JPH02266769A - Exposure controller - Google Patents

Abstract

PURPOSE:To stably control an aperture with a smooth operation by providing a correcting system which has the opposite characteristic to correct the nonlinearity based on the aperture value of the loop gain of an aperture control system. CONSTITUTION:The output of a computing element 8 is converted into a digital signal by an A/D converting circuit 17 and is supplied to an aperture correction control circuit 19 which corrects the change of the loop gain of an aperture control feedback loop due to the aperture value and to fix the degree of change of the aperture to a manipulated variable, and the aperture detection value subjected to gain correction based on information obtained by converting the aperture detection value of an encoder 13 obtained from a buffer amplifier 14 into a digital signal is supplied to an aperture driver 11 through a D/A converting circuit 15. Thus, the aperture control is performed with the fixed loop gain and is satisfactorily performed without the malfunction like hunting or unnaturalness.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exposure control device for a video camera or the like, and particularly to an exposure control device that can smoothly perform manual exposure control operations.

[Background technology]

In recent years, video cameras, video tape recorders (hereinafter referred to as VT)
The development of video equipment such as the VTR (abbreviated as "R") has been remarkable, and automatic exposure control devices have come to be equipped as standard, especially in camera-integrated VTRs and the like.

A conventional exposure control system for such a camera-integrated VTR will be described below with reference to FIG.

The light beam entering from optical system 1 is exposed to the exposure adjustment mechanism (iris).
2, the amount of light is adjusted and a subject image is formed onto the image sensor 3. A signal obtained from the image sensor 3 is sampled at a predetermined period by a sample hold circuit 4 and input to a camera signal processing circuit 5. Camera signal processing circuit 5
The signal is subjected to processing such as gamma correction and separated into a luminance signal and a color signal, and converted by the camera encoder 6 into a standardized television video signal such as NTSC.

On the other hand, the video luminance signal Y output from the sample and hold circuit 4 is integrated by an integrating circuit 7, and compared with a reference value 9a set in advance by a reference level setting variable resistor 9 in an arithmetic unit 8. , a difference signal corresponding to the difference is generated. The difference signal is supplied as an exposure control signal to the driver 11o, an actuator for driving the aperture, and the aperture 2 is controlled so that the relationship between the output level of the integrating circuit 7 and the reference value set by the variable resistor 9 for setting the reference value is constant. The amount of opening is controlled. Aperture 2 is controlled by a feedback loop as described above.

10 is a manual exposure control variable resistor for manually controlling the exposure state of the aperture 2;
By substantially changing the setting value of the variable resistor 9 for setting the reference value described above, the aperture amount of the diaphragm 2 can be variably controlled with respect to the set reference value.

(Problem to be Solved by the Invention) However, according to the above-mentioned device, only the voltage of the reference value 9a of the resistor for setting the reference value is changed, and the aperture itself constantly moves according to the incident light. Therefore, it is difficult to set the optimum exposure state as intended by the operator.

Furthermore, in manual exposure control, the aperture control means that controls the aperture opening amount simply consists of x4 variable resistors and a reference value that is supplied to the feedback loop, so the aperture amount can be adjusted smoothly and finely. It was difficult to set 3- to the optimum value.

In addition, the amount of movement of the actuator for aperture control relative to the amount of change in the aperture control signal changes relative to the amount by which the aperture is opened, and it becomes smaller on the open side, and increases when the aperture is advanced. . The relationship between this aperture value and the amount of actuator movement is shown in FIG.

Therefore, if we consider a feedback system using a video signal as in the above-mentioned device, the loop gain of the feedback loop increases as the iris narrows down from its open state, and conversely, as the aperture narrows down from its open state, the loop gain of the feedback loop increases; As the speed increases, the loop gain of the feedback loop becomes lower. In other words, when the aperture is close to the open side,
Even if the diaphragm aperture changes, the change in the amount of light is small, but as the diaphragm moves towards the small aperture side, even if the diaphragm aperture changes slightly, the brightness on the imaging surface becomes large. change,
This change causes a change in the responsiveness of the aperture control feedback loop, so the movement l of the actuator tends to increase as the aperture is narrowed down. This results in problems such as hunting, especially on the small aperture side, and also in that the aperture cannot be controlled smoothly.

In particular, when controlling the aperture manually, the aperture view for the same operation amount of the operation switch differs greatly between the small aperture side and the open aperture side, making manual exposure control difficult and difficult to control to the optimum value.

(Means for Solving the Problems) The present invention has been made to solve the above-mentioned problems, and is characterized by a diaphragm driving means for driving the diaphragm and changing the exposure amount. , an operation means for setting an exposure state of the aperture, a detection means for detecting aperture value information of the aperture, and a control means for controlling the aperture driving means based on the operation amount set by the operation means. An exposure control device is provided, wherein the aperture control means is configured to control the aperture drive means to change the amount of change in the aperture with respect to the operation amount according to the aperture value detected by the detection means.

[Effect]

As a result, in a feedback control system that controls the opening amount of the aperture based on changes in the amount of incident light that has passed through the aperture, it is possible to reversely correct changes in the loop gain of the feedback loop caused by changes in the aperture value. It is possible to keep the apparent loop gain constant regardless of the aperture value.

In addition, it is possible to easily and accurately set the optimal exposure intended by the shooting concept, and even in interchangeable lens systems, regardless of the type of lens or camera.
Regardless of the combination, it is possible to perform optimal exposure amount adjustment operation in manual exposure operation.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the automatic exposure apparatus according to the present invention shown in the figures will be described in detail below.

FIG. 1 is a block diagram showing a first embodiment of an automatic exposure device according to the present invention.

In addition, in the figure, the same reference numerals are given to the parts having the same configuration as those of the above-mentioned conventional example, and the explanation thereof will be omitted.

The difference from the conventional example shown in FIG. 9 is that after the output of the arithmetic unit 8 is converted into a digital signal by the A/D conversion circuit 17, the change in the loop gain of the aperture control feedback loop due to the aperture value described above is corrected and the operation is performed. The aperture correction control circuit 19 keeps the degree of change in the aperture constant relative to the amount, and the aperture detection value of the aperture encoder 13 obtained from the buffer amplifier 14 is converted into a digital signal by the A/D conversion circuit 16. D/A aperture control value that has been gain corrected based on the information
The configuration is such that the signal is supplied to the aperture driving driver 11 via the conversion circuit 15.

Manual exposure control is also set by the up/down counter 18 and the UP/DOWN switches 22 and 23 for setting the aperture value, and is set by the number of times the switch is pressed or the pressing time, and is digitally supplied to the aperture control feedback loop by the aperture correction control circuit 19. be done.

Note that 21 is an automatic mode in which aperture control is automatically controlled according to the amount of light incident on the image sensor 3, and a switch 22 for setting an aperture value.
．． This is an aperture adjustment mode changeover switch for switching between the manual mode and the manual mode set at 23.

The aperture correction control circuit 19 and the up/down counter 18 for setting the aperture value are controlled by a microcomputer 20.
It is constructed by incorporating it within.

With the above configuration, the lens optical system 1 allows the iris 2 to
A subject image formed on the imaging surface of an image sensor 3 such as a CCD is photoelectrically converted by the image sensor 3 and output as an image signal, and then processed by the image sensor 3 via a sample hold circuit 4 for camera signal processing. The imaging signal is supplied to the circuit 5, where it is subjected to gamma conversion, etc., and the color signal C and luminance signal Yγ are extracted as video signals, which are then passed through the camera encoder 6 for standardization into a television signal such as NTSC, and then converted into a composite video signal, etc. The image is output from the camera unit in the form of .

In addition, the luminance signal Y output from the camera signal processing circuit is input to an integrating circuit 7 and integrated in order to generate a control signal for controlling the aperture 2 to obtain appropriate exposure according to the luminance state of the screen. After that, the arithmetic unit 8 compares it with a set value 9a of a variable resistor 9 for setting a reference value, and generates a difference signal. This difference signal is converted into a digital signal by the A/D conversion circuit 17, and then supplied as an exposure control signal to the aperture correction control circuit 19. After being subjected to the correction described later, it is sent to the aperture drive actuator via the driver 11. Based on this, the aperture 2 is controlled so that the difference signal is at a constant level.

Via the driver 11, the aperture drive actuator 12
Based on this, the aperture 2 is controlled so that the difference signal is constant.

On the other hand, the aperture opening amount of the aperture is detected by the encoder 13, and the detected value is amplified to a predetermined level by the buffer amplifier 14, and then converted to a digital signal by the A/D conversion circuit and supplied to the aperture correction control circuit 19. correction is applied to the aperture control signal. The encoder 13, buffer amplifier 14, and correction control circuit 19 constitute an inverse correction circuit for changes in the loop gain of the feedback loop of the aperture control system, which is a feature of the present invention.

Here, the general optical characteristics of the aperture 2 are shown as follows:
As shown in Figure 18 above, the relationship between the amount of movement of the actuator for driving the aperture and the aperture value is non-linear, and the smaller the aperture, the more the aperture value changes with a slight movement of the actuator. It has become. In other words, the loop gain of the feedback loop is high on the small aperture side, and the actuator is moved significantly even in response to a slight change in the amount of light, and the change in aperture value relative to the amount of actuator movement is large on the small aperture side. It can be seen that hunting is more likely to occur. Curve A in FIG. 3 is a characteristic curve showing the relationship between the aperture value and the loop gain of the feedback loop for aperture control.

In the present invention, based on such conditions, the operation of the correction circuit that controls the gain of the diaphragm control system will be explained in the case where an diaphragm having the optical characteristics as shown in FIG. 8 is used.

The voltage output from the second encoder 13, which detects the opening amount of the aperture, that is, the aperture value, is input to the buffer amplifier 14, where it is amplified by a predetermined amplification factor and given a predetermined bias, and then A/D converted. The signal is converted into a digital signal by the circuit 16 and is led to the aperture correction control circuit 19. The aperture correction control circuit 19 takes in the output of the arithmetic unit 8 outputted from the A/D conversion circuit 17 and the voltage corresponding to the aperture value outputted from the A/D conversion circuit 16, and calculates the curve i, The loop gain shown by is multiplied by the loop gain characteristic of the inverse characteristic shown by curve β2, and thereby the curve f! , 3, correction is made to obtain a constant loop gain characteristic as shown in . As described above, on the small aperture side, even a slight change in the aperture value causes a large change in the amount of light, and as a result, the loop gain of the control system becomes high on the small aperture side. Therefore, the aperture correction control circuit adjusts the aperture value so that the aperture control signal outputted from the D/A converter circuit 15 is large near the open aperture state where the loop gain is low, and becomes smaller as the aperture is closed. It is set to apply corrections accordingly. As a result of this, the amount of actuator movement gradually decreases toward the small aperture side where the change in light amount is large even with a slight movement, making hunting less likely to occur.

That is, the voltage applied to the driver 1i varies depending on the aperture value of the diaphragm 2 even for the same change in the amount of light, and the amount of movement of the diaphragm 2 is controlled to increase as the diaphragm 2 approaches the open state.

FIG. 2 is a block diagram for explaining the internal configuration and operation of the aperture correction control circuit 19. The aperture correction control circuit 19 is composed of a microcomputer, but for convenience of explanation, it is divided into blocks.

The video signal level supplied from the A/D conversion circuit 17 is
The aperture control signal is input to a holding circuit 191 that holds the signal level. This holding circuit 191 is normally A
The output of the A/D conversion circuit 17 is passed through as is, and when the automatic/manual changeover switch 21 is switched to manual, the output of the A/D conversion circuit 17 immediately before the switch is held. The output of the holding circuit 191 is added to the output of the up/down counter 18 by an adder 192 and supplied to a gain correction circuit 193. The aperture control signal whose gain has been corrected by the gain correction circuit 193 is compared with the detection signal corresponding to the aperture value outputted from the A/D conversion circuit 6 by the subtracter 194, and then a signal corresponding to the difference is generated. The signal is supplied to the amplifier 195, amplified to a predetermined level, and supplied to the D/A conversion circuit 15. This forms an aperture control feedback loop for keeping the video signal level constant.

On the other hand, to explain the gain correction operation, a control signal corresponding to the aperture value outputted from the A/D conversion circuit 16 is manually inputted to the area discrimination circuit 196, and the aperture value is adjusted to a plurality of preset stages. Determine where the object is located (1), and supply the determination result to the gain correction circuit 193. The gain correction circuit 193 corrects the gain in the plurality of steps described above based on the aperture value information supplied from the area discrimination circuit 196. do. The gain correction characteristic is represented by the curve p in Fig. 3, and the dotted lines of the curve β represent its multiple stages.
It is highly detailed and highly accurate. Further, the stage of this gain correction can be selected and set as appropriate within the accuracy of the aperture encoder, so that curve 1 in the figure. The loop gain in state 1 without correction shown by curve 11
It is corrected to a constant loop gain of 3.

Now, with the above-described configuration, when the switch 21 is set to automatic, the output of the A/D conversion circuit 17 passes through the holding circuit 191 and is supplied to the adder 192. On the other hand, the up/down counter 18 is reset to the initial value by the switch 21 and remains inactive. Therefore, only a constant initial value is output to the adder, and the UP switch 22. which manually sets the aperture value. Even if the DOWN switch 23 is operated, it becomes invalid.

As a result, the control loop gain of the diaphragm 2 is corrected by the inverse characteristic shown by the curve fix to the characteristic shown by the curve 11 in the diagram 's3, as described above, and the curve 1. is almost constant. It is maintained by the characteristics shown in . Therefore, the aperture control loop gain is controlled to be almost constant over the entire movement range of the aperture,
Natural aperture control is possible.

Further, when the switch 21 is manually switched, the holding circuit 191 holds the output of the A/D conversion circuit 17 immediately before switching, and continues to output it to the adder 192. At the same time, the up/down counter becomes operational after being reset.

In this state, the output of the A/D conversion circuit 17 immediately before switching the switch 21 to manual becomes the initial value for manual operation.
The output of the up/down counter 18 for controlling the aperture value is added to this value, and the resultant value is supplied to the gain correction circuit 193, and the loop gain of the aperture control system is controlled to be constant as described above. As a result, the loop gain becomes constant over the entire variable aperture range. In other words, the exposure change with respect to the operation amount of the UP switch and DOWN switch for controlling the aperture becomes substantially constant throughout the variable aperture range. Therefore, the amount of aperture change with one press of the UP switch or DOWN switch is the same whether it is on the small aperture side or the open side, and the operability is greatly improved. By correcting the aperture so that it is constant regardless of the aperture value, the aperture can be made to respond in proportion to the up/down switch that changes the exposure amount, allowing optimal manual exposure operation.

In the above embodiment, the aperture correction control circuit is configured by a microprocessor, but it goes without saying that it is also possible to configure it by hardware without using a microprocessor.

FIG. 4 is a block diagram showing an example thereof.

In this figure, the same reference numerals are used for the same components as in FIG. 1, and the explanation thereof will be omitted. Furthermore, according to this embodiment, only in the case of manual aperture control, in which changes in loop gain due to aperture value have a strong influence on changes in exposure state, especially during operation, the third
The gain correction shown in the figure is performed.

In the figure, 10 is an aperture operation member that is a variable resistor that is linked to an aperture operation ring (not shown), and 24 is a buffer amplifier 1.
The aperture value detection signal corresponding to the aperture value output from 4 is compared with the control signal corresponding to the aperture setting value set by the aperture operation member, and an aperture control signal corresponding to the difference is sent to the drive circuit 11. A differential amplifier 25 that outputs , performs gain correction on the setting value of the aperture operating member based on the aperture value information supplied from the buffer amplifier 14, and keeps the loop gain of the aperture control feedback loop constant regardless of the aperture value. This is a gain correction circuit for The loop gain under this aperture control feedback loop is the curve fL in Figure 3.
t, and the gain correction circuit 25 corrects the characteristic as shown by the curve JZ2, which is the inverse characteristic of the gain correction circuit 25.
As a result, as shown in a3, a constant loop gain characteristic can be obtained regardless of the aperture value.

When the automatic 9-manual selector switch 21 is switched to automatic to set the automatic aperture control mode, information based on the difference between the video signal level output from the arithmetic circuit 8 and the reference value is transferred to the drive circuit 1.
1, and the actuator 12 is driven so that the aperture amount of the diaphragm 2 is varied so that the difference becomes constant or zero. That is, the automatic exposure mode is the same as that shown in FIG.

Next, when the automatic 0 manual changeover switch 21 is switched to manual to set the manual aperture control mode, the signal corresponding to the video signal level output from the calculator 8 is cut off, and the output of the differential amplifier is transferred to the actuator drive circuit 11. supplied to. Therefore, the signal corresponding to the aperture value output from the buffer amplifier 14 and the setting value of the variable resistor 10 for aperture operation supplied via the gain correction circuit 25 are supplied to the differential amplifier 24 and compared. , the aperture 2 is controlled according to the difference signal. , the dirt V is controlled to a value that corresponds to the value set by the variable resistor 10 for adjusting the aperture.

As shown in FIG. 3, the gain correction circuit 25 (,
- Therefore, there is no gain correction according to the aperture value in the loop gain of the aperture control feedback shown in the same diagram, as shown in the same diagram, and as a result, the herb gain is constant as shown by R8. Retained first. That is, as in the first embodiment, the relationship between the change in the aperture and the operator is always kept constant during manual operation, allowing natural aperture adjustment.

FIG. 5 shows an embodiment of FIG. 3 in which the exposure control device of the present invention is applied to an interchangeable lens type video camera.

In this figure, the same components as those in FIG. In the figure,
i and u are lens units, CU is a camera unit, and M is a mount unit that supplies the lens unit and camera unit. The mount M is provided with an electrical contact connector that connects the lens unit and the camera J to the unit, and a communication path 30 for transmitting control information between the two units 1 is formed.

According to this embodiment, the camera, camera, chive, chive)-CU side is equipped with an image sensor T3, a sample hold circuit 4, a camera signal processing circuit 5, and a camera encoder 6.
Integrating circuit 7 that integrates the luminance signal of the video signal output from sample hold circuit 4, the output of integrating circuit 7 and reference 1
Reference value 9 set by variable resistor 9 for novel setting
an A/D that converts the output of the arithmetic unit 8 into a digital signal;
Conversion circuit 17, iris automatic 1 manual adjustment switch 21
．． IJP switch for manual aperture setting 22°D OW
Regarding the point where the N switch 23 is arranged, the first
The embodiment and studs shown in the figure. The luminance signal is output from the A/D conversion circuit 1! The operation amount of the novel and the operation switch for setting the aperture value is supplied to the control microcomputer 26 on the camera side. Camera side microconvex
In the evening 26, the up/down counter 18 representing the operation amount of the manual aperture value setting switches 22 and 23 and the output of the A/D conversion circuit 17 are taken in and the aperture control signal is calculated 1.
Then, the camera communication block 27 converts the data into a form suitable for communication, and transmits it via a communication path 30 to a lens-side microcomputer 28 in the lens unit, which will be described later.

A lens-side control microcomputer 28 that exchanges control information with the camera-side control microcomputer 2G via a communication path 30 is disposed within the lens unit LU. That is, the lens side control microcomputer 2B receives aperture control information from the camera side microcomputer via the NONS communication block 29 tube,
Based on this control information, the aperture 2 is controlled via the aperture correction control circuit 19. The nozzle side control microcomputer 28 is connected to the aperture encoder 13. Buffer amplifier 14. The aperture value information is taken in through the A/D conversion circuit 16, and the aperture control information is received from the camera-side microcomputer 20. The r loop gain characteristic curve A shown in FIG.
is corrected so that the loop gain characteristic becomes constant like curve F. This corrected one-stop aperture control information is converted into an analog signal by the D/A converter circuit 15, and is supplied to the actuator drive circuit 11 to control the aperture 2.

The configuration inside the microcomputer 28 on the 17th lens side is
The aperture correction control block 19 shown in the figure is comprised of a communication block 29 for receiving and decoding aperture control information from the camera side.

With the above configuration, the self 1j+, manual changeover switch 21
When the automatic aperture value setting switch 22 is switched to automatic, the value of the up/down counter 18 is fixed to a predetermined value in the camera microcomputer, and the value of the up/down counter 18 is fixed to a predetermined value.
．． 23 is invalid. Therefore, the diaphragm control information is transmitted to the lens side and the diaphragm 2 is controlled so that the appropriate n light, that is, the luminance 1 novel of the video signal is constant according to the brightness state of the screen.

Further, when the switch 21 is switched to manual, the output signal of the up/down counter 18 given by the aperture value setting switches 22 and 23 is transferred to the A/Di conversion circuit 17.
This information is added to the video signal level information supplied by the controller, and the aperture can be controlled to a manually set value. The communication block 29 of the lens side microcomputer receives the communication from the communication block 27 of the camera side microcomputer.
/D conversion circuit 17 output signal and up/down counter 1
8 and outputs it to the aperture correction control circuit 19. The aperture correction control circuit 19 includes a holding circuit 191, an adder 192. Gain correction circuit 193. Area discrimination circuit 196. Subtractor 194. It consists of an amplifier 195, and its operation is the same as in the first embodiment except for the intervention of communication in the middle. That is, the output signal of the A/D conversion circuit 17 is transmitted to the holding circuit 19.
It is held at 1 and added to the output signal of the up/down counter 18 by an adder 192. The added signal is corrected by a gain correction circuit 193 so that the loop gain of the aperture is constant in the aperture debt region, and its output signal is
It is compared with the digital signal of the aperture value which is the output of the A/D conversion circuit 16, and the difference signal is amplified by the amplifier 195, and the D
The signal is input to the driver 11 via the /Ai conversion circuit 15.

Then, drive the actuator 12 with the driver 11,
Variable aperture amount. The aperture amount is converted as a voltage by an encoder 13, and then sent to a buffer amplifier 14 and an A/D conversion circuit 16.
It is then fed back to the aperture correction control circuit 19.

As explained above, in the interchangeable lens system, since the aperture correction control circuit 19 is configured on the lens side,
The camera side only receives the output signal of the up/down counter 18, and no matter what camera is connected,
Since the actuator 12 and the aperture 2 are corrected on the lens side, optimal manual exposure correction can be performed.

In addition, in the second embodiment of the present invention, switches 22 and 23 (or exposure variable resistors) for setting the aperture value are provided on the camera side.
and an up/down counter 18 are constructed, but it does not impede the implementation of the present invention even if they are constructed on the lens side.

In each of the above-mentioned embodiments, during manual aperture control, the amount of operation by the switch 22 or 23 for setting the aperture value is detected by an up-down counter, and the aperture drive amount corresponding to the amount of operation is corrected according to the aperture value. It is configured to be used.

Next, depending on the aperture value, the VP switch 22 for aperture value control
．． An embodiment is shown in which the change in the count of the up/down counter 18 is made different for the same amount of operation or number of operations of the DOWN switch 23. In this way,
Since the change in the aperture control information with respect to the output of the up/down counter 18 can be maintained in a constant relationship regardless of the aperture value, the calculation algorithm for the aperture control can be simplified.

That is, as the aperture value changes from the small aperture side to the open side, the change in the count value of the up/down counter with respect to one press of the UP switch or the DOWN switch increases. Therefore, there is no need to apply any special correction to subsequent aperture control.

346 shows a block diagram of this embodiment, except for the control microcomputer program.
This is similar to the first embodiment shown in the figure.

FIG. 7 is a flowchart for explaining the control operation.

In FIG. 6, AD to the control microcomputer 31
Conversion circuit 17.16 and switch for manual/aperture setting 22.23 Aperture control automatic (Auto) and manual (M
A switch 21 for switching the output (annual) is connected as a data input, and a D/A conversion circuit 15 is connected as a data output.

The control operation of the control microcomputer 31 will be explained below using the flowchart shown in FIG.

Aperture 2 detected by encoder 13 in step 01
The state is taken from the A/D conversion circuit 16 as data Db into the microcomputer 31, and in step 02, a correction value K is determined according to the aperture value data Db.
h from a correction value memory (not shown) in the microphone computer 31. The value of the coefficient K + depends on the aperture value according to the correction characteristic curve in Figure 3! , changes as follows.

In step 03, the image signal level information Da for exposure control is taken into the microcomputer 70 from the AD conversion circuit 17, and a target value Do (lc*Da) for controlling the aperture 2 is calculated.

In step 04, control error information (Do-Db), which is the difference between the target value and the aperture value, is calculated.

In step 05, the control error information is substituted into De, which is control output data.

Step 06 ``1'' Determine whether M (manual) or A (automatic) is in the state of switch 2i.

In the case of A, the process returns to step 01 and proceeds to the judgment of the case of 8M forming an automatic control loop.8 In step 07, determine whether the positive correction instruction (+) of the switch 27 or the negative correction instruction (-) of the switch 28 was pressed. Alternatively, it is determined whether neither is pressed, and it is divided into three parts: +, +, No.

The correction coefficient a K 2 in the case of (-) in step 08 is K
I Read from the memory table in the microcontroller as well.

Basically, like Kl, K is set so as to ride the gain correction curve shown in FIG. The difference is that summer (, is correction switch 2
2. This point is defined as the count number that occurs when 23 is pressed. t, that is, the amount of change in the count value of the up/down counter due to one suppression of the ribbon setting switch changes according to the aperture value, and settles to curve J22.
7-, the loop gain of the aperture control loop can be corrected to be constant. For example, when pressing the switch 1) once, it is equivalent to configuring a counter that is weighted such that when the aperture value is large, one count is added, and when the aperture value is small, several counts are added.

In step 09, the device 8 changes the target value pO to a value (D o -K2) that takes into account the correction value during manual control.

Correction coefficient K in case of (+) in step 10.

is read from the memory table in the microcontroller in the same way as Kl.

In step 11, the target value Do is replaced with a value (Do(·Ka)) that takes into account the correction value during manual control. In step 12, data Db from the AD converter iG is fetched and the current position of the diaphragm is reconfirmed.

In step 13, the latest control error (Do-In) is calculated. In step 14, the control error data is used as control data.
Assign 1 to o and return to step 06.

The °C aperture is controlled based on the data obtained in this manner.

As described above, the aperture control can be performed with a constant loop gain in both automatic and manual modes, and the aperture control can be performed with a good feeling of operation without any unnatural behavior such as hunting. It can be carried out.

〔Effect of the invention〕

As described above, according to the exposure control device of the present invention, in relation to exposure control of a video camera, etc., a correction system with an inverse characteristic that corrects nonlinearity based on the aperture value of the loop gain of the aperture control system is reduced. In particular, it is possible to obtain a substantially constant loop gain regardless of the aperture value, and the dynamic characteristics become large depending on the aperture value, so there is no deterioration in operability, and hunting, especially on the small aperture side. etc., and it is possible to perform live aperture control that operates smoothly and stably.

In addition, by preprogramming the correction characteristics of the diaphragm control system on a table in the microcomputer, the diaphragm control can be performed smoothly. However, it is sufficient to store control and correction data in accordance with the characteristics of the aperture lens optical system on the l/lens unit side, which has a great effect on lens compatibility.

Furthermore, since the correction characteristics can be set using the operating section, there is also the effect of simplifying the control system of the circuits after the operating section.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a first embodiment of the present invention, FIG. 2 is a block diagram illustrating the configuration of the aperture correction control circuit in FIG. 1, and FIG. 3 is an embodiment of the present invention. 344 is a block diagram showing the second embodiment of the present invention, FIG. 5 is a block diagram showing the third embodiment of the present invention, and FIG. 6 is a block diagram showing the third embodiment of the present invention. A block diagram showing the fourth embodiment of the invention, Fig. 7 is a flowchart for explaining the operation in the fourth embodiment of the invention, and Fig. '48 shows the aperture value and aperture control in a general aperture control system. A characteristic diagram showing the relationship between the amount of movement of the actuator, and FIG. 9 is a block diagram of a conventional aperture control system. f, IL2 28 4 5.6 8 I+ 1
6 ``匈・ksuq) 1st Uikumo, Nieku Teshika 4 (%) 1 thousand pieces, -17-old 1ゎ＠-Fw 1011 works■9 figures

Claims (1)

[Scope of Claims] Aperture driving means for driving an aperture to change the exposure amount; operating means for setting the exposure state of the aperture; detection means for detecting aperture value information of the aperture; control means for controlling the aperture drive means based on a set operation amount, the aperture control means changing the amount of change in the aperture with respect to the operation amount according to the aperture value detected by the detection means. An exposure control device characterized in that the exposure control device is configured to control the diaphragm driving means so as to control the aperture driving means.