JPH04256911A - Variable power optical system - Google Patents

Abstract

PURPOSE:To perform initialization and the correction of an error in a zoom lens where a lens group serves both for variable power and focusing actions. CONSTITUTION:By the input of a reset switch 43 for initialization, the present positions of the respective lens groups are detected, and compared with a value previously stored in a memory 48 in an arithmetic control circuit 49, and the respective lens groups are moved on a shaft until a range between the detected value and the stored value gets in an allowable range. The variable power and the focusing are realized with high accuracy in the zoom lens where the respective lens groups are driven by an electrical actuator independently of each other.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable magnification optical system suitable for optical equipment such as cameras and observation equipment, and more particularly to a variable magnification optical system equipped with a device for controlling the lens position using electrical signals.

0002

2. Description of the Related Art A typical example of a zoom lens mounted on a still camera or a video camera is shown in FIG.

In FIG. 7, reference numeral 1 denotes a first group lens (F lens) for focusing arranged at the tip of the lens barrel.
, 2 is a variator lens (V lens) for changing the magnification, 3 is a compensator lens (C lens) for correct focusing during magnification changing operation, and 4 is a relay lens (R lens) for forming an image on the image plane. lens).

[0004] Each lens group is normally composed of a plurality of component lenses for aberration correction, but in this application, for convenience, it will be shown as one lens. However, for the sake of compactness or when high image quality is not required, the lens group may actually be composed of a single component lens.

The movement of each lens group will be explained below.

FIG. 8 shows the relationship between the position of the F lens and the subject distance. FIG. 9 shows the relationship between the V lens, the C lens, and the focal length.

Usually, the F lens is called a focus section, and the V lens and C lens are called a zoom section, and the F lens moves independently along the optical axis for focusing, as shown in FIG.

As shown in FIG. 9, the V lens and C lens move together along the optical axis for the purpose of varying the magnification. In this configuration, the focusing action and the variable magnification action are separated, and the loci of movement of the V lens and C lens are uniquely determined, so the control is relatively simple, and the electromechanical control mechanism such as the cam The advantage is that it can be done with

FIG. 10 shows an interlocking mechanism between a V lens and a C lens in a conventional zoom lens.

In the figure, 5 and 6 are lens holding frames that hold the V lens and C lens, respectively, and 7 and 8
9 is a guide bar that guides the lens holding frames 5 and 6 along the optical axis, and 9 is a pin 5 provided on the lens holding frames 5 and 6.
10 is a fixed barrel fitted on the outer periphery of the cam barrel and fixed to a stationary member such as a lens barrel; 11 is a cam barrel 9; The zoom operation ring is fixed to the fixed cylinder 10 by a connecting portion 11a and is fitted so as to be able to rotate only relative to the outer circumferential surface of the fixed cylinder 10.

When the zoom operation ring 11 rotates, the cam cylinder 9 also rotates, and as a result, the relative position of the pin 5a in the cam groove 9a and the relative position of the pin 6a in the cam groove 9b change during magnification change. Since the positions change, the V lens holding frame 5 and the C lens holding frame 6 each move relative to each other along the optical axis.

Although the control mechanism using a cam cylinder is easy to control, it also has the disadvantage that the manufacturing cost is high because the fitting accuracy of the cam cylinder and the machining accuracy of the cam groove are extremely high.

In addition, with conventional zoom lenses, in order to focus on a subject at a close distance (for example, 1 m or less), the amount of extension of the F lens increases in proportion to the reciprocal of the subject distance. The diameter also becomes larger. As a result of the above, there is also the disadvantage that the length, aperture, and weight of the zoom lens become large.

In order to solve the above disadvantages, a so-called rear focus or inner focus type zoom lens has been proposed in which one or more lens groups on the image side of the first lens group are moved along the optical axis. It is assumed that an electric actuator such as a stepping motor or a voice coil will be used to move the lens group that moves for zooming also for focusing. This type of zoom lens does not move the first lens group when focusing, so it is possible to focus on subjects from normal subject distances to extremely close ranges without interruption, and the advantage is that the entire system can be made smaller. be.

On the other hand, even with lenses such as TV cameras for broadcasting stations that manually change the magnification or zoom while viewing the image, or other zoom lenses, the trajectory of the lens group movement is sensitive to the focal length or subject distance. Since the sensitivity is different, if you want to apply the effect from a low sensitivity area to a high sensitivity area, if you initialize the setting at the low sensitivity area, the image quality (for example, focusing Due to this problem, conventional zoom lenses are initially set to perform focusing at a highly sensitive point when changing magnification. Note that the sensitivity is the degree of movement of the image plane caused by a minute unit movement of the lens group.

However, in a rear focus or inner focus zoom lens, for example, the second group lens, the third group lens, and a part of the divided fourth group lens simultaneously participate in the variable power function and the focusing function. With this type, initial settings cannot be made like in the past, as three locations are moved to determine two elements (focal length and subject distance).

If initial settings cannot be made, the locus of movement of the lens group cannot be uniquely determined, making it difficult to achieve the desired effect.

In the early form of this type of zoom lens, the idea was to calculate the position that each lens group should occupy, but later a method was developed in which the positions that each lens group should occupy were stored in a table in a storage device. It looks like it's being taken. If the position on the optical axis that the lens group should occupy is expanded according to the focal length, it becomes the movement locus for zooming.

However, since the trajectory is stored in memory, there is no limit to the movement range, and lens movement due to control errors and external vibrations may make control impossible or cause the lens to move on a trajectory different from the intended one. may cause.

[0020]

[Problem to be Solved by the Invention] The problem to be solved is that it is not possible to position the lens group at a predetermined position in a type of zoom lens in which the lens group is simultaneously involved in variable power and focusing functions. . This should be dealt with during initial settings or when moving the lens group along a predetermined movement trajectory.

[0021]

[Means for Solving the Problems] The present invention detects the current position of the lens group using a position control device including a storage device in order to confirm that the lens group is in a predetermined position. It is characterized in that the lens group occupies the determined position. It also has a reset circuit with multiple modes, and automatically performs initial settings by operating reset 1, for example. Furthermore, by operating Reset 2, the lens position is automatically corrected.

The purpose of high-precision zooming and focusing has been achieved by using the main parts of the conventional system as is.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a zoom lens used in this system.

In the figure, 21 is a positive first group lens;
2 is a negative second group lens that mainly performs zooming, and 23 is a positive third group lens.
A group lens 24 is a positive fourth group lens, 25 is a positive fifth group lens, and 26 is a member for fixing the first group lens 21 to a lens barrel or the like.

If compared with the conventional zoom lens shown in FIG.
Lens 21 corresponds to lens 1, lens 22 corresponds to lens 2, lens 23 corresponds to lens 3, and lenses 24 and 25 correspond to lens 4.

FIG. 2 shows the relationship between lenses 22, 23, and 24, focal length, and object distance.

For convenience, the diagram depicts a movement trajectory for an immediate distance and a trajectory for an infinite distance, but it is assumed that there are also trajectories for object distances in between, which are determined according to the performance required of this lens. do. In addition, the focal length and object distance change by moving the lenses 22, 23, and 24, respectively, and in order to achieve the desired effect, three lens groups, the lenses 22, 23, and 24, must be moved at the same time. Indicates that the object must be moved along a trajectory uniquely determined by the focal length or subject distance.

FIG. 3 depicts the lens and control system shown in a block diagram.

The lens groups 21 to 25 are the same as in FIG. 1, except that 27 is the equivalent of a three-color separation prism, and 28 is one of the image pickup tubes or collective image pickup devices. Note that a group image sensor equipped with a color filter may be used instead of the prism and the image sensor. Next, 36 is a position detector for the second group lens 22, 37 is a position detector for the third group lens 23, 38 is a position detector for the fourth group lens 24, and 39 is a control circuit for moving the second group lens. A driver, 40 is a driver with a control circuit that moves the third lens group, 41 is a driver with a control circuit that moves the fourth lens group, 42 is an external control command device to be described later, 43 is a reset switch for initial setting, 44 is a reset switch for error correction, 45 is an action type detector, 46 is an action direction detector, 47 is an action speed detector, and 48 is a memory for storing a locus table. 49 is an arithmetic control circuit and has a separate memory.

This example will be explained as a TV camera for broadcasting equipment, but in the case of a TV camera, lens focusing is usually done by a cameraman while looking at a monitor. However, in a small video camera, the focus adjustment state may be determined by a focus detection device.

Before explaining the operation according to the present invention, the operation will be explained by taking a normal magnification change effect as an example.

[0032] In TV cameras for broadcasting equipment, variable magnification,
Three types of actions are required: a focusing action, and a combined action of magnification change and focusing. Each action has a direction, for example, a magnification change action such as reduction or multiplication. Moreover, the operating speed is used in a wide range from 0.6 sec to low speed. Therefore, the type, direction, and speed of action are to be controlled. For example, the type of action can be commanded manually by an externally attached switch, the direction of action can be commanded by the direction of rotation of the handle, and the speed of action can be manually commanded by the rotation angle of the handle. . Here, devices that issue control commands from the outside, such as switches and handles, are collectively referred to as external control command devices 42. The signal from the external control command device 42 is detected by a well-known action type detector 45, action direction detector 46, and action speed detector 47 to obtain the action type, action direction, and action speed.

The position detectors 36, 37 and 38 photoelectrically detect the lens group position from a marker attached to the lens group,
Alternatively, it is detected from the rotational speed of the motor that moves the lens group. As shown in FIG. 2, the focal length and object distance are determined from the lens group position determined here as well, and the focal length and object distance provide a reference state for control.

As shown in FIG. 2, the zooming action or the focusing action is performed by the second lens group 22, the third lens group 23, and the lens group 23, respectively.
and the fourth group lens 24 is independent along the optical axis (non-integrated)
This is done by moving the target. The memory 48 includes a second group lens 22, a third group lens 23, as shown in FIG.
The position where the locus of movement of the fourth group lens 24 serves as a reference for each divided area divided in terms of the amount of action is stored.

For example, each value is expressed by the following formula.

L32 (n, m)=L32 (Vn
,Fm)L33 (n,m)=L33 (Vn,F
m) L34 (n, m) = L34 (Vn, Fm)
Here, L22, L23, and L24 are the positions Vn and Fm of the second group lens 32, third group lens 33, and fourth group lens 34 on the optical axis, and the subject distance and focal length n,
m is the number of the divided area

First, a detailed explanation of the magnification change effect will be provided.

In the zooming action, the trajectories of the second group lens 22, the third group lens 23, and the fourth group lens 24 differ depending on the distance to the subject, so the position detectors 36, 37, and 38
Based on the positions of the second group lens 22, third group lens 23, and fourth group lens 24 detected in , the object distance is determined by the arithmetic circuit 49 based on the values in the memory 48.

Once the subject distance is determined, the loci for moving the second, third, and fourth lens groups are uniquely determined, so each lens group is moved according to the loci.

As can be seen from FIG. 2, in order to change the magnification at a constant speed, it is necessary to change the moving speed of the lens group according to the curvature of the trajectory, so controlling the movement of the lens group requires adjusting the moving amount and moving speed. It is necessary to find the focal length and subject distance as parameters.

This means that the amount of movement (difference value of the trajectory) and the movement speed (inclination of the trajectory) are determined by calculation from the data regarding the position of the trajectory of each lens group movement stored in the memory 48.

When a focusing effect is desired, it can be performed in the same manner as the variable magnification effect, except that the subject distance in the variable magnification effect is changed to the focal length.

Further, if it is desired to have a focusing effect and a magnification changing effect, this can be done by moving the object distance and the focal length so as to change monotonically.

The speed of action has not been mentioned so far, so it will be explained below.

As previously explained, the rate of action is obtained from the external control command 42 signal. Since the moving speed of the lens group is changed in proportion to the action speed, it is necessary to convert the moving speed of the memory 48.

Furthermore, when the action speed is high, due to the visual characteristics of moving images, even if the followability to the trajectory is slightly worse than when the action speed is low, the image quality will not deteriorate; therefore, the movement obtained from the memory 48 It is possible to convert the amount (a process in which a curved part on a trajectory is regarded as a straight line) to facilitate control.

What has been described above is based on the case where the action speed is low, and the value of the reference lens position of each divided area obtained by dividing the values of the subject distance and focal length, and the amount and speed of movement of the lens group are stored in memory. 48, and calculating the focal length or object distance from the position values of the lens groups detected by the position detectors 36, 37, and 38 in the arithmetic control circuit 49, the action type detector 45, the action direction detector 46, and This can be realized by converting the movement amount and movement speed with respect to the value of the action speed detector 47.

FIG. 4 shows a flowchart of the processing for the variable magnification effect.

In the figure, 50 is a process for reading out the action type, 51 is a branching process, 52 is a process for reading out the action direction,
53 is a process of reading out the action speed; 54 is a process of reading out the position of each lens group; 55 is a process of calculating the subject distance;
6 is a process of reading the position from the memory, 57 is a process of converting into a movement amount according to the action speed, 58 is a process of converting into a movement speed according to the action speed, and 59 is a control signal for the movement amount, movement speed, and control. 60 is a process for outputting the timing to a controller that moves each lens group; 60 is drive control for each lens group; 61 is a process for reading the position of each lens group; 62
63 is a state evaluation process, 63 is a judgment process, and 64 is a focusing operation, a magnification change, and a focusing operation.

The operation will be explained below.

The following processing is performed by an arithmetic control circuit 49 composed of a CPU or the like.

First, the action type reading process 50 reads out the memory value or set value in the action type detector 45 and stores it in the memory 1 of the arithmetic operation control circuit 49 . Branch processing 5
1 performs a magnification changing action, a focusing action, or a branching process of a magnification changing action and a focusing action, depending on the type of action.

In this embodiment, processing 5 for reading out the direction of action
The processing after 2 shows the processing of the magnification change effect.

The action direction reading process 52 reads out the memory value or set value in the action direction detector 46 and stores it in the memory 2 of the read calculation circuit 49 .

In the process 53 for reading out the operating speed, the memory value or set value in the operating speed detector 47 is read and stored in the memory 3 of the arithmetic operation circuit 49 .

The process 54 of reading out the position of each lens group uses the memory in the position detector 36 of the second lens group 22, the position detector 37 of the third lens group 23, and the position detector 38 of the fourth lens group 24. The values are read and stored in memory 4, memory 5, and memory 6 of calculation circuit 49.

In the process 55 for determining the object distance, the object distance at that time is determined by comparing the contents of the memory 48 that stores the trajectory, and is stored in the memory 7 of the arithmetic control circuit 49.

The process 56 of reading out the lens group position from the memory 48 is performed under the constant subject distance stored in the memory 7 and in accordance with the speed of action in the memory 3 and the direction of action in the memory 2, and the position of each lens group at the movement destination. Read the position,
The information is stored in memory 8, memory 9, and memory 10 of arithmetic control circuit 49.

Next, correspondence to the action speed will be explained. First, the memory 48 stores the position of each lens group based on the slow action speed, so when zooming at a speed n times the reference speed, the value of the nth position is read from the memory of the lens group position at that time. and use it.

The movement amount calculation process 57 calculates the movement destination position of each lens group stored in memory 8, memory 9, and memory 10 and the current position of each lens group stored in memory 4, memory 5, and memory 6. The difference is calculated and stored in memory 11, memory 12, and memory 13.

The processing 58 for converting the movement speed into a movement speed corresponding to the action speed divides the value in the memory 8 by the movement amount corresponding to the reference movement speed, calculates the movement speed as a multiple of the reference movement speed, and stores it in the memory 14 of the arithmetic circuit 44. Remember.

The control signal processing 59 controls the movement amount, movement speed, and control timing of the controller 3 for moving each lens group.
Output to 8.

The control process 60 is a process performed by the controller 38.

The process 61 for reading the position of each lens group is the same as the process 54 for reading the position of each lens group, and the position detector 36 of the second group lens and the position detector 36 of the third group lens are used. 37 and the memory values in the position detector 38 of the fourth group lens are read out and stored in the memory 4, memory 5, and memory 6 of the calculation circuit 49.

Process 5 of reading the position in order to execute the next action until a stop instruction is issued from the external control command unit 42
The process 61 of reading out the position of each lens group from 6 is repeated.

The above describes how the focusing action and magnification changing action are performed.

Next, a description will be given of the initial setting and reset processing for correcting the lens group position according to the present invention. The reset process itself can be executed by software using conventional processing functions.

FIG. 5 shows one embodiment of a flowchart of the initial setting process, and assumes that the configuration of FIG. 3 is operated. In FIG. 5, 70 is reset on, 71 is detection of the position of the lens group, 72 is reading of the initial setting position, 73 is calculation of the amount of movement, 74 is control signal processing, 75 is control processing, and 76 is the lens group position detection. 77 is a determination process, and 78 is a stop process.

First, in step 70, the following processes are executed by turning on the reset switch 43 for initial setting shown in FIG.

The following process is executed by the process 70 of turning on the initial setting reset switch 43.

Processing 71 for detecting the position of each lens group is as follows:
The memory 30 and the memory 31 of the arithmetic control circuit 49 read out the values or set values of the memories in the position detector 36 of the second group lens, the position detector 37 of the third group lens, and the position detector 38 of the fourth group lens. , and stored in the memory 32.

Initial setting position read processing 72 reads out the positions of each lens group sensitive to variable magnification and focusing effects stored in memory 48 in advance, and stores them in memory 33, memory 34, and memory 35 of arithmetic circuit 49. do.

[0073] Here, the positions of each lens group sensitive to variable magnification and focusing are determined at the stage of optical design and are stored in the memory 48 in a non-rewritable manner.

The movement amount calculation process 73 is performed based on the current position of the lens stored in the memory 30, memory 31, and memory 32 of the arithmetic circuit 49, and the memory 33, memory 34.
, and the initial setting position stored in the memory 35 is calculated and stored in the memory 36, the memory 37, and the memory 38 of the arithmetic circuit 49.

The control signal processing 74 outputs the amount of movement of the memory 36, the memory 37, and the memory 38, a predetermined movement speed, and control timing to the drivers 39 to 41 for moving each lens group.

The control process 75 is a process performed by the drivers 39-41.

The process 76 for detecting the position of each lens group is the same as the previous process 71 for detecting the position of each lens group, and the position detector 36 of the second lens group 22
, the values of the memories in the position detector 37 of the third lens group 23 and the position detector 38 of the fourth lens group 24 are read out and stored in the memory 30, the memory 31, and the memory 32 of the calculation circuit 49.

[0078] The determination process 77 is carried out by the memory 30, the memory 3
1 and the current position of the lens group stored in the memory 32 and the initial setting positions stored in the memory 33, the memory 34, and the memory 35, and it is determined whether or not the current position is within the allowable range. If it is not within the allowable range, the steps from movement amount calculation processing 73 to determination processing 77 are repeated. When it is within the allowable range, processing is completed in stop processing 78.

Initial setting processing is performed through the above processing.

FIG. 6 is a flowchart showing an example of correcting a shift in the position of each lens group when it occurs due to an unexpected situation.

In the figure, 80 is a reset-on process, and the following process is executed by turning on the error correction reset switch of FIG. That is, 81 detects the position of the lens group, 82 reads the target position, 83 calculates the amount of movement, 84 controls signal processing, 85 controls processing, 86 detects the position of the lens group, 87 semi-separate processing, 88 is a stop process. The error correction process is almost the same as the initial setting process except that the initial setting position read process 71 is replaced by the target position read process 82.

Therefore, only the target position reading process 82 will be explained.

This process 82 adjusts the position of the second lens group and the third lens group with respect to the focal length and object distance by controlling the error that occurs during the magnification change or focusing operation or by moving the lens due to unintentional vibration. This solves the problem that if the relationship between the positions of the lenses and the positions of the fourth group lens collapses, the variable power and focusing functions described above become impossible. That is, it becomes impossible to determine the focal length and subject distance from each lens position.

The above problem can be solved by performing a correction process so that the positional relationship of each lens with respect to a given value of the focal length and object distance stored in the memory 48 is satisfied.

The target position reading process 82 is based on the current position of each lens group found in the lens group position detection process 81.
Find the nearest position that satisfies the positional relationship of each lens with respect to the focal length and subject distance stored in the memory 48,
It is stored in memory 30, memory 31, and memory 32 of arithmetic circuit 49.

[0086] Hereafter, error correction is performed by performing the same processing as steps 83 to 77 in FIG.

[0087]

[Effects of the Invention] As explained above, since the device according to the present invention can carry out initial settings with a simple configuration, accurate focal length and object distance can be determined, and therefore highly accurate magnification changing and focusing effects can be achieved. Alternatively, since error correction can be performed so that the lens group moves along the correct trajectory, there is an effect that similarly highly accurate zooming and focusing operations can be performed.

[Brief explanation of the drawing]

FIG. 1 is an optical cross-sectional view of a zoom lens.

FIG. 2 is a diagram showing movement trajectories of lens groups constituting a zoom lens.

FIG. 3 is a diagram showing the overall configuration of the device.

FIG. 4 is a flowchart for explaining a magnification change effect.

FIG. 5 is a flowchart for explaining initial setting processing.

FIG. 6 is a flowchart for explaining error correction processing.

FIG. 7 is an optical cross-sectional view of a conventional zoom lens.

FIG. 8 is a diagram showing the relationship between the lens position for focus adjustment and the subject distance.

FIG. 9 is a diagram showing movement trajectories of lens groups as zooming occurs.

FIG. 10 is a sectional view of a lens barrel that drives a zoom section.

[Explanation of symbols]

21 First group lens 22 Second group lens 23 Third group lens 24 Fourth group lens 43 Initial setting reset switch 44 Error correction reset switch 4
8 Memory for storing trajectory 49 Arithmetic control circuit

Claims (3)

[Claims] 1. A control device that performs zooming by independently moving a plurality of lens groups in an optical axis direction according to a movement trajectory based on information stored in a memory, and at least one of the plurality of lens groups. A variable magnification optical system that performs focusing by moving, characterized in that the control device is provided with means for setting the plurality of lens groups at predetermined positions on a movement locus. . 2. The variable magnification optical system according to claim 1, wherein the means according to claim 1 has a function of resetting in a plurality of modes. 3. The means of claim 1 includes causing the control device to generate an output for moving the lens groups so as to eliminate the difference between the detected current position of each lens group and the position determined by the control device. Features variable magnification optical system.