JP2019174848A - Image capturing lens and image capturing device - Google Patents

Abstract

To provide a light-weight, inexpensive image capturing lens that exhibits little variations in in-focus position and field angle even when ambient temperature varies significantly, and offers good optical performance, and to provide an image capturing device.SOLUTION: An image capturing lens comprises a first lens Ghaving negative refractive power, and a succeeding lens group GRarranged in order from the object side. The succeeding lens group GRcomprises a second lens Ghaving positive refractive power, an aperture stop SP, a third lens Ghaving positive refractive power, and a forth lens Ghaving negative refractive power arranged in order from the object side. The third lens Gand fourth lens Gare made of resin, and are arranged next to each other on an optical axis with an air gap therebetween. The image capturing lens satisfies predefined conditional expressions.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging lens capable of ensuring good optical performance even at a low temperature or a high temperature, and an imaging apparatus including the imaging lens.

  In recent years, in an imaging apparatus provided with a solid-state imaging device such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS), miniaturization of the entire apparatus has been promoted in addition to high functionality. In particular, surveillance cameras, security cameras, in-vehicle cameras, and the like installed indoors and outdoors are required to be smaller because installation space is often limited. Along with this, there is a demand for further downsizing and higher performance in imaging lenses mounted on surveillance cameras, security cameras, vehicle-mounted cameras, and the like.

  As imaging lenses mounted on surveillance cameras, security cameras, vehicle-mounted cameras, etc., fixed focus lenses that do not require focus adjustment actuators are widely used from the viewpoint of reliability and low cost that can withstand long-term use. It has been. Surveillance cameras and security cameras are often installed outdoors, where the temperature changes greatly. Moreover, the vehicle-mounted camera may be installed in a vehicle that may become hot particularly in summer. For this reason, imaging lenses mounted on surveillance cameras, security cameras, and in-vehicle cameras not only ensure optical performance at room temperature, but also have little fluctuation in focus position even when temperature changes occur. It is required to maintain good optical performance even in high and low temperature environments. Accordingly, various imaging lenses that can be mounted on surveillance cameras, security cameras, vehicle-mounted cameras, and the like have been proposed to meet such demands (see, for example, Patent Documents 1 to 3).

JP 2010-107532 A JP 2011-257462 A Japanese Patent Laying-Open No. 2015-143796

  For example, the imaging lens described in Patent Document 1 is configured by arranging five lenses, a negative lens, a positive lens, a positive lens, a negative lens, and a positive lens, in order from the object side, and are all glass spherical lenses. Therefore, environmental resistance in a wide temperature range from low temperature to high temperature is enhanced. However, as in the imaging lens described in Patent Document 1, when all of the lenses are composed of spherical lenses, there is a problem that correction of curvature of field is particularly difficult and it is difficult to obtain a small size and good optical performance. In particular, since surveillance cameras, security cameras, in-vehicle cameras, and the like aim to increase the amount of information to be acquired, lenses that support high pixels are required, and it is difficult to obtain good optical performance. The imaging lens described in 1 is unsuitable.

  The imaging lens described in Patent Document 2 includes a negative lens, a positive lens, a negative lens, and a positive lens arranged in this order from the object side, and various aberrations such as field curvature are appropriately removed by providing an aspheric surface. Since good optical performance can be maintained, the problem of the imaging lens described in Patent Document 1 can be solved. However, since the aspherical surface is provided in the glass lens, it is expensive, and it is difficult to reduce the manufacturing cost.

  The imaging lens described in Patent Document 3 is configured by arranging, in order from the object side, a lens in which a negative lens, a positive lens, and two resin lenses are joined, and providing an aspheric surface to the resin lens, thereby providing good optical performance. Since the manufacturing cost can be reduced while maintaining the above, the problem of the imaging lens described in Patent Document 2 can be solved. However, the imaging lens described in Patent Document 3 is not preferable because the refractive power of the resin lens is not appropriate and the change in the angle of view is remarkable when the ambient temperature changes.

  In recent years, as the environmental resistance of resin lens materials has increased, it is becoming possible to use resin lenses for surveillance cameras, security cameras, in-vehicle cameras, and the like installed in places where the ambient temperature changes greatly. However, since a resin lens has a large change in refractive index and shape due to a temperature change as compared with a glass lens, a configuration in which a change in focus position during a temperature change is suppressed and optical performance is not deteriorated is required. Further, when sensing (information extraction based on the acquired image) is performed using information acquired by the imaging lens and the imaging element, there is a strong demand for no change in the angle of view of the acquired image due to a temperature change.

  The present invention eliminates the problems caused by the prior art described above, so that even when the ambient temperature changes greatly, there is little in-focus position variation and field angle variation, and a wide angle that can ensure good optical performance even at low and high temperatures. An object is to provide an inexpensive and lightweight imaging lens. It is another object of the present invention to provide an image pickup apparatus that has little in-focus position fluctuation and field angle fluctuation even when the ambient temperature changes greatly, and that can ensure good optical performance even at low and high temperatures.

In order to solve the above-described problems and achieve the object, an imaging lens according to the present invention includes a first lens having a negative refractive power and a subsequent lens group that is arranged in order from the object side and a plurality of lenses. The succeeding lens group includes at least one or more sets of resin lenses arranged adjacent to each other with an air space on the optical axis, and satisfies the following conditional expression.
(1) 30 <| frp | / f
Here, frp represents the combined focal length of any one set of resin lenses disposed in the subsequent lens group, and f represents the focal length of the entire imaging lens system.

  According to the present invention, even when the ambient temperature changes greatly, there is little fluctuation in focus position and field angle, good optical performance can be ensured even at low and high temperatures, and a wide-angle and lightweight imaging lens can be obtained at low cost. Can be provided.

  Furthermore, the imaging lens according to the present invention is characterized in that, in the invention, the first lens has a concave shape on both sides.

  According to the present invention, good optical performance can be ensured even if the diameter of the first lens is reduced.

Furthermore, the imaging lens according to the present invention is characterized in that, in the above invention, the following conditional expression is satisfied.
(2) 0.8 <| f1 | / f <2.0
Here, f1 represents the focal length of the first lens.

  According to the present invention, it is possible to reduce the diameter of the first lens and improve the optical performance.

  Furthermore, the imaging lens according to the present invention is characterized in that, in the above-described invention, a second lens having a positive refractive power is disposed on the most object side of the subsequent lens group.

  According to the present invention, it is possible to reduce the diameter of the lens subsequent to the second lens and promote the downsizing of the imaging lens.

Furthermore, the imaging lens according to the present invention is characterized in that, in the above invention, the following conditional expression is satisfied.
(3) 0.8 <f2 / f <4.0
Here, f2 represents the focal length of the second lens.

  According to the present invention, it is possible to reduce the size of an imaging lens and ensure good optical performance.

  Furthermore, the imaging lens according to the present invention is characterized in that, in the above invention, the second lens is convex on both sides.

  According to the present invention, the imaging lens can be reduced in size and optical performance can be improved.

Furthermore, the imaging lens according to the present invention is characterized in that, in the above invention, the following conditional expression is satisfied.
(4) 60.0 <ν2
(5) 10.0 <ν2-ν1
Where ν2 is the Abbe number of the second lens with respect to the d-line, and ν1 is the Abbe number of the first lens with respect to the d-line.

  According to the present invention, chromatic aberration can be favorably corrected.

Furthermore, the imaging lens according to the present invention is characterized in that, in the above invention, any one set of resin lenses arranged adjacent to each other in the subsequent lens group satisfies the following conditional expression.
(6) -2.0 <Rp1a / Rp2a <-0.5
However, Rp1a is the paraxial radius of curvature of the surface of the resin lens arranged on the object side having a strong curvature among the pair of resin lenses arranged adjacent to each other, and Rp2a is 1 arranged adjacently. The paraxial curvature radius of the surface where the curvature of the resin lens arranged on the image plane side is stronger among the pair of resin lenses is shown.

  According to the present invention, it is possible to suppress the change in the angle of view accompanying the change in the atmospheric temperature.

Furthermore, the imaging lens according to the present invention is characterized in that, in the above invention, any one set of resin lenses arranged adjacent to each other in the subsequent lens group satisfies the following conditional expression.
(7) -2.0 <Rp1b / Rp2b <-0.05
However, Rp1b is the paraxial radius of curvature of the surface of the resin lens arranged on the object side where the curvature is weaker among the pair of resin lenses arranged adjacently, and Rp2b is 1 arranged adjacently. The paraxial radius of curvature of the surface of the pair of resin lenses on which the curvature of the resin lens arranged on the image plane side is weak is shown.

  According to the present invention, it is possible to suppress the change in the angle of view accompanying the change in the atmospheric temperature.

  Furthermore, in the imaging lens according to the present invention, in any one of the above-described inventions, any one set of resin lenses disposed adjacent to each other in the subsequent lens group has an aspheric surface formed on at least one surface of each resin lens. It is characterized by that.

  According to the present invention, various aberrations can be corrected more satisfactorily.

  Furthermore, the imaging lens according to the present invention is the imaging lens according to the present invention, wherein the subsequent lens group includes, in order, a third lens having a positive refractive power and a negative lens having a negative refractive power on the image plane side of the second lens. And 4 lenses.

  According to the present invention, it is possible to reduce the size of an imaging lens and ensure good optical performance.

Furthermore, the imaging lens according to the present invention is characterized in that, in the above invention, the following conditional expression is satisfied.
(8) 0.8 <f3 / f <2.0
Here, f3 represents the focal length of the third lens.

  According to the present invention, it is possible to reduce the size of an imaging lens and ensure good optical performance.

