JPH04119337A - Exposure controller - Google Patents

Abstract

PURPOSE:To eliminate the unstability of exposure control by executing the control to change the size of a variable region in such a manner that the brightness level detected by an in-variable region photometric means equal to the brightness level detected by a central part photometric means by a region setting means. CONSTITUTION:A region control circuit 12 is controlled by using the metered quantity detected by the in-variable region photometric circuit 11 and the metered quantity detected by the central part photometric circuit 10 in such a manner that the size of the variable region is equaled to the size of the subject, in the region setting circuit 13. Namely, the size of the variable region (b) is reduced when the metered quantity B in the variable region (b) and the metered quantity A in the central part (a) are not equal. The region control circuit 12 is controlled to increase the size of the variable region (b) when the metered quantity B in the variable region (b) and the metered quantity A in the central part (a) are equal. The direction (i.e., control direction) where the size of the variable region (b) is changed is distinct in this way and the unstable exposure control arising from the generation of hunting, etc., is obviated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an exposure control device used in a camera such as a video camera.

[Prior Art] A conventional exposure control device is disclosed in, for example, Japanese Patent Application Laid-Open No. 1-12018.
As described in Publication No. 1, the size and position of the subject within the screen are determined based on the brightness difference (or difference in high frequency components) between the outside and outside of the photometric area, and the size and position of the subject are determined based on the size and position of the photometric area. By matching the positions, the drawbacks of photometry methods such as full-surface average photometry, peak photometry, center-weighted photometry, and spot photometry were solved.

A conventional exposure control device will be briefly explained using FIGS. 13 to 16.

FIG. 13 is a block diagram showing a conventional exposure control device, where l is a lens, 2 is an exposure control circuit, 3 is an image sensor, 5 is a power supply, 6 is a video signal output terminal, 7 is a photometry area position control circuit, 8 is a synchronizing signal input terminal, and 9 is a signal level detection circuit. Here, as shown in FIG. 14, the photometric area position control circuit 7 includes a photometric area size setting circuit 101, a photometric area position setting circuit 102, and a photometric area control signal ordering circuit 10.
It consists of 3. Furthermore, as shown in FIG. 15, the photometric area size setting circuit 101 includes a photometric area brightness level detection circuit 101a, a photometric area outside brightness level detection circuit 101a, and a brightness level detection circuit 101a for detecting brightness level outside the photometric area.
1b, subtraction circuit 101c, object size determination circuit 101
d, a photometric area size control circuit 101e, and a photometric area position setting circuit 102, as shown in FIG.
Brightness level detection circuit within photometry area 102a, brightness level detection circuit outside photometry area 102b, subtraction circuit 102c, subject position determination circuit 102d, photometry area position movement circuit 102e
It consists of

The subject image passing through the lens 1 enters the image sensor 3,
Here, it is converted into a video signal and inputted to the signal level detection circuit 9, and also inputted to the photometric area position control circuit 7.

The photometric area position control circuit 7 causes the photometric area to track the position of the subject within the screen, sets the size of the photometric area to a size corresponding to the subject (details will be described later), and sends a synchronizing signal and A photometric area control signal indicating the position and size of the photometric area within the screen is output to the signal level detection circuit 9 as a synchronized HV composite signal (horizontal and vertical synchronized composite signal).

The signal level detection circuit 9 generates an exposure control signal necessary for performing exposure control based on the video signal from the image sensor 3 and the photometry area control signal, and calculates, for example, the average value of the video signal within the photometry area. , or a value obtained by weighted addition of the video signal within the photometric area to the video signal of the entire screen is set as an exposure control signal and output to the exposure control circuit 2.

The exposure control circuit 2 controls, for example, the aperture state of the diaphragm so that the exposure control signal always has a constant level value corresponding to the exposure control target value generated by the power source 5.

Next, a method of adjusting the size and position of the photometric area to the size and position of the subject will be explained using FIG. 17.

In addition, in Fig. 17, r is the screen and m (m1m2) is the screen! n (n1 to n3) is a photometric area whose size changes according to the size of the object m,
It is.

When a video signal is input to the photometric area size setting circuit 101, the photometric area brightness level detection circuit 1 in the circuit is
01a detects the brightness level within the photometry area n (for example, this measurement area n is initially located at the center of the screen and its size is set to n2, for example), and detects the brightness level outside the photometry area. The brightness level detection circuit 101b detects the brightness level around the photometric area n, and outputs the detection results of each brightness level to the subtraction circuit 101c. Subtraction circuit 101c
calculates the difference between the input luminance levels and outputs it to the subject size determination circuit 101d.

When the photometric area control signal generation circuit 103 changes the size of the photometric area B within the screen A into three stages by gate control or the like, the subject size determination circuit 101cl calculates the difference in brightness between the inside and outside at each size. The size of the largest photometric area n is the screen of subject m at that time! In other words, the size of the subject m within the screen β is determined to be approximately the same as the size of the subject m within the screen β. That is, when changing the size of the photometric area n, the difference in brightness between the inside and outside becomes maximum when the size of the subject m almost matches the size of the photometric area n.
This is because if the size is larger or smaller than that, it will decrease.

The photometric area size control circuit 101e sets the size of the photometric area n at that time based on the result determined by the subject size determining circuit 101d. Here, since the detection area for determining the size of the subject m is associated with the photometry area, the photometry area with the largest difference in brightness between the inside and outside is set as the photometry area n at that time.

In this way, the photometry area size setting circuit 101 sets the photometry jl
The size of J*n is changed in three steps, the difference between the inside and outside brightness levels is checked, and the size of the photometry area is set so that the difference is maximized. As a result, the size of the photometric area n almost matches the size of the subject (Fig. 17(a)
), the photometric area n3 is the photometric area n3 in FIG.
1 is set as the photometric area at that time).

On the other hand, when a video signal is input to the photometric area position setting circuit 102, the photometric area brightness level detection circuit 102a in the circuit detects the brightness level in the photometric area n whose size is controlled as described above. Then, the brightness level detection circuit 102b outside the photometric area detects the brightness level around the photometric area n, and outputs the detection results of each brightness level to the subtraction circuit 102c. The subtraction circuit 102c calculates the difference between the output luminance levels and outputs it to the subject position determination circuit 102d.

The subject position determination circuit 102d temporarily holds the input difference between the inside and outside luminance levels, and the photometry area position signal generation circuit 103 determines the screen! When shifting the position of the photometric area n vertically or horizontally using gate control, etc., the difference in brightness between the inside and outside at each position is further obtained, and the position with the largest difference among these five brightness difference information is displayed on the screen. The position of the subject is determined to be within the range.

The photometric area position moving circuit 102e moves the photometric area n to the calculated subject position. This allows the screen! It becomes possible to track the movement of the subject m within the photometry area n in real time.

In addition, the photometry area control signal generation circuit 103 has a set screen! A photometric area size signal indicating the size of photometric area n within the screen! A photometry area control signal indicating the position of photometry area n within the area is input, and based on these signals, the screen! A photometric area control signal indicating the position and size of the photometric area n within the photometric area n is generated.

As described above, the position and size of the photometric area n corresponding to the position and size of the subject m within the screen i are determined.

[Problem to be solved by the invention]

In the conventional exposure control device described above, the size and position of the photometric area n can be made to match the size and position of the subject m, so that the screen! Optimum exposure can always be given even if the size and position of the subject m within the photographic subject change.

However, in the conventional exposure control device described above, when matching the size and position of the photometric area n with the size and position of the subject m, the difference in brightness (or difference in high frequency components) between the outside and outside of the photometric area n becomes maximum. As shown in Figure 2, the control is performed by changing the size and position of the photometric area n, which causes the following problems. For example, when setting the size of the photometric area n, the If the brightness difference between the inside and outside of the photometric area n becomes large after changing it in the direction of increasing or decreasing the brightness, it is approaching the maximum, so you can just change it in that direction. Since it is moving away from the current, it will change in the opposite direction. In this case, the size of the photometric area n changes by increasing and then decreasing (or decreasing and then increasing), so the exposure control signal that is finally obtained will also change accordingly. As a result, there is a problem that exposure control becomes unstable due to hunting or the like.

In this way, in the conventional exposure control device described above,
Since control is performed to change the size and position of photometric area n so that the difference in brightness (or difference in high frequency components) between the inside and outside of photometric area n is maximized, it is necessary to change the size and position of photometric area n. The direction (that is, the control direction) is unstable, and therefore there is a problem in that the exposure control becomes unstable due to hunting or the like.

Therefore, in order to solve this problem, we set up a dedicated detection area for detecting the size and position of the subject m, and when matching the size and position of the photometric area n with the size and position of the subject m, we first need to The size and position of the detection area are changed so that the difference in brightness (or the difference in high frequency components) between the inside and outside of the detection area is maximized, and the size and position of the subject m are detected. It is conceivable to change the size and position of the photometric area n so as to match the position.

However, when doing this, the detection area must of course be able to change its size and position in the same way as the photometric area n (for example, if the photometric area n changes in size in three steps, the detection area Similarly, the size of the detection area must be changeable in three steps), but in order to make small changes, there is a problem in that the scale of the circuit related to the detection area must be increased.

