JP6238547B2 - Focus adjustment apparatus and control method thereof - Google Patents

Description

The present invention relates to a focus adjustment device and a control method therefor, and more particularly to a focus adjustment technique based on imaging plane phase difference AF.

  In recent years, an imaging apparatus represented by a single-lens reflex camera has been frequently photographed while viewing a live view (LV) screen (hereinafter referred to as LV photographing). It is demanded.

There are a phase difference detection method and a contrast detection method as main automatic focus adjustment (autofocus: AF) methods of the imaging apparatus.
In the phase difference detection method, the defocus amount of the imaging optical system is determined from the phase difference between a pair of image signals obtained by imaging light beams from a subject that has passed through different exit pupil regions in the imaging optical system on a pair of line sensors. Ask. When the focus lens is moved by an amount corresponding to the defocus amount, the imaging optical system is in focus on the subject (see Patent Document 1). However, in a general configuration in which the optical path to the image sensor is interrupted when a light beam is imaged on the phase difference detection line sensor, focus adjustment by the phase difference detection method cannot be performed while performing LV imaging.

  On the other hand, in the contrast detection method, an in-focus state is obtained by searching for a focus lens position where a contrast evaluation value generated from an image pickup signal obtained using an image pickup element is maximized (see Patent Document 2). The contrast detection method is suitable for AF during LV shooting because it performs focus adjustment based on the imaging signal, and is the most mainstream AF method during LV shooting in recent years. However, the contrast detection method cannot easily determine the position and direction in which the focus lens is moved to focus on the subject. For this reason, the contrast detection method may require time for focusing, may cause the focus lens to move in the wrong direction, or may pass through the focus position. In particular, at the time of moving image shooting, an image shot while the focus lens is moving is also recorded. Therefore, the moving time and moving operation of the focus lens up to the in-focus state affect the image quality of the recorded moving image.

  Therefore, in AF control during moving image shooting, a high-quality focus adjustment operation that has a small influence on a recorded image is required rather than a speed (responsiveness) until a focused state is reached. For this reason, an imaging surface phase difference detection method has been proposed as a method capable of high-quality focus adjustment operation even during LV shooting. The imaging surface phase difference detection method is a method for obtaining a defocus amount based on a phase difference between a pair of signals obtained from an imaging element.

  As a method for realizing the imaging surface phase difference detection method, a method has been proposed in which the imaging pixel of the imaging element is pupil-divided by a microlens and light is received by a plurality of focus detection pixels to detect the defocus amount simultaneously with imaging. Yes. In Patent Document 3, each photodiode is configured to receive light from a different pupil plane of an imaging lens by dividing photodiodes collected by one microlens in one pixel. Has been. This makes it possible to adjust the focus by the imaging plane phase difference detection method from the outputs of the two photodiodes. By using the imaging surface phase difference detection method, it is possible to obtain the defocus amount and know the moving direction and the moving amount of the focus lens even during LV shooting, so that the focus lens can be moved at high speed and with high quality. .

  Further, in Patent Document 4, when the defocus amount calculated by the imaging surface phase difference detection method is reliable, the focus lens is driven based on the defocus amount, and when the reliability is poor, based on the contrast evaluation value. A method of driving the focus lens has been proposed.

Japanese Patent Laid-Open No. 09-054242 JP 2001-004914 A JP 2001-083407 A JP 2010-139842 A

  The pair of signals obtained by the imaging surface phase difference detection method cannot separate the two images as much as the signal output by the line sensor used in the phase difference detection method. There is a characteristic that the phase difference detection accuracy between the obtained signals deteriorates.

  If the imaging surface phase difference detection method and the contrast method are switched according to the reliability of the defocus amount obtained by the imaging surface phase difference detection method as in Patent Document 4, the defocus amount obtained by the imaging surface phase difference detection method. Even if the reliability of the camera is low, it is possible to increase the chance of focusing with high accuracy.

  However, in order to switch between the imaging surface phase difference detection method and the contrast method, it is necessary to generate an evaluation value to be used in each method, which increases the necessary circuit and processing load in the camera. Furthermore, since a plurality of methods are switched and used, the processing becomes more complicated and man-hours related to management and development tend to increase. In addition, as described above, when focus adjustment is performed using the contrast method during movie shooting, the focus adjustment operation tends to affect the image quality, particularly when controllability is poor, such as when the degree of freedom in setting the focus lens drive speed is low. Become.

  The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to improve the accuracy and quality of a focus adjustment operation using an imaging surface phase difference detection method.

The above-described object is to provide an image pickup device that can generate an image signal used for phase difference detection type automatic focus adjustment, a detection unit that detects a defocus amount based on the image signal, and a focus lens based on the defocus amount. And a control means for controlling the driving of the focus lens so that the focus lens is driven based on the defocus amount when the reliability of the defocus amount is higher than the first reliability. If the reliability of the defocus amount is not higher than the first reliability for a predetermined number of times, the first drive amount is determined if the defocus amount reliability is the second reliability. If the reliability of the defocus amount is the third reliability that is lower than the second reliability, the focus lens is set to a predetermined unit by setting the second drive amount larger than the first drive amount as a predetermined unit. Driving To control the drive of the focus lens so that the focus lens is driven by a step drive, the step driving in case the reliability of the defocus amount detected after the focus lens is driven is higher than the first reliability The focus adjustment device is characterized in that the drive of the focus lens is controlled so that the focus lens is driven based on the defocus amount.

  As described above, according to the present invention, the accuracy and quality of the focus adjustment operation using the imaging surface phase difference detection method can be improved.

1 is a block diagram illustrating an example of a functional configuration of an interchangeable lens camera as an example of an imaging apparatus according to an embodiment. The figure which shows the pixel structural example of a non-imaging surface phase difference detection system and an imaging surface phase difference detection system The flowchart which shows the imaging process in 1st Embodiment. The flowchart which shows the initialization process in 1st Embodiment The flowchart which shows the moving image shooting process in 1st Embodiment. The flowchart which shows the focus detection process in 1st Embodiment. The figure which showed typically an example of the focus detection range handled by the focus state detection process in 1st Embodiment, and a focus detection area | region. The figure which shows the example of the image signal obtained from the focus detection area | region shown in FIG. The figure which shows the example of a relationship between the shift amount and correlation amount of the image signal shown in FIG. FIG. 8 is a diagram showing an example of the relationship between the shift amount of the image signal and the correlation change amount ΔCOR shown in FIG. Flowchart showing the AF restart determination process in S508 of FIG. Flowchart showing the AF process in S507 of FIG. FIG. 12 is a flowchart illustrating lens drive setting in S804. (A) is a diagram schematically showing a problem of focus lens driving based on a defocus amount with low reliability, and (b) is a focus lens driving method switching and defocus amount reliability in the first embodiment. Diagram schematically showing the relationship between 12 is a flowchart showing the lens driving process in S805 of FIG. The flowchart which shows the search drive processing of S1004 of FIG. 16 is a flowchart showing the drive direction setting process in S1102 of FIG. Flowchart showing AF processing in the second embodiment The flowchart which shows the lens drive setting in 2nd Embodiment. The flowchart which shows the lens drive setting in 3rd Embodiment. The flowchart which shows the lens drive process in 3rd Embodiment.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiment described below is merely an example, and the present invention is not limited to the configuration described in the embodiment.

(First embodiment)
FIG. 1 is a block diagram illustrating a functional configuration example of an interchangeable lens camera as an example of an imaging apparatus to which the focus adjustment apparatus according to the first embodiment of the present invention can be applied .
An imaging device is composed of interchangeable lens unit 10 and the camera body 20. The lens control unit 106 that controls the overall operation of the lens and the camera control unit 212 that controls the overall operation of the camera system including the lens unit 10 can communicate with each other through terminals provided on the lens mount.

  First, the configuration of the lens unit 10 will be described. The fixed lens 101, the diaphragm 102, and the focus lens 103 constitute a photographing optical system. The diaphragm 102 is driven by the diaphragm driving unit 104 and controls the amount of light incident on the image sensor 201 described later. The focus lens 103 is driven by the focus lens driving unit 105, and the focusing distance of the imaging optical system changes according to the position of the focus lens 103. The aperture driving unit 104 and the focus lens driving unit 105 are controlled by the lens control unit 106 to determine the aperture amount of the aperture 102 and the position of the focus lens 103.

  The lens operation unit 107 is an input device group for the user to perform settings related to the operation of the lens unit 10 such as AF / MF mode switching, shooting distance range setting, camera shake correction mode setting, and the like. When the lens operation unit 107 is operated, the lens control unit 106 performs control according to the operation.

  The lens control unit 106 controls the aperture driving unit 104 and the focus lens driving unit 105 according to a control command and control information received from a camera control unit 212 described later, and transmits lens control information to the camera control unit 212. .

Next, the configuration of the camera body 20 will be described. The camera body 20 is configured to acquire an imaging signal from a light beam that has passed through the imaging optical system of the lens unit 10.
The image sensor 201 is composed of a CCD or a CMOS sensor. The light beam incident from the imaging optical system of the lens unit 10 forms an image on the light receiving surface of the image sensor 201, and is converted into a signal charge corresponding to the amount of incident light by a photodiode provided in a pixel arranged in the image sensor 201. The The signal charge accumulated in each photodiode is sequentially read out from the image sensor 201 as a voltage signal corresponding to the signal charge from a drive pulse output from the timing generator 215 in accordance with a command from the camera control unit 212.

  The image sensor 201 according to the present embodiment includes two photodiodes in one pixel, and generates an image signal used for automatic focus adjustment (hereinafter referred to as an imaging surface phase difference AF) by an imaging surface phase difference detection method. Is possible. 2A schematically illustrates an example of a pixel configuration that does not correspond to the imaging surface phase difference AF, and FIG. 2B schematically illustrates an example of a pixel configuration that corresponds to the imaging surface phase difference AF. Here, in any case, it is assumed that a Bayer array primary color filter is provided. In the pixel configuration of FIG. 2B corresponding to the imaging surface phase difference AF, one pixel in FIG. 2A is divided into two in the horizontal direction on the paper surface, and AB photodiodes (light receiving regions) are provided. . Note that the division method illustrated in FIG. 2B is an example, and other methods may be used, or different division methods may be applied depending on the pixels.

  The light beam incident on each pixel is separated by a microlens and received by two photodiodes provided in the pixel, whereby two signals for imaging and AF can be acquired by one pixel. That is, signals (A, B) obtained by two photodiodes A, B (A pixel, B pixel) in a pixel are two image signals for AF, and an addition signal (A + B) is an imaging signal. is there. Note that the pair of image signals used in the imaging plane phase difference AF is also a plurality of A so that the pair of image signals used in the normal phase difference detection AF is generated by a pair of line sensors having a plurality of pixels. It is obtained from the output of a pixel and a plurality of B pixels. Based on the AF signal, an AF signal processing unit 204 (to be described later) performs a correlation operation on the two image signals to calculate an image shift amount and various types of reliability information.

  The CDS / AGC / AD converter 202 performs correlated double sampling for removing reset noise, gain adjustment, and signal digitization on the imaging signal and AF signal read from the imaging element 201. The CDS / AGC / AD converter 202 outputs the imaging signal to the image input controller 203 and the imaging surface phase difference AF signal to the AF signal processing unit 204.

  The image input controller 203 stores the imaging signal output from the CDS / AGC / AD converter 202 in the SDRAM 209 via the bus 21. The image signal stored in the SDRAM 209 is read by the display control unit 205 via the bus 21 and displayed on the display unit 206. In the operation mode in which the image pickup signal is recorded, the image signal stored in the SDRAM 209 is recorded on the recording medium 208 by the recording medium control unit 207.

  The ROM 210 stores a control program executed by the camera control unit 212 and various data necessary for the control. The flash ROM 211 stores various setting information related to the operation of the camera body 20 such as user setting information. Yes.

  The AF signal processing unit 204 performs a correlation operation on the two image signals for AF output from the CDS / AGC / AD converter 202 to obtain an image shift amount, reliability information (two image coincidence degree, two image steepness degree, Contrast information, saturation information, scratch information, etc.). The AF signal processing unit 204 outputs the calculated image shift amount and reliability information to the camera control unit 212.

  The camera control unit 212 changes the setting of the AF signal processing unit 204 as necessary based on the image shift amount and reliability information obtained by the AF signal processing unit 204. For example, when the image shift amount is greater than or equal to a predetermined amount, a wide area for performing the correlation calculation is set, or the type of the band pass filter is changed according to the contrast information. Details of the correlation calculation will be described later with reference to FIGS. 7 to 9B.

  In the present embodiment, a total of three signals of the imaging signal and the two AF image signals are acquired from the imaging element 201, but the present invention is not limited to this method. Considering the load of the image sensor 201, for example, a total of two signals of an imaging signal and one AF image signal may be taken out, and the difference between the imaging signal and the AF signal may be used as another AF image signal.

  The camera control unit 212 performs control by exchanging information with each functional block in the camera body 20. The camera control unit 212 not only performs processing in the camera body 20, but also turns on / off the power, changes settings, starts recording, starts AF control, confirms recorded video, etc. according to input from the camera operation unit 214. The various camera functions operated by the user are executed. Further, the camera control unit 212 sends a control command / control information of the lens unit 10 to the lens control unit 106, and acquires information on the lens unit 10 from the lens control unit 106.

  The camera control unit 212 is, for example, one or more programmable processors, and implements the operation of the entire camera system including the lens unit 10 by executing a control program stored in the ROM 210, for example.

  The lens driving method switching unit 213 shows one part of the function of the camera control unit 212, and switches the driving method of the focus lens 103 via the lens control unit 106 and the focus lens driving unit 105 in the lens unit 10. The driving method of the focus lens in the present embodiment is a driving method based on the defocus amount obtained from the AF signal, and a driving method and driving amount set by the camera control unit 212 regardless of the defocus amount. These are two. Details will be described later with reference to a flowchart illustrating control of the camera body 20.

  Conventionally, a digital camera is mainly used for still image shooting, and a video camera is generally used for moving image shooting. However, in recent years, a demand for a moving image shooting function of a digital camera is increasing. Therefore, an increasing number of lenses suitable for moving image shooting, in which the driving speed can be set with a high degree of freedom from low speed to high speed. On the other hand, before the use of moving image shooting is considered, there is a lens that can be set only at a high driving speed specialized for still image shooting, and there are many such lenses especially in old lenses. The present invention is particularly effective for the latter lens.

  The lens driving method switching unit 213 obtains information regarding whether or not the lens unit 10 is a type that can be driven at a low speed from the lens control unit 106 in the lens unit 10 through the camera control unit 212. If the lens driving method switching unit 213 determines that the lens unit 10 is of a type that cannot be set for low-speed driving, the lens driving method switching unit 213 performs driving method switching control. Even if the lens unit 10 is of a type that cannot be set for low-speed driving, the driving quality at the time of focus adjustment can be improved by using a driving method that seems to drive slowly depending on the situation. If the lens driving method switching unit 213 determines that the lens unit 10 is a type that can be set for low-speed driving, the driving method is not switched.

Next, the operation of the camera body 20 will be described with reference to FIGS.
FIG. 3 is a flowchart showing the procedure of the photographing process of the camera body 20. In step S301, the camera control unit 212 performs initialization processing, and proceeds to step S302. Details of the initialization process will be described later with reference to FIG. In step S302, the camera control unit 212 determines whether the shooting mode of the camera body 20 is the moving image shooting mode or the still image shooting mode. If the shooting mode is the moving image shooting mode, the process proceeds to step S303. . In step S303, the camera control unit 212 performs moving image shooting processing, and proceeds to step S305. Details of the moving image shooting process in S303 will be described later with reference to FIG. If the still image shooting mode is selected in S302, the camera control unit 212 performs a still image shooting process in S304, and proceeds to S305. Details of the still image shooting process in S304 will be omitted.

