WO2015041123A1

WO2015041123A1 - Imaging lens, imaging device, and portable terminal

Info

Publication number: WO2015041123A1
Application number: PCT/JP2014/074011
Authority: WO
Inventors: 佐野永悟
Original assignee: コニカミノルタ株式会社
Priority date: 2013-09-19
Filing date: 2014-09-10
Publication date: 2015-03-26
Also published as: JP6451639B2; JPWO2015041123A1

Abstract

Provided is an imaging lens that has a compact size while comprising a five-lens configuration that has a bright F value and in which various aberrations are satisfactorily corrected. The imaging lens substantially comprises a first lens (L1) that has a positive refractive power, a second lens (L2) that has a negative refractive power and in which a concave surface thereof faces the image side, a third lens (L3), a fourth lens (L4), and a fifth lens (L5) that has a negative refractive power. An imaging lens (10) fulfills the conditional expressions 0.55 < TTL/2Y < 0.80 and 6.0 < ν3 - ν2 < 25.0, wherein TTL is the distance on the optical axis (AX) from the object-side surface (S11) of the first lens (L1) to the imaging surface (I), 2Y is the diagonal length of the imaging surface (I) of an imaging element (51), ν3 is the Abbe number of the third lens (L3), and ν2 is the Abbe number of the second lens (L2).

Description

Imaging lens, imaging device, and portable terminal

The present invention relates to a small imaging lens, and an imaging device and a portable terminal incorporating the same, and more particularly to an imaging lens and an imaging device that are suitable for reducing the height of five lenses.

In recent years, with the improvement in performance and miniaturization of solid-state imaging devices such as CCD (Charge-Coupled Device) type image sensors or CMOS (Complementary Metal-Oxide Semiconductor) type image sensors, Portable information terminals are becoming popular. Further, there is an increasing demand for further downsizing and higher performance of imaging lenses mounted on imaging devices provided in these portable devices. As an imaging lens for such an application, an imaging lens having a five-lens configuration has been proposed because it can be improved in performance as compared with a lens having three or four lenses.

As such a five-lens imaging lens, a first lens having positive refractive power in order from the object side, a second lens having negative refractive power with a convex surface facing the image side, and a third lens having negative refractive power. An imaging lens including a lens, a fourth lens having a positive refractive power, and a fifth lens having a negative refractive power is disclosed (for example, see Patent Documents 1 and 2).

However, the imaging lens described in Patent Document 1 has a long back focus with respect to the entire length of the optical system, and as a result, it is difficult to say that the imaging lens can be sufficiently downsized. Further, the F value is as dark as about F2.8, and it cannot cope with the recent increase in the number of pixels.
In addition, the imaging lens described in Patent Document 2 is difficult to say that aberration correction is sufficient as a whole, and the F value is as dark as about F2.4, so that performance is improved when the aperture is further increased. Difficult to achieve.

JP 2010-152042 A US Patent Application Publication No. 2013/0057968

The present invention has been made in view of the above-mentioned problems of the background art, and provides an imaging lens having a five-lens configuration that is smaller than a conventional type and has a small F-number in which various aberrations are well corrected and has a small F value. With the goal.

In order to achieve the above object, an imaging lens according to the present invention is an imaging lens for forming a subject image on an imaging surface of an imaging device, and in order from the object side, a first lens having a positive refractive power; The second lens having a negative refractive power in the vicinity of the optical axis and having a concave surface facing the image side, a third lens, a fourth lens, and a fifth lens having a negative refractive power. Furthermore, in the imaging lens according to the present invention, all the lenses are formed of a plastic material, the aperture stop is disposed on the object side of the third lens, and the sag amount on the image side surface of the third lens is a negative value at the peripheral portion. The image side surface of the fifth lens is aspheric and has an extreme value at a position other than the intersection with the optical axis, and the following conditional expression is satisfied.
0.55 <TTL / 2Y <0.80 (1)
6.0 <ν3-ν2 <25.0 (2)
However,
TTL: distance on the optical axis from the object side surface of the first lens to the imaging surface 2Y: diagonal length of the imaging surface of the imaging device (for example, diagonal length of the rectangular effective pixel region of the imaging device)
ν3: Abbe number of the third lens ν2: Abbe number of the second lens

The basic configuration according to the present invention for obtaining a compact imaging lens with good aberration correction is a first lens having a positive refractive power, a negative refractive power near the optical axis, and a concave surface on the image side. The second lens, the third lens, the fourth lens, and the fifth lens having negative refractive power. A so-called telephoto type in which a positive lens group including a first lens, a second lens, a third lens, and a fourth lens is disposed in order from the object side, and a negative fifth lens is disposed on the image side of the positive lens group. This lens configuration is advantageous in reducing the overall length of the imaging lens.

Further, in the above imaging lens, by using two or more of the five lens elements as negative lenses, the number of surfaces having a diverging action can be increased to facilitate correction of Petzval sum, and good imaging performance up to the periphery of the screen can be achieved. It is possible to obtain a secured imaging lens.

Furthermore, by disposing the aperture stop closer to the object side than the third lens, the exit pupil position of the imaging lens can be located closer to the object side, so that good telecentric characteristics can be obtained.

In recent years, for the purpose of downsizing the entire imaging apparatus, even a solid-state imaging device having the same number of pixels has been developed with a small pixel pitch and consequently a small imaging surface size. In such an imaging lens for a solid-state imaging device having a small imaging surface size, it is necessary to make the focal length of the entire system relatively short, so that the curvature radius and the outer diameter of each lens are considerably reduced. Therefore, when compared with glass lenses manufactured by time-consuming polishing, all lenses are made of plastic lenses manufactured by injection molding, so that even lenses with small curvature radii and outer diameters can be manufactured in large quantities at low cost. Production becomes possible. In addition, since the plastic lens can lower the press temperature, it is possible to suppress the wear of the molding die, and as a result, the number of replacements and maintenance times of the molding die can be reduced, and the cost can be reduced. Furthermore, since the plastic material is lightweight, the load on the actuator when the entire lens system is extended for focusing can be reduced.

In the imaging lens, since the image side surface of the second lens has a concave shape, a relatively strong divergence surface can be arranged on the object side so as to increase the passage height of the light beam. This is advantageous for correction.
In the imaging lens, by making the sag amount of the image side surface of the third lens a negative value in the peripheral portion, the shape of the image side surface of the third lens is the outlet with respect to the aperture stop in the same manner as the second lens. Therefore, various off-axis aberrations that occur on the image side surface of the third lens can be suppressed. Here, the “sag amount” is the amount of displacement in the optical axis direction from the surface vertex on the optical axis at the height h from the optical axis of the optical surface. The fact that the sag amount takes a negative value at a certain height h means that the displacement amount of the surface at the height h is located closer to the object side than the point on the optical axis.
In the imaging lens, by making the image side surface of the fifth lens disposed closest to the image side an aspherical surface, various aberrations at the periphery of the screen can be favorably corrected. Furthermore, the aspherical shape having an extreme value at a position other than the intersection with the optical axis makes it easy to ensure the telecentric characteristics of the image-side light beam. Here, “extreme value” refers to a curve of the lens cross-sectional shape within the effective radius, and on an aspheric surface where the tangent or tangent plane of the aspherical vertex is a line segment or plane perpendicular to the optical axis. It is a point.

In the imaging lens, conditional expression (1) is a conditional expression for achieving a small and lightweight imaging device and portable terminal.
By setting the total length of the imaging lens within the range of the conditional expression (1), it is possible to achieve a small and lightweight imaging device and portable terminal. Since all the lenses constituting this imaging lens are made of a plastic material, the degree of freedom of the shape of the flange portion is higher than that of other glass materials. For example, the positive first lens can be made thinner. As a result, it contributes to shortening of the entire length of the imaging lens. Therefore, in order to obtain a lens system that falls within the range of conditional expression (1), it is an important factor that all the lenses are made of a plastic material.
When a parallel plate such as an optical low-pass filter, an infrared cut filter, or a seal glass of the image pickup device package is disposed between the most image side surface of the image pickup lens and the image side focal position, the parallel plate is used. The part is assumed to be the air conversion distance and the TTL value is calculated. Here, the image side focal point refers to an image point when a parallel light beam parallel to the optical axis is incident on the imaging lens.
In addition, about the value of TTL / 2Y, the range of the following formula is more desirable.
0.60 <TTL / 2Y <0.75 (1) '

On the other hand, if the entire length of the imaging lens is set to a range that satisfies the conditional expression (1) while maintaining the telephoto type, the refractive power of the second lens becomes relatively weak, and chromatic aberration correction of the entire imaging lens system is achieved. Tend to be insufficient.
Therefore, in the imaging lens, by setting the material of the second lens and the material of the third lens so as to satisfy the conditional expression (2), chromatic aberration correction, which tends to become insufficient with downsizing, can be improved. Will be able to do.
For the value of ν3-ν2, the range of the following equation is more desirable.
6.0 <ν3-ν2 <23.0 (2) ′

According to a specific aspect of the present invention, the imaging lens described above satisfies the following conditional expression.
29.0 <ν3 <48.0 (3)

Conditional expression (3) is a conditional expression for satisfactorily correcting the chromatic aberration by appropriately setting the Abbe number of the third lens. The material of the second lens and the material of the third lens are combined so as to satisfy the above-mentioned conditional expression (2), and further, the material satisfying the conditional expression (3) is used for the third lens. Thus, the chromatic aberration of the entire imaging lens system can be corrected more satisfactorily.
In addition, about the value of (nu) 3, the range of the following formula is more desirable.
30.0 ≦ ν3 <46.0 (3) ′

According to another aspect of the present invention, the following conditional expression is satisfied.
20.0 <ν1-ν2 <70.0 (4)
However,
ν1: Abbe number of the first lens

Conditional expression (4) is a conditional expression for satisfactorily correcting the chromatic aberration of the entire imaging lens system.
When the value of conditional expression (4) exceeds the lower limit, chromatic aberrations such as axial chromatic aberration and lateral chromatic aberration can be corrected with good balance. On the other hand, when the value of conditional expression (4) is below the upper limit, it can be made of an easily available glass material.
For the value of ν1-ν2, the range of the following equation is more desirable.
25.0 <ν1-ν2 <45.0 (4) ′

According to still another aspect of the present invention, the following conditional expression is satisfied.
0.30 <r1 / f <0.50 (5)
However,
r1: radius of curvature of the object side surface of the first lens f: focal length of the entire imaging lens system

Conditional expression (5) is a conditional expression for appropriately setting the radius of curvature of the side surface of the first lens object to appropriately shorten the entire length of the imaging lens and correct the aberration.
When the value of conditional expression (5) is below the upper limit, the refractive power of the object side surface of the first lens can be maintained moderately, and the combination principal point of the first lens and the second lens is arranged closer to the object side. And the overall length of the imaging lens can be shortened. On the other hand, if the value of conditional expression (5) exceeds the lower limit, the refractive power of the object side surface of the first lens does not become excessively large, and higher-order spherical aberration and coma aberration that occur in the first lens are reduced. It can be kept small.
In addition, about the value of r1 / f, the range of the following Formula is more desirable.
0.33 <r1 / f <0.45 (5) ′

According to still another aspect of the present invention, the following conditional expression is satisfied.
0.60 <f1 / f <0.90 (6)
However,
f1: Focal length of the first lens

Conditional expression (6) is a conditional expression for appropriately setting the focal length of the first lens to appropriately shorten the entire imaging lens and correct aberrations.
When the value of conditional expression (6) is less than the upper limit, the refractive power of the first lens can be maintained moderately, and the composite principal point from the first lens to the fourth lens can be arranged closer to the object side. The overall length of the imaging lens can be shortened. On the other hand, when the value of conditional expression (6) exceeds the lower limit, the refractive power of the first lens does not become unnecessarily large, and high-order spherical aberration and coma generated in the first lens are suppressed to a small level. Can do.
In addition, about the value of f1 / f, the range of the following Formula is more desirable.
0.65 <f1 / f <0.85 (6) ′

According to still another aspect of the present invention, the following conditional expression is satisfied.
−1.70 <f2 / f <−0.90 (7)
However,
f2: focal length of the second lens

Conditional expression (7) is a conditional expression for appropriately setting the focal length of the second lens.
When the value of conditional expression (7) is less than the upper limit, the negative refractive power of the second lens does not become too strong, and coma and distortion occurring in the second lens can be suppressed to a low level. In addition, it is possible to suppress performance degradation when a manufacturing error occurs. On the other hand, when the value of conditional expression (7) exceeds the lower limit, the negative refractive power of the second lens can be appropriately maintained, and chromatic aberration can be corrected well.
In addition, about the value of f2 / f, the range of the following formula is more desirable.
-1.65 <f2 / f <-0.95 (7) '

According to still another aspect of the present invention, the aperture stop is disposed closer to the object side than the second lens. Thereby, a better telecentric characteristic can be obtained compared with the case where the aperture stop is disposed between the third lens and the second lens.

According to still another aspect of the present invention, the optical device further includes an optical element having substantially no power.

In order to achieve the above object, an imaging apparatus according to the present invention includes the imaging lens described above and an imaging element. By using the imaging lens of the present invention, it is possible to obtain a small imaging device capable of obtaining an image in which various aberrations are favorably corrected at a wide angle.

In order to achieve the above object, a mobile terminal according to the present invention includes the above-described imaging device. In other words, the mobile terminal according to the present invention includes an imaging device that is wide-angle, has a small F-number, is bright and is small, and has various aberrations corrected favorably.

It is a figure explaining an imaging device provided with the imaging lens of one embodiment of the present invention. It is a block diagram explaining a portable terminal provided with the imaging device of FIG. 3A and 3B are perspective views of the front side and the back side of the mobile terminal, respectively. 2 is a cross-sectional view of an imaging lens of Example 1. FIG. 5A to 5E are aberration diagrams of the imaging lens of Example 1. FIG. 6 is a cross-sectional view of an imaging lens of Example 2. FIG. 7A to 7E are aberration diagrams of the image pickup lens of Example 2. FIG. 6 is a cross-sectional view of an imaging lens of Example 3. FIG. 9A to 9E are aberration diagrams of the imaging lens of Example 3. FIG. 6 is a cross-sectional view of an imaging lens of Example 4. FIG. 11A to 11E are aberration diagrams of the imaging lens of Example 4. FIGS.

Hereinafter, an imaging lens according to an embodiment of the present invention will be described with reference to FIG. The imaging lens 10 illustrated in FIG. 1 has the same configuration as the imaging lens 11 of Example 1 described later.

