Focus control device, operation method for focus control device, operation program for focus control device, and imaging apparatus

Abstract

To provide a focus control device capable of suppressing the unsteadiness of the position of a focus lens caused when the fluctuations of a subject distance are large and to provide an operation method for the focus control device, an operation program for the focus control device, and an imaging apparatus.SOLUTION: A focus adjustment part derives and acquires the present position of a focus lens on an optical axis on the basis of the driving amount of a motor for focusing from a focus lens driving mechanism. A focusing derivation part derives and acquires the estimated focusing position of the focus lens when the focus lens is in the present position. When the absolute value of the difference between the present position and estimated focusing position of the focus lens is less than a threshold value, a speed setting part sets the moving speed of the focus lens as a first speed and a focus lens driving control part moves the focus lens at the first speed. On the other hand, when the absolute value of the difference between the present position and estimated focusing position of the focus lens is equal to or more than the threshold value, the speed setting part sets the moving speed of the focus lens as a second speed lower than the first speed and the focus lens driving control part moves the focus lens at the second speed.SELECTED DRAWING: Figure 16

Description

[Technical Field]

[0001] The technology of the present disclosure relates to a focus control device, an operating method for a focus control device, an operating program for a focus control device, and an imaging device.

[0002] Patent Document 1 describes an autofocus system that controls the focus of a camera's photographing optical system so that the camera's photographing optical system is in focus. The autofocus system includes a focus movement amount information acquisition means and a focus movement speed change means. The focus movement amount information acquisition means acquires information regarding the amount of focus movement required for the photographing optical system to move from its current focus state to an in-focus state. The focus movement speed change means uses the focus movement speed when the camera is stationary in a distance direction relative to a subject to be focused by the autofocus means as a reference speed, and changes the focus movement speed required for the photographing optical system to move from its current focus state to an in-focus state based on the information acquired by the focus movement amount information acquisition means. The focus movement speed change means increases the focus movement speed relative to the reference speed when the camera moves in a distance direction, thereby increasing the amount of focus movement required for the camera to move in focus. If the amount of focus movement required for the camera to move in a distance direction decreases, the focus movement speed change means increases the focus movement speed relative to the reference speed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-233668 Summary of the Invention

[0004] One embodiment of the technology disclosed herein provides a focus control device, an operating method for the focus control device, an operating program for the focus control device, and an imaging device that can suppress fluctuations in the position of the focus lens that occur when there is a large variation in subject distance. [Means for solving the problem]

[0005] The focus control device disclosed herein is a focus control device that performs focus control of a focus lens based on output from a phase difference detection pixel, and is equipped with a processor. The processor acquires the current position of the focus lens and an estimated focus position of the focus lens derived when the focus lens is at the current position, and moves the focus lens at a first speed if the absolute value of the difference between the current position and the estimated focus position is less than a first threshold, and moves the focus lens at a second speed slower than the first speed if the absolute value of the difference between the current position and the estimated focus position is equal to or greater than the first threshold.

[0006] The first threshold value is preferably set to an absolute value of the difference between the current position and the estimated focus position at which the phase difference detection accuracy falls outside a set range.

[0007] It is preferable that the processor sets the second speed to a speed that allows the derivation of the estimated focus position a set number of times while moving the focus lens based on the absolute value of the difference between the current position and the estimated focus position and the number of times the estimated focus position is derivated per unit time.

[0008] The set number of times is preferably changed according to the absolute value of the difference between the current position and the estimated focus position.

[0009] It is preferable that, when the absolute value of the difference between the current position and the estimated focus position becomes less than a second threshold while moving the focus lens at the second speed, the processor changes the movement speed of the focus lens based on the estimated focus position when the absolute value of the difference between the current position and the estimated focus position becomes less than the second threshold.

[0010] It is preferable that the processor derives the estimated focus position multiple times while moving the focus lens at the second speed, and stops the movement of the focus lens when the absolute value of the difference between the previous and current estimated focus positions becomes less than a third threshold value.

[0011] Preferably, when the processor determines that the current position of the focus lens has passed the estimated in-focus position while the focus lens is being moved at the second speed, the processor stops the movement of the focus lens.

[0012] Preferably, the processor determines that the current position has passed the estimated focus position when the sign of the difference between the current position and the estimated focus position is reversed.

[0013] It is preferable that the processor keeps the focus lens at the current position when the absolute value of the difference between the current position and the estimated focus position is less than a fourth threshold, and moves the focus lens when the absolute value of the difference between the current position and the estimated focus position is greater than or equal to the fourth threshold.

[0014] The operation method of the focus control device disclosed herein is a method for operating a focus control device that controls the focus of a focus lens based on an output from a phase difference detection pixel, and includes acquiring the current position of the focus lens and an estimated focus position of the focus lens derived when the focus lens is at the current position, moving the focus lens at a first speed if the absolute value of the difference between the current position and the estimated focus position is less than a first threshold, and moving the focus lens at a second speed slower than the first speed if the absolute value of the difference between the current position and the estimated focus position is equal to or greater than the first threshold.

[0015] The operating program for the focus control device disclosed herein is an operating program for the focus control device that performs focus control of the focus lens based on output from a phase difference detection pixel, and causes a computer to execute processing including: acquiring the current position of the focus lens and an estimated focus position of the focus lens derived when the focus lens is at the current position; moving the focus lens at a first speed if the absolute value of the difference between the current position and the estimated focus position is less than a first threshold; and moving the focus lens at a second speed slower than the first speed if the absolute value of the difference between the current position and the estimated focus position is equal to or greater than the first threshold.

[0016] The imaging device of the present disclosure includes the focus control device described above. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram illustrating a configuration of an imaging device. [Figure 2] FIG. 2 is a diagram showing the arrangement of pixels of an imaging element. [Figure 3] FIG. 2 is a diagram illustrating a configuration of a normal pixel. [Figure 4] FIG. 2 is a diagram illustrating a configuration of a first phase difference detection pixel. [Figure 5] FIG. 10 is a diagram illustrating a configuration of a second phase difference detection pixel. [Figure 6] 10 is a graph showing a phase difference between a first calculation signal and a second calculation signal. [Figure 7] FIG. 2 is a block diagram showing a detailed configuration of a control unit. [Figure 8] FIG. 2 is a block diagram showing a processing unit of a CPU. [Figure 9] These figures show scenes in which the subject distance changes significantly, where (A) shows a scene in which a distant mountain is the subject, and (B) shows a scene in which the subject is switched from a distant mountain to a person in the foreground. [Figure 10] 10 is a graph showing the relationship between the phase difference and the defocus amount. [Figure 11] 10A and 10B are diagrams showing the transition of the current position of the focus lens and the estimated in-focus position in a conventional example when switching from a distant view to a close view A. [Figure 12] 10A and 10B show the processing of a speed setting unit that sets the movement speed of the focus lens according to the result of comparing the absolute value of the difference between the current position of the focus lens and the estimated focus position with a threshold value, where (A) shows the case where the absolute value of the difference between the current position of the focus lens and the estimated focus position is less than the threshold value, and (B) shows the case where the absolute value of the difference between the current position of the focus lens and the estimated focus position is equal to or greater than the threshold value. [Figure 13] 10 is a graph showing the relationship between the absolute value of the difference between the current position of the focus lens and the estimated in-focus position and the number of settings. [Figure 14]This figure shows the processing of the focus lens drive control unit, which determines whether to keep the focus lens at its current position depending on the result of comparing the absolute value of the difference between the current position of the focus lens and the estimated focus position with a threshold value. (A) shows the case where the absolute value of the difference between the current position of the focus lens and the estimated focus position is less than the threshold value, and (B) shows the case where the absolute value of the difference between the current position of the focus lens and the estimated focus position is greater than or equal to the threshold value. [Figure 15] 10A and 10B are diagrams showing the transition of the current position of the focus lens and the estimated in-focus position when switching from a distant view to a close view B. FIG. [Figure 16] 10A and 10B are diagrams showing the transition of the current position of the focus lens and the estimated in-focus position when switching from a distant view to a close view A. FIG. [Figure 17] 10 is a flowchart showing a processing procedure of a control unit. [Figure 18] 10 is a flowchart showing a processing procedure of a control unit. [Figure 19] 10A and 10B are diagrams illustrating an example of determination as to whether the focus lens is stopped in a model in which the estimated focus position cannot be updated while the focus lens is moving. [Figure 20] 10A and 10B are diagrams illustrating another example of determining whether the focus lens has stopped in a model in which the estimated focus position cannot be updated while the focus lens is moving. [Figure 21] 10A and 10B are diagrams illustrating a third embodiment in which the movement speed of the focus lens is changed based on the estimated focus position when the absolute value of the difference between the current position of the focus lens and the estimated focus position is less than a threshold value. DETAILED DESCRIPTION OF THE INVENTION

[0018] [First embodiment] As an example, as shown in FIG. 1, the imaging device 10 is, for example, a mirrorless single-lens digital camera, and includes an imaging optical system 11 and an imaging element 12. The imaging optical system 11 has multiple types of lenses for focusing subject light on the imaging element 12. Specifically, the imaging optical system 11 includes an objective lens 13, a focus lens 14, and a zoom lens 15. These lenses 13 to 15 are arranged in this order from the object side (subject side) toward the image side (image element 12 side). Although simplified in FIG. 1, each of the lenses 13 to 15 is actually a lens group formed by combining multiple lenses. The imaging optical system 11 also includes an aperture 16. The aperture 16 is arranged closest to the image side of the imaging optical system 11. The imaging device 10 may be of a type in which a lens barrel incorporating the imaging optical system 11 and the like and a main body incorporating the image element 12 and the like are integrated, or it may be of a so-called interchangeable lens type in which the lens barrel and the main body are separate.

[0019] Focus lens 14 is provided with a focus lens drive mechanism 17, zoom lens 15 is provided with a zoom lens drive mechanism 18, and diaphragm 16 is provided with an diaphragm drive mechanism 19. Focus lens drive mechanism 17 holds focus lens 14 and includes a focus cam ring with cam grooves formed on its outer periphery, a focus motor that moves the focus cam ring along the optical axis OA by rotating the focus cam ring about the optical axis OA, and a focus motor driver, etc. Zoom lens drive mechanism 18 similarly holds zoom lens 15 and includes a zoom cam ring with cam grooves formed on its outer periphery, a zoom motor that moves the zoom cam ring along the optical axis OA by rotating the zoom cam ring about the optical axis OA, and a zoom motor driver, etc. Diaphragm drive mechanism 19 includes a diaphragm motor that opens and closes the multiple diaphragm blades of diaphragm 16, and a diaphragm motor driver, etc.

[0020] The focus motor, zoom motor, and diaphragm motor are, for example, stepping motors. In this case, the positions of focus lens 14 and zoom lens 15 on the optical axis OA and the opening of diaphragm 16 can be derived from the drive amounts of the focus motor, zoom motor, and diaphragm motor. Note that instead of the drive amounts of the focus motor and zoom motor, position sensors may be provided to detect the positions of focus lens 14 and zoom lens 15.

[0021] Electrical components such as motors or drivers of each of the drive mechanisms 17 to 19 are connected to the control unit 20. The electrical components of each of the drive mechanisms 17 to 19 are driven under the control of the control unit 20. More specifically, the control unit 20 issues drive signals in response to instructions from the user input via the operation unit 21, thereby driving the electrical components of each of the drive mechanisms 17 to 19. For example, when an instruction to change the angle of view to the telephoto side is input via the angle of view change switch of the operation unit 21, the control unit 20 issues a drive signal to a driver of a zoom motor of the zoom lens drive mechanism 18, thereby moving the zoom lens 15 to the telephoto side.

[0022] The focus motor, zoom motor, and diaphragm motor output their drive amounts to the control unit 20. The control unit 20 derives the positions of the focus lens 14 and zoom lens 15 on the optical axis OA and the opening of the diaphragm 16 from the drive amounts.

[0023] The imaging element 12 is, for example, a CMOS (Complementary Metal-Oxide-Semiconductor) image sensor, and has an imaging surface 42 (see FIG. 2) that captures light from a subject. The imaging element 12 is arranged so that the center of the imaging surface 42 coincides with the optical axis OA and the imaging surface 42 is perpendicular to the optical axis OA. Note that the terms "coincidence" and "orthogonality" used here refer to perfect coincidence and orthogonality, as well as coincidence and orthogonality that include errors generally accepted in the technical field to which the technology of the present disclosure pertains.

[0024] An imaging element driver 22 is connected to the imaging element 12. The imaging element driver 22 is connected to the control unit 20. Under the control of the control unit 20, the imaging element driver 22 controls the timing at which the imaging element 12 captures the subject light by supplying a vertical scanning signal and a horizontal scanning signal to the imaging element 12.

[0025] A shutter 23 is provided between the imaging optical system 11 and the image sensor 12. The shutter 23 is, for example, a focal plane shutter having front and rear curtains. A shutter drive mechanism 24 is connected to the shutter 23. The shutter drive mechanism 24 includes an electromagnet that holds the front and rear curtains and releases the hold to cause the front and rear curtains to move, as well as a driver for the electromagnet. The shutter drive mechanism 24 is driven under the control of the control unit 20 to open and close the shutter 23.

[0026] The control unit 20 is connected to various units, such as an image input controller 25, an image memory 26, and an image processing unit 27, via a bus line 28. Other units connected to the bus line 28 include a VRAM (Video Random Access Memory) 29, a display control unit 30, a media controller 31, and an instruction receiving unit 32. Although not shown in the figure, the bus line 28 is also connected to a strobe drive control unit that controls the drive of a strobe device, an external communication I / F (Interface) that communicates with an external device via a connection terminal such as a USB (Universal Serial Bus) terminal, or a wireless communication I / F.

[0027] Image data obtained by capturing an image of the subject light is input from the imaging element 12 to the image input controller 25. The image input controller 25 outputs the image data to the image memory 26. The image memory 26 is, for example, a Synchronous Dynamic Random Access Memory (SDRAM), and temporarily stores the image data.

[0028] The image processing unit 27 reads unprocessed image data from the image memory 26. The image processing unit 27 performs various image processing on the image data. The various image processing includes, for example, offset correction processing, sensitivity correction processing, pixel interpolation processing, white balance correction processing, gamma correction processing, demosaic processing, luminance signal and color difference signal generation processing, edge enhancement processing, color correction processing, etc. The image processing unit 27 writes the image data after the various image processing back to the image memory 26.

[0029] The VRAM 29 receives image data from the image memory 26, which has undergone various image processing and is to be displayed as a live view image (also called a through image). The VRAM 29 has an area for storing image data for two consecutive frames. The image data stored in the VRAM 29 is sequentially overwritten with new image data. The VRAM 29 sequentially outputs the newer image data of the two consecutive frames of image data to the display control unit 30.

[0030] The display control unit 30 functions as a so-called video encoder, converting image data from the VRAM 29 into video data and outputting it to either the viewfinder monitor 33 or the rear monitor 34. This allows the user to view a live view image through either the viewfinder monitor 33 or the rear monitor 34. The display frame rate of the live view image is, for example, 60 fps (frames per second).

[0031] Whether the video data is output to the viewfinder monitor 33 or the rear monitor 34 is determined, for example, as follows: An pupil detection sensor is provided in the viewfinder. If the pupil detection sensor detects that the user is looking through the viewfinder, the video data is output to the viewfinder monitor 33. On the other hand, if the pupil detection sensor detects that the user is not looking through the viewfinder, the video data is output to the rear monitor 34.

[0032] When an instruction to start shooting a still image or a moving image is issued by fully pressing the release button on the operation unit 21, the image processing unit 27 performs compression processing on the image data in the image memory 26. In the case of a still image, the image processing unit 27 performs compression processing on the image data in, for example, the JPEG (Joint Photographic Experts Group) format. In the case of a moving image, the image processing unit 27 performs compression processing on the image data in, for example, the MPEG (Moving Picture Experts Group) format. The image processing unit 27 outputs the compressed image data to the media controller 31.

[0033] The media controller 31 records the compressed image data from the image processing unit 27 on a memory card 35. The memory card 35 is detachably attached to a memory card slot (not shown).

[0034] When the image playback mode is selected via the mode selector switch of the operation unit 21, the media controller 31 reads image data from the memory card 35 and outputs it to the image processing unit 27. The image processing unit 27 performs decompression processing on the image data from the memory card 35. The image processing unit 27 outputs the decompressed image data to the display control unit 30. The display control unit 30 converts the image data into video data and outputs it to the rear monitor 34. This allows the user to view the played-back image on the rear monitor 34.

[0035] The instruction receiving unit 32 receives various operation instructions input by the user via the operation unit 21 and a touch panel 36 provided integrally with the rear monitor 34. The instruction receiving unit 32 outputs the received operation instructions to the control unit 20 via the bus line 28.

