JP3323839B2 - Camera with a small zoom 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 camera provided with a small zoom lens composed of two lens groups suitable for a lens shutter camera, a video camera, and the like, and more particularly to a camera having an appropriate lens configuration for each lens group. The present invention relates to a camera provided with a small zoom lens having a wide angle of view and a zoom ratio of about 2, which satisfactorily corrects aberrations and shortens the overall length of the lens (the distance from the first lens surface to the image surface). .

[0002]

2. Description of the Related Art Recently, with the miniaturization of lens shutter cameras, video cameras, and the like, a small zoom lens having a short overall lens length has been demanded. In particular, it is desired to mount a zoom lens even in the field of a small camera such as a lens shutter camera which does not perform lens replacement, and a small zoom lens having a length similar to that of a conventionally used single focus lens is demanded.

[0003] The present applicant has previously disclosed Japanese Patent Application Laid-Open No. 57-201213.
JP-A-60-170816, JP-A-60-170816
In JP-A-191216 and JP-A-62-56917, two lens groups, a first group having a positive refractive power and a second group having a negative refractive power, are sequentially arranged from the object side. A small so-called two-unit zoom lens that changes magnification by changing the interval has been proposed.

In this publication, a two-unit zoom lens having high optical performance which employs positive and negative refractive power arrangements in order from the object side to make the back focus relatively short and to shorten the overall length of the lens. Have achieved.

In addition, Japanese Patent Application Laid-Open Nos. Sho 62-284319, 62-256915, and 64-5
In Japanese Patent Application Laid-Open No. 2111 and Japanese Patent Application Laid-Open No. 1-193807, the first lens unit has a positive refractive power and the second lens unit has a negative refractive power, and both lens groups are moved forward while changing the distance between both lens groups. This discloses a two-unit zoom lens that changes the magnification.

In addition, Japanese Patent Application Laid-Open No.
In Japanese Patent Application Laid-Open No. 3-161422, the first group is defined as positive, negative, negative, positive,
A zoom lens that includes five positive lenses and has a shooting angle of view of about 55 degrees at the wide-angle end is disclosed.

Further, JP-A-62-90611, JP-A-62-113120, and JP-A-3-116110
In the publication, a first lens group is composed of four lenses of positive, negative, negative and positive, and a two-group zoom lens having a zoom ratio of about 1.5 is disclosed.

In Japanese Patent Application Laid-Open No. 2-284109, the first group is composed of five lenses of positive, negative, negative, positive and positive, and the second group is composed of three lenses of positive, negative and negative. The disclosed two-unit zoom lens is disclosed.

[0009]

SUMMARY OF THE INVENTION In the above-described two-unit zoom lens including the first lens unit having the positive refractive power and the second lens unit having the negative refractive power, the size of the entire lens system is reduced. To obtain good optical performance over the entire zoom range while having a zoom ratio of about 2 times, it is necessary to appropriately set the lens configuration of each lens group.

For example, the zoom lens disclosed in the above-mentioned JP-A-57-201213 and JP-A-1-193807 has a zoom ratio of about 1.5, and JP-A-63-25691.
In the zoom lens disclosed in Japanese Patent Application Laid-Open No. 5 (1993) -205, fluctuations in aberrations during zooming, particularly fluctuations in spherical aberration and field curvature, were large.

In the zoom lens disclosed in JP-A-64-52111, the F-number at the wide angle end is F4.5, and the brightness is not always sufficient.

In general, if the refractive power of both the first and second units is increased, the amount of movement of each lens unit during zooming is reduced, and the overall length of the lens can be reduced.

However, if the refractive power of each lens group is simply increased, the fluctuation of aberration due to zooming becomes large, and it becomes difficult to satisfactorily correct this.

According to the present invention, in a so-called two-group zoom lens, by appropriately setting the lens configuration of each lens group, it is possible to shorten the overall length of the lens, particularly while having a wide angle of view at a zoom ratio of about 2. It is another object of the present invention to provide a camera equipped with a small zoom lens having high optical performance over the entire zoom range.

[0015]

A camera having a small zoom lens according to the present invention has, in order from the object side, a first lens unit having a positive refractive power and a second lens unit having a negative refractive power. Small zoom lens that changes the distance between both lens groups and zooms
A first lens unit, wherein the first lens unit has a positive lens having a convex surface facing the object side, a negative lens, and a negative lens and a positive lens joined together.
The second group is composed of two lenses, a positive lens and a negative lens, and the focal length of the i-th group is f
i, when the principal point intervals of the first group and the second group at the wide-angle end and the telephoto end are eW12 and eT12, respectively, and the diagonal length of the effective screen is Y, 0.35 <f1 / Y <0.55 ( (A-1) -0.65 <f2 / Y <-0.35 (a-2) 1.5 <eW12 / eT12 <2.5 (a-3)

In particular, the distance from the first lens surface of the first group to the final lens surface is TD1, the distance from the first lens surface of the second group to the final lens surface is TD2, and the back focus at the wide-angle end is Skw. When the focal length of the entire system at the wide-angle end is Fw, 0.25 <TD1 / Y <0.34 (a-4) 0.15 <TD2 / Y <0.25 (...) E5) The following condition is satisfied: 0.25 <Skw / Fw <0.38 (E6)

The first group includes a positive meniscus first lens having a convex surface facing the object side, a negative second lens having both lens surfaces concave, and a third meniscus negative lens having a convex surface facing the object side. A lens and a fourth lens having a positive convex surface on both lens surfaces, the third lens and the fourth lens being cemented cemented lenses, and between the second lens and the third lens. An aperture is provided, and the second group includes a positive fifth lens and a negative sixth lens.

In particular, the lens surface on the image surface side of the second lens is formed of an aspheric surface whose negative refractive power becomes stronger from the center of the lens toward the periphery of the lens. The lens surface is formed of an aspheric surface having a positive refractive power that increases from the center of the lens toward the periphery of the lens.

[0019]

1 to 3 are lens sectional views of Numerical Examples 1 to 3 of the present invention. In the lens sectional views, (A) shows the zoom position at the wide angle end, (B) shows the middle position, and (C) shows the zoom position at the telephoto end.

In the figure, L1 is a first group having a positive refractive power, and L2 is a second group having a negative refractive power. While reducing the distance between the two lens groups, the two lens groups are moved toward the object side as shown by arrows. Moving the zoom from the wide-angle end to the telephoto end. SP is an aperture, and in Numerical Examples 1 to 3, the second lens in the first group and the third lens
The lens unit is disposed between the lens unit and the lens unit, and moves integrally with the first unit with zooming.

In this embodiment, by adopting such a zoom system and the lens configuration as described above, the overall length of the lens is shortened, particularly, the wide angle of view at the wide-angle end and the overall length of the lens are shortened. A magnification ratio of about 2 and aberration fluctuation accompanying zooming are corrected well, and high optical performance is obtained over the entire zoom range.

In particular, in the present invention, in order to satisfactorily correct fluctuations in various aberrations such as spherical aberration and curvature of field due to zooming, and to maintain the optical performance of the entire screen in a well-balanced manner, FIGS. In Numerical Examples 1 to 3, the first lens unit has a meniscus-shaped positive first lens with a convex surface facing the object side, both lens surfaces have a concave second negative lens, and a meniscus-shaped lens with a convex surface facing the object side. A fourth lens having a negative third lens, and a positive fourth lens having both lens surfaces convex, and the third lens and the fourth lens
The lens is composed of a cemented cemented lens, a stop is provided between the second lens and the third lens, and the second group is composed of two lenses, a positive fifth lens and a negative sixth lens. are doing.

This effectively prevents the lens diameter from increasing when widening the angle of view. In particular, Numerical Examples 1 to 3
In the first embodiment, the first and second lens units are appropriately set to correct the various aberrations in a well-balanced manner while reducing the number of lenses in the entire lens system, thereby obtaining high optical performance.

In Numerical Examples 1 to 3, by satisfying the conditional expressions in the above-described lens configuration, the size of the entire lens system is reduced while ensuring high optical performance over the entire zoom range.

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

The conditional expressions (A-1) and (A-2) relate to the ratio of the refractive power of the first unit and the second unit with respect to the effective screen Y, respectively. This is to reduce the size of the whole.

If the refractive power of the first lens unit becomes too weak beyond the upper limit value of the conditional expression (a-1), the back focus at the wide-angle end becomes short, and the diameter of the front lens increases. On the other hand, if the refractive power of the first lens unit becomes too strong beyond the lower limit, the amount of movement of each lens unit for securing a predetermined zoom ratio becomes large, and the entire lens system becomes large.

If the refractive power of the second lens unit becomes too weak beyond the upper limit of conditional expression (a-2), the amount of movement of the second lens unit for securing a predetermined zoom ratio increases, and the entire lens system Is getting bigger. On the other hand, if the refractive power of the second lens unit becomes too strong beyond the lower limit, it becomes difficult to obtain a predetermined back focus at the wide-angle end, and the rear lens diameter increases, which is not good.

The conditional expression (a-3) relates to the ratio of the principal point distance between the first and second lens units at the wide-angle end and the telephoto end. This is to reduce the size of the entire lens system while securing the zoom ratio. If the distance between the principal points at the telephoto end becomes too short beyond the upper limit value of the conditional expression (A-3), the first and second units mechanically interfere with each other. If the ratio between the principal points at the wide-angle end and the telephoto end becomes too small below the lower limit, it becomes difficult to secure a predetermined zoom ratio.

Conditional expressions (a-4) and (a-5) are respectively the first
With respect to the total lens length of the group and the second group (the length from the first lens surface to the final lens surface), the objective is to reduce the size of the entire lens system while correcting various aberrations in a well-balanced manner.
Exceeding the upper limits of conditional expressions (A-4) and (A-5), if the total length of the first and second lens units becomes too long, the front lens diameter and the rear lens diameter increase. Also, conditional expression (a-4),
If the total length of the first and second lens units is too short below the lower limit of (a-5), various aberrations such as coma flare will occur over the entire zooming range, and these various aberrations will accompany zooming. It becomes difficult to correct fluctuations in the balance.

Conditional expression (a-6) relates to the ratio between the back focus at the wide-angle end and the focal length at the wide-angle end. If the back focus exceeds the upper limit and the back focus is too long, the refractive power of the first lens unit becomes too strong, and This is not good because the amount of movement of each group increases with doubling. On the other hand, if the back focus exceeds the lower limit and the back focus becomes too short, the diameter of the rear lens increases and the entire lens system becomes large.

In Numerical Embodiments 1 to 3, the lens surface on the image plane side of the second lens is formed of an aspheric surface having a negative refractive power that increases from the center of the lens toward the periphery of the lens. The lens surface on the image plane side of the lens is formed of an aspheric surface having a positive refractive power that increases from the center of the lens toward the periphery of the lens, thereby increasing the angle of view to an angle of view of about 2ω = 73.8 degrees. Various aberrations are corrected well.

Next, numerical examples of the present invention will be described. In the numerical examples, Ri is the radius of curvature of the i-th lens surface in order from the object side, Di is the i-th lens thickness and air spacing from the object side, and Ni and νi are the i-th lens surfaces in order from the object side. The refractive index and Abbe number of glass.

The aspheric surface has an X-axis in the optical axis direction, an H-axis in a direction perpendicular to the optical axis, a positive traveling direction of light, R is a paraxial radius of curvature,
When A, B, C, D, and E are each aspheric coefficients

[0035]

(Equation 1)

This is expressed by the following equation.

Table 1 shows the relationship with each conditional expression in each numerical example. (Numerical Example 1) F = 28.8-54.5 FNO = 1: 4.1-7.8 2ω = 73.8 ° -43.3 ° R 1 = 16.14 D 1 = 1.38 N 1 = 1.51633 ν 1 = 64.2 R 2 = 18.75 D 2 = 1.30 R 3 = -38.72 D 3 = 1.50 N 2 = 1.58313 ν 2 = 59.4 R 4 = 72.64 D 4 = 3.44 R 5 = (Aperture) D 5 = 1.00 R 6 = 32.12 D 6 = 1.30 N 3 = 1.80518 ν 3 = 25.4 R 7 = 15.11 D 7 = 3.11 N 4 = 1.60311 ν 4 = 60.7 R 8 = -11.82 D 8 = Variable R 9 = -48.98 D 9 = 2.84 N 5 = 1.64769 ν 5 = 33.8 R10 = -19.33 D10 = 3.66 R11 = -9.88 D11 = 1.70 N 6 = 1.71300 ν 6 = 53.8 R12 = -381.07

[0038]

[Table 1]

R 4 surface Aspherical surface A = 0, B = 2.22 × 10 ^-4 , C = 2.03
× 10 ^-6 , D = 4.08 × 10 ^-8 , E = 7.97 × 10 ^-10 R10 surface Aspheric surface A = 0, B = -5.24 × 10 ^-4 , C = -3.49 × 10 ^-7 , D = 1.
75 × 10 ^-9 , E = -6.63 × 10 ^-11 (Numerical example 2) F = 28.8-54.5 FNO = 1: 4-7.8 2ω = 73.8 ° -43.3 ° R 1 = 17.58 D 1 = 1.46 N 1 = 1.51742 ν 1 = 52.4 R 2 = 20.91 D 2 = 1.28 R 3 = -34.10 D 3 = 1.50 N 2 = 1.58313 ν 2 = 59.4 R 4 = 102.01 D 4 = 3.14 R 5 = (Aperture) D 5 = 1.00 R 6 = 33.44 D 6 = 1.30 N 3 = 1.80518 ν 3 = 25.4 R 7 = 14.94 D 7 = 3.21 N 4 = 1.60311 ν 4 = 60.7 R 8 = -11.47 D 8 = Variable R 9 = -41.76 D 9 = 2.62 N 5 = 1.68893 ν 5 = 31.1 R10 = -19.93 D10 = 3.89 R11 = -9.91 D11 = 1.70 N 6 = 1.71300 ν 6 = 53.8 R12 = -227.09

[0040]

[Table 2]

R 4 surface Aspherical surface A = 0, B = 2.33 × 10 ^-4 , C = 1.74
× 10 ^-6 , D = 6.65 × 10 ^-8 , E = 4.65 × 10 ^-10 R10 surface Aspheric surface A = 0, B = -4.94 × 10 ^-5 , C = -2.67 × 10 ^-7 , D = 2.
70 × 10 ^-10 , E = -5.32 × 10 ^-11 (Numerical Example 3) F = 28.8-54.5 FNO = 1: 4-7.8 2ω = 73.8 ° -43.3 ° R 1 = 13.91 D 1 = 1.43 N 1 = 1.51633 ν 1 = 64.2 R 2 = 15.25 D 2 = 1.45 R 3 = -34.58 D 3 = 1.50 N 2 = 1.65844 ν 2 = 50.9 R 4 = 111.09 D 4 = 2.89 R 5 = (Aperture) D 5 = 1.00 R 6 = 34.36 D 6 = 1.30 N 3 = 1.84666 ν 3 = 23.9 R 7 = 17.63 D 7 = 3.04 N 4 = 1.60311 ν 4 = 60.7 R 8 = -10.96 D 8 = Variable R 9 = -49.87 D 9 = 2.72 N 5 = 1.68893 ν 5 = 31.1 R10 = -20.02 D10 = 3.66 R11 = -9.95 D11 = 1.70 N 6 = 1.77250 ν 6 = 49.6 R12 = -185.03

[0042]

[Table 3]

R 4 surface Aspherical surface A = 0, B = 2.49 × 10 ^-4 , C = 1.40
× 10 ^-6 , D = 1.01 × 10 ^-7 , E = 2.23 × 10 ^-10 R10 surface Aspheric surface A = 0, B = -5.40 × 10 ^-5 , C = -2.31 × 10 ^-7 , D = -1 .
00 × 10 ^-9 , E = -3.68 × 10 ^-11

[0044]

[Table 4]

[0045]

According to the present invention, the total lens length can be reduced by setting the lens configuration of each lens unit of a zoom lens that performs zooming by moving two lens units having a predetermined refractive power as described above. Accordingly, it is possible to achieve a camera equipped with a small-sized zoom lens having a simple configuration and high optical performance over the entire zooming range of about 2.

