Imaging lens

Abstract

The present invention provides an imaging lens, which is composed of a front imaging lens having a plurality of lenses before and after with respect to a diaphragm and a convex-concave Galilean system. The convex-concave Galilean system is composed of a convex lens on the front group side and a concave lens on the imaging surface side. In the imaging lens, focusing is performed by fixing the convex-concave Galilean system near the imaging surface and moving the front imaging lens. Among them, the imaging surface side of the lens at the end of the imaging surface side of the Galilean system is a flat surface, and this flat surface is in contact with the surface of the end of the imaging lens side of the image sensor. Alternatively, the front imaging lens adopts a 4-group 6-element Gauss type or a 4-group 7-element Sumita type, or a modified Sumita type with 5 groups and 7 elements obtained by separating the front doublet lens of the Sumita type.

Description

Technical Field

[0001] The present invention relates to an imaging lens, for example, an imaging lens for imaging light on a light-receiving portion of a CMOS image sensor. Background Art

[0002] The structure of a CMOS (Complementary Metal Oxide Semiconductor) image sensor is roughly divided into a front-illumination type and a back-illumination type. In the case of a front-illumination type CMOS image sensor, a photodiode is processed on a silicon wafer, and a wiring layer, a color filter, and a microlens are arranged upward. In recent years, with miniaturization, the number of wirings has increased, and the problem of light shielding of the light beam reaching the CMOS photodiode has become obvious.

[0003] In addition, the thickness of the wiring layer has also increased. Therefore, the photodiode of the CMOS element has a structure arranged at the bottom of a deep well, and the photodiode can only utilize light beams at a small angle with respect to the vertical line. Moreover, it also has the following disadvantages: the light beam that is shielded, reflected, and scattered in terms of area and the light beam that is reflected and scattered on the well wall described later reach the photodiode as flare light beams, reducing the contrast of the image.

[0004] On the other hand, in the case of a back-illumination type CMOS image sensor, a silicon wafer having a photodiode layer is bonded on a silicon wafer having a wiring layer, and the silicon wafer is etched until the photodiode layer is exposed to the surface to the limit, and a color filter and a microlens are processed. Since the back-illumination type arranges the photodiode layer before the wiring layer, the above-mentioned disadvantages of the surface type can be eliminated. Although the processing of the back-illumination type CMOS image sensor requires high technology, the replacement from the front-illumination type CMOS image sensor to the back-illumination type CMOS image sensor is in progress.

[0005] Moreover, a logic circuit is embedded in the wiring layer so as to have an image processor function, and it is also called a stacked CMOS image sensor.

[0006] In order to obtain an image with high image quality using such a CMOS image sensor, an imaging lens that matches the pixels of the fine CMOS image sensor is required. In order to confirm the image resolution required for the imaging lens, the size of the CMOS image element is confirmed.

[0007] The stacked CMOS image sensor is used as a versatile image input unit in digital cameras, smartphones ( = mobile phones), surveillance cameras, in-vehicle cameras, etc. In order to improve the image resolution, miniaturization of CMOS elements is underway, such that the CMOS elements of 35mm full-size / digital cameras are 3.5μm x 3.5μm, and those of industrial cameras with a size of 1 inch to 1 / 3 inch are 1.4μm x 1.4μm.

[0008] In the smartphone cameras of mobile phones, a CMOS image sensor has also been commercialized. This CMOS image sensor groups four 0.8μm x 0.8μm CMOS elements = R (red) + G (green) x 2 + B (blue) under one microlens. In the imaging lens, a microlens opening of 1.6μm x 1.6μm is required for the resolution.

[0009] In surface-type CMOS, 2.2μm x 2.2μm elements have been developed for industrial use in the APS-H size ( 29.2 x 20.2mm). Regarding an imaging lens capable of corresponding to such CMOS elements, for example, an imaging lens as described in Patent Document 1 has been proposed. For the imaging lens described in Patent Document 1, high optical performance has been confirmed through an actually prototyped imaging lens.

[0010] Prior Art Documents

[0011] Patent Documents

[0012] Patent Document 1: Japanese Patent No. 6725740 Summary of the Invention

[0013] Problems to be Solved by the Invention

[0014] However, in the imaging lens described in Patent Document 1, a floating mechanism in which the lens group on the imaging side moves is adopted for focusing, so the structure is complex and the operation is not easy to say.

[0015] Moreover, in the entire imaging surface of cameras equipped with CMOS image sensors with a size of 1 inch to 1 / 3 inch for industrial use, the size of the CMOS element (one pixel of the CMOS image sensor) is 1.4μm x 1.4μm. In terms of the reference value for obtaining a clear image, it is shown that imaging is generally performed with a contrast of MTF value of 20% or more, but for pixels of 1.4μm x 1.4μm, a lens that can achieve imaging with a contrast of MTF value of 20% or more has not been realized yet. The imaging lens described in Patent Document 1 also cannot always arrange the lens group on the imaging side near the imaging surface due to the movement of the lens group on the imaging side, and cannot obtain a contrast of MTF value of 20% or more at any shooting distance.

[0016] Accordingly, an object of the present invention is to solve the above problems, and it is an object to provide an imaging lens having a resolution corresponding to elements of a fine image sensor and capable of focusing with a simple structure.

[0017] Solution to the problem

[0018] To solve the above problems, an imaging lens according to one aspect of the present invention is composed of a front imaging lens having a plurality of lenses before and after with respect to a diaphragm, and a convex-concave Galilean system. The convex-concave Galilean system is composed of a convex lens on the front group side and a concave lens on the imaging surface side. In the imaging lens, focusing is performed by fixing the convex-concave Galilean system near the imaging surface and moving the front imaging lens.

[0019] Effect of the invention

[0020] As described above, according to the present invention, an imaging lens having a resolution corresponding to elements of a fine image sensor and capable of focusing with a simple structure can be provided. Description of the drawings

[0021] Figure 1 FIG. is a diagram showing Chart 1 corresponding to the first embodiment.

[0022] Figure 2a FIG. is a diagram showing Chart 2 (shooting distance t0 = ∞) corresponding to the first embodiment.

[0023] Figure 2b FIG. is a diagram showing Chart 2 (shooting distance t0 = 500 mm) corresponding to the first embodiment.

[0024] Figure 2c FIG. is a diagram showing Chart 2 (shooting distance t0 = 150 mm) corresponding to the first embodiment.

[0025] Figure 3 FIG. is a diagram showing Chart 3 corresponding to the first embodiment.

[0026] Figure 4 FIG. is a diagram showing Chart 4 corresponding to the second embodiment.

[0027] Figure 5a FIG. is a diagram showing Chart 5 (shooting distance t0 = ∞) corresponding to the second embodiment.

[0028] Figure 5b FIG. is a diagram showing Chart 5 (shooting distance t0 = 500 mm) corresponding to the second embodiment.

[0029] Figure 5c FIG. is a diagram showing Chart 5 (shooting distance t0 = 150 mm) corresponding to the second embodiment.

[0030] Figure 6 It is a diagram showing Diagram 6 corresponding to the third embodiment.

[0031] Figure 7a It is a diagram showing Diagram 7 (shooting distance t0 = ∞) corresponding to the third embodiment.

[0032] Figure 7b It is a diagram showing Diagram 7 (shooting distance t0 = 500 mm) corresponding to the third embodiment.

[0033] Figure 7c It is a diagram showing Diagram 7 (shooting distance t0 = 150 mm) corresponding to the third embodiment.

[0034] Figure 8 It is a diagram showing Diagram 8 corresponding to the fourth embodiment.

[0035] Figure 9a It is a diagram showing Diagram 9 (shooting distance t0 = ∞) corresponding to the fourth embodiment.

[0036] Figure 9b It is a diagram showing Diagram 9 (shooting distance t0 = 500 mm) corresponding to the fourth embodiment.

[0037] Figure 9c It is a diagram showing Diagram 9 (shooting distance t0 = 150 mm) corresponding to the fourth embodiment.

[0038] Figure 10 It is a diagram showing Diagram 10 corresponding to the fifth embodiment.

[0039] Figure 11a It is a diagram showing Diagram 11 (shooting distance t0 = ∞) corresponding to the fifth embodiment. Figure 11b It is a diagram showing Diagram 11 (shooting distance t0 = 500 mm) corresponding to the fifth embodiment.

[0040] Figure 11c It is a diagram showing Diagram 11 (shooting distance t0 = 150 mm) corresponding to the fifth embodiment.

[0041] Figure 12 It is a diagram showing Diagram 12 corresponding to the sixth embodiment.

[0042] Figure 13a It is a diagram showing Diagram 13 (shooting distance t0 = ∞) corresponding to the sixth embodiment. Figure 13b It is a diagram showing Diagram 13 (shooting distance t0 = 500 mm) corresponding to the sixth embodiment.

[0043] Figure 13cThis is a diagram showing Chart 13 corresponding to the sixth embodiment (shooting distance t0 = 150 mm).

[0044] Figure 14 This is a diagram showing Chart 14 corresponding to the seventh embodiment.

[0045] Figure 15a This is a diagram showing Chart 15 corresponding to the seventh embodiment (shooting distance t0 = ∞). Figure 15b This is a diagram showing Chart 15 corresponding to the seventh embodiment (shooting distance t0 = 500 mm).

[0046] Figure 15c This is a diagram showing Chart 15 corresponding to the seventh embodiment (shooting distance t0 = 150 mm).

[0047] Figure 16 This is a diagram showing Chart 16 corresponding to the eighth embodiment.

[0048] Figure 17a This is a diagram showing Chart 17 corresponding to the eighth embodiment (shooting distance t0 = ∞). Figure 17b This is a diagram showing Chart 17 corresponding to the eighth embodiment (shooting distance t0 = 500 mm).

[0049] Figure 17c This is a diagram showing Chart 17 corresponding to the eighth embodiment (shooting distance t0 = 150 mm).

[0050] Figure 18 This is a diagram showing Chart 18 corresponding to the ninth embodiment.

[0051] Figure 19a This is a diagram showing Chart 19 corresponding to the ninth embodiment (shooting distance t0 = ∞). Figure 19b This is a diagram showing Chart 19 corresponding to the ninth embodiment (shooting distance t0 = 500 mm).

[0052] Figure 19c This is a diagram showing Chart 19 corresponding to the ninth embodiment (shooting distance t0 = 150 mm).

[0053] Figure 20 This is a diagram showing Chart 20 corresponding to the tenth embodiment.

[0054] Figure 21a This is a diagram showing Chart 21 corresponding to the tenth embodiment (shooting distance t0 = ∞).

[0055] Figure 21b This is a diagram showing Chart 21 corresponding to the tenth embodiment (shooting distance t0 = 500 mm).

[0056] Figure 21cIt is a diagram showing Chart 21 (shooting distance t0 = 150 mm) corresponding to the tenth embodiment.

[0057] Figure 22 It is a diagram showing Chart 22 corresponding to the eleventh embodiment.

[0058] Figure 23a It is a diagram showing Chart 23 (shooting distance t0 = ∞) corresponding to the eleventh embodiment. Figure 23b It is a diagram showing Chart 23 (shooting distance t0 = 500 mm) corresponding to the eleventh embodiment.

[0059] Figure 23c It is a diagram showing Chart 23 (shooting distance t0 = 150 mm) corresponding to the eleventh embodiment.

[0060] Figure 24 It is a diagram showing Chart 24 corresponding to the twelfth embodiment.

[0061] Figure 25a It is a diagram showing Chart 25 (shooting distance t0 = ∞) corresponding to the twelfth embodiment. Figure 25b It is a diagram showing Chart 25 (shooting distance t0 = 500 mm) corresponding to the twelfth embodiment.

[0062] Figure 25c It is a diagram showing Chart 25 (shooting distance t0 = 150 mm) corresponding to the twelfth embodiment.

[0063] Figure 26 It is a diagram showing Chart 26 corresponding to the thirteenth embodiment.

[0064] Figure 27a It is a diagram showing Chart 27 (shooting distance t0 = ∞) corresponding to the thirteenth embodiment. Figure 27b It is a diagram showing Chart 27 (shooting distance t0 = 500 mm) corresponding to the thirteenth embodiment.

[0065] Figure 27c It is a diagram showing Chart 27 (shooting distance t0 = 150 mm) corresponding to the thirteenth embodiment.

[0066] Figure 28 It is a diagram showing Chart 28 corresponding to the fourteenth embodiment.

[0067] Figure 29a It is a diagram showing Chart 29 (shooting distance t0 = ∞) corresponding to the fourteenth embodiment. Figure 29b It is a diagram showing Chart 29 (shooting distance t0 = 500 mm) corresponding to the fourteenth embodiment.

[0068] Figure 29cThis is a diagram showing Chart 29 (shooting distance t0 = 150 mm) corresponding to the fourteenth embodiment.

[0069] Figure 30 This is a table summarizing the results of each embodiment. Detailed implementation mode

[0070] Hereinafter, with reference to the charts attached as the drawings, each embodiment of the present invention will be described. The embodiments shown below are used to embody the technical idea of the present invention, and unless otherwise specified, the present invention is not limited to the following content.

[0071] (Overall description)

[0072] In the present invention, an imaging lens is provided, which is composed of a front imaging lens having a plurality of lenses before and after with respect to a diaphragm, and a convex-concave Galilean system. The convex-concave Galilean system is composed of a convex lens on the front group side and a concave lens on the imaging surface side. In this imaging lens, focusing is performed by fixing the convex-concave Galilean system near the imaging surface and moving the front imaging lens.

[0073] In this imaging lens, due to the front imaging lens and the Galilean system, it has a resolution corresponding to the elements of a fine image sensor. Moreover, since the Galilean system is fixed near the imaging surface, focusing can be performed with a simple structure. Thus, an imaging lens having a resolution corresponding to the elements of a fine image sensor and capable of performing focusing with a simple structure can be provided.

[0074] If described in further detail, in the imaging lens of the present invention, from an infinite distance where the shooting distance t0 = ∞ to a close position where t0 = 150 mm, an MTF of 20% or more at 1.4 μmL&S (= 357 LP / mm) can be obtained over the entire imaging surface.

[0075] Here, L&S is called line and space, which refers to the width of a wiring and the interval between adjacent wirings. LP / mm is called line pairs per millimeter, which represents the resolution of an imaging system. When X [μmL&S] = Y [LP / mm], there is a relationship of X = 1000 / Y / 2.

[0076] In addition, MTF (Modulation Transfer Function) is one of the indexes for evaluating the performance of a lens. It expresses how faithfully the contrast of a subject can be reproduced as a spatial frequency characteristic in order to know the imaging performance of the lens.

[0077] Regarding the specific implementation mode for realizing the above, taking Figures 1 to 3 the first embodiment shown as an example for description.Figure 1 This is a diagram showing Diagram 1 corresponding to the first embodiment. Figure 2a This is a diagram showing Diagram 2 (shooting distance t0 = ∞) corresponding to the first embodiment. Figure 2b This is a diagram showing Diagram 2 (shooting distance t0 = 500 mm) corresponding to the first embodiment. Figure 2c This is a diagram showing Diagram 2 (shooting distance t0 = 150 mm) corresponding to the first embodiment. Figure 3 This is a diagram showing Diagram 3 corresponding to the first embodiment.

[0078] In the upper part of Diagram 3 ( Figure 3 (a)), data, an optical path diagram, and MTF of the front imaging lens of the first embodiment are shown. The part with a high image height on the imaging surface has a high MTF value. However, since the Petzval radius of curvature = -27.948 mm, the imaging surface with a large image height bends forward, and the MTF value drops sharply.

[0079] Here, the Petzval radius of curvature is the radius obtained by theorizing the curvature of the image plane in the third-order aberration region of Seidel. In the third-order aberration region of Seidel, the Petzval radius of curvature is theorized. The Petzval radius of curvature is the radius of curvature of the meridional image plane where the contrast of the line width in the diameter direction of the image plane is imaged well and the radius of curvature of the sagittal image plane where the contrast of the line width in the circumferential direction of the image plane is imaged well coincide, and there is no astigmatism.

[0080] It should be noted that if it is only a convex lens, the Petzval radius of curvature is a negative value, and the image plane bends in a shape close to the lens. If a concave lens is added to the lens configuration, the radius of curvature of the bend becomes larger and the image plane stands up. However, due to the addition of the concave lens, the focal length of the imaging lens becomes longer. What eliminates this is the position where the concave lens is arranged. If a concave lens is arranged near the focal plane of the convex lens imaging, the combined focal length of the convex lens and the concave lens will become approximately only the focal length of the convex lens.

[0081] In the middle part of Diagram 3 ( Figure 3 (a)), data and an optical path diagram of the Galilean system of the first embodiment are shown. The Petzval radius of curvature of the Galilean system = +32.073 mm. Therefore, the Petzval radius of curvature of the entire imaging lens = 1 / (1 / 32.073 - 1 / 27.948) = -217.309 mm, and the imaging surface stands up.

[0082] In Diagram 3 ( Figure 3In the lower part of (b)), the Galileo system was removed, and the front imaging lens was optimized with the same focal length and the same imaging area. The Petzval radius of curvature was set from -27.948 mm to -73.263 mm. However, when the F-number was reduced to 5.6, the resolving power decreased, but MTF 30% of 3.3 μm L&S = 150 LP / mm could be obtained over the entire imaging surface.

[0083] The front imaging lens can be a 4-group 6-element Gauss type, a 4-group 7-element Summitar type, or a modified Summitar type with 5 groups 7 elements by separating the front doublet of the Summitar type. In the case of this type of front imaging lens, good aberration performance can be achieved even when the F-number is around 5.6. In the present invention, a Galileo system is added to achieve MTF 20% or more of 1.4 μm L&S over the entire imaging surface at an F-number of 2.8 and over the entire imaging surface.

[0084] In the present invention, the imaging surface is based on a 1 / 1.8-inch ( 7.2 x 5.4 mm) with a viewing angle of ±14.0°, and the following specifications are adopted: the imaging surface size ranges from 1 / 3 inch ( 8 x 3.6 mm) to 1 inch ( 12.8 x 9.6 mm), and the viewing angle range is from ±9.8° to ±16.8°. By adopting such specifications, performance close to that of an aberration-free lens can be achieved.

[0085] In the present invention, the imaging lens is composed of a front imaging lens and a convex-concave Galileo system. The convex-concave Galileo system arranges a convex lens with positive optical power on the front imaging lens side and a concave lens with negative optical power on the imaging surface side. In the entire imaging lens, the convex-concave Galileo system is fixed near the imaging surface, so the Galileo system is placed near the focal position. Thus, the value obtained by dividing the focal length of the front imaging lens ((3) removing the convex-concave Galileo system) by the focal length of the entire imaging lens ((1)) can be controlled within the range of 0.9 to 1.2.

[0086] It should be noted that the numerical values enclosed in parentheses above correspond to the circled numbers shown in the diagrams (drawings). The same applies to the numerical values enclosed in parentheses shown below.

[0087] The data of the imaging from a distance in the first embodiment (Chart 1: t0 = ∞) is used to illustrate this (t0: shooting distance). When a lens with a negative optical power is added to the imaging lens, according to Petzval's formula, it can be known that the image plane stands up. According to the sum of the reciprocal (1 / P) of the Petzval radius of curvature P1 = -27.948 of the front component imaging lens and the reciprocal (1 / P2) of the Petzval radius of curvature P2 = 32.073 of the Galilean system in the data of the first embodiment, the Petzval radius of curvature P = -217.309 of the entire imaging lens can be obtained as follows.

[0088] 1 / P = 1 / P1 + 1 / P2

[0089] 1 / (-217.309) = 1 / (-27.948) + 1 / 32.073

[0090] In a thin-wall optical system, when the focal length of lens 1 is set to f1, the focal length of lens 2 is set to f2, and the principal point interval of the two lens groups is set to d, the focal length f of the entire lens can be obtained by the following formula.

[0091] 1 / f = 1 / f1 + 1 / f2 - d / (f1×f2)

[0092] When the front component imaging lens (f1 = 18.534), f2 is the Galilean system (f2 = -23.764), the principal point interval of the lens group d = 19.177, and the Galilean system is placed near the focus of the front component imaging lens, the focal length of the entire imaging lens is f = 18.046.

[0093] 1 / f = 1 / f1 + 1 / f2 - d / (f1xf2)

[0094] 1 / 18.046 = 1 / 18.534 + 1 / (-23.764) - 19.177 / {18.534x(-23.764)}

[0095] 0.0554 = 0.0540 - 0.0421 + 0.0435

[0096] In this way, by fixing the Galilean system near the imaging plane, even if a lens with a strong negative optical power is used in the Galilean system of f2, the focal length of the entire imaging lens will be close to the focal length of the front component imaging lens.

[0097] (3) The value obtained by dividing the focal length of the front imaging lens of the convex-concave Galilean system by (1) the focal length of the entire imaging lens ((3) / (1)) falling within the range of 0.9 to 1.2 means that the degree of freedom in which the focal length of the Galilean system does not much affect the overall focal length can be obtained. Thus, the field curvature of the front group can be easily corrected by the Galilean system. Based on the design criterion that the above value ((3) / (1)) falls within the range of 0.9 to 1.2, the front group and the Galilean system can be optimized separately, or the front group + Galilean system can be optimized so as to obtain an MTF of 20% or more at 1.4 μm L&S.

[0098] Regarding the correction for optimization, the value ((3) / (4)) obtained by dividing (3) the focal length of the front imaging lens by (4) the focal length of the Galilean system is a value representing the Petzval correction rate using the focal length ratio of the front group to the Galilean system. The value ((3) / (4)) becomes a small value when the Petzval radius of curvature of the front group is long, and conversely becomes a large value when the Petzval radius of curvature of the front group is short. In the case where the Petzval radius of curvature of the front group is long, optimization can be performed with the weak correction of the convex-concave Galilean system, and in the case where the Petzval radius of curvature of the front group is short, strong correction of the convex-concave Galilean system is required.

[0099] In the present invention, considering the correction based on the convex-concave Galilean system described later, the lens design is performed such that the value ((3) / (4)) obtained by dividing (3) the focal length of the front imaging lens by (4) the focal length of the Galilean system is within the range of minus 0.2 to minus 1.1.

[0100] In the first embodiment,

[0101] (3) / (4) = minus 0.780, falling within the range of minus 0.2 to minus 1.1,

[0102] The focal length of the entire imaging lens is 18.046 mm, and the Petzval radius of curvature is -217.309 mm,

[0103] The focal length of the front group is 18.534 mm, and the Petzval radius of curvature is -27.948 mm,

[0104] The focal length of the Galilean system is -23.764 mm, and the Petzval radius of curvature is 32.073 mm.

[0105] Regarding the correction in an optimized convex-concave Galilean system, the value obtained by dividing the focal length of the (6) concave lens of the convex-concave Galilean system by the focal length of the (5) convex lens ((6) / (5)) can be cited. The value ((6) / (5)) is the focal length ratio of the convex and concave lenses of the Galilean system. When the focal length of the concave lens is lengthened (i.e., the Petzval correction is made smaller), it becomes a large value, and when the focal length of the concave lens is shortened (i.e., the Petzval correction is made larger), it becomes a small value. In the present invention, if the image plane of the front group is erected, gentle Galilean correction is performed, and if the image plane is greatly curved, strong Galilean correction is performed, and control can be achieved through the convex and concave Galilean system.

[0106] In the present invention, in order to obtain an MTF of 20% or more at 1.4 μm L&S, the lens is designed such that the value obtained by dividing the focal length of the (6) concave lens of the convex-concave Galilean system by the focal length of the (5) convex lens ((6) /

[0107] (5)) is in the range of -0.08 to -0.8.

[0108] In the first embodiment,

[0109] (6) / (5) = -0.276, which falls within the range of -0.08 to -0.8,

[0110] The focal length of the entire imaging lens is 18.046 mm, and the Petzval radius of curvature is -217.309 mm,

[0111] The focal length of the front group is 18.534 mm, and the Petzval radius of curvature is -27.948 mm,

[0112] The focal length of the Galilean system is -23.764 mm, and the Petzval radius of curvature is 32.073 mm.

[0113] As described above, in the present invention, an imaging lens is provided that corresponds to an AI image input element in which the CMOS elements of a back-illuminated CMOS image sensor are miniaturized to 1.4 μm x 1.4 μm and further have an edge computer function through stacking. Conventional imaging lenses assume the advancement of a winding film for improvement, but the back-illuminated stacked CMOS image sensor has both high-speed electronic image transfer and an electronic shutter function. Therefore, the space up to the immediate front of the sensor can be effectively used, and it is also easy to arrange a Galilean system with a negative optical power that has a function of flattening the image plane. The image resolution has also been improved from more than ten μm of silver salt film to 1.4 μm with the miniaturization of CMOS elements.

[0114] Thus, with the imaging lens + back-illuminated stacked CMOS image sensor of the present invention, an AI image unit with an MTF contrast of 1.4 μm L&S is achieved over 20% of the entire CMOS surface.

[0115] (Description of each embodiment)

[0116] Hereinafter, embodiments of the present invention will be described.

[0117] In the following embodiments, the following relationships are satisfied:

[0118] The value obtained by dividing the focal length of the front group imaging lens in (3) above by the focal length of the entire imaging lens in (1) ((3) / (1)) is 0.9 to 1.2.

[0119] The value obtained by dividing the focal length of the front group imaging lens in (3) above by the Galilean focal length in (4) ((3) / (4)) is -0.2 to -1.1.

[0120] The value obtained by dividing the focal length of the concave lens in (6) above by the focal length of the convex lens of Galileo in (5) ((6) / (5)) is -0.08 to -0.8.

[0121] (First Embodiment)

[0122] As shown in Chart 1 and Chart 2 ( Figure 1 , Figures 2a to 2c ), in the first embodiment,

[0123]

[0124] Magnification = 1 / ∞ t0 = ∞ Viewing angle = ±14.0° Focal length = 18.046 F / 2.80 Front group focal length / entire focal length ∞ = 1.03 Galileo to cover glass = 1 mm CRA = 26.3°

[0125] Magnification = 0.0359x t0 = 500 mm Diagonal field of view = 244 mm Focal length = 17.545 F / 2.60 CRA = 25.3°

[0126] Magnification = 0.1292x t0 = 150 mm Diagonal field of view = 70 mm Focal length = 16.404 F / 2.35 CRA = 24.3°.

[0127] Here, the CRA (Chief Ray Angle) is also called the chief ray angle, which is the incident angle of the chief ray passing through the center of the pupil relative to the CMOS plane. For example, in the first embodiment, the chief ray from ∞ = infinity enters the periphery of the CMOS plane at CRA = 26.3°. In the case of a wide-angle lens with a large viewing angle, the CRA will become larger. In addition, the CRA also changes according to the lens type. In the second embodiment with the same viewing angle as the first embodiment, CRA = 20.9°.

[0128] In the first embodiment, the value obtained by dividing the focal length of the (3) front group imaging lens by the focal length of the (1) entire imaging lens ((3) / (1)) is 1.03 when t0 = ∞, 1.06 when t0 = 500 mm, and 1.13 when t0 = 150 mm. Therefore, the relationship 0.9 < (3) / (1) < 1.2 is satisfied.

[0129] In the first embodiment, the value obtained by dividing the focal length of the (3) front group imaging lens by the (4) Galilean focal length ((3) / (4)) is -0.780. Therefore, the relationship -0.2 > (3) / (4) > -1.1 is satisfied.

[0130] In the first embodiment, the value obtained by dividing the focal length of the concave lens of the (6) Galilean system by the focal length of the convex lens of the (5) Galilean system ((6) / (5)) is -0.276. Therefore, the relationship -0.08 > (6) / (5) > -0.8 is satisfied.

[0131] As shown in Chart 2 ( Figures 2a to 2c ), the MTF contrast of 357LP = 1.4 μmL&S is 28% when t0 = ∞, 28% when t0 = 500 mm, and 26% when t0 = 150 mm. Therefore, from infinity to close-up shooting at 150 mm, an MTF contrast of more than 20% is obtained over the entire image plane, which also roughly coincides with the theoretical value, achieving good aberration correction.

[0132] (Second Embodiment)

[0133] As shown in Chart 4 and Chart 5 ( Figure 4 、 Figures 5a to 5c ), in the second embodiment,

[0134] Magnification = 1 / ∞ t0 = ∞ Viewing angle = ±14.4° Focal length = 17.553 F / 2.80 Front group focal length / Entire focal length ∞ = 1.08 Galileo to cover glass = 1 mm CRA = 20.9°

[0135] Magnification = 0.0359x, t0 = 500mm, diagonal field of view = 251mm, focal length = 17.409, F / 2.65, CRA = 20.1°

[0136] Magnification = 0.1532x, t0 = 150mm, diagonal field of view = 72mm, focal length = 17.060, F / 2.50, CRA = 18.9°.

[0137] In the second embodiment, the value obtained by dividing the focal length of the front imaging lens (3) by the focal length of the entire imaging lens (1) ((3) / (1)) is 1.08 when t0 = ∞, 1.09 when t0 = 500mm, and 1.11 when t0 = 150mm. Therefore, the relationship 0.9 < (3) / (1) < 1.2 is satisfied.

[0138] In the second embodiment, the value obtained by dividing the focal length of the front imaging lens (3) by the Galilean focal length (4) ((3) / (4)) is -0.231. Therefore, the relationship -0.2 > (3) / (4) > -1.1 is satisfied.

[0139] In the second embodiment, the value obtained by dividing the focal length of the concave lens of the Galilean system (6) by the focal length of the convex lens of the Galilean system (5) ((6) / (5)) is -0.710. Therefore, the relationship -0.08 > (6) / (5) > -0.8 is satisfied.

[0140] When the front lens is separated into a plano-convex lens and a strongly meniscus-shaped concave lens, the Petzval radius of curvature of the front imaging lens stands up, and the correction based on the Galilean system near the imaging surface can be set as a gentle correction. Although it is a bit worse than the first embodiment, even if different lens types are further selected as the front imaging lens, by adding the Galilean system to stand up the imaging surface, the possibility of aberration improvement can be expected.

[0141] As shown in Chart 5( Figures 5a to 5c ), the MTF contrast of 357LP = 1.4μm L&S is 26% when t0 = ∞, 24% when t0 = 500mm, and 20% when t0 = 150mm. Therefore, from infinity to close-up shooting at 150mm, an MTF contrast of 20% or more is obtained over the entire imaging surface.

[0142] (Third Embodiment)

[0143] As shown in Chart 6 and Chart 7( Figure 6 、 Figures 7a to 7c ), in the third embodiment,

[0144]

[0145] Magnification = 1 / ∞, t0 = ∞, Viewing angle = ±16.2°, Focal length = 15.524, F / 2.95, Front group focal length / Overall focal length ∞ = 0.94, Galileo ~ Cover glass = 1mm, CRA = 29.3°

[0146] Magnification = 0.0314x, t0 = 500mm, Diagonal field of view = 287mm, Focal length = 15.162, F / 2.75, CRA = 28.9°

[0147] Magnification = 0.107x, t0 = 150mm, Diagonal field of view = 84mm, Focal length = 14.357, F / 2.50, CRA = 28.2°.

[0148] In the third embodiment, the value obtained by dividing the focal length of the (3) front - group imaging lens by the focal length of the (1) entire imaging lens ((3) / (1)) is 0.94 when t0 = ∞, 0.97 when t0 = 500mm, and 1.02 when t0 = 150mm. Therefore, the relationship 0.9 < (3) / (1) < 1.2 is satisfied.

[0149] In the third embodiment, the value obtained by dividing the focal length of the (3) front - group imaging lens by the (4) Galileo focal length ((3) / (4)) is - 0.718. Therefore, the relationship - 0.2 > (3) / (4) > - 1.1 is satisfied.

[0150] In the third embodiment, the value obtained by dividing the focal length of the concave lens of the (6) Galileo system by the focal length of the convex lens of the (5) Galileo system ((6) / (5)) is - 0.244. Therefore, the relationship - 0.08 > (6) / (5) > - 0.8 is satisfied.

[0151] As shown in Chart 7( Figures 7a to 7c ), the MTF contrast of 357LP = 1.4μm L&S is 20% when t0 = ∞, 22% when t0 = 500mm, and 22% when t0 = 150mm. Therefore, MTF contrast of 20% or more is obtained over the entire image plane from infinity to 150mm for close - up shooting.

[0152] (Fourth embodiment)

[0153] Figure 8 This is a diagram showing Chart 8 corresponding to the fourth embodiment. Figures 9a to 9c This is a diagram showing Chart 9 corresponding to the fourth embodiment. As shown in Chart 8 and Chart 9( Figure 8 、 Figures 9a to 9c ), in the fourth embodiment,

[0154]

[0155] Magnification = 1 / ∞, t0 = ∞, Viewing angle = ±10.8°, Focal length = 23.666, F / 2.90, Front group focal length / Overall focal length ∞ = 1.05, Galileo ~ Cover glass = 1mm, CRA = 20.1°

[0156] Magnification = 0.0491x, t0 = 500mm, Diagonal field of view = 183mm, Focal length = 22.847, F / 2.60, CRA = 19.5°

[0157] Magnification = 0.1792x, t0 = 150mm, Diagonal field of view = 50mm, Focal length = 20.930, F / 2.10, CRA = 18.5°.

[0158] In the fourth embodiment, the value obtained by dividing the focal length of the (3) front group imaging lens by the focal length of the (1) entire imaging lens ((3) / (1)) is 1.05 when t0 = ∞, 1.08 when t0 = 500mm, and 1.18 when t0 = 150mm. Therefore, the relationship 0.9 < (3) / (1) < 1.2 is satisfied.

[0159] In the fourth embodiment, the value obtained by dividing the focal length of the (3) front group imaging lens by the (4) Galileo focal length ((3) / (4)) is -0.737. Therefore, the relationship -0.2 > (3) / (4) > -1.1 is satisfied.

[0160] In the fourth embodiment, the value obtained by dividing the focal length of the concave lens of the (6) Galileo system by the focal length of the convex lens of the (5) Galileo system ((6) / (5)) is -0.369. Therefore, the relationship -0.08 > (6) / (5) > -0.8 is satisfied.

[0161] As shown in Chart 9( Figures 9a to 9c ), the MTF contrast of 357LP = 1.4μm L&S is 25% when t0 = ∞, 27% when t0 = 500mm, and 22% when t0 = 150mm. Therefore, from infinity to a close-up of 150mm, an MTF contrast of over 20% is obtained across the entire image plane.

[0162] (Fifth embodiment)

[0163] Figure 10 This is a diagram showing Chart 10 corresponding to the fifth embodiment. Figures 11a to 11c This is a diagram showing Chart 11 corresponding to the fifth embodiment. As shown in Chart 10 and Chart 11 (as Figure 10 , Figures 11a to 11c ), in the fifth embodiment,

[0164]

[0165] Magnification = 1 / ∞, t0 = ∞, Viewing angle = ±14.0°, Focal length = 18.077, F / 2.80, Front group focal length / Overall focal length ∞ = 1.02, Galileo ~ Cover glass = 1mm, CRA = 25.9°

[0166] Magnification = 0.0369x, t0 = 500mm, Diagonal field of view = 244mm, Focal length = 17.559, F / 2.60, CRA = 26.0°

[0167] Magnification = 0.1299x, t0 = 150mm, Diagonal field of view = 69mm, Focal length = 16.380, F / 2.30, CRA = 24.5°.

[0168] In the fifth embodiment, the value obtained by dividing the focal length of the (3) front - group imaging lens by the focal length of the (1) entire imaging lens ((3) / (1)) is 1.02 when t0 = ∞, 1.05 when t0 = 500mm, and 1.13 when t0 = 150mm. Therefore, the relationship 0.9 < (3) / (1) < 1.2 is satisfied.

[0169] In the fifth embodiment, the value obtained by dividing the focal length of the (3) front - group imaging lens by the (4) Galileo focal length ((3) / (4)) is - 0.806. Therefore, the relationship - 0.2 > (3) / (4) > - 1.1 is satisfied.

[0170] In the fifth embodiment, the value obtained by dividing the focal length of the concave lens of the (6) Galileo system by the focal length of the convex lens of the (5) Galileo system ((6) / (5)) is - 0.267. Therefore, the relationship - 0.08 > (6) / (5) > - 0.8 is satisfied.

[0171] In the fifth embodiment, the following changes were made from the first embodiment. The number of lens elements of the front - end lens was changed from 2 in the first embodiment to 1, the focal length was slightly changed from 18.046mm to 18.077mm, and the focal length of the Galileo system was also slightly changed from - 23.764mm to - 22.916mm, but the MTF contrast remained good.

[0172] As shown in Chart 11( Figures 11a to 11c ), the MTF contrast of 357LP = 1.4μm L&S is 28% when t0 = ∞, 28% when t0 = 500mm, and 21% when t0 = 150mm. Therefore, from infinity to close - up shooting at 150mm, an MTF contrast of 20% or more is obtained over the entire image plane.

[0173] (Sixth embodiment)

[0174] Figure 12 It is a figure showing Chart 12 corresponding to the sixth embodiment. Figures 13a to 13cThis is a diagram showing Chart 13 corresponding to the sixth embodiment. As shown in Chart 12 and Chart 13 ( Figure 12 , Figures 13a to 13c ), in the sixth embodiment,

[0175]

[0176] Magnification = 1 / ∞, t0 = ∞, Viewing angle = ±16.2°, Focal length = 15.464, F / 3.00, Front group focal length / Overall focal length ∞ = 1.00, Galileo to cover glass = 1mm, CRA = 28.1°

[0177] Magnification = 0.0312x, t0 = 500mm, Diagonal field of view = 288mm, Focal length = 15.089, F / 2.80, CRA = 27.7°

[0178] Magnification = 0.1065x, t0 = 150mm, Diagonal field of view = 85mm, Focal length = 14.259, F / 2.55, CRA = 27.0°.

[0179] In the sixth embodiment, the value obtained by dividing the focal length of the (3) front group imaging lens by the focal length of the (1) entire imaging lens ((3) / (1)) is 1.00 when t0 = ∞, 1.02 when t0 = 500mm, and 1.08 when t0 = 150mm. Therefore, the relationship 0.9 < (3) / (1) < 1.2 is satisfied.

[0180] In the sixth embodiment, the value obtained by dividing the focal length of the (3) front group imaging lens by the (4) Galileo focal length ((3) / (4)) is -0.801. Therefore, the relationship -0.2 > (3) / (4) > -1.1 is satisfied.

[0181] In the sixth embodiment, the value obtained by dividing the focal length of the (6) concave lens of the Galileo system by the focal length of the (5) convex lens of the Galileo system ((6) / (5)) is -0.220. Therefore, the relationship -0.08 > (6) / (5) > -0.8 is satisfied.

[0182] As shown in Chart 13 ( Figures 13a to 13c ), for 357LP = 1.4μm L&S, the MTF contrast is 20% when t0 = ∞, 20% when t0 = 500mm, and 20% when t0 = 150mm. Therefore, MTF contrast of 20% or more is obtained over the entire image plane from infinity to close-up shooting at 150mm.

[0183] (Seventh embodiment)

[0184] Figure 14 This is a diagram showing Chart 14 corresponding to the seventh embodiment. Figures 15a to 15cIt is a diagram showing Chart 15 corresponding to the seventh embodiment. As shown in Chart 14 and Chart 15 ( Figure 14 , Figures 15a to 15c ), in the seventh embodiment,

[0185]

[0186] Magnification = 1 / ∞ t0 = ∞ Viewing angle = ±11.9° Focal length = 21.406 F / 2.90 Front group focal length / Overall focal length ∞ = 1.03 Galileo to cover glass = 1 mm CRA = 22.0°

[0187] Magnification = 0.0441 t0 = 500 mm Diagonal field of view = 204 mm Focal length = 20.693 F / 2.60 CRA = 21.3°

[0188] Magnification = 0.1584x t0 = 150 mm Diagonal field of view = 57 mm Focal length = 19.050 F / 2.15 CRA = 20.6°.

[0189] In the seventh embodiment, the value obtained by dividing the focal length of the (3) front group imaging lens by the focal length of the (1) entire imaging lens ((3) / (1)) is 1.03 when t0 = ∞, 1.07 when t0 = 500 mm, and 1.16 when t0 = 150 mm. Therefore, the relationship 0.9 < (3) / (1) < 1.2 is satisfied.

[0190] In the seventh embodiment, the value obtained by dividing the focal length of the (3) front group imaging lens by the (4) Galileo focal length ((3) / (4)) is -0.790. Therefore, the relationship -0.2 > (3) / (4) > -1.1 is satisfied.

[0191] In the seventh embodiment, the value obtained by dividing the focal length of the (6) concave lens of the Galileo system by the focal length of the (5) convex lens of the Galileo system ((6) / (5)) is -0.322. Therefore, the relationship -0.08 > (6) / (5) > -0.8 is satisfied.

