JP2887352B2 - Control device for zoom lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a zoom lens control device used as a zoom lens based on an optical correction type zoom lens.

(Prior Art) As is well known, in a zoom lens, there are a mechanical correction method and an optical correction method as a method of correcting a movement of an imaging position, that is, a focus movement due to a zooming action.

For example, as shown in FIG. 5, for example, as shown in FIG. 5, the mechanical correction type zoom lens is provided with four first lens groups toward a film surface side which is an image forming surface determined from the object side. There is a first lens group A1, a second lens group A2, a third lens group A3, and a fourth lens group A4, and the second lens group A2
Constitutes a zoom lens group called a variator, and the third lens group A3 constitutes a compensator called a focus correction lens group independent of the variator. That is, until the wide-angle end to said wide from the telephoto end to said telephoto, when the second lens group A2 is displaced in the optical axis direction as indicated by the straight line a2, the third lens group A3, for example as shown by the solid curve a3 _∞ The image is displaced in the direction of the optical axis, and the image forming position is kept at a fixed position, that is, on the film surface with the magnification change.

The second lens group A2 and the third lens group A3
Normally, the second lens group A2 and the third lens group A3 are mechanically driven to be displaced by a cam provided on the lens barrel in order to realize nonlinear interlocking with the lens group. The fourth lens group A4 is fixed by a relay lens.

By the way, in a general zoom lens, in order to adjust an image forming position according to a distance to a subject, that is, to perform focusing, the second lens group A2, the third lens group A3, and the first lens group A1 are used as focusing lenses. 4th
The front-lens extension system in which the lens group A4 is displaced in the optical axis direction is employed. This is because if the first lens group A1 which is not linked to the second lens group A2 and the third lens group A3 and is on the object side is a focusing lens, the zooming relational expression becomes constant regardless of the object distance. There are two major reasons.

On the other hand, as shown in FIG. 5, for example, if the third lens unit A3 is a focusing lens,
When the lens group A2 is displaced as indicated by the straight line a2 and the subject distance is infinity ∞, the third lens group A3 is changed to a solid curve.
though must be displaced as indicated by A3∞, if the subject distance is close range N, must be displaced as indicated by the chain line curve a3 _N the third lens group A3, zooming by object distance The relational expression changes.

There is an advantage in focusing by the middle lens feeding method in which the third lens unit A3 and the like are focusing lenses, but it is difficult to deal with a zooming relational expression that varies depending on the subject distance with only a mechanical cam as described above.

Therefore, as disclosed in Japanese Patent Publication No. 52-15226, a method of electrically controlling the displacement of the third lens group A3 in order to make the third lens group A3 a focusing lens is known. . In this method, the position of the third lens group A3 is electrically controlled by a calculation based on signals from the position detection means of the second lens group A2 and the position detection means of the third lens group A3. It is.

Further, as described in JP-A-52-114321, data necessary for performing focusing by the second lens group A2 to the third lens group A3 is calculated in advance, and the calculation result is stored in a ROM. And a second lens group A2 and a third lens group based on the stored contents.
A method of controlling A3 is also known.

By the way, although the absolute value of the vertical magnification of the second lens unit A2 becomes larger on the telephoto side, the displacement of the third lens unit A3 for focusing is multiplied by the zoom magnification, so that the dotted arrow in FIG. As shown by, it becomes extremely large on the tele side. Therefore, the method described in Japanese Patent Publication No. 52-15226 or the like requires extremely precise position detection and calculation of the second lens group A2 and the third lens group A3, and position control of the third lens group A3. Therefore, the calculation result is
Even if it is stored in M or the like, a huge storage capacity is required for this ROM. That is, in FIG. 5, a third curve representing the locus of lens group A3 a3 _∞, although the figure surrounded by a3 _N is the control range of the third lens group A3, for each point within the control range, Data must be stored.

Therefore, in a lens based on a mechanical correction type zoom lens as shown in FIG. 5, it is practically impossible to electrically control the correction by using the third lens group A3 as a focusing lens.

