JP5267773B2 - IMAGING LENS, IMAGING DEVICE, DIGITAL DEVICE, AND IMAGING LENS MANUFACTURING METHOD - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive imaging lens, wherein image quality deterioration due to a paraxial image point position change caused by moisture absorption is prevented even in the case of the imaging lens which is improved in mass productivity, and to provide an imaging device, digital equipment, and a manufacturing method for an imaging lens. <P>SOLUTION: On a lens substrate, a lens lower in the rate of change in water absorption than the lens substrates is formed. Consequently, unlike an existing lens that freely expands, the paraxial curvature radius get small by expansion accompanying water absorption, resulting in variation of a paraxial image point position. At this time, variation of a paraxial image point position due to a change in a refractive index and a change in dimension has the same sign. By satisfying a predetermined condition, the variation of the paraxial image point position due to the change in dimension accompanying water absorption is allowed to be corrected by the variation of the paraxial image point position due to the change in the refractive index accompanying water absorption. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an imaging lens of an imaging apparatus using a solid-state imaging device such as a CCD (Charge Coupled Devices) type image sensor or a CMOS (Complementary Metal-Oxide Semiconductor) type image sensor, and more specifically for mass production. The present invention relates to an imaging lens which is an optical system using a suitable wafer scale lens, an imaging device using the imaging lens, a digital device, and a manufacturing method of the imaging lens.

  Compact and thin imaging devices (hereinafter also referred to as camera modules) are now installed in portable terminals that are compact and thin electronic devices such as mobile phones and PDAs (Personal Digital Assistants). It is possible to transmit not only audio information but also image information to each other.

  As an image pickup element used in these image pickup apparatuses, a solid-state image pickup element such as a CCD type image sensor or a CMOS type image sensor is used. In recent years, the number of pixels of an image sensor has been increased, and higher resolution and higher performance have been achieved. Further, as a lens for forming a subject image on these image sensors, a lens made of a resin material that can be mass-produced at low cost has been used for cost reduction. A lens made of a resin material can accurately transfer and form a complicated aspherical shape despite having good processability, and therefore can be applied to a high-resolution and high-performance imaging device.

  Here, as an imaging lens used in an imaging apparatus, an optical system configured by a resin material lens and an optical system configured by a glass lens and a resin material lens are well known. However, the conventional optical system is not sufficient particularly for use in an imaging device of a portable terminal, and there is a strong demand to achieve further ultra-compactness of these optical systems and mass productivity required for the portable terminal. However, it can be said that it is difficult to realize such compatibility at low cost.

In order to overcome such problems, a large number of camera modules are mass-produced by simultaneously forming a large number of lens elements on a several inch wafer by the replica method, combining the wafers with sensor wafers, and then separating them. Has been proposed. The lens manufactured by such a manufacturing method is sometimes called a wafer scale lens, and the camera module is sometimes called a wafer scale camera module. Regarding such a technique, Patent Document 1 and Patent Document 2 disclose an imaging lens including a lens portion on a lens substrate.
JP 2006-323365 A Japanese Patent No. 3929479

  Here, a resin material used for a general optical element is more likely to absorb water than a glass material when placed in a humid environment, whereby a refractive index change (increase) and a dimensional change (expansion). There is a characteristic that occurs simultaneously. However, when a general imaging lens that allows free expansion is formed from a resin material, the paraxial radius of curvature of the lens portion increases due to dimensional changes associated with water absorption. The change in the axial image point position and the change in the paraxial image point position due to a dimensional change (expansion) due to water absorption have different signs (one is positive and the other is negative). Therefore, even if water absorption occurs in the imaging lens, the change in the focal length is canceled out, so that no particular problem has occurred.

  By the way, a wafer scale lens is generally formed from an energy curable resin material such as a thermosetting resin. However, in some energy curable resin materials, the refractive index increases and decreases due to water absorption. What to do is mixed. However, when a wafer scale lens whose free expansion is constrained is formed from a resin material whose refractive index decreases due to water absorption, the paraxial radius of curvature of the lens portion decreases due to dimensional changes accompanying water absorption, so the refractive index associated with water absorption. The change in the paraxial image point position due to the change and the change in the paraxial image point position due to the dimensional change accompanying water absorption have the same sign (positive and positive or negative and negative). Therefore, when water absorption occurs in a wafer scale lens formed from a resin material whose refractive index decreases due to water absorption, the focal length change is synergistic, and the image focused on the light receiving surface of the image sensor is not in focus. May occur.

  The present invention has been made in view of such a situation, and even with an imaging lens with improved mass productivity, a low-cost imaging lens and imaging that prevent deterioration in image quality due to a change in paraxial image point position due to moisture absorption An object of the present invention is to provide an apparatus, a digital device, and an imaging lens manufacturing method.

The imaging lens according to claim 1 is a lens block as an optical element including a lens substrate that is a parallel plate and a lens unit that is formed on at least one of the object side surface and the image side surface and has a positive or negative power. Have
At least one specific lens part of the lens part and the lens substrate are different in material,
The specific lens portion is formed of a material whose refractive index decreases as the water absorption increases, and the dimensional change rate due to water absorption of the specific lens portion is larger than the dimensional change rate due to water absorption of the lens substrate. (1) is satisfied.
0.1% ≤ α ≤ 3.0% (1)
Where α is the dimensional change rate of the specific lens portion when the water absorption rate is changed from 0% to 50%, and dn is the refractive index of the specific lens portion when the water absorption rate is changed from 0% to 50%. It is a change.

When a lens part with a smaller dimensional change rate due to water absorption than the lens board is formed on the lens substrate, the paraxial radius of curvature of the lens part is larger due to the expansion of the lens board due to water absorption, unlike existing lenses that freely expand. will vary away paraxial image point position. At this time, the refractive index by water absorption as described above is changed to decrease, resulting in a variation of the same sign of the paraxial image point position due to dimensional changes. Therefore, in the present invention, by satisfying the predetermined condition, the variation in the paraxial image point position due to the dimensional change due to water absorption can be corrected by the variation in the paraxial image point position due to the change in refractive index due to water absorption. I have to. Examples of the “material whose refractive index decreases as the water absorption rate increases” include, for example, UV-curable resin materials including acrylic materials and UV-curable resin materials including epoxy materials.

The imaging lens described in claim 2 is characterized in that, in the invention described in claim 1, the following conditional expression (2) is satisfied.
−500 × 10 ⁻⁵ ≦ dn <0 (2)
However, dn is a change in the refractive index of the specific lens portion when the water absorption rate is changed from 0% to 50%.

  More specific optimum conditions are defined by conditional expression (1) and conditional expression (2). By setting the value α to be equal to or less than the upper limit of the conditional expression (1) and the value dn to be equal to or greater than the lower limit of the conditional expression (2), the change in the paraxial image point position caused by the dimensional change due to water absorption is caused by water absorption. It is possible to effectively correct the change in the paraxial image point position caused by the refractive index change. On the other hand, by causing the value α to be equal to or higher than the lower limit of the conditional expression (1) and the value dn to be equal to or lower than the upper limit of the conditional expression (2), the fluctuation of the paraxial image point position caused by the dimensional change due to water absorption is Correction can be effectively made by a change in paraxial image point position caused by a change in refractive index due to water absorption. In addition, according to the present invention, since the dimensional change due to water absorption does not become too large, not only the correction of the paraxial image point position but also the occurrence of field curvature aberration due to the dimensional change can be suppressed. Since the refractive index change does not become too large, the occurrence of various aberrations can be suppressed.

It is more desirable to satisfy the following conditional expressions (1 ′) and (2 ′).
0.1% ≤ α ≤ 2.0% (1 ')
−300 × 10 ⁻⁵ ≦ dn <0 (2 ′)
Thus, by satisfying the conditional expressions (1 ′) and (2 ′), not only can the paraxial image point position be corrected effectively, but also the occurrence of field curvature aberration due to dimensional change can be further improved. Can be suppressed.

More desirably, the following conditional expression (1 ″) and conditional expression (2 ″) are satisfied.
0.1% ≤ α ≤ 1.5% (1 ")
−250 × 10 ⁻⁵ ≦ dn <0 (2 ″)
By satisfying conditional expressions (1 ″) and (2 ″), not only can the paraxial image point position be corrected effectively, but also the occurrence of field curvature aberration due to dimensional changes can be suppressed. it can.

  The water absorption rate of 100% means that the resin material is in a saturated state where no more water is absorbed. For example, the water absorption rate of 50% is half of the weight of water contained in the state of water absorption rate of 100%. The state where water is absorbed by the same resin material.

According to a third aspect of the present invention, in the invention according to the first or second aspect, the specific lens unit satisfies the following conditional expression (3).
0.5 ≦ | f1 / f | ≦ 1.1 (3)
However, f1 is a focal length when the object side and the image side of the specific lens unit are in contact with air, and f is a combined focal length of the entire imaging lens system.

  By setting the value | f1 / f | to be equal to or greater than the lower limit of the conditional expression (3), the power of the lens unit does not become excessively strong, and the effect of correcting the paraxial image point position due to the refractive index change accompanying water absorption is excessive. It can be prevented from becoming too much. On the other hand, by setting the value | f1 / f | to be equal to or less than the upper limit of the conditional expression (3), the power of the lens unit can be sufficiently increased, and the paraxial image point due to the refractive index change accompanying water absorption. The position can be corrected effectively.

It is more desirable to satisfy the following conditional expression (3 ′).
0.5 ≦ | f1 / f | ≦ 0.7 (3 ′)
By satisfying the conditional expression (3 ′), it is possible to more effectively correct the fluctuation of the paraxial image point position due to the refractive index change accompanying water absorption.

  According to a fourth aspect of the present invention, in the imaging lens according to any one of the first to third aspects, the specific lens portion has an inclination of a lens surface shape in a region within an effective diameter excluding the lens center. The signs are the same.

  When a dimensional change due to water absorption occurs, internal stress is likely to occur particularly in locations such as a convex shape and a concave shape in the surface shape within the effective diameter excluding the lens center. However, if an internal stress is generated, birefringence and refractive index distribution are generated, which may cause deterioration of optical performance. Here, by making the sign of the inclination of the lens surface shape the same, it is possible to realize an optical system with little internal stress and less performance deterioration even when a dimensional change due to water absorption occurs. Note that “the same sign of the inclination of the lens surface shape” means that a cross section including the optical axis is taken in the imaging lens and the optical axis orthogonal direction is taken as the reference direction from the optical axis along the lens surface shape. The direction of the tangent at each point of the lens surface shape is always directed to the same side (left side or right side toward the reference direction) with respect to the reference direction while moving toward the effective diameter side.

The imaging lens according to claim 5 is the invention according to any one of claims 1 to 4, wherein the specific lens portion satisfies the following conditional expression (4) and has a concave shape. And
l / h ≤ 3.5 (4)
However, l is the length from the effective diameter of the specific lens part to the outer diameter of the specific lens part, and h is the effective radius of the specific lens part.

  By setting the value l / h to be equal to or less than the upper limit of the conditional expression (4), the volume of the resin material from the effective diameter to the outer diameter of the specific lens portion is within the effective diameter of the specific lens portion. The paraxial image point position due to dimensional change due to water absorption is pushed out by the resin material within the effective diameter from the resin material outside the effective diameter of the lens part due to dimensional change due to water absorption. It is possible to prevent the fluctuation of the value from becoming too large.

It is more desirable to satisfy the following conditional expression (4 ′).
1 / h ≦ 1.5 (4 ′)
By satisfying conditional expression (4 ′), it is possible to more effectively prevent the variation in the paraxial image point position due to the dimensional change accompanying water absorption.

  An imaging lens according to a sixth aspect is the imaging lens according to any one of the first to fifth aspects, wherein the lens substrate is made of a glass material, and at least the specific lens portion is made of a resin material. It is characterized by having one.

  By using a glass material for the lens substrate, which is a parallel plate, the polishing process can be facilitated, and the specific lens part with a complicated shape is made of a resin material with good processability, resulting in low cost and high performance. Is possible. In general, the difference in dimensional change due to water absorption between the glass material and the resin material is large, and the dimensional change due to water absorption of the specific lens portion can be easily corrected by the lens substrate.

  An imaging lens according to a seventh aspect is characterized in that, in the invention according to any one of the first to sixth aspects, the specific lens portion is made of an energy curable resin material.

  By configuring the specific lens portion with an energy curable resin material, it becomes possible to simultaneously cure a large amount of the specific lens portion with various energies with a mold on a wafer-shaped lens substrate, and mass productivity is improved. Can be improved. Here, the energy curable resin material refers to a resin material that is cured by heat, a resin material that is cured by light, or the like. The energy curable resin material is preferably composed of a UV curable resin material. By comprising a UV curable resin material, the curing time can be shortened and the mass productivity can be improved. In recent years, resins having excellent heat resistance and curable resin materials have been developed and may be used.

  An imaging lens according to an eighth aspect is characterized in that, in the invention according to the seventh aspect, inorganic fine particles having a maximum length of 30 nanometers or less are dispersed in the energy curable resin material.

  By dispersing inorganic fine particles of 30 nanometers or less in the specific lens part made of a resin material, performance deterioration and image point position fluctuation can be reduced even when the temperature changes, and light transmittance can be reduced. An imaging lens having excellent optical characteristics regardless of environmental changes can be provided without being reduced.

  In general, when fine particles are mixed in a transparent resin material, light scattering occurs and the transmittance decreases, so that it was difficult to use as an optical material. However, the size of the fine particles is made smaller than the wavelength of the transmitted light beam. Thus, the scattering can be substantially prevented. 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 resin 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 resin 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 resin 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］は分子屈折である。

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 the PMMA resin, the linear expansion coefficient α is 7 × 10 ⁻⁵ , and if it is substituted into the above formula, 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 as to cancel out the change due to the linear expansion of the first term. . Specifically, it is desirable to suppress the change of about −1.2 × 10 ^{−4 in the} past 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. Similarly, although the refractive index of the resin material increases due to water absorption, a material whose refractive index decreases can be obtained.

  The mixing ratio of the fine particles 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.

  An imaging lens according to a ninth aspect is the invention according to any one of the first to eighth aspects, wherein the lens substrate and at least the specific lens portion are interposed through at least one of an optical thin film and an adhesive. And at least one lens block that is indirectly bonded.

  By disposing and bonding an optical thin film having a function such as an aperture stop or an infrared cut filter between the specific lens portion and the lens substrate, the optical member can be simplified and the cost can be reduced. In addition, by adhering the lens substrate and the specific lens part with an adhesive or the like, it is possible to preferentially select optical characteristics even if the resin material of the specific lens part is poor in adhesion. Thus, high performance and high functionality can be realized. In addition, since both the optical thin film and the adhesive are extremely thin, the dimensional change rate due to water absorption of the optical thin film and the adhesive is almost negligible. Therefore, the dimensional change rate due to water absorption between the specific lens portion and the lens substrate The difference is also an important factor in a lens block that is indirectly bonded via an optical thin film and an adhesive.

  An imaging lens according to a tenth aspect is characterized in that, in the invention according to any one of the first to ninth aspects, all lens surfaces in contact with air are aspherical.

  By making the lens surface in contact with air an aspherical shape, the difference in refractive index is the largest on the boundary surface between the surface in contact with air and the lens part, and the effect of the aspheric surface can be utilized to the maximum. Further, by making the lens surfaces all aspherical, the occurrence of various aberrations can be minimized, and high performance can be easily achieved.

  An imaging lens according to an eleventh aspect is characterized in that, in the invention according to any one of the first to tenth aspects, the specific lens portion is disposed closest to the object side in the imaging lens.

  The lens part closest to the object side mainly bears the power of the imaging lens in order to shorten the entire length. If this is the specific lens part, the paraxial image generated by the dimensional change accompanying water absorption of the specific lens part By correcting the change in the point position with the change in the paraxial image point position caused by the change in the refractive index due to water absorption, even if the present invention is applied to one place of the image pickup lens, the water absorption of the entire image pickup lens system is caused. Most variations in paraxial image point position can be corrected.

  An imaging device according to a twelfth aspect of the present invention includes an optical image of a subject on a light receiving surface of an imaging device that converts an optical image into an electrical signal using the imaging lens according to any one of the first to eleventh aspects. Therefore, it is possible to provide an imaging device that can withstand use even in a low-cost and high-humidity environment.

  A digital device according to a thirteenth aspect includes the imaging device according to the twelfth aspect and an image sensor, and is provided with at least one function of still image shooting and moving image shooting of a subject. Therefore, a digital device that can withstand use in a low-cost and high-humidity environment can be provided.

  The digital device according to claim 14 is a portable terminal in the invention according to claim 13, and therefore provides a portable terminal that can withstand use even in a low-cost and high-humidity environment. Can do.

  An imaging lens manufacturing method according to claim 15 is the imaging lens manufacturing method according to any one of claims 1 to 11, wherein a unit including a plurality of the lens blocks arranged side by side is provided. A connecting step of arranging a spacer on at least a part of the periphery of the lens block and connecting the plurality of lens block units with the spacer interposed therebetween, and connecting the lens block units connected to each other along the spacer. In this case, the image pickup lens can be mass-produced at a lower cost because it includes a cutting step of separating each lens block by cutting.

  According to the present invention, a low-cost imaging lens, imaging device, digital device, which prevents image quality deterioration due to a change in paraxial image point position due to moisture absorption, even with an imaging lens with high heat resistance and improved mass productivity, And an imaging lens manufacturing method.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of an imaging apparatus 50 according to the present embodiment, and FIG. 2 is a cross-sectional view of the configuration of FIG. 1 taken along the line II-II and viewed in the direction of the arrow. As shown in FIG. 2, the imaging device 50 includes a CMOS image sensor 51 as a solid-state imaging device having a photoelectric conversion unit 51 a, an imaging lens 10 that causes the photoelectric conversion unit 51 a of the image sensor 51 to capture a subject image, A substrate 52 having an external connection terminal (not shown) for holding the image sensor 51 and transmitting / receiving the electric signal is provided, and these are integrally formed. Note that the imaging lens 10 includes a first lens block BK1 and a second lens block BK2.

  In the image sensor 51, a photoelectric conversion unit 51a 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. A processing circuit 51b is formed. The signal processing circuit 51b forms a picture signal output by using 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 the digital signal. It consists of a signal processing unit and the like. A number of pads (not shown) are arranged near the outer edge of the plane on the light receiving side of the image sensor 51, and are connected to the substrate 52 via wires (not shown). The image sensor 51 converts the signal charge from the photoelectric conversion unit 51a into an image signal such as a digital YUV signal, and outputs the image signal to a predetermined circuit on the substrate 52 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 substrate 52 that supports the image sensor 51 is communicably connected to the image sensor 51 through a wiring (not shown).

  The substrate 52 is connected to an external circuit (for example, a control circuit included in a host device of a portable terminal mounted with an imaging device) via an external connection terminal (not shown), and a voltage for driving the image sensor 51 from the external circuit. And a clock signal can be received, and a digital YUV signal can be output to an external circuit.

  The upper part of the image sensor 51 is sealed with a plate PT such as an infrared cut filter fixed to the upper surface of the substrate 52. The lower end of the spacer member B2 is fixed to the upper surface of the plate PT. Further, the second lens block BK2 is fixed to the upper end of the spacer member B2, the lower end of another spacer member B1 is fixed to the upper surface of the second lens block BK2, and the first end of the spacer member B1 is The lens block BK1 is fixed.

  The first lens block BK1 includes a lens substrate LS1 that is a parallel plate and lens portions L1 and L2 fixed to the object side and the image surface side thereof. The second lens block BK2 is a lens substrate LS2 that is a parallel plate. And lens portions L3 and L4 fixed to the object side and the image plane side. Here, all the lens portions L1 to L4 are specific lens portions, but at least one of the specific lens portions is sufficient. In addition, it is preferable to form an optical thin film having an aperture that forms a stop between the first lens portion L1 and the lens substrate LS1.

In the present embodiment, the dimensional change rate due to water absorption of the lens portions L1 to L4 is larger than the dimensional change rate due to water absorption of the lens substrates LS1 and LS2, and satisfies the following conditional expressions (1) and (2). It is.
0.1% ≤ α ≤ 3.0% (1)
−500 × 10 ⁻⁵ ≦ dn <0 (2)
Where α is the dimensional change rate of the lens portions L1 to L4 when the water absorption rate is changed from 0% to 50%, and dn is the lens portion L1 to L4 when the water absorption rate is changed from 0% to 50%. Refractive index change.

The lens portions L1 to L4 satisfy the following conditional expression (3).
0.5 ≦ | f1 / f | ≦ 1.1 (3)
However, f1 is a focal length when the object side and the image side of the lens portions L1 to L4 are in contact with air, and f is a combined focal length of the entire imaging lens 10 system.

  The lens portions L1 to L4 have the same sign of the inclination of the lens surface shape in a region within the effective diameter excluding the lens center.

The lens portions L2 and L4 satisfy the following conditional expression (4) and have a concave shape.
l / h ≤ 3.5 (4)
Here, l is the length from the effective diameter of the lens portions L2 and L4 to the outer diameter of the lens portions L2 and L4, and h is the effective radius of the lens portions L2 and L4, respectively.

  In the lens blocks BK1 and BK2, the lens substrates LS1 and LS2 are made of a glass material, and the lens portions L1 to L4 are made of a resin material.

  The lens portions L1 to L4 are preferably made of an energy curable resin material in which inorganic fine particles having a maximum length of 30 nanometers or less are dispersed.

  A usage mode of the imaging apparatus 50 described above will be described. FIG. 3 is a diagram illustrating a state in which the imaging device 50 is mounted on a mobile phone 100 as a mobile terminal that is a digital device. FIG. 4 is a control block diagram of the mobile phone 100.

  The imaging device 50 is disposed, for example, such that the object-side end surface of the imaging lens is provided on the back surface of the mobile phone 100 (the liquid crystal display unit side is the front surface) and corresponds to a position below the liquid crystal display unit.

  An external connection terminal (not shown) of the imaging device 50 is connected to the control unit 101 of the mobile phone 100 and outputs an image signal such as a luminance signal or a color difference signal to the control unit 101 side.

  On the other hand, as shown in FIG. 4, the mobile phone 100 controls each unit in an integrated manner, and also supports a control unit (CPU) 101 that executes a program corresponding to each process, and inputs a number and the like with keys. An input unit 60, a display unit 70 for displaying captured images and videos, a wireless communication unit 80 for realizing various information communications with an external server, a system program and various processing programs for the mobile phone 100, A storage unit (ROM) 91 that stores necessary data such as a terminal ID, and various processing programs and data executed by the control unit 101, processing data, imaging data by the imaging device 50, and the like are temporarily stored. And a temporary storage unit (RAM) 92 used as a work area for storage.

  When the photographer holding the mobile phone 100 points the imaging lens 10 of the imaging device 50 toward the subject, the image sensor 51 captures an image signal of a still image or a moving image. When the photographer presses the button BT shown in FIG. 3 at a desired photo opportunity, release is performed, and the image signal is taken into the imaging device 50. The image signal input from the imaging device 50 is transmitted to the control system of the mobile phone 100 and stored in the storage unit 92 or displayed on the display unit 70, and further, video information is transmitted via the wireless communication unit 80. Will be transmitted to the outside.

  A method for manufacturing the imaging lens according to the present embodiment will be described. FIG. 5 is a diagram illustrating a process of manufacturing the imaging lens according to the present embodiment. First, as shown in the sectional view of FIG. 5A, a lens block unit UT including a plurality of lens blocks BK arranged two-dimensionally is manufactured. Such a lens block unit UT can be manufactured by, for example, a replica method that can simultaneously produce a large number of lenses L and is low in cost (note that the number of lens blocks BK included in the lens block unit UT is one. May be more than one).

  The replica method is a method in which a curable resin is transferred in a lens shape onto a lens wafer using a mold. That is, in the replica method, a large number of lenses are simultaneously manufactured on the lens wafer.

  And the imaging lens 10 is manufactured from the lens block unit UT manufactured by such methods. An example of the manufacturing process of this imaging lens is shown in the schematic sectional view of FIG.

  The first lens block unit UT1 includes a first lens substrate LS1 that is a parallel plate, a plurality of first lens portions L1 bonded to one plane, and a plurality of second lens portions bonded to the other plane. L2. At this time, it is preferable that the first lens substrate LS1 and the lens portions L1 and L2 are indirectly bonded via an optical thin film or an adhesive. This is because when the optical thin film, the adhesive, or the like is provided on the infrared cut filter or the diaphragm, the total lens length in the optical axis direction can be made smaller than that provided separately. Further, if an antireflection coating (for example, a transparent thin film) is provided, reflection at the lens portion and the lens substrate can be prevented, and flare and ghost can be reduced.

  The second lens block unit UT2 includes a second lens substrate LS2 that is a parallel plate, a plurality of third lenses L3 bonded to one plane, and a plurality of fourth lenses L4 bonded to the other plane. , Composed of. At this time, it is preferable that the second lens substrate LS2 and the lens portions L3 and L4 are indirectly bonded via an adhesive or the like.

  A grid-like spacer member (spacer) B1 is provided between the first lens block unit UT1 and the second lens block unit UT2 (specifically, between the first lens substrate LS1 and the second lens substrate LS2). The distance between the lens block units UT1 and UT2 is kept constant. Further, another spacer member B2 is interposed between the plate PT and the second lens block unit 2, and the distance between the plate PT and the lens block unit UT2 is kept constant (that is, the spacer members B1 and B2 are 2). It can be said that it is a stepped grid). In such a state, the lens portions L1 to L4 are positioned in the lattice hole portions of the spacer members B1 and B2.

  The plate PT is a wafer level sensor chip size package including a microlens array, or a parallel flat plate such as a sensor cover glass or an infrared cut filter.

  Here, the spacer member B1 is interposed between the first lens block unit UT1 and the first lens block unit UT2, and the spacer member B2 is interposed between the second lens unit UT2 and the plate PT. Thereby, the lens substrates LS (the first lens substrate LS1 and the second lens substrate LS2) are sealed and integrated.

  Then, when the integrated first lens substrate LS1, second lens substrate LS2, spacer members B1, B2, and plate PT are cut along the lattice frame (position of the broken line Q) of the spacer members B1, B2, As shown in FIG. 5C, a plurality of imaging lenses 10 each having a two-lens structure integrated with each lens block are obtained. Thereafter, although not shown, the imaging device shown in FIG. 2 can be obtained by attaching the imaging lens 10 to the substrate 52 so that the image sensor 51 is sandwiched between the plate PT and the substrate 52.

  As described above, when the imaging lens 10 is manufactured by separating the members in which the plurality of lens blocks BK (the first lens block BK1 and the second lens block BK2) are incorporated, the lens interval of each imaging lens 10 is increased. Adjustment and assembly are not required. Therefore, mass production of imaging devices that are expected to have high image quality is possible.

  Moreover, since the spacer members B1 and B2 have a lattice shape, the spacer members B1 and B2 also serve as marks when the imaging lens 10 is separated from the members in which the plurality of lens blocks BK are incorporated. Therefore, the imaging lens 10 can be easily cut out from the members incorporated in the plurality of lens blocks BK, and it does not take time and effort. As a result, the imaging lens 10 can be mass-produced at a low cost.

  Based on the above, in the manufacturing method of the imaging lens 10, the spacer members B1 and B2 are arranged on at least a part of the periphery of the lens block BK, and the plurality of lens block units UT are connected with the spacer members Bl and B2 interposed therebetween. It can be said that it includes a connecting step and a cutting step of cutting the mutually connected lens block units UT along the spacer members B1 and B2. Such a manufacturing method is suitable for mass production of an inexpensive lens system. It is also possible to connect only a single lens block unit to the plate.

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 system
BF: Back focus
Fno: F number
Ymax: diagonal length of image surface r: paraxial radius of curvature of lens surface d: lens surface interval
Nd: Refractive index νd at lens d-line: Abbe number at lens d-line
w: Half angle of view
TL: Total lens length *: Aspherical position
stop: Aperture position

Further, the aspheric shape in the present invention is defined as follows. That is, the distance (sag amount) in the optical axis direction from the tangent plane of the surface vertex is x, the height from the optical axis is y, r is a paraxial radius of curvature, K is a conic constant, and A _n (= 4, 6 , 8,..., 14) is an n-th aspherical coefficient, and X can be expressed by the following equation [Equation 2].

Example 1
Table 1 shows lens data in the first example. In the following tables, a power of 10 (for example, 2.5 × 10 ⁻³ ) is represented by using e (for example, 2.5 × e-03). The F value, half angle of view, full length, and back focus described in the construction data table 1 of Example 1 below are all effective values for the total lens length, finite object distance, that is, the object distance in the table. The back focus is the distance from the lens final surface to the paraxial image plane expressed in terms of air length. The total lens length is the distance from the lens front surface to the lens final surface plus the back focus. .

  6 is a sectional view of the lens of Example 1. FIG. FIG. 7 is an aberration diagram of spherical aberration (a), astigmatism (b), and distortion (c) of the imaging lens according to the first example. Here, in the spherical aberration diagrams, g represents g-line, d represents d-line, and C represents spherical aberration with respect to C-line. In the astigmatism diagram, the solid line represents the sagittal plane, and the dotted line represents the meridional plane.

  The taking lens of the present embodiment has three lens blocks. More specifically, in order from the object side, the first lens block BK1 is configured by the first lens unit L1, the aperture stop S made of an optical thin film, the first lens substrate LS1, and the second lens unit L2, and then the first lens block BK1. The third lens unit L3, the second lens substrate LS2, and the fourth lens unit L4 constitute a second lens block BK2, and finally, the fifth lens unit L5, the third lens substrate LS3, and the sixth lens unit L6. A three-lens block BK3 is configured. Further, the surfaces of the lens portions that are in contact with all air are aspherical. Table 2 shows values of the examples corresponding to the respective conditional expressions.

  Here, taking the imaging lens of Example 1 as an example, the paraxial image at the time of water absorption with and without the lens portion having the effect of correcting the variation of the paraxial image point position due to water absorption in the present invention. The difference in the amount of change in the point position is shown. The resin material of Example 1 (UV curable resin including epoxy system) uses a low dispersion resin material having Nd of 1.52 and νd of 57 and a high dispersion resin material of Nd of 1.55 and νd of 32. doing. In this embodiment, two types of resin materials are used, but one type or three or more types of resin materials may be used.

In Example 1, the dimensional change rate α of the low dispersion resin material when the water absorption rate is changed from 0% to 50% is 0.4%, and when the water absorption rate is changed from 0% to 50%. The refractive index change dn is −65 × 10 ⁻⁵ . On the other hand, the dimensional change rate α of the highly dispersed resin material when the water absorption rate is changed from 0% to 50% is 0.2%, and the refractive index change when the water absorption rate is changed from 0% to 50%. dn is + 130 × 10 ⁻⁵ . At this time, the fluctuation amount of the paraxial image point position when the entire imaging lens changes from 0% to 50% is +0.002 [mm].

Further, in a comparative example that does not have a specific lens portion that has an effect of correcting the fluctuation of the paraxial image point position due to the water absorption rate, the dimensional change of the low dispersion resin material when the water absorption rate is changed from 0% to 50%. The rate α is 0.3%, and the refractive index change dn when the water absorption rate is changed from 0% to 50% is + 70 × 10 ⁻⁵ . On the other hand, the dimensional change rate α of the highly dispersed resin material when the water absorption rate is changed from 0% to 50% is 0.2%, and the refractive index change when the water absorption rate is changed from 0% to 50%. The dn is + 130 × 10 ⁻⁵ . At this time, the amount of change in the paraxial image point position when the entire imaging lens changes from 0% to 50% is +0.010 [mm].

  From the above, it can be seen that, in comparison with the comparative example that does not include the specific lens portion of the present invention, in Example 1, the amount of variation in the paraxial image point position at the time of water absorption is suppressed. In general, as the water absorption increases, the dimensional change rate α and the refractive index change dn also tend to increase, so the effect of reducing the amount of change in paraxial image point position according to the present invention becomes more prominent. In addition, a resin material having a different dimensional change rate α and refractive index change dn may be used for each lens portion. In this case, the contribution of the variation in the paraxial image point position at the time of water absorption of each lens By designing in consideration of the size, it is possible to prevent the entire imaging lens from changing the paraxial image point position at the time of water absorption.

It is a perspective view of the imaging device 50 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. It is a figure which shows the state equipped with the imaging device 50 in the mobile telephone 100 as a portable terminal. 3 is a control block diagram of the mobile phone 100. FIG. It is a figure which shows the process of manufacturing the imaging lens used for this Embodiment. It is sectional drawing of 1st Example. FIG. 6 is an aberration diagram of spherical aberration (a), astigmatism (b), and distortion (c) of the imaging lens according to the first example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Imaging lens 50 Imaging device 51 Image sensor 51a Photoelectric conversion part 51b Signal processing circuit 52 Board | substrate 60 Input part 70 Display part 80 Wireless communication part 92 Memory | storage part 100 Cellular phone 101 Control part LS1-LS3 Lens board | substrate L1-L6 Lens part

Claims (15)

A lens block as an optical element including a lens substrate that is a parallel plate, and a lens unit that is formed on at least one of the object side surface and the image side surface, and has a positive or negative power;
At least one specific lens part of the lens part and the lens substrate are different in material,
The specific lens portion is formed of a material whose refractive index decreases as the water absorption increases, and the dimensional change rate due to water absorption of the specific lens portion is larger than the dimensional change rate due to water absorption of the lens substrate. An imaging lens characterized by satisfying (1).
0.1% ≤ α ≤ 3.0% (1)
However, α is a dimensional change rate of the specific lens portion when the water absorption rate is changed from 0% to 50%. The imaging lens according to claim 1, wherein the following conditional expression (2) is satisfied.
−500 × 10 ⁻⁵ ≦ dn <0 (2)
However, dn is a change in the refractive index of the specific lens portion when the water absorption rate is changed from 0% to 50%. The imaging lens according to claim 1, wherein the specific lens unit satisfies the following conditional expression (3).
0.5 ≦ | f1 / f | ≦ 1.1 (3)
However, f1 is a focal length when the object side and the image side of the specific lens unit are in contact with air, and f is a combined focal length of the entire imaging lens system.   The imaging lens according to claim 1, wherein the specific lens unit has the same sign of the inclination of the lens surface shape in a region within the effective diameter excluding the lens center. The imaging lens according to claim 1, wherein the specific lens unit satisfies the following conditional expression (4) and has a concave shape.
l / h ≤ 3.5 (4)
However, l is the length from the effective diameter of the specific lens part to the outer diameter of the specific lens part, and h is the effective radius of the specific lens part.   The imaging lens according to claim 1, wherein the lens substrate is made of a glass material, and at least the lens block is made of at least the specific lens portion made of a resin material.   The imaging lens according to claim 1, wherein the specific lens portion is made of an energy curable resin material.   The imaging lens according to claim 7, wherein inorganic fine particles having a maximum length of 30 nanometers or less are dispersed in the energy curable resin material.   9. The lens substrate according to claim 1, wherein the lens substrate and at least the specific lens portion include at least one lens block that is indirectly bonded via at least one of an optical thin film and an adhesive. The imaging lens according to any one of the above.   The imaging lens according to claim 1, wherein all lens surfaces in contact with air are aspherical.   The imaging lens according to claim 1, wherein the specific lens unit is disposed closest to the object side in the imaging lens.   An image pickup apparatus, wherein an optical image of a subject is formed on a light receiving surface of an image pickup device that converts an optical image into an electrical signal using the image pickup lens according to claim 1. .   13. A digital apparatus comprising the image pickup apparatus according to claim 12 and an image pickup element, to which at least one function of still image shooting and moving image shooting of a subject is added.   The digital device according to claim 13, wherein the digital device is a mobile terminal.   12. The method of manufacturing an imaging lens according to claim 1, wherein a unit including a plurality of the lens blocks arranged side by side is a lens block unit, and a spacer is provided on at least a part of the periphery of the lens block. A connecting step of connecting a plurality of the lens block units through the spacers, and a cutting step of separating the lens block units connected to each other by cutting along the spacers. The manufacturing method of the imaging lens characterized by including these.

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