JP2015079175A - Image capturing lens, image capturing device, and portable terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image capturing lens which is compact, high-performing, and bright with an F-number of F2.2 or less, and to provide an image capturing device and portable terminal having the same.SOLUTION: An image capturing lens comprises five or more lenses including, in order from the object side, a first lens L1 being convex on the object side and having positive refractive power and a second lens L2 being convex on the object side and having negative refractive power. A lens L5 located on the most image side is biconcave near an optical axis and has at least one extremum on an image-side surface thereof. The image capturing lens satisfies the following conditional expressions: f/2α<2.2 (1), L/f<1.4 (2). The first lens L1 has an inflection point inside an effective diameter of an object-side surface thereof and satisfies the following conditional expression: 0.75<(R1+R2)/(R2-R1)<0.92 (3), where f represents a focal length of the entire image capturing lens system, α represents a radius of a flare stop located on the object side from the first lens L1, L represents an optical axial distance from the object-side surface of the first lens L1 to an image capturing plane when infinite light enters, R1 represents a curvature radius of the object-side surface of the first lens L1, and R2 represents a curvature radius of an image-side surface of the first lens L1.

Description

  The present invention relates to a small imaging lens for forming a subject image detected by a solid-state imaging device, an imaging apparatus including the imaging lens, and a portable terminal.

  In recent years, small-sized imaging devices using solid-state imaging devices such as CCD (Charge Coupled Device) type image sensors or CMOS (Complementary Metal Oxide Semiconductor) type image sensors have become portable terminals such as mobile phones and PDAs (Personal Digital Assistants), Furthermore, it is also installed in notebook personal computers and the like, and it is possible to transmit not only audio information but also image information to a remote place.

  In the solid-state imaging device used in such an imaging apparatus, in recent years, the pixel size has been reduced, and the imaging device has been increased in size and size. Further, it is possible to curve the imaging surface, and there is a demand for a compact and high-performance imaging lens that is optimal for such an imaging device.

  As a small and high-performance lens, an imaging lens having a five-lens configuration or a six-lens configuration has been proposed because of its high aberration correction function and higher performance than a three- or four-lens configuration lens.

  In Patent Document 1, a first lens having a positive refractive power, a second lens having a negative refractive power, a third lens, a fourth lens, and a fifth lens having a negative refractive power are sequentially formed from the object side. An imaging lens that aims to reduce the total lens length (distance on the optical axis from the lens surface closest to the object side to the image-side focal point of the entire imaging lens system) is disclosed.

International Publication No. 2011/021271 Pamphlet

  By the way, in order to increase the number of pixels without increasing the size, a solid-state imaging device with a reduced pixel pitch has been developed. In order to form a subject image on such a solid-state imaging device, an imaging lens with a smaller F number and a larger aperture is desired. The imaging lens of Patent Document 1 has a relatively small F-number while aiming for miniaturization. However, according to the examination result of the present inventor, a ghost is likely to occur in such an imaging lens. found.

  The present invention has been made in view of the problems of the background art described above, and an object of the present invention is to obtain a small and high-performance imaging lens that is bright at F2.2 or less, an imaging device including the imaging lens, and a portable terminal. .

In order to solve the above problems, an imaging lens according to the present invention is an imaging lens for forming a subject image on an imaging surface of a solid-state imaging device,
The imaging lens includes, in order from the object side, a first lens having a convex shape on the object side and having positive refractive power, and a second lens having a convex shape on the object side and having negative refractive power. The imaging is composed of two or more lenses, and the vicinity of the optical axis of the most image side lens has a biconcave shape, and the image side surface has at least one extreme value at a point other than the vicinity of the optical axis in the cross section in the optical axis direction. The lens satisfies the following conditional expression:
f / 2α <2.2 (1)
L / f <1.4 (2)
Further, the first lens is characterized in that the object side surface has an inflection point within the effective diameter in the cross section in the optical axis direction, and satisfies the following conditional expression.
0.75 <(R1 + R2) / (R2-R1) <0.92 (3)
However,
f: Focal length of the entire imaging lens (mm)
α: Radius (mm) of the light-shielding stop arranged on the object side from the first lens
L: Distance on the optical axis from the object side surface of the first lens to the imaging surface when infinite light is incident (mm)
R1: radius of curvature of object side surface of the first lens (mm)
R2: radius of curvature of the image side surface of the first lens (mm)

According to the present invention, an imaging lens having a small F-number and a large aperture can be provided by satisfying the formula (1), and further suitable for an imaging device that can be mounted on a portable terminal or the like by satisfying the formula (2). A small imaging lens can be provided. Preferably, the following conditional expression is satisfied.
f / 2α <2.1 (1 ′)
L / f <1.3 (2 ′)

