JPH118796A - Digital video camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a digital video camera capable of precisely judging backlight, excessive forward light and forward light and performing appropriate exposure control. SOLUTION: A state detection circuit 22 judges the backlight, the forward light and the excessive forward light based on a representative luminance matrix prepared in a representative luminance matrix generation circuit 21 and a ratio matrix prepared in a ratio matrix generation circuit 20, a correction amount generation circuit 23 calculates an exposure correction amount based on the judged result of the backlight, the forward light and the excessive forward light and an exposure control circuit 24 performs the exposure control based on the exposure correction amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a digital video camera, and more particularly, to a digital video camera that determines the state of backlight, forward light, or excessive forward light and controls exposure.

[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, over-direct light, or direct light, exposure control is performed by focusing on a central portion of a screen. In some cases, the state of backlight, over-directed light, or forward light is determined by comparing the brightness of the area with the peripheral area excluding the central part, and the exposure is controlled according to the state.

For example, in Japanese Patent Application Laid-Open No. Hei 6-225205, a two-dimensional image is divided into a plurality of blocks, luminance signals are accumulated for each block, and accumulated data is obtained. There is disclosed a video camera that determines whether an over-illuminated state is present based on block data and controls an iris to an appropriate state. Specifically, as shown in FIG. 14, the captured two-dimensional image is divided into 4 × 4 blocks (a to
p), and, for example, in a backlight state in which the central person is darkly sunk as shown in FIG. 15, f, g, j, k, n, o
The luminance of the block is compared with the luminance of the other blocks to determine the direct light or the backlight.

In Japanese Patent Application Laid-Open No. HEI 6-169427, according to the size of a subject in a screen, a plurality of pre-divided areas extending from the center to the outside are sequentially directed outward from a small area. There is disclosed an automatic iris control system of a television system that controls an iris by comparing average luminance levels, selecting a region having the highest contrast ratio, and judging the state of backlight or over-direct light.

[0005]

However, in the video camera described in JP-A-6-225205, since a luminance signal is simply accumulated in a block, a high luminance portion and a low luminance When the portions are mixed, the brightness corresponding to the backlight portion may not be accurately obtained. In addition, even when the subject is a small backlight, the luminance of the central portion corresponding to the backlight cannot be accurately obtained. The same applies to a case where the subject is not at the center. That is, since the difference in luminance between the central portion and the peripheral portion cannot be accurately obtained, it is not possible to accurately determine whether the light is direct or backlit, so that accurate exposure control cannot be performed.

The automatic iris control system of the television system described in Japanese Patent Application Laid-Open No. Hei 6-169427 also has direct / backlit light for the same reason as the video camera described in Japanese Patent Application Laid-Open No. Hei 6-225205. Since the determination cannot be performed accurately, there is a problem that accurate exposure control cannot be performed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a digital video camera capable of judging backlight, over-direct light, or direct light with high accuracy and performing appropriate exposure control. Aim.

[0008]

According to a first aspect of the present invention, there is provided a digital video camera for determining exposure to light, backlight, and excessive light, and performing exposure control. A part or the whole of the screen is divided into a plurality of blocks, the luminance signal is divided into a plurality of stages according to the level of the luminance, and the luminance signal is accumulated in each block at the same stage to accumulate the luminance for each stage. A luminance dividing means for calculating a cumulative luminance matrix, a weighted luminance matrix generating means for applying a weight to the cumulative luminance of the cumulative luminance matrix to generate a weighted luminance matrix, A ratio matrix generating means for calculating a ratio of the cumulative number of luminance signals for each cumulative luminance for each stage to the total cumulative number and generating a ratio matrix;
A representative luminance matrix for selecting a cumulative luminance of an arbitrary stage from a plurality of stages of cumulative luminance and selecting an arbitrary number of luminance signals to generate a representative luminance matrix based on the ratio matrix for each block from the cumulative luminance matrix. Generating means, state determining means for determining a state of forward light, back light, or excessively forward light based on the representative luminance matrix, and correction amount calculating means for calculating an exposure correction amount based on a determination result of the state determining means And an exposure control means for calculating an exposure control amount based on the exposure correction amount and performing exposure control based on the exposure control amount.

A digital video camera according to claim 2 is the digital video camera according to claim 1,
The state determination unit, when the average value or the maximum value of all the blocks in an area including any one or a plurality of blocks of the weighted luminance matrix is within a range of a reference luminance level, The state of forward light, back light, and excessive forward light is determined.

In a digital video camera according to a third aspect of the present invention, in the digital camera according to the first aspect, the weighted luminance matrix generating means generates a weighted luminance matrix by setting all weights to 1.0. , The state determination means may include any one of the weighted luminance matrices.
Alternatively, when the luminance levels obtained from the plurality of blocks are within the range of the reference luminance level, the state of the forward light, the backward light, or the over-direct light is determined.

In a digital video camera according to a fourth aspect of the present invention, in the digital camera according to the first aspect, the representative luminance matrix generating means refers to the ratio matrix, and in each block of the ratio matrix, When the ratio of the cumulative luminance of an arbitrary stage to the total cumulative number of luminance signals is larger than a predetermined threshold, the cumulative luminance of the arbitrary stage is selected, and the cumulative luminance of the arbitrary stage in the block of the cumulative luminance of the arbitrary stage is selected. While the representative luminance matrix is generated by averaging with the cumulative number of luminance signals, if the representative luminance matrix is equal to or less than a predetermined threshold, the cumulative luminance of all stages is selected and integrated, and then averaged with the total cumulative number. A representative luminance matrix is to be generated.

In a digital video camera according to a fifth aspect of the present invention, in the digital camera according to the first aspect, a brightness level obtained from any one or a plurality of blocks of the weighted brightness matrix is determined by the state determination means. When it is determined that the luminance level is within the range of the luminance level, the weighted luminance matrix generating means sets the weight of the accumulated luminance at the higher luminance level to be smaller than 1.0.

In a digital video camera according to a sixth aspect of the present invention, in the digital camera according to the first aspect, the state determination means uses the representative luminance matrix, the ratio matrix, and the weighted luminance matrix to direct light. ,
It was decided to determine the state of backlight and over-direct light.

According to a seventh aspect of the present invention, in the digital camera according to the fifth aspect, the state determining means divides the representative luminance matrix and the ratio matrix into a plurality of areas, and A result of comparing the contrast ratio of luminance between arbitrary regions with a predetermined threshold value and correction for setting a luminance level obtained from one or a plurality of blocks in the weighted luminance matrix as a reference luminance level Based on the amount, we decided to determine the state of forward light, backlight, and over-direct light

The digital video camera according to claim 8 is the digital camera according to claim 7, wherein the correction amount calculating means includes a determination result of the state determining means;
An exposure correction amount is calculated based on a correction amount for setting a luminance level obtained from an arbitrary one or a block in the weighted luminance matrix as a reference luminance level.

[0016]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

(Embodiment 1) FIG. 1 is a block diagram showing an embodiment (Embodiment 1) of a digital video camera according to the present invention.

In FIG. 1, reference numeral 1 denotes a digital video camera. This digital video camera 1 has a lens 11, an aperture 12, a CCD 13, a CDS (double correlation sampling) circuit 14, an AGC circuit 15, an A / D converter. Vessel 1
6, image signal processing circuit 17, luminance division circuit 18, weighted luminance matrix generation circuit 19, ratio matrix generation circuit 20, representative luminance matrix generation circuit 21, state detection circuit 22, correction amount generation circuit 23, and exposure control circuit 24 It has.

The CCD 13 converts an optical signal incident through the lens 11 into analog image data (electric signal). The CDS circuit 14 is connected to the output of the CCD 13, and performs correlated double sampling of the output signal of the CCD 13 to reduce noise in the CCD image sensor.

The AGC circuit 15 is connected to the CDS circuit 14 and corrects the level of the output signal of the CDS circuit 104. The A / D converter 16 is connected to the output of the AGC circuit 15 and converts the output signal of the AGC circuit 15 into an analog-digital signal at an optimal sampling frequency (for example, an integer multiple of the subcarrier frequency of the NTSC signal). To obtain digital image data.

The image signal processing circuit 17 includes the A / D converter 1
6 performs normal video signal processing such as gamma correction and color separation on the digital image data input from
A luminance signal and a color difference signal conforming to the C method are created.

The luminance dividing circuit 18 divides a part or the whole of the screen into a plurality of blocks, divides the luminance signal output from the image signal processing circuit 17 into a plurality of stages according to the level of the luminance, and , The luminance signal at the same stage is accumulated to calculate the accumulated luminance, and a cumulative luminance matrix is generated.

The weighted luminance matrix generation circuit 19
A weighted luminance matrix is generated by multiplying the accumulated luminance of the accumulated luminance matrix created by the luminance dividing circuit 18 by a weighting coefficient.

The ratio matrix generation circuit 20 calculates the ratio of the cumulative number of luminance signals accumulated in each block to the total cumulative number of luminance signals in each block based on the output of the luminance dividing circuit 18 and calculates the ratio matrix. Generate

Based on the ratio matrix created by the ratio matrix generation circuit 20, the representative luminance matrix generation circuit 21 arbitrarily outputs a luminance signal from an arbitrary level (luminance level) from the cumulative luminance at each block from the cumulative luminance matrix. A representative luminance matrix is generated by selecting the selected luminance matrix.

The state detection circuit 22 determines whether or not the luminance level obtained from the block of the weighted luminance matrix is within the range of the reference level, and determines whether the light is backlit, forward light, or over-direct light. The correction amount generation circuit 23 calculates a final exposure correction amount based on the state detection result of the state detection circuit 22. The exposure control circuit 24 includes the correction amount generation circuit 2
An exposure control amount is calculated based on the exposure correction amount calculated in step 3, and exposure control such as control of the aperture 12, shutter speed, and AGC is performed.

In the configuration shown in FIG. 1, the luminance dividing circuit 18 represents the luminance dividing means, the weighted luminance matrix generating circuit 19 represents the weighted luminance matrix generating means, and the ratio matrix generating circuit 20 represents the ratio matrix generating means. The luminance matrix generation circuit 21 implements a representative luminance matrix generation unit, the state detection circuit 22 implements a state determination unit, the correction amount generation circuit 23 implements a correction amount generation unit, and the exposure control circuit 24 implements an exposure control unit. .

Next, a luminance division circuit 18, a weighted luminance matrix generation circuit 19, a ratio matrix generation circuit 20, a representative luminance matrix generation circuit 21, a state detection circuit 22, a correction amount generation circuit 23, and an exposure control circuit 24
Will be described in order.

[Operation of Luminance Division Circuit 18]

The luminance dividing circuit 18 controls the input image (screen)
Is divided into m × n blocks, the luminance signal is divided into two stages according to the level of luminance, and the luminance of the same stage is accumulated in each block to generate an m × n accumulated luminance matrix. I do.

FIG. 2 is a diagram for explaining a method of dividing a luminance signal into two stages according to luminance levels. As shown in FIG. 2, the lowest level of the luminance signal is "0", the luminance level is "yh" when the luminance signal exceeds the threshold, and the luminance level is "yh" when the luminance signal does not exceed the threshold. To "y
m ”.

The luminance dividing circuit 18 is given by the following equations (1) and (2)
Is used to divide the luminance signal for each block by luminance level (y
h, ym) to calculate the cumulative luminance, and generate an m × n cumulative luminance matrix.

Yh (i, j) = {yh} (1) where h_num (i, j) is the cumulative number of one block (i = 1 to m, j = 1 to n).

Ym (i, j) = {ym} (2) where m_num (i, j) is the cumulative number of one block (i = 1 to m, j = 1 to n).

In the above equations (1) and (2), yh,
ym means an individual luminance signal belonging to the luminance level. Yh (i, j) is a function indicating the cumulative luminance of the luminance signal of the luminance level yh of each block. Ym
(I, j) is a function indicating the cumulative luminance of the luminance signal of the luminance level ym of each block.

The method of accumulation in a block may be accumulation for all pixels in the block, or may be accumulation by sampling pixels arbitrarily.

[Operation of Weighted Luminance Matrix Generating Circuit 19] The weighted luminance matrix generating circuit 19 multiplies the cumulative luminance of the m × n cumulative luminance matrix generated by the luminance dividing circuit 18 by an arbitrary weighting factor. Generate a luminance matrix.

The weighted luminance matrix generation circuit 19
An m × n weighted luminance matrix is generated by the following equation (3).

Yw (i, j) = Yh (i, j) × Wh + Ym (i, j) × Wm (3) where i = 1 to m, j = 1 to n

Here, Wh and Wm are weighting factors for each luminance level (stage) (Wh ≧ 0, Wm ≧ 0). Also,
Yw (i, j) is a function indicating the weighted cumulative luminance of each block.

[Operation of Ratio Matrix Generation Circuit 20] The ratio matrix generation circuit 20 calculates the ratio of the cumulative number of luminance signals of each luminance level (stage) to the total cumulative number of luminance signals in each block, and calculates the ratio matrix. Generate

The ratio matrix generation circuit 20 generates an m × n ratio matrix by the following equations (4) and (5).

Rh (i, j) = h — num (i, j) × 100 / all — num ‥‥‥ (4) where i = 1 to m, j = 1 to n

Rm (i, j) = m_num (i, j) × 100 / all_num ‥‥‥ (5) where i = 1 to m, j = 1 to n

Here, all_num is the total cumulative number of luminance signals in the block, and all_num = h_num (i, j) +
m_num (i, j) and Rh (i, j) are functions indicating the ratio of the cumulative number of luminance levels yh to the total cumulative number in each block, and Rm (i, j) is the function of each block. Is a function indicating the ratio of the cumulative number of luminance levels ym to the total cumulative number of.

[Operation of Representative Luminance Matrix Generating Circuit 21] The representative luminance matrix generating circuit 21 selects, in each block, any number of luminance signals of cumulative luminance at an arbitrary stage in each block based on the ratio matrix. Generate a matrix.

First, Rx (i, j) is Rh (i, j)
Or Rm (i, j). If Rx (i, j) is larger than a predetermined threshold value blck_thrd, Yr (i, j) = Yx (i, j) / x_num (i, j) where i = 1 to m, j = 1 to n Rx (i, j) is equal to or less than a predetermined threshold value blck_thrd, Yr (i, j) = (Yh (i, j) + Ym (i, j))
/ All_num (i, j) where i = 1 to m, j = 1 to n

Here, Yx (i, j) and x_num (i,
j) is a luminance level that satisfies the threshold value blck_thrd, and is Yh (i, j), h_num (i, j) or Ym (i, j), m_num (i, j). It is. Also, the threshold value blck_thrd is set to be larger than 50.

[State detection circuit 22 and correction amount generation circuit 2]
Operation 3) The state detection circuit 22 determines whether or not the luminance level is within the range of the reference level, and also determines whether the light is backlit, forward light, or over-direct light. The correction amount generation circuit 23 generates a final exposure correction amount based on the state detection result of the state detection circuit 22.

State detection circuit 22 and correction amount generation circuit 23
Will be described with reference to FIGS. FIG.
5 is a flowchart illustrating a correction amount calculation process performed by a state detection circuit 22 and a correction amount generation circuit 23. FIG. 5 is a diagram showing the backlight in the correction amount calculation process shown in FIG.
It is a flowchart for demonstrating an over-direct light and a direct-light determination process. FIG. 6 is a flowchart for explaining the brightness contrast comparison processing in the backlight, over-direct light, or forward light determination processing shown in FIG. FIG. 7 is a flowchart for explaining the area 3 and 4 comparison processing in the luminance contrast comparison processing shown in FIG.

FIG. 8 is a flow chart for explaining the RM and area 1 high luminance portion comparison processing in the luminance contrast comparison processing shown in FIG. FIG. 9 is a flowchart for explaining the RM and area 2 high luminance portion comparison processing in the RM and area 1 high luminance portion comparison processing shown in FIG. FIG. 10 is a flowchart for explaining the RH and area 1 middle luminance portion comparison processing in the luminance contrast comparison processing shown in FIG. FIG. 11 is a flowchart for explaining the RH and area 2 middle luminance portion comparison processing in the RH and area 1 middle luminance section comparison processing shown in FIG.

In the following, various luminance matrices are defined as 8 × 6
A block (i = 1 to 8, j = 1 to 6) is set, and the luminance is divided into two parts by the luminance division circuit 18 according to the level of the luminance, and the representative luminance matrix and the weighted luminance matrix are divided into regions as shown in FIG. The case will be described as an example. FIG.
In, the matrix is divided into area 1 to area 4. The area 4 does not include the area 3.

First, the correction amount calculation processing executed by the state detection circuit 22 and the correction amount generation circuit 23 will be described based on the flowchart of FIG. The processing within the dotted line in FIG. 4 is performed by the state detection circuit 22. still,
In FIG. 4, in the initial state, the luminance level is not within the range of the reference luminance level.

First, the weighted luminance matrix generation circuit 1
9 sets all weighting factors to 1.0, ie, Wh
= 1.0 and Wm = 1.0.

Next, under the control of the exposure control circuit 24,
The CCD 13 is exposed with pEV (step S
2).

The state detection circuit 22 determines whether or not the luminance level of the luminance signal obtained as a result of exposure with the exposure amount pEV is within the range of the reference luminance level, Y1_thrd <Yc <.
It is determined based on whether or not it is Yu_thrd (step S
3). Here, Y1_thrd and Yu_thrd are lower and upper thresholds that determine the range of the reference luminance level. Yc is calculated by the following equation (6) using, for example, the average value of all blocks in areas 3 and 4 in FIG.

Yc = {Yw (i, j) / 16} (6) where i = 3 to 6, j = 2 to 5 As described above, Yw (i, j) is the weight of each block. It is a function indicating the cumulative luminance.

As a result of this determination, Y1_thrd <Yc <Yu
If it is not within the range of _thrd, the exposure control circuit 24 changes the exposure amount to expose the CCD 13 with the exposure amount qEV (step S4), and obtains the luminance of the luminance signal obtained as a result of the exposure with the exposure amount qEV. Level is Y1_thrd <Y
It is determined whether or not c <Yu_thrd (step S3).

On the other hand, if Y1_thrd <Yc <Yu_thrd, the process proceeds to step S5, where the state detection circuit 22 calculates CV. Here, CV is W
The correction amount up to a reference value T using Yc as a reference luminance level when h = 1.0 and Wm = 1.0, and is calculated, for example, by the following equation (7).

Cv = −log2 (T / Yc) ‥‥‥ (7)

Next, the weighted luminance matrix generation circuit 19 sets Wh <1.0 and Wh = 1.0 (step S6). The exposure control circuit 24 corrects the exposure amount,
The CCD 13 is exposed with an exposure amount of p + CV (q + CV) EV (step S7).

The state detection circuit 22 calculates a correction amount CVw up to a reference value T using Ycw as a reference luminance level (step S8). Here, the correction amount CVw is calculated by the following equation (8).

CVw = −log2 (T / Ycw) ‥‥‥ (8)

In the above formula (8), Ycw is, for example,
Using the average value of all blocks in areas 3 and 4 in FIG.
It is calculated by the following equation (9) as in the above equation (6).

Y cw = {Y w (i, j) / 16} (9) where i = 3 to 6, j = 2 to 5

When implementing, CV, C
Vw may be calculated by linear interpolation or the like.
Further, as the pEV and qEV, at the time of photometry, an arbitrary EV that can cover the entire photometry range may be specified.
In a general scene, the subject of each luminance included in the screen has a range of about 5 EV. Therefore, for example, if the photometric range is 9 to 17 EV, p = 13, q
If = 16, the entire area can be covered.

Subsequently, the state detection circuit 22 performs a backlight, forward light, or over-direct light determination process to determine backlight, forward light, or over-direct light (step S9), and the correction amount generation circuit 23 More specifically, as described later, a final exposure correction amount is generated based on the state detection result of the state detection circuit 22 (step S10).

Next, the backlight, forward light, and excessive forward light determination processing in step S9 will be described with reference to the flowchart shown in FIG.

In FIG. 5, first, the state detection circuit 22 executes a brightness contrast comparison process (see FIG. 6).
Based on the luminance contrast ratio, provisional determination of backlight, over-direct light, or forward light is made (step S11). Next, the state detection circuit 2
2 makes a final determination of back light, over-forward light, and forward light based on the calculated CVw and the provisional determination result of back light, over-forward light, and forward light (step S12). The details of the final determination will be described later.

Next, the brightness contrast comparison processing in step S11 will be described with reference to FIG. In the brightness contrast comparison processing shown in FIG. 6, the matrix used is
It is a representative luminance matrix. vm1_blck, vm2_blck,
vm3_blck and vm34_blck are Ym in area 1, area 2, area 3, area 3 and area 4, respectively.
Represents the number of valid blocks for (i, j). vh1 _blc
k, vh2_blck, vh3_blck, and vh34_blck represent the number of effective blocks for Yh (i, j) in area 1, area 2, area 3, and area 4, respectively.

Here, the effective block is the threshold value
A block in which a luminance level satisfying the condition of blck_thrd is stored. ctr_thrd is a threshold value of valid blocks in areas 3 and 4, and core_thrd is a threshold value of valid blocks in area 3. RYm34
, RYh34 are the effective blocks Yr (i, j) in the areas 3 and 4, respectively.
The average value of Yr (i, j), which is an effective block with respect to the average value of (i, j) and Yh (i, j). Also, RY
m3 and RYh3 are Ym in area 3 respectively.
Yr (i, j) to be an effective block for (i, j)
Is the average value of Yr (i, j) which becomes an effective block with respect to Yh (i, j). RYm4 and RYh4 are the average values of Yr (i, j), which are effective blocks for Ym (i, j) in area 4, and Yh (i, j).
The average value of Yr (i, j) which becomes an effective block for j).

In FIG. 6, first, vm34_blck> ctr_
It is determined whether or not it is thrd (step S20),
If the result of this determination is that vm34_blck> ctr_thrd, processing proceeds to step S21, while vm34_blck> ctr_thrd.
If it is not the thrd, the process moves to step S31.

In step S21, vm3_blck> core_
It is determined whether or not it is thrd, and vm3_blck> core_
If it is thrd, the process proceeds to step S22,
If vm3_blck> core_thrd is not satisfied, step S2
Move to 8.

At step S22, it is determined whether or not vh34_blck = 0. If vh34_blck = 0, it is determined that vh34_blck = 0.
In step S23, RM is set to RYm3, and RM and area 1 high luminance comparison processing (see FIG. 8) are executed (step S24).

On the other hand, in step S22, vh34
If _blck = 0 is not satisfied, the process proceeds to step S25, where R
Ym34 and RYh34 are compared, and it is determined whether or not there is a contrast difference (step S2).
6) If there is a contrast difference, it is determined to be backlight. On the other hand, if there is no contrast difference in step S26, the process proceeds to step S23. Here, there is a contrast difference when the contrast ratio is equal to or more than a predetermined threshold value as compared with a predetermined threshold value of the contrast ratio between various luminances (the same applies hereinafter).

Now, in step S28, vh3_blck>
It is determined whether or not it is core_thrd, and vh3_blck>
If it is not the core_thrd, the process proceeds to step S41, where the comparison processing of the areas 3 and 4 (see FIG. 7) is performed.
On the other hand, if vh3_blck> core_thrd in step S28, the process proceeds to step S29, where RYm34 and R
The comparison of Yh3 is performed, and subsequently, it is determined whether or not there is a contrast difference. If there is a contrast difference, it is determined that the light is over-directed. You.

In step S31, vh34_blck>
It is determined whether or not ctr_thrd. If the result of this determination is that vh34_blck> ctr_thrd, step S
On the other hand, when vh34_blck> ctr_thrd is not satisfied, the flow shifts to step S41.

In step S32, vh3_blck> core_
It is determined whether or not it is thrd, and vh3_blck> core_
If it is thrd, the process proceeds to step S33,
If vh3_blck> core_thrd is not satisfied, step S3
Move to 8.

In step S33, it is determined whether or not vm34_blck = 0, and if vm34_blck = 0,
The process proceeds to step S34, where RH is set to RYh3, and the RH is compared with the luminance in the area 1 (see FIG. 10) (step S35).

On the other hand, in step S33, vm34
If _blck = 0 is not satisfied, the flow shifts to step S36, where R
The comparison between Yh34 and RYm34 is performed. If there is a contrast difference, it is determined that the light is over-directed. If there is no contrast difference, the process proceeds to step S34.

Now, in step S38, vm3_blck>
It is determined whether or not it is core_thrd, and vm3_blck>
If it is not the core_thrd, the process proceeds to step S41, where the comparison processing of the areas 3 and 4 (see FIG. 7) is performed.
On the other hand, if vm3_blck> core_thrd is satisfied in step S38, the process proceeds to step S39, where RYm3 and RYm3
Comparison with h34 is performed, and then it is determined whether or not there is a contrast difference (step S40). If there is a contrast difference, it is determined that the subject is backlit. Is determined.

Next, the comparison processing of area 3 and area 4 in step S41 will be described with reference to FIG. RY3,
RY4 is the average value of all the blocks in the areas 3 and 4, and RY1 and RYr are the average values of all the blocks in the areas 1 and 2.

In FIG. 7, first, RY3 and RY4 are compared (step S50), and it is determined whether or not there is a contrast difference (step S51). Then, the process proceeds to step S52, while if there is no contrast difference, the process proceeds to step S53.

In step S52, it is determined whether or not RY3 <RY4. If RY3 <RY4, it is determined that the subject is backlit. If RY3 <RY4, it is not determined.
It is determined that the light is over-ordered.

In the step S53, (RY3 + RY4)
/ RY is compared with RY1, and it is determined whether or not there is a contrast difference (step S54). If the result of this determination is that there is a contrast difference, the process proceeds to step S55. If there is no contrast difference, the process proceeds to step S56.

In step S55, (RY3 + RY4)
/ RY <RY1 is determined, and (RY3 +
If RY4) / 2 <RY1, it is determined that the subject is backlit,
If (RY3 + RY4) / 2 <RY1, it is determined that the light is over-directed.

In step S56, (RY3 + RY4)
/ RY is compared with RYr, and then it is determined whether there is a contrast difference (step S57). If the result of this determination is that there is no contrast difference, it is determined that the light is normal. . On the other hand, if there is a contrast difference in step S57, the flow shifts to step S58, where (RY3 + R
It is determined whether or not Y4) / 2 <RYr.
If Y3 + RY4) / 2 <RYr, it is determined to be backlight, and if not (RY3 + RY4) / 2 <RYr, it is determined to be over-ordered light.

Next, the RM and area 1 high-luminance portion comparison processing in step S24 of the luminance-contrast comparison processing in FIG.
This will be described based on the flowchart shown in FIG.

Each of RYm1 and RYh1 is an effective block for Ym (i, j) in area 1.
The average value of Yr (i, j), which is an effective block for Yh (i, j), is the average value of Yr (i, j). RYl is the same as above.

In FIG. 8, first, it is determined whether or not vh1_blck = 0 (step S60). If vh1_blck = 0, the process proceeds to step S61, while vh1_blck = 0.
If not, the process proceeds to step S69.

In step S61, it is determined whether or not vm1_blck = 0, and if vm1_blck = 0, it is determined that vm1_blck = 0.
While the process proceeds to step S62, if vm1_blck = 0 is not satisfied, the process proceeds to step S65.

In step S62, RM and RY1 are compared, and it is determined whether or not there is contrast (step S63). If there is no contrast difference, it is determined that the light is normal. On the other hand, if there is a contrast difference, the flow shifts to step S64, where RM <RY1
It is determined whether RM <RY1 or not. If RM <RY1, it is determined that the light is backlit. If RM <RY1 is not satisfied, it is determined that the light is over-directed.

Now, in step S65, RM and RYm1
Then, it is determined whether or not there is a contrast (step S66). If there is no contrast difference, the process shifts to step S68 to compare the RM with the area 2 high-luminance portion comparing process. (See FIG. 9). On the other hand, if there is a contrast difference, the process shifts to step S67 to determine whether or not RM <RYm1, and if RM <RYm1, it is determined that the subject is backlit. If it is not <RYm1, it is determined that the light is over-ordered.

In step S69, RM and RYh1 are compared, and it is determined whether or not there is a contrast (step S70). If there is a contrast difference, it is determined that the subject is backlit. If there is no contrast difference, the process shifts to step S68 to perform RM and area 2 high-luminance portion comparison processing (see FIG. 9).

Next, the details of the RM and area 2 high luminance comparison processing in step S68 of the RM and area 1 high luminance comparison processing of FIG. 8 will be described with reference to the flowchart shown in FIG.

RYmr and RYhr are the effective blocks of Ym (i, j) in area 2 respectively.
The average value of Yr (i, j), which is an effective block for Yh (i, j), is the average value of Yr (i, j). RYr is the same as above.

In FIG. 9, first, it is determined whether or not vh2_blck = 0 (step S80). If vh2_blck = 0, the process proceeds to step S81, while vh2_blck = 0.
If not, the process proceeds to step S88.

In step S81, it is determined whether or not vm2_blck = 0, and if vm2_blck = 0, it is determined that vm2_blck = 0.
While the process proceeds to step S82, if vm2_blck = 0 is not satisfied, the process proceeds to step S85.

In step S82, RM and RYr are compared, and it is determined whether or not there is a contrast (step S83). If there is no contrast difference, it is determined that the light is normal. On the other hand, if there is a contrast difference, the flow shifts to step S84, where RM <RYr
It is determined whether RM <RYr or not, and if RM <RYr, it is determined that the light is over-directed.

Now, in step S85, RM and RYmr
Then, it is determined whether or not there is a contrast (step S86). If there is no contrast difference, it is determined that the light is normal. Then, the process proceeds to step S87, where RM <
It is determined whether or not RYmr. If RM <RYmr, it is determined that the light is backlit. If RM <RYmr, it is determined that the light is over-directed.

In step S88, RM and RYhr are compared, and it is determined whether or not there is a contrast (step S89). If there is no difference, it is determined that the light is normal.

Next, the RH and the in-area 1 luminance comparison processing in step S35 of the luminance contrast comparison processing in FIG. 6 will be described with reference to the flowchart shown in FIG. RYm
1, RYh1 is Ym in area 1
Yr (i, j) to be an effective block for (i, j)
Is the average value of Yr (i, j) which becomes an effective block with respect to Yh (i, j). RY1 is the same as above.

In FIG. 10, first, it is determined whether or not vm1_blck = 0 (step S900), and vm1_blck = 0.
In the case of, the process proceeds to step S91, while vm1_bl
If ck = 0 is not satisfied, the flow shifts to step S99.

At step S91, it is determined whether or not vh1_blck = 0, and if vh1_blck = 0, it is determined that vh1_blck = 0.
On the other hand, when vh1_blck = 0 is not satisfied, the process proceeds to step S95.

In step S92, RH is compared with RY1, and it is determined whether or not there is a contrast (step S93). On the other hand, if there is a contrast difference, the process proceeds to step S94, where it is determined whether RH <RY1 or not. If RH <RY1, it is determined that the subject is backlit. Is determined.

Now, in step S95, RH and RYh1
Then, it is determined whether or not there is a contrast (step S97). If there is no contrast difference, the process shifts to step S98 to compare the RH with the area 2 medium brightness portion. (See FIG. 11), while
If there is a contrast difference, the flow shifts to step S96 to determine whether RH <RYh1 or not. If RH <RYh1, it is determined that the subject is backlit. Is done.

In step S99, RH is compared with RYm1, and it is determined whether or not there is a contrast (step S100). If there is no contrast difference, the flow shifts to step S98. The RH and middle area 2 middle luminance portion comparison processing (see FIG. 11) is performed. On the other hand, if there is a contrast difference, it is determined that the light is over-directed.

Next, the details of the RH and area 2 middle luminance comparison section comparison processing in step S98 of the RH and area 1 middle luminance section comparison processing of FIG. 10 will be described with reference to the flowchart shown in FIG. RYmr and RYhr are Yr which are effective blocks with respect to Ym (i, j) in area 2, respectively.
This is the average value of Yr (i, j) which becomes an effective block with respect to the average value of (i, j) and Yh (i, j). RYr is the same as above.

In FIG. 11, first, it is determined whether or not vm2_blck = 0 (step S110), and vm2_blck = 0.
In the case of, the process proceeds to step S111, while vm2_
If blck is not 0, the process proceeds to step S118.

In step S111, it is determined whether or not vh2_blck = 0. If vh2_blck = 0, the process proceeds to step S112. If vh2_blck = 0, the process proceeds to step S115. Move to

In step S112, RH and RYr are compared, and it is determined whether or not there is a contrast (step S113). If there is no contrast difference, it is determined that the light is normal. On the other hand, if there is a contrast difference, the flow shifts to step S114, where RH <
It is determined whether or not RYr. If RH <RYr, it is determined that the light is backlit. If RH <RYr, it is determined that the light is over-directed.

In step S115, RH and RY
The comparison with hr is performed, and it is then determined whether or not there is a contrast (step S116). Shifts to step S117,
It is determined whether or not RH <RYhr. If RH <RYhr, it is determined that the subject is backlit. If RH <RYhr, it is determined that the subject is over-directed.

In step S118, RH is compared with RYmr, then it is determined whether or not there is a contrast (step S119). If there is a contrast difference, it is determined that the light is over-directed. If there is no contrast difference, it is determined that the light is normal.

Next, the details of the final determination processing in step S12 in the backlight, over-direct light, or forward light determination processing of FIG. 5 will be described. As described above, step S1 in FIG.
At this point, the determination of backlight, over-forward light, or forward light performed in the luminance contrast comparison process (refer to FIGS. 6 to 11) is still provisional, that is, provisional backlight, provisional order. Light and temporary over-reversed forward light, and the final determination is performed by the final determination process of step S12 in FIG. 5 as follows, for example.

When the temporary forward light and CVw <nl_thrd, the normal forward light and the temporary forward light and when CVw ≧ nl_thrd, the special forward light and the temporary backlight, regardless of CVw, the backlight regardless of the CVw, regardless of the CVw Excessive light

Next, the relationship between CV and CVw will be described. FIG. 12 is a diagram showing transition of luminance values of Yc and Ycw around a reference luminance level at the time of backlight. The horizontal axis represents the luminance level on the over side and the under side centered on the reference luminance level, and the vertical axis represents the luminance value.

From FIG. 12 and the above equations (7) and (8),
Normally, CV and CVw have the following relationship. At the time of backlight or over-direct light, C
In many cases, V ≦ CVw. In the case of direct light, CVwCVw often occurs.

This is because, when Yc and CVw are created from blocks within a certain range, the determination of forward light, over-forward light, or forward light can be made regardless of the position of the subject due to the relationship between CV and CVw. Means possible.

Next, the content of the final correction amount generation processing of step S10 in the correction amount calculation processing of FIG. 4 will be described in detail.

The correction amount generating circuit 23 determines the final correction amount (exposure correction amount) as follows based on the CVw and the result of the determination of back light, over-direct light, or forward light by the final determination processing.
Determine mEV.

MEV = NL for normal forward light mEV = NW for special forward light mEV = NW (CVw) mEV = BL × BW (CWw) for overlit light mEV = OL × OW (CVw)

Here, NL, BL, and OL are predetermined correction amounts at the time of forward light, back light, and over-direct light, respectively. NW (C
Vw), BW (CVw), and OW (CVw) are weights for special forward light, backlight, and over-forward light, respectively, which means that the weight is arbitrarily changed depending on the magnitude of CVw.

[Operation of Exposure Control Circuit 24] The exposure control circuit 24 adjusts the aperture 12, shutter speed, and AGC exposure control amount based on the final correction amount (exposure correction amount) mEV of the output of the correction amount generation circuit 23. Exposure control is determined arbitrarily.

As described above, in the present embodiment,
Based on the representative luminance matrix created by the representative luminance matrix generation circuit 21, the state detection circuit 22 determines backlight, forward light, or over-forward light, and the correction amount generation circuit 23 determines the backlight, forward light, or over-light. The exposure control circuit 24 calculates the exposure correction amount based on the determination result of the direct light, and the exposure control circuit 24 performs the exposure control based on the exposure correction amount. Therefore, the high luminance portion and the low luminance portion are mixed in the block. Backlight, forward light, or over-direct light can be accurately determined even when the subject is small or the like, and the amount of exposure correction can be determined based on the determination result of the backlight, forward light, or over-direct light. Since it is determined, appropriate exposure control can be performed for a shooting scene.

In the above embodiment, the area 3,
Although the description has been made with the range of area 4 limited to the center,
Using the result of F or the like, a range equivalent to the subject may be obtained, and the same operation may be performed.

In the above-described embodiment, an example in which the number of screen blocks is set to 6 × 8 has been described. However, the present invention is not limited to this, and any number of screen blocks may be used.

(Embodiment 2) As shown in FIG. 13, a digital processing circuit such as a microprocessor is used to
It is possible to perform the same processing as the digital camera shown by.

FIG. 13 is a block diagram showing the configuration of an embodiment (Embodiment 2) of a digital video camera according to the present invention.

The digital video camera shown in FIG.
CD camera unit 31, A / D converter 32, image signal processing unit 33, frame memory 34 for storing image data, various luminance matrix generation units 35, exposure correction unit 36, memory card 37, CPU 38, CCD camera control unit 39 It is composed of

The CCD camera unit 31 is a lens
1. Aperture 12, CCD 13, CDS circuit 14, and AG
In the C circuit 15, various luminance matrix generation units 35
The luminance compensating circuit 36 includes a luminance dividing circuit 18, a weighted luminance matrix generating circuit 19, a ratio matrix generating circuit 20, and a representative luminance matrix generating circuit 21. The CCD camera control section 39 corresponds to the exposure control circuit 24, respectively. Further, the CPU 38 controls the operation of each section, and the exposure correction section 36 executes the correction amount calculation processing shown in FIGS.

[0131]

According to the first aspect of the present invention, the state detecting means determines back light, forward light, or over-direct light based on the representative luminance matrix and the ratio matrix. Based on the determination result, calculate the exposure correction amount,
Since the exposure control means is configured to perform exposure control based on the exposure correction amount, even when a high-luminance part and a low-luminance part are mixed in a block, or when a subject is small, backlight or forward light can be controlled. Light and over-direct light can be determined with high accuracy, and the amount of exposure correction is determined based on the results of the determination of back-light, over-light and over-direct light. Becomes

According to the second aspect of the present invention, the state determining means determines whether the average value of all the blocks in the area composed of any one or a plurality of blocks of the weighted luminance matrix or the maximum value in the entire blocks is obtained. When the weighted luminance matrix is within the range of the reference luminance level, the state of forward light, back light, or excessive forward light is determined. Since it is possible, it is possible to more accurately determine backlight, forward light, and excessive forward light.

According to the third aspect of the present invention, the weighted luminance matrix generating means sets all the weightings to 1.
A weighted luminance matrix is generated by setting the luminance level to 0, and if the luminance level obtained from any one or a plurality of blocks of the weighted luminance matrix is within the range of the reference luminance level, Since the backlight and over-directed light are determined, it is possible to eliminate the influence of level division depending on the level of the luminance, and to accurately determine whether the luminance is within the range of the reference luminance level. It is possible to more accurately determine the light and the over-order light.

According to the fourth aspect of the present invention, the representative luminance matrix generating means refers to the ratio matrix, and in each block of the ratio matrix, sets an arbitrary level with respect to the total cumulative number of luminance signals in the block. Is larger than a predetermined threshold value, the cumulative luminance at the arbitrary stage is selected and averaged by the cumulative number of luminance signals in the block of the cumulative luminance at the arbitrary stage to represent the representative value. On the other hand, when the brightness matrix is generated, if the brightness is equal to or less than a predetermined threshold value, the accumulated brightness of all stages is selected and integrated, and then the representative brightness matrix is generated by averaging with the total accumulated number. , The brightness level in the block can be accurately reflected, and the backlight, forward light, and over-direct light can be determined more accurately.

According to the fifth aspect of the present invention, the state determining means determines that the luminance level obtained from any one or a plurality of blocks of the weighted luminance matrix is within the range of the reference luminance level. In such a case, the weighted luminance matrix generation means is configured to set the weight of the accumulated luminance at the high luminance side to be smaller than 1.0.
Regardless of the position of the subject, it is possible to accurately determine whether the subject is backlit, forward-lit, or over-directed.

According to the invention described in claim 6, the state determining means determines the state of forward light, back light, and over-forward light using the representative luminance matrix, the ratio matrix, and the weighted luminance matrix. Backlit, forward light,
It is possible to more accurately determine over-ordered light.

According to the seventh aspect of the present invention, the state judging means divides the representative luminance matrix and the ratio matrix into a plurality of regions, and sets the contrast ratio of luminance between arbitrary regions of the representative luminance matrix to a predetermined threshold. As a result of comparing with the value,
In addition, a state of forward light, back light, or over-forward light is determined based on a correction amount for setting a luminance level obtained from any one or a plurality of blocks in the weighted luminance matrix as a reference luminance level. Therefore, it is possible to more accurately determine backlight, forward light, and excessive forward light.

According to the eighth aspect of the present invention, the correction amount calculating means uses the judgment result of the state judging means and a luminance level obtained from one or a plurality of arbitrary blocks in the weighted luminance matrix as a reference luminance level. Since the exposure correction amount is calculated based on the correction amount for
More appropriate exposure control can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment (Embodiment 1) of a digital video camera according to the present invention.

FIG. 2 is a diagram for explaining a method of dividing a luminance signal into two stages according to luminance levels.

FIG. 3 is a diagram illustrating an example of area division of a screen block.

FIG. 4 is a flowchart illustrating a correction amount calculation process performed by a state detection circuit 22 and a correction amount generation circuit 23;

FIG. 5 is a flowchart illustrating a backlight, over-direct light, or forward light determination process in the correction amount calculation process illustrated in FIG. 4;

FIG. 6 is a flowchart for explaining a brightness contrast comparison process in the backlight, over-forward light, or forward light determination process shown in FIG. 5;

FIG. 7 is a flowchart for explaining area 3 and 4 comparison processing in the luminance contrast comparison processing shown in FIG. 6;

8 is a flowchart for explaining RH and area 1 high luminance portion comparison processing in the luminance contrast comparison processing shown in FIG. 6;

9 is a flowchart for explaining the RM and area 2 high-luminance part comparison processing in the RM and area 1 high-luminance part comparison processing shown in FIG. 8;

FIG. 10 is a flowchart illustrating a process of comparing the RH and the luminance portion in area 1 in the brightness contrast comparison process illustrated in FIG. 6;

11 is a flowchart for explaining the RH and area 2 middle luminance part comparison processing in the RH and area 1 middle luminance part comparison processing shown in FIG. 10;

FIG. 12 is a diagram showing transition of luminance values of Yc and Ycw around a reference luminance level at the time of backlight.

FIG. 13 is a block diagram illustrating a configuration of a digital video camera according to an embodiment (Embodiment 2) of the present invention.

FIG. 14 illustrates a conventional technique, and illustrates an example of division of a screen (image).

FIG. 15 illustrates a conventional technique, and illustrates an example of division of a screen (image) in a backlight state.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Digital video camera 11 Lens 12 Aperture 13 CCD 14 CDS circuit 15 AGC circuit 16 A / D converter 17 Image signal processing circuit 18 Luminance division circuit 19 Weighted luminance matrix generation circuit 20 Ratio matrix generation circuit 21 Representative luminance matrix generation circuit 22 State detection circuit 23 Correction amount generation circuit 24 Exposure control circuit 31 CCD camera unit 32 A / D converter 33 Image signal processing unit 34 Frame memory 35 Various brightness matrix generation units 36 Exposure correction unit 37 Memory card 38 CPU 39 CCD camera control unit

Claims (8)

[Claims] 1. A digital video camera for performing exposure control by judging forward light, back light, and over-direct light, wherein a part or the whole of a screen is divided into a plurality of blocks, and a luminance signal is set to a high or low level of luminance. Depending on the stage,
A luminance dividing unit that accumulates the luminance signal for each stage in each block to calculate the cumulative luminance for each stage and generates a cumulative luminance matrix; and weights the cumulative luminance of the cumulative luminance matrix to generate a weighted luminance matrix. Weighted luminance matrix generating means, and a ratio matrix generating means for calculating, in each block, a ratio of the cumulative number of luminance signals for each cumulative luminance to the total cumulative number of luminance signals in the block to generate a ratio matrix. Based on the ratio matrix, for each block from the cumulative luminance matrix, select a cumulative luminance of an arbitrary stage from a plurality of cumulative luminances, select an arbitrary number of luminance signals, and generate a representative luminance matrix. A luminance matrix generating means, and a state determining means for determining a state of forward light, back light, or excessive forward light based on the representative luminance matrix. And a correction amount calculating means for calculating an exposure correction amount based on a determination result of the state determining means; calculating an exposure control amount based on the exposure correction amount; and performing exposure control based on the exposure control amount. A digital video camera, comprising: exposure control means. 2. The method according to claim 1, wherein the state determination unit determines that an average value of all the blocks in the area including one or a plurality of arbitrary blocks of the weighted luminance matrix or a maximum value in the entire blocks is within a range of a reference luminance level. If
2. The digital video camera according to claim 1, wherein a state of forward light, back light, and excessive forward light is determined. 3. The weighted luminance matrix generation means generates a weighted luminance matrix by setting all weights to 1.0, and the state determination means generates an arbitrary one or a plurality of blocks of the weighted luminance matrix. If the brightness level obtained from is within the range of the reference brightness level,
2. The digital video camera according to claim 1, wherein a state of forward light, back light, and excessive forward light is determined. 4. The representative luminance matrix generating means refers to the ratio matrix, and in each block of the ratio matrix, determines a ratio of cumulative luminance at an arbitrary stage to a total cumulative number of luminance signals in the block by a predetermined value. When the threshold value is larger than the threshold value, the arbitrary level of the cumulative luminance is selected and averaged by the cumulative number of the luminance signals in the block of the arbitrary level of the cumulative luminance to generate the representative luminance matrix, 2. The digital video camera according to claim 1, wherein when the difference is equal to or less than the threshold value, the accumulated luminance of all stages is selected and integrated, and then averaged by the total accumulated number to generate a representative luminance matrix. . 5. The weighted luminance, when the state determination means determines that a luminance level obtained from any one or a plurality of blocks of the weighted luminance matrix is within a range of a reference luminance level. 2. The digital video camera according to claim 1, wherein the matrix generating means sets the weight of the accumulated luminance at the high luminance side to be smaller than 1.0. 6. The apparatus according to claim 1, wherein the state determining unit determines the state of the forward light, the backward light, and the over-direct light using the representative luminance matrix, the ratio matrix, and the weighted luminance matrix. 2. The digital video camera according to 1. 7. The result of comparing the representative luminance matrix and the ratio matrix into a plurality of regions and comparing a contrast ratio of luminance between arbitrary regions of the representative luminance matrix with a predetermined threshold value. And determining the state of forward light, back light, or over-direct light based on a correction amount for setting a luminance level obtained from any one or a plurality of blocks in the weighted luminance matrix as a reference luminance level. The digital video camera according to claim 5, wherein 8. The correction amount calculating means for correcting a determination result of the state determining means and a luminance level obtained from any one or a plurality of blocks in the weighted luminance matrix as a reference luminance level. Based on quantity
The digital video camera according to claim 7, wherein an exposure correction amount is calculated.