Large-aperture-ratio ultra-wide-angle lens

Abstract

Provided is a large-aperture-ratio ultra-wide-angle lens having a half angle of view of 80 degrees or more and an F value of about 1.8 or less while achieving miniaturization and weight reduction, the lens being bright, and having good optical performance from the center to the periphery of a screen while ensuring a sufficient image circle. A large aperture ratio ultra wide angle lens according to the present invention comprises, in order from an object side, a first lens group (G1), an aperture stop (S), and a second lens group (G2), the first lens group (G1) being provided with a concave meniscus lens component (N1) having a convex surface facing the object side at a position closest to the object side; the first lens group (G1) has a concave meniscus lens component (N2) having a convex surface facing the object side at a position closer to the image side than the concave meniscus lens component (N1), and satisfies a predetermined conditional expression.

Description

Technical Field

[0001] The present invention relates to a large aperture ratio ultra-wide angle lens, which is used in imaging devices such as digital cameras and video cameras, and is suitable for photographic optical systems. Background Art

[0002] In recent years, while the mirrorless development of digital cameras, video cameras, etc. has advanced, high-performance cameras are mounted on smartphones or mobile data terminals. Therefore, in order for digital cameras to differentiate themselves from these mobile devices, models equipped with large sensors of 35mm full-size format or more have gradually become mainstream. Similarly, even in photographic optical systems for imaging devices, in order to differentiate themselves from smartphones, etc., the demand for large aperture ratio ultra-wide angle lenses with bright F values is increasing.

[0003] Moreover, in recent years, the high pixelization of imaging elements in digital cameras or video cameras has further advanced, and the demand for high performance of photographic optical systems has further increased.

[0004] Examples of large aperture ratio ultra-wide angle lenses with a maximum field of view angle of approximately 160 degrees or more and an F value of around 1.8 or less are described in Patent Document 1 and Patent Document 2.

[0005] Patent Document 1: Japanese Patent No. 4633379 Patent Document 2: Japanese Unexamined Patent Application Publication No. 2013-238684

[0006] Ultra-wide angle lenses with a maximum field of view angle of approximately 160 degrees or more mostly adopt an inverse telephoto lens structure, and mostly adopt a structure in which a concave meniscus lens with a convex surface facing the object side is arranged at the position closest to the object side. In such an optical system, the concave meniscus lens arranged at the position closest to the object side mostly has a large wall thickness deviation ratio and a concave surface close to a hemisphere, and sometimes reaches more than 50% of the total lens weight of the entire optical system. If the F value is reduced, the lens diameter becomes larger, and the weight of the optical system increases rapidly. When achieving a large aperture ratio, it is very important to be able to achieve high performance while preventing lens enlargement.

[0007] Patent Document 1 includes an embodiment of a bright large aperture ratio ultra-wide angle lens with a maximum field of view angle of 160 degrees or more and an F value of 1.6 or less. Although the large aperture ratio ultra-wide angle lens described in Patent Document 1 has high optical performance, its image circle is small. From the viewpoint of the size of the optical system relative to the image circle, it is a very large optical system, and there are problems in miniaturization.

[0008] In Patent Document 2, there is an embodiment of a bright large aperture ratio ultra-wide angle lens with an F value of about 1.8, but it is insufficient in terms of large magnification chromatic aberration from a low image height to high performance. Also, due to the long back focal length, it is an optical system that does not utilize the advantage of the short flange distance brought about by the recent mirrorless trend, and there is room for improvement in terms of miniaturization of the optical system. Summary of the Invention

[0009] The present invention has been completed in view of the above problems, and its object is to provide a large aperture ratio ultra-wide angle lens that is miniaturized and lightweight, has a half field angle of 80 degrees or more, is bright with an F value of about 1.8 or less, ensures a sufficient image circle, and has good optical performance from the center to the periphery of the image.

[0010] The large aperture ratio ultra-wide angle lens according to the present invention is characterized in that it is composed of a first lens group G1, an aperture stop S, and a second lens group G2 arranged in order from the object side. The first lens group G1 is provided with a concave meniscus lens component N1 with a convex surface facing the object side at the position closest to the object side, and the first lens group G1 has a concave meniscus lens component N2 with a convex surface facing the object side at a position closer to the image side than the concave meniscus lens component N1, and satisfies the following conditional expressions (1) to (4). (1) 2ω≥160.0° (2) Fno<1.9 (3) -6.0<N1OAh / iOAh<-1.1 (4) 0.50<SagN1 / SagN2<1.80 ω: Half field angle at infinity focus Fno: F value at infinity focus N1OAh: Off-axis principal ray height when a ray with an object-side incident angle of 90° is incident on the concave meniscus lens component N1 at infinity focus (where, in the case of 2ω<180°, it is the off-axis principal ray height with an object-side incident angle of ω) iOAh: Imaging height of the off-axis principal ray when a ray with an object-side incident angle of 90° forms an image on the image plane at infinity focus (where, in the case of 2ω<180°, it is the imaging height of the off-axis principal ray with an object-side incident angle of ω) SagN1: Depression amount of the concave meniscus lens component N1 with respect to the surface vertex on the image side (when calculating the depression amount, the ray height used is the off-axis principal ray height when a ray with an object-side incident angle of 90° exits from this surface at infinity focus. And, in the case of 2ω<180°, it is calculated using the off-axis principal ray height with an object-side incident angle of ω) SagN2: The amount of depression of the concave meniscus lens component N2 with respect to the surface vertex on the image side (when calculating the depression amount, the ray height used is the off-axis chief ray height when a ray with an object-side incident angle of 90° exits from this surface at infinite focus. Also, in the case where 2ω < 180°, the off-axis chief ray height calculated using the off-axis chief ray incident at the object-side incident angle ω is used). Advantages of the Invention

[0011] According to the present invention, a large aperture ratio ultra-wide angle lens can be provided, which while achieving miniaturization and light weight, has a half field angle of more than 80 degrees, an F value of about 1.8 or less and is bright, while ensuring a sufficient image circle, has good optical performance from the center to the periphery of the image plane. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The distortion aberration amount is illustrated in the longitudinal aberration diagrams at infinite focus in each embodiment. However, in any of Embodiments 1 to 14, the ideal image height is also defined according to the defining formula of the equal solid angle projection, and the distortion aberration is calculated. And the lateral aberration diagrams show the aberration diagrams when rays with 0%, 3%, 5%, 7%, 9%, and 10% of the maximum field angle are incident respectively. In addition, the object distance described below refers to the distance from the subject to the first surface closest to the object side of the lens. Figure 1 It is a lens structure diagram at infinite focus related to Embodiment 1 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 2 It is a longitudinal aberration diagram at infinite focus related to Embodiment 1 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 3 It is a lateral aberration diagram at infinite focus related to Embodiment 1 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 4 It is a longitudinal aberration diagram at a focus with an object distance of 222.34 mm related to Embodiment 1 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 5 It is a lateral aberration diagram at a focus with an object distance of 222.34 mm related to Embodiment 1 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 6 It is a lens structure diagram at infinite focus related to Embodiment 2 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 7 It is a longitudinal aberration diagram at infinite focus related to Embodiment 2 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 8 It is a lateral aberration diagram at infinite focus related to Embodiment 2 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 9 It is the longitudinal aberration diagram when focusing on an object at a distance of 220.20 mm in Embodiment 2 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 10 It is the lateral aberration diagram when focusing on an object at a distance of 220.20 mm in Embodiment 2 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 11 It is the lens structure diagram when focusing at infinity in Embodiment 3 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 12 It is the longitudinal aberration diagram when focusing at infinity in Embodiment 3 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 13 It is the lateral aberration diagram when focusing at infinity in Embodiment 3 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 14 It is the longitudinal aberration diagram when focusing on an object at a distance of 435.25 mm in Embodiment 3 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 15 It is the lateral aberration diagram when focusing on an object at a distance of 435.25 mm in Embodiment 3 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 16 It is the lens structure diagram when focusing at infinity in Embodiment 4 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 17 It is the longitudinal aberration diagram when focusing at infinity in Embodiment 4 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 18 It is the lateral aberration diagram when focusing at infinity in Embodiment 4 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 19 It is the longitudinal aberration diagram when focusing on an object at a distance of 220.00 mm in Embodiment 4 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 20 It is the lateral aberration diagram when focusing on an object at a distance of 220.00 mm in Embodiment 4 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 21 It is the lens structure diagram when focusing at infinity in Embodiment 5 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 22 It is the longitudinal aberration diagram when focusing at infinity in Embodiment 5 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 23 It is the lateral aberration diagram when focusing at infinity in Embodiment 5 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 24It is the longitudinal aberration diagram when focusing on an object at a distance of 219.02 mm in Embodiment 5 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 25 It is the lateral aberration diagram when focusing on an object at a distance of 219.02 mm in Embodiment 5 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 26 It is the lens structure diagram when focusing at infinity in Embodiment 6 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 27 It is the longitudinal aberration diagram when focusing at infinity in Embodiment 6 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 28 It is the lateral aberration diagram when focusing at infinity in Embodiment 6 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 29 It is the longitudinal aberration diagram when focusing on an object at a distance of 424.41 mm in Embodiment 6 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 30 It is the lateral aberration diagram when focusing on an object at a distance of 424.41 mm in Embodiment 6 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 31 It is the lens structure diagram when focusing at infinity in Embodiment 7 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 32 It is the longitudinal aberration diagram when focusing at infinity in Embodiment 7 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 33 It is the lateral aberration diagram when focusing at infinity in Embodiment 7 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 34 It is the longitudinal aberration diagram when focusing on an object at a distance of 207.23 mm in Embodiment 7 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 35 It is the lateral aberration diagram when focusing on an object at a distance of 207.23 mm in Embodiment 7 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 36 It is the lens structure diagram when focusing at infinity in Embodiment 8 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 37 It is the longitudinal aberration diagram when focusing at infinity in Embodiment 8 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 38 It is the lateral aberration diagram when focusing at infinity in Embodiment 8 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 39It is the longitudinal aberration diagram when focusing on an object at a distance of 435.59 mm in Embodiment 8 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 40 It is the lateral aberration diagram when focusing on an object at a distance of 435.59 mm in Embodiment 8 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 41 It is the lens structure diagram when focusing at infinity in Embodiment 9 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 42 It is the longitudinal aberration diagram when focusing at infinity in Embodiment 9 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 43 It is the lateral aberration diagram when focusing at infinity in Embodiment 9 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 44 It is the longitudinal aberration diagram when focusing on an object at a distance of 432.91 mm in Embodiment 9 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 45 It is the lateral aberration diagram when focusing on an object at a distance of 432.91 mm in Embodiment 9 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 46 It is the lens structure diagram when focusing at infinity in Embodiment 10 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 47 It is the longitudinal aberration diagram when focusing at infinity in Embodiment 10 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 48 It is the lateral aberration diagram when focusing at infinity in Embodiment 10 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 49 It is the longitudinal aberration diagram when focusing on an object at a distance of 224.26 mm in Embodiment 10 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 50 It is the lateral aberration diagram when focusing on an object at a distance of 224.26 mm in Embodiment 10 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 51 It is the lens structure diagram when focusing at infinity in Embodiment 11 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 52 It is the longitudinal aberration diagram when focusing at infinity in Embodiment 11 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 53 It is the lateral aberration diagram when focusing at infinity in Embodiment 11 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 54It is the longitudinal aberration diagram when focusing on an object at a distance of 205.25 mm in Embodiment 11 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 55 It is the lateral aberration diagram when focusing on an object at a distance of 205.25 mm in Embodiment 11 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 56 It is the lens structure diagram when focusing at infinity in Embodiment 12 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 57 It is the longitudinal aberration diagram when focusing at infinity in Embodiment 12 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 58 It is the lateral aberration diagram when focusing at infinity in Embodiment 12 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 59 It is the longitudinal aberration diagram when focusing on an object at a distance of 437.67 mm in Embodiment 12 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 60 It is the lateral aberration diagram when focusing on an object at a distance of 437.67 mm in Embodiment 12 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 61 It is the lens structure diagram when focusing at infinity in Embodiment 13 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 62 It is the longitudinal aberration diagram when focusing at infinity in Embodiment 13 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 63 It is the lateral aberration diagram when focusing at infinity in Embodiment 13 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 64 It is the longitudinal aberration diagram when focusing on an object at a distance of 225.06 mm in Embodiment 13 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 65 It is the lateral aberration diagram when focusing on an object at a distance of 225.06 mm in Embodiment 13 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 66 It is the lens structure diagram when focusing at infinity in Embodiment 14 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 67 It is the longitudinal aberration diagram when focusing at infinity in Embodiment 14 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 68 It is the lateral aberration diagram when focusing at infinity in Embodiment 14 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 69It is the longitudinal aberration diagram when focusing on an object distance of 443.32 mm in Embodiment 14 of the large aperture ratio ultra-wide angle lens of the present invention. Figure 70 It is the lateral aberration diagram when focusing on an object distance of 443.32 mm in Embodiment 14 of the large aperture ratio ultra-wide angle lens of the present invention. Detailed implementation manners

[0013] The lens components defined in the present invention refer to single lenses or cemented lenses formed by joining multiple single lenses. Thus, a concave meniscus lens component refers to a concave meniscus lens composed of a single lens, or a cemented lens in which multiple single lenses are joined and the whole has a negative refractive power and has a concave meniscus shape.

[0014] Moreover, in the present invention, the meniscus shape of the lens shape is defined as the surfaces on the object side and the image side being composed of curved surfaces with the same-sign radius of curvature. For example, a concave meniscus lens with a convex surface facing the object side refers to a lens in which the radii of curvature of the surfaces on the object side and the image side are both positive, and the radius of curvature of the surface on the image side is small. In addition, in the case of an aspherical lens, the lens shape is judged based on the paraxial radius of curvature.

[0015] Moreover, in the present invention, when counting the number of lenses, unless otherwise specified, a single lens is counted as one piece, and in the case of a cemented lens, each single lens constituting the cemented lens is counted as one piece. For example, if it is a cemented lens composed of a convex lens and a concave lens, it is counted as two pieces.

[0016] Moreover, in the present invention, when counting the lens components, both the lens component composed of a single lens and the lens component composed of a cemented lens are counted as one. For example, a lens component composed of a single lens is counted as one lens component, and a cemented lens composed of one convex lens and one concave lens is counted as one lens component.

[0017] It can also be seen from the numerical value embodiments or the lens structure diagrams of the embodiments that the large aperture ratio ultra-wide angle lens of the present invention is configured to be composed of a first lens group G1, an aperture stop S, and a second lens group G2 arranged in sequence from the object side. At the position closest to the object side of the first lens group G1, a concave meniscus lens component N1 with a convex surface facing the object side is arranged, and at a position closer to the image side than the concave meniscus lens component N1, there is a concave meniscus lens component N2 with a negative refractive power stronger than that of the concave meniscus lens component N1 and a convex surface facing the object side.

[0018] The large-aperture ratio ultra-wide-angle lens of the present invention is an ultra-wide-angle lens with a total field angle 2ω of more than 160°. Generally, in an ultra-wide-angle lens with a total field angle 2ω of more than 160°, an inverse telephoto lens structure is often adopted. In most cases, a concave meniscus lens is arranged at the position closest to the object side. The concave meniscus lens has its convex surface facing the object side. The radius of curvature of the image-side surface is significantly smaller than that of the object-side surface, and it has a concave surface close to a hemisphere with a large wall thickness deviation ratio. The concave meniscus lens as described above has the effect of significantly bending the off-axis light incident from the object side and reducing the light height of the off-axis light. Moreover, lenses with a field angle of 2ω of more than 160° are mostly fish-eye lenses. However, compared with general wide-angle lenses, there is a tendency for the wall thickness deviation ratio of the concave meniscus lens closest to the object side in fish-eye lenses to be larger. This is because in the case of a fish-eye lens, since negative distortion does not need to be corrected (the meaning of distortion here is defined by central projection for the ideal image height), even if the radius of curvature of the image-side surface is significantly reduced relative to the object side to enhance negative refractive power, there are fewer drawbacks, and the optical system can be miniaturized.

[0019] The large-aperture ratio ultra-wide-angle lens of the present invention is a very bright optical system as an ultra-wide-angle lens with an F number less than 1.9 and a total field angle 2ω of more than 160°. In such an optical system, the concave meniscus lens arranged at the position closest to the object side sometimes accounts for more than 50% of the total lens weight of the entire optical system. It becomes very important to achieve high performance while preventing the lens from becoming large.

[0020] It is expected that in the large-aperture ratio ultra-wide-angle lens of the present invention, in order to achieve high performance while suppressing the enlargement of the optical system, the following conditional expressions (1) to (4) are satisfied. (1) 2ω≥160° (2) Fno<1.9 (3) -6.0<N1OAh / iOAh<-1.1 (4) 0.50<SagN1 / SagN2<1.80 ω: Half field angle at infinity focus Fno: F number at infinity focus N1OAh: Off-axis principal ray height when light with an object-side incident angle of 90° is incident on the concave meniscus lens component N1 at infinity focus (where, in the case of 2ω<180°, it is the off-axis principal ray height with an object-side incident angle of ω) iOAh: Imaging height of the off-axis principal ray when light with an object-side incident angle of 90° forms an image on the image plane at infinity focus (where, in the case of 2ω<180°, it is the off-axis principal ray height with an object-side incident angle of ω) SagN1: The amount of depression of the concave meniscus lens component N1 with respect to the vertex of the surface on the image side (When calculating the amount of depression, the ray height is the off-axis chief ray height when a ray with an object-side incident angle of 90° exits from this surface during infinite focus. Also, in the case where 2ω < 180°, it is calculated using the off-axis chief ray height of a ray incident at the object-side incident angle ω). SagN2: The amount of depression of the concave meniscus lens component (N2) with respect to the vertex of the surface on the image side (When calculating the amount of depression, the ray height is the off-axis chief ray height when a ray with an object-side incident angle of 90° exits from this surface during infinite focus. Also, in the case where 2ω < 180°, it is calculated using the off-axis chief ray height of a ray incident at the object-side incident angle ω). In the case where the total field angle is 180° or more (2ω ≥ 180°), the off-axis chief ray height and the imaging height of the off-axis chief ray are defined using a ray with an object-side incident angle of 90°. For example, the embodiments describe optical systems with 2ω around 185° to 202°, but since they are all 2ω ≥ 180° (ω ≥ 90°), the off-axis chief ray height and the imaging height of the off-axis chief ray are defined using a ray with an object-side incident angle of 90°. In the case where 2ω < 180°, ω < 90°, a ray with an object-side incident angle of 90° will not be incident, and the off-axis chief ray height and the imaging height of the off-axis chief ray cannot be defined using a ray with an object-side incident angle of 90°. Therefore, in the case where 2ω < 180° (ω < 90°), the off-axis chief ray height and the imaging height of the off-axis chief ray are defined using the ray incident from the outermost end. For example, in the case where 2ω = 160°, ω = 80°, so the off-axis chief ray height and the imaging height of the off-axis chief ray are defined using a ray with an object-side incident angle of 80°.

[0021] Conditional expressions (1) and (2) respectively specify the total field angle and the F value during infinite focus of the large-aperture ratio ultra-wide-angle lens targeted by the present invention. By satisfying conditional expression (1), a sufficient field angle can be obtained during infinite focus of the large-aperture ratio ultra-wide-angle lens. Also, by satisfying conditional expression (2), a sufficient F value can be obtained during infinite focus of the large-aperture ratio ultra-wide-angle lens.

[0022] In addition, it is expected that the lower limit value of conditional expression (1) is set to 180°, and the upper limit value of conditional expression (2) is set to 1.6.

[0023] Conditional expression (3) stipulates the preferred range of the ratio of the off-axis chief ray height when a ray with an object-side incident angle of 90° is incident on the concave meniscus lens component N1 during infinity focusing (wherein, when 2ω < 180°, it is the off-axis chief ray height incident with an object-side incident angle of ω) to the imaging height of the off-axis chief ray when a ray with an object-side incident angle of 90° forms an image on the image plane (wherein, when 2ω < 180°, it is the imaging height of the off-axis chief ray incident with an object-side incident angle of ω). Additionally, since the values of N1OAh and iOAh are related to the ray height of the off-axis chief ray, a positive-negative relationship is generated. Specifically, the sign of the off-axis chief ray height is opposite before and after the aperture stop, so N1OAh and iOAh are always of different signs.

[0024] If it exceeds the upper limit of conditional expression (3) and the ratio of the off-axis chief ray height when a ray with an object-side incident angle of 90° is incident on the concave meniscus lens component N1 during infinity focusing to the imaging height of the off-axis chief ray when a ray with an object-side incident angle of 90° forms an image on the image plane approaches 0 and becomes larger, the diameter of the concave meniscus lens component N1 relative to the imaging height becomes too small, and it is necessary to further enhance the negative refractive power of the concave meniscus lens component N1, resulting in deterioration of the coma aberration or field curvature, so it is not preferred.

[0025] If it exceeds the lower limit of conditional expression (3) and N1OAh becomes smaller relative to iOAh, and the ratio of the off-axis chief ray height when a ray with an object-side incident angle of 90° is incident on the concave meniscus lens component N1 during infinity focusing to the imaging height of the off-axis chief ray when a ray with an object-side incident angle of 90° forms an image on the image plane moves away from 0 and becomes smaller, the diameter of the concave meniscus lens component N1 relative to the imaging height becomes too large, leading to enlargement of the optical system, so it is not preferred.

[0026] Additionally, regarding conditional expression (3), it is expected to stipulate the upper limit value as -1.2 and the lower limit value as -4.1, and further expected to stipulate the lower limit value as -3.5, whereby the aforementioned effects can be made more reliable.

[0027] The conditional expression (4) stipulates the ratio of the amount of indentation of the image-side surfaces of the concave meniscus lens component N1 and the concave meniscus lens component N2 (when calculating the amount of indentation, the off-axis chief ray height when a ray with an object-side incident angle of 90° exits from this surface is used for the ray height. And, in the case where 2ω < 180°, the off-axis chief ray height incident at the object-side incident angle ω is used for calculation). As described above, in an ultra-wide-angle lens with a total field angle 2ω of 160° or more, generally, a concave meniscus lens is disposed at the position closest to the object side, with the convex surface facing the object side. The radius of curvature of the image-side surface is significantly smaller than that of the object-side surface, and the amount of indentation of the image-side surface is large. In particular, in a fish-eye lens, most examples adopt a shape where the image-side surface is close to a hemisphere. However, it is difficult to improve the processing accuracy of such a concave surface with a large curvature and a large amount of indentation. Also, in the case of using a general interferometer as a means for measuring the surface accuracy of a lens, the larger the curvature, the smaller the measurable diameter. In the case of a concave surface close to a hemisphere, in most cases, it is also difficult to measure the peripheral part with an interferometer. In the case of a bright optical system with an F-number lower than 1.9 as in the present invention, since the depth of focus becomes shallow, it is required to process the optical element with high precision. The radius of curvature and the amount of indentation of the image-side surfaces of the concave meniscus component N1 and the concave meniscus component N2 need to fully consider the processability or the measurement accuracy.

[0028] If it exceeds the upper limit of the conditional expression (4) and the ratio of the amount of indentation of the image-side surface of the concave meniscus lens component N1 to the amount of indentation of the image-side surface of the concave meniscus lens component N2 increases, the amount of indentation of the image-side surface of the concave meniscus lens component N1 with a larger effective diameter increases, and the processability or the measurement accuracy deteriorates. Also, the negative refractive power of the concave meniscus lens component N1 becomes too strong, making it difficult to correct the astigmatism or the field curvature, and thus it is not preferable.

[0029] If it exceeds the lower limit of the conditional expression (4) and the ratio of the amount of indentation of the image-side surface of the concave meniscus lens component N1 to the amount of indentation of the image-side surface of the concave meniscus lens component N2 decreases, the amount of indentation of the image-side surface of the concave meniscus lens component N2 increases, and the processability or the measurement accuracy deteriorates. Also, the negative refractive power of the concave meniscus lens component N2 becomes too strong, making it difficult to correct the astigmatism or the field curvature, and thus it is not preferable.

[0030] Furthermore, regarding the conditional expression (4), it is expected to specify the upper limit value as 1.72 and the lower limit value as 0.60, and further expected to specify the upper limit value as 1.40 and the lower limit value as 0.70, whereby the aforementioned effects can be made more reliable.

[0031] It is expected that in the large-aperture ratio ultra-wide-angle lens of the present invention, the concave meniscus lens component N1 and the concave meniscus lens component N2 satisfy the following conditional expression (5). (5) 0.4 < fN1 / fN2 < 5.0 fN1: Focal length of the concave meniscus lens component N1 fN2: Focal length of the concave meniscus lens component N2

[0032] The conditional expression (5) stipulates the ratio of the focal lengths of the concave meniscus lens component N1 and the concave meniscus lens component N2. In the object-side lens of the large-aperture ratio ultra-wide-angle lens of the present invention, while maintaining high optical performance, if one attempts to reduce the F value or expand the field angle, it is likely to become large-sized. By appropriately setting the focal lengths of the concave meniscus lens component N1 and the concave meniscus lens component N2 and adopting a structure in which the two appropriately bear the negative refractive power, it is possible to suppress the enlargement of the optical system while maintaining high optical performance.

[0033] If it exceeds the upper limit of the conditional expression (5) and the ratio of the focal lengths of the concave meniscus lens component N1 and the concave meniscus lens component N2 becomes large, the negative refractive power of the concave meniscus lens component N2 becomes too strong, and it is difficult to correct the astigmatism or field curvature, so it is not preferred.

[0034] If it exceeds the lower limit of the conditional expression (5) and the ratio of the focal lengths of the concave meniscus lens component N1 and the concave meniscus lens component N2 becomes small, the negative refractive power of the concave meniscus lens component N1 becomes too strong, and it is difficult to correct the astigmatism or field curvature. Also, the curvature radius on the image side of the concave meniscus lens component N1 becomes small, the amount of depression increases, the workability or measurement accuracy deteriorates, and the wall thickness deviation ratio of the lens increases. Since the concave meniscus lens component N1 is closer to the object side and has a larger lens diameter than the concave meniscus lens component N2, the increase in the weight of the lens when the wall thickness deviation ratio increases is likely to be large in the concave meniscus lens component N1. Thus, it is likely to cause an increase in the weight of the entire optical system, so it is not preferred.

[0035] In addition, regarding the conditional expression (5), it is expected to specify the upper limit value as 4.3 and the lower limit value as 0.7, whereby the aforementioned effects can be made more reliable.

[0036] It is expected that in the large-aperture ratio ultra-wide-angle lens of the present invention, the concave meniscus lens component N1 satisfies the following conditional expression (6). (6) 1.5 < N1SF < 6.0 N1SF = (N1R1 + N1R2) / (N1R1 - N1R2) N1R1: Curvature radius of the surface on the object side of the concave meniscus lens component N1 N1R2: Curvature radius of the surface on the image side of the concave meniscus lens component N1

[0037] The conditional expression (6) defines the lens shape of the concave meniscus lens component N1, the so-called shape factor. Since the concave meniscus lens component N1 has a concave meniscus shape with the convex surface facing the object side, both N1R1 and N1R2 are greater than 0, N1R1 is greater than N1R2, the smaller the difference between N1R1 and N1R2, the larger N1SF, and the larger the difference between N1R1 and N1R2, the closer N1SF is to 1. Thus, if the refractive index of the concave meniscus lens component N1 remains unchanged, the closer N1SF is to 1, the stronger the negative refractive power of the concave meniscus lens component N1, and the larger the amount of depression on the image side surface of the concave meniscus lens component N1.

[0038] If it exceeds the upper limit of the conditional expression (6) and N1SF of the concave meniscus lens component N1 increases, the difference between N1R1 and N1R2 becomes smaller, the negative refractive power of the concave meniscus lens component N1 becomes weaker, and the insufficient refractive power is compensated by the concave meniscus lens component N2. The negative refractive power of the concave meniscus lens component N2 becomes too strong, making it difficult to correct the astigmatism or field curvature, so it is not preferred.

[0039] If it exceeds the lower limit of the conditional expression (6) and N1SF of the concave meniscus lens component N1 decreases and approaches 1, the difference between N1R1 and N1R2 becomes larger, the negative refractive power of the concave meniscus lens component N1 becomes too strong, resulting in deterioration of astigmatism or field curvature. Moreover, especially the radius of curvature N1R2 of the image side surface becomes smaller, resulting in an increase in the amount of depression, and the workability or measurement accuracy deteriorates. In addition, since the wall thickness deviation ratio of the concave meniscus lens component N1 with the largest lens diameter increases, the weight of the optical system increases, so it is not preferred.

[0040] In addition, regarding the conditional expression (6), it is expected to define the upper limit value as 4.5 and the lower limit value as 1.7, and further expected to define the upper limit value as 4.3 and the lower limit value as 2.2, whereby the above-mentioned effects can be made more reliable.

[0041] It is expected that in the large aperture ratio ultra-wide angle lens of the present invention, the concave meniscus lens component N2 satisfies the following conditional expression (7). (7) 1.2 < N2SF < 5.0 N2SF = (N2R1 + N2R2) / (N2R1 - N2R2) N2R1: The radius of curvature of the object side surface of the concave meniscus lens component N2 N2R2: The radius of curvature of the image side surface of the concave meniscus lens component N2

[0042] The conditional expression (7) defines the lens shape of the concave meniscus lens component N2, the so-called shape factor. Since the concave meniscus lens component N2 has a concave meniscus shape with the convex surface facing the object side, both N2R1 and N2R2 are greater than 0, N2R1 is greater than N2R2, the smaller the difference between N2R1 and N2R2, the larger N2SF, and the larger the difference between N2R1 and N2R2, the closer N2SF is to 1. Thus, if the refractive index of the concave meniscus lens component N2 remains unchanged, the closer N2SF is to 1, the stronger the negative refractive power of the concave meniscus lens component N2, and the larger the amount of depression on the image side surface of the concave meniscus lens component N2.

[0043] If it exceeds the upper limit of the conditional expression (7) and N2SF of the concave meniscus lens component N2 increases, the difference between N2R1 and N2R2 becomes smaller, the negative refractive power of the concave meniscus lens component N2 becomes weaker, and the insufficient refractive power is compensated by the concave meniscus lens component N1. The negative refractive power of the concave meniscus lens component N1 becomes too strong, making it difficult to correct the astigmatism or field curvature. At the same time, the difference in the radius of curvature between the object side surface and the image side surface of the concave meniscus lens component N1 becomes larger, especially the radius of curvature N1R2 of the image side surface becomes smaller. Therefore, the amount of depression increases, and the workability or measurement accuracy deteriorates. Also, since the wall thickness deviation ratio of the concave meniscus lens component N1 with the largest lens diameter increases, the weight of the optical system increases, so it is not preferred.

[0044] If it exceeds the lower limit of the conditional expression (7) and N2SF of the concave meniscus lens component N2 decreases and approaches 1, the negative refractive power of the concave meniscus lens component N2 becomes too strong, making it difficult to correct the astigmatism or field curvature. At the same time, the difference in the radius of curvature between the object side surface and the image side surface of the concave meniscus lens component N2 becomes larger, especially the radius of curvature N1R2 of the image side surface becomes smaller. Therefore, the amount of depression increases, and the workability or measurement accuracy deteriorates, so it is not preferred.

[0045] In addition, regarding the conditional expression (7), it is expected to define the upper limit value as 4.0 and the lower limit value as 1.6, so that the aforementioned effects can be made more reliable.

[0046] It is expected that in the large aperture ratio ultra-wide angle lens of the present invention, the concave meniscus lens component N1 and the concave meniscus lens component N2 satisfy the following conditional expression (8). (8) 0.4 < N1SF / N2SF < 3.0 N1SF = (N1R1 + N1R2) / (N1R1 - N1R2) N1R1: The radius of curvature of the object side surface of the concave meniscus lens component N1 N1R2: The radius of curvature of the image side surface of the concave meniscus lens component N1 N2SF = (N2R1 + N2R2) / (N2R1 - N2R2) N2R1: Radius of curvature of the object-side surface of the concave meniscus lens component N2 N2R2: Radius of curvature of the image-side surface of the concave meniscus lens component N2

[0047] Conditional expression (8) defines the ratio of the shape factors of the concave meniscus lens component N1 and the concave meniscus lens component N2. For the lens on the object side of a large aperture ratio ultra-wide-angle lens, when attempting to reduce the F value or expand the field angle while maintaining high optical performance, it tends to become larger in size. By appropriately setting the shape factors of the concave meniscus lens component N1 and the concave meniscus lens component N2, a structure can be adopted in which the two appropriately bear the negative refractive power. And, as described above, the concave meniscus lens component N1 and the concave meniscus lens component N2 need to be processed with high precision and need to be set to a shape that is easy to achieve such processing.

[0048] If it exceeds the upper limit of conditional expression (8) and the ratio of the shape factors of the concave meniscus lens component N1 and the concave meniscus lens component N2 becomes larger, it means that the value of N2SF becomes smaller relative to N1SF. If N2SF approaches 1 and becomes smaller, the difference in the radius of curvature between the object-side surface and the image-side surface of the concave meniscus lens component N2 becomes larger, especially the radius of curvature of the image-side surface becomes smaller, resulting in an increase in the amount of depression, and the workability or measurement accuracy deteriorates. Also, the negative refractive power of the concave meniscus lens component N2 becomes too strong, making it difficult to correct the astigmatism or field curvature, so it is not preferred.

[0049] If it exceeds the lower limit of conditional expression (8) and the ratio of the shape factors of the concave meniscus lens component N1 and the concave meniscus lens component N2 becomes smaller, it means that the value of N1SF becomes smaller relative to N2SF. If N1SF approaches 1 and becomes smaller, the difference in the radius of curvature between the object-side surface and the image-side surface of the concave meniscus lens component N1 becomes larger, especially the radius of curvature of the image-side surface becomes smaller, resulting in an increase in the amount of depression, and the workability or measurement accuracy deteriorates. Also, since the wall thickness deviation ratio of the concave meniscus lens component N1 with the largest lens diameter increases, the weight of the optical system increases, so it is not preferred. In addition, the negative refractive power of the concave meniscus lens component N1 becomes too strong, making it difficult to correct the astigmatism or field curvature, so it is not preferred.

[0050] In addition, regarding conditional expression (8), it is expected to define the upper limit value as 2.4 and the lower limit value as 0.5, whereby the aforementioned effects can be made more reliable.

[0051] It is expected that in the large aperture ratio ultra-wide-angle lens of the present invention, the concave meniscus lens component N1 satisfies the following conditional expression (9). (9) 1.8 < PLOAN1 / PLAN1 < 5.0 PLOAN1: The distance that the chief off-axis ray passes through the concave meniscus lens component N1 when the off-axis ray is defined as the ray with an object-side incident angle of 90° during infinite focusing (wherein, when 2ω < 180°, the ray incident with an object-side incident angle of ω is defined as the off-axis ray) PLAN1: The thickness of the concave meniscus lens component N1 on the optical axis

[0052] Conditional expression (9) stipulates the ratio of the passing distances of the on-axis ray and the chief off-axis ray passing through the concave meniscus lens component N1. In addition, the off-axis ray is defined as the ray with an object-side incident angle of 90° during infinite focusing (wherein, when 2ω < 180°, the ray incident with an object-side incident angle of ω is defined as the off-axis ray). The lens closest to the object side of the large aperture ratio ultra-wide angle lens according to the present invention is characterized in that due to the concave meniscus shape with the convex surface facing the object side, the passing distance of the off-axis ray in the lens relative to the on-axis ray is large. And if the lens shape is such that the radius of curvature of the image-side surface becomes smaller relative to the radius of curvature of the object-side surface (the lens shape with a large depression on the image-side surface and a large wall thickness deviation ratio), the difference in the passing distances of the off-axis ray and the on-axis ray in the lens becomes even greater. For the miniaturization of the ultra-wide angle lens, it is effective to use a high refractive index glass material in the lens closest to the object side. However, generally, the higher the refractive index of the glass material, the more likely the internal transmittance of the glass material is to decrease, especially the transmittance in the short wavelength side deteriorates, and thus the lens appears yellower. When such a glass material with a low internal transmittance is used for the concave meniscus lens component N1, if the difference in the passing distances of the on-axis ray and the off-axis ray is not within an appropriate range, a phenomenon of different hues according to the field angle will occur (the closer to the periphery of the image, the yellower the image), so it is not preferred. The same phenomenon also occurs in the concave meniscus lens component N2 with a similar optical path to the concave meniscus lens component N1, but the influence of the concave meniscus lens component N1 with a larger lens diameter and a longer passing distance of the light in the lens becomes greater.

[0053] If it exceeds the upper limit of conditional expression (9) and the ratio of the passing distances of the on-axis ray and the chief off-axis ray passing through the concave meniscus lens component N1 becomes larger, the passing distance of the off-axis ray becomes larger relative to the on-axis ray passing through the concave meniscus lens component N1. Therefore, the transmittance of the off-axis ray is significantly reduced relative to the transmittance of the on-axis ray, and the hue difference based on the field angle becomes larger, so it is not preferred.

[0054] If it exceeds the lower limit of conditional expression (9) and the ratio of the passing distances of the on-axis light and the off-axis chief ray through the concave meniscus lens component N1 becomes smaller, the negative refractive power of the concave meniscus lens component N1 is insufficient. To compensate for this insufficiency, the refractive power of the concave meniscus component N2 becomes too strong, resulting in deterioration of the astigmatism and field curvature. Therefore, this is not preferable.

[0055] In addition, regarding conditional expression (9), it is expected to specify the upper limit value as 4.2 and the lower limit value as 2.0, whereby the aforementioned effects can be made more reliable.

[0056] It is expected that in the large-aperture ratio ultra-wide-angle lens of the present invention, the concave meniscus lens component N1 and the concave meniscus lens component N2 satisfy the following conditional expression (10). (10) 0.3 < PLOAN1 / PLOAN2 < 3.5 PLOAN1: The distance that the off-axis chief ray passes through the concave meniscus lens component N1 when the light with an object-side incident angle of 90° at infinite focus is defined as the off-axis light (wherein, when 2ω < 180°, the light incident at the object-side incident angle ω is defined as the off-axis light) PLOAN2: The distance that the off-axis chief ray passes through the concave meniscus lens component N2 when the light with an object-side incident angle of 90° at infinite focus is defined as the off-axis light (wherein, when 2ω < 180°, the light incident at the object-side incident angle ω is defined as the off-axis light)

[0057] Conditional expression (10) defines the ratio of the passing distances of the off-axis chief rays through the concave meniscus lens component N1 and the concave meniscus lens component N2. In addition, the definition of the off-axis light defines the light with an object-side incident angle of 90° at infinite focus as the off-axis light (wherein, when 2ω < 180°, the light incident at the object-side incident angle ω is defined as the off-axis light). In the description of conditional expression (9), it is clearly shown that the difference in the passing distances of the on-axis light and the off-axis light of the concave meniscus lens component N1 affects the hue change based on the field angle. The same phenomenon will also occur in the concave meniscus lens component N2 with a similar lens shape and a similar light passing mode. Thus, by setting the passing distances of the off-axis lights through the concave meniscus lens component N1 and the concave meniscus lens component N2 within an appropriate range, a good image with less hue change based on the field angle can be obtained.

[0058] If it exceeds the upper limit of conditional expression (10) and the ratio of the passing distances of the off-axis principal rays through the concave meniscus lens component N1 and the concave meniscus lens component N2 increases, the distance of the off-axis rays passing through the concave meniscus lens component N1 increases, and it is likely to cause a change in hue based on the field angle. Also, since the wall thickness deviation ratio of the concave meniscus lens component N1 with the largest lens diameter changes in the increasing direction, the weight of the optical system increases, which is not preferable. In addition, the negative refractive power of the concave meniscus lens component N1 becomes too strong, making it difficult to correct the astigmatism or field curvature, which is not preferable.

[0059] If it is less than the lower limit of conditional expression (10) and the ratio of the passing distances of the off-axis principal rays through the concave meniscus lens component N1 and the concave meniscus lens component N2 decreases, the distance of the off-axis rays passing through the concave meniscus lens component N2 increases, and it is likely to cause a change in hue based on the field angle. Also, since the wall thickness deviation ratio of the concave meniscus lens component N2 changes in the increasing direction, the negative refractive power of the concave meniscus lens component N2 becomes too strong, resulting in deterioration of the astigmatism or field curvature, which is not preferable.

[0060] In addition, regarding conditional expression (10), it is expected to specify the upper limit value as 2.8 and the lower limit value as 0.6, whereby the aforementioned effects can be made more reliable.

[0061] It is expected that in the large aperture ratio ultra-wide-angle lens of the present invention, the second lens group G2 has a convex lens LP1 that satisfies the following conditional expressions (11) to (13). (11) 1.60 < ndLP1 (12) vdLP1 < 35.0 (13) 0.018 < ΔPgFLP1 ndLP1: refractive index of the convex lens LP1 vdLP1: Abbe number of the convex lens LP1 ΔPgFLP1: anomalous dispersion of the convex lens LP1

[0062] The conditional expressions (11) to (13) define the range of the refractive index, Abbe number, and anomalous dispersion of the convex lens LP1 included in the second lens group G2. Generally, in a convex lens closer to the image side than the stop in a retrofocus ultra-wide-angle lens, a glass material having positive anomalous dispersion is disposed. This is related to the generation tendency of lateral chromatic aberration and axial chromatic aberration in the retrofocus ultra-wide-angle lens. Regarding lateral chromatic aberration, the C line tends to remain in the upward direction, and when designed to correct the C line and the g line, the secondary spectrum remains in the upward direction. Also, regarding axial chromatic aberration, generally, in a single-focus lens, the C line tends to remain in the upward direction (synonymous with the C line having a longer focal length), and when designed to correct the C line and the g line, the secondary spectrum remains in the upward direction. If a glass material having positive anomalous dispersion is used in the convex lens disposed closer to the image side than the stop, the correction direction of lateral chromatic aberration coincides with the correction direction of axial chromatic aberration, and thus chromatic aberration can be corrected more effectively. Generally, as the glass material having positive anomalous dispersion, fluorite or a special low-dispersion glass equivalent thereto is often used. Since these special low-dispersion glasses are mostly glass materials having a low refractive index, if they are often used in the convex lens closer to the image side than the stop, it is not conducive to correcting the Petzval sum, and it is difficult to correct field curvature. The large-aperture ratio ultra-wide-angle lens of the present invention is configured to be bright because the F value is less than 1.9. Therefore, in high-performance improvement, correction of axial chromatic aberration is indispensable, and a special low-dispersion glass having positive anomalous dispersion has to be often used in the convex lens closer to the image side than the stop. However, in order to correct the deteriorated Petzval sum, a glass material having a refractive index of 1.6 or more and having positive anomalous dispersion (if it is a glass material of HOYA Corporation, it is E-FDS1-W, etc.) is disposed in the second lens group G2 closer to the image side than the stop, so that lateral chromatic aberration and axial chromatic aberration can be effectively corrected, and field curvature can also be appropriately corrected.

