JP6390198B2 - Imaging apparatus and imaging method - Google Patents

Description

  The present invention relates to an imaging apparatus and an imaging method that include a focus adjustment device and can detect a composition change.

  2. Description of the Related Art Conventionally, a focus adjusting device that recognizes a composition change using a change in defocus amount is known. In Patent Document 1, for the purpose of reducing the calculation load at the time of focus detection, defocus amounts of a plurality of focus areas detected at a first time and a second time after the first time are detected. The defocus amounts of the plurality of focus areas are compared to determine whether or not a composition change has occurred, and when it is determined that no composition change has occurred, the selection means selected at the first time. A focus adjustment device that performs focus adjustment based on the defocus amount at the second time in the focus area is described.

JP 2013-020123 A

  However, the conventional method of recognizing composition change using a change in defocus amount recognizes the composition change by focusing only on the change in defocus amount. For example, the composition does not involve a change in defocus amount. There is a problem that the composition change recognition accuracy is poor, for example, the composition change cannot be recognized when a change occurs.

It is an object of the present invention to obtain an imaging apparatus and an imaging method provided with a focus adjustment apparatus that improves composition change recognition accuracy.
An object of the present invention is to obtain an imaging apparatus and an imaging method provided with a focus adjustment device that can shorten the subsequent focus adjustment time when it is recognized that there is no composition change.

An image pickup apparatus according to the present invention that solves such a problem includes a light receiving unit that passes through a photographing optical system and photoelectrically converts a pair of subject light beams divided into pupils and outputs a pair of image signals; A composition change detection correlation calculating means for calculating a correlation value between the image signal output at the time of the first time and the image signal output at the second time after the first time; and calculated by the composition change detection correlation calculating means. Composition change determining means for determining that no composition change has occurred when the correlation value is within a predetermined value; calculating a relative image shift amount of a pair of image signals output by the light receiving means ; Defocus amount calculation means for calculating a defocus amount based on the shift amount; reliability determination means for determining reliability of the defocus amount; and when the defocus amount is within a predetermined focus reference value Copy A focus determination unit that determines that the subject is in focus; and when the focus determination unit does not determine that the subject is in focus, the focus adjustment unit of the photographing optical system is driven based on the defocus amount. The predetermined focus reference value so that the focus determination unit can easily determine that the focus is in focus when it is determined that the composition change has not occurred by the focus adjustment unit driving unit; A focus determination value changing means for changing; and when the composition change determining means determines that no composition change has occurred, the reliability determining means makes it easier for the reliability determining means to determine that there is reliability. And a reliability judgment value changing means for changing the reference value .

In the imaging apparatus of the present invention, the light receiving means passes through the photographing optical system and forms a pair in each of the first direction on the image plane and the second direction different from the first direction. The pair of subject luminous fluxes divided into pupils are respectively photoelectrically converted to output a pair of image signals, and the composition change detection correlation calculating means outputs a pair of first directions output at a first time by the light receiving means. one of the image signal and the first one correlation value of a pair of image signals of direction and a second direction which is output to the first time output to the first time the second time after the It calculates one and one correlation value in the second direction of the pair of image signals outputted to the second time the pair of image signals, the composition change determination means, is calculated by the composition change detecting correlation computing means The correlation value in the first direction and the correlation value in the second direction are both within a predetermined value. It is preferable to determine that composition change does not occur when.

  When the composition change determination means determines that one of the correlation value in the first direction and the correlation value in the second direction is not within a predetermined value and a composition change has occurred, the other may not determine the other. It is practical.

  In the imaging apparatus of the present invention, the focus adjustment operation setting changing unit that changes the setting of the focus adjustment operation by the focus adjustment unit driving unit, and between the first time and the second time, And a composition change detection correlation calculation prohibiting means for prohibiting the operation of the composition change detection correlation calculating means when the focus adjustment operation setting is changed by the operation of the focus adjustment operation setting changing means.

  The reliability determination means has reliability of one or both of the defocus amount calculated from the image signal in the first direction and the defocus amount calculated from the image signal in the second direction by the defocus amount calculation means. It is practical to determine that there is no reliability when there is not.

  In the imaging apparatus of the present invention, it is practical to set the focus reference value as the absolute value of the defocus amount.

  The focus adjustment operation setting changing unit is configured to stop the operation of at least the focus adjustment unit driving unit among the defocus amount calculation unit and the focus adjustment unit drive unit when the focus determination unit determines to be in focus. One focus adjustment operation and the second focus adjustment operation in which the defocus amount calculation means and the focus adjustment unit driving means continue to operate even after the focus determination means determines that the focus is achieved. Including changing the settings.

  The first direction and the second direction on the image plane are orthogonal to each other, and the light receiving unit receives a pair of subject light beams divided in pupils in the first direction and the second direction, respectively. It is practical to include a first light receiving unit that outputs a pair of image signals in the first direction and a second light receiving unit that outputs a pair of image signals in the second direction.

The present invention in the category of imaging method includes a photoelectric conversion step of photoelectrically converting a pair of subject light beams that have passed through the photographing optical system and divided into pupils to output a pair of image signals; and a first time by the light receiving means. A composition change detection correlation calculating step for calculating a correlation value between the image signal output at the second time and the image signal output at a second time after the first time; and the correlation calculated by the composition change detection correlation calculating means A composition change determining step for determining that a composition change has not occurred when the value is within a predetermined value; calculating a relative image shift amount of a pair of image signals output by the light receiving means ; A defocus amount calculation step for calculating a defocus amount based on the above; a reliability determination step for determining reliability of the defocus amount; and the defocus amount within a predetermined focus reference value A focus determination step for determining that the subject is in focus; and focus adjustment of the photographing optical system based on the defocus amount when it is not determined that the subject is in focus in the focus determination step A focus adjusting unit driving step for driving the unit; and when the composition change determining step determines that no composition change has occurred, the predetermined focus is set so that the in-focus determining step can easily determine that the focus is in focus. A focus determination value changing step for changing the focus reference value; and when it is determined that no composition change has occurred in the composition change determination step, the reliability determination step can easily determine that there is reliability. A reliability determination value changing step for changing a reference value for reliability determination .

  The present invention uses an image signal output by photoelectrically converting a pair of pupil-divided subject luminous fluxes, and outputs an image signal output at a first time and a second time after the first time. If the correlation value of the image signal is within a predetermined value, it is determined that no composition change has occurred (that is, if any correlation value is not within the predetermined value, it is determined that a composition change has occurred) The recognition accuracy of composition change can be improved.

1 is an external front view of an embodiment of an interchangeable lens single-lens reflex digital camera to which an imaging apparatus of the present invention is applied. 2 is an external rear view of the digital camera. FIG. It is a figure explaining the internal structure of the digital camera. It is a figure explaining the line sensor arrangement | positioning of a focus detection element. It is a figure explaining the arrangement | positioning of the focus detection area and line sensor on a finder. It is a flowchart explaining the flow of the whole focus adjustment operation | movement. It is a flowchart explaining composition change detection calculation operation. It is a flowchart explaining a focus detection calculation operation. It is a flowchart explaining a line sensor selection operation. It is a figure explaining the composition projected on the finder. (A) thru | or (f) are the figures explaining the different line sensor in the composition of FIG. 10, and the ranging signal in different time with a graph. (A) thru | or (d) is a figure explaining the composition change detection calculation by the ranging signal of FIG. 11 with a graph.

  1 and 2 are a front external view and an external configuration diagram of an embodiment in which the imaging apparatus of the present invention is applied to a single-lens reflex type digital camera 10 with interchangeable lenses, and FIG. 3 is an internal configuration diagram of the digital camera 10. is there. As shown in FIGS. 1 and 3, the digital camera 10 includes a camera body 100 and a photographing lens 200 that can be attached to and detached from the camera body 100. The photographing lens 200 includes a photographing lens group 202 including a focus lens group FL as a photographing optical system and a variable diaphragm 203 (FIG. 3) in a lens barrel 201. The camera body 100 includes a mount unit 160 to which the photographing lens 200 is attached and an attachment / detachment button 101 for attaching / detaching the photographing lens 200.

  The release button 102 is a two-stage button, and can detect two states, a half-pressed state (first switch SW1 on state) and a fully-pressed state (second switch SW2 on state). When the release button 102 is half-pressed and the first switch SW1 is turned on, the shooting preparation operation is performed, and focus adjustment control and the like are performed. When the release button 102 is further pressed and the second switch SW2 is turned on, a photographing operation is performed.

  The focus switch 103 is a switch for switching between auto focus (AF) for performing automatic focus adjustment and manual focus (MF) for performing manual focus adjustment. In manual focus (MF), a user manually turns a focus ring (focus adjustment ring) (not shown) provided in the photographic lens 200 to light the focus lens group FL (focus adjustment unit) in the photographic lens group 202. Move in the axial direction to adjust the focus.

  The focus mode setting button 104 is a button for setting various modes related to focus adjustment, and is operated by combining the front dial 105 and the rear dial 106 (FIG. 2). With the focus mode setting button 104 pressed, the front dial 105 is turned to switch the AF mode. In the AF mode, a focus adjustment operation is performed until focus is achieved (until focus is achieved), and when focus is achieved, the focus adjustment operation (at least the focus lens group drive) is stopped. S) and a servo AF mode (second focus adjustment operation, AF.C) in which the focus adjustment operation is continued even after focusing is selectable. Note that the AF mode can be switched only when the focus switch 103 is set to AF.

  Further, the focus area mode is switched by turning the rear dial 106 (FIG. 2) while the focus mode setting button 104 is pressed. The focus area mode is selected from the auto area mode that automatically selects the focus adjustment area from the multiple focus detection areas that are arranged in the shooting screen, and the select area mode that performs focus adjustment in any selected focus detection area. Is possible.

  The focus area setting button 107 is a button for setting a focus detection area for performing focus adjustment (FIG. 2). After the focus area setting button 107 is pressed, the focus detection area is selected by operating the cross button 108. The focus area can be set only when the focus area mode is set to the select area mode.

  A finder 133 is provided on the upper back of the camera body 100. The subject light that has passed through the photographing lens group 202 is reflected by the main mirror 120 and imaged on the focusing screen 130. The subject image formed on the focusing screen 130 is made upright by the pentaprism 131 and is visually recognized by the photographer through the eyepiece 132 and the viewfinder 133. The photographer can view the subject image guided from the photographing lens 200 by looking through the finder 133 and determine the composition.

  A memory card storage unit 174 is provided on the back surface of the camera body 100, and a memory card for recording captured images is stored in the memory card storage unit 174 so as to be detachable. A rear monitor 175 configured with a color liquid crystal display (LCD) is further provided on the rear surface of the camera body 100. On the rear monitor 175, camera setting information, captured images, and the like are displayed.

  An outline of the operation of the digital camera 10 in the first switch SW1 on state and the second switch SW2 on state will be described with reference to FIGS.

<Operation in the ON state of the first switch SW1>
The digital camera 10 starts a photometric operation when the first switch SW1 is turned on. A photometric element 134 is provided in the vicinity of the exit side of the pentaprism 131, and part of the subject light incident on the pentaprism 131 enters the photometric element 134. The photometric element 134 is an electric light according to the brightness of the subject light. The signal is output to the photometry control unit 142.

  Here, the camera control unit 140 includes a system LSI on which a DSP and a CPU are mounted, and includes a memory (RAM, ROM), an A / D converter, and the like. The camera control unit 140 calls a program stored in the ROM, and executes the program by a DSP or CPU, whereby composition conversion detection correlation value calculation means, composition change determination means, defocus amount calculation means, reliability determination means , Reliability determination value change means, focus determination means, focus determination value change means, focus adjustment operation setting change means, composition change detection correlation calculation prohibition means, focus adjustment unit drive means, and controls various camera members It realizes camera functions and operations such as photometry, focus adjustment, and shooting. The camera control unit 140 further has functions as a photometry control unit 142, a drive control unit 143, an image processing unit 144, and a display control unit 145.