Furthermore, the imaging lens according to the present invention is characterized in that, in the above invention, the following conditional expression is satisfied.
(9) -2.0 <f4 / f <-0.6
Here, f4 indicates the focal length of the fourth lens.

  According to the present invention, it is possible to reduce the size of an imaging lens and ensure good optical performance.

  Furthermore, the imaging lens according to the present invention is characterized in that, in the above invention, the third lens is convex on both sides.

  According to the present invention, the optical performance of the imaging lens can be improved.

  Furthermore, the imaging lens according to the present invention is characterized in that, in the invention, the fourth lens has a concave shape on both sides.

  According to the present invention, the optical performance of the imaging lens can be improved.

  An imaging apparatus according to the present invention includes the imaging lens and an imaging element that converts an image formed by the imaging lens into an electrical signal.

  According to the present invention, it is possible to provide an image pickup apparatus that has little in-focus position variation and field angle variation even when the ambient temperature changes greatly, and that can ensure good optical performance even at low and high temperatures.

  According to the present invention, even when the ambient temperature changes greatly, there is little fluctuation in focus position and angle of view, good optical performance can be secured even at low and high temperatures, and a lightweight imaging lens can be provided at low cost. There is an effect that can be. In addition, there is an effect that it is possible to provide an imaging apparatus that has little in-focus position variation and field angle variation even when the ambient temperature changes greatly, and that can ensure good optical performance even at low and high temperatures.

1 is a cross-sectional view along the optical axis showing the configuration of an imaging lens according to Example 1. FIG. FIG. 3 is a longitudinal aberration diagram of the imaging lens according to Example 1; FIG. 6 is a cross-sectional view along the optical axis showing the configuration of an imaging lens according to Example 2. 6 is a longitudinal aberration diagram of the imaging lens according to Example 2. FIG. FIG. 6 is a cross-sectional view along the optical axis showing the configuration of the imaging lens according to Example 3; 6 is a longitudinal aberration diagram of the imaging lens according to Example 3. FIG. FIG. 6 is a cross-sectional view along the optical axis showing the configuration of an imaging lens according to Example 4; FIG. 6 is a longitudinal aberration diagram of the imaging lens according to Example 4; FIG. 6 is a cross-sectional view along the optical axis showing the configuration of an imaging lens according to Example 5. FIG. 10 is a longitudinal aberration diagram of the imaging lens according to Example 5; FIG. 6 is a cross-sectional view along the optical axis showing the configuration of an imaging lens according to Example 6; FIG. 10 is a longitudinal aberration diagram of the imaging lens according to Example 6; FIG. 10 is a cross-sectional view along the optical axis showing the configuration of an imaging lens according to Example 7. FIG. 10 is a longitudinal aberration diagram of the imaging lens according to Example 7. It is a figure which shows one application example of the imaging device provided with the imaging lens concerning this invention.

  Hereinafter, preferred embodiments of an imaging lens and an imaging apparatus according to the present invention will be described in detail.

  It is an object of the present invention to provide a low-angle, lightweight imaging lens that can ensure good optical performance even at low or high temperatures, even when the ambient temperature changes greatly, at low cost. It is aimed.

  Accordingly, the imaging lens according to the present invention includes a first lens having a negative refractive power and a subsequent lens group including a plurality of lenses, which are sequentially arranged from the object side. The succeeding lens group is provided with at least one or more sets of resin lenses arranged adjacent to each other with an air space on the optical axis.

  In the imaging lens according to the present invention, the first lens arranged closest to the object side is a negative lens in order to correspond to an imaging device such as a surveillance camera, a security camera, and an in-vehicle camera aiming to expand the amount of information to be acquired. In this way, a wide angle (angle of view of about 60 to 70 °) is realized. Furthermore, it is possible to reduce the manufacturing cost and reduce the weight by providing the subsequent lens group with at least one set of resin lenses arranged adjacent to each other on the optical axis with an air gap. By placing the resin lenses next to each other, it becomes easier to cancel the refractive index change and shape change due to temperature changes compared to glass lenses, and even if the ambient temperature changes greatly, the in-focus position It is possible to suppress fluctuations and field angle fluctuations.

In particular, in the imaging lens according to the present invention, in order to suppress the change in the angle of view that occurs when the temperature changes, the composite focal length of any one set of resin lenses arranged in the subsequent lens group is assumed to be frp, assuming the above configuration. When the focal length of the entire imaging lens system is f, it is preferable that the following conditional expression is satisfied.
(1) 30 <| frp | / f

  Conditional expression (1) is an expression that defines the ratio of the combined focal length of any one set of resin lenses disposed in the subsequent lens group to the focal length of the entire imaging lens system. The imaging lens according to the present invention satisfies the conditional expression (1) based on the above configuration, so that even when the ambient temperature changes greatly, there is little fluctuation in focus position and angle of view, and even at low and high temperatures. A wide-angle and lightweight imaging lens that can ensure good optical performance can be provided at low cost.

  If the lower limit of conditional expression (1) is not reached, the combined refractive power of any one of the resin lenses arranged in the subsequent lens group becomes too strong, and the angle of view changes when the temperature changes, so that the optical This is not preferable because it causes performance degradation.

In addition, the said conditional expression (1) can anticipate a more preferable effect, if the range shown next is satisfied.
(1a) 32 <| frp | / f <80

  By satisfying the range defined by the conditional expression (1a), it is possible to more strongly suppress the field angle fluctuation that may occur at the time of temperature change, and to secure even better optical performance. If the upper limit of conditional expression (1a) is not exceeded, it is possible to prevent the convergence effect of any one set of resin lenses disposed in the subsequent lens group from being weakened, and as a result, the overall length of the imaging lens is extended. This is more preferable because it can be prevented.

  Furthermore, in the imaging lens according to the present invention, it is preferable that both surfaces of the first lens are concave. By making the first lens a biconcave shape, it is possible to disperse the negative refractive power between the object side and the image side, and to suppress the one-sided deterioration due to decentering. As a result, even if a strong negative refractive power is applied to the first lens and the diameter of the first lens is reduced, good optical performance can be ensured.

Furthermore, in the imaging lens according to the present invention, it is preferable that the following conditional expression is satisfied, where f1 is the focal length of the first lens and f is the focal length of the entire imaging lens system.
(2) 0.8 <| f1 | / f <2.0

  Conditional expression (2) defines the ratio of the focal length of the first lens to the focal length of the entire imaging lens system. By satisfying conditional expression (2), the diameter of the first lens can be reduced and the optical performance can be improved.

  If the lower limit of conditional expression (2) is not reached, the refractive power of the first lens becomes too strong, making it difficult to correct spherical aberration, and ensuring good optical performance becomes difficult. On the other hand, if the upper limit in conditional expression (2) is exceeded, the refractive power of the first lens will be too weak, and the aperture of the first lens will have to be increased to widen the angle. This is not preferable because it increases the size. Surveillance cameras, security cameras, in-vehicle cameras, and the like need to make the presence of the camera inconspicuous from the subject side, and therefore, downsizing of the apparatus is required. Therefore, an enlarged imaging lens is not preferable.

In addition, the said conditional expression (2) can anticipate a more preferable effect, if the range shown next is satisfied.
(2a) 1.2 <| f1 | / f <1.6

  Further, in the imaging lens according to the present invention, it is preferable that a second lens having a positive refractive power is disposed on the most object side of the second lens group. By disposing the second lens having positive refractive power on the most object side of the second lens group, the beam bundle from the first lens is narrowed down, the diameter of the lens following the second lens is reduced, and the imaging lens is reduced in size. Can be promoted.

Furthermore, in the imaging lens according to the present invention, it is preferable that the following conditional expression is satisfied, where f2 is the focal length of the second lens and f is the focal length of the entire imaging lens system.
(3) 0.8 <f2 / f <4.0

  Conditional expression (3) defines the ratio of the focal length of the second lens to the focal length of the entire imaging lens system. Satisfying conditional expression (3) makes it possible to reduce the size of the imaging lens and to ensure good optical performance.

  If the lower limit of conditional expression (3) is not reached, the refractive power of the second lens becomes too strong, making it difficult to correct coma and field curvature, and it becomes difficult to ensure good optical performance. Moreover, since the decentering sensitivity of the second lens is increased, the assembling property of the imaging lens is also deteriorated. On the other hand, exceeding the upper limit in conditional expression (3) is not preferable because the convergence effect of the second lens is weakened, the entire length of the imaging lens is extended, and it is difficult to reduce the size of the imaging lens.

In addition, if the said conditional expression (3) satisfies the range shown next, a more preferable effect can be anticipated.
(3a) 1.1 <f2 / f <1.7

  Furthermore, in the imaging lens according to the present invention, it is preferable that both surfaces of the second lens are convex. By making the second lens a biconvex shape, it is possible to disperse positive refractive power between the object side and the image side, suppress deterioration of spherical aberration due to decentering, and ensure good optical performance. Moreover, the total length of the imaging lens can be shortened by converging the light bundle by applying a strong positive refractive power to the second lens.

Further, in the imaging lens according to the present invention, when the Abbe number with respect to the d-line (587.56 nm) of the second lens is ν2, and the Abbe number with respect to the d-line of the first lens is ν1, the following conditional expression is satisfied. Is preferred.
(4) 60.0 <ν2
(5) 10.0 <ν2-ν1

  Conditional expression (4) defines the Abbe number with respect to the d-line of the second lens, and is an expression indicating conditions for satisfactorily correcting chromatic aberration.

