JP2011128422A - Imaging apparatus, lens device, and method for detecting focus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus, lens device, and method for detecting focus, which shortens a focus detecting time and improves focus detection accuracy. <P>SOLUTION: The imaging apparatus 200 allows the lens device 100 with a focus lens 101 to be attached to or detached from the imaging apparatus 200, and detects, as a focusing position, the peak position of a contrast value obtained by an imaging element 212 while continuously moving the focus lens in the direction of an optical axis. The imaging apparatus 200 has a system controller 230, which is configured as follows: among times of a natural number times of the imaging period of the imaging element, the shortest time, equal to or longer than a shorter time in the shortest time of a time interval for obtaining positional information of the focus lens and the time for which the focus lens is moved in the direction of the optical axis only by a set distance at the highest driving speed, is set as a time interval for evaluating a contrast value, and the driving speed of the focus lens is corrected so that the focus lens moves only by the set distance in the direction of the optical axis at the time interval. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an imaging device, a lens device, and a focus detection method.

  Patent Document 1 proposes contrast-type focus detection (contrast AF) that acquires a contrast value while continuously moving a focus lens. In order to shorten the AF time by the AF method of Patent Document 1, it is necessary to increase the frame rate, the focus lens, and the interval for acquiring the focus lens position information. Other conventional techniques include Patent Documents 2 to 4.

JP 2002-72073 A JP-A-6-141223 JP 2008-286880 A JP 2009-65320 A

  Some conventional interchangeable lenses, such as interchangeable lenses (lens devices) developed for the purpose of mounting on silver halide film single-lens reflex cameras, include high-speed communication between the camera body and interchangeable lenses, and focus lens positions. Some of them do not have a function to acquire frequently. In a digital single-lens reflex camera equipped with such an interchangeable lens, the position information of the focus lens is lost or the acquisition delay occurs, and the focus detection accuracy may be lowered.

  An object of the present invention is to provide an imaging device, a lens device, and a focus detection method capable of shortening a focus detection time and improving focus detection accuracy.

  An imaging apparatus according to one aspect of the present invention can be attached and detached with a lens device having a focus lens, and a peak position of a contrast value obtained from an image sensor while continuously moving the focus lens in the optical axis direction is an in-focus position. Detect as. Such an image pickup apparatus has a shortest time interval for acquiring the position information of the focus lens and a focus lens at a set distance at the fastest driving speed in the optical axis direction out of the natural number times the imaging cycle of the image sensor. The shortest time that is equal to or greater than the smaller time to move to is set as a time interval for evaluating the contrast value, and the focus lens is moved by the set distance in the optical axis direction during the time interval. You may have a processor which correct | amends the driving speed of a lens. Alternatively, such an imaging apparatus has a time period that is equal to or longer than the shortest time interval for acquiring the position information of the focus lens in a time that is a natural number times the imaging cycle of the image sensor, and the natural image capture cycle of the image sensor. When the condition that the product of several times the driving speed of the focus lens is equal to or less than the set interval is satisfied, the driving speed that satisfies the minimum natural number that satisfies the condition is set as the driving speed of the focus lens, You may have a processor which sets the said minimum natural number as a time interval which evaluates a contrast value. Furthermore, the imaging apparatus may include a processor that acquires the contrast value by moving the focus lens again in a region where the maximum contrast value is detected in a region where position information of the focus lens cannot be acquired. .

  According to the present invention, it is possible to provide an imaging device, a lens device, and a focus detection method that can shorten the focus detection time and increase the focus detection accuracy.

It is a block diagram which shows the structure of the digital camera common to Examples 1-3. It is a block diagram of contrast DSP shown in FIG. 3 is a flowchart showing the operation of the first embodiment. 4 is a flowchart showing details of an operation in S304 shown in FIG. 3. 10 is a flowchart showing the operation of the second embodiment. 10 is a flowchart illustrating the operation of the third embodiment.

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

  FIG. 1 is a block diagram illustrating a configuration of a digital camera common to the first to third embodiments. As shown in FIG. 1, a lens device (interchangeable lens) 100 is detachably attached to the digital camera 200 via a mount unit (not shown) having an electrical contact unit 107.

  The digital camera 200 itself is an imaging device, but the digital camera 200 to which the lens device 100 is attached also functions as an imaging device as a whole. That is, the lens device 100 constitutes a part of the imaging device.

  The digital camera 200 communicates with the lens device 100 via the electrical contact unit 107 to control driving of the focus lens 101 and the diaphragm 102 of the lens device 100.

  The lens apparatus 100 includes a lens unit including a focus lens 101, a diaphragm 102 that adjusts the amount of light, and a drive system and a control system thereof. The drive system includes a lens drive mechanism 103 that drives the focus lens 101 and an aperture drive mechanism 105 that drives the aperture 102. The control system includes a lens controller 108, a memory 109, a lens drive control circuit 104, an aperture control drive circuit 106, and a lens position information detection circuit 110. In FIG. 1, other lenses such as a variable power lens and a fixed lens other than the focus lens 101 of the lens apparatus 100 are omitted.

  The digital camera 200 includes a quick return mirror 203, a finder optical system, an image sensor 212, a control system including a system controller 230, a signal processing system including a camera DSP (digital signal processor) 227, and other members.

  The light flux from the subject is guided to the quick return mirror 203 of the digital camera 200 via the lens device 100. The quick return mirror 203 is disposed obliquely with respect to the optical axis in the photographing optical path, and has a first position (the illustrated position) for guiding the light beam from the subject to the finder optical system, and a second position for retracting outside the photographing optical path. , Can be moved between.

  The light beam reflected by the quick return mirror 203 reaches the eyes of the photographer via a finder optical system including a finder screen 202, a pentaprism 201, and an eyepiece lens 207 existing on the focus surface.

  When the quick return mirror 203 is raised to the second position, the light beam from the lens apparatus 100 reaches the image sensor 212 via the focal plane shutter 210 and the optical filter 211 that are mechanical shutters.

  The system controller 230 includes a processor such as a CPU or MPU, and controls the operation of each unit of the digital camera 200. The system controller 230 communicates with the lens controller 108 of the lens apparatus 100 via the electrical contact unit 107. Similarly, the lens controller 108 includes a processor such as a CPU or MPU, and controls the operation of each unit of the lens apparatus 100.

  The system controller 230 transmits to the lens controller 108 a drive command for the focus lens 101, a stop command, a drive amount, a required drive speed, a drive amount for the aperture 102, and a transmission request for various data on the lens side. The lens controller 108 transmits to the system controller 230 status information indicating whether the focus lens 101 and the aperture 102 are being driven, and various parameters on the lens side such as an open F value and a focal length.

  In AF, the system controller 230 instructs the lens controller 108 about a lens driving direction, a driving amount, and a driving speed. When the lens controller 108 receives a lens driving command from the system controller 230, the lens controller 108 controls the lens driving mechanism 103 that performs focus control by driving the focus lens 101 in the optical axis direction via the lens driving control circuit 104. Thereby, a subject image is formed on the image sensor 212. The lens driving mechanism 103 has a stepping motor or a DC motor as a driving source.

  When the lens controller 108 receives an aperture drive command from the system controller 230, the lens controller 108 controls the aperture drive mechanism 105 that drives the aperture 102 via the aperture control drive circuit 106, and drives the aperture 102 to the commanded value.

  The system controller 230 is also connected to the shutter control circuit 215 and the photometry circuit 209. The shutter control circuit 215 controls driving of the front and rear curtains of the focal plane shutter 210 in accordance with a signal from the system controller 230.

  The camera DSP (digital signal processor) 227 includes a circuit block that calculates a contrast value for contrast AF and a circuit block that determines the position and size of a region where the contrast value is calculated.

  The camera DSP 227 is connected to an A / D converter 217 via a timing generator 219 and a selector 222. The camera DSP 227 is also connected to the work memory 226.

  The image sensor 212 is driven by an output from a driver circuit 218 that controls horizontal driving and vertical driving for each pixel based on a signal from a timing generator 219 that determines the overall driving timing. Thereby, the subject image is photoelectrically converted to generate and output an image.

  When the imaging cycle (imaging frame rate) of the image sensor 212 is set by the input of the operation SW (switch) 232, the signal output from the timing generator 219 is changed according to the imaging cycle. As described above, the operation SW 232 functions as a setting unit that sets the imaging cycle of the imaging element 212.

  The output from the A / D converter 217 is input to the memory controller 228 via the selector 222 that selects a signal based on the signal from the system controller 230 and is transferred to the DRAM 229 which is a frame memory.

  In a video or a compact digital camera, a finder display (live view display) is performed by the monitor display unit 220 by periodically transferring the transfer result to the video memory 221 (for each frame) before shooting. In a single-lens reflex digital camera, live view display cannot be performed because the image sensor 212 is shielded from light by the quick return mirror 203 and the focal plane shutter 210 before photographing.

  When the quick return mirror 203 is raised and retracted from the photographing optical path and then the focal plane shutter 210 is opened, live view becomes possible. In addition, when the camera DSP 227 or the system controller 230 processes the image signal from the image sensor 212 during live view, a contrast value corresponding to the sharpness of the image can be obtained and contrast AF can be performed.

  At the time of shooting, each pixel data for one frame is read from the DRAM 229 according to a control signal from the system controller 230, subjected to image processing by the camera DSP 227, and temporarily stored in the work memory 226. Then, the data in the work memory 226 is compressed by the compression / decompression circuit 225 based on a predetermined compression format, and the result is stored in the nonvolatile memory 224.

  A display circuit 231 connected to the system controller 230 displays a state set or selected by the following switches. The operation SW 232 is an operation unit that performs operation input for various setting items of the digital camera 200. The release switch SW1 (233) is a switch for starting a shooting preparation operation such as photometry and focus detection. The release switch SW2 (234) is a switch for starting a photographing operation (charge accumulation and charge read operation for acquiring a still image). The live view mode SW is a switch for controlling on / off of the live view.

  The lens controller 108 is connected to the memory 109. The memory 109 stores performance information such as the focal length and open aperture value of the lens apparatus 100, identification information (ID information) of the lens apparatus 100, an acquisition interval of position information of the focus lens 101, information received from the system controller 230, and the like. To do.

  The performance information and identification information are transmitted to the system controller 230 by initial communication when the lens apparatus 100 is attached to the digital camera 200, and the system controller 230 stores them in the EEPROM 223.

  The lens position information detection circuit 110 detects position information (in the optical axis direction) of the focus lens 101. The lens position information is read by the lens controller 108 and used for driving control of the focus lens 101 and is transmitted to the system controller 230 via the electrical contact unit 107.

  The lens position information detection circuit 110 is configured by, for example, a pulse encoder that detects the number of rotation pulses of a motor that constitutes the lens driving mechanism. The output is connected to a hardware counter (not shown) of the lens controller 108, and when the focus lens 101 is driven, its position information is counted in hardware. When the lens controller 108 reads the lens position information, it accesses the internal hardware counter register and reads the stored counter value.

  FIG. 2 is a block diagram of the camera DSP 227. The camera DSP 227 includes a DSP internal memory 241, a focus detection area extraction block 242 and a contrast value calculation block 243.

  The image signal generated by the image sensor 212 is amplified by the CDS / AGC circuit 216 and converted into a digital signal by the A / D converter 217. The digitized image data is input to the camera DSP 227 via the selector 222.

  In order to calculate a contrast value used for contrast AF, the image data input to the camera DSP 227 is input to the focus detection area extraction block 242 via the DSP internal memory 241. The focus detection area extraction block 242 is a block for trimming an image of the focus detection area and its vicinity from the image data of the entire screen and sending it to the contrast value calculation block 243. The size of the focus detection area is, for example, about 1/5 to 1/10 with respect to the outer frame of the screen. The position and size of the focus detection area in the screen are set for the focus detection area extraction block 242 by the system controller 230.

  FIG. 3 is a flowchart for explaining the operation of this embodiment. In FIG. 3 and subsequent figures, “S” stands for a step. The release switch SW1 (233) or the operation SW232 is pressed to instruct the start of AF. It is assumed that the digital camera 200 is turned on in advance and live view display is performed. The same applies to FIGS. 5 and 6 described later.

  First, the system controller 230 determines whether or not the lens apparatus 100 is a lens corresponding to the shortening of the AF time in contrast AF in which a contrast value is acquired while continuously moving the focus lens 101 (S301).

  As described above, in order to shorten the AF time by the AF method of Patent Document 1, it is necessary to speed up the frame rate, speed up the focus lens 101, and shorten the acquisition interval of the position information of the focus lens 101. It becomes. Therefore, in S301, the system controller 230 determines whether the lens position information acquisition interval of the lens apparatus 100 and lens driving speed information can be acquired.

  The “lens position information acquisition interval” is a period (time interval) required for the lens position information detection circuit 110 to acquire the position information of the focus lens 101 once and again, and is stored in the memory 109 in advance. ing.

  If the cycle of the imaging operation (hereinafter referred to as “LV imaging cycle”) associated with the live view display set by the timing generator 219 is high and focus detection is to be performed at high speed, it is necessary to frequently acquire lens position information. . However, this may exceed the arithmetic processing capability of the lens controller 108 and the lens position information detection circuit 110. Therefore, the lens device 100 has a controllable range of the lens position information acquisition cycle based on the arithmetic processing capability of the lens device 100, particularly the arithmetic processing capability of the lens controller 108 and the lens position information detection circuit 110.

  Whether or not the lens position information acquisition interval information can be acquired is that the system controller 230 does not respond to the lens controller 108 for a predetermined time or more after sending an acquisition request to the lens controller 108 or returns a request error. Can be judged.

  The “lens driving speed” information is information regarding parameter values that can be set with respect to the driving speed of the focus lens 101, and includes parameters for the maximum and minimum lens driving speeds and parameters for all lens driving speeds. . Whether or not the lens drive speed information can be acquired depends on whether the system controller 230 sends an acquisition request to the lens controller 108 and does not respond to the lens controller 108 for a predetermined time or a request error. Can be judged.

  When the lens apparatus 100 is a lens compatible with high-speed contrast AF, the system controller 230 acquires lens position information acquisition interval information (S302) and lens driving speed information through the lens controller 108 (S303).

  Next, the system controller 230 sets a time interval for evaluating (calculating) the contrast value according to the lens position information acquisition interval information, the lens driving speed information, and the LV imaging cycle (S304).

  FIG. 4 is a flowchart for explaining details of S304.

  First, the system controller 230 calculates a time (hereinafter referred to as “unit drive time”) for moving the focus lens 101 by a set distance in the optical axis direction at the fastest drive speed (S401). The system controller 230 calculates the unit drive time from information on a focus interval that is set in advance to evaluate the contrast value and the fastest lens drive speed that can be set.

  Next, the system controller 230 compares the unit drive time with the shortest time of the lens position information acquisition interval (S402), and stores the shorter time as the constraint time (S403, S404).

  Next, the system controller 230 sets the shortest LV imaging cycle (hereinafter referred to as “shortest LV imaging cycle”) that can be set at a time greater than or equal to the constraint time as the time interval for evaluating the contrast value (S405).

  Here, when the monitor display unit 220 conforms to the NTSC system, when the drawing of each interlaced field image is regarded as a display drawing update unit, the display is displayed every 1/60 seconds (strictly, 1.001 / 60 seconds). The drawing is updated. In this case, the update period of the drawing data in the video memory 221 is also 1/60 seconds. Therefore, in order to set the LV imaging cycle to n / 60 seconds or 1 / (60 × n) seconds (where n is a natural number), the captured image data is transferred to the video memory 221 at a cycle of 1/60 seconds. Just forward. By not transferring the captured image that does not match the display timing to the video memory 221, the drawing settings of the monitor display unit 220 and the video memory 221 can be maintained even if the LV imaging cycle is changed. From the above, in this embodiment, the LV imaging cycle is set to n / 60 seconds or 1 / (60 × n) seconds (n: natural number).

  The system controller 230 evaluates the contrast value for the shortest time in the time range that is equal to or greater than the constraint time, among the times that are k times the set LV imaging cycle (here, k is a natural number and thus a natural number). The time interval is set (S405). As a result, the system controller 230 calculates (evaluates) the contrast value using one image per k captured images. Even if the LV imaging cycle is set short, the image used to evaluate the contrast value can be intermittently specified from the captured image data, so that it is not necessary to increase the lens driving speed and the lens position information It does not have to be acquired at extremely short intervals.

  Next, the system controller 230 corrects the lens driving speed so that the focus lens 101 moves by the set distance in the predetermined optical axis direction at the time interval for evaluating the contrast value (S305). Next, the system controller 230 performs contrast AF based on the time interval for evaluating the contrast value and the corrected lens driving speed (S306). That is, the system controller 230 detects the peak position of the contrast value obtained from the image sensor 212 as the in-focus position while continuously moving the focus lens 101 in the optical axis direction.

  On the other hand, when the system controller 230 determines that the lens apparatus 100 is a lens that does not support high-speed contrast AF (No in S301), the system controller 230 sets a time interval and a lens driving speed for evaluating a preset contrast value. (S307, S308). For example, it is assumed that the drawing data update period of the monitor display unit 220 and the video memory 221 is 1/60 seconds. In this case, the system controller 230 sets the time interval for evaluating the contrast value to 1/60 seconds and the lens driving speed to 60 × d (where d is an amount for driving the lens at the time interval for evaluating the contrast value). To do.

  This eliminates the need to increase the lens drive speed (thus shortening the lens position information acquisition cycle) even when the frame rate of the focus detection captured image is set high. It is suppressed, and skipping of the focus position can be suppressed. Further, since it is not necessary to perform AF again due to skipping of the focus position, it is possible to shorten the focusing time for contrast AF.

  In this embodiment, the system controller 230 requests the lens controller 108 for information on whether or not the lens apparatus 100 is a lens apparatus that supports high-speed contrast AF (S301), but the present invention is not limited to this. Not. For example, the system controller 230 stores this information in the digital camera 200 in advance for each piece of identification information of the lens apparatus 100, and uses the identification information of the lens apparatus 100 acquired by initial communication when the lens apparatus 100 is attached to the digital camera 200. You may judge based on.

  In this embodiment, the digital camera 200 acquires the position information of the focus lens 101 and performs focus detection. However, the lens apparatus 100 may acquire the contrast value from the digital camera 200 and perform focus detection. . Further, the time interval for evaluating the contrast value may be output to the lens apparatus 100, and the contrast value used for focus detection among the contrast values acquired by the lens apparatus 100 may be selected.

  In this embodiment, the operation is started when the release switch SW1 (233) is pressed and an AF start command is generated. However, a so-called continuous AF that always performs focus detection may be used. In this case, since there is a possibility that the imaging cycle of the image sensor 212 is changed by the input from the operation SW 232 during focus detection, the time interval at which the contrast value is evaluated every time the SW 232 sets the imaging cycle, the lens driving speed, The acquisition interval of the lens position information may be reset.

  In this embodiment, the time interval for evaluating the contrast is set in accordance with the lens position information acquisition interval information, the lens driving speed information, and the LV imaging cycle (S304), but the present invention is not limited to this. For example, since the depth of field changes when the aperture setting of the aperture 102 is changed, the time interval for evaluating the contrast value is changed according to the aperture setting of the aperture 102, or the lens driving speed is corrected in S305. Or you may. Thereby, when the depth of field becomes deep, it is not necessary to shorten the acquisition of the lens position information.

  In the second embodiment, the operation of the digital camera 200 is switched according to the lens position information acquisition interval under the condition that the lens position information can be acquired. FIG. 5 is a flowchart for explaining the operation of the second embodiment.

  First, the system controller 230 acquires lens position information acquisition interval information (S501) and lens driving speed information from the mounted lens apparatus 100 (S502). Next, the system controller 230 determines whether there is a lens driving speed that satisfies the following equation (S503). Here, T1 is the shortest time interval of the lens position information acquisition interval, T2 is an LV imaging cycle, k is a time interval for evaluating the contrast value, V is a settable lens driving speed, and D is a focus lens for evaluating the contrast value. 101 is the set interval.

  Formula 1 is equal to or longer than the shortest time of the acquisition interval of the lens position information among the natural number times the appearance cycle (imaging cycle) of the image frame used for evaluation of the contrast value among the captured images obtained in the LV imaging cycle. Request that. The time interval k for evaluating the contrast value is a natural number. When k = 1, all frames of the captured image captured in the live view state are used for evaluating the contrast value, and when k = 2, every other frame. used.

  Formula 2 requires that the product of the natural number multiple of the LV imaging period and the lens driving speed be equal to or less than the set interval.

  The presence of the lens driving speed V satisfying the mathematical expressions 1 and 2 means that the lens position information is obtained every time the contrast value is evaluated at least once while the focus lens 101 is continuously moved at the settable lens driving speed. Means that. Furthermore, it means that the contrast can be evaluated at a short interval that is equal to or shorter than a predetermined movement interval in the optical axis direction.

  If the system controller 230 determines that there is a lens driving speed that satisfies the mathematical expressions 1 and 2 (Yes in S503), the system controller 230 sets a contrast AF that continuously moves the focus lens 101 disclosed in Patent Document 1 (S504).

  Next, the system controller 230 sets the lens driving speed of the focus lens 101 to V satisfying the formulas 1 and 2 at the time interval for evaluating the minimum k, that is, the shortest contrast value (S505). Next, the system controller 230 sets the minimum k as a time interval for evaluating the contrast value (S506).

  Next, the system controller 230 executes contrast AF according to the setting conditions (S507).

  On the other hand, when the system controller 230 determines that there is no lens driving speed satisfying the mathematical expressions 1 and 2 (No in S503), the system controller 230 sets the contrast AF for intermittently moving the focus lens 101 disclosed in Patent Document 2 ( S508).

  Next, the system controller 230 sets the lens driving speed to the fastest settable value in order to shorten the AF time (S509). Next, the system controller 230 sets the minimum k satisfying Equation 2 as the time interval for evaluating the contrast value (S510).

  Next, the system controller 230 executes contrast AF according to the setting conditions (S507).

  As a result, lens position information is acquired at an acquisition interval that can be realized even if the frame rate of the captured image for focus detection is set high, so that acquisition delay and loss of lens position information can be suppressed, and the focus position can be skipped. Can be suppressed. In addition, since it is necessary to perform AF again due to skipping of the focus position, it is possible to shorten the focusing time of contrast AF.

  The third embodiment suppresses skipping of the focus position when a lens position information acquisition delay or loss occurs. FIG. 6 is a flowchart for explaining the operation of the third embodiment.

  First, the system controller 230 moves the focus lens 101 to the closest end of the focus movable range as preparation for performing the contrast AF described in Patent Document 1 over the entire focus area of the mounted lens apparatus 100.

  Next, the system controller 230 continuously moves the focus lens 101 to the infinite end (S602), and initially sets a value n for counting how many delays or defects have occurred in acquiring lens position information to 0. (S603). Next, the system controller 230 acquires the contrast value output from the contrast value calculation block 243 (S604).

  Next, the system controller 230 transmits a request command for requesting lens position information to the lens apparatus 100 via the electrical contact unit 107 (S605). Next, the system controller 230 determines whether lens position information has been acquired after acquiring the latest contrast value (S606).

  If the system controller 230 determines that the lens position information has not been acquired (No in S606), the system controller 230 determines whether the time interval for evaluating the contrast value has elapsed after acquiring the latest contrast value (S607). If it is determined that the time has elapsed (Yes in S607), the acquisition or delay of the lens position information has occurred, so the system controller 230 increments n (S608) and determines whether n has reached the threshold Th1. Judgment is made (S609).

  The threshold value Th1 is a threshold value that determines how many consecutive lens position information acquisition delays and defects are allowed, and is determined based on the number of contrast evaluations necessary for detecting a contrast peak when performing contrast evaluation. For example, in the case of determining a contrast peak from the maximum value of three contrast values preceding and following the lens position, if even one contrast value is missing, the evaluation value gradient cannot be obtained, and a steep evaluation value change cannot be detected. Therefore, in this case, the threshold value Th1 = 2 is set.

  When the time interval for evaluating the contrast value by the system controller 230 has not elapsed (No in S607) or when n <Th1 is determined (No in S609), the flow returns to S606.

  When the system controller 230 determines that n ≧ Th1 (Yes in S609), the system controller 230 determines whether the following equation is satisfied (S610). Here, E1 to E3 are the three most recent contrast values at which the lens position moves back and forth, and are set to E1, E2, and E3 from the oldest acquisition timing. Th2 is a simple peak detection threshold.

  Equations 3 and 4 are conditional expressions indicating that the contrast value E2 has a maximum value, and Expression 5 is a conditional expression indicating that at least one of the contrast values E1 and E2 is different from the contrast value E2 by Th2 or more. is there. When Expressions 3 to 5 are satisfied, there is a high possibility of a contrast peak where E2 represents the in-focus position.

  When the system controller 230 determines that Expressions 3 to 5 are satisfied (Yes in S610), the system controller 230 sets a lens position range including at least a period during which lens position information cannot be acquired as a rescan range (S611).

  Next, the system controller 230 moves the focus lens 101 close to the rescan range by reversing the moving direction of the focus lens 101, and continuously moves the focus lens 101 to the infinite end (S612). Thereby, the contrast peak can be detected again at the lens position where the lens position information could not be acquired.

  When determining that the lens position information has been acquired (S606) or after S612, the system controller 230 determines whether or not the in-focus position has been detected (S613). In S613, the system controller 230 determines whether or not the in-focus position has been detected based on whether or not the gradient of the contrast value obtained from the lens position information and the contrast value has become steep.

  If the system controller 230 determines that the in-focus position has been detected (Yes in S613), the system controller 230 drives the focus lens 101 to the in-focus position (S614). When the system controller 230 determines that the in-focus position has not been detected (No in S613), the system controller 230 determines whether or not the infinite end that is the end point of the search drive has been reached (S615).

  If the system controller 230 determines that the infinite end, which is the end point of the search drive, has been reached (Yes in S615), the focus position cannot be detected, and the operation is terminated as a focus detection impossible. Even after S614, the flow ends. If the system controller 230 determines that it has not reached the infinite end that is the end point of the search drive (No in S615), the flow returns to S602 to continue the contrast AF.

  In this embodiment, the focus lens is moved again in a region where the maximum (peak) of the contrast value is detected among regions where the lens position information cannot be acquired due to acquisition delay or loss, and the contrast value is acquired. Accordingly, it is possible to reduce the focus AF time by suppressing the skipping of the focus.

  In the third embodiment, search driving is performed to the infinite end, but search driving may be performed to the closest end. In the third embodiment, the rescan is performed in the infinite end direction, but may be performed in the close end direction.

  The method shown in FIGS. 3 to 6 also functions as a focus detection method, and can be realized as a program that causes the processor to perform the function of each step.

  The digital camera 200 has a connector to which a cable (not shown) (for example, a USB cable) is connected, and can be connected to a personal computer (PC) (not shown) through the USB cable. The system controller 230 may acquire some or all of the information shown in FIGS. 3 to 6 via a network such as the Internet connected to the PC with a LAN cable or the like. Alternatively, some or all of the calculations shown in FIGS. 3 to 6 may be executed by another processor connected to a network such as the Internet, and the imaging apparatus may acquire only the calculation results.

  The imaging device can be applied to imaging a subject.

DESCRIPTION OF SYMBOLS 100 Lens apparatus 101 Focus lens 108 Lens controller (processor)
212 Image sensor 200 Digital camera (imaging device)
230 System controller (processor)
232 Operation SW

Claims (11)

A lens apparatus having a focus lens is detachable, and is an imaging apparatus that detects a peak position of a contrast value obtained from an imaging element as an in-focus position while continuously moving the focus lens in the optical axis direction,
Of the time that is a natural number multiple of the imaging cycle of the image sensor, the shortest time interval for acquiring the position information of the focus lens and the time for moving the focus lens in the optical axis direction by the set distance at the fastest drive speed The shortest time over the smaller time is set as the time interval for evaluating the contrast value, and the driving speed of the focus lens is set so that the focus lens moves by the set distance in the optical axis direction during the time interval. An image pickup apparatus comprising a processor for correction.   The processor determines whether it is possible to acquire information on the time interval for acquiring the position information of the focus lens and the driving speed of the focus lens. If it is determined that the information can be acquired, the setting of the time interval and the driving speed are determined. When it is determined that the time interval for acquiring the position information of the focus lens or the information on the driving speed of the focus lens cannot be acquired, the time interval for evaluating the preset contrast value and the driving of the focus lens The imaging apparatus according to claim 1, wherein a speed is set. A setting unit for setting the imaging cycle of the imaging element;
The imaging apparatus according to claim 1, wherein the processor performs the setting of the time interval and the correction of the driving speed each time the setting unit sets the imaging cycle of the imaging device. A lens apparatus having a focus lens is detachable, and is an imaging apparatus that detects a peak position of a contrast value obtained from an imaging element as an in-focus position while continuously moving the focus lens in the optical axis direction,
Of the time that is a natural number multiple of the imaging cycle of the image sensor, it is at least the shortest time of the time interval for acquiring the position information of the focus lens, and the natural number of the imaging cycle of the image sensor and the focus lens When the condition that the product of the drive speeds is equal to or less than the set interval is satisfied, the drive speed that satisfies the minimum natural number that satisfies the condition is set as the drive speed of the focus lens, and the minimum natural number is set as the contrast. An imaging apparatus comprising: a processor that sets a time interval for evaluating a value. A lens apparatus having a focus lens is detachable, and is an imaging apparatus that detects a peak position of a contrast value obtained from an imaging element as an in-focus position while continuously moving the focus lens in the optical axis direction,
An imaging apparatus comprising: a processor that acquires the contrast value by moving the focus lens again in a region where the maximum contrast value is detected among regions in which position information of the focus lens cannot be acquired. A lens that has a focus lens and can be attached to and detached from the imaging device, and detects the peak position of the contrast value obtained from the imaging device of the imaging device as the in-focus position while continuously moving the focus lens in the optical axis direction A device,
Of the time that is a natural number multiple of the imaging cycle of the image sensor, the shortest time interval for acquiring the position information of the focus lens and the time for moving the focus lens in the optical axis direction by the set distance at the fastest drive speed The shortest time over the smaller time is set as the time interval for evaluating the contrast value, and the driving speed of the focus lens is set so that the focus lens moves by the set distance in the optical axis direction during the time interval. A lens apparatus comprising a processor for correcting. A lens that has a focus lens and can be attached to and detached from the imaging device, and detects the peak position of the contrast value obtained from the imaging device of the imaging device as the in-focus position while continuously moving the focus lens in the optical axis direction A device,
Of the time that is a natural number multiple of the imaging cycle of the image sensor, it is at least the shortest time of the time interval for acquiring the position information of the focus lens, and the natural number of the imaging cycle of the image sensor and the focus lens When the condition that the product of the driving speed is equal to or less than the set interval is satisfied, the driving speed that satisfies the minimum natural number that satisfies the condition is set as the driving speed of the focus lens, and the contrast value is evaluated based on the minimum natural number. A lens device comprising: a processor that sets the time interval to be set. A lens that has a focus lens and can be attached to and detached from the imaging device, and detects the peak position of the contrast value obtained from the imaging device of the imaging device as the in-focus position while continuously moving the focus lens in the optical axis direction A device,
A lens apparatus comprising: a processor that acquires the contrast value by moving the focus lens again in a region where the maximum contrast value is detected among regions in which position information of the focus lens cannot be acquired. A focus detection method for an image pickup apparatus in which a lens apparatus having a focus lens is detachable, and the peak position of a contrast value obtained from an image pickup element is detected as an in-focus position while continuously moving the focus lens in the optical axis direction. There,
Of the time that is a natural number multiple of the imaging cycle of the image sensor, the shortest time interval for acquiring the position information of the focus lens and the time for moving the focus lens in the optical axis direction by the set distance at the fastest drive speed The shortest time over the smaller time is set as the time interval for evaluating the contrast value, and the driving speed of the focus lens is set so that the focus lens moves by the set distance in the optical axis direction during the time interval. A focus detection method comprising a processor for correcting. A focus detection method for an image pickup apparatus in which a lens apparatus having a focus lens is detachable, and the peak position of a contrast value obtained from an image pickup element is detected as an in-focus position while continuously moving the focus lens in the optical axis direction. There,
Of the time that is a natural number multiple of the imaging cycle of the image sensor, it is at least the shortest time of the time interval for acquiring the position information of the focus lens, and the natural number of the imaging cycle of the image sensor and the focus lens When the condition that the product of the driving speed is equal to or less than the set interval is satisfied, the driving speed that satisfies the minimum natural number that satisfies the condition is set as the driving speed of the focus lens, and the contrast value is evaluated based on the minimum natural number. A focus detection method comprising: a processor configured to set a time interval to be detected. A focus detection method for an image pickup apparatus in which a lens apparatus having a focus lens is detachable, and the peak position of a contrast value obtained from an image pickup element is detected as an in-focus position while continuously moving the focus lens in the optical axis direction. There,
A focus detection method comprising: a processor that acquires the contrast value by moving the focus lens again in a region where the maximum contrast value is detected in a region where position information of the focus lens cannot be acquired.