JP2003329929A - Zoom lens for photography using replica layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an inexpensive zoom lens consisting of two groups, which is suitable for an electronic still camera by shortening the entire length of the lens. <P>SOLUTION: The zoom lens for photography using a replica layer is constituted of a 1st group 10 having negative refractive power and a 2nd group 20 having positive refractive power in order from an object side, and the 1st and the 2nd groups are respectively provided with at least one aspherical surface consisting of the replica layer made of ultraviolet curing acrylic resin. Thus, a shift of focus caused by temperature change is restrained and the number of lenses is reduced. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a first group having a negative refractive power and a second group having a positive refractive power, and each group has at least one aspherical surface made of a resin replica layer. The present invention relates to a zoom lens for photographing using a replica layer in which the number of lenses is reduced by using it.

[0002]

2. Description of the Related Art Heretofore, various short-type two-group zoom lenses have been proposed which consist of a first group having a negative refractive index and a second group having a positive refractive index. This type of zoom lens performs zooming by moving the second group, and corrects the image point position associated with zooming by moving the first group. The magnification of this type is about 2 times. JP 2001-2815A
In the lens shown in FIG. 43, the first group is composed of three lenses and the second group is composed of five lenses, that is, a total of eight lenses.
In this case, the number of lenses is large, for example, the first group is composed of three lenses and the second group is composed of four lenses. There is a strong demand to reduce the number of lenses and make them compact so that they can be used in digital still cameras.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a two-group zoom lens which is compact and inexpensive as a two-group zoom lens which exhibits excellent temperature characteristics by reducing the number of lenses. is there.

[0004]

In order to achieve the above object, a zoom lens for photographing using a replica layer according to claim 1 of the present invention is a negative meniscus lens convex to the object side. And a first lens unit having a negative refracting power composed of a meniscus positive second lens, and a positive third lens having a biconvex positive surface from the object side and a meniscus negative fourth lens having a positive refracting power. It is composed of a second lens group, and at least one aspherical surface made of a resin replica layer is arranged in each group.

A zoom lens for photographing using a replica layer according to a second aspect of the present invention is the lens according to the first aspect, wherein the replica layer is provided on each of the first lens, the second lens and the third lens. Has been. A zoom lens for photographing using the replica layer according to claim 3 of the present invention is the zoom lens for photographing using the replica layer according to claim 1 or 2, wherein a positive surface is included in each surface power of the replica layer. If the total power is φ (positive) and the total negative surface power is φ (negative), 0.5 <| φ
(Negative) | / φ (positive) <1.5.

By adding an aspherical surface composed of a replica layer to the image forming surface side of each lens of the first surface, coma aberration is suppressed and an aspherical surface composed of a replica layer is added to both surfaces of the convex lens of the second group. By doing so, the occurrence of spherical aberration is suppressed.
The aspherical surface formed of the replica layer has a temperature dependency larger than that of glass, and has a weak point that a focus movement is likely to occur due to a temperature change and image forming characteristics are easily deteriorated. In the present invention, of the surface powers of the resin replica layer, the total of the positive surface powers is φ (positive), and the total of the negative surface powers is φ.
(Negative) and the ratio is 0.5 <| φ (negative) | / φ
By setting (positive) <1.5, the focus movement due to temperature change is reduced, and the deterioration of the imaging characteristics is reduced.

In the above equation, | φ (negative) | / φ (positive)
Is smaller than 0.5, the φ (positive) surface power is large, and the focal point movement in the image direction occurs at a high temperature, and the focal point movement in the object direction occurs at a low temperature, resulting in deterioration of the imaging characteristics. Similarly, if | φ (negative) | / φ (positive) is greater than 1.5, φ
When the (negative) surface power is high and the temperature is high, the focal point movement in the object direction occurs, and when the temperature is low, the focal point movement in the image direction occurs. The invention of the present application is | φ (negative) | /
By setting φ (positive) within the above range, an excellent zoom lens can be obtained.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a zoom lens for photographing using a replica layer according to the present invention will be described below with reference to the drawings. FIG. 1 shows a basic lens configuration according to an embodiment of the present invention, showing the wide-angle end. FIG. 2 shows the middle and FIG. 3 shows the telephoto end. 4 to 6 are aberration diagrams at the wide-angle end, the middle, and the telephoto end of the example.

The first lens 11 of the first group is a negative meniscus lens convex to the object side, and has an aspherical surface formed by a replica layer for coma aberration correction on its concave surface. This is called the first replica. The second lens 12 of the first group is a positive meniscus lens and has an aspherical surface formed by a replica layer for coma aberration correction on its convex surface. This is called a second replica. The first lens 21 of the second group is a biconvex positive lens, and has aspherical surfaces formed by replica layers for spherical aberration correction on both surfaces. These are called the third and fourth replicas. Surface power of the first replica is -0.19, 0.200 Surface power of the second replica is 0.03, -0.005 Surface power of the third replica is 0.13, -0.005 Surface of the fourth replica Since the power is 0.08 and −0.08, | φ (negative) | / φ (positive) = 0.636, which satisfies the condition of claim 2.

[0010]

[Embodiment] This embodiment has a variable power ratio of about 2 times and an aperture ratio of 3.5-.
It is a zoom lens of about 4.7. FIG. 1 is a lens cross-sectional view at the wide-angle end. The first group 10 having negative refractive power is, from the object side, a first lens 11 having a meniscus negative lens convex to the object side and having an aspheric surface formed by a replica layer on the concave surface, and a positive meniscus lens having a convex surface. The second lens 12 has an aspherical surface formed by a replica layer. An ultraviolet curable acrylic resin is used as the replica layer. Second
The same applies to groups. The second lens unit 20 having a positive refractive power is composed of a positive lens biconvex from the object side, a third lens 21 having an aspheric surface formed by replica layers on both surfaces, and a fourth lens 22 which is a meniscus negative lens. Table 1 shows the radius of curvature R (mm) of each lens surface, the center thickness of each lens and each lens surface distance D (mm), the refractive index N of each lens surface at the d line, and the Abbe number ν in this example. Further, the focal length f (mm) and the aperture ratio are shown in the lower part of Table 1. The asterisk * of the surface number indicates an aspherical surface, and this aspherical surface shape is obtained by the following equation. X: Distance from a tangent plane at the lens surface apex of a point on the aspherical surface H: Height from optical axis R: Radius of curvature of aspherical apex K: Conical coefficient A _2i : Aspherical coefficient ₉ X = (1 / R ) H ² / [1+ {1- (1 + K) (1 / R) ² H ² } ^1/2 ] + ΣA _2i H ^{2i i = 2} Table 1 surface R D N ν 1 81.122 0.720 1.54440 56.14 2 2.673 0.080 1.50703 53.57 * 3 2.673 2.500 4 -197.380 1.520 1.58418 31.07 5 -15.779 0.0801 .50703 53.57 * 6 -15.779 D6 7 Aperture 1.000 * 8 3.892 0.040 1.50703 53.57 9 3.630 3.900 1.48749 70.44 10-5.665 0 0.040 1.50703 53.57 * 11 -6.040 0.600 12 32.350 .800 1.84666 20.88 13 ∞ D13 14 ∞ 3.200 15 ∞ Wide-angle end Mid-telephoto end D6 9.042 5.095 2.999 D13 6.477 8.617 Focal length 4.4426 6. 381 8.337 opening ratio 3.54 4.18 4.82 aspherical coefficient * 3 R = 2.673 K = -0.652994 A 4 = 3.80915E-3 A 6 = -1.70104E-3 A 8 _{= 9.01295E-4 A 10 = -1.60316E} -4 A 12 = -3.57019E-6 A 14 = 2.88174E-6 A 16 = -1.80076E-15 A 18 = 7.81196E-17 * 6 R = -15.779 K = 20.751288 A 4 = -2.00384E-3 A 6 = 9.72656E-4 A 8 = -4.69233E-4 A 10 = 9.65 _{05E-5 A 12 = -7.40643E-} 7 A 14 = -2.94991E-6 A 16 = 4.11802E-7 A 18 = -1.64741E-8 * 8 R = 3.892 K = -0. 206982 A ₄ = -9.597559E-4 A ₆ = 1.16164E-4 A ₈ = -1.54644E-4 A ₁₀ = 1.75692E-6 A ₁₂ = 0 A ₁₄ = 0 A ₁₆ = 0 A ₁₈ = 0 * 11 R = -6.040 K = -5.034996 A 4 = 1.95873E-3 A 6 = 2.74243E-4 A 8 = -2.93167E-4 A 10 = 5.31937E-6 A 12 = 0 A ₁₄ = 0 A ₁₆ = 0 A ₁₈ = 0

[0011]

As described above in detail, according to the present invention, it is possible to reduce the number of lenses and to make it compact and inexpensive.
A group zoom lens can be provided.

[Brief description of drawings]

FIG. 1 is a lens configuration diagram at a wide-angle end according to an embodiment of the present invention.

FIG. 2 is a lens configuration diagram in the middle of an example of the present invention.

FIG. 3 is a lens configuration diagram at a telephoto end according to an embodiment of the present invention.

FIG. 4 is an aberration diagram at a wide-angle end according to an example of the present invention.

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

FIG. 6 is an aberration diagram at a telephoto end according to an example of the present invention.

[Explanation of symbols]

10 First lens group 11 First lens 12 Second lens 20 Second lens group 21 3rd lens 22 4th lens 30 aperture 40 cover glass 50 image plane

Claims (3)

[Claims] 1. A first lens unit having a negative refracting power, which comprises a negative meniscus first lens element convex to the object side and a positive meniscus second lens element, and a positive third lens element biconvex from the object side. A lens and a second lens group having a negative meniscus fourth lens having a positive refractive power, and a replica layer formed by arranging at least one aspherical surface made of a resin replica layer in each group. The zoom lens used for shooting. 2. The replica layer includes the first lens and the second lens.
The zoom lens for photographing using the replica layer according to claim 1, which is provided in each of the lens and the third lens. 3. Of the surface powers of the replica layer, if the total of the positive surface powers is φ (positive) and the total of the negative surface powers is φ (negative), then 0.5 <| φ (negative ) | / Φ (positive) <1.5 The zoom lens for photographing using the replica layer according to claim 1 or 2.