JPH08125926A - Exposure controller for digital still video camera - Google Patents

Abstract

PURPOSE: To perform exposure control more suitable for an object by recognizing the position of the object in the scene of backlight, forward light and excessive forward light, etc. CONSTITUTION: In picture element blocks for which a part or the entire part of a photographing screen is divided into (m)×(n) pieces, the positions of the picture element blocks of the minimum value and maximum value of luminance are detected in a minimum value position detection circuit 5 or a maximum value position detection circuit 6. Then, on the photographing screen, the part where the positions where the minimum value or the maximum value is present are gathered is obtained and grouped in a minimum value group constitution circuit 7 or a maximum value group constitution circuit 8. In a decision circuit 9, a picture part where a group is formed is defined as the part equivalent to object pictures and the backlight the forward light and the excessive forward light are decided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure control device for a digital still video camera, which can record a picked-up image by digital signal processing.

[0002]

2. Description of the Related Art As an exposure control method for a conventional video camera or silver halide camera, the object in the center is emphasized, and correction is made by the output from the central photometric area and the exposure amount of the output from the peripheral photometric area. There is one in which the amount is determined so that the subject can obtain an appropriate exposure even in a backlit scene.

For example, as a backlight compensation circuit for a camera, there is one disclosed in Japanese Patent Application Laid-Open No. 2-108374. In this correction circuit, the backlight state is detected from the difference level between the output obtained from the central area and the output obtained from the peripheral area, and in the case of backlight, AGC (automatic gain control) control is performed with the signal in the central area. When it is not backlight, backlight compensation is performed by performing AGC control with the signal of the entire area.

Further, like the automatic exposure controller disclosed in Japanese Patent Laid-Open No. 2-141731, a detection frame as shown in 101 of FIG. 11 is set in the screen, and the detection frame 101 is wobbled up and down. By detecting the brightness pattern as shown in Fig. 12 to Fig. 14 and determining the metering mode, the exposure control is performed based on the result of the determination, so that an appropriate exposure can be obtained for a subject having a large brightness difference from the background. Some allow control.

[0005]

According to the backlight correction disclosed in Japanese Patent Laid-Open No. 2-108374 in the prior art, when the subject is in the center, the backlight is corrected.
That is, although the exposure control at the time of backlighting can be satisfactorily performed, there is a problem that the correction cannot be performed in the other cases.

According to the exposure control disclosed in Japanese Patent Application Laid-Open No. 2-141731, by wobbling the photometric frame up and down and detecting the brightness pattern, the background is vertically aligned as shown in FIGS. 12 to 14. Although it is effective for a subject having a large luminance difference, there is a problem that it is difficult to perform appropriate control when the subject is on the left and right or when the luminance difference occurs in the left and right directions.

In order to solve such a problem, an object of the present invention is to focus on only the central portion even in a backlit scene or to focus on the brightness difference in the vertical direction, and to position the subject. The object of the present invention is to provide an exposure control device for a digital still video camera capable of performing exposure control more suitable for a subject by recognizing.

[0008]

In order to achieve the above object, an exposure control device for a digital still video camera according to the present invention uses a solid-state image sensor to convert the brightness of a subject image into an electric signal and outputs it as a video signal. Then, in the digital still video camera for recording, a dividing means for dividing a part or the whole of the photographic screen into a plurality of blocks, and a detecting means for detecting an image portion exhibiting the same brightness by the brightness signal of each block, Based on the detection result, a grouping means for grouping image parts having similar brightness, and an image part where the group is formed are recognized as an image part corresponding to a subject image, and backlight, forward light, over-forward light And a control means for performing exposure control by generating a correction amount based on the determination result.

Further, the grouping means forms a group of minimum values or a group of maximum values in the divided blocks from the portions where the minimum value or the maximum value of the luminance signal exists in each row and each column. It is characterized in that it is configured to.

Further, in the judgment means, when only the group based on the maximum value of the luminance signal is formed in the divided blocks, the value obtained from the luminance signal in the group and the value obtained from the luminance signal other than the group are compared. In this case, when the ratio of the two values is equal to or more than a preset threshold value, it is determined as over-forward light, and when it is less than the threshold value, it is determined as forward light.

Further, the judging means compares the value obtained from the luminance signal in the group with the value obtained from the luminance signal other than the group, when only the group by the minimum value of the luminance signal is formed in the divided blocks. In this case, when the ratio between the two values is equal to or more than a preset threshold value, the backlight is determined, and when the ratio is less than the threshold value, the backlight is determined.

Further, when the group obtained by the minimum value of the luminance signal and the group obtained by the maximum value of the luminance signal are formed in the divided block, the determining means determines the value obtained from the luminance signal in the group based on the minimum value and the maximum value. When the values obtained from the luminance signals in the groups are compared, the ratio between the two values is equal to or greater than a preset threshold value, and the preset group weight value is large when the group is the minimum value backlight In addition, if the group having the maximum group weight value that is equal to or more than the threshold value is a group with a maximum value, it is over-forwarding, and the group weight value is equal to or more than the threshold value and the group weight value has a minimum value. If it is equal in the group according to the maximum value, it is determined to be forward light, and if it is not more than the threshold value, it is determined to be forward light. And butterflies.

Further, it is characterized in that the judging means is constituted so as to judge a case where the divided blocks do not form the group as a forward light.

In the case where the control means excludes the forward light when the ratio of the two values is equal to or more than the threshold value and the group weight values are equal in the group of the minimum value and the group of the maximum value, It is characterized in that the exposure control is performed by obtaining the exposure correction amount based on the value obtained from the luminance signal in the group.

Further, the control means is configured to perform forward light when the ratio of the two values is equal to or more than the threshold value and the group weight values are equal in the group with the minimum value and the group with the maximum value, and the group. When the image is not generated, the exposure control is performed by obtaining the exposure correction value based on the maximum value of the luminance signal in all the blocks.

[0016]

In the exposure control device of the digital still video camera according to the present invention having the above-described structure, the photographing screen is divided into a plurality of blocks, and an image portion having a luminance corresponding to a part of the subject image is generated by the luminance signal of each block. By detecting and grouping, it is possible to recognize the position and size of the object equivalent to the subject image, and therefore the situation of the shooting scene (backlight, forward light, over-light) can be easily determined, and Appropriate exposure control according to the scene becomes possible.

In general, when the area corresponding to the subject is backlit, the brightness level is considerably lower than the brightness levels other than the object, while the area corresponding to the object is over-illuminated. On the contrary, since it is high, it is possible to increase the ratio of identifying the backlit area by using the position where the minimum value exists in the block obtained by dividing the shooting screen into a plurality of parts. Further, by using the position where the maximum value is present, it is possible to increase the ratio of identifying the region in which the light is over-illuminated.

In the block, the luminance signal in the group in which the maximum value or the minimum value of the luminance signal is collected, the luminance signal other than the group, and the group weight value are appropriately compared, and the comparison result is compared with a preset threshold value. Thus, the determination of the backlight, the forward light, and the over-light is performed regardless of the position of the subject image in the captured image.

By making it possible to use the brightness signal and the scene condition of the image portion corresponding to the subject image when obtaining the exposure correction amount, more appropriate exposure control for the subject can be performed.

If the group is not formed, the ones having considerably low brightness levels or the ones having considerably high brightness levels are not often gathered in one place, and the whole screen is often regarded as a subject. Even when the defined group weight value is equal in the minimum value group and the maximum value group, it is often difficult to identify the subject, and it is often better to consider the entire screen as the subject. By using the maximum value of, it is possible to avoid partial saturation, and more appropriate exposure control for the entire screen becomes possible.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the structure of a first embodiment of the present invention, in which 1 is composed of a solid-state image pickup device composed of a CCD device in which photoelectric conversion elements are two-dimensionally arranged and a peripheral circuit. The CCD camera unit 2, 2 is an image signal processing circuit for converting the output from the CCD camera unit 1 into an image signal, 3
Responds to the timing signal from the timing generation circuit 4 by m × n for a part or the whole of the photographing screen as described later.
A signal distribution circuit 3a (1, 1) to 3a (m, which generates a block luminance signal corresponding to each pixel block of the divided pixel blocks and simultaneously averages the luminance signals of all blocks.
n) and 3b (1,1) to 3b (m, n) are installed in a number corresponding to each pixel block, and are a sampling circuit and an integrating circuit which constitute the signal distribution circuit 3.

Reference numerals 5 and 6 receive the output from the signal distribution circuit 3 and detect the positions of the minimum and maximum luminance values in each pixel block, and a minimum value position detection circuit and a maximum value position detection circuit. A circuit 7 is a minimum value group configuration circuit which receives an output from the minimum value position detection circuit 5 and obtains a position where the minimum value exists and performs grouping, and 8
Is a maximum value group configuration circuit which receives the output from the maximum value position detection circuit 6 and performs grouping by obtaining a location where the maximum values exist. 9 is the minimum value group configuration circuit 7 and the maximum value. A determination circuit for determining forward light, backlight, and over-light based on the output from the group configuration circuit 8,
An exposure correction amount generation circuit 10 outputs an exposure control signal to the CCD camera unit 1 based on the determination signal from the determination circuit 9.

Next, the operation of the first embodiment will be described.

The CCD camera unit 1 photoelectrically converts the received subject image and outputs it as an electrical signal. In the case of a black-and-white camera, the brightness signal from the CCD camera unit 1 can be used as it is for exposure control, but in the case of a color camera, the CCD camera unit 1 outputs three signals of red (R), green (G), and blue (B). Since the luminance signals of the colors are independently output, they cannot be used for exposure control as they are. Therefore, the image signal processing circuit 2 mixes luminance signals and color difference signals conforming to the NTSC system and converts them into video signals. The CCD device is usually composed of several hundreds × several hundreds, and several million to several hundred thousand photoelectric conversion elements (pixels).

FIG. 2 is an explanatory diagram of a pixel configuration of a CCD device. In this embodiment, pixels are arranged in a matrix of P columns and Q rows, and each pixel is divided into m × n blocks. (In the present embodiment, as shown in the drawing, a thick black frame portion is divided into five horizontally and four vertically). In addition,
In FIG. 2, pixel [f, g] = B (i, j) [1,1] means block B of pixel [f, g] in column f and row g in column i and column j in the entire CCD device. It is shown that it is equal to that of the position [1, 1] of (i, j).

The image signal is output in the form of FIG. That is, FIG. 3A is an explanatory diagram of an output state of a signal in units of rows, and FIG. 3B is an enlarged explanatory diagram of a pixel block B (i, j) portion.

Since the number of blocks used for exposure control is suitable to be several to several tens, it is necessary to collect pixel luminance signals that come serially in time for each block and perform integration or averaging. Therefore, the signal distribution circuit 3 generates a block luminance signal corresponding to each pixel block according to the timing signal from the timing generation circuit 4 and simultaneously averages the luminance signals of all blocks.

The pixel luminance signal is sampled by the sampling circuits 3a-1 to 3a-n of the corresponding block and output to the integrating circuits 3b-1 to 3b-n. Integration circuit 3b-1 to 3b
-n can output the average value of the input signal by adjusting the integration constant, and therefore the integration circuit 3
b-1 to 3b-n output the average value of pixel luminance signals of each pixel block B (i, j) (hereinafter, this is referred to as a block luminance signal, and the value is Y (i, j)).

Next, in the minimum value position detection circuit 5, the position of the minimum value in the m blocks in each row direction in the block (m columns and n rows), the minimum position in the n blocks in each column direction. Detect a position with a value and output it (Y
The signal indicating whether or not (i, j) is at the position with the minimum value is Y
m (i, j)).

Next, in the minimum value group forming circuit 7, the position where the minimum value exists is found based on the position of the minimum value detected in the m × n block, and grouping is performed. Grouping is performed as follows, for example.

FIG. 4 shows a sequence of luminance signals of m × n blocks in the screen showing a subject under backlight. The shaded object is the subject under backlight.

FIG. 5 is an explanatory diagram of a method of detecting a position having a minimum value in each row direction in a block, and FIG. 6 is an explanatory diagram of a method of detecting a position having a minimum value in each column direction in a block. In the directions (arrow directions in FIGS. 5A and 6A), the minimum value is found from each direction. That is, the minimum value Y (h, j) (h is the column having the minimum value in each row, i = 1 to
n) is found (FIG. 5 (a)). Minimum value Y (i, v) in each column direction (v is the row with the minimum value in each column, i = 1 to
Find m) (Fig. 6 (a)). The broken line portion in FIG. 5B is the minimum value Y (h, j) portion in the row direction, and the broken line portion in FIG. 6B is the minimum value Y (i, v) portion in the column direction.

Next, grouping will be described.

The condition for forming a group is that, when attention is paid to the horizontal direction, at all minimum values in the j-th row and the j + 1-th row,
Continuously in the horizontal direction (Y (i, k), Y (i + 1, k) ..., k
= Jor j + 1), or one interval (Y (i, k),
If the existence of Y (i + 2, k) ..., k = j orj + 1) is greater than or equal to the threshold gh of the group configuration in the horizontal direction, it is considered as a group.

When attention is paid to the vertical direction, i columns,
In all the minimum values in the i + 1 column, (Y (k, j), Y (k, j + 1) ..., k = i or i + 1) in the vertical direction,
Or one interval (Y (k, j), Y (k, j + 2) ...
, K = i or i + 1) is present, it is regarded as a group if it is equal to or larger than the threshold value gv of the group configuration in the vertical direction.

FIG. 7 shows an example of grouping from those shown in FIGS. In FIG. 7, a group within a dotted frame is a group.

As a result of the grouping, a value Gm obtained by the minimum value group forming circuit 7 from a group of luminance signals which are constituent elements of the group, and a value Em obtained from a group of luminance signals other than the constituent elements of the group , A signal Fm indicating whether or not a group is formed, and a group weight value Am arbitrarily determined in the m × n block is output. Gm, E
m and Am are calculated as follows, for example.

The components in the group are denoted by g _r (r = 1 to p),
If the elements other than the group are e _r (r = 1 to q),

[0040]

[Equation 1]

It can be obtained by Further, in the m × n block, arbitrary weighting w (i, j) (i = 1 to m, j = 1)
~ N) are defined, that is, when the 9 × 5 block shown in FIG. 8 is taken as an example, the weighting of the central part of the photographing screen is made larger than that of the outer peripheral part and, for example, an arbitrary group weight value (w1 to w6) ( w1 <w2 <w3 <w4 <w5 <w6) to w (9,5) (i = 1 to
9, j = 1 to 5), and from each constituent element in the group,

[0042]

[Equation 2]

It can be obtained by Here, x _r and y _r are the positions in the m × n block of each component g _r in the group.

A similar flow takes place for the maximum instead of the minimum. That is, in the maximum value position detection circuit 6, Y
M (i, j) (a signal indicating whether or not Y (i, j) is at a position having a maximum value), obtained from a group of luminance signals that are constituent elements of the group in the maximum value group configuration circuit 8. Value G
M, a value EM obtained from a set of luminance signals other than the constituent elements of the group, and a signal F indicating whether or not the group is formed
An arbitrarily determined group weight value AM in the M and m × n blocks and a maximum value P of the luminance signal in the m × n block are output.

Next, the determination of forward light, backlight, and over-light in the determination circuit 9 will be described.

When both Fm and FM are high and the following conditions are satisfied (when the minimum and maximum value groups are formed), (i)
Backlight if Gm ≦ T1 × GM when Am> AM, forward light (0 <T1 <1) otherwise, (ii) forward light when Am = AM, (iii) GM ≧ when Am <AM If it is T2 × Gm, it is over-lighting, otherwise it is light-forwarding (T2> 1).

When both Fm and FM are low (when a group of minimum value and maximum value is not formed), forward light. Fm low, FM
When high (when only maximum value group is configured), GM
If ≧ TM × EM, it is over-directed, otherwise it is normal (TM> 1).

In the case of Fm high and FM low (when only the minimum value group is configured), if Gm ≦ Tm × Em, backlighting,
Other than that, it is normal light (0 <Tm <1).

