Optical system, optical device, and method for manufacturing optical system

Abstract

The invention provides an optical system, an optical device and a method for manufacturing the optical system, wherein the optical system and the optical device are compact, light and good in optical performance. An optical system (OL) mounted on an optical device such as a camera (1) includes, in order from the object side, a first negative meniscus lens (L1) having a convex surface facing the object side and having a negative refractive power; a second negative meniscus lens (L2) having a convex surface facing the object side and having a negative refractive power; a third biconcave negative lens (L3) having a negative refractive power; the biconvex positive lens (L4) is configured so as to satisfy a condition based on a prescribed conditional expression.

Description

Technical Field

[0001] The present invention relates to an optical system, an optical device, and a method for manufacturing an optical system. Background Art

[0002] Conventionally, an optical system with a wide field of view angle and small size has been proposed (for example, refer to Patent Document 1). However, Patent Document 1 has a problem of achieving a balance between miniaturization, light weight, and good optical performance.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-056995 Summary of the Invention

[0006] The optical system according to the first aspect of the present invention is composed of, in order from the object side, a first negative meniscus lens having a convex surface facing the object side and a negative focal power, a second negative meniscus lens having a convex surface facing the object side and a negative focal power, a third biconcave negative lens having a negative focal power, and at least one lens, and the optical system satisfies the conditions of the following formula: 90.0° < ω 0.10 < R12 / (-fL1) < 0.80 wherein ω: the half field of view angle of the optical system, fL1: the focal length of the first negative meniscus lens, R12: the radius of curvature of the lens surface on the image side of the first negative meniscus lens.

[0007] The optical system according to the second aspect of the present invention is composed of, in order from the object side, a first negative meniscus lens having a convex surface facing the object side and a negative focal power, a second negative meniscus lens having a convex surface facing the object side and a negative focal power, a third biconcave negative lens having a negative focal power, and at least one lens, and the optical system satisfies the conditions of the following formula: 90.0° < ω 1.80 < R12 / D12 < 3.00 wherein ω: the half field of view angle of the optical system, D12: the axial air gap between the first negative meniscus lens and the second negative meniscus lens, R12: the radius of curvature of the lens surface on the image side of the first negative meniscus lens.

[0008] Method for manufacturing an optical system according to a first aspect of the present invention. The optical system includes, in order from the object side, a first negative meniscus lens with a convex surface facing the object side and having a negative optical power, a second negative meniscus lens with a convex surface facing the object side and having a negative optical power, a third biconcave negative lens having a negative optical power, and at least one lens, and is configured to satisfy the conditions of the following formula: 90.0° < ω 0.10 < R12 / (-fL1) < 0.80 wherein, ω: the half field angle of the optical system, fL1: the focal length of the first negative meniscus lens, R12: the radius of curvature of the lens surface on the image side of the first negative meniscus lens.

[0009] Method for manufacturing an optical system according to a second aspect of the present invention. The optical system includes, in order from the object side, a first negative meniscus lens with a convex surface facing the object side and having a negative optical power, a second negative meniscus lens with a convex surface facing the object side and having a negative optical power, a third biconcave negative lens having a negative optical power, and at least one lens, and is configured to satisfy the conditions of the following formula: 90.0° < ω 1.80 < R12 / D12 < 3.00 wherein, ω: the half field angle of the optical system, D12: the axial air gap between the first negative meniscus lens and the second negative meniscus lens, R12: the radius of curvature of the lens surface on the image side of the first negative meniscus lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a cross-sectional view showing the lens structure when the optical system of the first embodiment is focused on an infinitely distant object.

[0011] Figure 2 is a diagram of each aberration when the optical system of the first embodiment is focused on an infinitely distant object.

[0012] Figure 3 is a cross-sectional view showing the lens structure when the optical system of the second embodiment is focused on an infinitely distant object.

[0013] Figure 4 is a diagram of each aberration when the optical system of the second embodiment is focused on an infinitely distant object.

[0014] Figure 5 is a cross-sectional view showing the lens structure when the optical system of the third embodiment is focused on an infinitely distant object.

[0015] Figure 6 These are aberration diagrams when focusing on an infinitely distant object by the optical system of the third embodiment.

[0016] Figure 7 This is a cross-sectional view of a camera equipped with the above optical system.

[0017] Figure 8 This is a flowchart for explaining the manufacturing method of the above optical system. Detailed Embodiments

[0018] Hereinafter, preferred embodiments will be described with reference to the accompanying drawings.

[0019] (First Embodiment)

[0020] As Figure 1 shown, the optical system OL of the first embodiment sequentially includes, from the object side, a first negative meniscus lens L1 with a convex surface facing the object side and having a negative optical power, a second negative meniscus lens L2 with a convex surface facing the object side and having a negative optical power, a third biconcave negative lens L3 with a negative optical power, and at least one lens. By configuring in this way, it is possible to achieve both miniaturization, light weight, and good optical performance of the optical system OL.

[0021] In addition, the optical system OL of the first embodiment preferably satisfies the following conditional expression (1).

[0022] 90.0° < ω (1) Wherein, ω: Half field angle of the optical system OL

[0023] The conditional expression (1) defines the half field angle of the optical system OL. By satisfying this conditional expression (1), it is possible to obtain the field angle required for a fisheye lens. In addition, in order to make the effect of the conditional expression (1) reliable, it is preferable to set the lower limit value of the conditional expression (1) to 95.0°, and further to 100.0°. In addition, in order to make the effect of this conditional expression (1) reliable, it is preferable to set the upper limit value of the conditional expression (1) to 120.0° (ω < 120.0°), and further to 110.0°.

[0024] In addition, the optical system OL of the first embodiment preferably satisfies the following conditional expression (2).

[0025] 0.10 < R12 / (-fL1) < 0.80 (2) Wherein, fL1: Focal length of the first negative meniscus lens L1 R12: Curvature radius of the lens surface on the image side of the first negative meniscus lens L1

[0026] The conditional expression (2) defines the ratio of the radius of curvature of the lens surface on the image side of the first negative meniscus lens L1 to the focal length of the first negative meniscus lens L1. By satisfying this conditional expression (2), it is possible to achieve both miniaturization and weight reduction of the optical system OL and good optical performance. If it is lower than the lower limit value of the conditional expression (2), the entire optical system OL becomes larger, and in addition, it becomes difficult to correct the axial chromatic aberration and the lateral chromatic aberration. Therefore, it is not preferred. In addition, in order to make the effect of the conditional expression (2) reliable, it is preferred to set the lower limit value of the conditional expression (2) to 0.15, 0.25, 0.35, and further to 0.40. In addition, if it exceeds the upper limit value of the conditional expression (2), it becomes difficult to correct the spherical aberration. Therefore, it is not preferred. In addition, in order to make the effect of the conditional expression (2) reliable, it is preferred to set the upper limit value of the conditional expression (2) to 0.75, 0.65, 0.55, and further to 0.50.

[0027] (Second Embodiment)

[0028] As Figure 1 shown, the optical system OL of the second embodiment sequentially includes a first negative meniscus lens L1 with a convex surface facing the object side and having a negative optical power, a second negative meniscus lens L2 with a convex surface facing the object side and having a negative optical power, a third double concave negative lens L3 with a negative optical power, and at least one lens. By configuring in this way, it is possible to achieve both miniaturization and weight reduction of the optical system OL and good optical performance.

[0029] In addition, the optical system OL of the second embodiment preferably satisfies the above conditional expression (1). The effects obtained by satisfying this conditional expression (1) are as described above.

[0030] In addition, the optical system OL of the second embodiment preferably satisfies the conditional expression (3) shown below.

[0031] 1.80 < R12 / D12 < 3.00 (3) Wherein, D12: The axial air gap between the first negative meniscus lens L1 and the second negative meniscus lens L2 R12: The radius of curvature of the lens surface on the image side of the first negative meniscus lens L1

[0032] The conditional expression (3) defines the ratio of the radius of curvature of the lens surface on the image plane side of the first negative meniscus lens L1 to the axial air gap between the first negative meniscus lens L1 and the second negative meniscus lens L2. By satisfying the conditional expression (3), it is possible to achieve both miniaturization and weight reduction of the optical system OL and good optical performance. If it is lower than the lower limit value of the conditional expression (3), it becomes difficult to correct the image plane curvature and astigmatism, so it is not preferred. In addition, in order to make the effect of the conditional expression (3) reliable, it is preferred to set the lower limit value of the conditional expression (3) to 1.90, and further to 2.00. Additionally, if it exceeds the upper limit value of the conditional expression (3), the correction of the image plane curvature and astigmatism is insufficient, so it is not preferred. In addition, in order to make the effect of the conditional expression (3) reliable, it is preferred to set the upper limit value of the conditional expression (3) to 2.80, 2.65, and further to 2.50.

[0033] (Regarding the first embodiment and the second embodiment)

[0034] In addition, the optical system OL of the first embodiment and the second embodiment (hereinafter referred to as "the present embodiment") preferably satisfies the conditional expression (4) shown below.

[0035] φ12 / R12 < 1.90 (4) Wherein, R12: The radius of curvature of the lens surface on the image plane side of the first negative meniscus lens L1 φ12: The effective diameter of the lens surface on the image plane side of the first negative meniscus lens L1

[0036] The conditional expression (4) defines the ratio of the effective diameter of the lens surface on the image plane side of the first negative meniscus lens L1 to the radius of curvature of the lens surface on the image plane side of the first negative meniscus lens L1. By satisfying this conditional expression (4), it is possible to achieve both miniaturization and weight reduction of the optical system OL and good optical performance. If it exceeds the upper limit value of the conditional expression (4), although miniaturization becomes easy, the correction of the longitudinal chromatic aberration becomes difficult, and the processing of the lens becomes difficult. Furthermore, the degradation of the imaging performance due to manufacturing errors becomes significant, so it is not preferred. In addition, in order to make the effect of the conditional expression (4) reliable, it is preferred to set the upper limit value of the conditional expression (4) to 1.88, 1.85, and further to 1.83. Additionally, in order to make the effect of this conditional expression (4) reliable, it is preferred to set the lower limit value of the conditional expression (4) to 1.60 (1.60 < φ12 / R12), and further to 1.70.

[0037] In addition, the optical system OL of the present embodiment preferably satisfies the conditional expression (5) shown below.

[0038] φ22 / R22 < 1.90 (5) Wherein, R22: The radius of curvature of the lens surface on the image plane side of the second negative meniscus lens L2 φ22: The effective diameter of the lens surface on the image plane side of the second negative meniscus lens L2

[0039] The conditional expression (5) defines the ratio of the effective diameter of the lens surface on the image plane side of the second negative meniscus lens L2 to the radius of curvature of the lens surface on the image plane side of the second negative meniscus lens L2. By satisfying this conditional expression (5), it is possible to achieve both miniaturization and weight reduction of the optical system OL and good optical performance. If it exceeds the upper limit value of the conditional expression (5), although miniaturization becomes easier, correction of the longitudinal chromatic aberration becomes difficult, and lens processing becomes difficult. Furthermore, the degradation of the imaging performance due to manufacturing errors becomes significant, so it is not preferred. In addition, in order to make the effect of the conditional expression (5) reliable, it is preferable to set the upper limit value of the conditional expression (5) to 1.88, 1.85, and further to 1.83. Additionally, in order to make the effect of this conditional expression (5) reliable, it is preferable to set the lower limit value of the conditional expression (5) to 1.60 (1.60 < φ22 / R22), and further to 1.70.

[0040] In addition, the optical system OL of the present embodiment preferably satisfies the conditional expression (6) shown below.

[0041] 7.50 < R12 / DL1 < 11.00 (6) Wherein, DL1: The thickness on the optical axis of the first negative meniscus lens L1 R12: The radius of curvature of the lens surface on the image plane side of the first negative meniscus lens L1

[0042] The conditional expression (6) defines the ratio of the radius of curvature of the lens surface on the image plane side of the first negative meniscus lens L1 to the thickness on the optical axis of the first negative meniscus lens L1. By satisfying this conditional expression (6), it is possible to achieve both miniaturization and weight reduction of the optical system OL and good optical performance. If it is lower than the lower limit value of the conditional expression (6), correction of the field curvature and astigmatism becomes difficult, so it is not preferred. In addition, in order to make the effect of the conditional expression (6) reliable, it is preferable to set the lower limit value of the conditional expression (6) to 8.00, 8.50, and further to 8.80. Additionally, if it exceeds the upper limit value of the conditional expression (6), the overall size of the optical system OL becomes large. In addition, if the radius of curvature of the lens surface on the object side of the first negative meniscus lens L1 is reduced in order to mitigate this effect, correction of the astigmatism and field curvature becomes difficult, so it is not preferred. In addition, in order to make the effect of the conditional expression (6) reliable, it is preferable to set the upper limit value of the conditional expression (6) to 10.50, 10.00, and further to 9.50.

[0043] In addition, the optical system OL of the present embodiment preferably satisfies the conditional expression (7) shown below.

[0044] -3.50 < (R12 + R11) / (R12 - R11) < -2.00 (7) Wherein, R11: The radius of curvature of the lens surface on the object side of the first negative meniscus lens L1 R12: The radius of curvature of the lens surface on the image side of the first negative meniscus lens L1

[0045] The conditional expression (7) defines the shape factor of the first negative meniscus lens L1. By satisfying this conditional expression (7), it is possible to achieve both miniaturization and weight reduction of the optical system OL and good optical performance. If it is lower than the lower limit value of the conditional expression (7), it becomes difficult to correct spherical aberration, coma, and field curvature, so it is not preferred. In addition, in order to make the effect of the conditional expression (7) reliable, it is preferred to set the lower limit value of the conditional expression (7) to -3.40, -3.25, and further to -3.00. Additionally, if it exceeds the upper limit value of the conditional expression (7), it becomes difficult to obtain the amount of distortion required for a fish-eye lens, so it is not preferred. In addition, in order to make the effect of the conditional expression (7) reliable, it is preferred to set the upper limit value of the conditional expression (7) to -2.20, -2.35, and further to -2.50.

[0046] In addition, the optical system OL of the present embodiment preferably satisfies the following conditional expression (8).

[0047] 0.20 < R22 / (-fL2) < 0.80 (8) Wherein, fL2: The focal length of the second negative meniscus lens L2 R22: The radius of curvature of the lens surface on the image side of the second negative meniscus lens L2

[0048] The conditional expression (8) defines the ratio of the radius of curvature of the lens surface on the image side of the second negative meniscus lens L2 to the focal length of the second negative meniscus lens L2. By satisfying this conditional expression (8), it is possible to achieve both miniaturization and weight reduction of the optical system OL and good optical performance. If it is lower than the lower limit value of the conditional expression (8), the overall size of the optical system OL increases, and in addition, it becomes difficult to correct axial chromatic aberration and lateral chromatic aberration, so it is not preferred. In addition, in order to make the effect of the conditional expression (8) reliable, it is preferred to set the lower limit value of the conditional expression (8) to 0.30, 0.40, and further to 0.50. Additionally, if it exceeds the upper limit value of the conditional expression (8), it becomes difficult to correct spherical aberration, so it is not preferred. In addition, in order to make the effect of the conditional expression (8) reliable, it is preferred to set the upper limit value of the conditional expression (8) to 0.75, 0.70, and further to 0.65.

[0049] In addition, the optical system OL of the present embodiment preferably satisfies the conditional expression (9) shown below.

[0050] 6.50 < R22 / DL2 < 12.00 (9) wherein, DL2: Thickness on the optical axis of the second negative meniscus lens L2 R22: Curvature radius of the lens surface on the image side of the second negative meniscus lens L2

[0051] The conditional expression (9) defines the ratio of the curvature radius of the lens surface on the image side of the second negative meniscus lens L2 to the thickness on the optical axis of the second negative meniscus lens L2. By satisfying this conditional expression (9), it is possible to balance the miniaturization, weight reduction, and good optical performance of the optical system OL. If it is lower than the lower limit value of the conditional expression (9), it becomes difficult to correct field curvature and astigmatism, so it is not preferred. In addition, in order to make the effect of the conditional expression (9) reliable, it is preferable to set the lower limit value of the conditional expression (9) to 7.00, 7.50, and further to 8.00. In addition, if it exceeds the upper limit value of the conditional expression (9), the entire optical system OL becomes large. In addition, if the curvature radius of the lens surface on the object side of the second negative meniscus lens L2 is reduced in order to mitigate this influence, it becomes difficult to correct astigmatism and field curvature, so it is not preferred. In addition, in order to make the effect of the conditional expression (9) reliable, it is preferable to set the upper limit value of the conditional expression (9) to 11.50, 11.00, 10.50, and further to 10.00.

[0052] In addition, the optical system OL of the present embodiment preferably satisfies the conditional expression (10) shown below.

[0053] -2.50 < (R22 + R21) / (R22 - R21) < -1.00 (10) wherein, R21: Curvature radius of the lens surface on the object side of the second negative meniscus lens L2 R22: Curvature radius of the lens surface on the image side of the second negative meniscus lens L2

[0054] The conditional expression (10) defines the shape factor of the second negative meniscus lens L2. By satisfying this conditional expression (10), it is possible to achieve both miniaturization and weight reduction of the optical system OL and good optical performance. If it is lower than the lower limit value of the conditional expression (10), it becomes difficult to correct spherical aberration, coma, and field curvature, so it is not preferred. In addition, in order to make the effect of the conditional expression (10) reliable, it is preferred to set the lower limit value of the conditional expression (10) to -2.40, -2.25, -2.10, and further to -2.00. Additionally, if it exceeds the upper limit value of the conditional expression (10), it becomes difficult to obtain the amount of distortion required for a fish-eye lens, so it is not preferred. In addition, in order to make the effect of the conditional expression (10) reliable, it is preferred to set the upper limit value of the conditional expression (10) to -1.10, -1.20, -1.30, and further to -1.40.

[0055] In addition, the optical system OL of the present embodiment preferably satisfies the conditional expression (11) shown below.

[0056] 0.80 < R22 / D23 < 2.00 (11) Wherein, D23: The axial air interval between the second negative meniscus lens L2 and the third biconcave negative lens L3 R22: The radius of curvature of the lens surface on the image side of the second negative meniscus lens L2

[0057] The conditional expression (11) defines the ratio of the radius of curvature of the lens surface on the image side of the second negative meniscus lens L2 to the axial air interval between the second negative meniscus lens L2 and the third biconcave negative lens L3. By satisfying this conditional expression (11), it is possible to achieve both miniaturization and weight reduction of the optical system OL and good optical performance. If it is lower than the lower limit value of the conditional expression (11), it becomes difficult to correct field curvature and astigmatism, so it is not preferred. In addition, in order to make the effect of the conditional expression (11) reliable, it is preferred to set the lower limit value of the conditional expression (11) to 0.90, 0.95, 1.00, and further to 1.05. Additionally, if it exceeds the upper limit value of the conditional expression (11), the correction of field curvature and astigmatism is insufficient, so it is not preferred. In addition, in order to make the effect of the conditional expression (11) reliable, it is preferred to set the upper limit value of the conditional expression (11) to 1.80, 1.65, 1.50, and further to 1.40.

[0058] In addition, the optical system OL of the present embodiment preferably satisfies the conditional expression (12) shown below.

[0059] 2.00 < TL / Ymax < 5.00 (12) Wherein, Ymax: The maximum image height of the optical system OL TL: The overall optical length (air equivalent length) in the infinity focus state of the optical system OL

[0060] The conditional expression (12) defines the ratio of the overall optical length (air equivalent length) in the infinity focus state to the maximum image height of the optical system OL. By satisfying this conditional expression (12), it is possible to achieve both miniaturization and weight reduction of the optical system OL and good optical performance. If it is lower than the lower limit value of the conditional expression (12), it becomes difficult to correct various aberrations such as spherical aberration and coma, so it is not preferred. In addition, in order to make the effect of the conditional expression (12) reliable, it is preferred to set the lower limit value of the conditional expression (12) to 2.25, 2.50, 2.75, and further to 3.00. Additionally, if it exceeds the upper limit value of the conditional expression (12), the entire optical system OL becomes large, so it is not preferred. In addition, in order to make the effect of the conditional expression (12) reliable, it is preferred to set the upper limit value of the conditional expression (12) to 4.75, 4.50, 4.25, 4.00, and further to 3.80.

[0061] In addition, the optical system OL of the present embodiment preferably satisfies the following conditional expression (13).

[0062] 1.75 < (nd1 + nd2) / 2 < 1.95 (13) Wherein, nd1: The refractive index of the medium of the first negative meniscus lens L1 with respect to the d-line nd2: The refractive index of the medium of the second negative meniscus lens L2 with respect to the d-line

[0063] The conditional expression (13) defines the average value of the refractive indices of the media of the first negative meniscus lens L1 and the second negative meniscus lens L2 with respect to the d-line. By satisfying this conditional expression (13), it is possible to achieve both miniaturization and weight reduction of the optical system OL and good optical performance. If it is lower than the lower limit value of the conditional expression (13), the refractive indices of the media of the first negative meniscus lens L1 and the second negative meniscus lens L2 with respect to the d-line decrease, and it becomes difficult to correct field curvature and astigmatism, so it is not preferred. In addition, in order to make the effect of the conditional expression (13) reliable, it is preferred to set the lower limit value of the conditional expression (13) to 1.78, and further to 1.80. Additionally, if it exceeds the upper limit value of the conditional expression (13), an appropriate Petzval sum cannot be obtained, and it becomes difficult to correct astigmatism, so it is not preferred. In addition, in order to make the effect of the conditional expression (13) reliable, it is preferred to set the upper limit value of the conditional expression (13) to 1.94, 1.92, and further to 1.90.

[0064] In addition, the optical system OL of the present embodiment preferably satisfies the following conditional expression (14).

[0065] 30.0 < (νd1 + νd2) / 2 < 45.0 (14) wherein νd1: Abbe number of the medium of the first negative meniscus lens L1 with respect to the d-line νd2: Abbe number of the medium of the second negative meniscus lens L2 with respect to the d-line

[0066] The conditional expression (14) defines the average value of the Abbe numbers of the media of the first negative meniscus lens L1 and the second negative meniscus lens L2 with respect to the d-line. By satisfying this conditional expression (14), it is possible to achieve both miniaturization and weight reduction of the optical system OL and good optical performance. If it is lower than the lower limit value of the conditional expression (14), it becomes impossible to correct the chromatic aberration generated in the first negative meniscus lens L1 and the second negative meniscus lens L2 using other lenses, so it is not preferred. In addition, in order to make the effect of the conditional expression (14) reliable, it is preferred to set the lower limit value of the conditional expression (14) to 31.5, 32.5, 34.0, and further to 34.5. Also, if it exceeds the upper limit value of the conditional expression (14), the Abbe numbers of the media of the first negative meniscus lens L1 and the second negative meniscus lens L2 become small, and it becomes difficult to correct field curvature and astigmatism, so it is not preferred. In addition, in order to make the effect of the conditional expression (14) reliable, it is preferred to set the upper limit value of the conditional expression (14) to 43.0, 41.5, 40.0, and further to 38.0.

[0067] In addition, the optical system OL of the present embodiment preferably has an aperture (aperture stop S) and a positive lens (for example, if it is Figure 1 , then a biconvex positive lens L4 and a biconvex positive lens L5) disposed adjacent to the object side or the image side of the aperture. By configuring in this way, it is possible to achieve both miniaturization and weight reduction of the optical system OL and good optical performance.

[0068] In addition, the optical system OL of the present embodiment preferably has an aperture (aperture stop S) and satisfies the following conditional expression (15).

[0069] -0.80 < f / fa < 0.10 (15) wherein fa: Focal length of the most object-side conjugate lens CLa among the conjugate lenses on the image side of the aperture (aperture stop S) f: Focal length of the entire system in the infinite focus state of the optical system OL

[0070] The conditional expression (15) defines the ratio of the focal length of the entire system in the infinite focus state to the focal length of the cemented lens CL a, which is the cemented lens closest to the object side among the cemented lenses on the image plane side of the aperture (aperture stop S). By satisfying this conditional expression (15), it is possible to achieve both miniaturization and weight reduction of the optical system OL and good optical performance. If it is lower than the lower limit value of the conditional expression (15), it becomes difficult to correct the axial chromatic aberration, so it is not preferred. In addition, in order to make the effect of the conditional expression (15) reliable, it is preferable to set the lower limit value of the conditional expression (15) to -0.75, -0.70, -0.65, and further to -0.60. Additionally, if it exceeds the upper limit value of the conditional expression (15), it becomes difficult to correct the spherical aberration, so it is not preferred. In addition, in order to make the effect of the conditional expression (15) reliable, it is preferable to set the upper limit value of the conditional expression (15) to 0.05, 0.01, -0.01, -0.05, -0.10, -0.15, -0.20, -0.25, and further to -0.28.

[0071] In addition, the optical system OL of the present embodiment preferably has an aperture (aperture stop S) and satisfies the following conditional expression (16).

[0072] -0.30 < f / fb < 0.30 (16) Wherein, fb: The focal length of the second cemented lens CL b from the object side among the cemented lenses on the image plane side of the aperture (aperture stop S) f: The focal length of the entire system in the infinite focus state of the optical system OL

[0073] The conditional expression (16) defines the ratio of the focal length of the entire system in the infinite focus state to the focal length of the second cemented lens CL b from the object side among the cemented lenses on the image plane side of the aperture (aperture stop S). By satisfying this conditional expression (16), it is possible to achieve both miniaturization and weight reduction of the optical system OL and good optical performance. If it is lower than the lower limit value of the conditional expression (16), it becomes difficult to correct the lateral chromatic aberration, so it is not preferred. In addition, in order to make the effect of the conditional expression (16) reliable, it is preferable to set the lower limit value of the conditional expression (16) to -0.25, -0.20, -0.15, and further to -0.10. Additionally, if it exceeds the upper limit value of the conditional expression (16), it becomes difficult to correct the coma and the field curvature, so it is not preferred. In addition, in order to make the effect of the conditional expression (16) reliable, it is preferable to set the upper limit value of the conditional expression (16) to 0.25, 0.20, 0.15, and further to 0.10.

[0074] Further, in the optical system OL of the present embodiment, preferably, at least one lens surface of the lens Ln disposed closest to the image plane side has an aspherical surface with a curvature reversal. Further, preferably, at least one lens surface of the lens Ln-1 disposed adjacent to the object side of the lens Ln disposed closest to the image plane side has an aspherical surface with a curvature reversal. By configuring in this way, it is possible to achieve both miniaturization and weight reduction of the optical system OL and good optical performance.

[0075] In addition, the conditions and structures described above each exhibit the above effects, and are not limited to satisfying all the conditions and structures. Even if any one condition or structure, or any combination of conditions or structures is satisfied, the above effects can be obtained.

[0076] Next, Figure 7 A camera as an optical device equipped with the optical system OL of the present embodiment will be described. This camera 1 is a so-called mirrorless camera with an interchangeable lens that has the optical system OL of the present embodiment as a photographic lens 2. In this camera 1, light from an object (subject) (not shown) is condensed by the photographic lens 2, and a subject image is formed on the imaging surface of the imaging unit 3 via an OLPF (Optical Low Pass Filter: optical low pass filter) (not shown). Then, the subject image is photoelectrically converted by a photoelectric conversion element (imaging element) provided on the imaging unit 3, and an image of the subject is generated. This image is displayed on an EVF (Electronic View Finder: electronic viewfinder) 4 provided on the camera 1. Thus, the photographer can observe the subject via the EVF 4.

[0077] Further, when the photographer presses a release button (not shown), the image obtained by the photoelectric conversion by the imaging unit 3 is stored in a memory (not shown). In this way, the photographer can photograph the subject using this camera 1. In addition, in the present embodiment, an example of a mirrorless camera has been described. However, even when the optical system OL of the present embodiment is mounted on a single-lens reflex camera that has a quick-return mirror on the camera body and observes the subject through an optical viewfinder system, the same effects as those of the above camera 1 can be achieved.

[0078] In addition, the following descriptions can be appropriately adopted within the range that does not impair the optical performance.

[0079] In the present embodiment, an optical system OL composed of 9 or 10 lens components is shown. However, the above structural conditions and the like can also be applied to a structure with 8 or fewer or 11 or more lens components. In addition, a lens component refers to a single lens or a cemented lens in which a plurality of lenses are cemented.

[0080] Alternatively, a single or multiple lens groups or partial lens groups can be used as a focusing group, which moves along the optical axis direction to focus from an infinitely distant object to a nearby object. In this case, the focusing group can also be applied to autofocus and is suitable for motor drive (such as an ultrasonic motor) for autofocus.

[0081] Alternatively, a lens group or a partial lens group can be used as an anti-shake group, which moves in a manner having a displacement component in a direction orthogonal to the optical axis or rotates (swings) in a plane direction including the optical axis to correct image blur caused by hand shake.

[0082] In addition, the lens surface can be formed by a spherical surface or a plane surface, or can be formed by an aspherical surface. When the lens surface is a spherical surface or a plane surface, lens processing and assembly adjustment become easy, and deterioration of optical performance caused by errors in processing and assembly adjustment can be prevented, so it is preferred. In addition, even when the image plane is deviated, the deterioration of description performance is small, so it is preferred. When the lens surface is an aspherical surface, the aspherical surface can be any one of an aspherical surface processed by grinding, a glass molded aspherical surface in which glass is molded into an aspherical shape, and a composite aspherical surface in which resin is formed into an aspherical shape on the surface of glass. In addition, the lens surface can be a diffractive surface, or the lens can be a refractive index distribution type lens (GRIN lens) or a plastic lens.

[0083] The aperture stop S is preferably arranged near the center in the optical axis direction of the optical system OL, but a member serving as an aperture stop may not be provided, and the function thereof can be replaced by the frame of the lens.

[0084] Furthermore, in order to reduce glare and ghost images and achieve high optical performance with high contrast, an anti-reflection film having a high transmittance in a wide wavelength region can be applied to each lens surface.

[0085] Hereinafter, with reference to Figure 8 The outline of the manufacturing method of the optical system OL of the present embodiment will be described. First, a first negative meniscus lens L1 with a convex surface facing the object side and having a negative optical power, a second negative meniscus lens L2 with a convex surface facing the object side and having a negative optical power, a third biconcave negative lens L3 with a negative optical power, and at least one lens are prepared in order from the object side (step S100). Then, the lenses are arranged to satisfy specified conditions (for example, in the case of the first embodiment, the above conditional expressions (1) and (2), and in the case of the second embodiment, conditional expressions (1) and (3), etc.) (step S200).

[0086] In summary, it is possible to provide an optical system, an optical device, and a manufacturing method of the optical system that achieve miniaturization, light weight, and good optical performance.

[0087] Examples

[0088] Hereinafter, each embodiment will be described based on the drawings. In addition, Figure 1 , Figure 3 and Figure 5 are cross-sectional views showing the structures of the optical systems OL (OL1 to OL3) of the respective embodiments. In addition, at the lower part of these cross-sectional views, the moving direction of the focusing group along the optical axis when focusing from an infinitely distant object (∞) to a close object is indicated by an arrow.

[0089] In each embodiment, when the height in the direction perpendicular to the optical axis is set to y, the distance along the optical axis (recess amount) from the tangent plane of each aspherical surface at the vertex of each aspherical surface to each aspherical surface is set to S(y), the radius of curvature of the reference spherical surface (paraxial radius of curvature) is set to r, the conic constant is set to K, and the aspherical coefficient of the nth order is set to An, the aspherical surface is represented by the following formula (a). In addition, in the following embodiments, "e-n" represents "×10 -n ".

[0090] S(y)=(y 2 / r) / {1+(1-K×y 2 / r 2 ) 1 / 2}+A4×y 4 +A6×y 6 +A8×y 8 +A10×y 10 +A12×y 12 (a)

[0091] In addition, in each embodiment, the aspherical coefficient A2 of the second order is 0. In addition, in the tables of each embodiment, an asterisk mark is added to the right of the surface number for the aspherical surface.

[0092] [First Embodiment]

[0093] Figure 1Shows the structure of the optical system OL1 of the first embodiment. The optical system OL1 is composed of, in order from the object side, a negative meniscus lens (first negative meniscus lens) L1 with a convex surface facing the object side, a negative meniscus lens (second negative meniscus lens) L2 with a convex surface facing the object side, a negative lens (third biconcave negative lens) L3 with an aspherical biconcave shape formed by the lens surface on the object side and the lens surface on the image side, a positive biconvex lens L4, a positive lens (fifth positive biconvex lens) L5 with an aspherical biconvex shape formed by the lens surface on the object side and the lens surface on the image side, a cemented negative lens CLa formed by cementing a positive biconvex lens L6 and a negative biconcave lens L7, a cemented negative lens CLb formed by cementing a positive meniscus lens L8 with a concave surface facing the object side and a negative meniscus lens L9 with a concave surface facing the object side, a positive meniscus lens L10 (Ln-1) with a convex surface facing the object side and an aspherical shape formed by the lens surface on the object side and the lens surface on the image side, and a positive biconvex lens L11 (Ln) with an aspherical biconvex shape formed by the lens surface on the object side and the lens surface on the image side. In addition, the lens surface on the object side and the lens surface on the image side of the positive lens L10 (Ln-1), and the lens surface on the object side and the lens surface on the image side of the positive lens L11 (Ln) are aspherical surfaces with curvature reversal.

[0094] In addition, the aperture stop S is disposed between the positive lens L4 and the positive lens L5. Further, an optical filter FL is disposed between the positive lens L11 (Ln) closest to the image side and the image plane I.

[0095] In addition, when the optical system OL1 focuses from an infinite object to a close object, the whole moves toward the object side.

[0096] In Table 1 below, the parameter values of the optical system OL1 are described. In this Table 1, f shown as the overall parameter is the focal length of the entire system, FNo is the F-number, ω is the semi-field angle [°], Ymax is the maximum image height, TL is the overall optical length, Bf is the back focal length, and the values represent those for infinity focus. Here, the back focal length Bf represents the air-equivalent length of the distance on the optical axis from the lens surface closest to the image plane (the 22nd surface) to the image plane I. In addition, the overall optical length TL represents the length obtained by adding the air-equivalent length of the distance on the optical axis from the lens surface closest to the object side (the 1st surface) to the lens surface closest to the image side (the 22nd surface) and the back focal length. In addition, in the lens data, the first column m represents the order (surface number) of the lens surfaces starting from the object side along the direction of light travel, the second column r represents the curvature radius of each lens surface, the third column d represents the distance on the optical axis from each optical surface to the next optical surface (surface interval), the fourth column nd and the fifth column νd represent the refractive index and Abbe number for the d-line (λ = 587.6 nm), and the sixth column ip represents the position of the inflection point. In addition, for an aspherical surface with a curvature reversal, regarding the position of the inflection point, the position where its curvature is reversed is represented as the height in the direction perpendicular to the optical axis. In addition, a curvature radius of ∞ represents a plane, and the refractive index of air 1.000000 is omitted.

[0097] Here, in all the following parameter values, the units of the focal length f, curvature radius r, surface interval d, and other lengths are generally "mm", but the optical system can obtain equivalent optical performance even if it is scaled up or down, so it is not limited to this. In addition, the explanations of these symbols and the parameter table are the same in the subsequent embodiments.

[0098] (Table 1) First Embodiment

[0099] [Overall Parameters]

[0100] [Lens Data]

[0101] In this optical system OL1, the 5th, 6th, 10th, 11th, 18th, 19th, 20th, and 21st surfaces are formed in an aspherical shape. In the following Table 2, the aspherical data, that is, the conic constant K and the values of each aspherical constant A4 to A12 are shown.

[0102] (Table 2)

[0103] [Aspherical Data]

[0104] In Figure 2 The spherical aberration diagram, astigmatism diagram, and coma diagram of the optical system OL1 at infinity focus are shown. In each aberration diagram, FNo represents the F-number, and A represents the semi-field angle. In addition, in the spherical aberration diagram, the value of the F-number corresponding to the maximum aperture is shown, in the astigmatism diagram, the maximum value of the semi-field angle is shown, and in the coma diagram, the values of each semi-field angle are shown. d represents the d-line (λ = 587.6 nm), and g represents the g-line (λ = 435.8 nm). In addition, in the astigmatism diagram, the solid line represents the sagittal image plane, and the dashed line represents the meridional image plane. In addition, the same symbols as in this embodiment are also used in the aberration diagrams of the respective embodiments shown later. From these respective aberration diagrams, it can be seen that the optical system OL1 corrects each aberration well and has excellent imaging performance.

[0105] [Second Embodiment]

[0106] Figure 3 The structure of the optical system OL2 of the second embodiment is shown. The optical system OL2 is composed, in order from the object side, of a negative meniscus lens (first negative meniscus lens) L1 with a convex surface facing the object side, a negative meniscus lens (second negative meniscus lens) L2 with a convex surface facing the object side, a negative lens (third biconcave negative lens) L3 with an aspherical surface formed on the lens surface on the image side and having a biconcave shape, a biconvex positive lens L4, a biconvex positive lens L5 with an aspherical shape formed on the lens surface on the object side and the lens surface on the image side, a cemented negative lens CLa formed by cementing a biconvex positive lens L6 and a biconcave negative lens L7, a cemented positive lens CLb formed by cementing a biconvex positive lens L8 and a negative meniscus lens L9 with a concave surface facing the object side, a biconvex positive lens L10 (Ln-1) with an aspherical shape formed on the lens surface on the object side and the lens surface on the image side, and a positive meniscus lens L11 (Ln) with a convex surface facing the object side and an aspherical shape formed on the lens surface on the object side and the lens surface on the image side. In addition, the negative lens L3 is a composite lens with an aspherical surface formed by providing a resin layer on the lens surface on the image side of a glass lens body. In addition, the lens surface on the image side of the positive lens L10 (Ln-1), and the lens surface on the object side and the lens surface on the image side of the positive lens L11 (Ln) are aspherical surfaces with curvature reversal.

[0107] In addition, the aperture stop S is disposed between the positive lens L4 and the positive lens L5. In addition, an optical filter FL is disposed between the positive lens L11 (Ln) closest to the image side and the image plane I.

[0108] In addition, when the optical system OL1 focuses from an infinite object to a close object, the negative lens L2, the negative lens L3, and the positive lens L4 move toward the object side.

[0109] In Table 3 below, the parameter values of the optical system OL2 are described.

[0110] (Table 3) Second Embodiment

[0111] [Overall Parameters]

[0112] [Lens Data]

[0113] In this optical system OL2, the 7th, 11th, 12th, 19th, 20th, 21st, and 22nd surfaces are formed into aspherical shapes. In the following Table 4, the aspherical data, that is, the conic constant K and the values of the respective aspherical constants A4 to A12 are shown.

[0114] (Table 4)

[0115] [Aspherical Data]

[0116] In Figure 4 the spherical aberration diagram, astigmatism diagram, and coma diagram of the optical system OL2 at infinity focus are shown. From these respective aberration diagrams, it can be seen that the optical system OL2 corrects each aberration well and has excellent imaging performance.

[0117] [Third Embodiment]

[0118] Figure 5Shows the structure of the optical system OL3 of the third embodiment. The optical system OL3 includes, from the object side in sequence, a meniscus-shaped negative lens (first negative meniscus lens) L1 with a convex surface facing the object side, a meniscus-shaped negative lens (second negative meniscus lens) L2 with a convex surface facing the object side, a double-concave negative lens (third double-concave negative lens) L3, a double-convex positive lens L4, a positive lens L5 with a convex surface facing the object side and an aspherical shape on both the object-side lens surface and the image-side lens surface, a double-convex positive lens L6, a cemented negative lens CLa formed by cementing a double-convex positive lens L7 and a double-concave negative lens L8, a cemented negative lens CLb formed by cementing a double-convex positive lens L9 and a meniscus-shaped negative lens L10 with a concave surface facing the object side, a double-convex positive lens L11 (Ln - 1) with an aspherical shape on both the object-side lens surface and the image-side lens surface, and a double-convex positive lens L12 (Ln) with an aspherical shape on both the object-side lens surface and the image-side lens surface. In addition, the object-side lens surface of the positive lens L11 (Ln - 1), and the object-side lens surface and the image-side lens surface of the positive lens L12 (Ln) are aspherical surfaces with curvature reversal.

[0119] In addition, the aperture stop S is disposed between the positive lens L5 and the positive lens L6. Further, an optical filter FL is disposed between the positive lens L12 (Ln) closest to the image plane and the image plane I.

[0120] In addition, when the optical system OL3 focuses from an infinitely distant object to a nearby object, the negative lens L3 and the positive lens L4 move toward the image plane side.

[0121] In Table 5 below, the parameter values of the optical system OL3 are listed.

[0122] (Table 5) Third Embodiment

[0123] [Overall Parameters]

[0124] [Lens Data]

[0125] In this optical system OL3, the 9th, 10th, 20th, 21st, 22nd, and 23rd surfaces are formed as aspherical surfaces. In the following Table 6, the aspherical data, namely the conic constant K and the values of the aspherical constants A4 to A12, are shown.

[0126] (Table 6)

[0127] [Aspherical Data]

[0128] Shown are the spherical aberration diagram, astigmatism diagram, and coma diagram of the optical system OL3 at infinity focus. From these aberration diagrams, it can be seen that the optical system OL3 corrects various aberrations well and has excellent imaging performance. Figure 6

[0129] [Conditional formula corresponding values]

[0130] Shown in Table 7 below are the corresponding values of conditional formulas (1) to (16) in the first to third embodiments.

[0131] (Table 7) (1) ω (2) R12 / (-fL1) (3) R12 / D12 (4) φ12 / R12 (5) φ22 / R22 (6) R12 / DL1 (7) (R12 + R11) / (R12 - R11) (8) R22 / (-fL2) (9) R22 / DL2 (10) (R22 + R21) / (R22 - R21) (11) R22 / D23 (12) TL / Ymax (13) (nd1 + nd2) / 2 (14) (νd1 + νd2) / 2 (15) f / fa (16) f / fb

[0132] Reference numeral description 1 Camera (optical device) OL (OL1 to OL3) Optical system L1 First negative meniscus lens L2 Second negative meniscus lens L3 Third double concave negative lens S Aperture stop (iris)​

Claims

1. An optical system, wherein, the optical system is composed of, in order from the object side, a first negative meniscus lens with its convex surface facing the object side and having a negative focal power, a second negative meniscus lens with its convex surface facing the object side and having a negative focal power, a third biconcave negative lens with a negative focal power, and at least one lens; the optical system satisfies the conditions of the following formula: 90.0° < ω 0.10 < R12 / (-fL1) < 0.80 wherein, ω: the half field angle of the optical system; fL1: the focal length of the first negative meniscus lens; R12: the radius of curvature of the lens surface on the image side of the first negative meniscus lens.

