JP3402617B2 - 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 thereof.

[0002]

2. Description of the Related Art In recent years, video equipment such as a video camera has made remarkable progress, and various functions have been automated and operability has been improved. For example, equipment such as a zoom lens, automatic focus control, automatic exposure control, etc. can be automated. Is an indispensable factor, and when looking at automatic exposure control, for example, it is a demanding factor that determines the quality of captured images, and stable and good automatic exposure control must always be possible in all shooting environments. The importance of the automatic exposure control function is extremely high.

FIG. 18 is a block diagram showing the basic structure of an exposure control system of a general video camera. 101 is a taking lens optical system, 102 is an iris for adjusting the amount of incident light, and 103 is an iris.
Is an image pickup device such as a CCD which photoelectrically converts an image formed on the image pickup surface by the photographic lens optical system and whose light amount is adjusted by an iris into an image pickup signal, and 104 is 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 it into a standardized video signal,
Reference numeral 05 is a video signal output terminal, 106 is a motor that drives the iris 102 to change the aperture amount, and 107 is a motor 106.
A diaphragm drive circuit for driving and controlling the
The CCD drive circuit that controls the accumulation, reading, and reset timing of the image, and variably controls the accumulation time (exposure time) to set the desired shutter speed, and 109 is the level of the luminance signal output from the camera signal processing circuit. The exposure state is evaluated based on the aperture driving circuit 107, the CCD
An automatic exposure control circuit (AE circuit) that controls the drive circuit 108 to optimally control the exposure, and 110 is a switch panel that receives an input of a key operation.

Explaining the exposure control by the AE circuit 109, the luminance signal output from the camera signal processing circuit 104 is integrated, and the diaphragm drive circuit 107 is controlled so that the level is within a predetermined range, and the iris motor is controlled. A closed loop for iris control is formed which controls the drive current output by changing the opening amount of the iris and controls the CCD drive circuit 108 to switch the drive pulse according to the key operation of the switch panel 110. A control system is provided that controls the exposure time, that is, the shutter speed by varying the accumulation time of the image sensor 103 to obtain an appropriate exposure state.

Further, this accumulation 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 seconds per screen, it is about 1/100 to 1/10000 seconds. It is possible to select multiple stages of light storage time.

In the system configured as above,
If a high-speed electronic shutter is used, there will be an automatic exposure control mode that controls the diaphragm mechanism (iris) of the imaging optical system on the basis of this for each arbitrarily selected set exposure time, that is, for each shutter speed. , The so-called shutter priority mode is set. FIG. 19 shows the shutter priority mode, in which the shutter speed on the horizontal axis is selected, the shutter speed is fixed, and the aperture value on the vertical axis is variable.

[0007]

However, like the above-described video camera device, the iris control according to the brightness level of the image pickup signal, and the shutter priority mode, always realizes appropriate exposure control in various shooting environments and shooting situations. In many cases, it was not possible to achieve proper exposure control.

In particular, in a camera such as a silver-salt camera that captures a still image for a moment, it suffices if exposure control at the moment of capturing is appropriately performed. However, like a video camera, a moving image is captured over a long time. In such a case, it is necessary to naturally follow the shooting situation and shooting environment that change momentarily even during shooting, and always perform stable and optimal exposure control, and video that satisfies these conditions. Realization of a camera exposure control device is strongly desired.

It is an object of the present invention to provide an automatic exposure control device for a video camera which satisfies all of these conditions and can always perform optimum exposure control regardless of the shooting environment and shooting conditions.

[0010]

The present invention has been made for the purpose of solving the above-mentioned problems, and according to the invention described in claim 1, the incident image is formed on the image pickup screen. Imaging means for photoelectrically converting light, shooting mode selection means for selecting a shooting mode according to shooting conditions, and an evaluation reference value for controlling exposure when a predetermined shooting mode is selected by the shooting mode selection means And controlling the exposure by comparing the photometric result of a partial area selected according to the brightness level among a plurality of areas measured by dividing the imaging screen with the changed evaluation reference value. And an exposure control means for controlling the image pickup device. Further, according to the invention of claim 2 of the present application, in claim 1, the exposure control means, by the shooting mode selection means, a predetermined shooting mode assuming a shooting situation in which a wide range of an image pickup screen becomes high brightness. Is selected, the image pickup device is configured to increase the evaluation reference value. According to the invention of claim 3 of the present application, in claim 1,
When the predetermined shooting mode is selected, the exposure control unit divides the imaging screen into a plurality of small areas, and selects an area formed by N small areas from the highest brightness level. The image pickup device is configured to perform exposure control by performing photometry and comparing the photometry result with the evaluation reference value. Further, according to the invention of claim 4 of the present application, the input brightness level calculated based on the result of applying a predetermined weighting to the brightness level in each of the small areas obtained by dividing the imaging screen into a plurality of small areas. An exposure control means for performing exposure control by comparing with a predetermined evaluation reference value, and a shooting mode selection means for selecting an arbitrary shooting mode from a plurality of shooting modes provided according to shooting conditions, The exposure control means changes the weighting and the evaluation reference value according to the selected shooting mode by the shooting mode selection means, and a predetermined shooting mode for a high-luminance subject is selected by the shooting mode selection means. When
An imaging apparatus configured to increase the weighting of an area formed by N small areas from the higher brightness level of the plurality of small areas to perform priority photometry and to displace the evaluation reference value to a high level. Characterize. Further, according to the invention of claim 5 of the present application, when a predetermined shooting mode is selected from a plurality of shooting modes provided according to the shooting situation, the evaluation reference value for controlling the exposure is changed, and An image pickup method for controlling exposure by comparing a photometry result of a partial area selected according to a brightness level among a plurality of areas measured by dividing the image pickup screen with a changed evaluation reference value. To do.

[0011]

As a result, the optimum control for the set photographing mode can be performed, and even in a special photographing situation such as a snow scene or a sandy beach where a high-intensity part exists in a wide range, It is possible to perform appropriate exposure control for both the main subject and the background.

Further, since such control information can be automatically set according to the photographing mode, it is possible to always perform optimum photographing regardless of the photographing situation and the photographing environment.

[0013]

Embodiments of the image pickup apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the construction of an embodiment in which the image pickup apparatus of the present invention is applied to a video camera. In FIG. 1, 1 is a taking lens optical system, 2 is an iris for adjusting the amount of incident light, and 3 is an iris. An image pickup device such as a CCD for photoelectrically converting an image which is formed on the image pickup surface by the taking lens optical system and whose light amount is adjusted by an iris into an image pickup signal.
Is a double correlation sampling circuit (CDS) that reduces the noise of the accumulated charge of the image sensor, 5 is an AGC circuit that automatically adjusts the gain of the image signal, and 6 is a predetermined signal process 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; A video tape recorder 8 uses a magnetic tape as a recording medium.

On the other hand, 9 is an AGC for dividing the image pickup screen into a plurality of screens and extracting an image signal corresponding to an arbitrary area.
A gate circuit 10 which gates the signal output from the circuit 5 is an integrator which integrates an image pickup signal corresponding to a designated area in the image pickup screen selected by the gate circuit 9 to obtain an average light amount, 11 Is an A / D converter that converts the signal output from the integrator into a digital signal that can be processed by the system control circuit described later. The area specifying operation by the gate circuit 9 and the integrating operation of the integrator 10 relate to specification and weighting setting of the photometric area according to the photographing mode, and the selection characteristics thereof are output from the system control circuit 13 described later. It can be arbitrarily set by controlling the pulse and the integral reset pulse. The detailed processing will be described later.

Reference numeral 12 is a CCD drive circuit for controlling the accumulation operation, read operation, reset operation, etc. of the image pickup device 3, 13 is an iris motor for driving the iris 2, 14 is an iris drive circuit for driving the iris motor, and 15 is described later. D / A converter for converting the digital iris control signal output from the system control circuit into an analog signal, 1
Reference numeral 6 denotes an iris encoder configured by a Hall element or the like for detecting the aperture amount of the iris, that is, an aperture value, 17 an amplifier for amplifying the output of the iris encoder 16, and 18 an iris encoder amplified to a predetermined level by the amplifier 17. It is an A / D converter that converts an output into a digital signal that can be processed by a system control circuit described later.

Reference numerals 19a, 19b, 19c, ... Show a data reference table (LUT: memorized various data for exposure control).
In the present embodiment, three tables are shown so that a plurality of settings can be made according to the shooting conditions in the Look up table). In the shooting mode, the two data tables are selectively used. By the way, in this embodiment, as will be described later, the "indoor shooting mode", "sports shooting mode", "landscape shooting mode", "portrait mode", and "surf & snow shooting mode" are described.

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

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

Reference numeral 25 is a system control circuit constituted by a microcomputer for totally controlling the entire video camera system in this embodiment.

The system control circuit 25 sends D / A converters 22 and 23 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 unit 20. The gate pulse supplied to the gate circuit 9 is controlled according to the photographing mode, and the photometric area for detecting the light amount on the image pickup screen is set. Further, the integration reset pulse supplied to the integrator 10 is controlled to control the selection characteristic of the integration operation.

For example, FIG. 2 shows an example in which a photometric area is set on the image pickup screen. In the figure, the photometric area is set at the center of the image pickup screen, and signals in this area are mainly exposed. It shows a region setting state of "central part weighted photometry" used for control calculation.

This is based on the empirical rule that the probability that the main subject is located substantially in the center of the screen is high. During the exposure calculation, the signal inside the central region shown by the solid line is larger than the signal outside. The exposure is controlled by assigning a coefficient and increasing the weighting of the central portion.

Then, the integrated value corresponding to the photographing mode of the image pickup signal in the photometric area fetched through the gate circuit 9 is fetched, and the iris control according to the photographing situation is made with reference 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 through the converter 21 to control the gain of the AGC circuit 5 to be variable according to the shooting mode and shooting conditions. Further, a control signal is also supplied to the CCD drive circuit 12 to switch the shooting mode and shooting. Depending on the situation, the storage time (electronic shutter) of the image sensor, the read timing, the reset timing, etc. are controlled.

Further, these various controls are performed while referring to the output of the iris encoder 16 according to the photographing mode, various control parameters are calculated and set, and the above-mentioned respective controls are selectively or simultaneously or. It is executed in an appropriate combination.

In this way, the system control circuit 25
Is a combination of iris control based on integral value, gain control, drive control of the image sensor (for example, electronic shutter based on storage time control), etc., based on the shooting mode shooting status and iris drive status. By doing so, optimum exposure control is performed for all shooting situations.

The image pickup apparatus according to the present invention is constructed as described above, 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 opening amount (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. Is supplied to the iris motor 13 to drive it. The iris motor 13 controls the diaphragm state of the iris 2 accordingly.

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

On the contrary, when the integrated value supplied from the A / D converter 11 is smaller than the control value defined by the LUT 19, the iris motor 13 is driven in the opposite direction to drive the iris 2 contrary to the above. It is controlled to open and increase the amount of incident light and consequently increase the integral value. (2) Shutter speed (parameter 2) (see FIG. 3) The accumulation time setting signal D _{t of the} image pickup device is output from the system control circuit 25 in the form of a digital signal, and the CCD drive circuit 12 receives the signal and the CCD Pulses that determine various timings are generated and the storage time is controlled.

Since the method of setting the storage time and the setting range are largely different depending on the structure of the CCD which is the image pickup device, in the present embodiment, a CCD having a structure for discarding unnecessary charges in the OFD (overflow drain) is taken as an example. And explain.

FIG. 3 (a) is for explaining the operation of this CCD, and the settable range is the range allowed in terms of image quality such as the image pickup light amount and smear if it is within H blanking on the high speed side. Can be set with. It is substantially 1/10000 second. On the low speed side, up to 1/60 second in the case of NTSC H
It can be set in steps of the blanking cycle (about 63.5 μsec).

As a concrete 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 that has received the instruction in this way 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 substrate direction. In this way, an arbitrary shutter speed can be set. FIG. 3B shows this operation.

Then, 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.

To set the AGC gain, the AGCC amplifier is set to C.
The output signal of the DS4 is provided so that appropriate signal processing is performed by the camera signal processing circuit 6 of the next stage,
Conventionally, it has been treated as a part of the constituent element of the AE loop by iris, and it has not been the object of arbitrarily controlling only this.

In recent years, even if the S / N ratio of the CCD is improved and the amplification factor is increased by increasing the gain of the AGC, the noise of the image pickup system becomes less noticeable and the settable range as a control parameter is expanded.

Since the gain is a parameter with a fast control response in the image pickup system, it 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 defined in the LUT 19 corresponding to the integrated value from the A / D converter 11, the system control circuit 25
Updates the gain setting value to reduce the AGC gain.

On the contrary, the current AGC gain is A / D converter 2
If it 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 shooting condition and shooting mode. The exposure control used will be described. First, the setting of the photometric area on the imaging screen, which changes according to each exposure control mode, will be described.

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

Therefore, in consideration of the light conditions corresponding to the set typical scene, the brightness distribution in the screen is assumed, and the area A in the screen that provides effective information for determining the exposure amount is
It is necessary to have an automatic photographing mode in which the E (automatic exposure control) calculation coefficient is largely allocated and the photometric area is set so as to increase the weighting.

According to the present embodiment, as shown in FIG. 4, the image pickup screen is divided into 4 vertically and 6 horizontally, and the entire screen is divided into 24 small areas (in the figure, for convenience of explanation, Each area is numbered 1-24).

These division operations are controlled by the system control circuit 25. The gate pulse output from the system control circuit 25 controls the opening and closing of the gate circuit 9 to output the AGC circuit 5. The signal is extracted for each of the areas 1 to 24, and the integration processing is performed as an independent value in the integrator 10 for each area, and the result is A /
After being converted into a digital signal by the D converter 11, it is taken into the system control circuit 25.

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

FIG. 5 and FIG. 6 respectively show examples of the image pickup screen on which the weighting coefficient processing is performed.

FIG. 5 shows the above-mentioned "center portion weighted photometry" realized by the 24-division AE system of the present invention.
The weighting calculation coefficient in the areas 8 to 11 and 14 to 17 corresponding to the center of the screen is set to 1.0, and the weighting calculation coefficient in the surrounding areas is set to 0.5, and the AE control is focused on the central portion. . Specifically, if the iris, shutter speed, and gain are controlled based on the value obtained by adding the integral values of these weighted regions, the above-mentioned weighting can be reflected in these controls.

FIG. 6 shows an example of a photometric area suitable for "landscape photography" and the like. Generally, when shooting landscapes, it is often the case that both the ground and the sky are captured on the screen at the same time. In addition, the sky part often has a very high brightness compared to the ground part even in a slightly cloudy weather. For this reason, when a photograph is taken using the conventional AE control that does not consider the photometric area, a person or the like against the ground or the sky is often crushed in black due to insufficient light intensity.

In order to eliminate these inconveniences, the weighting coefficients of the areas 1 to 6 at the top of the screen, which correspond to the sky, are set to 0.0 and ignored substantially, and the coefficient above the center of the screen is set to 0.5.
And set the coefficient of the lower half of the screen to 1.0. By allocating the calculation coefficients in this way, it is possible to perform the AE calculation processing with emphasis on the lower portion of the screen corresponding to the ground. Details of this landscape photography mode will be described later.

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

Next, the actual AE control according to the shooting condition using the above-mentioned three parameters will be described. As mentioned above, the conventional iris control is not enough for shooting in various shooting situations.
In the present invention, more parameters are prepared so that these can be optimally controlled.

That is, in the present invention, a shooting control called "program mode" is provided in which, assuming several typical shooting situations, it is possible to shoot while automatically adjusting each under the optimal conditions. 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 and under various conditions of video shooting, 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 look-up tables (LUTs) storing control functions for controlling a plurality of parameters are set, and as shown in FIG.
A plurality of tables such as 19a, LUT 19b, LUT 19c ... Are prepared by a memory such as a ROM and are configured so that they can be selectively read from the system control circuit 25. This selection is made by a key operation of the operation unit 20. It is carried out.

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

FIG. 7 shows that the shutter speed of the parameter (2) can be set to 1/100 seconds as much as possible, and the iris of the parameter (1) or the parameter ( 3) A
FIG. 11 is a program diagram showing a program control operation for performing proper exposure control by varying a GC gain, which is stored in, for example, LUT 19a.

In this program mode, the power supply frequency is 5
This is for suppressing flickering of a fluorescent lamp that occurs when an NTSC video camera is used in an area of 0 Hz, and can be called, so to speak, "indoor shooting mode".

In the figure, the horizontal axis is the illuminance of the subject as an input parameter, and the vertical axis is the set value of each parameter. As is apparent from the figure, the setting range of each parameter is A, B, C3 depending on 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 objects in this area A.

On the other hand, in the area B, the illuminance is low and the iris is open, and the iris is constant at the open value as shown in the figure. Therefore, exposure control is performed by changing the shutter speed to 1/60 second. That is, in the NTSC system, since the data is originally stored and read at a cycle of 1/60 second, 1/60 second indicates the original operation timing.

When the illuminance further decreases, as shown in area 3, the iris and the shutter have reached their limits, so the exposure is controlled 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, the optimum exposure control according to the photographing situation can be performed.

FIG. 8 shows another program mode. For example, in the program diagram stored in the LUT 19b, the shutter speed (P2) is set to a high speed shutter of 1/500 seconds as much as possible, and movement is performed. This is a program mode prepared so that blurring can be suppressed and a screen can be clearly photographed for a fast subject, and will be referred to as a "sports photography mode" in the present invention.

