JP2000201295A - Digital still video camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a digital still video camera capable of performing appropri ate exposure control even when an object includes back light, excessive follow light and a local high luminance part. SOLUTION: This digital still video camera is provided with a block dividing circuit 18 which divides part or all of an image into plural blocks, a luminance change rate calculation circuit 20 which calculates the change rate of the luminance level of each block and the change rate of a luminance level distribution of the block, a back light and high luminance detection circuit 21 which discriminates back light, excessive follow light and a high luminance part on the basis of the calculation results of the circuit 20 and also eliminates a high luminance block, a correction quantity generation circuit 22 which calculates exposure correction quantity based on the decision results of the circuit 21 and an exposure control circuit 23 which calculates exposure control quantity based on the exposure correction quantity and performs exposure control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a digital still video camera, and more particularly, to a digital still video camera that determines backlight, over-directed light, and a high-luminance portion 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. 19, the captured two-dimensional image is divided into 4 × 4 blocks (a to
p) and, for example, in a backlight state where the central person is darkly sunk as shown in FIG. 20, 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.

[0004]

However, in the video camera described in Japanese Patent Laid-Open No. 6-225205, the backlight or the over-directed light is changed by changing the correction reference value. Depending on the position or size of the subject, the difference in luminance between the subject in the backlight state as shown in FIG. 20 and the other portions is not accurately reflected,
There is a problem that the detection of the backlight, the forward light, and the over-direct light fails, so that an appropriate exposure correction value cannot be calculated, and accurate exposure control cannot be performed. This problem is the same also when a high brightness thing is included locally.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made in consideration of a digital still which can perform appropriate exposure control even in a case of a subject including a backlight, an over-direct light, and a local high-luminance portion. It is intended to provide a video camera.

[0006]

In order to solve the above-mentioned problems, the invention according to claim 1 comprises a block dividing means for dividing a part or the whole of a screen into a plurality of blocks, and a luminance level of each block. A luminance change rate calculating means for calculating a change rate and a change rate of the distribution of the luminance level of the block; and, based on a calculation result of the luminance change rate calculating means, determining a backlight, an over-sequential light, and a high luminance portion, and A backlight high-luminance detecting means for deleting a high-luminance block; a correction-amount generating means for calculating an exposure correction amount based on a determination result of the backlight high-luminance detecting means; and an exposure control amount based on the exposure correction amount. Exposure control means for performing exposure control.

According to a second aspect of the present invention, in the first aspect of the present invention, the brightness change rate calculating means is configured to execute the block based on a brightness signal acquired at each lens position when a focus lens is moved. Calculating the rate of change of the luminance level for each of the blocks and the rate of change of the distribution of the luminance level of the block, wherein the backlight high luminance detecting means calculates the result of the luminance change rate calculating means and the divided blocks. The backlight, the over-order light, and the high-luminance portion are determined based on the luminance ratio between areas composed of arbitrary plural blocks.

According to a third aspect of the present invention, in the first aspect of the present invention, the backlight high-intensity detecting means focuses after moving the focus lens from infinity to a close side or in a hill-climbing scan. After detecting the position, the backlight, over-directed light, and high-luminance portion are determined, and the high-luminance block is deleted.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the backlight high-luminance detecting means converts a block having a luminance level or a change rate of the luminance level larger than a predetermined threshold into a high-luminance block. Is to be deleted.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the backlight high luminance detecting means includes a backlight, an over-normal light, and a high light based on a calculation result of the luminance change rate calculating means. The luminance constant is determined and a state constant is set, and the correction amount generation means calculates the exposure correction amount based on the state constant.

According to a sixth aspect of the present invention, in the first aspect of the present invention, the backlight high-luminance detecting means increases the high-luminance when the rate of change of the luminance level distribution of the block is larger than a predetermined threshold. It is determined that there is a copy.

[0012]

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

(Embodiment 1) FIG. 1 shows an embodiment of a digital still video camera according to the present invention (Embodiment 1).
FIG. 1, reference numeral 1 denotes a digital still video camera. This digital still video camera 1 has a lens 11, an aperture 12, a CCD 1
3. CDS (double correlation sampling) circuit 14, AGC
Circuit 15, A / D converter 16, image signal processing circuit 17,
A block generation circuit 18, a state detection circuit 19, a luminance change rate calculation circuit 20, a backlight high luminance detection circuit 21, a correction amount generation circuit 22, an exposure control circuit 23, a focus control circuit 24,
And a focus drive circuit 25.

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 correlatively double-samples the output signal of the CCD 13 to reduce noise of the output signal of the CCD 13.

The AGC circuit 15 is connected to the CDS circuit 14, and adjusts the gain of the output signal of the CDS circuit 14 to correct the signal level. 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 output digital image data.

The image signal processing circuit 17 includes an A / D converter 1
6 performs normal video signal processing such as gamma correction and color separation on the digital image data input from
It generates and outputs a luminance signal and a color difference signal conforming to the C system. The block generation circuit 18 divides a part or the whole of the screen into a plurality of blocks, and
Are accumulated in each block to calculate the accumulated luminance for each block.

The state detection circuit 19 determines whether or not the luminance level of the accumulated luminance of each block is within a reference range based on the output of the block generation circuit 18. Further, the luminance change rate calculation circuit 20 calculates the change rate of the luminance level for each block and the change rate of the distribution of the luminance levels of the blocks.

The backlight high-luminance detection circuit 21 detects a backlight, an over-direct light, a high-luminance part, and deletes a high-luminance block based on the calculation result of the luminance change rate calculation circuit 20. The correction amount generation circuit 22 calculates an exposure correction amount based on the determination result of the backlight high luminance detection circuit 21. Exposure control circuit 23
Calculates the exposure control amount based on the exposure correction amount calculated by the correction amount generation circuit 22, and calculates the aperture value of the aperture 12,
Exposure control is performed by controlling the shutter speed 13, the gain value of the AGC circuit 14, and the like. Also, the focus control circuit 2
Reference numeral 4 generates focus information and calculates a position where the subject is in focus (an in-focus position). Focus drive circuit 25
Drives the lens 11.

In the configuration shown in FIG. 1, the block generating circuit 18 is a block dividing means, the luminance change rate calculating circuit 20 is a luminance change rate calculating means, and the backlight high luminance detecting circuit 21 is a backlight high luminance detecting means. The correction amount generation circuit 22 realizes a correction amount generation unit, and the exposure control circuit 23 realizes an exposure control unit.

Next, detailed processing contents of the block generation circuit 18, the state detection circuit 19, the luminance change rate calculation circuit 20, the backlight high luminance detection circuit 21, the correction amount generation circuit 22, and the exposure control circuit 23 will be described in order. .

[Block Generation Circuit 18] As described above, the block generation circuit 18 divides an input image (screen) into a plurality of blocks, accumulates a luminance signal in each block, and calculates the accumulated luminance of each block. calculate. Hereinafter, a case in which the block generation circuit 18 generates the accumulated luminance of 8 × 6 blocks as shown in FIG. 2 will be described as an example. Assume that the accumulated luminance of the 8 × 6 block when the focus position is at the infinity position is Y (i, j) (i = 1 to 8, j =
1-6). Also, a case where an 8 × 6 block is divided into areas 1 to 6 as shown in FIG. 2 will be described as an example. In the figure, it is assumed that area 5 does not include area 6.

[State Detector 19] State Detector 19
Determines whether the luminance level of an arbitrary area is within the reference range based on the output of the block generation circuit 18 as described above. Here, the operation of the state detection circuit 19 is shown in FIG.
This will be described with reference to FIG. FIG. 3 is a flowchart for explaining the operation of the state detection circuit 19. In FIG. 3, it is assumed that the luminance level is not within the range of the reference luminance level in the initial state.

First, under the control of the exposure control circuit 23, C
The CD 13 is exposed by pEV (step S10).
1). The state detection circuit 19 determines whether or not the luminance level Yc of an arbitrary area 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 <Yu_Thrd (step S
102). Here, Y1_Thrd and Yu_Thrd are lower and upper thresholds that determine the range of the reference luminance level. Yc is, for example, the area 5 and the area 6 in FIG.
Is calculated as the average value of all the blocks in the following equation (1). Yc = {Y (i, j) / 16} (1) where i = 3-6, j = 2-5 As described above, Y (i, j) indicates the accumulated luminance of each block. .

As a result of this determination, Y1_Thrd <Yc <Yu
If it is not within the range of _Thrd, the exposure control circuit 23 changes the exposure amount to expose the CCD 13 with the exposure amount qEV (step S103), and obtains the luminance of the luminance signal obtained as a result of the exposure with the exposure amount qEV. Level is Y1_Thrd
It is determined whether <Yc <Yu_Thrd or not (step S102).

On the other hand, if it is within the range of Y1_Thrd <Yc <Yu_Thrd, the process proceeds to step S104, and the correction amount generation circuit 22 calculates CV. Where C
V is a correction amount up to a reference value T using Yc as a reference luminance level, and is calculated by, for example, the following equation (2). CV = −log 2 (T / Yc) ‥‥‥ (2)

Then, the exposure control circuit 23 uses the exposure amount of p + CV (q + CV) EV in the imaging for calculating the exposure correction amount mEV in the correction amount generation circuit 22 thereafter.
3 is exposed (step S105).

When implementing, CV
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, when the photometric range is 9 to 17 EV, p = 13,
If q = 16, the entire area can be covered.

The luminance level Yc of an arbitrary area is
Within the range of the reference luminance level (Y1_Thrd <Yc <Yu_
In the case of Thrd), the focus control circuit 24 calculates the in-focus position. Such an in-focus position is determined using, for example, a hill-climbing servo system. The focus control circuit 24 controls the focus drive circuit 25 to control the lens 1
The focus information is calculated by extracting a high frequency component of a luminance signal obtained by capturing an image while driving 1 by a band-pass filter or the like. Then, the focus control circuit 24 determines the lens position at which the high frequency component of the luminance signal is maximum as the focus position. Also, when driving a lens that performs a hill-climbing servo, photometry is performed at arbitrary step intervals,
Also, luminance information for determining a high luminance portion is acquired.

[Brightness Change Rate Calculation Circuit 20] The brightness change rate calculation circuit 20 calculates the change rate of the luminance signal for each block and the change rate of the luminance signal distribution of the block, as described above. Here, the operation of the luminance change rate calculation circuit 20 is shown in FIGS.
This will be described with reference to FIG. Hereinafter, a case will be described as an example where a luminance signal is obtained at n points from the infinity position to the close side of the focus area or until the in-focus position is detected by the hill-climbing scan. Note that it is difficult to obtain the luminance signal a plurality of times within the depth of field because the rate of change of the luminance signal is difficult to obtain even when the acquisition is performed a plurality of times within the depth of field. In this case, the cumulative luminance of the 8.times.6 block is defined as Y1 (i, j) to Yn (i, j) (where,
i = 1-8, j = 1-6).

FIG. 4 is a diagram showing an example of a scene on the screen. FIG. 5 shows a part of the screen of FIG. 4 as blocks A, B, and C, and the lens positions of the blocks A, B, and C are ∞ to Near.
The luminance level at each point (1 to n) is shown. In FIG. 4, a block A shows a part of the subject that is backlighting. Block B shows a case where a part of the block includes a considerably high luminance one and the high luminance part is located at infinity. Block C shows a case where the whole of the block has relatively high brightness.

In FIG. 5, the abscissa indicates a point position at which a luminance signal is obtained from infinity to the closest side of the focus area, and the ordinate indicates a luminance level. As shown in the drawing, the luminance levels increase in the order of blocks B, C, and A.

FIG. 6 shows an 8 × 6 image in the scene shown in FIG.
FIG. 7 shows an example of the distribution of the luminance level on the infinite side of the cumulative luminance of the block, and FIG. 7 shows an example of the distribution of the luminance level on the nearest side of the cumulative luminance of the 8 × 6 block in the scene shown in FIG.
6 and 7, the vertical axis represents the number of distributions, and the horizontal axis represents the luminance level.

By the way, except for an extremely dark case, the brightness level of a light source or the like having no local high-brightness portion is relatively constant regardless of the focus position. On the other hand, in the case where there is a local high-luminance portion such as a light source, the range of the high-luminance portion increases as the amount of blur increases, so that the proportion of the high-luminance portion in the block increases, and FIG. The luminance level distribution is as shown in FIG.

The luminance change rate calculation circuit 20 calculates the change rate of the luminance level for each block by, for example, the following equation (3). y_rate (i, j) = min {Yf (i, j)} / max {Yg (i, j)} (3) where i = 1 to 8, j = 1 to 6 y_rate (i, j): Rate of change in luminance level of an arbitrary block min {Yf (i, j)}: Y1 (i, j) to Yn (i, j)
j) the minimum value max {Yg (i, j)}: Y1 (i, j) to Yn (i, j)
the maximum value in j)

The luminance change rate calculation circuit 20 calculates the change rate of the distribution of the luminance levels of the blocks as follows. In the distributions shown in FIGS. 6 and 7, the distribution is divided into m parts Y1 to Ym according to the luminance level, and the number of distributions is obtained for each of Y1 to Ym. Let Ninf be the number of each distribution at infinity
(Y1) to Ninf (Ym), and when the distribution numbers on the nearest side are Nnear (Y1) to Nnear (Ym), Y
The absolute value differences D1 to Dm of the distribution numbers on the infinity side and the closest side in 1 to Ym can be represented by the following equations (4). D1 = | Ninf (Y1) -Nnear (Y1) | :::: Dm = | Ninf (Ym) -Nnear (Ym) | ‥‥‥ (4)

Then, the change rate Drate of the distribution of the luminance level
Can be expressed as in the following equation (5). Drate = {Dk / (total × 2) (k = 1 to m)} (5) where, total: total number of distributions (total number of blocks)

FIG. 8 shows D in the distributions of FIGS.
Examples of 1 to Dm are shown. The division according to the luminance level does not need to be performed in the whole range, but may be simply limited to a range of a predetermined luminance level or more and divided into Y1 to YP. In this case, the total number of distributions total is the total number of distributions at or above a predetermined luminance level, and this example is shown in FIG.

[Backlight high luminance detection circuit 21] The backlight high luminance detection circuit 21 is, as described above, a luminance change rate calculation circuit 20.
Based on the calculation result of (1), forward light, back light, over-forward light, detection of a high-luminance portion, and deletion of a high-luminance block are performed. here,
The operation of the backlight high luminance detection circuit 21 will be described with reference to FIGS. FIG. 10 is a flowchart for explaining the operation of the backlight high luminance detection circuit 21. FIG. 11 shows FIG.
9 is a flowchart illustrating a backlighting process of 0.
FIG. 12 is a flowchart for explaining the over-order light processing of FIG.

FIG. 10 shows an example when the center is emphasized. Y_a1, y_a2, y_a5, y_a6 shown in FIG.
Represents Y (i, i, y) in each of areas 1, 2, 5, and 6 shown in FIG.
j) indicates the average of the total blocks, st_nl1, st_nl2,
st_nl3 indicates a state constant of forward light.

In FIG. 10, the backlight high luminance detection circuit 21
Determines whether there is a luminance ratio between y_a5 and y_a6 (step S111). If there is a luminance ratio between y_a5 and y_a6, the process proceeds to step S112 while y_a5
If there is no luminance ratio between y_a6 and y_a6, step S115
Move to

More specifically, whether or not there is a luminance ratio between y_a5 and y_a6 is determined as follows. First, y_a5> y
In the case of _a6, it is determined that there is a luminance ratio when y_a6 × Y_THRD <y_a5 is satisfied, and there is no luminance ratio when y_a6 × Y_THRD <y_a5 is not satisfied. On the other hand, when y_a5 <y_a6, it is determined that there is a luminance ratio when y_a5 × Y_THRD <y_a6 is satisfied, and when there is not y_a5 × Y_THRD <y_a6, there is no luminance ratio. Here, Y_THRD is a predetermined threshold value for the luminance ratio, and Y_THRD ≧ 1. Note that y_a5 = y
In the case of _a6, there is no luminance ratio.

In step S112, the backlight high luminance detection circuit 21 determines whether y_a5> y_a6 or not, and y_a5> y.
If y_a6, it is determined that the light is backlit, and the backlight processing is performed (step S113). On the other hand, if y_a5> y_a6, it is determined that the light is over-directed and the over-light processing is performed (step S11).
4).

In step S115, the backlight high luminance detection circuit 21 determines whether or not there is a luminance ratio between y_a1 and y_a6 (step S111). If there is a luminance ratio between y_a1 and y_a6, Goes to step S116, while y
If there is no luminance ratio between _a1 and y_a6, step S1
Move to 17.

Specifically, the determination as to whether or not there is a luminance ratio between y_a1 and y_a6 is performed as follows. First, y_a1> y
In the case of _a6, it is determined that there is a luminance ratio when y_a6 × Y_THRD <y_a1 is satisfied, and it is determined that there is no luminance ratio when y_a6 × Y_THRD <y_a1 is not satisfied. On the other hand, when y_a1 <y_a6, it is determined that there is a luminance ratio when y_a1 × Y_THRD <y_a6 is satisfied, and when no y_a1 × Y_THRD <y_a6 is satisfied, there is no luminance ratio. Here, Y_THRD is a predetermined threshold value for the luminance ratio, and Y_THRD ≧ 1. Note that y_a1 = y
In the case of _a6, there is no luminance ratio.

In step S116, the backlight high luminance detection circuit 21 determines whether or not y_a1> y_a6, and y_a1> y.
If y_a6, it is determined that the light is backlit and the backlighting process is performed (step S113). On the other hand, if y_a1> y_a6, it is determined that the light is over-directed and the over-lighting process is performed (step S11).
4).

In step S117, the backlight high luminance detection circuit 21 determines whether or not there is a luminance ratio between y_a6 and y_a2. If there is a luminance ratio between y_a6 and y_a2, step S118. On the other hand, when there is no luminance ratio between y_a6 and y_a2, the flow shifts to step S119.

More specifically, whether or not there is a luminance ratio between y_a6 and y_a2 is determined as follows. First, y_a2> y
In the case of _a6, it is determined that there is a luminance ratio when y_a6 × Y_THRD <y_a2 is satisfied, and there is no luminance ratio when y_a6 × Y_THRD <y_a2 is not satisfied. On the other hand, in the case of y_a2 <y_a6, it is determined that there is a luminance ratio when y_a2 × Y_THRD <y_a6 is satisfied, and it is determined that there is no luminance ratio when y_a2 × Y_THRD <y_a6 is not satisfied. Here, Y_THRD is a predetermined threshold value for the luminance ratio, and Y_THRD ≧ 1. Note that y_a2 = y
In the case of _a6, there is no luminance ratio.

In step S118, the backlight high luminance detection circuit 21 determines whether or not y_a2> y_a6, and y_a2> y.
If _a6, it is determined that the subject is backlit, and a backlight process is performed (step S113). On the other hand, if y_a2> y_a6 is not satisfied, it is determined that the light is over-ordered, and the over-ordered light processing is performed (step S1).
14).

In step S119, the backlight high-luminance detection circuit 21 determines whether there is a light source in the areas 5 and 6. If it is determined that there is a light source in the areas 5 and 6, step S120. On the other hand, if it is determined that there is no light source in the areas 5 and 6, the process proceeds to step S122.

In step S120, the backlight high-luminance detection circuit 21 sets st_nl1 as a state constant of forward light, and performs high-luminance removal processing (step S121). The details of the high luminance removal processing will be specifically described. The backlight high luminance detection circuit 21 determines that Y (i, j)> high_
thrd or y_rate (i, j)> high_rate_thrd
Delete block. Here, high__thrd is a predetermined threshold for determining a high luminance level, and high_rate_thrd is a predetermined threshold for determining a luminance change rate of high luminance.

Block Y (i, j) that is not deleted
Is YM (i, j) and the number is Ym_co.
When _co is equal to or less than a predetermined threshold, the representative luminance RY can be expressed as in the following equation (6). When Ym_co is not equal to or less than the predetermined threshold, the representative luminance RY is expressed as in the following equation (7). be able to.

RY = {Y (i, j) / 16 (i = 3 to 6, j = 2 to 5)} (6) RY = {YM (i, j) / Ym_co} (7)

On the other hand, in step S122, the backlight high luminance detection circuit 21 determines whether or not there is a light source in the areas 1, 2, 3, and 4, and there is a light source in the areas 1, 2, 3, and 4. If it is determined that st_nl3 is set as the state constant (step S123), and if it is determined that there is no light source in the areas 1, 2, 3, and 4, st_nl2 is set as the state constant (step S124).

Next, the backlight process of step S113 will be described with reference to the flowchart of FIG. St in the figure
_Bl1 and st_bl2 indicate state constants of backlight. In FIG. 11, the backlight high luminance detection circuit 21 determines whether there is a light source in the areas 5 and 6 (step S131). As a result of this determination, if there is a light source in the areas 5 and 6, st_bl1 is set as the state constant of the backlight (step S13).
2) If there is no light source in the areas 5 and 6, st_bl2 is set as a state constant of backlight (step S133).
Specifically, the presence / absence of a light source is determined when the change rate Drate of the luminance level distribution is Drate> Drate_thrd, and it is determined that there is no light source when Drate> Drate_thrd is not satisfied. Here, Drate_thrd indicates a predetermined threshold for determining the presence or absence of a light source. The total number of distributions when calculating Drate indicates the total number of blocks in the area.

Next, the over-order light processing in step S114 will be described with reference to the flowchart in FIG. In the same figure
st_ol1 and st_ol2 indicate state constants of over-ordered light. FIG.
2, the backlight high luminance detection circuit 21
It is determined whether there is a light source inside (step S14)
1). As a result of this determination, if there is a light source in the areas 5 and 6, st_ol1 is set as a state constant of over-directed light (step S142). St_ol2 is set as a constant (step S133). The method of determining the presence or absence of a light source is the same as described above, and a description thereof will be omitted.

[Correction amount generation circuit 22] Correction amount generation circuit 2
Reference numeral 2 denotes the normal light (st_nl1, st_nl2, st_nl3) and the backlight (st_bl1,...) Of the backlight high luminance detection circuit 21 as described above.
The exposure correction amount mEV is calculated based on the determination results of the st_bl2) and the over-direct light (st_ol1, st_ol2). The operation of the correction amount generation circuit 22 will be described with reference to FIGS. FIG. 13 is a flowchart for explaining the operation of the correction amount generation circuit 22.

First, variables used in the description of the flowchart of FIG. 13 will be described. CMP: prescribed correction amounts w_bl1, w_bl2: respective correction coefficients w_ol1 and w_ol2 for st_bl1 and st_bl2: st_ol1 and correction coefficients w_nl1 for st_ol2 and w_nl2 for w_nl1 and st_nl2 for st_ol2 Correction coefficient w_nl31, w_nl32: correction coefficient ev_thrd in the case of st_nl3: a predetermined threshold value (Ev) representing luminance. In the figure, is the luminance greater than ev_thrd? Means that the absolute luminance (Ev) at the time of photometry using areas 5 and 6 is ev_th
Is it greater than rd? "

The above-mentioned correction coefficients w_bl1, w_bl2, w
_Ol1, w_ol2, w_nl1, w_nl2, w_nl31, w
_Nl32 has the following characteristics. | W_bl1 | ≧ | w_bl2 |, and w_bl1, w_
bl2 is a correction coefficient such that the reference value T is over the reference value T. | W_ol1 | ≦ | w_ol2 |, where w_ol1 and w_
ol2 is a correction coefficient that makes the reference value T be in an under direction. | W_nl31 | ≧ | w_nl32 |, and w_nl31, w_
nl32 is a correction coefficient that makes the reference value T exceed the reference value T. | W_nl2 | ≦ | w_nl32 |, where w_nl2 is a delicate correction coefficient such that the reference value T is over or under. w_nl1 is a delicate correction coefficient such that the reference value T is over or under.

In FIG. 13, the correction amount generation circuit 22
The state constant set by the backlight high luminance detection circuit 21 is determined, and the exposure correction amount mEV is calculated. Specifically, first,
The correction amount generation circuit 22 determines whether or not st_bl1 is set as a state constant (step S151). If st_bl1 is not set as the state constant, the correction amount generation circuit 22 proceeds to step S152,
If st_bl1 is set as the state constant, the exposure correction amount mEV is calculated by the following equation (8) (step S158). mEV = CMP × w_bl1 ‥‥‥ (8)

In step S152, the correction amount generation circuit 2
No. 2 determines whether or not st_bl2 is set as the state constant. The correction amount generation circuit 22 uses st as a state constant.
If _bl2 is not set, the process proceeds to step S153, while if st_bl2 is set as the state constant, the exposure correction amount mEV is calculated by the following equation (9) (step S159). mEV = CMP × w — bl2 (9)

In step S153, the correction amount generation circuit 2
Step 2 determines whether or not st_ol1 is set as the state constant. The correction amount generation circuit 22 uses st as a state constant.
If _ol1 is not set, the process proceeds to step S154, while if st_ol1 is set as the state constant, the exposure correction amount mEV is calculated by the following equation (10) (step S160). mEV = CMP × w_ol1 ‥‥‥ (10)

In step S154, the correction amount generation circuit 2
No. 2 determines whether or not st_ol2 is set as a state constant. The correction amount generation circuit 22 uses st as a state constant.
If _ol2 is not set, the process proceeds to step S155, while if st_ol1 is set as the state constant, the exposure correction amount mEV is calculated by the following equation (11) (step S161). mEV = CMP × w_ol2 ‥‥‥ (11)

In step S155, the correction amount generation circuit 2
2 determines whether or not st_nl1 is set as a state constant. The correction amount generation circuit 22 uses st as a state constant.
If _nl1 has not been set, the process proceeds to step S156, while if st_nl1 has been set as the state constant, the exposure correction amount mEV is calculated by the following equation (12) (step S162). mEV = −log 2 (T / RY) + CMP × w —nl1 (12)

In step S156, the correction amount generation circuit 2
No. 2 determines whether or not st_nl2 is set as a state constant. The correction amount generation circuit 22 uses st as a state constant.
If _nl2 is not set, the process proceeds to step S157, while if st_nl2 is set as the state constant, the exposure correction amount mEV is calculated by the following equation (13) (step S163). mEV = CMP × w — nl2 (13)

In step S157, the correction amount generation circuit 2
2 judges whether or not st_nl3 is set as a state constant. The correction amount generation circuit 22 uses st as a state constant.
If _nl3 is set, step S164
To determine whether the luminance is greater than ev_thrd. As a result of this determination, the correction amount generation circuit 22 determines that the luminance is ev_thrd
If it is larger, the flow shifts to step S165 to calculate the exposure correction amount mEV by the following equation (14). on the other hand,
If the luminance is not greater than ev_thrd, step S1
66, and the exposure correction amount mEV is calculated by the following equation (15).
Is calculated. mEV = CMP × w_nl31 (14) mEV = CMP × w_nl32 (15)

Next, specific image examples of the backlit state, the over-directed state, and the forward-lit state are shown in FIGS. In FIGS. 14 to 17, “Yes” and “No” correspond to FIG.
The luminance ratios between arbitrary areas, which are a group of predetermined blocks that are being compared, indicate “present” and “absent”, respectively.

FIG. 14 shows that the state constant is st_bl1 (backlit state).
The following is an example of the image. FIG. 3 is an example of an image including a high-luminance portion such as a light source, which is backlit. In the image shown in the drawing, there is a luminance ratio between the areas, and it is determined that the image is a backlight, and it is also determined that there is a high luminance part. Therefore, in the image as shown in FIG. 11, the image is backlit and the exposure is underexposed, including a local high-luminance portion such as a light source.

FIG. 15 shows an example of an image in which the state constant is st_ol1 (excessive light state). FIG. 3 is an example of an image that includes a local high-luminance portion such as a light source that is over-ordered light. In the image shown in the figure, there is a luminance ratio between the areas, it is determined that the light is over-ordered, and it is determined that there is a high luminance part. Therefore, the exposure is over-exposed, but also includes a local high-luminance portion such as a light source.

FIG. 16 shows that the state constant is st_nl1 (direct light state).
The following is an example of the image. This figure is an example of an image in which a subject is small, includes a local high-luminance portion such as a light source in a block, and has no luminance ratio between areas. In the image shown in the figure, the backlight is not determined from the luminance ratio between the areas,
It is determined that there is a high luminance portion. Therefore, since the image as shown in FIG. 7 includes a high luminance portion, the high luminance portion is deleted and photometry is performed again.

FIG. 17 shows that the state constant is st_nl3 (direct light state).
The following is an example of the image. This figure is an example of an image in which a peripheral portion includes a local high luminance portion such as a light source and the peripheral portion is considerably bright. Therefore, although there is no luminance ratio between the areas, in the image as shown in FIG. 11, the exposure is underexposed due to the influence of the peripheral portion, so that the correction is made relatively large toward the over side.

[Exposure control circuit 23] Exposure control circuit 23
Is the exposure correction amount mE output from the correction amount generation circuit 22.
The exposure control amount is calculated based on V, and the aperture value of the aperture 12
Exposure is controlled by controlling the shutter speed of the CCD 13, the gain value of the AGC circuit 16, and the like.

As described above, in the above-described embodiment, the block generation circuit 18 divides a part or the whole of the screen into a plurality of blocks, and
0 calculates the change rate of the luminance level for each block and the change rate of the distribution of the luminance level of the block, and the backlight high luminance detection circuit 21 calculates the backlight, the over-direct light, And the high-brightness part is determined, and the high-brightness block is deleted. The correction amount control circuit 22 calculates the exposure correction amount based on the determination result of the backlight high-brightness detection circuit 21, and the exposure control circuit 23 determines the exposure correction amount. Since the exposure control is performed by obtaining the exposure control amount based on the amount, appropriate exposure control can be performed even in the case of a subject including a backlight, an over-direct light, and a local high-luminance portion.

In the above-described embodiment, the luminance change rate calculating circuit 20 calculates the change rate of the luminance level for each block and the luminance of the block based on the luminance signal obtained at each lens position when the focus lens is moved. The change ratio of the level distribution is calculated, and the backlight high luminance detection circuit 21 calculates the luminance result between the luminance change ratio calculation circuit 20 and the luminance ratio between the areas formed by an arbitrary plurality of blocks among the plurality of divided blocks. , The backlight ratio, over-order light, and high-luminance portion are determined, so that the luminance ratio between small high-luminance portions and an arbitrary area in the block can be accurately determined. It is possible to determine the light and the high-luminance part, and to delete the high-luminance block.

Further, in the above-described embodiment, after the backlight high-luminance detecting circuit 21 moves the focus lens from infinity to the closest side, or after detecting the focus position by hill-climbing scan, the backlight or over-direct light is detected. , And the high-luminance portion are determined, and the high-luminance block is deleted. Therefore, it is possible to use the change rate of the luminance level and the change rate of the luminance level distribution in the block obtained after the focus lens is moved. It is possible to accurately determine the backlight, the over-order light, and the high-luminance portion, and to delete the block of the high-luminance portion.

In the above-described embodiment, the backlight high-luminance detection circuit 21 deletes a block whose luminance level or the rate of change of the luminance level is larger than a predetermined threshold value as a high-luminance block. It is possible to cope with a high-luminance part as a whole or a small high-luminance part in a block, and to accurately delete the high-luminance part.

In the above-described embodiment, the backlight high-luminance detection circuit 21 determines the backlight, the over-direct light, and the high-luminance portion based on the calculation result of the luminance change rate calculation circuit 20 and sets the state constant. However, since the correction amount generation circuit 22 calculates the exposure correction amount based on the state constant, it is possible to perform exposure control according to the degree of back light and excessive forward light.

In the above-described embodiment, the backlight high-luminance detection circuit 21 determines that there is a high-luminance portion when the rate of change in the distribution of the luminance levels of the blocks is larger than a predetermined threshold. It is possible to accurately determine a high-luminance portion.

(Embodiment 2) As shown in FIG. 18, a digital processing circuit such as a microprocessor
It is possible to perform the same processing as that of the digital still video camera shown by. FIG. 18 is a block diagram showing a configuration of an embodiment (Embodiment 2) of a digital still video camera according to the present invention.

The digital still video camera shown in FIG. 18 has a CCD camera section 31, an A / D converter 32, an image signal processing section 33, and a frame memory 3 for storing image data.
4, a block generator 35, an exposure corrector 36, a memory card 37, a focus controller 38, a CPU 39, and a CCD camera controller 40.

The CCD camera unit 31 includes the lens 1 shown in FIG.
Aperture 12, CCD 13, CDS circuit 14, and AGC
In the circuit 15, the block generation unit 35 is used in the block generation circuit 18 in FIG. 1, and the exposure correction unit 36 is used in the state detection circuit 19, the luminance change rate calculation circuit 20, the backlight high luminance detection circuit 2 in FIG.
1 and the focus control unit 3
Reference numeral 8 corresponds to the focus control circuit 24 in FIG. 1, and the CCD camera control unit 40 performs the same operation as described above, corresponding to the exposure control circuit 23 and the focus drive circuit 25 in FIG. The CPU 39 controls the operation of each unit.

The present invention is not limited to the above-described embodiment, but can be implemented with appropriate modifications without departing from the spirit of the invention. For example, in the above-described embodiment, an example in which the number of screen blocks is set to 8 × 6 has been described. However, the present invention is not limited to this, and any number of screen blocks may be used. Further, the division of the area is not limited to the above embodiment.

[0082]

As described above, according to the first aspect of the invention, the block dividing means divides a part or the whole of the screen into a plurality of blocks, and the luminance change rate calculating means calculates the luminance level for each block. Calculate the change rate of the distribution of the luminance level of the block and the rate of change, the backlight high luminance detection means, based on the calculation result of the luminance change rate calculation means, determine backlight, over-direct light, and high luminance portion, The high-brightness block is deleted, the correction amount generation unit calculates the exposure correction amount based on the determination result of the luminance detection unit, and the exposure control unit calculates the exposure control amount based on the exposure correction amount to perform exposure control. Therefore, appropriate exposure control can be performed even for a subject including a backlight, an over-direct light, and a local high-luminance portion.

According to a second aspect of the present invention, in the first aspect of the present invention, the luminance change rate calculating means is configured to block based on a luminance signal acquired at each lens position when the focus lens is moved. The change rate of the luminance level for each of the blocks and the change rate of the distribution of the luminance levels of the blocks are calculated, and the backlight high luminance detection means calculates the calculation result of the luminance change rate calculation means and any of the plurality of divided blocks. Backlight,
Since the over-order light and the high-luminance portion are determined, in addition to the effect of the invention described in claim 1, the luminance ratio between a small high-luminance portion and an arbitrary area in the block can be accurately determined. , With high accuracy, determination of backlight, over-ordered light and high brightness part,
In addition, high-luminance blocks can be deleted.

According to a third aspect of the present invention, in the first aspect of the present invention, the backlight high-luminance detecting means moves the focus lens from infinity to the closest side,
Alternatively, after detecting the in-focus position by the hill-climbing scan, the backlight, the over-order light, and the high-luminance portion are determined, and the high-luminance block is deleted. In addition to the above, the change rate of the luminance level and the change rate of the distribution of the luminance level in the block obtained after the movement of the focus lens can be used, and it is possible to accurately determine the backlight, the over-order light, the high-luminance portion, and the high luminance. It is possible to delete some blocks.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the backlight high-luminance detecting means detects a block whose luminance level or a change rate of the luminance level is larger than a predetermined threshold value. Since the block is deleted, in addition to the effect of the invention described in claim 1, it is possible to cope with the case where the whole block has a high luminance portion and the case where the block has a small high luminance portion. It is possible to delete the high luminance portion.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the backlight high-luminance detecting means includes a backlight, over-direct light,
And the high-luminance portion is determined to set a state constant, and the correction amount generating means calculates the exposure correction amount based on the state constant. Exposure can be controlled according to the degree of over-directed light.

According to a sixth aspect of the present invention, in the first aspect of the present invention, the backlight high-luminance detecting means increases the high-luminance when the change rate of the distribution of the luminance level of the block is larger than a predetermined threshold. Because it was decided that there is a part,
In addition to the effect of the first aspect, it is possible to determine a high-luminance portion with high accuracy.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing an example of screen blocks and area division.

FIG. 3 is a flowchart illustrating an operation of the state detection circuit of FIG. 1;

FIG. 4 is a diagram illustrating an example of a scene on a screen.

FIG. 5 shows a case where a part of the screen of FIG. 4 is made up of blocks A, B, and C, and the lens positions of the blocks A, B, and C are ∞ to Ne.
It is a figure which shows the brightness level in each point (1-n) until ar.

6 is a diagram showing an example of a distribution of luminance levels on the infinite side of the accumulated luminance of 8 × 6 blocks in the scene shown in FIG. 4;

7 is a diagram showing an example of a distribution of luminance levels on the closest side of the accumulated luminance of 8 × 6 blocks in the scene shown in FIG. 4;

FIG. 8 is an explanatory diagram (part 1) for describing the number of distributions of luminance levels.

FIG. 9 is an explanatory diagram (part 2) for describing the number of distributions of luminance levels.

FIG. 10 is a flowchart for explaining the operation of the backlight high luminance detection circuit.

FIG. 11 is a flowchart for explaining the backlight process of FIG. 10;

FIG. 12 is a flowchart illustrating the over-order light processing of FIG. 10;

FIG. 13 is a flowchart for explaining the operation of the correction amount generation circuit of FIG. 1;

FIG. 14 is a diagram illustrating a specific image example of a backlight state.

FIG. 15 is a diagram illustrating a specific image example of an over-ordered light state.

FIG. 16 is a view showing a specific image example (part 1) of a normal light state.

FIG. 17 is a diagram illustrating a specific image example (part 1) of a normal light state.

FIG. 18 is a block diagram showing a configuration of an embodiment (Embodiment 2) of a digital still video camera according to the present invention.

FIG. 19 illustrates a conventional technique, and illustrates an example of division of a screen (image).

FIG. 20 illustrates a conventional technique, and illustrates an example of dividing a screen (image) in a backlight state.

[Explanation of symbols]

 Reference Signs List 1 digital still video camera 11 lens 12 aperture 13 CCD 14 CDS circuit 15 AGC circuit 16 A / D converter 17 image signal processing circuit 18 block generation circuit 19 state detection circuit 20 brightness change rate calculation circuit 21 backlight high brightness detection circuit 22 correction Amount generation circuit 23 Exposure control circuit 24 Focus control circuit 25 Focus drive circuit 31 CCD camera unit 32 A / D converter 33 Image signal processing unit 34 Frame memory 35 Block generation unit 36 Exposure correction unit 37 Memory card 38 Focus control unit 39 CPU 40 CCD camera control unit

Claims (6)

[Claims] 1. A block dividing means for dividing a part or the whole of a screen into a plurality of blocks, and a luminance change rate calculation for calculating a change rate of a luminance level for each block and a change rate of a distribution of luminance levels of the blocks. Means, based on the calculation result of the brightness change rate calculation means, to determine backlight, over-ordered light, and high brightness portion, and a backlight high brightness detection means for deleting a high brightness block; and the backlight high brightness detection A correction amount generation unit that calculates an exposure correction amount based on a determination result of the unit; and an exposure control unit that calculates an exposure control amount based on the exposure correction amount and performs exposure control. Still video camera. 2. The method according to claim 1, wherein the luminance change rate calculation unit calculates a change rate of a luminance level of each block and a change of a luminance level distribution of the block based on a luminance signal acquired at each lens position when a focus lens is moved. Calculating the ratio, the backlight high-luminance detection means, based on the calculation result of the luminance change rate calculation means and the luminance ratio between areas composed of arbitrary plural blocks of the plurality of divided blocks, 2. The digital still video camera according to claim 1, wherein the digital still video camera is configured to determine over-illuminated light, high-order light, and high-luminance part. 3. The backlight high-intensity detecting means, after moving the focus lens from infinity to a close side, or
2. The digital still video camera according to claim 1, wherein after detecting a focus position in the hill-climbing scan, a backlight, an excessively-directed light, and a high-luminance portion are determined, and a high-luminance block is deleted. 4. The digital still video according to claim 1, wherein the backlight high luminance detecting means deletes a block having a luminance level or a change rate of the luminance level larger than a predetermined threshold value as a high luminance block. camera. 5. The backlight high-luminance detecting means determines a backlight, an over-direct light, and a high-luminance part and sets a state constant based on a calculation result of the luminance change rate calculating means, and the correction amount generating means 2. The digital still video camera according to claim 1, wherein the calculating unit calculates the exposure correction amount based on the state constant. 6. The backlight according to claim 1, wherein the backlight high-luminance detecting means determines that there is a high-luminance portion when a change rate of the distribution of the luminance level of the block is larger than a predetermined threshold. Digital still video camera.