JP5397628B2 - Imaging lens and imaging apparatus - Google Patents

Description

  The present invention is a small and thin imaging lens suitable for an imaging apparatus using a solid-state imaging device such as a CCD (Charged Coupled Device) type image sensor or a CMOS (Complementary Metal Oxide Semiconductor) type image sensor, and the imaging lens. The present invention relates to an imaging apparatus provided.

  In recent years, cellular phones and portable information terminals equipped with an imaging device using a solid-state imaging device such as a CCD type image sensor or a CMOS type image sensor are becoming widespread. In recent years, solid-state image sensors used in these image pickup devices have been further miniaturized, and a VGA image format (effective pixel number 640 × 480) sensor has a 1/10 inch size (pixel pitch 2.2 μm). ) And 1/12 inch size (pixel pitch 1.75 μm) solid-state imaging devices have been commercialized. Accordingly, there is an increasing demand for further downsizing and cost reduction of the imaging lens mounted on the imaging apparatus.

  As an imaging lens for such a use, an imaging lens having a single-lens configuration has been proposed that is more advantageous than a two-lens configuration in terms of cost reduction and cost reduction. In recent years, there has been proposed a method for further reducing the cost by forming a plurality of such small imaging lenses in a lump in the same manner as in the wafer technology of an imaging sensor and cutting them into pieces. Yes.

  In order to reduce the cost, it is necessary to mount the imaging lenses that are collectively formed and singulated in this way on a substrate on which solder has been potted in advance using other electronic components such as IC chips and reflow processing. It is valid. For this reason, the simultaneous formation of multiple imaging lenses using a junction type compound lens in which an energy curable resin such as a photocurable resin or a thermosetting resin is bonded to the surface of the glass substrate achieves both cost reduction and reflow. Attention has been paid.

  Such a junction type compound lens is a junction lens made of a plurality of types of materials, glass and resin, that can be manufactured at a lower cost than a glass mold lens, that is superior in strength to a resin integrated lens. Therefore, the optical characteristics can be adjusted with a degree of freedom by selecting not only the lens shape but also the material to be joined, which is advantageous in that the optical characteristics can be further improved and the size can be reduced. The following is known as a prior art of an imaging lens composed of such a single junction type compound lens.

JP 2008-287005 A JP 2009-222732 A

  Although the proposed imaging lens is a junction type compound lens having the above-mentioned advantages, it is important for downsizing and high optical performance, especially in obtaining an image format sensor such as a VGA with a small size and high definition. It is difficult to say that the lens has improved optical characteristics (astigmatism, curvature of field, coma) from the intermediate image height to the off-axis, which are excellent optical characteristics. In the prior art, a concave meniscus shape is formed on the object side in order to correct field curvature and astigmatism off the axis from the middle. However, there is no suggestion to obtain a high-definition image with an image format sensor such as VGA, and astigmatism and curvature of field are insufficiently corrected. As a result, it is not suitable for use in forming a subject image on the imaging surface of a sensor having a VGA image format that forms a high-definition image.

  The present invention has been made in view of such problems, and can be reduced in cost as a cemented compound lens, and has an image format such as VGA while maintaining a small size while having a degree of freedom in optical performance. An imaging lens and an imaging apparatus capable of providing a high-definition image over the periphery by correcting astigmatism and curvature of field satisfactorily for a sensor.

The imaging lens of the present invention is an imaging lens of a single junction type compound lens for forming an object image on the photoelectric conversion portion of the solid-state imaging device, the junction type compound lens comprises, in order from the object side, A first lens composed of a plano-concave lens concave on the object side, a second lens that is a parallel plate element, and a third lens composed of a plano-convex lens convex on the image side,
The first lens and the third lens are formed of an energy curable resin material,
The parallel plate element is formed of a glass material,
The first lens and the second lens, and the second lens and the third lens are joined together, and satisfy the following conditional expression.
−1.5 > rL11 / f > −5.0 (1)
0.09 <rL32 / rL11 <0.29 (5)
However,
rL11: local curvature radius of the side surface of the first lens object obtained by the following formula, f: focal length of the entire imaging lens system rL11 = {(h1) ² + (s1) ² } / (2s1)
In addition,
h1: 1/10 of the effective radius on the side surface of the first lens object, s1: the amount of displacement in the direction parallel to the optical axis from the surface vertex at the height h1 of the side surface of the first lens object
rL32: Local curvature radius of the third lens image side surface obtained by the following equation.
rL32 = {(h3) ² + (s3) ² } / (2s3)
h3: 1/10 of effective radius on the third lens image side surface, s3: distance between the foot of the perpendicular line dropped from the surface vertex to the optical axis at the height h3 of the third lens image side surface, and the vertex of the surface

  By placing a concave surface on the object side of the cemented compound lens and a convex surface on the image side, it becomes a so-called retrofocus type, and a stronger concave surface can be placed even at the same focal length to correct astigmatism and curvature of field. It is advantageous. In addition, since the first surface is a concave surface, the aperture efficiency is increased, and a lens that is bright to the periphery can be obtained.

  Further, by satisfying conditional expression (1), it is possible to obtain a lens in which astigmatism and field curvature are favorably corrected. Specifically, when rL11 / f falls below the upper limit value of conditional expression (1), the Petzpearl sum is reduced, and astigmatism and curvature of field can be corrected. Further, when rL11 / f exceeds the lower limit value of conditional expression (1), coma aberration can be prevented from becoming too large, and the overall length can be kept small.

  The concave surface mentioned here is a concave surface in which φm / φp is negative when φm is the power of the imaging lens at the position of the maximum ray height and φp is the power of the imaging lens at the paraxial axis. Open 2004-326097). “The first lens and the second lens, the second lens and the third lens are joined together” means that the first lens and the second lens are joined together, and the second lens and the third lens are joined together directly. Of course, this also includes the case of being indirectly joined via a light-shielding member such as an aperture stop that determines the F number between the lenses, that is, the first stop, another stop, and an IR cut coat.

In addition, the “curvature radius” mentioned here is based on the amount of sag measured using a contact-type method or non-contact-type method using an ultra-precise three-dimensional measuring machine UA3P (manufactured by Panasonic Corporation). The approximate value of the local curvature radius given by the equation is used as the curvature radius.
rL11 = {(h1) ² + (s1) ² } / (2s1)
However,
h1: 1/10 of the effective radius on the side surface of the first lens object, s1: the amount of displacement in the direction parallel to the optical axis from the surface vertex at the height h1 of the side surface of the first lens object (see FIG. 17), The effective radius of the lens surface is the point from the point where the light beam that passes the outermost (the position farthest from the optical axis of the lens) out of all the light rays that are imaged at the maximum image height to the optical axis, It means the distance in the direction perpendicular to the optical axis.

Moreover, according to the said aspect, it is preferable that the following conditional expressions are satisfied.
30 ≦ ν1 ≦ 59 (2)
1.50 ≦ N3 ≦ 1.65 (3)
ν1: Abbe number of the material of the first lens, N3: Refractive index of the material of the third lens

  The conditional expressions (2) and (3) define the Abbe number of the material used for the first lens of the junction type compound lens and the refractive index of the material used for the third lens. By using an appropriate material for the first lens and the third lens, coma, axial chromatic aberration, and lateral chromatic aberration can be favorably corrected. Occurrence of chromatic aberration can be suppressed by using, for the first lens, a material having an Abbe number that satisfies the conditional expression (2). Further, by using a material having a high refractive index that satisfies the conditional expression (3) for the third lens, the surface shape can be made gentler, so that the occurrence of coma aberration can be suppressed.

Further, according to the above aspect, the first diaphragm is disposed on the object side with respect to the image side surface of the third lens, and apart from the first diaphragm, the aperture diameter is larger than the first diaphragm. It is preferable to arrange a second diaphragm that satisfies the requirements.
Ra <H _a (4)
However,
Ra: radius of the second diaphragm, H _a: outermost ray at the maximum image height, the distance from the optical axis point that passes through the surface on which the second stop is formed

Conditional expression (4) defines the radius of the second diaphragm of the junction type compound lens. Here, H _a is the height at which the outermost light beam having the maximum image height passes through the surface on which the second diaphragm is disposed when the second diaphragm is not disposed, and can be obtained by general ray tracing. it can. The present invention will be described with reference to FIG. FIG. 1 shows a case where the second diaphragm is disposed on the side surface of the second lens image. In FIG. 1, the imaging lens includes a first lens L1 that is a concave / concave lens on the object side, a second lens L2 that is a parallel plate element, and a third lens L3 that is a convex / convex lens on the image side. The first diaphragm SH1 is disposed closer to the object side than the second diaphragm SH2. Further, as shown in FIG. 1, the second diaphragm has a radius SH2 of the second diaphragm as Ra, and the outermost light beam that has passed through the first diaphragm SH1 is perpendicular to the optical axis at a position where the second diaphragm SH2 is located. the distance from the optical axis of a point of intersection between a plane and H _a. At this time, when the conditional expression (4) is satisfied, the light beam on the outer peripheral side that has passed through the first diaphragm SH1 is shielded by the second diaphragm SH2, as indicated by double hatching. Further, the second diaphragm may be disposed closer to the object side than the first diaphragm. Since the F number is determined by the diaphragm having the smaller aperture diameter, the smaller diaphragm is the first diaphragm and the larger diameter is the second diaphragm even when the diaphragm position is changed. When the second diaphragm is disposed on the object side of the first diaphragm, the outermost light beam incident on the first diaphragm SH1 is shielded by the second diaphragm SH2.

  Since the retrofocus type imaging lens as in the present invention has high aperture efficiency, a lens that is sufficiently bright up to the periphery can be obtained even if the light beam on the outer peripheral side that has passed through the first diaphragm SH1 is cut. On the other hand, by disposing the second diaphragm SH2 that satisfies the conditional expression (4) separately from the first diaphragm, off-axis coma and higher-order aberrations harmful to performance can be cut. Thus, it is possible to obtain a subject image in which the aberration is corrected well. In addition, when the second aperture is closer to the first aperture, it is possible to cut coma and higher order aberrations from a low image height and obtain good performance from the periphery to the periphery. Therefore, it is possible to prevent an abrupt decrease in the amount of peripheral light, and to provide a high-quality captured image over the periphery while being small.

  According to the above aspect, it is preferable that the first diaphragm is disposed on the second lens object side surface or the image side surface.

  By disposing the first diaphragm on the object side of the second lens, the aperture efficiency increases more than when the first diaphragm is disposed on the object side of the first surface of the junction type compound lens, and the second diaphragm diameter is further increased. Since it can be made small, good performance can be obtained. Further, there is an advantage that the sensor incident angle can be reduced by disposing the first diaphragm on the object side. More desirably, the second diaphragm is disposed on the second lens image side. The diaphragm can be formed with higher accuracy by arranging the second diaphragm on the parallel plate element.

  By disposing the first diaphragm on the image side of the second lens, the aperture efficiency increases more than when the first diaphragm is disposed on the object side of the first surface of the junction type compound lens, and the second diaphragm diameter is further increased. Since it can be made small, good performance can be obtained. Further, the arrangement of the first stop closer to the image side has an advantage that the lateral chromatic aberration can be reduced because a light beam enters a lower side surface of the third lens image. More preferably, the second diaphragm is disposed on the second lens object side. The diaphragm can be formed with higher accuracy by arranging the second diaphragm on the parallel plate element.

  Conditional expression (5) defines the ratio of the radius of curvature of the first lens object side surface and the radius of curvature of the third lens image side surface of the junction type compound lens. By appropriately arranging the curvature radius of the side surface of the third lens image in accordance with the curvature radius of the side surface of the first lens object, it is possible to obtain a lens that secures good performance while suppressing the occurrence of coma aberration while keeping the overall length small. . Specifically, when the value of conditional expression (5) is below the upper limit, the overall length can be kept small, while when it exceeds the lower limit, the occurrence of coma aberration can be suppressed and good performance can be maintained. Become. Note that rL32 is determined in the same manner as rL11 with reference to FIG.

Moreover, according to the said aspect, it is preferable that the following conditional expressions are satisfied.
0.25 <dc / f <0.50 (6)
However,
dc: Thickness of the parallel plate element (however, when there are a plurality of parallel plate elements, the sum thereof)

  The conditional expression (6) defines the ratio between the parallel plate element and the focal length. A parallel plate element is disposed between the second lens and the solid-state imaging device, and dc / f exceeds the lower limit of conditional expression (6), thereby further correcting the curvature of field while suppressing an increase in astigmatism. Can do. On the other hand, when dc / f falls below the upper limit value of conditional expression (6), an increase in the total length of the imaging lens due to an increase in the air equivalent length of the parallel plate element can be suppressed. The parallel plate element may include a parallel plate such as an optical low-pass filter, an infrared cut filter, or a seal glass of a solid-state imaging device package.

Moreover, according to the said aspect, it is preferable that the following conditional expressions are satisfied.
0 <(D1 + D3) / D2 <1 (7)
However,
D1: thickness of the first lens, D2: thickness of the second lens, D3: thickness of the third lens

Conditional expression (7) defines the ratio between the total thickness of the resin used for the first lens and the third lens and the thickness of the parallel plate element used for the second lens. In the junction type compound lens, when the resin is too thick with respect to the parallel plate element, warping or cracking of the parallel plate element becomes a problem during molding. Even if the resin thickness of the front and rear is balanced so that the parallel plate element does not warp, if the resin itself is thick, the contraction force becomes strong, and therefore the parallel plate element breaks during molding. When the thickness ratio of the lens is less than the condition value of the conditional expression (7), it is possible to make a lens that does not warp and break the parallel plate element during molding. In particular, since the thickness balance on one side is easily biased, it is desirable to satisfy the conditional expression (7). In consideration of a small imaging lens, it is preferable that the optical axis thickness of the second lens satisfies 0.3 ≦ D2 ≦ 0.7. Since it is necessary to reduce the thickness of the substrate, warping is likely to occur. Therefore, it is desirable to satisfy the range of the following expression (7 ′).
0 <(D1 + D3) / D2 <0.8 (7) '

  Moreover, according to the said aspect, it is preferable to use an aspherical surface for at least one of the object side surface of the first lens and the image side surface of the third lens.

  By making at least one of the first lens object side surface and the third lens image side surface of the cemented compound lens an aspherical surface, it is possible to arrange an appropriate surface shape at each image height, and various aberrations are improved. It can be corrected.

  According to the above aspect, it is preferable to use an odd-order aspheric surface in which an odd-order term is added to at least one of the object side surface of the first lens and the image side surface of the third lens.

  By arranging an odd-order aspheric surface with an odd-order term added to at least one of the first lens object side surface and the third lens image side surface of the junction type compound lens, the surface shape particularly at a low image height can be made more appropriate. Arrangements can be made, and various aberrations can be corrected satisfactorily from the paraxial to the periphery.

  Further, according to the above aspect, the junction type compound lens is manufactured by forming a plurality of the first lens and the third lens on a glass parallel plate material and then cutting them into respective groups. Is preferred. Thereby, an imaging lens can be mass-produced collectively.

An image pickup apparatus according to the present invention includes an image pickup element having a sensor size of 1/10 inch or less (pixel pitch: 2.2 μm) and the above-described image pickup lens. Here, although it is a scale of a small imaging lens, in recent years, there is a tendency that an imaging device having a total length of 3.0 mm or less is required by a mobile phone manufacturer. Furthermore, in addition to the total length of the imaging lens, the thickness of the solid-state imaging device Is 0.3 mm, and the thickness of the cover member that protects the imaging lens is 0.2 mm. Therefore, the imaging lens according to the present invention has a condition that satisfies the conditional expressions (8) and (9). It aims at downsizing of the level which satisfies Formula (10). However, the present invention is not limited by the conditional expressions (8) to (10).
2.4 ≦ Fno ≦ 3.2 (8)
1.4μm ≦ P ≦ 2.2μm (9)
1.0mm <TTL <2.5mm (10)
However,
Fno: F number of the imaging lens P: Pixel pitch of the solid imaging lens TTL: Distance on the optical axis from the most object side lens surface of the entire imaging lens system to the image side focal point (however, “image side focal point” (This is the image point when a parallel ray parallel to the optical axis is incident on the imaging lens.)

  According to the present invention, it is possible to reduce the cost as a cemented compound lens and to provide a high-definition image even in an image format sensor such as a VGA while maintaining a small size while having a degree of freedom in optical performance. it can.

It is a figure for demonstrating the principle of this invention. It is sectional drawing of an imaging device. It is an external view of a mobile phone. It is a figure which shows the manufacturing method of an imaging lens. 2 is a cross-sectional view of an imaging lens of Example 1. FIG. FIG. 6 is an aberration diagram of Example 1. 6 is a cross-sectional view of an imaging lens of Example 2. FIG. FIG. 6 is an aberration diagram of Example 2. 6 is a cross-sectional view of an imaging lens of Example 3. FIG. FIG. 6 is an aberration diagram of Example 3. 6 is a cross-sectional view of an imaging lens of Example 4. FIG. FIG. 6 is an aberration diagram of Example 4. 6 is a cross-sectional view of an imaging lens of Example 5. FIG. FIG. 6 is an aberration diagram of Example 5. 6 is a cross-sectional view of an imaging lens of Example 6. FIG. FIG. 6 is an aberration diagram of Example 6. It is a figure which prescribes | regulates a sag amount.

An imaging lens of the present invention and an imaging apparatus using the imaging lens will be described with reference to FIG. The imaging lens includes, in order from the object side, a first lens L1 that is a concave-concave lens on the object side, a first aperture SH1 that defines an F number, a second lens L2 that is a parallel plate element, a second aperture SH2, an image It has a cemented compound lens CL composed of a third lens L3 that is a plano-convex lens convex on the side, and a parallel plate element PT composed of an optical low-pass filter, an IR cut filter, or a seal glass of a solid-state image sensor. The third lens L3 has a leg portion L3a that contacts the parallel plate element PT. The first diaphragm SH1 may be provided on the object side surface of the second lens L2 or the image side surface of the second lens L2. In addition, the second diaphragm SH2 may or may not be provided on the object side surface of the second lens L2. The imaging lens satisfies the following conditional expression.
−1.5 > rL11 / f > −5.0 (1)
However,
rL11: Local curvature radius of the first lens object side surface obtained by the following formula f: Focal length rL11 = {(h1) ² + (s1) ² } / (2s1) of the entire imaging lens system
In addition,
h1: 1/10 of the effective radius on the side of the first lens object
s1: Amount of displacement in the direction parallel to the optical axis from the surface apex at the height h1 of the first lens object side surface

  Each optical member described above is held by the lens frame 11. The image sensor C having an imaging surface for forming a subject image has a sensor size of 1/10 inch or less (pixel pitch 2.2 μm) and is mounted on the printed wiring board 12. 12 is fixed to the lens frame 11. The imaging device is configured as described above.

  Next, a mobile phone as an example of a mobile terminal equipped with an imaging device will be described with reference to the external view of FIG. 3A is a view of the folded mobile phone opened from the inside and FIG. 3B is a view of the folded mobile phone opened from the outside.

  In FIG. 3, in the mobile phone T, an upper housing 71 as a case having display screens D <b> 1 and D <b> 2 and a lower housing 72 having operation buttons B are connected via a hinge 73. The camera module is built under the display screen D2 in the upper casing 71, and the first lens L1 of the imaging lens is exposed on the outer surface of the upper casing 71.

  Note that this imaging device may be arranged above or on the side of the display screen D2 in the upper casing 71. Further, the mobile phone T is not limited to a folding type.

  Next, a manufacturing method of the junction type compound lens CL will be described with reference to FIG. In Examples 1 to 5, the first aperture is provided on the object side surface of the second lens L2, and in Example 6, the first aperture is provided on the image side surface of the second lens. As shown in FIG. 4A, when the first lens L1 is formed, a plurality of predetermined aperture diameters are formed on the upper surface of the parallel plate material GP made of glass by a thin film (black resist or the like) having a light shielding property. Each imprinting member forms a diaphragm member that functions as a first diaphragm, and imprinting is performed with an energy curable resin such as a photo-curable resin or a thermosetting resin disposed between the diaphragm member and a molding die M1 that molds the lens. The first lens L1 is formed by molding and curing. When the third lens L3 is formed, a diaphragm member functioning as a second diaphragm is formed on the lower surface of the parallel plate material GP by a thin film having a light-shielding property as in the first diaphragm described above. The first lens is opposed to the diaphragm member (but only when the second diaphragm is included) and the mold M2 having a plurality of transfer surfaces in the same array so that the transfer surface of the mold M1 is aligned with the optical axis. It is cured and formed in the same way as L1.

  After that, when the molds M1 and M2 are released, the first lens L1 formed by the transfer surface of the mold M1 is formed in an array on the upper surface of the parallel plate material GP, and on the lower surface of the parallel plate material GP. The third lens L3 (including the leg portion L3a) molded by the transfer surface of the mold M2 is formed in an array, that is, as shown in FIG. 4B, a plurality of junction type compound lenses CL are arrayed. The individually arranged lens blocks LB are formed.

  Then, the position shown with a dashed-dotted line is cut | disconnected with a cutter. That is, when viewed from above in FIG. 4 (b), it is cut in two orthogonal directions, and the cut cemented compound lens has a circular lens surface, but its outer shape is square, and this state The lens frame 11 (see FIG. 2) is assembled as it is. By manufacturing in this way, imaging lenses capable of forming high-definition images can be mass-produced at low cost.

Examples of the imaging lens of the present invention are shown below. Symbols used in each example are as follows.
FL: Focal length of the entire imaging lens system
Fno: F number ymax: Diagonal length of the imaging surface of the solid-state image sensor
w: Half angle of view TL: Distance on the optical axis from the most object-side lens surface of the entire imaging lens system to the image-side focal point
BF: Back focus r: Radius of curvature d: Distance between shaft upper surfaces
nd: Refractive index for d-line of lens material
vd: Abbe number with respect to the d-line of the lens material Further, the second diaphragm SH2 is formed on the surface indicated by “*” after the effective radius, and the radius is set to the same value as the effective radius. The surface described as “SPS” is a surface having an aspherical shape. The aspherical shape has an apex at the surface as an origin, an X axis in the optical axis direction, and a height perpendicular to the optical axis as h. Is expressed by the following equation (1).

但し、
Ａｉ：ｉ次の非球面係数（ｉ＝３，４，５，６，・・・・２０）
Ｒ（レンズデータ表ではｒ）：曲率半径
Ｋ：円錐定数
また、非球面係数において、１０のべき乗数（例えば２．５×１０^-02）をＥ（例えば２．５Ｅ−０２）を用いて表している。

However,
Ai: i-order aspherical coefficient (i = 3,4,5,6,... 20)
R (r in the lens data table): radius of curvature K: conic constant In addition, in the aspherical coefficient, a power of 10 (for example, 2.5 × 10 ⁻⁰² ) is expressed using E (for example, 2.5E-02). ing.

Example 1
Table 1 shows lens data of Example 1. 5 is a cross-sectional view of the imaging lens of Example 1. FIG. FIG. 6 is an aberration diagram of Example 1 (spherical aberration (a), astigmatism (b), distortion (c)). Here, in the spherical aberration diagram, the solid line represents the spherical aberration amount with respect to the d line and the dotted line, respectively, and in the astigmatism diagram, the solid line represents the sagittal surface and the dotted line represents the meridional surface (hereinafter the same). The imaging lens of Example 1 includes, in order from the object side, a first lens L1 that is a concave-concave lens on the object side, a first diaphragm SH1 that defines an F number, a second lens L2 that is a parallel plate element, and an image side. It has the 3rd lens L3 which is a convex plano-convex lens, the parallel plate element PT which consists of a sealing glass of an optical low-pass filter, IR cut filter, or a solid-state image sensor. IM is an imaging surface of the image sensor. Further, the surfaces of the lens portions that are in contact with all air are aspherical.

(Example 2)
Table 2 shows lens data of Example 2. FIG. 7 is a cross-sectional view of the imaging lens of the second embodiment. FIG. 8 is an aberration diagram of Example 2 (spherical aberration (a), astigmatism (b), distortion (c)). The imaging lens of Example 2 includes, in order from the object side, a first diaphragm SH1 that defines an F number, a first lens L2 that is a plano-concave lens that is concave on the object side, a second lens L2 that is a parallel plate element, and a second diaphragm. SH2, a third lens L3 that is a plano-convex lens convex on the image side, an optical low-pass filter, an IR cut filter, or a parallel plate element PT made of a seal glass of a solid-state image sensor. IM is an imaging surface of the image sensor. Further, the surfaces of the lens portions that are in contact with all air are aspherical.

(Example 3)
Table 3 shows lens data of Example 3. FIG. 9 is a cross-sectional view of the imaging lens of Example 3. FIG. 10 is an aberration diagram of Example 3 (spherical aberration (a), astigmatism (b), distortion (c)). The imaging lens of Example 3 includes, in order from the object side, a first lens L1 that is a concave-concave lens on the object side, a first aperture SH1 that defines an F number, a second lens L2 that is a parallel plate element, and a second aperture. SH2, a third lens L3 that is a plano-convex lens convex on the image side, an optical low-pass filter, an IR cut filter, or a parallel plate element PT made of a seal glass of a solid-state image sensor. IM is an imaging surface of the image sensor. Further, the surfaces of the lens portions that are in contact with all air are aspherical.

Example 4
Table 4 shows lens data of Example 4. FIG. 11 is a cross-sectional view of the imaging lens of Example 4. FIG. 12 is an aberration diagram of Example 4 (spherical aberration (a), astigmatism (b), distortion (c)). The imaging lens of Example 4 includes, in order from the object side, a first lens L1 that is a plano-concave lens that is concave on the object side, a first aperture SH1 that defines an F number, a second lens L2 that is a parallel plate element, and a second aperture. SH2, a third lens L3 that is a plano-convex lens convex on the image side, an optical low-pass filter, an IR cut filter, or a parallel plate element PT made of a seal glass of a solid-state image sensor. IM is an imaging surface of the image sensor. Further, the surfaces of the lens portions that are in contact with all air are aspherical.

(Example 5)
Table 5 shows lens data of Example 5. FIG. 13 is a cross-sectional view of the imaging lens of Example 5. FIG. 14 is an aberration diagram of Example 5 (spherical aberration (a), astigmatism (b), distortion (c)). The imaging lens of Example 5 includes, in order from the object side, a first lens L1 that is a concave-concave lens on the object side, a second lens L2 that is a parallel plate element, a first diaphragm SH1 that defines an F number, and an image side. It has the 3rd lens L3 which is a convex plano-convex lens, the parallel plate element PT which consists of a sealing glass of an optical low-pass filter, IR cut filter, or a solid-state image sensor. IM is an imaging surface of the image sensor. Further, the surfaces of the lens portions that are in contact with all air are aspherical.

(Example 6)
Table 6 shows lens data of Example 6. FIG. 15 is a sectional view of the imaging lens of Example 6. FIG. 16 is an aberration diagram of Example 6 (spherical aberration (a), astigmatism (b), distortion (c)). The imaging lens of Example 6 is, in order from the object side, a second diaphragm SH2, which is a parallel flat plate element, formed on the object side surface of the first lens L1 and the second lens L2 which are concave concave lenses on the object side. Lens L2, first aperture SH1 that defines the F-number formed on the image side surface of second lens L2, third lens L3 that is a plano-convex lens convex on the image side, optical low-pass filter, IR cut filter, or solid-state imaging device A parallel plate element PT made of a sealing glass. IM is an imaging surface of the image sensor. Further, the surfaces of the lens portions that are in contact with all air are aspherical.

  Table 7 shows values of the examples corresponding to the respective conditional expressions.

  In comparison with the known example, the scale is performed so that the maximum image height becomes the same value. In addition, each wavelength at c-line, d-line, and f-line (656.2725 nm, 587.5618 nm, 486.1327 nm) is set to the same weight, and each aberration at 80% image height is evaluated. Also, at this time, the sagittal peak position at 8 image height when the peak on the axis at the 1/4 Nyquist frequency is taken as the best is the curvature of field, and the sagittal peak position at 80% image height at 1/4 Nyquist frequency. Is the amount of astigmatism, the difference between the principal ray imaging position at 80% image height and the marginal ray imaging position is coma aberration, and c-line at 80% image height. Chromatic aberration of magnification is obtained by dividing the difference between the imaging positions of the f and f lines by the number of pixels.

In Example 1, astigmatism and lateral chromatic aberration are corrected satisfactorily with respect to known examples, and particularly coma is corrected well.
In Example 2, coma aberration and lateral chromatic aberration are corrected satisfactorily with respect to known examples, and in particular, astigmatism is corrected more satisfactorily.
In Example 3, coma and lateral chromatic aberration are corrected well compared to the known example, and in particular, field curvature and astigmatism are corrected more satisfactorily.
In Example 4, the curvature of field, astigmatism, coma aberration, and lateral chromatic aberration are all corrected satisfactorily with respect to the known example.
In Example 5, the curvature of field, astigmatism, and lateral chromatic aberration are corrected satisfactorily with respect to known examples, and particularly coma is corrected well.
In Example 6, the curvature of field, astigmatism, coma aberration, and lateral chromatic aberration are all corrected satisfactorily with respect to the known example.
Therefore, it is shown that the imaging lens of the present embodiment can provide an imaging lens that can obtain higher optical performance than the imaging lens of the known example.

  According to the present invention, it is possible to provide an imaging lens optimal for mass productivity and miniaturization. A mobile terminal is not limited to a mobile phone.

DESCRIPTION OF SYMBOLS 11 Lens frame 12 Printed wiring board 71 Upper housing | casing 72 Lower housing | casing 73 Hinge B Operation button C Image pick-up element CL Joint type compound lens D1, D2 Display screen GP Parallel plate L1 1st lens L2 2nd lens L3 3rd lens L3a Leg Part LB Lens block M1 Mold M2 Mold PT Parallel plate element SH1 First aperture SH2 Second aperture SM1 Light shield SM2 Light shield T Mobile phone

Claims (11)

An imaging lens consisting of a single junction type compound lens for forming an object image on the photoelectric conversion portion of the solid-state imaging device, the junction type compound lens comprises, in order from the object side, a plano-concave lens concave to the object side A first lens comprising: a second lens that is a parallel plate element; and a third lens comprising a plano-convex lens that is convex on the image side,
The first lens and the third lens are formed of an energy curable resin material,
The parallel plate element is formed of a glass material,
The imaging lens, wherein the first lens, the second lens, and the second lens and the third lens are joined directly or indirectly, and satisfy the following conditional expression.
−1.5 > rL11 / f > −5.0 (1)
0.09 <rL32 / rL11 <0.29 (5)
However,
rL11: local curvature radius of the side surface of the first lens object obtained by the following formula, f: focal length of the entire imaging lens system rL11 = {(h1) ² + (s1) ² } / (2s1)
In addition,
h1: 1/10 of the effective radius on the side surface of the first lens object, s1: the amount of displacement in the direction parallel to the optical axis from the surface vertex at the height h1 of the side surface of the first lens object
rL32: Local curvature radius of the third lens image side surface obtained by the following equation.
rL32 = {(h3) ² + (s3) ² } / (2s3)
h3: 1/10 of effective radius on the third lens image side surface, s3: distance between the foot of the perpendicular line dropped from the surface vertex to the optical axis at the height h3 of the third lens image side surface, and the vertex of the surface The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
30 ≦ ν1 ≦ 59 (2)
1.50 ≦ N3 ≦ 1.65 (3)
ν1: Abbe number of the material of the first lens, N3: Refractive index of the material of the third lens A second diaphragm that is disposed closer to the object side than the image side surface of the third lens, has a larger aperture diameter than the first diaphragm, and satisfies the following conditional expression: The imaging lens according to claim 1, wherein the imaging lens is arranged.
Ra <H _a (4)
However,
Ra: radius of the second diaphragm, H _a: outermost ray at the maximum image height, the distance from the optical axis point that passes through the surface on which the second stop is formed   The imaging lens according to claim 1, wherein the first diaphragm is formed on a side surface of the second lens object.   The imaging lens according to claim 1, wherein the first diaphragm is formed on a side surface of the second lens image. The imaging lens according to any one of claims 1 to 5, characterized by satisfying the following conditional expression.
0.25 <dc / f <0.50 (6)
However,
dc: Thickness of the parallel plate element (however, when there are a plurality of parallel plate elements, the sum thereof) And satisfies the following condition, the imaging lens according to any one of claims 1-6.
0 <(D1 + D3) / D2 <1 (7)
However,
D1: thickness in the optical axis direction on the paraxial axis of the first lens, D2: thickness in the optical axis direction on the paraxial axis of the second lens, D3: optical axis direction on the paraxial axis of the third lens Thickness of The imaging lens according to any one of claims 1 to 7, characterized in that it uses at least one aspherical surface of the image side surface of the object side surface and the third lens of the first lens. The imaging according to any one of claims 1 to 8 , wherein an odd-order aspheric surface in which an odd-order term is added to at least one of the object side surface of the first lens and the image side surface of the third lens is used. lens. 2. The junction type compound lens according to claim 1, wherein a plurality of the first lens and the third lens are formed on a parallel plate material made of glass and then cut into groups. The imaging lens according to any one of to 9 .   An image pickup apparatus comprising: an image pickup element having a sensor size of 1/10 inch size (pixel pitch: 2.2 μm) or less; and the image pickup lens according to claim 1.

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