WO2010134376A1

WO2010134376A1 - Image pickup lens, image pickup device, and portable terminal

Info

Publication number: WO2010134376A1
Application number: PCT/JP2010/054208
Authority: WO
Inventors: 恵子山田; 泰成福田; 大輔棚橋; 進山口
Original assignee: コニカミノルタオプト株式会社
Priority date: 2009-05-18
Filing date: 2010-03-12
Publication date: 2010-11-25
Also published as: JPWO2010134376A1

Abstract

Provided is a thin and compact image pickup lens having a high IR cutting filter function. To this end, the image pickup lens (LN) comprises lens blocks Cn (n=1, 2, 3), wherein a lens substrate (Ln2) formed of a parallel plate and a lens portion (Ln1, Ln3) having a positive or negative power are made of different materials. The third lens block c3 has a lens portion (L33) on only one of the surfaces of the lens substrate (L32) and has an IR cutting filter film (CT) on the other surface of the lens substrate (L32).

Description

Imaging lens, imaging device, and portable terminal

The present invention relates to an imaging lens, an imaging device, and a portable terminal. More specifically, for example, including a wafer-scale lens suitable for mass production, an image sensor (for example, a solid-state image sensor such as a charge coupled device (CCD) image sensor, a complementary metal-oxide semiconductor (CMOS) image sensor). The present invention relates to an imaging device having an imaging lens that forms an optical image on a light receiving surface, an imaging device that captures an optical image formed by the imaging lens and the imaging lens, and a mobile terminal equipped with the imaging device.

Compact and thin imaging devices are now installed in portable terminals (for example, mobile phones and PDAs (Personal Digital Assistants), etc.) that are compact and thin electronic devices. Is possible not only for audio information but also for image information. 2. Description of the Related Art An increase in the number of pixels and functionality of an image sensor (for example, a solid-state image sensor such as a CCD image sensor) mounted on an image pickup apparatus is rapidly progressing. In order to make full use of the performance, an imaging lens for forming a subject image on the imaging element is also required to have high optical performance. In addition, with the downsizing of portable terminals, the downsizing of imaging lenses has been further promoted.

¡Plastic lenses suitable for mass production are used for imaging lenses to reduce costs. Since the plastic lens has good processability, it is easy to form an aspherical surface. Therefore, the use of an aspherical shape can meet the demand for higher performance. From such a viewpoint, an imaging lens including a plastic lens is usually used for an imaging device with a built-in portable terminal. Generally known as such an imaging lens are an imaging lens having three plastic lenses, a three-lens imaging lens including one glass lens and two plastic lenses. However, it is difficult to achieve both compactness of these optical systems and mass productivity required for portable terminals.

In order to overcome such problems, a large number of lens parts are simultaneously molded and cured on a parallel plate several inch wafer-like lens substrate with a mold, and then the lens substrate is passed through a lattice-like spacer member. Development of a technique for mass-producing lens modules at low cost by sealing each other and cutting the integrated lens substrate and spacer member with a lattice frame of the spacer member is in progress. A lens manufactured by such a manufacturing method is called a “wafer level lens”, and a lens module is called a “wafer level lens module”.

Further, as the imaging lens is made more compact, the influence of the substrate thickness of an IR (InfraRed) cut filter disposed in the optical system becomes larger. In other words, the ratio of the IR cut filter to the total lens length increases, which is one factor that hinders the downsizing of the imaging lens. In order to reduce the thickness and size of the imaging lens,

Patent Documents

1 and 2 propose imaging lenses that have an IR cut filter function in a lens element or the like and do not have an IR cut filter substrate. For example,

Patent Documents

1 and 2 propose an imaging lens in which an IR cut coat is provided at the boundary between a lens substrate and a lens portion in a wafer level lens. Patent Document 1 proposes an imaging lens using an IR absorbing glass as a lens substrate of a wafer level lens.

US Patent Application Publication No. 2007/0024958 Special table 2008-508545 gazette

As proposed in

Patent Documents

1 and 2, if an IR cut coat is provided at the boundary between optical materials, the incident angle dependency of the wavelength characteristics increases, so that uniform IR cut characteristics can be obtained over the entire screen. It becomes difficult. In order to suppress changes in wavelength characteristics that strongly depend on the incident angle, a large number of coating layers are required, which causes an increase in cost. Further, as proposed in Patent Document 1, when an IR absorbing glass is used for a lens substrate, a sharp absorption characteristic cannot be obtained and it becomes difficult to reproduce the color tone of an object. It is also known that the filter substrate is omitted by providing an IR cut coat on the glass lens surface, but coating is performed at a low temperature on a lens part made of resin such as a wafer level lens. Therefore, it is difficult to realize sharp wavelength characteristics.

The present invention has been made in view of such a situation, and an object thereof is to provide a thin and compact imaging lens having a high IR cut filter function, an imaging device including the imaging lens, and a portable terminal. .

In order to achieve the above object, the imaging lens of the first invention is formed of a material different from the lens substrate on at least one of a parallel plate lens substrate and an object side surface and an image side surface of the lens substrate, An imaging lens including at least two lens blocks each including a lens unit having positive or negative power, wherein at least one of the lens blocks has a lens unit only on one surface of a lens substrate of the lens block. And having an IR cut filter film on the other surface.

An imaging lens according to a second aspect of the present invention is the imaging lens according to the first aspect, wherein the lens block is disposed opposite to the lens block having the IR cut filter film and adjacent to the IR cut filter film with an air gap. One surface of the lens substrate facing the IR cut filter film is not provided with a lens portion, or a lens portion having a weaker power than the lens portion provided on the other surface is provided. It is characterized by being.

The imaging lens of a third invention is characterized in that, in the first invention, the imaging lens has a lens portion on the image surface side of the lens substrate of the lens block closest to the image surface side.

An imaging lens of a fourth invention is characterized in that, in any one of the first to third inventions, the following conditional expression is satisfied.
0.08 <BF / DI <0.16
However,
BF: Back focus amount,
DI: Diameter of the image circle,
It is.

The imaging lens according to a fifth aspect of the present invention is the imaging lens according to any one of the first to fourth aspects, wherein the lens block is located between the most image side lens block and the lens block adjacent to the object side of the lens block. An IR cut filter film is provided on at least one optical surface constituting the air gap.

In the imaging lens of a sixth invention according to any one of the first to fifth inventions, an air interval with respect to the lens blocks located adjacent to each other is formed outside the effective diameter of the lens portion of the lens block. The spacer portion is adjusted.

The image pickup lens of a seventh invention is characterized in that, in any one of the first to sixth inventions, the lens substrate is made of a glass material.

The imaging lens according to an eighth aspect of the present invention is the imaging lens according to any one of the first to seventh aspects, wherein the lens substrates are sealed together via a lattice-shaped spacer member, the lens substrate integrated with the lens substrate, The lens block is manufactured by a manufacturing method including a step of cutting a spacer member with a lattice frame of the spacer member.

An image pickup apparatus according to a ninth aspect of the invention includes an image pickup lens according to any one of the first to eighth aspects of the invention, and an image pickup element that converts an optical image formed on a light receiving surface by the image pickup lens into an electrical signal. And.

A mobile terminal according to a tenth aspect includes the imaging device according to the ninth aspect.

According to the present invention, at least one lens block is configured to have a lens portion only on one surface of the lens substrate and an IR cut filter film on the other surface of the lens substrate. It is possible to obtain a uniform IR cut characteristic on the entire screen due to the sharp wavelength characteristic in which the incidence angle dependency is suppressed while achieving a thin and compact size. Therefore, it is possible to realize a thin and compact imaging lens having a high IR cut filter function, an imaging device including the imaging lens, and a portable terminal. For example, the above-described effect can be realized at low cost by adopting the above-described configuration in an imaging lens composed of a wafer level lens capable of mass production.

The optical block diagram of 1st Embodiment (Example 1). The optical block diagram of 2nd Embodiment (Example 2). FIG. 6 is an aberration diagram of Example 1. FIG. 6 is an aberration diagram of Example 2. The figure which shows the example of schematic structure of the portable terminal carrying an imaging device in a typical cross section. FIG. 6 is a schematic cross-sectional view illustrating an example of a manufacturing process of an imaging lens. The optical block diagram which shows embodiment of the type which has a spacer function outside the effective diameter of a lens part. The graph which shows the incident angle dependence of the transmittance | permeability characteristic of IR cut coat.

Hereinafter, an imaging lens, an imaging device, a portable terminal, and the like according to the present invention will be described with reference to the drawings. The imaging lens according to the present invention includes at least two lens blocks. However, the “lens block” refers to an optical element that includes 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 positive or negative power. The lens substrate and the lens portion assumed here are different in material.

Since the imaging lens according to the present invention includes at least two lens blocks as described above, the nth (n = 1, 2,...) Lens block from the object side to the image side is the nth lens block. Then, the block arrangement has a first lens block, a second lens block, and the like in order from the object side. At least one lens block has a lens portion only on one surface of the lens substrate, and an IR cut filter film (hereinafter also referred to as “IR cut coat”) on the other surface of the lens substrate. Yes.

As described above, when the lens portion is provided only on one surface of the lens substrate and the IR cut filter film is provided on the other surface of the lens substrate, the lens portion and the IR cut filter film cancel out the substrate distortion. be able to. Thereby, since the thickness of the lens substrate can be made thinner than the filter plate used only for the purpose of the IR cut filter function, it is possible to reduce the thickness of the entire imaging lens. In addition, since the lens block has an IR cut filter function, it is not necessary to separately install an IR cut filter plate, and as a result, it is possible to reduce the thickness, the size and the cost.

In the configuration in which the IR cut coat is applied on the lens substrate, when the lens substrate is made of glass, the IR cut coat can be formed at a high temperature. Since the selection range of the material is wide, the wavelength characteristics can be improved. In addition, the configuration in which the IR cut coat is applied to the boundary surface between the air and the lens substrate has a sharp wavelength in which the dependence on the incident angle is suppressed compared to the configuration in which the IR cut coat is applied to the boundary surface between the lens portion and the lens substrate. Due to the characteristics (that is, the wavelength characteristics change due to the change in the incident angle of the light beam on the IR cut filter film is small and sharp wavelength characteristics), it is possible to obtain a uniform IR cut characteristic on the entire screen. Therefore, a thin and compact imaging lens having a high IR cut filter function can be realized. For example, by adopting the above configuration in an imaging lens composed of a wafer level lens capable of mass production, it is possible to achieve both a reduction in thickness and size and improvement in imaging performance at a low cost.

Here, the incident angle dependency between the case where the IR cut coat is provided on the boundary surface between the air and the lens substrate and the case where the IR cut coat is provided on the boundary surface between the lens portion and the lens substrate. Explain the difference. The graph of FIG. 8 shows the incident angle dependency of the transmittance characteristic of the IR cut coat.

The graph of FIG. 8 shows a case where a general IR cut coat is arranged at the boundary between air and a lens substrate (refractive index 1.52) (hereinafter referred to as “AL configuration”. ) And when sandwiched between two lens substrates (refractive index 1.52) (hereinafter referred to as “LL configuration”. In the figure, the transmittance characteristic is indicated by a broken line). Simulation results of transmittance characteristics change when the light incident angle to the IR cut coat is changed to 0 °, 15 °, 30 ° (AL (0), AL (15), AL (30 ), LL (0), LL (15), LL (30): The numbers in parentheses indicate the light incident angle (unit: °). The IR cut coat has the same film configuration in the AL configuration and the LL configuration.

As can be seen from the graph of FIG. 8, the characteristic variation ΔAL of the AL configuration is smaller than the characteristic variation ΔL-L of the LL configuration. Therefore, the AL configuration in which the IR cut coat is formed on the boundary surface between the air and the lens substrate can realize the IR cut filter function with the same number of coat layers and less change in transmittance characteristics due to the incident angle. .

According to the characteristic configuration described above, it is possible to realize a thin and compact imaging lens having an high IR cut filter function and suitable for mass production at a low cost, and an imaging apparatus including the imaging lens. And if an imaging device provided with the imaging lens is used for digital equipment, such as a portable terminal, it can contribute to the compactness, cost reduction, high performance, etc. The conditions for obtaining such effects in a well-balanced manner and achieving further improvements in optical performance, shortening the overall length, improving productivity, and the like will be described below.

The lens block is arranged so as to be adjacent to the lens block having the IR cut filter film with an air gap from the IR cut filter film, and on the lens block on the surface of the lens substrate on the IR cut filter film side. It is desirable that the lens unit is not provided or a lens unit having a weaker power than the lens unit provided on the other surface of the lens substrate is provided. The two lens blocks located adjacent to each other in this way have the same power arrangement as that obtained by dividing a lens block having lens portions formed on both surfaces of the lens substrate into two by the lens substrate. Therefore, weakening the power of the opposing surface with respect to the IR cut coat provided on the other lens block makes it possible to absorb variations in the thickness of the lens substrate by adjusting the air spacing between the lens blocks. To do. When the lens substrate thickness deviates from the design value, the back focus length and the curvature of field change, so that the adjustment at the time of module assembly becomes complicated, leading to an increase in cost. By adjusting the air space between the lens blocks to minimize the back focus error and image plane position error of the entire lens block, the adjustment procedure at the time of module assembly can be reduced, leading to cost reduction. When the power of the opposing lens part is large, even if an attempt is made to adjust the air gap between the substrates in order to correct the substrate thickness, the difference in the image plane position variation between the angles of view is large, and the image plane position can be adjusted over the entire screen. It is difficult to correct.

As a result, it becomes possible to loosen the tolerance of the lens substrate thickness, which is effective in reducing the cost. Also, if the power of the opposing lens portion is weakened with respect to the IR cut coat provided on the other lens block, the aberration performance of the entire imaging lens is controlled by adjusting the air gap between the lens blocks. (For example, correcting curvature of field or the like). As a result, it is possible to relax the error sensitivity of the surface shape of the lens portion, and this is also effective in reducing costs.

The shape of the surface facing the IR cut coat surface across the air gap preferably satisfies the following conditional expression (1).
0 ≦ PB / DB <0.04 (1)
PB: Maximum height difference of the surface in the optical axis direction within the effective area of the surface facing the IR cut coat surface across the air interval DB: The effective radius lower limit value of the surface facing the IR cut coat surface across the air interval is , PB is 0, that is, the opposing surfaces are flat. When the upper limit is exceeded, the power of the opposing surface increases, and when the substrate thickness error is adjusted by the air interval, the difference in the amount of variation in the image plane position for each angle of view increases. Tolerances in the product must be tightened, leading to increased costs.

It is desirable to satisfy the following conditional expression (2).
0.08 <BF / DI <0.16 (2)
However,
BF: Back focus amount,
DI: Diameter of the image circle,
It is.

When the conditional expression (2) is satisfied, the height of the imaging lens can be reduced. If the lower limit of conditional expression (2) is not reached, the back focus amount becomes relatively small with respect to the image sensor size, so that the incident angle on the imaging surface of a light beam having a large angle of view becomes large, which causes shading. On the other hand, if the upper limit of conditional expression (2) is exceeded, the back focus amount becomes relatively large, and the proportion of the back focus increases when the height of the imaging lens is reduced. For this reason, it becomes difficult to achieve both low profile and imaging performance.

It is more desirable to satisfy the following conditional expression (2a).
0.08 <BF / DI <0.155 (2a)
The conditional expression (2a) defines a more preferable condition range based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (2).

It is desirable to have an IR cut filter film on at least one optical surface that constitutes an air space between the lens block closest to the image plane and the lens block located adjacent to the object side. In the vicinity of the image plane, the angle formed between the principal ray and the optical axis at each angle of view is smaller than the others, so if an IR cut filter film is provided on the optical surface, the wavelength of the IR cut filter accompanying the change in the incident angle A change in characteristics can be suppressed. In addition, since there are few regions where the light rays of each angle of view overlap in the vicinity of the image plane, the difference in aberration fluctuation at each angle of view is small when adjusting the air gap, which is advantageous in terms of imaging performance control by adjusting the air gap.

It is desirable that all lens substrates are parallel plates. Since all lens substrates are parallel plates, processing is easy and all lens substrates have no power at the interface with the lens part, reducing the influence of surface accuracy on the focal position on the image plane. Can do. Further, it is desirable that the lens substrates are all parallel flat plates having the same thickness. By making the lens substrate of each lens block have the same thickness, the glass substrate can be polished under the same conditions. Therefore, mass production at low cost becomes possible.

The lens substrate is preferably made of a glass material. Since glass has a higher softening temperature than resin, if the lens substrate is made of glass, it does not easily change even if reflow treatment is performed, and the cost can be reduced. More preferably, the lens substrate is made of glass having a high softening temperature. The lens part is preferably made of a resin material. As a material used for the lens portion, a resin material has better processability than a glass material and can be reduced in cost.

It is desirable that the resin material is an energy curable resin material. By configuring the lens portion with an energy curable resin material, it becomes possible to simultaneously cure and form a large number of lens portions with a mold on a wafer-like lens substrate. Therefore, mass productivity can be improved. The energy curable resin material here refers to a resin material that is cured by heat, a resin material that is cured by light, and the like, and various means for applying energy such as heat and light can be used for the curing.

It is desirable to use a UV curable resin material as the energy curable resin material. If a UV curable resin material is used, mass productivity can be improved by shortening the curing time. In recent years, curable resin materials with excellent heat resistance have been developed. By using heat-resistant resins, camera modules that can withstand reflow processing can be used, and a more inexpensive camera module can be provided. Can do. The reflow treatment here refers to printing solder paste on a printed circuit board (circuit board), placing a component (camera module) on it, applying heat to melt the solder, and external sensor terminals and circuit board This is a process of automatic welding.

It is desirable to use an athermal resin (a resin material having a small refractive index change due to a temperature change) as an optical material constituting the lens portion. The resin material has a large refractive index change at the time of temperature change, so that when the ambient temperature changes, there is a problem that the characteristics fluctuate due to the influence. However, recently, it has been found that the influence of temperature change can be reduced by mixing inorganic fine particles in a resin material. 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 smaller than the wavelength of the transmitted light beam. By doing so, scattering can be substantially prevented from occurring.

In addition, although the refractive index of the resin material decreases as the temperature increases, the refractive index of the inorganic particles increases as the temperature increases. Thus, by utilizing these temperature dependences and acting so as to cancel each other, almost no refractive index change can occur. Specifically, by dispersing inorganic particles having a maximum length of 20 nm or less in a resin material serving as a base material, a resin material with extremely low temperature dependency of the refractive index can be obtained. For example, by dispersing microparticles of niobium oxide in the acrylic resin (Nb 2 _O _5), it is possible to reduce the refractive index change by a temperature change. By using a resin material in which such inorganic particles are dispersed as the material of the lens portion, it is possible to suppress the characteristic fluctuation when the temperature changes.

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

... (FA)
However, in formula (FA),
α: linear expansion coefficient,
[R]: molecular refraction,
It is.

In the case of a resin material, the contribution of the second term is generally smaller than that of the first term in the formula (FA) and can be almost ignored. For example, in the case of PMMA (polymethyl methacrylate) resin, the linear expansion coefficient α is 7 × 10 ⁻⁵ , and when substituted into the above formula (FA), A = −1.2 × 10 ⁻⁴ [/ ° C.] It almost agrees with the value. Specifically, it is preferable to suppress the change A due to the temperature of the refractive index, which was conventionally about −1.2 × 10 ⁻⁴ [/ ° C.], to an absolute value of less than 8 × 10 ⁻⁵ [/ ° C.]. . Further, it is more preferable if the absolute value can be suppressed to less than 6 × 10 ⁻⁵ [/ ° C.].

The imaging lens according to the present invention is suitable for use in a digital device with an image input function such as a portable terminal, and by combining this with an imaging device or the like, an image of a subject is optically captured as an electrical signal. An imaging apparatus that outputs the image can be configured. The imaging device is an optical device that constitutes the main component of a camera used for still image shooting and moving image shooting of a subject. For example, an imaging lens that forms an optical image of an object in order from the object (that is, subject) side, And an imaging device that converts an optical image formed by the imaging lens into an electrical signal. Then, an imaging lens having the above-described characteristic configuration is arranged so that an optical image of a subject is formed on the light receiving surface of the imaging element, and an imaging device having high performance at low cost and the same are provided. A digital device (for example, a portable terminal) can be realized.

Examples of the camera include a digital camera, a video camera, a surveillance camera, an in-vehicle camera, a videophone camera, and the like, and also a personal computer, a mobile terminal (for example, a mobile phone, a mobile computer, etc., small and portable information) Apparatus terminals), peripheral devices (scanners, printers, etc.), cameras incorporated in or external to other digital devices, and the like. As can be seen from these examples, it is possible not only to configure a camera by using an imaging device, but also to add a camera function by mounting the imaging device on various devices. For example, a digital device with an image input function such as a mobile phone with a camera can be configured.

FIG. 5 shows a schematic cross-sectional example of a mobile terminal DU as an example of a digital device with an image input function. The imaging device LU mounted on the portable terminal DU shown in FIG. 5 includes an imaging lens LN (AX: optical axis) that forms an optical image (image plane) IM of the object, and a parallel plane in order from the object (subject) side. A face plate PT (corresponding to a cover glass or the like of the image pickup element SR) and an image pickup element SR that converts an optical image IM formed on the light receiving surface SS by the image pickup lens LN into an electrical signal are provided. When a mobile terminal DU having an image input function is configured by the imaging device LU, the imaging device LU is usually arranged inside the body. However, when realizing the camera function, a form as necessary is adopted. It is possible. For example, the unitized imaging device LU can be configured to be detachable or rotatable with respect to the main body of the portable terminal DU.

As the image sensor SR, for example, a solid-state image sensor such as a CCD image sensor or a CMOS image sensor having a plurality of pixels is used. Since the imaging lens LN is provided so that an optical image IM of the subject is formed on the light receiving surface SS of the imaging element SR, the optical image IM formed by the imaging lens LN is electrically converted by the imaging element SR. Converted to a signal.

The portable terminal DU includes a signal processing unit 1, a control unit 2, a memory 3, an operation unit 4, a display unit 5 and the like in addition to the imaging device LU. The signal generated by the image sensor SR is subjected to predetermined digital image processing, image compression processing, and the like as required by the signal processing unit 1 and recorded as a digital video signal in the memory 3 (semiconductor memory, optical disk, etc.) In some cases, the signal is transmitted to another device through a cable or converted into an infrared signal. The control unit 2 has a microcomputer, and centrally performs function control such as a photographing function and an image reproduction function, control of a lens moving mechanism for focusing, and the like. For example, the control unit 2 controls the imaging device LU so as to perform at least one of still image shooting and moving image shooting of a subject. The display unit 5 includes a display such as a liquid crystal monitor, and displays an image using an image signal converted by the image sensor SR or image information recorded in the memory 3. The operation unit 4 includes operation members such as an operation button (for example, a release button) and an operation dial (for example, a shooting mode dial), and transmits information input by an operator to the control unit 2.

As described above, the imaging lens LN includes at least two lens blocks (consisting of an nth lens block Cn (n = 1, 2,... In order from the object side)) on the light receiving surface SS of the imaging element SR. An optical image IM is formed. The optical image to be formed by the imaging lens LN is, for example, an optical low-pass filter (corresponding to the parallel flat plate PT in FIG. 5) having a predetermined cutoff frequency characteristic determined by the pixel pitch of the imaging element SR. By passing, the spatial frequency characteristic is adjusted so that so-called aliasing noise generated when converted into an electrical signal is minimized. Thereby, generation | occurrence | production of a color moire can be suppressed. However, if the performance around the resolution limit frequency is suppressed, there is no need to worry about the generation of noise without using an optical low-pass filter, and a display system in which noise is not noticeable (for example, a liquid crystal of a mobile phone) When a user performs shooting or viewing using a screen or the like, it is not necessary to use an optical low-pass filter.

The focus of the imaging lens LN may move the entire lens unit in the optical axis AX direction using an actuator, or may move a part of the lens in the optical axis AX direction. For example, if focusing is performed only with the first lens block C1, the actuator can be downsized. Further, the focus function may be realized by performing a process of increasing the depth of focus by software from the information recorded in the image sensor SR without focusing the lens by moving the lens in the optical axis direction. In that case, the actuator is not necessary, and the miniaturization and the cost reduction can be realized at the same time.

The imaging lens LN includes a step of sealing the lens substrates with a lattice-shaped spacer member, and a step of cutting the integrated lens substrate and the spacer member with a lattice frame of the spacer member. Preferably, the lens block is manufactured by a method. For example, in the imaging lens LN in which all the lenses are formed of lens blocks, in a manufacturing method for manufacturing a plurality of imaging lenses LN that form the subject image IM or imaging devices LU including the imaging lens LN, the lens substrates are connected to each other via a lattice spacer member. Can be easily produced by providing the step of sealing the lens substrate and the step of cutting the integrated lens substrate and spacer member with the lattice frame of the spacer member. Thereby, mass production of an inexpensive imaging lens becomes possible.

For example, a reflow method or a replica method is used as a manufacturing method for manufacturing a plurality of imaging lenses LN. In the reflow method, a low softening point glass film is formed by the CVD (Chemical Vapor Deposition) method, fine processing is performed by lithography and dry etching, and glass reflow is performed by heat treatment, so that a large number of lenses are simultaneously formed on the glass substrate. Is done. In the replica method, a large number of lenses are simultaneously formed on a lens wafer by transferring a large amount of lens shapes with a mold using a curable resin. In any method, a large number of lenses can be manufactured at the same time, so that the cost can be reduced. For example, when different lenses manufactured by the above-described method (two lenses having different lens parts manufactured by producing lens parts on a lens substrate and separated one by one) are bonded to each other, the first Lens block, a first parallel flat plate, a second parallel flat plate, and a second lens unit.

FIG. 6 is a schematic sectional view showing an example of the manufacturing process of the imaging lens LN. However, here, in order to simplify the description, a case of a three-block configuration (however, the third lens block C3 is omitted) will be described as an example, but an imaging lens LN consisting of four or more blocks is manufactured in the same manner. be able to. The first lens block C1 includes a first lens substrate L12 made of a parallel plate, a plurality of first object side lens portions L11 formed on one plane thereof, and a plurality of first image sides formed on the other plane. And a lens portion L13. The first lens substrate L12 may be constituted by one parallel flat plate, or may be constituted by bonding two parallel flat plates as described above. The second lens block C2 includes a second lens substrate L22 made of a parallel plate and a plurality of second object side lens portions L21 bonded to one of the planes. Similar to the first lens substrate L12, the second lens substrate L22 may be constituted by one parallel flat plate, or may be constituted by bonding two parallel flat plates as described above.

The third lens block (not shown) is also configured in the same manner as the first and second lens blocks C1 and C2, but the above-described IR cut filter film is formed on any lens substrate. For example, as in first and second embodiments described later, an IR cut filter film CT (FIGS. 1 and 2) is applied to one surface of the third lens substrate L32.

The grid-like spacer member B1 defines a distance between the lens blocks and keeps the lens block constant. The grid-like spacer member B1 is a three-stage grid, and each lens portion is disposed in a hole portion of the grid. The substrate B2 is a wafer level sensor chip size package including a microlens array, or a plane parallel plate such as a sensor cover glass (corresponding to the plane parallel plate PT in FIG. 5). The lens substrates are sealed on the substrate B2 via the spacer member B1, and the first lens substrate L12, the second lens substrate L22, the third lens substrate (not shown), and the spacer member B1 integrated with each other are separated from the spacer member B1. When cutting at a grid frame (position of broken line Q), a plurality of imaging lenses LN having a three-block configuration are obtained. As described above, when the imaging lens LN is separated from a state where a plurality of first lens blocks C1, second lens blocks C2, and third lens blocks (not shown) are assembled, adjustment and assembly of the lens interval can be performed. Since it is not necessary to carry out every LN, mass production becomes possible. In addition, by making the spacer member B1 into a lattice shape, it can be used as a mark when separating it. This is in accordance with the gist of the present technical field, and can contribute to mass production of an inexpensive lens system.

Next, the specific optical configuration of the imaging lens LN will be described in more detail with reference to the first and second embodiments. FIGS. 1 and 2 show the lens configurations of the first and second embodiments of the imaging lens LN in optical cross sections, respectively. The imaging lens LN of each embodiment is a single focus lens for imaging (for example, for a portable terminal) that forms an optical image IM with respect to the imaging element SR (FIG. 5). In the first and second embodiments, the imaging lens LN is configured by three lens blocks of the first lens block C1, the second lens block C2, and the third lens block C3 in order from the object side. Yes.

In the first and second embodiments, the lens blocks C1 to C3 are configured as follows in order from the object side. In the first lens block C1, the first object side lens portion L11, the first lens substrate L12, and the first image side lens portion L13 are arranged in this order. In the second lens block C2, the second object side lens portion L21 and the second lens substrate L22 are arranged in this order. In the third lens block C3, the third lens substrate L32 and the third image side lens portion L33 are arranged in this order. In the third lens substrate L32, an IR cut filter film CT is formed on the back surface of the substrate surface on which the third image side lens portion L33 is formed.

The power arrangements of the first to third lens blocks C1 to C3 are paraxial and positive and negative, and the lens surfaces are all aspherical. The nth object side lens portion Ln1 and the nth lens substrate Ln2 have different refractive indexes, and the nth lens substrate Ln2 and the nth image side lens portion Ln3 have different refractive indexes.

An aperture stop ST is disposed on the object side surface of the first lens substrate L12. Setting the aperture position on the lens substrate is effective in improving mass productivity and reducing costs, and can also reduce performance deterioration due to eccentricity. In addition, disposing the aperture stop ST on the object side surface of the first lens substrate L12 is effective in improving telecentricity.

A spacer may be formed of resin outside the effective diameter on the surface facing the IR cut filter film CT provided in the third lens block C3. FIG. 7 shows an embodiment of a type having a spacer function outside the effective diameter of the lens portion. In the second embodiment, the imaging lens LN has a configuration in which the second lens block C2 includes a second image side lens portion L23 made of a parallel plate. A spacer portion SP is formed outside the effective diameter of the second image side lens portion L23. As described above, it is desirable that the air gap between the adjacent lens blocks is adjusted by the spacer portion formed outside the effective diameter of the lens portion. By adjusting the air interval with the spacer portion SP, the air interval of a plurality of lens modules arranged on the same substrate can be collectively adjusted. Therefore, cost can be effectively reduced.

By providing the third image side lens portion L33 of the third lens block C3 on the final surface of the imaging lens LN, correction of field curvature and light rays to the imaging surface at the periphery of the screen can be achieved with a more compact configuration. The incident angle can be set to an appropriate size.

Hereinafter, the configuration and the like of the imaging lens embodying the present invention will be described more specifically with reference to the construction data of the examples. Examples 1 and 2 listed here are numerical examples corresponding to the first and second embodiments, respectively, and are optical configuration diagrams showing the first and second embodiments (FIGS. 1 and 2). 2) shows the lens configurations of the corresponding Examples 1 and 2, respectively.

In the construction data of each example, as surface data, in order from the left column, the surface number, the radius of curvature r (mm), the surface spacing d (mm) on the axis, and the refraction with respect to the d-line (wavelength: 587.56 nm). The Abbe number vd with respect to rate nd and d line is shown. A surface with * in the surface number is an aspheric surface, and the surface shape is defined by the following expression (AS) using a local orthogonal coordinate system (x, y, z) with the surface vertex as the origin. . As aspheric data, an aspheric coefficient or the like is shown. Incidentally, the coefficient of the term no notation in the aspherical surface data of the embodiment is 0, E-n for all data indicate that a × 10 ^-n.
z = (c × h ² ) / [1+ {1− (1 + K) × c ² × h ² } ^1/2 ] + Σ (Aj × h ^j ) (AS)
However,
h: height (h ² = x ² + y ² ) in a direction perpendicular to the z-axis (optical axis AX),
z: the amount of sag in the direction of the optical axis AX at the position of the height h (based on the surface vertex),
c: curvature at the surface vertex (the reciprocal of the radius of curvature r),
K: conic constant,
Aj: j-order aspheric coefficient,
It is.

As various data, focal length (f, mm), F number (Fno.), Half angle of view (ω, °), image height (y′max, mm), total lens length (TL, mm), back focus (BF) , Mm). In the back focus, the distance from the lens final surface to the paraxial image surface is expressed by an air conversion length, and the total lens length is obtained by adding the back focus to the distance from the lens front surface to the lens final surface. Furthermore, the paraxial focal length of each lens block is shown as lens block data, and the values corresponding to the conditional expression (2) and related data in each embodiment are shown in Table 1.

3 and 4 are aberration diagrams of Examples 1 and 2 (in-focus state), respectively. 3 and 4, (A) is a spherical aberration diagram, (B) is an astigmatism diagram, and (C) is a distortion diagram. The spherical aberration diagram shows the amount of spherical aberration with respect to the d-line (wavelength 587.56 nm) indicated by the solid line, the amount of spherical aberration with respect to the C-line (wavelength 656.28 nm) indicated by the alternate long and short dash line, and the g-line (wavelength 435.84 nm) indicated by the broken line. The amount of spherical aberration is represented by the amount of deviation in the optical axis AX direction from the paraxial image plane (unit: mm, horizontal axis scale: −0.200 to 0.200 mm), and the vertical axis represents the height of incidence on the pupil. A value obtained by normalizing the height by the maximum height (that is, the relative pupil height) is represented. In the astigmatism diagram, the broken line T is the tangential image plane with respect to the d line, the solid line S is the sagittal image plane with respect to the d line, and the amount of deviation in the optical axis AX direction from the paraxial image plane (unit: mm, horizontal scale: The vertical axis represents the image height (IMG HT, unit: mm). In the distortion diagram, the horizontal axis represents the distortion with respect to the d-line (unit:%, horizontal axis scale: -5.0 to 5.0%), and the vertical axis represents the image height (IMG HT, unit: mm). Represents. The maximum value of the image height IMG HT corresponds to the maximum image height y′max on the image plane IM (half the diagonal length of the light receiving surface SS of the image sensor SR).

The imaging lenses LN of Examples 1 and 2 shown in FIGS. 1 and 2, respectively, in order from the object side, a first object-side lens portion L11 having a paraxial convex shape on the object side, an aperture stop ST, and a first lens A first lens block C1 including a substrate L12 and a first image-side lens portion L13 having a concave shape on the image side with a paraxial axis, a second object-side lens portion L21 having a concave shape on the object side with a paraxial shape and a first axis. A second lens block C2 including a two-lens substrate L22, and a third lens block C3 including a third lens substrate L32 and a third image-side lens portion L33 having a paraxial concave shape on the image side. Yes. In addition, the surfaces of all the lens portions in contact with air have an aspheric shape.

Example 1
Unit: mm
Surface data surface number r d nd νd
Object ∞ ∞
1 * 0.7537 0.3049 1.520 60.00
2 (Aperture) ∞ 0.3000 1.517 65.26
3 ∞ 0.0880 1.580 40.00
4 * 2.0355 0.2773
5 * -2.7244 0.0500 1.580 40.00
6 ∞ 0.4756 1.517 65.26
7 ∞ 0.0500
8 ∞ 0.5242 1.517 65.26
9 ∞ 0.4000 1.580 40.00
10 * 1220.3090 0.2000
11 ∞ 0.3500 1.471 65.20
12 ∞ 0.0878
Image plane ∞
Aspheric data first surface
K = -0.3653,
A4 = 1.5292E-02, A6 = 1.4772E + 00, A8 = -6.3118E + 00, A10 = 1.1507E + 01,
4th page
K = 10.2658,
A4 = 4.5056E-01, A6 = -7.5131E-01, A8 = 1.5895E + 01, A10 = -9.6312E + 01,
5th page
K = 6.7493,
A4 = -7.8989E-01, A6 = 2.7821E + 00, A8 = -2.3786E + 01, A10 = 1.2869E + 02,
10th page
K = 30.0000,
A4 = -4.2587E-02, A6 = 1.6568E-01, A8 = -4.2494E-01, A10 = 4.3711E-01,
Various data focal lengths f 2.651
F number Fno. 2.70
Half angle of view ω 32.06
Statue height y'max 1.76
Total lens length TL 3.108
Back focus BF 0.53
Lens block data block surface Focal length
1 1- 4 2.023
2 5- 7 -4.697
3 8-10 -2103.981
(Example 2)
Unit: mm
Surface data surface number r d nd νd
Object ∞ ∞
1 * 0.7983 0.3518 1.520 60.00
2 (Aperture) ∞ 0.3000 1.517 65.26
3 ∞ 0.0668 1.580 40.00
4 * 2.1267 0.3458
5 * -2.6 139 0.1890 1.580 40.00
6 ∞ 0.3697 1.517 65.26
7 ∞ 0.1200
8 ∞ 0.5000 1.517 65.26
9 ∞ 0.4388 1.580 40.00
10 * 26.4629 0.0513
11 ∞ 0.4500 1.516 64.14
12 ∞ 0.0560
Image plane ∞
Aspheric data first surface
K = -0.7676,
A4 = 7.3872E-02, A6 = 1.5402E + 00, A8 = -5.2706E + 00, A10 = 9.4368E + 00,
A12 = 0.0000E + 00, A14 = 0.0000E + 00, A16 = 0.0000E + 00,
4th page
K = 8.8070,
A4 = 2.4493E-01, A6 = -8.1297E-01, A8 = 6.8594E + 00, A10 = -6.2622E + 00,
A12 = 0.0000E + 00, A14 = 0.0000E + 00, A16 = 0.0000E + 00,
5th page
K = -13.9883,
A4 = -3.8338E-01, A6 = -1.1242E + 00, A8 = 7.2035E + 00, A10 = -3.3860E + 01,
A12 = 5.0951E + 01, A14 = -2.9532E + 00, A16 = -8.3835E + 01,
10th page
K = 49.9978,
A4 = -7.1285E-02, A6 = 3.9890E-02, A8 = -2.8143E-02, A10 = 6.7296E-03,
A12 = 0.0000E + 00, A14 = 0.0000E + 00, A16 = 0.0000E + 00,
Various data focal length f 2.830
F number Fno. 2.88
Half angle of view ω 30.74
Statue height y'max 1.76
Total lens length TL 3.239
Back focus BF 0.40
Lens block data block surface Focal length
1 1- 4 2.162
2 5- 7 -5.027
3 8-10 -45.626

DU portable terminal LU imaging device LN imaging lens Cn nth lens block Ln1 nth object side lens unit Ln2 nth lens substrate Ln3 nth image side lens unit ST aperture stop (aperture)
SR Image sensor SS Light-receiving surface IM Image surface (optical image)
AX Optical axis B1 Spacer member SP Spacer part 1 Signal processing part 2 Control part 3 Memory 4 Operation part 5 Display part

Claims

A parallel plate lens substrate;
A lens portion formed of a material different from that of the lens substrate on at least one of the object side surface and the image side surface of the lens substrate, and having a positive or negative power;
An imaging lens including at least two lens blocks including:
An imaging lens, wherein at least one of the lens blocks has a lens portion only on one surface of a lens substrate of the lens block and an IR cut filter film on the other surface.
Opposite to the lens block having the IR cut filter film, on one surface of the lens substrate of the lens block arranged adjacent to the IR cut filter film with an air gap facing the IR cut filter film, 2. The imaging lens according to claim 1, wherein the lens unit is not provided, or a lens unit having a weaker power than the lens unit provided on the other surface is provided.
The imaging lens according to claim 1, further comprising a lens portion on the image plane side of the lens substrate of the lens block closest to the image plane side.
The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
0.08 <BF / DI <0.16
However,
BF: Back focus amount,
DI: Diameter of the image circle,
It is.
An IR cut filter film is provided on at least one optical surface constituting an air space between a lens block closest to the image plane and a lens block located adjacent to the object side of the lens block. The imaging lens according to any one of claims 1 to 4.
6. The air space between lens blocks positioned adjacent to each other is adjusted by a spacer portion formed outside the effective diameter of a lens portion included in the lens block. The imaging lens described in 1.
The imaging lens according to any one of claims 1 to 6, wherein the lens substrate is made of a glass material.
The lens includes: a step of sealing the lens substrates through a lattice-shaped spacer member; and a step of cutting the integrated lens substrate and the spacer member with a lattice frame of the spacer member. The imaging lens according to claim 1, wherein a block is manufactured.
The imaging lens according to any one of claims 1 to 8,
An image pickup apparatus comprising: an image pickup element that converts an optical image formed on a light receiving surface by the image pickup lens into an electrical signal.
A portable terminal comprising the imaging device according to claim 9.