JP2003262780A - Zoom optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a zoom optical system for focusing on an object at infinity to an close proximity, and following up quick zooming. <P>SOLUTION: The zoom optical system is equipped with a variable power unit 2 varying power while moving during zooming, a 1st focusing unit 1 positioned in front of the unit 2, a 2nd focusing unit 3 positioned at the rear side of the unit 2, a sensor 4 detecting the position of the unit 1, and a memory 7 storing the movement information of the unit 3 during zooming in accordance with the position of the unit 1. The moving locus of the unit 3 during zooming is changed based on positional information on the unit 1 detected by the sensor 4 and the information from the memory 7. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom optical system capable of selecting different focusing methods, and is suitable for optical equipment such as video cameras, digital cameras, still cameras, television cameras and the like.

[0002]

2. Description of the Related Art Conventionally, various focusing methods have been adopted for zoom lenses used in optical devices such as video cameras, digital cameras and television cameras.

For example, some zoom lenses in video cameras and the like can switch between two focus methods, manual focus and auto focus.

As the type of focusing method, depending on whether the lens unit in front of the variable power unit or the lens unit in the rear is used, a front lens focus system and a front lens inner focus system (hereinafter, these two systems are used. Are collectively referred to as a front focus method), and a competition and a rear focus method (hereinafter, these two methods are collectively referred to as a rear focus method).
The front focus method is in front of the zoom unit (on the object side)
The focus unit is moved so that the image position of the focus unit arranged at is always kept constant regardless of the subject distance. Therefore, the position of the focus unit is determined only by the object distance, and is irrelevant to the magnification change (zoom position), so that image plane fluctuation does not occur even when high-speed magnification change is performed.

However, since the large front lens unit is moved, the amount of movement is naturally limited, and
The effective diameter of the focus unit increases. Therefore,
The subject distance that can be photographed does not change in the entire zoom range, but the closest subject distance is generally from 1 m to 60 cm. Therefore, in such a front focus type zoom lens, a configuration is known in which one end of a cam of a variable power lens system is used for macro photography to enable extremely close-up photography (macro photography). However, since this method uses one end of the continuous portion of the zooming cam, the zooming operation cannot be performed in the macro shooting state.

[0006] Japanese Patent Application Laid-Open No. 2004-242242 proposes a method that enables extremely close-up photography. However, in the method proposed in the publication, the mechanism of the moving lens group is complicated and it is not suitable as a zoom lens used for a small video camera or the like.

The rear focus method, on the other hand, is generally capable of photographing even a short-distance object as compared with the front focus method.
In particular, at the wide-angle end, the amount of movement of the focus unit is very small, so that it has the advantage of being able to perform extremely close-up photography, and is widely used in consumer applications.

In the rear focus method, however, the amount of movement of the focus unit when focusing on a subject at a predetermined distance changes depending on the zoom position, so during zooming, an enormous amount is stored in advance in a microcomputer or the like. It is necessary to control the movement of the focus unit by calculation from the movement information table. Therefore,
The drive of the focus unit may not be in time for high-speed zooming or when the subject distance is variously changed while zooming. Therefore, in order to suppress the blur caused by this, there is a limit on the zoom speed,
The intention of the photographer was not always reflected in the shooting opportunity.

Further, in Patent Document 2, a part of the image forming lens is moved as a macro mechanism for performing focus adjustment (tracking adjustment) with the image forming surface of the camera when the zoom lens is attached to the video camera and very close shooting. It proposes a focus method to make it. In this publication, a part or all of the imaging lens is moved in the extremely close-up photography (macro photography). Therefore, when the zooming operation is performed in the macro state, focus movement occurs.

[0010]

[Patent Document 1] Japanese Patent Publication No. 56-13287

[Patent Document 2] Japanese Patent Laid-Open No. 59-71016

[0011]

As described above, the front focus method has a problem that it is difficult to continuously capture images from an infinitely distant object to a very close object. In addition, the rear focus method has a problem that it is difficult to follow the speed-up of zooming.

Therefore, an object of the present invention is to provide a zoom optical system capable of focusing from an object at infinity to an object at a very short distance, and capable of following quick zooming.

[0013]

In order to achieve the above object, the zoom optical system of the present invention comprises (1) a zooming unit for moving and zooming during zooming, and a zooming unit arranged in front of the zooming unit. A first focus unit, a second focus unit located behind the variable power unit, a sensor for detecting the position of the first focus unit, and a first focus unit according to the position of the first focus unit. And a memory storing movement information at the time of zooming of the second focus unit.
The second focus unit is characterized in that the movement locus at the time of zooming changes based on the position information of the first focus unit detected by the sensor and the information from the memory.