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

The camera module 50 includes an imaging lens 10 that forms a subject image, an imaging device 51 that detects a subject image formed by the imaging lens 10, and a wiring board 52 that holds the imaging device 51 from behind and has wiring and the like. And a lens barrel portion 54 having an opening OP for holding the imaging lens 10 and the like and allowing a light beam from the object side to enter. The imaging lens 10 has a function of forming a subject image on the imaging surface (projected surface) I of the imaging element 51. The camera module 50 is used by being incorporated in an imaging device to be described later.

The imaging lens 10 forms a subject image on the imaging surface (projected surface) I of the image sensor 51, and in order from the object side, the first lens L1, the second lens L2, and the third lens L3. And a fourth lens L4 and a fifth lens L5.

The image sensor 51 is a sensor chip made of a solid-state image sensor. The photoelectric conversion unit 51a of the image sensor 51 is composed of a CCD (charge coupled device) or a CMOS (complementary metal oxide semiconductor), photoelectrically converts incident light for each RGB, and outputs an analog signal thereof.

The wiring board 52 has a role of aligning and fixing the image sensor 51 to other members (for example, the lens barrel portion 54). The wiring board 52 can receive a voltage and a signal for driving the image pickup device 51 and the driving mechanism 55a from an external circuit, and can output a detection signal to the external circuit.

A parallel plate F such as an infrared cut filter or a seal glass of the image sensor is disposed and fixed on the image pickup lens 10 side of the image sensor 51 by a holder member (not shown) so as to cover the image sensor 51 and the like.

The lens barrel portion 54 houses and holds the imaging lens 10. The lens barrel portion 54 enables the focusing operation of the imaging lens 10 by moving any one or more of the lenses L1 to L5 constituting the imaging lens 10 along the optical axis AX. For example, it has a drive mechanism 55a. The drive mechanism 55a reciprocates the specific lens or all the lenses along the optical axis AX. The drive mechanism 55a includes, for example, a voice coil motor and a guide. The drive mechanism 55a can be configured by a stepping motor or the like instead of the voice coil motor or the like.

Next, an example of a mobile phone or other mobile communication terminal 300 equipped with the camera module 50 illustrated in FIG. 1 will be described with reference to FIGS. 2, 3A, and 3B.

The mobile communication terminal 300 is a smartphone-type mobile terminal, and includes a wireless communication unit 330 for realizing various information communication between the imaging apparatus 100 having the camera module 50 and an external system or the like via the antenna 331. It has. Although not shown, the mobile communication terminal 300 also includes an operation unit including a power switch and the like, a storage unit (ROM) that stores necessary data such as a system program, various processing programs, and a terminal ID.

In addition to the camera module 50 described above, the imaging apparatus 100 includes an optical system driving unit 101, an imaging interface (I / F) 102, an image processing circuit (ISP) 103, a temporary storage unit (RAM) 104, a data storage unit ( EEPROM) 105, CPU 106, display operation unit interface 107, auxiliary storage unit interface 108, display operation unit (LCD) 310, auxiliary storage unit (SD card, etc.) 320, and the like. Among these, the imaging interface 102, the image processing circuit 103, the temporary storage unit 104, the data storage unit 105, the CPU 106, the display operation unit interface 107, and the auxiliary storage unit interface 108 are the control unit 110 for driving the camera module 50 and the like. As a role. The control unit 110 also includes a communication unit interface 109. In addition, the image processing circuit 103, the temporary storage unit 104, the data storage unit 105, and the CPU 106 have a role as an image processing unit 111 that processes an image signal output from the camera module 50.

The optical system driving unit 101 controls the state of the imaging lens 10 by operating the driving mechanism 55a of the imaging lens 10 when performing focusing, exposure, and the like under the control of the CPU 106. The optical system driving unit 101 operates the driving mechanism 55a to appropriately move specific or all lenses in the imaging lens 10 along the optical axis AX, thereby causing the imaging lens 10 to perform a focusing operation.

The imaging interface 102 is a part for delivering the image signal output from the imaging element 51 to the control unit 110.

The image processing circuit 103 performs image processing on the image signal output from the image sensor 51. The image processing circuit 103 performs processing on the frame image constituting the image signal, for example, corresponding to a moving image. The image processing circuit 103 executes distortion correction processing on the image signal based on the lens correction data read from the data storage unit 105 in addition to normal image processing such as color correction, gradation correction, and zooming. .

The temporary storage unit 104 is used as a work area for temporarily storing various processing programs executed by the control unit 110, data necessary for the execution, processing data, imaging data by the imaging apparatus 100, and the like.

The data storage unit 105 stores lens correction data used for image processing. Specifically, in addition to data for color correction, gradation correction, etc., parameters for distortion correction are stored.

The CPU 106 comprehensively controls each unit and executes a program corresponding to each process. Further, the CPU 106 performs various image processing such as color correction, gradation correction, and distortion correction on the signal before processing by the image processing circuit 103 based on the lens correction data read from the data storage unit 105. Alternatively, the image signal processed by the image processing circuit 103 can be subjected to the same processing as the image processing circuit 103, compression, or other image processing.

The display operation unit interface 107 transfers the image signal output from the image processing circuit 103 or the CPU 106 to the display operation unit 310 and transfers the operation signal from the display operation unit 310 to the CPU 106.

The auxiliary storage unit interface 108 outputs the moving image and the image data as a still image output from the image processing circuit 103 or the like to the auxiliary storage unit 320.

The display operation unit 310 is a touch panel that displays data related to communication, captured images, and the like and accepts user operations.

The auxiliary storage unit 320 is detachable and is a part that records and stores the image signal processed by the image processing unit 111.

Here, the photographing operation of the mobile communication terminal 300 including the imaging device 100 will be described. When the camera mode in which the mobile communication terminal 300 is operated as a camera is set, subject monitoring (through image display) and image shooting execution are performed. In monitoring, an image of a subject obtained through the imaging lens 10 is formed on the imaging surface I (see FIG. 1) of the imaging element 51. The image sensor 51 is scanned and driven by an image sensor drive unit (not shown), and outputs one frame of a digital signal obtained by digitizing a photoelectric conversion output corresponding to an optical image formed at a fixed period. The digital signal is input to the image processing circuit 103 and the like, and an image signal (video signal) subjected to image processing is generated and output to the display operation unit 310 and the auxiliary storage unit 320. At this time, the image signal from the image sensor 51 or the image processing circuit 103 is temporarily stored in the temporary storage unit 104.

The display operation unit 310 functions as a finder in monitoring and displays captured images in real time. In this state, focusing, exposure, and the like of the imaging lens 10 are set by driving the optical system driving unit 101 based on an operation input performed by the user via the display operation unit 310 at any time.

In such a monitoring state, for example, still image data is captured when the user appropriately operates the display operation unit 310. One frame of image data (imaging data) stored in the temporary storage unit 104 is read and compressed in accordance with the operation content of the display operation unit 310. The compressed image data is recorded in the temporary storage unit 104 or the like via the control unit 110, for example.

Hereinafter, image processing of the mobile communication terminal 300 will be described. In FIG. 2, the image signal output from the imaging lens 10 is input to the control unit 110 via the imaging interface 102. Here, when the image signal to be displayed corresponds to a still image, for example, the image signal is stored in the temporary storage unit 104, the CPU 106 reads the lens correction data from the data storage unit 105, and the image processing circuit 103 Various image processing is performed on the image signal based on the correction data. Here, the image processing includes image processing for displaying on the display operation unit 310 and image processing for storing in the auxiliary storage unit 320. On the other hand, when the image signal to be displayed corresponds to a moving image, the image signal is input only to the image processing circuit 103, and the image processing circuit 103 reads the image signal based on the lens correction data read from the correction data. Various image processing is performed on the image. The image signal subjected to the image processing is displayed on the display operation unit 310 via the display operation unit interface 107. Further, the image signal subjected to image processing can be recorded in the auxiliary storage unit 320 via the auxiliary storage unit interface 108.

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

That is, the image pickup apparatus equipped with the camera module 50 or the image pickup lens 10 is not limited to the one built in the smartphone type mobile communication terminal 300, but is built into a mobile phone, a PHS (Personal Handyphone System), or the like. Alternatively, it may be incorporated in a PDA (Personal Digital Assistant), a tablet personal computer, a mobile personal computer, a digital still camera, a video camera, or the like.

Hereinafter, returning to FIG. 1, the imaging lens 10 according to an embodiment of the present invention will be described in detail. An imaging lens 10 shown in FIG. 1 includes, in order from the object side, an aperture stop S, a first lens L1 having a positive refractive power near the optical axis AX and a meniscus shape with a convex surface facing the object side, and an optical axis. A biconcave second lens L2 having a negative refractive power in the vicinity of AX; a substantially convex third lens L3 having a positive refractive power in the vicinity of the optical axis AX and having a convex surface directed toward the object; and an optical axis AX It substantially consists of a fourth lens L4 having a meniscus shape having a positive refractive power in the vicinity and a convex surface facing the image side, and a biconcave fifth lens L5 having a negative refractive power in the vicinity of the optical axis AX. . Here, all the lenses L1 to L5 are aspherical lenses. Further, the sag amount of the image side surface S32 of the third lens L3 has a negative value in the peripheral portion. The image side surface S52 of the fifth lens L5 has an aspherical shape and has an extreme value at a position P other than the intersection with the optical axis AX (see FIG. 1). The first lens L1 is not limited to a meniscus shape having a convex surface facing the object side in the vicinity of the optical axis AX, and may be, for example, a convex flat shape or a biconvex shape in the vicinity of the optical axis AX. The second lens L2 is not limited to a biconcave lens in the vicinity of the optical axis AX. For example, the second lens L2 may have a meniscus shape with a concave surface facing the image side in the vicinity of the optical axis AX. The aperture stop S is disposed on the object side surface S11 side of the first lens L1, but may be disposed on the object side with respect to the third lens L3. For example, the image side surface S12 and the second lens of the first lens L1. You may arrange | position between the object side surface S21 of L2.
The imaging lens 10 satisfies the conditional expressions (1) and (2) already described.
0.55 <TTL / 2Y <0.80 (1)
6.0 <ν3-ν2 <25.0 (2)
However, TTL is the distance on the optical axis AX from the object side surface S11 of the first lens L1 to the imaging surface I, and 2Y is the diagonal length of the imaging surface I of the imaging device 51 (the diagonal line of the rectangular effective pixel region of the imaging device 51). Ν3 is the Abbe number of the third lens L3, and ν2 is the Abbe number of the second lens L2.

The imaging lens 10 according to the embodiment has a so-called telephoto type configuration in which a positive lens group including first to fourth lenses L1 to L4 is disposed, and a negative fifth lens L5 is disposed on the image side of the positive lens group. It has become. The telephoto type lens configuration is advantageous in reducing the overall length of the imaging lens 10. Further, in the imaging lens 10, two or more (specifically, at least the second and fifth lenses L <b> 2 and L <b> 5) of the five-lens configuration are negative lenses, so that the surface having a diverging action is increased. The Petzval sum can be easily corrected, and good imaging performance can be secured up to the periphery of the screen.

Furthermore, by arranging the aperture stop S closer to the object side than the third lens L3, the exit pupil position of the imaging lens 10 can be located closer to the object side, so that good telecentric characteristics can be obtained. Become.

In the imaging lens 10 of the embodiment, all the lenses L1 to L5 are plastic lenses manufactured by injection molding, thereby configuring a small imaging lens to be combined with a recent imaging element 51 having a reduced imaging surface size. Even a lens with a small radius of curvature and outer diameter can be mass-produced at low cost. Further, by using lenses L1 to L5 as plastic lenses, it is possible to reduce costs by reducing the number of times the mold is replaced and the number of maintenance. Furthermore, since the plastic material is lightweight, the load on the actuator when the entire lens system is extended for focusing can be reduced.

In the imaging lens 10, since the image side surface S22 of the second lens L2 has a concave shape, a relatively strong divergence surface can be disposed closer to the object side with a higher light ray passing height. This is advantageous for correcting chromatic aberration. Further, the shape of the image side surface S32 of the third lens L3 is made concentric with respect to the aperture stop S by setting the sag amount of the image side surface S32 of the third lens L3 to a negative value in the peripheral portion. Therefore, various off-axis aberrations that occur on the image side surface S32 of the third lens L3 can be suppressed.

In the imaging lens 10, the image side surface S52 of the fifth lens L5 is aspherical, so that various aberrations at the periphery of the screen can be corrected satisfactorily. Furthermore, the aspherical shape having an extreme value at a position P other than the intersection with the optical axis AX makes it easy to ensure the telecentric characteristics of the image-side light beam. Here, the “extreme value” is a non-linear value such that the tangent plane or tangent of the aspherical vertex is a plane or line segment perpendicular to the optical axis AX when considering the curve of the lens cross-sectional shape within the effective radius. A line or point on a sphere.

In the imaging lens 10, conditional expression (1) is a conditional expression for achieving a small and lightweight imaging device and portable terminal.
By setting the total length of the imaging lens 10 within the range of the conditional expression (1), it is possible to achieve the small and lightweight imaging device 100 and the portable communication terminal 300. Here, since all the lenses L1 to L5 are formed of a plastic material and are easy to be thin, it contributes to shortening the overall length of the imaging lens 10.
It should be noted that an optical low-pass filter, an infrared cut filter, an image sensor package seal glass, or the like is provided between the image side lens surface (image side surface S52 of the fifth lens L5) of the imaging lens 10 and the image side focal position. When the parallel flat plate F is arranged, the TTL value is calculated after the parallel flat plate F portion is set as an air conversion distance.

In the imaging lens 10, conditional expression (2) is a conditional expression for satisfactorily correcting chromatic aberration that tends to be insufficient with downsizing.
If the entire length of the imaging lens 10 is set within a range that satisfies the conditional expression (1) while maintaining the telephoto type, the refractive power of the second lens L2 becomes weak, and chromatic aberration correction of the entire imaging lens 10 system is insufficient. There is a tendency to become. Therefore, by setting the materials of the first and second lenses L1 and L2 so as to satisfy the conditional expression (2), it is possible to satisfactorily correct chromatic aberration that tends to become insufficient as the size is reduced. Become.

In the imaging lens 10 of the embodiment, in addition to the conditional expressions (1) and (2), the conditional expression (3) already described.
29.0 <ν3 <48.0 (3)
Satisfied.

In the imaging lens 10 of the embodiment, in addition to the conditional expressions (1) and (2), the conditional expression (4) already described.
20.0 <ν1-ν2 <70.0 (4)
Satisfied. Where ν1 is the Abbe number of the first lens L1.

