JP2010025995A - Wide angle optical system and imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wide angle optical system of small size which is ready for a high density pixels of an image sensor and includes more excellent optical performance and an ultra wide image angle. <P>SOLUTION: The wide angle optical system 1 includes a front group 11, a diaphragm 12 and a back group 13, these being arranged in this order from the object side to the image side. The front group 11 includes a first lens 111 having negative optical power, a second lens 112 having negative optical power, a third lens 113 having positive optical power and a fourth lens 114, these lenses being arranged in this order from the object side to the image side. The back group 13 includes a fifth lens 131 having positive optical power. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is a wide-angle and compact wide-angle optical system that is suitably used for an imaging device such as an in-vehicle camera or a surveillance camera, and in particular, an ultra-wide angle with a full field angle of 180 degrees (half field angle of 90 degrees) or more. The present invention relates to a wide-angle optical system suitable for such a super wide-angle optical system. And this invention relates to an imaging device provided with this wide-angle optical system.

  In the case where surrounding video information is imaged over a wide range with a small number of cameras, a wide-angle optical system having a large shooting angle of view (wide angle of view) is generally employed. For example, such a wide-angle optical system is used in applications such as in-vehicle use and monitoring.

Such a wide-angle optical system is disclosed in, for example, Patent Documents 1 to 3. In the wide-angle optical system disclosed in Patent Document 1, so-called shading, which is likely to be a problem at an ultra-wide angle, can be suppressed with a small number of lenses such as about 4 or 5. In the wide-angle optical system disclosed in Patent Document 2, an ultra-wide angle is achieved with a small number of lenses of four. In the wide-angle optical system disclosed in Patent Document 3, relatively good optical performance is achieved by using six lenses.
JP 2005-227426 A JP 2006-259704 A JP 2007-249073 A

  Incidentally, in recent years, there has been a demand for optical systems with higher resolution and smaller size in applications such as in-vehicle use and monitoring. If it is a camera installed in the car, from a practical viewpoint that does not block the view of the living space and the driver, and if it is a camera installed outside the car, from the viewpoint of the aesthetic and safety of the car, There is a demand for a more compact optical system. Further, as the number of pixels of the image sensor increases, an optical system that is small and has good optical performance is also demanded.

  In the wide-angle optical system disclosed in Patent Document 1, three lenses having negative optical power from the object side to the image side are arranged. For this reason, the wide-angle optical system disclosed in Patent Document 1 has a problem that it is difficult to reduce the overall length of the optical system.

  Further, the wide-angle optical system disclosed in Patent Document 2 has a problem that it is difficult to achieve an optical system that can cope with an increase in the number of pixels of the imaging device with the small number of lenses.

  On the other hand, in the wide-angle optical system disclosed in Patent Document 3, relatively good optical performance is achieved by using six lenses. However, because six lenses are used in this way, There was a problem in dealing with the downsizing of the optical system.

  The present invention has been made in view of the above-described circumstances, and the object thereof is to cope with high pixels of an image sensor, and has better optical performance and a full angle of view of 180 degrees (half angle of view of 90 degrees). ) To provide a compact wide-angle optical system having the above-mentioned super-wide angle of view.

In order to solve the above technical problem, the present invention provides a wide-angle optical system and an imaging apparatus having the following configurations. 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 index for d line, F line (486.13 nm) and C line (656.28 nm) is nd, nF, nC and Abbe number is νd, respectively.
νd = (nd−1) / (nF−nC)
The Abbe number νd obtained by the definition formula
(C) The notation regarding the surface shape is a notation based on the paraxial curvature. Therefore, 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) 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.

  The wide-angle optical system according to one aspect of the present invention includes a front group, a stop, and a rear group in order from the object side to the image side, and the front group is negative in order from the object side to the image side. A first lens having a negative optical power, a second lens having a negative optical power, a third lens having a positive optical power, and a fourth lens. It is composed of a fifth lens having positive optical power.

  In the wide-angle optical system having such a configuration, by arranging the first to fifth lenses in the order described above, a wide angle of view, in particular, an ultra-wide angle of view is achieved, and optical performance is maintained while better optical performance is maintained. System miniaturization is also achieved. In addition, by arranging two negative lenses in order from the object side to the image side, the optical power of the negative lens is appropriately shared, and the off-axis ray incident angle on the image plane can be suppressed. By disposing the positive third lens and the fourth lens on the object side, aberration correction is shared by the third and fourth lenses, and better aberration correction becomes possible.

  In the above wide-angle optical system, it is preferable that the fourth lens has a positive optical power.

  According to this configuration, since the fourth lens is a positive lens, the optical power of the positive lens can be appropriately shared by the third and fourth lenses, so that the error sensitivity of the positive lens can be reduced. It becomes.

In the above-described wide-angle optical system, it is preferable that the following conditional expression (1) is satisfied.
ν3 <30 (1)
Where ν3 is the Abbe number of the third lens.

  In this configuration, when the upper limit of the conditional expression (1) is exceeded, the Abbe number balance between the first and second lenses having negative optical power and the third lens having positive optical power is increased. This is not preferable because it is difficult to correct both axial chromatic aberration and lateral chromatic aberration.

In the above-described wide-angle optical system, it is preferable that the following conditional expression (2) is satisfied.
ν5> 45 (2)
Where ν5 is the Abbe number of the fifth lens.

  In this configuration, if the lower limit of conditional expression (2) is not reached, the Abbe number balance in the front group and the rear group is lost, and it is difficult to correct axial chromatic aberration well, which is not preferable.

In the above-described wide-angle optical system, it is preferable that the following conditional expression (3) is satisfied.
−10 <R5f / R5r <0 (3)
Here, R5f is the radius of curvature of the fifth lens on the object side, and R5r is the radius of curvature of the fifth lens on the image plane side.

  In this configuration, if the upper limit of conditional expression (3) is exceeded, the fifth lens becomes a meniscus lens, which makes it difficult to satisfactorily correct spherical aberration and astigmatism, which is not preferable. On the other hand, if the lower limit of conditional expression (3) is not reached, the curvature and surface angle of the image side surface of the fifth lens become excessively large, making it difficult to manufacture, which is not preferable.

In the above-mentioned wide-angle optical system, it is preferable that the following conditional expression (4) is satisfied.
0 <Fr / Ff <1 (4)
Here, Ff is the focal length of the front group, and Fr is the focal length of the rear group.

  In this configuration, if the lower limit of conditional expression (4) is not reached, so-called retrofocusing occurs, so that the back focus is extended and it becomes difficult to downsize the optical system, which is not preferable. On the other hand, if the upper limit of conditional expression (4) is exceeded, the positive optical power of the front group becomes strong, which makes it difficult to achieve a super wide angle of view, which is not preferable.

In the above wide-angle optical system, it is preferable that the following conditional expression (5) is satisfied.
-1 <R4f / R4r <1 (5)
Here, R4f is the radius of curvature of the fourth lens on the object side, and R4r is the radius of curvature of the fourth lens on the image plane side.

  In this configuration, if the upper limit of the conditional expression (5) is exceeded, the fourth lens has an asymmetric shape with the fifth lens across the aperture, so that spherical aberration, coma and astigmatism are corrected well. It becomes difficult to do so. On the other hand, if the lower limit of conditional expression (5) is not reached, the optical power of the fourth lens becomes loose, which makes it difficult to correct various aberrations favorably.

  In the above-mentioned wide-angle optical system, it is preferable that the third lens is a meniscus lens convex on the object side.

  According to this configuration, various aberrations can be corrected more favorably by using the third lens as a meniscus lens convex toward the object side.

  In the above wide-angle optical system, it is preferable that each of the second to fifth lenses has at least one aspheric surface.

  According to this configuration, by adding at least one aspherical surface to the second to fifth lenses, it is effective to reduce the total optical length while reducing various aberrations.

  In the above wide-angle optical system, it is preferable that the first lens is a glass material lens.

  According to this configuration, it is possible to ensure the reliability in terms of robustness, chemical resistance, water resistance, and the like by configuring the first lens with a glass material lens.

  In the above wide-angle optical system, it is preferable that the fifth lens is a lens made of a resin material having at least one aspheric surface.

  According to this configuration, it is possible to obtain a high-performance lens at low cost by using a resin material lens as the fifth lens.

  An imaging apparatus according to another aspect of the present invention includes any one of the above-described wide-angle optical systems and an imaging element that captures an optical image of a subject formed by the wide-angle optical system. To do.

  According to this configuration, it is possible to provide an imaging apparatus including a wide-angle optical system having a relatively wide angle of view.

  In the above-described imaging device, it is preferable to further include an image processing unit that performs predetermined image processing on the output of the imaging element.

  According to this configuration, since the image processing unit performs predetermined image processing, it is possible to provide an imaging apparatus that can output an image having a desired image quality.

  In the above-described imaging apparatuses, it is preferable that the predetermined image processing includes distortion correction processing for correcting distortion in the optical image of the subject formed on the light receiving surface of the imaging element.

  In a wide-angle optical system, a large distortion occurs compared to a normal optical system (an optical system that is not wide-angle). According to this configuration, by correcting the distortion by image processing, the imaging apparatus can be applied to a relatively wide range, for example, for in-vehicle use or for monitoring use, and a user-friendly video input device (for example, a camera) Can be provided.

  In the above-described imaging devices, it is preferable that the predetermined image processing includes illuminance correction processing for correcting a decrease in peripheral illuminance in the optical image of the subject formed on the light receiving surface of the imaging element. .

  Further, in a wide-angle optical system, a decrease in illuminance is likely to occur in the peripheral portion as compared with a normal optical system (an optical system that is not wide-angle). According to this configuration, the image pickup apparatus can be applied to a relatively wide range such as in-vehicle use or monitoring, for example, by correcting the decrease in illuminance in the peripheral portion by image processing. Camera).

  ADVANTAGE OF THE INVENTION According to this invention, the small wide angle optical system which can respond to the high pixel of an image pick-up element, has a more favorable optical performance and a super-wide view angle is provided. And in this invention, the imaging device provided with such a wide-angle optical system is provided.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the 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.

<Description of wide-angle optical system>
FIG. 1 is a lens cross-sectional view schematically illustrating the configuration of the wide-angle optical system in the embodiment.

  In FIG. 1, this wide-angle optical system 1 has an optical image of an object (subject) on a predetermined imaging surface, for example, on a light receiving surface (image surface) of an image sensor 15 that converts an optical image into an electrical signal. The image pickup apparatus is preferably provided with an imaging device configured to form a front group 11, a diaphragm 12, and a rear group 13 in order from the object side to the image side. 11, in order from the object side to the image side, a first lens 111 having negative optical power, a second lens 112 having negative optical power, and a third lens 113 having positive optical power; The rear group 13 is an optical system including a fifth lens 131 having a positive optical power. The wide-angle optical system 1 illustrated in FIG. 1 has the same configuration as the wide-angle optical system 1A (FIG. 5) of Example 1 described later.

  In FIG. 1, the first lens 111 is a negative meniscus lens convex toward the object side, the second lens is a biconcave negative lens, and the third lens 113 is a positive meniscus lens convex toward the object side. In the present embodiment, the fourth lens is a positive meniscus lens convex toward the object side. The stop 12 is an aperture stop. The fifth lens 131 is a biconvex positive lens. In the present embodiment, the second to fifth lenses 112, 113, 114, and 131 are aspheric on both surfaces. In the present embodiment, the second and fifth lenses are lenses made of a resin material such as plastic.

  In such a wide-angle optical system 1 shown in FIG. 1, the first to fifth lenses 111, 112, 113, 114, 131 are arranged in this order, so that a wide angle of view, particularly a super-wide angle of 180 degrees or more is obtained. The size of the wide-angle optical system 1 can be reduced while the angle of view is achieved and better optical performance is maintained. Further, by arranging two negative lenses of the first and second lenses 111 and 112 in order from the object side to the image side, the optical power of the negative lens is appropriately shared, and the off-axis ray incident angle on the image plane Can be suppressed. By arranging the positive third lens 113 and the fourth lens 114 on the object side, the aberration correction is shared by the third and fourth lenses 113 and 114, and a better aberration correction is possible. .

  According to the wide-angle optical system 1 having such a configuration, a small-sized wide-angle optical system 1 that can cope with high pixels of the image sensor 15 and has better optical performance and an ultra-wide angle of view is provided.

  Further, a filter 14 and an image sensor 15 are disposed on the image side of the wide-angle optical system 1. The filter 14 is a parallel plate-like optical element, and schematically represents various optical filters, a cover glass of the image sensor, 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 15 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 formed by the wide-angle optical system 1, and performs predetermined conversion. This is an element that outputs to an image processing circuit (not shown in FIG. 1). As a result, the optical image of the object on the object side is guided by the wide-angle optical system 1 along the optical axis AX to the light receiving surface of the image sensor 15, and the optical image of the object is captured by the image sensor 15. Therefore, in the present embodiment, an imaging device including such a wide-angle optical system 1 is also provided.

  In the wide-angle optical system 1, each of the second to fifth lenses 112, 113, 114, and 131 has at least one aspheric surface. In the example shown in FIG. 1, the second to fifth lenses 112, 113, 114, and 131 are aspheric on both sides. Therefore, the wide-angle optical system 1 can effectively reduce the total optical length while reducing various aberrations.

  In the wide-angle optical system 1, the first lens 111 is a glass material lens. Therefore, the wide-angle optical system 1 can ensure reliability in terms of robustness, chemical resistance, water resistance, and the like. In particular, in a vehicle-mounted application, the lens front surface of the wide-angle optical system 1 is often exposed, so that robustness, chemical resistance, waterproofness, and the like are required. Therefore, this wide-angle optical system 1 is advantageous in terms of robustness, chemical resistance, waterproofness, and the like.

  In the wide-angle optical system 1, the third lens 113 is a positive meniscus lens convex toward the object side. Therefore, the wide-angle optical system 1 can correct various aberrations more favorably.

  In the wide angle optical system 1, the fourth lens 114 has positive optical power. Therefore, in this wide-angle optical system 1, the optical power of the positive lens can be appropriately shared by the third and fourth lenses 113 and 114, so that the error sensitivity of the positive lens can be reduced.

  In the wide-angle optical system 1, the fifth lens 131 is a resin material lens having at least one aspheric surface. In the example illustrated in FIG. 1, the fifth lens 131 has two aspheric surfaces. Therefore, with this wide-angle optical system 1, it is possible to obtain a high-performance lens at a low cost.

In the wide-angle optical system 1, it is preferable that the following conditional expression (1) is satisfied when the Abbe number of the third lens 113 is ν3.
ν3 <30 (1)

  In this configuration, if the upper limit of conditional expression (1) is exceeded, the Abbe numbers in the first and second lenses 111 and 112 having negative optical power and the third lens 113 having positive optical power are both present. This is unfavorable because it is difficult to correct both axial chromatic aberration and lateral chromatic aberration.

In the wide-angle optical system 1, it is preferable that the following conditional expression (2) is satisfied when the Abbe number of the fifth lens 131 is ν5.
ν5> 45 (2)

  In this configuration, if the lower limit of conditional expression (2) is not reached, the Abbe number balance in the front group 11 and the rear group 13 is lost, and it is difficult to satisfactorily correct axial chromatic aberration, which is not preferable.

In the wide-angle optical system 1, when the curvature radius on the object side of the fifth lens 131 is R5f and the curvature radius on the image plane side of the fifth lens 131 is R5r, the following conditional expression (3) is satisfied. It is to be.
−10 <R5f / R5r <0 (3)

  In this configuration, if the upper limit of conditional expression (3) is exceeded, the fifth lens 131 becomes a meniscus lens, which makes it difficult to satisfactorily correct spherical aberration and astigmatism, which is not preferable. On the other hand, if the lower limit of conditional expression (3) is not reached, the curvature and surface angle of the image side surface of the fifth lens 131 will become too large, making it difficult to manufacture, which is not preferable.

In the wide-angle optical system 1, it is preferable that the following conditional expression (4) is satisfied when the focal length of the front group 11 is Ff and the focal length of the rear group 13 is Fr.
0 <Fr / Ff <1 (4)

  In this configuration, if the lower limit of conditional expression (4) is not reached, so-called retrofocusing occurs, so that the back focus is extended and it becomes difficult to downsize the optical system 1, which is not preferable. If the upper limit of conditional expression (4) is exceeded, the positive optical power of the front group 11 becomes strong, which makes it difficult to achieve a super wide angle of view, which is not preferable.

In this wide-angle optical system 1, when the radius of curvature of the fourth lens 114 on the object side is R4f and the radius of curvature of the fourth lens 131 is on the image plane side, the following conditional expression (5) is satisfied. Is preferred.
-1 <R4f / R4r <1 (5)

  In this configuration, if the upper limit of the conditional expression (5) is exceeded, the fourth lens 114 has an asymmetric shape with the fifth lens 131 across the aperture, so that spherical aberration, coma and astigmatism are excellent. It becomes difficult to correct, which is not preferable. On the other hand, if the lower limit of conditional expression (5) is not reached, the optical power of the fourth lens 114 becomes loose, which makes it difficult to correct various aberrations favorably.

  In the wide-angle optical system 1, the lens surfaces facing the air are all aspherical surfaces except for the first lens 111 on the most object side. In the example shown in FIG. 1, the second to fifth lenses 112, 113, 114, and 131 are aspheric on both sides. Therefore, the wide-angle optical system 1 can achieve both compactness and high image quality of the wide-angle optical system 1.

  In this wide-angle optical system 1, the glass lens having an aspherical surface is a glass molded aspherical lens, a grounded aspherical glass lens, or a composite aspherical lens (aspherical resin is formed on the spherical glass lens. Thing). Glass molded aspherical lenses are preferable for mass production, and composite aspherical lenses have a high degree of design freedom because there are many types of glass materials that can serve as substrates. In particular, an aspherical lens using a high refractive index material is not easy to mold, so a composite aspherical lens is preferable. In the case of a single-sided aspherical surface, the advantages of the composite aspherical lens can be fully utilized.

<Description of digital equipment incorporating wide-angle optical system>
Next, a digital device provided with the above-described wide-angle optical system 1 will be described.

  FIG. 2 is a block diagram illustrating a configuration of the digital device according to the embodiment. In FIG. 2, the digital device 3 has 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 I / F unit for the imaging function. 37. As the digital device 3, for example, a digital still camera, a digital video camera, an imaging device such as a monitor camera for monitoring or in-vehicle use, a portable terminal having an imaging function such as a mobile phone or a personal digital assistant (PDA) Computers having an imaging function, such as personal computers and mobile computers, may include these peripheral devices (for example, a mouse, a scanner, a printer, and the like).

