Imaging optical system, lens unit, imaging device, and moving body

Abstract

An imaging optical system that suppresses changes in optical performance before and after a temperature change. When the half-angle of view is set to W, any angle of view within the half-angle of view W is set to Wi, the exit pupil distance at the angle of view Wi is set to gi, and the exit pupil distance on the optical axis is set to g0, it satisfies 30 < W and 0.9 < |gi / g0| < 1.1.

Description

Technical Field

[0001] The present invention relates to an imaging optical system, a lens unit, an imaging device, and a moving body. Background Art

[0002] In an imaging optical system mounted in an imaging device such as a digital camera or a video camera, generally, in addition to achieving high resolution and low distortion, it is required to satisfy various conditions such as a small F-number, a large aperture, and a small size so that good imaging recognition can be performed even in a dark environment such as at night.

[0003] Among such imaging optical systems, particularly, an imaging optical system for so-called sensing used in vehicles, surveillance, etc. is used outdoors more frequently, and is used in a harsh environment where the temperature changes greatly or the temperature changes repeatedly.

[0004] In an imaging optical system for sensing, it is required that the optical performance changes little even under the influence of such changes in the surrounding environment.

[0005] In addition, for example, in a lens unit, there is a case where, due to a change in the temperature environment, the lens constituting the lens unit is displaced in the vertical direction with respect to the optical axis, and thus the relative positional relationship of the lenses changes (hereinafter, referred to as lens eccentricity). Due to this lens eccentricity, the imaging position of light is shifted over the entire imaging surface.

[0006] In an imaging optical system for sensing, in addition to maintaining the resolution during temperature changes, in order to suppress such lens eccentricity and correctly obtain the size and shape of an object to be sensed, it is required to maintain the imaging position of the object before and after the temperature change (suppress the change in the imaging position in the vertical direction with respect to the optical axis).

[0007] <Prior Art Documents>

[0008] <Patent Documents>

[0009] Patent Document 1: Japanese Patent No. 6372744

[0010] Patent Document 2: Japanese Patent No. 6459521

[0011] Patent Document 3: Japanese Unexamined Patent Application Publication No. 2015-118152

[0012] Patent Document 4: Japanese Unexamined Patent Application Publication No. 2018-77291

[0013] Patent Document 5: Japanese Unexamined Patent Application Publication No. 2019-020505 Summary of the Invention

[0014] <Problems to be Solved by the Present Invention>

[0015] The present invention has been made in view of the above problems, and an object thereof is to provide an imaging optical system that suppresses changes in optical performance before and after a temperature change.

[0016] <Means for Solving the Problems>

[0017] To solve the above problems, in the imaging optical system of the present invention, a subject image is formed on an imaging element. When the half angle of view is set to W, any angle of view within the half angle of view W is set to Wi, the exit pupil distance in the angle of view Wi is set to gi, and the exit pupil distance on the optical axis is set to g0, 30 < W and 0.9 < |gi / g0| < 1.1 are satisfied.

[0018] <Effects of the Invention>

[0019] According to the present invention, it is possible to provide an imaging optical system that suppresses changes in optical performance before and after a temperature change. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 FIG. is an example showing the configuration of an imaging device in an embodiment of the present invention.

[0021] Figure 2 FIG. shows Figure 1 an example of the configuration of the imaging device shown.

[0022] Figure 3 FIG. is an example showing the configuration of the control unit of the imaging device.

[0023] Figure 4 FIG. is an example showing the configuration of the imaging optical system in the first embodiment of the present invention.

[0024] Figure 5 FIG. is an example showing a method of supporting a lens in the first embodiment of the present invention.

[0025] Figure 6 FIG. is Figure 5 an enlarged view in the embodiment shown.

[0026] Figure 7 FIG. is a longitudinal aberration diagram in Numerical Example 1 of the present invention.

[0027] Figure 8 FIG. is an example showing the influence of lens movement in Numerical Example 1.

[0028] Figure 9 FIG. is an example showing the configuration of the imaging optical system shown in Numerical Example 2.

[0029] Figure 10 is Figure 9 the longitudinal aberration diagram in the illustrated embodiment.

[0030] Figure 11 is a diagram showing an example of the influence of lens movement in Numerical Example 2.

[0031] Figure 12 is a diagram showing an example of the configuration of the imaging optical system shown in Numerical Example 3.

[0032] Figure 13 is Figure 12 the longitudinal aberration diagram in the illustrated embodiment.

[0033] Figure 14 is a diagram showing an example of the influence of lens movement in Numerical Example 3.

[0034] Figure 15 is a diagram showing an example of another configuration of the imaging device in the embodiment of the present invention.

[0035] Figure 16 is a diagram showing an example of the configuration of the stereo camera device in the embodiment of the present invention.

[0036] Figure 17 is showing Figure 16 an example of the operation of the illustrated stereo camera device.

[0037] Figure 18 is showing Figure 16 an example of the application of the illustrated stereo camera device.

[0038] Explanation of reference numerals

[0039] 1 Imaging optical system

[0040] 13 Imaging element (light-receiving element)

[0041] 20 Lens barrel (support structure)

[0042] 21 Inner wall surface

[0043] 22 Gap portion

[0044] 23 Pressing ring

[0045] 24 Spacer ring

[0046] 100 Imaging device (digital camera)

[0047] 200 Imaging unit

[0048] 300 Stereo camera device

[0049] L1 to L6 form the lenses of the imaging optical system

[0050] g0 exit pupil distance

[0051] gi exit pupil distance

[0052] IMG light-receiving surface of the imaging element and the light-receiving element

[0053] W half field of view

[0054] Wi field of view

[0055] L1a first side surface

[0056] L1b second side surface

[0057] φa diameter of the first side surface

[0058] φb diameter of the second side surface

[0059] AU moving body Detailed implementation mode

[0060] As an example of the imaging device of the present invention, a digital camera 100 is exemplified in Figure 1 、 Figure 2 The digital camera 100 is shown.

[0061] Figure 1 Fig. schematically shows the appearance of the digital camera 100 as viewed from the object side, i.e., the front surface side as the subject side.

[0062] Similarly Figure 2 Fig. schematically shows the appearance of the digital camera 100 as viewed from the photography side, i.e., the back side.

[0063] Although the digital camera 100 is a digital camera in the present embodiment, it can also be a camera device for sensing purposes such as a surveillance camera, a process surveillance camera for a production line, a vehicle-mounted camera, etc., or a stereo camera device.

[0064] The digital camera 100 includes a camera body, i.e., a housing 5, an imaging optical system 1 composed of a plurality of lenses, an optical viewfinder 2, an electronic flash type flash 3, a shutter button 4, a power switch 6, a liquid crystal display 7, an operation button 8, and a memory card slot 9.

[0065] In addition, as Figure 3 shown, the digital camera 100 has a central arithmetic unit of the control unit, i.e., a CPU 11, an image processing unit 12, a light-receiving element 13, a signal processing unit 14, a semiconductor memory 15, and a communication card 16 inside the housing 5.