  The electrical signal input to the photometric control unit 142 is converted into an image signal (photometric signal) by an A / D converter, and photometric calculation is performed based on the photometric signal, and exposure (aperture value, exposure time) at the time of shooting is calculated. decide. The photometry operation is continuously performed for several seconds to several tens of seconds even after the first switch SW1 is turned off.

  Next, the focus adjustment operation will be described. At least a part of the main mirror 120 is constituted by a half mirror, and a part of the subject light passes through the main mirror 120. The subject light transmitted through the main mirror 120 is reflected by the sub mirror 121 and enters the focus detection module 150. The focus detection module 150 is a pupil division type phase difference type focus detection module, and subject light incident on the focus detection module 150 passes through the condenser lens 151 and is reflected by the reflection mirror 152. The subject light reflected by the reflecting mirror 152 is divided into a plurality of pairs in the horizontal direction and the vertical direction (first direction and second direction) by the separator mask 153, and then the focus is detected by the re-imaging lens 154. Re-imaged on element 155. As shown in FIG. 4, the focus detection element 155 includes a plurality of charge accumulation type line sensors (focus detection sensors) such as CCDs in the horizontal direction and the vertical direction, and each line sensor includes a sensor (line sensor) and b. The sensor (line sensor) makes a pair. The separator mask 153 and the re-imaging lens 154 make a pair of the subject luminous flux that has passed through the photographing lens group 202 in a first direction on the image plane and a second direction different from the first direction. The pupil dividing means for dividing the pupil is configured.

  FIG. 5 is a diagram for explaining the arrangement of focus detection areas and line sensors on the finder 133. As shown in FIG. 5, one focus detection area includes two H sensors (line sensors) arranged in the horizontal direction and V sensors (line sensors) arranged in the vertical direction. Each of the H sensor and the V sensor has a pair of a sensor (line sensor) and b sensor (line sensor). The focus detection element 155 is connected to the distance measurement control unit 142, and the distance measurement control unit 142 controls the integration time and gain of the focus detection element 155 according to the subject light. The electric charge accumulated in the H sensor and the V sensor is output as an electric signal to the distance measurement control unit 142, and the electric signal input to the distance measurement control unit 142 is converted into an image signal (distance signal) by an A / D converter. The Each of the H sensor and the V sensor has a pair of subject luminous fluxes that are pupil-divided in the horizontal direction (first direction) and the vertical direction (second direction) by pupil dividing means (separator mask 153 and re-imaging lens 154). The first light receiving means and the second light receiving means for photoelectrically converting the signals and outputting a pair of image signals (ranging signal sequence) are configured.

  Next, the distance measurement control unit 142 performs a correlation operation on each pair of distance measurement signals of the H sensor and the V sensor, calculates a phase difference on the focus detection element 155, and calculates a defocus amount. The drive control unit 143 is connected to the lens control unit 204 via an electrical contact 161 provided in the mount unit 160, and the drive control unit 143 communicates to transmit the defocus amount to the lens control unit 204. Here, the lens control unit 204 is configured by a microcomputer including a CPU, a ROM, and the like, and various lens controls are realized by the CPU calling and executing a program stored in the ROM.

  The lens control unit 204 calculates the focus lens group drive amount from the defocus amount transmitted from the camera body 100, drives the lens drive mechanism 205, and moves the focus lens group FL in the optical axis direction by the lens drive amount. To control. As described above, the defocus amount calculation operation (focus detection operation) and the focus lens group drive operation (focus adjustment operation) have a certain amount of defocus amount that can be regarded as a state where the subject is in focus (focusing). Repeatedly until it is within the width.

<Operation in Second Switch SW2 ON>
When the switch detection unit 146 detects that the release button 102 is fully pressed and the second switch SW2 is turned on, the camera control unit 140 starts a shooting operation. First, the drive control unit 143 drives the mirror driving mechanism 122 to retract the main mirror 120 and the sub mirror 121 at the observation position to the photographing position above the photographing optical path.

  Next, the drive control unit 143 transmits the aperture value determined by the photometric operation to the lens control unit 204. The lens control unit 204 drives the aperture driving mechanism 206 so that the aperture value transmitted from the camera body 100 is obtained, and controls the variable aperture 203 to the aperture value. Further, the drive control unit 143 drives the shutter drive mechanism 171 to control the opening and closing of the shutter 170 so that subject light strikes the image sensor 172 for the exposure time determined by the photometric operation.

  The image sensor 172 is a light receiving element that converts subject light into an electrical signal by photoelectric conversion, and is constituted by a CCD or a CMOS. The electrical signal generated by the image sensor 172 is output to the image processing unit 144. The electric signal input to the image processing unit 144 is converted into an image signal by an A / D converter and subjected to digital image processing such as γ correction. The captured image (image signal) subjected to the digital image processing is temporarily stored in the image storage unit 173, subjected to image processing such as compression processing, and then stored in a memory card stored in the memory card storage unit 174. The The captured image temporarily stored in the image storage unit 173 is displayed on the rear monitor 175 via the display control unit 145. The photographer can check the photographed image immediately after photographing using the image displayed on the rear monitor 175.

  The automatic focus adjustment operation (AF operation) of the digital camera 10 will be described in more detail with reference to the flowcharts of FIGS. Here, the single AF mode AF. S is assumed that the select area mode is selected as the focus area mode, and the CC area (FIG. 5) is set as the focus area. This automatic focus adjustment operation is executed when an AF instruction signal is input, such as when the release button 102 is half-pressed, under comprehensive control by the camera control unit 140.

  The camera control unit 140 first determines whether or not the focus mode has been changed (S101). Specifically, switching between AF and MF is performed by operating the focus switch 103, and switching between single AF mode (AF.S) and servo AF mode (AF.C) is performed by operating the focus mode setting button 104 and the front dial 105. It is determined whether or not. When it is determined that the focus mode has not been changed (S101: NO), the camera control unit 140 proceeds to step S102, and when it is determined that the focus area mode has been changed (S101: YES), the process proceeds to step S103.

  The camera control unit 140 determines whether or not the focus area mode has been changed in step S102. Specifically, whether the focus area setting button 104 and the rear dial 106 are operated to switch between the auto area mode and the select area mode, and the focus area setting button 107 and the cross button 108 are operated to switch the focus detection area. Determine whether or not. When it is determined that the focus area mode has not been changed (S102: NO), the process proceeds to step S104. When it is determined that the focus area mode has been changed (S102: YES), the process proceeds to step S103.

