JP2003098432A - Zoom lens and optical equipment having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a zoom lens having a high variable power ratio and constituted so that a 1st lens group is compact, its entire length is short and its entire lens system is compact, and optical equipment using the zoom lens. SOLUTION: This zoom lens has a 1st lens group having a positive refractive power, a 2nd lens group having a negative refractive power and movable in the midst of zooming, a plurality of diaphragms including 1st and 2nd diaphragms, and a 3rd lens group having a positive refractive power in this order from the object, and luminous flux is restricted by the 1st diaphragm in a 1st zoom range of an entire zoom range, and is restricted by the 2nd diaphragm in a 2nd zoom range of the entire zoom range.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention is suitable for video lenses, lenses for silver halide cameras, digital still cameras, and the like.
The present invention relates to a zoom lens and an optical device using the same.

[0002]

2. Description of the Related Art Conventionally, it has been demanded that a zoom lens for an image pickup used in an optical apparatus has a small size as a whole, and accordingly various types of zoom lenses have been proposed. . However, when it is required to have a zoom ratio of 10 times or more like a zoom lens for a video camera these days, the zoom type adapted to it is also limited, so that the degree of freedom in design is reduced. Limited. As a zoom lens having a high zoom ratio, for example, in order from an object, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power are provided. There is a type of zoom lens that performs zooming by moving the lens group along the optical axis.

[0003]

A first lens group having a positive refracting power, a second lens group having a negative refracting power, and a third lens group having a positive refracting power are provided in this order from an object, and a second lens group is provided. The zoom type that performs zooming by moving the lens along the optical axis is easy to increase the zoom ratio while maintaining the imaging performance at a certain level or higher. However, in this zoom type, the total lens length becomes long and the front lens diameter also increases, so
It is disadvantageous in downsizing the lens system. In particular, since the lens diameter of the first lens group is large and the lens weight is also large,
A major challenge is to make the first lens group small.

It is an object of the present invention to provide a zoom lens having a high zoom ratio, a small first lens group, a short overall length, and a small overall lens system, and an optical apparatus using the same.

[0005]

A zoom lens according to a first aspect of the present invention comprises, in order from an object, a first lens group having a positive refractive power, a second lens group having a negative refractive power movable during zooming, a first lens group, and a second lens group. It has a plurality of diaphragms including two diaphragms and a third lens group having a positive refractive power. In the first zoom range of the entire zoom range, the light flux is limited by the first diaphragm and In the second zoom range, the light flux is limited by the second diaphragm.

According to a second aspect of the present invention, in the first aspect of the invention, the first diaphragm is located from the wide-angle end to the intermediate zoom position, and the image plane side is closer to the image side than the first diaphragm is from the intermediate zoom position to the telephoto end. It is characterized in that the light flux is limited by a certain second diaphragm.

According to a third aspect of the invention, in the invention of the first aspect, the light flux is limited by the second diaphragm located on the image plane side of the first diaphragm at and near the wide-angle end, and the quasi-wide-angle state and its vicinity. In (1), the light flux is limited by the first aperture stop, and the light flux is limited by the second aperture stop from an intermediate zoom position on the telephoto side of the quasi-wide-angle state to the telephoto end.

According to a fourth aspect of the invention, in the second or third aspect of the invention, at the telephoto end, part or all of the second lens group is located within the opening of the first diaphragm. .

According to a fifth aspect of the present invention, in the first aspect of the present invention, the first diaphragm has an opening diameter when a part or all of the second lens group is located in the opening of the first diaphragm. The feature is that it is larger than the aperture diameter when used as a diaphragm.

The invention of claim 6 is characterized in that, in the invention of any one of claims 1 to 5, the first and second diaphragms are fixed for zooming.

A seventh aspect of the present invention is the invention according to any one of the first to sixth aspects, wherein the third lens group has an image surface side having a positive refractive power for correcting an image surface variation due to zooming. It is characterized in that four lens groups are arranged.

A zoom lens system according to the present invention is, in order from the object, a first lens group having a positive refractive power, a second lens group having a negative refractive power movable during zooming, a first and a second diaphragm, and a positive lens group. It has a third lens group having a refractive power, and the first and second diaphragms are fixed for zooming, and the first diaphragm in the first zoom range out of the entire zoom range allows the light flux to be changed. In the second zoom range, the light flux is limited by the second diaphragm, and at the zoom position at the telephoto end, part or all of the second lens group is positioned within the opening of the first diaphragm. It has a feature.

According to a ninth aspect of the present invention, in the eighth aspect, the first zoom range is a wide-angle end to an intermediate zoom position, and the second zoom range is an intermediate zoom position to a telephoto end zoom position. It is characterized by being.

According to a tenth aspect of the invention, in the eighth or ninth aspect of the invention, the fourth lens group for correcting the image plane variation due to zooming is disposed on the image plane side of the third lens group. It has a feature.

An eleventh aspect of the invention is characterized in that, in the invention of any one of the first to tenth aspects, it is an optical system for forming an image on an image pickup device.

An optical apparatus according to a twelfth aspect of the present invention is characterized by including the zoom lens according to any one of the first to eleventh aspects.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of the essential portions of a first embodiment of the present invention. In FIG. 1, L1 is the first of positive refractive power
The lens unit L2 is the second negative refractive power movable during zooming.
The lens group L3 is a third lens group having a positive refractive power, and L4 is a fourth lens group having a positive refractive power. SP1 is the first aperture,
SP2 is a second diaphragm. The first and second diaphragms SP1,
The aperture diameter of each SP2 is variable. Also, although it is fixed for zooming, it may be moved if necessary. G is a glass block corresponding to a low-pass filter or an infrared cut filter.

IP is an image plane on which an image pickup surface of an image pickup device such as a CCD or a film is arranged.

By moving the second lens unit L2 from the object side to the image plane side along the optical axis La, zooming is performed from the wide-angle end to the telephoto end. At the time of zooming, the fourth lens unit L4 moves so as to compensate for image plane variation due to zooming, and plays the role of a so-called compensator.
The first lens unit L1 and the third lens unit L3 are fixed for zooming. FIG. 1A shows the arrangement of each lens group at the zoom position at the wide-angle end, and FIG. 1B shows the semi-wide-angle state (wide middle range, where 0.25Z to 0..0 when the zoom ratio is Z). The arrangement of each lens group at the zoom position (zoom position within the range of 4Z), and FIG. 1C shows the arrangement of each lens group at the zoom position at the telephoto end. Further, each oblique light flux represents an optical path at the maximum image height diagonal to the screen.

In the zoom lens of the type of the present embodiment, as a vignetting state of the luminous flux reaching the maximum angle of view (maximum image height), at the zoom position at the wide-angle end, the lower luminous flux (underline) LL is the second lens group. The effective diameter of the (variator) L2 (see FIG. 1A) is determined by the effective diameter of the first lens unit L1 at the underline LL in the quasi-wide-angle state (wide middle range). (See FIG. 1B). Therefore, especially in the semi-wide-angle state (wide middle range), if you try to reduce the vignetting of the underline and insert many underlines in order to secure a sufficient amount of peripheral light,
It is necessary to further increase the diameter of the first lens unit L1 having a large effective diameter. When the effective diameter of the first lens unit L1 is increased, the wall thickness of the first lens unit L1 also increases, resulting in an increase in the total lens length. On the other hand, if a large amount of the upper light flux (upper line) LH is to be inserted, the effective diameter of the lens group on the image plane side of the diaphragms (SP1, SP2) may be increased, and therefore the total lens length does not increase so much. However, when the diaphragm is located at the normal diaphragm position, that is, the position of the second diaphragm SP2 of the present embodiment, an unbalance of the passing amount of the vertical lines is caused, and the center of the light flux at the peripheral field angle passes near the center of the diaphragm. There is no so-called one-sided stop state, and the peripheral light amount is reduced when the stop is small, and more vignetting occurs.

In this embodiment, paying attention to the fact that the effective diameter of the variator (second lens group) L2 is small, the first diaphragm is located closer to the object side than the normal diaphragm position (in this case, the position of the second diaphragm SP2). SP1 is newly placed. Then, through the zoom position from the wide-angle end to the quasi-wide-angle state, up to a predetermined zoom position (a zoom position that is a substantially intermediate zoom position and is within a range of 0.4Z to 0.6Z when the zoom ratio is Z). The light flux is limited by the first aperture stop SP1 and the second aperture stop SP1 is provided from the substantially middle zoom position to the telephoto end zoom position.
2 is used so as to limit the luminous flux, and at the telephoto end, part or all of the second lens group (variator) L2 is positioned within the opening of the first diaphragm SP1 (FIG. 1C). reference). At this time, the aperture diameter of the first diaphragm when a part or the whole of the second lens unit L2 is located in the opening portion of the first diaphragm becomes larger than the aperture diameter when used as the diaphragm. There is.

Incidentally, at the telephoto end, the second lens group may be moved for zooming so that a part or the whole of the second lens group is located within the opening of the second diaphragm SP2.

As described above, the first and second diaphragms SP1, S
By appropriately setting the position of P2 and the moving condition of each lens unit during zooming, the moving amount of the second lens unit (variator) L2 is prevented from decreasing, and while maintaining a predetermined zoom ratio, 1 lens group L1, etc., diaphragm SP1,
Even if the effective diameter of the lens unit located closer to the object side than SP2 is made relatively small, the above-mentioned one-stop state is not achieved. In the state of FIG. 1 (A) and FIG. 1 (B), the light flux is limited by the first aperture stop SP1, and the second aperture stop SP2 is in between.
Is in an open state, and the light flux is limited by the second diaphragm SP2 in the state of FIG.
P1 is in an open state.

FIG. 2 is an explanatory diagram showing the relationship between the second lens unit L2 and the first diaphragm SP1 in FIG. 1 at the zoom position at the telephoto end. The symbols in FIG. 2 have the same meanings as in FIG. The object side lens of the second lens unit L2 is usually of small diameter, and for example, as shown in the figure, the lens holding method can be performed so that the final lens G23 in the second lens unit L2 is a so-called floating ball. For example, at the zoom position near the telephoto end, the first diaphragm SP1 and the first diaphragm SP1 can be nested.

The first aperture stop SP1 has a larger aperture diameter when a part of the second lens unit L2 is located inside the aperture portion of the first aperture stop SP1 than when it is used as an aperture stop. By doing so, it is possible to increase the amount of overlap in the nested state.

At the wide-angle end, the first diaphragm S is
In some cases, it may be more appropriate to use the second aperture stop SP2 than to use the P1 aperture. Therefore, at that time, at the zoom position at the wide-angle end and in the vicinity thereof, the second aperture stop SP1 is located closer to the image plane than the first aperture stop SP1. The light flux is limited by SP2, and the quasi-wide-angle state and its state (Fig. 1
(B)) At the zoom position near the first aperture stop SP1
It is also possible to limit the light flux with and to limit the light flux from the predetermined (intermediate) zoom position on the telephoto side to the telephoto end with respect to the quasi-wide-angle state by the second diaphragm SP2.

In addition, the first aperture stop SP1 is used from the wide-angle end zoom position to the quasi-wide-angle state, and the second aperture stop SP2 is used in the quasi-wide-angle state and its vicinity, and the quasi-wide-angle state zoom position is used. From the vicinity to the zoom position at the telephoto end, the first diaphragm SP1 may be used to limit the luminous flux. It is also possible to provide two or more diaphragms and limit the passing light flux in each target zoom area by each diaphragm.

The zoom lens in this embodiment is, in order from the object, a first lens group having a positive refractive power, a second lens group having a negative refractive power which is movable during zooming, a plurality of diaphragms, and a third lens having a positive refractive power. If the zoom lens has a group, the zoom lens is not limited to a zoom lens including four lens groups, and a zoom lens including three groups or a zoom lens including five or more lens groups can be similarly applied.

As described above, according to this embodiment, in order from the object, the first lens unit L1 having a positive refractive power, the second lens unit L2 having a negative refractive power which is movable during zooming, the plurality of diaphragms, and the positive lens unit are positive. By using the first diaphragm SP1 in the first zoom range and the second diaphragm SP2 in the second zoom range. The group L1 is downsized, the total lens length is shortened, and the front lens diameter is reduced.

In addition to this, according to the present embodiment, it is possible to easily increase the zoom ratio while maintaining good imaging performance above a certain level.
In particular, the outer diameter of the first lens group is made small and the weight is made light, and the total lens length is easily shortened.

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

In FIG. 3, 10 is a camera body, 11 is a photographing optical system constituted by the zoom lens of the present invention,
Reference numeral 12 denotes a CC for receiving a subject image by the photographing optical system 11.
An image pickup device such as D, 13 is a recording unit that records the subject image received by the image pickup device 12, and 14 is a finder for observing the subject image displayed on a display device (not shown).
The display element is composed of a liquid crystal panel or the like, and the subject image formed on the image pickup element 12 is displayed.

As described above, by applying the zoom lens of the present invention to an electronic camera such as a video camera or a digital still camera, an optical apparatus having a small size and high optical performance is realized.

[0034]

According to the present invention, the zoom ratio is high and the first
It is possible to achieve a zoom lens having a small lens group, a short overall length, and a small lens system as a whole, and an optical device using the zoom lens.

[Brief description of drawings]

FIG. 1 is a lens sectional view of an embodiment of a zoom lens of the present invention.

FIG. 2 is an explanatory diagram showing the relationship between the second lens group and the first aperture stop in FIG. 1 at the telephoto end.

FIG. 3 is a schematic view of a main part of an embodiment of an optical device of the present invention.

[Explanation of symbols]

L1 first lens group L2 second lens group L3 Third lens group L4 4th lens group SP1 First aperture SP2 Second aperture G glass block IP image plane 10 camera body 11 zoom lens 12 Image sensor 13 Recording means 14 Finder

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H044 EE01 EF01                 2H087 KA02 KA03 LA01 MA15 PA07                       PA20 PB10 QA02 QA07 QA17                       QA21 QA25 QA37 QA41 QA46                       RA32 RA42 RA43 SA23 SA27                       SA29 SA32 SA63 SA72 SA74                       SB04 SB14 SB23 SB33                 5C022 AB12 AB21 AB66 AC54 AC56

Claims (12)

[Claims] 1. A first lens group having a positive refractive power, a second lens group having a negative refractive power movable during zooming, a plurality of diaphragms including a first diaphragm and a second diaphragm, and a positive refractive power in order from an object. Of the third lens group, the luminous flux is limited by the first diaphragm in the first zoom range of the entire zoom range, and the luminous flux is limited by the second diaphragm in the second zoom range of the whole zoom range. A zoom lens that limits the light flux. 2. The first aperture stop from the wide-angle end to the middle zoom position, and the first aperture stop from the middle zoom position to the telephoto end.
2. The zoom lens according to claim 1, wherein a light flux is limited by the second diaphragm located closer to the image plane than the second diaphragm. 3. At the wide-angle end and in the vicinity thereof, the light flux is limited by the second diaphragm on the image plane side of the first diaphragm, and in the quasi-wide-angle state and its vicinity, the light flux is limited by the first diaphragm. 2. The zoom lens according to claim 1, wherein the light flux is limited by the second diaphragm from the intermediate zoom position on the telephoto side of the quasi-wide-angle state to the telephoto end. 4. The zoom lens according to claim 2, wherein at the telephoto end, part or all of the second lens group is located inside the opening of the first diaphragm. 5. The aperture diameter of the first diaphragm when a part or all of the second lens group is located inside the opening portion of the first diaphragm is larger than the aperture diameter when used as the diaphragm. The zoom lens according to claim 4, wherein the zoom lens is large. 6. The zoom lens according to claim 1, wherein the first and second diaphragms are fixed for zooming. 7. The fourth lens group having a positive refracting power for correcting an image plane variation due to zooming is disposed on the image plane side of the third lens group. The zoom lens according to any one of 6 above. 8. A first lens group having a positive refractive power, a second lens group having a negative refractive power movable during zooming, a first and a second diaphragm, and a third lens group having a positive refractive power in order from an object. And the first and second apertures are fixed for zooming, the first aperture limits the light flux in the first zoom range of the entire zoom range, and the second zoom The zoom lens is characterized in that the light flux is limited by the second diaphragm in the range, and at the zoom position at the telephoto end, part or all of the second lens group is located within the opening of the first diaphragm. 9. The method according to claim 8, wherein the first zoom range is a wide-angle end to a middle zoom position, and the second zoom range is a middle-zoom position to a telephoto end zoom position. The described zoom lens. 10. The zoom lens according to claim 8, wherein a fourth lens group for correcting an image plane variation due to zooming is disposed on the image plane side of the third lens group. lens. 11. The optical system for forming an image on an image pickup device as claimed in claim 1.
The zoom lens according to item. 12. An optical apparatus comprising the zoom lens according to claim 1. Description: