JP2000098224A - Lens and optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lens having the angle of view of about 50 deg. with simple constitution and having complete optical performance in practical use as a camera to be used for monitoring by constituting the lens so that a surface nearest to an image side is plane and an image-forming position comes to the vicinity of the plane and satisfying a specified condition. SOLUTION: This lens is a two bonded lens obtained by bonding a positive lens L1 being a homogeneous lens and a negative lens L2 being a homogeneous lens in order from an object side and is constituted so that the surface of the bonded lens nearest to an image side is plane and the image-forming position comes to the plane. A brightness diaphragm S is provided on the surface of the lens L1 on the object side and the bonded surface between the lenses L1 and L2 is made convex to the image side. Furthermore, the surface of the lens L1 on the object side is aspherical. The lens satisfies an expression -0.25<=db/f<=0.25. In the expression, db represents the back focus of the lens system and (f) represents the focal distance of the entire lens system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens used for a video camera or the like and an optical module using the same.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for a small-sized and low-cost imaging module capable of easily imaging.
Lens systems used in these imaging modules include:
In many cases, a lens having an angle of view of about 50 ° is required, and generally 4 to 6 lenses are used as a lens configuration. Particularly, when the number of lenses is small, there is a lens system disclosed in Japanese Patent Application Laid-Open No. 4-211214, which has a two-lens configuration including an imaging lens and a correction lens.

[0003]

However, in the conventional four to six lens arrangement, the number of lenses is large, and the lens frame arrangement for fixing the lens becomes complicated and the cost increases.
In the above-mentioned Japanese Patent Application Laid-Open No. 4-211214, although the number is small, a plurality of lenses and an image sensor are separately provided, and the cost is increased due to the necessity of adjustment after assembly.

The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object a simple structure of 50 °.
An object of the present invention is to provide a lens having an angle of view of about the same and having practically sufficient optical performance as a camera for surveillance or the like. Another object of the present invention is to provide a small-sized and low-cost imaging module with a simple configuration.

[0005]

According to the present invention, there is provided a lens according to the present invention, wherein (1) a surface closest to an image is a plane, and an image forming position is located near the plane. A two-element cemented homogeneous lens, which satisfies the condition (1).

[0006] _{-0.25 ≦ d b /f≦0.25 ··· (1} ) , however, d _b is the lens system back focus, f is the focal length of the entire lens system.

With this configuration, it is possible to provide a lens system having a simple configuration and better optical performance than one lens. Also, by joining the two lenses, assembly becomes easy, and the configuration of the lens frame can be made simple and low in cost. Further, since the surface closest to the image is flat and the image position can be located near this surface, it is convenient when the lens system is configured as a device integrated with an image pickup device such as a CCD.
The lens system can also serve as a cover glass.

By satisfying the condition (1), FIG.
As shown in FIG. 7, the image forming position is located near the most image-side surface of the lens system. If the condition (1) is not satisfied, the image will be blurred.

(2) In the above (1), a positive lens and a negative lens are arranged in order from the object side.
2. The cemented lens according to item 1.

In this configuration, light rays can be made incident on the image pickup surface of the image pickup element at a practically acceptable angle, and the aberration can be further corrected. In this configuration, it is desirable that the following condition (11) is satisfied.

0.0 ≦ | IH / ex | ≦ 0.5 (11) where IH is the maximum image height, and ex is the exit pupil at the maximum image height from the top of the most image-side surface of the lens system. It is the distance in the optical axis direction up to. By satisfying the condition (11), the aberration can be corrected in a state where there is no practical problem as an imaging module or the like.

Preferably, the Abbe number of both lenses is 30 or more. If the Abbe number of both lenses is less than 30, chromatic aberration will deteriorate and optical performance will deteriorate. Further, if the Abbe number of both lenses is 40 or more, it is possible to suppress the occurrence of axial chromatic aberration, and depending on the combination of the media, it is possible to balance the respective aberrations and suppress the chromatic aberration of magnification, thereby providing a better optical system. It can be a lens system with high performance.

(3) The two-element cemented lens according to (2), wherein the object side surface of the positive lens is a curved surface, and the cemented surface is convex toward the image side.

In this configuration, light rays can be made incident on the image pickup surface of the image pickup element at an angle that does not pose a practical problem, and it is possible to correct aberrations. In this configuration, it is desirable that the following condition (12) is satisfied.

−0.03 ≦ (n ₁ −1.0) × f / r ₁ ≦ 0.12 (12) where n ₁ is the refractive index of the positive lens, and f is the focal point of the entire lens system. distance, r ₁ is the radius of curvature of the object side surface of the positive lens. If the condition (12) is not satisfied, the astigmatic difference will increase.

In this configuration, the following condition (1)
It is desirable to satisfy 3). 0.8 ≦ | r ₂ | / d ₁ ≦ 1.2 (13) where r ₂ is the radius of curvature of the joint surface, and d ₁ is the surface interval of the positive lens. If the condition (13) is not satisfied, the astigmatic difference will increase.

Further, it is desirable that the following condition (13 ') is satisfied. 0.9 ≦ | r ₂ | / d ₁ ≦ 1.1 (13 ′) Further, it is desirable to satisfy the following condition (13 ″).

0.95 ≦ | r ₂ | / d ₁ ≦ 1.06 (13 ″) Also, (4) the object side surface of the positive lens is an aspherical surface. 2) or 2) described in (3).
Single cemented lens.

In this configuration, by making the spherical aberration negative by using an aspherical surface, the image position can be brought to a position where the optical performance is good not only on the optical axis but also at an off-axis image height.

It is preferable that the aspherical surface in this configuration is such that the negative power increases as the distance from the surface top in the direction perpendicular to the optical axis increases. If it is not such an aspherical surface, spherical aberration cannot be reduced to a negative value, and the position of good optical performance at the optical axis and at the off-axis image height will be shifted, and the optical performance at the off-axis image height will deteriorate. Resulting in.

(5) The two-element cemented lens described in (2) to (4), wherein the following condition (2) is satisfied.

0 <n ₁ −n ₂ (2) where n ₁ is the refractive index of the positive lens, and n ₂ is the refractive index of the negative lens. In this configuration, light rays can be made incident on the imaging surface of the imaging device at an angle that does not pose a practical problem, and aberrations can be further corrected.

(6) The two-element cemented lens as described in any of (2) to (5) above, which has a brightness stop and satisfies the following condition (3).

−0.02 <d _s /f<0.06 (3) where d _s is the distance in the optical axis direction from the object-side surface of the positive lens to the aperture stop, f Is the focal length of the entire lens system.

Further, light rays can be made incident on the image pickup surface of the image pickup device at an angle that does not pose a practical problem, and it becomes possible to correct aberrations. In particular, astigmatism and chromatic aberration of magnification can be favorably corrected.

(7) The following conditions (4) and (5)
The two-element cemented lens according to any one of (2) to (6), wherein

| N ₁ −n ₂ | ≦ 0.3 (4) 4.0 <d ₂ / d ₁ <7.0 (5) where n ₁ is the refractive index of the positive lens , N ₂ is the refractive index of the negative lens, d ₁ is the surface spacing of the positive lens, and d ₂ is the surface spacing of the negative lens.

