JP3324802B2 - Shooting lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photographing lens used for a vehicle-mounted camera or the like.

[0002]

2. Description of the Related Art As a photographing lens for a vehicle-mounted camera, there is, for example, a lens described in Japanese Patent Application Laid-Open No. 3-321213. This taking lens has a large number of constituent lenses of eight.
As a lens system for a video camera having a small number of constituent lenses, there is, for example, a lens system described in JP-A-2-7712 and a lens system described as a fifth embodiment in JP-A-2-208617. Of these lens systems, the former lens system is composed of two lenses, and the latter lens system is composed of three lenses.

[0003]

Among the above-mentioned prior arts , the lens system according to the fifth embodiment disclosed in JP-A-2-7712 and JP-A-2-208617 has a small number of components, and therefore has chromatic aberrations, especially chromatic aberrations of magnification. Is insufficiently corrected. These are lens systems having negative and positive power arrangements in order from the object side with a diaphragm interposed therebetween, which are advantageous for widening the angle and are of a type which can easily secure a back focus. However, because of the asymmetric power arrangement with respect to the stop, distortion and chromatic aberration of magnification tend to be insufficiently corrected.

A lens for an in-vehicle camera does not cause much problem because distortion is wider than that of a photographic lens, but chromatic aberration of magnification needs to be sufficiently corrected.

SUMMARY OF THE INVENTION An object of the present invention is to provide a photographing lens suitable for a vehicle-mounted camera lens in which various aberrations such as chromatic aberration of magnification are satisfactorily corrected even though the number is small.

[0006]

According to the present invention, there is provided a photographing lens comprising:
In order from the object side, a first unit having a negative refractive power and a second unit having a positive refractive power are provided. The first unit includes only one negative lens, and the second unit includes one negative meniscus. It is composed of two lenses, one lens and one biconvex lens. This lens system satisfies the following conditions (1), (2) and (3). (1) ν ₁ > 40 (2) ν _2p −ν _2n > 10 (3) (n _2n −n _2p ) × ｛2 / (| r _2n | + | r _2p
|)｝ × f> 0.48 where ν ₁ is the Abbe number of the negative lens of the first group, ν _2p , ν
_2n is the Abbe number of the positive lens and the negative lens (biconvex lens, negative meniscus lens) of the second group, and n _2p and n _2n are the refractive indexes of the positive lens and the negative lens of the second group, r _2p and r _{2n, respectively.} Is the radius of curvature of the facing surfaces of the positive lens and the negative lens of the second group, respectively (for a cemented lens, it is the radius of curvature of the cemented surface, r _2p = r _2n ), and f is the focal length of the entire system.

A lens for a vehicle-mounted camera needs to be able to observe a wide range from a distant view at about infinity to the vicinity of a vehicle body at the same time in focus. To this end, wide-be
It is desired that a lens system having a depth of field. In addition, general surveillance cameras are often used mainly in relatively dark places, such as indoors or at night, while in-vehicle cameras are used outdoors and frequently used during the day. Therefore, the in-vehicle camera may have a large F-number, which is advantageous for reducing the number of lenses.

From the above, the taking lens of the present invention has the above-described lens configuration.

In the case of the type like the above-mentioned lens system of the present invention, in order to minimize the number of lenses, the first group is composed of one negative lens, and the second group is composed of one positive lens. That is, in order to correct the chromatic aberration of magnification, it is necessary to add at least one more lens. In that case, it is most effective to add one negative lens to the second group. Further, it is preferable that the aforementioned conditions (1), (2), and (3) are further satisfied.

The conditions (1) and (2) are conditions for suppressing the occurrence of chromatic aberration in each group and for favorably correcting chromatic aberration as a whole.

If the condition (1) is not satisfied, chromatic aberration of magnification will be undercorrected. When the value exceeds the range of the condition (2), the chromatic aberration of magnification and the axial chromatic aberration are insufficiently corrected.

Condition (3) defines the refractive power of the facing surfaces of the positive lens and the negative lens of the second group, and
When the value exceeds the range of the condition (3), mainly the spherical aberration and the coma are insufficiently corrected.

The second lens unit may be a negative lens, a positive lens, a positive lens, or a negative lens in order from the object side.

In the photographic lens of the present invention, the first
It is more preferable that the second group and the second group satisfy the following conditions (4) and (5). (4) −4 <f ₁ /f<−0.95 (5) 0.85 <f ₂ / f <2 where f ₁ and f ₂ are the focal lengths of the first group and the second group, respectively.

The conditions (4) and (5) are mainly conditions for further reducing the size of the lens system, and define the refracting power of both groups, respectively. If the lower limit of the condition (4) or the condition (5) is exceeded, it is disadvantageous in securing the back focus, and it becomes difficult to dispose an optical material such as a filter. Also, the Petzval sum tends to be a large positive value. Conversely, exceeding the upper limit of the condition (4) or the condition (5) is preferable for securing the back focus, but the overall length tends to be large.

Furthermore, it is desirable to provide an aspherical surface in which the negative refractive power becomes weaker as the optical axis becomes farther from the first lens unit. In an on-vehicle camera lens system, the distortion of an image is neglected compared to the sharpness of the image. However, it is desirable that the distortion be corrected in order to confirm a more accurate and safe visual field. It is effective to use the above-mentioned aspherical surface for the first lens unit, whereby the distortion can be satisfactorily corrected.

Further, the on-vehicle camera requires an optical system which is directed sideways or obliquely depending on the positional relationship with the vehicle body. Therefore, in the lens system of the present invention, a reflecting member such as a prism or a mirror can be disposed between the first and second units, thereby enabling a side view or a perspective view.
The distance between the first and second units of the lens system of the present invention is low when the height of off-axis rays is low, and when a prism or a reflecting member is arranged here, these members can be made small, which is advantageous in reducing the size of the entire optical system. It is. However, the position of the reflection member may be arranged on the object side of the first group or on the image side of the second group.

The photographic lens of the present invention can be used as a lens system for a general video camera or a silver halide camera in addition to a vehicle-mounted camera.

[0019]

Next, embodiments of the taking lens according to the present invention will be described. Example 1 f = 7 mm, image height = 4.2 mm, 2ω = 62 °, F / 8, image position (from the last plane) = 1 mm r ₁ = 18.6732 d ₁ = 1.0000 n ₁ = 1.48749 ν ₁ = 70.20 r ₂ = 3.7831 (aspheric surface) d ₂ = 9.55367 r ₃ = ∞ (aperture) d ₃ = 0.7164 r ₄ = 5.0314 d ₄ = 2.4019 n ₂ = 1.84666 ν ₂ = 23.78 r ₅ = 2.7656 d ₅ = 3.6106 n ₃ = 1.48749 ν ₃ = 70.20 r ₆ = -6.4383 d ₆ = 7.1787 r ₇ = ∞ d ₇ = 4.5300 n ₄ = 1.54771 ν ₄ = 62.83 r ₈ = ∞ d ₈ = 0.8000 n ₅ = 1.52420 ν ₅ = 70.20 r ₉ = ∞ aspheric coefficient P = 1.0000, E = -0.99376 × 10 ^-3 , F = 0.11082 × 10 ^-4 G = -0.10100 × 10 ^-4 ν ₁ = 70.2, ν _2p −ν _2n = 46.42 (n _2n −n _2p ) × ｛2 / (| R _2n | + | r _2p |)｝ × f = 0.909 f ₁ /f=−1.42, f ₂ /f=1.26

Embodiment 2 f = 7 mm, image height = 4.2 mm, 2ω = 62 °, F / 8, image position (from the last plane) = 1 mm r ₁ = 7.6583 (aspherical surface) d ₁ = 1.1242 n ₁ = 1.48749 ν ₁ = 70.20 r ₂ = 3.3410 d ₂ = 3.3199 r ₃ = ∞ d ₃ = 6.8000 n ₂ = 1.51633 ν ₂ = 64.15 r ₄ = ∞ d ₄ = 1.0000 r ₅ = ∞ (aperture) d ₅ = 0.6968 r ₆ = _{6.1028 d 6 = 2.6923 n 3 =} 1.80518 ν 3 = 25.43 r 7 = 2.2505 d 7 = 2.4463 n 4 = 1.60342 ν 4 = 38.01 r 8 = -6.7210 ( _{aspherical) d 8 = 5.5492 r 9 =} ∞ d 9 = 4.5300 n ₅ = 1.54771 v ₅ = 62.83 r ₁₀ = ∞ d ₁₀ = 0.8000 n ₆ = 1.52420 v ₆ = 70.20 r ₁₁ = ∞ aspheric coefficient (first surface) P = 1.0000, E = 0.57683 × 10 ^-3 , F = 0.13353 × 10 ^-4 G = 0.61032 × 10 ^-6 (8th surface) P = 1.000, E = −0.706010 × 10 ^-3 , F = −0.19291 × 10 ^-3 G = −0.51452 × 10 ^-4 ν ₁ = 70.2 _{, ν 2p -ν 2n = 12.58 (} n 2n -n 2p) × {2 / (| r 2n | + | r 2p |)} _{f = 0.628 f 1 /f=-1.90, f} 2 /f=1.15

Embodiment 3 f = 7 mm, image height = 4.2 mm, 2ω = 62 °, F / 8, image position (from the last plane) = 1 mm r ₁ = 16.4159 d ₁ = 1.0000 n ₁ = 1.54814 ν ₁ = 45.78 r ₂ = 5.4595 d ₂ = 7.5840 r ₃ = ∞ d ₃ = 6.7200 n ₂ = 1.80610 ν ₂ = 40.95 r ₄ = ∞ d ₄ = 1.0000 r ₅ = ∞ (aperture) d ₅ = 0.3187 r ₆ = 4.1585 d ₆ = 1.8069 n ₃ = 1.84666 v ₃ = 23.78 r ₇ = 2.3370 d ₇ = 1.9711 n ₄ = 1.51633 v ₄ = 64.15 r ₈ = -13.2147 d ₈ = 5.2588 r ₉ = ∞ d ₉ = 4.5300 n ₅ = 1.54771 v ₅ = 62.83 r ₁₀ = ∞ d ₁₀ = 0.8000 n ₆ = 1.52420 ν ₆ = 70.20 r ₁₁ = ν ν ₁ = 45.78, ν _2p −ν _2n = 40.37 (n _2n −n _2p ) × ｛2 / (| r _2n | + | _{r 2p |)} × f =} 0.989 f 1 /f=-2.20, f 2 /f=1.22

Embodiment 4 f = 7 mm, image height = 4.2 mm, 2ω = 62 °, F / 5.6 image position (from the last surface) = 1 mm r ₁ = 12.6060 (aspherical surface) d ₁ = 0.9327 n ₁ = 1.48749 ν ₁ = 70.20 r ₂ = 3.2614 d ₂ = 3.4950 r ₃ = ∞ d ₃ = 6.7200 n ₂ = 1.51633 ν ₂ = 64.15 r ₄ = ∞ d ₄ = 1.0000 r ₅ = ∞ (aperture) d ₅ = 1.3995 r ₆ = 5.6433 _{d 6 = 2.0240 n 3 = 1.80518} ν 3 = 25.43 r 7 = 3.0491 d 7 = 2.5272 n 4 = 1.48749 ν 4 = 70.20 r 8 = -6.1979 ( _{aspherical) d 8 = 8.6927 r 9 =} ∞ d 9 = 4.5300 n ₅ = 1.54771 ν ₅ = 62.83 r ₁₀ = ∞ d ₁₀ = 0.8000 n ₆ = 1.52420 ν ₆ = 70.20 r ₁₁ = ∞ Aspherical coefficient (first surface) P = 1.0000, E = 0.95419 × 10 ^-3 , F = 0.46297 × 10 ⁻⁵ G = 0.40011 × 10 ⁻⁶ (8th surface) P = 1.0000, E = 0.16170 × 10 ⁻³ , F = −0.28453 × 10 ⁻⁴ G = −0.69306 × 10 ⁻⁵ ν ₁ = 70.2, ν _2p− ν _2n = 44.77 (n _2n −n _2p ) × {2 / (| r _2n | + | r _2p |)} × f = 0.729 f ₁ /f=1.33, f ₂ /f=1.26

Embodiment 5 f = 7 mm, image height = 4.2 mm, 2ω = 62 °, F / 8, image position (from the last plane) = 1 mm r ₁ = 16.4817 d ₁ = 1.0000 n ₁ = 1.48749 ν ₁ = 70.20 r ₂ = 5.9725 d ₂ = 9.6315 r ₃ = ∞ d ₃ = 7.0000 n ₂ = 1.51633 ν ₂ = 64.15 r ₄ = ∞ d ₄ = 1.0000 r ₅ = ∞ (aperture) d ₅ = 0.1000 r ₆ = 3.5922 d ₆ = _{1.8015 n 3 = 1.84666 ν 3 =} 23.78 r 7 = 2.5625 d 7 = 0.4860 r 8 = 3.7333 d 8 = 2.0000 n 4 = 1.48749 ν 4 = 70.20 r 9 = -12.1472 d 9 = 4.8432 r 10 = ∞ d 10 = 4.5300 n ₅ = 1.54771 v ₅ = 62.83 r ₁₁ = ∞ d ₁₁ = 0.8000 n ₆ = 1.52420 v ₆ = 70.20 r ₁₂ = ∞ v ₁ = 70.2, v _2p −v _2n = 46.42 (n _2n −n _2p ) × ｛2 / (| R _2n | + | r _2p |)｝ × f = 0.799 f ₁ /f=−2.83, f ₂ /f=1.30

Embodiment 6 f = 7 mm, image height = 4.2 mm, 2ω = 62 °, F / 8, image position (from the last surface) = 1 mm r ₁ = 7.4617 (aspherical surface) d ₁ = 1.0000 n ₁ = 1.48749 v ₁ = 70.20 r ₂ = 3.3305 d ₂ = 3.1641 r ₃ = ∞ d ₃ = 7.0000 n ₂ = 1.51633 v ₂ = 64.15 r ₄ = ∞ d ₄ = 1.0000 r ₅ = ∞ (aperture) d ₅ = 2.4335 r ₆ = 13.5521 d ₆ = 3.5000 n ₃ = 1.51633 ν ₃ = 64.15 r ₇ = -2.7701 d ₇ = 0.6254 n ₄ = 1.80518 ν ₄ = 25.43 r ₈ = -4.4712 d ₈ = 8.6714 r ₉ = ∞ d ₉ = 4.5300 n ₅ = 1.54771 ν ₅ = 62.83 r ₁₀ = ∞ d ₁₀ = 0.8000 n ₆ = 1.52420 ν ₆ = 70.20 r ₁₁ = ∞ Aspheric coefficient P = 1.0000, E = 0.48566 × 10 ^-3 , F = −0.84231 × 10 ^-7 G = 0.12811 × 10 ⁻⁵ ν ₁ = 70.2, ν _2p −ν _2n = 38.72 (n _2n −n _2p ) × {2 / (| r _2n | + | r _2p |)} × f = 0.730 f ₁ / f = − 1.92, f ₂ /f=1.29

Embodiment 7 f = 7 mm, image height = 4.2 mm, 2ω = 62 °, F / 8, image position (from the last surface) = 1 mm r ₁ = 9.4874 (aspherical surface) d ₁ = 1.0000 n ₁ = 1.48749 ν ₁ = 70.20 r ₂ = 2.8677 d ₂ = 3.1490 r ₃ = ∞ d ₃ = 6.7200 n ₂ = 1.80610 ν ₂ = 40.95 r ₄ = ∞ d ₄ = 1.0000 r ₅ = ∞ (aperture) d ₅ = 2.3182 r ₆ = _{6.7454 d 6 = 3.5000 n 3 =} 1.48749 ν 3 = 70.20 r 7 = -3.4453 d 7 = 0.5245 r 8 = -2.9242 d 8 = 0.6567 n 4 = 1.80518 ν 4 = 25.43 r 9 = -4.7291 d 9 = 8.9583 r 10 _{= ∞ d 10 = 4.5300 n 5} = 1.54771 ν 5 = 62.83 r 11 = ∞ d 11 = 0.8000 n 6 = 1.52420 ν 6 = 70.20 r 12 = ∞ aspherical coefficients P = 1.0000, E = 0.11449 × 10 -2, F = 0.12297 × 10 ⁻⁴ G = 0.12531 × 10 ⁻⁵ ν ₁ = 70.2, ν _2p −ν _2n = 44.77 (n _2n −n _2p ) × {2 / (| r _2n | + | r _2p |)} × f _{= 0.698 f 1 /f=-1.27, f 2} /f=1.26 where r _1, r _2, ·· The radius of curvature of each lens surface, d
_1, d _2, ··· wall thickness of each lens, n _1, n _2, ··· is the refractive index of each lens, ν _1, ν _2, ··· is the Abbe number of each lens.

The photographing lens according to the first embodiment has the structure shown in FIG. FIG addition to using 1 direct view as shown in, performs perspective by placing a reflecting mirror M ₁ as a reflecting member on the object side of the lens system as shown in FIG. 15 (imaging in an oblique direction of the object). Here, if the reflecting mirror M is made movable, the perspective direction can be changed. A reflecting mirror M ₁ as shown in Matazu 16 can also be placed between the first and second lens units. It is also possible to further place the reflecting mirror M ₁ to the image side of the second group as shown in Figure 17.

Embodiment 2 has a lens configuration shown in FIG. 2 and a reflecting prism M between the first and second units as shown in FIG.
It is assumed that ₂ is used. The symbol M _{2 in} FIG. 2 also indicates this prism, and r ₃ , r ₄ ,
d ₃ , n ₂ and ν ₂ indicate this prism.