  If the lower limit of conditional expression (4) is not reached, the longitudinal chromatic aberration and the lateral chromatic aberration are deteriorated, and the optical performance is deteriorated. Further, if the lower limit of conditional expression (4) is not reached, there are few glass materials for which the temperature coefficient (dn / dT) of the refractive index is negative. Therefore, the selection range of the glass materials constituting the second lens is narrowed, resulting in high costs. There is a fear. Therefore, it is preferable to select a glass material for forming the second lens and having a negative refractive index temperature coefficient that exists in a relatively large amount within the specified range of the conditional expression (4). The purpose of configuring the second lens using a glass material with a negative temperature coefficient of refractive index is to facilitate suppressing fluctuations in the in-focus position of the entire imaging lens system due to changes in the ambient temperature. (Details will be described later).

In addition, if the said conditional expression (4) satisfies the range shown next, a more preferable effect can be anticipated.
(4a) 65.0 <ν2 <96

  By satisfying the range defined by the conditional expression (4a), chromatic aberration can be corrected more favorably. Note that it is more preferable that the upper limit of the conditional expression (4a) is not exceeded because there is no possibility of the problem of excessive correction of chromatic aberration occurring.

  Conditional expression (5) defines the difference between the Abbe number of the second lens with respect to the d-line and the Abbe number of the first lens with respect to the d-line, and indicates a condition for satisfactorily correcting chromatic aberration.

  If the lower limit of conditional expression (5) is not reached, the longitudinal chromatic aberration and the lateral chromatic aberration are deteriorated and the optical performance is deteriorated.

In addition, the said conditional expression (5) can anticipate a more preferable effect, if the range shown next is satisfied.
(5a) 15.0 <ν2-ν1 <35

  By satisfying the range defined by the conditional expression (5a), chromatic aberration can be corrected more satisfactorily. Note that it is more preferable that the upper limit of the conditional expression (5a) is not exceeded because there is no possibility of the problem of excessive correction of chromatic aberration occurring.

  In the present invention, it is preferable to satisfy both conditional expressions (4) and (5) in order to suppress fluctuations in the focusing position of the entire imaging lens system due to changes in the ambient temperature. At this time, it is preferable that the temperature coefficient of the refractive index of the glass material constituting the second lens is negative and the temperature coefficient of the refractive index of the glass material constituting the first lens is positive. When the temperature coefficient of the refractive index of each glass material of the second lens and the first lens satisfies the above relationship, the refractive index change accompanying the temperature change can be offset. As a result, it is easy to obtain a clear subject image even under high temperature or low temperature environments by suppressing fluctuations in the focus position due to changes in the ambient temperature. For this reason, it becomes an imaging lens suitable also for the imaging device installed outdoors etc. where a temperature change can become large.

Furthermore, in the imaging lens according to the present invention, the paraxial curvature of the surface of the one of the resin lenses arranged adjacent to each other in the subsequent lens group that has a stronger curvature of the resin lens arranged on the object side. When the radius is Rp1a and the paraxial radius of curvature of the surface of the resin lens arranged on the image plane side having the higher curvature is Rp2a, it is preferable that the following conditional expression is satisfied.
(6) -2.0 <Rp1a / Rp2a <-0.5

  Conditional expression (6) is a paraxial radius of curvature of the surface of the resin lens arranged on the image plane side that has a strong curvature among the set of resin lenses arranged adjacent to each other in the subsequent lens group. It is a formula which prescribes the ratio of the paraxial curvature radius of the surface where the curvature of the resin lens arranged on the object side is strong. By satisfying conditional expression (6), the change in the angle of view can be suppressed by offsetting the change in the refractive power of each surface of the pair of resin lenses arranged adjacent to the subsequent lens group when the temperature changes. Can do.

  When outside the range defined in the conditional expression (6), the difference in paraxial curvature radius between the surfaces with stronger curvature is large in a pair of resin lenses arranged adjacent to each other in the subsequent lens group. As a result, the difference in the amount of change in the shape of the resin lens accompanying the change in the ambient temperature becomes remarkable, and the change in the angle of view when the temperature changes is increased. As a result, particularly when sensing is performed based on subject information, a result different from the assumed information is generated, which is not preferable.

In addition, when the conditional expression (6) satisfies the following range, a more preferable effect can be expected.
(6a) -1.5 <Rp1a / Rp2a <-0.8

Furthermore, in the imaging lens according to the present invention, the paraxial axis of the surface with the lower curvature in the resin lens arranged on the object side out of any one set of resin lenses arranged adjacent to each other in the subsequent lens group. When the radius of curvature is Rp1b and the paraxial radius of curvature of the surface of the resin lens disposed on the image plane side is Rp2b, it is preferable that the following conditional expression is satisfied.
(7) -2.0 <Rp1b / Rp2b <-0.05

  Conditional expression (7) is a paraxial radius of curvature of the surface of the resin lens arranged on the image plane side having a weaker curvature among the pair of resin lenses arranged adjacent to each other in the subsequent lens group. It is a formula which prescribes the ratio of the paraxial curvature radius of the surface where the curvature of the resin lens arranged on the object side is weak. By satisfying conditional expression (7), the change in the angle of view is suppressed by canceling out the change in the refractive power of each surface of the pair of resin lenses arranged adjacent to the subsequent lens group when the temperature changes. Can do.

  When outside the range defined in the conditional expression (7), in a pair of resin lenses arranged adjacent to each other in the succeeding lens group, the difference in paraxial curvature radius between the surfaces with weaker curvatures is different. When the temperature becomes too large, the difference in the amount of change in the shape of the resin lens accompanying the change in the ambient temperature becomes significant, and the change in the angle of view when the temperature changes becomes large. As a result, particularly when sensing is performed based on subject information, a result different from the assumed information is generated, which is not preferable.

In addition, when the conditional expression (7) satisfies the following range, a more preferable effect can be expected.
(7a) -1.5 <Rp1b / Rp2b <-0.1

  Furthermore, in the imaging lens according to the present invention, it is preferable that at least one surface of each resin lens has an aspheric surface in any one set of resin lenses arranged adjacent to each other in the subsequent lens group. By doing so, various aberrations can be corrected more satisfactorily. By forming at least one aspherical surface on the resin lens arranged on the object side among a pair of resin lenses arranged adjacent to each other in the subsequent lens group, particularly spherical aberration can be corrected well. It becomes possible. On the other hand, coma aberration can be particularly favorably corrected by forming at least one aspherical surface on the resin lens disposed on the image plane side.

  Further, in the imaging lens according to the present invention, the subsequent lens group includes, in order, a third lens having a positive refractive power and a fourth lens having a negative refractive power on the image plane side of the second lens. It is preferable to configure. By doing so, the imaging lens according to the present invention, in order from the object side, the first lens having a negative refractive power, the second lens having a positive refractive power, and the third lens having a positive refractive power. A lens and a fourth lens having a negative refractive power are arranged, and after achieving a wide angle of view of about 60 to 70 ° with a small number of lenses, good optical performance is ensured. It becomes possible.

  In the lenses constituting the subsequent lens group, good optical performance can be ensured even if the third lens is provided with a negative refractive power and the fourth lens is provided with a positive refractive power. However, as described above, it is more preferable that the third lens has a positive refractive power and the fourth lens has a negative refractive power. By applying a positive refractive power to the third lens, the positive refractive power can be dispersed by the second lens having the positive refractive power and the third lens, and even if it is a bright lens, it is a good optical element. It becomes possible to ensure performance.

Furthermore, in the imaging lens according to the present invention, it is preferable that the following conditional expression is satisfied, where f3 is the focal length of the third lens and f is the focal length of the entire imaging lens system.
(8) 0.8 <f3 / f <2.0

  Conditional expression (8) defines the ratio of the focal length of the third lens to the focal length of the entire imaging lens system. By satisfying conditional expression (8), it is possible to reduce the size of the imaging lens and ensure good optical performance.

  If the lower limit of conditional expression (8) is not reached, the refractive power of the third lens becomes too strong, making it difficult to correct spherical aberration, and it becomes difficult to ensure good optical performance. On the other hand, exceeding the upper limit in conditional expression (8) is not preferable because the convergence effect of the third lens becomes weak and the entire length of the imaging lens becomes long.

In addition, the said conditional expression (8) can anticipate a more preferable effect, if the range shown next is satisfied.
(8a) 1.2 <f3 / f <1.5

Furthermore, in the imaging lens according to the present invention, it is preferable that the following conditional expression is satisfied, where f4 is the focal length of the fourth lens and f is the focal length of the entire imaging lens system.
(9) -2.0 <f4 / f <-0.6

  Conditional expression (9) defines the ratio of the focal length of the fourth lens to the focal length of the entire imaging lens system. By satisfying conditional expression (9), it is possible to reduce the size of the imaging lens and ensure good optical performance.

  If the lower limit of conditional expression (9) is not reached, the refractive power of the fourth lens becomes too strong, making it difficult to correct curvature of field and ensuring good optical performance. On the other hand, exceeding the upper limit in conditional expression (9) is not preferable because the divergence effect of the fourth lens is weakened, and the entire length of the imaging lens has to be increased in order to ensure a desired image height.

  Furthermore, in the imaging lens according to the present invention, it is preferable that both surfaces of the third lens are convex. By making the third lens a biconvex shape, it is possible to disperse positive refracting power between the object side and the image side, suppress spherical aberration due to decentering and deterioration of one-sided blur, and improve optical performance.

  Furthermore, in the imaging lens according to the present invention, it is preferable that both surfaces of the fourth lens are concave. By making the fourth lens a biconcave shape, it is possible to disperse negative refracting power between the object side and the image side, suppress deterioration of one-sided blur due to decentering, and improve optical performance.

  As described above, the imaging lens according to the present invention has the above-described configuration and satisfies the above conditional expression, so that even when the ambient temperature changes greatly, there are few in-focus position fluctuations and field angle fluctuations. Good optical performance can be secured even at high temperatures. In addition, the use of a resin lens makes it light and inexpensive. Furthermore, high optical performance can be ensured even if the F number is reduced at a wide angle. The imaging lens of the present invention having such features is particularly suitable for a surveillance camera, a security camera, an in-vehicle camera, and the like that are used under conditions in which the ambient temperature changes significantly.

  It is another object of the present invention to provide an image pickup apparatus that has little in-focus position fluctuation and field angle fluctuation even when the ambient temperature changes greatly, and that can ensure good optical performance even at low and high temperatures. In order to achieve this object, an imaging apparatus may be configured by including an imaging lens having the above-described configuration and an imaging element that converts an image formed by the imaging lens into an electrical signal. By doing so, it is possible to realize an imaging apparatus suitable for use under a condition where the change in the ambient temperature is particularly significant.

  Hereinafter, embodiments of an imaging lens according to the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by the following examples.

FIG. 1 is a cross-sectional view along the optical axis showing the configuration of the imaging lens according to the first example. The imaging lens includes a first lens G ₁₁ having negative refractive power and a subsequent lens group GR ₁ arranged in order from the object side (not shown). The first lens G ₁₁ is composed of a biconcave lens. An optical block G is disposed between the subsequent lens group GR ₁ and the image plane IP. The optical block G corresponds to an optical filter, a face plate, a crystal low-pass filter, an infrared cut filter, or the like.

The subsequent lens group GR ₁ includes, in order from the object side, a second lens G ₁₂ having a positive refractive power, an aperture stop SP, a third lens G ₁₃ having a positive refractive power, and a first lens having a negative refractive power. a fourth lens G _14, is formed are disposed. The second lens G ₁₂ is a biconvex lens. The aperture stop SP is for limiting the light flux (light quantity) incident from the object side to the image plane IP side. The third lens G ₁₃ is a biconvex lens. The fourth lens G ₁₄ is composed of a biconcave lens. The third lens G ₁₃ and the fourth lens G ₁₄ are made of resin. The third lens G ₁₃ and the fourth lens G ₁₄ are arranged adjacent to each other with an air space on the optical axis. Further, the third lens G ₁₃ and the fourth lens G ₁₄ are each formed with an aspheric surface.

  Various numerical data related to the zoom lens according to Example 1 will be described below.

(Surface data)
r ₁ = -33.400
d ₁ = 0.600 nd ₁ = 1.5688 νd ₁ = 56.04
r ₂ = 4.830
d ₂ = 7.982
r ₃ = 6.050
d ₃ = 3.790 nd ₂ = 1.4971 νd ₂ = 81.56
r ₄ = -8.630
d ₄ = 0.150
r ₅ = ∞ (aperture stop)
d ₅ = 0.721
r ₆ = 25.000 (aspherical surface)
d ₆ = 3.190 nd ₃ = 1.5444 νd ₃ = 54.79
r ₇ = -4.339 (aspherical surface)
d ₇ = 0.384
r ₈ = -41.905 (aspherical surface)
d ₈ = 0.700 nd ₄ = 1.6397 νd ₄ = 23.53
r ₉ = 4.342 (aspherical surface)
d ₉ = 5.759
r ₁₀ = ∞
d ₁₀ = 0.800 nd ₅ = 1.5168 νd ₅ = 64.2
r ₁₁ = ∞
d ₁₁ = 0.125
r ₁₂ = ∞ (image plane)

Conical coefficient (k) and aspheric coefficient (A ₄ , A ₆ , A ₈ , A ₁₀ , A ₁₂ )
(Sixth surface)
k = 1.5469 × 10 ^-4 ,
A ₄ = -5.5335 × 10 ⁻³ , A ₆ = −1.9975 × 10 ⁻⁴ , A ₈ = −7.2714 × 10 ⁻⁵ ,
A ₁₀ = 1.1588 × 10 ⁻⁵ , A ₁₂ = −1.0882 × 10 ⁻⁶
(Seventh side)
k = 1.2651,
A ₄ = 9.2849 × 10 ⁻⁴ , A ₆ = 1.5161 × 10 ⁻⁵ , A ₈ = 9.3017 × 10 ⁻⁵ ,
A ₁₀ = -1.5837 × 10 ^-5 , A ₁₂ = 1.5942 × 10 ^-6
(8th page)
k = 1.2717 × 10 ^-4 ,
A ₄ = 1.3121 × 10 ⁻³ , A ₆ = 2.9631 × 10 ⁻⁴ , A ₈ = −3.3508 × 10 ⁻⁴ ,
A ₁₀ = 8.1224 × 10 ⁻⁵ , A ₁₂ = −6.6253 × 10 ⁻⁶
(9th page)
k = -7.4779 × 10 ^-3 ,
A ₄ = 2.8519 × 10 ⁻³ , A ₆ = 2.0695 × 10 ⁻⁴ , A ₈ = −3.8195 × 10 ⁻⁴ ,
A ₁₀ = 9.3914 × 10 ⁻⁵ , A ₁₂ = −8.5586 × 10 ⁻⁶

(Various data)
Focal length 5.4643
F number 2.4
Half angle of view (ω) 32.636
Statue height 3.15
Total lens length 24.2
Back focus (air equivalent length) 6.412

(Numerical values related to conditional expression (1))
| Frp | /f=57.37

(Numerical value related to conditional expression (2))
| F1 | /f=1.35

(Numerical values related to conditional expression (3))
f2 / f = 1.43

(Numerical values related to conditional expression (4))
ν2 = 81.56

(Numerical values related to conditional expression (5))
ν2−ν1 = 25.52

(Numerical values related to conditional expression (6))
Rp1a / Rp2a = -1.00

(Numerical values related to conditional expression (7))
Rp1b / Rp2b = -0.60

(Numerical value related to conditional expression (8))
f3 / f = 1.29

(Numerical value for conditional expression (9))
f4 / f = -1.12

  FIG. 2 is a longitudinal aberration diagram of the zoom lens according to the first example. In the spherical aberration diagram, the vertical axis represents the F number (indicated by Fno in the figure), the solid line is the d line (λ = 587.56 nm), the short broken line is the g line (λ = 435.84 nm), and the long broken line is the C line The characteristic of the wavelength corresponding to the line (λ = 656.28 nm) is shown. In the astigmatism graph, the vertical axis represents the image height (indicated by y in the figure), the solid line represents the sagittal plane (indicated by S in the figure), and the broken line represents d in the meridional plane (indicated by M in the figure). The characteristic of the wavelength corresponding to the line is shown. In the distortion diagram, the vertical axis represents the image height (indicated by y in the figure), and the solid line represents the wavelength characteristic corresponding to the d-line.

FIG. 3 is a cross-sectional view along the optical axis showing the configuration of the imaging lens according to the second example. The imaging lens includes a first lens G ₂₁ having negative refractive power and a subsequent lens group GR ₂ arranged in order from the object side (not shown). The first lens G ₂₁ is composed of a biconcave lens. An optical block G is disposed between the subsequent lens group GR ₂ and the image plane IP. The optical block G corresponds to an optical filter, a face plate, a crystal low-pass filter, an infrared cut filter, or the like.

The subsequent lens group GR ₂ includes, in order from the object side, a second lens G ₂₂ having a positive refractive power, an aperture stop SP, a third lens G ₂₃ having a positive refractive power, and a first lens having a negative refractive power. And four lenses G ₂₄ are arranged. The second lens G ₂₂ is composed of a biconvex lens. The aperture stop SP is for limiting the light flux (light quantity) incident from the object side to the image plane IP side. The third lens G ₂₃ is a biconvex lens. The fourth lens G ₂₄ is composed of a biconcave lens. The third lens G ₂₃ and the fourth lens G ₂₄ are made of resin. The third lens G ₂₃ and the fourth lens G ₂₄ are arranged adjacent to each other with an air space on the optical axis. In addition, the third lens G ₂₃ and the fourth lens G ₂₄ have an aspheric surface on either surface.

  Various numerical data related to the zoom lens according to Example 2 will be described below.

(Surface data)
r ₁ = -43.250
d ₁ = 0.850 nd ₁ = 1.5688 νd ₁ = 56.04
r ₂ = 5.430
d ₂ = 10.525
r ₃ = 5.900
d ₃ = 3.100 nd ₂ = 1.4971 νd ₂ = 81.56
r ₄ = -15.530
d ₄ = 0.150
r ₅ = ∞ (aperture stop)
d ₅ = 1.130
r ₆ = 8.568 (aspherical surface)
d ₆ = 3.180 nd ₃ = 1.5312 νd ₃ = 56.05
r ₇ = -6.231 (aspherical surface)
d ₇ = 0.178
r ₈ = -44.479 (aspherical surface)
d ₈ = 0.700 nd ₄ = 1.6355 νd ₄ = 23.91
r ₉ = 4.246 (aspherical surface)
d ₉ = 5.755
r ₁₀ = ∞
d ₁₀ = 0.800 nd ₅ = 1.5168 νd ₅ = 64.2
r ₁₁ = ∞
d ₁₁ = 0.121
r ₁₂ = ∞ (image plane)