  When it is determined that the focus area mode has been changed (S102: YES), the camera control unit 140 prohibits the current composition change detection (correlation) calculation in step S103, and proceeds to step S104. When the focus mode or the focus area mode is changed, it is considered that the composition change is highly likely to be performed, and composition change detection (correlation) calculation is prohibited. Note that the camera control unit 140 also prohibits the composition change detection calculation when the auto focus adjustment operation is started for the first time after the power is turned on or when a predetermined time or more has elapsed since the previous auto focus adjustment operation.

  In step S104, the camera control unit 140 performs an integration operation (exposure operation) of the focus detection element 155. In step S105, the camera detection unit 155 reads out the charges accumulated by the integration operation and generates a distance measurement signal. The process proceeds to S106.

  The camera control unit 140 (composition change detection correlation calculating means) performs composition change detection calculation in step S106. In step S107, the camera control unit 140 (defocus amount calculation means) obtains the defocus amount by focus detection calculation and proceeds to step S108. A specific description of the composition change detection calculation and the focus detection calculation will be given with reference to the flowcharts of FIGS.

  The camera control unit 140 determines whether or not the focus detection is OK in step S108, that is, whether or not the defocus amount has been obtained. When the camera control unit 140 determines that the defocus amount has been obtained (S108: YES), the camera control unit 140 proceeds to step S109. When it is determined that the amount has not been obtained (S108: NO), the process proceeds to step S110.

  When the defocus amount is obtained (S108: YES), the camera control unit 140 (focus determination unit) determines whether or not the subject is in focus in step S109. Specifically, if the defocus amount is within the in-focus range (in-focus reference value) α, it is determined that the subject is in focus (in-focus) (S109: YES), and if the de-focus amount is greater than the in-focus range α. It is determined that the subject is not in focus (out of focus) (S109: NO). The in-focus width α corresponds to the depth of focus, and is a value calculated from the open aperture value of the photographing lens 200 and the size (pixel size) of the image sensor 172. The defocus amount and the focus width α are absolute values.

  When it is determined that the camera is in focus (S109: YES), the camera control unit 140 ends the automatic focus adjustment operation (END), and when it is determined that it is out of focus (S109: NO), the process proceeds to step S110.

  The camera control unit 140 (focus adjustment unit driving unit) drives the focus lens group FL in step S110, returns to step S104, and repeats the processes in steps S104 to S109. The camera control unit 140 drives the focus lens group FL by the defocus amount when the defocus amount is found in the processing of steps S104 to S109, and when the defocus amount is not found, the camera lens unit FL. Steps S104 to S107 are repeated while driving the lens, and the search operation for finding the focus lens group position from which the defocus amount is obtained is repeated until focusing is performed. Here, “in focus” means that the defocus amount is equal to or less than the focus width α or α + α ′.

  FIG. 7 is a flowchart showing details of the composition change detection calculation operation executed in step S106. In step S111, the camera control unit 140 determines whether or not the composition change detection calculation is permitted. When it is determined to be permitted (S111: YES), the process proceeds to step S112. When it is determined to be prohibited (S111: NO), the process proceeds to step S120. move on. The composition change detection calculation is prohibited in step S103 and later-described step S144, and allowed in step S141.

  When the camera control unit 140 determines that the composition change detection calculation is permitted (S111: YES) and proceeds to step S112, the camera control unit 140 determines the previous (first time T1) H as one of the pair of image signal sequences (image signal sequence A). The first image signal sequence of the sensor a line sensor is set, and in step S113, the second of the H sensor a line sensor of this time (second time T2) is set as the other of the pair of image signal sequences (image signal sequence B). Set the image signal sequence. Then, the camera control unit 140 (composition change detection correlation calculation means) performs composition change detection correlation calculation on the pair of H sensor image signal sequences A and B set in steps S112 to S113 (S114).

One embodiment of the composition change detection correlation algorithm is as follows. Correlation values C (i) are obtained from the following equations (1) and (1 ′) for a pair of image signal sequences A and B each composed of N pixels.

In the equation (1), the parameter i is a relative shift amount in units of the pixel pitch of the pair of image signal sequences A and B. In the equation (1), the correlation value C (i) is the sum of the absolute differences of the output values of the corresponding pixels of the image signal sequence A and the image signal sequence B at the shift amount i for the range n. When the correlation of B is the highest, the correlation value C (i) is a minimum value. Let j be a shift amount that gives a minimum value to the correlation value C (i). Next, since the correlation value C (j) is the minimum value in the shift amount in pixel pitch units, the interpolation calculation shown in the equations (2) and (2 ′) is performed to obtain the minimum correlation value Cmin for the continuous correlation value. Ask.

  The minimum correlation value Cmin of the image signal sequences A and B of the pair of H sensors a line sensors is obtained by the above composition change detection correlation calculation. When the distance to the subject is the same subject and the distance to the subject has not changed, the shift amount j from which the minimum correlation value Cmin is obtained becomes 0. The larger the amount of change in the distance to the subject, the larger the absolute value of the shift amount j. Becomes larger.

In subsequent step S115, the camera control unit 140 (composition change determination means) determines the reliability T calculated by the following equations (3), (3 '), and (4) for the minimum correlation value Cmin of the H sensor. The reliability T is calculated before step S115, for example, at step S114.

  As shown in the equations (3) to (4), the reliability T is standardized with the minimum correlation value Cmin as the contrast value Contrast of the image signal sequences A and B at the shift amount i = j from which the minimum correlation value Cmin is obtained. It has become. In this embodiment, the reliability determination value β is an absolute value defined by Cmin / Contrast. The reliability determination value β is a value that requires higher reliability as it is smaller.

  The camera control unit 140 (composition change determination means) determines that there is reliability (that is, no composition change) if the reliability T is within a predetermined value (reliability determination value β or β + β ′) (S115: YES), and performs step The process proceeds to S116, and if the reliability T exceeds a predetermined value (reliability determination value β or β + β ′), it is determined that there is no reliability (that is, there is a composition change) (S115: NO), and the process proceeds to Step S120. If the minimum correlation value Cmin is not obtained, it is determined that there is no reliability (that is, there is a composition change) (S115: NO), and the process proceeds to step S120.

  In step S116, the camera control unit 140 sets the first image signal sequence of the V sensor a line sensor of the previous time (first time T1) as one of the pair of image signal sequences (image signal sequence A). In S117, the second image signal sequence of the V sensor a line sensor this time (second time T2) is set as the other (image signal sequence B) of the pair of image signal sequences. Then, in step S118, the camera control unit 140 (composition change detection correlation calculation means) performs composition change detection correlation using the same algorithm as in step S114 for the pair of V sensor image signal sequences set in steps S116 and S117. Perform the operation.

  In step S119, the camera control unit 140 (composition change determination means) determines the reliability T for the minimum correlation value Cmin of the V sensor. If the reliability T is within a certain value (reliability determination value β or β + β ′), the camera control unit 140 (composition change determination means) If the reliability T exceeds a predetermined value (reliability determination value β or β + β ′) in step S121, there is no reliability (that is, the composition has changed). (S119: NO) and the process proceeds to step S120. The camera control unit 140 (composition change determination means) also determines that there is no reliability (that is, there is a composition change) even if the minimum correlation value Cmin is not obtained (S119: NO), and proceeds to step S120.

  If the camera control unit 140 (composition change determination means) does not determine that there is reliability (S119: NO), it sets that there is a composition change in step S120, sets the focus width α in step S122, and step S124. Then, the reliability determination value β is set and the process returns to step S106 (RET). The focus width α is a value calculated from the open aperture value of the photographing lens 200 and the pixel size of the image sensor 172, and is an absolute value. The smaller the focus width α, the more accurate the value.

  When the camera control unit 140 (composition change determination means) determines that there is reliability (S119: YES), it sets no composition change in step S121. The camera control unit 140 (focus determination value changing means) sets the focus width α + α ′ in step S123, and the camera control unit 140 (reliability determination value changing means) subsequently sets the reliability determination value β + β in step S125. 'Is set and the process returns to step S106 (RET). The focus width α ′ corresponds to a variation in the amount of defocus caused by electrical noise of the focus detection element 155 when the same subject is repeatedly measured. The reliability determination value β ′ is a value corresponding to a variation in reliability T caused by electrical noise of the focus detection element 155 when the same subject is repeatedly measured. When no composition change is set (S121), by increasing the focus width α by the variation α ′ (S123), the focus width that is focused by the focus determination in step S109 becomes wider, which is unnecessary. It is possible to reduce the time required for focusing on the subject by suppressing the focus lens group drive (search operation). Further, by increasing the reliability determination value β by the value β ′ (S125), the reliability criterion determined as reliable in the reliability determination in steps S115 and S119 is lowered, and it is easy to determine that there is reliability. The time required for focusing on the subject can be shortened by suppressing unnecessary search operations.

  FIGS. 10A to 10C show composition examples (composition examples in the field of view of the finder 133) projected onto the finder 133 at different times. 11 (a) and (b), (c) and (d), and (e) and (f) are respectively at the same time (first time T1, second time T2, and third time T3). The state of the H sensor H_CC (a) signal and the V sensor V_CC (a) signal is shown. The H sensor H_CC (a) signal represents the image signal sequence (image signal sequence A) of the a line sensor of the H sensor H_CC, and the V sensor V_CC (a) signal represents the image signal sequence of the a line sensor of the V sensor V_CC ( An image signal sequence A) is shown. In the graph of FIG. 11, the horizontal axis represents the pixel number, and the vertical axis represents the output value (a.u.).

The relationship between the composition and the image signal sequences A and B in the composition change detection calculation operation will be described in detail with reference to FIGS.
FIG. 10A shows a composition projected on the finder 133 at the first time T1. At this time, the focus detection area CC detects the first subject 300, and the a-line sensors of the H sensor H_CC and the V sensor V_CC corresponding to the central focus detection area CC are shown in FIGS. 11 (a) and 11 (b). A ranging signal having a magnitude corresponding to the luminance of the first subject 300 shown is output.

  FIG. 10B shows a composition projected on the finder 133 at a second time T2 after the first time T1. At this time, the focus detection area CC detects the second subject 301, and the a-line sensors of the H sensor H_CC and the V sensor V_CC have the brightness of the second subject 301 shown in FIGS. 11 (c) and 11 (d). A distance measurement signal of a corresponding magnitude is output.

  The first time T1 is a time when the first subject 300 is focused, and the second time T2 is a release operation after the release button 102 is fully pressed immediately after the first time T1 and a shooting operation is performed. This is the time when the release of the button 102 is released, the composition is changed, and the release button 102 is half-pressed again. As shown in FIGS. 10A to 10C, the first subject 300 and the second subject 301 are arranged side by side and have the same shooting distance (distance to the subject).

  To detect the composition change, first, composition change detection calculation of the H sensor H_CC is performed. 12A shows the correlation between the H sensor H_CC (a) signal at the first time T1 shown in FIG. 11A and the H sensor H_CC (a) signal at the second time T2 shown in FIG. 11C. It is a graph which calculates and shows the correlation value C (i) and contrast value Contrast (i) about the shift amount i, and the minimum correlation value Cmin is obtained when the shift amount i = 0. In the graph of FIG. 12, the horizontal axis represents the shift amount (pixel pitch), and the vertical axis represents the contrast value and the minimum correlation value data (a.u.).

  Here, if the reliability T is 0.25 or less, that is, if the minimal correlation value Cmin is ¼ or less of the contrast value Contrast, it is assumed that there is reliability, the minimal correlation value Cmin is equal to the contrast value Contrast from FIG. Since it is 1/4 or less, it is determined that there is reliability, that is, the composition of the H sensor H_CC is not changed.

  Next, composition change detection calculation of the V sensor V_CC is performed. FIG. 12B shows the V sensor V_CC (a) signal at the first time T1 shown in FIG. 11B and the V sensor V_CC (a) signal at the second time T2 shown in FIG. FIG. 6 is a graph in which correlation calculation is performed to calculate a correlation value C (i) and a contrast value Contrast (i) for a shift amount i. When the shift amount i = 0, a minimal correlation value Cmin is obtained. From FIG. 12B, the minimal correlation value Cmin is ¼ or more of the contrast value Contrast, so it is determined that there is no reliability, that is, the composition of the V sensor V_CC has changed.

  From the above, the composition of the H sensor H_CC has not changed, but since the composition of the V sensor V_CC has changed, it is determined that a composition change has occurred in the focus detection area CC at the first time T1 and the second time T2. it can. As described above, according to the present embodiment, the composition change can be detected even when the subject is different at the first time T1 and the second time T2, but the shooting distance is the same, that is, the defocus amount is not changed.

  FIG. 10C shows a composition projected onto the viewfinder 133 at a third time T3 further after the second time T2. At this time, the focus detection area CC detects the second subject 301, and the a-line sensors of the H sensor H_CC and the V sensor V_CC have the brightness of the second subject 301 shown in FIGS. 11 (e) and 11 (f). The corresponding ranging signal is output. At the third time T3, immediately after the second time T2, the release button 102 is fully pressed (the second switch SW2 is turned on) to perform a photographing operation, and then the release button 102 is released from being pressed, and the composition is performed. And the release button 102 is half-pressed again (the first switch SW1 is turned on). The shooting distance of the second subject 301 is different between the second time T2 and the third time T3.

  FIG. 12C shows the H sensor H_CC (a) signal at the second time T2 shown in FIG. 11C and the H sensor H_CC (a) signal at the third time T3 shown in FIG. It is the graph which calculated correlation value C (i) and contrast value Contrast (i) about shift amount i by performing correlation calculation. FIG. 12C shows that the minimum correlation value Cmin is obtained when the shift amount i = −3. In the case of FIG. 12C, since the minimal correlation value Cmin is ¼ or more of the contrast value Contrast, it is determined that there is no reliability, that is, the composition of the H sensor H_CC is changed.

  FIG. 12D shows the V sensor V_CC (a) signal at the second time T2 shown in FIG. 11D and the V sensor V_CC (a) signal at the third time T3 shown in FIG. It is the graph which calculated correlation value C (i) and contrast value Contrast (i) about shift amount i by performing correlation calculation. FIG. 12D shows that the minimum correlation value Cmin is obtained when the shift amount i = 5. In the case of FIG. 12D, since the minimal correlation value Cmin is ¼ or more of the contrast value Contrast, it is determined that there is no reliability, that is, the composition of the V sensor V_CC is changed. Since the composition of the H sensor H_CC and the composition of the V sensor V_CC have also changed, it can be determined that a composition change has occurred in the focus detection area CC at the second time T2 and the third time T3.

  As described above, the digital camera 10 according to the present embodiment changes the composition even when the subject is the same and the shooting distance is different at the second time T2 and the third time T3, that is, when the defocus amount is changed. Can be detected.

  In the above embodiment, the composition change detection calculation is performed by the a-line sensor of the HV sensor, but may be performed by the b-line sensor. Furthermore, the composition change detection calculation may be performed by both the a-line sensor and the b-line sensor.

  The focus detection calculation operation executed in step S107 will be described in more detail with reference to FIG. FIG. 8 is a flowchart showing the flow of the focus detection calculation operation of the digital camera 10. In step S126, the camera control unit 140 sets the second image signal sequence of the H sensor a line sensor at this time (second time T2) as one of the pair of image signal sequences (image signal sequence A), In step S127, the second image signal sequence of the H sensor b line sensor at this time (second time T2) is set as the other of the pair of image signal sequences (image signal sequence B), and the process proceeds to step S128.

In step S128, the camera control unit 140 (defocus amount calculation means) sets the second image signal sequence (image signal sequence A and image) of the pair of H sensor a line sensor and b line sensor set in steps S126 and S127. A focus detection correlation calculation is performed on the signal sequence B). The focus detection correlation calculation is as follows. For a pair of image signal sequences A and B each composed of N pixels, the correlation value C (i) shown in equation (1) is calculated, and the correlation between the image signal sequences A and B is the highest. That is, the shift amount j at which the correlation value C (i) is a minimum value is obtained. Next, since the shift amount j is in units of pixel pitch, the interpolation amount shown in the equations (5) and (5 ′) is performed to obtain the shift amount S that gives the minimum correlation value Cmin for the continuous correlation value.

The shift amount S is a parameter that represents the amount of focus shift on the focus detection element 155. Finally, the focus shift amount, that is, the defocus amount of the focus lens group FL is obtained from the shift amount S by the following equation (6).
Defocus = S × Ksf (6)
In the equation (6), the coefficient Ksf is a conversion coefficient for converting the shift amount into a defocus amount per pixel interval of the focus detection element 155.

  In step S129, the camera control unit 140 (reliability determining means) determines the reliability T for the minimum correlation value Cmin (defocus amount) of the H sensor, and a certain value (reliability determination value β or If it is within β + β ′), it is determined that there is reliability (S129: YES), and the process proceeds to step S130. If the reliability T exceeds a predetermined value (reliability determination value β or β + β ′), it is determined that there is no reliability ( S129: NO) The process proceeds to step S131. The camera control unit 140 also determines that there is no reliability even when the minimum correlation value Cmin is not obtained (S129: NO), and proceeds to step S131.

  When it is determined that there is reliability (S129: YES), the camera control unit 140 sets H sensor focus detection OK in step S130, assuming that a reliable defocus amount has been obtained for the H sensor. Also, when the camera control unit 140 does not determine that there is reliability (S129: NO), in step S131, the H sensor focus detection NG is set on the assumption that a reliable defocus amount is not obtained for the H sensor. To do.

  In step S132, the camera control unit 140 sets the second image signal sequence of the V sensor a line sensor at this time (second time) as one of the pair of image signal sequences (image signal sequence A). In S133, the second image signal sequence of the current (second time) V sensor b line sensor is set as the other of the pair of image signal sequences (image signal sequence B). In step S134, the camera control unit 140 (defocus amount calculation means) performs focus detection correlation calculation for the pair of V sensor image signal sequences set in steps S132 to S133, and then proceeds to step S135.

  In step S135, the camera control unit 140 (reliability determination unit) determines the reliability T for the minimum correlation value Cmin (defocus amount) of the V sensor. If the reliability T is within a predetermined value (reliability determination value β or β + β ′), the camera control unit 140 (reliability determining means) determines that there is reliability (S135: YES), and proceeds to step S136. If T exceeds a predetermined value (reliability determination value β or β + β ′), it is determined that there is no reliability (S135: NO), and the process proceeds to step S137, and the reliability is also obtained when the minimum correlation value Cmin is not obtained. It is determined that there is no sex (S135: NO), and the process proceeds to step S137.

  In step S136, the camera control unit 140 sets V sensor focus detection OK on the assumption that a reliable defocus amount is obtained for the V sensor. In step S137, the camera control unit 140 obtains a reliable defocus amount for the V sensor. If not, V sensor focus detection NG is set and the process proceeds to step S138.

  In step S138, the camera control unit 140 determines whether there is a sensor for which a reliable defocus amount has been obtained, and determines that there is a focus detection OK if there is a sensor for which a reliable defocus amount has been obtained. (S138: YES), the process proceeds to step S139. If there is no reliable defocus amount sensor, it is determined that the focus detection is not OK (S138: NO), and the process proceeds to step S142.

  When a reliable defocus amount is obtained (S138: YES), the camera control unit 140 sets focus detection OK in step S139, selects an HV sensor for setting the defocus amount in step S140, and performs step S141. The next composition change detection calculation is permitted, the current (second time) ranging signal data is stored, and the process returns to step S107 (RET).

  When a reliable defocus amount is not obtained (S139: NO), the camera control unit 140 sets focus detection NG in step S142, and does not set a selection sensor in step S143, but in step S144. The next composition change detection calculation is prohibited and the process returns to step S107 (RET).

  Since the digital camera 10 of the present embodiment prohibits composition change detection calculation when a reliable defocus amount is not obtained (S138: NO, S142), it detects a composition change without focusing. Since no unnecessary composition change detection calculation is performed, the focus adjustment time can be shortened.

  FIG. 9 is a flowchart showing details of the sensor selection operation executed in step S140. When starting the sensor selection operation, the camera control unit 140 determines whether or not both the H sensor and the V sensor are in focus detection in step S145. When both the H sensor and the V sensor determine that the focus detection is OK (S145: YES), the camera control unit 140 proceeds to step S147, and when it is determined that at least one of the H sensor and the V sensor is not the focus detection OK (S145). : NO) Proceed to step S146.

  In step S146, the camera control unit 140 determines whether or not the H sensor is focus detection OK. When the H sensor determines that the focus detection is OK (S146: YES), the camera control unit 140 proceeds to step S150 and selects the H sensor (the selected sensor). When the H sensor determines that the focus detection is NG (S146: NO), the process proceeds to step S151, selects the V sensor (sets as the selected sensor), and returns to step S140 (RET).

  The camera control unit 140 determines whether or not there is a composition change in step S147, and when it is determined that there is a composition change (S147: YES), the process proceeds to step S148, and when it is determined that there is no composition change (S147: NO). Proceed to step S149.

  When it is determined that the composition has changed (S147: YES), the camera control unit 140 compares the defocus amounts of the H sensor and the V sensor in step S148 to determine whether the H sensor is closer. When it is determined that the H sensor is closer (S148: YES), the process proceeds to step S150 and the H sensor is selected. When the V sensor is determined to be closer (S148: NO), the process proceeds to step S151. Then, the V sensor is selected and the process returns to step S140 (RET).

  When it is not determined that the composition has changed (S147: NO), the camera control unit 140 determines whether or not the previous (first time T1) H sensor has been set as the selection sensor in step S149. When it is determined that the H sensor is selected (S149: YES), the process proceeds to step S150 and the H sensor is selected this time (second time T2), while it is determined that the previous V sensor is selected. When (S149: NO), the process proceeds to step S151, and this time (second time T2), the V sensor is selected and the process returns to step S140 (RET).

  As a result of the above sensor selection process, if one of the H sensor and the V sensor is focus detection NG, the H sensor is selected if the H sensor is focus detection OK, and the V sensor is selected if the H sensor is not focus detection OK. When there is a composition change, the H sensor or the V sensor that has obtained the defocus amount on the short distance side is selected, and when there is no composition change, the same H sensor or V sensor as the previous time is selected.

  In addition, when the focus area mode is changed, the probability that the composition is also changed is high. Therefore, in the present digital camera 10, even when the focus area mode is changed, the time required for focusing on the subject can be shortened by omitting the composition change detection calculation processing.

In the present embodiment, the first direction and the second direction for pupil division and the first direction and the second direction for arranging the H sensor and the V sensor are the horizontal direction and the vertical direction on the shooting screen. In the invention, one or both of the first direction and the second direction may be oblique.
Although the present embodiment is configured to detect the phase difference using the focus detection module 150, the present invention can also be applied to a so-called image plane phase difference detection apparatus using an image sensor.
The reliability T of the minimal correlation value Cmin as the composition change detection correlation calculation result (steps S115 and S119) and the reliability T of the minimal correlation value Cmin as the focus detection correlation calculation result (steps S129 and S135) are the same determination value. Although the determination is made based on (reliability determination value β or β + β ′), different determination values may be set.
The conditions for prohibiting the composition change calculation in step S103 may include a case where the focal length is changed, a case where the digital camera 10 is panned, a case where the focus area is changed due to face detection or the like.

10 Digital camera (imaging device)
DESCRIPTION OF SYMBOLS 100 Camera body 101 Release button 102 Release button 103 Focus switch 104 Focus mode setting button 105 Front dial 106 Rear dial 107 Focus area setting button 108 Cross button 120 Main mirror 122 Mirror drive mechanism 130 Focusing screen 131 Penta prism 132 Eyepiece 133 Viewfinder 134 Photometric element 140 Camera control unit (composition conversion detection correlation calculation means, composition change determination means, defocus amount calculation means, reliability determination means, reliability determination value change means, focus determination means, focus determination value change means, focus Adjustment operation setting change means, composition change detection correlation calculation prohibition means, focus adjustment unit drive means))
142 Photometry control unit 143 Drive control unit 144 Image processing unit 145 Display control unit 146 Switch detection unit 150 Focus detection module 151 Condenser lens 152 Reflection mirror 153 Separator mask (pupil dividing means)
154 Re-imaging lens (pupil division means)
155 Focus detection element 160 Image sensor 161 Electrical contact 170 Shutter 171 Shutter drive mechanism 172 Image sensor 173 Image storage unit 174 Memory card storage unit 175 Rear monitor 200 Shooting lens 201 Lens barrel 202 Shooting optical system 203 Variable aperture 204 Lens control unit 205 Lens Drive mechanism 206 Aperture drive mechanism 300 First subject 301 Second subject FL Focus lens group (focus adjustment unit)
α Focusing range (focusing reference value)
β Reliability judgment value

Claims (9)

Light- receiving means that passes through the photographing optical system and photoelectrically converts a pair of subject light beams that are divided into pupils, and outputs a pair of image signals;
Composition change detection correlation calculating means for calculating a correlation value between the image signal output at the first time by the light receiving means and the image signal output at the second time after the first time;
Composition change determination means for determining that no composition change has occurred when the correlation value calculated by the composition change detection correlation calculation means is within a predetermined value;
Defocus amount calculation means for calculating a relative image shift amount of the pair of image signals output by the light receiving means and calculating a defocus amount based on the image shift amount;
Reliability determination means for determining the reliability of the defocus amount;
Focusing determination means for determining that the subject is focused when the defocus amount is within a predetermined focusing reference value;
A focus adjustment unit drive unit that drives a focus adjustment unit of the photographing optical system based on the defocus amount when the focus determination unit does not determine that the image is in focus;
When the composition change determination unit determines that no composition change has occurred, the focus determination value change is performed to change the predetermined focus reference value so that the focus determination unit can easily determine that the composition is in focus. With means;
A reliability determination value change for changing a reference value for reliability determination so that the reliability determination unit can easily determine that there is reliability when the composition change determination unit determines that no composition change has occurred. With means;
An imaging apparatus comprising: 2. The imaging apparatus according to claim 1, wherein the light receiving means passes through the photographing optical system and forms a pair in each of a first direction on the image plane and a second direction different from the first direction. Each pair of pupil-divided subject luminous flux is photoelectrically converted to output a pair of image signals,
The composition change detecting correlation computing means, first output by one and a second time after the first time of the first direction of the pair of image signals output to the first time said light receiving means while the correlation values of the direction of the pair of image signals, and a second direction of the pair of image output to one and the second time in a second direction of the pair of image signals output to the first time Calculate one correlation value of the signal,
The composition change determination means determines that no composition change has occurred when both the correlation value in the first direction and the correlation value in the second direction calculated by the composition change detection correlation calculation means are within a predetermined value. An imaging device characterized by that. Te claim 1 or 2, the imaging apparatus odor, comprising: a focusing operation setting changing means for changing the setting of the focusing operation by the focusing unit driving means,
When the focus adjustment operation setting is changed by the operation of the focus adjustment operation setting change means between the first time and the second time, the composition change detection prohibits the operation of the composition change detection correlation calculation means. An imaging apparatus further comprising correlation calculation prohibiting means. 3. The imaging apparatus according to claim 2 , wherein the composition change determination unit determines that one of the correlation value in the first direction and the correlation value in the second direction is not within a predetermined value and a composition change has occurred. An imaging device that does not make a determination on the other. 5. The imaging apparatus according to claim 2 , wherein the reliability determination unit calculates the defocus amount calculated from the image signal in the first direction and the image signal in the second direction by the defocus amount calculation unit. An imaging apparatus that determines that there is no reliability when one or both of the defocus amounts are not reliable. The imaging apparatus according to claim 1 , wherein the focus reference value is an absolute value of a defocus amount. 4. The imaging apparatus according to claim 3 , wherein the focus adjustment operation setting change unit is at least the focus adjustment among the defocus amount calculation unit and the focus adjustment unit driving unit when the focus determination unit determines that the focus is achieved. A first focus adjustment operation in which the section driving means stops operating, and a second focus adjustment operation in which the defocus amount calculating means and the focus adjustment section driving means continue operating even after the in-focus determination means determines to be in focus. An imaging apparatus that changes the setting from one of the focus adjustment operations to the other. 6. The imaging device according to claim 2, 4 or 5 , wherein the first direction and the second direction on the image plane are orthogonal to each other, and the light receiving means includes the first direction and the second direction. A first light receiving means for receiving a pair of subject luminous fluxes whose pupils are divided in a direction and outputting a pair of image signals in a first direction; and a second light receiving means for outputting a pair of image signals in a second direction. An imaging apparatus comprising: A photoelectric conversion step of passing a photographing optical system and photoelectrically converting a pair of pupil-divided subject luminous fluxes to output a pair of image signals;
A composition change detection correlation calculating step of calculating a correlation value between the image signal output at the first time by the light receiving means and the image signal output at the second time after the first time;
A composition change determination step for determining that no composition change has occurred when the correlation value calculated by the composition change detection correlation calculating means is within a predetermined value;
A defocus amount calculation step of calculating a relative image shift amount of the pair of image signals output by the light receiving means, and calculating a defocus amount based on the image shift amount;
A reliability determination step of determining the reliability of the defocus amount;
A focus determination step of determining that the subject is focused when the defocus amount is within a predetermined focus reference value;
A focus adjustment unit driving step for driving a focus adjustment unit of the photographing optical system based on the defocus amount when it is not determined in the in-focus determination step;
When the composition change determination step determines that no composition change has occurred, the focus determination value change is performed to change the predetermined focus reference value so that the focus determination step can easily determine that the composition is in focus. Steps and;
When the composition change determination step determines that no composition change has occurred, the reliability determination value change is performed to change the reliability determination reference value so that the reliability determination step easily determines that there is reliability. Steps and;
An imaging method characterized by comprising:

Images