JP2014044250A - Image pickup lens and image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image pickup lens and an image pickup device that are bright and enable a wider angle.SOLUTION: An image pickup lens includes, in order from an object side, a first lens having negative refractive power, a second lens having positive refractive power, a third lens having negative refractive power, a fourth lens having positive or negative refractive power, a fifth lens having positive refractive power, and a sixth lens having negative refractive power. The image-sided surface of the sixth lens is formed as an aspherical shape having at least one inflection point other than an intersection point of the image-sided surface and an optical axis.

Description

  The present disclosure relates to a small camera module using an imaging element such as a CCD (Charge Coupled Devices) or a CMOS (Complementary Metal Oxide Semiconductor), for example, an imaging lens suitable for a camera module for a portable information terminal or a mobile phone terminal, and The present invention relates to an imaging apparatus using such an imaging lens.

  A lens configuration of four or less lenses is known as a lens for a camera module for a portable information terminal or a mobile phone terminal. With a lens configuration of four or less lenses, for example, a bright and high resolution with an F number of about 2.0 or less. It is difficult to achieve performance. Therefore, in order to realize brighter and higher resolution performance, a lens having five lenses has been developed (see Patent Documents 1 to 3).

JP 2009-294527 A JP 2010-262269 A JP 2011-209554 A

  However, with the widening of the camera angle and the large aperture ratio, aberrations cannot be completely corrected with the five-lens configuration lens. For example, there are currently five lenses represented by Patent Documents 1 to 3, etc., but the correction of aberrations is not in time as the aperture ratio increases, making it difficult to obtain good performance over the entire screen. Yes. When a wide angle and a large aperture ratio are promoted, for example, a lens configuration represented by Patent Document 3 cannot sufficiently correct spherical aberration, curvature of field, and coma.

  An object of the present disclosure is to provide an imaging lens and an imaging apparatus that are bright and capable of widening the angle.

  The imaging lens according to the present disclosure includes, in order from the object side, a first lens having negative refractive power, a second lens having positive refractive power, a third lens having negative refractive power, and positive or negative refraction. It consists of a fourth lens having power, a fifth lens having positive refractive power, and a sixth lens having negative refractive power. The image-side surface of the sixth lens has an aspherical shape having at least one inflection point other than the intersection with the optical axis.

  An imaging device according to the present disclosure includes an imaging lens and an imaging element that outputs an imaging signal corresponding to an optical image formed by the imaging lens, and the imaging lens is configured by the imaging lens according to the present disclosure.

  In the imaging lens or the imaging device according to the present disclosure, the configuration of each lens is optimized with the configuration of six lenses as a whole.

  According to the imaging lens or the imaging apparatus of the present disclosure, the configuration of the six lenses as a whole and the configuration of each lens are optimized, so that a bright and wide angle can be achieved. In particular, by arranging a negative lens as the first lens, the curvature of field can be favorably corrected, and further, the correction ratio of spherical aberration and coma aberration can be increased on other lens surfaces. In addition, it is possible to widen the angle of the lens by preceding the negative lens.

1 is a lens cross-sectional view illustrating a first configuration example of an imaging lens according to an embodiment of the present disclosure and corresponding to Numerical Example 1. FIG. 2 is a lens cross-sectional view illustrating a second configuration example of the imaging lens and corresponding to Numerical Example 2. FIG. 3 is a lens cross-sectional view illustrating a third configuration example of the imaging lens and corresponding to Numerical Example 3. FIG. 4 is a lens cross-sectional view illustrating a fourth configuration example of the imaging lens and corresponding to Numerical Example 4. FIG. 5 is a lens cross-sectional view illustrating a fifth configuration example of the imaging lens and corresponding to Numerical Example 5. FIG. 6 is a lens cross-sectional view illustrating a sixth configuration example of the imaging lens and corresponding to Numerical Example 6. FIG. 7 is a lens cross-sectional view illustrating a seventh configuration example of the imaging lens and corresponding to Numerical Example 7. FIG. 8 illustrates an eighth configuration example of the imaging lens and is a lens cross-sectional view corresponding to Numerical Example 8. FIG. FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, and distortion of the imaging lens corresponding to Numerical Example 1. 6 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion of the imaging lens corresponding to Numerical Example 2. FIG. FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion of the imaging lens corresponding to Numerical Example 3. FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion of the imaging lens corresponding to Numerical Example 4. 10 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion of the imaging lens corresponding to Numerical Example 5. FIG. 10 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion of the imaging lens corresponding to Numerical Example 6. FIG. 10 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion of the imaging lens corresponding to Numerical Example 7. FIG. FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion of the imaging lens corresponding to Numerical Example 8. It is a front view which shows the example of 1 structure of an imaging device. It is a rear view which shows the example of 1 structure of an imaging device.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The description will be given in the following order.
1. 1. Basic configuration of lens Action and effect 3. Application example to imaging device 4. Numerical example of lens Other embodiments

[1. Basic lens configuration]
FIG. 1 illustrates a first configuration example of an imaging lens according to an embodiment of the present disclosure. This first configuration example corresponds to the lens configuration of Numerical Example 1 described later. Similarly, FIGS. 2 to 8 show cross-sectional configurations of second to eighth configuration examples corresponding to lens configurations of numerical examples 2 to 8 described later. 1 to 8, the symbol Simg represents the image plane, and Z1 represents the optical axis.

  The imaging lens according to the present embodiment includes, in order from the object side along the optical axis Z1, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, and a fifth lens L5. The sixth lens L6 is substantially composed of six lenses.

  The first lens L1 has negative refractive power. The second lens L2 has a positive refractive power. The third lens L3 has negative refractive power. The fourth lens L4 has a positive or negative refractive power. The fifth lens L5 has a positive refractive power. The sixth lens L6 has negative refractive power. The sixth lens L6 has an aspherical shape with an inflection point such that the concave-convex shape changes midway as the image side surface moves from the center to the periphery, and at least other than the intersection with the optical axis Z1. It has one inflection point.

  In addition, it is preferable that the imaging lens according to the present embodiment satisfies a predetermined conditional expression described later.

[2. Action / Effect]
Next, functions and effects of the imaging lens according to the present embodiment will be described.

  This imaging lens has a total of six lens configurations, and the configuration of each lens is optimized, so that a bright and wide angle can be achieved. In particular, by disposing a negative lens as the first lens L1, the curvature of field can be corrected satisfactorily, and the correction ratio of spherical aberration and coma aberration can be increased on other lens surfaces. In addition, it is possible to widen the angle of the lens by preceding the negative lens.

  In this imaging lens, better performance can be obtained by making the lens shape as follows. The image side surface of the first lens L1 is preferably concave. The object side surface of the second lens L2 is preferably a convex surface. It is desirable that the third lens L3 has a meniscus shape with a convex surface facing the object side or a biconcave shape. The image side surface of the fifth lens L5 is preferably a convex surface. The first lens L1 is preferably a resin material.

(Explanation of conditional expressions)
In the imaging lens according to the present embodiment, by optimizing the configuration of each lens so as to satisfy at least one of the following conditional expressions, preferably a combination of two or more conditional expressions, better performance is achieved. Can be obtained.

| Ν2-ν3 |> 20 (1)
However,
ν2: Abbe number of second lens L2 ν3: Abbe number of third lens L3.

Conditional expression (1) is a conditional expression for defining an appropriate Abbe number difference between the second lens L2 and the third lens L3. By satisfying conditional expression (1), chromatic aberration can be corrected satisfactorily.
In order to correct chromatic aberration more satisfactorily, it is preferable to set the numerical range of the conditional expression (1) as the following conditional expression (1) ′.
80> | ν2-ν3 |> 20 (1) ′
More preferably, it may be set as the following conditional expression (1) ''.
80> | ν2-ν3 |> 30 (1) ''

2.2 <| f1 / fa | (2)
However,
fa: focal length of the entire system f1: the focal length of the first lens L1.

Conditional expression (2) defines an appropriate focal length of the first lens L1. If the negative power of the first lens L1 exceeds the lower limit of the conditional expression (2), the field curvature is overcorrected, and it is impossible to balance including aberrations other than the field curvature. Good image quality cannot be obtained.
Preferably, the numerical range of the conditional expression (2) is set as the following conditional expression (2) ′. When the upper limit is larger than 100, the role as a negative lens cannot be sufficiently achieved.
2.2 <| f1 / fa | <100 (2) ′

0.5 <| f2 / fa | <1.1 (3)
However,
f2: The focal length of the second lens L2.

Conditional expression (3) defines an appropriate focal length of the second lens L2. If the lower limit of conditional expression (3) is exceeded, the power of the second lens L2 becomes too strong and the field curvature falls to the object side. If the upper limit of conditional expression (3) is exceeded, the power of the second lens L2 becomes too weak and the field curvature falls to the image plane side.
In order to obtain better performance, it is preferable to set the numerical range of the conditional expression (3) as the following conditional expression (3) ′.
0.5 <| f2 / fa | <0.8 (3) ′

1.0 <| f3 / fa | <2.0 (4)
However,
f3: The focal length of the third lens L3.

  Conditional expression (4) defines an appropriate focal length of the third lens L3. When the lower limit of conditional expression (4) is exceeded, the power of the third lens L3 becomes too strong and the field curvature falls to the image side. When the upper limit of conditional expression (4) is exceeded, the power of the third lens L3 becomes too weak and the field curvature falls to the object side.

0.4 <| f345 / fa | <2.2 (5)
However,
f345: The combined focal length of the third lens L3, the fourth lens L4, and the fifth lens L5.

Conditional expression (5) defines an appropriate combined focal length of the third lens L3, the fourth lens L4, and the fifth lens L5. When the upper limit or lower limit of conditional expression (5) is exceeded, each of spherical aberration, curvature of field, and coma aberration cannot be balanced, and a good aberration correction effect cannot be obtained.
In order to obtain better performance, it is preferable to set the numerical range of the conditional expression (5) as the following conditional expression (5) ′.
0.8 <| f345 / fa | <2.0 (5) '

0.4 <| f6 / fa | <1.0 (6)
However,
f6: The focal length of the sixth lens L6.

  Conditional expression (6) defines an appropriate focal length of the sixth lens L6. When the lower limit of conditional expression (6) is exceeded, the focal length of the entire system becomes long, which is disadvantageous for widening the angle. On the other hand, if the upper limit is exceeded, it is advantageous for widening the angle, but it becomes difficult to correct curvature of field, and it becomes difficult to secure a necessary flange back amount.

[3. Application example to imaging device]
17 and 18 show a configuration example of an imaging apparatus to which the imaging lens according to this embodiment is applied. This configuration example is an example of a mobile terminal device (for example, a mobile information terminal or a mobile phone terminal) provided with an imaging device. This portable terminal device includes a substantially rectangular casing 201. A display unit 202 and a front camera unit 203 are provided on the front side (FIG. 17) of the housing 201. A main camera unit 204 and a camera flash 205 are provided on the back side (FIG. 18) of the housing 201.

  The display unit 202 is a touch panel that enables various operations, for example, by detecting a contact state with the surface. Thereby, the display unit 202 has a function of displaying various types of information and an input function that enables various types of input operations by the user. The display unit 202 displays various data such as an operation state and an image captured by the front camera unit 203 or the main camera unit 204.

  The imaging lens according to the present embodiment can be applied as a camera module lens of an imaging device (front camera unit 203 or main camera unit 204) in a portable terminal device as shown in FIGS. 17 and 18, for example. When used as such a lens for a camera module, a CCD (Charge Coupled Devices) or CMOS (Complementary) that outputs an imaging signal (image signal) corresponding to an optical image formed by the imaging lens near the image plane Simg of the imaging lens. An image sensor such as a metal oxide semiconductor is disposed. In this case, as shown in FIG. 1, an optical member such as a sealing glass SG for protecting the image sensor and various optical filters may be disposed between the sixth lens L6 and the image plane Simg.

  Note that the imaging lens according to the present embodiment is not limited to the above-described portable terminal device, but can also be applied as an imaging lens for other electronic devices such as a digital still camera and a digital video camera. In addition, the present invention can be applied to general small-sized imaging devices using a solid-state imaging device such as a CCD or CMOS, for example, an optical sensor, a portable module camera, and a WEB camera.

<4. Numerical Examples of Lens>
Next, specific numerical examples of the imaging lens according to the present embodiment will be described.
In addition, the meanings of symbols shown in the following tables and descriptions are as shown below. “R” indicates the value (mm) of the paraxial radius of curvature of the i-th surface, which is numbered so as to increase sequentially toward the image side, with the most object-side component surface being first. . “D” indicates the value (mm) of the distance on the optical axis between the i-th surface and the i + 1-th surface. “N” represents the value of the refractive index at the d-line (wavelength 587.6 nm) of the material of the optical element having the i-th surface. “Ν” indicates the value of the Abbe number at the d-line of the material of the optical element having the i-th surface. A surface having a radius of curvature of “INF” indicates a flat surface or a diaphragm surface. FNO indicates an F number.

In each embodiment, the shape of the aspheric surface is expressed by the following equation. In the aspheric coefficient data, the symbol “E” indicates that the next numerical value is a “power exponent” with a base of 10, and the numerical value represented by an exponential function with the base 10 is “E”. Indicates that the number before “is multiplied. For example, “1.0E-05” indicates “1.0 × 10 ⁻⁵ ”.

(Aspherical formula)
Z = (Y ² / R) / [1+ {1− (1 + K) (Y ² / R ² )} ^1/2 ] + ΣAi · Y ⁱ
However,
Z: Depth of aspheric surface Y: Height from optical axis R: Paraxial radius of curvature K: Conic constant (conic coefficient)
Ai: An aspheric coefficient of the i-th order (i is an integer of 3 or more).

(Configuration common to each numerical example)
Any of the imaging lenses according to the following numerical examples has a configuration that satisfies the basic configuration of the lens described above. In each imaging lens according to each numerical example, each lens surface of the first lens L1 to the sixth lens L6 is aspheric. A seal glass SG is disposed between the sixth lens L6 and the image plane Simg.

[Numerical Example 1]
[Table 1] to [Table 7] show specific lens data corresponding to the imaging lens according to the first configuration example shown in FIG. In particular, [Table 1] shows basic lens data, and [Table 2] to [Table 7] show data related to aspheric surfaces. [Table 1] also shows the values of the F number and the half angle of view.

  In the first configuration example, the fourth lens L4 has a negative refractive power. The aperture stop St is disposed between the first lens L1 and the second lens L2. The first lens L1 is a resin material.

[Numerical Example 2]
[Table 8] to [Table 14] show specific lens data corresponding to the imaging lens according to the second configuration example shown in FIG. In particular, [Table 8] shows basic lens data, and [Table 9] to [Table 14] show data related to aspheric surfaces. Table 8 also shows the F number and half angle of view values.

  In the second configuration example, the fourth lens L4 has a negative refractive power. The aperture stop St is disposed between the first lens L1 and the second lens L2. The first lens L1 is a resin material.

[Numerical Example 3]
[Table 15] to [Table 21] show specific lens data corresponding to the imaging lens according to the third configuration example shown in FIG. In particular, [Table 15] shows basic lens data, and [Table 16] to [Table 21] show data related to aspheric surfaces. Table 15 also shows the F number and half angle of view values.

  In the third configuration example, the fourth lens L4 has a positive refractive power. The aperture stop St is disposed between the first lens L1 and the second lens L2. The first lens L1 is a resin material.

[Numerical Example 4]
[Table 22] to [Table 28] show specific lens data corresponding to the imaging lens according to the fourth configuration example shown in FIG. In particular, [Table 22] shows basic lens data, and [Table 23] to [Table 28] show data related to aspheric surfaces. [Table 22] also shows the values of the F number and the half angle of view.

  In the fourth configuration example, the fourth lens L4 has a positive refractive power. The aperture stop St is disposed between the first lens L1 and the second lens L2. The first lens L1 is a resin material.

[Numerical Example 5]
[Table 29] to [Table 35] show specific lens data corresponding to the imaging lens according to the fifth configuration example shown in FIG. In particular, [Table 29] shows the basic lens data, and [Table 30] to [Table 35] show data on aspheric surfaces. [Table 29] also shows the values of the F number and the half angle of view.

  In the fifth configuration example, the fourth lens L4 has negative refractive power. The aperture stop St is disposed between the first lens L1 and the second lens L2. The first lens L1 is a resin material.

[Numerical Example 6]
[Table 36] to [Table 42] show specific lens data corresponding to the imaging lens according to the sixth configuration example shown in FIG. 6. In particular, [Table 36] shows basic lens data, and [Table 37] to [Table 42] show data relating to aspheric surfaces. Table 36 also shows the F number and half angle of view values.

  In the sixth configuration example, the fourth lens L4 has a negative refractive power. The aperture stop St is disposed between the first lens L1 and the second lens L2. The first lens L1 is a resin material.

[Numerical Example 7]
[Table 43] to [Table 49] show specific lens data corresponding to the imaging lens according to the seventh configuration example shown in FIG. In particular, [Table 43] shows basic lens data, and [Table 44] to [Table 49] show data related to aspheric surfaces. [Table 43] also shows the values of the F number and the half angle of view.

  In the seventh configuration example, the fourth lens L4 has positive refractive power. The aperture stop St is disposed between the first lens L1 and the second lens L2. The first lens L1 is a resin material.

[Numerical Example 8]
[Table 50] to [Table 56] show specific lens data corresponding to the imaging lens according to the eighth configuration example shown in FIG. In particular, [Table 50] shows basic lens data, and [Table 51] to [Table 56] show data related to aspheric surfaces. [Table 50] also shows the F number and the half angle of view.

  In the eighth configuration example, the fourth lens L4 has a negative refractive power. The aperture stop St is disposed between the first lens L1 and the second lens L2. The first lens L1 is a resin material.

[Other numerical data of each example]
[Table 57] shows a summary of values relating to the above-described conditional expressions for each numerical example. As can be seen from [Table 57], for each conditional expression, the value of each numerical example falls within the numerical range.

[Aberration performance]
9 to 16 show the aberration performance of each numerical example. In these drawings, spherical aberration, astigmatism, and distortion (distortion aberration) are shown as aberration diagrams. In the astigmatism diagram, S indicates the sagittal direction, and T indicates the aberration in the meridional (tangential) direction.

  As can be seen from each of the above aberration diagrams, an imaging lens with good aberration correction can be realized for each example.

<5. Other Embodiments>
The technology according to the present disclosure is not limited to the description of the above-described embodiments and examples, and various modifications can be made.
For example, the shapes and numerical values of the respective parts shown in the numerical examples are merely examples of embodiments for carrying out the present technology, and the technical scope of the present technology is interpreted in a limited manner by these. There should be no such thing.

  In the above-described embodiments and examples, the configuration including substantially six lenses has been described. However, a configuration further including a lens having substantially no refractive power may be used.

For example, this technique can take the following composition.
[1]
From the object side,
A first lens having negative refractive power;
A second lens having a positive refractive power;
A third lens having negative refractive power;
A fourth lens having positive or negative refractive power;
A fifth lens having positive refractive power;
A sixth lens having negative refractive power,
The imaging lens, wherein the image side surface of the sixth lens has an aspherical shape having at least one inflection point other than the intersection with the optical axis.
[2]
The imaging lens according to [1], wherein the following conditional expression is satisfied.
| Ν2-ν3 |> 20 (1)
However,
ν2: Abbe number of the second lens ν3: Abbe number of the third lens.
[3]
The imaging lens according to [1] or [2], wherein the following conditional expression is satisfied.
2.2 <| f1 / fa | (2)
However,
fa: focal length of the entire system f1: the focal length of the first lens.
[4]
The imaging lens according to any one of [1] to [3], wherein the following conditional expression is satisfied.
0.5 <| f2 / fa | <1.1 (3)
However,
f2: The focal length of the second lens.
[5]
The imaging lens according to any one of [1] to [4], wherein the following conditional expression is satisfied.
1.0 <| f3 / fa | <2.0 (4)
However,
f3: The focal length of the third lens.
[6]
The imaging lens according to any one of [1] to [5], wherein the following conditional expression is satisfied.
0.4 <| f345 / fa | <2.2 (5)
However,
f345: The combined focal length of the third lens, the fourth lens, and the fifth lens.
[7]
The imaging lens according to any one of [1] to [6], wherein the following conditional expression is satisfied.
0.4 <| f6 / fa | <1.0 (6)
However,
f6: The focal length of the sixth lens.
[8]
The imaging lens according to any one of [1] to [7], wherein the first lens is a resin material.
[9]
The imaging lens according to any one of [1] to [8], further including a lens that has substantially no refractive power.
[10]
An imaging lens, and an imaging element that outputs an imaging signal corresponding to an optical image formed by the imaging lens;
The imaging lens is
From the object side,
A first lens having negative refractive power;
A second lens having a positive refractive power;
A third lens having negative refractive power;
A fourth lens having positive or negative refractive power;
A fifth lens having positive refractive power;
A sixth lens having negative refractive power,
The imaging device wherein the image side surface of the sixth lens has an aspherical shape having at least one inflection point other than the intersection with the optical axis.
[11]
The imaging device according to [10], wherein the imaging lens further includes a lens having substantially no refractive power.

  L1 ... 1st lens, L2 ... 2nd lens, L3 ... 3rd lens, L4 ... 4th lens, L5 ... 5th lens, L6 ... 6th lens, SG ... Seal glass, St ... Aperture stop, Simg ... Image plane (Imaging element), Z1... Optical axis, 201... Casing, 202... Display unit, 203 .. front camera unit, 204.

Claims (9)

From the object side,
A first lens having negative refractive power;
A second lens having a positive refractive power;
A third lens having negative refractive power;
A fourth lens having positive or negative refractive power;
A fifth lens having positive refractive power;
A sixth lens having negative refractive power,
The imaging lens, wherein the image side surface of the sixth lens has an aspherical shape having at least one inflection point other than the intersection with the optical axis. The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
| Ν2-ν3 |> 20 (1)
However,
ν2: Abbe number of the second lens ν3: Abbe number of the third lens. The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
2.2 <| f1 / fa | (2)
However,
fa: focal length of the entire system f1: the focal length of the first lens. The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
0.5 <| f2 / fa | <1.1 (3)
However,
f2: The focal length of the second lens. The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
1.0 <| f3 / fa | <2.0 (4)
However,
f3: The focal length of the third lens. The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
0.4 <| f345 / fa | <2.2 (5)
However,
f345: The combined focal length of the third lens, the fourth lens, and the fifth lens. The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
0.4 <| f6 / fa | <1.0 (6)
However,
f6: The focal length of the sixth lens. The imaging lens according to claim 1, wherein the first lens is a resin material. An imaging lens, and an imaging element that outputs an imaging signal corresponding to an optical image formed by the imaging lens;
The imaging lens is
From the object side,
A first lens having negative refractive power;
A second lens having a positive refractive power;
A third lens having negative refractive power;
A fourth lens having positive or negative refractive power;
A fifth lens having positive refractive power;
A sixth lens having negative refractive power,
The imaging device wherein the image side surface of the sixth lens has an aspherical shape having at least one inflection point other than the intersection with the optical axis.

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