JP2000180695A - Focus adjusting device for image pickup lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focus adjusting device for an image pickup lens, capable of instantaneously switching the sensitivity to the low sensitivity as necessary without performing switching for the sensitivity by a special switch, by switching the sensitivity of focusing to a focus knob from the normal sensitivity to the low sensitivity by switching the operating direction of the focus knob. SOLUTION: A CPU 22 of a focus demand 8 detects the operating position of a focus knob from a potentiometer 16 and outputs a command signal to an image pickup lens 3 to move a focus lens 14 to the lens position corresponding to the operating position. When the CPU 22 detects that the operating direction of the focus knob is reversed, it reduces the moving amount of the focus lens 14 in relation to the operating amount of the focus knob and lowers the sensitivity of focusing to enable easy focusing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for adjusting the focus of a photographic lens, and more particularly to an apparatus for adjusting the focus of a photographic lens which is electrically driven by using a focus operation member such as a focus demand.

[0002]

2. Description of the Related Art A focus adjusting device for a photographing lens in a television camera or the like detects an operation position of a focus knob (focus operation member) of a focus demand operated by a cameraman, and moves the focus lens to a lens position corresponding to the operation position. Is moved by a motor. The position of the focus lens with respect to the operation position of the focus knob is moved so as to draw a control curve defining these positional relationships in advance, but is generally moved linearly. However, in recent years, in the case of a long-focus lens or when the depth of focus is small near the opening of the aperture, the response movement amount of the focus lens to the operation amount of the focus knob, that is, the sensitivity of focusing is made smaller than the standard. ,
There is a demand to make it easy to focus, and instead of simply making the control curve a straight line with a fixed slope, various control methods such as switching the slope according to the situation, devising the shape of the control curve, etc. Proposed. Incidentally, Japanese Patent Application Laid-Open No. 4-285920 discloses a device in which the focusing sensitivity is reduced as necessary to facilitate focusing.

[0003]

However, the focus control proposed in the prior art requires an operation for switching the focus sensitivity and an operation for setting an operation range of the focus knob which has a low sensitivity. It is difficult to cope with the case where it is necessary to instantly lower the focus sensitivity in a situation where there is no rehearsal.

The present invention has been made in view of such circumstances, and a photographing lens which can instantaneously switch to low sensitivity as needed without performing switching operation of a focusing sensitivity by a special switch or the like. It is an object to provide a focus adjustment device.

[0005]

According to the present invention, in order to achieve the above object, a focus adjustment of a photographing lens is performed by moving a focus lens to a position along a predetermined control curve with respect to an operation position of a focus operation member. In the apparatus, the predetermined control curve includes a control curve of a standard sensitivity and a low-sensitivity control curve having a smaller change rate than the control curve of the standard sensitivity, and the focus lens is moved along the control curve of the standard sensitivity. When the operation position of the focus operation member changes in the opposite direction when the focus lens is moved in a fixed direction, the focus lens is moved along the low-sensitivity control curve.

According to the present invention, the focusing sensitivity can be instantaneously switched from standard to low by simply reversing the operation direction of the focus operation member without performing a switching operation by a special switch or the like. become.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a focus adjusting device for a photographic lens according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is an overall view of a television camera system showing an example of use of a focus demand (focus operation device) to which the present invention is applied. As shown in FIG. 1, the television camera 1 includes a camera body 2 and a photographing lens 3, and is supported by a camera platform 5 on a pedestal dolly 4. Two operation rods 6A and 6B extend from the camera platform 5, and a zoom demand 7 for operating a zoom speed and a focus demand 8 for operating a focus are attached to ends of the operation rods 6A and 6B, respectively. . In addition, these zoom demand 7 and focus demand 8
Is connected to the photographing lens 3 via a cable.

The focus demand 8 is provided with a rotatable focus knob 9 operated by a cameraman, and a focus position command signal corresponding to the operation position is applied to the photographing lens 3 via a cable. I have. FIG. 2 is a block diagram showing a main configuration of the focus demand 8 and the photographing lens 3. The operating position of the focus knob 9 is detected by the potentiometer 16 of the focus demand 8 shown in FIG. The voltage signal output from the potentiometer 16 is supplied to the A / D converter 20 of the one-chip CPU 18.
After being converted into a digital signal by the A / D converter 20, the digital signal is input to the CPU 22 of the one-chip CPU 18.

On the other hand, the photographing lens 3 is provided with a potentiometer 24 for detecting the position of the zoom lens (zoom position) and a potentiometer 26 for detecting the position of the iris (iris position). The CPU 22 has these potentiometers. Voltage signals indicating the zoom position and the iris position are input from 24 and 26 via the A / D converter 20. The photographing lens 3 includes a photographing lens 3.
A lens code switch 28 for setting the optical specifications of the lens code as a lens code is provided.
The data is read by the I / O interface 30 of the one-chip CPU 18 and input to the CPU 22.

The CPU 22 determines a target position to which the focus lens 14 should be moved (hereinafter, referred to as a movement position) based on information such as the operation position, the zoom position, and the iris position of the focus knob 9 acquired as described above. It is determined by processing described later, and outputs a focus position command signal indicating the movement position to the motor driver 36 of the photographing lens 3 via the D / A converter 32 and the amplifier 34. Thereby, the focus drive motor 38 is driven based on the focus position command signal, and the focus lens 14 is moved to the moving position indicated by the focus position command signal.

Next, the principle of the focus control of the CPU 22 will be described. FIG. 3 shows the relationship between the voltage (input value x) of the potentiometer 16 input to the CPU 22 and C
Focus lens 1 that PU 22 outputs to photographing lens 3
4 is a diagram illustrating a relationship between an output value y indicating a movement position of No. 4 and a control curve (straight line) illustrating a movement position of the focus lens 14 with respect to an operation position of the focus knob 9. FIG.

As shown in FIG. 1, the control curve represented by the relationship between the input value x and the output value y of the CPU 22 includes a straight line m, a straight line n, and a line segment AB. Usually, the control curve is represented by a single straight line or a curve, but in the present invention, a plurality of control curves (straight line m, straight line n, line segment AB) are used, and these straight lines are used depending on the situation. Are used properly.

A straight line m shown in FIG. 1 is a control curve mainly used when the focus knob 9 is operated in a direction in which the input value x decreases, and has a slope a passing through the origin O (0, 0). As a straight line, it is represented by the following equation: y = ax. The straight line n is a control straight line mainly used when the focus knob 9 is operated in a direction in which the input value x increases, and a point P _max (x _max , at which the input value x and the output value y become _maximum) . y _max ) is represented by the following equation: y = ax−b. The straight line m and the straight line n have the same inclination, and these straight lines m and n are used when the focus lens 14 is controlled with a standard focus sensitivity with respect to the operation of the focus knob 9. Note that the straight lines m and n are not necessarily straight lines, and may be curves indicating a standard control curve.

On the other hand, when the operation direction of the focus knob 9 is switched, the line segment AB is an input / output point from the straight line m to the straight line n or from the straight line n to the straight line m (CPU 2).
2 is a line used when the point on the control curve indicating the position of the output value y that is actually output with respect to the input value x is shifted, and this line segment AB is expressed by the following equation: y = Cx + d. The value of d is obtained as a value such that the line segment AB passes through the input / output point, and the end points A and B of the line segment AB are obtained.
Is a straight line m as the input / output point moves along the straight lines m and n.
n. Therefore, the input / output point that has moved in one direction on the straight line m or the straight line n moves on the line segment AB at the same time when the operation direction of the focus knob 9 is switched, and moves on the line segment AB. To the other straight line.

The slope c of the line segment AB is set to a value smaller than the slope a of the straight lines m and n. Therefore, this line segment A-
When the focus lens 14 is controlled according to B, the response movement amount of the focus lens 14 to the operation amount of the focus knob 9 is small, and the sensitivity of focusing is lower than the standard sensitivity. That is, the CPU 22
According to the focus control described above, the sensitivity of focusing can be reduced only by switching the operation direction of the focus knob 9 without performing a sensitivity switching operation by a special switch operation or the like. For example, the photographer operates the focus knob 9 slightly beyond the position where the focus is assumed to be in focus, and switches the focus sensitivity from the standard to a lower sensitivity by reversing the operation direction of the focus knob 9 at that position. By this switching, accurate focusing can be easily performed.

Although the details will be described later, the focusing sensitivity in the line segment AB changes depending on changes in the zoom position and the iris position of the photographing lens 3 when the inclination c is constant. In order to keep the focusing sensitivity at −B constant regardless of the situation, the value of the slope c of the line segment AB is appropriately changed based on the zoom position and the iris position.

Next, the control curves (straight lines m and n, line segment A)
When the focus control of the CPU 22 using -B) is specifically described, it is now assumed that the input / output point P is on a straight line n as shown in FIG. If so, the CPU 22 outputs an output value y according to the straight line n. That is, the input / output point P
Output an output value y such that moves on a straight line n. Further, as the input / output point P moves on the straight line n, the CPU 22 moves the point A of the line segment AB to coincide with the input / output point P. Assuming that the zoom position and the iris position of the taking lens 3 do not change, the inclination c of the line segment AB is constant, so that the point B of the line segment AB moves along the straight line m as the point A of the line segment AB moves. Is moved by the same distance as point A. Next, when the input / output point P reaches an arbitrary point P1 on the straight line n shown in the figure, the rotation direction of the focus knob 9 is reversed, and the input value x
Is changed in a decreasing direction. At this time, CPU2
2 outputs the output value y so that the input / output point P moves not on the straight line n but on the line segment AB as shown in FIG. That is, when the furcus knob 9 is switched from a direction in which the input value x is increased to a direction in which the input value x is decreased, the focusing sensitivity is switched from a standard one to a low one. This allows the cameraman to perform focusing with low sensitivity.

Next, in FIG. 5, the input value x is represented by a line segment A.
If it decreases beyond the intersection B between -B and the straight line m, then C
After the input / output point P reaches the point B, the PU 22 outputs the output value y such that the input / output point P moves along the straight line m as shown in FIG. That is, when the focus knob 9 is operated by a predetermined amount in a state where the focusing sensitivity is low, the sensitivity is automatically switched to the standard sensitivity to control the focus lens 14 thereafter.

As shown in FIG. 5, the input / output point P is a line segment AB.
When the input value x is switched in a direction of increasing in the upper state, as shown in FIG.
Outputs an output value y so that the input / output point P moves on the line segment AB, and outputs an output value y so that the input / output point P moves on the straight line n after the input / output point P reaches the point A. . The above description shows the control in the case where the input / output point P is moved on the straight line n in the direction in which the input value x increases, and is switched to the direction in which the input value x decreases. When the output point P moves on the straight line m in the direction in which the input value x decreases, the control when switching to the direction in which the input value x increases is performed in exactly the same manner. For example, assuming that the input / output point P is on the straight line m as shown in FIG.
Outputs an output value y such that moves on a straight line m. Further, as the input / output point P moves on the straight line m, the CPU 22 moves the point B of the line segment AB so as to coincide with the input / output point P (the point A also moves). . If the rotation direction of the focus knob 9 is reversed when the input / output point P reaches an arbitrary point P2 on the straight line m shown in FIG.
Outputs an output value y such that the input / output point P moves not on the straight line m but on the line segment AB as shown in FIG. That is, when the focus knob 9 is switched from the direction in which the input value x is decreased to the direction in which the input value x is increased, the focusing sensitivity is switched from the standard one to the low one in the same manner as described above. This allows the cameraman to perform focusing with low sensitivity.

Next, a method of calculating the slope c of the line segment AB will be described. The symbols used below are defined as follows. f: focal length of the entire lens system fp: focal length of the moving focus group β: imaging magnification by the lens system excluding the moving focus group δ ′: minimum confusion circle diameter FN: aperture value (F number) Defocus amount by the focus group The relationship between (Δx) and the defocus amount (Δ′x) on the image forming side is represented by the following equation: Δ′x = β ² Δx (1)

On the other hand, the depth of focus S is given by the following equation: S = FN.δ '(2) From these equations (1) and (2), the defocus amount (Δx) when the defocus amount (Δ′x) on the imaging side is equal to the depth of focus S is given by the following equation: Δx = (1 / β ²⁾ ) · FN · δ ′ = (fp / f) ² · FN · δ ′ (3) (∵f = fp · β) In the equation (3), fp and δ 'can be specified by the lens code obtained from the lens code switch 28 shown in FIG. 2, and f and FN are the zoom position and the iris position from the photographing lens 3. Information can be obtained. Therefore, the defocus amount (Δ
x), that is, the position error of the focus lens that can be determined to be in focus can be obtained by equation (3).

The inclination c of the line segment AB, that is, the focusing sensitivity, must be reduced as the position error of the focus lens which can be determined to be in focus is smaller. Therefore, the slope c
Is calculated by the following equation, where k is a constant, and c = k · (Δx) (4). Note that the slope c may be set by another formula or another method.

FIG. 9 is a flowchart showing the processing procedure of the CPU 22. First, the CPU 22 reads the operation position of the focus knob 9 (step S1).
0), the sensitivity condition is read (step S12). The sensitivity condition is a condition for determining the inclination c of the line segment AB, and includes information on the optical specifications of the photographing lens 3 read from the lens code switch 28, the potentiometer 24,
26, and information on the zoom position and the iris position. Then, from this sensitivity condition, the above equations (3) and (4)
Is used to determine the equation of line segment AB (step S1)
4). Note that the equation of the initial line segment AB obtained here is determined such that the output point y is the middle point of the line segment AB when the operation position acquired in step S10 is the input value x.

Next, the operation position of the focus knob 9 is read again (step S14), and the input value x read here is operated beyond the point A with respect to the middle point on the line segment AB. That is, it is determined whether or not the input value x is larger than the x coordinate value of the point A (step S16). If the determination is YES here, the output value y is calculated using the equation of the straight line n (step S18), and the line segment AB is moved so that the current input / output point P and the point A coincide with each other (step S18). Step S
20).

On the other hand, if NO is determined in the step S16, it is determined whether or not the input value x read in the step S14 has been operated beyond the point B, that is, the input value x is smaller than the x coordinate value of the point B. It is determined whether or not (step S22).
If the determination is YES, the output value y is calculated using the equation of the straight line m (step S24), and the line segment AB is moved so that the current input / output point P and the point B match (step S2).
6).

If NO is determined in step S22, the output value y is calculated by the equation of line segment AB (step S2).
8). When the output value y is calculated for the input value x as described above, the CPU 22 outputs the output value y to the lens device 12 as a focus position command signal. Then CP
U22 reads the sensitivity condition from the photographing lens 3 and determines whether or not the sensitivity condition has been changed (step S3).
0), if NO, do not change the slope c of line segment AB,
On the other hand, if YES, the gradient c of the line segment AB is determined based on the changed sensitivity condition, and the equation of the line segment AB is calculated so as to pass through the current input / output point P.

When the above processing is completed, step S
Returning to step 16, the above processing is repeatedly executed. Thus, the processing shown in FIGS. 3 to 9 is performed. As described above, in the above-described embodiment, the focus control is executed by the CPU 22 of the focus demand 8. However, the CPU may be mounted on the photographic lens 3 and performed by the photographic lens 3.

Further, in the above embodiment, the slope a is set to a fixed value for the straight lines m and n which are the control curves of the standard sensitivity, but may be changed according to the situation.

[0029]

As described above, according to the photographing lens focus adjusting apparatus of the present invention, when the moving direction of the focus lens is reversed, the control of the focus lens by the control curve of the standard sensitivity is changed to the control curve of the low sensitivity. By switching to control of the focus lens, it is possible to instantaneously switch the focus sensitivity from standard to low sensitivity simply by reversing the operation direction of the focus operation member without performing a switching operation with a special switch etc. Focusing can be performed.

[Brief description of the drawings]

FIG. 1 is an overall view of a television camera system showing an example of use of a focus demand to which the present invention is applied.

FIG. 2 is a block diagram showing a main configuration of the focus demand and the photographing lens.

FIG. 3 is a diagram of a control curve showing a movement position of a focus lens with respect to an operation position of a focus knob.

FIG. 4 is an explanatory diagram used for explaining focus control by a CPU;

FIG. 5 is an explanatory diagram used for explaining focus control by a CPU;

FIG. 6 is an explanatory diagram used for explaining focus control by a CPU;

FIG. 7 is an explanatory diagram used for explaining focus control by a CPU;

FIG. 8 is an explanatory diagram used for explaining focus control by a CPU;

FIG. 9 is a flowchart illustrating a processing procedure of a CPU;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... TV camera 2 ... Camera body 3 ... Shooting lens 8 ... Focus demand 9 ... Focus knob 14 ... Focus lens 16 ... Potentiometer 22 ... CPU

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 5/232

Claims (3)

[Claims] 1. A focus adjusting device for a photographing lens for moving a focus lens to a position along a predetermined control curve with respect to an operation position of a focus operation member, wherein the predetermined control curve is a control curve of a standard sensitivity. And a low-sensitivity control curve having a smaller rate of change than the standard sensitivity control curve. In the case where the focus lens is moved in a certain direction along the standard sensitivity control curve, When the operation position changes in the opposite direction, the focus lens is moved along the low-sensitivity control curve. 2. The photographing apparatus according to claim 1, wherein when the focus lens is moved in a predetermined direction along the low-sensitivity control curve by a predetermined amount, the focus lens is moved along a standard control curve. Lens focus adjustment device. 3. The focus adjusting device for a photographing lens according to claim 1, wherein the rate of change of the low-sensitivity control curve is changed based on at least one of a zoom position and an aperture position.