JP5020865B2 - IMAGING DEVICE, IMAGING DEVICE CONTROL METHOD, AND IMAGING DEVICE CONTROL PROGRAM - Google Patents

Description

  The present invention relates to an imaging apparatus such as a digital camera having a function of performing focus adjustment by manual operation, a control method for the imaging apparatus, and a control program for the imaging apparatus.

  An imaging apparatus such as a digital camera may employ an autofocus system called a TV-AF system.

  In this autofocus method, the focus lens that adjusts the focus of the subject is moved within a specific range and sequentially shot, and the sharpness of the subject image is shown based on the image signal of the image sensor at each lens position obtained by shooting. A focus evaluation value is calculated, and an in-focus position is obtained from the calculated value. The focus evaluation value is calculated using a BPF filter or the like so that the signal increases as the focus state is approached, and the focus state is obtained by controlling the focus position at the peak position of this signal.

  On the other hand, the manual focus method includes means for moving the focus lens by a user operation, and the user can adjust the focus by moving the focus lens to an arbitrary position. The adjustable range of the focus position is set in advance, for example, from 50 cm to infinity.

  In any case, the focus control is performed by driving the focus lens by an actuator such as a stepping motor. Since focus control is controlled in units of actuator control, when calculating the corresponding subject distance, the subject distance and the number of steps from a predetermined reference position of the stepping motor are associated in advance and calculated based on that. There is a need to.

  However, the correspondence between the number of steps and the subject distance is not always perfect. For example, the correspondence between the number of steps and the subject distance may not be perfect due to a shift due to imperfectness in the correspondence method between the number of steps and the subject distance, a change in temperature conditions, a change with time, and the like.

  If the correspondence between the number of steps and the subject distance is not perfect, even if the user intends to control the focus position at a certain distance during manual focus, an error occurs in the conversion between the distance and the number of steps, and the focus is not controlled at the desired distance. The phenomenon that occurs. For this reason, usually, a subject is confirmed using a display unit such as a liquid crystal display panel provided in a digital camera, and control is performed while viewing the best focus position.

  However, it may be impossible for the user to control the best focus state, particularly at the end of the focus position setting range in manual focus. For example, even if the user sets the focus position at infinity, an error may occur in the conversion between the distance and the number of steps, and the focus may actually be in front of infinity.

  In this case, since the user does not have a means for controlling the focus position on the rear focus side, it is impossible to obtain an image of the best pin at infinity.

  It is also possible to allow the user to perform focus control from the infinity to a super-infinity far beyond infinity, assuming the above phenomenon in advance. However, there is a possibility that the user designates the end distance (super infinite) of the focus position setting range, and in this case, a state where the best focus cannot be obtained at infinity occurs.

  Therefore, a technique has been proposed in which an automatic focusing unit that automatically obtains a focusing position from the periphery of the set focus position is provided, and focus control is performed by the automatic focusing unit when the focus position is set to a predetermined position. (Patent Document 1).

In this proposal, when the predetermined position is set to the end of the settable range for manual focus, the focus position is corrected by the automatic focusing means after the focus lens reaches the end of the settable range by manual focus. As a result, even when a situation where the user cannot control the best focus state described above occurs, the focus lens can be controlled to be positioned at the best focus position.
JP 2006-189571 A

  However, in Patent Document 1, after the focus lens reaches the end of the settable range by the user's manual focus operation, the focus is adjusted independently of the user's operation by the automatic focusing means.

  In such a case, the user must receive a manual operation during the operation of the automatic focusing means, and after the operation of the automatic focusing means is stopped, a manual focus operation by the user operation must be started.

  Therefore, there is a possibility that a time lag occurs from when the user operates to when the focus actually starts to change, thereby impairing operability and responsiveness.

  In addition, when performing manual focus operation while displaying the image signal obtained from the image sensor on the display unit, if the auto focus unit performs focus adjustment independently of the user operation, the auto focus unit is provided on the display unit. The focus variation caused by the operation is displayed.

  Since this focus fluctuation is not linked to the user's manual focus operation, there is a possibility that the display will be uncomfortable for the user.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to maintain good operability and responsiveness even at the end of a focus position settable range during manual focus operation.

  It is another object of the present invention to prevent a focus fluctuation from being displayed near the end of the focus position settable range.

In order to achieve the above object, an imaging apparatus of the present invention includes an imaging element that captures a subject image formed by a focus lens that performs focus adjustment of the subject image, and an operation unit that performs a manual operation. An imaging apparatus capable of adjusting the position of the focus lens based on an operation of the operation means, a display means for displaying a live image on a display unit based on an image signal of the image sensor, and an operation of the operation means When adjusting the position of the focus lens based on the following, a prediction means for predicting the position of the focus lens to be reached at the exposure timing of the next live image, the position of the focus lens predicted by the prediction means and the current position The focus evaluation value indicating the sharpness of the subject image based on the image signal of the image sensor in a range set based on the position of the focus lens is a live image An acquisition unit that acquires in the displayed state, a calculation unit that calculates a focus position based on the focus evaluation value acquired by the acquisition unit, and a next step based on the focus position calculated by the calculation unit Changing means for changing the position of the focus lens for displaying live images.

An image pickup apparatus control method according to the present invention includes: an image pickup device that picks up a subject image formed by a focus lens that performs focus adjustment of a subject image; and an operation unit that performs a manual operation . An image pickup apparatus control method capable of adjusting the position of the focus lens based on an operation, the display step displaying a live image on a display unit based on an image signal of the image sensor, and an operation of the operation means When the position of the focus lens is adjusted, a prediction step for predicting the position of the focus lens that should be reached at the exposure timing of the next live image, the position of the focus lens predicted in the prediction step, and the current focus lens A focus evaluation value indicating the sharpness of the subject image based on the image signal of the image sensor in a range set based on the position of the live image. On the basis of the focus position calculated on the acquisition step, the calculation step for calculating the focus position based on the focus evaluation value acquired in the acquisition step, And a changing step of changing the position of the focus lens for displaying the next live image.

An imaging apparatus control program according to the present invention includes: an imaging element that captures a subject image formed by a focus lens that performs focus adjustment of a subject image; and an operation unit that performs a manual operation . An imaging device control program capable of adjusting the position of the focus lens based on an operation, a display step of displaying a live image on a display unit based on an image signal of the imaging element, and an operation of the operation means When the position of the focus lens is adjusted, a prediction step for predicting the position of the focus lens that should be reached at the exposure timing of the next live image, the position of the focus lens predicted in the prediction step, and the current focus lens Focus evaluation indicating the sharpness of the subject image based on the image signal of the image sensor in a range set based on the position of An acquisition step in which a live image is displayed, a calculation step for calculating a focus position based on the focus evaluation value acquired in the acquisition step, and a focus position calculated in the calculation step. And changing the position of the focus lens for displaying the next live image based on the computer.

  According to the present invention, at the time of manual focus operation, good operability and responsiveness can be maintained even at the end of the focus position settable range, and unpleasant focus fluctuations near the settable range end are not displayed. Can be. This makes it possible to obtain an image with high sharpness at the end of the focus position setting range without bothering the user.

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

[First Embodiment]
FIG. 1 is a control block diagram for explaining the imaging apparatus 100 according to the first embodiment of the present invention.

  As shown in FIG. 1, the imaging apparatus according to the present embodiment includes a photographing lens 101 including a zoom mechanism, an aperture and shutter control unit 102 that controls the amount of light, an AE processing unit 103, a strobe 106, an EF processing unit 107, and a focus lens control. Unit 104, AF processing unit 105, and the like.

  The focus lens control unit 104 performs control to focus on the image sensor 108 such as a CCD sensor that captures a subject image formed by the focus lens. The AF processing unit (calculation unit) 105 calculates a focus evaluation value indicating the sharpness of the subject image based on the image signal obtained from the image sensor 108.

  The diaphragm / shutter controller 102 includes various devices such as a diaphragm / shutter (not shown), an actuator for moving these, a drive circuit for controlling the actuator, and a D / A converter. In addition, the focus lens control unit 104 includes various devices such as a focus lens 208 (see FIG. 2) for adjusting the focus of the subject image, an actuator for moving the lens, a drive circuit for controlling the actuator, and a D / A converter. including.

  The imaging apparatus according to the present embodiment includes an A / D conversion unit 109, an image processing unit 110, a WB (white balance) processing unit 111, a format conversion unit 112, a DRAM 113, and a VRAM 116. The A / D conversion unit 109 includes a CDS circuit and a nonlinear amplifier circuit that remove output noise of the image sensor 108. The DRAM 113 is used as a high-speed buffer as a temporary image storage unit or a working memory for image compression / decompression.

  Further, in FIG. 1, the image recording unit 114 includes a recording medium such as a memory card and its interface. The system control unit 115 controls the entire imaging apparatus such as a shooting sequence. The operation display unit 117 displays a shooting screen, an AF area, and the like at the time of shooting, in addition to a live image display, a display for assisting operation, and a display of the state of the apparatus. The operation unit 118 is for operating the imaging apparatus from the outside.

  The operation unit 118 includes, for example, a menu switch for performing various settings such as a shooting function of the imaging apparatus and settings for image playback, a zoom lever for instructing a zoom operation of the shooting lens, and an operation mode switching for switching between a shooting mode and a playback mode. There are switches.

  The shooting mode switch 119 is a switch for setting shooting modes such as a program, a landscape, a person, and sports. A drive mode switch (SW) 120 is a switch for setting a drive mode such as one-time shooting, continuous shooting, and self-timer shooting.

  The main SW 121 is a switch for turning on the system. A switch (SW1) 122 is a switch for performing a shooting standby operation such as AF and AE. The switch (SW2) 123 is a switch for performing shooting after the switch (SW1) 122 is operated.

  The focus mode switch 124 is a switch for switching between an autofocus (hereinafter referred to as AF) mode for automatically performing focus adjustment and a manual focus (hereinafter referred to as MF) mode for performing focus adjustment by a photographer's operation.

  The focus operation unit 125 is for accepting a manual operation of the photographer in the MF mode and adjusting the position by moving the focus lens. The focus operation unit 125 accepts a manual operation by the photographer when the focus mode switch 124 is in the MF mode.

  The system control unit 115 receives a digital signal obtained by A / D converting an analog signal generated by the operation of the focus operation unit 125 as an input value, and focuses the control signal of the focus lens 208 according to the operation amount based on the digital signal. Output to the control unit 104. Thereby, the focus adjustment by the manual operation of the photographer, that is, the MF function is realized. The focus drive mechanism 126 is a mechanism for controlling the focus lens 208 and the image sensor 108 to realize high-speed focus change.

  FIG. 2 shows an example of the focus drive mechanism 126.

  The focus drive mechanism 126 includes a holding member 201 that holds the image sensor 108, a drive lever 202, an electrostrictive element 203, a motor 204 that drives the focus lens 208, a gear 205, and a nut member 206. The focus drive mechanism 126 includes a screw member 207, a lens holding member 290 that holds the focus lens 208, a guide shaft 210 that guides the focus lens 208 in the optical axis direction, and a spring that biases the focus lens 208 toward the image sensor 108. 211.

  The image sensor 108 is driven in the optical axis direction by the electrostrictive element 203 via the drive lever 202. The output of the electrostrictive element 203 at this time is amplified by the drive lever 202. The focus lens 208 is driven in the optical axis direction by converting the rotational output of the motor 204 into a linear motion via the gear 205, the screw member 207, and the nut member 206. Focus adjustment is performed by driving in the optical axis direction of at least one of the image sensor 108 and the focus lens 208.

  In general, the focus sensitivity of the focus lens 208 is less than 1 (often 0.6 or less). Therefore, driving the image sensor 108 changes the focus faster than driving the focus lens 208. Can do. Therefore, in the present embodiment, the focus is changed at high speed by simultaneously driving the image sensor 108 and the focus lens 208, and detailed focusing is performed by driving only the focus lens 208.

(Basic operation of MF)
Next, the basic operation of the MF will be described with reference to FIG. 3 and FIG.

  FIG. 3 illustrates a UI display displayed on the operation display unit 117 when the imaging apparatus is in the MF mode and a focus operation for accepting an instruction by a manual operation of the photographer when the focus lens 208 is moved in the optical axis direction. FIG.

  In FIG. 3, when the focus operation unit 125 is rotated clockwise, the focus lens 208 moves in an infinite direction, and when the focus operation unit 125 is rotated counterclockwise, the focus lens 208 moves in the closest direction. Further, the MF distance bar is displayed in conjunction with the operation display unit 117 according to the movement of the focus lens 208.

  FIG. 4 is a flowchart for explaining control of the focus lens when the imaging apparatus is in the MF mode. 4 is executed by the system control unit 115 after the control program stored in the storage unit (ROM, hard disk, or the like) is loaded into the DRAM 113.

  First, in step S100, the system control unit 115 detects whether the focus operation unit 125 is operated in the infinite direction or the closest direction, and if detected, the process proceeds to step S101.

  In step S101, the system control unit 115 determines whether or not the current focus mode is the MF mode. Specifically, when the AF mode is set by the focus mode switch 124, the system control unit 115 returns to step S100 and does not control the focus lens 208 by manual operation. On the other hand, if the MF mode is set by the focus mode switch 124, the system control unit 115 proceeds to step S102.

  In step S <b> 102, the system control unit 115 determines the driving condition of the focus lens 208 in conjunction with the manual operation according to the operation amount and the operation direction (infinite direction or closest direction) of the focus operation unit 125. In the present embodiment, the system control unit 115 refers to the table in Table 1 stored in a predetermined storage area, and sets the target position of the focus lens 208 (the lens at the current position) according to the operation amount of the focus operation unit 125. Position) and the control speed during movement are determined.

  Note that the range that can be manually adjusted by the MF varies depending on the focal length. Therefore, in step S102, the system control unit 115 calculates and stores not only the control speed and the movement amount of the focus lens 208 but also the control ends (butting positions) on the near side and the infinite side. In addition, when the target position of the focus lens 208 calculated according to the operation amount of the focus operation unit 125 exceeds the control end on the near side and the infinite side, the system control unit 115 changes the target position to the end on the side beyond To do.

  Next, in step S103, the system control unit 115 starts pre-reading MF control, which will be described later, according to the driving condition of the focus lens 208 determined in step S102. The system control unit 115 moves the focus lens 208 in the optical axis direction by the prefetch MF control process, and realizes focus adjustment according to the operation amount of the focus operation unit 117.

(Prefetch MF control)
Next, the prefetch MF control in step S103 of FIG. 4 will be described with reference to FIGS.

  FIG. 5 is a flowchart for explaining an example of a prefetch operation of the focus evaluation value during the MF operation.

  First, in step S200, the system control unit 115 determines whether it is the exposure timing of the live image displayed on the operation display unit 117. If it is not the exposure timing, the process returns to step S200. If it is the exposure timing, the process proceeds to step S201.

  In step S201, the system control unit 115 performs a process of predicting the position of the focus lens 208 that should be reached at the exposure timing of the next live image.

  Here, FIG. 6 shows the relationship between the live image display of the pre-reading operation of the focus evaluation value during the MF operation and the control timing of the focus lens 208. In the present embodiment, the image signal is read from the image sensor 108 in synchronization with, for example, a 1/140 second VD pulse. On the other hand, the generation of the live image is performed once every seven VD pulse periods and is updated every 1/20 second. That is, the image sensor 108 generates an image signal at a predetermined period even during a period during which one frame of the live image is being displayed.

  In step S200 of FIG. 5, the system control unit 115 determines whether it is the exposure timing for generating a live image such as Exp1 and Exp2 in FIG. In step 201 in FIG. 5, the system control unit 115 arrives at the next live image exposure based on the control speed of the focus lens 208 calculated in step S102 in FIG. 4 and the live image update cycle. The predicted position of the power focus lens 208 is calculated. That is, the system control unit 115 calculates the predicted position of the focus lens 208 to be reached in the next frame C at the exposure timing (position α, Exp1) of the frame B in FIG.

  Next, in step S202, the system control unit 115 determines whether or not the predicted position calculated in step S201 exceeds the position of the infinite control end calculated in step S102 in FIG. The process proceeds to S204, and if it exceeds, the process proceeds to Step S203.

  In step S203, the system control unit 115 sets the prefetch execution flag to ON. When this flag is ON, the system control unit 115 performs a focus evaluation value prefetching operation to be described later. On the other hand, in step S204, the system control unit 115 turns off the prefetch execution flag.

  Next, in step S205, the system control unit 115 determines a driving condition of the focus lens 208 for the prefetch operation of the focus evaluation value. In this process, the system control unit 115 obtains a focus evaluation value in a state where a live image is displayed based on the predicted position of the focus lens 208 calculated in step S201 and the current position of the focus lens 208. Set the range.

  Specifically, referring to FIG. 6, system control unit 115 executes the process of step S205 at the timing of Exp1. Then, the target position position β for performing the focus evaluation value look-ahead operation is calculated by calculating backward from the position position α at that time, the infinite abutting position, and the period from Exp1 to Exp2.

  On the other hand, as shown in FIG. 7, depending on the timing of the exposure period for the live image, the distance between the position of the focus lens 208 and the infinite abutting position at that time may be extremely narrow. Therefore, in step S205, when the range for acquiring the focus evaluation value is equal to or smaller than the predetermined value, the system control unit 115 places the infinite side abutting position at the center of the range for acquiring the focus evaluation value as shown in FIG. Set the range to be That is, the focus evaluation value acquisition start position is not the current position at Exp1, but the position α. In this way, the range for acquiring the focus evaluation value is determined.

  Next, in step S206, the system control unit 115 checks whether or not the exposure of the live image has been completed. In the present embodiment, it is assumed that the processing from step S201 to step S205 ends within the exposure period of the live image. Then, if the exposure of the live image has been completed, the system control unit 115 proceeds to step S207.

  In step S207, the system control unit 115 checks the state of the prefetch execution flag set in step S203. If the prefetch execution flag is OFF, the process proceeds to step S212. If the prefetch execution flag is ON, the process proceeds to step S208.

  In step S208, the system control unit 115 moves the focus lens 208 while sequentially controlling the focus drive mechanism 126 within a predetermined range according to the drive condition of the focus lens 208 determined in step S205. In addition, the system control unit 115 stores the focus evaluation value calculated by the AF processing unit 105 on the basis of the image signal periodically obtained from the imaging in a predetermined storage area in association with the position information of the focus lens 208.

  By this processing, a focus evaluation value of a predetermined number of points and the position of the focus lens 208 associated therewith are acquired between the position α and the position β shown in FIGS.

  Next, in step S209, the system control unit (calculation unit) 115 calculates a focus position based on the focus evaluation value obtained in step S208 and the position information of the focus lens 208. Details of the calculation of the in-focus position will be described later.

  Next, in step S210, the system control unit 115 determines whether or not the processing result in step S209 is in focus. If not in focus, the system control unit 115 proceeds to step S212. If in focus, the system control unit 115 proceeds to step S211. .

  In step S211, the system control unit (changing unit) 115 performs a pre-reading operation of the focus evaluation value, and the predicted lens position predicted in step S201 only when the result is in-focus is obtained in step S209. Change to the focal position. As a result, the predicted position of the focus lens 208 for the next live image display is changed to the in-focus position.

  In step S212, the system control unit 115 controls the motor 204 to move the focus lens 208 to the predicted lens position to be displayed in the next live image, and proceeds to step S213.

  In step S213, the system control unit 115 determines whether or not the movement of the focus lens 208 is completed. If the movement of the focus lens 208 is completed, the process proceeds to step S214.

  In step S214, the system control unit 115 determines whether or not the target position of the focus lens 208 calculated in step S102 in FIG. 4 has been reached. If the initial target position has been reached, the pre-reading MF control is terminated. The process returns to step S100 in FIG. On the other hand, if the target position has not been reached, the system control unit 115 returns to step S200.

  That is, the system control unit 115 repeats the processing described with reference to FIG. 5 until the target position calculated according to the operation amount of the focus operation unit 125 is reached. In the live image exposure period, only the simple movement of the focus lens 208 is performed as long as the next predicted lens position to be calculated does not exceed the infinite side abutting position. However, when the predicted lens position exceeds the infinite abutting position, the above-described focus evaluation value look-ahead operation is performed, and the state of the focus evaluation value up to the range exceeding the predicted lens position and the result of the abutting are reflected. Position correction is performed.

  Further, the range in which the state of the focus evaluation value is investigated by the prefetch operation of the focus evaluation value is implemented so as to include the initial infinite abutting position. Therefore, as shown in FIG. 8, depending on the state of the focus evaluation value obtained by the focus evaluation value look-ahead operation, the side closer to the far side (FIG. 8A) of the initial infinite abutting position (FIG. 8B). )) Is also corrected.

  Further, in a situation where the in-focus position cannot be specified from the focus evaluation value obtained by the focus evaluation value look-ahead operation, the motor 204 that drives the focus lens 208 is controlled so as to be positioned at the initial infinite abutting position. . Therefore, even in the case of an object with low illuminance or low contrast where the level of the focus evaluation value is lowered and the reliability is low, if the in-focus determination is NG, the same operation as in the case where the conventional look-ahead MF control is not performed is performed. To be implemented.

(Focus position calculation in pre-read MF control)
Next, the in-focus position calculation process in step S209 in FIG. 5 will be described with reference to FIGS.

First, except for special cases such as perspective conflict, the focus evaluation value has a mountain shape as shown in FIG. 12 when the horizontal axis represents the focus lens position and the vertical axis represents the focus evaluation value. Therefore, whether or not the focus evaluation value is mountain-shaped is determined by the difference between the maximum value and the minimum value of the focus evaluation value, the length of the inclined portion with an inclination of a certain value (SlopeThr) or more, and the inclination. Focus determination can be performed by determining from the gradient of the portion. The result of in-focus determination is output as ○, ×, Δ as shown below.
○: The focus of the subject can be adjusted from the peak position of the focus evaluation value.
X: The contrast of the subject is insufficient.
Δ: The subject is located at a distance outside the scanned distance range (there are ΔNEAR and ΔFAR depending on the direction of the focus position).

  Here, as shown in FIG. 12, the points where it is recognized that the inclination continues from the top of the mountain (point A) are D points and E points, and the width between the points D and E is the mountain width L. . The sum (SL1 + SL2) of the focus evaluation value difference SL1 between the points A and D and the focus evaluation value difference SL2 between the points A and E is SL.

  FIG. 9 is a flowchart for explaining the focus position calculation process in step S209 of FIG.

  First, in step S300, the system control unit 115 obtains a scan point io that is a point that gives the maximum value max and the minimum value min and the maximum value max of the focus evaluation value. Next, in step S301, the system control unit 115 initializes both a variable L representing the peak width of the focus evaluation value and a variable SL representing the mountain gradient to “0”.

  Next, in step S302, the system control unit 115 checks whether or not the scan point io giving the maximum value max is the position of the far side end in the predetermined range where the scan is performed. Go to and check for a monotonic decrease toward infinity. On the other hand, the system control unit 115 proceeds to step S304 if the scan point io giving the maximum value max is the position of the far end in the predetermined range where the scan is performed.

  FIG. 10 is a flowchart for explaining the processing for checking the monotonic decrease toward infinity in step S303.

  First, in step S400, the system control unit 115 initializes the counter variable i to io.

  Next, in step S401, the system control unit 115 sets the focus evaluation value d [i] at the scan point i and the focus evaluation value d at the scan point i-1 that is one scan point away from i. The difference from [i-1] is compared with a constant value SlopeThr.

  If d [i] −d [i−1] ≧ SlopeThr, the system control unit 115 determines that a monotonic decrease in the infinity direction has occurred, and proceeds to step S402.

In step S <b> 402, the system control unit 115 follows the variable L that represents the length (mountain width) of the portion where the focus evaluation value is inclined at a certain slope or more, and the variable SL that represents the amount of decrease in the monotonically decreasing section. Update according to the formula.
L = L + 1
SL = SL + (d [i] -d [i-1])
On the other hand, if d [i] −d [i−1] ≧ SlopeThr is not satisfied in step S401, the system control unit 115 determines that no monotonic decrease in the infinity direction has occurred, and monotonous in the infinity direction. The process of checking the decrease is terminated, and the process proceeds to step S304 in FIG.

  Next, in step S403, the system control unit 115 sets i = i−1, moves the detection point to the one scan point infinity side, and proceeds to step S404.

  In step S404, the system control unit 115 checks whether or not the counter i has reached the value (= 0) of the far end position in the predetermined range in which scanning has been performed. Then, the system control unit 115 checks the monotonic decrease in the infinity direction when the value of the counter i is 0, that is, when the start point for detecting the monotonic decrease reaches the far end position in the predetermined range where the scan is performed. Is finished, and the process proceeds to step S304 in FIG. On the other hand, if the value of the counter i is not 0, the system control unit 115 returns to step S401 and repeats the above-described processing. As described above, the monotonic decrease from i = io to infinity is checked.

  Returning to FIG. 9, in step S304, the system control unit 115 checks whether or not the scan point io giving the maximum value is the position of the nearest end in the predetermined range where the scan is performed. Proceeding to step S305, a monotonic decrease in the closest direction is examined. On the other hand, the system control unit 115 proceeds to step S306 if the scan point io giving the maximum value is the position of the closest end in the predetermined range where the scan is performed.

  FIG. 11 is a flowchart for explaining the processing for checking the monotonic decrease in the closest direction in step S305.

  First, in step S500, the system control unit 115 initializes the counter variable i to io.

  Next, in step S501, the system control unit 115 determines the focus evaluation value d [i] at the scan point i and the focus evaluation value d [1] at the scan point i + 1 that is one scan point closer to i than the i. The difference from i + 1] is compared with a constant value SlopeThr.

  If d [i] −d [i + 1] ≧ SlopeThr, the system control unit 115 determines that a monotonic decrease in the closest direction has occurred, and proceeds to step S502.

In step S <b> 502, the system control unit 115 follows the variable L that represents the length (mountain width) of the portion where the focus evaluation value is inclined at a certain slope or more, and the variable SL that represents the amount of decrease in the monotonically decreasing section. Update according to the formula.
L = L + 1
SL = SL + (d [i] -d [i + 1])
On the other hand, if d [i] −d [i + 1] ≧ SlopeThr is not satisfied in step S501, the system control unit 115 determines that no monotonic decrease in the closest direction has occurred, and checks for a monotonic decrease in the close direction. The process ends, and the process proceeds to step S306 in FIG.

  Next, in step S503, the system control unit 115 sets i = i + 1, moves the point to be detected closer to one scan point, and proceeds to step S504.

  In step S504, the system control unit 115 checks whether or not the counter i has reached the value (= N) of the closest end position in a predetermined range in which scanning has been performed. Then, when the value of the counter i is N, that is, when the starting point for detecting the monotonic decrease reaches the closest end position in the predetermined range where the scan is performed, the system control unit 115 checks the monotonic decrease in the closest direction. The process ends, and the process proceeds to step S306 in FIG. On the other hand, if the value of the counter i is not N, the system control unit 115 returns to step S501 and repeats the above-described processing. As described above, the monotonic decrease from i = io in the closest direction is checked.

  When the processing for checking the monotonic decrease in the infinity direction and the close-up direction is completed, the system control unit 115 determines whether or not the obtained focus evaluation value has a mountain shape, various coefficients, and respective threshold values. Compared with, judgment of ○, ×, △ is performed.

  Returning to FIG. 9, in step S <b> 306, the system control unit 115 determines whether or not the scan point io that gives the maximum focus evaluation value is the closest end in the predetermined range in which scanning was performed. In addition, the system control unit 115 sets the focus evaluation value d [n] at the closest scan point n and the focus evaluation value d [n] at the scan point n−1 that is one scan point away from n. −1] is determined whether or not the difference is equal to or greater than a certain value SlopeThr. If io = near end and d [n] −d [n−1] ≧ SlopeThr, the system control unit 115 proceeds to step S312; otherwise, the system control unit 115 proceeds to step S307.

  In step S307, the system control unit 115 determines whether or not the scan point io that gives the maximum focus evaluation value is the far end in the predetermined range where the scan is performed. In addition, the system control unit 115 sets the focus evaluation value d [0] at the far-side end scan point 0 and the focus evaluation value d [1] at the scan point 1 from the nearest end by one scan point from 0. It is determined whether or not the difference is equal to or greater than a certain value SlopeThr. The system control unit 115 proceeds to step S311 if io = far end and d [0] −d [1] ≧ SlopeThr, otherwise proceeds to step S308.

  In step S308, the system control unit 115 determines whether or not the length L of the portion inclined at a certain value or more is greater than or equal to a predetermined value Lo. Further, the system control unit 115 determines that the average value SL / L of the inclined portion is equal to or greater than the predetermined value SLo / Lo, and the difference between the maximum value max and the minimum value min of the focus evaluation value is equal to or greater than the predetermined value. Judge whether there is. If L ≧ Lo, SL / L ≧ SLo / Lo, and the maximum value max−minimum value min ≧ predetermined value of the focus evaluation value, the system control unit 115 proceeds to step S309, otherwise Proceed to step S310.

  In step S309, since the obtained focus evaluation value has a mountain shape and the subject can be adjusted in focus, the system control unit 115 sets the determination result to ◯. Then, the system control unit 115 performs an interpolation operation based on the maximum focus evaluation value acquired as the focus position and the adjacent focus evaluation value, and calculates the focus position.

  In step S310, since the obtained focus evaluation value is not mountain-shaped and the focus of the subject cannot be adjusted, the system control unit 115 sets the determination result to x.

  Steps S311 and S312 are cases where the subject is located at a distance outside the distance range scanned by the focus position. In step S311, the system control unit 115 determines ΔFAR indicating that the in-focus position is on the far side of the range, and in step S312, the system control unit 115 has the in-focus position on the near side of the range. Is determined to be ΔNEAR.

  As described above, in the present embodiment, when the predicted lens position exceeds the infinite side abutting position, pre-reading of the focus evaluation value and calculation of the in-focus position are performed with the live image displayed, and the result is obtained. Based on this, the focus position near the end of the focus position setting range is corrected.

  Therefore, it is possible to eliminate error factors such as deviation due to imperfectness in the correspondence method between the subject distance affected by the end of the focus position setting range and the number of steps of the focus lens, changes in temperature conditions, changes over time, etc. it can. As a result, the focus lens 208 can be positioned at an appropriate focus position.

  In addition, by performing the above-described processing in a state where the live image is displayed while performing the MF operation, the focus position can be set near the end of the settable range while maintaining the operability and responsiveness of the MF. It is possible to achieve focus adjustment that does not cause focus fluctuation. This makes it possible to obtain an image with high sharpness at the end of the focus position setting range without bothering the user.

[Second Embodiment]
Next, an imaging apparatus according to the second embodiment of the present invention will be described with reference to FIGS. Note that in this embodiment, everything except the prefetch MF control in the first embodiment is the same, and therefore only different parts will be described.

(Prefetch MF control)
FIG. 13 is a flowchart for explaining an example of a pre-reading operation of the focus evaluation value during the MF operation. Step S202 in FIG. 5 is changed to step S602.

  In the first embodiment, the focus evaluation value is pre-read based on whether or not the predicted lens position at the time of displaying the next live image predicted during the exposure period of the live image has reached the infinite side abutting position in step S202. The operation was starting.

  In contrast, in the present embodiment, in step S602, the system control unit 115 determines whether or not the predicted lens position at the time of the next live image display is within a predetermined range as shown in FIG. In this case, the focus evaluation value look-ahead operation is started. In the present embodiment, the position returned to the near side by two frames on the basis of the number of focus evaluation values that can be acquired during one frame on the basis of the infinite side abutting position is set as the starting point of the range. This is because the in-focus position is calculated appropriately based on the relationship between the position of the focus lens 208 and the infinite side abutting position in the exposure period for generating a live image, and the relationship of the mountain shape formed by the acquired focus evaluation value. This is because it may not be possible.

  In response to this problem, in the first embodiment, when the range in which the focus evaluation value is acquired is equal to or smaller than the predetermined value, as shown in FIG. 7, the infinite side abutting position is the center of the range in which the focus evaluation value is acquired. The range is set to be

  However, in the present embodiment, the focus evaluation value look-ahead operation is performed in advance from a position away from the infinite side abutting position, and in step S609, the acquired focus evaluation values of each frame are merged as shown in FIG. Then, the focus position is calculated using all the obtained focus evaluation values.

  As a result, it is possible to more accurately identify the in-focus position and perform focus correction near the infinite side abutting position. Other configurations and operational effects are the same as those of the first embodiment.

  In addition, this invention is not limited to what was illustrated to the said embodiment, In the range which does not deviate from the summary of this invention, it can change suitably.

  The object of the present invention is achieved by executing the following processing. That is, a storage medium that records a program code of software that realizes the functions of the above-described embodiments is supplied to a system or apparatus, and a computer (or CPU, MPU, etc.) of the system or apparatus is stored in the storage medium. This is the process of reading the code.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code and the storage medium storing the program code constitute the present invention.

  Moreover, the following can be used as a storage medium for supplying the program code. For example, floppy (registered trademark) disk, hard disk, magneto-optical disk, CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD + RW, magnetic tape, nonvolatile memory card, ROM or the like. Alternatively, the program code may be downloaded via a network.

  Further, the present invention includes a case where the function of the above-described embodiment is realized by executing the program code read by the computer. In addition, an OS (operating system) running on the computer performs part or all of the actual processing based on an instruction of the program code, and the functions of the above-described embodiments are realized by the processing. Is also included.

  Furthermore, a case where the functions of the above-described embodiment are realized by the following processing is also included in the present invention. That is, the program code read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Thereafter, based on the instruction of the program code, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing.

It is a control block diagram for demonstrating the imaging device which is the 1st Embodiment of this invention. It is a figure which shows an example of a focus drive mechanism. It is a figure which shows UI display displayed on an operation display part when an imaging device is in MF mode, and a focus operation part for receiving a photographer's instruction | indication when moving a focus lens to an optical axis direction. It is a flowchart for demonstrating control of the focus lens when an imaging device is in MF mode. It is a flowchart for demonstrating the example of prefetch operation | movement of the focus evaluation value during MF operation | movement. It is a graph which shows the relationship between the display of the live image of the prefetch operation | movement of the focus evaluation value during MF operation | movement, and the control timing of a focus lens. It is a graph which shows the relationship between the display of the live image of the prefetch operation | movement of the focus evaluation value during MF operation | movement, and the control timing of a focus lens. It is a graph which shows the state of the focus evaluation value in the prefetch operation | movement of a focus evaluation value. FIG. 6 is a flowchart for explaining an in-focus position calculation process in step S209 in FIG. 5. It is the flowchart figure for demonstrating the process which investigates the monotone decrease to the infinity direction in FIG.9 S303. FIG. 10 is a flowchart for explaining a process for examining a monotonic decrease in the closest direction in step S305 in FIG. 9; It is a graph which shows the relationship between a focus lens position and a focus evaluation value. It is a flowchart for demonstrating the example of prefetch operation | movement of the focus evaluation value in MF operation | movement in the imaging device which is the 2nd Embodiment of this invention. It is a graph which shows the relationship between the live image display of the focus evaluation value prefetch operation | movement in MF operation | movement, and the control timing of a focus lens. It is a graph for demonstrating the process which merges the focus evaluation value acquired by each flame | frame, and specifies an in-focus position.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Shooting lens 102 Aperture and shutter control unit 103 AE processing unit 104 Focus lens control unit 105 AF processing unit 106 Strobe 107 EF processing unit 108 Imaging element 110 Image processing unit 113 DRAM
114 Image recording unit 115 System control unit 117 Operation display unit 118 Operation unit 119 Shooting mode switch 120 Drive mode switch 121 Main switch 122 Switch (SW1)
123 switch (SW2)
124 focus mode switch 125 focus operation unit

Claims (5)

An image sensor that captures a subject image formed by a focus lens that performs focus adjustment of the subject image; and an operation unit that performs a manual operation. The position of the focus lens is determined based on an operation of the operation unit. An adjustable imaging device,
Display means for displaying a live image on a display unit based on an image signal of the image sensor;
When adjusting the position of the focus lens based on the operation of the operation means, prediction means for predicting the position of the focus lens that should be reached at the exposure timing of the next live image;
The live image has a focus evaluation value indicating the sharpness of the subject image based on the image signal of the image sensor in a range set based on the position of the focus lens predicted by the prediction unit and the current position of the focus lens. Acquisition means for acquiring in the displayed state;
Calculation means for calculating a focus position based on the focus evaluation value acquired by the acquisition means;
An imaging apparatus comprising: a changing unit that changes a position of a focus lens for displaying a next live image based on the in-focus position calculated by the calculating unit. And wherein the position of the focus lens which is predicted by the prediction means, when exceeding the range of the position of the adjustable the focus lens by said operating means, to implement the acquisition of the focus evaluation value by the acquisition unit, it The imaging device according to claim 1.   The imaging apparatus according to claim 1, wherein the focus evaluation value is acquired by the acquisition unit when the position of the focus lens predicted by the prediction unit is within a predetermined range. An image sensor that captures a subject image formed by a focus lens that performs focus adjustment of the subject image; and an operation unit that performs a manual operation. The position of the focus lens is determined based on an operation of the operation unit. An image pickup apparatus control method that can be adjusted ,
A display step of displaying a live image on a display unit based on an image signal of the image sensor;
When adjusting the position of the focus lens based on the operation of the operation means, a prediction step for predicting the position of the focus lens to be reached at the exposure timing of the next live image;
The live image has a focus evaluation value indicating the sharpness of the subject image based on the image signal of the image sensor in a range set based on the position of the focus lens predicted in the prediction step and the current position of the focus lens. An acquisition step to acquire in the displayed state;
A calculation step for calculating a focus position based on the focus evaluation value acquired in the acquisition step;
And a changing step of changing a position of a focus lens for displaying the next live image based on the in-focus position calculated in the calculating step. An image sensor that captures a subject image formed by a focus lens that performs focus adjustment of the subject image; and an operation unit that performs a manual operation. The position of the focus lens is determined based on an operation of the operation unit. An adjustable imaging device control program comprising:
A display step of displaying a live image on a display unit based on an image signal of the image sensor;
When adjusting the position of the focus lens based on the operation of the operation means, a prediction step for predicting the position of the focus lens to be reached at the exposure timing of the next live image;
The live image has a focus evaluation value indicating the sharpness of the subject image based on the image signal of the image sensor in a range set based on the position of the focus lens predicted in the prediction step and the current position of the focus lens. An acquisition step to acquire in the displayed state;
A calculation step for calculating a focus position based on the focus evaluation value acquired in the acquisition step;
A control program for an imaging apparatus, which causes a computer to execute a change step of changing a position of a focus lens for next live image display based on the in-focus position calculated in the calculation step.

Images