Optical system and image capturing apparatus including the same

Abstract

The optical system has, in order from the object side to the upper side, a first lens having a positive refractive power, a second lens having a negative refractive power and arranged adjacent to the upper side of the first lens, and a bending optical element arranged adjacent to the upper side of the second lens, satisfying a specific inequality, wherein NdG1 represents the refractive index of the material of the first lens for the d-line and νdG1 represents the Abbe number of the material of the first lens for the d-line.

Description

Technology Field

[0001] The present disclosure relates to an optical system and an imaging device having the same, and in particular to an imaging optical system suitable for a camera, digital still camera, video camera, etc., for a portable terminal including a smartphone, and an imaging device having the imaging optical system. Background Technology

[0002] Recently, imaging optical systems used in imaging devices such as cameras for mobile terminals including smartphones, digital still cameras, and video cameras are required to be small and have high optical performance.

[0003] In the specification of U.S. Patent Application Publication No. 2021 / 0165192, a telephoto lens is disclosed comprising two lenses arranged in order from the object side, a bending optical element, and a rear group having four lenses. means of solving the problem

[0004] According to one aspect of the present disclosure, an optical system comprises, in order from the object side to the upper side, a first lens having a positive refractive power, a second lens having a negative refractive power disposed adjacent to the upper side of the first lens, and a bending optical element disposed adjacent to the upper side of the second lens, satisfying the following inequality: 1.30 <NdG1<1.60, 및 73.0<νdG1<120.0, 이때 NdG1은 상기 제1렌즈의 재료의 d선에 대한 굴절률을 나타내고 νdG1은 상기 제1렌즈의 재료의 d선에 대한 아베수를 나타낸다.

[0005] Another feature of the present disclosure will become apparent from the following description of embodiments with reference to the accompanying drawings. The following description of embodiments is given by way of example. Brief explanation of the drawing

[0006] FIG. 1 is a cross-sectional view of an optical system according to Example 1. FIG. 2 is an aberration diagram of an optical system according to Example 1. FIG. 3 is a cross-sectional view of an optical system according to Example 2. FIG. 4 is an aberration diagram of an optical system according to Example 2. FIG. 5 is a cross-sectional view of an optical system according to Example 3. FIG. 6 is an aberration diagram of the optical system according to Example 3. FIG. 7 is a cross-sectional view of an optical system according to Example 4. FIG. 8 is an aberration diagram of the optical system according to Example 4. FIG. 9 is a cross-sectional view of an optical system according to Example 5. FIG. 10 is an aberration diagram of the optical system according to Example 5. FIG. 11 is a cross-sectional view of an optical system according to Example 6. FIG. 12 is an aberration diagram of an optical system according to Example 6. FIG. 13 is a cross-sectional view of an optical system according to Example 7. FIG. 14 is an aberration diagram of the optical system according to Example 7. FIG. 15 is a cross-sectional view of an optical system according to Example 8. FIG. 16 is an aberration diagram of the optical system according to Example 8. FIG. 17 is a cross-sectional view of an optical system according to Example 9. FIG. 18 is an aberration diagram of the optical system according to Example 9. FIG. 19 is a cross-sectional view of an optical system according to Example 10. FIG. 20 is an aberration diagram of an optical system according to Example 10. FIG. 21 is a cross-sectional view of an optical system according to Example 11. FIG. 22 is an aberration diagram of the optical system according to Example 11. FIG. 23 is a cross-sectional view of an optical system according to Example 12. FIG. 24 is an aberration diagram of an optical system according to Example 12. FIGS. 25a, FIGS. 25b and FIGS. 25c are drawings for illustrating embodiments of a folded optical element. FIG. 26 is a schematic diagram of the main parts of an imaging device to which the optical system of each embodiment is applied. Specific details for implementing the invention

[0007] Hereinafter, embodiments disclosed in this specification will be described in detail with reference to the drawings. In each drawing, the same reference numeral is used for identical components, and redundant descriptions are omitted.

[0008] FIGS. 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, and 23 are cross-sectional views of optical systems L0 according to Examples 1 to 12, respectively. Optical systems L0 according to each example are used in imaging devices such as digital still cameras, digital video cameras, surveillance cameras, vehicle-mounted cameras, and smartphones.

[0009] In each cross-sectional view, the left side corresponds to the object side (front side), and the right side corresponds to the upper side (rear side). The aperture diaphragm SP determines (limits) the luminous flux of the maximum aperture F number (Fno). The optical system L0 according to each embodiment has a plurality of lenses or optical elements. Additionally, the optical system L0 according to each embodiment may include an optical element that has substantially no refractive power, such as an aspherical lens, a Fresnel lens, a meta-lens, a diffractive optical element, or a cover glass.

[0010] When the optical system according to each embodiment is used in an imaging device such as a camera for a portable terminal, a video camera, or a digital camera, the upper surface IP corresponds to a solid-state imaging device (photoelectric conversion device) such as a charge-coupled device (CCD) sensor or a complementary metal-oxide-semiconductor (CMOS) sensor. When the optical system according to each embodiment is used in an imaging device of a silver halide film camera, the upper surface IP corresponds to a film surface.

