Wide-angle lens
The wide-angle lens configuration with specific power and Abbe number conditions addresses chromatic aberration issues, enabling effective application to large image sensors with minimized length and high resolution.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- NIDEC INSTR CORP
- Filing Date
- 2024-12-27
- Publication Date
- 2026-07-09
AI Technical Summary
Conventional wide-angle lenses struggle to achieve high optical performance when applied to large imaging devices, particularly in correcting chromatic aberration.
A wide-angle lens configuration comprising a front group with negative and positive power lenses, and a rear group with cemented lenses, where specific Abbe number conditions are met to correct chromatic aberration, allowing application to large image sensors.
The lens configuration effectively corrects chromatic aberration, enabling wide-angle lenses to be applied to large image sensors while minimizing overall length and maintaining high resolution.
Smart Images
Figure 2026115392000001_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to a wide-angle lens.
Background Art
[0002] Conventionally, in a wide-angle lens, a lens configuration for obtaining high resolution has been proposed. For example, in Patent Document 1, a wide-angle lens having a lens configuration in which, in order from the object side, a first lens and a second lens having negative power, a third lens having positive power, an aperture, a fourth lens and a fifth lens having positive power, a sixth lens having negative power, and a seventh lens having positive power are arranged is disclosed.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] In recent years, the size of imaging devices has been further increasing. However, with the wide-angle lens described in Patent Document 1, it is difficult to obtain the required optical performance when applied to a large imaging device. In particular, correcting chromatic aberration is difficult with the configuration of the wide-angle lens described in Patent Document 1.
[0005] The present disclosure provides a wide-angle lens with well-corrected chromatic aberration that is applicable to a large imaging device.
Means for Solving the Problems
[0006] A wide-angle lens according to one aspect of the present disclosure comprises, in order from the object side to the image side, a front group, an aperture, and a rear group. The front group includes, in order from the object side to the image side, a first group having negative power and a second group having positive power. The second group includes, in order from the object side to the image side, a first lens within the second group, a second lens within the second group, and a third lens within the second group. If the Abbe number of the d line of the second lens within the second group is ν4 and the Abbe number of the d line of the third lens within the second group is ν5, then the following conditions (1) and (2) are satisfied. ν4<30.00 ···(1) 44.00<ν5 ···(2) [Effects of the Invention]
[0007] According to this disclosure, chromatic aberration can be corrected effectively, making it possible to apply wide-angle lenses to large image sensors as well. [Brief explanation of the drawing]
[0008] [Figure 1] This is an explanatory diagram of a wide-angle lens according to Embodiment 1 of this disclosure. [Figure 2] Figure 1 shows the data for a wide-angle lens. [Figure 3] This figure shows the spherical aberration of the wide-angle lens shown in Figure 1. [Figure 4] Figure 1 shows the chromatic aberration of a wide-angle lens. [Figure 5] This figure shows the astigmatism and distortion shown in Figure 1. [Figure 6] This figure shows the lateral aberrations shown in Figure 1. [Figure 7] This is an explanatory diagram of a wide-angle lens according to Embodiment 2 of this disclosure. [Figure 8] Figure 7 shows the data for the wide-angle lens. [Figure 9] This figure shows the spherical aberration of the wide-angle lens shown in Figure 7. [Figure 10] Figure 7 shows the chromatic aberration of a wide-angle lens. [Figure 11]It is a diagram showing the aberration and distortion shown in FIG. 7. [Figure 12] It is a diagram showing the lateral aberration shown in FIG. 7. [Figure 13] It is an explanatory diagram of a wide-angle lens according to Embodiment 3 of the present disclosure. [Figure 14] It is a diagram showing the data of the wide-angle lens shown in FIG. 13. [Figure 15] It is a diagram showing the spherical aberration of the wide-angle lens shown in FIG. 13. [Figure 16] It is a diagram showing the chromatic aberration of magnification of the wide-angle lens shown in FIG. 13. [Figure 17] It is a diagram showing the aberration and distortion shown in FIG. 13. [Figure 18] It is a diagram showing the lateral aberration shown in FIG. 13. [Figure 19] It is an explanatory diagram of a wide-angle lens according to Embodiment 4 of the present disclosure. [Figure 20] It is a diagram showing the data of the wide-angle lens shown in FIG. 19. [Figure 21] It is a diagram showing the spherical aberration of the wide-angle lens shown in FIG. 19. [Figure 22] It is a diagram showing the chromatic aberration of magnification of the wide-angle lens shown in FIG. 19. [Figure 23] It is a diagram showing the aberration and distortion shown in FIG. 19. [Figure 24] It is a diagram showing the lateral aberration shown in FIG. 19. [Figure 25] It is an explanatory diagram of a wide-angle lens according to Embodiment 5 of the present disclosure. [Figure 26] It is a diagram showing the data of the wide-angle lens shown in FIG. 25. [Figure 27] It is a diagram showing the spherical aberration of the wide-angle lens shown in FIG. 25. [Figure 28] It is a diagram showing the chromatic aberration of magnification of the wide-angle lens shown in FIG. 25. [Figure 29] It is a diagram showing the aberration and distortion shown in FIG. 25. [Figure 30] It is a diagram showing the lateral aberration shown in FIG. 25. [Modes for carrying out the invention]
[0009] The wide-angle lens 1 will be described below with reference to the drawings. The wide-angle lens 1 is used, for example, in sensor devices such as those found in automobiles.
[0010] (Embodiment 1) Figure 1 is an explanatory diagram of a wide-angle lens 1 according to Embodiment 1 of the present disclosure. As shown in Figure 1, the wide-angle lens 1 of this embodiment comprises a front group 10, an aperture 30, and a rear group 20, in order from the object side La to the image side Lb.
[0011] The first group 10 includes a first group 110 having negative power and a second group 120 having positive power, arranged in order from the object side La to the image side Lb. The first group 110 consists of a first lens 111 and a second lens 112 within the first group, arranged in order from the object side La to the image side Lb. The second group 120 consists of a first lens 121, a second lens 122, and a third lens 123 within the second group, arranged in order from the object side La to the image side Lb.
[0012] The rear group 20 consists of a first lens 201, a second lens 202, a third lens 203, and a fourth lens 205, arranged in order from the object side La to the image side Lb. Furthermore, a translucent cover 40 and an image sensor 50 are arranged in order from the object side La to the image side Lb of the fourth lens 205. The image sensor 50 is positioned on the imaging plane of the image side Lb of the wide-angle lens 1.
[0013] The first lens 111 in the first group is, for example, a glass lens. The first lens 111 in the first group has negative power. The first lens 111 in the first group has a convex shape on the object-side lens surface 1111 and a concave shape on the image-side lens surface 1112. The second lens 112 in the first group is, for example, a resin lens. The second lens 112 in the first group has negative power. The second lens 112 in the first group has a convex shape on the object-side lens surface 1121 and a concave shape on the image-side lens surface 1122. The second lens 112 in the first group has aspherical shapes on both sides.
[0014] The first lens 121 in the second group is, for example, a resin lens. The first lens 121 in the second group has negative power. The first lens 121 in the second group has a concave shape on the object-side lens surface 1211 and a convex shape on the image-side lens surface 1212. The first lens 121 in the second group has aspherical shapes on both sides. The second lens 122 in the second group is, for example, a resin lens. The second lens 122 in the second group has positive power. The second lens 122 in the second group has a convex shape on the object-side lens surface 1221 and a convex shape on the image-side lens surface 1222. The second lens 122 in the second group has aspherical shapes on both sides. The third lens 123 in the second group is, for example, a resin lens. The third lens 123 in the second group has positive power. The third lens 123 in the second group has a concave shape on the object-side lens surface 1231 (La) and a convex shape on the image-side lens surface 1232 (Lb). The third lens 123 in the second group has aspherical shapes on both sides.
[0015] The first lens 201 in the rear group is, for example, a glass lens. The first lens 201 in the rear group has positive power. The first lens 201 in the rear group has a convex shape on the object-side lens surface 2011 and a convex shape on the image-side lens surface 2012. The second lens 202 in the rear group is, for example, a resin lens. The second lens 202 in the rear group has negative power. The second lens 202 in the rear group has a concave shape on the object-side lens surface 2021 and a concave shape on the image-side lens surface 2022. The second lens 202 in the rear group has aspherical shapes on both sides. The third lens 203 in the rear group is, for example, a resin lens. The third lens 203 in the rear group has positive power. The third lens 203 in the rear group has a convex shape on the object-side lens surface 2031 La and a convex shape on the image-side lens surface 2032 Lb. The third lens 203 in the rear group has aspherical shapes on both sides.
[0016] Here, the second lens 202 and the third lens 203 in the rear group are a cemented lens 204 formed by joining the image-side Lb lens surface 2022 of the second lens 202 and the object-side La lens surface 2031 of the third lens 203 with, for example, an adhesive (not shown). With this configuration, the rear group 20 includes a cemented lens 204, so chromatic aberration can be appropriately corrected.
[0017] The fourth lens element 205 in the rear group is, for example, a resin lens. The fourth lens element 205 in the rear group has positive power. The fourth lens element 205 in the rear group has a convex shape on the lens surface 2051 on the object side La and a concave shape on the lens surface 2052 on the image side Lb. The fourth lens element 205 in the rear group has aspherical shapes on both sides.
[0018] (Lens configuration) Figure 2 shows the data for the wide-angle lens 1 of Embodiment 1. Note that the values shown in Figure 2 have been rounded.
[0019] Figure 2 shows the following data. Here, the total length of the entire lens system is the distance along the optical axis L from the object-side lens surface 1111 of the first lens 111 in the first group to the imaging surface of the image sensor 50. The total length from the first lens 111 in the first group to the fourth lens 205 in the rear group is the distance along the optical axis L from the object-side lens surface 1111 of the first lens 111 in the first group to the image-side lens surface 2052 of the image-side Lb of the fourth lens 205 in the rear group.
[0020] The total focal length of the lens system, f0 (Effective Focal Length). Total length of the entire lens system d0 (Total Track) F-number (Image Space) for the entire lens system Maximum Field of Angle Pupil Diameter Total length between the first lens in the first group and the fourth lens in the rear group (L1R1-L9R2 Track)
[0021] Figure 2 also shows the lens data for each lens listed below. Surfaces marked with an asterisk (*) are aspherical. The units for radius of curvature, thickness, and focal length are mm.
[0022] Here, lens surface 1111 constitutes the first surface. Lens surface 1112 constitutes the second surface. Lens surface 1121 constitutes the third surface. Lens surface 1122 constitutes the fourth surface. Lens surface 1211 constitutes the fifth surface. Lens surface 1212 constitutes the sixth surface. Lens surface 1221 constitutes the seventh surface. Lens surface 1222 constitutes the eighth surface. Lens surface 1231 constitutes the ninth surface. Lens surface 1232 constitutes the tenth surface. The aperture 30 constitutes the eleventh surface. Lens surface 2011 constitutes the twelfth surface. Lens surface 2012 constitutes the thirteenth surface. Lens surface 2021 constitutes the fourteenth surface. Lens surfaces 2022 and 2031 constitute the fifteenth surface. Lens surface 2032 constitutes the sixteenth surface. Lens surface 2051 constitutes the 17th surface. Lens surface 2052 constitutes the 18th surface. Surface 401 on the object side La of the cover 40 constitutes the 19th surface, and surface 402 on the image side Lb constitutes the 20th surface.
[0023] Radius of curvature Thickness Refractive index (Nd) Abbe number (νd) of the d line Focal length (f) Lens radius (sd)
[0024] Furthermore, Figure 2 shows the aspheric coefficients, which indicate the shape of the aspheric surface for each surface number.
[0025] The wide-angle lens 1 of Embodiment 1 satisfies the following conditions (1) and (2), provided that the Abbe number of the d line of the second lens 122 in the second group is ν4 and the Abbe number of the d line of the third lens 123 in the second group is ν5. ν4<30.00 ···(1) 44.00<ν5 ···(2) In condition (2), more preferably, the following condition (2a) is satisfied. 50.00<ν5 ···(2a)
[0026] In this form, ν₄ = 21.62 ν5 = 56.13 Therefore, ν4 = 21.62, satisfying condition (1). Also, ν5 = 56.13, satisfying conditions (2) and (2a).
[0027] The wide-angle lens 1 of Embodiment 1 satisfies the following condition (3) when the total focal length of the lens system is f0 and the combined focal length of the second lens 122 and the third lens 123 within the second group is f45. 2.000 <f45 / f0<3.500 ···(3)
[0028] In this form, f0 = 2.872 mm f45 = 7.714 mm Therefore, f45 / f0 = 2.686, which satisfies condition (3).
[0029] The wide-angle lens 1 of Embodiment 1 satisfies the following condition (4) when the total focal length of the lens system is f0, and the combined focal length of the first lens 121, second lens 122, and third lens 123 in the second group is f345. 2.000 <f345 / f0<6.000 ···(4)
[0030] In this form, f0 = 2.872 mm f345 = 13.653 mm Therefore, f345 / f0 = 4.754, which satisfies condition (4).
[0031] The wide-angle lens 1 of Embodiment 1 satisfies the following condition (5) when the radius of curvature of the image-side lens surface Lb of the second lens 112 in the first group is R22, and the radius of curvature of the object-side lens surface La of the first lens 121 in the second group is R31. -1.000 <R22 / R31<-0.500 ···(5)
[0032] In this form, R22 = 3.823 mm R31 = -5.846 mm Therefore, R22 / R31 = -0.654, which satisfies condition (5).
[0033] The wide-angle lens 1 of Embodiment 1 satisfies the following conditions (6) and (7) when the focal length of the entire lens system is f0, the radius of curvature of the image-side lens surface Lb of the second lens 112 in the first group is R22, and the radius of curvature of the object-side lens surface La of the first lens 121 in the second group is R31. 1.100 <R22 / f0<3.000 ···(6) -3.000 <R31 / f0<-1.100 ···(7)
[0034] In this form, f0 = 2.872 mm R22 = 3.823 mm R31 = -5.846 mm Therefore, R22 / f0 = 1.331, satisfying condition (6). Also, R31 / f0 = -2.036, satisfying condition (7).
[0035] The wide-angle lens 1 of Embodiment 1 satisfies the following condition (8) when the refractive index of the d-line of the fourth lens 205 in the rear group is N9. 1.500 <N9 ···(8)
[0036] In this form, N9 = 1.663 Therefore, N9 = 1.663, and condition (8) is satisfied.
[0037] The wide-angle lens 1 of Embodiment 1 satisfies the following condition (9) when the radius of curvature of the lens surface on the object side La of the first lens 201 in the rear group is R61 and the radius of curvature of the lens surface on the image side Lb of the first lens 201 in the rear group is R62. |R61|>|R62| ···(9)
[0038] In this form, R61 = 8.512 mm R62 = -6.524 mm Therefore, condition (9) is satisfied.
[0039] The wide-angle lens 1 of Embodiment 1 satisfies the following conditions (10) and (11) when the Abbe number of the d line of the second lens 202 in the rear group is ν7 and the Abbe number of the d line of the third lens 203 in the rear group is ν8. ν7<30.00 ···(10) 50.00<ν8 ···(11)
[0040] In this form, ν7 = 21.62 ν8 = 56.13 Therefore, ν7 = 21.62, satisfying condition (10). Also, ν8 = 56.13, satisfying condition (11).
[0041] The wide-angle lens 1 of Embodiment 1 satisfies the following condition (12) when the inter-image distance of the entire lens system is d0 and the focal length of the entire lens system is f0. 6,000 <d0 / f0<12.000 ···(12)
[0042] In this form, d0 = 27.450 mm f0 = 2.872 mm Therefore, d0 / f0 = 9.558, which satisfies condition (12).
[0043] The wide-angle lens 1 of Embodiment 1 satisfies the following condition (13) when the maximum half-angle of view is ω. 75°<ω<110° ···(13)
[0044] In this form, ω=94° Therefore, condition (13) is satisfied.
[0045] (Effects / Actions) Since the wide-angle lens 1 in this form satisfies conditions (1) and (2), chromatic aberration can be corrected well, and therefore the wide-angle lens 1 can also be applied to a large image sensor 50.
[0046] The wide-angle lens 1 in this configuration satisfies condition (3), thus suppressing an increase in the overall length of the lens system and suppressing the occurrence of various aberrations. If the value of condition (3) falls below the lower limit, the combined power of the second lens 122 and the third lens 123 within the second group becomes too strong, making it difficult to suppress the occurrence of various aberrations. If the value of condition (3) exceeds the upper limit, the combined power of the second lens 122 and the third lens 123 within the second group becomes too weak, making it easy for the overall length of the lens system to increase.
[0047] The wide-angle lens 1 in this configuration satisfies condition (4), thus suppressing an increase in the overall length of the lens system and suppressing the occurrence of various aberrations. If the value of condition (4) falls below the lower limit, the combined power of the first lens 121, second lens 122, and third lens 123 in the second group becomes too strong, making it difficult to suppress the occurrence of various aberrations. If the value of condition (4) exceeds the upper limit, the combined power of the first lens 121, second lens 122, and third lens 123 in the second group becomes too weak, making it easy for the overall length of the lens system to increase.
[0048] In this embodiment, the second lens 122 in the second group has a convex surface on the object side and at least one inflection point, and the image-side lens surface is also convex, so astigmatism and field curvature can be properly corrected.
[0049] In this embodiment, the second lens 122 and / or the third lens 123 within the second lens group are made of resin, thus reducing manufacturing costs.
[0050] The wide-angle lens 1 in this configuration satisfies condition (5), thus suppressing an increase in the overall length and outer diameter of the lens system, as well as suppressing the occurrence of various aberrations. If the value of condition (5) falls below the lower limit, the combined power of the second lens 112 in the first group and the first lens 121 in the second group becomes too weak, making it easy for the overall length and outer diameter of the lens system to increase. If the value of condition (5) exceeds the upper limit, the combined power of the second lens 112 in the first group and the first lens 121 in the second group becomes too strong, making it difficult to suppress the occurrence of various aberrations.
[0051] The wide-angle lens 1 in this configuration satisfies conditions (6) and (7), thus suppressing an increase in the overall length and outer diameter of the lens system, and suppressing the occurrence of various aberrations. If the value of condition (6) falls below the lower limit, the radius of curvature R22 of the image-side lens surface of the second lens 112 in the first group becomes too small. In other words, the power of the image-side lens surface of the second lens 112 in the first group becomes too strong. As a result, it becomes difficult to suppress the occurrence of various aberrations. If the value of condition (6) exceeds the upper limit, the radius of curvature R22 of the image-side lens surface of the second lens 112 in the first group becomes too large. In other words, the power of the image-side lens surface of the second lens 112 in the first group becomes too weak. As a result, the overall length and outer diameter of the lens system tend to increase.
[0052] Furthermore, if the value of condition (7) falls below the lower limit, the radius of curvature R31 of the object-side lens surface of the first lens 121 in the second group becomes too large. In other words, the power of the object-side lens surface of the first lens 121 in the second group becomes too weak. As a result, the overall length and outer diameter of the lens system tend to increase. If the value of condition (7) exceeds the upper limit, the radius of curvature R31 of the object-side lens surface of the first lens 121 in the second group becomes too small. In other words, the power of the object-side lens surface of the first lens 121 in the second group becomes too strong. As a result, it becomes difficult to suppress the occurrence of various aberrations.
[0053] In this configuration, the wide-angle lens 1 satisfies condition (8), so the fourth lens 205 in the rear group has a high refractive index. Furthermore, since the fourth lens 205 in the rear group has a convex-concave lens surface with an inflection point, it becomes easier to correct the image height with respect to the angle of view, astigmatism, and field curvature.
[0054] Since the wide-angle lens 1 in this form satisfies condition (9), various aberrations can be properly corrected.
[0055] Since the wide-angle lens 1 in this form satisfies conditions (10) and (11), chromatic aberration can be properly corrected.
[0056] In this configuration, the fourth lens 205 in the rear group of the wide-angle lens 1 is a single lens with positive power, allowing for easy adjustment of the principal ray angle (hereinafter also called CRA (Chief Ray Angle)) and image height characteristics.
[0057] In this form of wide-angle lens 1, the condition (12) is satisfied, in other words, the ratio of the inter-image distance d0 of the entire lens system to the focal length f0 of the entire lens system exceeds the lower limit, thus enabling proper correction of spherical aberration and distortion. Furthermore, since the ratio of the inter-image distance d0 of the entire lens system to the focal length f0 of the entire lens system is below the upper limit, it is possible to suppress the lens diameter from becoming too large and to avoid increasing the overall length of the lens system. Therefore, it is possible to miniaturize the wide-angle lens.
[0058] The wide-angle lens 1 in this configuration satisfies condition (13), in other words, the maximum half-angle exceeds the lower limit, thus achieving a sufficiently wide angle of view. Furthermore, since the maximum half-angle is less than the upper limit, a decrease in the amount of information at each angle of view is prevented. If the maximum half-angle exceeds the upper limit, the amount of information at each angle of view decreases, leading to a decrease in resolution.
[0059] Figure 3 shows the spherical aberration of the wide-angle lens 1 shown in Figure 1. Figure 4 shows the lateral chromatic aberration of the wide-angle lens 1 shown in Figure 1, showing the lateral chromatic aberration at the maximum half-angle (93.6241 degrees). Figure 5 shows the astigmatism and distortion of the wide-angle lens 1 shown in Figure 1. Figure 6 shows the lateral aberration of the wide-angle lens 1 shown in Figure 1, showing the lateral aberration in the tangential direction (Y direction) and the sagittal direction (X direction).
[0060] Figures 3 to 6 show the aberrations at wavelengths of 486 nm, 546 nm, and 656 nm, denoted by B, G, and R, respectively. For astigmatism shown in Figure 5, the sagittal characteristic is denoted by S, and the tangential characteristic is denoted by T. Furthermore, the distortion shown in Figure 5 indicates the ratio of image change between the center and periphery of the image; the smaller the absolute value of the distortion, the higher the precision of the lens.
[0061] As shown in Figures 3 to 6, in the wide-angle lens 1 of this embodiment, spherical aberration, chromatic aberration, astigmatism (distortion), and lateral aberration are corrected to an appropriate level.
[0062] (Embodiment 2) Figure 7 is an explanatory diagram of a wide-angle lens 1 according to Embodiment 2 of the present disclosure. As shown in Figure 7, the wide-angle lens 1 of this embodiment comprises a front group 10, an aperture 30, and a rear group 20, in order from the object side La to the image side Lb.
[0063] The first group 10 includes a first group 110 having negative power and a second group 120 having positive power, arranged in order from the object side La to the image side Lb. The first group 110 consists of a first lens 111 and a second lens 112 within the first group, arranged in order from the object side La to the image side Lb. The second group 120 consists of a first lens 121, a second lens 122, and a third lens 123 within the second group, arranged in order from the object side La to the image side Lb.
[0064] The rear group 20 consists of a first lens 201, a second lens 202, a third lens 203, and a fourth lens 205, arranged in order from the object side La to the image side Lb. Furthermore, a translucent cover 40 and an image sensor 50 are positioned on the image side Lb of the fourth lens 205, also in order from the object side La to the image side Lb.
[0065] The first lens 111 in the first group is, for example, a glass lens. The first lens 111 in the first group has negative power. The first lens 111 in the first group has a convex shape on the object-side lens surface 1111 and a concave shape on the image-side lens surface 1112. The second lens 112 in the first group is, for example, a resin lens. The second lens 112 in the first group has negative power. The second lens 112 in the first group has a convex shape on the object-side lens surface 1121 and a concave shape on the image-side lens surface 1122. The second lens 112 in the first group has aspherical shapes on both sides.
[0066] The first lens 121 in the second group is, for example, a resin lens. The first lens 121 in the second group has negative power. The first lens 121 in the second group has a concave shape on the object-side lens surface 1211 and a convex shape on the image-side lens surface 1212. The first lens 121 in the second group has aspherical shapes on both sides. The second lens 122 in the second group is, for example, a resin lens. The second lens 122 in the second group has positive power. The second lens 122 in the second group has a convex shape on the object-side lens surface 1221 and a convex shape on the image-side lens surface 1222. The second lens 122 in the second group has aspherical shapes on both sides. The third lens 123 in the second group is, for example, a resin lens. The third lens 123 in the second group has positive power. The third lens 123 in the second group has a concave shape on the object-side lens surface 1231 (La) and a convex shape on the image-side lens surface 1232 (Lb). The third lens 123 in the second group has aspherical shapes on both sides.
[0067] The first lens 201 in the rear group is, for example, a glass lens. The first lens 201 in the rear group has positive power. The first lens 201 in the rear group has a convex shape on the object-side lens surface 2011 and a convex shape on the image-side lens surface 2012. The second lens 202 in the rear group is, for example, a resin lens. The second lens 202 in the rear group has negative power. The second lens 202 in the rear group has a concave shape on the object-side lens surface 2021 and a concave shape on the image-side lens surface 2022. The second lens 202 in the rear group has aspherical shapes on both sides. The third lens 203 in the rear group is, for example, a resin lens. The third lens 203 in the rear group has positive power. The third lens 203 in the rear group has a convex shape on the object-side lens surface 2031 La and a convex shape on the image-side lens surface 2032 Lb. The third lens 203 in the rear group has aspherical shapes on both sides.
[0068] Here, the second lens 202 and the third lens 203 in the rear group are a cemented lens 204 formed by joining the image-side Lb lens surface 2022 of the second lens 202 and the object-side La lens surface 2031 of the third lens 203 with, for example, an adhesive (not shown). With this configuration, the rear group 20 includes a cemented lens 204, so chromatic aberration can be appropriately corrected.
[0069] The fourth lens element 205 in the rear group is, for example, a resin lens. The fourth lens element 205 in the rear group has positive power. The fourth lens element 205 in the rear group has a convex shape on the lens surface 2051 on the object side La and a concave shape on the lens surface 2052 on the image side Lb. The fourth lens element 205 in the rear group has aspherical shapes on both sides.
[0070] (Lens configuration) Figure 8 shows the data for wide-angle lens 1 of Embodiment 2. Note that the values shown in Figure 8 have been rounded. Wide-angle lens 1 of this embodiment satisfies the conditions (1) to (13) described in Embodiment 1.
[0071] In this form, ν₄ = 21.62 ν5 = 56.13 Therefore, ν4 = 21.62, satisfying condition (1). Also, ν5 = 56.13, satisfying conditions (2) and (2a).
[0072] In this form, f0 = 2.872 mm f45 = 7.703 mm Therefore, f45 / f0 = 2.682, which satisfies condition (3).
[0073] In this form, f0 = 2.872 mm f345 = 13.172 mm Therefore, f345 / f0 = 4.586, which satisfies condition (4).
[0074] In this form, R22 = 3.787 mm R31 = -6.029 mm Therefore, R22 / R31 = -0.628, which satisfies condition (5).
[0075] In this form, f0 = 2.872 mm R22 = 3.787 mm R31 = -6.029 mm Therefore, R22 / f0 = 1.318, satisfying condition (6). Also, R31 / f0 = -2.099, satisfying condition (7).
[0076] In this form, N9 = 1.663 Therefore, N9 = 1.663, and condition (8) is satisfied.
[0077] In this form, R61 = 8.654 mm R62 = -6.643 mm Therefore, condition (9) is satisfied.
[0078] In this form, ν7 = 21.62 ν8 = 56.13 Therefore, ν7 = 21.62, satisfying condition (10). Also, ν8 = 56.13, satisfying condition (11).
[0079] In this form, d0 = 27.449 mm f0 = 2.872 mm Therefore, d0 / f0 = 9.558, which satisfies condition (12).
[0080] In this form, ω=94° Therefore, condition (13) is satisfied.
[0081] (Effects / Actions) The wide-angle lens 1 of Embodiment 2 satisfies the same conditions (1) to (13) as in Embodiment 1, and therefore can produce the same effects as in Embodiment 1.
[0082] Figure 9 shows the spherical aberration of the wide-angle lens 1 shown in Figure 7. Figure 10 shows the chromatic aberration of the wide-angle lens 1 shown in Figure 7. Figure 11 shows the astigmatism and distortion of the wide-angle lens 1 shown in Figure 7. Figure 12 shows the lateral aberration of the wide-angle lens 1 shown in Figure 7.
[0083] As shown in Figures 9 to 12, in the wide-angle lens 1 of this embodiment, spherical aberration, chromatic aberration, astigmatism (distortion), and lateral aberration are corrected to an appropriate level.
[0084] (Embodiment 3) Figure 13 is an explanatory diagram of a wide-angle lens 1 according to Embodiment 3 of the present disclosure. As shown in Figure 13, the wide-angle lens 1 of this embodiment comprises a front group 10, an aperture 30, and a rear group 20, in order from the object side La to the image side Lb.
[0085] The first group 10 includes a first group 110 having negative power and a second group 120 having positive power, arranged in order from the object side La to the image side Lb. The first group 110 consists of a first lens 111 and a second lens 112 within the first group, arranged in order from the object side La to the image side Lb. The second group 120 consists of a first lens 121, a second lens 122, and a third lens 123 within the second group, arranged in order from the object side La to the image side Lb.
[0086] The rear group 20 consists of a first lens 201, a second lens 202, a third lens 203, and a fourth lens 205, arranged in order from the object side La to the image side Lb. Furthermore, a translucent cover 40 and an image sensor 50 are positioned on the image side Lb of the fourth lens 205, also in order from the object side La to the image side Lb.
[0087] The first lens 111 in the first group is, for example, a glass lens. The first lens 111 in the first group has negative power. The first lens 111 in the first group has a convex shape on the object-side lens surface 1111 and a concave shape on the image-side lens surface 1112. The second lens 112 in the first group is, for example, a resin lens. The second lens 112 in the first group has negative power. The second lens 112 in the first group has a convex shape on the object-side lens surface 1121 and a concave shape on the image-side lens surface 1122. The second lens 112 in the first group has aspherical shapes on both sides.
[0088] The first lens 121 in the second group is, for example, a resin lens. The first lens 121 in the second group has negative power. The first lens 121 in the second group has a concave shape on the object-side lens surface 1211 and a convex shape on the image-side lens surface 1212. The first lens 121 in the second group has aspherical shapes on both sides. The second lens 122 in the second group is, for example, a resin lens. The second lens 122 in the second group has positive power. The second lens 122 in the second group has a convex shape on the object-side lens surface 1221 and a convex shape on the image-side lens surface 1222. The second lens 122 in the second group has aspherical shapes on both sides. The third lens 123 in the second group is, for example, a resin lens. The third lens 123 in the second group has positive power. The third lens 123 in the second group has a concave shape on the object-side lens surface 1231 (La) and a convex shape on the image-side lens surface 1232 (Lb). The third lens 123 in the second group has aspherical shapes on both sides.
[0089] The first lens 201 in the rear group is, for example, a glass lens. The first lens 201 in the rear group has positive power. The first lens 201 in the rear group has a convex shape on the object-side lens surface 2011 and a convex shape on the image-side lens surface 2012. The second lens 202 in the rear group is, for example, a resin lens. The second lens 202 in the rear group has negative power. The second lens 202 in the rear group has a concave shape on the object-side lens surface 2021 and a concave shape on the image-side lens surface 2022. The second lens 202 in the rear group has aspherical shapes on both sides. The third lens 203 in the rear group is, for example, a resin lens. The third lens 203 in the rear group has positive power. The third lens 203 in the rear group has a convex shape on the object-side lens surface 2031 La and a convex shape on the image-side lens surface 2032 Lb. The third lens 203 in the rear group has aspherical shapes on both sides.
[0090] Here, the second lens 202 and the third lens 203 in the rear group are a cemented lens 204 formed by joining the image-side Lb lens surface 2022 of the second lens 202 and the object-side La lens surface 2031 of the third lens 203 with, for example, an adhesive (not shown). With this configuration, the rear group 20 includes a cemented lens 204, so chromatic aberration can be appropriately corrected.
[0091] The fourth lens element 205 in the rear group is, for example, a resin lens. The fourth lens element 205 in the rear group has positive power. The fourth lens element 205 in the rear group has a convex shape on the lens surface 2051 on the object side La and a concave shape on the lens surface 2052 on the image side Lb. The fourth lens element 205 in the rear group has aspherical shapes on both sides.
[0092] (Lens configuration) Figure 14 shows the data for wide-angle lens 1 of Embodiment 3. Note that the values shown in Figure 14 have been rounded. The wide-angle lens 1 of this embodiment satisfies the conditions (1) to (13) described in Embodiment 1.
[0093] In this form, ν₄ = 21.62 ν5 = 56.13 Therefore, ν4 = 21.62, satisfying condition (1). Also, ν5 = 56.13, satisfying conditions (2) and (2a).
[0094] In this form, f0 = 2.870 mm f45 = 7.656mm Therefore, f45 / f0 = 2.667, which satisfies condition (3).
[0095] In this form, f0 = 2.870 mm f345 = 13.505 mm Therefore, f345 / f0 = 4.705, which satisfies condition (4).
[0096] In this form, R22 = 3.816 mm R31 = -5.812 mm Therefore, R22 / R31 = -0.657, which satisfies condition (5).
[0097] In this form, f0 = 2.870 mm R22 = 3.816 mm R31 = -5.812 mm Therefore, R22 / f0 = 1.329, satisfying condition (6). Also, R31 / f0 = -2.025, satisfying condition (7).
[0098] In this form, N9 = 1.663 Therefore, N9 = 1.663, and condition (8) is satisfied.
[0099] In this form, R61 = 8.510 mm R62 = -6.524 mm Therefore, condition (9) is satisfied.
[0100] In this form, ν7 = 21.62 ν8 = 56.13 Therefore, ν7 = 21.62, satisfying condition (10). Also, ν8 = 56.13, satisfying condition (11).
[0101] In this form, d0 = 27.450 mm f0 = 2.870 mm Therefore, d0 / f0 = 9.563, which satisfies condition (12).
[0102] In this form, ω=94° Therefore, condition (13) is satisfied.
[0103] (Effects / Actions) The wide-angle lens 1 of Embodiment 3 satisfies the same conditions (1) to (13) as in Embodiment 1, and therefore can produce the same effects as in Embodiment 1.
[0104] Figure 15 shows the spherical aberration of the wide-angle lens 1 shown in Figure 13. Figure 16 shows the lateral chromatic aberration of the wide-angle lens 1 shown in Figure 13. Figure 17 shows the astigmatism and distortion of the wide-angle lens 1 shown in Figure 13. Figure 18 shows the lateral aberration of the wide-angle lens 1 shown in Figure 13.
[0105] As shown in Figures 15 to 18, in the wide-angle lens 1 of this embodiment, spherical aberration, chromatic aberration, astigmatism (distortion), and lateral aberration are corrected to an appropriate level.
[0106] (Embodiment 4) Figure 19 is an explanatory diagram of a wide-angle lens 1 according to Embodiment 4 of the present disclosure. As shown in Figure 19, the wide-angle lens 1 of this embodiment comprises a front group 10, an aperture 30, and a rear group 20, in order from the object side La to the image side Lb.
[0107] The first group 10 includes a first group 110 having negative power and a second group 120 having positive power, arranged in order from the object side La to the image side Lb. The first group 110 consists of a first lens 111 and a second lens 112 within the first group, arranged in order from the object side La to the image side Lb. The second group 120 consists of a first lens 121, a second lens 122, and a third lens 123 within the second group, arranged in order from the object side La to the image side Lb.
[0108] The rear group 20 consists of a first lens 201, a second lens 202, a third lens 203, and a fourth lens 205, arranged in order from the object side La to the image side Lb. Furthermore, a translucent cover 40 and an image sensor 50 are positioned on the image side Lb of the fourth lens 205, also in order from the object side La to the image side Lb.
[0109] The first lens 111 in the first group is, for example, a glass lens. The first lens 111 in the first group has negative power. The first lens 111 in the first group has a convex shape on the object-side lens surface 1111 and a concave shape on the image-side lens surface 1112. The second lens 112 in the first group is, for example, a resin lens. The second lens 112 in the first group has negative power. The second lens 112 in the first group has a convex shape on the object-side lens surface 1121 and a concave shape on the image-side lens surface 1122. The second lens 112 in the first group has aspherical shapes on both sides.
[0110] The first lens 121 in the second group is, for example, a resin lens. The first lens 121 in the second group has negative power. The first lens 121 in the second group has a concave shape on the object-side lens surface 1211 and a convex shape on the image-side lens surface 1212. The first lens 121 in the second group has aspherical shapes on both sides. The second lens 122 in the second group is, for example, a resin lens. The second lens 122 in the second group has positive power. The second lens 122 in the second group has a convex shape on the object-side lens surface 1221 and a convex shape on the image-side lens surface 1222. The second lens 122 in the second group has aspherical shapes on both sides. The third lens 123 in the second group is, for example, a resin lens. The third lens 123 in the second group has positive power. The third lens 123 in the second group has a concave shape on the object-side lens surface 1231 (La) and a convex shape on the image-side lens surface 1232 (Lb). The third lens 123 in the second group has aspherical shapes on both sides.
[0111] The first lens 201 in the rear group is, for example, a glass lens. The first lens 201 in the rear group has positive power. The first lens 201 in the rear group has a convex shape on the object-side lens surface 2011 and a convex shape on the image-side lens surface 2012. The second lens 202 in the rear group is, for example, a resin lens. The second lens 202 in the rear group has negative power. The second lens 202 in the rear group has a concave shape on the object-side lens surface 2021 and a concave shape on the image-side lens surface 2022. The second lens 202 in the rear group has aspherical shapes on both sides. The third lens 203 in the rear group is, for example, a resin lens. The third lens 203 in the rear group has positive power. The third lens 203 in the rear group has a convex shape on the object-side lens surface 2031 La and a convex shape on the image-side lens surface 2032 Lb. The third lens 203 in the rear group has aspherical shapes on both sides.
[0112] Here, the second lens 202 and the third lens 203 in the rear group are a cemented lens 204 formed by joining the image-side Lb lens surface 2022 of the second lens 202 and the object-side La lens surface 2031 of the third lens 203 with, for example, an adhesive (not shown). With this configuration, the rear group 20 includes a cemented lens 204, so chromatic aberration can be appropriately corrected.
[0113] The fourth lens element 205 in the rear group is, for example, a resin lens. The fourth lens element 205 in the rear group has positive power. The fourth lens element 205 in the rear group has a convex shape on the lens surface 2051 on the object side La and a concave shape on the lens surface 2052 on the image side Lb. The fourth lens element 205 in the rear group has aspherical shapes on both sides.
[0114] (Lens configuration) Figure 20 shows the data for wide-angle lens 1 of Embodiment 4. Note that the values shown in Figure 20 have been rounded. The wide-angle lens 1 of this embodiment satisfies the conditions (1) to (13) described in Embodiment 1.
[0115] In this form, ν₄ = 21.62 ν5 = 56.13 Therefore, ν4 = 21.62, satisfying condition (1). Also, ν5 = 56.13, satisfying conditions (2) and (2a).
[0116] In this form, f0 = 2.871 mm f45 = 7.657mm Therefore, f45 / f0 = 2.667, which satisfies condition (3).
[0117] In this form, f0 = 2.871 mm f345 = 13.514 mm Therefore, f345 / f0 = 4.707, which satisfies condition (4).
[0118] In this form, R22 = 3.818 mm R31 = -5.808 mm Therefore, R22 / R31 = -0.657, which satisfies condition (5).
[0119] In this form, f0 = 2.871 mm R22 = 3.818 mm R31 = -5.808 mm Therefore, R22 / f0 = 1.330, satisfying condition (6). Also, R31 / f0 = -2.023, satisfying condition (7).
[0120] In this form, N9 = 1.663 Therefore, N9 = 1.663, and condition (8) is satisfied.
[0121] In this form, R61 = 8.509 mm R62 = -6.523 mm Therefore, condition (9) is satisfied.
[0122] In this form, ν7 = 21.62 ν8 = 56.13 Therefore, ν7 = 21.62, satisfying condition (10). Also, ν8 = 56.13, satisfying condition (11).
[0123] In this form, d0 = 27.450 mm f0 = 2.871 mm Therefore, d0 / f0 = 9.562, which satisfies condition (12).
[0124] In this form, ω=94° Therefore, condition (13) is satisfied.
[0125] (Effects / Actions) The wide-angle lens 1 of Embodiment 4 satisfies the same conditions (1) to (13) as in Embodiment 1, and therefore can produce the same effects as in Embodiment 1.
[0126] Figure 21 shows the spherical aberration of the wide-angle lens 1 shown in Figure 19. Figure 22 shows the chromatic aberration of the wide-angle lens 1 shown in Figure 19. Figure 23 shows the astigmatism and distortion of the wide-angle lens 1 shown in Figure 19. Figure 24 shows the lateral aberration of the wide-angle lens 1 shown in Figure 19.
[0127] As shown in Figures 21 to 24, in the wide-angle lens 1 of this embodiment, spherical aberration, chromatic aberration, astigmatism (distortion), and lateral aberration are corrected to an appropriate level.
[0128] (Embodiment 5) Figure 25 is an explanatory diagram of a wide-angle lens 1 according to Embodiment 5 of the present disclosure. As shown in Figure 25, the wide-angle lens 1 of this embodiment comprises a front group 10, an aperture 30, and a rear group 20, in order from the object side La to the image side Lb.
[0129] The first group 10 includes a first group 110 having negative power and a second group 120 having positive power, arranged in order from the object side La to the image side Lb. The first group 110 consists of a first lens 111 and a second lens 112 within the first group, arranged in order from the object side La to the image side Lb. The second group 120 consists of a first lens 121, a second lens 122, and a third lens 123 within the second group, arranged in order from the object side La to the image side Lb.
[0130] The rear group 20 consists of a first lens 201, a second lens 202, a third lens 203, and a fourth lens 205, arranged in order from the object side La to the image side Lb. Furthermore, a translucent cover 40 and an image sensor 50 are positioned on the image side Lb of the fourth lens 205, also in order from the object side La to the image side Lb.
[0131] The first lens 111 in the first group is, for example, a glass lens. The first lens 111 in the first group has negative power. The first lens 111 in the first group has a convex shape on the object-side lens surface 1111 and a concave shape on the image-side lens surface 1112. The second lens 112 in the first group is, for example, a resin lens. The second lens 112 in the first group has negative power. The second lens 112 in the first group has a convex shape on the object-side lens surface 1121 and a concave shape on the image-side lens surface 1122. The second lens 112 in the first group has aspherical shapes on both sides.
[0132] The first lens 121 in the second group is, for example, a resin lens. The first lens 121 in the second group has negative power. The first lens 121 in the second group has a concave shape on the object-side lens surface 1211 and a convex shape on the image-side lens surface 1212. The first lens 121 in the second group has aspherical shapes on both sides. The second lens 122 in the second group is, for example, a resin lens. The second lens 122 in the second group has positive power. The second lens 122 in the second group has a convex shape on the object-side lens surface 1221 and a convex shape on the image-side lens surface 1222. The second lens 122 in the second group has aspherical shapes on both sides. The third lens 123 in the second group is, for example, a resin lens. The third lens 123 in the second group has positive power. The third lens 123 in the second group has a concave shape on the object-side lens surface 1231 (La) and a convex shape on the image-side lens surface 1232 (Lb). The third lens 123 in the second group has aspherical shapes on both sides.
[0133] The first lens 201 in the rear group is, for example, a glass lens. The first lens 201 in the rear group has positive power. The first lens 201 in the rear group has a convex shape on the object-side lens surface 2011 and a convex shape on the image-side lens surface 2012. The second lens 202 in the rear group is, for example, a resin lens. The second lens 202 in the rear group has negative power. The second lens 202 in the rear group has a concave shape on the object-side lens surface 2021 and a concave shape on the image-side lens surface 2022. The second lens 202 in the rear group has aspherical shapes on both sides. The third lens 203 in the rear group is, for example, a resin lens. The third lens 203 in the rear group has positive power. The third lens 203 in the rear group has a convex shape on the object-side lens surface 2031 La and a convex shape on the image-side lens surface 2032 Lb. The third lens 203 in the rear group has aspherical shapes on both sides.
[0134] Here, the second lens 202 and the third lens 203 in the rear group are a cemented lens 204 formed by joining the image-side Lb lens surface 2022 of the second lens 202 and the object-side La lens surface 2031 of the third lens 203 with, for example, an adhesive (not shown). With this configuration, the rear group 20 includes a cemented lens 204, so chromatic aberration can be appropriately corrected.
[0135] The fourth lens element 205 in the rear group is, for example, a resin lens. The fourth lens element 205 in the rear group has positive power. The fourth lens element 205 in the rear group has a convex shape on the lens surface 2051 on the object side La and a concave shape on the lens surface 2052 on the image side Lb. The fourth lens element 205 in the rear group has aspherical shapes on both sides.
[0136] (Lens configuration) Figure 26 shows the data for the wide-angle lens 1 of Embodiment 5. Note that the values shown in Figure 26 have been rounded. The wide-angle lens 1 of this embodiment satisfies the conditions (1) to (13) described in Embodiment 1.
[0137] In this form, ν₄ = 21.62 ν5 = 56.13 Therefore, ν4 = 21.62, satisfying condition (1). Also, ν5 = 56.13, satisfying conditions (2) and (2a).
[0138] In this form, f0 = 2.872 mm f45 = 7.737 mm Therefore, f45 / f0 = 2.694, which satisfies condition (3).
[0139] In this form, f0 = 2.872 mm f345 = 13.312 mm Therefore, f345 / f0 = 4.634, which satisfies condition (4).
[0140] In this form, R22 = 3.804 mm R31 = -6.021 mm Therefore, R22 / R31 = -0.632, which satisfies condition (5).
[0141] In this form, f0 = 2.872 mm R22 = 3.804 mm R31 = -6.021 mm Therefore, R22 / f0 = 1.324, satisfying condition (6). Also, R31 / f0 = -2.096, satisfying condition (7).
[0142] In this form, N9 = 1.663 Therefore, N9 = 1.663, and condition (8) is satisfied.
[0143] In this form, R61 = 8.679 mm R62 = -6.653 mm Therefore, condition (9) is satisfied.
[0144] In this form, ν7 = 21.62 ν8 = 56.13 Therefore, ν7 = 21.62, satisfying condition (10). Also, ν8 = 56.13, satisfying condition (11).
[0145] In this form, d0 = 27.733 mm f0 = 2.872 mm Therefore, d0 / f0 = 9.655, which satisfies condition (12).
[0146] In this form, ω=94° Therefore, condition (13) is satisfied.
[0147] (Effects / Actions) The wide-angle lens 1 of Embodiment 5 satisfies the same conditions (1) to (13) as in Embodiment 1, and therefore can produce the same effects as in Embodiment 1.
[0148] Figure 27 shows the spherical aberration of the wide-angle lens 1 shown in Figure 25. Figure 28 shows the lateral chromatic aberration of the wide-angle lens 1 shown in Figure 25. Figure 29 shows the astigmatism and distortion of the wide-angle lens 1 shown in Figure 25. Figure 30 shows the lateral aberration of the wide-angle lens 1 shown in Figure 25.
[0149] As shown in Figures 27 to 30, in the wide-angle lens 1 of this embodiment, spherical aberration, chromatic aberration, astigmatism (distortion), and lateral aberration are corrected to an appropriate level.
[0150] Furthermore, this technology can be configured as follows:
[0151] (1) The lens group, arranged in order from the object side to the image side, consists of a front group, an aperture, and a rear group. The aforementioned group includes, in order from the object side toward the image side, a first group having negative power and a second group having positive power. The second group includes, in order from the object side to the image side, a first lens within the second group, a second lens within the second group, and a third lens within the second group. A wide-angle lens that satisfies the following conditions (1) and (2), where ν4 is the Abbe number of the d line of the second lens in the second group, and ν5 is the Abbe number of the d line of the third lens in the second group. ν4<30.00 ···(1) 44.00<ν5 ···(2)
[0152] (2) The wide-angle lens described in (1) satisfies the following condition (3), when the focal length of the entire lens system is f0, and the combined focal length of the second lens and the third lens within the second group is f45. 2.000 <f45 / f0<3.500 ···(3)
[0153] (3) The wide-angle lens described in (1) satisfies the following condition (4), given that the total focal length of the lens system is f0, and the combined focal length of the first lens in the second group, the second lens in the second group, and the third lens in the second group is f345. 2.000 <f345 / f0<6.000 ···(4)
[0154] (4) The wide-angle lens according to (1), wherein the second lens in the second group has a convex surface on the object side and has at least one inflection point, and the lens surface on the image side is a convex surface.
[0155] (5) The wide-angle lens according to (1), wherein the second lens in the second group and / or the third lens in the second group are made of resin.
[0156] (6) The first group includes, in order from the object side toward the image side, a first lens within the first group and a second lens within the first group. The second lens within the first group has negative power, and the image-side lens surface is a concave curved surface. The first lens in the second group has negative power, and the lens surface facing the object is a concave curved surface. The wide-angle lens described in (1), wherein the radius of curvature of the image-side lens surface of the second lens in the first group is R22, and the radius of curvature of the object-side lens surface of the first lens in the second group is R31, satisfies the following condition (5). -1.000 <R22 / R31<-0.500 ···(5)
[0157] (7) The first group includes, in order from the object side toward the image side, a first lens within the first group and a second lens within the first group. The second lens within the first group has negative power, and the image-side lens surface is a concave curved surface. The first lens in the second group has negative power, and the lens surface facing the object is a concave curved surface. The wide-angle lens described in (1), where the focal length of the entire lens system is f0, the radius of curvature of the image-side lens surface of the second lens in the first group is R22, and the radius of curvature of the object-side lens surface of the first lens in the second group is R31, satisfies the following conditions (6) and (7). 1.100 <R22 / f0<3.000 ···(6) -3.000 <R31 / f0<-1.100 ···(7)
[0158] (8) The rear group includes, in order from the object side to the image side, a first lens within the rear group, a second lens within the rear group, a third lens within the rear group, and a fourth lens within the rear group. The second lens and the third lens within the rear group are cemented lenses formed by joining the image-side lens surface of the second lens and the object-side lens surface of the third lens. The fourth lens in the rear group has positive power, the object-side lens surface is a convex surface with at least one inflection point, and the image-side lens surface is a concave surface with at least one inflection point. The wide-angle lens described in (1), which satisfies the following condition (8) when the refractive index of the d-line of the fourth lens in the rear group is N9. 1.500 <N9 ···(8)
[0159] (9) The rear group includes, in order from the object side to the image side, a first lens within the rear group, a second lens within the rear group, a third lens within the rear group, and a fourth lens within the rear group. The wide-angle lens described in (1), where R61 is the radius of curvature of the object-side lens surface of the first lens in the rear group, and R62 is the radius of curvature of the image-side lens surface of the first lens in the rear group, satisfies the following condition (9). |R61|>|R62| ···(9)
[0160] (10) The rear group includes, in order from the object side to the image side, a first lens within the rear group, a second lens within the rear group, a third lens within the rear group, and a fourth lens within the rear group. The wide-angle lens described in (1), which satisfies the following conditions (10) and (11), when the Abbe number of the d line of the second lens in the rear group is ν7 and the Abbe number of the d line of the third lens in the rear group is ν8. ν7<30.00 ···(10) 50.00<ν8 ···(11)
[0161] (11) The rear group includes, in order from the object side to the image side, a first lens within the rear group, a second lens within the rear group, a third lens within the rear group, and a fourth lens within the rear group. The fourth lens in the rear group is a single lens with positive power. (1) The wide-angle lens described above.
[0162] (12) A wide-angle lens described in any one of (1) to (11) that satisfies the following condition (12), where d0 is the distance between the images in the entire lens system and f0 is the focal length of the entire lens system. 6,000 <d0 / f0<12.000 ···(12)
[0163] (13) A wide-angle lens described in any one of (1) to (11) that satisfies the following condition (13), where ω is the maximum half-angle of view. 75°<ω<110° ···(13)
[0164] These novel embodiments can be implemented in a variety of other forms, and various omissions, substitutions, modifications, and combinations are permitted without departing from the spirit of the invention. These embodiments are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as described in the claims. [Explanation of Symbols]
[0165] 1…Wide-angle lens, 10…Front group, 20…Rear group, 30…Aperture, 50…Image sensor, 110…First group, 111…First lens within the first group, 112…Second lens within the first group, 120…Second group, 121…First lens within the second group, 122…Second lens within the second group, 123…Third lens within the second group, 201…First lens within the rear group, 202…Second lens within the rear group, 203…Third lens within the rear group, 204…Coupled lens, 205…Fourth lens within the rear group
Claims
1. The lens group, arranged in order from the object side to the image side, consists of a front group, an aperture, and a rear group. The aforementioned group includes, in order from the object side to the image side, a first group having negative power and a second group having positive power. The second group includes, in order from the object side toward the image side, a first lens within the second group, a second lens within the second group, and a third lens within the second group. A wide-angle lens that satisfies the following conditions (1) and (2), where ν4 is the Abbe number of the d-line of the second lens in the second group, and ν5 is the Abbe number of the d-line of the third lens in the second group. ν4<30.00...(1) 44.00<ν5...(2)
2. The wide-angle lens according to claim 1, wherein when the focal length of the entire lens system is f0, and the combined focal length of the second lens in the second group and the third lens in the second group is f45, the following condition (3) is satisfied. 2.000<f45 / f0<3.500...(3)
3. The wide-angle lens according to claim 1, wherein when the focal length of the entire lens system is f0, and the combined focal length of the first lens in the second group, the second lens in the second group, and the third lens in the second group is f345, the following condition (4) is satisfied. 2.000<f345 / f0<6.000...(4)
4. The wide-angle lens according to claim 1, wherein the second lens in the second group has a convex surface on the object side and has at least one inflection point, and the lens surface on the image side is a convex surface.
5. The wide-angle lens according to claim 1, wherein the second lens in the second group and / or the third lens in the second group are made of resin.
6. The first group includes, in order from the object side toward the image side, a first lens within the first group and a second lens within the first group. The second lens within the first group has negative power, and the image-side lens surface is a concave curved surface. The first lens in the second group has negative power, and the lens surface facing the object is a concave curved surface. The wide-angle lens according to claim 1, wherein when the radius of curvature of the image-side lens surface of the second lens in the first group is R22 and the radius of curvature of the object-side lens surface of the first lens in the second group is R31, the following condition (5) is satisfied. -1.000<R22 / R31<-0.500...(5)
7. The first group includes, in order from the object side toward the image side, a first lens within the first group and a second lens within the first group. The second lens within the first group has negative power, and the image-side lens surface is a concave curved surface. The first lens in the second group has negative power, and the lens surface facing the object is a concave curved surface. The wide-angle lens according to claim 1, wherein the following conditions (6) and (7) are satisfied when the focal length of the entire lens system is f0, the radius of curvature of the image-side lens surface of the second lens in the first group is R22, and the radius of curvature of the object-side lens surface of the first lens in the second group is R31. 1.100<R22 / f0<3.000...(6) -3.000<R31 / f0<-1.100...(7)
8. The rear group includes, in order from the object side to the image side, a first lens within the rear group, a second lens within the rear group, a third lens within the rear group, and a fourth lens within the rear group. The second lens and the third lens within the rear group are cemented lenses formed by joining the image-side lens surface of the second lens and the object-side lens surface of the third lens. The fourth lens in the rear group has positive power, the object-side lens surface is a convex surface with at least one inflection point, and the image-side lens surface is a concave surface with at least one inflection point. The wide-angle lens according to claim 1, wherein the refractive index of the d-line of the fourth lens in the rear group is N9, and the following condition (8) is satisfied. 1.500<N9...(8)
9. The rear group includes, in order from the object side to the image side, a first lens within the rear group, a second lens within the rear group, a third lens within the rear group, and a fourth lens within the rear group. The wide-angle lens according to claim 1, wherein when the radius of curvature of the object-side lens surface of the first lens in the rear group is R61 and the radius of curvature of the image-side lens surface of the first lens in the rear group is R62, the following conditional equation (9) is satisfied. |R61|>|R62| ...(9)
10. The rear group includes, in order from the object side to the image side, a first lens within the rear group, a second lens within the rear group, a third lens within the rear group, and a fourth lens within the rear group. The wide-angle lens according to claim 1, wherein when the Abbe number of the d line of the second lens in the rear group is ν7 and the Abbe number of the d line of the third lens in the rear group is ν8, the following conditions (10) and (11) are satisfied. ν7<30.00...(10) 50.00<ν8...(11)
11. The rear group includes, in order from the object side to the image side, a first lens within the rear group, a second lens within the rear group, a third lens within the rear group, and a fourth lens within the rear group. The fourth lens in the rear group is a single lens with positive power. The wide-angle lens according to claim 1.
12. A wide-angle lens according to any one of claims 1 to 11, wherein the following condition (12) is satisfied when the distance between objects in the entire lens system is d0 and the focal length of the entire lens system is f0. 6.000<d0 / f0<12.000...(12)
13. A wide-angle lens according to any one of claims 1 to 11, wherein the following condition (13) is satisfied when the maximum half-angle of view is ω. 75°<ω<110°...(13)