JPH0586702B2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a camera equipped with an automatic tracking focus detection device, and particularly relates to a camera equipped with an automatic tracking focus detection device. Concerning means of warning.

(Background Art) In a camera equipped with a conventional automatic focusing device with negligible difference, such as a video camera, the field of view for distance measurement is fixed at the center of the shooting screen as shown in FIG. As shown in the figure, if the subject you want to focus on (hereinafter referred to as the focus detection target subject; in this example, a person) moves, an object at a different distance from the target subject (in this example, a house) will be in focus. Since the person who is the subject to be focus detected becomes blurred, there is a drawback that the subject to be focus detected must always be placed at the center of the screen due to the screen configuration. For this reason, methods have been proposed to make the distance measurement field of view variable, but these methods require the photographer to change the distance measurement field of view by operating a knob, etc., and the subject may move during shooting. In some cases, it is difficult to maintain the distance measurement field position always above the focus detection object using these knobs.

In order to eliminate the above drawbacks, the applicant first sets a movable tracking field of view, extracts the features of the object to be ranged with respect to this tracking field of view, stores the extracted features, and Detects whether or not the object is moving based on the memorized features and newly extracted features of the object to be ranged, and moves the range measurement field of view to track the object's movement according to the relative movement of the object. We have proposed an automatic tracking focus detection device (Patent Application No. 105897 of 1983, title of the invention: "Automatic tracking focus detection device"), but the implementation of this proposal will be detailed later. In this way, if the tracked subject moves relatively away from the center of the shooting screen beyond a predetermined range, the focus detection target object may be replaced with another object that is expected to appear at or near the center of the screen. In order to switch to an object, etc., it is desirable to issue a warning that the tracked subject has moved relatively away beyond a predetermined range.

(Purpose) The present invention eliminates the above-mentioned drawbacks of conventional automatic focus detection devices, automatically detects the moving position of a moving subject, moves the distance measurement field of view to track the movement of the subject, and focuses the subject. To provide a camera equipped with a means for giving a warning when a tracked object moves away beyond a predetermined range from the center of a photographic screen when performing detection or focus adjustment.

(Description based on Examples) Hereinafter, with reference to FIGS. 1 to 13, etc., the means taken in this invention to achieve the above object will be exemplified and explained. The following explanation is an overall explanation of an embodiment of the camera of the present invention, as well as a limit area setting means, a subject movement detection means, and an automatic focus in the same embodiment, regarding an example in which features of a tracked subject are extracted using color signal information. The operations of the detection means, the focus detection mark setting means, and the embodiments of the present invention are performed in this order.

(Overall explanation of the embodiment of the camera of this invention) (First
Figure 1 shows the main parts of an embodiment of the camera according to the present invention, in which 1 is a lens group for adjusting the focus in the photographic optical system, and 2 is an example of the imaging means. It shows a solid-state image sensor such as a CCD.
As is well known, the solid-state image sensor 2 is controlled by an image sensor drive circuit (not shown) to photoelectrically convert light from a subject incident on its light-receiving surface. This photoelectrically converted signal is amplified by a preamplifier (not shown), subjected to various correction processes in the signal processing circuit 3, and a color difference signal (R
-Y), (B-Y) and a luminance signal Y are created. These color difference signals and luminance signals are combined with a synchronization signal by an encoder 15 to form an output video signal, such as an NTSC signal, which is supplied from an output terminal 16 to a device to be used, such as a video deck.

The above color difference signals (R-Y) and (B-Y), and if necessary, the luminance signal Y are input to the movement detection circuit 5 via the tracking gate circuit 4, and the circuit detects the moving direction or movement of the subject. amount is detected. Here, since the movement between the subject and the camera is relative, the above-mentioned movement of the subject includes cases in which the camera is fixed and the subject moves, as well as cases in which the subject stops and the camera moves, or This refers to a case where both move together, and the present invention is applicable to any of the above cases.

In the tracking gate circuit 4, the gate position for the color difference signal and the like is set by the gate pulse generated by the gate pulse generation circuit 11. As a result, the position of the tracking field of view is determined for extracting the features of the subject and the features of the background, for example, in the manner shown in FIGS. 5 to 8, which will be described later. In other words,
A range of the color difference signals and the like to be input to the movement detection circuit 5 is determined, and movement of the subject is detected based on changes in this signal. This object movement detection signal is supplied to a gate movement circuit 6, which generates a signal for moving the gate position of the tracking gate circuit 4, that is, the tracking field of view position, in accordance with the movement of the object to be tracked. This signal is supplied to a gate pulse generation circuit 11, which forms a gate pulse for extracting a color difference signal at a position corresponding to the movement of the tracked object. The gate pulse generation circuit 11 is
Horizontal synchronization signal f _H generated by the synchronization signal generation circuit 10
and operates in synchronization with the vertical synchronization signal _fV . Note that the synchronizing signal generating circuit 10 is controlled by a signal obtained by frequency-dividing a clock pulse generated by a clock pulse generating circuit (not shown) that controls the timing of the entire apparatus, and furthermore, the above-mentioned image sensor driving circuit is controlled by, for example, this frequency-divided signal. The encoder 15 described above is controlled by the synchronization signal, etc., and various types of synchronization control are performed, but since these synchronization control means are well known in video signal processing systems, a detailed explanation will not be provided. Also, illustrations are omitted except for parts particularly related to the description of the features of the present invention. Further, details of the movement detection circuit 5 will be described later with reference to FIGS. 5 to 8.

On the other hand, the luminance signal Y is inputted to an automatic focus detection device 8 via a distance measurement gate circuit 7, and focus detection or focus adjustment is performed by the same device. Ranging gate circuit 7
Then, the gate position with respect to the luminance signal Y is set to the same relative position as the tracking gate by the gate pulse generated by the gate pulse generation circuit 11,
This determines the range (hereinafter referred to as distance measurement field of view) of the luminance signal Y that is input to the automatic focus detection device 8 for detecting the focus of the subject. In the embodiments of the present invention, the tracking field of view and/or distance measurement field of view can be displayed on a display device such as an electronic viewfinder if necessary, but this is not an essential means.

In FIG. 1, the tracking gate circuit 4 and the ranging gate circuit 7 are provided separately, but both gate circuits may be provided in common, or the latter may be connected after the former and the distance measurement gate circuit 7 may be set by the former. The distance measurement field of view may be set in an even smaller area within the tracking field of view.
However, in any case, both fields of view must be set at the same relative position, in particular with the same center position, during the tracking operation. In the example shown in FIG. 1, the tracking field of view and the distance measurement field of view can each be set to arbitrary sizes. Furthermore, if the size of one or both of the fields of view is automatically adjusted by a gate size determining circuit (not shown) according to the shooting distance and the focal length of the lens, the tracking field of view of the optimum size or ( and) a distance measurement field of view can be obtained.

In the automatic focus detection device 8 connected after the ranging gate circuit 7, automatic focus detection is performed according to known means, and its output signal is sent to the lens drive device 17.
The lens group 1 is driven by the drive motor. When the focal point is detected, the control loop described above stops operating, and the lens group 1 also stops at that position. A specific example of the automatic focus detection means will be described later with reference to FIG.

The position information obtained from the gate movement circuit 6 is supplied to the character generator 12, where a focus detection mark signal indicating the object to be focus detected is formed, and this signal is outputted from the encoder 15 as an output video signal (NTSC signal). are added by an adder circuit 13, and a video signal and a mark (for example, FM in FIG. 11) indicating a focus detection target object are displayed on a display device, such as an electronic viewfinder (EVF) 14. The details of the character generator 12 will be described later with reference to FIG. 10.

Next, the tracking visual field return means in the embodiment shown in FIG. 1 will be explained. First, the limit area setting circuit 18 and the calculation circuit 19 are an example of main components for returning the tracking field of view to the initial position when the subject moves out of the shooting screen or a specific area of the limit area. Among these, the limit area setting circuit 18 is controlled by the horizontal synchronizing signal f _H and vertical synchronizing signal f _V generated by the synchronizing signal generating circuit 10 and follows the photographer's settings, for example as shown by BA in FIG. 11. Set the limit area. The limit area BA is provided for performing tracking operations only within the limit area BA, and the current position of the tracking field of view is determined in advance in the arithmetic circuit 19 according to the output signals of the limit area setting circuit 18 and the gate movement circuit 6. It is determined whether it is within the manually set limit area BA. When it is determined that the position of the tracking field of view, and therefore the position of the tracked subject on the screen, has left the limit area BA, the tracking field of view is returned to the initial position, for example, a position corresponding to the center of the shooting screen. .
One of the means for this purpose is a tracking gate circuit which resets the movement detection circuit 5 and the gate movement circuit 6 under the control of the arithmetic circuit 19 and is controlled by the gate pulse generated by the gate pulse generation circuit 11. The purpose is to move the gate position No. 4 to a position corresponding to the above-mentioned initial position. In the present invention, the limit area is a means for determining the range in which a tracking operation is performed, and does not necessarily need to be displayed on a viewfinder or the like. Further, the limit area can usually be set as a narrower range within the entire surface of the photographic screen, or as a narrower range within a part of the photographic screen.

As another means of returning the tracking field of view to its initial position, in order to perform stable tracking when the subject is moving rapidly, instead of resetting it immediately after the subject leaves the limit area BA, It is possible to configure the process to be performed after a settable predetermined time has elapsed. The time setting circuit 21 and timer 22 are provided for this purpose, and the operating time of the timer 22 is determined via the time setting circuit 21 according to the settings of the photographer. When it is determined that the tracked object has left the limit area BA, the arithmetic circuit 19 transfers the control signal a to the movement detection circuit 5 and the gate movement circuit 6 to stop the operation of these circuits, and starts the timer 22. The control signal b is transferred to start the operation. During its operation, the timer 22
The control signal c is transferred to the character generator 12, lens drive device 17, and warning circuit 20.
As a result, the character generator 12 stops displaying the focus detection mark, and the lens driving device 17 stops its operation, so that the focus detection state determined by the position of the lens group 1 at that time is maintained. Furthermore, the warning circuit 20 generates a warning that the tracked object has left the limit area BA, and notifies the photographer of this fact or that the tracking operation is currently stopped. As specific means for this purpose, various means are possible, such as flashing the boundary line (frame) of the limit area BA or generating an audible sound signal.

When the predetermined time set by the time setting circuit 21 has elapsed, the operation of the timer 22 ends, and the gate position of the tracking gate circuit 4 determined by the movement detection circuit 5 and the gate movement circuit 6 is changed to the initial position according to the control signal d. As a result, the tracking field of view moves to the initial position (for example, a position corresponding to the center of the photographing screen), and the movement detection circuit 5 again starts the object movement detection operation described later, and also ends the control signal c. As a result, the character generator 12 and the lens driving device 17 resume their operations, the warning circuit 20 stops its operation, and the automatic tracking operation is performed again. Note that if the limit area setting circuit 18 sets the entire shooting screen as the limit area by the photographer's operation, or if the entire shooting screen is fixedly set as the limit area, the tracked subject may move outside the shooting screen. It is determined that the tracking field has come out, and the above-mentioned tracking field of view is restored and related operations are performed. Further, in this specification, the meaning of the term "the subject moves out of the photographic screen or out of the limit area" will be described later with reference to FIG. 4. Note that the gate position of the ranging gate circuit 7 is also returned to a position corresponding to the center of the photographing screen following the tracking gate circuit 4.

(Limit Area Setting Means in the Embodiment of the Invention) (Figs. 1 to 4) Next, the limit area setting means in the embodiment of the invention will be described with reference also to Figs. 2 to 4. In FIG. 2, 30 and 31 indicate the boundaries in the x direction of the limit area BA, and 32 and 33 indicate the boundaries in the y direction, and the knob 40 in FIG.
Boundary line 3 that determines the position in the x direction by manual operation of
0, 31 move left and right, and lock button 41
The position is fixed by the operation. Similarly, the boundary lines 32 and 33 that define the position in the y direction are moved up and down by operating the knob 42 in FIG. 4B, and their positions are fixed by operating the lock button 43.
That is, the position of the limit area BA can be variably set by operating the knobs 40 and 42;
One additional knob may be provided in both the x direction and the y direction, and the boundary lines 30 and 31, as well as 32 and 33, may be set independently, so that the size of the limit area BA can also be variably set. In order to generate signals indicating the positions of the border lines 30 to 33 in response to the operations of the above-mentioned knobs and lock buttons, the positions of the horizontal scanning lines (corresponding to 32 and 33) corresponding to these border lines and the What is necessary is to select specific positions (corresponding to 30 and 31) in each horizontal scanning line with the horizontal scanning line as the upper and lower ends.

To do this, for the former, count the number of horizontal scanning lines in one field and select the horizontal scanning line with the number corresponding to the position of the boundary line 32, 33 set by the knob 42, etc., and for the latter, To generate a pulse train by multiplying the horizontal synchronizing signal frequency, count from the start of the horizontal scanning period and select the pulse number corresponding to the position of the boundary line 30, 31 set by the knob 40 etc. .
Alternatively, triangular waves synchronized with the horizontal and vertical synchronizing signals are generated, and these triangular waves are set at voltage levels corresponding to the positions of the boundary lines 30, 31 and 32, 33 set by the knobs 40, 42, etc., respectively. , generate a rectangular wave by clipping it with (See Japanese Unexamined Patent Application Publication No. 1983-4384 filed by the present applicant, title of the invention "Video camera"). Furthermore, the same means as the character generator 12 described later may be used.

Fig. 4 shows the timing relationship of the signals created as described above for one horizontal scanning period, where a shows a simplified video signal and b shows a limit area.For details, see Fig. 2. boundary line 3
Indicates the position where 0, 31 and the horizontal scanning line intersect,
c is the composite signal of the a signal and the b signal, d is the limit area width in the x direction (defined by the boundary lines 30 and 31) in FIG. 2, and e is the gate position by the tracking gate circuit 4 in FIG. 1. , f indicates the time axis, respectively. In this example, the signal indicating the limit area width of d is at a low level in the limit area and at a high level in other parts. Further, the tracking field of view is determined by the signal e indicating the gate position. Furthermore, the fourth
Although the figure does not show a signal representing the limit area in the y direction of FIG. 2, this limit area is also set in the same manner as that shown in FIG. 4. The limit area BA does not necessarily need to be displayed on a display device, but in order to display it on a display device such as the electronic viewfinder 14, the output signal of the limit area setting circuit 18 is sent to the character generator 12 or directly to the electronic viewfinder 14. All you have to do is supply it to and display it.

In the arithmetic circuit 19, the gate position by the tracking gate circuit 4, that is, the tracking field of view is in the limit area BA.
In order to determine whether the signal e exists within the range, it is determined by examining the position of the signal e on the time axis in FIG. 4 or the temporal relationship between the signal d and the signal e. That is, the former is the object to be tracked, in other words, assuming that the signal indicating the _gate position moves from right to _{left in FIG .} This is performed by calculating in the calculation circuit 19 whether the relationship T ₄ −T ₃ )<T _K (here, T _K is a positive constant determined in design) is satisfied. Generally, the position within the limit area BA of the tracking field of view can be found by calculating (T ₂ −T ₁ )/(T ₄ −T ₁ ). In the latter case, if the logical sum of the signal d and the signal e is low level, it is determined that the signal is within the limit area BA, and if it is high level, it is determined that the signal is outside the limit area BA. Tracking field of view is limited area BA
When it is determined that it is outside the limit area BA or that it has moved from the center of the limit area BA toward the outside of the area and is approaching within a certain range (for example, the above-mentioned T _K ) with respect to the boundary line, the arithmetic circuit 19 For example, the above-mentioned reset signal is sent to the movement detection circuit 5 and the gate movement circuit 6, and in conjunction with this, for example, the above-mentioned reset operation is performed.

In this specification, when the subject moves outside the shooting screen or outside the limit area, it means when the subject moves relatively completely outside these areas, or when the subject moves relatively from the center of the shooting screen to near the boundary line. This refers to the case where the above-mentioned relationship (T ₂ - T ₁ ) < T _K or (T ₄ - T ₃ ) < T _K is satisfied.

(Subject movement detection means in the embodiment of the present invention) (Figs. 1, 5 to 8) Next, the movement of the object to be tracked is detected and tracked, and the tracking gate circuit 4 of Fig. 1 A specific example of the movement detection circuit 5 for moving the gate position, that is, the tracking field of view, will be described with reference to FIGS. 5 to 8. The specific example below is an example in which the features of the tracked object are extracted as color signal information, but the features of the object can also be extracted using information such as a luminance signal, the shape of the object, temperature, or characteristic contrast in the object. This can also be done using .

To summarize the object movement detection and automatic tracking means described below, some parameters representing the characteristics of the object, such as the colors of the object and the background, are extracted with respect to the tracking field of view set by the tracking means,
The extracted features are stored, and based on the stored features and the newly extracted features of the subject, the presence or absence of movement of the subject and, if the subject moves, the direction or position of movement is detected. , moving the tracking field of view to track the movement of the subject;
Further, as the tracking field of view moves, the distance measurement field of view is moved in the same positional relationship.

In principle, the tracking field of view has a two-dimensional extent, but for the sake of simplicity, here, as shown in Figure 5A, the tracking field of view has a one-dimensional extent extending in the horizontal direction. Suppose there is. It is also assumed that the tracking field of view is divided into three parts ABC (each part is hereinafter referred to as a pixel). Note that to configure a two-dimensional tracking field of view, for example, pixel B or
Pixels extending vertically above and below AB and C may be provided.

As shown in FIG. 6, the color difference signals (R-Y) and (B-Y) obtained as time-series signals from each pixel are connected to integration circuits 50a and 50b, respectively.
Sample hold (S/H) circuits 51a, 51b
Then, the A/D conversion circuits 52a and 52b perform integration, sample hold, and A/D conversion processing, and store them in the memories 53a and 53b, respectively. This stored value is applied to each pixel A, B, and C.
When plotted on the orthogonal coordinates of (RY) and (BY), it is displayed as shown in FIG. 7, for example. In the figure, points A ₀ , B ₀ and C ₀ represent signals extracted from pixels A, B and C in FIG. 5A, respectively. 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 have different positions on the color difference signal coordinates.

Next, when the subject shown in Figure 5A moves to the right within the screen as shown in Figure 5B, the ratio of the subject to the background within pixels A and C changes, resulting in The resulting signal is shown in Figure 7.
They change as shown in A ₁ and C ₁ respectively. on the other hand,
Since pixel B remains within the subject as shown in FIG. 5B, the signal obtained from pixel B will hardly change if the subject's clothing is substantially monochromatic. Therefore, here, for simplicity, B ₁ =
Let B be ₀ . In this case, as shown in Figure 7, 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 the line segment A ₁ B ₁ becomes smaller than the line segment A ₀ B ₀ , it means that the subject is moving to the left in FIG. 5B. Assuming that the background color is the same on both sides of the subject, when the subject moves to the right in Figure 5B 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 invention can be applied to either of the above cases.

In order to detect the movement of the tracked object using the above-mentioned phenomenon, it is sufficient to detect, for example, a change in the length of the line segments AB and BC. For this purpose, the color detection circuit in the movement detection circuit 5 is used to detect the pixels A, B,
Detect the color of the object with respect to C and store it in the memory in the movement detection circuit 5, for example, via manual mechanical input means (registration of object characteristics);
At the next time, the newly extracted signal representing the color of the subject is compared with the signal stored in the memory to detect whether or not the subject has moved, and if the subject has moved, for example, the direction of movement. The above processing is performed at 1/60th of the period of one field of the television signal.
This is done according to its average value during a period of seconds or several fields thereof. In the following, both will be explained as being processed in one field period.

FIG. 8 shows an example of a specific circuit for executing the above processing, and this circuit also shows details of the movement detection circuit 5 of FIG. 1. From the (RY) and (B-Y) signals of pixels A and B, which have passed through the tracking gate circuit 4 of FIG.
-Y) Line segment on coordinates A ₀ B ₀ length D _A0

Claims (1)

[Scope of Claims] 1. An automatic tracking device that detects the movement of a subject to be tracked within a photographic screen and tracks the subject, comprising: a tracking area for tracking the subject within the photographic screen; tracking area setting means for setting the tracking area; tracking means for controlling the tracking area setting unit based on changes in the characteristics of the tracking subject within the tracking area to vary the set position of the tracking area; a focus adjustment means for performing focus adjustment based on image information at a set position of the region; a limit region setting means for setting a predetermined limit region indicating a range in which the tracking region can be set within the photographing screen; warning means for issuing a warning when it is determined that the tracking area has left the limit area; and when it is determined that the tracking area has left the limit area, the object tracking operation and the focus adjustment means are stopped for a predetermined period of time. a control means for returning the tracking area to a predetermined initial position within the photographing screen after a lapse of time, and restarting the tracking operation and focus adjustment operation after it is determined that the tracking area has returned to the initial position; A camera equipped with.