JP6076106B2 - Imaging apparatus and imaging method - Google Patents

Description

  The present invention relates to an imaging apparatus and an imaging method capable of capturing an image with high accuracy even for a subject whose speed changes rapidly.

  2. Description of the Related Art Conventionally, an imaging apparatus that performs control so that a moving object is focused has been put into practical use.

  For example, in Patent Document 1, position control is performed by the predicted position control unit so that the focus of the photographing lens matches the position of the subject image predicted at the time of exposure, and the defocus amount and the defocus amount are controlled by the position speed control unit. A technique is disclosed in which the focus of the photographic lens follows the movement trajectory of the subject image by feeding back the amount of time change to the lens driving means.

  Further, in Patent Document 2, a plurality of images of a subject are captured by focus bracket shooting while changing the focus lens position, sequentially stored in an image memory, an instruction area is set according to an operation of a photographer's operation unit, A technique is disclosed in which an AF evaluation value in an instruction area of each focus bracket image stored in a memory is calculated, and a focus bracket image having the highest AF evaluation value in the calculated instruction area is selected and displayed on a display unit. Yes.

JP-A-8-101335 JP 2009-111635 A

  In Patent Document 1, even if a moving subject is followed to some extent, a tracking delay occurs with respect to a subject whose speed changes rapidly, and the focus cannot be accurately adjusted. Further, cited document 2 relates to a technique for photographing a stopped subject, and it is impossible to focus on a moving subject with high accuracy.

  An object of the present invention is to provide an imaging apparatus and an imaging method capable of performing imaging while accurately focusing on a moving subject.

In order to solve the above-described problem, an imaging apparatus according to a first aspect of the present invention is an imaging apparatus that performs imaging by performing focus detection based on an image plane phase difference phase difference method, while driving a photographic lens. An imaging unit that performs imaging, a storage unit that temporarily stores image data of the predetermined number of frames, a focus detection unit that detects a focus position of the imaging lens every time imaging is performed by the imaging unit, and the focusing Each time a position is detected, a calculation unit that calculates a moving speed of the subject based on the in-focus position, a shooting lens driving unit that drives the shooting lens at a speed according to the moving speed of the subject, and the storage A selection unit that selects the image data with the best focus from image data of a predetermined number of frames stored in the unit, and a recording medium that stores the image data selected by the selection unit, and includes focus detection Take to do Calculates the standard speed that is the driving speed of the photographic lens so that the diameter of the circle of confusion of the image formed on the imaging surface changes by a value smaller than the diameter of the allowable circle of confusion during the period of repeatedly acquiring image data from the element An object that is the driving speed of the photographic lens by dividing the data representing the degree of variation in the position of the photographic lens at each time when a plurality of immediately preceding continuous image data is acquired by a predetermined time A subject position instability countermeasure speed calculating unit that calculates a position instability countermeasure speed, and the driving unit is configured to provide a speed corresponding to the moving speed of the subject, the standard speed, and the subject position instability countermeasure speed. The photographing lens is driven based on the above .

According to a second aspect of the present invention, the imaging apparatus according to the first aspect further includes a tracking unit that tracks a subject, and the focus detection unit detects a focal position of the subject tracked by the tracking unit. .

An imaging apparatus according to claim 3 is an imaging apparatus that performs imaging by performing focus detection based on an image plane phase difference phase difference method, and an imaging unit that performs imaging of a predetermined number of frames while driving an imaging lens; A storage unit that temporarily stores the image data of the predetermined number of frames, a focus detection unit that detects the in-focus position of the photographic lens every time the imaging unit performs imaging, and each time the in-focus position is detected A calculation unit that calculates a moving speed of the subject based on the in-focus position, a shooting lens driving unit that drives the shooting lens at a speed corresponding to the moving speed of the subject, and a predetermined frame stored in the storage unit. A selection unit that selects the most focused image data from a plurality of image data, and a recording medium that stores the image data selected by the selection unit, and performs a first-stage push-down operation by a user operation. When detected In addition, a release operation detection unit for detecting a second-stage push-down operation following the first-stage push-down operation is further provided, and until the second-stage push-down operation is detected, by the imaging unit, A predetermined number of frames are shot while the photographic lens is driven in the first cycle, and after the second-stage push-down operation is detected, the photographic lens is driven at a cycle shorter than the first cycle by the imaging unit. Shooting for a predetermined number of frames .

According to a fourth aspect of the present invention, there is provided an imaging method capable of performing focus detection based on an image plane phase difference phase difference method, and performing imaging of a predetermined number of frames while driving an imaging lens by an imaging unit. A step of temporarily storing the image data of the predetermined number of frames in a storage unit, a step of detecting a focus position of the taking lens every time the image pickup unit performs shooting by a focus detection unit, and the focus position Calculating the moving speed of the subject based on the in-focus position, driving the photographic lens at a speed corresponding to the moving speed of the subject, and a predetermined value stored in the storage unit In order to perform focus detection, the method includes the step of selecting the most focused image data from the image data of the number of frames and the step of storing the selected image data in a recording medium. The standard speed, which is the driving speed of the photographic lens, is such that the diameter of the circle of confusion of the image formed on the imaging surface changes by a value smaller than the diameter of the allowable circle of confusion during the period of repeatedly acquiring image data from the image sensor. The data representing the degree of variation in the position of the photographic lens at each time at which a plurality of immediately preceding consecutive image data is acquired is divided by a predetermined time to determine the subject position that is the photographic lens driving speed. A step of calculating a stability countermeasure speed, and in the step of driving the photographing lens, the speed based on the moving speed of the subject, the standard speed, and the subject position instability countermeasure speed Drive the taking lens .

According to a fifth aspect of the present invention, in the imaging method capable of performing focus detection based on the image plane phase difference phase difference method, a step of photographing a predetermined number of frames while driving the photographing lens by the imaging unit. A step of temporarily storing the image data of the predetermined number of frames in a storage unit, a step of detecting a focus position of the taking lens every time the image pickup unit performs shooting by a focus detection unit, and the focus position Calculating the moving speed of the subject based on the in-focus position, driving the photographic lens at a speed corresponding to the moving speed of the subject, and a predetermined value stored in the storage unit Selecting the most focused image data from the image data of the number of frames, and storing the selected image data in a recording medium. A step of detecting a step-down operation, and a step of detecting a step-down operation of the second step following the step-down operation of the first step, wherein the step of detecting the second step is detected in the step of shooting the predetermined number of frames. Until a predetermined number of frames are shot by the imaging unit while driving the imaging lens in the first period until the second-stage push-down operation is detected. A predetermined number of frames are shot while driving the taking lens at a cycle shorter than one cycle .

  According to the present invention, it is possible to capture an accurately focused image even for a subject whose speed changes rapidly.

It is a block diagram which shows the structure of the imaging device common to Embodiments 1-2 of this invention. It is a figure which shows the pixel arrangement | sequence of an image pick-up element common to Embodiments 1-2 of this invention. 2 shows a configuration of a photographing pixel common to Embodiments 1 and 2 of the present invention. 2 shows a configuration of a focus detection pixel in which a right region of a microlens is shielded, which is common to Embodiments 1 and 2 of the present invention. 4 shows a configuration of a focus detection pixel in which a left region of a microlens is shielded, which is common to Embodiments 1 and 2 of the present invention. It is a graph for demonstrating the drive of a focus lens common to Embodiment 1-2 of this invention. It is a flowchart showing the flow of camera operation | movement in Embodiment 1 of this invention. It is a subroutine showing the flow of the operation | movement of CAF control during 1st release operation continuation common to Embodiment 1-2 of this invention. This is focus history information common to the first and second embodiments of the present invention. It is a subroutine showing the flow of the operation | movement of this exposure drive start common to Embodiments 1-2 of this invention. It is a flowchart showing the flow of camera operation | movement in Embodiment 2 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
Embodiment 1 of the present invention will be described below with reference to the drawings.

  FIG. 1 is a configuration diagram of an imaging apparatus according to Embodiment 1 of the present invention. The imaging apparatus illustrated in FIG. 1 includes an interchangeable lens 100 and a camera body 200. In this imaging apparatus, the interchangeable lens 100 is detachably attached to the camera body 200 via a lens mount (not shown) provided on the camera body 200.

  The interchangeable lens 100 includes a photographing lens 101, a photographing lens driving unit 102, a photographing lens control unit 103, and a storage unit 104. Here, the actual interchangeable lens 100 further includes an aperture control mechanism, a zoom mechanism, and the like, which are not shown in FIG.

  The photographing lens 101 is an optical system including a focus lens, and generates an optical image of a subject on the image sensor 201 of the camera body 200. The taking lens driving unit 102 has a driving mechanism such as a motor, and moves the focus lens in the optical axis direction in accordance with a control signal from the lens control unit 103.

  The photographing lens control unit 103 is an LSI in which a microcomputer and a control circuit that controls each unit in the interchangeable lens 100 are integrated. The lens control unit 103 controls the driving of the photographing lens 101 by sending a control signal to the photographing lens driving unit 102 based on the control signal output from the main body control unit 203 of the camera body 200. Details of drive control of the photographic lens 101 will be described later.

  The storage unit 104 stores unique characteristic information for each interchangeable lens 100. The photographing lens control unit 103 transmits the characteristic information stored in the storage unit 104 to the main body control unit 203 in response to a request from the main body control unit 203.

  Here, in the above-described example, the photographing lens control unit 103 is an LSI in which a microcomputer and a control circuit that controls each unit in the interchangeable lens 100 are integrated. However, the microcomputer and the control circuit are not necessarily integrated, and may be constituted by a plurality of LSIs.

  The camera body 200 includes an image sensor 201, a liquid crystal display unit 202, a body control unit 203, a mount contact 204, a storage unit 205, and a recording medium 206.

  The image sensor 201 converts an optical image incident through the interchangeable lens 100 into an electric signal (image signal). The image sensor 201 is composed of a CCD image sensor, a MOS image sensor, or the like. Focus detection pixels based on a so-called phase difference method are arranged in the image generation pixels of the image sensor 201. A defocus amount (corresponding to a pin and a shift amount from the imaging position of the photographing lens 101 to the in-focus position) can be calculated based on the pixel signal for focus detection. The method of obtaining the defocus amount based on the pixel signal output from the focus detection pixel arranged in the image generation pixel is hereinafter referred to as an image plane phase difference method.

  The liquid crystal display unit 202 is, for example, a liquid crystal display unit provided on the back surface of the camera body 200. The liquid crystal display unit 202 displays an image represented by display image data generated by the main body control unit 203 based on the image signal output from the image sensor 201.

  The main body control unit 203 is an LSI in which a CPU, a control circuit that controls each unit in the camera main body 200, and a signal processing circuit that performs various signal processing are integrated. The main body control unit 203 controls each unit in the camera main body 200 and executes various operation sequences. The main body control unit 203 has a function as a control unit, and synchronizes the control signal to the lens control unit 103 via the lens mount and the exposure operation of the image sensor 201 and the drive operation of the focus lens. For this purpose, a synchronization signal VD is output. The main body control unit 203 also controls the operation of the image sensor 201 and converts an image signal output from the image sensor 201 into image data that is a digital signal. In this case, the main body control unit 203 performs various signal processing such as white balance control on the image data. Further, the main body control unit 203 controls the display of images on the liquid crystal display unit 202 by outputting image data obtained by various signal processes to the liquid crystal display unit 202.

  The main body control unit 203 calculates a defocus amount, outputs a control signal for driving the photographing lens 101 based on the defocus amount, and calculates a moving speed of the subject, and a storage unit 205. A selection unit that selects the most focused image from a plurality of frames of image data temporarily stored in the image, and a tracking unit that tracks a subject to be focused in a plane perpendicular to the optical axis of the photographing lens 101 have.

  A storage unit 205 is a volatile memory with a built-in camera body, and temporarily stores image data of a plurality of frames shot continuously. The recording medium 206 is a recording medium such as a memory card that can be attached to and detached from the camera body. On this recording medium 206, image data selected from a plurality of frames of continuous image data is recorded.

  Here, in the above-described example, the main body control unit 203 is an LSI in which a microcomputer, a control circuit that controls each unit in the camera main body 200, and a signal processing circuit that performs various signal processing are integrated. However, these may be constituted by a plurality of LSIs.

  The mount contact 204 is provided in the lens mount and is a contact for connecting the lens control unit 103 and the main body control unit 203 so as to communicate with each other.

  The release operation detecting unit 207 performs a first-step depression operation of the release operation button by the user operation (hereinafter referred to as “1st release operation”) and a release operation button by the user operation that operates following the 1st release operation. This is for detecting a two-stage push-down operation (hereinafter referred to as “2nd release operation”). Here, the actual camera body 200 includes a shooting condition setting unit for setting various shooting conditions such as a shooting mode, a shake correction unit for correcting the shake of the camera body 200, and the like. However, illustration is abbreviate | omitted.

  Of the configurations of the imaging apparatus described above, the imaging element 201 and the main body control unit 203 constitute an imaging unit and a focus detection unit of the present invention.

  FIG. 2 is a diagram illustrating a pixel array of the image sensor 201 in the present embodiment. As shown in FIG. 2, the imaging element 201 in the present embodiment includes a shooting pixel 2011 and a focus detection pixel row 2012. FIG. 2 shows a pixel arrangement of 3 pixels in the vertical direction and 16 pixels in the horizontal direction. However, the actual image sensor 201 is composed of a plurality of pixel groups in the vertical and horizontal directions, with a pixel group as shown in FIG. 2 as a unit.

   The imaging pixel 2011 is a pixel used for obtaining captured image data recorded on the recording medium 206, and is formed in a two-dimensional shape as shown in FIG. Here, FIG. 2 shows a Bayer array in which the pixel arrangement is a primary color system, a pixel having red sensitivity is indicated as an R pixel, a pixel having green sensitivity is indicated as a G pixel, and a pixel having blue sensitivity is indicated as a B pixel. Yes. However, the color filter array need not necessarily be a Bayer array. Note that a condensing microlens is disposed on the upper surface of each pixel in FIG. 2, but the microlens is not shown in FIG.

  The focus detection pixel row 2012 is a pixel used for autofocus (hereinafter referred to as “phase difference AF”) based on the phase difference method, and is formed in the imaging surface of the image sensor 201. In FIG. 2, the focus detection pixel row 2012 is formed along the horizontal direction of the image sensor 201. A plurality of focus detection pixel pairs are formed at the position of the G pixel in the focus detection pixel column 2012 as described above. Each focus detection pixel pair includes a focus detection pixel 2012l and a focus detection pixel 2012r that are spaced apart by a predetermined interval (one pixel in FIG. 2). Further, when viewed from the pixel rows, the focus detection pixels 2012l and the focus detection pixels 2012r are arranged apart from each other by a predetermined interval. FIG. 2 is an example in which 8 pixels are spaced apart.

  3 to 5 are diagrams illustrating a detailed configuration of pixels formed in the image sensor 202. FIG. Here, FIG. 3 shows a configuration of the imaging pixel 2011. FIG. 4 shows the configuration of the focus detection pixel 2012l, and FIG. 5 shows the configuration of the focus detection pixel 2012r.

   As illustrated in FIG. 3, the imaging pixel 2011 includes a microlens 301 and a photoelectric conversion element 302.

  The microlens 301 is a lens designed to form an image on the photoelectric conversion element 302 with light beams that have passed through different pupil regions divided symmetrically of the photographing lens 101. The photoelectric conversion element 302 is, for example, a photodiode, and converts the light beam imaged through the microlens 301 into an electric signal and outputs it.

  As shown in FIGS. 4 and 5, the focus detection pixel 20121 includes a microlens 301, a photoelectric conversion element 302, and a light shielding member 303.

  The microlens 301 and the photoelectric conversion element 302 are the same as those arranged in the photographing pixel 2011.

  As shown in FIG. 4, the light shielding member 303 of the focus detection pixel 2012l is formed so as to shield the right region of the microlens 301, and the light beam Ll incident from the left region of the microlens 301 is converted into the photoelectric conversion element 302. To form an image. As shown in FIG. 5, the light shielding member 303 of the focus detection pixel 2012r is formed so as to shield the left region of the microlens 301, and the photoelectric conversion element 302 converts the light beam Lr incident from the right region of the microlens 301. To form an image.

  By detecting the phase difference between the image signal generated by the focus detection pixel 2012l and the image signal generated by the focus detection pixel 2012r as described above, the defocus amount can be obtained by a known method. it can.

  Next, the operation of the camera of the present embodiment will be described with reference to FIGS.

  FIG. 6 is a graph for explaining the driving of the focus lens constituting the photographing lens 101 in the image pickup apparatus of the present embodiment. The horizontal axis represents time, the vertical axis represents the position of the focus lens of the photographing lens 101, and is on the paper surface. The direction is the position of the focus lens that focuses on the subject at the near distance (Near), and the lower direction is the position of the focus lens that focuses on the object at the far distance (Far). A solid line S is obtained by converting the image plane movement locus of the subject into the locus of the focus lens. A dotted line P is obtained by converting the image plane movement locus when the image plane of the subject is just located on the imaging plane of the imaging element 201 into the locus of the focus lens. The difference between the solid line S and the dotted line P corresponds to the defocus amount calculated based on the image plane phase difference method. Accordingly, when the solid line S and the dotted line P coincide with each other, it indicates that the imaging surface of the photographing lens and the imaging surface of the image sensor 201 are coincident and in focus. Further, when the solid line S is in the Far direction with respect to the dotted line P, the focus lens is driven in the Near direction in order to focus on the subject. Conversely, when the solid line S is in the Near direction with respect to the dotted line P, the focus lens is driven in the Far direction to focus on the subject.

  Next, the camera operation of this embodiment will be described based on the flowchart of FIG. Note that the operations described in this flowchart are controlled by the main body control unit 203 unless otherwise specified.

  In step S701, it is determined whether or not the first release operation has been detected by the user. Until the first release operation is detected by the user, the defocus amount is not detected and the lens is not driven. When the first release operation is detected in step S701, the defocus amount is calculated by the calculation unit in the main body control unit 203 in step S702. Next, the calculation unit in the main body control unit 203 instructs the photographing lens control unit 103 to control the focus lens included in the photographing lens 100 based on the calculated defocus amount. Until the second release operation is detected, the defocus amount is continuously detected by the image plane phase difference method, and the lens is driven in accordance with the moving speed of the subject. This is referred to as “1st release operation continuing CAF control”. Next, the CAF control during the 1st release operation will be described in detail with reference to FIG.

  FIG. 8 is a subroutine showing the flow of CAF control operation during the 1st release operation. First, in step S801, image data is acquired after the image sensor 201 is exposed, and the first defocus amount is calculated. In FIG. 6, triangles indicate the timing for acquiring image data in the CAF control during the 1st release operation.

  Next, in step S802, it is determined whether the defocus amount calculated in step S702 is reliable based on a known arithmetic expression. If it is determined in step S802 that there is no reliability, a scan operation for driving the focus lens of the photographing lens 201 back and forth is performed in step S803, and then the operations in steps S801 and S802 are repeated. If it is determined in step S802 that there is reliability, predetermined information is calculated based on the defocus amount calculated in step S801, and focusing history information as shown in FIG. 9 is stored. The data to be saved is as follows.

The focus history information shown in FIG. 9 is in FIFO format. When a new defocus amount is calculated, the data of elements 0 to 5 is copied to elements 1 to 6, the image number is pic_no [0], and the latest defocus amount is calculated. The focus amount is copied to def [0], the in-focus position is set to pos [0], and the image data acquisition time used to calculate the defocus amount is copied to time [0]. The in-focus position (pos []) is the number of pulses (hereinafter referred to as “LDP (Lens Drive Pulse)”) for driving the pulse motor included in the photographing lens driving unit 102, and can be calculated as follows.

(Expression 1) pos [0] = LDP + def2ldp (def [0]) at the time of acquisition of phase difference detection image data

Here, def2ldp (def [0]) is a function for converting the defocus amount (def [0]) to LDP. Specifically, an LDP corresponding to a predetermined defocus amount is obtained by referring to a memory that stores in advance information that tabulates the relationship between the LDP and the defocus amount.

  Next, in step S805, it is determined whether or not the defocus amount is large, that is, whether or not the absolute value of the defocus amount is large (for example, whether or not the defocus amount is 10 times or more of the permissible circle of confusion). If the absolute value of the defocus amount is large, the current lens position is greatly deviated from the in-focus position, and therefore in step S806, the lens is driven at high speed based on the detected defocus amount.

  If the defocus amount is not so large, it is next determined in step S807 whether or not the subject is moving. Whether the subject is moving is determined based on whether there is a temporal change in the defocus amount. If it is determined in step S807 that the subject is moving, in step S808, the focus lens constituting the photographing lens 101 is driven so that the subject is focused following the movement of the subject. Here, the moving speed of the subject is calculated as follows using the focusing history information of FIG.

First, from the focus history information (time [n], pos [n]), an approximate straight line of a linear expression as shown in Expression 2 is calculated by the least square method.

(Formula 2) pos = A × time + B

As the focus history information used for calculating the approximate expression, information of a preset number obtained by photographing a plurality of latest frames is used. For example, as the in-focus history information, information obtained by photographing the last six consecutive frames is used, and n = 0, 1, 2, 3,. In the present embodiment, 6 is used, but an appropriate positive integer such as 5, 7, 8 or the like may be used regardless of 6.

  This coefficient A [LDP / ms] indicates the moving speed of the subject, and the lens driving speed is set to this A.

  Next, in step 809, an image is displayed on the liquid crystal display unit 202 based on the image data acquired in step S801.

  Next, in step S810, it is determined whether or not the first release operation has been released. As a result, when the 1st release operation is released, the process returns from the CAF control subroutine while the 1st release operation continues. If it is determined in step S810 that the 1st release operation has not been released, it is next determined in step S811 whether or not the 2nd release operation has been detected by the user. If the 2nd release operation is not detected, the process returns to step S801 and the above-described operation is repeated. The repetition cycle is 1/60 [sec]. That is, in the CAF during the 1st release operation, calculation for focus detection is performed every time image data is acquired from the image sensor at a cycle of 60 [frame / s] from the image sensor, and the drive of the focus lens is updated. If a 2nd release operation is detected in step S811, the process returns from the CAF control subroutine while the 1st release operation is continuing.

  Therefore, until the 1st release operation is not canceled and the 2nd release operation is performed, focus detection is performed repeatedly at a predetermined cycle, for example, 60 fps, and the focus lens is adapted to follow the movement of the subject. Is driven.

  FIG. 6 shows an example in which a plurality of exposure operations are continuously performed and the photographic lens 101 is driven and controlled so as to follow the movement of the subject and be in focus. In the CAF control during the 1st release operation, as long as the speed of the subject changes smoothly, good follow-up performance in focus is shown. However, when the speed of the subject changes suddenly, problems such as a tracking delay occur. In the CAF control during the 1st release operation, the acquired image data is merely used for image display by the liquid crystal display unit 202, and thus no particular problem occurs. Even when the image is not displayed, it is only necessary to maintain the focus lens at a position close to the in-focus position so that shooting can be performed with smooth transition to the main exposure driving described below. Accuracy is not always necessary. However, since the image data provided for recording described below is required to have higher accuracy of focusing, as described below, drive control of the photographing lens 101 different from the CAF control during the 1st release operation is performed. Is going.

  Returning to FIG. 7, when the operation of the CAF control subroutine during the 1st release operation is completed, it is next determined in step S703 whether or not the 1st release operation has been released. When the 1st release operation is released, the process returns to step S701, and the operation described above is repeated.

  If the first release operation is not released in step S703, then in step S704, the calculation unit of the main body control unit 203 performs main exposure driving (after step S704 in FIG. 7 (2nd release) (step 2). The driving of the focus lens after the operation is referred to as the main exposure driving.) During continuous shooting in (), the driving control of the photographing lens 101 is instructed to focus. The photographing lens driving unit 102 controls driving of the photographing lens 101 based on an instruction from the photographing lens control unit 103.

  Next, with reference to FIG. 10, the operation of the subroutine for starting the main exposure drive in step S704 will be described.

In step S1001, the position of the focus lens is in the near direction with respect to the dotted line P based on the sign of the defocus amount calculated based on the image data acquired immediately before the start of the main exposure in the CAF control period during the 1st release operation. Or on the dotted line P or in the FAR direction. Next, the following processing is performed according to the determination result of step S1001.
(1) When the position of the focus lens is in the Near direction or on the dotted line P In step S1002, the focus lens drive speed (hereinafter referred to as "LD speed") is calculated based on Expression 3. In step S1003, the focus lens is driven in the Far direction.

(Expression 3) LD speed [LDP / s] = Standard speed + Subject position instability countermeasure speed + A

Here, the standard speed is defined as N1 [frame / s], which is a cycle for acquiring image data from the image sensor for focus detection, and is the most among the image data acquired in this N1 [frame / s] cycle. When the cycle of selecting focused image data and recording it on the recording medium 206 is N2 [frame / s], the standard speed is that the focus lens included in the taking lens 101 is driven by 1 / N1 [sec]. In this case, the diameter of the circle of confusion of the image formed on the image pickup surface of the image pickup device 201 changes at a rate that substantially corresponds to the diameter of the allowable circle of confusion.

That is, as a general formula for standard speed:
Standard speed [LDP / s] = def2ldp (Fδ) / (1 / N1) sec
And Here, F is the aperture value (Fno) at the time of main exposure, and δ is the diameter of the allowable circle of confusion.

In this embodiment, N1 = 120, N2 = 20,
Standard speed [LDP / s] = def2ldp (Fδ) / (1/120) [LDP / s]
It becomes.

The standard speed is a value in which the diameter of the circle of confusion of the image formed on the imaging surface of the image sensor 201 when the focus lens included in the photographing lens 101 is driven by 1 / N1 [sec] is smaller than the allowable circle of confusion. Only need to change speed, for example,
Standard speed [LDP / s] = def2ldp (Fδ × 5/6) / (1 / N1) [LDP / s]
It is good.

The subject position instability countermeasure speed is obtained by normalizing the residual S in unit time when the approximate straight line is calculated by the least square method based on Equation 2. In the present embodiment, when an average value S of residuals, which is a difference between the approximate straight line obtained by Expression 2 and each pos [x] (x = 0 to 5),
Subject position instability countermeasure speed = S / (1/120) [LDP / s]
And When the subject is firmly placed on the approximate straight line, the residual S is small, so the subject position instability countermeasure speed is small.

Note that the subject position instability countermeasure speed may be any value that represents the degree of variation in the movement speed of the subject.
(2) When the position of the focus lens is in the Far direction In step S1004, the LD speed is calculated based on Equation 4, and in step S1005, the focus lens is driven in the Near direction. In this case, only the sign differs from the case where the position of the focus lens is in the Near direction or on the dotted line P.

(Expression 4) LD speed [LDP / s] =-(standard speed + subject position instability countermeasure speed) + A

Here, A is the moving speed of the subject calculated last in the CAF control during the 1st release operation.

  Returning to FIG. 7, when the main exposure driving is started in step S704, main exposure image data is acquired in step S705. In step S705, image data for recording (hereinafter referred to as “main exposure image data”) is acquired. The circles in FIG. 6 represent the timing for acquiring the main exposure image data. The main exposure image data is acquired at a speed that is at least five times the number of images that the user wants to leave. In the present embodiment, as described above, the sampling cycle for acquiring the image data from the image sensor is 120 [frame / sec], which is faster than 60 [frame / sec], which is the sampling cycle during the CAF operation during the 1st release operation described above. Frame / s], and the cycle of selecting the most focused image data from the image data acquired in the sampling cycle of 120 [frame / s] and recording it on the recording medium 206 is 20 [frame / s]. To do. That is, every time six frames are taken, the most focused image data is recorded on the recording medium 206. The acquired image is subjected to various image processing and temporarily stored in the storage unit 205. The storage unit 205 is a temporary holding volatile memory and is built in the camera.

  Next, in step S706, a defocus amount is calculated based on the focus detection image data included in the acquired main exposure image data, and is stored in def [x] of the focus history information (x is 0 to 5). Variable). The defocus amount is calculated by a known method using the focus detection pixel data from the main exposure image data acquired at 60 [frame / s] fps. Next, the calculated defocus amount (def [x]) is converted into LDP, and the in-focus position (pos [x]) is calculated based on the equation (1) and stored as in-focus history information. Further, the time (time [x]) at the time of image data acquisition used for calculating the defocus amount and the image number (pic_no [x]) are stored as focusing history information.

  In step S707, the moving speed A of the subject is calculated based on Equation 2. Next, in step S708, it is determined whether the driving direction of the focus lens (hereinafter referred to as “LD direction”) should be maintained or reversed. This determination is made based on the following conditions.

  Judgment conditions: (Total number of shots after 2nd release)% (N1 / N2) == When 0, the LD direction is reversed.

  Here, “%” indicates a multiplication / revolution. In this embodiment, since N1 = 120 and N2 = 20, the LD direction is reversed when (total number of shots after 2nd release)% 6 == 0.

  If it is determined in step S708 that the LD direction is reversed, then in step S709, the LD direction is reversed and the LD speed is updated. Here, the LD speed is calculated based on the formula (3) or the formula (4). That is, if the LD speed before the LD direction is reversed in step S708 is calculated based on the formula (3), the LD speed is calculated using the formula (4). On the other hand, when the LD speed before reversing the LD direction is calculated based on Expression (4) in Step S708, the LD speed is calculated using Expression (3).

  Next, in step S710, the defocus amount (def [0] to def [) of the main exposure image data in which the lens drive has been in the same direction at the timing when the lens drive direction is reversed by the selection unit of the main body control unit 203. 5]), the image data number (pic_no []) corresponding to the smallest defocus amount is determined, and the image data corresponding to the determined number is stored in the recording medium 206.

  If it is determined in step S708 that the LD direction is not reversed, in step S711, the moving speed A of the subject is calculated based on equation 2 while maintaining the LD direction, and equation (3) or equation is calculated. The LD speed is updated based on (4).

  An example of the main exposure driving described above is shown in FIG. In FIG. 6, black circles represent acquisition timing of main exposure image data recorded on the recording medium 206.

  According to the present embodiment, a predetermined number of images are shot while driving the focus lens in the same direction so as to follow the moving speed of the subject, and then the drive lens is reversed and the focus lens is similarly set. The above-mentioned predetermined number of shots are taken while driving in the direction, and the most focused image data among the images taken in the same direction drive period is recorded on the recording medium. As a result, it is possible to capture an accurately focused image even for a subject whose speed changes rapidly.

  That is, according to the present embodiment, when the change in the subject speed is smooth, the subject position instability countermeasure speed is small, so the contribution of the subject position instability countermeasure speed to the LD speed is relatively small, and the standard speed A corresponding to the speed and the moving speed of the subject becomes dominant. Each time one frame is taken, the focus lens is converted into a change in the amount of blur on the imaging surface at a standard speed, and is moved six times in the same direction while moving by an amount corresponding to an allowable circle of confusion, and then the drive direction is reversed. Since the same operation is repeated, the image data whose blur amount is equal to or smaller than the diameter of the permissible circle of confusion is surely included in the image data of 6 frames for the stationary subject. On the other hand, the subject position instability countermeasure speed is dominant for a subject whose subject moving speed changes abruptly. It is possible to shoot a focused image.

  Further, according to the present embodiment, the focus lens is driven while shooting at a longer cycle than after the 2nd release operation after the 1st release operation is performed until the 2nd release operation is performed. The focus lens can be driven while reducing power consumption.

  In this embodiment, the sampling cycle for acquiring image data from the image sensor for focus detection is N1 [frame / s], and the image data acquired in the sampling cycle of N1 [frame / s] N2 = 20 and N2 = 20 when the cycle of selecting the most focused image data from N and recording on the recording medium 206 is N2 [frame / s]. However, the present invention is not limited to this. N1 = 60 and N2 = 10, and the value of N1 / N2 is not limited to 6, but may be 5 or 10, for example.

  Next, Embodiment 2 will be described with reference to FIG.

[Embodiment 2]
In the present embodiment, there are a plurality of distance measuring points in the imaging screen, and the first release operation similar to that in the first embodiment is continued while tracking the subject to be focused in a plane perpendicular to the optical axis of the photographing lens 101. CAF control and main exposure driving are performed.

  In the description of the present embodiment, only differences from the first embodiment will be described, and other descriptions will be omitted. In addition, in FIG. 11 according to the present embodiment, operation steps representing the same processes as those in FIG. 7 according to the first embodiment will be described with the same numbers.

  Steps S701 to S705 in FIG. 11 are the same as those in FIG. When the main exposure image data is acquired in step S705, in step S1101, the tracking unit of the main body control unit 203 tracks the subject to be focused in the captured image by a known method. In step S706, the defocus amount for the subject tracked in step S1101 is detected based on the same image plane phase difference method as that in the first embodiment. The operations in steps S707 to S712 are the same as those in the first embodiment.

  According to the present embodiment, since the focus lens is driven while shooting at a longer cycle than after the 2nd release operation after the 1st release operation is performed until the 2nd release operation is performed, power consumption is reduced. The follow-up drive of the focus lens can be performed while reducing. In this embodiment, the subject to be focused is tracked in a plane perpendicular to the optical axis of the photographing lens, and the focus lens is driven in the same direction so as to follow the moving speed of the tracked subject. The same number of shots are taken, and then the predetermined number of shots are taken, and then the predetermined number of shots are shot while the driving direction is reversed and the focus lens is driven in the same direction. Since the most focused image data among the images photographed in the period is recorded on the recording medium, in addition to the effect of the first embodiment described above, the speed rapidly increases while moving a wide area of the photographing screen. It is possible to shoot a focused image with high accuracy even for a changing subject.

  Note that the present invention is not limited to the above-described embodiment, and the constituent elements can be modified and embodied without departing from the spirit of the invention in the implementation stage. Various inventions can also be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined. Thus, various modifications and applications are possible without departing from the spirit of the invention.

DESCRIPTION OF SYMBOLS 100 ... Interchangeable lens 101 ... Shooting lens 102 ... Shooting lens drive part 103 ... Shooting lens control part 104 ... Memory | storage part 200 ... Camera body 201 ... Image pick-up element 202 ... Liquid crystal display part 203 ... Main body control part 204 ... Mount contact 205 ... Memory | storage part

Claims (5)

In an imaging device that performs imaging by performing focus detection based on an image plane phase difference phase difference method,
An imaging unit that captures a predetermined number of frames while driving the imaging lens;
A storage unit for temporarily storing the image data of the predetermined number of frames;
A focus detection unit that detects the in-focus position of the photographic lens every time shooting is performed by the imaging unit;
A calculation unit that calculates a moving speed of a subject based on the in-focus position each time the in-focus position is detected;
A photographic lens driving unit that drives the photographic lens at a speed corresponding to the moving speed of the subject;
A selection unit that selects image data that is most focused from image data of a predetermined number of frames stored in the storage unit;
A recording medium for storing the image data selected by the selection unit;
Equipped with a,
Driving a photographic lens so that the diameter of the circle of confusion of the image formed on the imaging surface changes by a value smaller than the diameter of the permissible circle of confusion during the period of repeatedly acquiring image data from the image sensor for focus detection A standard speed calculator that calculates the standard speed,
Calculates the subject position instability countermeasure speed, which is the driving speed of the photographic lens, by dividing the data representing the degree of variation in the position of the photographic lens at each time when a plurality of previous consecutive image data was acquired by a predetermined time. Subject position instability countermeasure speed calculation unit,
Further comprising
The drive unit includes a speed corresponding to the moving speed of the subject, and the standard speed, to that imaging device and drives the photographing lens based on the object position unstable measures speed.   The imaging apparatus according to claim 1, further comprising a tracking unit that tracks a subject, wherein the focus detection unit detects a focal position of the subject tracked by the tracking unit. In an imaging device that performs imaging by performing focus detection based on an image plane phase difference phase difference method,
An imaging unit that captures a predetermined number of frames while driving the imaging lens;
A storage unit for temporarily storing the image data of the predetermined number of frames;
A focus detection unit that detects the in-focus position of the photographic lens every time shooting is performed by the imaging unit;
A calculation unit that calculates a moving speed of a subject based on the in-focus position each time the in-focus position is detected;
A photographic lens driving unit that drives the photographic lens at a speed corresponding to the moving speed of the subject;
A selection unit that selects image data that is most focused from image data of a predetermined number of frames stored in the storage unit;
A recording medium for storing the image data selected by the selection unit;
With
A release operation detecting unit for detecting a first-stage push-down operation by a user operation and detecting a second-stage push-down operation following the first-stage push-down operation;
Until the second-stage push-down operation is detected, the imaging unit performs shooting for a predetermined number of frames while driving the photographing lens in the first cycle, and after the second-stage push-down operation is detected. is by the imaging unit, a first imaging device you and performs imaging of a predetermined number of frames while driving the photographing lens in a shorter period than the period. In an imaging method capable of performing focus detection based on an image plane phase difference phase difference method,
Taking a predetermined number of frames while driving the photographic lens by the imaging unit;
Temporarily storing image data of the predetermined number of frames in a storage unit;
A step of detecting a focus position of the photographing lens every time the image pickup unit performs photographing by the focus detection unit;
Calculating a moving speed of the object based on該合focus position for each of the upper Kigoase position is detected,
And driving the photographing lens at a speed corresponding to the moving speed of the upper Symbol subject,
Selecting image data that matches the most focus from image data of a predetermined number of frames stored in the upper term memory unit,
A step of storing the image data on hexene-option on a recording medium,
I have a,
Driving a photographic lens so that the diameter of the circle of confusion of the image formed on the imaging surface changes by a value smaller than the diameter of the permissible circle of confusion during the period of repeatedly acquiring image data from the image sensor for focus detection Calculating a standard speed which is a speed;
Calculates the subject position instability countermeasure speed, which is the driving speed of the photographic lens, by dividing the data representing the degree of variation in the position of the photographic lens at each time when a plurality of previous consecutive image data was acquired by a predetermined time. And steps to
Further comprising
In the step of driving the photographing lens, the photographing lens is driven based on the speed according to the moving speed of the subject, the standard speed, and the subject position instability countermeasure speed.
An imaging method characterized by the above. In an imaging method capable of performing focus detection based on an image plane phase difference phase difference method,
Taking a predetermined number of frames while driving the photographic lens by the imaging unit;
Temporarily storing image data of the predetermined number of frames in a storage unit;
A step of detecting a focus position of the photographing lens every time the image pickup unit performs photographing by the focus detection unit;
Calculating the moving speed of the subject based on the in-focus position each time the in-focus position is detected;
Driving the photographing lens at a speed corresponding to the moving speed of the subject;
Selecting the most focused image data from the image data of a predetermined number of frames stored in the storage unit;
Storing the selected image data in a recording medium;
Have
A step of detecting a first-stage push-down operation by a user operation and detecting a second-stage push-down operation following the first-stage push-down operation;
In the step of shooting the predetermined number of frames, until the second step-down operation is detected, the imaging unit performs shooting of the predetermined number of frames while driving the shooting lens in the first period, An imaging method characterized in that after the second-stage push-down operation is detected, the imaging unit performs imaging for a predetermined number of frames while driving the imaging lens at a cycle shorter than the first cycle.