JP5904714B2 - FOCUS DETECTION DEVICE, ITS CONTROL METHOD, AND IMAGING DEVICE HAVING FOCUS DETECTION DEVICE - Google Patents

Description

The present invention relates to a focus detection device and a control method thereof, and more particularly, to a focus detection device capable of automatic focus detection by a plurality of methods and a control method thereof.
The present invention also relates to an imaging device having a focus detection device.

  2. Description of the Related Art Conventionally, for example, imaging apparatuses capable of detecting multiple types of automatic focus are known, such as automatic focus detection (phase difference AF) using a phase difference detection method and automatic focus detection (contrast AF) using a contrast evaluation method. .

  Patent Document 1 proposes a method of correcting the focus detection result of the phase difference detection method based on the focus detection result of the contrast evaluation method in the manufacturing process of the imaging device. In the imaging apparatus described in Patent Document 1, the position of the focus lens is controlled based on the focus detection result of the contrast evaluation method by imaging the adjustment chart TC. Next, the position of the distance measuring sensor is finely adjusted so that the output of the distance measuring sensor matches the subject distance corresponding to the lens position obtained by the focus detection result of the contrast evaluation method.

JP 2001-272592 A

  As described above, the imaging apparatus described in Patent Literature 1 can improve the accuracy of the focus detection result of the phase difference detection method with excellent responsiveness by using the focus detection result of the contrast evaluation method with high accuracy. However, the drive mechanism of the focus lens usually has “play” so that it can be driven smoothly. Since the influence of play on the driving accuracy varies depending on the driving direction, even if driving control is performed to the same target position, the arrival position is shifted depending on the driving direction of the focus lens.

  For example, when the focus detection result of the phase difference detection method after driving the focus lens in the infinity direction is corrected with the focus detection result of the contrast evaluation method obtained by driving the focus lens from infinity to the closest direction. Think. In this case, the focus lens position for which the focus detection result (defocus amount) by the phase difference detection method is obtained is different from the focus lens position obtained by the focus detection by the contrast evaluation method. As described above, when the focus lens driving direction is different between the phase difference detection type focus detection and the contrast evaluation type focus detection, the correction accuracy decreases.

  The present invention has been made in view of the problems of the prior art. An object of the present invention is to enable accurate acquisition of a correction value of a focus detection result by a phase difference detection method in a focus detection apparatus and a control method thereof capable of automatic focus detection by a phase difference detection method and a contrast evaluation method. To do.

The above-described objects are a focus detection unit that detects a defocus amount of an imaging lens by a phase difference detection method, a drive control unit that controls driving of a focus lens included in the imaging lens, and an evaluation that acquires a contrast evaluation value of a captured image. A value acquisition unit and a control unit. The control unit acquires the captured images captured at different positions of the focus lens by the evaluation value acquisition unit while moving the focus lens in one direction by the drive control unit. Using the contrast evaluation value and the position of the corresponding focus lens, the peak position, which is the position of the focus lens with the maximum contrast evaluation value, is determined, and the defocus amount corresponding to the peak position is detected by the focus detection means. Corresponding to the peak position determined from the defocus amount detected by the focus detection means The correction value calculation process, which calculates the correction value of the defocus amount detected by the focus detection means by subtracting the defocus amount that is detected, is moved to the close side when the focus lens is moved to the infinity side. As a correction value for the defocus amount detected by the focus detection means, the correction value for driving the infinity side used when the focus lens is driven to the infinity side and moved to the in-focus position. This is achieved by a focus detection device that calculates a near-side drive correction value used when driving to the near side and moving to the in-focus position.

  According to the present invention, in a focus detection apparatus capable of automatic focus detection using a phase difference detection method and a contrast evaluation method, and a control method thereof, it is possible to accurately acquire a correction value of a focus detection result by the phase difference detection method. Become.

1 is a block diagram illustrating a configuration example of a digital single-lens reflex camera as an example of an imaging apparatus according to an embodiment of the present invention. The schematic diagram explaining the example of arrangement | positioning of a focus detection area | region. The functional block diagram of the camera DSP in FIG. 6 is a flowchart for explaining a phase difference AF correction value acquisition operation in the digital single-lens reflex camera according to the embodiment of the present invention. The flowchart for demonstrating the correction value calculation process in FIG.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.
(First embodiment)
<Configuration of digital camera>
FIG. 1 is a block diagram illustrating a configuration example of a digital still camera (hereinafter simply referred to as a camera) as an example of an imaging apparatus according to an embodiment of the present invention. The camera 200 of this embodiment is a single-lens reflex camera with interchangeable lenses, but the present invention can be applied to any camera capable of automatic focus detection using a phase difference detection method and a contrast evaluation method.

  An imaging lens 100 is detachably attached to the camera 200 via a lens mounting mechanism of a mount unit (not shown). An electrical contact unit 107 is provided on the mount portion. The electrical contact unit 107 includes a communication bus line terminal including a communication clock line, a data transfer line, a data reception line, and a synchronization signal line for transmitting the charge accumulation timing of the image signal from the camera side to the lens side. Terminals are provided.

  The system controller 230 of the camera 200 and the lens controller 108 of the imaging lens 100 can communicate with each other through the electrical contact unit 107. For example, the system controller 230 controls driving of the focus lens 101 and the diaphragm 102 that adjusts the amount of incident light in the imaging lens 100 through communication with the lens controller 108. FIG. 1 shows only the focus lens 101 among the lenses constituting the imaging lens 100, but the imaging lens 100 is provided with a variable power lens and a fixed lens.

  A light beam from a subject (not shown) is guided to a quick return mirror 203 in the camera 200 through a plurality of lenses (including the focus lens 101) in the imaging lens 100 and the diaphragm 102. The quick return mirror 203 is driven up and down by the mirror drive mechanism 213, whereby a first position (illustrated) for guiding the light beam from the subject to the upper finder optical system and a second position for retracting out of the imaging optical path. It is possible to move to a position.

  The central part of the quick return mirror 203 is a half mirror, and when the quick return mirror 203 is in the down state (first position), a part of the light beam from the subject passes through the half mirror part. The light beam transmitted through the half mirror portion is reflected by the sub mirror 204 provided on the back side of the quick return mirror 203 and guided to the phase difference AF sensor unit 205.

  The phase difference AF sensor unit 205 and the focus detection circuit 206 constitute a phase difference detection type automatic focus detection unit (phase difference AF unit). The phase difference AF sensor unit 205 includes a pair of pupil division optical systems and a pair of line sensor groups, and each line sensor pair is provided at a position corresponding to the focus detection region.

  FIG. 2 shows an example in which 45 focus detection areas 251 are arranged on a two-dimensional imaging plane 250. In this case, the phase difference AF sensor unit 205 is provided with 45 pairs of line sensors each corresponding to one of the 45 focus detection areas. The image signals detected by each of the 45 pairs of line sensors are output to the focus detection circuit 206. The charge accumulation time of the line sensor is also output to the focus detection circuit 206.

  Here, the charge accumulation time of the line sensor is a time that is the middle of the period from the start to the end of the charge accumulation of the line sensor, and is a time that indicates the center of gravity of the charge accumulation timing. The focus detection circuit 206 detects a known phase difference based on the correlation calculation from the input image signal output of each line sensor, and a shift amount (defocus amount) between the current position of the focus lens 101 and the focus position of the subject. Is calculated.

  The system controller 230 can acquire a correction value for defocus calculation correction from the memory 109 and the nonvolatile system memory 237 through the lens controller 108, and can provide the correction value to the focus detection circuit 206. The focus detection circuit 206 can correct the focus detection result by performing an operation of subtracting the correction value from the calculated defocus amount. The defocus amount is calculated for each focus detection region, but there are various methods for determining the final one defocus amount using the value, and directly with the present invention. Description is omitted because it is not related.

  When the focus detection circuit 206 determines the defocus amount, the focus detection circuit 206 converts the defocus amount into a requested drive amount of the focus lens 101 according to a predetermined correspondence relationship. The obtained drive request amount is notified to the lens controller 108 as drive control means through the system controller 230, and the lens controller 108 controls the focal position of the focus lens 101 based on the drive request amount.

  On the other hand, the light beam reflected upward by the quick return mirror 203 in the down state reaches the eye of the photographer via a finder optical system including a finder screen 202, a pentaprism 201, and an eyepiece lens 207 existing on the focus surface. .

  In addition, the photometric unit 209 arranged to observe the light beam bent by the pentaprism 201 obliquely is divided into a plurality of divided regions in an area corresponding to a two-dimensional imaging plane of the light beam. Photometry is performed. The photometric result of each segmented area is output from the photometric unit 209 to the system controller 230.

  When the quick return mirror 203 moves to the up state during imaging, the light flux from the imaging lens 100 reaches the image sensor 212 through the optical filter 211 from the opening of the focal plane shutter 210 that is a mechanical shutter. The optical filter 211 has a function of cutting infrared rays to guide visible light to the image sensor 212 and a function as an optical low-pass filter.

  The focal plane shutter 210 has a front curtain and a rear curtain, and controls transmission and blocking of a light beam from the imaging lens 100.

  The camera 200 has a system controller 230 that controls the entire system. The system controller 230 is configured by a CPU, an MPU, or the like, and controls the operation of each circuit in the camera 200 and also controls the operation of the imaging lens 100 via the lens controller 108 by communication through the electrical contact unit 107.

  Similarly to the system controller 230, the lens controller 108 is also configured by a CPU, MPU, and the like, and controls the operation of each circuit in the imaging lens 100.

  In communication between the system controller 230 and the lens controller 108, a drive command, a stop command, a drive amount, and a required drive speed for the focus lens 101 in the imaging lens 100 are transmitted from the system controller 230. Further, the system controller 230 transmits a driving amount of the diaphragm 102, a driving speed, and a transmission request for various data on the lens side.

  At the time of focus driving, the system controller 230 issues a command for the lens driving direction, driving amount, and driving speed to the lens controller 108 by communication.

  When the lens controller 108 receives a lens driving command from the system controller 230, the lens controller 108 controls the lens driving mechanism 103 via the lens driving control unit 104. The lens drive mechanism 103 has a stepping motor as a drive source, and drives the focus lens 101 along the optical axis.

  When the lens controller 108 receives the aperture control command from the system controller 230, the lens controller 108 controls the aperture drive mechanism 105 that drives the aperture 102 via the aperture control drive unit 106, and controls the aperture 102 according to the received drive amount.

  The system controller 230 is also connected to the shutter control unit 215 and the photometry unit 209. The shutter control unit 215 controls driving of the front curtain and rear curtain of the focal plane shutter 210 in accordance with a signal from the system controller 230. The front and rear curtains of the focal plane shutter 210 have a spring as a drive source, and after the shutter travels, a spring charge is required for the next operation. Therefore, the shutter charge mechanism 214 performs a spring charge. Further, the system controller 230 is a program line in which the relationship between the exposure amount obtained from the output of a predetermined photometry area in the photometry unit 209 or the image sensor 212 and the charge accumulation time, exposure sensitivity, and aperture value of the image sensor 212 is defined. The figure is stored in a nonvolatile memory (not shown).

  The camera DSP 227 executes a calculation related to automatic focus (contrast AF) using a contrast evaluation method. As will be described later, the camera DSP 227 includes components for calculating a contrast evaluation value and determining the position and size of a region where the contrast evaluation value is calculated. The contrast evaluation value is a value indicating the in-focus state of the optical system including the focus lens 101 in contrast AF.

  In addition to the system controller 230, a timing generator 219, an A / D converter 217 (via a selector 222), a video memory 221, and a work memory 226 are connected to the camera DSP 227.

  The image sensor 212 is controlled by an output from a driver 218 that controls horizontal driving and vertical driving for each pixel based on a signal from a timing generator 219 that determines the overall driving timing. The image sensor 212 photoelectrically converts the subject image to generate and output an image signal. The image signal generated by the image sensor 212 is amplified by the CDS / AGC circuit 216 and converted into a digital signal by the A / D converter 217. The camera 200 of this embodiment can set the imaging frame rate of the imaging element 212 by an operation input from the operation switch 232. When the timing generator 219 outputs according to the set imaging frame rate, the imaging frame rate of the imaging device 212 is controlled to be a set value. The imaging frame rate may be changed in accordance with a plurality of imaging modes including a moving image imaging mode for generating a moving image signal and a still image imaging mode for generating a still image signal.

  The output from the A / D converter 217 is input to the memory controller 228 via the selector 222 that selects a signal based on the signal from the system controller 230, and is all transferred to the DRAM 229 that is a frame memory.

  In a video camera or a compact digital camera, a finder display (live view) or the like is performed by the monitor display unit 220 by transferring the transfer result to the video memory 221 periodically (every frame) in an imaging standby state. On the other hand, in a normal single-lens reflex digital camera, live view display cannot be performed because the image pickup device 212 is shielded from light by the quick return mirror 203 and the focal plane shutter 210 in the image pickup standby state.

  However, live view is also possible with a single-lens reflex digital camera by opening the focal plane shutter 210 after the quick return mirror 203 is retracted from the imaging optical path. Further, when the camera DSP 227 or the system controller 230 processes the image signal from the image sensor 212 during live view, a contrast evaluation value indicating the in-focus state of the optical system including the focus lens 101 can be obtained. Then, contrast AF can be performed using this contrast evaluation value.

  At the time of imaging, each pixel data for one frame is read from the DRAM 229 according to a control signal from the system controller 230, subjected to image processing by the camera DSP 227, and temporarily stored in the work memory 226. Then, the data in the work memory 226 is compressed by the compression / decompression circuit 225 based on a predetermined compression format, and the result is stored in the external nonvolatile memory 224. As the nonvolatile memory 224, a detachable recording medium such as a semiconductor memory card is usually used. Further, any nonvolatile recording medium such as a magnetic disk or an optical disk can be used as the nonvolatile memory 224.

  Further, the display unit 231 connected to the system controller 230 displays the operation state of the camera set or selected by the switches included in the operation switch 232, such as a liquid crystal display panel, an LED (light emitting diode), an organic EL display panel, and the like. The display element displays.

  The operation switch 232 is an input device group for the user to perform operation input for various setting items of the camera 200, and may include an arbitrary input device. The release switch SW1 233 is turned on when the release button is half-pressed, and the system controller 230 starts imaging preparation operations such as photometry and focus detection when the SW1 233 is turned on. The release switch SW2 234 is turned on when the release button is fully pressed, and the system controller 230 starts an imaging operation (charge accumulation and charge readout operation for capturing a still image for recording) when the SW2 234 is turned on. Let The live view mode switch 235 is a switch for controlling on / off of the live view display. The moving image switch 236 is a switch for starting a continuous imaging operation (repeated charge accumulation and charge reading operation for acquiring a moving image).

  On the other hand, in the imaging lens 100 as a lens unit, a memory 109 is connected to the lens controller 108. At least a part of the memory 109 is non-volatile, and performance information such as the focal length of the imaging lens 100, an open aperture value, and aperture drive speed information that can be set, and a lens ID (specific information for identifying the imaging lens 100). Lens identification information) is stored. A correction value for correcting an output of a focus detection circuit 206 described later is also stored in the memory 109. When the camera 200 is not a lens interchangeable type, the constituent elements related to the control of the imaging lens 100 are included in the main body. In this case, the system controller 230 and a non-volatile memory (or EEPROM 223) not shown may function as the lens controller 108 and the memory 109. That is, the system controller 230

  The performance information and the lens ID (also referred to as lens information) are transmitted to the system controller 230 by initial communication performed between the system controller 230 and the lens controller 108 when the imaging lens 100 is attached to the camera 200. The The system controller 230 stores the received lens information in the EEPROM 223, for example.

  Further, the imaging lens 100 is provided with a lens position information detection unit 110 for detecting position information of the focus lens 101. The lens position information detected by the lens position information detection unit 110 is read by the lens controller 108. The lens position information is used for driving control of the focus lens 101 and is transmitted to the system controller 230 via the electrical contact unit 107.

  The lens position information detection unit 110 includes, for example, a pulse encoder that detects the number of rotation pulses of a motor that constitutes a lens driving mechanism. The output is connected to a hardware counter (not shown) in the lens controller 108, and when the lens is driven, its position information is counted by hardware. When the lens controller 108 reads the lens position information, it accesses the internal hardware counter register and reads the stored counter value.

Next, circuit blocks in the camera DSP 227 will be described with reference to FIG.
The image signal generated by the image sensor 212 is amplified by the CDS / AGC circuit 216 as described above, and converted into digital data by the A / D converter 217. The digitized image data is input to the camera DSP 227 via the selector 222.

  In order to calculate a contrast evaluation value used for contrast AF, image data input to the camera DSP 227 is first input to the focus detection area extraction block 242 via the DSP internal memory 241 in the camera DSP 227. The focus detection area extraction block 242 extracts the focus detection area and its neighboring image from the image data for the entire screen, and supplies the extracted image to the contrast evaluation value calculation block 243. The size of the focus detection area is desirably about 1/5 to 1/10, where the size of the entire screen is 1. It should be noted that the position and size of the focus detection area in the screen can be set for the focus detection area extraction block 242 by the system controller 230. The contrast evaluation value calculation block 243 extracts a predetermined frequency component from the focus detection area and the image in the vicinity thereof by digital filter calculation, and outputs the extracted frequency component to the system controller 230 as a contrast evaluation value.

<Phase difference AF correction value acquisition operation>
Next, the phase difference AF correction value acquisition operation in the camera 200 of the present embodiment will be described with reference to the flowchart of FIG. In the following operations, it is assumed that the subject distance is constant.

  The correction value acquisition operation is started in response to the system controller 230 detecting that a correction value acquisition instruction is input through the operation switch 232, for example. It is assumed that the camera 200 is powered on in advance.

  First, in step S <b> 401, the system controller 230 performs phase difference (defocus amount) detection using the phase difference AF sensor unit 205 and the focus detection circuit 206 in order to determine an initial position for contrast evaluation driving.

In step S402, the system controller 230 calculates a correction value for the near side drive. Details of the correction value calculation processing for the near side drive will be described with reference to the flowchart of FIG.
The system controller 230 differs from the defocus amount detected in S401 by a predetermined amount different from the defocus amount to the infinity side (or from the position corresponding to the detected defocus amount by a predetermined amount from the defocus amount to the infinity side. The focus lens 101 is moved to (position). Thereby, it is possible to start acquisition of the contrast evaluation value from the vicinity of the peak position of the contrast evaluation value, and to shorten the time until peak detection. Instead of detecting the phase difference, contrast AF may be performed, and the focus lens 101 may be moved to a position away from the in-focus position by a predetermined defocus amount toward the infinity side.

  That is, in order to search for the peak position of the contrast evaluation value, it is necessary to acquire the contrast evaluation value before and after the peak position, so the focus lens 101 is moved to a position shifted from the position corresponding to the detected defocus amount. doing. However, from the viewpoint of shortening the peak detection time, it is preferable to set the shift amount as small as possible within the range in which the peak can be detected. For example, the amount of deviation can be made to correspond to a distance of about 2 to 3 times the calculation interval of the contrast evaluation value during contrast evaluation driving. When the lens controller 108 notifies that the movement of the focus lens 101 is completed, the system controller 230 advances the process to S502.

  In S502, the system controller 230 moves the quick return mirror 203 to the second position outside the imaging optical path (mirror up) through the mirror driving mechanism 213 in order to perform contrast evaluation driving. Further, the focal plane shutter 210 is opened through the shutter control unit 215. Then, the system controller 230 starts a continuous imaging operation similar to that when performing live view display, for example.

  In step S503, the system controller 230 starts contrast evaluation driving with the position of the focus lens moved in step S501 (that is, a position on the infinity side from the in-focus lens position detected by the phase difference AF) as an initial position. . The system controller 230 communicates with the lens controller 108 and instructs the focus lens 101 to move in one direction (closest direction) at a predetermined speed. Then, for example, the camera DSP 227 periodically acquires an imaging contrast evaluation value by using captured image data obtained by continuous imaging, and detects the peak position by detecting that the evaluation value has changed from increasing to decreasing. Explore. During the search, the system controller 230 acquires the position information of the focus lens 101 through the lens controller 108 together with the acquisition of the contrast evaluation value.

  In step S504, the system controller 230 determines whether the position of the focus lens 101 has passed the peak position where the contrast evaluation value is maximized. For example, when detecting that the contrast evaluation value has changed from increasing to decreasing, the system controller 230 can determine that the position of the focus lens 101 has passed the peak position (a peak has been detected). If it is determined that the position of the focus lens 101 has passed the peak position where the contrast evaluation value is maximized, the system controller 230 shifts the processing to S505, and if not, shifts the processing to S503.

  In step S <b> 505, the system controller 230 stops driving the focus lens 101 and acquires the stop position of the focus lens 101 detected by the lens position information detection unit 110 through the lens controller 108. Then, the system controller 230 calculates the difference between the focus lens stop position and the peak position of the contrast evaluation value.

  First, the system controller 230 determines the peak position from the relationship between the contrast evaluation value and the position of the focus lens during contrast evaluation driving. The peak position can be determined by a known and arbitrary method. For example, the peak position can be obtained by interpolation calculation or the like from the relationship between a plurality of contrast evaluation values acquired before and after the peak position and the corresponding focus lens position. Alternatively, when the contrast evaluation value acquisition interval at the time of contrast evaluation driving is sufficiently fine, the focus lens position where the acquired contrast evaluation value is maximized may be set as the peak position.

  Next, the system controller 230 calculates the difference (deviation amount from the peak position) between the focus lens stop position and the peak position. This difference is the moving distance from when the focus lens 101 passes the peak position of the contrast evaluation value until the next time when the contrast evaluation value is acquired to detect the peak and the focus lens 101 is actually stopped by the stop instruction. It is. Then, the system controller 230 calculates a defocus amount corresponding to the difference (deviation amount).

  In step S <b> 506, the system controller 230 moves the quick return mirror 203 to the first position (mirror down) through the mirror driving mechanism 213 so that the light beam reflected by the sub mirror 204 is guided to the phase difference AF sensor unit 205.

  In step S <b> 507, the system controller 230 performs phase difference AF (detection of the defocus amount from the in-focus position) using the phase difference AF sensor unit 205 and the focus detection circuit 206. At this time, the focus lens 101 is not moved to the peak position, but remains stopped by the stop instruction. This is because when the focus lens 101 is moved to the peak position, it is driven in the opposite direction to that during contrast evaluation driving. Therefore, if the defocus amount is calculated by moving the focus lens 101 to the peak position, the accuracy of the correction value is increased. It is because it falls.

  The system controller 230 subtracts the defocus amount (calculated in S505) corresponding to the shift amount between the focus lens position detected by the focus detection circuit 206 and the peak position from the defocus amount obtained by the focus detection circuit 206. A correction value for the near side drive is calculated.

  In S403, the system controller 230 performs the same operation by reversing one direction for driving the focus lens in the contrast evaluation drive in S402 (infinite direction), and calculates a correction value for infinite side driving. The difference from S402 is that the initial position of the contrast evaluation drive is set to a position that is a predetermined amount away from the in-focus position obtained in S401. Thereby, the driving direction (peak direction) of the focus lens at the time of contrast evaluation driving becomes the infinity direction. The detailed operation is as described in the correction value calculation process for the near side drive with reference to FIG. 5 except that the initial position of the focus evaluation drive in S501 is different.

  In step S404, the system controller 230 performs at least one of two magnitude determinations. The first is a determination as to whether or not the difference in focus position obtained by contrast AF in both S402 and S403 is greater than or equal to a predetermined threshold. Thus, it can be determined how much the driving error of the focus lens varies depending on the driving direction. The second is a determination as to whether or not the difference between the near-field drive correction value obtained in S402 and the infinity-side drive correction value obtained in S403 is greater than or equal to a predetermined threshold. This is to determine the magnitude of the difference in correction value depending on the driving direction of the focus lens. As a result of the determination, if any of these two differences is greater than or equal to the threshold, the system controller 230 advances to S406. Otherwise, the process proceeds to S405. Note that an appropriate value can be set in advance for the threshold used for the determination in consideration of the required focusing accuracy.

  In S405, the system controller 230 can determine that the influence of the driving error due to the driving direction of the focus lens is small (can be ignored), and thus stores a correction value not depending on the driving direction in the memory 109 via the lens controller 108. The correction value stored here may be any of a correction value for infinity side driving, a correction value for near side driving, and an average value of these correction values.

  In step S <b> 406, the system controller 230 determines whether the correction value for each driving direction can be stored in the memory 109 included in the imaging lens 100. For this determination, for example, the free space in the memory 109 is inquired from the system controller 230 to the lens controller 108 and can be stored if there is free space equal to or larger than the total data size of the two correction values. When the system controller 230 determines that the correction value for each driving direction can be stored in the memory 109, the correction value for both the infinity side driving value and the correction value for the near side driving are supplied to the memory 109 through the lens controller 108. (S407).

  On the other hand, when it is determined that both correction values cannot be stored in the memory 109, the system controller 230 stores the average value of the correction value for infinity side driving and the correction value for the near side driving to the memory 109 through the lens controller 108. Store (S408).

  Further, the system controller 230 corrects the difference between the correction value for the infinity side drive and the correction value for the near side drive, and the correction value for the infinity side drive and the correction value for the near side drive. Calculate as the remaining amount. Then, the system controller 230 stores the calculated correction remaining amount in the nonvolatile system memory 237 in association with the identification information (lens ID) of the imaging lens 100 (S409). By storing the remaining correction amount in the camera 200, even when the memory 109 of the imaging lens 100 has no margin, it is possible to perform correction with high accuracy according to the driving direction of the focus lens. When it is not necessary to identify the imaging lens 100, such as when the imaging lens 100 is not interchangeable, it is not necessary to store it in association with the identification information of the imaging lens 100.

  The system controller 230 acquires the correction value stored in the memory 109 when the imaging lens 100 is attached to the camera 200 or when the camera 200 is turned on, for example. Then, the type and number of stored correction values are determined.

  The correction value is then used when the imaging lens 100 is attached to the camera 200 and phase difference AF is performed during imaging. For example, a correction is made for the defocus amount detected by the phase difference AF sensor unit 205 and the focus detection circuit 206 at the time of focus detection in the recording image pickup preparation operation, which is started when the release switch SW1 233 is turned on. A value can be applied. In this case, turning on the release switch SW1 233 (half-pressing the release switch) corresponds to an instruction to start the imaging preparation operation.

  When correcting the focus detection result by the phase difference AF, the system controller 230 determines a driving direction for moving the focus lens to the in-focus position from the current position of the focus lens and the defocus amount. Then, the system controller 230 corrects the defocus amount by using the correction value for infinite edge side driving if the driving direction is on the infinity side, and the correction value for near side driving if the driving direction is on the near side. As a result, even when the drive accuracy of the focus lens drive mechanism of the imaging lens 100 changes depending on the drive direction, it is possible to perform appropriate correction.

Further, when only the average correction value is stored in the imaging lens and the correction remaining amount for each driving direction is stored in the imaging apparatus body, the average correction value is associated with the lens ID of the mounted imaging lens. An appropriate correction value can be obtained from the correction remaining amount for each driving direction.
Further, if only one correction value that does not depend on the driving direction is stored in the imaging lens, the correction value is applied regardless of the driving direction of the focus lens.

  As described above, according to the present embodiment, in the focus detection device capable of correcting the focus detection result of the phase difference AF using the correction value calculated using the focus detection result of the contrast AF, for each driving direction of the focus lens. The correction value is calculated. Therefore, even when focus detection is performed using an imaging lens in which the drive error of the drive mechanism of the focus lens varies greatly depending on the drive direction, appropriate correction can be performed and the focus detection accuracy of phase difference AF can be improved. .

  Further, in the calculation of the correction value, the defocus amount is calculated without performing the drive for returning the focus lens stopped after the peak position during the contrast evaluation drive to the peak position. Then, the defocus amount corresponding to the peak position is obtained by subtracting the defocus amount corresponding to the difference between the peak position and the lens stop position, and the focus lens position corresponding to the defocus amount and the peak position detected by contrast AF Is calculated as a correction value. Therefore, compared to a configuration in which the focus lens is moved to the peak position before calculating the defocus amount, it is possible to suppress the influence of the drive tolerance of the focus lens on the correction value, and the automatic detection by the phase difference detection method. The accuracy of focus detection can be further improved.

(Other embodiments)
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 (9)

Focus detection means for detecting the defocus amount of the imaging lens by a phase difference detection method;
Drive control means for controlling drive of a focus lens included in the imaging lens;
Evaluation value acquisition means for acquiring a contrast evaluation value of a captured image;
Control means,
The control means includes
While moving the focus lens in one direction by the drive control unit, the contrast evaluation value acquired by the evaluation value acquisition unit for the captured images captured at different positions of the focus lens, and the corresponding position of the focus lens And determining a peak position that is the position of the focus lens at which the contrast evaluation value is maximized,
A defocus amount corresponding to the peak position is detected by the focus detection unit;
Calculating a correction value of the defocus amount detected by the focus detection unit by subtracting a defocus amount corresponding to the determined peak position from the defocus amount detected by the focus detection unit;
Correction value calculation process
When the focus lens is moved to the infinity side and when moved to the close side, the focus lens is moved to the infinity side as a correction value for the defocus amount detected by the focus detection unit. To calculate the infinity side correction value used when moving to the in-focus position and the near-side drive correction value used when driving to the near position and moving to the in-focus position. A focus detection device. The focus detection apparatus according to claim 1, wherein detection of a defocus amount by the focus detection unit and acquisition of the captured image are performed exclusively. In the correction value calculation process, the control means
It is determined whether the position of the focus lens has passed a peak position where the contrast evaluation value is maximum,
When it is determined that the position of the focus lens has passed the peak position, the movement of the focus lens is stopped, and the stop position of the focus lens is acquired.
The focus detection means detects the defocus amount without moving the focus lens from the stop position,
By subtracting the defocus amount corresponding to the difference between the determined peak position and the stop position from the defocus amount detected by the focus detection unit, the defocus amount detected by the focus detection unit is reduced. Calculate the correction value,
A focus detecting apparatus according to claim 1 or 2, characterized in that. The focus detection apparatus according to any one of claims 1 to 3 ,
An image sensor that captures the captured image;
An imaging apparatus, wherein the imaging lens is detachable. The imaging apparatus according to claim 4, wherein the control unit stores the correction value for driving the infinity side and the correction value for driving the near side in the imaging lens. The control means, when the amount of free space in the storage means of the imaging lens is insufficient to store the correction value for driving the infinity side and the correction value for driving the close side,
    Storing an average value of the correction value for driving the infinity side and the correction value for driving the near side in a storage unit included in the imaging lens;
    A storage unit included in the imaging device in which the difference between the average value and the correction value for driving the infinity side and the difference between the average value and the correction value for driving the near side are associated with identification information of the imaging lens. The imaging device according to claim 4, wherein the imaging device is stored in the storage device. The control means includes
In response to an instruction to start the imaging preparation operation of the recording image, the focus detection unit detects the defocus amount,
The direction in which the focus lens is moved is determined from the defocus amount and the position of the focus lens, and the correction corresponding to the direction is selected from the correction value for driving at infinity and the correction value for driving at the near side. Using the value to correct the defocus amount,
Causing the drive control means to move the focus lens with a focus lens position based on the corrected defocus amount as a focus position;
The imaging apparatus according to any one of claims 4 to 6, wherein the imaging apparatus is configured as described above. The imaging apparatus according to claim 4, wherein the drive control unit is provided in the imaging lens. Focus detection means for detecting the defocus amount of the imaging lens by a phase difference detection method;
Drive control means for controlling drive of a focus lens included in the imaging lens;
Evaluation value acquisition means for acquiring a contrast evaluation value of a captured image;
A focus detection device control method comprising:
The control means is
While moving the focus lens in one direction by the drive control unit, the contrast evaluation value acquired by the evaluation value acquisition unit for the captured images captured at different positions of the focus lens, and the corresponding position of the focus lens And determining a peak position that is the position of the focus lens at which the contrast evaluation value is maximized,
A defocus amount corresponding to the peak position is detected by the focus detection unit;
Calculating a correction value of the defocus amount detected by the focus detection unit by subtracting a defocus amount corresponding to the determined peak position from the defocus amount detected by the focus detection unit;
The correction value calculation process
When the focus lens is moved to the infinity side and when moved to the close side, the focus lens is moved to the infinity side as a correction value for the defocus amount detected by the focus detection unit. To calculate the infinity side correction value used when moving to the in-focus position and the near-side drive correction value used when driving to the near position and moving to the in-focus position. A method for controlling a focus detection apparatus.

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