JP6593496B2 - Interchangeable lens and camera body - Google Patents

Description

  The present invention relates to an interchangeable lens and a camera body.

  2. Description of the Related Art Conventionally, a focus detection device is known that calculates an evaluation value related to image contrast by an optical system while driving a focus adjustment lens, and detects a position where the evaluation value reaches a peak as a focus position (for example, Patent Document 1).

JP 2013-105043 A

  However, depending on the shooting environment, such as when the subject to be measured changes due to magnification fluctuations in the optical system or when there is a point light source with low contrast, the evaluation value may not be calculated appropriately. In such a case, in the related art, the peak of the evaluation value is detected at a lens position other than the actual focusing position, and as a result, false focusing may occur.

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

[1] An interchangeable lens according to the present invention includes an optical system having a focus adjustment lens, a storage unit storing information related to spatial frequency characteristics of the optical system, and position detection for detecting position information of the focus adjustment lens. A transmission unit that transmits the information and the position information to the camera body, and receives a drive signal for the focus adjustment lens from the camera body, and drives the focus adjustment lens based on the received drive signal. A control unit, and the drive signal is a ratio of change in the evaluation value on the near side of the peak of the evaluation value related to the contrast of the subject image captured while moving the focus adjustment lens, and on the infinity side of the peak. When a peak whose ratio to the change rate of the evaluation value is equal to or less than the first determination value can be detected, the focus adjustment lens of which the evaluation value is the peak is detected. A peak at which the ratio is equal to or less than the first determination value cannot be detected, and a peak at which the ratio is equal to or less than the second determination value greater than the first determination value was detected. In this case, the focus adjustment lens position is a signal that drives the focus adjustment lens to the in-focus position, with the position of the focus adjustment lens having a peak at which the evaluation value is equal to or less than the second determination value being used.
[2] A camera body according to the present invention includes an imaging unit that captures a subject image formed by an optical system of an interchangeable lens attached to the camera body and outputs a signal, information on a spatial frequency characteristic of the optical system, A focus for detecting the in-focus position of the focus adjustment lens using the reception unit that receives the position information of the focus adjustment lens of the optical system from the interchangeable lens, the signal, the information, and the position information. A detection unit, and a drive instruction unit that instructs to drive the focus adjustment lens to the in-focus position, and the focus detection unit evaluates a contrast of a subject image captured while moving the focus adjustment lens. A peak in which the ratio between the change rate of the evaluation value on the closest side of the peak of the value and the change rate of the evaluation value on the infinity side of the peak is equal to or less than the first determination value is detected. If the focus adjustment lens position at which the evaluation value is the peak is set as the in-focus position, a peak at which the ratio is less than or equal to the first determination value cannot be detected, and the ratio is When a peak that is equal to or smaller than the second determination value that is greater than one determination value can be detected, the position of the focus adjustment lens that is a peak whose evaluation value is equal to or less than the second determination value is detected as a focus position. .
[3] In the camera body according to the present invention, the focus detection unit includes at least one of a change rate of the evaluation value on the closest side of the peak of the evaluation value and a change rate of the evaluation value on the infinity side of the peak. This can be corrected based on the spatial frequency characteristics of the optical system.
[4] An interchangeable lens according to the present invention receives an optical system having a focus adjustment lens, a position detection unit that detects position information of the focus adjustment lens, and a drive signal for the focus adjustment lens from a camera body, and receives the received signal. A control unit that drives the focus adjustment lens based on the drive signal, and the drive signal is located on the near side of the peak of the evaluation value related to the contrast of the subject image captured while moving the focus adjustment lens. When the peak at which the ratio between the change rate of the evaluation value and the change rate of the evaluation value on the infinity side of the peak is equal to or less than the first determination value can be detected, the focus at which the evaluation value becomes the peak The position of the adjusting lens is the in-focus position, and a peak where the ratio is less than or equal to the first determination value cannot be detected, and the ratio is greater than the first determination value When a peak that is equal to or less than 2 determination values can be detected, the focus adjustment lens is set to the in-focus position with the position of the focus adjustment lens that is a peak where the evaluation value is equal to or less than the second determination value as a focus position. This signal is driven to the position.
[5] A camera body according to the present invention includes an imaging unit that captures a subject image formed by an optical system of an interchangeable lens attached to the camera body and outputs a signal, and positional information of a focus adjustment lens included in the optical system. A reception unit that receives from the interchangeable lens, a focus detection unit that detects a focus position of the focus adjustment lens using the signal and the position information, and an instruction to drive the focus adjustment lens to the focus position A drive instructing unit that performs the evaluation, and the focus detection unit includes a change rate of the evaluation value on the near side of the peak of the evaluation value related to the contrast of the subject image captured while moving the focus adjustment lens, and the peak When the peak whose ratio to the change rate of the evaluation value on the infinity side is equal to or less than the first determination value can be detected, the focus adjustment level at which the evaluation value becomes the peak. The peak where the ratio is equal to or less than the first determination value cannot be detected, and the peak where the ratio is equal to or less than the second determination value greater than the first determination value is detected. If it is possible, the position of the focus adjustment lens that has a peak at which the evaluation value is equal to or less than the second determination value is detected as a focus position.
[6] In the camera body according to the present invention, the focus detection unit includes at least one of a change ratio of the evaluation value on the near side of the peak of the evaluation value and a change ratio of the evaluation value on the infinity side of the peak. This can be corrected based on the spatial frequency characteristics of the optical system.

  According to the present invention, it is possible to appropriately detect the focus state of the optical system.

FIG. 1 is a block diagram showing a camera according to the present embodiment. FIG. 2 is a diagram for explaining an example of a focus detection method using a contrast detection method. FIG. 3 is a flowchart showing the operation of the camera according to the first embodiment. FIG. 4 is a diagram illustrating an example of the relationship between the focus lens position and the focus evaluation value. FIG. 5 is a diagram illustrating an example of the relationship between the focus lens position and the image plane movement coefficient. FIG. 6 is a flowchart showing the operation of the camera according to the second embodiment. FIG. 7 is a diagram for explaining the spatial frequency characteristics of the optical system. FIG. 8 is a diagram illustrating another example of the relationship between the focus lens position and the focus evaluation value. FIG. 9 is a diagram illustrating another example of the relationship between the focus lens position and the focus evaluation value. FIG. 10 is an enlarged view of an imaging surface of an imaging device according to another embodiment.

  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 an 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.

  Further, the lens control unit 37 receives a drive signal for driving the focus lens 32 from the camera control unit 21, and performs drive control of the focus lens 32 based on the received drive signal. The drive control of the focus lens 32 by the lens control unit 37 will be described later.

  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 photographing optical system using a contrast detection method based on the pixel data read from the image sensor 22. Specifically, the camera control unit 21 reads the output of the image sensor 22 and calculates a focus evaluation value based on the read output. This focus evaluation value can be obtained, for example, by extracting a high-frequency component of an image output from an imaging pixel of the image sensor 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 drive signal to the lens control unit 37 to drive the focus lens 32 at a predetermined sampling interval to obtain a focus evaluation value at each position, and a focus that maximizes the focus evaluation value. Focus detection is performed by a contrast detection method in which the position of the lens 32 is obtained as a 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. Can be obtained by performing an operation such as interpolation using the focus evaluation value.

  Here, FIG. 2 is a diagram for explaining an example of a focus detection method using a contrast detection method. In the example shown in FIG. 2, the focus lens 32 is located at P0 shown in FIG. 2. First, the focus lens 32 is driven from P0 to a predetermined scan start position (position P1 in FIG. 2). Initial drive is performed. Then, the focus lens 32 is driven from the scan start position (position P1 in FIG. 2) 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. Then, when the focus lens 32 is moved to the position P2 shown in FIG. 2, the peak position of the focus evaluation value (position P3 in FIG. 2) is detected as the focus position, and the detected focus position. Focusing driving for driving the focus lens 32 is performed up to (position P3 in FIG. 2).

  In this embodiment, the camera control unit 21 determines the reliability that the peak position of the focus evaluation value (the position P3 in FIG. 2) is the in-focus position, and the reliability is equal to or higher than a certain value. In addition, the peak position of the focus evaluation value is detected as the focus position. A method for determining the reliability that the peak position of the focus evaluation value is the in-focus position will be described later.

  The operation unit 28 is an input switch for a photographer to set various operation modes of the camera 1, such as a shutter release button, and switches between an autofocus mode / manual focus mode and a movie shooting mode / still image shooting mode. Can be done. 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. 3 is a flowchart showing the operation of the camera 1 according to this embodiment.

  First, in step S101, 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). When the first switch SW1 is turned on, the process proceeds to step S102. On the other hand, when the first switch SW1 is not turned on, the process waits at step S101, and at a predetermined interval until the first switch SW1 is turned on. The through image is displayed repeatedly.

  When the shutter release button is half-pressed, the process proceeds to step S102, and the drive of the focus lens 32 is started in step S102. Specifically, a drive signal for starting the drive of the focus lens 32 is transmitted from the camera control unit 21 to the lens control unit 37, and the focus lens drive motor 36 performs focus through the lens control unit 37. The driving of the lens 32 is started. Thereby, the focus lens drive motor 36 drives the focus lens 32 at a predetermined sampling interval (distance), for example, from the closest side to the infinity side.

  In step S103, the camera control unit 21 calculates a focus evaluation value. Specifically, the camera control unit 21 calculates a focus evaluation value at each lens position for each focus detection area while driving the focus lens 32. The calculated focus evaluation value is stored in the RAM of the camera control unit 21 in association with the lens position of the focus lens when the focus evaluation value is acquired.

  In step S104, the camera control unit 21 determines whether or not the peak position of the focus evaluation value has been detected. Here, FIG. 4 is a diagram illustrating an example of the relationship between the focus lens position and the focus evaluation value. In the present embodiment, the camera control unit 21 calculates the focus evaluation value at a predetermined sampling interval, and when the calculated focus evaluation value rises twice and then moves down twice, these five are evaluated. The peak of the focus evaluation value is detected by performing calculation such as interpolation using the focus evaluation value.

  For example, in the example shown in FIG. 4, since the focus evaluation value rises twice at the focus evaluation values P5 and P6 and then the focus evaluation value changes twice at the focus evaluation values P7 and P8, these 5 The focus evaluation value peak is detected using the two focus evaluation values P5 to P8. If the peak position of the focus evaluation value can be detected, the process proceeds to step S105. On the other hand, if the peak position of the focus evaluation value cannot be detected, the process proceeds to step S112.

