JP2012108230A - Imaging lens and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging lens which can be used, for example, in an imaging apparatus for a portable terminal, and which can photograph at a wide-angle of view and high resolution while allowing mass production and low cost, and an imaging apparatus using the imaging lens.SOLUTION: In a basic configuration of the invention for achieving a wide-angle of view and high resolution, an imaging lens comprises: in order from the object side, a biconvex first lens having positive power; an aperture diaphragm; a meniscus-shaped second lens having positive power with a concave surface on the object side and a convex surface on the image side; and a third lens. The imaging lens satisfies the conditional expression(1): 0.6<f1/f2<1.5 (1) (f1: a focal length of the first lens, and f2: a focal length of the second lens).

Description

  The present invention relates to a small and thin imaging lens, and more particularly to a small and thin imaging lens used for an imaging device using a solid-state imaging device, which is suitable for mounting on a notebook PC or a portable terminal. It is.

  Small and thin imaging devices are now installed in portable terminals, which are compact and thin electronic devices such as mobile phones and PDAs (Personal Digital Assistants), which enables not only audio information but also image information to be sent to remote locations. It is possible to transmit to each other.

  As an image pickup element used in these image pickup apparatuses, solid-state image pickup elements such as a CCD (Charge Coupled Device) type image sensor and a CMOS (Complementary Metal-Oxide Semiconductor) type image sensor are used. In recent years, the pixel pitch of the image sensor has been reduced, and higher resolution and higher performance have been achieved by increasing the number of pixels. On the other hand, the image sensor may be downsized while maintaining the pixels. In addition, recently, an increasing number of mobile terminals have a so-called videophone function that captures an image of a user who uses a mobile terminal, transmits the image to the other party, and displays the images of the other party having a conversation with each other. An imaging lens used in an imaging apparatus that realizes such a videophone function is required to have a wide-angle performance in order to photograph a user at a short distance using a mobile terminal, and a wide angle of view can increase the surroundings of the user. There is a need for resolution to capture the background scenery, etc., in which the range of reflection is widened.

  In addition to mass production of lens modules, as a method for mounting lens modules on a board at low cost and in large quantities, in recent years, with IC (Integrated Circuit) chips and other electronic components on boards that have been soldered in advance. A method has been proposed in which an electronic component and a lens module are simultaneously mounted on a substrate by reflow treatment (heating treatment) while the lens module is placed and melting the solder, and the heat resistance can withstand the reflow treatment. There is also a need for excellent imaging lenses.

  Furthermore, as a lens for an imaging device mounted on a portable terminal or the like, it is required to shorten the entire lens length as much as possible in order to reduce the thickness of the imaging device. Therefore, in order to meet such a demand, it is difficult to configure the lens with four or more lenses. On the other hand, in an imaging lens having one or two lenses, the overall length of the lens can be suppressed, but the aberration characteristics deteriorate, which is inconvenient in actual use. Therefore, it can be said that it is preferable to use an imaging lens having three lenses. As such an imaging lens, Patent Documents 1 to 3 have proposed three lenses.

JP 2006-227320 A JP 2008-139853 A Japanese Patent No. 4164103

  However, the lenses described in Patent Documents 1 and 2 have a problem that they do not achieve the wide-angle performance necessary for the above-described applications. Further, although the lens described in Patent Document 3 achieves wide-angle performance, there is a problem that correction of chromatic aberration of magnification is insufficient and good image quality cannot be obtained up to the periphery of the screen.

  The present invention has been made in view of such problems. For example, the present invention can be used in an imaging device for a portable terminal, enables mass production, achieves low cost, and enables wide-angle and high-resolution imaging. An object is to provide a possible imaging lens and an imaging device using the imaging lens.

The imaging lens according to claim 1, wherein the diagonal angle of the imaging element has a total angle of view of 65 degrees or more,
From the object side,
A first lens that is a biconvex positive lens;
Aperture stop,
It has a second lens and a third lens which are positive meniscus lenses that are concave on the object side and convex on the image side, and satisfy the following conditional expression.
0.6 <f1 / f2 <1.5 (1)
However,
f1: focal length of the first lens, f2: focal length of the second lens

  The basic configuration of the present invention for realizing a wide angle and high resolving power is the first lens having a positive power biconvex from the object side, an aperture stop, a meniscus shape having a concave surface on the object side and a convex surface on the image side, and a positive power. This is an imaging lens that includes a second lens and a third lens that satisfy the conditional expression (1).