[0011] FIGS. 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, and 24 are aberration diagrams of optical system L0 at infinity focus according to Examples 1 to 12, respectively.

[0012] In the spherical aberration diagram, Fno represents the F number. The solid line represents spherical aberration for the d-line (wavelength 587.6 nm), and the dotted line represents spherical aberration for the g-line (wavelength 435.8 nm). In the astigmatism diagram, the solid line S represents astigmatism of the sagittal image plane, and the dotted line M represents astigmatism of the meridional image plane. In the distortion aberration diagram, distortion aberration for the d-line is shown. In the chromatic aberration diagram, chromatic aberration for the g-line is shown, and ω represents the angle of half-angle [°].

[0013] Next, the characteristic configuration of the optical system L0 according to each embodiment is described.

[0014] An optical system L0 according to each embodiment has a first lens G1 which is positioned closest to the object side and has a positive refractive power, a second lens G2 which is positioned adjacent to the upper side of the first lens G1 and has a negative refractive power, and a bending optical element PR which is positioned adjacent to the upper side of the second lens G2.

[0015] By arranging a positive lens and a negative lens on the object side of the optical system L0, the optical power arrangement becomes a so-called telephoto type, and since the light rays are strongly converged by the first lens G1, the optical system L0 can be miniaturized. Aberrations generated by the positive lens G1 can be corrected by the negative lens G2. The bending optical element PR has the function of bending (refracting) the incident light beam, and includes, for example, optical elements such as prisms or mirrors having a reflective surface.

[0016] Next, the conditions that the optical system L0 according to each embodiment can satisfy are described.

[0017] The optical system L0 according to each embodiment may satisfy at least one of the following condition equations (1) to (16).

[0018] 1.30 <NdG1<1.60 (1)

[0019] 65.0<νdG1<120.0 (2)

[0020] 0.20<|fG1 / fG2|<1.20 (3)

[0021] 0.20<|fG2 / f|<2.00 (4)

[0022] 0.20 <fG1 / f<1.00 (5)

[0023] 0.01 <tG1 / f<0.35 (6)

[0024] -2.00<(G1R1+G1R2) / (G1R1-G1R2)<0.50 (7)

[0025] -3.00<(G2R1+G2R2) / (G2R1-G2R2)<7.00 (8)

[0026] 0.005<θgFG1-0.6438+0.001682×νdG1<0.100 (9)

[0027] 1.0<νdG1 / νdG2<8.0 (10)

[0028] 0.10 <LD / f<0.60 (11)

[0029] 0.40 <TTL / f<4.00 (12)

[0030] |1 / (fG1×νdG1)+1 / (fG2×νdG2)|<0.005 (13)

[0031] 4<ω<20 (14)

[0032] 0.10 <EA_IMG / EA_OBJ<1.00 (15)

[0033] 0.20 <LD / fG1<1.00 (16)

[0034] For each conditional expression, various values ​​are represented as follows.

[0035] The refractive index of the material of the first lens G1 for the d-line is denoted as NdG1, the Abbe number of the material of the first lens G1 for the d-line is denoted as νdG1, and the Abbe number of the material of the second lens G2 for the d-line is denoted as νdG2.

[0036] Let f be the focal length of the entire optical system L0, and TTL be the total optical length of the optical system L0.

[0037] The distance on the optical axis from the object-side lens surface of the first lens G1 to the object-side lens surface of the bent optical element PR is represented as LD.

[0038] The image half-angle corresponding to the maximum image height of optical system L0 is denoted as ω[°].

[0039] The focal length of the first lens G1 is denoted as fG1, and the focal length of the second lens G2 is denoted as fG2.

[0040] The radius of curvature of the object-side lens surface of the first lens G1 is denoted as G1R1, the radius of curvature of the upper-side lens surface of the first lens G1 is denoted as G1R2, the radius of curvature of the object-side lens surface of the second lens G2 is denoted as G2R1, and the radius of curvature of the upper-side lens surface of the second lens G2 is denoted as G2R2.

[0041] The thickness in the direction of the optical axis at the center of the optical axis of the first lens G1 is denoted as tG.

[0042] The partial dispersion ratio of the material of the first lens G1 is denoted as θgFG1.

[0043] The effective aperture diameter of the object-side lens surface of the lens closest to the object side of optical system L0 is denoted as EA_OBJ, and the effective aperture diameter of the upper-side lens surface of the lens closest to the upper side of optical system is denoted as EA_IMG.

[0044] Here, the technical meaning of each of the aforementioned conditional expressions is explained.

[0045] Conditional formula (1) specifies the refractive index of the first lens G1 for the d-line. If the value is greater than the upper limit of conditional formula (1), the dispersion of the material of the first lens G1 increases, and the correction of chromatic aberration becomes excessive, which is undesirable. If the value is smaller than the lower limit of conditional formula (1), the refractive index of the first lens G1 decreases, so the radius of curvature of the first lens G1 increases, and the optical system L0 becomes larger in the direction of the optical axis, which is undesirable.

[0046] The upper limit of condition (1) can be any one of 1.595, 1.590, 1.585, 1.580, 1.575, 1.570, 1.565, 1.560, 1.555, 1.550, 1.545, 1.540, 1.535, and 1.530.

[0047] The lower limit of condition (1) can be any one of 1.31, 1.32, 1.33, 1.34, 1.35, 1.36, 1.37, 1.38, 1.39, 1.40, 1.41, 1.42, and 1.43.

[0048] The conditional equation (2) specifies the Abbe number for the d-line of the first lens G1. If the value is greater than the upper limit of the conditional equation (2), it is undesirable because the correction of chromatic aberration becomes excessive. If the value is smaller than the lower limit of the conditional equation (2), the axial chromatic aberration and magnification chromatic aberration caused by the first lens G1 become excessively large, making it difficult to properly correct chromatic aberration throughout the entire optical system L0, so it is undesirable.

[0049] The upper limit of condition (2) can be any one of 118.0, 116.0, 114.0, 112.0, 110.0, 108.0, 106.0, 104.0, 102.0, 100.0, 98.0, 96.0.

[0050] The lower limit of condition (2) can be any one of 66.0, 66.5, 67.0, 67.5, 68.0, 68.5, 69.0, 69.5, 70.0, 70.5, 71.0, 71.5, 72.0, 72.5, 73.0, 73.5, 74.0.

[0051] Conditional formula (3) specifies the ratio of the refractive index of the first lens G1 to the refractive power of the second lens G2. If the value is greater than the upper limit of conditional formula (3), the air gap between the first lens G1 and the second lens G2 becomes excessively large, which is undesirable as it increases the overall length of the optical system L0. If the value is smaller than the lower limit of conditional formula (3), the refractive power of the second lens G2 becomes excessively weak, which is undesirable as it becomes difficult to correct the spherical aberration and axial chromatic aberration occurring in the first lens G1 with the second lens G2.

[0052] The conditional formula (4) specifies the refractive power of the second lens G2. If the value is greater than the upper limit of the conditional formula (4), the refractive power of the second lens G2 becomes excessively weak, making it difficult to correct the spherical aberration and axial chromatic aberration caused by the first lens G1 with the second lens G2, which is undesirable. If the value is smaller than the lower limit of the conditional formula (4), the refractive power of the second lens G2 becomes too strong, making it undesirable to excessively correct the spherical aberration and astigmatism caused by the first lens G1.

[0053] The conditional formula (5) specifies the refractive power of the first lens G1. If the value is greater than the upper limit of the conditional formula (5), the refractive power of the first lens G1 becomes excessively weak, which is undesirable because the height of the light rays incident on the lens placed above the first lens G1 increases, and the diameter of the lens placed above the first lens G1 increases. If the value is smaller than the lower limit of the conditional formula (5), the refractive power of the first lens G1 becomes excessively strong, which is undesirable because strong spherical aberration and coma aberration occur.

[0054] The conditional equation (6) specifies the thickness of the first lens G1 along the optical axis. If the value is greater than the upper limit of the conditional equation (6), the thickness of the first lens G1 becomes excessively large, which is undesirable because the optical system L0 becomes enlarged in the direction of the optical axis. If the value is smaller than the lower limit of the conditional equation (6), the thickness of the first lens G1 becomes excessively small, which is undesirable because the thickness of the bending optical element PR increases in the radial direction, and the optical system L0 becomes enlarged in the radial direction.

[0055] Conditional equation (7) defines the shape of the lens surface of the first lens G1. If the value is greater than the upper limit of conditional equation (7), the upper lens surface of the first lens G1 has a shape with a strong concave surface facing the object side, which is undesirable because strong coma aberration occurs in the first lens G1. If the value is smaller than the lower limit of conditional equation (7), the first lens G1 becomes a meniscus lens with a strong convex surface facing the object side, which is undesirable because strong spherical aberration occurs in the first lens G1.

[0056] Conditional equation (8) defines the shape of the lens surface of the second lens G2. If the value is greater than the upper limit of conditional equation (8), the second lens G2 becomes a meniscus lens with a strong convex surface facing the object side, which is undesirable because the correction of spherical aberration becomes excessive. If the value is smaller than the lower limit of conditional equation (8), the second lens G2 becomes a meniscus lens with a strong concave surface facing the object side, so light rays cannot be converged within the second lens G2, making it difficult to reduce the diameter of the optical element after the second lens G2.

[0057] The conditional formula (9) specifies the partial dispersion ratio for the g-line and F-line of the material of the first lens G1. If the value is greater than the upper limit of the conditional formula (9), it is undesirable because the correction of axial chromatic aberration and magnification chromatic aberration becomes excessive. If the value is smaller than the lower limit of the conditional formula (9), it is undesirable because the correction of axial chromatic aberration and magnification chromatic aberration cannot be sufficiently performed.

[0058] The condition equation (10) represents a condition regarding the ratio of the Abbe number of the first lens G1 to the Abbe number of the second lens G2. If the value is greater than the upper limit of the condition equation (10), it is undesirable because the correction of chromatic aberration caused by the second lens G2 becomes excessive. If the value is smaller than the lower limit of the condition equation (10), it is undesirable because the correction of chromatic aberration caused by the second lens G2 cannot be sufficiently achieved.

[0059] The conditional formula (11) defines the distance along the optical axis from the object-side lens surface of the first lens G1 to the object-side of the bending optical element PR. If the value is greater than the upper limit of the conditional formula (11), the distance along the optical axis from the first lens G1 to the bending optical element PR increases, which is undesirable because the optical system L0 increases in the direction of the optical axis. If the value is smaller than the lower limit of the conditional formula (11), the thickness of the first lens G1 and the second lens G2 placed on the object-side of the bending optical element PR decreases, which is undesirable because the refractive power of the first lens G1 and the second lens G2 becomes excessively weak.

[0060] Conditional equation (12) defines the ratio of the total optical length of the optical system L0 to the focal length of the entire optical system. The term "total optical length" used here refers to the distance along the optical axis from the lens surface closest to the object side to the image plane. If an optical element that has no substantial refractive power, such as a cover glass, is placed immediately before the image plane, this optical element is taken into account when calculating the total optical length here. However, if an optical element that has no substantial refractive power, such as a cover glass or a folded optical element, is placed on the object side of the lens surface closest to the object side, this optical element is not taken into account when calculating the total optical length.

[0061] If the value is greater than the upper limit of condition equation (12), the total optical length of the optical system L0 increases, which is undesirable because the optical system L0 becomes larger in the direction of the optical axis. If the value is smaller than the lower limit of condition equation (12), the refractive power of the first lens G1 and the second lens G2 becomes excessively strong, which is undesirable because it becomes difficult to correct various aberrations.

[0062] The conditional formula (13) is called the so-called color erasure condition. By satisfying the dry formula (13), chromatic aberration in the optical system L0 can be corrected well. If the value is greater than the upper limit of the conditional formula (13), it is undesirable because it becomes difficult to correct axial chromatic aberration and magnification chromatic aberration.

[0063] Conditional equation (14) defines the range of half-angles corresponding to the maximum image height of optical system L0. Here, the maximum image height of optical system L0 refers to the distance from the position on the optical axis on the image plane IP to the optical axis where the peripheral light intensity is 10%, assuming that the position on the optical axis has 100% light intensity. If the value is greater than the upper limit of conditional equation (14), the height of the off-axis light rays increases, so the lens diameter of the lens constituting optical system L0 increases, and optical system L0 becomes larger in the radial direction, which is undesirable. If the value is smaller than the lower limit of conditional equation (14), the height of the light rays incident on the first lens G1 becomes excessively small, so the optical path length TTL increases, and optical system L0 becomes larger in the optical axis direction, which is undesirable.

[0064] Conditional equation (15) defines the ratio of the effective aperture diameter of the object-side lens surface of the lens closest to the object side in the optical system L0 to the effective aperture diameter of the image-side lens surface of the lens closest to the image side. The term "lens" used here refers to a lens having refractive power. The effective diameter of optical elements such as cover glass, mirrors, and prisms that do not substantially have refractive power is not included in this equation.

[0065] If the value is greater than the upper limit of condition equation (15), the lens diameter of the lens positioned closest to the upper side of optical system L0 increases, causing optical system L0 to become enlarged in the radial direction, which is undesirable. If the value is smaller than the lower limit of condition equation (15), the refractive power of the lens positioned closest to the upper side of optical system L0 becomes excessively strong, making it difficult to correct aberrations, which is undesirable.

[0066] The conditional equation (16) defines the position of the bending optical element PR on the optical axis. If the value is greater than the upper limit of the conditional equation (16), the distance between the object-side lens surface of the first lens G1 and the optical axis of the bending optical element PR becomes excessively large, which is undesirable as it increases the overall length of the optical system L0.

[0067] If the value is smaller than the lower limit of condition equation (16), the distance between the object-side lens surface of the first lens G1 and the optical axis of the bending optical element PR becomes excessively small, making it difficult to place the lens on the object-side of the bending optical element PR, which is undesirable.

[0068] The numerical range of condition expressions (1) to (16) can be set as in the following condition expressions (1a) to (16a).

[0069] 1.40 <NdG1<1.57 (1a)

[0070] 73.0<νdG1<110.0 (2a)

[0071] 0.30<|fG1 / fG2|<1.10 (3a)

[0072] 0.30<|fG2 / f|<1.50 (4a)

[0073] 0.30 <fG1 / f<0.80 (5a)

[0074] 0.04 <tG1 / f<0.30 (6a)

[0075] -1.50<(G1R1+G1R2) / (G1R1-G1R2)<0.30 (7a)

[0076] -2.00<(G2R1+G2R2) / (G2R1-G2R2)<6.00 (8a)

[0077] 0.010<θgFG1-0.6438+0.001682×νdG1<0.080 (9a)

[0078] 1.3<νdG1 / νdG2<6.0 (10a)

[0079] 0.15 <LD / f<0.50 (11a)

[0080] 0.60 <TTL / f<3.00 (12a)

[0081] |1 / (fG1×νdG1)+1 / (fG2×νdG2)|<0.004 (13a)

[0082] 5<ω<17 (14a)

[0083] 0.30 <EA_IMG / EA_OBJ<0.90 (15a)

[0084] 0.30 <LD / fG1<0.85 (16a)

[0085] In addition, the numerical range of condition expressions (1) to (16) can be set as in the following condition expressions (1b) to (16b).

[0086] 1.42 <NdG1<1.55 (lb)

[0087] 85.0<νdG1<100.0 (2b)

[0088] 0.60<|fG1 / fG2|<0.90 (3b)

[0089] 0.40<|fG2 / f|<1.00 (4b)

[0090] 0.35 <fG1 / f<0.70 (5b)

[0091] 0.08 <tG1 / f<0.25 (6b)

[0092] -1.00<(G1R1+G1R2) / (G1R1-G1R2)<0.10 (7b)

[0093] -1.60<(G2R1+G2R2) / (G2R1-G2R2)<5.00 (8b)

[0094] 0.020<θgFG1-0.6438+0.001682×νdG1<0.050 (9b)

[0095] 1.5<νdG1 / νdG2<5.0 (10b)

[0096] 0.18 <LD / f<0.40 (1lb)

[0097] 0.80 <TTL / f<2.00 (12b)

[0098] |1 / (fG1×νdG1)+1 / (fG2×νdG2)|<0.003 (13b)

[0099] 6<ω<15 (14b)

[0100] 0.50 <EA_IMG / EA_OBJ<0.80 (15b)

[0101] 0.40 <LD / fG1<0.75 (16b)

[0102] Next, the configurations that can be satisfied in the optical system L0 according to each embodiment are described.

[0103] In the optical system L0 according to each embodiment, the folded optical element PR may be positioned adjacent to the upper side of the second lens G2. With this configuration, the axial ray height passing through the second lens G2 can be increased, thereby allowing for good correction of spherical aberration and axial chromatic aberration.

[0104] In the optical system L0 according to each embodiment, at least one of the object-side lens surface and the image-side lens surface of the first lens G1 may have an aspherical shape. By making the first lens G1 an aspherical lens, spherical aberration and coma aberration caused by the first lens G1 can be reduced. To further enhance the aforementioned effect, the aspherical shape of at least one of the object-side lens surface and the image-side lens surface of the first lens G1 may be a shape in which the positive refractive power weakens from the center of the optical axis toward the periphery.

[0105] Below, a shape in which the refractive power weakens from the center of the optical axis toward the periphery is described. This shape refers to a shape in which, when comparing the refractive power at the center of the optical axis, the refractive power at the point where the image height is 50%, and the refractive power at the periphery, the refractive power at the center of the optical axis is the strongest, the refractive power at the point where the image height is 50% is weaker than that at the center of the optical axis, and the refractive power at the periphery is weaker than that at the point where the image height is 50%. The same applies to the shape in which the refractive power weakens from the periphery toward the center of the optical axis.

[0106] In the optical system L0 according to each embodiment, at least one of the object-side lens surface and the image-side lens surface of the second lens G2 may have an aspherical shape. Since the second lens G2 is an aspherical lens, spherical aberration, coma aberration, and astigmatism caused by the first lens G1 can be effectively corrected. To further enhance the aforementioned effect, the aspherical shape of at least one of the object-side lens surface and the image-side lens surface of the second lens G2 may be a shape in which the negative refractive power becomes stronger from the center of the optical axis toward the periphery.

[0107] In the optical system L0 according to each embodiment, the bending optical element PR can reflect a light beam multiple times. By bending (refracting) the light beam multiple times, the overall length of the optical system L0 can be shortened, thereby enabling the miniaturization of the optical system L0.

[0108] In the optical system L0 according to each embodiment, among the optical elements included in the optical system L0, the number of lenses having refractive power may be four or fewer. By reducing the number of lenses constituting the optical system L0, the optical system L0 can be miniaturized.

[0109] Next, optical systems L0 according to Examples 1 to 12 will be described in detail. At this time, regarding the optical system L0 according to each example, descriptions of configurations similar to the optical system L0 according to Example 1 will be omitted, and the differences between the optical system L0 according to each example and the optical system L0 according to Example 1 will be described.

[0110] [Examples 1 to 7]

[0111] FIGS. 1, 3, 5, 7, 9, 11, and 13 are cross-sectional views of optical systems L0 according to Examples 1 to 7, respectively. Optical systems L0 according to Examples 1 to 7 consist of an aperture diaphragm SP, a first lens G1 having positive refractive power, a second lens G2 having negative refractive power, and a bending optical element PR, arranged in order from the object side.

[0112] In the optical system L0 according to Example 1, the folded optical element PR is positioned adjacent to the upper side of the second lens G2. With this configuration, the axial ray height passing through the second lens G2 can be increased, so spherical aberration and axial chromatic aberration can be corrected well.

[0113] In the optical system L0 according to Example 1, the upper lens surface of the first lens G1 has an aspherical shape in which the positive refractive power weakens from the center of the optical axis toward the periphery. The object-side lens surface of the second lens G2 has an aspherical shape in which the negative refractive power strengthens from the center of the optical axis toward the periphery.

[0114] An optical system L0 according to Examples 1 to 7 is provided, wherein the second lens G2 is made of a resin material.

[0115] [Example 8]

[0116] FIG. 15 is a cross-sectional view of an optical system L0 according to Example 8. The optical system L0 according to Example 8 is composed of an aperture diaphragm SP, a first lens G1 having positive refractive power, a second lens G2 having negative refractive power, a bending optical element PR, and a third lens G3 having negative refractive power, arranged in order from the object side. The second lens G2 and the third lens G3 are meniscus lenses having a concave surface facing upward.

[0117] In the optical system L0 according to Example 8, a third lens G3 having negative refractive power is disposed on the upper side of the bending optical element PR. Since the height of the axial light rays is small and the height of the out-of-axis light rays is large between the bending optical element PR and the upper plane, by disposing of the third lens G3 on the upper side of the bending optical element PR, it is possible to effectively correct out-of-axis aberrations such as astigmatism and coma aberration.

[0118] [Examples 9 and 10]

[0119] FIGS. 17 and 19 are cross-sectional views of optical systems L0 according to Examples 9 and 10, respectively. Optical systems L0 according to Examples 9 and 10 consist of an aperture diaphragm SP, a first lens G1 having positive refractive power, a second lens G2 having negative refractive power, and a bending optical element PR, arranged in order from the object side.

[0120] [Example 11]

[0121] FIG. 21 is a cross-sectional view of a lens of optical system L0 according to Example 11. Optical system LO according to Example 11 is composed of an aperture diaphragm SP, a first lens G1 having positive refractive power, a second lens G2 having negative refractive power, a bending optical element PR, a third lens G3 having positive refractive power, and a fourth lens GR having negative refractive power, arranged in order from the object side. The first lens G1 and the second lens G2 are meniscus lenses having a convex surface facing the object side. The fourth lens G4 is a meniscus lens having a convex surface facing upward.

[0122] In the optical system L0 according to Example 11, a third lens G3 having a positive refractive power and a fourth lens G4 having a negative refractive power are disposed on the upper side of the folded optical element PR. With this configuration, chromatic aberration occurring on the object side of the folded optical element PR can be corrected well.

[0123] [Example 12]

[0124] FIG. 23 is a cross-sectional view of a lens of optical system L0 according to Example 12. Optical system LO according to Example 12 is composed of an aperture diaphragm SP, a first lens G1 having positive refractive power, a second lens G2 having negative refractive power, a bending optical element PR, and a third lens G3 having negative refractive power, arranged in order from the object side. The second lens G2 is a meniscus lens having a convex surface facing the object side. The third lens G3 is a meniscus lens having a convex surface facing upward.

[0125] Hereinafter, numerical Examples 1 to 12 corresponding to Examples 1 to 12 are described. In each numerical example, the face number "i" indicates the order of the faces when counted from the object side. "r" indicates the radius of curvature (mm) of the i-th face from the object side, "d" indicates the lens thickness or air gap (mm) on the optical axis between the i-th face and the (i+1)-th face, and "nd" indicates the refractive index of the optical material with respect to the d-line between the i-th face and the (i+1)-th face. The sign of "d" is defined so that the direction from the object side toward the upper side on the optical axis is positive. "νd" indicates the Abbe number based on the d-line of the optical material between the i-th face and the (i+1)-th face. "θgF" indicates the partial dispersion ratio of the optical material between the i-th face and the (i+1)-th face.

[0126] "BF" indicates back focus (mm). The total length of the lens is the distance along the optical axis from the lens plane closest to the object side (foremost plane) of optical system L0 to the image plane.

[0127] If the optical surface is aspherical, a symbol (*) is attached to the right of the surface number. The aspherical shape is expressed by the following formula.

[0128] X=(h 2 / R) / [1+{1-(1+k)(h / R) 2}] 1 / 2 +A4×h 4 +A6×h 6 +A8×h 8 +A10×h 10 +A12×h 12

[0129] Here, X represents the displacement from the plane vertex in the direction of the optical axis, h represents the height from the optical axis in the direction perpendicular to the optical axis, R represents the paraxial radius of curvature, k represents the conic constant, and A4, A6, A8, A10, and A12 represent the aspherical coefficients of each order. For each aspherical coefficient, "e±XX" is "×10± XX It means "

[0130] [Numerical Example 1]

[0131]

[0132] [Numerical Example 2]

[0133]

[0134] [Numerical Example 3]

[0135]

[0136] [Numerical Example 4]

[0137]

[0138] [Numerical Example 5]

[0139]

[0140] [Numerical Example 6]

[0141]

[0142] [Numerical Example 7]

[0143]

[0144] [Numerical Example 8]

[0145]

[0146] [Numerical Example 9]

[0147]

[0148] [Numerical Example 10]

[0149]

[0150] [Numerical Example 11]

[0151]

[0152] [Numerical Example 12]

[0153]

[0154] Table 1 shows the numerical values ​​of the physical quantities described above according to each embodiment, and Table 2 shows the numerical values ​​of each conditional expression.

[0155]

[0156]

[0157] [Folded Optical Element]

[0158] Next, the bending optical element PR according to each embodiment will be described in detail with reference to FIGS. 25a, 25b, and 25c. FIGS. 25a, 25b, and 25c show an example of the configuration of the bending optical element PR in the optical system L0 according to Example 1.

[0159] In FIG. 25a, light rays are bent (refracted) at two surfaces, REF1 and REF2, inside the bending optical element PR. The bending angle is 45° for all surfaces. The values ​​of the distance L1 from the object-side surface of the bending optical element PR to the REF1 surface, the distance L2 from the REF1 surface to the REF2 surface, and the distance L3 from the REF2 surface to the top-side surface of the bending optical element PR are shown in FIG. 25a.

[0160] In FIG. 25b, a light ray is bent at two surfaces, REF1 and REF2, inside the bending optical element PR. The bending angle is 45° for all surfaces. The values ​​of the distance L1 from the object-side surface of the bending optical element PR to the REF1 surface, the distance L2 from the REF1 surface to the REF2 surface, and the distance L3 from the REF2 surface to the top-side surface of the bending optical element PR are shown in FIG. 25b.

[0161] In FIG. 25c, a light ray is bent by the REF1 surface inside the bending optical element PR.

[0162] The bending angle is 45°. The values ​​of the distance L1 from the object-side surface of the bent optical element PR to the REF1 surface and the distance L2 from the REF1 surface to the upper-side surface of the bent optical element PR are shown in FIG. 25c.

[0163] Therefore, regardless of the angle or number of times a ray is bent within the bending optical element PR, if the total optical axis distance within the bending optical element PR is the same, the resulting aberration is the same, so the imaging optical system can be considered the same.

[0164] In this embodiment, a prism is used as an example of a folded optical element PR. However, a mirror may be used instead of a prism. In the prism and mirror, the reflection angle may be 30°, 60°, or other angles instead of 45°. In addition, the reflective surface of the prism or mirror may have a curved surface or an aspherical surface.

[0165] [Imaging device]

[0166] Next, an embodiment of an imaging device using an optical system L0 according to each embodiment as an imaging optical system will be described with reference to FIG. 26. The camera body (20) shown in FIG. 26 has an imaging optical system (21) similar to any one of the optical systems L0 according to embodiments 1 to 12, and a solid-state imaging element (photoelectric conversion element) (22) embedded in the camera body (20) and receiving light from the image of a subject formed by the imaging optical system (21). The solid-state imaging element (22) is, for example, a CCD sensor or a CMOS sensor. The memory (23) is a recording unit that records the image of a subject received by the solid-state imaging element (22). The viewfinder (24) is a viewfinder formed on the solid-state imaging element (22) and for observing the image of a subject displayed on a display element (not shown).

[0167] The camera body (20) may be built into a single-lens reflex camera having a quick-return mirror, a mirrorless camera not having a quick-return mirror, or a portable terminal such as a smartphone.

[0168] The aforementioned solid imaging element (22) may be perpendicular to the incident light or inclined toward the incident light. In this case, the angle of inclination of the solid imaging element (22) toward the incident light and the angle of inclination of the reflective surface of the folded optical element PR can be appropriately set according to the configuration of the optical system L0 or the imaging device.

[0169] In this way, by applying the optical system L0 according to each embodiment to an imaging device such as a digital still camera, an imaging optical system that is small, lightweight, and has high optical performance, and an imaging device having the imaging optical system can be obtained.

[0170] Although preferred embodiments and examples of the disclosure have been described above, the disclosure is not limited to these embodiments and examples, and various combinations, modifications, and changes are possible within the scope of the disclosure.

[0171] In the optical system L0 according to each embodiment, the first lens G1 and the second lens G2 may be joined together to form a single joined lens. With this configuration, eccentric errors occurring in the first lens G1 and the second lens G2 can be suppressed, thereby improving the optical performance of the optical system L0.

[0172] In the optical system L0 according to each embodiment, all or some of the lenses included in the optical system L0 may be used as an image stabilization lens group, and an image stabilization function may be provided by moving the imaging plane in a direction parallel to the optical axis.

[0173] In the optical system L0 according to each embodiment, all or some of the lenses included in the optical system L0 may be used as lenses for focusing. Additionally, the optical system LO may include not only refractive optical elements and reflective optical elements, but also diffractive optical elements.

[0174] Although the present invention has been described with reference to exemplary embodiments, it is obvious that the invention is not limited to these embodiments. The scope of protection of the following claims shall be interpreted as broadly as possible to encompass all variations, equivalent structures, and functions.

Claims

Claim 1 An optical system having, arranged sequentially from the object side to the upper side, a first lens having a positive refractive power, a second lens having a negative refractive power and disposed adjacent to the upper side of the first lens, and a bending optical element disposed adjacent to the upper side of the second lens, satisfying the following inequality: 1.30 <NdG1<1.60, 및73.0<νdG1<120.0이때 NdG1은 상기 제1렌즈의 재료의 d선에 대한 굴절률을 나타내고 νdG1은 상기 제1렌즈의 재료의 d선에 대한 아베수를 나타낸다. Claim 2 In the first paragraph, an optical system satisfying the following inequality: 0.20 < |fG1 / fG2| < 1.20, where fG1 represents the focal length of the first lens and fG2 represents the focal length of the second lens. Claim 3 In the first paragraph, an optical system satisfying the following inequality: 0.20 < |fG2 / f| < 2.00, where fG2 represents the focal length of the second lens and f represents the focal length of the entire optical system. Claim 4 In claim 1, the first lens is an optical system having an aspherical shape. Claim 5 In claim 4, the aspherical shape of the first lens is an optical system in which the positive refractive power becomes weaker from the center of the optical axis toward the periphery. Claim 6 In Clause 1, an optical system satisfying the following inequality: 0.20 <fG1 / f<1.00이때 fG1은 상기 제1렌즈의 초점거리를 나타내고, f는 전체 광학계의 초점거리를 나타낸다. Claim 7 In claim 1, an optical system satisfying the following inequality: 0.01 <tG1 / f<0.35이때 tG1은 상기 제1렌즈의 광축 중심에 있어서의 광축 방향의 두께를 나타내고, f는 전체 광학계의 초점거리를 나타낸다. Claim 8 In claim 1, an optical system satisfying the following inequality: -2.00 < (G1R1 + G1R2) / (G1R1 - G1R2) < 0.50, where G1R1 represents the radius of curvature of the object-side lens surface of the first lens, and G1R2 represents the radius of curvature of the upper-side lens surface of the first lens. Claim 9 In claim 1, an optical system satisfying the following inequality: -3.00 < (G2R1 + G2R2) / (G2R1 - G2R2) < 7.00, where G2R1 represents the radius of curvature of the object-side lens surface of the second lens, and G2R2 represents the radius of curvature of the upper-side lens surface of the second lens. Claim 10 In the first paragraph, an optical system satisfying the following inequality: 0.005 < θgFG1 - 0.6438 + 0.001682 × νdG1 < 0.100, where θgFG represents the partial dispersion ratio of the material of the first lens. Claim 11 In the first paragraph, an optical system satisfying the following inequality: 1.0 < νdG1 / νdG2 < 8.0, where νdG2 represents the Abbe number for the d-line of the material of the second lens. Claim 12 In the first paragraph, an optical system satisfying the following inequality: 0.10 <LD / f<0.60이때 LD는 상기 제1렌즈의 물체측 렌즈면으로부터 상기 절곡 광학 소자의 물체측면까지의 광축 상의 거리를 나타내고, f는 전체 광학계의 초점거리를 나타낸다. Claim 13 In the first paragraph, an optical system satisfying the following inequality: 0.40 <TTL / f<4.00이때 TTL은 상기 광학계의 전체 광학 길이를 나타내고, f는 전체 광학계의 초점거리를 나타낸다. Claim 14 In claim 1, an optical system satisfying the following inequality: |1 / (fG1×νdG1)+1 / (fG2×νdG2)|<0.005, where fG1 represents the focal length of the first lens, fG2 represents the focal length of the second lens, and νdG2 represents the Abbe number for the d-line of the material of the second lens. Claim 15 In claim 1, an optical system satisfying the following inequality: 4 < ω < 20, where ω [°] represents the image half-angle of the optical system. Claim 16 In the first paragraph, an optical system satisfying the following inequality: 0.10 <EA_IMG / EA_OBJ<1.00이때 EA_OBJ는 상기 광학계에 있어서 물체측에 가장 가깝게 배치된 렌즈의 물체측 렌즈면의 유효 개구 직경을 나타내고, EA_IMG는 상기 광학계에 있어서 상측에 가장 가깝게 배치된 렌즈의 상측 렌즈면의 유효 개구 직경을 나타낸다. Claim 17 In Clause 1, an optical system satisfying the following inequality: 0.20 <LD / fG1<1.00이때 LD는 상기 제1렌즈의 물체측 렌즈면으로부터 상기 절곡 광학 소자의 물체측면까지의 광축 상의 거리를 나타내고, fG1는 상기 제1렌즈의 초점거리를 나타낸다. Claim 18 In claim 1, the second lens is an optical system having an aspherical shape. Claim 19 In claim 18, the aspherical shape of the second lens is an optical system having an aspherical shape in which the negative refractive power becomes stronger from the center of the optical axis toward the periphery. Claim 20 In claim 1, the bending optical element is an optical system that reflects an incident light ray multiple times within the bending optical element. Claim 21 An optical system according to claim 1, wherein the first lens, the second lens, and the bending optical element are arranged in order from the object side to the upper side to form the optical system. Claim 22 An optical system according to claim 1, further comprising a third lens having positive refractive power, wherein the first lens, the second lens, the bending optical element, and the third lens are arranged in order from the object side to the upper side. Claim 23 An optical system according to claim 1, further comprising a third lens having negative refractive power, wherein the first lens, the second lens, the bending optical element, and the third lens are arranged in order from the object side to the upper side. Claim 24 An optical system according to claim 1, further comprising a third lens having a positive refractive power and a third lens having a negative refractive power, wherein the first lens, the second lens, the bending optical element, the third lens, and the fourth lens are arranged in order from the object side to the upper side. Claim 25 An optical system having, in order from the object side to the upper side, a first lens having a positive refractive power, a second lens having a negative refractive power, and a bending optical element, wherein the object-side lens surface of the first lens is a convex surface facing the object side. Claim 26 An imaging device having an optical system described in any one of claims 1 to 25 and an imaging element configured to receive an image formed by the optical system.

Images