JPH06324251A - Lens position controller - Google Patents

Abstract

PURPOSE:To obtain a lens position controller capable of prolonging the life of a driving power source such as a battery in a lens system using an electronic cam. CONSTITUTION:A 1st lens group 102 for variable power and a 2nd lens group 105 correcting the fluctuation of an image surface associated with the variable power and performing focusing operation are provided. The 1st lens group 102 and the 2nd lens group 105 are simultaneously or alternately moved based on an output value from the driving power source by a controller 115 in the case of performing the variable power by moving the 1st and the 2nd lens groups 102 and 105 on an optical axis by the control means 115 by using a signal from a position storage means 116 storing the positional relation between the 1st and the 2nd lens groups 102 and 105 on the optical axis in the case of performing the variable power.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens position control device, and more particularly, to a lens system in which an electronic cam is used to move a part of lens groups of a variable power system on the optical axis. By appropriately setting the driving method of the lens group according to the state of the voltage value of the driving power source for driving the lens group,
The present invention relates to a lens position control device, which is suitable for an optical device such as a still camera or a video camera, so as to smoothly perform a zooming operation.

[0002]

2. Description of the Related Art Conventionally, many zoom types have been used as a so-called zoom lens having a variable focal length, which has been used in still cameras and video cameras.

In particular, the first lens group (focus lens group) for focus adjustment from the front of the optical axis, the second lens group (variable lens group) for zooming, and correction of image plane variation due to zooming A so-called four-group zoom lens composed of four lens groups, namely, a third lens group (correction lens group), and a fixed fourth lens group (relay lens group) for image formation is widely known.

In this four-group zoom lens, the second group and the third group perform a zoom operation (zooming) by interlocking in a predetermined relationship using a mechanical cam ring or the like.

On the other hand, in recent years, a so-called inner focus type or rear focus type in which focus adjustment (focusing) is performed by a lens group located rearward (on the image plane side) of a lens group for zooming (variable magnification lens group) Various zoom lenses have been proposed.

FIG. 5 is an explanatory diagram of an optical system of a rear focus type zoom lens of this type.

In FIG. 1, reference numeral 501 denotes a first group that is fixed during zooming and focusing, 502 is a second group (zooming lens group) for zooming, 503 is a diaphragm, and 504 is for zooming and focusing. A fixed third group 505 is a fourth group (focus lens group) for correcting an image plane variation during zooming and for focus adjustment.

In the case of such a rear-focus type zoom lens, the effective diameter of the first group is smaller than that of a zoom lens in which the first group is moved for focusing, and it is easy to downsize the entire lens system. In addition, close-up photography, especially very close-up photography, becomes easier, and because the relatively small and lightweight lens group is moved, the driving force of the lens group is small and quick focusing can be achieved. is there.

However, on the other hand, the movement locus of the focus lens group with respect to the variable power lens group for maintaining the focus during the zoom operation (during zooming) has the property that it varies depending on the object distance. There is a problem in that the structure of the entire lens barrel becomes complicated if it is attempted to use a conventional mechanical cam ring or the like.

FIG. 6 shows the position on the optical axis of the focus lens group 505 with respect to the focal length (the position on the optical axis of the variable power lens group 502) in the rear focus type zoom lens shown in FIG. FIG. 4 is an explanatory diagram showing each subject distance on an axis.

In the figure, W on the horizontal axis is the wide end, T is the tele end, N on the vertical axis is the close end (close object distance), F is the infinite end (infinite object distance), and curves 601, 602, 603 are shown. Shows the focusing locus of the focus lens group 505 with respect to the focal length when the subject distance is 50 cm, 2 m, and 10 m, respectively.

When the electronic zoom is used in the rear focus type zoom lens shown in FIG. 5 to change the magnification, the locus position (position on the optical axis) of the focus lens group for obtaining the focus shown in FIG. 6 is related. Data (information) is stored in advance on a ROM that is a storage element. Then, from the focal length during the zoom operation, that is, the position information on the optical axis of the variable power lens group 502 and the position information on the optical axis of the focus lens group 505, the R
The drive of the variable power lens group 502 and the focus lens group 505 is controlled by using the signal stored on the OM, thereby performing the variable power and focusing during the zoom operation.

FIG. 7 is a system block diagram showing the system configuration of such a rear focus type zoom lens. In the figure, the same elements as those shown in FIG. 5 are designated by the same reference numerals.

In the figure, reference numerals 706, 707, and 708 denote position encoders, each of which has a variable power lens group 502 and a diaphragm 5.
03, and the position of the focus lens group 505 on the optical axis is detected, and the detected position is converted into an electric signal and output. Reference numerals 720, 721, and 722 are driving means for the variable power lens group, diaphragm, and focus lens group, respectively, and actuators 709 and 710 for moving (driving) the variable power lens group 502, the diaphragm 503, and the focus lens group 505. , 711 and the actuator 709,
It is composed of drivers 712, 713, 714 that drive 710, 711 according to a drive command.

715 is a microcomputer (CPU)
Based on the output signals from the position encoders 706, 707, 708, the drivers 712, 713, 71
4 outputs a drive command to the zoom lens group 502 and diaphragm 50.
3, and the operation of the focus lens group 505 is controlled.

Reference numeral 716 is a ROM as a memory element,
For example, data (information) regarding the in-focus position of the focus lens group 505 for the focal length for each subject distance shown in FIG. 6 is stored. Reference numeral 717 is a zoom switch.

Here, for example, as shown in FIG. 8, it is assumed that a curve (moving locus) 801 is a focusing locus of the focus lens group 505 during a zoom operation with respect to a certain object distance. At this time, the positional relationship between the focus lens group 505 and the variable power lens group 502 at the start of zooming, for example, the point A, that is, the focal length is the position Z ₁ , and the position of the focus lens group 505 is the position F.
_{When 1,} the focal length is zoomed to position Z ₂ , position Z
_In order to maintain the focus when sequentially changing to ₃ , the position of the focus lens group 505 may be sequentially moved to the positions F ₂ and F ₃ .

There are generally two methods for controlling the drive of the focus lens group 505 and the variable power lens group 502 at this time.

First, there is a method of starting driving of the focus lens group 505 at the same time as the start of zooming. For example, when the variable power lens group 502 is at the position (focal length) Z ₂ , the focus lens group 505 is at the position F ₂ . In addition, when the variable power lens group 502 is at the position Z ₃ , the two lens groups 50 are arranged so that the focus lens group 505 is at the position F _3.
This is a simultaneous drive control method in which 2,505 are simultaneously driven and controlled.

The other method is to drive the variable power lens group 502 and the focus lens group 505 alternately.
For example, when the variable power lens group 502 reaches the position Z ₂ , the driving of the variable power lens group 502 is temporarily stopped, and the focus lens group 505 is driven to the position F ₂ during this period. When the focus lens group 505 reaches the position F _{2, the} zoom lens group 502 is driven again to the position Z _{3 in the same} manner as described above, and then the focus lens group 505 is driven to the position F ₃ again. It is a control method.

[0021]

Among the lens drive control methods described above, the simultaneous drive control method has an advantage that it is easy to increase the zoom speed. However, since the two actuators 711 and 709 as drive sources are driven at the same time, the load on the drive power source becomes heavy. For example, when a battery or the like is used as the drive power source, driving is performed as compared with the alternate drive control method described above. There is a problem that the life of the power supply is short and the power cannot be driven quickly.

On the other hand, the alternating drive control method has a longer life of the drive power source such as the battery than the simultaneous drive control method, but on the other hand, there is a problem that the zoom speed becomes slow because the lens groups are alternately driven. is there.

Therefore, each of the above-mentioned two lens drive control methods has advantages and disadvantages, which is not satisfactory as a lens drive control method for a lens system using an electronic cam.

According to the present invention, the second lens is used for moving the variable power lens group (first lens) by an ordinary mechanical cam mechanism, and for correcting the image plane variation accompanying the variable power and performing the focusing operation. In the lens system in which an electronic cam is used to move the lens unit (focusing lens unit), the first and the second
By appropriately setting the lens group driving method described above, it is possible to reduce the load on the driving power source, and to provide a lens position control device that can prolong the life of the battery when a battery or the like is used as the driving power source. And

[0025]

A lens position control apparatus according to the present invention comprises a first lens group for zooming, and a second lens group for correcting an image plane variation due to zooming and performing a focusing operation. A first lens group and a second lens group at the time of zooming, and the control means uses the signal from the position storage means that stores the positional relationship between the first lens group and the second lens group on the optical axis. When the zoom lens is moved by moving the second lens group and the second lens group on the optical axis,
The control means is characterized in that the first lens group and the second lens group are moved simultaneously or alternately based on the output value from the driving power source.

Further, the control means detects the position of the first lens group on the optical axis when the first lens group and the second lens group are alternately moved. The movement amount of each of the first and second lens groups is determined on the basis of the signal from the first lens group, the aperture value signal of the diaphragm that regulates the amount of passing light provided in the optical path, and the signal from the position storage means. It is characterized by being.

[0027]

FIG. 1 is a system block diagram of a first embodiment when the present invention is applied to a rear focus type zoom lens.

In the figure, 101 is a first group that is fixed during zooming and focusing, 102 is a second group for zooming (magnifying lens group), 103 is a diaphragm for adjusting the amount of incident light on the image pickup surface, and 1 is a diaphragm.
Reference numeral 04 designates a third lens unit which is fixed during zooming and focusing, and 105 designates a fourth lens unit for correcting and focusing an image plane variation accompanying zooming.
It is a group (focus lens group).

Reference numerals 106, 107 and 108 denote position encoders serving as position detecting means, respectively, and a variable power lens group 102.
The positions of the aperture stop 103, the diaphragm 103, and the focus lens group 105 on the optical axis are detected, and the detected positions are converted into an electric signal and output. Reference numerals 120, 121, and 122 denote driving means for the variable power lens group, the diaphragm, and the focus lens group, respectively.
The focus lens group 105 is made up of actuators 109, 110, 111 and drivers 112, 113, 114 for driving the actuators 109, 110, 111 in accordance with a drive command.

Reference numeral 115 is a microcomputer (CPU) as a control means, and each position encoder 106, 1
Drive commands are output to the drivers 112, 113, 114 based on the respective output signals from 07 and 108 to control the operations of the variable magnification lens group 102, the diaphragm 103, the focus lens group 105 and the like.

Reference numeral 116 denotes a ROM as position storage means (storage element), which is, for example, the in-focus position of the focus lens group 105 with respect to the focal length (position of the variable power lens group 102) for each subject distance shown in FIG. (Position on the optical axis)
Stores data (information) regarding 117 is a zoom switch.

Reference numeral 118 denotes an analog-digital converter (A /
Actuator 1 for moving (driving) the variable power lens group 102 and the focus lens group 105.
The voltage value (analog value) of the drive power supply when the power is supplied to the drivers 112 and 114 that drive the 09 and 111 is converted into a digital value.

In this embodiment, the digital signal (digital value) converted by the A / D converter 118 is taken into the CPU 115. Then, the state of the voltage value of the driving power supply for supplying power to the driving means 120 and 122 for the variable power lens group 102 and the focus lens group 105 is detected by the power supply voltage monitoring means (not shown). Then, the CPU 115 detects the present voltage value V _NOW and the minimum voltage value (minimum power supply voltage value) V of the drive power supply that is minimum required to drive the preset variable power lens group 102 and the focus lens group 105 at the same time. Comparing with _MIN . Then, based on the value of the driving power source, the variable power lens group 102 and the focus lens group 1
It is determined whether to control the driving of the motors 05 at the same time or alternately.

Next, the operation of the rear focus type zoom lens shown in FIG. 1 is shown in FIG. 2, FIG. 3 and FIG.
An explanation will be given using a flow chart of the control program stored in 5.

First, when the processing routine of the zooming operation in the CPU 115 starts in step 201, it is determined in step 202 whether the photographer operates the zoom switch 117.

At this time, if the zoom switch 117 is not pressed (OFF state), driving (moving) of the variable power lens group 102 is stopped in step 203 (however, the variable power lens group 102 has been driven until then). (Only when the zoom switch 117 is operated), the process returns to step 202 to detect whether or not the zoom switch 117 is operated.

On the other hand, in step 202, the sum switch 1
If 17 has been operated (ON state), step 20
4, the digital signal (digital value) converted by the A / D converter 118, that is, the driver 11 as driving means.
The current voltage value of the driving power supply to which power is supplied to 2,114 is read.

Next, in step 205, the minimum voltage value V of the drive power source which is the minimum required to simultaneously drive the variable power lens group 102 and the focus lens group 105 set in advance.
_MIN is compared with the read current variable power lens group 102 and the voltage value V _{NOW of the} driving power supplied to the drivers 112 and 114 of the focus lens group 105.

Here, when V _NOW ≧ V _MIN , that is, when the current voltage value V _NOW of the driving power source is higher than the minimum voltage value V _{MIN, the routine} proceeds to step 206 and the flag A is set.

On the other hand, when V _NOW ≤ V _MIN , that is, when the current voltage value V _NOW of the driving power source is lower than the minimum voltage value V _MIN , the process proceeds to step 207 and the flag A is cleared.

Next, in steps 208, 209 and 210, the current positions of the variable power lens group 102, the focus lens group 105 and the diaphragm 103 are detected from the output signals of the position encoders 106, 108 and 107, respectively. Next, at step 211, the state of the flag A is determined.

The flag A is the current voltage value V _NOW of the driving power source.
2 of the zoom lens group 102 and the focus lens group 105
It shows the state of the magnitude relationship with the minimum voltage value V _{MIN that} is the minimum required to drive two lens groups at the same time, and V _NOW ≧
In the case of V _MIN , the processing shifts to step 212 shown in FIG. On the other hand, if V _NOW ≤V _MIN , the process proceeds to step 223 shown in FIG.

In FIG. 3, the processing from step 212 to step 222 is a processing routine (simultaneous drive control method) for performing the zooming operation while simultaneously driving the zoom lens group 102 and the focus lens group 105.

First, in steps 212 and 213, the ROM 1
The next target position of the variable power lens group 102 and the focus lens group 105 for maintaining the focus when zooming from 18 is obtained by detecting the current position information of both lens groups 102 and 105 detected in steps 208 and 209. It is read based on.

This is because the current positional relationship between the variable power lens group 102 and the focus lens group 105 in FIG.
For example, if it is represented by the point A (Z ₁ , F ₁ ), the ROM
The storage location read from 118 is point B (Z ₂ , F ₂ ).
Becomes

Next, in step 214, the actuators 109 and 111 for moving the variable power lens group 102 and the focus lens group 105 are simultaneously started. In step 215, it is determined whether or not the variable power lens group 102 has reached the target position.

If the variable power lens group 102 has reached the target position, the routine proceeds to step 216, where the variable power lens group 102 is moved.
After the driving of No. 1 is stopped, the flag B is set at Step 217.

On the other hand, if the variable power lens group 102 has not reached the target position, the driving of the variable power lens group 102 is continued and the flag B is cleared at step 218.

Similarly, in step 219, it is determined whether or not the focus lens group 105 has reached the target position.

If the focus lens group 105 has reached the target position, the process proceeds to step 220, the drive of the focus lens group 105 is stopped, and the process proceeds to step 222.
If it has not arrived, the routine proceeds to step 221, and the state of the flag B is judged.

The flag B indicates whether or not the variable power lens group 102 has reached the target position. If it has reached, it is set, and if it has not reached, it is cleared.

If it is determined in step 221 that the flag B has been cleared, it means that neither lens group 102, 105 has reached the target position. In this case, the process returns to step 215 and both lens groups 102, 105. Drive continues.

If it is determined in step 222 that the flag B is set, it means that both lens groups 102 and 105 have reached the target positions, and the process is terminated and the process returns to the beginning.

If it is determined in step 222 that the flag B has been cleared, it means that the variable power lens group 102 has not yet reached the target position. In this case, the process returns to step 215 and the variable power lens group 102 is returned. Continue driving only.

By repeating the above processing, zooming can be performed while simultaneously driving the variable power lens group 102 and the focus lens group 105.

On the other hand, the processing from step 223 to step 230 shown in FIG. 4 is a processing routine (alternating drive) for performing the zooming operation while alternately driving the variable power lens group 102 and the focus lens group 105. Control method).

First, in steps 223 and 224, the ROM 1
The following target positions of the variable power lens group 102 and the focus lens group 105 for maintaining the focus when zooming from 18 are detected at steps 208, 209 and 210, and the current positions of both lens groups 102 and 105 are detected. It is read based on the position and the value of the diaphragm amount of the diaphragm 103.

This is because the current positional relationship between the variable power lens group 102 and the focus lens group 105 in FIG.
For example, if it is represented by the point A (Z ₁ , F ₁ ), the ROM
The storage position read from 118 is, for example, point B (Z ₂ , F ₂ ) when the aperture amount is small and the depth of field is shallow, and point C (Z ₃ , Z ₂ when the aperture amount is large and the depth of field is deep. F ₃ )
The read storage position is changed according to the aperture amount.

Next, at step 225, the zoom lens group 10
The actuator 109 that moves 2 is started.
Then, in step 226, it is determined whether or not the variable power lens group 02 has reached the target position, and if it has reached the target position, the process proceeds to step 227 and the driving of the variable power lens group 102 is stopped.

If the zoom lens group 102 has not reached the target position, the process returns to step 225 to zoom lens group 1
The drive of 02 is continued.

Next, at step 228, the actuator 111 that moves the focus lens group 105 is started.

In step 229, the focus lens group 1
It is judged whether or not 05 has reached the target position, and if it has reached the target position, the routine proceeds to step 230, the drive of the focus lens group 105 is stopped, the processing is terminated, and the process returns to the beginning.

If the focus lens group 105 has not reached the target position, the process returns to step 228 to continue driving the focus lens group 105.

By repeating the above processing, zooming can be performed while alternately driving the variable power lens group 102 and the focus lens group 105.

As described above, in this embodiment, during the zooming operation, the zoom lens group 102 and the focus lens group 105 are driven at the same time while the positional relationship between the two lens groups stored in the position storage means is maintained. Two drive control methods are used, that is, a simultaneous drive control method and an alternate drive control method in which the positional relationship between both lens groups stored in the position storage means is held while alternately driving the variable power lens group and the focus lens group. I am doing zooming.

That is, as described above, the state of the voltage value of the driving power supply for supplying power to the respective driving means for driving the variable power lens group 102 and the focus lens group 105 is detected by the power supply voltage monitoring means, and the monitoring means Output signal (current drive power supply voltage value V _NOW ) and the minimum voltage value V _MIN that is the minimum required to drive the two lens groups of the variable power lens group and the focus lens group at the same time. As a result, when the current voltage value V _NOW of the driving power supply is sufficient,
For example, in the case of a battery or the like, immediately after charging, the zoom lens group 102 and the focus lens group 105 are simultaneously driven by the simultaneous drive control method to enable quick zooming, and simultaneous drive is performed when the current voltage value V _NOW of the drive power source decreases. And the variable power lens group 102 and the focus lens group 105 are alternately driven by the alternating drive control method. This makes it possible to prolong the life of the drive power source such as the battery.

In this embodiment, as described above, the first group is a fixed lens group, the second group is a variable magnification lens group, the third group is a fixed lens group, and the fourth group is associated with variable magnification. An example in which the present invention is applied to a rear focus type zoom lens having a four-group configuration of lens groups for correcting image plane variation and focusing is shown, but the present invention is also applicable to rear focus type zoom lenses of other lens types. It can be applied similarly to the above-mentioned embodiment.

Further, in this embodiment, the variable power lens group 102 is used.
The voltage value of the driving power supply supplied to the second driving means 121 of the diaphragm 103 that is interlocked with the other driving means 120, 122.
Therefore, in the present invention, the lens driving method is controlled by including in the electric power supplied to the driving unit 120 for the variable power lens group.

[0069]

According to the present invention, in the zoom operation of the rear focus type zoom lens using the electronic cam as described above, the first lens unit for zooming and the correction of the image plane variation due to zooming are corrected. At the same time, the state of the voltage value of the driving power supply supplied to each driving means for driving the second lens group for performing the focusing operation is detected by the power supply voltage monitoring means, and based on the output signal from the monitoring means. By the control means, the first
Driving method for simultaneously driving the first lens group and the second lens group while maintaining the positional relationship between the two lens groups stored in the position storage means, and the first lens group and the second lens group are alternated. The alternate drive control method in which the positional relationship between the two lens groups stored in the position storage means is maintained while the lens is driven, and efficient zooming is performed by selecting one of them, thereby extending the life of the drive power supply such as the battery. It is possible to achieve a lens position control device that can last a long time.

[Brief description of drawings]

FIG. 1 is a system block diagram of a first embodiment when the present invention is applied to a rear focus type zoom lens.

FIG. 2 is a flowchart showing a lens control algorithm during zooming according to the present invention.

FIG. 3 is a flowchart showing a lens control algorithm during zooming according to the present invention.

FIG. 4 is a flowchart showing a lens control algorithm during zooming according to the present invention.

FIG. 5 is an explanatory diagram of an optical system of a rear focus type zoom lens.

6 is an explanatory diagram showing a locus of a focus position of a focus lens group according to a focal length in the zoom lens shown in FIG.

FIG. 7 is a system block diagram of a conventional lens position control device.

FIG. 8 is an explanatory diagram for explaining a method of following a focus locus of the focus lens group during zooming.

[Explanation of symbols]

 101 1st group 102 2nd group 103 Aperture 104 3rd group 105 4th group 106,107,108 Position encoder 109,110,111 Actuator 112,113,114 Driver 120,121,122 Driving means 115 Microcomputer 116 ROM 117 Zoom switch 118 A / D converter

Claims (2)

[Claims] 1. A first lens group for zooming, and a second lens group for correcting an image plane variation due to zooming and performing a focusing operation, the first lens group for zooming. Of the first lens group and the second lens group by the control means using a signal from the position storing means that stores the positional relationship between the second lens group and the second lens group. When the zoom lens is moved up to perform zooming, the control means simultaneously or alternately moves the first lens group and the second lens group based on the output value from the driving power source. Lens position control device. 2. The first position detection means for detecting the position on the optical axis of the first lens group when the control means alternately moves the first lens group and the second lens group. The movement amount of each of the first and second lens groups is determined on the basis of the signal from the means, the aperture value signal of the diaphragm that regulates the amount of passing light provided in the optical path, and the signal from the position storage means. The lens position control device according to claim 1, wherein: