Focus control device, method for operating focus control device, storage medium, computer program product, and imaging device

Abstract

The invention provides a focus control device, an operation method of the focus control device, a storage medium, a computer program product, and an imaging device capable of suppressing fluctuation of the position of a focus lens generated when the change of the subject distance is large. The focusing unit obtains the current position of the focus lens on the optical axis by deriving the current position of the focus lens on the basis of the drive amount of the focus motor from the focus lens drive mechanism. The focus derivation unit derives an estimated focus position of the focus lens when the focus lens is at the current 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, the speed setting unit sets the movement speed of the focus lens to a first speed. The focus lens drive control unit moves the focus lens at a first speed. On the other hand, when 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, the speed setting unit sets the movement speed of the focus lens to a second speed that is slower than the first speed. The focus lens drive control unit moves the focus lens at a second speed.

Description

Technical Field

[0001] The technology of the present invention relates to a focus control device, an operating method of the focus control device, a storage medium, a computer program product, and a camera device. Background Art

[0002] Patent Document 1 describes an autofocus system that performs autofocus control to bring a camera's photographic optical system into focus. The autofocus system includes a focus movement amount information acquisition mechanism and a focus movement speed change mechanism. The focus movement amount information acquisition mechanism acquires information regarding the focus movement amount of the photographic optical system from its current focus state until it is in focus. The focus movement speed change mechanism uses the focus movement speed of the camera when it stops in the near-far direction relative to a subject focused on by the autofocus mechanism as a reference speed. Based on the information acquired by the focus movement amount information acquisition mechanism, the focus movement speed of the photographic optical system from its current focus state until it is in focus is changed relative to the reference speed. The focus movement speed change mechanism increases the focus movement amount from the reference speed to the reference speed if the focus movement amount increases due to the camera moving in the near-far direction, and decreases the focus movement speed from the reference speed if the focus movement amount decreases.

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

[0004] One embodiment of the technology according to the present invention provides a focus control device, an operating method of the focus control device, a storage medium, a computer program product, and an imaging device capable of suppressing fluctuations in the position of a focus lens generated when the subject distance varies greatly.

[0005] The focus control device of the present invention performs focus control of the focusing lens based on the output from the phase difference detection pixel, wherein the focus control device includes a processor, and the processor performs the following processing: obtaining the current position of the focusing lens and the estimated focus position of the focusing lens derived when the focusing lens is at the current position; when the absolute value of the difference between the current position and the estimated focus position is less than the first threshold, moving the focusing lens at a first speed; and when the absolute value of the difference between the current position and the estimated focus position is greater than the first threshold, moving the focusing lens at a second speed slower than the first speed.

[0006] It is preferable that the first threshold be set with 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] Preferably, the processor sets the second speed to a speed capable of deriving the estimated focus position 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.

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

[0009] The preferred processor performs the following processing: when the absolute value of the difference between the current position and the estimated focus position becomes smaller than the second threshold while the focus lens is moved at the second speed, the moving speed of the focus lens is changed according to the estimated focus position when the absolute value of the difference between the current position and the estimated focus position becomes smaller than the second threshold.

[0010] Preferably, the processor derives the estimated focus position a plurality of times while the focus lens is moved at the second speed, and stops moving the focus lens when the absolute value of the difference between the previous and current estimated focus positions becomes smaller than a third threshold.

[0011] Preferably, the processor stops the movement of the focus lens when it is determined that the current position exceeds the estimated focus position while the focus lens is being moved at the second speed.

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

[0013] Preferably, 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 the 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 the fourth threshold.

[0014] The working method of the focus control device of the present invention performs focus control of the focusing lens based on the output from the phase difference detection pixel, and the working method of the focus control device includes the following steps: obtaining the current position of the focusing lens and the estimated focus position of the focusing lens derived when the focusing lens is at the current position; when the absolute value of the difference between the current position and the estimated focus position is less than the first threshold, moving the focusing lens at a first speed; and when the absolute value of the difference between the current position and the estimated focus position is greater than the first threshold, moving the focusing lens at a second speed slower than the first speed.

[0015] The working procedure of the focus control device of the present invention performs focus control of the focusing lens based on the output from the phase difference detection pixel, and the working procedure of the focus control device enables the computer to execute a process including the following steps: obtaining the current position of the focusing lens and the estimated focus position of the focusing lens derived when the focusing lens is at the current position; when the absolute value of the difference between the current position and the estimated focus position is less than the first threshold, moving the focusing lens at a first speed; and when the absolute value of the difference between the current position and the estimated focus position is greater than the first threshold, moving the focusing lens at a second speed slower than the first speed.

[0016] The imaging device of the present invention includes the focus control device described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a diagram showing the structure of an imaging device.

[0018] Figure 2 A diagram showing the arrangement of pixels of an imaging element.

[0019] Figure 3 This is a diagram showing the structure of a normal pixel.

[0020] Figure 4 This is a diagram showing the structure of a first phase difference detection pixel.

[0021] Figure 5 This is a diagram showing the structure of the second phase difference detection pixel.

[0022] Figure 6 It is a graph showing the phase difference between the first calculation signal and the second calculation signal.

[0023] Figure 7 It is a block diagram showing the detailed structure of the control unit.

[0024] Figure 8 This is a block diagram showing a processing unit of a CPU.

[0025] Figure 9 This is a diagram showing a scene where the subject distance changes significantly. Figure 9 (A) shows the case where the mountain in the distance is the subject. Figure 9 (B) shows a case where the subject is switched from a distant mountain to a near person.

[0026] Figure 10 It is a graph showing the relationship between phase difference and defocus amount.

[0027] Figure 11 1 and 2 are diagrams showing changes in the current position and estimated in-focus position of the focus lens in a conventional example when switching from a distant view to a close view A.

[0028] Figure 12 FIG. 1 is a diagram showing a process of a speed setting unit for setting the moving speed of the focus lens based on a comparison result of an absolute value of a difference between a current position of the focus lens and an estimated in-focus position with a threshold value. Figure 12 (A) indicates that the absolute value of the difference between the current position of the focus lens and the estimated focus position is smaller than the threshold value. Figure 12 (B) indicates a case where the absolute value of the difference between the current position of the focus lens and the estimated in-focus position is equal to or greater than a threshold value.

[0029] Figure 13 This 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 set number of times.

[0030] Figure 14 FIG. 1 is a diagram showing a process of a focus lens drive control unit for determining whether to keep the focus lens at the current position based on a comparison result of an absolute value of a difference between the current position of the focus lens and the estimated in-focus position with a threshold value. Figure 14 (A) indicates that the absolute value of the difference between the current position of the focus lens and the estimated focus position is smaller than the threshold value. Figure 14 (B) shows a case where the absolute value of the difference between the current position of the focus lens and the estimated in-focus position is equal to or greater than a threshold value.

[0031] Figure 15 1 and 2 are diagrams showing changes in the current position of the focus lens and the estimated in-focus position when switching from a distant view to a close view B.

[0032] Figure 16 1 and 2 are diagrams showing changes in the current position of the focus lens and the estimated in-focus position when switching from a distant view to a close view A.

[0033] Figure 17 This is a flowchart showing the processing procedure of the control unit.

[0034] Figure 18 This is a flowchart showing the processing procedure of the control unit.

[0035] Figure 19 This figure shows an example of focus lens stop determination in a model in which the estimated focus position cannot be updated while the focus lens is moving.

[0036] Figure 20 This is a diagram showing another example of focus lens stop determination in a model in which the estimated focus position cannot be updated during focus lens movement.