2. An optical system, wherein, the optical system is composed of, in order from the object side, a first negative meniscus lens with its convex surface facing the object side and having a negative focal power, a second negative meniscus lens with its convex surface facing the object side and having a negative focal power, a third biconcave negative lens with a negative focal power, and at least one lens; the optical system satisfies the conditions of the following formula: 90.0° < ω 1.80 < R12 / D12 < 3.00 wherein, ω: the half field angle of the optical system; D12: the axial air interval between the first negative meniscus lens and the second negative meniscus lens; R12: the radius of curvature of the lens surface on the image side of the first negative meniscus lens.

3. The optical system according to claim 1 or 2, wherein, the optical system satisfies the conditions of the following formula: φ12 / R12 < 1.90 wherein, R12: the radius of curvature of the lens surface on the image side of the first negative meniscus lens; φ12: the effective diameter of the lens surface on the image side of the first negative meniscus lens.

4. The optical system according to any one of claims 1 to 3, wherein, the optical system satisfies the conditions of the following formula: φ22 / R22 < 1.90 wherein, R22: the radius of curvature of the lens surface on the image side of the second negative meniscus lens; φ22: the effective diameter of the lens surface on the image side of the second negative meniscus lens.

5. The optical system according to any one of claims 1 to 4, wherein, the optical system satisfies the conditions of the following formula: 7.50 < R12 / DL1 < 11.00 wherein, DL1: the thickness on the optical axis of the first negative meniscus lens; R12: the radius of curvature of the lens surface on the image side of the first negative meniscus lens.

6. The optical system according to any one of claims 1 to 5, wherein, the optical system satisfies the conditions of the following formula: -3.50 < (R12 + R11) / (R12 - R11) < -2.00 wherein, R11: the radius of curvature of the lens surface on the object side of the first negative meniscus lens; R12: the radius of curvature of the lens surface on the image side of the first negative meniscus lens.

7. The optical system according to any one of claims 1 to 6, wherein, the optical system satisfies the conditions of the following formula: 0.20 < R22 / (-fL2) < 0.80 wherein, fL2: the focal length of the second negative meniscus lens; R22: the radius of curvature of the lens surface on the image side of the second negative meniscus lens.

8. The optical system according to any one of claims 1 to 7, wherein the optical system satisfies the condition of the following formula: 6.50 < R22 / DL2 < 12.00 wherein DL2: the thickness on the optical axis of the second negative meniscus lens, R22: the radius of curvature of the lens surface on the image side of the second negative meniscus lens.

9. The optical system according to any one of claims 1 to 8, wherein the optical system satisfies the condition of the following formula: -2.50 < (R22 + R21) / (R22 - R21) < -1.00 wherein R21: the radius of curvature of the lens surface on the object side of the second negative meniscus lens, R22: the radius of curvature of the lens surface on the image side of the second negative meniscus lens.

10. The optical system according to any one of claims 1 to 9, wherein the optical system satisfies the condition of the following formula: 0.80 < R22 / D23 < 2.00 wherein D23: the axial air gap between the second negative meniscus lens and the third biconcave negative lens, R22: the radius of curvature of the lens surface on the image side of the second negative meniscus lens.

11. The optical system according to any one of claims 1 to 10, wherein the optical system satisfies the condition of the following formula: 2.00 < TL / Ymax < 5.00 wherein Ymax: the maximum image height of the optical system, TL: the overall optical length of the optical system in the infinity focus state.

12. The optical system according to any one of claims 1 to 11, wherein the optical system satisfies the condition of the following formula: 1.75 < (nd1 + nd2) / 2 < 1.95 wherein nd1: the refractive index of the medium of the first negative meniscus lens for the d line, nd2: the refractive index of the medium of the second negative meniscus lens for the d line.

13. The optical system according to any one of claims 1 to 12, wherein the optical system satisfies the condition of the following formula: 30.0 < (νd1 + νd2) / 2 < 45.0 wherein νd1: the Abbe number of the medium of the first negative meniscus lens for the d line, νd2: the Abbe number of the medium of the second negative meniscus lens for the d line.

14. The optical system according to any one of claims 1 to 13, wherein the optical system has an aperture and a positive lens disposed adjacent to the object side or the image side of the aperture.

15. The optical system according to any one of claims 1 to 14, wherein the optical system has an aperture, the optical system satisfies the condition of the following formula: -0.80 < f / fa < 0.10 wherein fa: the focal length of the cemented lens disposed closest to the object side among the cemented lenses closer to the image side than the aperture, f: the focal length of the entire system of the optical system in the infinity focus state.

16. The optical system according to any one of claims 1 to 15, wherein the optical system has an aperture, the optical system satisfies the condition of the following formula: -0.30 < f / fb < 0.30 wherein fb: The focal length of the second cemented lens counted from the object side among the cemented lenses closer to the image plane than the aperture stop. f: The focal length of the entire optical system in the infinity focus state of the optical system.

17. An optical device comprising the optical system according to any one of claims 1 to 16.

18. A method for manufacturing an optical system, the optical system comprising, in order from the object side, a first negative meniscus lens with a convex surface facing the object side and having a negative optical power, a second negative meniscus lens with a convex surface facing the object side and having a negative optical power, a third biconcave negative lens having a negative optical power, and at least one lens, wherein It is configured to satisfy the conditions of the following formula: 90.0° < ω 0.10 < R12 / (-fL1) < 0.80 wherein ω: The half field angle of the optical system, fL1: The focal length of the first negative meniscus lens, R12: The radius of curvature of the lens surface on the image plane side of the first negative meniscus lens.

19. A method for manufacturing an optical system, the optical system comprising, in order from the object side, a first negative meniscus lens with a convex surface facing the object side and having a negative optical power, a second negative meniscus lens with a convex surface facing the object side and having a negative optical power, a third biconcave negative lens having a negative optical power, and at least one lens, wherein It is configured to satisfy the conditions of the following formula: 90.0° < ω 1.80 < R12 / D12 < 3.00 wherein ω: The half field angle of the optical system, D12: The axial air gap between the first negative meniscus lens and the second negative meniscus lens, R12: The radius of curvature of the lens surface on the image plane side of the first negative meniscus lens.

Images