JPH11103409A - Focus operating device of television lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adopt a rate demand for instructing the movement speed and the movement direction of a focus lens group as a focus operating means in a television lens by which automatic adjustment is executed at an optimum focus position by an automatic focusing function as against the focus lens group which is moved in accordance with the instruction of the focus operating means operated by a cameraman. SOLUTION: The operating direction and the manupulated variable of a seesaw switch (focus operating means) for instructing the movement speed and the movement direction of the focus lens group 12 are detected by a potentiometer 34 and CPU 26 controls a motor driving circuit 24 so as to realize a focus direction and focus speed in accordance with the operation of the seesaw switch. In the meantime, a focus evaluating value is detected based on an image signal from CCD 20 during the focus operation and the focus lens group 12 is automatically moved to a focus position (optimum focus position) where the focus evaluating value becomes the max. value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus operation device for a television lens, and more particularly to a focus operation device for a television lens that performs a focusing operation by using both a manual operation of a focus operation unit and an autofocus function.

[0002]

2. Description of the Related Art When performing focus adjustment and zoom adjustment by moving a focus lens group and a variable power lens group (zoom lens group) of a zoom lens for a television camera by a rotational driving force of a motor, a focus operation unit is provided with a focus lens. A position control servo system for controlling the position of the group is employed, and a speed control servo system for controlling the zoom speed is employed for the zoom operation unit.

That is, a cameraman operates a focus position demand for instructing a position of a focus lens group to perform focus adjustment, and a zoom speed for instructing a moving speed (zoom speed) of the zoom lens group and a tele / wide zoom direction. The zoom is adjusted by operating the rate demand. In order to move a wide movable range in a short time, the rate demand that indicates the moving direction and the moving speed has the advantage that the operation burden of the cameraman is less. Is used.

[0004]

However, when the focus adjustment is performed using the rate demand, it is difficult to finely adjust the focus lens group to the position of the best focus (just focus) and accurately position the focus lens group. There is a disadvantage that. In particular, since the focal depth becomes shallow on the telephoto side (long focal length side), it is extremely difficult to adjust the focus position to the just focus position by the rate demand.

The present invention has been made in view of such circumstances, and provides a focus operation device for a television camera which enables a focus operation by a rate demand and reduces the operation burden on a cameraman at the time of focus adjustment. The purpose is to:

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a television lens focus operating apparatus for adjusting the focus by moving a focus lens group of a television lens by driving a motor. A focus operation unit for instructing a direction and a movement speed, and a video signal obtained by using a photographic optical system and an imaging unit including the focus lens group during movement of the focus lens group by operating the focus operation unit. Evaluation value calculation means for obtaining a focus evaluation value indicating the sharpness of the subject image; detection means for detecting the position of the focus lens group; position of the focus lens group detected by the detection means; and calculation of the evaluation value for the position Storage means for storing the focus evaluation value obtained by the means, and the focus stored in the storage means Calculating means for obtaining a focus position at which the focus evaluation value becomes maximum based on the position of the lens group and the focus evaluation value; and a focus position obtained by the calculation means after the movement of the focus lens group instructed by the focus operation means is completed. And control means for controlling the motor so as to move the focus lens group.

According to the present invention, the moving direction (infinity side or closest side) of the focus lens group is instructed by manually operating the focus operation means, the moving speed is instructed, and the motor is operated based on the instruction. Is driven to move the focus lens group. During the focus operation by the speed control, the position of the focus lens group is sequentially detected and the focus evaluation value at the position is calculated, and the obtained position and focus evaluation value of the focus lens group are stored in the storage unit. Then, during or after the movement of the focus lens group instructed by the focus operation means, the focus position at which the focus evaluation value is maximized based on the focus lens position and focus evaluation value data stored in the storage means in the arithmetic means. Ask for. The focus position thus obtained indicates a so-called just focus position, and after the operation by the focus operation means,
The focus lens group is automatically moved to this focus position by position control to perform accurate focus adjustment.

[0008] Thus, the cameraman need only perform coarse adjustment of the focus by the focus operating means, and after the coarse adjustment, the automatic focus function automatically performs high-accuracy focus adjustment. In particular, in the present invention, since the focus control means related to the manual operation employs a speed control method for instructing the moving direction and the moving speed of the focus lens group, the operation burden on the cameraman can be further reduced.

Further, according to another aspect of the present invention, the moving speed instruction from the focus operating means is set to a constant value, and the focus operating means cannot be arbitrarily instructed to change the moving speed. When adopted, the setting of the moving speed is automatically changed according to the level of the focus sensitivity. That is, a sensitivity detecting means for detecting the focus sensitivity of the television lens, a moving speed setting means for setting an instruction value of the moving speed by the focus operating means to a constant value according to the focus sensitivity detected by the sensitivity detecting means, And the moving speed is set to be low as the focus sensitivity increases with the zoom operation. Thereby, the operability of the focus operation unit is improved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing a configuration of a focus operation device in a television camera to which the present invention is applied. As shown in FIG. 1, the photographing optical system of the television lens 10 includes a focus lens group 12, a variable power lens group 14, an aperture 16, a master lens group 18, and the like. CC
An image is formed on the image forming plane of D20 (imaging means). It should be noted that although simplified in the figure, each lens group 12, 14, 1
Reference numeral 8 includes one or a plurality of lenses.

The focus lens group 12 moves back and forth along the optical axis by transmitting the rotational driving force of the motor 22 via a gear transmission mechanism (not shown). The motor 22 is driven via a motor drive circuit 24, and its control is performed by a central processing unit (CPU) 26. The rotation speed of the motor 22 is detected by a tachometer generator 28, and the tachometer generator 2
The detection signal output from 8 is applied to the motor drive circuit 26. The tachometer generator 28 is means for converting the rotation speed of the motor 22 into a voltage signal, and the detection signal is used for feedback control of the speed command of the motor 22.

The position of the focus lens group 12 (hereinafter abbreviated as focus lens position) is detected by a potentiometer 30, and the potentiometer 30
Is sent to the motor drive circuit 24,
This is notified to the CPU 26 via the A / D converter 32.
Since the movement amount of the focus lens group 12 can be calculated from the movement speed and the movement time of the focus lens group 12, the focus lens position may be detected based on the calculation. In this case, the tachometer generator 28 for detecting the rotation speed of the motor 22 is converted into a digital signal to
Input to U26, and CPU 26 calculates the focus position.

Reference numeral 34 in the figure denotes a potentiometer for detecting an operation direction and an operation amount of a focus demand corresponding to a focus operation means. The focus demand used in this device is a late demand that instructs the moving direction and the moving speed of the focus lens group 12, and includes, for example, a seesaw switch or a midpoint return type lever switch that can swing based on a neutral position. Can be

Specifically, when the present invention is applied to a handy lens such as an ENG lens, a function of a focus rate demand is added to a drive unit attached to a lens barrel, and a known zoom seesaw control switch and a seesaw for focus operation are added. A mode in which the switches and the switches are arranged in two rows can be considered. In addition, a function of a focus rate demand is added to a known focus position demand that indicates the position of the focus lens group 12,
It is also possible to provide a selection means for selecting whether to use as a position demand or to use as a rate demand, and to switch and use the function as needed.

In the following description, an example in which a seesaw switch is used for the focus operation means will be described. The seesaw switch instructs the focus direction (moving direction of the focus lens group 12) on the infinity side or the closest side depending on the swing direction, and the focus speed (the focus lens group 12 Movement speed).
The movement speed increases as the operation amount increases.

The operation direction and operation amount of the seesaw switch are detected by a potentiometer 34, and an output signal (focus speed instruction signal) of the potentiometer 34 is A / A.
After being converted into a digital signal by the D converter 36
It is input to U26. The CPU 26 generates a motor control signal (speed instruction signal) for realizing the focus direction and the focus speed according to the operation of the seesaw switch based on the focus speed instruction signal output from the potentiometer 34. The motor control signal is D /
A is provided to the motor drive circuit 24 via the A converter 38,
The motor drive circuit 24 drives the motor 22 by amplifying the voltage of the input motor control signal.

Thus, when the photographer operates the seesaw switch (focus operation means), the focus lens group 12 moves according to the focus direction and the focus speed according to the operation, and focus adjustment (coarse adjustment) is performed. Will be Further, as described in detail later, the CPU 2
Reference numeral 6 denotes a just focus position (hereinafter, referred to as a focus target position) based on a focus evaluation value obtained from an image signal.
And outputs a motor control signal (position instruction signal) for moving the focus lens group 12 to the focus target position. And this motor control signal is D / A
It is provided to the motor drive circuit 24 via the converter 38, and automatically corrects the coarse adjustment position by manual operation of the cameraman to the just focus position.

Next, the means for automatic focus correction will be described. The CCD 20 shown in FIG. 1 photoelectrically converts the subject image formed on the image forming plane and inputs the image to the image pickup circuit 40 as an image signal. The imaging circuit 40 generates, for example, an NTSC video signal from the input image signal, and outputs this video signal to an external video display device 44 such as a viewfinder 42 or a monitor TV.
Output to As a result, the video being captured is displayed on the viewfinder 42 and the external video display device 44.

On the other hand, the imaging circuit 40 includes a high-pass filter (HPF) 46 for obtaining a focus evaluation value, an A / D converter 48, a focus area selection gate 50, and an adder 5.
2 are connected in order, and the imaging circuit 40 outputs a luminance signal generated from the image signal to the HPF 46, and outputs a synchronization signal in accordance with the video signal to the focus area selection gate 5.
0, output to the adder 52 and the CPU 26.

The HPF 46 extracts a high-frequency component contained in the luminance signal. The higher the sharpness of the image, the more the extracted high-frequency components are included. Therefore, by integrating the high-frequency components, the average sharpness of the image in the integration range can be quantified. And HPF
The high frequency component that has passed through 46 is converted into a digital signal by an A / D converter 48 and input to a focus area selection gate 50. The focus area selection gate 50 is a circuit for extracting only a signal corresponding to a focus area at the center on the imaging screen, and extracts only information on a subject (main subject) captured in the focus area.

The digital signal extracted by the focus area selection gate 50 is input to an adder 52, where the digital signal for one field is integrated. This integrated value is used as a focus evaluation value indicating the sharpness of the image by the CPU.
26. The CPU 26 controls the position of the focus lens group 12 and the adder 52 while the photographer manually operates the focus demand (seesaw switch).
Are recorded in a storage unit (storage means) (not shown) inside the CPU 26. When the focus operation of the cameraman is completed and the seesaw switch returns to the neutral position, the focus lens group 12 having the maximum focus evaluation value based on the position of the focus lens group 12 and the focus evaluation value recorded in the storage unit. Position P
_MAX (just focus position) is determined, and this is set as a focus target position, and the focus lens group 12 is moved to that position P.
Move to _MAX .

As a result, the focus adjustment by the manual operation of the cameraman is automatically corrected, and the focus adjustment with high accuracy is performed. Next, a focus adjustment method using a focus evaluation value will be described. FIG. 2 is an explanatory diagram showing an outline of a focus adjustment method using a focus evaluation value. The horizontal axis represents the position of the focus lens group, and the vertical axis represents the focus evaluation value. A point a to a point d shown in FIG. 4 represent a locus of the movement of the focus lens group 12 during the manual operation. At each of the positions from the point a to the point d, a focus evaluation value is detected, and the storage unit of the CPU 26 And the position of the focus lens group 12. E point indicated in the figure represents the position of the P _MAX, eventually moving the focus lens group 12 represents the position (focus target position) to stop.

FIG. 2A shows a case where the focus lens group 12 has passed the position where the focus evaluation value is maximized by manual operation. In this case, the focus lens position (points a to d) recorded in the storage unit of the CPU 26
Among them, the position (the position of the point c) where the focus evaluation value becomes the maximum is extracted, and this focus lens position is substituted for P _MAX . Then, it is determined whether or not the extracted point c is located at the end of the focus lens positions (points a to d) recorded in the storage unit of the CPU 26, and the just focus position is determined by manual operation. Is determined.

In the example shown in FIG.
Since the focus lens position (points a, b, c, and d) recorded in the storage unit of the PU 26 is not located at the extreme end (the extreme end is the point d), the just focus position is manually adjusted. It is judged that the original passed. Therefore, the extracted point c is determined to be the just focus position, and the focus lens group 12 is moved to the position of the point c (ie,
(The position of point e).

FIG. 2B shows the case where the focus evaluation value has not passed through the position where the focus evaluation value becomes maximum by manual operation. In this case, of the focus lens positions (points a to d) recorded in the storage unit of the CPU 26, the position of the point d is extracted as the position at which the focus evaluation value is maximized, and this focus lens position is substituted for P _MAX. You. However, in this case, since the point d is located at the end of the focus lens position recorded in the storage unit of the CPU 26, it is determined that the point d has not passed through the just focus position by manual operation. Therefore, the position P _{MAX at} which the focus evaluation value is truly maximum exists outside the area of points a to d, and its true maximum position (point e) is obtained by interpolation. For example, by referring to the focus lens positions and the focus evaluation values of the three points b, c, and d, the point e is obtained by Lacrangier interpolation.
Ask for.

The Lagrange's interpolation method is known and will not be described in detail in this specification.
It is possible to use the technique disclosed in JP-A-0336128. Next, the procedure of focus adjustment of the focus operating device configured as described above will be described.

FIG. 3 is a flowchart showing the flow of the processing of the CPU 26. When the focus adjustment processing is started, first, it is determined whether or not a seesaw switch as focus operation means is operated (step S10). That is, it is determined whether or not the seesaw switch has been pushed and the output voltage of the potentiometer 34 has changed.

The process of step S10 is repeated until the focus operation means is operated. When the focus operation is detected in step S10, a counter indicating the address of the storage unit in the CPU 26 is set to 0 (step S12). Then, the focus evaluation value is read from the adder 52, and the value is recorded at the address of the storage unit indicated by the counter (step S14). Next, the counter is incremented by 1 (step S16), the position of the focus lens group 12 is read, and this focus lens position is stored at the address indicated by the counter (S18).

Next, it is determined whether or not the focus operation is continued (step S20). If the focus operation is continued, the counter is incremented by 1 (step S20).
22) It is determined whether or not this counter exceeds the maximum address m (m is an odd number) of the storage unit (step S2).
4). If it exceeds the maximum address m, the counter is reset to 0 (step S26), and
Return to 14. The reason why the counter is reset to 0 is to rewrite old data into new data in order.

The processing from step S14 to step S26 is repeatedly performed while the manual operation is being performed, and is performed during the vertical blanking period. When the manual operation ends and the seesaw switch returns to the neutral position, the process shifts to step S30 by the determination processing of step S20. In step S30, the largest one among the focus evaluation values stored in the storage unit of the CPU 26 in the processing from step S14 to step S26 is detected.

When the maximum focus evaluation value is detected,
The focus lens position recorded at the address next to the address at which the maximum focus evaluation value is recorded (that is, the focus lens position when the maximum focus evaluation value is detected) is substituted for P _MAX (step S32). ), This P _MAX
It is determined whether or not the value is equal to the endmost focus lens position among the focus lens positions recorded in the storage unit of the CPU 26 (step S34).

If they are equal to each other, there is a possibility that there is a focus lens position at which the focus evaluation value becomes maximum other than the focus lens position of P _MAX. Based on the focus evaluation value, the position at which the focus evaluation value is maximum is calculated using, for example, Lagrange's interpolation method. Then, substituting the calculated focus lens position P _MAX (step S36).

[0033] Thus, when the focus lens position P _MAX that focus evaluation value is maximized is determined, switched to control mode CPU26 is moved by the position control of the focus lens group 12 (step S38), the position of the P _MAX The focus lens group 12 is moved (step S
40). Then, when it is confirmed that the focus lens group 12 is located at the _PMAX position, the control mode is returned to the control mode in which the focus lens group 12 is moved by speed control again to enable the focus operation by the seesaw switch (step S42). ). Thereafter, the process proceeds to step S1
It returns to 0 and waits until the focus operation is performed again. Thereafter, when the focus operation is performed, the above-described processing is repeatedly executed.

In the above embodiment, the case where the focus speed can be arbitrarily changed by the focus demand has been described as an example.
It is also possible to use a push button switch to directly indicate only the moving direction. That is, the moving speed is set in advance, and when one of the push buttons indicates the infinity direction, the focus lens group moves toward the infinity side at a predetermined moving speed, and the other push button indicates the closest direction. Then, it is possible to configure so that the focus lens group moves to the closest side at a predetermined moving speed.

In this case, it is not possible to change the moving speed, but if the speed at which the focus lens group passes near the just focus is constant, the peak (just focus) position of the focus evaluation value is obtained by interpolation. There is an advantage that the calculation is simplified. The CPU 26 can determine whether or not the speed at which the focus lens group 12 passes near the just focus is constant, and the interpolation calculation can be simplified according to the determination. Good.

Further, when the focus rate demand is simply constituted by two push-button switches as described above, a focus sensitivity detecting means is provided to automatically change the set speed according to the focus sensitivity. You may. That is, although not shown in FIG. 1, the focus operation device includes a unit for detecting the position (zoom position) of the variable power lens group 14 and a unit for detecting the aperture diameter (iris position) of the diaphragm 16. The CPU 26 is notified of the detected values of the zoom position and the iris position. Then, the CPU 26
From these detected values, the overall focal length f and aperture value FNo. Of the photographing optical system can be recognized, and the focus sensitivity is calculated.

In terms of specific formulas, the focal length f of the entire photographing optical system, the aperture value FNo., The focal length Ff of the movable focus group (focus lens group 12) determined by the lens characteristics, and the permissible circle of confusion. For δ, the focus sensitivity Fs is given by the following equation (1).

[0038]

Fs = β ² /2×FNo.×δ (1) where β = f / Ff. Here, β corresponds to the focal length excluding the moving focus group. The focus sensitivity Fs thus obtained has a larger value on the telephoto side, and the moving speed is set to a low speed on the telephoto side, and is set to a high speed on the wide side.

With this configuration, even when the rate demand is simply two push button switches, the focus lens group 12 moves at a low speed on the tele side and moves at a high speed on the wide side. Also, focus adjustment (coarse adjustment) by manual operation becomes easy.

[0040]

As described above, according to the television lens focus operating device according to the present invention, the rate demand for instructing the moving speed and the moving direction of the focus lens group is adopted as the focus operating means, and the focus operating means is used. Since the focus evaluation value is detected while the focus lens group is being moved by the operation of, the focus lens group is automatically moved to the focus position where the focus evaluation value becomes maximum after the focus operation is completed.
The focus lens group can be adjusted to the best image forming position without the cameraman performing accurate focus adjustment using the focus operation means.

Thus, the cameraman need only perform coarse adjustment of the focus by the focus operation means, and the operation burden on the cameraman is reduced. In particular, in the present invention, a speed control method for instructing a moving speed and a moving direction of the focus lens group is used for the focus operating means, so that the operation is further facilitated as compared with a conventional position control operating means.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a focus operation device of a television camera according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram used to explain a focus adjustment method using a focus evaluation value.

FIG. 3 is a flowchart showing a processing flow of a CPU shown in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Television lens 12 ... Focus lens group 14 ... Magnification lens group 20 ... CCD 22 ... Motor 30 ... Potentiometer 26 ... Central processing unit (CPU) 28 ... Tachometer generator 34 ... Potentiometer (focus operation means) 40 ... Imaging circuit 46 ... High-pass filter 50: Focus area selection gate 52: Adder

Claims (2)

[Claims] 1. A focus operation device for a television lens for performing focus adjustment by moving a focus lens group of a television lens by driving a motor, a focus operation means for instructing a moving direction and a moving speed of the focus lens group, and the focus Evaluation value calculation means for obtaining a focus evaluation value indicating the sharpness of a subject image based on a video signal obtained via an imaging optical system including the focus lens group and an imaging means during movement of the focus lens group by operation of an operation means Detection means for detecting the position of the focus lens group; storage means for storing the position of the focus lens group detected by the detection means; and the focus evaluation value obtained by the evaluation value calculation means for the position; Focus evaluation based on the focus lens position and the focus evaluation value stored in the means. Calculating means for obtaining a focus position at which the value becomes maximum; and controlling the motor to move the focus lens group to the focus position obtained by the calculating means after the movement of the focus lens group instructed by the focus operating means. A focus operation device for a television lens, comprising: control means; 2. A sensitivity detecting means for detecting a focus sensitivity of a television lens, and a moving speed setting for setting an instruction value of a moving speed by the focus operating means to a constant value according to the focus sensitivity detected by the sensitivity detecting means. 2. The focus operating device for a television lens according to claim 1, further comprising: means.