Imaging lens, interchangeable lens, imaging device, and information processing device

Abstract

The imaging lens includes a first lens group, a second lens group, an aperture stop, a third lens group, and a fourth lens group. The third lens group includes: a biconvex positive lens closest to the object in the third lens group; and a negative lens closest to the image in the third lens group, the negative lens having a concave surface facing the object. In the fourth lens group, the surface closest to the object is a concave surface facing the object; the surface closest to the image is a convex surface facing the image. The imaging lens satisfies the following conditional expression (1):-0.4 < f3-4 / f1-2 < 0.4 (1) where f1-2 represents a combined focal length of the first lens group and the second lens group, and f3-4 represents a combined focal length of the third lens group and the fourth lens group.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to an imaging lens, a replaceable lens, an imaging device, and an information processing device. Background Art

[0002] Patent Document 1 describes an imaging optical system that includes, in order from the object side, a first lens group having a positive refractive power, an aperture stop, a second lens group having a positive refractive power, and a third lens group having a negative refractive power.

[0003] Patent Document 2 describes a camera optical system that includes a front lens group located on the object side with respect to the aperture stop and a rear lens group located on the image side with respect to the aperture stop. The camera optical system is characterized in that the F-number of the entire lens system is 2.2 or less.

[0004] Patent Document 3 describes an imaging optical system that includes, in order from the object side toward the image side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, an aperture stop, a third lens group having a positive refractive power, and a fourth lens group.

[0005] Patent Document 4 describes a camera lens that generally includes six lenses: a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens, and a positive sixth lens arranged in order from the object side.

[0006] Citation List

[0007] Patent Documents

[0008] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2022-67328

[0009] [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2021-43376

[0010] [Patent Document 3] Japanese Patent No. 5895718

[0011] [Patent Document 4] Japanese Patent No. 5847829 Summary of the Invention

[0012] Technical Problem

[0013] However, through research by the present inventors, there is room for improvement in the optical systems disclosed in Patent Documents 1 to 4 in terms of miniaturization and wide-angleization.

[0014] Embodiments of the present invention have been completed based on the above insights, and an object thereof is to provide an imaging lens, a replaceable lens, an imaging device, and an information processing device that achieve miniaturization and wide-angleization.

[0015] Solution to the problem

[0016] Embodiments of the present disclosure provide an imaging lens, which sequentially includes, from the object side towards the image side: a first lens group having a negative refractive power, a second lens group having a positive refractive power, an aperture stop, a third lens group having a positive refractive power, and a fourth lens group. Among the first lens group, the second lens group, the third lens group, and the fourth lens group, the fourth lens group has the weakest refractive power. The first lens group includes a negative lens having a concave surface facing the image. The second lens group sequentially includes, from the object side towards the image side: a negative lens having a concave surface facing the object; and a cemented lens having an overall positive refractive power. The third lens group includes: a biconvex positive lens closest to the object in the third lens group; and a negative lens closest to the image in the third lens group, the negative lens having a concave surface facing the object. The fourth lens group includes a single lens or a cemented lens. In the fourth lens group, the surface closest to the object is a concave surface facing the object; the surface closest to the image is a convex surface facing the image. The imaging lens satisfies the following conditional expression (1):

[0017] -0.4 < f3-4 / f1-2 < 0.4 (1)

[0018] In the above conditional expression, f1-2 represents the combined focal length of the first lens group and the second lens group, and f3-4 represents the combined focal length of the third lens group and the fourth lens group.

[0019] Embodiments of the present disclosure provide an imaging lens, which sequentially includes, from the object side towards the image side: a first lens group having a negative refractive power, a second lens group having a positive refractive power, an aperture stop, a third lens group having a positive refractive power, and a fourth lens group. Among the first lens group, the second lens group, the third lens group, and the fourth lens group, the fourth lens group has the weakest refractive power. The first lens group includes a negative lens having a concave surface facing the image. The second lens group sequentially includes, from the object side towards the image side: a negative lens having a concave surface facing the object; and a cemented lens having an overall positive refractive power. The third lens group includes: a cemented lens of a negative lens closest to the image and a positive lens second closest to the image in the third lens group; and a positive lens of the third lens group located on the object side with respect to the cemented lens. The fourth lens group includes a single lens or a cemented lens. In the fourth lens group, the surface closest to the object is a concave surface facing the object; the surface closest to the image is a convex surface facing the image, and the imaging lens satisfies the following conditional expression (1):

[0020] -0.4 < f3-4 / f1-2 < 0.4 (1)

[0021] In the above conditional expression, f1-2 represents the combined focal length of the first lens group and the second lens group, and f3-4 represents the combined focal length of the third lens group and the fourth lens group.

[0022] An embodiment of the present disclosure provides an imaging lens, which sequentially includes from the object side to the image side: a first lens group with negative refractive power, a second lens group with positive refractive power, an aperture stop, a third lens group with positive refractive power, and a fourth lens group. Among the first lens group, the second lens group, the third lens group, and the fourth lens group, the fourth lens group has the weakest refractive power. The first lens group includes a negative lens with a concave surface facing the image. The second lens group sequentially includes from the object side to the image side: a negative lens with a concave surface facing the object; and a cemented lens with overall positive refractive power. The third lens group includes: a cemented lens of the negative lens closest to the image and the positive lens second closest to the image in the third lens group; and three or fewer optical components. The fourth lens group includes a single lens or a cemented lens. In the fourth lens group, the surface closest to the object is a concave surface facing the object; the surface closest to the image is a convex surface facing the image. The imaging lens satisfies the following conditional expression (1):

[0023] -0.4 < f3-4 / f1-2 < 0.4 (1)

[0024] In the above conditional expression, f1-2 represents the combined focal length of the first lens group and the second lens group, and f3-4 represents the combined focal length of the third lens group and the fourth lens group.

[0025] An embodiment of the present disclosure provides an imaging lens, which sequentially includes from the object side to the image side: a first lens group with negative refractive power, a second lens group with positive refractive power, an aperture stop, a third lens group with positive refractive power, and a fourth lens group. Among the first lens group, the second lens group, the third lens group, and the fourth lens group, the fourth lens group has the weakest refractive power. The first lens group includes a negative lens with a concave surface facing the image. The second lens group sequentially includes from the object side to the image side: a negative meniscus lens with a concave surface facing the object; and a positive lens or a cemented lens with overall positive refractive power. The third lens group includes: a cemented lens of the negative lens closest to the image and the positive lens second closest to the image in the third lens group; and three or fewer optical components. The fourth lens group includes a single lens or a cemented lens. In the fourth lens group, the surface closest to the object is a concave surface facing the object; the surface closest to the image is a convex surface facing the image. The imaging lens satisfies the following conditional expression (1):

[0026] -0.4 < f3-4 / f1-2 < 0.4 (1)

[0027] In the above conditional expression, f1-2 represents the combined focal length of the first lens group and the second lens group, and f3-4 represents the combined focal length of the third lens group and the fourth lens group.

[0028] Embodiments of the present disclosure provide an imaging lens that sequentially includes, from the object side towards the image side: a first lens group having a negative refractive power, a second lens group having a positive refractive power, an aperture stop, a third lens group having a positive refractive power, and a fourth lens group. Among the first lens group, the second lens group, the third lens group, and the fourth lens group, the fourth lens group has the weakest refractive power. The first lens group includes a negative lens having a concave surface facing the image. The second lens group sequentially includes, from the object side towards the image side: a negative lens having a concave surface facing the object; and a cemented lens sequentially including a positive lens and a negative lens from the object side towards the image side, and the cemented lens has a positive refractive power as a whole. The third lens group includes: a positive lens closest to the object in the third lens group; and a negative lens having a concave surface facing the object, and in the third lens group, the negative lens is located on the image side with respect to the positive lens closest to the object. The fourth lens group includes a singlet or a cemented lens. In the fourth lens group, the surface closest to the object is a concave surface facing the object; the surface closest to the image is a convex surface facing the image. The imaging lens satisfies the following conditional expression (1):

[0029] -0.4 < f3-4 / f1-2 < 0.4 (1)

[0030] In the above conditional expression, f1-2 represents the combined focal length of the first lens group and the second lens group, and f3-4 represents the combined focal length of the third lens group and the fourth lens group.

[0031] Effects of the present invention

[0032] According to one aspect of the present disclosure, the imaging lens, the interchangeable lens, the imaging device, and the information processing device can reduce the size and increase the viewing angle. Description of the drawings

[0033] The drawings are intended to depict example embodiments of the present disclosure and should not be construed as limiting its scope. Unless otherwise specified, the drawings should not be regarded as being drawn to scale. Also, in several views, the same or similar reference numerals denote the same or similar components.

[0034] Figure 1

[0035] Figure 1 is a cross-sectional view of the imaging lens of Embodiment 1 of the present invention.

[0036] Figure 2 ​​​​

[0037] Figure 2 It is a cross-sectional view of the imaging lens according to Embodiment 2 of the present invention.

[0038] Figure 3

[0039] Figure 3 It is a cross-sectional view of the imaging lens according to Embodiment 3 of the present invention.

[0040] Figure 4

[0041] Figure 4 It is a cross-sectional view of the imaging lens according to Embodiment 4 of the present invention.

[0042] Figure 5

[0043] Figure 5 It is a cross-sectional view of the imaging lens according to Embodiment 5 of the present invention.

[0044] Figure 6

[0045] Figure 6 It is a cross-sectional view of the imaging lens according to Embodiment 6 of the present invention.

[0046] Figure 7

[0047] Figure 7 It is a cross-sectional view of the imaging lens according to Embodiment 7 of the present invention.

[0048] Figure 8A , 8B , 8C and 8D]

[0049] Figure 8A , 8B , 8C and 8D are the aberration curves of the imaging lens according to Numerical Example 1 Figure 1 of.

[0050] Figure 9A , 9B , 9C and 9D]

[0051] Figure 9A , 9B , 9C and 9D are the aberration curves of the imaging lens according to Numerical Example 2 Figure 2 of.

[0052] Figure 10A , 10B , 10C and 10D]

[0053] Figure 10A , 10B , 10C and 10D are the aberration curves of the imaging lens according to Numerical Example 3 Figure 3 ​​​​​​​​​​​​​Aberration curve graph of the imaging lens.

[0054] Figure 11A 、 11B 、11C and 11D]

[0055] Figure 11A 、 11B 、11C and 11D are the aberration curve graphs of the imaging lens according to Numerical Example 4. Figure 4 Aberration curve graph of the imaging lens.

[0056] Figure 12A 、 12B 、12C and 12D]

[0057] Figure 12A 、 12B 、12C and 12D are the aberration curve graphs of the imaging lens according to Numerical Example 5. Figure 5 Aberration curve graph of the imaging lens.

[0058] Figure 13A 、 13B 、13C and 13D]

[0059] Figure 13A 、 13B 、13C and 13D are the aberration curve graphs of the imaging lens according to Numerical Example 6. Figure 6 Aberration curve graph of the imaging lens.

[0060] Figure 14A 、 14B 、14C and 14D]

[0061] Figure 14A 、 14B 、14C and 14D are the aberration curve graphs of the imaging lens according to Numerical Example 7. Figure 7 Aberration curve graph of the imaging lens.

[0062] Figure 15A and 15B

[0063] Figure 15A and 15B are the external views of the digital camera according to the embodiments of the present disclosure.

[0064] Figure 16

[0065] Figure 16 is the block diagram of the hardware configuration of the digital camera according to the embodiments of the present disclosure. Detailed implementation manners

[0066] ​​​​​​​​The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the present disclosure. As used herein, the singular forms "a", "an", and "the" are also intended to include the plural forms unless the context clearly indicates otherwise.

[0067] When describing the embodiments shown in the drawings, specific terms are used for clarity. However, the disclosure of this specification is not intended to be limited to the particular terms so selected, and it should be understood that each particular element includes all technical equivalents having similar functions, operating in a similar manner, and achieving similar results.

[0068] The imaging lens according to an embodiment of the present invention can be used, for example, in the optical system of a camera lens mounted on a digital camera. The imaging lens according to an embodiment of the present disclosure is an ultra-wide main lens having a focal length of 21 millimeters (mm), which is converted to be equivalent to a 35 mm film camera, which is generally referred to as the Leica format.

[0069] The object of the imaging lens according to an embodiment of the present invention is to balance ultra-wide angle and miniaturization. The imaging lens according to an embodiment of the present invention achieves wide-angleization by changing the focal length from 28 mm to 21 mm. This structure is based on, for example, the above-mentioned Patent Document 3, which has been applied for and patented by the applicant of the present application.

[0070] The imaging lens according to an embodiment of the present disclosure is, for example, an optical system (e.g., a capturing optical system and a projection optical system) installed in a digital camera (e.g., an interchangeable lens camera, a digital single-lens reflex (DSLR) camera), an information terminal device (e.g., a portable information terminal device), a video camera, a film camera, an optical sensor, and a projection optical system.

[0071] The digital camera market has penetrated deeply worldwide, and the demands from users for digital cameras are diverse. Among these demands, the types of compact cameras equipped with high-performance main lenses have received consistent support and high expectations from users. In addition to high-performance lenses, users also need lenses with a small F-number (i.e., a large aperture) while maintaining compactness and light weight.

[0072] To enhance performance, several requirements need to be met. For example, it is necessary to achieve a resolution suitable for image sensors ranging from 20 to 40,000,000 pixels. In addition, when the aperture is fully open, the coma aberration will be minimized, and even for the edges of the viewing angle, the point image will maintain high-contrast distortion-free. In addition, regions with minimal chromatic aberration and significant brightness differences will not produce unwanted coloring; and when the distortion aberration is reduced, a straight line can be depicted as a straight line.

[0073] To achieve a larger diameter, preferably, the F number is approximately less than 4 to distinguish it from typical compact cameras equipped with zoom lenses.

[0074] To reduce the size, the total optical path and diameter of the lens are to be reduced. To reduce the size during non-shooting times, a mechanism known in the art as a "retractable lens type" can be considered. This mechanism shortens the total lens length by reducing the air gap on the optical axis within the capture optical system during non-shooting times (e.g., the air gap between optical components before and after the aperture stop and the air gap corresponding to the rear focal point).

[0075] Some users strongly desire an ultra-wide-angle lens. Considering this desire, the imaging lens preferably has a viewing angle equal to that of a 35 mm film camera (commonly referred to as the Leica format) with a focal length equal to 21 mm. This means a viewing angle of 88 degrees or greater, i.e., a semi-viewing angle of approximately 44 degrees or greater.

[0076] Among various imaging lenses for digital cameras, a typical structure of a wide-angle single-focus lens is a retrofocus system. In this structure, a lens group with negative refractive power is arranged on the object side, and a lens group with positive refractive power is arranged on the image side. Due to the characteristics of area sensors where each pixel has a color filter and a microlens, it is required that the position of the exit pupil be far from the image plane so that peripheral light rays can enter the sensor at almost perpendicular angles. To meet such requirements, a retrofocus type is adopted.

[0077] However, it can also be seen from the fact that the purpose of the retrofocus type is to ensure the back focal length for using a wide-angle lens as a replacement lens for a single-lens reflex camera that the overall lens length (the distance between the surface closest to the object side and the image plane) is likely to increase.

[0078] Currently, with the improvement and optimization of, for example, on-chip microlenses and the progress of image processing technology, image sensors with a relatively large diagonal size ranging from approximately 20 mm to 45 mm can process light rays impinging on the sensor at an inclined angle without any trouble. Compared with the past, the requirement for peripheral light rays to impinge perpendicularly on the sensor has been relaxed, thus allowing the selection of a lens type more suitable for miniaturization.

[0079] As lens types more suitable for miniaturization than the retrofocus type, there can be mentioned a substantially symmetric type, a telephoto type with a lens group having negative refractive power arranged on the image side, etc. As comparative examples, the above Patent Documents 1 to 4 disclose such imaging lenses.

[0080] Patent Document 1 describes a relatively small wide-angle lens that is very similar to a symmetric system with negative optical power arranged on both the object-side closest and the image-side closest. However, the lens has a slightly small viewing angle of approximately 81 degrees and there is room for improvement.

[0081] Patent Document 2 describes a configuration very similar to a symmetric system, in which negative refractive power is arranged in the part closest to the object and the part closest to the image. This structure has been miniaturized, and its aperture has also been made larger. However, its maximum viewing angle is about 80 degrees, which is slightly small and there is room for improvement.

[0082] Patent Document 3 describes a structure having a certain level of performance in terms of size reduction, aperture increase, and imaging performance. However, this configuration exhibits telephoto characteristics and there is room for improvement in terms of ultra-wide angle.

[0083] Patent Document 4 describes retaining the characteristics of an inverse telephoto system and having a certain degree of performance in terms of aperture expansion and ultra-wide angle. However, this configuration makes the total thickness in the range from the surface closest to the object to the surface closest to the image thick, and there is room for improvement in terms of size reduction during non-shooting time.

[0084] The present invention is completed in view of the above problems, and its object is to realize a small and lightweight imaging lens, an interchangeable lens equipped with the imaging lens, an imaging device equipped with the imaging lens, and an information processing device equipped with the imaging lens. The imaging lens according to an embodiment of the present disclosure includes a wide-angle lens having high performance, a viewing angle of about 88 degrees, and a large aperture with an F-number of less than about 4.

[0085] Generally, as the wide-angle progresses, coma, astigmatism, chromatic aberration of magnification, field curvature, distortion, etc. are likely to increase. In addition to controlling these aberrations, in order to allow light rays with a wide viewing angle to pass through, the optical system is likely to increase both in the radial direction and the optical axis direction. The imaging lens according to an embodiment of the present disclosure optimally designs its lens structure and various conditional expressions in order to solve the problems of aberration correction and size increase.

[0086] The imaging lens 1000 according to an embodiment of the present disclosure sequentially includes a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, an aperture stop S, a third lens group G3 having positive refractive power, and a fourth lens group G4 from the object side toward the image side.

[0087] The fourth lens group G4 has positive refractive power or negative refractive power. In Numerical Examples 1 to 3 and 7 of the present invention below, the fourth lens group G4 has positive refractive power. In Numerical Examples 4 to 6 of the present invention below, the fourth lens group G4 has negative refractive power. That is, the imaging lenses of Examples 1 to 3 and 7 have a four-group structure of negative-positive-positive-positive, and the imaging lenses of Examples 4 to 6 have a four-group structure of negative-positive-negative-positive.

[0088] In all numerical examples 1 to 7, the first lens group G1 is composed of a negative lens 11A.

[0089] In numerical examples 1 to 5 and 7, the second lens group G2 is composed of a negative lens 21A, a positive lens 22A, and a negative lens 23A in order from the object side.

[0090] In numerical example 6, the second lens group G2 is composed of a negative lens 21B, a negative lens 22B, and a positive lens 23B in order from the object side.

[0091] In some embodiments, the second lens group G2 includes an additional positive lens disposed on the object side with respect to the negative lens 21A, or disposed between the negative lens 21A and the positive lens 22A. In some other embodiments, the second lens group G2 includes an additional positive lens disposed on the object side with respect to the negative lens 21B, or disposed between the negative lens 21B and the negative lens 22B.

[0092] In numerical examples 1, 2, and 6, the third lens group G3 is composed of a positive lens 31A, a positive lens 32A, and a negative lens 33A in order from the object side.

[0093] In numerical examples 3, 4, and 7, the third lens group G3 is composed of a positive lens 31B and a negative lens 32B in order from the object side.

[0094] In numerical example 5, the third lens group G3 is composed of a positive lens 31C, a negative lens 32C, and a positive lens 33C in order from the object side.

[0095] In numerical examples 1 to 3, the fourth lens group G4 is composed of a positive lens 41A.

[0096] In numerical examples 4 and 6, the fourth lens group G4 is composed of a negative lens 41B.

[0097] In numerical examples 5 and 7, the fourth lens group G4 is composed of a negative lens 41C and a positive lens 42C in order from the object side.

[0098] The refractive power of the fourth lens group G4 is the weakest among all the lens groups (i.e., the first lens group G1, the second lens group G2, the third lens group G3, and the fourth lens group G4). The optical power of the fourth lens group G4 can be positive or negative. However, in the fourth lens group G4, the radius of curvature of the lens surface closest to the object is very close to the radius of curvature of the lens surface closest to the image.

[0099] The first lens group G1 is composed of a negative lens 11A having a concave surface facing the image.

[0100] The second lens group G2 is composed of a negative lens (21A; 21B) having a concave surface facing the object and a cemented lens (22A, 23A; 22B, 23B) having a positive refractive power as a whole, in order from the object side toward the image side.

[0101] Alternatively, the second lens group G2 is composed of a negative meniscus lens (21A; 21B) having a concave surface facing the object, and a positive lens or a cemented lens (22A, 23A; 22B, 23B) having a positive refractive power as a whole, in order from the object side toward the image side.

[0102] Alternatively, the second lens group G2 is composed of a negative lens 21A having a concave surface facing the object and a cemented lens (22A, 23A), and the cemented lens (22A, 23A) is composed of a positive lens and a negative lens in order from the object side and has a positive refractive power as a whole.

[0103] The third lens group G3 is composed of a biconvex positive lens (31A; 31B) closest to the object and a negative lens (33A; 32B) having a concave surface facing the object at the position closest to the image.

[0104] Alternatively, the third lens group G3 is composed of a cemented lens (32A, 33A) of a negative lens closest to the image side and a positive lens second closest to the image side, and a positive lens (31A) located on the object side with respect to the cemented lens.

[0105] Alternatively, the third lens group G3 is composed of a cemented lens (32A, 33A; 31B, 32B) of a negative lens closest to the image side and a positive lens second closest to the image side, and three or fewer components (i.e., three or fewer optical components).

[0106] Alternatively, the third lens group G3 is composed of a positive lens (31A; 31B; 31C) closest to the object side and a negative lens (33A; 32B; 32C) having a concave surface facing the object located on the image side with respect to the positive lens (31A; 31B; 31C).

[0107] The fourth lens group G4 is composed of a singlet lens (41A; 41B) or a cemented lens (41C, 42C), where the surface closest to the object is a concave surface facing the object and the surface closest to the image is a convex surface facing the image.

[0108] In the imaging lens 1000 according to an embodiment of the present disclosure, the aperture stop S is located between positive optical powers, which are generated by a positive lens of the second lens group G2 or a cemented lens (22A, 23A; 22B, 23B) having an overall positive refractive power, and the third lens group G3 or a positive lens (31A; 31B; 31C) included therein. Outside the positive optical powers along the optical axis, a negative optical power is arranged. The negative optical power is generated by the first lens group G1 (i.e., the negative lens 11A), a negative lens (21A; 21B) in the second lens group G2 having a concave surface facing the object, a negative lens or a negative lens of a cemented lens in the third lens group G3 having a concave surface facing the object (33A; 32B; 32C), and the fourth lens group G4. That is, the imaging lens according to an embodiment of the present invention employs a substantially symmetric optical power configuration. This configuration facilitates the correction of coma, distortion, and lateral chromatic aberration.

[0109] The refractive power of the fourth lens group G4 is not limited to negative and can also be positive. However, since the refractive power of the fourth lens group G4 is weaker than that of other lens groups, the imaging lens 1000 can achieve an optical power configuration close to the above-mentioned substantially symmetric type even if the fourth lens group G4 has a positive refractive power.

[0110] In addition, the surface closest to the object in the fourth lens group G4 is set to be concave to correspond to the concave shapes of the surface closest to the image in the first lens group G1 and the surface closest to the object in the second lens group G2. This can perform a higher-level correction of the above-mentioned aberrations.

[0111] A biconvex air lens is formed between the first lens group G1 and the second lens group G2. The biconvex air lens has a negative refractive power and can well adjust the distribution of the refractive power between the first lens group G1 and the second lens group G2.

[0112] The air lens of the present invention is defined as follows. In other words, an air lens refers to an air gap between a first surface on the image side of a first lens on the object side of a second lens and a second surface on the object side of a second lens on the image side of the first lens. These two lenses, namely the first lens and the second lens, are adjacent to each other and separated along the optical axis. The first surface on the image side of the first lens is the surface on the object side of the air lens, and the second surface on the object side of the second lens is the surface on the image side of the air lens. The shape of the air lens is defined by the first surface on the image side of the first lens and the surface on the object side of the second lens.

[0113] In the above configuration, the surface of the second lens group G2 closest to the object is set to a concave surface (for example, the surface of the second lens group G2 closest to the object is a negative meniscus lens). This achieves a smaller diameter of the first lens group G1 and facilitates the correction of coma aberration of lower light rays. In addition, the surface on the object side of the lens in the third lens group G3 closest to the image is set to a concave surface. This facilitates the correction of spherical aberration and reduces the sensitivity to manufacturing errors within the third lens group G3. Thereby, miniaturization and high performance of the imaging lens 1000 can be achieved.

[0114] The imaging lens 1000 according to an embodiment of the present disclosure has the above-described substantially symmetric optical power configuration, which is not a completely symmetric type of optical power configuration. If the optical power configuration is made completely symmetric, there is room for improvement in terms of high performance of a camera lens used at a reduced magnification.

[0115] To avoid this situation, the imaging lens 1000 according to an embodiment of the present disclosure is configured as follows. The second lens group G2 is composed of two elements: a separated negative element and a positive element. This configuration provides greater flexibility in correcting various aberrations. In addition, the third lens group G3 is arranged to face the second lens group G2, where the aperture stop S is between the third lens group G3 and the second lens group G2, and includes a positive lens and a negative lens. This configuration further enhances the chromatic aberration correction performance.

[0116] In addition, the third lens group G3 includes a cemented lens of a negative lens closest to the image and a positive lens second closest to the image. According to this structure, chromatic aberration correction performance can be improved, the increase in sensitivity to manufacturing errors can be suppressed, and assembly can be easily performed. The third lens group G3 is composed of three or fewer components (i.e., three or fewer optical components). This configuration prevents an increase in size and facilitates assembly.

[0117] A lens assembly refers to a single lens unit that becomes integrated during assembly. Regardless of how many lenses are cemented together, a cemented lens is regarded as one lens assembly. This means that, for example, three single lenses, three groups of cemented lenses, one single lens and two groups of cemented lenses, and two single lenses and one group of cemented lenses all correspond to three or fewer components (i.e., three or fewer optical components).

[0118] In addition, as needed, cemented lenses are used in the second lens group G2 and the fourth lens group G4 to more advantageously correct chromatic aberrations such as lateral chromatic aberration and coma aberration.

[0119] The fourth lens group G4 is configured to have a refractive power weaker than that of other lens groups. This can control the exit pupil position so that the incident angle of the chief ray on the image plane at the peripheral image height is appropriate.

[0120] Preferably, the imaging lens 1000 according to an embodiment of the present disclosure satisfies the following conditional expression (1):

[0121] -0.4 < f3-4 / f1-2 < 0.4 (1)

[0122] In the above conditional expression, f1-2 represents the combined focal length of the first lens group and the second lens group, and f3-4 represents the combined focal length of the third lens group and the fourth lens group.

[0123] Preferably, the imaging lens 1000 according to an embodiment of the present disclosure satisfies the following conditional expression (1A) within the range defined by the conditional expression (1):

[0124] -0.25 < f3-4 / f1-2 < 0.25(1A)

[0125] The conditional expressions (1) and (1A) define a suitable range of the refractive power of the first lens group G1 and the second lens group G2 with respect to the imaging groups located behind the aperture stop S, i.e., the third lens group G3 and the fourth lens group G4. By satisfying the conditional expression (1), miniaturization, large aperture, wide angle, and high performance of the imaging lens 1000 can be achieved. By satisfying the conditional expression (1A), this effect can be further enhanced.

[0126] If this value exceeds the upper limit of the conditional expression (1), the positive refractive power of the front group in front of the aperture stop S (i.e., the first lens group G1 and the second lens group G2) becomes too strong, causing the entrance pupil to move along the optical axis towards the image. This results in peripheral light rays passing through the front group in front of the aperture stop S (i.e., the first lens group G1 and the second lens group G2) at an increased height, possibly expanding the lens system radially.

[0127] If this value is lower than the lower limit of the conditional expression (1), the negative refractive power of the front group in front of the aperture stop S (i.e., the first lens group G1 and the second lens group G2) becomes too strong. This involves an excessive increase in the positive refractive power of the rear group behind the aperture stop S (i.e., the third lens group G3 and the fourth lens group G4), and reduces the flexibility of aberration correction, possibly leading to an increased sensitivity to manufacturing errors.

[0128] Preferably, the imaging lens 1000 according to an embodiment of the present disclosure satisfies the following conditional expression (2):

[0129] 0 < (r1s + r2s) / (r1s - r2s) < 10 (2)

[0130] In the above conditional expression, r1s represents the radius of curvature of the lens surface adjacent to the object side of the aperture stop, and r2s represents the radius of curvature of the lens surface adjacent to the image side of the aperture stop.

[0131] Preferably, the imaging lens 1000 according to an embodiment of the present disclosure satisfies the following conditional expression (2A) within the range defined by the conditional expression (2):

[0132] 0.5 < (r1s + r2s) / (r1s - r2s) < 7.5 (2A)

[0133] The conditional expressions (2) and (2A) define an appropriate range of the symmetry of the shapes of the surfaces facing each other across the aperture stop S. By satisfying the conditional expression (2), astigmatism and coma can be better corrected, and more uniform high quality of the entire image can be achieved. By satisfying the conditional expression (2A), this effect can be further enhanced.

[0134] If this value exceeds the upper limit defined by the conditional expression (2) or drops below the lower limit defined by the conditional expression (2), the optical power of the surface closest to the object within the third lens group G3 becomes significantly smaller than the optical power of the surface closest to the image within the second lens group G2. This may lead to increased coma and astigmatism. When the optical power is too small, off-axis rays pass through the third lens group G3 at a higher position, and thus the diameter of the third lens group G3 may become larger.

[0135] Preferably, the imaging lens 1000 according to an embodiment of the present disclosure satisfies the following conditional expression (3):

[0136] 0.5 < L1h / Sh < 1.1 (3)

[0137] In the above conditional expression, L1h represents the height of the marginal ray on the optical axis of the object-side surface of the lens closest to the object side in the optical system, and Sh represents the height of the marginal ray on the optical axis of the aperture stop.

[0138] Preferably, the imaging lens 1000 according to an embodiment of the present disclosure satisfies the following conditional expression (3A) within the range defined by the conditional expression (3):

[0139] 0.65 < L1h / Sh < 0.95 (3A)

[0140] The conditional expressions (3) and (3A) define an appropriate range of the diameter of the axial light beam incident on the object-side surface of the lens closest to the object side in the optical system with respect to the diameter of the aperture stop. By satisfying the conditional expression (3), the optical power balance before and after the aperture stop S can be achieved, and good characteristics can be exhibited in a compact size. By satisfying the conditional expression (3A), this effect can be made more significant.

[0141] If this value exceeds the upper limit of the conditional expression (3), the entire lens system becomes overly telephoto, increasing the difficulty of aberration correction at the peripheral viewing angles. This also causes off-axis light rays to pass through the first lens group G1 and the second lens group G2 at elevated positions, potentially increasing their diameters. If it is lower than the lower limit of the conditional expression (3), the entire lens system becomes overly retrofocus, and it is possible that the overall lens length becomes too long.

[0142] Preferably, the imaging lens 1000 according to an embodiment of the present disclosure satisfies the following conditional expression (4):

[0143] -6 < r2F / f < -0.5 (4)

[0144] In the above conditional expression, r2F represents the radius of curvature of the surface of the second lens group closest to the object, and f represents the focal length of the entire imaging lens when the imaging lens forms an image of an object at infinity.

[0145] Preferably, the imaging lens 1000 according to an embodiment of the present disclosure satisfies the following conditional expression (4A) within the range defined by the conditional expression (4):

[0146] -5.5 < r2F / f < -1 (4A)

[0147] The conditional expressions (4) and (4A) specify the preferred range of the radius of curvature of the surface of the second lens group G2 closest to the object side. The surface of the second lens group G2 closest to the object is a concave surface. In this configuration, as the absolute value of its radius of curvature r2F decreases, the negative optical power of the lens surface (i.e., the surface of the second lens group G2 closest to the object) increases. By satisfying the conditional expression (4), astigmatism and coma can be better corrected, and more uniform high quality of the entire image can be achieved. By satisfying the conditional expression (4A), this effect can be further enhanced.

[0148] If this value exceeds the upper limit of the conditional expression (4), coma of lower light rays at the intermediate image height is likely to occur in the negative direction, and spherical aberration is likely to occur in the positive direction.

[0149] If this value is lower than the lower limit of the conditional expression (4), at the intermediate image height, coma of lower light rays is likely to occur in the positive direction, and astigmatism is also likely to occur. In addition, off-axis light rays passing through the first lens group G1 may travel at high positions, thus easily increasing the diameter of the first lens group G1.

[0150] Preferably, the imaging lens 1000 according to an embodiment of the present disclosure satisfies the following conditional expression (5):

[0151] 0.5 < r3R / f < 10 (5)

[0152] In the above conditional expression, r3R represents the radius of curvature of the surface closest to the image side in the third lens group, and f represents the focal length of the entire imaging lens when the imaging lens forms an image of an object at infinity.

[0153] Preferably, the imaging lens 1000 according to an embodiment of the present disclosure satisfies the following conditional expression (5A) within the range defined by the conditional expression (5):

[0154] 0.55 < r3R / f < 9 (5A)

[0155] The conditional expressions (5) and (5A) define the preferred range of the radius of curvature of the surface closest to the image side of the third lens group G3. The surface closest to the image in the third lens group G3 is a concave surface. In this configuration, as the absolute value of its radius of curvature r3R decreases, the negative optical power of the lens surface (i.e., the surface closest to the image in the third lens group G3) increases. By satisfying the conditional expression (5), various aberrations can be corrected well, and a high-performance imaging lens more suitable for miniaturization can be realized. By satisfying the conditional expression (5A), this effect can be further improved.

[0156] If this value exceeds the upper limit of the conditional expression (5), at the peripheral image height, coma aberration of the upper light rays is likely to occur in the negative direction, and astigmatism is likely to occur. In addition, the off-axis light rays of the fourth lens group G4 are likely to pass through at a high position, which is likely to increase the diameter of the fourth lens group G4.

[0157] If this value is lower than the lower limit of the conditional expression (5), at the peripheral image height, coma aberration of the upper light rays is likely to occur in the positive direction, and the field curvature may be overcorrected.

[0158] Preferably, the imaging lens 1000 according to an embodiment of the present disclosure satisfies the following conditional expression (6):

[0159] -0.4 < f1 / f4 < 0.4 (6)

[0160] In the above conditional expression, f1 represents the focal length of the first lens group, and f4 represents the focal length of the fourth lens group.

[0161] Preferably, the imaging lens 1000 according to an embodiment of the present disclosure satisfies the following conditional expression (6A) within the range defined by the conditional expression (6):

[0162] -0.3 < f1 / f4 < 0.2 (6A)

[0163] The conditional expressions (6) and (6A) are conditional expressions for achieving a good balance in the refractive powers of the first lens group G1 and the fourth lens group G4. The first lens group G1 has a negative refractive power. In this configuration, when the conditional expressions (6) and (6A) are satisfied, the refractive power of the fourth lens group G4 can be positive or negative. Since the optical power of the fourth lens group G4 is the weakest, the absolute value of the focal length f4 is greater than the absolute values of the focal lengths of the other lens groups. Satisfying the conditional expression (6) enhances the reduction in size and high performance while controlling the position of the exit pupil. By satisfying the conditional expression (6A), this effect can be further improved.

[0164] If the value exceeds the upper limit of the conditional expression (6), the refractive powers of both the first lens group G1 and the fourth lens group G4 become negative, and the refractive power of the fourth lens group G4 becomes greater than that of the first lens group G1. As a result, the imaging lens is likely to exhibit strong telephoto characteristics as a lens system. This causes the principal point to move toward the object side, excessively shortening the total lens length. Therefore, the degree of freedom in correcting various aberrations is more likely to be restricted. Or the sensitivity to manufacturing errors may increase. Additionally, the exit pupil moves toward the image, and the incident angle of the chief ray on the image plane at the peripheral image height tends to increase.

[0165] If the value is below the lower limit of the conditional expression (6), the negative refractive power of the first lens group G1 becomes relatively large, causing the lens system to exhibit strong retrofocus characteristics. This causes the principal point to move toward the image and makes it difficult to shorten the total lens length. Additionally, the exit pupil moves toward the object side, and the diameter of the fourth lens group G4 is likely to increase.

[0166] Preferably, the surface of the third lens group G3 closest to the image is concave to achieve better performance. This configuration can also form a biconvex air lens between the third lens group G3 and the fourth lens group G4. This biconvex air lens has a negative refractive power, enabling good adjustment of the refractive power distribution between the third lens group G3 and the fourth lens group G4.

[0167] In addition, the surface of the fourth lens group G4 closest to the object is set to be concave to correspond to the surface of the first lens group G1 closest to the image. Similarly, the surface of the third lens group G3 closest to the image is set to be concave to correspond to the concave surface of the second lens group G2 closest to the object. Thereby, coma aberration, distortion aberration, and chromatic aberration of magnification can be corrected at a higher level.

[0168] Preferably, the imaging lens 1000 according to an embodiment of the present disclosure satisfies the following conditional expression (7):

[0169] 1.0 < r2R / r3F < 10 (7)

[0170] In the above conditional expression, r2R represents the radius of curvature of the surface closest to the image side in the second lens group, and r3F represents the radius of curvature of the surface closest to the object side in the third lens group.

[0171] In order to satisfy the conditional expression (7), the surface shapes of the surfaces facing each other across the aperture stop S are optimized. As a result, the refractive powers of the two surfaces facing each other across the aperture stop S can be configured in a substantially symmetric pattern. By satisfying the conditional expression (7), astigmatism and coma can be better corrected, and more uniform high quality of the entire image can be achieved.

[0172] If this value exceeds the upper limit or is lower than the lower limit of the conditional expression (7), it becomes difficult to achieve a substantially symmetric refractive power configuration of the two surfaces facing each other across the aperture stop S.

[0173] Preferably, the imaging lens 1000 according to an embodiment of the present disclosure satisfies the following conditional expression (8):

[0174] 55 < νdn1 < 85 (8)

[0175] In the above conditional expression, νdn1 represents the Abbe number of the negative lens in the first lens group with respect to the d-line.

[0176] By satisfying the conditional expression (8), while maintaining the balance of chromatic aberration correction, a suitable glass material can be selected for the lens closest to the object side exposed to the external environment (i.e., the lens closest to the object side in the first group G1). As a result, both axial chromatic aberration and lateral chromatic aberration can be well corrected.

[0177] If the value exceeds the upper limit of the conditional expression (8), the optical material for the negative lens 11A of the first lens group G1 may be soft and easily damaged. In addition, its chemical durability is reduced, making the negative lens 11A not suitable as the lens closest to the object side exposed to the external environment.

[0178] If the value is lower than the lower limit of the conditional expression (8), it becomes difficult to maintain the balance of chromatic aberration correction and to well correct axial chromatic aberration and lateral chromatic aberration.

[0179] Preferably, the imaging lens 1000 according to an embodiment of the present disclosure satisfies the following conditional expression (9):

[0180] -3.0 < f1 / f < -0.6 (9)

[0181] In the above conditional expression, f1 represents the focal length of the first lens group, and f represents the focal length of the entire imaging lens when the imaging lens forms an image of an object at infinity.

[0182] The conditional expression (9) specifies a preferred range of the refractive power of the first lens group G1. By satisfying the conditional expression (9), a significant reduction in field curvature, a high flatness of the image plane, and a high contrast up to the picture edge can be achieved.

[0183] If the value exceeds the upper limit of the conditional expression (9), the refractive power of the first lens group G1 becomes too strong. This makes it more likely that astigmatism and coma remain, and it is difficult to maintain high imaging performance up to the peripheral part.

[0184] If the value is lower than the lower limit of the conditional expression (9), the refractive power of the first lens group G1 becomes too weak, resulting in a higher possibility of insufficient correction of field curvature. Therefore, it is difficult to maintain the flatness of the image plane.

[0185] Preferably, the imaging lens 1000 according to an embodiment of the present disclosure satisfies the following conditional expression (10):

[0186] 1.75 < ndP2-3 < 2.06 (10)

[0187] In the above conditional expression, ndP2-3 is the average refractive index for the d-line of the positive lenses included in the second lens group and the third lens group.

[0188] By satisfying the conditional expression (10), it is possible to select a lens material (glass material) considering the refractive index range and cost of existing optical glasses, and it is possible to correct field curvature and coma well.

[0189] If the value exceeds the upper limit of the conditional expression (10), it is difficult to select a lens material (glass material) considering the refractive index range and cost of existing optical glasses.

[0190] If the value is lower than the lower limit of the conditional expression (10), the correction of field curvature is likely to become insufficient, and inward coma is likely to remain at the intermediate image height, which is not desirable.

[0191] Preferably, the imaging lens 1000 according to an embodiment of the present disclosure satisfies the following conditional expression (11):

[0192] 1.0 < DT / f < 1.8 (11)

[0193] In the above conditional expression, DT represents the distance between the surface closest to the object in the first lens group and the surface closest to the image in the fourth lens group, and f represents the focal length of the entire imaging lens when the imaging lens forms an image of an object at infinity.

[0194] The conditional expression (11) is a conditional formula that defines the ratio of the total lens thickness to the focal length of the entire lens system. By satisfying the conditional expression (11), sufficient miniaturization can be achieved, and various aberrations can be corrected well.

[0195] If this value exceeds the upper limit of the conditional expression (11), a sufficient total lens thickness is achieved with respect to the focal length, which provides an advantage in terms of aberration correction. However, this may result in a larger lens size.

[0196] If this value is below the lower limit of the conditional expression (11), the lens is overly reduced in size, making aberration correction difficult.

[0197] Preferably, the imaging lens 1000 according to an embodiment of the present disclosure satisfies the following conditional expression (12):

[0198] 2.0 < L / f < 2.7 (12)

[0199] In the above conditional expression, L represents the distance between the surface closest to the object side in the first lens group when focusing on an object at infinity and the image plane, and f represents the focal length of the entire imaging lens when the imaging lens forms an image on an object at infinity.

[0200] The conditional formula (12) is a conditional formula for defining the most effective lens length of the lens system, that is, the distance between the surface closest to the object side in the first lens group and the image plane. By satisfying the conditional formula (12), sufficient miniaturization can be achieved, and various aberrations can be corrected well.

[0201] If this value exceeds the upper limit of the conditional expression (12), a sufficient total lens length is achieved with respect to the focal length, which provides an advantage in terms of aberration correction. However, this may result in a larger lens size.

[0202] If this value is below the lower limit of the conditional expression (12), the lens (i.e., the imaging lens) is overly reduced in size, making aberration correction difficult.

[0203] Preferably, the air lens including the aperture stop S is provided in a meniscus shape with a convex surface facing the object side, which is formed by the surface closest to the image in the second lens group G2 and the surface closest to the object in the third lens group G3. Such an air lens can well balance and compensate for the front and rear aberrations of the wide beam passing through the aperture stop S. When the viewing angle becomes wider, it becomes difficult to solve the coma aberration. However, by preventing overcompensation of aberrations, especially overcompensation of spherical aberration, the coma aberration can be advantageously corrected. The manufacturing error sensitivity of the spherical aberration of the lens group after the aperture stop S (i.e., the third lens group G3 and the fourth lens group G4) with respect to the lens group before the aperture stop S (i.e., the first lens group G1 and the second lens group G2) can be reduced.

[0204] Preferably, the imaging lens 1000 according to an embodiment of the present disclosure satisfies the following conditional expressions (13) and (14):

[0205] 0.8 < Y' / f < 1.2 (13)

[0206] 0.7 < tan(θPmax) < 1.0 (14)

[0207] In the above conditional expressions, Y' represents the maximum image height on the imaging surface, and f represents the overall focal length of the imaging lens when the imaging lens forms an image of an object at infinity. In addition, θPmax represents the incident angle of the principal ray reaching the maximum image height on the image surface.

[0208] By satisfying the conditional expression (13), the viewing angle with the best performance of the imaging lens can be specified. If this value exceeds the upper limit defined by the conditional expression (13) or drops below the lower limit defined by the conditional expression (13), the viewing angle of the imaging lens deviates from the viewing angle range where the best effect is exerted.

[0209] By satisfying the conditional expression (14), the incident angle of the off-axis ray to the image surface can be specified. Therefore, the best performance can be obtained in the imaging lens. If this value exceeds the upper limit defined by the conditional expression (14) or is lower than the lower limit defined by the conditional expression (14), the incident angle of the off-axis ray on the image surface deviates from the incident angle range where the best effect is exerted.

[0210] In the imaging lens 1000 according to an embodiment of the present disclosure, preferably, aspherical surfaces are provided in the first lens group G1 and the fourth lens group G4 to enhance the correction of various aberrations such as spherical aberration, coma, and distortion.

[0211] Hereinafter, Numerical Examples 1 to 7 will be specifically described. In the aberration graph, solid lines and dashed lines represent the d-line, and dotted lines and double-dotted lines represent the g-line. In astigmatism, solid lines and dotted lines represent "sagittal", and dashed lines and double-dotted lines represent "meridional".

[0212] The meanings of the symbols in the present disclosure are as follows. The unit of length is millimeter (mm).

[0213] f: Overall focal length of the optical system

[0214] F: F-number

[0215] w: Half viewing angle

[0216] Ya: Maximum image height

[0217] R: Radius of curvature

[0218] D: Spacing between surfaces

[0219] Refractive index of the Nd:d line

[0220] νd: Abbe number of the d line

[0221] BF: Back focal point

[0222] K: Conic constant of the aspheric surface

[0223] A4: Fourth-order aspheric coefficient

[0224] A6: Sixth-order aspheric coefficient

[0225] A8: Eighth-order aspheric coefficient

[0226] A10: Tenth-order aspheric coefficient

[0227] The aspheric surface is defined by using the reciprocal of the paraxial curvature radius (paraxial curvature) C and the height H from the optical axis, as follows:

[0228]

[0229] In the numerical examples, the glass materials are optical glass types named by HOYA Corporation (HOYA) and OHARA Corporation (OHARA).

[0230] Numerical Example 1

[0231] Figure 1 、 Figures 8A to 8D And Tables 1 to 4 are the imaging lens 1000 of Numerical Example 1 of the embodiments of the present invention. Figure 1 is a diagram showing the lens structure of the imaging lens 1000 of Numerical Example 1. Figure 1 is a cross-sectional view of the imaging lens 1000 according to Numerical Example 1. Figure 8A 、 8B 、8C and 8D are aberration curves of the imaging lens according to Numerical Example 1. Table 1 shows surface data, Table 2 shows aspheric surface data, Table 3 shows focal length data, and Table 4 shows conditional data.

[0232] The imaging lens 1000 according to Numerical Example 1 is composed of a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, an aperture stop S, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power in order from the object side. Filter sheets F1 and F2 (i.e., cover glasses) are arranged between the fourth lens group G4 and the image plane I.

[0233] The first lens group G1 is composed of a negative meniscus lens (i.e., negative lens 11A) having a convex surface facing the object.

[0234] The second lens group G2 is composed of, in order from the object side, a negative meniscus lens having a convex surface facing the image (i.e., negative lens 21A), a biconvex positive lens 22A, and a biconcave negative lens 23A. The surface on the object side of the negative meniscus lens (i.e., negative lens 21A) is an aspherical surface. The biconvex positive lens 22A and the biconcave negative lens 23A are joined together.

[0235] The third lens group G3 is composed of, in order from the object side, a biconvex positive lens 31A, a positive meniscus lens having a convex surface facing the image (i.e., positive lens 32A), and a biconcave negative lens 33A. The positive meniscus lens (i.e., positive lens 32A) and the biconcave negative lens 33A are joined together.

[0236] The fourth lens group G4 is composed of a positive meniscus lens having a convex surface facing the image (i.e., positive lens 41A). Both surfaces of the positive meniscus lens (i.e., positive lens 41A) are aspherical surfaces.

[0237] [Table 1]

[0238]

[0239] * indicates a rotationally symmetric aspherical surface [Table 2]

[0240] Surface number K A4 A6 A8 A10 3 -0.6704 -9.76999E-05 -3.73079E-07 -1.91918E-08 0.00000E+00 14 -0.9583 -3.70200E-05 2.86718E-05 9.49331E-07 -5.04121E-08 15 -0.9660 2.79491E-04 1.65754E-05 1.18765E-06 -3.49979E-08

[0241] [Table 3]

[0242] Focal length First lens group -18.58 Second lens group 20.01 Third lens group 18.64 Fourth lens group 102.62 First to second lens groups 165.16 Third to fourth lens groups 17.51

[0243] [Table 4]

[0244] Conditional expression (1) 0.106 (2) 4.152 (3) 0.838 (4) -1.922 (5) 7.991 (6) -0.181 (7) 1.635 (8) 81.54 (9) -1.341 (10) 1.881 (11) 1.345 (12) 2.271 (13) 1.020 (14) 0.789

[0245] Numerical Example 2

[0246] Figure 2 、 Figures 9A to 9D And Tables 5 to 8 are explanatory diagrams of the imaging lens 1000 of Numerical Example 2 of the present invention. Figure 2 is a diagram showing the lens structure of the imaging lens 1000 of Numerical Example 2. Figure 2 is a cross-sectional view of the imaging lens 1000 according to Numerical Example 2. Figure 9A 、 9B 、9C and 9D are aberration curves of the imaging lens according to Numerical Example 2. Table 5 shows surface data, Table 6 shows aspherical surface data, Table 7 shows focal length data, and Table 8 shows conditional data.

[0247] The structure of the imaging lens of Numerical Example 2 is the same as that of the imaging lens of Numerical Example 1.

[0248] [Table 5]

[0249]

[0250] * indicates rotationally symmetric aspheric surface [Table 6]

[0251] Surface number K A4 A6 A8 A10 3 -0.6704 -9.76999E-05 -3.73079E-07 -1.91918E-08 0.00000E+00 14 -0.9583 -3.70200E-05 2.86718E-05 9.49331E-07 -5.04121E-08 15 -0.9660 2.79491E-04 1.65754E-05 1.18765E-06 -3.49979E-08

[0252] [Table 7]

[0253] Focal length First lens group -18.08 Second lens group 22.00 Third lens group 17.45 Fourth lens group 80.81 First to second lens groups -553.99 Third to fourth lens groups 16.07

[0254] [Table 8]

[0255] Conditional expression (1) 0.029 (2) 5.120 (3) 0.832 (4) -2.024 (5) 2.418 (6) -0.224 (7) 1.485 (8) 67.74 (9) -1.306 (10) 1.908 (11) 1.345 (12) 2.289 (13) 1.020 (14) 0.789

[0256] Numerical Example 3

[0257] Figure 3 、 Figures 10A to 10D And Tables 9 to 12 are explanatory diagrams of the imaging lens 1000 of Numerical Example 3 of the present invention. Figure 3 It is a diagram showing the lens configuration of the imaging lens 1000 of Numerical Example 3. Figure 3 It is a cross-sectional view of the imaging lens 1000 of Numerical Example 3. Figure 10A 、 10B 、10C and 10D are aberration curves of the imaging lens according to Numerical Example 3. Table 9 shows surface data, Table 10 shows aspheric surface data, Table 11 shows focal length data, and Table 12 shows conditional data.

[0258] Except for the following points, the configuration of the imaging lens according to Numerical Example 3 is the same as that of the imaging lens according to Numerical Example 1.

[0259] (1) The third lens group G3 is successively composed of a biconvex positive lens 31B and a biconcave negative lens 32B from the object side. The biconvex positive lens 31B and the biconcave negative lens 32B are joined together.

