JP2001141991A - Shooting lens - Google Patents

Abstract

(57) [Problem] To provide a telecentric photographing lens having good optical performance with a small and simple lens configuration. In order from the object side, a first group consisting of a meniscus-shaped negative lens with a concave surface facing the image side, a second group consisting of a positive lens, and a third group consisting of a cemented lens in which a negative lens and a positive lens are cemented. A photographic lens having an aperture stop between the first and second groups, or between the second and third groups, and a fourth lens unit including a positive lens and a fourth lens unit. A first group focal length f1, a fourth group focal length f4,
The focal length f12 of the combined system composed of the first and second groups is set appropriately.

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 digital still camera, a video camera, a broadcast camera, a photographic camera, and the like.

[0002]

2. Description of the Related Art In recent years, digital still cameras have become widespread as image input devices for computers. In this digital still camera, processing is generally performed in which an output signal from a solid-state imaging device such as a CCD is A / D converted to image data, which is subjected to compression processing such as JPEG and recorded on a recording medium such as a flash memory. . The compressed data thus recorded is decompressed on a computer and then displayed on a monitor or the like.

[0003] In such a digital still camera, there has been an issue of improving the definition of a photographed image and miniaturizing the apparatus, and a photographing system used for the camera is required to have both high resolution and downsizing. In particular, in order to make a thin camera with an emphasis on portability, the photographing system is required to reduce the overall length (the length from the first lens surface to the image surface). In order to shorten the overall length, it is advantageous to use a taking lens having as few constituent lenses as possible.

[0004] Further, as a photographing lens having a long back focus, many retrofocus photographing lenses comprising a front group having a negative refractive power and a rear group having a positive refractive power are known. Particularly, as a retrofocus type photographing lens having a small number of constituent lenses, a lens in which the front group is constituted by one negative lens has been proposed.

As described above, USP (US Pat. No. 5,418,649) discloses a retrofocus type photographing lens in which the front group is composed of one negative lens, and includes a negative lens, a positive lens, and a positive lens in order from the object side. USP in 3 groups
In another embodiment of Japanese Patent No. 5,418,649, a negative lens, a positive lens, and a positive cemented lens are sequentially arranged in three groups from the object side. Japanese Patent Publication No. 5-37288 discloses a four-group four-lens configuration of a positive lens, a positive lens, a negative lens, and a positive lens in order from the object side. Japanese Patent Publication No. 20724 discloses a four-lens configuration including a negative lens, a positive lens, a positive lens, and a negative lens in order from the object side. Japanese Patent Publication No. 61-46807 discloses a negative lens, a positive lens, and a positive lens in order from the object side. Japanese Patent Publication No. 58-7 / 1983, Japanese Patent Application Laid-Open No. HEI 9-189, discloses a configuration in which a positive cemented lens has four groups and five elements.
No. 856 discloses a negative lens, a positive lens,
USP is composed of 5 elements, 4 groups of negative cemented lens and positive lens
No. 4,146,304 describes a four-group, five-lens configuration of a negative lens, a positive lens, a positive cemented lens, and a positive lens in order from the object side.
U.S. Pat. No. 4,674,844 discloses a four-group, five-lens configuration consisting of a negative lens, a positive lens, a positive cemented lens, and a negative lens in order from the object side. A five-group, five-lens configuration of a lens, a negative lens, a positive lens, and a positive lens is disclosed, respectively.

[0006] All of the photographing lenses proposed here are of the retrofocus type, in which the first lens is composed of a front group having a negative refractive power, and the second and subsequent lenses are composed of a rear group having a positive refractive power.

[0007]

In an imaging system using a solid-state image sensor, if the distance from the image plane to the exit pupil is short, the angle of incidence of off-axis rays (off-axis principal rays) on the light receiving surface increases. And problems such as shading occur. Therefore, the imaging lens used for such a solid-state imaging device is preferably a telecentric optical system in which the exit pupil is sufficiently separated from the image plane.

Specifically, the photographing lens is configured such that an off-axis principal ray of light incident at an angle corresponding to the optical axis and the angle of view is substantially parallel to the optical axis and reaches the image plane. Good to be. As the angle of view becomes wider, the refractive power required to bend the off-axis principal ray until it becomes parallel to the optical axis increases.

Generally, the angle of the off-axis principal ray with the optical axis is reduced by the negative refractive power on the object side of the stop and the positive refractive power on the image plane side of the stop. There is.

Therefore, in a retrofocus type photographing lens, since a front group having a negative refractive power is generally disposed on the object side of the stop, the angle formed by the front group with the optical axis of the off-axis chief ray. Can be smaller. In the rear group having a positive refracting power, the angle of the off-axis principal ray with the optical axis can be reduced by the positive lens on the image surface side of the stop. Therefore, both the front group with negative refractive power and the rear group with positive refractive power have the effect of separating the exit pupil from the image plane. If a telecentric exit pupil and a long back focus are required, retro-focus as a taking lens It is effective when it is a type.

Further, in order to shorten the overall length and sufficiently separate the exit pupil from the image plane, it is necessary that at least the last lens in the rear group is a positive lens. More preferably, the surface on the image plane side of the lens immediately before the final lens is convex toward the image plane. In this way, the function of bending the off-axis principal ray can be shared by the three lens surfaces including the final lens, so that the refractive power of the final lens does not need to be extremely high.
If the refractive power of the final lens is too strong, barrel-shaped distortion and astigmatism occur, which is not good.

As described above, in order to shorten the overall length and make it a telecentric photographing lens, the whole system is of a retrofocus type, the front group having a negative refractive power is only the first lens, and the last lens is the rear group having a positive refractive power. It is effective to make a positive lens,
Preferably, the lens surface on the image plane side of the lens immediately before the last lens is convex toward the image plane.

Further, in order to improve the flatness of the image plane, it is necessary to reduce the Petzval sum to some extent.
If there is no negative refractive power in the rear group, it is necessary to considerably increase the negative refractive power of the first lens of the front group to reduce the Petzval sum. When the negative refractive power of the first lens is increased in this manner, a very large barrel-shaped distortion occurs as a result. Large distortion is undesirable in a general camera including a digital still camera. When the rear group has a negative refractive power, the Petzval term in the rear group can be controlled to some extent. Since the Petzval term of the front group composed of one lens is not corrected in the group, the Petzval term of the rear group may be set so as to correct the front group. Therefore, in order to obtain good image surface characteristics, it is preferable that the rear group includes at least one concave lens (negative lens) or one group of cemented lenses having negative refractive power.

The above-mentioned Japanese Patent Publication No. 5-20724 and U.S. Pat.
In the lens configuration of SP 4,674,844, since the final lens is not a positive lens, there is a problem that the exit pupil cannot be sufficiently separated from the image plane when the back focus is shortened.

In the configuration of US Pat. No. 5,418,649 with three groups and three lenses, and in the configuration of Japanese Patent Publication No. Hei 7-122692, since the rear lens group has no concave lens (negative lens), the Petzval sum is reduced while the exit pupil is moved from the image plane. There is a problem that they cannot be separated sufficiently.

US Pat. No. 5,418,649, 3 groups, 4 elements, Japanese Patent Publication No. 61-46807, US Pat.
No. 6,304 has a negative lens in the rear group,
This constitutes a positive cemented lens. Although this negative lens is effective for chromatic aberration, it has a problem that the exit pupil is not sufficiently separated from the image plane while reducing the Petzval sum.

In Japanese Patent Publication No. 5-37288, the rear group has an independent negative lens. However, the negative lens is a lens immediately before the final lens, and the lens surface on the image plane side is concave, so that the exit pupil cannot be sufficiently separated from the image plane unless the refractive power of the final lens is considerably increased. Tokuhei 5
In the configuration of JP-A-37288, the refractive power of the final lens is not so strong as to sufficiently separate the exit pupil from the image plane. Further, if the refractive power of the final lens is extremely increased in order to sufficiently separate the exit pupil from the image plane, barrel distortion and astigmatism occur, which is not preferable. Also in the configuration of Japanese Patent Publication No. 58-7, the negative cemented lens located immediately before the final lens has a meniscus shape having a strong concave surface on the image surface side, and has the same problem.

The configuration disclosed in Japanese Patent Publication No. 60-32165 does not have these problems. However, there is a problem that the air gap between the third negative lens and the fourth positive lens has high sensitivity to each aberration. In particular, since the signs of the sensitivity to spherical aberration and curvature of field are different, if the air gap deviates from the design value, the center of the screen and the best focus position around the screen in the optical axis direction are opposite to the design best focus plane. Shift. As a result, curvature of field occurs, and when the image is focused on the center of the screen, the resolution becomes insufficient around the screen. In order to prevent this, it is necessary to control the tolerance for the air gap very strictly in manufacturing, which is not good because it leads to an increase in manufacturing cost.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a photographic lens which has a short overall length, sufficiently separates an exit pupil from an image plane, and has good optical performance.

[0020]

According to a first aspect of the present invention, there is provided a photographic lens comprising, in order from the object side, a first group consisting of a meniscus-shaped negative lens having a concave surface facing the image side, and a second group consisting of a positive lens.
A third group consisting of a cemented lens in which a negative lens and a positive lens are cemented, and a fourth group consisting of a positive lens, between the first group and the second group, or between the second group and the third group In a taking lens having an aperture stop between the focal lengths of the entire system, f is the focal length of the first group, f1 is the focal length of the first group, and f is the focal length of the fourth group.
4. The focal length of the combined system consisting of the first and second groups is f12
0.6 <| f1 | / f <3.5 {(1) 0.6 <f4 / f <4.0} (2) 2.5 <f12 / f <20. 0 ‥‥‥ (3).

According to a second aspect of the present invention, in the first aspect of the present invention, in the fourth group, when ri is a radius of curvature of the i-th surface, -0.1 <(r9 + r10) / (r9-r10) <0 .1 ‥‥‥ (4).

According to a third aspect of the present invention, when the distance from the aperture stop to the last lens surface of the fourth unit is DiL, 0.1 <DiL / f <1.4.条件 (5) is satisfied.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the positive lens of the second group has a meniscus shape having a convex surface facing the object side, and the cemented lens of the third group has both lens surfaces concave. The negative lens and both lens surfaces are composed of convex positive lenses, and the positive lens of the fourth group is characterized in that both lens surfaces are composed of convex shapes.

According to a fifth aspect of the present invention, in the first aspect of the invention, the positive lens of the second group has a meniscus shape in which both lens surfaces have a convex surface, and the cemented lens of the third group has a convex surface facing the object side. And the fourth lens unit is characterized in that both lens surfaces have a convex shape.

[0025]

FIG. 1, FIG. 3, FIG. 5, FIG. 7, and FIG. 9 are lens cross-sectional views of Numerical Examples 1 to 5 of the present invention, respectively. FIGS. 2, 4, 6, 8, and 10 are aberration diagrams of Numerical Examples 1 to 5, which will be described later, of the present invention.

In the sectional view of the lens, reference numeral 101 denotes a front group having a negative refractive power, and reference numeral 102 denotes a rear group having a positive refractive power. 103 is a first group having a negative refractive power, 104 is a second group having a positive refractive power, 1
Reference numeral 05 denotes a third lens unit including a negative lens and a positive lens and having a negative refractive power as a whole. Reference numeral 106 denotes a fourth lens unit having a positive refractive power.
Reference numeral 7 denotes a filter group including a quartz low-pass filter, an infrared cut filter, and the like, and reference numeral 108 denotes an imaging plane. S
P is an aperture stop.

The photographic lens of the present invention has, in order from the object side, a retrofocus type configuration including a front group 101 having a negative refractive power and a rear group 102 having a positive refractive power. The group 101 includes only a meniscus negative lens 103 having a concave surface facing the image surface side, and the positive rear group 102 has a meniscus positive lens having a convex surface facing the object side in order from the object side or a positive lens having both lens surfaces convex. 104, a cemented lens in which a negative lens with both lens surfaces concave and a positive lens with both lens surfaces convex or a meniscus-shaped negative lens with a convex surface facing the object side and a positive lens with both lens surfaces convex A cemented lens 105 and a positive lens 106 with both lens surfaces convex are provided, and the entire system is composed of four groups and five lenses.

By satisfying the above-mentioned conditional expressions (1) to (3), the exit pupil is kept away from the image plane, and high optical performance is obtained while maintaining good telecentricity.

Next, the technical meaning of the above conditional expression will be described.

Conditional expression (1) defines the focal length of the first lens unit, that is, the refractive power.

When the refractive power is weakened beyond the upper limit, the effect of moving the exit pupil away from the image plane in the first lens unit is weakened. If the exit pupil is moved away from the image plane with the refractive power of the rear group to compensate for this, the refractive power of the convex surface in the rear group must be increased, and the Petzval sum cannot be reduced, and the field curvature Is not good because it occurs. Further, if the exit pupil is moved away from the image plane without increasing the refracting power of the rear unit, the overall length becomes long, which makes it difficult to apply the present invention to a compact camera.

When the refractive power exceeds the lower limit, the first
Distortion and astigmatism are excessively generated in the group, and it is difficult to correct even if an aspherical surface is used. In addition, the back focus becomes long, and it becomes difficult to shorten the entire optical length.

Conditional expression (2) defines the focal length of the fourth lens group, that is, the refractive power.

If the refractive power is weakened beyond the upper limit, the exit pupil cannot be sufficiently separated from the image plane, which is not good.
If the refractive power is increased below the lower limit, excessive distortion, curvature of field, and astigmatism will occur in the fourth lens unit, and it will be difficult to correct even if an aspherical surface is used.

Conditional expression (3) is an expression that defines the focal length, that is, the refracting power of the combined system composed of the first and second groups.

When the refractive power is weakened beyond the upper limit, the back focus becomes long, and it becomes difficult to shorten the entire optical length. If the refractive power is increased beyond the lower limit, it becomes difficult to suppress the occurrence of various aberrations and obtain good optical performance. In particular, excessive spherical aberration occurs, and it becomes difficult to correct even if an aspherical surface is used.

In the photographic lens of the present invention, high optical performance is obtained over the entire screen by the above configuration, but it is more preferable to satisfy at least one of the following configurations.

(A-1) In the fourth group, when ri is the radius of curvature of the i-th surface, -0.1 <(r9 + r10) / (r9-r10) <0.1 (4) Is to satisfy the conditional expression.

Conditional expression (4) restricts the shape of the lens component of the fourth group, in which both lens surfaces of the rear group disposed closest to the image plane are convex, and maintains the telecentricity of the emission error. This is a condition for favorably correcting each aberration.

When this value is set to “0” or a value near “0”, the lens surfaces on the object side and the image side have substantially the same curvature. improves.

(A-2) When the distance from the aperture stop to the last lens surface of the fourth group is DiL, the following conditional expression is satisfied: 0.1 <DiL / f <1.4１ (5) To be satisfied.

Conditional expression (5) defines the distance from the aperture stop to the vertex of the lens surface closest to the image plane of the taking lens.

In the lens system of the present invention, the focal length for the image size is extremely small. In such a photographing lens, the condition for further improving the balance between the size and the assemblability and the design freedom and the lens barrel design is determined by the conditional expression (5).
It is. If the lower limit is exceeded, the lens system and the air gap become too small, making it difficult to design and assemble the lens barrel, which is not desirable. If the upper limit is exceeded, the size of the optical system becomes large, which is not desirable.

(A-3) The positive lens of the second group has a meniscus shape with the convex surface facing the object side, and the cemented lens of the third group has a negative lens with concave both lens surfaces and a convex lens with both lens surfaces. The positive lens of the fourth group is characterized in that both lens surfaces have a convex shape.

(A-4) The positive lens of the second group has both lens surfaces formed of convex surfaces, and the cemented lens of the third group has a negative meniscus lens whose convex surface faces the object side and both lens surfaces. The fourth group is composed of a positive lens having a convex surface, and the fourth lens group is configured such that both lens surfaces have a convex shape.

Next, features of the photographic lens according to the present invention other than the above-described configuration will be described.

In order to sufficiently separate the exit pupil from the image plane, the whole system is preferably of a retrofocus type. In order to shorten the overall length, it is preferable to minimize the number of lenses. In the taking lens of the present invention, the front lens group includes one negative lens, and the rear lens group includes the last lens as a positive lens. . Also, in order to keep the exit pupil away from the image plane without extremely increasing the refractive power of the final lens, the negative cemented lens, which is the lens immediately before the final lens, has a convex lens surface on the image surface side.

Further, a negative cemented lens is arranged in the rear group in order to improve image surface characteristics. Since the front group has one lens, no correction is made for the Petzval sum in the lens group. Therefore, by setting a negative refractive power in the rear group, the front group and the rear group are canceled and the Petzval sum is reduced in the entire system.

The third lens and the fourth lens are bonded to each other to form a cemented lens, as compared with a photographic lens having a five-group, five-lens structure consisting of a negative lens, a positive lens, a negative lens, a positive lens, and a positive lens in order from the object side. In the five-group five-lens configuration, there is no air gap with high sensitivity to eccentricity of the photographing lens. Therefore, there is an advantage that the imaging performance is hardly deteriorated due to a manufacturing error, an assembly error and the like throughout the entire system.

The photographic lens of the present invention comprises a first group 103
Between the second group 104 or the second group 104 and the third group 1
The aperture SP is provided between 05. In order to keep the exit pupil away from the image plane, it is preferable that the front group of the retrofocus type be disposed closer to the object side than the diaphragm.
It is located closer to the image plane than the group. If a stop is arranged between the third and fourth lens units, the refractive power of the fourth lens unit is excessively increased in order to keep the exit pupil away from the image plane while shortening the overall length, so that the Petzval sum cannot be reduced. Therefore, in order to achieve both the reduction of the overall length and the exit pupil, it is preferable that the stop be between the first and second units or between the second and third units.

The first lens 103 is preferably a meniscus lens having a concave surface on the image side. To move the exit pupil away from the image plane, the first lens needs to have a function of bending the off-axis principal ray to some extent. Therefore, the first lens needs a certain refractive power, but as a result, barrel-shaped distortion tends to occur in the first lens. In order to minimize the occurrence of the distortion, it is effective to minimize the angle at which the principal ray of the off-axis light beam enters the lens surface.
For example, if the radius of curvature is concentric, the incident angle of the off-axis ray can be set to 0, but this cannot have a certain negative refractive power as described above. Therefore, in the taking lens of the present invention, the lens surface on the object side has a large radius of curvature and the surface on the image surface side has a small radius of curvature with respect to the concentric shape to enhance the refractive power, but has a strong concave surface on the image surface side. The generation of distortion is minimized by maintaining the meniscus shape. Then, aberration correction is performed in the rear group so as to cancel this.

In the photographic lens of the present invention, it is preferable to use an aspheric surface for the fourth lens group 106, which is the final lens. With this configuration, the overall length can be further shortened and good imaging performance can be obtained.

In order to shorten the overall length by sufficiently separating the exit pupil from the image plane while maintaining good optical performance with the four-group, five-element configuration, it is necessary to increase the refractive power of the final lens. At this time, barrel-shaped distortion and under-surface field curvature occur. To correct these aberrations, it is preferable to use an aspherical surface for the final lens. According to this, while correcting various aberrations, it is possible to further reduce the overall length as compared with the configuration using only a spherical lens.

When an aspherical surface is set for the final lens, it is more effective to correct barrel-shaped distortion if the converging function (positive refractive power) is weakened from the optical axis toward the periphery. This is such a shape that the curvature becomes loose on the convex surface. In this way, both the curvature of the lens surface and the angle of incidence of the light rays serve to weaken the bending with respect to off-axis rays, thereby correcting barrel distortion.

Further, since the imaging effect is weakened for an off-axis light beam, there is a direction in which the under field curvature is corrected. Therefore, in the taking lens of the present invention, it is preferable to use such an aspherical surface as the final lens. According to this, it is possible to satisfactorily correct both distortion and field curvature while shortening the overall length. Although the refractive power of the periphery is relatively weakened with respect to the vicinity of the optical axis due to the aspherical shape, the refractive power of the fourth lens unit itself is increased by the introduction of the aspherical surface, so that the exit pupil remains sufficiently difficult from the image plane. Aberration correction is possible.

Further, in the taking lens of the present invention, it is preferable to use an aspheric surface for the second group. According to this, even when the overall length is shortened, it is possible to realize better imaging performance. After the off-axis light beam is bent by the first group, the principal ray enters the second group at an angle with the optical axis. At this time, coma aberration occurs unless the lens surface of the second group has a concentric curvature.

Therefore, coma can be reduced by setting the object side lens surface of the second lens unit to have a relatively small radius of curvature. In the axial light flux, an excessive spherical aberration occurs on the concave surface on the image side of the first group. If the second object side lens surface is made convex, an under spherical aberration occurs, and the first
Spherical aberration generated in the group can be corrected.

However, if the curvature of the object-side lens surface of the second lens unit is made too tight for wide-angle correction of coma aberration, the second lens unit will generate an undesirably low spherical aberration. An excessive spherical aberration occurs in the concave surface of the third lens unit, but if the degree of under light in the second lens unit is large, it cannot be corrected completely and the whole system is insufficiently corrected.

Therefore, by setting an aspherical surface in the second lens unit such that the convergence function is weakened from the optical axis toward the periphery, the under spherical aberration is corrected well. Since the on-axis land ray is bent at a position away from the optical axis on any surface of the second group, an aspheric surface for correcting spherical aberration is effective on any lens surface of the second group.

To make the angle of view wider,
It is effective to use an aspheric surface for the first group 103 in addition to the group 106.

For a given total length, it is necessary to increase the refractive power of the first group as the angle of view becomes wider. In the first lens unit, barrel distortion occurs, but if the refractive power is too strong, correction will be insufficient even if an aspherical surface is used in the fourth lens unit. In such a case, if an aspherical surface is used for the first lens unit, distortion can be corrected while using a wider-angle imaging lens.

As described above, the first group is a meniscus lens having a negative refractive power with respect to a concentric shape. Therefore, on the lens surface of the first group, the principal ray is bent at a larger incident angle as the off-axis light flux. In order to correct barrel-shaped distortion, it is preferable to use an aspherical surface such that the divergence gradually decreases from the optical axis toward the periphery. That is, the first lens unit has an aspheric surface having a sharp curvature from the optical axis toward the periphery of the lens surface on the object side, and the curvature of the lens surface on the image plane side decreases gradually from the optical axis toward the periphery. It is preferable to use a non-spherical shape.

Next, numerical examples of the present invention will be described. In the numerical examples, Ri is the radius of curvature of the i-th surface from the object side,
Di is the i-th and (i + 1) -th intervals in order from the object side,
Ni and νi are the refractive index and Abbe number of the i-th optical member in order from the object side. Table 1 shows the value of each conditional expression in each numerical example. [Numerical Example 1] f = 15.82748 fno = 1: 2.8 2ω = 21.9 ° R 1 = 17.260 D 1 = 1.10 N 1 = 1.61018 ν 1 = 48.3 R 2 = 5.859 D 2 = 1.13 R 3 = 5.970 D 3 = 1.71 N 2 = 1.84663 ν 2 = 23.8 R 4 = 10.809 D 4 = 1.69 R 5 = (Aperture) D 5 = 2.60 R 6 = -7.336 D 6 = 1.50 N 3 = 1.84580 ν 3 = 24.4 R 7 = 8.139 D 7 = 4.02 N 4 = 1.51783 ν 4 = 56.2 R 8 = -8.778 D 8 = 0.20 R 9 = 21.265 D 9 = 2.51 N 5 = 1.84243 ν 5 = 43.3 R10 = -17.813 D10 = 0.80 R11 = ∞ D11 = 3.10 N 6 = 1.51633 ν 6 = 64.1 R12 = ∞ [Numerical Example 2] f = 15.77070 fno = 1: 2.8 2ω = 22.0 ° R 1 = 30.104 D 1 = 1.10 N 1 = 1.68010 ν 1 = 53.9 R 2 = 6.091 D 2 = 0.67 R 3 = 6.164 D 3 = 1.81 N 2 = 1.78999 ν 2 = 25.6 R 4 = 20.526 D 4 = 1.45 R 5 = (Aperture) D 5 = 2.60 R 6 = -7.408 D 6 = 1.50 N 3 = 1.84459 ν 3 = 23.8 R 7 = 8.572 D 7 = 4.74 N 4 = 1.54098 ν 4 = 61.5 R 8 = -9.251 D 8 = 0.20 R 9 = 23.249 D 9 = 2.44 N 5 = 1.87140 ν 5 = 41.4 R10 = -21.355 D10 = 0.80 R11 = ∞ D11 = 3.10 N 6 = 1.51633 ν 6 = 64.1 R12 = ∞ [Numerical Example 3] f = 15.86706 fno = 1: 2.8 2ω = 22.0 ° R 1 = 7.749 D 1 = 1.10 N 1 = 1.52919 ν 1 = 55.9 R 2 = 5.699 D 2 = 1.37 R 3 = 5.734 D 3 = 1.35 N 2 = 1.84181 ν 2 = 24.0 R 4 = 6.622 D 4 = 3.13 R 5 = (aperture) D 5 = 2.60 R 6 = -7.173 D 6 = 1.50 N 3 = 1.83222 ν 3 = 24.9 R 7 = 8.146 D 7 = 3.66 N 4 = 1.54262 ν 4 = 52.0 R 8 = -9.148 D 8 = 0.20 R 9 = 20.300 D 9 = 2.46 N 5 = 1.88253 ν 5 = 40.8 R10 =- 17.628 D10 = 0.80 R11 = ∞ D11 = 3.10 N 6 = 1.51633 ν 6 = 64.1 R12 = ∞ [Numerical Example 4] f = 15.83969 fno = 1: 2.8 2ω = 22.0 ° R 1 = 14.526 D 1 = 1.10 N 1 = 1.76449 ν 1 = 39.6 R 2 = 6.335 D 2 = 1.17 R 3 = 5.959 D 3 = 1.70 N 2 = 1.84663 ν 2 = 23.8 R 4 = 11.803 D 4 = 1.61 R 5 = (Aperture) D 5 = 2.60 R 6 = -6.766 D 6 = 1.50 N 3 = 1.84899 ν 3 = 24.5 R 7 = 7.858 D 7 = 3.95 N 4 = 1.52295 ν 4 = 57.7 R 8 = -8.474 D 8 = 0.20 R 9 = 20.011 D 9 = 2.43 N 5 = 1.87649 ν 5 = 41.2 R10 = -19.698 D10 = 0.80 R11 = ∞ D11 = 3.10 N 6 = 1.51633 ν 6 = 64.1 R12 = ∞ [Numerical example 5] f = 16.13156 fno = 1: 2.8 2ω = 21.3 ° R 1 = 104.650 D 1 = 1.10 N 1 = 1.87903 ν 1 = 37.7 R 2 = 8.875 D 2 = 3.01 R 3 = 15.623 D 3 = 1.58 N 2 = 1.79405 ν 2 = 30.9 R 4 = -35.169 D 4 = 1.61 R 5 = ( Aperture) D 5 = 6.42 R 6 = 68.464 D 6 = 1.50 N 3 = 1.85922 ν 3 = 27.7 R 7 = 8.722 D 7 = 2.17 N 4 = 1.68052 ν 4 = 56.3 R 8 = -15.011 D 8 = 10.65 R 9 = 101.004 D 9 = 1.74 N 5 = 1.83730 ν 5 = 44.0 R10 = -101.004 D10 = 0.80 R11 = ∞ D11 = 3.10 N 6 = 1.51633 ν 6 = 64.1 R12 = ∞

[0064]

[Table 1]

[0065]

According to the present invention, by specifying each element as described above, it is possible to achieve a photographic lens which shortens the overall length, sufficiently separates the exit pupil from the image plane, and has good optical performance. Can be.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lens according to a numerical example 1 of the present invention.

FIG. 2 is an aberration diagram of a numerical example 1 of the present invention.

FIG. 3 is a sectional view of a lens according to a numerical example 2 of the present invention.

FIG. 4 is an aberration diagram of a numerical example 2 of the present invention.

FIG. 5 is a sectional view of a lens according to a numerical example 3 of the present invention.

FIG. 6 is an aberration diagram of a numerical example 3 of the present invention.

FIG. 7 is a sectional view of a lens according to a numerical example 4 of the present invention.

FIG. 8 is an aberration diagram of a numerical example 4 of the present invention.

FIG. 9 is a sectional view of a lens according to a numerical example 5 of the present invention.

FIG. 10 is an aberration diagram of a numerical example 5 of the present invention.

[Explanation of symbols]

 101 front group 102 rear group 103 first group 104 second group 105 third group 106 fourth group 107 glass block IP image plane SP stop d d-line g g-line ΔS sagittal image plane ΔM meridional image plane

Claims (5)

[Claims] 1. A first group consisting of a meniscus negative lens having a concave surface facing the image side, a second group consisting of a positive lens, and a second group consisting of a cemented lens in which a negative lens and a positive lens are cemented in order from the object side. In a photographing lens having three groups and a fourth group including a positive lens, and having an aperture stop between the first and second groups or between the second and third groups, f, the focal length of the first lens unit is f1, the focal length of the fourth lens unit is f4, and the focal length of the composite system including the first lens unit and the second lens unit is f.
12, the following conditional expression is satisfied: 0.6 <| f1 | / f <3.5 0.6 <f4 / f <4.0 2.5 <f12 / f <20.0 Shooting lens. 2. In the fourth lens unit, when ri is the radius of curvature of the i-th surface, −0.1 <(r9 + r10) / (r9−r10) <0.
The photographing lens according to claim 1, wherein the following conditional expression is satisfied. 3. A conditional expression 0.1 <DiL / f <1.4 when a distance from the aperture stop to the last lens surface of the fourth group is DiL. 1 or 2 taking lens. 4. The positive lens of the second group has a meniscus shape with the convex surface facing the object side, and the cemented lens of the third group has a negative lens with both lens surfaces concave and a positive lens with both lens surfaces convex. 2. The photographic lens according to claim 1, wherein said positive lens of said fourth group has both lens surfaces formed in a convex shape. 5. The positive lens of the second group has both lens surfaces formed of convex surfaces, and the cemented lens of the third group has a meniscus negative lens whose convex surface faces the object side and a positive lens whose both lens surfaces are convex. 2. The photographic lens according to claim 1, wherein said fourth lens unit comprises a lens, and both lens surfaces of said fourth lens unit have a convex shape.