JP2019109549A - Imaging system, imaging apparatus, lens device, and control method of imaging system - Google Patents

Abstract

To enhance the correction accuracy of focusing by acquiring sensitivity information and its correction information by communication between a lens device and a camera body part.SOLUTION: An imaging system includes an interchangeable lens 2 and a camera body part 1 capable of communicating with the interchangeable lens 2. The camera control part 9 of the camera body part 1 acquires focus sensitivity-related information (the sensitivity information at the image height of a center and the correction information of sensitivity changed by the image height) at a proper timing from the lens control part 26 of the interchangeable lens 2 by communication. The camera control part 9 corrects the change of the sensitivity by the image height by using the image height information of a focus detection area selected from a plurality of focus detection areas and the acquired focus sensitivity correction information. The camera control part 9 calculates the drive amount of a focus lens 22 from a focus detection signal by using focus sensitivity after correction, generates a control signal for instructing the drive amount, and transmits it to the lens control part 26.SELECTED DRAWING: Figure 1

Description

  The present invention relates to control technology of automatic focusing (AF) in an imaging system in which a lens device can be attached to a camera body.

  When driving the focus lens by the imaging device, the amount of drive of the lens is determined based on the focus sensitivity. The focus sensitivity is a coefficient for converting the defocus amount detected by the imaging device into the drive amount of the focus lens, and in the camera system of the interchangeable lens type, it is determined based on the optical information of the interchangeable lens.

  Patent Document 1 discloses a camera system in which the focus sensitivity is variable according to focal length information of a lens. According to the apparatus of Patent Document 1, the focus sensitivity can be appropriately set according to the focal length, and the focusing time can be shortened. Patent Document 2 discloses that focus correction data is determined in accordance with the state of a camera such as spatial frequency.

JP-A-59-151116 JP, 2014-29353, A

  The actual focus sensitivity changes due to not only focal length information of the lens but also the position of focus detection (image height). The prior art disclosed in Patent Document 1 does not consider the change in focus sensitivity caused by the image height. Therefore, it is not possible to set an appropriate focus sensitivity for focusing at the peripheral image height, and accurate focusing control can not be performed when hunting or the like occurs. In order to obtain more accurate focus sensitivity, it is necessary to acquire focus sensitivity for each image height.

On the other hand, with regard to focus sensitivity information, delivery is performed by communication between the camera body and the interchangeable lens via the mount terminal. The prior art disclosed in Patent Document 2 does not consider that the data to be communicated changes according to the image height. When different data are communicated for each image height, the amount of communication data increases in order to enhance the correction accuracy of focusing at the peripheral image height. In this case, it is necessary to transmit and receive necessary data within a limited communication band between the camera body and the interchangeable lens.
An object of the present invention is to obtain sensitivity information and its correction information by communication between a lens device and a camera body to enhance the accuracy of correction of focusing.

  An imaging system according to an embodiment of the present invention includes a lens apparatus and a camera body to which the lens apparatus can be attached. The lens device includes a lens for focusing, drive control means for controlling the drive of the lens, and first communication means for communicating with the camera body. The camera body unit includes a second communication unit for communicating with the lens device, a focus detection unit for acquiring focus detection signals in a plurality of focus detection areas set in an imaging surface, and the lens from the focus detection signal. And control means for generating a control signal for controlling the driving of the lens and transmitting the control signal to the lens apparatus through the first and second communication means. The control means of the camera body portion is sensitive from the lens device to the sensitivity information indicating the sensitivity information of the lens at the central image height and the change in sensitivity corresponding to the image height through the first and second communication means. Correction information of the degree is acquired, image height information of the focus detection area selected from the plurality of focus detection areas, and the acquired correction information correct the change of the sensitivity of the lens corresponding to the image height and correct the correction The control signal is generated which indicates the drive amount of the lens calculated using the sensitivity.

  According to the present invention, it is possible to obtain sensitivity information and its correction information by communication between the lens device and the camera body to enhance the correction accuracy of focusing.

It is a block diagram showing an imaging system concerning an embodiment of the present invention. It is a schematic diagram showing composition of an image sensor concerning an embodiment of the present invention. It is the schematic of the pixel part of the image pick-up element which concerns on embodiment of this invention. It is a conceptual diagram which shows a mode that the light beam which came out of the exit pupil of the imaging lens injects into an image pick-up element. It is explanatory drawing of the multipoint AF (autofocus) frame in embodiment of this invention. It is a figure explaining selection processing of a multipoint AF frame in an embodiment of the present invention. It is a time chart explaining timing control of a multipoint AF frame in an embodiment of the present invention. FIG. 10 is a flowchart for explaining selection of an AF frame and sensitivity correction processing at the time of multipoint AF in the first embodiment. FIG. It is a flowchart explaining selection of AF frame at the time of multipoint AF and sensitivity amendment processing in a 2nd embodiment. It is a graph explaining the sensitivity ratio and sensitivity correction ratio in a 2nd embodiment. It is a figure explaining the setting process of the sensitivity correction | amendment implementation range in 2nd Embodiment.

  Below, each embodiment of the present invention is described in detail based on an attached drawing. In each embodiment, a replaceable camera-lens system will be described as an example of the imaging system according to the present invention. The interchangeable camera-lens system comprises a lens device and a camera body to which the lens device can be mounted. The camera body having the focus detection function acquires drive characteristic information of the focus lens from the lens device, generates a control signal for performing drive control of the focus lens, and transmits the control signal to the lens device.

First Embodiment
FIG. 1 is a block diagram showing an example of the configuration of an interchangeable camera-lens system including a camera body 1 and an interchangeable lens 2 according to a first embodiment of the present invention. The camera body 1 can communicate with the removable interchangeable lens 2.
An electric circuit unit 3 in the camera body 1 includes an imaging device 4 and photoelectrically converts an object image formed by light passing through the interchangeable lens 2 into an electric signal. The imaging device 4 is a CCD (charge coupled device) sensor, a CMOS (complementary metal oxide semiconductor) sensor, or the like, and has a plurality of focus detection pixels having different image heights.

  The photometry unit 5 measures the amount (brightness) of light passing through the interchangeable lens 2 using the output from the image pickup device 4 and outputs the photometry result. The focus detection unit 6 calculates the defocus amount (defocus amount) of the interchangeable lens 2 using the outputs of the plurality of focus detection pixels provided in the image sensor 4 and having different image heights. The cycle of the focus detection process is synchronized with the frame rate corresponding to the imaging cycle (hereinafter referred to as VD), and the communication process between the camera body 1 and the interchangeable lens 2 is performed in synchronization with the VD signal.

  The shutter control unit 7 controls the operation of a shutter (not shown) that opens and closes in order to control the exposure amount of the imaging device 4. The image processing unit 8 performs various kinds of processing on the output from the imaging pixel of a predetermined number of pixels provided in the imaging element 4 to generate image data. The various processes include processes using stored information of the interchangeable lens 2 and stored information of the camera body 1.

  The camera control unit 9 is a control center unit of an imaging device including a CPU (central processing unit), a memory, and the like. The camera control unit 9 controls the operation of each component of the imaging device. The camera communication unit 11 is provided in the camera body unit 1, and the lens communication unit 25 is provided in the interchangeable lens 2. The camera control unit 9 communicates with the lens control unit 26 via these communication units. It is possible. The camera control unit 9 calculates an aperture value and a shutter speed at the time of imaging based on the luminance obtained from the photometry unit 5, and transmits an aperture drive instruction including the aperture value to the lens control unit 26. Furthermore, the camera control unit 9 calculates the drive direction and drive amount to the in-focus position of the focus lens 22 in the interchangeable lens 2 based on the focus detection information and the information acquired from the lens control unit 26. The focus detection information is the defocus amount calculated by the focus detection unit 6. The information acquired from the lens control unit 26 is focus sensitivity information at the center image height and information of the image height change coefficient of the focus sensitivity. The camera control unit 9 transmits, to the lens control unit 26, a control signal of a focus drive instruction that instructs the calculated drive direction and drive amount, and performs focus adjustment control of the imaging optical system. In the AF (Auto Focus) process on the camera body 1 side, the defocus amount is calculated in the focus detection operation, and the camera control unit 9 transmits a control signal of a focus drive command to the lens control unit 26. is there. The function of the imaging plane AF described later is performed every 1 V at the timing of the imaging frame rate. For this reason, communication of information such as focus sensitivity, focus position, and driving state is performed for each 1V. 1 V represents one vertical cycle, which corresponds to the cycle of the vertical synchronization signal.

  The lens attachment detection unit 10 includes a switch, a light detector, and the like, and detects that the interchangeable lens 2 is attached to the camera body 1. The lens attachment detection unit 10 outputs a detection signal to the camera control unit 9. The camera communication unit 11 is paired with the lens communication unit 25, and the camera control unit 9 acquires various information stored in the lens control unit 26. The various information is, for example, focus sensitivity information and sensitivity correction information. The sensitivity correction information is a sensitivity image height correction coefficient for correcting the focus sensitivity which changes depending on the image height. Below, these pieces of information are referred to as sensitivity related information. The camera control unit 9 stores the acquired information in a volatile memory (not shown).

  The control system power supply 12 in the camera body 1 supplies power to the image pickup device 4, the photometry unit 5, the focus detection unit 6, the image processing unit 8 and the display unit 33, the control system circuit of the interchangeable lens 2 and the like. A drive system power supply 13 in the camera body 1 supplies power to a shutter control unit 7 and drive system circuits of the interchangeable lens 2 and the like.

  The imaging preparation switch (SW1) 14 and the imaging start switch (SW2) 15 are operation switches used by the user at the time of imaging. The switch SW1 is turned on by half pressing the release button, and the switch SW2 is turned on by pressing the release button fully. In the AF control, the corresponding processing starts with each signal of SW1 and SW2 as a trigger.

  The image recording unit 16 performs control to record captured image data on a recording medium in a predetermined format. The operation unit includes various operation members and switches. FIG. 1 shows a focus detection point changing operation member 32 for selecting a focus detection point as an operation member related to the present embodiment. The display unit 33 displays the captured image and displays various information of the camera. The various types of information include a display frame that displays a plurality of focus detection areas set in the imaging plane.

  The imaging optical system of the interchangeable lens 2 includes a variable power lens 21, a focus lens 22, an image blur correction lens 23, and a stop 24. The variable magnification lens 21 moves in the optical axis direction of the imaging optical system to change the focal length. The focusing lens 22 is a focusing lens that moves in the optical axis direction to the imaging optical system. The image shake correction lens 23 moves in a direction orthogonal to the optical axis direction of the imaging optical system to correct an image shake due to camera shake such as camera shake. The aperture stop 24 changes the imaging light amount according to the aperture diameter by variable control of the aperture diameter (aperture value).

  The electric circuit unit 20 includes a lens communication unit 25, a lens control unit 26, and drive units. Each drive unit is a zoom drive unit 27, a focus drive unit 28, a shake correction drive unit 29, and an aperture drive unit 30. The lens control unit 26 receives, via the camera communication unit 11 and the lens communication unit 25, imaging information of the camera body 1, focus sensitivity information based on the imaging condition, a focus driving instruction, and the like. The lens control unit 26 outputs a focus drive signal to the focus drive unit 28 in accordance with the focus drive command.

  The focus drive unit 28 includes an actuator such as a stepping motor, a vibration motor, or a voice coil motor, and moves the focus lens 22 to the in-focus position according to the focus drive signal from the lens control unit 26. That is, in the AF processing on the interchangeable lens 2 side, processing from receiving the focus driving command to moving the focus lens 22 to the in-focus position is executed.

  The lens control unit 26 outputs a diaphragm drive signal to the diaphragm drive unit 30 in accordance with the diaphragm drive command acquired from the camera control unit 9. The diaphragm drive unit 30 has an actuator such as a stepping motor, and drives the diaphragm 24 in accordance with the diaphragm drive signal from the lens control unit 26.

  When the user operates the zoom operation ring (not shown) provided on the interchangeable lens 2, the lens control unit 26 receives a zoom drive signal for moving the magnification varying lens 21 at the zoom direction and zoom drive speed according to the operation. Output to the zoom drive unit 27. The zoom drive unit 27 has an actuator such as a stepping motor, and drives the variable power lens 21 in accordance with the zoom drive signal from the lens control unit 26.

  The lens control unit 26 outputs a shake driving signal to the shake correction driving unit 29 based on a shake detection signal from a shake detection sensor (an angular velocity sensor, an acceleration sensor, etc.) (not shown) provided in the interchangeable lens 2. The shake correction drive unit 29 has an actuator such as a voice coil motor, and drives the image shake correction lens 23 in accordance with a shake correction drive signal from the lens control unit 26.

  The storage unit 31 is configured of a storage device such as an EEPROM (Electrically Erasable Programmable Read-Only Memory) or a flash ROM. The storage unit 31 stores data including focus position shift information, focus sensitivity, and focus sensitivity image height correction coefficient information used to correct a focus detection result (defocus amount). The storage unit 31 may be disposed inside the lens control unit 26. The lens control unit 26 outputs the information read from the storage unit 31 to the lens communication unit 25, and the lens communication unit 25 transmits the information to the camera communication unit 11.

Next, an outline of the operation of the imaging device will be described.
When the user turns on the imaging preparation switch (SW1) 14, the camera control unit 9 causes the photometry unit 5 to execute a photometric operation and causes the focus detection unit 6 to execute a focus detection operation. In this embodiment, sensitivity to the optical axis (image height at the center) acquired from the interchangeable lens 2 and sensitivity to the image height correction coefficient changing with distance from the optical axis (image height component) are further acquired. Processing is performed. The corrected sensitivity is acquired from the image height component for which focus detection has been performed and the sensitivity image height correction coefficient. For the defocus amount obtained as the focus detection result, conversion processing to a drive amount (number of pulses) to be instructed to the focus drive unit 28 is performed using the corrected sensitivity information. The lens control unit 26 performs focus drive control in accordance with the drive amount instructed from the camera control unit 9. By repeatedly executing the focus detection operation and the lens drive, the defocus amount gradually decreases. In this process, so-called overlap drive is performed in which the focus lens drive and the focus detection process are folded when the detected defocus amount is large. As described later, in the present embodiment, the communication load between the camera body 1 and the interchangeable lens 2 and the calculation load can be reduced even during the overlap driving.

When the user turns on the imaging start switch (SW2) 15, the camera control unit 9 transmits a drive command of the diaphragm 24 to the lens control unit 26 to control to the aperture value at the time of imaging, and the shutter control unit 7 drives the shutter. Then, the imaging device 4 is exposed at a predetermined shutter speed. Also, the camera control unit 9 causes the image processing unit 8 to generate a recording image from the output of the imaging device 4. Since the imaging device 4 has focus detection pixels dedicated to AF, it is possible to obtain a focus detection signal together with the recording image. The AF of the phase difference detection method performed using the imaging element 4 is also referred to as imaging surface phase difference AF. In addition, you may perform focus detection using not only imaging surface phase difference AF but AF sensor only for phase difference detection.
After shooting, the camera control unit 9 instructs the image recording unit 16 to record a recording image signal on a recording medium (not shown) such as a semiconductor memory. The photographed image is a still image or a moving image. For example, when a still image shooting mode is selected by the mode selection switch, a still image is obtained, and when a live view mode or a moving image shooting mode is selected, a moving image is obtained. In an imaging apparatus provided with a recording start button for moving picture shooting, the operation of the button starts the moving picture recording operation. The user can select the recording image quality by operating the recording image quality setting switch provided on the camera body 1.

Next, a configuration for performing focus detection processing in the present embodiment will be described.
The configuration of the imaging device 4 will be described with reference to FIG. FIG. 2A is an overall schematic view of the imaging device 4, and FIG. 2B is a schematic diagram of one pixel in the imaging device 4. The imaging device 4 shown in FIG. 2A has a pixel portion 201 composed of a plurality of pixels arranged in a two-dimensional array. The vertical selection circuit 202 sequentially selects pixel signals of a plurality of rows of the pixel portion 201 and outputs the pixel signals to the readout circuit 203. The readout circuit 203 reads out a signal of a pixel selected by the vertical selection circuit 202 among the pixels of the pixel unit 201. The readout circuit 203 includes, for each column, a memory for accumulating a signal, a gain amplifier, an A / D converter, and the like. The horizontal selection circuit 204 sequentially selects, for each column, the plurality of pixel signals read out by the readout circuit 203. The serial interface (SI / F) unit 205 acquires information such as the operation mode of each circuit determined by the external device. In addition to the components shown in FIG. 2A, a timing generator that provides timing signals to the vertical selection circuit 202, the horizontal selection circuit 204, the readout circuit 203, and the like, a control circuit, and the like are provided.

  A pixel 206 illustrated in FIG. 2B includes one microlens 207 and two photodiodes 208 and 209. Two photodiodes (referred to as PD) constitute a photoelectric conversion unit for performing imaging plane phase difference AF. Note that in addition to the components shown in FIG. 2B, the pixel 206 includes a pixel amplifier for reading out the signal of the PD to the reading circuit 203, a selection switch for selecting a row, a reset switch for resetting the signal of PD, and the like. Equipped with

  FIG. 3 is a schematic view of the pixel section 201 in the imaging device 4. The pixel unit 201 is configured by arranging a large number of pixels in a two-dimensional array in order to provide a two-dimensional image. The pixels 301, 302, 303, and 304 are pixels having the configuration shown in FIG. The PDs 301L, 302L, 303L, and 304L correspond to the PD 208 shown in FIG. 2B, and the PDs 301R, 302R, 303R, and 304R correspond to the PD 209 shown in FIG. 2B. Although the two-division type photoelectric conversion unit is illustrated in the present embodiment, the division direction and the number of divisions can be arbitrarily changed according to the specifications of the apparatus.

  The state of light reception in the imaging device 4 will be described with reference to FIG. FIG. 4 is a conceptual view showing how a light flux emitted from the exit pupil of the photographing lens is incident on the image pickup element, schematically showing an image pickup surface phase difference detection method. In a partial cross section 401 of the imaging element 4, a microlens 402 (corresponding to the microlens 207 in FIG. 2B) and a color filter 403 are shown. The PD 404 and the PD 405 respectively correspond to the PD 208 and the PD 209 in FIG.

  The center of the light beam emitted from the exit pupil 406 of the photographing lens is indicated by an optical axis 409 with respect to the pixel having the microlens 402. The light flux emitted from the exit pupil 406 is incident on the imaging element 4 with the optical axis 409 as the center. The pupil partial regions 407 and 408 are partial regions of the exit pupil 406 of the photographing lens. Rays 410 and 411 are the outermost rays of the luminous flux passing through the pupil partial area 407. Rays 412 and 413 are outermost rays of the light beam passing through the pupil partial region 408. Among light fluxes emitted from the exit pupil 406, the light flux on the upper side of the light axis 409 is incident on the PD 405 and the light flux on the lower side is incident on the PD 404. That is, each of the PD 404 and the PD 405 receives a light flux that has passed through different regions at the exit pupil 406 of the imaging lens.

  Although two PDs are provided for one microlens in FIGS. 2B and 3, the present invention is not limited to this. For example, one PD may be used for one pixel, and the other PD may be used for the next pixel. That is, in the configuration in which an optical image passing through different regions in the exit pupil 406 of the imaging lens can be obtained on the imaging surface of the imaging element, imaging surface phase difference AF is possible.

  The imaging device 4 is configured by arranging A-line pixels and B-line pixels that receive light beams from different pupil partial regions in the imaging lens in a two-dimensional array. Specifically, in FIG. 3, among the pixels 301, 302, 303, and 304 in the row 305, the pixels of the PDs 301L, 302L, 303L, and 304L constitute an A-line pixel. In addition, pixels of PDs 301R, 302R, 303R and 304R constitute B line pixels. For each output of the A-line pixel and the B-line pixel, the distance between the two images (image distance) differs depending on whether it is the in-focus state, the front pin state, or the back pin state. A defocus amount corresponding to an image interval is calculated, and focusing is performed by moving the focus lens 22 so as to be in focus. That is, the amount of movement of the focus lens 22 can be calculated based on the amount of image shift of the two images. In the present embodiment, for convenience of explanation, the two images (the image of the A line pixel and the image of the B line pixel) have been described in the arrangement of adjacent pixels, but in practice the A line pixel and the B line Pixels are configured.

  In focus detection processing, an image formed by light beams passing through different pupil partial regions of the imaging optical system is photoelectrically converted to generate a pair of image signals. The focus detection unit 6 detects the defocus amount based on the phase difference (image shift amount) of the pair of image signals. The focus drive amount is calculated from the detected defocus amount, and drive control of the focus lens 22 according to the focus drive amount is performed.

  Next, multi-point AF control for performing focus detection in a wide range of image heights in imaging plane phase difference AF control according to the present embodiment will be described with reference to FIG. FIG. 5 is an explanatory view of a multipoint focus detection frame based on the phase difference detection method. The pixel area 500 in the imaging plane is a pixel area in the imaging element 4 in which the dedicated pixel of the phase difference detection method is arranged, and represents the imaging range. By arranging the dedicated pixels 501 of the phase difference detection method in the horizontal direction and the vertical direction, it is possible to acquire phase difference image signals of the subject in each direction. A rectangular area obtained by combining a plurality of lines having the dedicated pixel 501 is defined as an AF frame area 502. The AF frame area 503 is an area constituting one group shown by being surrounded by a dashed rectangular frame. In the coordinate system 504 shown in FIG. 5, an axis in the lateral direction is defined as an X axis, and an axis in the longitudinal direction is defined as an Y axis.

  When focus detection is performed with an AF frame arbitrarily designated by the user, focus detection processing is performed in the designated AF frame area 502. On the other hand, at the time of subject tracking such as face detection or multipoint AF, focus detection processing is performed on the entire AF frame covering the entire surface of the imaging range. In the example shown in FIG. 5, the focus detection process is performed with a total of 36 AF frames divided into six in the vertical direction and six in the horizontal direction. Numerals 1 to 36 shown in FIG. 5 are numbers attached from the upper left to the lower right to identify each AF frame.

  By the way, when it becomes difficult to perform focus detection processing during a 1V period as the number of pixels increases, the number of multi-point frames increases, and the frame rate increases, it is possible to collectively detect the entire imaging range. Can not. Therefore, the imaging range is divided into a plurality of ranges and the focus detection process is sequentially performed. Specifically, as shown in FIG. 6, processing for performing focus detection is executed for each of the plurality of divided focus detection areas. In FIG. 6, each focus detection is performed while being divided into nine groups of four regions. In this case, it has not yet been determined which AF frame is to be adopted at the stage of focus detection processing. Therefore, the camera control unit 9 acquires focus sensitivity related information from the lens control unit 26. Since the image height position information of each AF frame is necessary for the correction processing using the focus sensitivity related information, two-dimensional coordinate information is acquired by setting the coordinate system 504 in FIG. 5. The image height at the center of the coordinate system 504 is 0, and the position is expressed as coordinates (X, Y) on the XY plane.

  An area 510 (see AF frames 1, 2, 7, 8) shown in FIG. 6 corresponds to the dedicated pixel 501 of the phase difference detection method in FIG. A rectangular frame 511 indicated by a dotted line frame indicates an area where focus detection processing can be performed at one time by grouping a plurality of AF frames. The imaging range is covered by the rectangular frames 511 to 519, and the focus detection process is repeatedly performed using the outputs of the focus detection area obtained by grouping four frames into one set, that is, nine frames. Specifically, in the first 3 V (1 V to 3 V) period, the focus detection areas are sequentially shifted like the rectangular frames 511, 512, and 513, and the focus detection corresponding to the upper part of the imaging device 4 is performed. Is done. In the next 3V (4V to 6V) period, the focus detection areas are sequentially shifted like the rectangular frames 514, 515, and 516, and focus detection corresponding to the central portion of the imaging device 4 is performed. Further, in the next 3 V (7 V to 9 V) period, the focus detection areas are sequentially shifted like rectangular frames 517, 518, and 519, and focus detection corresponding to the lower part of the imaging device 4 is performed. In this way, a focus detection signal covering an imaging range is acquired over a period of 1V to 9V.

  Next, timing of focus detection in multipoint AF frames will be described with reference to FIG. FIG. 7 is a time chart in the case of repeatedly performing focus detection using the nine frames shown in FIG. A signal 601 indicates the behavior of the signal line of imaging in time series. The start timing of the imaging process is described at the falling point of the signal 601 in the cycle corresponding to the frame rate, that is, the cycle of the VD signal. A parallelogram 602 indicates the storage timing of the image sensor 4. The storage control of the imaging device 4 is performed within the cycle of the VD signal, the storage in the upper part of the imaging device is performed near the top of the VD, and the readout in the lower part of the imaging device is the storage in the second half of the cycle of the VD signal Is done. In the present embodiment, since dedicated pixels for phase difference detection are disposed in the imaging device 4, the accumulation timing of the AF pixels depends on the position of the AF frame. Hereinafter, the process of nine frames shown in FIG. 6 will be described in association with the time chart of FIG.

  In the first 3 V (1 V to 3 V), since the AF pixels existing in the upper region of the imaging device 4 are used, the phase difference detection signal is obtained at the timing 610 of “upper block AF accumulation”. At the next 3 V (4 V to 6 V), since an AF pixel existing at the central portion of the imaging device 4 is used, a phase difference detection signal is obtained at timing 611 of “central block AF accumulation”. Further, at the next 3 V (7 to 9 V), a signal for detecting a phase difference is obtained at timing 612 of “lower block AF accumulation” because an AF pixel existing in the lower part of the imaging device is used.

  On the other hand, with regard to focus sensitivity related information acquired by the camera control unit 9 from the lens control unit 26, timings 620 to 628 indicated by "acquisition of sensitivity related information (1) to (9)", that is, fall time of the signal 601 It is acquired by each. The camera control unit 9 stores time information corresponding to each frame (1 V to 9 V) in the memory in association with the acquired focus sensitivity related information. By obtaining focus detection results for nine frames, the defocus state of all the AF frames can be determined. Therefore, it becomes possible to select an AF frame at selection timing 629 shown in the “AF frame selection process”. As the selection criterion of the AF frame, for example, there is a criterion such as selecting the near side, or that the waveform reliability of the phase difference detection result of focus detection is high, and the judgment is made as necessary. In addition, it is also possible to perform so-called overlap control in which the focus lens is driven in the process of focus detection. In that case, it is necessary to consider the lens driving amount in the period from the timing when the focus detection processing is performed to the timing when the AF frame is determined as the idle amount. In order to obtain the free running amount of the lens, each of the times t1 to t9 at timings 630 to 638 shown by "time storage (1) to (9)" corresponding to the falling time of each VD signal of 9 frames. Data is stored in memory. Further, at the AF frame selection timing 639, the time t_sel at that time is acquired. In the lens free running amount calculation process, for example, when the rectangular frame 512 in FIG. 6 set to the 2V position is selected, it is considered that the focusing lens is driven at constant velocity during a period from time t2 to time t_sel. The amount of movement of the focusing lens that moves at constant velocity is calculated as the amount of lens free running. Then, the focus detection result obtained for the 2V eye is converted into the focus drive amount using the correct sensitivity obtained from the calculation formula (1) described later, and further necessary for focusing by subtracting the lens free running amount. The lens drive amount can be determined.

  Next, multi-point AF processing performed by the camera control unit 9 in the present embodiment will be described with reference to the flowchart in FIG. 8. In step S701, the user uses the focus detection point change operation member 32 constituting the operation unit of the camera to set an automatic selection mode of the focus detection point. When the imaging preparation switch (SW1) 14 is turned on, the camera control unit 9 starts multipoint AF processing.

  In S702, the camera control unit 9 sets control information in the focus detection unit 6 in order to set the area indicated by the rectangular frame 511 in FIG. 6 as the AF frame. In S703, the camera control unit 9 detects a VD signal for imaging, and determines the presence or absence of a VD interrupt. The VD interrupt is generated periodically according to the VD signal. If the VD signal is detected in S703, the process proceeds to S704, and if the VD signal is not detected, the determination process of S703 is repeated.

  In S704, the camera control unit 9 acquires focus sensitivity related information from the lens control unit 26 via the lens communication unit 25 and the camera communication unit 11. Of the focus sensitivity related information, “sensitivity information at the center image height” is information determined based on the optical information stored in the lens control unit 26. The optical information is information on each position information of the variable magnification lens 21, the focus lens 22, and the image blur correction lens 23, the aperture value of the diaphragm 24, and an accessory device (for example, an extender) not shown. The sensitivity information is information indicating a value at the center of the imaging surface, that is, a value at the image height 0 (image height at the center). In the “sensitivity image height correction coefficient” of the focus sensitivity related information, the focus sensitivity correction for correcting the focus sensitivity indicated by “sensitivity information at the center image height” acquired from the lens control unit 26 It is a coefficient. The coordinates of the origin, that is, the image height at the center in the XY plane of FIG. 5 is expressed as (0, 0). The sensitivity S (X, Y) of the image height coordinate (X, Y) can be calculated by a polynomial of X and Y as in the following equation (1).

式（１）においてＳ₀は、レンズ制御部２６から取得したフォーカス敏感度を表す。ａ₀からａ₅はフォーカス敏感度補正係数をそれぞれ表す。このように像高に応じた敏感度の変化量を表現する係数は、レンズ制御部２６からカメラ制御部９が取得するデータである。本実施形態での敏感度情報は、中心の像高におけるフォーカス敏感度の特性に対し、多項式近似により算出される情報であるが、直線近似により算出される情報でもよい。

In equation (1), S ₀ represents the focus sensitivity acquired from the lens control unit 26. a ₀ to a ₅ represent focus sensitivity correction coefficients, respectively. The coefficient expressing the amount of change in sensitivity according to the image height in this manner is data acquired by the camera control unit 9 from the lens control unit 26. The sensitivity information in the present embodiment is information calculated by polynomial approximation with respect to the characteristic of focus sensitivity at the center image height, but may be information calculated by linear approximation.

  Other than the above method, there is a method in which the camera control unit 9 instructs the lens control unit 26 to provide image height information, and the lens control unit 26 transmits sensitivity information on the instructed image height to the camera control unit 9. However, with this method, the communication bandwidth between the camera control unit 9 and the lens control unit 26 may run short, and the calculation load on these control units increases, with respect to the increase in the number of AF frames and the increase in frame rate. The possibility of doing so is a problem. Therefore, as in the present embodiment, it is preferable for the camera control unit 9 to acquire the focus sensitivity correction coefficient from the lens control unit 26 in order to reduce the calculation load.

  S 705 is a process of determining whether accumulation of AF dedicated pixels in the imaging device 4 is completed. The camera control unit 9 advances the process to S706 if the accumulation of AF dedicated pixels is completed, and waits until the accumulation of AF dedicated pixels is not completed. In S706, readout of AF dedicated pixels corresponding to the AF frame position set in S702 is executed, and the focus detection unit 6 acquires focus detection information in phase difference detection. In step S707, the camera control unit 9 associates the focus detection information acquired in step S706 with the sensitivity related information acquired in step S704 and stores the information in the memory.

  Step S710 is a process of determining whether or not the focus detection at the AF dedicated pixels of all the AF frames is completed. The camera control unit 9 determines whether or not the focus detection in the area shown by the rectangular frames 511 to 519 in FIG. 6 has been repeatedly performed. If the focus detection of all the AF frames is not completed, the camera control unit 9 returns the process to S702, resets the next focus detection area to the AF frame position, and continues the process. If the focus detection of all the AF frames is completed, the process proceeds to step S711.

  In S711, a process of selecting an AF frame position is performed. The optimum focus detection result is selected from all the focus detection results, specifically, the focus detection results for nine frames implemented over the regions shown by the rectangular frames 511 to 519 in FIG. The optimal focus detection result is determined by the camera control unit 9 according to a preset determination standard from among the focus detection signals that match the selection criteria of the AF frame. In step S712, the camera control unit 9 acquires, for the focus detection result selected in step S711, focus sensitivity related information associated with the focus detection result stored in step S707. That is, on the basis of the correspondence between the acquired focus detection information and the focus sensitivity related information, the focus sensitivity related information for the focus detection result selected in S711 is acquired. At this time, processing such as interpolation calculation is performed as necessary.

  In step S713, the camera control unit 9 applies the equation (1) to the image height position of the AF frame selected in step S711, using the focus sensitivity related information acquired in step S712, and executes arithmetic processing. Thereby, the focus sensitivity information accurately corrected is calculated. In S714, calculation processing from the focus detection result to the focus lens driving amount is performed using the focus sensitivity information calculated in S713. That is, the camera control unit 9 calculates the pulse count number when driving the focus lens 22 from the defocus amount which is the focus detection result. The camera control unit 9 transmits a drive command including the calculated pulse count number to the lens control unit 26, and requests focus drive. In step S715, the AF frame position selection process in multipoint AF control ends.

  In the present embodiment, for example, when the focus detection results are obtained according to the timing of a plurality of VD signals, the past focus detection results, that is, history data are read from the memory and used. In this case, processing for storing the focus detection result and the focus sensitivity related information in association with each other is performed. The camera body acquires, from the lens apparatus, along with the sensitivity information of the center image height, a correction coefficient for correcting the sensitivity with respect to the image height, and determines the AF frame position and then calculates the focus sensitivity information. In focusing at the peripheral image height, it is possible to correct the amount of change in focus sensitivity according to the position of focus detection in a method optimum for AF control. According to the present embodiment, even when the number of frames of multipoint AF is increased and the frame rate is improved, optimum sensitivity information can be applied while reducing the calculation processing load, so improvement in focus adjustment accuracy can be realized. Exchangeable camera-lens system can be provided.

  In the present embodiment, the multipoint AF mode has been described as a control mode in which the area of the imaging surface is divided into grids and focus detection is performed for each of the divided focus detection areas. The present invention is not limited to this, and is also applicable to the zone area AF mode in which focus detection is performed for each predetermined zone. This is the same in the embodiments described later.

