JP2019144573A - Imaging device - Google Patents

Abstract

To provide an imaging device that can properly control a drive of a focus adjustment lens.SOLUTION: An imaging device comprises: an image pick-up element that has a focus lens and captures an image by an optical system to output a signal; a contrast calculation unit that calculates an evaluation value about a contrast of the signal as causing the focus lens to move; a setting unit that sets drive range information on the focus lens; and a speed setting unit that sets a moving speed of the focus lens calculating the evaluation value at any slow speed of a first speed to be calculated by an aperture value of the optical system ans a second speed to be calculated based on the aperture value of the optical system, and calculates the evaluation value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging apparatus.

  2. Description of the Related Art Conventionally, a technique for limiting the driving range of a focus adjustment lens at the time of focus detection using a lens barrel that can limit the driveable range of the focus adjustment lens is known (for example, see Patent Document 1).

JP 2006-126330 A

  When driving the focus adjustment lens and calculating the evaluation value related to the contrast of the image by the optical system, and detecting the lens position where the evaluation value reaches the peak as the in-focus position, when performing focus detection by the contrast detection method, a predetermined number By using the above evaluation values (for example, 5 points or more) and performing calculations such as an interpolation method, the lens position at which the evaluation value peaks is detected. However, if the drive range of the focus adjustment lens is limited as in the prior art, depending on the drive speed of the focus adjustment lens instructed from the camera body, the drive speed of the focus adjustment lens becomes too high. In the limited driveable range of the focus adjustment lens, the number of evaluation values (for example, five points) necessary for focus detection cannot be calculated, and as a result, the focus position may not be detected properly.

  The present invention solves the above problems by the following means.

[1] An image pickup apparatus according to the present invention has a focus lens, picks up an image by an optical system and outputs a signal, and contrast for calculating an evaluation value related to the contrast of the signal while moving the focus lens A calculation unit; a setting unit that sets driving range information of the focus lens; and a first speed that is calculated based on an aperture value of the optical system, and a speed of movement of the focus lens that calculates the evaluation value. A speed setting unit that sets a slower speed of the second speed calculated based on the driving range information and calculates the evaluation value.
[2] In the invention related to the imaging apparatus, the imaging device performs imaging a plurality of times with a certain time, and the speed setting unit performs the first operation based on the aperture value of the optical system and the certain time. One speed may be calculated, and the second speed may be calculated based on the driving range information and the certain time.
[3] In the invention relating to the imaging apparatus, the setting unit determines the driving range of the focus lens based on information about a restriction on a driving range of the focus lens received from a lens barrel having the optical system. It can be constituted as follows.
[4] In the invention relating to the imaging apparatus, the speed setting unit may be configured to determine the second speed so that a plurality of the evaluation values can be calculated within the driving range.
[5] In the invention relating to the imaging apparatus, the speed setting unit may be configured to calculate the first speed based on a pixel size of the imaging element.
[6] In the invention relating to the imaging apparatus, the speed setting unit may be configured to calculate the first speed based on information on a moving distance of the image of the optical system with respect to a moving distance of the focus lens. it can.
[7] In the invention relating to the imaging apparatus, based on the signal, a deviation between the optical system and the imaging surface of the imaging element based on a positional deviation amount of an image due to light passing through different parts of the optical system. A defocus calculation unit that calculates a value related to the shift, a calculation of a value related to the deviation by the defocus calculation unit while moving the focus lens at a speed set by the speed setting unit, and the evaluation value by the contrast calculation unit And a control unit that performs the calculation of.
[8] In the invention relating to the imaging apparatus, the speed setting unit may include a display unit that indicates whether the first speed is set or the second speed is set.
[9] The invention relating to the imaging apparatus can be configured to have a lens barrel having the optical system.

  According to the present invention, it is possible to appropriately control the driving of the focus adjustment lens.

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 illustrating an example of a focusable range of the focus lens. FIG. 4 is a diagram for explaining an example of exchange of information between the lens barrel and the camera body. FIG. 5 is a diagram for explaining an example of a focus detection method using a contrast detection method. FIG. 6 is a flowchart showing the operation of the camera of this embodiment. FIG. 7 is a diagram illustrating an example of the 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 diagram illustrating another example of the search drive range. FIG. 10 is a diagram illustrating another example of an external view of a lens barrel.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a main part configuration diagram showing a digital camera 1 according to this embodiment of the present invention. A digital camera 1 according to the present embodiment (hereinafter simply referred to as a camera 1) includes 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. Yes.

  The lens barrel 3 is an interchangeable lens that can be attached to and detached from the camera body 2. As shown in FIG. 1, the lens barrel 3 includes a photographic optical system including lenses 31, 32, 33 and a diaphragm 34.

  The lens 32 is a focus lens, and can adjust the focal length of the photographing optical system by moving in the direction of the optical axis L1. 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.

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

  The diaphragm 34 is configured such that the aperture diameter around the optical axis L1 can be adjusted in order to limit the amount of light flux that passes through the photographing optical system and reaches the image sensor 22 and to adjust the blur amount. The adjustment of the aperture diameter by the diaphragm 34 is performed, for example, by sending 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 a manual operation by the operation unit 28 provided in the camera body 2. The aperture diameter of the aperture 34 is detected by an aperture sensor (not shown), and the lens controller 37 recognizes the current aperture diameter.

  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 a 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 a focus limit switch 38 for setting a focusable range, and the user operates the focus limit switch 38, By selecting the focus limit mode, a focusable range can be selected. FIG. 2 is an external view of the lens barrel 3 according to this embodiment.

FIG. 3 is a diagram illustrating an example of a focusable range that can be set in the present embodiment. In the present embodiment, as shown in FIG. 3A, a “FULL mode” in which a range from the infinitely far end soft limit SL _IP to the very close end soft limit SL _NP is set as a focusable range Rf1, As shown in FIG. 3 (B), the “closest limit mode” for setting the range from the infinitely far end soft limit SL _IP to the closest soft limit SL _NS as the focusable range Rf2, and FIG. As shown in the figure, select the three focus limit modes of “infinity limit mode” that sets the range from the infinity side soft limit SL _IS to the near end soft limit SL _NP as the focusable range Rf3. Can do. 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 limit mode” is set by adjusting “limit 1” shown in FIG. 2. Is set, and the “infinity side limit mode” is set by matching with “limit 2” shown in FIG.

  When one of the focus limit modes is selected by the user, focus limit information corresponding to the selected focus limit mode is transmitted from the lens barrel 3 to the camera body 2 as shown in FIG. The The focus limit information is stored in a ROM provided in 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. The infinity end soft limit SL _IP and the near end soft limit SL _NP , which are positions (ends), and the corresponding infinity end design value DV _IP and the nearest end design value DV _NP are transmitted to the camera body 2. To do.

In addition, when the “closest limit mode” shown in FIG. 3B is set by the focus limit switch 38, the lens control unit 37 can focus in the “closest limit mode” as the focus limit information. The limit position of the range Rf2, the infinity end soft limit SL _IP and the near side soft limit SL _NS, and the infinity end design value DV _IP and the near side design value DV _NS corresponding thereto are transmitted to the camera body 2. .

Similarly, when the “infinity limit mode” shown in FIG. 3C is set by the focus limit switch 38, the lens control unit 37 uses the “infinity limit mode” as the focus limit information. 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, and the corresponding infinity side design value DV _IS and the close end design value DV _NP 2 to send.

In the present embodiment, the lens barrel 3 uses 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 soft limit SL _NS , the close side design value DV _NS , the infinity side soft limit SL _IS , or the infinity side design value DV _IS corresponding to the zoom lens position from the ROM. Read and transmit to the camera body 2 as focus limit information.

  Furthermore, in the present embodiment, for example, information indicating whether or not the focusable range can limit the focusable range in the lens barrel 3, such as the focusable ranges Rf2 and Rf3, and The information on the focus limit mode selected by the user, such as “FULL mode” and “infinity limit mode”, is stored in the ROM of the lens control unit 37 as focus limit information. As the 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 are also transmitted from the lens barrel 3 to the camera body 2. Can be sent.

In FIG. 3A, the infinitely far end design value DV _IP is set to the infinity side of the lens position that guarantees that the lens barrel 3 is designed to focus on the subject in the “FULL mode”. a limit position, taking into account the design errors of the lens barrel 3, an infinite far soft limit SL _IP provided on the infinite side of the infinity end design value DV _IP, if up to the infinite far soft limit SL _IP Designed to enable detection of the focal position. Similarly, the near-end design value DV _NP is a limit position on the near side of the lens positions that guarantees that the lens barrel 3 is focused on the subject in design, and the design error of the lens barrel 3 is reduced. In consideration, the near end soft limit SL _NP is provided closer to the near end design value DV _{NP, and the in-} focus position can be detected up to the near end soft limit SL _NP . .

In FIG. 3B, the near side design value DV _NS is the closest side of the lens positions that guarantees that the lens barrel 3 is designed to focus on the subject in the “close side limit mode”. In consideration of the design error of the lens barrel 3, it is designed so that the in-focus position can be detected from the closest design value DV _NS to the closest soft limit SL _NS. ing. Similarly, in FIG. 3 (C), the infinity side design value DV _IS is the "infinity side restriction mode", the lens barrel 3, the design, of the lens position to ensure that focus on the subject The focus position can be detected from the limit value on the infinity side to the infinity-side soft limit SL _IS on the infinity side from the design value DV _IS on the infinity side in consideration of the design error of the lens barrel 3. It is designed to be possible.

  Further, as shown in FIG. 4, in addition to the focus limit information, information on the focus lens position is periodically transmitted from the lens barrel 3 to the camera body 2. In the camera body 2, the lens driving 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 driving amount is transmitted to the lens barrel 3. FIG. 4 is a diagram for explaining an example of information exchange between the lens barrel 3 and the camera body 2.

  On the other hand, the camera body 2 is provided with an imaging element 22 that receives the light beam L1 from the photographing optical system on a planned focal plane of the photographing optical system, and a shutter 23 is provided on the front surface thereof. The image sensor 22 is composed of a device such as a CCD or CMOS, converts the received optical signal into an electrical signal, and sends it to the camera control unit 21. The captured 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 a release button ( When (not shown) is fully pressed, the photographed image information is recorded in the camera memory 24 which is a recording medium. The camera memory 24 can be either a removable card type memory or a built-in memory.

  The camera body 2 is provided with an observation optical system for observing an image picked up by the image pickup device 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 driving circuit 25 that drives the electronic viewfinder (EVF) 26, and an eyepiece lens 27. The liquid crystal drive circuit 25 reads the captured image information captured by the image sensor 22 and sent to the camera control unit 21, and drives the electronic viewfinder 26 based on the read image information. Thereby, the user can observe the current captured image through the eyepiece lens 27. Note that, instead of or in addition to the observation optical system using the optical axis L2, a liquid crystal display may be provided on the back surface of the camera body 2, 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 through an electric signal contact unit 41 provided in the mount unit 4, receives lens information from the lens control unit 37, and drives the lens control unit 37 to drive the lens. Send information such as volume and aperture diameter. The camera control unit 21 reads out the pixel output from the image sensor 22 as described above, generates image information by performing predetermined information processing on the read out pixel output as necessary, and generates the generated image information. Is output to the liquid crystal driving circuit 25 and the memory 24 of the electronic viewfinder 26. The camera control unit 21 controls the entire camera 1 such as correction of image information from the image sensor 22 and detection of a focus adjustment state and an aperture adjustment state of the lens barrel 3.

  In addition to the above, the camera control unit 21 detects the focus state of the optical system using a contrast detection method. Specifically, the camera control unit 21 reads the output of the imaging pixel 221 of the imaging element 22 and calculates a focus evaluation value based on the read pixel output. This focus evaluation value can be obtained, for example, by extracting a high-frequency component of an image output from the imaging pixel 221 of the imaging element 22 using a high-frequency transmission filter. It can also be obtained 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 in which the position of the focus lens 32 is determined as the in-focus position. Note that this in-focus position is obtained when, for example, when the focus evaluation value is calculated while driving the focus lens 32, the focus evaluation value rises twice and then moves down twice. It can be obtained by performing calculations such as interpolation using five focus evaluation values.

  Here, FIG. 5 is a diagram for explaining an example of a focus detection method using a 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 drive is performed. Then, the focus lens 32 is driven from the search start position (position P1 in FIG. 5) from the infinity side to the close side, and the focus evaluation value is acquired by the contrast detection method at a predetermined interval. Driving is performed. When the focus lens 32 is moved to the position P2 shown in FIG. 5, the peak position of the focus evaluation value (position P3 in FIG. 5) is detected as the focus position, and the detected focus position is detected. Focusing driving for driving the focus lens 32 is performed up to (position P3 in FIG. 5).

  The operation unit 28 is an input switch for setting various operation modes of the camera 1 by a user such as a shutter release button, and can switch between an auto focus mode and a manual focus mode. 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. The shutter release button includes a first switch SW1 that is turned on when the button is half-pressed and a second switch SW2 that 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 regular intervals, 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 uses the focus limit information in the “FULL mode” as the focus limit information. Information including the infinity end soft limit SL _IP and the closest end soft limit SL _NP , which are the limit positions (ends) of Rf1, is periodically transmitted to the camera body 2. Thereby, the camera control unit 21 can acquire the focus limit information including the infinity end soft limit SL _IP and the closest end soft limit SL _NP .

Similarly, as shown in FIG. 3B, the camera control unit 21 can set the focusable range in the “close-side limit mode” when the “close-side limit mode” is set by the focus limit switch 38. Information including the infinitely far end soft limit SL _IP and the near side soft limit SL _NS , which is the limit position of Rf2, 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 acquired as focus limit information.

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

  In step S102, the camera control unit 21 calculates a focusable range of the focus lens 32 based on the focus limit information acquired in step S101, as shown in FIGS. .

For example, as shown in FIG. 3A, the camera control unit 21 is set to “FULL mode”, and the infinity end soft limit SL _IP and the near end soft limit SL _NP are acquired as focus limit information. If it is, the range from the infinity end soft limit SL _IP to the closest 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 infinity end soft limit SL _IP and the near side soft limit SL _NS are set as focus limit information. Is acquired, the range from the infinitely far end soft limit SL _IP to the closest soft limit SL _NS is calculated as the focusable range Rf2. Further, as shown in FIG. 3C, the camera control unit 21 is set to “infinity limit mode”, and the focus limit information includes the infinity side soft limit SL _IS and the near end soft limit SL. _{When NP} is acquired, the range from the infinitely far side soft limit SL _IS to the closest end soft limit SL _NP is calculated as the focusable range Rf3.

Depending on the type of the lens barrel 3, the focus limit function may not be obtained from the lens barrel 3 because the focus limit function is not provided. In such a case, as shown in FIG. 3A, the camera control unit 21 calculates a range Rf1 from the infinity end soft limit SL _IP to the closest end soft limit SL _{NP as} a focusable range. be able to.

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

Here, in the focus detection by the contrast detection method, the camera control unit 21 calculates the focus evaluation value at a predetermined sampling interval while driving the focus lens 32 as described above. 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 exceeding the peak position (P2 in FIG. 5). Thus, it is necessary to calculate the focus evaluation value. Therefore, for example, in order to detect the peak position (focus position) of the focus evaluation value with the infinity end soft limit SL _IP by the contrast detection method, the focus lens 32 is set to infinity from the infinity end soft limit SL _IP. It is necessary to calculate the focus evaluation value by driving to the side. Similarly, for example, in order to detect the peak position (in-focus position) of the focus evaluation value with the near-end soft limit SL _NP using the contrast detection method, the focus lens 32 is placed closer to the near-end soft limit SL _NP. It is necessary to calculate the focus evaluation value by driving to the side.

Therefore, when the focus limit mode is “FULL mode”, the camera control unit 21 starts from the lens position on the infinity side with respect to the infinity end soft limit SL _IP as shown in FIG. The range up to the lens position closer to the near end than the near end soft limit SL _NP is calculated as the search drive range Rs1. For example, in this embodiment, as shown in FIG. 5, when the focus evaluation value rises twice and then moves down twice, the focus evaluation value is calculated using these focus evaluation values. Therefore, the camera control unit 21 is closer to the near-end soft limit SL _NP from the lens position at which two focus evaluation values can be calculated on the infinity side than the infinity-end soft limit SL _IP. The range up to the lens position where two focus evaluation values can be calculated on the side can be calculated as the search drive range Rs1.

Further, when the focus limit mode is the “close-side limit mode”, the camera control unit 21 starts from the lens position on the infinity side with respect to the infinity end soft limit SL _IP as shown in FIG. The range from the closest soft limit SL _NS to the closest lens position is calculated as the search drive range Rs2. Similarly, when the focus limit mode is the “infinity limit mode”, the camera control unit 21, as shown in FIG. 7C, has a lens on the infinity side of the infinity side soft limit SL _IS. A range from the position to the lens position closer to the near end than the close end soft limit SL _NP is calculated as a search drive range Rs3.

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

  Here, when performing focus detection by the contrast detection method, by driving the focus lens 32, the image plane by the optical system is moved in the optical axis direction, whereby a plurality of focus evaluation values are obtained on different image planes. The lens position where the focus evaluation value reaches a peak is calculated as the focus position. However, if the moving speed of the image plane is made too fast, the distance between the image planes for calculating the focus evaluation value becomes too large, and the focus position cannot be detected properly. 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 this embodiment, for example, the camera control unit 21 sets the sampling interval of the focus evaluation value suitable for detection of the in-focus position as three times the depth of field, and calculates the focus evaluation value of the image plane. The moving speed of the image plane whose interval is three times the depth of field is calculated as the first target speed V1.

For example, when one point image captured by one pixel of the image sensor 22 is blurred, and the one point image is captured by pixels adjacent to the left and right sides of the one pixel (that is, one point that can be captured by one pixel) Even if a single point image is captured over three pixels), the human eye may be able to determine 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 the depth at which an image of one point is captured within the range of three pixels as the depth of field D, as shown in the following formula (1), and the pixel array Based on the direction width W and F value, the depth of field D is obtained.
Depth of field D = 3 pixels × width W × F value in the pixel arrangement direction (1)
For example, when the width of each pixel in the arrangement direction 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 formula (2), the camera control unit 21 calculates the focus evaluation value based on 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 speed 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 speed V1 as 50.4 mm / s based on the above equation (2). Can do.

  In the above formula (1), when a single point image 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, and the imaging element 22 These can be set as appropriate based on the configuration of each imaging pixel. Further, in the above formula (2), the moving speed of the image plane where the distance between the image planes for calculating the focus evaluation value is three times the depth of field is calculated as the moving speed of the image plane suitable for focus detection. However, the present invention is not limited to this configuration. For example, the moving speed of the image plane in which the distance between the image planes for calculating the focus evaluation value is twice or four times the depth of field is suitable for focus detection. It is good also as a structure calculated as a moving speed of an image surface.

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

  Here, in the present embodiment, when the focus evaluation value is calculated while the focus lens 32 is driven and the focus evaluation value rises twice and then moves down twice, these five points of focus are calculated. The peak of the focus evaluation value is calculated using the evaluation value. For this reason, in the present embodiment, when at least five focus evaluation values cannot be detected in the search drive range calculated in step S103, the focus evaluation value peak cannot be detected.

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

For example, the size of the focusable range from the infinity end soft limit SL _IP to the close end soft limit SL _NP is 50 pulses, and the minimum number of focus evaluation values N 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 speed V2 as 50/5/80 × 200 = 25 mm / s. Can do.

  In step S106, the camera controller 21 causes the slower one of the first target speed V1 calculated in step S104 and the second target speed V2 calculated in step S105 to be detected at the time of focus detection by the contrast method. It is set as a drive target speed for driving the focus lens 32. For example, in the example described above, the first target speed V1 is calculated as 50.4 mm / s, and the second target speed V2 is calculated as 25 mm / s. In this case, the camera control unit 21 can set the second target speed V2 as the drive 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 drive target speed.

  In step S107, the camera control unit 21 starts calculating the focus evaluation value. In the present embodiment, the focus evaluation value calculation process is performed by reading out the pixel output of the imaging pixel 221 of the imaging element 22, extracting a high-frequency component of the read-out pixel output using a high-frequency transmission filter, and accumulating these. Done. The focus evaluation value is calculated only when the specific focus detection position is selected by the user's manual operation or the subject recognition mode, and only the pixel output of the imaging pixel 221 corresponding to the selected focus detection position. It is good also as a structure which reads. The focus evaluation value calculation process is repeatedly executed at predetermined intervals.

  In step S108, the camera control unit 21 determines whether or not the shutter release button provided in the operation unit 28 is 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, if the first switch SW1 is not turned on, step S108 is repeated until the first switch SW1 is turned on. That is, the focus evaluation value calculation process is repeatedly executed while the drive of the focus lens 32 is stopped until the first switch SW1 is turned on.

  In step S109, the camera control unit 21 performs a process of starting driving the focus lens 32. Specifically, the camera control unit 21 starts drive control of the focus lens 32 so that the focus lens 32 is driven at the drive target speed set in step S106 in the search drive range calculated in step S103. To do.

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

  In step S110, the camera control unit 21 determines whether or not the peak position (focus position) of the focus evaluation value has been detected. If the in-focus position cannot 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 for driving the focus lens 32 to the in-focus position. Then, after driving the focus lens 32 to the in-focus position, the process proceeds to step S112, and in-focus display is performed. The in-focus display is performed by the electronic viewfinder 26, for example.

  On the other hand, if it is determined in step S110 that the in-focus position has not been detected, the process proceeds to step S113. In step S113, the camera control unit 21 determines whether or not the peak position (focus position) of the focus evaluation value has been detected in the entire search drive range calculated in step S103. When the focus evaluation value peak position (in-focus position) is not detected in the entire search drive range, the process returns to step S110, and the search drive is continued. On the other hand, if the focus evaluation value peak position (in-focus position) is detected in the entire search drive range, it is determined that the in-focus position cannot be detected, and the process proceeds to step S114, where the out-of-focus state is detected. Display is performed. 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 moving speed of the image plane in which the sampling interval of the focus evaluation value is suitable for focus detection is calculated as the first target speed V1, and is necessary for focus detection within the search drive range. The moving speed of the image plane that can calculate a large number of focus evaluation values is calculated as the second target speed V2. Then, the first target speed V1 and the second target speed V2 are compared, the slower speed is set as the drive target speed, and the focus lens 32 is driven so that the moving speed of the image plane becomes the drive target speed. . Thereby, in the present embodiment, the moving speed of the image plane accompanying the driving of the focus lens 32 is not a 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 (focus position) of the focus evaluation value cannot be properly detected. In the present embodiment, since the moving speed of the image plane accompanying the driving of the focus lens 32 is not a speed at which the sampling interval of the focus evaluation value is an interval suitable for focus detection, the focus evaluation value peak (in-focus) It is also possible to effectively prevent the position) from being posted with high accuracy.

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  For example, in the above-described embodiment, as illustrated in the above formula (2), the configuration in which the first target speed V1 is calculated based on the depth of field is illustrated. However, the configuration 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 speed 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 speed V1 can be calculated. Alternatively, 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 includes a rear monitor or an electronic view provided in the camera body 2. A configuration may be adopted in which the user is informed through the finder 26 that the focus lens 32 is driven at the second target speed V2. Thereby, it is possible to reduce the user's uncomfortable feeling caused by setting the driving speed of the focus lens 32 to the second target speed V2 different from the first target speed V1.

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

  In addition, in the above-described embodiment, the configuration for performing the focus detection by the contrast detection method is illustrated, but the configuration is not limited to this configuration. For example, the imaging device 22a illustrated in FIG. It may be configured to perform focus detection by a phase difference detection method. FIG. 8 is an enlarged view of a main part of an imaging surface of an imaging element 22a according to another embodiment. For example, the image pickup device 22a shown in FIG. 8 includes an image pickup device 221 for picking up an image and focus detection pixels 222a and 222b for detecting a phase difference, and outputs the focus detection pixels 222a and 222b to the respective distance measurement pupils. By collecting the output groups corresponding to the intensity groups, data relating to the intensity distribution of the pair of images is obtained, and image deviation detection calculation processing such as correlation calculation processing or phase difference detection processing is performed on the intensity distribution data, so-called It is possible to detect an image shift amount by the phase difference detection method. Then, a conversion calculation is performed on the obtained image shift amount according to the center-of-gravity interval of the pair of distance measuring pupils, thereby obtaining a 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 obtained, 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 image sensor 22a shown in FIG. 8, it is possible to perform a scanning operation that simultaneously performs focus detection by the contrast detection method and focus detection by the phase difference detection method. In this case, the scan drive range of the focus lens 32 in the scan operation can be set similarly to the search drive range of the above-described embodiment, and the number of focus evaluation values necessary for focus detection are calculated within the scan drive range. The second target speed can be calculated so as to be able to do so.

Further, in the above-described embodiment, when the “FULL mode” is set, as shown in FIG. 7A, the lens position is closer to the infinity side than the infinity end soft limit SL _IP. Although the configuration in which the range up to the lens position closer to the end soft limit SL _NP is set as the search drive range Rs1 is exemplified, the configuration is not limited to this configuration, and for example, as shown in FIG. A range from the far end soft limit SL _IP to the nearest end soft limit SL _NP may be set as the search drive range Rs1. FIG. 9 is a diagram illustrating another example of the search drive range.

Similarly, when the “close-side limit mode” is set, as shown in FIG. 7B, from the lens position on the infinity side to the infinity end soft limit SL _IP , the close-side soft limit SL is set. _Although the configuration in which the range up to the lens position closer to _NS than the _NS is calculated as the search drive range Rs2 is illustrated, the present invention is not limited to this configuration. For example, as shown in FIG. A range from the SL _IP to the lens position closer to the closest side than the closest soft limit SL _NS may be calculated as the search drive range Rs2. When the “infinity side limit mode” is set, as shown in FIG. 9C, the near end soft limit is determined from the lens position on the infinity side with respect to the infinity side soft limit SL _IS. The range up to SL _NP may be calculated as the search drive range Rs3.

  In the above-described embodiment, three modes of “FULL mode”, “near limit mode”, and “infinity limit mode” can be set, and predetermined in-focus ranges Rf1, Rf2 can be set. , Rf3 can be set, but 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 barrel 3a is provided with a focus limit switch 38 ′ and a preset storage switch 39, and the user sets the focus limit switch 38 ′ to “preset”. By pressing the preset storage switch 39 at the limit position (end part) on the infinity side and the limit position (end part) on the near side of the focusable range to be focused, the lens barrel 3 can be focused on as desired by the user. The possible range (preset range) can be stored, and then the focusable range can be limited to the preset range set by the user when the user sets the focus limit switch 38 ′ to “preset”.

In the above-described embodiment, the lens resolution coefficient γ is exemplified by a configuration that defines the drive amount of the focus lens 33 / the amount of movement of the image plane (unit: number of pulses / mm), but 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 driving amount of the focus lens 33 (mm / number of pulses). In this case, the second target speed V2 can be calculated based on the following formula (4) instead of the above formula (3).
Second target speed V2 = size of search drive range R / number of focus evaluation values N × lens resolution coefficient γ × frame rate fps (4)

  The camera 1 of the embodiment described above is not particularly limited, and 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.

DESCRIPTION OF SYMBOLS 1 ... Digital camera 2 ... Camera body 21 ... Camera control part 22 ... Imaging device 3 ... Lens barrel 32 ... Focus lens 36 ... Focus lens drive motor 37 ... Lens control part

Claims (9)

An imaging device having a focus lens, capturing an image by an optical system and outputting a signal;
A contrast calculation unit that calculates an evaluation value related to the contrast of the signal while moving the focus lens;
A setting unit for setting driving range information of the focus lens;
The speed of movement of the focus lens for calculating the evaluation value is one of a first speed calculated based on the aperture value of the optical system and a second speed calculated based on the driving range information. A speed setting unit for setting a slow speed and calculating the evaluation value;
An imaging apparatus comprising: The imaging element performs imaging a plurality of times with a certain time interval,
The speed setting unit calculates the first speed based on an aperture value of the optical system and the certain time, and calculates the second speed based on the driving range information and the certain time. The imaging apparatus according to 1.   3. The imaging apparatus according to claim 1, wherein the setting unit determines the driving range of the focus lens based on information about a restriction on a driving range of the focus lens received from a lens barrel having the optical system. .   The imaging apparatus according to claim 1, wherein the speed setting unit determines the second speed so that a plurality of the evaluation values can be calculated within the driving range.   The imaging apparatus according to claim 1, wherein the speed setting unit calculates the first speed based on a pixel size of the imaging element.   6. The imaging apparatus according to claim 1, wherein the speed setting unit calculates the first speed based on information on a moving distance of the image of the optical system with respect to a moving distance of the focus lens. A defocus calculation unit that calculates a value related to a deviation between the optical system and the imaging surface of the imaging element based on an amount of positional deviation of an image due to light that has passed through different parts of the optical system based on the signal;
A control unit that performs calculation of a value related to the shift by the defocus calculation unit and calculation of the evaluation value by the contrast calculation unit while moving the focus lens at a speed set by the speed setting unit;
The imaging device according to claim 1, comprising:   The imaging apparatus according to claim 1, further comprising a display unit that indicates whether the speed setting unit has set the first speed or the second speed.   The imaging apparatus according to claim 1, further comprising a lens barrel having the optical system.

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