In the imaging lens 10 of the embodiment, in addition to the conditional expressions (1) and (2), the conditional expression (5) already described.
0.30 <r1 / f <0.50 (5)
Satisfied. Here, r1 is the radius of curvature of the object side surface S11 of the first lens L1, and f is the focal length of the entire imaging lens 10.

In the imaging lens 10 of the embodiment, in addition to the conditional expressions (1) and (2), the conditional expression (6) already described.
0.60 <f1 / f <0.90 (6)
Satisfied. Here, f1 is the focal length of the first lens L1.

In the imaging lens 10 of the embodiment, in addition to the conditional expressions (1) and (2), the conditional expression (7) already described.
−1.70 <f2 / f <−0.90 (7)
Satisfied. Here, f2 is the focal length of the second lens.

Note that the imaging lens 10 of the embodiment may further include an optical element having substantially no power.

〔Example〕
Examples of the imaging lens of the present invention will be shown below. Symbols used in each example are as follows.
f: Focal length of the entire imaging lens system fB: Back focus F: F value 2Y: Diagonal length of the imaging surface of the imaging device ENTP: Entrance pupil position (distance from the first surface to the entrance pupil position)
EXTP: exit pupil position (distance from imaging surface to exit pupil position)
H1: Front principal point position (distance from first surface to front principal point position)
H2: Rear principal point position (distance from the final surface to the rear principal point position)
R: radius of curvature D: axial distance Nd: refractive index νd of lens material with respect to d-line: Abbe number of lens material In each example, the surface described with “*” after each surface number has an aspherical shape. The shape of the aspherical surface is expressed by the following “Equation 1” with the vertex of the surface as the origin, the X axis in the direction of the optical axis AX, and the height in the direction perpendicular to the optical axis AX as h.

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

Example 1
The overall specifications of the imaging lens of Example 1 are shown below.
f = 3.61mm
fB = 0.23mm
F = 2.24
2Y = 5.842mm
ENTP = 0mm
EXTP = -1.93mm
H1 = -2.44mm
H2 = -3.38mm

The lens surface data of Example 1 is shown in Table 1 below. In Table 1 below, infinity is represented as “infinity” and the aperture stop is represented as “STOP”.
[Table 1]
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 (STOP) infinity -0.214 0.81
2 * 1.283 0.490 1.54470 56.2 0.81
3 * 17.741 0.080 0.75
4 * -61.587 0.172 1.63470 23.9 0.75
5 * 2.526 0.291 0.77
6 * 5.775 0.299 1.58300 30.0 0.87
7 * infinity 0.732 0.97
8 * -6.132 0.395 1.54470 56.2 1.33
9 * -1.328 0.463 1.60
10 * -1.670 0.278 1.54470 56.2 2.29
11 * 2.564 0.400 2.46
12 infinity 0.110 1.51630 64.1 2.91
13 infinity 2.94

The aspheric coefficients of the lens surfaces of Example 1 are shown in Table 2 below. In the following it (including lens data in Tables), and represents an exponent of 10 (for example, 2.5 × ^{10 -02)} with E (e.g. 2.5E-02).
[Table 2]
Second side
K = -0.89947E-02, A4 = 0.99536E-02, A6 = -0.62845E-02, A8 = 0.12067E + 00,
A10 = -0.31260E + 00, A12 = 0.47572E + 00, A14 = -0.27747E + 00
Third side
K = -0.10000E + 01, A4 = -0.18962E + 00, A6 = 0.75111E + 00, A8 = -0.14867E + 01,
A10 = 0.21199E + 01, A12 = -0.19861E + 01, A14 = 0.70343E + 00
4th page
K = 0.10000E + 01, A3 = 0.00000E + 00, A4 = -0.44605E + 00, A5 = 0.00000E + 00,
A6 = 0.21065E + 01, A8 = -0.47962E + 01, A10 = 0.68751E + 01, A12 = -0.59227E + 01,
A14 = 0.21617E + 01
5th page
K = -0.48405E + 00, A3 = 0.00000E + 00, A4 = -0.34794E + 00, A5 = 0.00000E + 00,
A6 = 0.19209E + 01, A8 = -0.49014E + 01, A10 = 0.86395E + 01, A12 = -0.89405E + 01,
A14 = 0.42372E + 01
6th page
K = -0.60547E + 01, A3 = 0.00000E + 00, A4 = -0.25683E + 00, A5 = 0.00000E + 00,
A6 = 0.30105E-01, A8 = 0.31850E + 00, A10 = -0.87920E + 00, A12 = 0.12041E + 01,
A14 = -0.47516E + 00
7th page
K = 0.00000E + 00, A4 = -0.17820E + 00, A6 = 0.25199E-01, A8 = 0.99320E-02,
A10 = -0.57166E-01, A12 = 0.12756E + 00, A14 = 0.00000E + 00
8th page
K = 0.10000E + 01, A4 = -0.25161E-01, A6 = -0.18349E + 00, A8 = 0.30763E + 00,
A10 = -0.29171E + 00, A12 = 0.13383E + 00, A14 = -0.23897E-01
9th page
K = -0.13008E + 02, A3 = -0.14866E + 00, A4 = -0.62380E-01, A5 = 0.55091E-01,
A6 = 0.48618E-01, A8 = -0.15964E-01, A10 = -0.23059E-02, A12 = 0.21921E-02,
A14 = -0.49563E-03
10th page
K = -0.22936E + 01, A3 = -0.21089E-01, A4 = 0.13697E-01, A5 = 0.53683E-02,
A6 = 0.33780E-02, A8 = -0.39560E-03, A10 = -0.85814E-04, A12 = 0.13240E-05,
A14 = 0.13739E-05
11th page
K = -0.40396E + 02, A3 = -0.23898E-01, A4 = -0.12259E-01, A5 = 0.26471E-02,
A6 = -0.68778E-03, A8 = -0.52043E-03, A10 = 0.30694E-04, A12 = 0.16595E-05,
A14 = 0.67639E-06

The single lens data of Example 1 is shown in Table 3 below.
[Table 3]
Lens Start surface Focal length (mm)
1 2 2.512
2 4 -3.820
3 6 9.906
4 8 3.023
5 10 -1.815

FIG. 4 is a cross-sectional view of the imaging lens 11 and the like of the first embodiment. The imaging lens 11 has, in order from the object side, a first lens L1 having a positive refractive power near the optical axis AX and a meniscus shape with a convex surface facing the object side, and a negative refractive power near the optical axis AX. A biconcave second lens L2 that is close to a plano-concave, a convex third lens L3 having a positive refractive power near the optical axis AX and having a convex surface facing the object side, and a positive refraction near the optical axis AX. And a fourth lens L4 having a meniscus shape having a convex surface facing the image side, and a biconcave fifth lens L5 having a negative refractive power in the vicinity of the optical axis AX. All the lenses L1 to L5 are made of a plastic material. An aperture stop S is disposed on the image side from the object side vertex of the first lens L1 and on the object side from the periphery of the object side surface. A parallel plate F is disposed between the light exit surface of the fifth lens L5 and the imaging surface (image surface) I. The parallel plate F is assumed to be an optical low-pass filter, an IR cut filter, a seal glass of a solid-state imaging device, and the like (the same applies to the following examples).

5A to 5C show the spherical aberration, astigmatism, and distortion of the imaging lens 11 of Example 1, and FIGS. 5D and 5E show the meridional coma aberration of the imaging lens 11. FIG.

