JPH07143395A - Automatic diaphragm device of video camera - Google Patents

Abstract

PURPOSE:To improve various characteristics such as a response characteristic, etc., in the automatic diaphragm device of the video camera. CONSTITUTION:When a detection output SPOS of a detector 33 is showing a fact that a diaphragm value is smaller than a prescribed value being near the maximum value, it is permitted that a signal SCTL supplied to a drive means 5 becomes a level corresponding to a value ranging from the minimum value to the maximum value of the diaphragm. When the detection output SPOS of the detecting element 33 is showing a fact that the diaphragm value is above the prescribed value being near the maximum value, it is inhibited that the signal SCTL supplied to the drive means 5 exceeds the level corresponding to the prescribed value of the diaphragm value. Or based on the present diaphragm value detected by the detecting element 33 as a reference, the signal SCTL supplied to the drive means 5 is derived. Or the detector 33 measures the time required for detecting a unit variation of the diaphragm value. From this measured time, a variation speed of the diaphragm is derived, and also, this variation speed is limited.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic diaphragm device for video cameras.

[0002]

2. Description of the Related Art In a video camera, an aperture value (F value)
To adjust automatically, 1. Adjust the video signal level obtained by processing the imaging output,
The diaphragm control signal SCTL is formed by comparison with the reference level. 2. The diaphragm control signal SCTL controls the diaphragm mechanism. 3. At this time, the diaphragm mechanism is feedback-controlled so that the deviation (error) between the video signal level and the reference level becomes zero. Is being processed.

[0003]

By the way, when the above feedback control is performed, the following three problems occur.

That is, first, the aperture mechanism is a first-order lag element. For example, as shown in FIG. 6, when the aperture value indicated by the aperture control signal SCTL changes as shown by the solid line, the aperture of the aperture mechanism is changed. The value changes as shown by the broken line. That is, the larger the difference between the aperture value before change and the target aperture value indicated by the aperture control signal SCTL, the faster the aperture value of the aperture mechanism changes.

Therefore, in order to improve the response speed of the automatic diaphragm device, for example, as shown in FIG.
When the aperture control signal SCTL (shown by the solid line) is changed as much as possible from the aperture value before the change, and when the aperture value (shown by the broken line) of the aperture mechanism changes to near the target aperture value, you can return it to the target aperture value That would be good.

However, when changing the aperture value by rotating the aperture ring of the aperture mechanism, in general, the change amount of the aperture value with respect to the rotation angle of the aperture ring becomes larger as the aperture value increases.
Therefore, the change amount of the aperture value with respect to the aperture control signal SCTL increases as the aperture value increases. Therefore, when the aperture value is large, the aperture control signal SCTL
Changes in the video signal level due to changes in
Aperture control may become unstable near the maximum aperture value, for example, when the aperture value is 16 (F16) or more.

Therefore, in an actual automatic diaphragm device,
As shown in FIG. 8, even if the aperture value can be increased to, for example, a value of 16 or more by changing the aperture control signal SCTL, the change range of the aperture control signal SCTL is limited to set the automatic aperture control range to the value 16. Is limited to.

However, if such a limitation is made, when the aperture value is changed from the opening direction to the vicinity of the limitation value 16, FIG.
As described above, even if the aperture control signal SCTL is changed as much as possible from the aperture value before the change to improve the response speed, the aperture control signal SCTL is limited as shown in FIG. As a result, the response speed becomes slow.

Secondly, in the above feedback system, the aperture control signal SCTL is determined by the process of amplifying the deviation and the process of matching the video signal to the signal standard. LD: Reference level and video signal Deviation from the level.

LD = reference level-level of video signal GA: gain when amplifying deviation LD DC: intercept Assuming that the aperture control signal SCTL is an offset (fixed value), SCTL = LD × GA + DC (1)

In the case of the equation (1), the deviation LD in the steady state becomes large unless the gain GA is set sufficiently large. Further, when the diaphragm control signal SCTL converges while maintaining the difference from the intercept DC, a deviation obtained by dividing the difference by the gain GA is necessary.

Therefore, in order to reduce the deviation LD in the steady state, it is necessary to set the gain GA sufficiently large and set the intercept DC to the center value of the change range of the diaphragm control signal SCTL.

However, if the gain GA is increased, the system may become unstable and may diverge or vibrate. Therefore, there is a limit to increasing the gain GA. Even if the intercept DC is set to the center value, the aperture control signal SCTL
The deviation LD becomes large when is away from the central value.

Thirdly, in the feedback system as described above, if the changing speed of the aperture value of the aperture mechanism becomes too fast, vibration will occur. Therefore, in the above feedback system, the rotation speed of the diaphragm ring of the diaphragm mechanism is detected so that the speed of change of the diaphragm value does not become faster than necessary, and this is detected.
Need to return to CTL.

In order to detect the rotation speed of the aperture ring, it is common to find the rotation angle of the aperture ring per unit time. However, if this is performed by digital processing, the rotation angle of the aperture ring per unit time is small, so the rotation speed cannot be accurately detected unless the quantization level (resolution) during A / D conversion is reduced. . Therefore, an A / D converter having a large number of bits, for example, 10 bits or more is required.

The present invention is intended to solve the above problems.

[0017]

Therefore, in the present invention, when the reference numerals of the respective parts correspond to the embodiments described later, the driving means 5 for driving the diaphragm mechanism 2 of the video camera to control the diaphragm value. , A detection element 33 for detecting an aperture value,
It has a detection circuit 31 for processing a video signal of a video camera and detecting the signal level thereof, compares the detection output SDET of the detection circuit 31 with a reference level, and outputs this comparison output SCTL.
Is supplied to the driving means 5 to control the aperture value by feedback control so that the signal level becomes equal to the reference level. Then, if the aperture value is smaller than a predetermined value close to the maximum value,
When the detection output SPOS of the detection element 33 indicates,
The signal SCTL supplied to the driving means 5 is allowed to have a level corresponding to any value from the minimum value to the maximum value of the aperture value, and the aperture value is equal to or more than a predetermined value close to the maximum value. When the detection output SPOS of the detection element 33 indicates, the signal SCTL supplied to the driving means 5 is prohibited from exceeding the level corresponding to the predetermined aperture value. Alternatively, the signal SCTL supplied to the driving means 5 is obtained based on the current aperture value detected by the detection element 33. Alternatively, the detecting element 33 measures the time required to detect the unit change amount of the aperture value, obtains the changing speed of the aperture value from the measured time, and limits the changing speed. Is.

[0018]

The diaphragm control signal SCTL is limited only when the diaphragm value of the diaphragm mechanism 2 is larger than a predetermined value. In other cases,
The diaphragm control signal SCTL is not limited. In addition, the diaphragm mechanism 2
With reference to the current aperture value of, the deviation DC is processed as a relative value from the reference value. Further, the change rate of the aperture value can be obtained from the time required for the aperture value of the aperture mechanism 2 to change by a unit amount.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, 1 is an image pickup lens, 2 is a diaphragm mechanism, and 3R to 3B are CCD image pickup elements. Then, an image of a subject (not shown) is taken by the lens 1 and is separated into three primary color lights of red, green, and blue, and these three primary color lights are respectively supplied to the elements 3R to 3B, and red, green, and Converted to the three primary color signals of blue.

Further, the diaphragm mechanism 2 is provided on the optical path of the lens 1, and a driving motor 5 is rotatably coupled to the diaphragm ring 4. When the diaphragm control signal SCTL is supplied to the motor 5, the diaphragm ring 2 is rotationally driven by the motor 5, and the diaphragm value of the diaphragm mechanism 2 corresponds to the level of the diaphragm control signal SCTL as shown in FIG. 5, for example. It can be set to the specified value.

Further, 10R indicates a red signal processing circuit. That is, the red signal from the image pickup device 3R is sequentially supplied to the correlated double sampling circuit 11 and the trap circuit 12, the noise component peculiar to the CCD image pickup device is removed, and the red signal from which the noise component is removed is amplified. 1
3 and the sensitivity is adjusted.

Then, the red signal from the amplifier 13 is supplied to the analog signal processing circuit 14 to be subjected to processing such as shading correction, gain up, and clamp, and the red signal subjected to these processing is a low pass filter. A / D after unnecessary high frequency components are removed by 15
It is supplied to the converter 16 and converted into a digital red signal.

Then, this digital red signal is supplied to the digital signal processing circuit 17 and linear matrix,
Processing such as adding detail signals, adding pedestals, gamma correction, knee correction, and white clip is performed.
The digital red signal that has undergone these processes is the NTSC
It is supplied to the encoder circuit 21.

Reference numerals 10G and 10B denote a green signal processing circuit and a blue signal processing circuit. Since these processing circuits 10G and 10B have the same configuration as the processing circuit 10R, details thereof will be omitted. The green signal and the digital blue signal are extracted, and these signals are supplied to the encoder circuit 21.

Then, in the encoder circuit 21, the digital three primary color signals supplied thereto are converted into digital NT signals.
The video signal is encoded into an SC composite video signal, supplied to the D / A converter 22 and converted into an analog NTSC composite video signal, and this video signal is supplied to the low pass filter 23 to remove unnecessary high frequency components. And then taken out as camera output.

Further, in order to realize the automatic diaphragm function, it is constructed as follows. That is, the processing circuits 10R to 10R
The digital three primary color signals from the B A / D converters 16 to 16 are supplied to the detection circuit 31. This detection circuit 31
, A color signal (sample) having the maximum level is selected for each sample of the three primary color signals supplied thereto, and a signal indicating the peak level of the selection result and a signal indicating the average level are selected. Are added at a predetermined ratio, and the added signal is the detection signal S of the level of the video signal.
It is taken out as DET.

Then, the detection signal SDET is supplied to the microcomputer 32 for system control. Further, the diaphragm ring 4 is provided with a detection element 33 for detecting the rotational angle position of the diaphragm ring 4,
5, the aperture value detection signal SPOS in the direction in which the level increases as the aperture value of the aperture mechanism 2 decreases, is supplied to the microcomputer 32, as shown in FIG.

When the detection signal SPOS is supplied to the microcomputer 32, since the detection signal SPOS is an analog signal, it is A / D converted by an A / D converter (not shown) built in the microcomputer 32. To microcomputer 3
Taken in 2.

Then, in the microcomputer 32, for example, the routines 100 and 200 shown in FIGS. 2 and 3 are executed to form the aperture control signal SCTL, and the aperture control signal SC
TL is supplied to the motor 5 to realize the automatic diaphragm function.

The microcomputer 32 executes various processes in parallel, but here, for simplicity, the parts relating to the automatic diaphragm process are shown independently as routines 100 and 200, respectively. Further, in the following description, the aperture value of the aperture mechanism 2 and its aperture value detection signal SPOS
Therefore, even if the aperture mechanism 2 is controlled by the motor 5 to change the aperture value, the aperture value detection signal SPOS correctly detects the aperture value. And

Then, in the routine 100, the automatic aperture processing is executed as follows. That is, in step 101, the detection signal SDET of the level of the video signal is detected.
Is taken into the microcomputer 32, and the aperture value detection signal SPOS from the detecting element 6 is taken into the microcomputer 32. Next, in step 102, the aperture control signal SCT
L is calculated. However, at this time, the aperture control signal SCTL
Is formed according to equation (1), the aperture value detection signal SPOS captured in step 101 is used as the intercept DC of equation (1).

Subsequently, at step 103, the aperture value indicated by the aperture value detection signal SPOS fetched at step 101 is compared with a limit value of the automatic aperture, for example, a value of 16, and SPO
If S <16, the process proceeds from step 103 to step 106, where the aperture control signal SCTL calculated in step 102 is supplied to the motor 5. Then, after that, the process returns to step 101, and thereafter, step 101 and subsequent steps are repeated.

Therefore, when the (first) aperture value before change is smaller than the automatic aperture limit value 16 (when SPOS <16), for example, as shown in FIG. The aperture ring 4 of the aperture mechanism 2 is rotationally driven so that the aperture value indicated by the signal SCTL is obtained.

Thus, when the aperture value before change is smaller than the automatic aperture limit value 16, the aperture value of the aperture mechanism 2 changes to the target value at high speed.

However, in step 103, when the aperture value indicated by the aperture value detection signal SPOS detected in step 101 and the automatic aperture limit value 16 are SPOS ≧ 16,
The process proceeds from step 103 to step 104. Then, in this step 104, the aperture control signal SCTL calculated in step 102 is compared with the automatic aperture limit value 16, and if SCTL <16, the process proceeds to step 104.
To step 106.

Therefore, even if the aperture value before change is larger than the automatic aperture limit value 16 (SPOS ≧ 16), if the target value indicated by the aperture control signal SCTL is smaller than the automatic aperture limit value 16, Again, the aperture value of the aperture mechanism 2 is set to the target aperture value at high speed.

However, in step 104, when the aperture control signal SCTL calculated in step 102 and the automatic aperture limit value 16 are SCTL ≧ 16, the process proceeds from step 104 to step 106. Then, in step 105, the aperture control signal SCTL is set to a level corresponding to the automatic aperture limit value 16 (SCTL = 16), and then the process proceeds to step 106.

Therefore, the aperture value before change is greater than the automatic aperture limit value 16 (SPOS ≧ 16), and the target value indicated by the aperture control signal SCTL before change is the automatic aperture limit value 16
If it is larger than (SCTL ≧ 16), the aperture control signal SC
The TL is limited to the level corresponding to the value 16, and the automatic throttling is performed.

On the other hand, in the routine 200, in step 201, the aperture value detection signal S from the detection element 6 is detected.
POS is taken into the microcomputer 32, and then step 202
In step 201, the change of the aperture detection signal defined by ΔSPOS = SPOS−SMEM from the aperture value detection signal SPOS fetched in step 201 and the aperture value detection signal SMEM fetched one field before and stored in the memory. The amount ΔSPOS, that is, the signal ΔSPOS indicating the amount of change in the aperture value of the aperture mechanism 2 in one field period is calculated.

Subsequently, the process proceeds to step 203, and in this step 203, with respect to the change amount ΔSPOS of the aperture detection signal SPOS obtained in step 202, | ΔSPOS |> STH (2) STH: a predetermined value When the comparison represented by the threshold level is performed and the expression (2) is satisfied, that is, the change ΔSPOS of the aperture value of the aperture mechanism 2 is a predetermined value STH (the value STH is, for example, the signal SPOS, 32
Is larger than the (quantization level when A / D converted and captured), the process proceeds from step 203 to step 2
Go to 04.

Then, in this step 204, a value Δ represented by Δ = ΔSPOS / N · GB (3) is calculated, and this value Δ is calculated as the aperture control signal S.
Subtracted from CTL.

In this case, the value N indicates the number of field periods in which the expression (2) is not satisfied, and is a time parameter, as will be apparent from the following. Further, the value GB indicates the feedback rate in the feedback system of the routine 200.

Therefore, in the equation (3), ΔSPOS / N = unit change amount of aperture value / (1 field period × number of times of sampling) = rate of change of aperture value. Further, the value Δ is a speed control variable.

Then, the process proceeds to step 205, where N = 1 is initialized in step 205, and subsequently in step 206, the aperture value detection signal SPOS captured in step 201 is changed to step 20.
It is stored in memory as the value SMEM when 2 is executed.

Then, after that, in step 207, for example, by waiting until the vertical synchronizing signal is supplied, waiting for one field period is performed, and when one field period has elapsed, the process returns to step 201.

If the expression (2) is not satisfied in step 203, that is, if the change ΔSPOS of the aperture value of the aperture mechanism 2 is smaller than the predetermined value STH, the process proceeds from step 203 to step 208. move on.

Then, in this step 208, the speed control variable Δ represented by Δ = Δ / 2 · GB (4) is calculated, and this variable Δ is subtracted from the throttle control signal SCTL.

In this case, the purpose of halving the variable Δ is to define the time variation of the feedback amount. That is, when it is determined in step 203 that the aperture value of the aperture mechanism 2 has changed (when the expression (2) is satisfied), in step 204, if the speed control signal Δ is merely fed back, the signal Δ changes in time. It becomes an irregular signal. Therefore, in order to make the signal Δ apparently a regular signal in time, in this example, the processing of equation (4) is performed in step 208.

Then, following step 208, the process proceeds to step 209, in which step 209
The value N is incremented by "1", and then the process proceeds to step 209.

Therefore, when step 204 is executed, the value N indicates the number of field periods in which the equation (2) is not satisfied.

In this way, the changing speed of the aperture value of the aperture mechanism 2 is detected and the detected output Δ is fed back to the aperture control signal SCTL, so that the changing speed of the aperture value of the aperture mechanism 2 becomes too fast and vibration occurs. There is no such thing.

As described above, according to this automatic diaphragm device, when the diaphragm value of the diaphragm mechanism 2 does not exceed the limit value 16, the minimum diaphragm value of the diaphragm mechanism 2 is set as the diaphragm control signal SCTL ( Since any value from the open value) to the maximum value is permitted, the response speed of the diaphragm mechanism 2 can be improved.

Further, when the aperture value exceeds the limit value 16 of the automatic aperture, the value indicated by the aperture control signal SCTL is prevented from exceeding the limit value 16, so that the aperture control becomes unstable. There is no.

Further, when the aperture control signal SCTL is calculated according to the equation (1) in step 102, the aperture value detection signal SPOS fetched in step 101 is used as the intercept DC of the equation (1). The deviation LD is processed as a relative value from the current diaphragm value of the diaphragm mechanism 2 as a reference. As a result, when the aperture value of the aperture mechanism 2 converges to the target value, the aperture control signal S
Since CTL becomes equal to the intercept DC (SCTL = DC), the deviation LD becomes 0 at this time. That is, the steady deviation LD can be made zero.

Further, in order to prevent vibration from occurring due to the aperture value changing speed of the aperture mechanism 2 becoming too fast, it is necessary to detect the aperture value changing speed.
The time until the change in the aperture value can be detected is measured, and the changing speed of the aperture value is obtained from the measured time. Therefore, the microcomputer 32 uses the aperture value detection signal SPOS.
As an A / D converter for A / D conversion of, it is possible to use, for example, an 8-bit A / D converter with a small number of bits. Moreover, the changing speed of the aperture value can be accurately detected.

[0056]

According to the present invention, when the aperture value of the aperture mechanism 2 does not exceed the limit value, the aperture control signal SCTL
Since any value from the minimum value (open value) to the maximum value of the aperture value of the aperture mechanism 2 is permitted, the response speed of the aperture mechanism 2 can be improved.

However, when the aperture value exceeds the limit value, the aperture control signal SCTL is set so as not to exceed the limit value, so that the aperture control does not become unstable.

Further, according to the equation (1), the diaphragm control signal SC
Since the aperture value detection signal SPOS is used as the intercept DC of the equation (1) when calculating TL, when the aperture value of the aperture mechanism 2 converges to the target value, the aperture control signal SPOS is always used.
CTL becomes equal to the intercept DC, and the steady deviation LD can be made zero.

Further, the time until the change in the aperture value of the aperture mechanism 2 can be detected is measured, and the speed of change of the aperture value is obtained from this measured time. Therefore, the aperture value detection signal SPOS is A / An A / D converter with a small number of bits can be used for D conversion.
Moreover, the changing speed of the aperture value can be accurately detected.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of the present invention.

FIG. 2 is a flowchart showing an example of the present invention.

FIG. 3 is a flowchart showing another example of the present invention.

FIG. 4 is a diagram for explaining the present invention.

FIG. 5 is a characteristic diagram for explaining the present invention.

FIG. 6 is a diagram for explaining the present invention.

FIG. 7 is a diagram for explaining the present invention.

FIG. 8 is a characteristic diagram for explaining the present invention.

FIG. 9 is a diagram for explaining the present invention.

[Explanation of symbols]

 1 Imaging Lens 2 Aperture Mechanism 3R-3B CCD Imaging Device 5 Aperture Ring Drive Motor 10R Red Signal Processing Circuit 10G Green Signal Processing Circuit 10B Blue Signal Processing Circuit 21 NTSC Encoder Circuit 22 D / A Converter 31 Level Detection Circuit 32 Microcomputer 33 Aperture value detector

Claims (3)

[Claims] 1. A drive unit for driving an aperture mechanism of a video camera to control an aperture value, a detection element for detecting the aperture value, and a detection unit for processing a video signal of the video camera to detect its signal level. A circuit for comparing the detection output of the detection circuit with a reference level, and supplying the comparison output to the driving means to adjust the aperture value so that the signal level becomes equal to the reference level. In the automatic diaphragm device of the video camera, which is configured to perform feedback control, if the diaphragm value is smaller than a predetermined value close to the maximum value,
When the detection output of the detection element indicates, the signal supplied to the driving means is allowed to have a level corresponding to any value from the minimum value to the maximum value of the aperture value. Is greater than or equal to a predetermined value close to the maximum value, when the detection output of the detection element indicates that the signal supplied to the drive means exceeds a level corresponding to the predetermined value of the aperture value. An automatic iris device for video cameras that is prohibited. 2. A driving means for driving an aperture mechanism of a video camera to control an aperture value, a detection element for detecting the aperture value, and a detection device for processing a video signal of the video camera to detect its signal level. A circuit for comparing the detection output of the detection circuit with a reference level, and supplying the comparison output to the driving means to adjust the aperture value so that the signal level becomes equal to the reference level. An automatic diaphragm device for a video camera, wherein feedback control is performed, wherein a signal supplied to the driving means is obtained based on the current diaphragm value detected by the detection element. 3. A driving means for driving an aperture mechanism of a video camera to control an aperture value, a detection element for detecting the aperture value, and a detection device for processing a video signal of the video camera to detect its signal level. A circuit for comparing the detection output of the detection circuit with a reference level, and supplying the comparison output to the driving means to adjust the aperture value so that the signal level becomes equal to the reference level. In the automatic diaphragm device of a video camera that is feedback-controlled, the detection element measures the time required to detect the unit change amount of the diaphragm value, and from the measured time, the changing speed of the diaphragm value. The automatic diaphragm device for video cameras that seeks to limit the speed of change.