With this configuration, it is possible to satisfactorily correct each aberration. In particular, it is possible to favorably correct distortion and chromatic aberration of magnification. In this configuration, it is desirable to satisfy the following conditions (4 ′) and (5 ′).

0.2 ≦ | n ₁ −n ₂ | ≦ 0.3 (4 ′) 4.5 ≦ d ₂ / d ₁ ≦ 6.0 (5 ′) Condition (4 ′) By satisfying (5 ′), it is possible to obtain a lens system having better optical performance in which astigmatism and coma are corrected.

(8) The following conditions (6) and (7)
The two-element cemented lens according to any one of (2) to (6), wherein

0.3 <| n ₁ −n ₂ | (6) 2.5 <d ₂ / d ₁ <5.0 (7) where n ₁ is the refractive index of the positive lens. , N ₂ is the refractive index of the negative lens, d ₁ is the surface spacing of the positive lens, and d ₂ is the surface spacing of the negative lens.

In this configuration, it is possible to satisfactorily correct each aberration. In particular, it is possible to favorably correct distortion and chromatic aberration of magnification. It is desirable that the following condition (7 ′) is satisfied in this configuration.

3.0 ≦ d ₂ / d ₁ ≦ 4.5 (7 ′) By satisfying the condition (7 ′), astigmatism,
A lens system having better optical performance in which coma is corrected can be obtained. (9) The positive lens according to (2), wherein the positive lens has a sphere or a biconvex shape close to a sphere satisfying the following conditions (8) and (9), and the negative lens has a concave flat shape. 2) The cemented lens according to 2).

0.9 ≦ r ₁ / (d ₁ /2.0)≦1.1 (8) 0.0 ≦ | (r ₁ + r ₂ ) /f|≦0.15 ( 9) where r ₁ is the radius of curvature of the object-side surface of the positive lens,
d ₁ is the axial distance of said positive lens, r ₂ is the radius of curvature, f is the focal length of the entire lens system of the joint surface.

In this configuration, it is possible to satisfactorily correct each aberration. In particular, it is possible to favorably correct distortion and chromatic aberration of magnification. Further, since the shape of the positive lens is close to a sphere or a sphere, it is easy to manufacture and the cost is low. Further, by setting the stop position at the center of the spherical lens, it is easy to determine the stop position, which is convenient for manufacturing.
(10) The two-element cemented lens according to (9), wherein the following condition (10) is satisfied.

N ₁ −n ₂ <0 (10) where n ₁ is the refractive index of the positive lens, and n ₂ is the refractive index of the negative lens. In this configuration, it is possible to satisfactorily correct each aberration. In particular, it is possible to favorably correct distortion and chromatic aberration of magnification.

It is desirable that the following condition (10 ') is further satisfied. −0.4 <n ₁ −n ₂ ≦ −0.2 (10 ′) By satisfying the condition (10 ′), it is possible to obtain better optical performance in which astigmatism and coma are corrected. Lens system. (11) The two-element cemented lens according to (9) or (10), further comprising a brightness stop in the lens system.

In addition, each aberration can be satisfactorily corrected, and in particular, astigmatism, distortion, and coma can be satisfactorily corrected. In this configuration, the following condition (14)
It is desirable to satisfy

0.1 <d _s /f<0.5 (14) where d _s is the distance in the optical axis direction from the object-side surface of the positive lens to the aperture stop, and f is This is the focal length of the entire lens system. By satisfying the condition (14),
In particular, it is possible to obtain a lens system having better optical performance in which distortion, chromatic aberration of magnification, and coma are corrected.

It is desirable that the following condition (14 ') is satisfied. 0.25 <d _s /f<0.5 (14 ′) In this configuration, it is desirable that the following condition (15) is satisfied.

[0041] _{-0.05 ≦ (r 1 -d s)} /f≦0.13 ··· (15) However, r ₁ is the radius of curvature of the object side surface of the positive lens. By satisfying the condition (15), it is possible to obtain a lens system having better optical performance in which distortion, chromatic aberration of magnification, and coma are corrected. Also, (12)
The two-element cemented lens according to the above (1), comprising a negative lens and a positive lens in order from the object side.

In this configuration, each aberration can be satisfactorily corrected, and particularly, distortion and chromatic aberration of magnification can be satisfactorily corrected. (13) The two-element cemented lens according to (12), wherein the negative lens has a meniscus shape, and the positive lens has a convex flat shape.

In this configuration, each aberration can be satisfactorily corrected, and particularly, distortion and chromatic aberration of magnification can be satisfactorily corrected. In this configuration, the following condition (1)
It is desirable to satisfy 6).

0.2 <d ₁ /f<0.5 (16) where d ₁ is the surface distance of the positive lens, and f is the focal length of the entire lens system. By satisfying the condition (16), it is possible to obtain a lens system having better optical performance in which distortion, chromatic aberration of magnification, and coma are corrected.

In this configuration, the following condition (1)
It is desirable to satisfy 7). 0.1 <r ₂ /f<0.5 (17) where r ₂ is the radius of curvature of the joint surface, and f is the focal length of the entire lens system. By satisfying the condition (17), it is possible to obtain a lens system having better optical performance in which distortion, chromatic aberration of magnification, and coma are corrected. (14) The doublet cemented lens according to (12) or (13), further comprising a brightness stop in the lens system.

Further, it is possible to satisfactorily correct each aberration, and particularly to correct astigmatism, chromatic aberration of magnification, and coma. In this configuration, the following condition (1)
It is desirable to satisfy 8).

0.07 <d _s /f<2.0 (18) where d _s is the distance in the optical axis direction from the object-side surface of the positive lens to the aperture stop, and f is This is the focal length of the entire lens system. By satisfying the condition (18),
In particular, it is possible to obtain a lens system having better optical performance in which distortion, chromatic aberration of magnification, and coma are corrected. Also,
(15) The two-element cemented lens according to (1), comprising a positive lens and a positive lens in order from the object side.

In this configuration, each aberration can be satisfactorily corrected, and in particular, spherical aberration can be satisfactorily corrected. (16) The two-element cemented lens according to (15), wherein the positive lens on the object side has a meniscus shape, and the positive lens on the image side has a convex flat shape.

In this configuration, each aberration can be satisfactorily corrected, and in particular, spherical aberration can be satisfactorily corrected. In addition, it is possible to place the aperture on the joint surface because the surface shape of the joint surface is gentle, in which case, before joining the lenses, deposit chromium oxide etc. on one of the joint surfaces and provide a light shielding part The lens system can be easily manufactured.

In this configuration, the following condition (1)
It is desirable to satisfy 9). 0.1 <d ₁ /f<0.4 (19) where d ₁ is the surface distance of the positive lens, and f is the focal length of the entire lens system. By satisfying the condition (19), it is possible to obtain a lens system having better optical performance in which distortion, chromatic aberration of magnification, and coma are corrected. (17) The two-element cemented lens according to (15) or (16), further comprising a brightness stop in the lens system.

In this configuration, the following condition (2)
0) is preferably satisfied. 0.4 <d _s /f<1.5 (20) where d _s is the distance in the optical axis direction from the top of the positive lens on the object side to the aperture stop, and f is the entire lens system. Is the focal length. By satisfying the condition (20),
In particular, it is possible to obtain a lens system having better optical performance in which distortion, chromatic aberration of magnification, and coma are corrected. Further, the optical module of the present invention that achieves the above object provides (18)
An optical module, comprising: a two-element cemented homogeneous lens having a flat surface on the image side, which is disposed in close contact with an element for converting light intensity and electric signal.

The "element for converting light intensity and electric signal" is, for example, an image pickup element or a display element. (19) The double cemented lens is the double cemented lens according to any one of (1) to (17), and an imaging surface of an imaging element or a display surface of a display element is provided on a plane portion of the double cemented lens. The optical module according to the above (18), wherein the optical module is arranged in close contact.

When the optical module is configured as described above, variations in the lens, the lens holding member, the imaging surface of the imaging device, and the like can be extremely reduced, and the image forming surface of the lens system coincides with the imaging surface of the imaging device. It becomes easy to do. Further, in the case of an optical module requiring two optical systems for stereoscopic photography, AF, or the like, the optical axes of the optical systems are easily paralleled simply by attaching the lens system to the imaging area, and alignment is extremely easy.

In this configuration, the following condition (2)
It is desirable to satisfy 1) and (22). | N ₁ −n ₂ | ≦ 0.3 (21) 2.0 <d ₂ / d ₁ <4.0 (22) where n ₁ is the refractive index of the positive lens and n ₂ the refractive index of the negative lens, d ₁ is the axial distance of said positive lens, d ₂ is the spacing of the negative lens. By satisfying the conditions (21) and (22), light rays can be incident on the imaging surface of the imaging element at an angle that does not cause any practical problem, and it becomes possible to correct aberrations.

In this configuration, the following condition (2)
It is desirable to satisfy 3) and (24). 0.3 <| n ₁ −n ₂ | (23) 1.5 <d ₂ / d ₁ <3.0 (24) The above (6), (11), (14) In the configuration of (17), when the aperture stop is disposed inside the lens, as shown in FIG. 18, if a groove-shaped constricted portion is provided on the lens outer shape and black paint for light shielding is applied to the lens outer shape, aberrations may occur. It is possible to easily obtain a desired aperture configuration for correction without increasing the number of parts.

[0056]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the lens of the present invention and an optical module using the same will be described.

1 to 3 are lens sectional views of Examples 1 to 3, respectively. FIGS. 4 to 8 are lens sectional views of Examples 7 to 11, respectively. FIGS. 9 and 10 are Examples 13 and 14, respectively. FIG. 11 is an aberration curve diagram of Example 1, FIGS. 12 to 14 are aberration curve diagrams of Examples 7 to 9, respectively, and FIGS. 15 and 16 are aberration curve diagrams of Examples 11 and 14, respectively. Lens configuration of the first embodiment, as shown in FIG. 1, in order from the object side, a cemented doublet lens formed by bonding a negative lens L ₂ of the positive lens L ₁ and homogeneous lens of a homogeneous lens. The most image side surface of the cemented lens is a plane, and the image forming position is on this plane. Also, the positive lens L
₁ has an aperture stop S on the object-side surface, and has a positive lens L ₁
The bonding surface of the negative lens L ₂ is convex toward the image side. Furthermore, the object side surface of the positive lens L ₁ is aspherical. FIG.
9 shows an aberration curve diagram of the first embodiment.

[0058] lens configuration of the second embodiment, as shown in FIG. 2, is a cemented doublet lens in order from the object side, and joining the negative lens L ₂ of the positive lens L ₁ and homogeneous lens of homogeneous lens . The most image side surface of the cemented lens is a plane, and the image forming position is on this plane. In addition, the positive lens L ₁
Inside has an aperture stop S, the junction surface between the positive lens L ₁ and the negative lens L ₂ is convex toward the image side. Furthermore, the object side surface of the positive lens L ₁ is aspherical.

[0059] lens configuration of the third embodiment, as shown in FIG. 3, is a two cemented lens in order from the object side, and joining the negative lens L ₂ of the positive lens L ₁ and homogeneous lens of homogeneous lens . The most image side surface of the cemented lens is a plane, and the image forming position is on this plane. In addition, the positive lens L ₁
Has an aperture stop S toward the object side than the object-side surface of the bonding surface of the positive lens L ₁ and the negative lens L ₂ is convex toward the image side. Furthermore, the object side surface of the positive lens L ₁ is aspherical.

As in the case of the first embodiment, each of the lens configurations of the fourth to sixth embodiments is a double cemented lens in which a positive lens of a homogeneous lens and a negative lens of the homogeneous lens are cemented in order from the object side. The most image side surface of the cemented lens is a plane, and the image forming position is on this plane. In addition, there is a brightness stop on the object-side surface of the positive lens, and the joint surface between the positive lens and the negative lens has a convex shape on the image side. Further, the object-side surface of the positive lens is aspheric.

As shown by the numerical data described later, Examples 1 to 5 satisfy the conditions (1) to (5) and (11) to (13), and further satisfy the conditions (4 ') and (5'). ), (1)
3 ′) and (13 ″) are satisfied. In Example 6, the conditions (1) to (3), (6), (7), (11) to (13) are satisfied.
Is satisfied, and the conditions (7 ′), (13 ′), and (1) are satisfied.
3 ").

It is desirable that both the positive lens and the negative lens have an Abbe number of 30 or more as in the first to sixth embodiments. If the Abbe number of both lenses is less than 30, chromatic aberration will deteriorate and optical performance will deteriorate.

Further, when the Abbe number of both the positive lens and the negative lens is 40 or more as in Examples 4 to 6, the occurrence of axial chromatic aberration can be suppressed, and depending on the combination of media, the balance of each aberration can be reduced. Therefore, the chromatic aberration of magnification can be suppressed, and the lens system has better optical performance. The lens structure of Example 7, as shown in FIG. 4, a negative lens L of plano-concave shape positive lens L ₁ and homogeneous biconvex lens close to the object side in this order, the spherical homogeneous lens
_This is a two-element cemented lens obtained by cementing No. ₂ and No. 2. The most image side surface of the cemented lens is a plane, and the image forming position is on this plane. Also has an aperture stop S in the interior of the positive lens L _1,
Bonding surface between the positive lens L ₁ and the negative lens L ₂ is convex toward the image side. As apparent from the above, the object side surface of the positive lens L ₁ is a curved surface. FIG. 12 shows an aberration curve diagram of the seventh embodiment.

[0064] lens configuration of the eighth embodiment, as shown in FIG. 5, the negative lens of the plano-concave shape positive lens L ₁ and homogeneous lens spherical (biconvex) from the object side in this order, with homogeneous lens L _This is a two-element cemented lens obtained by cementing No. ₂ and No. 2. The most image side surface of the cemented lens is a plane, and the image forming position is on this plane. Also has an aperture stop S in the interior of the positive lens L _1, the junction surface of the positive lens L ₁ and the negative lens L ₂ is convex toward the image side. As apparent from the above, the object side surface of the positive lens L ₁ is a curved surface. FIG. 13 shows an aberration curve diagram of the eighth embodiment.

As shown by the numerical data described below, the seventh and eighth embodiments satisfy the conditions (1), (8) to (10), (14),
(15) is satisfied, and the conditions (10 ′) and (1) are satisfied.
4 ') is satisfied.

[0066] lens configuration of Example 9, as shown in FIG. 6, in order from the object side, a convex plane shape negative lens L ₁ and homogeneous meniscus lens having a convex surface on the object side with homogeneous lens This is a cemented _double lens in which the positive lens L2 is cemented. The most image-side surface of the cemented lens is a plane, and the image forming position comes near this plane. Also it has an aperture stop S in the interior of the negative lens L _1. FIG. 14 shows an aberration curve diagram of the ninth embodiment.

[0067] lens configuration of Example 10, as shown in FIG. 7, in order from the object side, a convex plane shape negative lens L ₁ and homogeneous meniscus lens having a convex surface directed toward the object side in the homogeneous lens positive lens a two cemented lens in which a L _2. The most image-side surface of the cemented lens is a plane, and the image forming position comes near this plane. Also it has an aperture stop S in the interior of the positive lens L _2.

As shown by the numerical data described later, the ninth and tenth embodiments satisfy the conditions (1), (17) and (18). Example 9 satisfies the condition (16). The lens structure of Example 11, as shown in FIG. 8, in order from the object side, a positive lens positive lens element convex planar shape by L ₁ and homogeneous lens L having a meniscus shape with a convex surface on the object side with homogeneous lens _This is a two-element cemented lens obtained by cementing No. ₂ and No. 2. The most image side surface of the cemented lens is a plane, and the image forming position is on this plane. Also it has the aperture stop S in the interior of the positive lens L ₂ to the image side. FIG. 15 shows an aberration curve diagram of the eleventh embodiment.

As in the case of the eleventh embodiment, the lens configuration of the twelfth embodiment includes, in order from the object side, a positive meniscus lens having a convex surface facing the object side with a homogeneous lens and a positive convex lens having a homogeneous lens with a convex flat surface. This is a cemented two-element lens. The most image-side surface of the cemented lens is a plane, and the image forming position comes near this plane. Further, a brightness stop is provided inside the positive lens on the image side.

[0070] lens configuration of Example 13, as shown in FIG. 9, in order from the object side, a meniscus shape with a convex surface on the object side with homogeneous lens positive lens L ₁ and the convex flat shape homogeneous lens This is a cemented _double lens in which the positive lens L2 is cemented. The most image side surface of the cemented lens is a plane,
The imaging position is on this plane. Also it has an aperture stop S on the joint surface of the positive lens L ₁ and the positive lens L _2.

As shown by the numerical data described later, Examples 11 to 13 satisfy the conditions (1) and (20). Examples 11 and 12 satisfy the condition (19). Example 14-
Reference numeral 18 denotes an example in which an optical module is formed by disposing the two-element cemented lens of the present invention in close contact with an image sensor such as a CCD having a cover glass.

As shown in FIG. 10, the lens configuration of the fourteenth embodiment is a double cemented lens in which a positive lens L ₁ of a homogeneous lens and a negative lens L _{2 of a} homogeneous lens are cemented in order from the object side (not shown). . The most image-side surface of the cemented lens is a flat surface, and the cover glass C of the image sensor is in close contact with this flat surface,
The imaging position is on the imaging plane I of the imaging device. FIG. 16 shows an aberration curve diagram of the fourteenth embodiment.

The two cemented lens portions of Examples 14 to 18 are common to Examples 1 to 4 and 6, respectively, except for the value of the surface distance of the image-side negative lens.
Is omitted.

As shown by the numerical data described later, Examples 14 to 17 satisfy the conditions (21) and (22). Example 18 satisfies the conditions (23) and (24). Below, numerical data of Examples 1 to 18 are shown. In each embodiment, in addition to the symbols described above, F _NO is an F number, ω is a half angle of view, r ₁ , r ₂ ,... Are radii of curvature of respective lens surfaces,
.., d ₁ , d _{2 ,.}
n _d2 ,... are the d-line refractive indices of each lens, ν _d1 , ν _d2 ,
... is the Abbe number of the d-line of each lens. The aspheric surface is represented by the following equation (a) when the x-axis is taken in the optical axis direction and the y-axis is taken in a plane perpendicular to the x-axis, with the intersection point with the optical axis as the origin.

X = (y ² / r) / [1+ {1− (k + 1) (y / r) ² }] + A ₄ y ⁴ + A ₆ y ⁶ +... (A) where r Is the paraxial radius of curvature, k is the conic coefficient, A ₄ , A ₆
Are fourth-order and sixth-order aspherical coefficients, respectively.

In the data, the aperture stop is set to the 0th plane (r
₀). Therefore, the brightness aperture
Surface distance between the 0th surface and the 1st surface
(D₀) Is a negative value. Examples 14 to 1
In the data of No. 8, r_Three~ R _FourIs the cover cover of the image sensor
Represents a lath. (Example 1) r₀= ∞ (aperture) d₀= 0.0000 r₁= 53.8802 (aspherical surface) d₁= 1.2161 n_d1 = 1.88300 ν_d1 = 40.76 r_Two= -1.2295 d_Two= 6.3034 n_d2 = 1.59270 ν_d2 = 35.30 r_Three= Ｄ d_b= 0.0000 f = 4.0000 F_NO = 2.8000 IH = 2.0000 2ω = 57.79 ° Aspheric coefficient first surface k = 0.0000 A_Four= -8.6502 × 10^-3 A₆= -3.5359 × 10^-2 (1) d_b/F=0.0 (2) n₁-N_Two= 0.29 (3) d_s/F=0.0 (4) | n₁-N_Two| = 0.29 (5) d_Two/ D₁= 5.18 (11) | IH / ex | = 0.449 (12) (n₁−1.0) × f / r₁= 0.066 (13) | r_Two| / D₁= 1.01 (Example 2) r₀= ∞ (aperture) d₀= -0.1502 r₁= -134.7101 (aspherical surface) d₁= 1.0730 n_d1 = 1.88300 ν_d1 = 40.76 r_Two= -1.1358 d_Two= 6.3949 n_d2 = 1.59270 ν_d2 = 35.30 r_Three= Ｄ d_b= 0.0000 f = 4.0000 F_NO = 2.8000 IH = 2.0000 2ω = 57.67 ° Aspheric coefficient first surface k = 0.0000 A_Four= -1.3522 × 10^-2 A₆= -5.6879 × 10^-2 (1) d_b/F=0.0 (2) n₁-N_Two= 0.29 (3) d_s/F=0.038 (4) | n₁-N_Two| = 0.29 (5) d_Two/ D₁= 5.96 (11) | IH / ex | = 0.478 (12) (n₁−1.0) × f / r₁= -0.026 (13) | r_Two| / D₁= 1.06 (Example 3) r₀= ∞ (aperture) d₀= 0.0790 r₁= 37.1598 (aspherical surface) d₁= 1.2945 n_d1 = 1.88300 ν_d1 = 40.76 r_Two= -1.2622 d_Two= 6.2667 n_d2 = 1.59270 ν_d2 = 35.30 r_Three= Ｄ d_b= 0.0000 f = 4.0000 F_NO = 2.8000 IH = 2.0000 2ω = 57.88 ° Aspheric coefficient first surface k = 0.0000 A_Four= -1.0007 × 10^-2 A₆= -3.0588 × 10^-2 (1) d_b/F=0.0 (2) n₁-N_Two= 0.29 (3) d_s/F=-0.0198 (4) | n₁-N_Two| = 0.29 (5) d_Two/ D₁= 4.84 (11) | IH / ex | = 0.433 (12) (n₁−1.0) × f / r₁= 0.095 (Example 4) r₀= ∞ (aperture) d₀= 0.0000 r₁= 93.9611 (aspherical surface) d₁= 1.0889 n_d1 = 1.77250 ν_d1 = 49.60 r_Two= -1.0795 d_Two= 5.7872 n_d2 = 1.50137 ν_d2 = 56.40 r_Three= Ｄ d_b= 0.0000 f = 4.0000 F_NO = 2.8000 IH = 2.0000 2ω = 59.43 ° Aspherical surface first surface k = 0.0000 A_Four= -2.5225 × 10^-2 A₆= -6.3253 × 10^-2 (1) d_b/F=0.0 (2) n₁-N_Two= 0.27 (3) d_s/F=0.0 (4) | n₁-N_Two| = 0.27 (5) d_Two/ D₁= 5.31 (11) | IH / ex | = 0.462 (12) (n₁−1.0) × f / r₁= 0.032 (13) | r_Two| / D₁= 0.991 (Example 5) r₀= ∞ (aperture) d₀= 0.0000 r₁= ∞ (aspherical surface) d₁= 1.0899 n_d1 = 1.77250 ν_d1 = 49.60 r_Two= -1.0845 d_Two= 6.0055 n_d2 = 1.50137 ν_d2 = 56.40 r_Three= ∞ f = 4.0000 F_NO = 2.8000 IH = 2.0000 2ω = 57.53 ° Aspheric coefficient first surface k = 0.0000 A_Four= -2.4131 × 10^-2 A₆= -5.9475 × 10^-2 (1) d_b/F=0.0 (2) n₁-N_Two= 0.27 (3) d_s/F=0.0 (4) | n₁-N_Two| = 0.27 (5) d_Two/ D₁= 5.51 (11) | IH / ex | = 0.446 (12) (n₁−1.0) × f / r₁= 0.0 (13) | r_Two| / D₁= 0.995 (Example 6) r₀= ∞ (aperture) d₀= 0.0000 r₁= 84.3952 (aspherical surface) d₁= 1.5082 n_d1 = 1.88300 ν_d1 = 40.76 r_Two= -1.5179 d_Two= 6.0145 n_d2 = 1.51633 ν_d2 = 64.14 r_Three= Ｄ d_b= 0.0000 f = 4.0000 F_NO = 2.8000 IH = 2.0000 2ω = 57.79 ° Aspheric coefficient first surface k = 0.0000 A_Four= -7.8028 × 10^-3 A₆= -2.1057 × 10^-2 (1) d_b/F=0.0 (2) n₁-N_Two= 0.37 (3) d_s/F=0.0 (6) | n₁-N_Two| = 0.37 (7) d_Two/ D₁= 3.99 (11) | IH / ex | = 0.423 (12) (n₁−1.0) × f / r₁= 0.042 (13) | r_Two| / D₁= 1.01 (Example 7) r₀= ∞ (aperture) d₀= -1.0752 r₁= 1.5186 d₁= 2.8754 n_d1 = 1.51821 ν_d1 = 65.04 r_Two= -1.1126 d_Two= 2.5542 n_d2 = 1.80518 ν_d2 = 25.43 r_Three= Ｄ d_b= 0.0000 f = 4.0000 F_NO = 2.8000 IH = 2.0000 2ω = 53.21 ° (1) d_b/F=0.0 (8) r₁/ (D₁/2.0) = 1.056 (9) | (r₁+ R_Two) /F|=0.101 (10) n₁-N_Two= -0.29 (14) d_s/F=0.269 (15) (r₁-D_s) /F=0.111 (Example 8) r₀= ∞ (aperture) d₀= -1.5738 r₁= 1.5738 d₁= 3.1476 n_d1 = 1.49700 ν_d1 = 81.54 r_Two= -1.5738 d_Two= 2.4262 n_d2 = 1.80518 ν_d2 = 25.43 r_Three= Ｄ d_b= 0.0000 f = 4.0000 F_NO = 2.8000 IH = 2.0000 2ω = 53.13 ° (1) d_b/F=0.0 (8) r₁/ (D₁/2.0)=1.0 (9) | (r₁+ R_Two) /F|=0.0 (10) n₁-N_Two= -0.31 (14) d_s/F=0.39 (15) (r₁-D_s) /F=0.0 (Example 9) r₀= ∞ (aperture) d₀= -0.8927 r₁= 1.6396 d₁= 1.0161 n_d1 = 1.88300 ν_d1 = 40.76 r_Two= 0.9007 d_Two= 4.2999 n_d2 = 1.51633 ν_d2 = 64.14 r_Three= Ｄ d_b= 0.0043 f = 4.0000 F_NO = 2.8000 IH = 2.0000 2ω = 52.89 ° (1) d_b/F=0.00107 (16) d₁/F=0.254 (17) r_Two/F=0.225 (18) d_s/F=0.223 (Example 10) r₀= ∞ (aperture) d₀= -2.9538 r₁= 18.1768 d₁= 2.3258 n_d1 = 1.51633 ν_d1 = 64.14 r_Two= 1.5826 d_Two= 7.2038 n_d2 = 1.88300 ν_d2 = 40.76 r_Three= Ｄ d_b= 0.0000 f = 4.0000 F_NO = 2.8000 IH = 2.0000 2ω = 55.43 ° (1) d_b/F=0.0 (17) r_Two/F=0.396 (18) d_s/ F = 0.738 (Example 11) r₀= ∞ (aperture) d₀= -4.0801 r₁= 3.0813 (aspherical surface) d₁= 1.0011 n_d1 = 1.88300 ν_d1 = 40.76 r_Two= 6.7301 d_Two= 5.4002 n_d2 = 1.59270 ν_d2 = 35.30 r_Three= Ｄ d_b= 0.0000 f = 4.0000 F_NO = 2.8000 IH = 2.0000 2ω = 51.87 ° Aspheric coefficient first surface k = 0.0000 A_Four= -6.8826 × 10^-Four A₆= -7.6584 × 10^-Five (1) d_b/F=0.0 (19) d₁/F=0.25 (20) d_s/F=1.02 (Example 12) r₀= ∞ (aperture) d₀= -3.0632 r₁= 2.5266 d₁= 1.6722 n_d1 = 1.51633 ν_d1 = 64.14 r_Two= 6.2227 d_Two= 5.8346 n_d2 = 1.75500 ν_d2 = 52.32 r_Three= Ｄ d_b= -0.0151 f = 4.0000 F_NO = 2.8000 IH = 2.0000 2ω = 51.07 ° (1) d_b/F=-0.00352 (19) d₁/F=0.391 (20) d_s/F=0.717 (Example 13) r₀= ∞ (aperture) d₀= -2.5904 r₁= 2.2259 d₁= 2.5904 n_d1 = 1.51633 ν_d1 = 64.14 r_Two= 7.9896 d_Two= 4.2381 n_d2 = 1.75500 ν_d2 = 52.32 r_Three= Ｄ d_b= 0.0000 f = 4.0000 F_NO = 2.8000 IH = 2.0000 2ω = 54.50 ° (1) d_b/F=0.0 (20) d_s/F=0.717 (Example 14) r₀= ∞ (aperture) d₀= 0.0000 r₁= 53.8802 (aspherical surface) d₁= 1.2161 n_d1 = 1.88300 ν_d1 = 40.76 r_Two= -1.2295 d_Two= 3.6603 n_d2 = 1.59270 ν_d2 = 35.30 r_Three= Ｄ d_Three= 1.0000 n_d3 = 1.51633 ν_d3 = 64.14 r_Four= ∞ f = 4.0000 F_NO = 2.8000 IH = 2.0000 2ω = 57.05 ° Aspheric coefficient first surface k = 0.0000 A_Four= -8.6502 × 10^-3 A₆= -3.5359 × 10^-2 (21) | n₁-N_Two| = 0.29 (22) d_Two/ D₁= 3.01 (Example 15) r₀= ∞ (aperture) d₀= -0.1502 r₁= -134.7101 (aspherical surface) d₁= 1.0730 n_d1 = 1.88300 ν_d1 = 40.76 r_Two= -1.1358 d_Two= 3.7518 n_d2 = 1.59270 ν_d2 = 35.30 r_Three= Ｄ d_Three= 1.0000 n_d3 = 1.51633 ν_d3 = 64.14 r_Four= ∞ f = 4.0000 F_NO = 2.8000 IH = 2.0000 2ω = 56.80 ° Aspherical surface first surface k = 0.0000 A_Four= -1.3522 × 10^-2 A₆= -5.6879 × 10^-2 (21) | n₁-N_Two| = 0.29 (22) d_Two/ D₁= 3.5 (Example 16) r₀= ∞ (aperture) d₀= 0.0790 r₁= 37.1598 (aspherical surface) d₁= 1.2945 n_d1 = 1.88300 ν_d1 = 40.76 r_Two= -1.2622 d_Two= 3.6236 n_d2 = 1.59270 ν_d2 = 35.30 r_Three= Ｄ d_Three= 1.0000 n_d3 = 1.51633 ν_d3 = 64.14 r_Four= ∞ f = 4.0000 F_NO = 2.8000 IH = 2.0000 2ω = 57.20 ° Aspheric coefficient first surface k = 0.0000 A_Four= -1.0007 × 10^-2 A₆= -3.0588 × 10^-2 (21) | n₁-N_Two| = 0.29 (22) d_Two/ D₁= 2.8 (Example 17) r₀= ∞ (aperture) d₀= 0.0000 r₁= 93.9611 (aspherical surface) d₁= 1.0889 n_d1 = 1.77250 ν_d1 = 49.60 r_Two= -1.0795 d_Two= 3.2957 n_d2 = 1.50137 ν_d2 = 56.40 r_Three= Ｄ d_Three= 1.0000 n_d3 = 1.51633 ν_d3 = 64.14 r_Four= ∞ f = 4.0000 F_NO = 2.8000 IH = 2.0000 2ω = 58.71 ° Aspheric coefficient first surface k = 0.0000 A_Four= -2.5225 × 10^-2 A₆= -6.3253 × 10^-2 (21) | n₁-N_Two| = 0.27 (22) d_Two/ D₁= 3.03 (Example 18) r₀= ∞ (aperture) d₀= 0.0000 r₁= 102.8507 (aspherical surface) d₁= 1.5663 n_d1 = 1.88300 ν_d1 = 40.76 r_Two= -1.5080 d_Two= 3.5057 n_d2 = 1.51633 ν_d2 = 64.14 r_Three= Ｄ d_Three= 1.0000 n_d3 = 1.51633 ν_d3 = 64.14 r_Four= ∞ f = 4.0000 F_NO = 2.8000 IH = 2.0000 2ω = 57.26 ° Aspherical surface first surface k = 0.0000 A_Four= 3.0631 × 10^-3 A₆= -3.4853 × 10^-2 (23) | n₁-N_Two| = 0.37 (24) d_Two/ D₁= 2.24 Next, the optical modules of Examples 14 to 18 will be described in detail.
I will explain.

FIG. 19 shows an example of the optical module of the present invention. 1 is a lens of the present invention, 2 is an imaging chip of an imaging device,
Reference numeral 3 denotes an imaging surface of the imaging device, and 4 denotes a ceramic substrate of the imaging device. The lens 1 and the imaging device are brought into close contact with each other by directly bonding the final surface 5 of the lens 1 which is a flat surface to the imaging chip 2. . An epoxy adhesive or the like is used for bonding. At this time, the image of the object at a predetermined distance is
With such a configuration as above, the image can be captured. Also, depending on the depth of field of the lens 1, an object located around a predetermined distance can be imaged in a considerably wide range.

FIG. 20 shows another example of the optical module of the present invention.
Shown in In this example, the gap between the lens 1 and the imaging chip 2 is filled with a resin 6 and integrated, and the final surface 5 and the imaging surface 3 of the lens 1 are integrated.
Are optically adhered to each other. At this time, the lens 1 is moved so that an image of an object at a predetermined distance
If the thickness of the resin 6 is adjusted, the image can be captured. Also, depending on the depth of field of the lens 1, an object located around a predetermined distance can be imaged in a considerably wide range.

The following advantages are obtained by configuring the optical module as described above. Usually, after assembling the imaging system, it is necessary to adjust the lens by moving the lens so that the imaging surface of the lens is exactly at the imaging surface. This is because the image forming surface of the lens shifts from the imaging surface after assembly due to variations in the lens itself, the lens holding member, the imaging surface of the imaging device, and the like. However, with the configuration as in the present invention, variations in the lens itself, the lens holding member, the imaging surface of the imaging device, and the like can be extremely reduced. As a result, the imaging surface of the lens can be imaged by the imaging device without adjustment. Can easily match the surface.

As described above, the doublet lens of the present invention is also suitable for forming an image pickup module integrated with an image pickup device. At this time, in the conventional image pickup system, the low-pass filter and the infrared cut filter disposed behind the lens system cannot be disposed as in the related art, but the following measures are possible. That is, first, for the infrared cut filter, a method of including an element that absorbs infrared light such as copper ions in the glass material constituting the lens, or a coating that cuts infrared light on the object side surface of the lens is used. And the like. As for the low-pass filter, a method of increasing the point image intensity distribution to a pixel pitch at which moiré is generated due to aberration and diffraction blur of the lens system,
There is a method of forming a diffraction pattern for eliminating moire on the object side surface of the lens. With the above configuration, integration of modules including a filter function can be achieved. Another example of the optical module of the present invention will be described.

When two optical systems are required for stereoscopic photography, AF, etc., it is necessary to accurately align the two lens systems. However, the alignment is troublesome and causes an increase in cost. . In conventional optical systems for electrically performing stereoscopic photography and phase detection AF,
It has been common practice to attach two separate lens systems to separate image sensors and use both optical systems in good alignment. Therefore, alignment of the two optical systems is required.

Therefore, in the present invention, as shown in FIG.
The two imaging areas 7 and 8 are provided on the same plane on one element substrate 9, and the final surfaces 1 of the two lenses 10 and 11 are provided.
The two lenses 10 and 11 are directly adhered to the two image pickup areas 7 and 8 after the planes 0 ′ and 11 ′ are planes and the image forming positions are located near the planes. In this case, the optical axes of the two lenses are easily parallel, so that the alignment is extremely easy. FIG. 21A is a front view of the optical module of this example viewed from the object side, and FIG. 21B is a side view.

The element substrate referred to here is a device in which an electric circuit pattern is formed on the surface of a flat wafer made of silicon or the like, and has a function of performing imaging and receiving and emitting light. Also, as the lens used at this time,
The two cemented lens of the present invention is effective. Since the doublet lens of the present invention is integrated, it can be bonded to the element substrate without using a lens frame. FIG. 22 shows still another example of the optical module of the present invention.

12 is a display element, 13 is a lens of the present invention,
Reference numeral 14 denotes a backlight, and the display element 12 and the lens 13
And are in close contact. This example is also used as a display optical system by placing a display element such as an LCD at the image forming position of the lens 13. The light from the display element 12 becomes almost parallel light by the lens 13,
By observing in close proximity to, an enlarged image of a display pattern (not shown) can be seen. The present invention can be configured as described below, in addition to the above.

(1) The double cemented lens according to claim 2, wherein the following condition (11) is satisfied. 0.0 ≦ | IH / ex | ≦ 0.5 (11) where IH is the maximum image height, and ex is the light from the top of the most image side surface of the lens system to the exit pupil of the maximum image height. Axial distance. (2) The doublet lens according to claim 3, wherein the following condition (12) is satisfied.

−0.03 ≦ (n ₁ −1.0) × f / r ₁ ≦ 0.12 (12) where n ₁ is the refractive index of the positive lens, and f is the focal point of the entire lens system. distance, r ₁ is the radius of curvature of the object side surface of the positive lens. (3) The doublet lens according to claim 3, wherein the following condition (13) is satisfied.

0.8 ≦ | r ₂ | / d ₁ ≦ 1.2 (13) where r ₂ is the radius of curvature of the joint surface, and d ₁ is the surface interval of the positive lens. (4) The two-element cemented lens according to claim 3, wherein the following condition (13 ') is satisfied.

0.9 ≦ | r ₂ | / d ₁ ≦ 1.1 (13 ′) where r ₂ is the radius of curvature of the joining surface, and d ₁ is the surface interval of the positive lens. (5) The doublet lens according to claim 3, wherein the following condition (13 ") is satisfied.

0.95 ≦ | r ₂ | / d ₁ ≦ 1.06 (13 ″) where r ₂ is the radius of curvature of the joining surface, and d ₁ is the surface spacing of the positive lens. The double cemented lens according to claim 7, wherein the following conditions (4 ') and (5') are satisfied.

0.2 ≦ | n ₁ −n ₂ | ≦ 0.3 (4 ′) 4.5 ≦ d ₂ / d ₁ ≦ 6.0 (5 ′) where n ₁ is The refractive index of the positive lens, n ₂ is the refractive index of the negative lens, d ₁ is the surface spacing of the positive lens, and d ₂ is the surface spacing of the negative lens. (7) The two-element cemented lens according to claim 8, wherein the following condition (7 ') is satisfied.

3.0 ≦ d ₂ / d ₁ ≦ 4.5 (7 ′) where d ₁ is the surface distance of the positive lens, and d ₂ is the surface distance of the negative lens. (8) The two-element cemented lens according to any one of claims 2 to 8, wherein both the positive lens and the negative lens have an Abbe number of 30 or more. (9) The two-element cemented lens according to any one of claims 2 to 8, wherein both the positive lens and the negative lens have an Abbe number of 40 or more. (10) The two-element cemented lens according to claim 10, wherein the following condition (10 ') is satisfied.

−0.4 <n ₁ −n ₂ ≦ −0.2 (10 ′) where n ₁ is the refractive index of the positive lens, and n ₂ is the refractive index of the negative lens. (11) The two-element cemented lens according to claim 11, wherein the following condition (14) is satisfied.

0.1 <d _s /f<0.5 (14) where d _s is the distance in the optical axis direction from the object-side surface of the positive lens to the aperture stop, and f is This is the focal length of the entire lens system. (12) The two-element cemented lens according to claim 11, wherein the following condition (14 ') is satisfied.

0.25 <d _s /f<0.5 (14 ′) where d _s is the distance in the optical axis direction from the object-side surface of the positive lens to the aperture stop, f Is the focal length of the entire lens system. (13) The two-element cemented lens according to claim 11, wherein the following condition (15) is satisfied.

−0.05 ≦ (r ₁ −d _s ) /f≦0.13 (15) where r ₁ is the radius of curvature of the object-side surface of the positive lens. (14) The two-element cemented lens according to claim 13, wherein the following condition (16) is satisfied.

0.2 <d ₁ /f<0.5 (16) where d ₁ is the surface distance of the positive lens, and f is the focal length of the entire lens system. (15) The doublet lens according to claim 13, wherein the following condition (17) is satisfied.

0.1 <r ₂ /f<0.5 (17) where r ₂ is the radius of curvature of the joint surface, and f is the focal length of the entire lens system. (16) The two-element cemented lens according to claim 14, wherein the following condition (18) is satisfied.

0.07 <d _s /f<2.0 (18) where d _s is a distance in the optical axis direction from the object-side surface of the positive lens to the aperture stop, and f is This is the focal length of the entire lens system. (17) The two-element cemented lens according to claim 16, wherein the following condition (19) is satisfied.

0.1 <d ₁ /f<0.4 (19) where d ₁ is the surface distance of the positive lens, and f is the focal length of the entire lens system. (18) The two-element cemented lens according to claim 17, wherein the following condition (20) is satisfied.

0.4 <d _s /f<1.5 (20) where d _s is the distance from the object-side surface of the positive lens to the aperture stop in the optical axis direction, and f is This is the focal length of the entire lens system. (19) The two-element cemented lens according to claim 19, wherein the following conditions (21) and (22) are satisfied.

| N ₁ −n ₂ | ≦ 0.3 (21) 2.0 <d ₂ / d ₁ <4.0 (22) where n ₁ is the refractive index of the positive lens. , N ₂ is the refractive index of the negative lens, d ₁ is the surface spacing of the positive lens, and d ₂ is the surface spacing of the negative lens. (20) The two-element cemented lens according to claim 19, wherein the following conditions (23) and (24) are satisfied.

0.3 <| n ₁ −n ₂ | (23) 1.5 <d ₂ / d ₁ <3.0 (24) where n ₁ is the refractive index of the positive lens. , N ₂ is the refractive index of the negative lens, d ₁ is the surface spacing of the positive lens, and d ₂ is the surface spacing of the negative lens.

[0103]

As is apparent from the above description, according to the present invention, a lens having an angle of view of about 50 ° with a simple configuration, and having practically sufficient optical performance as a camera for surveillance or the like is provided. A small, low-cost imaging module can be provided.

[Brief description of the drawings]

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

FIG. 2 is a sectional view of a lens according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a lens according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a lens according to a seventh embodiment of the present invention.

FIG. 5 is a sectional view of a lens according to Example 8 of the present invention.

FIG. 6 is a sectional view of a lens according to a ninth embodiment of the present invention.

FIG. 7 is a sectional view of a lens according to a tenth embodiment of the present invention.

FIG. 8 is a sectional view of a lens according to Example 11 of the present invention.

FIG. 9 is a sectional view of a lens according to a thirteenth embodiment of the present invention.

FIG. 10 is a sectional view of a lens according to a fourteenth embodiment of the present invention.

FIG. 11 is an aberration curve diagram according to the first embodiment of the present invention.

FIG. 12 is an aberration curve diagram of the seventh embodiment of the present invention.

FIG. 13 is an aberration curve diagram of the eighth embodiment of the present invention.

FIG. 14 is an aberration curve diagram of the ninth embodiment of the present invention.

FIG. 15 is an aberration curve diagram of the eleventh embodiment of the present invention.

FIG. 16 is an aberration curve diagram according to Example 14 of the present invention.

FIG. 17 is a diagram showing an image forming position of the lens of the present invention.

FIG. 18 is a diagram illustrating a method of arranging a brightness stop inside a lens.

FIG. 19 is a diagram showing an example of the optical module of the present invention.

FIG. 20 is a diagram showing another example of the optical module of the present invention.

FIG. 21 is a view showing still another example of the optical module of the present invention.

FIG. 22 is a view showing still another example of the optical module of the present invention.

[Explanation of symbols]

 S aperture stop C cover glass 1, 10, 11, 13 lens 2 imaging chip I, 3 imaging surface 4 ceramic substrate 5, 10 ', 11' final surface of lens 6 resin 7, 8 imaging area 9 element substrate 12 display element 14 backlight 15 eyes

Claims (19)

[Claims] An image-side surface is a plane, and an image-forming position is located near the plane. The following condition (1):
A two-element cemented homogeneous lens that satisfies the following. _{-0.25 ≦ d b /f≦0.25 ··· (1} ) , however, d _b is the lens system back focus, f is the focal length of the entire lens system. 2. The two-element cemented lens according to claim 1, comprising a positive lens and a negative lens in order from the object side. 3. The two-element cemented lens according to claim 2, wherein the object-side surface of the positive lens is a curved surface, and the cemented surface is convex on the image side. 4. The cemented lens according to claim 2, wherein an object-side surface of the positive lens is an aspherical surface. 5. The double cemented lens according to claim 2, wherein the following condition (2) is satisfied. 0 <n ₁ −n ₂ (2) where n ₁ is the refractive index of the positive lens, and n ₂ is the refractive index of the negative lens. 6. The two-element cemented lens according to claim 2, which has a brightness stop and satisfies the following condition (3). _{-0.02 <d s /f<0.06 ··· (3} ) However, d _s is the distance in the optical axis direction to the aperture the brightness from the vertex of the object side of the positive lens, f is the lens system This is the total focal length. 7. The two-element cemented lens according to claim 2, wherein the following conditions (4) and (5) are satisfied. | N ₁ −n ₂ | ≦ 0.3 (4) 4.0 <d ₂ / d ₁ <7.0 (5) where n ₁ is the refractive index of the positive lens and n ₂ the refractive index of the negative lens, d ₁ is the axial distance of said positive lens, d ₂ is the spacing of the negative lens. 8. The two-element cemented lens according to claim 2, wherein the following conditions (6) and (7) are satisfied. 0.3 <| n ₁ −n ₂ | (6) 2.5 <d ₂ / d ₁ <5.0 (7) where n ₁ is the refractive index of the positive lens and n ₂ the refractive index of the negative lens, d ₁ is the axial distance of said positive lens, d ₂ is the spacing of the negative lens. 9. The following condition (8):
3. The cemented double lens according to claim 2, wherein the negative lens has a spherical or biconvex shape that satisfies (9), and the negative lens has a concave flat shape. 0.9 ≦ r ₁ / (d ₁ /2.0)≦1.1 (8) 0.0 ≦ | (r ₁ + r ₂ ) /f|≦0.15 (9) , R ₁ is the radius of curvature of the object-side surface of the positive lens,
d ₁ is the axial distance of said positive lens, r ₂ is the radius of curvature, f is the focal length of the entire lens system of the joint surface. 10. The double cemented lens according to claim 9, wherein the following condition (10) is satisfied. n ₁ −n ₂ <0 (10) where n ₁ is the refractive index of the positive lens, and n ₂ is the refractive index of the negative lens. 11. The two-element cemented lens according to claim 9, further comprising a brightness stop in the lens system. 12. The cemented lens according to claim 1, comprising a negative lens and a positive lens in order from the object side. 13. The two-element cemented lens according to claim 12, wherein the negative lens has a meniscus shape, and the positive lens has a convex flat shape. 14. A two-element cemented lens according to claim 12, further comprising a brightness stop in the lens system. 15. The two-element cemented lens according to claim 1, comprising a positive lens and a positive lens in order from the object side. 16. The two-element cemented lens according to claim 15, wherein the positive lens on the object side has a meniscus shape, and the positive lens on the image side has a convex flat shape. 17. The two-element cemented lens according to claim 15, further comprising a brightness stop in the lens system. 18. An optical module comprising: a two-element cemented homogeneous lens having a flat surface on the image side, which is closely attached to an element for converting light intensity and electric signal. 19. The two-element cemented lens according to claim 1, wherein
19. The optical module according to claim 18, wherein the cemented lens according to claim 7, wherein an imaging surface of an imaging element or a display surface of a display element is disposed in close contact with a plane portion of the cemented lens.