  In order to achieve the wide-angle performance in which the total angle of view of the imaging element is 65 degrees or more, it is necessary to shorten the focal length f of the entire imaging lens system. For this purpose, positive power is applied to the first lens and the second lens, and an aperture stop is disposed between them to reduce the height of light rays passing through the first lens and the second lens, thereby generating spherical aberration and coma. The focal length f can be shortened efficiently while suppressing. Further, since the rear principal point can be made closer to the image plane by making the first lens biconvex, it is possible to further widen the angle.

Furthermore, when the value of conditional expression (1) is below the upper limit, the occurrence of lateral chromatic aberration by the second lens can be suppressed, and when the value of conditional expression (1) exceeds the lower limit, the occurrence of lateral chromatic aberration by the first lens. As a result, it is possible to secure good performance up to the periphery. More desirably, when the following range is satisfied, the lateral chromatic aberration can be corrected more satisfactorily.
0.7 <f1 / f2 <1.4 (1 ′)

The imaging lens according to claim 2 is characterized in that, in the invention according to claim 1, the imaging lens satisfies the following conditional expression (2).
0.75 <f1 / f <1.05 (2)
However,
f: Focal length of the entire system

  Conditional expression (2) defines conditions for achieving the wide-angle performance more effectively. When the value of conditional expression (2) is below the upper limit, the focal length of the entire system can be further shortened, and sufficient wide-angle performance can be achieved. In addition, when the value of conditional expression (2) exceeds the lower limit, the amount of curvature of field and astigmatism generated by the first lens can be suppressed, and the distance from the final lens surface to the image sensor is ensured. Can do.

The imaging lens according to a third aspect is characterized in that, in the invention according to the first or second aspect, the imaging lens satisfies the following conditional expression (3).
-0.7 <f / f23 <0.07 (3)
However,
f: focal length of the entire system f23: combined focal length of the second lens and the third lens

Conditional expression (3) is an expression that defines conditions for achieving high performance while achieving wide-angle performance. When the value of conditional expression (3) is below the upper limit, the Petzpearl sum can be reduced, astigmatism and field curvature can be corrected well, and axial chromatic aberration can be reduced. Further, when the value of conditional expression (3) exceeds the lower limit, the total lens length can be kept small. More desirably, by satisfying the following ranges, it is possible to more favorably correct astigmatism and curvature of field while keeping the overall length small.
−0.7 <f / f23 <−0.1 (3 ′)

The imaging lens according to a fourth aspect of the invention is characterized in that, in the invention according to any one of the first to third aspects, the imaging lens satisfies the following conditional expression (4).
0.02 <d4 / f <0.11 (4)
However,
d4: Air spacing on the paraxial axis of the second lens and the third lens f: Focal length of the entire system

  Conditional expression (4) is an expression that defines conditions for improving the productivity while keeping the lens diameter small. An imaging lens that satisfies the conditional expression (4) has a fixed lens interval.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the image side surface of the third lens of the imaging lens is aspherical and has a negative power in the paraxial direction, and from the optical axis. It is characterized by having a shape in which the negative power becomes weaker with increasing distance.

  By making the image side surface of the third lens an aspherical shape that has negative power on the paraxial axis and weakens as it moves away from the optical axis, it becomes easier to ensure the telecentric characteristics of the image-side light beam, and solid-state imaging It is preferable as an imaging lens for an element. In addition, astigmatism and coma generated off the axis can be corrected satisfactorily.

The imaging lens according to a sixth aspect is characterized in that, in the invention according to any one of the first to fifth aspects, the second lens of the imaging lens satisfies the conditional expression (5).
n2> 1.55 (5)
Where n2 is the refractive index of the second lens at the d-line

  By using a material that satisfies the conditional expression (5) for the second lens, the Petzpearl sum can be made smaller, so that astigmatism and curvature of field can be corrected well. Since the aberration can be corrected without the curvature being tight, it is easy to secure the sag amount of the lens, and the manufacturability can be improved.

  The imaging lens according to claim 7 is the invention according to any one of claims 1 to 6, wherein the first lens, the second lens, and the third lens are formed of a heat-resistant material. It is characterized by.

  The material having heat resistance is preferably a material that does not deform at 260 ° C. or higher, which is the internal temperature of the reflow bath. By configuring the imaging lens with a heat-resistant material, it can withstand reflow processing, electronic components and lens modules can be mounted on the substrate simultaneously, and can be mounted on the substrate at low cost. Production becomes possible.

  An imaging lens according to an eighth aspect is the invention according to any one of the first to seventh aspects, wherein the first lens, the second lens, and the third lens are formed of an energy curable resin. Features.

  When energy curable resin is used as the material of the imaging lens, it is possible to suppress a decrease in optical performance when exposed to high temperatures compared to a lens using a thermoplastic resin such as polycarbonate or polyolefin. It is effective for the reflow process, is easier to manufacture than a glass mold lens, is inexpensive, and can achieve both low cost and mass productivity of an imaging apparatus incorporating an imaging lens. The energy curable resin refers to both a thermosetting resin and an ultraviolet curable resin.

  An imaging lens according to a ninth aspect is characterized in that, in the invention according to the eighth aspect, inorganic fine particles of 30 nm or less are dispersed in the energy curable resin.

  Dispersion of inorganic fine particles of 30 nanometers or less in a single lens composed of a resin material such as energy curable resin can reduce performance deterioration and image point position fluctuations even when the temperature changes. An imaging lens having excellent optical characteristics regardless of environmental changes can be provided without reducing the transmittance. In general, mixing fine particles with a transparent resin material causes light scattering and decreases the transmittance, making it difficult to use as an optical material. However, the size of the fine particles should be smaller than the wavelength of the transmitted light beam. Thus, substantially no scattering can occur.

  In addition, the resin material has a disadvantage that the refractive index is lower than that of the glass material, but it has been found that the refractive index can be increased by dispersing inorganic particles having a high refractive index in the resin material as a base material. Specifically, by dispersing inorganic particles of 30 nanometers or less in the plastic material as the base material, preferably 20 nanometers or less, more preferably 15 nanometers or less in the resin material as the base material, A material having any temperature dependency can be provided.

  Furthermore, although the refractive index of the resin material decreases as the temperature rises, if inorganic particles whose refractive index increases as the temperature rises are dispersed in the resin material as the base material, these properties will cancel each other. It is also known that the refractive index change with respect to the temperature change can be reduced. On the other hand, it is also known that when the inorganic particles whose refractive index decreases as the temperature rises are dispersed in the resin material as the base material, the refractive index change with respect to the temperature change can be increased. Specifically, by dispersing inorganic particles of 30 nanometers or less in the plastic material as the base material, preferably 20 nanometers or less, more preferably 15 nanometers or less in the resin material as the base material, A material having any temperature dependency can be provided.

For example, by dispersing fine particles of aluminum oxide (Al ₂ O ₃ ) or lithium niobate (LiNbO ₃ ) in an acrylic resin, a plastic material with a high refractive index can be obtained, and the refractive index change with respect to temperature can be reduced. Can do.

  Next, the temperature change A of the refractive index will be described in detail. The temperature change A of the refractive index is expressed by the following equation by differentiating the refractive index n with respect to the temperature t based on the Lorentz-Lorentz equation.

但し、αは線膨張係数、［R］は分子屈折。

Where α is the linear expansion coefficient and [R] is molecular refraction.

In the case of a resin material, the contribution of the second term is generally smaller than the first term in the formula, and can be almost ignored. For example, in the case of PMMA resin, the linear expansion coefficient α is 7 × 10 ⁻⁵ , and if it is substituted into the above equation, dn / dt = −1.2 × 10 ⁻⁴ [/ ° C.], which is almost the same as the actually measured value. .

Here, by dispersing fine particles, desirably inorganic fine particles, in the resin material, the contribution of the second term of the above formula is substantially increased, so that the change due to the linear expansion of the first term can be canceled out. . Specifically, it is desirable to suppress the change, which was conventionally about −1.2 × 10 ⁻⁴ , to an absolute value of less than 8 × 10 ⁻⁵ .

  In addition, the contribution of the second term can be further increased to have temperature characteristics opposite to those of the base resin material. That is, it is possible to obtain a material whose refractive index increases instead of decreasing the refractive index as the temperature increases.

  The mixing ratio can be appropriately increased or decreased in order to control the rate of change of the refractive index with respect to the temperature, and a plurality of types of nano-sized inorganic particles can be blended and dispersed.

  Since the imaging device according to claim 10 includes the imaging lens according to any one of claims 1 to 9, it is possible to provide an imaging device capable of high-resolution and wide-angle imaging at a low cost. .

  According to the present invention, an imaging lens that can be used for, for example, an imaging device for a portable terminal, enables mass production and achieves cost reduction, and can perform wide-angle and high-resolution imaging, and an imaging device using the imaging lens. Can be provided.

It is a perspective view of imaging device LU concerning this embodiment. It is sectional drawing which cut | disconnected the structure of FIG. 1 by the arrow II-II line | wire, and looked at the arrow direction. 1 is a diagram showing a mobile phone T. FIG. 1 is a cross-sectional view of an imaging lens according to Example 1. FIG. FIG. 6 is an aberration diagram of spherical aberration (a), astigmatism (b), and distortion (c) of the imaging lens according to Example 1; 6 is a cross-sectional view of an imaging lens according to Example 2. FIG. FIG. 6 is an aberration diagram of spherical aberration (a), astigmatism (b), and distortion (c) of the imaging lens according to Example 2; 6 is a cross-sectional view of an imaging lens according to Example 3. FIG. FIG. 6 is an aberration diagram of spherical aberration (a), astigmatism (b), and distortion aberration (c) of the imaging lens according to Example 3; 6 is a cross-sectional view of an imaging lens according to Example 4. FIG. FIG. 6 is an aberration diagram of spherical aberration (a), astigmatism (b), and distortion aberration (c) of the imaging lens according to Example 4; 6 is a cross-sectional view of an imaging lens according to Example 5. FIG. FIG. 10 is an aberration diagram of spherical aberration (a), astigmatism (b), and distortion aberration (c) of the imaging lens according to Example 5; 6 is a cross-sectional view of an imaging lens according to Example 6. FIG. FIG. 10 is an aberration diagram of spherical aberration (a), astigmatism (b), and distortion (c) of the imaging lens according to Example 6; 10 is a cross-sectional view of an imaging lens according to Example 7. FIG. FIG. 10 is an aberration diagram of spherical aberration (a), astigmatism (b), and distortion (c) of the imaging lens according to Example 7; 10 is a cross-sectional view of an imaging lens according to Example 8. FIG. FIG. 10 is an aberration diagram of spherical aberration (a), astigmatism (b), and distortion (c) of the imaging lens according to Example 8;

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of an imaging apparatus LU according to the present embodiment, and FIG. 2 is a cross-sectional view of the configuration of FIG. 1 taken along line II-II and viewed in the direction of the arrow. As shown in FIG. 2, the imaging device LU is a CMOS type image sensor IM as a solid-state imaging device having a photoelectric conversion unit IMa, and imaging that causes the photoelectric conversion unit (light receiving surface) IMa of the image sensor IM to capture a subject image. A lens LN and an external connection terminal (electrode) ET for transmitting and receiving the electrical signal are provided, and these are integrally formed. The imaging lens LN is, in order from the object side (upper side in FIG. 2), a first lens L1 that is a biconvex positive lens, an aperture stop S, a second positive meniscus lens that is concave on the object side and convex on the image side. A lens L2 and a third lens L3 are included.

  In the image sensor IM, a photoelectric conversion unit IMa as a light receiving unit in which pixels (photoelectric conversion elements) are two-dimensionally arranged is formed in the center of a plane on the light receiving side, and signal processing (not shown) is performed. Connected to the circuit. Such a signal processing circuit includes a drive circuit unit that sequentially drives each pixel to obtain a signal charge, an A / D conversion unit that converts each signal charge into a digital signal, and a signal that forms an image signal output using the digital signal. It consists of a processing unit and the like. A number of pads (not shown) are arranged near the outer edge of the light receiving side plane of the image sensor IM, and are connected to the image sensor IM via wires (not shown). The image sensor IM converts the signal charge from the photoelectric conversion unit IMA into an image signal such as a digital YUV signal and outputs the image signal to a predetermined circuit via a wire (not shown). Here, Y is a luminance signal, U (= R−Y) is a color difference signal between red and the luminance signal, and V (= BY) is a color difference signal between blue and the luminance signal. Note that the solid-state imaging device is not limited to the CMOS image sensor, and other devices such as a CCD may be used.

  The image sensor IM is connected to an external circuit (for example, a control circuit included in a host device of a mobile terminal in which an imaging device is mounted) via an external connection terminal ET, and a voltage for driving the image sensor IM from the external circuit It is possible to receive supply of a clock signal and to output a digital YUV signal to an external circuit.

  The upper part of the image sensor IM is sealed with a plate IRCF such as an IR cut filter. On the upper surface (object side) of the plate IRCF, the flange portion of the third lens L3 is fixed, and on the object side, the second lens L2 is disposed so as to abut the third lens L3 and the flange portion. On the object side, the first lens L1 is disposed via the aperture member AP. The aperture member AP has an aperture stop S and is sandwiched between the flange portions of the first lens L1 and the second lens L2. The outside of these lenses L1 to L3 is covered with a housing BX.

That is, the imaging lens LN is, in order from the object side, a first lens L1 that is a biconvex positive lens, an aperture stop S, a second lens L2 that is a positive meniscus lens that is concave on the object side, and convex on the image side, and a third lens. L3 is satisfied, and the following conditional expression is satisfied.
0.6 <f1 / f2 <1.5 (1)
However,
f1: focal length of the first lens L1, f2: focal length of the second lens L2

  At least one of the lens portions L1 to L3 is preferably made of glass or a UV curable resin material in which inorganic fine particles having a maximum length of 30 nanometers or less are dispersed.

  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. In the present embodiment, the main imaging device MC for photographing a landscape or the like is provided on the surface side of the upper housing 71, and the imaging device LU including the above-described wide-angle imaging lens LN is the upper housing 71. And provided on the display screen D1.

  As shown in FIG. 3A, the imaging lens LN can capture an image of the upper body of the user who holds the mobile phone T with his / her hand, with the imaging device LU facing the imaging device LU. By transmitting the image signal to the mobile phone of the other party that is communicating and displaying the image of this user, a so-called videophone can be realized by making a normal call. In these imaging operations, the imaging lens LN has a wide field angle with the diagonal angle of the imaging element being 65 ° or more, so it can be used when imaging by a plurality of people or when including landscapes. You can also. The mobile phone T is not limited to a folding type.

(Example)
Next, examples suitable for the above-described embodiment will be described. However, the present invention is not limited to the following examples. The meaning of each symbol in the embodiment is as follows.
FL: Focal length of the entire imaging lens BF: Back focus Fno: F number w: Half field angle ymax: Diagonal length of the imaging surface of the solid-state imaging device TL: From the lens surface closest to the object side to the image-side focal point of the entire imaging lens system On the optical axis (where “image-side focal point” refers to an image point when parallel light rays parallel to the optical axis are incident on the imaging lens).
r: radius of curvature of refracting surface d: spacing between top surfaces of axis nd: refractive index of lens material d-line at normal temperature vd: Abbe number STO of lens material: aperture stop

  In each embodiment, the surface described with “*” after each surface number is a surface having an aspheric shape, and the shape of the aspheric surface has the vertex of the surface as the origin and the X axis in the optical axis direction. The height in the direction perpendicular to the optical axis is h and is expressed by the following “Equation 2”.

ただし、
Ａｉ：ｉ次の非球面係数
Ｒ ：基準曲率半径
Ｋ ：円錐定数
である。

However,
Ai: i-order aspherical coefficient R: reference radius of curvature K: conic constant.

In the following (including the lens data in the table), a power of 10 (for example, 2.5 × 10 ⁻⁰² ) is represented using E (for example, 2.5e−002). The surface number of the lens data was given in order with the object side of the first lens as one surface. In addition, the unit of the numerical value showing the length as described in an Example shall be mm.

Example 1
Table 1 shows lens data in Example 1. 4 is a sectional view of the lens of Example 1. FIG. The imaging lens of Example 1 includes, in order from the object side, a first lens L1 that is a biconvex positive lens, an aperture stop S, a second lens L2 that is a positive meniscus lens that is concave on the object side, and convex on the image side, and a second lens L2. It has 3 lenses L3. However, a parallel plate IRCF is provided between the imaging lens and the solid-state imaging device, assuming a sealing glass of the solid-state imaging device and an infrared cut filter. IM is an imaging surface of the solid-state imaging device. The field angle of Example 1 is 2w = 70.26 °. As is clear from FIG. 4, the image side surface of the third lens L3 is aspherical and has a negative power near the paraxial axis, and has a shape in which the negative power weakens as the distance from the optical axis increases.

  FIG. 5 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).

(Example 2)
Table 2 shows lens data in Example 2. 6 is a sectional view of the lens of Example 2. FIG. The imaging lens of Example 1 includes, in order from the object side, a first lens L1 that is a biconvex positive lens, an aperture stop S, a second lens L2 that is a positive meniscus lens that is concave on the object side, and convex on the image side, and a second lens L2. It has 3 lenses L3. However, a parallel plate IRCF is provided between the imaging lens and the solid-state imaging device, assuming a sealing glass of the solid-state imaging device and an infrared cut filter. IM is an imaging surface of the solid-state imaging device. The field angle of Example 2 is 2w = 70.26 °. Further, as apparent from FIG. 6, the image side surface of the third lens L3 is aspheric and has a negative power at the paraxial axis, and has a shape in which the negative power becomes weaker with increasing distance from the optical axis.

  FIG. 7 is an aberration diagram of Example 2 (spherical aberration (a), astigmatism (b), distortion (c)).

(Example 3)
Table 3 shows lens data in Example 3. FIG. 8 is a sectional view of the lens of Example 3. The imaging lens of Example 1 includes, in order from the object side, a first lens L1 that is a biconvex positive lens, an aperture stop S, a second lens L2 that is a positive meniscus lens that is concave on the object side, and convex on the image side, and a second lens L2. It has 3 lenses L3. However, a parallel plate IRCF is provided between the imaging lens and the solid-state imaging device, assuming a sealing glass of the solid-state imaging device and an infrared cut filter. IM is an imaging surface of the solid-state imaging device. The angle of view of Example 3 is 2w = 70.24 °. As is apparent from FIG. 8, the image side surface of the third lens L3 is aspheric and has a negative power near the paraxial axis, and has a shape in which the negative power weakens as the distance from the optical axis increases.

  FIG. 9 is an aberration diagram of Example 3 (spherical aberration (a), astigmatism (b), distortion (c)).

Example 4
Table 4 shows lens data in Example 4. FIG. 10 is a sectional view of the lens of Example 4. The imaging lens of Example 1 includes, in order from the object side, a first lens L1 that is a biconvex positive lens, an aperture stop S, a second lens L2 that is a positive meniscus lens that is concave on the object side, and convex on the image side, and a second lens L2. It has 3 lenses L3. However, a parallel plate IRCF is provided between the imaging lens and the solid-state imaging device, assuming a sealing glass of the solid-state imaging device and an infrared cut filter. IM is an imaging surface of the solid-state imaging device. The field angle of Example 4 is 2w = 70.28 °. As is apparent from FIG. 10, the image side surface of the third lens L3 is aspheric and has a negative power near the paraxial axis, and has a shape in which the negative power becomes weaker as the distance from the optical axis increases.

  FIG. 11 is an aberration diagram of Example 4 (spherical aberration (a), astigmatism (b), distortion (c)).

(Example 5)
Table 5 shows lens data in Example 5. 12 is a sectional view of the lens of Example 5. FIG. The imaging lens of Example 1 includes, in order from the object side, a first lens L1 that is a biconvex positive lens, an aperture stop S, a second lens L2 that is a positive meniscus lens that is concave on the object side, and convex on the image side, and a second lens L2. It has 3 lenses L3. However, a parallel plate IRCF is provided between the imaging lens and the solid-state imaging device, assuming a sealing glass of the solid-state imaging device and an infrared cut filter. IM is an imaging surface of the solid-state imaging device. The angle of view of Example 5 is 2w = 70.24 °. As is apparent from FIG. 12, the image side surface of the third lens L3 is aspheric and has a negative power near the paraxial axis, and has a shape in which the negative power becomes weaker as the distance from the optical axis increases.

  FIG. 13 is an aberration diagram of Example 5 (spherical aberration (a), astigmatism (b), distortion (c)).

(Example 6)
Table 6 shows lens data in Example 6. FIG. 14 is a sectional view of the lens of Example 6. The imaging lens of Example 1 includes, in order from the object side, a first lens L1 that is a biconvex positive lens, an aperture stop S, a second lens L2 that is a positive meniscus lens that is concave on the object side, and convex on the image side, and a second lens L2. It has 3 lenses L3. However, a parallel plate IRCF is provided between the imaging lens and the solid-state imaging device, assuming a sealing glass of the solid-state imaging device and an infrared cut filter. IM is an imaging surface of the solid-state imaging device. The angle of view of Example 6 is 2w = 70.84 °. As is apparent from FIG. 14, the image side surface of the third lens L3 is aspherical and has a negative power near the paraxial axis, and the negative power weakens as the distance from the optical axis increases.

  FIG. 15 is an aberration diagram of Example 6 (spherical aberration (a), astigmatism (b), distortion (c)).

(Example 7)
Table 7 shows lens data in Example 7. FIG. 16 is a sectional view of the lens of Example 7. The imaging lens of Example 1 includes, in order from the object side, a first lens L1 that is a biconvex positive lens, an aperture stop S, a second lens L2 that is a positive meniscus lens that is concave on the object side, and convex on the image side, and a second lens L2. It has 3 lenses L3. However, a parallel plate IRCF is provided between the imaging lens and the solid-state imaging device, assuming a sealing glass of the solid-state imaging device and an infrared cut filter. IM is an imaging surface of the solid-state imaging device. The field angle of Example 7 is 2w = 70.30 °. Further, as apparent from FIG. 16, the image side surface of the third lens L3 is aspheric and has a negative power near the paraxial axis, and has a shape in which the negative power becomes weaker with increasing distance from the optical axis.

  FIG. 17 is an aberration diagram of Example 7 (spherical aberration (a), astigmatism (b), distortion (c)).

(Example 8)
Table 8 shows lens data in Example 8. FIG. 18 is a sectional view of the lens of Example 8. The imaging lens of Example 1 includes, in order from the object side, a first lens L1 that is a biconvex positive lens, an aperture stop S, a second lens L2 that is a positive meniscus lens that is concave on the object side, and convex on the image side, and a second lens L2. It has 3 lenses L3. However, a parallel plate IRCF is provided between the imaging lens and the solid-state imaging device, assuming a sealing glass of the solid-state imaging device and an infrared cut filter. IM is an imaging surface of the solid-state imaging device. The field angle of Example 8 is 2w = 71.26 °. As is apparent from FIG. 18, the image side surface of the third lens L3 is aspherical and has a negative power near the paraxial axis, and has a shape in which the negative power becomes weaker as the distance from the optical axis increases.

  FIG. 19 is an aberration diagram of Example 8 (spherical aberration (a), astigmatism (b), distortion (c)).

  Table 9 summarizes the values of the examples corresponding to the respective conditional expressions.

B Operation buttons D1, D2 Display screen L1 First lens L2 Second lens L3 Third lens LN Imaging lens LU Imaging device IRCF Plate S Aperture stop IM Image sensor IMA Photoelectric conversion unit T Mobile phone

Claims (10)

In a lens with a total angle of view of 65 degrees or more at the diagonal of the image sensor,
From the object side,
A first lens that is a biconvex positive lens;
Aperture stop,
An imaging lens having a second lens and a third lens that are positive meniscus lenses that are concave on the object side and convex on the image side, and satisfy the following conditional expression:
0.6 <f1 / f2 <1.5 (1)
However,
f1: focal length of the first lens, f2: focal length of the second lens The imaging lens according to claim 1, wherein the imaging lens satisfies the following conditional expression (2).
0.75 <f1 / f <1.05 (2)
However,
f: Focal length of the entire system The imaging lens according to claim 1, wherein the imaging lens satisfies the following conditional expression (3).
-0.7 <f / f23 <0.07 (3)
However,
f: focal length of the entire system f23: combined focal length of the second lens and the third lens The imaging lens according to claim 1, wherein the imaging lens satisfies the following conditional expression (4).
0.02 <d4 / f <0.11 (4)
However,
d4: Air spacing on the paraxial axis of the second lens and the third lens f: Focal length of the entire system   The image side surface of the third lens of the imaging lens is aspherical and has a shape having a negative power near the paraxial axis, and a shape in which the negative power becomes weaker with increasing distance from the optical axis. The imaging lens described in 1. The imaging lens according to claim 1, wherein the second lens of the imaging lens satisfies the conditional expression (5).
n2> 1.55 (5)
Where n2 is the refractive index of the second lens at the d-line   The imaging lens according to claim 1, wherein the first lens, the second lens, and the third lens are made of a heat-resistant material.   The imaging lens according to claim 1, wherein the first lens, the second lens, and the third lens are formed of an energy curable resin.   The imaging lens according to claim 8, wherein inorganic fine particles of 30 nanometers or less are dispersed in the energy curable resin.   An imaging apparatus comprising the imaging lens according to claim 1.

Images