JPH0586704B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The invention of this application relates to a camera equipped with an automatic focus detection device, and more particularly to a means for switching the focus detection target subject at any time according to the photographer's intention.

(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, the subject to be focused on (hereinafter referred to as the focus detection target subject; in this example, a person) moves. An object at a different distance from the subject (in this example, a house) will be in focus, and the person, the subject of focus detection, will be out of focus, so the subject of focus detection must always be placed at the center of the screen due to the screen configuration. There were flaws. 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 1981, title of the invention: "Automatic tracking focus detection device"), but in implementing this proposal, it is necessary to During operation, depending on the photographer's intention, the focus detection target object can be switched to another object at any time, or when the object being tracked moves a certain distance from the center of the shooting screen, the tracking operation for this object can be changed. It is desirable to have a configuration in which the subject can be brought closer to the photographer's intention by stopping the camera and switching the focus detection target object to another object.

(Objective) Therefore, the first invention of this application solves the above-mentioned drawbacks of the conventional camera equipped with an automatic focus detection device, automatically detects the moving position of a moving subject, and performs distance measurement. When performing focus detection or focus adjustment by moving the field of view to track the movement of a subject, the focus detection target subject can be switched to another object at any time according to the photographer's operation during the tracking operation for a certain subject. The purpose is to provide a camera that is capable of

The second invention is that when the object being tracked moves away from the center of the shooting screen to a certain extent, the focus detection target object can be switched to another object, and the focus can be changed at any time according to the photographer's operation. It is an object of the present invention to provide a camera capable of switching a detection target object to another object.

(Explanation based on Examples) Hereinafter, the means taken in the invention of this application to achieve the above object will be exemplified and explained with reference to FIGS. 1 to 13 and the like. The following explanation is an overall explanation of an embodiment of the camera of the invention of this application, as well as a limit area setting means, a subject movement detection means, The operations of the automatic focus detection means, focus detection mark setting means, and the same embodiment are performed in the order shown.

(Overall description of an embodiment of the camera according to the invention of this application) (Fig. 1) Fig. 1 shows a main part of an embodiment of the camera according to the invention of this application. A lens group 2 for focus adjustment in the optical system indicates a solid-state imaging device such as a CCD, which is an example of an imaging 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 color difference signals (R-Y), (B-Y) are sent to the matrix circuit in the same circuit. ) and a luminance signal Y are created. These color difference signals and luminance signals are combined with a synchronization signal by the encoder 15 to form an output video signal, for example, an NTSC signal, which is sent to the output terminal 1.
6, the data is supplied to a device to be used, for example, 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 invention of this application 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 a change 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 operates in synchronization with the horizontal synchronization signal _fH and the vertical synchronization signal _fV generated by the synchronization signal generation circuit 10. 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 invention of this application. 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 invention of this application, 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 both cases, during the tracking operation, both fields of view must be set in the same relative position, in particular with the same central 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 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). is added by the adder circuit 13, and the video signal and a mark (for example, FM in FIG. 11) indicating the focus detection 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 field of view return means in the embodiment shown in FIG. 1 will be explained. First, limit area setting circuit 1
8 and the arithmetic circuit 19 are examples of main components for returning the tracking field of view to the initial position when the subject moves out of the shooting screen or the limit area that is a specific area of the screen. The 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 settings of the photographer, and sets a limit area indicated by BA in FIG. 11, for example. do. The marginal area BA is
The current position of the tracking field of view is set manually in advance in accordance with the output signals 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 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 photographing screen. One of the means for this purpose is to reset the movement detection circuit 5 and the gate movement circuit 6 under the control of the arithmetic circuit 19, and reset the gate pulse generation circuit 1.
1 is to move the gate position of the tracking gate circuit 4, which is controlled by the gate pulse generated by No. 1, to a position corresponding to the above-mentioned initial position. Note that the above-mentioned 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. Further, the limit area is usually 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.

Another way to return the tracking field of view to its initial position is to perform the return operation as soon as the subject leaves the limit area BA, in order to perform stable tracking when the subject is moving rapidly. Instead, it is possible to perform the process 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. The tracked subject is in the limit area
When it is determined that BA has been exited, 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 sends the same signal a to the timer 22. Forward. Thereby, the timer 22 transfers the control signal b to the control circuit 24 during the period set by the time setting circuit 21. The control circuit 24 outputs the control signal c while receiving the control signal b, and transfers it to the character generator 12 and the lens drive device 17, so that the former stops displaying the focus detection mark, and the latter stops the focus detection mark display operation. The device 17 is stopped to maintain the focus detection state determined by the position of the lens group 1 at that time. The control signal c is further transferred to the warning circuit 20, which warns the photographer that the tracking operation is currently stopped.
Various means are possible for this purpose, such as flashing the boundary line (frame) of the limit area BA or generating an audible 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 above-mentioned initial state by 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.

Furthermore, in the embodiment shown in FIG. 1, it is possible to return the tracking field of view to its initial position at any time in response to an operation by the photographer. Next, an example of a specific means for doing so will be described. That is, the control circuit 24
In addition to the signal b from the timer 22, the signal e generated when the photographer operates the initial button 25 is also input, and when this signal e is input, the signal b from the timer 22 is on. The control signal d is turned on and the control signal c is turned off, the tracking field of view returns to its initial position, the lens driving device 17, etc. resumes its operation, and at that point a new subject (for example, as shown in FIG. O ₂ ) exists within the tracking field of view, the tracking operation is performed by switching to the object O ₂ . Therefore, after the tracked subject leaves the limit area BA or reaches its boundary line,
The return of the tracking field of view to the initial position and related operations are performed until the initial button 25 is pressed or until a certain period of time set by the time setting circuit 21 has elapsed, whichever comes first. The tracking operation can be performed in a state that more closely matches the photographer's intention. 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 the position corresponding to the center of the photographing screen by the tracking gate circuit 4 at any time.

Furthermore, if the tracked subject is within the shooting screen or in a limited area,
Even if it is within BA, the tracking field of view can be returned to the initial position by operating the initial button 25.

(Limit area setting means in the embodiment of the invention of this application) (Figs. 1 to 4) Next, referring also to Figs. 2 to 4, regarding the limit area setting means in the embodiment of the invention of this application. explain. In Figure 2, 30 and 31 are the limit areas
32 and 33 are the x-direction boundaries of BA, and y
The boundary lines 30 and 31, which determine the position in the x direction, are moved left and right by manual operation of the knob 40 in FIG. 3A, and their positions are fixed by operation of the lock button 41. . Similarly, the boundary lines 32 and 33 that define the position in the y direction move 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, but one additional knob is provided in both the x and y directions, and the boundary lines 30 and 31, as well as 32 and 33, can be set variably.
may 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 clipped at voltage levels corresponding to the positions of boundaries 30, 31 and 32, 33 set by knobs 40, 42, etc., respectively. to generate a square wave,
and 1 corresponding to the front and rear ends of these square waves.
All you have to do is generate a pair of pulses and take the logical OR of one rectangular wave and the other pair of pulses.
(See title of invention "video camera"). Furthermore, the same means as the character generator 12 described later may be used.

FIG. 4 also 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 simplified version of the video signal.
indicates the limit area, specifically the position where the boundary lines 30 and 31 in FIG. 2 intersect with the horizontal scanning line, c indicates the composite signal of the a signal and b signal, and d indicates the x in FIG. 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 is also set 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. In general, 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 a low level, it is determined that the signal is within the limit area AB, and if it is a high level, it is determined that the signal is outside the limit area BA.

It is determined that the tracking field of view is outside the limit area BA, or 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. Then, the arithmetic circuit 19 sends, for example, the above-mentioned control signal a to the movement detection circuit 5 and the gate movement circuit 6, and in conjunction with this, for example, the above-mentioned initial position return operation is performed.

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

(Subject movement detection means in an embodiment of the invention of this application) (Fig. 1, Fig. 5 to Fig. 8) Next, the movement of the object to be tracked is detected and tracked, and the tracking gate of Fig. 1 A specific example of the movement detection circuit 5 for moving the gate position by the circuit 4, 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 subject movement detection and automatic tracking means described below, some parameters representing the characteristics of the subject, in this example, the colors of the subject and the background, are 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 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. When these stored values are plotted on (RY) and (BY) orthogonal coordinates for each pixel A, B, and C, they are 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 . The invention of this application 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 (registering the characteristics of the object);
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 described 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 and tracks the subject within a specific area within a photographic screen, which tracks the subject within the specific area. a tracking area setting means for setting a tracking area for the purpose of the tracking; automatic tracking means for controlling the tracking area setting means based on the change and varying the set position of the tracking area within the specific area; and extracting from the imaging signal corresponding to image information at the set position of the tracking area. a focus adjustment means for performing focus adjustment based on a predetermined signal component obtained by the automatic tracking means; A camera comprising: control means for returning the tracking area to a predetermined position and restarting the tracking operation and focus adjustment operation after it is determined that the tracking area has returned to the predetermined position. 2. The camera according to claim 1, wherein the predetermined position is a central position of the photographing screen. 3. An automatic tracking device that detects the movement of a subject to be tracked and tracks the subject within a specific area within a shooting screen, the tracking area being set within the specific area for tracking the subject to be tracked. a tracking area setting means for extracting a predetermined signal component indicating a characteristic of the tracking subject from an image signal corresponding to the tracking area, and determining the tracking based on a change in the predetermined signal component indicating the characteristic; automatic tracking means for controlling an area setting means and varying the set position of the tracking area within the specific area; automatic return means for returning to the initial position; focus adjustment means for performing focus adjustment based on a predetermined signal component extracted from the imaging signal corresponding to image information at the set position of the tracking area; , manual return means for stopping the tracking operation and focus adjustment operation of the automatic tracking means and forcibly returning the tracking area to the initial position regardless of its position within the screen; A camera comprising: control means that enables the tracking operation and focus adjustment operation to be restarted after it is determined that the tracking operation and focus adjustment operation have returned to normal.