JP3297485B2 - Imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging device such as a video camera.

[0002]

2. Description of the Related Art In recent years, the development of video equipment such as video cameras has been remarkable, and various functions have been automated and operability has been improved. For example, automation of zoom lens equipment, automatic focus control, automatic exposure control, etc. Is essential, and for example, when it comes to automatic exposure control, it is an important factor that determines the quality of a captured image, and in any shooting environment, stable and good automatic exposure control must always be possible. The importance of the automatic exposure control function is extremely high.

FIG. 23 is a block diagram showing a basic configuration of an exposure control system of a general video camera, 101 is a photographic lens optical system, 102 is an iris for adjusting the amount of incident light, 103
Denotes an image pickup device such as a CCD for photoelectrically converting an image formed on the image pickup surface of the image pickup lens by the photographic lens optical system and adjusting the amount of light by an iris to convert the image into an image pickup signal; 104, an image pickup signal output from the image pickup device; A camera signal processing circuit that performs predetermined signal processing on the video signal to convert the video signal into a standardized video signal.
05 is a video signal output terminal, 106 is a motor that drives the iris 102 to change the opening amount, 107 is a motor 106
Drive circuit for controlling the driving of the image pickup device 103
CCD drive circuit 109 for controlling the accumulation, readout, and reset timing of the CCD, and variably controlling the accumulation time (exposure time) to set a desired shutter speed. Reference numeral 109 denotes a level of the luminance signal output from the camera signal processing circuit. The aperture driving circuit 107 evaluates the exposure state based on the
An automatic exposure control circuit (AE circuit) 110 for controlling the driving circuit 108 to optimally control exposure, and a switch panel 110 for receiving an input of a key operation.

The exposure control by the AE circuit 109 will be described. The luminance signal output from the camera signal processing circuit 104 is integrated, and the aperture driving circuit 107 is controlled so that the level falls within a predetermined range. A closed loop for iris control is formed to control the output drive current to vary the iris opening amount, and the drive pulse is switched by controlling the CCD drive circuit 108 in accordance with the key operation of the switch panel 110. And a control system for controlling the exposure time, that is, the shutter speed, by varying the accumulation time of the image sensor 103 to obtain an appropriate exposure state.

This storage time control is what is called an electronic shutter. For example, in the case of NTSC, in addition to the usual exposure time of 1/60 second for each screen, a control of about 1/100 to 1/10000 second is performed. The light accumulation time can be selected in a plurality of stages up to the above.

In the system configured as described above,
When a high-speed electronic shutter is used, there is an automatic exposure control mode for controlling the aperture mechanism (iris) of the imaging optical system based on each arbitrarily selected set exposure time, that is, for each shutter speed. This is a so-called shutter priority mode. FIG. 24 shows a shutter priority mode in which the shutter speed on the horizontal axis is selected, and the shutter speed is fixed and the aperture value on the vertical axis is varied.

[0007]

However, in the iris control based on the brightness level of the image pickup signal and the shutter priority mode as in the above-mentioned video camera apparatus, appropriate exposure control is always realized in various photographing environments and photographing conditions. Cannot be performed, and proper exposure control cannot be performed in many cases.

[0008] In particular, in a camera such as a silver halide camera which captures a still image for a moment, exposure control at the moment of photography may be appropriately performed. However, as in a video camera, a moving image is captured for a long time. In such a case, a video that satisfies these conditions must always naturally follow the changing shooting conditions and shooting environment during shooting, and always perform stable and optimal exposure control. Realization of an exposure control device for a camera is strongly desired.

It is an object of the present invention to provide an automatic exposure control apparatus which satisfies all of these conditions and can always perform optimal exposure control regardless of a shooting environment and a shooting situation.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an image pickup means for photoelectrically converting incident light imaged on an image pickup screen, and a method for dividing the image pickup screen into a plurality of areas. Detecting means for detecting a luminance level of an area; generating means for generating histograms of the plurality of areas according to the luminance level based on an output of the detecting means; and a histogram generated by the generating means. A region selection unit for selecting a predetermined number of regions from a lower luminance level, and an exposure control unit for controlling exposure based on the luminance level of the region selected by the region selection unit. Is used.

[0011]

[0012]

[0013]

This makes it possible to carry out optimal control for the set photographing mode. In particular, it is possible to perform special control such as a subject having a high-luminance background such as landscape photography and a subject having a dark background such as a night scene. Even in an unusual photographing situation, the main subject to be photographed can be surely focused on the light, and appropriate exposure control can be performed.

[0014]

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an image pickup apparatus according to the present invention.

FIG. 1 is a block diagram showing the configuration of an embodiment in which the image pickup apparatus of the present invention is applied to a video camera. In FIG. 1, reference numeral 1 denotes a photographing lens optical system, 2 denotes an iris for adjusting the amount of incident light, and 3 denotes An image pickup device such as a CCD, which photoelectrically converts an image formed on the image pickup surface of the image pickup surface by a photographic lens optical system and whose light amount is adjusted by an iris to convert the image into an image pickup signal;
Is a double correlation sampling circuit (CDS) for reducing the noise of the charge accumulated in the image sensor, 5 is an AGC circuit for automatically adjusting the gain of the image signal, and 6 is a predetermined signal processing for the image signal output from the AGC circuit 5. A camera signal processing circuit for converting the video signal output from the camera signal processing circuit into a signal suitable for recording on a video tape recorder or the like; Reference numeral 8 denotes a video tape recorder using a magnetic tape as a recording medium.

On the other hand, reference numeral 9 denotes an AGC for dividing an imaged screen into a plurality of screens and extracting an image signal corresponding to an arbitrary area.
A gate circuit 10 for gating a signal output from the circuit 5; an integrator 10 for integrating an image signal corresponding to a designated area in the image screen selected by the gate circuit 9 to obtain an average light amount; An A / D converter converts a signal output from the integrator into a digital signal that can be processed by a system control circuit described later. The area designating operation by the gate circuit 9 and the integration operation of the integrator 10 relate to the designation of the photometric region and the setting of the weight in accordance with the photographing mode. It can be arbitrarily set by controlling the pulse and the integral reset pulse. The detailed processing will be described later.

Reference numeral 12 denotes a CCD drive circuit for controlling the accumulation operation, readout operation, reset operation, and the like of the image sensor 3, reference numeral 13 denotes an iris motor for driving the iris 2, reference numeral 14 denotes an iris drive circuit for driving the iris motor, and reference numeral 15 A D / A converter for converting a digital iris control signal output from a system control circuit into an analog signal,
Reference numeral 6 denotes an iris encoder constituted by a Hall element or the like for detecting the opening amount of the iris, that is, the aperture value. Reference numeral 17 denotes an amplifier for amplifying the output of the iris encoder 16; The A / D converter converts the output into a digital signal that can be processed by a system control circuit described later.

19a, 19b, 19c,... Are data reference tables (LUTs) storing various data for exposure control.
In the present embodiment, three tables are illustrated so that a plurality of settings are made according to the shooting conditions in the Look up table. However, the tables are provided for each of the prepared shooting modes. In the photographing mode, two data tables are selectively used. Incidentally, in the present embodiment, as will be described later, “indoor shooting mode”, “sport shooting mode”, “landscape shooting mode”, “portrait mode”, and “night scene mode” are described.

More specifically, information on control characteristics of parameters for exposure control such as iris, shutter speed, gain, etc., corresponding to each of a plurality of shooting modes is stored, and according to the set shooting mode. Necessary data is read out.

Reference numeral 20 denotes an operation unit including a plurality of operation keys for performing various operations. Reference numeral 21 denotes a D / D converter which converts a digital gain control signal output from a system control circuit into an analog control signal and supplies the analog control signal to an AGC circuit. The A converters 22 and 23 convert a digital control signal output from the system control circuit into an analog control signal in order to change or correct various characteristics in camera signal processing and image signal processing according to shooting conditions, respectively. It is a D / A converter to be supplied to the camera signal processing circuit 6 and the image processing circuit 7.

Reference numeral 25 denotes a system control circuit configured by a microcomputer, which comprehensively controls the entire video camera system in this embodiment.

The system control circuit 25 sends control signals for controlling the characteristics of the camera signal processing circuit 6 and the image signal processing circuit 7 to the D / A converters 22 and 23 in accordance with the shooting mode operated by the operation section 20. , And controls the gate pulse supplied to the gate circuit 9 in accordance with the photographing mode, and sets a photometric region for detecting the amount of light on the imaging screen. Further, it controls the integration reset pulse supplied to the integrator 10 to control the selection characteristic of the integration operation.

For example, FIG. 2 shows an example in which a photometry area is set on an image pickup screen. In FIG. 2, a photometry area is set at a central portion in the image pickup screen, and signals in this area are mainly exposed. FIG. 9 shows an area setting state of “center-weighted metering” used for control calculation.

This is based on an empirical rule that the probability that the main subject is located almost at the center of the screen is high. In the exposure calculation, the signal inside the central area indicated by the solid line is larger than the signal outside. Exposure control is performed by assigning coefficients to increase the weight at the center.

Then, the integrated value corresponding to the shooting mode of the image signal in the photometry area taken in through the gate circuit 9 is taken, and the iris control according to the shooting condition is performed by referring to the data of the LUTs 19a, 19b, 19c. The signal is calculated and supplied to the iris drive circuit 14 via the D / A converter 15 and the D / A signal is supplied to the AGC circuit 5.
A gain control signal is supplied via the converter 21 to control the gain of the AGC circuit 5 in accordance with the photographing mode and the photographing state. Further, a control signal is also supplied to the CCD drive circuit 12 to perform photographing mode and photographing. Depending on the situation, the control of the storage time (electronic shutter), readout timing, reset timing, etc. of the image sensor is performed.

These various controls are performed by referring to the output of the iris encoder 16 in the photographing mode, various control parameters are calculated and set, and the above-described controls are selectively, simultaneously, or simultaneously. They are executed in appropriate combinations.

As described above, the system control circuit 25
Operates the iris control, the gain control, the drive control of the image sensor (for example, the electronic shutter by the accumulation time control) based on the integral value, or the like, simultaneously or appropriately in combination based on the photographic mode and the iris drive state. By doing so, optimal exposure control is performed for all shooting situations.

The imaging apparatus according to the present invention has the above-described configuration, and its specific operation will be described below step by step.

First, various control parameters used for exposure control in the apparatus of the present invention will be described.

(1) Iris Aperture (Parameter P1) The iris control signal output from the system control circuit is converted into an analog signal by the D / A converter 15, and then supplied to the iris drive circuit 14. The current is amplified and supplied to the iris motor 13 to drive it. Thus, the iris motor 13 controls the aperture state of the iris 2.

Integrator 1 supplied from A / D converter 11
The integrated value of 0 corresponds to the LUT 19 corresponding to the shooting mode.
If the control value is larger than the control values defined by a, 19b, 19bc, etc., it means that the exposure is over. Therefore, the iris drive circuit 14 is controlled to drive the iris motor 13 in the direction to narrow down the iris 2, and the incident light amount To reduce the output level of the integrator 10 as a result.

On the other hand, when the integrated value supplied from the A / D converter 11 is smaller than the control value specified by the LUT 19, the iris motor 13 is driven in the opposite direction, and the iris 2 is driven. It is controlled to open to increase the amount of incident light and consequently to increase the integral value.

[0034] (2) shear accumulation time setting signal D _t ivy speed (parameter 2) image sensor is output in the form of a digital signal from the system control circuit 25, CCD driving circuit 12 receives this CCD various timing A pulse to be determined is generated, and the accumulation time is controlled.

Since the setting method and the setting range of the accumulation time are greatly different depending on the structure of the CCD which is the image pickup device, in the present embodiment, a CCD having a structure in which unnecessary charges are discarded to the OFD (overflow drain) during the H blanking period is taken as an example. This will be explained.

FIG. 3A is a diagram for explaining the operation of the CCD, and the range that can be set is a range allowable in terms of image quality such as image pickup light quantity and smear on the high-speed side if it is within H blanking. Can be set with. Substantially 1 / 10,000 seconds. The low speed side is H until 1/60 second in the case of NTSC.
It can be set in steps of the blanking cycle (about 63.5 μsec).

As a specific time control method, D _t
Is output from the system control circuit 25, the shutter speed T is determined by the following calculation. . T _NTSC ≒ (262.5-D _t ) * 63.5 μsec. T _PAL ≒ (312.5-D _t ) * 64.0 μsec

The CCD drive circuit 12 receiving the instruction in this way applies V _sub to realize the electronic shutter operation.
ΔV _sub is further added to (vertical substrate applied voltage) to change the potential distribution of the charge storage portion by photoelectric conversion, and unnecessary charges are discarded in the direction of the substrate. In this way, an arbitrary shutter speed can be set. FIG.
(B) shows this operation.

The system control circuit 25
Current shear ivy speed the D _t in order to slow down the Hayakere if shear ivy speed than the control value defined in LUT19 corresponding to the integral value from the A / D converter 11 to the current less than the value change, change the current value larger than the value of said D _t in order to increase the shear ivy speed as late than the control value defined in LUT19 reversed.

(3) Gain (Parameter P3) The D / A converter 21 outputs a gain setting signal for determining the amplification factor of the video signal, and supplies it to the AGC circuit 5.

The AGC gain is set by the AGCC amplifier
The output signal of the DS4 is provided so that appropriate signal processing is performed in the camera signal processing circuit 6 in the next stage.
Conventionally, it has been treated as a part of a component of an AE loop by an iris, and is not intended to be arbitrarily controlled.

In recent years, even if the S / N ratio of the CCD has been improved and the gain of the AGC has been increased to increase the gain, the noise of the image pickup system has become less conspicuous, and the settable range as a control parameter has been expanded.

Since the gain is a parameter having a fast control response in the imaging system, the gain is a parameter suitable for AE control in a situation where a quick reaction is required.

If the current AGC gain is larger than the control value specified in the LUT 19 corresponding to the integrated value from the A / D converter 11, the system control circuit 25
Updates the gain set value to reduce the AGC gain.

Conversely, if the current AGC gain is the A / D converter 2
If the control value is smaller than the control value defined by the LUT 25 corresponding to the integrated value from 5, the gain setting is updated to increase the gain of the AGC.

According to the present invention, by using the above three parameters, it is possible to maintain an appropriate exposure state of the image pickup system in accordance with a photographing state and a photographing mode. The exposure control used will be described. First, the setting of the photometry area on the imaging screen that changes according to each exposure control mode will be described.

The subject photographed by the video camera is a place,
It changes variously depending on the environment and shooting conditions at that time. Therefore, in order to always perform the optimum automatic exposure control in these shooting situations, the setting position of the photometry area in the image pickup screen and the weighting control of the photometry area are appropriately changed to perform control suitable for the situation. There is a need.

Therefore, in consideration of the light condition according to the set representative scene, a luminance distribution in the screen is assumed, and A is provided in an area in the screen which provides effective information for determining the exposure amount.
It is necessary to have an automatic photographing mode in which an E (automatic exposure control) operation coefficient is assigned to a large value and a photometric region is set so that the weighting is increased.

According to this embodiment, as shown in FIG. 4, an example is shown in which the imaging screen is divided vertically into four and horizontally into six, and the entire screen is divided into 24 small areas. Each region is numbered from 1 to 24).

These division operations are controlled by the system control circuit 25. The gate circuit 9 is controlled to open and close by the gate pulse output from the system control circuit 25, and the output of the AGC circuit 5 is controlled. The signal is extracted for each of the regions 1 to 24 and is integrated as an independent value by the integrator 10 for each region.
After being converted into a digital signal by the D converter 11, the digital signal is taken into the system control circuit 25.

In the system control circuit 25, processing is performed in which a weighting coefficient preset in accordance with the photographing mode is added to the integral value in each of these areas. Note that these processes can be performed by time division processing corresponding to 24 divisions.

FIG. 5 shows an example of an image-capturing screen on which weighting coefficient processing has been performed. The above-mentioned "center-weighted photometry" is realized by the 24-split AE system of the present invention, and corresponds to the center of the screen. Regions 8-11, 14-17
Is set to 1.0, the weighting operation coefficient of the surrounding area is set to 0.5, and AE control is performed with emphasis on the center. Specifically, if the iris, shutter speed, and gain are controlled based on a value obtained by adding the integrated values of these weighted areas, the above-mentioned weights can be reflected in these controls.

In addition, various AE characteristics can be set by setting a photographing mode according to a photographing condition and appropriately selecting a photometric area setting and a photographing program according to a photographing condition described later. It is.

Next, the actual AE control according to the photographing situation using the above three parameters will be described. As described above, conventional iris control alone is not enough to perform shooting adapted to various shooting situations.
In the present invention, more parameters are prepared, and these can be optimally controlled.

That is, in the present invention, a photographing control called a "program mode" in which photographing can be performed while assuming several typical photographing conditions and automatically adjusting each under the optimum conditions for each condition. Invented the scheme. These program modes can be arbitrarily selected and set by operating the keys of the operation unit 20.

In order to always perform good shooting in various places of video shooting and in various situations, a typical scene is set according to the shooting situation, and a plurality of scenes are set in order to optimize the scene. It is necessary to have an automatic shooting (exposure control) mode.

In order to solve this problem, a plurality of lookup tables (LUTs) storing control functions for controlling a plurality of parameters are set, and as shown in FIG.
A plurality of tables 19a, LUT 19b, LUT 19c,... Are prepared by a memory such as a ROM, and are configured to be selectively readable by a system control circuit 25. Performed.

FIGS. 6 and 7 show examples of control characteristics of each parameter controlled by data read from the LUTs 19a, 19b, 19c,...

FIG. 6 shows that the shutter speed of parameter (2) can be set to 1/100 second as much as possible, and the iris of parameter (1) or the parameter ( 3) A
FIG. 9 is a program diagram showing a program control operation for performing appropriate exposure control by changing a GC gain, and is stored in, for example, the LUT 19a.

In this program mode, when the power supply frequency is 5
This is for suppressing the flicker of the fluorescent lamp which occurs when using the NTSC video camera in the area of 0 Hz, and can be called an "indoor shooting mode".

In the figure, the horizontal axis is the subject illuminance as an input parameter, and the vertical axis is the set value of each parameter. As is clear from the figure, the setting range of each parameter is A, B, C3 according to the input parameter, that is, the illuminance of the subject.
It is divided into two areas, and exposure control is performed by combining three parameters in each area.

That is, looking at the area A, the shutter speed (P2) is fixed to 1/100 second and the gain (P3) is also fixed, and the iris (P1) is controlled according to the brightness. Exposure control is performed. It is possible to adapt to most subjects in this area A.

On the other hand, in the area B, the illuminance is low and the iris is open, which indicates that the iris is open and constant as shown in the figure. Therefore, the exposure control is performed by changing the shutter speed to 1/60 second. That is, in the NTSC system, accumulation and reading are originally performed at a period of 1/60 second, so 1/60 second indicates an original operation timing.

When the illuminance further decreases, as shown in area 3, the iris and the shutter have reached their limits, so that the exposure control is performed by increasing the gain (P3).

As described above, by changing the control parameters P1 to P3 according to the change of the input parameter indicating the illuminance of the subject, it is possible to perform the optimal exposure control according to the photographing situation.

FIG. 7 shows another program mode. For example, a program diagram stored in the LUT 19b sets the shutter speed (P2) to a high-speed shutter as short as 1/500 sec. This is a program mode prepared to suppress blurring of a fast-moving subject and to clearly capture a screen. In the present invention, the program mode is referred to as a "sport shooting mode".

As can be seen from the figure, the shutter speed in area A and area B is reduced to 1/500 as much as possible.
Seconds, and the iris (P
Exposure control is performed based on 1) and the gain (P3), and an operation is performed such that the illuminance of the subject is reduced and the shutter speed cannot be maintained for the first time in the area C where the shutter speed is gradually changed to 1/60 second.

FIG. 12, which will be described later, is a program diagram in the "landscape photographing mode". The actual program diagram is a graph as shown in FIGS. 6 and 7, but for the sake of simplicity, in FIG. 12, iris, shutter speed,
The operating range is shown sequentially from the top in the order of the gain.

That is, in the figure, I indicates an iris control parameter (P1), S indicates a shutter speed control parameter (P2), and G indicates a gain control parameter (P3). As shown on the right side of the figure, The iris control parameter (P1) operates between CLOSE and OPEN, and S
Is the shutter speed control parameter (P2) is constant, G
Means that the gain control parameter (P3) changes from an amplification factor 1 of ± 0 dB (THROUGH because an input signal is output as it is) to a predetermined value G1. However, in each variable area, its value changes in accordance with the luminance level which is an input parameter, similarly to the program diagrams of FIGS. 6 and 7 described above.

In the landscape photographing mode, there are many cases where there is no flicker, fast-moving subject, etc., so that the shutter speed (P2) is fixed at 1/60 second of the standard, and the control is centered on the iris (P1). Is released, the gain (P3) is controlled.

That is, as shown in the figure, the control range of the parameter is y according to the value of the subject luminance of the input parameter.
Is divided into two areas. The shutter speed (P2) is fixed at 1/60 second regardless of the value of the subject brightness of the input parameter, the AGC gain (P3) is fixed at ± 0 dB until the brightness decreases to y, and the iris (P1) Only control is performed. After the brightness becomes y or less and the iris is opened, the AGC gain is changed to perform the optimal exposure control.

As described above, a plurality of program modes are prepared in accordance with the shooting conditions, and by appropriately selecting the program modes by operating the keys of the operation unit 20, the optimum exposure mode can be obtained for any shooting conditions. Control can be performed.

When the photographing program mode is switched by the operation unit 20, the setting of the photometric area on the image pickup screen is simultaneously switched as described above. For example, FIG.
In the indoor photographing mode of FIG. 7 and the sports photographing mode of FIG. 7, a subject such as a normal person, which is usually positioned at the center of the screen, is often photographed. Also in the landscape shooting mode of FIG. 12, a histogram of the brightness distribution of the screen is created in order to make the photometry area on the imaging screen a weighting distribution suitable for the mode in conjunction with the operation of switching to the shooting mode, and the sky, water surface, etc. Exposure control is performed so as to eliminate the influence of the high luminance.

The control of each parameter in each program diagram described above has the following features.

That is, as is apparent from FIGS.
Each control parameter is stored in a plurality of areas (A,
B, C), and each area is selected according to the input parameter, that is, the change in the illuminance of the subject. When looking at each area, the variable parameter used for the AE control is one. Only one is specified and the other two
One is fixed (FIX). This is shown in the table below the program diagram.

That is, FIG. 6 shows that, in the area A, the parameter (P1) is variable and the other parameters are fixed, that is, when the iris control is performed, the shutter speed and the gain are fixed.

In the area B, the parameter (P2), that is, the shutter speed is variable and the others are fixed.
In this case, the parameter (P3), that is, the gain is variable, and the others are fixed.

As a result, although the control is performed by changing the three control parameters, the number of variable parameters is always one in each area unit, and the calculation processing of the fixed parameters is not required. The processing is the same as that of the conventional single parameter processing.

That is, according to the present invention, the complicated calculation process naturally caused by increasing the control parameters in order to cope with any photographing situation is divided into a plurality of parameter setting areas, and each of the variable areas is varied. By setting one parameter to be performed and fixing the other parameters, it is possible to simplify the handling of a variety of complicated imaging conditions and a plurality of parameters to be controlled, and realize optimal AE control without using a large-scale logic or a large-scale computer. Is what you can do.

The present invention has another feature in the above-described control parameter switching operation.

That is, in the present invention, although the number of parameters to be changed is always set to one and the other is fixed, the number of calculation processes is reduced.
The normal imaging target is a moving image, and the imaging conditions are constantly changing.

When each control parameter is set corresponding to an input parameter, the value of the input parameter may move between a plurality of divided areas according to a change in photographing conditions. At this time, a controlled parameter switching operation occurs, but the manner of change on the screen may vary greatly depending on the parameter. If this change occurs frequently, the screen is expected to be difficult to see. You.

As a countermeasure, it is conceivable to provide a hysteresis at the time of area transition to reduce the frequency of area transition. However, there is no effect when switching occurs, and it cannot be a fundamental measure. .

Accordingly, in the present invention, as a countermeasure against this, as shown in FIGS.
The control is performed so as to simultaneously change only the areas B1 and B2 near the boundary of the area.

In FIG. 6, a boundary portion B1 sandwiched between broken lines
Is a boundary region in which the parameters P1 and P2 operate simultaneously, and similarly, in the boundary portion B2, the parameters P2 and P3 operate simultaneously.

By simultaneously changing the two parameters in this way, an image change unique to each parameter occurs simultaneously and gradually, so that even when a parameter moves between areas, the screen changes. Can be visually visually uncomfortable.

The method of controlling the exposure in a plurality of photographing program modes has been described above. According to the present invention, the D / A is controlled by the command of the system control circuit 25 in accordance with the above-mentioned photographing mode switching. Control signals for changing various characteristics of various types of image processing and camera signal processing from the standard position according to the respective shooting conditions can be supplied via the converters 22 and 23.

That is, in order to always represent each scene optimally in various places and situations where photographing is performed, in addition to the control by the basic control parameters at the time of photographing, the camera signal processing circuit 6 shown in FIG. The control of the image signal processing circuit 7 and the like is also effective.

Therefore, taking into account the image capturing screen corresponding to the set representative scene, FIG.
The camera signal processing circuit 6 of FIG. 8 shows the non-linear conversion characteristics (knee characteristics and γ characteristics) of the video signal level as shown in FIGS.
It is possible to control the characteristics of the aperture correction circuit for changing the sharpness of the image or changing the sharpness of the image as shown in FIG. 3C, and the image signal processing circuit 7 in FIG. For example, it is conceivable to give a “fade effect” or “afterimage effect” to a captured video signal.

FIG. 9 shows a configuration example of the image signal processing circuit 6 having a function of providing such an additional effect, and the configuration and operation will be described below.

The color signal processing circuit 30 generates a color signal specified by a control signal * 1 from the system control circuit 25 (for example, a full blue background or a full white), and outputs the color signal and the video output. Is delayed by one screen by the field memory circuit 32, and 3
It is supplied to a selection switch 31 for making an alternative selection.

From the selection switch 31, information of one of the three selected by the instruction * 2 of the system control circuit 25 is supplied to the input terminal of the multiplier 33. The multiplier 33 executes a multiplication process using the coefficient output from the multiplication coefficient generator 34 according to the instruction * 3 of the system control circuit 25. The result of the multiplication is added by an adder 35 to a signal obtained by performing similar coefficient multiplication processing by a multiplier 38 to a video input signal input from an input terminal 36, and supplied to an output terminal 37. You.

In the process of processing such a signal, if the non-signal OFF terminal is selected by the selection switch, the adder 35
Is input only to the video signal from the input terminal 36, and this video input signal is output (through) to the video signal output terminal 37 as it is. At this time, the coefficient of the multiplier 38 is 1.0, which is a through value.

Next, when the output of the color signal generator 30 is selected by the selection switch 31, the multiplication coefficient generator 34 is controlled in accordance with an instruction from the system control circuit 25 (start / end timing or direct coefficient setting). An operation with the output is performed, and one of them appears as 0 → 1 and the other disappears as 1 → 0 in the inverse operation (1's complement relationship with the coefficient) to the input video signal from the video input terminal 36, and as a result, the color The signal and input signal are switched. Visually, the screen changes so as to gradually change from a blue screen to a moving image.

Also, when the output of the field memory is selected, the relationship between the coefficients of the multiplier 38 is a one's complement as described above. The difference is that the operation is performed at a fixed value of, for example, 0.5 without a temporal change.

In this case, the result of the addition and output is cyclically added at a predetermined rate with a delay of one screen, so that the input image is expressed as trailing in the time axis direction.

By operating such signal processing in, for example, a portrait photographing mode or the like in which a person is photographed with emphasis, in the above-described camera signal processing circuit, aperture characteristics and the like are changed to change the human characteristics. The image quality can be adjusted, for example, by lowering the frequency response in the vicinity of the sharpness of the visual characteristics, or about 2-3 MHz in the case of a television signal, so that a soft feeling can be given to the image.

By operating the circuit as shown in FIG. 9, it is possible to automatically give the effect of special image processing, such as applying a color fade to an image.

This portrait photographing mode is basically a photographing mode based on center-weighted light metering in which the light metering areas shown in FIG. 5 are weighted as shown in FIG. The diagram is set as shown in FIG. The actual program diagram is as shown in FIGS. 6 and 7, but for simplicity, Iris,
The operating range is shown sequentially from the top in the order of shutter speed and gain.

That is, in FIG. 10, I indicates an iris control parameter (P1), S indicates a shutter speed control parameter (P2), and G indicates a gain control parameter (P3). As shown in the right side of FIG. The iris control parameter (P1) operates between CLOSE and OPEN,
The shutter speed control parameter (P2) is displaced between High speed (T1) and the standard 1/60 second, and the gain control parameter (P3) is ± 0 dB amplification factor 1 (THROUGH because the input signal is output as it is. And
To a predetermined value G1.

However, as with the program diagrams shown in FIGS. 6 and 7, the values of each parameter change in accordance with the luminance level which is an input parameter, in the variable region.

This portrait mode assumes that the subject is a person, and therefore emphasizes taking a shallow depth of field.

As can be seen from the figure, two threshold values, y1 and y2, are provided for the illuminance of the object on the horizontal axis.
Is divided into two areas.

Regarding the iris, in the high luminance area A, the iris is controlled. However, since it is desired to secure the S / N at a high luminance, the gain of the AGC remains ± 0 dB until the iris becomes an open value. The iris is maintained, but the iris is controlled in consideration of a decrease in resolution due to a diffraction phenomenon caused by a small stop of the iris.

Specifically, when the input luminance level is equal to or less than y1, the iris is controlled to an open value. As a result, the iris is open at normal luminance, and the depth of field can be reduced to the minimum. That is, the control characteristic of the iris is y
The entire region from high luminance to low luminance can be switched to two stages of a variable region and an open region with 1 as a boundary.

Regarding the shutter speed, in the high-brightness region of y1 or more, the high-speed shutter speed T1, which is higher than the normal 1/60 second, is set. In order to make the depth of field as shallow as possible, the shutter speed is set to a somewhat higher value. Actually, it is set within a range of about 1/250 to 1/4000 second.

In addition, since this increases the S / N, there is also a meaning that control can be performed without increasing the AGC gain even when the luminance becomes low.

In the areas y1 to y2, the iris is at an open value, and the AGC gain is not desired to be increased from the point of S / N, so that the shutter speed is set between T1 and 1/60 second of the standard. Exposure control is performed by changing.

When the luminance level is equal to or less than y2, the shutter speed is set to 1/60 second (N) which is the standard value of the television signal.
TSC).

In this state, the exposure control is performed only by the AGC gain, and the exposure control is performed by increasing the gain within the allowable range of S / N.

As described above, the AGC gain is always fixed to ± 0 dB when the luminance is equal to or more than y2, and the AGC circuit 5 is controlled so as not to have an amplification effect. Since it occupies most of the area, it is possible to obtain a photographed image with a good S / N over the entire area.

When the input luminance level is equal to or less than y2, gain control is performed for the first time, and exposure control is performed within the allowable range of S / N by increasing the gain.

As described above, in the portrait mode, the image is photographed by center-weighted photometry. However, since photographing based on a person is premised, it is extremely effective to use the above-described image quality adjustment and image processing together.

The basic description has been given above regarding the setting of each control parameter in each shooting mode, the setting of the photometry area according to the shooting mode, and the switching of the characteristics of the signal processing system according to the shooting mode.

Next, the procedure for setting each control parameter such as the iris, shutter speed, and gain described above will be described.

FIG. 11 is a flowchart showing the parameter setting operation including the above-described parameter processing of the area boundary portion in the program photographing mode using the program charts of FIGS. 6 and 7, for example.

In the figure, when control is started, S
1 to monitor the power-on, and when the power is turned on, proceed to S2, confirm the photographing program mode (M) selected by the operation unit 20, proceed to S3, and proceed to S3. Reference program LUT 19a or 19b, 19c corresponding to mode (M), and set the specified program characteristics.

In S4, the data relating to the weighting of each of the 24 divisions set on the imaging screen is read from the specified LUT, weighting is performed according to the shooting mode as described above, and the flow advances to S5.

In S5, according to the designated photographing mode,
The contents and characteristics of image processing are read out from the LUT, and image quality adjustment by aperture control or image processing by color fade or the like is set in the above example, which is adapted to the shooting mode.

In S6, the current area on the reference parameter axis, that is, the current area is confirmed from the illuminance of the object corresponding to the input parameter.

Subsequently, the flow advances to S7, where a branch destination is determined according to the current area.

If it is determined that the area is A, the process proceeds to S8, where the iris control parameter P1 is calculated.
In step 9, the inside and outside of the area B1 is determined.
If it is outside 1, the process proceeds to S10, where the shutter speed control parameter P2 is held and fixed beforehand.
11 to calculate and update the shutter speed control P2, and then to S21, where the gain control parameter P3
Is held in front and fixed, and the process proceeds to S24.

If the area B is determined in S6,
In step S12, the shutter speed control parameter P2 is calculated, and the process proceeds to step S13, where the inside and outside of each of the boundary areas B1 and B2 are determined.
To calculate the iris control parameter P1 and proceed to S21, hold and fix the gain control parameter P3 in advance, and proceed to S24.

If it is within B2, the flow advances to S16 to calculate the gain control parameter P3, and the flow advances to S23. After the iris control parameter P1 is held and fixed beforehand, the flow advances to S24.

If neither B1 nor B2 belongs,
In S15, the iris control parameter P1 is pre-held and fixed, and in S22, the gain control parameter P3 is fixed. Then, the process proceeds to S24.

If it is determined in S7 that the area is C, the process proceeds to S17, where the gain control parameter P3
Then, in S18, the inside and outside of the area boundary area B2 is determined. If the area is outside the boundary B2, the process proceeds to S20, where the shutter speed control parameter P2 is pre-held and fixed, and if it is within B2. For example, the process proceeds to S19, in which the shutter speed control P2 is calculated and updated, and the process proceeds to S23.
Proceed to.

At S24, the values P1, P2, and P3 of the parameters set by the above-described processing, that is, the iris,
The control values of shutter speed and gain are output from the system control circuit 25 to control the iris 2, the image sensor 3, and the AGC circuit 5 according to their program modes, and the next processing time unit comes in S25. (In this embodiment, one operation is used for one frame as a basic unit). In step S26, the power supply is confirmed to be turned off.
If the power-off is instructed, the process ends.

As a result, various parameters can be controlled in accordance with each of the selected program modes, and exposure control is performed based on the control.

Further, in conjunction with the switching of the photographing program mode, the characteristics or additional functions of the photometry area and the image signal processing system on the photographing screen are switched to those suitable for the photographing situation. Optimum automatic exposure control and photographing can always be performed according to the photographing situation of the camera.

Further, even if the photographing condition changes, the photographing state of the camera does not unnaturally change, and the optimum control mode can be switched.

Next, the "landscape photographing mode" which is the program photographing mode of the present invention will be described. In addition to the "landscape photographing mode" as an example, setting and control of various photographing modes, and the internal structure of the data table LUT and its internal structure will be described. Control of control parameters by setting will be described in detail.

A high-brightness subject such as a bright sky or a water surface easily enters a normal screen, and a subject in a dark portion tends to be blackened by the influence of the high-brightness portion. Even if the center-weighted photometry is used, the high-brightness part is not always located at the center, and the high-brightness part is greatly affected.

The "landscape photographing mode" of the present invention is a program photographing mode in which an appropriate exposure value can be determined without being affected by the blackout caused by the influence of the high luminance portion. The selection can be made by operating the unit 20. This will be described in detail below.

FIG. 13 shows an internal structure of an LUT, that is, a data table storing definitions and characteristics of various control parameters necessary for control in the landscape photographing mode. Various control parameters defined and set by the LUT are shown. FIG. 12 is a program diagram showing the transition of the input parameter with respect to the luminance level.

In FIG. 12, a threshold value y1 is provided for the illuminance on the horizontal axis, which is an input parameter, and the whole area is divided into two areas. Exposure is controlled by iris and gain. The speed is fixed to the standard value.

The individual control parameters set in the spotlight photographing mode data table LUT will be sequentially described below.

(P1: Iris control parameter) The iris control parameter changes according to the input parameter Y, that is, the luminance level.
(y) is defined.

The input luminance level is the threshold value y shown in FIG.
When the value is higher than 1, the calculation (calcul) is displayed as “→ CAL”, as is apparent from the data column on the right side of FIG.
ation) is required.

To secure S / N with high luminance, AGC
With the gain kept at ± 0 dB (THROUGH), the control range is from the minimum aperture of the iris to the open value.

When the input luminance level is equal to or lower than y1, the control for setting the iris to open is designated by "→ OPEN".

In this state, it can be considered that the illuminance is fairly low, and when priority is given to continuation of photographing even if the S / N of the image is deteriorated, the area is increased by increasing the AGC gain.

As described above, the control characteristic of the iris is defined by dividing the entire region from high luminance to low luminance into two by the threshold value y1.

(P2: Shutter control parameter) It is shown that the shutter control parameter has a fixed attribute and is always fixed to a constant value regardless of the input luminance level.
The contents are set to “→ standard value” so as to be set to the standard value of the television standard, and no calculation is required.

Here, the standard value of the television signal means 1/60 second in NTSC and 1/50 second in PAL.

(P3: AGC gain) In the case where the AGC gain is used as a parameter to be processed, a function f (Y) of the input luminance is defined by the threshold value y, and the input luminance level is higher than y1. Is designated as "→ ± 0 dB", the AGC gain is fixed at ± 0 dB, and the gain is set so that the AGC circuit has no amplifying action. That is, when the exposure control can be performed by the iris, the AGC gain is fixed to prevent the deterioration of the S / N. In this case, the calculation is unnecessary.

Since this section is set so as to occupy most of the range of the illuminance of the subject, S / S is applied over the entire area.
N good imaging is possible.

When the input luminance level is equal to or less than y1, "→ CAL" is designated so that the optimum AGC gain is calculated and the gain control parameter is set.

In this state, the illuminance is extremely low, and the S
This is an area corresponding to increasing the AGC gain when photographing is desired to be continued even if / N is deteriorated.

Since other parameters have already been set to the maximum for the low illuminance countermeasure, the only controllable parameter remaining in this state is the AGC gain, and consideration is given to the balance with S / N deterioration. Meanwhile, the exposure control is executed by setting the gain up within an allowable range.

The relationship between the area divided into two by the threshold value y1 and the three control parameters is clear from FIG. 12, and here, the parameters to be calculated are always one in each of the two areas. The operation is simplified and the operation is simplified, and the arrangement is I, G from the area on the high luminance side.

(P4: AE weighting parameter =
FIG. 13 is a parameter for setting the photometric area distribution in the imaging screen and their weighting.
As can be seen, the attribute is f (Y), indicating that it is a function of the input luminance. Specifically, it is defined by a histogram created according to the input luminance signal,
Detecting the input luminance signal level in each of the 24 divided areas of the imaging screen and creating a histogram of the luminance level, accurately detecting a low-luminance portion on the imaging screen and emphasizing the area to prevent blackout Control such as photometry is performed.

In this embodiment, the luminance levels are detected for the 24 divided areas, and the lower N (= 12) areas of the luminance levels are extracted from the luminance histogram created from these areas. AE control is performed.

For this reason, even when there is a high-brightness portion in a part of the imaging screen such as the sky, an appropriate exposure value can be determined without being affected by a dark portion having no main subject. Can be.

FIG. 14 shows such a histogram. The upper part of the figure shows the luminance histogram, the horizontal axis indicates the level of the IRE, the level increases from left to right, and 0 to 6 on the vertical axis indicate the number of areas corresponding to each IRE level.

The lower part is a cumulative histogram of the upper part of the luminance histogram. The vertical axis represents the number of regions divided into 24.

[0156] In the figure, the lower 12 areas (1 to 12) are extracted from the 24 areas of the cumulative histogram.

In this manner, a low-luminance portion in the image-capturing screen can be detected, AE photometric characteristics can be set with emphasis on the low-luminance portion, and AE control that eliminates the influence of a high-luminance portion where a main subject does not exist is realized. can do.

(P5: AE reference value parameter) The parameter of the AE reference value indicates a brightness level which is a reference for exposure control, and is stored in a numerical definition. It is determined whether the exposure is excessive or insufficient based on the reference value. In this embodiment, the exposure is set to 50 IRE. The attribute of this parameter is also fixed, and is constant in the shooting mode regardless of the input luminance level.

(P6: Image Quality Adjustment Parameter) This parameter specifies image quality adjustment processing by aperture control or the like. The processing content is defined by a code. The attribute is fixed and set according to the shooting mode. And does not change depending on the input luminance level.

In this landscape photography mode, "NORMAL"
In this case, the basic image quality is set as a standard value, and no special image processing for changing the image quality using the above-described aperture control is performed.

(P7: Image Effect Processing Parameter) As described with reference to FIG. 9, this is a parameter for designating image processing such as fade, and the processing content is defined by a code.

"NORMAL" is specified.
The basic image quality is set to a standard value, indicating that no special processing is performed.

The attributes of these parameters are fixed and set according to the photographing mode, and do not change depending on the input luminance level.

As described above, the data table LUT according to the present invention stores the definitions and characteristics of various parameters necessary for control. A plurality of such LUTs are provided according to the shooting mode, and the designated shooting is performed. Because it can be selected according to the mode, for every shooting situation and shooting environment,
Optimal control can always be performed.

The data table LUT in which the control parameters are defined and the operating characteristics of the control parameters set thereby have been described above, taking the landscape shooting mode as an example.

Here, the operation of reading data from the LUT shown in FIG. 13 to the system control circuit to calculate control parameters and setting the control parameters as shown in FIG. 12 will be described in detail with reference to the flowchart of FIG. I do.

These processing operations are basically the same as those in FIG.
This is performed in the processing from the confirmation processing of the program photographing mode in S2 in the flowchart of FIG. 4 to the output of iris, shutter, and gain control data based on each control parameter in S24.

FIG. 15 is an operation flowchart showing the procedure of a data set for setting control characteristics according to the photographing program mode.
This routine is executed in parallel in the processing of steps S2 to S24. After the end of this routine, the process returns to step S25 in FIG.

When the control is started, a photographing mode is selected by the operation unit 20 shown in FIG. 1 in S101, and the result of the selection is taken into the system control circuit 25. In S102, the photographing mode is selected according to the selected photographing mode. The LUT is selected from the LUTs 19a to 19b.

In S103, a parameter counter n for designating a parameter is initialized to n = 01, and
In S104, the data of the parameter Pn specified in S103 is read.

The parameter specification will be described.
In the example of FIG. 13, when n = 01, data relating to the iris, when n = 02, data relating to the shutter speed, when n = 03, data relating to the AGC gain, n
= 04, data relating to AE weighting (weighting coefficient of the photometric area), n = 05, data relating to AE evaluation reference values, that is, a level serving as a reference for keeping the brightness level constant, and n = 06, image quality The data relating to the adjustment and the data relating to the specially effective image processing at n = 7 are read into the system control circuit 25, respectively.

In S105, the attribute of the read parameter is confirmed, and it is determined whether the data is dependent on the input parameter (f (Y)) or is fixed data corresponding to the mode without depending on the input parameter. Done.

That is, as shown in the table of FIG.
The attribute indicates whether the attribute changes according to a predetermined function f (Y) with respect to the input parameter, that is, the illuminance of the subject in the present embodiment, or whether the attribute is fixed regardless of the change of the input parameter. In S105, the attribute of the parameter is f
If (Y) depends on the input parameter, S10
The process proceeds to step S7, and if it is fixed, the process proceeds to step S106, and the value of the parameter is set assuming that the attribute of the data is fixed regardless of the luminance level.

At S107, 1 is set to the parameter counter n.
Is added to obtain n + 1. In S108, it is checked whether or not n has become larger than the maximum value in the LUT. Until n reaches the maximum value, the operations in S104 to S107 described above are repeated to read parameters. Are repeated, and if n exceeds the maximum value, the flow shifts to the data output processing of S109 and thereafter.

After S109, the LU is executed in S101 to S108.
This processing indicates output processing of control data based on parameters read from T. In S109, the parameter counter is reset to n = 01.

In S110, the attribute of the parameter is confirmed, and it is determined whether the parameter is dependent on the input parameter (f (Y)) or is a fixed one that does not depend on the input parameter and corresponds to the mode. S11 if f (Y)
1 if fixed, skip S111 and S112 and skip to S113
Proceed to.

In S111, the output of the integrator 10 is sampled by the A / D converter 11 every unit processing time (for example, one field period), and the luminance signal level as an input parameter is taken into the system control circuit 25. In accordance with the value of this input signal, the data definition of the LUT is referred to, and it is determined whether data operation is necessary or not. If the calculation conditions are satisfied, the process proceeds to S112, in which only the parameter specified in the current state is changed, the AE is controlled, and the optimum value of the parameter for adjusting to the proper exposure is calculated.

If it is determined in S111 that the calculation is unnecessary, the control output of S112 is skipped, and the process proceeds to S113.

In S113, 1 is added to the parameter counter n, and the process proceeds to S114 as n + 1, and returns to step S110 until the parameter counter n exceeds the maximum value of the parameter number of the LUT. When the parameter counter n exceeds the maximum value of the parameter number of the LUT, the process proceeds to the next S115, and returns to the process of S25 in the flowchart of FIG.

The above is the processing procedure from the reading of the characteristics of each parameter from the data reference table LUT to the calculation of the AE control data. In this way, the LUT corresponding to the set photographing mode changes the photographing condition. By reading out suitable control data and performing control, it is possible to execute optimal photographing.

As described above, the photographing state is controlled by using a plurality of parameters, and the control data setting condition suitable for the photographing situation is read from the data table corresponding to the photographing mode and controlled. Therefore, finer control can be performed as compared with the conventional apparatus, and an effect that optimal photographing can be performed only by selecting a photographing mode even under various photographing conditions.

By switching the shooting mode,
Since the photometric distribution is also switched to a setting suitable for the mode in conjunction with the mode, operability is improved, and there is an effect that a setting error or the like is prevented.

Next, the setting operation of the "night scene photographing mode" which is still another program photographing mode of the present invention, the internal structure of the data table LUT, and the control of control parameters by the setting will be described in detail.

The night scene photographing mode assumes a photographing situation in which a high-luminance subject usually exists in a part of a dark background, and can be selected by operating the operation unit 20.

In general, when performing photographing in the case where bright neon illumination or the like is present in a part of the dark background described above, if the average photometry of the entire imaging screen is performed as in the related art, a low luminance portion occupies most of the screen. It is pulled by the low-brightness part, and the bright main subject part is overexposed and causes overexposure.

Even if the center-weighted metering is used, the spot portion is not always located at the center, and even if the weight of the center portion is large, the area of the high luminance portion is small. Similarly, accurate exposure control cannot be performed.

The "night scene photographing mode" of the present invention is a program photographing mode in which good exposure control can be performed even in such a photographing situation, and will be described in detail below.

FIG. 16 shows an L in which the definitions and characteristics of various control parameters required for control in the night view photographing mode are stored.
UT, which indicates the internal structure of the data table,
The program diagram showing the transition of the input parameters of the various control parameters defined and set by the LUT with respect to the luminance level is the same as the “landscape shooting mode” shown in FIG. Accordingly, the control parameters will be described below with reference to FIG. 12, but the value of the threshold value y1 is set in each mode.

That is, in FIG. 12, a threshold value y1 is provided for the subject illuminance on the horizontal axis, which is an input parameter, the whole area is divided into two areas, and exposure control is performed by iris and gain. Shutter speed is fixed.

The individual control parameters set in the spotlight photographing mode data table LUT will be described below in order.

(P1: Iris control parameter) This is the same as the landscape shooting mode shown in FIG. 13 described above, and the description is omitted.

(P2: Shutter control parameter) This is the same as the landscape shooting mode shown in FIG. 13 described above, and a description thereof will be omitted.

(P3: AGC gain) This is the same as the landscape photography mode shown in FIG. 13 described above, and the description is omitted.

(P4: AE weighting parameter =
FIG. 16 is a parameter for setting the photometric area distribution in the imaging screen and their weighting.
As can be seen, the attribute is f (Y), indicating that it is a function of the input luminance. Specifically, it is defined by a histogram created according to the input luminance signal,
A luminance level histogram is created by detecting the input luminance signal level in each of the 24 divided areas of the imaging screen, thereby accurately detecting a portion of the imaging screen where a bright spotlight is hit. Control is performed such that weighted photometry is performed on the area.

In this embodiment, the luminance levels are detected for the 24 divided areas, and the upper N (= 2) areas are extracted from the luminance histogram created from them, and the AE control is performed using only these N areas. Be executed.

[0196] Therefore, even in the case of an illumination such as a spotlight which is biased to a part of the imaging screen, an appropriate exposure value can be determined without being affected by a dark portion having no main subject.

FIG. 17 shows such a histogram. The upper part of the figure shows the luminance histogram, the horizontal axis indicates the level of the IRE, the level increases from left to right, and 0 to 6 on the vertical axis indicate the number of areas corresponding to each IRE level.

The lower part is a cumulative histogram of the upper part of the luminance histogram. The vertical axis represents the number of regions divided into 24.

FIG. 23 shows that the upper two areas (,) are extracted from the 24 areas of the cumulative histogram.

[0200] In this manner, a high-luminance portion in the image-capturing screen can be detected, AE photometric characteristics can be set with emphasis on that portion, and AE control excluding the effect of a portion where a main subject does not exist can be realized. . Valid when present. If these are stored in the data table and are appropriately selected, the range of photographing can be expanded.

Therefore, even in a subject such as a night scene in which illumination such as neon is present in a part of the imaging screen, an appropriate exposure value can be set without being affected by the inner part of the main subject.

(P5: AE reference value parameter) The parameter of the AE reference value indicates a luminance level which is a reference for exposure control, and is stored in a numerical definition. It is determined whether the exposure is excessive or insufficient based on the reference value. In this embodiment, the value is set to 20 IRE, which is slightly lower than the general 50 IRE. The attribute of this parameter is also fixed, and is constant in the shooting mode regardless of the input luminance level.

(P6: Image Quality Adjustment Parameter) FIG.
This is the same as the landscape shooting mode shown in FIG.

(P7: Image Effect Processing Parameter) This is the same as the landscape photography mode shown in FIG. 13 described above, and a description thereof will be omitted.

(P8: Control Point of Compression Point and Compression Ratio) In the night scene mode, the compression ratio and the compression point are controlled as parameters in order to perform more appropriate exposure operation. In the present embodiment, the luminance level of each of the 24 divided areas is detected, and the average brightness of the imaged scene is compared with the ratio of the high-luminance portion to calculate the compression ratio of the high-luminance portion of the video signal. The compression point is changed to improve the latitude of the high brightness part.

FIG. 18 is a characteristic diagram showing the relationship between the input luminance level and the output luminance signal level, showing how the video signal is compressed. In the same figure, a is a case where processing such as luminance compression or clipping is not performed, b is a case where a video signal is clipped, c is a case where a high luminance portion is compressed, d is a compression ratio and a starting point for the characteristic of c. Is changed to show the characteristic of improving the latitude of the high luminance portion.

In this embodiment, the control is performed such that the characteristic c or d in FIG. 18 is selected when the ratio of the high luminance portion is large, and the characteristic b is selected when the ratio of the high luminance portion is small. Have been configured.

That is, in the present embodiment, when a photographic scene is dark, such as when photographing a night scene, overexposure occurs in a bright portion of the screen. Therefore, the compression point changes linearly depending on the ratio of the high luminance portion. In this way, it is possible to perform photographing without overexposure and without any unnaturalness.

The processing procedure from reading the characteristics of each parameter from the data reference table LUT to calculating the AE control data is the same as the processing described in the flowchart of FIG.

As described above, in the multi-area photometry system in which the image-capturing screen is divided into a plurality of areas and the exposure control is performed based on the luminance information of each area, the top N luminance histograms based on the luminance level for each area are provided. By performing AE using only the area No. 1, it is possible to take a high-quality image of a subject that has been proved as a night scene or neon, without overexposure. Since the compression ratio and the compression start point are automatically set, it is possible to improve the latitude of the high-luminance portion and the coloring of the high-luminance portion, and expand the dynamic range of the luminance signal.

Next, a second embodiment of the present invention will be described. 2. Description of the Related Art In recent years, a video camera has been equipped with a function of inputting an arbitrary title, message, BGM, or the like from the outside and performing a special effect of recording the image together with a captured image. These functions are stored in an IC card or the like that can be attached to and detached from the video camera main body. When this function is mounted on the video camera main body, the stored data is read, and together with the photographed image information, the recording medium such as a magnetic tape The data such as various titles, messages, and BGM can be selected by exchanging the IC card according to the content of the photographing.

In the embodiment described below, a photographing mode designating code for designating a photographing mode corresponding to the contents is built in an external IC card that can be attached to the video camera body.
When the IC card is inserted into the video camera body, the shooting mode of the video camera is automatically selected according to the read shooting mode designation code, and the selection and setting of various exposure control parameters are automatically performed. It is intended to be performed.

FIG. 19 is a block diagram showing the configuration of this embodiment. The same components as those in the block diagram of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

In the drawing, the difference from the block diagram in FIG. 1 is that a connection section 41 for attaching and detaching the IC card 50 is provided, and data such as titles, BGM, etc. stored from the attached IC card 50. And an IC card reading circuit 40 for reading various data such as a shooting mode designating code and inputting the data to the system control microcomputer 25. Further, before the recorder 8, an image processing circuit 7 output from the camera signal processing circuit 6 is provided. A title mixing circuit 4 for superimposing data such as a title read from the IC card by an IC card reading circuit 40 on an image signal subjected to predetermined image processing by the IC card reading circuit 40.
2 is arranged. The IC card reading circuit 40 and the title mixing circuit 42 are controlled by the system control microcomputer 25, respectively.

On the other hand, the IC card 50 is detachably attached to the video camera body via the connection section 41, and includes a title memory 52 storing title display data and data corresponding to each title, and a shooting mode. A memory 53 having a designated code therein is provided, and each data is read from these memos, and the micro computer 2 for system control on the video camera main body side is connected through contacts a and b.
5 is provided.

Therefore, when the IC card 50 is mounted on the video camera body and connected to the IC card reading circuit 40 by the connection section 41, various data stored in the IC card 50 can be read, and the title memory can be read. 5
2, the title data read by the control unit 51 is supplied to the title mixing circuit 42 via the IC card reading circuit 40, mixed with the image signal, and recorded by the recorder 8 on a recording medium such as a magnetic tape. Is done.

The shooting mode designating memory 53 stores a shooting mode designating code for performing optimal exposure control for each title, assuming a shooting situation in which the title is used. At the same time as being read from the title memory 52, it is read by the control unit 51 and supplied to the system control microcomputer 25 via the IC card reading circuit 40.
The shooting mode is selected according to the shooting mode designation code,
The setting is made, and shooting can be performed while automatically adjusting the exposure control conditions to be optimal for the shooting situation. For example, when a title related to skiing is selected, exposure control can be automatically set to control parameters optimal for a high-luminance subject, assuming shooting at a ski resort.

In this embodiment, the case where an IC card is used as a means for controlling the video camera from the outside has been described. However, the present invention is not limited to this, and the function of the video camera body can be controlled from the outside. It is only necessary that the optimal photographing mode can be automatically selected.

As described above, according to this embodiment, when the special effect functions such as the title and the BGM are controlled by the external control means, the optimal parameter control is performed by assuming the shooting conditions in which the title and the like are used. It is possible to automatically select a program mode to be performed and perform better shooting with a simple operation.

Next, a third embodiment of the present invention will be described.

As described in the above embodiments, a plurality of program exposure control modes are provided so that optimum photographing can always be performed regardless of photographing conditions. In actual photographing, each scene is reproduced. However, audio is an important factor, and not only the recording of video but also the recording of audio is important. In particular, in recent years, there has been a demand for a natural sound recording more suited to a shooting situation, such as a higher magnification of a zoom and a stereo sound recording. In view of this point, in the present embodiment, the program mode is switched to optimize both video and audio in accordance with the shooting situation.

FIG. 20 is a block diagram showing the structure of this embodiment. The same components as those in FIG. 1 are denoted by the same reference numerals, and their description is omitted.

Reference numeral 60 denotes a microphone for voice recording (hereinafter referred to as a microphone), which is a variable directional microphone composed of a unidirectional microphone unit and a bidirectional microphone unit, which will be described later in detail. Reference numeral 61 denotes a microphone sensitivity control circuit that controls sensitivity in each direction by changing a directional angle characteristic of the microphone, and 62 denotes a sound capable of controlling a frequency characteristic of a sound signal to suppress wind noise and the like. These circuits are configured to provide an audio effect suitable for the video being captured, and to faithfully reproduce the captured image. The audio signal processed to predetermined characteristics through the microphone sensitivity control circuit 61 and the audio circuit 62 is supplied to the recorder 8, and is recorded together with the video signal on a recording medium such as a magnetic tape (not shown).

The microphone sensitivity control circuit 61 and the audio circuit 6
2 is configured to be controlled to have characteristics according to the program photographing mode based on control signals supplied from the system control microcomputer 25 via the D / A converters 63 and 64, respectively.

FIG. 22 is a diagram for explaining the configuration and operation of a system for varying the directivity angle of a stereo microphone using the variable directivity microphone 60 composed of the above-described unidirectional microphone unit and bidirectional microphone unit. .

The microphone of this embodiment is composed of a unidirectional microphone unit 80 (hereinafter, referred to as MID microphone) and a bidirectional microphone unit 81 (hereinafter, SIDE microphone). The output of the MID microphone unit 80 is It is added to the output of the SIDE microphone unit 81 via the control circuit 82 and output as a left channel signal.
The output of the DE microphone unit is inverted by an inverter 84, added to the output of the MID microphone unit 80 whose level has been adjusted by the level control circuit 82, and output as a right channel signal.

FIG. 21A shows the MID microphone unit 8.
5 shows the sensitivity directivity characteristics of each of the 0, SIDE microphone units 81. The MID microphone unit 80 has a characteristic that it has a maximum sensitivity to the sound source in front of the microphone, the sensitivity decreases as the sound source shifts from the front, and the sensitivity becomes zero theoretically at the back.
The SIDE microphone 81 has the characteristic that the sensitivity to the sound source is maximum at the front and back of the microphone, and the sensitivity is theoretically zero in the directions of 90 ° and 270 °.

Therefore, the MID microphone unit 80 and the S
Install the IDE microphone unit 81 at a 90 ° angle.
The output of the IDE microphone unit is divided into phases, the positive-phase output is combined with the output of the MID microphone unit to produce a left output, and the reverse-phase output is combined with the output of the MID microphone unit to produce a right output. Thus, a stereo effect can be obtained.

When synthesizing signals, as shown in FIG. 21 (b), the sensitivity (Sm) and the SI
The directional angle is determined by the ratio Ss / Sm of the sensitivity (Ss) of the DE microphone unit.

[0230] When shooting a person, it is better to cut the surrounding sound and focus on the voice of the person in front of the camera. In the case where a person who can record the surrounding atmosphere, such as a place, produces a realistic image, it is effective to increase the directivity.

In the present application, in order to automatically control the switching of these microphone characteristics in accordance with the shooting conditions, information on the program shooting mode set from the system control microcomputer 25 is taken in, and the microphone characteristics according to the shooting are set. Is what you do.

For example, in the portrait mode, the microphone directivity is increased by increasing the front sensitivity to emphasize this, and the surrounding sensitivity is reduced to cut the surrounding noise. In the landscape mode, sports mode, etc., the directivity is expanded. It is configured to record surrounding sounds.

As described above, the sensitivity ratio between the MID microphone and the SIDE microphone is controlled by the system control microcomputer according to the photographing conditions, so that the microphone directivity can be varied and combined with AE control parameters. It is possible to obtain a simplified video and audio effect.

[0234]

As described above, according to the imaging apparatus of the present invention, the photographing state is controlled using a plurality of parameters, and the data table corresponding to the photographing mode is suitable for the photographing situation. The control conditions are read out from the control data and controlled, so that finer control can be performed as compared with the conventional apparatus, and under various shooting conditions, the optimum shooting can be performed only by selecting the shooting mode. .

In particular, even under shooting conditions that are significantly different from normal shooting conditions, such as landscape shooting and night view shooting, the optimum exposure can be set using the luminance level distribution histogram in the screen.

Looking at the actual control, the imaging screen is divided into a plurality of areas, and a multi-area photometry method is used. A luminance histogram based on the luminance level is created for each photometry area, and the upper N areas of the luminance are obtained. The AE mode is used to perform AE by using only the AE. Therefore, especially when there is a high brightness part such as the sky or the water surface in the screen as in landscape photography, or in a part of a dark background as in night scene photography. Optimal exposure control is always performed in various shooting situations, such as in the case where a small subject such as a bright neon light exists, in which it is conventionally difficult to control the proper exposure even in shooting. be able to.

[0237]

[0238]

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration in a case where an imaging device according to the present invention is applied to an exposure control device of a video camera.

FIG. 2 is a diagram showing a photometry area in central partial weight photometry.

FIG. 3 is a diagram for explaining the operation of the electronic shutter.

FIG. 4 is a diagram showing an area division state on an imaging screen according to the present invention.

FIG. 5 is a diagram for describing the setting and weighting of a photometry area of “center-weighted photometry” in the present invention.

FIG. 6 is a program diagram for explaining parameter processing according to the “indoor shooting mode” of the present invention.

FIG. 7 is a program diagram for explaining parameter processing according to the “sport shooting mode” of the present invention.

FIG. 8 is a diagram showing characteristics of a camera signal processing circuit performed in conjunction with switching of a shooting mode according to the present invention.

FIG. 9 is a diagram illustrating control of an image processing circuit performed in conjunction with switching of a shooting mode according to the present invention.

FIG. 10 is a program diagram for explaining parameter processing according to the “portrait shooting mode” of the present invention.

FIG. 11 is a flowchart for explaining processing for explaining parameter setting in each shooting mode.

FIG. 12 is a program diagram for explaining parameter processing according to the “landscape shooting mode” and the “night scene shooting mode” of the present invention.

FIG. 13 is a diagram illustrating the structure of a data table according to the “landscape shooting mode” of the present invention.

FIG. 14 is a diagram showing a luminance histogram for determining a photometric region according to the “landscape shooting mode” of the present invention.

FIG. 15 is a flow chart for explaining the processing of the flow chart of FIG. 11 in more detail;

FIG. 16 is a diagram for explaining the structure of a data table according to the “night view shooting mode” of the present invention.

FIG. 17 is a diagram showing a luminance histogram for determining a photometric area according to the “night scene photographing mode” of the present invention.

FIG. 18 is a diagram for explaining a luminance signal input / output characteristic performed in conjunction with switching of a shooting mode in the present invention.

FIG. 19 is a block diagram showing a second embodiment of the imaging apparatus according to the present invention.

FIG. 20 is a block diagram showing a third embodiment of the imaging apparatus according to the present invention.

FIG. 21 is a block diagram for explaining characteristics of a voice recording microphone according to a third embodiment of the imaging apparatus of the present invention.

FIG. 22 is a block diagram showing a configuration of an audio recording circuit in a third embodiment of the imaging apparatus of the present invention.

FIG. 23 is a block diagram illustrating an example of a conventional imaging device.

24 is a diagram illustrating a shutter-priority exposure control mode in the apparatus of FIG. 23;

──────────────────────────────────────────────────続 き Continuation of the front page (72) Koji Takahashi, inventor Canon Inc., 3-30-2 Shimomaruko, Ota-ku, Tokyo (56) References JP-A-2-141732 (JP, A) JP-A Heisei 4-340875 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04N 5/225-5/247

Claims (1)

(57) [Claims] An imaging unit configured to photoelectrically convert incident light imaged on the imaging screen; a detection unit configured to divide the imaging screen into a plurality of regions to detect a luminance level of each of the regions; Creating means for creating histograms of the plurality of areas according to the brightness level based on the brightness level, and selecting a predetermined number of areas from the lower brightness level among the histograms created by the creating means An image pickup apparatus comprising: an area selection unit; and an exposure control unit that controls exposure based on a luminance level of an area selected by the area selection unit.