On the other hand, the optical correction type zoom lens has at least three lens groups 1, B2, and B3 from the subject side to the imaging plane side as shown in FIG. 6, for example, and the second lens group B2 is fixed. , The third lens unit B3 and the first lens unit B1 have a straight line b
3, b1 _∞, the optical axis direction as indicated by b1 _N is for zooming action by displacing integrally. The first lens group
In an optical correction type zoom lens in which B1 is a focusing lens extended by a helicoid, an image is not formed on a predetermined imaging plane as shown by a dashed curve f due to a zooming operation. The optical end is designed so that an image is accurately formed on a defined image plane at the telephoto end, the wide end, and the three intermediate points between them. Instead of using three lens groups, the amount of focus movement accompanying zooming is set within the depth of field.

However, as described above, in the optical correction type zoom lens, since a focus movement occurs with a zooming operation, it is difficult to increase the aperture ratio.

As described above, in a lens based on a mechanical correction type zoom lens as shown in FIG. 5, it is practically impossible to electrically control the correction by using the third lens group A3 as a focusing lens. .

On the other hand, in an optical correction type zoom lens as shown in FIG. 6, it is desired that the correction be performed a little more accurately.

Incidentally, in the optical system shown in FIG. 6, the third lens unit B3 is due to being displaced as indicated by the straight line b3, the first lens unit B1 S-shaped curve b1 _∞ ', b1 _N' shown by With such a displacement, the image forming position is kept constant, and is accurately corrected. When the first lens unit B1 is a focusing lens, if the subject distance is large to some extent,
S-shaped curve b1 _∞ when the object distance is changed ', b1 _N'
Have almost congruent shapes, and can be regarded as having been moved in parallel in the optical axis direction. That may be considered in accordance with the subject approaches, shall S-shaped curve b1 _∞ 'is as Repetitive out.

Then, as described in JP-A-63-220208, the amount of displacement of the non-focusing lens group is detected, and the amount of displacement of the focusing lens group is detected. It is known that a shift amount based on a difference between the displacement amounts is stored, and the moving amount of the focusing lens group is corrected based on the shift amount when the focusing lens group is moved.

(Problems to be Solved by the Invention) However, the configuration described in JP-A-63-220208 does not specifically describe the relationship between the amount of displacement and the amount of displacement of the focusing lens group, and There is a problem that the correction of the shift amount when the group is displaced is not specifically known.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and based on an optical correction type zoom lens, it is possible to accurately and surely correct a shift of an imaging position due to a zooming operation, and to perform this correction with a simple structure. It is an object of the present invention to provide a zoom lens control device which can be extremely easily performed by using a zoom lens.

[Configuration of the invention]

(Means for Solving the Problems) The present invention has at least a focusing lens group, a non-focusing movable lens group and another lens group,
By displacing at least the focusing lens group and the non-focusing movable lens group in the optical axis direction with respect to the other lens groups, a zooming operation is performed while keeping the imaging position substantially constant, and the focusing lens group is moved to another position. This is a zoom lens control device based on an optical correction type zoom lens that adjusts an image forming position according to a distance to an object point by displacing the lens group in the optical axis direction, and measures a subject distance. Distance means, detecting means for detecting a magnification value as a displacement amount of the non-focusing movable lens group, displacement amount of the focusing lens group set corresponding to a subject distance, and corresponding to the magnification value. Storage means for storing in advance the correction amounts of the focusing lens groups to be set, and the object distances corresponding to the object distance measured by the distance measuring means. Adding means for calculating the amount of displacement of the focusing lens group by adding the amount of displacement and the correction amount corresponding to the variable power value detected by the detecting means; Control driving means for relatively displacing the focusing lens group with respect to the non-focusing movable lens group.

(Function) The present invention provides a method for measuring a distance when at least the focusing lens group and the non-focusing movable lens group are displaced in the optical axis direction with respect to the other lens groups to change the magnification, and the focusing lens group is displaced for focusing. Means for measuring the subject distance, detecting means for detecting a variable magnification value as a displacement amount of the non-focusing movable lens group, and detecting the displacement of the focusing lens group set in accordance with the subject distance stored in advance in the storage means. The amount of correction and the correction amount of the focusing lens group set in accordance with the variable power value are added by the adding means, and the control driving means moves the focusing lens group in a non-focusing manner in accordance with the displacement amount calculated by the adding means. Since the lens unit is displaced relative to the lens unit, the focusing lens unit is moved to a non-focus position in accordance with the added displacement amount. By simply displacing the focusing movable lens group relatively, the imaging position is always kept constant even if the magnification is set.

