JP3202041B2 - Lens control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera lens control device.

[0002]

2. Description of the Related Art In recent years, the use of a camera-integrated video tape recorder (VTR) has been remarkable, and the space and weight occupied by a lens unit and an automatic focusing device have been rapidly reduced due to their smaller size and lighter weight. I am doing it.

[0003] In such a background, an automatic focus adjusting device is a so-called active type having an infrared light projecting / receiving device, and a focus is detected from a video signal via an image pickup device without using the aforementioned light projecting / receiving device. It is shifting to a passive system.

On the other hand, in the lens section, a so-called inner-focus type lens which has a function of adjusting the focus of a lens that corrects the movement of the focal plane due to zooming, and further fixes the front lens to reduce the size is widely used. It came to be introduced.

FIG. 4 shows an example of the above-mentioned inner focus lens type. Reference numeral 101 denotes a fixed first lens group, 102 denotes a second lens group (zoom lens) for changing magnification, and 103 denotes an aperture. Reference numeral 104 denotes a fixed third lens group, and reference numeral 105 denotes a fourth lens group (a focus lens or a compensator lens) having both a function of correcting movement of a focal plane due to zooming and a function of focusing.
Reference numeral 106 denotes an image sensor, and the figure shows an image pickup surface thereof.

FIG. 5 shows the change of the focal length, that is, the position of the focus lens 105 for focusing on each object distance with respect to the position of the zoom lens 102. When there is no change in the focal length, that is, when the zoom lens 102 is stopped, the focus lens 10
5 can be adjusted by moving the lens 5 in parallel with the vertical axis on the corresponding focal length (horizontal axis) in FIG.
During the zoom operation, the trajectory of the focus lens 105 is selected from FIG. 5 according to each object distance, and drive control corresponding to the change in the focal length is performed on the focus lens 105 according to the trajectory. For example, the zoom operation can be performed while providing a focal plane correction and a focus adjustment function by zooming, and a video signal without blur during zooming can be obtained.

FIG. 6 is a view for explaining an example of a drive control method during the zoom operation of the focus lens 105. The method of obtaining coordinates is the same as that of FIG. FIG.
Are divided into a plurality of areas according to the position of the zoom lens (focal length) and the position of the focus lens (object distance), and the representative velocity of the focus lens is given to each area. In FIG. 6, an arrow whose angle is changing every moment indicates the speed of the focus lens 105.

In FIG. 6, the moving area (horizontal axis) of the zoom lens 102 is divided into 16 equal parts.
1 to Z16 are set. Here, each area after 16 equal divisions is referred to as a zoom zone. By dividing the curve in FIG. 5 for each zoom zone, it is possible to divide the curve into portions having substantially the same inclination in each zoom zone. When the driving speed of the zoom lens, that is, the zoom speed is constant, if the speed, that is, the inclination of the focus lens in each zoom zone is equal, the moving speed of the focus lens 105 can be equalized even if the subject distance is different. it can. Therefore, as shown in FIG. 6, the vertical axis is divided into portions having the same inclination for each zoom zone, and one representative speed is given to each region.

In this way, if focus is achieved at the start of zooming, the positions of the zoom lens and the focus lens are detected to determine the reference speed of the focus lens, and for example, the front speed from the AF device is determined. The zoom operation can be performed while correcting this by the post-pin information, and it is possible to always follow the locus of FIG. 5 at an appropriate moving speed of the focus lens 105.

[0010]

By the way, the zoom lens 102 is located at the wide end as shown in FIG. 5, and the focus lens 105 is focused on an object at an infinite distance, that is, near the point A. And As is clear from FIG. 5, at the wide end, the cam trajectory for each object distance is concentrated near point A, and depending on the F value of the lens or the aperture, for example, the infinity and the 3 m focusing lens position are within the depth. When you enter, things happen. In the case of the above-mentioned passive type automatic focusing device, especially when the position of the focus lens enters the depth, even if an infinite subject is photographed, the subject distance is 3 mm.
In many cases, the focus lens stops at the in-focus position of m. As described above, when it is determined that the lens is in focus at a lens position different from the actual object distance and the lens is stopped, zooming from the wide side to the tele side as shown in the conventional example causes a locus of a different position to be obtained. There is a drawback that the trajectory continues to follow, and the cam trajectories corresponding to the respective object distances are dispersed in a short time, and the blur is enlarged at a different depth. In particular, for a low-contrast subject such as a night scene subject, a foggy distant view, or a case where the ground is photographed from an airplane, for example, where the passive type automatic focusing device is weak, the blur correction determination during zooming may be incorrect. In many cases, in such a scene, it has been impossible to perform a zoom operation that hardly causes blurring.

For this reason, the present applicant proposes a method of forcibly applying a speed for following the cam trajectory with respect to the subject distance of the subject to the focus lens at the time of zooming for the above-mentioned zoom operation of the subject. did. According to this method, when it is determined that the focus is achieved at the starting point of the zoom, the zoom operation can be performed on the subject at the subject distance while maintaining the defocus amount at the starting point.

However, in this method, zooming without blur can be performed only when it is considered that focus is achieved at the starting point of the zooming operation. In order to execute the above method, manual focusing or the like must be performed in advance. It was necessary to perform a focusing operation.

[0013]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is characterized by a first lens unit for performing zooming and a second lens unit for performing focus adjustment. Lens group, focus detection means for detecting a focus state, and displacement of a focal plane caused by movement of the first lens group.
A first magnification unit that performs a magnification operation while maintaining a focused state by correcting the second lens group with a characteristic curve corresponding to the subject distance and an output of the focus detection unit; The characteristic that when the first lens group is moved, the second lens group is forcibly moved to an infinite subject distance, and is capable of performing a zoom operation while maintaining a focused state with respect to the infinite subject distance. Second scaling means controlling based on a curve;
A lens control device (Claim 1) characterized by comprising switching means for selectively switching between the first scaling means and the second scaling means, and a first means for performing scaling. A lens group, a second lens group for performing focus adjustment, focus detection means for detecting a focus state, and displacement of a focal plane caused by movement of the first lens group. A first zooming unit that performs a zooming operation while maintaining a focused state by performing correction based on a characteristic curve corresponding to a distance and an output of the focus detecting unit; the second lens group, a second variable magnification means for controlling, based on the zooming operable characteristic curve while maintaining an in-focus state with respect to an infinite object distance, or the first variable magnification means
The operation of switching from
And the first lens group
Forcibly move to infinite subject distance
Enables operation of the second scaling means in the focus state
In lens control apparatus characterized by and a control means to (claim 3).

[0014]

According to the first configuration (claim 1) , the focus lens is forcibly set to an infinite subject distance without performing correction by the AF device for a subject or the like which is likely to be blurred.
The zooming operation is performed while the in-focus state is maintained by switching to the second magnification means that controls based on a characteristic curve capable of performing a magnification operation while maintaining the in-focus state with respect to an infinite subject distance while moving the focus. Can be performed. According to the second configuration (claim 3), the subject that is likely to cause blur is
By switching to the second zooming means,
Infinite subject distance with manual focus
Forcibly move the focus lens to
Characteristic music that can be zoomed while maintaining focus on separation
By performing control based on the line, the magnification operation can be performed while maintaining the in-focus state for an infinite subject distance without correction by the AF device and without being affected by a malfunction of the AF device.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a lens control device according to the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a first example which best illustrates the features of the present invention.
In the configuration diagram of the embodiment, 101, 102, 103, 10
Reference numerals 4, 105, and 106 are the same as the various optical elements such as the lens and the aperture shown in FIG. 107, 108, 1
Reference numeral 09 denotes an actuator for moving the zoom lens 102, the aperture 103, and the focus lens 105, respectively. Reference numerals 110, 111, and 112 respectively control the actuators 107, 108, and 109 to signals from a system control circuit 119 described later for controlling the entire system. Drivers 113, 114, and 115 are position encoders for detecting the movement states of the zoom lens 102, the aperture 103, and the focus lens 105 and converting the movement states into electric signals, 113 is a zoom encoder,
114 is an iris encoder, and 115 is a focus encoder. 116, an amplifier for amplifying the output of the image sensor 106 to a predetermined level; 117, a band-pass filter for extracting a high-frequency component used for focus detection from the output signal of the image sensor 106 output from the amplifier 116;
Reference numeral 8 denotes an image sensor 1 using the output signal level of the amplifier 116.
An aperture control circuit 119 for controlling the state of the aperture so that the amount of light on the aperture 06 becomes appropriate controls the overall system as well as the zoom encoder 113, the iris encoder 114, the focus encoder 115, and the band pass filter 117. A system control circuit that controls the actuators 107 and 109 based on the output signal, and is constituted by a micro computer.

Reference numeral 120 denotes a focus switch for moving the focus lens 105 during manual focusing, and 121 denotes a zoom switch.

In the camera system configured as shown in FIG. 1, the trace operation of the locus drawn by the zoom lens and the focus lens shown in FIG. 5 is controlled by the system control circuit 119, and the speed shown in FIG. The information is stored as a table in the system control circuit 119, and the trajectory to be traced is determined by referring to the table based on the positions of the focus lens and the zoom lens, and the focus lens driving speed for following this is determined.

In the system control circuit 119, focus lens control for automatic focus adjustment is also performed. For example, the level of a high-frequency component of a video signal is detected from the output signal of the bandpass filter 117, and this level is detected. The focus lens 105 is driven and controlled via the driver 112 and the actuator 109 so as to be maximized. FIG. 8 is a diagram showing the relationship between the output signal level of the bandpass filter, that is, the focus voltage, which changes according to the position of the focus lens. As shown in FIG. 8, the focus voltage indicated by 801 is the maximum value at the focal point. Therefore, it is possible to determine the focus, the out-of-focus, the front focus, the rear focus, and the like from the change in the focus voltage.

Therefore, by using this automatic focus adjustment algorithm, it is possible to determine whether the subject is in focus or out of focus and to determine whether the subject is in focus or not, even during zooming.

FIG. 2 is a flowchart showing a processing procedure in the lens microcomputer 119.

In this embodiment, during the zoom operation, the AF
From the zoom operation state corresponding to the first zooming means for correcting the deviation of the focus lens from the cam locus based on the front focus and rear focus information from the device, a specific cam locus is used without using the output of the AF device. The operation of switching to the zoom operation state corresponding to the second variable magnification means for forcibly following is used during the zoom operation, for example, when driving the focus lens 105 of the manual focus switch 121 in the infinite direction. The operation is performed by operating an infinite direction button (F button). The operation button for performing this operation does not necessarily have to be the F button. However, as will be described later, the second zooming means that does not use the AF device focuses along the cam path corresponding to the infinite subject distance. Since the lens is configured to be controlled, it is extremely reasonable to use the F button for the operation for performing this operation.

In FIG. 2, when the process is started at 201, it is determined at 202 whether or not the zoom switch 121 is operated. If the zoom switch has not been operated, the flow advances to step 203 to perform a normal AF operation or manual focus adjustment, thereby moving the focus lens to the in-focus position. At 203, it is determined that the focus lens position adjustment is completed and the in-focus state has been achieved, and as a result of the determination processing at 202, the zoom switch 121 has been operated and the zoom operation has been performed in any direction. If so, the process proceeds to the process of 204, and the manual focus switch 121 in FIG.
The state of the infinite direction button (F button) used when driving the focus lens 105 in the infinite direction is confirmed. If the F button is not pressed, 205 to 20
8 is performed. The focus lens drive speed is read from the positions of the zoom lens and the focus lens using the focus lens drive speed reference table shown in FIG. 6, and the focus lens is driven during the zoom operation.

The driving method will be described in more detail.
, The focus direction (front focus, rear focus) is determined. At 206, the focus lens driving speed corresponding to the positions of the zoom lens and the focus lens is read from the reference table of FIG.
At 207, the speed read from the table is corrected so as to cancel the blur direction, and at 208, the focus lens is driven at the speed corrected at 207.

FIG. 3 shows the movement in each process. 5, reference numeral 301 denotes a cam locus for a certain subject distance among the cam locuses shown in FIG. 5, and 302 denotes a front focus and a rear focus with respect to the standard driving speed on the cam locus during the zoom operation as described above. Is the actual movement trajectory of the focus lens driven while correcting.

When the driving speed of the focus lens is controlled as indicated by reference numeral 302 in the same figure, blurring is likely to occur, particularly in zooming from wide to telephoto directions, as described in connection with the present invention. Because this 302
The focus lens control method shown in FIG. 1 is basically a method that is established by referring to the data in the table of FIG. Therefore, once the blur direction discrimination at 205 is erroneous and erroneous data starts to be picked up, the blur starts to expand rapidly.

Such blur direction discrimination errors often occur when a low-contrast subject or a high-brightness subject having extremely high brightness with respect to surrounding subjects is photographed. In general, distant hazy mountains and the ground or sky photographed from the window of an airplane are likely to be low contrast subjects, and night scenes are likely to be high brightness subjects. And these are all subjects at infinite distance.

Therefore, when photographing such a subject,
If it is not possible to perform a favorable zoom operation without causing blur, the photographer performs the zoom operation while pressing, for example, the F button.
Then, it is determined whether or not the focus lens is at the in-focus position. The determination as to whether or not the camera is at the in-focus position can be made by confirming whether or not the focus voltage is at a maximum. That is, the output signal level of the band-pass filter 117 changes according to the position of the focus lens as indicated by the curve 8 in FIG.
When the output signal changes like 01, it can be detected by confirming whether or not the output signal level has reached a maximum and whether or not a focus lens is present near the in-focus position.

If it is determined in step 209 that the focus lens is at the in-focus position, the zoom operation is performed in step 210 while giving an infinite trajectory following speed to the focus lens. Giving an infinite trajectory following speed to the focus lens means that the focus lens driving speed table shown in FIG. 6 is converted into only the cam trajectory of the infinite subject distance as shown in FIG. Means to do. That is, as shown in FIG. 6, by converting to a state in which a speed that can only follow an infinite trajectory is given, it is possible to avoid erroneous trajectory following an erroneous operation of the AF signal or the like.

In the lens configuration in the embodiment of FIG. 1, that is, in the inner focus type lens shown in FIG. 4, since the zoom lens is disposed closer to the subject than the focus lens, the focal length varies. There is almost no change in the amount of defocus (change in sensitivity) due to. Therefore, when the infinite cam trajectory following speed is forcibly given as in the present embodiment, if the focus is not focused at the starting point of the zoom operation, the zoom is performed while maintaining the blur amount at that time. . Therefore, in the present invention, first, the presence or absence of in-focus is determined in 209, and after the in-focus is confirmed, 21.
By going to 0 and automatically selecting the tracking speed of the infinite trajectory and forcing the focus lens to trace the infinite trajectory, regardless of whether the subject is weak or not , And a favorable infinite distance zoom operation can be performed.

If it is determined in step 209 that the camera is not in focus, the flow advances to step 211. In step 204, an instruction or command by pressing the F button or the like is ignored or temporarily held. Is displayed to the photographer, and the process proceeds to steps 205 to 208. As described above, based on the cam locus corresponding to the subject distance, the cam locus is corrected according to the output of the AF device. . That is, in this case, the position of the focus lens that focuses on the infinite subject distance is searched for, and after focusing, the operation shifts to the processing of steps 204 and 209.

As another application example of FIG. 2, if the subject is focused in the process of 203 and the zoom operation is performed while pressing the F button, "Before starting the zoom, the subject is manually focused manually and the zoom is performed. After the start, the zoom becomes infinite without using the AF device ", and the lens control can be performed on the weak subject without using the AF device at all.

In the so-called inner focus type lens system as in this embodiment, since the focus lens is disposed closer to the image pickup device than the zoom lens, the change in the focus lens position sensitivity with respect to the change in the focal length. Almost no. Therefore, when performing the zoom operation, if the speed following the cam locus is fixed after focusing within the depth, the infinite cam locus can be maintained with almost no blur while maintaining the defocus amount at the time of departure. Can follow. This has been confirmed by experiments by the inventor.

In the above description of the problem to be solved by the present invention, when zooming from wide to tele, starting from an in-focus position for another object distance within the depth causes blurring. I explained,
This is a phenomenon that occurs when an incorrect trajectory is selected when an appropriate trajectory is selected from a plurality of cam trajectories stored in the table as shown in FIG. There is no contradiction between the two.

As described above, when the photographer performs a zoom operation on a subject at or near infinity, particularly from the wide side to the telephoto side, if the infinite zoom mode is selected by the above-described operation, the subject is likely to be weak. Whether or not
Good zoom can be performed.

[0036]

As described above, according to the lens control device of the present invention (claim 1), it is possible to reduce the possibility of blurring from the zoom operation by the first zoom means.
Strong correction to infinite subject distance without correction by AF device
The focus state is maintained by moving the focus lens at the same time and switching to the second zooming means which controls based on a characteristic curve capable of zooming while maintaining the in-focus state for an infinite subject distance. The magnification operation can be performed as it is. Further, according to the lens control device of the present invention (claim 3), the photographer can easily shoot a subject such as a blur.
In contrast, manual operation can be performed by switching the zooming operation.
Focus and infinite subject distance
Move the focus lens in a
Based on the characteristic curve that allows zooming while maintaining the in-focus state.
Accordingly, the zooming operation can be performed with the in-focus state maintained at the infinite subject distance without being affected by the malfunction of the AF device without correction by the AF device. That is, according to the present invention, the infinite subject distance
The focus lens is forcibly moved to and controlled based on a characteristic curve capable of zooming while maintaining a focused state with respect to an infinite subject distance (claim 1).
Alternatively, by switching to the second magnification changing means,
Indefinite subject distance as well as manual focus
Forcibly move the focus lens to
Characteristic music that can be zoomed while maintaining focus on separation
By performing control based on the line (claim 3), it is possible to realize a good zoom operation without blur on the subject intended by the photographer without being affected by a malfunction of the AF device. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a lens control device according to the present invention.

FIG. 2 is a flowchart for explaining the operation of the lens control device of the present invention.

FIG. 3 is a diagram for explaining a control operation of a focus lens accompanying driving of a zoom lens.

FIG. 4 is a diagram showing a configuration of a general inner focus lens system.

FIG. 5 is a characteristic diagram showing a trajectory of a focus lens for following a change in focal length by a zoom lens while maintaining a focused state.

FIG. 6 is a diagram for explaining a configuration in a table in which a focus lens driving speed with respect to a zoom lens position is stored.

FIG. 7 is a characteristic diagram illustrating control based on an infinite trajectory of a focus lens when a zoom operation is performed on a poor subject.

FIG. 8 is a characteristic diagram showing a relationship between a focus lens position and a focal voltage.

[Explanation of symbols]

 105 Zoom lens 106 Image sensor 107-109 Actuator 110-112 Driver 113 Zoom encoder 114 Iris encoder 115 Focus encoder 117 Bandpass filter 118 Aperture control circuit 119 System control circuit 120 Manual focus switch 121 Zoom switch

Claims (3)

(57) [Claims] A first lens group for performing a magnification change; a second lens group for performing a focus adjustment; focus detection means for detecting a focus state; and a focal plane associated with movement of the first lens group. By correcting the displacement of the second lens group with a characteristic curve corresponding to the subject distance and the output of the focus detection unit,
A first zooming unit that performs a zooming operation while maintaining a focused state; and, when the first lens unit moves, the second lens unit:
A second scaling unit forcibly moving to an infinite subject distance and controlling based on a characteristic curve capable of performing a scaling operation while maintaining a focused state with respect to the infinite subject distance; lens control apparatus characterized by comprising a switching means for switching the means and the second variable magnification means selectively, the. 2. An operation according to claim 1, wherein said switching control means comprises a variable power switch for performing a variable power operation, and a manual focus adjustment switch for manually determining a driving direction of said second lens group. Lens control means for operating the second zooming means by operating the zooming switch and the manual focusing switch together. apparatus. 3. A first lens group for performing a magnification change, a second lens group for performing a focus adjustment, focus detection means for detecting a focus state, and a focal plane associated with movement of the first lens group. By correcting the displacement of the second lens group with a characteristic curve corresponding to the subject distance and the output of the focus detection unit,
A first zooming unit that performs a zooming operation while maintaining a focused state; and, when the first lens unit moves, the second lens unit:
A second magnification unit for controlling based on a characteristic curve capable of performing a magnification operation while maintaining a focused state with respect to an infinite subject distance , and switching from the first magnification unit to a second magnification unit;
By the operation, it will be in the manual focus state
The first lens group is forcibly moved to an infinite subject distance.
The second focus in the manual focus state.
A lens control device comprising: a control unit that enables an operation of a zooming unit .