[0066] The digital camera 100 includes an imaging optical system 1 and a light-receiving element 13 configured as an image sensor using a CMOS (Complementary Metal Oxide Semiconductor) imaging element or a CCD (Charge Coupled Device) imaging element, etc. The optical image of the subject formed by the imaging optical system 1 is read by the image sensor, i.e., the light-receiving element 13.

[0067] The optical image of the subject read by the light-receiving element 13 is appropriately processed by a signal processing unit 14 controlled by a CPU 11 and thus converted into digital image information. Moreover, prescribed image processing is performed by an image processing unit 12 and then stored in a semiconductor memory 15 serving as a non-volatile memory or the like, i.e., a storage unit.

[0068] As a storage unit or storage medium for storing such images, in addition to storing in the semiconductor memory 15, for example, it can be transmitted to an external information processing terminal using a communication card 16, or a memory card inserted into a memory card slot 9 can also be used.

[0069] The liquid crystal display 7 can display not only the photographed image data but also the image data stored in the semiconductor memory 15. In addition, setting changes of image processing performed by operating a button 8 are also displayed on the liquid crystal display 7.

[0070] It should be noted that although the liquid crystal display 7 is used as a display device in this embodiment, it is not limited to this configuration, and an organic EL display or other display devices can also be used.

[0071] As described later, the imaging optical system 1 is composed of a plurality of lenses for forming the imaging optical system, and the lens on the frontmost surface side (object side) is covered by a lens hood of the housing 5 when carrying the digital camera 100.

[0072] In this embodiment, when the operator operates the power switch 6 to turn on the power, the lens hood opens, and the object surface of the lens on the object side of the imaging optical system 1 is exposed from the housing 5.

[0073] The semiconductor memory 15 and the communication card 16 are loaded into a dedicated or general slot such as the memory card slot 9 for use.

[0074] The imaging optical system 1 of the digital camera 100 will be described.

[0075] The imaging optical system 1 for the digital camera 100 is an optical system similar to the so-called negative focal length type in this embodiment.

[0076] The negative focal length type imaging optical system has a lens group with a negative optical power arranged in the front group on the object side and a lens group with a positive optical power arranged in the rear group on the image side. Both the front group and the rear group have the effect of moving the exit pupil away from the image plane.

[0077] In addition, a space for disposing filtering elements such as an optical low-pass filter and an infrared cut-off filter is ensured between the imaging element, thereby achieving optical performance suitable for sensing applications.

[0078] In the present embodiment, as Figure 4 shown, the imaging optical system 1 is sequentially provided with a first lens L1 having a negative refractive power and a meniscus shape, a second lens L2 having a negative refractive power and a meniscus shape, a third lens L3 having a positive refractive power, a cemented lens L45 obtained by cementing a fourth lens L4 having a positive refractive power and a fifth lens L5 having a negative refractive power, and a sixth lens L6 having a positive refractive power from the object side.

[0079] In the arrangement configuration of the imaging optical system 1, an aperture stop S is disposed between the third lens L3 and the cemented lens L45, and a glass filter F1 such as an infrared cut-off filter and a low-pass filter is disposed on the image plane side with respect to the sixth lens L6. Further, a glass cover CG is disposed on the image plane side thereof. In addition, the light receiving surface IMG of the light receiving element 13 is of course on the most image plane side.

[0080] With this configuration, the imaging optical system 1 is an imaging optical system that forms a subject image on the light receiving surface IMG of the light receiving element 13.

[0081] The first lens L1 is a meniscus lens having a concave surface on the image plane side.

[0082] With this first lens L1, it is possible to adjust the distortion while maintaining a negative refractive power.

[0083] In addition, in order to ensure a wide viewing angle and a back focal length of the imaging optical system 1, and in order to bend off-axis chief rays over a wide range of viewing angles, a certain degree of larger negative refractive power is required for the first lens L1.

[0084] However, generally, the stronger the refractive power of a lens, the higher the sensitivity of the optical axis shift due to the decentration of the lens tends to be.

[0085] By adjusting the distortion in the first lens L1, it is possible to adjust the generation of distortion of each lens constituting the imaging optical system 1, thereby reducing the sensitivity of the optical axis shift distribution due to lens decentration.

[0086] For such distortion adjustment, it is known that adjusting the angle at which off-axis chief rays enter the lens surface is effective, but it is difficult to give it the aforementioned negative refractive power.

[0087] Therefore, by maintaining a certain degree of negative refractive power in the first lens L1 and minimizing the shift of the imaging position of light across the entire imaging surface, a meniscus shape with a convex surface on the object side is adopted, thereby minimizing the shift of the imaging position of light.

[0088] The second lens L2 is a meniscus lens with a concave surface on the object side.

[0089] The third lens L3 is a biconvex lens with positive refractive power, which corrects the spherical aberration generated in the first lens L1.

[0090] The fourth lens L4 and the fifth lens L5 are joined to form an integrated joined lens L45.

[0091] The joined lens L45 is effective in suppressing chromatic aberration and controlling higher-order aberrations. In addition, if the fourth lens L4 and the fifth lens L5 are joined, even when the eccentricity sensitivity in each lens is relatively high, the misalignment error can be suppressed, which is beneficial to improving the assembly accuracy.

[0092] The sixth lens L6 is a lens with at least one aspherical lens surface. While correcting various aberrations such as distortion, spherical aberration, field curvature, and coma, the overall length of the lens is set shorter than that of an imaging optical system composed only of spherical lenses, and the refractive power of the final lens is not made extremely strong.

[0093] The imaging optical system 1 uses an aspherical surface on either the object side or the image side of either the first lens L1 or the second lens L2, thereby reducing the shift of the light position within the imaging surface when the lens is eccentric while maintaining a wide viewing angle and good imaging performance.

[0094] In this way, by limiting the number of aspherical lenses, the imaging performance can be ensured without relying on expensive aspherical lenses, which is beneficial to cost reduction.

[0095] In addition, in the imaging optical system 1, when setting the half viewing angle: W, any viewing angle: Wi within the half viewing angle W, the exit pupil distance: gi at the viewing angle Wi, and the exit pupil distance: g0 on the optical axis, the following conditional expressions (1) and (2) are satisfied.

[0096] (Mathematical formula 1)

[0097] 30 < W ··· (1)

[0098] (Mathematical formula 2)

[0099] 0.9 < |gi / g0| < 1.1 * ·· (2)

[0100] The conditional expression (1) indicates that the half angle of view of the imaging optical system 1 is used in a wide-angle lens with an angle of view greater than 30°.

[0101] In addition, by restricting the ratio of the exit pupil distance within the angle of view to a range greater than 0.9 and less than 1.1 in the imaging plane, the image height shift in the imaging plane due to changes in the ambient temperature can be suppressed.

[0102] The exit pupil distance is the distance between the intersection point of the incident light ray on the image plane and the optical axis and the intersection point of the image plane and the optical axis.

[0103] When the ratio of the exit pupil distance is too large within the angle of view, a large difference occurs in the amount of change in the optical axis shift in the image plane when the lens is decentered. In this case, even if the optical power of each lens is sufficiently suppressed, it is difficult to fully satisfy the performance of the optical axis shift.

[0104] Therefore, in the present invention, the imaging optical system 1 using a wide-angle lens that satisfies the conditional expression (1) also satisfies the conditional expression (2), so that the ratio of the exit pupil distance is limited to a specified range within the angle of view. With this configuration, the image height shift in the imaging plane due to changes in the ambient temperature can be suppressed.

[0105] In order to ensure a wide angle of view and a long back focal length, it is necessary to make the lens on the object side such as the first lens L1 or the second lens L2 have the function of bending the off-axis chief ray. Therefore, in the present embodiment, a meniscus lens with a negative refractive power is arranged for the first lens L1 and the second lens L2. In order to further increase the refractive power, the surface of either the first lens L1 or the second lens L2 is an aspherical shape.

[0106] With this configuration, the imaging optical system 1 maintains the wide angle of view shown by the conditional expression (1).

[0107] As described above, in a lens with a large refractive power, the sensitivity of the optical axis shift based on the decentering of the lens tends to be high. That is, it is well known that the shift of the focal position due to changes in the ambient temperature tends to be large.

[0108] This is because in addition to, for example, the change in the optical path length due to thermal expansion caused by temperature changes, the so-called movement and tilt based on the thermal expansion of the lens mounting part, the shift of the focal position also occurs due to the change in the refractive index of the glass material.

[0109] Therefore, in the present embodiment, at least one of the first lens L1, the second lens L2, and the sixth lens L6, which have a large refractive power among the plurality of lenses constituting the imaging optical system 1, satisfies the following conditional expression (3).

[0110] Note that the temperature coefficient of the relative refractive index in air at 0°C to 20°C for light with a wavelength λ in the wavelength range of 580 nm to 640 nm is defined as dn / dt.

[0111] (Mathematical formula 3)

[0112] 5.3×10 -6 <dn / dt ··· (3)

[0113] In addition, in the present embodiment, for at least one of the first lens L1, the second lens L2, and the sixth lens L6, which have relatively large refractive powers among the plurality of lenses constituting the imaging optical system 1, the following conditional expression (4) is satisfied.

[0114] (Mathematical formula 4)

[0115] -5.7×10 -6 >dn / dt ··· (4)

[0116] The conditional expressions (3) and (4) will be described.

[0117] When the temperature rises in a lens with positive refractive power, if the temperature coefficient of the relative refractive index is positive, the focal position moves to the negative side.

[0118] Similarly, when the temperature coefficient of the relative refractive index is negative, the focal position moves to the positive side.

[0119] When the temperature rises in a lens with negative refractive power, conversely, if the temperature coefficient of the relative refractive index is positive, the focal position moves to the positive side.

[0120] Similarly, when the temperature coefficient of the relative refractive index is negative, the focal position moves to the negative side.

[0121] In this way, if a negative lens with a relatively large refractive power has a positive temperature coefficient of the relative refractive index that satisfies the conditional expression (3), the focal position moves to the positive side due to temperature changes.

[0122] In addition, if a positive lens with a relatively large refractive power has a negative temperature coefficient of the relative refractive index that satisfies the conditional expression (4), the focal position moves to the positive side due to temperature changes.

[0123] In this way, by having at least one lens formed of a glass material that satisfies the conditional expression (3) and a lens formed of a glass material that satisfies the conditional expression (4), respectively, the imaging optical system 1 can suppress the variation in the focal position during temperature changes.

[0124] It should be noted that preferably, this configuration is actually configured as described later to correct the shift of the focal position caused by the change in the air gap (surface gap) due to the thermal expansion of the lens barrel 20 and each lens caused by temperature changes. Therefore, in the present embodiment, particularly for the shift of the focal position caused by the material of the lens, the change in the focal position during temperature change is suppressed by a pair of lenses that respectively satisfy the conditional expressions (3) and (4).

[0125] Regarding the change in the focal position of such a lens, there are of course cases caused by the installation accuracy during manufacturing and the physical position change (lens eccentricity) of the lens due to thermal expansion.

[0126] Therefore, in the present embodiment, for the first lens L1, in order to suppress the change in position during lens eccentricity, through the support structure, i.e., the lens barrel 20 and the retaining ring 23, as Figure 5 shown, it is held. It should be noted that in the present embodiment, although it is set that the first lens L1 is installed and fixed between the lens barrel 20 and the separately installable retaining ring 23, it is not limited to this configuration. In addition, in the present embodiment, the lens barrel 20 and the retaining ring 23 together function as a "support structure" for supporting the lenses of the imaging optical system 1.

[0127] As Figure 5 shown, in the outer peripheral side surface of the first lens L1 extending in the optical axis direction of the lens, the lens side surface portion has a stepped structure, and has a first side surface L1a that does not contact the inner wall surface 21 of the lens barrel 20 and a second side surface L1b that contacts the inner wall surface 21 of the lens barrel 20.

[0128] Moreover, the diameter of the second side surface L1b of the first lens L1 is set to be smaller than the diameter of the first side surface L1a.

[0129] The second side surface L1b is installed in the internal space of the lens barrel 20 for positioning and holding the lens in the radial direction.

[0130] In other words, the first lens L1 has a protruding portion protruding from the side surface that is positioned by contacting the lens barrel 20, and a gap portion 22 is provided on the outer peripheral side surface of the protruding portion so as not to contact the lens barrel 20 and the retaining ring 23.

[0131] On the object surface side of the first lens L1, in order to sufficiently ensure the optical effective diameter and the optical outer diameter required to obtain a wide-angle field of view, it is necessary to ensure a large diameter.

[0132] On the other hand, if the first lens L1 is positioned at a large-diameter position, there is a problem that when there is a slight difference in installation accuracy and tilting from the plane perpendicular to the optical axis direction of the lens, the lens eccentricity amount becomes large.

[0133] Therefore, in the present embodiment, a second side surface L1b having a diameter smaller than that of the first side surface L1a is provided, and positioning is performed by abutting the second side surface L1b against the inner wall surface 21 of the lens barrel 20.

[0134] At this time, since the first side surface L1a is set to a shape that is not installed in the inner space of the lens barrel 20, the lens side surface L1a is not pressed by the inner wall surface 21 of the lens barrel 20. Moreover, when the first lens L1 is installed, the second side surface L1b of the first lens L1 is inserted along the optical axis direction so as to be installed in the inner space of the lens barrel 20, and is fixed by being pressed from the front surface by the retaining ring 23, thereby easily ensuring the accuracy during assembly.

[0135] In this way, since the diameter of the second side surface L1b that is positioned and held in the radial direction of the lens: φ1b is set to be smaller than the diameter of the first side surface L1a: φ1a, compared with the case where there is no second side surface and positioning and holding are performed on the first side surface, lens movement can be suppressed.

[0136] That is, in the present embodiment, when setting the diameter of the second side surface L1b: φb and the diameter of the first side surface L1a: φa that are positioned and held in the radial direction of the lens L, there is a lens that satisfies the conditional expression (5).

[0137] (Mathematical formula 5)

[0138] φa / φb < 0.9 ··· (5)

[0139] When the temperature changes, the lens is pressed by the inner wall surface 21 of the lens barrel 20, which is the lens support structure, resulting in lens movement. The amount of this lens movement is proportional to the outer diameter of the lens side surface in contact with the support structure and the difference in the linear expansion coefficients of the support structure and the lens. Therefore, it is effective to suppress lens movement by setting the outer diameter size of the lens side surface in contact with the support structure to be smaller in a manner that satisfies the conditional expression (5).

[0140] In addition, since there is a gap portion 22 between the first side surface L1a that is not installed in the inner space of the support structure and the inner space of the retaining ring that presses and supports the lens, the first side surface L1a is prevented from being pressed by the inner wall 23a of the retaining ring 23, and lens movement can be further suppressed.

[0141] In addition, in the present embodiment, on the object-side optical surface and the image-side optical surface of the first lens L1, a flat portion L1c extending in a direction orthogonal to the optical axis is provided outside the object-side optical surface having a larger optical surface. The abutting position Q of the retaining ring 23 on the flat portion L1c is farther from the optical axis than the second side surface L1b of the stepped lens.

[0142] With this configuration, it is possible to balance the ensuring of the light ray region required for wide-angleization and the suppression of lens movement.

[0143] Hereinafter, as a specific numerical example 1 of the imaging optical system 1, the optical performance of each lens is shown in Table 1.

[0144] It should be noted that in each of the following embodiments, the parallel plate disposed on the image plane side is assumed to be various filters F1 such as an optical low-pass filter / infrared cut-off filter, and the glass cover (sealing glass) CG of the light receiving element 13 such as a CCD sensor. The meanings of the common notations in each embodiment are as follows.

[0145] f: Focal length of the entire system

[0146] f Li : Focal length of the i-th lens

[0147] g0: Exit pupil position on the optical axis

[0148] g w / 2 : Exit pupil position of the half field of view W / 2

[0149] g w : Exit pupil position of the field of view W

[0150] Fno: Aperture value

[0151] L: Overall optical length

[0152] W: Half field of view (degrees)

[0153] R: Radius of curvature

[0154] D: Surface interval

[0155] Nd: Refractive index

[0156] vd: Abbe number

[0157] (Table 1)

[0158] R D Nd vd E Glass material dn / dt(×10-6 / ℃) <![CDATA[1 * > 13.31 1.3 1.768 49.2 4.82 MTAF101_HOYA 5.7 <![CDATA[2 * > 3.52 2.95 3.00 3 -4.74 2.5 1.834 37.2 2.67 SLAH60_OHARA 6.3 4 -7.6 0.2 2.90 5 15.72 2.69 1.794 37.1 2.76 SLAM73_OHARA -2 6 -21.72 0.39 2.58 7 1.00E+18 3.1 2.58 10.44 3.19 1.744 44.8 3.84 SLAM2_OHARA 2 9 -10.45 1.7 1.893 20.4 3.91 SNPH4_OHARA -1 10 20.09 0.29 3.90 <![CDATA[11 * > 7.74 3.5 1.497 81.5 4.46 SFPL51_OHARA -6.2 <![CDATA[12 * > -9.94 0.3 4.55 13 Inf. 1.1 1.523 54.5 4.51 D263TECO_SCHOTT 14 Inf. 4.5 4.48 15 Inf. 0.5 1.516 64.1 4.32 SBSL7_OHARA 2.2 16 Inf. 0.435 4.31 17 Inf. BF 4.35

[0159] In addition, in the aspherical lens, using a known formula (Mathematical formula 6), the aspherical coefficients were set as shown in Table 2.

[0160] (Mathematical formula 6)

[0161] x = (y 2 / R) / [1 + {1 - (K + 1)(y / R) 2}^ 1 / 2 + A4y 4 + A6y 6 + A8y 8 + A 10 y 10 + A 12 y12 +A 14 y 14

[0162] However, for an aspherical shape, x is set as the optical axis with the positive direction of light propagation, and y is set as the direction orthogonal to the optical axis.

[0163] In addition, E: the effective diameter of the lens, R: the paraxial curvature radius, K: the conic coefficient are set, and A4, A6, A8, A 10 、A 12 、A 14 are the aspherical coefficients of the 4th, 6th, 8th, 10th, 12th, and 14th orders, respectively.

[0164] (Table 2)

[0165] K <![CDATA[A4]]> <![CDATA[A6]]> <![CDATA[A8]]> <![CDATA[A 10 > <![CDATA[A 12 > <![CDATA[A 14 > <![CDATA[1 * > 3.067542428 -0.002485288 0.000115405 -3.3647E-06 3.7005E-08 6.1105E-10 -1.6574E-11 <![CDATA[2 * > -0.984935574 -0.001512848 0.000120769 1.4286E-05 -2.3923E-06 2.1866E-07 -5.8911E-09 <![CDATA[11 * > 0.834015813 -0.001062955 3.6390E-05 -5.4241E-06 4.2143E-07 -1.8383E-08 3.0209E-10 <![CDATA[12 * > 2.873466153 0.00108302 7.5853E-05 -1.0317E-05 8.6689E-07 -3.5795E-08 6.0737E-10

[0166] Next, Table 3 shows the parameters representing the respective optical performances of the aperture value, half field angle, overall length, and focal length of the imaging optical system 1, and Table 4 shows the calculation results (conditional formula values) of the conditional formulas related to the focal length.

[0167] (Table 3)

[0168]

[0169] (Table 4)

[0170] f1 -6.61038 f2 -25.0672 f3 11.8688 f4 44.3192 f5 9.37161 E1 4.83 E2 2.91 E3 2.75 E4 3.91 E5 4.55 ∑Ei / |fi| 1.652189421

[0171] (Table 5)

[0172] gW -26.3368 gW / 2 -25.7532 g0 -26.1019 gW / g0 1.008999345 gW / 2 / g0 0.986640819 g0 / g0 1

[0173] As shown in Table 5, in Numerical Example 1, when the half field angle: W, any angle of view Wi existing within the above half field angle W, the exit pupil distance gi of the above angle of view Wi, and the exit pupil distance g0 on the optical axis are set, Conditional formulas (1) and (2) are satisfied.

[0174] With this configuration, the imaging optical system 1 can sufficiently suppress the change in optical performance before and after the temperature change.

[0175] In Figure 8 the aberration diagrams of spherical aberration, astigmatism, distortion, and coma for an infinitely distant object in Numerical Example 1 are shown. It should be noted that in Figure 7 d represents the aberration in the d line (wavelength λ = 587.6 nm), and g represents the aberration in the g line (wavelength λ = 435.8 nm). In the astigmatism diagram, the solid line represents the sagittal aberration, and the dashed line represents the meridional aberration.

[0176] FromFigure 7 It is clearly known that the aberration of Numerical Example 1 is corrected at a high level, and the spherical aberration and axial chromatic aberration are small and do not cause problems. In addition to the astigmatism, field curvature, and lateral chromatic aberration being sufficiently small, the coma and the disorder of its chromatic aberration are well suppressed even up to the outermost periphery, and the absolute value of the distortion is also less than 2.0%.

[0177] Figure 8 The optical axis shift when each lens group is decentered by 1 μm is shown. In addition, "SUM_A" in the figure is the total value of the absolute values of the optical axis shift amounts when each of the first lens to the sixth lens is decentered by 1 μm, which represents the optical axis shift of the entire lens unit system (the entire imaging optical system 1) assuming that each lens group moves in the direction of enhancing the optical axis shift.

[0178] In addition, "SUM_A / Y'" shows the ratio of the axial shift distribution of the entire lens unit system with respect to the maximum image height.

[0179] In Numerical Example 1, even assuming that each lens group moves in the direction of enhancing the optical axis shift, as shown by Figure 8 "SUM_A / Y'", the optical axis shift of the entire lens unit system is 0.06% with respect to the maximum image height Y', and the sensitivity of the optical axis shift is sufficiently suppressed.

[0180] In addition, in the present embodiment, as shown in Table 1, for the relative refractive index temperature coefficient: dn / dt, the first lens L1 and the second lens L2 that satisfy the conditional expression (3) are provided.

[0181] Moreover, the sixth lens L6 that satisfies the conditional expression (4) is provided.

[0182] With this configuration, the focal position during temperature change is displaced in a direction that suppresses each other by the conditional expression (3) and the conditional expression (4), so that the imaging optical system 1 can sufficiently suppress the change in optical performance before and after the temperature change.

[0183] In addition, in the present embodiment, the imaging optical system 1 includes the first lens L1 closest to the object side and the second lens L2 second closest to the object side, and the first lens L1 and the second lens L2 are aspherical lenses in which at least one surface on the object side or the image side is an aspherical shape.

[0184] With this configuration, it is possible to sufficiently widen the angle of view and correct the aberration in the imaging optical system based on 6 lenses while restricting the number of expensive aspherical lenses.

[0185] In addition, in the present embodiment, there is a lens barrel 20, which is a supporting structure for holding the lenses such that the optical axes of the plurality of lenses are substantially aligned, a retaining ring 23 for pressing and supporting the first lens L1, and a spacer ring 24 disposed between the lenses to support the lenses and adjust the surface interval.

[0186] In addition, the first lens L1 is a stepped glass lens, which has a first side surface L1a that does not contact the inner wall surface 21 of the lens barrel 20 in the outer peripheral side surface extending in the optical axis direction of the lens, and a second side surface L1b that has a diameter smaller than that of the first side surface L1a and contacts the inner wall surface 21 of the lens barrel 20.

[0187] That is, "at least one of the lenses of the imaging optical system 1 includes a stepped glass lens having a first side surface that does not contact the supporting structure in the outer peripheral side surface extending in the optical axis direction of the lens, and a second side surface that has a diameter smaller than that of the first side surface and contacts the supporting structure".

[0188] With this configuration, the outer diameter size of the lens side surface in contact with the supporting structure can be set to be small, so that lens movement can be suppressed.

[0189] Moreover, in the first lens L1 of the present embodiment, when setting the diameter of the first side surface L1a: φa and the diameter of the second side surface L1b: φb, the conditional expression (5) is satisfied.

[0190] With this configuration, even if the object side surface is set to have a large diameter, by setting the positioning second side surface to be small, lens movement can be reduced, so that it is possible to balance ensuring the light ray region required for wide-angleization and suppressing lens movement.

[0191] As a second numerical example of the present invention, the Figure 9 imaging optical system 1 will be described.

[0192] In Numerical Example 2, similar to Numerical Example 1, the first lens L1 is a meniscus lens protruding on the object side, the second lens L2 is a meniscus lens recessed on the object side, the third lens L3 is a convex lens having a positive refractive power, the cemented lens L45 is a cemented lens that cements the fourth lens L4 and the fifth lens L5, and the sixth lens L6 has a positive refractive power.

[0193] In Numerical Example 2, as shown in Tables 6 and 7, the object side surface and the image side surface of the second lens L2 are aspherical surfaces.

[0194] (Table 6)

[0195] R D Nd vd E Glass material dn / dt(×10-6 / ℃) 1 23.57 1.3 1.905 35 4.45 SLAH93_OHARA 3.9 2 4.84 3.13 3.15 <![CDATA[3 * > -4.82 3.35 1.832 40.1 2.65 LLAH90_OHARA 5.5 <![CDATA[4 * > -10.26 0.2 2.73 5 8.39 1.88 1.805 25.4 2.68 STIH6_OHARA -0.5 6 140.36 0.23 2.59 7 Inf. 2.69 2.74 8 9.29 3.7 1.618 63.4 3.00 PCD4_HOYA -2.2 9 -5.01 1.25 1.847 23.7 3.56 STIH53W_OHARA -0.7 10 Inf. 0.9 3.95 <![CDATA[11 * > 8.19 2.93 1.595 67.7 4.54 SFPM2_OHARA -6.1 <![CDATA[12 * > -20.55 0.22 4.46 13 Inf. 1.1 1.516 64.1 4.43 SBSL7_OHARA 2.2 14 Inf. 5.27 4.37 15 Inf. 0.5 1.516 64.1 3.95 SBSL7_OHARA 2.2 16 Inf. 0.435 3.93 17 Inf. BF 3.89

[0196] In addition, in the aspherical lens, the aspherical coefficients were set as shown in Table 7 using the known formula (Mathematical Formula 6) as in Numerical Example 1.

[0197] However, for the aspherical shape, x is set as the optical axis with the positive direction of light propagation, and y is set as the direction orthogonal to the optical axis.

[0198] In addition, E: effective diameter of the lens, R: paraxial curvature radius, K: conic coefficient, A4, A6, A8, A 10 、A 12 、A 14 are the aspherical coefficients of the 4th, 6th, 8th, 10th, 12th, and 14th orders, respectively.

[0199] (Table 7)

[0200] K <![CDATA[A4]]> <![CDATA[A6]]> <![CDATA[A8]]> <![CDATA[A 10 > <![CDATA[A 12 > <![CDATA[A 14 > <![CDATA[3 * > -0.476866703 0.00063044 -1.32639E-05 5.39151E-06 -9.52294E-07 5.52598E-08 1.59508E-10 <![CDATA[4 * > -19.5873336 -0.001807865 0.000213607 -2.53014E-05 2.67881E-06 -1.79194E-07 5.26962E-09 <![CDATA[11 * > 0.76132235 -0.000451885 -1.24816E-05 2.26401E-06 -2.16065E-07 8.85268E-09 -1.42834E-10 <![CDATA[12 * > -63.97060855 2.32108E-05 3.783E-05 -6.45425E-07 -1.06914E-07 6.80254E-09 -1.28695E-10

[0201] Next, Table 8 shows the parameters of the respective optical performances representing the aperture value, half-angle of view, overall length, and focal length of the imaging optical system 1, and Table 9 shows the calculation results (conditional formula values) of the conditional formula related to the focal length.

[0202] (Table 8)

[0203]

[0204] (Table 9)

[0205] f1 -6.95764 f2 -15.1655 f3 11.0125 f4 35.9391 f5 10.2276 E1 4.92 E2 3.5 E3 2.91 E4 3.18 E5 3.64 ∑Ei / |fi| 1.646551227

[0206] (Table 10)

[0207] gW -28.4598 gW / 2 -26.4695 g0 -26.1852 gW / g0 1.086865863 gW / 2 / g0 1.010857278 g0 / g0 1

[0208] As shown in Table 10, in Numerical Example 2, when the half-angle of view: W, any viewing angle Wi within the above half-angle of view W, the exit pupil distance gi of the above viewing angle Wi, and the exit pupil distance g0 on the optical axis are set, Conditional Formulas (1) and (2) are satisfied.

[0209] With this configuration, the imaging optical system 1 can sufficiently suppress changes in optical performance before and after temperature changes.

[0210] Figure 10 Shows aberration diagrams of spherical aberration, astigmatism, distortion, and coma for an infinitely distant object in Numerical Example 2. It should be noted that in Figure 10 , d represents the aberration of the d-line (wavelength λ = 587.6 nm), and g represents the aberration of the g-line (wavelength λ = 435.8 nm). In the astigmatism diagram, the solid line represents the sagittal aberration and the dashed line represents the meridional aberration.

[0211] It is clearly known from Figure 10 that the aberration of Numerical Example 2 is corrected at a relatively high level, and the spherical aberration and axial chromatic aberration are small and do not cause problems. In addition to the astigmatism, field curvature, and lateral chromatic aberration being sufficiently small, the coma and its chromatic aberration disorder are also well suppressed up to the outermost periphery, and the absolute value of the distortion is also less than 2.0%.

[0212] Figure 11 The optical axis shift when each lens group is eccentric by 1 μm is shown. In addition, "SUM_A" and "SUM_A / Y'" in the figure are the same as those in Numerical Example 1, so the description is omitted.

[0213] In Numerical Example 2, even when each lens group is assumed to move in the direction of enhancing the optical axis shift, as Figure 11 shown by "SUM_A / Y'", the optical axis shift of the entire system of lens units is 0.07% with respect to the maximum image height Y', and the sensitivity of the optical axis shift is sufficiently suppressed.

[0214] In addition, in the present embodiment, as shown in Table 1, for the relative refractive index temperature coefficient: dn / dt, the second lens L2 that satisfies the conditional expression (3) is provided.

[0215] Moreover, the sixth lens L6 that satisfies the conditional expression (4) is provided.

[0216] With this configuration, the focal position during temperature change is displaced in a direction that suppresses each other through the conditional expression (3) and the conditional expression (4), so that the imaging optical system 1 can sufficiently suppress the change in optical performance before and after the temperature change.

[0217] In addition, in the present embodiment, the imaging optical system 1 has a first lens L1 located closest to the object side and a second lens L2 located second closest to the object side, and the second lens L2 is an aspherical lens in which at least one surface on the object side or the image side is an aspherical shape.

[0218] With this configuration, while limiting the number of expensive aspherical lenses, sufficient wide-angleization and aberration correction can be performed in the imaging optical system based on six lenses.

[0219] As the third numerical example of the present invention, Figure 12 the imaging optical system 1 will be described.

[0220] In Numerical Example 3, similar to Numerical Example 1, the first lens L1 is a meniscus lens convex on the object side, the second lens L2 is a meniscus lens concave on the object side, the third lens L3 is a meniscus lens with positive refractive power, the cemented lens L45 is a cemented lens that cements the fourth lens L4 and the fifth lens L5, and the sixth lens L6 has positive refractive power.

[0221] In Numerical Example 3, as shown in Table 11 and Table 12, the object side and the image side of the second lens L2 are aspherical surfaces, and the third lens L3 is a meniscus lens.

[0222] (Table 11)

[0223] R D Nd vd E Glass material dn / dt(×10-6 / ℃) 1 119.6769446 1.3 1.762 40.1 4.92 SLAM55_OHARA 2.6 2 5.249748388 2.968818039 3.43 <![CDATA[3 * > -4.903024521 2.418094577 1.854 40.4 3.12 LLAH85V_OHARA 5.8 <![CDATA[4 * > -6.970207752 2.753737705 3.50 5 8.502972943 1.852469253 1.717 29.5 2.91 EFD1_HOYA 2.5 6 44.36149258 0.821869373 2.69 7 Inf. 2.648474794 2.51 8 9.243390125 3.666357679 1.603 65.4 2.83 SPHM53_OHARA 9 -5.5 1 1.847 23.8 3.00 STIH53W_OHARA -0.7 10 -115.3827919 0.495380571 3.18 <![CDATA[11 * > 21.01308811 2.355879243 1.553 71.7 3.38 MFCD500_HOYA -6.1 <![CDATA[12 * > -9.841452588 0.2 3.65 13 Inf. 1.6 1.516 64.1 3.70 SBSL7_OHARA 2.2 14 Inf. 5 3.77 15 Inf. 0.5 1.516 64.1 4.07 SBSL7_OHARA 2.2 16 Inf. 0.435 4.09 17 Inf. BF 4.12

[0224] In addition, in the aspherical lens, the aspherical coefficients shown in Table 12 were set using the known formula (Equation 6) as in Numerical Example 1.

[0225] However, for the aspherical shape, x is set as the optical axis with the direction of light propagation being positive, and y is set as the direction orthogonal to the optical axis.

[0226] In addition, E: effective diameter of the lens, R: paraxial curvature radius, K: conic coefficient, A4, A6, A8, A 10 、A 12 、A 14 are the aspherical coefficients of the 4th, 6th, 8th, 10th, 12th, and 14th orders, respectively.

[0227] (Table 12)

[0228] K <![CDATA[A4]]> <![CDATA[A6]]> <![CDATA[A8]]> <![CDATA[A 10 > <![CDATA[A 12 > <![CDATA[A 14 > <![CDATA[3 * > 3.067542428 -0.002485288 0.000115405 -3.36E-06 3.70E-08 6.11E-10 -1.66E-11 <![CDATA[4 * > -0.984935574 -0.001512848 0.000120769 1.43E-05 -2.39E-06 2.19E-07 -5.89E-09 <![CDATA[11 * > 0.834015813 -0.001062955 3.64E-05 -5.42E-06 4.21E-07 -1.84E-08 3.02E-10 <![CDATA[12 * > 2.873466153 0.00108302 7.59E-05 -1.03E-05 8.67E-07 -3.58E-08 6.07E-10

[0229] Next, Table 13 shows the parameters of the respective optical performances representing the aperture value, half angle of view, overall length, and focal length of the imaging optical system 1, and Table 14 shows the calculation results (conditional formula values) of the conditional formulas related to the focal length.

[0230] (Table 13)

[0231]

[0232] (Table 14)

[0233] f1 -7.22704 f2 -41.8637 f3 14.3484 f4 29.6653 f5 12.4506 E1 4.92 E2 3.5 E3 2.91 E4 3.18 E5 3.64 ∑Ei / |fi| 1.366742697

[0234] (Table 15)

[0235] gW -21.6213 gW / 2 -21.6483 g0 -21.6327 gW / g0 0.99947302 gW / 2 / g0 1.000721131 g0 / g0 1

[0236] As shown in Table 15, in Numerical Example 3, when the half angle of view: W, any angle of view Wi existing within the above half angle of view W, the exit pupil distance gi of the above angle of view Wi, and the exit pupil distance g0 on the optical axis are set, Conditional formulas (1) and (2) are satisfied.

[0237] With this configuration, the imaging optical system 1 can sufficiently suppress changes in optical performance before and after temperature changes.

[0238] Figure 13Shows the aberration diagrams of spherical aberration, astigmatism, distortion, and coma for an infinitely distant object in Numerical Example 3. It should be noted that in Figure 13 , d represents the aberration of the d-line (wavelength λ = 587.6 nm), and g represents the aberration of the g-line (wavelength λ = 435.8 nm). In the astigmatism diagram, the solid line represents the sagittal aberration, and the dashed line represents the meridional aberration.

[0239] From Figure 13 it is clearly known that the aberrations of Numerical Example 3 are corrected at a relatively high level, and the spherical aberration and axial chromatic aberration are small and do not pose a problem. In addition to astigmatism, field curvature, and lateral chromatic aberration being sufficiently small, and coma and its chromatic aberration disorder being well suppressed even at the outermost periphery, the absolute value of distortion is less than 2.0%.

[0240] Figure 14 shows the optical axis shift when each lens group is decentered by 1 um. In addition, "SUM_A" and "SUM_A / Y'" in the figure are the same as those in Numerical Examples 1 and 2, so the description is omitted.

[0241] In Numerical Example 3, even when each lens group is assumed to move in the direction of enhancing the optical axis shift, as Figure 14 shown by "SUM_A / Y'", the optical axis shift of the entire system of lens units is 0.06% with respect to the maximum image height Y', and the sensitivity of the optical axis shift is sufficiently suppressed.

[0242] In addition, in the present embodiment, as shown in Table 11, for the relative refractive index temperature coefficient: dn / dt, the second lens L2 that satisfies the conditional expression (3) is provided.

[0243] Moreover, the sixth lens L6 that satisfies the conditional expression (4) is provided.

[0244] With this configuration, the focal position during temperature change is displaced in a direction that suppresses each other by the conditional expression (3) and the conditional expression (4), so the imaging optical system 1 can sufficiently suppress the change in optical performance before and after the temperature change.

[0245] In addition, in the present embodiment, the imaging optical system 1 has a first lens L1 located closest to the object side and a second lens L2 located second closest to the object side, and the second lens L2 is an aspherical lens in which at least one surface on the object side or the image side is an aspherical shape.

[0246] With this configuration, while restricting the number of high-cost aspherical lenses, sufficient wide-angle and aberration correction can be achieved in an imaging optical system based on six lenses.

[0247] In addition, for the mounting method of the lens barrel 20 and the first lens L1, although only used for the lens shape of Numerical Example 1 Figure 5 ,Figure 6 has been described, but for other numerical examples 2 and 3, the same configuration can also be used for installation.

[0248] In addition, at this time, it is preferable to satisfy the conditional expression (5).

[0249] As described above, the configuration of the "digital camera 100" using the imaging optical system 1 of the present invention has been described. However, the present invention is related to an imaging optical system, and in addition to the imaging device described above, it can also be used for various imaging devices such as "camera devices for photography", "camera devices for inspection", "stereo camera devices", "in-vehicle camera devices", and "monitoring camera devices".

[0250] For example, Figure 15 An embodiment shown as an "inspection camera device" will be described.

[0251] The inspection camera device 101 described below is an inspection device for performing so-called "product inspection".

[0252] Product inspection can have various inspections and inspection items. For simplicity, the case of inspecting the "presence or absence of damage" of products manufactured in large quantities will be described as an example.

[0253] In Figure 15 (a), reference numeral 200 denotes an "imaging unit", reference numeral 230 denotes an "inspection process execution unit", and reference numeral 240 denotes a "display unit". In addition, reference numeral W denotes a "product", and reference numeral 260 denotes a "product conveyor belt (hereinafter only referred to as the 'conveyor belt 260')."

[0254] The imaging unit 200 is a camera functional unit in the inspection device, and it has an imaging optical system 1 and an image processing unit 220.

[0255] Products W to be inspected are arranged at equal intervals above the conveyor belt 260 and are conveyed at a constant speed in the arrow direction (to the right in the figure) by the conveyor belt 260.

[0256] The imaging optical system 1 is used to image the image of the product W to be inspected, and it can use the imaging optical system 1 of the present invention, specifically any one of the numerical examples 1 to 3 described above.

[0257] Product inspection is carried out based on Figure 15 the "preparation process", "inspection process", and "result display process" shown in (b). The "inspection process and result display process" in these processes are the "inspection process".

[0258] In the "preparation process", inspection conditions are set.

[0259] That is, based on the size and shape of the product W conveyed by the conveyor belt 260, the part for inspecting the presence or absence of damage, etc., the photographing position and photographing state of the photographing optical system 1 (the orientation of the imaging lens, the distance from the photographing object, i.e., the object distance) are determined.

[0260] Moreover, based on the position and size of the "damage" for which the presence or absence is to be detected, the position of the photographing optical system 1 is set.

[0261] On the other hand, the "model product confirmed to have no damage" is placed at the inspection position on the conveyor belt 260, and it is photographed by the photographing unit 200.

[0262] The photographing is performed by photographing with an imaging element arranged in the image processing unit 220, and the image photographed by the imaging element is subjected to image processing for digital data conversion as "image information".

[0263] The digital data subjected to image processing is sent to the inspection process execution unit 230, and the inspection process execution unit 230 stores the digital data as "model data".

[0264] In the "inspection process", the product W is placed on the conveyor belt 260 in "the same state as the model product" and is sequentially conveyed by the conveyor belt 260. Each conveyed product W is photographed by the photographing optical system 1 when passing through the "inspection position", and is digitalized in the image processing unit 220, and then sent to the inspection process execution unit 230.

[0265] The inspection process execution unit 230 is configured as a "computer, CPU", which controls the image processing unit 220, and in addition, controls the photographing of the photographing optical system 1 through the image processing unit 220.

[0266] When the inspection process execution unit 230 receives the "image data of the product W" digitalized by the image processing unit 220, it performs matching of this image data with the above-mentioned stored model data.

[0267] In the case where there is "damage" in the photographed product W, since the image data does not match the model data, in this case, this product is determined to be a "defective product".

[0268] In addition, in the case where there is no damage in the product W, the image data of this product matches the model data, so in this case, this product is determined to be a "non-defective product".

[0269] The "result display process" is a process of displaying the determination results of "non-defective products, defective products" of each product based on the inspection process execution unit 230 on the display unit 240.

[0270] Note that in terms of the configuration of the device, the inspection process execution unit 230 and the display unit 240 constitute an "inspection process execution device".

[0271] Next, as the third embodiment of the present invention, refer to Figure 16 , and a stereo camera device 300 including an imaging optical system 1 will be described.

[0272] Figure 16 FIG. shows an external view of a stereo camera device 300 having an imaging optical system 1 as an optical system. The stereo camera device 300 includes a right camera device 100a and a left camera device 100b.

[0273] As Figure 17 shown, both the right camera device 100a and the left camera device 100b have imaging optical systems 1a, 1b identical to those of the digital camera 100, and light receiving elements 13a, 13b corresponding to their respective imaging optical systems 1.

[0274] Each component of the right camera device 100a and the left camera device 100b may have the same configuration as that of the digital camera 100, but is not limited to this configuration.

[0275] The stereo camera device 300 includes an image processing unit 220 for correcting and performing image processing on the image information respectively photographed by the right camera device 100a and the left camera device 100b.

[0276] The image processing unit 220 processes, for example, the object P imaged in the two images photographed by the right camera device 100a and the left camera device 100b.

[0277] Specifically, in the image Qa photographed by the right camera device 100a and the image Qb photographed by the left camera device 100b, a parallax Z is generated due to the different positions of the object P in the photographed images.

[0278] Here, a case where the position of the object P imaged in the left camera device 100b is estimated based on the position of the right camera device 100a will be described.

[0279] When the parallax Z and the baseline length B, which is the interval between the right camera device 100a and the left camera device 100b, are set, there is a correlation relationship of the following formula (7) between the focal length f of the entire imaging optical system 1 and the measurement distance D based on the principle of triangulation.

[0280] (Mathematical formula 7)

[0281] D = Bf / Z...(7)

[0282] Therefore, the image processing unit 220 can obtain the measured distance D by previously storing the values of the baseline length B and the focal length f, and obtaining the parallax Z from the two images respectively acquired by the right camera device 100a and the left camera device 100b.

[0283] However, in such a stereo camera device 300, if the focal position changes due to temperature changes, the imaging position of the light from the object P shifts, and thus is observed as a shift in the parallax Z.

[0284] This shift may result in a measurement error in the measured distance D. Therefore, it is important to use the imaging optical system 1 with a small change in the viewing angle during temperature changes for the stereo camera device 300.

[0285] Here, in the present embodiment, it is preferable to use the imaging optical systems 1 described in Numerical Examples 1 to 3 in the left camera device 100b and the right camera device 100a, respectively.

[0286] In this way, by incorporating the imaging optical system 1 into the stereo camera device 300, it is possible to suppress an increase in the measurement error due to the change in the focal position even with respect to the change in the ambient temperature.

[0287] Figure 18 It is a diagram schematically showing an embodiment in which Figure 17 the shown stereo camera device 300 is used as a vehicle-mounted camera device.

[0288] In Figure 18 , the stereo camera device 300 is mounted in the vehicle AU as a "vehicle-mounted camera device" for acquiring image information outside the vehicle.

[0289] As Figure 18 shown, the stereo camera device 300 includes an imaging optical system 1 and a control arithmetic unit 301. The imaging optical system 1 can use any one of the already described Numerical Examples 1 to 3. In addition, an optical system satisfying the conditions of conditional expressions (1), (2), etc. can be used.

[0290] The stereo camera device 300 mounted in the vehicle AU acquires image information outside the vehicle and digitizes it. The digitized image information is subjected to digital processing such as image processing in the control arithmetic unit 301 and displayed in an appropriate manner.

[0291] That is, for Figure 17 the shown stereo camera device, it can be mounted as a vehicle-mounted camera device on a moving body such as a vehicle.

[0292] Since Figure 1 the shown digital camera 100, based on Figure 15Explanation of the inspection camera device 101, based on Figure 16 , Figure 17 Explanation of the stereo camera device 300, based on Figure 18 Explanation of the in-vehicle camera device all use the imaging optical system of the present invention. Therefore, it is possible to capture bright and wide-angle images. In addition, since it is hardly affected by wide-range changes in the ambient temperature, it can be used in a wide range of usage environments.

[0293] As described above, although the preferred embodiments of the invention have been described, the present invention is not limited to the above specific embodiments. As long as it is not particularly limited in the above description, various modifications / variations are possible within the scope of the gist of the invention described in the claims.

[0294] For example, the camera device can be used as a video camera mainly for video shooting, and a camera device mainly dedicated to photography including a conventional film camera using so-called silver halide film.

[0295] In addition, not only such camera devices, but also various information devices including portable telephones, portable information terminal devices such as those called PDAs (personal data assistants), and portable terminal devices such as so-called smartphones and tablet terminals, often have an imaging function equivalent to that of a digital camera. The imaging optical system of the present invention can also be used in such information devices.

[0296] The effects described in the embodiments of the present invention are only examples of the preferred effects produced by the invention, and the effects of the invention are not limited to "the descriptions in the embodiments".

Claims

1. An imaging optical system that forms an image of a subject on an imaging element. The imaging optical system is composed of a first lens with a negative refractive power in a meniscus shape, a second lens with a negative refractive power in a meniscus shape, a third lens with a positive refractive power, a cemented lens formed by cementing a fourth lens with a positive refractive power and a fifth lens with a negative refractive power, and a sixth lens with a positive refractive power, which are arranged in sequence from the object side. The first lens is configured to have a concave surface on the image side and a convex surface on the object side. The second lens is configured to have a concave surface on the object side and a convex surface on the image side. The third lens is configured to have a convex surface on the object side. The fourth lens is configured to have a convex surface on the object side and a convex surface on the image side. The fifth lens is configured to have a concave surface on the object side. The sixth lens is configured to have a convex surface on the object side and a convex surface on the image side. When the imaging optical system sets the half field of view as W, any view angle within the half field of view W as Wi, the exit pupil distance in the view angle Wi as gi, and the exit pupil distance on the optical axis as g0, it satisfies 30 < W and 0.9 < |gi / g0| < 1.

1. When the relative refractive index temperature coefficient in air at 0°C to 20°C for light in the wavelength region of 580 nm to 640 nm is set as dn / dt, either the first lens or the second lens satisfies 5.3×10 ―6 < dn / dt, and the sixth lens satisfies -5.7×10 ―6 > dn / dt.

2. The imaging optical system according to claim 1, wherein At least one surface on the object side or the image side of at least one of the above-mentioned first lens and the above-mentioned second lens is an aspherical shape.

3. The imaging optical system according to claim 1 or 2, wherein At least one surface on the object side or the image side of the above-mentioned sixth lens is an aspherical shape.

4. An imaging device having the imaging optical system according to any one of claims 1 to 3.

5. A moving body having the imaging device according to claim 4.

Images