[0260] [Table 9]

[0261]

[0262] * indicates rotationally symmetric aspheric surface [Table 10]

[0263] Surface number K A4 A6 A8 A10 3 -0.8966 -8.48637E-05 -4.68177E-07 -1.18411E-08 0.00000E+00 12 0.4075 2.23352E-04 3.55494E-05 1.31376E-06 -6.11111E-08 13 -0.2337 4.23518E-04 1.59324E-05 1.31597E-06 -3.51685E-08

[0264] [Table 11]

[0265] Focal length First lens group -20.24 Second lens group 21.04 Third lens group 17.77 Fourth lens group 116.04 First to second lens groups 151.21 Third to fourth lens groups 17.30

[0266] [Table 12]

[0267] Conditional expression (1) 0.114 (2) 4.016 (3) 0.854 (4) -1.561 (5) 2.498 (6) -0.174 (7) 1.663 (8) 81.54 (9) -1.461 (10) 1.905 (11) 1.322 (12) 2.261 (13) 1.020 (14) 0.790

[0268] Numerical Example 4

[0269] Figure 4 、 Figures 11A to 11D Tables 13 to 16 are explanatory diagrams of the imaging lens 1000 according to Numerical Example 4 of the present invention. Figure 4 It is a diagram showing the lens configuration of the imaging lens 1000 according to Numerical Example 4. Figure 4 It is a cross-sectional view of the imaging lens 1000 according to Numerical Example 4. Figure 11A 、 11B 、11C and 11D are aberration curves of the imaging lens 1000 according to Numerical Example 4. Table 13 shows surface data, Table 14 shows aspherical data, Table 15 shows focal length data, and Table 16 shows conditional data.

[0270] Except for the following points, the configuration of the imaging lens according to Numerical Example 4 is the same as that of the imaging lens according to Numerical Example 1.

[0271] (1) In the second lens group G2, the biconvex positive lens 22A and the biconcave negative lens 23A are not joined.

[0272] (2) The third lens group G3 is composed of a biconvex positive lens 31B and a biconcave negative lens 32B in order from the object side. The object-side surface of the biconvex positive lens 31B is an aspherical surface.

[0273] (3) The fourth lens group G4 has a negative refractive power instead of a positive refractive power. The fourth lens group G4 is composed of a negative meniscus lens (i.e., negative lens 41B) having a convex surface facing the image. Both surfaces of the negative meniscus lens (i.e., negative lens 41B) are aspherical surfaces.

[0274] [Table 13]

[0275]

[0276] * indicates a rotationally symmetric aspherical surface [Table 14]

[0277] Surface number K A4 A6 A8 A10 3 0.0211 -3.17188E-06 5.49200E-07 -4.66081E-09 0.00000E+00 10 0.0000 4.35798E-06 5.77432E-07 8.18865E-08 0.00000E+00 14 -0.9122 8.15914E-04 2.90222E-05 9.46690E-08 -6.52595E-08 15 -1.0000 1.23007E-03 3.47952E-05 5.63714E-07 -4.96153E-08

[0278] [Table 15]

[0279] Focal length First lens group -16.22 Second lens group 21.05 Third lens group 15.70 Fourth lens group -342.49 First to second lens groups -546.23 Third to fourth lens groups 17.14

[0280] [Table 16]

[0281] Conditional expression (1) -0.031 (2) 1.471 (3) 0.776 (4) -1.167 (5) 1.597 (6) 0.047 (7) 5.243 (8) 70.70 (9) -1.171 (10) 1.905 (11) 1.373 (12) 2.360 (13) 1.020 (14) 0.844

[0282] Numerical Example 5

[0283] Figure 5 、 Figures 12A to 12D Tables 17 to 20 and the imaging lens 1000 according to Numerical Example 5 of the present invention.Figure 5 It is a diagram showing the lens configuration of the imaging lens 1000 of Numerical Example 5 of the numerical value. Figure 5 It is a cross-sectional view of the imaging lens 1000 of Numerical Example 5 of the numerical value. Figure 12A , 12B , 12C and 12D are aberration curves of the imaging lens 1000 according to Numerical Example 5 of the numerical value. Table 17 shows surface data, Table 18 shows aspherical data, Table 19 shows focal length data, and Table 20 shows conditional formula data.

[0284] Except for the following points, the configuration of the imaging lens according to Numerical Example 5 is the same as that of the imaging lens according to Numerical Example 1.

[0285] (1) The third lens group G3 includes, in order from the object side, a biconvex positive lens 31C, a biconcave negative lens 32C, and a positive meniscus lens having a convex surface facing the object (i.e., positive lens 33C). The biconvex positive lens 31C, the biconcave negative lens 32C, and the positive meniscus lens (i.e., positive lens 33C) are joined together.

[0286] (2) The fourth lens group G4 has a negative refractive power instead of a positive refractive power. The fourth lens group G4 is composed of, in order from the object side, a negative meniscus lens having a convex surface facing the image (i.e., negative lens 41C) and a positive meniscus lens having a convex surface facing the image (i.e., positive lens 42C). The negative meniscus lens (i.e., negative lens 41C) and the positive meniscus lens (i.e., positive lens 42C) are joined together. The surface on the object side of the negative meniscus lens (i.e., negative lens 41C) is an aspherical surface. The surface on the image side of the positive meniscus lens (i.e., positive lens 42C) is an aspherical surface.

[0287] [Table 17]

[0288]

[0289] * indicates a rotationally symmetric aspherical surface [Table 18]

[0290] Surface number K A4 A6 A8 A10 3 -0.6161 -1.00752E-04 -2.20895E-07 -2.17899E-08 0.00000E+00 13 0.1353 8.81120E-05 2.04243E-05 2.54209E-07 -2.20893E-08 15 -0.6635 2.68420E-04 1.25860E-05 1.90624E-07 -6.94792E-09

[0291] [Table 19]

[0292] Focal length First lens group -17.83 Second lens group 18.87 Third lens group 15.02 Fourth lens group -1073.26 First to second lens groups 118.88 Third to fourth lens groups 17.25

[0293] [Table 20]

[0294] Conditional expression (1) 0.145 (2) 2.130 (3) 0.827 (4) -1.879 (5) 2.910 (6) 0.017 (7) 2.770 (8) 63.33 (9) -1.350 (10) 1.905 (11) 1.499 (12) 2.379 (13) 1.070 (14) 0.821

[0295] Numerical Example 6

[0296] Figure 6 , Figures 13A to 13D And Tables 21 to 24 are explanatory diagrams of the imaging lens 1000 of Numerical Example 6 of the present invention. Figure 6This is a diagram showing the lens configuration of the imaging lens 1000 of Numerical Example 6. Figure 6 This is a cross-sectional view of the imaging lens 1000 according to Numerical Example 6. Figure 13A 、 13B 、13C and 13D are aberration curves of the imaging lens 1000 according to Numerical Example 6. Table 21 shows surface data, Table 22 shows aspherical data, Table 23 shows focal length data, and Table 24 shows conditional data.

[0297] Except for the following points, the configuration of the imaging lens according to Numerical Example 6 is the same as that of the imaging lens according to Numerical Example 1.

[0298] (1) The second lens group G2 is composed of a biconcave negative lens 21B, a negative meniscus lens with a convex surface facing the object (i.e., negative lens 22B), and a positive meniscus lens with a convex surface facing the object (i.e., positive lens 23B) in order from the object side. The surface on the object side of the biconcave negative lens 21B is an aspherical surface. The negative meniscus lens (i.e., negative lens 22B) and the positive meniscus lens (i.e., positive lens 23B) are joined together.

[0299] (2) In the third lens group G3, the positive lens 32A is not a positive meniscus lens but a biconvex positive lens.

[0300] (3) The fourth lens group G4 has a negative refractive power instead of a positive refractive power. The fourth lens group G4 is composed of a negative meniscus lens with a convex surface facing the image (i.e., negative lens 41B). Both surfaces of the negative meniscus lens (i.e., negative lens 41B) are aspherical surfaces.

[0301] [Table 21]

[0302]

[0303] * indicates a rotationally symmetric aspherical surface [Table 22]

[0304] Surface number K A4 A6 A8 A10 3 0.3008 -1.15015E-04 -1.83576E-07 -3.20340E-08 0.00000E+00 14 -0.7374 -3.91272E-05 1.33662E-05 1.75627E-06 -7.52673E-08 15 -0.6037 4.07738E-04 1.78386E-05 9.62561E-07 -3.15711E-08

[0305] [Table 23]

[0306] Focal length First lens group -16.16 Second lens group 22.16 Third lens group 14.04 Fourth lens group -200.72 First to second lens groups -149.10 Third to fourth lens groups 15.92

[0307] [Table 24]

[0308] Conditional expression (1) -0.107 (2) 3.064 (3) 0.783 (4) -4.861 (5) 1.194 (6) 0.081 (7) 1.969 (8) 67.730 (9) -1.167 (10) 1.905 (11) 1.340 (12) 2.258 (13) 1.020 (14) 0.818

[0309] Numerical Example 7

[0310] Figure 7 、 Figures 14A to 14D And Tables 25 to 28 are explanatory diagrams of the imaging lens 1000 of Numerical Example 7 of the present invention. Figure 7This is a diagram showing the lens structure of the imaging lens 1000 of Numerical Example 7. Figure 7 3 is a cross-sectional view of the imaging lens 1000 of Numerical Example 7. Figure 14A , 14B , 14C and 14D are aberration curve diagrams of the imaging lens 1000 according to Numerical Example 7. Table 25 shows surface data, Table 26 shows aspherical surface data, Table 27 shows focal length data, and Table 28 shows conditional expression data.

[0311] The configuration of the imaging lens according to Numerical Embodiment 7 is the same as the configuration of the imaging lens according to Numerical Embodiment 1 except for the following points.

[0312] (1) The third lens group G3 is composed of a biconvex positive lens 31B and a biconcave negative lens 32B in this order from the object side. The biconvex positive lens 31B and the biconcave negative lens 32B are cemented together.

[0313] (2) The fourth lens group G4 is composed of a negative meniscus lens (i.e., negative lens 41C) having a convex surface facing the image and a positive meniscus lens (i.e., positive lens 42C) having a convex surface facing the image in order from the object side. The negative meniscus lens (i.e., negative lens 41C) and the positive meniscus lens (i.e., positive lens 42C) are bonded together. The surface on the object side of the negative meniscus lens (i.e., negative lens 41C) is an aspherical surface. The surface on the image side of the positive meniscus lens (i.e., positive lens 42C) is an aspherical surface.

[0314] [Table 25]

[0315]

[0316] * indicates rotationally symmetric aspheric surface [Table 26]

[0317] Surface number K A4 A6 A8 A10 3 0.1623 -9.95233E-05 -1.23326E-06 -3.70434E-08 0.00000E+00 12 0.2844 5.26340E-05 2.22952E-05 8.76757E-07 -3.72401E-08 14 -0.1759 3.22735E-04 1.01687E-05 5.96690E-07 -1.31466E-08

[0318] [Table 27]

[0319] Focal length First lens group -18.23 Second lens group 21.22 Third lens group 15.27 Fourth lens group 343.80 First to second lens groups 338.02 Third to fourth lens groups 16.72

[0320] [Table 28]

[0321] Conditional expression (1) 0.049 (2) 2.049 (3) 0.811 (4) -1.647 (5) 3.888 (6) -0.053 (7) 2.907 (8) 76.45 (9) -1.371 (10) 1.905 (11) 1.518 (12) 2.434 (13) 1.062 (14) 0.787

[0322] Figure 15A and 15B is an external view of a digital camera 100 according to an embodiment of the present disclosure, which includes any one of the above-described imaging lenses according to an embodiment of the present disclosure. Figure 16is a block diagram of the hardware configuration of the digital camera 100. The digital camera 100 may include, or be composed of, an interchangeable lens, an imaging device, or an information processing device. When composed of an interchangeable lens, an imaging device, and an information processing device, the digital camera 100 can be read as an interchangeable lens, an imaging device, and an information processing device.

[0323] In terms of the interchangeable lens and the imaging device, the imaging lens according to an embodiment of the present disclosure can be used as an imaging optical system. In terms of the information processing device, the imaging lens according to an embodiment of the present invention can be used as an imaging optical system of the camera function unit of a portable information terminal device.

[0324] The digital camera 100 includes a camera body 101 (or housing), an imaging lens 102, a viewfinder 103, a flash 104, a shutter release button 105, a power button 106, a liquid crystal display (LCD) monitor 107, operation buttons 108, a memory card slot 109, and a zoom switch 110.

[0325] The camera body 101 houses the respective components of the digital camera 100. The imaging lens 102 can be, for example, a unit in which the imaging lens according to an embodiment of the present disclosure is assembled into a lens barrel, or can be a unit detachably mounted to the camera body 101. In this case, the imaging lens 102 can be an interchangeable lens.

[0326] The viewfinder 103 serves as a peephole for determining the subject and composition.

[0327] The flash 104 emits a flash for night or low-light shooting.

[0328] The shutter release button 105 is a physical switch for performing shooting using the digital camera 100.

[0329] The power button 106 is a physical switch for turning on and off the digital camera 100.

[0330] The LCD monitor 107 displays, for example, the images captured by the digital camera 100.

[0331] The operation buttons 108 are physical switches for setting, for example, the shooting mode of the digital camera 100.

[0332] The memory card slot 109 is a slot into which a memory card for storing data of the images captured by the digital camera 100, for example, is inserted.

[0333] The zoom switch 110 is a physical switch for zooming between the short focal length end and the long focal length end.

[0334] However, when the imaging lens (i.e., the single-focus lens) according to the embodiments of the present disclosure is mounted, the digital camera 100 does not use the zoom switch 110.

[0335] The digital camera 100 further includes a central processing unit (CPU) 111, an image processor 112, a light detector 113, a signal processor 114, a semiconductor memory 115, and a communication card 116 as functional components within the camera body 101.

[0336] The CPU 111 performs various computational processes within the digital camera 100.

[0337] The image processor 112 performs various image processing operations on the images captured by the digital camera 100. The light detector 113 captures external light for photometry processing. The signal processor 114 performs various signal processes, such as capture command signals and image processing signals. The semiconductor memory 115 serves as a temporary storage area for the images captured by the digital camera 100. The communication card 116 is used to implement wireless communication with external devices, for example.

[0338] The configuration of the digital camera 100 described above is merely an example, and various design modifications can be made. In other words, there is freedom in the specific embodiments of the digital camera 100.

[0339] Aspect 1

[0340] Embodiments of the present disclosure provide an imaging lens that sequentially includes, from the object side toward the image side: a first lens group having a negative refractive power, a second lens group having a positive refractive power, an aperture stop, a third lens group having a positive refractive power, and a fourth lens group. Among the first lens group, the second lens group, the third lens group, and the fourth lens group, the fourth lens group has the weakest refractive power. The first lens group includes a negative lens having a concave surface facing the image. The second lens group sequentially includes, from the object side toward the image side: a negative lens having a concave surface facing the object; and a cemented lens having an overall positive refractive power. The third lens group includes: a biconvex positive lens closest to the object in the third lens group; and a negative lens closest to the image in the third lens group, the negative lens having a concave surface facing the object. The fourth lens group includes a single lens or a cemented lens. In the fourth lens group, the surface closest to the object is a concave surface facing the object; the surface closest to the image is a convex surface facing the image. The imaging lens satisfies the following conditional expression (1):

[0341] -0.4 < f3-4 / f1-2 < 0.4 (1)

[0342] In the above conditional expression, f1-2 represents the combined focal length of the first lens group and the second lens group, and f3-4 represents the combined focal length of the third lens group and the fourth lens group.

[0343] Aspect 2

[0344] Embodiments of the present disclosure provide an imaging lens, which sequentially includes, from the object side towards the image side: a first lens group with negative refractive power, a second lens group with positive refractive power, an aperture stop, a third lens group with positive refractive power, and a fourth lens group. Among the first lens group, the second lens group, the third lens group, and the fourth lens group, the fourth lens group has the weakest refractive power. The first lens group includes a negative lens with a concave surface facing the image. The second lens group sequentially includes, from the object side towards the image side: a negative lens with a concave surface facing the object; and a cemented lens with overall positive refractive power. The third lens group includes: a cemented lens of the negative lens closest to the image and the positive lens second closest to the image in the third lens group; and a positive lens of the third lens group located on the object side with respect to the cemented lens. The fourth lens group includes a singlet or a cemented lens. In the fourth lens group, the surface closest to the object is a concave surface facing the object; the surface closest to the image is a convex surface facing the image, and the imaging lens satisfies the following conditional expression (1):

[0345] -0.4 < f3-4 / f1-2 < 0.4 (1)

[0346] In the above conditional expression, f1-2 represents the combined focal length of the first lens group and the second lens group, and f3-4 represents the combined focal length of the third lens group and the fourth lens group.

[0347] Aspect 3

[0348] Embodiments of the present disclosure provide an imaging lens, which sequentially includes, from the object side towards the image side: a first lens group with negative refractive power, a second lens group with positive refractive power, an aperture stop, a third lens group with positive refractive power, and a fourth lens group. Among the first lens group, the second lens group, the third lens group, and the fourth lens group, the fourth lens group has the weakest refractive power. The first lens group includes a negative lens with a concave surface facing the image. The second lens group sequentially includes, from the object side towards the image side: a negative lens with a concave surface facing the object; and a cemented lens with overall positive refractive power. The third lens group includes: a cemented lens of the negative lens closest to the image and the positive lens second closest to the image in the third lens group; and three or fewer optical components. The fourth lens group includes a singlet or a cemented lens. In the fourth lens group, the surface closest to the object is a concave surface facing the object; the surface closest to the image is a convex surface facing the image, and the imaging lens satisfies the following conditional expression (1):

[0349] -0.4 < f3-4 / f1-2 < 0.4 (1)

[0350] In the above conditional expression, f1-2 represents the combined focal length of the first lens group and the second lens group, and f3-4 represents the combined focal length of the third lens group and the fourth lens group.

[0351] Aspect 4

[0352] Embodiments of the present disclosure provide an imaging lens, which sequentially includes, from the object side towards the image side: a first lens group having a negative refractive power, a second lens group having a positive refractive power, an aperture stop, a third lens group having a positive refractive power, and a fourth lens group. Among the first lens group, the second lens group, the third lens group, and the fourth lens group, the fourth lens group has the weakest refractive power. The first lens group includes a negative lens having a concave surface facing the image. The second lens group sequentially includes, from the object side towards the image side: a negative meniscus lens having a concave surface facing the object; and a positive lens or a cemented lens having an overall positive refractive power. The third lens group includes: a cemented lens of a negative lens closest to the image and a positive lens second closest to the image in the third lens group; and three or fewer optical components. The fourth lens group includes a singlet or a cemented lens. In the fourth lens group, the surface closest to the object is a concave surface facing the object; the surface closest to the image is a convex surface facing the image. The imaging lens satisfies the following conditional expression (1):

[0353] -0.4 < f3-4 / f1-2 < 0.4 (1)

[0354] In the above conditional expression, f1-2 represents the combined focal length of the first lens group and the second lens group, and f3-4 represents the combined focal length of the third lens group and the fourth lens group.

[0355] Aspect 5

[0356] Embodiments of the present disclosure provide an imaging lens, which sequentially includes, from the object side towards the image side: a first lens group with negative refractive power, a second lens group with positive refractive power, an aperture stop, a third lens group with positive refractive power, and a fourth lens group. Among the first lens group, the second lens group, the third lens group, and the fourth lens group, the fourth lens group has the weakest refractive power. The first lens group includes a negative lens with a concave surface facing the image. The second lens group sequentially includes, from the object side towards the image side: a negative lens with a concave surface facing the object; and a cemented lens sequentially including a positive lens and a negative lens from the object side towards the image side, and the cemented lens has positive refractive power as a whole. The third lens group includes: a positive lens closest to the object in the third lens group; and a negative lens with a concave surface facing the object, and in the third lens group, the negative lens is located on the image side with respect to the positive lens closest to the object. The fourth lens group includes a single lens or a cemented lens. In the fourth lens group, the surface closest to the object is a concave surface facing the object; the surface closest to the image is a convex surface facing the image. The imaging lens satisfies the following conditional expression (1):

[0357] -0.4 < f3-4 / f1-2 < 0.4 (1)

[0358] In the above conditional expression, f1-2 represents the combined focal length of the first lens group and the second lens group, and f3-4 represents the combined focal length of the third lens group and the fourth lens group.

[0359] Aspect 6

[0360] The imaging lens according to any one of Aspects 1 to 5, wherein the imaging lens satisfies the following conditional expression (2):

[0361] 0 < (r1s + r2s) / (r1s - r2s) < 10 (2)

[0362] Here, r1s represents the radius of curvature of the lens surface adjacent to the object side of the aperture stop, and r2s represents the radius of curvature of the lens surface adjacent to the image side of the aperture stop.

[0363] Aspect 7

[0364] The imaging lens according to any one of Aspects 1 to 5, wherein the imaging lens satisfies the following conditional expression (3):

[0365] 0.5 < L1h / Sh < 1.1 (3)

[0366] Here, L1h represents the height of the marginal ray on the optical axis from the optical axis of the object-side surface of the lens closest to the object in the optical system of the imaging lens, and Sh represents the height of the marginal ray on the optical axis from the optical axis of the aperture stop.

[0367] Aspect 8

[0368] The imaging lens according to any one of Aspects 1 to 5, wherein the imaging lens satisfies the following conditional expression (4):

[0369] -6 < r2F / f < -0.5 (4)

[0370] Here, r2F represents the radius of curvature of the surface closest to the object in the second lens group, and f represents the overall focal length of the imaging lens when the imaging lens forms an image of an object at infinity.

[0371] Aspect 9

[0372] The imaging lens according to any one of Aspects 1 to 5, wherein the imaging lens satisfies the following conditional expression (5):

[0373] 0.5 < r3R / f < 10 (5)

[0374] Here, r3R represents the radius of curvature of the surface closest to the image in the third lens group, and f represents the overall focal length of the imaging lens when the imaging lens forms an image of an object at infinity.

[0375] Aspect 10

[0376] The imaging lens according to any one of Aspects 1 to 5, wherein the imaging lens satisfies the following conditional expression (6):

[0377] -0.4 < f1 / f4 < 0.4 (6)

[0378] Here, f1 represents the focal length of the first lens group, and f4 represents the focal length of the fourth lens group.

[0379] Aspect 11

[0380] A replaceable lens, comprising the imaging lens according to any one of Aspects 1 to 5.

[0381] Aspect 12

[0382] An imaging device, comprising the imaging lens according to any one of Aspects 1 to 5.

[0383] Aspect 13

[0384] An information processing device, comprising the imaging lens according to any one of Aspects 1 to 5.

[0385] The above embodiments are illustrative and do not limit the present invention. Therefore, many additional modifications and variations are possible in accordance with the above teachings. For example, within the scope of the present invention, elements and / or features of different illustrative embodiments can be combined with and / or replaced by each other.

[0386] This patent application claims priority based on Japanese Patent Application No. 2022-177252 filed with the Japan Patent Office on November 4, 2022, the entire disclosure of which is incorporated herein by reference.

[0387] List of Reference Numerals

[0388] 100 Digital camera (interchangeable lens, imaging device, information processing device)

[0389] G1 First lens group having negative refractive power 11A Negative lens

[0390] G2 Second lens group having positive refractive power 21A Negative lens

[0391] 22A Positive lens

[0392] 23A Negative lens

[0393] 21B Negative lens

[0394] 22B Negative lens

[0395] 23B Positive lens

[0396] G3 Third lens group having positive refractive power

[0397] 31A Positive lens

[0398] 32A Positive lens

[0399] 33A Negative lens

[0400] 31B Positive lens

[0401] 32B Negative lens

[0402] 31C Positive lens

[0403] 32C Negative lens

[0404] 33C Positive lens

[0405] G4 Fourth lens group having positive or negative refractive power

[0406] 41A Positive lens

[0407] 41B Negative lens

[0408] 41C Negative lens

[0409] 42C Positive lens

[0410] F1, F2 Filters (cover glass)

[0411] I Image plane

Claims

1. An imaging lens, which sequentially includes, from the object side toward the image side: a first lens group having a negative refractive power, a second lens group having a positive refractive power, an aperture stop, a third lens group having a positive refractive power, and a fourth lens group, wherein, among the first lens group, the second lens group, the third lens group, and the fourth lens group, the fourth lens group has the weakest refractive power, the first lens group includes a negative lens having a concave surface facing the image, the second lens group sequentially includes, from the object side toward the image side: a negative lens having a concave surface facing the object; and a cemented lens having an overall positive refractive power, the third lens group includes: a biconvex positive lens closest to the object in the third lens group; and a negative lens closest to the image in the third lens group, the negative lens having a concave surface facing the object, the fourth lens group includes a singlet lens or a cemented lens, wherein, in the fourth lens group, the surface closest to the object is a concave surface facing the object; the surface closest to the image is a convex surface facing the image, the imaging lens satisfies the following conditional expression (1): -0.4 < f3-4 / f1-2 < 0.4 (1) wherein, f1-2 represents the combined focal length of the first lens group and the second lens group, and f3-4 represents the combined focal length of the third lens group and the fourth lens group.

2. An imaging lens, which sequentially includes, from the object side toward the image side: a first lens group having a negative refractive power, a second lens group having a positive refractive power, an aperture stop, a third lens group having a positive refractive power, and a fourth lens group, wherein, among the first lens group, the second lens group, the third lens group, and the fourth lens group, the fourth lens group has the weakest refractive power, the first lens group includes a negative lens having a concave surface facing the image, the second lens group sequentially includes, from the object side toward the image side: a negative lens having a concave surface facing the object; and a cemented lens having an overall positive refractive power, the third lens group includes: a cemented lens of a negative lens closest to the image and a positive lens second closest to the image in the third lens group; and a positive lens of the third lens group located on the object side with respect to the cemented lens, the fourth lens group includes a singlet lens or a cemented lens, wherein, in the fourth lens group, the surface closest to the object is a concave surface facing the object; the surface closest to the image is a convex surface facing the image, the imaging lens satisfies the following conditional expression (1): -0.4 < f3-4 / f1-2 < 0.4 (1) wherein, f1-2 represents the combined focal length of the first lens group and the second lens group, and f3-4 represents the combined focal length of the third lens group and the fourth lens group.

3. An imaging lens, which sequentially includes, from the object side toward the image side: a first lens group having a negative refractive power, a second lens group having a positive refractive power, an aperture stop, a third lens group having a positive refractive power, and a fourth lens group, wherein, among the first lens group, the second lens group, the third lens group, and the fourth lens group, the fourth lens group has the weakest refractive power, The first lens group includes a negative lens having a concave surface facing the image. The second lens group includes, in order from the object side to the image side: a negative lens having a concave surface facing the object; and a cemented lens having positive refractive power as a whole. The third lens group includes: a cemented lens of a negative lens closest to the image and a positive lens second closest to the image in the third lens group; and three or fewer optical components. The fourth lens group includes a single lens or a cemented lens. Among them, in the fourth lens group, the surface closest to the object is a concave surface facing the object; the surface closest to the image is a convex surface facing the image. The imaging lens satisfies the following conditional expression (1): -0.4 < f3-4 / f1-2 < 0.4 (1) Among them, f1-2 represents the combined focal length of the first lens group and the second lens group, and f3-4 represents the combined focal length of the third lens group and the fourth lens group.

4. An imaging lens includes, in order from the object side to the image side: a first lens group having negative refractive power, a second lens group having positive refractive power, an aperture stop, a third lens group having positive refractive power, and a fourth lens group. Among them, in the first lens group, the second lens group, the third lens group, and the fourth lens group, the fourth lens group has the weakest refractive power. The first lens group includes a negative lens having a concave surface facing the image. The second lens group includes, in order from the object side to the image side: a negative meniscus lens having a concave surface facing the object; and a positive lens or a cemented lens having positive refractive power as a whole. The third lens group includes: a cemented lens of a negative lens closest to the image and a positive lens second closest to the image in the third lens group; and three or fewer optical components. The fourth lens group includes a single lens or a cemented lens. Among them, in the fourth lens group, the surface closest to the object is a concave surface facing the object; the surface closest to the image is a convex surface facing the image. The imaging lens satisfies the following conditional expression (1): -0.4 < f3-4 / f1-2 < 0.4 (1) Among them, f1-2 represents the combined focal length of the first lens group and the second lens group, and f3-4 represents the combined focal length of the third lens group and the fourth lens group.

5. An imaging lens includes, in order from the object side to the image side: a first lens group having negative refractive power, a second lens group having positive refractive power, an aperture stop, a third lens group having positive refractive power, and a fourth lens group. Among them, in the first lens group, the second lens group, the third lens group, and the fourth lens group, the fourth lens group has the weakest refractive power. The first lens group includes a negative lens having a concave surface facing the image. The second lens group includes, in order from the object side to the image side: a negative lens having a concave surface facing the object; and a cemented lens including a positive lens and a negative lens in order from the object side to the image side, and the cemented lens has positive refractive power as a whole. The third lens group includes: a positive lens closest to the object in the third lens group; and a negative lens having a concave surface facing the object, and in the third lens group, the negative lens is located on the image side with respect to the positive lens closest to the object. The fourth lens group includes a single lens or a cemented lens. Wherein, in the fourth lens group, the surface closest to the object is a concave surface facing the object; the surface closest to the image is a convex surface facing the image. The imaging lens satisfies the following conditional expression (1): -0.4 < f3-4 / f1-2 < 0.4 (1) Wherein, f1-2 represents the combined focal length of the first lens group and the second lens group, and f3-4 represents the combined focal length of the third lens group and the fourth lens group.

6. The imaging lens according to any one of claims 1 to 5, Wherein, The imaging lens satisfies the following conditional expression (2): 0 < (r1s + r2s) / (r1s - r2s) < 10 (2) Herein, r1s represents the radius of curvature of the lens surface adjacent to the object side of the aperture stop, and r2s represents the radius of curvature of the lens surface adjacent to the image side of the aperture stop.

7. The imaging lens according to any one of claims 1 to 5, Wherein, The imaging lens satisfies the following conditional expression (3): 0.5 < L1h / Sh < 1.1 (3) Herein, L1h represents the height of the marginal ray on the optical axis of the surface on the object side of the lens closest to the object in the optical system of the imaging lens, and Sh represents the height of the marginal ray on the optical axis of the aperture stop.

8. The imaging lens according to any one of claims 1 to 5, Wherein, The imaging lens satisfies the following conditional expression (4): -6 < r2F / f < -0.5 (4) Herein, r2F represents the radius of curvature of the surface closest to the object in the second lens group, and f represents the overall focal length of the imaging lens when imaging an object at infinity.

9. The imaging lens according to any one of claims 1 to 5, Wherein, The imaging lens satisfies the following conditional expression (5): 0.5 < r3R / f < 10 (5) Herein, r3R represents the radius of curvature of the surface closest to the image in the third lens group, and f represents the overall focal length of the imaging lens when imaging an object at infinity.

10. The imaging lens according to any one of claims 1 to 5, Wherein, The imaging lens satisfies the following conditional expression (6): -0.4 < f1 / f4 < 0.4 (6) Herein, f1 represents the focal length of the first lens group, and f4 represents the focal length of the fourth lens group.

11. A replaceable lens, comprising the imaging lens according to any one of claims 1 to 5.

12. An imaging device, comprising the imaging lens according to any one of claims 1 to 5.

13. An information processing device, comprising the imaging lens according to any one of claims 1 to 5.

Images