JPH0556342A - Image pickup device - Google Patents

Abstract

PURPOSE:To provide the automatic exposure controller for a video camera by which an optimal exposure control can be always attained regardless of a photographing circumstance or a photographing situation. CONSTITUTION:This device is a video camera equipped with an iris 2, storage time control means 12 which controls the light storage time of an imaging device 3, gain control means 5 which controls the gain of the output signal of the imaging device 3, data tables 19a, 19b, and 19c which are selected according to a photographing mode, and which store plural control characteristics, and control means 25 which operates the control data of the iris 2, the storage time of the imaging device 3, and the gain based on the data read from the data tables 19a, 19b, and 19c corresponding to the photographing mode. In the prescribed photographing mode, the quantity of light of the iris is increased, and the gain is made to be constant by setting the short storage time corresponding to the cycle of the screen of a standard television signal in a high luminance area, and then the storage time is lengthened, and the gain is increased according to the deterioration of the luminance, by the control means 25, so that the depth of an objective field can be held to be shallow.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In recent years, video equipment such as video cameras 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 essential, for example, in terms of automatic exposure control, it is a demanding factor that determines the quality of captured images, and stable and good automatic exposure control must be possible in all shooting environments. The importance of the automatic exposure control function is extremely high.

FIG. 16 is a block diagram showing the basic structure of an exposure control system of a general video camera. Reference numeral 101 is a photographic 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 for photoelectrically converting the image formed on the image pickup surface by the taking lens optical system and having the light amount adjusted by the 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 and converts 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. 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 and 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 that controls the drive current output by changing the opening amount of the iris is configured, and the CCD drive circuit 108 is controlled according to the key operation of the switch panel 110 to switch the drive pulse. 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.

This storage time control is what is called an electronic shutter, and 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 accumulation 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. 17 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 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 which takes a momentary still image, it suffices if the exposure control at the moment of taking the image is properly controlled. However, like a video camera, a moving image is taken 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. 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 optimum exposure control regardless of the shooting environment and shooting conditions.

[0010]

In order to achieve the above-mentioned object, the present invention comprises a light amount adjusting means for controlling the amount of transmitted light of an image pickup optical system, an image pickup device for accumulating the transmitted light and photoelectrically converting the transmitted light. Storage time control means for controlling the light storage time of the image sensor, gain control means for controlling the gain of the output signal of the image sensor, and storage means for storing a plurality of control characteristics selected according to the shooting mode, And a control unit for calculating control data of the light amount adjusting unit, the storage time control unit, and the gain control unit based on the data read from the storage unit corresponding to the shooting mode, the control unit in a predetermined shooting mode, By setting a short light accumulation time with respect to the screen period of the standard television signal in the high brightness region, the amount of transmitted light of the light amount adjusting means is increased and the gain is adjusted And then, with a decrease of the brightness, after performing an operation to increase the storage by controlling the accumulation time control unit time is controlled to increase the gain by controlling the gain control means.

[0011]

As a result, the optimum control can be performed for the set shooting mode, and in particular, for example, in the portrait shooting mode where it is desired to keep the depth of field shallow, a data table according to the shooting conditions can be created. By referring to this, it is possible to perform control using a parameter more suitable for the shooting situation, and it is possible to always perform optimal shooting regardless of the shooting situation and shooting environment.

[0012]

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 and an integrator 10 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 a 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 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 accumulating operation, reading operation, resetting operation of the image pickup device 3, 13 is an iris motor for driving the iris 2, 14 is an iris driving circuit for driving the iris motor, and 15 is a later-described. D / A converter for converting the digital iris control signal output from the system control circuit into an analog signal, 1
Reference numeral 6 is 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 is an amplifier that amplifies the output of the iris encoder 16, and 18 is an iris encoder that is 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, ... Are data reference tables (LUT: LUT) storing 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. Incidentally, in this embodiment, as will be described later, the "indoor shooting mode", "sports shooting mode", "landscape shooting mode", and "portrait 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 according to the set shooting mode. Necessary data can be read out.

Reference numeral 20 designates an operation section comprising a plurality of operation keys for performing various operations, and 21 designates a digital gain control signal outputted from the system control circuit, which is converted into an analog control signal and supplied 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 comprehensively controlling the entire video camera system in this embodiment.

The system control circuit 25 sends a control signal 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, to the D / A converters 22 and 23. And the gate pulse supplied to the gate circuit 9 is controlled according to the photographing mode to set the photometric area for detecting the light amount on the image pickup screen. In addition, 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 in the central portion of the image pickup screen, and signals in this area are mainly exposed. It shows a region setting state of "center partial weighted photometry" used for control calculation.

This is based on the empirical rule that the probability that the main subject is located in the approximate 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 driving circuit 14 via the D / A converter 15 and also D / A 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 changed according to the photographing mode and the photographing situation. Further, the control signal is also supplied to the CCD drive circuit 12 to control the photographing mode, photographing. Depending on the situation, the storage time (electronic shutter) of the image sensor, the read timing, the reset timing, etc. are controlled.

These various controls are performed by 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, gain control, drive control of the image sensor (for example, electronic shutter by storage time control), etc. based on the shooting mode shooting situation and iris drive state as described above. 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, so the iris drive circuit 14 is controlled to drive the iris motor 13 in the direction of narrowing the iris 2 and the amount of incident light. To reduce the output level of the integrator 10.

On the contrary, when the integral 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 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 outputs it. 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 greatly differ 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 amount of image pickup light 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 H for NTSC
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 which receives 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.

The system control circuit 25 is
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 If it is slower than the control value specified in the LUT 19, the D _t is changed to a value larger than the current value in order to increase the shutter speed. (3) Gain (Parameter P3) The D / A converter 21 outputs a gain setting signal that determines the amplification factor of the video signal, and supplies it to the AGC circuit 5.

The AGC gain is set by the AGCC amplifier to C.
The output signal of the DS4 is provided so that the camera signal processing circuit 6 of the next stage performs appropriate signal processing,
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 gain of the AGC is increased to increase the amplification factor, noise in 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. Conversely, if the current AGC gain is smaller than the control value defined by the LUT 25 corresponding to the integrated value from the A / D converter 25, the gain setting is updated to increase the AGC gain.

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 the shooting mode. The exposure control used will be described. First, the setting of the photometric 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 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 image pickup 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 assigned and the photometric area is set so that the weighting is increased.

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 regions (in the figure, for convenience of explanation, Each area is numbered 1 to 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 / 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 by 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 processed by giving a weighting coefficient preset according to the photographing mode. Note that these processes can be performed by time division processing corresponding to 24 divisions.

FIGS. 5 and 6 show examples of image pickup screens on which the weighting coefficient processing has been performed.

FIG. 5 shows the above-described "center-weighted photometry" realized by the 24-division AE system according to 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, so that 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 weighting can be reflected in these controls.

FIG. 6 shows an example of a photometric area suitable for "landscape photography" and the like. In general, 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 even if it is slightly cloudy compared to the ground part. 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.

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 coefficients 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 process with emphasis on the lower portion of the screen corresponding to the ground.

In addition to the two examples described above, various AE characteristics can be set by setting a shooting mode according to the shooting situation so that a photometric area setting and a shooting program according to the shooting situation described later can be appropriately selected. 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 several typical shooting situations are assumed and shooting is possible while automatically adjusting each under the optimum 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 19a, LUTs 19b, LUTs 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 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 changing 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 referred to as an "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 clear from the figure, the setting range of each parameter depends 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. By controlling the iris (P1) 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, and the iris is constant at the open value as shown in the figure. Therefore, the exposure control is performed by changing the shutter speed to 1/60 seconds. 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
Exposure control is performed by 1) and the gain (P3), and the operation is performed so that the shutter speed is gradually changed to 1/60 second 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 the order of operating range from the top.

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, and S
Is the constant shutter speed control parameter (P2), G
Means that the gain control parameter (P3) changes from an amplification factor of 1 of ± 0 dB (THROUGH because the input signal is output as it is) 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 described above.