Conical coefficient (k) and aspheric coefficient (A ₄ , A ₆ , A ₈ , A ₁₀ , A ₁₂ )
(Sixth surface)
k = 1.0047 × 10 ⁻³ ,
A ₄ = −3.0710 × 10 ⁻³ , A ₆ = −2.6848 × 10 ⁻⁴ , A ₈ = 2.0280 × 10 ⁻⁶ ,
A ₁₀ = -4.7505 × 10 ^-6 , A ₁₂ = 9.0567 × 10 ^-8
(Seventh side)
k = -1.4066 × 10 ^-3 ,
A ₄ = 1.7229 × 10 ⁻⁴ , A ₆ = −2.2191 × 10 ⁻³ , A ₈ = 3.5848 × 10 ⁻⁴ ,
A ₁₀ = -1.7068 × 10 ^-5 , A ₁₂ = -4.0588 × 10 ^-7
(8th page)
k = 6.6662 × 10 ⁻⁶ ,
A ₄ = 1.7280 × 10 ⁻³ , A ₆ = −7.99674 × 10 ⁻⁴ , A ₈ = −7.3621 × 10 ⁻⁴ ,
A ₁₀ = 2.4232 × 10 ^-4 , A ₁₂ = -2.1075 × 10 ^-5
(9th page)
k = -4.3396 × 10 ^-2 ,
A ₄ = 2.4375 × 10 ⁻³ , A ₆ = 1.0444 × 10 ⁻³ , A ₈ = −1.1384 × 10 ⁻³ ,
A ₁₀ = 2.9892 × 10 ⁻⁴ , A ₁₂ = −2.7174 × 10 ⁻⁵

(Various data)
Focal length 5.4684
F number 2.4
Half angle of view (ω) 32.65
Statue height 3.15
Total lens length 26.49
Back focus (air equivalent length) 6.404

(Numerical values related to conditional expression (1))
| Frp | /f=34.17

(Numerical value related to conditional expression (2))
| F1 | /f=1.54

(Numerical values related to conditional expression (3))
f2 / f = 1.65

(Numerical values related to conditional expression (4))
ν2 = 81.56

(Numerical values related to conditional expression (5))
ν2−ν1 = 25.52

(Numerical values related to conditional expression (6))
Rp1a / Rp2a = -1.47

(Numerical values related to conditional expression (7))
Rp1b / Rp2b = 0.19

(Numerical value related to conditional expression (8))
f3 / f = 1.34

(Numerical value for conditional expression (9))
f4 / f = -1.11

  FIG. 4 is a longitudinal aberration diagram of the zoom lens according to Example 2. In the spherical aberration diagram, the vertical axis represents the F number (indicated by Fno in the figure), the solid line is the d line (λ = 587.56 nm), the short broken line is the g line (λ = 435.84 nm), and the long broken line is the C line The characteristic of the wavelength corresponding to the line (λ = 656.28 nm) is shown. In the astigmatism graph, the vertical axis represents the image height (indicated by y in the figure), the solid line represents the sagittal plane (indicated by S in the figure), and the broken line represents d in the meridional plane (indicated by M in the figure). The characteristic of the wavelength corresponding to the line is shown. In the distortion diagram, the vertical axis represents the image height (indicated by y in the figure), and the solid line represents the wavelength characteristic corresponding to the d-line.

FIG. 5 is a cross-sectional view along the optical axis showing the configuration of the imaging lens according to the third example. The imaging lens includes a first lens G ₃₁ having negative refractive power and a subsequent lens group GR ₃ arranged in order from the object side (not shown). The first lens G ₃₁ is a biconcave lens. An optical block G is disposed between the subsequent lens group GR ₃ and the image plane IP. The optical block G corresponds to an optical filter, a face plate, a crystal low-pass filter, an infrared cut filter, or the like.

The subsequent lens group GR ₃ includes, in order from the object side, a second lens G ₃₂ having a positive refractive power, an aperture stop SP, a third lens G ₃₃ having a positive refractive power, and a first lens having a negative refractive power. a fourth lens G _34, is formed are disposed. The second lens G ₃₂ is composed of a biconvex lens. The aperture stop SP is for limiting the light flux (light quantity) incident from the object side to the image plane IP side. The third lens G ₃₃ is composed of a biconvex lens. The fourth lens G ₃₄ is composed of a biconcave lens. The third lens G ₃₃ and the fourth lens G ₃₄ are made of resin. The third lens G ₃₃ and the fourth lens G ₃₄ are arranged adjacent to each other with an air space on the optical axis. In addition, the third lens G ₃₃ and the fourth lens G ₃₄ each have an aspheric surface.

  Various numerical data relating to the zoom lens according to Example 3 will be described below.

(Surface data)
r ₁ = -33.430
d ₁ = 0.600 nd ₁ = 1.5688 νd ₁ = 56.04
r ₂ = 4.842
d ₂ = 7.941
r ₃ = 6.045
d ₃ = 3.836 nd ₂ = 1.4971 νd ₂ = 81.56
r ₄ = -8.455
d ₄ = 0.150
r ₅ = ∞ (aperture stop)
d ₅ = 0.699
r ₆ = 30.477 (aspherical surface)
d ₆ = 3.185 nd ₃ = 1.5444 νd ₃ = 54.79
r ₇ = -4.225 (aspherical surface)
d ₇ = 0.403
r ₈ = -40.049 (aspherical surface)
d ₈ = 0.700 nd ₄ = 1.6397 νd ₄ = 23.53
r ₉ = 4.363 (aspherical surface)
d ₉ = 5.853
r ₁₀ = ∞
d ₁₀ = 0.800 nd ₅ = 1.5168 νd ₅ = 64.2
r ₁₁ = ∞
d ₁₁ = 0.026
r ₁₂ = ∞ (image plane)

Conical coefficient (k) and aspheric coefficient (A ₄ , A ₆ , A ₈ , A ₁₀ , A ₁₂ )
(Sixth surface)
k = 5.6113 × 10 ^-5 ,
A ₄ = -5.7480 × 10 ⁻³ , A ₆ = −2.00839 × 10 ⁻⁴ , A ₈ = −7.00843 × 10 ⁻⁵ ,
A ₁₀ = 1.1431 × 10 ⁻⁵ , A ₁₂ = −1.0721 × 10 ⁻⁶
(Seventh side)
k = 1.1147,
A ₄ = 9.6863 × 10 ⁻⁴ , A ₆ = 1.2069 × 10 ⁻⁴ , A ₈ = 6.5798 × 10 ⁻⁵ ,
A ₁₀ = -1.2385 × 10 ^-5 , A ₁₂ = 1.3752 × 10 ^-6
(8th page)
k = -4.4878 × 10 ^-5 ,
A ₄ = 1.2444 × 10 ⁻³ , A ₆ = 4.7755 × 10 ⁻⁴ , A ₈ = −3.6257 × 10 ⁻⁴ ,
A ₁₀ = 8.2319 × 10 ⁻⁵ , A ₁₂ = −6.5960 × 10 ⁻⁶
(9th page)
k = 3.4610 × 10 ^-2 ,
A ₄ = 2.6446 × 10 ⁻³ , A ₆ = 2.8498 × 10 ⁻⁴ , A ₈ = −3.88834 × 10 ⁻⁴ ,
A ₁₀ = 9.3614 × 10 ⁻⁵ , A ₁₂ = −8.5603 × 10 ⁻⁶

(Various data)
Focal length 5.4643
F number 2.4
Half angle of view (ω) 32.636
Statue height 3.15
Total lens length 24.2
Back focus (air equivalent length) 6.407

(Numerical values related to conditional expression (1))
| Frp | /f=69.79

(Numerical value related to conditional expression (2))
| F1 | /f=1.35

(Numerical values related to conditional expression (3))
f2 / f = 1.42

(Numerical values related to conditional expression (4))
ν2 = 81.56

(Numerical values related to conditional expression (5))
ν2−ν1 = 25.52

(Numerical values related to conditional expression (6))
Rp1a / Rp2a = -0.97

(Numerical values related to conditional expression (7))
Rp1b / Rp2b = -0.76

(Numerical value related to conditional expression (8))
f3 / f = 1.29

(Numerical value for conditional expression (9))
f4 / f = -1.12

  FIG. 6 is a longitudinal aberration diagram of the zoom lens according to Example 3. In the spherical aberration diagram, the vertical axis represents the F number (indicated by Fno in the figure), the solid line is the d line (λ = 587.56 nm), the short broken line is the g line (λ = 435.84 nm), and the long broken line is the C line The characteristic of the wavelength corresponding to the line (λ = 656.28 nm) is shown. In the astigmatism graph, the vertical axis represents the image height (indicated by y in the figure), the solid line represents the sagittal plane (indicated by S in the figure), and the broken line represents d in the meridional plane (indicated by M in the figure). The characteristic of the wavelength corresponding to the line is shown. In the distortion diagram, the vertical axis represents the image height (indicated by y in the figure), and the solid line represents the wavelength characteristic corresponding to the d-line.

FIG. 7 is a cross-sectional view along the optical axis showing the configuration of the imaging lens according to the fourth example. The imaging lens includes a first lens G ₄₁ having a negative refractive power and a subsequent lens group GR _{4 in} order from the object side (not shown). The first lens G ₄₁ is composed of a biconcave lens. An optical block G is disposed between the subsequent lens group GR ₄ and the image plane IP. The optical block G corresponds to an optical filter, a face plate, a crystal low-pass filter, an infrared cut filter, or the like.

The subsequent lens group GR ₄ includes, in order from the object side, a second lens G ₄₂ having a positive refractive power, an aperture stop SP, a third lens G ₄₃ having a positive refractive power, and a first lens having a negative refractive power. a fourth lens G _44, is formed are disposed. The second lens G ₄₂ is a biconvex lens. The aperture stop SP is for limiting the light flux (light quantity) incident from the object side to the image plane IP side. The third lens G ₄₃ is a biconvex lens. The fourth lens G ₄₄ is composed of a biconcave lens. The third lens G ₄₃ and the fourth lens G ₄₄ are made of resin. The third lens G ₄₃ and the fourth lens G ₄₄ are arranged adjacent to each other with an air space on the optical axis. In addition, the third lens G ₄₃ and the fourth lens G ₄₄ each have an aspheric surface.

  Various numerical data relating to the zoom lens according to Example 4 will be described below.

(Surface data)
r ₁ = -214.700
d ₁ = 0.900 nd ₁ = 1.5688 νd ₁ = 56.04
r ₂ = 4.830
d ₂ = 9.426
r ₃ = 6.920
d ₃ = 4.000 nd ₂ = 1.5503 νd ₂ = 75.5
r ₄ = -9.640
d ₄ = 0.150
r ₅ = ∞ (aperture stop)
d ₅ = 1.027
r ₆ = 24.543 (aspherical surface)
d ₆ = 3.200 nd ₃ = 1.5444 νd ₃ = 54.79
r ₇ = -5.142 (aspherical surface)
d ₇ = 0.150
r ₈ = -245.430 (aspherical surface)
d ₈ = 0.880 nd ₄ = 1.6397 νd ₄ = 23.53
r ₉ = 4.500 (aspherical surface)
d ₉ = 5.411
r ₁₀ = ∞
d ₁₀ = 0.800 nd ₅ = 1.5168 νd ₅ = 64.2
r ₁₁ = ∞
d ₁₁ = 0.311
r ₁₂ = ∞ (image plane)

Conical coefficient (k) and aspheric coefficient (A ₄ , A ₆ , A ₈ , A ₁₀ , A ₁₂ )
(Sixth surface)
k = 0,
A ₄ = −4.99764 × 10 ⁻³ , A ₆ = −2.2736 × 10 ⁻⁴ , A ₈ = −6.9573 × 10 ⁻⁵ ,
A ₁₀ = 1.0562 × 10 ⁻⁵ , A ₁₂ = −1.0882 × 10 ⁻⁶
(Seventh side)
k = 2.2991,
A ₄ = -7.6754 × 10 ⁻³ , A ₆ = 1.4018 × 10 ⁻³ , A ₈ = −2.4462 × 10 ⁻⁵ ,
A ₁₀ = -1.2304 × 10 ^-5 , A ₁₂ = 1.5942 × 10 ^-6
(8th page)
k = -1.1813 × 10 ^-6 ,
A ₄ = -5.4771 × 10 ⁻³ , A ₆ = 5.2322 × 10 ⁻⁴ , A ₈ = −1.7533 × 10 ⁻⁴ ,
A ₁₀ = 6.3345 × 10 ⁻⁵ , A ₁₂ = −6.6253 × 10 ⁻⁶
(9th page)
k = 9.4182 × 10 ⁻³ ,
A ₄ = 3.4658 × 10 ⁻³ , A ₆ = −9.1146 × 10 ⁻⁴ , A ₈ = −7.8354 × 10 ⁻⁵ ,
A ₁₀ = 6.8723 × 10 ⁻⁵ , A ₁₂ = −8.5586 × 10 ⁻⁶

(Various data)
Focal length 5.4175
F number 2.4
Half angle of view (ω) 32.496
Statue height 3.15
Total lens length 26.26
Back focus (air equivalent length) 6.248

(Numerical values related to conditional expression (1))
| Frp | /f=60.82

(Numerical value related to conditional expression (2))
| F1 | /f=1.53

(Numerical values related to conditional expression (3))
f2 / f = 1.48

(Numerical values related to conditional expression (4))
ν2 = 75.50

(Numerical values related to conditional expression (5))
ν2−ν1 = 19.46

(Numerical values related to conditional expression (6))
Rp1a / Rp2a = -1.14

(Numerical values related to conditional expression (7))
Rp1b / Rp2b = −0.10

(Numerical value related to conditional expression (8))
f3 / f = 1.50

(Numerical value for conditional expression (9))
f4 / f = -1.27

  FIG. 8 is a longitudinal aberration diagram of the zoom lens according to Example 4; In the spherical aberration diagram, the vertical axis represents the F number (indicated by Fno in the figure), the solid line is the d line (λ = 587.56 nm), the short broken line is the g line (λ = 435.84 nm), and the long broken line is the C line The characteristic of the wavelength corresponding to the line (λ = 656.28 nm) is shown. In the astigmatism graph, the vertical axis represents the image height (indicated by y in the figure), the solid line represents the sagittal plane (indicated by S in the figure), and the broken line represents d in the meridional plane (indicated by M in the figure). The characteristic of the wavelength corresponding to the line is shown. In the distortion diagram, the vertical axis represents the image height (indicated by y in the figure), and the solid line represents the wavelength characteristic corresponding to the d-line.

FIG. 9 is a cross-sectional view along the optical axis showing the configuration of the imaging lens according to the fifth example. The imaging lens includes a first lens G ₅₁ having negative refractive power and a subsequent lens group GR ₅ arranged in order from the object side (not shown). The first lens G ₅₁ is composed of a biconcave lens. An optical block G is disposed between the subsequent lens group GR ₅ and the image plane IP. The optical block G corresponds to an optical filter, a face plate, a crystal low-pass filter, an infrared cut filter, or the like.

The subsequent lens group GR ₅ includes, in order from the object side, a second lens G ₅₂ having a positive refractive power, an aperture stop SP, a third lens G ₅₃ having a positive refractive power, and a first lens having a negative refractive power. And four lenses G ₅₄ are arranged. The second lens G ₅₂ is a biconvex lens. The aperture stop SP is for limiting the light flux (light quantity) incident from the object side to the image plane IP side. The third lens G ₅₃ is a biconvex lens. The fourth lens G ₅₄ is composed of a biconcave lens. The third lens G ₅₃ and the fourth lens G ₅₄ are made of resin. The third lens G ₅₃ and the fourth lens G ₅₄ are arranged adjacent to each other with an air space on the optical axis. In addition, the third lens G ₅₃ and the fourth lens G ₅₄ each have an aspheric surface.

  Various numerical data relating to the zoom lens according to Example 5 will be described below.

(Surface data)
r ₁ = -353.255
d ₁ = 0.870 nd ₁ = 1.5688 νd ₁ = 56.04
r ₂ = 4.435
d ₂ = 8.337
r ₃ = 5.587
d ₃ = 4.000 nd ₂ = 1.4971 νd ₂ = 81.56
r ₄ = -9.555
d ₄ = 0.150
r ₅ = ∞ (aperture stop)
d ₅ = 1.045
r ₆ = 56.339 (aspherical surface)
d ₆ = 3.200 nd ₃ = 1.5444 νd ₃ = 54.79
r ₇ = -3.971 (aspherical surface)
d ₇ = 0.150
r ₈ = -37.604 (aspherical surface)
d ₈ = 1.090 nd ₄ = 1.6397 νd ₄ = 23.53
r ₉ = 4.500 (aspherical surface)
d ₉ = 5.319
r ₁₀ = ∞
d ₁₀ = 0.800 nd ₅ = 1.5168 νd ₅ = 64.2
r ₁₁ = ∞
d ₁₁ = 0.206
r ₁₂ = ∞ (image plane)

Conical coefficient (k) and aspheric coefficient (A ₄ , A ₆ , A ₈ , A ₁₀ , A ₁₂ )
(Sixth surface)
k = 5.2325 × 10 ⁻⁷ ,
A ₄ = -5.7551 × 10 ⁻³ , A ₆ = −3.0223 × 10 ⁻⁴ , A ₈ = −7.6820 × 10 ⁻⁵ ,
A ₁₀ = 1.1293 × 10 ⁻⁵ , A ₁₂ = −1.0721 × 10 ⁻⁶
(Seventh side)
k = 8.2648 × 10 ⁻¹ ,
A ₄ = 7.9088 × 10 ⁻⁴ , A ₆ = −7.0891 × 10 ⁻⁵ , A ₈ = 1.2888 × 10 ⁻⁴ ,
A ₁₀ = -1.7393 × 10 ^-5 , A ₁₂ = 1.3752 × 10 ^-6
(8th page)
k = -9.8491 × 10 ^-6 ,
A ₄ = -4.2853 × 10 ⁻³ , A ₆ = 9.0332 × 10 ⁻⁴ , A ₈ = −3.2995 × 10 ⁻⁴ ,
A ₁₀ = 7.9621 × 10 ⁻⁵ , A ₁₂ = −6.5960 × 10 ⁻⁶
(9th page)
k = 5.4695 × 10 ^-2 ,
A ₄ = −4.0549 × 10 ⁻³ , A ₆ = 1.0037 × 10 ⁻³ , A ₈ = −4.5005 × 10 ⁻⁴ ,
A ₁₀ = 1.0148 × 10 ⁻⁴ , A ₁₂ = −8.5603 × 10 ⁻⁶

(Various data)
Focal length 5.4543
F number 2.4
Half angle of view (ω) 32.676
Statue height 3.15
Total lens length 25.16
Back focus (air equivalent length) 6.045

(Numerical values related to conditional expression (1))
| Frp | /f=51.85

(Numerical value related to conditional expression (2))
| F1 | /f=1.41

(Numerical values related to conditional expression (3))
f2 / f = 1.43

(Numerical values related to conditional expression (4))
ν2 = 81.56

(Numerical values related to conditional expression (5))
ν2−ν1 = 25.52

(Numerical values related to conditional expression (6))
Rp1a / Rp2a = -0.88

(Numerical values related to conditional expression (7))
Rp1b / Rp2b = -1.50

(Numerical value related to conditional expression (8))
f3 / f = 1.27

(Numerical value for conditional expression (9))
f4 / f = -1.14

  FIG. 10 is a longitudinal aberration diagram of the zoom lens according to Example 5. In the spherical aberration diagram, the vertical axis represents the F number (indicated by Fno in the figure), the solid line is the d line (λ = 587.56 nm), the short broken line is the g line (λ = 435.84 nm), and the long broken line is the C line The characteristic of the wavelength corresponding to the line (λ = 656.28 nm) is shown. In the astigmatism graph, the vertical axis represents the image height (indicated by y in the figure), the solid line represents the sagittal plane (indicated by S in the figure), and the broken line represents d in the meridional plane (indicated by M in the figure). The characteristic of the wavelength corresponding to the line is shown. In the distortion diagram, the vertical axis represents the image height (indicated by y in the figure), and the solid line represents the wavelength characteristic corresponding to the d-line.

FIG. 11 is a cross-sectional view along the optical axis showing the configuration of the imaging lens according to the sixth example. The imaging lens includes a first lens G ₆₁ having negative refractive power and a subsequent lens group GR ₆ arranged in order from the object side (not shown). The first lens G ₆₁ is a biconcave lens. An optical block G is disposed between the subsequent lens group GR ₆ and the image plane IP. The optical block G corresponds to an optical filter, a face plate, a crystal low-pass filter, an infrared cut filter, or the like.

The subsequent lens group GR ₆ includes, in order from the object side, a second lens G ₆₂ having a positive refractive power, an aperture stop SP, a third lens G ₆₃ having a negative refractive power, and a first lens having a positive refractive power. And four lenses G ₅₄ are arranged. The second lens _G62 is a biconvex lens. The aperture stop SP is for limiting the light flux (light quantity) incident from the object side to the image plane IP side. The third lens G ₆₃ is composed of a biconcave lens. The fourth lens G ₆₄ is a biconvex lens. The third lens G ₆₃ and the fourth lens G ₆₄ are made of resin. The third lens G ₆₃ and the fourth lens G ₆₄ are arranged adjacent to each other with an air space on the optical axis. In addition, the second lens G ₆₂ , the third lens G ₆₃ , and the fourth lens G ₆₄ each have an aspheric surface.

  Various numerical data relating to the zoom lens according to Example 6 will be described below.

(Surface data)
r ₁ = -92.771
d ₁ = 0.900 nd ₁ = 1.5688 νd ₁ = 56.04
r ₂ = 4.060
d ₂ = 7.422
r ₃ = 8.698 (aspherical surface)
d ₃ = 2.326 nd ₂ = 1.5503 νd ₂ = 75.5
r ₄ = -5.460 (aspherical surface)
d ₄ = 1.127
r ₅ = ∞ (aperture stop)
d ₅ = 2.871
r ₆ = -4.104 (aspherical surface)
d ₆ = 0.800 nd ₃ = 1.6355 νd ₃ = 23.91
r ₇ = 27.723 (aspherical surface)
d ₇ = 0.150
r ₈ = 3.531 (aspherical surface)
d ₈ = 1.954 nd ₄ = 1.5312 νd ₄ = 56.05
r ₉ = -30.796 (aspherical surface)
d ₉ = 5.235
r ₁₀ = ∞
d ₁₀ = 0.800 nd ₅ = 1.5168 νd ₅ = 64.2
r ₁₁ = ∞
d ₁₁ = 0.355
r ₁₂ = ∞ (image plane)

Conical coefficient (k) and aspheric coefficient (A ₄ , A ₆ , A ₈ , A ₁₀ , A ₁₂ )
(Third side)
k = 0,
A ₄ = -9.1032 × 10 ⁻⁴ , A ₆ = 1.4724 × 10 ⁻⁵ , A ₈ = −2.9406 × 10 ⁻⁶ ,
A ₁₀ = 8.0157 × 10 ^-8 , A ₁₂ = 0
(Fourth surface)
k = 0,
A ₄ = 1.4667 × 10 ⁻³ , A ₆ = 7.7049 × 10 ⁻⁶ , A ₈ = −4.4913 × 10 ⁻⁶ ,
A ₁₀ = 2.4527 × 10 ^-7 , A ₁₂ = 0
(Sixth surface)
k = 1.5045,
A ₄ = 4.0721 × 10 ⁻² , A ₆ = −9.7906 × 10 ⁻³ , A ₈ = 2.5670 × 10 ⁻³ ,
A ₁₀ = -3.9610 × 10 ^-4 , A ₁₂ = 2.7200 × 10 ^-5
(Seventh side)
k = 1.6000 × 10 ⁻³ ,
A ₄ = 1.8122 × 10 ⁻² , A ₆ = −4.1929 × 10 ⁻³ , A ₈ = 1.4953 × 10 ⁻³ ,
A ₁₀ = -3.0108 × 10 ^-4 , A ₁₂ = 2.1100 × 10 ^-5
(8th page)
k = 1.8123 × 10 ⁻¹ ,
A ₄ = -1.7674 × 10 ⁻² , A ₆ = 4.1438 × 10 ⁻³ , A ₈ = −4.8684 × 10 ⁻⁴ ,
A ₁₀ = 1.4479 × 10 ⁻⁵ , A ₁₂ = 4.0600 × 10 ⁻⁷
(9th page)
k = 3.3952 × 10 ⁻⁴ ,
A ₄ = 8.5219 × 10 ⁻⁴ , A ₆ = 2.1901 × 10 ⁻⁴ , A ₈ = 9.6280 × 10 ⁻⁵ ,
A ₁₀ = -6.7331 × 10 ^-6 , A ₁₂ = -9.0600 × 10 ^-8

(Various data)
Focal length 5.4599
F number 2.4
Half angle of view (ω) 32.66
Statue height 3.15
Total lens length 23.93
Back focus (air equivalent length) 6.106

(Numerical values related to conditional expression (1))
| Frp | /f=32.06

(Numerical value related to conditional expression (2))
| F1 | /f=1.25

(Numerical values related to conditional expression (3))
f2 / f = 1.19

(Numerical values related to conditional expression (4))
ν2 = 75.50

(Numerical values related to conditional expression (5))
ν2−ν1 = 19.46

(Numerical values related to conditional expression (6))
Rp1a / Rp2a = -1.16

(Numerical values related to conditional expression (7))
Rp1b / Rp2b = -0.90

  FIG. 12 is a longitudinal aberration diagram of the zoom lens according to Example 6. In the spherical aberration diagram, the vertical axis represents the F number (indicated by Fno in the figure), the solid line is the d line (λ = 587.56 nm), the short broken line is the g line (λ = 435.84 nm), and the long broken line is the C line The characteristic of the wavelength corresponding to the line (λ = 656.28 nm) is shown. In the astigmatism graph, the vertical axis represents the image height (indicated by y in the figure), the solid line represents the sagittal plane (indicated by S in the figure), and the broken line represents d in the meridional plane (indicated by M in the figure). The characteristic of the wavelength corresponding to the line is shown. In the distortion diagram, the vertical axis represents the image height (indicated by y in the figure), and the solid line represents the wavelength characteristic corresponding to the d-line.

FIG. 13 is a cross-sectional view along the optical axis showing the configuration of the imaging lens according to the seventh example. The imaging lens includes a first lens G ₇₁ having negative refractive power and a subsequent lens group GR ₇ arranged in order from the object side (not shown). The first lens G ₇₁ is composed of a biconcave lens. An optical block G is disposed between the subsequent lens group GR ₇ and the image plane IP. The optical block G corresponds to an optical filter, a face plate, a crystal low-pass filter, an infrared cut filter, or the like.

The subsequent lens group GR ₇ includes, in order from the object side, a second lens G ₇₂ having a positive refractive power, an aperture stop SP, a third lens G ₇₃ having a positive refractive power, and a first lens having a negative refractive power. A four lens G ₇₄ and a fifth lens G ₇₅ having a positive refractive power are arranged. The second lens G ₇₂ is a biconvex lens. The aperture stop SP is for limiting the light flux (light quantity) incident from the object side to the image plane IP side. The third lens G ₇₃ is a biconvex lens. The fourth lens G ₇₄ is composed of a biconcave lens. The third lens G ₇₃ and the fourth lens G ₇₄ are made of resin. The third lens G ₇₃ and the fourth lens G ₇₄ are arranged adjacent to each other with an air space on the optical axis. In addition, the third lens G ₇₃ and the fourth lens G ₇₄ are each formed with an aspheric surface.

  Various numerical data relating to the zoom lens according to Example 7 will be described below.

(Surface data)
r ₁ = -53.553
d ₁ = 0.810 nd ₁ = 1.5688 νd ₁ = 56.04
r ₂ = 4.124
d ₂ = 6.347
r ₃ = 5.913
d ₃ = 4.000 nd ₂ = 1.5503 νd ₂ = 75.5
r ₄ = -9.500
d ₄ = 0.150
r ₅ = ∞ (aperture stop)
d ₅ = 1.025
r ₆ = 16.660 (aspherical surface)
d ₆ = 3.200 nd ₃ = 1.5444 νd ₃ = 54.79
r ₇ = -4.960 (aspherical surface)
d ₇ = 0.150
r ₈ = -29.169 (aspherical surface)
d ₈ = 1.260 nd ₄ = 1.6397 νd ₄ = 23.53
r ₉ = 4.440 (aspherical surface)
d ₉ = 1.482
r ₁₀ = 47.027
d ₁₀ = 1.450 nd ₅ = 1.7292 νd ₅ = 54.67
r ₁₁ = -87.850
d ₁₁ = 2.600
r ₁₂ = ∞
d ₁₂ = 0.800 nd ₆ = 1.5168 νd ₆ = 64.2
r ₁₃ = ∞
d ₁₃ = 0.200
r ₁₄ = ∞ (image plane)

Conical coefficient (k) and aspheric coefficient (A ₄ , A ₆ , A ₈ , A ₁₀ , A ₁₂ )
(Sixth surface)
k = -3.9026 × 10 ^-3 ,
A ₄ = -4.5376 × 10 ^-3 , A ₆ = -1.9531 × 10 ^-4 , A ₈ = -9.8210 × 10 ^-5 ,
A ₁₀ = 9.9237 × 10 ^-6 , A ₁₂ = -1.1086 × 10 ^-6
(Seventh side)
k = 1.9240,
A ₄ = -5.7426 × 10 ⁻³ , A ₆ = 2.6955 × 10 ⁻⁴ , A ₈ = 1.6797 × 10 ⁻⁴ ,
A ₁₀ = -2.4889 × 10 ^-5 , A ₁₂ = 1.5752 × 10 ^-6
(8th page)
k = -2.5113 × 10 ^-3 ,
A ₄ = −9.0937 × 10 ⁻³ , A ₆ = 5.1726 × 10 ⁻⁴ , A ₈ = −1.7759 × 10 ⁻⁴ ,
A ₁₀ = 7.7173 × 10 ⁻⁵ , A ₁₂ = −7.8433 × 10 ⁻⁶
(9th page)
k = -9.8109 × 10 ^-4 ,
A ₄ = -3.3059 × 10 ⁻³ , A ₆ = 6.3848 × 10 ⁻⁴ , A ₈ = −4.4088 × 10 ⁻⁴ ,
A ₁₀ = 1.1927 × 10 ⁻⁴ , A ₁₂ = −1.0745 × 10 ⁻⁵

(Various data)
Focal length 5.4565
F number 2.4
Half angle of view (ω) 32.684
Statue height 3.15
Total lens length 23.48
Back focus (air equivalent length) 3.327

(Numerical values related to conditional expression (1))
| Frp | /f=49.91

(Numerical value related to conditional expression (2))
| F1 | /f=1.23

(Numerical values related to conditional expression (3))
f2 / f = 1.34

(Numerical values related to conditional expression (4))
ν2 = 75.50

(Numerical values related to conditional expression (5))
ν2−ν1 = 19.46

(Numerical values related to conditional expression (6))
Rp1a / Rp2a = -1.12

(Numerical values related to conditional expression (7))
Rp1b / Rp2b = -0.57

(Numerical value related to conditional expression (8))
f3 / f = 1.36

(Numerical value for conditional expression (9))
f4 / f = -1.09

  FIG. 14 is a longitudinal aberration diagram of the zoom lens according to Example 7. In the spherical aberration diagram, the vertical axis represents the F number (indicated by FNO in the figure), the solid line is the d line (λ = 587.56 nm), the short broken line is the g line (λ = 435.84 nm), and the long broken line is the C line The characteristic of the wavelength corresponding to the line (λ = 656.28 nm) is shown. In the astigmatism graph, the vertical axis represents the image height (indicated by y in the figure), the solid line represents the sagittal plane (indicated by S in the figure), and the broken line represents d in the meridional plane (indicated by M in the figure). The characteristic of the wavelength corresponding to the line is shown. In the distortion diagram, the vertical axis represents the image height (indicated by y in the figure), and the solid line represents the wavelength characteristic corresponding to the d-line.

In the numerical data in each of the above embodiments, r ₁ , r ₂ ,... Are the radii of curvature of the lens and aperture stop surface, and d ₁ , d ₂ ,. thickness or their surface separations, nd _1, nd _2, the refractive index with respect to ... the d-line, such as a lens _{(λ = 587.56nm), νd 1} , νd 2, d like ... lens The Abbe number for the line (λ = 587.56 nm) is shown. The unit of length is all “mm”, and the unit of angle is “°”.

In addition, each of the above aspheric shapes has a depth of the aspheric surface Z, a curvature c (1 / r), a height from the optical axis h, a cone coefficient k, 4th order, 6th order, 8th order, 10th order. When the next and twelfth aspherical coefficients are A ₄ , A ₆ , A ₈ , A ₁₀ , and A ₁₂ , respectively, and the light traveling direction is positive, they are expressed by the following equations.

  As described above, the imaging lenses of the above embodiments satisfy the above conditional expressions, so that there are few in-focus position fluctuations and field angle fluctuations even when the ambient temperature changes greatly, even at low or high temperatures. Good optical performance can be secured. Therefore, the imaging lens can be used without any problem for a surveillance camera installed outdoors where the temperature change is remarkable, a security camera, an in-vehicle camera provided in a vehicle that tends to be hot in summer, and the like. In addition, the use of a resin lens makes it light and inexpensive. Furthermore, high optical performance can be ensured even if the F number is reduced at a wide angle. The aberration correction capability can be improved by arranging a lens with an appropriately aspherical surface.

<Application example>
Hereinafter, the example which applied the imaging lens shown in Examples 1-7 of the present invention to an imaging device is shown. FIG. 15 is a diagram illustrating an application example of an imaging apparatus including the imaging lens according to the present invention. As illustrated in FIG. 15, the imaging device 200 includes an imaging lens 100 and a solid-state imaging device 201. The imaging lens 100 is shown in Examples 1-7.

  In the imaging apparatus 200 including the imaging lens 100 and the solid-state imaging element 201, the image plane IP shown in the first to seventh embodiments corresponds to the imaging plane 202 of the solid-state imaging element 201. As the solid-state imaging device 201, for example, a photoelectric conversion device such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) sensor can be used.

  In the imaging apparatus 200, light incident from the object side of the imaging lens 100 finally forms an image on the imaging surface 202 of the solid-state imaging device 201. Then, the light received by the solid-state image sensor 201 is photoelectrically converted and output as an electrical signal. This output signal is processed by a signal processing circuit (not shown) to generate a digital image corresponding to the image of the subject. The digital image can be recorded on a recording medium such as an HDD (Hard Disk Device), a memory card, an optical disk, or a magnetic tape. In addition, when the imaging device 200 is a silver salt film camera, the imaging surface 202 corresponds to a film surface.

  As described above, by providing the imaging lens 100, the imaging device 200 is realized that has little in-focus position variation and field angle variation even when the ambient temperature changes greatly, and can ensure good optical performance even at low and high temperatures. can do.

  As described above, the imaging lens according to the present invention is useful for imaging devices that require high optical performance in a wide temperature range from low temperature to high temperature, and is particularly useful for surveillance cameras, security cameras, in-vehicle cameras, and the like. Is suitable.

_{G 11, G 21, G 31} , G 41, G 51, G 61, G 71 first lens _{G 12, G 22, G 32} , G 42, G 52, G 62, G 72 second lens G _13, G _{23, G 33, G 43,} G 53, G 63, G 73 third lens _{G 14, G 24, G 34} , G 44, G 54, G 64, G 74 fourth lens G ₇₅ fifth lens GR _1, GR ₂ , GR ₃ , GR ₄ , GR ₅ , GR ₆ , GR ₇ Subsequent lens group SP Aperture stop G Optical block IP Image surface 100 Imaging lens 200 Imaging device 201 Solid-state imaging device 202 Imaging surface

Claims (12)

A first lens having negative refractive power, arranged in order from the object side, and a subsequent lens group composed of a plurality of lenses,
The first lens is concave on both sides,
The subsequent lens group has a set of resin lenses arranged adjacent to each other with an air interval on the optical axis, and is composed of three or four lenses.
The subsequent lens group includes a second lens having a positive refractive power, a third lens having a positive refractive power, and a fourth lens having a negative refractive power, which are arranged in order from the object side.
An imaging lens characterized by satisfying the following conditional expression:
(1) | frp | / f> 30
Here, frp represents the combined focal length of the set of resin lenses, and f represents the focal length of the entire imaging lens system. The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
(3) 0.8 <f2 / f <4.0
Here, f2 represents the focal length of the second lens.   The imaging lens according to claim 1, wherein both surfaces of the second lens are convex. The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
(4) 60.0 <ν2
(5) 10.0 <ν2-ν1
Where ν2 is the Abbe number of the second lens with respect to the d-line, and ν1 is the Abbe number of the first lens with respect to the d-line. The imaging lens according to claim 1, wherein the one set of resin lenses satisfies a conditional expression shown below.
(6) -2.0 <Rp1a / Rp2a <-0.5
However, Rp1a is a paraxial radius of curvature of the surface of the resin lens arranged on the object side having a higher curvature among the set of resin lenses, and Rp2a is arranged on the image plane side of the set of resin lenses. The paraxial curvature radius of the surface with the stronger curvature of the resin lens made is shown. The imaging lens according to claim 1, wherein the set of resin lenses satisfies the following conditional expression.
(7) -2.0 <Rp1b / Rp2b <-0.05
Where Rp1b is a paraxial radius of curvature of the surface of the resin lens disposed on the object side of the one set of resin lenses, and Rp2b is disposed on the image surface side of the set of resin lenses. The paraxial curvature radius of the surface with the weaker curvature of the resin lens is shown.   The imaging lens according to claim 1, wherein the one set of resin lenses has an aspheric surface formed on at least one surface of each resin lens. The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
(8) 0.8 <f3 / f <2.0
Here, f3 represents the focal length of the third lens. The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
(9) -2.0 <f4 / f <-0.6
Here, f4 indicates the focal length of the fourth lens.   The imaging lens according to claim 1, wherein both surfaces of the third lens are convex.   The imaging lens according to claim 1, wherein the fourth lens has a concave shape on both sides.   An imaging apparatus comprising: the imaging lens according to claim 1; and an imaging element that converts an image formed by the imaging lens into an electrical signal.

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