JPH03259670A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To display the ON/OFF state of an object automatic tracking at a current point of time on a monitor screen clearly by displaying a focus detection area onto the monitor screen and differentiating the display of the focus detection area from the fixed focus detection mode and the tracking detection mode. CONSTITUTION:When the automatic tracing mode is not selected, after the flow of the AF operation is finished, the tracking area is displayed on the screen of a monitor 23 via a display circuit 22 according to the setting of the lighting display of the tracking (focus detection) area. When the object automatic tracking mode is set and the setting of the position and the size of the focus detection area (tracking area) is finished, the blinking period of the display on the monitor screen of the focus detection area (tracking area) is changed to allow the operator to recognize the difference depending whether the tracking is implemented normally in the focused state to the object or the normal tracking is not implemented because of a large out of focus.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an automatic focusing device suitable for use in imaging devices such as video cameras and electronic still cameras.

(Prior Art) Conventionally, imaging devices such as video cameras detect the definition of images based on high frequency components of video signals output from the imaging means, and control the focusing lens position to maximize the definition. A method of focusing is known.

In addition, in a camera that uses such an image sensor to convert an optical image into an electrical signal, there is a method in which a part of the image capture screen is set as a focus detection area, and this is made to follow the movement of the subject to automatically adjust the focus state. proposed (for example, Japanese Patent Application Laid-Open No. 6
No. 0-249477).

According to this conventional device, by detecting the feature points of the subject within the focus detection area, the movement position of the subject is known, and the focus detection area is reset to a small area centered on the movement position. This allows you to keep a moving subject in focus.

(Problems to be Solved by the Invention) However, at present, such conventional devices do not perform focus adjustment with automatic tracking of the subject, or do they perform focus adjustment using a normal fixed focus detection area. The operator is not made aware of information such as whether or not the machine is currently operating, and the operator cannot immediately grasp the current operating state.

Therefore, it is not possible to accurately grasp the subject that is currently in focus, and the subject is not aware that the subject is being tracked other than the subject that the subject is trying to focus on. When the subject starts moving, the automatic tracking mode may not be activated, or conversely, the focus detection area may be fixed and focus detection may be performed.
Since the camera was in automatic tracking mode, when changing the subject to be focused on, the focus detection area would follow the previous subject, making it impossible to accurately focus on the main subject, resulting in various erroneous operations and malfunctions. This method had the problem that it was easy to cause.

(Means for Solving the Problems and Advantages) Therefore, an object of the present invention is to provide an imaging device that solves the conventional problems and allows the operator to clearly recognize the current focus adjustment operation mode. It was developed with the aim of a subject tracking means for displacing a set position of a detection area to follow a subject image; a first focus detection mode for performing a focusing operation by fixing the focus detection area at a predetermined position on the imaging screen;
a focus control means capable of setting a second focus detection mode in which a focusing operation is performed while tracking the detection area to a subject; The present invention provides an automatic focusing device including a display means for performing different displays depending on the focus detection mode and the second focus detection mode.

(Function) This clearly displays on the monitor screen whether the current focus detection mode is based on a fixed focus detection area or a focus detection area that moves according to the movement of the subject. This allows the operator to accurately recognize the current focus adjustment mode and prevents various malfunctions and erroneous operations.

(Embodiment) Hereinafter, an embodiment of the automatic focusing device according to the present invention will be described in detail with reference to the respective figures.

FIG. 1 is a block diagram showing a case where the automatic focusing device of the present invention is implemented in a video camera or the like.

In the figure, reference numeral 1 denotes a photographing lens system, which includes a focusing lens IA for performing focus adjustment and a zoom lens IB for performing a zoom operation. The focusing lens 1A is driven and controlled via a focusing motor drive circuit 9 and a focusing motor 10. Further, the zoom lens IB is driven and controlled via a zoom motor drive circuit 11 and a zoom motor 12. Reference numeral 2 denotes an aperture (iris) that controls the amount of incident light, and its drive is controlled via an iris drive circuit 7 and an ig meter 8 for driving the aperture.

Reference numeral 3 denotes an image sensor, such as a CCD, which photoelectrically converts the subject image formed on the imaging surface by the focusing lens 1 into an image signal, and 4 amplifies the image signal output from the image sensor 3 to a predetermined level. Preamplifier 5 performs gamma correction and blanking processing on the video signal output from preamplifier 4.

This is a process circuit that performs predetermined processing such as adding a synchronization signal, converts it into a standardized standard television signal, and outputs it from a video output terminal. The television signal output from the process circuit 5 is supplied to a monitor 23 such as a video recorder (not shown) or an electronic viewfinder.

Further, numeral 6 inputs the video signal output from the preamplifier 4, and controls the ig meter 8 via the iris drive circuit 7 in order to control the opening amount of the diaphragm 2 so that the level of the video signal is constant at a predetermined level. This is an iris control circuit that automatically controls.

Reference numeral 13 denotes a whole range filter set to be able to determine the magnitude of the contrast of the subject from the video signal output from the preamplifier 4, and 14 is a filter necessary for performing focus detection from the video signal output from the preamplifier 4. A bandpass filter extracts high frequency components, and 15 is a circuit that detects the blur width of the subject image (width of the edge portion of the subject image) from the video signal, making use of the property that the blur width of the subject decreases as it approaches the in-focus state. This is used to detect focus.

The focus detection method itself using this blur width detection circuit is well known, for example, from Japanese Patent Application Laid-Open No. 103616/1983, so a detailed explanation thereof will be omitted.

16 is a subject discrimination filter 13 and a bandpass filter 1
4. A gate circuit that applies a gate to the output of the blur width detection circuit 15 and allows only signals corresponding to a designated area on the imaging screen to pass. Only the signal corresponding to the specified area in the video signal for the 20 seconds passes through, thereby setting the pass area where high frequency components are extracted at an arbitrary position within the imaging screen, that is, the focus detection area where focus detection is performed. (FIG. 4 shows the focus detection area set on the imaging screen, and the states in each figure will be described later).

A peak position detection circuit 17 detects the position in the horizontal and vertical directions within the imaging screen where the peak value of the higher frequency component in the video signal corresponding to the focus detection area extracted by the gate circuit 16 is obtained. This peak position detection circuit detects in which block the focus detection area is divided into a predetermined number of blocks in the horizontal and vertical directions, and in which block the peak position detected in one field period is located. It outputs the vertical coordinate.

Further, 19 is a focus encoder that detects the moving position of the focusing lens 1A, 20 is a zoom encoder that detects focal length information varied by the zoom lens IB, and 21 is an iris encoder that detects the aperture amount of the diaphragm 2. These detection information are supplied to the logic control unit 18.

Reference numeral 18 denotes a logic control device that centrally controls the entire system, and is composed of, for example, a microcomputer. ). This logic control device includes a bandpass filter 1 outputted from a peak position detection circuit 17.
4, the peak value and its peak position coordinates within one field period of the high frequency component based on the output of 4, object contrast information based on the output of the object discrimination filter 13, blur width information based on the output of the blur width detection circuit 15, and each The detection information from the encoder is taken in and calculated according to a predetermined algorithm, and from these time-series changes,
It sets the position, size, movement direction, and movement response speed of the focus detection area on the imaging screen, that is, tracks the subject, and calculates the movement direction and movement speed of the focusing lens to obtain a focused point.

That is, based on the peak value within one field period of the high frequency component based on the output of the bandpass filter 14 and the coordinates of the peak position, the movement of the subject is detected for each field, and the changed peak position, that is, the subject position is detected. In order to set a focus detection area at a position centered on , a gate pulse is supplied to the gate circuit 16 to control opening and closing of the gate circuit 16, and only a portion of the video signal corresponding to the focus detection area of the video signal is passed through.

Furthermore, the logic control device unit 8 performs focus detection on the subject based on the video signal corresponding to the set focus detection area, and performs focus adjustment. That is, the blur width information supplied from the blur width detection circuit 15 and the peak value information of the high frequency component supplied from the band pass filter 14 are taken in, and the blur width in one field period is minimized and the peak value of the high frequency component is maximized. Focusing lens IA to the position where
In order to drive the focusing motor 10, control signals such as the rotational direction, rotational speed, and rotation/stop of the focusing motor 10 are supplied to the focus drive circuit 9 to control the focusing motor 10.

At this time, the logic control device 18 adjusts the size of the focus detection area according to the degree of focus and the depth of field calculated from the aperture value and focal length detected by the aperture encoder 21 and zoom encoder 20. control the speed, movement range, and movement response speed.

In this way, it is possible to keep the camera in focus while tracking a moving subject image.

Here, in the present invention, the blur width detection circuit 15 is used for focus detection.
The blur width signal output from the band pass filter 14
The reason why the peak value of the high frequency component outputted from the above is used is as follows.

In other words, the bokeh width becomes smaller as it approaches the in-focus point, and reaches its minimum value at the in-focus point, making it less susceptible to the effects of the contrast of the subject, which makes it possible to obtain high focus detection accuracy. If the focus is significantly off, sufficient detection accuracy cannot be obtained.

On the other hand, high-frequency components have a wide dynamic range and can obtain an output according to the degree of focus even if they are far out of focus, but they are greatly affected by contrast, and blur width information You can't get ruined accuracy.

Therefore, by combining these methods, it is possible to realize a focus detection method that has a wide dynamic range and provides high detection accuracy near the in-focus point.

Furthermore, the logic control unit 18 captures and constantly detects the contrast within the focus detection area within the imaging screen based on the output of the subject discrimination filter 13, thereby determining whether or not a subject is present within the imaging plane.

In other words, if the subject image is out of the imaging plane, or if it is so blurred that there is almost no contrast between the subject and the background, it will be difficult to distinguish the subject, and it will not be possible to accurately track it, making it likely to cause malfunctions. Focus adjustment cannot be performed accurately either.

The present invention takes this point into account, and determines the presence or absence of a subject from the contrast within the imaging plane, and if the subject is not present,
Moving the focus detection area, that is, stopping the subject tracking operation,
This prevents unnatural movement of the focus detection area and malfunctions due to erroneous detection of objects other than the subject.

In addition, in the present invention, when automatically tracking the subject described above, the depth of field is detected, and the size of the focus detection area,
It is configured to control the moving direction and response speed to perform optimal subject tracking.

Furthermore, the gate pulse output from the logic control device 18 is
After being subjected to predetermined signal processing not only through the gate circuit 16 but also through the display circuit 22, the signal is superimposed on the television signal output from the process circuit 5, is supplied to the monitor 23, and is focused on the monitor screen. It is configured so that the detection area can be superimposed, and the in-focus detection area can be displayed by lighting, blinking, etc. depending on the focus adjustment state.

Next, the overall control operation of the focus detection area by the automatic focusing device of the present invention will be explained step by step with reference to the flowchart shown in FIG.

Note that the automatic subject tracking operation in the present invention operates in the AF (automatic focus adjustment) mode, and is inactive in the manual focus adjustment mode, and the focus detection area is not displayed on the monitor screen.

Further, in the present invention, an AF mode with subject tracking operation,
A normal AF mode that does not involve a subject tracking operation is provided, and the currently operating mode is identified by a display on the monitor screen.

In FIG. 2, when the subject tracking control flow is started, it is determined in step S1 whether or not the subject automatic tracking mode is selected by a shooting mode changeover switch (not shown), and if the automatic tracking mode is not selected, step Proceeding to S27, the gate circuit 16 is controlled to fix the focus detection area at a predetermined set position in the center of the imaging screen, and the display circuit 22 is controlled to display the monitor 23.
Make settings to display the light on the screen.

Subsequently, in step S28, the aperture value F is read out, taken into the logic control device 18, and stored in the RAM (not shown). Similarly, in step S29, the focal length information f is read out from the zoom encoder 20, taken into the logic control device 18, and stored in the RAM (not shown).

In step S30, the depth of field DP is calculated from the aperture value and focal length information stored in the logic control device 18 by a method described later.

In step S31, the blur width information is fetched from the blur width detection circuit 15, and in step S32, the peak value of the high frequency component in the video signal is fetched from the band pass filter 14 and stored in a RAM (not shown) in the logic control device 18.

In step 333, as described above, with the focus detection area fixed, the driving direction and driving amount of the focusing lens IA are determined based on the high frequency component and blur width information output from the bandpass filter 14 and the blur width detection circuit, respectively. is calculated, and according to this information, the focusing lens 1A is actually driven in step S34.

After completing the flow of the AF operation, the process advances to step S35, and the tracking area is displayed on the screen of the monitor 23 via the display circuit 22 according to the lighting display setting of the tracking (focus detection) area made in step S27. indicate. In this way, in the normal automatic focus adjustment operation mode that does not involve a subject tracking operation, the tracking (focus detection) area is lit and displayed on the monitor screen.

In step S1, if the automatic subject tracking mode has been set using the shooting mode switch (not shown), the process advances to step S2, where the automatic subject tracking mode is set in which the movement of the subject is automatically tracked within the imaging screen and kept in focus. In order to indicate this, the tracking area (which also serves as the focus detection area) is set to blink on the monitor screen.

When the automatic subject tracking operation starts, the aperture value is read out from the iris encoder 21 in step S3, and the focal length information is read out from the zoom encoder 20 in step S4 at field intervals, and is imported into the logic control device 18. After converting it into, for example, a 1-byte digital signal by an A/D converter, it is stored in a RAM (not shown).

In step S5, step S3. Logic control unit 1 in S4
The depth of field DP is calculated based on the aperture value F and the focal length f taken into the range F8.

This depth of field calculation is performed in advance using R in the logic control device 18.
The determination is made using the depth of field determination table shown in FIG. 3 written in the OM.

That is, in the example of the information table shown in FIG.
and focal length f, the areas DPI, DP2 . DP3
The depth of field is determined in three stages. In the figure, the depth of field is DPI, DP2. The depth increases in the order of DP3.

In step S6, from the output of the peak position detection circuit 17,
Information about the horizontal and vertical positions of the peak position of the high frequency component of the luminance signal in the imaging screen in units of blocks during one field period is read into the logic control unit 18 .

In step S7, the analog contrast information in the field output from the subject discrimination filter 13 is A/D converted and read into a predetermined memory area in the logic control device 18, and in step S8, a predetermined calculation is performed to determine the contrast of the subject. Determine. Specifically, information on the brightness signal level output from the object discrimination filter 13 is compared with a predetermined threshold value to determine the contrast of the object, and highly accurate automatic tracking is possible based on changes in the peak value of high frequency components. It is determined whether the brightness is low or the object cannot be tracked due to low brightness.

If it is determined in step S8 that the contrast of the subject is sufficiently high that the subject is certainly present within the focus detection area and that highly accurate subject tracking is possible, the process advances to step S9 and thereafter. (Subject tracking area) size,
The moving direction and response speed are calculated based on the depth of field information DP obtained in step S5.

That is, in step S9, the depth DP of the depth of field obtained in step S5 is determined, and if the depth of field is the deepest DP3, the process proceeds to step S10,
Set the size of the focus detection area to the maximum and fix it at the center of the imaging screen. The position and size of this focus detection area may be the same as the initial setting area after starting automatic tracking focus adjustment, or may be set separately as appropriate.

If the depth of field is DP2, which is medium, the process proceeds to step Sll, where the size and response speed of the focus detection area are set to medium, and the moving direction is set to only the horizontal direction.

If the depth of field is the shallowest DPI, the process proceeds to step S12, and the size of the focus detection area is set to the minimum,
The response speed is maximized, and the movement direction is both horizontal and vertical.

Here, the reason why the size, response speed, and movement direction of the focus detection area are variably controlled based on the depth of field will be explained in detail using FIG. 4.

As shown in step S12, when the depth of field is the shallowest in DPI, the size of the focus detection area is set to the minimum as shown in FIG. 30% vertical to the screen.

The area is set to 30% horizontally. And the direction of movement is up and down,
Can be moved left, right, and diagonally.

Also, as shown in step Sll, the depth of field is DP2.
In the case of an intermediate level, as shown in Fig. 4(b),
The size of the focus detection area is set to an intermediate value of 40% vertically and 30% horizontally of the entire screen, and the movement direction is only horizontal.
The response speed is also set to an intermediate value.

Also, as shown in step SIO, the depth of field is DP3.
In the deepest case, the size of the focus detection area is 60% vertically and 60% horizontally of the entire screen, as shown in Figure 4(c).
% value and set to maximum. At this time, the focus detection area is fixed and does not move.

In general, when the depth of field is shallow, the degree of focus changes greatly between in-focus and out-of-focus states within the image capture screen, making it easier to focus on the main subject and distinguishing the main subject from the background. becomes clear, it is possible to accurately detect the high frequency component from the main subject, and it is also possible to accurately detect changes in the high frequency component due to out of focus or movement of the subject.

Therefore, the focus detection area is set to a minimum size in order to accurately capture and accurately track the main subject. In addition, when the depth of field is shallow, the focal length is long and the subject occupies a large proportion of the image field, and even the slightest movement will appear significantly within the image field, so the response speed of the focus detection area is also fast. is set to

Also, when the depth of field is deep, it is easy to focus on many points on the imaging screen regardless of the main subject, so the position of the peak point of the high frequency component of the image changes rapidly and becomes unstable.
Normal tracking operation becomes difficult. In other words, in such a state where the depth of field is deep and it is easy to focus, there is less need for a tracking operation for focusing. Also, especially when zooming a zoom lens to the wide side to deepen the depth of field, the angle of view becomes wider, the movement of the subject becomes relatively slower, and the direction of movement, especially in the vertical direction, becomes smaller. come. Therefore, the size of the focus detection area is increased to avoid malfunctions due to near and far conflicts, and the focus detection area is set large, and the focus detection area is fixed at the center of the imaging screen.

Furthermore, as shown in step Sll above, when the depth of field is at an intermediate level, it is an intermediate state between a deep depth of field and a shallow depth of field, so the size of the focus detection area , the response speed is set to an intermediate value, and the movement direction of the focus detection area is limited to the horizontal direction, where there is particularly a lot of movement.

In this way, depending on the depth of field, the size of the focus detection area,
By finely controlling the movement direction and response speed, unnecessary tracking operations can be eliminated and smoother tracking can be achieved.

Returning to the flowchart of FIG. 2 again, to continue the explanation, after determining the setting conditions for the focus detection area according to the shooting situation in the above-mentioned steps SIO, S11, and S12, the process proceeds to step 313. In step S6, the output from the peak position detection circuit 6 is output to the logic control device 1.
Based on the horizontal and vertical coordinates of the peak point detection position of the high frequency component in the current field stored in a predetermined memory area in 8, information on the response speed and movement direction of the focus detection area obtained in steps S10 to S12 is obtained. Taking this into account, the movement position of the focus detection area in the next field centered on the peak position is calculated.

At this time, the setting position of the focus detection area is not determined only by comparison with the information in the previous field, but by taking the average of the information in a predetermined number of past fields, stable positioning without the influence of noise etc. (for example, in the patent application No. 1-213 filed earlier by the applicant)
(The method for setting the focus detection area disclosed in No. 921 can be applied.)

In step S14, it is monitored in what direction the coordinate values of the focus detection area in the screen of the next field obtained in the previous step are changing with respect to the coordinate values of the current screen, and if the determined movement is If it is in a direction other than that, the setting is made so that it does not move in that direction.

In step S15, the size of the focus detection area is set based on the size of the focus detection area obtained in steps S10 to S12 described above.

In step S16, the gate circuit 1
6 to control the sampling position of the imaging signal within the imaging screen, that is, the setting position of the focus detection area (tracking area). As a result, the position and size of the focus detection area on the imaging screen are actually updated.

When the setting of the position and size of the focus detection area (tracking area) is completed, the process moves to display processing for displaying the status of the tracking operation shown in steps S17 to S20.

In other words, according to the present invention, when automatically tracking a subject, there are two cases: when the subject is in focus and the tracking operation is performed normally, and when the subject is far out of focus and normal tracking is not performed. By changing the blinking cycle of the display of the focus detection area (tracking area) on the monitor screen, the operator can recognize the focus detection area (tracking area).

When the process moves to step S17, it is determined whether or not it is near the in-focus point.

Specifically, from a characteristic curve showing the relationship between the focusing lens position and the high frequency component peak value or the level of the blur width information signal that changes accordingly, as shown in FIG. 6, it is determined whether the focus is near or not. is determined, and when the focusing lens IA is separated from the in-focus point, it is controlled to climb up a mountain according to the characteristic curve shown in the figure, and after stopping at the in-focus point, an out-of-focus determination is performed in preparation for restarting.

Therefore, in this embodiment, it is determined from the in-focus state, that is, the control state of the focusing lens, whether or not subject tracking is being performed normally.

Specifically, when the focusing lens is controlled for mountain climbing, the subject is either not yet in focus or the subject is not within the tracking area, and the subject is not being tracked normally. I judge that it is not.

On the other hand, if the out-of-focus determination is made, it is determined that the subject is currently in focus and that the subject is being normally tracked.

As a result of this determination, if the object tracking operation is being performed normally, the tracking area blinks faster, and if the object tracking operation is not being performed normally, the tracking area blinks slower.

As a result, while automatically tracking a subject, the operator can always clearly recognize whether or not the tracking operation is being performed normally.

If we look at the above operation in a flowchart, step S17
According to the focusing characteristic curve in FIG. ) on the monitor screen is set to faster than (fast
), and if it is determined in step S17 that the hill-climbing control is being performed and the distance is greater than the in-focus degree and the blur state is large, the process advances to step S19 to change the blinking cycle of the focus detection area (tracking area). slow < (slow)

After completing the setting of blinking control of the focus detection area, the process proceeds to step S20, and the display circuit 22 is controlled based on the information set in steps SIO to S12 and the blinking cycle information in steps 818 and S19. and displays it on the screen of the monitor 23.

In addition, in this embodiment, whether tracking is performed with the subject in focus normally is determined by whether the focusing lens IA is under mountain climbing control or if the focusing lens IA stops and is no longer in focus. The judgment is based on whether the focus judgment is performed, but even if this method is not used, the 6th
From the characteristic curve shown in the figure that shows the relationship between the output level of high-frequency components or blur width information and the degree of focus, when the level exceeds a predetermined level, it is considered that the focus is close to being lost, and the focus detection area (tracking area) is You can change the display (flashing cycle).

However, when using this level-based judgment method, if the level of the high-frequency component is simply used, the level will vary greatly depending on the brightness of the subject. (This information is related to the blur width and is not affected by changes in brightness because it is a value normalized by the brightness value.) Defocusing is determined using blur width information, which exhibits high detection sensitivity only near the focus area. It is better to

In step S21, the blur width information in the field output from the blur width detection circuit 15 is determined in step S22.
Then, the high frequency component peak value information in the field outputted from the band pass filter 14 is taken into the logic control device 18 at each field period, A/D converted therein, and read into a RAM (not shown). Then, in step S23, each step S5. S2
1. Depth of field information and blur width information obtained in S22,
Detects focus based on high-frequency component peak value information, and determines the driving speed according to the driving direction and degree of focus of the focusing lens IA. Calculate and decide. At this time, the speed of the focusing lens is corrected in consideration of the depth of field DP obtained from the aperture value F and focal length f.

When determining the depth of field and speed, as described above, the speed is determined based on the information table shown in FIG. By referring to the speed setting information table for determining the speed, the calculation time can be shortened and the program can be simplified.

When the calculation of the focusing lens drive information is completed, the process advances to step S24, and the focusing lens drive information (control signals for focusing motor drive speed, drive direction, drive/stop, etc.) calculated in step S23 is sent to the focus motor drive circuit. 9 to drive the focusing motor 10 and drive the focusing lens IA to the in-focus point.

This completes the control flow of the automatic focus adjustment operation accompanied by the subject tracking function, returns to step S1, and thereafter repeats this flow once per field.

In this way, it is possible to automatically track a moving subject by detecting the movement of its peak detection position, and it is also possible to accurately capture the subject and track it while focusing on the target subject. can do.

In addition, in the above-mentioned step S8, as a result of calculating the information on the subject brightness taken in by the subject discrimination filter 13, if it is determined that the subject has low luminance and highly accurate tracking is impossible, the subject is in focus. The object may not be within the detection area, or it may be extremely blurred, making it difficult to distinguish the object. If you continue to track the object, it will not only cause malfunctions, but also cause the movement of the focus detection area to become unstable, resulting in out-of-focus conditions. Since the focusing operation itself becomes difficult, the process proceeds to step S25, where the position of the focus detection area is forcibly set to, for example, a reset position at the center of the imaging screen, and the tracking operation is stopped. This reset operation is performed by setting the initial position coordinates and initial state size of the approximate center of the imaging screen that were set when tracking was started in step S1, and then proceeding to step 326, and then pulses a gate pulse corresponding to the reset position. This is done by outputting to the gate circuit 16.

After performing this operation of resetting the focus detection area when subject tracking is not possible, the process proceeds to step S27, where the mode shifts to the normal automatic focus adjustment mode that does not involve subject tracking, and the focus detection area is fixed within the monitor screen. Focusing operations are performed using the regions. Then, a fixed focus detection area is displayed lit on the screen of the monitor 23, allowing the operator to recognize that the focus adjustment mode has been switched.

This prevents malfunction of the focus detection area when tracking is impossible, makes the movement natural, and allows the operator to accurately recognize the current shooting situation.

In the above embodiment, it is determined whether the tracking operation is normal or not according to the focus control state, but as a step before stopping the tracking operation, it is determined from the output of the subject discrimination filter 13 that the tracking operation is normal. It may also be possible to determine whether or not this is being done and display this. In other words, when the output level of the subject discrimination filter 13 is high, it is determined that the screen contrast is sufficient and the subject tracking operation is performed normally, and when this level falls below a predetermined level, It is determined that the probability that the object tracking operation will be performed accurately is low, and the display such as the blinking cycle of the tracking area is changed as described above. Further, when the output level of the subject discrimination filter 13 reaches the regular value, the tracking operation itself may be stopped as shown in the above-described flowchart.

With this configuration, the photographing state can be recognized more precisely.

By repeating the above control flow at field intervals, it is possible to automatically track a moving subject while keeping it in focus.

Note that, according to the above-described embodiment, ON1 of the subject tracking operation
0 F F is displayed by turning on and blinking the focus detection area seven times, but the invention is not limited to this, and it is also possible to display by color other than blinking. In addition to the display, the shooting mode may also be displayed independently on the screen of the electronic viewfinder.

Further, according to the above embodiment, in setting the focus detection area, when the depth of field is at an intermediate level, the movement range of the focus detection area is limited to the horizontal direction. It is not necessary, and considering that the vertical movement is given less weight, for example, as shown in FIG. 5(a).
As shown in ~(c), it may be movable in the horizontal direction and upward direction. The correspondence between each figure is shown in Figures 4 (a) to (
Same as c).

Furthermore, in the above embodiment, the depth of field is controlled in three stages, but there is no need to limit the number of stages.
For example, control can be performed in five stages or even in two stages. however,
When changing the number of stages, it goes without saying that the size, movement range, and response speed of the focus detection area need to be optimized according to each divided depth of field.

Further, according to this embodiment, the area for tracking the subject and the focus detection area for detecting the focus state of the subject are configured in the same area, but these areas are provided separately, and the area for tracking the subject is Needless to say, it is possible to track the position of , and separately set a focus detection area at that position, and in this way, the size of each area can be set separately.

(Effects of the Invention) As described above, according to the automatic focusing device of the present invention, the first focus detection mode is such that the focus detection area is fixed at a predetermined position on the imaging screen and the focusing operation is performed. and a second one that performs a focusing operation while tracking the detection area to the subject.
If the focus detection mode can be set and the focus detection area is displayed on the monitor screen, the focus detection area can be set in the first focus detection mode and the second focus detection mode. Since the display is different, it is possible to clearly display which mode the current focus detection mode is, in other words, the current 0N10FF state of automatic subject tracking operation on the monitor screen, and the operator can see the current focus detection mode. The photographing state can be accurately recognized, various malfunctions and erroneous operations can be prevented, and stable and accurate subject tracking can be performed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an automatic focusing device according to the invention, FIG. 2 is a flowchart for explaining the control operation of the imaging device according to the invention, and FIG. 3 is a field of view in the imaging device according to the invention. A diagram showing a depth calculation table, FIG. 4 is a diagram showing the positional relationship of the focus detection area in the imaging plane in the imaging device of the present invention, and FIG. 5 is a diagram showing the positional relationship in the imaging plane of the focus detection region in the imaging device of the invention. FIG. 6 is a diagram for explaining display in the subject tracking mode in the present invention. DP3 (α) (b) P3 (α) (b) (C) Fig.

Claims (2)

[Claims] (1) Area setting means for setting a focus detection area on an imaging screen; and detecting movement of the subject image to control the area setting means to follow the set position of the focus detection area to the subject image. a first focus detection mode that performs a focusing operation while fixing the focus detection area at a predetermined position on the imaging screen; and a first focus detection mode that performs a focusing operation while making the detection area track a subject; The second to perform the action
a focus control means capable of setting a focus detection mode; displaying the focus detection area on a monitor screen;
An automatic focusing device comprising: a display means that displays different information in the first focus detection mode and the second focus detection mode. (2) In claim (1), the display means illuminates and displays the detection area within the monitor screen when in the first focus detection mode, and when in the second focus detection mode. An automatic focusing device characterized in that the automatic focusing device is configured to blink and display the detection area when