JP2007065374A - Imaging lens and imaging module having same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging lens in which various aberrations are satisfactorily corrected by a four-lens configuration even though its size is small, and to provide an imaging module having the imaging lens. <P>SOLUTION: The imaging lens 20 includes in order from the object side along an optical axis X: a diaphragm S; a first lens 11 with positive refracting power, the convex face of which is directed in the direction of the object side; a second lens 12 with positive refracting power, the concave face of which is directed in the direction of the object side; a third lens 13 with negative refracting power, the concave face of which is directed in the direction of the object side; and a fourth lens 14 with positive refracting power, the convex face of which is directed in the direction of the object side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a four-lens imaging lens suitable for an optical system of a solid-state imaging device or the like, for example, a CCD (Charge Coupled Device) type image sensor or a C-MOS (Complementary Metal Oxide Semiconductor) type image sensor. It is related with the imaging module provided with.

  In recent years, various image pickup apparatuses using a solid-state image pickup device such as a C-MOS sensor and a CCD have become widespread as an image pickup device. With the development of CCD manufacturing technology, the size of one pixel is reduced and the number of pixels is 300. High-density CCDs reaching the order of 10,000 to 5,000,000 are being used. Accordingly, high-resolution and high-performance imaging lenses for CCD cameras are demanded.

  In addition, imaging devices using these C-MOS sensors and CCDs are being mounted on mobile phones, personal computers, and the like due to higher performance and smaller size. With the downsizing of these mobile phones and personal computers or the increase in density due to the increase in functions, there is a demand for further downsizing of the imaging lens mounted on the imaging device in order to reduce the size of these imaging devices. Is growing.

  2. Description of the Related Art Conventionally, there is an imaging lens that can meet these demands, in which the number of lenses is one or two. However, since there are not enough refracting surfaces, axial chromatic aberration and curvature of field are not compatible, and high performance cannot be expected. Further, if this problem is to be avoided by taking an aspherical shape, the eccentricity sensitivity becomes large and it is difficult to manufacture.

  For this reason, it is desirable to use three or more lenses to satisfy high performance. However, even if it is composed of three sheets, there is a performance limit. For example, when used in a high pixel CCD camera of about 3 million pixels, the performance may be insufficient even if aspherical surfaces are used extensively.

Therefore, it is conceivable that the triplet is further increased by one and configured by four. As a lens type constituted by four lenses, a type in which positive, positive, negative, positive and lenses are arranged is known. For example, an imaging lens described in Patent Document 1 is known as one that meets such a demand. This lens is an imaging lens having a four-group four-lens configuration in which a diaphragm is provided between the second and third lenses.
JP 2004-302057 A

  However, although the imaging lens described in Patent Document 1 corrects various aberrations, particularly spherical aberration and astigmatism, the F number (F value) is dark, the overall length is large, and miniaturization can be achieved. There wasn't. Further, even in an imaging module including such an imaging lens, there is a problem that high performance cannot be realized and miniaturization becomes difficult.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an imaging lens in which various aberrations are favorably corrected by a four-lens configuration while having a small size, and an imaging module including the imaging lens. To do.

In order to achieve the above object, an imaging lens according to the first aspect of the present invention provides:
In order from the object side, the aperture, the first lens having a positive refractive power with the convex surface facing the object side, the second lens having the positive refractive power with the concave surface facing the object side, and the concave surface facing the object side An imaging lens in which a third lens having negative refractive power and a fourth lens having positive refractive power with a convex surface facing the object side are disposed,
The distance on the optical axis from the stop to the imaging surface is TL, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, and the fourth lens has a focal length of f3. The focal length is f4, the distance on the optical axis between the second lens and the third lens is D4, the distance on the optical axis between the third lens and the fourth lens is D6, and the Abbe number of the first lens is ν1. When the Abbe number of the second lens is ν2 and the focal length of the imaging lens is f, the following conditional expressions (1) to (8) are satisfied.
1.8 <f1 / f <2.5 (1)
0.2 <f2 / f <0.4 (2)
0.1 <| f3 | / f <0.5 (3)
0.3 <f4 / f <2 (4)
f / TL <0.7 (5)
0 <D4 / f <0.1 (6)
0 <D6 / f <0.1 (7)
0 ≦ ν1-ν2 (8)

  Further, any of the second lens, the third lens, and the fourth lens may have an aspheric surface on at least one surface.

  The first lens may be made of a glass material or a plastic material, and the second lens, the third lens, and the fourth lens may be made of a plastic material.

Further, the following conditional expression (9) may be satisfied.
0 degrees ≤ αi <30 degrees (9)
Where αi is the incident angle of the principal ray on the image plane at the maximum image height.

  An imaging module according to a second aspect of the present invention includes the imaging lens.

  A sector capable of controlling the amount of light incident on the imaging lens may be disposed on the object side of the stop.

  According to the present invention, it is possible to provide an imaging lens having a good telecentric characteristic and a good correction of various aberrations and an imaging module including the imaging lens with a four-lens configuration despite being small in size.

  An imaging lens according to an embodiment of the present invention and an imaging module including the imaging lens will be described below with reference to the drawings. In FIG. 1 to FIG. 3 showing the configuration example of the imaging module 1 according to the embodiment of the present invention, Ri (i = 1 to 10) is the optical axis X of the i-th lens in order from the object side. The upper radius of curvature is represented, and Di (i = 1 to 10) represents the thickness of the lens on the i-th optical axis X or the distance between the lenses in order from the object side.

  As shown in FIGS. 1 to 3, the imaging module 1 includes a lens 10, a diaphragm S, a shutter 15, a parallel plate glass 16, and a solid-state imaging device 17 in a case (not shown). . The imaging lens 20 is configured by the lens 10 and the diaphragm S.

  A lens 10 that collects an optical image of a subject has a first lens 11 having a positive refractive power with a convex surface directed toward the object side and a concave surface directed toward the object side along the optical axis X in order from the object side. A second lens 12 having positive refractive power, a third lens 13 having negative refractive power with a concave surface facing the object side, and a fourth lens 14 having positive refractive power with a convex surface facing the object side are disposed. The structure is adopted.

  As described above, the basic configuration of the lens 10 includes the positive first lens 11, the positive second lens 12, the negative third lens 13, and the positive fourth lens 14, and one lens is included in the triplet lens configuration. The configuration is added. By adopting such a configuration, an appropriate back focus and a thin imaging lens 20 in which the entire length of the lens 10 is short are obtained.

  As for the number of lenses 10, as a result of considering that performance is given top priority and miniaturization is also given top priority, four lenses are formed.

  If the number of lenses 10 is two or less, it is difficult to reduce the curvature of field, and the peripheral performance deteriorates. Obviously, the performance is further improved if the number of lenses 10 is three or more. In order to improve the peripheral performance while demanding a reduction in the size of the lens 10, the minimum number of lenses that can reduce field curvature and distortion is set to four.

  All of the second lens 12, the third lens 13, and the fourth lens 14 constituting the lens 10 have an aspherical surface on at least one surface (at least one of the object side and the image surface side). Desirably configured.

  The positive first lens 11 is a spherical surface, the second lens 12 is an aspherical surface having a positive refractive power, the third lens 13 is an aspherical surface having a negative refractive power, and By using an aspherical surface having positive refractive power for the fourth lens 14, various aberrations, particularly astigmatism and distortion, are corrected, and the total length of the lens system is shortened. The imaging lens 20 whose incident angle to the imaging surface is 30 degrees or less can be obtained.

  Further, by adopting an aspherical surface for the third lens 13 having negative refractive power, and appropriately arranging the distance between the second lens 12 and the third lens 13 and the distance between the third lens 13 and the fourth lens 14, It is possible to correct various aberrations (coma aberration, astigmatism correction and distortion aberration) at the periphery of the screen away from the optical axis X by utilizing the difference in passing height between the axial ray and the peripheral ray. it can.

  Further, it is desirable that the first lens 11 constituting the lens 10 is made of a glass material, and the second lens 12, the third lens 13 and the fourth lens 14 are all made of a plastic material. The lens 10 composed of a glass material and a plastic material includes those in which the surface of the plastic material is subjected to a coating treatment for the purpose of preventing reflection and improving the surface hardness. The lens 10 is a small lens. In the production of a small lens, a plastic material can use a manufacturing method such as injection molding rather than a glass material, and is suitable for mass production. Plastic lenses are suitable for mass production with reduced manufacturing costs.

  The diaphragm S adjusts the amount of subject light reaching the imaging surface of the solid-state imaging device 17. The diaphragm S is disposed on the object side of the lens 10. That is, the imaging lens 20 is arranged with an aperture S, a first lens 11, a second lens 12, a third lens 13, and a fourth lens 14 in order from the object side.

  In the imaging lens 20, since the stop S is disposed on the most object side, the incident angle to the solid-state imaging device 17 becomes small. In other words, when the stop S is disposed closest to the object side, the distance from the imaging plane to the exit pupil position can be made longer than in the case of the middle stop type in which a stop is provided between the lenses. When the exit pupil is far from the image pickup surface, the principal ray of the light beam emitted from the final surface of the lens 10 enters the solid-state image pickup device 17 at an angle close to the vertical, that is, the telecentric characteristic can be ensured well, and the peripheral portion of the screen Can reduce the shading phenomenon.

  In addition, since the aperture stop S is disposed in front of the first lens 11 close to the object side, it is difficult to correct peripheral performance, particularly chromatic aberration of magnification and distortion, and the positive first lens 11 is positive. The power of the second lens 12, the negative third lens 13, and the positive fourth lens 14 are arranged, and the respective lenses are arranged at a distance that can satisfactorily correct the central performance and the peripheral performance. Have good.

The imaging lens 20 is configured to satisfy the following conditional expressions (1) to (8).
1.8 <f1 / f <2.5 (1)
0.2 <f2 / f <0.4 (2)
0.1 <| f3 | / f <0.5 (3)
0.3 <f4 / f <2 (4)
f / TL <0.7 (5)
0 <D4 / f <0.1 (6)
0 <D6 / f <0.1 (7)
0 ≦ ν1-ν2 (8)
However,
f: Focal length of the entire imaging lens 20 TL: Distance on the optical axis X from the diaphragm S to the imaging surface (axial thickness from the diaphragm S to the imaging surface)
f1: Focal length of the first lens 11 f2: Focal length of the second lens 12 f3: Focal length of the third lens 13 f4: Focal length of the fourth lens D4: Optical axes of the second lens 12 and the third lens 13 A distance D6 on X: a distance ν1: an Abbe number of the first lens 11 ν2: an Abbe number of the second lens 12 on the optical axis X of the third lens 13 and the fourth lens 14.

  Conditional expressions (1), (2), and (3) define an optimum refractive power distribution for obtaining good optical performance for the imaging lens 20 configured with a small number of lenses.

  The basic features of the lens configuration of the photographic lens 20 of the present embodiment are that the first lens 11 having a large positive power, the second lens 12 having a relatively small positive power, and the subsequent relatively large negative power. The third lens 13 and the fourth lens 14 having the largest positive power on the image plane side, and having a so-called telephoto type power arrangement preceded by positive, positive, negative, positive and positive powers. It is.

  Furthermore, in order to correct chromatic aberration, the first lens 11, the second lens 12, and the third lens 13 having large power are mainly subjected to achromatic color. Accordingly, the first lens 11 and the second lens 12 mainly correct spherical aberration, coma aberration, and chromatic aberration near the optical axis X, and the fourth lens 14 corrects distortion aberration that is mainly off-axis aberration. In addition, the telecentricity is kept good.

  Further, if the refractive power of the first lens 11 and the second lens 12 is too large, the correction of astigmatism is too under, and the negative refractive power of the third lens 13 corresponding to that is required. Therefore, the lens of the present embodiment regulates the refractive power conditions of the conditional expressions (1) to (3).

  Conditional expression (1) defines the power of the first lens 11. If the upper limit of conditional expression (1) is exceeded, the power of the first lens 11 becomes small, so that the total length of the lens system becomes large and the compactness is impaired, and the coma of the light ray becomes large and the performance deteriorates. If the lower limit value of conditional expression (1) is not reached, the power of the first lens 11 increases, and coma aberration, spherical aberration, and chromatic aberration of the upper ray increase, and the performance deteriorates.

  Conditional expression (2) defines the power of the second lens 12 for balancing with the power of the positive first lens 11. When the upper limit of conditional expression (2) is exceeded, the positive refractive power of the second lens 12 becomes weak, and it becomes impossible to balance the refractive power of the positive first lens 11, and chromatic aberration and magnification on the optical axis X Chromatic aberration is worsened. In addition, the incident angle on the imaging surface is too large. If the lower limit of conditional expression (2) is not reached, the power of the positive first lens 11 becomes too strong, so that the chromatic aberration and the chromatic aberration of magnification on the optical axis X are deteriorated. In addition, a large curvature of field is not preferable. Furthermore, since chromatic aberration of magnification occurs, peripheral performance deteriorates.

  Conditional expression (3) defines the negative power of the third lens 13. It is necessary to correct aberration generated in the positive lens of the first lens 11 and the second lens 12 with the power of the negative third lens 13. When the negative power of the third lens 13 is increased, it becomes excessive with respect to the correction effect of the negative lens, so that the performance deteriorates. For this reason, it is preferable that the negative power of the third lens 13 be relatively weak. Therefore, it is preferable to satisfy the conditional expression (3).

  If the upper limit value of the conditional expression (3) is exceeded, the balance of aberration correction for on-axis aberration and off-axis aberration is lost, and correction of off-axis aberration cannot be performed satisfactorily. On the other hand, if the lower limit value of conditional expression (3) is not reached, the total length becomes longer, the beam height of the peripheral luminous flux becomes higher, the astigmatism becomes insufficiently corrected, and the peripheral performance deteriorates. Further, the incident angle to the solid-state imaging device 17 becomes large, and it is not preferable because it becomes difficult to ensure the telecentric characteristics on the image plane side.

  Conditional expression (4) defines the power of the fourth lens 14. Since this lens adopts a configuration in which one lens is added to the triplet type, if the balance with the negative power of the third lens 13 is lost, the total length of the imaging optical system increases or the performance deteriorates. That is, if the upper limit value of conditional expression (4) is exceeded, the power of the positive fourth lens 14 becomes too weak and the angle of incidence on the solid-state imaging device 17 becomes large, and coma and astigmatism corrections are made. Becomes insufficient. Further, it is disadvantageous for shortening the overall length of the imaging optical system. On the other hand, if the lower limit value of the conditional expression (4) is not reached, the power of the fourth lens 14 becomes too strong, and accordingly, the negative power of the third lens 13 must be made strong. As a result, the aberration generated in each lens increases, and in particular, correction of coma and astigmatism becomes excessive, making it difficult to ensure performance.

  Conditional expression (5) defines the total length of the lens system. If the upper limit of conditional expression (5) is exceeded, the total lens length becomes large, making it impossible to achieve compactness. Therefore, according to the configuration satisfying the conditional expression (5), the imaging lens 20 can be easily reduced in size and thickness.

  Conditional expression (6) is a conditional expression for defining the distance between the second lens 12 and the third lens 13. If the upper limit value of the conditional expression (6) is exceeded, the aberration correction balance between the on-axis aberration and the off-axis aberration is lost, and the off-axis aberration cannot be corrected satisfactorily. On the other hand, if the lower limit value of conditional expression (6) is not reached, curvature of field is greatly generated, and astigmatism is insufficiently corrected, so that peripheral performance is deteriorated.

  Conditional expression (7) is a conditional expression for defining the distance between the third lens 13 and the fourth lens 14. If the upper limit value of the conditional expression (7) is exceeded, the aberration correction balance between the on-axis aberration and the off-axis aberration is lost, and the off-axis aberration cannot be corrected satisfactorily. On the other hand, if the lower limit value of conditional expression (7) is not reached, curvature of field greatly occurs and astigmatism becomes insufficiently corrected, so that the peripheral performance is deteriorated.

  Conditional expression (8) defines the Abbe number of the material constituting the positive first lens 11 and the positive second lens 12. By satisfying the conditional expression (8), it is possible to correct the chromatic aberration on the optical axis X and the chromatic aberration of magnification.

  Further, the imaging lens 20 may be configured to satisfy the following expression (9).

0 degrees ≤ αi <30 degrees (9)
Here, αi is the incident angle of the principal ray on the imaging surface at the maximum image height.

  In the imaging lens 20 of the present embodiment, when a CCD or the like is used for the solid-state imaging device 17, if the off-axis light beam emitted from the imaging optical system is incident on the imaging surface at a large angle, the center of the image and the periphery of the image The brightness of the image changes at the part. If the incident angle with respect to the imaging surface is small, this problem is reduced, but the total length of the optical system is increased. Therefore, it is preferable that the conditional expression (9) is satisfied.

  The shutter 15 includes a shutter substrate 152 having an opening 151 and a sector 153 that can be moved back and forth so as to open and close the opening 151 by an actuator (not shown). The amount of light incident on the imaging lens 20 can be controlled by moving the sector 153 back and forth to adjust the opening diameter of the opening 151. The shutter 15 is disposed on the object side of the first lens 11 (the object side of the diaphragm S). If the shutter 15 is arranged on the object side of the first lens 11 in this way, the entire imaging lens 20 system and the mechanism of the shutter 15 can be configured separately, so that the imaging module 1 can be easily assembled. In addition, the imaging module 1 can be configured more compactly.

