WO2014034432A1

WO2014034432A1 - Imaging lens, imaging device, and portable terminal

Info

Publication number: WO2014034432A1
Application number: PCT/JP2013/071913
Authority: WO
Inventors: 佐野永悟
Original assignee: コニカミノルタ株式会社
Priority date: 2012-08-31
Filing date: 2013-08-14
Publication date: 2014-03-06

Abstract

Provided is an imaging lens having a four-lens construction which is compact and yet has a wide angle and a bright F-number of approximately 2.4, and which provides good correction of aberrations; also provided are an imaging device and a portable terminal equipped with this lens. This imaging lens, which is for forming the image of a photographic subject in a photoelectric conversion unit of a solid-state imaging element, comprises, in order from the object side: an aperture diaphragm; a first lens having positive refractive power; a second lens having negative refractive power and having a concave surface facing the object side in the vicinity of the light axis; a third lens having positive refractive power and having a convex surface facing the image side in the vicinity of the light axis; and a meniscus-shaped fourth lens having a convex surface facing the object side in the vicinity of the light axis. The image-side surface of the fourth lens has an aspheric shape and has an inflection point other than a point of intersection with the light axis. In addition, the imaging lens satisfies the following conditional expressions (1) and (2), where r1 is the radius of curvature (mm) of the object-side surface of the first lens, r2 is the radius of curvature (mm) of the image-side surface of the first lens, d6 is the air space (mm) between the third lens and the fourth lens on the light axis, and f is the focal distance (mm) of the entire imaging lens system. -3.0 < (r1+r2)/(r1-r2) ≤ -1.0 (1) 0.16 < d6/f < 0.40 (2)

Description

Imaging lens, imaging device, and portable terminal

The present invention relates to a low-profile imaging lens and imaging device using a solid-state imaging device such as a CCD image sensor or a CMOS image sensor, and a portable terminal equipped with the imaging lens.

In recent years, with the spread of mobile terminals equipped with solid-state imaging devices such as CCD (Charged Coupled Device) type image sensors or CMOS (Complementary Metal Oxide Semiconductor) type image sensors, higher quality images In order to obtain the above, those equipped with an imaging device using an imaging device having a high number of pixels have been supplied to the market. Conventional image pickup devices having a high number of pixels have been accompanied by an increase in size, but in recent years, pixels have become increasingly thinner and image pickup devices have become smaller. An imaging lens used for a highly thinned image sensor is required to have a high resolving power in order to cope with a highly thinned pixel. Here, the resolving power of the lens is limited by the F value, and a bright imaging lens is required because a bright lens with a small F value can obtain a high resolving power. On the other hand, in order to further reduce the size of the imaging apparatus, it is required to further reduce the overall length of the imaging lens. There is a limit to downsizing the imaging lens by power arrangement, device thickness and air spacing, and in recent years, wide-angle lenses with a shorter focal length are used to reduce the overall length of the optical system. Attempts have been made to do this. As an imaging lens for such a use, a four-lens imaging lens has been proposed because it can be improved in performance as compared with a two-lens or three-lens configuration.

As this four-lens imaging lens, a first lens having a positive refractive power in order from the object side, a second lens having a negative refractive power and a concave surface facing the object side, and a third lens having a positive refractive power A so-called telephoto type imaging lens is disclosed which is configured by a fourth lens having negative refractive power and aims to reduce the overall length of the imaging lens (see, for example, Patent Documents 1 and 2).

JP 2008-185807 A JP 2010-26387 A

However, the imaging lens described in Patent Document 1 has a small maximum field angle of about 65 °, and it cannot be said that the entire length of the imaging lens is sufficiently small. In addition, it is difficult to say that the F value is as dark as F2.8 and the optical performance is compatible with the recent increase in pixels.

The imaging lens described in Patent Document 2 is a wide-angle lens having a maximum field angle of about 75 °. However, it cannot be said that the overall length of the imaging lens is sufficiently small, and the aperture stop is the first lens. Since it is disposed between the second lens and the second lens, it is difficult to dispose the exit pupil position toward the object side when attempting to further reduce the overall length, and the telecentric characteristics are greatly deteriorated.

The present invention has been made in view of the above problems, and is a compact four-lens imaging lens having a wide angle and a bright F value of about F2.4, in which various aberrations are well corrected. It is another object of the present invention to provide an imaging device and a portable terminal using the same.

Here, although it is a scale of a small imaging lens, the present invention aims at miniaturization at a level satisfying the following expression. By satisfying this range, the entire imaging apparatus can be reduced in size and weight.
L / 2Y <0.80 (7)
However,
L: 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 2Y: diagonal length of the imaging surface of the solid-state imaging device (diagonal length of the rectangular effective pixel region of the solid-state imaging device)
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.

When a parallel plate such as an optical low-pass filter, an infrared cut filter, or a seal glass of a solid-state image sensor package is disposed between the image-side surface of the imaging lens and the image-side focal position, the imaging lens is parallel. The flat plate portion is calculated as the above L value after the air conversion distance. More preferably, the range of the following formula is good.
L / 2Y <0.75 (7) '

In recent years, smartphones and tablet terminals are rapidly spreading, and there is an increasing demand for further downsizing of image pickup apparatuses mounted on the smartphones and tablet terminals. Therefore, an image pickup apparatus equipped with an image pickup lens that satisfies the above expression (7) aims at a height of 5.0 mm or less, and more preferably a height of 4.5 mm or less.

The imaging lens according to claim 1 is an imaging lens for forming a subject image on a photoelectric conversion unit of a solid-state imaging device, in order from the object side.
Aperture stop,
A first lens having a positive refractive power;
A second lens having negative refractive power and having a concave surface facing the object side in the vicinity of the optical axis;
A third lens having positive refractive power and having a convex surface facing the image side in the vicinity of the optical axis;
A meniscus fourth lens having a convex surface facing the object side in the vicinity of the optical axis,
The image side surface of the fourth lens is aspheric, has an inflection point at a position other than the intersection with the optical axis, and satisfies the following conditional expression.
−3.0 <(r1 + r2) / (r1−r2) ≦ −1.0 (1)
0.16 <d6 / f <0.40 (2)
However,
r1: curvature radius (mm) of the side surface of the first lens object
r2: radius of curvature (mm) of the side surface of the first lens image
d6: Air space (mm) on the optical axis of the third lens and the fourth lens
f: Focal length (mm) of the entire imaging lens system

The basic configuration of the present invention for obtaining a compact imaging lens with good aberration correction is, in order from the object side, an aperture stop, a first lens having a positive refractive power, an optical axis having a negative refractive power. A second lens having a concave surface facing the object side in the vicinity, a third lens having a positive refractive power and a convex surface facing the image side near the optical axis, and a meniscus second lens having a convex surface facing the object side near the optical axis 4 lenses. By making the first lens to the third lens with relatively strong refractive power into one positive lens group, the combined principal point of the entire imaging lens system can be moved closer to the object side, and the overall length of the imaging lens can be reduced. This is an advantageous configuration.

Furthermore, by using the second lens having a relatively high passing light height as a negative lens, it is possible to easily correct the Petzval sum and obtain an imaging lens that secures good imaging performance up to the periphery of the screen. Become. In addition, by forming the second lens in a shape with a concave surface facing the object side in the vicinity of the optical axis, even when the incident field angle becomes a wide angle, the second lens has a shape that welcomes the light beam emitted from the first lens, It is possible to suppress coma aberration and higher-order spherical aberration that occur in the second lens.

Also, by making the image side surface of the fourth lens arranged closest to the image side aspherical, various aberrations at the periphery of the screen can be corrected well. Furthermore, by using an aspherical shape having an inflection point at a position other than the intersection with the optical axis, it becomes easy to ensure the telecentric characteristics of the image-side light beam. Here, the “inflection point” is a point on the aspheric surface where the tangent plane of the aspherical vertex is a plane perpendicular to the optical axis in the curve of the lens cross-sectional shape within the effective radius.

Furthermore, by making the fourth lens a meniscus shape with a convex surface facing the object side in the vicinity of the optical axis, the image side surface of the fourth lens, which is the most image side surface, can be a surface having a diverging action. Therefore, the back focus can be appropriately maintained even when the imaging lens is reduced in size.

Conditional expression (1) is a conditional expression for setting the shape of the first lens appropriately to achieve both the shortening of the total length of the imaging lens and the suppression of coma generated in the first lens. Specifically, the conditional expression (1) defines a so-called shaping factor representing the shape of the first lens. In the range of the conditional expression, the first lens has a meniscus shape with a convex surface facing the object side from the plano-convex lens. Set to range. When the value of conditional expression (1) is below the upper limit, the first lens has a meniscus shape, so that the principal point position of the entire imaging lens system can be moved closer to the object side. The overall length can be shortened. On the other hand, when the value of the conditional expression (1) exceeds the lower limit, the radius of curvature of the side surface of the first lens object does not become too small, and the coma aberration with respect to the ambient light having a large angle of view can be suppressed.

On the other hand, conditional expression (2) is a conditional expression for satisfactorily correcting off-axis aberrations while shortening the overall length of the imaging lens. When the value of the conditional expression (2) exceeds the lower limit, the first lens to the third lens having relatively strong refractive power and the fourth lens as an aberration correction lens having relatively weak refractive power are on the axis. The air space can be appropriately spaced. As an aspect of optical design, a method of designing the incident surface shape of the fourth lens so that the light beam is divided at every predetermined image height and the off-axis aberration can be corrected for each divided light beam emitted from the third lens. There is. However, by allowing the third lens and the fourth lens to be spaced so that the value of conditional expression (2) exceeds the lower limit, there is room for fine adjustment of the aspherical shape of the fourth lens. Due to the action of the spherical shape, off-axis aberrations at an arbitrary image height can be corrected satisfactorily. On the other hand, when the value of conditional expression (2) is less than the upper limit, the air gap between the third lens and the fourth lens is not unnecessarily increased, and as a result, the overall length of the imaging lens can be shortened. .

Also, if the clearance between the lens periphery of the third lens and the fourth lens is too large, it becomes difficult to take an assembly structure that abuts the flanges of the lenses, and the fourth lens is attached to a lens barrel (housing or the like). You have to take a structure that strikes against. In this case, compared to the case where the flanges of the lenses are abutted against each other, the lens interval accuracy is difficult to be obtained, and the air interval between the third lens and the fourth lens varies. As a result, there is a mass production variation of the field curvature. It gets bigger. Therefore, when the value of conditional expression (2) is less than the upper limit, it is possible to adopt a structure in which the third lens and the fourth lens are brought into contact with each other, and mass production variation in field curvature can be suppressed to a small value. It becomes like this. More preferably, the range of the following formula is good.
−2.5 <(r1 + r2) / (r1−r2) ≦ −1.0 (1) ′
0.16 <d6 / f <0.35 (2) ′

The imaging lens described in claim 2 is characterized in that, in the invention described in claim 1, the following conditional expression is satisfied.
0.7 <f3 / f <2.0 (3)
However,
f3: Focal length (mm) of the third lens
f: Focal length (mm) of the entire imaging lens system

Conditional expression (3) is a conditional expression for appropriately setting the focal length of the third lens. When the value of the upper limit expression (3) exceeds the lower limit, the focal length of the third lens does not become too small, and generation of higher-order spherical aberration and coma aberration can be suppressed. On the other hand, when the value of the upper limit expression (3) is less than the upper limit, the focal length of the third lens can be appropriately maintained, and the overall length of the imaging lens can be shortened. More preferably, the range of the following formula is good.
0.85 <f3 / f <1.90 (3) ′

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.
0.9 <f1 / f <1.5 (4)
However,
f1: Focal length (mm) of the first lens
f: Focal length of the entire imaging lens system (mm)

Conditional expression (4) 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 (4) is less than the upper limit, the refractive power of the first lens can be maintained moderately, and the composite principal point of the third lens from the first lens is arranged closer to the object side. And the overall length of the imaging lens can be shortened. On the other hand, when the value of the conditional expression (4) exceeds the lower limit, the refractive power of the first lens does not increase more than necessary, and high-order spherical aberration and coma generated in the first lens are reduced. Can be suppressed. More preferably, the range of the following formula is good.
0.95 <f1 / f <1.40 (4) ′

An imaging lens according to a fourth aspect of the invention is characterized in that, in the invention according to any one of the first to third aspects, the following conditional expression is satisfied.
1.5 <| f4 | / f <100 (5)
However,
f4: Focal length (mm) of the fourth lens
f: Focal length (mm) of the entire imaging lens system

Conditional expression (5) is a conditional expression for appropriately setting the focal length of the fourth lens. When the value of the upper limit formula (5) is less than the upper limit, the refractive power of the fourth lens can be maintained moderately, and the light beam that forms an image on the periphery of the imaging surface of the solid-state imaging device is excessively raised. The telecentric characteristic of the image side light beam can be easily secured. On the other hand, when the value of the upper limit expression (5) exceeds the lower limit, the refractive power of the fourth lens does not become excessively strong, shortening the entire lens length, and reducing off-axis aberrations such as field curvature and distortion. Correction can be performed satisfactorily. More preferably, the range of the following formula is good.
2.0 <| f4 | / f <90 (5) ′

The imaging lens described in claim 5 is characterized in that, in the invention described in any one of claims 1 to 4, the following conditional expression is satisfied.
0.01 <d4 / f <0.05 (6)
However,
d4: Air space (mm) on the optical axis of the second lens and the third lens
f: Focal length (mm) of the entire imaging lens system

When the value of conditional expression (6) is below the upper limit, the distance between the second lens and the third lens does not become too large, and as a result, the entire length of the imaging lens can be shortened. On the other hand, when the value of conditional expression (6) exceeds the lower limit, the clearance between the second lens and the third lens can be maintained moderately, and a light shielding member for preventing ghosts and flares is inserted. Space can be secured. More preferably, the range of the following formula is good.
0.01 <d4 / f <0.04 (6) ′

An imaging lens according to a sixth aspect of the present invention is the imaging lens according to any one of the first to fifth aspects, wherein the object side surface of the fourth lens has an aspherical shape, and the inflection point is at a position other than the intersection with the optical axis. It is characterized by having.

By making the object side surface of the fourth lens an aspherical shape and having an inflection point at a position other than the intersection with the optical axis, a shape such that both surfaces of the fourth lens have an inflection point Therefore, it is possible to obtain a shape that can easily secure the telecentric characteristics. Further, since the both surfaces of the fourth lens have aspherical shapes, it is possible to satisfactorily correct off-axis aberrations.

The imaging lens according to claim 7 is the imaging lens according to any one of claims 1 to 6, wherein the image side surface of the first lens has an aspherical shape, and an inflection point is located at a position other than the intersection with the optical axis. It is characterized by having.

By having an inflection point on the image side surface of the first lens having a high axial ray height, it is possible to satisfactorily correct off-axis aberrations while suppressing high-order spherical aberration occurring in the first lens. Will be able to.

The zoom lens according to claim 8 is the invention according to any one of claims 1 to 7, further comprising a lens having substantially no power. That is, even when a dummy lens having substantially no power is added to the configuration of claim 1, it is within the scope of application of the present invention.

An imaging device according to a ninth aspect includes the imaging lens according to any one of the first to eighth aspects.

A mobile terminal according to a tenth aspect includes the imaging device according to the ninth aspect.

According to the present invention, there are provided a four-lens imaging lens having a wide angle and a bright F-number of about F2.4, which is well-compensated with various aberrations, and an imaging device and a portable terminal using the same. can do.

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 mobile phone to which the imaging unit is applied, and the rear view (b) of the mobile phone to which the imaging unit is applied. It is a control block diagram of the smart phone of FIG. It is a block diagram of the image processing part concerning this embodiment. It is a figure which shows an example of the image (a) before image processing, and the image (b) after image processing. 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), and meridional coma aberration (d)). 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), and meridional coma aberration (d)). 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), and meridional coma aberration (d)). 6 is a cross-sectional view in the optical axis direction of an imaging lens of Example 4. FIG. FIG. 6 is an aberration diagram of Example 4 (spherical aberration (a), astigmatism (b), distortion (c), and meridional coma aberration (d)). 6 is a cross-sectional view in the optical axis direction of the imaging lens of Example 5. FIG. FIG. 6 is an aberration diagram of Example 5 (spherical aberration (a), astigmatism (b), distortion (c), and meridional coma aberration (d)).

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of the imaging unit 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 (= RY) 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 casing 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 so as to cover the image sensor 51 on the surface of the substrate 52 on which the image sensor 51 is provided. 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.

A cover glass CG is fixed between the imaging lens 10 and the imaging element 51 inside the housing 53 in which the flange portion 53a provided with a small opening (an opening for light incidence) is directed toward the object side. Has been placed. Besides this, an IR (infrared) cut filter may be provided.

The imaging lens 10 disposed in the housing 53 has, in order from the object side, an aperture stop S, a first lens L1 having a positive refractive power, a negative refractive power, and a concave surface on the object side in the vicinity of the optical axis. A second lens L2 that is directed, a third lens L3 having a positive refractive power and having a convex surface facing the image side in the vicinity of the optical axis, a meniscus fourth lens L4 having a convex surface facing the object side in the vicinity of the optical axis, The image side surface of the fourth lens L4 has an aspherical shape, has an inflection point at a position other than the intersection with the optical axis, and satisfies the following conditional expression.
−3.0 <(r1 + r2) / (r1−r2) ≦ −1.0 (1)
0.16 <d6 / f <0.40 (2)
However,
r1: radius of curvature of the first lens object side surface (mm)
r2: radius of curvature of the first lens image side surface (mm)
d6: Air spacing on the optical axis of the third lens and the fourth lens (mm)
f: Focal length of the entire imaging lens system (mm)

The lenses L1 to L4 have a lens spacing dimension accurately secured by abutting the flanges against each other. Spacers SP are disposed between the lens L4 and the cover glass CG, and between the cover glass CG and the substrate 52.

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. FIG. 5 is a block diagram illustrating a configuration of the image processing unit.

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.

When the imaging lens 10 has a focusing function, the CPU of the control unit 101 outputs a control signal to cause the imaging lens 10 to perform a focusing operation via the lens driving unit DR. In addition, control such as aperture, pixel shift, and camera shake may be performed. However, a fixed focus lens may be used. Further, the CPU of the control unit 101 outputs a control signal to the solid-state image sensor 51 on which the subject image is formed by the imaging lens 10 and outputs an image signal corresponding to the subject image.

The smartphone 100 operates by operating the input key unit 60, and can touch the icon 71 and the like displayed on the touch panel (display unit) 70 to operate the imaging unit 50 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.

Incidentally, there is a case where a higher quality image can be obtained by correcting distortion or the like generated in the imaging lens by image processing. Such image processing will be described. In FIG. 5, the control unit 101 stores lens correction data in an EEPROM. The lens correction data refers to a subject image (see FIG. 6A) that has been given a positive distortion by the imaging lens 10 and has a pincushion-shaped distortion, and has a rectangular shape (referred to as distortion correction processing). FIG. 6B shows data necessary for correction. For example, according to a design value, the signal value of a pixel (x, y) at a certain coordinate is changed to a pixel (x ± Δx, y ± Δy) at a different coordinate. Table data for conversion into (). The values of Δx and Δy change according to xy coordinates with the origin (0, 0) being the center of the photoelectric conversion unit 51a of the solid-state imaging device 51. However, in order to lighten the load on the image processing unit, the optical design is devised so that the vertical / horizontal size range of 1/2 of the vertical / horizontal size of the photoelectric conversion unit 51a with the origin at the center (in FIG. 6B). (Corresponding to the range indicated by the alternate long and short dash line) can be left as is without being processed. It should be noted that the pixel value may be converted using a function f (x, y) obtained by simulation or the like without using table data.

The image processing will be specifically described. In FIG. 5, the image signal output from the imaging lens 10 is input to the control unit 101 via the interface I / F. Here, if the input image signal corresponds to a still image that requires a large-scale memory with a large number of pixels but does not require real-time property, the input image signal is stored in the temporary memory MY. The CPU reads lens correction data from the EEPROM, and based on the read data, adds distortion correction processing by software to the image signal and performs normal image processing. On the other hand, if the input image signal has a relatively small number of pixels (for example, 2M pixels or less) and the required memory is small and corresponds to a moving image that requires real-time performance, it is input to the image processor ISP, Then, based on the lens correction data read from the EEPROM, real-time distortion correction processing by hardware is added to the image signal and normal image processing is performed. The image signal subjected to the image processing is displayed on the touch panel 70 via the LCD interface LCD I / F or is recorded on the memory card MC via the memory interface Mm I / F.

FIG. 6A is a diagram illustrating an example of a subject image based on an image signal before distortion correction processing, and the distortion is exaggerated. FIG. 6B is a diagram illustrating an example of a subject image based on the image signal after the distortion correction processing. If a subject image given positive distortion by the imaging lens 10 is displayed as it is without distortion correction processing, the pincushion type may be distorted as shown in FIG. In such a case, by performing a distortion correction process in the control unit 101, a rectangular image having no sense of incongruity as shown in FIG. 6B can be obtained.

[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 fB: Back focus F: F number 2Y: Diagonal length of imaging surface of solid-state imaging device
ENTP: Entrance pupil position (distance from first surface to entrance pupil position)
EXTP: Exit pupil position (distance from imaging surface to exit pupil position)
H1: Front principal point position (distance from the first surface to the 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 embodiment, the surface described with “*” after each surface number is a surface having an aspheric shape, and the shape of the aspheric surface has the vertex of the surface as the origin and the X axis in the optical axis direction. The height in the direction perpendicular to the optical axis is h, and is expressed by the following “Equation 1”.

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

Regarding the meaning of the paraxial radius of curvature described in the claims and the examples, in the actual lens measurement scene, in the vicinity of the center of the lens (specifically, the central region within 10% of the lens outer diameter) ) Can be regarded as the paraxial curvature radius when fitting the shape measurement value in the least square method. For example, when a secondary aspherical coefficient is used, a radius of curvature that takes into account the secondary aspherical coefficient in the reference curvature radius of the aspherical definition formula can be regarded as the paraxial curvature radius. (For example, refer to pages 41 to 42 of “Lens Design Method” by Yoshiya Matsui (Kyoritsu Publishing Co., Ltd.) for reference)

(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).

[Table 1]
Example 1

f = 2.68mm fB = 0.1mm F = 2.44 2Y = 4.82mm
ENTP = 0mm EXTP = -1.98mm H1 = -0.78mm H2 = -2.58mm

Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 (Aperture) ∞ -0.06 0.54
2 * 1.173 0.37 1.54470 56.2 0.57
3 * 5.281 0.19 0.62
4 * -2.770 0.31 1.63470 23.9 0.63
5 * 14.081 0.10 0.73
6 * 4.034 0.31 1.54470 56.2 0.91
7 * -3.519 0.79 1.00
8 * 1.237 0.41 1.54470 56.2 1.53
9 * 0.847 0.58 2.00
10 ∞ 0.11 1.51630 64.1 2.41
11 ∞ 2.46

Aspheric coefficient

2nd side 6th side
K = -0.32260E-01 K = -0.30000E + 02
A4 = -0.10943E-01 A4 = -0.94330E-01
A6 = -0.55905E-01 A6 = 0.19849E + 00
A8 = -0.76908E + 00 A8 = -0.12102E + 00
A10 = 0.33292E + 01 A10 = -0.11429E + 00
A12 = -0.79586E + 01 A12 = 0.35548E + 00
A14 = -0.23379E + 00

3rd surface 7th surface
K = 0.17877E + 02 K = -0.30000E + 02
A4 = -0.20107E + 00 A4 = -0.12505E + 00
A6 = -0.35276E + 00 A6 = 0.42388E + 00
A8 = -0.59395E + 00 A8 = -0.35224E + 00
A10 = 0.10136E + 00 A10 = 0.14692E + 00
A12 = -0.13183E + 01 A12 = 0.43143E-01
A14 = -0.68753E-01

4th side 8th side
K = -0.75385E + 01 K = -0.62205E + 01
A4 = -0.37021E + 00 A4 = -0.29602E + 00
A6 = -0.10623E + 00 A6 = 0.29662E-01
A8 = 0.52934E + 00 A8 = 0.19785E-01
A10 = -0.10211E + 01 A10 = 0.15346E-02
A12 = 0.38313E + 01 A12 = -0.67884E-03
A14 = -0.19388E + 01 A14 = -0.28253E-03

5th side 9th side
K = -0.30000E + 02 K = -0.61745E + 01
A4 = -0.27938E + 00 A3 = 0.29828E + 00
A6 = 0.46788E + 00 A4 = -0.54593E + 00
A8 = -0.39429E + 00 A5 = 0.16872E + 00
A10 = 0.90513E + 00 A6 = 0.72857E-01
A12 = 0.10800E + 01 A8 = -0.38785E-01
A14 = -0.14319E + 01 A10 = 0.85130E-02
A12 = -0.10218E-02
A14 = 0.55203E-04

Single lens data

Lens Start surface Focal length (mm)
1 2 2.68
2 4 -3.62
3 6 3.50
4 8 -7.89

FIG. 7 is a sectional view of the lens of Example 1. In the figure, L1 is a first lens having a positive refractive power, L2 is a negative lens having a negative refractive power, a second lens having a concave surface facing the object side in the vicinity of the optical axis, and L3 has a positive refractive power. A third lens having a convex surface facing the image side in the vicinity of the axis, and a meniscus fourth lens L4 having a convex surface facing the object side in the vicinity of the optical axis. The image side surface of the fourth lens L4 has an aspheric shape and has an inflection point at a position other than the intersection with the optical axis, and the object side surface of the fourth lens L4 has an aspheric shape and has an intersection with the optical axis. It has an inflection point at a position other than. S represents an aperture stop, and I represents an imaging surface. Further, F is a parallel plate assuming an optical low-pass filter, an IR cut filter, a seal glass of a solid-state image sensor, or the like. FIG. 8 is an aberration diagram of Example 1 (spherical aberration (a), astigmatism (b), distortion (c), and meridional coma aberration (d)). Here, in the spherical aberration diagram and the meridional coma aberration diagram, the solid line represents the spherical aberration amount and the coma aberration amount with respect to the d line and the dotted line, respectively. In the astigmatism diagram, the solid line S represents the sagittal surface and the dotted line M. Represents a meridional plane (hereinafter the same).

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

[Table 2]
Example 2

f = 2.71mm fB = 0.33mm F = 2.44 2Y = 4.82mm
ENTP = 0mm EXTP = -2.07mm H1 = -0.35mm H2 = -2.38mm

Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 (Aperture) ∞ -0.09 0.54
2 * 1.093 0.35 1.54470 56.2 0.56
3 * 3.043 0.28 0.59
4 * -1.796 0.21 1.63470 23.9 0.60
5 * -14.566 0.08 0.70
6 * 3.687 0.33 1.54470 56.2 0.91
7 * -3.157 0.71 1.01
8 * 0.812 0.29 1.54470 56.2 1.68
9 * 0.679 0.60 1.91
10 ∞ 0.11 1.51630 64.1 2.30
11 ∞ 2.34

Aspheric coefficient

2nd side 6th side
K = 0.19469E + 00 K = -0.30000E + 02
A4 = -0.37815E-02 A4 = -0.27598E + 00
A6 = 0.81180E-01 A6 = 0.31063E + 00
A8 = -0.82911E + 00 A8 = -0.11022E + 00
A10 = 0.32268E + 01 A10 = -0.76243E-01
A12 = -0.64859E + 01 A12 = 0.42599E + 00
A14 = -0.33043E + 00

3rd surface 7th surface
K = 0.13194E + 02 K = -0.40495E + 01
A4 = -0.11934E + 00 A4 = -0.10885E + 00
A6 = -0.32453E + 00 A6 = 0.32911E + 00
A8 = -0.41641E + 00 A8 = -0.36495E + 00
A10 = -0.49470E-01 A10 = 0.24750E + 00
A12 = -0.45790E + 01 A12 = 0.64256E-01
A14 = -0.10826E + 00

4th side 8th side
K = -0.16354E + 00 K = -0.22119E + 01
A4 = -0.40309E + 00 A4 = -0.33922E + 00
A6 = -0.36026E + 00 A6 = 0.44247E-01
A8 = 0.13704E + 01 A8 = 0.16934E-01
A10 = -0.10476E + 01 A10 = -0.44928E-03
A12 = -0.54097E + 00 A12 = -0.12063E-02
A14 = 0.14530E + 01 A14 = 0.12810E-03

5th side 9th side
K = 0.30000E + 02 K = -0.10251E + 01
A4 = -0.56313E + 00 A4 = -0.66934E + 00
A6 = 0.63613E + 00 A6 = 0.40529E + 00
A8 = -0.25297E + 00 A8 = -0.18386E + 00
A10 = 0.11268E + 01 A10 = 0.53358E-01
A12 = 0.98343E + 00 A12 = -0.88122E-02
A14 = -0.17629E + 00 A14 = 0.63136E-03

Single lens data

Lens Start surface Focal length (mm)
1 2 2.95
2 4 -3.25
3 6 3.18
4 8 -31.57

FIG. 9 is a sectional view of the lens of Example 2. In the figure, L1 is a first lens having a positive refractive power, L2 is a negative lens having a negative refractive power, a second lens having a concave surface facing the object side in the vicinity of the optical axis, and L3 has a positive refractive power. A third lens having a convex surface facing the image side in the vicinity of the axis, and a meniscus fourth lens L4 having a convex surface facing the object side in the vicinity of the optical axis. The image side surface of the fourth lens L4 has an aspheric shape and has an inflection point at a position other than the intersection with the optical axis, and the object side surface of the fourth lens L4 has an aspheric shape and has an intersection with the optical axis. It has an inflection point at a position other than. S represents an aperture stop, and I represents an imaging surface. Further, F is a parallel plate assuming an optical low-pass filter, an IR cut filter, a seal glass of a solid-state image sensor, or the like. FIG. 10 is an aberration diagram of Example 2 (spherical aberration (a), astigmatism (b), distortion (c), and meridional coma aberration (d)).

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

[Table 3]
Example 3

f = 2.89mm fB = 0.29mm F = 2.24 2Y = 4.82mm
ENTP = 0mm EXTP = -2.09mm H1 = -0.61mm H2 = -2.59mm

Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 (Aperture) ∞ -0.11 0.64
2 * 1.231 0.57 1.52500 70.4 0.67
3 * 3.545 0.25 0.71
4 * -9.817 0.24 1.63470 23.9 0.72
5 * 7.371 0.18 0.81
6 * 73.061 0.39 1.54470 56.2 0.95
7 * -2.803 0.55 1.10
8 * 1.050 0.40 1.54470 56.2 1.61
9 * 0.812 0.56 1.93
10 ∞ 0.11 1.51630 64.1 2.32
11 ∞ 2.36

Aspheric coefficient

2nd side 6th side
K = 0.22770E + 00 K = 0.30000E + 02
A4 = -0.30683E-01 A4 = -0.11716E + 00
A6 = 0.16497E + 00 A6 = 0.76455E-01
A8 = -0.82880E + 00 A8 = -0.16922E + 00
A10 = 0.17153E + 01 A10 = 0.57579E-01
A12 = -0.14506E + 01 A12 = 0.27344E + 00
A14 = -0.20181E + 00

3rd surface 7th surface
K = 0.18987E + 02 K = 0.22237E + 01
A4 = -0.13208E + 00 A4 = -0.22379E + 00
A6 = -0.11646E + 00 A6 = 0.38445E + 00
A8 = -0.32218E + 00 A8 = -0.39404E + 00
A10 = -0.23454E-02 A10 = 0.22491E + 00
A12 = -0.28209E + 00 A12 = 0.57336E-01
A14 = -0.73123E-01

4th side 8th side
K = -0.20370E + 02 K = -0.30039E + 01
A4 = -0.40087E + 00 A4 = -0.38893E + 00
A6 = 0.52889E-01 A6 = 0.77453E-01
A8 = -0.20146E + 00 A8 = 0.17949E-01
A10 = -0.83791E + 00 A10 = -0.19452E-02
A12 = 0.36254E + 01 A12 = -0.14384E-02
A14 = -0.25070E + 01 A14 = 0.18622E-03

5th side 9th side
K = 0.30000E + 02 K = -0.93055E + 00
A4 = -0.30567E + 00 A4 = -0.60506E + 00
A6 = 0.20964E + 00 A6 = 0.36186E + 00
A8 = -0.29681E + 00 A8 = -0.16701E + 00
A10 = 0.59757E + 00 A10 = 0.48707E-01
A12 = 0.56408E-01 A12 = -0.80380E-02
A14 = 0.75483E-01 A14 = 0.57326E-03

Single lens data
Lens Start surface Focal length (mm)
1 2 3.31
2 4 -6.60
3 6 4.96
4 8 -16.00

FIG. 11 is a sectional view of the lens of Example 3. In the figure, L1 is a first lens having a positive refractive power, L2 is a negative lens having a negative refractive power, a second lens having a concave surface facing the object side in the vicinity of the optical axis, and L3 has a positive refractive power. A third lens having a convex surface facing the image side in the vicinity of the axis, and a meniscus fourth lens L4 having a convex surface facing the object side in the vicinity of the optical axis. The image side surface of the fourth lens L4 has an aspheric shape and has an inflection point at a position other than the intersection with the optical axis, and the object side surface of the fourth lens L4 has an aspheric shape and has an intersection with the optical axis. It has an inflection point at a position other than. S represents an aperture stop, and I represents an imaging surface. Further, F is a parallel plate assuming an optical low-pass filter, an IR cut filter, a seal glass of a solid-state image sensor, or the like. FIG. 12 is an aberration diagram of Example 3 (spherical aberration (a), astigmatism (b), distortion (c), and meridional coma aberration (d)).

Example 4
Table 4 shows lens data of the imaging lens of Example 4.

[Table 4]
Example 4

f = 2.67mm fB = 0.23mm F = 2.44 2Y = 4.82mm
ENTP = 0mm EXTP = -2.19mm H1 = -0.28mm H2 = -2.44mm

Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 (Aperture) ∞ -0.03 0.54
2 * 1.308 0.53 1.54470 56.2 0.60
3 * 3.299 0.23 0.68
4 * -6.843 0.26 1.65060 21.0 0.70
5 * 2.728 0.05 0.80
6 * 1.767 0.36 1.54470 56.2 0.98
7 * -5.882 0.66 1.11
8 * 1.081 0.45 1.54470 56.2 1.61
9 * 0.930 0.57 2.00
10 ∞ 0.11 1.51630 64.1 2.32
11 ∞ 2.36

Aspheric coefficient

2nd side 6th side
K = -0.76965E-01 K = -0.13621E + 02
A4 = -0.17890E-01 A4 = -0.21309E + 00
A6 = 0.46209E-01 A6 = 0.22009E + 00
A8 = -0.61041E + 00 A8 = -0.22116E-01
A10 = 0.19927E + 01 A10 = -0.14351E + 00
A12 = -0.28559E + 01 A12 = 0.12662E + 00
A14 = -0.47390E-01

3rd surface 7th surface
K = 0.17977E + 02 K = -0.12906E + 02
A4 = -0.22185E + 00 A4 = -0.80077E-01
A6 = -0.13427E + 00 A6 = 0.31581E + 00
A8 = -0.50726E + 00 A8 = -0.31952E + 00
A10 = -0.53822E + 00 A10 = 0.10681E + 00
A12 = 0.70153E + 00 A12 = 0.39119E-01
A14 = -0.33612E-01

4th side 8th side
K = 0.30000E + 02 K = -0.13511E + 01
A4 = -0.46696E + 00 A4 = -0.36271E + 00
A6 = 0.17037E + 00 A6 = 0.46424E-01
A8 = -0.92602E-01 A8 = 0.18237E-01
A10 = -0.41822E + 00 A10 = -0.49141E-03
A12 = 0.23932E + 01 A12 = -0.98590E-03
A14 = -0.76425E + 00 A14 = 0.16133E-04

5th side 9th side
K = -0.30000E + 02 K = -0.27010E + 01
A4 = -0.61130E + 00 A3 = 0.19639E + 00
A6 = 0.64274E + 00 A4 = -0.49849E + 00
A8 = -0.38561E + 00 A5 = 0.17678E + 00
A10 = 0.40586E + 00 A6 = 0.51772E-01
A12 = 0.71706E + 00 A8 = -0.30269E-01
A14 = -0.49762E + 00 A10 = 0.62150E-02
A12 = -0.66034E-03
A14 = 0.31666E-04

Single lens data

Lens Start surface Focal length (mm)
1 2 3.64
2 4 -2.97
3 6 2.54
4 8 235.54

FIG. 13 is a sectional view of the lens of Example 4. In the figure, L1 is a first lens having a positive refractive power, L2 is a negative lens having a negative refractive power, a second lens having a concave surface facing the object side in the vicinity of the optical axis, and L3 has a positive refractive power. A third lens having a convex surface facing the image side in the vicinity of the axis, and a meniscus fourth lens L4 having a convex surface facing the object side in the vicinity of the optical axis. The image side surface of the fourth lens L4 has an aspheric shape and has an inflection point at a position other than the intersection with the optical axis, and the object side surface of the fourth lens L4 has an aspheric shape and has an intersection with the optical axis. It has an inflection point at a position other than. S represents an aperture stop, and I represents an imaging surface. Further, F is a parallel plate assuming an optical low-pass filter, an IR cut filter, a seal glass of a solid-state image sensor, or the like. FIG. 14 is an aberration diagram of Example 4 (spherical aberration (a), astigmatism (b), distortion (c), and meridional coma aberration (d)).

(Example 5)
Table 5 shows lens data of the imaging lens of Example 5.

[Table 5]
Example 5

f = 2.72mm fB = 0.11mm F = 2.44 2Y = 4.82mm
ENTP = 0mm EXTP = -2.16mm H1 = -0.53mm H2 = -2.61mm

Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 (Aperture) ∞ -0.03 0.54
2 * 1.513 0.60 1.54470 56.2 0.58
3 * ∞ 0.24 0.69
4 * -1.748 0.27 1.63470 23.9 0.70
5 * -6.900 0.05 0.83
6 * -7.235 0.33 1.54470 56.2 0.90
7 * -1.384 0.89 0.94
8 * 1.678 0.40 1.54470 56.2 1.60
9 * 1.007 0.53 2.06
10 ∞ 0.11 1.51630 64.1 2.40
11 ∞ 2.44

Aspheric coefficient

2nd side 6th side
K = -0.28005E + 00 K = 0.30000E + 02
A4 = -0.40599E-01 A4 = -0.11383E + 00
A6 = 0.11594E + 00 A6 = 0.25673E + 00
A8 = -0.10613E + 01 A8 = -0.58410E-01
A10 = 0.27742E + 01 A10 = -0.45093E-01
A12 = -0.36667E + 01 A12 = 0.34583E + 00
A14 = -0.30098E + 00

3rd surface 7th surface
K = 0.00000E + 00 K = -0.71167E + 01
A4 = -0.23427E + 00 A4 = -0.28764E + 00
A6 = -0.24923E + 00 A6 = 0.44677E + 00
A8 = -0.19330E + 00 A8 = -0.20819E + 00
A10 = -0.22575E + 00 A10 = 0.31596E + 00
A12 = 0.40552E + 00 A12 = 0.94944E-01
A14 = -0.24522E + 00

4th side 8th side
K = 0.12436E + 01 K = -0.10210E + 02
A4 = -0.40887E + 00 A4 = -0.26322E + 00
A6 = -0.20848E-01 A6 = 0.38413E-01
A8 = 0.29046E + 00 A8 = 0.15857E-01
A10 = -0.42154E + 00 A10 = -0.82770E-03
A12 = 0.31170E + 01 A12 = -0.89805E-03
A14 = -0.29765E + 01 A14 = 0.60839E-04

5th side 9th side
K = 0.18868E + 02 K = -0.87307E + 01
A4 = -0.32113E + 00 A3 = 0.34973E + 00
A6 = 0.46170E + 00 A4 = -0.57115E + 00
A8 = -0.48006E + 00 A5 = 0.18009E + 00
A10 = 0.34621E + 00 A6 = 0.67567E-01
A12 = 0.53190E + 00 A8 = -0.38080E-01
A14 = -0.52201E + 00 A10 = 0.86184E-02
A12 = -0.10416E-02
A14 = 0.54055E-04

Single lens data

Lens Start surface Focal length (mm)
1 2 2.78
2 4 -3.77
3 6 3.08
4 8 -5.86

FIG. 15 is a sectional view of the lens of Example 5. In the figure, L1 is a first lens having a positive refractive power, L2 is a negative lens having a negative refractive power, a second lens having a concave surface facing the object side in the vicinity of the optical axis, and L3 has a positive refractive power. A third lens having a convex surface facing the image side in the vicinity of the axis, and a meniscus fourth lens L4 having a convex surface facing the object side in the vicinity of the optical axis. The image side surface of the fourth lens L4 has an aspheric shape and has an inflection point at a position other than the intersection with the optical axis, and the object side surface of the fourth lens L4 has an aspheric shape and has an intersection with the optical axis. It has an inflection point at a position other than. S represents an aperture stop, and I represents an imaging surface. Further, F is a parallel plate assuming an optical low-pass filter, an IR cut filter, a seal glass of a solid-state image sensor, or the like. FIG. 16 is an aberration diagram of Example 5 (spherical aberration (a), astigmatism (b), distortion (c), and meridional coma aberration (d)).

Table 6 shows the values of each example corresponding to each conditional expression.

In recent years, as a method for mounting image pickup devices at low cost and in large quantities, a reflow process (heating process) is performed on a substrate on which solder is previously potted while an IC chip and other electronic components and optical elements are placed on the substrate. 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 to about 200 to 260 degrees together with the electronic components. At such a high temperature, a lens using a thermoplastic resin is thermally deformed. However, there is a problem that the optical performance deteriorates due to discoloration. As one of the methods for solving such a problem, a technology has been proposed that uses a glass mold lens having excellent heat resistance and achieves both miniaturization and optical performance in a high temperature environment. Since the cost is higher than the lens used, there is a problem that it is difficult to meet the demand for cost reduction of the imaging device.

Therefore, by using an energy curable resin as the material of the imaging lens, since the optical performance degradation when exposed to high temperatures is small compared to a lens using a thermoplastic resin such as polycarbonate or polyolefin, It is effective for the reflow process, is easier to manufacture than a glass mold lens, is inexpensive, and can achieve both low cost and mass productivity of an imaging apparatus incorporating an imaging lens. The energy curable resin refers to both a thermosetting resin and an ultraviolet curable resin.

The imaging lens of the present invention may be formed using the above-described energy curable resin.

In the present embodiment, the principal ray incident angle of the light beam incident on the imaging surface of the solid-state imaging device is not necessarily designed to be sufficiently small in the periphery of the imaging surface. However, recent techniques have made it possible to reduce shading by reviewing the arrangement of the color filters of the solid-state imaging device 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 of the image pickup device, the color filter or Since the on-chip microlens array is shifted to the optical axis side of the imaging lens, the obliquely incident light beam can be efficiently guided to the light receiving portion of each pixel. Thereby, the shading which generate | occur | produces with a solid-state image sensor can be restrained small. The present embodiment is a design example aiming at further miniaturization with respect to the portion where the requirement is relaxed.

Further, in this embodiment, there is a design that is not sufficiently corrected for lateral chromatic aberration and distortion. In recent years, however, cameras with a camera image processor ISP (image signal processor) installed in the camera body or solid-state imaging device have become widespread, and it is possible to correct lateral chromatic aberration and distortion by image processing. It is becoming. The present embodiment is a design example aiming at further miniaturization instead of relaxing the lateral chromatic aberration and distortion.

The present invention is not limited to the embodiments and examples described in the specification, and includes other modifications and examples from the embodiments, examples, and technical ideas described in the present specification. It will be apparent to those skilled in the art.

The present invention can provide an imaging lens suitable for a small portable terminal.

DESCRIPTION OF SYMBOLS 10 Imaging lens 50 Imaging unit 51 Solid-state image sensor 51a Photoelectric conversion part 52 Board | substrate 53 Housing | casing 53a Flange part 54 External connection terminal 55 Diaphragm member 60 Input part 70 Touch panel 80 Wireless communication part 91 Storage part 92 Temporary storage part 100 Smartphone 101 Control part 102 Correction chip I Imaging surface F Parallel flat plates L1 to L4 Lens S Aperture stop

Claims

An imaging lens for forming a subject image on a photoelectric conversion unit of a solid-state imaging device, in order from the object side,
Aperture stop,
A first lens having a positive refractive power;
A second lens having negative refractive power and having a concave surface facing the object side in the vicinity of the optical axis;
A third lens having positive refractive power and having a convex surface facing the image side in the vicinity of the optical axis;
A meniscus fourth lens having a convex surface facing the object side in the vicinity of the optical axis,
An imaging lens, wherein the image side surface of the fourth lens has an aspherical shape, has an inflection point at a position other than the intersection with the optical axis, and satisfies the following conditional expression.
−3.0 <(r1 + r2) / (r1−r2) ≦ −1.0 (1)
0.16 <d6 / f <0.40 (2)
However,
r1: curvature radius (mm) of the side surface of the first lens object
r2: radius of curvature (mm) of the side surface of the first lens image
d6: Air space (mm) on the optical axis of the third lens and the fourth lens
f: Focal length (mm) of the entire imaging lens system
The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
0.7 <f3 / f <2.0 (3)
However,
f3: Focal length (mm) of the third lens
f: Focal length (mm) of the entire imaging lens system
The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
0.9 <f1 / f <1.5 (4)
However,
f1: Focal length (mm) of the first lens
f: Focal length of the entire imaging lens system (mm)
The imaging lens according to any one of claims 1 to 3, wherein the following conditional expression is satisfied.
1.5 <| f4 | / f <100 (5)
However,
f4: Focal length (mm) of the fourth lens
f: Focal length (mm) of the entire imaging lens system
5. The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
0.01 <d4 / f <0.05 (6)
However,
d4: Air space (mm) on the optical axis of the second lens and the third lens
f: Focal length (mm) of the entire imaging lens system
The imaging lens according to any one of claims 1 to 5, wherein the object side surface of the fourth lens has an aspherical shape and has an inflection point at a position other than an intersection with the optical axis.
The imaging lens according to any one of claims 1 to 6, wherein an image side surface of the first lens has an aspherical shape and has an inflection point at a position other than an intersection with the optical axis.
The zoom lens according to any one of claims 1 to 7, further comprising a lens having substantially no power.
An image pickup apparatus comprising the image pickup lens according to any one of claims 1 to 8.
A portable terminal comprising the imaging device according to claim 9.