The main feature of the present invention is to solve the problems of the prior art described above,
An object of the present invention is to provide an exposure control device that can detect the size of a subject within a screen with a small circuit scale, and also enables stable exposure control and can always give the subject the optimum exposure state. .

[Means to solve the problem]

In order to achieve the above object, the present invention is configured by the means described below.

That is, in the first invention, the central part photometry means detects the brightness level in the central part of the screen based on the video signal from the image sensor; variable area photometry means for detecting a brightness level within a variable area centered on the central portion; area control means for changing the size of the variable area within the screen; and detection by the variable area photometry means. area setting means for controlling the area control means to change the size of the variable area so that the brightness level is equal to the brightness level detected by the central photometry means; and detection by the variable area photometry means. and an exposure control signal generation means for generating an exposure control signal based on the brightness level and the video signal from the image sensor, and the exposure control is performed based on the exposure control signal t generated by the exposure control signal generation means. I did it.

Further, in the second invention, the video signal 4 from the image sensor
y, a peripheral photometering means is newly provided for detecting the brightness level of the peripheral part in the screen, and the area designing means is configured to match the brightness level detected by the variable area photometry means to the one detected by the central photometering means. controlling the area control means to change the size of the variable area so that the brightness level detected by the peripheral photometer is equal to the internal division of the brightness level detected by the peripheral photometer at a predetermined internal division ratio; I did it like that.

Furthermore, in the third aspect of the invention, the center photometric means includes:
Based on the video signal from the image sensor, the brightness level of each part obtained by dividing the central part of the screen into a plurality of parts is detected, and the area control means controls the variable area within the screen. While changing the size of
The range in which the variable area can exist within the screen is limited, and the area control means changes the brightness level detected by the center photometer to the brightness level detected by the peripheral photometer, respectively. Among the parts obtained by dividing the central part, the brightness level detected by the central part photometric means is not equal to the forest intensity level detected by the peripheral part photometric means. , the region control means is controlled to limit the range in which the variable region can exist in a predetermined region including that portion, and the peripheral region photometry means controls the brightness level detected by the central region photometry means. Regarding a brightness level that is not equal to the brightness level detected by the variable area photometer (hereinafter referred to as the first brightness level), the brightness level detected by the variable area photometry means is equal to the first brightness level and the brightness level detected by the peripheral photometer The area control means is controlled to change the size of the variable area so that it is equal to the amount by which the brightness level is internally divided into a predetermined internal division ratio.

(Function) Among the above-described inventions, in the first invention, the area setting means sets the brightness level detected by the variable area photometry means to be equal to the brightness level detected by the center photometry means. Since control is performed to change the size of the variable area, the direction in which the size of the variable area should be changed (i.e., the control direction) is clear, and exposure control may cause hunting or the like and become unstable. Never.

Therefore, there is no need to provide a dedicated detection area for detecting the size of the object, and the circuit size does not increase.

Note that in order to prevent malfunctions when there is a black subject in the center of the screen, the area design means adjusts the size of the variable area when the brightness level detected by the center photometer is approximately zero. may be left unchanged or may be increased.

Further, in the second aspect of the invention, the area designing means determines that the brightness level detected by the variable area photometry means is different from the brightness level detected by the central part photometry means and the brightness level detected by the peripheral part photometry means. Since the size of the variable region is controlled so as to be equal to the amount internally divided to the internal division ratio of , the same effect as the above-described first invention can be obtained.

Furthermore, by appropriately setting the internal division ratio, even if the subject does not have a -like luminance distribution, the size of the variable area can be precisely matched to the subject. Optimal exposure conditions can be achieved.

In addition, in order to prevent malfunctions when areas other than the center and peripheral areas have high or low brightness, the peripheral area is compared to the area outside the variable area within the screen in order to obtain the brightness distribution of the entire screen. It may be all.

Furthermore, when the subject is the entire screen, that is, when the brightness level within the screen is uniform, in order to further increase the stability of the operation, the area setting means adjusts the brightness detected by the center photometry means. When the level and the luminance level detected by the peripheral photometer are approximately equal, the size of the variable area may be increased.

