JP2008310215A - Focus adjustment device and camera - Google Patents

Abstract

Provided is a focus adjustment device capable of reducing the influence of play related to driving of a focus adjustment lens in a search operation for acquiring a focus evaluation value.
A focus adjustment device for an interchangeable lens camera to which an interchangeable lens is attached and detached, and performs a search operation for driving a focus adjustment lens to obtain a focus evaluation value according to a focus adjustment command. In the focus adjustment device that performs focus adjustment based on the plurality of focus evaluation values acquired by the above, after the focus adjustment command and before performing the search operation, a predetermined drive amount is instructed to the drive source 240 of the focus adjustment lens 210c Thus, a control means 310 for preliminarily driving the focus adjustment lens 210c is provided.
[Selection] Figure 1

Description

  The present invention relates to a focus adjustment device and a camera.

  Contrast autofocus (AF), which performs focus adjustment using a focus evaluation value related to the contrast of a subject image, is mainly used in video cameras and compact digital cameras. In contrast AF, a search operation for obtaining a focus evaluation value is performed until the lens position (focus position) at which the focus evaluation value is maximum is passed, and the focus adjustment lens is driven in the reverse direction to move to the focus position. And move. For this reason, if there is a backlash in the lens driving mechanism, the lens cannot be moved to the in-focus position due to the influence.

  In order to cope with such a problem, a method of correcting the driving amount of the lens using a pre-stored play amount is known (for example, see Patent Documents 1 and 2).

  By the way, in the case of a lens having a long focal length, the focus adjustable range becomes wide, and therefore, a method of searching only a part of the focus adjustable range has been proposed (for example, see Patent Document 3).

Japanese Patent Laid-Open No. 08-265620 JP 11-271594 A JP 2004-94130 A

  However, when only a part of the focus adjustable range is searched, there is a problem of play at the start of AF, and if the amount of play is large, there is a problem that a desired area cannot be searched reliably.

According to a first aspect of the present invention, a focus adjustment is performed in which a focus adjustment lens is driven to perform a search operation for acquiring a focus evaluation value by driving a focus adjustment lens, and focus adjustment is performed based on a plurality of focus evaluation values acquired by the search operation. In the apparatus, the focus adjustment lens is driven by instructing a predetermined drive amount in the same direction as the drive direction at the start of the search operation after the focus adjustment command and before performing the search operation.
According to a second aspect of the present invention, there is provided a focus adjustment device for an interchangeable lens type camera to which an interchangeable lens is attached and detached, and a search operation for obtaining a focus evaluation value by driving the focus adjustment lens according to a focus adjustment command is performed. In a focus adjustment device that performs focus adjustment based on a plurality of focus evaluation values acquired by operation, a predetermined drive amount is instructed to the drive source of the focus adjustment lens after the focus adjustment command and before the search operation is performed. And a control means for preliminarily driving the focus adjustment lens.
According to a third aspect of the present invention, in the focus adjustment device according to the second aspect, the interchangeable lens is a first that can connect and disconnect the drive shaft of the focus adjustment lens and the drive shaft that transmits the drive force from the drive source. And a second coupling capable of connecting and disconnecting the shaft for transmitting the operation amount of the manual operation member for driving the focus adjustment lens and the drive shaft of the focus adjustment lens. Is an interchangeable lens that can be switched between an autofocus state in which the second coupling is disconnected and the second coupling is disconnected, and a manual focus state in which the second coupling is connected and the first coupling is disconnected. Is a drive amount capable of eliminating the backlash of the first coupling when switching from the manual focus state to the autofocus state. And features.
According to a fourth aspect of the present invention, in the focus adjustment apparatus according to the third aspect, the predetermined drive amount is a drive amount larger than the search drive range in the search operation.
According to a fifth aspect of the present invention, in the focus adjustment apparatus according to the second aspect, the interchangeable lens is a first that can connect and disconnect the drive shaft of the focus adjustment lens and the drive shaft that transmits the driving force from the drive source. And a second coupling capable of connecting and disconnecting the shaft for transmitting the operation amount of the manual operation member for driving the focus adjustment lens and the drive shaft of the focus adjustment lens. This is an interchangeable lens that can be switched between an autofocus state in which the second coupling is disconnected and the second coupling is disconnected, and a manual focus state in which the second coupling is connected and the first coupling is disconnected. Specify the first predetermined drive amount that can eliminate the backlash of the first coupling when the manual focus state is switched to the autofocus state. And a second predetermined driving amount in the same direction as the driving direction at the start of the search operation after the first preliminary drive and before the search operation after the first preliminary drive. And a second preliminary drive for driving the focus adjustment lens.
According to a sixth aspect of the present invention, in the focus adjustment apparatus according to any one of the third to fifth aspects of the present invention, the focus adjustment device further includes a switching detection unit that detects switching from the manual focus state to the autofocus state, and the switching detection unit switches the switching. Is detected, preliminary driving is performed.
According to a seventh aspect of the present invention, in the focus adjustment apparatus according to any one of the third to fifth aspects, the driving mechanism determination unit further includes a driving mechanism determination unit that determines a driving mechanism of the interchangeable lens attached to the camera. On the basis of the determination result, it is determined whether or not to perform preliminary driving.
According to an eighth aspect of the present invention, in the focus adjustment apparatus according to the seventh aspect, the drive mechanism determining means determines whether or not the drive mechanism includes a drive source, and the drive mechanism determining means includes the drive source. If it is discriminated, preliminary driving is not performed, and if the driving mechanism discriminating unit discriminates that the drive source is not provided, the preliminary driving is controlled.
According to a ninth aspect of the present invention, in the focus adjustment apparatus according to the seventh or eighth aspect, the drive mechanism determining means determines whether or not the backlash of the first coupling provided in the drive mechanism is equal to or higher than a predetermined level. When the driving mechanism discriminating means determines that the backlash is equal to or higher than the predetermined level, the preliminary driving is performed and then the search operation is performed. When the driving mechanism discriminating means determines that the backlash is less than the predetermined level, the preliminary driving is executed. The control is performed so that the search operation is performed.
A tenth aspect of the present invention is the focus adjustment apparatus according to the seventh or eighth aspect, further comprising an MF determination unit that determines whether or not the manual operation member has been operated, and the determination result of the drive mechanism determination unit and the MF determination unit On the basis of the determination result, it is determined whether or not to perform preliminary driving.
According to an eleventh aspect of the present invention, in the focus adjustment device according to the tenth aspect, the drive mechanism determining means determines whether or not the backlash of the first coupling provided in the drive mechanism is equal to or higher than a predetermined level, and When it is determined by the determining means that the backlash is equal to or higher than the predetermined level and the manual operation member is determined to be operated by the MF determining unit, control is performed so that the search operation is performed after the preliminary drive is executed. is there.
According to a twelfth aspect of the present invention, in the focus adjusting apparatus according to any one of the third to fifth aspects, the driving amount at the time of preliminary driving is determined according to the focal length of the interchangeable lens.
A camera according to a thirteenth aspect of the invention includes the focus adjustment device according to any one of the first to twelfth aspects.

  According to the present invention, it is possible to reduce the influence of backlash related to the driving of the focus adjustment lens in the search operation for acquiring the focus evaluation value.

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.
-First embodiment-
FIG. 1 is a block diagram showing a first embodiment of a camera provided with a focus adjusting apparatus according to the present invention. The camera shown in FIG. 1 is an interchangeable lens type camera, and an interchangeable lens 20 is attached to the camera body 10.

  The lens barrel 200 of the interchangeable lens 20 is provided with a lens optical system 210 having lenses 210a to 210d. The focal length adjustment lens 210b is configured to be movable in the optical axis direction. By manually rotating a zoom ring (not shown), the position of the focal length adjustment lens 210b changes, and the focal length of the entire lens optical system 210 changes accordingly. The position of the focal length adjustment lens 210b is monitored by the zoom encoder 220.

  The focus adjustment lens 210c is configured to be movable in the optical axis direction, and is driven in the optical axis direction by a focus drive motor 240. The position of the focus adjustment lens 210 c is monitored by the focus adjustment lens position encoder 230.

  The diaphragm 250 is an aperture diaphragm that adjusts the amount of light reaching the image sensor 22. The setting of the aperture 250 may be performed automatically by the camera or by the photographer, and is controlled by an unillustrated aperture control motor or the like according to the set value. For example, in the case of the program mode or the shutter speed priority mode, the aperture value is determined based on the output of the photometric element 40. In the aperture priority mode or manual mode, the photographer sets the aperture value.

  Position information monitored by the zoom encoder 220 and the focus adjustment lens position encoder 230 is sent to a lens microcomputer 260 provided in the lens barrel 200. The lens microcomputer 260 controls the focus drive motor 240, the aperture control motor, and the like. The lens microcomputer 260 stores lens information related to the interchangeable lens 20. When the lens barrel 200 is attached to a lens mount (not shown) of the camera body 10, the lens microcomputer 260 and the camera control unit 310 on the camera body side are connected via a contact 330 provided on the lens mount.

  The quick return mirror 70 in the camera body 10 is disposed on the optical axis of the image sensor 22 before exposure, and reflects light from the lens barrel 200 toward the pentaprism 30. At the time of exposure, the quick return mirror 70 moves to the lower side of the focusing screen 25 so that the light from the lens barrel 200 is guided to the image sensor 22.

  The focusing screen 25 is disposed at a position optically equivalent to the imaging surface of the image sensor 22, and an image similar to the image formed on the imaging surface is formed on the focusing screen 25. The image formed on the focusing screen 25 is observed by the photographer through the pentaprism 30, the relay lens 50, and the eyepiece 60. A photometric element 40 is disposed in the vicinity of the optical axis of the eyepiece optical system, and the brightness of the image is detected by the photometric element 40. The detection result is sent to the camera control unit 310 and used to determine the shutter speed and aperture value. The camera control unit 310 includes a CPU, RAM, ROM, and the like, and controls the entire camera.

  Near the center of the quick return mirror 70 is a half mirror, and a part of the light is introduced into the phase difference AF detection element 100 via the sub mirror 80 and the fixed mirror 90. In the phase difference AF detection element 100, incident light is divided into two by a mask (not shown) and then imaged on two line sensors (not shown). The shift amount of the image re-imaged on the phase difference AF detection element 100 corresponds to the focus shift amount (defocus amount). The detection result is sent to the camera control unit 310.

  On the other hand, a CCD image pickup device, a CMOS image pickup device, or the like is used as the image pickup device 22 that is a means for picking up a subject image, and the formed image is photoelectrically converted and output. The focus evaluation value calculation unit 300 calculates the focus evaluation value of the focus detection area based on the imaging signal of the imaging area corresponding to the focus detection area. The calculated focus evaluation value is sent to the camera control unit 310. The camera control unit 310 controls the AF operation based on the detection result of the phase difference AF detection element 100 and the focus evaluation value calculated by the focus evaluation value calculation unit 300.

  An AF motor 340 is provided in the camera body 10 and is driven and controlled by the motor control unit 320. In the case of an AF coupling type interchangeable lens, the focus adjustment lens 210c is driven in the optical axis direction by the AF motor 340 on the camera body 10 side. Based on the lens information of the lens microcomputer 260, the camera control unit 310 determines whether the lens is an interchangeable lens provided with the focus drive motor 240.

  When it is recognized that the attached interchangeable lens 20 includes the focus drive motor 240, an AF control signal is output to the lens microcomputer 260. On the other hand, when the mounted interchangeable lens is recognized as an AF coupling type interchangeable lens, an AF control signal is output to the motor control unit 320.

  In the camera of the present embodiment, in the AF mode, when the half-press switch is turned on by half-pressing the release button provided on the camera body 10, the contrast AF switch 110 is automatically turned on. Then, after performing a rough focus adjustment by the phase difference AF, a final focusing operation is performed by the contrast AF.

  When contrast AF is performed, a part of the focus adjustable range is search-driven to obtain a plurality of focus evaluation values, and a focal point is searched based on them. In the MF mode, the focus adjustment operation is performed by phase difference AF by manually operating the distance ring 290. At that time, by turning on the contrast AF switch 110 after the MF operation, it is possible to perform contrast AF based on the focus evaluation value.

  In the case of an interchangeable lens type camera, various interchangeable lenses can be attached to the camera body 10. FIG. 2 schematically shows a drive mechanism of the focus adjustment lens 210c of the interchangeable lens 20 including the focus drive motor 240 shown in FIG. The interchangeable lens 20 is provided with a switching operation unit 270 that switches between an autofocus (AF) state shown in FIG. 2A and a manual focus (MF) state shown in FIG. Information about whether the interchangeable lens 20 is in the AF state or the MF state is transmitted from the lens microcomputer 260 to the camera control unit 310.

  When the switching operation unit 270 is operated to the right side, the interchangeable lens 20 enters the AF state shown in FIG. In the AF state, the camera body side coupling 282 provided in the drive mechanism 280 of the focus adjustment lens 210 c is coupled to the coupling 242 provided on the drive shaft of the focus drive motor 240.

  The holding frame 284 that holds the focus adjustment lens 210c is driven in the optical axis direction by a drive shaft 286 on which a lead screw is formed. The coupling 282 is fixed to the camera body side of the drive shaft 286. When the focus drive motor 240 is driven to rotate the coupling 242, the coupling 282 and the drive shaft 286 rotate, and the holding frame 284 holding the focus adjustment lens 210 c moves in the optical axis direction.

  On the other hand, when the switching operation unit 270 is operated to the left from the AF state illustrated in FIG. 2A, the state is switched to the MF state illustrated in FIG. In the MF state, the coupling 288 provided on the distance ring side of the drive mechanism 280 is coupled to the coupling 292 that rotates in conjunction with the rotation of the distance ring 290. Thus, the drive mechanism 280 of the focus adjustment lens 210c is configured to be selectively connectable to the focus drive motor 240 and the distance ring 290.

  A gear 294 is provided on the drive shaft to which the coupling 292 is fixed, and the gear 294 meshes with a gear portion 296 formed on the distance ring 290. When the distance ring 290 is manually rotated, the gear 294 is rotated, and the coupling 292 is also rotated through the drive shaft. As a result, the holding frame 284 holding the focus adjustment lens 210c moves in the optical axis direction.

  In the case of the interchangeable lens 20 shown in FIG. 2, a focus drive motor 240 is provided in the lens barrel 200, and an AF operation can be performed without using the AF motor 340 in the camera body 10. On the other hand, in the case of an AF coupling type interchangeable lens that does not include the focus drive motor 240, the focus adjustment lens 210c is driven by the AF motor 340 on the camera body 10 side.

  FIG. 3 is a schematic view similar to that of FIG. 2 and shows an AF coupling type interchangeable lens 20. In the AF state shown in FIG. 3A, the coupling 282 on the camera body side of the drive mechanism 280 is coupled to the coupling 342 provided on the drive shaft of the AF motor 340. On the other hand, when the switching operation unit 270 is operated to the left side to enter the MF state, the coupling 288 on the distance ring side is coupled with the gear 294 that is interlocked with the rotation of the distance ring 290 as shown in FIG.

<Description of coupling play>
By the way, when the distance ring 290 is rotated in the MF state shown in FIGS. 2A and 3A to change the position of the focus adjustment lens 210c, the coupling 282 is also rotated in conjunction with the rotation of the distance ring 290. To do. On the other hand, since the couplings 242 and 342 on the motor 240 and 340 side are separated from the coupling 282, the rotational positions of the couplings 242 and 342 do not change.

  FIG. 4 is a view for explaining backlash in the couplings 282 and 242. FIG. 4A is a diagram showing the rotational positions of the couplings 282 and 242 in the AF state of FIG. 2A, and shows the positional relationship when the couplings 282 and 242 are viewed from the motor 240 side. A convex portion 282a is formed in the coupling 282, and a groove 242a having substantially the same cross-sectional shape as the convex portion 282a is formed in the coupling 242.

  When the convex portion 282a is fitted into the groove 242a, the coupling 282 and the coupling 242 are coupled. When the AF state is switched to the MF state, the coupling 282 and the coupling 242 are disconnected while maintaining the rotational position shown in FIG. Then, when the MF operation is performed by rotating the distance ring 290 in the state of FIG. 2B, only the coupling 282 rotates, and as shown in FIG. 4B, the inclination angle α of the convex portion 282a is a groove. It becomes different from the inclination angle (= 0) of 242a. In the present embodiment, the deviation of the rotation angle between the couplings is called backlash, and the amount of deviation (inclination angle α) is called the backlash amount of the coupling.

  In the state shown in FIG. 4B, when the switching operation portion 270 is operated to the right side to return to the AF state, the convex portion 282a does not fit into the concave portion 242a, and the coupling 282 and the coupling 242 are not in the coupled state. . For example, when the contrast AF operation is performed from the state of FIG. 4B, only the coupling 242 is initially rotated by the focus drive motor 240. When the inclination angle of the groove 242a of the coupling 242 becomes α, the play is eliminated, the coupling 282 and the coupling 242 are coupled, and driving of the focus adjustment lens 210c in the optical axis direction is started. It will be.

  Here, the backlash of the drive mechanism 280 of the focus detection lens 210c has been described due to coupling, but there is backlash due to gear backlash, and the backlash in this embodiment is not limited to that related to coupling. All play is assumed to be included. If the drive mechanism 280 has a backlash in this way, the following inconvenience occurs when switching to the AF state after the MF operation and performing contrast AF.

  In general, the driving range of the focus detection lens 210c in contrast AF is about 1 mm in terms of the amount of movement of the imaging plane in the optical axis direction. However, if the value obtained by converting the backlash amount to the image plane movement amount is larger than 1 mm, the focus adjustment lens 210c does not move at all even if the motors 240 and 340 are rotationally driven by an amount corresponding to the image plane movement amount 1 mm. become. Further, even when the value obtained by converting the backlash amount to the image plane movement amount is smaller than 1 mm, the focus adjustment lens 210c does not move until the backlash is clogged. Does not change, and the correct focus may not be obtained.

  Therefore, in the present embodiment, the contrast AF operation is performed by a method as shown in FIGS. FIG. 5 is a flowchart for explaining the contrast AF operation, and shows an AF control procedure processed by the camera control unit 310. That is, an operation when the switching operation unit 270 is switched from the MF state to the AF state and the contrast AF switch 110 is turned on after performing the focusing by the MF operation is shown.

  FIG. 6 is a diagram illustrating the position of the focus adjustment lens 210c during the contrast AF operation. As shown in FIG. 6, the contrast AF operation of the present embodiment includes pre-drive, search operation, and focus drive, and the search operation includes initial drive and search drive. In the following, the case where the interchangeable lens 20 shown in FIG. 2 is mounted will be described as an example, but the same applies to the case where the interchangeable lens driven by the AF motor 340 on the camera body side shown in FIG. 3 is mounted. be able to.

  The program shown in the flowchart of FIG. 5 is started when the camera is turned on. In step S100, the camera control unit 310 determines whether or not the contrast AF switch 110 is turned on. If it is determined in step S100 that the contrast AF switch 110 has been turned on, the process proceeds to step S300. In step S300, the pre-drive shown in FIG. 6 is executed. In FIG. 6, the horizontal axis indicates time, and the vertical axis indicates the position of the focus adjustment lens 210 c detected by the focus adjustment lens position encoder 230.

  In the pre-driving, the first operation (L11) for largely driving the focus adjustment lens 210c from the initial position, the second operation (L12) for largely reverse driving in the opposite direction to the first operation, and the inversion to the initial position again. It consists of a third operation (L13) to drive. Here, the initial position is the position of the focus adjustment lens 210c when the contrast AF switch 110 is turned on. In the present embodiment, the focus adjustment lens 210c is moved to the infinity side in the first operation, but the driving direction of the focus adjustment lens 210c at the start of the subsequent search operation, that is, the straight line L14 in FIG. It is necessary to align with the driving direction.

  In the first operation, the camera control unit 310 outputs an instruction drive amount that instructs the lens microcomputer 260 to drive at a predetermined size. Here, the instruction drive amount is set such that the amount of rotation of the coupling 242 by the focus drive motor 240 is large enough to eliminate coupling play. The instruction drive amount output from the camera control unit 310 is generally instructed by the amount of movement of the image plane. The lens microcomputer 260 calculates the drive amount of the focus adjustment lens 210c that gives the input image plane movement amount, and drives and controls the focus drive motor 240 according to the drive amount.

  The amount of coupling play varies depending on each interchangeable lens, but a large one may be several times as large as the search drive range (about 1 mm in image plane movement). Therefore, the instruction drive amount in the first operation for the purpose of removing the coupling play is set to a value larger than that of the interchangeable lens having a large play amount. For example, in consideration of an interchangeable lens whose backlash amount is unknown, the instruction drive amount is set to about 5 mm.

  In the example shown in FIG. 6, the first operation starts from time t1, but the position of the focus adjustment lens 210c is constant until the coupling play due to the tilt angle α shown in FIG. 4B is eliminated. Remains. When the play is eliminated and the couplings are in the coupled state, the focus adjustment lens 210c starts to move toward the infinity side as indicated by the straight line L11. That is, since the drive amount indicated by the indicated drive amount is the drive amount of the four drive motors 240, the actual drive amount of the focus adjustment lens 210c when there is a backlash is smaller than the indicated drive amount.

  Thereafter, as the second operation, the focus adjustment lens 210c is reversely driven in the reverse direction (straight line L12) with the same instruction drive amount as in the first operation. Since the backlash has already been eliminated by the first operation, the driving amount of the focus adjustment lens 210c in the second operation is larger than that in the first operation. Therefore, the focus adjustment lens 210c moves closer to the initial position.

  Further, in the third operation (L13), the focus adjustment lens 210c is moved to the initial position by driving in the infinity direction that is the same as the drive direction at the start of contrast AF. By this third operation, the backlash of the gear provided in the drive mechanism 280 of the focus adjustment lens 210c is also eliminated.

  In this way, if pre-driving is completed, the process proceeds to step S400, and the camera control unit 310 executes initial driving. In the initial drive, the focus adjustment lens 210c is driven to the search start position moved by a predetermined amount from the initial position. Since the backlash of the coupling and the backlash of the drive mechanism 280 are eliminated by the pre-driving in step S300, the focus adjustment lens 210c is not rotated by the backlash in the initial driving and the focus adjustment lens 210c is in accordance with the instructed driving amount from the camera control unit 310. Driven.

  In step S500, the camera control unit 310 performs search driving from the search start position toward the initial position. In the search drive, the focus evaluation value calculation unit 300 calculates a focus evaluation value every time the focus adjustment lens 210c is moved by a predetermined amount. The calculation result is stored in the camera control unit 310. Such an operation is repeated until an in-focus position is found.

  In step S600, the camera control unit 310 determines whether an in-focus position has been found. Since the focus evaluation value in the contrast AF has a peak at the in-focus position, in this determination, it is determined whether or not the in-focus position is found depending on whether the successively calculated focus evaluation values exceed the peak position. .

  If it is determined in step S600 that the in-focus position has been found, the process proceeds to step S700. If it is determined that the focus position is not found, the process proceeds to step S800. In step S700, the in-focus driving shown in FIG. 6 is executed. In the focus drive, the focus adjustment lens 210c is moved to a position passing through the focus position by reversal drive, and then the drive is reversed again to move the focus adjustment lens 210c to the focus position, and a series of contrast AF operations are performed. finish. Here, in order to remove the influence of gear backlash (backlash), the inversion drive is performed twice to move to the in-focus position.

  On the other hand, if it is determined in step S600 that the in-focus position is not found and the process proceeds to step S800, it is determined in step S800 whether or not the search drive for the predetermined search drive range has been completed. In step S800, if it is determined that the search drive for the predetermined search drive range has not ended (NO), the process returns to step S500 to continue the search drive, and it is determined that the search drive for the predetermined search drive range has ended (YES). Then, the process proceeds to step S900, where it is determined that the detection is impossible, and the series of contrast AF operations is terminated.

  By the way, in a camera equipped with a conventional focus adjusting device, the focus adjusting lens 210c cannot be driven according to the indicated drive amount due to coupling play. Further, when the backlash amount is large enough to exceed the search range, the search drive itself cannot be performed. On the other hand, in the above-described first embodiment, since the pre-drive for eliminating the play is performed before the initial drive after the contrast AF switch 110 is operated, the couplings 241 and 282 are performed. The search drive can be started almost without being affected by the play of the drive mechanism 280.

-Second Embodiment-
In the first embodiment described above, pre-driving is performed regardless of the type of interchangeable lens 20 mounted on the camera body 10. However, unlike the above-described interchangeable lens 20, in the case of an interchangeable lens in which the lens barrel 200 is not provided with the switching operation unit 270 for switching between the MF state and the AF state, the backlash of the drive mechanism 280 (mainly the gear back). Only rush). In the case of such an interchangeable lens, pre-driving is not necessary. Instead, pre-driving becomes extra driving, and the time until focusing becomes longer than necessary.

  Therefore, in the second embodiment, the camera control unit 310 determines whether or not the mounted interchangeable lens causes backlash due to coupling. FIG. 7 is a diagram showing a flowchart of the contrast AF operation in the second embodiment, and is obtained by adding the process of step S200 to the flowchart of FIG.

  In step S200, the camera control unit 310 reads lens type information regarding the interchangeable lens 20 from the lens microcomputer 260, and whether the mounted interchangeable lens 20 is an interchangeable lens having a mechanism for switching between the AF state and the MF state. It is determined whether or not the interchangeable lens has a large play. If it is determined in step S200 that the interchangeable lens has a large backlash, the process proceeds to step S300 and pre-driving is executed.

  On the other hand, if it is determined in step S200 that the lens is not a large backlash, the process proceeds to step S400 to perform initial driving. The processing of other steps is the same as the processing of the same reference numerals in the flowchart shown in FIG.

  As described above, in the second embodiment, since pre-drive is performed only when an interchangeable lens having a large play that causes play related to coupling is mounted, an interchangeable lens having a small play is mounted. When it is, the feeling of use and the focusing speed are not impaired. When an interchangeable lens with a large backlash is attached, the same effects as those of the first embodiment can be obtained.

  In the second embodiment, the entire pre-driving is omitted in the case of an interchangeable lens that does not have a large backlash. However, as shown in FIG. It may be done before. Thus, by driving in advance in the same direction as the driving direction of the initial operation, the influence of gear play in the search operation can be reduced.

[Modification]
FIG. 9 is a flowchart showing a modification of the second embodiment. In the modification shown in FIG. 9, the processing of step S50 and step S250 is added to the flowchart of FIG. Other processes are the same as those in the second embodiment described above. In the second embodiment described above, when the interchangeable lens 20 having a large backlash is attached, the pre-drive is performed even if the MF operation is not performed.

  However, even when the interchangeable lens 20 with large play is attached, as long as the MF operation is not performed and the AF lens is used only in the AF state, play due to coupling does not occur. Therefore, in the modification shown in FIG. 8, the pre-drive is performed only when the MF operation is performed before the contrast AF.

  The camera control unit 310 determines whether or not an MF operation has been performed. For example, when the detected value of the focus adjustment lens encoder 230 sent from the lens microcomputer 260 changes even though the command drive amount is not output from the camera control unit 310, there is an MF operation (MF interrupt). It is determined that

  First, in step S50 of FIG. 9, the camera control unit 310 performs an MF interrupt detection process, and if an MF interrupt is detected, stores that detected. In step S100, it is determined whether or not the contrast AF switch 110 is turned on. When it is determined that the contrast AF switch 110 is turned on, the process proceeds to step S300, and when it is determined that the contrast AF switch 110 is turned off, the process returns to step S50.

  In step S200, it is determined whether or not the mounted interchangeable lens has a large backlash. If it is determined that the backlash is large, the process proceeds to step S250. Otherwise, the process proceeds to step S400 to perform initial driving. In step S250, it is determined whether or not there is an MF interrupt. If it is determined that there is an MF interrupt, the process proceeds to step S300 to perform pre-drive, and if it is determined that there is no MF interrupt, the process proceeds to step S400. The processing after step S400 is the same as in the second embodiment described above, and a description thereof is omitted.

  As described above, in the modified example, since the pre-drive is performed only when the MF operation is performed before performing the contrast AF, the MF operation is performed even when the large interchangeable interchangeable lens 20 is mounted. If the actual play is not small, unnecessary pre-driving can be avoided. Here, whether or not the MF operation has been performed is detected, but whether or not the pre-drive is executed is determined by whether or not the switching operation unit 270 has switched to the MF state regardless of whether or not the MF operation has been performed. You may make it determine.

-Third embodiment-
As described above, when the drive amount is instructed from the camera control unit 310 to the lens microcomputer 260, generally, an instruction value of the moving amount of the image plane position is transmitted to the lens microcomputer 260 as the instruction drive amount. The amount of movement of the image plane position with respect to the driving amount of the focus adjustment lens 210c in the optical axis direction changes according to the focal length of the lens optical system 210. On the other hand, the drive amount for driving the focus drive motor 240 to eliminate the play of the couplings 242 and 282 is determined regardless of the focal length.

  For example, when the focal length of the lens optical system 210 is 50 mm, it is assumed that when the focus driving motor 240 is pulse-driven, the backlash is clogged with 10 pulses. Assume that the amount of movement of the image plane position when the focal length is driven by 200 pulses of 200 mm is 1 mm. On the other hand, even when the focal length of the lens optical system 210 is 200 mm, the number of pulses necessary to reduce the backlash is 10 pulses. However, since the focal length is 200 mm, when the focus adjustment lens 210c is driven by 10 pulses, the amount of movement of the image plane position is approximately 4 mm. That is, the amount of movement of the image plane position is almost proportional to the focal length ratio.

  Therefore, in the third embodiment, the camera control unit 310 reads the focal length information of the interchangeable lens 20 and the detection value of the zoom encoder from the lens microcomputer 260, and calculates the focal length f based on these values. In the camera control unit 310, an arithmetic expression m = G (f) for calculating an instruction drive amount m that is an instruction value of the image plane movement amount is stored in advance. For example, since the amount of movement of the image plane position is substantially proportional to the ratio of the focal lengths, the command drive amount m is obtained by multiplying the proportional coefficient k such that m = k · f.

  Then, the instruction drive amount m is calculated from the calculated focal length f and the arithmetic expression, and the calculated instruction drive amount m is output to the lens microcomputer 260. The lens microcomputer 260 calculates the drive amount of the focus adjustment lens 210c based on the instruction drive amount m, and drives the focus drive motor 240.

  As described above, in the third embodiment, since the instruction drive amount m is calculated based on the focal length of the interchangeable lens 20, the play can be surely eliminated by the pre-drive.

  In the above-described embodiment, an interchangeable lens type camera has been described as an example. However, the operation for eliminating gear play as shown in FIG. 8 is not limited to an interchangeable lens type, and is also effective for a lens-integrated camera. It is. The above description is merely an example, and the present invention is not limited to the above embodiment as long as the characteristics of the present invention are not impaired.

It is a block diagram which shows 1st Embodiment of the camera provided with the focus adjustment apparatus by this invention. The drive mechanism of the focus adjustment lens 210c of the interchangeable lens 20 provided with the focus drive motor 240 is schematically shown. (A) shows the AF state, and (b) shows the MF state. The drive mechanism of the focus adjustment lens 210c of the AF coupling type interchangeable lens 20 is schematically shown. (A) shows the AF state, and (b) shows the MF state. It is a figure explaining the play in coupling 242 and 282, (a) shows AF state, (b) shows the state after MF operation. It is a flowchart explaining a contrast AF operation. It is a figure explaining the position of the focus adjustment lens 210c at the time of contrast AF operation | movement. It is a flowchart explaining the contrast AF operation | movement in 2nd Embodiment. It is a figure explaining the position of the focus adjustment lens 210c at the time of contrast AF operation | movement. It is a flowchart explaining the modification of 2nd Embodiment.

Explanation of symbols

  10: Camera body, 20: Interchangeable lens, 110: Contrast AF switch, 200: Lens barrel, 210c: Focus adjustment lens, 220: Zoom encoder, 230: Focus adjustment lens position encoder, 240: Focus drive motor, 242, 282 , 288, 292, 342: coupling, 242a: convex part, 282a: groove, 260: lens microcomputer, 270: switching operation part, 280: drive mechanism, 286: drive shaft, 290: distance ring, 300: focus evaluation value Calculation unit, 310: camera control unit, 340: AF motor

Claims (13)

In a focus adjustment device that performs a search operation to acquire a focus evaluation value by driving a focus adjustment lens according to a focus adjustment command, and performs focus adjustment based on a plurality of focus evaluation values acquired by the search operation.
After the focus adjustment command and before the search operation, the focus adjustment lens is driven by instructing a predetermined drive amount in the same direction as the drive direction at the start of the search operation. Focus adjustment device. A focus adjustment device for an interchangeable lens type camera, to which an interchangeable lens is attached and detached, and performs a search operation for obtaining a focus evaluation value by driving the focus adjustment lens according to a focus adjustment command, and a plurality of focal points acquired by the search operation In a focus adjustment device that performs focus adjustment based on an evaluation value,
Control means for instructing a predetermined drive amount to the focus adjustment lens drive source to perform preliminary drive of the focus adjustment lens after the focus adjustment command and before performing the search operation. Focus adjustment device characterized. The focusing apparatus according to claim 2, wherein
The interchangeable lens includes a first coupling capable of connecting and disconnecting a driving shaft of the focusing lens and a driving shaft for transmitting driving force from the driving source, and a manual for driving the focusing lens. A second coupling capable of connecting and disconnecting a shaft for transmitting an operation amount of the operation member and a drive shaft of the focus adjustment lens; and connecting the first coupling to the second coupling. An interchangeable lens that can be switched between an autofocus state in which the second coupling is disconnected and a manual focus state in which the second coupling is connected and the first coupling is disconnected.
The focus adjustment apparatus according to claim 1, wherein the predetermined drive amount is a drive amount capable of eliminating the play of the first coupling when the manual focus state is switched to the autofocus state. The focus adjustment apparatus according to claim 3.
The focus adjustment apparatus, wherein the predetermined drive amount is a drive amount larger than a search drive range in the search operation. The focusing apparatus according to claim 2, wherein
The interchangeable lens includes a first coupling capable of connecting and disconnecting a driving shaft of the focusing lens and a driving shaft for transmitting driving force from the driving source, and a manual for driving the focusing lens. A second coupling capable of connecting and disconnecting a shaft for transmitting an operation amount of the operation member and a drive shaft of the focus adjustment lens; and connecting the first coupling to the second coupling. An interchangeable lens that can be switched between an autofocus state in which the second coupling is disconnected and a manual focus state in which the second coupling is connected and the first coupling is disconnected.
In the preliminary driving, a first predetermined driving amount that can eliminate the play of the first coupling when switching from the manual focus state to the autofocus state is instructed to drive the focus adjustment lens. 1 pre-drive and after the first pre-drive and before the search operation, the second predetermined drive amount in the same direction as the drive direction at the start of the search operation is indicated and the focus And a second preliminary drive for driving the adjusting lens. In the focus adjustment apparatus according to any one of claims 3 to 5,
Further comprising switching detection means for detecting switching from the manual focus state to the autofocus state,
The focus adjustment apparatus according to claim 1, wherein when the switching is detected by the switching detection unit, the control unit performs the preliminary driving. In the focus adjustment apparatus according to any one of claims 3 to 5,
Drive mechanism discriminating means for discriminating the drive mechanism of the interchangeable lens mounted on the camera;
The focus adjustment apparatus, wherein the control unit determines whether or not to perform the preliminary drive based on a determination result of the drive mechanism determination unit. The focus adjustment device according to claim 7.
The drive mechanism determining means determines whether or not the drive mechanism includes the drive source;
The control means does not perform the preliminary drive when the drive mechanism determination means determines that the drive source is provided, and does not perform the preliminary drive when the drive mechanism determination means determines that the drive source is not provided. A focus adjustment device that controls to perform driving. The focusing apparatus according to claim 7 or 8,
The drive mechanism determining means determines whether or not the backlash of the first coupling provided in the drive mechanism is equal to or higher than a predetermined level;
The control means performs the search operation after executing the preliminary drive when the play mechanism determining means determines that the backlash is greater than or equal to a predetermined level, and the drive mechanism determining means determines that the backlash is less than the predetermined level. When it is determined, the focus adjustment device controls to perform the search operation without executing the preliminary drive. The focusing apparatus according to claim 7 or 8,
An MF determination unit for determining whether or not the manual operation member has been operated;
The focus adjustment apparatus, wherein the control unit determines whether or not to perform the preliminary drive based on a determination result of the drive mechanism determination unit and a determination result of the MF determination unit. The focus adjustment apparatus according to claim 10.
The drive mechanism determining means determines whether or not the backlash of the first coupling provided in the drive mechanism is equal to or higher than a predetermined level;
When the driving mechanism determining unit determines that the backlash is equal to or higher than a predetermined level and the MF determining unit determines that the manual operation member has been operated, the control unit performs the preliminary driving and then performs the preliminary driving. A focus adjustment device that controls to perform a search operation. In the focus adjustment apparatus according to any one of claims 3 to 5,
The focus adjustment apparatus, wherein the control means determines a drive amount during the preliminary drive according to a focal length of the interchangeable lens.   A camera comprising the focus adjustment device according to claim 1.

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