JPH06289276A - Method and device for controlling lens position - Google Patents

Abstract

PURPOSE:To accurately move a lens along a track and to obtain an image of good quality by executing an adaptive control in accordance with an overall condition of characteristics on the track, an action speed and a mutual relation between plural lens groups on the track. CONSTITUTION:The signal of an external control indicator 42 is detected by an action kind detector 45, an acting direction detector 46 and an action speed detector 47 so as to obtain the action kind, the acting direction and the action speed. An object distance and a focal distance are obtained based on the positions of a 2nd lens group 32, a 3rd lens group 33 and a 4th lens group 34 detected by position detectors 36 and 37. The moving extent is calculated based on the overall condition constituted of the characteristics on the track, the action speed and the mutual relation between plural lens groups on the track obtained in such a way, and then, the adaptive control is executed. And in order to process for a practical use, the variation of the focal distance of respective lens groups, or of the object distance is obtained based on fuzzy inference by applying fuzzy rules having the characteristics on the track and the action speed as an antecedent part and having the focal distance, or the object distance obtained after the lenses are moved as a consequent part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for controlling a lens position in an optical device such as a camera or an observation device. Further, it is suitable for a control method in which directions and speeds of focusing action and zooming action are commanded by an operating device.

[0002]

2. Description of the Related Art Conventionally, a zoom lens mounted on a video camera is composed of four lens groups as shown in FIG.

In FIG. 9, 1 is a first lens group (F lens) for focusing, which is arranged at the tip of the lens barrel, 2 is a variator lens (V lens) for performing zooming, and 3 is a variable lens. A compensator lens (C lens) for correctly focusing at the time of double operation, and 4 are relay lenses (B lens) for forming an image on an image plane.

The movement of each lens group will be described below.

FIG. 10 shows the relationship between the position of the F lens and the subject distance. FIG. 11 shows the relationship between the V lens 2 and the C lens 3 and the focal length.

Usually, the F lens is referred to as a focus section, and the V lens and the C lens are referred to as a zoom section. The F lens independently moves along the optical axis for focusing action as shown in FIG. Then, as shown in FIG. 11, the V lens and the C lens move in conjunction with each other along the optical axis in order to cause a zooming effect. In this configuration, the collating action and the zooming action are separated, and the trajectories of the movements of the V lens and the C lens are uniquely determined. Therefore, the control is relatively simple, and an electromechanical control mechanism such as a cam is used. It has the advantage that it can be done.

FIG. 12 shows an interlocking mechanism of a V lens and a C lens in a conventional zoom lens. In the figure, 5 and 6 are lens holding frames for holding V lenses and C lenses, 7 and 8 are guide bars for guiding the lens holding frames 5 and 6 along the optical axis, and 9 is a lens holding frame 5.
A cam barrel 10 having cam grooves 9a and 9b for inserting the pins 5a and 6a provided on the cylinders 6 and 6 is fitted on the outer periphery of the cam barrel and fixed to a stationary member such as a lens barrel. , 11 are sume operation rings which are fixed to the cam cylinder 9 by the connecting portion 11a and which are fitted so as to be rotatable only relative to the outer peripheral surface of the fixed cylinder 10. When the zoom operation ring 11 rotates, the cam cylinder 9 operates when the zooming action is performed.
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, so that the V lens holding frame 5 and the C lens holding frame 6 respectively have optical axes. Will be moved relative to.

Although the control mechanism using the cam barrel is easy to control, it has a disadvantage that the manufacturing cost is high because the fitting precision of the cam barrel and the machining precision of the cam groove are extremely high. In addition, in the conventional zoom lens, in order to focus on a subject at a close range (for example, 1 m or less), the amount of extension of the F lens increases in proportion to the reciprocal of the subject distance, and therefore the aperture of the F lens also increases. Become. As a result of the above, there is also a disadvantage that the length, aperture, and weight of the zoom lens become large.

In order to solve the above disadvantages, there has been proposed a so-called inner focus type zoom lens which performs focusing without moving the F lens.

FIG. 1 shows an example of the structure of an inner focus zoom lens. In the figure, 21 is a positive first lens group, 22 is a negative second lens group, 23 is a positive third lens group, 24 is a positive fourth lens group, 25 is a positive fifth lens group, and 26 is It is a support member for fixing the first lens group 21 to a lens barrel or the like.

FIG. 2 shows the relationship between the lens group 22, the lens group 23 and the lens group 24 and the focal length and the subject distance.
Here, the focal length and the subject distance are changed by moving the lens group 22, the lens group 23, and the lens group 24, respectively, and three lens groups of the lens 22, the lens 23, and the lens 24 are used to perform a desired operation. It is necessary to move at the same time along a locus uniquely determined by the focal length or the subject distance. Here, for the sake of convenience, the loci for the near distance and the infinity are drawn, but it is assumed that the moving loci are filled between these.

[0012]

SUMMARY OF THE INVENTION The present invention is to realize a zoom system in which a plurality of lens groups are independently moved to perform a focusing action and a zooming action, and in particular, the lens units can be smoothly moved. The problem is to prevent deterioration of image quality.

[0013]

A method for controlling a lens position in which a plurality of lens groups are moved along an optical axis according to a locus for moving a predetermined lens group stored in memory to perform a zooming action and a focusing action, on a locus. The adaptive control is performed according to the total conditions of the characteristics, the action speed, and the relative relationship on the locus between the plurality of lens groups.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 is a conceptual diagram of the basic configuration. In the figure,
31 is a first positive lens group, 32 is a second negative lens group, 33
Is a positive third lens group, 34 is a positive fourth lens group, and 35 is a positive fifth lens group. However, the lens group may be a single lens. 36 is a position detector for the second lens group,
37 is a position detector for the third lens group, 38 is a position detector for the fourth lens group, 39 is a controller for moving the second lens group, 40 is a controller for moving the third lens group, and 41 is a fourth controller. A controller that moves the lens group. 42 is an external control command device, 45 is an action type detector, 46 is an action direction detector, 4
Reference numeral 7 is an action speed detector. Reference numeral 48 is a memory for storing each locus of the moving lens group, and 49 is an arithmetic circuit such as a microcomputer.

Before describing the operation of the present invention, the operation will be described by taking a normal zooming action as an example.

In a TV camera for broadcasting equipment, a zooming effect,
Three types of actions are required, a focusing action and a combined action of zooming and focusing. And each action has a direction. For example,
The scaling effect has the direction of reduction or expansion. Further, its operating speed is used in a wide range from 0.6 sec to low speed.

Therefore, the type of action, the direction, and the action speed are controlled. For example, the action type is manually operated by the switch attached to the outside, by the rotation direction of the handle in the action direction, and by the rotation angle of the handle. You can order with. Here, external control command devices 42 such as switches and handles that issue control commands from the outside are generically called.

The signal of the external control command device 42 is supplied to the action type detector 45, the action direction detector 46 and the action speed detector 47.
To obtain the action type, action direction, and action speed.

The position detectors 36, 37 and 38 can employ a desired method such as detecting the lens group position from a marker attached to the lens group, or detecting from the number of rotations of a motor for moving the lens group. Then, the focal length and the subject distance are obtained from the correlation positions of the lens groups.

The zooming action or the focusing action is to move on the locus shown in FIG. 6, but this is performed with the second lens group 32, the third lens group 33, and the fourth lens group 34 as optical axes. Therefore, it is realized by moving in a predetermined relationship.

The memory 48 has a second lens group 32 and a third lens group 32.
The loci of movements of the lens group 33 and the fourth lens group 34 are stored.

Generally, the locus can be represented by the following relationship.

L ₂ = L ₂ (V, F) (1) L ₃ = L ₃ (V, F) (2) L ₄ = L ₄ (V, F) (3) where L ₂ and L ₃ , And L ₄ are positions on the optical axis of the second lens group 32, the third lens group 33, and the fourth lens group 34. V and F are focal lengths and subject distances. First, a detailed description will be given of the zooming effect.

In the zooming action, the loci of the second lens group, the third lens group, and the fourth lens group are different depending on the object distance, so the second lens group, the third lens group, and the third lens group detected by the position detectors 36, 37, and 38, respectively. From the positions of the third lens group and the fourth lens group, the value of the memory 48, that is, the subject distance F and the focal length V are obtained from the equations (1) to (3).

When the subject distance F is determined, the second lens group, the third lens group, and the fourth lens group are moved when the subject distance F is fixed and the focal length is changed by a predetermined amount (that is, zooming action). Find the amount.

As can be seen from FIG. 2, when the zooming action is performed at a constant speed, the moving amount and the moving speed change depending on the curvature of the locus, so that it is necessary to control the moving amount and the moving speed.

When a focusing action is desired, it can be performed in the same manner as the zooming action except that the subject distance in the zooming action changes to the focal length. Further, when it is desired to perform the focusing action and the zooming action at the same time, the subject distance and the focal length can be moved so as to change monotonously.

Next, the action speed will be described.

Support for the working speed is obtained from the external control commander 42. Since the movement amount and movement speed of the lens differ depending on the action speed, a reference focal length change amount corresponding to the reference action speed is provided in advance,

[0030]

[Outer 1] From this equation (4), the amount of change in focal length can be obtained. The movement amount of the lens is obtained from the obtained focal length change amount and the equations (1) to (3).

The moving speed can be obtained from the equation (5) by previously setting the reference moving amount and the reference moving speed.

[0032]

[Outside 2] FIG. 4 shows a flow chart of the processing of the zooming action. In the figure, 5
0 is a process for reading the action type of the lens operation, 51 is a branch process, 52 is a process for reading the action direction, 53 is a process for reading the action speed, 54 is a process for reading the position of each lens group, 55 is a subject distance and a focal length. Processing for obtaining 5
6 is a process for calculating the amount of change in the focal length, 57 is a process for calculating the amount of movement, 58 is a process for calculating the moving speed, and 59 is a control signal that moves the amount of moving, the moving speed, and the control timing for each lens group. Outputting to the controller, 60 is drive control, and 61 is processing to read the position of each lens group.

The operation will be described below.

The following processing is performed by the arithmetic circuit 49 including a CPU and the like. First, in the process 50 for reading the action type, the value stored in the memory in the action type detector 45 is read out and stored in 1 of the memory in the arithmetic circuit 49. The branching process 51 performs a scaling process, a focusing process, or a scaling process and a focusing process depending on the type of action.

In the present embodiment, the process 52 for reading the action direction
The processing of the zooming action will be described below.

In the process 52 for reading the action direction, the value of the memory in the action direction detector 46 is stored in the memory 2 of the read operation circuit 48.

In the process 53 of reading the action speed, the value of the memory in the action speed detector 47 is read and stored in the memory 3 of the arithmetic circuit 49.

The processing 54 for reading the position of each lens group reads the value of the memory in the position detector 36 of the second lens group, the position detector 37 of the third lens group, and the position detector 38 of the fourth lens group. It is stored in the memory 4, the memory 5, and the memory 6 of the arithmetic circuit 49.

Process 5 for obtaining subject distance and focal length
Reference numeral 5 obtains the subject distance and the focal length from the equations (1) to (3) of the loci stored in the memory 48, and stores them in the memory 7 and the memory 8 of the arithmetic circuit 49.

The process 56 for calculating the change amount of the focal length is a process for obtaining the amount of change in the focal length within a predetermined unit time, and the action direction of the memory 2 and the action of the memory 3 of the arithmetic circuit 49. Based on the speed, the reference focal length change amount of the memory 100 (not shown) stored in advance and the reference action speed of the memory 101 (not shown), (4)
The change amount ΔV of the focal length is obtained from the calculation processing of the formula and stored in the memory 9 of the calculation circuit 49.

The movement amount calculation process 57 is performed by the position L ₂ of the first lens group 4 in the memory 4 of the arithmetic circuit 49 and the position 5 of the memory 5.
Position L ₃ of the second lens group, position L ₄ of the third lens group 6 of the memory, subject distance 7 of the memory, focal length V ₀ of the memory 8 and focal length change amount ΔV of the memory 9 1) Calculation process of focal length V after movement V = V ₀ + ΔV (6) Here, V is the focal length after movement V ₀ is the current focal length ΔV is the change amount of the focal length 2) The movement amount ΔL _n calculation L _n '= L _n' in (V, F) (7) at _{ΔL n = L n '-L n} (8) where, n = 2 to 4 (the number of each lens group) L _n is the current For the position L _n ′ of the lens group, the amount of movement ΔL _n is calculated by processing the position of the lens group after movement, and is stored in the memory 10 of the arithmetic circuit 49.

The moving speed calculation process 58 is based on the reference moving speed of the memory 102 (not shown) stored in advance, the reference moving amount of the memory 103 (not shown) and the moving amount ΔL _n of 10 of the memory, and the equation (5) is used. Is calculated and stored in the memory 11 of the arithmetic circuit 49. Further, the focal length after the movement is stored in the memory 8 for processing in the next cycle.

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

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

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

Processing 5 for reading the position to execute the next action until the external control command device 42 gives a stop instruction.
The process 61 of reading the position of each lens group from 6 is repeated.

In the above example, (7)-
In order to perform the arithmetic processing of the equation (8), the locus which is originally the curvature is approximated by the folding line. For this reason, it is not possible to accurately move along the locus, and especially at the curvature on the locus, it greatly deviates from the locus, which causes deterioration of image quality.

Therefore, the amount of movement is calculated from the total condition consisting of the characteristic on the locus, the action speed, and the relative relationship on the locus between a plurality of lens groups, and appropriate cormorant control is performed. In particular, in order to perform processing suitable for practical use, individual lens groups are obtained by fuzzy inference from fuzzy rules with the characteristics and action speed on the trajectory as the antecedent and the focal length or object distance after movement as the antecedent. The amount of change in the focal length or the subject distance is calculated. First of all, as a common sense to move the lens group as faithfully as possible along the locus, it is necessary to use the knowledge 1: fold line approximation divided into fine pitches at a portion having a large curvature on the locus.

Knowledge 2: In view of the visual characteristics of a TV image, when the action speed (change speed of the image) is very fast, it is not necessary to give importance to the bend on the locus.

Knowledge 3: When at least one of the three lens groups approaches the bending angle, the other lens groups also need to move in synchronization. There is. Although these matters are natural for each individual,
It is extremely difficult to correlate and quantify these pieces of knowledge, and even if strict correlation and quantification can be performed, the control means becomes complicated and often not suitable for practical use.

In the present embodiment, in order to carry out practical control in view of the above points, knowledge is described by fuzzy rules, and movement amount calculation processing is performed to calculate movement amounts by fuzzy rule inference. is there.

An embodiment of fuzzy rules and fuzzy inference will be described below.

The fuzzy rule is a description in which the above knowledge is described by a fuzzy production rule and quantified by a corresponding membership function. For example, in the zooming action, the fuzzy rules for knowledge 1 and knowledge 2 are: If the action speed is normal or less and there is a large curvature portion in the next movement range Then Shortening the amount of change in the focal length If The action speed is fast And there is a part with a small curvature in the moving range Then The amount of change in the focal length is shortened a little If The action speed is very fast And there is a part with a small curvature in the next moving range Then Do not change the amount of change in focal length If The action speed is fast, and there is a very small curvature part in the next moving range. Then The amount of change in focal length is short. If The action speed is very fast, and there is a very small curvature part in the next moving range. The focal length change distance is shortened a little, and so on.

In the above production rule,
The action speed is expressed by the membership function of the action speed in FIG. 5, using an ambiguous expression that the action speed is below normal, fast, or very fast. Similarly, using a vague expression that the curvature within the movement range (for example, the reference movement range of the focal length where the curvature of the movement locus is small) is smaller than normal, or very small, the curvature of FIG. Expressed as a membership function. Regarding the amount of change in the focal length or subject distance, the reference amount of change is reduced (pitch is reduced) according to the action speed and curvature, but it is not changed at this time as well, and it is ambiguous that it is shortened or shortened. Using expressions,
It is expressed by the membership function of the amount of change in FIG.

These fuzzy production rules are used when calculating the amount of change from the unambiguous input values of the action speed and the curvature.

The method of calculating the amount of change from the input value and the fuzzy production rule is a known fuzzy inference process (for example, Max-Min composition rule and Mamdan).
The movement amount is calculated by the processing of the implication rule of i), and the barycentric method processing for obtaining a reliable value from the characteristic on the trajectory, the action speed, and the fuzzy amount is performed.

By performing the above-described change amount calculation processing on each lens group, the change amount of each lens group can be obtained. Since what is obtained here does not guarantee parallelism (synchronization) between the lens groups, a process for synchronizing the lens groups of knowledge 3 is required. This process can be realized by searching the lens group having the smallest change amount and using this as a common change amount.

FIG. 8 is a flowchart of the embodiment. In the figure, 70 is the calculation of the amount of change in the focal length of each lens,
Reference numeral 71 is a calculation of the minimum change amount of the focal length.

The present embodiment is the same as the basic embodiment shown in FIG. 4 except for the calculation process 70 of the change amount of the focal length of each lens group and the calculation process 71 of the minimum change amount of the focal length. Therefore, only the operation of the part different from FIG. 4 will be described.

In the calculation process 70 of the variation of the focal length of each lens group, the variation ΔV of the focal length of 9 in the memory of the arithmetic circuit 49 obtained in the process 56 of calculating the variation of the focal length is used as the reference variation. Executes fuzzy production rules, fuzzy inference processing, and barycentric method processing in which the pre-programmed action speed and the curvature of the trajectory are the antecedent parts, and the rate of change in the focal length is the antecedent part, and the focal length changes The change amount of each lens group is calculated from the ratio and the reference change amount, and stored in the memory 100 of the arithmetic circuit 49.

In the above calculation, the working speed is read from the working speed reading process 53, and the curvature on the locus is read from the locus of the memory 48 for storing the locus.

Calculation processing 71 of the minimum variation in focal length
Is calculated from the change amount of the focal length of each lens group stored in the memory 100 of the arithmetic circuit 49 and stored in the memory 101 of the arithmetic circuit 49. The amount of change in the focal length obtained here is the amount of change actually moved. These are controlled by moving the lens group in the same manner as described with reference to FIG.

[0063]

EFFECTS OF THE INVENTION By performing the control using the fuzzy inference, the control satisfying the complicated total condition can be performed by the simple calculation and the movement along the locus can be performed with high precision, so that a high quality image can be obtained. To be

[Brief description of drawings]

FIG. 1 is a relationship diagram of a V lens and a C lens, and a focal length and a subject distance.

FIG. 2 is a conceptual diagram of a basic configuration of a zoom system.

FIG. 3 is a flowchart of processing of a variable power operation.

FIG. 4 is a diagram showing a membership function of action speed.

FIG. 5 is a diagram showing a membership function of a curvature of a locus.

FIG. 6 is a diagram showing a membership function of a rate of change.

FIG. 7 is a flowchart characteristic of the embodiment.

FIG. 8 is a sectional view of a zoom lens mounted on a television camera.

FIG. 9 is a relationship diagram between the position of the F lens and the subject distance.

FIG. 10 is a relationship diagram of a V lens, a C lens, and a focal length.

FIG. 11 is a diagram showing a conventional interlocking mechanism of a V lens and a C lens of a zoom lens.

FIG. 12 is a cross-sectional view showing a configuration example of an inner focus zoom lens.

[Explanation of symbols]

 31 1st lens group 32 2nd lens group 33 3rd lens group 34 4th lens group 35 5th lens group 36, 37, 38 Position detector 39, 40, 41 Controller 42 External control command device 45 Action type detector 46 Action direction detector 47 Action speed detector 48 Memory for storing locus 49 Arithmetic circuit 70 Calculation of change amount of focal length of each lens group 71 Calculation of change amount of minimum focal length

Claims (4)

[Claims] 1. A method for controlling a lens position in which a plurality of lens groups are moved along an optical axis according to a locus for moving a predetermined lens group stored in memory to perform a zooming action and a focusing action. A method for controlling a lens position, which is characterized by performing adaptive control according to a comprehensive condition of a speed and a relative relationship on a locus between a plurality of lens groups. 2. The characteristics on the trajectory and the speed of action are expressed in the antecedent part,
2. The lens position control method according to claim 1, wherein the amount of movement is calculated by fuzzy inference from a fuzzy rule having a consequent part as a method of calculating the amount of movement. 3. A plurality of lens groups and a drive means for independently moving each lens group along the optical axis, a storage means for storing a trajectory for moving a predetermined lens group, and a trajectory stored in the storage means. Position control, which is provided for the purpose of performing adaptive control in accordance with the total conditions of the characteristics, action speed, or relative positional relationship on the locus between a plurality of lens groups, and a calculation means for outputting a signal therefor to the driving means. apparatus. 4. The calculation means calculates the amount of movement by fuzzy inference from a fuzzy rule in which the characteristics and action speed on the trajectory are the antecedent and the method of calculating the amount of movement is the antecedent. The lens position control device according to claim 3.