JPH0582786B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention relates to an automatic tracking device for a moving subject in an automatic focus detection or automatic focus adjustment device for a camera, especially a video camera, and particularly relates to an automatic tracking device for a moving subject. The present invention relates to a means for making it possible to switch the focus detection target object to another object by a simple means when the object moves away from the object.

(Background Art) In a camera equipped with a conventional automatic focus detection device with negligible difference, such as a video camera, the distance measurement field of view 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 (a house in this example) will be in focus, and the focus will be changed. Since the person who is the subject to be 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 for varying the distance measurement field of view, but these methods require the photographer to change the distance measurement field of view by operating a knob or the like, and this is difficult if the subject moves during shooting. Furthermore, 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. When the subject to be tracked moves a certain distance away from the center of the photographic screen, the tracking operation for this subject is stopped, and the focus detection target subject is moved to, for example, another object that is expected to appear at or near the center of the screen. It is desirable to have a configuration that allows switching to bring the image closer to the photographer's intention.

(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. It is an object of the present invention to provide an automatic tracking device that includes means for switching the focus detection target object to another object when the tracked object moves away from the center of the photographic screen to some extent during detection or focus adjustment. purpose.

(Explanation based on Examples) Hereinafter, with reference to FIGS. 1 to 12, etc., the means taken in this invention to achieve the above object will be exemplified and explained. The following description will explain the overall configuration of an embodiment of the automatic tracking device of the present invention, as well as the limit area setting means in the embodiment, with respect to an example in which features of a tracked subject are extracted using color signal information.
The automatic focus detection means, focus detection mark setting means, and limit area functions are performed in this order.

(Overall configuration of embodiment of automatic tracking device of this invention)
(Fig. 1) Fig. 1 shows the overall configuration of an embodiment of the automatic tracking device of the present invention, in which 1 is a lens group for focus adjustment in the photographing optical system, and 2 is an imaging lens group. A solid-state image sensor such as a CCD is shown as an example of the means. 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 is processed into color difference signals R-Y, B-Y and luminance signals by a matrix circuit in the same circuit. Y is created. These color difference signals and luminance signals are combined with a synchronizing signal by an encoder 15 to form an output video signal, for example, 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 movement direction or amount of movement of the subject is detected by the same circuit. Ru. 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 as required, 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, during the tracking operation, both fields of view must be set at the same relative position, in particular with the same center position. 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.

The limit area setting circuit 18 is an example of limit area setting means which is a main feature of the present invention, and is controlled by the horizontal synchronizing signal _fH and the vertical synchronizing signal _fV generated by the synchronizing signal generating circuit 10. For example, the limit area indicated by BA in FIG. 11 is set according to the photographer's settings. 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 manually set in advance in accordance with the outputs of the limit area setting circuit 18 and the gate movement circuit 6 in the arithmetic circuit 19. It is determined whether it is within the set limit area BA. Then, when it is determined that the position of the tracking operation, and therefore the position of the tracked subject on the screen, has left the limit area BA, means for returning the tracking field of view to the initial position, for example, a position corresponding to the center of the shooting screen. One of them is to reset the movement detection circuit 5 and the gate movement circuit 6 under the control of the arithmetic circuit 19, and to adjust the gate position of the tracking gate circuit 4 controlled by the gate pulse generated by the gate pulse generation circuit 11. is moved to a position corresponding to the above initial position. In the embodiment of the present invention, the limit area is a means for determining the range in which the tracking operation is performed, and does not necessarily need to be displayed on a viewfinder or the like. Also, the limit area is
As a narrower area within the entire shooting screen,
Alternatively, it is possible to set a narrower range within a part of the photographic screen.

The above initial position return means can be set in order to perform stable tracking operations when the subject moves rapidly, instead of returning to the initial position immediately when the subject leaves the limit area BA. It is possible to configure the process to be performed after a predetermined period of 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 also starts the timer 22.
The control signal b is transferred to start the operation.
During its operation, the timer 22 transmits the control signal c to the character generator 12 and the lens drive device 17.
In the former case, the display operation of the focus detection mark is stopped, and in the latter case, the driving device 17 is stopped to maintain the focus detection state determined by the position of the lens group 1 at that time. timer 22
When the operation is completed, the tracking gate circuit 4 and the gate position determined by the movement detection circuit 5 and the gate movement circuit 6 are returned to the position corresponding to the initial position by the control signal d, and the movement detection circuit 5 is operated again as described below. The object movement detection operation is started, and the control signal c
By the end of character generator 12
The lens driving device 17 also resumes its operation.
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 this invention)
(FIGS. 1 to 4) Next, the limit area setting means in the embodiment of the present invention will be explained with reference 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, 32, which define the position in the y direction, are moved up and down by operating the knob 42 in Figure B, and the 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, but one more knob is provided in both the x and y directions, and the boundaries 30 and 31, as well as 32 and 33, can be set independently. , and the size of the limit area BA may also be set variably.

