JP2015087703A - Automatic focus adjustment unit, control method of automatic focus adjustment unit, control program of automatic focus adjustment unit, and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic focus adjustment unit with a system that uses both an imaging plane phase difference AF (Auto Focus) method and a contrast AF method, capable of using a detection result that is more appropriate depending on an image-capturing condition.SOLUTION: An automatic focus adjustment unit includes: image capturing means which receives a light flux entering via an image-capturing optical system including a focus lens and performs photo-electric conversion of the light flux; first detection means which detects a phase difference between paired image signals generated by the image capturing means; second detection means which detects contrast information from signals generated by the image capturing means; and control means which controls driving of the focusing lens based on at least either of a detection result obtained by the first detection means and a detection result obtained by the second detection means. When the detection result obtained by the first detection means satisfies a predetermined condition, the control means uses the detection result obtained by the first detection means to control driving of the focusing lens and modifies the predetermined condition in accordance with the contrast information.

Description

  The present invention relates to an automatic focus adjustment device equipped with a phase difference detection method and a contrast detection method.

  In recent years, an imaging apparatus typified by a single-lens reflex camera has greatly increased the weight for a shooting method while viewing an LV (live view) screen. In particular, the demand for moving image shooting is increasing, and in moving image shooting, it is important that shooting can be performed comfortably while looking at the LV screen.

  Various methods have been proposed as an AF (autofocus) method for an imaging apparatus in LV, and a contrast detection method is a main method. In the contrast detection method, a focused 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 while moving the focus lens.

  However, the above contrast detection method cannot easily determine the position and direction of focusing for focusing on the subject. For this reason, the contrast detection method may behave poorly when it takes time to focus, or when the direction to be focused is wrong or the focus position is passed. In particular, in moving image shooting, since all the focusing operations are recorded, it is not desirable that the behavior be poor.

  Therefore, an AF method has been proposed that can perform focusing with high quality even during LV shooting. One of the methods is an imaging surface phase difference detection (imaging surface phase difference AF) method in which the phase difference detection method is performed on the image sensor surface. In the phase difference detection method, the defocus amount is calculated from the phase difference between a pair of image signals obtained by receiving light beams that have passed through different exit pupil regions in the photographing optical system. Then, the in-focus state is obtained by moving the focus lens by a movement amount corresponding to the defocus amount.

  As one of imaging plane phase difference detection methods, a system using a configuration in which a plurality of photoelectric conversion elements are provided under the same microlens in an imaging pixel of an imaging element has been proposed as in Patent Document 1. In this configuration, light that has passed through different areas of the exit pupil area is received by each of the plurality of photoelectric conversion elements, so that focus detection can be performed simultaneously with imaging. Specifically, phase difference detection AF can be performed by comparing the outputs of a plurality of photoelectric conversion elements. By using the imaging surface phase difference detection method, AF can be performed using the phase difference detection method even in LV shooting, and focusing can be performed at high speed with high quality.

  Patent Document 2 discloses a configuration in which focus detection pixels are provided in an image sensor to perform phase difference detection AF as one of imaging surface phase difference detection methods. In addition, a configuration is disclosed in which higher-quality AF is realized by compensating for the demerits of contrast AF and phase difference AF by a system that combines the imaging surface phase difference detection method and the contrast detection method. For example, in Patent Document 2, when a distance measurement result by phase difference AF cannot be obtained, wobbling driving is performed, and the focus lens is driven based on a result calculated earlier between phase difference AF and contrast AF.

JP 2001-083407 A JP 2013-025129 A

  However, in the method of driving the focus lens based on the result calculated earlier as in Patent Document 2, there is a possibility that the drive direction of the focus lens is wrong. For example, when it is far from the in-focus position (large blur), the image plane phase difference AF tends to break the symmetry of the image signal, and a clear peak of image coincidence cannot be identified, and an erroneous result may be calculated. Becomes higher. In such a case, even if the result of the phase difference AF is calculated earlier, it is more risky to use the result of the phase difference AF, and the contrast AF is more likely to detect a focusing direction that is more reliable. However, with the method of Patent Document 2, it is not possible to determine an appropriate detection result depending on the shooting situation between phase difference AF and contrast AF.

  Therefore, an object of the present invention is to provide an automatic focus adjustment apparatus that can use a more appropriate detection result in accordance with a shooting situation in a system that uses both imaging plane phase difference AF and contrast AF.

  In order to achieve the above object, the first aspect of the present invention is an image pickup means for receiving and photoelectrically converting a light beam incident through a photographing optical system including a focus lens, and a pair of images output from the image pickup means. At least one of a first detection unit that detects a phase difference of the signal, a second detection unit that detects contrast information from a signal output from the imaging unit, and the first detection unit and the second detection unit. An automatic focus adjustment device having a control unit for controlling the driving of the focus lens based on one detection result, wherein the control unit is configured such that the detection result by the first detection unit satisfies a predetermined condition The driving of the focus lens is controlled using the detection result of the first detection means, and the predetermined condition is changed according to the contrast information.

  The second aspect of the present invention is a method of controlling an automatic focus adjustment apparatus having an imaging unit that receives and photoelectrically converts a light beam incident through a photographing optical system including a focus lens, and is output from the imaging unit. A first detection step for detecting a phase difference between a pair of image signals; a second detection step for detecting contrast information from a signal output from the imaging means; the first detection step and the second detection; And a control step for controlling the driving of the focus lens based on the detection result of at least one of the steps. In the control step, when the detection result by the first detection step satisfies a predetermined condition, the first step The driving result of the focus lens is controlled using the detection result of the first detection step, and the predetermined condition is changed according to the contrast information. And wherein the Rukoto.

  As described above, according to the present invention, it is possible to use a more appropriate detection result in accordance with the shooting situation in a system that uses both imaging plane phase difference AF and contrast AF.

The block diagram which shows the structure of the camera and lens unit in this embodiment. The figure which shows the pixel structure of the imaging surface phase difference system in this embodiment. Flow chart showing imaging processing in the present embodiment Flowchart showing moving image shooting processing in the present embodiment Flowchart showing focus detection processing in this embodiment Flowchart showing AF restart determination in this embodiment Flowchart showing AF processing in the present embodiment The flowchart which shows the lens drive setting process in 1st embodiment. The flowchart which shows the lens drive process in 1st embodiment. Flowchart showing search drive processing in this embodiment The flowchart which shows the direction determination process by 1st focus information and 2nd focus information in 1st embodiment. The figure which shows the ranging area in this embodiment The figure which shows the image signal obtained from the ranging area in this embodiment The figure explaining the correlation calculation method in this embodiment The flowchart which shows the effectiveness determination process in 1st embodiment The flowchart which shows the effective area number calculation process by the 1st focus information in this embodiment. The figure which shows the simple focus degree calculation method in this embodiment The flowchart which shows the micro drive process in 1st embodiment Conceptual diagram showing the minute driving process in the present embodiment The flowchart which shows the lens drive setting process during zoom in 2nd embodiment. A flowchart showing lens driving processing during zooming in the second embodiment The flowchart which shows the direction determination process by the 1st focus information in zoom in 2nd embodiment. The flowchart which shows the micro drive process during zoom in 2nd embodiment The flowchart which shows the effectiveness determination process during zoom in 2nd embodiment

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiment described below is an example as means for realizing the present invention, and the present invention is not limited to the following embodiment.

(First embodiment)
FIG. 1 is a block diagram showing a configuration of a lens interchangeable camera including a lens unit and a camera body in the present embodiment. As shown in FIG. 1, the camera system according to this embodiment includes a lens unit 10 and a camera body 20. The lens control unit 106 that controls the overall operation of the lens unit 10 and the camera control unit 207 that controls the overall operation of the camera communicate data.