Embodiments 3 to 7 correspond to FIGS. 3 to 7, respectively.
As in the case of the second embodiment, FIG.
It is assumed that prisms are arranged as shown in FIG.

The aspherical surface used in the embodiment of the present invention is expressed by the following equation when the optical axis direction is the x axis and the direction perpendicular to the x axis is the y axis.

Where C = 1 / r (r is the radius of curvature of the top of the aspherical surface), P is the conic constant, and E, F, G,... Are the aspherical surface coefficients.

In the figure, F is a filter. Further, a roof mirror or a roof prism may be used as the reflection member.

Each embodiment of the present invention has an F number of 5.6 to
As a result, a clear image can be obtained from as far as infinity to near the vehicle body with a large depth of field. If the aperture diameter is fixed, the drive mechanism can be omitted, the lens frame can be simplified, and the size can be reduced.

[0033]

The photographic lens of the present invention is a lens system suitable for an in-vehicle camera, in which various aberrations such as chromatic aberration of magnification are well corrected despite the small number of three lenses.

[Brief description of the drawings]

FIG. 1 is a sectional view of a first embodiment of the present invention.

FIG. 2 is a sectional view of a second embodiment of the present invention.

FIG. 3 is a sectional view of a third embodiment of the present invention.

FIG. 4 is a sectional view of a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a fifth embodiment of the present invention.

FIG. 6 is a sectional view of a sixth embodiment of the present invention.

FIG. 7 is a sectional view of a seventh embodiment of the present invention.

FIG. 8 is an aberration curve diagram according to the first embodiment of the present invention.

FIG. 9 is an aberration curve diagram according to the second embodiment of the present invention.

FIG. 10 is an aberration curve diagram according to the third embodiment of the present invention.

FIG. 11 is an aberration curve diagram according to the fourth embodiment of the present invention.

FIG. 12 is an aberration curve diagram according to the fifth embodiment of the present invention.

FIG. 13 is an aberration curve diagram according to the sixth embodiment of the present invention.

FIG. 14 is an aberration curve diagram according to the seventh embodiment of the present invention.

FIG. 15 is a diagram showing a configuration in which a reflecting member is arranged on the object side of the lens system of the present invention.

FIG. 16 is a diagram showing a configuration in which a reflecting member is arranged between a first unit and a second unit of the lens system of the present invention.

FIG. 17 is a diagram showing a configuration in which a reflecting member is arranged on the image side of the second group of the lens system according to the present invention;

FIG. 18 is a diagram illustrating a configuration in which a reflecting prism is disposed between the first and second units of the lens system according to the present invention.

Claims (7)

(57) [Claims] 1. A first group having a negative refractive power, in order from the object side,
The second lens unit includes a second lens unit having a positive refractive power. The first lens unit includes only one negative lens. The second lens unit includes a negative meniscus lens and a biconvex lens arranged in the order of negative, positive, or positive and negative. Is a lens system composed of the following conditions (1), (2),
An imaging lens that satisfies (3). (1) ν ₁ > 40 (2) ν _2p −ν _2n > 10 (3) (n _2n −n _2p ) × {2 / (| r _2n | + | r _2p |)} × f> 0.48 ν ₁ is the Abbe number of the negative lens of the first group, ν _2p , ν
_2n is the Abbe number of the positive and negative lenses of the second group, n _2p and n _2n are the refractive indexes of the positive and negative lenses of the second group, respectively, and r _2p and r _2n are the positive lenses of the second group, respectively. The radius of curvature of the surfaces of the negative lens facing each other (for a cemented lens, the radius of curvature of the cemented surface, r _2p = r _2n ), f
Is the focal length of the whole system. 2. The photographic lens according to claim 1, wherein said first and second units satisfy the following conditions (4) and (5). (4) −4 <f ₁ /f<−0.95 (5) 0.85 <f ₂ / f <2 where f ₁ and f ₂ are the focal lengths of the first group and the second group, respectively. 3. The photographic lens according to claim 2, wherein an aspherical surface having a negative refractive power weakens as the optical axis moves away from said first lens unit. 4. The photographic lens according to claim 1, wherein a reflecting member is disposed between said first group and said second group. 5. The photographic lens according to claim 1, wherein a reflecting member is disposed on the object side of said first group. 6. The photographic lens according to claim 1, wherein a reflecting member is arranged on the image side of said second group. 7. The photographing lens according to claim 5, wherein a movable reflecting mirror capable of changing a photographing direction of an oblique object is arranged as said reflecting member.