In this embodiment, the camera control unit 21 calculates a focus evaluation value at a sample interval based on the image plane movement amount. Specifically, the camera control unit 21 has an image in which the distance between adjacent focus evaluation values (for example, P4 and P5, P5 and P6, P6 and P7, and P7 and P8 in the example shown in FIG. 4) is constant. Focus evaluation values are calculated at intervals corresponding to the amount of surface movement. The image plane movement amount is the image plane movement amount accompanying the driving of the focus lens 32. In the present embodiment, the ratio of the image plane movement amount to the lens drive amount (image plane movement amount / lens drive amount) is stored in advance in the RAM of the lens control unit 37 as the image plane movement coefficient K, and the camera control unit 21. Is calculated by multiplying the lens driving amount (number of pulses) of the focus lens 32 by the image plane movement coefficient K acquired from the lens control unit 37, as shown in the following formula (1). be able to.
Image plane movement amount = Image plane movement coefficient K × Lens drive amount of the focus lens 32 (1)

  Further, the image plane movement amount may vary depending on the type of the lens barrel 3 and the focus lens position. In this case, the image plane movement coefficient K is also different for each type of the lens barrel 3 and for each focus lens position. Different values. Here, FIG. 5 is a diagram illustrating an example of the relationship between the focus lens position and the image plane movement coefficient K in the present embodiment. In the present embodiment, due to the optical characteristics of the lens barrel 3, the image plane movement amount with respect to the drive amount of the focus lens 32 is larger on the closer side than on the infinity side. Therefore, as shown in FIG. The image plane movement coefficient K is larger on the near side than on the far side. In the present embodiment, the camera control unit 21 acquires the image plane movement coefficient K corresponding to each focus lens position from the lens control unit 37, thereby appropriately calculating the image plane movement amount for each focus lens position. be able to.

  In step S105, the camera controller 21 causes the change rate θ1 in the vicinity of the peak position of the focus evaluation value in the vicinity of the focus evaluation value among the change ratio of the focus evaluation value to the movement of the focus lens 32, and infinity of the peak position of the focus evaluation value. The change ratio θ2 in the vicinity of the side is calculated. For example, in the example illustrated in FIG. 4, the camera control unit 21 determines the absolute slope of the straight line L1 connecting the focus evaluation values P4 and P6 among the five focus evaluation values P4 to P8 near the peak position of the focus evaluation value. The value is calculated as the change rate θ1 in the vicinity of the focus evaluation value peak position in the vicinity, and the absolute value of the slope of the straight line L2 connecting the focus evaluation values P6 and P8 is calculated in the vicinity of the focus evaluation value peak position at infinity. It is calculated as the change rate θ2 at.

Specifically, as shown in FIG. 4, the camera control unit 21 sets the vertical coordinate indicating the focus evaluation value as the Y coordinate and the horizontal coordinate indicating the image plane movement amount as the X coordinate. When the Y coordinates of the values P4 to P8 are respectively Y (P4) to Y (P8) and the X coordinates of the focus evaluation values P4 to P8 are respectively X (P4) to X (P8), the following formula (2 ), The absolute value of the slope of the straight line L1 is calculated as a change rate θ1 in the vicinity of the peak position of the focus evaluation value, and the absolute value of the slope of the straight line L2 is calculated based on the following equation (3). It is calculated as a change rate θ2 in the vicinity of the infinity side of the peak position of the focus evaluation value.

なお、上記式（４）において、ｍａｘ（）は、θ１およびθ２のうちの最大値を選択的に算出する関数であり、ｍｉｎ（）は、θ１およびθ２のうちの最小値を選択的に算出する関数である（なお、下記式（７）においても同様。）。 In subsequent step S106, the camera control unit 21 calculates the ratio R between the change rate θ1 in the vicinity of the peak position of the focus evaluation value in the vicinity and the change rate θ2 in the vicinity of the peak position of the focus evaluation value at infinity. Is called. Specifically, the camera control unit 21 changes the change rate θ1 in the vicinity of the focus evaluation value peak position in the vicinity and the change rate in the vicinity of the focus evaluation value peak position at infinity based on the following equation (4). The ratio R with θ2 is calculated.

In the above equation (4), max () is a function that selectively calculates the maximum value of θ1 and θ2, and min () selectively calculates the minimum value of θ1 and θ2. (The same applies to the following formula (7).)

In step S107, the camera control unit 21 determines whether or not the ratio R calculated in step S106 is equal to or less than a predetermined determination value b as shown in the following equation (5).

  Here, in general, when the shooting environment is good and the focus evaluation value can be calculated appropriately, the focus evaluation value when the focus evaluation value is calculated while driving the focus lens 32 as shown in FIG. The shape (plot) tends to be a symmetrical bell shape around the peak position (P3 in FIG. 2) of the focus evaluation value. Thus, when the shape of the focus evaluation value is symmetrical with respect to the peak position of the focus evaluation value (P3 in FIG. 2), the change rate θ1 in the vicinity of the closest position of the peak position of the focus evaluation value, The change rate θ2 in the vicinity of the infinity side of the peak position of the focus evaluation value is equal, θ1 in the vicinity of the close position of the peak position of the focus evaluation value, and the change rate θ2 in the vicinity of the infinity side of the peak position of the focus evaluation value The ratio R is calculated as “1”. Further, the higher the symmetry of the shape of the focus evaluation value, the closer the change rate θ1 near the peak position of the focus evaluation value to the change rate θ2 near the infinity side of the peak position of the focus evaluation value. The ratio R becomes a value close to 1.

  On the other hand, for example, when there is a competing subject on the near side and the infinity side, or when the focus evaluation value fluctuates due to the influence of a high-brightness subject such as a point light source, or the focus detection area varies due to the magnification fluctuation of the optical system The focus evaluation value cannot be appropriately calculated when the subject in the image fluctuates. In such a case, the shape of the focus evaluation value when the focus evaluation value is calculated while driving the focus lens 32 is as follows. 2 tends to be deviated from the symmetrical bell shape as shown in FIG. Thus, when the shape of the focus evaluation value becomes asymmetric, the change rate θ1 in the vicinity of the peak position of the focus evaluation value near the near side, and the change rate θ2 in the vicinity of the peak position of the focus evaluation value near infinity Therefore, the ratio R between the change rate θ1 and the change rate θ2 increases.

  Therefore, in the present embodiment, as shown in the above formula (5), the change rate θ1 in the vicinity of the peak position of the focus evaluation value near the near side and the change rate θ2 in the vicinity of the peak position of the focus evaluation value near infinity. It is determined whether or not the ratio R is equal to or less than a predetermined determination value b. When the ratio R is equal to or less than the determination value b, the focus evaluation value is captured under good shooting conditions, and the focus evaluation value It is determined that there is a certain degree of reliability that the peak position is the in-focus position, and the process proceeds to step S108. On the other hand, when the ratio R between the change rate θ1 in the vicinity of the peak position of the focus evaluation value and the change ratio θ2 in the vicinity of the peak position of the focus evaluation value near infinity is larger than a predetermined determination value b, It is determined that the reliability that the peak position of the focus evaluation value is the in-focus position is less than a certain value, and the process proceeds to step S111. In step S111, the camera control unit 21 determines the peak position of the focus evaluation value. It is determined that the focus position is not reached.

  In the above formula (5), the value of the determination value b is not particularly limited, and can be set as appropriate by experiments or the like. For example, in the present embodiment, the determination value b can be set to “2”. In the present embodiment, the determination value b can be set to a different value depending on the shooting mode. For example, in the moving image shooting mode, the determination value b can be set to a smaller value than in the still image shooting mode. Thereby, higher focusing accuracy can be obtained during still image shooting, and moving image shooting can be performed at a constant frame rate during moving image shooting.

  Next, in step S108, since the reliability that the peak position of the focus evaluation value is the in-focus position is determined to be a certain value or more in step S107, the camera control unit 21 determines the peak of the focus evaluation value. The position is detected as the in-focus position. In step S109, when the lens control unit 37 performs the focus drive for driving the focus lens 32 to the focus position detected in step S108, and the drive to the focus position of the focus lens 32 is completed, In step S110, the camera control unit 21 displays a focus indication.

  In the present embodiment, a plurality of focus detection areas are set in the imaging screen, and the ratio R of the change ratios θ1 and θ2 in the vicinity of the peak position of the focus evaluation value is calculated in each of the plurality of focus detection areas. The And the camera control part 21 specifies the focus detection area for detecting a focus position based on the magnitude | size of the peak of a focus evaluation value, and the ratio R among these several focus detection areas. For example, in order to detect a focus position in a focus detection area in which the peak of the focus evaluation value is the highest among the focus detection areas in which the peak of the focus evaluation value with the ratio R equal to or greater than the predetermined determination value b is detected. The focus detection area is specified, and the focus drive is performed based on the focus position detected in the focus detection area. A focus detection area for detecting a focus position is a focus detection area in which a peak of a focus evaluation value having the highest ratio R is detected among focus detection areas having a peak evaluation value peak size equal to or greater than a predetermined value. It is good also as a structure specified as.

  On the other hand, if the peak position of the focus evaluation value cannot be detected in step S104, or if it is determined in step S107 that the ratio R of the change rate of the focus evaluation value is greater than the predetermined value b, step Proceed to S112. In step S112, the camera control unit 21 determines whether or not the peak position of the focus evaluation value has been detected in the entire driveable range of the focus lens 32. When the peak position of the focus evaluation value is detected in the entire driveable range of the focus lens 32, the process proceeds to step S113 where the drive of the focus lens 32 is ended by the camera control unit 21, and then step In S <b> 114, the camera control unit 21 performs an in-focus display.

  On the other hand, if the focus evaluation value peak position is not detected in the entire driveable range of the focus lens 32 in step S112, the process returns to step S103, and the focus evaluation is performed again while driving the focus lens 32. The scanning operation for calculating the value is continued. That is, in the present embodiment, the focus lens 32 can be driven until the focus evaluation value peak position where the ratio R of the change ratios θ1 and θ2 near the peak position of the focus evaluation value is equal to or less than the predetermined value b is detected. A scan operation that repeats the calculation of the focus evaluation value while driving the focus lens 32 is performed until the peak position of the focus evaluation value is detected in the entire range.

  As described above, the operation of the camera 1 according to the first embodiment is executed.

  As described above, in the first embodiment, of the change rate of the focus evaluation value with respect to the movement of the focus lens 32, the change rate θ1 in the vicinity of the peak position of the focus evaluation value and the infinity of the peak position of the focus evaluation value. The change rate θ2 in the vicinity of the side of the focus evaluation value is calculated, and the ratio R between the change rate θ1 in the vicinity of the peak position of the focus evaluation value and the change ratio θ2 in the vicinity of the peak position of the focus evaluation value is a predetermined determination value. If it is less than or equal to b, it is determined that the reliability that the peak position of the focus evaluation value is the in-focus position is a certain value or more, and the peak position of the focus evaluation value is detected as the in-focus position. As a result, for example, when there is a competing subject on the close side and the infinity side, or when a high-brightness subject such as a point light source is blurred, or due to fluctuations in the magnification of the optical system, Since the focus evaluation value cannot be appropriately calculated when the subject fluctuates and the focus evaluation value is calculated while driving the focus lens 32, the shape of the focus evaluation value is asymmetrical between the left and right of the peak position. Then, even when the peak position of the focus evaluation value cannot be detected at the actual focus position and false focus occurs, in the present embodiment, the peak position of the focus evaluation value is the focus position. Since it is determined that the reliability is less than a certain value, it is possible to effectively prevent such a peak position of the focus evaluation value from being erroneously detected as an in-focus position.