[0192] As shown in Chart 15 ( Figures 15a to 15c ), for 357 LP = 1.4 μm L&S's MTF contrast is 26% when t0 = ∞, 28% when t0 = 500 mm, and 23% when t0 = 150 mm. Therefore, from infinity to close-up shooting at 150 mm, an MTF contrast of 20% or more is obtained over the entire image plane.

[0193] (Eighth embodiment)

[0194] Figure 16 It is a diagram showing Chart 16 corresponding to the eighth embodiment. Figures 17a to 17cThis is a diagram showing Diagram 17 corresponding to the eighth embodiment. As shown in Diagram 16 and Diagram 17 ( Figure 16 , Figures 17a to 17c ), in the eighth embodiment,

[0195]

[0196] Magnification = 1 / ∞ t0 = ∞ Viewing angle = ±14.0° Focal length = 24.127 F / 2.80 Front group focal length / Entire focal length ∞ = 1.04 Galileo to cover glass = 1.3mm CRA = 25.6°

[0197] Magnification = 0.04986x t0 = 500mm Diagonal field of view = 241mm Focal length = 23.288 F / 2.60 CRA = 25.2°

[0198] Magnification = 0.1802x t0 = 150mm Diagonal field of view = 67mm Focal length = 21.352 F / 2.20 CRA = 23.3°.

[0199] In the eighth embodiment, the value obtained by dividing the focal length of the (3) front group imaging lens by the focal length of the (1) entire imaging lens ((3) / (1)) is 1.04 at t0 = ∞, 1.08 at t0 = 500mm, and 1.18 at t0 = 150mm. Therefore, the relationship 0.9 < (3) / (1) < 1.2 is satisfied.

[0200] In the eighth embodiment, the value obtained by dividing the focal length of the (3) front group imaging lens by the (4) Galileo focal length ((3) / (4)) is -0.728. Therefore, the relationship -0.2 > (3) / (4) > -1.1 is satisfied.

[0201] In the eighth embodiment, the value obtained by dividing the focal length of the concave lens of the (6) Galileo system by the focal length of the convex lens of the (5) Galileo system ((6) / (5)) is -0.303. Therefore, the relationship -0.08 > (6) / (5) > -0.8 is satisfied.

[0202] As shown in Diagram 17 ( Figures 17a to 17c ), for 357LP = 1.4μm L&S's MTF contrast is 21% at t0 = ∞, 22% at t0 = 500mm, and 20% at t0 = 150mm. Therefore, MTF contrast of 20% or more is obtained over the entire image plane from infinity to close-up shooting at 150mm.

[0203] (Ninth embodiment)

[0204] Figure 18 This is a diagram showing Diagram 18 corresponding to the ninth embodiment. Figures 19a to 19cThis is a diagram showing Diagram 19 corresponding to the ninth embodiment. As shown in Diagram 18 and Diagram 19 ( Figure 18 , Figures 19a to 19c ), in the ninth embodiment,

[0205]

[0206] Magnification = 1 / ∞ t0 = ∞ Viewing angle = ±14.0° Focal length = 12.009 F / 2.80 Front group focal length / Entire focal length ∞ = 0.99 Galileo to cover glass = 1mm CRA = 24.1°

[0207] Magnification = 0.0241x t0 = 500mm Diagonal field of view = 249mm Focal length = 11.795 F / 2.60 CRA = 24.0°

[0208] Magnification = 0.08137x t0 = 150mm Diagonal field of view = 74mm Focal length = 11.319 F / 2.25 CRA = 23.0°.

[0209] In the ninth embodiment, the value obtained by dividing the focal length of the (3) front group imaging lens by the focal length of the (1) entire imaging lens ((3) / (1)) is 0.99 when t0 = ∞, 1.01 when t0 = 500mm, and 1.05 when t0 = 150mm. Therefore, the relationship 0.9 < (3) / (1) < 1.2 is satisfied.

[0210] In the ninth embodiment, the value obtained by dividing the focal length of the (3) front group imaging lens by the (4) Galileo focal length ((3) / (4)) is -0.755. Therefore, the relationship -0.2 > (3) / (4) > -1.1 is satisfied.

[0211] In the ninth embodiment, the value obtained by dividing the focal length of the concave lens of the (6) Galileo system by the focal length of the convex lens of the (5) Galileo system ((6) / (5)) is -0.241. Therefore, the relationship -0.08 > (6) / (5) > -0.8 is satisfied.

[0212] In the ninth embodiment, the following changes are made from the first embodiment. The focal length is also shortened from 18.046mm to 12.009mm, which is shortened to 0.67 times.

[0213] As shown in Diagram 19 ( Figures 19a to 19c ), for 357LP = 1.4μm L&S's MTF contrast is 25% when t0 = ∞, 28% when t0 = 500mm, and 28% when t0 = 150mm. Therefore, MTF contrast of 20% or more is obtained over the entire image plane from infinity to 150mm of close-up shooting.

[0214] (Tenth Embodiment)

[0215] Figure 20 This is a diagram showing Diagram 20 corresponding to the tenth embodiment. Figures 21a to 21c This is a diagram showing Diagram 21 corresponding to the tenth embodiment. As shown in Diagram 20 and Diagram 21 ( Figure 20 , Figures 21a to 21c ), in the tenth embodiment,

[0216]

[0217] Magnification = 1 / ∞ t0 = ∞ Viewing angle = ±14.2° Focal length = 17.748 F / 2.80 Front group focal length / Overall focal length ∞ = 0.99 Galileo to cover glass = 3.6 mm CRA = 20.4°

[0218] Magnification = 0.0361x t0 = 500 mm Diagonal field of view = 249 mm Focal length = 17.404 F / 2.60 CRA = 20.1°

[0219] Magnification = 0.1250x t0 = 150 mm Diagonal field of view = 72 mm Focal length = 16.611 F / 2.30 CRA = 19.5°.

[0220] In the tenth embodiment, the value obtained by dividing the focal length of the front group imaging lens (3) by the focal length of the entire imaging lens (1) ((3) / (1)) is 0.99 when t0 = ∞, 1.01 when t0 = 500 mm, and 1.09 when t0 = 150 mm. Therefore, the relationship 0.9 < (3) / (1) < 1.2 is satisfied.

[0221] In the tenth embodiment, the value obtained by dividing the focal length of the front group imaging lens (3) by the Galileo focal length (4) ((3) / (4)) is -0.554. Therefore, the relationship -0.2 > (3) / (4) > -1.1 is satisfied.

[0222] In the tenth embodiment, the value obtained by dividing the focal length of the concave lens of the Galileo system (6) by the focal length of the convex lens of the Galileo system (5) ((6) / (5)) is -0.436. Therefore, the relationship -0.08 > (6) / (5) > -0.8 is satisfied.

[0223] In the tenth embodiment, the optical axis interval from the back surface of the concave lens of the Galileo system to the incident surface of the CMOS cover glass is increased from 1 mm in the second embodiment to 3.6 mm.

[0224] As shown in Diagram 21 ( Figures 21a to 21c) As shown, the MTF contrast of 357LP = 1.4μmL&S is 20% at t0 = ∞, 22% at t0 = 500mm, and 22% at t0 = 150mm. Therefore, when the distance between Galileo and the cover glass is increased to 3.6mm, there is a tendency for the MTF to deteriorate, but MTF contrast of 20% or more is obtained over the entire image plane for close-ups from infinity to 150mm.

[0225] (Eleventh Embodiment)

[0226] Figure 22 It is a diagram showing Chart 22 corresponding to the eleventh embodiment. Figures 23a to 23c It is a diagram showing Chart 23 corresponding to the eleventh embodiment. As shown in Chart 22 and Chart 23 ( Figure 22 , Figures 23a to 23c ), in the eleventh embodiment,

[0227]

[0228] Magnification = 1 / ∞ t0 = ∞ Viewing angle = ±14.1° Focal length = 17.926 F / 2.80 Front group focal length / Overall focal length ∞ = 1.01 Galileo - cover glass = 2mm CRA = 22.9°

[0229] Magnification = 0.0365x t0 = 500mm Diagonal field of view = 247mm Focal length = 17.492 F / 2.60 CRA = 22.4°

[0230] Magnification = 0.12728x t0 = 150mm Diagonal field of view = 71mm Focal length = 16.503 F / 2.30 CRA = 21.6°.

[0231] In the eleventh embodiment, the value obtained by dividing the focal length of the front - group imaging lens (3) by the focal length of the entire imaging lens (1) ((3) / (1)) is 1.01 at t0 = ∞, 1.03 at t0 = 500mm, and 1.09 at t0 = 150mm. Therefore, the relationship 0.9 < (3) / (1) < 1.2 is satisfied.

[0232] In the eleventh embodiment, the value obtained by dividing the focal length of the front - group imaging lens (3) by the Galileo focal length (4) ((3) / (4)) is - 0.686. Therefore, the relationship - 0.2 > (3) / (4) > - 1.1 is satisfied.

[0233] In the eleventh embodiment, the value obtained by dividing the focal length of the concave lens of the Galileo system (6) by the focal length of the convex lens of the Galileo system (5) ((6) / (5)) is - 0.322. Therefore, the relationship - 0.08 > (6) / (5) > - 0.8 is satisfied.

[0234] In the eleventh embodiment, when the optical axis interval from the back surface of the concave lens of the Galileo system to the incident surface of the CMOS cover glass is reduced from 3.6 mm in the tenth embodiment to 2 mm, a contrast close to that of the second embodiment can be obtained.

[0235] As shown in Chart 23( Figures 23a to 23c ), the MTF contrast of 357 LP = 1.4 μm L&S is 24% when t0 = ∞, 23% when t0 = 500 mm, and 24% when t0 = 150 mm. Therefore, from infinity to a close-up of 150 mm, an MTF contrast of 20% or more is obtained over the entire image plane.

[0236] (Twelfth embodiment)

[0237] Figure 24 It is a diagram showing Chart 24 corresponding to the twelfth embodiment. Figures 25a to 25c It is a diagram showing Chart 25 corresponding to the twelfth embodiment. As shown in Chart 24 and Chart 25( Figure 24 , Figures 25a to 25c ), in the twelfth embodiment,

[0238]

[0239] Magnification = 1 / ∞ t0 = ∞ Viewing angle = ±13.8° Focal length = 18.295 F / 2.80 Front group focal length / Entire focal length ∞ = 1.02 Galileo to cover glass = 0 mm (bonded) CRA = 26.6°

[0240] Magnification = 0.0373x t0 = 500 mm Diagonal field of view = 241 mm Focal length = 17.664 F / 2.60 CRA = 25.4°

[0241] Magnification = 0.1306x t0 = 150 mm Diagonal field of view = 57 mm Focal length = 16.265 F / 2.30 CRA = 24.0°.

[0242] In the twelfth embodiment, the value obtained by dividing the focal length of the (3) front group imaging lens by the focal length of the (1) entire imaging lens ((3) / (1)) is 1.02 when t0 = ∞, 1.06 when t0 = 500 mm, and 1.15 when t0 = 150 mm. Therefore, the relationship of 0.9 < (3) / (1) < 1.2 is satisfied.

[0243] In the twelfth embodiment, the value obtained by dividing the focal length of the (3) front group imaging lens by the (4) Galileo focal length ((3) / (4)) is -0.964. Therefore, the relationship of -0.2 > (3) / (4) > -1.1 is satisfied.

[0244] In the twelfth embodiment, the value obtained by dividing the focal length of the concave lens of the Galilean system (6) by the focal length of the convex lens of the Galilean system (5) ((6) / (5)) is -0.113. Therefore, the relationship -0.08 > (6) / (5) > -0.8 is satisfied.

[0245] In the twelfth embodiment, on the basis of the Gauss deformation (Summitar) + Galilean type of the first embodiment, the incident side of the convex lens and the concave lens constituting the Galilean system is concave, and the exit side is flat. The flat surface is bonded to the cover glass of a solid-state imaging device such as a CMOS. When the concave lens of the Galilean system is bonded to the cover glass of the CMOS, the number of reflecting surfaces for air is reduced by two, and the reflection loss is reduced. Moreover, if the concave lens and the cover glass are integrated, the number of components is also reduced by one.

[0246] Since the degree of freedom in design is reduced because the exit surface is restricted to a flat surface in the twelfth embodiment, the incident concave surface is made aspherical to compensate for the deterioration of aberration.

[0247] As shown in Chart 25 ( Figures 25a to 25c ), the MTF contrast of 357 LP = 1.4 μm L&S is 27% at t0 = ∞, 27% at t0 = 500 mm, and 24% at t0 = 150 mm. Therefore, from infinity to close-up shooting at 150 mm, an MTF contrast of 20% or more is obtained over the entire image plane.

[0248] The bonding or integration of the concave lens of the Galilean system and the cover glass in the twelfth embodiment can also be performed in the second to eleventh embodiments, and the aberration also reproduces the aberration horizontal plane difference correction of each embodiment.

[0249] (Thirteenth Embodiment)

[0250] Figure 26 It is a diagram showing Chart 26 corresponding to the thirteenth embodiment. Figures 27a to 27c It is a diagram showing Chart 27 corresponding to the thirteenth embodiment. As shown in Chart 26 and Chart 27 ( Figure 26 、 Figures 27a to 27c ), in the thirteenth embodiment,

[0251]

[0252] Magnification = 1 / ∞ t0 = ∞ Viewing angle = ±16.7° Focal length = 14.954 F / 2.80 Front group focal length / overall focal length ∞ = 1.01 Galileo - cover glass = 0 mm (bonded) CRA = 29.2°

[0253] Magnification = 0.03033x t0 = 500 mm Diagonal field of view = 297 mm Focal length = 14.493 F / 2.60 CRA = 27.5°

[0254] Magnification = 0.10455 x t0 = 150 mm Diagonal field of view = 152 mm Focal length = 13.480 F / 2.35 CRA = 26.6°.

[0255] In the thirteenth embodiment, the value obtained by dividing the focal length of the front group imaging lens ((3)) by the focal length of the entire imaging lens ((1)) ((3) / (1)) is 1.01 when t0 = ∞, 1.04 when t0 = 500 mm, and 1.12 when t0 = 150 mm. Therefore, the relationship 0.9 < (3) / (1) < 1.2 is satisfied.

[0256] In the thirteenth embodiment, the value obtained by dividing the focal length of the front group imaging lens ((3)) by the Galilean focal length ((4)) ((3) / (4)) is -1.056. Therefore, the relationship -0.2 > (3) / (4) > -1.1 is satisfied.

[0257] In the thirteenth embodiment, the value obtained by dividing the focal length of the concave lens of the Galilean system ((6)) by the focal length of the convex lens of the Galilean system ((5)) ((6) / (5)) is -0.105. Therefore, the relationship -0.08 > (6) / (5) > -0.8 is satisfied.

[0258] As shown in Chart 27 ( Figures 27a to 27c ), the MTF contrast of 357 LP = 1.4 μm L&S is 28% when t0 = ∞, 29% when t0 = 500 mm, and 26% when t0 = 150 mm. Therefore, MTF contrast of 20% or more is obtained over the entire image plane from infinity to 150 mm of close-up shooting.

[0259] The adhesion or integration of the concave lens of the Galilean system and the cover glass in the thirteenth embodiment can also be performed in the second to eleventh embodiments, and the aberration also reproduces the aberration horizontal plane difference correction of each embodiment.

[0260] (Fourteenth embodiment)

[0261] Figure 28 This is a diagram showing Chart 28 corresponding to the fourteenth embodiment. Figures 29a to 29c This is a diagram showing Chart 29 corresponding to the fourteenth embodiment. As shown in Chart 28 and Chart 29 ( Figure 28 , Figures 29a to 29c ), in the fourteenth embodiment,

[0262]

[0263] Magnification = 1 / ∞ t0 = ∞ Angle of view = ±16.6° Focal length = 15.051 F / 2.80 Front group focal length / entire focal length ∞ = 1.01 Galileo - cover glass = 0 mm (adhesion) CRA = 29.2°

[0264] Magnification = 0.03046x, t0 = 500 mm, diagonal field of view = 295 mm, focal length = 14.500, F / 2.60, CRA = 27.5°

[0265] Magnification = 0.1059x, t0 = 150 mm, diagonal field of view = 85 mm, focal length = 13.458, F / 2.30, CRA = 26.3°.

[0266] In the fourteenth embodiment, the value obtained by dividing the focal length of the front - group imaging lens ((3)) by the focal length of the entire imaging lens ((1)) ((3) / (1)) is 1.01 when t0 = ∞, 1.05 when t0 = 500 mm, and 1.13 when t0 = 150 mm. Therefore, the relationship 0.9 < (3) / (1) < 1.2 is satisfied.

[0267] In the fourteenth embodiment, the value obtained by dividing the focal length of the front - group imaging lens ((3)) by the Galilean focal length ((4)) ((3) / (4)) is - 1.076. Therefore, the relationship - 0.2 > (3) / (4) > - 1.1 is satisfied.

[0268] In the fourteenth embodiment, the value obtained by dividing the focal length of the concave lens of the Galilean system ((6)) by the focal length of the convex lens of the Galilean system ((5)) ((6) / (5)) is - 0.089. Therefore, the relationship - 0.08 > (6) / (5) > - 0.8 is satisfied.

[0269] As shown in Chart 29( Figures 29a to 29c ), the MTF contrast of 357 LP = 1.4 μm L&S is 27% when t0 = ∞, 29% when t0 = 500 mm, and 26% when t0 = 150 mm. Therefore, from infinity to a close - up of 150 mm, an MTF contrast of more than 20% is obtained over the entire image plane.

[0270] The adhesion or integration of the concave lens of the Galilean system in the fourteenth embodiment with the cover glass can also be carried out in the second to eleventh embodiments, and the aberration also reproduces the aberration horizontal - plane difference correction of each embodiment.

[0271] (Summary of embodiments)

[0272] Figure 30 This is a table summarizing the results of each embodiment. In the imaging lens of the present invention, the convex - concave Galilean system is fixed near the imaging plane. In the above - mentioned embodiments, the cases where the lens surface on the image - sensor side of the concave lens of the convex - concave Galilean system is in contact with the cover glass of the image sensor (the twelfth to fourteenth embodiments) to the case where they are separated by 3.6 mm (the tenth embodiment) are shown.

[0273] The closer the distance between the end on the image sensor side and the end on the lens side of the Galilean system is to the image sensor, the easier the aberration correction becomes. It should be noted that as the definition of "fixing the convex-concave Galilean system near the imaging surface" mentioned above, it also depends on the focal length and the imaging surface size. However, it can be exemplified that the distance between the end on the image sensor side and the end on the lens side of the Galilean system is in the range of 0 mm to 8 mm, and the range of 0 mm to 6 mm can be exemplified as a preferred range, and the range of 0 mm to 4 mm can be exemplified as a more preferred range.

[0274] For example, in the second embodiment, the front group focal length / Galilean focal length ((3) / (4)) = -0.231, and the focal length of the Galilean system is long. Since the focal length of the Galilean system is long, the Petzval radius of curvature of the Galilean system also gradually becomes longer because the image surface curvature is corrected by the Galilean system. This means that the front group Petzval radius of curvature in the second embodiment stands at -55.540 mm, so a weak correction is sufficient.

[0275] Conversely, in the twelfth embodiment, the front group focal length / Galilean system focal length ((3) / (4)) = -0.964, and the focal length of the Galilean system is short. This means that the front group Petzval radius of curvature is -28.360 mm, and the image surface curvature bends forward, so a strong correction needs to be applied through the Galilean system.

[0276] In order to reduce the Petzval radius of curvature in the Galilean system, it is necessary to increase the negative value of the concave lens. Therefore, in the second embodiment, the concave lens focal length / convex lens focal length ((6) / (5)) = -0.710 of the Galilean system becomes a relatively large value, and in the twelfth embodiment, the concave lens focal length / convex lens focal length ((6) / (5)) = -0.113 of the Galilean system becomes a relatively small value.

[0277] As confirmed in the above embodiments, since the convex-concave Galilean system is fixed near the imaging surface, the Galilean system is placed near the focal position. Thus, the value obtained by dividing the focal length of the front group imaging lens of the convex-concave Galilean system by the focal length of the entire imaging lens ((3) / (1)) falls within the range of 0.9 to 1.2. This means that even if a lens with a strong negative optical power is used in the Galilean system, the focal length of the entire imaging lens will be close to the focal length of the front group imaging lens. That is to say, the degree of freedom that the focal length of the Galilean system does not affect the overall focal length can be obtained. As a result, the image surface curvature of the front group can be easily corrected by the Galilean system, and an MTF of 20% or more at 1.4 μm L&S can be obtained.

[0278] The value obtained by dividing the focal length of the front - group imaging lens (3) by the focal length of the Galilean system (4) ((3) / (4)) is a value representing the Petzval correction rate in terms of the focal - length ratio between the front group and the Galilean system. When the Petzval curvature radius of the front group is long, it becomes a small value, and conversely, when the Petzval curvature radius of the front group is short, it becomes a large value.

[0279] As confirmed in the above - mentioned embodiment, the lens design is carried out such that the value obtained by dividing the focal length of the front - group imaging lens (3) by the focal length of the Galilean system (4) ((3) / (4)) falls within the range of - 0.2 to - 1.1.

[0280] Regarding the value obtained by dividing the focal length of the concave lens (6) of the convex - concave Galilean system by the focal length of the convex lens (5) of the convex - concave Galilean system ((6) / (5)) related to the correction of the convex - concave Galilean system, when the focal length of the concave lens is made longer ( = making the Petzval correction smaller), it becomes a large value, and when the focal length of the concave lens is made shorter ( = making the Petzval correction larger), it becomes a small value. If the image plane of the front group is erected, gentle Galilean correction is performed, and if the image plane is highly curved, strong Galilean correction is performed, and it can be controlled by the convex - and - concave Galilean system.

[0281] As confirmed in the above - mentioned embodiment, in order to obtain an MTF of 20% or more at 1.4μm L&S, the lens design is carried out such that the value obtained by dividing the focal length of the convex lens (5) of the convex - concave Galilean system by the focal length of the concave lens (6) of the convex - concave Galilean system ((5) / (6)) falls within the range of - 0.08 to - 0.8.

[0282] Through the above - described correction, an MTF of 20% or more at 1.4μm L&S ( = 357 LP / mm) can be obtained over the entire imaging surface from an infinite distance where the distance t0 = ∞ to a close - up position where t0 = 150 mm.

Claims

1. An imaging lens, characterized in that, It is composed of a front imaging lens with multiple lenses before and after separated by a diaphragm and a convex-concave Galilean system. The convex-concave Galilean system is composed of a convex lens on the front group side and a concave lens on the imaging surface side. In the imaging lens, focusing is performed by fixing the convex-concave Galilean system near the imaging surface and sending out the front group imaging lens. The surface on the imaging surface side of the lens at the end on the imaging surface side of the Galilean system is a plane, and this plane is in contact with the surface at the end on the imaging lens side of the image sensor. The value obtained by dividing the focal length of the front group imaging lens of the convex-concave Galilean system by the focal length of the entire imaging lens is in the range greater than 0.9 and less than 1.

2.

2. An imaging lens, characterized in that, It is composed of a front imaging lens with multiple lenses before and after separated by a diaphragm and a convex-concave Galilean system. The convex-concave Galilean system is composed of a convex lens on the front group side and a concave lens on the imaging surface side. In the imaging lens, focusing is performed by fixing the convex-concave Galilean system near the imaging surface and sending out the front group imaging lens. The front group imaging lens adopts a 4-group 6-element Gauss type or a 4-group 7-element Sumita type or a modified Sumita type with 5 groups 7 elements obtained by separating the front doublet lens of the Sumita type. The value obtained by dividing the focal length of the front group imaging lens of the convex-concave Galilean system by the focal length of the entire imaging lens is in the range greater than 0.9 and less than 1.

2.

3. The imaging lens according to claim 1 or 2, characterized in that, The value obtained by dividing the focal length of the front group imaging lens by the focal length of the convex-concave Galilean system is in the range less than -0.2 and greater than -1.

1.

4. The imaging lens according to claim 1 or 2, characterized in that, The value obtained by dividing the focal length of the concave lens of the convex-concave Galilean system by the focal length of the convex lens is in the range less than -0.08 and greater than -0.

8.

5. The imaging lens according to claim 1 or 2, characterized in that, The imaging surface is 1 / 1.8 inches, that is Taking 7.2x5.4mm and a viewing angle of ±14.0° as the reference specifications, the imaging surface size range is set to 1 / 3 inch, that is, 4.8x3.6mm to 1 inch, that is, 12.8x9.6mm, and the viewing angle range is set to ±9.8° to ±16.8°.

Images