JP3346623B2 - High-performance shooting lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to the present invention, in which the aperture ratio is F / 1.4-.
The present invention relates to a small, high-performance single focus photographing lens having an F / 2.8 of about an angle of view of about 60 to 75 °.

[0002]

2. Description of the Related Art As a conventional example of a photographic lens of the same kind as the photographic lens of the present invention, a lens system described in Japanese Patent Application Laid-Open No. 5-80252 is known. This conventional photographic lens,
In order from the object side, a first lens group having a positive refractive power composed of a cemented lens in which a biconcave lens and a biconvex lens are bonded, and a second lens having a negative refractive power composed of a cemented lens in which a biconvex lens and a biconcave lens are laminated. 2 lens groups, aperture,
A third lens group having a positive refractive power with the convex surface facing the image side, a fourth lens group having a positive refractive power composed of a cemented lens obtained by bonding a biconcave lens and a biconvex lens, and a biconvex lens and a biconcave lens. A fifth lens unit having a positive refractive power, which is composed of cemented cemented lenses, is configured such that the power of the front unit before the stop is very weak, and the power of the rear unit after the stop is relatively strong. This is a lens configuration.

[0003]

In the conventional photographic lens, the power of the front group is very weak, and the power of the rear group is relatively strong. The effect is large, particularly, the influence of the curvature of field is large, and adversely affects the image. Further, since the configuration length from the first surface of the lens to the stop is large, the distance from the first surface of the lens to the entrance pupil position is long, and the diameter of the front lens becomes very large in order to ensure a sufficient amount of peripheral light. In recent years, as the demand for miniaturization has increased, it cannot be said that the lens system meets this demand.

In order to reduce the size of the entire camera, it is possible to use a mechanical method such as collapsing the lens system. However, the outer diameter of the lens system such as the front lens diameter is determined by such a mechanical method. It cannot be used, and it is desired to reduce the size of the lens system by optical design.

The present invention achieves the miniaturization of the lens system including the outer diameter by appropriately maintaining the lens configuration and the power distribution with the minimum necessary number of lenses, and the optical performance up to the peripheral portion of the screen. It is an object of the present invention to provide a high-performance photographing lens with good image quality.

[0006]

According to the present invention, there is provided a photographing lens comprising:
A first lens group having a positive refractive power, in order from the object side;
A second lens group having a negative refractive power, a stop, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. The lens system has a concave surface and further satisfies the following condition (1).

(1) 0.25 <f _R / f _F <1.3 where f _F is the combined focal length of the lens group before the stop,
f _R is the composite focal length of the lens group after the stop.

When the first lens surface is concave, it is relatively easy to secure the peripheral light amount than when it is convex. Therefore, if the first surface is made concave, the lens diameter is increased only to secure the light amount. A vicious circle such as causing the lens to be avoided can be avoided, the distance from the lens first surface to the entrance pupil position can be shortened, and the lens system can be downsized.

It is desirable that the ratio of the radius of curvature between the first lens surface and the last lens surface be determined so as to satisfy the following condition (2).

[0010] _{(2) 1 <| r a} / r b | <3.5 However r _a is the radius of curvature of the first surface of the lens, r _b is the radius of curvature of the last lens surface.

The condition (1) defines the ratio of the focal lengths of the lens groups before and after the stop. By optimizing the power distribution before and after the stop, various aberrations up to the peripheral portion of the screen are reduced. This is to correct the balance well and to reduce the size of the lens system.

If the upper limit of 1.3 to condition (1) is exceeded, various aberrations can be corrected in a well-balanced manner. At that time, in order to reduce the occurrence of off-axis aberrations such as coma, it is necessary to reduce the final lens surface. Must be convex on the image side, in which case the overall length of the lens system becomes longer, which is contrary to the object of the present invention.

When the lower limit of 0.25 to condition (1) is exceeded,
The power of the rear group (the entire lens group closer to the image side than the diaphragm) becomes extremely strong, the amount of aberration generated on each lens surface of the rear group becomes large, and it becomes difficult to secure good optical performance. Also,
The air gap between the front group and the rear group tends to increase, which is contrary to downsizing the lens system.

By keeping the value of | r _a / r _b | within the range of the condition (2), the total length of the lens system, the size of the front lens diameter, the peripheral light amount, and the like are appropriately balanced, so that a small photographing lens is provided. Is easier to obtain.

When the value exceeds the upper limit of the condition (2), the first lens
The radius of curvature of the surface becomes relatively gentle, and the effect of securing the peripheral light amount and shortening the entrance pupil distance as described above is reduced. Therefore, there is a possibility that the diameter of the front lens is particularly increased.

When the value goes below the lower limit of the condition (2), the radius of curvature of the final lens surface becomes relatively gentle, and good performance can be ensured, but the overall length of the lens system becomes long. In order to achieve the object of the present invention, it is preferable that the second lens group having a negative refractive power is constituted by one negative lens.

As described above, the length of the front group of the lens group before the stop greatly affects the diameter of the front lens. Therefore, it is desirable to keep the number of lenses to a minimum number as long as the optical performance is not deteriorated. To this end, it is preferable that the second lens group be a single lens and the second lens group be configured so that the optical system is as symmetrical as possible with respect to the diaphragm. The meniscus lens having the second lens group with the convex surface facing the object side Is desirable.

The negative lens is also important for maintaining the Petzval sum of the lens system at an appropriate value. To this end, the focal length f ₂ of the second lens group must satisfy the following condition (3). It is desirable to satisfy the following.

(3) 1.5f <| f ₂ | <4.5f where f is the focal length of the entire system.

Exceeding either the upper limit of 4.5f or the lower limit of 1.5f in the above condition (3) is not preferable in setting the Petzval sum of the lens system to an appropriate value.

In the condition (1) relating to the value of f _R / f _F , it is more preferable to set the lower limit to 0.4 in order to correct various aberrations in a photographing lens having a large aperture ratio in a well-balanced manner. That is, it is more desirable to satisfy the following condition (1-a).

(1-a) 0.4 <f _R / f _F <1.3 When the value exceeds the lower limit of 0.4 in the condition (1-a), the influence of spherical aberration and coma becomes particularly strong, and the aperture becomes large. It becomes difficult to maintain a high-performance photographic lens with a high ratio.

As to the upper limit of the condition (1), setting the upper limit to 1.0 is effective for further improving the aberration correcting effect, and particularly for preventing the deterioration of the image due to the curvature of field. That is, it is more preferable to satisfy the following condition (1-b).

(1-b) 0.25 <f _R / f _F <1.0 Preferred configurations of the photographic lens of the present invention include the following. That is, in order from the object side, one biconcave lens and one
A first lens group composed of two biconvex lenses, a second lens group composed of one negative meniscus lens having a convex surface facing the object side, and a cemented lens obtained by bonding a biconcave lens and a biconvex lens. And a fourth lens group of a cemented lens in which a biconvex lens and a biconcave lens are bonded to each other.

[0025]

Next, embodiments of the high-performance photographic lens of the present invention will be described. Example 1 f = 36.00 mm, F / 2.88, 2ω = 63.2 °, f _B = 30.04 mm r ₁ = −37.9763 d ₁ = 1.000 n ₁ = 1.53256 ν ₁ = 45.91 r ₂ = 22.5199 d ₂ = 0.100 r ₃ = 16.5729 (aspheric surface) d ₃ = 3.975 n ₂ = 1.786650 v ₂ = 50.00 r ₄ = -51.5406 d ₄ = 0.100 r ₅ = 13.9701 d ₅ = 1.000 n ₃ = 1.62374 v ₃ = 47.10 r ₆ = 10.8113 d ₆ = 3.370 r ₇ = ∞ (aperture) d ₇ = 2.577 r ₈ = -14.6718 d ₈ = 1.000 n ₄ = 1.68893 ν ₄ = 31.08 r ₉ = 54.6154 d ₉ = 3.197 n ₅ = 1.77250 ν ₅ = 49.66 r ₁₀ = -16.3614 d _{10 = 0.100 r 11 = 52.9164 d} 11 = 2.765 n 6 = 1.83481 ν 6 = 42.72 r 12 = -27.4284 d 12 = 1.000 n 7 = 1.54072 ν 7 = 47.20 r 13 = 29.9742 ( aspherical) aspherical coefficients (third Surface) A ₄ = -0.34430 × 10 ^-4 , A ₆ = -0.81137 × 10
^-7 A ₈ = -0.36683 × 10 ^-9 , A ₁₀ = 0.32507 × 10 ^-11 (13th surface) A ₄ = 0.13923 × 10 ^-4 , A ₆ = -0.64905 ×
_{^{10 -7 A 8 = 0.23589 × 10}} -9, A 10 = -0.13877 × 10 -11 f R / f F = 0.871, f 2 = -87.27mm, f 2 /f=-2.4 | r a / r b | = | R ₁ / r ₁₃ | = 1.27

Example 2 f = 36.00 mm, F / 1.85, 2ω = 62.4 °, f _B = 24.77 mm r ₁ = −79.9547 d ₁ = 4.034 n ₁ = 1.53256 ν ₁ = 45.91 r ₂ = 26.7201 d ₂ = 0.100 r ₃ = 18.6977 (aspherical surface) d ₃ = 7.062 n ₂ = 1.786650 ν ₂ = 50.00 r ₄ = -98.6469 d ₄ = 0.100 r ₅ = 17.6483 d ₅ = 1.500 n ₃ = 1.62374 ν ₃ = 47.10 r ₆ = 12.4473 d ₆ = 4.810 r ₇ = ∞ _{(stop) d 7 = 3.254 r 8 =} -20.2572 d 8 = 1.000 n 4 = 1.68893 ν 4 = 31.08 r 9 = 23.2955 d 9 = 5.970 n 5 = 1.77250 ν 5 = 49.66 r 10 = _{-22.0958 d 10 = 0.100 r 11 =} 34.0591 d 11 = 5.139 n 6 = 1.83481 ν 6 = 42.72 r 12 = -43.7842 d 12 = 2.000 n 7 = 1.54072 ν 7 = 47.20 r 13 = 23.6790 ( aspherical) aspheric coefficients (Third surface) A ₄ = -0.19163 × 10 ^-4 , A ₆ = -0.46899 × 10
^-7 A ₈ = 0.35187 × 10 ^-11 , A ₁₀ = -0.25979 × 10 ^-12 (13th surface) A ₄ = 0.15219 × 10 ^-4 , A ₆ = -0.28391 ×
_{^{10 -8 A 8 = -0.23584 × 10}} -10, A 10 = 0.61377 × 10 -12 f R / f F = 0.573, f 2 = -76.15mm, f 2 /f=-2.1 | r a / r b | = | R ₁ / r ₁₃ | = 3.38

Example 3 f = 28.51 mm, F / 2.88, 2ω = 73.6 °, f _B = 21.62 mm r ₁ = -39.1331 d ₁ = 1.000 n ₁ = 1.54814 ν ₁ = 45.78 r ₂ = 16.5650 d ₂ = 0.100 r ₃ = 14.1361 (aspherical surface) d ₃ = 4.804 n ₂ = 1.78650 ν ₂ = 50.00 r ₄ = -40.4301 d ₄ = 0.100 r ₅ = 13.28287 d ₅ = 1.000 n ₃ = 1.62374 ν ₃ = 47.10 r ₆ = 9.9256 d ₆ = 2.997 r ₇ = ∞ (aperture) d ₇ = 2.997 r ₈ = -17.3974 d ₈ = 1.000 n ₄ = 1.67741 ν ₄ = 28.52 r ₉ = 26.8634 d ₉ = 4.280 n ₅ = 1.78650 ν ₅ = 50.00 r ₁₀ = _{-17.2924 d 10 = 0.100 r 11 =} 36.9784 d 11 = 3.729 n 6 = 1.88300 ν 6 = 40.78 r 12 = -28.6091 d 12 = 1.000 n 7 = 1.54814 ν 7 = 45.78 r 13 = 18.8953 ( aspherical) aspheric coefficients (Third surface) A ₄ = -0.51912 × 10 ^-4 , A ₆ = -0.22098 × 10
^-6 A ₈ = 0.19546 × 10 ^-9 , A ₁₀ = -0.31807 × 10 ^-12 (13th surface) A ₄ = 0.16710 × 10 ^-4 , A ₆ = -0.24854 ×
10 ⁻⁷ A ₈ = −0.24711 × 10 ⁻⁹ , A ₁₀ = 0.22013 × 10 ⁻¹¹ f _R / f _F = 0.613, f ₂ = −71.10 mm, f ₂ /f=−2.5 | r _a / r _b | = | R ₁ / r ₁₃ | = 2.23

Example 4 f = 36.03 mm, F / 1.44, 2ω = 62.2 °, f _B = 23.94 mm r ₁ = -49.5585 d ₁ = 0.992 n ₁ = 1.53256 v ₁ = 45.91 r ₂ = 37.6853 d ₂ = 0.100 r ₃ = 25.4653 (aspherical surface) d ₃ = 6.952 n ₂ = 1.786650 ν ₂ = 50.00 r ₄ = −57.5064 d ₄ = 0.100 r ₅ = 20.6431 d ₅ = 2.997 n ₃ = 1.62374 ν ₃ = 47.10 r ₆ = 14.8765 d ₆ = 5.449 r ₇ = ∞ _{(stop) d 7 = 3.618 r 8 =} -22.8849 d 8 = 1.990 n 4 = 1.68893 ν 4 = 31.08 r 9 = 28.9776 d 9 = 6.650 n 5 = 1.77250 ν 5 = 49.66 r 10 = _{-23.7098 d 10 = 1.182 r 11 =} 28.7068 d 11 = 4.481 n 6 = 1.83481 ν 6 = 42.72 r 12 = -81.4475 d 12 = 1.594 n 7 = 1.54072 ν 7 = 47.20 r 13 = 22.1814 ( aspherical) aspheric coefficients (Third surface) A ₄ = -0.12266 × 10 ^-4 , A ₆ = -0.29341 × 10
^-7 A ₈ = 0.56800 × 10 ^-10 , A ₁₀ = -0.62395 × 10 ^-13 (13th surface) A ₄ = 0.18445 × 10 ^-4 , A ₆ = -0.24748 ×
10 ^-7 A ₈ = 0.64803 × 10 ^-10 , A ₁₀ = 0.44126 × 10 ^-12 f _R / f _F = 0.530, f ₂ = -106.678 mm, f ₂ / f =-
3.0 | r _a / r _b | = | r ₁ / r ₁₃ | = 2.07 where r ₁ , r ₂ ,...
_.. , D ₂ ,...
₁ , n ₂ ,... Are the refractive indices of each lens, ν ₁ , ν ₂ ,.
The Abbe number of each lens, f _B is the back focus.

The first embodiment has a configuration as shown in FIG. 1 and includes, in order from the object side, a first lens group composed of a biconcave lens and a biconvex lens and having a positive refractive power as a whole, and a convex surface directed to the object side. A second lens group of a negative meniscus lens, a stop, a third lens group having a positive refractive power as a whole, and a biconvex lens and a biconcave lens are bonded together. It is composed of a cemented lens and a fourth lens group having a positive refractive power as a whole.

The photographic lens of the first embodiment has a focal length of 36 mm and an F-number of 2.88. Example 1
The state of aberration at the object point at infinity is as shown in FIG. 5, the optical performance is extremely good up to the periphery of the screen, the total length is 50.2 mm, and the length from the first surface to the last surface of the lens system is This is a small photographing lens having a length Δd of 20.2 mm.

In the second embodiment, the configuration shown in FIG.
This is the same configuration as. In the second embodiment, the focal length is 36
This is a photographic lens with an mm and F number of 1.85.

In the second embodiment, FIG.
In the aberration situation shown in FIG. 7, the optical performance is extremely good up to the periphery of the screen, and the total length is 59.8 mm, Δd.
Is a small photographing lens of 35.1 mm.

In the third embodiment, the configuration shown in FIG.
A lens system having the same configuration as that of
The lens system has a number of 2.88.

In the third embodiment, the aberration at the object point at infinity is as shown in FIG. 7 and excellent optical performance is obtained up to the periphery of the screen, and the total length is 44.7 mm and Δd is 25. It is a small photographing lens of 3 mm.

The fourth embodiment is a lens system having the same configuration as that of the first embodiment, having a configuration as shown in FIG. 4 and having a focal length of 36 mm and an F-number of 1.44.

In the fourth embodiment, the aberration at the object point at infinity is as shown in FIG. 8 and the optical performance is good up to the periphery of the screen, and the total length is 60.0 mm and Δd is 36.
It is a small 1mm shooting lens.

The shape of the aspherical surface used in each of the embodiments is represented by the following equation, where x is the optical axis direction and y is the direction orthogonal to the optical axis.

X = y ² / [r + r ｛1− (y / r) ² ｝ ^1/2 ] + A ₄ y ⁴ + A ₆ y ⁶ + A ₈ y ⁸ + A ₁₀ y ¹⁰ +... Where r is an aspherical surface Radius of curvature on the optical axis of A ₄ , A ₆ ,
A ₈ , A ₁₀ ... Are aspherical coefficients.

[0039]

According to the present invention, an unprecedented high-performance and compact photographing lens can be realized by appropriately setting the lens configuration, the aperture, and the power distribution before and after.

[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 an aberration curve diagram according to the first embodiment of the present invention.

FIG. 6 is an aberration curve diagram according to the second embodiment of the present invention.

FIG. 7 is an aberration curve diagram according to the third embodiment of the present invention.

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

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B 13/18 G02B 9/60

Claims (12)

(57) [Claims] 1. A first lens having a positive refractive power in order from the object side.
A lens group, a second lens group having a negative refractive power, aperture and, a third lens group having positive refractive power, is more structure and a fourth lens group having positive refractive power, the third lens group
Is a cemented lens consisting of a biconcave lens and a biconvex lens
Wherein the fourth lens group is a biconvex lens and a biconcave lens.
The first lens consists of a cemented lens
A high-performance photographic lens that has a concave surface and a final lens surface and satisfies the following conditions: (1) 0.25 <f _R / f _F <1.3 (2) 1 <| r _a / r _b | <3.5 where f _F is the combined focal length of the lens group before the stop,
f _R is the composite focal length of the lens group after the stop, r _a Les
Lens curvature of the first surface radius, r _b is the radius of curvature <br/> of the last lens surface. 2. A first lens having a positive refractive power in order from the object side.
A first lens surface including a lens group, a second lens group having a negative refractive power, a stop, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. And the last lens surface are concave, and the first lens group is composed of one biconcave lens and one biconvex lens.
The lens group is constituted by one negative meniscus lens having a convex surface facing the object side, the third lens group is constituted by a cemented lens obtained by bonding a biconcave lens and a biconvex lens, and the fourth lens group is constituted by a biconvex lens A high-performance photographic lens that satisfies the following conditions: (1) 0.25 <f _R / f _F <1.3 where f _F is the combined focal length of the lens group before the stop,
f _R is the combined focal length of the lens group after the stop. 3. A first lens having a positive refractive power in order from the object side.
A first lens surface including a lens group, a second lens group having a negative refractive power, a stop, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. A high-performance photographic lens that satisfies the following conditions, with the concave surface of the lens and the final surface of the lens. (1-1) 0.4 <f _R / f _F <0.93 where f _F is the combined focal length of the lens group before the diaphragm,
f _R is the combined focal length of the lens group after the stop. 4. A first lens having a positive refractive power in order from the object side.
A first lens surface including a lens group, a second lens group having a negative refractive power, a stop, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. A high-performance photographic lens that satisfies the following conditions, with the concave surface of the lens and the final surface of the lens. (1) 0.25 <f _R / f _F <1.3 (2-1) 1.2 <| r _a / r _b | <3.4 where f _F is the combined focal point of the lens group before the stop. distance,
f _R is the composite focal length of the lens group after the stop, r _a is the radius of curvature of the first surface of the lens, is r _b is the radius of curvature of the last lens surface. 5. A first lens having a positive refractive power in order from the object side.
A first lens surface including a lens group, a second lens group having a negative refractive power, a stop, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. A high-performance photographic lens that satisfies the following conditions, with the concave surface of the lens and the final surface of the lens. _{(1) 0.25 <f R /} f F <1.3 (3-1) 1.7f <| f 2 | <4.0f However, f _F is the composite focal length of the front lens group from the diaphragm,
f _R is the combined focal length of the lens group after the stop, f is the focal length of the entire system, and f ₂ is the focal length of the second lens group. 6. A high-performance photographic lens according to claim 1, wherein said second lens group is constituted by a meniscus lens having a convex surface facing the object side. 7. The optical system according to claim 1, wherein a focal length f ₂ of said second lens group satisfies the following condition (3).
3, 4 or 6 high-performance photographic lenses. (3) 1.5f <| f ₂ | <4.5f where f is the focal length of the entire system. 8. The first lens group includes one biconcave lens and one lens.
The second lens group is constituted by one negative meniscus lens having a convex surface facing the object side, and the third lens group is constituted by bonding a biconcave lens and a biconvex lens. 6. The high-performance photographic lens according to claim 3, wherein said fourth lens group is constituted by a cemented lens in which a biconvex lens and a biconcave lens are bonded. 9. The first lens group is composed of one biconcave lens and one
2. The high-performance photographic lens according to claim 1, wherein said second lens group comprises a single negative meniscus lens having a convex surface facing the object side. 10. The first lens group comprises one biconcave lens and one biconvex lens, and the third lens group comprises a cemented lens in which a biconcave lens and a biconvex lens are bonded. 7. The high-performance photographic lens according to claim 6, wherein said fourth lens group is constituted by a cemented lens obtained by bonding a biconvex lens and a biconcave lens. 11. The method according to claim 1, wherein the aperture ratio is from F / 1.4 to F / 2.8.
7, 8, 9 or 10 high-performance photographic lenses. 12. The method according to claim 1, wherein the angle of view is from 60 ° to 75 °.
10 or 11 high-performance photographic lenses.