JP6164978B2 - FOCUS ADJUSTMENT DEVICE, ITS CONTROL METHOD, CONTROL PROGRAM, AND IMAGING DEVICE - Google Patents

Description

  The present invention relates to a focus adjustment apparatus, a control method thereof, a control program, and an imaging apparatus, and more particularly to a focus adjustment apparatus used when a subject is designated to perform moving image shooting.

  Conventionally, in an imaging device such as a video camera or a digital camera, control is performed to automatically recognize a subject and automatically adjust the focus on the recognized subject. There is an imaging apparatus that recognizes a plurality of subjects and performs focus adjustment by switching the priorities of these subjects (see Patent Document 1).

  By the way, in a focus adjustment device (that is, an autofocus device) used in an imaging device, the sharpness is detected as an AF evaluation value based on a video signal obtained by photoelectrically converting a subject image (optical image) by an imaging device. To do. Then, the focus adjustment is performed by driving and controlling the position of the focus lens so that the AF evaluation value is maximized.

  In general, as the AF evaluation value, a high-frequency component level in a video signal extracted using a band-pass filter that passes a predetermined frequency band is used. When the subject is photographed, the AF evaluation value increases as the subject is focused, and the position of the focus lens that maximizes the AF evaluation value becomes the in-focus position.

  However, since the AF evaluation value is obtained according to the video signal, the spatial frequency in the photographed image (that is, the video signal) is reduced due to the influence of blurring or the like, and the high frequency component is reduced. For this reason, the AF evaluation value may decrease regardless of the distance to the subject.

  Due to the decrease in the spatial frequency, the imaging apparatus may enter an operation of searching for a focus position by determining that the distance to the subject has changed even though the user has focused on the subject intended by the user. is there. As a result, a subject unintended by the user may be focused.

  Furthermore, when performing focus adjustment, there is a so-called micro-drive operation in which the focus lens is intermittently driven to obtain an AF evaluation value, and the focus lens is controlled in a direction in which the AF evaluation value increases. Further, there is a hill climbing operation in which an AF evaluation value is obtained while driving the focus lens in a specific direction, and a focus position is specified according to a shape in which a plurality of AF evaluation values are plotted.

  There are the following problems when focus adjustment is performed using a plurality of such focus adjustment methods.

  First, when the direction of the in-focus position and the in-focus position are specified by performing a minute drive operation, the AF evaluation value changes when there is an influence of the above-described blurring compared to the case where the captured image is stable. It is difficult to detect. For this reason, it takes time to specify the in-focus position and its direction.

  As a result, a transition to hill-climbing operation is performed during focus adjustment, and the focus position is searched in a wide range. It is easy to receive. For this reason, the focus lens may stop at a position other than the original in-focus position due to erroneous determination. Furthermore, the follow-up operation to the in-focus position may become unstable.

  In particular, when shooting a moving image, an image obtained when performing the follow-up operation to the in-focus position is recorded as a moving image, and thus the obtained moving image may be unsightly.

JP 2008-206018 A

  If the user can arbitrarily stop the focusing operation with respect to the above-described problems, the usability of the imaging apparatus is improved. On the other hand, there is an image pickup apparatus that includes a touch panel and designates a subject to be focused by touching a subject intended by a user in a so-called through image displayed on a display unit.

  However, in such an imaging apparatus, an operation for designating a subject to be focused on the touch panel is different from an operation for stopping the focusing operation, which makes the operation complicated and unusable.

  Accordingly, an object of the present invention is to provide a focus adjustment device that can focus on a subject intended by a user without impairing operability in a situation where an image is affected by blurring, a control method thereof, a control program, and an imaging To provide an apparatus.

  In order to achieve the above object, a focus adjustment apparatus according to the present invention includes a focus lens that is connected to an imaging optical system that includes a focus lens according to image data obtained according to an optical image. A focus adjustment device that performs focus adjustment by moving along an optical axis, wherein a subject is detected in a first focus adjustment mode for focusing on a subject specified in an image corresponding to the image data and the image data And a control unit that selectively performs a second focus adjustment mode that focuses on the detected subject, and the control unit specifies a subject in the image during the first focus adjustment mode. Then, after focusing on the designated subject, the focus position of the focus lens is fixed, and the second focus adjustment mode is executed. After the object is focused on the specified is the designated object in the image, characterized by continuing the focus adjustment by the focusing lens.

  An image pickup apparatus according to the present invention includes an image pickup optical system including a focus lens, an image pickup unit that obtains image data according to an optical image incident through the image pickup optical system, and the focus adjustment apparatus described above. To do.

  According to the control method of the present invention, the focus lens is moved along the optical axis of the imaging optical system in accordance with image data obtained according to an optical image incident through the imaging optical system including the focus lens. A control method of a focus adjustment apparatus that performs adjustment, wherein a first control step of performing a first focus adjustment mode for focusing on a subject specified in an image corresponding to the image data, and a subject in the image data And a second control means for performing a second focus adjustment mode for detecting the detected subject and focusing on the detected subject. In the first control step, in the first focus adjustment mode, When a subject is specified in the image, the focus position of the focus lens is fixed after focusing on the specified subject, and in the second control step, When running a second focal point adjustment mode, after the subject in the image is focused on the specified is the designated object, characterized by continuing the focus adjustment by the focusing lens.

  The control program according to the present invention moves the focus lens along the optical axis of the imaging optical system according to image data obtained according to an optical image incident through the imaging optical system including the focus lens. A control program used in a focus adjustment apparatus that performs adjustment, wherein a first focus adjustment mode is performed in which a computer included in the focus adjustment apparatus performs a first focus adjustment mode for focusing on a subject specified in an image corresponding to the image data. And a second control means for detecting a subject as a detection subject in the image data and performing a second focus adjustment mode for focusing on the detection subject. In the first control step, In the first focus adjustment mode, when a subject is designated in the image, after focusing on the designated subject, When the focus position of the focus lens is fixed and the subject is designated in the image in the second control step when the second focus adjustment mode is executed, the designated subject is focused. After that, the focus adjustment by the focus lens is continued.

  According to the present invention, it is possible to focus on a subject intended by a user without impairing operability in a situation where an image is affected by blurring or the like.

It is a block diagram which shows the structure about an example of an imaging device provided with the focus adjustment apparatus by the 1st Embodiment of this invention. It is a block diagram which shows the example about the structure of the AF process part shown in FIG. FIG. 2 is a diagram for explaining a relationship between the position of the focus lens described in FIG. 1, an AF evaluation value, and a focus degree, and (a) is a diagram illustrating a relationship between the position of the focus lens and an AF evaluation value; ) Is a diagram showing the relationship between the position of the focus lens and the degree of focus. 3 is a flowchart for explaining an example of a focus adjustment process performed by the camera shown in FIG. 1. 5 is a flowchart for explaining an example of a minute driving operation shown in FIG. 4. It is a flowchart for demonstrating an example of the mountain climbing operation | movement shown in FIG. 6 is a flowchart for explaining an example of an AF evaluation value monitoring process shown in FIG. 4. 5 is a flowchart for explaining an example of a subject designation process shown in FIG. 4. It is a transition diagram for demonstrating an example of the state transition in the focus adjustment operation | movement performed with the camera shown in FIG. It is a transition diagram for demonstrating an example of the state transition in the focus adjustment operation | movement performed with the camera which concerns on the 2nd Embodiment of this invention.

  Hereinafter, an example of an imaging apparatus including a focus adjustment apparatus according to an embodiment of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram illustrating a configuration of an example of an imaging apparatus including a focus adjustment apparatus according to the first embodiment of the present invention.

<Configuration of the entire imaging device>
The illustrated imaging apparatus is, for example, a digital camera (hereinafter simply referred to as a camera) and has a so-called moving image shooting function. The system control unit 115 controls the entire camera and includes, for example, a CPU, a RAM, and a ROM. Then, the CPU uses the RAM as a work area according to a program recorded in advance in the ROM, and controls the operation of the camera.

  As will be described later, the system control unit 115 specifies a focus position (also referred to as a focus position) based on the focus evaluation value calculated by the AF processing unit 105. Then, the system control unit 115 controls the focus lens control unit 104 to move the focus lens along the optical axis to perform an automatic focus adjustment (AF) process. The focus evaluation value is a numerical value serving as a contrast index in the distance measurement area.

  The taking lens unit (hereinafter simply referred to as a taking lens) 100 has a zoom function. The zoom lens control unit 101 drives and controls a zoom lens that changes the focal length under the control of the system control unit 115.

  The aperture / shutter controller 102 drives and controls an aperture and a shutter that adjust the amount of light under the control of the system controller 115. The focus lens control unit 104 drives and controls the focus lens under the control of the system control unit 115 to focus on the light receiving surface (also referred to as an imaging surface) of the image sensor 108.

  Although not shown, the zoom lens control unit 101, the aperture / shutter control unit 102, and the focus lens control unit 104 are necessary for driving optical elements such as lenses, mechanisms such as an aperture / shutter, and the like. Equipped with various devices. Various devices include an optical element and an actuator for driving the above mechanism, a circuit for controlling the actuator, a D / A converter, and the like.

  The light emitting device (strobe) 106 emits light toward the surroundings to adjust the luminance of the subject. When receiving the flash-on signal from the system control unit 115, the EF processing unit 107 controls the flash 106 to emit light. When the system control unit 115 determines that the strobe 106 needs to emit light, the system control unit 115 sends the aforementioned flash-on signal to the EF processing unit 107.

  The image sensor 108 outputs an electrical signal (analog signal) corresponding to incident light (optical image). For example, the imaging element 108 is a CCD or CMOS image sensor, and includes a plurality of photoelectric conversion elements, and photoelectrically converts incident light to generate an imaging signal (image signal) that is an analog signal.

  The imaging processing unit 109 includes a CDS (correlated double sampling) circuit, a nonlinear amplification circuit, and an A / D conversion unit. The CDS circuit removes noise in the imaging signal that is the output of the imaging device 108 by correlated double sampling. The nonlinear amplifier circuit performs signal amplification (gain control) on the imaging signal from which noise has been removed. The A / D converter converts the signal-amplified imaging signal into a digital signal (image data).

  Note that the imaging element 108 and the imaging processing unit 109 function as an imaging unit that obtains image data by imaging a subject.

  The image processing unit 110 performs predetermined image processing such as gamma correction and contour correction on the image data. Further, the image processing unit 110 performs white balance processing on the image data under the control of the WB processing unit 111.

  The format converter 112 converts the processed image data, which is the output of the image processor 110, into a format suitable for recording and display.

  A DRAM (Random Access Memory) 113 is a high-speed built-in memory, and is used as a high-speed buffer that temporarily stores image data that has undergone format conversion (converted image data). The DRAM 113 is also used as a working memory when compressing / decompressing the converted image data.

  The image recording unit 114 includes a recording medium such as a memory card and an interface, and converted image data stored in the DRAM 113 is recorded in the image recording unit 114.

  The AE processing unit 103 obtains a photometric value corresponding to the brightness of the subject based on the image data output from the imaging processing unit 109. That is, the AE processing unit 103 and the imaging processing unit 109 function as an exposure condition detection unit that detects an exposure condition when photographing a subject.

  Further, the AE processing unit 103 determines a signal amplification amount (gain amount) for amplifying the imaging signal and maintaining a proper exposure when the luminance of the subject is low (less than a predetermined luminance level). In other words, the AE processing unit 103 determines a signal amplification amount (gain amount) for correcting the imaging signal to an appropriate exposure.

  The system control unit 115 controls the aperture / shutter control unit 102 and the nonlinear amplification circuit of the imaging processing unit 109 based on the photometric value obtained by the AE processing unit 103. Accordingly, the system control unit 115 automatically adjusts the exposure amount. That is, the system control unit 115 performs automatic exposure (AE) processing using the exposure conditions (that is, photometric values) detected by the AE processing unit 103 that is an exposure condition detection unit.

  The AF processing unit 105 obtains an AF evaluation value according to the image data that is the output of the imaging processing unit 109. Then, the system control unit 115 controls the focus lens control unit 104 according to the AF evaluation value and performs an automatic focus adjustment (AF) process.

  FIG. 2 is a block diagram showing an example of the configuration of the AF processing unit 105 shown in FIG.

  The AF processing unit 105 includes a distance measurement gate 122, and the distance measurement gate 122 extracts a part of the screen (for example, an area indicated by an AF frame) from the image data (hereinafter, this image data is extracted image data). Called). The extracted image data is given to a band pass filter (BPF) 123 and a low pass filter (LPF) 125.

  The BPF 123 extracts a high frequency component in a predetermined frequency band and sends the high frequency component to the detection (detection) unit (DET) 124. The DET 124 performs peak hold processing and integration processing on the high-frequency component, and outputs the integration processing result as an AF evaluation value.

  The illustrated AF processing unit 105 obtains a degree of focus indicating how much the image data is in focus. As described above, the extracted image data is given to the LPF 125, and the LPF 125 passes only a predetermined low frequency component. In other words, the LPF 125 removes the high frequency component and sends the low frequency component to the line maximum value portion (Line · Max) 126 and the line minimum value portion (Line · Min) 127.

  Line · Max 126 detects the maximum value in one horizontal line, while Line · Min 127 detects the minimum value in one horizontal line.

  The adder 128 calculates a difference (maximum value−minimum value) between the maximum value and the minimum value of one horizontal line. The peak hold unit (Peak Hold) 129 receives the difference for each horizontal line from the adding unit 128 and detects the peak value MM of the difference (maximum value−minimum value) in all the lines in the extracted image data. This peak value MM corresponds to the maximum contrast value in the extracted image data.

  The division unit 130 is given the AF evaluation value (here, the peak hold value) and the peak value MM. Then, the division unit 130 divides the peak hold value by the peak value MM and outputs the division result as a focus degree.

  FIG. 3 is a diagram for explaining the relationship between the position (lens position) of the focus lens described in FIG. 1, the AF evaluation value, and the degree of focus. FIG. 3A shows the relationship between the lens position and the AF evaluation value, and FIG. 3B shows the relationship between the lens position and the degree of focus.

  As described above, since the AF evaluation value is the result of the integration process, the AF evaluation value is not easily affected by noise or the like. Changes significantly (see FIG. 3A). That is, in the illustrated area A, the AF evaluation value is extremely high, but in the area B, the AF evaluation value changes drastically. In region C, the AF evaluation value is low.

  On the other hand, by normalizing the in-focus degree, the in-focus position approaches a predetermined value (Max shown in FIG. 3B), and the value tends to decrease as the image is blurred. For this reason, as will be described later, the AF process is performed using the AF evaluation value and the degree of focus during the automatic focus adjustment process (AF process).

  Referring to FIG. 1 again, format-converted image data (here, display image data) is recorded in VRAM (image display memory) 116. The operation display unit 117 performs image display, display for assisting operation, and display of the camera state under the control of the system control unit 115.

  The operation display unit 117 displays an image corresponding to the image data temporarily recorded in the VRAM 116 at the time of shooting as a shooting screen. Furthermore, the operation display unit 117 includes various buttons and a touch panel, and the user can operate the camera using the operation display unit 117.

  The main switch (main SW) 118 is a switch for turning on / off the power of the camera. The first switch (SW1) 119 is a switch for performing a shooting standby operation (shooting preparation operation) such as AF and AE. The second switch (SW2) 120 is a switch that is operated when imaging is performed after the first switch 119 is operated.

<Basic operation>
FIG. 4 is a flowchart for explaining an example of the focus adjustment process performed by the camera shown in FIG.

  The processing according to the flowchart shown in the figure is continuously performed during moving image recording and standby by the camera. Furthermore, the processing according to the flowchart is stored in a ROM provided in the system control unit 115 as a computer program (software). Then, after the power is turned on by the operation of the main SW 118 and the camera is activated, the system control unit 115 executes processing according to the program stored in the ROM.

  When the focus adjustment process is started, the system control unit 115 first performs a minute driving operation described later (step S200). Here, the minute driving operation refers to the direction of the in-focus position and the in-focus position (focal point) according to the change in the AF evaluation value obtained intermittently by moving the focus lens little by little along the optical axis. To identify).

  After specifying the direction of the in-focus position and the in-focus position by the minute driving operation, the system control unit 115 performs subject designation processing described later (step S201). In the subject designation process, when the user designates a subject on the screen using the touch panel provided in the operation display unit 117, the subject to be focused is set by the focus adjustment operation.

  Further, in the subject specifying process, a partial area (for example, an AF frame area) of the image data extracted by the distance measuring gate 122 described with reference to FIG. 2 is set. In addition, in the subject designation process, the state transition of the focus adjustment operation is changed as will be described later.

  Subsequently, the system control unit 115 determines whether or not to transition to the AF evaluation value monitoring process according to the processing results of steps S200 and S201 (step S202). If it is determined that the transition to the AF evaluation value monitoring process is not made (NO in step S202), the system control unit 115 determines whether or not the transition is made to a hill climbing operation (step S203). If it is determined that the transition to the hill-climbing operation is not made (NO in step S203), the system control unit 115 returns to the process of step S200 and continues the minute driving operation.

  If it is determined that a transition is made to a hill-climbing operation (YES in step S203), system control unit 115 performs a hill-climbing operation described later (step S204). Here, the hill-climbing operation is a method for specifying the in-focus position in accordance with changes in a plurality of AF evaluation values obtained as a result of continuously moving the focus lens along the optical axis.

  After the processing in step S204, the system control unit 115 performs subject designation processing described later (step S205). In the subject designation process in step S205, the state transition of the focus adjustment operation is changed according to whether or not the user has designated a subject on the screen using the touch panel provided in the operation display unit 117.

  Subsequently, the system control unit 115 determines whether or not to shift to the minute driving operation according to the processing results of steps S204 and S205 (step S206). If it is determined that the micro drive operation is not changed (NO in step S206), the system control unit 115 determines whether or not the operation is shifted to the AF evaluation value monitoring process (step S207).

  If it is determined that the transition to the AF evaluation value monitoring process is not made (NO in step S207), the system control unit 115 returns to the process in step S204 and performs a hill climbing operation. On the other hand, if it is determined to shift to the AF evaluation value monitoring process (YES in step S207), the system control unit 115 determines the state of the AF fixed flag (step S208). Here, the system control unit 115 determines whether or not the AF fixed flag is FALSE.

  Here, the AF fixed flag is a flag set in the subject specifying process. Then, depending on the state of the AF fixed flag, whether the system control unit 115 continues the transition of the AF evaluation value monitoring process or whether the AF is fixed without completing the AF evaluation value monitoring process and the focus adjustment operation is terminated. To decide.

  When the AF fixed flag is FALSE (YES in step S208), the system control unit 115 stores the AF evaluation value at the in-focus position specified in step S200 described above or the lens position interrupted as out-of-focus (step S208). S209). Then, the system control unit 115 performs AF evaluation value monitoring processing (step S210).

  In the AF evaluation value monitoring process performed in step S210, the system control unit 115 compares the stored AF evaluation value with the periodically obtained AF evaluation value and monitors the change.

  Subsequently, the system control unit 115 performs subject designation processing (step S211). In the subject designation process in step S211, the state transition of the focus adjustment operation is changed according to whether or not the user designates the subject using the touch panel provided in the operation display unit 117.

  After the process of step S211, the system control unit 115 determines whether or not to make a transition to the minute driving operation according to the process results of steps S210 and S211 (step S212). If it is determined that a transition to the minute driving operation is made (YES in step S212), the system control unit 115 returns to the process of step S200 and performs the minute driving operation.

  On the other hand, when it is determined that the transition to the minute driving operation is not made (NO in step S212), the system control unit 115 returns to the process of step S210 and performs the AF evaluation value monitoring process.

  If the AF fixed flag is not FALSE (NO in step S208), that is, if the AF fixed flag is TRUE, the system control unit 115 sets the AF fixed flag to FALSE (step S213) and fixes AF (step S214). ). Then, the system control unit 115 ends the focus adjustment process.

  If it is determined in step S206 that the mode is to be changed to the minute driving operation (YES in step S206), the system control unit 115 returns to the process in step S200 and performs the minute driving operation. If it is determined in step S202 that the process proceeds to the AF evaluation value monitoring process (YES in step S202), the system control unit 115 proceeds to the process of step S208 and determines whether or not the AF fixed flag is FALSE. .

  As described above, in the focus adjustment process, the system control unit 115 selects any one of the minute driving operation, the hill-climbing operation, and the AF evaluation value monitoring process, and maintains the focused state according to various scene changes. Thus, the focus lens is controlled.

<Small drive operation>
FIG. 5 is a flowchart for explaining an example of the minute driving operation shown in FIG.

  As described above, the micro-drive operation is to specify the direction of the in-focus position and the in-focus position according to the change in the AF evaluation value obtained as a result of intermittently moving the focus lens along the optical axis. It is a technique to do.

  When the minute driving operation is started, the system control unit 115 acquires an AF evaluation value from the AF processing unit 105 (step S300). Subsequently, the system control unit 115 acquires the degree of focus from the AF processing unit 105 (step S301).

  Next, the system control unit 115 sets the movement amount of the focus lens in the minute driving (step S302). Here, the closer the in-focus position is, the smaller the amount of movement of the focus lens is, and the farther the distance from the in-focus position is, the larger the amount of movement of the focus lens is.

  For this reason, the system control unit 115 sets the amount of movement of the focus lens in accordance with the degree of focus acquired in step S301 (that is, the current degree of focus).

  Referring to FIG. 3B, for example, the first focus threshold value α, the second focus threshold value β, and the third focus threshold value γ are set with respect to the focus degree, and α> β> γ. It shall be in the relationship. Using the first to third focus threshold values α to γ, the system control unit 115 sets the movement amount of the focus lens as follows.

  When the degree of focus> α, the system control unit 115 sets the movement amount of the focus lens as the movement amount Step1. When α ≧ focus degree> β, the system control unit 115 sets the movement amount of the focus lens as the movement amount Step2. When β ≧ focus degree> γ, the system control unit 115 sets the movement amount of the focus lens as the movement amount Step3. When γ ≧ focus degree, the system control unit 115 sets the movement amount of the focus lens as the movement amount Step4.

  Note that Step1 <Step2 <Step3 <Step4.

  Next, the system control unit 115 determines whether or not the current AF evaluation value is larger than (immediate AF evaluation value + change threshold A) (step S303). Here, the change threshold A is a threshold for determining that the AF evaluation value has clearly increased, and is set in consideration of variations due to noise components in addition to the increase amount of the AF evaluation value.

  If current AF evaluation value> immediate AF evaluation value + change threshold A (YES in step S303), system control unit 115 increments a built-in direction specifying counter (step S304). This direction specifying counter is for specifying the direction of the in-focus position, and indicates that the AF evaluation value increases stably toward the in-focus position as the count value of the direction specifying counter increases. Yes.

  Subsequently, the system control unit 115 controls the focus lens control unit 104 to move the focus lens from the current lens position along the optical axis according to the movement amount set in step S302 (step S305). At this time, the movement direction is the same as the previous movement direction.

  On the other hand, if the current AF evaluation value ≦ the previous AF evaluation value + the change threshold A (NO in step S303), the system control unit 115 determines that the current AF evaluation value is (the previous AF evaluation value−the change threshold A). It is determined whether it is larger than (step S306). In the process of step S306, the system control unit 115 detects a decreasing tendency of the AF evaluation value.

  If the current AF evaluation value ≧ the previous AF evaluation value−the change threshold A, the focus lens is moved along the optical axis from the current lens position in accordance with the movement amount set in step S302 (step S307). In step S307, the system control unit 115 controls the focus lens control unit 104 to move the focus lens along the optical axis.

  At this time, since an increase or decrease in the explicit AF evaluation value cannot be detected, the system control unit 115 does not perform counting by the direction specifying counter.

  If current AF evaluation value <immediate AF evaluation value−change threshold A (YES in step S306), system control unit 115 clears the direction specifying counter (step S308). Then, the system control unit 115 controls the focus lens control unit 104 to move the focus lens from the current lens position along the optical axis in the direction opposite to the previous movement direction according to the movement amount set in step S302. (Step S309).

  Following the processing of step S305, S307, or S309, the system control unit 115 determines whether or not the focus lens has reciprocated within the same area a predetermined number of times (step S310).

  Referring to FIG. 3A, for example, when the lens position converges to the vicinity of the in-focus position as indicated by region A, the AF evaluation value decreases when the in-focus position is passed in the minute driving operation. The AF evaluation value is inverted at the next control timing. When the minute driving operation is continued, the focus lens finally reciprocates across the in-focus position. Therefore, if the focus lens reciprocates within the same area a predetermined number of times, it can be estimated that the focus lens is in the in-focus position.

  Referring to FIG. 5 again, if the focus lens does not reciprocate within the same area a predetermined number of times (NO in step S310), system control unit 115 determines that the count value of the direction specifying counter is equal to or greater than the predetermined count value. It is determined whether or not there is (step S311). If the count value of the direction specifying counter is less than the predetermined count value (NO in step S311), a series of minute driving operations are performed a predetermined number of times, and the degree of focus acquired in step S301 is lower than the predetermined threshold value. Is determined (step S312).

  Referring to FIG. 3A, for example, in an area (area) where the AF evaluation value hardly changes like the area C, the in-focus position and its direction may not be specified within a predetermined number of times. That is, if the search range is wide as in the region C and the current lens position is too far from the focus position, it is difficult to search for the focus position, or the focus position exists outside the search range. Sometimes. In such a situation, it is difficult to search for the in-focus position and its direction even if the minute driving operation is continued.

  Referring to FIG. 5 again, if the series of micro driving operations are performed a predetermined number of times and the degree of focus is not lower than the predetermined threshold (NO in step S312), system control unit 115 performs micro driving operations. Is determined to continue (step S313), and the process returns to the focus adjustment process.

  When a series of micro drive operations are performed a predetermined number of times and the in-focus degree is lower than a predetermined threshold (YES in step S312), system control unit 115 determines that the focus is not in focus, and the micro drive operation is performed. To hill-climbing operation (step S314). Then, the system control unit 115 returns to the focus adjustment process.

  If the count value of the direction specifying counter is equal to or greater than the predetermined count value (YES in step S311), system control unit 115 determines that the direction is specified, and transitions from a minute driving operation to a hill climbing operation (step S315). Then, the system control unit 115 returns to the focus adjustment process.

  If the focus lens reciprocates within the same area a predetermined number of times (YES in step S310), system control unit 115 determines that the focus is in focus, and transitions from the micro drive operation to the AF evaluation value monitoring process (step S316). ). Then, the system control unit 115 returns to the focus adjustment process.

  In the processing from step S310 to step S316, the system control unit 115 detects a change in the AF evaluation value obtained periodically and makes a determination in the minute driving operation based on the detection result.

<Mountain climbing action>
FIG. 6 is a flowchart for explaining an example of the mountain climbing operation shown in FIG.

  As described above, the hill-climbing operation is a method for specifying the in-focus position in accordance with changes in a plurality of AF evaluation values obtained as a result of continuously moving the focus lens along the optical axis.

  When the mountain climbing operation is started, the system control unit 115 acquires an AF evaluation value and a focus lens position (lens position) corresponding to the AF evaluation value from the AF processing unit 105 (step S400). Next, the system control unit 115 acquires the degree of focus from the AF processing unit 105 (step S401).

  Subsequently, the system control unit 115 sets the moving speed (lens speed) of the focus lens in the hill climbing operation according to the degree of focus (step S402). Here, the lens speed is decreased as the focus lens approaches the in-focus position, and the lens speed is increased as the focus lens moves out of the in-focus position so that the focus tracking can be stably performed in the hill-climbing operation.

  Referring to FIG. 3B, as described above, assuming that the first focus threshold value α> the second focus threshold value β> the third focus threshold value γ, the lens speed is as follows: Become.

  When the degree of focusing is greater than α, the system control unit 115 sets the lens speed to speed Speed1. When α ≧ focus degree> β, the system control unit 115 sets the lens speed to speed Speed2. When β ≧ focus degree> γ, the system control unit 115 sets the lens speed to speed Speed3. When γ ≧ focus degree, the system control unit 115 sets the lens speed to speed Speed4.

  Note that Speed1 <Speed2 <Speed3 <Speed4.

  Referring to FIG. 6 again, after setting the lens speed, the system control unit 115 determines whether or not the focus lens is stopped (step S403). Note that the focus lens is stopped either immediately after transition from the minute driving operation to the hill-climbing operation or when the focus lens reaches the end of the search range during the hill-climbing operation.

  If the focus lens is stopped (YES in step S403), the system control unit 115 determines whether or not the current lens position is the moving end (step S405). If the lens position is not the moving end (NO in step S405), the system control unit 115 determines that the focus lens has just shifted from the minute driving operation to the mountain climbing operation. Then, the focus lens is moved by taking the traveling direction in the minute driving operation as the designated direction (step S406).

  If the lens position is the moving end (YES in step S405), the system control unit 115 moves the focus lens in the direction opposite to the traveling direction so far (step S407).

  Following the processing of step S406 or S407, the system control unit 115 determines whether or not the focus lens has reached the moving end a predetermined number of times (step S408). If the focus lens is not stopped (NO in step S403), the system control unit 115 proceeds to the process of step S408. When the focus lens reaches the moving end a predetermined number of times (YES in step S408), system control unit 115 stops the focus lens by focus lens control unit 104 (step S409).

  Referring to FIG. 3A, if the in-focus position cannot be specified even if at least both ends (moving ends) of the search range are reached, the entire search range has the AF evaluation value as in region C. It is an area where the change is scarce, and it can be estimated that the in-focus position is outside the search range of the focus lens. If the mountain climbing operation is continued under such circumstances, the focus variation becomes large, and the state where the focus variation is large is repeated.

  In order to avoid such a state, as described above, when the focus lens reaches the moving end a predetermined number of times, the system control unit 115 causes the focus lens control unit 104 to stop the focus lens. Then, the system control unit 115 sets the determination result in the hill climbing operation as out-of-focus, shifts to the AF evaluation value monitoring process (step S410), and returns to the focus adjustment process.

  On the other hand, if the focus lens does not reach the moving end a predetermined number of times (NO in step S408), system control unit 115 compares the current AF evaluation value with the immediately preceding AF evaluation value. Then, it is determined whether or not the current AF evaluation value is larger than the immediately preceding AF evaluation value (step S411). If the current AF evaluation value> the previous AF evaluation value (YES in step S411), the system control unit 115 determines to continue the hill-climbing operation, and continues the hill-climbing operation (step S412). Then, the system control unit 115 returns to the focus adjustment process.

  As shown in FIG. 3A, when an upward trend of the AF evaluation value can be detected such as when the hill-climbing operation is correctly performed in the direction of the in-focus position in the region B, the hill-climbing operation is performed in the direction. Will be.

  If the current AF evaluation value ≦ the previous AF evaluation value (NO in step S411), the system control unit 115 determines whether or not the AF evaluation value has decreased beyond the peak (step S413). When the AF evaluation value decreases beyond the peak (YES in step S413), system control unit 115 causes focus lens control unit 104 to stop the focus lens (step S414).

  For example, when a hill-climbing operation is performed from region B to region A shown in FIG. 3A, the AF evaluation value decreases beyond the peak.

  After the process of step S414, the system control unit 115 shifts to the micro drive operation with the determination result in the hill climbing operation as the focus (step S415). Then, the system control unit 115 causes the focus lens control unit to move the focus lens to a position where the AF evaluation value shows a peak (step 416), and returns to the focus adjustment processing.

  On the other hand, if the AF evaluation value does not decrease beyond the peak (NO in step S413), the system control unit 115 reverses the moving direction of the focus lens and moves the focus lens in the opposite direction (step S417).

  For example, if the mountain climbing operation is performed in the direction opposite to the in-focus position in the region B shown in FIG. 3A, the AF evaluation value does not decrease beyond the peak.

  After the process of step S417, the system control unit 115 determines that the mountain climbing operation is continued, and continues the mountain climbing operation (step S418). Then, the system control unit 115 returns to the focus adjustment process.

  In the processes from step S408 to S418, a change in the AF evaluation value obtained periodically is detected, and a determination in the hill climbing operation is performed based on the change.

<AF evaluation value monitoring process>
FIG. 7 is a flowchart for explaining an example of the AF evaluation value monitoring process shown in FIG. As described above, the AF evaluation value monitoring process is a process for detecting whether or not the current AF evaluation value has changed with respect to the previously stored AF evaluation value.

  When the AF evaluation value monitoring process is started, the system control unit 115 acquires an AF evaluation value (this is the latest AF evaluation value) from the AF processing unit 105 (step S500). Next, the system control unit 115 compares the AF evaluation value stored in step S209 shown in FIG. 4 with the latest AF evaluation value, and the variation amount (variation value) that is the difference is determined based on a predetermined variation threshold. Is also larger (step S501).

  If the fluctuation amount is larger than the fluctuation threshold (YES in step S501), that is, if the AF evaluation value fluctuates greatly, the system control unit 115 transitions to a minute driving operation (step S502). Then, the system control unit 115 returns to the focus adjustment process.

  If the fluctuation amount is equal to or less than the fluctuation threshold (NO in step S501), the system control unit 115 determines to continue the AF evaluation value monitoring process, and continues the AF evaluation value monitoring process (step S503). Then, the system control unit 115 returns to the focus adjustment process.

  As can be easily understood from the above description, in the processing of step S209 to step S212 shown in FIG. 4, when the fluctuation of the AF evaluation value is small and stable, the AF evaluation value monitoring processing is periodically continued. Will be done.

<Subject designation processing>
FIG. 8 is a flowchart for explaining an example of the subject designation process shown in FIG.

  As described above, in the subject designation process, a subject to be focused is set by the focus adjustment operation (focus adjustment process) when the subject is designated by the user's operation. Further, an image data area (an AF frame area) to be extracted by the distance measuring gate 122 (FIG. 2) is set. Then, the state transition in the focus adjustment operation is changed.

  When the subject designation processing is started, the system control unit 115 determines whether or not the user has designated a subject on the screen using the touch panel provided in the operation display unit 117 (step S600). When the subject is designated by a user operation (YES in step S600), system control unit 115 sets the state to be changed in the focus adjustment operation to the minute drive operation (step S601).

  Subsequently, the system control unit 115 determines whether the AF frame automatic mode (second focus adjustment mode) or the AF frame designation mode (first focus adjustment mode) is set (step S602). In the AF frame automatic mode (second focus adjustment mode), the AF frame setting mode automatically sets the position of the AF frame to the position of the subject (detected subject) detected from the image data. In the AF frame designation mode (first focus adjustment mode), the position of the AF frame is set to a position designated by the user.

  If the AF frame setting mode is the AF frame designation mode (YES in step S602), system control unit 115 sets the AF frame at the position designated by the user (step S603), and sets the AF fixed flag to TRUE. (Step S604). Then, the system control unit 115 returns to the focus adjustment process.

  The system control unit 115 selectively performs an AF frame designation mode and an AF frame automatic mode.

  On the other hand, when the AF frame mode is the AF frame automatic mode (NO in step S602), the system control unit 115 sets the subject to be focused by the focus adjustment operation to the subject designated by the user (step S605). Thereafter, the system control unit 115 sets the AF fixed flag to FALSE (step S606), and returns to the focus adjustment process.

  Note that the AF fixed flag is stored in the DRAM 113. If the subject is not designated by the user operation (NO in step S600), the system control unit 115 returns to the focus adjustment process (focus adjustment operation).

  In this way, when a subject is specified by a user operation, the position of the subject or AF frame to be focused by the focus adjustment operation is set, and the focus adjustment operation is shifted to a minute drive operation. Then, the system control unit 115 redoes the focus adjustment operation for the designated subject or AF frame position.

<Focus adjustment operation state transition>
FIG. 9 is a transition diagram for explaining an example of state transition in the focus adjustment operation performed by the camera shown in FIG.

  Now, when the camera is activated in the moving image mode, the operation state in the focus adjustment operation transitions to the minute drive operation state, and the aforementioned minute drive operation is performed. In the minute drive operation state, a series of processes in steps S200 to S203 shown in FIG. 4 are repeated.

  If the transition condition for transitioning to the hill-climbing operation state is satisfied during the processing, the operation state in the focus adjustment operation transitions to the hill-climbing operation state. In addition, when a transition condition for transitioning to the AF evaluation value monitoring state is satisfied during the series of processing in steps S200 to S203 illustrated in FIG. 4, the operation state in the focus adjustment operation transitions to the AF evaluation value monitoring state.

  In the hill-climbing operation state, a series of processes in steps S204 to S207 shown in FIG. 4 are repeated. When the transition condition for transitioning to the minute driving operation state is satisfied during the processing, the operation state in the focus adjustment operation transitions to the minute driving operation state.

  In addition, when a transition condition for transitioning to the AF evaluation value monitoring processing state is satisfied during the series of steps S204 to S207 illustrated in FIG. 4, the operation state in the focus adjustment operation transitions to the AF evaluation value monitoring processing state.

  In the AF evaluation value monitoring process state, a series of processes in steps S210 to S212 shown in FIG. 4 are repeated. When the transition condition for transitioning to the minute driving operation state is satisfied during the processing, the operation state in the focus adjustment operation transitions to the minute driving operation state.

  In this way, in the focus adjustment operation, the operation state continuously changes to the minute drive operation state, the hill-climbing operation state, or the AF evaluation value monitoring state according to the transition condition, and responds to changes in various scenes. To maintain the in-focus state.

  Here, when the user designates a subject by operating the touch panel provided in the operation display unit 117 during the focus adjustment operation, a series of processes in steps S601 to S606 shown in FIG. 8 are performed. By this processing, the operation state in the focus adjustment operation is changed to the minute drive operation state, and the focus adjustment operation is performed again on the subject specified by the user. When the AF frame setting mode is the AF frame designation mode, the AF fixed flag is set to TRUE.

  Then, after the focus adjustment operation is performed again through a series of state transitions of the focus adjustment operation starting from the minute drive operation state, the state shifts to the AF evaluation value monitoring processing state. At this time, if the AF fixed flag is set to TRUE, the focus adjustment operation is stopped and the AF fixed state is set.

  In the flowchart shown in FIG. 4, when transitioning to the AF evaluation value monitoring processing state in step S202 or step S207, the state of the AF fixed flag stored in the DRAM 113 is determined in step S208.

  If the AF fixed flag is TRUE, after the AF fixed flag is set to FALSE in step S213, AF is fixed (stops the focus adjustment operation) in step S214, and the focus adjustment operation ends.

  As described above, when the subject is instructed by the user while performing the minute driving operation, the hill climbing operation, or the AF evaluation value monitoring process continuously, a series of focus adjustment operations are performed again on the designated subject. After the focus is adjusted, AF is fixed.

  When the subject is specified in the AF fixed state, the operation state in the focus adjustment operation is changed to the minute drive state as shown in FIG. 9, and the focus adjustment operation is resumed.

  As described above, in the first embodiment of the present invention, when a subject is instructed by a user operation during the focus adjustment operation (focus adjustment processing), a series of focus adjustment operations are performed again to the designated subject. On the other hand, AF is fixed after the focus is adjusted.

  As a result, even if the AF evaluation value does not show the expected change tendency under the situation where camera shake or the like affects the image, the subject intended by the user is focused without impairing the operability. be able to.

[Second Embodiment]
Subsequently, a camera provided with a focus adjustment apparatus according to a second embodiment of the present invention will be described. The configuration of the camera according to the second embodiment is the same as that of the camera shown in FIGS.

  FIG. 10 is a transition diagram for explaining an example of state transition in the focus adjustment operation performed by the camera according to the second embodiment of the present invention.

  Here, the focus adjustment operation when the camera is not focused even if a predetermined time elapses due to the effects of camera shake, etc. during the recording of moving images (that is, during recording of moving image data) and during the standby operation The state transition in will be described. Since other state transitions are the same as those in the first embodiment, description thereof will be omitted.

  In FIG. 10, in the minute drive operation state or the hill-climbing operation state, when the in-focus state is not achieved even after a predetermined time has elapsed, the system control unit 115 stops the focus adjustment operation as a timeout and sets the AF fixed state.

  As a result, when the in-focus state is not achieved even after a predetermined time due to camera shake or the like, the AF is fixed at the focus position at that time, and the focus adjustment operation can be prevented from straying. .

  In the subject specifying process described above, the AF fixed flag may be set according to the degree of focus (the reliability of the AF evaluation value). For example, when the degree of focus is higher than a predetermined value, the AF fixed flag is set to TRUE. On the other hand, if the degree of focus is less than or equal to a predetermined value, the AF fixed flag is set to FALSE.

  Thus, when the reliability of the AF evaluation value is low, the subject is instructed by the user, a series of focus adjustment operations are performed again, and the AF is not fixed after the focus is adjusted with respect to the designated subject. The focus adjustment operation is continuously performed.

  As a result, even if the AF evaluation value does not show the expected change tendency, it is possible to focus on the subject intended by the user.

  Further, in the subject specifying process, the AF fixed flag may be set according to the aperture amount. For example, if the focus adjustment accuracy is relatively not required due to the large aperture amount and the deep depth of field, the AF fixed flag is set to TRUE. On the other hand, the AF fixed flag is set to FALSE when the focus adjustment accuracy is required due to the small amount of aperture and the shallow depth of field.

  As a result, when focus adjustment accuracy is required, the user designates the subject, performs a series of focus adjustment operations again, and after the focus is adjusted for the designated subject, AF is fixed. The focus adjustment operation is continuously performed.

  As a result, it is possible to focus on the subject intended by the user even when the focus adjustment accuracy is required due to the small aperture amount and the shallow depth of field.

  In addition, in the subject designation process, the system control unit 115 may determine whether the subject is a moving object according to the image data and set the AF fixed flag. For example, if the subject is not a moving object, the AF fixed flag is set to TRUE, and if the subject is a moving object, the AF fixed flag is set to FALSE.

  As a result, when the subject is a moving object, after the user designates the subject and performs a series of focus adjustment operations again to adjust the focus on the designated subject, the focus adjustment operation is performed without fixing the AF. Continued.

  As a result, even when a moving subject (moving body) is designated, it is possible to focus on the subject intended by the user.

  In the subject designation process, an AF sensor may be used to determine whether the camera is fixed to a tripod or the like using an acceleration sensor or the like and set the AF fixing flag. For example, when the camera is fixed to a tripod, the AF fixing flag is set to TRUE, and when the camera is not fixed to a tripod or the like, the AF fixing flag is set to FALSE.

  As a result, when the AF evaluation value does not show the expected change tendency due to camera shake or the like, after the user designates the subject and performs a series of focus adjustment operations again, the focus is adjusted with respect to the designated subject. AF is continuously performed.

  As a result, even if the AF evaluation value does not show the expected change tendency, it is possible to focus on the subject intended by the user.

  When the AF is fixed, if the aperture is reduced by a predetermined amount, the focus fluctuation after the AF is fixed by setting the depth of field deep can be allowed to some extent.

  In this manner, in the embodiment of the present invention, it is possible to focus on the subject intended by the user without impairing operability in a situation where the image is affected by blurring or the like.

  As is apparent from the above description, in the example shown in FIG. 1, the system control unit 115 functions as a control unit, and the AF processing unit 105 functions as a focus evaluation value calculation unit. In addition, the system control unit 115 and the focus lens control unit 104 function as a first focus adjustment unit and a second focus adjustment unit.

  Furthermore, the system control unit 115 functions as a moving body determination unit, and the acceleration sensor and the system control unit 115 function as a fixed determination unit. The photographing lens, zoom lens, aperture / shutter, and focus lens constitute an imaging optical system, and the imaging element 108 and the imaging processing unit function as imaging means.

  In the example shown in FIG. 1, at least the focus lens control unit 104, the AF processing unit 105, the system control unit 115, and the operation display unit 117 constitute a focus adjustment device.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to these embodiment, Various forms of the range which does not deviate from the summary of this invention are also contained in this invention. .

  For example, the function of the above-described embodiment may be used as a control method, and this control method may be executed by the focus adjustment apparatus. Further, a program having the functions of the above-described embodiments may be used as a control program, and the control program may be executed by a computer included in the focus adjustment apparatus. The control program is recorded on a computer-readable recording medium, for example.

  Each of the above control method and control program has at least a first control step and a second control step.

  The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various recording media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

DESCRIPTION OF SYMBOLS 100 Shooting lens 102 Aperture / shutter control unit 104 Focus lens control unit 105 AF processing unit 108 Imaging element 109 Imaging processing unit 110 Image processing unit 112 Format conversion unit 115 System control unit 117 Operation display unit

Claims (13)

A focus adjustment device that performs focus adjustment by moving the focus lens along the optical axis of the imaging optical system in accordance with image data obtained according to an optical image incident through an imaging optical system including a focus lens. There,
A first focus adjustment mode for focusing on a subject specified in an image corresponding to the image data and a second focus adjustment mode for detecting the subject as a detection subject in the image data and focusing on the detection subject are selected. Control means to perform automatically
In the first focus adjustment mode, when the subject is designated in the image, the control means focuses the designated subject and then fixes the focus position of the focus lens, and the second focus adjustment mode. A focus adjustment apparatus, wherein when a subject is specified in the image while performing a focus adjustment mode, the focus adjustment by the focus lens is continued after focusing on the specified subject. A focus evaluation value calculating means for obtaining a focus evaluation value indicating the contrast of the image data according to the image data;
First focus adjustment means for specifying a focus position according to a change in the focus evaluation value obtained by intermittently moving the focus lens along the optical axis;
Second focus adjustment means for specifying a focus position according to a change in the focus evaluation value obtained by continuously moving the focus lens;
2. The control unit according to claim 1, wherein the control unit performs focus adjustment by selecting one of the first focus adjustment unit and the second focus adjustment unit based on the focus evaluation value. Focus adjustment device.   3. The focus according to claim 1, wherein the control unit selectively performs the first focus adjustment mode and the second focus adjustment mode when the image data is moving image data. 4. Adjustment device.   3. The focus position of the focus lens is fixed when the focus adjustment by the first focus adjustment unit and the second focus adjustment unit is not completed in a predetermined time. Focus adjustment device.   When the control means performs the first focus adjustment mode, the control means focuses the designated subject in accordance with a focus degree indicating a focus degree with respect to the image data, and then determines a focus position of the focus lens. The focus adjustment apparatus according to claim 1, wherein it is determined whether or not to fix the focus adjustment apparatus.   6. The control unit according to claim 5, wherein, when the degree of focus is equal to or less than a predetermined threshold, the control unit continues focus adjustment by the focus lens after focusing on the designated subject. Focus adjustment device. The imaging optical system is provided with a diaphragm,
The control means determines whether or not to fix the focus position of the focus lens after focusing on the designated subject in accordance with the aperture amount of the aperture when performing the first focus adjustment mode. The focus adjusting apparatus according to claim 1, wherein The imaging optical system is provided with a diaphragm,
The focus adjustment apparatus according to claim 1, wherein the control unit narrows the aperture by a predetermined amount after fixing the focus position of the focus lens. Moving object determining means for determining whether or not the designated subject is a moving object according to the image data;
When the moving object determining means determines that the designated subject is a moving object, the control means focuses the designated object after performing the first focus adjustment mode, and then performs the focus. The focus adjustment apparatus according to claim 1, wherein the focus adjustment by the lens is continued. An imaging optical system including a focus lens;
Imaging means for obtaining image data according to an optical image incident through the imaging optical system;
The focus adjustment apparatus according to any one of claims 1 to 9,
An imaging device comprising: Having a fixing determination means for determining whether or not the imaging device is fixed;
If it is determined by the fixing determination means that the imaging device is not fixed, the control means focuses the designated subject and then the focus lens when performing the first focus adjustment mode. The imaging apparatus according to claim 10, wherein the focus adjustment is continued. A focus adjustment device that performs focus adjustment by moving the focus lens along the optical axis of the imaging optical system in accordance with image data obtained according to an optical image incident through an imaging optical system including a focus lens. A control method,
A first control step of performing a first focus adjustment mode for focusing on a subject specified in an image according to the image data;
Second control means for detecting a subject as a detection subject in the image data and performing a second focus adjustment mode for focusing on the detection subject;
In the first control step, in the first focus adjustment mode, when a subject is specified in the image, the focus position of the focus lens is fixed after focusing on the specified subject. In the second control step, when the subject is specified in the image while the second focus adjustment mode is being executed, the focus adjustment by the focus lens is continued after focusing on the specified subject. A control method characterized by: A focus adjustment device that performs focus adjustment by moving the focus lens along the optical axis of the imaging optical system in accordance with image data obtained according to an optical image incident through an imaging optical system including a focus lens. A control program used,
A computer provided in the focus adjustment device,
A first control step of performing a first focus adjustment mode for focusing on a subject specified in an image according to the image data;
Executing a second focus adjustment mode for detecting a subject as a detection subject in the image data and focusing on the detection subject;
In the first control step, in the first focus adjustment mode, when a subject is specified in the image, the focus position of the focus lens is fixed after focusing on the specified subject. In the second control step, when the subject is specified in the image while the second focus adjustment mode is being executed, the focus adjustment by the focus lens is continued after focusing on the specified subject. A control program characterized by:

Images