Camera lens

Abstract

The application relates to the field of optical lenses, and provides a camera lens which is sequentially composed of a first lens with negative refractive power, a second lens with negative refractive power, a third lens with negative refractive power, a fourth lens with positive refractive power, a fifth lens with negative refractive power, a sixth lens with positive refractive power and a seventh lens with positive refractive power from an object side to an image side, and satisfies the following relationship: -50.10<=f2 / f<= -22.90; 9.20<=d2 / d4<=30.00; -11.10<=R5 / f<= -9.55.

Description

TECHNICAL FIELD

[0001] The present application relates to an imaging lens. In particular, the present application relates to an imaging lens suitable for a surround sensor camera using a high-pixel imaging element such as a CCD, a CMOS, or the like, having a suitable field angle and good optical characteristics, and an imaging lens composed of seven lenses with a bright F number (hereinafter referred to as FNO) of 1.83 or less. BACKGROUND

[0002] In recent years, there is a demand for high image recognition accuracy of a subject (surrounding vehicles, obstacles, road signs, and the like) by a surround sensor camera for automatic driving. Therefore, in order to improve the image recognition accuracy, there is a tendency toward large size and high resolution of the sensor. In addition, in order to improve the recognition performance at night, an imaging lens with a brighter FNO is required.

[0003] Although the imaging lens disclosed in the embodiment of Patent Literature 1 is composed of a first lens having a negative refractive power, a second lens having a negative refractive power, a third lens having a negative refractive power, a fourth lens having a positive refractive power, a fifth lens having a negative refractive power, a sixth lens having a positive refractive power, and a seventh lens having a positive refractive power in this order from the object side, and has good optical characteristics, the relationship between the focal length of the second lens and the focal length of the entire imaging lens, the relationship between the axial distance from the image side surface of the first lens to the object side surface of the second lens and the axial distance from the image side surface of the second lens to the object side surface of the third lens, and the relationship between the radius of curvature of the object side surface of the third lens and the focal length of the entire imaging lens are not sufficient, and the imaging lens becomes dark when the FNO is 2.40, and thus is not sufficient.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Laid-Open No. 2006-337691 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] An object of the present application is to provide an imaging lens having good optical characteristics and composed of seven lenses with a bright FNO.

[0009] MEANS FOR SOLVING THE PROBLEMS

[0010] In order to achieve the above object, the inventors of the present application have intensively studied the relationship between the focal length of the second lens and the focal length of the entire camera lens, the relationship between the on-axis distance from the image side surface of the first lens to the object side surface of the second lens and the on-axis distance from the image side surface of the second lens to the object side surface of the third lens, and the relationship between the radius of curvature of the object side surface of the third lens and the focal length of the entire camera lens in a camera lens composed of, in order from the object side, a first lens having a negative refractive power, a second lens having a negative refractive power, a third lens having a negative refractive power, a fourth lens having a positive refractive power, a fifth lens having a negative refractive power, a sixth lens having a positive refractive power, and a seventh lens having a positive refractive power, and as a result, have found a camera lens in which the problems of the prior art can be improved, and have conceived the present application.

[0011] A camera lens according to an embodiment of the present application is composed of, in order from the object side, a first lens having a negative refractive power, a second lens having a negative refractive power, a third lens having a negative refractive power, a fourth lens having a positive refractive power, a fifth lens having a negative refractive power, a sixth lens having a positive refractive power, and a seventh lens having a positive refractive power, and satisfies the following relational expressions (1) to (3):

[0012] -50.10 ≤ f2 / f ≤ -22.90 (1)

[0013] 9.20 ≤ d2 / d4 ≤ 30.00 (2)

[0014] -11.10 ≤ R5 / f ≤ -9.55 (3)

[0015] wherein,

[0016] f: the focal length of the entire camera lens;

[0017] f2: the focal length of the second lens;

[0018] R5: the radius of curvature of the object side surface of the third lens;

[0019] d2: the on-axis distance from the image side surface of the first lens to the object side surface of the second lens;

[0020] d4: the on-axis distance from the image side surface of the second lens to the object side surface of the third lens.

[0021] Preferably, the following relational expression (4) is satisfied:

[0022] -753.70 ≤ f2 / d4 ≤ -109.00 (4)

[0023] wherein,

[0024] f2: the focal length of the second lens;

[0025] d4: an axial distance on the optical axis of the image-side surface of the second lens to the object-side surface of the third lens.

[0026] Preferably, the following relation (5) is satisfied:

[0027] 4.60 ≤ f2 / R4 ≤ 14.60 (5)

[0028] wherein,

[0029] f2: a focal length of the second lens;

[0030] R4: a radius of curvature of the image-side surface of the second lens.

[0031] Preferably, the following relation (6) is satisfied:

[0032] -25.00 ≤ f2 / f6 ≤ -12.00 (6)

[0033] wherein,

[0034] f2: a focal length of the second lens;

[0035] f6: a focal length of the sixth lens.

[0036] Preferably, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are all made of glass.

[0037] Preferably, the second lens and the seventh lens are glass aspherical lenses.

[0038] Inventive Effects

[0039] Advantages of the present application are as follows.

[0040] According to the present application, in particular, it is possible to provide a camera lens suitable for a vehicle-mounted surround sensing camera using a high-pixel camera element such as a CCD, a CMOS, or the like, having a suitable field angle and good optical characteristics, and composed of seven lenses having a bright FNO. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 is a diagram showing the schematic structure of the camera lens LA of Embodiment 1 of the present application.

[0042] Figure 2 is a diagram showing the axial aberration of the camera lens LA of Embodiment 1 of the present application.

[0043] Figure 3 is a diagram showing the field curvature, distortion of the camera lens LA of Embodiment 1 of the present application.

[0044] Figure 4is a graph showing a lateral chromatic aberration of the imaging lens LA of Embodiment 1 of the present application.

[0045] Figure 5 is a graph showing a schematic structure of the imaging lens LA of Embodiment 2 of the present application.

[0046] Figure 6 is a graph showing an axial chromatic aberration of the imaging lens LA of Embodiment 2 of the present application.

[0047] Figure 7 is a graph showing a field curvature, distortion of the imaging lens LA of Embodiment 2 of the present application.

[0048] Figure 8 is a graph showing a lateral chromatic aberration of the imaging lens LA of Embodiment 2 of the present application.

[0049] Figure 9 is a graph showing a schematic structure of the imaging lens LA of Embodiment 3 of the present application.

[0050] Figure 10 is a graph showing an axial chromatic aberration of the imaging lens LA of Embodiment 3 of the present application.

[0051] Figure 11 is a graph showing a field curvature, distortion of the imaging lens LA of Embodiment 3 of the present application.

[0052] Figure 12 is a graph showing a lateral chromatic aberration of the imaging lens LA of Embodiment 3 of the present application. DETAILED DESCRIPTION

[0053] The present application will be further described below in conjunction with the accompanying drawings and embodiments. To make the objectives, technical solutions and merits of the present application clearer, the embodiments of the present application will be described in detail below in conjunction with the accompanying drawings. However, those skilled in the art can understand that, in the embodiments of the present application, many technical details are presented in order to make the readers better understand the present application. However, the technical solutions claimed by the present application can be realized even without these technical details and based on various changes and modifications of the following embodiments.

[0054] Embodiments of the imaging lens of the present application will be described. The imaging lens LA has a seven-piece lens system composed of, in order from the object side to the image side, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens L7. A glass flat plate GF is disposed between the seventh lens L7 and the image plane. As the glass flat plate GF, a glass cover plate and various filters and the like can be assumed. In the present application, the glass flat plate GF can be disposed at a different position, or can be omitted. In addition, the first lens L1 to the seventh lens L7 can all be of glass.

[0055] The first lens L1 is a lens having a negative refractive power, the second lens L2 is a lens having a negative refractive power, the third lens L3 is a lens having a negative refractive power, the fourth lens L4 is a lens having a positive refractive power, the fifth lens L5 is a lens having a negative refractive power, the sixth lens L6 is a lens having a positive refractive power, and the seventh lens L7 is a lens having a positive refractive power. In order to correct various aberrations well, it is desirable to set the surfaces of the second lens L2 and the seventh lens L7 to aspherical shapes.

[0056] The imaging lens LA satisfies the following relationship (1):

[0057] -50.10 ≤ f2 / f ≤ -22.90 (1)

[0058] The relationship (1) prescribes the ratio of the focal length f2 of the second lens L2 to the focal length f of the imaging lens LA as a whole. When FNO is 1.83, correction of various aberrations is easily achieved within the range of the relationship (1), and thus is preferable.

[0059] The imaging lens LA satisfies the following relationship (2):

[0060] 9.20 ≤ d2 / d4 ≤ 30.00 (2)

[0061] The relationship (2) prescribes the ratio of the on-axis distance d2 from the image side surface S2 of the first lens L1 to the object side surface S3 of the second lens L2 to the on-axis distance d4 from the image side surface S4 of the second lens L2 to the object side surface S5 of the third lens L3. When FNO is 1.83, correction of various aberrations is easily achieved within the range of the relationship (2), and thus is preferable.

[0062] The imaging lens LA satisfies the following relationship (3):

[0063] -11.10 ≤ R5 / f ≤ -9.55 (3)

[0064] The relational expression (3) defines a ratio of the radius of curvature R5 of the object side S5 of the third lens L3 to the focal length f of the entire photographing lens LA. When the FNO is 1.83 within the range of the relational expression (3), correction of each aberration is easily achieved, and thus is preferable.

[0065] The photographing lens LA satisfies the following relational expression (4):

[0066] -753.70 ≤ f2 / d4 ≤ -109.00 (4)

[0067] The relational expression (4) defines a ratio of the focal length f2 of the second lens L2 to the on-axis distance d4 from the image side S4 of the second lens L2 to the object side S5 of the third lens L3. When the FNO is 1.83 within the range of the relational expression (4), correction of each aberration is easily achieved, and thus is preferable.

[0068] The photographing lens LA satisfies the following relational expression (5):

[0069] 4.60 ≤ f2 / R4 ≤ 14.60 (5)

[0070] The relational expression (5) defines a ratio of the focal length f2 of the second lens L2 to the radius of curvature R4 of the image side S4 of the second lens L2. When the FNO is 1.83 within the range of the relational expression (5), correction of each aberration is easily achieved, and thus is preferable.

[0071] The photographing lens LA satisfies the following relational expression (6):

[0072] -25.00 ≤ f2 / f6 ≤ -12.00 (6)

[0073] The relational expression (6) defines a ratio of the focal length f2 of the second lens L2 to the focal length f6 of the sixth lens L6. When the FNO is 1.83 within the range of the relational expression (6), correction of each aberration is easily achieved, and thus is preferable.

[0074] By the seven lenses constituting the photographing lens LA satisfying the above-described configurations and relational expressions, a photographing lens suitable for a wrap-around camera having a suitable angle of view and good optical characteristics, and having an FNO of 1.83 or less can be obtained.

[0075] (Embodiments)

[0076] The photographing lens LA of the present application is described below using embodiments. The symbols described in each embodiment are shown below. Note that the units of distance, radius, and on-axis thickness are all millimeters (mm).

[0077] f: focal length of the entire photographing lens LA;

[0078] f1: focal length of the first lens L1;

[0079] f2: focal length of the second lens L2;

[0080] f3: focal length of the third lens L3;

[0081] f4: focal length of the fourth lens L4;

[0082] f5: focal length of the fifth lens L5;

[0083] f6: focal length of the sixth lens L6;

[0084] f7: focal length of the seventh lens L7;

[0085] FNO: F-number (ratio of effective focal length of the photographing lens to diameter of entrance pupil), F value;

[0086] 2ω: full field angle;

[0087] STOP: stop;

[0088] R: radius of curvature of an optical surface, central radius of curvature in case of a lens;

[0089] R1: radius of curvature of the object side surface S1 of the first lens L1;

[0090] R2: radius of curvature of the image side surface S2 of the first lens L1;

[0091] R3: radius of curvature of the object side surface S3 of the second lens L2;

[0092] R4: radius of curvature of the image side surface S4 of the second lens L2;

[0093] R5: radius of curvature of the object side surface S5 of the third lens L3;

[0094] R6: radius of curvature of the image side surface S6 of the third lens L3;

[0095] R7: radius of curvature of the object side surface S7 of the fourth lens L4;

[0096] R8: radius of curvature of the image side surface S8 of the fourth lens L4;

[0097] R9: radius of curvature of the object side surface S9 of the fifth lens L5;

[0098] R10: radius of curvature of the image side surface S10 of the fifth lens L5 and radius of curvature of the object side surface S10 of the sixth lens L6;

[0099] R11: radius of curvature of the image side surface S11 of the sixth lens L6;

[0100] R12: radius of curvature of the object side surface S12 of the seventh lens L7;

[0101] R13: radius of curvature of the image side surface S13 of the seventh lens L7;

[0102] R14: radius of curvature of the object side surface S14 of the glass flat GF1;

[0103] R15: radius of curvature of the image side surface S15 of the glass flat GF1;

[0104] R16: radius of curvature of the object side surface S16 of the glass flat GF2;

[0105] R17: radius of curvature of the image side surface S17 of the glass flat GF2;

[0106] d: on-axis thickness of a lens, or on-axis distance between lenses;

[0107] d1: on-axis thickness of the first lens L1;

[0108] d2: on-axis distance from the image side surface S2 of the first lens L1 to the object side surface S3 of the second lens L2;

[0109] d3: on-axis thickness of the second lens L2;

[0110] d4: on-axis distance from the image side surface S4 of the second lens L2 to the object side surface S5 of the third lens L3;

[0111] d5: on-axis thickness of the third lens L3;

[0112] d6: on-axis distance from the image side surface S6 of the third lens L3 to the object side surface S7 of the fourth lens L4;

[0113] d7: on-axis thickness of the fourth lens L4;

[0114] d8: on-axis distance from the image side surface S8 of the fourth lens L4 to the stop STOP;

[0115] d9: on-axis distance from the stop STOP to the object side surface S9 of the fifth lens L5;

[0116] d10: on-axis thickness of the fifth lens L5;

[0117] d11: on-axis thickness of the sixth lens L6;

[0118] d12: on-axis distance from the image side surface S11 of the sixth lens L6 to the object side surface S12 of the seventh lens L7;

[0119] d13: on-axis thickness of the seventh lens L7;

[0120] d14: an on-axis distance from the image side surface S13 of the seventh lens L7 to the object side surface S14 of the glass flat plate GF1;

[0121] d15: an on-axis thickness of the glass flat plate GF1;

[0122] d16: an on-axis distance from the image side surface S15 of the glass flat plate GF1 to the object side surface S16 of the glass flat plate GF2;

[0123] d17: an on-axis thickness of the glass flat plate GF2;

[0124] d18: an on-axis distance from the image side surface S17 of the glass flat plate GF2 to the image plane;

[0125] nd: a refractive index at the d line;

[0126] nd1: a refractive index at the d line of the first lens L1;

[0127] nd2: a refractive index at the d line of the second lens L2;

[0128] nd3: a refractive index at the d line of the third lens L3;

[0129] nd4: a refractive index at the d line of the fourth lens L4;

[0130] nd5: a refractive index at the d line of the fifth lens L5;

[0131] nd6: a refractive index at the d line of the sixth lens L6;

[0132] nd7: a refractive index at the d line of the seventh lens L7;

[0133] nd8: a refractive index at the d line of the glass flat plate GF1;

[0134] nd9: a refractive index at the d line of the glass flat plate GF2;

[0135] νd: an Abbe number;

[0136] ν1: an Abbe number of the first lens L1;

[0137] ν2: an Abbe number of the second lens L2;

[0138] ν3: an Abbe number of the third lens L3;

[0139] ν4: an Abbe number of the fourth lens L4;

[0140] ν5: an Abbe number of the fifth lens L5;

[0141] ν6: an Abbe number of the sixth lens L6;

[0142] ν7: an Abbe number of the seventh lens L7;

[0143] V8: Abbe number of the glass flat plate GF1

[0144] V9: Abbe number of the glass flat plate GF2

[0145] TTL: total track length of the imaging lens (axial distance from the object side surface S1 of the first lens L1 to the image plane)

[0146] LB: axial distance from the image side surface S13 of the seventh lens L7 to the image plane (including the thickness of the glass flat plate GF)

[0147] IH: image height

[0148] (Example 1)

[0149] Figure 1 is a configuration diagram showing the configuration of the imaging lens LA of Example 1. The radius of curvature R, the on-axis thickness of the lens or the on-axis distance d between lenses, the refractive index nd, and the Abbe number vd of each of the object side surface and the image side surface of the first lens L1 to the seventh lens L7 constituting the imaging lens LA of Example 1 are shown in Table 1, the conic constant k and the asphericity coefficient are shown in Table 2, and 2ω, FNO, f, f1, f2, f3, f4, f5, f6, f7, TTL, LB, and IH are shown in Table 3.

[0150]

Table 1

[0151]

[0152] Reference wavelength = 588 nm

[0153]

Table 2

[0154]

[0155] where k is the conic constant, and A4, A6, A8, A10, A12, A14, and A16 are the asphericity coefficients.

[0156] y = (x2 / R) / [1 + {1-(k+1)(x2 / R2)}1 / 2] + A4x4 + A6x6 + A8x8 + A10x10 + A12x12 + A14x14 + A16x16 (7)

[0157] where x is the perpendicular distance of a point on the aspheric curve from the optical axis, and y is the aspheric depth (the perpendicular distance between the point on the aspheric curve at a distance x from the optical axis and the tangent plane at the vertex of the aspheric curve).

[0158] For convenience, the aspheric surface of each lens surface uses the aspheric surface shown in the above formula (7), but is not particularly limited to the aspheric polynomial form represented by the formula (7).

[0159] [Table 3]

[0160]

[0161] Table 10 appearing later shows each value in each of Examples 1 to 3 and the value corresponding to the parameter prescribed in each of the relational expressions (1) to (6).

[0162] As shown in Table 10, Example 1 satisfies the relational expressions (1) to (6).

[0163] Figures 2-4 Fig. 8 shows the axial aberration, the field curvature, the distortion, and the magnification chromatic aberration of the imaging lens LA of Example 1. Figure 2 、 Figure 4 Figs. 9A to 9C respectively show the axial aberration and the magnification chromatic aberration of light having a wavelength of 486 nm, 588 nm, and 656 nm after passing through the imaging lens LA of Example 1. Figure 3 Fig. 10 shows the field curvature and the distortion of light having a wavelength of 588 nm after passing through the imaging lens LA of Example 1. Note that the field curvature S in the drawing is the field curvature with respect to the sagittal image surface, and T is the field curvature with respect to the tangent image surface, and the same applies to Examples 2 to 3. As can be seen from Table 3, the imaging lens LA of Example 1 becomes bright when FNO = 1.83, and has good optical characteristics as shown in Table 3. Figures 2-4

[0164] (Example 2)

[0165] Figure 5 Fig. 7 is a structural view showing the configuration of the imaging lens LA of Example 2. Table 4 shows the radius of curvature R, the on-axis thickness of the lens or the on-axis distance d between lenses, the refractive index nd, and the Abbe number vd of each object side surface and each image side surface of the first lens L1 to the seventh lens L7 constituting the imaging lens LA of Example 2, Table 5 shows the conic constant k and the asphericity coefficient, and Table 6 shows 2ω, FNO, f, fl, f2, f3, f4, f5, f6, f7, TTL, LB, and IH.

[0166] [Table 4]

[0167]

[0168] Reference wavelength = 588 nm

[0169] [Table 5]

[0170]

[0171] [Table 6]

[0172]

[0173] ​As shown in Table 10, the embodiment 2 satisfies the relational expressions (1) to (6).

[0174] Figures 6-8 The axial aberration, the field curvature, the distortion, and the magnification chromatic aberration of the photographing lens LA of the embodiment 2 are shown in FIGS. 12A to 12D. Figure 6 , Figure 8 The axial aberration and the magnification chromatic aberration of light with wavelengths of 486 nm, 588 nm, and 656 nm after passing through the photographing lens LA of the embodiment 2 are shown in FIGS. 13A to 13C, respectively. Figure 7 The field curvature and the distortion of light with a wavelength of 588 nm after passing through the photographing lens LA of the embodiment 2 are shown in FIG. 14. As shown in Table 6, the photographing lens LA of the embodiment 2 becomes bright when FNO = 1.83, and as shown in FIG. 14, has good optical characteristics. Figures 6-8

[0175] (Embodiment 3)

[0176] Figure 9 is a configuration diagram showing the photographing lens LA of the embodiment 3. The radius of curvature R, the on-axis thickness of the lens or the on-axis distance d between lenses, the refractive index nd, and the Abbe number vd of each object side and image side of the first lens L1 to the seventh lens L7 constituting the photographing lens LA of the embodiment 3 are shown in Table 7, the conic constant k and the asphericity coefficient are shown in Table 8, and 2ω, FNO, f, f1, f2, f3, f4, f5, f6, f7, TTL, LB, and IH are shown in Table 9.

[0177] [Table 7]

[0178]

[0179] Reference wavelength = 588 nm

[0180] [Table 8]

[0181]

[0182] [Table 9]

[0183]

[0184] As shown in Table 10, the embodiment 3 satisfies the relational expressions (1) to (6).

[0185] Figures 10-12 The axial aberration, the field curvature, the distortion, and the magnification chromatic aberration of the photographing lens LA of the embodiment 3 are shown in FIGS. 22A to 22D. Figure 10 , Figure 12 The axial aberration and the magnification chromatic aberration of light with wavelengths of 486 nm, 588 nm, and 656 nm after passing through the photographing lens LA of the embodiment 3 are shown in FIGS. 23A to 23C, respectively. Figure 11 ​The field curvature and distortion of light with a wavelength of 588 nm after passing through the camera lens LA of Example 3 are shown in FIG. 9. As can be seen, the camera lens LA of Example 3, as shown in Table 9, becomes bright when FNO = 1.83, and, as shown in FIG. 9, has good optical characteristics. Figures 10-12

[0186]

Table 10

[0187]

[0188] It will be understood by those of ordinary skill in the art that the above-described embodiments are specific embodiments of implementing the present application, and that various changes in form and details can be made therein without departing from the spirit and scope of the present application.​

Claims

1. A camera lens, characterized in that, The camera lens consists of, from the object side to the image side, a first lens with negative refractive power, a second lens with negative refractive power, a third lens with negative refractive power, a fourth lens with positive refractive power, a fifth lens with negative refractive power, a sixth lens with positive refractive power, and a seventh lens with positive refractive power. The first lens has a convex object-side surface and a concave image-side surface, respectively; the second lens has a concave object-side surface and a convex image-side surface near the axis, respectively; the third lens has a concave object-side surface and a concave image-side surface; the fourth lens has a convex object-side surface and a convex image-side surface; the fifth lens has a convex object-side surface and a concave image-side surface, respectively; the sixth lens has a convex object-side surface and a convex image-side surface; and the seventh lens has a convex object-side surface and a concave image-side surface near the axis, respectively. Wherein, the overall focal length of the camera lens is f, the focal length of the second lens is f2, the radius of curvature of the object side surface of the third lens is R5, the axial distance from the image side surface of the first lens to the object side surface of the second lens is d2, the axial distance from the image side surface of the second lens to the object side surface of the third lens is d4, and the following relationships (1)~(3) are satisfied: -50.10≤f2 / f≤-22.90(1) 9.20≤d2 / d4≤30.00(2) -11.10≤R5 / f≤-9.55(3).

2. The camera lens according to claim 1, characterized in that, The following relation (4) must be satisfied: -753.70≤f2 / d4≤-109.00(4).

3. The camera lens according to claim 1, characterized in that, The radius of curvature of the image-side surface of the second lens is R4, and it satisfies the following relationship (5): 4.60≤f2 / R4≤14.60(5).

4. The camera lens according to claim 1, characterized in that, The focal length of the sixth lens is f6, and it satisfies the following relationship (6): -25.00≤f2 / f6≤-12.00(6).

5. The camera lens according to any one of claims 1 to 4, characterized in that, The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are all made of glass.

6. The camera lens according to any one of claims 1 to 4, characterized in that, The second lens and the seventh lens are glass aspherical lenses.

Images