JPH04211214A - Image pickup lens - Google Patents

Abstract

PURPOSE:To attain necessary performance as an image pickup lens by means of the minimum constitutive number of lenses by using an image formation lens in combination with a correcting lens having the aspheric surfaces on both sides. CONSTITUTION:An image pickup lens is constituted of an image formation lens 10 having the aspheric surfaces on both sides and a correcting lens 20 having the aspheric surfaces on both sides and being arranged on the image side. A sensor to read image signals to form an image is arranged on the image side of the correcting lens 20. Furthermore, the sensor is sealed up by means of a cover glass 30 so that the light receiving surface is not exposed directly to moisture, and nitrogen gas is filled in the space between the light receiving surface and the cover glass. The correcting lens forms a convex shape on the object side when its both surface is put in a paraxial position, and has a specific configuration such as the displacement direction on aspheric surface becomes inverse to radius of curvature in the paraxial position of the aspheric surface.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] This invention relates to an imaging lens that forms an image of a subject on an image receiving surface, ranging from compact lenses with a small number of lenses to those with a large number of lenses and high performance.
It also includes a zoom lens.

0002

2. Description of the Related Art In devices requiring high resolution, an imaging lens is required to have an imaging performance equivalent to that of a single-lens reflex camera lens, for example.

On the other hand, in devices requiring relatively low resolution, such as small video telephones, compactness is more important than imaging performance, and it is required to be configured as compactly as possible by minimizing the number of lenses. Ru.

Conventionally, for this type of use, an imaging lens composed of, for example, three spherical glass lenses has been generally used. In order to obtain a certain level of imaging performance using spherical lenses, it is difficult to further reduce the number of lenses.

FIG. 51 shows a conventional imaging lens composed of three lenses 1, 2, and 3, and FIG.
shows the lateral aberration due to this configuration. Note that the reference numeral 4 in the figure indicates a cover glass.

Further, FIG. 53 shows an example of an imaging lens constructed of one aspherical lens 5 for the purpose of reducing the number of lenses. FIG. 54 shows various aberrations of this lens.

[0007]

The imaging lens shown in FIG. 51 satisfies the performance of this type of lens, but it has a large number of lenses. On the other hand, although the lens shown in FIG. 53 has the smallest number of elements, the performance deteriorates particularly in the peripheral area.

[0008]

OBJECTS OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide an imaging lens that can secure necessary performance with a smaller number of lenses.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the imaging lens according to the present invention is characterized in that it uses a combination of an imaging lens and a correction lens whose both surfaces are aspherical.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on the drawings.

First, various conditions satisfied by the imaging lens according to the embodiment will be explained.

The focal length of the entire system at the dominant wavelength is f, the focal length of the imaging lens is f1, and the focal length of the correction lens is f2.
, where r1 is the paraxial radius of curvature of the first surface of the imaging lens, and d1 is the axial thickness of the imaging lens, 0.75<f/f1<1.0...(1)-0.10<
f/f2<0...(2)0.3<r1/d1<1
．． 0...It is characterized by satisfying (3).

Equations (1) and (2) are conditions regarding field curvature and astigmatism difference, and the lower limit of equation (1) or (2)
If the upper limit of equation (1) or the lower limit of equation (2) is exceeded, the sagittal field curvature will become excessive, and conversely, if the upper limit of equation (1) or the lower limit of equation (2) is exceeded, the astigmatism difference will increase and the imaging lens and correction lens will The refractive power becomes excessive and coma aberration occurs.

Equation (3) is a condition regarding field curvature and coma aberration; when the upper limit is exceeded, the meridional field curvature becomes large, and when the lower limit is below, coma aberration occurs.

Furthermore, the 4th, 6th, 8th, etc. aspheric coefficients An of the lens, the conic coefficient K, and the curvature of the aspheric apex (1/r
) is C, and the deviation △XN(Y) from the paraxial curvature surface on the aspheric surface at the height Y from the optical axis of the object side (N = 1) and image side (N = 2) of the correction lens is calculated as a number. When defined as in 4,

[Math 3] It is characterized by satisfying the following conditions.

[0016]

[Math 4]

Equations (4) and (5) are conditions regarding astigmatism and distortion; when the lower limit of both equations is below, negative distortion occurs in the low image height range, and when the upper limit is exceeded, meridional The curvature of field becomes larger, and the astigmatism difference becomes larger.

In order for the correction lens to work effectively, the entrance pupil of the correction lens must be located within the imaging lens, and the distance from the object side surface of the correction lens to the entrance pupil of the correction lens must be d0, and the entire system When the focal length of is f, -0.4<d0/
It is preferable to set the condition to satisfy f<−0.2 (6).

Equation (6) is a condition that defines the position of the entrance pupil of the correction lens, and if this condition is not satisfied, astigmatism increases and imaging performance deteriorates.

(First Embodiment) FIGS. 1 to 3 show a first embodiment of an imaging lens according to the present invention. This imaging lens is composed of an imaging lens 10 having aspherical surfaces on both sides, and a correction lens 20 having aspherical surfaces on both sides disposed on the image side thereof. Correction lens 20
A sensor (not shown) is provided on the image side of the image plane to read signals of the formed image.

The sensor is sealed with a cover glass 30 so that the light receiving surface is not directly exposed to moisture, and the space between the light receiving surface and the cover glass is filled with nitrogen gas. The correction lens 20 has a special shape in which both surfaces are convex toward the object side in the paraxial direction, and the direction of displacement of the aspheric surface is opposite to the paraxial radius of curvature of the aspheric surface. Such an aspherical shape can be easily realized by using a plastic material.

The specific numerical structure of this lens is shown in Table 1. The symbols in the table are Fno. is the F number, f is the focal length at the main wavelength, m is the magnification, r is the radius of curvature of the surface, d is the lens thickness or air spacing, nd is the refractive index of the lens at the d-line (588 nm), ν is the Abbe number, ne is the e-line of the lens (546nm)
is the refractive index at .

In the explanation of the table, the numerical value in the radius of curvature column of the aspherical surface is assumed to be the radius of curvature of the apex of the aspherical surface. The aspheric surface is
The distance from the tangent plane of the aspherical apex on the aspherical surface with height Y from the optical axis is X, the curvature (1/r) of the aspherical apex is C, the conic coefficient is K, and the 4th to 10th order aspheric surface The coefficients are given by the following equation 5 with A4 to A10, and the conic coefficient and aspheric coefficient of each surface are as shown in the lower part of Table 1. FIG. 2 shows various aberrations due to the configuration shown in Table 1, and FIG. 3 shows lateral aberrations.

[0024]

[Math 5]

[0025]

[Table 1]

(Second Embodiment) FIG. 4 shows a second embodiment of the imaging lens according to the present invention. In this example, a correction lens 20 provided on the image side of the imaging lens 10 also serves as a cover for the sensor. The specific numerical structure of the lens is as shown in Table 2. The symbols in the table are the same as in the first example. FIG. 5 shows various aberrations due to the configuration shown in Table 2.

[0027]

[Table 2]

(Third Embodiment) FIG. 6 shows a third embodiment of the imaging lens according to the present invention.

Similar to the first embodiment, this lens is composed of an imaging lens 10 and a correction lens 20, and a sensor cover glass 30 is provided on the image side.

The specific numerical configuration of this example is shown in Table 3, and the various aberrations due to this configuration are as shown in FIG.

In the third, fourth, and fifth embodiments, APO (amorphous polyolefin: trade name) is used for the imaging lens 10 and the correction lens 20. PMMA has traditionally been used as a material for plastic lenses.
(Polymethyl methacrylate) has a problem in that its refractive state changes greatly due to changes in temperature and humidity, and its optical performance changes greatly depending on changes in the environment. In particular, if there is a change in humidity, not only will the focus shift, but the wavefront of the luminous flux will be disturbed.

[0032] This APO was developed by Mitsui Petrochemicals Co., Ltd. as a low hygroscopic plastic, and has a water absorption rate of 0.01% or less, which is an order of magnitude lower than conventional plastics, so it is hardly affected by changes in humidity. Therefore, APO on the lens
By using this, the performance of the lens system can be further stabilized.

[0033]

[Table 3]

(Fourth Embodiment) FIG. 8 shows a fourth embodiment of the imaging lens according to the present invention.

Similar to the first embodiment, this lens is composed of an imaging lens 10 and a correction lens 20, and a sensor cover glass 30 is provided on the image side.

[0036] The specific numerical structure is shown in Table 4,
Various aberrations due to this configuration are as shown in FIG.

[0037]

[Table 4]

(Fifth Embodiment) FIG. 10 shows a fifth embodiment of the imaging lens according to the present invention.

In this example, similarly to the second embodiment, the correction lens 20 provided on the image side of the imaging lens 10 also serves as a cover for the sensor, and both lenses are made of APO.

In the case where the correction lens 20 also serves as a cover glass, if a highly hygroscopic resin such as PMMA is used, there is a risk that moisture permeation will occur through absorption and removal of moisture, resulting in deterioration of sensor performance. AP correction lens as in this example.
When set to O, the light-receiving surface can be protected from moisture and deterioration of sensor performance can be prevented.

The specific numerical structure of the lens is shown in Table 5, and its various aberrations are shown in FIG.

[0042]

[Table 5]

(Sixth Embodiment) FIG. 12 shows a sixth embodiment of the imaging lens according to the present invention.

In this example, as in the second embodiment, the correction lens 20 provided on the image side of the imaging lens 10 also serves as a cover for the sensor.

The specific numerical structure of the lens is shown in Table 6, and its various aberrations are shown in FIG.

[0046]

[Table 6]

[0047] In addition, each of the above-mentioned embodiments and conditional expressions (1) to
The correspondence with (6) is shown in Table 7.

[0048]

[Table 7]

The first to sixth embodiments relate to an imaging lens used in a small camera such as a videophone camera or a doorbell camera. In order to meet such demands, the imaging lenses of the first to sixth embodiments are compactly constructed as a whole with one imaging lens and one correction lens.

Seventh Embodiment In the following embodiments, a plurality of lenses are used as the imaging lens to provide an imaging lens with higher imaging performance than the above example. Furthermore, the seventh
~The ninth embodiment is a zoom lens.

(Seventh Embodiment) FIG. 14 shows a seventh embodiment of the imaging lens according to the present invention. This lens consists of an imaging lens with three groups, and a correction lens with aspherical surfaces on both sides and a negative focal length on the paraxial axis. , a negative second lens group, and a positive third lens group are arranged. This lens is a zoom lens that changes the focal length by moving the first and second lens groups in the optical axis direction, and focusing is performed by moving the first lens group in the optical axis direction.

FIG. 15 is an enlarged view showing the shape of the correction lens.

The specific numerical structure of the lens is shown in Table 8, and its various aberrations are shown in Figure 1 for a focal length of 10 mm.
6. Figure 17 shows the case of focal length 20mm, focal length 40m.
The case of m is shown in FIG.

[0054]

[Table 8]

(Eighth Embodiment) FIG. 19 shows an eighth embodiment of the imaging lens according to the present invention. This lens consists of an imaging lens with four groups, and a correction lens that has aspherical surfaces on both sides and has a negative focal length on the paraxial axis. , a negative second lens group, a negative third lens group, and a positive fourth lens group are arranged. This lens is a zoom lens that changes the focal length by moving the second and third lens groups in the optical axis direction, and focusing is performed by moving the first lens group in the optical axis direction.

The specific numerical structure of the lens is shown in Table 9, and its various aberrations are shown in Figure 2 for a focal length of 10 mm.
0, focal length 20mm is shown in Figure 21, focal length 40m
The case of m is shown in FIG.

[0057]

[Table 9]

For comparison, various aberrations of only the imaging lens excluding the correction lens are shown in FIG. 23 for a focal length of 10 mm, FIG. 24 for a focal length of 20 mm, and FIG. 25 for a focal length of 40 mm. show.

(Ninth Embodiment) FIG. 26 shows a ninth embodiment of the imaging lens according to the present invention. This lens consists of an imaging lens with four groups, and a correction lens that has aspherical surfaces on both sides and has a positive focal length on the paraxial axis. , a negative second lens group, a negative third lens group, and a positive fourth lens group are arranged. This lens is a zoom lens that changes the focal length by moving the second and third lens groups in the optical axis direction, and focusing is performed by moving the first lens group in the optical axis direction.

FIG. 27 is an enlarged view showing the shape of the correction lens.

The specific numerical structure of the lens is shown in Table 10, and its various aberrations are shown in Figure 2 for a focal length of 8 mm.
8. Figure 29 shows the case of focal length 20mm, focal length 48m.
The case of m is shown in FIG.

[0062]

[Table 10]

(Tenth Embodiment) FIG. 31 shows a tenth embodiment of the imaging lens according to the present invention. This lens is composed of an imaging lens with a four-group configuration, and a correction lens that has aspherical surfaces on both sides and has a negative focal length on the paraxial axis.The imaging lens includes, in order from the object side, a negative first lens,
A positive second lens, a negative third lens, and a positive fourth lens are arranged and configured.

The specific numerical structure of the lens is shown in Table 11, and the various aberrations at a magnification of -0.168 times are shown in FIG.

[0065]

[Table 11]

(Eleventh Embodiment) FIG. 33 shows an eleventh embodiment of the imaging lens according to the present invention. This lens is composed of a four-element imaging lens, and a correction lens that has aspherical surfaces on both sides and has a negative focal length on the paraxial axis.The imaging lens includes, in order from the object side, a positive first lens,
A negative second lens, a positive third lens, and a negative fourth lens are arranged, and the third lens and the fourth lens are cemented.

FIG. 34 is an enlarged view showing the shape of the correction lens. The specific numerical configuration of the lens is shown in Table 12, and the various aberrations at a magnification of -0.112x are shown in Figure 3.
5. Note that FIG. 36 shows various aberrations of only the imaging lens when the correction lens is excluded.

[0068]

[Table 12]

(Twelfth Embodiment) FIG. 37 shows a twelfth embodiment of the imaging lens according to the present invention. 1st
The imaging lenses shown in Examples 2 to 18 are constructed by arranging, in order from the object side, a correction lens that is biconcave on the paraxial axis and has a negative focal length, and a single-element positive imaging lens. A cover glass is provided on the image side. The correction lens has aspherical surfaces on both sides, and the direction of displacement of the object-side surface from the spherical surface is opposite to the paraxial radius of curvature.

With this configuration, the aspheric surface on the object side of the correction lens forms a good object image with respect to the entrance pupil of the imaging lens. When the imaging surface of the imaging lens is viewed as an object, the Petzval image surface is a curved surface that is convex toward the object, and is formed closer to the object than the correction lens. The Petzval image surface created by the negative correction lens is a curved surface that is convex toward the object side, and is formed as a virtual image closer to the object side than the correction lens. When the position of these Petzval image planes and the degree of curvature match, an image of the object is formed on the light receiving surface without field curvature or astigmatism.

According to the above structure, it is possible to provide a small lens with a wide angle of view and low cost with a simple structure. Further, by arranging the negative lens on the object side of the positive imaging lens, a long back focus can be ensured, and even when the focal length of the lens is shortened, the lens and the cover glass do not come into contact with each other.

In the 12th, 13th, 14th, and 16th embodiments, the diaphragm is located in the imaging lens, and in the 15th, 17th, and 18th embodiments, the diaphragm is located on the image-side surface of the imaging lens.

The specific numerical structure of the lens of the twelfth example is shown in Table 13, and its various aberrations are shown in FIG.

[0074]

[Table 13]

(Thirteenth Embodiment) FIG. 39 shows a thirteenth embodiment of the imaging lens according to the present invention. The specific numerical structure of the lens is shown in Table 14, and its various aberrations are shown in FIG.

[0076]

[Table 14]

(Fourteenth Embodiment) FIG. 41 shows a fourteenth embodiment of the imaging lens according to the present invention. The specific numerical structure of the lens is shown in Table 15, and its various aberrations are shown in FIG.

[0078]

[Table 15]

(Fifteenth Embodiment) FIG. 43 shows a fifteenth embodiment of the imaging lens according to the present invention. The specific numerical structure of the lens is shown in Table 16, and its various aberrations are shown in FIG.

[0080]

[Table 16]

(Sixteenth Embodiment) FIG. 45 shows a 16th embodiment of the imaging lens according to the present invention. The specific numerical structure of the lens is as shown in Table 17, and its various aberrations are shown in FIG.

[0082]

[Table 17]

(Seventeenth Embodiment) FIG. 47 shows a seventeenth embodiment of the imaging lens according to the present invention. The specific numerical structure of the lens is as shown in Table 18, and its various aberrations are shown in FIG.

[0084]

[Table 18]

(Eighteenth Embodiment) FIG. 49 shows an eighteenth embodiment of the imaging lens according to the present invention. The specific numerical structure of the lens is as shown in Table 19, and its various aberrations are shown in FIG.

[0086]

[Table 19]

As explained above, according to the present invention,
By using a double-sided aspherical correction lens in combination with an imaging lens, the configuration of the imaging lens can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a first embodiment of an imaging lens according to the present invention.

FIG. 2 is a diagram showing various aberrations of the first embodiment.

FIG. 3 is a lateral aberration diagram of the first embodiment.

FIG. 4 is a sectional view of a lens according to a second embodiment.

FIG. 5 is a diagram showing various aberrations of the second embodiment.

FIG. 6 is a sectional view of a lens according to a third embodiment.

FIG. 7 is a diagram showing various aberrations of the third embodiment.

FIG. 8 is a cross-sectional view of a lens according to a fourth embodiment.

FIG. 9 is a diagram showing various aberrations of the fourth embodiment.

FIG. 10 is a sectional view of a lens according to a fifth embodiment.

FIG. 11 is a diagram showing various aberrations of the fifth embodiment.

FIG. 12 is a sectional view of a lens according to a sixth embodiment.

FIG. 13 is a diagram showing various aberrations of the sixth embodiment.

FIG. 14 is a cross-sectional view of a lens with a focal length of 10 mm in a seventh embodiment.

FIG. 15 is an enlarged sectional view of a correction lens according to a seventh embodiment.

FIG. 16 is a diagram of various aberrations at a focal length of 10 mm in the seventh embodiment.

FIG. 17 is a diagram of various aberrations at a focal length of 20 mm in the seventh embodiment.

FIG. 18 is a diagram of various aberrations at a focal length of 40 mm in the seventh embodiment.

FIG. 19 is a cross-sectional view of a lens with a focal length of 10 mm in an eighth embodiment.

FIG. 20 is a diagram of various aberrations at a focal length of 10 mm when the auxiliary lens of the eighth embodiment is excluded.

FIG. 21 is a diagram of various aberrations at a focal length of 20 mm when the auxiliary lens of the eighth embodiment is excluded.

FIG. 22 is a diagram of various aberrations at a focal length of 40 mm when the auxiliary lens of the eighth embodiment is excluded.

FIG. 23 is a diagram of various aberrations at a focal length of 10 mm in the eighth embodiment.

FIG. 24 is a diagram of various aberrations at a focal length of 20 mm in the eighth embodiment.

FIG. 25 is a diagram of various aberrations at a focal length of 40 mm in the eighth embodiment.

FIG. 26 is a cross-sectional view of a lens with a focal length of 8 mm in a ninth embodiment.

FIG. 27 is an enlarged sectional view of the correction lens of the ninth embodiment.

FIG. 28 is a diagram of various aberrations at a focal length of 8 mm in the ninth embodiment.

FIG. 29 is a diagram showing various aberrations at a focal length of 20 mm in the ninth embodiment.

FIG. 30 is a diagram showing various aberrations at a focal length of 48 mm in the ninth embodiment.

FIG. 31 is a cross-sectional view of a lens according to a tenth embodiment.

FIG. 32 is a diagram showing various aberrations at −0.168 times in the tenth embodiment.

FIG. 33 is a cross-sectional view of a lens with a focal length of 10 mm in an eleventh embodiment.

FIG. 34 is an enlarged cross-sectional view of the correction lens of the eleventh embodiment.

FIG. 35 is a diagram of various aberrations at −0.112 times in the eleventh embodiment.

FIG. 36 is a diagram showing various aberrations when the correction lens of the eleventh embodiment is excluded.

FIG. 37 is a cross-sectional view of the lens of the twelfth embodiment.

FIG. 38 is a diagram showing various aberrations of the twelfth embodiment.

FIG. 39 is a cross-sectional view of a lens according to a thirteenth embodiment.

FIG. 40 is a diagram showing various aberrations of the thirteenth embodiment.

FIG. 41 is a sectional view of the lens of the fourteenth embodiment.

FIG. 42 is a diagram showing various aberrations of the fourteenth embodiment.

FIG. 43 is a sectional view of the lens of the fifteenth embodiment.

FIG. 44 is a diagram showing various aberrations of the 15th example.

FIG. 45 is a sectional view of the lens of the 16th embodiment.

FIG. 46 is a diagram showing various aberrations of the 16th embodiment.

FIG. 47 is a cross-sectional view of the lens of the seventeenth embodiment.

FIG. 48 is a diagram showing various aberrations of the 17th embodiment.

FIG. 49 is a cross-sectional view of the lens of the 18th embodiment.

FIG. 50 is a diagram showing various aberrations of the 18th embodiment.

FIG. 51 is a sectional view of a conventional three-lens imaging lens.

52 is a lateral aberration diagram of the conventional example shown in FIG. 51. FIG.

FIG. 53 is a cross-sectional view of a conventional single-lens imaging lens.

54 is a lateral aberration diagram of the conventional example shown in FIG. 53. FIG.

[Explanation of symbols]

10 Imaging lens 20 Correction lens 30 Cover glass

Claims (16)

[Claims] 1. An imaging lens comprising: an imaging lens; and a meniscus correction lens which is an aspherical surface disposed on the image side of the imaging lens and whose both surfaces are convex toward the object side in the paraxial direction. . 2. The aspherical displacement direction of the correction lens is
The imaging lens according to claim 1, wherein the radius of paraxial curvature of the aspheric surface is opposite to that of the aspheric surface. 3. The imaging lens according to claim 1, wherein the correction lens serves as a cover for a light receiving element provided on the image side of the correction lens. 4. The imaging lens according to claim 3, wherein focus adjustment is performed by moving only the imaging lens in the optical axis direction. 5. The imaging lens according to claim 1, wherein the correction lens is formed of a low hygroscopic resin. 6. The imaging lens according to claim 5, wherein the low hygroscopic resin is an amorphous polyolefin. 7. The imaging lens according to claim 1, wherein the imaging lens is composed of one lens having at least one aspherical surface. 8. The imaging lens includes, in order from the object side:
A positive first lens group, a negative second lens group, and a positive third lens group are arranged, and the focal length can be adjusted by moving the first and second lens groups in the optical axis direction. The imaging lens according to claim 1, wherein the imaging lens is changed. 9. The imaging lens includes, in order from the object side:
A positive first lens group, a negative second lens group, a negative third lens group, and a positive fourth lens group are arranged, and the second and third lens groups are aligned in the optical axis direction. 2. The imaging lens according to claim 1, wherein the focal length is changed by moving the lens. 10. The imaging lens includes, in order from the object side, a negative first lens, a positive second lens, a negative third lens, and a positive fourth lens. The imaging lens according to claim 1, characterized in that: 11. The imaging lens includes, in order from the object side, a positive first lens, a negative second lens, a positive third lens, and a negative fourth lens, The imaging lens according to claim 1, wherein the third lens and the fourth lens are cemented. 12. Comprising an imaging lens and a correction lens with aspherical surfaces on both sides disposed on the image side, wherein the focal length of the entire system at the dominant wavelength is f, the focal length of the imaging lens is f1, and the correction lens An imaging lens that satisfies 0.75<f/f1<1.0 -0.10<f/f2<0, where f2 is the focal length of . 13. An imaging lens, and a correction lens having aspherical surfaces on both sides disposed on the image side of the imaging lens.
The paraxial radius of curvature of the surface is r1, and the axial thickness of the imaging lens is d.
1, an imaging lens that satisfies 0.3<r1/d1<1.0. 14. It has an imaging lens and a correction lens with aspherical surfaces on both sides disposed on the image side, and the focal length of the entire system is set to f, an aspherical coefficient An of the 4th order, 6th order, 8th order, etc. , where K is the conic coefficient, C is the curvature (1/r) of the apex of the aspherical surface, and the height Y from the optical axis of the object side (N=1) and image side (N=2) of the correction lens is on the aspherical surface. The deviation from the paraxial curvature surface △X
An imaging lens that satisfies the following condition when N(Y) is defined as shown in equation 2. [Math 2] 15. An imaging lens, and a correction lens having aspherical surfaces on both sides disposed on the image side thereof, wherein an entrance pupil of the correction lens is within the imaging lens, and an object side surface of the correction lens is located within the imaging lens. An imaging lens that satisfies the following condition: -0.4<d0/f<-0,2, where d0 is the distance from the entrance pupil of the correction lens to f, and f is the focal length of the entire system. 16. An imaging lens comprising: an imaging lens; and a biconcave correction lens having aspherical surfaces on both sides and disposed on the object side of the imaging lens.