JPH0588593B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a camera, mainly a video camera, equipped with an automatic exposure adjustment means, and in particular a means that can obtain proper exposure and perform stable exposure adjustment. Regarding.

(Prior Art) Conventionally, an automatic exposure adjustment device for a video camera uses a luminance signal in a video signal corresponding to a certain area within the shooting screen (hereinafter referred to as exposure measurement field of view) as shown by EF in FIG. 14A. It was based on a system in which an exposure adjustment unit such as an aperture was controlled so that the integrated value remained constant.

By the way, it is known that with such an exposure measurement field of view setting means, a difference occurs in the amount of exposure depending on the drawing conditions at the time of photographing. As a metering method for adjusting the exposure, methods such as partial metering, average metering, center-weighted metering, split metering, or spot metering, each with their own unique weighting, have been proposed, but the influence of the background light source It had its pros and cons, such as being easily affected by light and the exposure adjustment being unstable when it comes to moving subjects.

FIG. 15 shows the main parts of an example of a video camera equipped with a conventional automatic exposure adjustment device.
In the figure, 1 is a focusing lens, 2 is a zoom lens, 3 is an aperture, 4 is a relay lens, and 5 is an imaging means.
It is a CCD that receives the luminous flux from the subject, is driven by the image sensor drive circuit 6 and outputs a time series signal, and this signal undergoes modulation and correction processing in the signal processing circuit 7, and is combined with a synchronization signal. An output video signal (for example, an NTSC signal) is formed and supplied to the utilization device. 8 is a gate circuit (hereinafter referred to as AE gate circuit) for setting an exposure measurement field of view for exposure adjustment, and is composed of an analog multiplier and the like. 9
1 is an automatic exposure adjustment circuit including an integrator, and 10 is an aperture drive device, which is often configured together with the aperture 3 as an iris meter.

11' is a gate signal generation circuit (hereinafter referred to as AE) for generating a gate signal for the AE gate circuit 8.
The waveform of the gate signal (hereinafter referred to as AE gate signal) that it generates differs depending on the photometry method, with average metering covering the entire screen, and partial metering and spot metering covering the center of the screen and A rectangular pulse is output that opens the gate only in that vicinity. Furthermore, in a method having intermediate characteristics between average photometry and partial photometry, such as center-weighted photometry, a trapezoidal or chevron-shaped waveform is output instead of a rectangular one.

In the above configuration, the luminance signal component in the video signal output from the signal processing circuit 7 is supplied to the automatic exposure adjustment circuit 9 via the AE gate circuit 8, added to the integrator in the circuit 9, and integrated. be done. Then, the diaphragm driving device 10 drives the diaphragm 3 in the direction of closing the diaphragm 3 when the integral value is larger than a predetermined threshold value, and drives the iris 3 in the direction of opening the iris 3 when it is smaller than the predetermined threshold value. Closed-loop automatic control is performed so that the integral value is maintained at a predetermined value.

According to the above-mentioned conventional technology, whether or not an exposure amount matching the photographer's intention can be obtained largely depends on the photometry method. That is, average photometry, which is said to be for general use, can adjust the exposure to a certain extent for most image creation conditions, but in the case of backlighting, the exposure will be significantly undervalued with respect to the target subject. On the other hand, partial metering, which is preferred by people with relatively advanced photographic skills, can provide appropriate exposure for the target subject, but when the subject moves, etc., the exposure measurement field may deviate from the field of view, as shown in Figure 14B. If this happens often, exposure adjustment becomes unstable. Methods such as center-weighted metering and split metering have been proposed to alleviate the drawbacks of the above two methods, but in the end these methods only provide intermediate characteristics. is the actual situation.

(Purpose) The present invention reduces or eliminates the above-mentioned drawbacks of cameras equipped with conventional automatic exposure adjustment devices, and enables proper exposure for a target subject such as partial metering or spot metering; It is an object of the present invention to provide a camera equipped with an automatic exposure adjustment means capable of performing stable exposure adjustment such as photometry or split photometry.

(Explanation based on Examples) Hereinafter, the means taken in this invention to achieve the above object will be exemplified and explained with reference to the examples shown in FIGS. 1 to 13 and the like. The explanation below is
The overall configuration of an embodiment of the camera of the present invention will be described in order, followed by a modified embodiment of the present invention in which the embodiment includes automatic detection field of view setting means and automatic tracking focus detection means.

(Overall Configuration of an Embodiment of the Camera of the Invention) (FIG. 1) FIG. 1 shows the overall configuration of an embodiment of the camera of the invention. 10 has basically the same configuration and function as the conventional example shown in FIG. 15, so detailed explanation will be omitted. Note that the imaging means 5 described above may be either an imaging tube or a solid-state imaging device such as a CCD, but here it is assumed that it is a CCD. Also CCD
The image sensor driving circuit 6 that drives the image sensor driving circuit 6 is driven by a signal obtained by frequency-dividing a clock pulse generated by a clock pulse generation circuit (not shown), and the above-mentioned synchronization signal is generated by a synchronization signal generation circuit (not shown) based on this frequency division signal. However, since these are also well-known means, detailed explanation will be omitted.

The automatic exposure adjustment function itself in the apparatus shown in FIG. 1 is similar to that of the conventional example shown in FIG. The value is compared with a predetermined threshold value (adjustable), and depending on the magnitude thereof, automatic closed-loop control is performed to close or open the diaphragm 3.

The feature of the device shown in FIG. 1 is that the focus detection field position information is transferred from the focus detection field setting device 12 to the AE gate signal generation circuit 11, and the circuit 11 generates the
The timing of the AE gate signal is controlled by this position information, and the exposure measurement field of view is moved in conjunction with the focus detection field of view. The AE gate signal generation circuit 11 is the same as the AE gate signal generation circuit 11' shown in FIG. The difference is that it is controlled by position information.

To set the position of the focus detection field of view in the focus detection field setting device 12, (1) move the focus detection field position by operating a knob, etc., (2) move any one of the plurality of preset focus detection field divisions. (3) Tracking a moving subject and moving the position of the focus detection field of view.

On the other hand, an AE that sets a corresponding exposure measurement field of view according to position information from the focus detection field of view setting device 12.
In order to generate the gate signal, the timing of the AE gate signal may be controlled based on the analog signal or digital signal generated by the device 12. Here, an example of processing based on a digital signal will be described. The AE gate signal generation circuit 11 includes a programmable counter, and this counter is programmed using the above-mentioned digital signal. Then, the required AE gate signal may be generated in synchronization with the pulse generated when the programmed value is counted.

The waveform of the above AE gate signal is generally
Although any waveform conventionally used in automatic exposure adjustment devices may be used, partial metering, spot metering, or weighted metering where the focused area is relatively narrow in the center (the center of the focus detection field of view) is preferable. The characteristics of each method can be exhibited at or near that point.

A gate signal corresponding to the focus detection field of view set by the focus detection field of view setting device 12 is supplied to the AF gate circuit 13, and a luminance signal, for example, in the output video signal is supplied to the automatic focus detection circuit 14 via the AF gate circuit 13. Here, for example, the well-known mountain-climbing servo system (for example, "HNK Technical Research" Vol. 17, No. 1 (volume 86), published in 1965, page 21, Ishida et al., "Automatic focus adjustment of television cameras using the mountain-climbing servo system") (see) to perform focus detection.
As is well known, the output signal is supplied to the AF motor drive device 15, and the device 15 drives the AF motor M.
, and controls the position of the focusing lens 1 to perform automatic focus adjustment.

Although the focus detection field described above is not an essential requirement for this invention, it can be displayed on a viewfinder screen, etc., whereas the exposure measurement field is a means for extracting signals for automatic exposure adjustment. Therefore, it is not normally displayed on the finder screen.

(Focus detection field of view setting means in an embodiment of the present invention) (FIGS. 2 to 10) As a means for embodying the focus detection field of view setting device 12 of FIG. 1, the focus detection field of view setting device 12 of FIG. There are two possible modes: a setting mode, and a mode where the subject is automatically tracked and the focus detection field of view is automatically moved. The first type of the former is to move the focus detection field of view using a knob or the like, and in this case, the required focus detection field of view is moved.
To generate the AE gate signal, the focus detection field of view setting signal generated by operating a knob or the like in the focus detection field of view setting device 12 is sent to the AE gate setting circuit 1.
1, which generates the same circuit 11.
All you have to do is control the timing of the AE gate signal.

The second mode of manual setting is to select a plurality of preset focus detection visual field sections, an example of which is shown in FIGS. 2 and 3. In Fig. 2, FR indicates the entire photographing screen, and A indicates the division corresponding to the focus detection field of view fixed at the center in a conventional focus adjustment device.
It is assumed that a total of 9 categories, RO to RI, are set for both sides.

FIG. 3 shows an example of a focus detection field setting device for selecting an arbitrary section from the focus detection field sections shown in FIG. 2, and this example also includes means for displaying the focus detection field on an electronic viewfinder. In FIG. 3, 20 is a CCD as an imaging means, and 21 is an image sensor driving circuit, which corresponds to 5 and 6 in FIG. 1, respectively. 22 is a clock pulse generation circuit; 23 is a frequency divider which receives the clock pulse from the clock pulse generation circuit 22 and divides the frequency;
The required frequency-divided signal is output to the CCD 20, as well as a synchronization signal generation circuit 24 and a character generator 29, which will be described later. 24 is a synchronization signal generation circuit; 25 is a signal processing circuit that performs necessary modulation and correction processing on the output signal of the CCD 20 and outputs a video signal; this video signal is combined with the synchronization signal by an encoder 26; Output video signal (e.g.
NTSC signal) is formed.

Reference numeral 27 indicates a joy stick as a focus detection field selection means, but any other device can be used as long as it can specify the focus detection field divisions. For example, the same number of pushbutton switches as the number of focus detection field divisions can be used. They may be arranged in accordance with the above classifications. 28 is a microcomputer that receives a signal from the joystick 27 to select, for example, the focus detection field of view section RO, and operates an analog switch 32 (corresponding to the AF gate circuit 13 in FIG. 1).
AE gate signal generation circuit 1
Transfer to 1 as well. The AE gate signal generation circuit 11 is
The AE gate signal is transferred to the analog switch 8' (corresponding to the AE gate circuit 8 in FIG. 1) in the same manner as described with reference to FIG. As a result, focus detection is performed using the luminance signal extracted in the focus detection field section selected by the joystick 27, and the luminance signal extracted in the exposure measurement field that moves in conjunction with the selection of the focus detection field section 27. Exposure adjustment is performed.

The microcomputer 28 further receives, for example, a signal for selecting the above-mentioned focus detection visual field section RO, and outputs a corresponding focus detection visual field section selection signal to the character generator 29. The character generator 29 receives the frequency division signal from the frequency divider 23 and the focus detection field division selection signal, and outputs an area signal, which is a focus detection field position designation signal, to the signal synthesis circuit 30. teeth,
This area signal and the video signal are combined,
The composite video signal is transferred to the electronic viewfinder 31, and bright lines are displayed on both the left and right sides of the focus detection field of view on the viewfinder screen using the pulse portion of the video signal. Note that the shaded area (b) in FIG. 2 emphasizes this bright line distribution. 34 is a power-on clear circuit, and a clear signal generated when the device is started is inputted to the microcomputer 28, so that the focus detection field of view is always located at the center of the photographing screen shown by A in FIG. 2 at the time of startup. (Patent application filed by the applicant in 1982-
82709).

Returning to FIG. 1, the AE gate signal generation circuit 11
The AE gate signal generated is controlled by the focus detection field position information generated by the focus detection field setting device 12 (the joystick 27 and the microcomputer 28 in Fig. 3), so the exposure measurement field for automatic exposure adjustment is controlled by the focus detection field position information. Since it is linked to the focus detection field of view, it is possible to perform appropriate exposure for the target subject using partial metering and spot metering, as well as stable exposure adjustment such as average metering and split metering. The waveform of the gate signal itself for exposure adjustment can be made into a waveform suitable for exposure adjustment (photometering) regardless of the waveform of the gate signal for setting the focus detection field of view.

Next, regarding a means for automatically tracking a moving subject and moving the focus detection field of view in accordance with the movement of the subject, patent application No. 59-105897 filed by the present applicant describes
The outline will be explained according to the specification of the issue. Figures 9 and 10 show specific examples,
Prior to the explanation, the principle of the automatic subject tracking function will be explained with reference to FIGS. 4 to 8.

In conventional automatic focus detection or automatic focus adjustment devices, the focus detection field of view is fixed at the center of the shooting screen as shown in Figure 4A, so the focus detection field is fixed at the center of the photographic screen as shown in Figure 4B. When the subject (in this example, a person) moves,
This method has the disadvantage that an object (a house in this example) at a different distance from the target subject is in focus, and the target subject, a person, becomes blurred.

On the other hand, in the case of a camera equipped with automatic subject tracking means, if the target subject (person) in the state shown in FIG. 4A moves toward the upper right of the screen while maintaining the same distance as shown in FIG. 5A, The tracking means described later automatically detects the movement of the subject and moves the focus detection field of view to track the movement of the subject (as shown in the figure).
FF), focus detection can be performed at that moving position. Furthermore, the exposure measurement field of view (EF) can be moved in conjunction with the focus detection field of view, and exposure adjustment can be performed at the movement position, that is, the movement position of the subject.
Note that, as described later, the focus detection field or the tracking field may also serve as the exposure adjustment field.

More specifically, some parameter representing the feature of the subject is extracted with respect to the tracking field of view set by the tracking means, the extracted feature is stored, and the newly extracted feature is combined with the stored feature. The tracking field of view is moved to track the movement of the subject by detecting whether or not the subject is moving, and if the subject moves, the moving direction or moving position based on the characteristics of the subject. As the lens moves, the focus detection field of view and, by extension, the exposure measurement field of view are moved in the same positional relationship. As the parameters representing the characteristics of the object mentioned above, color signal information, luminance signal information, information such as the object's shape, temperature, or its characteristic contrast can be used. An example of extraction based on signal information will be explained.

In Figure 5 A, the distance is the same, so there is no need to adjust the focusing lens of the photographing lens, but in Figure 5 B, the distance changes as the subject moves to the upper right of the screen. , the focusing lens moves according to the distance measurement results. Therefore, the size of the tracking field of view is changed by a tracking gate size determining means, which will be described later, and is always maintained at a size suitable for the subject, and focus detection and exposure adjustment are performed in this state. Although the exposure measurement field is not shown in FIG. 5B, it occupies the same relative position as that shown in FIG. 5A.

Here, since the movement between the subject and the camera is relative, the tracking effect described above applies not only when the camera is fixed and the subject moves, but also when the subject stops and the camera moves. Alternatively, it works effectively when both move together, and the size of the tracking field of view is also effective when the subject distance changes.
It can also be adjusted to change the focal length of the lens.

In principle, the tracking field of view has a two-dimensional extent, but to simplify the explanation, here, the tracking field of view has a one-dimensional extent extending in the horizontal direction, as shown in Figure 6A. Suppose there is. It is also assumed that the tracking visual field is divided into three parts A, B, and C (each part is hereinafter referred to as a pixel). Note that to configure a two-dimensional tracking field of view, for example, pixel B in the same figure
Alternatively, pixels extending vertically above and below A, B, and C may be provided. As shown in FIG.
H) The circuits 101a and 101b and the A/D conversion circuits 102a and 102b perform integration, sample and hold, and A/D conversion processes and store them in the memories 103a and 103b, respectively. This stored value is converted to R- for each pixel A, B and C.
When plotted on the orthogonal coordinates of Y and B-Y, it is displayed as shown in FIG. 8, for example. In the figure A ₀ ,
The points B ₀ and C ₀ are respectively A and A in FIG. 6A.
It represents signals extracted from each pixel of B and C. Here, it is assumed that from pixel B, a signal representing only the clothing of the subject, for example, is extracted, and from pixels A and C, a signal in which signals representing the clothing of the subject and the background are added together is extracted. Furthermore, assume that the background colors on the left and right sides of the subject in the figure are different. Therefore, points A ₀ and C ₀
The positions on the color difference signal coordinates are different.

Next, when the object shown in FIG. 6A moves to the right within the screen as shown in FIG. The obtained signal is shown in Figure 8.
They change as shown in A ₁ and C ₁ respectively. on the other hand,
Since pixel B remains within the object as shown in FIG. 6B, the signal obtained from pixel B will hardly change if the clothing is substantially monochromatic. Therefore, here, for simplicity, B ₁ =
Let B be ₀ . In this case, as shown in Figure 8, the point
C ₁ approaches point B ₀ (=B ₁ ), and point A ₁ approaches point B ₀ (=B ₁ )
As it moves away from , line segment B ₁ C ₁ becomes smaller than line segment B ₀ C ₀ , and line segment A ₁ B ₁ becomes larger than line segment A ₀ B ₀ . Conversely, line segment B ₁ C ₁ becomes larger than line segment B ₀ C ₀ ,
If line segment A ₁ B ₁ becomes smaller than line segment A ₀ B ₀ , it means that the subject is moving to the left in FIG. 6B. Assuming that the background color is the same on both sides of the subject, when the subject moves to the right in Figure 6B within the screen, the above point _A1 will be located on the extension of the line segment _{A0B0 .} , and the point C ₁ is located on the line segment B ₀ C ₀ . This automatic tracking means can be applied to either of the above cases.

In order to detect the movement of the tracked subject based on the above-mentioned principle, for example, line segments AB and
It is sufficient to detect changes in the length of BC. Figure 9 shows
An example of a circuit that performs the above processing is shown in FIG.
In the figure, details of the color detection circuit 42, memory 43, and movement determination circuit 44 are shown. In FIG. 9, elements or circuits having the same configuration and function as those in FIG. 1 or 3 are designated by the same reference numerals, and detailed description thereof will be omitted.

The signal processing circuit 7 simultaneously sends the color difference signals R-Y and B-Y to a tracking gate setting circuit 40, and sends the luminance signal Y to an AF gate setting circuit 41 and an AE gate circuit 8.
Output to. The output of the tracking gate setting circuit 40 is supplied to a color detection circuit 42 to detect the color of the subject, and this is stored in a memory 43 via manual mechanical input means such as a switch (not shown). Note that the color detection circuit 42 includes an integrating circuit 100, a sample hold circuit 101, and an A/
It includes a D conversion circuit 102 and a memory 103 that temporarily stores its output. The above processing is performed according to the average value during 1/60 second, which is the period of one field of the television signal, or during a period of several fields thereof. In the following, both will be explained as being processed in one field period.

In the next field, the newly extracted signal and the signal stored in the memory 43 are compared in the movement determination circuit 23, and the presence or absence of movement of the subject and the direction of movement of the subject are detected. When movement occurs, the tracking gate setting circuit 40 is controlled by the gate movement circuit 45 to move the tracking field of view, perform the same calculation in the next field, and then repeat the above process until tracking is completed. Repeat.

When tracking is completed, the gate moving circuit 45 sets the focus detection field of view set by the AF gate setting circuit 41 to the same relative position as the tracking field of view, and the video signal within this focus detection field of view (signal processing circuit 7 The automatic focus detection circuit 14 uses the output of
For example, focus detection is performed by a known means such as mountain climbing control, and the output thereof drives a motor M via an AF motor drive device 15 to control the position of the focusing lens 1.

Furthermore, in the device of FIG. 9, the gate moving circuit 45
The AF gate movement signal generated by is also transferred to the AE gate signal generation circuit 11, and the AE generated by the same circuit
Since the timing of the gate movement signal is controlled according to the AF gate movement signal, the exposure measurement field of view can be moved to track the focus detection field of view, and automatic exposure adjustment can be performed at the new movement position.

In Fig. 9, P ₁ is a position sensor that detects the absolute position of the focusing lens 1 (corresponding to the subject distance), and P ₂ is a position sensor that detects the absolute position of the zoom lens 2 (corresponding to the focal length). It is a position sensor that detects the position, and based on these signals, the tracking gate size determination circuit 46 controls the tracking gate setting circuit 40, the AF gate setting circuit 41, and the AE gate signal generation circuit 11, and adjusts the tracking field of view and the AE gate signal generation circuit 11, respectively. Define the size of the focus detection field of view and the exposure measurement field of view.

FIG. 10 shows the color detection circuit 42 and memory 4 described above.
3 and the movement determination circuit 44, the distance calculation circuit 51 calculates the Line segment A ₀ B ₀ length D _A0 on R-Y and B-Y coordinates in the diagram

Claims (1)

[Scope of Claims] 1. Imaging means for photoelectrically converting a subject image formed on a photographing plane and outputting an imaging signal; and detecting characteristics of the subject image within the imaging plane from the imaging signal; Subject movement detection means for detecting movement of the subject based on changes in image characteristics; Focus detection field setting means for setting a focus detection field of view for performing focus control within an imaging plane; and the focus detection field of view. automatic focus adjustment means for performing focus adjustment based on the imaging signal within the focus detection field of view set by the setting means; and exposure measurement for setting an exposure measurement field of view for performing exposure control within the imaging plane. a field of view setting means; an exposure adjustment means for adjusting exposure based on the imaging signal within the exposure measurement field of view set by the exposure measurement field of view setting means; and an exposure adjustment means for adjusting the exposure based on the output of the subject movement detection means. Controlling the visual field setting means and the exposure measurement visual field setting means, and moving the set positions of the focus detection visual field and the exposure measurement visual field within the imaging plane to follow the movement of the subject detected by the subject movement detection means. A camera comprising: a control means;