[0036] As described above, the operation unit 21 includes a field angle change switch, a release button, and a mode change switch. The release button is a two-stage push button that can be pressed halfway or all the way. Pressing the release button halfway issues an instruction to prepare for shooting a still image or video, and pressing it all the way issues an instruction to start shooting a still image or video. In addition to these, the operation unit 21 also includes a menu button for displaying various setting menus on the rear monitor 34, a cross key used for setting numerical values ​​and switching between options, and a confirmation button operated to confirm settings, etc. The touch panel 36 is superimposed on the display surface of the rear monitor 34. The touch panel 36 recognizes various operation instructions from the user by detecting contact with a dedicated indicator such as the user's finger or a stylus pen.

[0037] Modes that can be switched using the mode selector switch include still image capture mode, video capture mode, image playback mode, and setting mode. Still image capture mode includes not only a normal capture mode in which one still image is captured, but also a continuous capture mode in which still images are captured continuously at a predetermined capture interval (for example, a frame rate of 5 fps to 10 fps). Continuous capture mode is activated, for example, when the release button is pressed all the way down for a predetermined period of time or more (for example, one second or more). Continuous capture mode ends when the release button is released from its fully pressed state.

[0038] As an example, as shown in FIG. 2, the image sensor 12 is provided with a photoelectric conversion unit 40. The photoelectric conversion unit 40 is made up of a plurality of pixels 41 arranged two-dimensionally along the X and Y directions. The plurality of pixels 41 form an image pickup surface 42. As is well known, the pixels 41 are made up of microlenses 45, color filters 46, and photoelectric conversion elements 47 such as photodiodes (see FIGS. 3 to 5 for all of these). The X and Y directions are the horizontal and vertical directions when the bottom surface of the image pickup device 10 is placed on a horizontal surface.

[0039] Scanning lines parallel to the X direction are wired between rows of pixels 41. Furthermore, signal lines parallel to the Y direction are wired between columns of pixels 41. The pixels 41 (photoelectric conversion elements 47) are connected to the signal lines via amplifiers and switches. The switches are also connected to the scanning lines. In the case of a storage operation in which signal charges corresponding to subject light are stored in the pixels 41 (photoelectric conversion elements 47), an OFF signal is supplied as a vertical scanning signal through the scanning lines to turn the switches OFF. In the case of a readout operation in which an image signal (voltage signal) 43 corresponding to the signal charges is read from the pixels 41 (photoelectric conversion elements 47), an ON signal is supplied as a vertical scanning signal through the scanning lines to turn the switches ON. The ends of the signal lines are connected to a CDS (Correlated Double Sampling) circuit and an ADC (Analog to Digital Converter) circuit. The CDS circuit performs correlated double sampling on the image signal 43 input through the signal lines. The ADC circuit converts the correlated double sampled image signal 43 into a digital image signal 43.

[0040] Depending on the type of color filter 46, the pixels 41 are divided into three types: green pixels (denoted as "G" in FIG. 2) that are sensitive to light in the green wavelength band, red pixels (denoted as "R" in FIG. 2) that are sensitive to light in the red wavelength band, and blue pixels (denoted as "B" in FIG. 2) that are sensitive to light in the blue wavelength band. The three types of pixels 41 are regularly arranged in a predetermined array. As an example of the predetermined array, a so-called Bayer array is shown here, in which two green pixels, one blue pixel, and one red pixel are arranged in a 2×2 matrix.

[0041] The pixels 41 include normal pixels 41N and phase difference detection pixels 41P. The phase difference detection pixels 41P further include first phase difference detection pixels 411P and second phase difference detection pixels 412P. There are three types of normal pixels 41N: green pixels, blue pixels, and red pixels, but the phase difference detection pixels 41P are only green pixels.

[0042] The phase difference detection pixels 41P are arranged at predetermined intervals in the X direction and the Y direction. In FIG. 2, the phase difference detection pixels 41P are arranged at intervals of five pixels in the X direction and at intervals of two pixels in the Y direction. The phase difference detection pixels 41P are arranged so that the first phase difference detection pixels 411P and the second phase difference detection pixels 412P alternate in the X direction and the Y direction. For example, in the fourth row, the phase difference detection pixels 41P are arranged from left to right in the order of the second phase difference detection pixel 412P, the first phase difference detection pixel 411P, .... In addition, in the tenth column, the phase difference detection pixels 41P are arranged from top to bottom in the order of the second phase difference detection pixel 412P, the first phase difference detection pixel 411P, the second phase difference detection pixel 412P, the first phase difference detection pixel 411P, .... The first phase difference detecting pixel 411P and the second phase difference detecting pixel 412P adjacent to each other in the X direction and the Y direction form one pair for detecting the phase difference α (see FIG. 6).

[0043] As an example, as shown in FIGS. 3 to 5, the normal pixel 41N, the first phase difference detection pixel 411P, and the second phase difference detection pixel 412P have the same basic configuration, and are composed of a microlens 45, a color filter 46, and a photoelectric conversion element 47 arranged in this order from the object side.

[0044] 3, the photoelectric conversion element 47 of the normal pixel 41N outputs an image generation signal 43N corresponding to the subject light that has been collected by the microlens 45 and transmitted through the color filter 46 as the image signal 43. The image generation signal 43N is stored in the image memory 26 as part of the image data.

[0045] 4 and 5, a light-shielding member 49 is disposed between the color filter 46 and the photoelectric conversion element 47 of the first phase difference detection pixel 411P and the second phase difference detection pixel 412P. This light-shielding member 49 is not disposed in the normal pixel 41N. The light-shielding member 49 of the first phase difference detection pixel 411P shields the right half of the photoelectric conversion element 47 when viewed from the object side. In contrast, the light-shielding member 49 of the second phase difference detection pixel 412P shields the left half of the photoelectric conversion element 47 when viewed from the object side.

[0046] The photoelectric conversion element 47 of the first phase difference detection pixel 411P outputs, as the image signal 43, a first calculation signal 431P corresponding to subject light that is collected by the microlens 45, transmitted through the color filter 46, and whose right half is shielded by the light blocking member 49. In contrast, the photoelectric conversion element 47 of the second phase difference detection pixel 412P outputs, as the image signal 43, a second calculation signal 432P corresponding to subject light that is collected by the microlens 45, transmitted through the color filter 46, and whose left half is shielded by the light blocking member 49. The first calculation signal 431P and the second calculation signal 432P are stored in the image memory 26 as part of image data, similar to the image generation signal 43N. The first calculation signal 431P and the second calculation signal 432P are an example of "output from a phase difference detection pixel" according to the technology of the present disclosure. In the following description, unless there is a particular need to distinguish between them, the first calculation signal 431P and the second calculation signal 432P will be collectively referred to as the calculation signal 43P.

[0047] 6, a phase difference α appears between a first calculation signal 431P and a second calculation signal 432P output from a first phase difference detection pixel 411P and a second phase difference detection pixel 412P that are adjacent in the X and Y directions. This phase difference α indicates in which direction and by how much the focus lens 14 needs to be moved to achieve the in-focus position. The imaging device 10 derives an estimated in-focus position of the focus lens 14 based on the phase difference α, and performs autofocus control to automatically move the focus lens 14 to the estimated in-focus position.

[0048] The region from which the estimated focus position is derived (hereinafter referred to as the focus adjustment region) is a region preset in the center of the imaging surface 42. The focus adjustment region may be a region specified by the user or a region surrounding a specific subject recognized by well-known subject recognition technology. The specific subject may be the pupil, face, or torso of a person, the pupil, face, or torso of an animal, or the front or torso of a vehicle such as an automobile, railroad vehicle, or airplane. Here, the pupil of a person or animal refers to the pupil, or the black part of the eye. The face of a person or animal refers to the part of the body that includes the forehead, cheeks, chin, eyes, nose, mouth, ears, etc. The torso of a person or animal refers to the part excluding the head, neck, limbs, and tail. The front of a vehicle refers to the front body of an automobile, the part of the lead car that includes the destination display, front window, headlights, etc. of a railroad vehicle, or the nose of an airplane that includes the radome, front window, etc. The fuselage of a vehicle refers to the entire body excluding the wheels in the case of an automobile, the entire body excluding the wheels in the case of a railway vehicle, regardless of whether it is the lead car, middle car or last car, and the entire body excluding the front, main wings, tail, etc. in the case of an airplane.

[0049] As the name suggests, the image generation signal 43N is used to generate an image such as a live view image. In contrast, the calculation signal 43P is used only to calculate the phase difference α and is not used to generate an image. Therefore, in the pixel interpolation process, the image processing unit 27 interpolates the pixel value of the phase difference detection pixel 41P using the image generation signals 43N of the normal pixels 41N surrounding the phase difference detection pixel 41P.

[0050] 7, the control unit 20 includes a storage 55, a CPU (Central Processing Unit) 56, and a memory 57. The storage 55, the CPU 56, and the memory 57 are interconnected via a bus line 58. The control unit 20 is an example of a "focus control device" and a "computer" according to the techniques of the present disclosure.

[0051] The storage 55 is a non-volatile storage device such as an EEPROM (Electrically Erasable Programmable Read-Only Memory). The storage 55 stores various programs and various data associated with the programs. Instead of the EEPROM, the storage 55 may be a Ferroelectric Random Access Memory (FeRAM) or a Magnetoresistive Random Access Memory (MRAM).

[0052] The memory 57 is a work memory for the CPU 56 to execute processing. The CPU 56 loads a program stored in the storage 55 into the memory 57 and executes processing in accordance with the program. In this way, the CPU 56 comprehensively controls each unit of the imaging device 10. The CPU 56 is an example of a "processor" according to the technology of the present disclosure. The memory 57 may be built into the CPU 56.

[0053] 8, an operating program 65 is stored in the storage 55. The operating program 65 is a program for causing the CPU 56 to perform automatic focus control and the like. In other words, the operating program 65 is an example of an "operating program for a focus control device" according to the technology of the present disclosure.

[0054] When the operating program 65 is started, the CPU 56 cooperates with the memory 57 and the like to function as a focus adjustment unit 70. The focus adjustment unit 70 includes a focus derivation unit 71, a speed setting unit 72, and a focus lens drive control unit 73. In addition to functioning as the focus adjustment unit 70, the CPU 56 also functions as various other processing units.

[0055] A driving amount 75 of the focus motor is input to the focus adjustment unit 70 from the focus lens driving mechanism 17. The focus adjustment unit 70 derives the position of the focus lens 14 on the optical axis OA (hereinafter referred to as the current position) from the driving amount 75.

[0056] The focus derivation unit 71 reads out the calculation signal 43P from the image memory 26. Specifically, the calculation signal 43P is data in which a plurality of first calculation signals 431P output from the first phase difference detection pixels 411P are two-dimensionally arranged in the X direction and the Y direction following the arrangement of the first phase difference detection pixels 411P, and data in which a plurality of second calculation signals 432P output from the second phase difference detection pixels 412P are two-dimensionally arranged in the X direction and the Y direction following the arrangement of the second phase difference detection pixels 412P. Therefore, the calculation signal 43P can be treated as two-dimensional image data.

[0057] The focus derivation unit 71 calculates the phase difference α shown in FIG. 6 from the calculation signal 43P of the focus adjustment area. Based on the phase difference α, the focus derivation unit 71 derives an estimated focus position of the focus lens 14 when the focus lens 14 is at its current position. The focus derivation unit 71 outputs the derivation result 76 of the estimated focus position to the speed setting unit 72 and the focus lens drive control unit 73. Note that the method of deriving the estimated focus position of the focus lens 14 based on the phase difference α is well known, so a detailed description thereof will be omitted here.

[0058] Speed ​​setting unit 72 sets a moving speed V of focus lens 14 from the current position to the estimated focus position based on an absolute value |ΔA| of the difference between the current position of focus lens 14 derived from drive amount 75 and the estimated focus position of focus lens 14 represented by derivation result 76 from focus derivation unit 71. Speed ​​setting unit 72 outputs set speed information 77 including the set moving speed V of focus lens 14 (hereinafter may be referred to as set speed) to focus lens drive control unit 73.

[0059] Focus lens drive control unit 73 controls the drive of focus lens drive mechanism 17 and, ultimately, focus lens 14. Specifically, focus lens drive control unit 73 moves focus lens 14 from the current position to the estimated in-focus position at a set speed V via focus lens drive mechanism 17. Strictly speaking, when focus lens drive control unit 73 moves focus lens 14, it means that focus lens drive control unit 73 issues a drive signal to a driver of a focus motor of focus lens drive mechanism 17, causing the focus motor to move focus lens 14. Note that if the current position of focus lens 14 and the estimated in-focus position are the same, then of course, focus lens drive control unit 73 does nothing and focus lens 14 is not moved.

[0060] In the focus adjustment unit 70, the focus derivation unit 71 derives the estimated focus position, the speed setting unit 72 sets the movement speed V of the focus lens 14, and the focus lens drive control unit 73 controls the drive of the focus lens 14 for each frame. Therefore, the derivation result 76 of the estimated focus position by the focus derivation unit 71 is updated for each frame. Therefore, the number of times the estimated focus position is derived per unit time is one time per frame.

[0061] Here, consider the scene shown in Figure 9 as an example. That is, (A) shows a case where a video is being shot with a distant mountain 80 as the subject. If the subject is switched from the state shown in (A) to a person 81 in the foreground, as shown in (B), the subject distance will change significantly. Note that the subject distance is the distance between the imaging device 10 and the main subject. The main subject is, for example, a subject that exists within the focus adjustment area. In the case of (A), the main subject is the mountain 80, and in the case of (B), the main subject is the person 81.

[0062] As an example, as shown in Figure 10, the relationship between the phase difference α and the defocus amount maintains a proportional relationship (linearity) when -αX ≤ α ≤ αX, but the proportional relationship breaks down when αX < α and α < -αX, resulting in a decrease in the accuracy of phase difference detection. Therefore, in situations where the subject distance fluctuates significantly, such as those shown in Figure 9, the estimated focus position deviates from the actual focus position (see Figure 11). The defocus amount is the difference between the current position of focus lens 14 and the actual focus position.

[0063] 11 shows the transition of the current position of focus lens 14 and the estimated in-focus position in a conventional example when the subject is switched from a distant view to a close-up view A at time TA. Switching the subject from a distant view to a close-up view A is a situation in which the subject distance changes significantly, as shown in FIG. 9, and the phase difference detection accuracy decreases. As a result, the estimated in-focus position PA at time TA is shifted from the original in-focus position of the close-up view A, which is indicated by the dashed dotted line.

[0064] At time TA, focus lens drive control unit 73 starts moving focus lens 14 toward estimated in-focus position PA at set speed VA. At time TC, two frames after time TA, focus lens drive control unit 73 stops focus lens 14 at estimated in-focus position PA. Focus lens drive control unit 73 keeps the current position of focus lens 14 at estimated in-focus position PA until time TD. Note that set speed VA is, for example, the fastest movement speed of focus lens 14. Furthermore, "stopped" does not mean that focus lens 14 is stopped permanently at a specific position, but rather that it is stopped temporarily.

[0065] As the difference |ΔA| between the current position of focus lens 14 and the estimated focus position decreases with the movement of focus lens 14 toward estimated focus position PA, the phase difference detection accuracy recovers, and the estimated focus position gradually converges to the original focus position. Therefore, at time TD, the estimated focus position is updated to estimated focus position PD, which is closer to the original focus position than estimated focus position PA. Therefore, at time TD, focus lens drive controller 73 starts moving focus lens 14 toward estimated focus position PD at set speed VA. Between time TD and time TE, focus lens drive controller 73 stops focus lens 14 at estimated focus position PD.

[0066] At time TE, the estimated in-focus position is updated to an estimated in-focus position PE that is closer to the original in-focus position than the estimated in-focus position PD. Therefore, at time TE, the focus lens drive control unit 73 starts moving the focus lens 14 toward the estimated in-focus position PE at the set speed VA. The focus lens drive control unit 73 stops the focus lens 14 at the estimated in-focus position PE between time TE and time TF. In this way, in a scene where the subject distance fluctuates greatly as shown in FIG. 9, the position of the focus lens 14 fluctuates due to the estimated in-focus position deviating from the original in-focus position. If the position of the focus lens 14 fluctuates and the out-of-focus state persists, the appearance of the captured video will deteriorate.

[0067] Therefore, in the technology of the present disclosure, as shown in FIG. 12A, for example, when the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated in-focus position is less than the threshold value THA, the speed setting unit 72 sets the movement speed of the focus lens 14 to a set speed VB, which is slower than the set speed VA, when the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated in-focus position is equal to or greater than the threshold value THA, as shown in FIG. 12B. The threshold value THA is stored in the storage 55. The absolute value |ΔA| of the difference between the current position and the estimated in-focus position, at which the phase difference detection accuracy falls outside the set range, is set as the threshold value THA. A case in which the "phase difference detection accuracy falls outside the set range" refers to a case in which fluctuations in the subject distance may cause the position of the focus lens 14 to fluctuate (the image may remain out of focus) and be noticeable to the user. The threshold value THA is an example of a "first threshold" according to the technology of the present disclosure. The set speed VA is an example of a "first speed" according to the technology of the present disclosure. The set speed VB is an example of a "second speed" according to the technology of the present disclosure.

[0068] Speed ​​setting unit 72 sets set speed VB to a speed at which an estimated focus position can be derived a set number of times while moving focus lens 14, based on the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated focus position, and the number of times the estimated focus position is derived per unit time. The set number of times is set to a number at which the estimated focus position can be expected to converge to the original focus position.

[0069] 13, the set number of times to derive the estimated focus position is changed depending on the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated focus position. More specifically, when the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated focus position is less than 5000% (depth of focus), the set number is 5 times. When the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated focus position is 5000% or more and less than 20000%, the set number gradually increases from 5 times to 10 times. When the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated focus position is 20000% or more, the set number is 10 times.

[0070] 14A, for example, when the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated in-focus position is less than the threshold value THB, the focus lens drive control unit 73 keeps the focus lens 14 at the current position. That is, when the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated in-focus position is less than the threshold value THB, the current position of the focus lens 14 and the estimated in-focus position are considered to be the same. In other words, a margin is provided in determining whether to move the focus lens 14. On the other hand, when the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated in-focus position is equal to or greater than the threshold value THB, the focus lens drive control unit 73 moves the focus lens 14. The absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated in-focus position at which the user can recognize the image as out of focus is set as the threshold value THB. The threshold value THB is stored in the storage 55. The threshold value THB is an example of a "fourth threshold" according to the technology of the present disclosure.

[0071] FIG. 15 shows the transition of the current position of focus lens 14 and the estimated in-focus position when the subject is switched from a distant view to a near view B at time TA. Near view B is closer to the distant view than near view A, and switching the subject from a distant view to near view B occurs when the phase difference detection accuracy is within the set range. In other words, FIG. 15 corresponds to the case where the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated in-focus position is less than threshold value THA. Therefore, the estimated in-focus position PA at time TA matches the original in-focus position of near view B, indicated by the dashed dotted line. Note that matching the estimated in-focus position with the original in-focus position not only means a perfect match, but also includes a case where the absolute value of the difference between the estimated in-focus position and the original in-focus position is less than threshold value THB.

[0072] Speed ​​setting unit 72 sets the movement speed of focus lens 14 to set speed VA. At time TA, focus lens drive control unit 73 starts moving focus lens 14 at set speed VA toward estimated focus position PA. Focus lens drive control unit 73 stops focus lens 14 at estimated focus position PA between time TA and time TB. In this way, if the phase difference detection accuracy is within the set range and the estimated focus position matches the original focus position, focus lens drive control unit 73 quickly moves focus lens 14 to the estimated focus position at set speed VA.

[0073] At times TC and TE, the estimated in-focus position is slightly deviated from the original in-focus position. However, because the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated in-focus position is less than threshold value THB, focus lens drive controller 73 keeps focus lens 14 at the current position.

[0074] 11, Fig. 16 shows the transition of the current position of focus lens 14 and the estimated in-focus position when the subject is switched from a distant view to a close view A at time TA. The case where the subject is switched from a distant view to a close view A corresponds to the case where the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated in-focus position is equal to or greater than threshold value THA.

[0075] Speed ​​setting unit 72 sets the movement speed of focus lens 14 to set speed VB. At time TA, focus lens drive control unit 73 starts moving focus lens 14 at set speed VB toward estimated focus position PA. Here, speed setting unit 72 sets set speed VB to a speed at which an estimated focus position can be derived a set number of times, five times, while focus lens 14 is being moved to estimated focus position PA. The five derivations of the estimated focus position in this case correspond to the derivation of the estimated focus position at times TA, TB, TC, TD, and TE.

[0076] At time TD, the estimated focus position has converged and been updated to estimated focus position PD, which coincides with the original focus position. Therefore, focus lens drive control unit 73 stops focus lens 14 at estimated focus position PD between time TD and time TE. Note that in the extremely rare case where the estimated focus position does not converge to the original focus position after the set number of times of derivation, and the absolute value |ΔA| of the difference between the current position of focus lens 14 and the newly updated estimated focus position after focus lens 14 has stopped becomes equal to or greater than threshold value THB, focus lens drive control unit 73 moves focus lens 14 to the newly updated estimated focus position.

[0077] 15, the estimated in-focus position is slightly deviated from the original in-focus position at times TH and TJ. However, because the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated in-focus position is less than threshold value THB, focus lens drive controller 73 keeps focus lens 14 at the current position.

[0078] Next, the operation of the above configuration will be described with reference to the flowcharts shown in Figures 17 and 18 as an example. As shown in Figure 8, CPU 56 functions as a focus adjustment unit 70 when operating program 65 is started. Focus adjustment unit 70 includes a focus derivation unit 71, a speed setting unit 72, and a focus lens drive control unit 73.

[0079] When the release button is pressed all the way down in video shooting mode and a video shooting start instruction is received by the instruction receiving unit 32, the image sensor 12 accumulates signal charge according to the subject light under the control of the control unit 20. Then, an image signal 43 according to the signal charge is read out. The image signal 43 is stored in the image memory 26 via the image input controller 25. The image signal 43 is subjected to various image processes by the image processing unit 27 and then written back to the image memory 26.

[0080] The calculation signal 43P is read from the image memory 26 to the focus derivation unit 71. Then, the focus derivation unit 71 calculates a phase difference α from the calculation signal 43P of the focus adjustment region, and derives an estimated focus position of the focus lens 14 based on the phase difference α (step ST100). The derivation result 76 of the estimated focus position is output from the focus derivation unit 71 to the speed setting unit 72 and the focus lens drive control unit 73. Furthermore, the focus adjustment unit 70 derives the current position of the focus lens 14 on the optical axis OA based on the drive amount 75 of the focus motor from the focus lens drive mechanism 17 (step ST110).

[0081] If the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated in-focus position is equal to or greater than threshold value THB (YES in step ST120), the process proceeds to step ST130. On the other hand, if the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated in-focus position is less than threshold value THB (NO in step ST120), the process proceeds to step ST140 in Fig. 18. In step ST140, as shown in Fig. 14(A), focus lens 14 is kept at the current position by focus lens drive control unit 73, and the process ends.

[0082] In step ST130, the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated in-focus position is compared with a threshold value THA. If the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated in-focus position is less than the threshold value THA, the speed setting unit 72 sets the movement speed of focus lens 14 to a set speed VA (step ST150), as shown in FIG. 12(A). On the other hand, if the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated in-focus position is equal to or greater than the threshold value THA, the speed setting unit 72 sets the movement speed of focus lens 14 to a set speed VB (step ST160), as shown in FIG. 12(B). At this time, the speed setting unit 72 determines the set number of times according to the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated in-focus position, with reference to the graph shown in FIG. 13. Then, the set speed VB is set to a speed at which an estimated in-focus position can be derived a set number of times while moving the focus lens 14. Thereafter, the set speed information 77 is output from the speed setting unit 72 to the focus lens drive control unit 73.

[0083] Under the control of focus lens drive control unit 73, focus lens 14 is moved to the estimated in-focus position at set speed VA or VB via focus lens drive mechanism 17 (step ST170). These processes of ST100 to ST170 are continued until the release button is fully pressed again and an instruction to end video shooting is received by instruction receiving unit 32.

[0084] As described above, the imaging device 10 includes the control unit 20, which is a focus control device that controls the focus of the focus lens 14 based on the output from the phase difference detection pixel 41P. The CPU 56 of the control unit 20 functions as the focus adjustment unit 70. The focus adjustment unit 70 includes a focus derivation unit 71, a speed setting unit 72, and a focus lens drive control unit 73. The focus adjustment unit 70 obtains the current position of the focus lens 14 on the optical axis OA by deriving it based on the drive amount 75 of the focus motor from the focus lens drive mechanism 17. The focus derivation unit 71 obtains the estimated focus position of the focus lens 14 when it is located at its current position by deriving it. If the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position is less than the threshold value THA, the speed setting unit 72 sets the movement speed of the focus lens 14 to the set speed VA. The focus lens drive control unit 73 moves the focus lens 14 at the set speed VA. On the other hand, if the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated in-focus position is equal to or greater than threshold value THA, speed setting unit 72 sets the movement speed of focus lens 14 to set speed VB, which is slower than set speed VA. Focus lens drive control unit 73 moves focus lens 14 at set speed VB. This makes it possible to suppress fluctuations in the position of focus lens 14 that occur when the subject distance fluctuates greatly.

[0085] 12, the threshold value THA is set to the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated in-focus position at which the phase difference detection accuracy falls outside the set range. This makes it possible to effectively suppress fluctuations in the position of the focus lens 14 that occur when the fluctuation in the subject distance is so large that the phase difference detection accuracy falls outside the set range.

[0086] 12, speed setting unit 72 sets set speed VB to a speed at which an estimated focus position can be derived a set number of times while moving focus lens 14, based on the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated focus position, and the number of times an estimated focus position is derived per unit time. The phase difference detection accuracy of the estimated focus position recovers with each iteration, gradually converging to the intended focus position. Therefore, by setting set speed VB to a speed at which an estimated focus position can be derived a set number of times while moving focus lens 14, focus lens 14 can be stopped at the intended focus position without overshooting.

[0087] 13, the set number of times is changed according to the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated in-focus position. Therefore, it is possible to set a set speed VB that is appropriate for the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated in-focus position.

[0088] 14, when the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated in-focus position is less than threshold value THB, focus lens drive control unit 73 keeps focus lens 14 at the current position. On the other hand, when the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated in-focus position is equal to or greater than threshold value THB, focus lens drive control unit 73 moves focus lens 14. Therefore, even if there is a slight difference between the current position of focus lens 14 and the estimated in-focus position that the user may not perceive as being out of focus, focus lens 14 is moved each time, and frequent repetition of movement of focus lens 14 can be prevented.

[0089] [Second embodiment] In the first embodiment described above, an example was given in which the derivation result 76 of the estimated focus position by the focus derivation unit 71 is updated for each frame. However, depending on the model of the imaging device 10, the estimated focus position may not be updated while the focus lens 14 is moving. Therefore, in the second embodiment, a method for determining whether the focus lens 14 has stopped will be described for models in which the estimated focus position may not be updated while the focus lens 14 is moving.

[0090] 11 and 16, FIG. 19 shows the transition of the current position of focus lens 14 and the estimated in-focus position when the subject is switched from a distant view to a near view A at time TA. Speed ​​setting unit 72 sets the movement speed of focus lens 14 to set speed VB. At time TA, focus lens drive control unit 73 starts moving focus lens 14 at set speed VB. In this case, focus lens drive control unit 73 moves focus lens 14 toward the drive end on the near view side of focus lens 14, rather than toward estimated in-focus position PA. As in the first embodiment, speed setting unit 72 sets set speed VB to a speed that allows the derivation of an estimated in-focus position to be performed a set number of times while moving focus lens 14. The set number of times is changed depending on the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated in-focus position.

[0091] Focus lens drive control unit 73 starts moving focus lens 14 and simultaneously starts calculating the absolute value |ΔB| of the difference between the previous and current estimated focus positions (previous frame and current frame). The absolute value |ΔB| of the difference between the previous and current estimated focus positions is, specifically, the absolute value |ΔB| of the difference between the estimated focus position PA at time TA and the estimated focus position PB at time TB, the absolute value |ΔB| of the difference between the estimated focus position PB at time TB and the estimated focus position PC at time TC, the absolute value |ΔB| of the difference between the estimated focus position PC at time TC and the estimated focus position PD at time TD, etc. The former estimated focus position corresponds to the previous estimated focus position (previous frame), and the latter estimated focus position corresponds to the current estimated focus position (current frame).

[0092] The focus lens drive control unit 73 compares the absolute value |ΔB| of the difference between the previous and current estimated focus positions with a threshold THC. If the absolute value |ΔB| of the difference between the previous and current estimated focus positions for two consecutive frames is less than the threshold THC, the focus lens drive control unit 73 makes a stop determination JA. The threshold THC is stored in the storage 55. The threshold THC is an example of a "third threshold" according to the technology of the present disclosure. FIG. 19 illustrates a case in which the absolute value |ΔB| of the difference between the estimated focus position PB at time TB and the estimated focus position PC at time TC, and the absolute value |ΔB| of the difference between the estimated focus position PC at time TC and the estimated focus position PD at time TD, are both less than the threshold THC, and the stop determination JA is made at time TD.

[0093] The focus lens drive control unit 73 stops the focus lens 14 at the estimated in-focus position at which the stop determination JA was made. Fig. 19 illustrates a case where the focus lens 14 is stopped at the estimated in-focus position PD at the time TD at which the stop determination JA was made, between the time TD and the time TE.

[0094] As shown in the figure, after the focus lens 14 is stopped based on the stop determination JA, if the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated in-focus position is less than the threshold value THB, the focus lens drive control unit 73 keeps the focus lens 14 at the current position. After the focus lens 14 is stopped based on the stop determination JA, if the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated in-focus position is equal to or greater than the threshold value THB but less than the threshold value THA, the focus lens drive control unit 73 moves the focus lens 14 at the set speed VA. Furthermore, although this is an extremely rare case, after the focus lens 14 is stopped based on the stop determination JA, if the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated in-focus position is equal to or greater than the threshold value THA, the focus lens drive control unit 73 moves the focus lens 14 at the set speed VB.

[0095] The condition for making the stop determination JA is not limited to the case where the absolute value |ΔB| of the difference between the previous and current estimated focus positions is less than the threshold value THC for two consecutive frames as illustrated, but may also be the case where the absolute value |ΔB| of the difference between the previous and current estimated focus positions is less than the threshold value THC for three or four consecutive frames, or even the case where the absolute value |ΔB| of the difference between the previous and current estimated focus positions is less than the threshold value THC for just one frame.

[0096] 20 shows the transition of the current position of focus lens 14 and the estimated in-focus position when the subject is switched from a distant view to a close-up view C at time TA. Switching the subject from a distant view to a close-up view C is a situation in which the subject distance changes significantly, similar to when the subject is switched from a distant view to a close-up view A, and the phase difference detection accuracy decreases. For this reason, the estimated in-focus position PA at time TA is shifted from the original in-focus position of the close-up view C, which is indicated by the dashed dotted line.

[0097] Speed ​​setting unit 72 sets the movement speed of focus lens 14 to set speed VB. At time TA, focus lens drive control unit 73 starts moving focus lens 14 at set speed VB toward the drive end of focus lens 14 on the near side. As in the first embodiment, set speed VB is set by speed setting unit 72 to a speed at which an estimated in-focus position can be derived a set number of times while focus lens 14 is being moved. The set number of times is changed depending on the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated in-focus position.

[0098] At the same time as starting movement of focus lens 14, focus lens drive control unit 73 starts monitoring whether the current position of focus lens 14 has passed the estimated in-focus position. Whether the current position of focus lens 14 has passed the estimated in-focus position can be determined by whether the sign of the difference between the current position of focus lens 14 and the estimated in-focus position is reversed between the previous and current frame (previous frame and current frame). To make this determination, focus lens drive control unit 73 calculates the difference between the current position of focus lens 14 and the estimated in-focus position while knowing whether it is positive or negative.

[0099] If it is determined that the current position of focus lens 14 has passed the estimated in-focus position for two consecutive frames, focus lens drive control unit 73 makes a stop decision JB and stops focus lens 14. Fig. 20 illustrates an example in which it is determined that the current position of focus lens 14 has passed the estimated in-focus position at times TE and TF, and the stop decision JB is made at time TF, causing focus lens 14 to stop at estimated in-focus position PA.

[0100] The focus lens drive control unit 73 keeps the focus lens 14 at the estimated in-focus position PA until time TG. At time TG, the focus lens drive control unit 73 starts moving the focus lens 14 toward the estimated in-focus position PG at the set speed VA. At time TH, the focus lens drive control unit 73 stops the focus lens 14 at the estimated in-focus position PG.

[0101] As shown in the figure, after the focus lens 14 is stopped due to the stop determination JB, if the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated in-focus position is less than the threshold value THB, the focus lens drive control unit 73 keeps the focus lens 14 at the current position. After the focus lens 14 is stopped due to the stop determination JB, if the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated in-focus position is equal to or greater than the threshold value THB but less than the threshold value THA, the focus lens drive control unit 73 moves the focus lens 14 at the set speed VA. Furthermore, although this is an extremely rare case, after the focus lens 14 is stopped due to the stop determination JB, if the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated in-focus position is equal to or greater than the threshold value THA, the focus lens drive control unit 73 moves the focus lens 14 at the set speed VB.

[0102] The condition for making the stop determination JB is not limited to when it is determined that the current position of focus lens 14 has passed the estimated in-focus position for two consecutive frames as illustrated, but may also be when it is determined that the current position of focus lens 14 has passed the estimated in-focus position for three or four consecutive frames, or when it is determined that the current position of focus lens 14 has passed the estimated in-focus position for just one frame.

[0103] As described above, in the second embodiment, as shown in FIG. 19 , the speed setting unit 72 derives the estimated focus position multiple times while moving the focus lens 14 at the set speed VB. The focus lens drive control unit 73 stops the movement of the focus lens 14 when the absolute value |ΔB| of the difference between the previous and current estimated focus positions becomes less than the threshold value THC. Furthermore, as shown in FIG. 20 , the focus lens drive control unit 73 stops the movement of the focus lens 14 when it determines that the current position of the focus lens 14 has passed the estimated focus position while moving the focus lens 14 at the set speed VB. Therefore, even in a camera model that cannot update the estimated focus position while the focus lens 14 is moving, it is possible to suppress fluctuations in the position of the focus lens 14 that occur when the subject distance fluctuates significantly.

[0104] 20, focus lens drive control unit 73 determines that the current position of focus lens 14 has passed the estimated in-focus position when the sign of the difference between the current position of focus lens 14 and the estimated in-focus position is reversed. Therefore, by monitoring whether the sign of the difference between the current position of focus lens 14 and the estimated in-focus position is reversed, it can be easily determined that the current position of focus lens 14 has passed the estimated in-focus position.

[0105] In the second embodiment, the set speed VB is set to a speed that allows the estimated focus position to be calculated a set number of times while the focus lens 14 is being moved, and the set number of times is changed depending on the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position. The following effect is achieved. Specifically, if the set number of times is set small and the set speed VB is increased even when the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position is large, the current position of the focus lens 14 will overshoot the estimated focus position before the estimated focus position converges to the intended focus position. This makes it impossible to stop the focus lens 14 based on the stop decision JA, and the focus lens 14 must be stopped based on the stop decision JB. When the focus lens 14 is stopped based on the stop decision JB, the position of the focus lens 14 will fluctuate somewhat, as can be seen in FIG. 20 . Therefore, it is desirable to avoid stopping the focus lens 14 based on the stop decision JB. Therefore, if the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated in-focus position is large, the set number of times is set accordingly to be large and the set speed VB is slowed down, thereby increasing the possibility of stopping the focus lens 14 at the stop judgment JA.

[0106] The set speed VB may be set faster when the estimated focus position can be updated while focus lens 14 is moving, as in the first embodiment, than when the estimated focus position cannot be updated while focus lens 14 is moving, as in the second embodiment. This is because, in the first embodiment, if the estimated focus position can be derived even once while focus lens 14 is moving, focus lens 14 can be stopped at an estimated focus position that is closer to the actual focus position.

[0107] [Third embodiment] 21, in the third embodiment, the movement speed of focus lens 14 is changed based on the estimated focus position when the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated focus position is less than threshold value THD. Note that, as in the second embodiment, Fig. 21 is based on the assumption that image capture device 10 cannot update the estimated focus position while focus lens 14 is moving.

[0108] 11 and 16, FIG. 21 shows the transition of the current position of focus lens 14 and the estimated in-focus position when the subject is switched from a distant view to a near view A at time TA. Speed ​​setting unit 72 sets the movement speed of focus lens 14 to set speed VB1. At time TA, focus lens drive control unit 73 starts moving focus lens 14 at set speed VB1 toward estimated in-focus position PA. Here, speed setting unit 72 sets set speed VB1 to a speed at which the derivation of the estimated in-focus position can be performed a set number of times, five times, while moving focus lens 14 to estimated in-focus position PA. The derivation of the five estimated in-focus positions in this case corresponds to the derivation of the estimated in-focus position at times TA, TB, TC, TD, and TE.

[0109] The speed setting unit 72 starts comparing the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated in-focus position with a threshold value THD at the same time as starting the movement of the focus lens 14. When the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated in-focus position becomes less than the threshold value THD, the speed setting unit 72 changes (resets) the movement speed of the focus lens 14 based on the estimated in-focus position when the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated in-focus position becomes less than the threshold value THD. The threshold value THD is stored in the storage 55. The threshold value THD is an example of a "second threshold value" according to the technology of the present disclosure.

[0110] 21 illustrates a case where the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated focus position at time TC is less than threshold value THD. Also illustrated is a case where speed setting unit 72 changes the movement speed of focus lens 14 to set speed VB2 based on estimated focus position PC at time TC. Here, speed setting unit 72 sets set speed VB2 to a speed at which an estimated focus position can be derived a set number of times, five times, while moving focus lens 14 to estimated focus position PC. The five derivations of the estimated focus position in this case correspond to the derivation of the estimated focus position at times TC, TD, TE, TF, and TG.

[0111] At time TC, focus lens drive control unit 73 starts moving focus lens 14 toward estimated in-focus position PC at the changed set speed VB2. Then, based on stop determination JA at time TE, focus lens 14 is stopped at estimated in-focus position PF at time TF.

[0112] As described above, in the third embodiment, if the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated in-focus position becomes less than threshold value THD while moving focus lens 14 at set speed VB1, speed setting unit 72 changes the movement speed of focus lens 14 based on the estimated in-focus position at which the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated in-focus position becomes less than threshold value THD. Therefore, if the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated in-focus position is a value that requires, for example, 10 setting times, the following can be done. That is, the set speed is set to set speed VB1 corresponding to 5 setting times, which is faster than the set speed corresponding to 10 setting times, and the current position of focus lens 14 is brought closer to the estimated in-focus position in a short time. Then, when the current position of focus lens 14 approaches the estimated in-focus position (when the absolute value |ΔA| of the difference between the current position of focus lens 14 and the estimated in-focus position becomes less than threshold value THD), the set speed is reduced to set speed VB2, and focus lens 14 is stopped at stop determination JA. In this way, the current position of focus lens 14 can be aligned with the original in-focus position in a shorter time than when focus lens 14 is moved at a set speed corresponding to the 10 set times.

[0113] In the above embodiments, the case where a distant view is switched to a close view has been described as an example, but this is not limiting. Conversely, the case where a close view is switched to a distant view can also be applied to the technology of the present disclosure. Furthermore, in the above embodiments, the case where a moving image is captured has been described as an example, but this is not limiting. The technology of the present disclosure may also be applied when a live view image is displayed before still image capture or moving image capture.

[0114] The imaging device according to the technique of the present disclosure is not limited to the exemplified mirrorless single-lens digital camera, but may also be a compact digital camera, a video camera, a surveillance camera, a smartphone, or a tablet terminal.

[0115] In each of the above embodiments, the following various processors can be used as the hardware structure of the processing units that perform various processes, such as the image processing unit 27, the display control unit 30, the instruction receiving unit 32, the focus adjustment unit 70, the focus derivation unit 71, the speed setting unit 72, and the focus lens drive control unit 73. The various processors include the CPU 56, which is a general-purpose processor that executes software (operating program 65) and functions as various processing units, as well as programmable logic devices (PLDs) that are processors whose circuit configuration can be changed after manufacture, such as an FPGA (Field Programmable Gate Array), and / or dedicated electrical circuits that are processors having a circuit configuration designed specifically for performing specific processes, such as an ASIC (Application Specific Integrated Circuit).

[0116] A single processing unit may be configured with one of these various processors, or may be configured with a combination of two or more processors of the same or different types (e.g., a combination of multiple FPGAs and / or a combination of a CPU and an FPGA). Also, multiple processing units may be configured with a single processor.

[0117] Examples of configuring multiple processing units with a single processor include, first, a form in which one processor is configured with a combination of one or more CPUs and software, and this processor functions as multiple processing units, as typified by client and server computers. Second, a form in which a processor is used to realize the functions of an entire system including multiple processing units with a single IC (Integrated Circuit) chip, as typified by System on Chip (SoC). In this way, various processing units are configured using one or more of the above-mentioned various processors as a hardware structure.

[0118] Furthermore, more specifically, the hardware structure of these various processors can be an electric circuit that combines circuit elements such as semiconductor elements.

[0119] From the above description, the technology described in the following supplementary paragraphs can be understood.

[0120] [Additional note 1] A focus control device that controls the focus of a focus lens based on an output from a phase difference detection pixel, a processor; The processor: acquiring a current position of the focus lens and an estimated in-focus position of the focus lens derived when the focus lens is at the current position; If the absolute value of the difference between the current position and the estimated focus position is less than a first threshold, the focus lens is moved at a first speed; When an absolute value of the difference between the current position and the estimated focus position is equal to or greater than the first threshold value, the focus lens is moved at a second speed that is slower than the first speed. Focus control device. [Additional note 2] 2. The focus control device according to claim 1, wherein the first threshold value is set to an absolute value of the difference between the current position and the estimated focus position at which the phase difference detection accuracy falls outside a set range. [Additional note 3] The processor: A focus control device according to claim 1 or 2, wherein the second speed is set to a speed that allows the estimated focus position to be derived a set number of times while the focus lens is moved, based on the absolute value of the difference between the current position and the estimated focus position and the number of times the estimated focus position is derived per unit time. [Additional note 4] 4. The focus control device according to claim 3, wherein the set number of times is changed according to an absolute value of a difference between the current position and the estimated focus position. [Additional note 5] The processor: A focus control device according to any one of appendix 1 to appendix 4, wherein, when the absolute value of the difference between the current position and the estimated focus position becomes less than a second threshold while the focus lens is being moved at the second speed, the movement speed of the focus lens is changed based on the estimated focus position at which the absolute value of the difference between the current position and the estimated focus position becomes less than the second threshold. [Additional note 6] The processor: deriving the estimated focus position multiple times while moving the focus lens at the second speed; The focus control device according to any one of claims 1 to 5, wherein the movement of the focus lens is stopped when the absolute value of the difference between the previous and current estimated focus positions is less than a third threshold value. [Additional note 7] The processor: A focus control device according to any one of claims 1 to 6, wherein the focus control device stops the movement of the focus lens if it is determined that the current position has passed the estimated focus position while the focus lens is being moved at the second speed. [Additional note 8] The processor: 8. The focus control device according to claim 7, wherein when the sign of the difference between the current position and the estimated in-focus position is reversed, it is determined that the current position has passed the estimated in-focus position. [Additional note 9] The processor: If the absolute value of the difference between the current position and the estimated focus position is less than a fourth threshold, the focus lens remains at the current position; The focus control device according to any one of supplementary items 1 to 8, wherein the focus control device moves the focus lens when the absolute value of the difference between the current position and the estimated focus position is equal to or greater than the fourth threshold value. [Additional Note 10] An imaging device comprising the focus control device according to any one of supplementary items 1 to 9.

[0121] The technology of the present disclosure can be appropriately combined with the various embodiments and / or various modified examples described above. Furthermore, it is not limited to the above-described embodiments, and various configurations can be adopted without departing from the spirit of the present disclosure. Furthermore, the technology of the present disclosure extends not only to programs but also to storage media that non-temporarily store programs.

[0122] The above-described description and illustrations are a detailed explanation of the parts related to the technology of the present disclosure and are merely an example of the technology of the present disclosure. For example, the above description of the configuration, functions, actions, and effects is an explanation of an example of the configuration, functions, actions, and effects of the parts related to the technology of the present disclosure. Therefore, it goes without saying that unnecessary parts may be deleted, new elements may be added, or replacements may be made to the above-described description and illustrations within the scope of the gist of the technology of the present disclosure. Furthermore, to avoid confusion and facilitate understanding of the parts related to the technology of the present disclosure, the above-described description and illustrations omit explanations of common technical knowledge that do not require particular explanation to enable the implementation of the technology of the present disclosure.

[0123] In this specification, "A and / or B" is synonymous with "at least one of A and B." In other words, "A and / or B" means that it may be only A, only B, or a combination of A and B. Furthermore, in this specification, the same concept as "A and / or B" is also applied when three or more things are expressed connected by "and / or."

[0124] All publications, patent applications, and technical standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, or technical standard was specifically and individually indicated to be incorporated by reference. [Explanation of symbols]

[0125] 10. Imaging device 11 Imaging optical system 12 Image sensor 13 Objective Lens 14 Focus Lens 15 Zoom Lens 16 apertures 17 Focus lens drive mechanism 18 Zoom lens drive mechanism 19 Aperture drive mechanism 20 Control Unit 21 Control section 22 Image sensor driver 23 Shutter 24 Shutter drive mechanism 25 Image Input Controller 26 Image Memory 27 Image processing section 28, 58 bus lines 29 VRAM 30 Display control unit 31 Media Controller 32 Instruction Reception Department 33 Finder Monitor 34 Rear monitor 35 Memory Card 36 Touch Panel 40 Photoelectric conversion unit 41 pixels 41N normal pixels 41P Phase difference detection pixel 42 imaging surface 43 Image Signal 43N Image generation signal 43P Calculation signal 45 Microlenses 46 Color Filter 47 Photoelectric conversion element 49 Light blocking material 55 Storage 56 CPU 57 Memory 65 Operating Program 70 Focus adjustment section 71 Focus derivation section 72 Speed ​​setting section 73 Focus lens drive control unit 75 Drive amount 76 Derivation results 77 Setting speed information 80 mountains 81 People 411P 1st phase difference detection pixel 412P Second phase difference detection pixel 431P 1st calculation signal 432P Second calculation signal α, αX phase difference |ΔA| Absolute value of the difference between the current position of the focus lens and the estimated in-focus position |ΔB| Absolute value of the difference between the previous and current estimated focus positions JA, JB suspension judgment OA optical axis PA, PB, PC, PD, PE, PF, PG Estimated focus position ST100, ST110, ST120, ST130, ST140, ST150, ST160, ST170 Step TA, TB, TC, TD, TE, TF, TG, TH, TI, TJ Time THA, THB, THC, THD thresholds V Focus lens movement speed (set speed) VA setting speed VB, VB1, VB2 setting speed

Claims

1. A focus control device that controls the focus of a focus lens based on an output from a phase difference detection pixel, a processor; The processor: acquiring a current position of the focus lens and an estimated in-focus position of the focus lens derived when the focus lens is at the current position; If the absolute value of the difference between the current position and the estimated focus position is less than a first threshold, the focus lens is moved at a first speed; When an absolute value of the difference between the current position and the estimated focus position is equal to or greater than the first threshold value, the focus lens is moved at a second speed that is slower than the first speed. Focus control device.

2. 2. The focus control device according to claim 1, wherein the first threshold value is set to an absolute value of the difference between the current position and the estimated in-focus position at which the phase difference detection accuracy falls outside a set range.

3. The processor:

2. The focus control device according to claim 1, wherein the second speed is set to a speed that enables the derivation of the estimated focus position a set number of times while moving the focus lens based on the absolute value of the difference between the current position and the estimated focus position and the number of times the estimated focus position is derived per unit time.

4. 4. The focus control device according to claim 3, wherein the set number of times is changed according to an absolute value of a difference between the current position and the estimated in-focus position.

5. The processor:

2. The focus control device according to claim 1, wherein, while the focus lens is being moved at the second speed, if the absolute value of the difference between the current position and the estimated focus position becomes less than a second threshold, the movement speed of the focus lens is changed based on the estimated focus position when the absolute value of the difference between the current position and the estimated focus position becomes less than the second threshold.

6. The processor: deriving the estimated focus position multiple times while the focus lens is being moved at the second speed; The focus control device according to claim 1 , wherein when an absolute value of the difference between the previous and current estimated focus positions is less than a third threshold, movement of the focus lens is stopped.

7. The processor:

2. The focus control device according to claim 1, wherein the movement of the focus lens is stopped when it is determined that the current position has passed the estimated in-focus position while the focus lens is being moved at the second speed.

8. The processor:

8. The focus control device according to claim 7, wherein when the sign of the difference between the current position and the estimated in-focus position is reversed, it is determined that the current position has passed the estimated in-focus position.

9. The processor: If the absolute value of the difference between the current position and the estimated focus position is less than a fourth threshold, the focus lens remains at the current position; The focus control device according to claim 1 , wherein the focus lens is moved when the absolute value of the difference between the current position and the estimated in-focus position is equal to or greater than the fourth threshold value.

10. A method for operating a focus control device that controls the focus of a focus lens based on an output from a phase difference detection pixel, comprising: acquiring a current position of the focus lens and an estimated in-focus position of the focus lens derived when the focus lens is at the current position; If an absolute value of a difference between the current position and the estimated focus position is less than a first threshold, moving the focus lens at a first speed; and When an absolute value of a difference between the current position and the estimated focus position is equal to or greater than the first threshold value, moving the focus lens at a second speed that is slower than the first speed; A method of operating a focus control device, comprising:

11. An operation program for a focus control device that performs focus control of a focus lens based on an output from a phase difference detection pixel, acquiring a current position of the focus lens and an estimated in-focus position of the focus lens derived when the focus lens is at the current position; If an absolute value of a difference between the current position and the estimated focus position is less than a first threshold, moving the focus lens at a first speed; and When an absolute value of a difference between the current position and the estimated focus position is equal to or greater than the first threshold value, moving the focus lens at a second speed that is slower than the first speed; An operating program for a focus control device that causes a computer to execute processing including the steps of:

12. An imaging device comprising the focus control device according to claim 1.

Images