  The imaging unit 30 includes the wide-angle optical system 1 and the imaging element 15. The wide-angle optical system 1 forms an optical image of a subject on a predetermined image plane, on the image sensor 15 in the example shown in FIG. Light rays from the subject are imaged on the light receiving surface of the image sensor 15 by the wide-angle optical system 1 and become an optical image of the subject.

  The imaging element 15 is an element that converts the optical image of the subject guided by the wide-angle optical system 1 into an electrical signal. As described above, the optical image of the subject imaged by the wide-angle optical system 1 is R, The signal is converted into an electrical signal (image signal) of G and B color components, and is output to the image generation unit 31 as an image signal of each color of R, G, and B. The image pickup device 15 is controlled by the control unit 35 to pick up either a still image or a moving image or to read out an output signal of each pixel in the image pickup device 15 (horizontal synchronization, vertical synchronization, transfer) and the like. . The image sensor 15 may be a solid-state image sensor such as a CCD or a CMOS, or may be a color image sensor or a monochrome image sensor.

  The image generation unit 31 performs amplification processing, digital conversion processing, and the like on the analog output signal from the image sensor 15, 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 of each pixel 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. It is composed of a RAM (Random Access Memory).

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

  In addition, if necessary, the image processing unit 33 could not be corrected by the wide-angle 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 image sensor 15. 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 15 by the wide-angle optical system 1 is distorted, it is possible to generate a natural image with substantially no distortion.

  Further, the image processing unit 33 may include a known peripheral illuminance decrease correction process that corrects a peripheral illuminance decrease in the optical image of the subject formed on the light receiving surface of the image sensor 15 as necessary. 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 dependency of the sensitivity in the image sensor 15, the vignetting of the lens, the cosine fourth law, etc., the correction data has a predetermined value that corrects the decrease in illuminance caused by these factors. Is set. By configuring in this way, even if the peripheral illuminance drops in the optical image of the subject guided to the image sensor 15 by the wide-angle optical system 1, it is possible to generate an image having sufficient illuminance to the periphery. It becomes.

  The drive unit 34 is a circuit that performs focusing of the wide-angle optical system 1 by operating a lens drive device (not shown) that moves the lens in the optical axis direction based on a control signal output from the control unit 35.

  The control unit 35 includes, for example, a microprocessor, a storage element, and peripheral circuits thereof, 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. The operation of each part of the / F unit 37 is controlled according to its function. In other words, the digital device 3 is controlled by the control unit 35 so as 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, a rewritable nonvolatile memory, or the like. 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 taking a still image, the control unit 35 controls each unit of the digital device 3 to take a still image and operates the lens driving device (not shown) via the drive unit 34 to perform focusing. I do. As a result, the focused optical image is periodically and repeatedly formed on the light receiving surface of the image sensor 15, converted into R, G, and B color component image signals, 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 (display device) (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. In this state, when a so-called unillustrated shutter button is pressed, 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 each unit of the digital device 3 to perform moving image shooting. After that, as in the case of still image shooting, the photographer refers to the display and adjusts so that the image of the subject obtained through the wide-angle optical system 1 falls within a desired position on the screen. be able to. In this case, as with still image shooting, moving image shooting is started by pressing the shutter button.

  During moving image shooting, the control unit 35 controls each unit of the digital device 3 to perform moving image shooting, and operates the lens driving device (not shown) via the drive unit 34 to perform focusing. As a result, the focused optical image is periodically and repeatedly formed on the light receiving surface of the image sensor 15, 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 the display (not shown). Then, when the shutter button 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 can correspond to the high pixels of the image sensor 15, and includes the small wide-angle optical system 1 having better optical performance and an ultra-wide angle of view. A simple imaging element 15 can be employed.

  Next, as specific examples of the digital apparatus provided with the wide-angle optical system 1, a case where the wide-angle optical system 1 is mounted on a mobile phone and a case where the wide-angle optical system 1 is mounted on an in-vehicle monitor camera are respectively described below. explain.

  FIG. 3 is an external configuration diagram of a camera-equipped cellular phone showing an embodiment of a digital device. 3A shows an operation surface of the mobile phone, and FIG. 3B shows a back surface of the operation surface, that is, a back surface.

  In FIG. 3, the mobile phone 5 is provided with an antenna 51 at the top, and on its operation surface, as shown in FIG. 3A, a rectangular display 52, activation of image shooting mode, still image shooting and moving image An image shooting button 53 for switching to shooting, a shutter button 55, and a dial button 56 are provided. The cellular phone 5 incorporates a circuit for realizing a telephone function using a cellular phone network, and includes the above-described imaging unit 30, image generating unit 31, image data buffer 32, image processing unit 33, and driving unit. 34, the control part 35, and the memory | storage part 36 are incorporated, and the wide angle optical system 1 of the imaging part 30 faces the back surface.

  When the image capturing button 53 is operated, a control signal indicating the operation content is output to the control unit 35, and the control unit 35 executes an operation corresponding to the operation content. When the shutter button 55 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. In this way, a still image or a moving image is captured.

  The wide-angle optical system 1 according to the present embodiment is attached to a predetermined position, and is a monitor camera that images a subject in a predetermined area around the attached position, for example, an in-vehicle monitor camera that images a peripheral area of a vehicle. It is suitably mounted.

  FIG. 4 is a diagram for explaining an overview of an in-vehicle monitor camera showing an embodiment of a digital device. In FIG. 4, the in-vehicle monitor camera 7 is installed at a predetermined position at the rear of the vehicle 9 so as to image the rear of the vehicle 9, for example, and the captured subject image is installed on a dashboard, for example. Is displayed on the monitor (not shown). The in-vehicle monitor camera 7 is normally attached to the vehicle 9 in a posture inclined obliquely downward so that the optical axis AX faces obliquely downward because an upward visual field of the vehicle 9 is not required. And in the vertical direction, it has an angle of view 2φ with the horizontal line passing through the mounting position of the monitor camera 7 as the upper end. In this specification, the angle of view in the left-right direction is also 2φ as in the up-down direction.

  The flow of processing when the vehicle-mounted camera 7 having such a configuration is used as a back monitor will be outlined below. For example, the user (driver) turns the vehicle body 7 back while looking at a monitor (display device) (not shown) installed on the dashboard of the vehicle body 9. At this time, if the area that the driver wants to check is different from the area that the in-vehicle camera 7 is capturing, the driver performs a predetermined operation such as operating an operation button (not shown) provided on the dashboard. I do.

  In response to this operation, the control unit 35 controls the drive unit 34 to adjust the orientation of the imaging unit 30. Subsequently, the control unit 35 drives the lens driving device of the imaging unit 30 to perform focusing of the wide-angle optical system 1. As a result, a focused optical image is formed on the light receiving surface of the image sensor 15, converted into image signals of R, G, and B color components, and then output to the image generator 31. The image signal is temporarily stored in the image data buffer 32, and image processing is performed by the image processing unit 33. In this way, a substantially natural image of the region that the driver wants to confirm is displayed on the monitor installed on the dashboard.

<Description of More Specific Embodiment of Wide Angle Optical System>
Hereinafter, a specific configuration of the wide-angle optical system 1 shown in FIG. 1, that is, the wide-angle optical system 1 provided in the imaging unit 30 mounted on the digital device 3 as shown in FIG. 3 will be described with reference to the drawings. To do.

  FIG. 5 is a cross-sectional view showing the arrangement of lens groups in the wide-angle optical system of Example 1. 10 and 11 are aberration diagrams in the wide-angle optical system of Example 1. FIG.

  As shown in FIG. 5, the wide-angle optical system 1A according to the first embodiment includes a front group Grf, a stop ST, and a rear group Grr in order from the object side to the image side. In order from the image side to the image side, a negative meniscus lens (first lens L1) convex toward the object side, a negative biconcave lens (second lens L2), and a positive meniscus lens (third lens L3) convex toward the object side And a positive meniscus lens convex to the object side (fourth lens L4), the stop ST is an aperture stop, and the rear group Grr is a biconvex positive lens (fifth lens). 131). Each of the second to fifth lenses L2 to L5 is aspheric on both surfaces, and the second and fifth lenses L2 and L5 are lenses made of a resin material such as plastic.

  Then, on the image side of the rear group Grr (the image side of the fifth lens L5), the light receiving surface of the imaging element SR is disposed through a parallel plate FT as a filter. The parallel plate FT is a cover glass of various optical filters or an image sensor.

  In FIG. 5, 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 1). It is assumed that a surface marked with “*” in ri is an aspherical surface. The aperture stop ST, both surfaces of the parallel plate FT, and the light receiving surface of the image sensor SR are also handled as one surface. The meaning of such handling and symbols is the same for Examples 2 to 5 described later (FIGS. 6 to 9). However, it does not mean that they are exactly the same. For example, in FIGS. 5 to 9 of the first to fifth embodiments, the lens surface arranged closest to the object side is denoted by the same reference numeral (r1). However, it does not mean that these curvatures and the like are the same throughout the first to fifth embodiments.

  Under such a configuration, the light beam incident from the object side sequentially has the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the aperture stop ST, the fifth, along the optical axis AX. An optical image of the object is formed on the light receiving surface of the image sensor SR through the lens L5 and the parallel plate FT. In the image sensor SR, the optical image is converted into an electrical signal. This electrical signal is subjected to predetermined digital image processing as necessary, and recorded as a digital video signal, for example, in a memory of a digital device such as a digital camera or transmitted to another digital device by wired or wireless communication. Or

  The construction data of each lens in the wide-angle optical system 1A of Example 1 is shown below.

Numerical example 1
Unit mm
Surface data surface number r d nd νd
Object ∞ ∞
1 16.70 0.70 1.883 40.81
2 4.94 3.12
3 * -49.95 0.80 1.53048 55.72
4 * 1.83 0.65
5 * 1.76 1.36 1.847 23.82
6 * 1.56 1.14
7 * 2.44 1.10 1.77601 23.99
8 * 5.96 0.32
9 (Aperture) ∞ 0.51
10 * 4.36 1.98 1.53048 55.72
11 * -1.01 1.21
12 ∞ 0.50 1.51680 64.20
13 ∞ 1.24
Image plane ∞
Aspheric data 3rd surface K = -100, A4 = 0, A6 = -3.95E-06, A8 = -1.65E-07
Fourth surface K = −1.0, A4 = 0, A6 = −4.81E-04, A8 = −2.74E-05
5th surface K = -0.8, A4 = 0, A6 = -8.35E-06, A8 = -4.55E-06
6th surface K = -3.3, A4 = 0, A6 = -1.07E-03, A8 = 1.76E-04
7th surface K = -8.5, A4 = 0, A6 = 0.19E-03, A8 = 6.86E-04
8th surface K = 31.0, A4 = 0, A6 = 7.14E-02, A8 = -3.56E-02
10th surface K = -4.6, A4 = 0, A6 = 4.06E-03, A8 = -5.28E-04
11th surface K = -1.7, A4 = 0, A6 = 9.91E-03, A8 = -7.52E-04
Various data focal length 0.839
F number 2.762
Half angle of view 95.548
Statue height 2.389
Total lens length 15.342
BF 1.665
In the above-described surface data, the surface number corresponds to the number i of the symbol ri (i = 1, 2, 3,. A surface marked with * in the number i indicates an aspheric surface (aspherical refractive optical surface or a surface having a refractive action equivalent to an aspheric surface).

  Also, “r” is the radius of curvature of each surface (unit is mm), “d” is the distance between the lens surfaces on the optical axis in the infinite focus state (axis upper surface distance), and “nd” is The refractive index “νd” of each lens with respect to the d-line (wavelength 587.56 nm) indicates the Abbe number. Since the aperture stop ST, both surfaces of the plane parallel plate FT, and each of the light receiving surfaces of the image sensor SR 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). The aspherical shape of the optical surface is defined by the following equation using a local orthogonal coordinate system (x, y, z) in which the surface vertex is the origin and the direction from the object toward the image sensor is the positive z-axis direction. is doing.
z (h) = ch ² / [1 + √ {1- (1 + K) c ² h ² }] + ΣAi · h ⁱ
However, z (h): Amount of displacement in the z-axis direction at the position of height h (based on the surface vertex)
h: height in a direction perpendicular to the z-axis (h ² = x ² + y ² )
c: Paraxial curvature (= 1 / radius of curvature)
Ai: i-th order aspheric coefficient
K: quadratic surface parameter (cone coefficient)
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”.

  Each aberration in the wide-angle optical system 1A of Example 1 under the lens arrangement and configuration as described above is shown in FIGS. 10 and 11, respectively. 10A shows spherical aberration (sine condition) (LONGITUDINAL SPHERICAL ABERRATION), FIG. 10B shows astigmatism (ASTIGMATISM FIELD CURVER), and FIG. 10C shows distortion aberration. Indicates (DISTORTION). The horizontal axis of the spherical aberration represents the focal position shift in mm, and the vertical axis represents the value normalized by the 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 angle of view in units of degrees (here, up to a half angle of view of 90 degrees). Show). Moreover, in the figure of astigmatism, the broken line represents sagittal, and the solid line represents tangential. In the diagram of spherical aberration, aberrations of three wavelengths, d-line (wavelength 587.56 nm) are shown by a one-dot chain line, g-line (wavelength 435.84 nm) is shown by a broken line, and C-line (wavelength 656.28 nm) is shown by a solid line. is there. The diagrams of astigmatism and distortion are the results when the d-line (wavelength 587.56 nm) is used. FIG. 11 shows lateral aberration, the left side shows the case of a tangential (meridional) surface, the right side shows the case of a sagittal (radial) surface, and in the case of the maximum field angle and the intermediate field angle in order from the top. And the case on the axis, respectively. The incident ray height with respect to the chief ray is expressed in mm, and the vertical axis represents the deviation from the chief ray on the image plane in mm. In the diagram of transverse aberration, aberrations at three wavelengths, d-line (wavelength 587.56 nm) as a solid line, g-line (wavelength 435.84 nm) as a broken line, and C-line (wavelength 656.28 nm) as a dashed-dotted line are shown. is there.

  The above handling is the same in the construction data according to Examples 2 to 5 shown below and FIGS. 12 to 19 showing the respective aberrations.

  FIG. 6 is a cross-sectional view showing the arrangement of lens groups in the wide-angle optical system of Example 2. 12 and 13 are aberration diagrams in the wide-angle optical system of Example 2. FIG.

  As shown in FIG. 6, the wide-angle optical system 1B according to the second embodiment includes a front group Grf, a stop ST, and a rear group Grr in order from the object side to the image side. In order from the image side to the image side, a negative meniscus lens (first lens L1) convex toward the object side, a negative biconcave lens (second lens L2), and a positive meniscus lens (third lens L3) convex toward the object side And a positive meniscus lens convex to the object side (fourth lens L4), the stop ST is an aperture stop, and the rear group Grr is a biconvex positive lens (fifth lens). 131). Each of the second to fifth lenses L2 to L5 is aspheric on both surfaces, and the fifth lens L5 is a lens made of a resin material such as plastic.

  Then, on the image side of the rear group Grr (the image side of the fifth lens L5), the light receiving surface of the imaging element SR is disposed through a parallel plate FT as a filter. The parallel plate FT is a cover glass of various optical filters or an image sensor.

  The construction data of each lens in the wide-angle optical system 1B of Example 2 is shown below.

Numerical example 2
Unit mm
Surface data surface number r d nd νd
Object ∞ ∞
1 16.228 0.98 1.792 47.7
2 5.931 3.78
3 * -214.363 0.90 1.773 49.7
4 * 1.848 1.36
5 * 2.296 2.92 1.847 23.8
6 * 1.766 0.73
7 * 1.742 1.40 1.795 47.3
8 * 7.956 0.36
9 (Aperture) ∞ 0.59
10 * 4.063 1.92 1.53048 55.7
11 * -1.231 0.50
12 ∞ 0.50 1.51680 64.20
13 ∞ 0.57
Image plane ∞
Aspheric data 3rd surface K = 500, A4 = 0, A6 = -5.99E-06, A8 = 4.75E-09
4th surface K = -1.1, A4 = 0, A6 = -1.44E-04, A8 = -9.39E-06
5th surface K = -0.7, A4 = 0, A6 = -2.29E-04
6th surface K = -2.9, A4 = 0, A6 = 8.57E-05, A8 = 1.80E-04
7th surface K = -2.2, A4 = 0, A6 = 3.69E-03, A8 = 1.82E-03
8th surface K = 47.7, A4 = 0, A6 = 4.95E-02, A8 = -2.95E-02
10th surface K = −2.8, A4 = 0, A6 = 2.41E-03, A8 = −3.93E-04
Eleventh surface K = −2.6, A4 = 0, A6 = 9.38E-03, A8 = -1.28E-03
Various data focal length 0.936
F number 2.762
Half angle of view 98.000
Statue height 2.654
Total lens length 16.337
BF 1.403
The spherical aberration (sinusoidal condition), astigmatism and distortion in the wide-angle optical system 1B of Example 2 under the lens arrangement and configuration as described above are shown in FIGS. 12 (C), and the lateral aberration diagram is shown in FIG.

  FIG. 7 is a sectional view showing the arrangement of lens groups in the wide-angle optical system of Example 3. 14 and 15 are aberration diagrams of the lens unit in the wide-angle optical system of Example 3. FIG.

  As shown in FIG. 7, the wide-angle optical system 1C according to the third embodiment includes a front group Grf, a stop ST, and a rear group Grr in order from the object side to the image side. In order from the image side to the image side, a negative meniscus lens (first lens L1) convex toward the object side, a negative biconcave lens (second lens L2), and a positive meniscus lens (third lens L3) convex toward the object side And a positive meniscus lens convex to the object side (fourth lens L4), the stop ST is an aperture stop, and the rear group Grr is a biconvex positive lens (fifth lens). 131). The second lens L2 has an aspheric surface on the image side (single-sided aspheric surface), and the third to fifth lenses L3 to L5 have both aspheric surfaces. The fifth lens L5 is a lens made of a resin material such as plastic.

  Then, on the image side of the rear group Grr (the image side of the fifth lens L5), the light receiving surface of the imaging element SR is disposed through a parallel plate FT as a filter. The parallel plate FT is a cover glass of various optical filters or an image sensor.

  The construction data of each lens in the wide-angle optical system 1C of Example 3 is shown below.

Numerical Example 3
Unit mm
Surface data surface number r d nd νd
Object ∞ ∞
1 15.29 1.67 1.883 40.81
2 6.02 3.95
3 -52.78 0.80 1.694 53.39
4 * 1.80 0.36
5 * 1.75 2.17 1.828 23.86
6 * 1.58 1.39
7 * 2.27 1.34 1.734 41.51
8 * 11.25 0.37
9 (Aperture) ∞ 0.54
10 * 4.22 2.00 1.53048 55.72
11 * -1.06 0.50
12 ∞ 0.50 1.51680 64.20
13 ∞ 0.74
Image plane ∞
Aspheric data 4th surface K = -0.9, A4 = 0, A6 = -3.11E-04, A8 = -1.84E-05
5th surface K = -0.8, A4 = 0, A6 = -5.70E-04, A8 = -1.89E-05
6th surface K = -2.7, A4 = 0, A6 = -1.14E-03, A8 = 2.00E-04
7th surface K = -4.6, A4 = 0, A6 = 1.29E-03, A8 = 1.27E-03
8th surface K = 77.9, A4 = 0, A6 = 3.50E-02, A8 = -1.09E-02
10th surface K = -5.7, A4 = 0, A6 = 3.80E-03, A8 = -3.87E-04
11th surface K = -2.0, A4 = 0, A6 = 5.66E-03
Various data focal length 0.85
F number 2.762
Half angle of view 97.0
Statue height 2.564
Total lens length 16.152
BF 1.572
The spherical aberration (sinusoidal condition), astigmatism and distortion in the wide-angle optical system 1C of Example 3 under the lens arrangement and configuration as described above are shown in FIGS. 14 (C), and the lateral aberration diagram is shown in FIG.

  FIG. 8 is a sectional view showing the arrangement of lens groups in the wide-angle optical system of Example 4. FIGS. 16 and 17 are aberration diagrams in the wide-angle optical system of Example 4. FIGS.

  As shown in FIG. 8, the wide-angle optical system 1D according to the fourth embodiment includes, in order from the object side to the image side, a front group Grf, a stop ST, and a rear group Grr. In order from the image side to the image side, a negative meniscus lens (first lens L1) convex toward the object side, a negative biconcave lens (second lens L2), and a positive meniscus lens (third lens L3) convex toward the object side And a positive meniscus lens convex to the object side (fourth lens L4), the stop ST is an aperture stop, and the rear group Grr is a biconvex positive lens (fifth lens). 131). Each of the second to fifth lenses L2 to L5 is aspheric on both surfaces, and the second and fifth lenses L2 and L5 are lenses made of a resin material such as plastic.

  Then, on the image side of the rear group Grr (the image side of the fifth lens L5), the light receiving surface of the imaging element SR is disposed through a parallel plate FT as a filter. The parallel plate FT is a cover glass of various optical filters or an image sensor.

  The construction data of each lens in the wide-angle optical system 1D of Example 4 is shown below.

Numerical Example 4
Unit mm
Surface data surface number r d nd νd
Object ∞ ∞
1 19.652 0.815 1.883 40.8
2 7.397 4.607
3 * -200.000 0.932 1.544 57.1
4 * 1.744 1.118
5 * 2.144 2.151 1.847 23.8
6 * 2.055 1.692
7 * 2.766 1.398 1.633 31.7
8 * 7.554 0.375
9 (Aperture) ∞ 0.552
10 * 5.290 2.334 1.544 57.1
11 * -1.205 0.582
12 ∞ 0.582 1.51680 64.20
13 ∞ 0.902
Image plane ∞
Aspheric data 3rd surface K = 0, A4 = 0, A6 = -2.70E-06, A8 = 3.07E-08
4th surface K = -1.0, A4 = 0, A6 = -1.67E-04, A8 = -8.41E-06
5th surface K = -0.7, A4 = 0, A6 = -5.87E-05, A8 = -1.25E-05
6th surface K = -2.6, A4 = 0, A6 = -4.45E-04, A8 = 4.19E-05
7th surface K = -5.5, A4 = 0, A6 = 7.79E-04, A8 = 4.39E-04
8th surface K = 37.6, A4 = 0, A6 = 3.21E-02, A8 = -1.38E-02
Tenth surface K = -7.3, A4 = 0, A6 = 1.84E-03, A8 = -1.82E-04
11th surface K = −1.7, A4 = 0, A6 = 2.87E-03, A8 = −7.84E-05
Various data focal length 0.929
F number 2.762
Half angle of view 97.0
Statue height 2.874
Total lens length 17.843
BF 1.869
FIG. 16A, FIG. 16B, and FIG. 16 show spherical aberration (sine condition), astigmatism, and distortion in the wide-angle optical system 1D of Example 4 under the lens arrangement and configuration as described above. 16 (C), and the lateral aberration diagram is shown in FIG.

  FIG. 9 is a sectional view showing the arrangement of lens groups in the wide-angle optical system of Example 5. 18 and 19 are aberration diagrams of the wide-angle optical system of Example 5. FIG.

  As shown in FIG. 9, the wide-angle optical system 1E of Example 5 includes, in order from the object side to the image side, a front group Grf, a stop ST, and a rear group Grr. In order from the image side to the image side, a negative meniscus lens (first lens L1) convex toward the object side, a negative biconcave lens (second lens L2), and a positive meniscus lens (third lens L3) convex toward the object side And a positive meniscus lens convex to the object side (fourth lens L4), the stop ST is an aperture stop, and the rear group Grr is a biconvex positive lens (fifth lens). 131). Each of the second to fifth lenses L2 to L5 is aspheric on both surfaces, and the second and fifth lenses L2 and L5 are lenses made of a resin material such as plastic.

  Then, on the image side of the rear group Grr (the image side of the fifth lens L5), the light receiving surface of the imaging element SR is disposed through a parallel plate FT as a filter. The parallel plate FT is a cover glass of various optical filters or an image sensor.

  The construction data of each lens in the wide-angle optical system 1E of Example 5 is shown below.

Numerical Example 5
Unit mm
Surface data surface number r d nd νd
Object ∞ ∞
1 14.95 0.60 1.883 40.81
2 5.19 3.56
3 * -39.05 1.03 1.530 55.72
4 * 1.27 0.91
5 * 1.67 1.52 2.001 25.46
6 * 1.93 0.64
7 * 2.38 1.13 1.659 30.82
8 * 67.21 0.33
9 (Aperture) ∞ 0.52
10 * 6.86 2.32 1.530 55.72
11 * -0.99 0.84
12 ∞ 0.50 1.51680 64.20
13 ∞ 0.10
Image plane ∞
Aspheric data 3rd surface K = 53, A4 = 0, A6 = −6.03E-06, A8 = 6.90E-07
4th surface K = -0.9, A4 = 0, A6 = 1.32E-03, A8 = -1.70E-04
5th surface K = -1.0, A4 = 0, A6 = 4.52E-04, A8 = -1.26E-04
6th surface K = -3.5, A4 = 0, A6 = -1.28E-03, A8 = 4.82E-04
7th surface K = -3.3, A4 = 9.64.E-03, A6 = 2.77E-03, A8 = 2.13E-03
8th surface K = 50, A = 4.19.E-02, A6 = -4.84E-03, A8 = -5.17E-03
10th surface K = −383.7, A4 = 0, A6 = 3.18E-03, A8 = −6.63E-03
11th surface K = -1.4, A4 = 0, A6 = -7.87E-03, A8 = 2.11E-03
Various data focal length 1.05
F number 2.762
Half angle of view 95.0
Image height 2.304
Total lens length 13.849
BF 1.289
FIG. 18A, FIG. 18B, and FIG. 18 show spherical aberration (sine condition), astigmatism, and distortion in the wide-angle optical system 1E of Example 5 under the lens arrangement and configuration as described above. 18 (C), and the lateral aberration diagram is shown in FIG.

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

  As described above, the wide-angle optical systems 1A to 1E in Embodiments 1 to 5 satisfy the requirements according to the present invention, and as a result, can cope with the high pixels of the image sensor, and have better optics. When it is mounted on a digital device, it is sufficiently small, especially when it is mounted on an in-vehicle monitor camera or a portable terminal. In addition, the wide-angle optical systems 1A to 1E in Examples 1 to 5 above are super wide angles, in particular, a full field angle of 180 degrees (half field angle of 90 degrees) or more, more specifically 200 degrees (half field angle of 100 degrees) or more. Can be achieved.

  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.

It is a lens sectional view showing the composition typically for explanation of the wide angle optical system in an embodiment. 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. It is a figure for demonstrating the outline | summary of the vehicle-mounted monitor camera which shows one Embodiment of digital equipment. FIG. 3 is a cross-sectional view illustrating the arrangement of lens groups in the wide-angle optical system of Example 1. 6 is a cross-sectional view illustrating an arrangement of lens groups in a wide-angle optical system of Example 2. FIG. 6 is a cross-sectional view illustrating an arrangement of lens groups in a wide-angle optical system of Example 3. FIG. 6 is a cross-sectional view illustrating an arrangement of lens groups in a wide-angle optical system of Example 4. FIG. 10 is a cross-sectional view illustrating an arrangement of lens groups in a wide-angle optical system of Example 5. FIG. FIG. 6 is an aberration diagram (No. 1) in the wide-angle optical system of Example 1. FIG. 6 is an aberration diagram (part 2) in the wide-angle optical system of Example 1. FIG. 6 is an aberration diagram (No. 1) in the wide-angle optical system of Example 2. FIG. 6 is an aberration diagram (No. 2) in the wide-angle optical system of Example 2. FIG. 6 is an aberration diagram (No. 1) in the wide-angle optical system of Example 3. FIG. 10 is an aberration diagram (No. 2) in the wide-angle optical system of Example 3. FIG. 10 is an aberration diagram (No. 1) in the wide-angle optical system of Example 4. FIG. 10 is an aberration diagram (No. 2) in the wide-angle optical system of Example 4. FIG. 12 is an aberration diagram (No. 1) in the wide-angle optical system of Example 5. FIG. 10 is an aberration diagram (No. 2) in the wide-angle optical system of Example 5.

Explanation of symbols

AX Optical axis 1, 1A to 1J Wide-angle optical system 3 Digital device 5 Mobile phone 7 Monitor camera 9 Vehicle 11, Grf front group 12, ST aperture 13, Grr rear group 15, SR image sensor 111, L1 first lens 112, L2 Second lens 113, L3 Third lens 114, L4 Fourth lens 131, L5 Fifth lens

Claims (15)

In order from the object side to the image side, it consists of a front group, a stop, and a rear group.
The front group includes, in order from the object side to the image side, a first lens having negative optical power, a second lens having negative optical power, a third lens having positive optical power, It consists of 4 lenses,
The rear group includes a fifth lens having a positive optical power. The wide-angle optical system according to claim 1, wherein the fourth lens has a positive optical power. The wide-angle optical system according to claim 1 or 2, wherein the following conditional expression (1) is satisfied.
ν3 <30 (1)
However,
ν3: Abbe number of the third lens The wide-angle optical system according to any one of claims 1 to 3, wherein the following conditional expression (2) is satisfied.
ν5> 45 (2)
However,
ν5: Abbe number of the fifth lens The wide-angle optical system according to any one of claims 1 to 4, wherein the following conditional expression (3) is satisfied.
−10 <R5f / R5r <0 (3)
However,
R5f: radius of curvature of the fifth lens on the object side R5r: radius of curvature of the fifth lens on the image plane side The wide-angle optical system according to claim 1, wherein the following conditional expression (4) is satisfied.
0 <Fr / Ff <1 (4)
However,
Ff: focal length of the front group Fr: focal length of the rear group The wide-angle optical system according to claim 1, wherein the following conditional expression (5) is satisfied.
-1 <R4f / R4r <1 (5)
However,
R4f: radius of curvature of the fourth lens on the object side R4r: radius of curvature of the fourth lens on the image plane side The wide-angle optical system according to any one of claims 1 to 7, wherein the third lens is a meniscus lens convex toward the object side. The wide-angle optical system according to any one of claims 1 to 8, wherein each of the second to fifth lenses has at least one aspherical surface. The wide angle optical system according to any one of claims 1 to 9, wherein the first lens is a lens made of a glass material. The wide-angle optical system according to any one of claims 1 to 10, wherein the fifth lens is a lens made of a resin material having at least one aspherical surface. The wide-angle optical system according to any one of claims 1 to 11,
An image pickup apparatus comprising: an image pickup device that picks up an optical image of a subject formed by the wide-angle optical system. The imaging apparatus according to claim 12, further comprising an image processing unit that performs predetermined image processing on an output of the imaging element. The imaging apparatus according to claim 13, wherein the predetermined image processing includes distortion correction processing for correcting distortion in the optical image of the subject formed on a light receiving surface of the imaging element. The imaging apparatus according to claim 13, wherein the predetermined image processing includes illuminance correction processing for correcting a decrease in peripheral illuminance in an optical image of the subject formed on a light receiving surface of the imaging element.

Images