Furthermore, in the third aspect of the invention, the area control means controls the brightness level detected by the central photometry means, respectively.
It is determined whether the brightness level is equal to the brightness level detected by the peripheral photometering means. Among the parts obtained by dividing the central part, for a part where the brightness level detected by the central part photometric means is not equal to the brightness level detected by the peripheral part photometric means, a predetermined portion including that part is divided. Control is performed to limit the range in which the variable region can exist. Further, among the brightness levels detected by the central photometer, the first brightness level that is not equal to the brightness level detected by the peripheral photometer, the brightness level detected by the variable area photometry circuit is Control is performed to change the size of the variable area so that it is equal to the amount by which the first brightness level and the brightness level detected by the peripheral photometer are divided into a predetermined internal division ratio.

Therefore, the position (i.e., the range in which it should exist) and the direction in which the size should be changed (i.e., the control direction) of the variable region are clear, and exposure control will not become unstable due to hunting or the like. .

Therefore, there is no need to provide a dedicated detection area for detecting the position and size of the subject, and the circuit scale does not increase.

In addition, even if the subject deviates from the center of the screen due to movement or panning of the subject, the position and size of the variable area can be precisely matched to the position and size of the subject, so the subject can be photographed with optimal exposure. It can be a state.

〔Example〕

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

FIG. 1 is a block diagram showing a first embodiment of the present invention, and the same parts as in FIG. 13 are given the same reference numerals.

The parts that are different from FIG. 13 are a central photometry circuit 10 that detects the brightness level (photometric amount) at the center of the screen, and a variable area photometry circuit that detects the brightness level (photometric amount) within the variable area within the screen. A circuit 11, an area control circuit 12 that changes the size of a variable area within the screen, and a photometric amount detected by the variable area photometry circuit 11 and a central photometry circuit 10.
The area setting circuit 13 controls the area control circuit 12 so that the size of the variable area matches the size of the subject using the photometric amount detected in the area setting circuit 13.

Now, the operation of this embodiment will be explained using the second session.

FIG. 2 is an explanatory diagram showing a subject within the screen and an area to be photometered in the first embodiment.

In Figure 2, l is the screen, m is the subject, a is the center,
b is a variable region.

The subject image passing through the lens 1 enters the image sensor 3, is converted into a video signal, and is input to a signal level detection circuit 9, as well as a central photometry circuit 10 and a variable area photometry circuit 11. The central photometric circuit 10 is a screen! Central part a within
The photometric amount is detected and output to the area setting circuit 13.

Further, the area control circuit 12 generates an HV composite signal synchronized with a synchronization signal, which determines the size of the variable area based on the control from the area setting circuit 13. The variable area photometry circuit 11 inputs the HV composite signal that determines the size of the variable area generated by the area control circuit 12, gates the video signal (luminance signal) using this HV composite signal, and measures the inside of the variable area. The photometric amount is detected and output to the area setting circuit 13.

The area setting circuit 13 uses the two input photometric amounts, that is, the photometric amount of the central portion a and the photometric amount within the variable area A.
The size of the subject m is detected, and the area control circuit 12 is controlled to change the size of the variable area so that the size of the variable area matches the size of the subject m.

The operating algorithm of the area setting circuit 11 is shown in FIG.

In FIG. 3, A is the photometric amount at the central portion a, and B is the photometric amount within the variable area.

That is, when the size of the variable area S is larger than the size of the subject m, the area setting circuit 11 determines the amount of photometry within the variable area S because the photometric amount B within the variable area S is not equal to the photometric amount A at the center a. If the photometric amount B and the photometric amount A of the central portion a are not equal, the area control circuit 12 is controlled to reduce the size of the variable area S. Conversely, when the size of the variable area S is smaller than the size of the subject m, the photometric amount B in the variable area S and the photometric amount A at the center a are equal, so the photometric amount B in the variable area S and the center When the photometric amount A of part a is equal, the area control circuit 12 is controlled to increase the size of the variable area A. Thereby, the size of the variable area can be made to match the size of the subject m.

The signal level detection circuit 9 generates an exposure control signal necessary for performing exposure control based on the video signal from the image sensor 3 and the photometric amount detected by the variable area photometry circuit 11. The average value of the video signals within the variable area, or the weighted value obtained by adding the video signal within the variable area to the video signal of the entire screen, is set as an exposure control signal and output to the exposure control circuit 2.

The exposure control circuit 2 uses the input exposure control signal as a measure of exposure, and controls the aperture state of the diaphragm so that this signal is always at a constant level value corresponding to the exposure control target value generated by the power source 5.

In this embodiment, in the area setting circuit 13, the judgment when changing the size of the variable area is based on whether or not the photometric amount B in the variable area is equal to the photometric amount A in the center part a. However, the criterion for judgment may be whether the difference between the two is within a certain range.

In this embodiment, if the photometric amount B in the variable area A is not equal to the photometric amount A at the center a, the size of the variable area A is made smaller, and the photometric amount B in the variable area Part a
When the photometric amount A is equal, the area control circuit 12 is controlled to increase the size of the variable area. Therefore, the direction in which the size of the variable area should be changed (i.e., control direction) is clear, so
Unlike conventional methods, exposure control does not become unstable due to hunting or the like.

Therefore, there is no need to provide a dedicated detection area for detecting the size of the object, and the circuit scale does not increase.

FIG. 4 is a block diagram showing a second embodiment of the present invention, and the same parts as in FIG. 1 are given the same reference numerals. The parts that differ from FIG. 1 are the peripheral photometry circuit 14 and the area setting circuit 15.
It is.

Now, the operation of this embodiment will be explained using FIG. 5.

FIG. 5 is an explanatory diagram showing a subject within a screen and an area to be photometered in the second embodiment.

In FIG. 5, C is the peripheral part.

The peripheral photometry circuit 14 is a screen! The brightness level (photometric amount) of the peripheral area C within the area is detected and output to the area setting circuit 15. The area setting circuit 15 detects the size of the subject m based on the three input photometric amounts, that is, the photometric amount of the central portion a, the photometric amount of the peripheral portion C, and the photometric amount within the variable area. so that the size of the object m matches the size of the subject m.
The area control circuit 12 is controlled to change the size of the variable area.

The operating algorithm of the area setting circuit 15 is shown in FIG.

1 In FIG. 6, C is the photometric amount of the peripheral area C.

That is, the area setting circuit 15 sets the photometric amount B in the variable area to be an amount that internally divides the photometric amount A of the central portion a and the photometric amount C of the peripheral portion C at an internal division ratio of 1:K. , area control circuit 1
2 to change the size of the variable area.

First, the amount to internally divide the target value of the photometric amount A of the central portion a and the photometric amount C of the peripheral portion C at an internal division ratio of 1:K (KA+C/+
1) is determined, the target value is compared with the photometric amount B in the variable area, and the two conditions are divided into three events: "equal,""larger," and "smaller."

In the case of an "equal" event, the process ends without changing the size of the variable area. Also, "large" or "small"
In the case of an event, in order to bring the photometric amount B in the variable area closer to the target value, the direction (control direction) in which the size of the variable area should be changed is determined by adjusting the photometric amount A in the center part a and the photometric amount A in the peripheral part C. It is determined based on the magnitude relationship with the photometric amount C, that is, the conditional branching of Arc.

In other words, in the case of a "large" event, Figure 7(a) or (
In the case of b), as in (a), the photometric amount A at the center a
is larger than the photometric amount C of the peripheral portion C, the size of the variable area A is increased, and when the photometric amount A of the central portion a is smaller than the photometric amount C of the peripheral portion C as shown in (b), reduces the size of the variable area.

On the other hand, in the case of a "small" event, Figure 7 (C) or (
In the case of d), the photometric amount A at the center part a as shown in (C)
is larger than the photometric amount C of the peripheral portion C, the size of the variable area is made smaller, and when the photometric amount A of the central portion a is smaller than the photometric amount C of the peripheral portion C as shown in (d), increases the size of the variable region.

Then, the size of the variable area is changed in a desired direction and the process ends.

As explained above, in this embodiment as well, the direction in which the size of the variable area should be changed (i.e., the control direction)
Since this is clear, the exposure control does not become unstable due to hunting or the like as in the conventional case.

Therefore, there is no need to provide a dedicated detection area for detecting the size of the object, and the circuit scale does not increase.

In addition, in this embodiment, the screen! Peripheral area C within
The screen! By setting all the areas outside the variable area within the screen, information on the brightness distribution of the entire screen can be obtained, so malfunctions can be avoided when areas other than the central area A and the peripheral area C have high or low brightness. can be prevented.

In addition, in this embodiment, by appropriately setting the internal division ratio 1:K when dividing the photometric amount A of the central portion a and the photometric amount C of the peripheral portion C, as shown in FIG. If the subject is -
In addition to cases where the subject has a similar brightness distribution, even when the subject does not have a -like brightness distribution as shown in FIG. 8(b), it is possible to accurately match the size of the variable area to the size of the subject m. Therefore, the subject can be exposed to the optimum condition.

Further, in this embodiment, when the following conditional judgment is added to the operation of the area setting circuit 15, further effects can be obtained.

In other words, when the photometric amount A of the central portion a is equal to the photometric amount B of the peripheral portion, it is considered that the subject m covers the entire screen, that is, the brightness level within the screen l is uniform, and therefore the variable area is all increase the size of This results in
The stability of operation will further increase. Note that here, the criterion for judgment is whether the photometric amount A of the central portion a and the photometric amount C of the peripheral portion C are equal, but the criterion is whether the difference between the two is within a certain range. It's good as well.

FIG. 9 is a block diagram showing a third embodiment of the present invention, and the same parts as in FIG. 4 are given the same reference numerals. The parts that differ from FIG. 4 are a central photometry circuit 10a that is divided into two parts;
10b, an area control circuit 16, and an area setting circuit 17.

Now, the operation of this embodiment will be explained using FIG. 1O.

FIG. 1O is an explanatory diagram showing a subject in the screen and a photometered area in the third embodiment.

In FIG. 10, al is the left side of the center, and a2 is the right side of the center.

The central photometric circuit 10a measures the brightness level (photometric amount) of the central left side a1 within the screen r, and the central photometric circuit 10b measures the brightness level (photometric amount) of the center left side a1 within the screen r. The brightness level (photometric amount) on the right side a2 of the central portion within the area is detected and output to the area setting circuit 17. The area control circuit 16 changes the size of the variable area within the screen r, and also changes the size of the variable area within the screen r. The range within which variable regions can exist can be restricted. The area setting circuit 17 determines the subject m based on the four input photometric amounts, that is, the photometric amount on the center left side a1, the photometric amount on the center right side a2, the photometric amount on the peripheral area C, and the photometric amount in the variable area. detecting the position and size of the variable area, controlling the area control circuit 16 to change the size of the variable area so that the position and size of the variable area match the position and size of the subject m, This limits the range in which variable regions can exist.

The operating algorithm of the area setting circuit 17 is shown in FIG.

In Fig. 11, A1 is the photometric amount of a1 on the left side of the center, A
2 is the photometric amount of the center right side a2.

That is, the area setting circuit 17 controls the screen! Subject m within
The position of the subject m is detected, and the area control circuit 16 is controlled so that the position of the variable area matches the detected position of the subject m. After that, the photometric amount B in the variable area A becomes the photometric amount A in the center part a.
The area control circuit 16 is controlled to change the size of the variable area so that the photometric amount C of the peripheral area C is divided internally at an internal division ratio of 1:K.

First, the photometric amount AI of the center left side a1 and the center right side a2
The photometric amount A2 of each is compared with the photometric amount C of the peripheral area C, and if it is equal to the photometric amount C of the peripheral area C, it is assumed that the subject m does not exist on the screen side corresponding to that side, and the peripheral area If the photometric amount C is not equal to the photometric amount C, it is assumed that the subject m exists on the screen side corresponding to that side.

That is, whether the photometric amount A1 on the left side a1 of the central portion is equal to the photometric amount C on the peripheral portion C, and the photometric amount A on the right side a2 of the central portion
2 and the photometric amount C of the peripheral area C are equal or not. ■Event 1: A1=C and A2=C ■Event 2: A1=C and A2≠C ■Event 3: A1 ≠C and A2=C ■Event 4: There are four events, such as A1≠C and A2≠C, and the actions are as follows.

In the case of event 1, it is assumed that the object m is not present on the left side of the screen (the left half area of the screen l) and the right side of the screen (the right half area of the screen r), but in this case, the object m is considered to be the entire screen. Therefore, increase the size of the variable area. This further increases the stability of operation.

In the case of event 2, it is assumed that the subject m exists on the right side of the screen, and in order to prevent the variable area from entering the left side of the screen, the range where the variable area can exist is limited to the right side of the screen, and the area on the right side of the center The same operation as the operation algorithm shown in FIG. 6 above is performed by setting the photometric amount A2 of a2 to the photometric amount A of the central portion a.

In the case of event 3, it is assumed that the subject m exists on the left side of the screen, and in order to prevent the variable area from entering the right side of the screen, the range where the variable area can exist is limited to the left side of the screen, and the left side of the center The same operation as the operation algorithm shown in FIG. 6 described above is performed by setting the photometric amount AI of a1 to the photometric amount A of the central portion a.

Furthermore, in the case of event 4, it is assumed that the subject m exists on the left side of the screen and the right side of the screen, that is, in the center of the screen, and the photometry IAI of the left side a1 of the center part is set as the photometry ii of the center part a.
A, or set the photometric amount A2 at the center right side a2 as the photometric amount A at the center a, or set the photometric amount A at the center left side a1.
1 and the photometric amount A2 of center right side a2 (A1+A
2) The same operation as the operation algorithm shown in FIG. 6 described above is performed by setting /2 as the photometric amount A of the central portion a.

As described above, the position and size of the variable region S can be made to match the position and size of the subject m.

In this embodiment, the area setting circuit 17 makes a judgment when detecting the position of the subject m by determining whether the photometric amount A1 of the center left side al is equal to the photometric amount C of the peripheral area C. The criterion is whether the photometric amount A2 of the right side a2 and the photometric amount C of the peripheral area C are equal or not, but the difference between the two may be within a certain range (it may also be within a certain range proportional to the difference). The judgment criterion may be whether or not there is one.

In addition, in this example, the screen! I divided the central part a in the inside into two parts, the left side al of the center and the right side a2 of the center, and detected the photometric amount of each, but the screen! For example, as shown in FIG. 12, the center part a in the center part a3. Center upper right side a4. Center part lower left side a5. By dividing the photometry into four areas a6 on the upper left side of the center and detecting the respective photometric amounts, the position of the variable area can be made to match the position of the subject m with higher accuracy.

As explained above, in this embodiment as well, the direction in which the size of the variable area should be changed (i.e., the control direction)
Since this is clear, the exposure control does not become unstable due to hunting or the like as in the conventional case.

Therefore, there is no need to provide a dedicated detection area for detecting the size of the object, and the circuit scale does not increase.

In addition, in this embodiment, the same effect as in the second embodiment described above can be obtained, and even if the subject m deviates from the center of the screen due to movement or vanning of the subject, the position and size of the variable area can be accurately adjusted to the position and size of the subject m, so that the subject can be brought into an optimal exposure state.

In the above three embodiments, the area setting circuits 13, 15.
Regarding the operation No. 17, adding the following conditional judgment will further increase the effect.

That is, when the photometric amount A at the central portion a is extremely small, the size of the variable area S is not changed, or the size of the variable area S is increased. This is to distinguish the case where there is a black subject m in the center part a of the screen l from the case where the subject m is blurred due to backlighting. This has the effect of preventing malfunctions even in the case of

In the above three embodiments, the exposure control circuit 2 controls the aperture state of the diaphragm based on the exposure control signal, but the present invention is not limited to this. speed and signal processing circuit (not shown)
A similar effect can be obtained by controlling the gain of .

〔Effect of the invention〕

As explained above, according to the present invention, since the direction in which the size (and position) of the variable region should be changed (i.e., the control direction) is clear, stable exposure control is possible without causing hunting etc. Therefore, the optimum exposure condition can always be given to the subject.

Therefore, there is no need to provide a dedicated detection area for detecting the size (and position) of the subject;
and position) can be realized with a small circuit scale.

Further, depending on the configuration of the present invention, even if the subject does not have a -like luminance distribution, the size of the variable area can be precisely matched to the size of the subject, so the subject can be placed in an optimal exposure state. I can do it.

Furthermore, depending on the configuration of the present invention, even if the subject moves away from the center of the screen due to movement or panning, the position and size of the variable area can be accurately adjusted to the position and size of the subject. It is possible to bring the subject into an optimal exposure state.

In addition, when the brightness level detected by the central photometer is almost zero, if the size of the variable area is left unchanged or increased, malfunctions can be prevented when there is a black subject in the center of the screen. can do.

In addition, if the peripheral area is defined as the entire area outside the variable area within the screen, the brightness distribution of the entire screen can be obtained, so malfunctions can occur when areas other than the center and peripheral areas have high or low brightness. can be prevented.

In addition, when the brightness level detected by the center photometer and the brightness level detected by the peripheral photometer are almost equal, and the size of the variable area is increased, if the subject is the entire screen, i.e. , the stability of operation can be further increased when the brightness level within the screen is uniform.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the present invention;
The figure is an explanatory diagram showing the subject on the screen and the area to be photometered in the first embodiment, FIG. 3 is a flowchart showing the operation algorithm of the area setting circuit in the first embodiment, and FIG. 2 is a block diagram showing the second embodiment, FIG. 5 is an explanatory diagram showing the subject on the screen and the area to be photometered in the second embodiment, and FIG. 6 is an operational algorithm of the area setting circuit in the second embodiment. Flowchart shown, No. 7
The figure is an explanatory diagram showing the brightness distribution to explain each phenomenon in Figure 6, FIG. 8 is an explanatory diagram showing the brightness distribution to explain the effect of the first embodiment, and FIG. A block diagram showing the third embodiment, FIG. 10 is an explanatory diagram showing the subject on the screen and the area to be photometered in the third embodiment, and FIG. 11 is an operation algorithm of the area setting circuit in the third embodiment. FIG. 12 is an explanatory diagram showing another example of the subject in the screen and the area to be photometered in the third embodiment, and FIG. 13 is a block diagram showing a conventional exposure control device.
14 is a block diagram showing the configuration of the photometric area position control circuit in FIG. 13, FIG. 15 is a block diagram showing the configuration of the photometric area size setting circuit in FIG. 14, and FIG. 16 is a block diagram showing the configuration of the photometric area size setting circuit in FIG. Block diagram showing the configuration of the area position control circuit, No. 17
The figure is an explanatory diagram showing a subject in a screen and a photometered area in a conventional exposure control device. Explanation of symbols 2...Exposure control device, 3...Image sensor, 9...Signal level detection circuit, 10.10a, 10b...Central photometry circuit, 11...Variable area photometry circuit, 12.16
--- Area control circuit, 13, 15.17... Area setting circuit, 14... Peripheral photometry circuit.・Tamezutaro @2 Figure 3 Figure 714 Figure 115 Figure α Figure 6 @ 7 Figure (α) (C) (α) (b) °Rekikuzai A1 Small and medium-sized part of the book α1's 1st 12rA 113 Figure 415 Figure

Claims (1)

[Claims] 1. Center photometry means for detecting the brightness level at the center of the screen based on the video signal from the image sensor; variable area photometry means for detecting a brightness level within a variable area centered on the central portion; area control means for changing the size of the variable area within the screen; and detection by the variable area photometry means. area setting means for controlling the area control means to change the size of the variable area so that the brightness level is equal to the brightness level detected by the central photometry means; and detection by the variable area photometry means. and an exposure control signal generation means for generating an exposure control signal based on the brightness level and the video signal from the image sensor, and performing exposure control using the exposure control signal generated by the exposure control signal generation means. An exposure control device characterized by: 2. A center photometer for detecting a brightness level in a central part of the screen based on a video signal from an image sensor; and a center photometer for detecting a brightness level in a peripheral part of the screen based on a video signal from the image sensor. peripheral photometry means for detecting;
variable area photometry means for detecting a brightness level within a variable area centered on the center portion within the screen based on a video signal from the image sensor; and changing the size of the variable area within the screen. and an area control means for internally dividing the brightness level detected by the variable area photometry means into the brightness level detected by the center photometer and the brightness level detected by the peripheral photometer at a predetermined internal division ratio. area setting means for controlling the area control means to change the size of the variable area so that the brightness level detected by the variable area photometry means and the video signal from the image sensor 1. An exposure control apparatus comprising: an exposure control signal generating means for generating an exposure control signal based on the exposure control signal, and performing exposure control using the exposure control signal generated by the exposure control signal generating means. 3. A central part photometer for detecting the brightness level of each part obtained by dividing the central part of the screen into a plurality of parts based on the video signal from the image sensor; peripheral area photometry means for detecting a brightness level in a peripheral area within the screen based on a video signal from the image sensor; and variable area photometry means for detecting a brightness level within a variable area within the screen based on a video signal from the image sensor. an area control means capable of changing the size of the variable area within the screen and limiting a range in which the variable area can exist within the screen; and a brightness level detected by the central photometry means. , respectively, and determine whether the brightness level detected by the central part photometric means is equal to the brightness level detected by the peripheral part photometric means, and among the parts obtained by dividing the central part, the brightness level detected by the central part photometric means is equal to the brightness level detected by the peripheral part photometric means. For a portion that is not equal to the luminance level detected by the central photometer, the area control means is controlled to limit the range in which the variable area can exist in a predetermined area including that portion, and the central photometer is Of the brightness levels detected by the peripheral area photometer, for a brightness level that is not equal to the brightness level detected by the peripheral photometer (hereinafter referred to as a first brightness level), the brightness level detected by the variable area photometer is controlling the area control means to change the size of the variable area so that the brightness level of 1 and the brightness level detected by the peripheral photometer are divided internally by a predetermined internal division ratio; and an exposure control signal generating means for generating an exposure control signal based on the luminance level detected by the variable area photometry means and the video signal from the image sensor, An exposure control device characterized in that exposure control is performed using an exposure control signal generated by a generating means. 4. In the exposure control device according to claim 1, 2 or 3, when the brightness level detected by the center photometry means is approximately zero, the area setting means controls the area control means to control the variable An exposure control device characterized by not changing the size of the area or increasing the size of the area. 5. The exposure control device according to claim 2 or 3,
The exposure control device is characterized in that the peripheral area is the entire area outside the variable area within the screen. 6. The exposure control device according to claim 2 or 3,
The area setting means controls the area control means to increase the size of the variable area when the brightness level detected by the center photometer and the brightness level detected by the peripheral photometer are substantially equal. Characteristic exposure control device.