In the landscape photography mode, there are often no flickers, fast-moving subjects, etc., 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 brightness 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 shooting conditions, and these are appropriately selected by operating the keys of the operation unit 20, so that optimum exposure can be achieved for all shooting conditions. Control can be performed.

When the photographing program mode is switched by the operation unit 20, the setting of the photometric area on the image pickup screen is 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 taken, the “center portion weighted metering” screen as shown in FIG. 5 is displayed.

Also in the landscape photography mode of FIG. 9, the photometry area on the image pickup screen is switched to the photometry area for "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 fixed parameter calculation processing. 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 which naturally occurs due to the increase of the control parameters in order to cope with all photographing 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 above-mentioned control parameter switching operation.

That is, although the present invention reduces the calculation processing by always setting one variable parameter and fixing the other, the characteristic peculiar to a video camera is as follows.
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.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 region 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 way, 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 unnatural.

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 in accordance with 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 shown in FIG. 6. Control of the image signal processing circuit 7 is also effective.

Therefore, the image pickup screen corresponding to the set typical scene is taken into consideration, and according to the set photographing mode, as shown in FIG.
In the camera signal processing circuit 6 of FIG. 11, the nonlinear conversion characteristics (knee characteristics and γ characteristics) of the video signal level are shown in FIG.
It is not possible to control the characteristics of the aperture correction circuit that changes the sharpness of the image, such as b and c, and the image signal processing circuit 7 in FIG. As the processing, for example, it is conceivable to give a "fade effect" or "afterimage effect" to the imaged video 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 image output. The field memory circuit 32 delays the signal by 1 screen, and
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 indicates a through.

Next, when the output of the color signal generator 30 is selected by the selection switch 31, the multiplication coefficient generator 34 operates according to an instruction from the system control circuit 25 (start / end timing or direct coefficient setting). The output is calculated, and one side appears as 0 → 1 and the other side disappears as 1 → 0 due to the inverse operation (1's complement relationship by 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 is tailed in the time axis direction.

By operating such signal processing in a portrait photographing mode, which will be described later, such as photographing a person in a focused manner, the aperture characteristic or the like is changed in the above-mentioned camera signal processing circuit. The image quality can be adjusted, for example, by giving a soft feeling to an image by lowering the frequency response in the vicinity of 2 to 3 MHz in a television signal, which frequency is involved in the sharpness of human visual characteristics. ..

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.

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 of the setting operation of each control parameter 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-described 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, data regarding weighting for each of the 24 divisions set on the image pickup screen is read from the designated LUT, weighting is performed according to the photographing mode 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 from the LUT, and in the above example, the image quality adjustment by the aperture control and the image processing by the color fade or the like, which are adapted to the shooting mode, are set.

In 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.

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

When the area A is determined, the process proceeds to S8, the iris control parameter P1 is calculated, and then S
At 9, the inside / outside of the boundary area B1 of the area is determined, and the boundary B
If it is out of 1, proceed to S10 to hold the shutter speed control parameter P2 in advance and fix it, and if it is in 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, and if it is within B1, S14.
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 procedure proceeds to S20, in which the shutter speed control parameter P2 is held in advance and fixed, and then within B2. 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 front 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 their program modes, and the next processing time unit comes at S25. Waiting (until one frame is a basic unit in this embodiment), the power-off is confirmed in S26, and if the power-on is continued, 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 each 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 photographing according to the photographing situation of.

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 setting and control of the portrait photographing mode will be described in detail.

The portrait photography mode is set by the operation of the operation unit 20, and is basically a photography mode by center-weighted photometry in which the photometry area as shown in FIG. 5 is weighted as shown in FIG. , References when this mode is selected, definition of various control parameters necessary for its control,
Figure 1 shows the internal structure of the data table LUT that stores the characteristics.
3 shows.

The program diagram showing the operation of various control parameters defined and set by this LUT is shown in FIG.
It looks like 4. The figure shows the transition of the control parameter corresponding to the program diagram with respect to the brightness level of the input parameter. Actual program diagrams are drawn as shown in FIGS. 7 and 8, but for simplicity, FIG.
Similarly, the iris, shutter speed, and gain are shown in this order from the top in order of operating range.

That is, in FIG. 14, two threshold values y1 and y2 are provided for the subject illuminance on the horizontal axis which is an input parameter, and the entire area is divided into three areas, and I is an iris control parameter ( P1) and S are shutter speed control parameters (P2) and G is a gain control parameter (P3). As shown on the right side of the figure, the iris control parameter (P1) is CLOSE and O.
Operating between PEN, the shutter speed control parameter (P2) is High speed (T1) and 1/60 of standard
The gain control parameter (P3) changes within ±
Amplification factor 1 of 0 dB (Because the input signal is output as it is
It is meant to change from a value of HROUGH) to a predetermined value G1.

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

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.

The individual parameters in each drawing will be described below in order. (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 clear from the data column on the right side of FIG. 13, the calculation is performed by the display of “→ CAL” (calcul).
ation) 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 so as to be fully opened up to the open value in consideration of the small aperture measure against the reduction of resolution due to the diffraction phenomenon of light by the small aperture of the iris.

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

By controlling in this manner, the depth of field is set to be the shallowest, and a subject such as a person being photographed can be made to stand out against the background. This state is the basic state of control characteristics in portrait photography mode.

In this way, the control characteristic of the iris is defined by dividing the entire region from high luminance to low luminance with one threshold value y1. (P2: Shutter Control Parameter) As the shutter control parameter, a function f (Y) of the brightness 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 high speed T1.
It is set to be fixed to. In this case, no calculation is necessary.

As described above, T1 is set to a somewhat high shutter speed in order to set the depth of field to be shallow in addition to the measures against the small aperture as described above.

Actually, it is selected within the range of about 1/250 to 1/4000 seconds.

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

When the input brightness level is between y1 and y2,
“→ CAL” is set, which indicates that the optimum shutter speed according to the input luminance level is calculated and the control parameter value is set.

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, the gain is controlled within the range allowable in terms of S / N deterioration, and exposure control is performed. (P3: AGC gain) Even when the AGC gain is used as the parameter to be processed, the function f (Y) of the input luminance is defined by a plurality of threshold values, and if the input luminance level is higher than y2, " → ± 0 dB ”is specified and A
The gain is fixed so that the GC gain is fixed at ± 0 dB and no amplification effect is provided. That is, when the exposure control is possible by the iris and the shutter, the AGC gain is fixed to prevent the S / N from deteriorating, and in this case also, the calculation is unnecessary.

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

Since the other parameters have already been set to the maximum for the low illuminance measure, the only controllable parameter left in this state is the AGC gain, and the balance with the S / N deterioration is taken into consideration. However, the exposure is controlled by adjusting the gain up within an allowable range.

The relationship between the area divided into three by these threshold values y1 and y2 and the three control parameters is as follows:
As is clear from FIG. 14, the parameters to be calculated here are also arranged so as to be always one in each of the three areas, and the calculation is simplified.
The arrangement is I, S, G from the area on the high brightness side. (P4: AE weighting parameter = photometric region weighting setting) As shown in FIGS. 5 and 6, this is a parameter for setting the photometric region distribution in the imaging screen and their weighting. As is clear from FIG. It is stored in the MAP format and the attribute is fixed. That is, although the set value differs for each LUT depending on the shooting mode, it is fixed within one shooting mode and does not change depending on the luminance signal level.

In the present embodiment, the areas of 24 divisions are directly allocated like a map. In this portrait photography mode, 1.0 is assigned to the central 2 × 4 8 region and 0.5 to the peripheral 16 regions, which are lighter than the central portion. It is designated as the metering area of "partial weighted metering". (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 is set to 50 IRE in this embodiment. 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 the case of "NORMAL", the basic image quality is set to the standard value, no special image processing is performed, and in the case of "SOFT", the frequency characteristic is changed with respect to the standard value of the basic image quality.

The setting in the portrait photographing mode is "SOFT". Specifically, as described above, specifically, the frequency related to the sharpness of human visual characteristics, that is, in the vicinity of 2M to 3MHz in the television signal. By setting the frequency characteristics with reduced response, it is set to obtain a soft image quality. (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.

