JPWO2014119283A1 - Imaging optical system, imaging apparatus and digital apparatus - Google Patents

Abstract

An imaging optical system, an imaging apparatus, and a digital apparatus according to the present invention include positive, negative, positive, positive, and negative first to fifth lenses in order from the object side to the image side. The first lens is convex on the object side. The second lens and the fifth lens are biconcave, and the fifth lens has at least one aspheric surface having an inflection point, and has an Abbe number νd3 of the third lens, The paraxial radius of curvature r9 on the object side surface of the lens and the focal length f of the entire system satisfy 15 <νd3 <50 and −14.3 <r9 / f <−0.2.

Description

  The present invention relates to an imaging optical system that forms an optical image of a subject on a predetermined surface. The present invention relates to an imaging apparatus and a digital device using this imaging optical system.

  In recent years, performance and miniaturization of an image sensor using a solid-state image sensor such as a CCD (Charge Coupled Device) type image sensor or a CMOS (Complementary Metal Oxide Semiconductor) type image sensor have been expanded. Digital devices such as mobile phones and personal digital assistants equipped with image pickup devices using various image pickup devices are becoming widespread. An imaging optical system (imaging lens) for forming (imaging) an optical image of an object on the light-receiving surface of the solid-state imaging device, which is mounted on these imaging devices, is further reduced in size and performance. The demand is growing. In particular, in recent years, higher resolution has been demanded of the imaging optical system due to the progress of pixel miniaturization in solid-state imaging devices. In such an imaging optical system, since a higher performance can be achieved as compared with a three-element or four-element optical system, a five-element optical system has been proposed.

  Such an imaging optical system is disclosed in Patent Document 1 and Patent Document 2, for example. The imaging optical systems disclosed in Patent Document 1 and Patent Document 2 are a first lens having a positive refractive power in order from the object side to the image side, a second lens having a negative refractive power, The lens includes a third lens having a positive refractive power, a fourth lens having a positive refractive power, and a fifth lens having a negative refractive power.

  By the way, in the imaging optical systems described in Patent Document 1 and Patent Document 2, the shapes of the first, second, and fifth lenses and the Abbe number of the third lens are not sufficiently optimized, and the chromatic aberration is not improved. There is room for improvement in terms of correction and correction of field curvature.

US Patent Application Publication No. 2010/134904 International Publication No. 2011/004467

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an imaging optical system that is more compact and corrects various aberrations better, and an imaging apparatus and a digital device using the imaging optical system. Is to provide.

  An imaging optical system, an imaging apparatus, and a digital apparatus according to the present invention include first, fifth, and fifth lenses that are positive, negative, positive, positive, and negative in order from the object side to the image side. It has a meniscus shape with a convex surface, the second and fifth lenses are biconcave, and the fifth lens has an inflection point when it goes from the intersection of the optical axes to the end of the effective area in the contour of the lens cross section 15 is provided when at least one aspherical surface having at least one surface is provided, and the Abbe number of the third lens, the paraxial radius of curvature of the object side surface of the fifth lens, and the focal length of the entire imaging optical system are νd3, r9, and f, respectively. <Νd3 <50 and −14.3 <r9 / f <−0.2 are satisfied. Although the imaging optical system according to the present invention is small, it can correct various aberrations better. In addition, the imaging device and the digital device according to the present invention can be reduced in size and performance.

  The above and other objects, features and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.

It is a lens sectional view showing the composition typically for explanation of an image pick-up optical system in an embodiment. It is a schematic diagram which shows the definition of the image surface incident angle of a chief ray. It is a block diagram which shows the structure of the digital device in embodiment. It is an external appearance block diagram of the mobile phone with a camera which shows one Embodiment of a digital device. FIG. 3 is a cross-sectional view showing the arrangement of lenses in the imaging optical system of Example 1. FIG. 6 is a cross-sectional view showing the arrangement of lenses in the imaging optical system of Example 2. FIG. 6 is a cross-sectional view showing the arrangement of lenses in the imaging optical system of Example 3. FIG. 6 is a cross-sectional view illustrating an arrangement of lenses in an imaging optical system according to Example 4. FIG. 10 is a cross-sectional view illustrating an arrangement of lenses in an imaging optical system according to Example 5. FIG. 10 is a cross-sectional view illustrating an arrangement of lenses in an imaging optical system according to Example 6. FIG. 3 is an aberration diagram of the imaging optical system in Example 1. FIG. 6 is an aberration diagram of the image pickup optical system in Example 2. FIG. 6 is an aberration diagram of the image pickup optical system in Example 3. FIG. 6 is an aberration diagram of the image pickup optical system in Example 4. 10 is an aberration diagram of the image pickup optical system in Example 5. FIG. FIG. 10 is an aberration diagram of the image pickup optical system according to the sixth embodiment.

In the present embodiment, in order to solve the above-described technical problem, an imaging optical system, an imaging apparatus, and a digital device having the following configurations are provided. Note that the terms used in the following description are defined as follows in this specification.
(A) A refractive index is a refractive index with respect to the wavelength (587.56 nm) of d line | wire.
(B) Abbe number is determined when the refractive indices for d-line, F-line (wavelength 486.13 nm) and C-line (wavelength 656.28 nm) are nd, nF and nC, respectively, and Abbe number is νd.
νd = (nd−1) / (nF−nC)
The Abbe number νd obtained by the definition formula
(C) When the notation “concave”, “convex” or “meniscus” is used for the lens, these represent the lens shape near the optical axis (near the center of the lens).
(D) The notation of refractive power (optical power, reciprocal of focal length) in each single lens constituting the cemented lens is power when both sides of the lens surface of the single lens are air.
(E) Since the resin material used for the composite aspherical lens has only an additional function of the substrate glass material, it is not treated as a single optical member, but is treated as if the substrate glass material has an aspherical surface, and the number of lenses Shall be handled as one sheet. The lens refractive index is also the refractive index of the glass material serving as the substrate. The composite aspherical lens is a lens that is aspherical by applying a thin resin material on a glass material to be a substrate.
(F) The inflection point is within the effective radius of the lens and is the contour line at each point on the contour line of the lens cross section (the lens cross section including the optical axis along the optical axis) along the optical axis. Is the point where the sign of the sign is reversed. The effective area refers to an area set as an area that is optically used as a lens by design. In this specification, the term “miniaturization” refers to the distance on the optical axis from the lens surface closest to the object side to the image-side focal point of the entire imaging optical system as L, and the diagonal length of the imaging surface (for example, a rectangular effective When the diagonal length of the pixel region is 2Y, it means that L / 2Y <0.9 is satisfied, and more preferably L / 2Y <0.8 is satisfied. When a parallel plate such as an optical low-pass filter, an infrared cut filter, and a seal glass of a solid-state imaging device package is disposed between the most image-side surface and the image-side focal position of the imaging optical system, The value of the distance L is calculated for the parallel plate portion after the air conversion distance.

<Description of Imaging Optical System of One Embodiment>
Hereinafter, an embodiment according to the present invention will be described with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted suitably. The number of lenses in the cemented lens is not represented by one for the entire cemented lens, but is represented by the number of single lenses constituting the cemented lens.

  FIG. 1 is a lens cross-sectional view schematically illustrating the configuration of an imaging optical system in the embodiment. FIG. 2 is a schematic diagram showing the definition of the image plane incident angle of the chief ray. In the following, the image plane incident angle of the chief ray is the angle (deg, degree) of the chief ray having the maximum field angle among the incident rays to the imaging surface with respect to the vertical line standing on the image plane, as shown in FIG. The image plane incident angle α is the principal ray angle when the exit pupil position is on the object side with respect to the image plane.

  In FIG. 1, an imaging optical system 1 is formed by forming an optical image of an object (subject) on a light receiving surface of an image sensor 17 that converts an optical image into an electrical signal. This is an optical system composed of five lenses of first to fifth lenses 11 to 15 arranged in order from the image side to the image side. The image sensor 17 is arranged such that its light receiving surface substantially coincides with the image plane of the imaging optical system 1 (image plane = imaging plane).

  In the imaging optical system 1, focusing is performed by moving the first to fifth lenses 11 to 15 in the optical axis direction by extending all the balls.

  The first lens 11 is a meniscus positive meniscus lens having a positive refractive power and a convex surface facing the object side, and the second lens 12 is a biconcave negative lens having a negative refractive power. The third lens 13 is a positive lens having a positive refractive power, the fourth lens 14 is a positive lens having a positive refractive power, and the fifth lens 15 is a biconcave having a negative refractive power. It is a negative lens. Further, the fifth lens 15 has at least one aspherical surface having an inflection point when it goes from the intersection of the optical axis AX to the effective region end along the optical axis AX along the contour of the lens cross section including the optical axis AX. I have. In the example shown in FIG. 1, the fifth lens 15 has two aspheric surfaces, and has an inflection point P on the image side surface of the fifth lens 15.

  The fifth lens 15 may be an aspheric surface having one inflection point on one side, and the fifth lens 15 has an aspheric surface on both surfaces, or on the object side surface. An inflection point P may be included. In the example shown in FIG. 1, the first to fourth lenses 11 to 14 are also aspheric on both sides, but the first to fourth lenses 11 to 14 may not be aspheric on both sides. Alternatively, one surface may be an aspheric surface. That is, the first to fourth lenses 11 to 14 may be spherical on both sides or may not be aspheric on one side.

  These first to fifth lenses 11 to 15 are resin material lenses formed of, for example, plastic, more specifically, a resin material such as polycarbonate or cyclic olefin resin. In the example shown in FIG. 1, each of the first to fifth lenses 11 to 15 is a resin material lens, but may be a glass lens, for example, a glass mold lens.

In the imaging optical system 1, the Abbe number of the third lens 13 is νd3, the paraxial radius of curvature of the object side surface of the fifth lens 15 is r9, and the focal length of the entire imaging optical system 1 is f. In this case, the following conditional expressions (1) and (2) are satisfied. Conditional expression (1) is a conditional expression for appropriately setting the Abbe number of the third lens 13 and achieving good aberration correction. r9 / f represents the ratio of the refractive power burden imposed on the object surface of the fifth lens 15 with respect to the refractive power of the entire system, and the conditional expression (2) appropriately sets the radius of curvature of the fifth lens 15 on the object side. This is a conditional expression.
15 <νd3 <50 (1)
-14.3 <r9 / f <-0.2 (2)

  In the imaging optical system 1, an optical aperture 18 such as an aperture stop is disposed on the object side of the first lens 11, and the imaging optical system 1 is a front aperture type.

  Further, a filter 16 and an image sensor 17 are disposed on the image side of the image pickup optical system 1. The filter 16 is an optical element having a parallel plate shape, and schematically represents various optical filters, a cover glass of the imaging element, and the like. An optical filter such as a low-pass filter or an infrared cut filter can be appropriately arranged depending on the usage, imaging device, camera configuration, and the like. The image sensor 17 performs photoelectric conversion to image signals of R (red), G (green), and B (blue) components in accordance with the amount of light in the optical image of the subject imaged by the imaging optical system 1, and performs predetermined conversion. This is an element that outputs to a processing circuit (not shown). The image sensor 17 is a solid-state image sensor such as a CCD image sensor or a CMOS image sensor. As a result, the optical image of the object on the object side is guided to the light receiving surface of the image sensor 17 at a predetermined magnification along the optical axis AX by the imaging optical system 1, and the optical image of the object is captured by the image sensor 17. .

  The imaging optical system 1 having such a configuration is composed of five first to fifth lenses 11 to 15, and each of the first to fifth lenses 11 to 15 has the above optical characteristics, and these By disposing the five first to fifth lenses 11 to 15 in order from the object side to the image side, various aberrations can be corrected more favorably while being small.

  More specifically, the lens configuration of the imaging optical system 1 is a so-called telephoto type that extends the focal length of the convex lens by disposing a concave lens on the image side of the convex lens, and has a total length of the imaging optical system (imaging lens). The lens configuration is advantageous for shortening. Since the principal point position of the entire imaging optical system 1 can be moved closer to the object side by making the first lens 11 a meniscus shape having a convex surface facing the object side, such an imaging optical system 1 The overall length can be shortened.

  By using the two second and fifth lenses 12 and 15 as negative lenses in the five-lens configuration, the number of surfaces having a diverging action is increased, and the Petzval sum can be easily corrected. As a result, such an imaging optical system 1 can ensure good imaging performance up to the periphery of the screen.

  By making the second lens 12 into a biconcave shape, the angle of light incident on the object side surface can be suppressed, and thus the imaging optical system 1 can correct spherical aberration and coma aberration well. it can. In addition, the imaging optical system 1 can suppress aberrations in a well-balanced manner by suppressing the negative refractive power of the image side surface from becoming too strong.

  By making the fifth lens 15 into a biconcave shape, such an imaging optical system 1 can prevent the principal point position of the fifth lens 15 from going too far toward the image side, and the height of the axial ray passing through the fifth lens 15. Therefore, it is possible to maintain the thickness moderately, which is advantageous for correction of longitudinal chromatic aberration.

  Of the five-lens configuration, the fifth lens 15 disposed closest to the image side has an aspherical surface, and thus such an imaging optical system 1 can satisfactorily correct various aberrations at the periphery of the screen. . From this viewpoint, it is preferable that the aspheric surface of the fifth lens is an image side surface. In addition, since the fifth lens includes at least one aspheric surface having an inflection point, such an imaging optical system can easily ensure the telecentric characteristics of the image-side light beam.

  Conditional expression (1) is a conditional expression for achieving an appropriate aberration correction by appropriately setting the Abbe number of the third lens. By falling below the upper limit of the conditional expression (1), such an imaging optical system 1 can appropriately increase the dispersion of the third lens 13 and suppress the refractive power of the third lens 13 while reducing the off-axis light flux. It is possible to satisfactorily correct chromatic aberration such as chromatic aberration and lateral chromatic aberration. Also, by falling below the upper limit of conditional expression (1), such an imaging optical system 1 can appropriately correct chromatic aberration on the axis. On the other hand, by exceeding the lower limit of the conditional expression (1), the imaging optical system 1 can be made of an easily available material.

  Conditional expression (2) is a conditional expression for appropriately setting the radius of curvature of the fifth lens on the object side. By falling below the upper limit of the conditional expression (2), such an imaging optical system 1 does not jump up the light beam excessively, and it becomes easy to ensure telecentricity. On the other hand, by exceeding the lower limit of conditional expression (2), such an imaging optical system 1 causes off-axis rays that are strongly bounced up by the second lens to enter the fifth lens 15 while keeping the refraction angle small. As a result, the off-axis aberration can be suppressed more favorably.

  Therefore, such an imaging optical system 1 can correct various aberrations better while being small.

From the above viewpoint, conditional expression (1) is preferably conditional expression (1A) below, and more preferably conditional expression (1B) below.
15 <νd3 <47 (1A)
15 <νd3 <30 (1B)

Further, from the above viewpoint, the conditional expression (2) is preferably the following conditional expression (2A), and more preferably the following conditional expression (2B).
−11 <r9 / f <−0.3 (2A)
−6 <r9 / f <−0.4 (2B)

  In the imaging optical system 1, all the lenses included in the imaging optical system 1 (first to fifth lenses 11 to 15 in the present embodiment) are formed of a resin material.

  In recent years, the entire solid-state imaging device has been required to be further downsized, and even a solid-state imaging device having the same number of pixels has a small pixel pitch, and as a result, an imaging surface size has been reduced. In such an imaging optical system 1 for a solid-state imaging device having a small imaging surface size, it is necessary to relatively shorten the focal length f of the entire system, so that the radius of curvature and the outer diameter of each lens become considerably small. . Therefore, such an imaging optical system 1 is composed of a resin material lens manufactured by injection molding, and compared with a glass lens manufactured by a troublesome polishing process, the curvature radius and Even a lens having a small outer diameter can be produced in large quantities at a low cost. In addition, since the lens made of resin material can lower the press temperature, it can suppress the wear of the molding die, and as a result, the number of times of replacement and maintenance of the molding die can be reduced, thereby reducing the cost. Can do.

  Further, the imaging optical system 1 includes an optical aperture 18 on the object side of the first lens 11. In such an imaging optical system 1, since the optical aperture 18 is disposed on the object side of the first lens 11, the incident angle of the off-axis light beam with respect to the fifth lens 15 can be reduced, and the off-axis light beam by focusing is reduced. Good telecentric characteristics can be realized while suppressing changes in the spot position.

In the above-described case, it is preferable that the imaging optical system 1 satisfies the following conditional expression (3) when the combined focal length of the first lens 11 and the second lens 12 is f12. f12 / f represents the ratio of the refractive power to be borne by the first and second lenses 11 and 12 with respect to the refractive power of the entire system, in order to appropriately set the combined focal length of the first lens 11 and the second lens 12. This is a conditional expression.
1 <f12 / f <1.8 (3)

  By falling below the upper limit of the conditional expression (3), such an imaging optical system 1 can appropriately maintain the positive composite focal length of the first lens 11 and the second lens 12, so The principal point position can be further arranged on the object side, and the entire length of the imaging optical system 1 can be shortened. On the other hand, by exceeding the lower limit of conditional expression (3), in such an imaging optical system 1, the positive combined focal length of the first lens 11 and the second lens 12 does not become unnecessarily small, and the first lens 11 and the second lens 12 can suppress high-order spherical aberration and coma aberration, and by appropriately suppressing the refractive power of each of the first and second lenses 11 and 12, the image plane variation with respect to manufacturing errors can be reduced. Can be reduced.

From the above viewpoint, conditional expression (3) is preferably conditional expression (3A) below, and more preferably conditional expression (3B) below.
1.15 <f12 / f <1.65 (3A)
1.25 <f12 / f <1.5 (3B)

In these cases, the imaging optical system 1 preferably satisfies the following conditional expression (4) when the paraxial radius of curvature of the image side surface of the second lens 12 is r4. r4 / f represents the ratio of the refractive power burden imposed on the image side surface of the second lens 12 with respect to the refractive power of the entire system, and the conditional expression (4) appropriately sets the radius of curvature of the image side surface of the second lens 12. This is a conditional expression.
0.4 <r4 / f <1.4 (4)

  According to this configuration, since the image side surface of the second lens 12 is a strong diverging surface that satisfies the conditional expression (4), such an imaging optical system 1 is generated by the first lens 11 having a positive refractive power. The longitudinal chromatic aberration thus corrected can be favorably corrected by the second lens 12. Moreover, by exceeding the lower limit of conditional expression (4), the imaging optical system 1 does not have a too small radius of curvature and does not impair workability. On the other hand, by falling below the upper limit of conditional expression (4), the imaging optical system 1 can correct chromatic aberration well while keeping the Petzval sum small.

From the above viewpoint, conditional expression (4) is preferably conditional expression (4A) below, and more preferably conditional expression (4B) below.
0.55 <r4 / f <1.25 (4A)
0.6 <r4 / f <1 (4B)

In these cases, the imaging optical system 1 preferably satisfies the following conditional expression (5) when the focal length of the fifth lens 15 is f5. f5 / f represents the ratio of the refractive power burden imposed on the fifth lens 15 with respect to the refractive power of the entire system, and is a conditional expression for appropriately setting the focal length of the fifth lens 15.
-1 <f5 / f <-0.3 (5)
However, f5 is the above-mentioned.

  By falling below the upper limit of the conditional expression (5), in such an imaging optical system 1, the negative focal length of the fifth lens 15 does not become excessively small, and an image is formed on the periphery of the screen of the solid-state imaging device. Therefore, the telecentricity of the image-side light beam can be easily ensured. On the other hand, by exceeding the lower limit of conditional expression (5), such an imaging optical system 1 can appropriately lengthen the negative focal length of the fifth lens 15, shortening the overall length of the imaging optical system 1, and Various aberrations such as field curvature and distortion can be corrected satisfactorily.

In addition, from the above viewpoint, the conditional expression (5) is preferably the following conditional expression (5A), and more preferably the following conditional expression (5B).
−0.96 <f5 / f <−0.4 (5A)
−0.8 <f5 / f <−0.43 (5B)

  In the above-described imaging optical system 1, it is preferable that the third lens 13 has a shape with a convex surface facing the object side. In such an imaging optical system 1, since the third lens 13 has a convex shape on the object side surface, the combined principal point position from the first lens 11 to the third lens 13 can be brought closer to the object side. This is advantageous for shortening the overall length.

  In the above-described imaging optical system 1, it is preferable that the fourth lens 14 has a meniscus shape with a convex surface facing the image side. In such an imaging optical system 1, since the fourth lens 14 has a meniscus shape in which the image side surface is convex, the off-axis light beam that is strongly bounced by the second lens 12 is suppressed to a small refraction angle on each surface. However, it can be guided to the fifth lens 15, and off-axis aberrations can be satisfactorily suppressed.

  Further, in the above-described cases, when using a lens made of a resin material, it is preferably a lens molded using a material in which particles having a maximum length of 30 nanometers or less are dispersed in plastic (resin material).

In general, mixing fine particles with a transparent resin material scatters light and reduces the transmittance, making it difficult to use as an optical material. However, the size of the fine particles should be smaller than the wavelength of the transmitted light beam. The light is not substantially scattered. And although a resin material will have a refractive index falling with a temperature rise, an inorganic particle will raise a refractive index with a temperature rise conversely. For this reason, it is possible to make the refractive index change hardly occur with respect to the temperature change by acting so as to cancel each other by utilizing such temperature dependency. More specifically, by dispersing inorganic fine particles having a maximum length of 30 nanometers or less in a resin material as a base material, a resin material with reduced temperature dependency of the refractive index is obtained. For example, fine particles of niobium oxide (Nb ₂ O ₅ ) are dispersed in acrylic. In the imaging optical system 1 described above, a resin material in which such inorganic particles are dispersed is used for a lens having a relatively large refractive power or all the lenses, so that the temperature of the entire imaging optical system 1 can be changed. Image point position fluctuation can be suppressed to a small level.

  Such a lens made of a resin material in which inorganic fine particles are dispersed is preferably molded as follows.

The temperature change n (T) of the refractive index is expressed by the formula Fa by differentiating the refractive index n with respect to the temperature T based on the Lorentz-Lorentz equation.
n (T) = ((n ² +2) × (n ² −1)) / 6n × (−3α + (1 / [R]) × (∂ [R] / ∂T)) (Fa)
Where α is a linear expansion coefficient and [R] is molecular refraction.

In the case of a resin material, in general, the contribution of the refractive index to the temperature dependence is smaller in the second term than in the first term in the formula Fa, and can be almost ignored. For example, in the case of PMMA resin, the linear expansion coefficient α is 7 × 10 ⁻⁵ , and when it is substituted into the formula Fa, it becomes n (T) = − 12 × 10 ⁻⁵ (/ ° C.), which is approximately the actual measurement value. Match.

Specifically, the temperature change n (T) of the refractive index, which was conventionally about −12 × 10 ⁻⁵ [/ ° C.], can be suppressed to an absolute value of less than 8 × 10 ⁻⁵ [/ ° C.]. preferable. More preferably, the absolute value is less than 6 × 10 ⁻⁵ [/ ° C.].

Therefore, as such a resin material, a polyolefin resin material, a polycarbonate resin material, or a polyester resin material is preferable. In the polyolefin resin material, the temperature change n (T) of the refractive index is about −11 × 10 ⁻⁵ (/ ° C.), and in the polycarbonate resin material, the temperature change n (T) of the refractive index is about −14 × 10 ⁻⁵ (/ ° C.), and in the case of a polyester-based resin material, the temperature change n (T) of the refractive index is about −13 × 10 ⁻⁵ (/ ° C.).

<Description of digital equipment incorporating imaging optical system>
Next, a digital device in which the above-described imaging optical system 1 is incorporated will be described.

  FIG. 3 is a block diagram illustrating a configuration of a digital device according to the embodiment. For example, as shown in FIG. 3, for the imaging function, an imaging unit 30, an image generation unit 31, an image data buffer 32, an image processing unit 33, a drive unit 34, a control unit 35, a storage unit 36, and an interface unit (I / F section) 37. Examples of the digital device 3 include a digital still camera, a video camera, a surveillance camera (monitor camera), a portable terminal such as a mobile phone or a personal digital assistant (PDA), a personal computer, and a mobile computer. Mouse, scanner and printer, etc.). In particular, the imaging optical system 1 of the present embodiment is sufficiently compact when mounted on a mobile terminal such as a mobile phone or a personal digital assistant (PDA), and is preferably mounted on this mobile terminal.

  The imaging unit 30 is an example of the imaging device 21 and includes the imaging optical system 1 as illustrated in FIG. 1 that functions as an imaging lens and the imaging element 17. In the present embodiment, the imaging optical system 1 is provided with a lens driving device (not shown) for performing focusing by driving a lens for focusing in the optical axis direction. Light rays from the subject are imaged on the light receiving surface of the image sensor 17 by the imaging optical system 1 and become an optical image of the subject.

  As described above, the imaging device 17 converts the optical image of the subject formed by the imaging optical system 1 into an electrical signal (image signal) of R, G, and B color components, and each of the R, G, and B colors. It outputs to the image generation part 31 as an image signal. The imaging device 17 is controlled by the control unit 35 for imaging operation such as imaging of either a still image or a moving image or reading of output signals of each pixel (horizontal synchronization, vertical synchronization, transfer) in the imaging device 17. .

  The image generation unit 31 performs amplification processing, digital conversion processing, and the like on the analog output signal from the image sensor 17 and determines an appropriate black level, γ correction, and white balance adjustment (WB adjustment) for the entire image. Then, known image processing such as contour correction and color unevenness correction is performed to generate image data from the image signal. The image data generated by the image generation unit 31 is output to the image data buffer 32.

  The image data buffer 32 is a memory that temporarily stores image data and is used as a work area for performing processing described later on the image data by the image processing unit 33. For example, the image data buffer 32 is a volatile storage element. A RAM (Random Access Memory) or the like is used.

  The image processing unit 33 is a circuit that performs predetermined image processing such as resolution conversion on the image data in the image data buffer 32.

  Further, if necessary, the image processing unit 33 could not be corrected by the imaging optical system 1 such as a known distortion correction process for correcting distortion in the optical image of the subject formed on the light receiving surface of the imaging element 17. It may be configured to correct aberrations. In the distortion correction, an image distorted by aberration is corrected to a natural image having a similar shape similar to a sight seen with the naked eye and having substantially no distortion. With this configuration, even if the optical image of the subject guided to the image sensor 17 by the imaging optical system 1 is distorted, it is possible to generate a natural image with substantially no distortion. Further, in the configuration in which such distortion is corrected by image processing by information processing, in particular, only other aberrations other than distortion aberration need to be considered, so that the degree of freedom in designing the imaging optical system 1 is increased and the design is improved. It becomes easier. In addition, in the configuration in which such distortion is corrected by image processing based on information processing, the aberration burden due to the lens close to the image plane is reduced, so that the exit pupil position can be easily controlled, and the lens shape is easy to process. It can be shaped.

  Further, the image processing unit 33 may include a known peripheral illuminance decrease correction process for correcting the peripheral illuminance decrease in the optical image of the subject formed on the light receiving surface of the image sensor 17 as necessary. The digital device 3 can obtain a better image by further including such a peripheral illumination fall correction process. The peripheral illuminance drop correction (shading correction) is executed by storing correction data for performing the peripheral illuminance drop correction in advance and multiplying the image (pixel) after photographing by the correction data. Since the decrease in ambient illuminance mainly occurs due to the incident angle dependence of the sensitivity in the image sensor 17, the vignetting of the lens, the cosine fourth law, and the like, the correction data has a predetermined value that corrects the decrease in illuminance caused by these factors. Is set. With such a configuration, even if the peripheral illuminance drops in the optical image of the subject guided to the image sensor 17 by the imaging optical system 1, it is possible to generate an image having sufficient illuminance to the periphery. It becomes.

  The driving unit 34 drives the lens for focusing in the imaging optical system 1 so as to perform desired focusing by operating the lens driving device (not shown) based on a control signal output from the control unit 35. To do.

  The control unit 35 includes, for example, a microprocessor and its peripheral circuits, and includes an imaging unit 30, an image generation unit 31, an image data buffer 32, an image processing unit 33, a drive unit 34, a storage unit 36, and an I / F unit. The operation of each part 37 is controlled according to its function. In other words, the imaging device 21 is controlled by the control unit 35 to execute at least one of the still image shooting and the moving image shooting of the subject.

  The storage unit 36 is a storage circuit that stores image data generated by still image shooting or moving image shooting of a subject. For example, a ROM (Read Only Memory) that is a nonvolatile storage element or a rewritable nonvolatile memory It comprises an EEPROM (Electrically Erasable Programmable Read Only Memory) that is a storage element, a RAM, and the like. That is, the storage unit 36 has a function as a still image memory and a moving image memory.

  The I / F unit 37 is an interface that transmits / receives image data to / from an external device. For example, the I / F unit 37 is an interface that conforms to a standard such as USB or IEEE1394.

  Next, the imaging operation of the digital device 3 having such a configuration will be described.

  When capturing a still image, the control unit 35 controls the imaging unit 30 (imaging device 21) to capture a still image, and the lens (not shown) of the imaging unit 30 via the drive unit 34. Focusing is performed by operating the driving device and moving all balls. As a result, the focused optical image is periodically and repeatedly formed on the light receiving surface of the image sensor 17, converted into image signals of R, G, and B color components, and then output to the image generation unit 31. . The image signal is temporarily stored in the image data buffer 32, and after image processing is performed by the image processing unit 33, an image based on the image signal is displayed on a display (not shown). The photographer can adjust the main subject so as to be within a desired position on the screen by referring to the display. When a so-called shutter button (not shown) is pressed in this state, image data is stored in the storage unit 36 as a still image memory, and a still image is obtained.

  In addition, when performing moving image shooting, the control unit 35 controls the imaging unit 30 to perform moving image shooting. After that, as in the case of still image shooting, the photographer refers to the display (not shown) so that the image of the subject obtained through the imaging unit 30 is in a desired position on the screen. Can be adjusted. When a shutter button (not shown) is pressed, moving image shooting is started. At the time of moving image shooting, the control unit 35 controls the imaging unit 30 to shoot a moving image and operates the lens driving device (not shown) of the imaging unit 30 via the driving unit 34 to perform focusing. Do. As a result, a focused optical image is periodically and repeatedly formed on the light receiving surface of the image sensor 17, converted into image signals of R, G, and B color components, and then output to the image generation unit 31. . The image signal is temporarily stored in the image data buffer 32, and after image processing is performed by the image processing unit 33, an image based on the image signal is displayed on a display (not shown). Then, when the shutter button (not shown) is pressed again, the moving image shooting is completed. The captured moving image is guided to and stored in the storage unit 36 as a moving image memory.

  Such a digital device 3 and the imaging device 21 (imaging unit 30) use the imaging optical system 1 that can correct various aberrations while reducing the size, so that the size and the image quality can be improved. it can. That is, the small-sized and high-quality digital device 3 and the imaging device 21 (imaging unit 30) are provided. For this reason, it is suitable for mobile phones that are becoming thinner, particularly so-called smartphones. As an example, a case where the imaging device 21 is mounted on a mobile phone will be described below.

  FIG. 4 is an external configuration diagram of a camera-equipped mobile phone showing an embodiment of a digital device. 4A shows an operation surface of the mobile phone, and FIG. 4B shows a back surface of the operation surface, that is, a back surface.

  For example, as shown in FIG. 4, the mobile phone 5 includes a display unit 51 that displays predetermined information, an input operation unit 52 that receives input of a predetermined instruction, and a telephone function that performs communication using a mobile phone network. The communication part 53 of the omission of illustration which implement | achieves, each part 30-37 shown in FIG. 3, and the thin plate-shaped housing | casing HS which accommodates these each part 51-53, 30-37 are provided. A rectangular display surface of the display unit 51 faces one main surface (front surface) of the housing HS, and an input operation unit 52 is disposed on one end side (lower side) of the display surface. The display surface of the display unit 51 is provided with a touch panel that accepts input by touching the display surface with a fingertip or a pen, and an instruction input that cannot be input by the input operation unit 52 is displayed on the touch panel and the display unit 51. It is realized by combining it with information. For example, the display unit 51 displays an image shooting mode start button, an image shooting button for switching between still image shooting and moving image shooting, a shutter button, and the like, and touches the display surface of the displayed button position. The instruction indicated by the button is input to the mobile phone 5. The touch panel may be of a known type such as a so-called capacitance type. The imaging unit 30 (imaging device 21) faces the other main surface (back surface) of the housing HS.

  In such a cellular phone 5, when the start button of the image capturing mode is operated, a control signal indicating the operation content is output to the control unit 35, and the control unit 35 activates the image capturing function. When the image shooting button is operated, a control signal indicating the operation content is output to the control unit 35, and the control unit 35 activates and executes the still image shooting mode and starts and executes the moving image shooting mode. The operation according to the operation content is executed. When the shutter button is operated, a control signal indicating the operation content is output to the control unit 35, and the control unit 35 performs an operation corresponding to the operation content, such as still image shooting or moving image shooting. .

<Description of More Specific Embodiment of Imaging Optical System>
Hereinafter, a specific configuration of the imaging optical system 1 as shown in FIG. 1 will be described with reference to the drawings. Note that the imaging optical systems 1A to 1F described below are provided in the imaging device 21 mounted on the digital device 3 and the mobile phone 5 as shown in FIGS. 3 and 4 respectively.

[Example]
5 to 10 are cross-sectional views illustrating lens arrangements in the imaging optical systems 1A to 1F according to the first to sixth embodiments.

  As shown in FIGS. 5 to 10, the imaging optical systems 1 </ b> A to 1 </ b> F of Embodiments 1 to 6 generally form an optical image of a subject on a predetermined surface and are sequentially arranged from the object side to the image side. The five first to fifth lenses L1 to L5 are provided, and when focusing (focusing), these five first to fifth lenses L1 to L5 are extended in the optical axis direction AX when all the balls are extended. Move together. The fifth lens L5 arranged closest to the image side has at least one inflection point when it goes from the intersection of the optical axes AX to the end of the effective area on the contour line of the lens cross section along the optical axis AX. At least one aspheric surface is provided.

  More specifically, in the imaging optical systems 1A to 1F of the first to sixth embodiments, the first to fifth lenses L1 to L5 are sequentially arranged from the object side to the image side, and are configured as follows.

  First, in the case of the imaging optical systems 1A to 1D of Examples 1 to 4, the first lens L1 is a meniscus positive meniscus lens having a positive refractive power and having a convex surface facing the object side. The second lens L2 is a negative lens having negative refractive power and a biconcave shape. The third lens L3 is a positive meniscus lens having positive refractive power and convex toward the object side. The fourth lens L4. Is a meniscus positive meniscus lens having a positive refractive power and a convex surface facing the image side, and the fifth lens L5 is a biconcave negative lens having a negative refractive power. Each of the first to fifth lenses L1 to L5 is a lens made of a resin material, and both surfaces are aspherical surfaces. The image side surface of the fifth lens L5 has one inflection point Pa to Pd when moving from the intersection of the optical axis AX to the effective region end on the contour line of the lens cross section along the optical axis AX.

  The case of the imaging optical system 1E of Example 5 will be described. The imaging optical system 1E of Example 5 is different from the imaging optical systems 1A to 1D of Examples 1 to 4 in the third lens L3. That is, the third lens L3 in the imaging optical system 1E of Example 5 is a biconvex positive lens having positive refractive power, and the first, second, fourth, and fifth lenses L1, L2, L4 and L5 are the same as the first, second, fourth, and fifth lenses L1, L2, L4, and L5 in the imaging optical system 1A of Embodiment 1, respectively. Each of the first to fifth lenses L1 to L5 is a lens made of a resin material, and both surfaces are aspherical surfaces. The image side surface of the fifth lens L5 has one inflection point Pe when it goes from the intersection of the optical axes AX to the end of the effective area on the contour line of the lens cross section along the optical axis AX.

  The case of the imaging optical system 1F of Example 6 will be described. The imaging optical system 1F of Example 6 differs from the imaging optical systems 1A to 1D of Examples 1 to 4 in the third lens L3. That is, the third lens L3 in the imaging optical system 1F of Example 6 is a single flat positive lens having a positive refractive power and a convex shape on the object side, and the first, second, fourth, and fifth lenses. The lenses L1, L2, L4, and L5 are the same as the first, second, fourth, and fifth lenses L1, L2, L4, and L5 in the imaging optical system 1A of the first embodiment, respectively. Each of the first to fifth lenses L1 to L5 is a lens made of a resin material, and both surfaces are aspherical surfaces. The image side surface of the fifth lens L5 has one inflection point Pf when it goes from the intersection of the optical axes AX to the end of the effective area on the contour line of the lens cross section along the optical axis AX.

  In the imaging optical systems 1A to 1F of Examples 1 to 6, the optical aperture stop ST is disposed on the object side of the first lens L1, and the imaging optical systems 1A to 1F of Examples 1 to 6 are of the front aperture type. The optical diaphragm ST may be an aperture diaphragm, a mechanical shutter, or a variable diaphragm in each of the first to sixth embodiments.

  In each of the first to sixth embodiments, the light receiving surface of the image sensor SR is disposed via the parallel plate FT on the image side of the fifth lens L5 that is disposed closest to the image side. The parallel plate FT is a cover glass of various optical filters or an image sensor.

  In each of FIGS. 5 to 10, the number ri (i = 1, 2, 3,...) Given to each lens surface is the i-th lens surface when counted from the object side (however, The cemented surface of the lens is counted as one surface), and the surface marked with “*” in ri indicates an aspherical surface. The surface of the optical aperture stop ST and both surfaces of the filter FT are also handled as one surface. The meaning of such handling and symbols is the same for each embodiment. However, it does not mean that they are exactly the same. For example, the lens surface arranged closest to the object side is denoted by the same symbol (r1) in each drawing of each embodiment, but the construction described later is used. As shown in the data, it does not mean that these curvatures and the like are the same throughout the first to sixth embodiments.

  Under such a configuration, in the imaging optical systems 1A to 1F according to the first to sixth embodiments, the light beams incident from the object side sequentially form the optical aperture stop ST, the first lens L1, and the second lens along the optical axis AX. L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the filter FT are passed, and an optical image of the object is formed on the light receiving surface of the image sensor IS.

  In the image pickup optical systems 1A to 1F of the first to sixth embodiments, the image pickup element IS converts an optical image into an electrical signal. This electric signal is subjected to predetermined digital image processing as necessary, and is recorded as a digital video signal in a memory of a digital device such as a digital camera, or other digital signal is transmitted by wired or wireless communication via an interface. Or transmitted to the device.

  The construction data of each lens in the imaging optical systems 1A to 1F of the first to sixth embodiments is as follows.

  First, the construction data of each lens in the imaging optical system 1A of Example 1 is shown below.

Numerical example 1
Unit mm
Surface data surface number r d nd νd ER
Object ∞ ∞
1 (aperture) ∞ -0.23 0.88
2 * 1.465 0.56 1.54470 56.2 0.90
3 * 59.718 0.15 0.90
4 * -13.777 0.20 1.63470 23.9 0.89
5 * 2.993 0.34 0.91
6 * 7.489 0.34 1.63470 23.9 1.03
7 * 588.940 0.52 1.13
8 * -4.289 0.60 1.54470 56.2 1.51
9 * -0.984 0.36 1.69
10 * -1.820 0.30 1.54470 56.2 2.08
11 * 2.167 0.50 2.33
12 ∞ 0.11 1.51680 64.1 3.00
13 ∞ 3.00
Image plane ∞
Aspherical data second surface K = 0.72884E-01, A4 = 0.33660E-02, A6 = 0.12279E-01, A8 = −0.18413E-01, A10 = 0.22499E-01, A12 = 0.29979E-01, A14 = -0.45640E-01
Third surface K = 0.60566E + 01, A4 = 0.21515E-01, A6 = 0.11625E-01, A8 = 0.98701E-02, A10 = -0.48161E-01, A12 = -0.44961E-01, A14 = 0.15975 E-01
Fourth surface K = 0.36749E + 01, A4 = 0.28884E-01, A6 = 0.76568E-01, A8 = −0.10018E + 00, A10 = −0.87637E-01, A12 = −0.44571E-02, A14 = 0.60985E-01
5th surface K = -0.18897E + 02, A4 = 0.10397E + 00, A6 = 0.57724E-01, A8 = -0.29105E-01, A10 = -0.53714E-02, A12 = -0.10522E + 00, A14 = 0.13687E + 00
6th surface K = 0.30000E + 02, A4 = -0.13469E + 00, A6 = 0.38115E-01, A8 = -0.82757E-01, A10 = 0.18262E + 00, A12 = -0.60602E-01, A14 = -0.17832E-01
7th surface K = -0.30000E + 02, A4 = -0.66969E-01, A6 = -0.91449E-01, A8 = 0.21128E + 00, A10 = -0.29862E + 00, A12 = 0.27004E + 00, A14 = -0.85032E-01
Eighth surface K = 0.39148E + 01, A4 = −0.12358E-01, A6 = 0.75713E-01, A8 = −0.93827E-01, A10 = 0.50489E-01, A12 = −0.12097E-01, A14 = 0.10941E-02
9th surface K = -0.31904E + 01, A4 = -0.47454E-01, A6 = 0.82007E-01, A8 = -0.38274E-01, A10 = 0.12186E-01, A12 = -0.29797E-02, A14 = 0.33342E-03
10th surface K = -0.75735E + 01, A4 = -0.17381E-01, A6 = -0.22081E-01, A8 = 0.20514E-01, A10 = -0.57307E-02, A12 = 0.69535E-03, A14 = -0.31475E-04
11th surface K = −0.21747E + 02, A4 = −0.58501E-01, A6 = 0.15375E-01, A8 = −0.31294E-02, A10 = 0.302103E-03, A12 = −0.10364E-04, A14 = 0.71439E-07
Various data focal length (f) 3.92 (mm)
F number 2.24
Half angle of view (w) 36.6 (degree)
Image height (maximum) (2Y) 5.892 (mm)
Back focus (Bf) 0.51 (mm)
Total lens length (TL) 4.49 (mm)
ENTP 0 (mm)
EXTP -2.3 (mm)
H1 -1.57 (mm)
H2 -3.42 (mm)
Focal length of each lens (mm)
1st lens L1 2.747
Second lens L2 -3.857
Third lens L3 11.949
4th lens L4 2.204
5th lens L5 -1.769

  Next, construction data of each lens in the imaging optical system 1B of Example 2 is shown below.

Numerical example 2
Unit mm
Surface data surface number r d nd νd ER
Object ∞ ∞
1 (aperture) ∞ -0.17 0.82
2 1.459 0.49 1.54470 56.2 0.88
3 * 39.697 0.15 0.89
4 * -25.847 0.20 1.63470 23.9 0.88
5 * 3.018 0.36 0.88
6 * 7.577 0.32 1.63470 23.9 0.98
7 * 11.769 0.40 1.12
8 * -4.203 0.89 1.54470 56.2 1.42
9 * -0.986 0.35 1.68
10 * -6.645 0.30 1.54470 56.2 2.27
11 * 1.286 0.50 2.47
12 ∞ 0.11 1.51680 64.1 3.00
13 ∞ 3.00
Image plane ∞
Aspherical data second surface K = 0.98302E-01, A4 = 0.30431E-02, A6 = 0.12513E-01, A8 = -0.14462E-01, A10 = 0.17843E-01, A12 = 0.18983E-01, A14 = -0.55503E-01
Third surface K = -0.80000E + 02, A4 = 0.18666E-01, A6 = 0.17229E-01, A8 = -0.90640E-03, A10 = -0.63111E-01, A12 = -0.57988E-01, A14 = 0.35662E-01
Fourth surface K = 0.63034E + 02, A4 = 0.30390E-01, A6 = 0.87016E-01, A8 = -0.10151E + 00, A10 = -0.10166E + 00, A12 = -0.20298E-01, A14 = 0.98694E-01
5th surface K = -0.20536E + 02, A4 = 0.11449E + 00, A6 = 0.59355E-01, A8 = -0.33642E-01, A10 = 0.43117E-02, A12 = -0.84442E-01, A14 = 0.12296E + 00
6th surface K = −0.33210E + 02, A4 = −0.15018E + 00, A6 = 0.26479E-01, A8 = −0.17400E-01, A10 = 0.22070E-02, A12 = 0.155497E + 00, A14 = -0.10842E + 00
7th surface K = -0.30000E + 02, A4 = -0.94268E-01, A6 = -0.28864E-01, A8 = 0.84229E-01, A10 = -0.13610E + 00, A12 = 0.15314E + 00, A14 = -0.52638E-01
8th surface K = 0.33201E + 00, A4 = 0.11352E-02, A6 = 0.56942E-01, A8 = -0.79069E-01, A10 = 0.45432E-01, A12 = -0.11018E-01, A14 = 0.92460 E-03
9th surface K = −0.33603E + 01, A4 = −0.43096E-01, A6 = 0.37735E-01, A8 = −0.34891E-02, A10 = −0.87322E-03, A12 = −0.41582E-03, A14 = 0.14111E-03
10th surface K = -0.12697E + 01, A4 = -0.19969E-01, A6 = -0.86012E-02, A8 = 0.11098E-01, A10 = -0.31192E-02, A12 = 0.37818E-03, A14 = -0.17615E-04
11th surface K = -0.88018E + 01, A4 = -0.59624E-01, A6 = 0.17895E-01, A8 = -0.39888E-02, A10 = 0.54324E-03, A12 = -0.30208E-04, A14 = 0.11500E-06
Various data focal length (f) 3.95 (mm)
F number 2.41
Half angle of view (w) 36.3 (degree)
Image height (maximum) (2Y) 5.892 (mm)
Back focus (Bf) 0.63 (mm)
Total lens length (TL) 4.70 (mm)
ENTP 0 (mm)
EXTP -2.45 (mm)
H1 -1.11 (mm)
H2 -3.32 (mm)
Focal length of each lens (mm)
1st lens L1 2.768
Second lens L2 -4.246
Third lens L3 32.557
Fourth lens L4 2.155
5th lens L5 -1.952

  Next, construction data of each lens in the imaging optical system 1C of Example 3 is shown below.

Numerical Example 3
Unit mm
Surface data surface number r d nd νd ER
Object ∞ ∞
1 (aperture) ∞ -0.21 0.82
2 * 1.437 0.51 1.54470 56.2 0.83
3 * 9.588 0.18 0.84
4 * -32.016 0.15 1.63470 23.9 0.84
5 * 3.852 0.41 0.86
6 * 5.273 0.30 1.63470 23.9 1.05
7 * 5.474 0.31 1.23
8 * -4.571 1.00 1.54470 56.2 1.52
9 * -0.946 0.35 1.74
10 * -13.166 0.25 1.54470 56.2 2.41
11 * 1.117 0.50 2.62
12 ∞ 0.11 1.51680 64.1 3.00
13 ∞ 3.00
Image plane ∞
Aspherical data second surface K = 0.11308E + 00, A4 = 0.40996E-02, A6 = 0.12945E-01, A8 = −0.15466E-01, A10 = 0.38884E-01, A12 = 0.24778E-01, A14 = -0.58391E-01
3rd surface K = -0.80000E + 02, A4 = 0.15481E-01, A6 = 0.17262E-01, A8 = -0.10720E-02, A10 = -0.62066E-01, A12 = -0.48592E-01, A14 = 0.17688E-01
4th surface K = −0.80000E + 02, A4 = 0.42317E-01, A6 = 0.97551E-01, A8 = −0.13217E + 00, A10 = −0.12396E + 00, A12 = −0.27502E-01, A14 = 0.13254E + 00
5th surface K = −0.32894E + 02, A4 = 0.13858E + 00, A6 = 0.83275E-01, A8 = −0.59625E-01, A10 = −0.48923E-01, A12 = −0.998740E-01, A14 = 0.21608E + 00
6th surface K = -0.40359E + 02, A4 = -0.12150E + 00, A6 = -0.40384E-01, A8 = 0.13991E + 00, A10 = -0.16705E + 00, A12 = 0.14205E + 00, A14 = -0.51939E-01
7th surface K = -0.30000E + 02, A4 = -0.82043E-01, A6 = -0.77530E-01, A8 = 0.14555E + 00, A10 = -0.14093E + 00, A12 = 0.92533E-01, A14 = -0.23585E-01
8th surface K = 0.14778E + 01, A4 = 0.155250E-01, A6 = −0.18611E-01, A8 = −0.25509E-01, A10 = 0.41425E-01, A12 = −0.16283E-01, A14 = 0.20629E-02
9th surface K = −0.39826E + 01, A4 = −0.10743E + 00, A6 = 0.11510E + 00, A8 = −0.10612E + 00, A10 = 0.65195E-01, A12 = −0.19257E-01, A14 = 0.21094E-02
10th surface K = 0.12168E + 02, A4 = −0.55463E-01, A6 = −0.74804E-02, A8 = 0.155454E-01, A10 = −0.44452E-02, A12 = 0.53796E-03, A14 = -0.24831E-04
11th surface K = −0.75695E + 01, A4 = −0.74021E-01, A6 = 0.22963E-01, A8 = −0.50374E-02, A10 = 0.65611E-03, A12 = −0.32844E-04, A14 = -0.16506E-06
Various data focal length (f) 3.91 (mm)
F number 2.38
Half angle of view (w) 36.5 (degree)
Image height (maximum) (2Y) 5.892 (mm)
Back focus (Bf) 0.64 (mm)
Total lens length (TL) 4.70 (mm)
ENTP 0 (mm)
EXTP -2.46 (mm)
H1 -1.02 (mm)
H2 -3.27 (mm)
Focal length of each lens (mm)
First lens L1 3.036
Second lens L2 -5.409
Third lens L3 143.839
4th lens L4 1.997
5th lens L5 -1.878

  Next, construction data of each lens in the imaging optical system 1D of Example 4 is shown below.

Numerical Example 4
Unit mm
Surface data surface number r d nd νd ER
Object ∞ ∞
1 (aperture) ∞ -0.21 0.84
2 * 1.396 0.53 1.54470 56.2 0.84
3 * 103.891 0.16 0.77
4 * -24.285 0.20 1.63470 23.9 0.72
5 * 2.854 0.42 0.69
6 * 7.884 0.32 1.63470 23.9 0.84
7 * 18.687 0.36 0.98
8 * -1.766 0.44 1.54470 56.2 1.14
9 * -1.120 0.43 1.27
10 * -43.478 0.60 1.54470 56.2 1.70
11 * 2.208 0.50 2.13
12 ∞ 0.11 1.51680 64.1 3.00
13 ∞ 3.00
Image plane ∞
Aspherical data second surface K = 0.58839E-01, A4 = 0.15222E-02, A6 = 0.93385E-02, A8 = −0.18623E-01, A10 = 0.16790E-01, A12 = 0.240403E-01, A14 = -0.42743E-01
3rd surface K = -0.30000E + 02, A4 = 0.19766E-01, A6 = 0.28338E-02, A8 = 0.18830E-01, A10 = -0.34316E-01, A12 = -0.39474E-01, A14 = 0.14994E-01
4th surface K = -0.25461E + 02, A4 = 0.39029E-01, A6 = 0.82855E-01, A8 = -0.68228E-01, A10 = -0.40818E-01, A12 = 0.10765E-02, A14 = 0.20119E-01
5th surface K = −0.15410E + 02, A4 = 0.11717E + 00, A6 = 0.76854E-01, A8 = −0.18925E-01, A10 = 0.50185E-01, A12 = −0.72496E-01, A14 = 0.99776E-01
6th surface K = 0.30000E + 02, A4 = -0.19447E + 00, A6 = -0.31563E-01, A8 = 0.20109E + 00, A10 = -0.52622E + 00, A12 = 0.020204E + 00, A14 = -0.30075E + 00
7th surface K = -0.30000E + 02, A4 = -0.16196E + 00, A6 = 0.30519E-01, A8 = 0.30784E-01, A10 = -0.44397E-01, A12 = 0.80833E-01, A14 = -0.35326E-01
Eighth surface K = -0.10509E + 01, A4 = -0.10270E + 00, A6 = 0.12530E-01, A8 = 0.37094E + 00, A10 = -0.36867E + 00, A12 = 0.13838E + 00, A14 = -0.18857E-01
9th surface K = −0.24800E + 01, A4 = −0.16610E + 00, A6 = 0.72581E-01, A8 = 0.155339E + 00, A10 = −0.12837E + 00, A12 = 0.35701E-01, A14 = -0.33667E-02
10th surface K = -0.30000E + 02, A4 = -0.20898E + 00, A6 = 0.22827E + 00, A8 = -0.16102E + 00, A10 = 0.59429E-01, A12 = -0.10622E-01, A14 = 0.73536E-03
11th surface K = −0.21748E + 02, A4 = −0.72014E-01, A6 = 0.31421E-01, A8 = −0.13110E-01, A10 = 0.26363E-02, A12 = −0.24540E-03, A14 = 0.64352E-05
Various data focal length (f) 4.08 (mm)
F number 2.43
Half angle of view (w) 35.1 (degree)
Image height (maximum) (2Y) 5.842 (mm)
Back focus (Bf) 0.55 (mm)
Total lens length (TL) 4.6 (mm)
ENTP 0 (mm)
EXTP -2.55 (mm)
H1 -1.29 (mm)
H2 -3.53 (mm)
Focal length of each lens (mm)
1st lens L1 2.593
Second lens L2 -4.013
Third lens L3 21.245
4th lens L4 4.538
5th lens L5 -3.841

  Next, construction data of each lens in the imaging optical system 1E of Example 5 is shown below.

Numerical Example 5
Unit mm
Surface data surface number r d nd νd ER
Object ∞ ∞
1 (aperture) ∞ -0.20 0.82
2 * 1.383 0.53 1.54470 56.2 0.85
3 * 52.939 0.16 0.86
4 * -6.667 0.20 1.63470 23.9 0.86
5 * 4.858 0.45 0.84
6 * 51.722 0.32 1.63470 23.9 0.94
7 * -124.308 0.53 1.11
8 * -3.176 0.61 1.54470 56.2 1.46
9 * -0.847 0.30 1.64
10 * -1.637 0.35 1.54470 56.2 2.03
11 * 2.186 0.50 2.31
12 ∞ 0.11 1.51680 64.1 3.00
13 ∞ 3.00
Image plane ∞
Aspherical data second surface K = 0.71554E-01, A4 = 0.34028E-02, A6 = 0.59347E-02, A8 = -0.19941E-01, A10 = 0.18004E-01, A12 = 0.21511E-01, A14 = -0.61874E-01
Third surface K = -0.30000E + 02, A4 = -0.14196E-02, A6 = 0.51051E-02, A8 = 0.12903E-01, A10 = -0.45651E-01, A12 = -0.45498E-01, A14 = 0.22095E-01
Fourth surface K = −0.30000E + 02, A4 = 0.51293E-01, A6 = 0.71871E-01, A8 = −0.63686E-01, A10 = −0.39005E-01, A12 = 0.12737E-01, A14 = 0.42568E-01
Fifth surface K = −0.25612E + 02, A4 = 0.10939E + 00, A6 = 0.88578E-01, A8 = −0.22872E-01, A10 = 0.34326E-01, A12 = −0.667610E-01, A14 = 0.16182E + 00
6th surface K = 0.30000E + 02, A4 = -0.22581E + 00, A6 = 0.22411E-01, A8 = -0.21552E-02, A10 = -0.18564E + 00, A12 = 0.41011E + 00, A14 = -0.19354E + 00
7th surface K = -0.30000E + 02, A4 = -0.18396E + 00, A6 = 0.36664E-01, A8 = 0.71360E-02, A10 = -0.77096E-01, A12 = 0.13681E + 00, A14 = -0.51158E-01
8th surface K = 0.19938E + 01, A4 = -0.12538E + 00, A6 = 0.14796E + 00, A8 = -0.81730E-01, A10 = 0.52525E-01, A12 = -0.22784E-01, A14 = 0.36188E-02
9th surface K = -0.24172E + 01, A4 = -0.38979E-01, A6 = -0.79014E-02, A8 = 0.904905E-01, A10 = -0.47339E-01, A12 = 0.10829E-01, A14 = -0.94479E-03
10th surface K = −0.87539E + 01, A4 = 0.026263E-01, A6 = −0.26060E-01, A8 = −0.14713E-02, A10 = 0.39816E-02, A12 = −0.92093E-03, A14 = 0.65768E-04
11th surface K = −0.21748E + 02, A4 = −0.32957E-01, A6 = 0.56135E-02, A8 = −0.32748E-02, A10 = 0.91917E-03, A12 = −0.13956E-03, A14 = 0.90303E-05
Various data focal length (f) 3.97 (mm)
F number 2.42
Half angle of view (w) 35.8 (degree)
Image height (maximum) (2Y) 5.712 (mm)
Back focus (Bf) 0.47 (mm)
Total lens length (TL) 4.52 (mm)
ENTP 0 (mm)
EXTP -2.47 (mm)
H1 -1.38 (mm)
H2 -3.5 (mm)
Focal length of each lens (mm)
First lens L1 2.598
Second lens L2 -4.398
Third lens L3 57.588
4th lens L4 1.942
5th lens L5 -1.665

  Next, construction data of each lens in the imaging optical system 1F of Example 6 is shown below.

Numerical Example 6
Unit mm
Surface data surface number r d nd νd ER
Object ∞ ∞
1 (aperture) ∞ -0.20 0.84
2 * 1.448 0.52 1.54470 56.2 0.87
3 * 68.031 0.16 0.88
4 * -86.766 0.20 1.63470 23.9 0.87
5 * 2.561 0.34 0.89
6 * 9.009 0.32 1.63470 23.9 1.01
7 * ∞ 0.67 1.10
8 * -4.055 0.54 1.54470 56.2 1.50
9 * -1.049 0.37 1.70
10 * -2.169 0.31 1.54470 56.2 2.23
11 * 2.000 0.50 2.47
12 ∞ 0.11 1.51680 64.1 3.00
13 ∞ 3.00
Image plane ∞
Aspherical data second surface K = 0.55012E-01, A4 = 0.155877E-02, A6 = 0.99060E-02, A8 = -0.17869E-01, A10 = 0.244244E-01, A12 = 0.294446E-01, A14 = -0.50480E-01
Third surface K = −0.30000E + 02, A4 = 0.24167E-01, A6 = 0.95438E-02, A8 = 0.14098E-01, A10 = −0.42664E-01, A12 = −0.44374E-01, A14 = 0.10370E-01
4th surface K = -0.17259E + 02, A4 = 0.23414E-01, A6 = 0.58814E-01, A8 = -0.88451E-01, A10 = -0.82390E-01, A12 = -0.13705E-01, A14 = 0.46098E-01
Fifth surface K = -0.14286E + 02, A4 = 0.11552E + 00, A6 = 0.64740E-01, A8 = -0.24225E-01, A10 = 0.44351E-02, A12 = -0.10750E + 00, A14 = 0.10838E + 00
6th surface K = 0.30000E + 02, A4 = -0.12185E + 00, A6 = 0.43043E-02, A8 = 0.84454E-01, A10 = -0.11958E + 00, A12 = 0.25260E + 00, A14 =- 0.14718E + 00
7th surface K = −0.30000E + 02, A4 = −0.63934E-01, A6 = −0.12137E + 00, A8 = 0.37423E + 00, A10 = −0.58114E + 00, A12 = 0.51743E + 00, A14 = -0.16674E + 00
8th surface K = 0.44533E + 01, A4 = 0.12128E-01, A6 = −0.18051E-01, A8 = 0.25707E-01, A10 = −0.32961E-01, A12 = 0.16468E-01, A14 = − 0.25045E-02
9th surface K = −0.44692E + 01, A4 = −0.10752E + 00, A6 = 0.14472E + 00, A8 = −0.10711E + 00, A10 = 0.52346E-01, A12 = −0.14038E-01, A14 = 0.14703E-02
10th surface K = -0.89548E + 01, A4 = -0.26346E-01, A6 = -0.26850E-01, A8 = 0.28838E-01, A10 = -0.91422E-02, A12 = 0.12905E-02, A14 = -0.70655E-04
11th surface K = −0.21747E + 02, A4 = −0.448536E-01, A6 = 0.34632E-02, A8 = 0.30531E-02, A10 = −0.14491E-02, A12 = 0.25771E-03, A14 = -0.16113E-04
Various data focal length (f) 4.09 (mm)
F number 2.44
Half angle of view (w) 35.1 (degree)
Image height (maximum) (2Y) 5.842 (mm)
Back focus (Bf) 0.47 (mm)
Total lens length (TTL) 4.52 (mm)
ENTP 0 (mm)
EXTP -2.32 (mm)
H1 -1.91 (mm)
H2 -3.62 (mm)
Focal length of each lens (mm)
1st lens L1 2.708
Second lens L2 -3.916
Third lens L3 14.194
4th lens L4 2.444
5th lens L5 -1.861

  Here, the total lens length (TL) of the above various data is the total lens length (distance from the first lens object side surface to the imaging surface) when the object distance is infinite, and the parallel plate is calculated as an air conversion length. Yes. ENTP is the distance from the entrance pupil to the first surface, and is 0 when the entrance pupil = a stop. EXTP is the distance from the final surface (cover glass image surface side) to the exit pupil, H1 is the distance from the first surface to the object side principal point, and H2 is the final surface (cover glass image surface side). To the image side principal point.

  In the above surface data, the surface number corresponds to the number i of the symbol ri (i = 1, 2, 3,...) Given to each lens surface shown in FIGS. The surface marked with * in the number i indicates an aspherical surface (aspherical refractive optical surface or a surface having a refractive action equivalent to an aspherical surface).

  Further, “r” is a radius of curvature (unit: mm) of each surface, and “d” is an interval between lens surfaces on the optical axis in an infinitely focused state (a focused state at an infinite distance) ( The distance between the upper surfaces of the axes (unit: mm), “nd” is the refractive index of each lens with respect to the d-line (wavelength 587.56 nm), “νd” is the Abbe number, and “ER” is the effective radius ( Units; mm) are shown respectively. Since both surfaces of the optical aperture stop ST, the filter FT, and the light receiving surface of the image sensor SI are flat surfaces, their radii of curvature are ∞ (infinite).

  The above-mentioned aspheric surface data includes the quadric surface parameter (cone coefficient K) and the aspheric surface coefficient Ai (i = 4, 6, 6) of the surface that is an aspheric surface (the surface with the number i added to * in the surface data). 8, 10, 12, 14, 16).

In each embodiment, the shape of the aspherical surface is defined by the following equation when the surface vertex is the origin, the X axis is taken in the optical axis direction, and the height in the direction perpendicular to the optical axis is h.
X = (h ² / R) / [1+ (1− (1 + K) h ² / R ² ) ^1/2 ] + ΣA _i · h ⁱ
Where Ai is an i-th order aspheric coefficient, R is a reference radius of curvature, and K is a conic constant.

  Note that the paraxial radius of curvature (r) described in the claims, embodiments, and examples is in the vicinity of the center of the lens (more specifically, within 10% of the lens outer diameter) in the actual lens measurement scene. The approximate curvature radius when the shape measurement value in the center region of the curve is fitted by the least square method can be regarded as the paraxial curvature radius. For example, when a secondary aspherical coefficient is used, a curvature radius that takes into account the secondary aspherical coefficient in the reference curvature radius of the aspherical definition formula can be regarded as a paraxial curvature radius (for example, reference literature). (See P41-P42 of “Lens Design Method” by K. Matsui, Kyoritsu Publishing Co., Ltd.).

  In the aspheric data, “En” means “10 to the power of n”. For example, “E + 001” means “10 to the power of +1”, and “E-003” means “10 to the power of −3”.

  FIGS. 11 to 16 show aberration diagrams at an infinite distance. FIGS. A, B, and C in each figure are in this order, spherical aberration (sine condition) (Longitudinal SPHERICAL ABERRATION). , Longitudinal aberrations of astigmatism (ASTIGMATISM FIELD CURVES) and distortion (DISTORTION) are shown. The abscissa of the spherical aberration represents the focal position shift in mm, and the ordinate represents the value normalized by the maximum incident height. The horizontal axis of astigmatism represents the focal position shift in mm, and the vertical axis represents the image height in mm. The horizontal axis of the distortion aberration represents the actual image height as a percentage (%) with respect to the ideal image height, and the vertical axis represents the image height in mm. In the graph of spherical aberration, the solid line is the d-line (wavelength 587.56 nm), the broken line is the g-line (wavelength 435.84 nm), and the alternate long and short dash line is the result for the c-line (wavelength 656.28 nm). Represents. In the figure of astigmatism, the broken line represents the result on the tangential (meridional) surface (M), and the solid line represents the result on the sagittal (radial) surface (S). The diagrams of astigmatism and distortion are the results when the d-line (wavelength 587.56 nm) is used.

  11 to 16 show lateral aberration diagrams (meridional coma aberration), and D and E in each figure represent the case of the maximum image height Y and 50%, respectively. The case of image height Y is shown. The horizontal axis represents the entrance pupil position in mm, and the vertical axis represents the lateral aberration. In the lateral aberration diagram, the solid line represents the d-line, the broken line represents the g-line, and the alternate long and short dash line represents each result for the c-line.

  Table 1 shows numerical values when the above-described conditional expressions (1) to (5) are applied to the imaging optical systems 1A to 1F of Examples 1 to 6 listed above.

  As described above, the imaging optical systems 1A to 1F in Examples 1 to 6 described above have a five-lens configuration and satisfy the above-described conditions. As a result, various aberrations can be achieved while reducing the size. Can be corrected more favorably. And the imaging device and digital apparatus using such imaging optical systems 1A-1F can achieve size reduction and high image quality.

  The present specification discloses various aspects of the technology as described above, and the main technologies are summarized below.

  An imaging optical system according to an aspect includes, in order from the object side to the image side, a first meniscus lens having a positive refractive power and a convex surface facing the object side, and a biconcave shape having a negative refractive power. The second lens includes a third lens having a positive refractive power, a fourth lens having a positive refractive power, and a fifth lens having a negative refractive power and a biconcave shape. (1) and (1) and (a) having at least one aspherical surface having an inflection point when it goes from the intersection of the optical axes toward the end of the effective region in the contour line of the lens cross section including the optical axis along the optical axis. Each conditional expression of 2) is satisfied. Such an imaging optical system can correct various aberrations better while being small.

  In another aspect, the above-described imaging optical system satisfies the conditional expression (3). By satisfying the conditional expression (3), such an imaging optical system can shorten its overall length, and can suppress high-order spherical aberration and coma generated in the first lens and the second lens. Therefore, the image plane variation with respect to the manufacturing error can be reduced.

  In another aspect, in the above-described imaging optical system, the conditional expression (4) is satisfied. Such an imaging optical system can satisfactorily correct the axial chromatic aberration generated in the first lens with the second lens. By satisfying conditional expression (4), such an imaging optical system can correct chromatic aberration satisfactorily while maintaining the Petzval sum small without impairing workability.

  In another aspect, in the above-described imaging optical system, the conditional expression (5) is satisfied. By satisfying the conditional expression (5), such an imaging optical system can easily ensure the telecentricity of the image-side light beam, shortening the overall length of the imaging optical system, field curvature, distortion, etc. Various aberrations can be corrected satisfactorily.

  In another aspect, in the above-described imaging optical system, the third lens has a shape with a convex surface facing the object side. Such an imaging optical system can bring the combined principal point position from the first lens to the third lens closer to the object side, which is advantageous for shortening the overall length of the imaging optical system.

  In another aspect, in the above-described imaging optical system, the fourth lens has a meniscus shape with a convex surface facing the image side. Such an imaging optical system can guide off-axis rays strongly bounced by the second lens to the fifth lens while suppressing the refraction angle at each surface to be small, and can effectively suppress off-axis aberrations. it can.

  In another aspect, the above-described imaging optical system further includes an optical diaphragm on the object side of the first lens. Such an imaging optical system can reduce the incident angle of the off-axis light beam with respect to the fifth lens, and can realize a good telecentric characteristic while suppressing the change of the spot position in the off-axis light beam due to focusing. .

  In another aspect, in the above-described imaging optical system, all the lenses included in the imaging optical system are formed of a resin material. Such an imaging optical system can be produced in a large amount at a low cost even with a lens having a small radius of curvature or outer diameter, as compared with a glass lens manufactured by a time-consuming polishing process. In addition, since the lens made of resin material can lower the press temperature, it can suppress the wear of the molding die, and as a result, the number of times of replacement and maintenance of the molding die can be reduced, thereby reducing the cost. Can do.

  An imaging apparatus according to another aspect includes any of the above-described imaging optical systems and an imaging element that converts an optical image into an electrical signal, and the imaging optical system is on the predetermined surface as the imaging An optical image of the object can be formed on the light receiving surface of the element.

  According to this configuration, it is possible to provide an imaging apparatus using an imaging optical system having a five-lens configuration that can correct various aberrations better while being small. Therefore, such an imaging apparatus can be reduced in size and performance.

  A digital apparatus according to another aspect includes the above-described imaging device, and a control unit that causes the imaging device to perform at least one of shooting a still image and a moving image of a subject, and the imaging optical system of the imaging device Is assembled so that an optical image of the object can be formed on the light receiving surface of the image sensor. Preferably, the digital device comprises a mobile terminal.

  According to this configuration, it is possible to provide a digital device or a portable terminal using an imaging optical system having a five-lens configuration that can correct various aberrations in a small size. Therefore, such digital devices and portable terminals can be reduced in size and performance.

  This application is based on Japanese Patent Application No. 2013-19205 filed on Feb. 4, 2013, the contents of which are included in the present application.

  In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Therefore, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not covered by the claims. To be construed as inclusive.

According to the present invention, an imaging optical system, an imaging apparatus, and a digital device can be provided.

Claims (11)

From the object side to the image side,
A first meniscus lens having positive refractive power and having a convex surface facing the object side;
A second lens having negative refractive power and a biconcave shape;
A third lens having positive refractive power;
A fourth lens having a positive refractive power;
A negative birefringent fifth lens having negative refractive power,
The fifth lens includes at least one aspherical surface having an inflection point when moving from the intersection of the optical axes toward the end of the effective region on the contour of the lens cross section including the optical axis along the optical axis,
An imaging optical system characterized by satisfying the following conditional expressions (1) and (2):
15 <νd3 <50 (1)
-14.3 <r9 / f <-0.2 (2)
However,
νd3; Abbe number of the third lens r9; Paraxial radius of curvature of the object side surface of the fifth lens f; Focal length of the entire imaging optical system The imaging optical system according to claim 1, wherein the following conditional expression (3) is satisfied.
1 <f12 / f <1.8 (3)
However,
f12: Composite focal length of the first lens and the second lens The imaging optical system according to claim 1, wherein the following conditional expression (4) is satisfied.
0.4 <r4 / f <1.4 (4)
However,
r4: Paraxial radius of curvature of the image side surface of the second lens The imaging optical system according to any one of claims 1 to 3, wherein the following conditional expression (5) is satisfied.
-1 <f5 / f <-0.3 (5)
However,
f5: Focal length of the fifth lens The imaging optical system according to any one of claims 1 to 4, wherein the third lens has a shape with a convex surface facing the object side. The imaging optical system according to any one of claims 1 to 5, wherein the fourth lens has a meniscus shape with a convex surface facing the image side. The imaging optical system according to any one of claims 1 to 6, further comprising an optical aperture on the object side of the first lens. The imaging optical system according to any one of claims 1 to 7, wherein all lenses included in the imaging optical system are made of a resin material. The imaging optical system according to any one of claims 1 to 8,
An image sensor that converts an optical image into an electrical signal,
An image pickup apparatus, wherein the image pickup optical system is capable of forming an optical image of an object on the light receiving surface of the image pickup element on the predetermined surface. An imaging device according to claim 9,
A controller that causes the imaging device to perform at least one of still image shooting and moving image shooting of a subject;
The digital apparatus, wherein the imaging optical system of the imaging device is assembled so that an optical image of an object can be formed on a light receiving surface of the imaging device.   The digital device according to claim 10, comprising a mobile terminal.

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