Second Embodiment
Next, a second embodiment of the present invention will be described. In this embodiment, when the camera control unit 9 performs AF control of the phase difference detection method, it has a drive range for determining the focus detection result (defocus amount) used for final drive of the focus lens 22. This drive range is a range corresponding to a length obtained by multiplying the diameter of the permissible circle of confusion of the imaging device 4 by an arbitrary ratio, and hereinafter, will be referred to as a “final drive range”. The camera control unit 9 determines the implementation range of the sensitivity correction from the final drive range, and determines whether the focus detection result (defocus amount) is within the implementation range. When the focus detection result is within the operation range, the focus detection result is used for the final drive. Thereby, the focusing operation can be realized by the AF control without the hunting phenomenon. In the present embodiment, by using the reference numerals already used for the same constituent elements as in the case of the first embodiment, the detailed description thereof will be omitted, and the differences will be mainly described.

  The multipoint AF processing on the camera body side in the present embodiment will be described with reference to the flowchart in FIG. In S801, AF frame position selection processing starts, and the processing of S802 and S803 is executed. Description of processes of S802 and S803 being the same as the processes of S702 and S703 of FIG. 8 is omitted.

  In the next S804, the camera control unit 9 acquires focus sensitivity related information from the lens control unit 26 via the lens communication unit 25 and the camera communication unit 11. The sensitivity indicated by “sensitivity information at the center image height” in the focus sensitivity related information is a value at the center of the imaging surface, that is, a value at the image height 0 (center image height). The processes of S805, S806, S807, and S810 are the same as the processes of S705, S706, S707, and S710 in FIG. However, in S807, the focus detection information acquired in S806 and the sensitivity related information (sensitivity information at image height 0) acquired in S804 are associated with each other and stored in the memory.

  If the focus detection of all the AF frames is completed in S810, the process proceeds to S811. In step S811, the camera control unit 9 sets the sensitivity correction execution range. First, the camera control unit 9 acquires focal distance information of the imaging optical system via the lens communication unit 25 and the camera communication unit 11. Next, the camera control unit 9 is farthest from the image height at the center from all focus detection results, specifically, nine frames worth of focus detection results repeatedly performed in the areas shown by the rectangular frames 511 to 519 in FIG. The sensitivity correction implementation range is calculated based on the image height information of the AF frame of the position. The calculation method will be described later with reference to FIG.

  The processes of S812 and S813 are the same as the processes of S711 and S712 in FIG. However, in S813, the focus sensitivity related information (sensitivity information at the image height 0) associated with the focus detection result stored in S807 is acquired for the focus detection result selected in S812.

  In step S814, the camera control unit 9 determines whether to execute the sensitivity correction process using the sensitivity correction execution range set in step S811 and the focal length information acquired in step S811. Based on the focus detection result at the AF frame position selected in step S812 and the focus sensitivity related information acquired in step S813, calculation of the defocus amount is performed. The camera control unit 9 determines that the sensitivity correction process is to be performed when the calculated defocus amount is within the sensitivity correction implementation range set in S811. If the defocus amount is not within the sensitivity correction implementation range set in S811, it is determined that the sensitivity correction process is not performed. The details of the determination process will be described later with reference to FIG. In addition, when the focal length is larger than a predetermined threshold, the camera control unit 9 determines that the sensitivity correction process is not performed. If it is determined that the sensitivity correction process is to be performed, the process proceeds to step S815. If it is determined that the sensitivity correction process is not to be performed, the process proceeds to step S817. In addition, regarding the determination standard of the implementation of the sensitivity correction process, a determination standard other than this embodiment may be adopted as needed.

  In S815, the camera control unit 9 acquires data of the “sensitivity image height correction coefficient” from the lens control unit 26 via the lens communication unit 25 and the camera communication unit 11. This data is data of a focus sensitivity correction coefficient for correcting the focus sensitivity of the central image height. The calculation of the sensitivity S (X, Y) is performed by applying the equation (1). Each process of S816 and S817 is the same as each process of S713 and S714 of FIG. In S818, the AF frame position selection process in the multipoint AF process ends.

Next, with reference to FIG. 10, a method of calculating the sensitivity correction implementation range will be described. FIG. 10 is a graph in which the image height (unit: mm) is taken on the horizontal axis and the ratio is taken on the vertical axis, and the sensitivity ratio and sensitivity correction ratio at focal lengths A and B (unit: mm) are illustrated. is there.
The camera control unit 9 calculates the sensitivity correction ratio from the stored coefficient according to the focal length (denoted as α) and the image height. The image height is determined by the following equation (2) from the image height coordinates (X, Y) of the AF frame farthest from the center image height set in step S811 in FIG. The sensitivity correction ratio can be obtained by substituting the image height and the coefficient α into the following equation (3).
Image height = ((X ² + Y ² ) (2)
Sensitivity correction ratio = 1 + (image height × α) (3)

  In FIG. 10, a graph curve 901 indicated by a solid line indicates the sensitivity ratio at the focal length A mm, and a graph curve 902 indicated by the solid line indicates the sensitivity ratio at the focal distance B mm. The sensitivity ratios are all 1 at an image height of zero, and increase as the image height increases. When the sensitivity ratio at the focal length A mm is the characteristic shown in the graph curve 901, the sensitivity correction ratio calculated from the equation (2) and the equation (3) is indicated by the dashed-dotted line graph line 903. The value of the sensitivity correction ratio is 1 at image height zero, and increases linearly with image height increase. When the sensitivity ratio at the focal length B mm is the characteristic shown in the graph curve 902, the sensitivity correction ratio calculated from the equations (2) and (3) is indicated by the dashed dotted line graph line 904. The value of the sensitivity correction ratio is 1 at image height zero, and increases linearly as the image height increases, and its slope is larger than the slope of the graph line 903.

The camera control unit 9 calculates the sensitivity correction execution range by substituting the calculated sensitivity correction ratio and the final drive range into the following equation (4).
Sensitivity correction implementation range = sensitivity correction ratio × final drive range (4)
In the present embodiment, the image height is expressed by a linear interpolation equation as a calculation equation of the sensitivity correction ratio, and the calculation equation of the sensitivity correction implementation range is expressed as a linear equation of the sensitivity correction ratio. Arbitrary interpolation formulas and calculation formulas may be applied. Alternatively, the camera control unit 9 may obtain data of the coefficient α from the lens control unit 26 via the lens communication unit 25 and the camera communication unit 11.

  The setting method of the sensitivity correction execution range and the execution determination of the sensitivity correction processing will be described with reference to FIG. FIG. 11 is an explanatory diagram of the relationship between the defocus amount, the final drive range 1001, the sensitivity correction execution range 1002, and the sensitivity correction non-execution range 1003. The sensitivity correction execution range 1002 is calculated by the equation (4) in S811 of FIG. 9 and is set around the final drive range 1001. The final drive range 1001 is a predetermined range based on the position where the defocus amount is zero, and a range obtained by multiplying the final drive range 1001 by the sensitivity correction ratio is the sensitivity correction execution range 1002. The camera control unit 9 determines whether the defocus amount calculated based on the focus detection result selected in S812 and the focus sensitivity related information acquired in S813 is within the sensitivity correction execution range 1002 or the sensitivity correction non-execution range 1003. Determine if it is within. If the defocus amount is within the sensitivity correction execution range 1002, it is determined in S814 of FIG. 9 that the sensitivity correction process is to be performed, and if the defocus amount is the sensitivity correction non-execution range 1003, the process proceeds to S814. It is determined that the sensitivity correction process is not to be performed.

  In the present embodiment, the focus sensitivity correction process is performed only in the sensitivity correction implementation range in which the change in focus sensitivity caused by the image height is added, which is set near the final drive range. According to the present embodiment, it is possible to realize improvement in focus adjustment accuracy while further reducing the communication load between the camera body and the lens apparatus and the calculation load of the camera body, and the number of frames of multipoint AF is increased. , And effective for speeding up of the frame rate.

Reference Signs List 1 camera body 2 interchangeable lens 4 imaging device 6 focus detection unit 9 camera control unit 22 focus lens 26 lens control unit 28 focus drive unit

Claims (10)

What is claimed is: 1. An imaging system comprising: a lens device;
The lens device is
A lens for focus adjustment and a drive control means for controlling the drive of the lens;
A first communication unit for communicating with the camera body;
The camera body is
Second communication means for communicating with the lens device;
Focus detection means for acquiring focus detection signals in a plurality of focus detection areas set in an imaging plane;
A control unit configured to generate a control signal for controlling the driving of the lens from the focus detection signal and to transmit the control signal to the lens device via the first and second communication units;
The control means of the camera body portion is sensitive from the lens device to the sensitivity information indicating the sensitivity information of the lens at the central image height and the change in sensitivity corresponding to the image height through the first and second communication means. Correction information of the degree is acquired, image height information of the focus detection area selected from the plurality of focus detection areas, and the acquired correction information correct the change of the sensitivity of the lens corresponding to the image height and correct the correction An imaging system characterized by generating the control signal indicating a driving amount of the lens calculated using the sensitivity;   The image pickup system according to claim 1, wherein the control means of the camera body calculates the sensitivity by the polynomial approximation or the linear approximation with respect to the characteristic of the sensitivity of the lens at the central image height. An imaging apparatus capable of mounting a lens apparatus having a lens for focusing,
Communication means for communicating with the lens device;
Focus detection means for acquiring focus detection signals in a plurality of focus detection areas set in an imaging plane;
The control unit generates a control signal for controlling the drive of the lens by the focus detection signal, and transmits the control signal to the lens device through the communication unit.
The control means acquires, from the lens device, sensitivity information of the lens at a central image height and sensitivity correction information indicating a change in sensitivity corresponding to the image height, through the communication means, The lens calculated by using the corrected sensitivity, correcting the change in sensitivity of the lens corresponding to the image height with the image height information of the focus detection area selected from the focus detection area of the lens and the acquired correction information An image pickup apparatus generating the control signal indicating a drive amount of the image pickup apparatus;   The control means calculates the drive amount of the lens using the corrected sensitivity when the defocus amount indicated by the focus detection signal is within the set execution range. 3. The imaging device according to 3.   5. The imaging apparatus according to claim 4, wherein the control unit sets the implementation range using a sensitivity correction ratio calculated from an image height.   The control means acquires the sensitivity information from the lens device at each timing of focus detection in a control mode in which focus detection is performed at different timings for the plurality of focus detection areas. The imaging device of any one of 5.   The control means associates the focus detection signal acquired at different timings with the acquired sensitivity information in the control mode, stores the same in the storage means, and selects a focus detection area selected from the plurality of focus detection areas. 7. The image pickup apparatus according to claim 6, wherein the sensitivity information corresponding to is acquired from the storage unit.   8. The image pickup apparatus according to claim 6, wherein the control mode is a mode in which an area of the imaging surface is divided into a grid and focus detection is performed for each of the divided focus detection areas. A lens device used by being attached to a camera body,
A lens for focusing and driving means for the lens;
Communication means for communicating with the camera body;
A control unit configured to control driving of the lens;
The control means is characterized in that sensitivity information of the lens at a central image height and sensitivity correction information indicating a change in sensitivity corresponding to the image height are transmitted to the camera body through the communication means. And a lens device. A lens device having a lens for focusing, and a control method executed in an imaging system including a camera body capable of mounting the lens device,
The focus detection means acquires focus detection signals in a plurality of focus detection areas set in the imaging plane;
The control means of the camera body acquires the sensitivity information of the lens at the central image height and sensitivity correction information indicating a change in sensitivity corresponding to the image height from the lens device through the communication means. Step and
Correcting the change in sensitivity of the lens corresponding to the image height based on image height information of a focus detection area selected from the plurality of focus detection areas and the acquired correction information;
The control means calculates the drive amount of the lens using the focus detection signal and the corrected sensitivity, generates a control signal indicating the calculated drive amount, and transmits the lens via the communication means. A control method of an imaging system, comprising the step of transmitting to an apparatus.

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