(Example 2)
The overall specifications of the imaging lens of Example 2 are shown below.
f = 3.62mm
fB = 0.34mm
F = 2.24
2Y = 5.842mm
ENTP = 0mm
EXTP = -1.96mm
H1 = −2.08mm
H2 = -3.28mm

The lens surface data of Example 2 is shown in Table 4 below.
[Table 4]
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 (STOP) infinity -0.218 0.81
2 * 1.269 0.455 1.54470 56.2 0.81
3 * 5.514 0.106 0.76
4 * 8.144 0.170 1.63470 23.9 0.76
5 * 2.469 0.303 0.77
6 * 8.458 0.321 1.58300 30.0 0.88
7 * infinity 0.631 0.98
8 * -5.720 0.364 1.54470 56.2 1.22
9 * -1.276 0.475 1.45
10 * -1.751 0.270 1.54470 56.2 2.20
11 * 2.832 0.400 2.38
12 infinity 0.110 1.51630 64.1 3.00
13 infinity 3.00

The aspherical coefficient of the lens surface of Example 2 is shown in Table 5 below.
[Table 5]
Second side
K = 0.57675E-01, A4 = 0.10693E-01, A6 = -0.39321E-01, A8 = 0.12919E + 00,
A10 = -0.87256E-01, A12 = 0.00000E + 00
Third side
K = -0.10000E + 01, A4 = -0.23893E + 00, A6 = 0.46810E + 00, A8 = -0.34488E + 00,
A10 = 0.00000E + 00
4th page
K = 0.10000E + 01, A3 = 0.00000E + 00, A4 = -0.58831E + 00, A5 = 0.00000E + 00,
A6 = 0.16382E + 01, A8 = -0.18768E + 01, A10 = 0.75285E + 00, A12 = 0.00000E + 00,
A14 = 0.00000E + 00
5th page
K = -0.30077E + 01, A3 = 0.00000E + 00, A4 = -0.42334E + 00, A5 = 0.00000E + 00,
A6 = 0.15662E + 01, A8 = -0.19275E + 01, A10 = 0.11452E + 01, A12 = 0.00000E + 00,
A14 = 0.00000E + 00
6th page
K = -0.60546E + 01, A3 = 0.00000E + 00, A4 = -0.29452E + 00, A5 = 0.00000E + 00,
A6 = 0.29308E + 00, A8 = -0.53072E + 00, A10 = 0.83016E + 00, A12 = -0.34321E + 00,
A14 = 0.00000E + 00
7th page
K = 0.00000E + 00, A4 = -0.19388E + 00, A6 = 0.53551E-01, A8 = 0.81980E-02,
A10 = -0.59693E-01, A12 = 0.11579E + 00
8th page
K = 0.10000E + 01, A4 = -0.71880E-01, A6 = -0.64501E-01, A8 = 0.44105E-01,
A10 = -0.24352E-01
9th page
K = -0.83780E + 01, A3 = -0.10244E + 00, A4 = -0.84445E-01, A5 = 0.31555E-01,
A6 = 0.47101E-01, A8 = -0.78191E-02, A10 = -0.43156E-03, A12 = 0.14257E-02,
A14 = -0.91484E-03
10th page
K = -0.22560E + 01, A3 = -0.18875E-01, A4 = 0.13634E-01, A5 = 0.55911E-02,
A6 = 0.35914E-02, A8 = -0.37488E-03, A10 = -0.10174E-03, A12 = -0.28283E-05,
A14 = 0.22980E-05
11th page
K = -0.40000E + 02, A3 = -0.22624E-01, A4 = -0.16366E-01, A5 = 0.23360E-02,
A6 = -0.11426E-03, A8 = -0.45958E-03, A10 = 0.20822E-04, A12 = 0.65478E-07,
A14 = 0.11071E-05

The single lens data of Example 2 is shown in Table 6 below.
[Table 6]
Lens Start surface Focal length (mm)
1 2 2.915
2 4 -5.647
3 6 14.508
4 8 2.932
5 10 -1.946

FIG. 6 is a cross-sectional view of the imaging lens 12 and the like of the second embodiment. The imaging lens 12 has, in order from the object side, a first lens L1 having a positive refractive power near the optical axis AX and a meniscus shape with a convex surface facing the object side, and a negative refractive power near the optical axis AX. A second lens L2 having a meniscus shape with a convex surface facing the object side, a convex third lens L3 having a positive refractive power near the optical axis AX and a convex surface facing the object side, and the vicinity of the optical axis AX And a fourth lens L4 having a meniscus shape having a positive refractive power and a convex surface facing the image side, and a biconcave fifth lens L5 having a negative refractive power in the vicinity of the optical axis AX. All the lenses L1 to L5 are made of a plastic material. An aperture stop S is disposed on the image side from the object side vertex of the first lens L1 and on the object side from the periphery of the object side surface. A parallel plate F is disposed between the light exit surface of the fifth lens L5 and the imaging surface (image surface) I.

7A to 7C show the spherical aberration, astigmatism, and distortion of the imaging lens 12 of Example 2, and FIGS. 7D and 7E show the meridional coma aberration of the imaging lens 12. FIG.

Example 3
The overall specifications of the imaging lens of Example 3 are shown below.
f = 3.6mm
fB = 0.25mm
F = 2.26
2Y = 5.712mm
ENTP = 0mm
EXTP = -2.18mm
H1 = -1.73mm
H2 = -3.34mm

The lens surface data of Example 3 is shown in Table 7 below.
[Table 7]
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 (STOP) infinity -0.177 0.80
2 * 1.473 0.448 1.54470 56.2 0.82
3 * -39.273 0.094 0.83
4 * 46.173 0.200 1.63470 23.9 0.84
5 * 2.369 0.339 0.86
6 * 7.315 0.466 1.54000 45.0 0.97
7 * infinity 0.620 1.12
8 * -7.562 0.520 1.54470 56.2 1.48
9 * -1.031 0.398 1.69
10 * -1.531 0.290 1.54470 56.2 2.34
11 * 2.098 0.500 2.52
12 infinity 0.110 1.51630 64.1 3.00
13 infinity 3.00

The aspherical coefficients of the lens surfaces of Example 3 are shown in Table 8 below.
[Table 8]
Second side
K = 0.10635E + 00, A4 = 0.57234E-02, A6 = -0.42528E-04, A8 = 0.34316E-02,
A10 = 0.42662E-01, A12 = -0.17661E-01, A14 = -0.34191E-01
Third side
K = 0.40982E + 02, A4 = 0.51090E-01, A6 = 0.21525E-01, A8 = 0.48727E-02,
A10 = -0.83271E-01, A12 = -0.40499E-01, A14 = 0.38435E-01
4th page
K = -0.50000E + 02, A4 = 0.15141E-01, A6 = 0.11741E + 00, A8 = -0.12071E + 00,
A10 = -0.10087E + 00, A12 = -0.17401E-01, A14 = 0.99259E-01
5th page
K = -0.17370E + 02, A4 = 0.12160E + 00, A6 = 0.29487E-01, A8 = -0.34402E-01,
A10 = 0.13207E-01, A12 = -0.70731E-01, A14 = 0.11898E + 00
6th page
K = 0.17284E + 02, A4 = -0.12750E + 00, A6 = 0.21338E-01, A8 = -0.41553E-01,
A10 = 0.36000E-01, A12 = 0.76601E-01, A14 = -0.39837E-01
7th page
K = 0.00000E + 00, A4 = -0.80607E-01, A6 = -0.22201E-01, A8 = 0.67598E-02,
A10 = -0.25860E-03, A12 = -0.28112E-03, A14 = 0.15083E-01
8th page
K = 0.24016E + 02, A4 = -0.62617E-01, A6 = 0.38178E-01, A8 = -0.15761E-01,
A10 = -0.59179E-02, A12 = 0.86329E-03, A14 = 0.11669E-02
9th page
K = -0.30808E + 01, A4 = -0.69175E-01, A6 = 0.60722E-01, A8 = -0.10030E-01,
A10 = -0.11506E-02, A12 = 0.10993E-03, A14 = 0.64721E-05
10th page
K = -0.46990E + 01, A4 = -0.16736E-01, A6 = 0.85842E-02, A8 = 0.67419E-04,
A10 = -0.23912E-03, A12 = 0.12242E-04, A14 = 0.12284E-05
11th page
K = -0.20494E + 02, A4 = -0.45043E-01, A6 = 0.12681E-01, A8 = -0.28506E-02,
A10 = 0.23806E-03, A12 = -0.35985E-05, A14 = 0.24488E-06

The single lens data of Example 3 is shown in Table 9 below.
[Table 9]
Lens Start surface Focal length (mm)
1 2 2.617
2 4 -3.942
3 6 13.547
4 8 2.132
5 10 -1.581

FIG. 8 is a cross-sectional view of the imaging lens 13 and the like of the third embodiment. The imaging lens 13 includes, in order from the object side, a biconvex first lens L1 that has a positive refractive power near the optical axis AX and is nearly convex, and a negative refractive power near the optical axis AX. A second lens L2 having a meniscus shape close to a plano-concave with a convex surface facing, a convex third lens L3 having a positive refractive power near the optical axis AX and a convex surface facing the object side, and the vicinity of the optical axis AX And a fourth lens L4 having a meniscus shape having a positive refractive power and a convex surface facing the image side, and a biconcave fifth lens L5 having a negative refractive power in the vicinity of the optical axis AX. All the lenses L1 to L5 are made of a plastic material. An aperture stop S is disposed on the image side from the object side vertex of the first lens L1 and on the object side from the periphery of the object side surface. A parallel plate F is disposed between the light exit surface of the fifth lens L5 and the imaging surface (image surface) I.

FIGS. 9A to 9C show spherical aberration, astigmatism, and distortion of the imaging lens 13 of Example 3, and FIGS. 9D and 9E show meridional coma aberration of the imaging lens 13. FIG.

Example 4
The overall specifications of the imaging lens of Example 4 are shown below.
f = 3.7mm
fB = 0.41mm
F = 2.06
2Y = 5.842mm
ENTP = 0.39mm
EXTP = -1.95mm
H1 = -1.73mm
H2 = -3.29mm

The lens surface data of Example 4 is shown in Table 10 below.
[Table 10]
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 * 1.417 0.491 1.54470 56.2 0.90
2 * -159.523 0.020 0.85
3 (STOP) infinity 0.020 0.85
4 * 11.065 0.170 1.64250 22.5 0.85
5 * 2.148 0.450 0.85
6 * 11.347 0.351 1.54000 45.0 0.95
7 * infinity 0.467 1.08
8 * -3.439 0.401 1.54470 56.2 1.24
9 * -1.221 0.646 1.50
10 * -4.598 0.288 1.54470 56.2 2.29
11 * 1.744 0.300 2.45
12 infinity 0.210 1.51630 64.1 2.85
13 infinity 2.90

The aspherical coefficients of the lens surfaces of Example 4 are shown in Table 11 below.
[Table 11]
First side
K = 0.60945E + 00, A4 = -0.17164E-01, A6 = -0.20389E-01, A8 = 0.70516E-02,
A10 = -0.39606E-01, A12 = 0.78888E-01, A14 = -0.70524E-01
Second side
K = 0.80000E + 02, A3 = 0.00000E + 00, A4 = 0.21113E-01, A5 = 0.00000E + 00,
A6 = 0.64864E-01, A7 = 0.00000E + 00, A8 = -0.71629E-01, A10 = 0.99869E-02,
A12 = 0.40640E-02, A14 = -0.20598E-01
4th page
K = -0.33717E + 02, A4 = -0.32548E-01, A6 = 0.21007E + 00, A8 = -0.18777E + 00,
A10 = -0.42435E-01, A12 = 0.11417E + 00, A14 = -0.52121E-01
5th page
K = -0.15716E + 02, A3 = 0.00000E + 00, A4 = 0.16362E + 00, A5 = 0.00000E + 00,
A6 = -0.18641E-01, A7 = 0.00000E + 00, A8 = 0.90964E-01, A10 = -0.21273E-01,
A12 = -0.11677E + 00, A14 = 0.14921E + 00
6th page
K = 0.20251E + 02, A3 = -0.14941E-01, A4 = -0.15166E-01, A5 = -0.20493E + 00,
A6 = 0.23849E-01, A7 = 0.10664E + 00, A8 = -0.30767E-01, A10 = -0.80772E-01,
A12 = 0.73562E-03, A14 = 0.82164E-02
7th page
K = 0.00000E + 00, A4 = -0.89521E-01, A6 = -0.70669E-01, A8 = -0.45438E-01,
A10 = 0.24503E-01, A12 = -0.19699E-02, A14 = -0.16414E-01
8th page
K = -0.46968E + 01, A3 = -0.44781E-02, A4 = -0.23378E-01, A5 = -0.14141E-01,
A6 = -0.73483E-03, A7 = 0.57397E-02, A8 = -0.42723E-02, A10 = -0.24293E-01,
A12 = -0.93516E-02, A14 = 0.71925E-02
9th page
K = -0.31464E + 01, A4 = -0.87915E-01, A6 = 0.70235E-01, A8 = -0.16324E-01,
A10 = 0.22373E-02, A12 = -0.61879E-03, A14 = 0.11267E-03
10th page
K = -0.11677E + 02, A3 = -0.15960E + 00, A4 = 0.10311E-01, A5 = 0.21485E-01,
A6 = 0.23314E-02, A7 = 0.50336E-03, A8 = -0.45243E-04, A10 = -0.10243E-03,
A12 = -0.22571E-04, A14 = 0.36357E-05
11th page
K = -0.84356E + 01, A3 = -0.17667E + 00, A4 = 0.87094E-01, A5 = -0.29675E-01,
A6 = 0.45114E-02, A7 = 0.91882E-03, A8 = -0.12265E-02, A10 = 0.73063E-04,
A12 = 0.25579E-05, A14 = 0.52643E-06

The single lens data of Example 4 is shown in Table 12 below.
[Table 12]
Lens Start surface Focal length (mm)
1 1 2.582
2 4 -4.180
3 6 21.013
4 8 3.267
5 10 -2.285

FIG. 10 is a cross-sectional view of the imaging lens 14 and the like of the fourth embodiment. In order from the object side, the imaging lens 14 has a biconvex first lens L1 having a positive refractive power in the vicinity of the optical axis AX and close to a convex plane, and a negative refractive power in the vicinity of the optical axis AX. A second lens L2 having a meniscus shape with a convex surface, a convex third lens L3 having a positive refractive power near the optical axis AX and a convex surface facing the object side, and positive refraction near the optical axis AX And a fourth lens L4 having a meniscus shape having a convex surface facing the image side, and a biconcave fifth lens L5 having a negative refractive power in the vicinity of the optical axis AX. All the lenses L1 to L5 are made of a plastic material. An aperture stop S is disposed between the first lens L1 and the second lens L2. A parallel plate F is disposed between the light exit surface of the fifth lens L5 and the imaging surface (image surface) I.

FIGS. 11A to 11C show spherical aberration, astigmatism, and distortion of the imaging lens 14 of Example 4, and FIGS. 11D and 11E show meridional coma aberration of the imaging lens 14. FIG.

Table 13 below summarizes the values of Examples 1 to 4 corresponding to the conditional expressions (1) to (7).
[Table 13]

As mentioned above, although this invention was demonstrated according to embodiment and an Example, this invention is not limited to the said embodiment etc. In the first to fourth embodiments, the third lens L3 and the fourth lens L4 have a positive refractive power, but as described above, the composition of the first lens L1 to the fourth lens L4 is positive. If the refractive power is satisfied, two or more of the five-lens configuration, that is, the third lens L3 and / or the fourth lens L4 may be configured as a negative lens in order to facilitate correction of the Petzval sum. In consideration of ease of correction of chromatic aberration, either the third lens L3 or the fourth lens L4 may be a negative lens.

In recent years, as a method for mounting an image pickup apparatus at a low cost and in large quantities, a reflow process (heating process) is performed on a substrate on which a solder has been potted in advance, with an IC chip and other electronic components and optical elements placed on the board. A technique has been proposed in which an electronic component and an optical element are simultaneously mounted on a substrate by melting the substrate. In order to perform mounting using such a reflow process, it is necessary to heat the optical element together with the electronic components to about 200 to 260 ° C. Under such a high temperature, the lens using the thermoplastic resin is heated. There is a problem that the optical performance deteriorates due to deformation or discoloration. As one of the methods for solving such problems, a technology that uses a glass mold lens having excellent heat resistance performance and achieves both miniaturization and optical performance in a high temperature environment has been proposed. Generally, the cost is higher than the lens using the lens. For this reason, there has been a problem that it is impossible to meet the demand for cost reduction of the imaging apparatus. Therefore, when an energy curable resin is used as the material of the imaging lenses 11 to 14 of Examples 1 to 4, when the lens is exposed to a higher temperature than a lens using a thermoplastic resin such as polycarbonate or polyolefin. The decrease in optical performance can be reduced. Therefore, the imaging lenses 11 to 14 are effective for the reflow process, are easier to manufacture than the glass mold lens, are inexpensive, and can achieve both low cost and mass productivity of the imaging device incorporating the imaging lens. Therefore, the lenses L1 to L5 of this embodiment may be formed using the energy curable resin. The energy curable resin generally refers to a thermosetting resin, an ultraviolet curable resin, or the like.

In Examples 1 to 4, the principal ray incident angle of the light beam incident on the imaging surface I of the image sensor 51 is not necessarily designed to be sufficiently small in the peripheral portion of the imaging surface I. However, with recent technology, it has become possible to reduce shading by reviewing the arrangement of the color filters of the image sensor 51 and the on-chip microlens array. Specifically, if the pitch of the arrangement of the color filters and the on-chip microlens array is set slightly smaller than the pixel pitch of the image pickup surface I of the image pickup device 51, the pixel is closer to the periphery of the image pickup surface I. Since the color filter and the on-chip microlens array are shifted to the optical axis AX side of the imaging lens 10 (11 to 14), the obliquely incident light beam can be efficiently guided to the light receiving portion of each pixel. Thereby, the shading which generate | occur | produces in the image pick-up element 51 can be restrained small. The above-described Examples 1 to 4 are design examples aiming at further miniaturization for the portion in which the above requirement is relaxed.

Further, in this specification, “convex surface in the vicinity of the optical axis” means a point (for example, 0.05 mm) away from the optical axis AX regardless of the numerical value of the function defining the shape of the surface. If the sag amount of the lens surface is the object side surface of the lens, it means a surface having a positive value and a negative value on the image side surface. Conversely, “convex surface in the vicinity of the optical axis” means a negative value if the sag amount of the surface at a point (for example, 0.05 mm) away from the optical axis AX by a minute amount is an object side surface of the lens. Then, it means a surface that takes a positive value. Here, if a discontinuous shape different from the function of the optical surface is added to the center of the lens surface for the purpose of detecting the amount of eccentricity of the lens or adjusting the eccentricity, the discontinuous shape is The sag amount is calculated by a function of the original optical surface without considering it. If the approximate curvature radius when the shape measurement value near the center of the lens (specifically, the central region within 10% of the lens outer diameter) is fitted by the least square method is positive, the optical axis AX It can be regarded as a convex surface in the vicinity. For example, when a secondary aspherical coefficient is used, a curvature radius that takes into account the secondary aspherical coefficient in the reference curvature radius of the aspherical definition formula can be regarded as a paraxial curvature radius (for example, reference literature). (See pages 41-42 of “Lens Design Method” written by Yoshiya Matsui (Kyoritsu Publishing Co., Ltd.)).

Claims

An imaging lens for forming a subject image on an imaging surface of an imaging element,
From the object side,
A first lens having a positive refractive power;
A second lens having negative refractive power in the vicinity of the optical axis and having a concave surface facing the image side;
A third lens;
A fourth lens;
A fifth lens having a negative refractive power,
All lenses are made of plastic material,
An aperture stop is disposed closer to the object side than the third lens;
The amount of sag on the image side surface of the third lens is a negative value at the periphery,
The image side surface of the fifth lens is aspheric and has an extreme value at a position other than the intersection with the optical axis,
An imaging lens that satisfies the following conditional expression.
0.55 <TTL / 2Y <0.80 (1)
6.0 <ν3-ν2 <25.0 (2)
However,
TTL: distance on the optical axis from the object side surface of the first lens to the imaging surface 2Y: diagonal length of the imaging surface of the imaging element ν3: Abbe number of the third lens ν2: Abbe number of the second lens
The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
29.0 <ν3 <48.0 (3)
However,
ν3: Abbe number of the third lens
The imaging lens according to claim 1, wherein the imaging lens satisfies the following conditional expression.
20.0 <ν1-ν2 <70.0 (4)
However,
ν1: Abbe number of the first lens ν2: Abbe number of the second lens
The imaging lens according to any one of claims 1 to 3, wherein the following conditional expression is satisfied.
0.30 <r1 / f <0.50 (5)
However,
r1: radius of curvature of object side surface of the first lens f: focal length of the entire imaging lens system
The imaging lens according to any one of claims 1 to 4, which satisfies the following conditional expression.
0.60 <f1 / f <0.90 (6)
However,
f1: Focal length of the first lens f: Focal length of the entire imaging lens system
The imaging lens according to any one of claims 1 to 5, which satisfies the following conditional expression.
−1.70 <f2 / f <−0.90 (7)
However,
f2: focal length of the second lens f: focal length of the entire imaging lens system
The imaging lens according to any one of claims 1 to 6, further comprising an optical element having substantially no power.
The imaging lens according to any one of claims 1 to 7, wherein the aperture stop is disposed closer to the object side than the second lens.
An imaging apparatus comprising the imaging lens according to any one of claims 1 to 8 and the imaging element.
A portable terminal comprising the imaging device according to claim 9.