[0037] Figure 21 This is a diagram showing a third embodiment in which the moving 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 becomes smaller than a threshold value. DETAILED DESCRIPTION

[0038] [First embodiment]

[0039] As an example, Figure 1 As shown, the imaging device 10 is, for example, a single-lens digital camera without a reflector, and includes an imaging optical system 11 and an imaging element 12. The imaging optical system 11 includes a plurality of lenses for imaging the subject light on the imaging element 12. Specifically, the imaging optical system 11 includes an objective lens 13, a focusing lens 14, and a zoom lens 15. These lenses 13 to 15 are arranged in order from the object side (the subject side) toward the imaging side (the imaging element 12 side). Although Figure 1 Although simplified in the figure, each lens 13-15 is actually a lens group composed of multiple lenses. The imaging optical system 11 also has an aperture 16. The aperture 16 is arranged on the imaging side closest to the imaging optical system 11. Furthermore, the imaging device 10 may be of a type in which a lens barrel containing the imaging optical system 11 and the like and a main body containing the imaging element 12 and the like are integrated, or it may be of a so-called lens-exchange type in which the lens barrel and the main body are separate components.

[0040] The focus lens 14 is provided with a focus lens drive mechanism 17, the zoom lens 15 is provided with a zoom lens drive mechanism 18, and the aperture 16 is provided with an aperture drive mechanism 19. The focus lens drive mechanism 17 includes a focus cam ring with a cam groove formed on its outer circumference, which holds the focus lens 14; a focus motor that moves the focus cam ring along the optical axis OA by rotating the focus cam about the optical axis OA; and a driver for the focus motor. Similarly, the zoom lens drive mechanism 18 includes a zoom cam ring with a cam groove formed on its outer circumference, which holds the zoom lens 15; a zoom motor that moves the zoom cam ring along the optical axis OA by rotating the zoom cam about the optical axis OA; and a driver for the zoom motor. The aperture drive mechanism 19 includes an aperture motor that opens and closes the multiple aperture blades of the aperture 16; and a driver for the aperture motor.

[0041] The focus motor, zoom motor, and iris motor are, for example, stepping motors. In this case, the position of the focus lens 14 and the zoom lens 15 on the optical axis OA, as well as the aperture of the iris 16, can be derived based on the drive amounts of the focus motors, zoom motors, and iris motors. Alternatively, instead of providing the drive amounts of the focus motors and zoom motors, position sensors may be provided to detect the positions of the focus lens 14 and the zoom lens 15.

[0042] The electrical components, such as motors and drivers, of each drive mechanism 17 to 19 are connected to the control unit 20. The electrical components of each drive mechanism 17 to 19 are driven under the control of the control unit 20. More specifically, the control unit 20 issues drive signals corresponding to commands, etc., input from the user via the operation unit 21 to drive the electrical components of each drive mechanism 17 to 19. For example, if a command to change the angle of view to the telephoto side is input via the angle of view change switch on the operation unit 21, the control unit 20 issues a drive signal to the driver of the zoom motor of the zoom lens drive mechanism 18, thereby moving the zoom lens 15 toward the telephoto side.

[0043] The focus motor, zoom motor, and diaphragm motor output drive amounts to the control unit 20. The control unit 20 derives the position of the focus lens 14 and the position of the zoom lens 15 on the optical axis OA and the aperture of the diaphragm 16 based on the drive amounts.

[0044] The imaging element 12 is, for example, a CMOS (Complementary Metal-Oxide-Semiconductor) image sensor, and has an imaging surface 42 (see FIG. Figure 2 ). The imaging element 12 is configured so that the center of the imaging surface 42 is aligned with the optical axis OA, and the imaging surface 42 is orthogonal to the optical axis OA. In addition, the "aligned" and "orthogonal" mentioned here mean not only completely aligned and orthogonal, but also aligned and orthogonal in the sense of errors generally allowed in the technical field to which the technology of the present invention belongs.

[0045] 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 supplies vertical scanning signals, horizontal scanning signals, and the like to the imaging element 12, thereby controlling the timing of imaging light captured by the imaging element 12.

[0046] A shutter 23 is provided between the imaging optical system 11 and the imaging element 12. For example, the shutter 23 is a focal plane shutter having a front curtain and a rear curtain. 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 them to advance them, along with a driver. The shutter drive mechanism 24 is driven under the control of the control unit 20 to open and close the shutter 23.

[0047] The control unit 20 is connected to various components, such as the image input controller 25, image memory 26, and image processing unit 27, via a bus 28. In addition to bus 28, VRAM (Video Random Access Memory) 29, a display control unit 30, a media controller 31, and a command receiving unit 32 are also connected. Although not shown, bus 28 also connects to a flash drive control unit that controls the driving of the flash device, an external communication interface (I / F) that communicates with external devices via a connection terminal such as a USB (Universal Serial Bus) terminal, and a wireless communication I / F.

[0048] Image data obtained by capturing 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, an SDRAM (Synchronous Dynamic Random Access Memory) and temporarily stores the image data.

[0049] 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. Examples of these image processing include offset correction, sensitivity correction, pixel interpolation, white balance correction, gamma correction, demosaicing, brightness signal and color difference signal generation, edge enhancement, and color correction. The image processing unit 27 rewrites the image data after these various image processing steps into the image memory 26.

[0050] Image data for display as a live preview image (also called a live view image), i.e., image data after various image processing, is input from the image memory 26 to the VRAM 29. The VRAM 29 has an area for storing two consecutive frames of image data. The image data stored in the VRAM 29 is sequentially overwritten with new image data. The VRAM 29 sequentially outputs the new image data from the two consecutive frames of image data to the display control unit 30.

[0051] The display control unit 30 functions as a so-called video encoder, converting image data from the VRAM 29 into video data and outputting the data to either the viewfinder monitor 33 or the rear monitor 34. This allows the user to visually view a live preview image on either the viewfinder monitor 33 or the rear monitor 34. The live preview image is displayed at a frame rate of, for example, 60 fps (frames per second).

[0052] Furthermore, for example, the determination of which of the viewfinder monitor 33 and the rear monitor 34 the video data is output to is made as follows. Specifically, a pupil detection sensor is provided in advance on the viewfinder. When the pupil detection sensor detects that the user is looking at the viewfinder, the video data is output to the viewfinder monitor 33. On the other hand, when the pupil detection sensor detects that the user is not looking at the viewfinder, the video data is output to the rear monitor 34.

[0053] When a command to start capturing a still image or a moving image is issued by fully pressing the release button of the operation unit 21, the image processing unit 27 compresses the image data in the image memory 26. For still images, the image processing unit 27 compresses the image data using, for example, the JPEG (Joint Photographic Experts Group) format. For moving images, the image processing unit 27 compresses the image data using, for example, the MPEG (Moving Picture Experts Group) format. The image processing unit 27 outputs the compressed image data to the media controller 31.

[0054] The media controller 31 records the compressed image data from the image processing unit 27 in the memory card 35. The memory card 35 is detachably mounted in a memory card slot (not shown).

[0055] When the image playback mode is selected via the mode switch on 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 decompresses 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 visually view the playback image on the rear monitor 34.

[0056] The command receiving unit 32 receives various operation commands input from the user via the operation unit 21 and the touch panel 36 provided integrally with the rear monitor 34. The command receiving unit 32 outputs the received various operation commands to the control unit 20 via the bus 28.

[0057] As described above, the operating unit 21 includes a view angle change switch, a release button, and a mode switching switch. The release button is a push button that can be pressed in two stages: half-pressed and fully pressed. A half-press operation of the release button is used to issue a command to prepare for shooting a still image or a moving image, and a full-press operation is used to issue a command to start shooting a still image or a moving image. In addition to these, the operating unit 21 also includes components such as a menu button for displaying various setting menus on the back monitor 34, a cross key for setting numerical values ​​and switching options, and an OK button for operations such as confirming settings. The touch panel 36 is superimposed on the display surface of the back monitor 34. The touch panel 36 recognizes various operation commands from the user by detecting contact with a dedicated commander such as a user's finger or a stylus.

[0058] The modes that can be switched using the mode switch include still image shooting mode, movie shooting mode, image playback mode, and setup mode. Still image shooting mode includes, of course, a normal shooting mode for capturing a single still image, as well as a continuous shooting mode for capturing still images continuously at a specified interval (e.g., a frame rate of 5 to 10 fps). Continuous shooting mode is activated by, for example, holding the release button fully pressed for a specified time (e.g., one second or longer). Continuous shooting mode ends when the release button is released.

[0059] As an example, Figure 2 As shown in FIG. 1 , a photoelectric conversion unit 40 is provided on the imaging element 12. The photoelectric conversion unit 40 is composed of a plurality of pixels 41 arranged two-dimensionally along the X and Y directions. The plurality of pixels 41 form an imaging surface 42. As is well known, the pixels 41 are composed of a microlens 45, a color filter 46, and a photoelectric conversion element 47 such as a photodiode (all refer to FIG. 1 ). Figures 3 to 5 ) In addition, the X direction and the Y direction are the horizontal direction and the vertical direction in a state where the bottom surface of the imaging device 10 is placed on a horizontal surface.

[0060] Scan lines parallel to the X direction are wired between the rows of pixels 41. Furthermore, signal lines parallel to the Y direction are wired between the columns of pixels 41. Pixels 41 (their photoelectric conversion elements 47) are connected to the signal lines via amplifiers and switches. The switches are also connected to scan lines. During the accumulation operation, signal charges corresponding to subject light are accumulated in pixels 41 (their photoelectric conversion elements 47). An off signal is supplied as a vertical scan signal via the scan lines, closing the switches. During the readout operation, image signals (voltage signals) 43 corresponding to the signal charges are read from pixels 41 (their photoelectric conversion elements 47). An on signal is supplied as a vertical scan signal via the scan lines, opening the switches. 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 signals 43 input via the signal lines. The ADC circuit converts the correlated double sampled image signals 43 into digital image signals 43.

[0061] The pixels 41 are classified into green pixels (in the green wavelength band) that are sensitive to light according to the type of the color filter 46. Figure 2 "G" in the figure), a red pixel sensitive to light in the red wavelength band (in the Figure 2 "R" in the figure) and a blue pixel that is sensitive to light in the blue wavelength band (in the figure Figure 2 The three types of pixels 41 are arranged according to a predetermined arrangement rule. As an example of a predetermined arrangement, the so-called Bayer arrangement is exemplified here, in which two green pixels, one blue pixel, and one red pixel are arranged in a 2×2 pixel array.

[0062] 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. While the normal pixels 41N include three types: green, blue, and red, the phase difference detection pixels 41P are only green.

[0063] The phase difference detection pixels 41P are arranged at predetermined intervals in the X and Y directions. Figure 2In the image, 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. Furthermore, the phase difference detection pixels 41P are arranged so that the first phase difference detection pixel 411P and the second phase difference detection pixel 412P alternate in the X and Y directions. For example, when viewing the 4th 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, ... . Furthermore, when viewing the 10th 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 detection pixel 411P and the second phase difference detection pixel 412P adjacent to each other in the X direction and the Y direction are configured to detect the phase difference α (refer to Figure 6 ) of 1 group.

[0064] As an example, Figures 3 to 5 As shown, the normal pixel 41N, the first phase difference detection pixel 411P, and the second phase difference detection pixel 412P have the same basic structure, 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.

[0065] like Figure 3 As shown, the photoelectric conversion element 47 of the normal pixel 41N outputs an image generation signal 43N corresponding to the subject light focused 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.

[0066] like Figure 4 and Figure 5 As shown, 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 blocks 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 blocks the left half of the photoelectric conversion element 47 when viewed from the object side.

[0067] The photoelectric conversion element 47 of the first phase difference detection pixel 411P outputs a first calculation signal 431P corresponding to subject light focused by the microlens 45, transmitted through the color filter 46, and shielded by the light shielding member 49 on the right side as the image signal 43. In contrast, the photoelectric conversion element 47 of the second phase difference detection pixel 412P outputs a second calculation signal 432P corresponding to subject light focused by the microlens 45, transmitted through the color filter 46, and shielded by the light shielding member 49 on the left side as the image signal 43. The first calculation signal 431P and the second calculation signal 432P, like the image generation signal 43N, are stored in the image memory 26 as part of the image data. The first calculation signal 431P and the second calculation signal 432P are examples of "outputs from the phase difference detection pixels" according to the technology of the present invention. In addition, hereinafter, when there is no need to distinguish them in particular, the first calculation signal 431P and the second calculation signal 432P are collectively described as the calculation signal 43P.

[0068] As an example, Figure 6 As shown, a phase difference α appears between the first calculation signal 431P and the second calculation signal 432P output from the first phase difference detection pixel 411P and the second phase difference detection pixel 412P, which are adjacent in the X and Y directions. This phase difference α indicates the direction and amount required to move the focus lens 14 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.

[0069] The area from which the estimated focus position is derived (hereinafter referred to as the focusing area) is pre-set in the center of the imaging surface 42. Furthermore, the focusing area can be a user-specified area or an area surrounding a specific subject identified using known subject recognition technology. Specific subjects include the eyes, face, or torso of a person; the eyes, face, or torso of an animal; or the front end or fuselage of a vehicle such as an automobile, a railway vehicle, or an aircraft. Here, the eyes of a person or animal refer to the pupil, also known as the black pupil. The face of a person or animal refers to the forehead, cheeks, chin, eyes, nose, mouth, ears, etc. The torso of a person or animal refers to the portion excluding the head, neck, limbs, and tail. The front end of a vehicle refers to the front of the vehicle in the case of an automobile; the portion of the front car with the destination display, front window, headlights, etc. in the case of a railway vehicle; and the nose portion of an aircraft with the radome and front window, etc. The so-called fuselage of a vehicle, if it is a car, is the entire body of the vehicle except the wheels; if it is a railway vehicle, it is the entire body of the vehicle except the wheels regardless of the front vehicle, middle car, and tail car; if it is an airplane, it is the entire fuselage except the nose, main wings, tail wing, etc.

[0070] As its name suggests, the image generation signal 43N is used to generate images such as live preview images. In contrast, the calculation signal 43P is used only to calculate the phase difference α and is not used to generate an image. Therefore, during pixel interpolation processing, the image processing unit 27 uses the image generation signal 43N for the normal pixels 41N surrounding the phase difference detection pixel 41P to interpolate the pixel value of the phase difference detection pixel 41P.

[0071] As an example, Figure 7 As shown, the control unit 20 includes a storage device 55, a CPU (Central Processing Unit) 56, and a memory 57. The storage device 55, CPU 56, and memory 57 are connected to each other via a bus 58. The control unit 20 is an example of a "focus control device" and a "computer" according to the present invention.

[0072] The storage device 55 is a nonvolatile storage device such as an EEPROM (Electrically Erasable Programmable Read-Only Memory). The storage device 55 stores various programs and associated data. Alternatively, FeRAM (Ferroelectric Random Access Memory) or MRAM (Magnetoresistive Random Access Memory) can be used as the storage device 55 instead of the EEPROM.

[0073] Memory 57 is working memory used by CPU 56 to execute processing. CPU 56 loads programs stored in storage device 55 into memory 57 and executes processing according to the programs. This allows CPU 56 to centrally control various components of imaging device 10. CPU 56 is an example of a "processor" within the context of the present invention. Alternatively, memory 57 may be built into CPU 56.

[0074] As an example, Figure 8 As shown, an operation program 65 is stored in the storage device 55. The operation program 65 is a program for causing the CPU 56 to perform autofocus control, etc. That is, the operation program 65 is an example of an "operation program of a focus control device" according to the technology of the present invention.

[0075] When the operating program 65 is activated, the CPU 56 cooperates with the memory 57 and other components 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 the focus adjustment unit 70, the CPU 56 also functions as various processing units.

[0076] The focus adjustment unit 70 receives a driving amount 75 of the focus motor 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) based on the driving amount 75 .

[0077] The focus derivation unit 71 reads the calculation signal 43P from the image memory 26. Specifically, the calculation signal 43P comprises a plurality of first calculation signals 431P output from the first phase difference detection pixels 411P, arranged two-dimensionally in the X and Y directions according to the arrangement of the first phase difference detection pixels 411P; and a plurality of second calculation signals 432P output from the second phase difference detection pixels 412P, arranged two-dimensionally in the X and Y directions according to the arrangement of the second phase difference detection pixels 412P. Therefore, the calculation signal 43P can be processed as two-dimensional image data.

[0078] The focus deriving unit 71 calculates the focus area based on the calculation signal 43P. Figure 6 The phase difference α shown is shown. The focus deriving unit 71 derives the estimated focus position of the focus lens 14 when the focus lens 14 is at the current position based on the phase difference α. The focus deriving 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. The method of deriving the estimated focus position of the focus lens 14 based on the phase difference α is well known, and therefore a detailed description thereof is omitted here.

[0079] The speed setting unit 72 sets a moving speed V of the focus lens 14 from the current position to the estimated focus position based on the absolute value |ΔA| of the difference between the current position of the focus lens 14 derived from the drive amount 75 and the estimated focus position of the focus lens 14 indicated by the derivation result 76 from the focus derivation unit 71. The speed setting unit 72 outputs set speed information 77 including the set moving speed V of the focus lens 14 (hereinafter sometimes referred to as the set speed) to the focus lens drive control unit 73.

[0080] The focus lens drive control unit 73 controls the focus lens drive mechanism 17, and thereby controls the drive of the focus lens 14. Specifically, the focus lens drive control unit 73 moves the focus lens 14 from its current position to the estimated focus position at a set speed V via the focus lens drive mechanism 17. Strictly speaking, when the focus lens drive control unit 73 moves the focus lens 14, it means that the focus lens drive control unit 73 sends a drive signal to the driver of the focus motor of the focus lens drive mechanism 17, thereby moving the focus lens 14 via the focus motor. If the current position of the focus lens 14 is the same as the estimated focus position, the focus lens drive control unit 73 naturally does not perform any operation, and the focus lens 14 does not move.

[0081] The focusing unit 70 performs the derivation of the estimated focus position by the focus derivation unit 71, the setting of the moving speed V of the focus lens 14 by the speed setting unit 72, and the drive control of the focus lens 14 by the focus lens drive control unit 73 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 derivations of the estimated focus position per unit time is once per frame.

[0082] Here, as an example, consider Figure 9 The scene shown. That is, (A) represents a case where a moving image is taken with a distant mountain 80 as the subject. From the state shown in (A), as shown in (B), when the subject is switched from the distant mountain 80 to the near person 81, the subject distance changes significantly. In addition, the subject distance refers to the distance between the camera device 10 and the main subject. The main subject is, for example, a subject that exists in the focusing 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.

[0083] As an example, Figure 10 As shown in FIG, the relationship between the phase difference α and the defocus amount maintains a proportional relationship (linear) in the case of -αX≤α≤αX, but the proportional relationship is destroyed in the case of αX<α and α<-αX, and the phase difference detection accuracy is reduced. Figure 9 In scenes where the subject distance changes significantly, the focus position is expected to deviate from the original focus position (refer to Figure 11 ). In addition, the defocus amount refers to the difference between the current position of the focus lens 14 and the original focus position.

[0084] Figure 11 The current position and estimated focus position of the focus lens 14 of the conventional example are shown when the subject is switched from a distant view to a close view A at a time TA. Figure 9The scene in which the subject distance changes significantly indicates a decrease in phase difference detection accuracy. Therefore, the estimated focus position PA at time TA deviates from the original focus position of the near scene A indicated by the one-dot chain line.

[0085] At time TA, the focus lens drive control unit 73 starts moving the focus lens 14 toward the estimated focus position PA at a set speed VA. Two frames after time TA, the focus lens drive control unit 73 stops the focus lens 14 at the estimated focus position PA for a period of time TC. The focus lens drive control unit 73 maintains the current position of the focus lens 14 at the estimated focus position PA until time TD. The set speed VA is, for example, the maximum movement speed of the focus lens 14. Furthermore, "stopping" refers to a temporary stop, not to permanently stopping the focus lens 14 at a specific position.

[0086] As the focus lens 14 moves toward the estimated focus position PA, the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position decreases, the phase difference detection accuracy is restored, and the estimated focus position gradually converges to the original focus position. Therefore, at time TD, the estimated focus position PD is updated to be closer to the original focus position than the estimated focus position PA. Therefore, at time TD, the focus lens drive control unit 73 starts moving the focus lens 14 toward the estimated focus position PD at a set speed VA. The focus lens drive control unit 73 stops the focus lens 14 at the estimated focus position PD between time TD and time TE.

[0087] At time TE, the estimated focus position PE is updated to be closer to the original focus position than the estimated focus position PD. Therefore, at time TE, the focus lens drive control unit 73 starts moving the focus lens 14 toward the estimated focus position PE at the set speed VA. The focus lens drive control unit 73 stops the focus lens 14 at the estimated focus position PE between time TE and time TF. Figure 9 In the scene shown where the subject distance varies significantly, the estimated focus position deviates from the original focus position, causing the position of the focus lens 14 to fluctuate. If the focus lens 14 position fluctuates and the blurred focus state continues for a long time, the visual quality of the captured moving image will deteriorate.

[0088] Therefore, in the technology of the present invention, as an example, Figure 12As shown in (A), 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 moving speed of the focus lens 14 to the set speed VA. On the other hand, as shown in (B), when the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated in-focus position is greater than or equal to the threshold value THA, the speed setting unit 72 sets the moving speed of the focus lens 14 to the set speed VB, which is slower than the set speed VA. The threshold value THA is stored in the memory 55. The threshold value |ΔA| is set to the absolute value 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. "Phase difference detection accuracy falling outside the set range" means that the position of the focus lens 14 may fluctuate (continuation of a blurred focus state) that is noticeable to the user due to changes in the subject distance. The threshold value THA is an example of the "first threshold" involved in the technology of the present invention. The set speed VA is an example of the "first speed" involved in the technology of the present invention. The set speed VB is an example of the “second speed” according to the technique of the present invention.

[0089] The speed setting unit 72 sets the set speed VB to a speed that enables the estimated focus position to be derived a set number of times while the focus lens 14 is moved, based on the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position and the number of estimated focus position derivations per unit time. The number of times the estimated focus position can be expected to converge to the original focus position is set in the set number of times.

[0090] As an example, Figure 13 As shown, the number of times the estimated focus position is derived is changed based on the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position. More specifically, when the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position is less than 5000% (depth of focus), the number of times is set to 5. When the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position is greater than or equal to 5000% and less than or equal to 20000%, the number of times is gradually increased from 5 to 10. When the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position is greater than or equal to 20000%, the number of times is set to 10.

[0091] And, as an example, Figure 14As shown in (A), when the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position is less than a threshold value THB, the focus lens drive control unit 73 keeps the focus lens 14 at its current position. Specifically, when 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 THB, the current position of the focus lens 14 is deemed to be the same as the estimated focus position. In other words, a margin is provided in the determination of 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 focus position is greater than or equal to the threshold value THB, the focus lens drive control unit 73 moves the focus lens 14. The threshold value THB is set to the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position at which the user can recognize the focus as out of focus. The threshold value THB is stored in the memory 55. The threshold value THB is an example of the "fourth threshold" involved in the technology of the present invention.

[0092] Figure 15 The current position of the focus lens 14 and the estimated focus position change when the subject switches from the distant view to the near view B at time TA. The near view B is closer to the distant view than the near view A. The case where the subject switches from the distant view to the near view B means that the phase difference detection accuracy is within the set range. That is, Figure 15 This corresponds to the case where the absolute value of the difference |ΔA| between the current position of focus lens 14 and the estimated focus position is less than threshold value THA. Therefore, estimated focus position PA at time TA coincides with the original focus position of near view B, indicated by the dashed line. The term "the estimated focus position coincides with the original focus position" does not necessarily mean a complete coincidence but also includes the case where the absolute value of the difference between the estimated focus position and the original focus position is less than threshold value THB.

[0093] The speed setting unit 72 sets the movement speed of the focus lens 14 to a set speed VA. At time TA, the focus lens drive control unit 73 causes the focus lens 14 to begin moving toward the estimated focus position PA at the set speed VA. Between time TA and time TB, the focus lens drive control unit 73 stops the focus lens 14 at the estimated focus position PA. In this way, if the phase difference detection accuracy is within the set range and the estimated focus position matches the original focus position, the focus lens drive control unit 73 causes the focus lens 14 to move to the estimated focus position at the set speed VA as quickly as possible.

[0094] At time TC and time TE, the estimated focus position slightly deviates from the original focus position. However, the absolute value of the difference |ΔA| between the current position of the focus lens 14 and the estimated focus position is less than the threshold value THB, so the focus lens drive control unit 73 keeps the focus lens 14 at the current position.

[0095] Figure 16 and Figure 11 Similarly, the figure shows the changes in the current position and estimated focus position of the focus lens 14 when the subject switches from a distant view to a near view A at time TA. The case where the subject switches from a distant view to a near view A corresponds to a case where the absolute value |ΔA| of the difference between the current position and the estimated focus position of the focus lens 14 is greater than or equal to a threshold value THA.

[0096] The speed setting unit 72 sets the moving speed of the focus lens 14 to a set speed VB. At time TA, the focus lens drive control unit 73 starts moving the focus lens 14 toward the estimated focus position PA at the set speed VB. The speed setting unit 72 sets the set speed VB to a speed that allows the estimated focus position to be derived a set number of times, i.e., five times, while the focus lens 14 is moved to the estimated focus position PA. These five estimated focus position derivations correspond to the derivations of the estimated focus position at times TA, TB, TC, TD, and TE.

[0097] At time TD, the estimated focus position converges and is updated to an estimated focus position PD that matches the original focus position. Therefore, the focus lens drive control unit 73 stops the focus lens 14 at the estimated focus position PD between time TD and time TE. However, although this is a very rare situation, if the estimated focus position fails to fully converge to the original focus position within the set number of derivations, and the absolute value of the difference |ΔA| between the current position of the focus lens 14 and the newly updated estimated focus position after the focus lens 14 stops exceeds the threshold value THB, the focus lens drive control unit 73 moves the focus lens 14 to the newly updated estimated focus position.

[0098] and Figure 15 Similarly to the cases of time TC and time TE, at time TH and time TJ, the estimated focus position slightly deviates from the original focus position. However, the absolute value of the difference |ΔA| between the current position of the focus lens 14 and the estimated focus position is less than the threshold value THB, so the focus lens drive control unit 73 keeps the focus lens 14 at the current position.

[0099] Next, as an example, refer to Figure 17 and Figure 18 The flowchart shown in FIG. 1 illustrates the function of the above structure. Figure 8 As shown, the CPU 56 functions as a focus adjustment unit 70 by activating the operation program 65. The focus adjustment unit 70 includes a focus derivation unit 71, a speed setting unit 72, and a focus lens drive control unit 73.

[0100] When the release button is fully pressed in the movie shooting mode and the command receiving unit 32 receives a command to start shooting a movie, the imaging element 12 accumulates signal charge corresponding to the subject light under the control of the control unit 20. Next, an image signal 43 corresponding to the signal charge is read out. The image signal 43 is stored in the image memory 26 via the image input controller 25. After the image signal 43 is subjected to various image processing by the image processing unit 27, it is written back to the image memory 26.

[0101] The calculation signal 43P is read from the image memory 26 to the focus derivation unit 71. The focus derivation unit 71 then calculates the phase difference α based on the calculation signal 43P of the focus area and derives the estimated focus position of the focus lens 14 based on the phase difference α (step ST100). The estimated focus position derivation result 76 is output from the focus derivation unit 71 to the speed setting unit 72 and the focus lens drive control unit 73. The focus adjustment unit 70 then 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).

[0102] If the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position is greater than or equal to the 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 the focus lens 14 and the estimated focus position is less than the threshold value THB ("NO" in step ST120), the process proceeds to step ST130. Figure 18 In step ST140, Figure 14 As shown in (A), the focus lens 14 is kept at the current position by the focus lens drive control unit 73, and the process ends.

[0103] In step ST130, the absolute value of the difference |ΔA| between the current position of the focus lens 14 and the estimated focus position is compared with the threshold value THA. If the absolute value of the difference |ΔA| between the current position of the focus lens 14 and the estimated focus position is smaller than the threshold value THA, the focus lens 14 is automatically adjusted. Figure 12 As shown in FIG. 1A , the speed setting unit 72 sets the moving speed of the focus lens 14 to the set speed VA (step ST150). On the other hand, when the absolute value of the difference |ΔA| between the current position of the focus lens 14 and the estimated focus position is greater than the threshold value THA, as shown in FIG. Figure 12 As shown in FIG. 2B , the speed setting unit 72 sets the moving speed of the focus lens 14 to the set speed VB (step ST160). Figure 13The graph shown in FIG. 1 determines the number of times the estimated focus position is derived, corresponding to the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position. Furthermore, the set speed VB is set to a speed that enables the estimated focus position to be derived the set number of times while the focus lens 14 is moved. Subsequently, the set speed information 77 is output from the speed setting unit 72 to the focus lens drive control unit 73.

[0104] Under the control of the focus lens drive control unit 73, the focus lens 14 is moved to the estimated focus position at the set speed VA or VB via the focus lens drive mechanism 17 (step ST170). The processes ST100 to ST170 continue until the release button is fully pressed again and the command receiving unit 32 receives a command to end the moving image shooting.

[0105] 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 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 the focus lens 14 is at the current position. When the absolute value of the difference |ΔA| 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 moving 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 of the difference |ΔA| between the current position of the focus lens 14 and the estimated in-focus position is greater than or equal to the threshold value THA, the speed setting unit 72 sets the moving speed of the focus lens 14 to a set speed VB that is slower than the set speed VA. The focus lens drive control unit 73 moves the focus lens 14 at the set speed VB. This can suppress fluctuations in the position of the focus lens 14 that occur when the subject distance fluctuates significantly.

[0106] like Figure 12 As shown, 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, which would cause the phase difference detection accuracy to fall outside the set range. This effectively suppresses fluctuations in the position of the focus lens 14 that occur when the subject distance fluctuates more as the phase difference detection accuracy falls outside the set range.

[0107] like Figure 12As shown, the speed setting unit 72 sets the set speed VB to a speed that allows the estimated focus position to be derived a set number of times while the focus lens 14 is moving, based on the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position, and the number of estimated focus position derivations per unit time. With each overlapping derivation of the estimated focus position, phase difference detection accuracy is restored, gradually converging to the original focus position. Therefore, by setting the set speed VB to a speed that allows the estimated focus position to be derived a set number of times while the focus lens 14 is moving, the focus lens 14 can be stopped at the original focus position without exceeding it.

[0108] like Figure 13 As shown, the setting number is changed according to the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position. Therefore, the setting speed VB can be set to suit the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position.

[0109] like Figure 14 As shown, 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 a threshold value THB, the focus lens drive control unit 73 causes the focus lens 14 to remain at the current position. 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 greater than or equal to the threshold value THB, the focus lens drive control unit 73 causes the focus lens 14 to move. Therefore, even when there is a subtle difference between the current position of the focus lens 14 and the estimated in-focus position that is not noticeable to the user as blurred focus, it is possible to prevent the focus lens 14 from being moved every time, thereby preventing it from being frequently and repeatedly moved.

[0110] [Second embodiment]

[0111] In the first embodiment described above, an example was described in which the estimated focus position derivation result 76 by the focus derivation unit 71 is updated every frame. However, depending on the model of the imaging device 10, some models may not be able to update the estimated focus position while the focus lens 14 is moving. Therefore, in this second embodiment, a method for determining whether to stop the focus lens 14 in models in which the estimated focus position cannot be updated while the focus lens 14 is moving will be described.

[0112] Figure 19 and Figure 11 and Figure 16Similarly, the change in the current position and estimated focus position of the focus lens 14 when the subject switches from the distant view to the near view A at time TA is shown. The speed setting unit 72 sets the moving speed of the focus lens 14 to the set speed VB. At time TA, the focus lens drive control unit 73 starts moving the focus lens 14 at the set speed VB. In this case, the focus lens drive control unit 73 moves the focus lens 14 toward the drive end on the near view side of the focus lens 14 instead of the estimated focus position PA. As in the first embodiment described above, the speed setting unit 72 sets the set speed VB to a speed at which the estimated focus position can be derived a set number of times while the focus lens 14 is moved. In addition, the set number of times is changed according to the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position.

[0113] The focus lens drive control unit 73 simultaneously starts calculating the absolute value |ΔB| of the difference between the previous and current estimated focus positions (the previous frame and the current frame) when starting to move the focus lens 14. Specifically, the absolute value |ΔB| of the difference between the previous and current estimated focus positions includes 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, 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. The former estimated focus position corresponds to the previous estimated focus position (the previous frame), while the latter estimated focus position corresponds to the current estimated focus position (the current frame).

[0114] The focus lens drive control unit 73 compares the absolute value of the difference |ΔB| between the estimated focus position last time and this time with the threshold value THC. And, when the absolute value of the difference |ΔB| between the estimated focus position last time and this time becomes smaller than the threshold value THC for two consecutive frames, the focus lens drive control unit 73 makes a stop judgment JA. The threshold value THC is stored in the memory 55. The threshold value THC is an example of the "third threshold value" involved in the technology of the present invention. Figure 19 , there is illustrated a case where 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 smaller than the threshold THC, and a stop judgment JA is made at time TD.

[0115] The focus lens drive control unit 73 stops the focus lens 14 at the estimated focus position at which the stop determination JA is made. Figure 19 , a case where the focus lens 14 is stopped at the estimated in-focus position PD at the time TD when the stop determination JA is made between the time TD and the time TE is exemplified.

[0116] As shown in the figure, after the focus lens 14 is stopped by the stop judgment JA, if the absolute value of the difference |ΔA| 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 causes the focus lens 14 to remain at the current position. After the focus lens 14 is stopped by the stop judgment JA, if the absolute value of the difference |ΔA| between the current position of the focus lens 14 and the estimated in-focus position is greater than or equal to the threshold value THB and less than the threshold value THA, the focus lens drive control unit 73 causes the focus lens 14 to move at the set speed VA. Furthermore, although this is a very rare case, after the focus lens 14 is stopped by the stop judgment JA, if the absolute value of the difference |ΔA| between the current position of the focus lens 14 and the estimated in-focus position is greater than or equal to the threshold value THA, the focus lens drive control unit 73 causes the focus lens 14 to move at the set speed VB.

[0117] Furthermore, the condition for making the stop determination JA is not limited to the illustrated case where the absolute value of the difference |ΔB| between the previous and current estimated focus positions is less than the threshold value THC for two consecutive frames. Alternatively, the condition may be where the absolute value of the difference |ΔB| between the previous and current estimated focus positions is less than the threshold value THC for three or four consecutive frames, or where the absolute value of the difference |ΔB| between the previous and current estimated focus positions is less than the threshold value THC for at least one frame.

[0118] Figure 20 This figure shows the change in the current position and estimated focus position of the focus lens 14 when the subject switches from distant view to close view C at time TA. Switching from distant view to close view C, like switching from distant view to close view A, involves a significant change in subject distance, leading to a decrease in phase difference detection accuracy. Therefore, the estimated focus position PA at time TA deviates from the original focus position for close view C, indicated by the dashed line.

[0119] The speed setting unit 72 sets the moving speed of the focus lens 14 to a set speed VB. At time TA, the focus lens drive control unit 73 begins moving the focus lens 14 at the set speed VB toward the drive end on the near-field side of the focus lens 14. As in the first embodiment described above, the speed setting unit 72 sets the set speed VB to a speed that allows a set number of estimated focus position derivations to be performed while the focus lens 14 is moving. The set number of derivations is changed based on the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position.

[0120] The focus lens drive control unit 73 simultaneously starts to monitor whether the current position of the focus lens 14 exceeds the estimated focus position. Whether the current position of the focus lens 14 exceeds the estimated focus position can be determined by whether the sign of the difference between the current position of the focus lens 14 and the estimated focus position has reversed between the previous and current frames (the previous and current frames). To make this determination, the focus lens drive control unit 73 calculates the difference between the current position of the focus lens 14 and the estimated focus position, with the sign known.

[0121] When it is determined that the current position of the focus lens 14 has exceeded the estimated focus position for two consecutive frames, the focus lens drive control unit 73 makes a stop determination JB to stop the focus lens 14. Figure 20 In FIG. 1 , a case is illustrated in which it is determined that the current position of the focus lens 14 exceeds the estimated focus position at time TE and time TF, and a stop determination JB is made at time TF to stop the focus lens 14 at the estimated focus position PA.

[0122] The focus lens drive control unit 73 keeps the focus lens 14 at the estimated 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 focus position PG at a set speed VA. At time TH, the focus lens drive control unit 73 stops the focus lens 14 at the estimated focus position PG.

[0123] As shown in the figure, after the focus lens 14 is stopped by the stop judgment 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 causes the focus lens 14 to remain at the current position. After the focus lens 14 is stopped by the stop judgment 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 greater than or equal to the threshold value THB and less than or equal to the threshold value THA, the focus lens drive control unit 73 causes the focus lens 14 to move at the set speed VA. Furthermore, although this is a very rare case, after the focus lens 14 is stopped by the stop judgment 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 greater than or equal to the threshold value THA, the focus lens drive control unit 73 causes the focus lens 14 to move at the set speed VB.

[0124] Furthermore, the condition for making the stop determination JB is not limited to the case where the current position of the focus lens 14 is determined to have exceeded the estimated focus position for two consecutive frames. It may be the case where the current position of the focus lens 14 is determined to have exceeded the estimated focus position for three or four consecutive frames, or it may be the case where the current position of the focus lens 14 is determined to have exceeded the estimated focus position for at least one frame.

[0125] Thus, in the second embodiment, as Figure 19 As shown in FIG. 1 , the speed setting unit 72 derives the estimated focus position multiple times while moving the focus lens 14 at the set speed VB. When the absolute value of the difference |ΔB| between the previous and current estimated focus positions becomes smaller than the threshold value THC, the focus lens drive control unit 73 stops the movement of the focus lens 14. Figure 20 As shown, when the focus lens drive control unit 73 determines that the current position of the focus lens 14 exceeds the estimated focus position while the focus lens 14 is being moved at the set speed VB, it stops the movement of the focus lens 14. Therefore, even in a model in which the estimated focus position cannot be updated 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.

[0126] Furthermore, in the second embodiment, as Figure 20 As shown in FIG. 1 , when the sign of the difference between the current position of the focus lens 14 and the estimated focus position is reversed, the focus lens drive control unit 73 determines that the current position of the focus lens 14 has exceeded the estimated focus position. Therefore, by simply monitoring whether the sign of the difference between the current position of the focus lens 14 and the estimated focus position is reversed, it is possible to easily determine whether the current position of the focus lens 14 has exceeded the estimated focus position.

[0127] In the second embodiment, when the set speed VB is set to a speed at which the estimated focus position can be derived a set number of times while the focus lens 14 is moved, and the set number of times is changed according to 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. That is, if the set speed VB is increased by setting the set number of times to be smaller regardless of the fact that the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position is larger, the current position of the focus lens 14 will exceed the estimated focus position before the estimated focus position converges to the original focus position. As a result, the focus lens 14 cannot be stopped by the stop judgment JA, and has to be stopped by the stop judgment JB. In the case where the focus lens 14 is stopped by the stop judgment JB, as shown in FIG. Figure 20 As can be seen, the position of the focus lens 14 fluctuates slightly. Therefore, it is desirable to minimize the possibility of the focus lens 14 being stopped by the stop determination JB. Therefore, when 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 large to slow the set speed VB, thereby increasing the likelihood that the focus lens 14 will be stopped by the stop determination JA.

[0128] In the case where the estimated focus position can be updated during the movement of the focus lens 14, as in the first embodiment, the set speed VB can be set faster than in the case where the estimated focus position cannot be updated during the movement of the focus lens 14, as in the second embodiment. This is because, in the first embodiment, as long as the estimated focus position can be derived once during the movement of the focus lens 14, the focus lens 14 can be stopped at an estimated focus position closer to the original focus position.

[0129] [Third embodiment]

[0130] As an example, Figure 21 As shown in the third embodiment, the moving speed of the focus lens 14 is changed according to the estimated focus position when the absolute value of the difference |ΔA| between the current position of the focus lens 14 and the estimated focus position becomes smaller than the threshold value THD. Figure 21 In the embodiment described above, similarly to the second embodiment, the imaging device 10 is assumed to be unable to update the estimated focus position while the focus lens 14 is moving.

[0131] Figure 21 and Figure 11 and Figure 16 Similarly, the following figure shows the changes in the current position and estimated focus position of the focus lens 14 when the subject switches from a distant view to a close view A at time TA. The speed setting unit 72 sets the movement speed of the focus lens 14 to a set speed VB1. At time TA, the focus lens drive control unit 73 begins moving the focus lens 14 toward the estimated focus position PA at the set speed VB1. The speed setting unit 72 sets the set speed VB1 to a speed that allows the estimated focus position to be derived a set number of times, i.e., five times, while the focus lens 14 is moved to the estimated focus position PA. These five estimated focus position derivations correspond to the estimated focus position derivations at times TA, TB, TC, TD, and TE.

[0132] When the speed setting unit 72 starts moving the focus lens 14, it also begins comparing the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position with the threshold value THD. If the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position falls below the threshold value THD, the speed setting unit 72 changes (resets) the moving speed of the focus lens 14 based on the estimated focus position at which the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated focus position falls below the threshold value THD. The threshold value THD is stored in the memory 55. The threshold value THD is an example of the "second threshold value" involved in the technique of the present invention.

[0133] exist Figure 21, illustrates a case where the absolute value of the difference |ΔA| between the current position of the focus lens 14 and the estimated focus position at time TC becomes less than a threshold value THD. Furthermore, the speed setting unit 72 changes the moving speed of the focus lens 14 to a set speed VB2 based on the estimated focus position PC at time TC. Here, the speed setting unit 72 sets the set speed VB2 to a speed that enables the estimated focus position to be derived a set number of times, i.e., five times, while the focus lens 14 is moved to the estimated focus position PC. These five estimated focus position derivations correspond to the derivations of the estimated focus positions at times TC, TD, TE, TF, and TG.

[0134] At time TC, the focus lens drive control unit 73 starts moving the focus lens 14 toward the estimated focus position PC at the changed set speed VB2, and stops the focus lens 14 at the estimated focus position PF at time TF through the stop determination JA at time TE.

[0135] Thus, in the third embodiment, when the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated in-focus position falls below the threshold value THD while the focus lens 14 is being moved at the set speed VB1, the speed setting unit 72 changes the moving speed of the focus lens 14 based on the estimated in-focus position at which the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated in-focus position falls below the threshold value THD. Therefore, if the absolute value |ΔA| of the difference between the current position of the focus lens 14 and the estimated in-focus position reaches a value that requires a set number of 10 times, for example, the following approach can be adopted. Specifically, the set speed VB1 corresponding to a set number of 5 times, which is faster than the set speed corresponding to the set number of 10 times, is set, so that the current position of the focus lens 14 approaches the estimated in-focus position in a shorter period of time. Then, if the current position of the focus lens 14 approaches the estimated focus position (if the absolute value of the difference |ΔA| between the current position of the focus lens 14 and the estimated focus position becomes smaller than the threshold value THD), the set speed is reduced to the set speed VB2, and the focus lens 14 is stopped by the stop determination JA. In this way, the current position of the focus lens 14 can be aligned with the original focus position in a shorter time than when the focus lens 14 is moved at the set speed corresponding to the set number of times 10.

[0136] While the above embodiments illustrate the case of switching from a distant view to a close view, the present invention is not limited to this. The technology of the present invention can also be applied to the reverse case of switching from a close view to a distant view. Furthermore, while the above embodiments illustrate the case of shooting a moving image, the present invention is not limited to this. The technology of the present invention can also be applied to displaying a live preview image before shooting a still image or a moving image.

[0137] The imaging device according to the technology of the present invention 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.

[0138] In each of the above-described embodiments, various processors described below can be used as the hardware configuration of the processing units (processing units) that perform various processes, such as the image processing unit 27, the display control unit 30, the command receiving unit 32, the focusing unit 70, the focus derivation unit 71, the speed setting unit 72, and the focus lens drive control unit 73. These various processors include a general-purpose processor, namely the CPU 56, which performs the functions of the various processing units by executing software (the operating program 65). Furthermore, processors such as FPGAs (Field Programmable Gate Arrays) whose circuit configuration can be modified after manufacturing, namely programmable logic devices (PLDs), and / or ASICs (Application Specific Integrated Circuits), which are processors having circuit configurations specifically designed to perform specific processes, namely dedicated circuits.

[0139] A single processing unit may be composed of one of these various processors, or 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). Furthermore, a single processor may constitute multiple processing units.

[0140] Examples of multiple processing units composed of a single processor include the following: First, as exemplified by computers such as client computers and servers, a single processor is composed of a combination of one or more CPUs and software, with the processor functioning as multiple processing units. Second, as exemplified by system-on-chips (SoCs), a processor is used that implements the overall functionality of a system including multiple processing units using a single IC (Integrated Circuit) chip. In this manner, the various processing units are constructed as hardware using one or more of the various processors described above.

[0141] Furthermore, as the hardware configuration of these various processors, more specifically, a circuit (Circuitry) formed by combining circuit elements such as semiconductor elements can be used.

[0142] From the above contents, the techniques described in the following supplementary notes can be understood.

[0143] [Supplementary Note 1]

[0144] A focus control device performs focus control of a focus lens based on output from a phase difference detection pixel, wherein:

[0145] The focus control device includes a processor,

[0146] The processor performs the following processing:

[0147] obtaining a 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;

[0148] When the absolute value of the difference between the current position and the estimated focus position is smaller than a first threshold, moving the focus lens at a first speed; and

[0149] When an absolute value of a difference between the current position and the estimated in-focus position is equal to or greater than the first threshold, the focus lens is moved at a second speed that is slower than the first speed.

[0150] [Supplementary Note 2]

[0151] The focus control device according to Supplementary Note 1, wherein:

[0152] The first threshold is set with an absolute value of a difference between the current position and the estimated focus position at which the phase difference detection accuracy falls outside a set range.

[0153] [Supplementary Note 3]

[0154] The focus control device according to Supplementary Note 1 or 2, wherein:

[0155] The processor performs the following processing:

[0156] The second speed is set to a speed that enables derivation of the estimated focus position 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 derivations of the estimated focus position per unit time.

[0157] [Supplementary Note 4]

[0158] The focus control device according to Supplementary note 3, wherein:

[0159] The set number of times is changed according to the absolute value of the difference between the current position and the estimated focus position.

[0160] [Supplementary Note 5]

[0161] The focus control device according to any one of Supplementary Notes 1 to 4, wherein:

[0162] The processor performs the following processing:

[0163] While the focusing 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 smaller than a second threshold, the moving speed of the focusing lens is changed according to the estimated focus position when the absolute value of the difference between the current position and the estimated focus position becomes smaller than the second threshold.

[0164] [Supplementary Note 6]

[0165] The focus control device according to any one of Supplementary Notes 1 to 5, wherein:

[0166] The processor performs the following processing:

[0167] deriving the estimated focus position a plurality of times while the focus lens is moved at the second speed; and

[0168] When the absolute value of the difference between the previous estimated focus position and the current estimated focus position becomes smaller than a third threshold, the movement of the focus lens is stopped.

[0169] [Supplementary Note 7]

[0170] The focus control device according to any one of Supplementary Notes 1 to 6, wherein:

[0171] The processor performs the following processing:

[0172] When it is determined that the current position exceeds the estimated focus position while the focus lens is being moved at the second speed, the movement of the focus lens is stopped.

[0173] [Supplementary Note 8]

[0174] The focus control device according to Supplementary note 7, wherein:

[0175] The processor performs the following processing:

[0176] When the sign of the difference between the current position and the estimated focus position is reversed, it is determined that the current position exceeds the estimated focus position.

[0177] [Supplementary Note 9]

[0178] The focus control device according to any one of Supplementary Notes 1 to 8, wherein:

[0179] The processor performs the following processing:

[0180] When the absolute value of the difference between the current position and the estimated focus position is smaller than a fourth threshold, keeping the focus lens at the current position; and

[0181] 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, the focus lens is moved.

[0182] [Supplementary Note 10]

[0183] An imaging device comprising the focus control device according to any one of Supplementary Items 1 to 9.

[0184] The technology of the present invention can also be appropriately combined with the various embodiments and / or various modifications described above. Furthermore, the technology is not limited to the aforementioned embodiments, and various structures can be adopted without departing from the main purpose. Furthermore, the technology of the present invention relates not only to programs but also to storage media that non-temporarily store programs.

[0185] The records and illustrations shown above are detailed descriptions of the parts involved in the technology of the present invention, and are only an example of the technology of the present invention. For example, the descriptions related to the above-mentioned structure, function, action and effect are descriptions related to an example of the structure, function, action and effect of the parts involved in the technology of the present invention. Therefore, without departing from the scope of the technical purpose of the present invention, it is of course possible to delete unnecessary parts of the records and illustrations shown above, or to add or replace new elements. In addition, in order to avoid complex situations and facilitate understanding of the parts involved in the technology of the present invention, descriptions related to technical common sense that does not particularly need to be explained in terms of enabling the implementation of the technology of the present invention are omitted in the records and illustrations shown above.

[0186] In this specification, "A and / or B" has the same meaning as "at least one of A and B." That is, "A and / or B" can mean only A, only B, or a combination of A and B. Furthermore, in this specification, the same concept as "A and / or B" applies when three or more items are linked and labeled with "and / or."

[0187] All documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each individual document, patent application, or technical standard were specifically and individually indicated to be incorporated by reference.

[0188] Explanation of symbols

[0189] 10-Camera, 11-Camera optical system, 12-Imaging element, 13-Objective lens, 14-Focus lens, 15-Zoom lens, 16-Aperture, 17-Focus lens drive mechanism, 18-Zoom lens drive mechanism, 19-Aperture drive mechanism, 20-Control unit, 21-Operation unit, 22-Imaging element driver, 23-Shutter, 24-Shutter drive mechanism, 25-Image input controller, 26-Image memory, 27-Image processing unit, 28, 58-Bus, 29-VRAM, 30-Display control unit, 31-Interface Quality controller, 32-Command receiving unit, 33-Viewfinder monitor, 34-Rear monitor, 35-Memory card, 36-Touch panel, 40-Photoelectric conversion unit, 41-Pixel, 41N-Normal pixel, 41P-Phase difference detection pixel, 42-Image plane, 43-Image signal, 43N-Image generation signal, 43P-Calculation signal, 45-Microlens, 46-Color filter, 47-Photoelectric conversion element, 49-Light shielding component, 55-Storage device, 56-CPU, 57-Memory, 65-Working program, 70-Focus adjustment , 71-focus derivation unit, 72-speed setting unit, 73-focus lens drive control unit, 75-drive amount, 76-derivation result, 77-set speed information, 80-mountain, 81-person, 411P-first phase difference detection pixel, 412P-second phase difference detection pixel, 431P-first 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 focus position, |ΔB|-absolute value of the difference between the previous estimated focus position and the current estimated focus position, J A, JB-stop judgment, OA-optical axis, PA, PB, PC, PD, PE, PF, PG-estimated focus position, ST100, ST110, ST120, ST130, ST140, ST150, ST160, ST170-steps, TA, TB, TC, TD, TE, TF, TG, TH, TI, TJ-time, THA, THB, THC, THD-threshold, V-moving speed of focusing lens (set speed), VA-set speed, VB, VB1, VB2-set speed.

Claims

1. A focus control device, wherein: The focus control device includes a processor, The processor performs the following processing: obtaining a current position of a focus lens and an estimated focus position of the focus lens derived when the focus lens is at the current position; When the absolute value of the difference between the current position and the estimated focus position is smaller 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 in-focus position is equal to or greater than the first threshold, the focus lens is moved at a second speed that is slower than the first speed.

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

3. The focus control device according to claim 1, wherein: The processor performs the following processing: The second speed is set to a speed that enables derivation of the estimated focus position 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 derivations of the estimated focus position per unit time.

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

5. The focus control device according to claim 1, wherein: The processor performs the following processing: While the focusing 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 smaller than a second threshold, the moving speed of the focusing lens is changed according to the estimated focus position when the absolute value of the difference between the current position and the estimated focus position becomes smaller than the second threshold.

6. The focus control device according to claim 1, wherein: The processor performs the following processing: deriving the estimated focus position a plurality of times while the focus lens is moved at the second speed; and When the absolute value of the difference between the previous estimated focus position and the current estimated focus position becomes smaller than a third threshold, the movement of the focus lens is stopped.

7. The focus control device according to claim 1, wherein: The processor performs the following processing: When it is determined that the current position exceeds the estimated focus position while the focus lens is being moved at the second speed, the movement of the focus lens is stopped.

8. The focus control device according to claim 7, wherein: The processor performs the following processing: When the sign of the difference between the current position and the estimated focus position is reversed, it is determined that the current position exceeds the estimated focus position.

9. The focus control device according to claim 1, wherein: The processor performs the following processing: When the absolute value of the difference between the current position and the estimated focus position is less than a fourth threshold, causing the focus lens to remain at the current position; and 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, the focus lens is moved.

10. A method for operating a focus control device, comprising the following steps: obtaining a current position of a focus lens and an estimated focus position of the focus lens derived when the focus lens is at the current position; When the absolute value of the difference between the current position and the estimated focus position is smaller 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 in-focus position is equal to or greater than the first threshold, the focus lens is moved at a second speed that is slower than the first speed.

11. A storage medium capable of being read by a computer, the storage medium storing an operating program of a focus control device, the operating program of the focus control device causing the computer to execute a process comprising the following steps: obtaining a current position of a focus lens and an estimated focus position of the focus lens derived when the focus lens is at the current position; When the absolute value of the difference between the current position and the estimated focus position is smaller 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 in-focus position is equal to or greater than the first threshold, the focus lens is moved at a second speed that is slower than the first speed.

12. A computer program product comprising an operating program of a focus control device, wherein the operating program of the focus control device causes a computer to execute a process comprising the following steps: obtaining a current position of a focus lens and an estimated focus position of the focus lens derived when the focus lens is at the current position; When the absolute value of the difference between the current position and the estimated focus position is smaller 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 in-focus position is equal to or greater than the first threshold, the focus lens is moved at a second speed that is slower than the first speed. 13 . An imaging device comprising the focus control device according to claim 1 .

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