  First, the configuration of the lens unit 10 will be described. The lens unit 10 includes a photographing optical system that includes a fixed lens 101, a zoom lens 108, a diaphragm 102, and a focus lens 103. 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 performs focus adjustment. The zoom lens 108 is driven by a zoom lens driving unit 109 to adjust zoom. In the present embodiment, the zoom lens 108 and the zoom lens driving unit 109 are not essential components.

  The aperture driving unit 104, the focus lens driving unit 105, and the zoom lens driving unit 109 are controlled by the lens control unit 106, and the aperture amount of the aperture 102 and the positions of the focus lens 103 and the zoom lens 108 are determined. When the user performs operations such as focusing and zooming via the lens operation unit 107, the lens control unit 106 performs control according to the user operation. The lens control unit 106 controls the aperture driving unit 104, the focus lens driving unit 105, and the zoom lens driving unit 109 according to a control command / control information received from a camera control unit 207, which will be described later. It transmits to the control part 207.

  Next, the configuration of the camera body 20 including the automatic focus adjustment device according to the present embodiment will be described. The camera body 20 is configured to be able 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 configured by a CCD or CMOS sensor. The light beam that has passed through the photographing optical system forms an image on the light receiving surface of the image sensor 201, and the formed subject image is converted (photoelectric conversion) into charges corresponding to the amount of incident light by the photodiode. The electric charge accumulated in each photodiode is sequentially read out from the image sensor 201 as a voltage signal corresponding to the electric charge based on a drive pulse given from the timing generator 209 in accordance with an instruction from the camera control unit 207.

  In the case of an imaging device that does not support imaging surface phase difference type focus adjustment (hereinafter referred to as imaging surface phase difference AF), for example, the pixel configuration has a Bayer array as shown in FIG. On the other hand, in order to perform imaging surface phase difference AF, the image sensor 201 of the present embodiment has a plurality of (two in this embodiment) photodiodes (photoelectric conversion elements) in one pixel as shown in FIG. ). By separating the light beam with a microlens and forming an image with these two photodiodes, two signals for imaging and AF can be acquired. A signal (A + B) obtained by adding the signals of two photodiodes is an image pickup signal, and signals (A, B) of individual photodiodes are two image signals for AF. Here, the configuration is not limited to reading each of the two image signals. For example, in consideration of a processing load, the added signal (A + B) and one image signal (for example, A) are read, and the other image signal is calculated from the difference. (For example, B) may be acquired. An AF signal processing unit 204, which will be described later, performs correlation calculation on two AF image signals to calculate an image shift amount and various reliability information.

  In the present embodiment, one pixel has two photodiodes, but the number of photodiodes is not limited to two and may be more. In addition, the configuration of the imaging device corresponding to the imaging plane phase difference AF is not limited to the configuration in which a plurality of photodiodes are provided in one pixel as in the present embodiment, but a focus is formed in the imaging device as in Patent Document 2 described above. A configuration in which pixels for detection are provided may be used.

  The imaging signal and AF signal read from the imaging element 201 are input to the CDS / AGC converter 202, and correlated double sampling for removing reset noise, gain adjustment, and signal digitization are performed. The CDS / AGC converter 202 outputs the imaging signal to the camera signal processing unit 203 and the AF evaluation value generation unit 210, and outputs the imaging surface phase difference AF signal to the AF signal processing unit 204.

  The camera signal processing unit 203 transmits the imaging signal output from the CDS / AGC converter 202 to the display unit 205. The display unit 205 is a display device such as an LCD or an organic EL, and displays an imaging signal. In the mode for recording the imaging signal, the imaging signal is recorded in the recording unit 206.

  The AF signal processing unit 204 performs a correlation calculation based on the two image signals for AF output from the CDS / AGC converter 202, and detects image shift amount and reliability information (two-image coincidence, two-image steepness, contrast Information, saturation information, scratch information, etc.). Then, the calculated image shift amount and reliability information are output to the camera control unit 207. Details of the correlation calculation will be described later with reference to FIGS.

  The AF evaluation value generation unit 210 extracts a high frequency component from the imaging signal, generates an AF evaluation value, and outputs the AF evaluation value to the camera control unit 207. The AF evaluation value represents the sharpness (contrast state) of an image generated based on the output signal from the image sensor 201, and the sharpness varies depending on the focus state (degree of focus) of the photographing optical system. As a result, the signal represents the focus state of the photographing optical system. Note that the area on the image sensor 201 used for generating the AF evaluation value includes an area corresponding to an area used for generating an image signal for phase difference detection.

  The camera control unit 207 performs control by exchanging information with each configuration in the camera body 20. In response to input from the camera operation unit 208, not only processing within the camera body 20, but also user operation such as power ON / OFF, setting change, start of recording, start of AF control, confirmation of recorded image, etc. Perform camera functions. In addition, as described above, information is exchanged with the lens control unit 106 in the lens unit 10, and a control command / control information for the photographing optical system is transmitted, or information in the lens unit is acquired.

  Next, the operation of the camera body 20 in the present embodiment will be described with reference to the drawings.

  FIG. 3 is a flowchart showing the procedure of the photographing process of the camera body 20. First, in steps S301 to S303, the camera control unit 207 performs initialization processing. In step S301, the camera control unit 207 performs various initial value settings for the camera. Here, when the shooting process is started or when the shooting mode is changed, the initial value is set based on information such as the user setting and the shooting mode at that time. In step S302, the focus stop flag is turned off. In step S303, the search drive flag is turned off and the process ends.

  The focus stop flag that is initialized in step S302 is a characteristic part of the present embodiment. When it is determined that the focus lens 103 is stopped during moving image shooting and the focus lens 103 is stopped, the focus stop flag is turned on. If the focus lens 103 is not being driven, it is turned off. By switching on / off of the focus stop flag, it is determined whether the focus lens 103 is currently driven or stopped.

  The search drive flag to be initialized in step S303 is turned off when the defocus amount detected by the imaging surface phase difference detection method is reliable when driving the focus lens 103, and turned on when the focus lens 103 is not reliable. The case where the defocus amount is reliable is a case where the accuracy of the defocus amount and the defocus direction are certain, that is, a state where the reliability is higher than a certain level. For example, there is a high possibility that the defocus amount is reliable in a state where the main subject is focused in the vicinity of the in-focus state or a state where the main subject is already in focus. In this case, the focus lens 103 is driven with reliability of the defocus amount. On the other hand, the case where the defocus amount is not reliable is a case where the defocus amount is not certain, that is, a state where the reliability is lower than a certain level. For example, when the subject is largely out of focus, there is a high possibility that the defocus amount cannot be calculated correctly. In this case, since the calculated defocus amount is not reliable, search drive (drive for searching the focus position by driving the focus lens 103 in a certain direction without using the defocus amount) is performed.

  In step S304, it is determined whether the shooting setting of the camera is the moving image shooting mode or the still image shooting mode. If it is in the moving image shooting mode, the process proceeds to step S305. If it is in the still image shooting mode, the process proceeds to step S306. In step S305, a moving image shooting process is performed, and the process proceeds to step S307. Details of the moving image shooting processing in step S305 will be described later with reference to FIG. On the other hand, in step S306, a still image shooting process is performed and the process proceeds to step S307. Details of the still image shooting process in step S306 are omitted.

  In step S307, it is determined whether the shooting process has been stopped. If the shooting process has not been stopped, the process proceeds to step S308. If the shooting process has not been stopped, the shooting process is terminated. The shooting process is stopped when the camera is turned off, or when an operation other than shooting is performed, such as user setting processing for the camera, playback processing for checking captured images / movies, etc. .

  In step S308, it is determined whether or not the shooting mode has been changed. If changed, the process returns to step S301, and if not changed, the process returns to step S304. If the shooting mode has not been changed, the processing of the current shooting mode is continued. If the shooting mode has been changed, initialization processing is performed in steps S301 to S303 and then the changed shooting mode is processed. .

  Next, the moving image shooting process in step S305 in FIG. 3 will be described with reference to FIG. In steps S401 to S404, control relating to moving image recording is performed. In step S401, the camera control unit 207 determines whether or not the moving image recording switch is turned on. If the moving image recording switch is turned on, the process proceeds to step S402, and if not, the process proceeds to step S405.

  In step S402, the camera control unit 207 determines whether a moving image is currently being recorded. If the moving image is not being recorded, the process proceeds to step S403, where the moving image recording is started and the process proceeds to step S405. On the other hand, if the moving image is being recorded, the process proceeds to step S404, where the moving image recording is stopped and the process proceeds to step S405. In this embodiment, the moving image recording is started / stopped by pressing the moving image recording switch. However, the recording start / stop may be performed by another method such as a changeover switch.

  In step S405, focus detection processing is performed. Here, it is a process of acquiring defocus information and reliability information for performing imaging plane phase difference AF performed by the camera control unit 207 and the AF signal processing unit 204 of FIG. Details will be described later with reference to FIG.

  In step S406, sharpness information is acquired. Here, the AF evaluation value generation unit 210 is processing for acquiring sharpness information (AF evaluation value) from the imaging signal of the set distance measurement area. Since this process is a conventional technique, details are omitted.

  In step S407, the camera control unit 207 determines whether the focus is currently stopped. If the focus is not stopped, the process proceeds to step S408. If the focus is stopped, the process proceeds to step S409. Whether or not the focus is stopped is determined by turning on / off the focus stop flag described above. In step S408, AF processing is performed, and the moving image shooting processing ends. Step S408 performs AF control based on the information detected in steps S405 and S406, and details will be described later with reference to FIG.

  In step S409, AF restart determination is performed, and the moving image shooting process ends. Step S409 is processing for determining whether or not AF control is to be started again if the subject has changed since the in-focus state was stopped. Details will be described later with reference to FIG.

  Next, the focus detection process in step S405 in FIG. 4 will be described with reference to FIG. First, in step S501, the camera control unit 207 acquires a pair of image signals from an arbitrarily set ranging range. In step S502, the camera control unit 207 calculates a correlation amount from the pair of image signals acquired in step S501.

  Subsequently, in step S503, the camera control unit 207 calculates a correlation change amount from the correlation amount calculated in step S502. In step S504, the camera control unit 207 calculates a focus shift amount from the correlation change amount calculated in step S503.

  In step S505, the camera control unit 207 calculates reliability indicating how reliable the amount of focus deviation calculated in step S504 is. These processes are performed for the number of distance measurement areas existing in the distance measurement range. In step S506, the camera control unit 207 converts the focus shift amount into the defocus amount for each distance measurement area. Finally, in step S507, the camera control unit 207 determines a distance measurement area to be used for AF and ends the focus detection process.

  Next, the focus detection process described in FIG. 5 will be described in detail with reference to FIGS.

  FIG. 12 is a diagram illustrating an example of a region in which an image signal indicating a distance measurement range handled in the focus detection process is acquired. FIG. 12A is a diagram showing a distance measurement range 1202 on the pixel array 1201. An area 1204 necessary for performing the correlation calculation is an area obtained by combining the distance measurement range 1202 and the shift area 1203 necessary for the correlation calculation. In FIG. 12A, p, q, s, and t represent coordinates in the x-axis direction, respectively. Here, p to q represent the region 1204, and s to t represent the distance measurement range 1202.

  FIG. 12B is a diagram showing ranging areas 1205 to 1209 in which the ranging area 1202 is divided into five. As an example, in this embodiment, a focus shift amount is calculated for each distance measurement area unit, and focus detection is performed. Further, the distance measurement result of the most reliable area is selected from the plurality of divided distance measurement areas, and the focus shift amount calculated in the area is used for AF. Note that the number of divisions of the distance measurement range is not limited to the above.

  FIG. 12C is a diagram showing a temporary distance measurement area 1210 obtained by connecting the distance measurement areas 1205 to 1209 in FIG. As an example of the embodiment, a focus shift amount calculated from an area obtained by connecting the distance measurement areas as described above may be used for AF.

  Further, when there are restrictions on the distance measurement area, or when there is a restriction on the focus detection processing time and a plurality of distance measurement areas cannot be arranged on the screen, for example, as shown in FIG. A method in which one ranging area is configured by a plurality of areas may be used. FIG. 12D is a diagram showing the arrangement of ranging areas, and there are seven ranging areas 1211 to 1217. In the figure, two areas (1211, 1217) have a size with a horizontal ratio of 25% with respect to the shooting screen, and five areas (1212 to 1216) have a size of 12.5%. Located in the center of the shooting screen. In this way, a plurality of distance measuring areas having different sizes are arranged so that the ratio to the shooting screen is 12.5% of the number of areas> 25% of the number of areas. Then, by combining the distance measurement results obtained from the seven distance measurement areas, one effective defocus amount and effective defocus direction are calculated, and the focus lens 103 is moved using the effective defocus amount or effective defocus direction. Drive to focus.

  In this way, in the example of FIG. 12D, it is possible to focus on the subject at the center of the shooting screen by arranging a large number of distance measuring areas with a small ratio to the shooting screen. In addition, by reducing the ratio of the distance measurement area to the shooting screen, the influence on the AF due to subjects with different distances is reduced. Further, by arranging not only an area with a small ratio of the distance measuring area to the shooting screen but also an area with a large ratio, the fluctuation of the focus caused by the removal of the subject from the distance measuring area is reduced. That is, even if the subject temporarily leaves the distance measurement area, it is possible to maintain the focus while capturing the subject in an area having a large ratio to the shooting screen. In addition, the arrangement method of the distance measurement area, the size of the area, and the like are not limited to those described in the present embodiment, and may be in a form that does not depart from the gist of the invention.

  FIG. 13 is a diagram showing an image signal acquired from the distance measurement area set in FIG. From s to t represents a distance measurement range, and from p to q represents a range necessary for distance measurement calculation based on the shift amount. Further, x to y represent one divided distance measuring area.

  FIG. 13A is a diagram showing a waveform of the image signal before the shift. A solid line 1301 indicates the image signal A, and a broken line 1302 indicates the image signal B. Areas 1205 to 1209 represent the divided ranging areas in FIG.

  13B is a diagram in which the image waveform before the shift in FIG. 13A is shifted in the plus direction, and FIG. 13C is a minus with respect to the image waveform before the shift in FIG. It is the figure shifted to the direction. When calculating the correlation amount, the image signal A 1301 and the image signal B 1302 are shifted bit by bit in the directions of the arrows, respectively.

  Next, a method for calculating the correlation amount COR will be described. First, as described in FIGS. 13B and 13C, the image signal A and the image signal B are shifted bit by 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. Here, the shift amount is represented by i, the minimum shift number is ps in FIG. 13, and the maximum shift number is qt in FIG. Further, x is the start coordinate of the distance measurement area, and y is the end coordinate of the distance measurement area. Using these, the correlation amount COR can be calculated by the following equation (1).

  FIG. 14A is a diagram showing the correlation amount as a waveform. The horizontal axis of the graph indicates the shift amount, and the vertical axis indicates the correlation amount. In the correlation amount waveform 1401, 1402 and 1403 indicate the vicinity of the extreme value. Among these, the smaller the correlation amount, the higher the coincidence between the A image and the B image.

  Next, a method for calculating the correlation change amount ΔCOR will be described. First, the correlation change amount is calculated from the difference in the correlation amount after skipping one shift from the correlation amount waveform shown in FIG. At this time, the shift amount is represented by i, the minimum shift number is ps in FIG. 13, and the maximum shift number is qt in FIG. Using these, the correlation change amount ΔCOR can be calculated by the following equation (2).