In the zoom optical system of each embodiment described later, in (2) and (1), the first mode in which focusing is performed by the first focus unit and the second mode in which focusing is performed by the second focus unit. (3) having a switch for switching between modes and (2), when the switch is switched to the first mode, the second focus unit moves to a predetermined position,
(4) In (1) to (3), the first mode is a manual focus mode in which focusing is performed manually, and the second mode is an autofocus mode in which focusing is automatically performed according to the in-focus state. , (5)
In (1) to (4), the second focus unit does not move for focus in the first mode, and the first focus unit does not move for focus in the second mode, (6) In (1) to (5),
From the front to the rear, in order, a first lens group having a positive refractive power, a second lens group having a negative refractive power moving for zooming, and a third lens group having a negative refractive power moving for zooming,
4th lens group having positive refractive power, 5th lens group having positive refractive power
A lens unit, the first lens unit is a first focus unit, the fifth lens unit is a second focus unit, (7) (1) to (5), from front to back , A first lens unit having a positive refractive power, a second lens unit having a negative refractive power which moves for zooming, a third lens unit having a positive refractive power which moves for zooming, a fourth lens unit having a positive refractive power A lens unit, a first lens unit is a first focus unit, a fourth lens unit is a second focus unit, (8) (1) to (7),
When the focal length of the entire system at an arbitrary zoom position is fL, and the combined focal length of the system on the front side of the second focus unit at the same arbitrary zoom position is fAL, the condition is -3 <fL / fAL <4. To be satisfied at all zoom positions, (9)
In (1) to (8), the focal length of the entire system at an arbitrary zoom position is fL, and the combined focal length of the system on the front side of the second focus unit at the same arbitrary zoom position is fAL, f.
When L / fAL = KL, the value of KL at the wide-angle end is KW, and the value of KL at the telephoto end is KT, the condition 0.9 <KW / KT <1.1 is satisfied. It has a feature.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view showing the basic arrangement of a zoom optical system (zoom lens) according to the present invention. The zoom lens of this embodiment has a configuration in which a lens unit in front (on the object side) and a lens unit in the rear (on the image side) of the variable power unit can be selectively used as focus units. A focus method capable of selecting different focus units in this way is referred to as a "hybrid focus method" in this specification.

In FIG. 1, 1 is a front focus lens group (first focus unit), 2 is a variable power unit,
It has a variator for performing zooming, a compensator for correcting image plane variation due to zooming, and a relay lens for guiding a light beam from the compensator to a lens group that follows. Reference numeral 3 denotes a rear focus lens group (second focus unit). IP is an image plane, on which an image pickup means (photosensitive film, solid-state image pickup device such as CCD or CMOS) is arranged.

Reference numeral 4 is a position detection sensor for detecting the position of the front focus lens group 1 in the optical axis direction, 5 is an actuator for moving the rear focus lens group 3 on the optical axis, and 6 is light of the rear focus lens group 3. A reference position detection sensor for detecting a position on the axis, 7 is a memory in which movement information during zooming of the rear focus lens group 3 is stored in advance, 8 is a microcomputer, and various operations (position detection sensor 4, Actuator 5) is controlled. 9
Is the movement information of the rear focus lens group 3 stored in the memory 7, and there is information about a plurality of movement loci corresponding to the position of the front focus lens group 1 and the subject distance. Although the rear focus lens group 3 is not always moved by using the cam mechanism, its movement locus corresponds to the shape of the cam, and therefore, for example, the movement locus is the cam locus, and movement information 9 in which information related to the cam locus is stored. Will be called a cam table.

In FIG. 1, the variable power section 2 and the rear focus lens group 3 are depicted as separate members, but the variable power section 2 arranged behind the variator, which is a variable power unit.
All or a part of the above may be used as the rear focus lens group 3. Specifically, a compensator or a relay lens may be used as the rear focus lens group 3. In this case, the rear focus lens group 3 constitutes a part of the variable power unit 2. Further, depending on the zoom type, there is a type in which it is not possible to distinguish between a variator that performs zooming and a compensator that corrects image plane variation due to zooming. In the case of such a zoom type, the lens group behind the lens group that mainly performs zooming (the change in magnification is largest) can be the rear focus lens group in this embodiment.

In the hybrid focus system of this embodiment, a manual focus mode and an auto focus mode are switched by an AF switch (not shown).
When the manual focus mode is selected by the AF switch, the front focus lens group 1 is manually moved to perform the focus operation, and when the auto focus mode is selected, the rear focus lens group 3 is focus-detected. The focus operation is performed by automatically moving based on the output of the device. The focus detection device is, for example, an imaging plane IP.
It is conceivable that the microcomputer 8 determines the in-focus state based on the contrast information from the solid-state image pickup device placed at. In addition, although not shown in FIG. 1, an active type focus detection device having a light projecting system and a light receiving system and a phase difference detection type device for detecting a deviation of an image passing through different pupil positions are separately provided. Is also good. Then, at the time of zooming when the autofocus mode is selected, the microcomputer 8 selects a cam locus suitable for the position information from the cam table based on the position information of the front focus lens group 1 in the optical axis direction. The amount of movement of the rear focus lens group 3 is calculated and moved so that there is no change in the image plane due to.

FIGS. 2A, 2B and 2C are flow charts for performing hybrid focusing. Figure 2
(A) shows a flow of focus mode selection. When the AF switch is ON, the mode shifts to the autofocus mode, and when the AF switch is OFF, the mode shifts to the manual focus mode.

2B and 2C are detailed flow charts of the autofocus mode and the manual focus mode, respectively. In the autofocus mode, first, the rear focus lens group 3 is automatically moved based on the information from the focus detection device to perform the focusing operation.
This operation is omitted when the desired subject is already in focus. Subsequently, when performing zooming, the microcomputer 8 selects an appropriate movement locus from the cam table based on the position information of the front focus lens group 1 (complements by calculation if there is no suitable one), and rear focus The lens group 3 is moved to compensate for the movement of the image plane due to zooming.

In the manual focus mode, the rear focus lens group 3 is first moved to the reference position. Then, the front focus lens group 1 is manually moved to focus. The reason why the rear focus lens group 3 is first moved to the reference position in the manual focus mode is that manual focus may not be performed depending on the position of the rear focus lens group 3.

Next, a specific embodiment of the zoom lens adopting the hybrid focus system will be described. 3, 8, 13, and 18 are lens cross-sectional views of the zoom lenses according to Embodiments 1 to 4 of the present invention. In the lens cross-sectional views, (A), (B), and (C) are in order from the wide-angle end,
The state is shown at the middle zoom position and at the telephoto end. 3, FIG. 8, FIG. 13, and FIG. 18, Li is an i-th lens group, SP is an aperture stop, G is an infrared cut filter, a filter corresponding to an optical low-pass filter, or an optical member corresponding to a prism or the like. Is. IP is the image plane.

FIGS. 4, 9, 14 and 19 show focusing (object distance 3) by the front focus lens group (first lens group) in the zoom lenses of Embodiments 1 to 4, respectively.
m) is an aberration diagram at the wide-angle end, and FIGS. 5, 10, 15, and 20 show the rear focus lens group (the fifth lens group or the fourth lens group) in the zoom lenses of Embodiments 1 to 4, respectively. FIG. 6, FIG. 11, FIG. 16, FIG. 2 are aberration diagrams at the wide-angle end when focusing (object distance: 3 m) with a lens group).
1 is an aberration diagram at the telephoto end when focusing (object distance 3 m) is performed by the front focus lens group (first lens group) in the zoom lenses of Embodiments 1 to 4, FIG.
2, FIG. 17, and FIG. 22 show the zoom lens of Embodiments 1 to 4 at the telephoto end when the rear focus lens group (the fifth lens group or the fourth lens group) performs focusing (object distance: 3 m). It is an aberration diagram.

In the first embodiment shown in FIG. 3, the first lens unit L1 having a positive refractive power and the second lens unit having a negative refractive power are arranged in this order from the object side.
The lens unit L2 includes a third lens unit L3 having a negative refractive power, a fourth lens unit L4 having a positive refractive power, and a fifth lens unit L5 having a positive refractive power. The first lens unit L1 has a structure that is movable on the optical axis for focusing. Second lens group L
2 is for zooming, and the third lens unit L3 moves on the optical axis as indicated by the arrow in order to correct the image plane variation due to zooming. The fourth lens unit L4 makes the divergent light flux from the third lens unit L3 substantially afocal. The fifth lens unit L5 includes
It has a function of forming an image on the imaging plane IP and is movable on the optical axis for focusing.

Further, the position detection sensor 4 described with reference to FIG. 1 is arranged in the first lens unit L1. The position detection sensor 4 uses the microcomputer 8 to determine at which position of the subject distance the first lens group L1 is in focus.
To inform.

In the manual focus mode, the first lens unit L1 is moved. Since the first lens unit L1 is arranged in front of the second lens unit L2 which is a variable power unit, the zooming position and the first lens unit L1
The position on the optical axis is completely free (independent), and the position on the optical axis is the same for any zoom position at the same subject distance. In the auto focus mode, the fifth lens unit L5 is moved and focused based on the information from the focus detection device. When performing zooming in the auto focus mode, an appropriate movement locus is selected from the cam table 9 based on the position information on the optical axis of the first lens unit L1.

In FIG. 3, the symbols ,,, respectively represent the positions of the first lens unit L1 when focusing on three subjects at different distances of infinity, an object distance of 3 m, and an object distance of 1 m. Also, the unit of the numerical example described later is mm
That is the case. All the same below). In this embodiment, five cam loci 1a to 1e are prepared as the cam table 9 of the fifth lens group L5, 1a to 1c are positions, 1b to 1d are positions, and 1c to 1e are cams at positions. Each locus is shown. That is, when the first lens unit L1 is focused and fixed on an object at infinity in the manual focus mode and the mode is switched to the auto focus mode,
The information is transmitted to the microcomputer 8 by the position detection sensor 4, and at the time of zooming, the fifth lens unit L5 is moved using any of the cam loci 1a to 1c corresponding to the control information. Therefore, in this state, the fifth lens unit L5 has a cam locus 1c for an object at infinity and does not move on the optical axis during zooming. However, as the object distance approaches 3 m and 1 m, and the subject approaches, the fifth lens group L
Since 5 is delivered (moves to the object side), the movement amount at the time of zooming increases like the cam loci 1b and 1a.

The moving amount (extending amount) of the fifth lens unit L5 during focusing varies depending on the zoom position, and is the smallest at the wide-angle end and the largest at the telephoto end.

In the manual focus mode, the first
Focus the lens group L1 at an object distance of 3 m and fix it,
When switching to the auto focus mode, any of the cam loci 1b to 1d corresponding to the position information is selected. When the object distance remains 3 m, the cam locus 1c is obtained, and the fifth lens unit L5 does not move during zooming. However, focusing with the fifth lens unit L5
When an object other than a distance of 3 m is focused, for example, when the object is an infinite object, the cam locus is 1d, and the fifth lens unit L5.
Needs to be moved to the image plane IP side, and the amount of movement increases toward the telephoto side. On the contrary, when the fifth lens unit L5 is used to focus on an object located closer than 3 m, it is necessary to move the fifth lens unit L5 to the object side like the cam locus 1b. Is larger on the telephoto side. First in manual focus mode
Even when the lens unit L1 is focused on a subject at a distance other than the above and fixed, the above-mentioned infinity subject, subject distance 3
In the same way as when focusing on m, by switching to an appropriate cam locus each time and performing movement control during zooming of the fifth lens unit L5, smooth focusing operation (switching between manual focus mode and auto focus mode) ) Is possible.

Further, no matter where the fifth lens unit L5 is located on the optical axis in the auto focus mode, when the mode is switched to the manual focus mode, the signal from the reference position detection sensor 6 is used to output the fifth lens. The group L5 is returned to the reference position on the optical axis. This allows the focusing operation in the first lens unit L1 to be performed normally. In the present embodiment, the reference position is set to the first lens group L.
The positions of the first and fifth lens units L5 are set to the positions of the fifth lens unit L5 when focusing on an infinite object.

In the first embodiment, the fifth lens unit L5 is preferably moved by a stepping motor, a DC motor with a position detecting function, or the like, because there are several types of selected cam loci. On the other hand, the second and third lens units L2,
Since the movement locus of L3 does not change, the zoom operation may be performed by a mechanical cam ring, but the present invention does not prevent the zoom operation by an operating means such as a stepping motor.

The second embodiment shown in FIG. 8 is, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a negative refractive power. It is composed of a fourth lens group of power. The first lens unit L1 has a movable structure for focusing. The second lens unit L2 moves on the optical axis in order to correct the magnification, and the third lens unit L3 moves on the optical axis to correct the image plane variation due to the magnification change. The fourth lens unit L4 has a function of forming an image and is movable on the optical axis for focusing. Further, the position detection sensor 4 shown in FIG. 1 is arranged in the first lens group L1. The position detection sensor 4 notifies the microcomputer 8 at which subject distance position the first lens unit L1 is focused.

In the manual focus mode, the first lens unit L1 is moved. Since the first lens unit L1 is arranged in front of the second lens unit L2, which is a variable power unit, at the same object distance at any zoom position, in the optical axis direction of the first lens unit L1. The positions are the same.

In the autofocus mode, focusing is performed by moving the fourth lens unit L4 based on the information from the focus detection device. When performing zooming, an appropriate movement locus is selected from the cam table 9 based on the position information of the first lens unit L1 as in FIG.

In FIG. 8,. ,, respectively represent the positions of the first lens unit L1 when focusing on three subjects at different distances of infinity, object distance 3 m, and object distance 1 m. In this embodiment, five cam loci 1a to 1e are prepared as the cam table 9 of the fourth lens unit L4, 1c to 1e are positions, 1b to 1d are positions,
Reference numerals 1a to 1c represent cam loci at the time of position. That is, in the manual focus mode, the first lens unit L1 is focused on an object at infinity and fixed, and when the mode is switched to the auto focus mode, the position detection sensor 4 transmits the information to the microcomputer 8 and controls during zooming. Cam locus 1c corresponding to the position as information
The fourth lens unit L4 is moved using any one of 1e.

Therefore, in this state, the fourth lens unit L
4 is a cam locus 1c for an object at infinity, and does not move on the optical axis during zooming. However, the object distance 3
As the subject approaches m, 1 m, the fourth lens unit L4
Is moved (moves to the image side), so the cam locus 1
As in d and 1e, the amount of movement during zooming increases.
The amount of movement (retraction amount) of the fourth lens unit L4 during focusing varies depending on the zoom position, and becomes the largest at the telephoto end.

In the manual focus mode, the first
Focus the lens group L1 at an object distance of 3 m and fix it,
When switching to the auto focus mode, any of the cam loci 1b to 1d corresponding to the position information is selected. When the object distance remains 3 m, the cam locus 1c is obtained, and it is not necessary to move the fourth lens unit L4 during zooming. However, when the fourth lens group is focused to focus on an object other than the distance of 3 m, for example, when the object is an infinite object, it is necessary to move the fourth lens group L4 to the object side by the cam locus 1b. Yes, the amount of movement increases toward the telephoto end. On the contrary, when focusing is performed by the fourth lens unit L4 to focus on an object at a distance closer than 3 m, the fourth lens unit L4 needs to be moved to the image side as in the cam locus 1b, and the movement is also required. The amount becomes larger on the telephoto side.

First in the manual focus mode
Even when the lens unit L1 is focused on a subject at a distance other than the above and fixed, the above-mentioned infinity subject, subject distance 3
Similar to the case of focusing on m, a smooth focus operation is possible by switching to an appropriate cam locus each time and performing movement control during zooming of the fourth lens unit L4.

Further, no matter where the fourth lens unit L4 is located on the optical axis in the auto focus mode, the fourth lens unit L4 uses the signal from the reference position detection sensor 6 when it is switched to the manual focus. L4 is returned to the reference position on the optical axis. This allows the focusing operation in the first lens unit L1 to be performed normally. In this embodiment, the reference position is set to the position of the fourth lens unit L4 when the first lens unit L1 and the fourth lens unit L4 are focused on the object at infinity.

In the second embodiment, the fourth lens unit L4 is preferably moved by a stepping motor, a DC motor with a position detecting function, or the like, because there are several types of selected cam loci. On the other hand, the second and third lens units L2,
Since the movement locus of L3 does not change, zoom operation may be performed by a mechanical cam ring. However, these also do not prevent the zooming operation by the operation means such as the stepping motor.

In the third embodiment shown in FIG. 13, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a third lens group having a positive refractive power are arranged in this order from the object side. Composed. The first lens unit L1 has a movable structure for focusing. The second lens unit L2 moves on the optical axis for zooming, and the third lens unit L3 moves on the optical axis for correcting the image plane variation due to zooming. The fourth lens unit L4 has an imaging function and is movable for focusing. Further, the position detection sensor 4 described with reference to FIG. 1 is arranged in the first lens group L1. Position detection sensor 4
Informs the microcomputer 8 at which subject distance position the first lens group is focused.

In the manual focus mode, the first lens unit L1 is moved for focusing. Since the first lens unit L1 is arranged in front of the second lens unit L2, which is a variable power unit, it is assumed that the first lens unit L1 has the same position on the optical axis at the same object distance at any zoom position. Become.

In the autofocus mode, as in the embodiment shown in FIG. 8, the fourth focus detection is performed based on the information from the focus detection device.
Focusing is performed by moving the lens unit L4. When performing zooming in the auto focus mode, an appropriate movement locus is selected from the cam table 9 based on the position information of the first lens unit L1.

In FIG. 13 ,,,, respectively,
3 at different distances: infinity, object distance 3m, object distance 1m
The position of the first lens unit L1 when one subject is in focus is shown. In the third embodiment, the fourth lens unit L
Five cam loci 1a to 1e are prepared as the 4th cam table 9, 1a to 1c are positions, 1b to 1d are positions, and 1c to 1e are cam loci at positions.

That is, the first in the manual focus mode
When the lens unit L1 is focused on an object at infinity and fixed and the mode is switched to the autofocus mode, the position detection sensor 4 transmits the information to the microcomputer 8, and during zooming, the cam locus corresponding to the position as control information. The fourth lens unit L4 is moved using any one of 1a to 1c. Therefore, in this state, the fourth lens unit L4 has a cam locus 1c for an object at infinity and does not move on the optical axis during zooming. However, since the fourth lens unit L4 is extended (moves to the object side) as the object distance approaches 3 m, 1 m and the object approaches, the movement amount during zooming increases like the cam loci 1b, 1a.

Further, the moving amount (extending amount) of the fourth lens unit L4 during focusing varies depending on the zoom position, and the moving amount becomes maximum at the telephoto end. Further, when the first lens unit L1 is focused and fixed to the object distance 3 m in the manual focus mode and switched to the auto focus mode, any of the cam loci 1b to 1d corresponding to the position information is selected. When the object distance remains 3 m, the cam locus is 1c, and the fourth lens unit L is used for zooming.
There is no need to move 4. However, the fourth lens unit L4
When the subject is focused on to focus on an object other than a distance of 3 m, for example, when the object is an object at infinity, the cam locus is 1d, and it is necessary to move the fourth lens unit L4 to the image side. It becomes larger on the telephoto side. On the contrary, when the fourth lens unit L4 is focused to focus on an object located closer than 3 m, it is necessary to move the fourth lens unit L4 to the object side like the cam locus 1b. Is larger on the telephoto side. Also in the manual focus mode, when the first lens unit L1 is focused and fixed on a subject at a distance other than the above, as in the case of focusing on the infinite subject and the subject distance of 3 m, the appropriate cam locus is switched each time, Fourth lens unit L4
By performing movement control during zooming, smooth focus operation is possible.

Further, no matter where the fourth lens unit L4 is located on the optical axis in the auto focus mode, when the mode is switched to the manual focus mode, the signal from the reference position detection sensor 6 is used to make the fourth lens unit L4. L4 is returned to the reference position on the optical axis. Thereby, the first lens unit L1
The focus operation in can be performed normally. In this embodiment, the reference position is set to the first lens group L1,
The position of the fourth lens group L4 is set to the position of the fourth lens group L4 when focusing on an object at infinity.

In the present embodiment, the fourth lens group L4 is preferably moved by a stepping motor, a DC motor with a position detecting function, or the like, since there are several types of selected cam loci. On the other hand, the second and third lens units L2 and L
In No. 3, since the movement locus does not change, zoom operation may be performed by a mechanical cam ring. However, this does not prevent the zooming operation of these with an operating means such as a stepping motor.

The fourth embodiment shown in FIG. 18 is, in order from the object side, a first lens unit having a positive refractive power, a second lens unit L2 and a third lens unit L3 having a negative refractive power, and a fourth lens unit having a positive refractive power. , The fifth lens unit L4, L5. The first lens unit L1 has a structure that is movable on the optical axis for focusing. The second lens unit L2 moves on the optical axis as indicated by an arrow in order to correct the image plane variation due to the magnification change, and the third lens unit L3 moves for the magnification change. The fourth lens unit L4 makes the divergent light flux from the third lens unit L3 substantially afocal. Fifth lens unit L
Reference numeral 5 is a structure that has an image forming action on the imaging plane IP and is movable on the optical axis for focusing.

Further, the position detection sensor 4 described with reference to FIG. 1 is arranged in the first lens unit L1. The position detection sensor 4 informs the microcomputer 8 at which object distance position the first lens unit L1 is focused.

In the manual focus mode, the first lens unit L1 is moved. Since the first lens unit L1 is arranged in front of the second lens unit L2, which is a variable power unit, the position on the optical axis is the same at the same object distance at any zoom position. In the auto-focus mode, the fifth lens group is moved to focus as in the first embodiment. When performing zooming in the auto focus mode, the first lens unit L
An appropriate movement locus is selected from the cam table 9 based on the position information on the optical axis of 1.

In FIG. 18, respectively, and
3 at different distances: infinity, object distance 3m, object distance 1m
The position of the first lens unit L1 when one subject is in focus is shown. In the fourth embodiment, the fifth lens unit L
Five cam loci 1a to 1e are prepared as five cam tables 9, 1a to 1c are positions, 1b to 1d are positions, and 1c to 1e are cam loci at positions. That is, in the manual focus mode, the first lens unit L1 is focused and fixed by an object at infinity, and when switched to the auto focus mode, the position detection sensor 4 transmits the information to the microcomputer 8, and during zooming, the control is performed. Cam locus 1a corresponding to
The fifth lens unit L5 is moved by using any one of 1c.

Therefore, in this state, the fifth lens unit L5 has a cam locus 1c for an object at infinity and does not move on the optical axis during zooming. However, the object distance is 3m, 1
Since the fifth lens unit L5 is extended (moves toward the object side) as m and the object get closer, the cam loci 1b, 1
As indicated by a, the amount of movement during zooming increases.

The amount of movement (extending amount) of the fifth lens unit L5 during focusing varies depending on the zoom position, and becomes the largest at the telephoto end.

In the manual focus mode, the first
The lens unit L1 is focused and fixed at an object distance of 3 m,
When switching to the auto focus mode, any of the cam loci 1b to 1d corresponding to the position information is selected. When the object distance remains 3 m, the cam locus 1c is obtained, and the fifth lens unit L5 does not move during zooming. However, focusing with the fifth lens unit L5
When an object at a distance other than 3 m is focused, for example, when the object is an infinite object, the cam locus is 1b, and it is necessary to move the fifth lens unit L5 toward the image side. The amount of movement increases toward the telephoto side. .

On the contrary, when the fifth lens unit L5 is focused to focus on an object located closer than 3 m, it is necessary to move the fifth lens unit L5 to the object side like the cam locus 1b. The amount of movement increases toward the telephoto side.

First in the manual focus mode
Even when the lens unit L1 is focused and fixed on a subject at a distance other than the above, as in the case of focusing on the infinite subject and the subject distance of 3 m, the cam locus is switched to an appropriate cam locus each time and the fifth lens unit L5 A smooth focus operation is possible by controlling the movement during zooming.

Further, no matter where the fifth lens unit L5 is located on the optical axis in the auto focus mode, when the mode is switched to the manual focus mode, the signal from the reference position detection sensor 6 is used to output the fifth lens. The group L5 is returned to the reference position. This allows the focusing operation in the first lens unit L1 to be performed normally. In this embodiment, the reference position is set to the position of the fifth lens unit L5 when the first lens unit L1 and the fifth lens unit L5 are focusing on the object at infinity.

In the present embodiment, the fifth lens unit L5 is preferably moved by a stepping motor, a DC motor with a position detecting function, or the like, because there are several types of selected cam loci. On the other hand, the second and third lens units L2,
Since the movement locus of L3 does not change, zoom operation may be performed by a mechanical cam ring. However, this does not prevent the zooming operation using an operating means such as a stepping motor.

In the zoom lenses of the respective embodiments, the focal length of the entire system at an arbitrary zoom position is fL, and the frontmost lens group at the same zoom position (first lens group L).
The combined focal length from 1) to the lens group immediately before the rear focus lens group (the fourth lens group L4 in the first and fourth embodiments and the third lens group L3 in the second and third embodiments) is fAL. At this time, it is preferable that the condition of −3 <fL / fAL <4 is satisfied at all zoom positions.

The above expression represents the degree of convergence of the light beam incident on the rear focus lens group, and if either the upper limit value or the lower limit value is exceeded, a large amount of aberration variation due to focusing during autofocus occurs, which is not preferable.

When fL / fAL = KL, the value of KL at the wide-angle end is KW, and the value of KL at the telephoto end is KT, basically, KW / KT≈1.0. preferable. Specifically, it is preferable to satisfy the condition of 0.9 <KW / KT <1.1.

This conditional expression is used when the rear focus lens group (the fifth lens group L5 in the first and fourth embodiments and the fourth lens group L4 in the second and third embodiments) returns to the reference position during manual focusing. It defines the error amount depending on the zoom position. When the upper limit value and the lower limit value are exceeded, the focus fluctuation due to zooming with manual focus cannot be ignored.

In the embodiment of the present invention, by moving any one of the lens groups or a part of the lens groups perpendicularly to the optical axis, a shift in the direction perpendicular to the optical axis of the image due to camera shake or the like is caused. It is also possible to make a correction.

Next, numerical examples 1 to 4 corresponding to the first to fourth embodiments of the present invention will be shown. In each numerical example,
i represents the order of the optical surfaces from the object side, Ri represents the radius of curvature of the i-th optical surface (i-th surface), and Di represents the i-th surface and the i + th surface.
The spacing between the first surface and Ni and νi respectively indicate the refractive index and Abbe number of the material of the i-th optical member with respect to the d-line.
f is the focal length, Fno is the F number, and ω is the half angle of view.

R24 to R2 in the numerical value example 1
6, R31 to R32 in the numerical example 2, R22 to R23 in the numerical example 3, and R2 in the numerical example 4.
6 to R27 are optical members G, which are provided by design corresponding to, for example, an infrared cut glass, an optical low-pass filter, a protective glass for a solid-state image sensor, and the like.

Further, k is eccentricity, B, C, D, E, F ...
When is the aspherical coefficient and x is the displacement in the optical axis direction at the position of height h from the optical axis with reference to the surface vertex, the aspherical shape is

[Outer 1]

It is displayed with. However, R is a radius of curvature.

Also, for example, the display of "eZ" is "10
^-Z "is meant. Table 1 shows the correspondence with the above-described conditional expressions in each numerical example.

[0072]

[Outside 2]

[0073]

[Outside 3]

[0074]

[Outside 4]

[0075]

[Outside 5]

[0076]

[Table 1]

Next, FIG. 2 shows an embodiment of a video camera using the zoom lens of each of the above-mentioned embodiments as a photographing optical system.
3 will be used for the explanation.

In FIG. 23, 10 is a video camera main body, 11 is a photographing optical system constituted by the zoom lens of each embodiment, 12 is a solid-state image pickup device (such as CCD or CMOS) for receiving a subject image by the photographing optical system 11 ( A photoelectric conversion element), 13 is a recording unit for recording the subject image received by the image pickup element 12, and 14 is a finder for observing the subject image displayed on a display element (not shown). The display device is composed of a liquid crystal panel or the like, and includes an image sensor 12
The subject image formed above is displayed. Reference numeral 15 is a liquid crystal display panel having the same function as the finder.

As described above, by applying the zoom lens of each of the above-described embodiments to an optical device such as a video camera, an optical device having a small size and high optical performance can be realized.

[0080]

As described above, according to the present invention,
It is possible to realize a zoom optical system capable of focusing from an object at infinity to a very close object and also capable of following quick zooming.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a zoom optical system of the present invention.

FIG. 2 is a flowchart of a hybrid focus method.

FIG. 3 is a lens cross-sectional view of the zoom lens of Embodiment 1 and an explanatory diagram of a cam table of a rear focus unit.

FIG. 4 is an aberration diagram at a wide-angle end when focusing (object distance: 3 m) is performed by the first group in the zoom lens according to the first embodiment.

FIG. 5 is an aberration diagram at a wide-angle end when focusing (object distance: 3 m) is performed by the fifth lens group in the zoom lens according to the first embodiment.

FIG. 6 is an aberration diagram at a telephoto end when focusing (object distance: 3 m) is performed by the first group in the zoom lens according to the first embodiment.

FIG. 7 is an aberration diagram at the telephoto end when focusing (object distance: 3 m) is performed by the fifth lens group in the zoom lens according to the first embodiment.

FIG. 8 is a lens cross-sectional view of a zoom lens of Embodiment 2 and an explanatory diagram of a cam table of a rear focus unit.

FIG. 9 is an aberration diagram at a wide-angle end when focusing (object distance: 3 m) is performed by the first lens group in the zoom lens according to the second embodiment.

FIG. 10 is an aberration diagram at a wide-angle end when focusing (object distance: 3 m) is performed by the fourth lens group in the zoom lens according to the second embodiment.

FIG. 11 is an aberration diagram at a telephoto end when focusing (object distance: 3 m) is performed by the first group in the zoom lens according to the second embodiment.

FIG. 12 is an aberration diagram at a telephoto end when focusing (object distance: 3 m) is performed by the fourth lens group in the zoom lens according to the second embodiment.

FIG. 13 is a lens cross-sectional view of a zoom lens of Embodiment 3 and an explanatory diagram of a cam table of a rear focus unit.

FIG. 14 is an aberration diagram at a wide-angle end when focusing (object distance: 3 m) is performed by the first group in the zoom lens according to the third embodiment.

FIG. 15 is an aberration diagram at a wide-angle end when focusing (object distance: 3 m) is performed by the fourth lens group in the zoom lens according to the third embodiment.

FIG. 16 is an aberration diagram at a telephoto end when focusing (object distance: 3 m) is performed by the first lens group in the zoom lens according to the third embodiment.

FIG. 17 is an aberration diagram at a telephoto end when focusing (object distance: 3 m) is performed by the fourth lens group in the zoom lens according to the third embodiment.

FIG. 18 is a lens cross-sectional view of a zoom lens of Embodiment 4 and an explanatory diagram of a cam table of a rear focus unit.

FIG. 19 is an aberration diagram at a wide-angle end when focusing (object distance: 3 m) is performed by the first group in the zoom lens according to the fourth embodiment.

FIG. 20 is an aberration diagram at a wide-angle end when focusing (object distance: 3 m) is performed by the fifth lens group in the zoom lens according to the fourth embodiment.

FIG. 21 is an aberration diagram at a telephoto end when focusing (object distance: 3 m) is performed by the first group in the zoom lens according to the fourth embodiment.

FIG. 22 is an aberration diagram at a telephoto end when focusing (object distance: 3 m) is performed by the fifth lens group in the zoom lens according to the fourth embodiment.

FIG. 23 is a schematic view of a main part of a video camera.

[Explanation of symbols]

L1 first lens group L2 second lens group L3 Third lens group L4 4th lens group L5 5th lens group SP aperture stop G glass block IP image plane d d line ΔM meridional image plane ΔS sagittal image plane

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H044 DA01 DA02 DA04 DB01 DB02                       DC04 DE06 EF04                 2H087 KA02 KA03 MA12 MA15 MA19                       PA09 PA10 PA11 PA13 PA16                       PA19 PB11 PB12 PB13 PB17                       QA02 QA07 QA17 QA21 QA25                       QA34 QA42 QA45 QA46 RA05                       RA12 RA42 SA23 SA27 SA29                       SA30 SA32 SA33 SA63 SA64                       SA72 SA75 SB04 SB14 SB15                       SB22 SB25 SB35 SB47

Claims (7)

[Claims] 1. A zooming unit for moving and zooming during zooming, a first focus unit arranged in front of the zooming unit for moving and focusing, and a rear side of the zooming unit. A second focus unit that is arranged and moves to perform focusing, a sensor that detects the position of the first focus unit, and a zooming unit for the second focus unit according to the position of the first focus unit. And a memory that stores movement information at the time of zooming, the second focus unit based on position information of the first focus unit detected by the sensor and information from the memory during zooming. A zoom optical system characterized in that the movement trajectory changes. 2. The switch according to claim 1, further comprising a switch for switching between a first mode in which focusing is performed by the first focus unit and a second mode in which focusing is performed by the second focus unit. Zoom optics. 3. The first mode is a manual focus mode in which focusing is manually performed, and the second mode
Is an autofocus mode in which focusing is automatically performed according to a focus state, and when the switch is switched to the first mode, the second focus unit moves to a predetermined position. The zoom optical system according to claim 2. 4. When the focal length of the entire system at an arbitrary zoom position is fL and the combined focal length of the system on the front side of the second focus unit at the arbitrary zoom position is fAL, -3 <fL / 4. The zoom optical system according to claim 1, wherein the condition of fAL <4 is satisfied at all zoom positions. 5. The focal length of the entire system at an arbitrary zoom position is fL, and the combined focal length of the system on the front side of the second focus unit at the arbitrary zoom position is fAL, fL / fAL =
KL, the value of KL at the wide-angle end is KW, and the value at the telephoto end is KL.
The zoom optical system according to any one of claims 1 to 4, wherein a condition of 0.9 <KW / KT <1.1 is satisfied when the value of is KT. 6. The zoom optical system according to claim 1, wherein an image is formed on the solid-state image sensor. 7. A camera, comprising: the zoom optical system according to claim 1; and a solid-state image sensor that receives an image formed by the zoom optical system.