JP2013024892A - Image pickup lens and image pickup apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact and high-performance image pickup lens for forming an image on a solid state imaging device with a curved imaging surface, capable of suppressing shading, consisting of lenses with favorable moldability, and having superior moldability.SOLUTION: An image pickup lens 10 includes a first lens L1, a second lens L2, and a third lens L3. The imaging surface I of a solid state imaging device 51 is curved into a shallow concave spherical shape. The image-side surface 3b of the third lens L3 that is located closest to the image side is configured into an aspherical shape so as to have a field curvature accommodating to the curved imaging surface I while securing favorable telecentric characteristics. The image pickup lens 10 satisfies a conditional expression (1): 0.50<EXPD/EXPC<2.00...(1), where EXPD is an exit pupil position in a maximum field angle luminous flux and EXPC is a paraxial exit pupil position.

Description

  The present invention relates to a small imaging lens for forming an image on a solid-state imaging device having a curved imaging surface, and an imaging apparatus including the same.

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

  In recent years, with regard to the solid-state image sensor used in such an image pickup apparatus, the pixel size has been reduced and the image pickup element has been increased in size and size. Furthermore, it is possible to curve the imaging surface (see, for example, Patent Document 1), and there is a demand for a compact and high-performance imaging lens that is optimal for such an imaging device.

  In Patent Document 1, a solid-state imaging device is curved into a polynomial surface shape to correct the curvature of field and distortion generated by the lens in a well-balanced manner, thereby providing a small and high-resolution imaging apparatus. However, since the solid-state imaging device has a CIF size (352 pixels × 288 pixels) and the imaging lens has a single lens configuration, chromatic aberration is not sufficiently corrected, and a high-performance solid-state imaging device is used. It is not possible to obtain an imaging device.

  Patent Documents 2 to 4 disclose imaging lenses for compact cameras and film units with lenses. Among these, the imaging lens of Patent Document 2 has a curved imaging surface, a shooting angle of view of about 70 to 75 degrees, and has a brightness of about F10. The imaging surface is curved, the shooting angle of view is about 77 degrees, and the brightness is about F5.7 to F6.2. Regarding the lens configuration, in the case of Patent Document 2, a two-lens configuration including an aperture stop, a positive or negative first lens, and a positive second lens is used. In Patent Documents 3 and 4, a positive first is used. This is a triplet type lens having a rear stop including a lens, a negative second lens, a positive third lens, and an aperture stop.

  However, all of the imaging lenses of Patent Documents 2 to 4 have a low F value, and if the F value is further increased, sufficient performance cannot be obtained and the back focus is long. An imaging device will be enlarged.

  Patent Documents 2 to 4 are directed to an imaging lens for a film camera. That is, the performance is improved by curving the film surface (imaging surface) in accordance with the curvature of field generated by the imaging lens. However, since both are imaging lenses for old cameras that use a roll film, the film surface is a so-called cylindrical imaging surface that curves only in the long side direction of the screen due to the structure of the camera. As a result, good performance can be obtained in the long side direction of the screen, but in the short side direction of the screen, the image pickup surface remains flat and the performance cannot be improved. It may be inviting. That is, it is difficult to obtain high performance over the entire screen only by bending the imaging surface only in the long side direction as in Patent Documents 2 to 4. Therefore, it is common to darken the F value of the lens and set the depth of focus deep so that the blur in the planar direction is not noticeable, and it is therefore difficult to increase the F value.

  Furthermore, since what is disclosed in Patent Documents 2 to 4 is an imaging lens for a film camera as described above, the chief ray incident angle is not necessarily designed to be sufficiently small in the periphery of the imaging surface. On the other hand, in an imaging lens for forming a subject image on the photoelectric conversion unit of a solid-state image sensor, if the principal ray incident angle characteristic of the light beam incident on the imaging surface, so-called telecentric characteristics, deteriorates, the light beam is applied to the solid-state image sensor. On the other hand, the light is incident obliquely, and a phenomenon (shading) in which the substantial aperture efficiency is reduced in the periphery of the imaging surface occurs, resulting in insufficient peripheral light amount. For this reason, in a small lens for a solid-state imaging device, the image side surface of the most image side lens is aspherical, and the peripheral portion of the most image side lens has a positive refractive power, so that the light incident angle on the image pickup surface is increased. In general, the design is intended to keep the value small. However, if the peripheral part has a positive refractive power, the lens tends to have a large ratio of the thickness between the central part of the lens and the peripheral part, the so-called thickness deviation ratio. If the thickness deviation ratio is large, the moldability may be impaired. there were.

  Japanese Patent Application Laid-Open No. H10-228688 describes that it can be applied not only to a film camera but also to an electronic still camera. However, the imaging lens described in Patent Document 2 uses a solid-state imaging device because it is dark at about F10, the back focus is long, the imaging lens is large, and the telecentric characteristics are not sufficiently good. It is considered difficult to apply to the small-sized imaging device.

  Patent Document 5 describes a small four-lens lens having a flat imaging surface. Although the imaging lens described in Patent Document 5 has a short overall lens length and a small size, in order to correct telecentric characteristics, the positive power at the peripheral portion is strong in the most image side lens, and the thickness deviation ratio is extremely high. It has become bigger.

JP 2004-356175 A JP-A-8-334684 JP-A-8-68935 JP2000-292688 JP2010-102162A

  The present invention is an imaging lens for forming an image on a solid-state imaging device having a curved imaging surface, which is small and has high performance, can suppress shading, has a small deviation ratio of the most image side lens, and has good moldability. An object of the present invention is to provide a holding imaging lens.

  Moreover, an object of this invention is to provide an imaging device provided with the above imaging lenses.

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 a solid-state imaging device, and the imaging surface of the solid-state imaging device has an arbitrary cross section toward the periphery of the screen. It is curved so as to fall to the object side, is composed of two or more lenses, has an aperture stop at a position other than between the most image side lens and the solid-state image sensor, and the image side surface of the most image side lens is It has an aspherical shape and the following conditional expression is satisfied.
0.50 <EXPD / EXPC <2.00 (1)
However,
EXPD: Maximum viewing angle exit pupil position
(Distance on the optical axis between the exit pupil position and the imaging surface at the maximum field angle luminous flux)
EXPC: Paraxial exit pupil position
(Distance on paraxial exit pupil position and imaging surface on the optical axis)

  The imaging surface on which image formation is performed by the imaging lens of the present invention is not curved only in the long side direction as in a conventional film camera, but curved so as to have curvature in all directions of 360 degrees around the optical axis. A curved surface is assumed.

  Since the imaging surface of the solid-state imaging device is curved, both miniaturization and high performance can be achieved. If the imaging surface is curved toward the imaging lens side, it is advantageous for correcting the chief ray incident angle of the light beam incident on the imaging surface, that is, correcting so-called telecentric characteristics. In other words, since the chief ray incident angle of the light beam incident on the imaging surface is smaller when the imaging surface is curved toward the imaging lens side than when the imaging surface is flat, the telecentric characteristics are corrected by the imaging lens. Even if it is not performed sufficiently, the aperture efficiency is not reduced and the occurrence of shading can be suppressed. In addition, correction of field curvature, distortion, coma, etc. is facilitated, and miniaturization is also possible. In the present invention, it is assumed that the curved shape of the imaging surface is curved so that both the long side direction and the short side direction of the screen are inclined toward the object side toward the peripheral part of the screen. It is not always necessary to have a spherical shape, and any surface shape that can be expressed by an arbitrary mathematical expression such as an aspherical shape, a paraboloid shape, an XY polynomial surface shape, etc. may be used. By adopting a shape that fits, the performance can be improved over the entire screen.

  The imaging lens of the present invention is composed of two or more lenses, has an aperture stop at a position other than between the most image side lens and the solid-state image sensor, and the image side surface of the most image side lens has an aspheric shape. Have. In the present invention, by using two or more lenses, higher performance is achieved as compared with a single lens. In addition, when a so-called rear stop having a stop between the most image side lens and the solid-state image sensor, the incident angle to the image pickup surface becomes very large and cannot be compensated only by curving the image pickup surface. Therefore, it is desirable to have an aperture stop between the constituent lenses (lens group) or the most object side of the constituent lenses (lens group). Furthermore, by making the image side surface of the most image side lens an aspherical surface, it is possible to obtain a curvature of field suitable for a curved imaging surface while ensuring good telecentric characteristics.

  Conditional expression (1) is for appropriately setting the ratio of the distance between the imaging surface and the exit pupil on the optical axis at the maximum field angle light flux and the distance between the imaging surface and the exit pupil on the optical axis in the axial light flux. Conditional expression. Here, the imaging surface is not an actual setting imaging surface but a paraxial imaging surface. In addition, 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 surface closest to the image side of the imaging lens and the imaging surface, the parallel plate portion Is an air conversion distance, and calculates the distance between the exit pupil position and the imaging surface.

  As the overall length of the imaging lens is shortened, the exit pupil position approaches the imaging surface, and if the exit pupil position is close to the imaging surface, the telecentric characteristics deteriorate. Therefore, as described above, in a small imaging lens for a mobile phone or the like, in order to improve the telecentric characteristics of the peripheral luminous flux as much as possible, a positive power is applied to the peripheral portion of the most image side lens by using an aspherical shape. In general, the exit pupil position in the peripheral luminous flux is kept away from the imaging surface. However, the fact that the exit pupil position in the axial light beam and the exit pupil position in the peripheral light beam are significantly different means that the refractive action inside the imaging lens system is greatly different between the axial light beam and the peripheral light beam. This leads to an increase in error sensitivity and an increase in performance degradation when focusing on a short-distance subject. Therefore, since the imaging surface is curved so as to be tilted toward the object side, the telecentric characteristics of the peripheral light flux are improved, and it is not necessary to force the exit pupil position of the peripheral light flux away from the imaging surface.

  When the value of conditional expression (1) exceeds the lower limit, the exit pupil position of the peripheral light beam can be appropriately moved away from the imaging surface, which is advantageous for telecentric characteristics. On the other hand, when the value is lower than the upper limit, it is not necessary to force the exit pupil position of the peripheral light beam away from the imaging surface, and it is possible to reduce error sensitivity and to reduce performance degradation when focusing on a short-distance subject. In addition, since the positive power at the periphery of the most image side lens can be kept small, the deviation ratio of the most image side lens can be reduced, and good moldability can be ensured.

Further, from the above viewpoint, the value EXPD / EXPC is more preferably set in the range of the following equation.
0.70 <EXPD / EXPC <1.80 (1) '

In a specific aspect or aspect of the present invention, in the imaging lens, the curved amount of the curved imaging surface satisfies the following conditional expression.
0.05 <SAGI / Y <0.50 (2)
However,
SAGI: Amount of displacement in the optical axis direction of the imaging surface at the maximum image height Y: Maximum image height

  Conditional expression (2) is a conditional expression for appropriately setting the amount of curvature of the imaging surface. Beyond the lower limit, the amount of curvature of the imaging surface can be maintained moderately, and the correction of telecentric characteristics and field curvature in the imaging lens can be prevented, so the Petzval sum does not become too small and coma aberration. And chromatic aberration can be corrected well. On the other hand, if the value is below the upper limit, the amount of curvature of the imaging surface does not become too large, and overcorrection of field curvature can be prevented. Further, it is possible to prevent the final surface of the imaging lens from being too close to the imaging surface, and to ensure a sufficient air space for inserting a parallel plate such as an IR cut filter.

From the above viewpoint, the value SAGI / Y is more preferably in the range of the following equation.
0.10 <SAGI / Y <0.40 (2) '

In another aspect of the present invention, the curved imaging surface has a spherical shape and satisfies the following conditional expression.
−8.0 <RI / Y <−1.0 (3)
However,
RI: Radius of curvature of imaging surface Y: Maximum image height

  By making the imaging surface spherical, the imaging surface does not have a complicated shape, and the difficulty of the manufacturing process for bending the imaging surface can be reduced.

  Conditional expression (3) is a conditional expression for appropriately setting the amount of curvature of the imaging surface. If the lower limit is exceeded, the amount of curvature of the imaging surface can be maintained moderately, and the telecentric characteristics and field curvature correction burden of the imaging lens can be prevented from increasing, so the Petzval sum does not become too small and coma aberration. And chromatic aberration can be corrected well. On the other hand, if the value is below the upper limit, it is possible to prevent the amount of curvature of the imaging surface from becoming excessively large and excessive correction of field curvature. Further, it is possible to prevent the final surface of the imaging lens from being too close to the imaging surface, and to ensure a sufficient air space for inserting a parallel plate such as an IR cut filter.

From the above viewpoint, the value RI / Y is more preferably set to the range of the following equation.
−7.0 <RI / Y <−1.5 (3) ′

In still another aspect of the present invention, the following conditional expression is satisfied.
0.30 <SAGI / SAGL <10.50 (4)
However,
SAGI: Amount of displacement in the optical axis direction of the imaging surface at the maximum image height SAGL: Amount of displacement in the optical axis direction of the image side surface of the most image side lens at the maximum effective diameter

  Conditional expression (4) appropriately sets the ratio between the displacement amount of the imaging surface at the maximum image height and the displacement amount at the maximum effective diameter of the image side surface of the most image side lens through which the light beam formed at the maximum image height passes. It is a conditional expression for setting. By exceeding the lower limit, the amount of displacement around the image side lens image side surface does not become excessively large and the positive power around the image side surface does not become too strong, so that distortion and coma aberration can be suppressed. On the other hand, by being below the upper limit, a sufficient clearance between the most image side lens and the peripheral portion of the imaging surface can be secured.

From the above viewpoint, the value SAGL is more preferably set in the range of the following equation.
0.40 <SAGI / SAGL <10.40 (4) ′

In still another aspect of the present invention, the following conditional expression is satisfied.
0.40 <Y / EXPC <2.00 (5)
However,
Y: Maximum image height EXPC: Paraxial exit pupil position
(Distance on paraxial exit pupil position and imaging surface on the optical axis)

  Conditional expression (5) is a conditional expression for appropriately setting the exit pupil position per imaging surface size. By exceeding the lower limit, the exit pupil position can be appropriately brought close to the imaging surface, and as a result, the overall length of the imaging lens can be shortened. On the other hand, by falling below the upper limit, the exit pupil position does not excessively approach the imaging surface, and the imaging lens can be downsized and good telecentric characteristics can be ensured.

From the above viewpoint, it is more desirable to set the value Y / EXPC within the range of the following equation.
0.40 <Y / EXPC <1.50 (5) '

In still another aspect of the present invention, the following conditional expression is satisfied.
0.15 <fb / f <1.30 (6)
However,
fb: Back focus of the imaging lens f: Focal length of the entire imaging lens system

  Conditional expression (6) is a conditional expression for appropriately setting the back focus of the lens system. By exceeding the lower limit, the most image side lens and the imaging surface are not brought too close to each other, and a space for inserting a parallel plate such as an optical low-pass filter or an infrared cut filter can be secured. On the other hand, by being below the upper limit, the back focus does not become unnecessarily large, and as a result, the entire length of the imaging lens can be shortened. Here, the back focus means a parallel plate 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 most image side lens and the imaging surface. The part refers to the distance on the optical axis between the most image side lens and the imaging surface in terms of air conversion distance. More preferably, the range of the following formula is good.

From the above viewpoint, the value fb / f is more preferably in the range of the following equation.
0.15 <fb / f <1.20 (6) ′

  In still another aspect of the present invention, an aperture stop is disposed on the most object side of two or more lenses constituting the imaging lens. By providing the aperture stop on the most object side of the constituent lens, that is, the lens group, the exit pupil position can be moved away from the imaging surface, and good telecentric characteristics can be secured.

  In still another aspect of the present invention, an aperture stop is disposed between the first lens closest to the object side and the second lens adjacent to the image side of the first lens among the two or more lenses constituting the imaging lens. ing. By arranging an aperture stop between the first lens and the second lens, the refraction angle of the peripheral marginal ray passing through the object side surface of the first lens does not become too large, and the imaging lens is downsized and good aberration correction is performed. And both.

  In order to achieve the above object, an imaging apparatus according to the present invention includes the imaging lens described above and a solid-state imaging device. By using the imaging lens of the present invention, it is possible to obtain an imaging apparatus having an imaging lens that is small and has high performance, can suppress shading, and has good moldability.

It is a figure explaining the imaging device of one embodiment of the present invention. It is a figure explaining the exit pupil position etc. of a peripheral light beam. 2 is a cross-sectional view of an imaging lens of Example 1. FIG. (A)-(E) are the aberrational figures of the imaging lens of 1st Example. 6 is a cross-sectional view of an imaging lens of Example 2. FIG. (A)-(E) are the aberrational figures of the imaging lens of 2nd Example. 6 is a cross-sectional view of an imaging lens of Example 3. FIG. (A)-(E) are the aberrational figures of the imaging lens of 3rd Example. 6 is a cross-sectional view of an imaging lens of Example 4. FIG. (A)-(E) are the aberrational figures of the imaging lens of 4th Example. 6 is a cross-sectional view of an imaging lens of Example 5. FIG. (A)-(E) are the aberrational figures of the imaging lens of 5th Example. 6 is a cross-sectional view of an imaging lens of Example 6. FIG. (A)-(E) are the aberrational figures of the imaging lens of 6th Example.

  FIG. 1 is a cross-sectional view showing an imaging apparatus 100 according to one embodiment. The imaging apparatus 100 includes an imaging unit 50 for forming an image signal, and a processing unit 60 that functions as the imaging apparatus 100 by operating the imaging unit 50 as appropriate.

  The imaging unit 50 includes an imaging lens 10 that forms a subject image, a solid-state imaging device 51 that is a CMOS image sensor that detects a subject image formed by the imaging lens 10, and the solid-state imaging device 51 is curved. A supporting body 52 to be held, a substrate 53 that supports the supporting body 52 from behind and provided with wiring and the like, and a light-shielding housing 54 having an opening OP for allowing a light beam from the object side to enter. Are integrally formed.

  The imaging lens 10 includes, for example, a first lens L1, an aperture stop S, a second lens L2, and a third lens L3 in order from the object side.

  The solid-state imaging device 51 includes a photoelectric conversion unit 51a as a light receiving unit, and a signal processing circuit 51b is formed around the photoelectric conversion unit 51a. The photoelectric conversion unit 51a has an imaging surface I on which pixels (photoelectric conversion elements) are two-dimensionally arranged. The signal processing circuit 51b includes, for example, 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 the like. Note that the solid-state imaging device 51 is not limited to the above-described CMOS type image sensor, and may be another image sensor such as a CCD.

  The support body 52 is formed of a hard material, and has a role of maintaining and fixing the solid-state imaging device 51 in a concave shape that is symmetrically recessed around the optical axis AX. Thereby, the imaging surface I of the solid-state imaging device 51 is in a curved state (specifically, a hemispherical concave surface) that is tilted toward the imaging lens 10 so as to be directed to the central optical axis AX in an arbitrary cross section including the optical axis AX. It becomes. Note that a signal processing circuit 52 a having a function of controlling the operation of the signal processing circuit 51 b can be formed on the support body 52.

  The substrate 53 includes a main body portion 53a that supports the support body 52 and the housing 54 on one surface side, and a flexible printed circuit board 53b that has one end connected to the other surface side of the main body portion 53a. The main body portion 53a is connected to the solid-state imaging device 51 via the bonding wire W on the one surface side, and is connected to the flexible printed board 53b on the other surface side.

  The flexible printed circuit board 53b connects the main body portion 53a and an external circuit (not shown) (for example, a control circuit included in a host device on which the imaging unit 50 is mounted), and drives the solid-state imaging device 51 from the external circuit. It is possible to receive a voltage or a clock signal and to output a digital pixel signal such as YUV to an external circuit.

  The housing 54 houses and holds the imaging lens 10 assembled to the lens frame 55. The casing 54 is provided on the surface of the substrate 53 on the solid-state image sensor 51 side so as to cover the solid-state image sensor 51. That is, the housing 54 is widely opened so as to surround the solid-state imaging device 51 on the back surface side and is fixed to the support substrate 52a, and is formed in a cylindrical shape with a flange having an opening OP of a predetermined size on the front surface side. Yes. Inside the housing 54, a parallel plate F having an infrared light cut function is fixed and disposed between the imaging lens 10 and the solid-state imaging device 51. The parallel plate F is supported by the lens frame 55 in the same manner as the imaging lens 10.

  The processing unit 60 includes a control unit 61, an input unit 62, a storage unit 63, and a display unit 64. The control unit 61 causes the imaging unit 50 to perform an imaging operation. The input unit 62 is a part that receives user operations, the storage unit 63 is a part that stores information necessary for the operation of the imaging apparatus 100, image data acquired by the imaging unit 50, and the display unit 64. This is a part for displaying information to be presented to the user, captured images, and the like. For example, the control unit 61 can perform various image processing on the image data obtained by the imaging unit 50.

  Although detailed description is omitted, specific functions of the processing unit 60 are appropriately adjusted according to whether the imaging apparatus 100 is incorporated in a digital camera, a mobile phone, a PDA, or the like.

  Hereinafter, the imaging lens 10 of the embodiment 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.

  As shown in FIG. 1, the imaging lens 10 of the embodiment forms a subject image on the solid-state imaging device 51, and includes two or more lenses, specifically, a first lens L1 and a second lens. L2 and a third lens L3. The imaging lens 10 includes a parallel plate F as an optical element having substantially no power. The imaging surface I of the solid-state imaging device 51 is curved in a shallow concave spherical shape, and is a rotational surface having symmetry around the optical axis AX. The imaging lens 10 has an aperture stop S at a position other than between the third lens L3 that is the most image side lens and the solid-state imaging device 51, specifically between the first lens L1 and the second lens L2. The image side surface 3b of the third lens L3 that is the most image side lens of the imaging lens 10 has an aspherical shape.

  Since the imaging surface I of the solid-state imaging device 51 on which the image light from the imaging lens 10 is incident is curved, it is possible to achieve both downsizing and high performance of the imaging lens 10 and the like. Specifically, since the imaging surface I is curved toward the imaging lens 10 at the periphery, the chief ray incident angle of the light beam incident on the imaging surface I becomes small. Therefore, the imaging lens 10 corrects the telecentric characteristic. Even if it is not performed sufficiently, the aperture efficiency does not decrease and the occurrence of shading can be suppressed. In addition, correction of curvature of field, distortion, coma, and the like is facilitated, and the imaging lens 10 and the like can be downsized.

  This imaging lens 10 uses two or more lenses, specifically, three lenses L1, L2, and L3, and achieves higher performance than a case where, for example, a single lens is used. . Further, by providing the aperture stop S between the first lens L1 and the second lens L2, it is possible to prevent the incident angle of the light beam on the imaging surface I from becoming very large. Furthermore, by making the image side surface 3b of the third lens L3, which is the most image side lens, an aspherical shape, it is possible to obtain a curvature of field suitable for the curved imaging surface I while ensuring good telecentric characteristics. .

The imaging lens 10 described above has the conditional expression (1) already described.
0.50 <EXPD / EXPC <2.00 (1)
Satisfied. Here, EXPD is the maximum field angle exit pupil position (distance on the optical axis between the exit pupil position and the imaging surface at the maximum field angle beam), and EXPC is the paraxial exit pupil position (exit pupil in the paraxial beam). The distance on the optical axis between the position and the imaging surface).

  Conditional expression (1) appropriately sets the ratio of the distance between the imaging surface I and the exit pupil on the optical axis AX in the light flux with the maximum angle of view and the distance on the optical axis AX between the imaging surface I and the exit pupil in the axial light flux. It is a conditional expression for setting. Here, the imaging plane I is not an actual setting imaging plane but a paraxial imaging plane.

  Since the value of conditional expression (1) exceeds the lower limit, the exit pupil position of the peripheral light beam can be appropriately moved away from the imaging surface I, which is advantageous for telecentric characteristics. On the other hand, by falling below the upper limit, it is not necessary to forcibly move the exit pupil position in the peripheral luminous flux away from the imaging surface I, and it becomes possible to reduce the error sensitivity and to reduce the performance deterioration at the time of focusing on a short-distance subject. . In addition, since the positive power at the periphery of the third lens L3 that is the most image side lens can be suppressed to be small, the deviation ratio of the third lens L3 that is the most image side lens can be reduced, which is favorable. Formability can be ensured.

  FIG. 2 is a reference diagram for explaining the exit pupil position of the imaging lens 10. The point at which the principal ray intersects the optical axis AX among the peripheral light fluxes (specifically, the maximum light flux angle) from the paraxial image plane IC is the exit pupil position of the maximum light flux angle. The distance on the optical axis AX from the axial image plane IC is the maximum field angle exit pupil position EXPD.

More preferably, the imaging lens 10 satisfies the following expression (1) ′ that further restricts the conditional expression (1).
0.70 <EXPD / EXPC <1.80 (1) '

The imaging lens 10 according to the embodiment has the conditional expression (2) already described in addition to the conditional expression (1).
0.05 <SAGI / Y <0.50 (2)
Satisfied. Here, SAGI is the amount of displacement in the optical axis direction of the imaging surface I at the maximum image height, and Y is the maximum image height.

More preferably, the imaging lens 10 satisfies the following expression (2) ′ that further restricts the conditional expression (2).
0.10 <SAGI / Y <0.40 (2) '

In the imaging lens 10 of the embodiment, in addition to the conditional expression (1), the conditional expression (3) already described.
−8.0 <RI / Y <−1.0 (3)
Satisfied. Here, RI is the radius of curvature of the imaging surface I.

More preferably, the imaging lens 10 satisfies the following expression (3) ′ that further restricts the conditional expression (3).
−7.0 <RI / Y <−1.5 (3) ′

In the imaging lens 10 of the embodiment, in addition to the conditional expression (1), the conditional expression (4) already described.
0.30 <SAGI / SAGL <10.50 (4)
Satisfied. Here, SAGI is the amount of displacement in the optical axis direction of the imaging surface I at the maximum image height, and SAGL is the amount of displacement in the optical axis direction of the image side surface 3a of the third lens L3 at the maximum effective diameter.

More preferably, the imaging lens 10 satisfies the following expression (4) ′ that further restricts the conditional expression (4).
0.40 <SAGI / SAGL <10.4 (4) ′

In the imaging lens 10 of the embodiment, in addition to the conditional expression (1), the conditional expression (5) already described.
0.40 <Y / EXPC <2.00 (5)
Satisfied. Here, Y is the maximum image height, and EXPC is the paraxial exit pupil position.

More preferably, the imaging lens 10 satisfies the following expression (5) ′ that further restricts the conditional expression (5).
0.40 <Y / EXPC <1.50 (5) '

In the imaging lens 10 of the embodiment, in addition to the conditional expression (1), the conditional expression (6) already described.
0.15 <fb / f <1.30 (6)
Satisfied. Here, fb is the back focus of the imaging lens 10, and f is the focal length of the entire imaging lens 10 system.

More preferably, the imaging lens 10 satisfies the following expression (6) ′ that further restricts the conditional expression (6).
0.15 <fb / f <1.20 (6) ′

ただし、
Ａｉ：ｉ次の非球面係数
Ｒ ：曲率半径
Ｋ ：円錐定数 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 number 2Y: Diagonal length ENTP on the imaging surface of the solid-state imaging device: 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 aspherical surface shape is expressed by the following “Equation 1”, where the vertex of the surface is the origin, the X axis is taken in the optical axis direction, and the height in the direction perpendicular to the optical axis is 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 = 2.38mm
fB = 0.76mm
F = 2.4
2Y = 3.5mm
ENTP = 0.41mm
EXTP = −1.07mm
H1 = −0.31mm
H2 = −1.63mm

The lens surface data of Example 1 is shown in Table 1 below. The aperture means the aperture stop S, and the imaging plane means the imaging plane I.
[Table 1]
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 * 1.161 0.49 1.54470 56.2 0.66
2 * 4.222 0.03 0.47
3 (Aperture) ∞ 0.07 0.45
4 * 3.788 0.37 1.54470 56.2 0.48
5 * -6.689 0.48 0.55
6 * -1.910 0.54 1.63470 23.9 0.68
7 * -5.978 0.74 1.15
8 (Shooting surface) -6.354

The aspherical coefficient of the lens surface of Example 1 is shown below.
First side
K = -0.25843E + 01, A4 = 0.45319E-01, A6 = -0.20599E + 00, A8 = -0.68537E + 00,
A10 = 0.55464E + 00
Second side
K = -0.30000E + 02, A4 = -0.21862E + 00, A6 = -0.77470E + 00, A8 = 0.21693E + 01,
A10 = -0.14820E + 01
4th page
K = 0.15140E + 02, A4 = 0.32865E-01, A6 = -0.31885E + 00, A8 = 0.40411E + 01,
A10 = -0.38145E + 01
5th page
K = -0.30000E + 02, A4 = 0.11738E + 00, A6 = 0.87909E + 00, A8 = -0.25596E + 01,
A10 = 0.94636E + 01
6th page
K = -0.64696E + 00, A4 = -0.57777E + 00, A6 = 0.63229E + 00, A8 = -0.51960E + 01,
A10 = 0.14167E + 02, A12 = -0.20902E + 02
7th page
K = 0.25667E + 02, A4 = -0.11673E + 00, A6 = -0.31995E-01, A8 = 0.71497E-01,
A10 = -0.51129E-01, A12 = -0.17970E-03

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).

The single lens data of Example 1 is shown in Table 2 below.
[Table 2]
Lens Start surface Focal length (mm)
1 1 2.784
2 4 4.497
3 6 -4.660

  FIG. 3 is a cross-sectional view of the imaging lens 11 or the imaging unit 50 according to the first embodiment. The imaging lens 11 has a positive refractive power and is convex toward the object side, a meniscus first lens L1, a positive birefringent second lens L2 having a positive refractive power, and a negative refractive power and has an image side. And a meniscus third lens L3. All the lenses L1 to L3 are made of a plastic material. An aperture stop S is disposed between the first lens L1 and the second lens L2. In the present embodiment, the imaging surface I has a spherical shape. A parallel plate F shown in FIG. 1 can be arranged between the convex surface of the third lens L3 and the concave imaging surface I.

  4A to 4C show aberration diagrams (spherical aberration, astigmatism, distortion) of the imaging lens 11 of Example 1, and FIGS. 4D and 4E show Examples. 2 shows the meridional coma aberration of one imaging lens 11.

(Example 2)
The overall specifications of the imaging lens of Example 2 are shown below.
f = 2.39mm
fB = 0.6mm
F = 2.4
2Y = 3.5mm
ENTP = 0.44mm
EXTP = -1.26mm
H1 = −0.23mm
H2 = -1.78mm

The lens surface data of Example 2 is shown in Table 3 below.
[Table 3]
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 * 1.191 0.48 1.54470 56.2 0.68
2 * 2.315 0.05 0.46
3 (Aperture) ∞ 0.07 0.44
4 * 2.015 0.45 1.54470 56.2 0.50
5 * -5.096 0.38 0.60
6 * -2.010 0.90 1.63470 23.9 0.65
7 * -9.570 0.60 1.32
8 (Shooting surface) -6.969

The aspherical coefficient of the lens surface of Example 2 is shown below.
First side
K = -0.23484E + 01, A4 = 0.622251E-01, A6 = -0.11697E + 00, A8 = -0.39497E + 00,
A10 = 0.19543E + 00
Second side
K = -0.41745E + 01, A4 = -0.11680E + 00, A6 = -0.65316E + 00, A8 = 0.91685E + 00,
A10 = -0.75003E + 00
4th page
K = 0.45036E + 01, A4 = -0.67987E-01, A6 = -0.42921E + 00, A8 = 0.97000E + 00,
A10 = -0.76215E + 00
5th page
K = -0.30000E + 02, A4 = -0.93881E-01, A6 = 0.38334E + 00, A8 = -0.22038E + 01,
A10 = 0.35467E + 01
6th page
K = -0.39257E + 01, A4 = -0.55727E + 00, A6 = 0.50788E + 00, A8 = -0.59853E + 01,
A10 = 0.16419E + 02, A12 = -0.25388E + 02
7th page
K = -0.30000E + 02, A4 = -0.22108E-01, A6 = -0.11785E + 00, A8 = 0.11587E + 00,
A10 = -0.66301E-01, A12 = 0.14855E-01

The single lens data of Example 2 is shown in Table 4 below.
[Table 4]
Lens Start surface Focal length (mm)
1 1 3.918
2 4 2.712
3 6 -4.203

  FIG. 5 is a cross-sectional view of the imaging lens 12 or the imaging unit 50 according to the second embodiment. The imaging lens 12 includes a first meniscus lens L1 that has positive refractive power and is convex toward the object side, a second lens L2 that has positive refractive power and is biconvex, and has a negative refractive power and has an image side. And a meniscus third lens L3. All the lenses L1 to L3 are made of a plastic material. An aperture stop S is disposed between the first lens L1 and the second lens L2. In the present embodiment, the imaging surface I has a spherical shape. A parallel plate F shown in FIG. 1 can be arranged between the convex surface of the third lens L3 and the concave imaging surface I.

  6A to 6C show aberration diagrams (spherical aberration, astigmatism, distortion) of the imaging lens 12 of Example 2, and FIGS. 6D and 6E show Examples. 2 shows the meridional coma of the image pickup lens 12.

(Example 3)
The overall specifications of the imaging lens of Example 3 are shown below.
f = 3mm
fB = 1.73mm
F = 2.8
2Y = 4.536mm
ENTP = 0mm
EXTP = -1.71mm
H1 = 0.38mm
H2 = -1.27mm

The lens surface data of Example 3 is shown in Table 5 below.
[Table 5]
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 (Aperture) ∞ -0.06 0.53
2 * 1.218 0.65 1.54470 56.2 0.56
3 * 2.107 0.60 0.65
4 * -801.679 0.61 1.54470 56.2 1.03
5 * -3.248 1.72 1.33
6 (Shooting surface) -6.893

The aspherical coefficient of the lens surface of Example 3 is shown below.
Second side
K = -0.83589E-01, A4 = 0.63341E-02, A6 = 0.17877E + 00, A8 = -0.62056E + 00,
A10 = 0.16155E + 01, A12 = -0.18854E + 01
Third side
K = 0.43853E + 01, A4 = 0.72575E-01, A6 = -0.65234E-02, A8 = -0.10661E + 00,
A10 = 0.80743E + 00, A12 = -0.73994E + 00
4th page
K = -0.94483E + 05, A4 = 0.30860E-01, A6 = -0.10667E + 00, A8 = 0.14926E + 00,
A10 = -0.23616E + 00, A12 = 0.18440E + 00, A14 = -0.66932E-01
5th page
K = -0.34691E + 02, A4 = -0.44080E-01, A6 = 0.55225E-01, A8 = -0.22438E-01,
A10 = -0.25165E-01, A12 = 0.21006E-01, A14 = -0.51705E-02

The single lens data of Example 3 is shown in Table 6 below.
[Table 6]
Lens Start surface Focal length (mm)
1 2 4.216
2 4 5.985

  FIG. 7 is a cross-sectional view of the imaging lens 13 or the imaging unit 50 according to the third embodiment. The imaging lens 13 includes a first meniscus lens L1 having a positive refractive power and convex toward the object side, and a second meniscus lens L2 having a positive refractive power and convex toward the image side. All the lenses L1, L2 are made of a plastic material. An aperture stop S is disposed on the object side of the first lens L1. In the present embodiment, the imaging surface I has a spherical shape. A parallel plate F shown in FIG. 1 can be arranged between the convex surface of the second lens L2 and the concave imaging surface I.

  8A to 8C show aberration diagrams (spherical aberration, astigmatism, distortion) of the imaging lens 13 of Example 3, and FIGS. 8D and 8E show Examples. 3 shows the meridional coma aberration of the third imaging lens 13.

Example 4
The overall specifications of the imaging lens of Example 4 are shown below.
f = 4.68mm
fB = 1.03mm
F = 2.88
2Y = 6.973mm
ENTP = 0mm
EXTP = -3.82mm
H1 = 0.16mm
H2 = -3.65mm

The lens surface data of Example 4 is shown in Table 7 below.
[Table 7]
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 (Aperture) ∞ -0.01 0.81
2 * 3.484 1.59 1.54470 56.2 0.85
3 * -4.706 0.06 1.30
4 * -7.921 0.40 1.63200 23.4 1.33
5 * 6.574 0.26 1.54
6 * 12.758 1.28 1.54470 56.2 1.77
7 * -5.217 0.81 1.98
8 * 3.523 0.73 1.54470 56.2 2.30
9 * 2.618 0.40 3.06
10 ∞ 0.15 1.51630 64.1 3.47
11 ∞ 3.52
12 (Shooting surface) -9.840

The aspherical coefficient of the lens surface of Example 4 is shown below.
Second side
K = 0.26831E + 00, A4 = -0.49640E-02, A6 = -0.35249E-02, A8 = 0.41901E-02,
A10 = -0.30654E-02
Third side
K = 0.34256E + 01, A4 = -0.34442E-02, A6 = 0.10763E-01, A8 = -0.59391E-02,
A10 = 0.37082E-03
4th page
K = -0.17415E + 02, A4 = -0.23971E-01, A6 = 0.19654E-01, A8 = -0.88369E-02,
A10 = 0.11981E-02
5th page
K = -0.19173E + 02, A4 = -0.59634E-02, A6 = 0.11854E-01, A8 = -0.55652E-02,
A10 = 0.14173E-02, A12 = -0.14817E-03
6th page
K = 0.19634E + 02, A4 = -0.55092E-02, A6 = 0.37558E-02, A8 = -0.64978E-03,
A10 = 0.16145E-03, A12 = -0.16946E-04
7th page
K = -0.29973E + 01, A4 = -0.25718E-01, A6 = 0.83725E-02, A8 = -0.20725E-02,
A10 = 0.44531E-03, A12 = -0.20066E-04
8th page
K = -0.11658E + 02, A4 = -0.41840E-01, A6 = -0.12657E-02, A8 = 0.82939E-03,
A10 = -0.12381E-03, A12 = 0.92004E-05
9th page
K = -0.64839E + 00, A4 = -0.55582E-01, A6 = 0.72567E-02, A8 = -0.83289E-03,
A10 = 0.59449E-04, A12 = -0.19144E-05

The single lens data of Example 4 is shown in Table 8 below.
[Table 8]
Lens Start surface Focal length (mm)
1 2 3.946
2 4 -5.624
3 6 6.973
4 8 -26.180

  FIG. 9 is a cross-sectional view of the imaging lens 14 or the imaging unit 50 of the fourth embodiment. The imaging lens 14 includes a biconvex first lens L1 having a positive refractive power, a biconcave second lens L2 having a negative refractive power, a biconvex third lens L3 having a positive refractive power, A fourth meniscus lens L4 having negative refractive power and convex toward the object side. All the lenses L1 to L4 are made of a plastic material. An aperture stop S is disposed on the object side of the first lens L1, and an optical low-pass filter, an IR cut filter, and a solid-state image sensor seal are provided between the exit side surface of the fourth lens L4 and the concave imaging surface I. A parallel plate F assuming glass or the like is arranged. In the present embodiment, the imaging surface I has a spherical shape.

  10A to 10C show aberration diagrams (spherical aberration, astigmatism, distortion aberration) of the imaging lens 14 of Example 4, and FIGS. 10D and 10E show Examples. 4 shows the meridional coma of the image pickup lens 14.

(Example 5)
The overall specifications of the imaging lens of Example 5 are shown below.
f = 3.52mm
fB = 1.04mm
F = 2.8
2Y = 5.744mm
ENTP = 0mm
EXTP = -2.89mm
H1 = 0.37mm
H2 = -2.48mm

The lens surface data of Example 5 is shown in Table 9 below.
[Table 9]
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 (Aperture) ∞ -0.05 0.67
2 * 2.379 0.98 1.54470 56.2 0.67
3 * -2.832 0.05 0.92
4 * -3.018 0.30 1.63200 23.4 0.94
5 * -235.830 0.27 1.07
6 * -28.219 0.71 1.54470 56.2 1.29
7 * -5.145 0.77 1.47
8 * 7.781 0.68 1.54470 56.2 1.95
9 * 8.171 1.04 2.34
10 (Shooting plane) -5.000

The aspherical coefficient of the lens surface of Example 5 is shown below.
Second side
K = -0.12146E + 01, A4 = -0.12881E-01, A6 = -0.21281E-01, A8 = 0.14977E-01,
A10 = -0.45090E-01
Third side
K = 0.77739E + 01, A4 = -0.87252E-01, A6 = 0.12099E + 00, A8 = 0.10957E-01,
A10 = -0.15074E-02
4th page
K = 0.83353E + 01, A4 = 0.60055E-02, A6 = 0.11417E + 00, A8 = 0.13321E-01,
A10 = -0.64017E-02
5th page
K = 0.50000E + 02, A4 = 0.75714E-01, A6 = 0.26850E-01, A8 = -0.37066E-01,
A10 = 0.35778E-01, A12 = -0.15596E-01
6th page
K = 0.46169E + 02, A4 = -0.23820E-01, A6 = 0.29470E-01, A8 = 0.66328E-02,
A10 = -0.58642E-02, A12 = 0.79812E-03
7th page
K = 0.35966E + 01, A4 = -0.50298E-01, A6 = 0.32881E-01, A8 = -0.89186E-02,
A10 = 0.58415E-02, A12 = -0.12032E-02
8th page
K = -0.50000E + 02, A4 = -0.80417E-01, A6 = 0.42909E-02, A8 = 0.57286E-02,
A10 = -0.22401E-02, A12 = 0.27244E-03
9th page
K = 0.10651E + 02, A4 = -0.73689E-01, A6 = 0.14902E-01, A8 = -0.29045E-02,
A10 = 0.40555E-03, A12 = -0.36409E-04

The single lens data of Example 5 is shown in Table 10 below.
[Table 10]
Lens Start surface Focal length (mm)
1 2 2.543
2 4 -4.840
3 6 11.426
4 8 185.132

  FIG. 11 is a cross-sectional view of the imaging lens 15 or the imaging unit 50 according to the fifth embodiment. The imaging lens 15 includes a biconvex first lens L1 having a positive refractive power, a negative meniscus second lens L2 having a negative refractive power and convex on the image side, and a positive refractive power on the image side. A convex meniscus third lens L3 and a positive meniscus fourth lens L4 having positive refractive power on the object side are provided. All the lenses L1 to L4 are made of a plastic material. An aperture stop S is disposed on the object side of the first lens L1. In the present embodiment, the imaging surface I has a spherical shape. A parallel plate F shown in FIG. 1 can be disposed between the concave surface of the fourth lens L4 (paraxial and concave but overall convex) and the concave imaging surface I.

  12A to 12C show aberration diagrams (spherical aberration, astigmatism, distortion) of the imaging lens 15 of Example 5, and FIGS. 12D and 12E show Examples. 5 shows the meridional coma of the imaging lens 15.

(Example 6)
The overall specifications of the imaging lens of Example 6 are shown below.
f = 0.84mm
fB = 0.99mm
F = 2.8
2Y = 3mm
ENTP = 1.19mm
EXTP = -1.44mm
H1 = 1.74mm
H2 = 0.16mm

The lens surface data of Example 6 is shown in Table 13 below.
[Table 11]
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 * 1.702 0.40 1.72920 54.7 1.64
2 * 0.597 1.02 1.02
3 * 1.605 0.83 1.84670 23.8 0.76
4 * 2.736 0.08 0.32
5 (Aperture) ∞ 0.09 0.23
6 * 1.973 0.88 1.58910 61.1 0.39
7 * -0.525 0.05 0.61
8 * -1.511 0.35 1.84670 23.8 0.63
9 * -6.628 0.99 0.93
10 (Shooting plane) -10.000

The aspheric coefficient of the lens surface of Example 6 is shown below.
First side
K = -0.19685E + 01, A4 = 0.41315E-01, A6 = -0.42606E-01, A8 = -0.21322E-02,
A10 = 0.60628E-02, A12 = -0.99529E-03
Second side
K = -0.83050E + 00, A4 = 0.37019E-01, A6 = -0.33652E-01, A8 = -0.59534E + 00,
A10 = 0.30779E + 00, A12 = 0.66336E-01
Third side
K = 0.23986E + 01, A4 = -0.16324E + 00, A6 = 0.75684E + 00, A8 = -0.31843E + 01,
A10 = 0.56471E + 01, A12 = -0.35225E + 01
4th page
K = -0.17897E + 02, A4 = 0.69636E + 00, A6 = -0.41079E + 01, A8 = 0.55261E + 02,
A10 = -0.14580E + 03
6th page
K = 0.49674E + 01, A4 = 0.88013E-01, A6 = -0.78245E + 00, A8 = 0.27750E + 01,
A10 = 0.42642E + 00
7th page
K = -0.64733E + 00, A4 = 0.12551E + 01, A6 = -0.72027E + 01, A8 = 0.37169E + 02,
A10 = -0.10538E + 03, A12 = 0.11507E + 03
8th page
K = -0.22819E + 02, A4 = -0.54575E + 00, A6 = -0.38032E + 00, A8 = 0.18040E + 01,
A10 = -0.29671E + 01, A12 = -0.16462E + 02
9th page
K = 0.46532E + 02, A4 = -0.12441E + 00, A6 = 0.43294E + 00, A8 = -0.10241E + 01,
A10 = 0.68322E + 00, A12 = -0.13325E + 00

The single lens data of Example 6 is shown in Table 12 below.
[Table 12]
Lens Start surface Focal length (mm)
1 1 -1.487
2 3 3.434
3 6 0.810
4 8 -2.387

  FIG. 13 is a cross-sectional view of the imaging lens 17 or the imaging unit 50 of the sixth embodiment. The imaging lens 17 has a negative refractive power and is convex toward the object side, and has a first meniscus lens L1. The imaging lens 17 has a negative refractive power and is convex toward the object side and has a meniscus second lens L2. A biconvex third lens L3 and a fourth meniscus lens L4 having negative refractive power and convex toward the image side. All the lenses L1 to L4 are made of a plastic material. An aperture stop S is disposed between the second lens L2 and the third lens L3. In the present embodiment, the imaging surface I has a spherical shape. A parallel plate F shown in FIG. 1 can be arranged between the convex surface of the second lens L2 and the concave imaging surface I.

  14A to 14C show aberration diagrams (spherical aberration, astigmatism, distortion) of the imaging lens 17 of Example 6, and FIGS. 14D and 14E show Examples. 7 shows the meridional coma aberration of the image pickup lens 17.

For reference, Table 13 below summarizes the values of Examples 1 to 6 corresponding to the conditional expressions (1) to (6).
[Table 13]

  Regarding the meaning of the paraxial radius of curvature described in the claims and examples, in the actual lens measurement scene, in the vicinity of the center of the lens (specifically, the center within 10% of the lens outer diameter). The approximate curvature radius when the shape measurement value in the region) is fitted by the method of least squares can be regarded as the paraxial curvature radius.

  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 to 42 of “Lens Design Method” by K. Matsui, Kyoritsu Publishing Co., Ltd.).

  Moreover, although the imaging lenses 11-15 of the said Example are comprised with 2-4 lenses of the lenses L1-L2 (L3, L4), before or after the lenses L1-L2 (L3, L4). One or more lenses having substantially no power can be added.

  DESCRIPTION OF SYMBOLS 10 ... Imaging lens, 11-17 ... Imaging lens, 50 ... Imaging unit, 51 ... Solid-state image sensor, 51a ... Photoelectric conversion part, 60 ... Processing part, F ... Parallel plate, I ... Imaging surface, L1-L4 ... Lens, AX ... Optical axis

Claims (10)

An imaging lens for forming a subject image on a solid-state imaging device,
The imaging surface of the solid-state imaging device is curved so as to fall to the object side at an arbitrary cross section toward the screen periphery,
Consists of two or more lenses,
Having an aperture stop at a position other than between the most image side lens and the solid-state image sensor,
The image side surface of the most image side lens has an aspheric shape,
An imaging lens satisfying the following conditional expression:
0.50 <EXPD / EXPC <2.00 (1)
However,
EXPD: Maximum viewing angle exit pupil position
(Distance on the optical axis between the exit pupil position at the maximum luminous flux and the imaging surface)
EXPC: Paraxial exit pupil position
(Distance on the optical axis between the paraxial exit pupil position and the imaging surface) The imaging lens according to claim 1, wherein the curved amount of the curved imaging surface satisfies the following conditional expression.
0.05 <SAGI / Y <0.50 (2)
However,
SAGI: Amount of displacement in the optical axis direction of the imaging surface at the maximum image height Y: Maximum image height The imaging lens according to claim 1, wherein the curved imaging surface has a spherical shape and satisfies the following conditional expression.
−8.0 <RI / Y <−1.0 (3)
However,
RI: radius of curvature of the imaging surface Y: maximum image height The imaging lens according to any one of claims 1 to 3, wherein the following conditional expression is satisfied.
0.30 <SAGI / SAGL <10.50 (4)
However,
SAGI: Displacement amount in the optical axis direction of the imaging surface at the maximum image height SAGL: Displacement amount in the optical axis direction of the image side surface of the most image side lens at the maximum effective diameter The imaging lens according to any one of claims 1 to 4, wherein the following conditional expression is satisfied.
0.40 <Y / EXPC <2.00 (5)
However,
Y: Maximum image height EXPC: Paraxial exit pupil position
(Distance on the optical axis between the paraxial exit pupil position and the imaging surface) The imaging lens according to any one of claims 1 to 5, wherein the following conditional expression is satisfied.
0.15 <fb / f <1.30 (6)
However,
fb: Back focus of the imaging lens f: Focal length of the entire imaging lens system   The imaging lens according to any one of claims 1 to 6, wherein an aperture stop is disposed closest to the object side of two or more lenses constituting the imaging lens.   The aperture stop is disposed between a first lens closest to the object side and a second lens adjacent to the image side of the first lens among two or more lenses constituting the imaging lens. The imaging lens according to any one of 1 to 6.   The imaging lens according to claim 1, further comprising a lens having substantially no power.   An imaging device comprising the imaging lens according to claim 1 and the solid-state imaging device.

Images