JP2008076833A - Iris control circuit, video input device, iris control method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an iris control circuit capable of accurately setting an initial adjustment value representing an iris stop original point for a reference voltage at the start, and to provide a video input device that has the function of the iris control circuit. <P>SOLUTION: The iris control circuit includes a drive circuit section (iris control analog circuit 5) that supplies a control voltage Vcon to an iris 2, together with a reference voltage Vref; and a control circuit section (EVR 6 and microcomputer 8) that inputs brightness information (signal S42 from EVR 6) on the output side of the iris 2, that provides the iris control analog circuit 5 with a quantity of control being exerted, when the control voltage Vcon. is convergence-controlled, until the desired brightness is obtained according to the brightness information, and that is capable of an initial adjustment for the reference voltage Vref. The microcomputer 8 controls the iris control analog circuit 5, thereby obtaining a first reference voltage (parameter X), when the control voltage Vcon. is convergence-controlled from the fully closed state of the iris 2, and a second reference voltage (parameter Y), when the iris 2 is convergence-controlled from the fully opened state of the iris 2. Thus, the initial adjustment value for the reference voltage Vref. is set to be between the parameters X and Y. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an iris control circuit that controls an iris that mechanically limits the amount of light passing through according to a voltage difference between an input control voltage and a reference voltage, the iris, the iris control circuit, an imaging device, and a video signal processing circuit And a video input device having a control circuit, and an iris control method and program.

  Iris (hereinafter referred to as “mechanical iris”) that mechanically limits the amount of passing light according to a voltage difference with respect to a reference voltage of an input control voltage is widely used in video input devices such as video cameras and digital still cameras. .

The mechanical iris may be provided in the lens or supplied as an individual component. In another classification, the mechanical iris is, for example, a DC servo type that drives a coil of a mechanical iris based on a direct current (DC) control amount from a control unit such as a CPU (central processing unit) or a microcomputer, and a video signal. It can be divided into a video servo type that controls the driving of the mechanical iris based on (video signal).
A driving circuit for an auto iris lens to which a DC servo type can be applied is disclosed in, for example, Patent Document 1, and Patent Document 2 is known as an application example of a video servo type.

  According to Patent Document 1, a subtracter that detects an output of an S / H (sample hold) circuit and subtracts a detected voltage from a set voltage, or a comparator that adjusts the set voltage, for example, an operational amplifier (OP An analog circuit such as an amplifier is used.

According to Patent Document 2, a detection circuit that detects an output of a CDS (Correlated Double Sampling) circuit and extracts a luminance signal, a comparator that compares the detection circuit with a reference voltage, and controls an iris based on a result of the comparison. The iris control unit is provided in a lens called a video servo lens. In this case, the reference voltage can be changed by, for example, an adjusting screw.
Further, when a detection circuit and a comparator are not provided in the video servo lens, a circuit that generates a luminance signal (a DC voltage correlated with luminance) from the output of the CDS circuit and amplifies the DC level with a video amplifier is an imaging processing circuit. Is provided inside. The video amplifier converts the control amount from the microcomputer into a voltage by EVR (electronic volume), and amplifies the luminance signal by applying the voltage to the control input of the video amplifier, and the iris is supplied to the iris drive circuit in the video servo lens. give.

As described above, both of the DC servo type and the video servo type detect the analog signal output from the imaging device, and the feedback control circuit based on the detection result is composed of the analog circuit.
JP 05-292391 A JP 2001-255568 A

In general iris control, feedback control is performed based on brightness information such as a luminance signal level so that the brightness becomes a target value suitable for an appropriate exposure amount of automatic exposure control. The iris control signal is controlled to converge to a constant value, that is, a voltage value such that the screen brightness becomes the target value.
For example, in the configuration described in Patent Document 2, a control amount input to the EVR from a control unit such as a microcomputer generally represents a numerical value determined according to the target value. In this case, the EVR outputs a voltage value (gain voltage) indicating the feedback loop gain to the gain amplifier.

On the other hand, the control voltage itself for driving the iris is compared with a reference voltage whose value changes so as to obtain a target value, and the voltage difference is controlled by a feedback loop control amount (a control amount indicating how much control is required later). ).
This reference voltage corresponds to a reference voltage when a function of detection and voltage comparison is provided in the video servo lens in Patent Document 2. However, since this reference voltage cannot be automatically controlled, the gain voltage of the video amplifier output from the EVR has the same function as the reference voltage in another configuration described in Patent Document 2.

  Here, the target value is not directly used as the reference voltage, and the numerical value corresponding to the target value is voltage-converted by EVR because the target value is an AE mode of an automatic exposure (AE) control program for backlight correction, indoor, outdoor, etc. Therefore, in this case, a numerical value (digital signal) indicating the voltage value is output from the control unit side, and the voltage is generated by the voltage conversion circuit (EVR). This is because it is preferable in terms of configuration and is less susceptible to voltage fluctuations due to noise.

  However, in feedback control that uses the voltage difference between the reference voltage and the control voltage as a control amount, a shift occurs between the reference voltage and the target value, and it is necessary to correct it. Further, in the driving method of Patent Document 2 in which the same function as the reference voltage is given as the gain of the gain amplifier, there may be a difference between the gain and the target value.

  There are various causes for this deviation, but as described above, the circuit that performs feedback control is an analog circuit, and there are variations in characteristics of analog components such as OP amplifiers and gain amplifiers. A change can be cited as a factor. In addition, the iris has a mechanical tolerance (tolerance), and errors due to the temperature characteristics of the sensor for detecting the iris opening / closing position occur, and these are caused by a complex factor added to the variation of the analog parts. A relatively large voltage shift is considered to occur.

The problems to be solved by the present invention include an iris control circuit capable of accurately setting an initial adjustment value representing an iris stop origin of a reference voltage at the time of start-up, and a video input device having a function of the iris control circuit Is to provide.
In addition, another problem to be solved by the present invention is to provide an iris control method capable of accurately setting an initial adjustment value representing an iris stop origin of a reference voltage at the time of starting or the like, and a program including a procedure of the method. It is to be.

  An iris control circuit according to the present invention is an iris control circuit that controls an iris that mechanically limits the amount of passing light according to a voltage difference between an input control voltage and a reference voltage, and is capable of changing the control voltage. A drive circuit unit that generates and supplies the control voltage to the iris together with the reference voltage, and brightness information on the output side of the iris, and inputs a desired brightness on the output side of the iris according to the brightness information. And a control circuit unit capable of calculating an initial adjustment value for the reference voltage while giving a control amount to the drive circuit unit when the control voltage is controlled to converge until the control voltage is obtained. When the initial adjustment of the reference voltage, the brightness of the output side of the iris and the desired brightness when the control voltage is controlled to converge from the fully closed state of the iris A first reference voltage that is less than or equal to a certain value, and a second reference voltage that causes the difference in brightness to be less than or equal to a certain value when the control voltage is controlled to converge from a fully open state of the iris. The initial adjustment value is set between the first reference voltage and the second reference voltage.

  In the present invention, preferably, when the first reference voltage is obtained, a first error amount range in which a difference between the brightness on the output side of the iris and the desired brightness is a predetermined value or less, and the second reference voltage are obtained. A storage unit that stores a second error amount range in which the difference in brightness is sometimes less than or equal to a certain value in a changeable manner by a user designation, and the control circuit unit stores the first error range in the storage unit And the second error amount range is stored, the iris is fully closed to perform the convergence control, and the convergence control is performed again each time the reference voltage is adjusted, and the difference in brightness is It is determined whether or not the first error amount range is entered, the reference voltage when the brightness difference enters the first error amount range is set as the first reference voltage, the iris is fully opened, and the convergence control is performed. And the reference voltage is adjusted. The convergence control is performed again to determine whether the brightness difference falls within the second error amount range, and the reference voltage when the brightness difference falls within the second error amount range is determined. The second reference voltage is used.

In the present invention, it is preferable that the control circuit unit sets the initial adjustment value to an intermediate value between the first reference voltage and the second reference voltage.
Alternatively, preferably, the control circuit unit has the intermediate value between the first reference voltage and the second reference voltage, or a voltage defined by two limits separated from the intermediate value by a predetermined value in each of positive and negative directions. Set the initial adjustment value.

  In the present invention, it is preferable that the control circuit unit monitors an error amount of automatic exposure control having a positive / negative polarity indicating a difference between a current exposure amount and an optimum exposure amount, and the polarity of the error amount is the first value. When the reference voltage is reversed from the polarity corresponding to the initial state (fully closed) of the iris control, the drive circuit unit is controlled again to perform the convergence control from the fully closed side. If the polarity inversion is not detected in the second convergence control, the convergence value of the control voltage in the second convergence control is the first reference voltage, and the polarity in the first convergence control from the fully closed side is The convergence value of the inverted control voltage is set as the second reference voltage, and the initial adjustment value is set between the first and second reference voltages.

  An image input apparatus according to the present invention includes an iris that mechanically limits the amount of light that passes through according to a voltage difference between an input control voltage and a reference voltage, an imaging device that inputs light after passing through the iris, and the imaging A video signal processing circuit including a detection unit for detecting screen brightness obtained from a video signal output from a device, and the control voltage is generated in a changeable manner, and the control voltage is supplied to the iris together with the reference voltage. When the brightness information of the screen is input from the iris driving circuit that drives the iris and the detection unit, and the control voltage is converged and controlled until a desired brightness is obtained on the screen according to the brightness information. And a control circuit capable of initial adjustment of the reference voltage by controlling the iris drive circuit. In the initial adjustment of the reference voltage, the control circuit controls the first reference voltage when the control voltage is converged from the fully closed state and the control voltage is controlled from the fully open state. Is obtained by controlling the iris driving circuit, and the initial adjustment value is set between the first reference voltage and the second reference voltage.

An iris control method according to the present invention is an iris control method in which an initial adjustment value of the reference voltage is set for an iris that mechanically limits the amount of passing light according to a voltage difference between the input control voltage and the reference voltage. The first step of acquiring brightness information on the output side of the iris, and using the reference voltage that is currently set until a desired brightness is obtained on the output side of the iris according to the brightness information. A second step of controlling the control voltage to converge, a first reference voltage when the control voltage is controlled to converge from a state where the iris is fully closed, and a control for converging the control voltage from a state where the iris is fully opened. A second reference voltage obtained by performing the first step and the second step at least twice, and the third step obtained in the third step. 1 See updates the reference voltage between the voltage and the second reference voltage, and a fourth step of outputting to the iris.
The program according to the present invention includes the first to fourth steps, and sets an initial adjustment value of the reference voltage for an iris that mechanically limits the amount of light passing through according to a voltage difference between the input control voltage and the reference voltage. This is a program for executing a setting procedure using a computer.

According to the above configuration, for example, in the iris control circuit, when brightness information is input to the control circuit unit, the control circuit unit obtains a desired brightness on the output side of the iris in accordance with the brightness information. Until it is done, the drive circuit unit is controlled to control the drive of the iris. More specifically, the drive circuit unit generates a control voltage, and the control circuit unit generates a control amount when the control voltage is converged and controlled according to the brightness information and the desired brightness. Give to the department. For example, the control circuit unit monitors the error amount that represents the difference between the current exposure amount and the optimum exposure amount in automatic exposure control and has positive and negative polarities. This error amount corresponds to the difference between the brightness information and the desired brightness.
In addition, the control circuit unit can perform initial adjustment of the reference voltage that is a reference for the convergence control. The reference voltage is usually fixed after the initial adjustment.

In the initial adjustment of the reference voltage, brightness information on the output side of the iris is acquired (by the control circuit unit) (first step). The control voltage is set using the currently set reference voltage until a desired brightness is obtained on the output side of the iris in accordance with the brightness information (by a drive circuit unit controlled by the control circuit). Convergence control is performed (second step).
The first reference voltage (on the program executed by the control circuit unit) when the control voltage is controlled to converge from the fully closed state (by the third step that repeats the first and second steps at least twice). And a second reference voltage (a variable on the program executed by the control circuit unit) when the control voltage is controlled to converge from the fully open state of the iris (by the control circuit unit). Then, for example (by the control circuit unit), an initial adjustment value of the reference voltage is set between the first reference voltage and the second reference voltage (fourth step).

According to the present invention, it is possible to provide an iris control circuit capable of accurately setting an initial adjustment value representing an iris stop origin of a reference voltage at the time of start-up, and a video input device having a function of the iris control circuit. Is possible.
In addition, according to the present invention, it is possible to provide an iris control method capable of accurately setting an initial adjustment value representing the iris stop origin of the reference voltage at the time of startup or the like, and a program including the procedure of the method.

  Embodiments of the present invention will be described below with reference to the drawings. Although the following is a description of the DC servo type, the present invention can also be applied to the video servo type, and therefore, a point peculiar to the video servo type in the iris control will be described each time.

<< First Embodiment >>
FIG. 1 is a block diagram of a video input device (camera) that employs DC servo iris control according to the present embodiment.
The illustrated camera 1 includes a lens (not shown) or a mechanical iris 2 fixed to the lens, an imaging device 3, a video signal processing circuit 4, an iris control analog circuit 5 as a drive circuit unit, an EVR 6, and a nonvolatile memory. And a microcomputer (μ-Com.) 8 for controlling them.

The video signal processing circuit 4 is provided in a signal processing circuit 9 that performs audio signal processing in addition to video signal processing. In the video signal processing circuit 4, a signal processing unit 41 that performs processing for separating a luminance signal and a color difference signal, gamma correction, various color adjustment processing, and the like, and an OPD (optical detector) 42 as a detection unit are provided. The luminance signal separated by the processing in the signal processing unit 41 can be input to the OPD 42.
Although the microcomputer 8 is partially omitted in FIG. 1, the mechanical iris 2, the imaging device 3, the video signal processing circuit 4, the iris control analog circuit 5, the EVR 6 and the nonvolatile memory 7 can be controlled. It is connected to the. In particular, as control related to the feature of the present embodiment, the microcomputer 8 can input the detection result (signal S42) from the OPD 42 and output a signal S81 for voltage control to the EVR 6 based on the detection result. Further, a signal S82 for AGC (auto gain control) and a signal S83 for shutter control can be output from the microcomputer 8 to the imaging device 3.

The imaging device 3 is a CCD image sensor or a CMOS image sensor. The imaging device 3 is fixed within a range in which light (image) from an optical component including the lens and the mechanical iris 2 can be imaged on the imaging surface. The image pickup device 3 has a large number of photosensors arranged in a matrix, and color filters are formed on the light incident side of the image pickup surface so as to form a fixed arrangement in units of several adjacent photosensors (pixel units). .
In FIG. 1, signals S82 and S83 for AGC control and shutter control can be input to the imaging device 3. This is for controlling the gain of the gain amplifier in the analog circuit provided in the imaging device 3 and further the electronic shutter function of the imaging unit during exposure adjustment. Although not shown in FIG. 1, the electronic shutter control is normally performed via a timing generator that generates various drive pulses (clock signal, vertical synchronization signal, horizontal synchronization signal, etc.) for driving the imaging device 3. Is called. This timing generator may be built in the imaging device 3 or externally attached.

The signal processing unit 41 in the video signal processing circuit 4 is a circuit that performs various video signal processing such as primary color separation, white balance, and gamma correction.
The OPD 42 is a circuit that inputs a luminance signal obtained by primary color separation, integrates the luminance signal level in units of screen such as one field or one frame, and acquires information on the average luminance (brightness) of the screen. The OPD 42 outputs a signal S42 indicating the brightness information to the microcomputer 8.

As described above, the microcomputer 8 controls the entire camera. With respect to the features of the present embodiment, the microcomputer 8 particularly serves as means for executing an automatic exposure (AE) control program having an iris initial adjustment function. This AE control program is preinstalled in a predetermined memory or the like, and the microcomputer 8 reads and executes the AE control program.
At this time, exposure adjustment is performed by controlling the mechanical iris control amount (signal S81) together with the shutter value (signal S83) and the AGC value (signal S82).

The non-volatile memory 7 can store an automatic exposure (AE) control program by applying the present invention, and can store an adjusted value (a variable (parameter) on the program). This corresponds to the storage unit of the invention. The AE control program may be stored in the nonvolatile memory 7 or may be stored in another read-only memory (not shown).
This AE control program corresponds to an example of a “program” of the present invention in which the procedure of the iris control method according to the present embodiment is added to a normal AE control program. The iris control method will be described later.

  The EVR 6 is a circuit having a so-called D / A converter function for converting a signal S81 representing a digital numerical value into a multi-channel analog voltage. In the DC servo type, two of these channels are used, whereby the voltage V1 that defines the level of the control voltage Vcon. And the voltage V2 that defines the level of the reference voltage Vref. Are output from the EVR 6 to the iris control analog circuit 5. The

The iris control analog circuit 5 is a circuit that generates a control voltage Vcon. And a reference voltage Vref. Based on the voltages V1, V2 output from the EVR 6 and outputs them to the mechanical iris 2. The iris control analog circuit 5 mainly amplifies the voltage V1 to determine the DC level of the control voltage Vcon. The iris control analog circuit 5 also has a function of performing a smooth iris control by applying a slight brake when an iris control of a rapid change is instructed by a voltage from the EVR 6.
In order to perform these processes, the iris control analog circuit 5 includes an analog circuit device such as an operational amplifier (OP amplifier).

The mechanical iris 2 is controlled by the microcomputer 8 and performs exposure adjustment. The mechanical iris 2 performs exposure adjustment on the imaging device 3 by limiting the amount of light passing through a voltage (for example, a difference voltage between a control voltage and a reference voltage) applied to a built-in coil. In general, the area of the iris opening through which light passes is controlled by stacking a number of blade-shaped light shielding plates and rotating them. A coil is used for this rotational drive.
The mechanical iris 2 compares the control voltage Vcon. With the reference voltage Vref., And controls the rotational drive amount and the opening / closing direction according to the potential difference (control amount having positive and negative polarities).

Imaging and signal processing, which are basic operations of the camera 1, are executed as follows.
A subject image incident from a lens (not shown) passes through the mechanical iris 2 and forms an image on the imaging surface of the imaging device 3. A video signal obtained by photoelectric conversion in the imaging device 3 is amplified by, for example, an analog front end (AFE) circuit that processes an analog imaging signal in the imaging device 3, and noise is removed. The digital signal is converted by the A / D converter. The AFE circuit performs CDS (correlation double sampling) on the imaging signal from the imaging device 3 to remove fixed pattern noise contained in the imaging signal and stabilize the signal level by AGC (automatic gain control). Circuit.

The output of the A / D converter enters the signal processing circuit 9 that performs digital signal processing, and the video signal processing is performed by the video signal processing circuit 4 provided therein. In particular, when primary color separation is performed by the signal processing unit 41 provided in the video signal processing circuit 4, the luminance signal obtained thereby is used for iris control described later.
The luminance signal is also subjected to predetermined signal processing, while the color signal (primary color signal or color difference signal) is subjected to processing such as auto white balance and color correction, and the processed color signal is converted to the luminance signal. And is further converted into an analog signal by a D / A converter (not shown), and a synchronization signal is superimposed to form, for example, an NTSC (National Television System Committee) signal.

  Next, the necessity of opening / closing control of the mechanical iris, mechanical iris control by AE, and initial adjustment of the reference voltage will be described in order.

[Mechanical iris open / close control]
2A and 2B schematically show a voltage difference between the control voltage Vcon. Supplied to the mechanical iris 2 from the iris control analog circuit 5 shown in FIG. 1 and the reference voltage Vref.
The mechanical iris 2 uses as input the voltage V1, V2 output from the EVR 6 adjusted by the iris control analog circuit 5 (control voltage Vcon. And reference voltage Vref.), And the difference between the input voltages (difference voltage) is large. Open and close depending on the size.
Specifically, as shown in FIG. 2A, when the control voltage Vcon. Is larger than the reference voltage Vref., The mechanical iris 2 has an iris opening area that determines a passing light amount with a driving force according to the difference voltage. Close operation to make it smaller.
On the other hand, as shown in FIG. 2B, when the control voltage Vcon. Is smaller than the reference voltage Vref., The mechanical iris 2 performs an opening operation to increase the iris opening area with a driving force corresponding to the voltage difference. .

Here, in the DC servo type iris control, as shown in FIGS. 1 and 2, the control voltage Vcon. For performing the opening / closing control and the reference voltage Vref. Serving as a reference for the voltage difference are input to the mechanical iris 2. . The reference voltage Vref. Can be adjusted with an initial value as will be described later, but once adjusted, the reference voltage Vref. Is fixed until the next adjustment is required.
More specifically, based on the error amount calculated by the microcomputer 8 according to the AE control program, the control voltage Vcon. Is converged (feedback control) until the error amount falls within a predetermined range. Using this feedback control function, an initial adjustment value of a reference voltage described later can be automatically set. Here, the reference voltage Vref. Can be manually adjusted by a volume resistor or the like in the mechanical iris 2, but in the DC servo type, the reference voltage Vref. Is further supplied via the microcomputer 8, the EVR 6, and the iris control analog circuit 5. Can be automatically changed.

On the other hand, in the video servo type iris control in the present embodiment, the feedback control is common to the DC servo type, but the reference voltage Vref. Cannot be automatically changed. The reference voltage Vref. Can be adjusted only manually by a volume resistor or the like in the mechanical iris 2.
In the video servo type employed in the present embodiment, opening / closing control is performed by inputting a pseudo CCD output calculated by AE as a control voltage. Although details will be described later, the microcomputer 8 obtains the reference voltage Vref. At the time of initial adjustment as a variable on the program, and adjusts the offset amount for shifting the control voltage Vcon., So that the reference voltage Vref. Is automatically changed. The same effect is obtained.
The present invention can also be applied to the video servo type described in Patent Document 2.

FIG. 3 schematically shows a control area of the mechanical iris control.
The horizontal axis in FIG. 3 indicates 256 levels from the minimum value to the maximum value of the numerical value (signal S81) given to the EVR 6 from the microcomputer 8 shown in FIG. 1, that is, the value defining the level of the control voltage Vcon. The minimum value is “0x00” and the maximum value is “0xFF”. In this notation, the upper 2 digits “0x” represents a hexadecimal number, and the lower 2 digits “00” to “FF” represent 256 numerical values. Since the numerical value and the magnitude of the control voltage Vcon. And the reference voltage Vref. Have a positive correlation, FIG. 3 shows the relationship between the numerical value and the voltage on the same horizontal axis.
For example, when the output range of the control voltage Vcon. Is 3.0 [V] to 5.0 [V], “0x00” is 3.0 [V], “0x80” is 4.0 [V], “ “0xFF” represents 5.0 [V].

As shown in FIG. 3, the mechanical iris has three areas of “open”, “close”, and “stop”. The region of “stop” is called a dead zone, and the iris control analog circuit 5 controls the operation so that the iris control stops as soon as the control voltage Vcon. Enters the dead zone.
The dead zone has a range from “0x80−N” to “0x80 + M”. N and M are arbitrary natural numbers, and are numerical values representing a region where the mechanical iris cannot move when the driving force is too weak due to an analog circuit or mechanical characteristics.
Therefore, “0x00” to “0x80-N” are “open” areas, and “0x80 + M” to “0xFF” are “closed” areas.
Normally, the iris control analog circuit 5 is designed so that “0x80”, which is an intermediate value between the minimum value “0x00” and the maximum value “0xFF”, is the center of the “stop” region (dead zone) (N = M). However, N and M may take different values depending on the characteristics of the iris control analog circuit 5 and the mechanical iris 2.

  On the other hand, for the reference voltage Vref., The iris control analog circuit 5 is designed with “0x80” being an intermediate value between the minimum value “0x00” and the maximum value “0xFF” as a design target.

[Mechanical iris control by AE]
In the AE control, mechanical iris control is performed based on an error amount representing a difference between the current exposure amount and an appropriate exposure amount determined according to the exposure mode and having a positive / negative polarity. For example, the error amount correlates with the difference between the brightness obtained from the OPD 42 shown in FIG. 1 and the appropriate brightness (desired brightness) in light of the exposure mode with respect to the brightness information. Is calculated by the microcomputer 8 executing the AE control program.
When the error amount is positive (the exposure amount is too large), the relationship is as shown in FIG. 2A, and is larger than the numerical value corresponding to the current control voltage Vcon. And “0x80 + M” to “0xFF”. The control voltage Vcon. Corresponding to the numerical value in the “closed region” of “” is generated by the iris control analog circuit 5 and applied to the mechanical iris 2, and the mechanical iris 2 is closed.
In this way, the larger the error amount, the larger the control voltage Vcon. Corresponding to a larger numerical value than the present in which the error amount is generated. For this reason, the absolute value of the error amount decreases each time the brightness control is performed and the feedback control for changing the control amount (numerical value) indicated by the signal S81 from the microcomputer 8 is repeated, and the numerical value also gradually decreases. Then, the control voltage Vcon. Eventually enters the “stop” region (dead zone) of the mechanical iris and stops.

When the error amount is negative (the exposure amount is too small), the relationship is as shown in FIG. 2B, so that it is smaller than the numerical value corresponding to the current control voltage Vcon. And “0x00” to “0x80”. The control voltage Vcon. Corresponding to the numerical value in the “open region” of −N ″ is generated by the iris control analog circuit 5 and applied to the mechanical iris 2, and the mechanical iris 2 is opened.
In this case, contrary to the case of closing, a smaller numerical value is used as the error amount is larger. Therefore, as the feedback control advances and the absolute value of the error amount decreases, the numerical value given to the EVR 6 by the microcomputer 8 increases. Then, the control voltage Vcon. Eventually enters the “stop” region (dead zone) of the mechanical iris and stops.

Thus, since the driving force of the mechanical iris 2 is determined by the magnitude of the numerical value shown on the horizontal axis of FIG. 3, the control speed of the mechanical iris 2 increases as the numerical value becomes farther from “0x80”. Therefore, the speed is high at first, and the speed decreases as the target is approached, and smooth convergence control is possible.
Although a dead zone exists, it does not actually occur, but when the error amount is 0, a numerical value “0x80” corresponding to the stop voltage is used.

[Necessity for initial adjustment of mechanical iris]
As shown in FIG. 3, “0x80” is ideally the midpoint of the “stop” region. However, in practice, the midpoint of the “stop” region is shifted from “0x80” as shown in FIG.
Since the AE control is performed on the assumption that “0x80” is the midpoint of the “stop” region, the numerical value “0x80” is used to represent the reference voltage Vref. When an appropriate exposure amount is obtained. However, the center of the dead zone may deviate from the numerical value “0x80”. In this case, as shown in FIG. 4, even if the mechanical iris is intended to be stopped by the AE control, the mechanical iris opens and closes and deviates from an appropriate exposure point.

Also, if the midpoint of the “stop” area is shifted, the error amount when entering the “stop” area of the mechanical iris will also differ depending on the convergence from the closing side and the convergence from the opening side, as will be described later. become.
As a result, unintentional variations will occur in the accuracy of exposure control by the mechanical iris.

[Mechanical iris initial adjustment method]
In order to solve such a problem, it is necessary to make an adjustment so that the mechanical iris stops when AE control is performed using at least “0x80”. This is the mechanical iris initial adjustment (initial adjustment of the reference voltage).

  The outline of the adjustment method will be described. When a DC servo type iris is used, the optimal reference voltage (first reference voltage) when the mechanical iris 2 performs the AE control from the fully closed state and the AE control from the fully opened state. When this is done, the optimum reference voltage (second reference voltage) is obtained, and the reference voltage Vref. Of the mechanical iris 2 is automatically set to the intermediate value.

On the other hand, when a video servo type mechanical iris is used, the first and second reference voltages are obtained and the intermediate value is calculated until the intermediate value is calculated. The offset amount for moving the entire control voltage value is adjusted according to the difference from the reference voltage Vref.
For example, when the numerical value used when the error amount is −1000, 0, 1000 is “0x40”, “0x80”, “0xC0”, by adjusting the offset amount of the control voltage, for example, “0x43”, “0x83” "," 0xC3 ", etc., so that the whole has an offset.
For this adjustment procedure, the iris level, which is an exposure level adjustment function mounted on the video servomechanism iris itself, is adjusted in advance. Other than this, there is no difference between the DC servo type and the video servo.

  Next, the details of the mechanical iris initial adjustment method will be mainly described in the DC servo type.

FIG. 5 is a flowchart showing the procedure of the initial adjustment. Moreover, FIGS. 6-14 is explanatory drawing of the state in each procedure.
Hereafter, according to this FIG. 5, each procedure is demonstrated, referring FIG. 1 and FIGS. 6-14.

  In step ST1 of FIG. 5, the microcomputer 8 shown in FIG. 1 sets the shutter value and the AGC value defined by the AE control program to fixed values so that exposure control can be performed using only the mechanical iris.

  In step ST2, the microcomputer 8 outputs a signal S81 indicating a numerical value “0xFF” to the EVR 6. As a result, as shown in FIG. 6, the control voltage Vcon. Output from the iris control analog circuit 5 is increased to a position corresponding to the maximum numerical value “0xFF”, and the mechanical iris is in a fully closed state.

In the “first convergence” of step ST3, in this state, the microcomputer 8 executes a program routine for normal mechanical iris AE control. Then, since the mechanical iris is closed and the screen detected by the OPD 42 is completely dark, the microcomputer 8 determines that the screen brightness is insufficient with respect to the desired brightness determined in the current AE mode. And set a large negative error amount. Therefore, as shown by the broken line in FIG. 7, the control voltage Vcon. First moves to a position corresponding to the vicinity of the minimum numerical value “0x00”.
From this state, while the feedback of AE control is repeated several times, the control voltage Vcon. Moves to the right in the figure and converges to the lower limit “0x80-N” of the dead zone. In the first convergence state, since the reference voltage Vref. Is fixed, an error amount (negative) remains.

In the “first adjustment” in step ST4, the reference voltage Vref. Is adjusted with the goal that the absolute value of the error amount remaining after convergence falls within the error amount specified by the user as an absolute value using a parameter.
The user-specified error amount is specified based on the center point “0x80” in FIG. Here, the user specifies the error amount in one numerical range. In this case, the user-specified error amount range (first error amount range) is negative on the basis of “0x80” in the first adjustment. In the second adjustment described later, the user-specified error amount range (second error amount range) is set to the positive side with reference to “0x80”. It is also possible to set the first and second error amount ranges to different sizes.

As a specific adjustment procedure, the value of the reference voltage Vref. Is automatically or manually increased by a predetermined step (in the case of manual adjustment, for example, one or several steps that can be adjusted by a volume resistance or the like), and the AE control is executed again. To do. At this time, the microcomputer 8 checks whether the user-specified error amount is satisfied. If it is satisfied, the adjustment is completed. If not satisfied, the above adjustment is repeated until a user-specified error amount is obtained. At this time, as indicated by an arrow in FIG. 8, when the reference voltage Vref. Is increased, the convergence position of the control voltage Vcon.
Although the dead band is fixed because the reference voltage Vref. Is fixed until FIG. 7, the dead band also changes when the reference voltage Vref. Is changed, and the convergence point of the control voltage Vcon. As shown in FIG. It is possible to move.

FIG. 9 shows an adjustment end state in which the user-specified error amount is satisfied.
In this state, the control voltage Vcon. Converges to the lower limit of the error amount specified by the user (there may be a slightly larger position depending on the adjustment width of the step), and the reference voltage Vref. Becomes larger than “0x80”. ing.
In FIG. 9, the negative side width of the dead zone at this time is represented by a numerical value “N”. Further, the current position of the reference voltage Vref. Is represented by a parameter “X”.

  Next, in step ST5 of FIG. 5, the microcomputer 8 outputs a signal S81 indicating a numerical value “0x00” to the EVR 6. As a result, as shown in FIG. 10, the control voltage Vcon. Output from the iris control analog circuit 5 increases to a position corresponding to the minimum numerical value “0x00”, and the mechanical iris is fully opened.

In the “second convergence” of step ST6, in this state, the microcomputer 8 executes a program routine for normal mechanical iris AE control. Then, since the mechanical iris is fully opened and the screen detected by the OPD 42 is very bright, the microcomputer 8 determines that the screen brightness is too high for the desired brightness determined in the current AE mode. And set a large positive error amount. Therefore, as indicated by the broken line in FIG. 11, the control voltage Vcon. First moves to a position corresponding to the vicinity of the maximum numerical value “0xFF”.
From this state, while the feedback of AE control is repeated several times, the control voltage Vcon. Moves to the left in the figure and converges to the upper limit “0x80 + M” of the dead zone. In the second convergence state, since the reference voltage Vref. Is fixed (returned to the original “0x80”), the error amount (positive) remains.

  The “second adjustment” in step ST7 is an error amount range specified by the user on the opposite side with the absolute value of the error amount remaining at the time of convergence being the same as that used in the first adjustment and “0x80” as a reference. The reference voltage Vref. Is adjusted with the goal of being within the range.

As a specific adjustment procedure, the value of the reference voltage Vref. Is automatically or manually reduced by a predetermined step (in the case of manual, for example, one or several steps that can be adjusted by a volume resistor or the like), and the AE control is executed again. To do. At this time, the microcomputer 8 checks whether the user-specified error amount is satisfied. If it is satisfied, the adjustment is completed. If not satisfied, the above adjustment is repeated until a user-specified error amount is obtained. At this time, as indicated by an arrow in FIG. 12, when the reference voltage Vref. Is reduced, the convergence position of the control voltage Vcon.
At this time, as in the first adjustment, the dead zone also changes when the reference voltage Vref. Is changed, and the convergence point of the control voltage Vcon. As shown in FIG. 12 can be moved.

FIG. 13 shows an adjustment end state in which the user-specified error amount is satisfied.
In this state, the control voltage Vcon. Converges to the upper limit of the error amount specified by the user (there may be a slightly smaller position depending on the adjustment width of the step), and the reference voltage Vref. Becomes smaller than “0x80”. ing.
In FIG. 13, the width on the positive side of the dead zone at this time is represented by a numerical value “M”. Further, the position of the current reference voltage Vref. Is represented by the parameter “Y”.

The reference voltage Vref. Position (parameter X representing the first reference voltage) that satisfies the user-specified error amount in AE control from fully closed and the user-specified error amount in AE control from full open The position of the reference voltage Vref. (Parameter Y representing the second reference voltage) was obtained.
However, the two reference voltage positions are still different. This means that an error amount variation due to an analog circuit or the like occurs depending on which direction the AE control is performed. In addition, a different bias occurs in the dead zone depending on which direction the AE control is performed.

  Therefore, in this embodiment, in the next step ST8, as shown in FIG. 14, between the first reference voltage (parameter X) and the second reference voltage (parameter Y), for example, an intermediate value (X + Y) / 2 is reduced. The computer 8 calculates. The intermediate value (X + Y) / 2 is set as a mechanical iris initial adjustment value (final adjustment value).

Alternatively, a value obtained by adding the shift amount A to the intermediate value may be used as the final adjustment value of the mechanical iris. The shift amount A is a value that can be designated by the user using a parameter, and can be either positive or negative.
The reference voltage Vref. After the final adjustment is written into the nonvolatile memory 7, and the value of the reference voltage Vref. Is used thereafter. The microcomputer 8 holds the values of the parameters X and Y and calculates the initial adjustment value from the held values. However, the values of the parameters X and Y may be written in the nonvolatile memory 7 in the middle, and read and used when necessary.

In the above adjustment method, the difference in convergence accuracy can be absorbed by the convergence control from the close side and the convergence control from the open side.
At this time, when the shift amount A is “0” (FIG. 14), the size of the dead band width on both the open side and the close side becomes equal.
On the other hand, when the shift amount A is positive, as shown in FIG. 15A, the dead zone width on the opening side is increased, and the dead zone width on the closing side is reduced. Further, when the shift amount A is negative, as shown in FIG. 15B, the dead zone width on the opening side is reduced and the dead zone width on the closing side is increased.

In this way, the convergence state of the mechanical iris can be controlled by specifying the sign of the shift amount A and specifying the magnitude, so that it can be used properly according to the purpose.
For example, the shift amount A is set to 0 when it is desired to eliminate the bias of the mechanical iris control. Further, when it is desired to increase the exposure amount as much as possible, the shift amount A is set to a negative value so that it is easy to open and difficult to close. Furthermore, it is possible to set the shift amount A to be positive and easy to close and difficult to open.

However, in the mechanical iris initial adjustment algorithm of this embodiment, it is necessary to correctly perform adjustment from the close side and adjustment from the open side.
The reason why the adjustment is not performed correctly is that, for example, the first convergence shown in FIG. 7 should converge with a negative error amount as shown in FIG. In some cases, such as extremely high, the error amount is reversed and the error amount may converge with a positive error amount as in the second convergence shown in FIG.
In this case, convergence from the close side is synonymous with convergence from the open side. For this reason, if the second adjustment is performed from the open side, both adjustments are performed from the open side in two adjustments. As a result, even if the midpoint of the adjustment value from the same direction is taken, there is almost no difference, and as a result, the same bias as in the conventional adjustment is obtained.

In order to prevent this, in the algorithm of this embodiment, when the microcomputer 8 detects that the first convergence is reversed to a positive error amount, the first adjustment from step ST2 to ST4 in FIG. Substituting with processing from the open side, the parameter Y is first obtained.
Then, the process from the full close side (steps ST2 to ST4) and the process from the full open side (steps ST5 to ST7) are tried again. As a result, in either one of the processes, since a negative error amount is obtained at the time of convergence, the parameter X is obtained by the process in which the negative error amount is obtained.
Thereafter, the final adjustment value in step ST8 is calculated using the obtained parameters X and Y, and the initial value of the actual reference voltage Vref. Of the mechanical iris 2 is adjusted. Alternatively, in the case of the video servo type, the offset amount of the control voltage Vcon. Is determined according to the calculated final adjustment value.
If the above measures are taken, the first adjustment can be made from the open side (synonymous with the second), and the second adjustment can be made from the close side. A value can be obtained.

According to the present embodiment, when the shutter and AGC are fixed and exposure control is performed using only the mechanical iris, exposure control that does not cause a difference in convergence accuracy between convergence from the open side and convergence from the close side is possible. It is.
Further, since it can be realized by software, exposure control with a mechanical iris can be improved at low cost.
Furthermore, even if the luminance of the subject at the time of initial adjustment of the mechanical iris varies to some extent, it is possible to perform adjustment with high accuracy.

It is a block diagram of the video input device (camera) which employ | adopted DC servo type iris control concerning this embodiment. (A) And (B) is a figure which shows typically the voltage difference of a control voltage and a reference voltage. It is a state explanatory view showing the control area of mechanical iris control schematically. It is state explanatory drawing when the midpoint of a dead zone has shifted | deviated. It is a flowchart which shows the procedure of the mechanical iris initial adjustment method in connection with this embodiment. It is a state explanatory drawing of a full close. It is a state explanatory view at the time of the first convergence. It is state explanatory drawing in the 1st adjustment. It is a state explanatory view at the end of the first adjustment. It is a state explanatory drawing of a full open. It is state explanatory drawing at the time of the 2nd convergence. It is state explanatory drawing in the 2nd adjustment. It is a state explanatory view at the end of the second adjustment. It is a state explanatory view after final adjustment value calculation. (A) is a state explanatory diagram when the allowable value is positive, and (B) is a state explanatory diagram when the allowable value is negative.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Video input device (camera), 2 ... Mechanical iris, 3 ... Imaging device, 4 ... Video signal processing circuit, 5 ... Iris control analog circuit, 6 ... EVR, 7 ... Non-volatile memory, 8 ... Microcomputer, 9 ... Signal processing circuit 41... Signal processing unit 42. OPD Vref. Reference voltage Vcon. Control voltage X, Y Parameter (first and second reference voltage values) A Shift amount

Claims (8)

An iris control circuit that controls an iris that mechanically limits the amount of light passing through according to a voltage difference with respect to a reference voltage of an input control voltage,
A drive circuit unit that variably generates the control voltage and supplies the control voltage to the iris together with the reference voltage;
Input the brightness information on the output side of the iris and control the amount of control when the control voltage is controlled to converge until the desired brightness is obtained on the output side of the iris according to the brightness information. And a control circuit unit capable of calculating an initial adjustment value for the reference voltage;
Have
In the initial adjustment of the reference voltage, the control circuit unit causes the difference between the brightness on the output side of the iris and the desired brightness to be a certain value or less when the control voltage is controlled to converge from the fully closed state of the iris. The drive circuit unit is controlled with a first reference voltage that becomes and a second reference voltage that causes the difference in brightness to be less than or equal to a certain value when the control voltage is controlled to converge from a state in which the iris is fully open. And an iris control circuit that sets the initial adjustment value of the reference voltage between the first reference voltage and the second reference voltage. The first error amount range in which the difference between the brightness on the output side of the iris and the desired brightness when obtaining the first reference voltage is equal to or less than a certain value, and the brightness when obtaining the second reference voltage A storage unit that stores a second error amount range in which the difference is equal to or less than a certain value in a changeable manner by a user designation;
When the first and second error amount ranges are stored in the storage unit, the control circuit unit performs the convergence control with the iris fully closed, and again every time the reference voltage is adjusted. The convergence control is performed to determine whether or not the brightness difference falls within the first error amount range, and a reference voltage when the brightness difference falls within the first error amount range is determined as the first voltage. Whether or not the brightness difference falls within the second error amount range by setting the reference voltage, performing the convergence control with the iris fully opened, and performing the convergence control again each time the reference voltage is adjusted. 2. The iris control circuit according to claim 1, wherein a reference voltage when the brightness difference is within the second error amount range is determined as the second reference voltage. The iris control circuit according to claim 1, wherein the control circuit unit sets the initial adjustment value to an intermediate value between the first reference voltage and the second reference voltage. The control circuit unit sets the initial adjustment value to an intermediate value of the first reference voltage and the second reference voltage, or a voltage defined by two limits that are separated from the intermediate value by a predetermined value positively and negatively, respectively. The iris control circuit according to claim 1, wherein the iris control circuit is set. The control circuit unit monitors an error amount of automatic exposure control that expresses a difference between the current exposure amount and the optimum exposure amount and has positive and negative polarities, and the polarity of the error amount corresponds to the iris voltage at the first reference voltage. When the polarity corresponding to the initial state of control (fully closed) is reversed, the drive circuit unit is controlled again to perform the convergence control from the fully closed side, and the second convergence control performs the convergence control. When polarity inversion is not detected, the convergence value of the control voltage in the second convergence control is set as the first reference voltage, and the control voltage in which the polarity is inverted in the convergence control from the first fully closed side is set. The iris control circuit according to claim 1, wherein a convergence value is the second reference voltage, and the initial adjustment value is set between the first and second reference voltages. An iris that mechanically limits the amount of light passing through according to the voltage difference between the input control voltage and the reference voltage;
An imaging device for inputting light after passing through the iris;
A video signal processing circuit including a detection unit for detecting brightness of a screen obtained from a video signal output from the imaging device;
An iris driving circuit that generates the control voltage in a changeable manner and supplies the control voltage to the iris together with the reference voltage to drive the iris;
The brightness information of the screen is inputted from the detection unit, and a control amount for controlling the control voltage to converge until the desired brightness is obtained on the screen according to the brightness information is given to the iris driving circuit. A control circuit capable of controlling the iris driving circuit to perform initial adjustment for the reference voltage;
Have
In the initial adjustment of the reference voltage, the control circuit controls the convergence of the control voltage from the first reference voltage when the control voltage is converged from the fully closed state, and the iris is fully opened. A second reference voltage obtained by controlling the iris driving circuit, and setting the initial adjustment value between the first reference voltage and the second reference voltage. An iris control method for setting an initial adjustment value of the reference voltage for an iris that mechanically limits the amount of light passing in accordance with a voltage difference between the input control voltage and the reference voltage,
A first step of acquiring brightness information on the output side of the iris;
A second step of performing convergence control of the control voltage using the currently set reference voltage until a desired brightness is obtained on the output side of the iris according to the brightness information;
The first reference voltage when the control voltage is controlled to converge from the fully closed state of the iris, and the second reference voltage when the control voltage is controlled to converge from the fully open state of the iris, the first reference voltage. A third step obtained by performing the first and second steps at least twice;
A fourth step of updating the reference voltage between the first reference voltage and the second reference voltage acquired in the third step, and outputting the reference voltage to the iris;
Including an iris control method. A program including a procedure for setting the initial adjustment value for an iris that mechanically limits the amount of light passing in accordance with a voltage difference with respect to a reference voltage of an input control voltage,
A first step of acquiring brightness information on the output side of the iris;
A second step of performing convergence control of the control voltage using the currently set reference voltage until a desired brightness is obtained on the output side of the iris according to the brightness information;
The first reference voltage when the control voltage is controlled to converge from the fully closed state of the iris, and the second reference voltage when the control voltage is controlled to converge from the fully open state of the iris, the first reference voltage. A third step obtained by performing the first and second steps at least twice;
A fourth step of updating the reference voltage between the first reference voltage and the second reference voltage acquired in the third step, and outputting the reference voltage to the iris;
A program for executing a procedure including: using a computer.

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