The above result is output to the exposure correction amount generation circuit 10.

On the basis of the judgment signal from the judgment circuit 9, the exposure correction amount generation circuit 10 outputs Gm from the minimum value group formation circuit 7 or from the maximum value group formation circuit 8 in the case of forward light when the group is formed. GM, P in the case of normal light when a group is not formed, Gm in the case of backlight, and GM in the case of excessive light are processed and output to the CCD camera unit 1 as an exposure control signal.

An example of the exposure compensation amount generation method is as follows.
When the EV correction value CV from a certain luminance signal RY to the target value T that is appropriate for the CCD device is represented by an EV value,

[0052]

## EQU3 ## CV = -log ₂ (T / RY).

When the group is formed as the RY (except when the group weight values are the same when both the minimum value group and the maximum value group are formed), the light is

[0054]

RY = Gm × NW1 or RY = GM × NW2 When the groups are not configured, and when the group weight values are the same when both the minimum value group and the maximum value group are configured, RY at the time of forward lighting = P x NW3.

When a group is formed, RY is provided at the time of backlighting.
= Gm × BW, and RY = GM × OW at the time of excessive light. Here, NW1 and NW2 are for normal light when the group is formed, NW3 is for normal light when the group is not formed, and BW and OW are for back light and over-light when the group is formed. Each represents a weighting.

FIG. 9 is a block diagram showing the configuration of the second embodiment of the present invention. It is also possible to perform the same arithmetic processing as that of the first embodiment by using a digital processing circuit such as a microprocessor. Reference numeral 21 denotes a CCD camera unit composed of a solid-state image sensor including a CCD device in which photoelectric conversion elements are two-dimensionally arranged and a peripheral circuit, and 22 a video signal for converting an output from the CCD camera unit 21 into a video signal. A processing unit 23 is an analog / digital (A / D) converter for converting an analog video signal from the video signal processing unit 22 into a digital video signal, 24
Is a frame memory, 25 is a screen division unit that divides a part or all of the shooting screen into a plurality of (m × n) blocks, and 26 is the same processing as in the first embodiment for each block by the screen division unit 25. An exposure control unit having a function to perform, 27 is a CPU that controls camera constituent members, 28 is a memory card that is detachably attached to the camera body for recording video signals, 29 is an exposure control unit 26 and CPU 27 It is a CCD camera control unit that controls the CCD camera unit 21 in response to a control signal from the CCD camera unit 21.

In the second embodiment, the screen dividing section 25 divides the video signal of one frame recorded in the frame memory 24 into m × n blocks as in the first embodiment. In response to the output from the screen division unit 25, the exposure control unit 26 calculates the same exposure correction amount as in the first embodiment shown in the flowchart of FIG. 10 and outputs it to the CPU 27.

In FIG. 10, signal names, value names, etc. specified and used in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. First, the positions of the maximum value and the minimum value are detected from the m × n block (S1), and the groups are grouped by the maximum value or the minimum value (S2). Then, when the minimum value group is configured (YES in S3), Gm, Em, and Am are obtained (S4), and when the maximum value group is configured (YES in S5), GM, EM, and AM are Sought (S
6), Am and AM are compared (S7).

When Am> AM (YES in S7), Gm≤T
When it is determined whether or not 1 × GM and Gm ≦ T1 × GM
(YES at S8), the exposure correction amount CV at the time of backlighting is obtained based on Gm (S9), and the control signal is output from the CPU 27 to the CCD camera control unit 29 according to the correction amount CV, and the CCD
The camera section 21 is controlled (S10). Gm ≦ T1 ×
When it is not GM (NO in S8), the correction amount CV at the time of forward light is obtained based on Gm (S11).

In the step (S5), when the maximum value group is not formed (NO in S5), Gm ≦ Tm × Em
It is determined whether or not, and when Gm ≦ Tm × Em,
(YES in S12), the correction amount CV at the time of backlighting is calculated based on Gm (S13), and when Gm ≦ Tm × Em is not satisfied (S12
NO) and Gm, the correction amount CV at the time of forward light is obtained (S14).

In the step (S7), Am> AM
Not (S7 NO), if Am <AM (S15 YES), GM
It is determined whether or not ≧ T2 × Gm, and when GM ≧ T2 × Gm (YES in S16), the correction amount CV at the time of over-forward light is calculated based on GM (S17), and GM ≧ T2 × Gm is not satisfied. Sometimes (NO in S16), the correction amount CV at the time of forward light is obtained based on GM (S18).

In the step (S15), Am = AM
In the case of (NO in S15), the maximum value P in the m × n block is obtained (S19), and the correction amount CV at the time of forward light is obtained based on P (S20).

In the step (S3), if the minimum value group is not formed (NO in S3) and the maximum value group is formed (YES in S21), GM, EM and AM are obtained.
(S22), it is determined whether GM ≧ TM × EM, and GM ≧ T
When M × EM (YES in S23), the correction amount CV at the time of over-forward light is obtained based on GM (S24), and GM ≧ TM × EM
If not (NO in S23), the correction amount CV at the time of forward light is obtained based on GM (S25).

In the step (S21), when the maximum value group is not formed (NO in S21), the maximum value P in the m × n block is obtained (S26), and the correction amount at the time of forward light is calculated based on P. CV is required (S27).

In the above embodiment, the grouping is performed based on the minimum value and the maximum value of the brightness, but any detection means capable of detecting the same brightness level can be used without limiting the size of the brightness. Is.

[0066]

As described above, according to the configuration of the digital still video camera of the present invention, the exposure control device according to the first aspect makes it possible to group the photographing screen portions corresponding to the subject images. It is possible to recognize the position and size of an object, which makes it easy to determine the situation of a scene, and to perform appropriate exposure control according to each scene.

According to the second aspect of the invention, by using the position where the minimum value exists in the block obtained by dividing a part or the whole of the screen into a plurality of parts, the ratio of identifying the backlit area is increased. By using the position where the maximum value exists, it is possible to increase the ratio of identifying the region in which the over-lighting occurs.

According to the third aspect of the present invention, the same effect as that of the first aspect can be obtained regardless of the position of the subject on the screen for the determination of normal light and overlight.

According to the structure of claim 4, the discrimination between the forward light and the backlight is independent of the position of the subject on the screen.
The same effect as the described configuration can be obtained.

According to the fifth aspect of the present invention, the same effect as that of the first aspect can be obtained regardless of the location of the subject on the screen for determining whether the subject is a forward light, a back light or an over-forward light.

According to the structure described in claim 6, the same effect as the structure described in claim 1 can be obtained regardless of the position of the subject on the screen for the determination of the forward light.

According to the seventh aspect of the invention, the exposure correction amount can be obtained by using the luminance signal of the object corresponding to the subject and the scene condition, and the exposure control more suitable for the subject can be performed.

According to the structure described in claim 8, when the group is not formed, or when the arbitrarily determined group weight value is equal in the group by the minimum value and the group by the maximum value, the entire screen is regarded as the subject. Better,
By using the maximum value of the luminance signal in all blocks,
It is possible to avoid a part of the image being saturated, and it is possible to perform more suitable exposure control for the entire screen.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of an exposure control device for a digital still video camera according to the present invention.

FIG. 2 is an explanatory diagram of a pixel configuration of a CCD device.

FIG. 3 is an explanatory diagram of image signal output.

FIG. 4 is an explanatory diagram of a luminance signal of a block representing a subject at the time of backlighting.

FIG. 5 is an explanatory diagram of a method of detecting a position having a minimum value in each row direction in a block.

FIG. 6 is an explanatory diagram of a method of detecting a position having a minimum value in each column direction in a block.

FIG. 7 is an explanatory diagram of grouping.

FIG. 8 is an explanatory diagram of group weight values.

FIG. 9 is a block diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 10 is a flowchart relating to calculation of an exposure correction amount according to the second embodiment of the present invention.

FIG. 11 is an explanatory diagram of conventional exposure control.

FIG. 12 is an explanatory diagram of conventional exposure control.

FIG. 13 is an explanatory diagram of conventional exposure control.

FIG. 14 is an explanatory diagram of conventional exposure control.

[Explanation of symbols]

1, 21 ... CCD camera section, 2 ... Image signal processing circuit,
3 ... Signal distribution circuit, 3a (1,1) to 3a (m, n) ... Sampling circuit, 3b (1,1) to 3b (m, n) ... Integrating circuit, 4
... Timing generation circuit, 5 ... Minimum value position detection circuit,
6 ... Maximum value position detection circuit, 7 ... Minimum value group configuration circuit, 8 ... Maximum value group configuration circuit, 9 ... Judgment circuit,
10 ... Exposure correction amount generation circuit, 22 ... Video signal processing unit, 23
... A / D converter, 24 ... Frame memory, 25 ... Screen division unit, 26 ... Exposure control unit, 27 ... CPU, 28 ... Memory card, 29 ... CCD camera control unit.

Claims (8)

[Claims] 1. A digital still video camera, which uses a solid-state image sensor to convert the luminance of a subject image into an electric signal and outputs the electric signal as a video signal for recording. In a digital still video camera, part or all of a shooting screen is divided into a plurality of blocks. Dividing means, a detecting means for detecting image portions exhibiting similar luminance by the luminance signal of each block, a grouping means for grouping image portions exhibiting similar luminance according to the detection result, and the group A determination means for recognizing an image portion to be formed as an image portion corresponding to a subject image and determining backlight, forward light, and over-forward light, and control means for generating a correction amount based on the determination result and performing exposure control. An exposure control device for a digital still video camera, comprising: 2. The grouping means is configured to select a group of minimum values or a group of maximum values from a portion of the divided blocks where a minimum value or a maximum value of a luminance signal exists in each row and each column. The exposure control device for a digital still video camera according to claim 1, wherein the exposure control device is configured to be formed. 3. The determining means uses the divided blocks to generate a value obtained from a luminance signal within a group and a value obtained from a luminance signal other than a group when only a group having the maximum value of a luminance signal is formed. In comparison, when the ratio of the two values is equal to or more than a preset threshold value, it is determined as over-forward light, and when it is less than the threshold value, it is determined as forward light. Item 1. An exposure control device for a digital still video camera according to item 1 or 2. 4. The determining means uses the divided blocks to generate a value obtained from a luminance signal within the group and a value obtained from a luminance signal other than the group when only a group having the minimum value of the luminance signal is formed. When compared, the backlight when the ratio of the two values is equal to or greater than a preset threshold value,
3. The exposure control device for a digital still video camera according to claim 1, wherein the exposure control device is configured to determine that the light is normal when it is less than the threshold value. 5. The determining means, in the case where the divided blocks form both a group having a minimum value and a group having a maximum value of a luminance signal, a value and a maximum value obtained from the luminance signal in the group having the minimum value. When the values obtained from the luminance signals in the group are compared, the ratio of the two values is equal to or more than a preset threshold value, and if the preset group weight value is large is the minimum value group, Backlight, if the group weight value is greater than or equal to the threshold value and the group weight value is the maximum value, the group is over-forward light, and the group weight value is greater than or equal to the threshold value and the group weight value is the minimum value group. It is configured such that it is determined to be forward light when they are equal to each other in the group by the maximum value and forward light when they are not equal to or more than the threshold value. An exposure control device for a digital still video camera according to claim 1 or 2. 6. The digital still video camera according to claim 1, wherein the determination means is configured to determine that the group is not formed in the divided blocks as normal light. Exposure control device. 7. The control means excludes the forward light when the ratio of the two values is equal to or more than the threshold value and the group weight values are equal in the group by the minimum value and the group by the maximum value. The exposure control is performed by obtaining an exposure correction amount based on a value obtained from a luminance signal in a group.
An exposure control device for a digital still video camera according to 3, 4, or 5. 8. The control means, when the ratio of the two values is equal to or more than the threshold value, and the group weight value is equal in the group of the minimum value and the group of the maximum value, when the forward light, and 7. The digital according to claim 1, 2, 5 or 6, wherein when a group is not formed, an exposure correction value is obtained based on a maximum value of a luminance signal in all blocks and exposure control is performed. Exposure control device for still video cameras.