[0063] If the lower limit of the conditional expression (11) is exceeded and the refractive index of the convex lens LP1 decreases, the Petzval sum deteriorates, and it is difficult to correct field curvature, so this is not preferred.

[0064] In addition, regarding the conditional expression (11), it is expected to define the lower limit value as 1.65, and further expected to define it as 1.85, whereby the above-described effects can be made more reliable.

[0065] Generally, the smaller the Abbe number of the glass material within the range of the conditional expression (11), the greater the positive anomalous dispersion. If the Abbe number increases, the positive anomalous dispersion decreases, and depending on the glass material, it has negative anomalous dispersion. Thus, if the upper limit of the conditional expression (12) is exceeded and the Abbe number of the convex lens LP1 increases, the anomalous dispersion decreases, and it is difficult to correct lateral chromatic aberration and axial chromatic aberration, so this is not preferred.

[0066] In addition, regarding conditional expression (12), it is expected to specify the upper limit value as 32.0, and further expected to specify it as 28.0, whereby the aforementioned effects can be made more reliable.

[0067] If it exceeds the lower limit of conditional expression (13) and the anomalous dispersion of the convex lens LP1 becomes smaller, it becomes difficult to correct the magnification chromatic aberration and axial chromatic aberration, so it is not preferable.

[0068] In addition, regarding conditional expression (13), it is expected to specify the lower limit value as 0.020, and further expected to specify the lower limit value as 0.025, whereby the aforementioned effects can be made more reliable.

[0069] It is expected that in the large aperture ratio ultra-wide angle lens of the present invention, the first lens group G1 has a negative refractive power and satisfies the following conditional expression (14). (14) -0.40 < f / f1 < 0.70 f: Focal length of the large aperture ratio ultra-wide angle lens at infinite focus f1: Focal length of the first lens group G1 at infinite focus

[0070] Conditional expression (14) specifies the ratio of the focal length of the large aperture ratio ultra-wide angle lens at infinite focus to the focal length of the first lens group G1 at infinite focus. By satisfying conditional expression (14), while realizing the wide field angle conversion of the optical system, the enlargement of the optical system is prevented.

[0071] If it exceeds the upper limit of conditional expression (14) and the ratio of the focal length of the large aperture ratio ultra-wide angle lens at infinite focus to the focal length of the first lens group G1 at infinite focus becomes larger, then f1 takes a positive value and approaches 0, and the positive refractive power of the first lens group G1 increases, so it becomes difficult to realize the wide field angle conversion, so it is not preferable.

[0072] If it exceeds the lower limit of conditional expression (14) and the ratio of the focal length of the large aperture ratio ultra-wide angle lens at infinite focus to the focal length of the first lens group G1 at infinite focus becomes smaller, then f1 takes a negative value and approaches 0, and the negative refractive power of the first lens group G1 becomes too strong, and the astigmatism or field curvature deteriorates, so it is not preferable.

[0073] In addition, regarding conditional expression (14), it is expected to specify the upper limit value as 0.60 and the lower limit value as -0.25, whereby the aforementioned effects can be made more reliable.

[0074] It is expected that in the large aperture ratio ultra-wide angle lens of the present invention, the first lens group G1 and the second lens group G2 having a positive refractive power satisfy the following conditional expression (15). (15) -0.8 < f2 / f1 < 2.7 f1: Focal length of the first lens group G1 at infinite focus f2: Focal length of the second lens group G2 at infinity focus

[0075] Conditional expression (15) stipulates the ratio of the focal length of the second lens group G2 at infinity focus to the focal length of the first lens group G1 at infinity focus. By satisfying conditional expression (15), while achieving a wide field angle of view of the optical system, the enlargement of the optical system is prevented.

[0076] If it exceeds the upper limit of conditional expression (15) and the ratio of the focal length of the second lens group G2 at infinity focus to the focal length of the first lens group G1 at infinity focus becomes larger, then f1 takes a positive value and approaches 0, and the positive refractive power of the first lens group G1 is enhanced. Therefore, it is difficult to achieve a wide field angle of view, so it is not preferred.

[0077] If it exceeds the lower limit of conditional expression (15) and the ratio of the focal length of the second lens group G2 at infinity focus to the focal length of the first lens group G1 at infinity focus becomes smaller, then f1 takes a negative value and approaches 0, and the negative refractive power of the first lens group G1 becomes too strong, resulting in deterioration of the coma aberration or field curvature. Therefore, it is not preferred.

[0078] In addition, regarding conditional expression (15), it is expected to stipulate the upper limit value as 2.6 and the lower limit value as -0.7, whereby the aforementioned effects can be made more reliable.

[0079] It is expected that in the large aperture ratio ultra-wide angle lens of the present invention, the second lens group G2 has at least one convex lens satisfying the following conditional expression (16), and it is expected to satisfy the following conditional expression (17). (16) 0.3 < G2LPAXh / G2LPOAh < 2.7 (17) 0.004 < G2LPAve G2LPAXh: Height of the on-axis marginal ray incident on the convex lens at infinity focus with the aperture open G2LPOAh: Height of the off-axis chief ray when a ray with an object-side incident angle of 90° is incident on the convex lens at infinity focus (wherein, in the case of 2ω < 180°, it is the height of the off-axis chief ray incident with an object-side incident angle of ω) G2LPAve: Average value of the anomalous dispersion of the convex lens satisfying conditional expression (16)

[0080] Generally, the longitudinal chromatic aberration of an optical system composed of thin-walled lenses is given as the sum of each lens by the following (Reference formula 1), and the axial chromatic aberration is given by (Reference formula 2). (Reference formula 1) Σ(h · hb · φ / v) (Reference formula 2) Σ(h · h · φ / v) h: Height of the on-axis marginal ray hb: Height of the off-axis chief ray φ: Dioptric power v: Abbe number

[0081] As can be seen from (Reference Formula 1) and (Reference Formula 2), the greater the height of the chief ray off the axis passing through a lens position, the greater the influence of the longitudinal chromatic aberration; the greater the height of the marginal ray on the axis passing through a lens position, the greater the influence of the lateral chromatic aberration. Therefore, by appropriately setting the height difference between the marginal ray on the axis and the chief ray off the axis and the dispersion characteristics of the glass material, the longitudinal chromatic aberration and the lateral chromatic aberration can be highly corrected.

[0082] Conditional formula (16) defines the ratio of the height of the marginal ray on the axis to the height of the chief ray off the axis incident on the convex lens included in the second lens group G2. In addition, the height of the marginal ray on the axis and the height of the chief ray off the axis incident on the convex lens included in the second lens group G2 both define the ray height at the time of incidence, and thus correspond to the ray height on the object side surface of each convex lens. As described above, if a glass material with a large positive anomalous dispersion is used in the convex lens of the second lens group G2 arranged at a position closer to the image side than the aperture stop, it is effective for correcting both the longitudinal chromatic aberration and the lateral chromatic aberration. In particular, by arranging the convex lens using a glass material with a positive anomalous dispersion within the range satisfying conditional formula (16), the effect can be further improved. In addition, G2LPAXh defines the height of the marginal ray on the axis incident on the convex lens included in the second lens group G2. Since the marginal ray on the axis does not produce a positive / negative inversion of the ray height before and after the aperture stop, it is always calculated as a positive value in the calculation of this conditional formula. And G2LPOAh defines the height of the chief ray off the axis when a ray with an object-side incident angle of 90° is incident on the convex lens during infinite focus, and can take both positive and negative values. However, in the calculation of this conditional formula, the chief ray off the axis taking a positive value closer to the image side than the aperture stop is calculated.

[0083] If the ratio of the height of the marginal ray on the axis to the height of the chief ray off the axis incident on the convex lens included in the second lens group G2 exceeds the upper limit of conditional formula (16) and becomes larger, the height of the marginal ray on the axis decreases relative to the height of the chief ray off the axis. Therefore, the correction effect of the longitudinal chromatic aberration decreases, which is not preferable.

[0084] If the ratio of the height of the marginal ray on the axis to the height of the chief ray off the axis incident on the convex lens included in the second lens group G2 is less than the lower limit of conditional formula (16) and becomes smaller, the height of the chief ray off the axis decreases relative to the height of the marginal ray on the axis. Therefore, the correction effect of the lateral chromatic aberration decreases, which is not preferable.

[0085] Conditional formula (17) defines the average value of the anomalous dispersion of the convex lens included in the second lens group G2 that satisfies conditional formula (16). The greater the use of a glass material with a large positive anomalous dispersion, the more the correction effects of the longitudinal chromatic aberration and the lateral chromatic aberration are improved.

[0086] If the average value of the anomalous dispersion of the convex lens that exceeds the lower limit of conditional expression (17) and is included in the second lens group G2 and satisfies conditional expression (16) becomes smaller, the correction effects of the chromatic aberration of magnification and the axial chromatic aberration are weakened, so this is not preferable.

[0087] In addition, regarding conditional expression (17), it is expected to specify the lower limit value as 0.009, whereby the aforementioned effects can be made more reliable.

[0088] In the large aperture ratio ultra-wide angle lens of the present invention, it is expected that the concave meniscus lens component N1 includes a concave lens that satisfies the following conditional expression (18). (18) 1.7 < ndN1n ndN1n: The refractive index of the concave lens included in the concave meniscus lens component N1

[0089] Conditional expression (18) stipulates the refractive index of the concave lens included in the concave meniscus lens component N1 with the convex surface facing the object side. By using a high refractive index material for the concave lens, the optical system can be miniaturized.

[0090] If the refractive index of the concave lens included in the concave meniscus lens component N1 that exceeds the lower limit of conditional expression (18) and has the convex surface facing the object side decreases, the radius of curvature (N1R2) of the image side surface of the concave meniscus lens component N1 becomes smaller to maintain the refractive power, and the astigmatism or the field curvature deteriorates, so this is not preferable. Also, it acts in the direction of increasing the wall thickness deviation ratio of the concave meniscus lens component N1, and the weight of the concave meniscus lens component N1 increases, so this is not preferable.

[0091] In addition, regarding conditional expression (18), it is expected to specify the lower limit value as 1.8, whereby the aforementioned effects can be made more reliable.

[0092] It is expected that the large aperture ratio ultra-wide angle lens of the present invention satisfies the following conditional expression (19). (19) 5.00 < LT / BF < 12.00 LT: The distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side when focused at infinity BF: The distance on the optical axis from the lens surface closest to the image side to the image plane when focused at infinity

[0093] The conditional expression (19) defines the ratio of the distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side in the case of infinity focusing, and the distance on the optical axis from the lens surface closest to the image side to the image surface in the case of infinity focusing. In addition, adjacent parallel plates that are not adjacent to the image surface and have an air gap are not counted as lenses. Further, when calculating the distance on the optical axis from the lens surface closest to the image side to the image surface, it is calculated using the air conversion length obtained by replacing the parallel plate with air. By satisfying the conditional expression (19), miniaturization of the optical system can be achieved.

[0094] If it exceeds the upper limit of the conditional expression (19) and the ratio of the distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side in the case of infinity focusing and the distance on the optical axis from the lens surface closest to the image side to the image surface in the case of infinity focusing becomes larger, the optical system becomes larger, and thus it is not preferable.

[0095] If it exceeds the lower limit of the conditional expression (19) and the ratio of the distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side in the case of infinity focusing and the distance on the optical axis from the lens surface closest to the image side to the image surface in the case of infinity focusing becomes smaller, it is necessary to reduce LT, and it is difficult to correct spherical aberration, astigmatism, and field curvature while maintaining a large aperture ratio of less than F1.9, and thus it is not preferable.

[0096] In addition, regarding the conditional expression (19), it is expected to define the upper limit value as 11.00 and the lower limit value as 5.35, and further expected to define the upper limit value as 10.00 and the lower limit value as 6.20, whereby the above-described effects can be made more reliable.

[0097] It is expected that the large aperture ratio ultra-wide angle lens of the present invention satisfies the following conditional expression (20). (20) 2.5 < |LT / iOAh| < 18.0 LT: The distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side in the case of infinity focusing iOAh: The imaging height of the off-axis principal ray when a ray with an object side incident angle of 90° forms an image on the image surface in the case of infinity focusing (wherein, in the case of 2ω < 180°, it is the imaging height of the off-axis principal ray incident at the object side incident angle ω)

[0098] The conditional expression (20) defines the absolute value of the ratio of the distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side in the case of infinity focusing and the imaging height of the off-axis principal ray when a ray with an object side incident angle of 90° forms an image on the image surface in the case of infinity focusing (wherein, in the case of 2ω < 180°, it is the imaging height of the off-axis principal ray incident at the object side incident angle ω). By satisfying the conditional expression (19), miniaturization of the optical system can be achieved.

[0099] If the upper limit of conditional expression (20) is exceeded and the ratio of the distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side in the case of infinite focusing to the imaging height of the chief ray off the axis when a ray with an object-side incident angle of 90° forms an image on the image plane in the case of infinite focusing increases, the optical system becomes larger in size relative to the maximum imaging height of the optical system, which is therefore not preferable.

[0100] If the lower limit of conditional expression (20) is exceeded and the ratio of the distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side in the case of infinite focusing to the imaging height of the chief ray off the axis when a ray with an object-side incident angle of 90° forms an image on the image plane in the case of infinite focusing decreases, it is necessary to reduce LT, and it is difficult to correct spherical aberration, astigmatism, and field curvature while maintaining a large aperture ratio of less than F1.9, which is therefore not preferable.

[0101] In addition, regarding conditional expression (20), it is expected to specify the upper limit value as 16.0 and the lower limit value as 3.1, and further expected to specify the upper limit value as 14.0 and the lower limit value as 4.1, whereby the aforementioned effects can be made more reliable.

[0102] It is expected that in the large-aperture ratio ultra-wide-angle lens of the present invention, the concave meniscus lens component N2 is the concave meniscus lens component with the convex surface facing the object side and is the second concave meniscus lens component with the convex surface facing the object side arranged starting from the concave meniscus lens component closest to the object side. The concave meniscus lens component N2 serves to introduce off-axis light incident from the object side at an angle close to the optical axis. Therefore, by arranging it at a position closer to the object side, off-axis light can be introduced while preventing the enlargement of the optical system.

[0103] It is expected that in the large-aperture ratio ultra-wide-angle lens of the present invention, the concave meniscus lens component N1 and the concave meniscus lens component N2 are arranged continuously starting from the position closest to the object side. Both the concave meniscus lens component N1 and the concave meniscus lens component N2 serve to slowly introduce off-axis light incident from the object side at an angle close to the optical axis. Therefore, by arranging them continuously starting from the position closest to the object side, the enlargement of the optical system can be suppressed.

[0104] It is expected that in the large-aperture ratio ultra-wide-angle lens of the present invention, the concave meniscus lens component N1 and the concave meniscus lens component N2 are composed of spherical lenses. By using spherical lenses in the concave meniscus lens component N1 and the concave meniscus lens component N2, the processability of the optical element becomes easier, the degree of freedom in selecting the glass material is increased, and it is easy to correct chromatic aberration of magnification.

[0105] It is expected that the large aperture ratio ultra-wide angle lens of the present invention has a focusing function from infinity to a close object. At this time, focusing is achieved by moving a part to all of the optical system in the optical axis direction.

[0106] Next, the lens structure and numerical examples of the embodiments related to the large aperture ratio ultra-wide angle lens of the present invention will be described. In addition, in the following description, the lens structure is described in the order from the object side to the image side.

[0107] Embodiments 1 to 14 of the present invention are all fisheye lenses using the equal solid angle projection method. When evaluating the object surface when outputting each aberration diagram, the object surface is evaluated as a plane (curvature radius is ∞). Thus, especially in the evaluation of a finite distance with a small object distance, since the object surface is a plane, significant field curvature appears in the aberration diagram.

[0108] In [surface data], the surface number is the number of the lens surface or the aperture stop S counted from the object side, r is the curvature radius of each lens surface, d is the interval between each lens surface, nd is the refractive index with respect to the d line (wavelength 587.56 nm), vd is the Abbe number with respect to the d line, and ΔPgF is a value calculated by the formula of PgF - 0.64833 + 0.00180 × vd. And, as an example of the glass corresponding to the refractive index, Abbe number, and ΔPgF described in [surface data], the glass material names of HOYA Corporation, OHARA Inc., and HIKARI GLASS Co., Ltd are described for the corresponding glass materials.

[0109] The * (asterisk) attached to the surface number indicates an aspherical surface from its lens surface shape. And BF represents the back focal length, and the distance of the object surface represents the distance from the subject to the first lens surface.

[0110] The (stop) attached to the surface number indicates that the aperture stop S is located at this position. ∞ (infinity) is entered for the curvature radius with respect to the plane or the aperture stop S.

[0111] In [aspherical surface data], the values of the coefficients of the aspherical surface shape given to the lens surface with * attached in [surface data] are shown. The aspherical surface shape is represented by the following formula. In the following formula, y represents the displacement from the optical axis to the direction orthogonal to the optical axis, z represents the displacement (recess amount) from the intersection of the optical axis and the aspherical surface to the optical axis direction, r represents the curvature radius of the reference spherical surface, and K represents the conic coefficient. And the aspherical surface coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th orders are represented by A4, A6, A8, A10, A12, A14, and A16 respectively.

[0112] In [various data], the focal length equivalent values in the focusing state at each shooting distance are shown.

[0113] The variable intervals and BF values in various photographic distance focusing states are shown in [Variable Interval Data].

[0114] The surface number closest to the object side of each lens group and the combined focal length of the entire group are shown in [Lens Group Data].

[0115] In [Convex lens in the second lens group G2 that satisfies conditional expression (16)], the object side surface number of the convex lens in the second lens group G2 that satisfies conditional expression (16), the corresponding glass material, the height of the marginal ray on the axis incident on this convex lens at infinity focus with the aperture open (G2LPAXh), the height of the chief ray off the axis when a ray with an object side incident angle of 90° is incident on this convex lens at infinity focus (where, in the case of 2ω < 180°, the height of the chief ray off the axis incident with an object side incident angle of ω: G2LPOA h), the ratio of G2LPAXh to G2LPOAh, and the ΔPgF value are shown.

[0116] Moreover, in the aberration diagrams corresponding to the respective embodiments, d, g, and C represent the d-line, g-line, and C-line respectively, and ΔS and ΔM represent the sagittal image plane and meridional image plane respectively.

[0117] In addition, in all the following specification values, unless otherwise stated, the units of the focal length f, radius of curvature r, lens surface interval d, and other lengths are in millimeters (mm). However, in an optical system, the same optical performance can be obtained even in magnification and reduction, so it is not limited to this.

[0118] Moreover, as the lens names, the lens arranged at the position closest to the object side is sequentially called L1, the second lens arranged towards the image side is called L2, and the third lens arranged is called L3.

[0119] Moreover, in the lens structure diagrams of the respective embodiments, I is the image plane, F is the filter, and the single dotted line passing through the center is the optical axis.

[0120] [Embodiment 1] Figure 1 It is the lens structure diagram at infinity focus of the large aperture ratio ultra-wide angle lens related to Embodiment 1.

[0121] Figure 1 The large aperture ratio ultra-wide angle lens is composed of a first lens group G1 with negative refractive power, an aperture stop S, and a second lens group G2 with positive refractive power arranged in sequence from the object side.

[0122] The first lens group G1 is composed of a concave meniscus lens component N1 consisting of a concave meniscus lens L1 with its convex surface facing the object side, arranged in order from the object side, a concave meniscus lens component N2 consisting of a concave meniscus lens L2 with its convex surface facing the object side, a cemented lens of a convex meniscus lens L3 with its convex surface facing the image side and a biconcave lens L4, a cemented lens of a biconcave lens L5 and a convex meniscus lens L6 with its convex surface facing the object side, a biconvex lens L7, a biconvex aspherical lens L8, and a cemented lens of a concave meniscus lens L9 with its convex surface facing the object side and a convex meniscus lens L10 with its convex surface facing the object side.

[0123] The second lens group G2 is composed of a convex meniscus lens L11 with its convex surface facing the image side, arranged in order from the object side, a cemented lens composed of a convex meniscus lens L12 with its convex surface facing the image side and a concave meniscus lens L13 with its convex surface facing the image side, a biconvex lens L14, a biconvex lens L15, a biconvex lens L16, a cemented lens composed of a biconvex lens L17 and a biconcave lens L18, and a biconvex aspherical lens L19.

[0124] As an example of focusing, among the lenses constituting the first lens group G1, by moving the lenses L7 to L10 as a unit along the optical axis toward the image side, focusing can be achieved from an infinitely distant object to a nearby object. Nevertheless, focusing can also be performed by moving part or all of the optical system along the optical axis direction.

[0125] Hereinafter, the specification values of the large aperture ratio ultra-wide angle lens according to Embodiment 1 are shown.

[0126] Numerical Example 1 Unit: mm [Surface Data] [Aspherical Data] [Various Data] [Variable Interval Data] [Lens Group Data] Group Starting Surface Focal Length G1 1 -111.1800 G2 19 28.2728 [Convex Lenses in the Second Lens Group G2 Satisfying Conditional Expression (16)]

[0127] [Embodiment 2] Figure 6 It is a lens structure diagram when the large-aperture ratio ultra-wide-angle lens related to Embodiment 2 is focused at infinity.

[0128] Figure 6 The large-aperture ratio ultra-wide-angle lens is composed of a first lens group G1 with negative refractive power, an aperture stop S, and a second lens group G2 with positive refractive power, which are arranged in sequence from the object side.

[0129] The first lens group G1 is composed of a concave meniscus lens component N1 composed of a concave meniscus lens L1 with its convex surface facing the object side, a concave meniscus lens component N2 composed of a concave meniscus lens L2 with its convex surface facing the object side, a cemented lens of a convex meniscus lens L3 with its convex surface facing the image side and a biconcave lens L4, a cemented lens of a biconcave lens L5 and a biconvex lens L6, a biconvex lens L7, a biconvex aspherical lens L8, and a cemented lens of a concave meniscus lens L9 with its convex surface facing the object side and a convex meniscus lens L10 with its convex surface facing the object side.

[0130] The second lens group G2 is composed of a convex meniscus lens L11 with its convex surface facing the image side, a cemented lens of a convex meniscus lens L12 with its convex surface facing the image side and a concave meniscus lens L13 with its convex surface facing the image side, a convex meniscus lens L14 with its convex surface facing the image side, a biconvex lens L15, a convex meniscus lens L16 with its convex surface facing the object side, a cemented lens of a biconvex lens L17 and a biconcave lens L18, and a biconvex aspherical lens L19.

[0131] As an example of focusing, among the lenses constituting the first lens group G1, by moving the lenses L7 to L10 as a unit along the optical axis toward the image side, focusing can be achieved from an infinite object to a close object. Nevertheless, focusing can also be performed by moving a part or all of the optical system along the optical axis direction.

[0132] Hereinafter, the specification values of the large-aperture ratio ultra-wide-angle lens related to Embodiment 2 are shown.

[0133] Numerical Example 2 Unit: mm [Surface Data] [Aspherical Data] [Various Data] [Variable Interval Data] [Lens group data] Group Starting surface Focal length G1 1 -76.3147 G2 19 29.7796 [Convex lens within the second lens group G2 that satisfies conditional expression (16)]

[0134] [Embodiment 3] Figure 11 is the lens structure diagram during infinity focusing of the large aperture ratio ultra-wide-angle lens related to Embodiment 3.

[0135] Figure 11 The large aperture ratio ultra-wide-angle lens is composed of a first lens group G1 with negative refractive power, an aperture stop S, and a second lens group G2 with positive refractive power, which are arranged in sequence from the object side.

[0136] The first lens group G1 is composed of a meniscus lens component N1 consisting of a concave meniscus lens L1 with its convex surface facing the object side, arranged in sequence from the object side, a meniscus lens component N2 consisting of a concave meniscus lens L2 with its convex surface facing the object side, a cemented lens of a convex meniscus lens L3 with its convex surface facing the image side and a biconcave lens L4, a cemented lens of a biconcave lens L5 and a biconvex lens L6, a biconcave lens L7, a convex meniscus lens L8 with its convex surface facing the object side, a biconvex aspherical lens L9, and a cemented lens of a concave meniscus lens L10 with its convex surface facing the object side and a convex meniscus lens L11 with its convex surface facing the object side.

[0137] The second lens group G2 is composed of a biconvex lens L12, a cemented lens of a biconvex lens L13 and a concave meniscus lens L14 with its convex surface facing the image side, arranged in sequence from the object side, a biconvex lens L15, a cemented lens of a concave meniscus lens L16 with its convex surface facing the object side and a biconvex lens L17, a biconvex lens L18, a cemented lens of a biconvex lens L19 and a biconcave lens L20, and a biconvex aspherical lens L21.

[0138] As an example of focusing, among the lenses constituting the first lens group G1, by moving L8 axially towards the image side, focusing can be achieved from an infinite object to a nearby object. Nevertheless, focusing can also be performed by moving part or all of the optical system axially.

[0139] Hereinafter, the specification values of the large aperture ratio ultra-wide-angle lens related to Embodiment 3 are shown.

[0140] Numerical Example 3 Unit: mm [Surface data] [Aspherical data] [Various data] [Variable interval data] [Lens group data] Group starting surface Focal length G1 1 -111.4197 G2 21 41.1473 [Convex lens in the second lens group G2 that satisfies the conditional expression (16)]

[0141] [Example 4] Figure 16 is the lens structure diagram of the large aperture ratio ultra-wide angle lens involved in Example 4 during infinite focus.

[0142] Figure 16 The large aperture ratio ultra-wide angle lens is composed of a first lens group G1 with negative refractive power, an aperture stop S, and a second lens group G2 with positive refractive power, which are arranged in sequence from the object side.

[0143] The first lens group G1 is composed of a meniscus lens component N1 consisting of a concave meniscus lens L1 with its convex surface facing the object side, arranged in sequence from the object side; a meniscus lens component N2 consisting of a cemented lens of a concave meniscus lens L2 with its convex surface facing the object side and a concave meniscus lens L3 with its convex surface facing the object side; a cemented lens of a convex meniscus lens L4 with its convex surface facing the image side and a concave meniscus lens L5 with its convex surface facing the image side; a convex meniscus lens L6 with its convex surface facing the image side; a cemented lens of a biconcave lens L7 and a convex meniscus lens L8 with its convex surface facing the object side; a biconvex lens L9; a biconvex aspherical lens L10; and a cemented lens of a concave meniscus lens L11 with its convex surface facing the object side and a convex meniscus lens L12 with its convex surface facing the object side.

[0144] The second lens group G2 is composed of a convex meniscus lens L13 with its convex surface facing the image side, arranged in sequence from the object side; a cemented lens of a convex meniscus lens L14 with its convex surface facing the image side and a concave meniscus lens L15 with its convex surface facing the image side; a biconvex lens L16; a biconvex lens L17; a biconvex lens L18; a cemented lens of a biconvex lens L19 and a biconcave lens L20; and a biconvex aspherical lens L21.

[0145] As an example of focusing, among the lenses constituting the first lens group G1, by moving the lenses L9 to L12 as a unit along the optical axis toward the image side, focusing can be achieved from an infinitely distant object to a nearby object. Nevertheless, focusing can also be performed by moving a part or all of the optical system in the optical axis direction.

[0146] Hereinafter, the specification values of the large aperture ratio ultra-wide angle lens according to Embodiment 4 are shown.

[0147] Numerical Example 4 Unit: mm [Surface Data] [Aspherical Surface Data] [Various Data] [Variable Interval Data] [Lens Group Data] Group Starting Surface Focal Length G1 1 -104.0373 G2 22 28.5547 [Convex Lens in the Second Lens Group G2 Satisfying Conditional Expression (16)]

[0148] [Embodiment 5] Figure 21 It is a lens structure diagram at infinity focus of the large aperture ratio ultra-wide angle lens according to Embodiment 5.

[0149] Figure 21 The large aperture ratio ultra-wide angle lens is composed of a first lens group G1 having negative refractive power, an aperture stop S, and a second lens group G2 having positive refractive power, which are arranged in order from the object side.

[0150] The first lens group G1 is composed of a meniscus lens component N1 consisting of a convex meniscus lens L1 with its convex surface facing the object side and a concave meniscus lens L2 with its convex surface facing the object side, arranged in sequence from the object side; a meniscus lens component N2 consisting of a concave meniscus lens L3 with its convex surface facing the object side; a cemented lens of a convex meniscus lens L4 with its convex surface facing the image side and a biconcave lens L5; a cemented lens of a biconcave lens L6 and a convex meniscus lens L7 with its convex surface facing the object side; a biconvex lens L8; a biconvex aspherical lens L9; and a cemented lens of a concave meniscus lens L10 with its convex surface facing the object side and a convex meniscus lens L11 with its convex surface facing the object side.

[0151] The second lens group G2 is composed of a convex meniscus lens L12 with its convex surface facing the image side, a cemented lens of a convex meniscus lens L13 with its convex surface facing the image side and a concave meniscus lens L14 with its convex surface facing the image side, a biconvex lens L15, a biconvex lens L16, a biconvex lens L17, a cemented lens of a biconvex lens L18 and a biconcave lens L19, and a biconvex aspherical lens L20, arranged in sequence from the object side.

[0152] As an example of focusing, among the lenses constituting the first lens group G1, by moving the lenses L8 to L11 as a unit along the optical axis toward the image side, focusing can be achieved from an infinitely distant object to a nearby object. Nevertheless, focusing can also be performed by moving a part or all of the optical system along the optical axis direction.

[0153] Hereinafter, the specification values of the large aperture ratio ultra-wide-angle lens according to Embodiment 5 are shown.

[0154] Numerical Example 5 Unit: mm [Surface Data] [Aspherical Data] [Various Data] [Variable Interval Data] [Lens Group Data] Group Starting Surface Focal Length G1 1 -105.6709 G2 20 28.3077 [Convex Lenses in the Second Lens Group G2 Satisfying Conditional Expression (16)]

[0155] [Embodiment 6] Figure 26 It is the lens structure diagram when the large-aperture ratio ultra-wide-angle lens involved in Embodiment 6 is focused at infinity.

[0156] Figure 26 The large-aperture ratio ultra-wide-angle lens is composed of a first lens group G1 with positive refractive power, an aperture stop S, and a second lens group G2 with positive refractive power, which are arranged in sequence from the object side.

[0157] The first lens group G1 is composed of a concave meniscus lens component N1 composed of a concave meniscus lens L1 with its convex surface facing the object side, a concave meniscus lens component N2 composed of a concave meniscus lens L2 with its convex surface facing the object side, a cemented lens of a biconvex lens L3 and a biconcave lens L4, a cemented lens of a biconcave lens L5 and a biconvex lens L6, a convex meniscus lens L7 with its convex surface facing the image side, a biconvex aspherical lens L8, and a cemented lens of a biconcave lens L9 and a convex meniscus lens L10 with its convex surface facing the object side.

[0158] The second lens group G2 is composed of a biconvex lens L11, a cemented lens of a convex meniscus lens L12 with its convex surface facing the image side and a concave meniscus lens L13 with its convex surface facing the image side, a convex meniscus lens L14 with its convex surface facing the object side, a biconvex lens L15, a biconvex lens L16, a cemented lens of a biconvex lens L17 and a biconcave lens L18, and a biconvex aspherical lens L19, which are arranged in sequence from the object side.

[0159] As an example of focusing, among the lenses constituting the first lens group G1, by moving the lenses L7 to L10 as a unit along the optical axis toward the image side, focusing can be achieved from an infinite object to a near object. Nevertheless, focusing can also be performed by moving a part or all of the optical system along the optical axis direction.

[0160] Hereinafter, the specification values of the large-aperture ratio ultra-wide-angle lens involved in Embodiment 6 are shown.

[0161] Numerical Example 6 Unit: mm [Surface Data] [Aspherical Data] [Various Data] [Variable Interval Data] [Lens Group Data] Group Starting Surface Focal Length G1 1 1309.1203 G2 19 42.6388 [Convex lens within the second lens group G2 that satisfies conditional expression (16)]

[0162] [Embodiment 7] Figure 31 It is a lens structure diagram during infinity focusing of a large aperture ratio ultra-wide angle lens related to Embodiment 7.

[0163] Figure 31 The large aperture ratio ultra-wide angle lens is composed of a first lens group G1 with negative refractive power, an aperture stop S, and a second lens group G2 with positive refractive power, which are arranged in sequence from the object side.

[0164] The first lens group G1 is composed of a concave meniscus lens component N1 composed of a concave meniscus lens L1 with its convex surface facing the object side, arranged in sequence from the object side, a concave meniscus lens component N2 composed of a concave meniscus lens L2 with its convex surface facing the object side, a cemented lens of a convex meniscus lens L3 with its convex surface facing the image side and a concave meniscus lens L4 with its convex surface facing the image side, a cemented lens of a biconcave lens L5 and a convex meniscus lens L6 with its convex surface facing the object side, a biconvex lens L7, a biconvex aspherical lens L8, and a cemented lens of a concave meniscus lens L9 with its convex surface facing the object side and a convex meniscus lens L10 with its convex surface facing the object side.

[0165] The second lens group G2 is composed of a convex meniscus lens L11 with its convex surface facing the image side, arranged in sequence from the object side, a cemented lens of a convex meniscus lens L12 with its convex surface facing the image side and a concave meniscus lens L13 with its convex surface facing the image side, a biconvex lens L14, a biconvex lens L15, a biconvex lens L16, a cemented lens of a biconvex lens L17 and a biconcave lens L18, and a biconvex aspherical lens L19.

[0166] As an example of focusing, among the lenses constituting the first lens group G1, by moving the lenses L7 - L10 as a unit along the optical axis toward the image side, focusing can be achieved from an infinite object to a near object. Nevertheless, focusing can also be performed by moving part or all of the optical system along the optical axis direction.

[0167] Hereinafter, the specification values of the large aperture ratio ultra-wide angle lens related to Embodiment 7 are shown.

[0168] Numerical Example 7 Unit: mm [Surface data] [Aspherical data] [Various data] [Variable interval data] [Lens group data] Group starting surface Focal length G1 1 -73.7389 G2 19 27.7005 [Convex lens within the second lens group G2 that satisfies conditional expression (16)]

[0169] [Example 8] Figure 36 is the lens structure diagram during infinity focusing of the large aperture ratio ultra-wide angle lens related to Example 8.

[0170] Figure 36 The large aperture ratio ultra-wide angle lens is composed of a first lens group G1 with positive refractive power, an aperture stop S, and a second lens group G2 with positive refractive power, which are arranged in sequence from the object side.

[0171] The first lens group G1 is composed of a meniscus lens component N1 composed of a concave meniscus lens L1 with its convex surface facing the object side, arranged in sequence from the object side, a meniscus lens component N2 composed of a concave meniscus lens L2 with its convex surface facing the object side, a cemented lens of a concave meniscus lens L3 with its convex surface facing the image side and a convex meniscus lens L4 with its convex surface facing the image side, a concave meniscus lens L5 with its convex surface facing the image side, a double concave lens L6, a cemented lens of a double convex lens L7 and a double concave lens L8, a convex meniscus lens L9 with its convex surface facing the object side, a double convex aspherical lens L10, and a cemented lens of a double convex lens L11 and a concave meniscus lens L12 with its convex surface facing the image side.

[0172] The second lens group G2 is composed of a concave meniscus lens L13 with its convex surface facing the object side, a double convex lens L14, a double convex lens L15, a cemented lens of a double concave lens L16 and a double convex lens L17, a double concave lens L18, and a double convex aspherical lens L19, which are arranged in sequence from the object side.

[0173] As an example of focusing, among the lenses constituting the first lens group G1, by moving L9 along the optical axis towards the image side, focusing can be achieved from an infinite object to a nearby object. Nevertheless, focusing can also be performed by moving part or all of the optical system along the optical axis direction.

[0174] The following shows the specification values of the large aperture ratio ultra-wide angle lens related to Example 8.

[0175] Numerical Example 8 Unit: mm [Surface Data] [Aspherical Surface Data] [Various Data] [Variable Interval Data] [Lens Group Data] Group Starting Surface Focal Length G1 1 28.4098 G2 23 70.6349 [Convex Lens in the Second Lens Group G2 Satisfying Conditional Expression (16)]

[0176] [Example 9] Figure 41 It is the lens structure diagram of the large aperture ratio ultra-wide angle lens related to Example 9 when focused at infinity.

[0177] Figure 41 The large aperture ratio ultra-wide angle lens is composed of a first lens group G1 with positive refractive power, an aperture stop S, and a second lens group G2 with positive refractive power, which are arranged in sequence from the object side.

[0178] The first lens group G1 is composed of a concave meniscus lens component N1 composed of a concave meniscus lens L1 with its convex surface facing the object side, a concave meniscus lens component N2 composed of a concave meniscus lens L2 with its convex surface facing the object side, a cemented lens of a biconcave lens L3 and a biconvex lens L4, a biconcave lens L5, a biconcave lens L6, a cemented lens of a biconvex lens L7 and a concave meniscus lens L8 with its convex surface facing the image side, a convex meniscus lens L9 with its convex surface facing the object side, a biconvex aspherical lens L10, and a cemented lens of a biconcave lens L11 and a plano-convex lens L12 with its convex surface facing the object side.

[0179] The second lens group G2 is composed of a cemented lens of a biconvex lens L13 and a concave meniscus lens L14 with its convex surface facing the image side, arranged in order from the object side, a biconvex lens L15, a cemented lens of a concave meniscus lens L16 with its convex surface facing the object side and a biconvex lens L17, a cemented lens of a biconvex lens L18 and a biconcave lens L19, and a biconvex aspherical lens L20.

[0180] As an example of focusing, among the lenses constituting the first lens group G1, by moving L9 axially toward the image side, focusing can be achieved from an infinitely distant object to a nearby object. Nevertheless, focusing can also be performed by moving part or all of the optical system axially.

[0181] Hereinafter, the specification values of the large aperture ratio ultra-wide-angle lens according to Embodiment 9 are shown.

[0182] Numerical Example 9 Unit: mm [Surface Data] [Aspherical Surface Data] [Various Data] [Variable Interval Data] [Lens Group Data] Group Starting Surface Focal Length G1 1 128.6077 G2 23 48.8800 [Convex Lenses in the Second Lens Group G2 Satisfying Conditional Expression (16)]

[0183] [Embodiment 10] Figure 46 It is a lens structure diagram at infinity focus of the large aperture ratio ultra-wide-angle lens according to Embodiment 10.

[0184] Figure 46 The large aperture ratio ultra-wide-angle lens is composed of a first lens group G1 with negative refractive power, an aperture stop S, and a second lens group G2 with positive refractive power, arranged in order from the object side.

[0185] The first lens group G1 is composed of a concave meniscus lens component N1 consisting of a concave meniscus lens L1 with its convex surface facing the object side, arranged in order from the object side, a concave meniscus lens component N2 consisting of a concave meniscus lens L2 with its convex surface facing the object side, a cemented lens of a convex meniscus lens L3 with its convex surface facing the image side and a biconcave lens L4, a cemented lens of a biconcave lens L5 and a convex meniscus lens L6 with its convex surface facing the object side, a biconvex lens L7, a biconvex aspherical lens L8, and a cemented lens of a concave meniscus lens L9 with its convex surface facing the object side and a convex meniscus lens L10 with its convex surface facing the object side.

[0186] The second lens group G2 is composed of a convex meniscus lens L11 with its convex surface facing the image side, arranged in order from the object side, a cemented lens of a convex meniscus lens L12 with its convex surface facing the image side and a concave meniscus lens L13 with its convex surface facing the image side, a biconvex lens L14, a biconvex lens L15, a biconvex lens L16, a cemented lens of a biconvex lens L17 and a biconcave lens L18, and a biconvex aspherical lens L19.

[0187] As an example of focusing, among the lenses constituting the first lens group G1, by moving the lenses L7 to L10 as a unit along the optical axis toward the image side, focusing can be achieved from an infinitely distant object to a close object. Nevertheless, focusing can also be performed by moving a part or all of the optical system along the optical axis direction.

[0188] Hereinafter, the specification values of the large aperture ratio ultra-wide angle lens according to Embodiment 10 are shown.

[0189] Numerical Example 10 Unit: mm [Surface Data] [Aspherical Data] [Various Data] [Variable Interval Data] [Lens Group Data] Group Starting Surface Focal Length G1 1 -88.9270 G2 19 28.0433 [Convex Lenses in the Second Lens Group G2 Satisfying Conditional Expression (16)]

[0190] [Embodiment 11] Figure 51 It is a lens structure diagram when the large-aperture ratio ultra-wide-angle lens involved in Embodiment 11 is focused at infinity.

[0191] Figure 51 The large-aperture ratio ultra-wide-angle lens is composed of a first lens group G1 with negative refractive power, an aperture stop S, and a second lens group G2 with positive refractive power, which are arranged in sequence from the object side.

[0192] The first lens group G1 is composed of a meniscus lens component N1 consisting of a concave meniscus lens L1 with its convex surface facing the object side, a meniscus lens component N2 consisting of a concave meniscus lens L2 with its convex surface facing the object side, a cemented lens of a biconvex lens L3 and a biconcave lens L4, a cemented lens of a concave meniscus lens L5 with its convex surface facing the image side and a convex meniscus lens L6 with its convex surface facing the image side, a biconvex lens L7, a biconvex aspherical lens L8, and a concave meniscus lens L9 with its convex surface facing the object side.

[0193] The second lens group G2 is composed of a cemented lens of a biconvex lens L10 and a concave meniscus lens L11 with its convex surface facing the image side, a biconvex lens L12, a biconvex lens L13, a convex meniscus lens L14 with its convex surface facing the object side, a cemented lens of a biconvex lens L15 and a biconcave lens L16, and a biconvex aspherical lens L17.

[0194] As an example of focusing, among the lenses constituting the first lens group G1, by moving the lenses L7 to L9 as a unit along the optical axis toward the image side, focusing can be achieved from an infinite object to a near object. Nevertheless, focusing can also be performed by moving part or all of the optical system along the optical axis direction.

[0195] Hereinafter, the specification values of the large-aperture ratio ultra-wide-angle lens involved in Embodiment 11 are shown.

[0196] Numerical Example 11 Unit: mm [Surface Data] [Aspherical Data] [Various Data] [Variable Interval Data] [Lens Group Data] Group Starting Surface Focal Length G1 1 -40.3001 G2 18 25.0935 [Convex lens within the second lens group G2 that satisfies conditional expression (16)]

[0197] [Example 12] Figure 56 It is the lens structure diagram during infinity focusing of the large aperture ratio ultra-wide angle lens related to Example 12.

[0198] Figure 56 The large aperture ratio ultra-wide angle lens is composed of a first lens group G1 with negative refractive power, an aperture stop S, and a second lens group G2 with positive refractive power, which are arranged in sequence from the object side.

[0199] The first lens group G1 is composed of a concave meniscus lens component N1 composed of a concave meniscus lens L1 with its convex surface facing the object side, arranged in sequence from the object side, a concave meniscus lens component N2 composed of a concave meniscus lens L2 with its convex surface facing the object side, a cemented lens of a convex meniscus lens L3 with its convex surface facing the image side and a biconcave lens L4, a biconcave lens L5, a cemented lens of a biconvex lens L6 and a biconcave lens L7, a convex meniscus lens L8 with its convex surface facing the object side, a biconvex aspherical lens L9, and a cemented lens of a biconcave lens L10 and a biconvex lens L11.

[0200] The second lens group G2 is composed of a cemented lens of a biconvex lens L12 and a convex meniscus lens L13 with its convex surface facing the image side, arranged in sequence from the object side, a convex meniscus lens L14 with its convex surface facing the object side, a cemented lens of a concave meniscus lens L15 with its convex surface facing the object side and a biconvex lens L16, a cemented lens of a biconvex lens L17 and a biconcave lens L18, and a biconvex aspherical lens L19.

[0201] As an example of focusing, among the lenses constituting the first lens group G1, by moving L8 axially towards the image side, focusing can be achieved from an infinite object to a close object. Nevertheless, focusing can also be performed by moving part or all of the optical system axially along the optical axis.

[0202] Hereinafter, the specification values of the large aperture ratio ultra-wide angle lens related to Example 12 are shown.

[0203] Numerical Example 12 Unit: mm [Surface data] [Aspherical data] [All kinds of data] [Variable interval data] [Lens group data] Group starting surface Focal length G1 1 -134.6293 G2 21 40.8737 [Convex lens within the second lens group G2 that satisfies conditional expression (16)]

[0204] [Example 13] Figure 61 It is a lens structure diagram at infinity focus of a large aperture ratio ultra-wide angle lens related to Example 13.

[0205] Figure 61 The large aperture ratio ultra-wide angle lens is composed of a first lens group G1 with positive refractive power, an aperture stop S, and a second lens group G2 with positive refractive power, which are arranged in sequence from the object side.

[0206] The first lens group G1 is composed of a concave meniscus lens component N1 composed of a concave meniscus lens L1 with its convex surface facing the object side, a concave meniscus lens component N2 composed of a concave meniscus lens L2 with its convex surface facing the object side, a convex meniscus lens L3 with its convex surface facing the image side, a double concave lens L4, a double concave lens L5, a cemented lens of a double convex lens L6, a double convex lens L7, and a convex meniscus aspherical lens L8 with its convex surface facing the object side.

[0207] The second lens group G2 is composed of a cemented lens of a convex meniscus lens L9 with its convex surface facing the image side and a concave meniscus lens L10 with its convex surface facing the image side, a convex meniscus lens L11 with its convex surface facing the object side, a cemented lens of a concave meniscus lens L12 with its convex surface facing the object side and a double convex lens L13, a cemented lens of a double convex lens L14 and a double concave lens L15, and a double convex aspherical lens L16.

[0208] As an example of focusing, among the lenses constituting the first lens group G1, by moving the lenses L7 to L8 as a unit along the optical axis toward the image side, focusing can be performed from an infinite object to a near object. Nevertheless, focusing can also be achieved by moving a part or all of the optical system along the optical axis direction.

[0209] The following shows the specification values of the large aperture ratio ultra-wide angle lens related to Embodiment 13.

[0210] Numerical Example 13 Unit: mm [Surface Data] [Aspherical Data] [Various Data] [Variable Interval Data] [Lens Group Data] Group Starting Surface Focal Length G1 1 31.8976 G2 17 30.5733 [Convex lens in the second lens group G2 that satisfies conditional expression (16)]

[0211] [Embodiment 14] Figure 66 It is the lens structure diagram of the large aperture ratio ultra-wide angle lens related to Embodiment 14 when focused at infinity.

[0212] Figure 66 The large aperture ratio ultra-wide angle lens is composed of a first lens group G1 with negative refractive power, an aperture stop S, and a second lens group G2 with positive refractive power, which are arranged in sequence from the object side.

[0213] The first lens group G1 is composed of a concave meniscus lens component N1 composed of a concave meniscus lens L1 with its convex surface facing the object side, a concave meniscus lens component N2 composed of a concave meniscus lens L2 with its convex surface facing the object side, a cemented lens of a biconvex lens L3 and a biconcave lens L4, a biconcave lens L5, a cemented lens of a convex meniscus lens L6 with its convex surface facing the object side and a concave meniscus lens L7 with its convex surface facing the object side, a convex meniscus lens L8 with its convex surface facing the object side, a biconvex aspherical lens L9, and a cemented lens of a biconcave lens L10 and a biconvex lens L11, which are arranged in sequence from the object side.

[0214] The second lens group G2 is composed of a cemented lens of a biconvex lens L12 and a concave meniscus lens L13 with its convex surface facing the image side, arranged in order from the object side, a biconvex lens L14, a concave meniscus lens L15 with its convex surface facing the object side and a convex meniscus lens L16 with its convex surface facing the object side, a biconvex lens L17, a cemented lens of a biconvex lens L18 and a biconcave lens L19, and a biconvex aspherical lens L20.

[0215] As an example of focusing, among the lenses constituting the first lens group G1, by moving L8 along the optical axis toward the image side, focusing can be performed from an infinitely distant object to a nearby object. Nevertheless, focusing can also be performed by moving a part or all of the optical system in the optical axis direction.

[0216] Hereinafter, the specification values of the large aperture ratio ultra-wide angle lens according to Embodiment 14 are shown.

[0217] Numerical Example 14 Unit: mm [Surface Data] [Aspherical Data] [Various Data] [Variable Interval Data] [Lens Group Data] Group Starting Surface Focal Length G1 1 -190.0438 G2 21 46.1252 [Convex Lenses in the Second Lens Group G2 Satisfying Conditional Expression (16)]

[0218] Moreover, a list of the corresponding values of the conditional expressions in these respective embodiments is shown.

[0219] [Conditional Expression Corresponding Values] [Table 1] Conditional EX1 EX2 EX3 EX4 EX5 EX6 EX7 EX8 EX9 EX10 EX11 EX12 EX13 EX14 (1) 2ω 185.73 185.73 185.73 185.73 185.73 185.73 202.00 185.73 185.73 185.73 202.00 185.73 185.73 185.73 (2) Fno 1.26 1.03 1.46 1.26 1.26 1.26 1.26 1.46 1.46 1.26 1.26 1.46 1.26 1.58 (3) N10Ah / i0Ah -2.62 -2.99 -1.82 -3.03 -3.13 -2.10 -3.02 -1.81 -1.84 -2.53 -3.32 -1.71 -2.36 -1.30 (4) SagN1 / SagN2 1.307 1.106 0.905 1.706 1.309 0.90 1.546 1.348 1.186 1.253 1.227 0.850 1.372 1.674 (5) fN1 / fN2 3.45 2.74 3.87 2.31 1.57 3.81 3.90 0.82 1.88 1.02 4.18 3.07 2.06 1.07 (6) N1SF 3.44 3.53 3.17 2.57 2.24 3.92 3.99 1.88 2.60 2.28 4.19 2.86 2.68 1.87 (7) N2SF 1.98 2.40 1.72 2.11 2.59 1.72 1.91 2.87 1.78 3.55 2.07 2.19 2.42 1.98 (8) N1SF / N2SF 1.74 1.47 1.84 1.22 0.86 2.28 2.08 0.65 1.47 0.64 2.03 1.30 1.11 0.94 (9) PLOAN1 / FLAN1 2.80 2.95 2.94 3.84 2.11 2.54 2.76 4.04 3.11 3.61 2.79 2.99 4.09 3.83 (10) PLOAN1 / PLOAN2 1.07 1.02 0.79 1.02 2.45 0.69 1.04 1.97 1.09 1.94 0.88 0.94 1.38 1.75 (11) ndLP1 1.946 1.946 1.986 1.946 1.893 1.946 1.946 1.946 1.946 1.946 1.946 1.870 1.946 1.664 (12) vdLP1 17.98 17.98 16.48 17.98 20.36 17.98 17.98 17.98 17.98 17.98 17.98 20.02 17.98 27.35 (13) ΔPgFLP1 0.0385 0.0385 0.0468 0.0385 0.0276 0.0385 0.0385 0.0385 0.0385 0.0385 0.0385 0.031 0.0385 0.0327 (14) f / f1 -0.073 -0.107 -0.139 -0.078 -0.077 0.012 0.104 0.546 0.121 -0.092 -0.191 -0.115 0.256 -0.082 (15) f2 / f1 -0.25 -0.39 -0.37 -0.27 -0.27 0.03 -0.38 2.49 0.38 -0.32 -0.62 -0.30 0.96 -0.24 (17) G2LPAve 0.0346 0.0366 0.0382 0.0329 0.0324 0.0404 0.0346 0.00173 0.0099 0.0346 0.0266 0.0293 0.0354 0.0361 (18) ndN1n 1.85 1.95 1.88 1.88 1.87 1.95 1.95 1.95 2.00 1.95 1.95 1.88 1.87 2.05 (19) LT / BF 6.746 7.723 8.601 6.846 6.977 7.062 6.886 6.253 6.455 6.521 6.061 6.154 5.384 7.494 (20) |LT / i0Ah| 9.90 11.34 6.85 10.05 10.30 6.58 10.82 6.36 6.49 9.73 9.98 5.66 7.90 6.21

[0220] Moreover, the present technology can also adopt the following structure. [Item 1] A large aperture ratio ultra-wide angle lens, characterized in that It is composed of a first lens group G1, an aperture stop S, and a second lens group G2 arranged in sequence from the object side. The first lens group G1 is provided with a concave meniscus lens component N1 with a convex surface facing the object side at the position closest to the object side. The first lens group G1 has a concave meniscus lens component N2 with a convex surface facing the object side at a position closer to the image side than the concave meniscus lens component N1, and satisfies the following conditional expressions (1) to (4). (1) 2ω ≥ 160.0° (2) Fno < 1.9 (3) -6.0 < N1OAh / iOAh < -1.1 (4) 0.50 < SagN1 / SagN2 < 1.80 ω: Half field angle at infinity focus Fno: F - number at infinity focus N1OAh: Off - axis principal ray height when a ray with an object - side incident angle of 90° is incident on the concave meniscus lens component N1 at infinity focus (where, when 2ω < 180°, it is the off - axis principal ray height with an object - side incident angle of ω) iOAh: Imaging height of the off - axis principal ray when a ray with an object - side incident angle of 90° forms an image on the image plane at infinity focus (where, when 2ω < 180°, it is the imaging height of the off - axis principal ray with an object - side incident angle of ω) SagN1: Depression amount of the concave meniscus lens component N1 with respect to the vertex of the surface on the image side (the ray height used for calculating the depression amount is the off - axis principal ray height when a ray with an object - side incident angle of 90° exits from this surface at infinity focus. And when 2ω < 180°, it is calculated using the off - axis principal ray height with an object - side incident angle of ω) SagN2: Depression amount of the concave meniscus lens component N2 with respect to the vertex of the surface on the image side (the ray height used for calculating the depression amount is the off - axis principal ray height when a ray with an object - side incident angle of 90° exits from this surface at infinity focus. And when 2ω < 180°, it is calculated using the off - axis principal ray height with an object - side incident angle of ω) [Item 2] The large - aperture ratio ultra - wide - angle lens according to [Item 1], characterized in that It satisfies the following conditional expression (5). (5) 0.4 < fN1 / fN2 < 5.0 fN1: Focal length of the concave meniscus lens component N1 fN2: Focal length of the concave meniscus lens component N2 [Item 3] The large-aperture ratio ultra-wide-angle lens according to [Item 1] or [Item 2], characterized in that The concave meniscus lens component N1 satisfies the following conditional expression (6). (6) 1.5 < N1SF < 6.0 N1SF = (N1R1 + N1R2) / (N1R1 - N1R2) N1R1: The radius of curvature of the surface on the object side of the concave meniscus lens component N1 N1R2: The radius of curvature of the surface on the image side of the concave meniscus lens component N1 [Item 4] The large-aperture ratio ultra-wide-angle lens according to any one of [Item 1] to [Item 3], characterized in that the concave meniscus lens component N2 satisfies the following conditional expression (7). (7) 1.2 < N2SF < 5.0 N2SF = (N2R1 + N2R2) / (N2R1 - N2R2) N2R1: The radius of curvature of the surface on the object side of the concave meniscus lens component N2 N2R2: The radius of curvature of the surface on the image side of the concave meniscus lens component N2 [Item 5] The large-aperture ratio ultra-wide-angle lens according to any one of [Item 1] to [Item 4], characterized in that The concave meniscus lens component N1 and the concave meniscus lens component N2 satisfy the following conditional expression (8). (8) 0.4 < N1SF / N2SF < 3.0 N1SF = (N1R1 + N1R2) / (N1R1 - N1R2) N1R1: The radius of curvature of the surface on the object side of the concave meniscus lens component N1 N1R2: The radius of curvature of the surface on the image side of the concave meniscus lens component N1 N2SF = (N2R1 + N2R2) / (N2R1 - N2R2) N2R1: The radius of curvature of the surface on the object side of the concave meniscus lens component N2 N2R2: The radius of curvature of the surface on the image side of the concave meniscus lens component N2 [Item 6] The large-aperture ratio ultra-wide-angle lens according to any one of [Item 1] to [Item 5], characterized in that the concave meniscus lens component N1 satisfies the following conditional expression (9). (9) 1.8 < PLOAN1 / PLAN1 < 5.0 PLOAN1: The distance that the chief off-axis ray passes through the concave meniscus lens component N1 when the off-axis ray is defined as the ray with an object-side incident angle of 90° at infinite focus (where, when 2ω < 180°, the ray with an object-side incident angle of ω is defined as the off-axis ray) PLAN1: The thickness of the concave meniscus lens component N1 on the optical axis [Item 7] The large-aperture ratio ultra-wide-angle lens according to any one of [Item 1] to [Item 6], characterized in that The concave meniscus lens component N1 and the concave meniscus lens component N2 satisfy the following conditional expression (10). (10) 0.3 < PLOAN1 / PLOAN2 < 3.5 PLOAN1: The distance that the chief off-axis ray passes through the concave meniscus lens component N1 when the off-axis ray is defined as the ray with an object-side incident angle of 90° at infinite focus (where, when 2ω < 180°, the ray with an object-side incident angle of ω is defined as the off-axis ray) PLOAN2: The distance that the chief off-axis ray passes through the concave meniscus lens component N2 when the off-axis ray is defined as the ray with an object-side incident angle of 90° at infinite focus (where, when 2ω < 180°, the ray with an object-side incident angle of ω is defined as the off-axis ray) [Item 8] The large-aperture ratio ultra-wide-angle lens according to any one of [Item 1] to [Item 7], characterized in that the second lens group G2 has a convex lens LP1 that satisfies the following conditional expressions (11) to (13). (11) 1.60 < ndLP1 (12) vdLP1 < 35.0 (13) 0.018 < ΔPgFLP1 ndLP1: The refractive index of the convex lens LP1 vdLP1: The Abbe number of the convex lens LP1 ΔPgFLP1: The anomalous dispersion of the convex lens LP1 [Item 9] The large-aperture ratio ultra-wide-angle lens according to any one of [Item 1] to [Item 8], characterized in that the first lens group G1 has a negative refractive power and satisfies the following conditional expression (14). (14) -0.40 < f / f1 < 0.70 f: The focal length of the large-aperture ratio ultra-wide-angle lens at infinite focus f1: The focal length of the first lens group G1 at infinite focus [Item 10] The large-aperture ratio ultra-wide-angle lens according to any one of [Item 1] to [Item 9], wherein the second lens group G2 has a positive refractive power and satisfies the following conditional expression (15). (15) -0.8 < f2 / f1 < 2.7 f1: Focal length of the first lens group G1 when focused at infinity f2: Focal length of the second lens group G2 when focused at infinity [Item 11] The large-aperture ratio ultra-wide-angle lens according to any one of [Item 1] to [Item 10], wherein the second lens group G2 has at least one convex lens satisfying the following conditional expression (16) and satisfies the following conditional expression (17). (16) 0.3 < G2LPAXh / G2LPOAh < 2.7 (17) 0.004 < G2LPAve G2LPAXh: Height of the on-axis marginal ray incident on the convex lens when focused at infinity with the aperture open G2LPOAh: Height of the off-axis chief ray when a ray with an object-side incident angle of 90° is incident on the convex lens when focused at infinity (wherein, when 2ω < 180°, it is the height of the off-axis chief ray incident with an object-side incident angle of ω) G2LPAve: Average value of the anomalous dispersion of the convex lens satisfying conditional expression (16) [Item 12] The large-aperture ratio ultra-wide-angle lens according to any one of [Item 1] to [Item 11], wherein the concave meniscus lens component N1 includes a concave lens satisfying conditional expression (18). (18) 1.7 < ndN1n ndN1n: Refractive index of the concave lens included in the concave meniscus lens component N1 [Item 13] The large-aperture ratio ultra-wide-angle lens according to any one of [Item 1] to [Item 12], wherein the following conditional expression (19) is satisfied. (19) 5.00 < LT / BF < 12.00 LT: Distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side when focused at infinity BF: Distance on the optical axis from the lens surface closest to the image side to the image plane when focused at infinity [Item 14] The large-aperture ratio ultra-wide-angle lens according to any one of [Item 1] to [Item 13], characterized in that The following conditional formula (20) is satisfied. (20) 2.5 < |LT / iOAh| < 18.0 LT: The distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side when focused at infinity iOAh: The image height of the chief ray off-axis when a ray with an object-side incident angle of 90° forms an image on the image plane when focused at infinity (where, when 2ω < 180°, it is the image height of the chief ray off-axis incident with an object-side incident angle of ω) [Item 15] The large-aperture ratio ultra-wide-angle lens according to any one of [Item 1] to [Item 14], characterized in that The concave meniscus lens component N2 is the concave meniscus lens component with its convex surface facing the object side and is the second concave meniscus lens component with its convex surface facing the object side arranged starting from the concave meniscus lens component closest to the object side. [Item 16] The large-aperture ratio ultra-wide-angle lens according to any one of [Item 1] to [Item 15], characterized in that The concave meniscus lens component N1 and the concave meniscus lens component N2 are arranged continuously starting from the position closest to the object side. [Item 17] The large-aperture ratio ultra-wide-angle lens according to any one of [Item 1] to [Item 16], characterized in that The concave meniscus lens component N1 and the concave meniscus lens component N2 are composed of spherical lenses. [Item 18] The large-aperture ratio ultra-wide-angle lens according to any one of [Item 1] to [Item 17], characterized in that Part or all of the optical system is moved in the optical axis direction to perform focusing from infinity to a nearby object.

[0221] The description of the above embodiments has described an example of the large-aperture ratio ultra-wide-angle lens of the present invention. The present invention is not limited to these embodiments within the scope of not departing from its gist. Various design changes, modified implementations, combinations, and sub-combinations are all included within the equivalent scope of the present invention. Symbol Explanation

[0222] G1 - the first lens group, G2 - the second lens group, S - the aperture stop, N1 - a concave meniscus component, N2 - a concave meniscus component, LP1 - a convex lens, F - a filter, I - the image plane.

Claims

1. A large aperture ratio ultra-wide angle lens, characterized in that: The lens comprises a first lens group (G1), an aperture stop (S), and a second lens group (G2) which are arranged in order from the object side, wherein the first lens group (G1) is provided with a concave meniscus lens component (N1) with a convex surface facing the object side at a position closest to the object side, and the first lens group (G1) has a concave meniscus lens component (N2) with a convex surface facing the object side at a position closer to the image side than the concave meniscus lens component (N1), and the large aperture ratio ultra wide angle lens satisfies the following conditional expressions (1) to (4), (1) 2ω ≥ 160.0° (2) Fno<1.9 (3) -6.0<N1OAh / iOAh<-1.1 (4) 0.50<SagN1 / SagN2<1.80 ω is the half field of view when focusing at infinity, Fno is the F value when focusing at infinity. N1OAh is the off-axis principal ray height when light with an incident angle of 90° on the object side is incident on the concave meniscus lens component (N1) when focusing at infinity, wherein, in the case of 2ω<180°, it is the off-axis principal ray height incident at the object side incident angle ω, iOAh is the imaging height of the off-axis principal ray when the light with an incident angle of 90° on the object side is imaged on the image plane when focusing at infinity, wherein, in the case of 2ω<180°, it is the imaging height of the off-axis principal ray incident at the incident angle ω on the object side, SagN1 is the amount of depression of the concave meniscus lens component (N1) relative to the surface vertex of the image side surface, SagN2 is the amount of concavity of the concave meniscus lens component (N2) relative to the surface vertex of the image side surface.

2. The large aperture ratio ultra-wide angle lens according to claim 1, characterized in that: The following condition (5) is satisfied: (5)0.4<fN1 / fN2<5.0 fN1 is the focal length of the concave meniscus lens component (N1), fN2 is the focal length of the concave meniscus lens component (N2).

3. The large aperture ratio ultra-wide angle lens according to claim 1, characterized in that: The concave meniscus lens component (N1) satisfies the following conditional formula (6): (6) 1.5<N1SF<6.0 N1SF=(N1R1+N1R2) / (N1R1-N1R2) N1R1 is the radius of curvature of the surface on the object side of the concave meniscus lens component (N1), N1R2 is the radius of curvature of the image-side surface of the concave meniscus lens component (N1).

4. The large aperture ratio ultra-wide angle lens according to claim 1, characterized in that: The concave meniscus lens component (N2) satisfies the following conditional formula (7), (7) 1.2<N2SF<5.0 N2SF=(N2R1+N2R2) / (N2R1-N2R2) N2R1 is the radius of curvature of the surface on the object side of the concave meniscus lens component (N2), N2R2 is the radius of curvature of the image-side surface of the concave meniscus lens component (N2).

5. The large aperture ratio ultra-wide angle lens according to claim 1, characterized in that: The concave meniscus lens component (N1) and the concave meniscus lens component (N2) satisfy the following conditional formula (8), (8) 0.4<N1SF / N2SF<3.0 N1SF=(N1R1+N1R2) / (N1R1-N1R2) N1R1 is the radius of curvature of the surface on the object side of the concave meniscus lens component (N1), N1R2 is the radius of curvature of the image-side surface of the concave meniscus lens component (N1), N2SF=(N2R1+N2R2) / (N2R1-N2R2) N2R1 is the radius of curvature of the surface on the object side of the concave meniscus lens component (N2), N2R2 is the radius of curvature of the image-side surface of the concave meniscus lens component (N2).

6. The large aperture ratio ultra-wide angle lens according to claim 1, characterized in that: The concave meniscus lens component (N1) satisfies the following conditional formula (9): (9)1.8<PLOAN1 / PLAN1<5.0 PLOAN1 is the distance of the off-axis principal ray passing through the concave meniscus lens component (N1) when the ray with an incident angle of 90° on the object side during infinity focus is set as an off-axis ray, wherein when 2ω<180°, the ray incident at the object side incident angle ω is set as an off-axis ray, PLAN1 is the thickness of the concave meniscus lens component (N1) on the optical axis.

7. The large aperture ratio ultra-wide angle lens according to claim 1, characterized in that: The concave meniscus lens component (N1) and the concave meniscus lens component (N2) satisfy the following conditional formula (10): (10) 0.3<PLOAN1 / PLOAN2<3.5 PLOAN1 is the distance of the off-axis principal ray passing through the concave meniscus lens component (N1) when the ray with an incident angle of 90° on the object side during infinity focus is set as an off-axis ray, wherein when 2ω<180°, the ray incident at the object side incident angle ω is set as an off-axis ray, PLOAN2 is the distance of the off-axis principal ray passing through the concave meniscus lens component (N2) when the ray with an incident angle of 90° on the object side during infinity focus is set as an off-axis ray, wherein when 2ω<180°, the ray incident at an incident angle ω on the object side is set as an off-axis ray.

8. The large aperture ratio ultra-wide angle lens according to claim 1, characterized in that: The second lens group (G2) includes a convex lens (LP1) satisfying the following conditional expressions (11) to (13), (11)1.60<ndLP1 (12)vdLP1<35.0 (13) 0.018<ΔPgFLP1 ndLP1 is the refractive index of the convex lens (LP1), vdLP1 is the Abbe number of the convex lens (LP1), ΔPgFLP1 is the anomalous dispersion of the convex lens (LP1).

9. The large aperture ratio ultra-wide angle lens according to claim 1, characterized in that: The first lens group (G1) has negative refractive power and satisfies the following conditional formula (14): (14) -0.40<f / f1<0.70 f is the focal length of the large aperture ratio ultra wide angle lens when focusing at infinity, f1 is the focal length of the first lens group (G1) when focusing at infinity.

10. The large aperture ratio ultra-wide angle lens according to claim 1, characterized in that: The second lens group (G2) has positive refractive power and satisfies the following conditional formula (15): (15) -0.8<f2 / f1<2.7 f1 is the focal length of the first lens group (G1) when focusing at infinity, f2 is the focal length of the second lens group (G2) when focusing at infinity.

11. The large aperture ratio ultra-wide angle lens according to claim 1, characterized in that: The second lens group (G2) has at least one convex lens satisfying the following conditional formula (16) and the following conditional formula (17). (16)0.3<G2LPAXh / G2LPOAh<2.7 (17) 0.004<G2LPAve G2LPAXh is the height of the on-axis marginal ray incident on the convex lens when the aperture is open and the focus is infinite. G2LPOAh is the off-axis chief ray height when the light with an incident angle of 90° on the object side is incident on the convex lens when focusing at infinity, wherein, in the case of 2ω<180°, it is the off-axis chief ray height incident at the incident angle ω on the object side, G2LPAve is the average value of the anomalous dispersion of the convex lens that satisfies conditional expression (16).

12. The large aperture ratio ultra-wide angle lens according to claim 1, characterized in that: The concave meniscus lens component (N1) includes a concave lens satisfying the following conditional formula (18): (18)1.7<ndN1n ndN1n is the refractive index of the concave lens included in the concave meniscus lens component (N1).

13. The large aperture ratio ultra-wide angle lens according to claim 1, characterized in that: The following condition (19) is satisfied: (19)5.00<LT / BF<12.00 LT is the distance on the optical axis from the lens surface closest to the object to the lens surface closest to the image when focusing at infinity. BF is the distance on the optical axis from the lens surface closest to the image side to the image plane when focusing at infinity.

14. The large aperture ratio ultra-wide angle lens according to claim 1, characterized in that: The following condition (20) is satisfied: (20)2.5<|LT / iOAh|<18.0 LT is the distance on the optical axis from the lens surface closest to the object to the lens surface closest to the image when focusing at infinity. iOAh is the imaging height of the off-axis principal ray when the light with an incident angle of 90° on the object side is imaged on the image plane when focusing at infinity, wherein, when 2ω<180°, it is the imaging height of the off-axis principal ray incident at the object side angle ω.

15. The large aperture ratio ultra-wide angle lens according to claim 1, characterized in that: The concave meniscus lens component (N2) is a concave meniscus lens component with a convex surface facing the object side, which is arranged second from the concave meniscus lens component closest to the object side among the concave meniscus lens components with a convex surface facing the object side.

16. The large aperture ratio ultra-wide angle lens according to claim 1, characterized in that: The concave meniscus lens component (N1) and the concave meniscus lens component (N2) are arranged continuously from the position closest to the object side.

17. The large aperture ratio ultra-wide angle lens according to claim 1, characterized in that: The concave meniscus lens component (N1) and the concave meniscus lens component (N2) are composed of spherical lenses.

18. The large aperture ratio ultra-wide angle lens according to claim 1, characterized in that: Move part or all of the optical system along the optical axis to focus from infinity to close objects.

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