(Embodiment) Hereinafter, an embodiment of a control device for a zoom lens according to the present invention will be described with reference to FIG. 1 to FIG.

The lens configuration of the zoom lens is as shown in FIG.
A first lens group C1, a second lens group C2, and a third lens group C3 are arranged from the object side, that is, the object side, that is, from the front side to the image forming surface side, and a three-group optical correction type zoom lens is configured. It is. That is, while the second lens group C2 is fixed, the third lens group C3 is displaced in the optical axis direction,
It is based on an optical correction type zoom lens that performs a zooming operation, that is, zooms, while keeping the image forming position almost constant by displacing the first lens unit C1 in the optical axis direction integrally with C3. Further, the first lens group C1 is different from the second lens group.
A focusing lens group that adjusts an image forming position in accordance with a subject distance that is a distance to an object point by displacing in the optical axis direction with respect to C2 and the third lens group C3.

Next, the configuration of the zoom lens barrel is shown in FIGS.
This will be described with reference to the drawings.

As shown in the figure, reference numeral 11 denotes a lens barrel main body, and a fixed frame 12 is fixed to the lens barrel main body 11 at a rear end thereof with screws 13 or the like. And, a middle ball frame portion provided integrally with the front end portion of the fixed frame 12
The second lens group C2 is fixedly held by 12a, and a plurality of straight cam grooves 12b are formed in the fixed frame 12 in parallel with the optical axis.

Reference numeral 14 denotes a movable cylinder, and a plurality of projections 14a are integrally formed on the inner peripheral side of the movable cylinder 14, and these projections 14a are slidably fitted to the respective linear cam grooves 12b of the fixed frame 12. In the engaged state, the movable cylinder 14 is slidably fitted on the outer peripheral side of the fixed frame 12. Thus, the movable cylinder 14 is coupled to the fixed frame 12 so as to be movable only in the optical axis direction, that is, in the front-back direction, and the rotation about the optical axis is locked. On the outer peripheral side of the movable cylinder 14, a helicoid male screw 14b is formed at a front part, and a rack part 14c is formed at a rear part. The rack portion 14c is provided on the movable cylinder 14 in the optical axis direction.

Further, the third lens group C1 is fixedly held by a rear lens frame 15, and the rear lens frame 15 is fixed to the protrusion 14a of the movable cylinder 14 by a plurality of screws 16, and is located in the fixed cylinder 12. ing.

The first lens group C1 is fixedly held by a front lens frame 17. A helicoid female screw 17a is formed on the inner peripheral side at the rear of the front lens frame 17, and a spur gear portion 17b is formed on the outer peripheral side. Is formed. The spur gear portion 17b is located on a circumference around the optical axis, and has teeth parallel to the optical axis. The helicoid female screw 17a is screwed to the helicoid male screw 14b of the moving cylinder 14. In this manner, the front lens frame 17 is coupled to the movable barrel 14 so as to move in the optical axis direction with rotation about the optical axis.

Further, the lens barrel main body 11 is provided with a focusing motor 18 constituting a control drive means, and the focusing motor 18 drives the front lens frame 17 to rotate. That is, the output shaft of the focusing motor 18 is
Through the spur gear portion 17b of the front lens frame 17.

A zooming motor 20 is similarly provided on the lens barrel main body 11, and the zooming motor 20 drives the moving cylinder 14 straight through a rack and pinion. That is, the output shaft of the zooming motor 20 is connected to the moving cylinder 14 via the reduction gear train 21.
Of the rack portion 14c.

Further, an electric circuit 22 is provided on the lens barrel body 11,
Focusing motor 18 and zooming motor 20
And a circuit for detecting the number of rotations of the zooming motor 20 is also built in.

Then, a cover 23 which forms an outer shell of the lens barrel is fixed to the lens barrel body 11 at a portion not shown, and the cover 23 covers all components from outside.

With such a configuration, it is possible to obtain a lens barrel that does not cause optical axis shift, that is, so-called eccentricity, when each lens group is slid in the variable power operation.

Next, the configuration of the electric circuit 22 will be described with reference to FIG.

In FIG. 4, reference numeral 31 denotes a microcomputer constituting control driving means. The microcomputer 31 receives signals from a zoom switch 32, an AF (auto focus) distance measuring circuit 33 as a distance measuring means, or a manual focus switch. By inputting, the driving of the focusing motor 18 and the zooming motor 20 is controlled via the zoom drive circuit 35 or the focus drive circuit 36. Note that the zoom switch 32 is manually operated and the manual focus switch 34 is also manually operated, and is constituted by, for example, a mechanical seesaw switch.

On the other hand, the AF distance measuring circuit 33 automatically measures the distance to the subject and outputs a signal corresponding to the distance to the microcomputer 31. The AF ranging circuit 33 is not a TTL method, but has a light emitting unit and a light receiving unit separately from the taking lens.
The distance is measured by reflecting the infrared light emitted from the light emitting unit on the object and receiving the infrared light on the light receiving unit.

Further, the electric circuit 21 detects a rotation number of the zooming motor 20, and includes a zoom position detection circuit 37 as a detection unit for detecting a position that is a movement amount of the movable barrel 14 with respect to the fixed frame 12 based on the rotation number. Have. That is, the zoom position detection circuit 37 detects a variable power value as a displacement amount of the third lens group C3 which is a non-focusing movable lens group.

Further, the microcomputer 31 has a
It has ROM38. The ROM 38 stores, for example, the amount of displacement of the displacement of the first lens unit C1 from the displacement of the third lens unit C3 when the image forming position is kept constant due to the zooming action for an object point at infinity ∞. Is stored in advance in association with the magnification value. The amount of displacement is determined by the corresponding focusing motor 18
May be stored as the number of rotations.

Further, the microcomputer 31 moves the first lens group C1 relative to the third lens group C1 based on the detected position of the moving cylinder 14 by the shift amount stored in the corresponding ROM 38, It has a function of controlling the focusing motor 18 via the focus drive circuit 36.

When zooming, that is, zooming, the zoom switch 32 not shown in FIGS. 1 and 3 is operated. The microcomputer 31 controls the zooming motor 20 via a zoom drive circuit 35 by inputting a zooming signal from the zoom switch 32, and the zooming motor 20 drives the zoom switch.
The moving cylinder 14 moves by an amount corresponding to the operation of 32.

At the time of zooming, the rotation of the zooming motor 20 drives the moving cylinder 14 straight forward via the reduction gear train 21 and the rack portion 14c. That is, the moving cylinder 14 moves in the optical axis direction with respect to the fixed frame 12 while the protrusion 14a of the moving cylinder 14 slides along the straight cam groove 12b of the fixed frame 12. Along with this,
The front lens frame 17 connected to the moving cylinder 14 by the helicoid male screw 14b and the helicoid female screw 17a moves together with the moving cylinder 14.

Therefore, the first lens group C1 held by the front lens frame 17
Then, the third lens group C3 held by the movable barrel 14 via the rear lens frame 15 is displaced in the optical axis direction while keeping a constant interval, and the focal length of the entire zoom lens changes.

Adjustment of the image forming position according to the subject distance, that is, focusing, can be switched between AF and manual. At the time of AF, for example, the AF distance measurement circuit 33 operates in conjunction with the shutter button press operation, and the microcomputer
31 inputs the ranging signal output from the AF ranging circuit 33,
Focusing motor via focus drive circuit 36
By controlling the focusing motor 18, the front lens frame 17 is moved. On the other hand, at the time of manual operation, when a manual focus switch 34 not shown in FIG. 1 and FIG.
The microcomputer 31 controls the focusing motor 18 in response to the input from the controller 20, and the driving of the focusing motor 18 causes the front lens frame 17 to move as much as the manual focus switch 34 is operated.

When focusing, the focusing motor 18
, The front lens frame 17 is rotationally driven via the reduction gear train 19 and the spur gear portion 17b. The front lens frame 17 is formed by a helicoid male screw 14b and a helicoid female screw 17a.
The moving cylinder 14 is connected to a straight cam groove 12 parallel to the optical axis.
Since the rotation about the optical axis is locked with respect to the fixed frame 12 by the engagement between the b and the projection 14a, the front lens frame 17 is driven, Move along the optical axis while rotating. Thereby, the first lens group C1 is
The second lens group C2 and the third lens group C3 held by the fixed frame 12
Is displaced back and forth with respect to and is focused.

By the way, at the time of zooming described above, the zoom position detection circuit 37 detects the number of rotations of the zooming motor 20, and
The amount of movement of the movable cylinder 14 with respect to the fixed frame 12 is detected.

At the time of focusing described above, particularly at least during AF, the microcomputer 31 controls the focusing motor 18 to move the front lens frame 17 by the amount specified by the distance measurement signal from the AF distance measurement circuit 33, and furthermore, The shift amount corresponding to the detected movement amount of the movable cylinder 14 is
Reading is performed with reference to the ROM 38, and the front lens frame 17 is displaced by the amount of displacement. That is, the displacement amount corresponding to the detected movement amount of the movable barrel 14 is added to the displacement amount of the first lens group C1 designated by the distance measurement signal by the adding means, and the first lens is added by the added amount. The group C1 is displaced.

In addition, since the shift amount is a difference between the displacement amount of the first lens unit C1 and the displacement amount of the third lens unit C3 when the imaging position is kept constant due to the zooming action, the difference between the displacement amounts is By adding and displacing the first lens unit C1, the image is focused on the basis of the distance measurement signal from the AF distance measurement circuit 33 irrelevant to the photographing lens. An image is formed on the film surface. In other words, the movement of the imaging position due to the magnification effect is corrected, and the imaging position is always kept constant regardless of the magnification value, and the optimum focusing state is always obtained.

Here, the operation will be described with reference to FIG.

As described above, three first lens groups C1 and second lens groups
The lens configuration of C2 and the third lens group C3 is an optical correction zoom lens, and the second lens group C2 is fixed as shown by the straight line c2, and the third lens group C3 is shown by the straight line c3.
When the first lens group C1 is displaced while keeping the distance d between the third lens group C3 and the third lens group C3 completely constant as shown by a straight line c1, the zooming operation causes a change from the wide end to the tele end. As shown by the curve f, the focal plane slightly moves in an S-shape.

On the other hand, when the third lens group C3 is displaced as shown by the straight line c3, if the first lens group C1 is displaced as shown by the curve c1 ', the zooming action as shown by the straight line f' is obtained. The focal plane does not change over the entire range, and the same focal plane can always be maintained.

Then, the electric circuit 22 detects the amount of displacement α of the third lens group C3, rotates the focusing motor 18 based on the amount of displacement α, and moves the first lens group C1 by β to the position indicated by the curve c1 ′. Displace. Therefore, regardless of the scaling value,
The same focal plane is automatically maintained. Here, the displacement amount β of the displacement of the first lens group C1 corresponding to the displacement amount α of the third lens group C3 is determined in advance by the lens configuration, and therefore the relationship between α and β stored in the ROM 38 in advance. Is corrected based on the data on

Note that the correction is not performed when the third lens group C3 is displaced, but is performed at the time of subsequent focusing immediately before photographing, for example, at the time of AF. Depending on the zoom ratio and the subject distance, the displacement amount of the first lens group C1 is, for example, It is determined as shown in the table on the next page. The leftmost column of this table shows the subject distance, and the top row shows the magnification value as the focal length when the subject distance is infinity∞. The displacement amount of the first lens unit C1 is 0 when the subject distance is infinity な い し at the telephoto end or the wide end, and values 0, γ ₁ , γ ₂ , γ determined according to the respective object distances.
_3, the gamma _4, shift amounts 0 described above corresponding to each magnification value, beta _1,
beta ₂ is added as the correction amount.

By the way, although the focusing is the front lens feeding method, since the first lens group C1 that is displaced when performing the magnification change operation is the focusing lens group, when the subject distance changes, the shape of the curve c1 ′ is strictly Not kept constant. That is, the deviation β of the displacement of the first lens unit C1 from the displacement of the third lens unit C3 when the imaging position is kept constant due to the magnification change is very small according to the subject distance. Yes, but it changes. However, since the first lens group C1 is a focusing lens group, if the subject distance is large to some extent, the curve when the subject distance changes
The shape of c1 'can be considered almost congruent. Therefore, even if the correction amount β of the displacement of the first lens unit C1 is determined only from the displacement amount α of the third lens unit C3, there is no practical problem at all.

Thus, according to the above configuration, although the structure of the zoom lens barrel is as simple as that of the conventional optical correction type zoom lens, the deviation of the imaging position due to the zooming operation can be accurately determined. Can be corrected. Then, as described above, the first lens group is obtained only from the displacement amount α of the third lens group C3.
Since the correction amount β of the displacement of C1 can be determined, the storage capacity of the ROM 38 and the memory for storing the data necessary for that can be extremely small, and the processing in the detection circuit 37 and the microcomputer 31 is also extremely simple. Can be corrected accurately and reliably.

Further, since the focusing motor 18 can be used also as a drive source for driving the first lens group C1 for correction, the structure can be further simplified.

It should be noted that the correction, that is, the displacement of the first lens unit C1 relative to the third lens unit C3 by the shift amount β corresponding to the zoom value is performed at the time of focusing, particularly at the time of AF. This may be performed when the three-lens group C3 is displaced to change the magnification.

〔The invention's effect〕

According to the present invention, at least the focusing lens group and the non-focusing movable lens group are displaced in the optical axis direction with respect to the other lens groups to change the magnification, and the focusing lens group is relatively moved with respect to the non-focusing movable lens group. When focusing by shifting, the distance measuring means measures the subject distance, and the detecting means detects the magnification value as the displacement of the non-focusing movable lens group, and corresponds to the subject distance stored in the storage means in advance. The amount of displacement of the focusing lens group that is set as described above, and the amount of correction of the focusing lens group that is set in accordance with the amount of zooming, are added by the adding unit, and the control driving unit adds the amount of displacement calculated by the adding unit. Since the focusing lens group is correspondingly displaced relative to the non-focusing movable lens group, the added By simply displacing the focusing lens group relative to the non-focusing movable lens group in accordance with the amount, it is possible to accurately correct the deviation of the imaging position due to the magnification change operation, and the storage amount of the storage means is Since the amount of displacement is set in accordance with the distance and the amount of correction is set in accordance with the zoom value, the amount of storage may be extremely small, and the processing can be made very simple by adding only by adding means. Since the driving device can also be used to drive the focusing lens group, the structure can be further simplified.

[Brief description of the drawings]

FIG. 1 is a half sectional view of a zoom lens barrel according to an embodiment of the zoom lens control apparatus of the present invention, FIG. 2 is an explanatory view of a zooming operation of the zoom lens, and FIG. FIG. 4 is a perspective view, FIG. 4 is a block diagram of the electric circuit, FIG. 5 is an explanatory view of a conventional mechanical correction type zoom lens, and FIG. 6 is an explanatory view of a conventional optical correction type zoom lens. 18 Focusing motor constituting control driving means 31 Microcomputer constituting control driving means 33 AF ranging circuit as distance measuring means 37 Zoom position detecting circuit as detecting means 38 ROM as storage means, C1... A first lens group which is a focusing lens group, C2... A second lens group, C3... A third lens group which is a non-focusing movable lens group.

Claims (1)

(57) [Claims] 1. A camera comprising at least a focusing lens group, a non-focusing movable lens group and another lens group,
By displacing at least the focusing lens group and the non-focusing movable lens group in the optical axis direction with respect to the other lens groups, a zooming operation is performed while keeping the imaging position substantially constant, and the focusing lens group is moved to another position. A zoom lens control device based on an optical correction type zoom lens that adjusts an image forming position according to a distance to an object point by displacing the lens group in the direction of the optical axis. Distance means, detecting means for detecting a magnification value as a displacement amount of the non-focusing movable lens group, displacement amount of the focusing lens group set corresponding to a subject distance, and corresponding to the magnification value A storage unit which stores in advance the correction amounts of the focusing lens groups to be set, and a distance corresponding to the subject distance measured by the distance measuring unit. Adding means for calculating the amount of displacement of the focusing lens group by adding the amount of displacement to be corrected and the amount of correction corresponding to the variable power value detected by the detecting means; A control drive unit for displacing the focusing lens group relative to the non-focusing movable lens group.