JP6511714B2 - Camera body and imaging device - Google Patents

Description

  The present invention relates to a camera body and an imaging device.

  Conventionally, there has been known a technique for limiting the drive range of a focusing lens at the time of focus detection using a lens barrel capable of limiting the drivable range of the focusing lens (see, for example, Patent Document 1).

Unexamined-Japanese-Patent No. 2006-126330

  When performing focus detection by contrast detection method that calculates the evaluation value regarding the contrast of the image by the optical system while driving the focusing lens and detects the lens position where the evaluation value is peak as the in-focus position The lens position at which the evaluation value peaks is detected by performing an operation such as interpolation using the above (e.g., five or more) evaluation values. However, if the drivable range of the focusing lens is limited as in the prior art, the driving speed of the focusing lens may be too high depending on the driving speed of the focusing lens instructed from the camera body. In the drivable range of the limited focusing lens, evaluation values of the number (for example, 5 points) necessary for focus detection can not be calculated, and as a result, the focus position may not be properly detected.

  The present invention solves the above-mentioned subject by the following solution means.

[1] A camera body according to the present invention includes: a focus detection unit for detecting a focusing state of an optical system including an aperture stop for limiting a light beam and a focusing lens; driving range information of the focusing lens A receiving unit for receiving data from a lens barrel having the optical system; an imaging device for capturing an image of the optical system and outputting imaging data at a first time interval ; the first time interval; and the aperture stop Drive target for driving the focusing lens at the time of focus detection, whichever is slower of the first target speed calculated from the information of the first target, the drive range information, and the second target speed calculated from the first time interval A determination unit that determines the speed as the velocity, and a transmission unit that transmits, to the lens barrel, information on the drive target velocity that is determined by the determination unit.
[2] In the camera body according to the present invention, the determination unit can calculate the first target velocity based on the information of the aperture stop of the optical system and the size of the pixel of the imaging device.
[3] A camera body according to the present invention is a notification means for notifying a user that the focusing lens is driven at the second target speed when the second target speed is determined as the drive target speed. It can further be provided.
[4] An imaging device according to the present invention can include the camera body.

  According to the present invention, the drive of the focusing lens can be appropriately controlled.

FIG. 1 is a block diagram showing a camera according to the present embodiment. FIG. 2 is an external view of the lens barrel according to the present embodiment. FIG. 3 is a diagram showing an example of the focusable range of the focus lens. FIG. 4 is a diagram for explaining an example of transmission and reception of information between the lens barrel and the camera body. FIG. 5 is a diagram for explaining an example of a focus detection method by the contrast detection method. FIG. 6 is a flowchart showing the operation of the camera of this embodiment. FIG. 7 is a diagram showing an example of a search drive range. FIG. 8 is an enlarged view of a main part of an imaging surface of an imaging device according to another embodiment. FIG. 9 is a view showing another example of the search drive range. FIG. 10 is a view showing another example of the external view of the lens barrel.

  Hereinafter, embodiments of the present invention will be described based on the drawings.

  FIG. 1 is a main part configuration diagram showing a digital camera 1 according to the present embodiment of the present invention. The digital camera 1 (hereinafter simply referred to as the camera 1) of the present embodiment is composed of a camera body 2 and a lens barrel 3, and the camera body 2 and the lens barrel 3 are detachably coupled by a mount unit 4 There is.

  The lens barrel 3 is an interchangeable lens that is detachable from the camera body 2. As shown in FIG. 1, the lens barrel 3 incorporates a photographing optical system including lenses 31, 32, 33 and a diaphragm 34.

  The lens 32 is a focus lens, and can move in the direction of the optical axis L1 to adjust the focal length of the imaging optical system. The focus lens 32 is provided so as to be movable along the optical axis L1 of the lens barrel 3, and its position is adjusted by the focus lens drive motor 36 while its position is detected by the encoder 35.

  The current position information of the focus lens 32 detected by the encoder 35 is sent to the camera control unit 21 described later via the lens control unit 37, and the focus lens drive motor 36 calculates the focus lens 32 calculated based on this information. The drive position is driven by being sent from the camera control unit 21 via the lens control unit 37.

  The aperture 34 is configured to adjust the aperture diameter centered on the optical axis L1 in order to limit the light amount of the light flux passing through the imaging optical system and reaching the imaging device 22 and to adjust the blur amount. Adjustment of the aperture diameter by the aperture stop 34 is performed, for example, by transmitting an appropriate aperture diameter calculated in the automatic exposure mode from the camera control unit 21 via the lens control unit 37. Further, the set aperture diameter is input from the camera control unit 21 to the lens control unit 37 by the manual operation by the operation unit 28 provided in the camera body 2. The aperture diameter of the diaphragm 34 is detected by a diaphragm aperture sensor (not shown), and the lens controller 37 recognizes the current aperture diameter.

  Further, in the lens barrel 3 according to the present embodiment, the focusable range of the focus lens 32 can be limited. The focusable range is a range that is determined to be in focus when the in-focus position is detected within the focusable range. In the present embodiment, as shown in FIGS. 1 and 2, the lens barrel 3 is provided with the focus limit switch 38 for setting the focusable range, and the user operates the focus limit switch 38, By selecting the focus limit mode, the focusable range can be selected. FIG. 2 is an external view of the lens barrel 3 according to the present embodiment.

Moreover, FIG. 3 is a figure which shows an example of the focusable range which can be set by this embodiment. In the present embodiment, as shown in FIG. 3A, “FULL mode” in which the range from infinite far end soft limit SL _IP to near end soft limit SL _NP is set as focusable range Rf 1, as shown in FIG. As shown in FIG. 3 (C), as shown in FIG. 3 (C), the “near-side limit mode” in which the range from the infinite distance end soft limit SL _IP to the near side soft limit SL _NS is set as the focusable range Rf 2 as shown in FIG. as shown, the range of infinity from the far side soft limit SL _iS to the closest end soft limit SL _NP, set as an in-focus range Rf3 of "infinite side limit mode", to select three focus limit mode Can. In the present embodiment, the "FULL mode" is set by setting the focus limit switch 38 to "FULL" shown in FIG. 2, and the "close side restriction mode" by setting it to "limit 1" shown in FIG. Is set, and the "infinity side limit mode" is set by adjusting to "limit 2" shown in FIG.

  When one of the focus limit modes is selected by the user, as shown in FIG. 4, focus limit information corresponding to the selected focus limit mode is transmitted from the lens barrel 3 to the camera body 2. Ru. The focus limit information is stored in the ROM of the lens control unit 37 for each focus limit mode.

For example, when the "FULL mode" shown in FIG. 3A is set by the focus limit switch 38, the lens control unit 37 sets the limit of the focusable range Rf1 in the "FULL mode" as the focus limit information. Transmits to the camera body 2 the infinite end soft limit SL _IP and the near end soft limit SL _NP which are positions (ends) and the corresponding infinite end design value DV _IP and the near end design value DV _NP Do.

When the “near-side limit mode” shown in FIG. 3B is set by the focus limit switch 38, the lens control unit 37 can focus on the “near-side limit mode” as focus limit information. Send infinitely far-end soft limit SL _IP and near-side soft limit SL _NS , which are limit positions in range Rf 2, and the corresponding far-end design value DV _IP and near-side design value DV _NS to camera body 2 .

Similarly, when the “infinity side limit mode” shown in FIG. 3C is set by the focus limit switch 38, the lens control unit 37 sets the focus limit information in the “infinity side limit mode”. In-focus side soft limit SL _IS and near-end soft limit SL _NP which are limit positions in the focusable range Rf 3 and the corresponding infinite-end design value DV _IS and the near-end design value DV _NP , respectively, the camera body Send to 2

In the present embodiment, the lens barrel 3 sets the near-side soft limit SL _NS , the near-side design value DV _NS , the infinity-side soft limit SL _IS , or the infinity-side design value DV _IS for each zoom lens position. The lens control unit 37 stores the near-side software limit SL _NS , the near-side design value DV _NS , the infinity-side software limit SL _IS , or the infinity-side design value DV _IS according to the zoom lens position from the ROM. It is read out and transmitted to the camera body 2 as focus limit information.

  Furthermore, in the present embodiment, for example, information indicating whether the in-focusable range can limit the in-focusable range in the lens barrel 3 as in the in-focusable ranges Rf2, Rf3 and the like, and Information on the focus limit mode selected by the user, such as “FULL mode” or “infinite side limit mode”, is stored in the ROM of the lens control unit 37 as focus limit information. The camera body 2 also receives, as focus limit information, information indicating whether or not the focusable range in the lens barrel 3 can be limited, and information on the focus limit mode selected by the user. Can be sent.

In FIG. 3A, the infinite distance design value DV _IP is on the infinity side of the lens positions which ensure that the lens barrel 3 is focused on the object in the “FULL mode”. This is the limit position, and in consideration of the design error of the lens barrel 3, the infinite far end soft limit SL _IP is provided on the infinity side of the infinite far end design value DV _IP , and this infinite far end soft limit SL _IP It is designed to enable detection of the in-focus position. Similarly, the closest end design value DV _NP is a limit position on the closest side of the lens positions that ensures that the lens barrel 3 is focused on the subject in design, and the design error of the lens barrel 3 Considering this, the near end soft limit SL _NP is provided on the near side of the near end design value DV _NP, and it is designed to be able to detect the in-focus position up to the near end soft limit SL _NP . .

Further, in FIG. 3B, the close design value _DVNS is the closest side of the lens positions that ensure that the lens barrel 3 is focused on the object in the “close limit mode”. of a limit position, taking into account the design errors of the lens barrel 3, than the close side design value DV _NS to the closest side soft limit SL _NS of the near side is designed so as to allow detection of the focusing position ing. Similarly, in FIG. 3C, the infinity design value DV _IS is a lens position that ensures that the lens barrel 3 is focused on the object in the “infinity limit mode”. infinite is the limit position of the distance side, taking into account the design errors of the lens barrel 3, indefinitely until infinity side soft limit SL _iS infinity side than the far side design value DV _iS, the detection of the focusing position It is designed to be possible.

  Further, as shown in FIG. 4, in addition to the focus limit information, information of the focus lens position is periodically transmitted from the lens barrel 3 to the camera body 2. Then, in the camera body 2, the lens drive amount of the focus lens 32 is calculated based on the focus limit information and the position information of the focus lens 32, and the calculated lens drive amount is transmitted to the lens barrel 3. FIG. 4 is a diagram for explaining an example of transmission and reception of information between the lens barrel 3 and the camera body 2.

  On the other hand, in the camera body 2, an imaging element 22 for receiving the light flux L1 from the imaging optical system is provided on a planned focal plane of the imaging optical system, and a shutter 23 is provided on the front surface thereof. The imaging device 22 is configured of a device such as a CCD or a CMOS, converts the received light signal into an electric signal, and sends it to the camera control unit 21. The photographed image information sent to the camera control unit 21 is sequentially sent to the liquid crystal drive circuit 25 and displayed on the electronic viewfinder (EVF) 26 of the observation optical system, and the release button (provided in the operation unit 28) When the full depression (not shown) is performed, the photographed image information is recorded in the camera memory 24 which is a recording medium. The camera memory 24 can use any of a removable card type memory and a built-in type memory.

  The camera body 2 is provided with an observation optical system for observing an image captured by the image sensor 22. The observation optical system of the present embodiment includes an electronic viewfinder (EVF) 26 composed of a liquid crystal display element, a liquid crystal drive circuit 25 for driving the same, and an eyepiece lens 27. The liquid crystal drive circuit 25 reads the photographed image information picked up by the image pickup device 22 and sent to the camera control unit 21, and drives the electronic viewfinder 26 based on this. Thus, the user can observe the current captured image through the eyepiece 27. A liquid crystal display may be provided on the back surface of the camera body 2 or the like instead of or in addition to the above observation optical system according to the optical axis L2, and a photographed image may be displayed on the liquid crystal display.

  A camera control unit 21 is provided in the camera body 2. The camera control unit 21 is electrically connected to the lens control unit 37 by the electrical signal contact unit 41 provided in the mount unit 4, receives lens information from the lens control unit 37, and drives the lens to the lens control unit 37. Send information such as the amount and aperture diameter. In addition, as described above, the camera control unit 21 reads out the pixel output from the imaging device 22 and generates image information by performing predetermined information processing on the read out pixel output as necessary, and the generated image information Are output to the liquid crystal drive circuit 25 and the memory 24 of the electronic viewfinder 26. Further, the camera control unit 21 controls the entire camera 1 such as correction of image information from the image pickup device 22 and detection of a focusing state of the lens barrel 3, an aperture adjusting state, and the like.

  Further, in addition to the above, the camera control unit 21 detects the focus state of the optical system by the contrast detection method. Specifically, the camera control unit 21 reads the output of the imaging pixel 221 of the imaging element 22, and calculates the focus evaluation value based on the read pixel output. The focus evaluation value can be obtained, for example, by extracting the high frequency component of the image output from the imaging pixel 221 of the imaging device 22 using a high frequency transmission filter. It can also be determined by extracting high frequency components using two high frequency transmission filters having different cutoff frequencies.

  Then, the camera control unit 21 sends a control signal to the lens control unit 37 to drive the focus lens 32 at a predetermined sampling interval (distance) to obtain a focus evaluation value at each position, and the focus evaluation value is maximum. The focus detection by the contrast detection method is performed to obtain the position of the focus lens 32 as the in-focus position. It should be noted that, for example, when the focus evaluation value is calculated while driving the focus lens 32, the in-focus position is further lowered twice after the focus evaluation value rises twice. It can obtain | require by performing calculations, such as an interpolation method, using five focus evaluation values.