  The parallel flat glass 16 corresponds to a filter or a glass block. The parallel flat glass 16 is disposed on the image plane side of the fourth lens 14. The solid-state imaging device 17 captures a subject image formed by the imaging lens 20 and converts it into an electrical signal. The solid-state image sensor 17 is constituted by, for example, a CCD image sensor, a CMOS image sensor, or the like. The solid-state image sensor 17 is electrically connected to and held by a substrate (not shown).

  As described above, in the imaging lens of the present embodiment and the imaging module including the imaging lens, the diaphragm S is disposed on the object side of the first lens 11, the aspherical lens is used for the second to fourth lenses, and the power distribution and surface By appropriately setting the shape, it is possible to achieve a high performance such as a bright F-number, and to make the lens system itself compact, with a simple lens configuration with a small number of lenses.

  In the present embodiment, the distance (height) from the stop S to the imaging surface of the solid-state imaging device 17 can be reduced to about 8 mm or less, so that downsizing, weight reduction, and high-quality imaging are possible. It is possible to realize mobile devices such as portable terminals.

Hereinafter, the configuration of the imaging lens 20 embodying the present invention and the imaging module 1 including the imaging lens 20 will be described more specifically with reference to construction data and aberration diagrams. In addition, the structure of the imaging lens 20 and the imaging module 1 is not limited to a present Example. Here, symbols used in each example and not described in the above embodiment are as follows.
F: F number TL: Total length of the imaging lens 20 Nd: Refractive index νd of each lens etc. dd: Abbe number of each lens etc.

In each embodiment, the shape of the aspheric surface is represented by the following aspheric expression (9) in an orthogonal coordinate system in which the vertex of the surface is the origin and the optical axis direction is the X axis.
Z = C × h ² / {1+ (1−K × C ² × h ² ) ^1/2 } + A ₄ h ⁴ + A ₆ h ⁶ + A ₈ h ⁸ + A ₁₀ h ¹⁰ +... + A _2n h ^2n. (10)
here,
Z: length of perpendicular line drawn from the point on the aspherical surface at a height h from the optical axis X to the tangent plane of the aspherical vertex (plane perpendicular to the optical axis X) C: reciprocal of the paraxial radius of curvature R of the aspherical surface h: Height from optical axis X K: Eccentricity n: Natural number greater than or equal to 2 A ₄ , A ₆ , A ₈ , A ₁₀ ,..., A _2n : _4th , ₆ , ₈ , ₁₀ ,. Aspheric coefficient

  The configuration examples of the imaging lens 20 and the imaging module 1 shown in FIGS. 1 to 3 in the above embodiment correspond to the configuration examples of the imaging lens 20 and the imaging module 1 according to Examples 1 to 3, respectively.

Example 1
Table 1 shows the construction data of Example 1.

  Table 2 shows the aspheric coefficient and the eccentricity for Example 1.

  FIG. 4 shows the aberration performance (spherical aberration, astigmatism, distortion) of the imaging lens 20 according to Example 1 shown in Table 1. Each figure represents aberrations with respect to d-line and F-line.

  FIG. 4 shows that the imaging lens 20 according to Example 1 has good optical performance.

  In addition, as will be described later, this example satisfies the conditional expressions (1) to (8).

(Example 2)
Table 3 shows the construction data of Example 2.

  Table 4 shows the aspheric coefficient and the eccentricity for Example 2.

  FIG. 5 shows the aberration performance (spherical aberration, astigmatism, distortion) of the imaging lens 20 according to Example 2 shown in Table 2. Each figure represents aberrations with respect to d-line and F-line.

  FIG. 5 shows that the imaging lens 20 according to Example 2 has good optical performance.

  In addition, as will be described later, this example satisfies the conditional expressions (1) to (8).

(Example 3)
Table 5 shows the construction data of Example 3.

  Table 6 shows the aspheric coefficient and the eccentricity for Example 3.

  FIG. 6 shows the aberration performance (spherical aberration, astigmatism, distortion) of the imaging lens 20 according to Example 3 shown in Table 3. Each figure represents aberrations with respect to d-line and F-line.

  FIG. 6 shows that the imaging lens 20 according to Example 3 has good optical performance.

  In addition, as will be described later, this example satisfies the conditional expressions (1) to (8).

  Table 7 shows values corresponding to the conditional expressions (1) to (8) in the imaging lens 20 of each of the first to third embodiments.

  Each of Examples 1 to 3 satisfies all the conditional expressions (1) to (8).

  While the present invention has been described with reference to the embodiment and each example, the present invention is not limited to the above embodiment and each example, and various modifications can be made. For example, in the said embodiment and each Example, although the example which provides the parallel plate glass 16 was demonstrated, the parallel plate glass 16 does not necessarily need to be provided. In the above-described embodiment and each example, an example in which the shutter 15 and the diaphragm S are separately provided has been described. However, the opening 151 of the shutter 15 may have the same diameter as the opening of the diaphragm S, and the opening 151 may be the diaphragm. In this case, the shutter substrate 152 is provided at the position where the diaphragm S was provided. Further, the shutter 15 may be formed with a small stop aperture having a smaller diameter than the stop S for controlling the amount of light incident on the imaging lens 20, or may have a small stop function for reducing the amount of light with an ND filter or the like. Good. Further, a lens barrier may be provided instead of the shutter 15. The first lens 11 may be made of a plastic material instead of a glass material.

  The data given in each of the above embodiments is merely an example, and other values can be taken as long as the requirements of the present invention are satisfied.

1 is a configuration diagram of an imaging lens according to an embodiment of the present invention and an imaging module including the imaging lens, and is a configuration diagram of an imaging lens according to Example 1 and an imaging module including the imaging lens. FIG. It is a block diagram of the imaging lens which concerns on embodiment of this invention, and an imaging module provided with this imaging lens, and is a block diagram of the imaging module which concerns on Example 2, and an imaging module provided with this imaging lens. It is a block diagram of the imaging lens which concerns on embodiment of this invention, and an imaging module provided with this imaging lens, and is a block diagram of the imaging module which concerns on Example 3, and this imaging lens. FIG. 6 is an aberration diagram (spherical aberration, astigmatism, distortion) of the imaging lens according to Example 1; FIG. 6 is an aberration diagram (spherical aberration, astigmatism, distortion) of the imaging lens according to Example 2. FIG. 6 is an aberration diagram (spherical aberration, astigmatism, distortion) of the imaging lens according to Example 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging module 10 Lens 11 1st lens 12 2nd lens 13 3rd lens 14 4th lens S Aperture 20 Imaging lens 15 Shutter 153 Sector 16 Parallel plate glass 17 Solid-state image sensor X Optical axis

Claims (6)

In order from the object side, a first lens having a positive refractive power with a diaphragm, a convex surface facing the object side, a second lens having a positive refractive power with a concave surface facing the object side, and a concave surface facing the object side An imaging lens in which a third lens having negative refractive power and a fourth lens having positive refractive power with a convex surface facing the object side are disposed,
The distance on the optical axis from the stop to the imaging surface is TL, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, and the fourth lens has a focal length of f3. The focal length is f4, the distance on the optical axis between the second lens and the third lens is D4, the distance on the optical axis between the third lens and the fourth lens is D6, and the Abbe number of the first lens is ν1. An imaging lens satisfying the following conditional expressions (1) to (8) when the Abbe number of the second lens is ν2 and the focal length of the imaging lens is f.

1.8 <f1 / f <2.5 (1)
0.2 <f2 / f <0.4 (2)
0.1 <| f3 | / f <0.5 (3)
0.3 <f4 / f <2 (4)
f / TL <0.7 (5)
0 <D4 / f <0.1 (6)
0 <D6 / f <0.1 (7)
0 ≦ ν1-ν2 (8)   2. The imaging lens according to claim 1, wherein each of the second lens, the third lens, and the fourth lens has an aspheric surface on at least one surface.   The imaging lens according to claim 1 or 2, wherein the first lens is made of a glass material or a plastic material, and the second lens, the third lens, and the fourth lens are all made of a plastic material. . The imaging lens according to any one of claims 1 to 3, wherein the following conditional expression (9) is satisfied.
0 degrees ≤ αi <30 degrees (9)
Where αi is the incident angle of the principal ray on the image plane at the maximum image height.   An imaging module comprising the imaging lens according to claim 1. 6. The imaging module according to claim 5, wherein a sector capable of controlling the amount of light incident on the imaging lens is disposed on the object side of the diaphragm.

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