As a result of diligent research, the present inventor has found that the shape on the peripheral side of the first lens greatly affects the ghost. More specifically, when the shape on the peripheral side of the first lens is a shape gradually toward the image side in the vicinity of the effective diameter, a plurality of rays incident from outside the angle of view are incident on the object side surface and the image side surface of the first lens. It has been found that after being reflected once, it is emitted from the periphery of the first lens, condensed on the imaging surface of the solid-state imaging device, and detected as a ghost. Based on this knowledge, the present inventor has an inflection point within the effective diameter on the object side surface of the first lens in the cross section in the optical axis direction, so that the light incident from outside the angle of view is emitted from the periphery of the first lens. When emitted, the light is not condensed on the image pickup surface of the solid-state image pickup device, thereby making it difficult for ghosts to occur. Here, the “extreme value” is expressed by first-order differentiation (dx (h) / dh) = 0, where x (h) is the distance in the optical axis direction and h is the height from the optical axis. The point to be done. The “inflection point” is a second-order differential (d ² x (h) / dh ² ) = when the distance in the optical axis direction is x (h) and the height from the optical axis is h. The point represented by 0. More preferably, the inflection point on the object side surface of the first lens is within 95% of the effective diameter. The effect of the present invention is not limited to the number of lenses of the imaging lens, but is particularly effective for five or more lenses.

  Conditional expression (3) is a conditional expression for appropriately setting the shape of the first lens, that is, a so-called shaping factor. More specifically, when the value of conditional expression (3) is less than the upper limit, the refractive power on the side surface of the first lens object does not become too small, and a predetermined telephoto property can be ensured. It becomes easy. On the other hand, if the value of conditional expression (3) exceeds the lower limit, the refractive power on the side surface of the first lens object will not become too large, and higher-order spherical aberration and coma aberration generated on the side surface of the first lens object will be reduced. Furthermore, when the light beam incident from outside the angle of view is reflected by the object side surface and the image side surface of the first lens a plurality of times, it is difficult to totally reflect, and the intensity of the ghost light emitted from the periphery of the first lens is reduced. It becomes possible to do.

The imaging lens described in claim 2 is characterized in that, in the invention described in claim 1, the following conditional expression is satisfied.
25 <θmax <40 (4)
However,
θmax: Maximum surface angle (°) within the effective diameter of the object side surface of the first lens

  When the value of conditional expression (4) exceeds the lower limit, the positive refractive power of the first lens does not become too weak, and telephoto type characteristics can be ensured. On the other hand, generation of a ghost can be effectively suppressed because the value of conditional expression (4) is lower than the upper limit value.

The imaging lens described in claim 3 is characterized in that, in the invention described in claim 1 or 2, the following conditional expression is satisfied.
−2.5 <f2 / f <−1.0 (5)
However,
f2: Focal length (mm) of the second lens

  When the value of conditional expression (5) is below the upper limit, the negative refractive power of the second lens is strengthened, so that the principal point position can be brought closer to the image plane, which is advantageous for widening the angle. On the other hand, when the value of conditional expression (5) exceeds the lower limit, it is possible to prevent the occurrence of spherical aberration and coma aberration and increase in error sensitivity due to the negative refractive power of the second lens becoming too strong.

The imaging lens of Claim 4 satisfies the following conditional expressions in the invention of any one of Claims 1-3.
20 <ν1-ν2 <40 (6)
However,
ν1: Abbe number in the d-line of the material constituting the first lens ν2: Abbe number in the d-line of the material constituting the second lens

  Conditional expression (6) is a conditional expression for satisfactorily correcting the chromatic aberration of the entire imaging lens system. When the value of conditional expression (6) exceeds the lower limit, chromatic aberrations such as axial chromatic aberration and lateral chromatic aberration can be corrected in a well-balanced manner. On the other hand, when the value of conditional expression (6) is below the upper limit, it can be made of a readily available glass material.

The imaging lens of Claim 5 satisfies the following conditional expressions in the invention in any one of Claims 1-4, It is characterized by the above-mentioned.
0.9 <f12 / f <2.0 (7)
However,
f12: Composite focal length (mm) of the first lens and the second lens

  Conditional expression (7) is a conditional expression for appropriately setting the combined focal length of the first lens and the second lens. When the value of conditional expression (7) exceeds the lower limit, the combined refractive power of the first lens and the second lens can be appropriately maintained, and the overall length of the imaging lens can be shortened. On the other hand, since the value of conditional expression (7) is less than the upper limit, the combined refractive power does not become excessively strong, the error sensitivity of the first lens and the second lens can be reduced, and the manufacturing difficulty of the assembly process Can be lowered.

  The imaging lens according to claim 6 is the imaging lens according to any one of claims 1 to 5, wherein the object side lens adjacent to the most image side lens has a convex shape on the image side surface and a positive refractive power. It is characterized by having.

  By giving positive refractive power to the object side lens adjacent to the lens closest to the image side, the distance from the front principal point position of the imaging lens to the aperture stop is increased. As a result, the exit pupil position of the photographic lens can be positioned farther from the imaging plane, and thus good image side telecentric characteristics can be obtained. Furthermore, by making the image side surface of the object side lens adjacent to the most image side lens convex, the incident angle of light on the image surface can be kept small.

The imaging lens of Claim 7 satisfies the following conditional expressions in the invention in any one of Claims 1-6, It is characterized by the above-mentioned.
−0.6 <fe / f <−0.4 (8)
However,
fe: Focal length (mm) of the lens closest to the image side

  Conditional expression (8) is a conditional expression for appropriately setting the focal length of the lens closest to the image side. When the value of conditional expression (8) exceeds the lower limit, the negative refractive power of the lens on the most image side does not become larger than necessary, and the light beam that forms an image on the periphery of the imaging surface of the imaging element excessively jumps up. Therefore, it is possible to easily secure the telecentric characteristic of the image side light beam. On the other hand, when the value of conditional expression (8) is less than the upper limit, the negative refractive power of the lens closest to the image side can be appropriately maintained, and the length of the lens can be shortened and axes such as field curvature and distortion aberration can be maintained. It is possible to satisfactorily correct external aberrations.

An imaging lens according to an eighth aspect of the invention according to any one of the first to seventh aspects satisfies the following conditional expression.
0.15 <d1 / f <0.2 (9)
However,
d1: On-axis thickness of the first lens (mm)

  Conditional expression (9) is a conditional expression for appropriately setting the core thickness of the first lens to achieve shortening of the total length and good moldability. When the value of conditional expression (9) exceeds the lower limit, the edge thickness of the first lens can be sufficiently ensured, so that good moldability can be ensured. On the other hand, when the value of conditional expression (9) is below the upper limit, the core thickness of the first lens does not become too thick, and the entire length of the imaging lens can be shortened.

  An imaging lens according to a ninth aspect is characterized in that in the invention according to any one of the first to eighth aspects, all the lenses are made of plastic.

  By molding a large amount of each lens from plastic, the imaging lens can be made lightweight and inexpensive.

  An imaging apparatus according to a tenth aspect includes the imaging lens according to any one of the first to ninth aspects and a solid-state imaging element.

  A portable terminal according to an eleventh aspect includes the imaging device according to the tenth aspect.

  According to the present invention, it is possible to obtain a small and high-performance imaging lens that is bright at F2.2 or less, an imaging device including the imaging lens, and a portable terminal.

It is a perspective view of the imaging unit 50 concerning this Embodiment. 3 is a diagram schematically showing a cross section along the optical axis of an imaging optical system of the imaging unit 50. FIG. It is the front view (a) of the smart phone as a portable terminal to which an imaging unit is applied, and the back view (b) of the smart phone to which the imaging unit is applied. It is a control block diagram of the smart phone of FIG. 3 is a cross-sectional view in the optical axis direction of the imaging lens of Example 1. FIG. FIG. 4 is an aberration diagram of Example 1 (spherical aberration (a), astigmatism (b), distortion (c)). FIG. 6 is a cross-sectional view in the optical axis direction of the imaging lens of Example 2. FIG. 6 is an aberration diagram of Example 2 (spherical aberration (a), astigmatism (b), distortion (c)). 6 is a cross-sectional view in the optical axis direction of the imaging lens of Embodiment 3. FIG. FIG. 6 is an aberration diagram of Example 3 (spherical aberration (a), astigmatism (b), distortion (c)). It is a peripheral side cross section of the 1st lens of an Example and a comparative example. It is a figure which shows the condensing state in the periphery of the imaging surface of a stray light about an Example. It is a figure which shows the condensing state in the imaging surface periphery of a stray light about a comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of an imaging unit (imaging device) 50 according to the present embodiment, and FIG. 2 is a diagram schematically showing a cross section along the optical axis of the imaging lens of the imaging unit 50.

  As shown in FIGS. 1 and 2, the imaging unit 50 includes a CMOS type imaging device 51 as a solid-state imaging device having a photoelectric conversion unit 51 a and an imaging lens 10 that causes the photoelectric conversion unit 51 a of the imaging device 51 to image a subject image. A substrate 52 that holds the image sensor 51 and transmits / receives an electric signal thereof, and a housing 53 as a lens barrel that has an opening for light incidence from the object side and is made of a light shielding member. It is integrally formed.

  As shown in FIG. 2, the imaging element 51 has a photoelectric conversion part 51 a as a light receiving part in which pixels (photoelectric conversion elements) are two-dimensionally arranged at the center of the plane on the light receiving side. A signal processing circuit (not shown) is formed around the periphery. Such a signal processing circuit includes a drive circuit unit that sequentially drives each pixel to obtain a signal charge, an A / D conversion unit that converts each signal charge into a digital signal, and a signal that forms an image signal output using the digital signal. It consists of a processing unit and the like. A number of pads (not shown) are arranged in the vicinity of the outer edge of the plane on the light receiving side of the image sensor 51, and are connected to the substrate 52 via wires (not shown). The image sensor 51 converts the signal charge from the photoelectric conversion unit 51a into an image signal such as a digital YUV signal, and outputs it to a predetermined circuit on the substrate 52 via a wire (not shown). Here, Y is a luminance signal, U (= R−Y) is a color difference signal between red and the luminance signal, and V (= BY) is a color difference signal between blue and the luminance signal. Note that the image sensor is not limited to the above CMOS image sensor, and other devices such as a CCD may be used.

  The substrate 52 supports the image sensor 51 and the housing 53 on the upper surface thereof. Although not shown, the substrate 52 has a large number of signal transmission pads, and is connected to the image sensor 51 via wiring (not shown).

  In FIG. 2, a substrate 52 is connected to an external circuit (for example, a control circuit included in a host device on which an imaging unit is mounted), and receives a voltage and a clock signal for driving the imaging element 51 from the external circuit. In addition, the digital YUV signal can be output to an external circuit.

  In FIG. 2, the housing 53 is fixedly disposed on the surface of the substrate 52 on which the image sensor 51 is provided so as to cover the image sensor 51. That is, the casing 53 is wide open so that the part on the image sensor 51 side surrounds the image sensor 51, and the other end (object side end) forms a flange 53a having a small opening. An end on the image sensor 51 side (image side end) is abutted and fixed on the substrate 52.

The imaging lens 10 disposed in the housing 53 includes, in order from the object side, a first lens L1 having a positive refractive power, a second lens L2 having a negative refractive power, a third lens L3, and a fourth lens. It has a lens L4 and a fifth lens L5 having negative refractive power. The fifth lens L5, which is the lens closest to the image side, has a biconcave shape in the vicinity of the optical axis, and has at least one extreme value at a point other than the vicinity of the optical axis on the image side surface in the cross section in the optical axis direction. The imaging lens 10 satisfies the following conditional expression.
f / 2α <2.2 (1)
L / f <1.4 (2)

Further, the first lens L1 has an inflection point within the effective diameter on the object side surface in the cross section in the optical axis direction, and satisfies the following conditional expression.
0.75 <(R1 + R2) / (R2-R1) <0.92 (3)
However,
f: Focal length of the entire imaging lens (mm)
α: Radius (mm) of the light-shielding stop arranged on the object side from the first lens
L: Distance on the optical axis from the object side surface of the first lens to the imaging surface when infinite light is incident (mm)
R1: radius of curvature of object side surface of first lens (mm)
R2: radius of curvature of the image side surface of the first lens (mm)

  A light shielding member AP is disposed between the flange portions of the first lens and the second lens to define the interaxial distance. The AP may have a function as an aperture stop. A light shielding member SH is disposed between the flange portions of the lenses L2 to L5, and the distance between the axes is defined. Spacers SP are arranged between the flange portion of the fifth lens L5 and the IR cut filter F, and between the IR cut filter F and the substrate 52, respectively, and define the distance between the axes.

  The operation of the imaging unit 50 described above will be described. FIG. 3 is a diagram illustrating a state in which the imaging unit 50 is mounted on the smartphone 100 as a mobile terminal. FIG. 4 is a control block diagram of the smartphone 100.

  In the imaging unit 50, for example, the object-side end surface of the housing 53 is provided on the back surface of the smartphone 100 (see FIG. 3B), and is disposed at a position corresponding to the back side of the touch panel 70.

  The imaging unit 50 is connected to the control unit 101 of the smartphone 100 and outputs an image signal such as a luminance signal or a color difference signal to the control unit 101 side.

  On the other hand, as shown in FIG. 4, the smartphone 100 performs overall control of each unit, and also inputs a control unit (CPU) 101 that executes a program corresponding to each process, and inputs a number and the like with a key. Unit 60, a liquid crystal display unit 70 for displaying captured images in addition to predetermined data, a wireless communication unit 80 for realizing various information communication with an external server, a system program for mobile phone 100, Obtained by a storage unit (ROM) 91 storing various processing programs and necessary data such as a terminal ID, and various processing programs and data executed by the control unit 101, or processing data, or the imaging unit 50 And a temporary storage unit (RAM) 92 that is used as a work area for temporarily storing imaging data and the like.

  The smartphone 100 operates by operating the input key unit 60, and touches an icon 71 or the like displayed on the touch panel (display unit) 70, whereby the imaging unit 50 can be operated to perform imaging. The image signal input from the imaging unit 50 is subjected to image processing to be described later in the control unit 101, stored in the storage unit 92 or displayed on the touch panel 70 by the control system of the smartphone 100, and wirelessly It is transmitted to the outside as video information via the communication unit 80.

[Example]
Examples of the imaging lens of the present invention will be shown below. In each example, the surface on which the aspheric coefficient is described is a surface having an aspheric shape, and the aspheric shape has an apex at the surface as an origin, an X axis in the optical axis direction, and is perpendicular to the optical axis. The height of the direction is represented by the following “Equation 1” where h.

ただし、
Ａｉ：ｉ次の非球面係数
Ｒ ：曲率半径
Ｋ ：円錐定数

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

(Example 1)
Table 1 shows lens data of Example 1. In the following (including the lens data in the table), a power of 10 (for example, 2.5 × 10 ⁻⁰² ) is expressed using E (for example, 2.5E-02). Moreover, the value regarding the length is mm unless otherwise indicated. In each lens, S1 represents an object side surface, and S2 represents an image side surface. A surface on which an aspheric coefficient is described is an aspheric surface. IRCF is an IR cut filter.

[Table 1]
Example 1

Surface number Curvature radius Interval Refractive index Abbe number Aperture (effective radius)
Object ∞ ∞
Aperture ∞ -0.288 0.990
L1-S1 1.690 0.670 1.5447 56.0 0.988
L1-S2 -17.129 0.050 0.921
L2-S1 7.652 0.170 1.6347 23.9 0.904
L2-S2 2.146 0.423 0.932
L3-S1 9.575 0.535 1.5447 56.0 1.106
L3-S2 ∞ 0.460 1.239
L4-S1 17.437 0.745 1.5447 56.0 1.407
L4-S2 -1.380 0.300 1.699
L5-S1 -4.526 0.342 1.5447 56.0 2.069
L5-S2 1.244 0.450 2.514
IRCF-S1 ∞ 0.110 1.5163 64.1 3.300
IRCF-S2 ∞ 0.276 3.300
Image plane ∞

Aspheric coefficient

S1 (side of object) S2 (side of image)
L1 K = -1.6099E + 00 K = -5.0000E + 01
A3 = 0.0000E + 00 A3 = 0.0000E + 00
A4 = 4.2509E-02 A4 = -8.0097E-02
A5 = 0.0000E + 00 A5 = 0.0000E + 00
A6 = -2.4907E-02 A6 = 3.4510E-01
A8 = 9.6714E-02 A8 = -5.9251E-01
A10 = -2.0014E-01 A10 = 4.3589E-01
A12 = 1.8931E-01 A12 = -1.3901E-01
A14 = -7.6314E-02 A14 = 0.0000E + 00
L2 K = 3.8417E + 01 K = -1.4022E + 01
A3 = 0.0000E + 00 A3 = 0.0000E + 00
A4 = -2.5522E-01 A4 = -1.9126E-02
A5 = 0.0000E + 00 A5 = 0.0000E + 00
A6 = 7.9024E-01 A6 = 3.4238E-01
A8 = -1.2284E + 00 A8 = -5.2334E-01
A10 = 9.4293E-01 A10 = 4.4676E-01
A12 = -3.0120E-01 A12 = -1.5009E-01
A14 = 0.0000E + 00 A14 = 0.0000E + 00
L3 K = 2.1484E + 01 K = 0.0000E + 00
A3 = 0.0000E + 00 A3 = 0.0000E + 00
A4 = -8.7540E-02 A4 = -9.4188E-02
A5 = 0.0000E + 00 A5 = 0.0000E + 00
A6 = -9.7850E-02 A6 = 5.2351E-04
A8 = 3.6161E-01 A8 = -3.2026E-02
A10 = -5.7724E-01 A10 = 6.5498E-02
A12 = 4.4668E-01 A12 = -6.0565E-02
A14 = -1.2141E-01 A14 = 2.2566E-02
L4 K = 5.0000E + 01 K = -7.6240E + 00
A3 = -4.2649E-02 A3 = -1.1300E-01
A4 = 4.8067E-02 A4 = 1.0455E-02
A5 = -1.0040E-01 A5 = 3.2856E-03
A6 = 1.4611E-02 A6 = 3.0690E-03
A8 = 1.0093E-02 A8 = 3.7157E-04
A10 = -1.0196E-02 A10 = -2.0447E-03
A12 = 1.0353E-03 A12 = 1.2798E-03
A14 = 0.0000E + 00 A14 = -2.2925E-04
L5 K = 7.9050E-01 K = -8.5142E + 00
A3 = -2.4413E-01 A3 = -1.5196E-01
A4 = 4.6216E-02 A4 = 7.4618E-02
A5 = 3.5437E-02 A5 = -1.5556E-02
A6 = 2.9272E-03 A6 = 2.8003E-04
A8 = -1.3992E-03 A8 = -3.0821E-04
A10 = -1.0781E-04 A10 = -4.4514E-06
A12 = 7.5523E-06 A12 = 3.4227E-06
A14 = 1.8354E-06 A14 = 1.7208E-07

  5 is a cross-sectional view of the imaging lens of Example 1. FIG. In the drawing, the imaging lens includes, in order from the object side, a first lens L1 having a convex shape on the object side and having positive refractive power, and a second lens L2 having a convex shape on the object side and having negative refractive power. The third lens L3, the fourth lens L4 having a convex image side surface and positive refractive power, and a biconcave shape in the vicinity of the optical axis, and the image side surface other than the vicinity of the optical axis in the cross section in the optical axis direction. And a fifth lens L5 having at least one extreme value. I is an imaging surface (projection surface), and F is an IR cut filter. FIG. 6 is an aberration diagram of Example 1 (spherical aberration (a), astigmatism (b), distortion (c)). Here, in the spherical aberration diagram, the amount of spherical aberration with respect to the light beam of 656 nm, the light beam of 588 nm, and the light beam of 486 nm is shown, respectively. ).

Regarding Example 1, each value is shown below.
F (F number): 1.83
f (focal length of the entire system): 3.619 mm
Y (maximum image height): 2.921 mm

(Example 2)
Table 2 shows lens data of the imaging lens of Example 2.

[Table 2]
Example 2

Surface number Curvature radius Interval Refractive index Abbe number Aperture (effective radius)
Object ∞ ∞
Aperture ∞ -0.297 0.995
L1-S1 1.663 0.600 1.5447 56.0 0.994
L1-S2 -23.145 0.061 0.941
L2-S1 6.845 0.170 1.6347 23.9 0.920
L2-S2 2.095 0.443 0.938
L3-S1 9.869 0.550 1.5447 56.0 1.123
L3-S2 ∞ 0.468 1.246
L4-S1 15.531 0.753 1.5447 56.0 1.426
L4-S2 -1.439 0.310 1.747
L5-S1 -4.993 0.337 1.5447 56.0 2.138
L5-S2 1.264 0.450 2.545
IRCF-S1 ∞ 0.110 1.5163 64.1 3.300
IRCF-S2 ∞ 0.279 3.300
Image plane ∞

Aspheric coefficient

S1 (object side) S2 (image side)
L1 K = -1.5475E + 00 K = -5.0000E + 01
A3 = 0.0000E + 00 A3 = 0.0000E + 00
A4 = 4.0287E-02 A4 = -6.5168E-02
A5 = 0.0000E + 00 A5 = 0.0000E + 00
A6 = 4.4796E-03 A6 = 2.6332E-01
A8 = -1.6498E-03 A8 = -4.1375E-01
A10 = -3.9525E-02 A10 = 2.8647E-01
A12 = 6.7797E-02 A12 = -9.5420E-02
A14 = -4.3573E-02 A14 = 0.0000E + 00
L2 K = 3.7349E + 01 K = -1.2723E + 01
A3 = 0.0000E + 00 A3 = 0.0000E + 00
A4 = -2.3952E-01 A4 = -1.5216E-02
A5 = 0.0000E + 00 A5 = 0.0000E + 00
A6 = 6.7367E-01 A6 = 3.2583E-01
A8 = -9.7164E-01 A8 = -4.6862E-01
A10 = 7.1142E-01 A10 = 3.9702E-01
A12 = -2.2759E-01 A12 = -1.3449E-01
A14 = 0.0000E + 00 A14 = 0.0000E + 00
L3 K = 2.1484E + 01 K = 0.0000E + 00
A3 = 0.0000E + 00 A3 = 0.0000E + 00
A4 = -8.9097E-02 A4 = -9.8376E-02
A5 = 0.0000E + 00 A5 = 0.0000E + 00
A6 = -6.2296E-02 A6 = 1.6030E-02
A8 = 2.6351E-01 A8 = -5.3536E-02
A10 = -4.3966E-01 A10 = 8.1095E-02
A12 = 3.5704E-01 A12 = -6.3653E-02
A14 = -9.9879E-02 A14 = 2.2004E-02
L4 K = -5.0000E + 01 K = -8.1848E + 00
A3 = -3.9088E-02 A3 = -1.0888E-01
A4 = 4.2886E-02 A4 = 9.7430E-03
A5 = -9.5715E-02 A5 = 4.2689E-03
A6 = 1.7343E-02 A6 = 4.4695E-03
A8 = 8.7354E-03 A8 = 3.7844E-04
A10 = -1.0532E-02 A10 = -2.1306E-03
A12 = 1.5969E-03 A12 = 1.2591E-03
A14 = 0.0000E + 00 A14 = -2.2405E-04
L5 K = 6.0791E-01 K = -8.3919E + 00
A3 = -2.4051E-01 A3 = -1.5130E-01
A4 = 4.4933E-02 A4 = 7.5344E-02
A5 = 3.4890E-02 A5 = -1.5587E-02
A6 = 2.7588E-03 A6 = -3.5796E-05
A8 = -1.4032E-03 A8 = -2.6548E-04
A10 = -1.0793E-04 A10 = -2.1366E-06
A12 = 7.3068E-06 A12 = 3.5065E-06
A14 = 1.8561E-06 A14 = 1.1685E-07

  FIG. 7 is a sectional view of the lens of Example 2. In the drawing, the imaging lens includes, in order from the object side, a first lens L1 having a convex shape on the object side and having positive refractive power, and a second lens L2 having a convex shape on the object side and having negative refractive power. The third lens L3, the fourth lens L4 having a convex image side surface and positive refractive power, and a biconcave shape in the vicinity of the optical axis, and at least one pole on the image side surface in the cross section in the optical axis direction. And a fifth lens L5 having a value. I is an imaging surface (projection surface), and F is an IR cut filter. FIG. 8 is an aberration diagram of Example 2 (spherical aberration (a), astigmatism (b), distortion (c)).

Regarding Example 2, each value is shown below.
F (F number): 1.83
f (focal length of the entire system): 3.636 mm
Y (maximum image height): 2.921 mm

(Example 3)
Table 3 shows lens data of the imaging lens of Example 3.

[Table 3]
Example 3

Surface number Curvature radius Interval Refractive index Abbe number Aperture (effective radius)
Object ∞ ∞
Aperture ∞ -0.309 0.980
L1-S1 1.674 0.550 1.5447 56.0 0.981
L1-S2 -22.691 0.072 0.957
L2-S1 6.962 0.170 1.6347 23.9 0.930
L2-S2 2.009 0.438 0.947
L3-S1 9.940 0.302 1.5447 56.0 1.112
L3-S2 -13.735 0.050 1.190
L4-S1 -24.490 0.250 1.5447 56.0 1.231
L4-S2 ∞ 0.492 1.281
L5-S1 11.305 0.674 1.5447 56.0 1.518
L5-S2 -1.669 0.375 1.848
L6-S1 -6.450 0.330 1.5447 56.0 2.250
L6-S2 1.300 0.450 2.566
IRCF-S1 ∞ 0.110 1.5163 64.1 3.300
IRCF-S2 ∞ 0.265 3.300
Image plane ∞

Aspheric coefficient

S1 (object side) S2 (image side)
L1 K = -1.2847E + 00 K = -5.0000E + 01
A3 = 0.0000E + 00 A3 = 0.0000E + 00
A4 = 4.0920E-02 A4 = -2.9611E-02
A5 = 0.0000E + 00 A5 = 0.0000E + 00
A6 = -1.5338E-02 A6 = 1.9164E-01
A8 = 7.9381E-02 A8 = -3.3373E-01
A10 = -1.6796E-01 A10 = 2.9305E-01
A12 = 1.7685E-01 A12 = -1.2121E-01
A14 = -7.5838E-02 A14 = 0.0000E + 00
L2 K = 3.7674E + 01 K = -1.2591E + 01
A3 = 0.0000E + 00 A3 = 0.0000E + 00
A4 = -2.2228E-01 A4 = -1.0165E-02
A5 = 0.0000E + 00 A5 = 0.0000E + 00
A6 = 5.6872E-01 A6 = 2.6379E-01
A8 = -8.1060E-01 A8 = -3.7560E-01
A10 = 6.3908E-01 A10 = 3.4567E-01
A12 = -2.3210E-01 A12 = -1.2510E-01
A14 = 0.0000E + 00 A14 = 0.0000E + 00
L3 K = 2.1484E + 01 K = 4.0539E + 01
A3 = 0.0000E + 00 A3 = 1.9943E-02
A4 = -4.5079E-02 A4 = -8.1325E-03
A5 = 0.0000E + 00 A5 = -1.7823E-02
A6 = -1.9485E-01 A6 = -1.5766E-02
A8 = 4.6306E-01 A8 = -5.8080E-03
A10 = -6.7401E-01 A10 = -1.0188E-03
A12 = 5.0711E-01 A12 = -3.9936E-05
A14 = -1.3734E-01 A14 = 0.0000E + 00
L4 K = 5.0000E + 01 K = 0.0000E + 00
A3 = -1.8244E-02 A3 = 0.0000E + 00
A4 = -1.0207E-02 A4 = -1.3881E-01
A5 = -2.6867E-04 A5 = 0.0000E + 00
A6 = 2.0787E-03 A6 = 8.8590E-02
A8 = 2.0643E-04 A8 = -1.1415E-01
A10 = -5.2193E-04 A10 = 9.5340E-02
A12 = 2.1645E-04 A12 = -3.9880E-02
A14 = 0.0000E + 00 A14 = 9.4104E-03
L5 K = 4.9907E + 01 K = -1.2347E + 01
A3 = -2.8678E-02 A3 = -1.2934E-01
A4 = 3.0400E-02 A4 = 2.9908E-02
A5 = -8.8640E-02 A5 = 1.0283E-02
A6 = 2.3643E-02 A6 = 3.6489E-03
A8 = 6.5699E-03 A8 = -6.4009E-04
A10 = -1.1414E-02 A10 = -2.3000E-03
A12 = 2.5220E-03 A12 = 1.2754E-03
A14 = 0.0000E + 00 A14 = -2.0285E-04
L6 K = 1.3451E + 00 K = -9.1398E + 00
A3 = -2.5974E-01 A3 = -1.4920E-01
A4 = 4.3475E-02 A4 = 7.3435E-02
A5 = 3.6855E-02 A5 = -1.6681E-02
A6 = 3.6439E-03 A6 = 9.1273E-04
A8 = -1.4050E-03 A8 = -2.9024E-04
A10 = -1.2174E-04 A10 = -1.5986E-05
A12 = 5.2842E-06 A12 = 2.6097E-06
A14 = 1.9797E-06 A14 = 5.0012E-07

  FIG. 9 is a sectional view of the lens of Example 3. In the drawing, the imaging lens includes, in order from the object side, a first lens L1 having a convex shape on the object side and having positive refractive power, and a second lens L2 having a convex shape on the object side and having negative refractive power. The third lens L3, the fourth lens L4, the fifth lens L5 having a convex image side surface and positive refractive power, and a biconcave shape in the vicinity of the optical axis and an image in a cross section in the optical axis direction. The side surface includes a sixth lens L6 having at least one extreme value. I is an imaging surface (projection surface), and F is an IR cut filter. FIG. 10 is an aberration diagram of Example 3 (spherical aberration (a), astigmatism (b), distortion (c)).

Regarding Example 3, each value is shown below.
F (F number): 1.85
f (focal length of the entire system): 3.625 mm
Y (maximum image height): 2.921 mm

  Table 4 shows values of conditional expressions (1) to (9) corresponding to the examples.

  11-13 is a figure for demonstrating the examination result of this inventor. FIG. 11A is a schematic cross-sectional view showing the periphery of the first lens L1 of the five-lens imaging lens corresponding to the embodiment, and FIG. 11B is a five-lens imaging corresponding to the comparative example. FIG. 4 is a schematic cross-sectional view showing the periphery of the first lens L1 of the lens, where the S1 surface is the object side surface and the S2 surface is the image side surface. In the embodiment, since the inflection point is provided on the object side surface of the first lens L1, the maximum surface angle θmax is relatively small and 34 °. On the other hand, in the comparative example, since there is no inflection point on the object side surface of the first lens L1, the periphery of the object side surface has a relatively steep shape, and the maximum surface angle θmax is relatively large and is 43 °.

  When light is incident on the first lens L1 of the imaging lens from the outside of the angle of view, the light incident from the S1 surface repeatedly reflects on the S2 surface and the S1 surface, travels toward the peripheral side, and exits from the S2 surface. Here, in the comparative example shown in FIG. 11B, since the maximum surface angle θmax is relatively large, the stray light emitted from the S2 surface is likely to be locally collected. On the other hand, in the embodiment shown in FIG. 11A, since the maximum surface angle θmax is relatively small, stray light emitted from the S2 surface is easily diffused.

  FIGS. 12 and 13 are diagrams showing the degree of stray light imaging on the imaging surface I of the solid-state imaging device in the example and the comparative example. In the case of the comparative example in FIG. 13, it can be seen that stray light is condensed on the line within the imaging surface I and is easily recognized as a ghost. On the other hand, in the embodiment of FIG. 12, stray light is diffused over a wide range on the imaging surface I, and is difficult to be recognized as a ghost.

  The imaging lens according to the present invention is not limited to the five-lens configuration or the six-lens configuration, and may include seven or more lenses.

DESCRIPTION OF SYMBOLS 10 Imaging lens 50 Imaging unit 51 Imaging element 51a Photoelectric conversion part 52 Substrate 53 Lens barrel 60 Input part 70 Touch panel 80 Wireless communication part 91 Storage part 92 Temporary storage part 100 Smartphone 101 Control part I Imaging surface L1-L6 Lens

Claims (11)

An imaging lens for forming a subject image on an imaging surface of a solid-state imaging device,
The imaging lens includes, in order from the object side, a first lens having a convex shape on the object side and having positive refractive power, and a second lens having a convex shape on the object side and having negative refractive power. The imaging is composed of two or more lenses, and the vicinity of the optical axis of the most image side lens has a biconcave shape, and the image side surface has at least one extreme value at a point other than the vicinity of the optical axis in the cross section in the optical axis direction. The lens satisfies the following conditional expression:
f / 2α <2.2 (1)
L / f <1.4 (2)
Furthermore, the first lens has an inflection point within the effective diameter in the cross section in the optical axis direction, and satisfies the following conditional expression.
0.75 <(R1 + R2) / (R2-R1) <0.92 (3)
However,
f: Focal length of the entire imaging lens system (mm)
α: Radius (mm) of the light-shielding stop arranged on the object side from the first lens
L: Distance on the optical axis from the object side surface of the first lens to the imaging surface when infinite light is incident (mm)
R1: radius of curvature of object side surface of the first lens (mm)
R2: radius of curvature of the image side surface of the first lens (mm) The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
25 <θmax <40 (4)
However,
θmax: Maximum surface angle (°) within the effective diameter of the object side surface of the first lens The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
−2.5 <f2 / f <−1.0 (5)
However,
f2: Focal length (mm) of the second lens The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
20 <ν1-ν2 <40 (6)
However,
ν1: Abbe number in the d-line of the material constituting the first lens ν2: Abbe number in the d-line of the material constituting the second lens The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
0.9 <f12 / f <2.0 (7)
However,
f12: Composite focal length (mm) of the first lens and the second lens   The imaging lens according to claim 1, wherein the object side lens closest to the image side lens has a convex image side surface and a positive refractive power. The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
−0.6 <fe / f <−0.4 (8)
However,
fe: Focal length (mm) of the lens closest to the image side The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
0.15 <d1 / f <0.2 (9)
However,
d1: On-axis thickness of the first lens (mm)   All the lenses are plastics, The imaging lens in any one of Claims 1-8 characterized by the above-mentioned.   An imaging apparatus comprising the imaging lens according to claim 1 and a solid-state imaging device.   A portable terminal comprising the imaging device according to claim 10.

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