JP2002318341A - Device and method for automatic focusing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To omit unnecessary focusing operation by deciding the possibility of focusing by automatic focusing(AF) and stopping focusing operation when it is judged that the focusing is impossible as to a device and a method for AF which use an evaluated value calculated from the high-frequency component of an image signal. SOLUTION: A focusing area is searched (roughly) at relatively large search intervals and the evaluated value obtained here is used to decided the possibility of focusing. For the decision making, two thresholds (T1>T2) are set; when the maximum evaluated value Afmax is larger than the large threshold T1, it is judged that the focusing is possible and the focusing area is searched (in detail) at smaller search intervals, and when the maximum evaluated value is smaller than the small threshold T2, it is judged that the focusing is impossible and the detailed search is inhibited. When the maximum evaluated value is between the small threshold and large threshold, it is decided whether the evaluated value of the rough search has a peak; when the evaluated value has no peak, the 2nd search is inhibited and when the evaluated value has a peak, the 2nd search is made.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focusing apparatus and a method therefor, and more particularly, to detecting a high-frequency component of an image based on an output signal from an image sensor, and using the detection result to perform auto-focusing. The present invention relates to a technique for performing AF) control.

[0002]

2. Description of the Related Art In a video camera which captures an image of a subject and outputs a video signal thereof, the video camera captures an image while moving a focus lens of a photographic optical system which acts on focus adjustment, and extracts a high-frequency component from the output video signal. To calculate an evaluation value for focusing. When the evaluation value increases as a result of the movement of the focus lens, the lens continues to be driven in the same direction, and when the evaluation value decreases with the movement of the lens, it is driven in the opposite direction to search for the peak of the evaluation value. That is, a so-called "hill climbing servo system" is employed.

In a digital still camera,
A “contrast AF method” is employed in which a focus lens is driven from a point close to an object to infinity and the focus lens is driven and focused where the evaluation value is maximized.

[0004]

The purpose of these conventional automatic focus adjustment functions is to change the out-of-focus state to the in-focus state. If it is known that focusing cannot be performed, performing AF processing wastes time. As a method of prohibiting unnecessary focusing operation, Japanese Patent Application Laid-Open No. Hei 6-311412 discloses a method in which a focusing operation is once performed in a video camera, and then the aperture is changed. It discloses a method of stopping the focusing operation if it is detected and focused. Japanese Patent Application Laid-Open No. 2000-350082 proposes a method of prohibiting a focusing operation when obtaining white balance data in an electronic camera.

However, in these conventional methods, the focusing operation is continued even when focusing is impossible, or the focusing operation is prohibited only under the limited condition of obtaining white balance data. If focusing cannot be performed even after performing AF, there is a problem that useless focusing operation is performed.

The present invention has been made in view of such circumstances, and determines the possibility of focusing by automatic focus adjustment. When it is determined that focusing is impossible, the focusing operation is stopped to stop unnecessary focusing. It is an object of the present invention to provide an automatic focusing apparatus and a method capable of omitting a focusing operation.

[0007]

According to a first aspect of the present invention, there is provided an imaging apparatus for converting an optical image of a subject incident through a lens into an electric signal.
In an automatic focus adjustment device that adjusts a focal position of the lens based on an evaluation value indicating a sharpness of an image calculated using an image signal output from the imaging unit, the device adjusts a focus adjustment area of the lens. Extracting a contrast component of the subject from an image signal output from the imaging unit for each lens position moved by the lens moving unit, and an evaluation value corresponding to the contrast component Evaluation value calculating means for calculating
First search means for performing a first search for obtaining an evaluation value at each lens position while moving the lens at a relatively large interval in the focus adjustment area; and an evaluation obtained by the first search. After moving the lens near the position corresponding to the peak of the value, the evaluation value is calculated at each lens position while moving the lens near the position corresponding to the peak at a smaller interval than the first search. A second search means for performing a second search to be obtained;
And a search control unit for prohibiting the second search when the maximum value of the evaluation values obtained by the search is smaller than a preset threshold.

According to the present invention, the first search operation (rough search) in which the interval between search points (search step) is large in the focus adjustment area is performed, and the vicinity of the peak of the evaluation value obtained as a result is searched in the small search step. If the maximum value of the evaluation values obtained in the first search is smaller than a predetermined threshold value when the AF method of performing a detailed search in the second search operation (detailed search) is employed, the second search is executed. Also determines that the in-focus position cannot be detected (in-focus is impossible),
Is controlled to prohibit the search. Thereby, unnecessary focusing operation can be omitted. In the case where the second search is prohibited, since focusing by AF is impossible, measures such as moving the focus lens to a predetermined focus position (for example, a position where the object distance is 2 m) are taken. .

According to the second aspect, another threshold value larger than the threshold value is set, and the maximum value of the evaluation values obtained by the first search exceeds the other threshold value. The second search is executed, and the lens position corresponding to the peak of the evaluation value is determined to be the focus position based on the evaluation value obtained by the second search, and the lens is moved to the focus position. It is characterized by being moved.

[0010] A plurality of thresholds as criteria for determining whether to execute the second search are set (two thresholds having different values are set).
If the maximum evaluation value obtained in the first search is smaller than the lower threshold value (lower threshold value), the second search is prohibited, but the maximum evaluation value obtained in the first search is higher. If it is larger than (upper threshold), it is determined that the in-focus position can be detected by the second search (focusing is possible), and the second search is executed. The detection of the peak corresponding position (in-focus position) corresponds not only to the lens position where the evaluation value is actually calculated, but also to the peak of the evaluation value by interpolation or the like from the evaluation values discretely acquired in a predetermined search step. The lens position may be determined.

Further, when the other threshold value is referred to as an "upper threshold value" and the lower threshold value is referred to as a "lower threshold value", the evaluation value obtained by the first search is determined. A peak discriminating means for discriminating the presence or absence of a peak of the evaluation value based on the evaluation value obtained by the first search, when the maximum value of the search control is between the lower threshold and the upper threshold. The means is characterized in that the second search is prohibited when the peak discriminating means obtains a discrimination that no peak exists.

When the maximum evaluation value obtained in the first search falls between the lower threshold value and the upper threshold value, whether or not a peak of the evaluation value (an extreme value at which the evaluation value curve switches from increasing to decreasing) exists. Is determined. As a result, if there is no peak, it is determined that focusing is impossible and the second search is prohibited, and if there is a peak, it is determined that focusing is possible and the second search is executed.

According to a fourth aspect of the present invention, there is provided an image pickup device for converting an optical image of a subject incident through a lens into an electric signal, and an image calculated using an image signal output from the image pickup device. An automatic focus adjustment device that adjusts the focal position of the lens based on an evaluation value indicating the sharpness of
The apparatus includes a lens moving unit that moves the lens within a focus adjustment area, and extracts a contrast component of the subject from an image signal output from the imaging unit for each lens position moved by the lens moving unit. Evaluation value calculation means for calculating an evaluation value according to the contrast component; and a first search for obtaining an evaluation value at each lens position while moving the lens at relatively large intervals in the focus adjustment area. A first search means to be implemented;
After moving the lens near the position corresponding to the peak of the evaluation value obtained by the search, while moving the lens near the position corresponding to the peak at a smaller interval than in the first search, Second search means for performing a second search for obtaining an evaluation value at each lens position, and peak determining means for determining whether or not a peak of the evaluation value exists based on the evaluation value obtained by the first search. And a search control unit for prohibiting the second search when the peak determination unit determines that no peak exists.

According to the present invention, when the peak of the evaluation value is not detected by the first search operation in which the search step is relatively large, it is determined that focusing is impossible, and the control for prohibiting the second search is performed. Do. Thereby, unnecessary focusing operation can be omitted.

According to a fifth aspect of the present invention, as the method for determining the presence or absence of a peak, the peak determining means does not continuously reduce or increase the evaluation value a predetermined number of times in the first search. In this case, it is determined that there is no peak in the case where the peak is present. The difference between whether the evaluation value continuously decreases or increases depends on the lens moving direction (search direction).

According to a sixth aspect, in accordance with the depth of field of the photographing optical system at the time of automatic focusing (AF),
A first search execution determining means for determining whether or not to execute the first search; and when the first search execution determining means determines that the first search is not to be executed, A search for obtaining an evaluation value at each lens position is performed while moving the lens at a search interval equivalent to the second search in the focus adjustment area, and the search corresponds to the peak of the evaluation value obtained in the search. It is characterized in that the lens position is determined to be a focus position, and the lens is moved to the focus position.

AF for performing a second search after the first search
The method is an effective method for achieving high-speed AF when the depth of field is shallow (when the focus adjustment area is wide). If the depth of field is deep (the focus adjustment area is narrow), a situation may occur in which the merits of performing the first search and the second search cannot be obtained. It is preferable to determine whether or not to perform the first search and automatically select a method that can perform AF at a higher speed.

According to the aspect shown in claim 7, the first
The search execution determining means determines whether or not to execute the first search by referring to determination reference data defined by a combination of a focal length and an aperture of a zoom lens constituting the imaging optical system, The criterion data,
It is characterized in that whether to execute the first search is switched on the basis of which can perform the AF at a higher speed depending on whether the first search is performed or not. And

In order to provide a method for achieving the above-mentioned object, the invention according to claim 8 converts an optical image of a subject incident through a lens into an electric signal by an image pickup means, Calculating an evaluation value indicating the sharpness of the image using the image signal output from the camera, and adjusting the focal position of the lens based on the obtained evaluation value. Extracting a contrast component of the subject from an image signal output from the image pickup unit at each lens position while moving the lens at a relatively large interval within, and calculating an evaluation value according to the contrast component. A search step, a step of comparing the maximum value of the evaluation values obtained in the first search step with a preset threshold value, and an evaluation obtained in the first search step. A second search step of the maximum value of the may be performed is larger than the threshold value, the first
Moving the lens near the position corresponding to the peak of the evaluation value obtained in the search step, and then moving the lens near the position corresponding to the peak at a smaller interval than in the first search step A second search step of acquiring an evaluation value at each lens position while performing the second search step, and a step of prohibiting the second search when the maximum value of the evaluation values obtained in the first search step is smaller than the threshold value And is characterized by including.

According to the ninth aspect, another threshold value larger than the threshold value is set, and the maximum value of the evaluation values obtained in the first search step exceeds the other threshold value. In this case, the second search step is performed, and based on the evaluation value obtained in the second search step,
The method is characterized in that it includes a step of determining a lens position corresponding to the peak of the evaluation value as a focus position and moving the lens to the focus position.

According to a tenth aspect of the present invention, when the maximum value of the evaluation values obtained in the first search step is between the lower threshold value and the upper threshold value, the evaluation value obtained in the first search step is obtained. A peak discriminating step of discriminating the presence or absence of a peak of the evaluation value based on the obtained evaluation value, and prohibiting the second search step if the peak discriminating step determines that no peak exists. It is characterized by.

According to an eleventh aspect of the present invention, an optical image of a subject incident through a lens is converted into an electric signal by an image pickup means, and the sharpness of the image is indicated using an image signal output from the image pickup means. An automatic focus adjustment method for calculating an evaluation value and adjusting a focal position of the lens based on the obtained evaluation value, the method comprising: moving each of the lenses at relatively large intervals within a focus adjustment area. A first search step of extracting a contrast component of the subject from an image signal output from the imaging means at a position and calculating an evaluation value corresponding to the contrast component; and an evaluation obtained by the first search step. A peak discriminating step of discriminating the presence or absence of a peak of the evaluation value based on the value, and a second discriminating step that can be performed when the peak discriminating step determines that a peak exists. In the search step, after moving the lens near a position corresponding to the peak of the evaluation value obtained in the first search step, the first search step is performed near the position corresponding to the peak. A second search step of obtaining an evaluation value at each lens position while moving the lens at a smaller interval, and a second search step when the peak determining means determines that no peak exists. And a step of prohibiting.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an automatic focusing apparatus and method according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an external view of a digital camera to which the present invention is applied. A photographing lens 12, a viewfinder window 14, a strobe light emitting unit 1
6, a shutter button 18 is provided on the top of the camera.
And a power switch 20. A memory card 24 is provided on the side of the camera opposite to the grip 22.
Is provided with a card slot 26 for mounting the card.

A variable focal length lens (for example, a zoom lens) is used as the photographing lens 12.
A CCD image sensor (not shown in FIG. 1; described as 52 in FIG. 3; hereinafter, referred to as CCD) is disposed behind the image sensor. The shutter button 18 is divided into two stages depending on the position where the shutter button is pressed.
When 1 is pressed, automatic focusing (AF) and automatic exposure control (AE) are performed, and when S2, which is deeper than S1, is pressed, photographing operations for recording (exposure and reading) are performed. .

The power switch 20 is also used as a mode change switch, and has an "OFF position" at which the power is turned off,
"Shooting ON position" which is turned on in still image shooting mode,
And the "reproduction ON position" which is turned on in the reproduction mode.
The position can be switched. It should be noted that instead of the power switch (hereinafter, referred to as a power / mode switch) 20 as in this example, a power switch only for power ON / OFF and a mode switching means such as a mode dial for switching between a still image shooting mode and a reproduction mode are provided. May be provided.

FIG. 2 is a rear view of the digital camera 10. On the back of the digital camera 10, a finder 28, a liquid crystal monitor 30, a zoom switch 32, a cross button 34, a menu key 38, an execution key 40, and a cancel key 42 are provided. The liquid crystal monitor 30 is a display means that can be used as an electronic finder for confirming the angle of view during photographing, and can display a preview image of a photographed image, a reproduced image read from the memory card 24, and the like. Selection of menus using the cross button 34 and setting of various items in each menu are also performed using the display screen of the liquid crystal monitor 30.

The zoom switch 32 is composed of a lever switch that can be operated in the up and down direction. The switch is zoomed in the telephoto (TELE) direction by operating the switch upward, and the wide angle (WIDE) is operated by operating the switch downward. ) Zoom in the direction. The cross button 34 is a multi-function button capable of inputting four directions of up, down, left, and right. The cross button 34 is used as an operation button for instructing selection of various setting items on the menu screen and changing of setting contents. It is used as a means for instructing adjustment and forwarding / returning of a playback frame.

The menu key 38 is used to make a transition from the normal screen of each mode to the menu screen. The execution key 40 is used, for example, when confirming the selected contents or instructing execution (confirmation) of processing. The cancel key 42 is used to cancel (cancel) an item selected from the menu or to return to the previous operation state.

The photographer operates the zoom switch 32 to determine the angle of view while checking the real-time image (through image) displayed on the viewfinder 28 or the liquid crystal monitor 30, and presses the shutter button 18 to perform photographing. .

FIG. 3 is a block diagram showing the internal configuration of the digital camera 10. The taking lens 12 includes a four-group inner-focus zoom lens including a fixed lens 44, a variable power lens 46A, a correction lens 46B, and a focus lens 48.

The variable power lens 46A and the correction lens 46B
The camera moves along the optical axis while the positional relationship between the two is regulated by a cam mechanism (not shown), and changes the focal length. In addition,
For convenience of description, a variable power optical system including a variable power lens 46A and a correction lens 46B will be referred to as a "zoom lens 46".

The light that has passed through the taking lens 12 is
After the light amount is adjusted by the above, the light enters the CCD 52. C
Photosensors are arranged in a plane on the light-receiving surface of the CD 52. The subject image formed on the light-receiving surface of the CCD 52 via the photographing lens 12 has a signal charge corresponding to the amount of incident light by each photosensor. Is converted to In addition, CCD
Reference numeral 52 denotes the charge accumulation time (shutter speed) of each photosensor according to the timing of the shutter gate pulse.
, Which is a so-called electronic shutter function.

The signal charge stored in each photosensor is:
The signals are sequentially read out as voltage signals (image signals) corresponding to the signal charges based on the pulses supplied from the CCD driver 54. The image signal output from the CCD 52 is sent to the analog processing unit 56. The analog processing unit 56 includes a signal processing circuit such as a sampling hold circuit, a color separation circuit, and a gain adjustment circuit. In the analog processing unit 56, correlated double sampling (CDS) processing,
Each of the G and B color signals is subjected to color separation processing, and the signal level of each color signal is adjusted (pre-white balance processing).

The signal output from the analog processing section 56 is converted into a digital signal by the A / D converter 58 and stored in the memory 60. The timing generator (TG) 62 gives a timing signal to the CCD driver 54, the analog processing unit 56, and the A / D converter 58 in accordance with a command from the CPU 64, and the circuits are synchronized by the timing signal. .

The data stored in the memory 60 is transmitted to the bus 6
6 to the signal processing section 68. Signal processing unit 68
Is a digital signal processor (D) including a luminance / color difference signal generation circuit, a gamma correction circuit, a sharpness correction circuit, a contrast correction circuit, a white balance correction circuit, and the like.
SP), and processes an image signal in accordance with a command from the CPU 64.

The image data input to the signal processing unit 68 includes a luminance signal (Y signal) and a color difference signal (Cr, Cb signal).
After being converted to, and subjected to predetermined processing such as gamma correction, the data is stored in the memory 60. When displaying the captured image, the image data is read from the memory 60,
The data is transferred to the display memory 70. The data stored in the display memory 70 is a signal of a predetermined system for display (for example,
After being converted to an NTSC color composite video signal)
The data is output to the liquid crystal monitor (LCD) 30 via the D / A converter 72. Thus, the image content of the image data is displayed on the screen of the liquid crystal monitor 30.

The image data in the memory 60 is periodically rewritten by the image signal output from the CCD 52,
The video signal generated from the image data is transmitted to the liquid crystal monitor 3
By being supplied to 0, an image input via the CCD 52 is displayed on the liquid crystal monitor 30 in real time.

When the photographer operates the zoom switch 32, an instruction signal is input to the CPU 64,
Controls the zoom drive unit 74 based on the signal from the zoom switch 32 to move the zoom lens 46 in the tele (TELE) direction or the wide (WIDE) direction. Zoom drive 7
Reference numeral 4 includes a motor (not shown), and the zoom lens 46 is driven by the driving force of the motor. The position (zoom position) of the zoom lens 46 is detected by a zoom position sensor 76, and a detection signal from the sensor 76 is input to the CPU 64.

Similarly, the focus driving section 78 includes a motor (not shown), and the focus lens 48 moves back and forth along the optical axis by the driving force of the motor. The position of the focus lens 48 (focus position) is detected by a focus position sensor 80, and the detection signal of the sensor 80 is C
It is input to PU64.

When the still image shooting mode is set by the power / mode switch 20 and the shutter button 18 is "half-pressed" (S1 = ON), AE and AF processes are performed. That is, the CPU 64 controls the focus driving unit 78 to move the focus lens 48 to the in-focus position based on the result of the evaluation value calculation described later, and calculates the aperture diameter of the diaphragm 50 and the electronic shutter value of the CCD 52. The subject image is displayed as a moving image on the liquid crystal monitor 30 to follow the subject during AF.

When the shutter button 18 is fully pressed (S2 = ON), a photographing start instruction (release ON)
A signal is emitted. The CPU 64 detects a release ON signal and executes an imaging operation for recording. That is, CP
U64 performs exposure control based on the result of the AE operation,
A command is sent to the flash control circuit 82 as needed to control the light emission of the flash light emitting unit 16.

In this way, in response to the pressing operation of the shutter button 18, the capture of the image data for recording is started, and the required signal processing is performed. When the mode for compressing and recording image data is selected, the CPU 64 sends a command to the compression / expansion circuit 84. The compression / expansion circuit 84 compresses the image data taken into the memory 60 according to JPEG or another predetermined format.

The compressed image data is recorded on the memory card 24 via the card interface 86.
Mode for recording uncompressed image data (uncompressed mode)
Is selected, the compression processing by the compression / expansion circuit 84 is omitted, and the image data is recorded on the memory card 24 without being compressed.

In the digital camera 10 of this embodiment, for example, smart media (So
lid-State Floppy Disk Card) is applied. The form of the recording medium is not limited to this, and may be a PC card, a compact flash (registered trademark), a magnetic disk, an optical disk, a magneto-optical disk, a memory stick (registered trademark), or the like, and may be electronic, magnetic, optical, Alternatively, various media that can be read and written according to a system based on a combination thereof can be used. Signal processing means and interfaces corresponding to the medium used are applied. A configuration may be adopted in which a plurality of media can be mounted irrespective of different types or the same type of recording media. The means for storing images is not limited to a removable medium, but may be a recording medium (internal memory) built in the digital camera 10. In the case of storing images in the internal memory, a communication interface for transferring data to an external device such as a personal computer is provided.

When the reproduction mode is set by the power / mode switch 20, an image file is read from the memory card 24. The read image data is subjected to expansion processing by a compression / expansion circuit 84 as necessary, and output to the liquid crystal monitor 30 via the display memory 70.

The CPU 64 is a control section for controlling the circuits of the camera system. The CPU 64 controls the operation of the corresponding circuits based on input signals received from the power / mode switch 20, the shutter button 18, the zoom switch 32, and other operation units, and controls display on the liquid crystal monitor 30, auto focus (AF). Control and automatic exposure (AE) control are performed. Note that the memory 6
0 is also used as a work area of the CPU 64, and evaluation value data and other data necessary for calculation are stored in the memory 60.

Here, the auto focus control will be described. The image signal converted into a digital signal by the A / D converter 58 is input to the evaluation value calculation unit 88. The evaluation value calculation unit 88 includes a high frequency component extraction circuit 90 and an integration circuit 9
2, the G component data of the input image signal is sampled, and the AF detection target area (reference numeral 94 in FIG. 4) is used.
Hereinafter, it is referred to as a focus area. ), The absolute value of the high frequency component is extracted, and the absolute value data is integrated within the set area, and a value (corresponding to an evaluation value) obtained by the integration is provided to the CPU 64.

The target area for AF detection does not need to be the entire image area. As shown in FIG. 4, a partial area at the center of the image is set as the focus area 94. During the AF process, the CPU 64
While moving 8 from infinity to close (or from close to infinity) in the focus adjustment area, the contrast of the central part of the image is detected at a plurality of AF detection points (search points), and the evaluation value is calculated. The evaluation value calculated at each search point is integrated, the lens position where the evaluation value reaches a peak (maximum value or local maximum value) is determined as the focus position, and the focus lens 48 is moved to the calculated focus position. To control the focus driving section 78.

FIG. 5 shows an example in which evaluation values are obtained by AF search. When only one main subject exists in the focus area 94, only one peak of the evaluation value appears as shown in FIG. In this case, the lens position (P) corresponding to the peak is set as the focus position, and the focus lens 48 may be moved here.

As the focal length of the photographing lens 12 becomes longer and the aperture diameter of the aperture 50 becomes larger, the depth of field becomes shallower and the focusing range becomes narrower. FIG. 6 shows the relationship between the focal length of the taking lens 12 and the focus adjustment area 300. In the figure, the focal length is changed from 7 mm to 2
An example of the photographing lens 12 that can be changed stepwise to 1 mm is shown, and as the focal length of the photographing lens 12 increases, the focus adjustment area 300 of the focus lens 48 increases. For example, when the focal length is 7 mm, the movable range of the focus lens 48 from infinity to the closest distance is 8.17 μm, and when the focal length is 21 mm, the focus adjustment area 300 is 735 μm. The CPU 64 sets the AF step width 302 indicating the width of the lens position (search point) for calculating the evaluation value and the number of steps (the number of detection points) according to the size of the focus adjustment area 300.

As the focal length of the taking lens 12 becomes longer, the focus feed amount (the number of motor drive pulses) of the focus adjustment area 300 (from infinity to the closest) increases, and A
The F time becomes longer. Therefore, when the focus adjustment area 300 is widened, in order to speed up the AF time, a “rough search” is performed in which the evaluation value is obtained once in the focus adjustment area 300 at a relatively large focus feed amount (search interval). A "detailed search" for obtaining an evaluation value at a finer search interval is performed in the vicinity of the peak of the evaluation value obtained by the rough search, and control for detecting the in-focus position is performed.

FIG. 7 is a conceptual diagram of the rough search and the detailed search. For example, it is assumed that the focus feed amount from infinity to close distance is 240 pulses, the number of focus feed pulses during rough search is set to 20, and the number of focus feed pulses during detailed search is set to 2 pulses. According to the figure, first, a rough search is started from infinity in the NEAR direction. In the rough search, a search point is changed every 20 pulses, and an evaluation value is calculated at each point.

When a peak is detected in the rough search and, for example, the interruption of the evaluation value acquisition processing is determined at the position of 100 pulses, the focus is moved to the initial position (Pds) of the detailed search, and the detailed search is performed in the FAR direction. Be started. In the detailed search, the search point is changed every two pulses, the evaluation value is calculated at each point, and after the peak is detected, if the evaluation value continuously decreases a predetermined number of times, the interruption of the evaluation value acquisition processing is determined, and the peak corresponding position is determined. The focus lens 48 is driven to (focus position).

As shown in FIG. 8, when a plurality of subjects having different distances exist in the focus area 94, it is impossible to focus on both subjects, and one of the subjects is not focused. It is necessary to focus. Generally, when a plurality of subjects having different distances are detected, focusing is performed on the subject on the closest side.

FIG. 9 shows an example of a result of obtaining an evaluation value when a plurality of subjects at different distances exist in the focus area 94. As described with reference to FIG. 8, when a plurality of subjects with different distances exist in the focus area 94, two or more peaks exist in the evaluation value curve as shown in FIG. In this case, a detailed search near the nearest peak position is performed.

Conventionally, when no peak was detected in the rough search, the peak was detected by performing a detailed search of the entire focus adjustment area. However, it takes a long time, and when focusing cannot be finally performed, time is wasted.

Therefore, in the present embodiment, it is determined whether or not focusing can be finally performed at the end of the rough search, and when it is determined that focusing is possible, a detailed search is performed.
If it is determined that focusing cannot be performed, the detailed search is prohibited and unnecessary focusing operations are omitted. As a method of determining the possibility of focusing after the rough search, there is the following example.

When the subject is extremely dark and cannot be focused, such as when the subject is out of the focusable distance range, the contrast component is low in the focus adjustment area, and the evaluation value obtained by the rough search is low. Therefore, there is a method of determining whether or not to execute a detailed search based on whether a maximum evaluation value obtained by a rough search exceeds a predetermined threshold value.

There is also a method of performing a detailed search when a peak is detected in the rough search, and prohibiting the detailed search when no peak is detected in the rough search. Specifically, when the evaluation value continuously decreases or increases a predetermined number of times, it is determined that "there was a peak".

Further, a method combining the above two methods is also preferable. That is, two thresholds (T1>
T2) is set and compared with the maximum evaluation value in the rough search. If the maximum evaluation value exceeds the first threshold value T1 (larger one), a detailed search is performed. If the maximum evaluation value is less than the second threshold value T2 (smaller one), the detailed search is prohibited. And
When the maximum evaluation value is between the first threshold value T1 and the second threshold value T2 (when the possibility of focusing cannot be determined only by the maximum evaluation value), it is determined whether or not a peak exists in the rough search (evaluation value). Whether or not the detailed search has been executed is determined based on whether or not has been reduced by a predetermined number of times.

The control procedure will be described in detail with reference to FIGS. FIG. 10 is a flowchart at the time of AF.
When the AF process is started by half-pressing the shutter button 18 (S1 = ON), the CPU 64 first
The focus area 94 is set (step S10).
1). Next, the current value of the focal length of the photographing lens 12, that is, information on the current zoom position (ZOOMPOS) is obtained (step S102).

Next, a process for determining whether or not to perform a rough search is performed (step S104). Whether or not rough search is performed is determined based on which can perform AF at a higher speed when rough search is performed and when rough search is not performed. Specifically, the determination is made according to a determination program described below.

FIG. 11 is a flowchart of rough search execution determination processing, and FIG. 12 is a chart showing an example of determination reference data. In the example shown in the figure, the focal length of the taking lens 12 is 44.93 mm (ZOOMPOS = 1) to 8.10 mm.
(ZOOMPOS = 20) A zoom lens capable of changing the focal length stepwise is used, and the aperture (aperture value: AV value) for switching the execution of rough search for each zoom position is defined as shown in FIG. Have been. This criterion data is stored in a non-volatile storage unit (EE, not shown).
PROM, etc.), and the CPU 64 refers to it as needed. Aperture is from F2.8 (3AV) to F11
It is assumed that there are 13 types in the range of (7AV) in 1 / 3AV increments, and the aperture used during AF is automatically determined from the aperture according to the brightness of the subject.

The CPU 64 reads the information on the zoom position and the aperture at the time of AF and compares the information with the data table shown in FIG. 12 to determine whether or not to execute the rough search. That is, when the rough search execution determination processing shown in FIG. 11 starts, first, aperture information (AFAV) at the time of AF
Is acquired (step S410). Then, step S
Proceeding to 412, referring to the data table shown in FIG. 12, the switching aperture for executing the rough search (AV_TABLE [ZOOMPOS])
And the magnitude relationship of the acquired AFAV is compared. Step S4
In 12, when AFAV <AV_TABLE [ZOOMPOS] is satisfied (when YES is determined), it is determined that a rough search is to be executed (step S 414). On the other hand, step S4
If AFAV ≧ AV_TABLE [ZOOMPOS] is satisfied in 12 (NO determination), it is determined not to execute the rough search (step S416). After determining whether or not to execute the rough search in step S414 or S416, the process returns to the flowchart of FIG.
Proceed to 106.

In step S106, it is determined whether or not to execute a rough search based on the result of the rough search execution determination processing. If the determination of no rough search (NO determination) is obtained in step S106, the rough search process is omitted and the process proceeds to step S142. On the other hand, if it is determined in step S106 that there is a rough search (YES determination), the process proceeds to step S110 to execute a rough search. That is, in step S110, the focus lens 48 is moved to the initial position where the rough search is started. Then, an evaluation value at the focus stage (search point) is calculated (step S116).
The calculated evaluation value is input to the CPU 64 and the CPU 64
Stores the evaluation value at the search point in the memory 60.

Then, the process proceeds to a step S120, wherein a process for determining whether or not to interrupt the search operation is performed. Here, the subroutine of the interruption determination processing will be described. As is apparent from a comparison between FIG. 5 and FIG. 9, in the graph of FIG. 5, after the peak of the evaluation value is detected by the AF search operation from infinity to the closest, the evaluation value is further obtained by moving the lens in the same direction. When the focus lens 48 moves away from the peak position P by a certain distance d, the evaluation value decreases to near zero level, whereas when a plurality of subjects exist as shown in FIG. However, the evaluation value did not fall to near the zero level, but started to increase again.

By paying attention to this fact, if the evaluation value at a position separated by a certain distance d from the lens position where the peak of the evaluation value is detected is equal to or less than a predetermined threshold value TH, it is determined that the subject does not exist beyond that. Then, the AF search can be ended. On the other hand, if the evaluation value at a position separated by a certain distance d from the lens position at which the peak of the evaluation value is detected is a value larger than the predetermined threshold value TH, another subject may exist ahead of it. And the AF search operation in the same direction is continued. Note that the distance d from the peak position P is preferably set to about 10 to 20 times the allowable circle of confusion. If a plurality of peaks (maximum values) are detected by the AF search operation, the closest peak position is determined as the focus position.

By the way, when the subject is dark or the like, noise of the imaging signal occurs, and as shown in FIG.
A situation can occur in which the evaluation value does not fall below the threshold value TH. However, as is apparent from a comparison between FIG. 13 and FIG. 9, when another subject exists on the close side (FIG. 9),
It is recognized that the evaluation value tends to increase from a position slightly before the closest distance. On the other hand, when the evaluation value does not decrease due to noise or the like (FIG. 13), the evaluation value does not change to an increasing tendency even if the evaluation value is more than a certain distance w from the closest distance.

Therefore, it is possible to determine whether or not another subject exists on the close side by determining whether or not the evaluation value is in the increasing direction at a distance more than a certain distance w from the closest. If there is no evaluation value in the increasing direction at a distance more than a certain distance w from the closest distance, it is determined that no subject exists on the close side and A
The F search operation ends. Note that in FIG.
The AR search side has been described. However, in the AF search operation in the infinity (FAR) direction, similarly, if the evaluation value does not tend to increase at a position separated from the infinity by a certain distance w, it is assumed that the subject exists at the infinity side. I can judge.

In consideration of the circumstances described above, a processing program for determining whether or not to suspend the rough search is configured. FIG. 14 shows a subroutine of this interruption determination processing. When the interruption determination process shown in the figure starts, it is first determined whether or not a peak at which the evaluation value changes from increasing to decreasing is detected (step S510). This determination is made based on the state of a “peak presence flag” described later.

If no peak is detected in step S510 (NO determination), the flow advances to step S512 to determine whether or not the evaluation value has decreased. Step S
If a negative determination is obtained in 512, continuation of the evaluation value acquisition processing is determined (step S518), and this subroutine is terminated, and the flow returns to the flowchart of FIG.

If it is detected in step S512 of FIG. 14 that the evaluation value has decreased, the flow branches to step S514. In step S514, it is determined whether or not the evaluation value before the decrease has been increasing. Step S5
If a YES determination is made in step 14, the maximum (AFmax) and minimum (AFmax) evaluation values calculated by the AF search operation are calculated.
It is determined whether or not the difference from (min) is greater than a predetermined value L (step S515). In step S515, Y
If ES determination is obtained, "Peak flag" is turned ON.
And the data of the variable P indicating the focus position (peak position) at which the peak was detected is updated (step S516). After step S516, or if a NO determination is obtained in step S515, the process proceeds to step S518, and continuation of the evaluation value acquisition process is determined.

When the "peak presence flag" is set to ON, a YES determination is made in step S510. In this case, the process proceeds to step S520, and it is determined whether the search direction is the NEAR direction. When the search direction is the NEAR direction (when YES is determined), it is determined whether or not the current focus position (search point) is closer than a predetermined distance (d) from the peak position P to the nearest side ( Step S522). If the current position is within a predetermined distance d from the peak position P (NO determination), step S52 is performed.
Then, it is determined whether the number of remaining detection points in the search direction is smaller than a predetermined value (m). This predetermined value m is a value corresponding to the distance w described in FIG.

In step S528, when the number of remaining detection points is equal to or larger than the predetermined value m (NO determination), continuation of the evaluation value acquisition process is determined (step S532), and the process returns to the flowchart of FIG. On the other hand, if a YES determination is obtained in step S528 in FIG. 14, the process proceeds to step S530, and it is determined whether the evaluation value has increased.

If an increase in the evaluation value is detected in step S530 (when YES is determined), the flow advances to step S532 to determine continuation of the evaluation value acquisition process (step S53).
2) If the evaluation value has not increased in step S530 (NO determination), the process moves to step S536 to determine the interruption of the evaluation value acquisition process, and returns to the flowchart of FIG.

If the current focus position is closer than the predetermined distance d from the peak position P at step S522 in FIG. 14 (YES determination), the flow branches to step S524. In step S524, it is determined whether the evaluation value at the current focus position is smaller than a predetermined threshold value TH.

If the evaluation value is equal to or larger than the threshold value TH in step S524 (when NO is determined), the process proceeds to step S528 in consideration of the possibility that the subject exists closer than the current position. On the other hand, when the evaluation value is smaller than the threshold value TH in step S524 (when YES is determined), it is determined that the subject does not exist closer to the current position than the current position, and the interruption of the evaluation value acquisition process is determined ( Step S536).

If the determination in step S520 is NO, that is, if the search direction is the FAR direction, step S520
Proceed to 526. In step S526, it is determined whether the evaluation value has continuously decreased a predetermined number of times. A reference value serving as a criterion for determining the number of continuous reductions is appropriately set in consideration of the depth of field and the like.

If a negative determination is obtained in step S526, the flow advances to step S528, and a determination of interruption or continuation is made in steps S528 to S536 described above. On the other hand, if a YES determination is obtained in step S526, the flow advances to step S538 to determine interruption of the evaluation value acquisition process, and the flow returns to the flowchart in FIG.

When the interruption determination process described with reference to FIG. 14 is completed and the process returns to the flowchart of FIG.
Proceed to 124. In step S124 shown in FIG.
The interruption or continuation of the search operation is determined based on the result of the above-described interruption determination processing. If you get a "continue" decision,
Proceeding to step S126, it is determined whether or not the focus lens 48 has reached the position of the last stage of the search point.

If a NO determination is obtained in step S126, the process proceeds to step S128, in which the focus lens 48 is moved by one search step (AF step width 302) from the current focus stage, and returns to step S116. . In this manner, the evaluation value is moved to the next search point, and the evaluation value is calculated from the frame image data having different focus positions. The processing of steps S116 to S128 is repeated for each point in the focus adjustment area 300, and the evaluation value of each point is sequentially acquired.

If the determination of "interruption" is obtained in step S124, the process proceeds to step S142. Step S
In step 142, an operation for obtaining a range of the detailed search based on the result of the rough search is performed. The range of the detailed search is, for example, a predetermined range before and after the peak corresponding position of the evaluation value detected by the rough search. If the rough search is omitted and the process proceeds to step S142 due to the determination of NO in step S106, the all-focus adjustment area is set as the range of the detailed search.

Next, a process of driving the focus lens 48 to a detailed search start position (detailed search initial position) is performed according to the detailed search range obtained in step S142 (step S144). Thus, the detailed search starts, and the evaluation value at the search point is calculated (step S146). The evaluation value obtained is
4 and the CPU 64 stores the evaluation value at the search point in the memory 60.

Then, the flow advances to step S148 to perform a process for determining whether or not to suspend the AF search (detailed search). FIG. 15 shows the content of the “interruption determination (2)”. When the interruption determination (2) process starts, first, a table value “C_TABLE” corresponding to the current focal length [ZOOMPOS] is set in the register C (step S710).
This is because when the evaluation value calculated at each focus stage (search point) continuously decreases, the interruption determination value C serving as a criterion for determining to suspend the AF search.
This is the process of setting.

The interruption determination value C is set to the same numerical value as the number of focus steps (“4” in the example of FIG. 5) on the short focus side (wide side) or a value close thereto, so that the interruption processing is not substantially performed. Is set to In addition, the interruption determination value C becomes larger as approaching the long focal length side (tele side),
It is set to an integer value of about 50% to 30% of the number of focus steps.

Next, the flow advances to step S712 to determine whether or not the obtained evaluation value has decreased. When the evaluation value has not decreased (NO determination), the continuation of the AF search is determined (step S722), and the process exits this subroutine and returns to the flowchart of FIG.

When it is determined in step S712 in FIG. 15 that the evaluation value has decreased (when the determination is YES), the value of the register n (the initial value is set to n = 0) is set to 1
Is added (step S214), and the subsequent step S71
At 6, it is determined whether the value of the register n exceeds the value of the register C. If the value of the register n is equal to or less than the value of the register C (NO determination), the process proceeds to step S722 to determine continuation of the AF search, and returns to the flowchart of FIG. Thus, the AF search is continued until the evaluation value continuously decreases C times.

YES in step S716 in FIG.
When the determination is obtained, that is, when it is detected that the evaluation value continuously decreases C times, the process proceeds to step S718. In step S718, it is determined whether the difference between the maximum value (AFmax) and the minimum value (AFmin) of the evaluation values calculated by the AF search operation is larger than a predetermined value K. When the difference between the evaluation values is larger than the predetermined value K (when YES is determined), it indicates that there is a predetermined contrast, so that
The interruption of the AF search is determined (step S220).
If the difference between the evaluation values is equal to or smaller than the predetermined value K (when NO is determined), the process proceeds to step S722, and continuation of the AF search is determined.

When "interruption" or "continuation" is determined in step S720 or S722, the present subroutine ends, and the flow shifts to step S150 in the flowchart of FIG.

In step S150 of FIG. 10, C is determined based on the result of the interruption determination (2) processing (step S148).
The PU 64 determines whether to suspend or continue the AF search (Step S150). When the determination of “continue” is obtained in step S150, the process proceeds to step S152, and it is determined whether the final position of the search point has been reached.

If a NO determination is obtained in step S152, the flow advances to step S154 to move the focus lens 48 from the current focus position by one step (two pulses) of the AF search step.
Return to 46. In this manner, the evaluation value is moved to the next search point, and the evaluation value is calculated from the frame image data having different focus positions. The processing of steps S146 to S154 is repeated for each point in the detailed search range, and the evaluation value of each search point is obtained.

If the determination of "interruption" is obtained in step S150, or if the focus lens 48 has reached the final position of the search point in step S152, the process proceeds to step S162. In step S162, a lens position (in-focus position) at which the maximum value of the evaluation value is obtained is obtained, and a process of moving the focus lens 48 to the in-focus position is performed. When the operation of moving the lens to the in-focus position is completed, the in-focus state is achieved, and the shooting and recording are permitted (step S164).

When the focus lens 48 has reached the position of the last stage in the rough search step S126 (Y
(At the time of ES determination), the process proceeds to step S132. Step S
At 132, a process of determining whether or not the in-focus position can be obtained from the result of the evaluation value obtained by the rough search is performed. FIG. 16 shows a subroutine of this focusing possibility determination processing.

When the focusing possibility determination process shown in FIG. 16 starts, first, the maximum value AF of the evaluation values obtained by the rough search
It is determined whether max is greater than a first threshold (upper threshold) T1 (step S810). Step S810
If a YES determination is made in step S820, it is determined that focusing is possible (step S820), and the process returns to the flowchart of FIG.

If the determination in step S810 in FIG. 16 is NO, the process branches to step S812. In step S812, the maximum value AF of the evaluation values obtained by the rough search
It is determined whether max is smaller than a second threshold value (lower threshold value) T2 (step S812). Second threshold T2
Is set to a value lower than the first threshold value T1 (T2 <T1), and when the maximum evaluation value AFmax is smaller than the second threshold value T2 (when YES is determined), it is determined that focusing cannot be performed. (Step S830), and the process returns to the flowchart of FIG.

When the determination in step S812 in FIG. 16 is NO, that is, when the maximum evaluation value AFmax is
Between the first threshold value T1 and the second threshold value T2 (T2≤AFmax≤
If T1), the process proceeds to step S814. In step S814, it is determined whether the evaluation value has continuously decreased a predetermined number of times. This determination corresponds to determining whether the curve of the evaluation value obtained by the rough search has a peak. If a YES determination is obtained in step S814, it is determined that "in-focus possible" (step S820), and if a NO determination is obtained in step S814, it is determined that "in-focus is impossible" (step S830).

After the determination of “focusable” or “unfocusable” is made in step S820 or S830, the process proceeds to step S134 in the flowchart of FIG. In step S134, it is determined whether or not focusing is possible based on the result of the focusing possibility determination processing described above (step S134), and when it is determined that focusing is possible (YES determination).
Proceeds to step S142, and performs a detailed search.

On the other hand, if it is determined in step S134 that focusing cannot be performed, the detailed search is omitted, and the flow advances to step S164, where photographing and recording are permitted (step S164). When it is determined that focusing is impossible, a predetermined pan focus position (for example, the subject distance 2
The focus lens 48 is moved to a predetermined position such as a position where the focus is adjusted to m. Further, when focusing is impossible, it is preferable to notify the photographer by displaying a warning on the screen of the liquid crystal monitor 30 or the like. Thus, the automatic focus adjustment processing ends.

When the photographing and recording permission state is obtained in step S164, the state of the shutter button 18 is monitored by the CPU 64, and the subject is imaged in response to the full depression of the shutter button 18 (S2 = ON). The captured image is recorded on the memory card 24 together with the accessory information through predetermined signal processing.

As described above, the digital camera 10 according to the present embodiment determines the possibility of focusing at the end of the rough search. If the focusing is possible by AF, the process proceeds to the detailed search. Since the detailed search is prohibited and the AF is ended, unnecessary focusing operation can be omitted. Further, before starting the rough search, it is determined whether or not to execute the rough search based on the depth of field of the photographing optical system, and the rough search is selectively executed only when it can contribute to shortening the search time. Higher speed can be realized.

[0102]

As described above, according to the present invention, the search within the focusing area is performed at a relatively large search interval (first search).
Is determined using the evaluation value obtained here, and if it is determined that focusing is possible, the focus adjustment area is searched at a smaller search interval (second search). Search), the focus operation is stopped if it is determined that focusing is impossible in the focus possibility determination after the first search, so that unnecessary focus operation can be omitted.

[Brief description of the drawings]

FIG. 1 is an external view of a digital camera to which the present invention is applied.

FIG. 2 is a rear view of the digital camera shown in FIG. 1;

FIG. 3 is a block diagram showing an internal configuration of the digital camera of the present embodiment.

FIG. 4 is a diagram showing an example of a focus area set at the center of the screen;

FIG. 5 is a graph showing an example of an evaluation value that changes as the focus lens moves.

FIG. 6 is a diagram showing a change in a focus adjustment area (AF search range) according to a zoom position and a focus position.

FIG. 7 is a conceptual diagram of an AF method combining a rough search and a detailed search.

FIG. 8 is a diagram showing a state in which a plurality of subjects having different distances exist in a focus area;

FIG. 9 is a graph showing an example of an evaluation value that changes with movement of a focus lens when a plurality of subjects having different distances exist;

FIG. 10 is a flowchart illustrating a procedure of AF control according to the present embodiment.

FIG. 11 is a flowchart of a rough search execution determination process in FIG. 10;

FIG. 12 is a chart showing an example of switching determination data for rough search execution;

FIG. 13 is a graph illustrating a phenomenon in which the evaluation value does not decrease due to the influence of noise or the like.

14 is a flowchart of an interruption determination process in FIG.

FIG. 15 is a flowchart of an interruption determination (2) process in FIG. 10;

FIG. 16 is a flowchart of a focusing possibility determination process in FIG. 10;

[Explanation of symbols]

10 digital camera, 12 photographing lens, 18 shutter button, 48 focus lens, 52 CCD
(Imaging means), 64... CPU (first search means, second search means)
Search means, search control means, peak discriminating means, first
Search execution determining means), 78: focus driving section (lens moving means), 88: evaluation value calculating section (evaluation value calculating means), 94: focus area

Claims (11)

[Claims] 1. An evaluation value indicating image sharpness calculated using an image signal output from an image signal output from an image signal output from an image signal output from the image pickup device. In an automatic focus adjustment device that adjusts the focal position of the lens based on: a lens moving unit that moves the lens within a focus adjustment region; and for each lens position that is moved by the lens moving unit, An evaluation value calculation unit that extracts a contrast component of the subject from an image signal output from the imaging unit and calculates an evaluation value according to the contrast component; and the lens is disposed at a relatively large interval in the focus adjustment area. First search means for performing a first search for acquiring an evaluation value at each lens position while moving; a peak of the evaluation value obtained by the first search; After moving the lens near the corresponding position, the evaluation value is acquired at each lens position while moving the lens near the position corresponding to the peak at a smaller interval than the first search. Second search means for performing a search of: and search control means for prohibiting the second search when the maximum value of the evaluation values obtained by the first search is smaller than a preset threshold value. An automatic focusing device, comprising: 2. The method according to claim 1, wherein another threshold larger than the threshold is set, and when the maximum value of the evaluation values obtained by the first search exceeds the another threshold, the second search is executed. Determining, based on the evaluation value obtained by the second search, a lens position corresponding to a peak of the evaluation value as a focus position, and moving the lens to the focus position. 2. The automatic focusing device according to 1. 3. When the other threshold value is referred to as an “upper threshold value” and the lower threshold value is referred to as a “lower threshold value”, the maximum value of the evaluation values obtained by the first search is equal to the lower threshold value and the lower threshold value. A peak discriminating unit for discriminating the presence or absence of a peak of the evaluation value based on the evaluation value obtained by the first search when the value is between the upper thresholds; 3. The automatic focusing apparatus according to claim 2, wherein the second search is prohibited when it is determined that there is no. 4. An evaluation value indicating image sharpness calculated using an image signal output from the imaging means, comprising imaging means for converting an optical image of a subject incident through a lens into an electric signal. An automatic focus adjustment device that adjusts the focal position of the lens based on: a lens moving unit that moves the lens within a focus adjustment area; and for each lens position that is moved by the lens moving unit, An evaluation value calculation unit that extracts a contrast component of the subject from an image signal output from the imaging unit and calculates an evaluation value according to the contrast component; and the lens is disposed at a relatively large interval in the focus adjustment area. First search means for performing a first search for acquiring an evaluation value at each lens position while moving, and a peak of the evaluation value obtained by the first search After moving the lens near the corresponding position, the evaluation value is acquired at each lens position while moving the lens near the position corresponding to the peak at a smaller interval than the first search. A second search means for performing a search, a peak determination means for determining the presence or absence of a peak of an evaluation value based on the evaluation value obtained by the first search, and a message indicating that no peak exists by the peak determination means. And a search control unit for prohibiting the second search when the determination of (1) is obtained. 5. The apparatus according to claim 1, wherein the peak determining means determines that no peak exists when the evaluation value does not continuously decrease or increase a predetermined number of times in the first search. 5. The automatic focusing device according to 3 or 4. 6. A first search execution determining means for determining whether or not to execute the first search in accordance with a depth of field of an imaging optical system at the time of automatic focusing (AF), When the first search execution determination means obtains a determination not to execute the first search, each lens is moved within the focus adjustment area at a search interval equivalent to the second search. A search for obtaining an evaluation value at a position is performed, a lens position corresponding to a peak of the evaluation value obtained in the search is determined to be a focus position, and the lens is moved to the focus position. The automatic focusing device according to claim 1. 7. The first search execution determining means executes the first search with reference to determination reference data defined by a combination of a focal length and a stop of a zoom lens constituting the photographing optical system. Shall be determined,
The determination criterion data is set so as to switch the execution of the first search based on which can perform the AF at a higher speed depending on whether the first search is performed or not. 7. The automatic focusing apparatus according to claim 6, wherein the automatic focusing is performed. 8. An optical image of a subject incident through a lens is converted into an electric signal by an imaging unit, and an evaluation value indicating a sharpness of an image is calculated using an image signal output from the imaging unit. An automatic focusing method for adjusting the focal position of the lens based on the obtained evaluation value, the method comprising: moving the lens at a relatively large interval within a focusing area and outputting from the imaging means at each lens position. Extracting a contrast component of the subject from the image signal
A first search step of calculating an evaluation value according to the contrast component; a step of comparing a maximum value of the evaluation values obtained in the first search step with a preset threshold value; A second search step that can be performed when the maximum value of the evaluation values obtained in the search step is larger than the threshold value, wherein the position of the position corresponding to the peak of the evaluation value obtained in the first search step is A second search step of obtaining an evaluation value at each lens position while moving the lens in the vicinity of the position corresponding to the peak after moving the lens to the vicinity at a smaller interval than in the first search step; And a step of prohibiting the second search when the maximum value of the evaluation values obtained in the first search step is smaller than the threshold value. 9. The method according to claim 1, wherein another threshold value larger than the threshold value is set, and the maximum value of the evaluation values obtained in the first search step exceeds the other threshold value. And determining the lens position corresponding to the peak of the evaluation value as the in-focus position based on the evaluation value obtained in the second search step, and moving the lens to the in-focus position 9. The automatic focusing method according to claim 8, wherein: 10. When the other threshold value is referred to as an “upper threshold value” and the smaller threshold value is referred to as a “lower threshold value”, a maximum value of the evaluation values obtained in the first search step is equal to the lower threshold value. A peak discriminating step of discriminating the presence / absence of a peak of the evaluation value based on the evaluation value obtained in the first search step when the peak value is between the upper thresholds; 10. The automatic focus adjustment method according to claim 9, wherein the second search step is prohibited when the determination is made. 11. An optical image of a subject incident through a lens is converted into an electric signal by an imaging unit, and an evaluation value indicating the sharpness of an image is calculated using an image signal output from the imaging unit. An automatic focus adjustment method for adjusting a focal position of the lens based on the obtained evaluation value, the method comprising: moving the lens at a relatively large interval within a focus adjustment area; Extracting a contrast component of the subject from the image signal
A first search step of calculating an evaluation value according to the contrast component; a peak discrimination step of discriminating the presence or absence of a peak of the evaluation value based on the evaluation value obtained in the first search step; A second search step that can be performed when a determination that a peak exists is obtained in the determination step;
After moving the lens near the position corresponding to the peak of the evaluation value obtained in the first search step, the vicinity of the position corresponding to the peak is moved at a smaller interval than in the first search step. A second search step of acquiring an evaluation value at each lens position while moving the lens, and a step of prohibiting the second search when the peak discriminating unit obtains a decision that no peak exists. An automatic focusing method comprising: