JP6320095B2 - Imaging device, control method thereof, and control program - Google Patents

Description

  The present invention relates to an imaging apparatus, a control method thereof, and a control program, and more particularly to an imaging apparatus including a varifocal type photographing lens unit that changes a focal position when a focal length is changed by a zoom operation.

  In general, a varifocal type photographing lens unit is known in which the focal position changes when the focal length is changed by a zoom operation. This photographing lens unit can be made smaller than a general zoom lens, and further has an advantage that a subject at a close distance can be photographed.

  On the other hand, in a varifocal type photographing lens unit (hereinafter simply referred to as a varifocal lens), the focus lens is made to follow the zoom operation so that the focal position does not change even if the focal length is changed by the zoom operation. It will be necessary. That is, in an imaging apparatus equipped with a varifocal lens, it is necessary to store in advance the drive amount of the focus lens that accompanies the zoom operation and drive the focus lens in accordance with the zoom operation amount.

  Furthermore, there is an imaging apparatus in which a varifocal lens is mounted on an imaging apparatus body as an interchangeable lens unit. In this case, the imaging apparatus body includes a focus detection unit for detecting the focus of the subject, and the focus lens provided in the interchangeable lens unit is provided with the imaging apparatus body according to the focus detection result by the focus detection unit. Drive to the in-focus position.

  In an imaging apparatus equipped with the varifocal lens described above, when performing focus detection during zoom operation and driving the focus lens to focus, zooming is performed in consideration of the timing difference between zoom operation and focus detection. There is one in which high-precision focusing is performed even if focus detection is performed during operation (see Patent Document 1).

JP-A-4-350612

  However, in the imaging apparatus described in Patent Document 1 described above, the focus lens cannot be driven in time for the change in the focus position in response to the zoom operation, and the focus position shift amount increases, making it difficult to detect the focus. is there. In particular, in a single-lens reflex type imaging device, a photographer's manual zoom operation mechanism is employed, and if the speed of the zoom operation by the photographer is high, the drive speed of the focus lens is not in time. As a result, the focal position shift becomes large.

  In this case, since the optical image is in a so-called large blur state in the focus detection unit, it is necessary to search and drive the focus lens until an image capable of focus detection is detected. When the direction of search driving is opposite to the in-focus direction, the time until in-focus is extremely long.

  Accordingly, an object of the present invention is to provide an imaging apparatus capable of accurately performing focus detection in a short time, a control method thereof, and a control program even when the focus position shift amount due to zoom operation is large and focus detection is difficult. It is to provide.

In order to achieve the above object, an image pickup apparatus according to the present invention includes a zoom lens and a focus lens, and includes a varifocal type photographing lens unit that changes a focal position of the focus lens when a focal length is changed by a zoom operation. An imaging device for obtaining an image corresponding to an optical image formed through the photographing lens unit, wherein the focus lens is driven and controlled to be a predetermined focal position according to a change in a focal position by the zoom operation. A focus tracking unit that performs focus detection according to an optical image obtained through the photographing lens unit, and the predetermined focus position and the current position when performing the focus detection during or after the zoom operation. When the amount of deviation from the focal position of the lens is greater than a predetermined threshold, the focus lens is moved in a direction that reduces the amount of deviation. Driven, and having a control unit that drives the focus lens until it becomes possible to focus detection by said focus detecting means.

A control method according to the present invention includes a zoom lens and a focus lens, and includes a varifocal type photographing lens unit in which a focal position of the focus lens changes when a focal length is changed by a zoom operation. A method for controlling an imaging apparatus that obtains an image according to an optical image formed, and a focus follow-up step that drives and controls the focus lens so that a predetermined focus position is obtained in accordance with a change in the focus position caused by the zoom operation; A focus detection step for performing focus detection according to an optical image obtained through the photographing lens unit, and when performing the focus detection during or after the zoom operation, the predetermined focus position and the current focus position When the amount of deviation is larger than a predetermined threshold value, the focus lens is driven in a direction to reduce the amount of deviation. Characterized by and a control step of driving the focusing lens to thereby enabling the focus detection by said focus detecting means.

A control program according to the present invention includes a zoom lens and a focus lens, and includes a varifocal type photographing lens unit in which a focal position of the focus lens changes when a focal length is changed by a zoom operation, through the photographing lens unit. A control program used in an imaging device that obtains an image according to an optical image that has been formed, the computer having the imaging device having a predetermined focal position according to a change in a focal position caused by the zoom operation A focus follow-up step for driving and controlling the focus lens; a focus detection step for performing focus detection according to an optical image obtained via the photographing lens unit; and when performing the focus detection during or after a zoom operation The amount of deviation between the current focal position and the current focal position is greater than a predetermined threshold The drives the focus lens in the direction of displacement amount is reduced, characterized in that to execute a control step of driving the focusing lens to thereby enabling the focus detection by said focus detecting means.

According to the present invention, when the amount of deviation is larger than the predetermined threshold, the focus lens is driven in a direction in which the amount of deviation decreases , and the focus lens is driven until focus detection becomes possible . That is, when the focus position shift amount due to the zoom operation is large and focus detection is difficult, focus detection is performed after the shift amount is reduced. As a result, focus detection can be performed accurately in a short time.

1 is a cross-sectional view for explaining an optical system of a varifocal type photographing lens unit mounted on an imaging apparatus according to a first embodiment of the present invention. It is a figure for demonstrating the relationship between the focal distance of the varifocal lens shown in FIG. 1, and the position of a focus lens. It is a block diagram for demonstrating an example of the imaging device with which the varifocal lens shown in FIG. 1 was mounted | worn. FIG. 4A is a diagram for explaining a follow-up delay in a zoom operation in the image pickup apparatus shown in FIG. 3, and (A) is zoomed toward a telephoto end at a predetermined speed while focusing on an object at infinity at the wide-angle end. FIG. 5B is a diagram showing the amount of shift of the focal position after, and FIG. 5B shows the amount of shift of the focal position immediately after zooming toward the telephoto end over a predetermined time while focusing on an object at a close distance at the wide angle end. FIG. 2 is a flowchart for explaining a focus following operation by a zoom operation in the imaging apparatus shown in FIG. 1. 4 is a flowchart for explaining a focus detection process when a tracking delay occurs in the imaging apparatus shown in FIG. 3. It is a flowchart for demonstrating the focus detection process performed with the imaging device by the 2nd Embodiment of this invention.

  Hereinafter, an example of an imaging apparatus according to an embodiment of the present invention will be described with reference to the drawings. Here, an imaging device in which the photographing lens unit is replaceable with respect to the imaging device main body will be described as an example, but the same applies to an imaging device in which the photographing lens unit is integrated with the imaging device main body. be able to.

[First Embodiment]
FIG. 1 is a cross-sectional view for explaining an optical system (imaging optical system) of a varifocal type imaging lens unit mounted on an imaging apparatus according to a first embodiment of the present invention.

  A varifocal type photographing lens unit (hereinafter simply referred to as a varifocal lens) has a diaphragm disposed in the vicinity of the first to sixth lens groups L1 to L6 and the third lens group L3. The first lens unit L1 has a positive refractive power, and the second lens unit L2 has a negative refractive power. The third lens unit L3 has a positive refractive power, and the fourth lens unit L4 has a positive refractive power. The fifth lens unit L5 has a negative refractive power, and the sixth lens unit L6 has a positive refractive power. In the drawing, an imaging surface (not shown) is defined on the right side of the sixth lens unit L6, and an imaging element such as a CMOS image sensor is disposed on the imaging surface.

  The varifocal lens shown in FIG. 1 is shown in the wide-angle end state, and when zooming to the telephoto end side, the first lens unit L1 and the third lens unit L3 move to the left side in the figure, Further, the fourth lens group L4, the fifth lens group L5, and the sixth lens group L6 move integrally to the left in the drawing.

  Since the focal position changes with zooming, it is necessary to move the fifth lens unit L5 independently so as to keep the focal position constant. This point will be described later.

  The illustrated varifocal lens has a so-called rear focus configuration in which the fifth lens unit L5 is moved to the imaging surface side when focusing from an object at infinity to an object at a close distance. Therefore, the focus lens (fifth lens unit L5) can be reduced in size even when high magnification zoom is performed.

  Further, since the fifth lens unit L5 can be reduced in size, for example, a wobbling operation for moving image shooting and high-speed driving for still image shooting can be achieved using an inexpensive and small actuator. In the illustrated varifocal lens, when focusing from an object at infinity to an object at a close distance, the amount of movement of the fifth lens unit L5 differs at the wide-angle end and the telephoto end, and from the wide-angle end side to the telephoto end side. As the distance increases, the moving amount of the fifth lens unit L5 increases.

  FIG. 2 is a diagram for explaining the relationship between the focal length of the varifocal lens shown in FIG. 1 and the position of the focus lens.

  In FIG. 2, the horizontal axis indicates the focal length by zoom operation, the origin side is the wide angle end, and the right side in the figure is the telephoto end. The vertical axis indicates the position of the focus lens (fifth lens unit L5) in the optical axis direction, and the origin side is the object side in FIG. In the drawing, the upper side corresponds to the image plane side shown in FIG. A movement locus 101 indicates a movement locus of the focus lens with respect to an object at a close distance, and a movement locus 102 indicates a movement locus of the focus lens with respect to an object at infinity. A movement locus 103 indicates a movement locus of the focus lens with respect to the standard distance object.

  When zooming from the wide-angle end to the telephoto end side, the fourth lens unit L4, the fifth lens unit L5, and the sixth lens unit L6 move together. At this time, the fifth lens unit L5 is moved along the movement locus 101, 102, or 103 shown in FIG. 2 in order to keep the focal position constant with respect to the change of the focal position due to zoom.

  That is, when the subject exists at a close distance, the fifth lens unit L5 is moved along the movement locus 101. As a result, the fifth lens unit L5, which is a focus lens, moves from close W to close T in the figure, and the amount of movement is large.

  On the other hand, when the subject exists at infinity, the fifth lens unit L5 is moved along the movement locus 102. As a result, the fifth lens unit L5, which is a focus lens, moves from infinity W to infinity T in the figure, and the amount of movement is small.

  As described above, it is understood that when the zoom operation is performed from the wide-angle end to the telephoto end side, it is necessary to move the fifth lens unit L5, which is the focus lens, more greatly for the object on the close side than on the object at infinity. . Even during the zoom operation, if the focus lens is moved along the movement locus shown in FIG. 2, the focal position can be kept constant.

  FIG. 3 is a block diagram for explaining an example of an imaging apparatus to which the varifocal lens shown in FIG. 1 is attached. In FIG. 3, the right side of the broken line corresponds to the imaging device (that is, the imaging device main body), and the left side of the broken line corresponds to the varifocal lens (hereinafter also referred to as a photographing lens). The photographing lens is exchangeably connected to the imaging apparatus main body by a mount mechanism (not shown).

  The imaging apparatus main body has an imaging apparatus control unit 201, and the imaging apparatus control unit 201 controls the entire imaging apparatus. The imaging device input / output unit 202 inputs and outputs data with the imaging lens. Similarly, the taking lens control unit 301 controls the taking lens. Although not shown, the imaging apparatus main body is provided with an imaging device such as a CMOS image sensor, and outputs an image corresponding to an optical image formed on the imaging device via a photographing lens.

  The photographic lens includes a photographic lens input / output unit 302, and the photographic lens input / output unit 302 inputs and outputs data related to the imaging device main body and the photographic lens via the imaging device input / output unit 201.

  The imaging apparatus main body is provided with a focus detection unit 203, and the focus detection unit 203 detects the focus position of the focus lens according to the light beam that has passed through the photographing lens. The imaging device control unit 201 performs focus adjustment by driving and controlling the focus lens group LF (fifth lens group L5 shown in FIG. 1) according to the detection result by the focus detection unit 203 in accordance with the focus adjustment program.

  As described above, the photographing lens includes the zoom lens group LZ. The zoom lens group LZ is moved in accordance with the zoom operation. The first lens group L1, the third lens group L3, and the fourth lens group L4. , Corresponding to the fifth lens group L5 and the sixth lens group L6 (see FIG. 1).

  The photographic lens is provided with a zoom operation member 303, and the photographer directly operates the zoom operation member 303 to perform zooming. This zoom operation member 303 is connected to the zoom lens group LZ by a mechanical mechanism (not shown). Accordingly, the zoom lens group LZ moves directly along the optical axis according to the operation amount and operation time by the photographer.

  The zoom position detection unit 304 is connected to the zoom operation member 201 by a mechanical mechanism (not shown). The zoom position detection unit 304 detects the operation amount, the operation direction, and the operation speed of the zoom operation member 201 and outputs them to the photographing lens control unit 301 as zoom operation information.

  The focus operation member 305 is directly operated by the photographer. The focus operation member 305 is not directly connected to the focus lens group LF by a mechanical mechanism or the like. As will be described later, the focus lens group LF is driven along the optical axis by the focus motor 307 according to the operation of the focus operation member 305. Is done.

  The focus operation amount detection unit 306 detects the operation amount, the operation direction, and the operation speed of the focus operation member 305 and outputs them as focus operation information to the lens control unit 301.

  The focus lens group LF is connected to a focus motor 307 by a mechanical mechanism (not shown) and is driven by the focus motor 307. Here, as the focus motor 307, for example, a stepping motor that drives the focus lens group LF in a predetermined step unit is used. A lens barrel holding the focus lens group LF is rack-engaged with a screw screw (not shown) provided integrally with the rotation shaft of the focus motor 307, and the focus lens group LF is driven by screw feed.

  The focus lens position detection unit 308 detects the position of the focus lens group LF. As described above, a stepping motor is used as the focus motor 307. Accordingly, the focus lens position detection unit 308 detects the position of the focus lens group LF by detecting the origin position of the stepping motor using the photo interrupter and the light shielding plate, and incrementing (that is, counting) the drive pulse of the stepping motor. I do.

  Now, for example, it is assumed that the zoom operation member 303 is operated by the photographer to zoom to the telephoto end when the subject at the wide-angle end is in focus. Here, before the zoom operation, the photographic lens control unit 301 obtains the distance to the subject (subject distance) corresponding to the current focal position according to the focal length and the focus lens position.

  After the zoom operation, zoom operation information that is an output of the zoom position detection unit 304 is sent to the photographing lens control unit 301. The photographic lens control unit 301 stores in advance data (see FIG. 2) indicating a movement locus for driving the focus lens group LF so that the focus position does not change when the zoom position changes. The photographic lens control unit 301 selects the movement locus as described above according to the subject distance, and drives and controls the focus motor 307 based on the movement locus. Thus, the photographer can perform a zoom operation without any change in the focal position and without feeling uncomfortable.

  However, if the zoom operation by the photographer is fast, the speed of the focus motor 307 reaches the limit, and the drive of the focus lens group LF is delayed. In particular, since the zoom operation member 303 is directly connected to the zoom lens group LZ by a mechanical mechanism, the photographer can easily perform a high-speed zoom operation depending on the operation. As a result, the following delay occurs. Further, in the telephoto zoom, as described with reference to FIG. 2, the driving range of the focus lens group LF becomes very large at the close end, and thus a tracking delay is likely to occur.

  FIG. 4 is a diagram for explaining the follow-up delay in the zoom operation in the imaging apparatus shown in FIG. FIG. 4A is a diagram showing the amount of shift of the focal position after zooming toward the telephoto end at a predetermined speed while focusing on an object at infinity at the wide-angle end, and FIG. ) Is a diagram showing the amount of shift of the focal position immediately after zooming toward the telephoto end over a predetermined time while focusing on an object at close range at the wide angle end.

  In FIG. 4, the horizontal axis indicates the zoom position, the left origin position is the wide-angle end, and the right side is the telephoto end. The vertical axis indicates the focal position deviation amount, that is, the focus deviation amount. A broken line 401 shown in FIG. 4A represents a shift amount of the focal position after zooming toward the telephoto end at a predetermined speed in a state where the object at infinity is focused at the wide-angle end. Also, a broken line 402 shown in FIG. 4B is a focal position shift amount immediately after zooming toward the telephoto end over a predetermined time while focusing on an object at a close distance at the wide-angle end.

  In the example shown in FIG. 4A, since the subject is an object at infinity, the drive range of the focus lens group LF accompanying the zoom operation is small as described with reference to FIG. Therefore, the drive speed of the focus motor 307 does not reach the limit, and the drive of the focus lens group LF is sufficiently in time. As a result, as shown in the figure, no shift amount of the focal position occurs. That is, there is no delay in focus tracking.

In the example shown in FIG. 4B, since the subject is a close-range object, the driving range of the focus lens group LF accompanying the zoom operation is very large as described with reference to FIG. Therefore, the drive speed of the focus motor 307 reaches the limit, and the focus lens group LF cannot be driven in time. As a result, as shown in the drawing, the focal position shifts from the middle, and the amount of deviation becomes maximum at the telephoto end. That is, a delay due to focus tracking occurs.

  As described above, if the drive range of the focus lens group LF is large, a delay in focus tracking tends to occur. This follow-up delay also depends on the operation speed of the zoom operation member 303, and the follow-up delay tends to occur as the operation speed increases.

  On the other hand, if the operation speed of the zoom operation member 303 is slow, no follow-up delay occurs. In addition, since this follow-up delay is caused by the speed limit of the focus motor 307, the delay gradually disappears after a lapse of time and the focus state is restored.

  However, if the focus detection is performed by the focus detection unit 203 in a state where the follow-up delay is large and the shift amount of the focus position is large, the focus detection becomes difficult because the optical image is in a largely blurred state. Therefore, it is necessary to search drive the focus lens LF until an optical image capable of focus detection by the focus detection unit 203 is obtained. At this time, as described above, if the direction of the search drive is opposite to the in-focus direction, the time is increased until the in-focus state is achieved.

  Therefore, in the imaging apparatus shown in FIG. 3, when performing focus detection in a state where a delay due to focus tracking occurs, a focus detection algorithm described later can be used to perform accurate focus detection in a short time. .

  FIG. 5 is a flowchart for explaining a focus tracking operation by a zoom operation in the imaging apparatus shown in FIG. The process according to the flowchart shown in the drawing is performed by executing an operation program stored in the photographing lens control unit 301.

  When the focus tracking operation is started, the photographing lens control unit 301 determines whether or not the zoom operation by the zoom operation member 303 has been executed (step S501). If the zoom operation is not performed (NO in step S501), the photographic lens control unit 301 stands by.

  When the zoom operation is performed (YES in step S501), the photographic lens control unit 301 detects the zoom operation direction, the zoom operation amount, and the zoom speed by the zoom position detection unit 304, and obtains zoom operation information (step). S502).

  Subsequently, the photographing lens control unit 301 calculates the subject distance according to the focal length immediately before the zoom operation and the position of the focus lens group (step S503). Then, the photographing lens control unit 310 obtains the driving amount and the moving speed of the focus lens group LF based on the zoom operation information and the subject distance.

  Note that the driving amount of the focus lens group LF corresponding to the subject distance and corresponding to the zoom operation information is stored in advance in the memory area of the lens control unit 301 as the movement locus shown in FIG.

  Next, the photographic lens control unit 301 drives and controls the focus motor 307 based on the calculated drive amount and moving speed to drive the focus lens group LF (step S505). Then, the photographing lens control unit 301 ends the focus tracking operation.

  The processes in steps S501 to S505 are repeatedly performed with a period of several tens of msec. Accordingly, it is possible to perform focus tracking with improved responsiveness to a zoom operation by a photographer.

  However, as shown in FIG. 4B, when a delay occurs in the focus tracking for the zoom operation, the focus lens LF corresponding to the zoom operation information cannot be driven in time. That is, there is a delay in driving the focus motor 307 in the process of step S505, and the focus motor 307 is in a standby state.

  FIG. 6 is a flowchart for explaining focus detection processing when a tracking delay occurs in the imaging apparatus shown in FIG. Note that the processing according to the illustrated flowchart is performed by executing an operation program stored in the imaging device control unit 201.

  At the start of the focus detection process, the imaging apparatus control unit 201 determines whether or not a focus detection instruction has been issued by the photographer in the imaging apparatus (step S601). When the focus detection instruction is not performed (NO in step S601), the imaging device control unit 201 stands by.

  When a focus detection instruction is issued (YES in step S601), the imaging apparatus control unit 201 receives drive information indicating whether or not the focus lens group LF is being driven for focus tracking by a zoom operation from the photographing lens. . Then, the imaging apparatus control unit 201 determines whether or not the focus lens group LF is being driven according to the drive information (step S602).

  If the focus lens group LF is being driven (YES in step S602), the imaging apparatus control unit 201 instructs the photographing lens to calculate the amount of shift of the focal position due to the zoom operation when the focus detection instruction is given. Do. Then, the imaging apparatus control unit 201 obtains the focal position deviation amount from the photographing lens control unit 301 (step S603: calculation of focal position deviation amount).

  Subsequently, the imaging device control unit 201 determines whether or not the focal position shift amount is larger than a preset threshold value (step S604).

  By the way, in the imaging apparatus shown in FIG. 3, the output of the imaging element such as a focus detection unit (hereinafter referred to as a first focus detection unit) by a phase difference method using a secondary imaging optical system and a CMOS image sensor is used. It is assumed that a focus detection unit (hereinafter referred to as a second focus detection unit) using the phase difference method used is provided. In this case, the focus position shift amounts (defocus amounts) that can be detected by the first and second focus detection units are different.

  For example, the first focus detection unit can detect a relatively large defocus amount, but the second focus detection unit has a small defocus amount that can be detected. Therefore, the above threshold is set corresponding to the first and second focus detection units (that is, the first and second thresholds are set). Then, the imaging device control unit 201 switches the first and second threshold values (that is, changes the threshold value) according to the focus detection unit designated by the photographer.

  This makes it possible to perform optimum focus detection according to the focus detection method. Here, the two focus detection units are provided. However, the present invention can be similarly applied to a case where a plurality of focus detection units are provided.

  When the focal position deviation amount is larger than the threshold (YES in step S604), the imaging apparatus control unit 201 determines that the deviation according to the focal position deviation amount obtained in step S603 is the in-focus position of the focus lens group LF. On the other hand, it is detected which direction is shifted. Then, the imaging device control unit 201 determines the drive direction of the focus lens group LF according to the direction of deviation, that is, according to the direction in which the amount of deviation is reduced (step S605).

  Next, the imaging device control unit 201 sends the driving amount of the focus lens group LF according to the driving direction and the shift amount determined in step S605 to the photographing lens. Then, the photographic lens control unit 301 drives and controls the focus motor 307 according to the driving direction and the driving amount to drive the focus lens LF along the optical axis (step S606). Note that the driving speed of the focus motor 307 at this time can be driven at a speed higher than the driving speed during the focus tracking operation shown in FIG. This is because, in the focus follow-up operation shown in FIG. 5, the follow-up operation is performed by the photographer operating the zoom operation member. On the other hand, the driving in step 605 can use the maximum speed of the focus motor 307 because the predetermined driving amount is driven in the shortest time.

  Subsequently, the imaging apparatus control unit 201 performs focus detection by the focus detection unit 203 (step S607). If the focus lens group LF is not being driven (NO in step S602), the imaging device control unit 201 proceeds to the process of step S607. Similarly, if the focal position shift amount is equal to or smaller than the threshold value (NO in step S604), the imaging device control unit 201 proceeds to the process of step S607.

  Next, the imaging device control unit 201 determines whether or not focus detection is possible according to the image signal sent to the focus detection unit 203 (step S608). If focus detection is not possible (NO in step S608), the imaging apparatus control unit 210 returns to the process of step S606, and the photographic lens control unit 301 drives and controls the focus motor 307. The processes in steps S605 to S608 are repeatedly performed at predetermined intervals. When the drive direction is determined, focus detection is performed while driving the focus lens LF in the drive direction until focus detection is possible. .

  As a result, the shift amount of the focal position becomes small and the focus can be detected. For a general stationary subject, focus detection can be performed only once by driving the focus lens LF (step S606). However, focus detection may not be possible depending on the contrast of the subject. Therefore, when the focus lens group LF is driven to the driving end, although not shown, the imaging device control unit 201 notifies the photographer that focus detection is impossible and ends the focus detection processing.

  If focus detection is possible (YES in step S608), the imaging apparatus control unit 201 calculates the drive amount of the focus lens LF based on the focus detection result by the focus detection unit 203 (step S609). Then, the imaging device control unit 201 drives the focus lens group LF by driving the focus motor 307 according to the driving amount obtained in step S609 by the photographing lens control unit 301 (step S610). As a result, the focus lens group LF reaches the in-focus position. Thereafter, the imaging device control unit 201 ends the focus detection process.

  In this way, in the first embodiment of the present invention, if there is a focus detection instruction during or after the zoom operation, if the focus position shift amount at that time is greater than a predetermined threshold, the focus position shift amount. Focus detection is performed while the focus lens group LF is driven in the direction in which the value decreases. Therefore, when the focus position shift amount due to the zoom operation is large, the focus lens group LF is not driven in a direction in which the shift amount is further increased, and the focusing can be performed accurately in a short time.

[Second Embodiment]
Subsequently, an example of an imaging apparatus according to the second embodiment of the present invention will be described. Note that the configuration of the imaging apparatus according to the second embodiment is the same as that of the imaging apparatus shown in FIG. The configuration of the varifocal lens, that is, the photographing lens is the same as that of the photographing lens shown in FIG.

  FIG. 7 is a flowchart for explaining a focus detection process performed by the imaging apparatus according to the second embodiment of the present invention.

  Note that the processing according to the illustrated flowchart is performed by executing an operation program stored in the imaging device control unit 201 and an operation program stored in the photographing lens control unit 301. In FIG. 7, the same steps as those in the flowchart shown in FIG. 6 are denoted by the same reference numerals.

  In step S <b> 601, when there is a focus detection instruction from the photographer, the imaging device control unit 201 sends a message to that effect to the photographing lens control unit 301. Then, the photographing lens control unit 301 determines whether or not the focus lens group LF is being driven (step S702).

  If the focus lens group LF is being driven (YES in step S702), the photographic lens control unit 301 calculates the amount of shift of the focus position due to the zoom operation at the time when the focus detection instruction is given (step S703). Subsequently, the photographing lens control unit 301 obtains a predetermined threshold value for determining the shift amount from the imaging device control unit 201, and determines whether or not the shift amount of the focal position is larger than the threshold value (step S704). .

  When the focal position deviation amount is larger than the threshold (YES in step S704), the photographing lens control unit 301 detects that the deviation according to the focal position deviation amount obtained in step S703 is the in-focus position of the focus lens group LF. On the other hand, it is detected which direction is shifted. Then, the photographic lens control unit 301 determines the drive direction of the focus lens group LF according to the direction of deviation, that is, according to the direction in which the amount of deviation is reduced (step S705).

  Next, the photographic lens control unit 301 drives and controls the focus motor 307 according to the drive amount of the focus lens group LF according to the drive direction and the shift amount determined in step S705 to move the focus lens LF along the optical axis. Drive (step S706). Thereafter, the photographic lens control unit 301 returns to the process of step S704.

  If the shift amount of the focal position is equal to or smaller than the threshold (NO in step S704), the photographic lens control unit 301 sends a message to that effect to the imaging device control unit 201. Thereby, the imaging apparatus control unit 201 performs focus detection by the focus detection unit 203 in step S607. If the focus lens group LF is not being driven (NO in step S702), the photographing lens control unit 301 sends a message to that effect to the imaging device control unit 201. Thereby, the imaging device control unit 201 performs the process of step S607.

  Thereafter, in step S609, the imaging apparatus control unit 201 calculates the driving amount of the focus lens LF based on the focus detection result by the focus detection unit 203. In step S610, the imaging apparatus control unit 201 drives the focus lens group LF by controlling the focus motor 307 according to the driving amount obtained in step S609 by the photographing lens control unit 301. As a result, the focus lens group LF reaches the in-focus position. Thereafter, the imaging device control unit 201 ends the focus detection process.

  Thus, in the second embodiment of the present invention, if there is a focus detection instruction during or after the zoom operation, if the focus position shift amount at that time is greater than a predetermined threshold, the focus position shift amount Focus detection is performed while the focus lens group LF is driven in the direction in which the value decreases. Therefore, when the focus position shift amount due to the zoom operation is large, the focus lens group LF is not driven in a direction in which the shift amount is further increased, and the focusing can be performed accurately in a short time.

  In the second embodiment, since the processing of steps S702 to S706 is performed by the photographing lens control unit, the communication amount between the imaging apparatus main body and the photographing lens can be reduced. As a result, the focus detection process can be speeded up to save power.

  As is clear from the above description, in the example shown in FIG. 3, the photographing lens control unit 301 and the focus motor 307 function as focus tracking means, and the focus detection unit 203 and the imaging device control unit 201 function as focus detection means. To do. The imaging device control unit 201 functions as a control unit. Further, the photographing lens control unit 301 functions as a first control unit, and the imaging device control unit 201 functions as a second control unit.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to these embodiment, Various forms of the range which does not deviate from the summary of this invention are also contained in this invention. .

  For example, the function of the above embodiment may be used as a control method, and this control method may be executed by the imaging apparatus. Further, a program having the functions of the above-described embodiments may be used as a control program, and the control program may be executed by a computer included in the imaging apparatus. The control program is recorded on a computer-readable recording medium, for example.

  Each of the above control method and control program has at least a focus tracking step, a focus detection step, and a control step.

  The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various recording media, and the computer (or CPU, MPU, etc.) of the system or apparatus reads the program. To be executed.

DESCRIPTION OF SYMBOLS 201 Imaging device control part 203 Focus detection part 301 Shooting lens control part 303 Zoom operation member 304 Zoom position detection part 305 Focus operation member 306 Focus operation amount detection part 307 Focus motor 308 Focus lens position detection part

Claims (8)

A zoom lens and a focus lens are provided, and a varifocal type photographic lens unit that changes the focal position of the focus lens when the focal length is changed by a zoom operation is provided, according to an optical image formed through the photographic lens unit. An imaging device that obtains images,
A focus follower for driving and controlling the focus lens so as to be a predetermined focus position in accordance with a change in the focus position by the zoom operation;
Focus detection means for performing focus detection according to an optical image obtained through the photographing lens unit;
When performing the focus detection during or after the zoom operation, if the shift amount between the predetermined focus position and the current focus position is larger than a predetermined threshold, the focus lens is driven in a direction in which the shift amount is reduced. And a control means for driving the focus lens until the focus detection is enabled by the focus detection means,
An imaging device comprising: The focus detection means performs focus detection according to a focus detection instruction from a photographer,
The control means has a deviation amount between the predetermined focus position and the current focus position larger than a predetermined threshold when the focus detection instruction is given during drive control of the focus lens by the focus tracking means. The imaging apparatus according to claim 1, wherein the focus lens is driven in a direction in which the shift amount is reduced, and the focus lens is driven until focus detection can be performed by the focus detection unit. The photographing lens unit includes the varifocal type photographing optical system, a zoom operation member for performing the zoom operation, and the focus following unit.
The imaging apparatus according to claim 1 or 2, wherein the photographing lens unit is the focus detecting means and the control means to the image pickup apparatus main body is replaceably mounted is provided.   When the focus detection is enabled by the focus detection unit, the control unit obtains a drive amount of the focus lens based on a focus detection result by the focus detection unit, and drives and controls the focus lens according to the drive amount. The imaging device according to any one of claims 1 to 3, wherein A plurality of focus detection means having different detection methods from each other,
The imaging apparatus according to claim 1, wherein the control unit changes the threshold value according to a focus detection unit used for focus detection. The control means includes a first control unit that drives the focus lens in a direction in which the shift amount decreases when the shift amount is greater than a predetermined threshold;
A second control unit that performs focus detection by the focus detection unit when the first control unit determines that the deviation amount is equal to or less than a predetermined threshold;
The photographing lens unit includes the varifocal type photographing optical system, a zoom operation member for performing the zoom operation, the focus follower, and the first controller.
The imaging apparatus according to claim 1, wherein the focus detection unit and the second control unit are provided in an imaging apparatus body on which the photographing lens unit is replaceably mounted. A zoom lens and a focus lens are provided, and a varifocal type photographic lens unit that changes the focal position of the focus lens when the focal length is changed by a zoom operation is provided, according to an optical image formed through the photographic lens unit. A method for controlling an imaging device that obtains an image,
A focus follow-up step for driving and controlling the focus lens so as to be a predetermined focus position in accordance with a change in the focus position due to the zoom operation;
A focus detection step of performing focus detection according to an optical image obtained through the photographing lens unit;
When performing the focus detection during or after the zoom operation, if the shift amount between the predetermined focus position and the current focus position is larger than a predetermined threshold, the focus lens is driven in a direction in which the shift amount is reduced. A control step of driving the focus lens until focus detection is enabled by the focus detection means ;
A control method characterized by comprising: A zoom lens and a focus lens are provided, and a varifocal type photographic lens unit that changes the focal position of the focus lens when the focal length is changed by a zoom operation is provided. A control program used in an imaging device for obtaining a captured image,
In the computer provided in the imaging device,
A focus follow-up step for driving and controlling the focus lens so as to be a predetermined focus position in accordance with a change in the focus position due to the zoom operation;
A focus detection step of performing focus detection according to an optical image obtained through the photographing lens unit;
When performing the focus detection during or after the zoom operation, if the shift amount between the predetermined focus position and the current focus position is larger than a predetermined threshold, the focus lens is driven in a direction in which the shift amount is reduced. A control step of driving the focus lens until focus detection is enabled by the focus detection means ;
A control program characterized by causing

Images