Imaging optical system and optical imaging device

Abstract

The present disclosure provides an optical system (10) comprising: a first lens (11) having a negative refractive power, and a surface (11b) on the image side thereof being a concave surface; a second lens (12) having a negative refractive power, and a surface (12b) on the image side thereof being a concave surface; a third lens (13) having a positive refractive power, and a surface (13b) on the image side thereof being a concave surface; a fourth lens (14) having a positive refractive power, and a surface (14b) on the image side thereof being a convex surface; a fifth lens (15) having a positive refractive power, and a surface (15a) on the object side thereof being a concave surface, and a surface (15b) on the image side thereof being a convex surface; a sixth lens (16) having a negative refractive power, and a surface (16a) on the object side thereof being a concave surface, and a surface (16b) on the image side thereof being a convex surface; a seventh lens (17) having a positive refractive power, and a surface (17a) on the object side thereof being an aspherical surface having a convex central portion and at least one inflection point on a peripheral portion of the central portion, and a surface (17b) on the image side thereof being a convex surface; and an eighth lens (18) having a surface (18a) on the object side thereof being a concave surface, and a surface (18b) on the image side thereof being an aspherical surface having a concave central portion and at least one inflection point on a peripheral portion of the central portion.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an imaging optical system having a plurality of lenses, and an optical imaging device having the same. BACKGROUND

[0002] Image photographing devices are increasingly used in a wide range of applications, such as vehicle-mounted applications, identification recognition applications, entertainment applications, and home appliance AI support applications, and thus contribute to the development of science and technology. In particular, mobile terminals are very important projects as a civil use.

[0003] In particular, in image photographing devices mounted on mobile terminals, in recent years, three or more imaging devices are generally provided.

[0004] For example, a camera lens (imaging optical system) having a general zoom mechanism is a lens in which an optical zoom lens satisfying all field angles from a wide angle to a telephoto is mounted. In the zoom lens, the ratio of the focal length from the widest angle end to the longest telephoto end is referred to as the zoom ratio, which is an important parameter of the zoom lens.

[0005] However, for the optical zoom lens, since two or more lens elements (groups) moving in the optical axis direction are generally required inside the lens, the size of the zoom lens itself becomes large, and thus it is not realistic to mount the optical zoom lens on a mobile terminal from the viewpoint of securing a movable space.

[0006] Therefore, in the image photographing device mounted on the mobile terminal, a plurality of imaging devices (for example, an imaging device dedicated to a super wide angle, an imaging device dedicated to a standard field angle, and an imaging device dedicated to a telephoto) each having a single focal length different lens (optical system) are arranged, and the same zoom effect as the optical zoom lens is achieved electronically by combining output images output from each imaging device.

[0007] In the mobile terminal, as in the general camera lens, enlargement of the zoom ratio is a demand of the market, and each company has mounted a lens having a longer focal length as a lens dedicated to a telephoto.

[0008] On the other hand, as a lens dedicated to a wide angle, a lens having a field angle (hereinafter referred to as "FOV") of about 120° is mounted, and in the lens dedicated to a wide angle, each company has also proposed various proposals.

[0009] For example, in Patent Documents 1 and 2 CNA-107577031, CNA-107305274, a super wide angle lens having a FOV of 130° or more for a surveillance camera and a motion close-up is proposed.

[0010] These are so-called reverse telephoto type (retro focus type) optical systems that have a concave-convex lens having a large negative refractive power disposed on a lens on the object side (front), and a lens having a positive refractive power disposed on the image side of the lens, and an aperture stop disposed in the middle of the optical system, and a large number of spherical glass lenses are used. In this type of optical system, the field angle can be expanded, and the pupil magnification can be easily expanded, whereby the amount of peripheral light can be substantially ensured. However, since the overall length and the back focal length of the lens (optical system) itself need to be lengthened, the size becomes large, and it is difficult to mount in a mobile terminal or the like.

[0011] On the other hand, in Patent Literature 3 and Patent Literature 4, a wide-angle lens whose size can be mounted in a mobile terminal and whose field angle is about 120° is proposed. These are optical systems called so-called telephoto type, which are generally used in mobile terminals. This wide-angle lens of the telephoto type can shorten the overall length while removing aberration by using a large number of aspherical lenses, thereby ensuring sufficient imaging performance.

[0012] However, in this optical system, in the case of further expanding the field angle, since it is not a type that compensates for the decrease in the amount of peripheral light caused by the Cos4 power law using the pupil magnification as in the reverse telephoto type optical system, a structure that compensates for the decrease in the amount of peripheral light using the light convergence caused by the distortion aberration is required. In this case, in the lens of the present proposal, since it is required to greatly change the shape of the end portion away from the optical axis compared to the vicinity of the center in the lenses of L1, L4, L5, and L6, the lens is difficult to shape, thereby resulting in not only a decrease in productivity but also difficulty in ensuring the imaging performance itself.

[0013] Prior Art Documents

[0014] Patent Literature

[0015] Patent Literature 1: Published Patent Application CN107577031A

[0016] Patent Literature 2: Published Patent Application CN107305274A

[0017] Patent Literature 3: Published Patent Application CN108732716A

[0018] Patent Literature 4: Published Patent Application CN107957621A SUMMARY

[0019] PROBLEMS TO BE SOLVED BY THE INVENTION

[0020] Therefore, an object of the present disclosure is to provide an imaging optical system that can maintain sufficient imaging performance despite being small, and that can obtain a large field angle, and an optical imaging device having the same.

[0021] Solutions for resolving the problem

[0022] The camera optical system of the present disclosure has:

[0023] a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged in order in a direction from an object side to an image side;

[0024] The first lens has a negative refractive power, and an image-side surface thereof is a concave surface;

[0025] The second lens has a negative refractive power, and an image-side surface thereof is a concave surface;

[0026] The third lens has a positive refractive power, and an image-side surface thereof is a concave surface;

[0027] The fourth lens has a positive refractive power, and an image-side surface thereof is a convex surface;

[0028] The fifth lens has a positive refractive power, and an object-side surface thereof is a concave surface, and an image-side surface thereof is a convex surface;

[0029] The sixth lens has a negative refractive power, and an object-side surface thereof is a concave surface, and an image-side surface thereof is a convex surface;

[0030] The seventh lens has an object-side surface that is an aspherical surface having a convex central portion and at least one inflection point on a peripheral portion of the central portion, and an image-side surface that is a convex surface;

[0031] The eighth lens has an object-side surface that is a concave surface, and an image-side surface that is an aspherical surface having a concave central portion and at least one inflection point on a peripheral portion of the central portion;

[0032] When a focal length of the first lens is set as f1, a focal length of the second lens is set as f2, a composite focal length of the first lens and the second lens is set as f12, a focal length of the third lens is set as f3, a distance along an optical axis from an image-side surface of the third lens to an object-side surface of the fourth lens is set as T34, and a distance along the optical axis from an image-side surface of the sixth lens to an object-side surface of the seventh lens is set as T67, the following is satisfied:

[0033] |f1 / f2| < 6

[0034] |f12 / f3| < 0.5

[0035] 0 < T67 / T34 < 1.0.

[0036] The camera optical system has an aperture stop, and the aperture stop is disposed between the third lens and the fourth lens;

[0037] When a distance along the optical axis from the object side surface of the first lens to the imaging surface is set as TL, and a maximum image height is set as ImgH, the following can be satisfied:

[0038] TL / ImgH < 3.

[0039] Further, in the imaging optical system,

[0040] When a radius of curvature of the object side surface of the fourth lens is set as R7, and a radius of curvature of the image side surface of the fourth lens is set as R8, the following can be satisfied:

[0041] 0 < (R7+R8) / (R7-R8) < 1.0.

[0042] Further, in the imaging optical system,

[0043] When a distance along the optical axis from the image side surface of the first lens to the object side surface of the second lens is set as T12, a distance along the optical axis from the image side surface of the second lens to the object side surface of the third lens is set as T23, and a distance along the optical axis from the image side surface of the third lens to the object side surface of the fourth lens is set as T34, the following can be satisfied:

[0044] 0 < T12 / T23 < 3.0

[0045] 0 < T23 / T34 < 2.0.

[0046] Further, in the imaging optical system,

[0047] When one-half of a maximum field angle is set as HFOV, and an F number is set as Fno, the following can be satisfied:

[0048] 2.0 < tan(HFOV)

[0049] 1.4 < Fno < 3.0.

[0050] Further, in the imaging optical system,

[0051] When a maximum effective radius of the object side surface of the first lens is set as Y11, and a maximum effective radius of the image side surface of the eighth lens is set as Y82, the following can be satisfied:

[0052] 0.8 < Y11 / Y82 < 1.5.

[0053] Further, in the imaging optical system,

[0054] When a dispersion coefficient of the sixth lens is set as V6, and a dispersion coefficient of the seventh lens is set as V7, the following can be satisfied:

[0055] 0 < V6 / V7 < 0.50.

[0056] Further, in the imaging optical system,

[0057] When a focal length of the imaging optical system is set as f, a focal length of the fourth lens is set as f4, and a focal length of the fifth lens is set as f5, it is possible to satisfy:

[0058] 0 < (f / f4) - (f / f5) < 2.0.

[0059] Further, in the imaging optical system,

[0060] When a distance along the optical axis from the image side surface of the sixth lens to the object side surface of the seventh lens is set as T67, a thickness along the optical axis of the seventh lens is set as CT7, a distance along the optical axis from the image side surface of the seventh lens to the object side surface of the eighth lens is set as T78, and a thickness along the optical axis of the eighth lens is set as CT8, it is possible to satisfy:

[0061] T67 / CT7 < 0.50

[0062] T78 / CT8 < 0.70.

[0063] Further, in the imaging optical system,

[0064] When a radius of curvature of the object side surface of the seventh lens is set as R13, a radius of curvature of the image side surface of the seventh lens is set as R14, a radius of curvature of the object side surface of the eighth lens is set as R15, a radius of curvature of the image side surface of the eighth lens is set as R16, a thickness along the optical axis of the seventh lens is set as CT7, a distance along the optical axis from the image side surface of the seventh lens to the object side surface of the eighth lens is set as T78, a thickness along the optical axis of the eighth lens is set as CT8, a distance along the optical axis from the object side surface of the first lens to the imaging surface is set as TL, and a focal length of the entire imaging optical system is set as f, it is possible to satisfy:

[0065] 2.0 < (|R13| + |R16|) / (CT7 + T78 + CT8) < 4.5

[0066] 0.6 < |R14 / R15| / 1.3

[0067] 2.0 < TL / f < 4.0.

[0068] Further, in the imaging optical system,

[0069] When a displacement amount in the optical axis direction from the intersection with the optical axis in the object side surface of the first lens to the position of the maximum effective radius of the object side surface is set as Sag11, and a displacement amount in the optical axis direction from the intersection with the optical axis in the object side surface of the third lens to the position of the maximum effective radius of the object side surface is set as Sag31, the following can be satisfied:

[0070] |Sag11 / Sag31| < 5.0.

[0071] In addition, in the imaging optical system,

[0072] When an amount of distortion aberration at the maximum image height is set as DST1.0, an amount of distortion aberration at the image height of 70% of the maximum image height is set as DST0.7, and the maximum field angle is set as FOV, the following can be satisfied:

[0073] |DST1.0 / FOV| < 0.5 (% / degree)

[0074] |DST1.0 / DST0.7| < 10.

[0075] In addition, the imaging optical system of the present disclosure has:

[0076] a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged in this order in the direction from the object side to the image side;

[0077] The first lens has a negative refractive power;

[0078] The image side surface of the second lens is a concave surface;

[0079] The image side surface of the third lens is a concave surface;

[0080] The image side surface of the fourth lens is a convex surface;

[0081] The fifth lens has a positive refractive power, and the image side surface thereof is a convex surface;

[0082] The sixth lens has a negative refractive power, and the object side surface thereof is a concave surface, and the image side surface thereof is a convex surface;

[0083] The seventh lens has a positive refractive power, and the object side surface thereof is an aspherical surface having a convex central portion and at least one inflection point on a peripheral portion of the central portion;

[0084] The eighth lens has an image side surface that is an aspherical surface having a concave central portion and at least one inflection point on a peripheral portion of the central portion;

[0085] In a case where a focal length of the first lens is set as f1, a focal length of the second lens is set as f2, a composite focal length of the first lens and the second lens is set as f12, a focal length of the third lens is set as f3, a focal length of the optical system as a whole constituted by the first to eighth lenses is set as f, a thickness of the seventh lens along the optical axis is set as CT7, a distance along the optical axis from the image side surface of the seventh lens to the object side surface of the eighth lens is set as T78, and a thickness of the eighth lens along the optical axis is set as CT8, the following conditions are satisfied:

[0086] 0.3 < f / (CT7 + T78 + CT8) < 3.5

[0087] 1.0 < CT7 / CT8 < 2.0

[0088] |f1 / f2| < 6

[0089] |f12 / f3| < 0.5.

[0090] In addition, in the photographing optical system,

[0091] the image side surface of the first lens is a concave surface;

[0092] In a case where a radius of curvature of the object side surface of the seventh lens is set as R13, a radius of curvature of the image side surface of the seventh lens is set as R14, a radius of curvature of the object side surface of the eighth lens is set as R15, a radius of curvature of the image side surface of the eighth lens is set as R16, a thickness of the seventh lens along the optical axis is set as CT7, a distance along the optical axis from the image side surface of the seventh lens to the object side surface of the eighth lens is set as T78, and a thickness of the eighth lens along the optical axis is set as CT8, the following condition can be satisfied:

[0093] 2.0 < (|R13| + |R16|) / (CT7 + T78 + CT8) < 4.5

[0094] 0.6 < |R14 / R15| / 1.3.

[0095] In the photographing optical system, the following condition can be satisfied:

[0096] 0.3 < |f / f12| + |f / f3| < 1.5.

[0097] In addition, in the photographing optical system,

[0098] In a case where a focal length of the sixth lens is set as f6, the following condition can be satisfied:

[0099] 0.5 < f12 / f6 < 1.5.

[0100] In addition, the photographing optical system has an aperture stop;

[0101] When a distance along the optical axis of a surface from the aperture stop to the image side of the eighth lens is set as SD, a distance along the optical axis of a surface from the object side of the first lens to the image side of the eighth lens is set as TD, a maximum effective radius of the object side surface of the first lens is set as Y11, and a maximum effective radius of the image side surface of the eighth lens is set as Y82, the following can be satisfied:

[0102] 0.45 < SD / TD < 0.65

[0103] 0.8 < Y11 / Y82 < 1.5.

[0104] Further, in the photographing optical system,

[0105] When a distance in a direction orthogonal to the optical axis of a maximum inflection point of the image side surface of the eighth lens and the optical axis is set as Yc82, the following can be satisfied:

[0106] 0.45 < Yc82 / f < 0.75.