  Here, FIG. 5 is a diagram for explaining an example of the focus detection method by the contrast detection method. In the example shown in FIG. 5, the focus lens 32 is located at P0 shown in FIG. 5. First, the focus lens 32 is driven from P0 to a predetermined search start position (position P1 in FIG. 5). Initial driving is performed. Then, while the focus lens 32 is driven from the infinite distance side to the near side from the search start position (position P1 in FIG. 5), the search is performed to obtain the focus evaluation value by the contrast detection method at predetermined intervals. Driving is performed. Then, when the focus lens 32 is moved to the position P2 shown in FIG. 5, the peak position of the focus evaluation value (the position P3 in FIG. 5) is detected as the in-focus position, and the detected in-focus position Focusing drive for driving the focus lens 32 is performed up to (position P3 in FIG. 5).

  The operation unit 28 is an input switch for a user such as a shutter release button to set various operation modes of the camera 1, and can switch between an auto focus mode and a manual focus mode. The various modes set by the operation unit 28 are sent to the camera control unit 21, and the operation of the entire camera 1 is controlled by the camera control unit 21. Further, the shutter release button includes a first switch SW1 which is turned on when the button is half pressed, and a second switch SW2 which is turned on when the button is fully pressed.

  Next, an operation example of the camera 1 according to the present embodiment will be described. FIG. 6 is a flowchart showing the operation of the camera 1.

  First, in step S101, the camera control unit 21 acquires focus limit information. In the present embodiment, focus limit information corresponding to the focus limit mode set in the lens barrel 3 is periodically transmitted from the lens control unit 37 to the camera control unit 21 at a constant interval, and the camera control unit 21 Focus limit information corresponding to the currently set focus limit mode can be acquired from the lens control unit 37.

For example, as shown in FIG. 3A, when the “FULL mode” is set by the focus limit switch 38, the lens control unit 37 sets the focus possible range in the “FULL mode” as the focus limit information. Information including an infinite far-end soft limit SL _IP and a near-end soft limit SL _NP , which are limit positions (ends) of Rf 1, is periodically transmitted to the camera body 2. Thereby, the camera control unit 21 can acquire focus limit information including the infinity end soft limit SL _IP and the near end soft limit SL _NP .

Similarly, as shown in FIG. 3B, when the “near-side limit mode” is set by the focus limit switch 38, the camera control unit 21 sets the focusable range in the “near-side limit mode”. Information including an infinite far-end soft limit SL _IP and a near-side soft limit SL _NS which are limit positions of Rf 2 is acquired as focus limit information, and as shown in FIG. When the "infinity side limit mode" is set, the infinity side soft limit SL _IS and the near end soft limit SL _NP which are the limit positions of the focusable range Rf3 in the "infinity side limit mode" Can be obtained as focus limit information.

  Even when the focus limit mode is the same, the focusable ranges Rf1 to Rf3 of the focus lens 32 may be different from each other depending on the type of the lens barrel 3. Therefore, the camera control unit 21 acquires focus limit information unique to the lens barrel 3 from the lens barrel 3.

  In step S102, as shown in FIGS. 3A to 3C, calculation of the focusable range of the focus lens 32 is performed by the camera control unit 21 based on the focus limit information acquired in step S101. .

For example, as shown in FIG. 3A, the camera control unit 21 is set to the “FULL mode”, and the infinity far end soft limit SL _IP and the near end soft limit SL _NP are acquired as the focus limit information. If it is, the range from the infinite end soft limit SL _IP to the near end soft limit SL _NP is calculated as the focusable range Rf1.

Similarly, as shown in FIG. 3B, the camera control unit 21 is set to the “near-side limit mode”, and the far-end soft limit SL _IP and the near-side soft limit SL _NS are used as focus limit information. Is acquired, the range from the infinity end soft limit SL _IP to the near-side soft limit SL _NS is calculated as the focusable range Rf2. Further, as shown in FIG. 3C, the “infinite distance side limit mode” is set in the camera control unit 21. As the focus limit information, the infinite distance side soft limit SL _IS and the near end soft limit SL are obtained. If _{the NP} is acquired, a range of infinity from the far side soft limit _{SL iS} to the closest end soft limit _{SL NP,} calculated as an in-focus range Rf3.

Depending on the type of the lens barrel 3, the focus limit function may not be obtained, and the focus limit information may not be obtained from the lens barrel 3. In such a case, as shown in FIG. 3A, the camera control unit 21 calculates the range Rf1 from the infinite end soft limit SL _IP to the near end soft limit SL _NP as the focusable range. be able to.

  In step S103, the camera control unit 21 calculates a drive range of the focus lens 32 for performing focus detection by the contrast detection method as a search drive range. FIG. 7 is a diagram showing an example of a search drive range. As shown in FIGS. 7A to 7C, search driving ranges Rs1 to Rs3 include focusable ranges Rf1 to Rf3 shown in FIGS. 3A to 3C, and focusable range Rf1. It is calculated as a range wider than Rf3.

Here, in focus detection by the contrast detection method, as described above, the camera control unit 21 calculates the focus evaluation value at a predetermined sampling interval while driving the focus lens 32. Then, in order to detect the peak position (focus position) of the focus evaluation value by the contrast detection method, as shown in FIG. 5, the focus lens 32 is driven to a position (P2 in FIG. 5) beyond the peak position. It is necessary to calculate the focus evaluation value. Therefore, for example, by contrast detection method, in order to detect the peak position of the focus evaluation value (focus position) in an infinite far soft limit SL _IP is infinity than the focus lens 32 infinitely far soft limit SL _IP It is necessary to drive to the side to calculate the focus evaluation value. Similarly, for example, in order to detect the peak position (focus position) of the focus evaluation value at the near end soft limit SL _NP by the contrast detection method, the focus lens 32 is closer than the near end soft limit SL _NP. It is necessary to drive to the side to calculate the focus evaluation value.

Therefore, when the focus limit mode is “FULL mode”, the camera control unit 21 starts from the lens position on the infinity side of the infinity far-end soft limit SL _IP as shown in FIG. 7A. A range to the lens position closer to the near-end soft limit SL _NP is calculated as a search drive range Rs1. For example, in the present embodiment, as shown in FIG. 5, when the focus evaluation value rises twice and then descends two more times, a peak of the focus evaluation value is calculated using these focus evaluation values. Therefore, the camera control unit 21 is closer than the closest end soft limit SL _NP from the lens position where it is possible to calculate two focus evaluation values on the infinity side of the infinite end soft limit SL _IP. A range up to the lens position where it is possible to calculate two focus evaluation values on the side can be calculated as a search drive range Rs1.

In addition, when the focus limit mode is the “near-side limit mode”, the camera control unit 21 starts from the lens position on the infinity side of the infinity far-end soft limit SL _IP as shown in FIG. 7B. the range up to the lens position of the near side than the near side soft limit SL _NS, calculated as a search drive range Rs2. Similarly, the camera control unit 21, when the focus limit mode is "infinite side limit mode", as shown in FIG. 7 (C), the infinity side software limit SL infinity side of the lens than _IS A range from the position to the lens position closer to the near end than the soft limit SL _NP is calculated as a search drive range Rs3.

  In step S104, the camera control unit 21 calculates the first target velocity V1. Specifically, the camera control unit 21 sets the lens driving speed of the focus lens 32 at the time of focus detection by the contrast detection method to the first target based on the depth of field of the optical system and the frame rate of the imaging device 22. Calculated as the velocity V1.

  Here, when focus detection is performed by the contrast detection method, the image plane by the optical system is moved in the optical axis direction by driving the focus lens 32, and thereby, a plurality of focus evaluation values in different image planes are obtained. A lens position at which the focus evaluation value reaches a peak is calculated as the in-focus position. However, if the moving speed of the image plane is made too fast, the distance between the image planes for which the focus evaluation value is calculated becomes too large, and it becomes impossible to appropriately detect the in-focus position. On the other hand, if the moving speed of the image plane is made too slow, the time required for focus detection increases, and the influence of disturbance such as camera shake increases. Therefore, in the present embodiment, the camera control unit 21 sets, for example, the sampling interval of the focus evaluation value suitable for detecting the in-focus position as three times the depth of field, and calculates the focus evaluation value. The movement speed of the image plane at which the interval is three times the depth of field is calculated as the first target speed V1.

For example, when an image of one point imaged by one pixel of the imaging device 22 is blurred, and an image of the one point is imaged at pixels adjacent to the left and right of the one pixel (ie, one point When the image of (1) is blurred, even if a single-point image is captured over three pixels, the human eye may be able to distinguish only one point. In this case, it can be determined that this one-point image exists within the depth of field. Therefore, in the present embodiment, the camera control unit 21 defines, as the depth of field D, the depth at which an image of one point is captured within the range of three pixels as shown in the following formula (1). The depth of field D is obtained based on the width W of the direction and the F value.
Depth of field D = 3 pixels × width in the arrangement direction of pixels W × F value (1)
For example, when the width in the array direction of each pixel is 5 μm and the F value is 5.6, the camera control unit 21 calculates the depth of field as 84 μm based on the above equation (1). be able to.

Then, as shown in the following equation (2), the camera control unit 21 calculates the focal point evaluation value on the basis of the depth of field D and the frame rate fps so that the distance between the image planes is the depth of field. The moving speed of the image plane that is tripled is calculated as the first target speed V1.
First target velocity V1 = 3 × depth of field D × frame rate fps (2)
For example, when the depth of field is 84 μm and the frame rate is 200 fps, the camera control unit 21 obtains the first target velocity V1 as 50.4 mm / s based on the equation (2). Can.

  In the above equation (1), when an image at one point is blurred and captured over a plurality of pixels, the number of pixels considered to be within the depth of field is not limited to three pixels. It can set up suitably based on composition of each image pick-up pixel. Further, in the above equation (2), the movement speed of the image plane at which the distance between the image planes for which the focus evaluation value is calculated is three times the depth of field is calculated as the movement speed of the image plane suitable for focus detection. However, the present invention is not limited to this configuration. For example, the movement speed of the image plane at which the distance between the image planes for which the focus evaluation value is calculated is twice or four times the depth of field is suitable for focus detection. The movement speed of the image plane may be calculated.

  Next, in step S105, the camera control unit 21 calculates the second target velocity V2. Specifically, the camera control unit 21 sets the moving speed of the image plane capable of calculating a focus evaluation value of a predetermined number or more necessary for focus detection within the search drive range set in step S103 as the second target. Calculated as the velocity V2.

  Here, in the present embodiment, the focus evaluation value is calculated while driving the focus lens 32, and after the focus evaluation value rises twice and then falls twice further, these five points are focused. The peak of the focus evaluation value is calculated using the evaluation value. Therefore, in the present embodiment, when the focus evaluation value of at least five points can not be detected in the search drive range calculated in step S103, the peak of the focus evaluation value can not be detected.

Therefore, in the present embodiment, as shown in the following equation (3), the camera control unit 21 determines the size R (unit: number of pulses) of the search drive range and the number of minimum focus evaluation values required for focus detection. The movement speed of the image plane capable of calculating a focus evaluation value of a predetermined number N or more within the focusable range based on N, the lens resolution coefficient γ (unit: pulse number / mm), and the frame rate fps The maximum velocity of the velocity is calculated as the second target velocity V2.
Second target speed V2 = size of search drive range R / number of focus evaluation values N / lens decomposition coefficient γ × frame rate fps (3)
The lens decomposition coefficient γ is a value indicating the correspondence between the drive amount of the focus lens 33 and the movement amount of the image plane, and is, for example, the ratio between the drive amount of the focus lens 33 and the movement amount of the image plane . The lens decomposition coefficient γ is a coefficient determined by the design of the optical system, the structure of the lens barrel 3 and the performance of the focus lens drive motor 36, and the camera control unit 21 controls each lens barrel 3. The unique lens resolution coefficient γ can be acquired from the lens control unit 37.

For example, the size of the focusable range from infinite end soft limit SL _IP to near end soft limit SL _NP is 50 pulses, and the number N of minimum focus evaluation values required for focus detection is 5 points. When the lens resolution coefficient γ is 80 pulses / mm and the frame rate is 200 fps, the camera control unit 21 calculates the second target velocity V2 as 50/5/80 × 200 = 25 mm / s. Can.

  Then, in step S106, the slower one of the first target velocity V1 calculated in step S104 and the second target velocity V2 calculated in step S105 is detected by the camera control unit 21 when the focus is detected by the contrast method. The target speed for driving the focus lens 32 is set. For example, in the above-described example, the first target velocity V1 is calculated as 50.4 mm / s, and the second target velocity V2 is calculated as 25 mm / s. In this case, the camera control unit 21 can set the second target speed V2 as the driving target speed. When the first target speed V1 and the second target speed V2 are the same speed, the camera control unit 21 can set the second target speed V2 as the driving target speed.

  In step S107, the camera control unit 21 starts calculation of the focus evaluation value. In the present embodiment, the calculation process of the focus evaluation value is performed by reading out the pixel output of the imaging pixel 221 of the imaging device 22, extracting the high frequency component of the read pixel output using a high frequency transmission filter, and integrating it. To be done. The focus evaluation value is calculated only by the pixel output of the imaging pixel 221 corresponding to the selected focus detection position when a specific focus detection position is selected by the manual operation of the user or by the subject recognition mode or the like. May be read out. The calculation process of the focus evaluation value is repeatedly performed at predetermined intervals.

  In step S108, the camera control unit 21 determines whether the shutter release button provided on the operation unit 28 has been half-pressed (the first switch SW1 is turned on). If the first switch SW1 is turned on, the process proceeds to step S109. On the other hand, when the first switch SW1 is not turned on, step S108 is repeated until the first switch SW1 is turned on. That is, the calculation process of the focus evaluation value is repeatedly executed while the driving of the focus lens 32 is stopped until the first switch SW1 is turned on.

  In step S109, the camera control unit 21 performs processing for starting driving of the focus lens 32. Specifically, the camera control unit 21 starts drive control of the focus lens 32 so as to drive the focus lens 32 at the drive target speed set in step S106 in the search drive range calculated in step S103. Do.

  Specifically, the camera control unit 21 instructs the lens control unit 37 to start driving the focus lens 32 at the drive target speed set in step S106 in the search drive range calculated in step S103. Send out Thereby, the lens control unit 37 drives the focus lens drive motor 36 based on the command from the camera control unit 21. As a result, the focus lens 32 can be driven at the drive target speed in the search drive range. it can. The search drive of the focus lens 32 may be performed from the infinity end to the near end, or may be performed from the near end to the infinity end.

  In step S110, the camera control unit 21 determines whether the peak position (focus position) of the focus evaluation value has been detected. If the in-focus position can not be detected, the process proceeds to step S113. If the in-focus position can be detected, the process proceeds to step S111.

  In step S111, since it is determined that the in-focus position has been detected, the camera control unit 21 performs in-focus driving to drive the focus lens 32 to the in-focus position. Then, after the focus lens 32 is driven to the in-focus position, the process proceeds to step S112, and in-focus display is performed. The in-focus display is performed by, for example, the electronic viewfinder 26.

  On the other hand, if it is determined in step S110 that the in-focus position can not be detected, the process proceeds to step S113. In step S113, it is determined by the camera control unit 21 whether or not detection of the peak position (focus position) of the focus evaluation value has been performed over the entire search drive range calculated in step S103. If the detection of the peak position (focus position) of the focus evaluation value is not performed in the entire search drive range, the process returns to step S110, and the search drive is continuously performed. On the other hand, when the peak position (in-focus position) of the focus evaluation value is detected in the entire search drive range, it is determined that the in-focus position can not be detected, and the process proceeds to step S114. Display is done. The out-of-focus display is also performed by the electronic viewfinder 26, for example.

  As described above, the operation of the camera 1 according to the present embodiment is performed.

  As described above, in the present embodiment, the movement speed of the image plane at which the sampling interval of the focus evaluation value becomes an interval suitable for focus detection is calculated as the first target velocity V1 and necessary for focus detection within the search drive range. The moving speed of the image plane capable of calculating a number of focus evaluation values is calculated as the second target speed V2. Then, the first target velocity V1 and the second target velocity V2 are compared, the slower one is set as the drive target velocity, and the focus lens 32 is driven so that the movement velocity of the image surface becomes the drive target velocity. . Thereby, in the present embodiment, the moving speed of the image plane accompanying the driving of the focus lens 32 is not the speed at which the number of focus evaluation values necessary for focus detection can be calculated within the focusable range. It can be effectively prevented that the peak of the focus evaluation value (the in-focus position) can not be detected properly. Further, in the present embodiment, the movement speed of the image plane accompanying the driving of the focus lens 32 is not the speed at which the sampling interval of the focus evaluation value becomes an interval suitable for focus detection. It can be effectively prevented that the position can not be displayed with high accuracy.

  The embodiments described above are described to facilitate the understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents that fall within the technical scope of the present invention.

  For example, in the embodiment described above, the configuration for calculating the first target velocity V1 based on the depth of field as illustrated in the above equation (2) is exemplified, but the present invention is not limited to this configuration. A table indicating the relationship between the depth of field (or F value) of the system and the second target velocity V2 is stored in advance in the ROM of the camera control unit 21, and the depth of field (or F value) of the optical system From this, the first target velocity V1 can be calculated. Further, the first target speed V1 may be stored in advance in the ROM of the camera control unit 21 as a fixed value determined in advance.

  Further, in addition to the above-described embodiment, when the second target speed V2 based on the focus limit information is set as the drive target speed, the camera control unit 21 controls the rear monitor or the electronic view provided in the camera body 2. The user may be notified via the finder 26 that the focus lens 32 is driven at the second target velocity V2. This makes it possible to reduce the user's discomfort due to the drive speed of the focus lens 32 being set to the second target speed V2 different from the first target speed V1.

  Furthermore, in the embodiment described above, the configuration for calculating the second target velocity V2 based on the search drive range of the focus lens 32 as illustrated in the above equation (3) is exemplified, but the present invention is not limited to this configuration. For example, the second target velocity V2 may be calculated using the focusable range shown in FIG. 3 instead of the search drive range of the focus lens 32 in the above equation (3).

  In addition, although the configuration for performing focus detection by the contrast detection method has been illustrated in the above-described embodiment, the present invention is not limited to this configuration. For example, focus detection using the contrast detection method is provided with the imaging device 22a shown in FIG. It may be configured to perform focus detection by a phase difference detection method. FIG. 8 is an enlarged view of an essential part of an imaging surface of an imaging device 22a according to another embodiment. For example, the image pickup device 22a shown in FIG. 8 has an image pickup device 221 for image pickup and focus detection pixels 222a and 222b for phase difference detection, and outputs the respective focus detection pixels 222a and 222b as distance measurement pupils By collecting the data on the intensity distribution of a pair of images by combining them into output groups corresponding to the image, and performing image shift detection operation processing such as correlation operation processing or phase difference detection processing on this intensity distribution data, The image shift amount can be detected by the phase difference detection method. Then, a conversion operation according to the distance between the center of gravity of the pair of distance measuring pupils is performed on the obtained image shift amount to obtain the current focal plane with respect to the planned focal plane (the focal point corresponding to the position of the microlens array on the planned focal plane). The deviation of the focal plane in the detection area, that is, the defocus amount can be determined, and the focus state of the optical system can be adjusted by driving the focus lens 32 based on the calculated defocus amount. it can.

  Further, by providing the imaging element 22a shown in FIG. 8, a scanning operation may be performed in which focus detection by the contrast detection method and focus detection by the phase difference detection method are simultaneously performed. In this case, the scan drive range of the focus lens 32 in the scan operation can be set in the same manner as the search drive range of the embodiment described above, and the number of focus evaluation values necessary for focus detection is calculated within the scan drive range. As can be done, the second target speed can be calculated.

Further, in the embodiment described above, when the “FULL mode” is set, as shown in FIG. 7A, from the lens position on the infinity side of the infinity far-end soft limit SL _IP , Although the configuration to set the range up to the lens position closer to the end soft limit SL _NP as the search drive range Rs1 has been exemplified, the present invention is not limited to this configuration. For example, as shown in FIG. The range from the far end soft limit SL _IP to the near end soft limit SL _NP may be set as the search drive range Rs1. FIG. 9 is a view showing another example of the search drive range.

Similarly, when the “near-side limit mode” is set, as shown in FIG. 7B, the near-side soft limit SL is taken from the lens position on the infinity side of the far-end soft limit SL _{IP. Although} the configuration to calculate the range up to the lens position closer to _NS than _NS as the search drive range Rs2 has been illustrated, the present invention is not limited to this configuration. For example, as shown in FIG. A range from SL _IP to a lens position closer to the near side soft limit SL _NS may be calculated as a search drive range Rs2. In addition, when the “infinity side restriction mode” is set, as shown in FIG. 9C, from the lens position on the infinity side with respect to the infinity side soft limit SL _IS , the near end soft limit The range up to SL _NP may be calculated as the search drive range Rs3.

  Further, in the above-described embodiment, three modes “FULL mode”, “close side restriction mode”, and “infinity side restriction mode” can be set, and predetermined focusable ranges Rf1 and Rf2 can be set. , And Rf3 can be set, respectively. However, the present invention is not limited to this configuration. For example, a range desired by the user may be set as a focusable range.

  For example, as shown in FIG. 10, the camera lens barrel 3a is provided with a focus limit switch 38 'and a preset storage switch 39, and the user desires the state with the focus limit switch 38' set to "preset". By pressing the preset storage switch 39 at the infinite distance side limit position (end portion) and the near limit position (end portion) of the focusable range to be focused, the user can focus on the lens barrel 3 as desired by the user. The possible range (preset range) can be stored, and then, when the user sets the focus limit switch 38 'to "preset", the focusable range can be limited to the preset range set by the user.

In the embodiment described above, the lens resolution coefficient γ is defined as the drive amount of the focus lens 33 / the movement amount of the image plane (unit: number of pulses / mm), but it is not limited to this configuration. For example, the lens resolution coefficient γ may be defined by the amount of movement of the image plane / the amount of drive of the focus lens 33 (mm / number of pulses). In this case, the second target velocity V2 can be calculated based on the following equation (4) instead of the equation (3).
Second target velocity V2 = size of search driving range R / number of focus evaluation values N × lens decomposition coefficient γ × frame rate fps (4)

  The camera 1 according to the embodiment described above is not particularly limited. For example, the present invention may be applied to other optical devices such as a digital video camera, a lens-integrated digital camera, and a camera for a mobile phone.

Reference Signs List 1 digital camera 2 camera body 21 camera control unit 22 imaging device 3 lens barrel 32 focus lens 36 focus lens driving motor 37 lens control unit

Claims (4)

A focus detection unit that detects an in-focus state of an optical system including an aperture stop for limiting a light flux and a focusing lens;
A receiver configured to receive drive range information of the focusing lens from a lens barrel having the optical system ;
An imaging device that outputs an imaging data in a first time interval and capturing an image of the optical system,
Focus detection is performed for the first target speed calculated based on the first time interval and the information on the aperture stop, or the second target speed calculated based on the driving range information and the first time interval. A determination unit that determines a driving target speed for driving the focusing lens at times;
A transmitter configured to transmit information on the target drive speed determined by the determination unit to the lens barrel. A camera body according to claim 1, wherein
A camera body that calculates the first target velocity based on information on the aperture stop of the optical system and a size of a pixel of the imaging device ; A camera body according to claim 1 or 2,
  A camera body further comprising notification means for notifying a user of driving the focusing lens at the second target speed when the second target speed is determined as the drive target speed. An imaging apparatus comprising the camera body according to any one of claims 1 to 3.

Images