Focus control device, focus control method, and imaging device

Abstract

To provide a focus control device, a focus control method, and an imaging apparatus, which can suppress differences in changes in focusing degrees due to differences in lens units by performing appropriate focus lens drive control depending on a lens unit.SOLUTION: A focus control device controls driving of a focus lens included in a lens unit during moving image shooting. The focus control device acquires a drive pattern determined in advance for driving the focus lens to an in-focus position and controls the driving of the focus lens. If the drive pattern has a fine-driving section in which it is necessary to drive the focus lens at a drive speed less than a minimum drive speed set in advance, and it is determined that the lens unit is not suitable for fine driving of the focus lens, the focus control device continuously drives the focus lens at the minimum drive speed in the fine-driving section.SELECTED DRAWING: Figure 13

Description

Technical Field

[0001] The present invention relates to a focus control device, a focus control method, and an imaging device.

Background Art

[0002] In an imaging device having an autofocus function that automatically drives a focus lens, if the driving speed of the focus lens changes significantly during video shooting, the in-focus degree of the video may change abruptly, giving an unnatural impression. Therefore, in Patent Document 1, the driving speed of the focus lens is prevented from changing from a constant mode to a variable mode until the defocus amount becomes less than a predetermined value, thereby suppressing a sudden change in the driving speed of the focus lens.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to control the in-focus degree to change smoothly, it is necessary to drive the focus lens at a low speed near the in-focus state. On the other hand, the weight and driving mechanism of the focus lens vary depending on the lens unit. Therefore, the delay from when a driving command for the focus lens is transmitted until the focus lens actually starts moving, as well as the change in the driving speed of the focus lens, also vary depending on the lens unit. Therefore, even if appropriate driving control for a certain lens unit is applied to other lens units, the desired driving speed may not be achievable.

[0005] One object of the present invention is to provide a focus control device, a focus control method, and an imaging device capable of suppressing the difference in the change in the focus degree due to the difference in the lens unit by performing appropriate focus lens drive control according to the lens unit.

Means for Solving the Problems

[0006] The above object is achieved by a focus control device that controls the drive of a focus lens included in a lens unit during video shooting, the focus control device including: an acquisition unit that acquires a predetermined drive pattern for driving the focus lens to a focus position; and a control unit that controls the drive of the focus lens, wherein when the drive pattern has a minute drive section in which the focus lens needs to be driven at a drive speed lower than a predetermined minimum drive speed and the lens unit is determined to be not suitable for the minute drive of the focus lens, the control unit continuously drives the focus lens at the minimum drive speed for the minute drive section.

Effects of the Invention

[0007] According to the present invention, it is possible to provide a focus control device, a focus control method, and an imaging device capable of suppressing the difference in the change in the focus degree due to the difference in the lens unit by performing appropriate focus lens drive control according to the lens unit.

Brief Description of the Drawings

[0008]

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Best Mode for Carrying Out the Invention

[0009] Hereinafter, the present invention will be described in detail based on its exemplary embodiments with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Also, although a plurality of features are described in the embodiments, not all of them are essential to the invention, and a plurality of features may be arbitrarily combined. Furthermore, in the accompanying drawings, the same or similar configurations are denoted by the same reference numerals, and redundant explanations are omitted.

[0010] In the following embodiments, the present invention will be described in the case of being implemented in an interchangeable-lens digital video camera. However, the present invention can be implemented in any electronic device capable of video imaging using different types of lens units. Such electronic devices include video cameras, computer devices (personal computers, tablet computers, media players, PDAs, etc.), mobile phones, smartphones, game machines, robots, drones, and drive recorders. These are examples, and the present invention can be implemented in other electronic devices as well.

[0011] ● <First Embodiment> Hereinafter, a first embodiment of the present invention will be described. FIG. 1 is a block diagram showing a functional configuration example of a camera system as an example of an imaging device using a focus control device according to the first embodiment of the present invention.

[0012] The camera system is an interchangeable-lens video camera system and is composed of a main body 20 which is an imaging device according to the present embodiment, and a lens unit 10 detachable from the main body 20. The main body 20 and the lens unit 10 are mechanically and electrically connected through the mount portions they each have. The camera control unit 212 in the main body 20 and the lens control unit 106 in the lens unit 10 can transmit and receive information and commands through communication via the mount portion.

[0013] First, the configuration of the lens unit 10 will be described. The fixed lens 101, the aperture 102, and the focus lens 103 constitute the imaging optical system. The aperture 102 is driven by an aperture drive unit 104 to control the amount of incident light to the imaging element 201 described later. The focus lens 103 is driven along the optical axis by a focus lens drive unit 105 composed of a DC motor and its control circuit. The focal length of the imaging optical system changes according to the position of the focus lens 103.

[0014] The lens control unit 106 controls the operations of the aperture drive unit 104 and the focus lens drive unit 105 according to commands from the camera control unit 212, and controls the aperture amount of the aperture 102 and the position of the focus lens 103. The drive control of the focus lens, which will be described later, is also realized by the lens control unit 106 controlling the focus lens drive unit 105 according to commands from the camera control unit 212. In addition, the lens control unit 106 transmits information about the lens unit stored in the non-volatile memory of the lens control unit 106, information about the position of the focus lens, etc. to the camera control unit 212.

[0015] The lens operation unit 107 is a general term for the input device group provided in the lens unit. The lens operation unit 107 includes an AF (Auto Focus) / MF (Manual Focus) mode changeover switch, a focus ring, an aperture ring, a focus limiter, a shake correction mode changeover switch, etc. These are merely examples and are not essential, and input devices assigned with other functions may also be included. The operations of the lens operation unit 107 are detected by the lens control unit 106, and the lens control unit 106 performs control according to the detected operations.

[0016] The lens control unit 106 has, for example, a CPU, a ROM, and a RAM, and controls each part in the lens unit 10 and communicates with the camera control unit 212 by reading the program stored in the ROM into the RAM and executing it.

[0017] Next, the configuration of the main body 20 will be described. The imaging element 201 is, for example, a CMOS image sensor, and pixels in which photodiodes are formed are two-dimensionally arranged. The imaging optical system of the lens unit 10 forms an optical image of the subject on the imaging surface of the imaging element 201. In each pixel of the imaging element 201, the photodiode generates charges according to the incident light amount, and generates a pixel signal obtained by converting the charge amount into a voltage.

[0018] In accordance with the command of the camera control unit 212, pixel signals are sequentially read out, for example, in units of pixel rows, by drive pulses output from the timing generator 214. A series of processes are repeatedly executed with the period of reading out pixel signals from all effective pixels of the image sensor 201 defined as the camera control period.

[0019] Also, the image sensor 201 used in this embodiment is assumed to be capable of generating a pair of parallax signals for realizing image plane phase difference AF. For example, each pixel has one microlens and two photodiodes A and B, and the photodiodes A and B are configured to receive light fluxes from different partial regions of the exit pupil of the imaging optical system. For a plurality of pixels within the focus detection region, an A image signal obtained by concatenating A signals read out from the photodiode A and a B image signal obtained by concatenating B signals read out from the photodiode B form a pair of parallax signals. By detecting the phase difference of this pair of parallax signals and converting the phase difference into the defocus amount and defocus direction of the imaging optical system, the position of the focus lens can be driven to the in-focus position.

[0020] Note that, by adding the signals of the photodiodes A and B in each pixel, a normal pixel signal (A + B signal) can be obtained. Since the normal pixel signal is used for generating image data, it is also called an imaging signal. On the other hand, since the A signal and the B signal are used for automatic focus detection (autofocus), they are also called AF signals.

[0021] The front end 202 performs correlated double sampling, gain adjustment, and AD conversion on the signals read out from the image sensor 201 to remove reset noise. The front end 202 outputs the signals subjected to these processes to the image input controller 203 and the AF signal processing unit 204 according to the type of the signals. Specifically, the front end 202 outputs the A + B signal to the image input controller 203 and the A signal and the B signal to the AF signal processing unit 204. The AF signals may be read out only from the pixels within a preset focus detection region, or may be read out from all the pixels.

[0022] In addition, when the A signal and the A + B signal are read out from the imaging device and the B signal is not read out, the front end 202 outputs the difference between the A + B signal and the A signal as the B signal to the AF signal processing unit 204. Similarly, when the B signal and the A + B signal are read out from the imaging device and the A signal is not read out, the front end 202 outputs the difference between the A + B signal and the B signal as the A signal to the AF signal processing unit 204.

[0023] The image input controller 203 applies predetermined image processing to the imaging signal output from the front end 202 to generate display image data and recording image data. The predetermined image processing includes processes such as color interpolation, white balance adjustment, various corrections, scaling, and encoding.

[0024] The image input controller 203 stores the generated image data in the SDRAM 209 via the bus 21. The display image data stored in the SDRAM 209 is read out by the display control unit 205 via the bus 21 and displayed on the display unit 206. Also, the recording image data stored in the SDRAM 209 is read out by the recording medium control unit 207 and recorded on a recording medium 208 such as a semiconductor memory card.

[0025] The camera control unit 212 is, for example, a CPU. By reading the program stored in the ROM 210 into the SDRAM 209 and executing it, the operations of the main body 20 and the lens unit 10 are controlled, and the functions of the entire camera system are realized. The functional blocks of the camera control unit 212 shown in the figure schematically describe the functions realized by the camera control unit 212 executing the program. Note that some of the functions realized by the camera control unit 212 executing the program may be implemented by a hardware circuit such as an ASIC.

[0026] The ROM 210 is, for example, an electrically rewritable non-volatile memory. The ROM 210 stores a program executed by the camera control unit 212, various data necessary for the execution of the program, various setting values, the unique information of the main body 20, and the like.

[0027] The subject detection unit 2121 in the camera control unit 212 detects a region (subject region) related to a specific subject from the image data stored in the SDRAM 209, and obtains the position and size of the detected subject region. Further, the subject detection unit 2121 detects the movement of the subject region between frames. The specific subject is, for example, a face of a person or an animal, or a region having a high similarity to a partial region within the screen designated by the user with the camera operation unit 213.

[0028] The subject tracking unit 2122 is used to track the subject region across frames when the subject region detected by the subject detection unit 2121 is set as the focus detection region. The subject tracking unit 2122 detects the subject region by a method different from that of the subject detection unit 2121, for example, by color information or the like.

[0029] The AF signal processing unit 204 as a focus detection device generates an A image signal and a B image signal from the A signal and the B signal output from the front end 202, and calculates the amount of image shift (phase difference) between the A image signal and the B image signal, and the reliability of the amount of image shift. The amount of image shift can be calculated as the shift amount at which the correlation amount is maximized while relatively shifting the A image signal and the B image signal. The reliability can be calculated based on the correlation amount corresponding to the amount of image shift, the steepness of the change in the correlation amount near the amount of image shift, the contrast signals of the A image signal and the B image signal, and the like. Note that there is no particular limitation on the method for calculating the amount of image shift and its reliability, and any known method can be used.

[0030] The generation of the A-image signal and the B-image signal, and the calculation of the amount of image shift and its reliability may be executed for a plurality of regions within the screen. For example, in a case where an AF signal is obtained across the entire screen, the AF signal processing unit 204 can set a focus detection region based on the amount of image shift obtained for a plurality of regions and its reliability.

[0031] The AF signal processing unit 204 outputs information on the amount of image shift obtained for the focus detection region and its reliability to the camera control unit 212. The AF control unit 2123 within the camera control unit 212 converts the amount of image shift calculated by the AF signal processing unit 204 into a defocus amount. Then, the AF control unit 2123 transmits a lens drive command including the drive amount and drive direction of the focus lens determined based on the defocus amount to the lens control unit 106. The lens control unit 106 controls the focus lens drive unit 105 based on the lens drive command to drive the focus lens 103. Thereby, the focus adjustment of the imaging optical system is performed so that the focus detection region is in focus.

[0032] The AF control switching unit 2124 switches the operation mode of the AF control unit 2123 based on the determination result by the motion determination unit 2127 and the operation on the camera operation unit 213. The prediction unit 2125 predicts the position to be focused on next based on the change over time of the defocus amount. The prediction unit 2125 can be used for the subject tracking function.

[0033] The memory control unit 2126 stores various types of information related to the drive control of the focus lens, including information indicating the drive pattern (drive characteristics) of the focus lens corresponding to the defocus amount obtained for the focus detection region, in the memory circuit 215. The memory circuit 215 may be a region of the SDRAM 209.

[0034] The motion determination unit 2127 estimates the movement amount of the focus lens based on the relationship between the movement amount of the focus lens 103 instructed to the lens control unit 106 and the actual movement amount. The AF control unit 2123 is the AF Cut-offControls the operations of the substitution unit 2124, the memory control unit 2126, and the motion determination unit 2127. In the above configuration, the AF signal processing unit 204 and the camera control unit 212 constitute the focus control device according to the embodiment.

[0035] Hereinafter, the autofocus operation in video shooting in the main body 20 will be described in detail. The video shooting may be video shooting for display (for example, video shooting for causing the display unit 206 to function as an EVF) or video shooting for recording. FIG. 2 is a flowchart describing the operation from the start of the main body 20 from the viewpoint of the autofocus operation.

[0036] When activation is instructed by an operation of the power switch of the camera operation unit 213 or the like, the camera control unit 212 executes activation processing in S202.

[0037] The activation processing will be described using the flowchart shown in FIG. 3. First, the camera control unit 212 checks whether the lens unit 10 is attached. Here, it is assumed that the lens unit 10 is attached. In S302, the camera control unit 212 communicates with the lens control unit 106 to acquire lens information. The lens information includes type information, control cycle, drive speed information, and minimum drive amount information. The type information is information that can identify the product, such as the model name of the lens unit 10. The control cycle is the repetition cycle of the control operation of the lens unit. Drive The drive speed information indicates the drive speed of the focus lens that can be set in the lens unit 10. The drive speed of the focus lens depends on the weight of the focus lens, the performance of the drive mechanism, and the drive control method, and may vary depending on the model of the lens unit 10. The minimum drive amount information indicates the minimum drive amount DS0 of the focus lens.

[0038] When specifying the driving speed of the focus lens with respect to the lens unit 10 from the main body 20, specify the speed indicated in the driving speed information. Also, when specifying the driving amount of the focus lens, specify a driving amount equal to or greater than the minimum driving amount DS0. Even if a driving amount less than the minimum driving amount DS0 is specified, the focus lens will not move.

[0039] For example, assume that the driving amount of the focus lens is represented by the number of drive pulses and the minimum driving amount DS0 is 120 pulses. In this case, even if a drive command specifying 100 pulses as the driving amount is sent to the lens control unit 106, the focus lens will not move.

[0040] In S303, the camera control unit 212 performs a reset operation on the lens unit 10. Specifically, the camera control unit 212 drives the focus lens 103 to the end of the physically drivable range and then resets the sensor that measures the position of the focus lens. Thereby, the position information of the focus lens is reset.

[0041] In S304, the camera control unit 212 performs an operation test on the focus lens. Specifically, the camera control unit 212 sets the minimum driving speed among the driving speeds indicated by the driving speed information and the first target driving amount for measuring the actual minimum driving amount, and sends a focus lens drive command to the lens control unit 106. The first target driving amount may be, for example, the minimum driving amount DS0 obtained from the lens unit 10, but other driving amounts may also be used. When receiving a response to the command from the lens control unit 106, the camera control unit 212 acquires the actual movement amount of the focus lens from the lens control unit 106. The camera control unit 212 stores the actual movement amount with respect to the first target driving amount as the driving amount information DS1 in, for example, the memory circuit 215.

[0042] The influence of gravity on the focus lens 103 changes depending on the shooting posture, particularly the angle in the vertical direction of the optical axis. In addition, there are variations in the assembly accuracy and component tolerances in the lens unit 10. On the other hand, the minimum driving amount DS0 obtained from the lens unit 10 is a design value assuming specific conditions. Therefore, the minimum driving amount in the actual environment may be different from DS0. For this reason, the actual driving amount is measured when the operation of the lens unit is reset. Note that the driving amount information DS1 may be obtained by converting the actual movement amount obtained for the first target driving amount slightly larger than DS0.

[0043] Next, the camera control unit 212 sets the minimum driving speed and a specified second target driving amount larger than the first target driving amount, and transmits a focus lens driving command to the lens control unit 106. The second target driving amount is determined to measure the driving amount error when the focus lens 103 is moved largely. Then, the camera control unit 212 acquires the actual movement amount, and stores the difference between the second target driving amount and the actual driving amount as the driving amount information DL0 in, for example, the memory circuit 215.

[0044] Then, the camera control unit 212 drives the focus lens to return it to the default position after the reset operation. Thereby, the operation test is ended.

[0045] In S305, the camera control unit 212 initializes the standby count to 0 and ends the startup process. The standby count is a variable referred to in the process of extending the substantial control cycle. The standby count will be described later.

[0046] Returning to FIG. 2, when the startup process ends, the camera control unit 212 executes the process in the shooting standby state. The camera control unit 212 continuously executes, for example, video shooting, generation of display image data, and display on the display unit 206 based on the display image data, and controls each unit so that the display unit 206 functions as an electronic viewfinder (EVF).

[0047] In S203, the camera control unit 212 determines whether autofocus is enabled. If the autofocus is set to be enabled through the menu screen or the lens operation unit 107, the camera control unit 212 executes S204; if it is set to be disabled (manual focus), the camera control unit 212 executes S205.

[0048] In S205, the camera control unit 212, for example, sets the focused flag stored in the memory circuit 215 or the SDRAM 209 to OFF (e.g., 0), and then executes S203 again.

[0049] In S204, the camera control unit 212 determines whether the focused flag is ON (e.g., 1). If the focused flag is ON, there is no need to perform AF processing, so the camera control unit 212 skips S206 and executes S203. On the other hand, if the focused flag is OFF, the camera control unit 212 executes AF processing in S206.

[0050] In this way, in S203 to S206, the camera control unit 212 executes AF processing every control cycle when autofocus is set to be enabled and the camera is not in a focused state.

[0051] Next, with reference to the flowchart shown in FIG. 4, the AF processing in S206 of FIG. 2 will be further described. In S402, the camera control unit 212 obtains, for example, the lens drive speed setting from the ROM 210. The lens drive speed setting can be set by the user, for example, by operating the menu screen using the camera operation unit 213. In subsequent processing, the drive speed of the focus lens is determined based on the lens drive speed setting.

[0052] In S403, the camera control unit 212 causes the AF signal processing unit 204 to detect the amount of image shift for the main subject area and obtain the defocus amount. Here, the main subject area may be the focus detection area specified by the user, or may be an area among the subject areas detected by the subject detection unit 2121 that satisfies predetermined conditions regarding position and size.

[0053] The subject tracking process is realized by searching for the main subject area over a plurality of frames of the video. Hereinafter, the AF process of driving the focus lens so as to focus on the main subject area, with the main subject area as the focus detection area, will be described.

[0054] In S404, the camera control unit 212 calculates a curve (base curve) representing the reference focus lens driving characteristics based on the defocus amount calculated for the main subject area. FIG. 5 is a flowchart regarding the base curve calculation process in S404. In S502, the camera control unit 212 determines whether or not the reliability of the defocus amount of the main subject is equal to or greater than a predetermined value. This determination may be a comparison between the reliability obtained from the AF signal processing unit 204 as the reliability of the image shift amount used for calculating the defocus amount and the predetermined value. If the camera control unit 212 determines that the reliability of the defocus amount is equal to or greater than the predetermined value, it executes S503, and if it determines that the reliability of the image shift amount is not equal to or greater than the predetermined value, it ends the base curve calculation process.

[0055] In S503, the camera control unit 212 calculates a base curve based on the defocus amount calculated in S402. The camera control unit 212 calculates a base curve based on the reference driving characteristics stored in the memory circuit 215 and the defocus amount calculated in S402. The base curve indicates how to drive the focus lens for each control cycle until the focus lens reaches the in-focus position from the current position.

[0056] FIG. 6 is an exemplary base curve and is a diagram showing a portion corresponding to a deceleration period described later. The horizontal axis represents time, and the vertical axis represents the defocus amount. The upper left is the origin, corresponding to a defocus amount of 0 and the driving start time. Since the defocus amount is converted according to the focus lens position, the vertical axis can be regarded as the relative lens position with the in-focus position as the reference point. Note that the defocus amount is an absolute value.

[0057] Note that in the figure, Fδ indicates the focusing range (depth of focus). F is the aperture value, and δ is the allowable circle of confusion diameter. The in-focus state is achieved within the range of ±Fδ centered on the focus lens position where the defocus amount is 0. Here, the signs indicate the front side and the back side. Let the focus lens position 604 corresponding to Fδ be CP1.

[0058] The base curve 602 is designed such that the focus lens reaches the in-focus position through an acceleration period, a constant-speed period, and a deceleration period. Due to the shape of the base curve 602, the way the degree of focus changes due to the movement of the focus lens varies, resulting in different visual effects on the moving image. Therefore, the memory circuit 215 stores the reference drive characteristics for each visual effect.

[0059] Here, as an example, the calculation of a base curve with a relatively long deceleration period that brings about an effect such that the in-focus subject switches slowly will be described. Specifically, · Accelerate and drive to a predetermined speed within a specified period (acceleration period), · Then drive at a constant speed to the position 603 (CP0) which is 100Fδ from the in-focus position (constant-speed period), · Decelerate and drive from the position 603 and stop at the in-focus position (deceleration period) Let it be such a base curve. Note that the switching conditions for each period may be changed.

[0060] The camera control unit 212 reads out the reference drive characteristics that bring about the corresponding effect from among the reference drive characteristics stored in the memory circuit 215. Then, by scaling the reference drive characteristics according to the current defocus amount, the base curve can be calculated. Note that this method is merely an example, and the base curve may be calculated by other methods.

[0061] As described above, FIG. 6 shows the portion of the base curve 602 corresponding to the deceleration period. The slope of the base curve indicates the driving speed of the focus lens. Also, the equally spaced vertical lines indicate the control period of the focus lens.

[0062] When it is possible to drive to the target position (focus position) along the base curve while maintaining a driving speed equal to or higher than the lowest speed (minimum driving speed) achievable with the specified speed control, the focus lens may be driven while adjusting the driving speed so as to follow the base curve. However, when the base curve has a characteristic such that the change in the degree of focus (defocus amount) becomes gentle as it approaches the focus position, there is a section ( Micro driving section) where the minimum driving speed or higher cannot be maintained. Micro In the driving section, it is necessary to set a target position that is separated from the current position by the minimum driving amount and repeat driving and stopping at the minimum driving amount.

[0063] A mode in which the focus lens is driven while adjusting the driving speed without stopping at the final target position is called a speed control mode. When driving the focus lens according to the base curve, Micro it can be driven in the speed control mode outside the driving section. On the other hand, a mode in which the focus lens is driven to the final target position while repeating driving and stopping at the minimum driving amount is called a position control mode. When driving the focus lens according to the base curve, Micro the driving section needs to be driven in the position control mode.

[0064] In the example of the deceleration period shown in FIG. 6, driving is continued at the minimum driving amount while reducing the driving speed from position 603 (CP0), and it is assumed that the minimum driving speed is reached at time T0. That is, the driving is by the speed control mode until time T 0 On the other hand, after time T0, Micro since it becomes the driving section, the driving shifts to the position control mode. At time T1, the focus lens reaches position 604 which is the boundary of the in-focus range, and further reaches the focus position at time T2 and stops driving. In this example, the focus lens is driven until it reaches the focus position, but the driving may be stopped at any timing after time T1 when it enters the in-focus range.

[0065] When calculating the base curve in S503, the camera control unit 212 stores the data of the base curve in, for example, the memory circuit 215 or the SDRAM 209, and ends the base curve calculation process.

[0066] Returning to FIG. 4, in S405, the camera control unit 212 performs a drive mode determination process for the focus lens. The drive mode is an operation mode related to the drive speed, target position, and drive timing of the focus lens. The camera control unit 212 determines which drive mode to drive the focus lens in among a plurality of drive modes.

[0067] In S406, the camera control unit 212 calculates control characteristics for actually controlling the drive of the focus lens according to the drive mode determined in S405 based on the base curve, and determines the drive speed, target position, and drive timing. Details of the processes in S405 and S406 will be described later.

[0068] In S407, the camera control unit 212 performs a drive control process. Details of the drive control process in S407 will be described using the flowchart shown in FIG. 7. In S702, the camera control unit 212 determines whether or not the defocus amount (absolute value) of the main subject obtained in S403 is less than or equal to a predetermined value. If the camera control unit 212 determines that the defocus amount is less than or equal to the predetermined value, it executes S704; otherwise, it executes S703. Here, the predetermined value may be, for example, a defocus amount corresponding to Fδ.

[0069] In S704, the camera control unit 212 turns on (sets to 1) the in-focus flag stored in, for example, the SDRAM 209, and ends the drive control process. This is because there is no need to drive the focus lens if the main subject is in focus.

[0070] In S703, the camera control unit 212 changes the in-focus flag to OFF (0) and executes S705. In S705, the camera control unit 212 determines, for example, whether the lens control flag stored in the SDRAM 209 is ON (1). If the camera control unit 212 determines that the lens control flag is ON, it executes S706; if not, it ends the drive control process. If the lens control Your flag is not ON, i.e., OFF, the focus lens is not controlled.

[0071] In S706, the camera control unit 212 transmits a lens drive command including the drive speed and target position determined by S406 to the lens control unit 106 and ends the drive control process. The lens control unit 106 that has received the lens drive command controls the focus lens drive unit 105 according to the drive speed and target position included in the command and drives the focus lens 103. Thereby, the AF process shown in FIG. 4 ends. The AF processes S401 to S408 are repeatedly executed for each control cycle.

[0072] Next, the details of the drive mode determination process in S405 will be described using the flowchart shown in FIG. 8. In S802, the camera control unit 212 determines whether the reliability of the defocus amount of the main subject is equal to or greater than a predetermined value. This determination may be a comparison between the reliability obtained from the AF signal processing unit 204 as the reliability of the image shift amount used for calculating the defocus amount and the predetermined value, similar to S502. The magnitude of the predetermined value may be the same as or different from that in S502. If the camera control unit 212 determines that the reliability of the defocus amount is equal to or greater than the predetermined value, it executes S804; if not, it executes S803.

[0073] In S803, the camera control unit 212 determines drive mode A in order to drive the focus lens to a position where a defocus amount with high reliability can be obtained and executes S814. In S814, the camera control unit 212 sets the lens control flag to ON and ends the drive mode determination process.

[0074] In S804, after the camera control unit 212 acquires the base curve calculated in S404 from the memory circuit 215 or the SDRAM 209, it executes S805.

[0075] In S805, the camera control unit 212 determines whether the minimum driving amount of the focus lens is equal to or greater than a predetermined value (for example, the number of pulses corresponding to 0.5Fδ). F may be, for example, the currently set aperture value, and δ may be, for example, the pixel pitch of the imaging device 201. The minimum driving amount here may be either DS0 or DS1 (for example, the larger one) described above.

[0076] If it is determined that the minimum driving amount is less than the predetermined value, the camera control unit 212 executes S806. It is considered that the lens unit 10 with a minimum driving amount less than the predetermined value is suitable for fine driving in the position control mode. Therefore, in S806, the camera control unit 212 determines the driving mode B suitable for the lens unit suitable for fine driving. In S814, the camera control unit 212 sets the lens control flag to ON and ends the driving mode determination process.

[0077] On the other hand, if it is determined in S805 that the minimum driving amount is equal to or greater than the predetermined value, the camera control unit 212 executes S807. It is considered that the lens unit 10 with a minimum driving amount equal to or greater than the predetermined value is not suitable for fine driving in the position control mode. Therefore, the camera control unit 212 executes the subsequent S807 and determines a driving mode suitable for the lens unit 10 not suitable for fine driving.

[0078] In S807, the camera control unit 212 calculates the ideal in-focus time when driving the focus lens using the base curve acquired in S804. Here, the ideal in-focus time is the time from when the position control mode is started until the focus lens reaches the in-focus position when the focus lens can be driven according to the base curve. In the example of FIG. 6, it corresponds to the length from time T0 to time T2 (the difference between time T2 and time T0).

[0079] Regarding the processing in S808 to S811, it will be described with reference to FIG. 13. FIG. 13 shows the deceleration period of the base curve 1301, similar to FIG. 6. Note that it should be noted that the times T0 to T4 in FIG. 13 do not correspond to those in FIG. 6.

[0080] In S808, the camera control unit 212 determines the maximum time difference allowed with respect to the ideal focusing time. Here, the maximum time difference is the difference between the shortest focusing time when focusing occurs at the ideal focusing time and the visual effect until focusing occurs, where no noticeable difference is felt, and the ideal focusing time. For example, it can be determined experimentally based on the ideal focusing time.

[0081] For example, in the example shown in FIG. 13, the ideal focusing time corresponds to the length (T4 - T1) from time T1 to time T4. In contrast, the maximum time difference can be obtained as a predetermined ratio of (T4 - T1). In FIG. 13, the maximum time difference 1302 is (T4 - T3). Here, in order to avoid the time until focusing being later than the ideal focusing time, the longest focusing time when no noticeable difference is felt in the visual effect until focusing occurs when focusing occurs at the ideal focusing time is not considered.

[0082] Next, in S809, the camera control unit 212 calculates the time from time T1 until the focusing position is reached when the focus lens 103 is driven at the lowest speed with the focusing position as the target while remaining in the speed limit mode even after time T1 when it should switch to the position control mode. This corresponds to the length (T2 - T1) from time T1 to time T2 in FIG. 13.

[0083] In S810, the camera control unit 212 determines whether the focus time T2 when the focus lens is driven at the minimum speed in the speed control mode even after the time T1 when the mode should be switched to the position control mode is within the allowable range with respect to the focus time by ideal control. Specifically, if the sum of the time (T2 - T1) obtained in S809 and the maximum time difference (T4 - T3) obtained in S808 is equal to or greater than the ideal focus time (T4 - T1), it can be determined that it is within the allowable range. Note that it may be determined that it is within the allowable range when the difference between the time obtained in S809 and the ideal focus time is equal to or less than the maximum time difference obtained in S808.

[0084] When it is determined that the difference between the focus time when the camera control unit 212 drives to the focus position in the speed control mode and the focus time in the case of ideal driving according to the base curve is within the allowable range, S811 is executed; when it is not determined, S812 is executed.

[0085] In S811, the camera control unit 212 determines the drive mode C. In S814, the camera control unit 212 sets the lens control flag to ON and ends the drive mode determination process.

[0086] The process in S812 will be described with reference to FIG. 15. In S812, the camera control unit 212 determines whether the focus time when the focus lens is driven while maintaining the minimum speed from the start of the deceleration period is within the allowable range with respect to the focus time by ideal control. The maximum time difference 1504 defining the allowable range uses the value determined in S808, similar to S810. However, for the sake of explanation here, it is shorter than the maximum time difference 1302 shown in FIG. 13.

[0087] FIG. 15 shows the deceleration period of the base curve 1501. Time T0 is the start time of the deceleration period. After time T1 when it is necessary to switch to the position control mode, the speed control mode is maintained, and an example is shown in which the focusing time T2 when driving is continued at the minimum driving speed is not included in the allowable range (times T3 to T5) with respect to the focusing time T5 by ideal control. In such a case, in S812, the camera control unit 212 examines whether the focusing time becomes a time within the allowable range (or whether the difference in the focusing time falls within the allowable range) by changing the start timing of driving at the minimum driving speed to time T0.

[0088] 1503 shows the lens locus when driving is started at the minimum driving speed from the start time T0 of the deceleration period of the base curve 1501. In this case, the focus lens reaches the in-focus position at time T5. Time T5 is included in the allowable range (from time T3 to time T6) of the in-focus time T6 by ideal control according to the base curve.

[0089] Thus, if the in-focus time within the allowable range can be realized by starting driving at the minimum driving speed from the start time T0 of the deceleration period of the base curve 1501, it is considered that characteristics similar to those of the base curve 1501 can be realized while maintaining the speed control mode. If it is determined that the camera control unit 212 can set the focusing time to a time within the allowable range by changing the start timing of driving at the minimum driving speed to time T0, S813 is executed. In S813, the camera control unit 212 determines the drive mode D. In S814, the camera control unit 212 sets the lens control flag to ON and ends the drive mode determination process.

[0090] On the other hand, if the in-focus time within the allowable range cannot be realized even by starting driving at the minimum driving speed from the start time T0 of the deceleration period of the base curve 1501, it is considered that characteristics similar to those of the base curve 1501 cannot be realized while maintaining the speed control mode. If it is not determined that the camera control unit 212 can set the focusing time to a time within the allowable range by changing the start timing of driving at the minimum driving speed to time T0, S815 is executed. In S815, the camera control unit 212 determines the drive mode E and ends the drive mode determination process.

[0091] Next, the details of the focus tracking calculation process in S406 will be described using the flowchart shown in FIG. 9. In S902, the camera control unit 212 acquires a base curve in the same manner as in S804. If the base curve acquired in S804 remains, it may be reused.

[0092] In S903, the camera control unit 212 acquires the minimum drive amount DS and the minimum drive speed from the lens information acquired in the startup process. The minimum drive amount DS is set to either DS0 acquired from the lens unit or DS1 acquired in the lens reset operation (for example, the larger one).

[0093] In S904, the camera control unit 212 acquires the defocus amount for the main subject calculated in S403. It may also be newly calculated in S904.

[0094] In S905, the camera control unit 212 checks the drive mode determined in the drive mode determination process. If the drive mode A is determined, the camera control unit 212 executes S906; if the drive mode B is determined, it executes S907; if the drive mode C is determined, it executes S908; if the drive mode D is determined, it executes S909; if the drive mode E is determined, it executes S910.

[0095] (Drive mode A) The process in S906 will be described using the flowchart shown in FIG. 10. The drive mode A is determined when the reliability of the defocus amount of the main subject is less than a predetermined value. Therefore, in the drive mode A, an operation according to the reliability in the defocus direction is performed.

[0096] In S1002, the camera control unit 212 determines whether the reliability in the defocus direction detected for the main subject is greater than or equal to a predetermined value. The reliability in the defocus direction Degree isis notified from the AF signal processing unit 204 to the camera control unit 212 together with the reliability of the image shift amount. If it is determined that the reliability in the defocus direction is equal to or greater than a predetermined value (reliable), the camera control unit 212 executes S1003; otherwise, it executes S1004.

[0097] In S1003, the camera control unit 212 sets the end in the defocus direction among both ends of the lens drivable range as the target position and ends the process of drive mode A. When the reliability in the defocus direction is high, the focus lens is driven in the direction of increasing the reliability to search for the in-focus position.

[0098] In S1004, the camera control unit 212 sets the end with the longer distance (farther end) from the current position of the focus lens among both ends of the lens drivable range as the target position and ends the process of drive mode A. When the reliability in the defocus direction is not high, an in-focus position with high reliability is searched in a wider range.

[0099] (Drive mode B) Regarding the process in S907, it will be described using the flowchart shown in FIG. 11. Drive mode B is determined for a lens unit considered suitable for fine driving. Therefore, in drive mode B, the focus lens is driven so as to realize the driving characteristics shown in the base curve.

[0100] In S1102, the camera control unit 212 sets the driving speed and target position according to the base curve and completes the drive mode B process.

[0101] (Drive mode C) Regarding the process in S908, it will be described using the flowchart shown in FIG. 12. Drive mode C is determined for a lens unit considered not suitable for fine driving. Therefore, in drive mode C, while giving priority to the driving characteristics of the base curve, the focus lens is continuously driven only in the speed control mode (while maintaining a speed equal to or higher than the minimum driving speed).

[0102] In S1202, the camera control unit 212 sets the driving speed and target position according to the base curve. In S1203, the camera control unit 212 determines whether the driving speed set in S1202 is less than the minimum driving speed. If it is determined that the speed is less than the minimum driving speed, S1204 is executed; otherwise, the driving mode C process ends.

[0103] In S1204, the camera control unit 212 changes the driving speed to the minimum driving speed. The target position remains unchanged at the in-focus position. As a result, the speed control mode is maintained even after time T1 in FIG. 13, and the focus lens is driven as shown by the solid line. Then, the camera control unit 212 ends the process of driving mode C.

[0104] (Driving mode D) Regarding the process in S909, it will be described using the flowchart shown in FIG. 14. The driving mode D is determined when, for a lens unit considered not suitable for fine driving, the difference from the ideal in-focus time in driving mode C does not fall within the allowable range (exceeds the allowable range). Therefore, in driving mode D, by changing the driving characteristics during the deceleration period of the base curve, the focus lens is driven only in the speed control mode (while maintaining a speed equal to or higher than the minimum driving speed).

[0105] In S1402, the camera control unit 212 sets the target in-focus time. The driving mode D is determined when, in S812, it is determined that an in-focus time within the allowable range with respect to the ideal in-focus time can be achieved when the focus lens is driven at the minimum driving speed from the start point of the deceleration period.

[0106] In the example of FIG. 15, when the focus lens is driven at the minimum driving speed from time T0, the in-focus time T5 when focusing occurs exists within the allowable range (times T3 to T6) with respect to the ideal in-focus time T6. When the driving characteristic (lens locus) 1503 that linearly drives at the minimum driving speed from time T0 is changed to a driving characteristic similar to the base curve 1501, the in-focus time becomes earlier than time T5. Therefore, the camera control unit 212 can set the target in-focus time within the range of times T3 to T5. Here, as an example, it is assumed that time T4 is set as the target in-focus time.

[0107] S 140 In step S3, the camera control unit 212 changes the driving characteristic during the deceleration period of the base curve. For example, the camera control unit 212 determines a certain time (referred to as Tx) from the start time T0 of the deceleration period to the target in-focus time T4 as the start time of the constant-speed driving at the minimum driving speed. Then, the camera control unit 212 sets a driving characteristic in which the section from time T0 to Tx is a deceleration driving section to the minimum driving speed, and the section from time Tx to T4 is a constant-speed driving section at the minimum driving speed. 1502 in FIG. 15 shows an example of the changed driving characteristic.

[0108] Note that only the deceleration period of the base curve is changed for the driving characteristic, and the base curve is maintained for the previous acceleration period and constant-speed period. Also, time Tx may be set to time T0, and in this case, the driving speed becomes higher than the minimum driving speed. Furthermore, the target in-focus time may be set to T5, and constant-speed driving may be performed at the minimum driving speed from time T0 (the driving characteristic of 1503).

[0109] In step S1404, the camera control unit 212 sets the driving speed and the target position according to the changed driving characteristic, and ends the driving mode D process.

[0110] (Driving mode E) Regarding the processing in S910, it will be described using the flowchart shown in FIG. 16. The drive mode E is determined for a lens unit that is considered not suitable for fine driving, when the difference from the ideal focusing time exceeds the allowable range in drive modes C and D. Therefore, in drive mode E, by controlling the interval at which the lens drive command is sent, driving at a speed lower than the minimum drive speed in the speed control mode is pseudo-realized.

[0111] In S1602, the camera control unit 212 acquires lens information. Note that the lens information may be reused as that acquired during the startup process, or may be acquired anew. The minimum drive amount DS is set to one of DS0 and DS1 (for example, the larger one). Here, it is assumed that the minimum drive speed of the focus lens is 10 mm / second, which is the image plane speed (the moving speed of the imaging plane). Also, the control period is set to 1 / 60 second, synchronized with the frame rate of the video.

[0112] Note that the camera control unit 212 converts the value of the drive pulse unit of the focus lens into the value of the depth of focus Fδ unit for the minimum drive amount DS. Specifically, the physical drive amount represented by the number of pulses is converted into the image plane movement amount using the sensitivity of the lens's image plane, and the value denoted as DSFδ is calculated by dividing by the current aperture value (assumed to be F2) and the allowable confusion circle diameter. DSFδ is an index of the minimum drive amount required to move the focus lens.

[0113] In S1603, the camera control unit 212 acquires the base curve. The base curve acquired in other processes may be reused. In S1604, the camera control unit 212 sets the drive speed and target position according to the base curve.

[0114] In S1605, the camera control unit 212 determines whether the drive speed set in S1604 is lower than the minimum drive speed. If it is determined to be lower than the minimum drive speed, S1606 is executed; otherwise, S1617 is executed.

[0115] In S1617, the camera control unit 212 sets the lens control flag to ON and executes S1618. In S1618, the camera control unit 212 sets, for example, the standby count (details will be described later), which is a variable stored in the SDRAM 209, to 0 and ends the drive mode E process.

[0116] In S1606 to S1609, the camera control unit 212 Micro calculates the drive characteristics in the drive interval. Micro In the drive interval, a drive speed lower than the minimum drive speed is required in the speed control mode, and conventionally, it is the interval where driving is performed in the position control mode.

[0117] The in-focus trajectory calculation process in the minute drive interval will be described with reference to FIG. 17. FIG. 17 is a diagram for explaining the processing of S1606 to S1609 with respect to the base curve shown in FIG. 6. In FIG. 17(A), CP2 indicates the defocus amount corresponding to the depth of focus Fδ. Also, it is assumed that the minimum drive amount DS is 0.7Fδ. The dotted line 1702 indicates the defocus amount corresponding to 0.7Fδ. FIG. 17(B) shows the lens drive mode, and FIG. 17(C) shows the drive speed for each control cycle. Up to time T0, the focus lens is driven while decelerating in the speed control mode, and from time T0, the focus lens is driven in the position control mode at the minimum drive speed.

[0118] In S1606, the camera control unit 212 calculates the lens position PL immediately before reaching the in-focus state. The position PL is the lens position at the time of sending the last drive command. Here, the lens position corresponding to the defocus amount (0.8Fδ) obtained by adding an offset amount of 0.1Fδ to the minimum drive amount DS is set as the last lens position PL. Therefore, the camera control unit 212 calculates the point where the defocus amount becomes 0.8Fδ at the timing of the control cycle on or near the base curve. The position PL calculated in 1703 is shown.

[0119] In S1607, the camera control unit 212 sets the drive characteristic 1701 passing through the position PL based on the base curve.

[0120] At S1608, the camera control unit 212 calculates the movement amount for each control period. The lens control timing shown in FIG. 17(D) corresponds to the vertical lines described in FIG. 17(A). The control timing corresponds to the start timing of the control period, and the camera control unit 212 normally periodically transmits a drive command to the lens control unit 106 according to the control timing. The difference in the vertical axis coordinates of the intersections of two adjacent vertical lines and the control characteristic 1701 indicates the movement amount of the focus lens in the control period defined by the two vertical lines.

[0121] At S1609 to S1616, a process of correcting the control timing is performed by excluding the control timing of the control period in which the movement amount of the focus lens is smaller than the minimum drive amount DS. In the control characteristic 1701, the control timing immediately before the control timing corresponding to the position 1703 is the position 1708. However, since the movement amount between the positions 1708 and 1703 is less than the minimum drive amount DS, the control timing corresponding to the position 1708 is excluded. Furthermore, since the movement amount between the positions 1709 and 1703 one cycle earlier is still less than the minimum drive amount DS, the control timing corresponding to the position 1709 is also excluded.

[0122] Since the movement amount between the positions 1704 and 1703 one cycle earlier exceeds the minimum drive amount DS, the control timing corresponding to the position 1704 is maintained. Similarly, the control timings corresponding to the positions 1706 and 1707 are maintained, but the control timings between the positions 1704 and 1705 and between the positions 1705 and 1706 are excluded.

[0123] The corrected control timing is shown in FIG. 17(E). In this way, by thinning out the control timing of the control period in which the drive amount is less than the minimum drive amount DS, it is possible to specify a drive amount of not less than the minimum drive amount DS at each control timing. The camera control unit 212 does not transmit a lens drive command to the lens control unit 106 in the control period in which the control timing is thinned out.

[0124] The processing of each step will be described below. In S1609, the camera control unit 212 determines whether the standby count is greater than 0. If it is determined to be greater than 0, S1611 is executed; otherwise, S1610 is executed. If the standby count is greater than 0, it indicates that the control timing of the processing target is thinned out. Therefore, the camera control unit 212 stops driving the focus lens.

[0125] In S1611, the camera control unit 212 decrements the standby count by 1. In S1612, the camera control unit 212 sets the lens control flag to OFF and ends the drive mode E processing.

[0126] On the other hand, if the standby count is not greater than 0 (i.e., 0), it indicates that the control timing of the processing target is not thinned out. Therefore, the camera control unit 212 performs the drive processing of the focus lens. In S1610, the camera control unit 212 changes the lens control flag to ON and executes S1613. In S1613, the camera control unit 212 determines whether the movement amount acquired in S1608 is less than the minimum drive amount. If it is determined to be less than the minimum drive amount, S1614 is executed; otherwise, the drive mode E processing is ended.

[0127] When the movement amount is less than the minimum drive amount, it is necessary to wait until the control timing at which the focus lens can be driven is reached, and the movement amount specified at the control timing of the processing target is less than the minimum drive amount. Therefore, in S1614, the camera control unit 212 sequentially adds the movement amount of the subsequent control cycles to the movement amount acquired in S1608, and detects the nearest control timing at which the total becomes equal to or greater than the minimum drive amount.

[0128] In S1615, the camera control unit 212 sets the drive speed and the target position to be specified at the control timing detected in S1614. The target position is a position separated from the current position by the movement amount added in S1614. The drive speed may be the minimum drive speed.

[0129] In S1616, the camera control unit 212 sets the number of control periods to wait until the control timing detected in S1614 in the wait count, and completes the drive mode E process.

[0130] By setting the target position and the driving speed as described above, it is possible to realize a drive in which the driving amount per control cycle is made less than the minimum driving amount by driving at the minimum driving speed.

[0131] According to the present embodiment, in order to realize a predetermined ideal driving characteristic, it is necessary to drive the focus lens in the position control mode. Micro Regarding the drive section, the drive method is changed according to the focus lens drive characteristic of the lens unit. Specifically, for a lens unit determined not to be suitable for the minute drive of the focus lens, Micro Regarding the drive section, the focus lens is driven in the speed control mode instead of the position control mode.

[0132] Micro When driving in the position control mode in the drive section, it is necessary to repeat the driving and stopping of the focus lens. Therefore, driving a lens unit not suitable for minute drive in the position control mode becomes a factor delaying the focusing time. On the other hand, in the speed control mode, since the focus lens is not stopped until the focusing position is reached, it is possible to prevent the delay of the focusing time.

[0133] Micro By driving in the speed control mode in the drive section, the amount of movement of the focus lens per unit time becomes larger than when driving in the position control mode, so that focusing is achieved earlier than the ideal driving characteristic. MicroWhen the difference between the focusing time when driving in the speed control mode and the focusing time based on the ideal driving characteristics exceeds the allowable range, the ideal driving characteristics are changed so that the driving can be performed only in the speed control mode so that the difference in the focusing time falls within the allowable range. Thereby, the visual effect of the moving image can be not significantly changed and the delay of focusing can be prevented.

[0134] ●<Second Embodiment> Next, a second embodiment of the present invention will be described. Since the second embodiment is the same as the first embodiment except for the drive mode determination process (FIG. 8), the description will focus on the differences in the drive mode determination process.

[0135] FIG. 18 is a flowchart of the drive mode determination process in the present embodiment. The same reference numerals are given to the steps that perform the same processing as in the first embodiment, and the description thereof is omitted. Further, since the processing of the determined drive mode may be the same as in the first embodiment, the description thereof is omitted.

[0136] In S1801, the camera control unit 212 acquires a micro drive enable flag and a speed control enable flag. These flags may be acquired from the lens unit 10 as lens information, or the type information and the values of these flags may be associated and stored in, for example, the ROM 210, and the ROM 210 may be referred to and acquired based on the type information of the attached lens unit.

[0137] The micro drive enable flag is a flag indicating whether the lens unit is suitable for micro drive. For example, for a lens unit not suitable for micro drive, such as a type of lens unit that drives a large focus lens using a DC motor (e.g., a large cinema lens), the micro drive enable flag is set to OFF.

[0138] Also, the speed control enable flag is set to OFF for a lens unit for which, for example, driving of the focus lens in the speed control mode is not assumed (not corresponding to a drive command specifying a drive speed).

[0139] S802 to S804 are the same processes as in the first embodiment. After obtaining the base curve in S804, in S1803, the camera control unit 212 determines whether the micro drive enable flag is ON. If it is determined that the micro drive enable flag is ON, S80 5 is executed. If not, S1804 is executed. It is considered that the lens unit for which the micro drive enable flag is set to ON can perform driving according to the base curve using the position control mode.

[0140] In S1804, the camera control unit 212 determines whether the speed control enable flag is ON. If it is determined that the speed control enable flag is ON, since driving in the speed control mode is possible, the camera control unit 212 executes S807. The processing after S807 is the same as in the first embodiment.

[0141] On the other hand, if it is not determined that the speed control enable flag is ON, the drive mode C, D using the speed control mode 5 cannot be applied, so the camera control unit 212 executes S80 In S805, the camera control unit 212 determines whether the minimum drive amount DS is equal to or greater than a predetermined value (0.5Fδ or more).

[0142] If it is not determined that the minimum drive amount is equal to or greater than the predetermined value, the camera control unit 212 executes S1805. It is considered that the lens unit 10 with a minimum drive amount less than the predetermined value is suitable for micro driving in the position control mode. Therefore, in S1805, the camera control unit 212 determines the drive mode B suitable for the lens unit suitable for micro driving. In S814, the camera control unit 212 sets the lens control flag to ON and ends the drive mode determination process.

[0143] On the other hand, when it is determined in S805 that the minimum driving amount is equal to or greater than a predetermined value, the camera control unit 212 executes S1806. It is considered that the lens unit 10 with a minimum driving amount equal to or greater than the predetermined value is not suitable for fine driving in the position control mode. Therefore, the camera control unit 212 determines the driving mode E in S1806 and ends the driving mode determination process.

[0144] As described above, in the second embodiment, control with a changed mode branch is implemented. In this example, the mode branch is implemented according to the fine driving enable flag and speed control enable flag obtained from the lens, but the branch conditions for each mode may be changed as needed.

[0145] (Other Embodiments) In the above-described embodiment, a configuration for detecting the defocus amount by the image plane phase difference detection method has been described. However, the present invention is also applicable to a configuration for detecting the defocus amount using a dedicated phase difference detection sensor.

[0146] Also, in the above-described embodiment, it is determined whether the lens unit is suitable for fine driving based on the magnitude of the minimum driving amount and the fine driving enable flag. However, it may be determined whether the lens unit is suitable for fine driving based on other criteria. Examples considered below are given. · Delay time from when a drive command is sent until the focus lens starts to move (if it is longer than a predetermined time, it is not suitable for fine driving). · Delay time from when a drive command is sent until the focus lens starts to move / time from when a drive command is sent until the focus lens reaches the specified speed (if it is longer than a predetermined time, it is not suitable for fine driving). · Actual movement amount from when a drive command is sent until the focus lens reaches the specified speed / ideal movement amount from when a drive command is sent until the focus lens reaches the specified speed (if it is less than a predetermined Displacement value, it is not suitable for fine driving).

[0147] The present invention can also be realized by supplying a program that implements one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and causing one or more processors in a computer of the system or apparatus to read and execute the program. It can also be realized by a circuit (for example, an ASIC) that implements one or more functions.

Explanation of Reference Numerals

[0148] 10... lens unit, 103... focus lens, 106... lens control unit, 20... main body, 201... imaging element, 204... AF signal processing unit, 209... SDRAM, 210... ROM, 212... camera control unit, 215... memory circuit

Claims

1. A focus control device that controls the driving of a focus lens included in a lens unit during video shooting, comprising: an acquisition means for acquiring a predetermined driving pattern for driving the focus lens to a focused position; a control means for controlling the driving of the focus lens, wherein when the driving pattern has a minute driving section in which the focus lens needs to be driven at a driving speed lower than a predetermined minimum driving speed, and it is determined that the lens unit is not suitable for the minute driving of the focus lens, the control means continuously drives the focus lens at the minimum driving speed for the minute driving section. The focus control device is characterized by this.

2. The focus control device according to claim 1, wherein when the driving pattern has a minute driving section in which the focus lens needs to be driven at a driving speed lower than a predetermined minimum driving speed, and it is determined that the lens unit is suitable for the minute driving of the focus lens, the control means repeatedly executes the minute driving of the focus lens for the minute driving section.

3. The focus control device according to claim 1 or 2, wherein when the difference between the focusing time when the focus lens is continuously driven at the minimum driving speed for the minute driving section and the focusing time when the focus lens is driven according to the driving pattern exceeds a predetermined allowable range for the minute driving section, the control means changes the driving pattern and continuously drives the focus lens at the minimum driving speed from the time point based on the changed driving pattern so that the difference does not exceed the allowable range.

4. The focus control device according to claim 3, wherein when the difference still exceeds the allowable range even after changing the driving pattern, or when the lens unit does not respond to a driving command specifying a driving amount equal to or greater than the minimum driving amount of the focus lens in the minute driving section, the control means changes the interval at which the driving command for the focus lens is transmitted so that the focus lens can be driven using a driving command specifying a driving amount equal to or greater than the minimum driving amount of the focus lens in the minute driving section.

5. The control means changes the interval by not transmitting a drive command for the focus lens at a control timing in which the movement amount of the focus lens until the next control timing among predetermined periodic control timings is less than the minimum drive amount of the focus lens. The focus control device according to claim 4, characterized in that.

6. The control means determines whether the lens unit is suitable for fine driving based on the minimum drive amount of the focus lens. The focus control device according to any one of claims 1 to 5, characterized in that.

7. The focus control device according to claim 6, characterized in that the minimum drive amount is the minimum drive amount acquired from the lens unit.

8. The focus control device according to claim 6, characterized in that the minimum drive amount is the minimum drive amount acquired in the reset operation of the lens unit.

9. The control means determines whether the lens unit is suitable for fine driving based on the information acquired from the lens unit. The focus control device according to any one of claims 1 to 5, characterized in that.

10. The focus control device according to claim 9, characterized in that the information is information indicating whether it is suitable for fine driving, which is set in advance in association with the lens unit.

11. Calculating means for calculating the defocus amount of the mounted lens unit; The focus control device according to any one of claims 1 to 10, which drives a focus lens included in the lens unit based on the defocus amount; An imaging device, characterized by comprising.

12. A focus control method executed by a focus control device for controlling driving of a focus lens included in a lens unit during video shooting, comprising: An acquisition step of acquiring a predetermined drive pattern for driving the focus lens to a focused position; A control step of controlling driving of the focus lens, and in the control step, when the drive pattern has a fine drive section in which the focus lens needs to be driven at a drive speed less than a predetermined minimum drive speed, and the lens unit is determined not to be suitable for fine driving of the focus lens, the focus lens is continuously driven at the minimum drive speed for the fine drive section. A focus control method, characterized in that.

13. ​ A program for causing a computer to function as each means included in the focus control device according to any one of claims 1 to 10.

Images