JPH10142505A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly compensate for color aberration employing a small number of lenses by specifying the number of lenses for a positive first group and for a negative second groups and providing a diffraction optical surface. SOLUTION: Starting from a body side, the zoom lenses are constituted of a first group Gr1 having a positive refractive power and a second group Gr2 having a negative refractive power. In order to conduct a zooming from a wide angle end W to a telephone end T, and groups Gr1 and Gr2 are moved so as to reduce a mutal interval d3 (refer to arrows m1 and m2). The group Gr1 is constituted of one lens and the group Gr2 is made of at least two lenses and at least one diffraction optical surface (indicated by a [DOE] symbol) is provided in the entire system. For example, starting from the body side, the group Gr1 is constituted of a concave positive meniscus lens (both surfaces r1 and r2 are * symboled aspherical surfaces and an image side surface r2 is a [DOE] symboled diffraction optical surface) and a diaphragm A. Starting from the body side, the group Gr2 is constituted of a convex positive meniscus lens (both r4 and r5 are aspherical surfaces) to the image side and a concave negative meniscus lens to the body side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens, and more particularly, to a small-sized zoom lens suitable as a photographing lens for a lens shutter camera.

[0002]

2. Description of the Related Art Most conventional zoom lenses for lens shutter cameras each have at least two lenses. Reducing the number of components in each group is important for achieving a compact camera and a low cost. JP-A-3-127003, JP-A-3-15
JP-A-881 proposes a positive / negative two-unit zoom lens in which the number of constituent members of each unit is reduced by using many aspherical surfaces. The first group is composed of two lenses, while the second group is reduced to one lens.

[0003]

However, the above-mentioned 2)
In the group zoom lens, color correction in each group is insufficient due to the reduction in the number of lenses. Therefore, it cannot be said that sufficient performance has been achieved in terms of correcting chromatic aberration.

As a means for correcting chromatic aberration, spherical aberration, and the like, a combination of a diffractive optical surface and a refractive optical surface has attracted attention in recent years, and various optical systems using the same have been proposed. For example, JP-A-6-324262 discloses an application to a taking lens.
Japanese Patent Application Laid-Open No. 242373 discloses an application to an objective lens or the like for an optical disk.

The present invention has been made by focusing on a diffractive optical surface as a means for reducing the number of lenses while maintaining optical performance, and an object of the present invention is to correct chromatic aberration favorably with a small number of lenses. It is to provide a zoom lens.

[0006]

In order to achieve the above object, a zoom lens according to a first aspect of the present invention includes, 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. When zooming from the wide-angle end to the telephoto end,
In the zoom lens in which the first group and the second group move so as to reduce the distance between each other, the first group is configured by one lens, and the second group is configured by at least two lenses. Further, at least one diffractive optical surface is provided in the entire zoom lens system.

According to a second aspect of the present invention, in the zoom lens system according to the first aspect, the diffractive optical surface is provided in the first group.

A third aspect of the present invention is the zoom lens according to the first aspect, wherein the diffractive optical surface is provided in the second group.

According to a fourth aspect of the present invention, in the zoom lens system according to the first aspect, each of the groups provided with the diffractive optical surfaces satisfies the following conditional expression. 0.03 <| φdoe / φr | <0.15 where φdoe is the power of the diffractive optical surface, and φr is the combined power of the group including the diffractive optical surface.

According to a fifth aspect of the present invention, there is provided a zoom lens according to the first aspect, wherein the following conditional expression is satisfied. 2 <| R2 × Hmax / λ0 | <25, where R2 is the second-order phase function coefficient (1 / mm) of the diffractive optical surface, and Hmax is the effective diameter (m) of the lens on which the diffractive optical surface is provided.
m), λ0: Design center wavelength (mm) of the diffractive optical surface.

A zoom lens according to a sixth aspect of the present invention is characterized in that, in the configuration of the second aspect, the following conditional expression is satisfied. 0.03 <φdoe1 / φr1 <0.10, where φdoe1: power of the diffractive optical surface provided in the first group, φr1: combined power of the first group.

A zoom lens according to a seventh aspect of the present invention is characterized in that, in the configuration of the third aspect, the following conditional expression is satisfied. 0.06 <φdoe2 / φr2 <0.15 where φdoe2 is the power of the diffractive optical surface provided in the second lens unit, and φr2 is the combined power of the second lens unit.