As is clear from the figure, the shutter speed in area A and area B is 1/500 as much as possible.
The iris (P
The exposure control is performed by 1) and the gain (P3), and the operation is performed so as to gradually change to 1/60 seconds for the first time in the area C where the illuminance of the subject is lowered and the shutter speed cannot be maintained.

FIG. 9 is a program diagram in the "landscape photographing mode" shown in FIG. Actual program diagrams are as shown in Fig. 7 and Fig. 8, but for simplicity,
In FIG. 9, the iris, the shutter speed, and the gain are shown in this order from the top in order of operating range.

That is, in the figure, I is the iris control parameter (P1), S is the shutter speed control parameter (P2), and G is the gain control parameter (P3). As shown on the right side of the figure, The iris control parameter (P1) operates between CLOSE and OPEN, the shutter speed control parameter (P2) is constant, the gain control parameter (P3) is an amplification factor of ± 0 dB (input signal is output as it is, THROUGH It means that it changes from the predetermined value G1.
However, in the variable region, the value of each parameter is changed in accordance with the brightness level which is an input parameter, as in the program diagrams of FIGS. 7 and 8 described above.

In the landscape photography mode, flickers, fast-moving subjects, etc. are often not present, so the shutter speed (P2) is fixed at the standard 1/60 second, and the iris (P1) center control is performed. After is opened, the gain (P3) is controlled.

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

As described above, a plurality of program modes are prepared in accordance with the shooting conditions, and these are appropriately selected by the key operation of the operation unit 20, so that the optimum exposure for all shooting conditions is obtained. 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 also switched at the same time as described above. Figure 7 for example
In the indoor shooting mode of FIG. 8 and the sports shooting mode of FIG. 8, since a subject such as a person usually located in the center of the screen is often photographed, the “center part weighted metering” screen shown in FIG. 5 is used. Also in the landscape photography mode of FIG. 9, the photometry area on the imaging screen is switched to the photometry area for the “landscape photography mode” shown in FIG. 6 in conjunction with the operation of switching to this photography mode.

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 this embodiment) to change the input parameter, that is, the illuminance of the subject. Each area is selected according to 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, the parameter (P1) is variable and the others are fixed in the area A, that is, the shutter speed and the gain are fixed when the iris control is performed.

In area B, the parameter (P2), that is, the shutter speed is variable and the others are fixed, and area C
Then, 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, there is always one variable parameter in each area unit, which eliminates the need for a fixed parameter calculation process. The process is no different from the conventional single parameter process.

That is, the present invention divides the parameter setting area into a plurality of areas and changes the complicated operation processing that naturally occurs due to the increase of the control parameters in order to cope with all shooting situations. By setting one parameter to be fixed and the other to be fixed, it is possible to simplify the handling of a wide variety of imaging conditions and multiple parameters to be controlled, and realize optimal AE control without using a large-scale logic or a large-scale computer. Is something that can be done.

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

That is, although the present invention is intended to reduce the arithmetic processing by always setting one variable parameter and fixing the other, as a characteristic peculiar to a video camera,
The object of normal shooting is a moving image, and the shooting conditions change every second.

When each control parameter is set corresponding to the input parameter, the value of the input parameter may move between the plurality of divided areas due to the change of the photographing condition. At this time, the controlled parameter switching operation occurs, but the way of changing on the screen may vary greatly depending on the parameter, and if this change occurs frequently, it is expected that the screen becomes difficult to see. It

As a countermeasure against this, it is conceivable to provide a hysteresis at the time of area transfer and suppress the frequency of area transfer to a low level, but when switching occurs, it has no effect and cannot be a fundamental measure. .

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

In FIG. 7, a boundary portion B sandwiched by broken lines
1 is a boundary area in which the parameters P1 and P2 operate simultaneously, and similarly, in the boundary portion B2, the parameters P2 and P3 are
And are running at the same time.

By simultaneously changing the two parameters in this manner, image changes peculiar to the respective parameters occur simultaneously and gradually, so that the screen changes even when the parameters move between areas. Can be visually uncomfortable.

Although the method of controlling the exposure by 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 switching of the photographing modes. A control signal for changing various characteristics of various image processings and camera signal processings from the standard position according to the respective photographing conditions can be supplied via the converters 22 and 23.

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

Therefore, the image pickup screen corresponding to the set typical scene is taken into consideration, and in accordance with the set photographing mode, as shown in FIG.
In the camera signal processing circuit 6 of FIG. 11, the nonlinear conversion characteristic (knee characteristic or γ characteristic) of the video signal level is shown in FIG.
It is not possible to control the characteristics of the aperture correction circuit that changes the image sharpness of the image, such as b and c, and the image signal processing circuit 7 shown in FIG. As the processing, for example, it is possible to give a "fade effect" or "afterimage effect" to the picked-up image signal.

FIG. 12 shows a configuration example of the image signal processing circuit 6 having a function of applying such an additional effect, and the configuration and operation thereof will be described below.

The color signal processing circuit 30 generates a color signal designated by the control signal * 1 from the system control circuit 25 (for example, all-blue blue back or all-white), and outputs the color signal and video output. The field memory circuit 32 delays the signal by 1 screen, and 3
It is supplied to a selection switch 31 which makes an alternative selection.

Information of one of the three selected by the instruction * 2 of the system control circuit 25 is supplied from the selection switch 31 to the input terminal of the multiplier 33. The multiplier 33 executes the multiplication process using the coefficient output from the multiplication coefficient generator 34 according to the instruction * 3 of the system control circuit 25. The multiplication result is added by the adder 35 to the signal resulting from the same coefficient multiplication process performed by the multiplier 38 on the video input signal input from the input terminal 36, and the result is supplied to the output terminal 37. It

In the process of processing such a signal, if the OFF terminal of no signal is selected by the selection switch, the adder 35
Since only the video signal from the input terminal 36 is input to, the video input signal is directly output to the video signal output terminal 37 (through). At this time, the coefficient of the multiplier 38 is 1.0, which is a through.

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

Also when the output of the field memory is selected, the coefficient relationship of the multiplier 38 is a one's complement as described above. The difference is that there is no change with time, and the operation is fixed at 0.5, for example.

In this case, since the result of addition and output is cyclically added at a predetermined ratio with a delay of one screen, the input image is represented as if it were tailed 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, the above-mentioned camera signal processing circuit changes the aperture characteristic or the like, and The image quality can be adjusted by, for example, giving a soft feeling to the image by lowering the frequency response related to the sharpness of the visual characteristics of the television signal and the frequency response in the vicinity of 2-3 MHz in the television signal.

By operating the circuit as shown in FIG. 12, the color fade can be applied to the image.
The effect of special image processing can be automatically added.

This portrait photographing mode is basically a photographing mode with center-weighted photometry in which the photometric areas as shown in FIG. 5 are weighted as shown in the figure. The photographing program mode is as follows. The diagram is set as shown in FIG. The actual program diagram is as shown in FIGS. 7 and 8, but for simplification, the operating range is shown in order of iris, shutter speed, and gain from the top in the same manner as in FIG.

That is, in FIG. 13, I is the iris control parameter (P1), S is the shutter speed control parameter (P2), and G is the gain control parameter (P3), as shown on the right side of the figure. Iris control parameter (P1) operates between CLOSE and OPEN,
The shutter speed control parameter (P2) is displaced between the high speed (T1) and the standard 1/60 second, and the gain control parameter (P3) is an amplification factor of ± 0 dB (the input signal is output as it is, THROUGH And)
To a predetermined value G1.

However, in the variable region, the value of each parameter is changed in accordance with the brightness level which is an input parameter, as in the program diagrams of FIGS. 7 and 8.

In this portrait mode, it is assumed that the subject is a person, and therefore importance is attached to taking a shallow depth of field.

As is clear from the figure, two threshold values y1 and y2 are set for the object illuminance on the horizontal axis, and 3
It is divided into two areas.

Looking at the iris, in the high brightness area A, control is performed by the iris, but since it is desired to secure S / N at high brightness, the AGC gain remains ± 0 dB until the iris reaches the open value. Although held, the iris is controlled in consideration of the decrease in resolution resulting from the diffraction phenomenon due to the small aperture of the iris.

Specifically, when the input luminance level is y1 or less, the iris is controlled to the open value. As a result, the iris is opened at normal brightness, and the depth of field can be made the shallowest. That is, the control characteristic of the iris is y
With 1 as the boundary, the entire area from high brightness to low brightness can be switched between two levels, a variable area and an open area.

Looking at the shutter speed, the high shutter speed T1 which is faster than the normal 1/60 second is set in the high brightness region of y1 or more, and this is possible even in the high brightness in addition to the small aperture measure. As far as possible, the depth of field is shallow, so the shutter speed is set somewhat higher. Actually, it is set within the range of about 1/250 to 1/4000 seconds.

Since this increases the S / N ratio, it also has the meaning that control can be performed without raising the AGC gain even when the brightness becomes low.

In the areas y1 to y2, the iris is at the open value, and I do not want to raise the AGC gain from the point of S / N. Therefore, the shutter speed is between T1 and the standard 1/60 second. The exposure is controlled by changing the exposure.

When the brightness level is y2 or less, the shutter speed is 1/60 seconds (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 S / N allowable range.

As described above, the AGC gain is always fixed to ± 0 dB when the luminance is y2 or more, and the AGC circuit 5 itself is controlled so as not to have an amplifying action. 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 brightness level is y2 or less, the gain control is performed for the first time, and the gain control is performed to perform the exposure control within the range allowed by the S / N.

As described above, in the portrait mode, the image is taken with center-weighted photometry, but since it is premised on a person-based image pickup, it is extremely effective to use the above-mentioned 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 photometric 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 the control parameters such as the iris, shutter speed, and gain described above will be described.

FIG. 10 is a flow chart showing a parameter setting operation including the above-mentioned parameter processing of the area boundary portion in the program photographing mode using the program diagram of FIG. 7, for example.

In the figure, when control is started, S
The power-on is monitored at 1, and when the power is turned on, the process proceeds to S2, the photographing program mode (M) selected by the operation unit 20 is confirmed, and the process proceeds to S3 to select the selected program. Set the designated program characteristic by referring to the LUT 19a or 19b, 19c corresponding to the mode (M).

In S4, the data relating to the weighting of each of the 24 divisions set on the image pickup screen is read from the designated LUT, the weighting according to the photographing mode is performed as described above, and the process proceeds to S5.

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

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

Then, the process proceeds to S7, and the branch destination is determined according to the current area.

If the area A is determined, the process proceeds to S8, the iris control parameter P1 is calculated, and then S
The inside / outside of the boundary area B1 of the area is judged at 9 and the boundary B
If it is outside 1, the process proceeds to S10 to hold the shutter speed control parameter P2 in advance and fix it, and if it is within B1, S
After proceeding to 11 and calculating and updating the shutter speed control P2, proceeding to S21, 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 to determine whether the boundary areas B1 and B2 of the area are inside or outside.
Then, the iris control parameter P1 is calculated and the process proceeds to S21. The gain control parameter P3 is held in advance and fixed, and then the process proceeds to S24.

If it is within B2, the process proceeds to S16, the gain control parameter P3 is calculated, the process proceeds to S23, the iris control parameter P1 is held in advance and fixed, and then the process proceeds to S24.

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

If the area C is determined in S7, the process proceeds to S17, in which the gain control parameter P3 is set.
Then, in S18, the inside / outside of the boundary area B2 of the area is determined. If it is outside the boundary B2, the process proceeds to S20 to pre-hold and fix the shutter speed control parameter P2. For example, the program proceeds to S19 where the shutter speed control P2 is calculated and updated, and the program proceeds to S23 where the iris control parameter P1 is held in advance and fixed, and then S24.
Go to.

At S24, the values P1, P2, P3 of the respective parameters set by the above-mentioned processing, that is, the iris,
The control values of the shutter speed and the gain are output from the system control circuit 25 to control the iris 2, the image sensor 3 and the AGC circuit 5 respectively according to the program mode, and the next processing time unit comes at S25. Wait until (in this embodiment, one calculation is performed for one frame as a basic unit), the power-off is confirmed in S26, and if the power-on continues, the process returns to S1 to repeat the above-mentioned processing,
If the power-off is instructed, the process ends.

As a result, various parameters can be controlled according to the selected program mode, and the exposure control is performed based on this.

Further, in association with the switching of the photographing program mode, the characteristics of the photometric area and the image signal processing system on the image pickup screen or the additional functions are changed to those suitable for the photographing situation. It is possible to always perform optimum automatic exposure control and shooting according to the shooting situation.

Moreover, even if the photographing condition changes, the photographing condition of the camera does not change unnaturally, and the optimum control mode switching can be performed.

Next, the "surf & snow shooting mode", which is still another program shooting mode of the present invention, will be explained, and the "surf & snow shooting mode" will be taken as an example to set and control various shooting modes and data. The internal structure of the table LUT and the control of the control parameter by the setting will be described in detail.

The "surf & snow shooting mode" is a program shooting mode which is assumed to be a shooting situation in which a wide area of the screen has high brightness such as a snow scene or a beach.

In general, when a main subject is photographed with such a screen as a background, the main subject is pulled by the high brightness of the background and "blackout" occurs.

In order to prevent this, it is conceivable to correct the exposure to prevent the black crush of the main subject, but if such a method is simply adopted, the brightness is high, such as in a snow scene or a beach. If the background is in a wide range, it is difficult to perform appropriate exposure control on both the background and the main subject, and conversely, the background becomes unnatural such as white becomes gray.

The "surf & snow shooting mode" of the present invention is a program shooting mode which enables good exposure control even in such a shooting situation and enables shooting without any unnaturalness. Is set.

FIG. 14 shows the internal structure of the data table LUT which is referred to when this mode is selected and stores the definitions and characteristics of various control parameters necessary for the control.

Further, the program diagram showing the operation of various control parameters defined and set by this LUT, that is, the transition of each control parameter with respect to the input brightness level is a design of the control parameter transition diagram in the portrait photographing mode shown in FIG. Is the same as. Therefore, in the present application, the setting of the control parameters in the surf & snow photographing mode will be described with reference to FIG.

However, only the design is the same, the two threshold values, the shutter speed, and the gain control value are set separately between these photographing modes.
In order to distinguish them, two thresholds are set to y
1 ', y2', the high speed shutter speed is T1 ', and the gain control value is G1'.

The individual parameters in each figure will be described in order below. (P1: Iris control parameter) The iris control parameter changes according to the input parameter Y, that is, the brightness level, and the function f (y) is defined as its attribute.

The input luminance level is the threshold value y shown in FIG.
When it is higher than 1 ', as is apparent from the data column on the right side of FIG.
is required.

Since it is desired to secure S / N with high brightness, AGC
The gain is maintained at ± 0 dB (THRUGH), and the iris is controlled to be fully opened to the open value in consideration of the small aperture measure that the resolution is lowered due to the diffraction phenomenon of light by the small aperture of the iris.

When the input luminance level is y1 'or less, the control for setting the iris to open is indicated by "→ OPEN".

In this way, the control characteristic of the iris is defined by dividing the entire area from high brightness to low brightness by one threshold value y1. (P2: Shutter Control Parameter) As for the shutter control parameter, the brightness function f (Y) of the input parameter is defined by the threshold values y1 'and y2'.

When the input luminance level is higher than y1 ', "→ T1'" is designated, and the shutter speed is set to the high speed T1. In this case, calculation is unnecessary.

Here, as described above, T1 is set to a somewhat higher shutter speed as a measure against the small aperture.

Actually, it is selected within a range of about 1/125 to 1/500 seconds.

At this stage, in order to earn S / N,
Even if the brightness becomes low, the AGC gain is controlled without increasing as much as possible.

Between the input brightness levels y1 'and y2', "→ CAL" is set, and the optimum shutter speed corresponding to the input brightness level is calculated and the control parameter value is set. It indicates to control to do.

The control variable width here is between the above-mentioned T1 'and the standard screen frequency (standard value) of the television.

"→ standard value" indicates that the shutter speed should be set to the standard value of the television signal when the input luminance level is y2 'or less.

The standard value of the television signal mentioned here means 1/60 second in NTSC and 1/50 second in PAL.

In this state, since only the AGC gain remains as a controllable parameter, gain control is performed within a range that is allowable in terms of S / N deterioration, and exposure control is performed. (P3: AGC gain) Even when the AGC gain is used as a parameter to be processed, the function f (Y) of the input luminance is defined by a plurality of thresholds, and when the input luminance level is higher than y2 ′, "→ ± 0 dB" is specified,
The AGC gain is fixed at ± 0 dB, and the gain is set so as not to have an amplification effect. That is, when the exposure control is possible by the iris and the shutter, the AGC gain is fixed to prevent the deterioration of the S / N, and in this case, the calculation is unnecessary.

Further, since this section is set so as to occupy most of the range of the illuminance of the subject, S /
It is possible to pick up a good image of N.

When the input luminance level is y2 'or less, "→ CAL" is designated so that the optimum AGC gain is calculated and the gain control parameter is set.

The other parameters have already reached their limits, and the controllable parameters left in this state are A
Since only the GC gain is used, the exposure control is executed by adjusting the gain up within an allowable range while considering the trade-off with S / N deterioration.

The relationship between the area divided into three by these threshold values y1 'and y2' and the three control parameters is clear from FIG. 13, and the parameters to be calculated here are the three areas. Each of them is arranged in a dispersed manner so that there is always one, and the calculation is simplified, and the arrangement is I, S, and G from the area on the high-luminance side. (P4: AE weighting parameter = photometric area weighting setting) This is a parameter for setting the photometric area distribution in the imaging screen and their weighting. As is clear from FIG. 14, the attribute is f (Y) and the input luminance It is shown to be a function.

Specifically, it is defined by a histogram created in accordance with the input luminance signal, and the
The input luminance signal level in each divided area is detected to create a histogram of the luminance level, which accurately detects the distribution state of the high-luminance and low-luminance areas on the imaging screen, and determines the area for priority photometry. decide.

In the present embodiment, the brightness level of each of the 24 divided regions is detected and the brightness histogram created from these is used to determine the upper N% (in this embodiment, N = 50%, that is, 24/2 = 12). However, this value may be provided in plural according to the degree), and the exposure control is performed using only the luminance information of the 12 areas.

Expressed as a coefficient, each of the extraction regions has 1.
AE control calculation is executed by assigning 0 to each of the non-extracted areas and 0.0.

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

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

In the figure, the top 12 areas (1 to 12) which are 50% in the 24 areas of this cumulative histogram.
Is to be extracted. Further, FIG. 16 shows a photometric area distribution in which 24 divided areas in the imaging screen are weighted based on this histogram. The weighting calculation coefficient of 1.0 is assigned to the region extracted by the above histogram.

In this way, it is possible to select a half of 12 in the image pickup screen from the one with the highest brightness and set the AE photometric characteristics with emphasis on that part, and to emphasize the part with high brightness within the screen to perform the intensive photometry. Therefore, even in a shooting situation where there are a lot of high-intensity areas such as snow scenes and sandy beaches, the result of performing exposure compensation to prevent underexposure of the main subject or underexposure of a part of the screen It is possible to prevent poor-quality shooting in which the image in the high-brightness part of the image becomes overexposed and becomes unnatural, and it is possible to obtain a natural shot image on the entire screen. (P5: AE reference value parameter) The AE reference value parameter indicates the brightness level that serves as a reference for exposure control, and is stored in a numerical definition. It is determined whether the exposure is excessive or insufficient based on this reference value, and in the present embodiment, it is assumed that there are a large number of high-luminance portions in the image capturing screen, such as snow scenes and beaches. Since the shooting mode is set, the AE reference value is set to 80 IRE, which is slightly higher than the general IRE reference value, so that the high-brightness subject portion can be clearly imaged as a whole. This parameter is also constant in the shooting mode regardless of the input brightness level. (P6: Image quality adjustment parameter) It is a parameter that specifies the image quality adjustment processing by the aperture control described above, the processing content is defined by a code, the attribute is fixed, and is set according to the shooting mode. It does not change depending on the brightness level.

In this photographing mode, "NORMAL" is set, and the basic image quality is set to the standard value. (P7: Image effect processing parameter) As described with reference to FIG. 12, it is a parameter for designating image processing such as a fade, and the processing content is defined by a code.

"NORMAL" is designated,
The special effect of the image is set not to be performed.

As described above, the data table LUT of the present invention stores the definitions and characteristics of various parameters required for control, and a plurality of such LUTs are provided in accordance with the photographing mode, and the designated photographing is performed. Since you can select according to the mode, it can be used in all shooting situations and environments.
Optimal control can always be performed.

As described above, the data table LUT according to the present invention stores the definitions and characteristics of various parameters required for control, and a plurality of such LUTs are provided according to the photographing mode, and the designated photographing is performed. Since you can select according to the mode, it can be used in all shooting situations and environments.
Optimal control can always be performed.

The data table L defining the control parameters of the "surf & snow shooting mode" has been described above as an example.
The operating characteristics of the UT and the control parameters set thereby have been described.

The operation of reading the data from the LUT shown in FIG. 14 to the system control circuit to calculate the control parameters and setting the control parameters as shown in FIG. 13 will be described in detail with reference to the flowchart of FIG. To do.

These processing operations are basically shown in FIG.
This is performed in the processing from the confirmation processing of the program photographing mode of S2 in the flow chart of the above to the output of the iris, shutter and gain control data based on each control parameter of S24.

FIG. 17 is an operation flow chart showing the procedure of the data set for setting the control characteristic according to the photographing program mode.
It is a routine that is executed in parallel in the processes of 2 to S24, and after the completion of this routine, the process returns to S25 of FIG.

When the control is started, the photographing mode is selected by the operation unit 20 of FIG. 1 in S101, and the selection result is fetched into the system control circuit 25, and 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, the parameter counter n for designating the parameters is initialized to n = 01,
In S104, the data of the parameter Pn designated in S103 is read.

Explaining this parameter specification,
In the example of FIG. 14, when n = 01, data regarding the iris, when n = 02, data regarding the shutter speed, when n = 03, data regarding the AGC gain, n
= 04, data relating to AE weighting (weighting coefficient of photometric area); data for AE evaluation reference values, that is, a level used as a reference for adjusting the brightness level to a constant value when n = 05; and image quality when n = 06. Data relating to adjustment and data relating to specially effective image processing when n = 7 are read into the system control circuit 25.

At S105, the attribute of the read parameter is confirmed, and it is determined whether the attribute depends on the input parameter (f (Y)) or whether the data 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 it changes according to a predetermined function f (Y) with respect to the input parameter, that is, the illuminance of the subject in this embodiment, or is fixed regardless of the change of the input parameter. The attribute of the parameter is f in S105.
If (Y) depends on the input parameter, S10
If the attribute of the data is fixed regardless of the brightness level, the value of the parameter is set.

In S107, the parameter counter n is set to 1
Is added to make n + 1, and in S108, it is confirmed whether or not n is larger than the maximum value in the LUT, and the above-described operations of S104 to S107 are repeated until n reaches the maximum value, and the parameter is read. The attribute discrimination operation is repeated and when n exceeds the maximum value, the process proceeds to the data output process of S109 and thereafter.

After S109, LU is set in S101 to S108.
This shows a process of performing control data output calculation based on the parameters read from T. In S109, the parameter counter is reset to n = 01.

At S110, the attribute of the parameter is confirmed, and it is determined whether the attribute depends on the input parameter (f (Y)) or the fixed attribute corresponding to the mode without depending on the input parameter. If f (Y), S11
If fixed, skip S111 and S112 and skip to S113.
Go 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. The data definition of the LUT is referred to according to the value of the input signal, and the necessity / non-necessity of data calculation is determined. If the calculation conditions are met, the process proceeds to S112, where only the instructed parameter 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 calculation process in S112 is skipped and the process proceeds to S113.