  FIG. 14B is a diagram showing the correlation change amount ΔCOR as a waveform. The horizontal axis of the graph indicates the shift amount, and the vertical axis indicates the correlation change amount. In the correlation change amount waveform 1404, reference numerals 1405 and 1406 indicate the vicinity in which the correlation change amount changes from positive to negative. When the correlation change amount becomes 0 from 1405, this is called zero crossing, and the degree of coincidence between the A image and the B image is the highest, and the shift amount at that time is the focus shift amount.

  FIG. 14C is an enlarged view of the portion 1405 in FIG. 14B, and 1407 is a portion of the correlation variation waveform 1404. A method of calculating the focus shift amount PRD will be described with reference to FIG. First, the focus shift amount is divided into an integer part β 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 FIG.

Subsequently, the decimal part β can be calculated by the following equation (4) from FIG.
β = k−1 (4)

  As described above, the focus shift amount PRD can be calculated from the sum of α and β.

  Further, when there are a plurality of zero crosses as shown in FIG. 14B, the first zero cross is defined as a point where the steepness maxder (hereinafter referred to as steepness) of the correlation amount change at the zero cross 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 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 deviation amount will be described. Reliability can be defined by the steepness and the degree of coincidence fnclvl (hereinafter referred to as the degree of coincidence of two images) of the two images of the image signals A and B. The degree of coincidence between the two images is an index representing the accuracy of the amount of focus deviation.

  FIG. 14D is an enlarged view of the portion 1402 in FIG. 14A, and 1408 is a portion of the correlation amount waveform 1401. The degree of coincidence between two images can be calculated by the following equation (6).

  Next, the AF restart determination in step S409 of FIG. 4 will be described using the flowchart of FIG. The AF restart determination is a process for determining whether to drive the focus lens again from a state where the focus lens is stopped after focusing.

  First, in step S601, the camera control unit 207 determines whether or not the reliability calculated in step S505 in FIG. 5 is better than a predetermined threshold value. If the value is good, the process proceeds to step S602. If the value is bad, the process proceeds to step S604.

  In step S602, the camera control unit 207 determines whether the calculated defocus amount is smaller than a predetermined multiple of the depth. If it is smaller, the process proceeds to step S603, and if not, the process proceeds to step S604.

  In step S603, the AF restart counter is reset, and the process proceeds to step S605. On the other hand, in step S604, an AF restart counter is added, and the process proceeds to step S605.

  As described above, if the defocus amount is larger than the predetermined value or the reliability is lower than the predetermined value, the main subject being photographed may be changed, so the AF restart counter is added in step S604. To prepare for restarting AF. If the detected defocus amount is smaller than the predetermined value and the state of high reliability is maintained, the AF restart counter is reset in step S603 in order to keep the focus lens stopped.

  Here, the threshold value of the defocus amount (a predetermined multiple of the depth) set in step S602 makes it easy to restart when the main subject changes, and makes it difficult to restart unexpectedly when the main subject has not changed. Tune in consideration of the above. As an example, 1 time is set to a depth at which the blur of the main subject becomes visible. For the reliability threshold value set in step S601, for example, a value with which the distance calculated from the defocus amount can be trusted is set. As described above, the threshold value set in steps S601 and S602 is determined depending on the case where the main subject is changed.

  In step S605, it is determined whether the AF restart counter is greater than or equal to the AF restart threshold. If it is greater than or equal to the AF restart threshold, the process proceeds to step S606. If it is less than the AF restart threshold, the process ends. In step S606, the focus stop flag is turned off, AF restart is performed, and the processing is ended so as to restart the focus lens drive.

  Next, the AF process in step S408 of FIG. 4 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 S701, the camera control unit 207 determines whether the defocus amount is within the depth and whether the reliability calculated in step S505 in FIG. 5 shows a value better than a predetermined value. As the reliability threshold value, for example, a value at which the distance calculated from the defocus amount is reliable is set. If this condition is met, the process proceeds to step S702; otherwise, the process proceeds to step S703. In the present embodiment, the threshold used in step S701 is set to be 1 time the depth, but may be set larger or smaller as necessary.

  In step S702, the focus stop flag is turned on and the process ends. As described above, when it is determined that the subject is in focus, the process proceeds from the state in which the focus lens is driven to the stop state, and then whether or not the focus lens is to be driven again is determined in step S409 in FIG. Perform a restart judgment with.

  On the other hand, in step S703, the camera control unit 207 determines the lens driving speed and the driving method, and proceeds to step S704. Details of the lens drive setting in step S703 will be described later with reference to FIG. In step S704, the camera control unit 207 performs a lens driving process and ends the process. Details of the lens driving process in step S704 will be described later with reference to FIG.

  A series of processing described below is a characteristic part of the present embodiment, and an outline will be described first. In the case where the reliability of the image signal used for phase difference AF is low and the defocus amount based on the phase difference is unreliable (the defocus direction is reliable), in the present embodiment, a minute drive that drives the focus lens infinitely infinitely is executed. To do. Thereby, it is possible to acquire not only the phase difference AF but also the in-focus direction by the contrast AF. Here, in order to use the more reliable AF result, which AF is prioritized based on the reliability of the phase difference AF (the number of areas determined to be valid) and the focusing degree (focusing degree) by contrast AF. It is then determined whether to use for setting the driving direction. This determination process will be described in detail with reference to FIG. By changing the AF result used for setting the drive direction based on the determination result, it is possible to more reliably determine the in-focus direction.

  Next, the lens drive setting in step S703 of FIG. 7 will be described using the flowchart of FIG. In step S801, the camera control unit 207 determines whether the reliability of the image signal is a value better than the predetermined value γ. Here, the predetermined value γ (second level) is set to a threshold value with which the defocus amount calculated based on the phase difference of the image signal is sufficiently reliable. If the reliability is better than the predetermined value γ, it is determined that the distance to the subject has been measured, and the process proceeds to step S802. In step S802, since focus lens driving is performed for the measured distance, the search drive shift search counter is reset, and the process ends.

  On the other hand, if the reliability of distance measurement is worse than the predetermined value γ in step S801, the process proceeds to step S803, and the camera control unit 207 performs direction determination processing based on the first focus information (phase difference). This process will be described later with reference to FIG.

  In step S804, the camera control unit 207 performs direction determination processing based on the second focus information (contrast). This process will be described later with reference to FIG.

  Step S805 is a process for determining the effectiveness of the first and second focus information, which AF is in an effective state according to the reliability of the phase difference AF and the focus of the contrast AF. Make a decision. This process will be described later with reference to FIG.

  In step S806, the camera control unit 207 determines which of the first and second focus information is valid based on the result determined in step S805. If the first focus information is valid, the process proceeds to step S809, and if the second focus information is valid, the process proceeds to step S807.

  In step S807, the camera control unit 207 determines whether the direction determination (second direction determination) in contrast AF is completed. If completed, the process proceeds to step S810, and if not completed, the process proceeds to step S808.

  In step S808, the camera control unit 207 determines whether or not an elapsed time (first direction determination end count) after the phase difference AF result is specified is greater than or equal to a threshold value TH. If the first direction determination end count is greater than or equal to the threshold value TH, the process proceeds to step S810, and if not, the process proceeds to step S811. In this embodiment, the threshold value is 0.7 seconds, but can be set to an arbitrary value.

  Step S809 is a case where the phase difference AF is effective, and confirms whether or not the phase difference direction determination (first direction determination) has been completed. If completed, the process proceeds to step S810, and if not completed, the process proceeds to step S811.

  In step S810, since the drive direction has been determined, the search flag for starting the search drive is turned ON, and the process ends. On the other hand, in step S811, since the drive direction is not yet determined, the process ends in a search drive waiting state. In step S811, it may be shifted to search drive when a predetermined time has elapsed.

  Next, the lens driving process in step S704 in FIG. 7 will be described with reference to the flowchart in FIG.

  In step S901, the camera control unit 207 determines whether the search drive flag is off. If it is off, the process proceeds to step S902. If it is on, the process proceeds to step S903.

  In step S902, distance driving is performed based on the defocus amount calculated based on the phase difference of the image signal, and the lens driving process is terminated. The distance driving process is a process of converting the defocus amount calculated by the camera control unit 207 into the driving amount of the focus lens 103 and giving a driving command to the focus lens driving unit 105. On the other hand, in step S903, search (direction) driving is performed and the lens driving process is terminated.

  Next, the search drive processing in step S903 in FIG. 9 will be described using the flowchart in FIG. In step S1001, it is determined whether search driving is the first time. If it is the first time, the process proceeds to step S1002, and if it is not the first time, the process proceeds to step S1007.

  Steps S1002 to S1006 are processes for setting the drive direction. When search driving is the first time, it is necessary to determine the driving direction of the focus lens.

  In step S1002, the camera control unit 207 determines whether the direction is determined in step S807 or step S809 described above. If the direction is determined, the process proceeds to step S1003. If the direction is not determined, the process proceeds to step S1004. In step S1003, the camera control unit 207 sets the determined direction as the driving direction.

  On the other hand, in step S1004, the camera control unit 207 determines whether or not the current lens position is close to the closest end. If it is close to the close end, the process proceeds to step S1005, and if close to the infinite end, the process proceeds to step S1006.

  In step S1005, the camera control unit 207 sets the lens driving direction at the start of search driving to the closest direction. On the other hand, in step S1006, the lens driving direction at the start of search driving is set to an infinite direction. By setting the driving direction in this way, it is possible to shorten the time for searching and driving the entire lens driving region, and to shorten the longest time required to find the in-focus position by search driving. When the focus lens drive direction is set by the processing in steps S1002 to S1006, the process proceeds to step S1007.

  In step S1007, the camera control unit 207 controls to drive the focus lens with the set lens driving direction and lens driving speed, and the process proceeds to step S1008. In step S1008, the camera control unit 207 determines whether the focus lens has reached the closest end or the infinite end. If the end has been reached, the process proceeds to step S1009, and if not, the process proceeds to step S1010. In step S1009, the driving direction of the focus lens is reversed and the process proceeds to step S1010.

  In step S1010, the camera control unit 207 determines whether the reliability is better than the predetermined value γ. If the reliability is higher than the predetermined value γ, the process proceeds to step S1012. Otherwise, the process proceeds to step S1011.

  In step S1011, it is determined whether or not both the near end and the infinite end of the focus lens have been reached. If so, the process proceeds to step S1012. If not, the search drive process is terminated. In step S1012, the search drive flag is turned off and the search drive process is terminated.

  The condition for terminating the search drive is when the reliability becomes better than the predetermined value γ in step S1010, or when both the near end and the infinite end of the focus lens are reached in step S1011. The reliability threshold value γ set in S1010 is a value with which the defocus amount calculated based on at least the phase difference of the image signal can be trusted, similarly to the threshold value γ set in S901 in FIG. If the reliability is better than the threshold value γ, it can be determined that the in-focus position has been approached, so the search drive is stopped and the control is switched to the distance drive based on the defocus amount again. In addition, the fact that both the near end and the infinite end have been reached in step S1011 means that the entire focus drive area has been driven and the subject could not be specified. In this case, the search drive flag is turned off to return to the initial processing state. In a different form from the present embodiment, when the subject cannot be specified, it may be controlled to continue the search drive without turning off the search drive flag.

  Next, the direction determination process based on the first focus information in step S803 in FIG. 8 will be described with reference to FIG. Step S1101 is a process of adding a direction detection counter (search drive transition counter). The counter is added and the process proceeds to step S1102.

  In step S1102, the camera control unit 207 determines whether the search drive transition counter is equal to or greater than a predetermined number. If it is the predetermined number of times or more, the process proceeds to step S1103, and if not, the process proceeds to step S1105.

  In step S1103, the camera control unit 207 turns on a determination flag for direction determination based on the first focus information. In this embodiment, the direction determination flag is referred to, and the focus lens search drive is started.

  Step S1104 is processing to add a determination end count. This determination end counter monitors the elapsed time since the direction determination is completed, and is referred to in step S808 of FIG.

  On the other hand, step S1105 is processing to clear the determination end count. Since this process is performed when the search drive transition counter is less than the predetermined number of times and the direction cannot be specified, the counter is cleared. The above processing is performed and the processing is terminated.

  Next, the direction determination process based on the second focus information in step S804 in FIG. 8 will be described with reference to FIG. Step S1106 is processing for performing minute driving of the focus lens. This minute driving process will be described later with reference to FIGS.

  Step S1107 is processing for determining whether or not direction determination based on the second focus information has been completed. If the direction determination for minute driving has been completed by the process described later, the process proceeds to step S1108; otherwise, the process ends.

  In step S1108, a determination flag for determining the direction based on the second focus information is turned ON. The focus lens search drive is started with reference to this direction determination flag. The above processing is performed and the processing is terminated.

  Next, using FIG. 15A, the first and second focus information validity determination processing in step S805 in FIG. 8 is performed. Step S1501 is an effective area number calculation process based on the first focus information. Here, when there are a plurality of areas in the distance measurement frame as shown in FIG. 12D, the effective area is determined and the number thereof is calculated. Details of this processing will be described later with reference to FIG.

  Step S1502 is a focus degree calculation process based on the second focus information. Here, the degree of focus is calculated from the acquired contrast information. Details of this processing will be described later with reference to FIG.

  In step S1503, the camera control unit 207 determines whether or not there is a large blur based on the degree of focus calculated in step S1502. The large blurred state is a state where the degree of focus is low and the focus is greatly blurred. If so, the process proceeds to step S1504. Otherwise, the process proceeds to step S1505.

  In step S1504, it is determined whether the number of effective areas calculated in step S1501 is greater than TH1. If it is greater than TH1, the process proceeds to step S1508, and if it is less than TH1, the process proceeds to step S1509.

  On the other hand, in step S1505, the camera control unit 207 determines whether or not there is a small blur based on the degree of focus. The small blur state is a state in which the degree of focus is lower than that in the case where it is determined as the in-focus state, but the degree of focus is higher than the above-described large blur state. If it is a small blur state, the process proceeds to step S1506, and if not, it is determined that the focus state is achieved, and the process proceeds to step S1507.

  In step S1506, it is determined whether the number of effective areas calculated in step S1501 is greater than or equal to TH2. If it is greater than TH2, the process proceeds to step S1508, and if it is less than TH2, the process proceeds to step S1509. Here, TH2 is smaller than TH1.

On the other hand, in step S1507, it is determined whether or not the number of effective areas calculated in step S1501 is greater than or equal to TH3. If it is equal to or greater than TH3, the process proceeds to step S1508, and if it is less than TH3, the process proceeds to step S1509. Here, TH3 is smaller than TH2.
Step S1508 is processing to be reached when the effectiveness of the first focus information is high. Here, the valid flag of the first focus information is set, and the process ends. This flag is referred to in step S806 in FIG.

  Step S1509 is processing to be reached when the effectiveness of the second focus information is high. Here, a valid flag for the second focus information is set, and the process is terminated. This flag is referred to in step S806 in FIG.

  A schematic representation of this process is shown in FIG. C in the table indicates that the second focus information (contrast AF) is effective, and P indicates that the first focus information (phase difference AF) is effective. In the present embodiment, in the phase difference AF, a threshold is set based on the number of areas (reliability) whose directions are detected. When it is determined that the in-focus state is based on the second focus information, the threshold value for validating the phase difference AF result is set to 3 areas in the example of FIG. That is, if the number of effective areas calculated in step S1501 is 3 or more, it is determined that the detection result of phase difference AF is valid. On the other hand, in the case of large blur, the threshold value for validating the phase difference AF result is 5 areas. That is, this is a process of actively using the result of phase difference AF when the degree of focus based on contrast information is high, and actively using the result of contrast AF when the degree of focus is low.

  If the effective area of the phase difference AF is small, there is a high possibility that an incorrect defocus direction is determined. In particular, in the imaging plane phase difference AF, the symmetry of the pair of image signals is likely to be lost when away from the in-focus position, and the reliability of the AF result tends to be low. Therefore, in this embodiment, the degree of focus is simply determined using the contrast information, and the threshold value for enabling the phase difference AF is changed according to the determination result. Specifically, if the degree of focus is high, the threshold for enabling phase difference AF is set low, and if the degree of focus is low, the threshold for enabling phase difference AF is set high. .

  As described above, the feature of the present embodiment is that the condition for using the result of the phase difference AF is changed using the contrast information. In particular, in the case where the focus direction is determined and search drive is performed in a situation where the reliability of the phase difference AF is not high (the defocus amount is not reliable), it is determined whether the focus direction based on the phase difference AF is reliable. To do. Therefore, when the phase difference AF is reliable, it is possible to quickly perform the AF operation using the direction determination result of the phase difference AF, and when the phase difference AF is not reliable, the reliability is higher. An AF operation can be performed using a focusing direction based on contrast AF.

  Next, the calculation process of the number of effective areas based on the first focus information in step S1501 in FIG. 15A will be described with reference to FIG. In step S1601, the camera control unit 207 checks the distance measurement results for the total number of distance measurement area sensors as illustrated in FIG. The area number is incremented.

  In step S1602, the camera control unit 207 determines whether or not the reliability of the phase difference AF is better than the predetermined value δ based on the acquired image signal in the determination target area (detection region). . Here, the predetermined value δ (first level) is set to a threshold value at which the defocus direction is reliable based on the phase difference of the image signal. If the reliability is better than the predetermined value δ, it is determined that the area can identify the direction to the subject, and the process proceeds to step S1603. On the other hand, if the reliability is lower than δ, it is determined that the area cannot be specified, and the process proceeds to step S1604.

  In step S1603, the camera control unit 207 counts the number of effective areas. In step S1604, the camera control unit 207 determines whether all areas have been checked. If the determination has been completed, the process proceeds to step S1605. If not, the process proceeds to step S1601.

  In step S1605, the camera control unit 207 holds the number of effective areas. The number of retained areas is referred to in steps S1504, S1506, and S1507 in FIG. After the area holding process, the process ends.

  Next, the focus degree calculation process will be described with reference to FIG. FIG. 17A is a graph showing the contrast value generated from the imaging signal, with the horizontal axis indicating the position of the focus lens and the vertical axis indicating the evaluation value. There are two types of evaluation values in the present embodiment: MMP (1701) indicating the peak value of luminance contrast, and TEP (1702) that detects a specific frequency component from the imaging signal. In this embodiment, a frequency band of 1.5 MHz is used, but this is an example. The TEP has a mountain shape around the in-focus position (1703). This is a peak at the in-focus position because the edge of the subject becomes clearer as the focus lens approaches the in-focus state from a large blur, and the high-frequency component increases from the low-frequency component. On the other hand, since the MMP indicating the luminance contrast is a peak value, the size hardly changes unless the subject in the screen changes.

  FIG. 17B shows the simple degree of focus calculated using this characteristic. The simple focus degree 1704 is obtained by dividing TEP by MMP, and has a mountain shape as shown in FIG. In this embodiment, when this mountain shape is displayed at 100%, it is determined that 55% or more is in focus, 40% or more is small blur, and less than that is large blur. This value is an example, and may be changed depending on the subject and conditions.

  The lower the simple focus degree, the higher the possibility that the position of the focus lens is away from the focus position. The higher the simple focus degree, the higher the possibility that the focus lens is closer to the focus position. The focus degree determination result calculated here is referred to in steps S1503 and S1505 in FIG. 15A in order to determine a threshold value for the number of effective areas of phase difference AF.

  Next, the minute driving process in step S1106 of FIG. 11B will be described with reference to FIG. In step S1801, it is determined whether the counter indicating the operation state of minute driving is currently zero. If the counter is 0, the process proceeds to step S1802, and if it is not 0, the process proceeds to step S1803.

  In step S1802, the current AF evaluation value level is held as processing when the focus lens is on the close side. The AF evaluation value here is based on an imaging signal generated from charges accumulated in the imaging element when the focus lens is on the infinite side in step S1810 described later.

  On the other hand, in step S1803, it is determined whether or not the current counter is 1. If the counter is 1, the process proceeds to step S1804. If it is not 1, the process proceeds to step S1809.

  In step S1804, the vibration amplitude and the center movement amplitude for driving the focus lens in step S1808 described later are calculated. Usually, these amplitudes are generally set within the depth of focus.

  In step S1805, the infinite AF evaluation value level held in step S1802 is compared with the close AF evaluation value level held in step S1810 described later. If the former is large, the process proceeds to step S1806, and if the latter is large, the process proceeds to step S1807.

  In step S1806, the vibration amplitude and the center movement amplitude are added to obtain a drive amplitude. On the other hand, in step S1807, the vibration amplitude is set as the drive amplitude. That is, when the AF evaluation value on the infinite side is larger, the center position of the vibration is moved to the infinite side.

  In step S1808, based on the drive amplitude obtained in step S1806 or S1807, the camera control unit 207 controls to drive the focus lens in an infinite direction.

  On the other hand, in step S1809, it is determined whether or not the current counter is 2. If it is 2, the process proceeds to step S1810. If it is not 2, the process proceeds to step S1811.

  In step S1810, the current AF evaluation value level is held as processing when the focus lens is on the infinity side. The AF evaluation value here is based on the imaging signal generated from the charge accumulated in the imaging device when the focus lens is on the close side in step S1802.

  On the other hand, in step S1811, the vibration amplitude and center movement amplitude for driving the focus lens in step S1815 described later are calculated. Usually, these amplitudes are generally set within the depth of focus.

  In step S1812, the closest AF evaluation value level held in step S1810 is compared with the infinite AF evaluation value level held in step S1802. If the former is large, the process proceeds to step S1813. If the latter is large, the process proceeds to step S1814.

  In step S1813, the vibration amplitude and the center movement amplitude are added to obtain a drive amplitude. On the other hand, in step S1814, the vibration amplitude is set as the drive amplitude. That is, when the AF evaluation value on the near side is larger, the center position of the vibration is moved to the near side.

  In step S1815, the camera control unit 207 drives the focus lens in the closest direction based on the drive amplitude obtained in step S1813 or S1814.

  In step S1816, the camera control unit 207 determines whether a focal point exists in the same direction continuously for a predetermined number of times. If it exists, the process proceeds to step S1817. If it does not exist, the process proceeds to step S1818.

  In step S1817, it is determined that the direction can be determined, and the process proceeds to step S1818. In step S1818, if the counter indicating the operation state of minute driving is 3, the counter is reset to 0, and if it is any other value, the counter is added.

  The time course of the focus lens operation in this minute driving is shown in FIG. The upper part of the figure shows the vertical synchronization signal of the imaging signal, and the lower part of the figure shows the time on the horizontal axis and the position of the focus lens on the vertical axis. The AF evaluation value EVA for the charge accumulated in the image sensor at the time of label A is taken into the camera control unit at time TA. Also, the AF evaluation value EVB for the charge accumulated in the image sensor at the time of label B is taken into the camera control unit at time TB. At time TC, the AF evaluation values EVA and EVB are compared, and the vibration center is moved only when EVB in the figure is large. Note that the movement of the focus lens here is set to a movement amount that cannot be recognized on the screen with reference to the depth of focus.

  As described above, in the present embodiment, when the reliability of the phase difference AF is low (the defocus amount is unreliable) in the imaging apparatus including the imaging surface phase difference AF and the contrast AF, the contrast information is used. The threshold value for enabling the phase difference AF is changed. In particular, if AF is performed using the result of the phase difference in a state far away from the in-focus position (large blurring state), the possibility of driving the focus lens in the wrong direction increases. Thus, by using the degree of focus based on the contrast information and changing the use frequency of the result of the phase difference, it is possible to select an appropriate AF method according to the shooting situation.

(Second embodiment)
Next, the second embodiment will be described. The second embodiment performs different processing depending on whether or not zooming is in progress. In addition, about 2nd embodiment, only the difference with 1st embodiment is described, and the part which is the same content shall be abbreviate | omitted.

  Also in this embodiment, the configuration of the interchangeable lens camera shown in FIG. 1 is applied. In the present embodiment, the zoom lens 108 and the zoom lens driving unit 109 are configured.

  A series of processing described below is a characteristic part of processing during zooming in the present embodiment, and an outline will be described first. Since the F value and the focal length change during zooming, the reliability of the phase difference AF becomes low, and if the focus lens is driven using a defocus amount based on the result of the phase difference, blurring may occur. Therefore, in order to prevent blur, it is desirable to drive the focus lens using the contrast AF as much as possible during zooming.

  In the present embodiment, minute driving is performed to drive the focus lens to the close side and the infinite side during zooming. This makes it possible to determine the in-focus direction based on the contrast information. However, it may take a very long time to specify the in-focus position when the subject situation changes during zoom driving in the in-focus direction based on contrast information. Therefore, in the present embodiment, if the condition is satisfied, the result of the phase difference AF is used together, and the condition is changed using the degree of focus based on the contrast information. Specifically, when the degree of focus is relatively high, that is, close to the in-focus position to some extent, the result of phase difference AF is also used together if the phase difference reliability (number of effective areas) is good. On the other hand, when the degree of focus is low (large blur), priority is given to driving to the vicinity of the in-focus position quickly, and the results of contrast AF and phase difference AF are used in combination. These determination processes will be described later with reference to FIG. By determining whether to use phase difference AF together based on the determination result, smoother AF is possible even during zooming.

  Also in the present embodiment, the processes of FIGS. 4 to 7 described above are performed as in the first embodiment. The lens drive setting of this embodiment in step S703 in FIG. 7 will be described with reference to FIG.

  First, in step S2001, the camera control unit 207 determines whether the zoom lens is driven. If the zoom lens is driven, the process proceeds to step S2002. If the zoom lens is not driven, the process proceeds to step S2003. In step S2002, since the zoom drive is not being performed, the same lens drive setting (FIG. 8) as in the first embodiment is performed.

  On the other hand, in step S2003, the camera control unit 207 performs direction determination processing based on first focus information (phase difference) during zooming. This process will be described later with reference to FIG. When the direction is determined based on the first focus information, the process proceeds to step S2004.

  In step S2004, the camera control unit 207 determines the effectiveness of the first and second focus information. This process will be described later with reference to FIG. When the effectiveness is determined, the process proceeds to step S2005.

  In step S2005, the camera control unit 207 performs a determination process according to the degree of focus calculated in step S2402 of FIG. When the determined in-focus state is large blur, the process proceeds to step S2006, and when it is not large blur, the process proceeds to step S2007.

  In step S2006, the camera control unit 207 determines whether the direction determination flag based on the first focus information is ON. If it is ON, the process proceeds to step S2008, and the center movement flag based on the first focus information is set to ON. If it is not ON, the process proceeds to step S2009, and the center movement flag based on the first focus information is turned OFF.

  On the other hand, when the process proceeds to step S2007, the camera control unit 207 refers to the determination of the validity calculated in step S2004 and determines whether the first focus information is valid. If the first focus information is valid, the process proceeds to step S2006. If the first focus information is not valid, the process proceeds to step S2009.

  Next, the lens driving process of the present embodiment in step S704 in FIG. 7 will be described with reference to FIG. First, in step S2101, the camera control unit 207 determines whether the zoom lens is driven. When the zoom lens is driven, the process proceeds to step S2103, and when the zoom lens is not driven, the process proceeds to step S2102. In step S2102, since the zoom lens is not being driven, a lens driving process (FIG. 9) similar to that of the first embodiment is performed.

  In step S2103, the camera control unit 207 performs minute driving based on the second focus information. This process will be described later with reference to FIG.

  Next, the direction determination process based on the first focus information (phase difference) during zooming in step S2003 in FIG. 20 will be described with reference to FIG. In step S2201, the camera control unit 207 determines whether the reliability of the first focus information is better than the predetermined value δ. Here, a threshold value is set for the predetermined value δ so that the defocus direction based on the phase difference result is reliable. If the reliability is better than the predetermined value δ, the process proceeds to step S2202.

  In step S2202, the in-focus direction is specified based on the first focus information, and the process proceeds to step S2203. The predetermined value δ is set to a threshold value with which the defocus direction is reliable. In step S2203, the camera control unit 207 performs a process of turning on the direction determination flag of the first focus information, and then ends the process.

  On the other hand, if the reliability is worse than the predetermined value δ, the process proceeds to step S2204. In step S2204, the camera control unit 207 performs processing for turning off the direction determination flag of the first focus information, and then ends the processing.

  Next, the second focus information fine driving process executed in step S2103 of FIG. 21 will be described with reference to FIG. Since this process is the same flow as the flowchart of FIG. 18 described in the first embodiment, only the differences will be described. Note that the lower two digits of the numbers shown in this flowchart are the same as those in FIG.

  In step S2319, the camera control unit 207 refers to the above-described center movement flag to determine whether to move the vibration center position. Even when the center movement is unnecessary as a result of determining the center movement based on the AF evaluation value as in the first embodiment, the center movement flag based on the first focus information is set to ON in step S2008. Moves the center. Therefore, when the center movement flag is ON, the process proceeds to step S2306, and when it is OFF, the process proceeds to step S2307. When the process proceeds to step S2306, the drive amplitude of the focus lens is set so that the vibration center position is moved to the infinity side, and when the process proceeds to step S2307, the drive amplitude of the focus lens is set without moving the vibration center position. .

  Similarly, in step S2320, the camera control unit 207 determines whether to move the vibration center position with reference to the center movement flag. When the center movement flag is ON, the process proceeds to step S2313, and when it is OFF, the process proceeds to step S2314. If the process proceeds to step S2313, the focus lens drive amplitude is set so as to move the vibration center position to the closest side, and if the process proceeds to step S2314, the focus lens drive amplitude is set without moving the vibration center position. .

  Next, the effectiveness determination process during zooming in step S2004 of FIG. 20 will be described with reference to FIG. First, in step S2401, the camera control unit 207 performs the effective area number calculation process of the first focus information. This process is the same as step S1501 in FIG.

  Next, in step S2402, the camera control unit 207 performs a focus degree calculation process based on the second focus information. This process is the same as step S1502 in FIG.

  Next, in step S2403, the camera control unit 207 determines whether or not the degree of focus calculated in step S2402 is large blur. If so, the process proceeds to step S2407. If not, the process proceeds to step S2404.

  In step S2407, the camera control unit 207 sets a valid flag for the first focus information because it is in a large-blur state. In step S2408, the second focus information valid flag is set, and the process ends.

  On the other hand, in step S2404, the camera control unit determines whether the blur is small. If it is small blur, the process proceeds to step S2405. If it is not small blur (in-focus), the process proceeds to step S2406.

  In step S2405, the camera control unit 207 determines whether the number of effective areas calculated in step S2401 is greater than or equal to the threshold value TH4. If it is greater than TH4, the process proceeds to step S2409, and if it is less than TH4, the process proceeds to step S2410.

  On the other hand, in step S2406, it is determined whether the number of effective areas calculated in step S2401 is greater than or equal to the threshold value TH5. If it is greater than TH5, the process proceeds to step S2409, and if it is less than TH5, the process proceeds to step S2410. Here, TH5 is a value larger than TH4. Note that the thresholds TH4 and TH5 in this embodiment are set higher than the thresholds TH1 to TH3 in the first embodiment. This is because the F value and focal length change during zooming, and therefore, when the focus lens is driven using the first focus information, there is a higher possibility of blurring compared to when the zoom lens is not zooming.

  Step S2409 is processing when it is determined that the first focus information is a valid condition, and the camera control unit 207 sets the first focus information valid flag and ends the processing.

  On the other hand, step S2410 is processing when it is determined that the second focus information is a valid condition, and the camera control unit 207 sets the second focus information valid flag and ends the processing.

  A schematic diagram of this process is shown in FIG. C in the table indicates that the second focus information (contrast AF) is effective, and P indicates that the first focus information (phase difference AF) is effective. First, in the present embodiment, a threshold value based on the number of areas (reliability) in which directions are detected is set in the phase difference AF. In the example of FIG. 24B, when the focus state is determined based on the second focus information, the threshold value for validating the phase difference AF result is set to 7 areas. In the case of small blur, the threshold value for validating the phase difference AF result is set to 6 areas. This is because, during zooming, the reliability of the phase difference AF decreases due to changes in the F value and the focal length, and therefore the phase difference AF is used together only when the reliability of the first focus information is sufficiently high. Therefore, when the reliability of the first focus information is low, AF is performed using only the second focus information.

  On the other hand, in the case of large blurring, AF is performed using the first focus information and the second focus information regardless of the number of areas in which the direction is detected (reliability). This is because in the case where the degree of focus is low and the blur is large, it is more efficient to perform AF using both the contrast AF and the phase difference AF in order to drive the focus position as soon as possible. Note that if the in-focus direction determined by the first focus information is opposite to the in-focus direction determined by the second focus information, the result of the second focus information is given priority. This is because in the imaging plane phase difference AF, there is a high possibility that the distance measurement performance is lowered due to the symmetry of the image signal being lost in the case of large blurring. Note that the value shown in FIG. 24B can be set to an arbitrary value, and is not limited to this value.

  As described above, in the present embodiment, during zooming, basically, the result of the second focus information (contrast AF) is used positively, and when the focus level is low and it is desired to drive quickly to the focus position. The result of the first focus information (phase difference AF) is also used. With such control, a high-quality AF operation with less blur can be performed even during zooming.

(Other embodiments)
The object of the present invention can also be achieved as follows. That is, a storage medium storing a program code of software in which a procedure for realizing the functions of the above-described embodiments is stored is supplied to the system or apparatus. A computer (or CPU, MPU, etc.) of the system or apparatus reads out and executes the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the novel function of the present invention, and the storage medium storing the program code and the control program constitute the present invention.

  Examples of the storage medium for supplying the program code include a flexible disk, a hard disk, an optical disk, and a magneto-optical disk. Further, a CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD-R, magnetic tape, nonvolatile memory card, ROM, or the like can also be used.

  Further, by making the program code read by the computer executable, the functions of the above-described embodiments are realized. Furthermore, when the OS (operating system) running on the computer performs part or all of the actual processing based on the instruction of the program code, the functions of the above-described embodiments are realized by the processing. Is also included.

  Furthermore, the following cases are also included. First, the program code read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Thereafter, based on the instruction of the program code, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing.

  Although the present invention has been described in detail based on the preferred embodiments thereof, the present invention is not limited to these specific embodiments, and various forms within the scope of the present invention are also included in the present invention. It is.

DESCRIPTION OF SYMBOLS 20 Camera main body 103 Focus lens 105 Focus lens drive part 106 Lens control part 201 Image pick-up element 204 AF signal processing part 207 Camera control part 210 AF evaluation value generation part

Claims (15)

Imaging means for receiving and photoelectrically converting a light beam incident through a photographing optical system including a focus lens;
First detection means for detecting a phase difference between a pair of image signals output from the imaging means;
Second detection means for detecting contrast information from a signal output from the imaging means;
Control means for controlling the driving of the focus lens based on a detection result of at least one of the first detection means and the second detection means;
When the detection result by the first detection unit satisfies a predetermined condition, the control unit controls the driving of the focus lens using the detection result by the first detection unit, and the control unit controls the driving of the focus lens according to the contrast information. An automatic focusing apparatus characterized by changing a predetermined condition.   As the degree of focus determined based on the contrast information is higher, the control unit changes the predetermined condition so that the detection result by the first detection unit can be easily used for driving the focus lens. The automatic focusing apparatus according to claim 1.   When the detection result by the first detection means does not satisfy a predetermined condition, the control means does not use the detection result by the first detection means but uses the detection result by the second detection means. 3. The automatic focus adjusting apparatus according to claim 1, wherein the driving of the focus lens is controlled. The imaging means comprises a plurality of detection areas,
The first detection means detects a phase difference of the image signal output from each detection region,
The automatic focus adjustment according to any one of claims 1 to 3, wherein the predetermined condition is satisfied when the number of detection regions whose detection result reliability is higher than the first level is equal to or greater than a threshold value. apparatus.   The automatic focus adjustment apparatus according to claim 4, wherein the control unit sets the threshold smaller as the degree of focus determined based on the contrast information is higher. In the detection region used for driving the focus lens, when the reliability of the detection result by the first detection unit is lower than the second level, the control unit determines whether the detection result satisfies the predetermined condition. Determine whether
6. The automatic focusing apparatus according to claim 4, wherein the second level shows higher reliability than the first level. The control means detects a defocus amount and a focus direction based on detection results from the plurality of detection areas by the first detection means,
7. The second level according to claim 6, wherein the defocus amount is set to a reliable value, and the first level is set to a value at which the in-focus direction is reliable. Automatic focusing device. The photographing optical system further includes a zoom lens,
8. The control unit according to claim 4, wherein when the zoom lens is driven, the control unit sets the threshold value to be larger than that when the zoom lens is stopped. The automatic focusing device described in 1.   9. The control means, when the zoom lens is driven, the control means sets the threshold value larger as the degree of focus determined based on the contrast information is higher. The automatic focusing device described in 1.   When the zoom lens is driven and the detection result by the first detection means satisfies the predetermined condition, the control means detects the detection results of the first detection means and the second detection means. 10. The automatic focus adjustment apparatus according to claim 8, wherein the driving of the focus lens is controlled based on the above.   In the case where the zoom lens is driven, when the degree of focus determined based on the contrast information is lower than a predetermined degree, the control unit is configured to control the first detection unit and the second detection unit. The automatic focus adjustment apparatus according to claim 8, wherein the driving of the focus lens is controlled based on a detection result.   The automatic focus adjustment apparatus according to any one of claims 1 to 11, wherein a region in which the contrast information is detected by the second detection unit in the imaging unit includes a region corresponding to the detection region. . A method for controlling an automatic focus adjustment apparatus having an imaging means for receiving and photoelectrically converting a light beam incident through a photographing optical system including a focus lens,
A first detection step of detecting a phase difference between a pair of image signals output from the imaging means;
A second detection step of detecting contrast information from a signal output from the imaging means;
A control step for controlling the driving of the focus lens based on a detection result of at least one of the first detection step and the second detection step;
In the control step, when the detection result of the first detection step satisfies a predetermined condition, the driving of the focus lens is controlled using the detection result of the first detection step, and the detection is performed according to the contrast information. A control method for an automatic focusing apparatus, wherein a predetermined condition is changed.   A control program for an automatic focus adjustment device, characterized in that the computer is configured to cause a computer to execute the control method for an automatic focus adjustment device according to claim 13.   15. A storage medium storing a control program for the automatic focusing apparatus according to claim 14.

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