JP3262348B2 - Imaging device and imaging method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus such as a video camera and an image pickup method.

[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. 11 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. 12 shows the 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.

An object of the present invention is to provide an automatic exposure control device for a video camera which satisfies all of these conditions and can always perform optimal exposure control irrespective 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 apparatus which performs exposure control by changing at least a shutter speed and an AGC gain in accordance with the brightness of a subject. When the subject luminance obtained by the photometric means is lower than a predetermined luminance level, a storage means for storing a plurality of exposure control programs including an exposure control program for performing exposure control by changing a shutter speed without changing an AGC gain. And exposure control means for performing exposure control according to an exposure control program selected from a plurality of exposure control programs stored in the storage means.

[0011]

As a result, a plurality of control parameters can be set, and each parameter can be controlled in accordance with the photographing conditions, so that optimal photographing can always be performed according to the photographing situation and the photographing environment. .

[0012]

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 photographic 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.

Reference numerals 19a and 19b denote data reference tables (LUT: Look up tabl) storing various data for exposure control.
In this embodiment, two tables are provided so that a plurality of settings are made according to the shooting situation in e). More specifically, iris,
Information on control characteristics of exposure control parameters such as shutter speed and gain is stored, and necessary data is read out according to the set photographing mode.

Reference numeral 20 denotes an operation unit including a plurality of operation keys for performing various operations, and 21 denotes a D / D 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 constituted by a micro computer for comprehensively controlling the entire video camera system in the present embodiment.

The system control circuit 25 transmits control signals for controlling the characteristics of the camera signal processing circuit 6 and the image signal processing circuit 7 in accordance with the photographing mode operated by the operation section 20, to D / A converters 22, 23. , 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 the image pickup screen. FIG. 2 shows an example in which a photometry area is set at the center of 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 shown by the solid line is larger than the signal outside the central area. Exposure control is performed by assigning coefficients to increase the weight at the center.

Then, an integrated value corresponding to the photographing mode of the image pickup signal in the photometry area taken in through the gate circuit 9 is taken in, and an iris control signal corresponding to the photographing state is calculated while referring to the data of the LUT 19, In addition to supplying the signal to the iris drive circuit 14 via the D / A converter 15 and the gain control signal to the AGC circuit 5 via the D / A converter 21, the AGC circuit 5 5 and a control signal is also supplied to the CCD drive circuit 12 to control the image pickup device's accumulation time (electronic shutter), readout timing, reset timing, etc. according to the photographing mode and photographing situation. Perform

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 in order.

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 for current amplification. Then, it is 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 is the LUT 19a corresponding to the shooting mode.
Alternatively, if the control value is larger than the control value defined in 19b, the exposure is over. Therefore, the iris drive circuit 14 is controlled to drive the iris motor 13 in a direction to narrow down the iris 2 to reduce the amount of incident light. As a result, the integrator 10
Decrease the output level.

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. (2) shear ivy speed (parameter 2) (see Figure 3) accumulation time setting signal D _t of the imaging device is output in the form of a digital signal from the system control circuit 25, CCD driving circuit 12 receives this as a CCD A pulse for determining various timings is generated to control the accumulation time.

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 this 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. The range that can be set is a range permitted on the high-speed side in terms of image-capturing light quantity and image quality such as smear 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 driving circuit 12 thus instructed further adds ΔV _sub to V _sub (vertical substrate applied voltage) in order to realize the electronic shutter operation. Is added 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. 3B shows this operation.

The system control circuit 25
The current value is less than value the D _t in order to slow down the shear ivy speed if Hayakere than the predetermined value is defined in LUT19 corresponding to the integral value from the current shear ivy speed A / D converter 11 change to change the of D _t in order to increase the shear ivy speed as late than the value defined in LUT19 reversed to a value larger than the current value. (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, the iris is treated as a part of an AE loop component, and is not an object that can be arbitrarily controlled.

In recent years, even when the S / N of the CCD has been improved and the gain of the AGC is increased to increase the gain, the noise of the imaging system has become less noticeable, 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, it is a parameter suitable for AE control in a situation where a quick response 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 according to the photographing state and the 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 optimal automatic exposure control in these photographing 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 suit the situation. Control is needed.

Therefore, in consideration of the light conditions 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 into four parts vertically and six parts horizontally, 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 opened and closed by a 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, a process is performed in which a weighting coefficient set in advance according to the shooting mode is added to the integrated value in each of these areas. Note that these processes can be performed by time division processing corresponding to 24 divisions.

FIG. 5 and FIG. 6 show examples of image pickup screens subjected to weighting coefficient processing.

FIG. 5 shows the above-mentioned “center-weighted metering” realized by the 24-split AE system of the present invention.
The weighting calculation coefficients in the areas 8 to 11 and 14 to 17 corresponding to the center of the screen are set to 1.0, and the weighting calculation coefficients in the surrounding areas are set to 0.5, so that 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.

FIG. 6 shows an example of a photometry area suitable for "landscape photography". In general, when performing landscape photography, both the ground and the sky are often simultaneously projected on a screen. In addition, the sky portion often has very high brightness even in a slightly cloudy sky compared to the ground portion. For this reason, when photographing is performed using the conventional AE control that does not consider the photometric area, a person or the like against the ground or the sky often becomes black due to insufficient light quantity.

In order to eliminate these inconveniences, the weighting coefficients of the areas 1 to 6 at the top of the screen corresponding to the sky are set to 0.0 and substantially ignored, and the coefficients above the center of the screen are set to 0.5.
, And the lower half coefficient of the screen is set to 1.0. By allocating the calculation coefficients in this manner, the AE calculation processing can be performed with a weight placed on the lower part of the screen corresponding to the ground.

In addition to the above two examples, various AE characteristics can be set by setting a photographing mode according to a photographing situation and appropriately selecting a photometric area setting and a photographing program according to a photographing situation described later. Is possible.

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 a photographing can be performed while automatically adjusting each of the photographing conditions under an optimum condition under the assumption of some typical photographing conditions. Invented the scheme.

These program modes can be arbitrarily selected and set by operating the keys on the operation unit 20.

In order to always perform good shooting in various places of video shooting and in various situations, a representative 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, at least two lookup tables (LUTs) storing control functions for controlling a plurality of parameters are set, and two tables LUT 19a and LUT 19b are provided as shown in FIG. (Actually provided for each program photographing mode described later, the number is appropriately increased or decreased) is prepared by a memory such as a ROM, and is configured to be selectively readable from the system control circuit 25. This selection is made by key operation of the operation unit 20.

FIGS. 7 and 8 show examples of control characteristics of each parameter controlled by data read from the LUT 19a and LUT 19b.

FIG. 7 shows that the shutter speed of the parameter (2) can be set to 1/100 second as much as possible, and the iris of the 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 at 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. 8 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 drawing, 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. 9 is a program diagram in the "landscape photographing mode" shown in FIG. The actual program diagram is as shown in Figs. 7 and 8, but for simplicity,
In FIG. 9, the operating range is shown in the order of iris, shutter speed, and gain from the top.

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 the variable region, the value of each parameter changes in accordance with the luminance level as an input parameter, as in the program diagrams of FIGS.

In the landscape photographing mode, there are many cases where there is no flicker, fast-moving subject, or the like. Therefore, the shutter speed (P2) is fixed to 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 photographing 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 photographing conditions. Control can be performed.

When the photographing program mode is switched by the operation unit 20, the setting of the photometry area on the image pickup screen is simultaneously switched as described above. For example, FIG.
In the indoor photographing mode of FIG. 8 and the sport photographing mode of FIG. 8, a subject such as a normal person, which is usually located at the center of the screen, is often photographed. Also in the scenery photographing mode of FIG. 9, the light metering area on the image pickup screen is switched to the light metering area for the "landscape photographing mode" shown in FIG. 6 in conjunction with the operation of switching to the photographing mode.

By the way, the control of each parameter in each program diagram described above has the following features.

That is, as is apparent from FIGS. 7 and 8, each control parameter is divided into a plurality of areas (three areas A, B, and C in the present embodiment), and the input parameters, that is, the change in the illuminance of the subject. Each area is selected in accordance with each area.
Only one variable parameter used for control is designated, and the other two are fixed (FIX). This is shown in the table below the program diagram.

That is, in FIG. 7, in the area A, the parameter (P1) is variable and the other parameters are fixed, that is, when the iris control is being 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 parameters to be changed 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 all photographing situations 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 control parameter switching operation described above.

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

When each control parameter is set in accordance with an input parameter, the value of the input parameter may move between a plurality of divided areas due 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 suppress the frequency of area transition, but when switching occurs, there is no effect and it cannot be a fundamental measure. .

Therefore, in the present invention, as a countermeasure against this, as shown in FIGS. 7 and 8, two parameters of the adjacent area are controlled so as to be simultaneously changed only in the areas B1 and B2 of the boundary part near the boundary of the area. are doing.

In FIG. 7, a boundary portion B sandwiched between broken lines
1 is a boundary region where the parameters P1 and P2 operate simultaneously, and similarly, in the boundary portion B2, the parameters P2 and P3
And are operating at the same time.

By simultaneously changing 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.

FIG. 10 is a flowchart showing a parameter setting operation including the above-described parameter processing of the area boundary portion in a program photographing mode using the program diagram of FIG. 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. Set a specified program characteristic with reference to the LUT 19a or 19b corresponding to the mode (M).

At S4, 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 in accordance with the shooting mode as described above, and the flow advances to S5.

In S5, 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 S6, where a branch destination is determined according to the current area.

If the area is determined as A, the process proceeds to S7, where the iris control parameter P1 is calculated.
In step 8, the inside and outside of the area B1 are determined.
If it is outside 1, the process proceeds to S9, where the shutter speed control parameter P2 is pre-held and fixed.
After proceeding to 0 and calculating and updating the shutter speed control P2, the process proceeds to S20, where the gain control parameter P3 is held and fixed beforehand, and the process proceeds to S23.

When the area B is determined in S5,
In step S11, the shutter speed control parameter P2 is calculated, and the process proceeds to step S12, 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 S20, hold and fix the gain control parameter P3 in advance, and proceed to S23.

If it is within B2, the flow advances to S15 to calculate a gain control parameter P3, and the flow advances to S22. After the iris control parameter P1 is held and fixed beforehand, the flow advances to S23.

If neither B1 nor B2 belongs,
After pre-holding and fixing the iris control parameter P1 in S14, and fixing the gain control parameter P3 in S21, the process proceeds to S23.

If it is determined in step S6 that the area is the area C, the process proceeds to step S16, where the gain control parameter P3
Then, in S17, the inside / outside of the boundary area B2 of the area is determined. If it is outside the boundary B2, the process proceeds to S19, in which the shutter speed control parameter P2 is held and fixed beforehand. For example, the process proceeds to S18, where the shutter speed control P2 is calculated and updated, and the process proceeds to S22, where the iris control parameter P1 is pre-held and fixed, and then S23
Proceed to.

At S23, the values P1, P2, and P3 of the respective parameters set by the above-described processing, that is, the iris,
The control values of the shutter speed and the gain are output from the system control circuit 25, and the iris 2, the image pickup device 3, and the AGC circuit 5 are respectively controlled according to the program mode, and the next processing time unit comes in S24. (In this embodiment, one operation is used for one frame as a basic unit). In step S25, power-off is confirmed. If power-on is continued, the process returns to step S1 to repeat the above processing.
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 the exposure control is performed based on these parameters. In addition, since the photometry area on the imaging screen is switched to the one suitable for the shooting situation in conjunction with the switching of the shooting program mode, the optimal automatic exposure control is always performed according to each shooting situation. be able to.

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.

[0096]

As described above, according to the imaging apparatus of the present invention, the shooting state is controlled using a plurality of parameters, and a plurality of shooting modes (programs / programs) are controlled in accordance with various shooting situations. Mode) can be selected, so that more fine-grained control can be performed as compared with the conventional apparatus, and under various shooting conditions, there is an effect that optimum shooting can be performed only by selecting a shooting mode. .

Further, since the single parameter control is performed for each of the reference parameters divided into areas according to the conditions of the photographing environment and the other parameters are fixed, the calculation scale is reduced and the speed can be increased.

The priority order is set for a plurality of parameters, and a single parameter is controlled for each area of the reference parameter. However, at the time of transition between areas, two adjacent parameters are simultaneously controlled so that the screen is displayed. Switching can be performed so as not to cause a sense of incongruity in the change, and it is possible to reduce the change in the image itself which cannot be removed even with the hysteresis.

Further, it is possible to reduce the displacement of the image due to the difference in the threshold value of the luminance area setting due to the variation of each product, and also has the advantage that the mass productivity is improved.

[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 diagram for explaining setting and weighting of a photometric area in a “landscape shooting mode” according to the present invention.

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

FIG. 8 is a program diagram for explaining parameter processing according to another photographing mode of the present invention.

FIG. 9 is a program diagram for explaining parameter processing according to still another shooting mode of the present invention.

FIG. 10 is a flowchart for explaining processing for explaining parameter setting in FIG. 7 and the like;

FIG. 11 is a block diagram showing a configuration when a general imaging device is applied to an exposure control device of a video camera.

FIG. 12 is a diagram for explaining a shutter priority mode.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kyoji Tamura 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-2-60378 (JP, A) JP-A-4 -70277 (JP, A) JP-A-4-237269 (JP, A) JP-A-1-277221 (JP, A) JP-A-63-98639 (JP, A) (58) Fields investigated (Int. . ^7, DB name) H04N 5/235 G03B 7/08 101

Claims (2)

(57) [Claims] 1. An image pickup apparatus that performs exposure control by changing at least a shutter speed and an AGC gain in accordance with a subject brightness, wherein a photometric unit and a subject brightness obtained by the photometric unit are lower than a predetermined brightness level. Storage means for storing a plurality of exposure control programs including an exposure control program for changing the shutter speed without changing the AGC gain, and selecting one of the plurality of exposure control programs stored in the storage means. An exposure control unit for performing exposure control in accordance with the set exposure control program. 2. The imaging apparatus according to claim 1, wherein at least one of the plurality of exposure control programs stored by the storage unit changes an aperture.