Large-aperture ultra wide-angle lens

Abstract

To provide a large-aperture ultra wide-angle lens which is reduced in size and weight, features a half view angle of 80 degrees or more and a bright F-number of approximately 1.8 or less, ensures a sufficient image circle, and offers good optical performance from the screen center to the periphery.SOLUTION: A large-aperture ultra wide-angle lens of the present invention comprises 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 comprises a concave meniscus lens component N1 with a convex surface facing the object side located on the most object side, and a concave meniscus lens component N2 with a convex surface facing the object side located on the image side of the concave meniscus lens component N1. The large-aperture ultra wide-angle lens satisfies predetermined conditional expressions.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In recent years, with the progress of mirrorless digital cameras and video cameras, and at the same time, high-performance cameras have been installed in smartphones and mobile data terminals. Therefore, in order to differentiate digital cameras from these mobile devices, models equipped with large sensors of 35mm full-size format or more have become mainstream. Similarly, in the photographing optical systems used in imaging devices, the demand for large-aperture ratio ultra-wide-angle lenses with bright F-values is increasing in order to differentiate from smartphones and the like.

[0003] In addition, in recent years, digital cameras and video cameras have further advanced in the high pixel count of image sensors, and the demand for higher performance in photographing optical systems has increased even more.

[0004] Patent Document 1 and Patent Document 2 describe examples of large-aperture ratio ultra-wide-angle lenses having a maximum angle of view of approximately 160 degrees or more and an F-value of about 1.8 or less.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Ultra-wide-angle lenses with a maximum drawing angle of approximately 160 degrees or more often adopt a retrofocus type lens configuration, and often have a configuration in which a concave meniscus lens with a convex surface facing the object side is arranged on the object side most. In such an optical system, the concave meniscus lens arranged on the object side most often has a concave surface with a large eccentricity ratio and close to a hemisphere, and may reach 50% or more of the total lens weight of the entire optical system. When the F value is reduced, the lens diameter increases, and the weight of the optical system increases rapidly. When aiming for a large aperture ratio, it is important to realize high performance while preventing the lens from becoming bulky.

[0007] Patent Document 1 includes an example of a bright large aperture ratio ultra-wide-angle lens with a maximum drawing angle of 160 degrees or more and an F value of 1.6 or less. The large aperture ratio ultra-wide-angle lens described in Patent Document 1 has high optical performance, but has a small image circle, and is a very large optical system from the perspective of the size of the optical system with respect to the image circle, and has problems in terms of miniaturization.

[0008] Patent Document 2 includes an example of a large aperture ratio ultra-wide-angle lens with an F value of about 1.8 and is bright, but has a large magnification chromatic aberration from a low image height and is insufficient in terms of high performance. In addition, since the back focus is long, it is an optical system that does not take advantage of the short flange back due to the recent mirrorless trend, and there is still room for improvement in terms of miniaturization of the optical system.

[0009] The present invention has been made in view of the above problems, and aims to provide a large aperture ratio ultra-wide-angle lens that realizes miniaturization and weight reduction, has a semi-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 screen.

Means for Solving the Problems

[0010] The large-aperture ratio ultra-wide-angle lens according to the present invention is composed of a first lens group G1, an aperture stop S, and a second lens group G2 in order from the object side. The first lens group G1 has a concave meniscus lens component N1 with a convex surface facing the object side arranged on the most object side, and has a concave meniscus lens component N2 with a convex surface facing the object side on the image side of the concave meniscus lens component N1, and is characterized by satisfying 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 chief 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 (however, when 2ω < 180°, the off-axis chief ray height incident at the object-side incident angle ω) iOAh: Image 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 at infinity focus (however, when 2ω < 180°, the image height of the off-axis chief ray incident at the object-side incident angle ω) SagN1: Sag amount from the vertex of the image-side surface of the concave meniscus lens component N1 (the ray height for calculating the sag amount uses the off-axis chief ray height when a ray with an object-side incident angle of 90° exits from the surface at infinity focus. Also, when 2ω < 180°, it is calculated using the off-axis chief ray height incident at the object-side incident angle ω) SagN2: Sag amount from the vertex of the image-side surface of the concave meniscus lens component N2 (the ray height for calculating the sag amount uses the off-axis chief ray height when a ray with an object-side incident angle of 90° exits from the surface at infinity focus. Also, when 2ω < 180°, it is calculated using the off-axis chief ray height incident at the object-side incident angle ω)

Effect of the Invention

[0011] According to the present invention, it is possible to provide a large-aperture ratio ultra-wide-angle lens that has a half angle of view 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 screen while achieving miniaturization and weight reduction.

Brief Description of the Drawings

[0012] Although the distortion aberration amount is illustrated in the longitudinal aberration diagrams at infinity focus of each embodiment, in any of the first to fourteenth embodiments, the ideal image height was defined based on the definition formula of equi-solid angle projection, and the distortion aberration was calculated. Further, the lateral aberration diagrams show aberration diagrams when light rays at the angles of view of 0%, 3%, 5%, 7%, 9%, and 10% of the maximum angle of view are incident respectively. Note that the object distance described below refers to the distance from the subject to the first surface on the object side of the lens.

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Embodiments for Carrying Out the Invention

[0013] The lens component defined in the present invention refers to a single lens or a cemented lens formed by joining a plurality of single lenses. Therefore, the concave meniscus lens component refers to a concave meniscus lens composed of a single lens or a cemented lens formed by joining a plurality of single lenses and having a negative refractive power as a whole and a concave meniscus shape.

[0014] In addition, the meniscus that defines the shape of the lens in the present invention refers to a curved surface in which the object-side and image-side surfaces have 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 object-side and image-side surfaces are both positive, and the radius of curvature of the image-side surface is smaller. In the case of an aspherical lens, the lens shape is determined by the paraxial radius of curvature.

[0015] In addition, when counting the number of lenses in the present invention, unless otherwise specified, a single lens is counted as 1, and in the case of a cemented lens, each single lens constituting it is counted as 1. For example, a cemented lens composed of a convex lens and a concave lens is counted as 2.

[0016] In addition, when counting lens components in the present invention, both a lens component composed of a single lens and a lens component composed of a cemented lens are counted as 1. For example, a lens component composed of a single lens is counted as 1 as a lens component, and a cemented lens composed of one convex lens and one concave lens is counted as 1 as a lens component.

[0017] As can be seen from each numerical example and the lens configuration diagrams of each example, the large aperture ratio ultra-wide angle lens of the present invention is composed of a first lens group G1, an aperture stop S, and a second lens group G2 in order from the object side. On the most object side of the first lens group G1, a concave meniscus lens component N1 with a convex surface facing the object side is arranged. On the image side of the concave meniscus lens component N1, it has a configuration having a concave meniscus lens component N2 with a stronger negative refractive power than 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 an overall angle of view 2ω of 160° or more. Generally, in an ultra-wide angle lens with an overall angle of view 2ω of 160° or more, a retrofocus type lens configuration is often adopted. On the most object side, there is often arranged a concave meniscus lens with a convex surface facing the object side and a concave surface that is significantly smaller in the radius of curvature of the image side surface than that of the object side surface and is close to a hemisphere with a large decentration ratio. The above-mentioned concave meniscus lens has the effect of greatly bending the off-axis light rays incident from the object side and reducing the ray height of the off-axis light rays. Also, a lens with an angle of view of 2ω of 160° or more is often a fish-eye lens. In a fish-eye lens, the decentration ratio of the concave meniscus lens on the most object side tends to be larger than that of a general wide-angle lens. This is because in the case of a fish-eye lens, there is no need to correct negative distortion (here, the meaning of distortion refers to the case where the ideal image height is defined by central projection). Therefore, even if the radius of curvature of the image side surface is made significantly smaller than that of the object side to strengthen the negative refractive power, there are few adverse effects and it is possible to miniaturize the optical system.

[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 value of less than 1.9 and an overall angle of view 2ω of 160° or more. In such an optical system, the concave meniscus lens arranged on the most object side may reach 50% or more of the total lens weight of the entire optical system. It becomes important how to achieve high performance while preventing the enlargement of the lens.

[0020] 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, it is desirable to satisfy the following conditional expressions (1) to (4). (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 chief ray height when a ray with an object-side incident angle of 90° enters the concave meniscus lens component N1 at infinity focus (however, when 2ω < 180°, the off-axis chief ray height when incident at the object-side incident angle ω) iOAh: Image 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 at infinity focus (however, when 2ω < 180°, the image height of the off-axis chief ray when incident at the object-side incident angle ω) SagN1: Sag amount from the vertex of the image-side surface of the concave meniscus lens component N1 (the ray height for calculating the sag amount uses the off-axis chief ray height when a ray with an object-side incident angle of 90° exits from the surface at infinity focus. Also, when 2ω < 180°, it is calculated using the off-axis chief ray height when incident at the object-side incident angle ω) SagN2: Sag amount from the vertex of the image-side surface of the concave meniscus lens component N2 (the ray height for calculating the sag amount uses the off-axis chief ray height when a ray with an object-side incident angle of 90° exits from the surface at infinity focus. Also, when 2ω < 180°, it is calculated using the off-axis chief ray height when incident at the object-side incident angle ω)

[0021] Conditional expressions (1) and (2) respectively define the full field angle and F-number at infinity 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 at infinity focus of the large aperture ratio ultra-wide angle lens. Also, by satisfying conditional expression (2), a sufficient F-number can be obtained at infinity focus of the large aperture ratio ultra-wide angle lens.

[0022] For the conditional expression (1), it is desirable that the lower limit value be 180°, and for the conditional expression (2), it is desirable that the upper limit value be 1.6.

[0023] The conditional expression (3) defines the desirable range of the ratio between the off-axis chief ray height when a ray with an object-side incident angle of 90° enters the concave meniscus lens component N1 at infinite focus (however, when 2ω < 180°, it is the off-axis chief ray height when entering with an object-side incident angle of ω) and the imaging height of the off-axis chief ray when the ray with an object-side incident angle of 90° forms an image on the image plane (however, when 2ω < 180°, it is the imaging height of the off-axis chief ray when entering with an object-side incident angle of ω). Note that since the numerical values of N1OAh and iOAh handle the ray height of the off-axis chief ray, a positive-negative relationship occurs. Specifically, since the sign of the off-axis chief ray height reverses before and after the aperture stop, N1OAh and iOAh always have opposite signs.

[0024] When the ratio between the off-axis chief ray height when a ray with an object-side incident angle of 90° enters the concave meniscus lens component N1 at infinite focus and the imaging height of the off-axis chief ray when the ray with an object-side incident angle of 90° forms an image on the image plane approaches 0 and increases beyond the upper limit of the conditional expression (3), the diameter of the concave meniscus lens component N1 with respect to the imaging height becomes too small, and it becomes necessary to further strengthen the negative refractive power of the concave meniscus lens component N1, leading to deterioration of the aberration and field curvature, which is not preferable.

[0025] When N1OAh becomes smaller than iOAh beyond the lower limit of the conditional expression (3), and the ratio between the off-axis chief ray height when a ray with an object-side incident angle of 90° enters the concave meniscus lens component N1 at infinite focus and the imaging height of the off-axis chief ray when the 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 with respect to the imaging height becomes too large, leading to enlargement of the optical system, which is not preferable.

[0026] Regarding the conditional expression (3), it is desirable to define the upper limit value as -1.2 and the lower limit value as -4.1, and more desirably, by defining the lower limit value as -3.5, it becomes possible to more surely achieve the above-mentioned effects.

[0027] The conditional expression (4) defines the ratio of the sag amounts of the image-side surfaces of the concave meniscus lens component N1 and the concave meniscus lens component N2 (when calculating the sag amount, the ray height at the time of calculating the sag amount uses the off-axis chief ray height when a ray with an object-side incident angle of 90° at infinite focus exits from the surface. Also, when 2ω < 180°, it is calculated using the off-axis chief ray height incident at the object-side incident angle ω). As described above, in an ultra-wide-angle lens with a total angle of view 2ω of 160° or more, the concave meniscus lens with a convex surface facing the object side, the radius of curvature of the image-side surface being significantly smaller than that of the object-side surface, and the sag amount of the image-side surface being large is generally arranged on the object side. Particularly in a fish-eye lens, there are many examples where the shape of 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 sag amount. Also, when using a general interferometer as a means to measure the surface accuracy of the lens, the measurable diameter becomes smaller as the curvature increases, and in the case of a concave surface close to a hemisphere, it is often difficult to measure the peripheral part with an interferometer. In the case of a bright optical system with an F-number less than F1.9 like the present invention, the depth of focus becomes shallow, so it is required to process the optical element with higher accuracy, and it is necessary to fully consider the radius of curvature and sag amount of the image-side surfaces of the concave meniscus component N1 and the concave meniscus component N2 in terms of processability and measurement accuracy.

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

[0029] When the ratio of the sag amount of the image-side surface of the concave meniscus lens component N1 and the sag amount of the image-side surface of the concave meniscus lens component N2 is less than the lower limit of the conditional expression (4), the sag amount of the image-side surface of the concave meniscus lens component N2 increases, and the processability and measurement accuracy deteriorate. Also, if the negative refractive power of the concave meniscus lens component N2 becomes too strong, it becomes difficult to correct the aberration and field curvature, which is not preferable.

[0030] Regarding the conditional expression (4), it is desirable to define the upper limit as 1.72, the lower limit as 0.60, and more preferably, the upper limit as 1.40 and the lower limit as 0.70, so that the above-described effects can be ensured more reliably.

[0031] In the large aperture ratio ultra-wide angle lens of the present invention, it is desirable that 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) defines the ratio of the focal lengths of the concave meniscus lens component N1 and the concave meniscus lens component N2. In the case of an ultra-wide angle lens with a large aperture ratio such as the present invention, when the lens on the object side is to maintain high optical performance and reduce the F value or increase the angle of view, it easily becomes bulky. By appropriately setting the focal lengths of the concave meniscus lens component N1 and the concave meniscus lens component N2 and adopting a configuration in which the negative refractive powers are appropriately shared between the two, it becomes possible to suppress the enlargement of the optical system while maintaining high optical performance.

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

[0034] When the ratio of the focal lengths of the concave meniscus lens component N1 and the concave meniscus lens component N2 becomes smaller than the lower limit of the conditional expression (5), the negative refractive power of the concave meniscus lens component N1 becomes too strong, making it difficult to correct for aberration and field curvature. Also, the curvature radius on the image side of the concave meniscus lens component N1 becomes smaller, the sag amount increases, the workability and measurement accuracy deteriorate, and the eccentricity ratio of the lens increases. Since the concave meniscus lens component N1 is on 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 eccentricity ratio increases is more likely to be larger for the concave meniscus lens component N1. Therefore, it easily leads to an increase in the weight of the entire optical system, which is not preferable.

[0035] Regarding the conditional expression (5), it is desirable to define the upper limit value as 4.3 and the lower limit value as 0.7 to make the above-described effects more certain.

[0036] In the large-aperture ratio ultra-wide-angle lens of the present invention, it is desirable 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 curvature radius of the surface on the object side of the concave meniscus lens component N1 N1R2: The 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, so-called shape factor. Since the concave meniscus lens component N1 has a concave meniscus shape with a convex surface facing the object side, both N1R1 and N1R2 are larger than 0, N1R1 is larger than N1R2, N1SF becomes larger as the difference between N1R1 and N1R2 becomes smaller, and N1SF approaches 1 as the difference between N1R1 and N1R2 becomes larger. Therefore, if the refractive index of the concave meniscus lens component N1 does not change, the closer N1SF is to 1, the stronger the negative refractive power of the concave meniscus lens component N1, and the larger the sag amount of the surface on the image side of the concave meniscus lens component N1.

[0038] When the N1SF of the concave meniscus lens component N1 exceeds the upper limit of conditional expression (6) and becomes large, the difference between N1R1 and N1R2 becomes small, the negative refractive power of the concave meniscus lens component N1 becomes weak, and the insufficient refractive power is compensated by the concave meniscus lens component N2. As a result, the negative refractive power of the concave meniscus lens component N2 becomes too strong, making it difficult to correct the aberration and field curvature, which is not preferable.

[0039] When the N1SF of the concave meniscus lens component N1 is less than the lower limit of conditional expression (6) and approaches 1, the difference between N1R1 and N1R2 becomes large, and the negative refractive power of the concave meniscus lens component N1 becomes too strong, leading to deterioration of the aberration and field curvature. In addition, since the radius of curvature N1R2 of the image-side surface is particularly small, the sag amount increases, deteriorating the workability and measurement accuracy. Furthermore, since the decentration ratio of the concave meniscus lens component N1 with the largest lens diameter increases, the weight of the optical system increases, which is not preferable.

[0040] Regarding conditional expression (6), it is desirable to define the upper limit value as 4.5, the lower limit value as 1.7, and more preferably, the upper limit value as 4.3 and the lower limit value as 2.2, so that the above-mentioned effects can be made more certain.

[0041] In the large-aperture ratio ultra-wide-angle lens of the present invention, it is desirable 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: 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

[0042] The conditional expression (7) defines the lens shape of the concave meniscus lens component N2, that is, the so-called shape factor. Since the concave meniscus lens component N2 has a concave meniscus shape with a convex surface facing the object side, both N2R1 and N2R2 are greater than 0, N2R1 is greater than N2R2, and the smaller the difference between N2R1 and N2R2, the larger N2SF becomes. N2SF approaches 1 as the difference between N2R1 and N2R2 increases. Therefore, 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 sag amount of the image-side surface of the concave meniscus lens component N2 becomes.

[0043] If N2SF of the concave meniscus lens component N2 increases beyond the upper limit of the conditional expression (7), the difference between N2R1 and N2R2 decreases, the negative refractive power of the concave meniscus lens component N2 weakens, and the insufficient refractive power will be compensated by the concave meniscus lens component N1. As a result, the negative refractive power of the concave meniscus lens component N1 becomes too strong, making it difficult to correct spherical aberration and 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 increases, especially the radius of curvature N1R2 of the image-side surface becomes smaller, so the sag amount increases, and the workability and measurement accuracy deteriorate. In addition, since the eccentricity ratio of the concave meniscus lens component N1 with the largest lens diameter increases, the weight of the optical system increases, which is not preferable.

[0044] If N2SF of the concave meniscus lens component N2 decreases and approaches 1 beyond the lower limit of the conditional expression (7), the negative refractive power of the concave meniscus lens component N2 becomes too strong, making it difficult to correct spherical aberration and 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 increases, especially the radius of curvature N1R2 of the image-side surface becomes smaller, so the sag amount increases, and the workability and measurement accuracy deteriorate, which is not preferable.

[0045] Regarding the conditional expression (7), it is desirable to define the upper limit value as 4.0 and the lower limit value as 1.6 to make the above-mentioned effects more certain.

[0046] In the large aperture ratio ultra-wide angle lens of the present invention, it is desirable 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: Curvature radius of the object side surface of the concave meniscus lens component N1 N1R2: Curvature radius of the image side surface of the concave meniscus lens component N1 N2SF = (N2R1 + N2R2) / (N2R1 - N2R2) N2R1: Curvature radius of the object side surface of the concave meniscus lens component N2 N2R2: Curvature radius of the image side surface of the concave meniscus lens component N2

[0047] The conditional expression (8) defines the ratio of the shape factors of the concave meniscus lens component N1 and the concave meniscus lens component N2. When trying to reduce the F value or widen the angle of view while maintaining high optical performance, the lens on the object side of the large aperture ratio ultra-wide angle lens easily becomes bulky. By appropriately setting the shape factors of the concave meniscus lens component N1 and the concave meniscus lens component N2, it becomes possible to adopt a configuration in which the negative refractive powers are appropriately shared between the two. Also, as described above, the concave meniscus lens component N1 and the concave meniscus lens component N2 need to be processed with high precision, and it is necessary to set them to a shape that is easy to realize.

[0048] When the ratio of the shape factors of the concave meniscus lens component N1 and the concave meniscus lens component N2 exceeds the upper limit of the conditional expression (8), it means that the numerical value of N2SF becomes smaller with respect to N1SF. When N2SF approaches 1 and becomes smaller, the difference in curvature radius between the object side surface and the image side surface of the concave meniscus lens component N2 increases, and particularly the curvature radius of the image side surface becomes smaller, so the sag amount increases and the workability and measurement accuracy deteriorate. Also, the negative refractive power of the concave meniscus lens component N2 becomes too strong, making it difficult to correct the astigmatism and field curvature, which is not preferable.

[0049] When the ratio of the shape factors of the concave meniscus lens component N1 and the concave meniscus lens component N2 becomes smaller than the lower limit of the conditional expression (8), it means that the numerical value of N1SF becomes smaller with respect to N2SF. When 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 increases. In particular, since the radius of curvature of the image-side surface becomes smaller, the sag amount increases, and the workability and measurement accuracy deteriorate. In addition, since the decentering ratio of the concave meniscus lens component N1 with the largest lens diameter increases, the weight of the optical system increases, which is not preferable. Furthermore, the negative refractive power of the concave meniscus lens component N1 becomes too strong, making it difficult to correct the aberration and field curvature, which is not preferable.

[0050] Regarding the conditional expression (8), it is desirable to define the upper limit value as 2.4 and the lower limit value as 0.5 to make the above-described effects more certain.

[0051] In the large-aperture ratio ultra-wide-angle lens of the present invention, it is desirable that the concave meniscus lens component N1 satisfies the following conditional expression (9). (9) 1.8 < PLOAN1 / PLAN1 < 5.0 PLOAN1: When the light ray with an object-side incident angle of 90° at infinity focus is used as an off-axis ray, the distance that the off-axis chief ray passes through the concave meniscus lens component N1 (however, when 2ω < 180°, the light ray incident at the object-side incident angle ω is used as an off-axis ray) PLAN1: The thickness on the optical axis of the concave meniscus lens component N1

[0052] Conditional expression (9) defines the ratio of the passing distances of the on-axis ray and the off-axis chief ray passing through the concave meniscus lens component N1. The definition of the off-axis ray is that a ray with an object-side incident angle of 90° when focused at infinity is defined as the off-axis ray (however, when 2ω < 180°, a ray incident at the object-side incident angle ω is defined as the off-axis ray). Since the lens on the object side of the large aperture ratio ultra-wide angle lens according to the present invention has a concave meniscus shape with a convex surface facing the object side, it has the characteristic that the passing distance of the off-axis ray within the lens is large with respect to the on-axis ray. Also, when the lens shape is such that the radius of curvature of the surface on the image side is smaller than that of the surface on the object side (a lens shape with a large sag amount on the image side surface and a large decentration ratio), the difference in the passing distances of the off-axis ray and the on-axis ray within the lens becomes larger. For miniaturizing the ultra-wide angle lens, it is effective to use a high refractive index optical material for the lens on the object side. However, generally, the higher the refractive index of the optical material, the lower the internal transmittance of the optical material tends to be, and particularly the transmittance on the short wavelength side deteriorates, so that the lens appears yellowish. When such an optical 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 kept within an appropriate range, a phenomenon where the color tone varies depending on the angle of view (the image becomes more yellowish toward the periphery of the screen) occurs, which is not preferable. The same phenomenon also occurs in the concave meniscus lens component N2 that takes a similar optical path to the concave meniscus lens component N1, but the concave meniscus lens component N1 with a larger lens diameter and a longer ray passing distance within the lens has a greater influence.

[0053] When the ratio of the passing distances of the on-axis ray and the off-axis chief ray passing through the concave meniscus lens component N1 exceeds the upper limit of conditional expression (9), the passing distance of the off-axis ray becomes larger with respect to the on-axis ray passing through the concave meniscus lens component N1. Therefore, the transmittance of the off-axis ray decreases significantly with respect to the transmittance of the on-axis ray, and the difference in color tone depending on the angle of view becomes large, which is not preferable.

[0054] When the ratio of the passing distances of the on-axis ray and the off-axis chief ray passing through the concave meniscus lens component N1 becomes smaller than the lower limit of conditional expression (9), the negative refractive power of the concave meniscus lens component N1 is insufficient, and to compensate for this, the refractive power of the concave meniscus component N2 becomes too strong, leading to deterioration of the astigmatism and field curvature, which is not preferable.

[0055] Regarding conditional expression (9), it is desirable to define the upper limit value as 4.2 and the lower limit value as 2.0 to make the above-described effect more certain.

[0056] In the large aperture ratio ultra-wide angle lens of the present invention, it is desirable 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: When a ray with an object-side incident angle of 90° at infinity focus is used as the off-axis ray, the distance that the off-axis chief ray passes through the concave meniscus lens component N1 (however, when 2ω < 180°, the ray incident at the object-side incident angle ω is used as the off-axis ray) PLOAN2: When a ray with an object-side incident angle of 90° at infinity focus is used as the off-axis ray, the distance that the off-axis chief ray passes through the concave meniscus lens component N2 (however, when 2ω < 180°, the ray incident at the object-side incident angle ω is used as the off-axis ray)

[0057] Conditional expression (10) defines the ratio of the passing distances of chief off-axis rays passing through the concave meniscus lens component N1 and the concave meniscus lens component N2. Note that the off-axis ray is defined as the ray with an object-side incident angle of 90° when focused at infinity (however, when 2ω < 180°, the ray incident at the object-side incident angle ω is defined as the off-axis ray). In the explanation of conditional expression (9), it was specified that the difference in the passing distances of the on-axis ray and the off-axis ray of the concave meniscus lens component N1 may affect the change in color tone due to the angle of view. The same phenomenon also occurs in the concave meniscus lens component N2 with a similar lens shape and a similar ray path. Therefore, by setting the passing distances of the off-axis rays passing through the concave meniscus lens component N1 and the concave meniscus lens component N2 within an appropriate range, it is possible to obtain a good image with less change in color tone due to the angle of view.

[0058] When the ratio of the passing distances of the chief off-axis rays passing through the concave meniscus lens component N1 and the concave meniscus lens component N2 exceeds the upper limit of conditional expression (10), the distance of the off-axis ray passing through the concave meniscus lens component N1 increases, and the change in color tone due to the angle of view is likely to occur. Also, since the decentration ratio of the concave meniscus lens component N1 with the largest lens diameter changes in the direction of increasing, the weight of the optical system increases, which is not preferable. Furthermore, the negative refractive power of the concave meniscus lens component N1 becomes too strong, making it difficult to correct the astigmatism and field curvature, which is not preferable.

[0059] When the ratio of the passing distances of the chief off-axis rays passing through the concave meniscus lens component N1 and the concave meniscus lens component N2 is less than the lower limit of conditional expression (10), the distance of the off-axis ray passing through the concave meniscus lens component N2 increases, and the change in color tone due to the angle of view is likely to occur. Also, since the decentration ratio of the concave meniscus lens component N2 changes in the direction of increasing, the negative refractive power of the concave meniscus lens component N2 becomes too strong, leading to the deterioration of astigmatism and field curvature, which is not preferable.

[0060] Regarding conditional expression (10), it is desirable to define the upper limit value as 2.8 and the lower limit value as 0.6 to make the above effects more certain.

[0061] In the large aperture ratio ultra-wide angle lens of the present invention, it is desirable 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: Refractive index of the convex lens LP1 vdLP1: Abbe number of the convex lens LP1 ΔPgFLP1: Abnormal dispersibility of the convex lens LP1

[0062] Equations (11) to (13) define the desirable refractive index, Abbe number, and anomalous dispersion range of the convex lens LP1 of the second lens group G2. For a convex lens on the image side of the aperture of a retrofocus type ultra-wide-angle lens, it is common to arrange a glass material with positive anomalous dispersion. This is related to the tendency of magnification chromatic aberration and axial chromatic aberration to occur in a retrofocus type ultra-wide-angle lens. For magnification chromatic aberration, the C-line tends to remain in the over direction, and when designed to correct the C-line and g-line, the secondary spectrum will remain in the over direction. Also, for axial chromatic aberration, in a general single-focus lens, the C-line tends to remain in the over direction (equivalent to the focal length of the C-line becoming longer), and when designed to correct the C-line and g-line, the secondary spectrum will remain in the over direction. By using a glass material with positive anomalous dispersion for the convex lens arranged on the image side of the aperture, the correction directions of magnification chromatic aberration and axial chromatic aberration coincide, making it possible to correct chromatic aberration more effectively. Generally, as glass materials with positive anomalous dispersion, fluorite and special low-dispersion glasses equivalent to it are often used. Since these special low-dispersion glasses have many low-refractive-index glass materials, using them frequently for the convex lens on the image side of the aperture will work disadvantageously for the correction of the Petzval sum and make it difficult to correct field curvature. Since the large aperture ratio ultra-wide-angle lens of the present invention has an F-number of less than 1.9 and is bright, correction of axial chromatic aberration is essential for high performance, and it is necessary to frequently use a special low-dispersion glass with positive anomalous dispersion for the convex lens on the image side of the aperture. However, in order to correct the deteriorating Petzval sum, a glass material (such as E-FDS1-W if it is a glass material of HOYA) with a refractive index of 1.6 or more and positive anomalous dispersion is arranged in the second lens group G2 on the image side of the aperture, so that magnification chromatic aberration and axial chromatic aberration can be effectively corrected and field curvature can also be appropriately corrected.

[0063] When the refractive index of the convex lens LP1 drops beyond the lower limit of Equation (11), the Petzval sum deteriorates and it becomes difficult to correct field curvature, which is not preferable.

[0064] Regarding the conditional expression (11), it is desirable to define the lower limit as 1.65, and more desirably as 1.85, so that the above-described effect can be made more certain.

[0065] For the optical material within the range of the conditional expression (11), generally, the smaller the Abbe number, the greater the positive abnormal dispersibility. As the Abbe number increases, the positive abnormal dispersibility decreases, and some optical materials have negative abnormal dispersibility. Therefore, if the Abbe number of the convex lens LP1 exceeds the upper limit of the conditional expression (12), the abnormal dispersibility decreases, making it difficult to correct the magnification chromatic aberration and the axial chromatic aberration, which is not preferable.

[0066] Regarding the conditional expression (12), it is desirable to define the upper limit as 32.0, and more desirably as 28.0, so that the above-described effect can be made more certain.

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

[0068] Regarding the conditional expression (13), it is desirable to define the lower limit as 0.020, and more desirably as 0.025, so that the above-described effect can be made more certain.

[0069] In the large-aperture ratio ultra-wide-angle lens of the present invention, it is desirable 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 entire system when focused at infinity f1: The focal length of the first lens group G1 when focused at infinity

[0070] The conditional expression (14) defines the ratio of the focal length of the entire system when focused at infinity to the focal length of the first lens group G1 when focused at infinity. By satisfying the conditional expression (14), while realizing the wide-angleization of the optical system, the enlargement of the optical system is prevented.

[0071] If the ratio of the focal length of the entire system at infinity focus to the focal length of the first lens group G1 at infinity focus exceeds the upper limit of conditional expression (14) and increases, f1 will approach 0 while taking a positive value, and the positive refractive power of the first lens group G1 will increase, making it difficult to achieve a wide-angle effect, which is not preferable.

[0072] If the ratio of the focal length of the entire system at infinity focus to the focal length of the first lens group G1 at infinity focus is less than the lower limit of conditional expression (14), f1 will approach 0 while taking a negative value, and the negative refractive power of the first lens group G1 will become too strong, leading to deterioration of spherical aberration and field curvature, which is not preferable.

[0073] Regarding conditional expression (14), it is desirable to define the upper limit value as 0.60 and the lower limit value as -0.25 to more surely achieve the above-mentioned effects.

[0074] In the large aperture ratio ultra-wide angle lens of the present invention, it is desirable that the first lens group G1 and the second lens group G2 having 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 infinity focus f2: Focal length of the second lens group G2 at infinity focus

[0075] Conditional expression (15) defines 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-angle effect of the optical system, the enlargement of the optical system is prevented.

[0076] If 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 exceeds the upper limit of conditional expression (15) and increases, f1 will approach 0 while taking a positive value, and the positive refractive power of the first lens group G1 will increase, making it difficult to achieve a wide-angle effect, which is not preferable.

[0077] When the ratio of the focal length of the second lens group G2 to the focal length of the first lens group G1 at infinity focus becomes smaller than the lower limit of conditional expression (15), f1 approaches 0 while taking a negative value, and the negative refractive power of the first lens group G1 becomes too strong, leading to deterioration of astigmatism and field curvature, which is not preferable.

[0078] Regarding conditional expression (15), it is desirable to define the upper limit value as 2.6 and the lower limit value as -0.7, so that the above-mentioned effects can be made more certain.

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

[0080] Generally, the longitudinal chromatic aberration of an optical system composed of thin lenses is given by the following (Reference formula 1) as the sum of each lens, 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: Axial marginal ray height hb: Off-axis chief ray height φ: Refractive power v: Abbe number

[0081] From (Reference Formula 1) and (Reference Formula 2), it can be seen that the lateral chromatic aberration has a greater impact on lenses passing through positions with higher off-axis chief ray heights, and the axial chromatic aberration has a greater impact on lenses passing through positions with higher axial marginal ray heights. Therefore, by appropriately setting the difference in height between the axial marginal ray height and the off-axis chief ray height, and the dispersion characteristics of the optical material, it becomes possible to highly correct the lateral chromatic aberration and the axial chromatic aberration.

[0082] Condition formula (16) defines the ratio of the axial marginal ray height to the off-axis chief ray height incident on the convex lens included in the second lens group G2. Note that both the axial marginal ray height and the off-axis chief ray height incident on the convex lens included in the second lens group G2 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, when using an optical material with a large positive anomalous dispersion for the convex lens of the second lens group G2 arranged on the image side of the aperture stop, it is effective for correcting both the lateral chromatic aberration and the axial chromatic aberration. In particular, by arranging a convex lens using an optical material having a positive anomalous dispersion within the range satisfying condition formula (16), it becomes possible to further enhance the effect. Note that G2LPAXh defines the axial marginal ray height incident on the convex lens included in the second lens group G2. Since the axial marginal ray does not experience a reversal in the positive or negative of the ray height before and after the aperture stop, it is always calculated as a positive value in the calculation of this condition formula. Also, G2LPOAh defines the off-axis chief ray height when a ray with an object-side incident angle of 90° is incident on the convex lens in the case of infinite focus. Although it can take both positive and negative values, in the calculation of this condition formula, it is calculated for the off-axis chief ray that takes a positive value on the image side of the aperture stop.

[0083] When the ratio of the axial marginal ray height to the off-axis chief ray height incident on the convex lens included in the second lens group G2 exceeds the upper limit of condition formula (16), the axial marginal ray height decreases with respect to the off-axis chief ray height, so that the correction effect of the axial chromatic aberration deteriorates, which is not preferable.

[0084] When the ratio of the on-axis marginal ray height to the off-axis chief ray height incident on the convex lens included in the second lens group G2 becomes smaller than the lower limit of conditional expression (16), the off-axis chief ray height decreases with respect to the on-axis marginal ray height, and the correction effect of longitudinal chromatic aberration deteriorates, which is not preferable.

[0085] Conditional expression (17) defines the average value of the anomalous dispersibility of the convex lens that satisfies conditional expression (16) included in the second lens group G2. The greater the use of a glass material with a large positive anomalous dispersibility, the higher the correction effect of longitudinal chromatic aberration and axial chromatic aberration.

[0086] When the average value of the anomalous dispersibility of the convex lens that is included in the second lens group G2 and satisfies conditional expression (16) becomes smaller than the lower limit of conditional expression (17), the correction effect of longitudinal chromatic aberration and axial chromatic aberration weakens, which is not preferable.

[0087] Regarding conditional expression (17), it is desirable to define the lower limit value as 0.009 to make the above-described effect more certain.

[0088] In the large aperture ratio ultra-wide angle lens of the present invention, it is desirable 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) defines 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, it becomes possible to miniaturize the optical system.

[0090] When the refractive index of the concave lens included in the concave meniscus lens component N1 with the convex surface facing the object side becomes lower beyond the lower limit of the conditional expression (18), the radius of curvature (N1R2) of the image side surface of the concave meniscus lens component N1 becomes smaller in order to maintain the refractive power, and the aberration and field curvature deteriorate, which is not preferable. Further, it acts in the direction of increasing the eccentric thickness ratio of the concave meniscus lens component N1, and since the weight of the concave meniscus lens component N1 increases, it is not preferable.

[0091] Regarding the conditional expression (18), it is desirable to define the lower limit value as 1.8 so that the above-described effects can be made more certain.

[0092] The large-aperture ratio ultra-wide-angle lens of the present invention preferably satisfies the following conditional expression (19). (19) 5.00 < LT / BF < 12.00 LT: The distance on the optical axis from the most object-side lens surface to the most image-side lens surface when focused at infinity BF: The distance on the optical axis from the most image-side lens surface 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 most object-side lens surface to the most image-side lens surface when focused at infinity to the distance on the optical axis from the most image-side lens surface to the image plane when focused at infinity. Note that a parallel flat plate that is not adjacent to the image plane or has an air gap and is adjacent is not counted as a lens. Further, when calculating the distance on the optical axis from the most image-side lens surface to the image plane, it is calculated with the air-equivalent length obtained by replacing the parallel flat plate with air. By satisfying the conditional expression (19), it becomes possible to achieve miniaturization of the optical system.

[0094] When the ratio of the distance on the optical axis from the most object-side lens surface to the most image-side lens surface when focused at infinity to the distance on the optical axis from the most image-side lens surface to the image plane when focused at infinity becomes larger beyond the upper limit of the conditional expression (19), the optical system becomes enlarged, which is not preferable.

[0095] When the ratio of the distance on the optical axis from the most object-side lens surface to the most image-side lens surface at infinity focus to the distance on the optical axis from the most image-side lens surface to the image plane at infinity focus becomes smaller than the lower limit of conditional expression (19), it becomes necessary to reduce LT, and it becomes difficult and undesirable to correct spherical aberration, astigmatism, and field curvature while maintaining an aperture ratio of less than F1.9.

[0096] Regarding conditional expression (19), it is desirable to define the upper limit value as 11.00 and the lower limit value as 5.35, and more preferably, the upper limit value as 10.00 and the lower limit value as 6.20, so that the above-described effects can be made more certain.

[0097] The large-aperture ratio ultra-wide-angle lens of the present invention preferably satisfies the following conditional expression (20). (20) 2.5 < |LT / iOAh| < 18.0 LT: The distance on the optical axis from the most object-side lens surface to the most image-side lens surface at infinity focus iOAh: The image height of the off-axis chief ray when a ray with an object-side incident angle of 90° at infinity focus forms an image on the image plane (however, when 2ω < 180°, it is the image height of the off-axis chief ray incident at the object-side incident angle ω)

[0098] Conditional expression (20) defines the absolute value of the ratio of the distance on the optical axis from the most object-side lens surface to the most image-side lens surface at infinity focus to the image height of the off-axis chief ray when a ray with an object-side incident angle of 90° at infinity focus forms an image on the image plane (however, when 2ω < 180°, it is the image height of the off-axis chief ray incident at the object-side incident angle ω). By satisfying conditional expression (19), it becomes possible to achieve miniaturization of the optical system.

[0099] When the ratio of the distance on the optical axis from the most object-side lens surface to the most image-side lens surface at infinity focus to the image height of the off-axis chief ray when a ray with an object-side incident angle of 90° at infinity focus forms an image on the image plane becomes larger than the upper limit of conditional expression (20), the optical system becomes enlarged with respect to the maximum image height of the optical system, which is not preferable.

[0100] When the ratio of the distance on the optical axis from the most object-side lens surface to the most image-side lens surface at infinity focus to the off-axis chief ray imaging height when a ray with an object-side incident angle of 90° at infinity focus forms an image on the image plane is less than the lower limit of conditional expression (20), it becomes necessary to reduce LT. While maintaining a large aperture ratio of less than F1.9, it becomes difficult to correct spherical aberration, astigmatism, and field curvature, which is not preferable.

[0101] Regarding conditional expression (20), it is desirable to define the upper limit value as 16.0 and the lower limit value as 3.1, and more preferably, the upper limit value as 14.0 and the lower limit value as 4.1, so that the above-described effects can be made more certain.

[0102] In the large-aperture ratio ultra-wide-angle lens of the present invention, the concave meniscus lens component N2 is preferably the concave meniscus lens component with a convex surface facing the object side that is arranged second from the most object side among the concave meniscus lens components with a convex surface facing the object side. Since the concave meniscus lens component N2 plays a role of introducing off-axis light rays incident from the object side at an angle close to the optical axis, by being arranged more on the object side, it becomes possible to introduce off-axis light rays while preventing the enlargement of the optical system.

[0103] In the large-aperture ratio ultra-wide-angle lens of the present invention, it is desirable that the concave meniscus lens component N1 and the concave meniscus lens component N2 are arranged continuously from the most object side. Since both the concave meniscus lens component N1 and the concave meniscus lens component N2 play a role of gently introducing off-axis light rays incident from the object side at an angle close to the optical axis, by being arranged continuously from the most object side, it becomes possible to suppress the enlargement of the optical system.

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

[0105] The large aperture ratio ultra-wide angle lens of the present invention has a focusing function from infinity to a close object. In this case, it is desirable to focus by moving part or all of the optical system in the optical axis direction.

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

[0107] Examples 1 to 14 of the present invention are all fisheye lenses using the equal solid angle projection method. The object plane when outputting each aberration diagram is a plane (curvature radius is ∞) for evaluation. Therefore, particularly in the evaluation at a finite distance where the object distance is small, significant field curvature appears in the aberration diagram because the object plane is a plane.

[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 for the d-line (wavelength 587.56 nm), vd is the Abbe number for the d-line, and ΔPgF is a numerical value calculated from the formula of PgF - 0.64833 + 0.00180 × vd. Also, as examples of the glass corresponding to the refractive index, Abbe number, and ΔPgF described in [surface data], the names of the glass materials of HOYA Corporation, Ohara Corporation, and Hikari Glass Co., Ltd. are described.

[0109] An asterisk (*) attached to the surface number indicates that the lens surface shape is an aspherical surface. Also, BF is the back focus, and the object plane distance indicates the distance from the subject to the first lens surface.

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

[0111] [Aspherical Data] shows the values of the coefficients that give the aspherical shape of the lens surface marked with * in [Surface Data]. The shape of the aspherical surface is represented by the following formula. In the following formula, the displacement in the direction perpendicular to the optical axis from the optical axis is y, the displacement in the optical axis direction from the intersection of the aspherical surface and the optical axis (sag amount) is z, the radius of curvature of the reference spherical surface is r, and the conic coefficient is represented by K. Also, the aspherical coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th orders are represented by A4, A6, A8, A10, A12, A14, and A16, respectively. TIFF2025099854000002.tif17166

[0112] [Various Data] shows values such as the focal length in the in-focus state for each shooting distance.

[0113] [Variable Interval Data] shows the values of the variable interval and BF in the in-focus state for various shooting distances.

[0114] [Lens Group Data] shows the surface number closest to the object side that constitutes each lens group and the combined focal length of the entire group.

[0115] [Convex Lens in the Second Lens Group G2 that Satisfies Conditional Expression (16)] shows the object-side surface number of the convex lens in the second lens group G2 that satisfies conditional expression (16), the corresponding optical material, the on-axis marginal ray height (G2LPAXh) incident on the convex lens at infinity focus with the aperture wide open, the off-axis principal ray height when a ray with an object-side incident angle of 90° is incident on the convex lens at infinity focus (however, when 2ω < 180°, it is the off-axis principal ray height incident at the object-side incident angle ω: G2LPOAh), the ratio of G2LPAXh to G2LPOAh, and the value of ΔPgF.

[0116] Also, in the aberration diagrams corresponding to each embodiment, 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] Note that, unless otherwise specified, the units of the focal length f, the radius of curvature r, the lens surface interval d, and other lengths described in all the following specifications are millimeters (mm). However, in the optical system, the same optical performance can be obtained in proportional magnification and reduction, so it is not limited to this.

[0118] Also, as the lens name, the lens arranged closest to the object side is designated as L1, and the lenses arranged second and third toward the image side thereafter are sequentially designated as L2 and L3, respectively.

[0119] Also, in the lens configuration diagrams of each embodiment, I is the image plane, F is the filter, and the dashed-dotted line passing through the center is the optical axis.

[0120] [Embodiment 1] FIG. 1 is a lens configuration diagram of the large-aperture ratio ultra-wide-angle lens according to Embodiment 1 at infinity focus.

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

[0122] The first lens group G1 is composed of, in order from the object side, a meniscus lens component N1 consisting of a concave meniscus lens L1 with a convex surface facing the object side, a meniscus lens component N2 consisting of a concave meniscus lens L2 with a convex surface facing the object side, a cemented lens of a convex meniscus lens L3 with a 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 a 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 a convex surface facing the object side and a convex meniscus lens L10 with a convex surface facing the object side.

[0123] The second lens group G2 consists of, in order from the object side, a cemented lens composed of a convex meniscus lens L11 with a convex surface facing the image side, a convex meniscus lens L12 with a convex surface facing the image side, and a concave meniscus lens L13 with a 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 from L7 to L10 integrally along the optical axis toward the image side, focusing from an infinite object to a close object is possible. Nevertheless, it is also possible to perform focusing by moving part or all of the optical system in the optical axis direction.

[0125] The specifications of the large aperture ratio ultra-wide angle lens according to Example 1 are shown below.

[0126] Numerical Example 1 Unit: mm [Surface Data] Surface number r d nd vd ΔPgF Corresponding optical material 0 (d0) 1 59.3307 3.0000 1.85033 42.69 -0.0072 TAFD34 2 32.6012 7.3330 3 51.6525 2.0000 2.00069 25.46 0.0110 TAFD40-W 4 16.9776 12.5575 5 -57.0174 3.6235 1.85451 25.15 0.0071 NBFD25 6 -27.5516 1.0000 1.43700 95.10 0.0564 FCD100 7 760.8918 4.4992 8 -25.4905 1.4563 1.80100 34.97 0.0009 S-LAM66 9 28.4681 4.4072 1.86966 20.02 0.0310 FDS20-W 10 204.3417 (d10) 11 118.3888 3.9558 1.49700 81.61 0.0373 FCD1 12 -49.6092 0.9510 *13 88.3904 4.5768 1.85135 40.10 -0.0067 M-TAFD305 *14 -76.6548 0.4190 15 59.7344 0.9958 1.80611 40.73 -0.0080 NBFD13 16 25.9394 3.4660 2.05090 26.94 0.0052 TAFD65 17 40.2507 (d17) 18 (Aperture) ∞ 4.0123 19 -216.5603 2.9894 1.49700 81.61 0.0373 FCD1 20 -61.2064 2.4673 21 -61.5955 7.5045 1.43700 95.10 0.0564 FCD100 22 -19.7410 1.0214 1.85451 25.15 0.0071 NBFD25 23 -51.7120 0.3919 24 147.9068 4.1953 1.55032 75.50 0.0274 FCD705 25 -65.3241 1.7129 26 32.2779 6.6442 1.43700 95.10 0.0564 FCD100 27 -142.0192 0.8259 28 214.5952 3.2005 1.94595 17.98 0.0385 FDS18-W 29 -127.3539 0.3026 30 48.9128 6.1022 1.43700 95.10 0.0564 FCD100 31 -35.2153 0.8500 1.85451 25.15 0.0071 NBFD25 32 28.3382 1.2521 *33 29.8464 5.8960 1.80610 40.73 -0.0058 M-NBFD130 *34 -87.4854 14.4500 35 ∞ 2.5000 1.51680 64.20 0.0014 BSC7 36 ∞ (BF) [Aspherical Data] Surface 13, Surface 14, Surface 33, Surface 34 K 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A4 -4.77407E-08 2.55930E-06 -9.17184E-06 1.08522E-07 A6 -1.39344E-09 -1.20340E-09 -2.11056E-08 -2.25595E-08 A8 -1.29188E-12 -2.76024E-11 5.62697E-11 7.12380E-11 A10 -1.16182E-13 3.94546E-14 -6.92083E-13 -6.26716E-13 A12 -9.32650E-17 -4.40567E-16 -4.35790E-16 -1.58415E-15 A14 5.68935E-19 4.92346E-19 0.00000E+00 4.13406E-18 A16 -1.15739E-21 -5.23936E-22 0.00000E+00 0.00000E+00 [Various Data] Wide Angle (INF) Focal Length 8.15 F Number 1.26 Full Picture Angle 2ω 185.73 Image Height Y 11.94 Overall lens length 133.27 [Variable interval data] INF Close distance (d0) ∞ 222.3414 (d10) 5.3549 5.6265 (d17) 6.3575 6.0858 (BF) 1.0000 1.0000 [Lens group data] Group Starting surface Focal length G1 1 -111.1800 G2 19 28.2728 [Convex lens within the second lens group G2 that satisfies conditional expression (16)] Surface number Corresponding optical material G2LPAXh G2LPOAh G2LPAXh / G2LPOAh ΔPgF 24 FCD705 12.832 6.437 2.0 0.0274 26 FCD100 12.719 8.574 1.5 0.0564 28 FDS18-W 11.729 9.549 1.2 0.0385 30 FCD100 10.492 9.824 1.1 0.0564 33 M-NBFD130 8.302 10.554 0.8 -0.0058

[0127] [Example 2] Fig. 6 is a lens configuration diagram at infinity focus of the large aperture ratio ultra-wide angle lens according to Example 2.

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

[0129] The first lens group G1 is composed of, in order from the object side, a concave meniscus lens component N1 consisting of a concave meniscus lens L1 with a convex surface facing the object side, a concave meniscus lens component N2 consisting of a concave meniscus lens L2 with a convex surface facing the object side, a cemented lens of a convex meniscus lens L3 with a 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 a convex surface facing the object side and a convex meniscus lens L10 with a convex surface facing the object side.

[0130] The second lens group G2 is composed of, in order from the object side, a cemented lens of a convex meniscus lens L11 with a convex surface facing the image side, a convex meniscus lens L12 with a convex surface facing the image side, and a concave meniscus lens L13 with a convex surface facing the image side, a convex meniscus lens L14 with a convex surface facing the image side, a biconvex lens L15, a convex meniscus lens L16 with a 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 from L7 to L10 integrally along the optical axis toward the image side, focusing from an infinite object to a close-distance object is possible. Nevertheless, it is also possible to perform focusing by moving part or all of the optical system in the optical axis direction.

[0132] The specifications of the large aperture ratio ultra-wide angle lens according to Example 2 are shown below.

[0133] Numerical Example 2 Unit: mm [Surface Data] Surface number r d nd vd ΔPgF Corresponding optical material 0 (d0) 1 70.9430 3.0000 1.95375 32.32 -0.0002 TAFD45 2 39.6332 6.3946 3 49.5611 2.0000 2.00069 25.46 0.0110 TAFD40-W 4 20.4420 15.0704 5 -615.5293 3.7743 1.91082 35.25 -0.0028 TAFD35 6 -68.3304 1.0000 1.43700 95.10 0.0564 FCD100 7 31.0972 9.0087 8 -25.8197 1.0000 1.91082 35.25 -0.0028 TAFD35 9 38.3086 5.7129 1.86966 20.02 0.0310 FDS20-W 10 -155.2260 (d10) 11 3423.5606 5.3753 1.49700 81.61 0.0373 FCD1 12 -40.1836 0.3004 *13 88.0834 5.6688 1.85135 40.10 -0.0067 M-TAFD305 *14 -124.6795 1.2998 15 57.3790 0.9997 1.77250 49.62 -0.0088 TAF1 16 25.5128 4.9391 2.05090 26.94 0.0052 TAFD65 17 40.6599 (d17) 18 (Diaphragm) ∞ 3.5448 19 -2749.0125 3.1260 1.43700 95.10 0.0564 FCD100 20 -107.9561 2.1000 21 -181.7676 10.1370 1.43700 95.10 0.0564 FCD100 22 -22.4977 1.0000 1.85451 25.15 0.0071 NBFD25 23 -90.9572 0.3000 24 -1318.8089 5.9392 1.49700 81.61 0.0373 FCD1 25 -40.5459 0.3000 26 30.6100 8.2176 1.43700 95.10 0.0564 FCD100 27 -1160.6200 0.3213 28 89.2221 3.2047 1.94595 17.98 0.0385 FDS18-W 29 335.8016 0.3000 30 26.7314 7.8895 1.43700 95.10 0.0564 FCD100 31 -77.2159 0.8500 1.85451 25.15 0.0071 NBFD25 32 28.0958 2.6306 *33 40.2346 5.4564 1.80610 40.73 -0.0058 M-NBFD130 *34 -107.6407 14.4500 35 ∞ 2.5000 1.51680 64.20 0.0014 BSC7 36 ∞ (BF) [Aspherical Data] Surface 13, Surface 14, Surface 33, Surface 34 K 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A4 6.67394E-07 1.73143E-06 -1.26529E-05 -2.58659E-06 A6 -1.61981E-09 -2.26287E-10 -4.95945E-08 -4.98148E-08 A8 1.28312E-12 -2.33718E-11 9.44730E-11 9.96431E-11 A10 -7.63542E-14 5.79288E-14 -8.71214E-13 -5.70081E-13 A12 4.57302E-17 -2.56856E-16 -4.35790E-16 -1.58415E-15 A14 5.68935E-19 4.92346E-19 0.00000E+00 4.13406E-18 A16 -2.04827E-21 -1.12558E-21 0.00000E+00 0.00000E+00 [Various data] Wide angle (INF) Focal length 8.15 F-number 1.03 Full angle of view 2ω 185.73 Image height Y 11.93 Overall lens length 149.99 [Variable interval data] INF Close distance (d0) ∞ 220.2021 (d10) 4.3946 4.6802 (d17) 6.7828 6.4972 (BF) 1.0000 1.0000 [Lens group data] Group Starting surface Focal length G1 1 -76.3147 G2 19 29.7796 [Convex lens in the second lens group G2 that satisfies conditional expression (16)] Surface number Corresponding optical material G2LPAXh G2LPOAh G2LPAXh / G2LPOAh ΔPgF 24 FCD1 17.148 6.373 2.7 0.0373 26 FCD100 17.312 8.740 2.0 0.0564 28 FDS18-W 16.139 9.814 1.6 0.0385 30 FCD100 13.829 10.153 1.4 0.0564 33 M-NBFD130 10.555 10.514 1.0 -0.0058

[0134] [Example 3] FIG. 11 is a lens configuration diagram at infinity focus of the large aperture ratio ultra-wide angle lens according to Example 3.

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

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

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

[0138] As an example of focusing, among the lenses constituting the first lens group G1, by moving L8 toward the image side along the optical axis, focusing from an infinite object to a near object is possible. Nevertheless, it is also possible to perform focusing by moving a part or the whole of the optical system in the optical axis direction.

[0139] The specifications of the large aperture ratio ultra-wide angle lens according to Example 3 are shown below.

[0140] Numerical Example 3 Unit: mm [Surface Data] Surface Number r d nd vd ΔPgF Applicable Material 0 (d0) 1 109.2625 3.2000 1.88300 40.80 -0.0094 TAFD30 2 56.8200 7.4594 3 97.5361 2.2000 2.00100 29.13 0.0035 TAFD55-W 4 25.8504 16.9680 5 -919.4422 6.3047 1.88300 40.80 -0.0094 TAFD30 6 -56.4257 1.3369 1.43700 95.10 0.0564 FCD100 7 63.8170 9.8914 8 -37.0971 1.2936 1.48749 70.44 0.0090 FC5 9 76.4236 6.0467 2.00100 29.13 0.0035 TAFD55-W 10 -97.1124 0.1875 11 -129.7405 1.2480 1.60311 60.64 0.0022 S-BSM14 12 111.4369 (d12) 13 70.5891 2.3511 1.68893 31.07 0.0079 S-TIM28 14 133.3264 (d14) *15 79.7484 5.8668 1.77377 47.17 -0.0078 MC-TAF401 *16 -115.3962 3.9562 17 192.5212 0.9990 1.86966 20.02 0.0310 FDS20-W 18 35.2125 3.6459 2.00100 29.13 0.0035 TAFD55-W 19 64.9829 4.8785 20 (Aperture) ∞ 3.5080 21 539.5023 3.9395 1.59282 68.62 0.0192 FCD515 22 -83.4488 2.6689 23 1065.0975 8.0417 1.48071 85.29 0.0413 FCD915 24 -28.6941 0.9990 1.85451 25.15 0.0071 NBFD25 25 -150.6573 0.4573 26 129.2499 4.6033 1.98613 16.48 0.0468 FDS16-W 27 -106.5875 0.3000 28 78.2500 0.9950 1.76634 35.82 -0.0047 S-NBH59 29 26.5216 7.5754 1.43700 95.10 0.0564 FCD100 30 -641.5498 1.5000 31 37.1997 8.4302 1.43700 95.10 0.0564 FCD100 32 -59.4924 1.7256 33 43.4097 6.9530 1.49700 81.61 0.0373 FCD1 34 -62.0139 0.8477 1.91082 35.25 -0.0028 TAFD35 35 29.7524 3.3928 *36 133.7065 3.7491 1.80610 40.73 -0.0058 MC-NBFD130 *37 -199.3448 14.8136 38 ∞ 2.5000 1.51680 64.20 0.0014 BSC7 39 ∞ (BF) [Aspherical Data] Surface 15, Surface 16, Surface 36, Surface 37 K 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A4 -2.23652E-06 4.05148E-07 -1.04802E-06 1.87054E-06 A6 -2.25040E-09 -3.08367E-09 -1.09807E-08 -7.69431E-09 A8 3.84549E-12 1.68754E-12 -3.35729E-12 -8.98365E-11 A10 3.11662E-15 2.86917E-14 1.59525E-13 6.98929E-13 A12 -6.72119E-17 -1.86935E-16 -2.69304E-16 -2.03111E-15 A14 1.49463E-19 4.08499E-19 0.00000E+00 2.18373E-18 A16 -8.65376E-23 -2.97153E-22 0.00000E+00 0.00000E+00 [Various data] Wide angle (INF) Focal length 15.50 F-number 1.46 Full angle of view 2ω 185.73 Image height Y 22.39 Overall lens length 168.50 [Variable interval data] INF Close distance (d0) ∞ 435.2537 (d12) 3.9500 5.9915 (d14) 8.7163 6.6748 (BF) 1.0000 1.0000 [Lens group data] Group Starting surface Focal length G1 1 -111.4197 G2 21 41.1473 [Convex lens within the second lens group G2 that satisfies conditional expression (16)] Surface number Corresponding optical material G2LPAXh G2LPOAh G2LPAXh / G2LPOAh ΔPgF 26 FDS16-W 16.60 7.01 2.4 0.0468 29 FCD100 14.96 8.47 1.8 0.0564 31 FCD100 13.85 11.29 1.2 0.0564 33 FCD1 10.54 12.56 0.8 0.0373 36 MC-NBFD130 7.01 13.32 0.5 -0.0058

[0141] [Example 4] FIG. 16 is a lens configuration diagram at infinity focus of a large aperture ratio ultra-wide angle lens according to Example 4.

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

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

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

[0145] As an example of focusing, among the lenses constituting the first lens group G1, by moving the lenses from L9 to L12 integrally along the optical axis toward the image side, focusing from an infinite object to a close-distance object is possible. Nevertheless, it is also possible to perform focusing by moving part or all of the optical system in the optical axis direction.

[0146] The specifications of the large aperture ratio ultra-wide angle lens according to Example 4 are shown below.

[0147] Numerical Example 4 Unit: mm [Surface Data] Surface number r d nd vd ΔPgF Corresponding optical material 0 (d0) 1 76.0166 3.0000 1.88300 40.80 -0.0094 TAFD30 2 33.4076 9.4277 3 46.7261 4.2743 1.85451 25.15 0.0071 NBFD25 4 59.2616 2.0000 1.94595 17.98 0.0385 FDS18-W 5 16.7084 13.1427 6 -34.2629 3.1403 1.85451 25.15 0.0071 NBFD25 7 -24.9850 1.0000 1.43700 95.10 0.0564 FCD100 8 -3096.5243 2.8099 9 -79.1069 2.8052 1.85451 25.15 0.0071 NBFD25 10 -39.5852 2.7846 11 -23.7094 1.0000 1.77250 49.62 -0.0088 TAF1 12 33.2902 3.2581 1.86966 20.02 0.0310 FDS20-W 13 124.4257 (d13) 14 118.5925 3.9283 1.49700 81.61 0.0373 FCD1 15 -51.3653 0.3000 *16 520.2443 4.2446 1.85135 40.10 -0.0067 M-TAFD305 *17 -58.1074 0.3000 18 35.7963 1.0000 1.65160 58.54 -0.0041 S-LAL7Q 19 25.1332 3.1571 2.00100 29.13 0.0035 TAFD55-W 20 33.9522 (d20) 21 (Aperture) ∞ 3.5021 22 -35542.9790 3.9342 1.49700 81.61 0.0373 FCD1 23 -40.5698 2.1000 24 -50.7128 6.8888 1.43700 95.10 0.0564 FCD100 25 -20.0308 1.0000 1.85451 25.15 0.0071 NBFD25 26 -80.7330 0.3000 27 165.5981 3.5062 1.59282 68.62 0.0192 FCD515 28 -93.8173 0.3000 29 26.1052 7.1747 1.43700 95.10 0.0564 FCD100 30 -127.6923 0.7636 31 170.8089 2.9191 1.94595 17.98 0.0385 FDS18-W 32 -207.3386 0.3000 33 42.0574 5.6832 1.43700 95.10 0.0564 FCD100 34 -36.7982 0.8500 1.85451 25.15 0.0071 NBFD25 35 25.7957 0.8626 *36 24.5956 5.6765 1.80610 40.73 -0.0058 M-NBFD130 *37 -132.3414 14.4500 38 ∞ 2.5000 1.51680 64.20 0.0014 BSC7 39 ∞ (BF) [Aspherical Data] Surface 16, Surface 17, Surface 36, Surface 37 K 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A4 1.93585E-06 2.53223E-06 -7.64682E-06 1.04361E-05 A6 2.07469E-09 4.77753E-09 -1.24828E-08 -5.03599E-09 A8 2.10019E-11 -1.64410E-11 8.31091E-11 9.35222E-11 A10 -9.10124E-14 1.22810E-13 -3.11642E-13 -6.63784E-14 A12 -2.62256E-16 -6.75655E-16 -4.35758E-16 -1.58419E-15 A14 5.68925E-19 4.92352E-19 0.00000E+00 4.13406E-18 A16 -1.15124E-21 -4.86103E-22 0.00000E+00 0.00000E+00 [Various data] Wide angle (INF) Focal length 8.15 F-number 1.26 Full picture angle 2ω 185.73 Image height Y 11.93 Overall lens length 135.00 [Variable interval data] INF Near distance (d0) ∞ 220.0000 (d13) 3.5000 3.7405 (d20) 6.2164 5.9759 (BF) 1.0000 1.0000 [Lens group data] Group Starting surface Focal length G1 1 -104.0373 G2 22 28.5547 [Convex lens in the second lens group G2 that satisfies conditional expression (16)] Surface number Corresponding optical material G2LPAXh G2LPOAh G2LPAXh / G2LPOAh ΔPgF 27 FCD515 12.46051 5.86111 2.1 0.0192 29 FCD100 12.54806 7.35643 1.7 0.0564 31 FDS18-W 11.49705 8.54917 1.3 0.0385 33 FCD100 10.29538 8.90658 1.2 0.0564 36 M-NBFD130 8.27639 9.82554 0.8 -0.0058

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

[0149] The large-aperture ratio ultra-wide-angle lens of FIG. 21 is composed of a first lens group G1 having a negative refractive power, an aperture stop S, and a second lens group G2 having a positive refractive power, 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 a convex surface facing the object side and a concave meniscus lens L2 with a convex surface facing the object side, in order from the object side, a meniscus lens component N2 consisting of a concave meniscus lens L3 with a convex surface facing the object side, a cemented lens of a convex meniscus lens L4 with a 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 a 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 a convex surface facing the object side and a convex meniscus lens L11 with a convex surface facing the object side.

[0151] The second lens group G2 is composed of a convex meniscus lens L12 with a convex surface facing the image side, in order from the object side, a cemented lens of a convex meniscus lens L13 with a convex surface facing the image side and a concave meniscus lens L14 with a 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.

[0152] As an example of focusing, among the lenses constituting the first lens group G1, by moving the lenses from L8 to L11 integrally along the optical axis toward the image side, focusing from an infinite object to a close-distance object is possible. Nevertheless, it is also possible to perform focusing by moving a part or the whole of the optical system in the optical axis direction.

[0153] The specifications of the large-aperture ratio ultra-wide-angle lens according to Example 5 are shown below.

[0154] Numerical Example 5 Unit: mm [Surface Data] Surface number r d nd vd ΔPgF Corresponding optical material 0 (d0) 1 78.1841 5.8899 1.65844 50.88 -0.0008 S-BSM25 2 98.6169 1.9999 1.87071 40.73 -0.0069 TAFD32 3 29.9011 6.8179 4 44.1964 1.9997 2.00100 29.13 0.0035 TAFD55-W 5 19.5714 16.1960 6 -52.0691 3.3481 2.00100 29.13 0.0035 TAFD55-W 7 -30.6034 1.3500 1.43700 95.10 0.0564 FCD100 8 231.8150 5.0695 9 -25.9907 1.0478 1.80100 34.97 0.0009 S-LAM66 10 32.1522 4.2042 1.86966 20.02 0.0310 FDS20-W 11 248.2593 (d11) 12 130.7311 3.9395 1.49700 81.61 0.0373 FCD1 13 -50.6408 0.3567 *14 91.5376 4.5291 1.85135 40.10 -0.0067 M-TAFD305 *15 -82.3330 0.3000 16 37.5071 1.0001 1.80420 46.50 -0.0075 TAF3D 17 20.5675 3.7743 1.95375 32.32 -0.0002 TAFD45 18 30.1702 (d18) 19 (Diaphragm) ∞ 3.7348 20 -305.9715 2.9272 1.49700 81.61 0.0373 FCD1 21 -63.7074 2.4122 22 -67.4760 7.2451 1.43700 95.10 0.0564 FCD100 23 -20.8552 1.0571 1.85451 25.15 0.0071 NBFD25 24 -54.3257 0.4218 25 136.7619 3.9872 1.55032 75.50 0.0274 FCD705 26 -75.3445 0.3000 27 32.5023 6.2497 1.43700 95.10 0.0564 FCD100 28 -167.1194 0.8577 29 160.9965 3.2738 1.89286 20.36 0.0276 S-NPH4 30 -126.2144 0.4042 31 48.1172 5.9576 1.43700 95.10 0.0564 FCD100 32 -35.9886 0.8500 1.85451 25.15 0.0071 NBFD25 33 30.1966 1.4700 *34 34.2985 5.3761 1.80610 40.73 -0.0058 M-NBFD130 *35 -82.2760 14.5474 36 ∞ 2.5000 1.51680 64.20 0.0014 BSC7 37 ∞ (BF) [Aspherical Data] Surface 14, Surface 15, Surface 34, Surface 35 K 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A4 -3.07739E-07 2.80585E-06 -9.39927E-06 2.25624E-08 A6 -1.94032E-09 -6.51496E-10 -2.78573E-08 -2.93477E-08 A8 5.68308E-13 -2.66578E-11 4.65482E-11 3.97997E-11 A10 -9.63453E-14 4.66964E-14 -8.77629E-13 -6.81332E-13 A12 -9.28204E-17 -3.82840E-16 -4.35791E-16 -1.58415E-15 A14 5.68937E-19 4.92344E-19 0.00000E+00 4.13406E-18 A16 -1.15701E-21 -5.47469E-22 0.00000E+00 0.00000E+00 [Various data] Wide angle (INF) Focal length 8.15 F number 1.26 Full angle of view 2ω 185.73 Image height Y 11.93 Overall lens length 138.00 [Variable interval data] INF Near distance (d0) ∞ 219.0202 (d11) 5.2521 5.5152 (d18) 6.3532 6.0902 (BF) 1.0000 1.0000 [Lens group data] Group Starting surface Focal length G1 1 -105.6709 G2 20 28.3077 [Convex lens in the second lens group G2 that satisfies conditional expression (16)] Surface number Corresponding optical material G2LPAXh G2LPOAh G2LPAXh / G2LPOAh ΔPgF 25 FCD705 12.85 6.14 2.1 0.0274 27 FCD100 12.77 7.61 1.7 0.0564 29 S-NPH4 11.81 8.68 1.4 0.0276 31 FCD100 10.48 9.04 1.2 0.0564 34 M-NBFD130 8.28 9.87 0.8 -0.0058

[0155] [Example 6] FIG. 26 is a lens configuration diagram at infinity focus of the large aperture ratio ultra-wide angle lens according to Example 6.

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

[0157] The first lens group G1 is composed of, in order from the object side, a concave meniscus lens component N1 consisting of a concave meniscus lens L1 with a convex surface facing the object side, a concave meniscus lens component N2 consisting of a concave meniscus lens L2 with a 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 a convex surface facing the image side, a biconvex aspherical lens L8, a biconcave lens L9, and a cemented lens of a convex meniscus lens L10 with a convex surface facing the object side.

[0158] The second lens group G2 is composed of, in order from the object side, a biconvex lens L11, a cemented lens of a convex meniscus lens L12 with a convex surface facing the image side and a concave meniscus lens L13 with a convex surface facing the image side, a convex meniscus lens L14 with a 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.

[0159] As an example of focusing, among the lenses constituting the first lens group G1, by moving the lenses from L7 to L10 integrally along the optical axis toward the image side, focusing from an infinite object to a close object is possible. Nevertheless, it is also possible to perform focusing by moving part or all of the optical system in the optical axis direction.

[0160] The specifications of the large aperture ratio ultra-wide angle lens according to Example 6 are shown below.

[0161] Numerical Example 6 Unit: mm [Surface Data] Surface No. r d nd vd ΔPgF Corresponding optical material 0 (d0) 1 105.0884 4.0000 1.95375 32.32 -0.0002 TAFD45 2 62.3697 8.0986 3 96.5425 2.4000 1.79952 42.24 -0.0049 S-LAH52Q 4 25.6052 18.2653 5 431.7667 6.1930 1.85451 25.15 0.0071 NBFD25 6 -73.7267 1.7495 1.43700 95.10 0.0564 FCD100 7 36.5412 12.0807 8 -29.4512 1.4008 1.71736 29.50 0.0087 E-FD1L 9 1220.0710 3.6809 1.94595 17.98 0.0385 FDS18-W 10 -133.0022 (d10) 11 -1415.9797 4.9937 1.49700 81.61 0.0373 FCD1 12 -52.2108 0.7207 *13 53.3910 9.2920 1.85135 40.10 -0.0067 M-TAFD305 *14 -66.6961 0.8637 15 -107.7114 0.9992 1.77047 29.74 0.0002 NBFD29 16 42.1147 4.2984 2.05090 26.94 0.0052 TAFD65 17 81.4727 (d17) 18 (Diaphragm) ∞ 3.5000 19 493.3890 3.6904 1.49700 81.61 0.0373 FCD1 20 -120.1125 2.1000 21 -176.3604 9.3077 1.43700 95.10 0.0564 FCD100 22 -29.2381 1.0000 1.85451 25.15 0.0071 NBFD25 23 -63.4867 0.3000 24 64.4652 4.2523 1.43700 95.10 0.0564 FCD100 25 460.1202 0.3000 26 33.6927 8.0870 1.43700 95.10 0.0564 FCD100 27 -195.6035 0.3681 28 156.2083 3.2258 1.94595 17.98 0.0385 FDS18-W 29 -459.9519 0.3000 30 161.1771 9.7675 1.43700 95.10 0.0564 FCD100 31 -33.8619 0.8500 1.80000 29.84 0.0070 S-NBH55 32 44.8498 0.9528 *33 59.9308 4.6568 1.80610 40.73 -0.0058 M-NBFD130 *34 -244.2526 17.5000 35 ∞ 2.5000 1.51680 64.20 0.0014 BSC7 36 ∞ (BF) [Aspherical Data] Surface 13, Surface 14, Surface 33, Surface 34 K 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A4 -3.17059E-07 2.16094E-06 -4.39558E-06 4.57987E-06 A6 5.33641E-10 8.18081E-10 7.32350E-10 1.36979E-09 A8 6.57168E-12 7.55549E-13 2.08542E-11 -4.99721E-12 A10 -1.62374E-14 -3.38820E-15 1.90632E-13 5.87530E-13 A12 -1.19807E-16 -1.12747E-16 2.65861E-16 -1.78009E-15 A14 5.75716E-19 5.09977E-19 0.00000E+00 4.13406E-18 A16 -6.81690E-22 -6.19402E-22 0.00000E+00 0.00000E+00 [Various data] Wide angle (INF) Focal length 15.29 F number 1.26 Full angle of view 2ω 185.73 Image height Y 22.11 Overall lens length 163.26 [Variable interval data] INF Close distance (d0) ∞ 424.4124 (d10) 3.6964 4.1236 (d17) 6.8718 6.4446 (BF) 1.0000 1.0000 [Lens group data] Group Starting surface Focal length G1 1 1309.1203 G2 19 42.6388 [Convex lens in the second lens group G2 that satisfies conditional expression (16)] Surface number Applicable optical material G2LPAXh G2LPOAh G2LPAXh / G2LPOAh ΔPgF 24 FCD100 17.593 8.290 2.1 0.0564 26 FCD100 16.740 10.217 1.6 0.0564 28 FDS18-W 15.170 11.582 1.3 0.0385 30 FCD100 13.858 11.911 1.2 0.0564 33 M-NBFD130 9.543 13.335 0.7 -0.0058

[0162] [Example 7] FIG. 31 is a lens configuration diagram at infinity focus of the large aperture ratio ultra-wide angle lens according to Example 7.

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

[0164] The first lens group G1 is composed of, in order from the object side, a concave meniscus lens component N1 consisting of a concave meniscus lens L1 with a convex surface facing the object side, a concave meniscus lens component N2 consisting of a concave meniscus lens L2 with a convex surface facing the object side, a convex meniscus lens L3 with a convex surface facing the image side and a cemented lens of a concave meniscus lens L4 with a convex surface facing the image side, a cemented lens of a biconcave lens L5 and a convex meniscus lens L6 with a 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 a convex surface facing the object side and a convex meniscus lens L10 with a convex surface facing the object side.

[0165] The second lens group G2 is composed of, in order from the object side, a convex meniscus lens L11 with a convex surface facing the image side, a cemented lens of a convex meniscus lens L12 with a convex surface facing the image side and a concave meniscus lens L13 with a 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 from L7 to L10 integrally along the optical axis toward the image side, focusing from an infinite object to a close object is possible. Nevertheless, it is also possible to perform focusing by moving part or all of the optical system in the optical axis direction.

[0167] The specifications of the large aperture ratio ultra-wide angle lens according to Example 7 are shown below.

[0168] Numerical Example 7 Unit: mm [Surface Data] Surface number r d nd vd ΔPgF Corresponding optical material 0 (d0) 1 57.5656 3.0000 1.95375 32.32 -0.0002 TAFD45 2 34.4906 10.0000 3 52.6007 2.0000 2.00100 29.13 0.0035 TAFD55-W 4 16.4925 14.3440 5 -43.0810 3.7168 1.85451 25.15 0.0071 NBFD25 6 -24.1033 1.0000 1.43700 95.10 0.0564 FCD100 7 -103.3559 3.8100 8 -23.9752 1.0084 1.80420 46.50 -0.0075 TAF3D 9 37.1560 3.5509 1.86966 20.02 0.0310 FDS20-W 10 130.1216 (d10) 11 97.1994 4.0662 1.49700 81.61 0.0373 FCD1 12 -46.6097 0.3065 *13 144.9762 4.3599 1.85135 40.10 -0.0067 M-TAFD305 *14 -65.1909 0.4067 15 38.5469 0.9996 1.80611 40.73 -0.0080 NBFD13 16 25.0162 2.9914 2.05090 26.94 0.0052 TAFD65 17 32.1087 (d17) 18 (Aperture) ∞ 4.5190 19 -205.3714 3.1058 1.49700 81.61 0.0373 FCD1 20 -59.4551 2.4492 21 -61.0121 7.7636 1.43700 95.10 0.0564 FCD100 22 -19.6631 1.0003 1.85451 25.15 0.0071 NBFD25 23 -54.8875 0.5835 24 222.0073 4.2554 1.55032 75.50 0.0274 FCD705 25 -56.9266 1.3121 26 28.5159 6.9065 1.43700 95.10 0.0564 FCD100 27 -375.7035 0.8801 28 119.4415 3.3450 1.94595 17.98 0.0385 FDS18-W 29 -195.2717 0.3120 30 44.4274 5.9592 1.43700 95.10 0.0564 FCD100 31 -38.4161 0.8640 1.85451 25.15 0.0071 NBFD25 32 26.4842 1.3541 *33 27.2323 6.1787 1.80610 40.73 -0.0058 M-NBFD130 *34 -110.8318 14.4500 35 ∞ 2.5000 1.51680 64.20 0.0014 BSC7 36 ∞ (BF) [Aspherical Data] Surface 13, Surface 14, Surface 33, Surface 34 K 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A4 6.55853E-07 1.91717E-06 -8.88512E-06 2.19582E-06 A6 -2.29219E-09 -1.09209E-09 -2.18487E-08 -2.31128E-08 A8 -1.63019E-12 -2.62880E-11 4.87875E-11 7.01848E-11 A10 -1.07318E-13 4.15624E-14 -7.28767E-13 -6.46356E-13 A12 -6.86909E-17 -4.43982E-16 -4.83940E-16 -1.57392E-15 A14 6.59535E-19 5.03346E-19 0.00000E+00 4.13402E-18 A16 -1.09599E-21 -2.69038E-22 0.00000E+00 0.00000E+00 [Various Data] Wide Angle (INF) Focal Length 7.70 F Number 1.26 Full Angle of View 2ω 202.00 Image Height Y 11.89 Overall lens length 135.68 [Variable interval data] INF Close distance (d0) ∞ 207.2333 (d10) 5.0518 5.2879 (d17) 6.3314 6.0953 (BF) 1.0000 1.0000 [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)] Surface number Corresponding optical material G2LPAXh G2LPOAh G2LPAXh / G2LPOAh ΔPgF 24 FCD705 12.755 6.568 1.9 0.0274 26 FCD100 12.808 8.629 1.5 0.0564 28 FDS18-W 11.793 9.517 1.2 0.0385 30 FCD100 10.538 9.700 1.1 0.0564 33 M-NBFD130 8.354 10.310 0.8 -0.0058

[0169] [Example 8] Figure 36 is a lens configuration diagram of the large aperture ratio ultra-wide angle lens according to Example 8 at infinity focus.

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

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

[0172] The second lens group G2 is composed of, in order from the object side, a concave meniscus lens L13 with a convex surface facing the object side, a double convex lens L14, a double convex lens L15, a combined 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.

[0173] As an example of focusing, among the lenses constituting the first lens group G1, by moving L9 toward the image side along the optical axis, focusing from an infinite object to a close-distance object is possible. Nevertheless, it is also possible to perform focusing by moving a part or the whole of the optical system in the optical axis direction.

[0174] The specifications of the large aperture ratio ultra-wide angle lens according to Example 8 are shown below.

[0175] Numerical Example 8 Unit: mm [Surface Data] Surface number r d nd vd ΔPgF Corresponding optical material 0 (d0) 1 112.3138 4.0000 1.95375 32.32 0.0003 S-LAH98 2 34.2660 8.7111 3 55.2718 2.8000 1.83481 42.72 -0.0068 TAFD5G 4 26.7269 17.7777 5 -80.6582 1.6980 1.49700 81.61 0.0373 FCD1 6 -983.3216 5.9013 1.95375 32.32 -0.0002 TAFD45 7 -57.9494 3.0030 8 -41.5288 1.5482 1.64769 33.84 0.0049 E-FD2 9 -708.8133 6.2185 10 -43.2268 1.2490 1.49700 81.61 0.0373 FCD1 11 107.1727 0.3000 12 52.8607 8.6416 1.88300 40.80 -0.0094 TAFD30 13 -76.5204 1.2483 1.43700 95.10 0.0564 FCD100 14 84.1545 (d14) 15 79.1535 3.2271 1.94595 17.98 0.0385 FDS18-W 16 198.2362 (d16) *17 92.7539 4.7726 1.59271 66.97 0.0088 MC-PCD5170 *18 -85.5420 0.3000 19 322.3327 9.5384 1.77250 49.62 -0.0088 TAF1 20 -23.9034 1.0000 2.05090 26.94 0.0052 TAFD65 21 -69.0134 2.5000 22(Diaphragm) ∞ 2.5000 23 567.9832 1.0000 1.67270 32.17 0.0058 E-FD5 24 29.7016 2.7592 25 38.1242 9.3236 1.43700 95.10 0.0564 FCD100 26 -44.9424 0.5000 27 167.2352 5.2510 1.94595 17.98 0.0385 FDS18-W 28 -73.7899 0.3000 29 -620.9350 1.0967 1.68893 31.16 0.0066 E-FD8 30 21.2617 14.5557 1.59282 68.62 0.0192 FCD515 31 -34.9210 0.3000 32 -51.2896 1.0000 1.85451 25.15 0.0071 NBFD25 33 91.4301 3.5000 *34 148.0573 3.4850 1.80610 40.73 -0.0058 M-NBFD130 *35 -450.0000 19.9335 36 ∞ 2.1000 1.51680 64.20 0.0014 BSC7 37 ∞ (BF) [Aspherical Data] Surface 17, Surface 18, Surface 34, Surface 35 K 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A4 -5.20870E-06 2.40548E-06 -9.85290E-06 -8.77603E-06 A6 1.68908E-10 -3.25984E-09 -2.18389E-09 9.04754E-10 A8 -6.31999E-12 1.32317E-12 1.25848E-10 1.01128E-10 A10 1.92312E-14 0.00000E+00 -2.23659E-13 -9.72629E-14 A12 0.00000E+00 0.00000E+00 8.49746E-17 -6.12395E-17 A14 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A16 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 [Various data] Wide angle (INF) Focal length 15.51 F number 1.46 Full picture angle 2ω 185.73 Image height Y 22.40 Overall lens length 162.54 [Variable interval data] INF Near distance (d0) ∞ 435.5949 (d14) 2.5000 4.1313 (d16) 7.0000 5.3687 (BF) 1.0000 1.0000 [Lens group data] Group Starting surface Focal length G1 1 28.4098 G2 23 70.6349 [Convex lens in the second lens group G2 that satisfies conditional expression (16)] Surface number Applicable optical material G2LPAXh G2LPOAh G2LPAXh / G2LPOAh ΔPgF 27 FDS18-W 15.14826 6.9084 2.2 0.0385 30 FCD515 12.74823 8.46934 1.5 0.0192 34 M-NBFD130 8.71565 12.87559 0.7 -0.0058

[0176] [Example 9] Figure 41 is a lens configuration diagram at infinity focus of the large aperture ratio ultra-wide angle lens according to Example 9.

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

[0178] The first lens group G1 is composed of, in order from the object side, a concave meniscus lens component N1 consisting of a concave meniscus lens L1 with a convex surface facing the object side, a concave meniscus lens component N2 consisting of a concave meniscus lens L2 with a 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 a convex surface facing the image side, a convex meniscus lens L9 with a convex surface facing the object side, a biconvex aspherical lens L10, a cemented lens of a biconcave lens L11 and a plano-convex lens L12 with a convex surface facing the object side.

[0179] The second lens group G2 is composed of, in order from the object side, a cemented lens of a biconvex lens L13 and a concave meniscus lens L14 with a convex surface facing the image side, a biconvex lens L15, a cemented lens of a concave meniscus lens L16 with a 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 toward the image side along the optical axis, focusing from an infinite object to a close-distance object is possible. Nevertheless, focusing can also be performed by moving part or all of the optical system in the optical axis direction.

[0181] The specifications of the large-aperture ratio ultra-wide-angle lens according to Example 9 are shown below.

[0182] Numerical Example 9 Unit: mm [Surface Data] Surface number r d nd vd ΔPgF Corresponding optical material 0 (d0) 1 98.7053 4.0000 2.00069 25.46 0.0110 TAFD40-W 2 43.9390 9.5217 3 97.2080 2.8000 1.88300 40.80 -0.0094 TAFD30 4 27.2191 16.2160 5 -213.5111 1.6981 1.43700 95.10 0.0564 FCD100 6 185.5420 6.5692 1.77047 29.74 0.0002 NBFD29 7 -72.4901 3.4403 8 -45.3581 1.5485 1.59410 60.47 0.0156 FCD600 9 276.3884 7.5756 10 -39.1252 1.2494 1.49700 81.61 0.0373 FCD1 11 254.1854 0.3000 12 62.1410 8.4310 1.83481 42.72 -0.0068 TAFD5G 13 -64.8431 1.2489 1.61340 44.27 -0.0054 S-NBM51 14 -1674.5692 (d14) 15 68.8448 3.4012 1.95375 32.32 0.0003 S-LAH98 16 165.1776 (d16) *17 154.6546 4.8709 1.59271 66.97 0.0088 MC-PCD5170 *18 -65.8469 2.2392 19 -70.3351 1.0000 1.73037 32.23 -0.0005 NBFD32 20 38.3564 5.5908 1.95375 32.32 0.0003 S-LAH98 21 ∞ 2.5000 22 (Aperture) ∞ 2.5000 23 163.5955 7.6894 1.43700 95.10 0.0564 FCD100 24 -26.4662 0.9923 1.85451 25.15 0.0071 NBFD25 25 -159.1732 0.3000 26 66.7799 4.4880 1.94595 17.98 0.0385 FDS18-W 27 -1051.7542 0.3000 28 54.6478 0.9940 1.85451 25.15 0.0071 NBFD25 29 31.2809 9.2065 1.59522 67.73 0.0177 S-FPM2 30 -86.8624 0.9834 31 119.2742 12.0000 1.59522 67.73 0.0177 S-FPM2 32 -25.2449 0.9984 1.73037 32.23 -0.0005 NBFD32 33 45.9157 3.5000 *34 58.9965 4.5763 1.80610 40.73 -0.0058 M-NBFD130 *35 -450.0000 19.6699 36 ∞ 2.1000 1.51680 64.20 0.0014 BSC7 37 ∞ (BF) [Aspherical Data] Surface 17 Surface 18 Surface 34 Surface 35 K 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A4 -8.73064E-07 2.93720E-06 -1.36912E-05 -7.92100E-06 A6 3.33444E-09 1.20867E-09 -1.14939E-08 -6.93770E-09 A8 -1.10489E-12 4.39165E-12 -7.65401E-11 -9.93617E-11 A10 1.28985E-14 0.00000E+00 2.20186E-13 3.27569E-13 A12 0.00000E+00 0.00000E+00 1.08085E-16 -8.89676E-17 A14 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A16 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 [Various data] Wide angle (INF) Focal length 15.51 F number 1.46 Full picture angle 2ω 185.73 Image height Y 22.42 Overall lens length 165.00 [Variable interval data] INF Near distance (d0) ∞ 432.9120 (d14) 2.5000 4.1549 (d16) 7.0010 5.3462 (BF) 1.0000 1.0000 [Lens group data] Group Starting surface Focal length G1 1 128.6077 G2 23 48.8800 [Convex lens in the second lens group G2 that satisfies conditional expression (16)] Surface number Corresponding optical material G2LPAXh G2LPOAh G2LPAXh / G2LPOAh ΔPgF 29 S-FPM2 14.944 5.722 2.6 0.0177 31 S-FPM2 13.033 8.241 1.6 0.0177 34 M-NBFD130 8.748 12.745 0.7 -0.0058

[0183] [Example 10] FIG. 46 is a lens configuration diagram at infinity focus of a large aperture ratio ultra-wide angle lens according to Example 10.

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

[0185] The first lens group G1 is composed of, in order from the object side, a concave meniscus lens component N1 consisting of a concave meniscus lens L1 with a convex surface facing the object side, a concave meniscus lens component N2 consisting of a concave meniscus lens L2 with a convex surface facing the object side, a cemented lens of a convex meniscus lens L3 with a 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 a 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 a convex surface facing the object side and a convex meniscus lens L10 with a convex surface facing the object side.

[0186] The second lens group G2 is composed of, in order from the object side, a convex meniscus lens L11 with a convex surface facing the image side, a cemented lens of a convex meniscus lens L12 with a convex surface facing the image side and a concave meniscus lens L13 with a 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 from L7 to L10 integrally along the optical axis toward the image side, focusing from an infinite object to a close object is possible. Nevertheless, it is also possible to perform focusing by moving a part or the whole of the optical system in the optical axis direction.

[0188] The specifications of the large aperture ratio ultra-wide angle lens according to Example 10 are shown below.

[0189] Numerical Example 10 Unit: mm [Surface Data] Surface No. r d nd vd ΔPgF Corresponding Optical Material 0 (d0) 1 66.8969 3.0000 1.95375 32.32 0.0003 S-LAH98 2 26.0915 5.2825 3 31.6843 2.0000 1.95375 32.32 0.0003 S-LAH98 4 17.7585 12.9593 5 -79.9016 3.3649 1.85451 25.15 0.0071 NBFD25 6 -35.5849 1.6504 1.43700 95.10 0.0564 FCD100 7 82.9243 5.4787 8 -25.1965 1.0883 1.80100 34.97 0.0009 S-LAM66 9 31.9192 4.1874 1.86966 20.02 0.0310 FDS20-W 10 230.0159 (d10) 11 146.1103 4.0237 1.49700 81.61 0.0373 FCD1 12 -44.6598 0.3000 *13 117.2465 4.4343 1.85135 40.10 -0.0067 M-TAFD305 *14 -70.8792 1.1490 15 40.2335 0.9999 1.80440 39.58 -0.0010 S-LAH63Q 16 22.4130 3.2875 2.05090 26.94 0.0052 TAFD65 17 31.2387 (d17) 18 (Aperture) ∞ 4.2749 19 -291.0489 2.8532 1.49700 81.61 0.0373 FCD1 20 -65.9825 2.4054 21 -71.0126 7.4724 1.43700 95.10 0.0564 FCD100 22 -20.2989 1.0000 1.85451 25.15 0.0071 NBFD25 23 -56.5038 0.5986 24 223.1596 4.2656 1.55032 75.50 0.0274 FCD705 25 -55.7988 0.7680 26 32.3637 6.5820 1.43700 95.10 0.0564 FCD100 27 -164.2584 0.7552 28 159.3632 3.2913 1.94595 17.98 0.0385 FDS18-W 29 -142.3318 0.3000 30 45.2517 5.9578 1.43700 95.10 0.0564 FCD100 31 -37.1225 0.8500 1.85451 25.15 0.0071 NBFD25 32 29.8468 1.4869 *33 34.0201 5.5673 1.80610 40.73 -0.0058 M-NBFD130 *34 -88.7909 14.7372 35 ∞ 2.5000 1.51680 64.20 0.0014 BSC7 36 ∞ (BF) [Aspherical Data] Surface 13, Surface 14, Surface 33, Surface 34 K 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A4 2.43982E-07 2.61027E-06 -8.74514E-06 -1.12943E-06 A6 -2.49273E-09 -1.30700E-09 -2.53563E-08 -2.52830E-08 A8 -2.32133E-12 -2.88783E-11 6.38673E-11 5.83737E-11 A10 -1.14082E-13 4.33693E-14 -7.47845E-13 -5.16445E-13 A12 -9.13500E-17 -4.44549E-16 -5.45248E-17 -1.55588E-15 A14 5.57097E-19 5.00316E-19 0.00000E+00 4.13406E-18 A16 -1.17000E-21 -5.13779E-22 0.00000E+00 0.00000E+00 [Various data] Wide angle (INF) Focal length 8.15 F number 1.26 Full angle of view 2ω 185.73 Image height Y 11.93 Overall lens length 131.59 [Variable interval data] INF to close distance (d0) ∞ 224.2633 (d10) 5.3643 5.6235 (d17) 6.3544 6.0951 (BF) 1.0000 1.0000 [Lens group data] Group Starting surface Focal length G1 1 -88.9270 G2 19 28.0433 [Convex lens in the second lens group G2 that satisfies conditional expression (16)] Surface number Applicable optical material G2LPAXh G2LPOAh G2LPAXh / G2LPOAh ΔPgF 24 FCD705 12.848 6.596 1.9 0.0274 26 FCD100 12.824 8.469 1.5 0.0564 28 FDS18-W 11.866 9.464 1.3 0.0385 30 FCD100 10.579 9.739 1.1 0.0564 33 M-NBFD130 8.383 10.385 0.8 -0.0058

[0190] [Example 11] Figure 51 is a lens configuration diagram at infinity focus of the large aperture ratio ultra-wide angle lens according to Example 11.

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

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

[0193] The second lens group G2 is composed of, in order from the object side, a cemented lens of a biconvex lens L10 and a concave meniscus lens L11 with a convex surface facing the image side, a biconvex lens L12, a biconvex lens L13, a convex meniscus lens L14 with a 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 from L7 to L9 integrally along the optical axis toward the image side, focusing from an infinite object to a close-distance object is possible. Nevertheless, it is also possible to perform focusing by moving a part or the whole of the optical system in the optical axis direction.

[0195] The specifications of the large aperture ratio ultra-wide angle lens according to Example 11 are shown below.

[0196] Numerical Example 11 Unit: mm [Surface Data] Surface number r d nd vd ΔPgF Corresponding optical material 0 (d0) 1 67.2900 3.0000 1.95375 32.32 0.0003 S-LAH98 2 41.3838 8.7352 3 52.1615 2.0000 2.00100 29.13 0.0035 TAFD55-W 4 18.1324 15.5164 5 179.1485 4.3635 1.85478 24.80 0.0085 S-NBH56 6 -57.8236 1.0000 1.43875 94.66 0.0560 S-FPL55 7 21.0637 8.5020 8 -19.0241 1.0000 1.90043 37.37 -0.0045 TAFD37A 9 -169.3560 4.2124 1.86966 20.02 0.0310 FDS20-W 10 -30.6058 (d10) 11 157.1560 2.7797 1.49700 81.61 0.0373 FCD1 12 -161.0009 0.3000 *13 41.3631 5.5534 1.85135 40.10 -0.0067 M-TAFD305 *14 -55.9387 0.9864 15 778.6812 1.0000 1.77250 49.62 -0.0088 TAF1 16 33.5791 (d16) 17 (Aperture) ∞ 3.5000 18 337.9519 8.0673 1.43875 94.66 0.0560 S-FPL55 19 -21.0961 1.0000 1.85478 24.80 0.0085 S-NBH56 20 -220.9655 0.3000 21 66.9199 4.8116 1.53775 74.70 0.0254 S-FPM3 22 -64.8593 0.3000 23 41.7438 5.4048 1.59522 67.73 0.0177 S-FPM2 24 -218.6134 0.5009 25 91.4489 2.9745 1.94595 17.98 0.0385 FDS18-W 26 1224.3490 0.3000 27 21.4816 6.7604 1.43875 94.66 0.0560 S-FPL55 28 -109.9546 0.8500 1.80518 25.46 0.0131 FD60-W 29 25.9991 1.8290 *30 38.7592 4.4495 1.80610 40.73 -0.0058 M-NBFD130 *31 -162.2004 15.3592 32 ∞ 2.5000 1.51680 64.20 0.0014 BSC7 33 ∞ (BF) [Aspherical Data] Surface 13, Surface 14, Surface 30, Surface 31 K 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A4 -2.81080E-06 1.93216E-06 -6.35491E-06 1.64485E-05 A6 -1.25716E-09 2.08091E-09 5.30275E-08 6.01955E-08 A8 -1.95942E-12 -3.40050E-11 -2.75847E-11 -2.31795E-11 A10 -1.89149E-13 -6.57967E-14 1.35764E-12 1.72479E-12 A12 4.66222E-16 7.00762E-16 -5.04259E-16 -1.53100E-15 A14 4.77965E-18 1.71629E-18 0.00000E+00 4.09144E-18 A16 -5.95085E-20 -5.29005E-20 0.00000E+00 0.00000E+00 [Various data] Wide angle (INF) Focal length 7.70 F-number 1.26 Full angle of view 2ω 202.00 Image height Y 11.88 Overall lens length 128.00 [Variable interval data] INF Near distance (d0) ∞ 205.2527 (d10) 3.5000 4.0317 (d16) 5.6438 5.1120 (BF) 1.0000 1.0000 [Lens group data] Group Starting surface Focal length G1 1 -40.3001 G2 18 25.0935 [Convex lens in the second lens group G2 that satisfies conditional expression (16)] Surface number Applicable material G2LPAXh G2LPOAh G2LPAXh / G2LPOAh ΔPgF 23 S-FPM2 12.856 6.071 2.1 0.0177 25 FDS18-W 12.278 7.176 1.7 0.0385 27 S-FPL55 10.927 7.768 1.4 0.0560 30 M-NBFD130 8.557 8.354 1.0 -0.0058

[0197] [Example 12] FIG. 56 is a lens configuration diagram at infinity focus of the large aperture ratio ultra-wide angle lens according to Example 12.

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

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

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

[0201] As an example of focusing, among the lenses constituting the first lens group G1, by moving L8 toward the image side along the optical axis, focusing from an infinite object to a close object is possible. Nevertheless, it is also possible to perform focusing by moving part or all of the optical system in the optical axis direction.

[0202] The specifications of the large aperture ratio ultra-wide angle lens according to Example 12 are shown below.

[0203] Numerical Example 12 Unit: mm [Surface Data] Surface number r d nd vd ΔPgF Corresponding optical material 0 (d0) 1 107.7115 3.2000 1.88300 40.80 -0.0094 TAFD30 2 51.8324 5.0000 3 61.6766 2.2000 2.00100 29.13 0.0035 TAFD55-W 4 23.0469 17.0075 5 -437.9084 6.0155 1.91082 35.25 -0.0028 TAFD35 6 -46.3851 1.0000 1.43700 95.10 0.0564 FCD100 7 39.7177 9.3614 8 -30.5889 1.2909 1.63980 34.47 0.0059 S-TIM27 9 613.6154 0.2000 10 81.5892 3.7398 2.00100 29.13 0.0035 TAFD55-W 11 -431.5214 1.2478 1.49700 81.61 0.0373 FCD1 12 182.9894 (d12) 13 49.2579 3.8959 1.95375 32.32 -0.0002 TAFD45 14 314.0027 (d14) *15 177.2163 2.7755 1.77377 47.17 -0.0078 MC-TAF401 *16 -330.8819 2.3588 17 -183.2441 1.0000 1.80518 25.42 0.0134 S-TIH6 18 134.6389 3.1728 2.00100 29.13 0.0035 TAFD55-W 19 -819.5687 2.5000 20 (Aperture) ∞ 3.4884 21 112.4142 11.3509 1.48071 85.29 0.0413 FCD915 22 -23.2781 1.0000 1.85451 25.15 0.0071 NBFD25 23 -41.1422 0.3000 24 51.9123 4.6218 1.86966 20.02 0.0310 FDS20-W 25 1230.0149 0.3000 26 37.1727 1.0000 1.85451 25.15 0.0071 NBFD25 27 20.6943 10.7654 1.43700 95.10 0.0564 FCD100 28 -54.8713 0.3000 29 342.6779 5.2180 1.49700 81.61 0.0373 FCD1 30 -32.1179 1.0000 1.85883 30.00 0.0035 NBFD30 31 58.9286 4.2268 *32 165.5922 5.1795 1.80610 40.73 -0.0058 MC-NBFD130 *33 -138.4515 17.5000 34 ∞ 2.5000 1.51680 64.20 0.0014 BSC7 35 ∞ (BF) [Aspherical Data] Surface 15, Surface 16, Surface 32, Surface 33 K 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A4 -6.32687E-06 -9.74442E-08 -1.69670E-06 2.34273E-06 A6 6.99614E-09 2.18933E-09 4.57151E-08 2.95505E-08 A8 -7.12822E-12 2.01425E-11 -3.68763E-10 -2.15074E-10 A10 2.55926E-14 -7.39304E-14 1.88482E-12 9.16473E-13 A12 -6.73556E-17 -1.62263E-16 -3.23696E-15 -9.68715E-16 A14 4.97415E-20 1.17443E-18 0.00000E+00 -9.69817E-19 A16 -1.19614E-23 -1.75009E-21 0.00000E+00 0.00000E+00 [Various Data] Wide Angle (INF) Focal Length 15.50 F-Number 1.46 Full Angle of View 2ω 185.73 Image Height Y 22.36 Overall Length of Lens 145.00 [Variable Interval Data] INF - Close Distance (d0) ∞ 437.6737 (d12) 3.9500 4.5211 (d14) 5.3334 4.7622 (BF) 1.0000 1.0000 [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)] Surface number Applicable optical material G2LPAXh G2LPOAh G2LPAXh / G2LPOAh ΔPgF 27 FCD100 13.600 7.162 1.9 0.0564 29 FCD1 11.254 9.294 1.2 0.0373 32 MC-NBFD130 8.218 12.618 0.7 -0.0058

[0204] [Example 13] FIG. 61 is a lens configuration diagram at infinity focus of a large aperture ratio ultra-wide angle lens according to Example 13.

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

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

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

[0208] As an example of focusing, among the lenses constituting the first lens group G1, by moving the lenses from L7 to L8 integrally toward the image side along the optical axis, focusing from an infinite object to a close object becomes possible. Nevertheless, it is also possible to perform focusing by moving a part or the whole of the optical system in the optical axis direction.

[0209] The specifications of the large aperture ratio ultra-wide angle lens according to Example 13 are shown below.

[0210] Numerical Example 13 Unit: mm [Surface Data] Surface number r d nd vd ΔPgF Corresponding optical material 0 (d0) 1 54.0869 2.1998 1.87071 40.73 -0.0069 TAFD32 2 24.6840 6.9595 3 35.3626 1.7998 2.00100 29.13 0.0035 TAFD55-W 4 14.6760 11.6757 5 -81.2294 2.9502 1.86966 20.02 0.0310 FDS20-W 6 -39.5419 2.2419 7 -29.8698 1.0000 1.43700 95.10 0.0564 FCD100 8 45.4095 5.1697 9 -23.2533 1.0000 1.80400 46.53 -0.0070 S-LAH65VS 10 977.2188 2.8777 1.95375 32.32 0.0003 S-LAH98 11 -79.6200 (d11) 12 60.9734 4.9016 1.85150 40.78 -0.0055 S-LAH89 13 -56.5096 0.3000 *14 39.1505 4.7890 1.85135 40.10 -0.0067 M-TAFD305 *15 330.8734 (d15) 16 (Aperture) ∞ 4.3340 17 -102.1298 5.0253 1.43875 94.66 0.0560 S-FPL55 18 -18.1293 1.0000 1.85478 24.80 0.0085 S-NBH56 19 -136.6592 0.3000 20 53.2499 2.9047 1.94595 17.98 0.0385 FDS18-W 21 185.3580 0.3000 22 28.9648 1.0000 1.76182 26.52 0.0129 S-TIH14 23 16.8004 8.3747 1.43875 94.66 0.0560 S-FPL55 24 -63.7401 0.3000 25 20.6577 6.0332 1.43875 94.66 0.0560 S-FPL55 26 -106.2575 0.8500 1.85478 24.80 0.0085 S-NBH56 27 73.7830 1.1962 *28 44.6728 4.0690 1.80610 40.73 -0.0058 M-NBFD130 *29 -300.0000 14.4500 30 ∞ 2.5000 1.51680 64.20 0.0014 BSC7 31 ∞ (BF) [Aspherical Data] Surface 14, Surface 15, Surface 28, Surface 29 K 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A4 4.95784E-06 8.30571E-06 -4.30974E-05 -2.34518E-05 A6 1.95158E-08 1.78240E-08 -8.49095E-08 -1.29468E-07 A8 -5.48172E-11 -1.42424E-10 1.03060E-11 7.62476E-10 A10 1.02975E-13 6.56869E-13 1.46055E-13 -5.01269E-12 A12 1.90218E-17 -2.22330E-15 8.03092E-15 1.93846E-14 A14 1.46327E-19 -8.40293E-19 0.00000E+00 4.09600E-18 A16 -8.16597E-21 5.32357E-21 0.00000E+00 0.00000E+00 [Various data] Wide angle (INF) Focal length 8.15 F number 1.26 Full angle of view 2ω 185.73 Image height Y 11.93 Overall lens length 110.00 [Variable interval data] INF - Near distance (d0) ∞ 225.0631 (d11) 3.5000 3.7160 (d15) 4.9981 4.7820 (BF) 1.0000 1.0000 [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)] Surface number Applicable optical material G2LPAXh G2LPOAh G2LPAXh / G2LPOAh ΔPgF 23 S-FPL55 10.70675 5.36386 2.0 0.0560 25 S-FPL55 9.71243 8.38196 1.2 0.0560 28 M-NBFD130 8.07256 9.25816 0.9 -0.0058

[0211] [Example 14] FIG. 66 is a lens configuration diagram at infinity focus of the large aperture ratio ultra-wide angle lens according to Example 14.

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

[0213] The first lens group G1 is composed of, in order from the object side, a concave meniscus lens component N1 consisting of a concave meniscus lens L1 with a convex surface facing the object side, a concave meniscus lens component N2 consisting of a concave meniscus lens L2 with a 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 a convex surface facing the object side and a concave meniscus lens L7 with a convex surface facing the object side, a convex meniscus lens L8 with a 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.

[0214] The second lens group G2 is composed of, in order from the object side, a cemented lens of a biconvex lens L12 and a concave meniscus lens L13 with a convex surface facing the image side, a biconvex lens L14, a concave meniscus lens L15 with a convex surface facing the object side and a convex meniscus lens L16 with a 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 toward the image side along the optical axis, focusing from an infinite object to a close object is possible. Nevertheless, focusing can also be performed by moving part or all of the optical system in the optical axis direction.

[0216] The specifications of the large aperture ratio ultra-wide angle lens according to Example 14 are shown below.

[0217] Numerical Example 14 Unit: mm [Surface Data] Surface number r d nd vd ΔPgF Corresponding optical material 0 (d0) 1 93.2051 2.8000 2.05090 26.94 0.0052 TAFD65 2 28.3327 9.2593 3 77.3086 2.2000 2.05090 26.94 0.0052 TAFD65 4 25.4934 8.3772 5 95.7644 4.3183 1.85451 25.15 0.0071 NBFD25 6 -282.9514 1.4736 1.43875 94.66 0.0560 S-FPL55 7 231.4955 7.1593 8 -28.8409 1.2854 1.43875 94.66 0.0560 S-FPL55 9 50.7551 0.2000 10 33.5428 7.9415 1.55298 55.07 -0.0046 J-KZFH4 11 532.1293 1.2498 1.49700 81.61 0.0373 FCD1 12 113.4705 (d12) 13 43.9162 4.5145 1.85451 25.15 0.0071 NBFD25 14 142.3024 (d14) *15 77.1154 6.2706 1.77377 47.17 -0.0078 MC-TAF401 *16 -277.6205 3.7431 17 -110.5563 1.0000 1.85451 25.15 0.0071 NBFD25 18 100.9979 3.6066 2.00100 29.13 0.0035 TAFD55-W 19 -575.0909 2.5000 20 (Aperture) ∞ 3.4844 21 321.0180 13.1263 1.48071 85.29 0.0413 FCD915 22 -20.1401 1.0000 1.85451 25.15 0.0071 NBFD25 23 -33.2861 0.3000 24 41.4022 5.7466 1.66382 27.35 0.0327 J-SFH4 25 -721.4485 0.3000 26 49.4849 1.0000 1.90043 37.37 -0.0045 TAFD37A 27 21.9142 5.4423 1.43700 95.10 0.0564 FCD100 28 27.1029 1.8583 29 25.8168 8.2863 1.43700 95.10 0.0564 FCD100 30 -55.1118 0.3000 31 33.3478 6.7126 1.49700 81.61 0.0373 FCD1 32 -62.0234 0.9624 1.95375 32.32 0.0003 S-LAH98 33 23.3478 3.5312 *34 80.0000 5.9223 1.80610 40.73 -0.0058 MC-NBFD130 *35 -219.5578 15.4983 36 ∞ 2.5000 1.51680 64.20 0.0014 BSC7 37 ∞ (BF) [Aspherical data] Surface 15, Surface 16, Surface 34, Surface 35 K 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A4 7.15947E-06 1.56123E-05 6.16616E-07 -3.95320E-06 A6 9.08446E-09 1.26004E-08 6.36098E-08 7.58097E-09 A8 -4.13213E-11 -5.07839E-11 -8.77432E-10 7.09101E-11 A10 -4.04508E-15 1.38009E-14 5.67449E-12 -2.38867E-12 A12 1.29524E-17 -1.41088E-16 -1.49240E-14 1.50632E-14 A14 -4.83809E-19 -1.45961E-18 0.00000E+00 -3.65299E-17 A16 5.59008E-23 2.65009E-21 0.00000E+00 0.00000E+00 [Various data] Wide angle (INF) Focal length 15.50 F-number 1.58 Full picture angle 2ω 185.73 Image height Y 22.30 Overall lens length 155.00 [Variable interval data] INF - Close distance (d0) ∞ 443.3234 (d12) 4.8777 5.3944 (d14) 5.2521 4.7354 (BF) 1.0000 1.0000 [Lens group data] Group start surface Focal length G1 1 -190.0438 G2 21 46.1252 [Convex lens in the second lens group G2 that satisfies conditional expression (16)] Surface number Corresponding optical material G2LPAXh G2LPOAh G2LPAXh / G2LPOAh ΔPgF 27 FCD100 13.79965 6.79814 2.0 0.0564 29 FCD100 12.72132 8.98006 1.4 0.0564 31 FCD1 10.28047 10.42632 1.0 0.0373 34 MC-NBFD130 6.96538 12.5552 0.6 -0.0058

[0218] In addition, a list of corresponding values of the conditional expressions in each of these embodiments is shown.

[0219] [Conditional expression corresponding values] [Table 1]

[0220] In addition, the present technology can also adopt the following configuration. [Item 1] Composed of a first lens group G1, a diaphragm S, and a second lens group G2 in order from the object side. The first lens group G1 has a concave meniscus lens component N1 with a convex surface facing the object side arranged on the most object side, and a concave meniscus lens component N2 with a convex surface facing the object side on the image side of the concave meniscus lens component N1. A large-aperture ratio ultra-wide-angle lens characterized by satisfying 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: Semi-field angle at infinite focus Fno: F-number at infinite focus N1OAh: Off-axis chief ray height when a ray with an object-side incident angle of 90° enters the concave meniscus lens component N1 at infinite focus (however, when 2ω < 180°, the off-axis chief ray height when the ray enters with an object-side incident angle of ω is used) iOAh: Image 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 at infinite focus (however, when 2ω < 180°, the image height of the off-axis chief ray when the ray enters with an object-side incident angle of ω is used) SagN1: Sag amount from the vertex of the image-side surface of the concave meniscus lens component N1 (the ray height used for calculating the sag amount 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, when 2ω < 180°, it is calculated using the off-axis chief ray height when the ray enters with an object-side incident angle of ω) SagN2: Sag amount from the vertex of the image-side surface of the concave meniscus lens component N2 (the ray height used for calculating the sag amount 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, when 2ω < 180°, it is calculated using the off-axis chief ray height when the ray enters with an object-side incident angle of ω) [Item 2] The large-aperture ratio ultra-wide-angle lens according to [Item 1], characterized by satisfying 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 concave meniscus lens component N1 satisfies the following conditional expression (6), and the large-aperture ratio ultra-wide-angle lens according to [Item 1] or [Item 2] is characterized thereby. (6) 1.5 < N1SF < 6.0 N1SF = (N1R1 + N1R2) / (N1R1 - N1R2) N1R1: Curvature radius of the object-side surface of the concave meniscus lens component N1 N1R2: Curvature radius of the image-side surface of the concave meniscus lens component N1 [Item 4] The concave meniscus lens component N2 satisfies the following conditional expression (7), and is the large aperture ratio ultra-wide angle lens according to [Item 1] to [Item 3]. (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 [Item 5] The concave meniscus lens component N1 and the concave meniscus lens component N2 satisfy the following conditional expression (8), and is the large aperture ratio ultra-wide angle lens according to [Item 1] to [Item 4]. (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: 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 [Item 6] The concave meniscus lens component N1 satisfies the following conditional expression (9), and is the large aperture ratio ultra-wide angle lens according to [Item 1] to [Item 5]. (9) 1.8 < PLOAN1 / PLAN1 < 5.0 PLOAN1: When the light ray with an object side incident angle of 90° at infinity focus is taken as an off-axis ray, the distance that the off-axis chief ray passes through the concave meniscus lens component N1 (however, when 2ω < 180°, the light ray incident at the object side incident angle ω is taken as the off-axis ray) PLAN1: The thickness on the optical axis of the concave meniscus lens component N1 [Item 7] The concave meniscus lens component N1 and the concave meniscus lens component N2 satisfy the following conditional expression (10), and are characterized as the large aperture ratio ultra-wide angle lens according to [Item 1] to [Item 6]. (10) 0.3 < PLOAN1 / PLOAN2 < 3.5 PLOAN1: When the light ray with an object-side incident angle of 90° at infinity focus is regarded as an off-axis ray, the distance that the off-axis chief ray passes through the concave meniscus lens component N1 (however, when 2ω < 180°, the light ray incident at the object-side incident angle ω is regarded as an off-axis ray) PLOAN2: When the light ray with an object-side incident angle of 90° at infinity focus is regarded as an off-axis ray, the distance that the off-axis chief ray passes through the concave meniscus lens component N2 (however, when 2ω < 180°, the light ray incident at the object-side incident angle ω is regarded as an off-axis ray) [Item 8] The second lens group G2 has a convex lens LP1 that satisfies the following conditional expressions (11) to (13), and is characterized as the large aperture ratio ultra-wide angle lens according to [Item 1] to [Item 7]. (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 first lens group G1 has a negative refractive power and satisfies the following conditional expression (14), and is characterized as the large aperture ratio ultra-wide angle lens according to [Item 1] to [Item 8]. (14) -0.40 < f / f1 < 0.70 f: The focal length of the entire system at infinity focus f1: The focal length of the first lens group G1 at infinity focus [Item 10] The second lens group G2 has a positive refractive power and satisfies the following conditional expression (15), and is characterized as the large aperture ratio ultra-wide angle lens according to [Item 1] to [Item 9]. (15) -0.8 < f2 / f1 < 2.7 f1: Focal length of the first lens group G1 at infinity focus f2: Focal length of the second lens group G2 at infinity focus [Item 11] The second lens group G2 has at least one convex lens satisfying the following conditional expression (16) and satisfies the following conditional expression (17). The large aperture ratio ultra-wide angle lens according to [Item 1] to [Item 10]. (16) 0.3 < G2LPAXh / G2LPOAh < 2.7 (17) 0.004 < G2LPAve G2LPAXh: Axial marginal ray height incident on the convex lens at infinity focus with the aperture wide open G2LPOAh: Off-axis chief ray height when a ray with an object-side incident angle of 90° is incident on the convex lens at infinity focus (however, when 2ω < 180°, it is the off-axis chief ray height incident at an object-side incident angle of ω) G2LPAve: Average value of the abnormal dispersibility of the convex lens satisfying the conditional expression (16) [Item 12] The concave meniscus lens component N1 includes a concave lens satisfying the conditional expression (18). The large aperture ratio ultra-wide angle lens according to [Item 1] to [Item 11]. (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 [Item 1] to [Item 12] is characterized by satisfying the following conditional expression (19). (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 at infinity focus BF: Distance on the optical axis from the lens surface closest to the image side to the image plane at infinity focus [Item 14] The large aperture ratio ultra-wide angle lens according to [Item 1] to [Item 13] is characterized by satisfying 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 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 (however, when 2ω < 180°, it is the image height of the chief ray off-axis incident at an object-side incident angle of ω) [Item 15] The concave meniscus lens component N2 is the concave meniscus lens component with a convex surface facing the object side, which is the second one arranged from the object side among the concave meniscus lens components with a convex surface facing the object side, and is characterized by the large-aperture ratio ultra-wide-angle lens according to [Item 1] to [Item 14]. [Item 16] The concave meniscus lens component N1 and the concave meniscus lens component N2 are characterized by being arranged continuously from the object side, and are the large-aperture ratio ultra-wide-angle lens according to [Item 1] to [Item 15]. [Item 17] The concave meniscus lens component N1 and the concave meniscus lens component N2 are characterized by being composed of spherical lenses, and are the large-aperture ratio ultra-wide-angle lens according to [Item 1] to [Item 16]. [Item 18] The large-aperture ratio ultra-wide-angle lens according to [Item 1] to [Item 17] is characterized by moving part or all of the optical system in the optical axis direction to perform focusing from infinity to a close-distance object.

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

Explanation of Reference Signs

[0222] G1 First lens group G2 Second lens group S Aperture stop N1 Concave meniscus component N2 Concave meniscus component LP1 Convex lens F filter I image plane

Claims

1. It is composed of a first lens group G1, a diaphragm S, and a second lens group G2 in order from the object side. In the first lens group G1, a concave meniscus lens component N1 with a convex surface facing the object side is arranged closest to the object side. On the image side of the concave meniscus lens component N1, it has a concave meniscus lens component N2 with a convex surface facing the object side. A large-aperture ratio ultra-wide-angle lens characterized by satisfying 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 infinite focus Fno: F-number at infinite focus N1OAh: 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 at infinite focus (however, when 2ω < 180°, it is the off-axis chief ray height incident at an object-side incident angle of ω). iOAh: Image 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 at infinite focus (however, when 2ω < 180°, it is the image height of the off-axis chief ray incident at an object-side incident angle of ω). SagN1: Sag amount from the vertex of the image-side surface of the concave meniscus lens component N1 (when calculating the sag amount, 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 at infinite focus. Also, when 2ω < 180°, it is calculated using the off-axis chief ray height incident at an object-side incident angle of ω). SagN2: Sag amount from the vertex of the image-side surface of the concave meniscus lens component N2 (when calculating the sag amount, 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 at infinite focus. Also, when 2ω < 180°, it is calculated using the off-axis chief ray height incident at an object-side incident angle of ω).

2. The large-aperture ratio ultra-wide-angle lens according to Claim 1, characterized by satisfying 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

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 expression (6). (6) 1.5 < N1SF < 6.0 N1SF = (N1R1 + N1R2) / (N1R1 - N1R2) N1R1: Curvature radius of the object-side surface of the concave meniscus lens component N1 N1R2: Radius of curvature of the image-side surface of the concave meniscus lens component N1 **Claim 4** The concave meniscus lens component N2 satisfies the following conditional expression (7), and the large-aperture ratio ultra-wide-angle lens according to claim 1 is characterized thereby. **(7) 1.2 < N2SF < 5.0** 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 **Claim 5** The concave meniscus lens component N1 and the concave meniscus lens component N2 satisfy the following conditional expression (8), and the large-aperture ratio ultra-wide-angle lens according to claim 1 is characterized thereby. **(8) 0.4 < N1SF / N2SF < 3.0** N1SF = (N1R1 + N1R2) / (N1R1 - N1R2) N1R1: Radius of curvature of the object-side surface of the concave meniscus lens component N1 N1R2: 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 **Claim 6** The concave meniscus lens component N1 satisfies the following conditional expression (9), and the large-aperture ratio ultra-wide-angle lens according to claim 1 is characterized thereby. **(9) 1.8 < PLOAN1 / PLAN1 < 5.0** PLOAN1: When the light ray with an object-side incident angle of 90° at infinity focus is regarded as an off-axis ray, the distance that the off-axis chief ray passes through the concave meniscus lens component N1 (however, when 2ω < 180°, the light ray incident at the object-side incident angle ω is regarded as an off-axis ray) PLAN1: Thickness on the optical axis of the concave meniscus lens component N1 **Claim 7** The concave meniscus lens component N1 and the concave meniscus lens component N2 satisfy the following conditional expression (10), and the large-aperture ratio ultra-wide-angle lens according to claim 1 is characterized thereby. **(10) 0.3 < PLOAN1 / PLOAN2 < 3.5** PLOAN1: When the light ray with an object-side incident angle of 90° at infinity focus is regarded as an off-axis ray, the distance that the off-axis chief ray passes through the concave meniscus lens component N1 (however, when 2ω < 180°, the light ray incident at the object-side incident angle ω is regarded as an off-axis ray) PLAN2: When the light ray with an object-side incident angle of 90° at infinite focus is taken as an off-axis ray, the distance that the off-axis chief ray passes through the concave meniscus lens component N2 (however, when 2ω < 180°, the light ray incident at the object-side incident angle ω is taken as the off-axis ray).

8. The second lens group G2 has a convex lens LP1 that satisfies the following conditional expressions (11) to (13), and the large-aperture ratio ultra-wide-angle lens according to claim 1 is characterized in that. (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 dispersibility of the convex lens LP1

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

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

11. The second lens group G2 has at least one convex lens that satisfies the following conditional expression (16) and satisfies the following conditional expression (17), and the large-aperture ratio ultra-wide-angle lens according to claim 1 is characterized in that. (16) 0.3 < G2LPXh / G2LPOAh < 2.7 (17) 0.004 < G2LP Ave G2LPXh: The on-axis marginal ray height incident on the convex lens at infinite focus with the aperture wide open G2LPOAh: The off-axis chief ray height when a light ray with an object-side incident angle of 90° is incident on the convex lens at infinite focus (however, when 2ω < 180°, the off-axis chief ray height incident at the object-side incident angle ω) G2LP Ave: The average value of the anomalous dispersibility of the convex lens that satisfies the conditional expression (16)

12. The concave meniscus lens component N1 includes a concave lens that satisfies the following conditional expression (18), and the large-aperture ratio ultra-wide-angle lens according to claim 1 is characterized in that. (18) 1.7 < ndN1n ndN1n: 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 it 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

14. The large-aperture ratio ultra-wide-angle lens according to claim 1, characterized in that it 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 when focused at infinity iOAh: The off-axis chief ray image height when a ray with an object-side incident angle of 90° forms an image on the image plane when focused at infinity (however, when 2ω < 180°, it is the off-axis chief ray image height when incident with an object-side incident angle of ω)

15. The large-aperture ratio ultra-wide-angle lens according to claim 1, characterized in that the concave meniscus lens component N2 is the concave meniscus lens component with a convex surface facing the object side that is arranged second from 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 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 part or all of the optical system is moved in the optical axis direction to perform focusing from infinity to a close-distance object.

Images