JP2002303789A - Photographing lens and optical equipment using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a retrofocus type photographic lens suitable for a video camera and a digital camera or the like by which high optical performance is easily obtained, and to provide optical equipment using it. SOLUTION: This lens consists of the first meniscus lens of negative refracting power whose convex surface faces an object side, the second meniscus lens of positive refracting power whose convex surface faces an image surface side, a diaphragm, the third lens of the positive refracting power, the fourth lens of the negative refracting power whose both lens surfaces are concave surfaces and the fifth lens of the positive refracting power in order from the object side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photographic lens and an optical apparatus using the same, and is used for, for example, a film camera, a digital camera, a video camera, and an image input device. The present invention relates to a bright photographing lens which is compact as a whole and has little distortion and an optical apparatus using the same.

[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 into 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 expanded on a computer and then displayed on a monitor or the like.

[0003] In such digital still cameras, there is a need to improve the definition of photographed images and reduce the size of the apparatus, and a photographing system is required to have a wide angle of view, high resolution, and downsizing.

For example, a photographing system is required to have a small image distortion (distortion) and a large amount of peripheral light, and to have a short overall lens length for a thin digital camera with emphasis on portability.

Conventionally, a retrofocus type photographic lens composed of a front group having a negative refractive power and a rear group having a positive refractive power has been known as a photographic lens which can easily widen the angle of view. JP-A-54-139725 and JP-A-54-8
No. 9630, for example.

In addition, as a retrofocus type photographing lens, for example, Japanese Patent Publication No. 61-46807 discloses a negative lens, a positive lens, a positive lens, and a positive cemented lens in which a positive lens and a negative lens are cemented in order from the object side. No. 58-7, JP-A-9-1898.
No. 56,146,30 discloses a negative lens, a positive lens, a negative cemented lens in which a negative lens and a positive lens are cemented, and a four-group, five-lens structure including a positive lens.
Reference numeral 4 designates a lens configuration of a negative lens, a positive lens, a positive cemented lens obtained by cementing a positive lens and a negative lens, and a positive lens in four groups in that order from the object side, and USP 4,674,844, in order from the object side. Japanese Patent Publication No. Sho 60-32165 discloses a negative lens, a positive lens in order from the object side, including a negative lens, a positive lens, a positive cemented lens obtained by cementing a positive lens and a negative lens, and a negative lens in four groups. , A negative lens, a positive lens, and a positive lens are disclosed.

[0007]

A retrofocus type photographing lens has a strong concave lens (negative lens) on the object side, and is particularly used for a long back focus photographing lens having a pentaprism on the image plane side. I have.

Since this type of photographing lens is asymmetric with respect to the diaphragm, various types of aberrations are generated and distortion is particularly large. In addition, as described above, the back focus is long, and the entire lens system tends to be larger than the focal length of the entire system.

In a photographing lens using a solid-state image pickup device such as a CCD, if an incident light beam does not enter the peripheral pixels of the screen almost perpendicularly, a shade called shading appears in an image. Need to be close to telecentric to the CCD. However, many conventional retrofocus type photographing lenses tend to have a shorter exit pupil with respect to the image size.

Japanese Patent Application Laid-Open No. Hei 7-218825 discloses a photographic lens having a configuration similar to a retrofocus type, but has a positive refractive power on the object side of the aperture and a positive refractive power on the image side of the aperture. Therefore, widening of the angle is not sufficient, the overall length of the lens is long, and the number of lenses to be configured is large.

A photographic lens having a wide angle of view and a small number of lenses is disclosed in Japanese Patent Application Laid-Open No. 52-33526.
JP-A-58-142512, JP-A-58-179
808, JP-A-62-78520, JP-A-5-203871, and the like.
The number is lower than 2.8 and the brightness is not enough. Also, JP-A-63-81414, JP-A-3-636
No. 13 discloses a relatively bright photographing lens, but the wide angle of view is not sufficient. JP-A-1-26521
Japanese Patent Laid-Open No. 6 discloses a photographing lens that is bright and has a wide angle of view, but tends to increase distortion.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a photographic lens having a simple lens configuration, a wide angle of view, a bright angle, a small size, little generation of distortion and high optical performance, and an optical apparatus using the same. .

[0013]

According to a first aspect of the present invention, there is provided a photographic lens having a meniscus first lens having a negative refractive power with a convex surface facing the object side and a convex surface facing the image surface, in order from the object side. A meniscus-shaped second lens having a positive refractive power, an aperture, a third lens having a positive refractive power, both lens surfaces being a concave fourth lens having a negative refractive power, and a fifth lens having a positive refractive power. Features.

According to a second aspect of the present invention, in the first aspect of the invention, the combined focal length of the lens disposed on the object side of the stop is negative, and the combined focal length of the lens disposed on the image side of the stop is positive. It is characterized by.

According to a third aspect of the present invention, in the first or second aspect, the combined focal length of the first lens and the second lens is F.
f, when the combined focal length of the third lens, the fourth lens, and the fifth lens is Fr, a conditional expression of -300 <Ff / Fr <-1.0 is satisfied.

According to a fourth aspect of the present invention, when the focal lengths of the first lens and the second lens are f1 and f2 in the first, second, and third aspects, respectively, -0.6 <f1 / f2 <-0. .2 are satisfied.

The invention of claim 5 is the invention of claim 1, 2, 3, or 4.
The present invention is characterized in that, when the distance between the first lens and the second lens is L12 and the focal length of the entire system is F, the condition 0.5 <L12 / F <1.3 is satisfied.

According to a sixth aspect of the present invention, the distance from the object-side surface of the third lens to the image surface is G3i (the image surface side of the fifth lens is a CCD).
If there is a small crystal low-pass filter, cover glass, etc., when these lengths are added to the air equivalent length),
When the focal length of the entire system is F, the condition of 2.5 <G3i / F <3.3 is satisfied.

According to a seventh aspect of the present invention, there is provided an optical apparatus including the photographing lens according to any one of the first to sixth aspects.

[0020]

FIG. 1, FIG. 3, FIG. 5, FIG. 7, and FIG. 9 are lens cross-sectional views of Numerical Examples 1 to 5, which will be described later. 2, 4, 6, 8, and 10 show a numerical example 1 described later.
FIG.

The retrofocus type photographing lens of this embodiment has five lenses as a whole. L1-L
Reference numeral 5 denotes first to fifth lenses. SP is aperture, G is glass block such as optical filter and cover glass, IP
Is the image plane.

The retrofocus type photographing lens of this embodiment has a meniscus first lens L1 having a negative refractive power whose convex surface faces the object side in order from the object side, and a meniscus positive positive lens having a convex surface facing the image side. Second lens L2 of refractive power, stop S
P, a third lens L3 having a positive refractive power with both lens surfaces being convex,
Both lens surfaces are constituted by a concave fourth lens L4 having a negative refractive power, and both lens surfaces are constituted by a fifth lens L5 having a convex positive refractive power.

In general, in a retrofocus type photographing lens, the direction of the distortion generated by the first lens is the same as the direction of the distortion generated in the rear group on the image plane side of the stop, so that the entire lens system is very large. Distortion occurs. For this reason, in the present embodiment, the distortion generated by the first lens is favorably corrected as a meniscus-shaped lens having a positive refractive power with the convex surface facing the image surface side of the second lens in front of the stop. That is, the first lens and the second lens are respectively assigned to correct the correction of the occurrence of distortion, whereby the distortion is appropriately corrected in the entire system.

In the present embodiment, the second lens is formed in a meniscus shape with the convex surface facing the image surface side, so that it is easy to reduce the number of lenses and to downsize the entire lens system.

According to the present embodiment, by setting each element as described above, a retrofocus having a simple lens configuration, a wide angle of view, a small size, little distortion, and high optical performance. Achieving a type of shooting lens.

The objective lens of the present invention, which is aimed at at the initial stage, can be achieved by the above-described configuration. To further correct various aberrations and obtain high optical performance over the entire screen, one or more of the following configurations are required. Good to be satisfied.

The combined focal length of the lens disposed on the object side of the stop is negative, and the composite focal length of the lens disposed on the image side of the stop is positive. According to this, it is easy to increase the angle of view and reduce the size of the entire lens system.

When the combined focal length of the first lens and the second lens is Ff, and the combined focal length of the third lens, the fourth lens, and the fifth lens is Fr, -300 <Ff / Fr < −1.0 (1)

Conditional expression (1) is used to reduce the total length of the lens system and further increase the exit pupil to achieve a wide angle of view.
This is a condition for making a lens system sufficiently close to telecentric for a solid-state imaging device such as a CD.

If the lower limit of conditional expression (1) is exceeded, the lens unit on the object side with respect to the stop becomes large, and the first lens having a strong negative refractive power is not far from the stop, but the distortion is larger than 5 and 7. It will increase.

At the same time, the exit pupil becomes too short and the Petzval sum increases in the positive direction, which is not appropriate.

If the upper limit of conditional expression (1) is exceeded, the size of the lens unit on the image side of the stop increases, the telephoto ratio increases, and the aberration coefficient of each lens unit increases. It is not suitable because the generation is large.

It is more preferable that the numerical value range of the conditional expression (1) is -280 <Ff / Fr <-2.0 (1a).

When the focal lengths of the first lens and the second lens are f1 and f2, respectively, by satisfying the following condition: -0.6 <f1 / f2 <-0.2 (2) is there.

Conditional expression (2) is a condition for appropriately adjusting the distortion of the entire lens system, shortening the overall length of the lens, and setting the exit pupil to an appropriate value.

When the value exceeds the upper limit of conditional expression (2), the aberration generated in the front unit (first and second lenses) becomes large, and particularly the distortion generated in the second lens becomes excessively corrected.
The occurrence of coma aberration also increases, which is not appropriate.

If the lower limit of conditional expression (2) is exceeded, the total lens length tends to be large and the exit pupil tends to be short. Also,
The first lens moves away from the stop, and the distortion generated here is insufficiently corrected, which is not appropriate.

It is more preferable that the numerical value range of the conditional expression (2) is -0.58 <f1 / f2 <-0.22 (2a).

When the distance between the first lens and the second lens is L12 and the focal length of the entire system is F, the following condition is satisfied: 0.5 <L12 / F <1.3 (3) That is.

The conditional expression (3) is mainly applied to a retrofocus type photographing lens. This is a condition for reducing distortion of the barrel and reducing the overall length of the lens.

When the value exceeds the upper limit of conditional expression (3), the first lens moves away from the stop, so that the distortion generated in the first lens is insufficiently corrected, and the barrel distortion increases.
Further, the overall length of the lens becomes large, which is not suitable.

If the lower limit of conditional expression (3) is exceeded, not only does the ratio of overcorrection of distortion of the second lens increase, but also various aberrations, particularly coma, occurring in the first and second lenses. Is large and is not suitable.

It is more preferable that the numerical value range of the conditional expression (3) is set to 0.55 <L12 / F <1.2 (3a).

The distance from the object side surface of the third lens to the image plane is G3i (when a small crystal low-pass filter such as a CCD or a cover glass is provided on the image side of the fifth lens, the length is G3i). When the focal length of the entire system is F, the following condition is satisfied: 2.5 <G3i / F <3.3 (4)

Conditional expression (4) is intended mainly to provide the rear lens group on the image side of the stop with an appropriate share of distortion and to reduce the overall length of the lens.

If the lower limit value of conditional expression (4) is exceeded, not only the back focus will be shortened, but also the power of each lens will become severe, and the deterioration of aberrations such as coma will increase.

When the value exceeds the upper limit, not only the overall length of the lens becomes large but also the barrel distortion generated in the fifth lens furthest from the stop becomes large, which is not appropriate.

It is more preferable that the numerical range of the conditional expression (4) is set to 2.55 <G3i / F <3 (4a).

The lens surfaces of the third lens and the fourth lens have substantially the same curvature on the front and back surfaces, and the front and back surfaces are difficult to distinguish.
It is preferable from the viewpoint of manufacture that one or both of them have the same curvature on both the front and back surfaces.

Hereinafter, numerical examples of the present invention will be described. In each numerical example, i indicates the order of the surface from the object side,
Ri is the radius of curvature of the lens surface, and Di is the ith surface and the ith surface + 1.
The lens thickness and air gap between the lens and the surface, and Ni and νi indicate the refractive index and Abbe number for the d-line, respectively. The two surfaces closest to the image are filter members such as a quartz low-pass filter and an infrared cut filter.

Table 1 shows the relationship between the above-described conditional expressions and various numerical values in the numerical examples.

[0052]

[Outside 1]

[0053]

[Outside 2]

[0054]

[Outside 3]

[0055]

[Outside 4]

[0056]

[Outside 5]

[0057]

[Table 1]

Next, an embodiment of a digital camera using the taking lens of the present invention as a taking optical system will be described with reference to FIG.

In FIG. 11, reference numeral 10 denotes a camera body;
Is a photographing optical system constituted by the zoom lens of the present invention, 12 is a flash built in the camera body, 13 is an external finder, and 14 is a shutter button.

As described above, by applying the photographic lens of the present invention to an optical device such as a digital camera, an optical device having a small size and high optical performance is realized.

[0061]

According to the present invention, with a simple lens configuration,
It is possible to achieve a photographic lens which is bright, has a wide angle of view, is small, has little distortion, and has high optical performance, and an optical apparatus using the same.

In addition, according to the present invention, the overall length is reduced while leaving the exit pupil sufficiently away from the image plane, and the optical pupil has good optical performance.
It is possible to achieve a retrofocus type photographing lens having a large aperture of about 2.8.

[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 a diagram showing various aberrations of Numerical Embodiment 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 a diagram showing various aberrations of 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 a diagram illustrating various aberrations 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 a diagram showing various aberrations of 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 a diagram showing various aberrations of Numerical Example 5 of the present invention.

FIG. 11 is a schematic diagram of the optical apparatus of the present invention.

[Explanation of symbols]

 L1 first lens L2 second lens L3 third lens L4 fourth lens L5 fifth lens SP stop G glass block IP image plane S sagittal image plane M meridional image plane d d-line g g-line

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H087 KA02 KA03 LA03 PA05 PA17 PB05 QA02 QA07 QA17 QA21 QA25 QA34 QA42 QA45 RA32 RA42

Claims (7)

[Claims] 1. A meniscus-shaped first lens having a negative refractive power having a convex surface facing the object side, a meniscus-shaped positive lens having a positive refractive power having a convex surface facing the image surface side, and an aperture in order from the object side. A third lens having a positive refractive power, a fourth lens having negative concave refractive power on both lens surfaces, and a fifth lens having a positive refractive power. 2. The photographing lens according to claim 1, wherein a combined focal length of a lens disposed on the object side of the stop is negative, and a composite focal length of a lens disposed on the image side of the stop is positive. . 3. When the combined focal length of the first lens and the second lens is Ff and the combined focal length of the third lens, the fourth lens, and the fifth lens is Fr, −300 <Ff / Fr. The photographing lens according to claim 1, wherein the following conditional expression is satisfied. 4. When the focal lengths of the first lens and the second lens are f1 and f2, respectively, a conditional expression of −0.6 <f1 / f2 <−0.2 is satisfied. 1, 2, or 3
Shooting lens. 5. When the distance between the first lens and the second lens is L12 and the focal length of the entire system is F, the condition of 0.5 <L12 / F <1.3 is satisfied. Claims 1, 2, 3
Or 4 taking lens. 6. The distance from the object-side surface of the third lens to the image plane is G3i (when a small crystal low-pass filter such as a CCD, a cover glass, or the like is provided on the image plane side of the fifth lens,
When these lengths are added as air-equivalent lengths) and the focal length of the entire system is F, the condition 2.5 <G3i / F <3.3 is satisfied. 5. The photographing lens according to any one of the above items 5. 7. An optical apparatus comprising the photographic lens according to claim 1. Description: