JP2583874B2 - Autofocus device and driving method of zoom lens group - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an autofocus apparatus suitable for use in a video camera or the like and a driving method of a zoom lens group.

[Conventional technology]

Conventionally, as an autofocus device for a video camera, for example, “National Technical Report” Vol.31
As disclosed in No. 6 (Dec. 1985) pp. 65-66, an infrared distance measuring system, a TTL video system, and the like are known.

The infrared focusing auto-focusing device is based on triangulation and emits infrared light with an infrared light emitting diode to irradiate a subject, and receives reflected infrared light from the subject to receive it. The position of the subject is detected, and the position of the front lens for distance adjustment arranged in front of the zoom lens system is automatically adjusted. In addition, the autofocus device of the TTL video system has a maximum high-frequency component of the video signal obtained from the image sensor at the time of focusing, so that the high-frequency component of the video signal is detected and a focus voltage is generated. The position of the front lens is automatically adjusted so that the focal voltage becomes maximum.

As described above, in any of the methods, the auto focus operation is performed by controlling the front lens.

By the way, the area where such a front lens can focus is 1 m to ∝, and in an area closer to this, it is impossible to focus on the subject with the front lens.
Note that an area in which the front lens can focus is referred to as a normal shooting area, and an area closer to the focus is referred to as a macro shooting area.

In order to enable shooting in the macro shooting area (close-up shooting, subject shooting), a zoom lever is provided on a zoom ring operated for zooming, and a zoom lens is operated by operating the zoom ring (hereinafter referred to as a variator). ) And a compensator (hereinafter referred to as the compensator) are set to the closest zooming position (the widest end position) in the normal shooting area, and then the operating lever is operated to further rotate the zoom ring. In general, it is possible to rotate in the direction opposite to the telephoto direction, whereby the variator is fixed and the position of the compensator is finely variable, and the subject is focused by finely adjusting the compensator manually. And is realistic.

Here, with reference to FIG. 5, a zoom lens that enables macro photography as described above will be described. In the figure, 1 is a zoom lens, 2 is a movable distance ring, 3 is a zoom ring, 4 is a fixed index, 5 is a diaphragm device, 6 is a master lens system, 7 is a zoom lever, and 8 is a push button switch.

Although not shown, each lens system of a front lens, a variator, and a compensator is provided in the zoom lens, and an optical system is configured by the master lens system 6 and the diaphragm device 5 fixed thereto. The front lens is moved in the optical axis direction by the rotation of the movable distance ring 2. This movable distance ring 2
A distance index is provided around the zoom lens 1, and the value of the distance index matching the fixed index 4 fixed to the lens barrel of the zoom lens 1 indicates the distance to the subject. The variator and compensator are moved in the optical axis direction by the rotation of the zoom ring 3. Around the zoom ring 3,
An index indicating a zoom value (f-value) in a normal shooting area and an index indicating a macro shooting area are provided. The normal shooting area is divided into an index of ∝ indicating the maximum telephoto end and an index of W indicating the widest angle end. Have been. The macro shooting area is bordered by the index W and the normal shooting area, and an index “MACRO” is provided.
The index of the zoom ring 3 that matches the fixed index 4 indicates the zoom value during normal shooting or the macro shooting.

The zoom ring 3 is also provided with a zoom lever 7 provided with a push button switch 8, whereby switching between a normal photographing region and a macro photographing region can be performed.

At the time of normal photographing, the fixed index 4 matches any index in the normal photographing area of the zoom ring 3, and the zoom ring 3 is rotated to perform zooming. Further, by rotating the movable distance ring 2, it is possible to focus on a desired subject. When shifting from the normal shooting area to the macro shooting area, first, the zoom ring 3 is rotated until the index of W coincides with the fixed index 4. The zoom lens is also provided with a click mechanism. When the index of W of the zoom ring 3 matches the fixed index 4, the zoom ring 3 cannot be further rotated by the click mechanism. When the push button switch 8 is operated in this state, the click mechanism is released, and the zoom ring 3 can be rotated by the zoom lever 7 so that the zoom ring 3 can enter the macro shooting area. In this macro photography area, as described above, the variator is fixed at the wide-angle end position, and the compensator moves by rotating the zoom ring 3 to bring the system to a short distance of several cm to 1 m. It is possible to focus on a certain desired subject.

The reason why the click mechanism is provided is to prevent inconvenience such as erroneously entering the macro shooting area during operation of the zoom ring 3 during normal shooting and the shot image is greatly blurred. When moving from the macro shooting region to the normal shooting region, the click mechanism is not operated, and the zoom ring 3 can be smoothly rotated relatively without any sense of resistance. The mechanism may be activated.

[Problems to be solved by the invention]

In the macro shooting area in the vicinity of several cm to 1 m, if the front lens is to be controlled and focused, it is necessary to extremely increase the amount of movement (movement) of the front lens. Above is unrealistic.

In particular, in the infrared focusing type auto-focus device, since the position of the triangulation unit and the photographing lens is displaced, there is a variance (parallax) between them.
At a close distance of about 1 cm to 1 m, the error between the distance to the subject measured by the triangulation unit and the actual distance from the image sensor to the subject increases, and the focusing accuracy decreases significantly. If a triangulation unit is provided to prevent this, the structure becomes very complicated and impractical.

As described above, in the infrared distance measuring type auto focus device, automation in the macro shooting area is impossible in principle, and in the TTL video type auto focus device, the measured distance to the subject and the actual distance are also different. However, it is not realistic to draw out the front lens in the macro shooting area, and therefore, as described above, the focus adjustment is manually performed in the macro shooting.

As described above, in the conventional auto-focus apparatus, in the macro shooting area, the focusing operation on the subject must be performed by the fine adjustment of the zoom ring, and there is a problem in operability.

SUMMARY OF THE INVENTION An object of the present invention is to provide an autofocus apparatus and a driving method of a zoom lens group capable of solving such a problem, enabling an autofocus in a macro shooting area, and further improving operability. It is in.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a TTL video system auto focus apparatus, wherein a zoom ring driving means,
Switching means for selectively supplying a focus control voltage corresponding to the amount of the high frequency component of the video signal to one of the movable distance ring driving means and the zoom ring driving means is provided.

[Action]

The switching means supplies a focus control voltage to the movable distance ring driving means in a normal photographing area. The movable distance ring driving means drives the movable distance ring in accordance with a focus control voltage obtained by manually operating the zoom ring, and performs a focusing operation on a desired subject for desired zooming. When the switching operation from the normal photographing region to the macro photographing region is performed by the push button, the switching unit switches the focus control voltage from the movable distance ring driving unit to the zoom ring driving unit. The zoom ring driving means drives the zoom ring in the macro shooting area in accordance with the focus control voltage, and performs a focusing operation on a desired subject at a close distance.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an autofocus device and a driving method of a zoom lens group according to the present invention.
9 is an image sensor, 10 is a camera circuit, 11 is a focus voltage detection circuit, 12 is a focus control circuit, 13 is an open / close switch, and 14 and 1
5 is a switching switch, 16 and 17 are drive circuits, 18 and 19 are motors, 2
Numerals 0 and 21 are gears, 22 is a zooming control circuit, 23W and 23T are zooming switches, and 24 is a power zoom circuit, and the parts corresponding to those in FIG.

In FIG. 1, a zoom lens 1 has the same configuration as that of FIG. 5, and light incident through the zoom lens 1 is applied to an image sensor 9. The imaging element 9 generates and outputs a video signal by scanning an image formed on the imaging surface. This video signal is subjected to predetermined processing by the camera circuit 10.

This video signal is supplied to the focus voltage detection circuit 11. The focus voltage detection circuit 11 includes a high-pass filter or a low-pass filter, a detection circuit, an integration circuit, and the like. The focus voltage detection circuit 11 separates, detects, and integrates a high-frequency component of the video signal to obtain a focus voltage VF having a level corresponding to the amount of the high-frequency component. Generate. In this case, the integration range is a range of the video signal corresponding to a predetermined range including the subject to be focused in the visual field viewed from the image sensor 9. This focus voltage is applied to the focus control voltage by the focus control circuit 12.
Converted to CF and switched via switch 13
Of the switching switch 15 and the M contact of the switching switch 15. The M contact of the open / close switch 14 is an open contact, and the open / close switch 14
A zoom control voltage CZ is supplied to the N contact 15 from a power zoom circuit 24 including zooming switches 23W and 23T and a zooming control circuit 22. These open / close switches 1
Reference numerals 4 and 15 are linked with the zoom ring 3 and are switched when one of the normal shooting area and the macro shooting area is shifted to the other.

On the other hand, the movable distance ring 2 of the zoom lens 1 is connected to a motor 18 via a gear 20 or the like, and the zoom ring 3 is connected to a motor 19 via a gear 21 or the like. The motor 18 is a drive circuit to which the focus control voltage CF is supplied from the switching switch 14.
The motor 19 is driven by a driving circuit 17 to which a zooming control voltage CZ or a focus CF is supplied from a switching switch 15.

In such a configuration, during normal shooting, the switching switch
Both 14 and 15 are closed to the N contact side. Then, the zooming control voltage CZ is supplied from the power zoom circuit 24 to the drive circuit 17 via the switching switch 15, and the zoom ring 3 is rotated by the forward or reverse rotation of the motor 19,
While the zooming switch 23W is being operated, the zoom ring 3 rotates in the direction in which the variator and compensator move to the widest end, and while the zooming switch 23T is being operated, the zoom ring 3 is turned on when the variator and the compensator are at the maximum. It rotates in the direction to move to the telephoto end. Accordingly, zooming can be performed by operating the zoom lever 7 by operating the zoom lever 7 (manual zooming), and zooming can be performed by appropriately operating the zooming switches 23W and 23T. (Power zooming) is also possible.

On the other hand, the focus control voltage CF generated by the focus control circuit 12 is supplied to the drive circuit 16 via the opening / closing switch 13 and the switching switch 14, and the movable distance ring 2 is rotated by the forward or reverse rotation of the motor 18. The movable distance ring 2 stops when the front lens moves and the integrated value of the high frequency component of the video signal obtained by the focal voltage detection circuit 11 reaches the maximum. As a result, the desired subject is brought into focus.

When the zoom ring 3 is manually operated to match the index of W with the fixed index 4 during the normal photographing, the zoom ring 3 cannot be rotated by a click mechanism (not shown). When the provided push button switch 8 is operated, the click mechanism is released, and the zoom ring 3 is further rotatable in the same direction and moves to the macro shooting area. At the same time, the switching switches 14 and 15 are switched to the M contact side.

Therefore, the input side of the drive circuit 16 is opened, the movable distance ring 2 is fixed, the front lens is fixed at the final position during normal photographing, and the zooming control voltage CZ from the power zoom circuit 24 is switched by the switching switch. Blocked by 15.
On the other hand, the focus control voltage CF from the focus control circuit 12 is supplied to the drive circuit 17 via the opening / closing switch 13 and the switching switch 15, and the zoom ring 3 rotates accordingly. At this time, the variator is fixed at the widest angle position, and only the compensator moves with the rotation of the zoom ring 3 to perform a focusing operation. Focus voltage detection circuit 11
When the integral value obtained in (1) becomes maximum, the zoom ring 3 stops, and the subject in the macro shooting area is focused. in this case,
Since the variator is fixed at the widest angle position, the photographing range of the subject in the macro photographing area can be maximized.

When switching from macro shooting to normal shooting, the zoom ring 3 may be manually rotated until the W index exceeds the fixed index. When shifting from the macro shooting area to the normal shooting area, the switching switches 14 and 15 are set to N
Switches to the contact side.

The open / close switch 13 is for switching between a manual focus and an auto focus. This opening and closing switch 13
When the shutter is closed, the focus control voltage CF from the focus control circuit 12 is supplied to the drive circuit 16 or 17 so that the auto focus operation is performed both in normal shooting and macro shooting, but when the open / close switch 13 is opened, the focus is opened. The voltage CF is cut off, allowing manual focus operation for both normal shooting and macro shooting.

As described above, in this embodiment, the auto focus function can be provided relatively easily even during macro shooting by simply providing the switching switches 14 and 15 linked to the zoom ring 3 without impairing the conventional functions. be able to.

FIG. 2 is a block diagram showing a main part of another embodiment of an autofocus apparatus and a driving method of a zoom lens group according to the present invention. Reference numerals 25 and 26 denote switching switches, and portions corresponding to FIG. The same reference numerals are given and duplicate descriptions are omitted.

In FIG. 2, a focus control voltage CF generated by the focus control circuit 12 is supplied to a movable contact of a switching switch 26 via an opening / closing switch 13. This switch
Reference numeral 26 is linked to the zoom ring 3 (FIG. 1) in the same manner as the switching switches 14 and 15 in FIG.
The M contacts are respectively connected to the A contacts of the switching switch 25. The switching switch 25 has a B contact connected to the power switch circuit 24 and a movable contact connected to the drive circuit 17, respectively, and is always closed to the A side, but the operation period of the zooming switches 23T and 23W of the power switch circuit 24. Only close to B side. Other parts are the same as those in FIG.

Therefore, first, during normal shooting, the switching switch
Reference numeral 26 is closed to the N-contact side, and a focus control voltage CF is supplied from the focus control circuit 12 to the drive circuit 16 via the opening / closing switch 13 and the switching switch 26. When one of the zooming switches 23T and 23W is operated, the switching switch 25 is closed to the B contact side by the zooming control circuit 22 during the operation, and the zooming is performed from the power zoom circuit 24 to the drive circuit 17 via the switching switch 25. The control voltage CZ is supplied. Thus, the auto focus operation and the zooming operation are performed.

At the time of macro photography, the switching switch 26 is closed to the M contact side, similarly to the switching switches 14 and 15 in FIG. Here, since the switching switch 25 is always closed to the A contact side, the focus control voltage CF is normally supplied to the drive circuit 17 via the opening / closing switch 13 and the switching switches 26 and 25, and the auto focus operation by the compensator is performed. Is performed.

When one of the zooming switches 23T and 23W is operated in such a state, the operation period switching switch 25 closes to the B contact side, and the zooming voltage CZ becomes a focus voltage.
It is supplied to the drive circuit 17 via the switching switch 25. Thereby, the focusing operation by the compensator is performed.
Therefore, the focusing operation by the zooming switches 23T and 23W, that is, the power focus operation can also be performed.

In the embodiment shown in FIG. 1, the manual focus operation and the auto focus operation can be performed by turning on and off the opening / closing switch 13 during macro shooting, but in the embodiment shown in FIG. In addition, power focus operation by the power zoom circuit 24 becomes possible, further improving usability.

As described above, if the auto focus is performed in the macro shooting area, the click mechanism operates even if the zoom ring 3 rotates until the index of W and the fixed index 4 match during normal shooting. There is no particular problem because it does not shift to the macro shooting area, but conversely, there is no zoom mechanism provided when the macro shooting is performed and the click mechanism that operates when the W index of the zoom ring 3 matches the fixed index. At the time of macro photography or auto focus, the lens may settle into a focal point after performing unnecessary operations, the subject may be momentarily deviated from the field of view of the image sensor 1, or the power zoom circuit 24 shown in FIG. If the power focus operation is erroneously performed, the camera may naturally shift to the normal shooting area without any resistance. In this case, an operation for shifting to the macro image capturing area is required again, which causes a problem in operability.

FIG. 3 is a block diagram showing a specific example of a macro photographing area deviation prevention device for solving such a problem, wherein 27 is a macro photographing area index, 28 is a movable conductor piece, 29 is a fixed conductor piece,
Reference numeral 30 denotes a macro shooting area detection circuit, which is shown in FIGS.
Parts corresponding to those in the figures are given the same reference numerals.

In FIG. 3, the lens barrel of the zoom lens 1 is provided with a fixed conductor piece 29 on the opposite side of the zoom ring 3 from the fixed index 4 side. A movable conductor piece 28 is provided so as to face the end portion A of the macro shooting region index representing the macro shooting region on the side of the normal shooting region, that is, the index position of W. Therefore, zoom ring 3
Is rotated, and the index of W and the fixed index 4 match, the movable conductor piece 28 and the fixed conductor piece 29 come into contact with each other.

Now, at the time of macro photography in which the macro photography area index 27 and the fixed index 4 are opposed to each other, the zoom ring 3 rotates and W
If the movable conductor piece 28 comes into contact with the fixed conductor piece 29 when the index of the fixed index 4 and the fixed index 4 match, the macro imaging region detection circuit 30
Detects this and outputs a detection signal. The focus control circuit 12 outputs a focus voltage CF such that the rotation direction of the motor 19 (FIGS. 1 and 2) is reversed according to the detection signal. Thus, the rotation direction of the zoom ring 3 is also reversed, and the transition from the macro shooting area to the normal shooting area is prevented.

FIG. 4 is a block diagram showing another specific example of the macro photographing area departure prevention device, in which 31 is a resistor, 32 is a macro photographing area detecting circuit, and portions corresponding to FIG. I'm wearing it.

In FIG. 4, a resistor 31 is provided on a side opposite to the fixed index 4 side with respect to the zoom ring 3 from a position facing the index W in parallel with the zoom ring 3 to a position facing the fixed index 4. I have. The movable conductor piece 28 is provided at a position facing the index of W on the zoom ring 3, and the movable conductor piece 28 is always in contact with the resistor 31 in the macro photography region. The macro imaging region detection circuit 32 constantly detects the resistance value between the movable conductor piece 28 and the point B of the resistor 31 facing the fixed index 4.

Now, in macro photography, if the index of W matches the fixed index 4 by the rotation of the zoom ring 3, the movable conductor piece 28 overlaps the point B of the resistor 31, and the movable conductor piece 28, the point B
The resistance value between them becomes equal to or less than a predetermined value. When the macro photography area detection circuit 32 detects this, it outputs a detection signal, whereby the focus control circuit 12 reverses the rotation direction of the zoom ring 3 as in the specific example of FIG. Therefore,
Also in this specific example, it is possible to prevent the macro photography area from unduly shifting to the normal photography area.

In FIGS. 2 and 3, when shifting from the macro shooting area to the normal shooting area, the zoom ring 3 may be manually rotated as described above. Further, the installation positions of the movable conductor piece 28, the fixed conductor piece 29, and the resistor 31 are not limited to the above positions as long as a boundary with a normal imaging area can be detected during macro imaging. In addition, movable conductor pieces
Needless to say, instead of the fixed conductor piece 29 and the resistor 31, other means such as a potentiometer or a mechanical switch may be used.

〔The invention's effect〕

As described above, according to the present invention, it is possible to perform auto focus in a macro shooting region by simply adding a simple switching unit without impairing the conventional auto focus function, and operability is further improved. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of an autofocus device and a driving method of a zoom lens group according to the present invention, and FIG. 2 shows another embodiment of an autofocus device and a driving method of a zoom lens group according to the present invention. FIGS. 3 and 4 are configuration diagrams showing a specific example of a macro image capturing area deviation prevention device which can be used in these embodiments, and FIG. 5 is a configuration diagram showing an example of a zoom lens. . 1 ... Zoom lens, 2 ... Movable distance ring, 3 ... Zoom ring, 7 ... Zoom lever, 8 ... Push button switch, 9 ...
Image sensor, 11 Focus voltage detection circuit, 12 Focus control circuit, 14, 15 Switching switch, 18, 19 Motor,
25,26 ... Switch.

Claims (2)

(57) [Claims] 1. A lens system comprising: a front lens group for focusing in a normal photographing area; a variable power lens and a correction lens connected by a cam mechanism; The zooming is performed by moving the lens in conjunction with the lens, and in the macro shooting area, the zooming lens group for moving the correction lens to perform focusing, the front lens group, and the zooming lens group. And a master lens system that forms a photographic optical image on the photographic element by using a zoom lens group. The imaging element extracts a high-frequency component of a video signal obtained by capturing the photographic optical image, and A focus control signal of an amount corresponding to the degree of matching is generated, and by the focus control signal,
An auto-focusing device having a control loop configured to control the position of the front lens group or the correction lens so that the amount of the high frequency component is maximized. The focus control signal is supplied to a driving unit of the front lens group, and when photographing in a macro photographing area,
Photographing mode switching means for manually switching the focus control signal so as to supply the focus control signal to the driving means for the zooming lens group; and driving means for driving the front lens group by the photographing mode switching means. The switching of the focus control signal to the driving unit of the zooming lens group is performed when the variable power lens of the zooming lens group is set at a predetermined position near the wide angle end in the normal photographing area and fixed. When photographing in the macro photographing area, the variable magnification lens is fixed at the predetermined position, and the correction lens is displaced in accordance with the focus control signal to perform focusing. An auto-focusing device, wherein an auto-focusing operation is enabled in both the photographing region and the macro photographing region. 2. A zoom lens system comprising: a front lens group for focusing in a normal photographing area; a variable power lens and a correction lens connected by a cam mechanism; The zooming is performed by moving the lens in conjunction with the lens, and in the macro shooting area, the zooming lens group for moving the correction lens to perform focusing, the front lens group, and the zooming lens group. And a master lens system for forming a photographic optical image on the photographic element. The image pickup element extracts a high-frequency component of a video signal obtained by capturing the photographic optical image, and A focus control signal of an amount corresponding to the degree of matching is generated, and by the focus control signal,
A method of driving a zoom lens group of an auto-focusing apparatus having a control loop configured to control the position of the front lens group or the correction lens so that the amount of the high frequency component is maximized, In response to an operation, a control signal for electric zooming is generated. At the time of photographing in a normal photographing area, the focus control signal is supplied to a driving means of the front lens group to perform an autofocus operation, and A control signal is supplied to the driving unit of the zooming lens group, and the zoom lens and the correction lens are driven to perform a zooming operation. From a shooting mode in a normal shooting area to a shooting mode in a macro shooting area. Can be switched by fixing the zoom lens at a predetermined position near the wide-angle end in the normal shooting area. The zoom lens is fixed to the predetermined position, and one of the focus control signal and the electric zooming control signal is selectively supplied to the driving unit of the zooming lens group, so that the autofocus operation by the correction lens is performed. And a manual focusing operation can be selectively performed.