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 each horizontal scanning period and select the pulse number corresponding to the position of the boundary line 30, 31 set by the knob 40 etc. good.
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 Publication No. 59-4384 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. Diagram border 3
Indicates the position where 0, 31 and the horizontal scanning line intersect,
c is the composite signal of signal a and b, and d is x in Figure 2.
The limit region width in the direction (defined by the boundary lines 30 and 31), e indicates the gate position by the tracking gate circuit 4 in FIG. 1, and f indicates the time axis. 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 position of the tracking field of view is determined by the signal e indicating the gate position. Although FIG. 4 does not show a signal representing the limit area in the y direction of FIG. 2, this limit area will also be explained in the same manner as shown in FIG.

The above 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 must be sent to the character generator 12 or directly to the electronic display device. It is sufficient to supply the data to the view index 14 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, in the former case, assuming that the tracked subject, in other words, 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.

It is determined that the tracking arrow is outside the limit area BA, or is moving 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. Then, the arithmetic circuit 19 sends, for example, the above-mentioned reset signal 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, the subject moving out of the limit area refers to when the subject moves relatively completely outside the limit area, or when the subject moves relatively from the center of the shooting screen to the vicinity of the boundary line. of (T ₂ − _{T 1} )
This refers to the case where the relationship of <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 following and specific examples are examples of extracting the features of the tracked subject as color signal information, but the feature extraction of the subject can also be performed using information such as the brightness signal, the shape of the subject, temperature, or characteristic contrast in the subject. This can also be done using .

To summarize the object movement detection and automatic tracking means described below, any parameter representing the characteristics of the object, such as the color of the object and the background, is extracted with respect to the tracking field of view set by the tracking means, and this extracted The 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 is detected, and if the subject moves, the direction or position of movement is detected,
The above-mentioned tracking field of view is moved to track the movement of the subject, and as the tracking field of view is moved, 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 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. 6, the color difference signals R-Y and B-Y obtained as time-series signals from each pixel described above are processed by integrating circuits 50a and 50b, sample and hold (S/H) circuits 51a and 51b, and Integration, sample hold, and A/D conversion are performed by A/D conversion circuits 52a and 52b and stored in memories 53a and 53b, respectively. When these stored values are plotted on the R-Y and B-Y rectangular coordinates for each pixel A, B, and C, they are displayed as shown in FIG. 7, for example. In the figure, each point A ₀ , B ₀ and C ₀ is
It represents the signals extracted from each pixel of A, B, and C of . 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, point A ₀ and
The position on the color difference signal coordinates is different from C ₀ .

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 .} Therefore, the point C ₁ will occupy a position 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. A distance calculation circuit 6 uses the R-Y signal and B-Y signal of pixels A and B that have passed through the tracking gate circuit 4 in FIG.
0a, the length D _{A0 B0} of the line segment A ₀ B ₀ on the R-Y and B-Y coordinates in FIG. 7 is determined and stored in the memory 61a.
is memorized. D _A1 · _B1 or D _A1 · _B0 is obtained in the same way from the signal of the next field. Here, for the sake of simplicity, considering the case where B ₁ =B ₀ , D _A1 · _B1 =D _A1 · _B0 , and D _A1 · _B1 /D _A0 · _B0 is calculated by the divider 62a. This value is the threshold value setter 63a
The comparison circuit 64a compares the change with a first threshold value set by the first threshold value, and outputs "1" to the movement determination circuit 65 if there is a change exceeding the threshold value. Similarly, D _C1 · _B1 /D _C0 · _B0 is calculated by the circuits from the distance calculation circuit 60b to the comparison circuit 64b, and a change exceeding the second threshold value set by the threshold value setting device 63b is calculated. If so, the comparison circuit 64b outputs "1" to the movement determination circuit 65. To explain a specific numerical example, in the example shown in Fig. 7, both the first and second thresholds are set to 2, D _A1・_B1 /D _A0・_B0 = 2.2, D _C1・_B1 /D _C0 - Since _B0 = 0.36, only the comparator circuit 64a outputs "1". In this case, the movement determination circuit 65 generates a signal that delays the gate setting timing by a predetermined time (eg, about 1/125 of one horizontal scanning period in the case of the NTSC system). Conversely, only the comparison circuit 64b is “1”
When outputting , the movement determination circuit 65 generates a signal that advances the gate setting timing by the above-mentioned predetermined time. The latter case is when the subject moves to the left in FIG.

Therefore, in response to the output "1" of the comparator circuit 64a or 64b, the movement determination circuit 65 generates a signal that changes the gate setting timing by, for example, the above-mentioned predetermined time, and in response to this signal, the gate movement circuit 6 and By controlling the gate circuits 4 and 7 by the gate pulse generation circuit 11, it is possible to move the tracking field of view and the distance measurement field of view in the direction in which the subject moves, and to perform focus detection at that position.

As mentioned above, instead of detecting changes in the distance between the positions on the color difference signal coordinates of each pixel, that is, changes in the lengths of line segments AB and BC, etc., we detect changes in the angle between these positions with respect to the origin O. It is possible to detect the movement of the subject by detecting the For example, calculate the ratio of angles between each pixel and the origin O, θ _A1・_B1 /θ _A0・_B0 and θ _C1・_B1 /θ _C0・_B0 , and move the subject depending on which of them exceeds the set threshold. The direction may also be determined.

In addition, two-dimensional coordinates based on the (RY/Y) and (B-Y/Y) signals, which are normalized by dividing the aforementioned color difference signals R-Y and B-Y signals by the luminance signal Y, are used to By calculating the change in distance or change in angle between points representing pixels, when the brightness of illumination light changes over time, the coordinates representing each pixel can be calculated regardless of whether the subject moves or not. It is possible to prevent the phenomenon in which the point approaches the origin O (when it becomes dark) or moves away from the origin (when it becomes bright), and performs a stable tracking operation. Furthermore, in FIG. 8, the movement determination circuit 65
The reason for outputting "1" is to ensure stable tracking operation that does not cause hunting or overshoot.

(Automatic focus detection means in an embodiment of the present invention) (FIGS. 1 and 9) The automatic focus detection device 8 shown in FIG. A method for performing focus detection using the middle high frequency components will be explained. In Figure 9, 70
1 is a band filter, 71 is a level detection circuit, and 72 is a focusing direction detection circuit.The band filter 70 extracts the contour component, that is, the high frequency component, from the output luminance signal of the ranging gate circuit 7 in FIG. The level of the high frequency component is detected by a level detection circuit 71,
A focusing direction detecting circuit 72 controls this detection level to be maximum, and a signal representing a moving direction for focus detection is outputted from the focusing direction detecting circuit 72 to the lens driving device 17.

In carrying out the present invention, in addition to the above-mentioned means, appropriately known means such as infrared TTL focus detection means can be used as means for focus detection.

(Focus detection mark setting means in the embodiment of the present invention) (Figs. 1 and 10) In the embodiment of the invention, the focus detection mark (FM in Fig. 11) indicates the object to be focus detected.
is set by the character generator 12, for example. The character generator 12 is supplied with a horizontal synchronization signal _fH and a vertical synchronization signal _fV from the synchronization signal generation circuit 10, and is also supplied with a signal indicating the position of the tracking field of view, that is, the position of the subject, from the gate movement circuit 6. Note that instead of the synchronization signal,
The frequency-divided signal obtained by frequency-dividing the clock pulse generated by the clock pulse generation circuit (the synchronization signal generation circuit 10 is controlled by this frequency-divided signal) may be directly supplied to the character generator 12. The character generator 12 receives these signals and generates a focus detection mark signal in the manner shown in FIG. That is, FIG. 10a shows the video signal generated in the signal processing circuit 3 of FIG.
Figure b shows an output video signal (NTSC signal) in which this video signal and the synchronization signal are combined by the encoder 15.
FIG. 3C shows a focus detection mark position selection signal generated based on the output of the gate moving circuit 6, and FIG.
Figure e shows a composite video signal obtained by adding this area signal and the output video signal in the adder circuit 13. This composite video signal is transferred to the electronic viewfinder 14, and its pulse portion is displayed on the viewfinder surface. A bright line showing the outline of the focus detection mark is displayed. To display the focus detection mark FM on the viewfinder surface, display pixels A, B, and C in Figure 5, especially pixel B in the center. It's okay. Further, the above-mentioned limit area BA may be displayed on the electronic viewfinder 14 if necessary. In order to display the focus detection mark FM and the limit area BA on the viewfinder surface, instead of the white (bright line) display described above, use a black display with the brightness of the outline particularly reduced, or use other methods over the entire area. It is also possible to display the image by changing the brightness or color tone of each part.

(Function of limit area in embodiments of this invention)
(Fig. 1, Fig. 11, Fig. 12) Fig. 11 shows the function of the limit area BA in the embodiment of the present invention, especially when the tracked object _O1 is outside the shooting screen or in the limit area in the sense defined earlier. BA
This is to explain the function of returning the tracking field of view to the initial position, for example, a position corresponding to the center of the limit area BA when going outside. Assuming that the relative movement between the camera and the subject is done, for example, by panning the camera, Figure A shows the initial state, and Figure B shows the camera moving to the right on the screen after a certain amount of time has passed. As a result, the object _O1 has moved relatively to the left on the screen and has reached the boundary line of the limit area BA. In this example, when the state shown in FIG. The position is returned to a position equivalent to the initial position, thereby returning the tracking field of view to the initial position. Then, when the tracking field of view returns to the initial position, if there is a next object O ₂ at or near the same position, the characteristics of this object O ₂ are registered again, and the tracking action is performed using the same object.

FIG. 11C shows this state, and
In this state, the previous object O ₁ has moved out of the limit area BA, and the focus detection mark FM is pointing to the next object O ₂ . In addition, in the above process, the object O ₁
or (and) _O2 may be transferred. Next, if the tracked object O ₁ moves to the left on the screen, it is basically the same as above, but in this case, move the camera to the right on the screen and capture the next object O ₂ . Good too.

In the tracking field of view return operation described above, if the subject is moving rapidly, etc., as explained earlier with reference to the time setting circuit 21, timer 22, control signals a to d, etc. in FIG. When O ₁ moves out of the limit area BA, the operation of the movement detection circuit 5 and the gate movement circuit 6 is immediately stopped by the control signal a from the arithmetic circuit 19, and the operation of the movement detection circuit 5 (for example, the 8th The data storing the characteristics of the subject stored in the memories 61a and 61b in the figure is cleared, and after a predetermined period of time, the tracking field of view is returned to the initial position, and the next subject to be photographed, such as O ₂ , is located at this position. If the object exists, stable tracking can be achieved by registering the characteristics of the object again and performing the tracking operation based on this. Alternatively, even if the tracking field of view returns to the initial position, do not immediately register the characteristics of the object, but use the electronic viewfinder 14 etc. to confirm that the next object O ₂ has entered the initial position. It is also possible to perform a tracking operation by registering the characteristics of the subject through an operation (for example, a button operation) by the photographer. Furthermore, if the characteristics of the background or the target subject are present at the position where the tracking field exists, the features are registered, and if the configuration is configured to update this registered value sequentially at the cycle of one field or several fields, the tracking field of view can be adjusted to the initial position. Even if the target subject does not exist at that position when the camera returns to the position, the tracking operation can be automatically and smoothly performed when the target subject enters the position or its vicinity. Note that the previous object O ₁ may re-enter the initial position where the tracking field of view has returned before object O ₂ , but
In this case, there is no problem of updating the registered data of the characteristics of the subject.

As described above, when the operation of the movement detection circuit 5 and the gate movement circuit 6 is stopped, the display operation of the focus detection mark by the character generator 12 is stopped, and the operation of the lens driving device 17 is also stopped. The focus detection state determined by the position of the lens group 1 at the time is maintained. When the movement detection circuit 5 and the gate movement circuit 6 start the tracking operation again, the focus detection mark display operation and the focus detection operation are also restarted. Note that as the gate position of the tracking gate circuit 4 moves, the gate position of the ranging gate circuit 7 also moves to the same related position.
Naturally, focus detection is performed on the subject at the position to which the tracking field of view has moved. Furthermore, the relationship between the relative positions of the limit area BA and the tracked object _O1 in which the above-mentioned reset signal should be transmitted should be determined by considering various conditions. It is not limited to the relative position shown in FIG. 11B.

On the other hand, in the comparative example shown in Fig. 12, since the limit area is not set, the camera is panned to the right on the screen from the initial state of Fig. 12A, and after a certain amount of time has elapsed, the limit area is In the state shown in C in the same figure, where further time has elapsed, the object O ₁ has reached near the left edge of the screen, and the next object O ₂ , which the photographer naturally intended to focus on, is Even if the subject is in the center of the screen, complete focus detection cannot be performed for the subject _O2 . In other words, a disadvantage arises in that a focused state cannot be obtained.

Furthermore, by setting a limit area, a warning will be issued when the tracked subject moves out of this area, or the focal length of the photographing optical system will be shortened when the subject within the limit area approaches the boundary line. By changing the focal length, the tracking operation range can be effectively widened near the boundary line, and focus detection or focus adjustment can be performed more accurately.

(Effects) As described above, according to the present invention, there is provided an automatic tracking device that detects the movement of a tracking subject to be tracked within a shooting screen and tracks the tracking subject, tracking area setting means for setting a tracking area for tracking a tracking subject; controlling the tracking area setting unit based on changes in the characteristics of the tracking subject within the tracking area; tracking means for varying the tracking area, limit area setting means for setting a predetermined limit area indicating a range in which the tracking area can be set within the photographing screen, and determining that the tracking area has left the limit area. When the subject tracking operation is stopped, the tracking area is returned to an initial position in the center of the photographing screen after a predetermined period of time has elapsed, and after it is determined that the tracking area has returned to the initial position, the tracking operation is resumed. When the tracked subject moves a certain distance away from a position corresponding to the center of the shooting screen,
The focus detection target object can be easily switched to another object, and an automatic tracking device that can be brought closer to the photographer's drawing intention can be obtained. Furthermore, when the tracked subject goes outside this limit area, a warning is issued.
Alternatively, when a tracked subject that is inside the limit area approaches the boundary line, the focal length of the photographing optical system is switched to a shorter focal length to effectively widen the tracking range near the boundary line, and the focus is detected. Or focus adjustment can be performed more accurately.

In addition, even if the tracking area leaves the limit area, the tracking area does not return to the initial position immediately, but only after a predetermined period of time has elapsed. The tracking area may be returned to the initial position due to exiting the limit area, or the tracking area may be returned to the initial position simply due to noise. It is possible to prevent such malfunctions.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the automatic tracking device of the present invention, and FIGS. 2 to 4 illustrate limit area setting means in the embodiment of FIG. 1, and FIG. 3A and 3B are explanatory diagrams of the knobs and lock buttons for setting the boundaries of the limit area in the x and y directions of FIG. 2, respectively. Explanatory diagram explaining timing of signals to be set, fifth
8 to 8 are for explaining the subject movement detection operation in the embodiment of FIG. 1, and FIG.
and B are explanatory diagrams showing the relationship between the divided tracking field of view and the subject image, FIG. 6 is a block diagram of a device that processes signals obtained from the divided tracking field of view of FIG. 5, and FIG. The signal obtained from the device shown in the figure is
An explanatory diagram showing a situation plotted on a dimensional plane, FIG. 8 is a block diagram showing details of the movement detection circuit 5 in FIG. 1, and FIG. 9 is a block diagram showing details of the automatic focus detection device 8 in FIG. 1. , FIGS. 10A to 10E are waveform diagrams for explaining the function of setting the focus detection mark in the embodiment of FIG. 1, and FIGS. 11A to C illustrate the function of the limit area in the embodiment of the present invention. FIGS. 12A to 12C are explanatory diagrams showing the relationship between the tracked subject and the focus detection mark in a comparative example in which no limit area is provided; 13A and 13B are explanatory diagrams showing the relationship between the distance measurement field of view and the subject image in a conventional camera. Explanation of symbols 1: Lens group for focus adjustment,
2: solid-state imaging device which is an example of an imaging means, 3: signal processing circuit, 4: tracking gate circuit, 5: movement detection circuit, 6: gate movement circuit, 7: ranging gate circuit, 8: automatic focus detection device, 10: Synchronization signal generation circuit, 11: Gate pulse generation circuit, 12: Character generator, 13: Addition circuit, 14:
Electronic viewfinder, 15: Encoder, 1
7: Lens drive device, 18: Limit area setting circuit,
19: Arithmetic circuit, BA: Limit area, FM: Focus detection mark.

Claims (1)

[Scope of Claims] 1. An automatic tracking device that detects the movement of a tracking subject to be tracked within a shooting screen and tracks the tracking subject, comprising: an automatic tracking device for tracking the tracking subject within the shooting screen; tracking area setting means for setting a tracking area; tracking means for controlling the tracking area setting means based on changes in characteristics of the tracking subject within the tracking area to vary the set position of the tracking area; limit area setting means for setting a predetermined limit area indicating a range in which the tracking area can be set within the photographing screen; and stopping the subject tracking operation when it is determined that the tracking area has exited the limit area. and a control means for returning the tracking area to an initial position in the center of the photographing screen after a predetermined period of time has elapsed, and restarting the tracking operation after it is determined that the tracking area has returned to the initial position. An automatic tracking device for a camera that can be used. 2. The automatic tracking device for a camera according to claim 1, further comprising means for variably setting the limit area.