JP2580295B2 - Automatic exposure control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an automatic exposure control device arranged in a video camera or the like.

BACKGROUND OF THE INVENTION Photometric methods for video cameras mainly include average photometry, weighted photometry of a screen specifying unit, peak photometry for keeping the peak value of a signal level constant, and a combination thereof. Although each of these photometric methods has advantages and disadvantages, it has been empirically found that the frame-weighted metering method that specifies the screen specific part with a frame and weights that part in general live-action photography has a wide range of application. I have.

By the way, in this type of frame-weighted metering method, since the frame position is fixed at a fixed position in the screen, proper exposure is performed only when a subject and a luminance portion similar to the subject exist in that portion. In addition, when a high-luminance portion such as a background was included in the frame, the subject was easily lost in black.

For example, the example of FIG. 5 (1) is a model of a backlighting state in which the sky is in the upper part of the screen in a general outdoor actual shooting, where 201 is the full screen, 301 is the subject part, and 302 is the sky ( Reference numeral 303 denotes a photometry frame for performing weighted photometry.

In this example, a horizontally long photometry frame 303 is fixed at a slightly lower portion of the screen, and weighted photometry is performed.
03 is entered, and an appropriate exposure is obtained for the subject 301. In general, objects that cause backlight, such as the sky and light sources, often exist at the top of the screen, and if the horizontally long photometry frame 303 is fixed to the bottom of the screen as shown in FIG. It has been empirically known that it can cope with proper exposure of a scene. Photometry frame 303
Is set to be horizontally long because it is considered preferable to take in the brightness information of the subject portion as much as possible and to perform the exposure control unless the high brightness portion causing the backlight falls within the frame.

However, when the photometric frame is set as described above, in a backlight scene having the intensity of the object shape as shown in FIG.
A part of the high-luminance background 305 along with the subject 304 largely enters the photometry frame 303, and as a result, the subject 304 is lost in black.

As a countermeasure, as shown in FIG.
When the photometric frame 306 having a reduced width is fixed to the lower position of the screen, if the photometric frame 305 matches the position of the subject 306, the subject 306 is properly exposed, but the subject 306 moves. The relative positional relationship between the photometric frame 304 and the subject 306 changes due to dripping or camera shake, and when the high-brightness background 305 enters the photometric frame 306, the exposure rapidly changes, and the subject 306 is blacked out. I will.

(Object of the Invention) It is an object of the present invention to provide an automatic exposure control device capable of always giving a proper exposure to a subject moving in a screen.

(Features of the Invention) In order to achieve the above object, according to the present invention, there is provided an automatic exposure control apparatus for performing exposure control based on a video signal obtained in a photometry area specified in a screen,
Area setting means for setting a detection area in a screen, detection means for detecting difference information of a luminance component in a video signal in an area inside and outside the detection area, and the detection area in a predetermined direction with respect to the set position. While moving at a predetermined cycle, the difference information detected by the detection means at each of the movement positions is compared, and the area setting means is configured to change a setting position of the detection area in a direction in which the difference information increases. And a photometric region setting unit for setting the photometric region at a setting position of the detection region.

According to another aspect of the present invention, there is provided an automatic exposure control apparatus for performing exposure control based on a video signal obtained in a photometry area specified in a screen. Area setting means for setting an area, and moving the detection area in a predetermined direction with respect to the set position at a predetermined cycle, and at each of the movement positions, a luminance component of a video signal in an area inside and outside the detection area. Area control means for detecting difference information and tracking the detection area to a subject by outputting a position control signal to the area setting means to change a setting position of the detection area in a direction in which the difference information increases, An exposure correction unit for correcting a video signal obtained in the photometry area based on luminance difference information inside and outside the detection area.

Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 1 shows an embodiment of the present invention, in which a lens is shown.
101, optical information passing through the aperture 102 forms an image on a CCD 103, where it is converted into an electric signal, and then passed through a buffer 104 to AGC.
It is output to 105 and the aperture metering circuit 107a. Aperture metering circuit 1
The output of 07a is sent to the aperture driving circuit 108 and used as a signal for controlling the aperture 102. On the other hand, the output of the AGC 105 is sent to the signal processing circuit 106 and the AGC photometry circuit 107b. The AGC photometry circuit 107b receiving the output has a function of controlling the gain of the AGC 105. The output of the signal processing circuit 106 is sent to a signal level detection circuit 113 and a subsequent signal processing circuit (not shown). The photometric circuits 107a and 107b receive a photometric frame signal 111 generated by a frame signal generating circuit 109 (details will be described later) and perform weighted photometry on the portion.

 The above is a main configuration example of the video signal level control system.

Next, detection of a luminance pattern and control of a photometric circuit will be described.

The frame signal generation circuit 109 receives the synchronization signal 112 and generates a detection frame signal 110 and a photometric frame signal 111. FIG. 2A shows an example of a detection frame formed in a screen based on the detection frame signal 110. In FIG. 2, reference numeral 201 denotes a full screen, 202 denotes a subject, 203 denotes a high-luminance background, and intensity backlight. It is in a state. Reference numerals 204 to 206 denote detection frames whose positions and shapes can be changed. The detection frames 204 and 206 are wobbled right and left around the detection frame 204.

The signal level detection circuit 113 receives the detection frame signal 110 and detects signal levels inside and outside the frame. The microcomputer 115 inputs the output of the signal level detection circuit 113 through the A / D converter 114, determines the position of the subject 202, and positions the detection frame 204 and the photometry frame to be described below so as to track the subject 202. Control. The frame signal generation circuit 109 synchronizes with the synchronization signal 112 at the position determined by the microcomputer 115,
A detection frame signal 110 is generated.

The determination of the subject position is performed as follows. It is assumed that the positional relationship between the subject and the detection frame is as shown in FIG. The microcomputer 115 sets the detection frame for each field as shown in FIG. 204 → 205 → 206 → 204 →.
→ 206 → 204 →... At this time, the signal level difference ΔS inside and outside the detection frame becomes maximum at the position of the detection frame 204. That is, ｛| ΔS204 |> | ΔS205 | and |
ΔS204 |> | ΔS206 |｝. If the subject 202 moves rightward, ｛| ΔS206 | <| ΔS205 | <| ΔS204 |｝. In this case, the microcomputer 115 sets the center of wobbling (204
位置 | ΔS204 |> | ΔS205 | and | ΔS204 |> |
Move rightward to the condition position of ΔS206 |｝. Subject 2
When 02 moves to the left, the opposite is true. In this way, the determination of the subject position and the tracking of the detection frame are realized.

FIG. 2B shows the movement of the photometric frame. The photometric frame 207 must track the movement of the subject 202 in the left-right direction.
This can be achieved by setting the photometry frame position at the center of wobbling of the detection frame position described above.

The tracking function described above is only a movement in the horizontal direction, but may be performed in the vertical direction. However, in this case, if the number of detection frame signal lines is one, it takes time to determine the moving direction of the subject, and the followability of the photometric frame is deteriorated. In general actual shooting, it is considered that the subject 202 is often a person. In this case, tracking the movement in the left-right direction is considered to be extremely effective in practical use.

In the above configuration example, the photometry frame 207 and the detection frames 204 to 206 are separate, but these frames may be the same. In this case, as shown in FIG. 2 (1), there is a time when the subject slightly deviates from the subject due to wobbling, but it can be ignored in practical use.

In the example described so far, the photometry circuits 107a and 107b are circuits that perform frame-weighted photometry.
If the determination can be made by the above, the microcomputer 115 may control these photometric circuits. This example is shown in FIG.

The difference from FIG. 1 is that the frame signal generating circuit 109 does not generate the photometric frame signal 111, but instead controls the photometric circuits 107a and 107b by the output of the microcomputer 115 via the D / A converter 401. The microcomputer 115 calculates an exposure correction amount based on the output data of the signal level detection circuit 113.

FIG. 4 is a configuration example of the photometric circuits 107a and 107b. The input video signal is averaged by a resistor 501 and a capacitor 502 and output. At this time, exposure correction control is performed by controlling the output of the photometric circuit via the control line 402 and the resistor 503.

In the above embodiment, the backlight state has been described as an example.
Conversely, the same control can be performed in a normal light state where the subject brightness is higher than the background.

According to the present embodiment, a detection frame is set in the screen, wobbled to detect and track the position of the subject, and the photometry frame is matched with the detection frame or the exposure is corrected. Appropriate exposure control can be performed even for a moving subject, a backlit scene, a direct light scene, or another shooting scene that could not be handled by the frame-weighted metering method.

(Correspondence between the Invention and the Embodiment) In the present embodiment, the frame signal generation circuit 109 includes a signal level detection circuit 113
The microcomputer 115 corresponds to the detecting means according to claim 1.
The microcomputer 115 and the frame signal generation circuit 109 are included in the area control means according to the embodiment of the present invention.
Each corresponds.

Further, the frame signal generation circuit 109 is provided with the signal level detection circuit 113 and the microcomputer 1 as the area setting means according to claim 2 of the present invention.
Reference numeral 15 corresponds to the area control means described in claim 2, and the microcomputer 115 corresponds to the exposure correction means described in claim 2 of the present invention.

(Effects of the Invention) As described above, according to the present invention, the detection area is moved at a predetermined cycle in a predetermined direction with respect to the set position, and the difference detected by the detection means at each of the movement positions is obtained. Area control means for comparing information and controlling an area setting means to change a setting position of the detection area in a direction in which the difference information increases, and a photometry area setting means for setting a photometry area at the setting position of the detection area And moving the detection area in a predetermined direction in a predetermined cycle with respect to the set position, and detecting difference information of a luminance component in a video signal in an area inside and outside the detection area at each of the movement positions. Causing a subject to track the detection area by outputting a position control signal to an area setting means to change a setting position of the detection area in a direction in which the difference information increases. Because you are configured to include a region control means, it is possible to provide a constantly correct exposure for an object that moves around the screen.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 (1) is a view for explaining the shape and moving state of a detection frame in the screen, and FIG. 2 (2) is also in the screen. 3 is a block diagram showing another embodiment of the present invention, FIG. 3 is a circuit diagram showing a configuration example of a photometric circuit shown in FIG. 5
FIG. 1 is a diagram for explaining the relationship between a conventional photometric frame position and various luminance patterns. 107a, 107b: photometric circuit, 109: frame signal generating circuit, 113
…… Signal lens detection circuit, 114 …… A / D converter, 115
... microcomputer, 204 to 206 ... detection frame, 207 ... photometry frame, 4
01 ... D / A converter.

Claims (2)

(57) [Claims] 1. An automatic exposure control device for performing exposure control based on a video signal obtained in a photometry area specified in a screen, wherein: an area setting means for setting a detection area in the screen; Detecting means for detecting difference information of a luminance component in a video signal in an area; moving the detection area in a predetermined direction with respect to a set position in a predetermined cycle; Comparing the obtained difference information, the area control means for controlling the area setting means to change the set position of the detection area in a direction in which the difference information becomes large, and the photometric area at the set position of the detection area An automatic exposure control device comprising: a photometric area setting unit for setting. 2. An automatic exposure control apparatus for performing exposure control based on a video signal obtained in a photometry area specified in a screen, wherein the area setting means sets a detection area in the screen, and While moving in a predetermined direction in a predetermined direction with respect to the set position, the difference information of the luminance component in the video signal in the area inside and outside the detection area is detected at each of the movement positions, and the difference information is increased Area control means for causing a subject to track the detection area by outputting a position control signal to the area setting means to change the set position of the detection area; and the photometry based on luminance difference information inside and outside the detection area. An automatic exposure control device comprising: an exposure correction unit for correcting a video signal obtained in a region.