  In step S305, which is performed after moving image shooting processing in S303 or still image shooting processing in S304, the camera control unit 212 determines whether the shooting processing has been stopped. If not, the process proceeds to S306 and stops. If so, the shooting process is terminated. When shooting processing is stopped, operations other than shooting, such as when the power of the camera body 20 is turned off through the camera operation unit 214, user setting processing of the camera, playback processing for checking captured images / moving images, etc. Is done. In step S <b> 306, the camera control unit 212 determines whether the shooting mode has been changed. If the shooting mode has not been changed, the process proceeds to step S <b> 301. Return processing. If the shooting mode has not been changed, the camera control unit 212 continues the processing of the current shooting mode. If the shooting mode has been changed, the processing of the changed shooting mode is performed after performing the initialization process in S301. I do.

  Next, the initialization process in S301 of FIG. 3 will be described with reference to the flowchart of FIG. In step S401, the camera control unit 212 sets various initial values of the camera and advances the process to step S402. The camera control unit 212 sets initial values based on information such as user settings and shooting modes at the time when shooting processing is started or when the shooting mode is changed. In S402 and S403, the camera control unit 212 initializes a flag used in this embodiment. In step S402, the camera control unit 212 turns off the focus stop flag and advances the process to step S403. In step S403, the camera control unit 212 turns off the search drive flag and advances the process to step S404. In step S404, the camera control unit 212 turns off the lens stop flag and ends the process.

  The focus stop flag that is initialized in S402 is turned on when it is determined that the camera is in focus during movie shooting and the lens is stopped, and is off when it is determined that the lens is not yet focused and the lens is driven. Has a value. The search drive flag initialized in S403 has an off value when the defocus amount detected by the imaging surface phase difference detection method is reliable when driving the lens, and an on value when the defocus amount is not reliable.

  When the defocus amount is reliable, not only when the accuracy of the defocus amount can be determined to be reliable, but also when the defocus direction is determined to be reliable, the reliability is higher than a certain degree. is there. For example, when it can be determined that the main subject is in focus or when it is already in focus. In such a state, the defocus amount is trusted, and the focus lens is driven based on the defocus amount.

  On the other hand, when the defocus amount is unreliable, the defocus amount and direction (for example, represented by the sign of the defocus amount) cannot be determined to be certain, that is, the reliability is lower than a certain level. is there. For example, there is a state where the defocus amount cannot be calculated correctly, such as when the main subject is greatly blurred. In this case, driving the focus lens with the defocus amount reliable affects the image quality of the captured video, so search drive (the focus lens is driven by a predetermined amount in a certain direction regardless of the defocus amount Search for driving).

  In this embodiment, search driving is performed by step driving (repetition of minute driving). Since step driving has a small driving amount, even a lens whose driving speed cannot be set to a low speed can be driven at a low speed. In the present invention, when the lens unit 10 is of a type that cannot be set at low speed driving, the driving quality is improved by using step driving at the time of moving image shooting. Details will be described later.

  The lens stop flag to be initialized in S404 is a flag for stopping the focus lens 103. For example, the reliability of the defocus amount temporarily deteriorated as in the case where another subject crosses the main subject. When it is determined that the value is on. When the lens stop flag is on, the focus lens 103 is not driven, thereby preventing a change in the focus state caused by following a temporary defocus amount change.

  Next, the moving image shooting process in S303 of FIG. 3 will be described with reference to FIG. In steps S501 to S504, the camera control unit 212 performs control related to moving image recording. In step S501, the camera control unit 212 determines whether the moving image recording switch is turned on. If the moving image recording switch is turned on, the process proceeds to step S502. If not, the process proceeds to step S505. In step S502, the camera control unit 212 determines whether the moving image is currently being recorded. If the moving image is not being recorded, the moving image recording is started in step S503 and the process proceeds to step S505. If the moving image is being recorded, the moving image recording is performed in step S504. Stop and proceed to S505. In this embodiment, each time the moving image recording switch is pressed, the recording of the moving image is started and stopped. Recording is started and stopped by other methods such as using different buttons for starting and stopping the recording or using a changeover switch or the like. You may do.

  In step S505, the camera control unit 212 performs focus state detection processing, and advances the processing to step S506. The focus state detection process is a process of acquiring defocus information and reliability information for performing imaging plane phase difference AF by the camera control unit 212 and the AF signal processing unit 204, and details will be described later with reference to FIG. . In step S506, after the focus state detection process is performed in step S505, the camera control unit 212 determines whether the focus is currently stopped. If the focus is not stopped, the process proceeds to step S507. Advances the process to S508. Whether the focus is stopped can be determined by turning on / off the focus stop flag described above. In step S507, which is performed when it is determined that the in-focus state is not stopped in step S506, the camera control unit 212 performs AF processing and ends the moving image shooting processing. S507 performs AF control based on the information detected in S505, and details will be described later with reference to FIG. In S508, which proceeds when it is determined in S506 that the in-focus state is stopped, the camera control unit 212 performs AF restart determination and ends the moving image shooting process. In step S508, it is determined whether or not AF control is to be started again when the main subject has moved or changed since the in-focus state has been stopped. Details will be described later with reference to FIG.

  Next, the focus state detection process in S505 of FIG. 5 will be described with reference to FIG. First, in step S601, the AF signal processing unit 204 acquires a pair of image signals for AF from pixels included in an arbitrarily set focus detection range. Next, in S602, the AF signal processing unit 204 calculates a correlation amount between the acquired image signals. Subsequently, in S603, the AF signal processing unit 204 calculates a correlation change amount from the correlation amount calculated in S602. In step S604, the AF signal processing unit 204 calculates a focus shift amount from the correlation change amount. In step S <b> 605, the AF signal processing unit 204 calculates reliability indicating how reliable the amount of focus deviation is. These processes are performed for the number of focus detection areas existing in the focus detection range. In step S606, the AF signal processing unit 204 converts the focus shift amount into the defocus amount for each focus detection region. Finally, the AF signal processing unit 204 determines a focus detection area used for AF in S607, and ends the focus state detection process.

The focus state detection process described in FIG. 6 will be described in more detail with reference to FIGS. 7 to 9B.
FIG. 7 is a diagram schematically illustrating an example of a focus detection range and a focus detection region handled in the focus state detection process.
FIG. 7A shows an example of a focus detection range 1502 in the pixel array 1501 of the image sensor 201. The shift area 1503 is an area necessary for correlation calculation. Accordingly, a region 1504 obtained by combining the focus detection range 1502 and the shift region 1503 is a pixel region necessary for the correlation calculation. In the drawing, p, q, s, and t respectively represent coordinates in the x-axis direction, p and q represent the x-coordinates of the start point and end point of the pixel region 1504, and s and t represent the x and x of the start point and end point of the focus detection range 1502, respectively. Represents coordinates.

FIG. 7B is a diagram showing an example in which the focus detection range 1502 is divided into five focus detection areas 1505 to 1509. In the present embodiment, the focus shift amount is calculated for each focus detection region obtained by dividing the focus detection range in this way, and the most reliable focus shift amount is used.
FIG. 7C is a diagram showing a temporary focus detection area in which the focus detection areas 1505 to 1509 in FIG. 7B are connected. In this way, the amount of focus deviation calculated from the area where the focus detection areas are connected may be used. The arrangement of the focus detection area, the area size, and the like are not limited to the configuration illustrated here, and other configurations may be used.

FIG. 8 shows an example of an AF image signal acquired from the pixels included in the focus detection areas 1501 to 1509 set in FIG. The solid line 1601 is the image signal A, and the broken line 1602 is the image signal B.
FIG. 8A shows an example of the image signal before the shift.
FIGS. 8B and 8C show a state where the image waveform before the shift in FIG. 8A is shifted in the plus direction and the minus direction. When calculating the correlation amount, both the image signal A 1601 and the image signal B 1602 are shifted one bit at a time in the direction of the arrow. Next, a method for calculating the correlation amount COR will be described.

First, as shown in FIGS. 8B and 8C, each of the image signal A1601 and the image signal B1602 is shifted by 1 bit, and the sum of the absolute values of the differences between the image signal A and the image signal B at that time is calculated. calculate. At this time, the shift amount is represented by i, the minimum shift amount is ps in FIG. 8, and the maximum shift amount is qt in FIG. Further, x is the start coordinate of the focus detection area 1508, and y is the end coordinate of the focus detection area 1508. Using these, the correlation amount COR in the focus detection area 1508 can be calculated by the following equation (1).

  FIG. 9A shows an example of the relationship between the shift amount and the correlation amount. The horizontal axis indicates the shift amount, and the vertical axis indicates the correlation amount. Of the extreme values 1702 and 1703 in the correlation amount waveform 1701, the smaller the correlation amount, the higher the degree of coincidence between the image signal A and the image signal B. Next, a method for calculating the correlation change amount ΔCOR will be described.

First, the correlation change amount is calculated from the correlation amount difference of one shift skipping from the correlation amount waveform of FIG. The shift amount is represented by i, the minimum shift amount is ps in FIG. 8, and the maximum shift amount is qt in FIG. Using these, the correlation change amount ΔCOR can be calculated by the following equation (2).

  FIG. 10A shows an example of the relationship between the shift amount and the correlation change amount ΔCOR. The horizontal axis indicates the shift amount, and the vertical axis indicates the correlation change amount. In the correlation change amount waveform 1801, 1802 and 1803 are the vicinity where the correlation change amount becomes positive to negative. This is called a state zero cross where the correlation change amount is 0, and the degree of coincidence between the image signals is the highest, and the shift amount at the time of zero cross becomes the focus shift amount.

続いて整数部分βは、図１０（ｂ）中より以下の式（４）によって算出することができる。
β＝ｋ−１ （４）
αとβの和からピントずれ量ＰＲＤを算出することができる。 FIG. 10B is an enlarged view of the portion 1802 in FIG. 10A, and 1901 is a part of the correlation variation waveform 1801. A method of calculating the focus shift amount PRD will be described with reference to FIG.
Here, the shift amount (k−1 + α) at the time of zero crossing is divided into an integer part β (= k−1) and a decimal part α. The decimal part α can be calculated by the following equation (3) from the similar relationship between the triangle ABC and the triangle ADE in the figure.

Subsequently, the integer part β can be calculated by the following formula (4) from FIG.
β = k−1 (4)
The focus shift amount PRD can be calculated from the sum of α and β.

以上のように、ゼロクロスが複数存在する場合は、急峻性によって第１のゼロクロスを決定する。続いてピントずれ量の信頼性の算出法について説明する。 Also, as shown in FIG. 10A, when there are a plurality of shift amounts that become zero crosses, the first zero cross is defined as a point where the steepness of the correlation amount change at the zero crosses is large. This steepness is an index indicating the ease of AF. The larger the value, the easier it is to perform AF. The steepness maxder can be calculated by the following equation (5).

As described above, when there are a plurality of zero crosses, the first zero cross is determined based on steepness. Next, a method for calculating the reliability of the focus shift amount will be described.

The reliability can be defined by the steepness described above and the matching degree fnclvl (hereinafter referred to as two-image matching degree) of the image signals A and B. The degree of coincidence of two images is an index representing the accuracy of the amount of focus deviation, and the smaller the value, the better the accuracy.
FIG. 9B is an enlarged view of the portion 1702 in FIG. 9A, and 2001 is a portion of the correlation amount waveform 1701. A method for calculating steepness and the degree of coincidence of two images will be described with reference to FIG.
The two-image coincidence degree fnclvl can be calculated by the following equation (6).

  As described above, in this embodiment, the focus lens driving method is switched according to the reliability of the defocus amount. The imaging surface phase difference AF method is characterized in that the reliability of two-image coincidence, steepness, and the like decreases as the focus shift increases as compared with the conventional phase difference AF method using a dedicated AF sensor. . This is because in the imaging plane phase difference AF method, a difference in the amount of light incident on the pupil A and the pupil B that generate the image signal A and the image signal B occurs, and the image signal A and the image signal B become asymmetric. In the present embodiment, the feature of the imaging surface phase difference AF is used for switching the driving method of the focus lens. Details will be described later with reference to FIG. In the present embodiment, the case where the degree of coincidence of two images is used as the reliability of the defocus amount will be described. However, steepness may be used, or other information that can be used as an indicator of the degree of reliability of the defocus amount may be used. May be. A combination of these indices may be used.

Next, the AF restart determination in S508 of FIG. 5 will be described using the flowchart of FIG. The AF restart determination is a process for determining whether to drive the focus lens 103 again when it is determined that the focus lens 103 is in focus and the focus lens 103 is stopped.
In step S701, the camera control unit 212 determines whether the defocus amount calculated by the AF signal processing unit 204 is smaller than a predetermined multiple of the depth of focus. If small, the process proceeds to step S702. In step S702, the camera control unit 212 determines whether the reliability calculated by the AF signal processing unit 204 is better than a predetermined value. If the reliability is higher than the predetermined value, the process proceeds to step S703. If not, the process proceeds to step S704. In step S703, the camera control unit 212 resets the AF restart counter and advances the process to step S705. In step S704, the camera control unit 212 adds an AF restart counter and advances the process to step S705.

  As described above, when the defocus amount is greater than or equal to the predetermined amount or the reliability of the defocus amount is worse than the predetermined value, the camera control unit 212 determines that the main subject being shot has changed, and restarts AF. Preparation is made (re-driving the focus lens 103). On the other hand, when it is determined that the main subject has not changed from the size of the defocus amount and the reliability, the AF is not restarted (the stopped state of the focus lens 103 is maintained).

  The threshold value of the defocus amount set in S701 is set empirically or experimentally so that AF restart is performed when the main subject is changed, and AF restart is difficult when the main subject is not changed. Further, the reliability threshold value set in S702 is set such that AF restart is performed when the reliability is so low that it is difficult to trust the defocus direction, for example. As described above, the determinations in S701 and S702 can be said to be determination processing as to whether or not the main subject has been changed. Therefore, it can be replaced with an arbitrary process capable of the same determination, and the type and value of the threshold used according to the processing method are set.

  In step S705, the camera control unit 212 determines whether the value of the AF restart counter is greater than a predetermined value. If the value is larger than the predetermined value, the process proceeds to step S706, and if smaller, the AF restart determination process ends. In step S <b> 706, the camera control unit 212 restarts AF by turning off the focus stop flag, and ends the AF restart determination process. In determining AF restart in S706, the camera control unit 212 determines in S705 whether the value of the AF restart counter added in S704 is greater than a predetermined value. In the AF restart counter addition and value determination, the determination of whether or not the main subject has changed is not performed based on a single determination of the amount of defocus or the reliability. This is based on statistics. By doing this, it is determined that the main subject has changed due to a very temporary defocus amount or a change in reliability even though the main subject has not actually changed, and AF is restarted. Prevent impact on image quality.

Next, the AF process in S507 of FIG. 5 will be described using the flowchart of FIG. The AF processing is processing for driving the focus lens in a state where focusing is not stopped and for determining whether focusing is stopped.
In step S <b> 801, the camera control unit 212 determines whether the lens unit 10 is compatible with the low-speed driving setting based on the lens information acquired from the lens control unit 106. If the camera control unit 212 determines that the low-speed drive setting is not supported, the camera control unit 212 proceeds to step S802. If the camera control unit 212 determines that the low-speed drive setting is not supported, the camera control unit 212 proceeds to step S806. In step S806, the camera control unit 212 performs AF processing using the low-speed drive setting compatible lens, and ends the processing. As described above, since this embodiment is an invention that is particularly effective when using a lens that is not suitable for moving image shooting, in which the drive speed cannot be set to a high degree of freedom from low speed to high speed, the details of S806 are omitted. To do.

  In step S <b> 802, the camera control unit 212 determines whether the defocus amount is within the depth of focus and the defocus amount reliability is better than a predetermined value. The process proceeds to S803, and if not, the process proceeds to S804. In step S803, since the defocus amount is within the depth of focus and the reliability is high, the camera control unit 212 determines that the in-focus state is achieved, turns on the in-focus stop flag, and ends the process. The reliability threshold value set in S802 is set to a value that can at least guarantee the focusing accuracy.

  In step S804, when the defocus amount is still within the depth of focus and the reliability is not better than the predetermined value in step S802, the camera control unit 212 performs setting for lens driving and advances the process to step S805. In step S804, the camera control unit 212 performs lens drive setting processing, which is a characteristic part of the present embodiment. Here, the focus lens driving method is switched or set. Details will be described later with reference to FIG. In step S805, after the lens drive setting is performed in step S804, the camera control unit 212 performs lens drive processing and ends the AF processing. Details of the lens driving process in S805 will be described later with reference to FIG.

Next, the lens drive setting in S804 of FIG. 12 will be described using the flowchart of FIG. In the lens drive setting in the present embodiment, the focus lens drive method is switched depending on the reliability of the defocus amount. Also, the step drive amount at the time of search drive execution is set.
In step S901, the camera control unit 212 (lens driving method switching unit 213) determines whether the evaluation value indicating the reliability of the defocus amount is a value better than the predetermined value α (whether the reliability is higher than the predetermined reliability). . If the value is better than the predetermined value α, the process proceeds to S902. If not, the process proceeds to S903. In step S902, the camera control unit 212 resets the search drive counter and advances the process to step S907.

  In step S901, when the reliability is not better than the predetermined value α (the reliability is not higher than the predetermined reliability), the camera control unit 212 adds a search drive transition counter in step S903, and proceeds to step S904. . In step S904, the camera control unit 212 determines whether the value of the search drive transition counter is equal to or greater than a predetermined value. If the value of the search drive transition counter is equal to or greater than the predetermined value, the camera control unit 212 advances the process to S905, turns on the search drive flag, and advances the process to S907. If the value of the search drive transition counter is less than the predetermined value, the camera control unit 212 advances the process to S906, turns on the lens drive flag, and advances the process to S907.

  In S907 performed after any one of S902, S905, and S906, the camera control unit 212 determines whether or not the search drive flag is on. If the search drive flag is on, the process proceeds to S908. The drive setting process ends. In step S908, the camera control unit 212 determines whether the reliability of the defocus amount is better than the predetermined value γ. If the defocus amount reliability is higher than the predetermined value γ, the process proceeds to step S909. If not, the process proceeds to step S910. In step S909, the camera control unit 212 sets the step drive amount to A and ends the lens drive setting process. In step S910, the camera control unit 212 sets the step drive amount to B (A <B) and ends the lens drive setting process.

The reliability threshold values α and γ set in FIG. 13 have the following relationship.
α <γ (α indicates that reliability is better)
In this embodiment, since the two-image coincidence is used as the reliability, the smaller the value, the better the reliability. Therefore, α <γ. In the present embodiment, when the reliability is better than α, the focus lens 103 is driven based on the defocus amount. When the reliability is not better than α, the set step drive amount is not based on the defocus amount. Based on this, the focus lens 103 is driven.

  As described above, the imaging plane phase difference AF is not uniform in the pupil intensity distribution for acquiring the image signals A and B, and therefore the reliability such as the degree of coincidence of two images and steepness decreases as the defocus amount increases. There are features. In particular, if the focus lens is driven based on the defocus amount when the defocus direction is not reliable, the image quality may be greatly affected. This point will be described with reference to FIG.

  FIG. 14A is a diagram schematically illustrating the relationship between the driving operation of the focus lens and the reliability of the defocus amount. In FIG. 14A, the horizontal direction represents the position of the focus lens and the reliability of the defocus amount. FIG. 14A shows an example of driving the focus lens based on the defocus amount when the defocus direction is not reliable, and an example of the movement range of the focus lens in that case. If even the defocus direction is unreliable and the focus lens is driven based on the defocus amount, it will continue to hunt, drive in the direction opposite to the in-focus direction, or drive with an excessive defocus amount. There is a risk of passing through the in-focus position.

  Therefore, when the defocus amount is unreliable reliability, the AF control without using the defocus amount can be performed. Therefore, the reliability threshold value α set in S901 is set to a value that can determine that at least the direction is reliable, at least of the defocus direction and amount. On the other hand, when the defocus direction is determined to be unreliable (is worse than α), search driving is performed. Search drive is a method of setting the defocus direction and driving the focus lens within the drive range by a predetermined unit (step drive amount) in that direction regardless of the defocus amount.

  If the defocus direction is unreliable reliability (bad than α) in S901, the camera control unit 212 adds a search drive transition counter in S903. Image quality by following a temporary decrease in reliability while ensuring the reliability of the determination to shift to search drive by determining to shift to search drive when low reliability is detected a predetermined number of times To prevent the impact. If it is determined in S904 to shift to search driving, the camera control unit 212 turns on the search driving flag in S905. When the search drive flag is on, the camera control unit 212 sets a step drive amount (S908 to S910) based on the determination in S907. First, in step S908, the camera control unit 212 determines the reliability of the defocus amount. When the reliability is better than γ, the step drive amount A (first drive amount) is set, and when not, the step larger than the step drive amount A is set. A drive amount B (second drive amount) is set.

  As described above, since γ is less reliable than α that has a reliable defocus direction, if the reliability is not better than γ, the defocus amount of the main subject is considered to be considerably large. In this case, the step drive amount is set larger in order to shorten the time until focusing. Details of the search driving process will be described later with reference to the flowchart of FIG.

  In S901, the reliability is lower than the predetermined value α, and it is better not to drive the focus lens by believing in the defocus amount while determining whether to shift to search driving in S903. Therefore, the lens stop flag is turned on in S906 so that the lens is not driven. This temporarily stops the lens. If the reliability continues to be lower than the predetermined value α, the operation shifts to search driving, and if the reliability becomes better than the predetermined value α again (for example, when another subject crosses the main subject), Keep driving based on defocus amount.

  As a feature of the present embodiment, the focus lens is step-driven during search driving. As described above, when moving image AF control is performed, the driving quality of the focus lens is important. For example, driving at too high a speed or unnecessary driving should be avoided. However, when the lens unit 10 does not support low-speed driving, the focus lens is driven at high speed even during moving image recording. Therefore, for example, when the focus lens is driven based on an erroneous defocus direction or amount as shown in FIG.

  If the reliability of the defocus amount is low (is worse than α), the focus lens may be driven unnecessarily large. Therefore, a minute drive amount is set, and step driving is performed repeatedly for each frame. . For this reason, even when using a lens that cannot drive a low-speed focus lens, the amount of movement of the focus lens per hour can be suppressed, and substantial low-speed drive can be realized. In addition, by moving by a predetermined drive amount using step drive, the change in the focus state due to the movement of the focus lens is observed more smoothly, and the quality of the moving image during AF can be improved.

  FIG. 14B schematically shows the relationship between the focus lens driving method used in this embodiment and the reliability of the defocus amount, and the movement of the focus lens by driving, as in FIG. Yes. In the present embodiment, when the reliability of the defocus amount is not low (better than α), the focus lens is driven based on the defocus amount, and otherwise, search driving is performed by step driving. Therefore, according to the present embodiment, it is possible to perform better-quality moving image AF control even with a lens that cannot be set for low-speed driving.

Next, the lens driving process in S805 of FIG. 12 will be described using the flowchart of FIG. The lens driving process is a process of driving the focus lens 103 based on the setting of various flags set by the lens driving setting described in S804.
In step S1001, the camera control unit 212 determines whether the lens stop flag is off. If it is off, the process proceeds to step S1002, and if it is on, the process proceeds to step S1005. In step S1005, the camera control unit 212 turns off the lens stop flag and ends the lens driving process.

  When the lens stop flag is turned on in S906 in FIG. 13, that is, when the direction of the defocus amount is not reliable and it is determined whether or not to shift to search driving, the focus lens 103 is not driven. The process ends. By doing so, the focus lens 103 is not driven when the reliability of the defocus amount temporarily deteriorates, for example, when another subject crosses in front of the main subject. Reduction can be suppressed.

  The processing in S1002 that is performed when it is determined in S1001 that the lens driving flag is OFF is characteristic processing in the present embodiment. In step S1002, the camera control unit 212 determines whether the search drive flag is off. If the search drive flag is off, the process proceeds to step S1003. The camera control unit 212 performs lens driving based on the defocus amount, and ends the lens driving process. . If the search drive flag is on, the process proceeds to S1004, the search drive process is performed, and the lens drive process ends. Details of the search drive processing in S1004 will be described later with reference to FIG.

  Next, the search drive process in S1004 of FIG. 15 will be described using the flowchart of FIG. The search drive process is a process that is performed when the search drive flag is turned on in S905 of FIG. 13, and performs step drive with the step drive amount set in S909 or S910.

  In S1101, the camera control unit 212 determines whether or not the search drive is the first time. If it is not the first time, the process proceeds directly to S1103. If it is the first time, the drive direction is set in S1102 and then the process proceeds to S1103. When the search drive is the first time, it is necessary to determine which of the focus lenses 103 is driven. The drive direction setting process in S1102 will be described later with reference to FIG.

  In step S <b> 1103, the camera control unit 212 drives the focus lens 103 with the set driving direction and step driving amount through the lens control unit 106, and advances the process to step S <b> 1104. In step S1104, the camera control unit 212 determines whether the focus lens 103 has reached the near end or the infinite end. If the focus lens 103 has reached, the process proceeds to step S1105, and if not, the process proceeds to step S1106. In step S1105, the camera control unit 212 reverses the driving direction and advances the process to step S1106. In step S1106, the camera control unit 212 determines whether the reliability is a value better than the predetermined value α. If the reliability is higher than the predetermined value α, the process proceeds to step S1107. If not, the process proceeds to step S1108. In step S1108, the camera control unit 212 determines whether the focus lens 103 has reached both the near end and the infinite end during the search driving process. If the focus lens 103 has reached, the process proceeds to step S1107. The search driving process ends. In step S1107, the camera control unit 212 turns off the search drive flag and ends the search drive process.

  The conditions for terminating the search drive are when the reliability becomes better than the predetermined value α in S1106, or when the focus lens 103 reaches both the closest end and the infinite end in S1108. The reliability threshold value α set in step S1106 is the same as the threshold value α set in step S901 in FIG. 13, and is a value with which at least the defocus amount direction can be determined to be reliable. If the reliability is better than the threshold value α, it can be determined that the subject has come close to the in-focus state. Therefore, the search driving, that is, step driving is stopped and the control is switched to driving based on the defocus amount again. If it is determined in S1108 that both the near end and the infinite end have been reached, the entire focus drive range is driven, that is, the subject cannot be specified. In this case, the search drive flag is turned off to return to the initial processing state. If the subject cannot be specified, the search drive may be continued without turning off the search drive flag.

  Next, the drive direction setting process in S1102 of FIG. 16 will be described using the flowchart of FIG. In step S1201, the camera control unit 212 determines whether the current position of the focus lens 103 is closer to the closest end than the infinite end. If the current position of the focus lens 103 is closer to the close end, the process proceeds to step S1202. Proceed to the process.

  In step S1202, the camera control unit 212 sets the driving direction of the focus lens 103 at the start of search driving to the closest direction, and ends the driving direction setting process. On the other hand, in S1203, the camera control unit 212 sets the driving direction of the focus lens 103 at the start of search driving to an infinite direction, and ends the driving direction setting process. By setting the drive direction in this way, it is possible to shorten the time for searching and driving the entire focus lens drive region, and to shorten the maximum time required to find the subject by the search drive.

As described above, the focus adjustment device according to the present embodiment switches the focus lens driving method during AF control based on the defocus amount reliability information detected by the imaging plane phase difference detection. When it is determined that the reliability is good, the focus lens is driven based on the detected defocus amount. When the reliability of the defocus amount is poor, the step drive amount and the drive direction are set, and search drive is performed by step drive. Therefore, even when moving image shooting is performed with a lens that cannot be driven at a low speed, the focus lens can be prevented from moving greatly in a short time, and adverse effects on image quality can be suppressed. In addition, it is possible to drive a focus lens of high quality that appears to move smoothly.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described. In this embodiment, in addition to the first embodiment, the history of detected reliability information and defocus amount information is held in the SDRAM 209 of FIG. The lens driving method switching unit 213 in the camera control unit 212 switches the driving method of the focus lens based not only on the latest reliability information but also on the reliability and defocus amount history.

Since the configuration of the interchangeable lens camera including the lens unit and the camera body in the present embodiment is the same as the configuration described based on FIG. 1 in the first embodiment, the description thereof is omitted.
In addition, since the operation of the camera body 20 described with reference to the flowcharts of FIGS. 3, 4, 5, 6, 11, 15, 16, and 17 in the first embodiment is the same in this embodiment, the description thereof is omitted. .

  First, the AF processing in S507 of FIG. 5 will be described using the flowchart of FIG. The processing from S1301 to S1303 in FIG. 18 is the same as the processing from S801 to S803 in FIG. Also, the processing in S1306 and S1307 in FIG. 18 is the same as the processing in S805 and S806 in FIG.

  If the condition that the defocus amount is within the depth of focus and the reliability is better than the predetermined value is not satisfied in S1302 of FIG. 18, the camera control unit 212 sends AF information such as the defocus amount and reliability to the SDRAM 209 in S1304. Store and proceed to S1305. The defocus amount and reliability history held in the SDRAM 209 are used to determine the lens driving method in the lens driving setting process of FIG. 19 described later. In step S1305, the camera control unit 212 performs lens drive setting and advances the process to step S1306. Details of S1305 will also be described later with reference to FIG.

  Next, the lens drive setting in S1305 of FIG. 18 will be described using the flowchart of FIG. Since S1401 is the same process as S901 of FIG. 13 in the first embodiment, a description thereof will be omitted. As a difference from the first embodiment, this embodiment does not use the search drive transition counter used in the first embodiment. Further, S1404 to S1409 are the same as the processes from S905 to S910 of FIG. 13 in the first embodiment, and thus description thereof is omitted.

  In this embodiment, in the state where the reliability is lower than the predetermined value α in S1401, that is, in the state where the defocus direction is unreliable, more suitable control is realized by using the defocus amount and the reliability history. In S1402, which proceeds when the reliability is lower than the predetermined value α, the camera control unit 212 continues to determine whether the reliability is lower than the predetermined value α continuously for a predetermined period. If yes, the process proceeds to S1403. Advances the process to S1405. In step S1403, the camera control unit 212 determines whether the defocus direction indicates a certain direction over a predetermined period. If yes, the process proceeds to step S1406. If not, the process proceeds to step S1404. In step S1404, the camera control unit 212 turns on the search drive flag and proceeds to step S1410. The process proceeds to step S1404, which is performed when the period in which the defocus direction is constant is less than the predetermined period in step S1403.

  In the first embodiment, when the reliability in the direction of the defocus amount is not reliable, a search drive transition counter is provided, and the lens stop flag is turned on in S906 until the counter value exceeds a predetermined value. The focus lens 103 was stopped. When the counter value, which is the number of determinations that the reliability of the defocus amount is low, exceeds a predetermined value, the search drive flag is turned on in S905 and switching to search drive is determined. On the other hand, in this embodiment, the shift to the search drive is determined based on the history of the reliability and the defocus amount, not the search drive shift counter. In S1402, the camera control unit 212 controls to turn on the lens stop flag and stop the focus lens 103 in S1405 until the determination that the reliability is worse than the predetermined value α continues for a predetermined period. If it is determined that the reliability is lower than the predetermined value α continuously for a predetermined period, the camera control unit 212 determines whether or not it is necessary to shift to search driving in S1403.

S1403 is a characteristic part of the present embodiment. Even when it is determined in S1402 that the reliability is continuously lower than the threshold value α, if the defocus amount seems to be reliable to some extent, the search drive is not switched. Continue driving based on the defocus amount. This is due to the following reasons, for example.
・ Search drive takes time to focus, so I want to drive using defocus amount as much as possible ・ As a reliability threshold, it is important to determine whether the defocus direction is reliable or not according to the conditions of the subject and camera Difficult because it depends on parameters

  That is, even when the reliability is lower than the threshold value α, the defocus direction may be reliable, and in that case, the aim is to drive by believing in the defocus amount. Although it is determined that the reliability is low continuously for a predetermined period, if the defocus direction indicates a certain direction during that period, it is determined that the defocus direction is reliable. If the reliability is low continuously for a predetermined period and the defocus direction is not one direction, it is determined that the defocus amount is not reliable, and the process proceeds to search drive in S1404. By controlling in this way, it is possible to increase the chance of driving the lens by believing in the defocus direction even when the reliability is lower than the threshold value α.

  As described above, according to the present embodiment, the switching determination from the driving method based on the defocus amount to the driving method not based on the defocus amount is determined using the past history of the defocus amount. did. Therefore, the state to be switched to the driving method of the focus lens not based on the defocus amount can be detected with higher accuracy, and as a result, more driving based on the defocus amount with a high focusing speed can be performed. In addition to the effect of the form, the focusing time can be shortened.

(Third embodiment)
Hereinafter, a third embodiment of the present invention will be described. In the present embodiment, unlike the second embodiment, even if the defocus direction is reliable, it is driven by step driving. Depending on the reliability of the defocus amount, whether to use the defocus direction, Change the driving amount.

Since the configuration of the interchangeable lens camera including the lens unit and the camera body in the present embodiment is the same as the configuration described based on FIG. 1 in the first embodiment, the description thereof is omitted.
The operation of the camera body 20 described with reference to the flowcharts of FIGS. 3, 4, 5, 6, 11, 12, 16, and 17 in the first embodiment is the same in this embodiment, and thus the description thereof is omitted. .

In the present embodiment, the lens drive setting performed in S804 of FIG. 12 will be described using the flowchart of FIG.
The processes in S2303 and S2304 in FIG. 20 are the same as the processes in S901 and S902 in FIG. The processing from S2309 to S2316 is the same as the processing from S903 to S910 in FIG.
In step S2301, the camera control unit 212 determines whether the image height of the focus detection area in the screen set in step S607 is higher than a predetermined value. If the image height is higher than the predetermined value, the process proceeds to step S2302. In step S2302, the camera control unit 212 sets the reliability threshold values α and β used in steps S2303 and S2306 to a value larger than a normal value (a value used when the image height is equal to or lower than a predetermined value in step S2301). ) Is set, and the process proceeds to S2303.

  As described above, there is an intensity difference between the pupils A and B that acquire the image signals A and B as the characteristics of the imaging surface phase difference detection method. However, the difference in the amount of light incident on the pupils A and B increases as the image height increases. Since it increases, the pupil intensity difference increases as the image height increases. That is, as the image height increases, the reliability of the image signals A and B, such as the degree of coincidence of two images and steepness, tends to be calculated worse. When the reliability threshold value for switching the lens driving method is constant, the reliability decreases as the defocus amount detected at a position where the image height is high. Therefore, in order to suppress the difference depending on the location, when the image height of the focus detection area is higher than the processing value, the reliability threshold value for switching the lens driving method is changed to a value corresponding to the lower reliability.

  In S2303, it is determined that the reliability of the defocus amount is better than the predetermined value α, and after the search drive transition counter is reset in S2304, the camera control unit 212 sets the step drive amount to X (first drive amount) in S2305. The process proceeds to S2313. In step S2306, when the reliability is determined to be lower than the predetermined value α, the camera control unit 212 determines whether the reliability is higher than the predetermined value β. If the reliability is good, the process proceeds to step S2307. Advances the process to S2309. In step S2307, the camera control unit 212 resets the search drive transition counter and advances the process to step S2308. In step S2308, the camera control unit 212 sets the step drive amount to Y (second drive amount) and advances the process to step S2313.

The reliability threshold values α, β, and γ set in the present embodiment have the following relationship.
α <β <γ (α is the most reliable)
In the first and second embodiments, α is a value at least reliable in the defocus direction, but in the present embodiment, this value is β. In the present embodiment, the reliability threshold value α is set to a value that is more reliable than at least the value β in which the defocus direction is reliable.

The step drive amounts A, B, X, and Y set in the present embodiment have the following relationship.
X <Y <A <B
In this embodiment, even when the reliability is better than β, that is, when the defocus direction is a reliable value, control is performed using only the defocus direction without using the defocus amount. At this time, the step drive amount is set in the same manner as in the search drive, and control is performed so that the drive is performed with the step drive amount set in the defocus direction. As described above, in this embodiment, the control for performing the step drive using the defocus direction and the step drive control for performing the search drive without using the defocus information are switched. Controlling in this way has the following advantages.
Even in the vicinity of in-focus, the substantial drive speed of the focus lens can be reduced and high-quality focus lens drive can be executed.
Since the step of driving the focus lens can be varied even when the defocus amount is highly reliable, it is possible to realize driving of a high-quality focus lens that varies the drive amount as the in-focus state is achieved.

  When the reliability is better than the threshold value α (first reliability), the step drive amount is set to X, and when the reliability is not better than the threshold value α but better than the threshold value β (second reliability). The step drive amount is set to Y (> X). Since the imaging surface phase difference detection method tends to increase the reliability of the defocus amount as it comes closer to the in-focus state, the higher the reliability, the smaller the step drive amount is set. It can appear to be slowing down. Note that the step drive amount set when performing step drive using the defocus direction is set to be smaller than the step drive amount (A, B) (third drive amount) used in step drive during search drive. In search driving, priority is given to searching for the subject as soon as possible, but when the defocus amount is highly reliable (= in the vicinity of in-focus), the quality of focusing on the subject and the focus of the subject This is because priority is given to suppressing the phenomenon of passing through. However, in this embodiment, since the driving quality of the focus lens is given priority over the in-focus time, and the defocus amount is reliable, it is operated by step driving, so that the in-focus state is higher than in the first and second embodiments. Time is slow.

  In step S <b> 2317, the camera control unit 212 multiplies the step drive amount set in any of S <b> 2305, S <b> 2308, S <b> 2315, and S <b> 2316 on the basis of the information on the diaphragm 102 obtained via the lens control unit 106 and performs lens drive setting processing. Exit. Specifically, in the present embodiment, the gain is applied so that the second aperture value on the open side is larger than the first aperture value in the case of the first aperture value. . In particular, a gain that is larger as the aperture is closer to the open side and smaller as the aperture is smaller is applied. This is because the depth of field is shallower on the open side, and the depth of field becomes deeper as the aperture is reduced. The more the aperture is reduced, the easier it is to overshoot when the lens is driven with a large step drive amount, and the overfocus is reduced by focusing with a smaller step drive amount. To improve. Another reason is that the closer to the open side, the more likely it is to drive in a larger step because blurring is more noticeable when there is a change in the main subject.

  Next, the lens driving process in S805 of FIG. 12 will be described with reference to FIG. The processing of S2401, S2402, S2404, and S2405 in FIG. 21 is the same as S1001, S1002, S1004, and S1005 in FIG. In step S2401, it is determined that the lens stop flag is off. In step S2403, when the search drive flag is determined to be off, the camera control unit 212 sets the defocus direction calculated in FIG. The step driving is performed with the step driving amount, and the process is terminated.

  As described above, in the present embodiment, the step drive control using the defocus direction and the step drive control performing the search drive without using the defocus information according to the reliability of the defocus amount. Switch. Therefore, even when the defocus amount is reliable, the focus lens can be driven at a substantially low speed, and high-quality driving in which the drive speed decreases as the focus position is approached can be realized.

  In addition, the reliability threshold value for switching the lens driving method is changed according to the height of the image height of the focus detection area where AF is performed using the imaging surface phase difference detection method. Thereby, a difference in the focus lens driving operation due to the image height of the focus detection area can be suppressed. Also, by varying the step drive amount according to the aperture value, it is possible to focus more quickly on the open side where blurring is noticeable, and it is possible to suppress the occurrence of overshoot on the small aperture side where overshoot is likely to occur. .

  Although the present invention has been described in detail based on the exemplary embodiments thereof, the present invention is not limited to these specific embodiments, and various modifications can be made within the scope of the invention described in the claims. Modifications can be made.

(Other embodiments)
The change of the threshold according to the image height of the focus detection area in the third embodiment can also be implemented in the first and second embodiments. When applied to the first and second embodiments, it is possible to increase the opportunity to perform driving based on the defocus amount even when performing AF at a position where the image height is high. A configuration in which the step drive amount during search drive is adjusted according to the aperture value can also be applied to the first and second embodiments.

  In the above-described embodiment, for ease of explanation and understanding, the number of steps such as the step driving amount set according to the reliability is set to 2, but the relationship between the reliability and the step driving amount is more finely defined. It is also possible to set the number of steps to 3 or more.

  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 storage 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.

Claims (15)

An image sensor capable of generating an image signal used for automatic focus adjustment of a phase difference detection method;
Detection means for detecting a defocus amount based on the image signal;
Control means for controlling the driving of the focus lens based on the defocus amount,
The control means includes
When the reliability of the defocus amount is higher than the first reliability, the driving of the focus lens is controlled so that the focus lens is driven based on the defocus amount;
If the reliability of the defocus amount is not higher than the first reliability over a predetermined number of times, if the reliability of the defocus amount is the second reliability, the first drive amount is set as a predetermined unit, as the defocus amount reliability the second reliability lower than the third predetermined unit a large second driving amount than the first drive amount when the reliability of the predetermined said focusing lens Control the drive of the focus lens so that the focus lens is driven by step drive that drives unit by unit,
If the reliability of the defocus amount detected after the focus lens is driven by the step driving it is higher than the first reliability, so that the focus lens is driven based on the defocus amount And a focus adjustment device that controls driving of the focus lens. An image sensor capable of generating an image signal used for automatic focus adjustment of a phase difference detection method;
  Detection means for detecting a defocus amount based on the image signal;
  Control means for controlling the driving of the focus lens based on the defocus amount,
  The control means includes
    When the reliability of the defocus amount is higher than the first reliability, the driving of the focus lens is controlled so that the focus lens is driven based on the defocus amount;
    When the reliability of the defocus amount is not higher than the first reliability over a predetermined period and the defocus direction indicated by the defocus amount is not constant over the predetermined period, the focus lens is driven by a predetermined unit. Controlling the drive of the focus lens so that the focus lens is driven by step drive;
    The focus lens is driven based on the defocus amount when the reliability of the defocus amount detected after the focus lens is driven by the step driving is higher than the first reliability. And a focus adjustment device that controls driving of the focus lens. Wherein when the defocus amount reliability not higher than the first reliability for the predetermined period, and a defocus direction indicated by the defocus amount is constant over the predetermined period, the The focus adjustment apparatus according to claim 2 , wherein the focus lens drive is controlled so that the focus lens is driven based on a defocus direction indicated by a defocus amount. The control unit controls the drive of the focus lens so that the focus lens is driven based on a defocus direction indicated by the defocus amount detected before the step drive is determined to be performed. The focus adjusting apparatus according to claim 3 . The control means corrects the predetermined unit so that the aperture value is larger when the aperture value is the second value on the open side than the first value than when the aperture value is the first value. The focus adjustment apparatus according to any one of claims 1 to 4 , wherein the focus adjustment apparatus includes: An image sensor capable of generating an image signal used for automatic focus adjustment of a phase difference detection method;
Detection means for detecting a defocus amount based on the image signal;
Control means for controlling the driving of the focus lens based on the defocus amount,
The control means controls the drive of the focus lens so that the focus lens is driven by step drive that drives the focus lens by a predetermined unit, and the reliability of the defocus amount is higher than a predetermined value. If the reliability is the first drive amount, the second drive amount is larger than the first drive amount if the reliability of the defocus amount is the second reliability that is not higher than the predetermined value. A focus adjustment device that controls driving of the focus lens so that the focus lens is driven by step driving in the predetermined unit. When the reliability of the defocus amount is higher than a predetermined reliability that is reliable for the defocus direction, the control unit determines the drive direction of the focus lens at the start of the step drive as the defocus amount. The focus adjustment device according to claim 6 , wherein the focus adjustment device is determined based on a defocus direction indicated by the The focus adjustment apparatus according to claim 7 , wherein the second reliability is higher than a reliability reliable in the defocus direction. When the reliability of the defocus amount is not higher than the reliability reliable in the defocus direction, the control means has a third drive amount larger than the second drive amount and a drive range of the focus lens 9. The focus adjustment apparatus according to claim 8 , wherein driving of the focus lens is controlled so that the focus lens is driven in the camera. The controller drives the third drive so that the aperture value is larger when the aperture value is the second value on the open side than the first value than when the aperture value is the first value. The focus adjustment apparatus according to claim 9 , wherein the amount is corrected. The detection means detects the defocus amount based on the image signal obtained from a pixel included in a focus detection area among pixels included in the imaging element,
Wherein, the higher the image height of the focus detection area, the focus adjusting apparatus according to any one of claims 1 to 10, characterized in that the set lower the first reliability. Focusing device according to any one of claims 1 to 11 in which the operation of the control means characterized by being performed during moving image shooting. A control method of a focus adjustment apparatus having an image sensor capable of generating an image signal used for phase difference detection type automatic focus adjustment,
A detection step of detecting a defocus amount based on the image signal;
A control step of controlling the driving of the focus lens based on the defocus amount,
In the control step,
When the reliability of the defocus amount is higher than the first reliability, the driving of the focus lens is controlled so that the focus lens is driven based on the defocus amount;
If the reliability of the defocus amount is not higher than the first reliability over a predetermined number of times, if the reliability of the defocus amount is the second reliability, the first drive amount is set as a predetermined unit, as the defocus amount reliability the second reliability lower than the third predetermined unit a large second driving amount than the first drive amount when the reliability of the predetermined said focusing lens Control the drive of the focus lens so that the focus lens is driven by step drive that drives unit by unit,
If the reliability of the defocus amount detected after the focus lens is driven by the step driving it is higher than the first reliability, so that the focus lens is driven based on the defocus amount And controlling the driving of the focus lens. A control method of a focus adjustment apparatus having an image sensor capable of generating an image signal used for phase difference detection type automatic focus adjustment,
  A detection step of detecting a defocus amount based on the image signal;
  A control step of controlling the driving of the focus lens based on the defocus amount,
  In the control step,
    When the reliability of the defocus amount is higher than the first reliability, the driving of the focus lens is controlled so that the focus lens is driven based on the defocus amount;
    When the reliability of the defocus amount is not higher than the first reliability over a predetermined period and the defocus direction indicated by the defocus amount is not constant over the predetermined period, the focus lens is driven by a predetermined unit. Controlling the drive of the focus lens so that the focus lens is driven by step drive;
    The focus lens is driven based on the defocus amount when the reliability of the defocus amount detected after the focus lens is driven by the step driving is higher than the first reliability. And controlling the driving of the focus lens. A control method of a focus adjustment apparatus having an image sensor capable of generating an image signal used for phase difference detection type automatic focus adjustment,
A detection step of detecting a defocus amount based on the image signal;
A control step of controlling the driving of the focus lens based on the defocus amount,
In the control step, the driving of the focus lens is controlled so that the focus lens is driven by step driving of driving the focus lens by a predetermined unit, and the reliability of the defocus amount is higher than a predetermined value. If the reliability is the first drive amount, the second drive amount is larger than the first drive amount if the reliability of the defocus amount is the second reliability that is not higher than the predetermined value. A method for controlling a focus adjusting apparatus, comprising: controlling the focus lens drive so that the focus lens is driven by step drive in the predetermined unit.

Images