JP2003021783A - Zoom lens and optical equipment using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a compact zoom lens whose optical performance is excellent and whose chromatic difference of magnification, especially, is made small by using a diffraction optical element. SOLUTION: This zoom lens has a 1st lens group having negative refractive power, a 2nd lens group having positive refractive power and a 3rd lens group having positive refractive power in order from an object side. In the case of varying power from a wide angle end to a telephoto end, the 1st lens group and the 2nd lens group are moved. One or more lens groups include a plastic lens, and the plastic lens has a diffraction optical surface rotationally symmetric with respect to an optical axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for a photographic camera, a video camera, a digital camera, and the like. The present invention relates to a lead zoom lens and an optical apparatus having the same.

[0002]

2. Description of the Related Art In recent years, as optical devices such as home video cameras have become smaller and lighter, zoom lenses for image pickup have become smaller.
Significant progress has been made in improving image quality. Various optical systems have been proposed to realize the originally contradictory propositions of miniaturization achieved by simplification of the configuration and high performance achieved by the complexity of the configuration.

As one optical system for achieving these objects, a so-called negative lead in which a first lens unit on the object side is constituted by a lens unit having a negative refractive power, and the first lens unit is moved to perform zooming. Are known zoom lenses.

In general, a negative-lead zoom lens has a smaller effective diameter after the second lens group than a zoom lens that performs zooming with the first lens group fixed, thereby facilitating miniaturization of the entire lens system. . In addition, if focusing is performed by the first lens group, it is possible to perform imaging without focus fluctuation due to zooming during close-up imaging, and a simpler lens group configuration can be employed. Also, the second
If focusing is performed after the lens group, the focus lens group is a light lens group having a small lens diameter, and thus has features such as a small driving force, a short driving stroke, and quick focusing.

[0005] Such a negative lead type zoom lens has been proposed in, for example, JP-A-1-191820, JP-A-3-203709, and JP-A-3-240011. These publications have, in order from the object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a positive refractive power. There is disclosed a zoom lens which performs zooming by correcting the image plane variation accompanying zooming in the first lens group. With such a configuration, the diameter of the front lens can be made relatively small, and a compact zoom lens is achieved.

However, in recent years, C
There is a great demand for a zoom lens that achieves a high degree of chromatic aberration correction by increasing the number of CD elements, and there is a demand for further miniaturization while maintaining good optical performance.

In general, in order to correct chromatic aberration, it is necessary to reduce the chromatic aberration generated in each lens group by increasing the number of lenses constituting each lens group and reducing the aberration sharing of each lens. is there. However, this method goes against the miniaturization of the lens system.

In order to correct this chromatic aberration, in addition to a method of correcting by combining glass materials having different dispersions, an optical system corrected by providing a diffractive optical element having a diffractive effect on a lens surface or a part of the optical system is used, for example. JP-A-4-213421, JP-A-6-324262, JP-A-9-19
No. 7,274, Japanese Patent Application Laid-Open No. 9-212329, and US Pat. No. 5,268,790.

In order to correct various aberrations and reduce the number of lenses, it has been conventionally known to use an aspherical surface. When this aspherical surface is used, the effect of reducing the number of lenses and correcting aberrations that cannot be obtained with a spherical surface can be expected and is effective.

[0010]

SUMMARY OF THE INVENTION In a zoom lens aiming at obtaining high image quality, various types of aberration correction are required.
In particular, correction of chromatic aberration is important. In a zoom lens having a fixed first lens group on the object side of the movable lens group that moves during zooming, it is one of the main lens groups that is one of the movable lens groups unless the generation of chromatic aberration of the first lens group is kept small. The movement of the magnification lens group (for example, the second lens group) causes a large variation in chromatic aberration.

For this purpose, conventionally, the first lens group is achromatized (correction of chromatic aberration) by using one or two negative lenses made of a high dispersion material and one or two positive lenses made of a low dispersion material. I have. Further, a configuration in which a negative lens and a positive lens are bonded to each other may be used, so that the number of lenses constituting the first lens group increases.

As a method for suppressing the occurrence and fluctuation of chromatic aberration to a small extent, the above-mentioned Japanese Patent Application Laid-Open Nos. Hei 4-213421 and Hei 6-61, in which a diffractive optical surface (diffractive optical element) is applied to an imaging optical system.
Japanese Patent Application Laid-Open No. 324262 discloses an application to an imaging lens having a single focal length. In these publications, there is no consideration or description of removal of chromatic aberration fluctuation due to zooming (magnification change) peculiar to a zoom lens, and no application to a zoom lens is performed.

US Pat. No. 5,268,790 shows an application to a zoom lens. In this case, a diffractive optical element is used for a second lens group as a main variable power lens group or a third lens group as a correction lens group. Propose that.

The first lens group does not use any diffractive optical element. In this configuration, when chromatic aberration occurs in the first lens group, the chromatic aberration is increased or fluctuated by the movement of the variable power lens group such as the second lens group as it is during zooming.
It reaches the image plane. Further, as an example, a zoom lens of about 10 times is described, but there is a description that higher magnification is achieved with the same size than that known in this publication. However, there are still many lenses and there is room for miniaturization.

In Japanese Patent Application Laid-Open No. 2000-9999, a diffractive optical element is used in a zoom lens comprising a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a positive or negative refractive power. An applied configuration has been proposed, but no configuration for obtaining a zoom ratio of 2 or more has been proposed.

In Japanese Patent Application Laid-Open Nos. 11-52237 and 2000-147380, the applicant of the present invention disclosed a lens system which performs advanced chromatic aberration correction corresponding to a high-pixel CCD and maintains good optical performance. The company proposes a zoom lens that achieves overall miniaturization.

In general, in a negative-lead zoom lens for the purpose of shortening the entire length of the lens, the radius of curvature of each lens surface tends to become smaller as the refractive power of each lens group becomes stronger. Generally, it is not preferable that the radius of curvature is small from the viewpoint of aberration correction and difficulty in manufacturing. Therefore, there is a tendency to select a glass material having a high refractive index in order to increase the radius of curvature without changing the refractive power.

On the other hand, in consideration of cost, it is preferable to use a resin material for the diffractive optical surface, but the resin material usually used for optical applications often has a low refractive index.

According to the present invention, in a negative lead type zoom lens which is preceded by a lens unit having a negative refractive power, by appropriately setting the lens configuration of each lens unit, various aberrations including chromatic aberration can be satisfactorily corrected. It is an object of the present invention to provide a zoom lens which has high optical performance over the entire zoom range and has a small overall lens system, and an optical apparatus using the same.

Another object of the present invention is to provide a compact zoom lens in which a chromatic aberration is favorably corrected using a diffractive optical surface, and an optical apparatus using the same.

[0021]

According to a first aspect of the present invention, there is provided a zoom lens having a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a second lens unit having a positive refractive power. A zoom lens having three lens groups and moving the first lens group and the second lens group when changing magnification from the wide-angle end to the telephoto end, wherein the one or more lens groups include a plastic lens; Are characterized by having a diffraction optical surface rotationally symmetric with respect to the optical axis.

A zoom lens according to a second aspect of the present invention includes, in order from the object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a positive refractive power. A zoom lens for moving the first lens group and the second lens group at the time of zooming from a wide-angle end to a telephoto end, wherein the one or more lens groups have a surface provided with a diffraction grating surface on a resin aspherical layer. It is characterized by things.

According to a third aspect of the present invention, in the first or second aspect, the diffractive optical surface comprises a laminated diffraction grating.

According to a fourth aspect of the present invention, in the first, second, or third aspect, the focal length at the wide-angle end is Fw, the focal length at the telephoto end is Ft, and the focal length Fm in the middle of zooming is Fm.

[0025]

(Equation 2)

When zooming from the wide-angle end to the telephoto end, the first lens group moves from the object side to the image side, and the second lens group moves from the image side to the object side. The third lens unit is moved toward the image side when the magnification is changed from F to intermediate zoom (Fm).

According to a fifth aspect of the present invention, in the first aspect of the present invention, the first lens group includes, in order from the object side, an absolute value of a refractive power of a surface on an image plane side as compared with the object side. , And a negative lens having a large shape, and a positive meniscus lens having a convex surface facing the object side.

According to a sixth aspect of the present invention, in any one of the first to fourth aspects, the first lens group includes, in order from the object side, an absolute value of a refractive power of a surface on an image surface side as compared with the object side. It is composed of a negative lens with a larger shape, a negative lens with a larger absolute value of the refracting power of the image plane side than the object side, and a meniscus positive lens with a convex surface facing the object side. And

According to a seventh aspect of the present invention, in the first aspect of the present invention, the second lens unit includes a positive lens having both convex lens surfaces and a negative lens having both concave lens surfaces. It is characterized by having.

According to an eighth aspect of the present invention, in the first aspect of the present invention, the second lens group includes a positive lens having both lens surfaces convex, a negative lens having both lens surfaces concave, and It is characterized in that the lens surface has a convex positive lens.

According to a ninth aspect of the present invention, in any one of the first to eighth aspects of the present invention, the third lens group includes a single lens component composed of a single lens or a cemented lens.

The optical device according to the tenth aspect of the present invention is the optical device according to the first aspect.
9. The zoom lens according to any one of claims 1 to 9,

[0033]

FIG. 1 is a sectional view of a zoom lens according to a first numerical embodiment of the present invention. FIGS. 2 and 3 show zoom positions at the wide-angle end and the telephoto end of the zoom lens according to the first numerical embodiment of the present invention. FIG. 4 is a sectional view of a zoom lens according to a second numerical example of the present invention at the wide-angle end. FIGS. 5 and 6 are aberration diagrams of the zoom lens according to the second numerical example of the present invention at the wide-angle end and the telephoto end. It is. FIG. 7 shows a third embodiment of the present invention.
8 and 9 are aberration diagrams at the wide-angle end and telephoto end of the zoom lens according to Numerical Example 3 of the present invention at the zoom position. FIG. 10 is a numerical example 4 of the present invention.
11 and 12 are aberration diagrams at the wide-angle end and telephoto end of the zoom lens according to Numerical Example 4 of the present invention.

In the sectional view of the lens, L1 is a first group (first lens group) having a negative refractive power, L2 is a second group (second lens group) having a positive refractive power, and L3 is a third group having a positive refractive power. This is a group (third lens group).

Arrows indicate the moving direction of each lens unit when zooming from the wide-angle side to the telephoto side. SP is an aperture, and IP is an image plane. G is a glass block such as a face plate and a color filter.

In this embodiment, when zooming from the wide-angle end to the telephoto end, the first lens unit L1 is moved to the image side.
The second lens unit L2 is moved to the object side. Also, the third
The lens unit is moved to the image side when zooming from the wide-angle end to the zoom intermediate focal length, and is moved to the object side when zooming from the zoom intermediate focal length to the telephoto end.

Here, the zoom intermediate focal length Fm is defined assuming that the focal lengths at the wide-angle end and the telephoto end are Fw and Ft, respectively.

[0038]

[Equation 3]

Is a value defined by

The wide-angle end and the telephoto end refer to zoom positions when the zooming lens group is located at both ends of a movable range on the optical axis in terms of mechanism.

At least one of the first lens unit L1, the second lens unit L2, and the third lens unit L3 made of a resin material has a diffraction optical surface rotationally symmetric with respect to the optical axis. One is provided.

The first lens unit L1 and the second lens unit L
A stop SP is provided between the stop lens 2 and the stop SP. The stop SP moves independently or has an integrated locus with the second lens unit L2 during zooming. If the stop SP is moved independently during zooming, it is easy to keep the front lens diameter small. When the stop is moved integrally with the second lens unit L2, the driving mechanism can be simplified, which is effective for downsizing the lens system.

The third lens unit L3 moves to the image side when zooming from the wide-angle end to the zoom intermediate focal length (at the time of zooming).
This is effective in suppressing the overall length of the zoom lens when the zoom lens is increased in magnification, suppressing the front lens diameter, and favorably maintaining various aberrations in the entire zoom range.

By arranging a diffractive optical surface (diffractive optical element) in the first lens unit L1 and appropriately selecting the phase of the diffractive optical element, the chromatic aberration of magnification occurring in the first lens unit L1, for example, the d-line The chromatic aberration of magnification at two wavelengths such as the g-line is suppressed small, and the change in chromatic aberration of magnification accompanying zooming is suppressed to a small value. At this time, the width itself of the axial chromatic aberration (secondary spectrum) at the telephoto end does not deteriorate.

Further, by disposing a diffractive optical surface in the second lens unit L2 and appropriately selecting the phase of the diffractive optical element, chromatic aberration of magnification occurring in the second lens unit L2, for example, d-line and g-line Chromatic aberration of two wavelengths such as
Fluctuations in chromatic aberration of magnification due to zooming are kept small. At this time, the width of the axial chromatic aberration (secondary spectrum) at the telephoto end does not deteriorate.

In the conventional three-unit zoom lens, the first lens unit L1 uses one or two negative lenses made of a high dispersion material and one or two positive lenses made of a low dispersion material. And achromatism was performed by sharing with multiple lenses.

On the other hand, in the present embodiment, a diffractive optical element is used for the first lens unit L1, and chromatic aberration is corrected thereby, thereby reducing the number of lenses in the first lens unit L1. Also, the second lens unit L2 is
A group zoom lens uses two or one negative lens made of a low dispersion material and two positive lenses made of a high dispersion material, and further attaches the negative lens and the positive lens, or shares the color with a plurality of lenses. Had been erased.

On the other hand, in the present embodiment, the number of lenses in the second lens group is reduced by using a diffractive optical element for the second lens L2 and correcting chromatic aberration by this. The same can be said for the case where a diffractive optical element is used for the third lens group.

According to the present embodiment, the chromatic aberration correction is satisfactorily corrected, and the overall size of the lens system is reduced while maintaining high optical performance.

The aspherical shape of the lens surface in the above embodiment is such that the X axis is in the optical axis direction, the H axis is perpendicular to the optical axis (distance in the radial direction), the traveling direction of light is positive, and R is paraxial. When the radius of curvature, K is the eccentricity, B, C, and D are aspherical coefficients, respectively, and the magnification in the optical axis direction at a height H from the optical axis is X with respect to the surface vertex, X = (H ² / R) / [1+ {1+ (1 + K) (H / R) ² } ^1/2 ] + BH ⁴ + CH ⁶ + DH ⁸ (1)

Assuming that φ (h) is a phase, λ is a reference wavelength, Ci is a coefficient representing a phase, and h is a height from the optical axis, φ (h) = λ (C1 · h ² + C2 · ^{h 4 + ···· + Ci · h} 2 · i) represents ... (2) made of a formula.

What can be understood from the equation (2) is that the phase can be adjusted by the distance h from the optical axis. The greater the lens diameter, the greater the effect of higher order coefficients. In a consumer zoom lens described in the present embodiment, particularly a zoom lens for video, the entire lens system is being reduced in size, and an excessively large lens, that is, a lens having a large height h is not preferable. In addition, in order to achieve effective aberration correction by efficiently utilizing the coefficient even in a small lens, the following conditional expression is satisfied.

1 · 10 ⁻⁴ <| C2 / C1 | <1 (3) As described above, these expressions are for effectively correcting aberrations when the lens diameter is small. . If these conditions are not satisfied, not only is it difficult to correct aberrations, but also it becomes difficult to manufacture a diffractive optical surface, which is not appropriate.

As a specific configuration of the first lens unit L1, in Numerical Embodiments 1, 2, and 4, it is composed of a positive lens and a negative lens. In Numerical Embodiment 3, two negative lenses and one positive lens are provided. A diffractive optical surface is provided on one of the lens surfaces. In each numerical example, the positive lens and the negative lens may be bonded. Further, as another configuration of the first lens unit L1, the first lens unit L1 is composed of two negative lenses, and at least one diffractive optical element is provided before and after (object-side or image-side) or an intermediate surface. A plate (optical member) having a surface may be arranged.

In any case, it is preferable not to dispose a diffractive optical surface on the surface closest to the object, except in a special case where correction of aberration is unavoidable. The diffractive optical element has a rather narrow width,
For example, it is composed of grooves on the order of several μm or sub-μm, and if dust or dirt enters there, the optical characteristics are degraded.
For this reason, in order to protect the surface of the diffractive optical element from dust and the like, it is preferable not to dispose it on the surface closest to the object.

One specific configuration of the second lens unit L2 is composed of a total of three lenses, two positive lenses and one negative lens, and at least one diffraction lens on the front, back, or intermediate surface. It is preferable to arrange a plate having an optical surface.

As another configuration of the second lens unit L2, the second lens unit L2 is composed of two lenses, a positive lens and a negative lens, or a negative lens and a positive lens. It is good to arrange an optical surface. The third lens unit L3 is composed of a single lens component composed of a single lens or a cemented lens.

In Numerical Examples 1 and 2, the image-side lens surface of the object-side lens of the first lens unit L1 and the most object-side lens surface and the most image-side lens surface of the second lens unit L2 are aspheric. And The first lens unit L according to Numerical Example 3 is also described.
1, the image-side lens surface of the intermediate lens, the second lens unit L2
The most object-side lens surface and the object-side lens surface of the third lens unit L3 are aspheric.

In the numerical example 4, the first lens unit L1
The image-side lens surface of the object-side lens, the second lens unit L2
The image-side lens surface of the object-side lens and the object-side lens surface of the third lens group are aspherical.

Further, the diffractive optical surface is the image-side lens surface of the lens closest to the object side of the first lens unit L1 in Numerical Embodiment 1, and the most object-side lens surface of the second lens unit L2 in Numerical Embodiment 2. In Numerical Embodiment 3, the third lens unit L3 is formed on the most object side lens surface, and in Numerical Embodiment 4, the first lens unit L1 is formed on the image side replica surface of the most object side lens. Here, the replica surface is a method in which an aspherical shape is formed by a resin film on a base spherical lens, and the introduction of a diffractive optical surface on this surface is a molding constraint depending on the lens shape as an aspherical surface. Is small,
This is extremely effective because the aspherical surface and the diffractive optical surface can be formed simultaneously.

As described above, in the first lens unit L1 or in the second lens unit L1,
The chromatic aberration (secondary spectrum) generated in each lens group is suppressed small by the diffractive optical surface arranged in the lens unit L2 or the third lens unit L3, and the fluctuation due to the zooming of the chromatic aberration due to the movement of the second lens unit L2. I keep it small. If the refractive power of the diffractive optical surface is increased, the difference between the saw-shaped pitches at the center of the lens and the periphery of the lens becomes large, making the production difficult, and the diffraction efficiency of the finished product is not good. Therefore, when chromatic aberration correction is performed on the diffractive optical surface instead of achromatization of the cemented lens surface of the first lens unit L1, the second lens unit L2, or the third lens unit L3, the refractive power is not so necessary. . Here, a refractive power may be provided for correcting some off-axis aberrations, particularly curvature of field and distortion.

Generally, chromatic aberration opposite to chromatic aberration caused by ordinary refraction occurs on a diffractive optical surface. For example, when removing a lens that has been achromatized by a conventional bonding surface or the like and reducing the number of lenses, diffracting a surface that has chromatic aberration sharing opposite to the chromatic aberration sharing that occurred on the bonding surface It may be an optical surface.

By using the diffractive optical surface in this way, chromatic aberration opposite to the chromatic aberration generated by ordinary refraction occurs on the diffractive optical surface, and the direction is the same as the chromatic aberration generation direction on the originally bonded surface. And achromatization such as bonding can be performed with a single lens.

From the viewpoint of the chromatic aberration coefficient (published by Kyoritsu Shuppan Co., Ltd., Yoshiya Matsui, “Lens Design Method”, page 89),
On the surface on the object side of the stop, the diffractive optical surface is arranged on the surface having the same sign of the axial chromatic aberration coefficient L and the magnification chromatic aberration coefficient T. It is preferable to arrange the surfaces.

In the present embodiment, the first lens unit L1 or the second lens unit L2 may be constituted by one using a diffractive optical element.

As described above, according to the present embodiment,
Negative-lead type zoom lens with relatively small front lens diameter, wide angle of view, and high zoom ratio, adopting plastic lens (resin material lens) to facilitate introduction of diffractive optical surface and achieve full zoom High performance is achieved at low cost in the area.

The diffractive optical element according to the present invention may be manufactured by binary optics, which is an optical element binary-manufactured by a lithographic technique, which is a technique for producing a holographic optical element (HOE). Further, it may be manufactured by a mold prepared by these methods.
Alternatively, it may be formed by a method of transferring a film of plastic or the like to the optical surface as the diffractive optical surface (a so-called replica aspheric surface).

As the diffraction grating shape of the diffractive optical element, for example, a kinoform shape shown in FIG. 13 can be applied. FIG.
Shows the wavelength dependence of the first-order diffraction efficiency of the diffractive optical element shown in FIG. The actual configuration of the diffraction grating is
2 is coated with an ultraviolet curable resin, and a wavelength of 53
A grating thickness d such that the first-order diffraction efficiency becomes 100% at 0 nm.
Is formed.

As is clear from FIG. 14, the diffraction efficiency at the design order decreases as the distance from the optimized wavelength of 530 nm increases, while the 0th-order and second-order diffracted lights near the design order increase. The increase in diffracted light other than the design order causes a flare, which leads to a decrease in resolution of the optical system.

Therefore, the laminated diffraction grating shown in FIG. 15 may be used as the grating shape of the diffractive optical element in the embodiment of the present invention.

FIG. 16 shows the wavelength dependence of the first-order diffraction efficiency of the diffractive optical element having this configuration. As a specific configuration,
UV curable resin (nd = 1.499, νd = 5) on the substrate
A first diffraction grating 104 made of 4) is formed, and another ultraviolet curable resin (nd = 1.598, νd = 28) is formed thereon.
Is formed. In this combination of materials, the grating thickness d1 of the first diffraction grating portion is d1 = 18.8 μm, and the grating thickness d2 of the second diffraction grating portion is d2 = 10.5 μm.

As can be seen from FIG. 16, the diffraction efficiency of the design order has a high diffraction efficiency of 95% or more over the entire operating wavelength range by using a diffraction grating having a laminated structure.

In addition, a two-layer structure with an air gap as shown in FIG. 17 can be applied.

The two diffraction gratings 106 and 10 shown in FIG.
FIG. 18 shows the wavelength dependence of the diffraction efficiency of the first-order diffracted light of the diffractive optical element using No. 7.

In FIG. 17, a first diffraction grating 106 made of an ultraviolet curable resin is formed on a substrate 102, and the first diffraction grating 106 is formed on the substrate 102 '.
A second diffraction grating 107 made of an ultraviolet curable resin is formed thereon.

As can be seen from FIG. 18, the diffraction efficiency of the design order has a high diffraction efficiency of 95% or more over the entire wavelength range used.

As described above, by using a diffraction grating having a laminated structure as the diffractive optical element of the embodiment of the present invention, the optical performance is further improved.

Incidentally, the material of the diffractive optical element having the above-mentioned laminated structure is not limited to the ultraviolet curable resin, but other plastic materials and the like can be used. It may be formed on a substrate.

In this embodiment, since the diffractive optical element is provided on the optical plastic surface, the diffraction grating 104
Can be directly formed on the base material 102, which is advantageous in terms of productivity and cost. Alternatively, as shown in Numerical Example 4, by forming a diffraction grating on a replica aspherical surface,
Since the aspherical effect and the effect as a diffractive optical element can be obtained by one molding, improvement in mass productivity can be expected.

Further, it is not necessary for the respective grating thicknesses to be different, and depending on the combination of materials, the two grating thicknesses can be made equal as shown in FIG. In this case, since the grating shape is not formed on the surface of the diffractive optical element, it is excellent in dust resistance, the workability of assembling the diffractive optical element is improved, and a more inexpensive optical system can be provided.

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

In FIG. 20, reference numeral 10 denotes a camera body;
Is a photographing optical system constituted by the zoom lens of the present invention, and 12 is a finder for observing a subject image.

13 is a strobe device, 14 is a measurement window, 15
Is a liquid crystal display window for notifying the operation of the camera, 16 is a release button, and 17 is an operation switch for switching various modes.

FIG. 21 is a schematic view of a main part of an optical apparatus when the zoom lens of the present invention is applied to a single-lens reflex camera such as a film camera or a digital camera.

In FIG. 21, reference numeral 20 denotes a camera body, reference numeral 21 denotes a zoom lens of the present invention, and reference numeral 22 denotes an image pickup means, which comprises a film, a CCD and the like. Reference numeral 23 denotes a finder system, which has a focusing plate 25 on which a subject image is formed, and a pentaprism 26 serving as an image reversing means. An eyepiece 27 for observing the subject image on the focusing plate 25. 24 is a quick return mirror.

The numerical data of Numerical Examples 1 to 4 will be shown below. In each numerical example, i indicates the order of the surface from the object side, Ri is the radius of curvature of each surface, and Di is the i-th surface and the i-th surface.
The member thickness or air gap between the +1 plane and Ni and νi indicate the refractive index and Abbe number for the d-line, respectively. The two surfaces closest to the image are glass blocks G corresponding to a quartz low-pass filter, an infrared cut filter, and the like.

The aspherical shape and the shape of the diffractive optical element are represented by the above-mentioned equations (1) and (2).

[0088]

[Outside 1]

[0089]

[Outside 2]

[0090]

[Outside 3]

[0091]

[Outside 4]

[0092]

According to the present invention, in a negative lead type zoom lens which is preceded by a lens unit having a negative refractive power, by appropriately setting the lens configuration of each lens unit, various aberrations including chromatic aberration can be improved. Thus, a zoom lens having high optical performance over the entire zoom range and miniaturizing the entire lens system and an optical apparatus using the same can be achieved.

In addition, according to the present invention, it is possible to achieve a compact zoom lens in which chromatic aberration is favorably corrected by using a diffractive optical surface, and an optical apparatus using the same.

[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 at a wide angle end according to Numerical Embodiment 1 of the present invention.

FIG. 3 is an aberration diagram at a telephoto end in Numerical Example 1 of the present invention;

FIG. 4 is a sectional view of a lens according to a numerical example 2 of the present invention.

FIG. 5 is an aberration diagram at a wide-angle end according to Numerical Example 2 of the present invention.

FIG. 6 is an aberration diagram at a telephoto end in Numerical Example 2 of the present invention.

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

FIG. 8 is an aberration diagram at a wide angle end according to Numerical Example 3 of the present invention.

FIG. 9 is an aberration diagram at a telephoto end in Numerical Example 3 of the present invention.

FIG. 10 is a sectional view of a lens according to a numerical example 4 of the present invention.

FIG. 11 is an aberration diagram at a wide angle end according to Numerical Example 4 of the present invention.

FIG. 12 is an aberration diagram at a telephoto end in Numerical Example 4 of the present invention.

FIG. 13 is an explanatory view of a diffractive optical element according to the present invention.

FIG. 14 is an explanatory diagram of a wavelength dependence characteristic of the diffractive optical element according to the present invention.

FIG. 15 is an explanatory view of a diffractive optical element according to the present invention.

FIG. 16 is an explanatory diagram of a wavelength dependence characteristic of the diffractive optical element according to the present invention.

FIG. 17 is an explanatory view of a diffractive optical element according to the present invention.

FIG. 18 is an explanatory diagram of a wavelength dependence characteristic of the diffractive optical element according to the present invention.

FIG. 19 is an explanatory view of a diffractive optical element according to the present invention.

FIG. 20 is an explanatory diagram of the optical apparatus of the present invention.

FIG. 21 is an explanatory diagram of an optical apparatus according to the invention.

[Explanation of symbols]

L1 First group L2 2nd group L3 3rd group SP aperture dd line g g line ΔS sagittal image plane ΔM Meldional image plane 101 Diffractive optical element 102 substrate 103, 104, 105 layers 10,20 camera body 11 Shooting optical system 12 Finder 13 Strobe device 14 Measurement window 15 LCD display window 16 Release button 17 Operation switch 21 Zoom lens 22 Imaging means 23 Viewfinder 24 quick return mirror 25 Focus version

Continuation of front page    F-term (reference) 2H044 DA02                 2H049 AA03 AA17 AA18 AA51 AA55                       AA63 AA65                 2H087 KA01 LA01 PA04 PA05 PA07                       PA17 PA18 PB05 PB07 QA02                       QA06 QA07 QA17 QA21 QA22                       QA25 QA32 QA34 QA41 QA42                       QA45 QA46 RA04 RA12 RA13                       RA43 RA46 SA14 SA16 SA19                       SA62 SA63 SA64 SB03 SB04                       SB13 SB22

Claims (10)

[Claims] 1. A first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a positive refractive power are arranged in order from the object side. In the zoom lens for moving the first lens group and the second lens group during zooming, the one or more lens groups include a plastic lens, and the plastic lens has a diffraction optical surface rotationally symmetric with respect to an optical axis. A zoom lens, characterized in that: 2. A lens system comprising, in order from the object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a positive refractive power. A zoom lens for moving the first lens group and the second lens group during zooming, wherein the at least one lens group has a surface provided with a diffraction grating surface on a resin aspherical layer. 3. The zoom lens according to claim 1, wherein said diffractive optical surface comprises a laminated diffraction grating. 4. The focal length at the wide-angle end is Fw, the focal length at the telephoto end is Ft, and the focal length Fm in the middle of zooming is When zooming from the wide-angle end to the telephoto end, the first lens group moves from the object side to the image side, the second lens group moves from the image side to the object side, and 4. The zoom lens according to claim 1, wherein the third lens group moves to the image side when zooming to (Fm). 5. The first lens group includes, in order from the object side,
5. A negative lens having a shape in which the absolute value of the refractive power of the image surface side is larger than that of the object side, and a meniscus positive lens having a convex surface facing the object side. Or the zoom lens of item 1. 6. The first lens group includes, in order from the object side,
A negative lens with a shape whose absolute value of the refractive power of the image surface side is larger than that of the object side, a negative lens with a shape whose absolute value of the refractive power of the image surface side is larger than that of the object side, and a convex surface with the object side The zoom lens according to any one of claims 1 to 4, wherein the zoom lens is configured by a meniscus-shaped positive lens directed toward the lens. 7. The second lens group according to claim 1, wherein the second lens group includes a positive lens having both lens surfaces convex, and a negative lens having both lens surfaces concave. Zoom lens. 8. The second lens group includes a positive lens having both lens surfaces convex, a negative lens having both lens surfaces concave, and a positive lens having both lens surfaces convex. Item 7. The zoom lens according to any one of Items 1 to 6. 9. The zoom lens according to claim 1, wherein the third lens group includes a single lens component including a single lens or a cemented lens. 10. An optical apparatus comprising the zoom lens according to claim 1. Description: