JP2016021011A - Wide-angle lens, imaging optical device, and digital equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wide-angle lens which has a wide view angle of a shooting view angle in excess of 80 degrees and a bright F-number and yet offers reduced chromatic and coma aberrations and uniform image quality over an entire image, and further to provide an imaging optical device and digital equipment having the same.SOLUTION: A wide-angle lens LN comprises a negative first group Gr1 and a positive second group Gr2 in an order from an object side, the first group Gr1 including at least one cemented lens LS having positive power. Focusing on an object at a short distance is done by moving the second group Gr2 toward the object side while keeping the first group Gr1 stationary. The wide-angle lens satisfies following conditional expressions: 0.3<(R2+R1)/(R2-R1)<1.2, Fno<2.4, and fov>80°, where R2 represents a curvature radius of an image-side surface of a cemented lens located on the most object side in the first group, R1 represents a curvature radius of an object-side surface of the cemented lens located on the most object side in the first group, Fno represents an aperture F-number, and fov represents a total view angle.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wide-angle lens, an imaging optical device, and a digital device. More specifically, the present invention relates to an image of an object as an imaging device (for example, a CCD (Charge Coupled Device) type image sensor, a CMOS (Complementary Metal-Oxide Semiconductor) type image. A compact and large-diameter wide-angle lens suitable for interchangeable lens digital cameras captured by a solid-state image sensor such as a sensor, and an imaging optical device that outputs an image of a subject captured by the wide-angle lens and the image sensor as an electrical signal; The present invention relates to a digital device with an image input function such as a digital camera equipped with the imaging optical device.

  In recent years, digital cameras have become common as interchangeable lens cameras. In digital cameras, it is possible for a user to view a photographed image at the same magnification on a monitor. Therefore, improvement in MTF (Modulation Transfer Function) performance and reduction in chromatic aberration are increasingly required. In particular, in order to increase the shutter speed in shooting night scenes and stars, it is required to form a point image when shooting a point light source (such as a streetlight or a star) together with a lens having a small F value. In order to meet these demands, Patent Documents 1 and 2 have proposed wide-angle lenses suitable as interchangeable lenses for interchangeable lens digital cameras.

JP 05-034592 A Japanese Patent Laid-Open No. 11-211978

  The wide-angle lens proposed in Patent Document 1 realizes a wide angle of view, but the aberration is insufficiently corrected, and the F value is about 2.8. In addition, the wide-angle lens proposed in Patent Document 2 achieves a bright F-number of about 1.4, but the shooting angle of view is as narrow as about 65 degrees.

  The present invention has been made in view of such a situation, and an object of the present invention is to reduce chromatic aberration and coma aberration while realizing a wide angle of view exceeding 80 degrees and a bright F value, and to reduce the entire image. It is an object of the present invention to provide a wide-angle lens capable of obtaining uniform image quality, an imaging optical device including the same, and a digital device.

In order to achieve the above object, the wide-angle lens of the first invention comprises, in order from the object side, a first group having negative power and a second group having positive power.
The first group has at least one cemented lens having a positive power,
Focusing on a short-distance object is performed by moving the second group to the object side with the position of the first group fixed.
The following conditional expressions (1) to (3) are satisfied.
0.3 <(R2 + R1) / (R2-R1) <1.2 (1)
Fno <2.4 (2)
fov> 80 ° (3)
However,
R2: radius of curvature of the image side surface of the cemented lens closest to the object side in the first group,
R1: radius of curvature of the object side surface of the cemented lens closest to the object side in the first group,
Fno: aperture F value,
fov: full angle of view
It is.

The wide-angle lens of the second invention is characterized in that, in the first invention, the following conditional expression (4) is satisfied.
−10 <f1 / f <−1 (4)
However,
f1: focal length of the first group,
f: focal length of the entire system,
It is.

  A wide-angle lens according to a third aspect of the invention is characterized in that, in the first or second aspect of the invention, a positive lens is provided on the image side of the cemented lens in the first group.

The wide-angle lens according to a fourth aspect of the invention is characterized in that, in any one of the first to third aspects of the invention, the following conditional expression (5) is satisfied.
1 <tp / tn <8 (5)
However,
tp: the thickness on the optical axis of the positive lens constituting the most object-side cemented lens in the first group,
tn: the thickness on the optical axis of the negative lens constituting the most object side cemented lens in the first lens group,
It is.

The wide-angle lens according to a fifth aspect of the present invention includes the cemented lens in the first group having at least one lens satisfying the following conditional expression (6) in any one of the first to fourth aspects. It is characterized by.
Nd> 1.8 (6)
However,
Nd: refractive index for d-line,
It is.

  A wide-angle lens according to a sixth invention is characterized in that, in any one of the first to fifth inventions, the first group has three negative lenses in succession in order from the object side.

  A wide-angle lens according to a seventh invention is characterized in that, in any one of the first to sixth inventions, at least one negative lens in the first group has an aspherical surface.

A wide-angle lens according to an eighth invention is characterized in that, in any one of the first to seventh inventions, at least one negative lens in the first group satisfies the following conditional expression (7): To do.
νd> 70 (7)
However,
νd: Abbe number,
It is.

  The wide-angle lens of a ninth invention is characterized in that, in any one of the first to eighth inventions, the lens closest to the object side in the second group is a negative lens.

  A wide-angle lens according to a tenth aspect of the invention is characterized in that, in any one of the first to ninth aspects, an aperture stop is provided in the second group, and the lens is positioned before and after the aperture stop. .

  A wide-angle lens according to an eleventh aspect of the invention is any one of the first to tenth aspects of the invention, further comprising an aperture stop in the second group, and at least one aspheric surface on the image side from the aperture stop. It is characterized by.

  An imaging optical device according to a twelfth aspect includes the wide-angle lens according to any one of the first to eleventh aspects, and an imaging element that converts an optical image formed on the imaging surface into an electrical signal. And the wide-angle lens is provided so that an optical image of a subject is formed on the imaging surface of the imaging device.

  According to a thirteenth aspect of the present invention, a digital apparatus includes the imaging optical device according to the twelfth aspect of the present invention, to which at least one function of still image shooting and moving image shooting of a subject is added.

  According to the present invention, a wide-angle lens and an imaging optical device that can reduce chromatic aberration and coma while realizing a wide field angle exceeding 80 degrees and a bright F value and obtain uniform image quality over the entire image are realized. be able to. By using the wide-angle lens or the imaging optical device for a digital device (for example, a digital camera), a high-performance image input function can be added to the digital device in a compact manner.

The lens block diagram of 1st Embodiment (Example 1). The lens block diagram of 2nd Embodiment (Example 2). The lens block diagram of 3rd Embodiment (Example 3). The lens block diagram of 4th Embodiment (Example 4). The lens block diagram of 5th Embodiment (Example 5). FIG. 3 is a longitudinal aberration diagram of Example 1. FIG. 6 is a longitudinal aberration diagram of Example 2. FIG. 6 is a longitudinal aberration diagram of Example 3. FIG. 6 is a longitudinal aberration diagram of Example 4. FIG. 6 is a longitudinal aberration diagram of Example 5. FIG. 4 is a lateral aberration diagram of Example 1. FIG. 4 is a lateral aberration diagram of Example 2. FIG. 4 is a lateral aberration diagram of Example 3. FIG. 6 is a lateral aberration diagram of Example 4. FIG. 6 is a lateral aberration diagram of Example 5. FIG. 3 is a schematic diagram illustrating a schematic configuration example of a digital device including an imaging optical device.

Hereinafter, a wide-angle lens, an imaging optical device, and a digital device according to the present invention will be described. The wide-angle lens according to the present invention includes, in order from the object side, a first group having negative power and a second group having positive power (power: an amount defined by the reciprocal of the focal length). There is at least one cemented lens having positive power in the group, and the second group is moved to the object side in a state where the position of the first group is fixed, thereby focusing on a short distance object, The following conditional expressions (1) to (3) are satisfied.
0.3 <(R2 + R1) / (R2-R1) <1.2 (1)
Fno <2.4 (2)
fov> 80 ° (3)
However,
R2: radius of curvature of the image side surface of the cemented lens closest to the object side in the first group,
R1: radius of curvature of the object side surface of the cemented lens closest to the object side in the first group,
Fno: aperture F value,
fov: full angle of view,
It is.

  By having a negative and positive power arrangement, it is possible to secure a lens back that is relatively easy compared to the focal length of the entire system. Further, by having a cemented lens in the first group, it is possible to effectively correct chromatic aberration. Then, in an imaging lens having a bright F-number satisfying the conditional expressions (2) and (3) and having a wide angle of view, a cemented lens having positive power in the first group is a conditional expression (1). ) Can be suppressed, the occurrence of various aberrations can be suppressed, the occurrence of chromatic aberration is small despite the wide angle, and uniform image quality can be achieved from the center of the screen to the periphery. Then, by lowering the upper limit of conditional expression (1), the deterioration of spherical aberration and coma aberration (particularly sagittal coma aberration) is suppressed, and by exceeding the lower limit of conditional expression (1), spherical aberration and coma aberration (particularly, particularly Since the deterioration of the meridional coma aberration in the middle of the screen can be suppressed, uniform image quality from the screen center to the screen periphery can be achieved.

  According to the above-mentioned characteristic configuration, a wide-angle lens and an imaging optical device that achieve a uniform image quality over the entire image by reducing chromatic aberration and coma aberration while realizing a wide angle of view exceeding 80 degrees and a bright F-number. can do. If the wide-angle lens or imaging optical device is used in a digital device such as a digital camera, a high-performance image input function can be added to the digital device in a lightweight and compact manner, and the digital device can be made compact and low in cost. , Can contribute to higher performance and higher functionality. In the following, conditions for obtaining such effects in a well-balanced manner and achieving higher optical performance, light weight, downsizing, etc. will be described.

It is desirable to satisfy the following conditional expression (4).
−10 <f1 / f <−1 (4)
However,
f1: focal length of the first group,
f: focal length of the entire system,
It is.

  By exceeding the lower limit of the conditional expression (4), it is effective to prevent the negative power of the first group from becoming too weak compared to the focal length of the entire system and to cause deterioration of image quality due to insufficient correction of chromatic aberration. Can be prevented. Also, by falling below the upper limit of the conditional expression (4), the negative power of the first group does not become too strong compared to the focal length of the entire system, and the aberration variation during focusing by the second group is effective. Can be suppressed.

It is desirable to satisfy the following conditional expression (4a), and it is more desirable to satisfy conditional expression (4b).
−8 <f1 / f <−1.5 (4a)
−5 <f1 / f <−2 (4b)
These conditional expressions (4a) and (4b) define more preferable condition ranges based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (4). Therefore, the above effect can be further enhanced by preferably satisfying conditional expression (4a), more preferably satisfying conditional expression (4b).

  It is desirable to have a positive lens on the image side of the cemented lens in the first group. If comprised in this way, the division | segmentation of the positive power of a junction lens can reduce the burden of a junction lens. Therefore, it is possible to reduce the occurrence of various aberrations.

It is desirable to satisfy the following conditional expression (5).
1 <tp / tn <8 (5)
However,
tp: the thickness on the optical axis of the positive lens constituting the most object-side cemented lens in the first group,
tn: the thickness on the optical axis of the negative lens constituting the most object side cemented lens in the first lens group,
It is.

  By exceeding the lower limit of conditional expression (5), it becomes possible to effectively correct chromatic aberration. Further, by falling below the upper limit of the conditional expression (5), the positive lens is not excessively thick, and the size can be reduced.

It is more desirable to satisfy the following conditional expression (5a).
3 <tp / tn <5 (5a)
This conditional expression (5a) defines a more preferable condition range based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (5). Therefore, the above effect can be further increased preferably by satisfying conditional expression (5a).

It is desirable that the cemented lens in the first group has at least one lens that satisfies the following conditional expression (6).
Nd> 1.8 (6)
However,
Nd: refractive index for d-line,
It is.

  By satisfying conditional expression (6), it is possible to reduce the power of the target lens surface, and therefore it is possible to effectively reduce the occurrence of various aberrations.

  The first group preferably has three negative lenses continuously in order from the object side. With such a configuration, since a light beam from a high angle of view that is incident at a large incident angle can be gradually bent by the three negative lenses, it is possible to effectively suppress the occurrence of coma. In addition, since the lens diameter can be reduced by using the first lens located closest to the object side as a negative lens, it is possible to effectively reduce the size of the imaging lens.

  It is desirable that at least one negative lens in the first group has an aspherical surface. By disposing a negative lens in the first group, it is possible to widen the angle, but on the other hand, a large distortion aberration may occur, which may cause a problem. Therefore, if an aspherical surface is provided on the negative lens in the first lens group, it is possible to effectively correct distortion occurring in the negative lens.

It is desirable that at least one negative lens in the first group satisfies the following conditional expression (7).
νd> 70 (7)
However,
νd: Abbe number,
It is.

  When at least one negative lens in the first group satisfies the conditional expression (7), the lateral chromatic aberration can be effectively reduced.

  In the second group, it is desirable that the most object side lens is a negative lens. By using the most object side lens in the second lens group as a negative lens, it is possible to effectively correct curvature of field.

  It is desirable to have an aperture stop in the second group, and the lens is positioned before and after the aperture stop. With this configuration, the effective optical diameter of the second group, which is the focus group, can be reduced, and the size can be reduced. This also makes it possible to reduce the noise and increase the speed during focusing.

  It is desirable to have an aperture stop in the second group and to have at least one aspheric surface on the image side from the aperture stop. If comprised in this way, it will become possible to correct | amend effectively the spherical aberration and the coma aberration which arose on the object side from the aperture stop by the aspherical surface.

  The wide-angle lens according to the present invention is suitable for use as an imaging lens for a digital device with an image input function (for example, a digital camera). By combining this with an imaging device or the like, an image of a subject is optically captured. Thus, an imaging optical device that outputs an electrical signal can be configured. The imaging optical device is an optical device that constitutes a main component of a camera used for still image shooting or moving image shooting of a subject, for example, a wide-angle lens that forms an optical image of an object in order from the object (i.e., subject) side, And an imaging device that converts an optical image formed by the wide-angle lens into an electrical signal. Further, the wide-angle lens having the above-described characteristic configuration is arranged so that an optical image of the subject is formed on the light receiving surface (that is, the imaging surface) of the imaging device. An imaging optical device and a digital device including the imaging optical device can be realized.

  Examples of digital devices with an image input function include cameras such as digital cameras, video cameras, surveillance cameras, security cameras, in-vehicle cameras, and videophone cameras. In addition, personal computers, portable digital devices (for example, mobile phones, smart phones (high performance mobile phones), tablet terminals, mobile computers, etc.), peripheral devices (scanners, printers, mice, etc.), and other digital devices (drives) Recorders, defense equipment, etc.) with built-in or external camera functions. As can be seen from these examples, it is possible not only to configure a camera by using an imaging optical device, but also to add a camera function by mounting the imaging optical device on various devices. For example, a digital device with an image input function such as a mobile phone with a camera can be configured.

  FIG. 16 is a schematic cross-sectional view showing a schematic configuration example of a digital device DU as an example of a digital device with an image input function. The imaging optical device LU mounted in the digital device DU shown in FIG. 16 includes, in order from the object (that is, the subject) side, a wide-angle lens LN (AX: optical axis) that forms an optical image (image plane) IM of the object, An image sensor SR that converts the optical image IM formed on the light receiving surface (imaging surface) SS by the wide-angle lens LN into an electrical signal, and a parallel plane plate (for example, the image sensor SR) as necessary. (Corresponding to an optical filter such as an optical low-pass filter and an infrared cut filter, which are arranged as necessary). When a digital device DU with an image input function is constituted by this imaging optical device LU, the imaging optical device LU is usually arranged inside the body, but when necessary to realize the camera function, a form as necessary is adopted. Is possible. For example, the unitized imaging optical device LU can be configured to be detachable or rotatable with respect to the main body of the digital device DU.

  The wide-angle lens LN is a wide-angle lens composed of two negative and positive groups, and the second group is moved to the object side along the optical axis AX while the position of the first group is fixed. The optical image IM is formed on the light receiving surface SS of the image sensor SR by performing focusing. As the image sensor SR, for example, a solid-state image sensor such as a CCD image sensor or a CMOS image sensor having a plurality of pixels is used. Since the wide-angle lens LN is provided so that the optical image IM of the subject is formed on the light-receiving surface SS that is a photoelectric conversion unit of the image sensor SR, the optical image IM formed by the wide-angle lens LN is the image sensor It is converted into an electric signal by SR.

  The digital device DU includes a signal processing unit 1, a control unit 2, a memory 3, an operation unit 4, a display unit 5 and the like in addition to the imaging optical device LU. The signal generated by the image sensor SR is subjected to predetermined digital image processing, image compression processing, and the like in the signal processing unit 1 as necessary, and recorded as a digital video signal in the memory 3 (semiconductor memory, optical disc, etc.) In some cases, it is transmitted to other devices via a cable or converted into an infrared signal or the like (for example, a communication function of a mobile phone). The control unit 2 is composed of a microcomputer, and controls functions such as shooting functions (still image shooting function, movie shooting function, etc.) and image playback functions; focusing, lens movement mechanism control for camera shake correction, etc. Do it. For example, the control unit 2 controls the imaging optical device LU so as to perform at least one of still image shooting and moving image shooting of a subject. The display unit 5 includes a display such as a liquid crystal monitor, and performs image display using an image signal converted by the image sensor SR or image information recorded in the memory 3. The operation unit 4 is a part including operation members such as an operation button (for example, a release button) and an operation dial (for example, a shooting mode dial), and transmits information input by the operator to the control unit 2.

  Next, specific optical configurations of the wide-angle lens LN will be described in more detail with reference to first to fifth embodiments. FIGS. 1 to 5 are lens configuration diagrams corresponding to the wide-angle lenses LN constituting the first to fifth embodiments, respectively, and show the lens arrangement in an object infinite state in an optical section. Both have a negative and positive two-group configuration, and during focusing, the second group Gr2 moves to the object side along the optical axis AX while the position of the first group Gr1 is fixed. That is, the second group Gr2 that is the focus group moves to the object side during focusing on a short-distance object, as indicated by an arrow mF.

  In the wide-angle lens LN (FIG. 1) of the first embodiment, each group is configured as follows. The first group Gr1 is a biconvex lens element composed of three negative meniscus lenses L11, L12, and L13 concave on the image side, a biconvex positive lens L14, and a negative meniscus lens L15 concave on the object side. It is composed of a positive power cemented lens LS, a biconvex positive lens L16, and a biconvex positive power cemented lens composed of a negative meniscus lens L17 that is concave on the object side, and the image side surface of the negative meniscus lens L12. It is aspheric. The second group Gr2 includes a biconvex positive lens, a cemented lens composed of a biconvex positive lens and a biconcave negative lens, an aperture stop ST, a negative meniscus lens concave on the object side, and a biconvex positive lens. (Double-sided aspheric surface) and a positive meniscus lens convex on the image side.

  In the wide-angle lens LN (FIG. 2) of the second embodiment, each group is configured as follows. The first group Gr1 is a biconvex lens element composed of three negative meniscus lenses L11, L12, and L13 concave on the image side, a biconvex positive lens L14, and a negative meniscus lens L15 concave on the object side. The negative side meniscus lenses L12 and L13 are aspherical on the image side surfaces. The second group Gr2 includes a biconcave negative lens L21, a biconvex positive lens, a cemented lens including a biconvex positive lens and a negative meniscus lens concave on the object side, an aperture stop ST, and a biconcave negative lens. The lens includes a biconvex positive lens (double-sided aspheric surface), and a cemented lens including a biconcave negative lens and a biconvex positive lens.

  In the wide-angle lens LN (FIG. 3) of the third embodiment, each group is configured as follows. The first group Gr1 is a biconvex lens element including three negative meniscus lenses L11, L12, and L13 that are concave on the image side, a negative meniscus lens L14 that is concave on the image side, and a biconvex positive lens L15 in order from the object side. And a positive power cemented lens LS, and the image side surface of the negative meniscus lens L12 is aspheric. The second group Gr2 includes a biconvex positive lens, a cemented lens including a positive meniscus lens convex on the image side and a negative meniscus lens concave on the object side, an aperture stop ST, and a negative meniscus lens concave on the image side. And a negative meniscus lens concave on the object side, a biconvex positive lens (double-sided aspheric surface), and a cemented lens made up of a biconcave negative lens and a biconvex positive lens.

  In the wide-angle lens LN (FIG. 4) of the fourth embodiment, each group is configured as follows. The first group Gr1 includes, in order from the object side, negative meniscus lenses L11 and L12 that are concave on the image side, a biconcave negative lens L13, a biconvex positive lens L14, and a negative meniscus lens that is concave on the object side. It is composed of a biconvex positive power cemented lens LS consisting of L15 and a positive meniscus lens L16 convex on the object side, and the image side surface of the negative meniscus lens L12 is aspheric. The second group Gr2 includes a negative meniscus lens L21 concave on the image side, a biconvex positive lens, a cemented lens including a positive meniscus lens convex on the image side and a negative meniscus lens concave on the object side, and an aperture stop ST. And a negative meniscus lens concave on the object side, a biconvex positive lens (double-sided aspheric surface), and a positive meniscus lens convex on the image side.

  In the wide-angle lens LN (FIG. 5) of the fifth embodiment, each group is configured as follows. The first group Gr1 is a biconvex lens element including three negative meniscus lenses L11, L12, and L13 that are concave on the image side, a negative meniscus lens L14 that is concave on the image side, and a biconvex positive lens L15 in order from the object side. The negative meniscus lens L12 has two aspheric surfaces. The cemented lens LS has a positive power. The second group Gr2 includes a negative meniscus lens L21 concave on the image side, a biconvex positive lens, a cemented lens including a positive meniscus lens convex on the image side and a negative meniscus lens concave on the object side, and an aperture stop ST. And a biconcave negative lens, a biconvex positive lens (double-sided aspheric surface), and a cemented lens made up of a biconcave negative lens and a biconvex positive lens.

  Hereinafter, the configuration and the like of the wide-angle lens embodying the present invention will be described more specifically with reference to the construction data of the examples. Examples 1 to 5 (EX1 to 5) listed here are numerical examples corresponding to the first to fifth embodiments, respectively, and are lens configuration diagrams illustrating the first to fifth embodiments. (FIGS. 1 to 5) show the optical configurations of the corresponding Examples 1 to 5, respectively.

In the construction data of each embodiment, as surface data, in order from the left column, surface number i (ST: stop), radius of curvature r (mm) in paraxial, axis top surface distance d (mm), d line (wavelength: wavelength). 587.56 nm) and the Abbe number vd for the d-line. The surface with * in the surface number i is an aspheric surface, and the surface shape is defined by the following formula (AS) using a local orthogonal coordinate system (x, y, z) with the surface vertex as the origin. The As aspheric data, an aspheric coefficient or the like is shown. It should be noted that the coefficient of the term not described in the aspherical data of each example is 0, and E−n = × 10 ⁻ⁿ for all data.
z = (c · h ² ) / [1 + √ {1− (1 + K) · c ² · h ² }] + Σ (Aj · h ^j ) (AS)
However,
h: height in the direction perpendicular to the z axis (optical axis AX) (h ² = x ² + y ² ),
z: the amount of sag in the direction of the optical axis AX at the position of height h (based on the surface vertex),
c: curvature at the surface vertex (the reciprocal of the radius of curvature r),
K: conic constant,
Aj: j-order aspheric coefficient,
It is.

  As various data, the focal length (f, mm), back focus (fB, mm), F number (F), total lens length (TL, mm), diagonal length of the imaging surface SS of the image sensor SR (2Y ′) , Mm; Y ′: maximum image height), entrance pupil position (ENTP, distance from first surface to entrance pupil position, mm), exit pupil position (EXTP, distance from imaging surface SS to exit pupil position, mm) , Front principal point position (H1, distance from first surface to front principal point position, mm), rear principal point position (H2, distance from final surface to rear principal point position, mm). The back focus fB represents the distance from the image side surface of the parallel plate PT to the image plane IM. Furthermore, the focal length (mm) of each group Gr1, Gr2 is shown as lens group data. Table 1 shows values corresponding to the conditional expressions of the respective examples.

  FIGS. 6 to 10 are longitudinal aberration diagrams corresponding to Examples 1 to 5 (EX1 to EX5), (A) is a spherical aberration diagram, (B) is an astigmatism diagram, and (C) is a graph showing astigmatism. It is a distortion aberration figure. The spherical aberration diagram shows the amount of spherical aberration with respect to the d-line (wavelength 587.56 nm) indicated by the solid line, the amount of spherical aberration with respect to the C-line (wavelength 656.28 nm) indicated by the alternate long and short dash line, and the g-line (wavelength 435.84 nm) indicated by the broken line. The amount of spherical aberration is represented by the amount of deviation (unit: mm) in the optical axis AX direction from the paraxial image plane, and the vertical axis is a value obtained by normalizing the height of incidence on the pupil by its maximum height (ie, (Relative pupil height). In the astigmatism diagram, the broken line T is the tangential (meridional) image plane with respect to the d line, the solid line S is the sagittal image plane with respect to the d line, and the amount of deviation (unit: mm) in the optical axis AX direction from the paraxial image plane. The vertical axis represents the image height (IMG HT, unit: mm). In the distortion diagrams, the horizontal axis represents distortion (unit:%) with respect to the d-line, and the vertical axis represents image height (IMG HT, unit: mm). Note that the maximum value of the image height IMG HT corresponds to the maximum image height Y ′ on the image plane IM (half the diagonal length of the light receiving surface SS of the image sensor SR).

  FIGS. 11 to 15 are lateral aberration diagrams corresponding to Examples 1 to 5 (EX1 to EX5), respectively. In each of FIGS. 11 to 15, (A) to (E) show transverse aberration (mm) with a tangential (meridional) light beam, and (F) to (J) show transverse aberration with a sagittal light beam ( mm). In addition, the lateral aberration at the image height ratio (half angle of view ω °) represented by RELATIVE FIELD HEIGHT indicates the d line (wavelength 587.56 nm) indicated by a solid line, and the C line (wavelength 656.28 nm) indicated by a one-dot chain line. , The g-line (wavelength 435.84 nm) indicated by a broken line. The image height ratio is a relative image height obtained by normalizing the image height with the maximum image height Y ′.

Example 1
Unit: mm
Surface data
ir (mm) d (mm) Nd νd
1 57.886 2.00 1.72916 54.7
2 23.439 4.92
3 33.220 1.95 1.72916 54.7
4 25.603 0.08 1.51380 53.0
5 * 20.473 7.72
6 87.334 1.90 1.49700 81.6
7 24.442 5.72
8 111.781 6.97 1.76182 26.6
9 -28.428 0.01 1.51400 42.8
10 -28.428 1.90 1.84666 23.8
11 -471.762 0.10
12 65.367 11.77 1.80000 29.8
13 -40.283 0.01 1.51400 42.8
14 -40.283 1.40 1.72916 54.7
15 -687.279 7.88
16 37.550 5.47 1.61800 63.4
17 -46.916 0.15
18 231.956 3.75 1.61800 63.4
19 -31.882 0.01 1.51400 42.8
20 -31.882 1.10 1.80000 29.8
21 55.213 2.20
22 (ST) ∞ 5.16
23 -21.793 1.15 1.90366 31.3
24 -121.754 0.40
25 * 312.500 4.88 1.74320 49.3
26 * -26.653 2.76
27 -64.081 7.57 1.59282 68.6
28 -21.156 36.14
29 ∞ 2.00 1.51680 64.2
30 ∞

Aspheric data 5th surface
K = -0.45914E-01
A4 = -0.13206E-04
A6 = -0.46045E-07
A8 = 0.10984E-09
A10 = -0.72622E-12
A12 = 0.19273E-14
A14 = -0.26769E-17

Aspheric data 25th surface
K = 0
A4 = 0.96369E-05
A6 = 0.17691E-06
A8 = 0.10120E-09

Aspheric data 26th surface
K = -0.10360E + 01
A4 = 0.26610E-04
A6 = 0.14012E-06
A8 = 0.64503E-09

Various data
f = 20.6mm
fB = 1.00mm
F = 1.86
TL = 128.07mm
2Y '= 43.2mm
ENTP = 23.89mm
EXTP = -31.79mm
H1 = 38.45mm
H2 = 17.86mm

Lens group data Group Start surface Focal length (mm)
1 1 -75.931
2 16 38.535

Example 2
Unit: mm
Surface data
ir (mm) d (mm) Nd νd
1 53.489 2.11 1.77250 49.6
2 22.442 4.42
3 29.503 2.20 1.77250 49.6
4 22.246 0.08 1.51380 53.0
5 * 18.235 5.02
6 28.818 1.90 1.49700 81.6
7 20.121 0.08 1.51380 53.0
8 * 18.639 13.10
9 51.781 10.00 1.80610 33.3
10 -50.672 0.01 1.51400 42.8
11 -50.672 1.50 1.77250 49.6
12 -1557.668 7.97
13 -1617.135 1.45 1.77250 49.6
14 43.193 0.23
15 27.725 6.56 1.69680 55.5
16 -52.981 0.15
17 211.701 4.63 1.64769 33.8
18 -27.202 0.01 1.51400 42.8
19 -27.202 1.10 1.80518 25.5
20 -121.555 1.74
21 (ST) ∞ 5.45
22 -21.825 1.19 1.90366 31.3
23 194.154 0.63
24 * 196.429 4.34 1.69350 53.2
25 * -27.322 1.22
26 -106.930 1.70 1.67270 32.2
27 178.017 0.01 1.51400 42.8
28 178.017 7.33 1.59282 68.6
29 -21.445 36.22
30 ∞ 2.00 1.51680 64.2
31 ∞

Aspheric data 5th surface
K = -0.10080E + 01
A4 = -0.17829E-05
A6 = -0.14365E-08
A8 = 0.67090E-10
A10 = -0.33234E-12
A12 = 0.10684E-14
A14 = -0.12259E-17

Aspheric data 8th surface
K = 0
A4 = 0.78014E-07
A6 = -0.26526E-07
A8 = -0.19602E-09
A10 = 0.97499E-12
A12 = -0.45670E-14
A14 = 0.38118E-17

Aspheric data 24th surface
K = 0
A4 = 0.13018E-04
A6 = 0.91149E-07
A8 = 0.34567E-09

Aspheric data 25th surface
K = -0.12363E + 01
A4 = 0.27799E-04
A6 = 0.10203E-06
A8 = 0.70258E-09

Various data
f = 20.5mm
fB = 1.00mm
F = 1.86
TL = 125.35mm
2Y '= 43.2mm
ENTP = 23.25mm
EXTP = -67.67mm
H1 = 37.63mm
H2 = -19.5mm

Lens group data Group Start surface Focal length (mm)
1 1 -67.999
2 13 38.078

Example 3
Unit: mm
Surface data
ir (mm) d (mm) Nd νd
1 47.237 2.00 1.80610 33.3
2 22.794 4.40
3 30.367 1.95 1.77250 49.6
4 23.831 0.08 1.51380 53.0
5 * 19.635 7.62
6 65.453 1.90 1.49700 81.6
7 23.090 10.17
8 47.609 2.99 1.77250 49.6
9 30.123 0.01 1.51400 42.8
10 30.123 10.00 1.72825 28.3
11 -270.528 8.17
12 54.190 5.33 1.65412 39.7
13 -37.601 0.35
14 -67.182 4.00 1.62280 57.1
15 -20.790 0.01 1.51400 42.8
16 -20.790 1.10 1.68893 31.2
17 -165.801 1.81
18 (ST) ∞ 1.13
19 155.658 1.10 1.83400 37.4
20 90.825 4.74
21 -21.330 1.20 1.75520 27.5
22 -153.822 0.40
23 * 312.500 4.89 1.69350 53.2
24 * -26.893 1.62
25 -83.531 1.50 1.80610 33.3
26 68.633 0.01 1.51400 42.8
27 68.633 8.77 1.60311 60.7
28 -21.530 36.17
29 ∞ 2.00 1.51680 64.2
30 ∞

Aspheric data 5th surface
K = -0.19226E + 01
A4 = 0.21577E-04
A6 = -0.96242E-07
A8 = 0.65635E-09
A10 = -0.29966E-11
A12 = 0.68530E-14
A14 = -0.62825E-17

Aspheric data 23rd surface
K = 0
A4 = 0.11703E-04
A6 = 0.18459E-06
A8 = 0.92494E-10

Aspheric data 24th surface
K = -0.12664E + 01
A4 = 0.27461E-04
A6 = 0.14234E-06
A8 = 0.62405E-09

Various data
f = 20.6mm
fB = 1.00mm
F = 1.86
TL = 126.42mm
2Y '= 43.2mm
ENTP = 23.57mm
EXTP = -74.94mm
H1 = 38.59mm
H2 = -19.6mm

Lens group data Group Start surface Focal length (mm)
1 1 -61.399
2 12 38.246

Example 4
Unit: mm
Surface data
ir (mm) d (mm) Nd νd
1 44.748 2.05 1.72916 54.7
2 21.684 6.42
3 37.165 1.70 1.72916 54.7
4 21.292 0.08 1.51380 53.0
5 * 17.396 10.52
6 -164.083 1.90 1.49700 81.6
7 41.317 2.75
8 73.126 5.75 1.80610 33.3
9 -50.534 0.01 1.51400 42.8
10 -50.534 1.89 1.84666 23.8
11 -217.291 0.15
12 55.437 9.28 1.80518 25.5
13 508.643 7.51
14 173.481 1.00 1.80420 46.5
15 40.958 0.20
16 26.018 6.47 1.63854 55.5
17 -45.032 0.15
18 -157.818 3.82 1.59282 68.6
19 -25.619 0.01 1.51400 42.8
20 -25.619 1.10 1.80610 33.3
21 -86.163 1.50
22 (ST) ∞ 7.31
23 -18.136 1.10 1.90366 31.3
24 -663.566 0.40
25 * 310.584 4.88 1.69350 53.2
26 * -26.434 2.20
27 -106.408 5.85 1.61800 63.4
28 -20.279 36.31
29 ∞ 2.00 1.51680 64.2
30 ∞

Aspheric data 5th surface
K = -0.14701E + 00
A4 = -0.14200E-04
A6 = -0.91344E-07
A8 = 0.57092E-09
A10 = -0.38761E-11
A12 = 0.11697E-13
A14 = -0.16800E-16

Aspheric data 25th surface
K = 0
A4 = 0.16819E-04
A6 = 0.11963E-06
A8 = 0.53088E-09
A10 = -0.71472E-12
A12 = -0.18781E-13
A14 = 0.76960E-16

Aspheric data 26th surface
K = -0.63616E + 00
A4 = 0.35114E-04
A6 = 0.11816E-06
A8 = 0.86824E-09
A10 = -0.89067E-12
A12 = 0.52841E-15
A14 = -0.17693E-16

Various data
f = 20.6mm
fB = 1.00mm
F = 1.86
TL = 125.31mm
2Y '= 43.2mm
ENTP = 23.25mm
EXTP = -72.23mm
H1 = 38.14mm
H2 = -18.6mm

Lens group data Group Start surface Focal length (mm)
1 1 -82.275
2 14 38.687

Example 5
Unit: mm
Surface data
ir (mm) d (mm) Nd νd
1 41.583 2.00 1.80610 33.3
2 21.320 5.02
3 * 40.033 2.16 1.69350 53.2
4 * 22.522 8.85
5 131.724 1.90 1.49700 81.6
6 27.852 9.00
7 49.576 4.40 1.74330 49.2
8 30.916 0.01 1.51400 42.8
9 30.916 5.66 1.71736 29.5
10 -122.863 7.91
11 103.141 1.45 1.83481 42.7
12 34.268 0.32
13 24.763 7.00 1.65844 50.9
14 -55.429 1.00
15 -86.824 4.14 1.61800 63.4
16 -22.722 0.01 1.51400 42.8
17 -22.722 1.10 1.67270 32.2
18 -65.922 1.95
19 (ST) ∞ 5.32
20 -20.272 1.15 1.80610 33.3
21 540.320 0.51
22 * 312.500 4.64 1.69350 53.2
23 * -29.894 1.35
24 -186.897 1.50 1.80518 25.5
25 135.378 0.01 1.51400 42.8
26 135.378 7.39 1.59282 68.6
27 -22.169 36.23
28 ∞ 2.00 1.51680 64.2
29 ∞

Aspheric data 3rd surface
K = 0.24480E + 01
A4 = 0.35939E-04
A6 = -0.12663E-06
A8 = 0.20699E-09
A10 = -0.20556E-12
A12 = -0.13151E-15
A14 = -0.16385E-20

Aspheric data 4th surface
K = 0.36782E + 00
A4 = 0.35308E-04
A6 = -0.12271E-06
A8 = -0.63349E-10
A10 = 0.52309E-12
A12 = -0.18607E-14
A14 = 0.10871E-18

Aspheric data 22nd surface
K = -0.12777E + 02
A4 = 0.15107E-04
A6 = 0.17749E-06
A8 = -0.33563E-09
A10 = 1.34967E-12
A12 = -4.20527E-15

Aspheric data 23rd surface
K = -0.85209E + 00
A4 = 0.30262E-04
A6 = 0.16913E-06
A8 = 0.12746E-09
A10 = 1.66232E-12
A12 = -8.25461E-15

Various data
f = 20.6mm
fB = 1.00mm
F = 1.86
TL = 124.98mm
2Y '= 43.2mm
ENTP = 23.65mm
EXTP = -66.59mm
H1 = 37.97mm
H2 = -19.6mm

Lens group data Group Start surface Focal length (mm)
1 1 -72.351
2 11 39.243

DU Digital equipment LU Imaging optical device LN Wide angle lens Gr1 First group Gr2 Second group ST Aperture (aperture stop)
SR Image sensor SS Light-receiving surface (imaging surface)
IM image plane (optical image)
AX Optical axis 1 Signal processing unit 2 Control unit 3 Memory 4 Operation unit 5 Display unit

Claims (13)

In order from the object side, the first group having a negative power and the second group having a positive power,
The first group has at least one cemented lens having a positive power,
Focusing on a short-distance object is performed by moving the second group to the object side with the position of the first group fixed.
A wide-angle lens satisfying the following conditional expressions (1) to (3);
0.3 <(R2 + R1) / (R2-R1) <1.2 (1)
Fno <2.4 (2)
fov> 80 ° (3)
However,
R2: radius of curvature of the image side surface of the cemented lens closest to the object side in the first group,
R1: radius of curvature of the object side surface of the cemented lens closest to the object side in the first group,
Fno: aperture F value,
fov: full angle of view,
It is. The wide-angle lens according to claim 1, wherein the following conditional expression (4) is satisfied:
−10 <f1 / f <−1 (4)
However,
f1: focal length of the first group,
f: focal length of the entire system,
It is.   The wide-angle lens according to claim 1, further comprising a positive lens on the image side of the cemented lens in the first group. The wide-angle lens according to claim 1, wherein the following conditional expression (5) is satisfied:
1 <tp / tn <8 (5)
However,
tp: the thickness on the optical axis of the positive lens constituting the most object-side cemented lens in the first group,
tn: the thickness on the optical axis of the negative lens constituting the most object side cemented lens in the first lens group,
It is. The wide-angle lens according to claim 1, wherein the cemented lens in the first group includes at least one lens that satisfies the following conditional expression (6):
Nd> 1.8 (6)
However,
Nd: refractive index for d-line,
It is.   The wide-angle lens according to claim 1, wherein the first group includes three negative lenses in order from the object side.   The wide-angle lens according to claim 1, wherein at least one negative lens in the first group has an aspherical surface. The wide-angle lens according to any one of claims 1 to 7, wherein at least one negative lens in the first group satisfies the following conditional expression (7).
νd> 70 (7)
However,
νd: Abbe number,
It is.   The wide-angle lens according to claim 1, wherein the lens closest to the object side in the second group is a negative lens.   The wide-angle lens according to claim 1, wherein an aperture stop is provided in the second group, and the lens is positioned before and after the aperture stop.   11. The wide-angle lens according to claim 1, further comprising an aperture stop in the second group, and at least one aspheric surface on the image side from the aperture stop.   A wide-angle lens according to any one of claims 1 to 11 and an image sensor that converts an optical image formed on an imaging surface into an electrical signal, and a subject on the imaging surface of the image sensor. An imaging optical apparatus, wherein the wide-angle lens is provided so that an optical image is formed.   13. A digital apparatus comprising the imaging optical device according to claim 12 to which at least one function of still image shooting and moving image shooting of a subject is added.

Images