<< Second Embodiment >>
Next, 2nd Embodiment of this invention is described based on drawing. In the second embodiment, the camera 1 shown in FIG. 1 is the same as the first embodiment except that the camera 1 operates as shown in FIG. FIG. 6 is a flowchart showing the operation of the camera 1 according to the second embodiment.

  Specifically, as shown in FIG. 6, in steps S201 to S206, as in steps S101 to S106 of the first embodiment, when the shutter release button is half-pressed (step S201 = Yes), the focus lens. 32 is started (step S202), and a focus evaluation value is calculated (step S203). If the peak position of the focus evaluation value can be detected (step S204 = Yes), the change ratio of the focus evaluation value in the vicinity of the closest position of the focus evaluation value among the change ratio of the focus evaluation value with respect to the movement of the focus lens 32. A ratio R between θ1 and the change ratio θ2 near the infinity side of the peak position of the focus evaluation value is calculated (steps S205 and S206).

  In step S207, the ratio R between the change rate θ1 of the focus evaluation value peak position near the near side and the change rate θ2 of the focus evaluation value peak position near the infinity side is equal to or less than a predetermined first determination value. A determination is made as to whether or not. When the ratio R between the change ratio θ1 and the change ratio θ2 is equal to or less than a predetermined first determination value, it is determined that the reliability that the peak position of the focus evaluation value is the in-focus position is a certain value or more. In step S208, the peak position of the focus evaluation value is detected as the focus position. Then, after focus drive is performed in step S209, focus display is performed in step S210.

  On the other hand, when the ratio R between the change rate θ1 in the vicinity of the peak position of the focus evaluation value and the change ratio θ2 in the vicinity of the infinity side of the peak position of the focus evaluation value is larger than a predetermined first determination value. In step S211, it is determined whether or not the peak position of the focus evaluation value has been detected in the entire driveable range of the focus lens 32. If the peak position of the focus evaluation value is not detected in the entire driveable range of the focus lens 32, the process returns to step S203 until the peak position where the ratio R is equal to or less than the first determination value is detected. Alternatively, the processes of steps S203 to S207 and S211 are repeated until the peak position of the focus evaluation value is detected in the entire driveable range of the focus lens 32. As described above, in the present embodiment, the scanning operation for calculating the focus evaluation value while driving the focus lens 32 is continued until the peak position of the focus evaluation value at which the ratio R is equal to or less than the first determination value is detected. .

  On the other hand, when the peak position of the focus evaluation value is detected in the entire driveable range of the focus lens 32 without detecting the peak position where the ratio R is equal to or less than the first determination value, the process proceeds to step S212. In step S212, the peak position of the focus evaluation value at which the ratio R is equal to or less than the second determination value as a result of detection of the peak position of the focus evaluation value by the camera control unit 21 in the entire driveable range of the focus lens 32. A determination is made whether it has been detected. Here, the second determination value is a value larger than the first determination value in step S207. As a result of detecting the peak position of the focus evaluation value in the entire driveable range of the focus lens 32, if the peak position of the focus evaluation value at which the ratio R is equal to or less than the second determination value is detected, the process proceeds to step S208. The peak position of the detected focus evaluation value is detected as the in-focus position.

  On the other hand, as a result of detecting the peak of the focus evaluation value in the entire driveable range of the focus lens 32 in step S212, if the peak position where the ratio R is equal to or less than the second determination value cannot be detected, the process proceeds to step S213. Then, the driving of the focus lens 32 is finished, and thereafter, in-focus impossible display is performed in step S214.

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

  As described above, in the second embodiment, the ratio R between the change rate θ1 in the vicinity of the peak position of the focus evaluation value near the near side and the change ratio θ2 in the vicinity of the peak position of the focus evaluation value near infinity is a predetermined first value. If it is less than or equal to one determination value, the peak position of the focus evaluation value is detected as the in-focus position. Thereby, the detection accuracy of a focus position can be improved similarly to 1st Embodiment. In particular, in the second embodiment, the ratio R between the change rate θ1 near the peak position of the focus evaluation value near the near side and the change rate θ2 near the infinity side of the peak position of the focus evaluation value is equal to or less than the first determination value. In this case, the focus lens 32 is immediately moved to the peak position (focus position) of the focus evaluation value at which the ratio R is equal to or less than the first determination value without driving the focus lens 32 in the entire driveable range. By driving, the focus adjustment time of the focus lens 32 can be shortened.

  In the second embodiment, when the focus evaluation value peak at which the ratio R is equal to or less than the first determination value cannot be detected, the scan operation for calculating the focus evaluation value is continued while the focus lens 32 is driven. If the focus evaluation value peak at which the ratio R of the change rate of the focus evaluation value is equal to or smaller than the first determination value cannot be detected in the entire driveable range of the focus lens 32, the focus lens 32 can be driven. It is determined whether or not the peak of the focus evaluation value at which the ratio R is equal to or smaller than the second determination value larger than the first determination value has been detected in the entire region. If the peak of the focus evaluation value at which the ratio R is equal to or less than the second determination value can be detected, the peak of the focus evaluation value at which the ratio R is equal to or less than the second determination value is detected as the in-focus position. As a result, in the second embodiment, the focus lens 32 is within the drivable range even when the focus evaluation value peak at which the ratio R is equal to or smaller than the first determination value cannot be obtained over the entire drivable range of the focus lens 32. The focus evaluation value is detected with high accuracy by detecting the focus evaluation value peak at which the ratio R is equal to or lower than the second determination value as a focus position, with the focus evaluation value peak detection result at It becomes possible to do.

<< Third Embodiment >>
Next, 3rd Embodiment of this invention is described based on drawing. In the third embodiment, the camera 1 shown in FIG. 1 is the same as the first embodiment except that the camera 1 operates as described below.

  Specifically, in the third embodiment, in consideration of the spatial frequency characteristics (MTF characteristics) of the optical system, out of the change rate of the focus evaluation value with respect to the movement of the focus lens 32, the peak position of the focus evaluation value is at infinity. The change rate θ2 in the vicinity is corrected. Then, based on the ratio R between the change rate θ1 in the vicinity of the peak position of the focus evaluation value and the corrected change rate θ2 ′, the reliability that the peak position of the focus evaluation value is the in-focus position is determined. To do.

  Here, FIG. 7 is a diagram for explaining the spatial frequency characteristics of the optical system, in which the vertical axis indicates the focus evaluation value and the horizontal axis indicates the focus lens position. In general, since the contrast of the image of the subject is highest at the in-focus position, as shown in FIG. 7, the focus evaluation value is also calculated as the highest value at the in-focus position. On the other hand, even when the focus lens 32 is moved by the same drive amount from the in-focus position in the closest direction and the infinity direction, there is a difference in contrast between the close side and the infinity side depending on the spatial frequency characteristics of the optical system. As a result, there may be a difference in the focus evaluation value between the close side and the infinity side. For example, in the example shown in FIG. 7, the focus evaluation value is sharply decreased in the vicinity of the focus position closer to the infinite distance side than the focus position near the infinity side due to the spatial frequency characteristics of the optical system.

  In order to reduce the influence of such spatial frequency characteristics of the optical system, in the third embodiment, the correction coefficient k is stored in a RAM provided in the lens control unit 37. Then, the camera control unit 21 acquires the correction coefficient k from the lens control unit 37, and corrects the change rate θ2 near the infinity side of the peak position of the focus evaluation value using the acquired correction coefficient k.

Specifically, as shown in the following formula (6), the camera control unit 21 corrects the change rate θ2 near the infinity side of the peak position of the focus evaluation value to θ2 ′ using the correction coefficient k.
θ2 ′ = θ2 × k (6)
As shown in FIG. 7, since the spatial frequency characteristic of the optical system varies depending on the lens position, the correction coefficient k is also stored for each lens position. That is, in this embodiment, the camera control unit 21 obtains the correction coefficient k corresponding to the focus lens position from the lens control unit 37, thereby focusing the change rate θ2 near the infinity side of the peak position of the focus evaluation value. It can correct | amend appropriately according to a lens position.

そして、算出した比率Ｒに基づいて、焦点評価値のピーク位置が合焦位置であるとの信頼度を判断する。なお、信頼度の判断方法は、第１実施形態と同様に行うことができる。 Then, as shown in the following formula (7), the camera control unit 21 changes the change rate θ1 in the vicinity of the focus evaluation value peak position in the vicinity and the corrected change in the focus evaluation value peak position in the vicinity of the infinity side. The ratio R with the ratio θ2 ′ is calculated.

Then, based on the calculated ratio R, the reliability that the peak position of the focus evaluation value is the in-focus position is determined. The reliability determination method can be performed in the same manner as in the first embodiment.

  As described above, in the third embodiment, the correction coefficient k corresponding to the spatial frequency characteristic (MTF characteristic) of the optical system is acquired from the lens barrel 3, and the focus evaluation value of the focus evaluation value is calculated based on the acquired correction coefficient k. The change rate θ2 near the infinity side of the peak position is corrected. Thus, in the third embodiment, even when the shape of the focus evaluation value is asymmetric due to the spatial frequency characteristics of the optical system, the peak position of the focus evaluation value is based on the symmetry of the shape of the focus evaluation value. Therefore, it is possible to appropriately determine the reliability.

  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 shown in FIG. 4, when the focus evaluation value has moved down twice after the focus evaluation value has risen twice, these five focus evaluation values P4 to P8 are used. Then, the peak of the focus evaluation value is detected, and among these five focus evaluation values P4 to P8, the absolute value of the slope of the straight line L1 connecting the focus evaluation values P4 and P6 is the closest side of the peak position of the focus evaluation value. Although the calculation is performed as the change rate θ1 in the vicinity, the absolute value of the slope of the straight line L2 connecting the focus evaluation values P6 and P8 is illustrated as the change rate θ2 in the vicinity of the infinity side of the peak position of the focus evaluation value. However, the present invention is not limited to this configuration. For example, as shown in FIG. 8, when the focus evaluation value moves down once after the focus evaluation value rises once, these three focus evaluation values P9 to P9˜ Focus evaluation value using P11 And the absolute value of the slope of the straight line L3 connecting the focus evaluation values P9 and P10 among the three focus evaluation values P9 to P11 in the vicinity of the peak position of the focus evaluation value is determined as the peak position of the focus evaluation value. It is also possible to calculate the change rate θ1 in the vicinity of the closest side and calculate the absolute value of the slope of the straight line L4 connecting the focus evaluation values P10 and P11 as the change rate θ2 in the vicinity of the infinity side of the peak position of the focus evaluation value. Good. FIG. 8 is a diagram illustrating another example of the relationship between the focus lens position and the focus evaluation value.

  Further, as shown in FIG. 9, when the focus evaluation value changes once after the focus evaluation value has risen twice, the focus evaluation value is obtained using these four focus evaluation values P12 to P15. Of these four focus evaluation values P12 to P15, the absolute value of the slope of the straight line L5 connecting the focus evaluation values P12 and P14, and the change rate of the focus evaluation value in the vicinity of the peak position The absolute value of the inclination of the straight line L6 connecting the focus evaluation values P14 and P15 may be calculated as θ1 and calculated as the change rate θ2 near the infinity side of the peak position of the focus evaluation value. FIG. 9 is a diagram illustrating another example of the relationship between the focus lens position and the focus evaluation value.

  Furthermore, in the above-described embodiment, the configuration in which the focus evaluation value is calculated at the sample interval at which the image plane movement amount is a constant amount is exemplified. However, for example, the sample in which the drive amount (pulse number) of the focus lens 32 is a constant amount. The focus evaluation value may be calculated at intervals.

In the above-described embodiment, the image plane movement coefficient K is described as the image plane movement coefficient K = (image plane movement amount / drive amount of the focus lens 32). However, the present invention is not limited to this configuration. It can also be defined as a movement coefficient K = (drive amount of focus lens 32 / image plane movement amount). In this case, the image plane movement amount can be calculated based on the following formula (8) instead of the above formula (1).
Image plane movement amount = drive amount of focus lens 32 / image plane movement coefficient K (8)

  Furthermore, in the second embodiment described above, when the still image shooting mode is set, the camera 1 shown in FIG. 6 is operated. When the moving image shooting mode is set, the camera shown in FIG. It is good also as a structure which performs 1 operation | movement.

  In addition to the above-described embodiment, for example, when the still image shooting mode is set, an image having a constant luminance and a certain size is detected as a point light source, and the point light source is detected. In this case, the determination value b may be changed to a small value. Thereby, it is possible to effectively prevent the false focusing from occurring due to the influence of the point light source. Note that the determination value b may be changed to a smaller value when a point light source is detected not only when the still image shooting mode is set but also when the moving image shooting mode is set. .

  In addition, in the above-described embodiment, the camera 1 that performs focus detection by the contrast detection method has been described as an example. However, the present invention is not limited to this configuration. For example, the present invention is not limited to focus detection by the contrast detection method. You may apply to the camera in which the focus detection by a phase difference detection system is possible. For example, as shown in FIG. 10, the image sensor 22 includes an image sensor 221 for imaging an image and focus detection pixels 222a and 222b for phase difference detection, and outputs the focus detection pixels 222a and 222b respectively. By collecting the output groups corresponding to the distance measurement pupils, data relating to the intensity distribution of the pair of images is acquired, and image deviation detection calculation processing such as correlation calculation processing or phase difference detection processing is performed on the intensity distribution data. Thus, the image shift amount may be detected by a so-called 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. FIG. 10 is an enlarged view of the imaging surface of the imaging element 22 according to another embodiment.

  Furthermore, in the above-described embodiment, the configuration for correcting the change rate θ2 near the infinity side of the peak position of the focus evaluation value based on the correction coefficient k corresponding to the spatial frequency characteristic of the optical system is exemplified. For example, the focus evaluation value near the peak position is corrected based on a coefficient corresponding to the spatial frequency characteristic of the optical system, and the peak position of the focus evaluation value is determined based on the corrected focus evaluation value. It is also possible to calculate the change rate θ1 in the vicinity of the near side and the change rate θ2 in the vicinity of the infinity side of the peak position of the focus evaluation value. Alternatively, the change rate θ1 in the vicinity of the close position of the peak position of the focus evaluation value may be corrected based on a coefficient corresponding to the spatial frequency characteristic of the optical system.

  In the present embodiment, the correction coefficient k is acquired from the lens barrel 3 as information on the spatial frequency characteristics of the optical system, and based on the acquired correction coefficient k, the focus evaluation value near the infinity side of the peak position. Although the configuration for correcting the change rate θ2 has been illustrated, the present invention is not limited to this configuration. For example, information other than the correction coefficient k may be acquired from the lens barrel 3 as information regarding the spatial frequency characteristics of the optical system. For example, the configuration of acquiring information on the spatial frequency characteristics of the optical system as shown in FIG. 7 and correcting the peak position of the focus evaluation value calculated by interpolation based on the acquired information on the spatial frequency characteristics of the optical system. It is good. Further, the driving speed of the focus lens 32 for calculating the focus evaluation value may be determined based on the information on the spatial frequency characteristics of the optical system. For example, in the example shown in FIG. 7, since the focus evaluation value changes more rapidly near the infinity side than the vicinity of the in-focus position, near the infinity side of the in-focus area, The scan driving speed of the focus lens 32 can be reduced.

  Further, in the above-described second embodiment, when the peak position of the focus evaluation value at which the ratio R is equal to or less than the first determination value cannot be detected, the scan drive is continued and the focus is focused on the entire driveable range of the focus lens 32. Although the configuration for detecting the peak position of the evaluation value is illustrated, the present invention is not limited to this configuration. For example, when the peak position of the focus evaluation value at which the ratio R is equal to or less than the first determination value cannot be detected, a predetermined drive Scan driving is continued in the target range (a range narrower than the driveable range of the focus lens 32), and it is determined whether or not the peak position of the focus evaluation value whose ratio R is equal to or smaller than the second determination value can be detected in the drive target range. It is good also as composition to do.

  Further, in the present embodiment, as shown in FIG. 4, the absolute value of the slope of the straight line L1 is calculated as the change rate θ1 in the vicinity of the close position of the peak position of the focus evaluation value based on the above formula (2). Based on the above equation (3), the ratio R is calculated as a positive value by calculating the absolute value of the slope of the straight line L2 as the change rate θ2 near the infinity side of the peak position of the focus evaluation value. Although R and the determination value b are compared, the present invention is not limited to this configuration. For example, the slope of the straight line L1 is calculated as the change rate θ1 in the vicinity of the peak position of the focus evaluation value, and the slope of the straight line L2 is calculated. May be calculated as the change rate θ2 near the infinity side of the peak position of the focus evaluation value. In this case, since the ratio R is calculated as a negative value, it is determined whether the ratio R is within a predetermined determination range, thereby determining the reliability that the peak of the focus evaluation value is the in-focus position. It can be set as the structure to do.

  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 (6)

An optical system having a focusing lens;
A storage unit storing information on the spatial frequency characteristics of the optical system;
A position detector for detecting position information of the focusing lens;
A transmitter for transmitting the information and the position information to the camera body;
A control unit that receives a drive signal of the focus adjustment lens from the camera body and drives the focus adjustment lens based on the received drive signal;
The drive signal includes a change rate of the evaluation value on the near side of the peak of the evaluation value related to the contrast of the subject image captured while moving the focus adjustment lens, and a change rate of the evaluation value on the infinity side of the peak. If the peak at which the ratio is less than or equal to the first determination value is detected, the position of the focus adjustment lens at which the evaluation value is the peak is set as the in-focus position, and the ratio is equal to or less than the first determination value. When a peak cannot be detected, and a peak whose ratio is equal to or less than a second determination value greater than the first determination value can be detected, a peak whose evaluation value is equal to or less than the second determination value A signal for driving the focus adjusting lens to the in-focus position with the position of the focus adjusting lens as the in-focus position.
interchangeable lens. A camera body,
An imaging unit that captures a subject image formed by an optical system of an interchangeable lens attached to the camera body and outputs a signal;
A receiver that receives information about the spatial frequency characteristics of the optical system and position information of the focus adjustment lens of the optical system from the interchangeable lens;
A focus detection unit that detects an in-focus position of the focus adjustment lens using the signal, the information, and the position information;
A drive instructing unit for instructing to drive the focus adjustment lens to the in-focus position,
The focus detection unit includes a change rate of the evaluation value on the near side of the peak of the evaluation value related to the contrast of the subject image captured while moving the focus adjustment lens, and a change rate of the evaluation value on the infinity side of the peak. If the peak at which the ratio is less than or equal to the first determination value is detected, the position of the focus adjustment lens where the evaluation value is the peak is the in-focus position, and the ratio is less than or equal to the first determination value. A peak at which the evaluation value is less than or equal to the second determination value when a peak at which the ratio is less than or equal to the second determination value greater than the first determination value can be detected. Detecting the position of the focus adjustment lens as an in-focus position,
Camera body. The focus detection unit uses, as a spatial frequency characteristic of the optical system, at least one of a change rate of the evaluation value on the near side of the peak of the evaluation value and a change rate of the evaluation value on the infinity side of the peak. The camera body according to claim 2, wherein correction is performed based on the correction. An optical system having a focusing lens;
A position detector for detecting position information of the focusing lens;
A control unit that receives a drive signal of the focus adjustment lens from a camera body and drives the focus adjustment lens based on the received drive signal;
The drive signal includes a change rate of the evaluation value on the near side of the peak of the evaluation value related to the contrast of the subject image captured while moving the focus adjustment lens, and a change rate of the evaluation value on the infinity side of the peak. If the peak at which the ratio is less than or equal to the first determination value is detected, the position of the focus adjustment lens at which the evaluation value is the peak is set as the in-focus position, and the ratio is equal to or less than the first determination value. When a peak cannot be detected, and a peak whose ratio is equal to or less than a second determination value greater than the first determination value can be detected, a peak whose evaluation value is equal to or less than the second determination value A signal for driving the focus adjusting lens to the in-focus position with the position of the focus adjusting lens as the in-focus position.
interchangeable lens. A camera body,
An imaging unit that captures a subject image formed by an optical system of an interchangeable lens attached to the camera body and outputs a signal;
A receiver that receives position information of a focus adjustment lens included in the optical system from the interchangeable lens;
A focus detection unit that detects an in-focus position of the focus adjustment lens using the signal and the position information;
A drive instructing unit for instructing to drive the focus adjustment lens to the in-focus position,
The focus detection unit includes a change rate of the evaluation value on the near side of the peak of the evaluation value related to the contrast of the subject image captured while moving the focus adjustment lens, and a change rate of the evaluation value on the infinity side of the peak. When the peak at which the ratio is less than or equal to the first determination value can be detected, the position of the focus adjustment lens at which the evaluation value is the peak is the in-focus position, and the ratio is equal to or less than the first determination value. A peak at which the evaluation value is less than or equal to the second determination value when a peak at which the ratio is less than or equal to the second determination value greater than the first determination value can be detected. Detecting the position of the focus adjustment lens as an in-focus position,
Camera body. The focus detection unit uses, as a spatial frequency characteristic of the optical system, at least one of a change rate of the evaluation value on the near side of the peak of the evaluation value and a change rate of the evaluation value on the infinity side of the peak. The camera body according to claim 5, wherein correction is performed based on the correction.

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