An eighth aspect of the present invention is the zoom lens according to the first aspect, wherein the diffractive optical surface is provided on a surface of a refractive optical surface having an aspherical shape.

A ninth aspect of the present invention is the zoom lens according to the first aspect, wherein the diffractive optical surface is provided on a surface of a plastic lens.

A tenth aspect of the present invention is a zoom lens according to the first aspect.
In the constitution of the invention, the lenses forming the first group and the second group are all plastic lenses.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a zoom lens embodying the present invention will be described with reference to the drawings. 1 to 3 are lens configuration diagrams respectively corresponding to the zoom lenses of the first to third embodiments, and show the lens arrangement at the wide-angle end (W). Arrows m1 and m2 in the lens configuration diagram are at the wide-angle end.
First group Gr in zooming from (W) to telephoto end (T)
The movements of the first lens unit Gr and the second lens unit Gr2 are schematically shown. Also, in the lens configuration diagram, the surface with ri (i = 1, 2, 3, ...) is the i-th surface counted from the object side, and di (i = 1, 2,
The axial top surface interval marked with (3, ...) is the i-th axial top surface interval counted from the object side. The surface marked with * for ri is an aspheric surface, and the surface marked with [DOE] for ri is a diffractive optical surface.

The zoom lens according to the first to third embodiments includes, in order from the object side, a first group Gr1 having a positive refractive power.
And a second lens unit Gr2 having a negative refractive power.
When zooming from (W) to the telephoto end (T), the first group G
This is a zoom lens that moves so that the distance d3 between r1 and the second group Gr2 is reduced.

In the first embodiment, the first lens unit Gr1
Is a positive meniscus lens concave to the object side in order from the object side
(Aspherical surfaces on both surfaces, diffractive optical surface on the image side) and stop A, and the second group Gr2 is a positive meniscus lens convex on the image side (both aspherical surfaces) in order from the object side. And a negative meniscus lens concave on the object side.

In the second embodiment, the first lens unit Gr1
Is a positive meniscus lens concave to the object side in order from the object side
(Both surfaces are aspherical surfaces, diffractive optical surfaces on the image side) and stop A, and the second group Gr2 is a positive meniscus lens convex on the image side (both aspherical surfaces) in order from the object side. And a negative meniscus lens concave on the object side.

In the third embodiment, the first lens unit Gr1
Is a positive meniscus lens concave to the object side in order from the object side
(Aspherical surfaces on both surfaces, diffractive optical surface on the image side) and an aperture A, and the second group Gr2 is a positive meniscus lens convex on the image side (both aspherical surfaces, (A diffractive optical surface on the image side) and a negative meniscus lens concave on the object side.

As described above, in each of the zoom lenses according to the embodiments, the first group Gr1 includes one lens, and the second group Gr2 includes two lenses. First group G
By configuring r1 with one lens, the lens barrel configuration can be simplified, and it is also advantageous for downsizing and cost reduction. The second group Gr2 is at least 2
With the use of a single lens, off-axis coma can be favorably corrected. The first group Gr1 is 1
Although it is composed of a single lens, the chromatic aberration caused by the reduction in the number of sheets does not become insufficiently corrected unlike the above-described conventional example including only the refractive optical surface. This is because chromatic aberration can be favorably corrected by at least one diffractive optical surface provided in the entire zoom lens system. Note that one lens constituting the first group Gr1 is not limited to a single lens but may be a cemented lens.

Generally, the axial chromatic aberration is given by the following equation (A) when dealing with a thin-walled system. L = φR / νR + φdoe / νdoe (A) where L: axial chromatic aberration, φR: refractive power of the refractive optical surface, νR: dispersion value of the refractive optical surface (that is, Abbe number), φdoe: diffraction optical surface Power, νdoe: dispersion value of the diffractive optical surface (corresponding to Abbe number), and νR, νdoe are represented by the following equations (B), (C). νR = (Nd−1) / (Nf−Nc) (B) νdoe = λd / (λf−λc) = − 3.45 (C) where, Nd: the refractive optical surface with respect to the d line on the lens optical axis. Refractive index, Nf: Refractive index on the lens optical axis of the refractive optical surface for the f line, Nc: Refractive index on the lens optical axis of the refractive optical surface for the c line, λd: Wavelength of the d line, λf: f line Λc: wavelength of c-line.

As can be seen from the above equation (C), the diffractive optical surface has a large negative dispersion (−3.45). If a refractive optical surface is used in combination with a diffractive optical surface, a positive φR / νR
Is canceled by negative φdoe / νdoe, it is possible to correct the chromatic aberration generated on the refractive optical surface by the diffractive optical surface. In the zoom lens of each embodiment, chromatic aberration is corrected by using the characteristic of the diffractive optical surface to correct the chromatic aberration generated on the refractive optical surface by the diffractive optical surface.

In each of the embodiments, a diffraction-refraction hybrid lens in which a diffraction optical surface is provided on the surface of a refractive optical surface is used as a part of a zoom lens. Diffraction
If a diffractive optical surface is introduced using a refraction hybrid lens, the diffractive optical surface will be given the power for color correction, and will be generated on the refraction optical surface without adding a new color correction lens. Chromatic aberration can be satisfactorily corrected by the diffractive optical surface. Therefore, good optical performance is achieved even though each group is composed of a small number of lenses, and as a result, a compact zoom lens having a high zoom ratio can be realized.

As in the first to third embodiments, it is desirable to provide at least one diffractive optical surface in the first lens unit Gr1. By providing at least one diffractive optical surface in the first group Gr1, the chromatic aberration generated in the first group Gr1 can be satisfactorily corrected even if the first group Gr1 is composed of one lens.

As in the third embodiment, it is desirable to provide at least one diffractive optical surface in the second lens unit Gr2. By providing at least one diffractive optical surface in the second group Gr2, chromatic aberration of magnification can be satisfactorily corrected, and the amount of chromatic aberration generated during zooming can be reduced.

As in the above embodiments, at least one diffractive optical surface is provided in the entire system, and the first group Gr1 composed of one lens and the second group G1 composed of at least two lenses.
In a positive / negative two-unit zoom lens in which r2 moves so as to reduce the distance (d3) from each other during zooming from the wide-angle end (W) to the telephoto end (T), a diffractive optical surface is provided. It is desirable that each group satisfy the following conditional expression (1). 0.03 <| φdoe / φr | <0.15 (1) where φdoe is the power of the diffractive optical surface, and φr is the combined power of the group including the diffractive optical surface.

When the value exceeds the upper limit of the conditional expression (1), the power of the diffractive optical surface in the group becomes too strong, and the color correction on the diffractive optical surface becomes excessive. Conversely, if the lower limit of conditional expression (1) is exceeded, the power of the diffractive optical surface in the group will be too weak, and the color correction power on the diffractive optical surface will be insufficient.

As in the above embodiments, at least one diffractive optical surface is provided in the whole system, and the first group Gr1 composed of one lens and the second group G1 composed of at least two lenses.
In a positive / negative two-unit zoom lens in which r2 moves so as to reduce the distance (d3) from each other during zooming from the wide-angle end (W) to the telephoto end (T), the following conditional expression (2) It is desirable to satisfy 2 <| R2 × Hmax / λ0 | <25 (2) where R2 is a second-order phase function coefficient (1 / mm) of the diffractive optical surface, and Hmax is an effective diameter of the lens provided with the diffractive optical surface ( m
m), λ0: Design center wavelength (mm) of the diffractive optical surface.

This conditional expression (2) defines a desirable condition range in manufacturing the diffractive optical surface. If the lower limit of conditional expression (2) is exceeded, aberration correction by the diffractive optical surface will be insufficient, making it difficult to satisfactorily correct chromatic aberration. On the other hand, when the value exceeds the upper limit of the conditional expression (2), not only the correction of the chromatic aberration becomes excessive, but also the pitch of the diffractive optical surface in the periphery becomes too small, so that sufficient diffraction efficiency cannot be obtained. Further, when the pitch of the diffractive optical surfaces is too small, there is a problem that manufacturing becomes difficult.

As in the first to third embodiments, at least one diffractive optical surface is provided in the first group Gr1, and the first group Gr1 composed of one lens and the second group Gr1 composed of at least two lenses are provided. In a positive / negative two-unit zoom lens in which the second unit Gr2 moves so as to reduce the distance (d3) between the wide-angle end (W) and the telephoto end (T) during zooming, the following conditional expression ( It is desirable to satisfy 3). 0.03 <φdoe1 / φr1 <0.10 (3) where φdoe1: power of the diffractive optical surface provided in the first group Gr1, φr1: combined power of the first group Gr1.

Conditional expression (3) indicates that the diffractive optical surface is the first lens unit Gr1.
Stipulates a desirable power range of the diffractive optical surface. When the value exceeds the upper limit of the conditional expression (3), the power of the diffractive optical surface in the first lens unit Gr1 becomes too strong, and the color correction on the diffractive optical surface becomes excessive. Further, the pitch of the diffractive optical surface is too small, which is not desirable in manufacturing. Conversely, if the lower limit of conditional expression (3) is exceeded, the first group G
Since the power of the diffractive optical surface in r1 becomes too weak,
The color correction power on the diffractive optical surface is insufficient, and the chromatic aberration is insufficiently corrected in the entire zoom lens system.

As in the third embodiment, at least one diffractive optical surface is provided in the second group Gr2, and the first group Gr1 includes one lens and the second group Gr2 includes at least two lenses. In a positive / negative two-unit zoom lens that moves so as to reduce the distance (d3) from each other during zooming from the wide-angle end (W) to the telephoto end (T), the following conditional expression
It is desirable to satisfy (4). 0.06 <φdoe2 / φr2 <0.15 (4) where φdoe2 is the power of the diffractive optical surface provided in the second group Gr2, and φr2 is the combined power of the second group Gr2.

Conditional expression (4) indicates that the diffractive optical surface is the second lens unit Gr2.
Stipulates a desirable power range of the diffractive optical surface. When the value exceeds the upper limit of the conditional expression (4), the power of the diffractive optical surface in the second lens unit Gr2 becomes too strong, and the color correction on the diffractive optical surface becomes excessive. Further, the pitch of the diffractive optical surface is too small, which is not desirable in manufacturing. Conversely, if the lower limit of conditional expression (4) is exceeded, the second group G
Since the power of the diffractive optical surface in r2 becomes too weak,
The color correction power on the diffractive optical surface is insufficient, and the chromatic aberration is insufficiently corrected in the entire zoom lens system.

As in the first to third embodiments, the diffractive optical surface is desirably provided on the surface of a refractive optical surface having an aspherical shape. If the base surface of the surface on which the diffractive optical surface is provided is an aspherical surface, for example, when forming the diffractive optical surface by mechanical processing, the aspherical shape and the diffractive optical surface shape can be simultaneously processed, and Shortening and high-precision processing are possible. Therefore, providing a diffractive optical surface on the surface of a refractive optical surface having an aspherical shape is very effective in manufacturing. Also, in order to reduce the number of lenses, it is necessary to correct spherical aberration and coma with an aspheric surface.
It is possible to perform better aberration correction than when the base surface of the diffractive optical surface is a spherical surface.

Since the phase shape of the diffractive optical surface can be freely designed, it is possible to design a diffractive optical surface that is optically equivalent to an aspheric surface in the refractive optical surface. Therefore, it is possible to correct not only chromatic aberration but also spherical aberration on the diffractive optical surface. However, if the spherical aberration is corrected only by the phase shape of the diffractive optical surface, the spherical aberration at the design wavelength is corrected. The amount of generation will increase. For this reason, it is desirable to correct the spherical aberration by using a refractive optical surface. In each embodiment, the spherical aberration and off-axis coma are favorably corrected by the aspheric surface composed of the refractive optical surface, and the axial chromatic aberration and the chromatic aberration of magnification are corrected by the diffractive optical surface provided on the surface of the refractive optical surface. , A good optical performance is achieved.

The diffractive optical surface is desirably provided on the surface of a refractive optical element made of plastic (ie, a plastic lens). First group Gr1 and second group Gr2
It is even better if all of the lenses constituting are plastic lenses. When a diffractive optical surface is formed on a plastic lens, for example, integral manufacturing such as injection molding is possible. Therefore, forming a diffractive optical surface on the surface of a plastic lens is much more effective in reducing costs than forming a diffractive optical surface on the surface of a glass lens.

Preferably, the diffractive optical surface is blazed (saw-shaped). By blazing the diffractive optical surface, diffraction efficiency can be improved. Such a blazed diffractive optical surface is formed by molding a glass or plastic material with a mold manufactured by precision cutting, a method of approximating a saw shape with a step shape using semiconductor manufacturing technology or the like (binary optics). And a method of molding a diffractive optical surface on a resin layer formed on a glass lens.

As in each embodiment, it is desirable that the image-side surface of the first lens unit Gr1 be a diffractive optical surface. Generally, when the stop A is located between the first lens unit Gr1 and the second lens unit Gr2, the effect of the surface provided with the diffractive optical surface is the first lens unit G1.
At r1, the effective diameter becomes larger as the lens is closer to the object.
Therefore, if the image side surface of the first lens unit Gr1 is a diffractive optical surface, the effective diameter of the diffractive optical surface can be reduced, which is very effective in manufacturing.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a zoom lens embodying the present invention will be described more specifically with reference to construction data, aberration diagrams, and the like. Examples 1 to 3 given here as examples are examples respectively corresponding to the above-described first to third embodiments, and FIGS. 1 to 3 showing the first to third embodiments are as follows.
4 shows lens arrangements at the wide-angle end (W) of Examples 1 to 3, respectively.

In the construction data of each embodiment, ri (i = 1, 2, 3,...) Indicates the radius of curvature of the i-th surface counted from the object side, and di (i = 1, 2, , 3,...) Indicate the i-th axial upper surface distance counted from the object side. The shaft upper surface interval (variable interval) d3 that changes due to zooming is the wide-angle end (W)
It is the surface distance between the respective groups at the intermediate focal length state (M) to the telephoto end (T). Ni (i = 1,2,3) and νi (i = 1,2,3) are the refractive index (N
d) and Abbe number (νd). In addition, wide angle end (W)
The focal length f and the F-number FNO of the entire system from the intermediate focal length state (M) to the telephoto end (T) are shown together with the construction data.

A surface marked with an asterisk (*) has a radius of curvature ri, which is a surface constituted by an aspheric surface, and is defined by the following equation (AS) representing the surface shape of the aspheric surface.

[0043]

(Equation 1)

In the equation (AS), Y: displacement amount from the reference plane in the optical axis direction, X: height in the direction perpendicular to the optical axis, C: paraxial curvature, ε: quadratic surface parameter Ai: The aspheric coefficient of the following expression:

The surface with the [DOE] mark added to the radius of curvature ri indicates that the surface is a refractive optical surface on which a diffractive optical surface is formed, and the following equation representing the phase shape that determines the pitch of the diffractive optical surface:
(DS).

[0046]

(Equation 2)

In the formula (DS), ψ (X): phase function of the diffractive optical surface, Ri: i-th phase function coefficient of the diffractive optical surface, X: height in a direction perpendicular to the optical axis, λ0: Design center wavelength of the diffractive optical surface (= 585.75 × 10 ⁻⁶ mm).

<< Example 1 >>

[Aspherical surface coefficient] r1: ε = 1.0000 A4 = -5.06810 × 10 ^-4 A6 = 7.89450 × 10 ^-6 A8 = -1.51723 × 10 ^-6 A10 = 1.16596 × 10 ^-7 A12 = -7.06037 × 10 ^{− 10} A14 = -2.20494 × 10 ^-10 r2: ε = 1.0000 A4 = -0.156896 × 10 ^-3 A6 = 0.852515 × 10 ^-5 A8 = -0.425178 × 10 ^-6 A10 = 0.109571 × 10 ^-7 r4: ε = 1.0000 A4 ^{= -6.93937 × 10 -5 A6 = 5.45272} × 10 -6 A8 = -2.19136 × 10 -7 A10 = 2.58014 × 10 -9 A12 = 4.45085 × 10 -12 A14 = -2.14069 × 10 -13 A16 = 7.47946 × 10 - ^{16 r5: ε = 1.0000 A4 =} -7.49983 × 10 -5 A6 = 1.35208 × 10 -6 A8 = 2.07437 × 10 -8 A10 = -2.59620 × 10 -9 A12 = 4.41162 × 10 -11 A14 = -2.18639 × 10 - ¹³

[0050]

<< Embodiment 2 >>

[Aspherical surface coefficient] r1: ε = 1.0000 A4 = -5.27500 × 10 ^-4 A6 = 6.19560 × 10 ^-6 A8 = -7.74378 × 10 ^-7 A10 = 2.92740 × 10 ^-8 A12 = 2.36962 × 10 ^-9 A14 = -2.20494 × 10 ^-10 r2: ε = 1.0000 A4 = -0.135035 × 10 ^-3 A6 = 0.502407 × 10 ^-5 A8 = -0.250180 × 10 ^-6 A10 = 0.835102 × 10 ^-8 r4: ε = 1.0000 A4 = ^{-6.06687 × 10 -5 A6 = 5.75569 ×} 10 -6 A8 = -3.30651 × 10 -7 A10 = 5.73424 × 10 -9 A12 = -2.61719 × 10 -11 A14 = -1.08150 × 10 -13 A16 = 5.13656 × 10 - ¹⁶ r5: ε = 1.0000 A4 = -8.04087 × 10 ^-5 A6 = 2.22370 × 10 ^-6 A8 = -1.82096 × 10 ^-8 A10 = -2.71279 × 10 ^-9 A12 = 5.83952 × 10 ^-11 A14 = -3.29099 × 10 ^-13

[0053]

<< Embodiment 3 >>

[Aspherical surface coefficient] r1: ε = 1.0000 A4 = -5.95580 × 10 ^-4 A6 = 4.06040 × 10 ^-5 A8 = -1.25117 × 10 ^-5 A10 = 1.92444 × 10 ^-6 A12 = -1.40597 × 10 ^{− 7} A14 = 3.85081 × 10 ^-9 r2: ε = 1.0000 A4 = -0.218116 × 10 ^-3 A6 = 0.165267 × 10 ^-4 A8 = -0.104547 × 10 ^-5 A10 = 0.261682 × 10 ^-7 r4: ε = 1.0000 A4 = 9.41188 × 10 ^-6 A6 = 4.18634 × 10 ^-6 A8 = -1.04362 × 10 ^-7 A10 = 2.42448 × 10 ^-9 A12 = -3.08900 × 10 ^-11 A14 = 1.94111 × 10 ^-13 A16 = -4.70429 × 10 ^-16 r5: ε = 1.0000 A4 = 0.147440 × 10 ^-4 A6 = 0.735909 × 10 ^-7 A8 = 0.265375 × 10 ^-7 A10 = -0.153544 × 10 ^-9

[0056]

In the third embodiment, the first lens unit Gr1 and the second lens unit Gr1
The lenses constituting the group Gr2 are all plastic lenses. Therefore, cost reduction of the zoom lens can be effectively achieved. Examples 1 to 3
Conditional expressions (1) to (4) are satisfied. In Table 1 below,
Corresponding values of conditional expressions (1) to (4) {
Conditional expression (1): | φdoe / φr |, Conditional expression (2): | R2 × Hmax
/ Λ0 |, conditional expression (3): φdoe1 / φr1, conditional expression (4): φ
doe2 / φr2}.

[0058]

[Table 1]

FIGS. 4 to 6 are aberration diagrams of the first embodiment, FIGS. 7 to 9 are aberration diagrams of the second embodiment, and FIGS. 10 to 12 are aberration diagrams of the third embodiment. , Intermediate focal length state
(M) and various aberrations at the telephoto end (T). Each aberration diagram represents, in order from the left, spherical aberration, astigmatism, and distortion. In each aberration diagram, the broken line is c-line (wavelength: λc = 656.3 nm).
, The solid line represents the aberration with respect to the d-line (wavelength: λd = 587.6 nm), and the dashed line represents the aberration with respect to the g-line (wavelength: λg = 435.8 nm). The vertical axis of the spherical aberration (horizontal axis, mm) represents h / h0 in which the incident height h is normalized by its maximum height h0, and the astigmatism (horizontal axis, mm) and the distortion (horizontal axis) ,%) Represents the half angle of view ω (°). The solid line M represents astigmatism on the meridional surface, and the solid line S represents astigmatism on the sagittal surface.

[0060]

As described above, according to the first to tenth aspects, since at least one diffractive optical surface is provided in the entire zoom lens system, chromatic aberration can be favorably corrected with a small number of lenses. Zoom lens can be realized. Since the number of components in each group can be reduced while maintaining optical performance, the camera can be made compact and low cost.

According to the second aspect of the present invention, since the diffractive optical surface is provided in the first group, even if the first group is constituted by one lens, the chromatic aberration generated in the first group is favorably corrected. be able to. According to the third aspect, since the diffractive optical surface is provided in the second group, chromatic aberration of magnification can be favorably corrected, and the amount of chromatic aberration generated during zooming can be reduced. .

According to the fourth aspect, since the power of the diffractive optical surface is appropriately set by satisfying the conditional expression (1), more excellent aberration performance can be achieved. Further, according to the fifth aspect, the phase function coefficient of the diffractive optical surface is appropriately set by satisfying the conditional expression (2), so that a diffractive optical surface having an appropriate pitch can be obtained. According to the sixth or seventh aspect of the present invention, since the conditional expression (3) or (4) is satisfied, chromatic aberration can be corrected more favorably, and the diffractive optical surface can be easily manufactured.

According to the eighth aspect, since the diffractive optical surface is provided on the surface of the refractive optical surface having the aspherical shape,
It is possible to favorably correct not only chromatic aberration but also other aberrations. According to the ninth aspect, since the diffractive optical surface is provided on the surface of the plastic lens, it can be manufactured at low cost. According to the tenth aspect, since the lenses forming the first group and the second group are all plastic lenses, the cost can be further reduced and the manufacturing becomes easy.

[Brief description of the drawings]

FIG. 1 is a lens configuration diagram of a first embodiment.

FIG. 2 is a lens configuration diagram of a second embodiment.

FIG. 3 is a lens configuration diagram of a third embodiment.

FIG. 4 is an aberration diagram at a wide-angle end (W) of the first embodiment.

FIG. 5 is an aberration diagram of the first embodiment in an intermediate focal length state (M).

FIG. 6 is an aberration diagram at a telephoto end (T) in the first embodiment.

FIG. 7 is an aberration diagram at a wide-angle end (W) of the second embodiment.

FIG. 8 is an aberration diagram of Example 2 in an intermediate focal length state (M).

FIG. 9 is an aberration diagram at a telephoto end (T) in the second embodiment.

FIG. 10 is an aberration diagram at a wide-angle end (W) of the third embodiment.

FIG. 11 is an aberration diagram of Example 3 in an intermediate focal length state (M).

FIG. 12 is an aberration diagram at a telephoto end (T) in the third embodiment.

[Explanation of symbols]

 Gr1 First group Gr2 Second group A Aperture

Claims (10)

[Claims] 1. A zoom lens system comprising: a first lens unit having a positive refractive power and a second lens unit having a negative refractive power in order from the object side, and when zooming from a wide-angle end to a telephoto end, the first unit and the second unit In a zoom lens in which the two groups move so as to reduce the distance between each other, the first group includes one lens, the second group includes at least two lenses, and the diffractive optical surface is zoomed. A zoom lens, wherein at least one surface is provided in the entire lens system. 2. The zoom lens according to claim 1, wherein the diffractive optical surface is provided in the first group. 3. The zoom lens according to claim 1, wherein the diffractive optical surface is provided in the second group. 4. The zoom lens according to claim 1, wherein each of the groups provided with the diffractive optical surfaces satisfies the following conditional expression: 0.03 <| φdoe / φr | <0.15 , Φdoe: power of the diffractive optical surface, φr: composite power of the group including the diffractive optical surface. 5. The zoom lens according to claim 1, wherein the following conditional expression is satisfied: 2 <| R2 × Hmax / λ0 | <25, where R2 is a second-order phase function of the diffractive optical surface. Coefficient (1 / mm), Hmax: Effective diameter of the lens provided with the diffractive optical surface (m
m), λ0: Design center wavelength (mm) of the diffractive optical surface. 6. The zoom lens according to claim 2, wherein the following conditional expression is satisfied: 0.03 <φdoe1 / φr1 <0.10, where φdoe1: power of the diffractive optical surface provided in the first lens unit Φr1: combined power of the first group. 7. The zoom lens according to claim 3, wherein the following conditional expression is satisfied: 0.06 <φdoe2 / φr2 <0.15, where φdoe2: power of the diffractive optical surface provided in the second lens unit Φr2: combined power of the second group. 8. The zoom lens according to claim 1, wherein the diffractive optical surface is provided on a surface of a refractive optical surface having an aspherical shape. 9. The zoom lens according to claim 1, wherein the diffractive optical surface is provided on a surface of a plastic lens. 10. The zoom lens according to claim 1, wherein the lenses forming the first group and the second group are all plastic lenses.