JPS6139009A - Camera - Google Patents

Abstract

PURPOSE:To switch immediately and safely a subject to be detected at its focus to another substance and to track the switched substance by providing a camera with a means for holding a focus detecting system at a constant state during the period from the outgoing of the subject to the outside of a specific area to the transfer of a control signal by an initial position restoring means. CONSTITUTION:When deciding that the position of a subject to be tracked on a screen has gone out to the outside of a limited area in accordance with the output signals of a limited area setting circuit 18 and a gate moving circuit 6 in an arithmetic circuit 19, a control signal is outputted (a) to a movement detecting circuit 5 and a gate moving circuit 6 to stop their operation. The control signal (a) is also transferred to a control circuit 24 to stop the operation of a lens driving device 17 and the focus detecting system is held at the status fixed by the stop position of the lens group 1. When an operator depresses an initial button 25 under said status, the tracking field is moved to the initial position and the lens driving device 17 is restarted at its operation. When the tracking field is returned to the initial position, the succeeding subject on the same position or near the position can be tracked under the stable focus detecting operation.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a camera equipped with an automatic tracking focus detection device, and more particularly to a means for quickly switching the subject for focus detection 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 photographing screen as shown in FIG. 14(A). (B
), 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 subject (in this example, a house) will be in focus. However, since the person who is the object of focus detection becomes blurred, there is a drawback that the object of focus detection 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 allow the photographer to change the distance measurement field of view by operating a knob or the like, and this is difficult to do when the subject moves during shooting. It is difficult to maintain the distance measurement field position always above the focus detection target 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,
The presence or absence of movement of the object is detected based on the memorized characteristics and the newly extracted characteristics of the object to be ranged, and the distance measurement field of view is tracked to the movement of the object according to the relative movement of the object. We proposed a moving 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, as will be detailed later. , when the tracked subject moves relatively away from the center of the shooting screen beyond a predetermined range, the focus detection target subject is quickly moved to, for example, another object that is expected to appear at or near the center of the screen. It is desirable to be able to switch, and it is desirable that unstable fluctuations not occur in the focus detection system during the above switching.

(Objective) Therefore, the present invention solves the above-mentioned drawbacks of a conventional camera equipped with an automatic focus detection device, automatically detects the moving position of a moving subject, and adjusts the distance measurement field of view to the moving subject. To provide a camera capable of quickly switching a focus detection target object to another object according to a photographer's operation during a tracking operation for a certain object when performing focus detection or focus adjustment by tracking and moving the camera. With the goal.

Furthermore, the present invention achieves the above-mentioned objects, and
It is an object of the present invention to provide a camera in which there is no risk of unstable fluctuations in focus detection operation when switching the focus detection target object to another object.

(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 detection means in the same embodiment, regarding an example in which features of a tracked subject are extracted using color signal information. and the focus detection mark setting means, and the operations of the same embodiment are performed in this order.

(Overall description of an embodiment of the camera of the present invention) (Fig. 1) Fig. 1 shows a main part of an embodiment of the camera of the present invention, and in the figure, 1 indicates the photographic optical system. A lens group for focus adjustment, 2 is an example of an imaging means C, C, D,
This shows a solid-state image sensor such as . 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 converted into a color difference signal (R-Y) by a matrix circuit in the same circuit.
, (B-Y) and a luminance signal Y are 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 NTSCM 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 characteristics of the subject,
Furthermore, the position of the tracking field of view for extracting background features, for example, in the manner shown in FIGS. 5 to 8, which will be described later, is determined.

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 f and the vertical synchronization signal fv generated by the synchronization signal generation circuit IO. Note that the synchronization signal generation circuit IO is controlled by a signal obtained by frequency-dividing a clock pulse generated by a clock pulse generation 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. controlled by
The aforementioned encoder 15 is controlled by the aforementioned 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 be omitted, and in particular, this synchronization control means will be omitted. Illustrations are omitted except for parts related to the detailed description of the 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. In the measurement/distance gate circuit 7, the gate position for the luminance signal Y is set to the same interposition position as the tracking gate by the gate pulse generated by the gate pulse generation circuit ll, so that the focus detection of the object in the luminance signal Y is performed. The range input to the automatic focus detection device 8 for
(hereinafter referred to as a distance measurement field of view) is determined. 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 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, during the tracking operation, both fields of view must be set at the same relative position, especially with the same center position. In the example shown in Figure 1, the tracking field of view and the ranging field of view are , each can be set to any size. Furthermore, depending on the shooting distance and the focal length of the lens,
By automatically adjusting the size of one or both of the fields of view using a gate size determining circuit (not shown), it is possible to always obtain the optimal size of the tracking field of view and/or distance measurement field of view.

An automatic focus detection device 8 connected after the ranging gate circuit 7 performs automatic focus detection according to known means, and its output signal controls a lens drive device 17, and its drive motor drives the lens group 1. do. 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 focus detection target object 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 and generator 12 will be described later with reference to FIG. 1θ.

Next, the tracking field of view return means in the embodiment shown in FIG. 1 will be explained. The limit area setting circuit 18, the calculation circuit 19, the control circuit 24, and the initial button 25 are the main functions for returning the tracking field of view to the initial position when the subject goes outside the shooting screen or outside the limit area, which is a specific area. Among these, the limit area setting circuit 18 is an example of a constituent part, and is controlled by the horizontal synchronizing signal fH and vertical synchronizing signal fv generated by the synchronizing signal generating circuit 1O, and follows the settings of the photographer. The limit area indicated by BA in the figure is set. 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 control signal a is transferred from the arithmetic circuit 19 to the movement detection circuit 5 and the gate movement circuit 6. The data is transmitted to the control circuit 24 to stop these operations. When the control signal a is transferred, the control circuit 24 outputs the control signal C, and this control signal C stops the operation of the lens drive device 17, thereby stopping the lens group l at this position, and the focus detection system is maintained in a state determined by the position of the lens group l at the time when the tracking field of view leaves the limit area BA. Furthermore, the control signal C is the character generator 1
2 and stops its focus detection mark display operation.
The information is also transferred to a warning circuit 20, which is provided as necessary, to warn that the focus detection system is not operating.

When the photographer operates the initial button 25 in this state, a control signal e is transferred to the control circuit 24, and a control signal d is transferred from the control circuit 24 to the movement detection circuit 5 and gate movement circuit 6 to reset these circuits. However, the gate position of the tracking gate circuit 4 due to the gate pulse generated by the gate pulse generating circuit 11 moves to a position corresponding to the initial position, and the tracking field of view moves to the initial position. At the same time, upon input of the control signal e, the control circuit 24 turns off the control signal C, and the lens driving device 17 resumes 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. Therefore, when the tracking operation and focus detection operation are restarted and the tracking field of view returns to the initial position, if there is a next subject (for example, 02 in FIG. 11) at or near the same position, the tracking operation will continue It is done for.

As mentioned above, when the control signal C turns off, the character
The generator 12 resumes the focus detection mark display operation,
If the warning circuit 20 is operating, its operation is stopped. In the embodiment of the present invention, the limit area BA is a means for determining the range in which a tracking operation is performed, and does not necessarily need to be displayed on a finder or the like. The other limit area BA 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. However, 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 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.

In the embodiment shown in FIG. 1, it is possible to return the tracking field of view to the initial position by operating the initial button 25 even when the subject is within the photographic screen or within the limit area BA.

(Limit area setting means in the embodiment of this invention) (First
(FIGS. 2 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 Figure 2, 30.31 indicates the boundary line in the X direction of the limit area BA, and 32
．． 33 also indicates the boundary line in the X direction, and there is
By manually operating the knob 40 in Figure (A), the boundary lines 30 and 31 that define the position in the X direction move left and right, and by operating the lock button 41, the position is fixed. Similarly,
The boundary lines 32 and 33 that define the position in the X direction are moved up and down by operating the knob 42 in FIG. 4B, 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 direction and the boundary line 30 and 31, the same <3
2 and 33 may be set independently, and the size of the limit area BA may also be set variably.

Boundary line 3 depending on the operation of the above knob and button 7.
In order to generate a signal indicating the positions 0 to 33, the positions of the horizontal scanning lines corresponding to these boundary lines (corresponding to 32 and 33) and the respective horizontal scanning lines whose upper and lower ends are these horizontal scanning lines are required. To select a specific position (corresponding to 30, 31) in the middle, for the former, count the number of horizontal scanning lines in the l field, and select the border line 32, 33 set by the knob 42, etc. The horizontal scanning line numbered corresponding to the position is selected, and for the latter, the horizontal synchronizing signal frequency is multiplied to generate a pulse train, and the boundary line 30 is counted from the beginning of each horizontal scanning period and set by the knob 40 or the like. It is sufficient to select the pulse number corresponding to the position .31.

Alternatively, triangular waves synchronized with the horizontal and vertical synchronizing signals are generated, and these triangular waves are connected to the boundary lines (30, 3) set by the knobs 40 and 42, etc.
A square wave is generated by clipping at the voltage level corresponding to the positions of 1) and (32, 33), and a pair of pulses corresponding to the front and rear ends of these rectangular waves are generated. The square wave and the other pair of pulses may be logically summed (see Japanese Patent Laid-Open No. 59-438 filed by the present applicant).
(See Publication No. 4, title of 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, and (a
) shows the video signal in a simplified manner, (b) shows the limit area, specifically the position where the boundary lines 30 and 31 in FIG. 2 intersect with the horizontal scanning line, and (c) shows the limit area (a) ) @ and (
b) the composite signal with the signal, (d) the critical region width in the X direction (defined by the boundaries 30 and 31) in FIG. 2, and (e
) is the gate position by the tracking gate circuit in Figure 1, and (f
) indicate the time axis. In this example, (
The signal indicating the limit area width in 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 a limit area in the X direction of FIG. 2, this limit area is also set in the same manner as that shown in FIG. The above-mentioned limit area HA 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 transmitted to the character, generator 12 or directly. What is necessary is to supply it to the electronic viewfinder 14 and display it.

In the arithmetic circuit 19, in order to determine whether the gate position by the tracking gate circuit 4, that is, the tracking field of view exists within the limit area BA, the position on the time axis of the signal (e) in FIG. 4 or the signal ( This is done by examining the temporal relationship between signal (d) and signal (e). That is, in the former case, the tracked subject, in other words, the signal indicating the gate position is the fourth one.
Assuming that we move from right to left in the figure, (T2-T1)<TK
, or moving from left to right (T4-T3)<TK
This is done by calculating in the calculation circuit 19 whether the following relationship (TK is a positive constant determined by design) is satisfied. Generally, the position within the limit area BA of the tracking field of view can be found by calculating (T2-Tt)/(T4-Tl). In the latter case, if the logical sum of the signal (d) and the signal (e) is low, it is determined that the signal is within the limit area BA, and if it is high, it is determined that the signal is outside the limit area BA.

The tracking field of view is outside the limit area BA, or the limit area BA
When it is determined that the gate has moved from the center of the gate to the outside of the area and is approaching within a certain range (for example, the TK mentioned above) with respect to the boundary line, the arithmetic circuit 19 sends a signal to the movement detection circuit 5 and the gate movement circuit 6. On the other hand, the control circuit 24 transfers the control signal a to stop the operation of these circuits, and then, when the photographer operates the initial button 25, the control circuit 24 transfers the control signal d.
is transferred to these circuits to return the tracking field of view to its initial position.

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. (T2-T1)
) <TK or (T4-T3)<TK.

(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 .

The following object movement detection and automatic tracking means can be summarized as follows:
Some parameters representing the characteristics of the object, in this example, the color of the object and the background, are extracted with respect to the tracking field of view set by the tracking means, the extracted characteristics are stored, and the stored characteristics are combined with the newly extracted characteristics. Based on the characteristics of the subject, it is possible to determine whether or not the subject is moving, and if the subject moves, to determine the direction of movement, and to move the tracking field of view to follow the movement of the subject. Along with the movement, the distance measuring field of view is moved in the same positional relationship.

In principle, the tracking field of view has a two-dimensional extent, but to simplify the explanation, it is shown in Fig. 5 (A).
Assume that the tracking field of view has a one-dimensional extension extending in the horizontal direction as shown in FIG. Also, the tracking field of view is A, B,
Suppose that it is divided into three parts (hereinafter each part is referred to as a pixel) of C. Note that in order to configure a two-dimensional tracking field of view, for example, pixels may be provided that extend vertically above and below pixel B or A, B, and C in the same figure as the center.

Color difference signal obtained as a time series signal from each pixel above (
RY) and (B-Y), as shown in FIG.
S/H) circuits 51a, 51b and A/D change circuit 52a
, 52b perform integration, sample hold, and A/D conversion processing, and store them in memories 53a and 53b, respectively. - If this stored value is plotted on the (R-Y) and (B-Y) Cartesian coordinates for each pixel A, B and C, it will be displayed e.g.
In the figure, points Ao, B, and CO are respectively shown in Figure 5 (
It represents the signals extracted from each pixel of A, B, and C in A). 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 Ao and Co have different positions on the color difference signal coordinates.

Next, when the subject shown in Fig. 5 (A) moves to the right within the screen as shown in Fig. 5 (B), the ratio of the subject to the background in pixels A and C changes, resulting in The signals obtained from A and C change as shown at 1 and C1 in FIG. 7, respectively. On the other hand, since pixel B remains within the subject as shown in FIG.
1) A sword, an axe, here.

For simplicity, it is assumed that Bl=B. In this case, as shown in FIG. 7, point C1 approaches point Bo (=Bt), and point A1
moves away from point Bo (=Bt), so line segment BICI becomes smaller than line segment noco, and line segment AIB becomes line segment AO.
B. Becomes larger. Conversely, line segment BIC, is line segment noc
If the line segment AIBI becomes larger than the line segment AOBO and the line segment AIBI becomes smaller than the line segment AOBO, it means that the subject is moving to the left in FIG. 5(B). If the background color is the same on both sides of the subject, the subject will appear in the screen as shown in Figure 5 (B).
When moving to the right, the above point A1 is located on the extension of the line segment AOBO, and one point C1 is located on the line segment noco. This invention can be applied to either of the above cases.

In order to detect the movement of the tracked subject using the above-mentioned phenomenon, for example, it is sufficient to detect the change in the length of the line segments AB and BC. In the circuit, the pixels A and B mentioned above.

The movement detection circuit 5 detects the color of the subject with respect to C.
A signal representing the newly extracted color of the object and a signal stored in the memory are stored in the memory of the camera, for example, through manual mechanical input means (registration of object characteristics). The comparison is made 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 according to the average value during 1/60 second, which is the period of one field of the television signal, or during a period of several fields thereof. In the following, both will be explained as being processed in one field period.

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. The (RY) signals of pixels A and B that have passed through the tracking gate circuit 4 in FIG.
-Y) from the distance calculation circuit 60a in FIG.
-Y) and the length DA of the line segment AoB on the (B-Y) coordinates
DA1.O-80 is obtained and DA1. B1 or D
Al, 8O is required. Here, for simplicity, B1=
B, then DAl, B1=DA1. B
O, and the divider 62a calculates DAI-81/DAO,BO. This value is compared with a first threshold value set by the threshold setting device 63a in the comparison circuit 64a, and if there is a change exceeding the threshold value, "1" is output to the movement determination circuit 65. Similarly, the circuits from the distance calculation circuit 60b to the comparison circuit 64b produce Del-at/Dco, tl.

is calculated, and if there is a change in this that exceeds the second threshold set by the threshold setting unit 63b, the comparison circuit 64b outputs "1" to the movement determination circuit 65. To explain a specific numerical example, in the sequence shown in FIG. 7, both the first and second threshold values are set to 2.

DA-1,81/DAO,BO=2.2°Dcz,at
/Dco-Bo=0-36, so the comparison circuit 64a
only outputs “l”. In this case, the movement determination circuit 6
5 sets the gate setting timing for a predetermined time (for example, NTSC
In the case of this method, a signal that is delayed by about 17125 times one horizontal scanning period is generated. Conversely, only the comparison circuit 64b is “L”
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 1, for example, by the predetermined time described above, and in response to this signal, the gate movement circuit 6 and the gate pulse By controlling the gate circuits 4 and 7 by the 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.

(Automatic focus detection means in the embodiment of this invention) (First
Although the automatic focus detection device 8 shown in FIG. 1 can utilize known means, a method of detecting focus using high frequency components in a luminance signal will be described as an example. In FIG. 9, 70 is a bandpass filter, 71 is a level detection circuit, and 72 is a focusing direction detection circuit.The bandpass filter 70 extracts the outline component, that is, the high frequency component, from the output luminance signal of the gate circuit 7 in FIG. The level of this high-frequency component is detected by a level detection circuit 71, and the focusing direction detection circuit 72 controls the detection level so that this detection level becomes maximum. A signal representing the direction is output to the lens driving device 17 described above.

In carrying out the present invention, in addition to the above-mentioned means, suitable known means 1 such as infrared TT
L focus detection means or the like can be used.

(Focus detection mark setting means in the embodiment of this invention)
(FIGS. 1 and 1θ) In the embodiment of the present invention, a focus detection mark (FM in FIG. 11) that indicates the focus detection target object is set by the character fist generator 12, for example. The character generator 12 is supplied with a horizontal synchronizing signal f■ and a vertical synchronizing signal fV from the synchronizing signal generating circuit lO,
Further, the gate moving circuit 6 supplies a signal indicating the position of the tracking field of view, that is, the position of the subject. Note that instead of the synchronization signal, the frequency-divided signal obtained by dividing the clock pulse generated by the clock pulse generation circuit (the synchronization signal generation circuit 10 is controlled by this frequency division signal) is directly supplied to the character generator 12. It's okay. The character generator 12 receives these signals and generates a focus detection mark signal in the manner shown in FIG. That is, FIG. 10(a) shows a video signal generated by the signal processing circuit 3 in FIG. 1, and FIG. ), (c) of the figure shows a focus detection mark position selection signal generated based on the output of the gate moving circuit 6, and (d) of the figure shows a focus detection mark position selection signal generated by the character generator 12 in response to this focus detection mark position selection signal. (e) in the same figure shows a composite video signal in which this area signal and the output video signal are added in the adder circuit 13, and this composite video signal is transferred to the electronic viewfinder 14 and its A bright line indicating the outline of the focus detection mark is displayed on the finder surface by the pulse portion.

In order to display the focus detection mark FM on the finder surface, the pixels A, B, and C1 in FIG. 5, particularly the pixel B in the center thereof, may be displayed. Further, the limit area BA may be displayed on the electronic viewfinder 14 if necessary. And focus detection mark FM and limit area B
To display A 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 change the brightness or color tone across these areas compared to other parts. It is also possible to display the

(Function of the embodiment of this invention) (Fig. 1, Fig. 11 to Fig. 1)
Fig. 3) Fig. it shows the function of the limit area BA in the embodiment of the present invention, in particular, when the tracked object o1 goes outside the photographing screen or outside the limit area BA in the sense defined above, the tracking field of view is changed. This is to explain the function of returning to the initial position, for example, a position corresponding to the center of the limit area BA.

First, let us assume that the relative movement between the camera and the subject is done, for example, by panning the camera.
(B) shows the initial state, and (B) shows that after a certain amount of time has passed and the camera is moved to the right on the screen, the object o1 moves relatively to the left on the screen, and the limit area BA is This indicates that the boundary has been reached. In this example, when the state shown in FIG. 2B is reached, the control signal a is transferred from the arithmetic circuit 19 to the movement detection circuit 5 and the gate movement circuit 6 to stop their operations, as described above.
It is also transferred to the control circuit 24. When the control signal a is transferred, the control circuit 24 outputs a control signal C, and this control signal C stops the operation of the lens drive device 17, thereby stopping the lens group l at that position and performing focus detection. The system is maintained in a state determined by the position of the lens group l at the time when the tracking field of view leaves the limit area BA. Furthermore, the control signal C
is transferred to the character generator 12 to stop displaying the focus detection mark, and is also transferred to the warning circuit 20 to warn that the focus detection system is not operating.

Next, when the photographer operates the initial button 25, the control signal e is transferred to the control circuit 24, and along with this, the control signal d is transferred from the control circuit 24 to the movement detection circuit 5 and the gate movement circuit 6. The circuit is reset, and the gate position of the tracking gate circuit 4 by the gate pulse generated by the gate pulse generating circuit 11 is returned to a position corresponding to the initial position, and the tracking field of view is returned to the initial position. At the same time, upon input of the control signal e, the control circuit 24 turns off the control signal C, and the lens driving device fi17 resumes its operation.
Further, the focus detection mark display operation by the character generator 12 is restarted, and the warning operation of the warning circuit 20 is stopped. When the tracking field of view returns to the initial position, if there is a next subject 02 at or near the same position, the tracking operation is performed on the subject 02. Note that as the gate position of the tracking gate circuit 4 moves, the gate position of the ranging gate circuit 7, and therefore the ranging field of view, 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.

FIG. 11(C) shows this state, in which the previous object O] has moved out of the limit area BA, and the focus detection mark FM indicates the next object 02. Note that the subject 01 or (and) 02 may move during the above process. Next, when the tracked subject 01 moves to the left on the screen, it is basically the same as above, and in this case, the camera may be moved to the right on the screen to capture the next subject 02. .

As described above, in the apparatus shown in FIG. 1, the tracking operation stops after the object being tracked moves out of the limit area BA until the photographer operates the initial button 25, and the focus detection system The focus detection state at the time of leaving the limit area BA is maintained, and when the photographer operates the initial button 25, the tracking field of view returns to the initial position, and the tracking operation and focus detection operation are restarted. Therefore, if the subject being tracked leaves the limit area BA, the photographer must press the initial button 25.
By operating the camera, the tracking field of view can be returned to its initial position at any time, and the focus detection target object can be quickly switched to another object according to the photographer's intention. Furthermore, since the hot spot detection system is held in the current state from the time the tracked subject exits the limit area BA until the tracking field of view returns to its initial position, there may be unstable fluctuations in focus detection operation when switching subjects. There is no risk of this occurring. Furthermore, since the tracking system circuit also stops operating during this time, there is no risk of unstable fluctuations in the tracking operation. Furthermore, since the tracking field of view is restored after a time lag between when the tracked subject leaves the limit area BA and when the photographer operates the initial button 25, it is possible to easily cross the boundary line of the limit area BA in both directions when the subject is moving rapidly. Even in the case of intersections, the tracking field of view is returned to the initial position based on stable changes after a certain period of time, rather than temporary changes in the subject position, so the automatic focus detection operation for that subject is It is possible to do this stably.

Next, after the tracking field of view returns to the initial position, the next subject 0
Various methods can be considered for the means for registering the characteristics of the subject 02 in order to automatically track the subject 02, and some of them will be exemplified and explained. First, the previous subject o
If it is known in advance that both subject 1 and the next subject 02 have the same characteristics, for example color information, the data registered for the previous subject 01 can be used as is. In this case, it is possible to continue the tracking operation for the next object o2 based on the registered data specified in advance by a color specifying circuit (not shown) or the like. Second, when the subject 01 moves out of the limit area BA, the operation of the movement detection circuit 5 and the gate movement circuit 6 is temporarily stopped by the control signal a from the arithmetic circuit 19;
Inside the movement detection circuit 5 (for example, the memory 61a in FIG. 8).

61b), and when the tracking field of view returns to the initial position -1 If the background or the next object o2 exists at that position, register its characteristics; It is also possible to track the next subject 02 based on the latter registered data. Thirdly, even if the tracking field of view returns to the initial position, the characteristics of the subject etc. are not registered immediately, and the photographer confirms that the next subject 02 has entered the initial position using the electronic viewfinder 14 etc. It is also possible to perform a tracking operation by registering the characteristics of the subject by operating the camera (for example, by operating a button). Fourth
It is also possible to register the characteristics of the background or the target object, if any, at the position where the tracking field of view exists, and update this registered value sequentially at the cycle of one field or several fields. In this case, even if the target object does not exist at that position when the tracking field of view returns to the initial position, when the target object enters the position or its vicinity, the tracking operation can be performed automatically and smoothly. In the apparatus shown in FIG. 1, the tracking field of view can be returned to the initial position by operating the initial button 25 even when the subject is within the photographing screen or within the limit area.
It is possible to use the fourth method. In addition, the previous subject 0
1 may re-enter the initial position where the tracking field of view has returned, before the subject 02, but in this case, the problem of updating the registered data of the subject's characteristics does not occur.

In the above description of the apparatus shown in FIG. 1, it has been explained that the limit area BA is used as a reference to determine whether or not the subject goes outside of the limit area BA. It is also possible to determine that the tracked subject has moved out of the photographic screen, and then restore the tracking field of view and perform various operations related thereto. In addition, the relationship between the relative positions of the photographing screen or the marginal area MBA and the tracked object 01 in which the control signal a, etc. described above should be transmitted should be determined by considering various conditions. However, it is not limited to the relative position shown in FIG. 11CB).

On the other hand, the comparative example shown in FIG. 12 does not have the above-mentioned return means, so the camera is panned to the right on the screen from the initial state shown in FIG. In state (B), subject 01 has reached near the left edge of the screen, and even if the next subject 02, which the photographer naturally intended to focus on, is in the center of the screen, This results in the drawback that complete focus detection cannot be performed, that is, it is not possible to obtain an in-focus state.

FIG. 13 is a flowchart explaining the main operations of the device shown in FIG. 80).

Next, the photographer sets a focus detection mark (FM in FIG. 11) at an initial position, for example, at the center of the photographing screen while looking at a display device such as the electronic viewfinder 14. “At this time, the tracking field of view is also at its initial position (step 81), and the tracking operation is first performed for subject 01 at the initial position (step 82), but the photographer presses the initial button 2.
5, the tracking field of view returns to the initial position at any time (step 83). If the initial button 25 is not operated, the subject 01 will be displayed on the shooting screen or in the limit area BA (hereinafter referred to as the first
In Figure 3 and its explanation, both are collectively referred to as the limit area)
The tracking operation continues as long as the
), when the subject 01 moves out of the limit area BA, the movement detection circuit 5 and gate movement circuit 6 in FIG. 1 stop operating, the lens drive device 17 stops at that point, and the focus detection system (step 85), the focus detection mark display operation of the character generator 12 is stopped, and if the warning circuit 20 is provided, a warning operation is performed. This state continues until the photographer operates the initial button 25. When the photographer operates the initial button 25, the tracking field of view returns to the initial position and the focus detection system resumes the focus detection operation (step 86). .81) At this time, the focus detection mark display operation described above is restarted and the warning operation is stopped.

(Effects) As described above, according to the present invention, there is provided a means for automatically tracking a subject within a shooting screen or a specific area thereof;
a return means for returning a movably set tracking field of view to its initial position in response to an operation by a photographer; and a return means for returning a tracking field of view set to be movable to its initial position; Since the camera is equipped with a means for maintaining the focus detection system in the state at the point in time until the control signal is transferred, during the tracking operation for a certain subject, the focus detection system can be quickly moved to another subject according to the photographer's operation. In addition to being able to switch to another object, there is no risk of unstable fluctuations in the focus detection operation when switching the focus detection target to another object.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the main parts of an embodiment of the camera of the present invention, and FIGS. 2 to 4 illustrate the limit area setting means in the embodiment of FIG. is an explanatory diagram of the limit region, and Figures 3 (A) and (B) are the second diagram, respectively.
An explanatory diagram of the knob and lock button for setting the boundary line of the limit area in the X direction and the X direction in the figure, and FIG. 4 (a) to f) is an explanatory diagram explaining the timing of the signal for setting the limit area. , FIGS. 5 to 8 explain the subject movement detection means in the embodiment of FIG. 1, and FIGS. 5(A) and 5(B) show 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 in FIG.
FIG. 7 is an explanatory diagram showing a situation in which signals obtained from the device of FIG. 6 are plotted on a two-dimensional plane, FIG. 8 is a block diagram showing details of the movement detection circuit 5 in FIG. 1, and FIG. FIG. 1 is a block diagram showing details of the automatic focus detection device 8, 1st θ
Figures (a) to e) are waveform diagrams for explaining the action of setting the focus detection mark in the embodiment of Figure 1, and Figures 11 (A) to C) are waveform diagrams for explaining the effect of setting the focus detection mark in the embodiment of Figure 1. Explanatory diagram showing the relationship between the tracked subject and the focus detection mark for the purpose of explaining the function of the qn range, 12th
Figures (A) to C) 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, and Figure 13 is a flowchart explaining the operation of the device in Figure 1.
FIGS. 14(A) and 14(B) 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, 22 Solid-state imaging device which is an example of imaging means, 3: Signal processing circuit, 4: Tracking gate circuit, 5: Movement detection circuit, 6: Gate movement circuit, 7 : Distance measurement 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, 17. : Lens driving device, 18: Limit area setting circuit, 19: Arithmetic circuit, 24
: control circuit, 25: initial button, BA: limit area, FM: focus detection mark. Bubbles 2 figure 3? Fig. 3 (A) (B) Fig. 4 Fig. 5 Fig. 6 Fig. 7 -Y Fig. 8 Heat) 2 Two demons Fig. 9 Fig. 10 (c) 1111(d,)L
-■-pressure''LyuIL---□(e,),I''1 drama T
Ding ---, n 口 n fig. 11 % 12 fig. (A) ' (A) 范 fig. 14

Claims (1)

[Scope of Claims] Means for automatically tracking a subject within a photographic screen or a specific area thereof; and a return means for returning a movably set tracking field of view to its initial position in response to an operation by a photographer. and means for maintaining the focus detection system in the state at the time from the time when the subject relatively moves out of the photographing screen or the specific area until the control signal is transferred from the return means. A camera to carry.