[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 sectional view of a lens according to a numerical example 2 of the present invention.

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

FIG. 4 is an aberration diagram at a wide angle end according to Numerical Embodiment 1 of the present invention.

FIG. 5 is an intermediate aberration diagram of the numerical example 1 of the present invention.

FIG. 6 is an aberration diagram at a telephoto end in Numerical Example 1 of the present invention.

FIG. 7 is an aberration diagram at a wide angle end according to Numerical Example 2 of the present invention.

FIG. 8 is an intermediate aberration diagram of the numerical example 2 of the present invention.

FIG. 9 is an aberration diagram at a telephoto end in Numerical Example 2 of the present invention.

FIG. 10 is an aberration diagram at a wide angle end according to Numerical Example 3 of the present invention.

FIG. 11 is an intermediate aberration diagram of the numerical example 3 of the present invention.

FIG. 12 is an aberration diagram at a telephoto end in Numerical Example 3 of the present invention.

[Explanation of symbols]

 L1 First lens unit L2 Second lens unit SP stop d d-line g g-line S sagittal image plane M meridional image plane

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-160713 (JP, A) JP-A-62-90611 (JP, A) JP-A-2-219011 (JP, A) JP-A-63-9061 104010 (JP, A) JP-A-61-3112 (JP, A) JP-A-61-292611 (JP, A) JP-A-4-257817 (JP, A) JP-A-1-193807 (JP, A) JP-A-4-37810 (JP, A) JP-A-6-34884 (JP, A) JP-A-4-22911 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 9/00-17/08 G02B 21/02-21/04 G02B 25/00-25/04

Claims (5)

(57) [Claims] 1. A compact zoom having two lens groups, a first group having a positive refractive power and a second group having a negative refractive power, in order from the object side, and performing zooming by changing the distance between both lens groups. including the lens
In the camera , the first group includes a positive lens having a convex surface facing the object side, a negative lens, and a bonding in which a negative lens and a positive lens are joined.
The second group is composed of two lenses, a positive lens and a negative lens, the focal length of the i-th group is fi, and the principal points of the first group and the second group at the wide-angle end and the telephoto end. When the intervals are eW12 and eT12, and the diagonal length of the effective screen is Y, 0.35 <f1 / Y <0.55-0.65 <f2 / Y <-0.35 1.5 <eW12 / eT12 < 2.5 A camera equipped with a small zoom lens , characterized by satisfying the following conditions: 2. The distance from the first lens surface of the first group to the final lens surface is TD1, the distance from the first lens surface of the second group to the final lens surface is TD2, and the back focus at the wide-angle end is Skw. When the focal length of the entire system at the wide-angle end is Fw, the following condition is satisfied: 0.25 <TD1 / Y <0.34 0.15 <TD2 / Y <0.25 0.25 <Skw / Fw <0.38 2. A camera comprising the small zoom lens according to claim 1, wherein the camera is satisfied. 3. A first meniscus positive first lens having a convex surface facing the object side, a negative second lens having both lens surfaces concave, and a negative meniscus lens having a convex surface facing the object side. A third lens and a fourth lens having a convex surface on both lens surfaces, the third lens and the fourth lens being a cemented cemented lens; 2. A camera having a small zoom lens according to claim 1, wherein an aperture is provided between said first lens group and said second lens group, said second lens group comprising a positive fifth lens and a negative sixth lens.
La . 4. A lens surface on the image surface side of the second lens, the lens surface comprising an aspheric surface having a negative refractive power increasing from the center of the lens toward the periphery of the lens.
A camera with a small zoom lens. 5. A lens surface on the image plane side of the fifth lens, comprising an aspheric surface having a positive refractive power increasing from the center of the lens toward the periphery of the lens.
Camera with a compact zoom lens.