[0107] Further, in the photographing optical system,

[0108] When a distortion aberration amount at a maximum image height is set as DST1.0, a distortion aberration amount at an image height of 70% of the maximum image height is set as DST0.7, and a maximum field angle is set as FOV, the following can be satisfied:

[0109] |DST1.0 / FOV| < 0.5 (% / degree)

[0110] |DST1.0 / DST0.7| < 10.

[0111] Further, the photographing optical system of the present disclosure has:

[0112] a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged in this order from the object side toward the image side;

[0113] the first lens has a negative refractive power;

[0114] the image side surface of the second lens is a concave surface;

[0115] the object side surface of the third lens is a convex surface;

[0116] the object side surface of the fourth lens is a convex surface;

[0117] the fifth lens has a positive refractive power;

[0118] the sixth lens has a negative refractive power, the object side surface thereof is a concave surface, and the image side surface thereof is a convex surface;

[0119] The seventh lens has a positive refractive power, and the image-side surface thereof is a convex surface;

[0120] The eighth lens has an image-side surface that is an aspherical surface having a concave central portion and at least one inflection point on a peripheral portion of the central portion;

[0121] When a thickness of the first lens along the optical axis is denoted by CT1 and a thickness of the eighth lens along the optical axis is denoted by CT8, the following is satisfied:

[0122] 0.5 < CT1 / CT8 < 1.5.

[0123] In the imaging optical system,

[0124] When a combined focal length of the first lens and the second lens is denoted by f12 and a focal length of the fifth lens is denoted by f5, the following can be satisfied:

[0125] 0.8 < |f5 / f12| < 2.5.

[0126] Further, in the imaging optical system,

[0127] When a displacement amount in the optical axis direction from an intersection with the optical axis of the object-side surface of the first lens to a position of the maximum effective radius of the object-side surface is denoted by Sag11 and a displacement amount in the optical axis direction from an intersection with the optical axis of the object-side surface of the third lens to a position of the maximum effective radius of the object-side surface is denoted by Sag31, the following can be satisfied:

[0128] |Sag11 / Sag31| < 5.0.

[0129] Further, in the imaging optical system,

[0130] When a distance along the optical axis from the image-side surface of the first lens to the object-side surface of the second lens is denoted by T12, a distance along the optical axis from the image-side surface of the second lens to the object-side surface of the third lens is denoted by T23, a distance along the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens is denoted by T34, a distance along the optical axis from the image-side surface of the fourth lens to the object-side surface of the fifth lens is denoted by T45, a distance along the optical axis from the image-side surface of the fifth lens to the object-side surface of the sixth lens is denoted by T56, a distance along the optical axis from the image-side surface of the sixth lens to the object-side surface of the seventh lens is denoted by T67, and a distance along the optical axis from the image-side surface of the seventh lens to the object-side surface of the eighth lens is denoted by T78, the following can be satisfied:

[0131] (T12+T23+T67+T78) / (T34+T45+T56) < 1.5.

[0132] Further, in the imaging optical system,

[0133] When a maximum value of the refractive index in each of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, and the eighth lens is set as Nmax, the following can be satisfied:

[0134] 1.60 < Nmax < 1.72.

[0135] In addition, the optical imaging device of the present disclosure has:

[0136] any of the above-described imaging optical systems;

[0137] a driving section that drives all or part of the first to eighth lenses included in the imaging optical system; and

[0138] a photoelectric conversion element disposed on an imaging surface of the imaging optical system. BRIEF DESCRIPTION OF DRAWINGS

[0139] Figure 1 is a schematic view showing the structure of the optical imaging device of the present embodiment.

[0140] Figure 2 is a graph showing a parameter Y11 of the first lens included in the optical system included in the optical imaging device.

[0141] Figure 3 is a graph showing a parameter Y82 of the eighth lens included in the optical system.

[0142] Figure 4 is a graph showing a parameter Sag11 of the first lens included in the optical system.

[0143] Figure 5 is a graph showing a parameter Sag31 of the third lens included in the optical system.

[0144] Figure 6 is a graph showing a parameter Yc82 of the eighth lens included in the optical system.

[0145] Figure 7 is a schematic view showing the structure of the optical imaging device of Embodiment 1.

[0146] Figure 8 is an aberration graph of the spherical aberration, the astigmatism, and the distortion of Embodiment 1.

[0147] Figure 9 is a schematic view showing the structure of the optical imaging device of Embodiment 2.

[0148] Figure 10 is an aberration graph of the spherical aberration, the astigmatism, and the distortion of Embodiment 2.

[0149] Figure 11 Schematic diagram showing the structure of an optical imaging device according to Example 3.

[0150] Figure 12 These are aberration diagrams showing spherical aberration, astigmatism, and distortion in Example 3.

[0151] Figure 13 Schematic diagram showing the structure of an optical imaging device according to a fourth embodiment.

[0152] Figure 14 These are aberration diagrams showing spherical aberration, astigmatism, and distortion in Example 4.

[0153] Figure 15 Schematic diagram showing the structure of an optical imaging device according to Example 5.

[0154] Figure 16 These are aberration diagrams showing spherical aberration, astigmatism, and distortion in Example 5.

[0155] Figure 17 Schematic diagram showing the structure of an optical imaging device according to Example 6.

[0156] Figure 18 These are aberration diagrams showing spherical aberration, astigmatism, and distortion in Example 6.

[0157] Figure 19 Schematic diagram showing the structure of an optical imaging device according to Example 7.

[0158] Figure 20 These are aberration diagrams showing spherical aberration, astigmatism, and distortion in Example 7. DETAILED DESCRIPTION

[0159] Hereinafter, one embodiment of the present disclosure will be described with reference to the accompanying drawings.

[0160] The optical imaging device 1 of this embodiment (hereinafter referred to as "imaging device") is as follows: Figure 1 As shown, the imaging device 1 includes an imaging optical system (hereinafter referred to as the "optical system") 10 and a photoelectric conversion element 2 disposed on an imaging surface 10a of the optical system 10. Specifically, the imaging device 1 includes the optical system 10 having a plurality of lenses 11 to 18, a sensor holder 3 that holds the photoelectric conversion element 2, and a drive unit 4 that drives the optical system 10. The imaging device 1 of this embodiment further includes an IR cut filter F disposed between the optical system 10 and the photoelectric conversion element 2.

[0161] The sensor holder 3 holds the photoelectric conversion element 2 so that the photoelectric conversion element 2 is located at the imaging plane 10a of the optical system 10. Specifically, the sensor holder 3 holds the photoelectric conversion element 2 so that the light-receiving surface of the photoelectric conversion element 2 is orthogonal to the optical axis of the optical system 10. The photoelectric conversion element 2 converts an image composed of incident visible light into an electric signal and transmits (outputs) it to an image processor or the like of a later stage, not shown. The photoelectric conversion element 2 of the present embodiment is an image sensor such as a CMOS, and can be adhesively fixed to the sensor holder 3 after adjusting the posture of the sensor holder 3 or the optical system 10 with respect to the optical axis.

[0162] In addition, an IR cut filter F is also fixed to the sensor holder 3. The IR cut filter F removes light in the infrared region that is not needed for image formation among light rays passing through the optical system 10, and allows only light in the visible light region to pass therethrough. Specifically, the IR cut filter F has a transmittance characteristic in which the transmittance of light of any wavelength in the wavelength range of 380 nm to 430 nm is 50% (half value), the transmittance of light in the wavelength range of 500 nm to 600 nm is 80% or more, and the transmittance of light in the wavelength range of 730 nm to 800 nm is 10% or less. The IR cut filter F is formed by attaching a multilayer coating that is a multilayer structure of TiO2 film and SiO2 film as an alternating layer to the surface of an infrared-absorbing glass base. Since the surfaces on both sides of the IR cut filter F are substantially planar, even if it is disposed between the optical system 10 and the photoelectric conversion element 2, it does not affect the imaging of light rays.

[0163] In addition, the IR cut filter can also be a general transparent glass flat plate (D263Teco manufactured by SCHOTT, etc.) to which infrared-absorbing ink is applied, and an AR coating for antireflection is applied to the upper portion thereof. The same transmittance characteristic as the above-described IR cut filter F can also be achieved with this IR cut filter.

[0164] The drive section 4 is a driver such as a VCM (voice coil motor) that drives the optical system 10 in a direction (optical axis direction) that is substantially perpendicular to the light-receiving surface of the photoelectric conversion element 2.

[0165] The optical system 10 has a lens group including a plurality of lenses, an aperture stop 5 disposed between the lenses, and a lens holding member (lens barrel) 6 that holds the lens group. In addition, the optical system 10 has a light shielding member 7 disposed at the end on the object side (light incident side), at least one light shielding plate 8 disposed between the lenses, and a lens pressing ring 9 that pushes the lens group against the lens holding member 6.

[0166] The lens group includes, in order from the object side to the image side, a first lens 11, a second lens 12, a third lens 13, a fourth lens 14, a fifth lens 15, a sixth lens 16, a seventh lens 17, and an eighth lens 18. The total number of lenses in the lens group of the present embodiment is eight, and the fourth to sixth lenses 14 to 16 constitute a main lens group that determines the imaging performance of the optical system 10.

[0167] Each of these first to seventh lenses 11 to 17 has a stacked structure using bevels at the peripheral portion. When these lenses 11 to 17 are held by the lens holding member 6, these stacked structures are fitted to each other by the adjacent lenses, and each lens 11 to 17 can be arranged at the arrangement position with high precision. That is, the lens position accuracy can be obtained with high precision. Further, between the seventh lens 17 and the eighth lens 18, there is provided a light-shielding and spacing adjustment gasket 8a that has a function of cutting off unnecessary stray light and is used for adjusting the image surface curvature. In actual mass production, due to various tolerance errors, there can be a deterioration in the image surface curvature, which causes a deterioration in the image quality. In order to correct this image surface curvature, by changing the thickness of the light-shielding and spacing adjustment gasket 8a to adjust the spacing between the seventh lens 17 and the eighth lens 18 in the optical axis direction, the generated image surface curvature can be eliminated. Further, the details of these first to eighth lenses 11 to 18 will be described later.

[0168] The lens holding member 6 is a cylindrical member that holds the first to eighth lenses 11 to 18 inside. Specifically, the lens holding member 6 holds, in order from the object side to the image side, the first lens 11, the light-shielding gasket 8, the second lens 12, the light-shielding gasket 8, the third lens 13, the aperture stop 5, the fourth lens 14, the light-shielding gasket 8, the fifth lens 15, the light-shielding gasket 8, the sixth lens 16, the light-shielding gasket 8, the seventh lens 17, the light-shielding and spacing adjustment gasket 8a, and the eighth lens 18. In the lens holding member 6 of the present embodiment, in a state where these first to eighth lenses 11 to 18, the plurality of light-shielding gaskets 8, and the light-shielding and spacing adjustment gasket 8a are inserted inside in the above order, the lens pressing ring 9 suppresses these members with an appropriate pressure, and they are fixed to the lens holding member 6 with an adhesive such as UV-hardening resin.

[0169] The aperture stop 5 arranged between the third lens 13 and the fourth lens 14 has a function of determining the aperture value of the entire optical system 10. Further, the light-shielding member 7 is installed to the opening portion of the front surface (object side) of the cylindrical lens holding member 6, and thus, the unnecessary light rays of the image peripheral portion are restricted from intruding into the optical system 10.

[0170] The light shielding sheet 8 is provided in the peripheral portion between the lenses to remove unnecessary light (i.e., block interfering light) that is reflected from the structure outside the effective portion of the lens. This improves the quality of the image captured by the camera 1. The optical system 10 has at least one light shielding sheet 8. The optical system 10 of this embodiment has multiple ( Figure 1 In the example shown, there are five very thin light shielding sheets 8. Specifically, the light shielding sheets 8 are respectively arranged between the first lens 11 and the second lens 12, between the second lens 12 and the third lens 13, between the fourth lens 14 and the fifth lens 15, between the fifth lens 15 and the sixth lens 16, and between the sixth lens 16 and the seventh lens 17.

[0171] Next, each of the lenses 11 to 18 will be described in detail.

[0172] The first lens 11 and the second lens 12 each have negative refractive power. The four lens interfaces 11a, 11b, 12a, and 12b formed by these first and second lenses 11 and 12 ensure a viewing angle of at least 130 degrees in the optical system 10 (imaging device 1) while also achieving the desired distortion shape. If the first and second lenses 11 and 12 consist of a single lens with negative refractive power, since there are only two lens interfaces, it would be difficult to achieve the desired distortion shape corresponding to the field angle of light incident on the optical system 10.

[0173] The object-side surface (lens interface) 11a of the first lens 11 is a surface specifically used to adjust the field of view. In the optical system 10 of this embodiment, the balance of the generated distortion aberration is shared by the surface (lens interface) closer to the image side than the object-side surface 11a of the first lens 11.

[0174] Furthermore, the image-side surfaces 11b and 12b of the first lens 11 and the second lens 12 are concave surfaces (surfaces that are recessed toward the object). Thus, by adjusting the negative distortion generated on the image-side surfaces 11b and 12b for each incident angle, it is possible to adjust the distortion (perspective distortion) of a three-dimensional object while miniaturizing the optical system 10.

[0175] The object-side surface 12a of the second lens 12 can adjust the aberrations generated by the distance between the first lens 11 and the second lens 12. Specifically, when the first lens 11 and the second lens 12 are each composed of a lens having negative refractive power, the overall size of the optical system 10 (imaging device 1) increases. However, by allowing flexibility in the shape of the object-side surface 12a of the second lens 12, the generation of aberrations can be suppressed even when the distance between the first lens 11 and the second lens 12 is small.

[0176] The third lens 13 has a positive refractive power. The object side surface 13a of the third lens 13 is a convex surface, and the image side surface 13b of the third lens 13 is a concave surface. The third lens 13 assists the miniaturization of the optical system 10 (the imaging device 1) by condensing light rays of a wide range of field angles which have passed through the first lens 11 and the second lens 12 in the optical system 10.

[0177] By making the object side surface 13a of the third lens 13 a convex surface, light rays of a wide range of field angles are easily received in the optical system 10. Further, when light rays reflected at the image side surface 13b of the third lens 13 are retroreflected on the object side surface 13a, total reflection can occur, but by making the object side surface 13a of the third lens 13 a convex surface, the unnecessary total reflection light rays can be removed.

[0178] Further, by making the image side surface 13b of the third lens 13 a concave surface, in the optical system 10, a suitable balance between the aberration correction ability of the lens group after the fourth lens 14 and the aberration correction ability of the entire optical system 10 is obtained, and as a result, the imaging quality in the optical system 10 can be improved, and the imaging can be made more vivid.

[0179] The fourth lens 14 has a positive refractive power. The object side surface 14a of the fourth lens 14 is a convex surface, and the image side surface 14b of the fourth lens 14 is a convex surface. The fourth lens 14 shares the positive refractive power with the fifth lens 15 in order to avoid excessive aberration or stray light due to excessive surface curvature of the fourth lens 14. Further, by making the image side surface 14b of the fourth lens 14 a convex surface, in the fourth lens 14, the generation of aberration is suppressed, and the symmetry in the optical system 10 is improved.

[0180] The fifth lens 15 has a positive refractive power. The object side surface 15a of the fifth lens 15 is a concave surface, and the image side surface 15b of the fifth lens 15 is a convex surface. The fifth lens 15 cooperates with the fourth lens 14 to ensure sufficient light collecting ability. Further, by making the image side surface 15b of the fifth lens 15 a convex surface, sufficient light collecting ability is obtained in the peripheral portion of the field angle range of the optical system 10, and as a result, the peripheral light amount in the optical system 10 of a wide field angle range is easily ensured.

[0181] The sixth lens 16 has a negative refractive power. The object side surface 16a of the sixth lens 16 is a concave surface, and the image side surface of the sixth lens 16 is a convex surface. The sixth lens 16 particularly well corrects the lateral chromatic aberration of the high image height portion by being composed of a highly dispersive material. Further, in the sixth lens 16, by making the object side surface 16a a concave surface and the image side surface 16b a convex surface, the sixth lens 16 becomes a structure which is favorable to non-axial aberrations such as astigmatism.

[0182] The seventh lens 17 has a positive refractive power. The central portion (the vicinity of the center) 171a of the object side face 17a of the seventh lens 17 is a convex surface, and the image side face 17b is a convex surface. Further, the object side face 17a is an aspheric surface having at least one inflection point on the peripheral portion 172a of the central portion 171a. This seventh lens 17 cooperates with the eighth lens 18 to adjust the astigmatism.

[0183] The eighth lens 18 has a negative refractive power. The object side face 18a of the eighth lens 18 is a concave surface, and the central portion (the vicinity of the center) 181b of the image side face 18b is a concave surface. Further, the image side face 18b is an aspheric surface (refer to Fig. 6) having at least one inflection point on the peripheral portion 182b of the central portion 181b. This eighth lens 18 cooperates with the seventh lens 17 to adjust the astigmatism. Figure 3 ) The eighth lens 18 cooperates with the seventh lens 17 to adjust the astigmatism.

[0184] According to these seventh lens 17 and eighth lens 18, by sharing the adjustment of the astigmatism by the seventh lens 17 and the eighth lens 18, the shape of each lens is easily formed uniformly, thereby making the formability of the seventh lens 17 and the eighth lens 18 good. Further, since the air lens between the image side face 17b of the seventh lens 17 and the object side face 18a of the eighth lens 18 can be used to adjust the curvature of field aberration and the distortion aberration, a more clear image is obtained.

[0185] Further, by making the image side face 18b of the eighth lens 18 an aspheric surface as described above, the angle (CRA) of the light rays reaching the photoelectric conversion element 2 from the seventh lens 17 can be optimized. Further, by adjusting the distortion aberration generated in the eighth lens 18 and the distortion aberration generated in the first lens 11 and the second lens 12, the back focus of the imaging device 1 can be optimized, and the entire imaging device 1 can be downsized.

[0186] Further, in this optical system 10, by providing the aperture stop 5 between the third lens 13 and the fourth lens 14, the symmetry in the optical system 10 can be improved.

[0187] Further, in this optical system 10, when the focal length of the first lens 11 is f1 and the focal length of the second lens 12 is f2, it is preferable to satisfy:

[0188] |f1 / f2| < 6.

[0189] Under this condition, by sharing the negative refractive power by the first lens 11 and the second lens 12, the expansion of the field angle and the optimization of the amount of the distortion aberration are achieved. Further, the shape of the large-sized first lens 11 can be smoothed, thereby improving the productivity of the first lens 11.

[0190] Further, in the optical system 10, when the combined focal length of the first lens 11 and the second lens 12 is set to f12, and the focal length of the third lens 13 is set to f3, it is preferable to satisfy:

[0191] |f12 / f3| < 0.5;

[0192] More preferably, it satisfies:

[0193] |f12 / f3| < 0.3.

[0194] By satisfying this condition, the negative power obtained by the two lenses of the first lens 11 and the second lens 12 can be sufficiently increased, and thus a sufficient field of view (FOV) can be obtained in the optical system 10.

[0195] Further, in the optical system 10, when the distance along the optical axis from the image side surface 13b of the third lens 13 to the object side surface 14a of the fourth lens 14 is set to T34, and the distance along the optical axis from the image side surface 16b of the sixth lens 16 to the object side surface 17a of the seventh lens 17 is set to T67, it is preferable to satisfy:

[0196] 0 < T67 / T34 < 1.0;

[0197] More preferably, it satisfies:

[0198] 0 < T67 / T34 < 0.6.

[0199] By satisfying this condition, the spatial configuration in the optical system 10 is optimized, and the correction ability of the image surface curvature aberration is improved, and thus a sharp image can be obtained up to the image peripheral portion.

[0200] Further, in the optical system 10, when the focal length of the entire optical system 10 is set to f, the thickness of the seventh lens 17 along the optical axis is set to CT7, the distance along the optical axis from the image side surface of the seventh lens to the object side surface of the eighth lens is set to T78, and the thickness of the eighth lens along the optical axis is set to CT8, it is preferable to satisfy:

[0201] 0.3 < f / (CT7+T78+CT8) < 3.5

[0202] 1.0 < CT7 / CT8 < 2.0;

[0203] More preferably, it satisfies:

[0204] 0.8 < f / (CT7+T78+CT8) < 3.2

[0205] 1.2 < CT7 / CT8 < 1.8;

[0206] More preferably, it satisfies:

[0207] 1.5 < f / (CT7 + T78 + CT8) < 2.8

[0208] 1.4 < CT7 / CT8 < 1.6.

[0209] Under this condition, by optimizing the shapes of the seventh lens 17 and the eighth lens 18, the astigmatism can be effectively suppressed. In addition, the moldability in mass production is also improved.

[0210] In addition, in this optical system 10, when the thickness of the first lens 11 along the optical axis is set to CT1, and the thickness of the eighth lens 18 along the optical axis is set to CT8, it is preferable to satisfy:

[0211] 0.5 < CT1 / CT8 < 1.5.

[0212] By satisfying this condition, since the thicknesses of the most object side lens (the first lens 11) and the most image side lens (the eighth lens 18) of the optical system 10 are optimized, the astigmatism is reduced, and thus the stability of the imaging device 1 is improved.

[0213] In addition, in this optical system 10, when the distance along the optical axis from the object side face 11a of the first lens 11 to the imaging face 10a is set to TL, and the maximum image height of the optical system 10 is set to ImgH, it is preferable to satisfy:

[0214] TL / ImgH < 3;

[0215] More preferably, it satisfies:

[0216] 1.8 < TL / ImgH < 2.6.

[0217] By satisfying this condition, the miniaturization of the optical system 10 (the imaging device 1) is achieved. In addition, while obtaining a wide-angle imaging range, the image quality is improved by increasing the peripheral light flux.

[0218] In addition, in this optical system 10, when the radius of curvature of the object side face 14a of the fourth lens 14 is set to R7, and the radius of curvature of the image side face 14b of the fourth lens 14 is set to R8, it is preferable to satisfy:

[0219] 0 < (R7 + R8) / (R7 - R8) < 1.0;

[0220] More preferably, it satisfies:

[0221] 0 < (R7 + R8) / (R7 - R8) < 0.5.

[0222] By optimizing the curvature radius of the fourth lens 14 under this condition, the shape symmetry of the entire optical system 10 is obtained, whereby the generation of spherical aberration is reduced, and as a result, the image quality is improved.

[0223] Further, in this optical system 10, when a distance along the optical axis from the image side surface 11b of the first lens 11 to the object side surface 12a of the second lens 12 is set as T12, a distance along the optical axis from the image side surface 12b of the second lens 12 to the object side surface 13a of the third lens 13 is set as T23, and a distance along the optical axis from the image side surface 13b of the third lens 13 to the object side surface 14a of the fourth lens 14 is set as T34, it is preferable to satisfy:

[0224] 0 < T12 / T23 < 3.0, and 0 < T23 / T34 < 2.0;

[0225] More preferably, it satisfies:

[0226] 0.8 < T12 / T23 < 2.2, and 0.5 < T23 / T34 < 1.2.

[0227] Under this condition, by optimizing the distance along the optical axis from the image side surface 11b of the first lens 11 to the object side surface 12a of the second lens 12, and the distance along the optical axis from the image side surface 12b of the second lens 12 to the object side surface 13a of the third lens 13, respectively, the effective radius of each lens of the first lens 11 and the second lens 12 can be reduced, whereby the optimization of the size of the optical system 10 can be achieved.

[0228] Further, in this optical system 10, when a distance along the optical axis from the image side surface 11b of the first lens 11 to the object side surface 12a of the second lens 12 is set as T12, a distance along the optical axis from the image side surface 12b of the second lens 12 to the object side surface 13a of the third lens 13 is set as T23, and a distance along the optical axis from the image side surface 13b of the third lens 13 to the object side surface 14a of the fourth lens 14 is set as T34, it is preferable to satisfy:

[0229] 2.0 < tan(HFOV);

[0230] More preferably, it satisfies:

[0231] 3.0 < tan(HFOV).

[0232] By satisfying this condition, a wide photographing (imaging) range, which is a characteristic of a wide-angle lens, is obtained in the optical system 10.

[0233] Further, in this optical system 10, when an aperture value is set as Fno, it is preferable to satisfy:

[0234] 1.4 < Fno < 3.0.

[0235] Under this condition, by optimizing the amount of light incident into the photoelectric conversion element 2, a sufficient amount of light can be obtained while limiting the disturbance light caused by the excess amount of light.

[0236] Further, in the optical system 10, it is preferable to satisfy:

[0237] 2.4 < Fno < 3.0.

[0238] By satisfying this condition, the depth of field can be deepened, and thus, since the structure for driving the lens in the optical axis direction (the driving section 4) can be eliminated, the photoelectric conversion element 2 can be fixed to the optical system 10.

[0239] Further, in the optical system 10, as shown in Figure 2 and Figure 3 Y82, it is preferable to satisfy:

[0240] 0.8 < Y11 / Y82 < 1.5;

[0241] More preferably, it is preferable to satisfy:

[0242] 0.9 < Y11 / Y82 < 1.3.

[0243] By satisfying this condition, the unevenness of the sizes of the object side portion and the image side portion in the optical system 10 can be suppressed, and the entire optical system 10 can be downsized. Further, when the lower limit value of the above relationship is exceeded (decreased), the curvature of the aspherical shape of the object side surface 18a increases, and thus, the moldability easily deteriorates, and further, the deterioration of the distortion aberration and the decrease in the peripheral light amount are caused. On the other hand, when the upper limit value of the above relationship is exceeded (increased), the optical system 10 becomes too large.

[0244] Further, in the optical system 10, when the dispersion coefficient of the sixth lens 16 is set to V6, and the dispersion coefficient of the seventh lens 17 is set to V7, it is preferable to satisfy:

[0245] 0 < V6 / V7 < 0.50.

[0246] By satisfying this condition, the chromatic aberration of magnification of the optical system 10 can be reduced, and thus, the shift of the image signal when the three-color or four-color color image sensor signals are synthesized can be reduced.

[0247] Further, in the optical system 10, when the focal length of the entire optical system 10 is set to f, the focal length of the fourth lens 14 is set to f4, and the focal length of the fifth lens 15 is set to f5, it is preferable to satisfy:

[0248] 0 < (f / f4) - (f / f5) < 2.0;

[0249] More preferably, it is preferable to satisfy:

[0250] 0.3 < (f / f4) - (f / f5) < 1.0.

[0251] Under this condition, by suppressing the difference in the refractive power of the fourth lens 14 and the fifth lens 15, it is possible to suppress an increase in the coma aberration.

[0252] Further, in the optical system 10, when a distance along the optical axis from a surface 16b on the image side of the sixth lens 16 to a surface 17a on the object side of the seventh lens 17 is set to T67, a thickness along the optical axis of the seventh lens 17 is set to CT7, a distance along the optical axis from a surface 17b on the image side of the seventh lens 17 to a surface 18a on the object side of the eighth lens 18 is set to T78, and a thickness along the optical axis of the eighth lens 18 is set to CT8, it is preferable to satisfy:

[0253] T67 / CT7 < 0.50

[0254] T78 / CT8 < 0.70;

[0255] More preferably, it is preferable to satisfy:

[0256] T67 / CT7 < 0.30

[0257] T78 / CT8 < 0.40.

[0258] By satisfying this condition, since it is possible to appropriately use the space on the image side of the optical system 10, it is possible to miniaturize the seventh lens 17 and the eighth lens 18 which are disposed on the image side.

[0259] Further, in the optical system 10, when a radius of curvature of the surface 17a on the object side of the seventh lens 17 is set to R13, a radius of curvature of the surface 18b on the image side of the eighth lens 18 is set to R16, a thickness along the optical axis (center thickness) of the seventh lens 17 is set to CT7, a distance along the optical axis from the surface on the image side of the seventh lens to the surface on the object side of the eighth lens is set to T78, and a thickness along the optical axis of the eighth lens is set to CT8, it is preferable to satisfy:

[0260] 2.0 < (|R13| + |R16|) / (CT7 + T78 + CT8) < 4.5.

[0261] Under this condition, by optimizing the combined shape of the seventh lens 17 and the eighth lens 18, it is possible to optimize the correction ability of the astigmatism and the curvature of field caused by the seventh lens 17 and the eighth lens 18.

[0262] Further, in the optical system 10, when a radius of curvature of the surface 17b on the image side of the seventh lens 17 is set to R14, and a radius of curvature of the surface 18a on the object side of the eighth lens 18 is set to R15, it is preferable to satisfy:

[0263] 0.6 < |R14 / R15| / 1.3

[0264] Under this condition, by optimizing the shape of the air lens between the seventh lens 17 and the eighth lens 18, it is possible to optimize the correction ability of the field curvature and the distortion of the seventh lens 17 and the eighth lens 18, particularly in the peripheral portion.

[0265] In addition, in the optical system 10, when a distance along the optical axis from the surface 11a on the object side of the first lens 11 to the imaging surface 10a is set to TL, and a focal length of the entire optical system 10 is set to f, it is preferable to satisfy:

[0266] 2.0 < TL / f < 4.0.

[0267] By satisfying this condition, it is possible to achieve the best balance between the size and the wide-angle characteristics of the optical system 10 while achieving thinning of the optical system 10 in the optical axis direction.

[0268] In addition, in the optical system 10, as shown in Figure 4 and Figure 5 In the optical system 10, when a displacement amount in the optical axis direction from the intersection with the optical axis in the surface 11a on the object side of the first lens 11 to the position of the maximum effective radius of the surface 11a on the object side is set to Sag11, and a displacement amount in the optical axis direction from the intersection with the optical axis in the surface 13a on the object side of the third lens 13 to the position of the maximum effective radius of the surface 13a on the object side is set to Sag31, it is preferable to satisfy:

[0269] |Sag11 / Sag31| < 5.0;

[0270] More preferably, it is preferable to satisfy:

[0271] |Sag11 / Sag31| < 3.0;

[0272] More preferably, it is preferable to satisfy:

[0273] |Sag11 / Sag31| < 2.0.

[0274] Under this condition, by optimizing the size of the lens opening on the object side of the optical system 10, it is possible to reduce the burden on the lens barrel structure.

[0275] In addition, in the optical system 10, when a distortion aberration amount of the maximum image height is set to DST1.0, a distortion aberration amount of the 70% image height of the maximum image height is set to DST0.7, and the maximum field angle is set to FOV, it is preferable to satisfy:

[0276] |DST1.0 / FOV| < 0.5 (% / degree);

[0277] and |DST1.0 / DST0.7| < 10.

[0278] By satisfying this condition, it is possible to suppress the deformation (perspective distortion) of the subject of the stereoscopic object while suppressing the reduction in the light quantity of the image peripheral portion, which is often a problem of a wide-angle lens.

[0279] In addition, in the optical system 10, when the focal length of the entire optical system 10 is set to f, the composite focal length of the first lens 11 and the second lens 12 is set to f12, and the focal length of the third lens 13 is set to f3, it is preferable to satisfy:

[0280] 0.3 < |f / f12| + |f / f3| < 1.5;

[0281] More preferably, it is preferable to satisfy:

[0282] 0.5 < |f / f12| + |f / f3| < 1.3;

[0283] More preferably, it is preferable to satisfy:

[0284] 0.7 < |f / f12| + |f / f3| < 1.1.

[0285] By satisfying this condition, sufficient diopter is obtained on the object side of the optical system 10, and thus it is possible to ensure a large field angle.

[0286] In addition, in the optical system 10, when the composite focal length of the first lens 11 and the second lens 12 is set to f12, and the focal length of the sixth lens is set to f6, it is preferable to satisfy:

[0287] 0.5 < f12 / f6 < 1.5.

[0288] Under this condition, by optimizing the distribution of negative diopter in the object side and the image side of the optical system 10, a small wide-angle lens (optical system 10) is obtained.

[0289] In addition, in the optical system 10, when the distance along the optical axis from the aperture stop 5 to the image side face 18b of the eighth lens 18 is set to SD, and the distance along the optical axis from the object side face 11a of the first lens 11 to the image side face 18b of the eighth lens 18 is set to TD, it is preferable to satisfy:

[0290] 0.45 < SD / TD < 0.65.

[0291] By satisfying this condition, it is possible to increase the passing range of light rays that occupies the entire optical system 10, and thus it is possible to miniaturize the optical system 10 and optimize the optical performance.

[0292] In addition, in the optical system 10, as Figure 6As shown, when a distance of a maximum inflection point of the surface 18b on the image side of the eighth lens 18 and the optical axis in a direction orthogonal to the optical axis is set as Yc82, and a focal length of the optical system 10 as a whole is set as f, it is preferable to satisfy:

[0293] 0.45 < Yc82 / f < 0.75.

[0294] By satisfying this condition, the light ray incident angle into the photoelectric conversion element 2 can be appropriately set, and further, generation of astigmatism can be suppressed.

[0295] Further, in the optical system 10, when a composite focal length of the first lens 11 and the second lens 12 is set as f12, and a focal length of the fifth lens 15 is set as f5, it is preferable to satisfy:

[0296] 0.8 < |f5 / f12| < 2.5;

[0297] More preferably, it is preferable to satisfy:

[0298] 1.0 < |f5 / f12| < 2.0.

[0299] Under this condition, by appropriately distributing the bending power (negative component) of the first lens 11 and the second lens 12 and the bending power (positive component) of the fifth lens 15, the image quality can be improved.

[0300] Further, in the optical system 10, when a distance along the optical axis from the surface 11b on the image side of the first lens 11 to the surface 12a on the object side of the second lens 12 is set as T12, a distance along the optical axis from the surface 12b on the image side of the second lens 12 to the surface 13a on the object side of the third lens 13 is set as T23, a distance along the optical axis from the surface 13b on the image side of the third lens to the surface 14a on the object side of the fourth lens is set as T34, a distance along the optical axis from the surface 14b on the image side of the fourth lens 14 to the surface 15a on the object side of the fifth lens 15 is set as T45, a distance along the optical axis from the surface 15b on the image side of the fifth lens 15 to the surface 16a on the object side of the sixth lens 16 is set as T56, a distance along the optical axis from the surface 16b on the image side of the sixth lens 16 to the surface 17a on the object side of the seventh lens 17 is set as T67, and a distance along the optical axis from the surface 17b on the image side of the seventh lens 17 to the surface 18a on the object side of the eighth lens 18 is set as T78, it is preferable to satisfy:

[0301] (T12+T23+T67+T78) / (T34+T45+T56) < 1.5.

[0302] By satisfying this condition, the interval of T12+T23+T67+T78, which is dominant in the setting of the field angle range, the reduction of the curvature of field aberration, and the setting of the appropriate distortion aberration, and the interval of T34+T45+T56, which is dominant in the reduction of the spherical aberration and the coma aberration of the left and right imaging performance, can be effectively corrected.

[0303] Further, in the optical system 10, when the maximum value of the refractive index in each lens of the first lens 11, the second lens 12, the third lens 13, the fourth lens 14, the fifth lens 15, the sixth lens 16, the seventh lens 17, and the eighth lens 18 is set as Nmax, it is preferable to satisfy:

[0304] 1.60 < Nmax < 1.72.

[0305] By satisfying this condition, the balance of the lenses of the optical system 10 as a whole can be achieved, and a lens shape that is easy to shape while reducing aberration can be realized.

[0306] The material of each lens 11 to 18 of the above optical system 10 can be plastic or glass. When the material of the lens is plastic, the material cost is inexpensive, the workability is excellent, and the processing time is short, so the production cost can be reduced. Further, when the material of the lens is glass, since the refractive index is generally higher than that of plastic, the design freedom of the lens is improved, and higher resolution or smaller size can be achieved.

[0307] Further, the object side surfaces 11a to 18a and the image side surfaces 11b to 18b of each lens 11 to 18 of the optical system 10 are preferably aspherical surfaces having a much greater degree of freedom than spherical surfaces. Thereby, aberration can be reduced, a high-resolution captured image can be obtained, or the entire optical system 10 can be downsized.

[0308] According to the above optical system 10 and the imaging device 1 provided with the optical system 10, sufficient imaging performance can be maintained despite being small, and a large field angle can be obtained. Regarding the field angle, the field angle of a wide-angle lens of about 120 degrees in the past, for example, is greatly expanded to about 150 degrees. Details are as follows.

[0309] With the structure in which the first lens 11 and the second lens 12 are each a concave lens and the third lens 13 is a convex lens (three-piece concave-concave-convex structure), in the optical system 10, the incidence of light rays in a super-wide angle range (wide-angle converter) can be realized, and the desired distortion aberration can be ensured even when the full field angle is about 150 degrees.

[0310] Further, in the optical system 10, the fourth to sixth lenses 14 to 16 constitute a main lens group that determines the imaging performance of the optical system 10 (lenses). Further, by making the fourth lens 14 a convex lens, the fifth lens 15 a convex lens, and the sixth lens 16 a concave lens, and making the image-side surfaces 14b, 15b, 16b of the respective lenses 14, 15, 16 convex with respect to the photoelectric conversion element 2, the spherical aberration and the coma aberration in the optical system 10 are favorably corrected.

[0311] Further, in the case where the sixth lens 16 is formed of a highly dispersible material, the lateral chromatic aberration of the part of a high image height can be particularly favorably corrected. Further, in the sixth lens 16, by making the object-side surface 16a concave and the image-side surface 16b convex, the sixth lens 16 becomes a structure that is favorable to non-axial aberrations such as astigmatism.

[0312] Further, by making the seventh lens 17 a convex lens and the eighth lens 18 a concave lens, the seventh lens 17 and the eighth lens 18 are configured to cooperatively adjust astigmatism. According to these seventh and eighth lenses 17 and 18, by sharing the adjustment of astigmatism by the seventh and eighth lenses 17 and 18, the shape of each lens is easily uniformly shaped, thereby making the seventh and eighth lenses 17 and 18 good in formability. Further, since the air lens between the image-side surface 17b of the seventh lens 17 and the object-side surface 18a of the eighth lens 18 can be used to adjust the curvature of field aberration and the distortion aberration, a more clear image is obtained.

[0313] Further, by making the image-side surface 18b (in detail, the central portion 181b) of the eighth lens 18 concave, the angle of the light rays (CRA) reaching the photoelectric conversion element 2 from the seventh lens 17 can be optimized. Further, by adjusting the distortion aberration generated in the eighth lens 18 and the distortion aberration generated in the first and second lenses 11 and 12, the back focal length of the imaging device 1 can be optimized, and the entire imaging device 1 can be downsized.

[0314] Further, in the optical system 10 and the imaging device 1 of the present embodiment, since the same field angle specifications as those of the imaging device loaded on a motion shot (example: product name GoPro (registered trademark)) can be achieved, and the size can be loaded on a mobile terminal, by the recent expansion of the 5G environment, the same ultra-wide-angle image as the motion shot can be transmitted in real time from the mobile terminal, and the expansion of the use of the mobile terminal can be achieved.

[0315] Next, the embodiments 1 to 7 of the optical imaging device of the present disclosure will be described. First, the common structure will be described, and then the structure of each embodiment will be described.

[0316] [Common Structure]

[0317] The basic structure of the optical imaging apparatus of each embodiment is the same as that of the optical imaging apparatus 1 of the above-described embodiment. Specifically, the optical imaging apparatus of each embodiment includes an optical system, a driving unit, an IR cut filter, and a photoelectric conversion element.

[0318] The optical system has eight lenses. Specifically, the optical system has, in order from the object side to the image side, a first lens, a second lens, a third lens, an aperture stop, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens. The optical system of each embodiment images the object-side subject information (light from the object side) on the surface (light-receiving surface) of the photoelectric conversion element as an imaging surface through the IR cut filter.

[0319] [Embodiment 1]

[0320] Figure 7 is a schematic view of the optical imaging apparatus 1 of this embodiment 1, Figure 8 is an aberration diagram showing, in order from left to right, the spherical aberration, the coma, and the distortion (distortion aberration) in the optical system 10 of embodiment 1.

[0321] In the optical system 10 of this embodiment 1:

[0322] The first lens 11 has a negative refractive power and is formed of a plastic material. In the first lens 11, the object-side face 11a is a convex face, and the image-side face 11b is a concave face. Both the object-side face 11a and the image-side face 11b of this first lens 11 are aspherical faces.

[0323] The second lens 12 has a negative refractive power and is formed of a plastic material. In the second lens 12, the object-side face 12a is a concave face, and the image-side face 12b is a concave face. Both the object-side face 12a and the image-side face 12b of this second lens 12 are aspherical faces.

[0324] The third lens 13 has a positive refractive power and is formed of a plastic material. In the third lens 13, the object-side face 13a is a convex face, and the image-side face 13b is a concave face. Both the object-side face 13a and the image-side face 13b of this third lens 13 are aspherical faces.

[0325] The fourth lens 14 has a positive refractive power and is formed of a plastic material. In the fourth lens 14, the object-side face 14a is a convex face, and the image-side face 14b is a convex face. Both the object-side face 14a and the image-side face 14b of this fourth lens 14 are aspherical faces.

[0326] The fifth lens 15 has a positive refractive power and is formed of a plastic material. In the fifth lens 15, the object-side surface 15a is a concave surface, and the image-side surface 15b is a convex surface. Both the object-side surface 15a and the image-side surface 15b of the fifth lens 15 are aspherical surfaces.

[0327] The sixth lens 16 has a negative refractive power and is formed of a plastic material. In the sixth lens 16, the object-side surface 16a is a concave surface, and the image-side surface 16b is a convex surface. Both the object-side surface 16a and the image-side surface 16b of the sixth lens 16 are aspherical surfaces.

[0328] The seventh lens 17 has a positive refractive power and is formed of a plastic material. In the seventh lens 17, the object-side surface 17a is a convex surface, and the image-side surface 17b is a convex surface. Both the object-side surface 17a and the image-side surface 17b of the seventh lens 17 are aspherical surfaces.

[0329] The eighth lens 18 has a negative refractive power and is formed of a plastic material. In the eighth lens 18, the object-side surface 18a is a concave surface, and the image-side surface 18b is a concave surface. Both the object-side surface 18a and the image-side surface 18b of the eighth lens 18 are aspherical surfaces.

[0330] The aspherical surface formulas of the respective lenses 11 to 18 of the optical system 10 of this embodiment 1 are shown below.

[0331] Formula 1

[0332]

[0333] In addition, in calculating the values in the table of this embodiment 1, the terms of 15th order or higher (n≥15) of Formula (1) are calculated as 0.

[0334] In addition, in the following Table 1, actual numerical values are listed for the structures of the lenses, in Table 2, actual numerical values are listed for the aspherical surface coefficients of the respective lens surfaces, and in Table 3, actual numerical values are listed for the conditional expressions of the present disclosure.

[0335] Table 1

[0336]

[0337]

[0338] Table 2

[0339]

[0340] Table 3

[0341]

[0342] Whether each value of Table 3 satisfies each conditional expression of the present disclosure is shown below.

[0343] • Table 3 |f1 / f2| = 1.713 satisfies |f1 / f2| < 6.

[0344] • Table 3 |f12 / f3| = 0.201 satisfies |f12 / f3| < 0.5.

[0345] • Table 3 T67 / T34 = 0.328 satisfies 0 < T67 / T34 < 1.0.

[0346] • Table 3 TL / ImgH = 2.556 satisfies TL / ImgH < 3.

[0347] • Table 3 (R7+R8) / (R7-R8) = 0.379 satisfies 0 < (R7+R8) / (R7-R8) < 1.0.

[0348] • Table 3 T12 / T23 = 1.774 satisfies 0 < T12 / T23 < 3.0.

[0349] • Table 3 T23 / T34 = 0.871 satisfies 0 < T23 / T34 < 2.0.

[0350] • Table 3 tan(HFOV) = 2.228 satisfies 2.0 < tan(HFOV).

[0351] • Table 3 Fno = 2.80 satisfies 1.4 < Fno < 3.0.

[0352] • Table 3 Y11 / Y82 = 1.066 satisfies 0.8 < Y11 / Y82 < 1.5.

[0353] • Table 3 V6 / V7 = 0.329 satisfies 0 < V6 / V7 < 0.50.

[0354] • Table 3 (f / f4)-(f / f5) = 0.750 satisfies 0 < (f / f4)-(f / f5) < 2.0.

[0355] • Table 3 T67 / CT7 = 0.214 satisfies T67 / CT7 < 0.50.

[0356] • Table 3 T78 / CT8 = 0.257 satisfies T78 / CT8 < 0.70.

[0357] • Table 3 (|R13|+|R16|) / (CT7+T78+CT8) = 3.900 satisfies

[0358] 2.0 < (|R13|+|R16|) / (CT7+T78+CT8) < 4.5.

[0359] • Table 3's |R14 / R15| = 1.045 satisfies 0.6 < |R14 / R15| < 1.3.

[0360] • Table 3's TL / f = 3.166 satisfies 2.0 < TL / f < 4.0.

[0361] • Table 3's |Sag11 / Sag31| = 0.277 satisfies |Sag11 / Sag31| < 5.0.

[0362] • Table 3's |DST1.0 / FOV| = 0.337 satisfies |DST1.0 / FOV| < 0.5.

[0363] • Table 3's |DST1.0 / DST0.7| = 2.173 satisfies |DST1.0 / DST0.7| < 10.

[0364] • Table 3's f / (CT7+T78+CT8)7 = 2.049 satisfies 0.3 < f / (CT7+T78+CT8) < 3.5.

[0365] • Table 3's CT7 / CT8 = 1.500 satisfies 1.0 < CT7 / CT8 < 2.0.

[0366] • Table 3's |f / f12| + |f / f3| = 0.973 satisfies 0.3 < |f / f12| + |f / f3| < 1.5.

[0367] • Table 3's f12 / f6 = 0.953 satisfies 0.5 < f12 / f6 < 1.5.

[0368] • Table 3's SD / TD = 0.558 satisfies 0.45 < SD / TD < 0.65.

[0369] • Table 3's YC82 / f = 0.524 satisfies 0.45 < YC82 / f < 0.75.

[0370] • Table 3's CT1 / CT8 = 1.125 satisfies 0.5 < CT1 / CT8 < 1.5.

[0371] • Table 3's |f5 / f12| = 1.749 satisfies 0.8 < |f5 / f12| < 2.5.

[0372] • Table 3's (T12+T23+T67+T78) / (T34+T45+T56) = 1.097 satisfies

[0373] (T12+T23+T67+T78) / (T34+T45+T56) < 1.5.

[0374] • Nmax = 1.680 of Table 3 satisfies 1.60 < Nmax < 1.72.

[0375] As above, it is confirmed that each value of Table 3 of the optical system 10 of Example 1 satisfies each conditional expression of the present disclosure.

[0376] [Example 2]

[0377] Figure 9 is a schematic view of the optical imaging device 1 of the present Example 2, Figure 10 is an aberration diagram showing, in order from left to right, the spherical aberration, the coma, and the distortion (distortion aberration) in the optical system 20 of Example 2.

[0378] In the optical system 20 of the present Example 2:

[0379] The first lens 21 has a negative refractive power and is formed of a plastic material. In the first lens 21, the object-side face 21a is a concave face, and the image-side face 21b is a concave face. Both the object-side face 21a and the image-side face 21b of the first lens 21 are aspherical faces.

[0380] The second lens 22 has a negative refractive power and is formed of a plastic material. In the second lens 22, the object-side face 22a is a concave face, and the image-side face 22b is a concave face. Both the object-side face 22a and the image-side face 22b of the second lens 22 are aspherical faces.

[0381] The third lens 23 has a positive refractive power and is formed of a plastic material. In the third lens 23, the object-side face 23a is a convex face, and the image-side face 23b is a concave face. Both the object-side face 23a and the image-side face 23b of the third lens 23 are aspherical faces.

[0382] The fourth lens 24 has a positive refractive power and is formed of a plastic material. In the fourth lens 24, the object-side face 24a is a convex face, and the image-side face 24b is a convex face. Both the object-side face 24a and the image-side face 24b of the fourth lens 24 are aspherical faces.

[0383] The fifth lens 25 has a positive refractive power and is formed of a plastic material. In the fifth lens 25, the object-side face 25a is a concave face, and the image-side face 25b is a convex face. Both the object-side face 25a and the image-side face 25b of the fifth lens 25 are aspherical faces.

[0384] The sixth lens 26 has a negative refractive power and is formed of a plastic material. In the sixth lens 26, the object-side face 26a is a concave face, and the image-side face 26b is a convex face. Both the object-side face 26a and the image-side face 26b of the sixth lens 26 are aspherical faces.

[0385] The seventh lens 27 has a positive refractive power and is formed of a plastic material. In the seventh lens 27, the object-side surface 27a is a convex surface, and the image-side surface 27b is a convex surface. Both the object-side surface 27a and the image-side surface 27b of the seventh lens 27 are aspherical surfaces.

[0386] The eighth lens 28 has a negative refractive power and is formed of a plastic material. In the eighth lens 28, the object-side surface 28a is a concave surface, and the image-side surface 28b is a concave surface. Both the object-side surface 28a and the image-side surface 28b of the eighth lens 28 are aspherical surfaces.

[0387] The optical system 20 of this Embodiment 2 has the same aspherical surface formulae for the respective lenses 21 to 28 as the formula (1) of Embodiment 1. In this Embodiment 2, the terms of 15th order or higher (n≥15) of the formula (1) are also calculated as 0 when the values in the following tables are calculated.

[0388] In addition, actual numerical values are listed in Table 4 for the structures of the lenses, in Table 5 for the aspherical coefficients of the respective lens surfaces, and in Table 6 for the conditional formulae of the present disclosure.

[0389] Table 4

[0390]

[0391]

[0392] Table 5

[0393]

[0394] Table 6

[0395]

[0396] Whether each value of Table 6 satisfies each conditional formula of the present disclosure is as follows.

[0397] • The |f1 / f2| = 2.473 of Table 6 satisfies |f1 / f2| < 6.

[0398] • The |f12 / f3| = 0.167 of Table 6 satisfies |f12 / f3| < 0.5.

[0399] • The T67 / T34 = 0.331 of Table 6 satisfies 0 < T67 / T34 < 1.0.

[0400] • The TL / ImgH = 2.195 of Table 6 satisfies TL / ImgH < 3.

[0401] • The (R7+R8) / (R7-R8) = 0.367 of Table 6 satisfies 0 < (R7+R8) / (R7-R8) < 1.0.

[0402] • T12 / T23 = 1.391 of Table 6 satisfies 0 < T12 / T23 < 3.0.

[0403] • T23 / T34 = 0.951 of Table 6 satisfies 0 < T23 / T34 < 2.0.

[0404] • tan(HFOV) = 3.723 of Table 6 satisfies 2.0 < tan(HFOV).

[0405] • Fno = 2.80 of Table 6 satisfies 1.4 < Fno < 3.0.

[0406] • Y11 / Y82 = 1.042 of Table 6 satisfies 0.8 < Y11 / Y82 < 1.5.

[0407] • V6 / V7 = 0.329 of Table 6 satisfies 0 < V6 / V7 < 0.50.

[0408] • (f / f4)-(f / f5) = 0.637 of Table 6 satisfies 0 < (f / f4)-(f / f5) < 2.0.

[0409] • T67 / CT7 = 0.200 of Table 6 satisfies T67 / CT7 < 0.50.

[0410] • T78 / CT8 = 0.238 of Table 6 satisfies T78 / CT8 < 0.70.

[0411] • (|R13| + |R16|) / (CT7 + T78 + CT8) = 3.522 of Table 6 satisfies

[0412] 2.0 < (|R13| + |R16|) / (CT7 + T78 + CT8) < 4.5.

[0413] • |R14 / R15| = 0.839 of Table 6 satisfies 0.6 < |R14 / R15| < 1.3.

[0414] • TL / f = 3.010 of Table 6 satisfies 2.0 < TL / f < 4.0.

[0415] • |Sag11 / Sag31| = 0.216 of Table 6 satisfies |Sag11 / Sag31| < 5.0.

[0416] • |DST1.0 / FOV| = 0.422 of Table 6 satisfies |DST1.0 / FOV| < 0.5.

[0417] • |DST1.0 / DST0.7| = 4.125 of Table 6 satisfies |DST1.0 / DST0.7| < 10.

[0418] • f / (CT7+T78+CT8) of Table 6 = 2.126 satisfies 0.3 < f / (CT7+T78+CT8) < 3.5.

[0419] • CT7 / CT8 of Table 6 = 1.531 satisfies 1.0 < CT7 / CT8 < 2.0.

[0420] • |f / f12| + |f / f3| of Table 6 = 0.920 satisfies 0.3 < |f / f12| + |f / f3| < 1.5.

[0421] • f12 / f6 of Table 6 = 0.982 satisfies 0.5 < f12 / f6 < 1.5.

[0422] • SD / TD of Table 6 = 0.569 satisfies 0.45 < SD / TD < 0.65.

[0423] • YC82 / f of Table 6 = 0.610 satisfies 0.45 < YC82 / f < 0.75.

[0424] • CT1 / CT8 of Table 6 = 1.200 satisfies 0.5 < CT1 / CT8 < 1.5.

[0425] • |f5 / f12| of Table 6 = 1.410 satisfies 0.8 < |f5 / f12| < 2.5.

[0426] • (T12+T23+T67+T78) / (T34+T45+T56) of Table 6 = 1.012 satisfies

[0427] (T12+T23+T67+T78) / (T34+T45+T56) < 1.5.

[0428] • Nmax of Table 6 = 1.680 satisfies 1.60 < Nmax < 1.72.

[0429] As above, it can be confirmed that each value of Table 6 of the optical system 20 of Example 2 satisfies each conditional expression of the present disclosure.

[0430] [Example 3]

[0431] Figure 11 is a schematic view of the optical imaging device 1 of the present Example 3, Figure 12 is an aberration diagram showing, in order from left to right, the spherical aberration, the coma, and the distortion (distortion aberration) in the optical system 30 of Example 3.

[0432] In the optical system 30 of the present Example 3:

[0433] The first lens 31 has a negative refractive power and is formed of a plastic material. In the first lens 31, the object-side surface 31a is a convex surface, and the image-side surface 31b is a concave surface. Both the object-side surface 31a and the image-side surface 31b of the first lens 31 are aspherical surfaces.

[0434] The second lens 32 has a negative refractive power and is formed of a plastic material. In the second lens 32, the object-side surface 32a is a convex surface, and the image-side surface 32b is a concave surface. Both the object-side surface 32a and the image-side surface 32b of the second lens 32 are aspherical surfaces.

[0435] The third lens 33 has a positive refractive power and is formed of a plastic material. In the third lens 33, the object-side surface 33a is a convex surface, and the image-side surface 33b is a concave surface. Both the object-side surface 33a and the image-side surface 33b of the third lens 33 are aspherical surfaces.

[0436] The fourth lens 34 has a positive refractive power and is formed of a plastic material. In the fourth lens 34, the object-side surface 34a is a convex surface, and the image-side surface 34b is a convex surface. Both the object-side surface 34a and the image-side surface 34b of the fourth lens 34 are aspherical surfaces.

[0437] The fifth lens 35 has a positive refractive power and is formed of a plastic material. In the fifth lens 35, the object-side surface 35a is a concave surface, and the image-side surface 35b is a convex surface. Both the object-side surface 35a and the image-side surface 35b of the fifth lens 35 are aspherical surfaces.

[0438] The sixth lens 36 has a negative refractive power and is formed of a plastic material. In the sixth lens 36, the object-side surface 36a is a concave surface, and the image-side surface 36b is a convex surface. Both the object-side surface 36a and the image-side surface 36b of the sixth lens 36 are aspherical surfaces.

[0439] The seventh lens 37 has a positive refractive power and is formed of a plastic material. In the seventh lens 37, the object-side surface 37a is a convex surface, and the image-side surface 37b is a convex surface. Both the object-side surface 37a and the image-side surface 37b of the seventh lens 37 are aspherical surfaces.

[0440] The eighth lens 38 has a negative refractive power and is formed of a plastic material. In the eighth lens 38, the object-side surface 38a is a concave surface, and the image-side surface 38b is a concave surface. Both the object-side surface 38a and the image-side surface 38b of the eighth lens 38 are aspherical surfaces.

[0441] The aspherical surface formulas of the respective lenses 31 to 38 of the optical system 30 of this embodiment are the same as the formula (1) of Embodiment 1. Also in this Embodiment 3, when the values in the table are calculated, the terms of 15th order or higher (n > 15) of the formula (1) are calculated as 0.

[0442] Further, actual numerical values are listed in Table 7 for the structure of the lenses, in Table 8 for the aspherical coefficients of each lens surface, and in Table 9 for the conditional expressions of the present disclosure.

[0443] Table 7

[0444]

[0445]

[0446] Table 8

[0447]

[0448] Table 9

[0449]

[0450] Whether each numerical value of Table 9 satisfies each conditional expression of the present disclosure is shown below.

[0451] • |f1 / f2| = 2.416 of Table 9 satisfies |f1 / f2| < 6.

[0452] • |f12 / f3| = 0.235 of Table 9 satisfies |f12 / f3| < 0.5.

[0453] • T67 / T34 = 0.395 of Table 9 satisfies 0 < T67 / T34 < 1.0.

[0454] • TL / ImgH = 2.208 of Table 9 satisfies TL / ImgH < 3.

[0455] • (R7+R8) / (R7-R8) = 0.409 of Table 9 satisfies 0 < (R7+R8) / (R7-R8) < 1.0.

[0456] • T12 / T23 = 1.923 of Table 9 satisfies 0 < T12 / T23 < 3.0.

[0457] • T23 / T34 = 0.954 of Table 9 satisfies 0 < T23 / T34 < 2.0.

[0458] • tan(HFOV) = 3.721 of Table 9 satisfies 2.0 < tan(HFOV).

[0459] • Fno = 2.80 of Table 9 satisfies 1.4 < Fno < 3.0.

[0460] • Y11 / Y82 = 1.051 of Table 9 satisfies 0.8 < Y11 / Y82 < 1.5.

[0461] • Table 9 V6 / V7 = 0.329 satisfies 0 < V6 / V7 < 0.50.

[0462] • Table 9 (f / f4)-(f / f5) = 0.525 satisfies 0 < (f / f4)-(f / f5) < 2.0.

[0463] • Table 9 T67 / CT7 = 0.237 satisfies T67 / CT7 < 0.50.

[0464] • Table 9 T78 / CT8 = 0.216 satisfies T78 / CT8 < 0.70.

[0465] • Table 9 (|R13| + |R16|) / (CT7 + T78 + CT8) = 3.581 satisfies

[0466] 2.0 < (|R13| + |R16|) / (CT7 + T78 + CT8) < 4.5.

[0467] • Table 9 |R14 / R15| = 0.897 satisfies 0.6 < |R14 / R15| < 1.3.

[0468] • Table 9 TL / f = 2.941 satisfies 2.0 < TL / f < 4.0.

[0469] • Table 9 |Sag11 / Sag31| = 0.439 satisfies |Sag11 / Sag31| < 5.0.

[0470] • Table 9 |DST1.0 / FOV| = 0.429 satisfies |DST1.0 / FOV| < 0.5.

[0471] • Table 9 |DST1.0 / DST0.7| = 7.363 satisfies |DST1.0 / DST0.7| < 10.

[0472] • Table 9 f / (CT7 + T78 + CT8) = 2.229 satisfies 0.3 < f / (CT7 + T78 + CT8) < 3.5.

[0473] • Table 9 CT7 / CT8 = 1.500 satisfies 1.0 < CT7 / CT8 < 2.0.

[0474] • Table 9 |f / f12| + |f / f3| = 0.919 satisfies 0.3 < |f / f12| + |f / f3| < 1.5.

[0475] • Table 9 f12 / f6 = 1.089 satisfies 0.5 < f12 / f6 < 1.5.

[0476] • SD / TD = 0.558 of Table 9 satisfies 0.45 < SD / TD < 0.65.

[0477] • YC82 / f = 0.616 of Table 9 satisfies 0.45 < YC82 / f < 0.75.

[0478] • CT1 / CT8 = 1.000 of Table 9 satisfies 0.5 < CT1 / CT8 < 1.5.

[0479] • |f5 / f12| = 1.162 of Table 9 satisfies 0.8 < |f5 / f12| < 2.5.

[0480] • (T12+T23+T67+T78) / (T34+T45+T56) = 1.225 of Table 9 satisfies

[0481] (T12+T23+T67+T78) / (T34+T45+T56) < 1.5.

[0482] • Nmax = 1.680 of Table 9 satisfies 1.60 < Nmax < 1.72.

[0483] As above, it can be confirmed that each value of Table 9 regarding the optical system 30 of Example 3 satisfies each conditional expression of the present disclosure.

[0484] Example 4

[0485] [Example 4]

[0486] Figure 13 is a schematic view of the optical imaging device 1 of the present Example 4, Figure 14 is an aberration diagram showing, in order from left to right, the spherical aberration, the coma, and the distortion (distortion aberration) in the optical system 40 of Example 4.

[0487] In the optical system 40 of the present Example 4:

[0488] The first lens 41 has a negative refractive power and is formed of a plastic material. In the first lens 41, the object-side face 41a is a convex face and the image-side face 41b is a concave face. Both the object-side face 41a and the image-side face 41b of the first lens 41 are aspherical faces.

[0489] The second lens 42 has a negative refractive power and is formed of a plastic material. In the second lens 42, the object-side face 42a is a convex face and the image-side face 42b is a concave face. Both the object-side face 42a and the image-side face 42b of the second lens 42 are aspherical faces.

[0490] The third lens 43 has a positive refractive power and is formed of a plastic material. In the third lens 43, the object-side surface 43a is a convex surface, and the image-side surface 43b is a concave surface. Both the object-side surface 43a and the image-side surface 43b of the third lens 43 are aspherical surfaces.

[0491] The fourth lens 44 has a positive refractive power and is formed of a plastic material. In the fourth lens 44, the object-side surface 44a is a convex surface, and the image-side surface 44b is a convex surface. Both the object-side surface 44a and the image-side surface 44b of the fourth lens 44 are aspherical surfaces.

[0492] The fifth lens 45 has a positive refractive power and is formed of a plastic material. In the fifth lens 45, the object-side surface 45a is a concave surface, and the image-side surface 45b is a convex surface. Both the object-side surface 45a and the image-side surface 45b of the fifth lens 45 are aspherical surfaces.

[0493] The sixth lens 46 has a negative refractive power and is formed of a plastic material. In the sixth lens 46, the object-side surface 46a is a concave surface, and the image-side surface 46b is a convex surface. Both the object-side surface 46a and the image-side surface 46b of the sixth lens 46 are aspherical surfaces.

[0494] The seventh lens 47 has a positive refractive power and is formed of a plastic material. In the seventh lens 47, the object-side surface 47a is a convex surface, and the image-side surface 47b is a convex surface. Both the object-side surface 47a and the image-side surface 47b of the seventh lens 47 are aspherical surfaces.

[0495] The eighth lens 48 has a negative refractive power and is formed of a plastic material. In the eighth lens 48, the object-side surface 48a is a concave surface, and the image-side surface 48b is a concave surface. Both the object-side surface 48a and the image-side surface 48b of the eighth lens 48 are aspherical surfaces.

[0496] The aspherical surface formula of each lens 41 to 48 of the optical system 40 of this embodiment is the same as the formula (1) of Embodiment 1. In addition, in this embodiment 4, when the values in the following table are calculated, the terms of 15th order or higher (n≥15) of the formula (1) are calculated as 0.

[0497] In addition, actual numerical values are listed for the structure of the lenses in Table 10 below, actual numerical values are listed for the aspherical surface coefficients of each lens surface in Table 11, and actual numerical values are listed for the conditional expressions of the present disclosure in Table 12.

[0498] Table 10

[0499]

[0500]

[0501] Table 11

[0502]

[0503] Table 12

[0504]

[0505] Whether each value of Table 12 satisfies each condition formula of the present disclosure is shown below.

[0506] • |f1 / f2| = 2.312 of Table 12 satisfies |f1 / f2| < 6.

[0507] • |f12 / f3| = 0.180 of Table 12 satisfies |f12 / f3| < 0.5.

[0508] • T67 / T34 = 0.379 of Table 12 satisfies 0 < T67 / T34 < 1.0.

[0509] • TL / ImgH = 2.181 of Table 12 satisfies TL / ImgH < 3.

[0510] • (R7+R8) / (R7-R8) = 0.422 of Table 12 satisfies 0 < (R7+R8) / (R7-R8) < 1.0.

[0511] • T12 / T23 = 1.596 of Table 12 satisfies 0 < T12 / T23 < 3.0.

[0512] • T23 / T34 = 0.904 of Table 12 satisfies 0 < T23 / T34 < 2.0.

[0513] • tan(HFOV) = 3.738 of Table 12 satisfies 2.0 < tan(HFOV).

[0514] • Fno = 2.56 of Table 12 satisfies 1.4 < Fno < 3.0.

[0515] • Y11 / Y82 = 0.999 of Table 12 satisfies 0.8 < Y11 / Y82 < 1.5.

[0516] • V6 / V7 = 0.329 of Table 12 satisfies 0 < V6 / V7 < 0.50.

[0517] • (f / f4)-(f / f5) = 0.645 of Table 12 satisfies 0 < (f / f4)-(f / f5) < 2.0.

[0518] • T67 / CT7 = 0.231 of Table 12 satisfies T67 / CT7 < 0.50.

[0519] • T78 / CT8 = 0.218 of Table 12 satisfies T78 / CT8 < 0.70.

[0520] • The (|R13| + |R16|) / (CT7 + T78 + CT8) = 3.593 of Table 12 satisfies

[0521] 2.0 < (|R13| + |R16|) / (CT7 + T78 + CT8) < 4.5.

[0522] • The |R14 / R15| = 0.924 of Table 12 satisfies 0.6 < |R14 / R15| < 1.3.

[0523] • The TL / f = 2.927 of Table 12 satisfies 2.0 < TL / f < 4.0.

[0524] • The |Sag11 / Sag31| = 0.400 of Table 12 satisfies |Sag11 / Sag31| < 5.0.

[0525] • The |DST1.0 / FOV| = 0.428 of Table 12 satisfies |DST1.0 / FOV| < 0.5.

[0526] • The |DST1.0 / DST0.7| = 7.403 of Table 12 satisfies |DST1.0 / DST0.7| < 10.

[0527] • The f / (CT7 + T78 + CT8) = 2.212 of Table 12 satisfies 0.3 < f / (CT7 + T78 + CT8) < 3.5.

[0528] • The CT7 / CT8 = 1.500 of Table 12 satisfies 1.0 < CT7 / CT8 < 2.0.

[0529] • The |f / f12| + |f / f3| = 0.855 of Table 12 satisfies 0.3 < |f / f12| + |f / f3| < 1.5.

[0530] • The f12 / f6 = 1.079 of Table 12 satisfies 0.5 < f12 / f6 < 1.5.

[0531] • The SD / TD = 0.565 of Table 12 satisfies 0.45 < SD / TD < 0.65.

[0532] • The YC82 / f = 0.617 of Table 12 satisfies 0.45 < YC82 / f < 0.75.

[0533] • The CT1 / CT8 = 1.196 of Table 12 satisfies 0.5 < CT1 / CT8 < 1.5.

[0534] • The |f5 / f12| = 1.272 of Table 12 satisfies 0.8 < |f5 / f12| < 2.5.

[0535] • (T12+T23+T67+T78) / (T34+T45+T56) of Table 12 = 1.059 satisfies

[0536] (T12+T23+T67+T78) / (T34+T45+T56) < 1.5.

[0537] • Nmax of Table 12 = 1.680 satisfies 1.60 < Nmax < 1.72.

[0538] As above, it can be confirmed that each value of Table 12 regarding the optical system 40 of Example 4 satisfies each conditional expression of the present disclosure.

[0539] [Example 5]

[0540] Figure 15 is a schematic view of the optical imaging device 1 of the present Example 5, Figure 16 is an aberration diagram showing, in order from left to right, the spherical aberration, the coma, and the distortion (distortion aberration) in the optical system 50 of Example 5.

[0541] In the optical system 50 of the present Example 5:

[0542] The first lens 51 has a negative refractive power and is formed of a plastic material. In the first lens 51, the object-side face 51a is a convex face, and the image-side face 51b is a concave face. Both the object-side face 51a and the image-side face 51b of the first lens 51 are aspherical faces.

[0543] The second lens 52 has a negative refractive power and is formed of a plastic material. In the second lens 52, the object-side face 52a is a convex face, and the image-side face 52b is a concave face. Both the object-side face 52a and the image-side face 52b of the second lens 52 are aspherical faces.

[0544] The third lens 53 has a positive refractive power and is formed of a plastic material. In the third lens 53, the object-side face 53a is a convex face, and the image-side face 53b is a concave face. Both the object-side face 53a and the image-side face 53b of the third lens 53 are aspherical faces.

[0545] The fourth lens 54 has a positive refractive power and is formed of a plastic material. In the fourth lens 54, the object-side face 54a is a convex face, and the image-side face 54b is a convex face. Both the object-side face 54a and the image-side face 54b of the fourth lens 54 are aspherical faces.

[0546] The fifth lens 55 has a positive refractive power and is formed of a plastic material. In the fifth lens 55, the object-side face 55a is a concave face, and the image-side face 55b is a convex face. Both the object-side face 55a and the image-side face 55b of the fifth lens 55 are aspherical faces.

[0547] The sixth lens 56 has a negative refractive power and is formed of a plastic material. In the sixth lens 56, the object-side surface 56a is a concave surface, and the image-side surface 56b is a convex surface. Both the object-side surface 56a and the image-side surface 56b of the sixth lens 56 are aspherical surfaces.

[0548] The seventh lens 57 has a positive refractive power and is formed of a plastic material. In the seventh lens 57, the object-side surface 57a is a convex surface, and the image-side surface 57b is a convex surface. Both the object-side surface 57a and the image-side surface 57b of the seventh lens 57 are aspherical surfaces.

[0549] The eighth lens 58 has a negative refractive power and is formed of a plastic material. In the eighth lens 58, the object-side surface 58a is a concave surface, and the image-side surface 58b is a concave surface. Both the object-side surface 58a and the image-side surface 58b of the eighth lens 58 are aspherical surfaces.

[0550] The aspherical surface formulas of the respective lenses 51 to 58 of the optical system 50 of this embodiment are the same as the formula (1) of Embodiment 1. In this Embodiment 5, in calculating the values in the following tables, the terms of 15th order or higher (n≥15) of the formula (1) are calculated as 0.

[0551] In addition, in Table 13 below, actual numerical values are listed for the structures of the lenses, in Table 14, actual numerical values are listed for the aspherical surface coefficients of the respective lens surfaces, and in Table 15, actual numerical values are listed for the conditional expressions of the present disclosure.

[0552] Table 13

[0553]

[0554]

[0555] Table 14

[0556]

[0557] Table 15

[0558]

[0559] Whether each value of Table 15 satisfies each conditional expression of the present disclosure is as follows.

[0560] • |f1 / f2| = 3.439 of Table 15 satisfies |f1 / f2| < 6.

[0561] • |f12 / f3| = 0.181 of Table 15 satisfies |f12 / f3| < 0.5.

[0562] • T67 / T34 = 0.324 of Table 15 satisfies 0 < T67 / T34 < 1.0.

[0563] • Table 15's TL / ImgH = 2.156 satisfies TL / ImgH < 3.

[0564] • Table 15's (R7+R8) / (R7-R8) = 0.440 satisfies 0 < (R7+R8) / (R7-R8) < 1.0.

[0565] • Table 15's T12 / T23 = 1.604 satisfies 0 < T12 / T23 < 3.0.

[0566] • Table 15's T23 / T34 = 0.866 satisfies 0 < T23 / T34 < 2.0.

[0567] • Table 15's tan(HFOV) = 3.750 satisfies 2.0 < tan(HFOV).

[0568] • Table 15's Fno = 2.38 satisfies 1.4 < Fno < 3.0.

[0569] • Table 15's Y11 / Y82 = 0.992 satisfies 0.8 < Y11 / Y82 < 1.5.

[0570] • Table 15's V6 / V7 = 0.329 satisfies 0 < V6 / V7 < 0.50.

[0571] • Table 15's (f / f4)-(f / f5) = 0.628 satisfies 0 < (f / f4)-(f / f5) < 2.0.

[0572] • Table 15's T67 / CT7 = 0.195 satisfies T67 / CT7 < 0.50.

[0573] • Table 15's T78 / CT8 = 0.284 satisfies T78 / CT8 < 0.70.

[0574] • Table 15's (|R13|+|R16|) / (CT7+T78+CT8) = 3.506 satisfies

[0575] 2.0 < (|R13|+|R16|) / (CT7+T78+CT8) < 4.5.

[0576] • Table 15's |R14 / R15| = 0.943 satisfies 0.6 < |R14 / R15| < 1.3.

[0577] • Table 15's TL / f = 2.872 satisfies 2.0 < TL / f < 4.0.

[0578] • Table 15's |Sag11 / Sag31| = 0.545 satisfies |Sag11 / Sag31| < 5.0.

[0579] • |DST1.0 / FOV| = 0.430 of Table 15 satisfies |DST1.0 / FOV| < 0.5.

[0580] • |DST1.0 / DST0.7| = 6.983 of Table 15 satisfies |DST1.0 / DST0.7| < 10.

[0581] • f / (CT7+T78+CT8) = 2.175 of Table 15 satisfies 0.3 < f / (CT7+T78+CT8) < 3.5.

[0582] • CT7 / CT8 = 1.500 of Table 15 satisfies 1.0 < CT7 / CT8 < 2.0.

[0583] • |f / f12| + |f / f3| = 0.843 of Table 15 satisfies 0.3 < |f / f12| + |f / f3| < 1.5.

[0584] • f12 / f6 = 1.096 of Table 15 satisfies 0.5 < f12 / f6 < 1.5.

[0585] • SD / TD = 0.569 of Table 15 satisfies 0.45 < SD / TD < 0.65.

[0586] • YC82 / f = 0.614 of Table 15 satisfies 0.45 < YC82 / f < 0.75.

[0587] • CT1 / CT8 = 1.125 of Table 15 satisfies 0.5 < CT1 / CT8 < 1.5.

[0588] • |f5 / f12| = 1.217 of Table 15 satisfies 0.8 < |f5 / f12| < 2.5.

[0589] • (T12+T23+T67+T78) / (T34+T45+T56) = 1.057 of Table 15 satisfies

[0590] (T12+T23+T67+T78) / (T34+T45+T56) < 1.5.

[0591] • Nmax = 1.680 of Table 15 satisfies 1.60 < Nmax < 1.72.

[0592] As above, it can be confirmed that each value of Table 15 regarding the optical system 50 of Example 5 satisfies each conditional expression of the present disclosure.

[0593] [Example 6]

[0594] Figure 17 is a schematic view of the optical imaging device 1 of the present Example 6,Figure 18 is an aberration diagram showing, in order from the left, the spherical aberration, the coma, and the distortion (distortion aberration) in the optical system 60 of Embodiment 6.

[0595] In the optical system 60 of this Embodiment 6:

[0596] The first lens 61 has a negative refractive power and is formed of a plastic material. In the first lens 61, the object-side face 61a is a convex face, and the image-side face 61b is a concave face. Both the object-side face 61a and the image-side face 61b of this first lens 61 are aspherical faces.

[0597] The second lens 62 has a negative refractive power and is formed of a plastic material. In the second lens 62, the object-side face 62a is a concave face, and the image-side face 62b is a concave face. Both the object-side face 62a and the image-side face 62b of this second lens 62 are aspherical faces.

[0598] The third lens 63 has a positive refractive power and is formed of a plastic material. In the third lens 63, the object-side face 63a is a convex face, and the image-side face 63b is a concave face. Both the object-side face 63a and the image-side face 63b of this third lens 63 are aspherical faces.

[0599] The fourth lens 64 has a positive refractive power and is formed of a plastic material. In the fourth lens 64, the object-side face 64a is a convex face, and the image-side face 64b is a convex face. Both the object-side face 64a and the image-side face 64b of this fourth lens 64 are aspherical faces.

[0600] The fifth lens 65 has a positive refractive power and is formed of a plastic material. In the fifth lens 65, the object-side face 65a is a concave face, and the image-side face 65b is a convex face. Both the object-side face 65a and the image-side face 65b of this fifth lens 65 are aspherical faces.

[0601] The sixth lens 66 has a negative refractive power and is formed of a plastic material. In the sixth lens 66, the object-side face 66a is a concave face, and the image-side face 66b is a convex face. Both the object-side face 66a and the image-side face 66b of this sixth lens 66 are aspherical faces.

[0602] The seventh lens 67 has a positive refractive power and is formed of a plastic material. In the seventh lens 67, the object-side face 67a is a convex face, and the image-side face 67b is a convex face. Both the object-side face 67a and the image-side face 67b of this seventh lens 67 are aspherical faces.

[0603] The eighth lens 68 has a negative refractive power and is formed of a plastic material. In the eighth lens 68, the object-side face 68a is a concave face, and the image-side face 68b is a concave face. Both the object-side face 68a and the image-side face 68b of this eighth lens 68 are aspherical faces.

[0604] The optical system 60 of this embodiment has the same aspherical surface formulae of the respective lenses 61 to 68 as the formula (1) of Embodiment 1. In addition, in this Embodiment 6, in calculating the values in the table, the terms of 15th order or higher (n≥15) of the formula (1) are calculated as 0.

[0605] In addition, in Table 16 below, actual numerical values are listed for the structure of the lenses, in Table 17, actual numerical values are listed for the aspherical surface coefficients of the respective lens surfaces, and in Table 18, actual numerical values are listed for the conditional expressions of the present disclosure.

[0606] Table 16

[0607]

[0608]

[0609] Table 17

[0610]

[0611] Table 18

[0612]

[0613] Whether each value of Table 18 satisfies each conditional expression of the present disclosure is as follows.

[0614] • |f1 / f2| = 5.660 of Table 18 satisfies |f1 / f2| < 6.

[0615] • |f12 / f3| = 0.208 of Table 18 satisfies |f12 / f3| < 0.5.

[0616] • T67 / T34 = 0.270 of Table 18 satisfies 0 < T67 / T34 < 1.0.

[0617] • TL / ImgH = 2.216 of Table 18 satisfies TL / ImgH < 3.

[0618] • (R7+R8) / (R7-R8) = 0.416 of Table 18 satisfies 0 < (R7+R8) / (R7-R8) < 1.0.

[0619] • T12 / T23 = 1.681 of Table 18 satisfies 0 < T12 / T23 < 3.0.

[0620] • T23 / T34 = 0.875 of Table 18 satisfies 0 < T23 / T34 < 2.0.

[0621] • tan(HFOV) = 3.700 of Table 18 satisfies 2.0 < tan(HFOV).

[0622] • Table 18 Fno = 2.20 satisfies 1.4 < Fno < 3.0.

[0623] • Table 18 Y11 / Y82 = 1.232 satisfies 0.8 < Y11 / Y82 < 1.5.

[0624] • Table 18 V6 / V7 = 0.329 satisfies 0 < V6 / V7 < 0.50.

[0625] • Table 18 (f / f4)-(f / f5) = 0.619 satisfies 0 < (f / f4)-(f / f5) < 2.0.

[0626] • Table 18 T67 / CT7 = 0.167 satisfies T67 / CT7 < 0.50.

[0627] • Table 18 T78 / CT8 = 0.250 satisfies T78 / CT8 < 0.70.

[0628] • Table 18 (|R13| + |R16|) / (CT7 + T78 + CT8) = 3.394 satisfies

[0629] 2.0 < (|R13| + |R16|) / (CT7 + T78 + CT8) < 4.5.

[0630] • Table 18 |R14 / R15| = 0.791 satisfies 0.6 < |R14 / R15| < 1.3.

[0631] • Table 18 TL / f = 2.953 satisfies 2.0 < TL / f < 4.0.

[0632] • Table 18 |Sag11 / Sag31| = 0.333 satisfies |Sag11 / Sag31| < 5.0.

[0633] • Table 18 |DST1.0 / FOV| = 0.428 satisfies |DST1.0 / FOV| < 0.5.

[0634] • Table 18 |DST1.0 / DST0.7| = 6.213 satisfies |DST1.0 / DST0.7| < 10.

[0635] • Table 18 f / (CT7 + T78 + CT8) = 2.202 satisfies 0.3 < f / (CT7 + T78 + CT8) < 3.5.

[0636] • Table 18 CT7 / CT8 = 1.500 satisfies 1.0 < CT7 / CT8 < 2.0.

[0637] • |f / f12| + |f / f3| = 0.856 of Table 18 satisfies 0.3 < |f / f12| + |f / f3| < 1.5.

[0638] • f12 / f6 = 1.084 of Table 18 satisfies 0.5 < f12 / f6 < 1.5.

[0639] • SD / TD = 0.553 of Table 18 satisfies 0.45 < SD / TD < 0.65.

[0640] • YC82 / f = 0.644 of Table 18 satisfies 0.45 < YC82 / f < 0.75.

[0641] • CT1 / CT8 = 1.202 of Table 18 satisfies 0.5 < CT1 / CT8 < 1.5.

[0642] • |f5 / f12| = 1.222 of Table 18 satisfies 0.8 < |f5 / f12| < 2.5.

[0643] • (T12+T23+T67+T78) / (T34+T45+T56) = 1.088 of Table 18 satisfies

[0644] (T12+T23+T67+T78) / (T34+T45+T56) < 1.5.

[0645] • Nmax = 1.680 of Table 18 satisfies 1.60 < Nmax < 1.72.

[0646] As described above, it is confirmed that each value of Table 18 of the optical system 60 of Example 6 satisfies each conditional expression of the present disclosure.

[0647] [Example 7]

[0648] Figure 19 is a schematic view of the optical imaging device 1 of the present Example 7, Figure 20 is an aberration diagram showing, in order from left to right, the spherical aberration, the coma, and the distortion (distortion aberration) in the optical system 70 of Example 7.

[0649] In the optical system 70 of the present Example 7:

[0650] The first lens 71 has a negative refractive power and is formed of a plastic material. In the first lens 71, the object-side face 71a is a convex face and the image-side face 71b is a concave face. Both the object-side face 71a and the image-side face 71b of the first lens 71 are aspherical faces.

[0651] The second lens 72 has a negative refractive power and is formed of a plastic material. In the second lens 72, the object-side face 72a is a concave face, and the image-side face 72b is a concave face. Both the object-side face 72a and the image-side face 72b of the second lens 72 are aspherical faces.

[0652] The third lens 73 has a positive refractive power and is formed of a plastic material. In the third lens 73, the object-side face 73a is a convex face, and the image-side face 73b is a concave face. Both the object-side face 73a and the image-side face 73b of the third lens 73 are aspherical faces.

[0653] The fourth lens 74 has a positive refractive power and is formed of a plastic material. In the fourth lens 74, the object-side face 74a is a convex face, and the image-side face 74b is a convex face. Both the object-side face 74a and the image-side face 74b of the fourth lens 74 are aspherical faces.

[0654] The fifth lens 75 has a positive refractive power and is formed of a plastic material. In the fifth lens 75, the object-side face 75a is a concave face, and the image-side face 75b is a convex face. Both the object-side face 75a and the image-side face 75b of the fifth lens 75 are aspherical faces.

[0655] The sixth lens 76 has a negative refractive power and is formed of a plastic material. In the sixth lens 76, the object-side face 76a is a concave face, and the image-side face 76b is a convex face. Both the object-side face 76a and the image-side face 76b of the sixth lens 76 are aspherical faces.

[0656] The seventh lens 77 has a positive refractive power and is formed of a plastic material. In the seventh lens 77, the object-side face 77a is a convex face, and the image-side face 77b is a convex face. Both the object-side face 77a and the image-side face 77b of the seventh lens 77 are aspherical faces.

[0657] The eighth lens 78 has a negative refractive power and is formed of a plastic material. In the eighth lens 78, the object-side face 78a is a concave face, and the image-side face 78b is a concave face. Both the object-side face 78a and the image-side face 78b of the eighth lens 78 are aspherical faces.

[0658] The aspherical face formulas of the respective lenses 71 to 78 of the optical system 70 of this embodiment are the same as the formula (1) of Embodiment 1. In addition, in this embodiment 7, when the values in the following table are calculated, the terms of 15th order or higher (n≥15) of the formula (1) are calculated as 0.

[0659] In addition, in the following Table 19, actual numerical values are listed for the structures of the lenses, in Table 20, actual numerical values are listed for the aspherical coefficients of the respective lens faces, and in Table 21, actual numerical values are listed for the conditional formulas of the present disclosure.

[0660] Table 19

[0661]

[0662]

[0663] Table 20

[0664]

[0665] Table 21

[0666]

[0667] Whether each value of Table 21 satisfies each conditional expression of the present disclosure is shown below.

[0668] • |f1 / f2| = 5.803 of Table 21 satisfies |f1 / f2| < 6.

[0669] • |f12 / f3| = 0.212 of Table 21 satisfies |f12 / f3| < 0.5.

[0670] • T67 / T34 = 0.270 of Table 21 satisfies 0 < T67 / T34 < 1.0.

[0671] • TL / ImgH = 2.200 of Table 21 satisfies TL / ImgH < 3.

[0672] • (R7+R8) / (R7-R8) = 0.415 of Table 21 satisfies 0 < (R7+R8) / (R7-R8) < 1.0.

[0673] • T12 / T23 = 1.578 of Table 21 satisfies 0 < T12 / T23 < 3.0.

[0674] • T23 / T34 = 0.869 of Table 21 satisfies 0 < T23 / T34 < 2.0.

[0675] • tan(HFOV) = 3.702 of Table 21 satisfies 2.0 < tan(HFOV).

[0676] • Fno = 2.08 of Table 21 satisfies 1.4 < Fno < 3.0.

[0677] • Y11 / Y82 = 1.214 of Table 21 satisfies 0.8 < Y11 / Y82 < 1.5.

[0678] • V6 / V7 = 0.329 of Table 21 satisfies 0 < V6 / V7 < 0.50.

[0679] • (f / f4)-(f / f5) = 0.615 of Table 21 satisfies 0 < (f / f4)-(f / f5) < 2.0.

[0680] • T67 / CT7 = 0.167 of Table 21 satisfies T67 / CT7 < 0.50.

[0681] • T78 / CT8 = 0.250 of Table 21 satisfies T78 / CT8 < 0.70.

[0682] • (|R13| + |R16|) / (CT7 + T78 + CT8) = 3.385 of Table 21 satisfies

[0683] 2.0 < (|R13| + |R16|) / (CT7 + T78 + CT8) < 4.5.

[0684] • |R14 / R15| = 0.787 of Table 21 satisfies 0.6 < |R14 / R15| < 1.3.

[0685] • TL / f = 2.940 of Table 21 satisfies 2.0 < TL / f < 4.0.

[0686] • |Sag11 / Sag31| = 0.326 of Table 21 satisfies |Sag11 / Sag31| < 5.0.

[0687] • |DST1.0 / FOV| = 0.427 of Table 21 satisfies |DST1.0 / FOV| < 0.5.

[0688] • |DST1.0 / DST0.7| = 6.346 of Table 21 satisfies |DST1.0 / DST0.7| < 10.

[0689] • f / (CT7 + T78 + CT8) = 2.195 of Table 21 satisfies 0.3 < f / (CT7 + T78 + CT8) < 3.5.

[0690] • CT7 / CT8 = 1.500 of Table 21 satisfies 1.0 < CT7 / CT8 < 2.0.

[0691] • |f / f12| + |f / f3| = 0.853 of Table 21 satisfies 0.3 < |f / f12| + |f / f3| < 1.5.

[0692] • f12 / f6 = 1.082 of Table 21 satisfies 0.5 < f12 / f6 < 1.5.

[0693] • SD / TD = 0.556 of Table 21 satisfies 0.45 < SD / TD < 0.65.

[0694] • YC82 / f = 0.645 of Table 21 satisfies 0.45 < YC82 / f < 0.75.

[0695] • CT1 / CT8 = 1.205 of Table 21 satisfies 0.5 < CT1 / CT8 < 1.5.

[0696] • |f5 / f12| = 1.216 of Table 21 satisfies 0.8 < |f5 / f12| < 2.5.

[0697] • (T12+T23+T67+T78) / (T34+T45+T56) = 1.051 of Table 21 satisfies

[0698] (T12+T23+T67+T78) / (T34+T45+T56) < 1.5.

[0699] • Nmax = 1.680 of Table 21 satisfies 1.60 < Nmax < 1.72.

[0700] As above, it can be confirmed that each value of Table 21 regarding the optical system 70 of Example 7 satisfies each conditional expression of the present disclosure.

[0701] While the present disclosure has been described above by way of embodiments, with reference to the accompanying drawings, adequately and sufficiently to express the present disclosure, it should be recognized by those skilled in the art that modifications and / or improvements of the above-described embodiments are easily realized. Therefore, as long as the modified or improved manner implemented by those skilled in the art is not at a level that deviates from the scope of the claims recited in the claims, it can be interpreted that the modified or improved manner is included in the scope of the claims.

[0702] Explanation of Reference Numerals:

[0703] 1: Optical imaging device

[0704] 2: Photoelectric conversion element

[0705] 3: Sensor holder

[0706] 4: Driving portion

[0707] 5: Aperture stop

[0708] 6: Lens holding member

[0709] 7: Light shielding member

[0710] 8: Light shielding plate

[0711] 8a: Light shielding and interval adjustment spacer

[0712] 9: Lens pressing ring

[0713] F: IR cut filter

[0714] 10, 20, 30, 40, 50, 60, 70: Imaging optical system

[0715] 10a: imaging surface

[0716] 11, 21, 31, 41, 51, 61, 71: first lens

[0717] 11a, 21a, 31a, 41a, 51a, 61a, 71a: object side surface of first lens

[0718] 11b, 21b, 31b, 41b, 51b, 61b, 71b: image side surface of first lens

[0719] 12, 22, 32, 42, 52, 62, 72: second lens

[0720] 12a, 22a, 32a, 42a, 52a, 62a, 72a: object side surface of second lens

[0721] 12b, 22b, 32b, 42b, 52b, 62b, 72b: image side surface of second lens

[0722] 13, 23, 33, 34, 35, 36, 37: third lens

[0723] 13a, 23a, 33a, 43a, 53a, 63a, 73a: object side surface of third lens

[0724] 13b, 23b, 33b, 43b, 53b, 63b, 73b: image side surface of third lens

[0725] 14, 24, 34, 44, 45, 46, 47: fourth lens

[0726] 14a, 24a, 34a, 44a, 54a, 64a, 74a: object side surface of fourth lens

[0727] 14b, 24b, 34b, 44b, 54b, 64b, 74b: image side surface of fourth lens

[0728] 15, 25, 35, 45, 55, 56, 57: fifth lens

[0729] 15a, 25a, 35a, 45a, 55a, 65a, 75a: object side surface of fifth lens

[0730] 15b, 25b, 35b, 45b, 55b, 65b, 75b: image side surface of fifth lens

[0731] 16, 26, 36, 46, 56, 66, 67: sixth lens

[0732] 16a, 26a, 36a, 46a, 56a, 66a, 76a: object side surface of the sixth lens

[0733] 16b, 26b, 36b, 46b, 56b, 66b, 76b: image side surface of the sixth lens

[0734] 17, 27, 37, 47, 57, 67, 77: seventh lens

[0735] 17a, 27a, 37a, 47a, 57a, 67a, 77a: object side surface of the seventh lens

[0736] 17b, 27b, 37b, 47b, 57b, 67b, 77b: image side surface of the seventh lens

[0737] 171a: central portion of the object side surface of the seventh lens

[0738] 172a: peripheral portion of the object side surface of the seventh lens

[0739] 18a, 28a, 38a, 48a, 58a, 68a, 78a: object side surface of the eighth lens

[0740] 18b, 28b, 38b, 48b, 58b, 68b, 78b: image side surface of the eighth lens

[0741] 181b: central portion of the image side surface of the eighth lens

[0742] 182b: peripheral portion of the image side surface of the eighth lens

[0743] F: focal length of the entire optical system

[0744] Fno: aperture value

[0745] FOV: maximum field angle

[0746] HFOV: half of the maximum field angle

[0747] TL: distance along the optical axis from the object side surface of the first lens to the imaging surface

[0748] ImgH: maximum image height of the optical system

[0749] f1: focal length of the first lens

[0750] f2: focal length of the second lens

[0751] f3: focal length of the third lens

[0752] f4: focal length of the fourth lens

[0753] f5: focal length of the fifth lens

[0754] f6: focal length of the sixth lens

[0755] f12: combined focal length of the first lens and the second lens

[0756] SD: distance along the optical axis from the stop to the image-side surface of the seventh lens

[0757] TD: distance along the optical axis from the object-side surface of the first lens to the image-side surface of the eighth lens

[0758] CT1: center thickness of the first lens

[0759] CT7: center thickness of the seventh lens

[0760] CT8: center thickness of the eighth lens

[0761] T12: distance along the optical axis from the image-side surface of the first lens to the object-side surface of the second lens

[0762] T23: distance along the optical axis from the image-side surface of the second lens to the object-side surface of the third lens

[0763] T34: distance along the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens

[0764] T45: distance along the optical axis from the image-side surface of the fourth lens to the object-side surface of the fifth lens

[0765] T56: distance along the optical axis from the image-side surface of the fifth lens to the object-side surface of the sixth lens

[0766] T67: distance along the optical axis from the image-side surface of the sixth lens to the object-side surface of the seventh lens

[0767] T78: distance along the optical axis from the image-side surface of the seventh lens to the object-side surface of the eighth lens

[0768] R7: radius of curvature of the object-side surface of the fourth lens

[0769] R8: radius of curvature of the image-side surface of the fourth lens

[0770] R13: radius of curvature of the object-side surface of the seventh lens

[0771] R14: radius of curvature of the image-side surface of the seventh lens

[0772] R15: radius of curvature of the object-side surface of the eighth lens

[0773] R16: radius of curvature of the image-side surface of the eighth lens

[0774] V6: Abbe number of the sixth lens

[0775] V7: Abbe number of the seventh lens

[0776] Y11: Maximum effective radius of the object-side surface of the first lens

[0777] Y82: Maximum effective radius of the image-side surface of the eighth lens

[0778] Yc82: Distance from the vertex of the image-side surface of the eighth lens to the maximum inflection point of the image-side surface of the eighth lens in a direction orthogonal to the optical axis

[0779] Sag11: Amount of displacement in the optical axis direction from the intersection with the optical axis in the object-side surface of the first lens to the position of the maximum effective radius of the object-side surface of the first lens

[0780] Sag31: Amount of displacement in the optical axis direction from the intersection with the optical axis in the object-side surface of the third lens to the position of the maximum effective radius of the object-side surface of the third lens

[0781] DST1.0: Distortion aberration amount at the maximum image height

[0782] DST0.7: Distortion aberration amount at 70% of the maximum image height

[0783] Nmax: Refractive index maximum value of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens

Claims

1. An imaging optical system, characterized in that: With: lens group, The lens group is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged in order from the object side to the image side; The first lens has negative refractive power, and its image side surface is concave; The second lens has negative refractive power, and its image side surface is concave; The third lens has positive refractive power, and its image side surface is concave; The fourth lens has positive refractive power, and its image-side surface is convex; The fifth lens has positive refractive power, and its object-side surface is concave and its image-side surface is convex; The sixth lens has negative refractive power, and its object-side surface is concave and its image-side surface is convex; The seventh lens has an object-side surface that is an aspheric surface with a convex center portion and at least one inflection point in a peripheral portion of the center portion, and a convex image-side surface. The eighth lens has a concave object-side surface and an aspheric image-side surface with a concave center and at least one inflection point at a periphery of the center. When the focal length of the first lens is f1, the focal length of the second lens is f2, the combined focal length of the first lens and the second lens is f12, the focal length of the third lens is f3, the distance along the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens is T34, and the distance along the optical axis from the image-side surface of the sixth lens to the object-side surface of the seventh lens is T67, the following conditions are satisfied: |f1 / f2|<6 |f12 / f3|<0.5 0<T67 / T34<1.

0.

2. The imaging optical system according to claim 1, wherein have: an aperture stop, the aperture stop being disposed between the third lens and the fourth lens; When the distance along the optical axis from the object-side surface of the first lens to the imaging plane is set to TL and the maximum image height is set to ImgH, the following is satisfied: TL / ImgH<3.

3. The imaging optical system according to claim 1, wherein When the curvature radius of the object-side surface of the fourth lens is set to R7 and the curvature radius of the image-side surface of the fourth lens is set to R8, the following conditions are satisfied: 0<(R7+R8) / (R7-R8)<1.

0.

4. The imaging optical system according to claim 1, wherein When the distance along the optical axis from the image-side surface of the first lens to the object-side surface of the second lens is set to T12, the distance along the optical axis from the image-side surface of the second lens to the object-side surface of the third lens is set to T23, and the distance along the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens is set to T34, the following conditions are satisfied: 0<T12 / T23<3.0 0<T23 / T34<2.

0.

5. The imaging optical system according to claim 1, wherein When half of the maximum field of view angle is set to HFOV and the aperture value is set to Fno, the following conditions are satisfied: 2.0<tan(HFOV) 1.4<Fno<3.

0.

6. The imaging optical system according to claim 1, wherein: When the maximum effective radius of the object-side surface of the first lens is set to Y11, and the maximum effective radius of the image-side surface of the eighth lens is set to Y82, the following conditions are satisfied: 0.8<Y11 / Y82<1.

5.

7. The imaging optical system according to claim 1, wherein: When the Abbe coefficient of the sixth lens is set to V6 and the Abbe coefficient of the seventh lens is set to V7, the following conditions are satisfied: 0<V6 / V7<0.

50.

8. The imaging optical system according to claim 1, wherein When the focal length of the imaging optical system is set to f, the focal length of the fourth lens is set to f4, and the focal length of the fifth lens is set to f5, the following conditions are satisfied: 0<(f / f4)-(f / f5)<2.

0.

9. The imaging optical system according to claim 1, wherein When the distance along the optical axis from the image-side surface of the sixth lens to the object-side surface of the seventh lens is set to T67, the thickness along the optical axis of the seventh lens is set to CT7, the distance along the optical axis from the image-side surface of the seventh lens to the object-side surface of the eighth lens is set to T78, and the thickness along the optical axis of the eighth lens is set to CT8, the following conditions are satisfied: T67 / CT7<0.50 T78 / CT8<0.

70.

10. The imaging optical system according to claim 1, wherein When the radius of curvature of the object-side surface of the seventh lens is R13, the radius of curvature of the image-side surface of the seventh lens is R14, the radius of curvature of the object-side surface of the eighth lens is R15, the radius of curvature of the image-side surface of the eighth lens is R16, the thickness of the seventh lens along the optical axis is CT7, the distance along the optical axis from the image-side surface of the seventh lens to the object-side surface of the eighth lens is T78, the thickness of the eighth lens along the optical axis is CT8, the distance along the optical axis from the object-side surface of the first lens to the imaging plane is TL, and the focal length of the entire imaging optical system is f, the following is satisfied: 2.0<(|R13|+|R16|) / (CT7+T78+CT8)<4.5 0.6<|R14 / R15| / 1.3 2.0<TL / f<4.

0.

11. The imaging optical system according to claim 1, wherein When the displacement in the optical axis direction from the intersection of the object-side surface of the first lens with the optical axis to the maximum effective radius position of the object-side surface is set as Sag11, and the displacement in the optical axis direction from the intersection of the object-side surface of the third lens with the optical axis to the maximum effective radius position of the object-side surface is set as Sag31, the following conditions are satisfied: |Sag11 / Sag31|<5.

0.

12. The imaging optical system according to claim 1, wherein When the distortion aberration amount at the maximum image height is set to DST1.0, the distortion aberration amount at 70% of the maximum image height is set to DST0.7, and the maximum field of view angle is set to FOV, the following conditions are satisfied: |DST1.0 / FOV|<0.5% / degree |DST1.0 / DST0.7|<10.

13. An imaging optical system, characterized in that: With: lens group, The lens group is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged in order from the object side to the image side; The first lens has negative refractive power; The image-side surface of the second lens is concave; The image side surface of the third lens is concave; The image-side surface of the fourth lens is a convex surface; The fifth lens has positive refractive power, and its image-side surface is convex; The sixth lens has negative refractive power, and its object-side surface is concave and its image-side surface is convex; The seventh lens element has positive refractive power, and its object-side surface is an aspherical surface with a convex surface at the center and at least one inflection point at the periphery of the center; The image-side surface of the eighth lens is an aspheric surface with a concave center portion and at least one inflection point at a periphery of the center portion; When the focal length of the first lens is f1, the focal length of the second lens is f2, the combined focal length of the first lens and the second lens is f12, the focal length of the third lens is f3, the focal length of the entire optical system consisting of the first to eighth lenses is f, the thickness of the seventh lens along the optical axis is CT7, the distance along the optical axis from the image-side surface of the seventh lens to the object-side surface of the eighth lens is T78, and the thickness of the eighth lens along the optical axis is CT8, the following conditions are satisfied: 0.3<f / (CT7+T78+CT8)<3.5 1.0<CT7 / CT8<2.0 |f1 / f2|<6 |f12 / f3|<0.

5.

14. The imaging optical system according to claim 13, wherein: The image-side surface of the first lens is concave; When the radius of curvature of the object-side surface of the seventh lens is set to R13, the radius of curvature of the image-side surface of the seventh lens is set to R14, the radius of curvature of the object-side surface of the eighth lens is set to R15, the radius of curvature of the image-side surface of the eighth lens is set to R16, the thickness of the seventh lens along the optical axis is set to CT7, the distance along the optical axis from the image-side surface of the seventh lens to the object-side surface of the eighth lens is set to T78, and the thickness of the eighth lens along the optical axis is set to CT8, the following conditions are satisfied: 2.0<(|R13|+|R16|) / (CT7+T78+CT8)<4.5 0.6<|R14 / R15| / 1.

3.

15. The imaging optical system according to claim 13, wherein satisfy: 0.3<|f / f12|+|f / f3|<1.

5.

16. The imaging optical system according to claim 13, wherein: When the focal length of the sixth lens is set to f6, the following is satisfied: 0.5<f12 / f6<1.

5.

17. The imaging optical system according to claim 13, wherein: have: Aperture stop; When the distance along the optical axis from the aperture stop to the image-side surface of the eighth lens is SD, the distance along the optical axis from the object-side surface of the first lens to the image-side surface of the eighth lens is TD, the maximum effective radius of the object-side surface of the first lens is Y11, and the maximum effective radius of the image-side surface of the eighth lens is Y82, the following conditions are satisfied: 0.45<SD / TD<0.65 0.8<Y11 / Y82<1.

5.

18. The imaging optical system according to claim 13, wherein When the distance between the maximum inflection point of the image-side surface of the eighth lens and the optical axis in a direction perpendicular to the optical axis is Yc82, the following is satisfied: 0.45<Yc82 / f<0.

75.

19. The imaging optical system according to claim 13, wherein When the distortion aberration amount at the maximum image height is set to DST1.0, the distortion aberration amount at 70% of the maximum image height is set to DST0.7, and the maximum field of view angle is set to FOV, the following conditions are satisfied: |DST1.0 / FOV|<0.5% / degree |DST1.0 / DST0.7|<10.

20. An optical camera device, characterized in that: have: The imaging optical system according to any one of claims 1 to 19; a driving unit that drives all or part of the first to eighth lenses included in the imaging optical system; and The photoelectric conversion element is arranged on the imaging surface of the imaging optical system.

Images