a predetermined data In addition, a display unit 330 for displaying captured images and the like, a wireless communication unit 340 for realizing various information communication with an external server or the like via the antenna 341, the imaging device 100, and the mobile communication terminal 300 A storage unit (ROM) 360 that stores necessary data such as system programs, various processing programs, and terminal IDs, and various processing programs, data, processing data executed by the control unit 310, or imaging by the imaging apparatus 100 And a temporary storage unit (RAM) 370 used as a work area for temporarily storing data and the like.

  Note that the control unit 103 (see FIG. 2) of the imaging device 100 and the control unit 310 of the mobile communication terminal 300 are communicably connected. In such a case, the display unit 112 on the imaging device 100 side illustrated in FIG. The functions of the operation unit 113 and the like can be provided on the mobile communication terminal 300 side, and the display unit 112 and the operation unit 113 can be omitted. 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 communication terminal 300, and a release signal is transmitted from the mobile communication terminal 300 side to the imaging device 100 side. The obtained image signals or image data such as luminance signals and color difference signals are output from the imaging device 100 side to the control unit 310 side. Such an image signal is stored in the storage unit 360 or displayed on the display unit 330 by the control system of the mobile communication terminal 300, and can be transmitted to the outside as video information via the wireless communication unit 340. .

  Hereinafter, referring back to FIG. 1, the zoom lens 10 according to an embodiment of the present invention will be described in detail. The zoom lens 10 shown in FIG. 1 forms a subject image on the image sensor 51. The projection surface IM of the image sensor 51 is curved in a shallow concave spherical shape, and is a rotational surface having symmetry around the optical axis AX. By curving the projection surface IM into a concave spherical shape, the imaging device 100 can be both downsized and improved in performance. That is, since the chief ray incident angle of the light beam incident on the projection surface IM is relatively small, it is advantageous for correcting the telecentric characteristic, and the occurrence of shading can be suppressed. Further, distortion and coma can be easily corrected, and the zoom lens 10 and the camera module 50 or the imaging device 100 can be downsized. By matching the amount of curvature of the projection surface IM with the curvature of field of the zoom lens 10, the performance can be improved over the entire screen. Further, since it is not necessary to sufficiently correct the curvature of field with the zoom lens 10, it is not necessary to reduce the Petzval sum, and the degree of freedom in selecting a glass material is increased, so that chromatic aberration can be corrected well.

The zoom lens 10 according to the embodiment includes a first lens group GR1 having a negative refractive power, a second lens group GR2 having a positive refractive power, and a third lens group GR3 having a positive refractive power. The zoom lens 10 includes a lens having a weak refractive power and a parallel plate F such as an IR cut filter as an optical element having substantially no refractive power. The zoom lens 10, during zooming from the wide-angle end to the telephoto end, changing the distance between the lens units of the first to third lens groups GR1～GR3. Specifically, for example, the first to third lens groups GR1 to GR3 are individually displaced along the optical axis AX. Further, the aperture stop S is disposed around the central second lens group GR2 in consideration of the convenience of aberration correction and the ease of installation.

  Since the zoom lens 10 according to the embodiment has a configuration close to a so-called retrofocus type, it is possible to ensure a long back focus as compared with a focal length, and it is easy to arrange a parallel plate F that is a filter or a cover glass. . Further, since the first first lens group GR1 has a negative power, the front lens diameter can be relatively small even when the wide angle of view is set.

The imaging apparatus 100 described above has the conditional expressions (1) and (2) already described.
2.44 ≦ f2 / fW <3.0 (1)
0.3 <f2 / fT ≦ 0.61 (2)
Satisfied. Here, f2 is the focal length of the second lens group GR2, fW is the focal length of the entire system at the wide angle end, and fT is the focal length of the entire system at the telephoto end.

  When the values f2 / fW and f2 / fT of the conditional expressions (1) and (2) exceed the lower limit, the refractive power of the second lens group GR2 does not become too strong, and the generated aberration becomes too large. The optical performance change due to the manufacturing error in the second lens group GR2 does not become too large. On the other hand, since the values f2 / fW and f2 / fT of the conditional expressions (1) and (2) are below the upper limit, the refractive power of the second lens group GR2 does not become too weak, so the second lens necessary for zooming It is possible to prevent the zoom lens 10 from becoming excessively large in order to ensure the amount of movement of the group GR2 and the like.

In addition to the conditional expressions (1) and (2), the imaging apparatus 100 according to the embodiment includes the conditional expression (3) already described.
−12 <RIT / L <−7 (3)
Satisfied. However, RIT is the radius of curvature of the projection surface IM at the telephoto end when the object distance is infinity, and L is the maximum image height (here, the image height is the curved projection surface IM). The length of the arc along.).

  If the value RIT / L of the conditional expression (3) exceeds the lower limit, the curvature of the projection surface IM becomes large, and it is possible to prevent the telecentric characteristics and the field curvature correction burden on the zoom lens 10 from increasing. On the other hand, when the value RIT / L is less than the upper limit, the curvature of the projection surface IM becomes small, and it is possible to prevent the correction burden of the field curvature from increasing. In addition, it is possible to prevent the final surface of the zoom lens 10 and the projection surface IM from being too close, and to ensure a sufficient air space for inserting the parallel plate F.

In the imaging apparatus 100 of the embodiment, in addition to the conditional expressions (1) and (2), the conditional expression (4) already described.
3.9 <| P′W × RIW | <7.0 (4)
Satisfied. However, P′W = Σ [(h _jw / h _1w ) × (1 / r _j ) × {(1 / n _j ) − (1 / n _{j + 1} )}], and h _jw is the lens number at the wide angle end. The paraxial axial ray height at the j plane, h _1w is the paraxial axial ray height at the lens first surface S1 at the wide angle end, and r _j is the radius of curvature of the lens jth surface. , N _j is the refractive index of the medium on the object side from the lens j-th surface, and n _{j + 1} is the refractive index of the medium on the image side from the lens j-th surface. RIW is the radius of curvature of the projection surface at the wide-angle end when the object distance is infinity.

  If the value | P′W × RIW | of the conditional expression (4) is within the lower and upper limits, the difference between the curvature of field at the wide-angle end and the amount of curvature of the projection surface IM can be suppressed to be small. Optical performance can be maintained.

In the imaging apparatus 100 of the embodiment, in addition to the conditional expressions (1) and (2), the conditional expression (5) already described
1.0 <| P′T × RI T | <1.5 (5)
Satisfied. However, P′T = Σ [(h _jt / h _1t ) × (1 / r _j ) × {(1 / n _j ) − (1 / n _{j + 1} )}], where h _jt is the lens number at the telephoto end. The paraxial axial ray height on the j plane, and h _1t is the paraxial axial ray height on the lens first surface S1 at the telephoto end. r _{j, n j,} defined such as _{n j} + 1, RI T, the above conditional expression (3) is the same as (4).

If the value | P′T × RI T | of the conditional expression (5) is within the lower limit and the upper limit, the difference between the field curvature at the telephoto end and the curvature amount of the projection surface IM can be suppressed to be small. Good optical performance can be maintained.

In the zoom lens 10 according to the embodiment, in addition to the conditional expressions (1) and (2), the conditional expression (6) already described.
−0.15 <L / EW <−0.07 (6)
Satisfied. Here, L is the maximum image height, and EW is the exit pupil position at the wide angle end.

  If the value L / EW of conditional expression (6) is within the lower and upper limits, the image on the projection surface IM can be obtained by appropriately separating the exit pupil position from the projection surface IM while suppressing an increase in the total lens length. The incident angle of light can be kept moderate, and problems such as shading and color misregistration can be suppressed.

〔Example〕
Specific examples of the zoom lens according to the present invention will be described below.

[Example 1]
The lens outline of Example 1 is shown below. Note that Example 1 does not belong to the present invention.
Wide-angle end focal length = 5.05
Intermediate position focal length = 10.21
Telephoto end focal length = 20.21
Wide-angle end F-number = 2.4
Intermediate position F number = 3.17
Telephoto end F number = 4.8
Zoom ratio = 4.0

  The lens surface data of Example 1 is shown in Table 1 below. In Table 1, “R” means the radius of curvature, “D” means the axial distance, “Nd” means the refractive index for the d-line, and “νd” means the Abbe number for the d-line. To do. The “imaging surface” corresponds to the projection surface IM.

[Table 1]
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
0 (object) ∞
1 * -42.729 1.00 1.75500 51.2 7.53
2 * 10.038 2.44 6.20
3 * 15.384 1.62 1.92290 20.9 6.20
4 * 29.218 d1 6.20
5 (Aperture) ∞ 0.00 2.71
6 * 6.121 2.26 1.49710 81.6 2.87
7 * -21.136 0.15 2.81
8 9.010 1.63 1.69680 55.5 2.76
9 -14.934 0.40 1.62000 36.3 2.59
10 4.680 d2 2.35
11 * 21.912 1.80 1.55330 71.7 4.45
12 * -12.303 d3 4.46
13 ∞ 0.40 1.51680 64.2 4.24
14 ∞ 1.00 4.21
Imaging surface -31.711 4.12

ただし、
Ａｉ：ｉ次の非球面係数
Ｒ ：曲率半径
Ｋ ：円錐定数In Table 1 above, “d1”, “d2”, and “d3” indicate that the interval is variable. Further, the symbol “*” is written after the specific surface number, which means that this surface has an aspherical shape. In Example 1 and the following examples, the aspherical shape is as follows, with the apex of the surface as the origin, the X axis in the optical axis AX direction, and the height in the direction perpendicular to the optical axis AX as h. This is expressed by “Expression 1”.
[Equation 1]

However,
Ai: i-order aspheric coefficient R: radius of curvature K: conic constant

  The aspherical coefficients of the lens surfaces of the zoom lens of Example 1 are shown in Table 2 below.

[Table 2]
First side
K = 0.00000E + 00, A4 = 0.11075E-03, A6 = -0.11187E-05, A8 = 0.69151E-07,
A10 = -0.12910E-08, A12 = 0.73609E-11
Second side
K = 0.00000E + 00, A4 = -0.21631E-03, A6 = 0.17564E-04, A8 = -0.41942E-06,
A10 = 0.76857E-08, A12 = -0.74344E-10
Third side
K = 0.00000E + 00, A4 = -0.43875E-03, A6 = 0.23060E-04, A8 = -0.62343E-06,
A10 = 0.38848E-08, A12 = -0.72233E-11
4th page
K = 0.00000E + 00, A4 = -0.36042E-03, A6 = 0.18852E-04, A8 = -0.63985E-06,
A10 = 0.52915E-08, A12 = -0.54674E-11
6th page
K = 0.00000E + 00, A4 = -0.23013E-03, A6 = 0.18755E-04, A8 = -0.67857E-06,
A10 = 0.20980E-06
7th page
K = 0.00000E + 00, A4 = 0.68046E-03, A6 = 0.29619E-04, A8 = -0.12579E-05,
A10 = 0.34337E-06
11th page
K = 0.00000E + 00, A4 = 0.11250E-02, A6 = -0.91769E-04, A8 = 0.11420E-05,
A10 = 0.10130E-06, A12 = -0.31219E-08
12th page
K = 0.00000E + 00, A4 = 0.28344E-02, A6 = -0.21118E-03, A8 = 0.69824E-05,
A10 = -0.54926E-07, A12 = -0.12981E-08

In the following (including the lens data in Table 2), a power of 10 (for example, 2.5 × 10 ⁻⁰² ) is expressed using E (for example, 2.5E-02).

  Table 3 below shows the specifications of the zoom lens of Example 1 at the wide-angle end, the intermediate position, and the telephoto end. In Table 3, “focal length f” means the focal length of the zoom lens, “Fno” means the F-number of the zoom lens, “view angle” means the view angle of the zoom lens, and “2Y”. Means the diagonal length of the projection surface IM or the imaging surface, and “lens total length” means the total length of the zoom lens. “D1”, “d2”, and “d3” mean the variable intervals in Table 1, that is, between the groups.

[Table 3]
Wide-angle end Intermediate position Telephoto end focal length f 5.05 10.21 20.21
Fno 2.40 3.17 4.80
Angle of view 75.4 41.9 21.9
2Y 6.767 7.981 8.252
Total lens length 43.76 33.39 35.25
d1 22.30 7.15 0.44
d2 6.89 11.55 20.88
d3 1.88 1.99 1.23

  Lens group data of the zoom lens of Example 1 is shown in Table 4 below.

[Table 4]
Lens group Start surface Focal length (mm)
GR1 1 -16.96
GR2 5 11.76
GR3 11 14.51

  FIG. 4 is a cross-sectional view of the zoom lens 11 or the imaging unit 50 according to the first embodiment. Among the first to third lens groups GR1 to GR3 constituting the zoom lens 11, the first negative lens group GR1 as a whole has a negative refractive power and a biconcave first lens L11 and a positive refractive power. And a second meniscus lens L12 that is convex on the object side. The positive second lens group GR2 as a whole has a positive refractive power, a biconvex first lens L21, a positive refractive power, a biconvex second lens L22, and a negative refractive power. And a biconcave third lens L23. Here, the second lens L22 and the third lens L23 are cemented lenses. The positive third lens group GR3 as a whole has a positive refractive power and a biconvex first lens L31. All the lenses L11 to L31 constituting the zoom lens 11 are made of, for example, a glass material. An aperture stop S is disposed between the first lens group GR1 and the second lens group GR2 in the vicinity of the second lens group GR2. In the present embodiment, the projection surface IM has a spherical shape. A parallel flat plate F can be disposed between the light exit surface of the first lens L31 of the third lens group GR3 and the concave projection surface IM.

  5A shows the zoom lens 11 at the wide-angle end, FIG. 5B shows the zoom lens 11 at the intermediate position, and FIG. 5C shows the zoom lens 11 at the telephoto end. As is apparent from the figure, at the time of zooming, the first lens group GR1 to the third lens group GR3 individually move along the optical axis AX.

  6A to 6C show aberration diagrams (spherical aberration, astigmatism, distortion) at infinity at the wide angle end of the zoom lens 11 according to the first embodiment.

  6D to 6F show aberration diagrams (spherical aberration, astigmatism, distortion aberration) at infinity at the intermediate position of the zoom lens 11 according to the first embodiment.

  6G to 6I show aberration diagrams (spherical aberration, astigmatism, distortion) at the telephoto end of the zoom lens 11 according to the first embodiment.

[Example 2]
The lens outline of Example 2 is shown below.
Wide-angle end focal length = 4.6
Intermediate position focal length = 12.09
Telephoto end focal length = 32.21
Wide angle end F number = 2.42
Intermediate position F number = 3.89
Telephoto end F number = 6.08
Zoom ratio = 7.0

  The lens surface data of Example 2 is shown in Table 5 below. The meanings of the specifications in Table 5 are the same as the meanings of the specifications in Table 1 of Example 1.

[Table 5]
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
0 (object) ∞
1 * -93.067 1.00 1.75500 51.2 8.30
2 * 8.429 2.30 6.66
3 * 11.062 1.81 2.00180 19.3 6.68
4 * 16.653 d1 6.60
5 (Aperture) ∞ 0.00 Variable
6 * 7.096 2.01 1.49710 81.6 3.50
7 * -16.475 0.37 3.44
8 9.738 2.04 1.69680 55.5 3.21
9 -26.635 1.29 1.67270 32.2 2.88
10 4.737 d2 2.35
11 * 26.678 1.80 1.85130 40.1 4.85
12 * -16.027 d3 4.83
13 ∞ 0.40 1.51680 64.2 4.39
14 ∞ 1.00 4.32
Imaging surface -46.497 4.10

  Table 6 below shows the aspheric coefficients of the lens surfaces of the zoom lens of Example 2.

[Table 6]
First side
K = 0.00000E + 00, A4 = 0.13165E-03, A6 = -0.40795E-05, A8 = 0.96804E-07,
A10 = -0.10775E-08, A12 = 0.43258E-11
Second side
K = 0.00000E + 00, A4 = -0.32307E-03, A6 = 0.13155E-04, A8 = -0.39247E-06,
A10 = 0.71247E-08, A12 = -0.65518E-10
Third side
K = 0.00000E + 00, A4 = -0.60480E-03, A6 = 0.21841E-04, A8 = -0.45543E-06,
A10 = 0.23544E-08, A12 = -0.51489E-11
4th page
K = 0.00000E + 00, A4 = -0.52490E-03, A6 = 0.22100E-04, A8 = -0.59436E-06,
A10 = 0.49518E-08, A12 = -0.12007E-10
6th page
K = 0.00000E + 00, A4 = -0.38937E-03, A6 = 0.61091E-05, A8 = -0.12886E-05,
A10 = 0.73588E-07
7th page
K = 0.00000E + 00, A4 = 0.24578E-03, A6 = 0.45790E-05, A8 = -0.11214E-05,
A10 = 0.78574E-07
11th page
K = 0.00000E + 00, A4 = 0.93080E-03, A6 = -0.53705E-04, A8 = 0.27577E-06,
A10 = 0.49136E-07, A12 = -0.11531E-08
12th page
K = 0.00000E + 00, A4 = 0.17046E-02, A6 = -0.84433E-04, A8 = 0.70498E-06,
A10 = 0.56858E-07, A12 = -0.13353E-08

  Table 7 below shows the specifications of the zoom lens of Example 2 at the wide-angle end, the intermediate position, and the telephoto end. The meanings of the specifications in Table 7 are the same as the meanings of the specifications in Table 3 of Example 1. The “diaphragm diameter” means the aperture diameter of the diaphragm S in the zoom lens.

[Table 7]
Wide-angle end Intermediate position Telephoto end focal length f 4.60 12.09 32.21
Fno 2.42 3.89 6.08
Angle of View 80.6 35.8 13.8
2Y 6.768 8.181 8.194
Total lens length 46.37 37.14 49.23
Diaphragm diameter 5.15 5.15 6.72
d1 24.84 7.25 0.65
d2 5.02 13.62 33.46
d3 2.50 2.25 1.11

  Other specifications of the zoom lens of Example 2 are shown in Table 8 below. The meanings of the specifications in Table 8 are the same as the meanings of the specifications in Table 4 of Example 1.

[Table 8]
Lens group Start surface Focal length (mm)
GR1 1 -16.68
GR2 5 12.27
GR3 11 11.99

  FIG. 7 is a cross-sectional view of the zoom lens 12 or the imaging unit 50 according to the second embodiment. Of the first to third lens groups GR1 to GR3 constituting the zoom lens 12, the negative first lens group GR1 as a whole has a negative refractive power and a biconcave first lens L11 and a positive refractive power. And a second meniscus lens L12 that is convex on the object side. The positive second lens group GR2 as a whole has a positive refractive power, a biconvex first lens L21, a positive refractive power, a biconvex second lens L22, and a negative refractive power. And a biconcave third lens L23. Here, the second lens L22 and the third lens L23 are cemented lenses. The positive third lens group GR3 as a whole has a positive refractive power and a biconvex first lens L31. All the lenses L11 to L31 constituting the zoom lens 11 are made of, for example, a glass material. An aperture stop S is disposed between the first lens group GR1 and the second lens group GR2 in the vicinity of the second lens group GR2. In the present embodiment, the projection surface IM has a spherical shape. A parallel flat plate F can be disposed between the light exit surface of the first lens L31 of the third lens group GR3 and the concave projection surface IM.

  8A shows the zoom lens 12 at the wide-angle end, FIG. 8B shows the zoom lens 12 at the intermediate position, and FIG. 8C shows the zoom lens 12 at the telephoto end. As is apparent from the figure, at the time of zooming, the first lens group GR1 to the third lens group GR3 individually move along the optical axis AX.

  9A to 9C illustrate aberration diagrams (spherical aberration, astigmatism, distortion) at the wide-angle end of the zoom lens 12 according to the second embodiment.

  9D to 9F show aberration diagrams (spherical aberration, astigmatism, distortion) at the intermediate position of the zoom lens 12 according to the second embodiment.

  9G to 9I illustrate aberration diagrams (spherical aberration, astigmatism, distortion) at the telephoto end of the zoom lens 12 according to the second embodiment.

Example 3
The lens outline of Example 3 is shown below.
Wide-angle end focal length = 4.4
Intermediate position focal length = 10.18
Telephoto end focal length = 23.93
Wide angle end F number = 2.42
Intermediate position F number = 3.89
Telephoto end F number = 6.08
Zoom ratio = 5.4

  The lens surface data of Example 3 is shown in Table 9 below. The meanings of the specifications in Table 9 are the same as the meanings of the specifications in Table 1 of Example 1.

[Table 9]
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
0 (object) ∞
1 * -107.383 1.00 1.75500 51.2 8.73
2 * 8.366 2.93 7.21
3 * 13.415 1.81 2.00180 19.3 7.18
4 * 22.423 d1 7.25
5 (Aperture) ∞ 0.00 2.74
6 * 7.158 2.79 1.49710 81.6 2.92
7 * -17.466 0.31 3.00
8 9.608 1.89 1.69680 55.5 2.99
9 -36.557 1.11 1.67270 32.2 2.81
10 4.825 d2 2.54
11 * 16.803 2.24 1.85130 40.1 4.82
12 * -26.057 d3 4.72
13 ∞ 0.40 1.51680 64.2 4.39
14 ∞ 1.00 4.32
Imaging surface -46.500

  Table 10 below shows the aspheric coefficients of the lens surfaces of the zoom lens of Example 3.

[Table 10]
First side
K = 0.00000E + 00, A4 = 0.80666E-04, A6 = -0.40094E-05, A8 = 0.97831E-07,
A10 = -0.10618E-08, A12 = 0.40023E-11
Second side
K = 0.00000E + 00, A4 = -0.40074E-03, A6 = 0.12510E-04, A8 = -0.40591E-06,
A10 = 0.70806E-08, A12 = -0.66987E-10
Third side
K = 0.00000E + 00, A4 = -0.59789E-03, A6 = 0.22540E-04, A8 = -0.46175E-06,
A10 = 0.23242E-08, A12 = -0.13666E-11
4th page
K = 0.00000E + 00, A4 = -0.52704E-03, A6 = 0.22205E-04, A8 = -0.58016E-06,
A10 = 0.50432E-08, A12 = -0.13162E-10
6th page
K = 0.00000E + 00, A4 = -0.34764E-03, A6 = 0.43347E-05, A8 = -0.10751E-05,
A10 = 0.53614E-07
7th page
K = 0.00000E + 00, A4 = 0.25687E-03, A6 = 0.79588E-06, A8 = -0.76753E-06,
A10 = 0.52706E-07
11th page
K = 0.00000E + 00, A4 = 0.70383E-03, A6 = -0.32969E-04, A8 = -0.10512E-06,
A10 = 0.56334E-07, A12 = -0.14258E-08
12th page
K = 0.00000E + 00, A4 = 0.17295E-02, A6 = -0.92650E-04, A8 = 0.13722E-05,
A10 = 0.50612E-07, A12 = -0.17434E-08

  Table 11 below shows the specifications of the zoom lens of Example 3 at the wide-angle end, the intermediate position, and the telephoto end. In addition, the meaning of the item in Table 11 is the same as that of the item in Table 3 of Example 1. The “diaphragm diameter” means the aperture diameter of the diaphragm S in the zoom lens.

[Table 11]
Wide-angle end Intermediate position Telephoto end focal length f 4.41 10.18 23.93
Fno 2.42 3.89 6.08
Angle of view 83.0 42.0 18.5
2Y 6.626 8.011 8.206
Total lens length 52.20 39.80 45.51
Diaphragm diameter 5.48 5.48 5.48
d1 28.75 9.83 1.80
d2 6.04 12.70 27.24
d3 1.94 1.81 1.00

  Other specifications of the zoom lens of Example 3 are shown in Table 12 below. The meanings of the specifications in Table 12 are the same as the meanings of the specifications in Table 4 of Example 1.

[Table 12]
Lens group Start surface Focal length (mm)
GR1 1 -16.95
GR2 5 13.02
GR3 11 12.29

  FIG. 10 is a cross-sectional view of the zoom lens 13 or the imaging unit 50 according to the third embodiment. Among the first to third lens groups GR1 to GR3 constituting the zoom lens 13, the first negative lens group GR1 as a whole has a negative refractive power and a biconcave first lens L11 and a positive refractive power. And a second meniscus lens L12 that is convex on the object side. The positive second lens group GR2 as a whole has a positive refractive power, a biconvex first lens L21, a positive refractive power, a biconvex second lens L22, and a negative refractive power. And a biconcave third lens L23. Here, the second lens L22 and the third lens L23 are cemented lenses. The positive third lens group GR3 as a whole has a positive refractive power and a biconvex first lens L31. All the lenses L11 to L31 constituting the zoom lens 11 are made of, for example, a glass material. An aperture stop S is disposed between the first lens group GR1 and the second lens group GR2 in the vicinity of the second lens group GR2. In the present embodiment, the projection surface IM has a spherical shape. A parallel flat plate F can be disposed between the light exit surface of the first lens L31 of the third lens group GR3 and the concave projection surface IM.

  FIG. 10 shows the zoom lens 13 at the wide angle end. In the zoom lens 13 at the intermediate position and the telephoto end, as in FIGS. 5B and 5C of Example 1, the first lens group GR1 to the third lens group GR3 individually move along the optical axis AX.

  11A to 11C show aberration diagrams (spherical aberration, astigmatism, distortion) at the wide-angle end of the zoom lens 13 according to the third embodiment.

  11D to 11F show aberration diagrams (spherical aberration, astigmatism, distortion) at the intermediate position of the zoom lens 13 according to the third embodiment.

  11G to 11I show aberration diagrams (spherical aberration, astigmatism, distortion) at the telephoto end of the zoom lens 13 according to the third embodiment.

Example 4
The lens outline of Example 4 is shown below. Note that Example 4 does not belong to the present invention.
Wide-angle end focal length = 5.8
Intermediate position focal length = 11.55
Telephoto end focal length = 23.30
Wide angle end F number = 2.42
Intermediate position F number = 3.89
Telephoto end F number = 6.09
Zoom ratio = 4.0

  The lens surface data of Example 4 is shown in Table 13 below. The meanings of the specifications in Table 13 are the same as the meanings of the specifications in Table 1 of Example 1.

[Table 13]
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
0 (object) ∞
1 * -46.360 1.00 1.75500 51.2 6.48
2 * 10.055 2.17 5.75
3 * 18.755 1.65 2.00180 19.3 5.74
4 * 42.701 d1 5.75
5 (Aperture) ∞ 0.00 Variable
6 * 7.523 2.85 1.49710 81.6 3.11
7 * -14.489 0.20 3.21
8 8.614 2.03 1.69680 55.5 3.17
9 -42.919 0.98 1.67270 32.2 2.93
10 4.598 d2 2.59
11 * 31.692 1.94 1.85130 40.1 4.50
12 * -17.735 d3 4.45
13 ∞ 0.40 1.51680 64.2 4.18
14 ∞ 1.00 4.12
Imaging surface -46.133

  Table 14 below shows the aspheric coefficients of the lens surfaces of the zoom lens of Example 4.

[Table 14]
First side
K = 0.00000E + 00, A4 = 0.61620E-05, A6 = -0.34965E-05, A8 = 0.11169E-06,
A10 = -0.15888E-08, A12 = 0.90602E-11
Second side
K = 0.00000E + 00, A4 = -0.33255E-03, A6 = 0.13395E-04, A8 = -0.44867E-06,
A10 = 0.60414E-08, A12 = -0.21775E-10
Third side
K = 0.00000E + 00, A4 = -0.67425E-03, A6 = 0.19497E-04, A8 = -0.56031E-06,
A10 = 0.22343E-08, A12 = 0.74779E-10
4th page
K = 0.00000E + 00, A4 = -0.59368E-03, A6 = 0.15536E-04, A8 = -0.54982E-06,
A10 = 0.69270E-08, A12 = -0.67109E-11
6th page
K = 0.00000E + 00, A4 = -0.38647E-03, A6 = -0.64151E-05, A8 = 0.46617E-07,
A10 = -0.18124E-07
7th page
K = 0.00000E + 00, A4 = 0.20527E-03, A6 = -0.88285E-05, A8 = 0.22609E-06,
A10 = -0.21048E-07
11th page
K = 0.00000E + 00, A4 = 0.87532E-03, A6 = -0.43258E-04, A8 = 0.18956E-06,
A10 = 0.90036E-07, A12 = -0.27203E-08
12th page
K = 0.00000E + 00, A4 = 0.18785E-02, A6 = -0.12028E-03, A8 = 0.31607E-05,
A10 = 0.43083E-07, A12 = -0.28136E-08

  Table 15 below shows the specifications of the zoom lens of Example 4 at the wide-angle end, the intermediate position, and the telephoto end. The meanings of the specifications in Table 15 are the same as the meanings of the specifications in Table 3 of Example 1. The “diaphragm diameter” means the aperture diameter of the diaphragm S in the zoom lens.

[Table 15]
Wide-angle end Intermediate position Telephoto end focal length f 5.83 11.55 23.30
Fno 2.42 3.89 6.09
Angle of view 67.7 37.4 19.0
2Y 6.627 8.011 8.207
Total lens length 43.90 35.06 38.10
Diaphragm diameter 5.84 4.88 4.88
d1 21.17 7.25 0.65
d2 6.97 11.94 22.23
d3 1.54 1.65 1.00

  Other specifications of the zoom lens of Example 4 are shown in Table 16 below. The meanings of the specifications in Table 16 are the same as the meanings of the specifications in Table 4 of Example 1.

[Table 16]
Lens group Start surface Focal length (mm)
GR1 1 -17.73
GR2 5 11.95
GR3 11 13.60

  FIG. 12 is a cross-sectional view of the zoom lens 14 or the imaging unit 50 according to the fourth embodiment. Of the first to third lens groups GR1 to GR3 constituting the zoom lens 14, the negative first lens group GR1 as a whole has a negative refractive power and a biconcave first lens L11 and a positive refractive power. And a second meniscus lens L12 that is convex on the object side. The positive second lens group GR2 as a whole has a positive refractive power, a biconvex first lens L21, a positive refractive power, a biconvex second lens L22, and a negative refractive power. And a biconcave third lens L23. Here, the second lens L22 and the third lens L23 are cemented lenses. The positive third lens group GR3 as a whole has a positive refractive power and a biconvex first lens L31. All the lenses L11 to L31 constituting the zoom lens 11 are made of, for example, a glass material. An aperture stop S is disposed between the first lens group GR1 and the second lens group GR2 in the vicinity of the second lens group GR2. In the present embodiment, the projection surface IM has a spherical shape. A parallel flat plate F can be disposed between the light exit surface of the first lens L31 of the third lens group GR3 and the concave projection surface IM.

  FIG. 12 shows the zoom lens 14 at the wide-angle end. In the zoom lens 14 at the intermediate position and the telephoto end, as in FIGS. 5B and 5C of Example 1, the first lens group GR1 to the third lens group GR3 move individually along the optical axis AX.

  13A to 13C illustrate aberration diagrams (spherical aberration, astigmatism, distortion) at the wide-angle end of the zoom lens 14 according to the fourth embodiment.

  13D to 13F show aberration diagrams (spherical aberration, astigmatism, distortion aberration) at the intermediate position of the zoom lens 14 according to the fourth embodiment.

  13G to 13I illustrate aberration diagrams (spherical aberration, astigmatism, distortion) at the telephoto end of the zoom lens 14 according to the fourth example.

Example 5
The lens outline of Example 5 is shown below.
Wide-angle end focal length = 4.9
Intermediate position focal length = 9.69
Telephoto end focal length = 19.58
Wide-angle end F-number = 2.41
Intermediate position F number = 3.13
Telephoto end F number = 4.82
Zoom ratio = 4.0

  The lens surface data of Example 5 is shown in Table 17 below. The meanings of the specifications in Table 17 are the same as the meanings of the specifications in Table 1 of Example 1.

[Table 17]
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
0 (object) d0
1 * -41.849 1.00 1.75500 51.2 7.88
2 * 10.035 2.59 6.48
3 * 15.996 1.66 2.00180 19.3 6.44
4 * 32.335 d1 6.49
5 (Aperture) ∞ 0.00 2.67
6 * 6.076 2.28 1.49710 81.6 2.91
7 * -21.143 0.20 2.91
8 9.341 1.58 1.69680 55.5 2.91
9 -13.917 0.50 1.67270 32.2 2.80
10 4.647 d2 2.57
11 * 14.670 2.05 1.85 130 40.1 4.82
12 * -17.039 d3 4.82
13 ∞ 0.40 1.51680 64.2 4.26
14 ∞ 1.00 4.21
Variable imaging surface

  Table 18 below shows the aspheric coefficients of the lens surfaces of the zoom lens of Example 5.

[Table 18]
First side
K = 0.00000E + 00, A4 = 0.11366E-03, A6 = -0.12518E-05, A8 = 0.69818E-07,
A10 = -0.12902E-08, A12 = 0.70658E-11
Second side
K = 0.00000E + 00, A4 = -0.22337E-03, A6 = 0.16935E-04, A8 = -0.40488E-06,
A10 = 0.75238E-08, A12 = -0.85834E-10
Third side
K = 0.00000E + 00, A4 = -0.43783E-03, A6 = 0.22806E-04, A8 = -0.61957E-06,
A10 = 0.39087E-08, A12 = -0.12484E-10
4th page
K = 0.00000E + 00, A4 = -0.36042E-03, A6 = 0.18852E-04, A8 = -0.63985E-06,
A10 = 0.52915E-08, A12 = -0.54674E-11
6th page
K = 0.00000E + 00, A4 = -0.26285E-03, A6 = 0.17888E-04, A8 = -0.86765E-06,
A10 = 0.21140E-06
7th page
K = 0.00000E + 00, A4 = 0.67617E-03, A6 = 0.25600E-04, A8 = -0.11943E-05,
A10 = 0.33611E-06
11th page
K = 0.00000E + 00, A4 = 0.10236E-02, A6 = -0.69325E-04, A8 = 0.75715E-06,
A10 = 0.88377E-07, A12 = -0.28582E-08
12th page
K = 0.00000E + 00, A4 = 0.25183E-02, A6 = -0.19730E-03, A8 = 0.70141E-05,
A10 = -0.80414E-07, A12 = -0.89769E-09

  Table 19 below shows specifications of the zoom lens of Example 5 at the wide-angle end, the intermediate position, and the telephoto end. The meanings of the specifications in Table 19 are the same as the meanings of the specifications in Table 3 of Example 1. The “diaphragm diameter” means the aperture diameter of the diaphragm S in the zoom lens.

[Table 19]
Wide angle end 1 Intermediate position 1 Telephoto end 1
Focal length f 4.90 9.69 19.58
Fno 2.41 3.13 4.82
Angle of view 77.2 43.9 22.6
2Y 6.599 7.722 8.065
Total lens length 44.91 33.89 35.39
d0 ∞ ∞ ∞
d1 23.30 7.73 0.65
d2 6.51 10.87 20.46
d3 1.85 2.02 1.02
Image plane R -29.653 -28.757 -28.997

Wide angle end 2 Middle position 2 Telephoto end 2
Focal length f 4.79 9.41 18.05
Fno 2.35 3.04 4.45
Angle of view 78.8 45.1 24.8
2Y 6.627 7.712 8.061
Total lens length 44.91 33.89 35.39
d0 100 300 500
d1 23.30 7.73 0.65
d2 6.07 10.27 18.90
d3 2.29 2.63 2.58
Image plane R -28.307 -40.972 -154.132

  Other specifications of the zoom lens of Example 5 are shown in Table 20 below. The meanings of the specifications in Table 20 are the same as the meanings of the specifications in Table 4 of Example 1.

[Table 20]
Lens group Start surface Focal length (mm)
GR1 1 -17.23
GR2 5 11.96
GR3 11 14.58

  FIG. 14 is a cross-sectional view of the zoom lens 15 or the imaging unit 50 according to the fifth embodiment. Of the first to third lens groups GR1 to GR3 constituting the zoom lens 15, the first negative lens group GR1 as a whole has a negative refractive power and a biconcave first lens L11, and a positive refractive power. And a second meniscus lens L12 that is convex on the object side. The positive second lens group GR2 as a whole has a positive refractive power, a biconvex first lens L21, a positive refractive power, a biconvex second lens L22, and a negative refractive power. And a biconcave third lens L23. Here, the second lens L22 and the third lens L23 are cemented lenses. The positive third lens group GR3 as a whole has a positive refractive power and a biconvex first lens L31. All the lenses L11 to L31 constituting the zoom lens 11 are made of, for example, a glass material. An aperture stop S is disposed between the first lens group GR1 and the second lens group GR2 in the vicinity of the second lens group GR2. In the present embodiment, the projection surface IM has a spherical shape. A parallel flat plate F can be disposed between the light exit surface of the first lens L31 of the third lens group GR3 and the concave projection surface IM.

In the present embodiment, the curvature radius R of the projection surface IM is fixed by changing the curvature radius R of the projection surface IM according to the curvature of field that changes according to the focal length f and the object distance. Better optical performance than ever.

  FIG. 14 shows the zoom lens 15 at the wide-angle end. In the zoom lens 15 at the intermediate position and the telephoto end, as in FIGS. 5B and 5C of Example 1, the first lens group GR1 to the third lens group GR3 individually move along the optical axis AX.

  15A to 15C show aberration diagrams (spherical aberration, astigmatism, distortion) at infinity at the wide-angle end of the zoom lens 15 according to the fifth embodiment.

  15D to 15F show aberration diagrams (spherical aberration, astigmatism, distortion aberration) at infinity at the intermediate position of the zoom lens 15 according to the fifth embodiment.

  FIGS. 15G to 15I show aberration diagrams (spherical aberration, astigmatism, distortion aberration) at infinity at the telephoto end of the zoom lens 15 according to the fifth embodiment.

  16A to 16C show aberration diagrams (spherical aberration, astigmatism, distortion aberration) at a distance of 100 mm from the object side at the wide-angle end of the zoom lens 15 according to the fifth embodiment.

  16D to 16F show aberration diagrams (spherical aberration, astigmatism, distortion) at a distance of 300 mm from the object side at the intermediate position of the zoom lens 15 according to the fifth embodiment.

  16G to 16I are aberration diagrams (spherical aberration, astigmatism, distortion) at a distance of 500 mm from the object side at the telephoto end of the zoom lens 15 according to the fifth embodiment.

For reference, Table 21 below shows values f2 / fW, f2 / fT, RIT / L, and | P′W × RIW | in each of Examples 1 to 5 corresponding to the conditional expressions (1) to (6). , | P′T × RI T |, L / EW.

[Table 21]

  In the above, the present invention has been described based on the embodiments and examples, but the present invention is not limited to the above-described embodiments and the like.

  For example, in the above-described embodiment, the zoom lenses 11, 12, 13, 14, and 15 of the above-described example are configured by three groups of the first to third lens groups GR1 to GR3. One or more lenses having substantially no power can be added before and after or between.

  Note that the meaning of the paraxial radius of curvature when the lens surface described in the claims and examples is an aspherical surface in the actual lens measurement scene (specifically, outside the lens). The approximate curvature radius when fitting the shape measurement value in the central region within 10% with respect to the diameter by the method of least squares can be regarded as the paraxial curvature radius.

  For example, when a secondary aspherical coefficient is used, a curvature radius that takes into account the secondary aspherical coefficient in the reference curvature radius of the aspherical definition formula can be regarded as a paraxial curvature radius (for example, reference literature). (See pages 41 to 42 of “Lens Design Method” by K. Matsui, Kyoritsu Publishing Co., Ltd.)

Claims (7)

A zoom lens for forming a subject image on the projection surface;
An imaging device having an imaging element in which the projection surface is curved at an arbitrary cross section toward the periphery of the screen,
The zoom lens includes, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power,
When zooming from the wide-angle end to the telephoto end, the distance between each lens group is changed,
An imaging apparatus that satisfies the following conditional expression.
2.44 ≦ f2 / fW <3.0 (1)
0.3 <f2 / fT ≦ 0.61 (2)
3.9 <| P′W × RIW | <7.0 (4)
1.0 <| P′T × RIT | <1.5 (5)
Where f2: focal length of the second lens group fW: focal length of the entire system at the wide angle end fT: focal length of the entire system at the telephoto end
P′W = Σ [(h _jw / h _1w ) × (1 / r _j ) × {(1 / n _j ) − (1 / n _{j + 1} )}]
h _jw : Paraxial axial ray height on the lens j-th surface at the wide-angle end
r _j : radius of curvature of the lens j-th surface
n _j : Refractive index of the medium on the object side from the lens j-th surface
n _{j + 1} : refractive index of the medium on the image side from the lens j-th surface
RIW: radius of curvature of the projection surface at the wide angle end when the object distance is infinity
P′T = Σ [(h _jt / h _1t ) × (1 / r _j ) × {(1 / n _j ) − (1 / n _{j + 1} )}]
h _jt : Paraxial axial ray height on the lens j-th surface at the telephoto end
RIT: radius of curvature of the projection surface at the telephoto end when the object distance is infinity The imaging device according to claim 1, wherein the following conditional expression is satisfied.
−12 <RIT / L <−7 (3)
Where RIT: radius of curvature of the projection surface at the telephoto end when the object distance is infinite L: maximum image height The imaging device according to claim 1, wherein the following conditional expression is satisfied.
−0.15 <L / EW <−0.07 (6)
L: Maximum image height EW: Exit pupil position at wide angle end   The imaging apparatus according to claim 1, wherein the third lens group includes one positive lens and performs focusing by moving the third lens group.   The imaging device according to claim 1, further comprising a lens having substantially no power.   The imaging apparatus according to claim 1, wherein a curvature amount of the projection surface is changed according to a focal length of the zoom lens. Depending on the focus distance of the zoom lens, wherein varying the amount of curvature of the projection plane, the imaging apparatus according to any one of claims 1 and 6.

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