JP2011209554A - Image pickup lens, image pickup device and portable terminal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image pickup lens and an image pickup device for attaining high-resolution performance.SOLUTION: The image pickup device includes in order from an object side: a first lens G1 having a convex surface on the object side in the vicinity of the optical axis and having a positive refractive power; a second lens G2 having a negative refractive power; a third lens G3 having a concave surface on the image side in the vicinity of the optical axis and having a positive refractive power; a fourth lens G4 having a convex surface on the image side in the vicinity of the optical axis and having a positive refractive power; and a fifth lens G5 having a negative refractive power in the vicinity of the optical axis. The following conditional formula is satisfied: (1) 0.8<f/f1≤1.2, wherein f1 is a focal length of the first lens, and f is a focal length of the entire system.

Description

  The present invention relates to an imaging lens that forms an optical image of a subject on an imaging device such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS), and a digital still camera that performs imaging by mounting the imaging lens. And a portable terminal device such as a mobile phone with a camera and a portable information terminal (PDA: Personal Digital Assistance).

  In recent years, with the spread of personal computers to ordinary homes and the like, digital still cameras that can input image information such as photographed landscapes and human images to personal computers are rapidly spreading. In addition, camera modules for image input are often mounted on mobile phones. An image sensor such as a CCD or a CMOS is used for a device having such an image capturing function. In recent years, these image pickup devices have been made more compact, and the entire image pickup apparatus and the image pickup lens mounted thereon are also required to be compact. At the same time, the number of pixels of the image sensor is increasing, and there is a demand for higher resolution and higher performance of the imaging lens. In order to satisfy such a demand, an imaging lens having a configuration using four lenses as a whole has been developed in the past, but recently, in order to achieve higher resolution and higher performance, the number of lenses has been increased. It tends to increase.

Japanese Patent No. 3788133 JP 2007-264180 A JP 2007-279282 A

  Patent Documents 1 to 3 disclose imaging lenses that have five lenses to improve performance, but in recent years, higher resolution performance is required than the imaging lenses described in these documents. .

  The present invention has been made in view of such problems, and an object of the present invention is to provide an imaging lens and an imaging apparatus, and a portable terminal device that can obtain high resolution performance.

An imaging lens according to the present invention has, in order from the object side, a first lens having a positive refractive power, a second lens having a negative refractive power, a third lens having a positive refractive power, and a positive refractive power. And a fifth lens having a negative refractive power in the vicinity of the optical axis.
And the following conditional expressions are satisfied. Here, f1 is the focal length of the first lens, and f is the focal length of the entire system.
0.8 <f / f1 ≦ 1.2 (1)

The imaging lens according to the present invention has a five-lens configuration as a whole, and the number of lenses is increased as compared with the conventional four-lens imaging lens, and the configuration of each lens is optimized to increase the number of pixels. A corresponding high resolution lens system can be obtained.
Further, by adopting and satisfying the following preferable configuration as appropriate, it becomes easier to achieve higher performance.

The imaging lens according to the present invention preferably satisfies the following conditional expression in order to be applied to a small imaging device.
f <5.0mm (2)

In order to obtain higher resolution performance, it is preferable to satisfy at least one of the following conditional expressions.
f1 <| f2 | <f3 (3)
νd2 <35 (4)
f4 <f1 (5A)
f4 <| f2 | (5B)
f4 <f3 (5C)
Here, f2 is the focal length of the second lens, f3 is the focal length of the third lens, and f4 is the focal length of the fourth lens. νd2 is the Abbe number related to the d-line of the second lens.

  In the imaging lens according to the present invention, the object-side surface of the first lens is convex toward the object side in the vicinity of the optical axis, and the image-side surface of the fourth lens is convex toward the image side near the optical axis. It is preferable.

  In the imaging lens according to the present invention, it is preferable that both the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are aspheric on both surfaces.

  In particular, the image-side surface of the fifth lens is preferably concave in the vicinity of the optical axis, and has a region in which the negative refractive power becomes weaker as compared to the vicinity of the optical axis.

  An imaging apparatus according to the present invention includes an imaging lens according to the present invention and an imaging element that outputs an imaging signal corresponding to an optical image formed by the imaging lens.

  A portable terminal device according to the present invention includes the imaging device according to the present invention and display means for displaying an image captured by the imaging device.

  In the imaging apparatus or the portable terminal device according to the present invention, a high-resolution imaging signal is obtained based on the high-resolution optical image obtained by the imaging lens of the present invention.

  According to the imaging lens of the present invention, since the shape of each lens is appropriately optimized in a lens configuration of five as a whole, high resolution performance can be obtained.

  In addition, according to the imaging device or the portable terminal device of the present invention, since the imaging signal corresponding to the optical image formed by the imaging lens having the high resolution performance of the present invention is output, the high resolution shooting is performed. An image can be obtained.

1 is a lens cross-sectional view illustrating a first configuration example of an imaging lens according to an embodiment of the present invention and corresponding to Example 1. FIG. 2 is a lens cross-sectional view illustrating a second configuration example of the imaging lens and corresponding to Example 2. FIG. 3 illustrates a third configuration example of the imaging lens and is a lens cross-sectional view corresponding to Example 3. FIG. 4 is a lens cross-sectional view illustrating a fourth configuration example of the imaging lens and corresponding to Example 4; FIG. 5 is a lens cross-sectional view illustrating a fifth configuration example of the imaging lens and corresponding to Example 5. FIG. 6 is a lens cross-sectional view illustrating a sixth configuration example of the imaging lens and corresponding to Example 6. FIG. 7 is a lens cross-sectional view illustrating a seventh configuration example of the imaging lens and corresponding to Example 7. FIG. 8 illustrates an eighth configuration example of the imaging lens, and is a lens cross-sectional view corresponding to Example 8. FIG. 9 shows a ninth configuration example of the imaging lens, and is a lens cross-sectional view corresponding to Example 9. FIG. 10 is a lens cross-sectional view illustrating a tenth configuration example of the imaging lens and corresponding to Example 10. FIG. 11 shows an eleventh configuration example of the imaging lens and is a lens cross-sectional view corresponding to Example 11. FIG. 12 illustrates a twelfth configuration example of the imaging lens and is a lens cross-sectional view corresponding to Example 12. FIG. 13 is a lens cross-sectional view illustrating a thirteenth configuration example of the imaging lens and corresponding to Example 13. FIG. FIG. 4 is an aberration diagram illustrating various aberrations of the imaging lens according to Example 1, where (A) shows spherical aberration, (B) shows astigmatism, and (C) shows distortion. FIG. 6 is an aberration diagram showing various aberrations of the imaging lens according to Example 2, wherein (A) shows spherical aberration, (B) shows astigmatism, and (C) shows distortion. FIG. 6 is an aberration diagram illustrating various aberrations of the imaging lens according to Example 3, where (A) illustrates spherical aberration, (B) illustrates astigmatism, and (C) illustrates distortion. FIG. 6A is an aberration diagram illustrating various aberrations of the imaging lens according to Example 4; (A) illustrates spherical aberration, (B) illustrates astigmatism, and (C) illustrates distortion. FIG. 6A is an aberration diagram illustrating various aberrations of the imaging lens according to Example 5, where (A) illustrates spherical aberration, (B) illustrates astigmatism, and (C) illustrates distortion. FIG. 7A is an aberration diagram illustrating various aberrations of the imaging lens according to Example 6, wherein (A) illustrates spherical aberration, (B) illustrates astigmatism, and (C) illustrates distortion. FIG. 9A is an aberration diagram illustrating various aberrations of the imaging lens according to Example 7, in which (A) illustrates spherical aberration, (B) illustrates astigmatism, and (C) illustrates distortion. FIG. 9A is an aberration diagram illustrating various aberrations of the imaging lens according to Example 8; (A) illustrates spherical aberration, (B) illustrates astigmatism, and (C) illustrates distortion. FIG. 10A is an aberration diagram illustrating various aberrations of the imaging lens according to Example 9, in which (A) illustrates spherical aberration, (B) illustrates astigmatism, and (C) illustrates distortion. FIG. 11A is an aberration diagram illustrating various aberrations of the imaging lens according to Example 10; (A) illustrates spherical aberration, (B) illustrates astigmatism, and (C) illustrates distortion. FIG. 14 is an aberration diagram illustrating various aberrations of the imaging lens according to Example 11, where (A) illustrates spherical aberration, (B) illustrates astigmatism, and (C) illustrates distortion. FIG. 14 is an aberration diagram illustrating various aberrations of the imaging lens according to Example 12, where (A) illustrates spherical aberration, (B) illustrates astigmatism, and (C) illustrates distortion. FIG. 14A is an aberration diagram illustrating various aberrations of the imaging lens according to Example 13; (A) illustrates spherical aberration, (B) illustrates astigmatism, and (C) illustrates distortion. It is an external view which shows the example of 1 structure of the mobile telephone with a camera as a portable terminal device which concerns on one embodiment of this invention. It is a perspective view which shows one structural example of the camera module as an imaging device which concerns on one embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a first configuration example of an imaging lens according to an embodiment of the present invention. This configuration example corresponds to the lens configuration of the first numerical example described later. Similarly, cross-sectional configurations of second to thirteenth configuration examples corresponding to lens configurations of second to thirteenth numerical examples described later are shown in FIGS. In FIG. 1 to FIG. 13, the reference symbol Ri is assigned i so that the surface of the constituent element closest to the object side including the aperture stop St is first, and increases sequentially toward the image side (imaging side). Indicates the radius of curvature of the second surface. The symbol Di indicates the surface interval on the optical axis Z1 between the i-th surface and the i + 1-th surface. Since the basic configuration is the same for each configuration example, the following description is based on the first configuration example shown in FIG.

  27A and 27B show a camera-equipped mobile phone as an example of the mobile terminal device according to this embodiment. FIG. 28 shows a configuration example of a camera module as an imaging apparatus according to the present embodiment. The camera-equipped mobile phone shown in FIGS. 27A and 27B includes an upper housing 2A and a lower housing 2B, both of which are configured to be rotatable in the direction of the arrow in FIG. . The lower housing 2B is provided with operation keys 21 and the like. The upper housing 2A is provided with a camera unit 1 (FIG. 27B), a display unit (display means) 22 (FIG. 27A), and the like. The display unit 22 includes a display panel such as an LCD (liquid crystal panel) or an EL (Electro-Luminescence) panel. The display part 22 is arrange | positioned at the side used as an inner surface at the time of folding. The display unit 22 can display various menus related to the telephone function and images taken by the camera unit 1. The camera unit 1 is disposed, for example, on the back side of the upper housing 2A. However, the position where the camera unit 1 is provided is not limited to this.

  The camera unit 1 has a camera module as shown in FIG. 28, for example. As shown in FIG. 28, the camera module corresponds to the lens barrel 3 in which the imaging lens 20 is accommodated, the support substrate 4 that supports the lens barrel 3, and the imaging surface of the imaging lens 20 on the support substrate 4. And an image sensor (not shown) provided at a position to be operated. The camera module is also configured to be connected to a flexible substrate 5 electrically connected to the image pickup device on the support substrate 4 and to a signal processing circuit on the telephone body side while being electrically connected to the flexible substrate 5. And an external connection terminal 6. These components are integrally configured.

  In the camera unit 1, the optical image formed by the imaging lens 20 is converted into an electrical imaging signal by the imaging device, and the imaging signal is output to a signal processing circuit on the device body side. By using the imaging lens according to the present embodiment as the imaging lens 20 in such a camera-equipped mobile phone, a high-resolution imaging signal with sufficient aberration correction can be obtained. On the telephone body side, a high-resolution image can be generated based on the imaging signal.

  Note that the imaging lens according to the present embodiment can be applied to various imaging devices or portable terminal devices using imaging elements such as a CCD and a CMOS. The imaging device or portable terminal device according to the present embodiment is not limited to a camera-equipped mobile phone, and may be, for example, a digital still camera or a PDA. In addition, the imaging lens according to the present embodiment is particularly suitable for an imaging apparatus or a portable terminal device having a small, high-pixel imaging device having a pixel number of 2 megapixels or more and a pixel pitch of 3 μm or less. Can do.

  This imaging lens includes a first lens G1, a second lens G2, a third lens G3, a fourth lens G4, and a fifth lens G5 in order from the object side along the optical axis Z1. The optical aperture stop St is disposed on the front side of the first lens G1, more specifically, for example, on the object side of the image side surface of the first lens G1 on the optical axis Z1. However, as in the configuration examples of FIGS. 4 to 9, it is also possible to arrange an aperture stop St between the image side surface of the first lens G1 and the object side surface of the second lens G2.

  An imaging element such as a CCD is disposed on the imaging surface Simg of the imaging lens. Various optical members GC may be disposed between the fifth lens G5 and the image sensor in accordance with the configuration on the camera side where the lens is mounted. For example, a flat optical member such as a cover glass for protecting the imaging surface or an infrared cut filter may be disposed. In this case, as the optical member GC, for example, a flat cover glass provided with a coating having a filter effect such as an infrared cut filter or an ND filter may be used. In this imaging lens, all of the first lens G1 to the fifth lens G5 or at least one lens surface is coated with a filter effect coating such as an infrared cut filter or an ND filter, or an antireflection coating. Also good.

  The first lens G1 has a positive refractive power. The first lens G1 is a positive lens whose surface on the object side is convex toward the object side, for example, in the vicinity of the optical axis. For example, the first lens G1 has a biconvex shape in the vicinity of the optical axis or a meniscus shape convex toward the object side.

  The second lens G2 has a negative refractive power. The second lens G2 preferably has a concave surface on the image side in the vicinity of the optical axis.

  The third lens G3 is a positive lens having a concave surface on the image side in the vicinity of the optical axis, for example, a positive meniscus lens having a concave surface on the image side in the vicinity of the optical axis.

  The fourth lens G4 has a positive refractive power in the vicinity of the optical axis. For example, the fourth lens G4 has an image-side surface convex toward the image side in the vicinity of the optical axis.

  The fifth lens G5 has a negative refractive power in the vicinity of the optical axis. For example, the fifth lens G5 has a concave surface on the image side on the image side in the vicinity of the optical axis. The fifth lens may have a meniscus shape (for example, the configuration example in FIG. 1) in the vicinity of the optical axis, or may have a biconcave shape in the vicinity of the optical axis (for example, the configuration example in FIG. 10).

This imaging lens is configured to satisfy the following conditional expression.
0.8 <f / f1 ≦ 1.2 (1)
Here, f1 is the focal length of the first lens G1, and f is the focal length of the entire system.

The imaging lens preferably satisfies the following conditional expression in order to be applied to a small imaging device.
f <5.0mm (2)

In order to obtain higher resolution performance, it is preferable to satisfy at least one of the following conditional expressions. Here, f2 is the focal length of the second lens G2, f3 is the focal length of the third lens G3, and f4 is the focal length of the fourth lens G4. νd2 is the Abbe number related to the d-line of the second lens G2.
f1 <| f2 | <f3 (3)
νd2 <35 (4)
f4 <f1 (5A)
f4 <| f2 | (5B)
f4 <f3 (5C)

  In this imaging lens, it is preferable that both the first lens G1, the second lens G2, the third lens G3, the fourth lens G4, and the fifth lens G5 are aspheric on both surfaces. In particular, it is preferable that the fourth lens G4 and the fifth lens G5 have an aspherical shape in which the vicinity of the optical axis and the peripheral portion have different uneven shapes.

  For example, the image-side surface of the fifth lens G5 is preferably concave in the vicinity of the optical axis, and has a region in which the negative refractive power becomes weaker as compared to the vicinity of the optical axis. The image-side surface of the fifth lens G5 is preferably an aspherical shape having an inflection point within the effective diameter. The image-side surface of the fifth lens G5 is preferably an aspherical shape having a pole other than the center of the optical axis within the effective diameter. Specifically, for example, the image-side surface of the fifth lens G5 is preferably an aspherical surface having a concave shape in the vicinity of the optical axis and a convex shape in the peripheral portion. Furthermore, it is preferable that the object side surface of the fifth lens G5 has an aspherical shape having an inflection point within the effective diameter.

In general, the aspherical expression is represented by the following expression (A).
Z = C · h ² / {1+ (1−K ′ · C ² · h ² ) ^1/2 } + ΣA _i · h ⁱ (A)
However,
K '= 1 + K
K: Eccentricity Z: Depth of aspheric surface (mm)
h: Distance from the optical axis to the lens surface (height) (mm)
C: Paraxial curvature = 1 / R
(R: paraxial radius of curvature)
ΣA _i · h ⁱ : Sum of A _i · h ⁱ when i = 1 to n (n = an integer of 3 or more)
A _i : i-th aspherical coefficient

  Z represents the length (mm) of a perpendicular line drawn from a point on the aspheric surface at a height h from the optical axis to the tangent plane (plane perpendicular to the optical axis) of the apex of the aspheric surface. That is, Z indicates the sag amount (depth) of the aspheric surface with reference to the surface vertex position at the height h from the optical axis.

[Action / Effect]
Next, operations and effects of the imaging lens configured as described above will be described.
This imaging lens has a five-lens configuration as a whole, increases the number of lenses compared to the conventional four-lens imaging lens, and optimizes the configuration of each lens, so that it can cope with higher pixels. A lens system with high resolution performance can be obtained.

  In particular, by making the image side surface of the third lens G3 concave, and by making the distance between the third lens G3 and the fourth lens G4 relatively wide, it is easy to obtain high resolution performance. If the distance between the third lens G3 and the fourth lens G4 is relatively narrow, the curvature of field becomes large and high resolution performance cannot be obtained.

  Conditional expression (1) relates to the refractive power of the first lens G1. In this imaging lens, an optical system with a short overall length can be obtained by occupying the main imaging function of the first lens G1 so as to satisfy the conditional expression (1). If the lower limit of conditional expression (1) is not reached, the total length becomes long. Exceeding the upper limit is advantageous for shortening the overall length, but the field curvature becomes large, and high resolution performance cannot be obtained.

  Conditional expression (2) relates to the focal length f of the entire system. When the conditional expression (2) is satisfied, a lens system suitable for a small imaging device can be obtained. For example, the present invention can be favorably applied to an image pickup apparatus including a small, high-pixel image pickup device having a pixel number of 2 megapixels or more and a pixel pitch of 3 μm or less.

Conditional expression (3) shows an appropriate relationship among the focal lengths of the first lens G1, the second lens G2, and the third lens G3. Conditional expression (4) relates to an appropriate Abbe number of the second lens G2. Satisfying conditional expression (3) and conditional expression (4) is advantageous for chromatic aberration correction. In particular, if the upper limit of conditional expression (4) is exceeded, chromatic aberration correction will be insufficient.
In order to perform chromatic aberration correction better, it is preferable that the upper limit of conditional expression (4) satisfies the following conditional expression (4A).
νd2 <25 (4A)

Conditional expressions (5A), (5B), and (5C) show an appropriate relationship between the focal lengths of the first lens G1, the second lens G2, and the third lens G3 with respect to the focal length of the fourth lens G4. . When the conditional expressions (5A), (5B), and (5C) are satisfied, the F-number is reduced and a bright lens system can be easily realized.
In order to obtain brighter and higher resolution performance, the focal lengths of the first lens G1, the second lens G2, the third lens G3, and the fourth lens G4 may have the following conditional expression (5D). preferable.
f4 <f1 <| f2 | <f3 (5D)

  In this imaging lens, the aspherical shape of the fourth lens G4 and the fifth lens G5 arranged on the image side with respect to the other lenses is different from that of the uneven shape in the vicinity of the optical axis and in the peripheral portion. By doing so, it is possible to satisfactorily correct the curvature of field from the center to the periphery of the image plane. In particular, the image-side surface of the fifth lens G5 has a region in which the negative refractive power becomes weaker as it goes toward the periphery, so that the curvature of field can be corrected well and high resolution can be achieved. Image performance is obtained.

  As described above, according to the imaging lens according to the present embodiment, in the lens configuration of five as a whole, the shape of each lens is appropriately set and the predetermined conditional expression is satisfied. High resolution performance can be obtained. Further, according to the imaging device or the mobile terminal device according to the present embodiment, since the imaging signal corresponding to the optical image formed by the imaging lens with high resolution performance according to the present embodiment is output, A high-resolution captured image can be obtained.

  Next, specific numerical examples of the imaging lens according to the present embodiment will be described. Hereinafter, a plurality of numerical examples will be described in part.

[Example 1]
[Table 1] to [Table 2] show specific lens data corresponding to the configuration of the imaging lens shown in FIG. In particular, [Table 1] shows the basic lens data, and [Table 2] shows aspherical data. In the field of the surface number Si in the lens data shown in [Table 1], for the imaging lens according to Example 1, the surface of the component closest to the object side is the first, and sequentially increases toward the image side. The number of the i-th surface (i = 1 to 13) denoted by reference numerals is shown. In the column of the curvature radius Ri, the value (mm) of the curvature radius of the i-th surface from the object side is shown in correspondence with the reference symbol Ri in FIG. Similarly, the column of the surface interval Di indicates the interval (mm) on the optical axis between the i-th surface Si and the i + 1-th surface Si + 1 from the object side. In the columns of Ndj and νdj, the values of the refractive index and the Abbe number for the d-line (587.6 nm) of the j-th optical element from the object side are shown.

  In the imaging lens according to Example 1, the first lens G1, the second lens G2, the third lens G3, the fourth lens G4, and the fifth lens G5 are all aspherical on both surfaces. The basic lens data in [Table 1] shows numerical values of the radius of curvature near the optical axis as the radius of curvature of these aspheric surfaces.

[Table 2] shows aspherical data in the imaging lens according to Example 1. In the numerical values shown as aspherical data, the symbol “E” indicates that the subsequent numerical value is a “power exponent” with a base of 10, and the numerical value represented by an exponential function with the base of 10 is Indicates that the value before “E” is multiplied. For example, “1.0E-02” indicates “1.0 × 10 ⁻² ”.

As the aspheric surface data of the imaging lens according to Example 1, the values of the coefficients A _i and K in the aspheric shape expression represented by the above-described aspheric expression (A) are described. The imaging lens according to Example 1 is represented by effectively using coefficients up to the 10th order as the aspheric coefficient A _i . Although omitted in the table, the primary and secondary aspherical coefficients A ₁ and A ₂ are set to 0 (that is, A ₁ = 0, A ₂ = 0).

[Numerical Examples 2 to 13]
Similar to the imaging lens according to Numerical Example 1 described above, specific lens data corresponding to the configuration of the imaging lens shown in FIG. 2 is shown as Numerical Example 2 in [Table 3] to [Table 4]. . Similarly, specific lens data corresponding to the configuration of the imaging lens shown in FIGS. 3 to 13 are shown in [Table 5] to [Table 26] as Numerical Examples 3 to 13.

  In any imaging lens of Examples 2 to 13, as in the imaging lens according to Example 1, all lens surfaces are aspherical.

[Other numerical data of each example]
[Table 27] shows a summary of values related to the conditional expressions (1) to (4) and (5A), (5B), and (5C) for each example. As can be seen from [Table 27], each example satisfies at least one of the conditional expressions. [Table 27] also shows the F number (FNO.) Value as various data.

[Aberration performance]
14A to 14C respectively show spherical aberration, astigmatism, and distortion (distortion aberration) in the imaging lens according to Numerical Example 1. FIG. These aberration diagrams also show aberrations for the C line (wavelength 656.27 nm) and the F line (wavelength 486.13 nm) with the d line as the reference wavelength. In the graph showing astigmatism, (S) shows the sagittal direction, and (T) shows the tangential aberration. ω indicates a half angle of view. In FIG. 14A, the vertical axis indicates the F number.

  Similarly, various aberrations of the imaging lens according to Numerical Example 2 are shown in FIGS. Similarly, various aberrations of the imaging lenses according to Numerical Examples 3 to 13 are shown in FIGS. 16 to 26 (A) to (C). In FIGS. 26B and 26C, the vertical axis indicates the image height Y (mm).

  As can be seen from the above numerical data and aberration diagrams, a high-resolution imaging lens system can be realized with a total of five lens configurations for each example.

  In addition, this invention is not limited to the said embodiment and each Example, A various deformation | transformation implementation is possible. For example, the radius of curvature, the surface interval, and the refractive index of each lens component are not limited to the values shown in the above numerical examples, and may take other values.

  GC ... optical member, G1 ... first lens, G2 ... second lens, G3 ... third lens, G4 ... fourth lens, G5 ... fifth lens, St ... aperture stop, Ri ... i-th lens from the object side The radius of curvature of the surface, Di: the distance between the i-th lens surface and the i + 1-th lens surface from the object side, Z1,.

Claims (16)

From the object side,
A first lens having a positive refractive power;
A second lens having negative refractive power;
A third lens having positive refractive power;
A fourth lens having a positive refractive power;
An imaging lens comprising: a fifth lens having negative refractive power in the vicinity of the optical axis, and satisfying the following conditional expression:
0.8 <f / f1 ≦ 1.2 (1)
However,
f1: Focal length of the first lens f: The focal length of the entire system. The imaging lens according to claim 1, further satisfying the following conditional expression:
f <5.0mm (2) Furthermore, the following conditional expressions are satisfied. The imaging lens according to claim 1 or 2 characterized by things.
f1 <| f2 | <f3 (3)
However,
f2: focal length of the second lens f3: focal length of the third lens. The imaging lens according to any one of claims 1 to 3, further satisfying the following conditional expression.
νd2 <35 (4)
However,
νd2: Abbe number related to the d-line of the second lens. The imaging lens according to any one of claims 1 to 4, further satisfying the following conditional expression.
f4 <f1 (5A)
However,
f4: The focal length of the fourth lens. The imaging lens according to any one of claims 1 to 5, further satisfying the following conditional expression.
f4 <| f2 | (5B) The imaging lens according to any one of claims 1 to 6, further satisfying the following conditional expression.
f4 <f3 (5C) The object side surface of the first lens is convex toward the object side in the vicinity of the optical axis,
8. The imaging lens according to claim 1, wherein an image-side surface of the fourth lens is convex toward the image side in the vicinity of the optical axis. The first lens, the second lens, the third lens, the fourth lens, and the fifth lens are all aspherical on both surfaces. The imaging lens described in 1. 10. The imaging lens according to claim 1, wherein an object-side surface of the fifth lens has an aspheric shape having an inflection point within an effective diameter. The image-side surface of the fifth lens has a concave shape in the vicinity of the optical axis, and has a region in which the negative refractive power becomes weaker as compared to the vicinity of the optical axis. The imaging lens according to any one of the above. The imaging lens according to any one of claims 1 to 11, wherein the image-side surface of the fifth lens has an aspherical shape having an inflection point within an effective diameter. The imaging lens according to any one of claims 1 to 12, wherein the image-side surface of the fifth lens has an aspheric shape having a pole other than the center of the optical axis within the effective diameter. The imaging lens according to any one of claims 1 to 13,
An imaging device comprising: an imaging element that outputs an imaging signal corresponding to an optical image formed by the imaging lens. The imaging device according to claim 14, wherein the imaging device has a number of pixels of 2 megapixels or more and a pixel pitch of 3 µm or less. An imaging device according to claim 14 or 15,
A portable terminal device comprising: display means for displaying an image picked up by the image pickup device.

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