In S113, 1 is added to the parameter counter n, the value is set to n + 1, and the process proceeds to S114. Then, the process returns to step S110 until the parameter counter n exceeds the maximum value of the parameter number of the LUT, and the above-mentioned S110 to S113 are performed for all parameters. 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 of the flow chart of FIG.

The above is the processing procedure until the characteristics of each parameter are read from the data reference table LUT and the AE control data is calculated. In this way, the LUT corresponding to the set shooting mode is used to determine the shooting status. Optimal shooting can be performed by reading out suitable control data and performing control.

[0181]

As described above, according to the image pickup apparatus of the present invention, the photographing state is controlled using a plurality of parameters, and the data table according to the photographing mode is suitable for the photographing situation. Since the setting conditions of the control data are read and controlled, more detailed control is possible compared to conventional devices, and optimal shooting is possible by simply selecting the shooting mode even under various shooting conditions. Have an effect.

Regarding the actual control, the image pickup screen is divided into a plurality of areas to provide a multi-area photometric system, a brightness histogram based on the brightness level is created for each photometric area, and the upper N% area of the brightness is calculated. Since it is equipped with a metering mode that determines the metering area using only the AE control and changes the evaluation reference value of AE control to perform AE, the conventional method that includes a wide range of high-brightness subjects such as snow scenes and beaches Even in shooting situations where it was difficult to control the proper exposure, it is possible to perform exposure control that is well balanced for both the high-brightness part and the main subject, and that does not cause overexposure or underexposure. Optimal exposure control can always be performed for the shooting conditions of.

By switching the photographing mode,
Since the photometric distribution is linked to switch to the setting suitable for the mode, operability is improved, and setting mistakes can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration when an image pickup device according to the present invention is applied to an exposure control device of a video camera.

FIG. 2 is a diagram showing a photometric region in central partial weighted 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 explaining setting and weighting of a photometric area of “center partial weighted photometry” in the present invention.

FIG. 6 is a diagram for explaining photometry area setting and weighting in the “landscape shooting mode” according to the present invention.

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

FIG. 8 is a program diagram for explaining parameter processing according to the “sports shooting mode” of the present invention.

FIG. 9 is a program diagram for explaining parameter processing according to the “landscape shooting mode” of the present invention.

FIG. 10 is a flowchart for explaining processing for explaining parameter setting in FIGS. 7 and 8.

FIG. 11 is a diagram showing characteristics of a camera signal processing circuit which is performed in conjunction with switching of shooting modes according to the present invention.

FIG. 12 is a diagram for explaining the control of the image processing circuit, which is performed in conjunction with the switching of the shooting mode in the present invention.

FIG. 13 is a program diagram for explaining parameter processing according to a “portrait shooting mode” and a “surf & snow shooting mode” of the present invention.

FIG. 14 is a diagram for explaining the structure of a data table according to the “surf & snow shooting mode” of the present invention.

FIG. 15 is a diagram showing a luminance histogram for determining a photometric area according to the “surf & snow shooting mode” of the present invention.

16 is a diagram showing an image pickup screen on which a photometric area is set and weighted based on the histogram of FIG.

17 is a flow chart for explaining the processing of the flow chart of FIG. 10 in more detail.

FIG. 18 is a block diagram showing a configuration when a general image pickup device is applied to an exposure control device of a video camera.

FIG. 19 is a diagram for explaining a shutter priority mode.

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yuji Tsuda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-59-91778 (JP, A) JP-A-2 -60378 (JP, A) JP-A-62-147872 (JP, A) JP-A-4-70277 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04N 5/235

Claims (5)

(57) [Claims] 1. An imaging means for photoelectrically converting incident light imaged on an imaging screen, a shooting mode selecting means for selecting a shooting mode according to a shooting situation, and a predetermined shooting mode selected by the shooting mode selecting means. In this case, the evaluation reference value for controlling the exposure is changed, and the photometry result of a partial area selected according to the brightness level is selected from the plurality of areas measured by dividing the imaging screen. An image pickup apparatus, comprising: an exposure control unit that controls exposure by comparing with a changed evaluation reference value. 2. The evaluation standard according to claim 1, wherein the exposure control means, when the photographing mode selecting means selects a predetermined photographing mode assuming a photographing situation in which a wide range of an image pickup screen has high brightness. An imaging device, which is configured to increase a value. 3. The exposure control means according to claim 1, when the predetermined photographing mode is selected by the mode selection means, the exposure control means divides the image pickup screen into a plurality of small areas and sets the brightness of the divided areas. While measuring the area formed by N small areas from the higher level,
An image pickup apparatus configured to perform exposure control by comparing the photometric result with the evaluation reference value. 4. An input brightness level calculated based on a result of applying a predetermined weighting to a brightness level in each of the small areas obtained by dividing the imaging screen into a plurality of small areas, and comparing the input brightness level with a predetermined evaluation reference value. Exposure control means for performing exposure control, and shooting mode selection means for selecting an arbitrary shooting mode from a plurality of shooting modes provided according to shooting conditions, wherein the exposure control means selects the shooting mode. The weighting and the evaluation reference value are changed according to the photographing mode selected by the means, and when the predetermined photographing mode for the high-luminance subject is selected by the photographing mode selecting means, the brightness of the plurality of small areas The weighting of the area formed by the N small areas from the higher level is increased to perform the priority photometry, and the evaluation reference value is increased. Imaging apparatus characterized by being configured to coordinating. 5. When a predetermined shooting mode is selected from a plurality of shooting modes provided according to the shooting situation, the evaluation reference value for controlling the exposure is changed, and the shooting screen is divided to perform photometry. Of the plurality of areas to be exposed, the exposure is controlled by comparing the photometric result of a partial area selected according to the brightness level with a changed evaluation reference value.