JP2000004394A - Digital still video camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable proper exposure control even in the case of both rear light and excessive front light by dividing an image-pickup picture plane into blocks, finding the representative luminance with respect to an arbitrary area as a set of specific blocks determined according to the distance to a subject, and finding an exposure controlled variable according to the rate of blocks meeting specific threshold conditions for the arbitrary area. SOLUTION: An image-pickup image plane 122 is divided into 8×6 blocks to make 1st to 6th areas. The size of the arbitrary area as the set of the specified blocks determined according to the distance from the subject to a CCD image-pickup element is set large to all the blocks in the 5th and 6th areas, when the distance is short and small to all the blocks in the 6th area, when it is long. Then the rate of the blocks meeting the specified threshold conditions for the arbitrary area is found. Consequently, the size of the subject can be reflected, and the precision of rear light and excessive front light can be viewed accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video camera, and more particularly, to a digital still video camera using a CCD image pickup device, in which the ratio of the ratio of luminance to the screen and the change thereof are based on backlight and over-direct light. The present invention relates to a digital still video camera using an exposure control method for determining a correction amount of a video.

[0002]

2. Description of the Related Art Conventionally, in a video camera or a silver halide camera, as a method of judging the state of back light or over-direct light and controlling the exposure, attention is paid to the center of the screen, and the brightness of the center area and the center are determined. By comparing the luminance of the peripheral area excluding the part, the state of backlight, over-direct light is determined, and according to the result,
There is a type in which correction is performed separately for backlight and over-directed light to control exposure.

A conventional video camera using this type of exposure control is, for example, one disclosed in Japanese Patent Application Laid-Open No. 6-225205. This method divides a two-dimensional image into blocks, accumulates luminance data for each block, obtains accumulated data, determines whether the central portion of the screen is in a backlight state or an over-ordered light state from the block data, and performs photometry. The iris is controlled to an appropriate state by changing the reference value.

That is, a conventional video camera converts an image signal obtained by an image sensor into a digital signal.
By dividing image data for one screen consisting of digital signals obtained by the / D conversion means and the A / D conversion means into a plurality of blocks, and accumulating the image data of each block, the accumulated data for each block is obtained. Accumulating means for forming
Detecting means for detecting the maximum value in one screen; multiplying the accumulated data and the maximum value for each block by a desired coefficient;
Calculating means for forming the added photometric value data; reference brightness setting means for judging whether the central portion of the screen is in a backlight state or an over-directed light state from the data of the block and changing a photometric reference value; Control means for controlling the iris and the automatic gain control circuit based on the data and the reference luminance.

In such a video camera, a video signal obtained by an image pickup device is converted into a digital signal by an A / D converter, and the digital signal obtained from the obtained digital signal is converted into a digital signal.
The image data for the screen is divided into a plurality of blocks, and the accumulation means accumulates the image data for each block to form accumulated data. The accumulated data and the maximum value in one screen are each multiplied by a predetermined coefficient and added to form photometric data. It is determined from the data of the block whether the central part of the screen is in a backlight state or an over-light state, and the photometric reference value is changed. Iris and AGC based on photometric data and reference brightness
It is disclosed that an appropriate iris operation can be realized by controlling an (Automatic Gain Control) circuit.

More specifically, the conventional video camera shown in FIG. 10 includes a charge coupled device (CCD) 1A, an iris 2A, and an automatic gain control (AGC).
trol: automatic gain control) circuit 3A, A / D conversion circuit 4A,
A timing generation circuit 5A, a block-by-block accumulation circuit 6A, a maximum value detection circuit 7A, a photometric value calculation circuit 8A, a D / A conversion circuit 9A, an OP amplifier 10A, an iris drive circuit 11A,
Backlight / excessive light detection circuit 12A, block data averaging circuits 13A and 14A, comparator 15A, reference value generation circuit 16A
Was composed of

In a video camera having such a functional configuration,
As shown in FIG. 12, a captured two-dimensional image is divided into 16 blocks, luminance data included in each of the blocks is added, and a maximum value is calculated as photometric data. The signal is converted into a digital signal by the A / D conversion circuit 4A, and is stored in the block-by-block accumulation circuit 6A and the maximum value detection circuit 7A.
Outputs the accumulated data for each block and the maximum value of the entire screen.

The timing generation circuit 5A is a circuit for generating a timing control signal for a block. In the photometric value calculation circuit 8A, a weighted photometric value is obtained by multiplying 16 block accumulated data by a coefficient and adding them together.

For example, by increasing the coefficient of the lower part, lower-priority photometry is performed. The value output from the maximum value detection circuit 7A is multiplied by a coefficient and added to the photometric value to obtain a total photometric value. In a conventional video camera, a block-by-block accumulation circuit 6A and a maximum value detection circuit 7
A also outputs data to the backlight / excessive light detection circuit 12A.

[0010] At this time, a typical example of the backlight state is a state in which the person in the center sinks dark as shown in FIG. The over-directed light state is the reverse of this, in which the surroundings are completely dark and the person is floating white.

The back light / over-order light detection circuit 12A compares the state of the blocks f, g, j, k, n, and o with the other blocks according to the data of each block and the location of the maximum value. If it is determined, the reference value generation circuit 16A changes the data as shown in FIG. 13 so that the backlight is corrected by the comparison value, and in the case of over-direct light, the reverse operation is performed.

The photometric value output from the photometric value calculation circuit 8A is converted by a D / A conversion circuit 9A.
By comparing the reference voltage output from 6A with the OP amplifier 10A, an appropriate iris and AGC control output can be obtained. That is, the two-dimensional image is divided into blocks, luminance data is accumulated for each block, the accumulated data is obtained, and it is determined from the data of the block whether the central part of the screen is in a backlight state or an over-sequential light state. In order to control the iris to an appropriate state by changing the value, for example, FIG.
In a typical backlight state shown in FIG. 12, when divided into 4 × 4 blocks as shown in FIG. 12, blocks f, g, j, k, n, o
And the other blocks are compared, and corrected to the reference at the time of backlight.

[0013]

However, in the exposure control performed by such a conventional digital still video camera, a correction reference value is changed when backlighting or over-directing light is performed. Depending on the position and size of the object, the difference in luminance between the subject in the backlight state as shown in FIG. 11 and the other parts is not accurately reflected, and an appropriate correction value cannot be obtained, so that the accuracy is high. There was a problem that exposure could not be controlled.

An object of the present invention is to solve such a conventional problem. In particular, even in the case of backlight or over-directed light, an optimum correction value is obtained, and the exposure is controlled in accordance with the optimum correction value. It is an object of the present invention to provide a digital still video camera that performs exposure control capable of performing various exposure controls.

[0015]

According to the first aspect of the present invention, there is provided an image processing apparatus, comprising: Exposure control is performed using an exposure control method that determines the amount of correction, the brightness of the imaging screen of the subject is converted into an electric signal using a solid-state imaging device, and image information is generated. In a digital still video camera that records in a form and reproduces image information from a recorded electric signal, a block generation unit that divides a part or the whole of an imaging screen into a plurality of blocks, and a luminance level obtained from a predetermined block. Is a set of predetermined blocks determined according to the distance to the subject, and state detection means for determining whether or not is included in a predetermined luminance range centered on a predetermined reference luminance level. A representative luminance calculating means for calculating a representative luminance of the area for an arbitrary area, and a ratio calculating means for calculating a ratio of blocks satisfying a predetermined threshold condition to the arbitrary area, which is a set of the predetermined blocks, A correction amount calculating unit that generates a correction amount based on the obtained ratio; and an exposure control unit that calculates an exposure control amount based on the obtained correction amount and performs exposure control according to the exposure control amount. Digital still video camera.

According to the first aspect of the present invention, the correction amount is determined based on the ratio of blocks satisfying a predetermined threshold condition in an arbitrary area which is a group of predetermined blocks and a change thereof, so that backlighting and over-ordering are performed. Exposure control more appropriate for light and their degree can be performed.

According to a second aspect of the present invention, in the digital still video camera according to the first aspect, the representative brightness calculating means is a set of predetermined blocks determined according to a distance from the subject. The high luminance and low luminance blocks that satisfy the predetermined threshold condition for the arbitrary area are excluded, and the representative luminance is obtained by averaging the luminance of each block. It is a digital still video camera.

According to the invention of claim 2, according to claim 1,
In addition to the effects described in the above, in an arbitrary area that is a set of predetermined blocks determined according to the distance to the subject,
The representative luminance calculating means for calculating the luminance representative of the area is a high luminance block which satisfies a predetermined threshold condition and a low luminance which satisfies a predetermined threshold condition in an arbitrary area which is a set of predetermined blocks determined according to a distance from a subject. By excluding and averaging the blocks, luminance information excluding peculiar information can be obtained, so that an appropriate luminance ratio can be obtained.

According to a third aspect of the present invention, in the digital still video camera according to the first aspect, the ratio calculating means collects the predetermined blocks in accordance with a distance from the subject from which the representative luminance is obtained. And determining the area to be excluded from the arbitrary area, and comparing the ratio between the luminance of each block and the representative luminance in a set of predetermined blocks in the arbitrary area excluding the excluded area, A digital still video camera configured to calculate a ratio of a block satisfying a predetermined threshold condition to the arbitrary area which is a group of blocks.

According to the invention of claim 3, according to claim 1,
In addition to the effects described in the above, the ratio calculating means for calculating the ratio of blocks satisfying a predetermined threshold condition in an arbitrary area which is a group of predetermined blocks, the distance between the representative luminance and the subject for which the representative luminance is calculated And comparing the ratio of the luminance with the blocks in an arbitrary area which is a set of predetermined blocks excluding an area determined according to the ratio of blocks satisfying a predetermined threshold condition in an arbitrary area which is a set of predetermined blocks. Since the calculation is performed, it is possible to accurately check the accuracy of the backlight and the over-directed light.

According to a fourth aspect of the present invention, in the digital still video camera according to the first aspect, the correction amount calculating means is a group of predetermined blocks obtained by the ratio calculating means. Is a digital still video camera configured to determine a correction amount according to each of the above ratios.

According to the invention described in claim 4, according to claim 1,
In addition to the effects described in the above, the correction amount calculating means calculates the ratio of blocks satisfying a predetermined threshold condition in an arbitrary area which is a predetermined group of blocks, Since the correction amount is determined according to the respective ratios in the arbitrary area, it is possible to cope with various degrees of backlight and over-direct light.

According to a fifth aspect of the present invention, in the digital still video camera according to the fourth aspect, the correction amount calculating means is configured to determine that the predetermined threshold condition occupying the arbitrary area, which is a group of the predetermined blocks. The digital still video camera is configured to increase the correction amount when the ratio of blocks that satisfy the condition is large.

According to the invention set forth in claim 5, according to claim 4,
In addition to the effects described in the above, when the ratio of blocks satisfying a predetermined threshold condition in an arbitrary area that is a group of predetermined blocks is large, the correction amount calculation unit increases the correction amount compared with the case of direct light. Therefore, it is possible to cope with the degree of the backlight and the over-order light.

According to a sixth aspect of the present invention, in the digital still video camera according to the fourth aspect, the ratio calculating means uses a plurality of types of the predetermined threshold conditions to calculate the ratio of the block satisfying each of the threshold conditions. The digital still video camera is configured to determine a change in a ratio in an arbitrary area and to calculate the correction amount based on the change in the ratio.

According to the invention of claim 6, according to claim 4,
In addition to the effects described in the above, the correction amount calculating means uses several types of predetermined threshold conditions in the means for calculating the proportion of blocks satisfying the predetermined threshold condition in an arbitrary area which is a group of the predetermined blocks. Therefore, since the correction amount is determined based on the change in the ratio of blocks that satisfy the threshold condition,
It is possible to cope with the degree of backlight or over-directed light, and appropriate exposure control can be performed.

According to a seventh aspect of the present invention, in the digital still video camera according to the first aspect, the arbitrary area, which is a set of predetermined blocks determined according to the distance to the subject, is a distance from the subject. When the distance is far, the size of the area is set smaller than a predetermined value by a predetermined amount, and when the distance to the subject is closer, the size of the area is set larger by a predetermined amount than the predetermined value. Is a digital still video camera.

According to the invention of claim 7, according to claim 1,
In addition to the effects described in the above, when an arbitrary area, which is a set of predetermined blocks determined according to the distance to the subject, is set to be smaller than a predetermined area when the distance to the subject is far, Since the area is set to be larger than a predetermined distance when the distance from the object is on the near side, the size of the subject can be reflected more, and the accuracy of backlight and over-direct light can be accurately observed. .

[0029]

FIG. 1 is a functional block diagram for explaining an embodiment of a digital still video camera A of the present invention.

FIG. 1 shows the basic configuration of the digital still video camera A. In FIG. 1, reference numeral 11 denotes a lens, 12 denotes an aperture, 13 denotes a CCD image pickup device (solid-state image pickup device), 1
Reference numeral 4 denotes a double correlation sampling circuit CDS for reducing noise of accumulated charges in the image sensor, 15 an AGC circuit for automatically adjusting the gain of the image signal, 16 an A / D conversion circuit, and 17 an A
An image signal processing circuit that mixes the / D-converted imaging signal into a luminance signal and a color difference signal conforming to the NTSC system and changes into a divided video signal. Reference numeral 18 denotes a luminance signal output from the image signal processing circuit 17 in each block. A block generation circuit (block generation means) 19 for accumulating the data in the block and generating a block includes a state detection circuit (state detection means) for determining whether or not the luminance level is within a reference luminance level range from the block generation circuit 18. ), 20 is a representative luminance calculating circuit (representative luminance calculating means) for obtaining a luminance signal representative of the area in an arbitrary area, and 21 is a percentage of an arbitrary area satisfying a threshold condition and a ratio of obtaining a change thereof. A detection circuit (ratio calculation means) 22 is a ratio detection circuit 21
A correction amount calculation circuit (correction amount calculation means) for generating a correction amount mEV from the correction amount mEV in the correction amount calculation circuit 22
Control amount based on the aperture, shutter speed, AG
An exposure control circuit (exposure control means) for controlling C; a focus control circuit for generating focus information and calculating a distance between the subject 121 and the CCD image sensor 13;
Is a focus drive circuit for driving a lens.

The digital still video camera A shown in FIG. 1 employs an exposure control method that determines a correction amount mEV in backlight or over-direct light based on the ratio of the luminance ratio occupying the imaging screen 122 and its change. Exposure control is performed, the brightness of the imaging screen 122 of the subject 121 is converted into an electric signal using the CCD imaging device 13 to generate image information, and the generated image information is recorded in the form of an electric signal. A block generating circuit 18, a state detecting circuit 19, and a representative luminance calculating circuit 2.
0, a ratio detection circuit 21, a correction amount calculation circuit 22, and an exposure control circuit 23.

The block generation circuit 18 includes an imaging screen 122
Is a circuit having a function of dividing a part of the image into a plurality of blocks, or a function of dividing the entire imaging screen 122 (the entire imaging screen 122) into a plurality of blocks.

The state detecting circuit 19 is a circuit having a function of determining whether or not a luminance level obtained from a predetermined block falls within a predetermined luminance range centered on a predetermined reference luminance level.

The representative luminance calculating circuit 20 has a function of obtaining a representative luminance for an arbitrary area which is a set of predetermined blocks determined according to the distance between the subject 121 and the CCD image pickup device 13. It is a circuit having.

In the present embodiment, an arbitrary area, which is a set of predetermined blocks determined according to the distance between the subject 121 and the CCD image pickup device 13, is determined when the distance between the subject 121 and the CCD image pickup device 13 is far. The size of the area is set smaller than a predetermined value by a predetermined amount, and
When the distance from the CD imaging device 13 is on the near side, the size of the area is set to be larger by a predetermined amount than a predetermined value.

Accordingly, an arbitrary area which is a set of predetermined blocks determined according to the distance between the subject 121 and the CCD image pickup device 13 is determined when the distance between the subject 121 and the CCD image pickup device 13 is far. Is set to be smaller than a predetermined value, and when the distance between the subject 121 and the CCD image pickup device 13 is on the near side, the area is set to be larger than the predetermined value, so that the size of the subject 121 can be more reflected, Thus, the accuracy of over-ordered light can be accurately observed.

The representative luminance calculating circuit 20 calculates the subject 12
For an arbitrary area, which is a set of predetermined blocks determined according to the distance between the block 1 and the CCD imaging device 13, blocks with high luminance that satisfy predetermined threshold conditions are excluded, and blocks with low luminance are satisfied. This is a circuit having a function of executing the elimination of, and averaging the luminance of each block to obtain a representative luminance.

By providing such a function, in an arbitrary area which is a group of predetermined blocks determined according to the distance between the subject 121 and the CCD image pickup device 13,
The representative luminance calculation circuit 20 for calculating the luminance representative of the area has a high luminance satisfying a predetermined threshold condition in an arbitrary area which is a set of predetermined blocks determined according to the distance between the subject 121 and the CCD image sensor 13. By averaging and excluding certain blocks or blocks having low luminance, luminance information excluding specific information can be obtained, so that an appropriate luminance ratio can be obtained.

The ratio detection circuit 21 is a circuit having a function of calculating the ratio of blocks satisfying a predetermined threshold condition to an arbitrary area which is a group of predetermined blocks.

The ratio detecting circuit 21 calculates an area to be excluded from an arbitrary area, which is a set of predetermined blocks, in accordance with the distance between the subject 121 for which the representative luminance has been obtained and the CCD image pickup device 13. A function of comparing the ratio between the luminance of each block and the representative luminance in a group of predetermined blocks in an arbitrary area excluding, and calculating a ratio of blocks satisfying a predetermined threshold condition to an arbitrary area which is a group of predetermined blocks Is a circuit having

By providing such a function, the ratio detecting circuit 21 for calculating the ratio of blocks satisfying a predetermined threshold condition in an arbitrary area, which is a group of predetermined blocks, calculates the representative luminance and the representative luminance. Subject 12
1 and the CCD image sensor 13, except for an area determined according to the distance, and compares the ratio of luminance with blocks in an arbitrary area which is a set of predetermined blocks, and determines a predetermined ratio in an arbitrary area which is a set of predetermined blocks. Since the ratio of blocks satisfying the threshold condition is calculated, it is possible to accurately check the accuracy of backlight and over-direct light.

The ratio detecting circuit 21 calculates the change in the ratio of blocks satisfying each threshold condition in an arbitrary area using several types of predetermined threshold conditions, and calculates a correction amount calculating circuit 22.
Is a circuit configured to obtain the correction amount mEV based on the change in the ratio.

By providing such a function, the correction amount calculating circuit 22 uses several kinds of predetermined types of means in the means for calculating the proportion of blocks satisfying a predetermined threshold condition in an arbitrary area which is a group of the predetermined blocks. Since the correction amount mEV is determined based on the change in the ratio of the blocks satisfying the threshold condition using the threshold condition described above, it is possible to cope with the degree of backlight or over-direct light and to perform appropriate exposure control.

The correction amount calculating circuit 22 is a circuit having a function of generating a correction amount mEV based on the obtained ratio.

The correction amount calculating circuit 22 is a circuit configured to determine the correction amount mEV according to each ratio in an arbitrary area which is a group of predetermined blocks, obtained by the ratio detecting circuit 21. .

By providing such a function, the correction amount calculating circuit 22 determines a ratio of blocks satisfying a predetermined threshold condition in an arbitrary area which is a group of predetermined blocks, based on a result of a means for obtaining a predetermined ratio. Since the correction amount mEV is determined according to each ratio in an arbitrary area which is a group of blocks, it is possible to cope with various degrees of back light and excessive forward light.

The correction amount calculating circuit 22 is configured to increase the correction amount mEV when the ratio of blocks satisfying a predetermined threshold condition in an arbitrary area which is a group of predetermined blocks is large. .

By providing such a function, when the proportion of blocks satisfying a predetermined threshold condition in an arbitrary area, which is a group of predetermined blocks, is large, the correction amount calculation circuit 22 can perform an Since the correction amount mEV is increased, it is possible to cope with the degree of backlight or over-directed light.

The exposure control circuit 23 includes a correction amount calculation circuit 22
Is a circuit having a function of obtaining an exposure control amount based on the obtained correction amount mEV and, at the same time, executing exposure control according to the exposure control amount.

Hereinafter, the digital still video camera A will be described in detail.

In the following description, the entire imaging screen 122 (the entire imaging screen 122) is divided into eight horizontal blocks and six vertical blocks by the block generation circuit 18 (hereinafter, this divided imaging screen 122 is divided by 8 × 6 blocks),
An example in which the accumulated luminance of 8 × 6 blocks is generated will be described.

The block generation circuit 18 is a circuit having a function of dividing a part of the imaging screen into a plurality of blocks or a function of dividing the entire imaging screen (the entire imaging screen) into a plurality of blocks.

The cumulative luminance of the 8 × 6 block is calculated by the block Y
The case where (i, j) (i = 1 to 8, j = 1 to 6) is taken as an example. FIG. 2 shows an imaging screen divided into a first area to a sixth area. However, as shown in FIG. 2, the fifth area does not include the sixth area.

FIG. 3 is a flowchart for explaining an embodiment of the state detection processing flow executed by the state detection circuit 19. However, in the initial state, it is assumed that the luminance is not within the range of the reference luminance level.

The state detection circuit 19 is a circuit having a function of determining whether or not a luminance level obtained from a predetermined block falls within a predetermined luminance range centered on a predetermined reference luminance level.

When it is determined whether or not the luminance level obtained from the predetermined block falls within a predetermined luminance range centered on a predetermined reference luminance level (step S51).
The determination as to whether or not the luminance is within the range of the reference luminance level is made by Y
1_thrd <Yc <Yu_thrd (step S5
2).

As Yc, for example, an average value of all blocks in the fifth area and the sixth area shown in FIG. 2 is used. That is, Yc = Σblock Y (i, j) / 16 (i = 3 to 6, j
= 2-5) Here, Y1_thrd and Yu_thrd are lower and upper thresholds that determine the range of the reference luminance level.

CV is a reference value T which is a reference luminance level.
The correction amount mEV up to, for example, is obtained as follows (step S53).

CV = -log ₂ (T / Yc) In implementation, CV may be obtained by executing linear interpolation or the like.

As the pEV (step S51) and qEV (step S56), at the time of photometry, an arbitrary EV that can cover the entire photometry range may be specified. In a general scene, the subject 121 of each luminance included in the screen
Is in the range of about 5 EV.

Therefore, for example, the range where photometry can be performed is 9-1.
In the case of 7 EV, if p = 13 and q = 16, the entire area can be covered.

When the brightness is within the range of the reference luminance level, the focus control circuit 24 and the focus drive circuit 2
From 5, the distance between the subject 121 and the CCD 13 is determined.

In the focus control circuit 24, the focus information is obtained by extracting the high frequency component of the luminance signal by a band-pass filter or the like while driving the lens by the distance measuring sensor (not shown) or the focus drive circuit 25.

The subject 121 and the CCD image pickup device 13
When the focus information is a high-frequency component of a luminance signal, the distance to the maximum distance is determined as the focus position. That is,
The distance is obtained based on the result of the so-called hill climbing method.

Next, a representative luminance is calculated in an arbitrary area. Hereinafter, an embodiment of the processing of the representative luminance calculation circuit 20 will be described.

The representative luminance calculation circuit 20 has a function of obtaining a representative luminance for an arbitrary area which is a set of predetermined blocks determined according to the distance between the subject 121 and the CCD image pickup device 13. Have,
For an arbitrary area, which is a set of predetermined blocks determined according to the distance between the subject 121 and the CCD imaging device 13, blocks with high luminance that satisfy predetermined threshold conditions are excluded, and low luminance is set. This is a circuit having a function of executing block elimination and averaging the luminance of each block to obtain a representative luminance.

The size of an arbitrary area, which is a set of predetermined blocks determined according to the distance between the subject 121 and the CCD 13, is changed by the distance between the subject 121 and the CCD 13.

For example, the subject 121 and the CCD image sensor 1
When the distance to 3 is on the near side, the size of the area is set to be relatively large, and the size of an arbitrary area is set to all blocks in the fifth area and the sixth area in FIG.

The subject 121 and the CCD 13
When the distance to is far, the size of the area is set smaller, and the size of an arbitrary area is set as all the blocks in the sixth area in FIG.

In all these blocks, Low_thr
Those that satisfy d <block Y (i, j) <High_thrd are YM (i, j), and the number is Ym_co.

Here, Low_thrd and High_thrd are predetermined thresholds for excluding low-luminance blocks and high-luminance blocks.

When Ym_co is equal to or less than a predetermined threshold value, and
When the distance between the subject 121 and the CCD image pickup device 13 is on the near side, the representative luminance RY is represented by the following expression.
６，6, j = 2-5).

In the same manner, in the case of the far side, the representative luminance R
Y is representative luminance RY = Σblock Y (i, j) / 4 (i = 4 to
5, j = 3 to 4).

In other cases, the representative luminance RY is as follows: representative luminance RY = ΣYM (i, j) / Ym_co.

By providing such a function, in an arbitrary area which is a group of predetermined blocks determined according to the distance between the subject 121 and the CCD image pickup device 13, a representative luminance calculation for obtaining a luminance representative of the area. The circuit 20 excludes high-brightness blocks and low-brightness blocks satisfying a predetermined threshold condition in an arbitrary area that is a group of predetermined blocks determined according to the distance between the subject 121 and the CCD imaging device 13. By averaging, luminance information excluding specific information can be obtained, so that an appropriate luminance ratio can be obtained.

Next, an embodiment of the processing of the ratio detecting circuit 21 will be described. Here, the first area will be described as a representative example. The ratio detection circuit 21 has a function of calculating a ratio of blocks satisfying a predetermined threshold condition to an arbitrary area which is a group of predetermined blocks, and a distance between the subject 121 whose representative luminance is calculated and the CCD imaging device 13. An area to be excluded is obtained from an arbitrary area, which is a group of predetermined blocks, and the ratio between the luminance of each block and the representative luminance in the group of predetermined blocks in any area except the excluded area is compared. A function of calculating a ratio of blocks satisfying a predetermined threshold condition with respect to an arbitrary area which is a group of predetermined blocks, and a change of a ratio of a block satisfying each threshold condition to an arbitrary area using several types of predetermined threshold conditions. This is a circuit that has the required function.

Now, the representative luminance RY is compared with the blocks Y (i, j) in the first area, and the ratio of the blocks satisfying the following conditions to all the blocks in the first area is obtained.

The ratio (backlight ratio) satisfying the relationship of “representative luminance RY × backlight threshold BL_THRD1 <block Y (i, j)” is defined as a first area backlight ratio BL_RATE1 (%). Also, representative luminance RY> block Y (i, j) × over-order light threshold OL_T
The ratio of those satisfying HRD1 (over-direct light ratio) is defined as the first area over-direct light ratio OL_RATE1 (%), and the other ratio (direct light ratio) is defined as the first area forward-light ratio NL_RATE1 (%).

The backlight threshold BL_THRD1, the over-order light threshold OL_TH
RD1 is a predetermined threshold value for the backlight and the over-direct light in order, and is a backlight threshold BL_THRD1 ≧ 1, and an over-direct light threshold OL_THRD1 ≧ 1.

First area backlight ratio BL_RATE1, first area over-direct light ratio OL_RATE1, first area forward light ratio NL_RAT
E1 is compared, and the one with the highest ratio is defined as the ratio (representative ratio) R_RATE1 of the first area.

Similarly, the backlight threshold BL_THRD2 and the over-direct light threshold OL_THRD2, which are predetermined thresholds for backlight and over-direct light, are similarly represented by “representative luminance RY × backlight threshold BL_THRD2 <block Y”.
The ratio (backlight ratio) satisfying (i, j) is defined as the first area backlight ratio BL2_RATE1 (%), representative luminance RY> block Y (i, j) × overorder light threshold OL.
The ratio of those satisfying _THRD2 (excessive forward light ratio) is defined as the first area excess forward light ratio OL2_RATE1 (%), and the other ratio (direct light ratio)
Is the first area forward light ratio NL2_RATE1 (%). The first area backlight ratio BL2_RATE1, the first area excessive forward light ratio OL2_RATE1, and the first area forward light ratio NL2_RATE1 are compared, and the highest ratio is defined as the first area ratio (representative ratio) R2_RATE1.

The backlight threshold BL_THRD1 <backlight threshold BL_THRD2, over-direct light threshold OL_THRD1 <over-direct light threshold OL_THRD2, backlight threshold BL_THRD2 ≧ 1, over-direct light threshold OL_THRD2 ≧
1,

Next, a coefficient for a change in the ratio due to a difference in the predetermined threshold value is obtained.

When the first area coefficient C_TRNS1 is changed by a first area representative ratio R_RATE1 and a first area representative ratio R2_RATE1 when a predetermined threshold value for backlight or over-direct light is changed, the first area backlight ratio BL_RATE1, One area over-direct light ratio OL_RATE1, first area forward-light ratio NL_RATE1, first
Area backlight ratio BL2_RATE1, first area over-direct light ratio O
L2_RATE1, a coefficient based on a change in the first area forward light ratio NL2_RATE1. The threshold is changed from the backlight threshold BL_THRD1 → the backlight threshold BL_THRD2, the over-direct light threshold OL_THRD1 → the over-direct light threshold O
When changed to L_THRD2, the first area representative ratio R_RA
The change of the first area representative ratio R2_RATE1 from TE1 is the first area backlight ratio BL_RATE1 → the first area backlight ratio BL2_RA.
The coefficient at the time of TE1 is the first area coefficient c_bl1, the first area backlight ratio BL_RATE1 → the first area forward light ratio NL2_RATE1 is the first area coefficient c_bl2, the first area forward light ratio NL_RATE1 → the first area forward light The coefficient for the ratio NL2_RATE1 is the first area coefficient c_n1, and the first area
The coefficient when L_RATE1 → first area forward light ratio NL2_RATE1 is the first area coefficient c_ol2, and the first area over-forward light ratio OL_
A coefficient when RATE1 → first area over-order light ratio OL2_RATE1 is a first area coefficient c_ol1. However, here, the first area coefficient c_bl1> the first area coefficient c_bl2> the first area coefficient c_n11, the first area coefficient c_ol1> the first area coefficient c_o
l2> first area coefficient c_n1, and a coefficient corresponding to each change is selected to be a first area coefficient C_TRNS1.

That is, the change from the first area representative ratio R_RATE1 to the first area representative ratio R2_RATE1 is changed from the first area backlight ratio BL_RATE1 to the first area backlight ratio BL2_RATE1.
, The first area coefficient C_TRNS1 = the first area coefficient c_bl
Select the coefficient as in 1.

When the change from the first area representative ratio R_RATE1 to the first area representative ratio R2_RATE1 is the first area backlight ratio BL_RATE1 → the first area forward light ratio NL2_RATE1, the first area coefficient C_TRNS1 = the first area coefficient c_bl2. The selection of the coefficient is performed as follows.

When the change from the first area representative ratio R_RATE1 to the first area representative ratio R2_RATE1 is the first area forward light ratio NL_RATE1 → the first area forward light ratio NL2_RATE1, the first area coefficient C_TRNS1 = the first area coefficient Select a coefficient like c_n1.

When the change from the first area representative ratio R_RATE1 to the first area representative ratio R2_RATE1 is the first area over-direct light ratio OL_RATE1 → the first area forward light ratio NL2_RATE1, the first area coefficient C_TRNS1 = the first area Coefficient c_ol2
The selection of the coefficient is performed as follows.

Also, the change from the first area representative ratio R_RATE1 to the first area representative ratio R2_RATE1 changes from the first area over-direct light ratio OL_RATE1 to the first area over-direct light ratio OL2_RATE1.
, The first area coefficient C_TRNS1 = the first area coefficient c_ol
Make a choice like 1.

Although the first area has been described above, the same processing is performed for the second to fourth areas.

In the correction amount calculating circuit 22, the ratio detecting circuit 2
Based on the result of the calculated ratio of 1, as follows:
The correction amount mEV is determined. The correction amount mEV is: correction amount mEV = W (first area representative ratio R_RATE1) × first area coefficient C_TRNS1 × first area default correction value NL1 +
W (second area representative ratio R_RATE2) × second area coefficient C
_TRNS2 × second area default correction value NL2 + W (third area representative ratio R_RATE3) × third area coefficient C_TRNS3 × third area default correction value NL3 + W (fourth area representative ratio R_RATE)
4) × fourth area coefficient C_TRNS × fourth area default correction value N
L4,

Here, the first area default correction value NL1 to the fourth area default correction value NL4 are the default correction values of the first area to the fourth area.

W (first area representative ratio R_RATE1) to W
(4th area representative ratio R_RATE4) is from 1st area to 4th area
The weight of the area means that the weight is arbitrarily changed according to the ratio in each area.

The first area representative ratio R_RATE1 to the fourth area representative ratio R_RATE4 are representative ratios of the first area to the fourth area.

Here, W (first area representative ratio R_RATE)
1) means a weight for correcting the reference value T in the over direction when the first area representative ratio R_RATE1 is the first area backlight ratio BL_RATE1, taking the first area as an example.

The first area representative ratio R_RATE1 is the first area representative ratio R_RATE1.
In the case of the area over-order light rate OL_RATE1, W (first area representative rate R_RATE1) means a weight for performing correction in the under direction with respect to the reference value T.

The first area representative ratio R_RATE1 is the first area representative ratio R_RATE1.
In the case of the area forward light ratio NL_RATE1, W (first area representative ratio R_RATE1) is a weight for performing correction in the over or under direction with respect to the reference value T, and means a weight independent of the ratio. Regarding the second area to the fourth area, the method of determining the second area representative ratio R_RATE2 to the fourth area representative ratio R_RATE4 is the same.

FIG. 4 is a graph for explaining how to determine W (first area representative ratio R_RATE1) for the first area. The vertical axis is W (first area representative ratio R_RATE1), and the horizontal axis is the first area representative ratio R_RATE1 (%), BL, OL,
NL is a symbol indicating a backlight ratio, an over-light ratio, and a forward light ratio, respectively, and the first area representative ratio R_RATE1 is the first area representative ratio R_RATE1.
Area backlight ratio BL_RATE1, 1st area over-order light ratio OL
_RATE1, the first area forward light ratio NL_RATE1.

The first area coefficient C_TRNS1 to the fourth area coefficient C_TRNS4 are the percentage of backlight occupied by the representative percentage of the first area to the fourth area when the predetermined threshold value for backlight and excessive light is changed. It is a coefficient based on a change in the over-light ratio and the forward light ratio.

A specific image is shown in FIGS. FIGS. 5 and 6 show the backlight threshold BL_THRD1 and the over-order light threshold OL_THRD.
FIGS. 7 and 8 are imaging screens when the backlight threshold value is BL_THRD2 and the over-direct light threshold value OL_THRD2 is 1, respectively. 5 and 7
Are the same scenes with different thresholds. FIG.
The same applies to FIG.

The numbers in the figure represent the first area representative ratio R_RAT.
This is a representative ratio (%) from E1 to the fourth area representative ratio R_RATE4 and the first area representative ratio R2_RATE1 to the fourth area representative ratio R4_RATE1.

When the threshold is changed from FIG. 5 to FIG. 7,
Since the representative ratios of the first area to the fourth area hardly change and the types of the backlight ratio, the over-forward light ratio, and the forward light ratio selected by the representative ratio do not change, the weight of the representative ratio and the coefficient Area coefficient C_TRNS1 to fourth area coefficient C
_TRNS4 is increased (that is, the degree of backlight is high, so the correction is increased).

When the threshold value is changed from FIG. 6 to FIG.
Since the types of the representative ratio of the first area to the fourth area and the backlight ratio, the over-direct light ratio, and the forward light ratio selected by the representative ratio change, the weight of the representative ratio,
Coefficient first area coefficient C_TRNS1 to fourth area coefficient C_TRNS4
(I.e., the degree of backlight is smaller than in the above case, so the correction is not so great).

The exposure control circuit 23 arbitrarily determines the aperture, shutter speed, and AGC exposure control amount based on the correction amount mEV output from the correction amount calculation circuit 22 with respect to the reference value T, and controls the exposure.

FIG. 9 is a functional block diagram for explaining an embodiment of a digital still video camera realized using a digital processing circuit such as a microprocessor.

As another embodiment of the present invention, the same processing can be performed by using a digital processing circuit such as a microprocessor as shown in FIG.

The CCD camera unit 1101 includes a lens 11,
Aperture 12, CCD imaging device (solid-state imaging device) 13,
This corresponds to the double correlation sampling circuit (CDS) 14 and the AGC circuit 15. The block generation unit 1105 corresponds to the block generation circuit 18. A / D 1102 corresponds to A / D conversion circuit 16. The image signal processing unit 1103 corresponds to the image signal processing circuit 17.

The exposure correction section 1106 includes a state detection circuit (state detection means) 19, a representative luminance calculation circuit (representative luminance calculation means) 20, a ratio detection circuit (ratio calculation means) 21, and a correction amount calculation circuit (correction amount calculation means). ) 22.

The CCD camera control unit 1109 corresponds to the exposure control circuit 23 and the focus drive circuit 25. The focus control unit 10 corresponds to the focus control circuit 24.

Block generation unit 1105, exposure correction unit 11
06, each of the CCD camera control units 1109 is managed by program control using a microprocessor (CPU) 1107.

As described above, according to this embodiment, the correction amount mEV is determined based on the ratio of blocks satisfying a predetermined threshold condition in an arbitrary area, which is a group of predetermined blocks, and its change. Exposure control can be performed more appropriately for over-directed light and for the degree thereof.

[0112]

According to the first aspect of the present invention, the correction amount is determined based on a ratio of blocks satisfying a predetermined threshold condition in an arbitrary area which is a group of predetermined blocks and a change thereof, so that backlight, Exposure control can be performed more appropriately for over-ordered light and also for the degree of over-ordered light.

According to the invention described in claim 2, according to claim 1
In addition to the effects described in the above, in an arbitrary area that is a set of predetermined blocks determined according to the distance to the subject,
The representative luminance calculating means for calculating the luminance representative of the area is a high luminance block or a low luminance satisfying a predetermined threshold condition in an arbitrary area which is a set of predetermined blocks determined according to a distance from a subject. By excluding and averaging blocks, luminance information excluding specific information can be obtained, so that an appropriate luminance ratio can be obtained.

According to the third aspect of the present invention, the first aspect
In addition to the effects described in the above, the ratio calculating means for calculating the ratio of blocks satisfying a predetermined threshold condition in an arbitrary area which is a group of predetermined blocks, the distance between the representative luminance and the subject for which the representative luminance is calculated And comparing the ratio of the luminance with the blocks in an arbitrary area which is a set of predetermined blocks excluding an area determined according to the ratio of blocks satisfying a predetermined threshold condition in an arbitrary area which is a set of predetermined blocks. Since the calculation is performed, it is possible to accurately check the accuracy of the backlight and the over-directed light.

According to the fourth aspect of the present invention, the first aspect is provided.
In addition to the effects described in the above, the correction amount calculating means calculates the ratio of blocks satisfying a predetermined threshold condition in an arbitrary area which is a predetermined group of blocks, Since the correction amount is determined according to the respective ratios in the arbitrary area, it is possible to cope with various degrees of backlight and over-direct light.

According to the invention set forth in claim 5, according to claim 4,
In addition to the effects described in the above, when the ratio of blocks satisfying a predetermined threshold condition in an arbitrary area that is a group of predetermined blocks is large, the correction amount calculation unit increases the correction amount compared with the case of direct light. Therefore, it is possible to cope with the degree of the backlight and the over-order light.

According to the invention described in claim 6, according to claim 4,
In addition to the effects described in the above, the correction amount calculating means uses several types of predetermined threshold conditions in the means for calculating the proportion of blocks satisfying the predetermined threshold condition in an arbitrary area which is a group of the predetermined blocks. Therefore, since the correction amount is determined based on the change in the ratio of blocks that satisfy the threshold condition,
It is possible to cope with the degree of backlight or over-directed light, and appropriate exposure control can be performed.

According to the invention of claim 7, according to claim 1,
In addition to the effects described in the above, when an arbitrary area, which is a group of predetermined blocks determined according to the distance to the subject, is set to be smaller than a predetermined area when the distance to the subject is far, Since the area is set to be larger than a predetermined distance when the distance from the object is on the near side, the size of the subject can be reflected more, and the accuracy of backlight and over-direct light can be accurately observed. .

[Brief description of the drawings]

FIG. 1 is a functional block diagram illustrating an embodiment of a digital still video camera according to the present invention.

FIG. 2 shows an imaging screen divided into a first area to a sixth area.

FIG. 3 is a flowchart illustrating an embodiment of a flow of a state detection process executed by a state detection circuit.

FIG. 4 is a diagram showing a relation between W (first area representative ratio R) and a first area;
It is a graph for explaining how to determine _RATE1).

FIG. 5 is a specific example of an imaging screen when the backlight threshold value is BL_THRD1.

FIG. 6 is a specific example of an imaging screen when the over-order light threshold OL_THRD1 is set.

FIG. 7 is a specific example of an imaging screen when the backlight threshold value is BL_THRD2.

FIG. 8 is a specific example of an imaging screen when the over-order light threshold OL_THRD2 is set.

FIG. 9 is a functional block diagram illustrating an embodiment of a digital still video camera realized using a digital processing circuit such as a microprocessor.

FIG. 10 is a configuration diagram for explaining a conventional video camera.

FIG. 11 is a diagram showing an image in a backlight state by a conventional video camera.

12 is a diagram illustrating an example of block division of a two-dimensional image captured by the video camera in FIG.

FIG. 13 is a diagram showing an image in a backlight state by a conventional video camera or the video camera of the present invention.

[Explanation of symbols]

 A: Digital still video camera 11: Lens 12: Aperture 13: CCD imaging device (solid-state imaging device) 14: Double correlation sampling circuit (CDS) 15: AGC circuit 16: A / D conversion circuit 17: Image signal processing circuit 18 ... block generation circuit (block generation means) 19 ... state detection circuit (state detection means) 20 ... representative luminance calculation circuit (representative luminance calculation means) 21 ... ratio detection circuit (ratio calculation means) 22 ... correction amount calculation circuit (correction amount) Calculation means) 23: exposure control circuit (exposure control means) 24: focus control circuit 25: focus drive circuit

Claims (7)

[Claims] An exposure control is performed using an exposure control method that determines a correction amount in backlight or over-direct light based on a ratio of a luminance ratio occupying an imaging screen and a change thereof, and a solid-state imaging device is used. In a digital still video camera that converts the luminance of an imaging screen of a subject into an electric signal to generate image information, records the generated image information in the form of an electric signal, and reproduces the image information from the recorded electric signal A block generating means for dividing a part or the whole of the imaging screen into a plurality of blocks; and determining whether a luminance level obtained from the predetermined block is included in a predetermined luminance range centered on a predetermined reference luminance level. A state detecting means for determining, and a representative luminance calculating means for obtaining a representative luminance of the area for an arbitrary area which is a set of predetermined blocks determined according to the distance to the subject. A step, a ratio calculating unit that calculates a ratio of blocks satisfying a predetermined threshold condition with respect to the arbitrary area that is a group of the predetermined blocks, a correction amount calculating unit that generates a correction amount based on the obtained ratio, A digital still video camera, comprising: an exposure control unit that obtains an exposure control amount based on the obtained correction amount and executes exposure control according to the exposure control amount. 2. The high-brightness block that satisfies the predetermined threshold condition for the arbitrary area, which is a set of predetermined blocks determined according to the distance to the subject, 2. The digital still video camera according to claim 1, wherein the representative luminance is obtained by averaging the luminance of each block while excluding a block having low luminance. 3. The ratio calculating means obtains an area to be excluded from the arbitrary area, which is a group of the predetermined blocks, according to a distance from the subject from which the representative luminance is obtained, and excludes the excluded area. The ratio of the luminance of each block in the set of predetermined blocks in the arbitrary area to the representative luminance is compared, and the ratio of blocks satisfying a predetermined threshold condition to the arbitrary area, which is the set of predetermined blocks, is calculated. The digital still video camera according to claim 1, wherein the digital still video camera is configured to calculate. 4. The correction amount calculation means is configured to determine a correction amount according to each of the ratios in the arbitrary area, which is a group of predetermined blocks, obtained by the ratio calculation means. The digital still video camera according to claim 1, wherein: 5. The correction amount calculating means is configured to increase the correction amount when a ratio of blocks satisfying the predetermined threshold condition in the arbitrary area which is a group of the predetermined blocks is large. The digital still video camera according to claim 4, wherein: 6. The ratio calculating unit obtains a change in a ratio of a block satisfying each of the threshold conditions in the arbitrary area using several types of the predetermined threshold conditions, and the correction amount calculating unit calculates the ratio of the ratio. The digital still video camera according to claim 4, wherein the digital still video camera is configured to obtain the correction amount based on a change. 7. The arbitrary area, which is a set of predetermined blocks determined according to a distance to a subject, sets the size of the area to be smaller than a predetermined value by a predetermined amount when the distance to the subject is far. 2. The digital still video camera according to claim 1, wherein the size of the area is set to be larger than a predetermined value by a predetermined amount when the distance to the subject is on the near side. .