JP2011007869A - Imaging lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging lens capable of completely meeting demands for downsizing, reduction of weight and further improvement in optical performance, and further improving manufacturability.SOLUTION: The imaging lens includes, in order from an object side to an image surface side, a diaphragm 2, a first lens 3 as a positive meniscus lens turning its convex surface to the object side, and a second lens 4 as a positive meniscus lens turning its convex surface to the image surface side. The imaging lens satisfies respective conditional expressions; 0.8≤L/fl≤1.25, 0.9≤f/fl≤1.0, 10≤f/fl≤25 and 0.5≤d/d≤1.0 (provided that L: entire length of a lens system, fl: focal length of the entire lens system, f: focal length of the first lens, f: focal length of the second lens, d: center thickness of the first lens, and d: space between the first lens and the second lens on an optical axis).

Description

  The present invention relates to an imaging lens, and in particular, forms an image of an object such as a landscape or a person on an imaging surface of a solid-state imaging device such as a CCD or CMOS mounted on a portable computer, a videophone, a cellular phone, or the like. The present invention relates to an imaging lens having a two-lens configuration that can be used in an imaging device to be reduced in size and weight, improve optical performance, and improve productivity.

  In recent years, for example, a demand for a camera using a solid-state imaging device such as a CCD or a CMOS to be mounted on a mobile phone, a portable computer, a video phone, or the like has increased remarkably. Since such a camera needs to be mounted in a limited installation space, it is desired that the camera be small and lightweight.

  For this reason, an imaging lens used in such a camera is also required to be small and light. Similarly, as such an imaging lens, a single lens having a single lens has been conventionally used. A system is used.

  Such a one-lens lens system can sufficiently cope with application to a solid-state imaging device called CIF having a resolution of about 110,000 pixels, but in recent years, about 300,000 called VGA. The use of a solid-state imaging device having a resolution as high as a pixel has been studied, and in order to fully exhibit the resolution capability of such a high-resolution solid-state imaging device, There is a problem that it can not cope.

  For this reason, various proposals have been made for a two-lens lens system or a three-lens lens system that is superior in optical performance as compared with a single-lens lens system.

  In this case, in the three-lens lens system, it is possible to effectively correct each aberration that leads to a decrease in optical performance, so that it is possible to obtain extremely high optical performance. However, since the number of parts is large, it is difficult to reduce the size and weight, and high accuracy is required for each component part, resulting in an increase in manufacturing cost.

  In contrast, a two-lens lens system cannot achieve the same optical performance as a three-lens lens system, but can obtain higher optical performance than a single-lens lens system. It can be said that this is a lens system suitable for a solid-state imaging device with a resolution.

  As such a two-lens lens system, many lens systems combining a negative lens and a positive lens called a retrofocus type have been proposed. However, with such a retrofocus lens system, it is possible to reduce the cost by reducing the number of parts. However, since the back focus distance is increased, the size and weight of the lens system can be reduced to the same level as a single lens system. In view of its configuration, it is virtually impossible.

  In addition, as another two-lens configuration lens system, there is a lens system combining a positive lens and a negative lens called a telephoto type. However, such a telephoto type lens system was originally developed for silver halide photography, the back focus distance is too short, and there is also a problem of telecentricity, and as it is as an imaging lens for a solid-state imaging device. It is difficult to apply.

  Furthermore, conventionally, in a two-lens configuration or a three-lens configuration, a configuration in which a diaphragm is disposed between two lenses adjacent to each other in the optical axis direction has been the mainstream (for example, Patent Document 1 and 2).

JP 2004-163850 A JP 2006-91638 A

  However, in recent years, in this type of imaging lens, there is an increasing demand for further improvement in optical performance in addition to the reduction in size and weight. As in the imaging lenses described in Patent Documents 1 and 2, two lenses are used. In the configuration in which the diaphragm is disposed between the lenses, it is difficult to achieve both reduction in size and weight and further improvement in optical performance, and it is difficult to match the characteristics of the sensor (incident angle to the sensor). Have the following problems.

  Therefore, the present invention has been made in view of such problems, and an imaging lens that can sufficiently meet the demands for reduction in size and weight and further improvement in optical performance and can further improve manufacturability. It is intended to provide.

  In this specification, manufacturability means manufacturability when mass-producing imaging lenses (for example, moldability and cost when mass-producing imaging lenses by injection molding), and imaging. It also includes the meaning of the ease of processing, production, etc. of the equipment used to manufacture the lens (for example, the ease of processing of the mold used for injection molding).

In order to achieve the above-described object, a feature of the imaging lens according to claim 1 of the present invention is an imaging lens used for forming an image of an object on an imaging surface of a solid-state imaging device, from the object side. In order toward the image surface side, the first lens is a meniscus lens having a positive power with a diaphragm and a convex surface facing the object side, and a meniscus lens having a positive power with a convex surface facing the image surface side. 2 lenses are arranged, and the following conditional expressions (1) to (4):
0.8 ≦ L / fl ≦ 1.25 (1)
0.9 ≦ f ₁ /fl≦1.0 (2)
10 ≦ f ₂ / fl ≦ 25 (3)
0.5 ≦ d ₂ / d ₁ ≦ 1.0 (4)
However,
L: total length of the lens system fl: focal length of the entire lens system f ₁ : focal length of the first lens f ₂ : focal length of the second lens d ₁ : center thickness of the first lens d ₂ : first on the optical axis The distance between the lens and the second lens is satisfied.

  According to the first aspect of the present invention, it is possible to secure high telecentricity by arranging the stop closest to the object side, and to reduce the incident angle of the light beam with respect to the sensor of the solid-state imaging device. it can.

  In the present invention, disposing the diaphragm closest to the object side means that the diaphragm is disposed at the same position in the optical axis direction as the point on the optical axis of the object-side surface (convex surface) of the first lens, or It does not prevent the vicinity of the optical axis of the object side surface of the first lens from being located on the object side of the stop through the stop. Even in such a case, as a physical arrangement, it can be said that the diaphragm is arranged on the object side with respect to the entire first lens, and this does not contradict the description of the claims.

  According to the invention of claim 1, the first lens is a meniscus lens having a positive power with the convex surface facing the object side, the second lens is a meniscus lens having a positive power, and each By defining the lens power as in the conditional expressions (1) to (4), it is possible to improve manufacturability while reducing size and weight.

  Furthermore, according to the first aspect of the present invention, since the second lens is formed on the meniscus lens, the optical performance of the peripheral portion is improved without imposing a burden on the shape of the first lens and the second lens. In addition, it is possible to more effectively use light rays incident on the periphery of the solid-state imaging device.

  According to the imaging lens of the first aspect of the present invention, it is possible to realize an imaging lens that is small and light, has excellent optical performance, and has good manufacturability.

1 is a schematic configuration diagram showing an embodiment of an imaging lens according to the present invention. 1 is a schematic configuration diagram showing a first embodiment of an imaging lens according to the present invention. Aberration diagram showing astigmatism and distortion of the imaging lens shown in FIG. Schematic configuration diagram showing a second embodiment of the imaging lens according to the present invention Aberration diagram showing astigmatism and distortion of the imaging lens shown in FIG. Schematic configuration diagram showing a third embodiment of the imaging lens according to the present invention. Aberration diagram showing astigmatism and distortion of the imaging lens shown in FIG. Schematic configuration diagram showing a fourth embodiment of the imaging lens according to the present invention. Aberration diagram showing astigmatism and distortion of the imaging lens shown in FIG.

  Hereinafter, an embodiment of an imaging lens according to the present invention will be described with reference to FIG.

  As shown in FIG. 1, the imaging lens 1 according to the present embodiment is a resin-made meniscus lens having a positive power with a diaphragm 2 and a convex surface facing the object side in order from the object side to the image surface side. The first lens 3 and a resin-made second lens 4 which is a meniscus lens having a positive power with the convex surface facing the image surface side.

  Hereinafter, the object-side and image-side lens surfaces of the first lens 3 and the second lens 4 are referred to as a first surface and a second surface, respectively.

  Further, on the second surface side of the second lens 4, various filters 6 such as a cover glass, an IR cut filter, a low-pass filter, and an imaging surface 7 that is a light receiving surface of an imaging element such as a CCD or a CMOS are disposed. Yes. The various filters 6 can be omitted as necessary.

  Here, the closer the position of the stop 2 is to the image plane side, the closer the exit pupil position is to the image plane side. This makes it difficult to ensure telecentricity, and off-axis rays emitted from the imaging lens 1 are obliquely incident on the sensor of the solid-state imaging device.

  On the other hand, in this embodiment, the exit pupil position can be set at a position far from the sensor surface (imaging surface) of the solid-state image sensor by disposing the diaphragm 2 on the most object side.

  Thereby, in this embodiment, it becomes possible to ensure high telecentricity, and the incident angle of the light beam with respect to the sensor of a solid-state image sensor can be relieved.

  In the present embodiment, the diaphragm 2 is disposed on the object side of the first lens 3 and the first lens 3 is formed in a meniscus shape having a convex surface facing the object side, whereby the center is located on the opposite side of the diaphragm. It becomes the composition which arranges the curved surface which has. Thereby, since the refractive power of the light beam in the peripheral portion can be improved, the second surface of the first lens 3 can be effectively used.

  Furthermore, in the present embodiment, since the shape of the second surface of the second lens 4 is convex toward the image surface side, higher telecentricity can be ensured, and the sensor of the solid-state image sensor The incident angle with respect to can be more effectively controlled. Furthermore, the shape of the second surface of the second lens 4 is more preferably an aspherical surface whose curvature increases with distance from the optical axis 8. By doing so, higher telecentricity can be ensured, and the incident angle of the solid-state imaging device with respect to the sensor can be controlled more effectively.

  Furthermore, in the present embodiment, the second lens 4 is formed as a meniscus lens, thereby improving the optical performance of the peripheral portion without imposing a burden on the shape of the first lens 3 and the second lens 4. In addition, it is possible to more effectively use the light rays incident on the periphery of the solid-state imaging device.

Furthermore, in the present embodiment, the imaging lens 1 satisfies the following conditional expressions (1) to (4).
0.8 ≦ L / fl ≦ 1.25 (1)
0.9 ≦ f ₁ /fl≦1.0 (2)
10 ≦ f ₂ / fl ≦ 25 (3)
0.5 ≦ d ₂ / d ₁ ≦ 1.0 (4)
However, L in the expression (1) is the total length of the lens system, that is, the optical distance from the physically closest object side surface to the imaging surface. More specifically, when the vicinity of the optical axis 8 of the first surface of the first lens 3 is located on the image plane side with respect to the diaphragm 2, the distance from the diaphragm 2 to the imaging surface is L. On the other hand, as described above, when the vicinity of the optical axis 8 of the first surface of the first lens 3 is positioned closer to the object side than the stop 2 through the stop 2, the first surface of the first lens 3 is not the stop 2. The distance from the image pickup surface to L is L. When the diaphragm 2 is arranged at the same position in the optical axis 8 direction as the point on the first surface of the first lens 3 on the optical axis 8, imaging is performed from the diaphragm 2 and the first surface of the first lens 3. The distance to the surface is L. Further, fl in the equations (1) to (3) is the focal length of the entire lens system. Further, f ₁ in the formula (2) is a focal length of the first lens 3. Furthermore, f ₂ in the expression (3) is the focal length of the second lens 4. Further, d ₁ in the formula (4) is the center thickness of the first lens 3. Further, d ₂ in the equation (4) is the distance between the first lens 3 and the second lens 4 on the optical axis 8.

  Here, if the value of L / fl increases beyond the value (1.25) shown in the equation (1), the entire optical system becomes large, which is contrary to the demand for reduction in size and weight. On the other hand, if the value of L is smaller than the value (0.8) shown in the equation (1), the entire optical system is downsized, resulting in a decrease in manufacturability and difficulty in maintaining optical performance. Furthermore, it becomes difficult to secure a necessary back focus distance.

  Therefore, according to the present embodiment, by satisfying the conditional expression (1) for the value of L / fl, the entire optical system is sufficiently reduced in size and weight while ensuring the necessary back focus distance. It is possible to maintain good optical performance, and it is possible to improve manufacturability.

  The relationship between L and fl is more preferably 1.0 ≦ L / fl ≦ 1.2.

Furthermore, if the value of f ₁ / fl exceeds the value (1.0) shown in the equation (2), the back focus distance becomes too long, and it becomes difficult to reduce the size and weight. On the other hand, when the value of f ₁ / fl is smaller than the value (0.9) shown in the equation (2), the manufacturability of the first lens 3 is lowered, and further, it is difficult to secure a necessary back focus distance. It becomes.

Therefore, according to the present embodiment, by further satisfying the conditional expression (2) for the value of f ₁ / fl, further reduction in size and weight and manufacturability are ensured while ensuring the necessary back focus distance. Can be improved.

The relationship between f ₁ and fl is more preferably 0.92 ≦ f ₁ /fl≦0.98.

Further, when the value of f ₂ / fl exceeds the value (25) shown in the expression (3), the power of the first lens 3 becomes too strong relative to the power of the second lens 4, and the manufacturability. Will be reduced. On the other hand, when the value of f ₂ / fl is smaller than the value (10) shown in the expression (3), the power of the second lens 4 becomes too strong relative to the power of the first lens 3, When the back focus distance becomes too long, it is difficult to reduce the size and weight.

Therefore, according to the present embodiment, the size / weight can be further reduced by further satisfying the conditional expression (3) for the value of f ₂ / fl.

The relationship between f ₂ and fl is more preferably 10 ≦ f ₂ / fl ≦ 20.

Furthermore, when the value of d ₂ / d ₁ exceeds the value (1) shown in the equation (4), the power of the first lens 3 and the second lens 4 must be increased. 4 is difficult to manufacture. Further, since the height of the light beam passing through the image plane side surface of the second lens 4 is increased, the power of the aspheric surface is increased, and the manufacture becomes difficult. On the other hand, when the value of d ₂ / d ₁ is smaller than the value (0.5) shown in the equation (4), the center thickness of the first lens 3 is thicker than the center thickness of the second lens 4. As a result, it becomes difficult to ensure the back focus distance. Furthermore, the distance between the first lens 3 and the second lens 4 becomes too narrow, and it becomes difficult to insert a light quantity limiting plate that effectively limits the light quantity between the lenses 3 and 4.

Therefore, according to the present embodiment, by making the value of d ₂ / d ₁ satisfy the conditional expression (4), it is possible to further improve the manufacturability and the necessary back-up. The focus distance can be further appropriately secured, and the optical performance can be further satisfactorily maintained.

The relationship between d ₂ and d ₁ is more preferably 0.5 ≦ d ₂ / d ₁ ≦ 0.67.

  By doing so, it is possible to make the configuration more suitable for a lens for a camera module mounted on a portable terminal or the like.

  Further, the resin material for molding the first lens 3 and the second lens 4 may have any composition as long as it has transparency used for molding optical parts, such as acrylic, polycarbonate, and amorphous polyolefin resin. However, from the viewpoint of further improving the manufacturing efficiency and further reducing the manufacturing cost, it is desirable to unify the resin materials of both lenses 3 and 4 into the same resin material.

  Next, an embodiment of the present invention will be described with reference to FIGS.

  Here, in this embodiment, Fno is the F number, and r 1 is the radius of curvature of the optical surface (in the case of a lens, the center radius of curvature). D indicates the distance to the next optical surface. Further, nd represents the refractive index of each optical system when irradiated with d-line (yellow), and νd represents the Abbe number of each optical system when similarly irradiated with d-line.

  k, A, B, C, and D represent coefficients in the following equation (5). That is, the aspherical shape of the lens is such that the Z-axis is in the direction of the optical axis 8, the X-axis is in the direction orthogonal to the optical axis 8, the light traveling direction is positive, k is the conic coefficient, A, B, C, When D is an aspheric coefficient and r is a radius of curvature, it is expressed by the following equation.

^{Z (X) = r -1 X} 2 / [1+ {1- (k + 1) r -2 X 2} 1/2]
+ AX ⁴ + BX ⁶ + CX ⁸ + DX ¹⁰ (5)

Further, in the following examples, the symbol E used for the numerical values representing the conic coefficient and the aspherical coefficient indicates that the subsequent numerical value is an exponent that should be base 10, and that 10 should be base. Indicates that the numerical value represented by the index is multiplied by the numerical value before E. For example, -1.48E-1 indicates -1.48 × 10 ⁻¹ .

<First embodiment>
FIG. 2 shows a first embodiment of the present invention. In this embodiment, the aperture 2 is formed on the object side of the first surface of the first lens 3 in the same manner as the imaging lens 1 having the configuration shown in FIG. The cover glass as the filter 6 is disposed between the second surface of the second lens 4 and the imaging surface 7. The diaphragm 2 is disposed closer to the image plane than the point on the optical axis 8 of the first surface of the first lens 3.

The imaging lens 1 of the first embodiment is set under the following conditions.

Lens data

L = 1.51 mm, fl = 1.36 mm, f ₁ = 1.26 mm, f ₂ = 14.75 mm, d ₁ = 0.280 mm, d ₂ = 0.182 mm, Fno = 2.85

Surface number r d nd νd
(Object point)
1 (aperture)
2 (1st lens 1st surface) 0.377 0.280 1.531 56.0
3 (1st lens 2nd surface) 0.641 0.182
4 (1st surface of the second lens) -1.250 0.445 1.531 56.0
5 (2nd lens 2nd surface) -1.212 0.090
6 (Cover glass first side) 0.000 0.210 1.516 64.0
7 (cover glass second side) 0.000
(Image plane)

Surface number k A B C D
2 -6.78 1.48E + 1 -1.51E + 2 1.62E + 3 -6.14E + 3
3 5.54 7.57E-1 -6.82 -1.68E + 2 6.01E + 3
4 1.66E + 1 1.59 -1.94E + 2 3.68E + 3 -3.45E + 4
5 4.22 6.14E-2 -4.44 1.13E + 1 -1.14E + 2

Under such conditions, L / fl = 1.11 was achieved, thereby satisfying the expression (1). F ₁ /fl=0.92 was achieved, thereby satisfying the expression (2). F ₂ / f _l = 10.84 was achieved, thereby satisfying the expression (3). D ₂ / d ₁ = 0.65 was achieved, thereby satisfying the expression (4).

  FIG. 3 shows spherical aberration, astigmatism and distortion in the imaging lens 1 of the first embodiment.

  According to this result, it is understood that all of spherical aberration, astigmatism and distortion are almost satisfactory, and sufficient optical characteristics can be obtained.

<Second embodiment>
FIG. 4 shows a second embodiment of the present invention. In this embodiment, the aperture 2 is formed on the object side of the first surface of the first lens 3 in the same manner as the imaging lens 1 having the configuration shown in FIG. The cover glass as the filter 6 is disposed between the second surface of the second lens 4 and the imaging surface 7. The diaphragm 2 is disposed closer to the image plane than the point on the optical axis 8 of the first surface of the first lens 3.

The imaging lens 1 of the second embodiment is set under the following conditions.

Lens data

L = 1.45 mm, fl = 1.31 mm, f ₁ = 1.19 mm, f ₂ = 19.15 mm, d ₁ = 0.30 mm, d ₂ = 0.180 mm, Fno = 2.85

Surface number r d nd νd
(Object point)
1 (aperture)
2 (first surface of the first lens) 0.377 0.300 1.531 56.0
3 (1st lens 2nd surface) 0.667 0.180
4 (1st surface of the second lens) -1.250 0.440 1.531 56.0
5 (2nd surface of the second lens) -1.250 0.090
6 (cover glass first side) 0.000 0.000 1.516 64.0
7 (cover glass second side) 0.000
(Image plane)

Surface number k A B C D
2 -6.41 1.44E + 1 -1.59E + 2 1.89E + 3 -8.50E + 3
3 6.12 5.06E-1 -3.41E + 1 8.05E + 2 -9.13E + 3
4 2.21E + 1 -1.99E-1 -1.70E + 2 4.02E + 3 -4.43E + 4
5 4.93 -5.54E-2 -8.03 3.45E + 1 -1.27E + 2

Under such conditions, L / fl = 1.11 was achieved, thereby satisfying the expression (1). F ₁ /fl=0.91 was achieved, thereby satisfying the expression (2). F ₂ /fl=14.60 was achieved, thereby satisfying the expression (3). D ₂ / d ₁ = 0.60 was achieved, thereby satisfying the expression (4).

  FIG. 5 shows spherical aberration, astigmatism and distortion in the imaging lens 1 of the second embodiment.

  According to this result, it is understood that all of spherical aberration, astigmatism and distortion are almost satisfactory, and sufficient optical characteristics can be obtained.

<Third embodiment>
FIG. 6 shows a third embodiment of the present invention. In this embodiment, the aperture 2 is formed on the object side of the first surface of the first lens 3 in the same manner as the imaging lens 1 having the configuration shown in FIG. The cover glass as the filter 6 is disposed between the second surface of the second lens 4 and the imaging surface 7. The diaphragm 2 is disposed closer to the image plane than the point on the optical axis 8 of the first surface of the first lens 3.

The imaging lens 1 of the third embodiment is set under the following conditions.

Lens data

L = 1.52 mm, fl = 1.39 mm, f ₁ = 1.27 mm, f ₂ = 27.69 mm, d ₁ = 0.28 mm, d ₂ = 0.18 mm, Fno = 2.85

Surface number r d nd νd
(Object point)
1 (aperture)
2 (first surface of the first lens) 0.385 0.280 1.531 56.0
3 (1st lens 2nd surface) 0.667 0.180
4 (1st surface of the second lens) -1.250 0.430 1.531 56.0
5 (2nd lens 2nd surface) -1.290 0.090
6 (cover glass first side) 0.000 0.000 1.516 64.0
7 (cover glass second side) 0.000
(Image plane)

Surface number k A B C D
2 -6.87 1.44E + 1 -1.63E + 2 1.82E + 3 -7.72E + 3
3 4.25 5.62E-1 -4.10E + 1 9.20E + 2 -1.01E + 4
4 2.51E + 1 4.97E-2 -1.72E + 2 3.98E + 3 -4.52E + 4
5 5.63 -1.78E-2 -6.83 2.90E + 1 -1.47E + 2

Under such conditions, L / fl = 1.09 was achieved, thereby satisfying the expression (1). F ₁ /fl=0.91 was achieved, thereby satisfying the expression (2). F ₂ /fl=19.92 was achieved, thereby satisfying the expression (3). D ₂ / d ₁ = 0.64 was achieved, thereby satisfying the expression (4).

  FIG. 7 shows spherical aberration, astigmatism and distortion in the imaging lens 1 of the third embodiment.

  According to this result, it is understood that all of spherical aberration, astigmatism and distortion are almost satisfactory, and sufficient optical characteristics can be obtained.

<Fourth embodiment>
FIG. 8 shows a fourth embodiment of the present invention. In this embodiment, the aperture 2 is formed on the object side of the first surface of the first lens 3 in the same manner as the imaging lens 1 having the configuration shown in FIG. The cover glass as the filter 6 is disposed between the second surface of the second lens 4 and the imaging surface 7. The diaphragm 2 is disposed closer to the image plane than the point on the optical axis 8 of the first surface of the first lens 3.

The imaging lens 1 of the fourth embodiment is set under the following conditions.

Lens data

L = 1.54 mm, fl = 1.43 mm, f ₁ = 1.33 mm, f ₂ = 14.72 mm, d ₁ = 0.28 mm, d ₂ = 0.185 mm, Fno = 2.85

Surface number r d nd νd
(Object point)
1 (aperture)
2 (first surface of the first lens) 0.385 0.280 1.531 56.0
3 (1st lens 2nd surface) 0.625 0.185
4 (1st surface of the second lens) -1.212 0.420 1.531 56.0
5 (2nd lens 2nd surface) -1.176 0.090
6 (cover glass first side) 0.000 0.000 1.516 64.0
7 (cover glass second side) 0.000
(Image plane)

Surface number k A B C D
2 -6.93 1.44E + 1 -1.49E + 2 1.49E + 3 -5.04E + 3
3 4.57 5.07E-1 -1.57E + 1 4.33 3.42E + 3
4 2.04E + 1 -2.79E-1 -1.10E + 2 2.41E + 3 -2.71E + 4
5 4.40 -3.25E-2 -3.42 5.41 -1.05E + 2

Under such conditions, L / fl = 1.07 was achieved, thereby satisfying the expression (1). F ₁ /fl=0.93 was achieved, thereby satisfying the expression (2). F ₂ / f ₁ = 10.27 was achieved, thereby satisfying the expression (3). D ₂ / d ₁ = 0.66 was achieved, thereby satisfying the expression (4).

  FIG. 9 shows spherical aberration, astigmatism, and distortion in the imaging lens 1 of the fourth example.

  According to this result, it is understood that all of spherical aberration, astigmatism and distortion are almost satisfactory, and sufficient optical characteristics can be obtained.

  In addition, this invention is not limited to the thing of the said Example, It can change variously as needed.

  For example, a light amount limiting plate may be disposed between the second surface of the first lens 3 and the first surface of the second lens 4 as necessary.

DESCRIPTION OF SYMBOLS 1 Imaging lens 2 Aperture 3 1st lens 4 2nd lens 6 Filter 7 Imaging surface

Claims (1)

An imaging lens used to form an image of an object on an imaging surface of a solid-state imaging device,
A first lens having a positive meniscus lens having a positive power with an aperture and a convex surface facing the object side in order from the object side to the image surface side, and a meniscus lens having a positive power with a convex surface facing the image surface side The second lens is arranged, and the following conditional expressions (1) to (4):
0.8 ≦ L / fl ≦ 1.25 (1)
0.9 ≦ f ₁ /fl≦1.0 (2)
10 ≦ f ₂ / fl ≦ 25 (3)
0.5 ≦ d ₂ / d ₁ ≦ 1.0 (4)
However,
L: total length of the lens system fl: focal length of the entire lens system f ₁ : focal length of the first lens f ₂ : focal length of the second lens d ₁ : center thickness of the first lens d ₂ : first on the optical axis An imaging lens characterized by satisfying a distance between the lens and the second lens.

Images