JPH08327876A - Optical system - Google Patents

Abstract

PURPOSE: To prevent step out from synchronism between lenses caused by disturbance in an optical system. CONSTITUTION: In the system having a zoom lens executing variable power by moving at least two lenses such as a variable power lens and a correction lens correcting an image plane fluctuated by the variable power by independent driving parts on an optical axis, the prevention of the step out from synchronism is realized by a lens position calculating means 3 calculating the position of the lens for every lens, a position storing means storing the position of every lens, a lens position control means 6 moving the lens by driving the driving part based on a position signal stored in the position storing means, and position detection means 9a and 9b detecting the position of the lens on the optical axis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system, for example, having a structure in which a lens unit for moving by zooming is provided by an independent drive unit, and zoom position information input from a zooming operation member is received. When each lens group is moved to change the magnification based on the above, high optical performance is required to correct the fluctuation of the focus shift amount due to errors due to tracking delay, disturbance during zooming. The present invention relates to an optical system suitable for a television camera or the like.

[0002]

2. Description of the Related Art FIG. 1 shows a variable power unit composed of a plurality of lens units for moving the variable power on the optical axis, and a focusing unit including at least a part of the lens units for moving the variable power unit on the optical axis. It is a figure which shows the structure in case the optical system which has a zoom lens which was made to perform a focus, and has two lens groups. This system comprises a focal length varying means for changing the focal length to the telephoto side or the wide angle side and for determining the changing speed, and a focal length for computing a focal length command signal based on the output signal of the focal length varying means 1. A computing means 2, an object distance information setting means 4 for setting object distance information, a lens group position computing means 3 for computing the position of each lens group on the optical axis from these focal length and object distance, and the first lens group. Driving means 7a for moving the first lens group position, position detecting means 9a for detecting the speed, speed detecting means 10a, and driving means 7b for moving the second lens group and the second lens group position For detecting the position, speed detecting means 9b, speed detecting means 10b, first lens group and second lens group target position generating means 3, first lens group driving means 7a, and second lens group. Having a control means 5 for determining a control input signal to the motion means 7b. FIG. 4 shows an example of a conventional control method for such a system. Here, the first axis is the first lens group and the second axis is the second lens group. The first axis to be controlled in FIG. 4 is a secondary system 3a in the figure, and the second axis is a secondary system 3b in the figure. The controlled object 3a corresponds to the first lens group driving means 7a and the first lens group 8a in FIG. 1, and the controlled object 3b corresponds to the second lens group driving means 7b and the second lens group 8b in FIG. Further, the position signals 8a and 8b in FIG. 4 correspond to the first lens group position detecting means 9a and the second lens group position detecting means 9b in FIG. 1, respectively.
It corresponds to the output signal of. Speed signals 10a, 1 of FIG.
0b measures speed information by the speed detecting means 10a and 10b in FIG. The position target value signals 1a and 1b in FIG. 4 are output signals of the lens group position target value generating means 3 in FIG. The control device 2 of FIG.
Corresponding to.

The target generating means generates a position target value so that the two axes are always in the target positional relationship, and the first axis and the second axis are generated.
Command the axis position control system. At this time, the target value signal is instructed so that the synchronous relationship between the two axes is always maintained. For example, when a circular locus is to be drawn in two spatial axes, the position command signal generating means 1 outputs a sine wave and a cosine wave as position command values for each axis component, which correspond to each axis based on the control means. A circular locus can be drawn by simultaneously controlling the positions of the controlled objects. The synchronous relationship between the two axes can be known by considering a plane having the first axis as the horizontal axis and the second axis as the vertical axis, and drawing a movement locus in this plane. When the two axes are in a synchronous relationship, the tracking locus moves on the curve indicating the target trajectory. The deviation from this curve indicates that the synchronization relationship is broken. In this way, the control performed while maintaining the multi-axis synchronous relationship can be treated as a problem similar to the route control in space.

In the control system of FIG. 4, the two-axis control system has the same structure, and is a position control system having a speed control system for stabilization as a minor loop. As described above, in the conventional control method, the control input to the first axis is obtained from the target position command value of the first axis and the position and speed information of the first axis, and the control input to the second axis is the control input of the second axis. The target position command value and the position of the second axis,
Obtained from the speed information, the two axes are controlled independently of each other. Such a position control system is a control system having a relatively low gain position control loop and a relatively high gain speed control loop inside thereof. The characteristics of this control system are that the rigidity of the control system against disturbance can be set high by the high gain of the speed control loop, and the position control loop has a low gain, so that a response that does not give an excessive impact to the mechanical system can be easily obtained. Is.

[0005]

However, the above-mentioned conventional position control method has the following problems. (1) It is premised that the responsiveness of each axis is exactly the same. (2) In order to improve the route accuracy, the gain of the position control loop must be set high. These problems will be described in detail below.

Consider a case where the position control system of the above-mentioned conventional position control method is provided and path control is performed by two axes, the first axis being the X axis and the second axis being the Y axis. Consider drawing a circle on a plane with this biaxial position control system. In order to draw a circle on a plane with two linear axes of the X axis and the Y axis, for example, a sine wave and a cosine wave are synchronized with the X axis and the Y axis, respectively, and given as position target values.
If the X-axis and the Y-axis completely follow this target value, an accurate circle can be drawn.

FIG. 8 is a diagram showing the characteristics of the conventional system.
The locus C0 is a target circular locus. Conventional method is usually X
Axis and Y-axis responsiveness are set to the same value. X like this
The locus when the position control loop gains of the axes Y and Y are set to be the same is shown as C1. The locus C1 is a circular locus although the radius is smaller than the target circle except for the start point and the end point of the route. Next, in order to investigate the above problem (1), the X axis and Y
Set the axis position control loop gain to different values and
Path control is performed by changing the responsiveness of the axis and the Y axis. The locus at this time is shown as C2 in FIG. As is clear from the figure, the locus C2 is not a target circle but an ellipse.
From this example, it is understood that it is necessary to make the responsiveness of the X axis and the Y axis identical.

Next, the relationship between the path accuracy and the gain of the position control loop, which is the problem (2), is examined. Here, it is assumed that the X-axis and the Y-axis have the same responsiveness. The locus C1 in FIG. 8 is the X axis,
It was a follow-up trajectory for the target circle path when the Y-axis responsiveness was the same. In this example as well, the following trajectory has an error with respect to the target circle path. At this time, if the path error between the target circle path and the following trajectory in the steady state is represented by the radius reduction amount dR, dR can be calculated by the following equation.

[0009]

[Outside 3] That is, when a circle with the same speed Vo and radius R is drawn as the target locus, the path error decreases in inverse proportion to the square of the position loop gain Wo. Conversely, in order to draw a highly accurate circle, it is necessary to set the position loop gain high.
On the other hand, in order to set the position loop gain high, the gain W of the speed control loop of the inner loop of the position control loop is set.
It is necessary to set o high. However, setting the speed control loop gain high usually causes some vibrations of the mechanical system, and thus has a certain limit. Therefore, it is difficult to set the position loop gain high, and it becomes difficult to keep the accuracy of the trajectory within the target path error as the speed of the target circle trajectory becomes faster and the radius of the circle becomes smaller.

[0010]

According to the present invention, unlike the conventional method, a control loop is not formed independently for each axis to be controlled, but the state quantity and the target value are not limited to the target axis, but also to other axes. A control loop is formed using the state quantity of the shaft and the target value.

Therefore, the objective route control is performed by defining an evaluation function unique to the present invention and constructing a control system for optimizing this evaluation function. In order to configure a control system, an evaluation function such as the following (Equation 1) including an area evaluation term is defined, and an optimum control input that minimizes this function is set as a state quantity of a control target and a target value. It is realized by sequentially obtaining from the above with a computer or the like and sequentially instructing this control input to the controlled object. That is, configuring the control system means calculating the optimum control input that minimizes the evaluation function of (Equation 1). A configuration diagram at this time is shown in FIG. An optimum control input that minimizes the evaluation function as in (Equation 1) is, for example, DP (Dynamic Program).
It can be determined by a method such as g) method.

[0012]

[Outside 4] Here, R target value vector y = CX output vector X state vector U control input vector k time M integration time Q weighting function H weighting function

[0013]

【Example】

(Embodiment 1) FIG. 2 shows an embodiment of the present invention. The correspondence with FIG. 1 is the same as the correspondence shown in the description of the conventional system except for the configuration of the control device 2 in FIG. 2, which corresponds to the lens group position control means 6 in FIG. In FIG. 1, the position information and the speed information are represented by different lines, but in FIG. 2, the state quantity representing the position information and the speed information is one line. This is a state vector indicating a plurality of information and is a vector quantity. The other lines are vector quantities as well. The characteristic of the controlled object is represented by a state equation. (Equation 6) is a transformation of this state equation into a discrete time system equation. Here, φ and G are matrices representing the characteristics of the system.

X (k + 1) = φX (k) + GU (k) (Equation 6) X state vector U control input vector The evaluation function is (Equation 1). Here, the evaluation function is an expression including evaluation terms such as the following (Expression 2) and (Expression 3).

S1 _k = e _K ^T qke _k (Formula 2) S2 _k = e _K ^T qk + 1e _k (Formula 3)

[0016]

[Outside 5] e _k Position error vector ΔR Target value increment vector I _o Identity matrix

[0017] This section is called the area evaluation section represents the area of a closed region made with two curves of FIG 7S1 _k, S2 target position command value and the follow-up value as shown in _k. Either or both of S1 _k and S2 _{k in} FIG. 7 are used as the evaluation term. Both will be used in this embodiment.

S1 _k = e _K ^T qke _k S2 _k = e _K ^T qk + 1e _k Therefore, the weighting function of (Equation 1) is expressed as follows.

Q _i = q _o + q1 ^* q _i + q2 ^* q _{i + 1} qo constant matrix q1, q2 constants

The model of the actual controlled object is 2 as shown in FIG.
The following inertial system is used. The optimum control input U (k) that minimizes the evaluation function of (Equation 1) is obtained as follows. The control system can be realized by calculating this equation in real time.

[0021]

[Outside 6]

As described above, by introducing the area evaluation term, in the control system that minimizes the evaluation function of (Equation 1), originally independent control objects interfere with each other, and the control system also uses speed information. become. At this time, the target position command value uses not only the current value but also a value after a finite time. This value is obtained from the target position command value storage means 13. That is, the control input to the first axis is obtained from the target position command values for the first and second axes and the position and speed information of the first axis. Also,
Similarly, the control input to the second axis is obtained from the target position command values for the first and second axes and the position and speed information of the second axis. As described above, in the control system of the present invention, the target values of the first axis and the second axis interfere with each other to perform control. That is, by constructing a control system that optimizes the evaluation function including the area evaluation term, it is possible to create a control device in which the target values interfere with each other.

FIG. 9 is a locus when the two axes are controlled so that the first lens group and the second lens group move in an arc orbit. In the figure, C0 shows a target trajectory, C1 shows a follow-up trajectory of the conventional method, and C2 shows a follow-up trajectory of this control system. in this way,
The control system based on this control method can maintain good synchronization relation of each axis.

(Second Embodiment) Disturbance Estimation In the control method of the first embodiment, when a disturbance is applied,
The effect cannot be suppressed sufficiently. In this embodiment, the disturbance is estimated by the disturbance estimator and the value W1 is used in (Equation 8) to suppress the disturbance. Here, W1 is the output of the disturbance estimator.

X (k + 1) = A (k) X (k) + B (k) U (k) + W1 (k) (Equation 8) X state vector U control input vector W1 estimated disturbance vector

There are various types of disturbance estimators, but here, a Kalman filter as shown in FIG. 5 is used. The model of the actual controlled object is a secondary inertial system as shown in FIG. 6, and the disturbance generation model is a primary system, which constitutes the disturbance estimator. The disturbance estimation value output from the disturbance estimator is used to configure a control system that minimizes the same evaluation function as in the first embodiment.

As a result of configuring the control system as described above, the first
The control input to the axis is obtained from target position command values for the first and second axes and the position and speed information of the first and second axes. Similarly, the control input to the second axis is obtained from target position command values for the first axis and the second axis and the position and speed information of the first axis and the second axis. Thus, in the control system of the present invention, the target position command value is controlled by the first axis and the second axis interfering with each other. Further, the position and speed information also interferes with each other for control. That is, it is possible to create a control device in which the target value and the state quantity interfere with each other by constructing a control system that estimates the disturbance applied to the controlled object and optimizes the evaluation function including the area evaluation term. .

FIG. 3 is a diagram collectively showing the configurations of the second embodiment and the following third and fourth embodiments. In this embodiment, FIG.
From the above, the virtual control target and the disturbance measuring means are removed.

FIG. 10 is a locus when the two axes are controlled so that the first lens group and the second lens group move in circular arc orbits. In the figure, C0 indicates a target locus, C1 indicates a following locus of the first embodiment, and C2 indicates a following locus of the control system of the present embodiment. FIG.
0 indicates a tracking locus at the point D when the step disturbance is applied to the first axis. C1 has a steady deviation with respect to the step disturbance. As described above, according to the control method of the present embodiment, it is possible to realize a control system having high rigidity against disturbance as compared with the first embodiment.

(Third Embodiment) Virtual Axis In the first and second embodiments, a large overshoot occurs at the trailing end of the track. A virtual axis is introduced to suppress this overshoot. As the virtual axis, a virtual control axis is considered in addition to the existing control target axis, and this axis is included in the control target to configure a control system as in the first or second embodiment. FIG. 3 shows the configuration of the control system when the virtual axis is used. The characteristics of the first and second axes to be controlled and the target position value are the same as in the first embodiment. Here, it is assumed that the characteristics of the virtual axis are the same as those of the first axis, and the position target value signal for the virtual axis moves at a constant speed after the movement of the two axes is stopped. C2 in FIG. 11 is the response of this system. C1 is the response of the control system having no virtual axis in the first embodiment, and C0 is the target route. As shown in the figure, the overshoot at the terminal end is small in the control system using the virtual axis.

(Fourth Embodiment) Disturbance Forecasting In the first and second embodiments, the configuration in which the disturbance cannot be known in advance is shown. However, when the torque disturbance corresponding to the target position is known in advance, better control can be performed by performing control using this information. In this case, the characteristic of the controlled object is expressed as in (Equation 9), and the control system is configured. Here, W1 is the second embodiment
W2 is an estimated value of the disturbance estimator used in step 1, and W2 is a known disturbance known in advance. The configuration of this system is also shown in FIG.

X (k + 1) = A (k) X (k) + B (k) U (k) + W1 (k) + W2 (k) (Equation 9)

FIG. 3 shows the configuration of the control system including all of the first, second and third embodiments. The position target value and the disturbance similar to those in the second embodiment are applied to the control system thus configured. When the disturbance is given at the same value as the previously known value at the same timing, the influence of the disturbance hardly appears in the response of the control system, and good control is possible. The response when the known value of the disturbance is half the value of the actual disturbance is shown in C2 of FIG. Also, C0 and C in the figure
Reference numeral 1 is a target position trajectory, and a tracking trajectory when the disturbance is not known in advance. Comparing C1 and C2, it can be seen that when the disturbance is known in advance, the fluctuation due to the disturbance is smaller in C2.

(Embodiment 5) Others (1) Here, an embodiment in which the number of control axes is two has been described, but the number of axes is not limited, and the system can be configured with arbitrary N axes. (2) It is also possible to calculate the speed information from the position information and use the value as the speed information to configure the control system. (3) Although the characteristic of the virtual axis is set to be the same as that of the first axis in the third embodiment, this characteristic may be any convenient one. (4) In the fourth embodiment, the control system when the disturbance signal is known is shown. The known disturbance signal may be determined by the target position command value, or may be obtained by providing a disturbance signal detecting means.

[0035]

By applying the present invention, it is possible to make an optical system having a zoom lens system having good characteristics, with less deviation of the synchronization relationship between the lens groups and less focus deviation due to disturbance.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of the configuration of an optical system.

FIG. 2 is a block diagram showing an outline of a configuration of an embodiment of the present invention.

FIG. 3 is a block diagram showing the outline of the configuration of another embodiment of the present invention.

FIG. 4 is a block diagram showing an outline of a configuration of a conventional system.

FIG. 5 is a block diagram showing the configuration of an observer.

FIG. 6 is a block diagram showing a configuration of a controlled object and a disturbance generation model.

FIG. 7 is a diagram illustrating an area term.

FIG. 8 is a diagram showing a problem of the conventional method.

FIG. 9 is a diagram showing the trackability of the system of the present invention with respect to a circular orbit.

FIG. 10 is a diagram showing the effect of disturbance estimation.

FIG. 11 is a diagram showing an effect of a virtual axis.

FIG. 12 is a diagram showing an effect when a disturbance is known.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Focal length changing means 2 Focal length calculating means 3 Lens group position calculating means 4 Object distance setting means 6 Lens group position controlling means 7a, 7b Lens group driving means 8a, 8b Lens group 9a, 9b Lens group position detecting means

Claims (8)

[Claims] 1. A system having a zoom lens for performing zooming by moving at least two lenses, a zooming lens and a correction lens for correcting a screen changed by zooming, on the optical axis by independent driving units, respectively. A lens position calculating means for calculating each lens position for each lens, a position storing means for storing a position signal for each lens, and a driving unit driven based on the position signal stored in the position storing means. An optical system comprising: a lens position control means for moving the lens; and a position detection means for detecting the position of each lens on the optical axis. 2. The system according to claim 1, wherein the control means includes not only a position signal of each corresponding lens group,
An optical system characterized in that a drive signal for each lens group is also generated using position signals of other lens groups. 3. The method according to claim 1, further comprising speed detecting means for detecting the speed of each lens group, wherein the control means determines the control input signal using the speed information. The described optical system. 4. The optical system according to claim 1, wherein the control input signal output by the control means is determined so as to minimize the following evaluation function. [Outside 1] Here, R target value vector y = CX output vector X state vector U control input vector k time M integration time Q weighting function H weighting function 5. The optical system according to claim 1, wherein the evaluation function includes the following area evaluation term. S1 _k = e _K ^T qke _k (Equation 2) S2 _k = e _K ^T qk + 1e _k (Equation 3) where: e _k Position error vector ΔR Target value increment vector I _o Identity matrix 6. An optical system configured to estimate a disturbance applied to a controlled object and use the estimated disturbance to configure. 7. A virtual axis which does not physically exist as a controlled object and a target position command value for this virtual axis are added to the virtual axis according to any one of claims 1, 2 and 3, and are configured. An optical system according to claims 1, 2, and 3. 8. The optical system according to claim 1, wherein the control system is constructed by using the known disturbance when the disturbance applied to the controlled object is known in advance.