When "NORMAL" is designated, it means that the basic image quality is set to the standard value and no special processing is performed.

In this portrait shooting mode, “WHI
TE-FADE ”, which has the effect of gradually turning the entire screen white by operating the white fade circuit used during normal scene changes. Specifically, in the circuit shown in FIG. 12, the system control circuit 25 instructs the color signal generator 30 to generate white (* 1), switches the switch to the 30 side (* 2), and mixes white. It can be operated by setting the multiplication coefficient to about 0.1 to 0.5 (* 3) so that the ratio is around 30%, for example.

This parameter also has a fixed attribute and is set according to the photographing mode, and does not change depending on the input brightness level.

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 it according to the mode,
Optimal control can always be performed.

As described above, in the portrait mode, the image is taken with center-weighted photometry, but since it is premised that the image is based on a person, it is extremely effective to use the image quality adjustment and the image processing described above together.

Taking the portrait photography mode as an example,
A data table LUT defining the control parameters,
And the operating characteristics of the control parameters set accordingly.

Here, the operation of reading data from the LUT shown in FIG. 13 to the system control circuit to calculate each control parameter and setting each control parameter as shown in FIG. 14 will be described in detail with reference to the flowchart of FIG. Explained.

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. 15 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, a parameter counter n for designating 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. 15, when n = 01, data relating to iris, when n = 02, data relating to shutter speed, when n = 03, data relating to AGC gain, n
= 04, data relating to AE weighting (weighting coefficient of photometric area), n = 05, data relating to evaluation reference value of AE, that is, a level used as a reference for adjusting the brightness level to a constant level, and image quality when n = 06 Data relating to adjustment and data relating to specially effective image processing at n = 07 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 with respect to the input parameter, that is, the object illuminance in this embodiment, according to a predetermined function f (Y) 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 field discriminating 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 an output calculation of control data based on the parameter read from T. In S109, the parameter counter is reset to n = 01.

In S110, the attribute of the parameter is confirmed, and it is determined whether the 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.

In accordance with the value of this input signal, the data definition of the LUT is referred to, and the necessity / unnecessity of the data operation 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. To do.

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, and 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 indicates the shooting condition. Optimal shooting can be performed by reading out suitable control data and performing control.

[0162]

As described above, according to the image pickup apparatus of the present invention, the photographing state is controlled by 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 out and controlled, for example, when performing portrait photography, even if the photography environment changes, the depth of field peculiar to the photography mode is made shallow to bring out the subject. Can keep the effect, etc.
More precise control is possible compared to conventional devices,
Even under various shooting conditions, there is an effect that optimum shooting can be performed only by selecting a shooting mode.

[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 part 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.

10 is a flow chart for explaining a process for explaining parameter setting in FIGS. 7 and 8. FIG.

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

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

FIG. 13 is a diagram for explaining the structure of a data table according to the “portrait shooting mode” of the present invention.

FIG. 14 is a parameter transition diagram for explaining parameter processing according to the “portrait photographing mode” of the present invention.

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

FIG. 16 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. 17 is a diagram for explaining a shutter priority mode.

Front page continuation (72) Inventor Yuji Tsuda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (1)

[Claims] 1. A light quantity adjusting means for controlling a transmitted light quantity of an image pickup optical system, an image pickup element for photoelectrically converting the transmitted light by accumulating the transmitted light, a storage time control means for controlling a light storage time of the image pickup element, Gain control means for controlling the gain of the output signal of the image sensor, storage means for storing a plurality of control characteristics selected according to the shooting mode, and the light amount based on the data read from the storage means corresponding to the shooting mode. A control means for calculating control data of the adjusting means, the storage time control means, and the gain control means, wherein the control means has a short optical storage with respect to a screen cycle of a standard television signal in a high brightness region in a predetermined photographing mode. By setting the time, the amount of transmitted light of the light amount adjusting means is increased and the gain is kept constant, and the storage time control means is controlled by controlling the storage time as the brightness decreases. An image pickup device configured to control the gain control means to increase the gain after performing an operation of increasing the product time.