Imaging device and its control method, program, and storage medium

Abstract

The present invention provides an imaging device that can perform stable focus adjustment operations even when the detection direction of the phase difference is switched. [Solution] In order to perform phase difference detection based on light beams passing through different pupil regions of the optical system, the system comprises an image sensor in which a plurality of pixels capable of outputting a pair of focus detection signals are arranged two-dimensionally in a first direction and a second direction, a control unit that controls the readout mode of the signal from the image sensor, and a focus detection unit that detects phase difference information in the first direction and phase difference information in the second direction based on the signal output from the image sensor. The control unit sets the readout mode of the image sensor to the first readout mode during the standby period when no instruction to start shooting preparation operation is input, and switches the readout mode of the image sensor from the first readout mode to the second readout mode when an instruction to start shooting preparation operation is input. The focus detection unit detects phase difference information in the first direction during the standby period, and detects phase difference information in the first direction and phase difference information in the second direction when an instruction to start shooting preparation operation is input.

Description

Technical Field

[0001] The present invention relates to an imaging device and a control method thereof.

Background Art

[0002] In recent years, in imaging devices such as digital cameras, higher definition has been demanded and the number of pixels has been increasing. Along with this, the processing time and power consumption when reading an image signal from an image sensor increase, but this is suppressed by thinning out pixels or performing addition averaging and then reading.

[0003] Also, as a focus detection method in a general imaging device, an imaging plane phase difference detection method is known. The imaging plane phase difference detection method is a method in which pupil division is performed by one microlens provided for each pixel of an image sensor and a pair of photoelectric conversion units, and the focus state (defocus amount) is obtained from the phase difference between a pair of image signals obtained from the pair of photoelectric conversion units.

[0004] In Patent Document 1, the read mode is changed according to the shooting control state. Specifically, at the time of still image shooting, it is set to a mode of reading all pixels (non-thinning read), and at the time of moving image shooting or otherwise (during autofocus (AF) control or in a standby state), it is set to a mode of thinning out pixels and reading (thinning read). Thereby, it is possible to obtain a high-definition still image and shorten the processing time in moving image shooting or the like. In particular, during AF control immediately before still image shooting, high-precision autofocus is realized by not thinning out pixels in the pupil division direction.

[0005] Also, with the increase in high definition, more accurate focus detection has been demanded. When pupil division is in only one direction in the above-described focus detection method, there are cases where focus detection cannot be performed. For example, when a subject has edges only in the same direction as the pupil division direction, the phase difference cannot be detected and the defocus amount cannot be calculated (focus detection).

[0006] Patent Document 2 discloses the following imaging device: In pixels where a pair of photoelectric converters are arranged horizontally, pupil division is performed in the horizontal direction, and in pixels where a pair of photoelectric converters are arranged vertically, pupil division is performed in the vertical direction. This allows for the determination of defocus amounts in both the horizontal and vertical directions. In this case, since both the horizontal and vertical directions are pupil division directions, in order to achieve high-precision autofocus, it is necessary to read out all pixels without downsampling in both the horizontal and vertical directions. In other words, even during AF control before still image capture, it is necessary to set the device to readout mode without downsampling.

[0007] On the other hand, during standby mode, it is necessary to set the camera to a decimated readout mode to reduce processing time and power consumption. Also, if autofocus (standby AF control) is to be performed during standby mode, the pupil division direction must be limited to one direction and pixels must be decimated. For example, if the pupil division direction is horizontal, the camera should be set to a mode that decimates and reads pixels in the vertical direction (vertical decimated readout mode). In this case, the phase-detection direction will be different for AF control before still image shooting and for AF control during standby. Therefore, when switching from AF control during still image shooting to AF control during standby, problems may occur such as the focus suddenly being lost even though the subject has not changed.

[0008] Specifically, in AF control before still image capture, omnidirectional focus detection is possible by using both the horizontal and vertical pupil division image signals. On the other hand, in standby AF control, the pupil division direction is only horizontal, so as mentioned above, focus detection is not possible for subjects where the edges are only in the same direction as the pupil division direction (for example, subjects with horizontal stripes). Therefore, the focus may suddenly be lost when switching to standby AF control.

[0009] Patent Document 3 discloses a countermeasure to prevent changes in the calculation result when the phase difference detection direction switches due to the movement of the subject, in cases where areas for horizontal and vertical phase difference detection are mixed within a single image area. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2005-107252 [Patent Document 2] Japanese Patent Publication No. 2020-141122 [Patent Document 3] Japanese Patent Publication No. 2017-187589 [Overview of the project] [Problems that the invention aims to solve]

[0011] However, Patent Document 3 assumes a case where phase difference detection can be performed in both the horizontal and vertical directions, and does not consider subjects where focus detection can only be performed in one direction or the other. Therefore, in the case of subjects with horizontal or vertical stripes, there is a possibility that the focus may suddenly be lost when the direction of phase difference detection is switched.

[0012] The present invention has been made in view of the above-mentioned problems, and its objective is to provide an imaging device that can perform stable focus adjustment even when the detection direction of the phase difference is switched. [Means for solving the problem]

[0013] The imaging device according to the present invention comprises an image sensor in which a plurality of pixels capable of outputting a pair of focus detection signals are arranged two-dimensionally in a first direction and a second direction in order to perform phase difference detection based on light beams passing through different pupil regions of an optical system; control means for controlling the readout mode of the signal from the image sensor; and focus detection means for detecting phase difference information in the first direction and phase difference information in the second direction based on the signal output from the image sensor. The control means sets the readout mode of the image sensor to a first readout mode during a waiting period when no instruction to start shooting preparation operation has been input, and switches the readout mode of the image sensor from the first readout mode to the second readout mode when an instruction to start shooting preparation operation has been input. The focus detection means detects the phase difference information in the first direction during the waiting period, and detects the phase difference information in the first direction and the phase difference information in the second direction when an instruction to start shooting preparation operation has been input. [Effects of the Invention]

[0014] According to the present invention, stable focus adjustment operation can be performed even when the detection direction of the phase difference is switched. [Brief explanation of the drawing]

[0015] [Figure 1] A block diagram showing the configuration of an imaging device according to a first embodiment of the present invention. [Figure 2] A diagram showing the configuration of the pixel array of an image sensor. [Figure 3] A flowchart illustrating the imaging process in the first embodiment. [Figure 4] A flowchart illustrating the standby AF processing in the first embodiment. [Figure 5] A flowchart illustrating the scene change detection process in the first and second embodiments. [Figure 6] A flowchart illustrating the focus detection process in the first and second embodiments. [Figure 7] Flowcharts illustrating the AF control process in the first and second embodiments. [Figure 8]Flowchart showing the shooting process in the second embodiment. [Figure 9] Flowchart showing the read mode setting process in the second embodiment. [Figure 10] Flowchart showing the AF process during standby in the second embodiment.

Mode for Carrying Out the Invention

[0016] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential for the invention, and the plurality of features may be arbitrarily combined. Further, in the accompanying drawings, the same or similar configurations are denoted by the same reference numerals, and redundant descriptions are omitted.

[0017] (First Embodiment) FIG. 1 is a block diagram showing the configuration of an imaging device 100 according to a first embodiment of the present invention. The imaging device 100 of the present embodiment mainly includes a lens unit 101 and a camera body 102. A lens control unit 117 that comprehensively controls the operation of the entire lens unit 101 and a camera control unit 141 that comprehensively controls the operation of the entire imaging device 100 including the lens unit 101 can communicate with each other through terminals provided on the lens mount.

[0018] First, an outline of the configuration and operation of the lens unit 101 will be described.

[0019] The lens unit 101 is a type of interchangeable lens that can be attached to and detached from the camera body 102. The lens unit 101 in FIG. 1 is a single-lens reflex lens and is an example of a normal lens. The photographing lens 111 (optical system) includes a fixed lens 112, an aperture 113, and a focus lens 114.

[0020] The aperture control unit 115 adjusts the aperture diameter of the aperture 113 by driving the aperture 113, thereby adjusting the amount of light during shooting. The focus lens 114 is a lens for adjusting the focus, and although it is simply shown as a single lens in Figure 1, it is usually composed of multiple lenses. As will be described later, the focus control unit 116 receives the lens drive amount determined by the camera control unit 141 via the lens control unit 117, and adjusts the focus by driving the focus lens 114. AF control is realized by this movement control of the focus lens 114 by the focus control unit 116. The aperture control unit 115 and the focus control unit 116 are controlled by the lens control unit 117.

[0021] Next, the configuration and operation of the camera body 102 will be described in general terms. The image sensor 121 has multiple photoelectric conversion elements that photoelectrically convert the subject image (optical image) into electric charge, and is composed of, for example, a CCD or CMOS sensor. The light beam incident through the photographic lens 111 of the lens unit 101 is imaged on the light-receiving surface of the image sensor 121, and is converted into electric charge in each photoelectric conversion element according to the amount of light and stored. The charge stored in each photoelectric conversion element is sequentially read out from the image sensor 121 as a voltage signal corresponding to the charge by a drive pulse output by the timing generator 122.

[0022] The configuration of the image sensor 121 will now be explained with reference to Figures 2(a), (b), and (c).

[0023] Figure 2(a) shows the arrangement of pixels 211 on the imaging surface of the image sensor 121, as seen from the lens unit 111 side, in a range of 8 horizontal (x direction) x 6 vertical (y direction) pixels. A Bayer color filter is provided on the imaging surface, with red (R) and green (G) color filters arranged alternately from left to right for pixels in odd-numbered rows, and green (G) and blue (B) color filters arranged alternately from left to right for pixels in even-numbered rows.

[0024] Figure 2(b) shows pixel 211R with a red (R) color filter. 212 represents an on-chip microlens. Inside the on-chip microlens 212 are a pair of photoelectric conversion units (first pair of photoelectric conversion units) 213A and 213B, which are divided in the x direction. Pixel 211Gr with a green (G) color filter and pixel 211B with a blue (B) color filter are configured similarly.

[0025] Figure 2(c) shows pixel 211Gb with a green (G) color filter. Inside the on-chip microlens 212 are a pair of photoelectric conversion units (second pair of photoelectric conversion units) 213C, 213D, which are divided in the y direction.

[0026] Thus, the image sensor 121 in this embodiment has pixels 211R, 211Gr, and 211B in which the photoelectric conversion unit is divided into two in the x direction, and a pixel 211Gb in which the photoelectric conversion unit is divided into two in the y direction. Here, the pupil division directions are shown as horizontal and vertical, but it may also be divided diagonally.

[0027] Using the photoelectric conversion signals output from each of a pair of photoelectric conversion units in multiple pixels, a pair of image signals (focus detection signals) and disparity image data for display / recording 3D image observation are generated. In addition, using the imaging signal output by adding the pair of photoelectric conversion signals from each of the multiple pixels, image data for brightness determination and normal display / recording image data are generated.

[0028] Returning to Figure 1, the CDS / AGC / AD circuit 123 performs correlated double sampling to remove reset noise, adjusts the sensor gain, and digitizes the voltage signals (imaging signal and focus detection signal) read from the image sensor 121. The CDS / AGC / AD circuit 123 then outputs the processed imaging signal to the imaging signal processing unit 124 and the focus detection signal to the focus detection signal processing unit 125.

[0029] The focus detection signal processing unit 125 sets and arranges the focus detection area for focus detection. Here, it extracts focus detection signals from pixels included in a predetermined area from the focus detection signals output from the CDS / AGC / AD circuit 123.

[0030] Here, we will explain the focus detection method using image plane phase difference detection. In the pixel 211R (211Gr, 211B) shown in Figure 2(b), the microlens 212 performs pupil division in the x direction by imaging light beams from different regions in the x direction of the exit pupil of the optical system onto the photoelectric conversion unit 213A and the photoelectric conversion unit 213B. In the pixel 211Gb shown in Figure 2(c), the microlens 212 performs pupil division in the y direction by imaging light beams from different regions in the y direction of the exit pupil of the optical system onto the photoelectric conversion unit 213C and the photoelectric conversion unit 213D. In other words, it detects the phase difference in a first direction of the light image caused by light passing through different pupil regions of the optical system, and the phase difference in a second direction different from the first direction.

[0031] In the focus detection signal processing unit 125, an A image signal is generated by combining the photoelectric conversion signals obtained from one of the pair of photoelectric conversion units 213A and 213B for each of the multiple pixels 211R within a predetermined range (focus detection area). A B image signal is generated by combining the photoelectric conversion signals obtained from the other unit.

[0032] Similarly, in the focus detection signal processing unit 125, a C image signal is generated by combining the photoelectric conversion signals obtained from one of the paired photoelectric conversion units 211C and 211D for each of the multiple pixels 211Gb within the focus detection area. A D image signal is also generated by combining the photoelectric conversion signals obtained from the other unit.

[0033] Correlation calculations are performed on these pairs of image signals (A image signal and B image signal, C image signal and D image signal) to determine the amount of defocus and reliability information (degree of two-image agreement, degree of two-image steepness).

[0034] In this embodiment, AF control before still image capture is performed using readout in non-decimation readout mode, and the correlation calculation result (horizontal focus detection) between the A image signal and the B image signal, and the correlation calculation result (vertical focus detection) between the C image signal and the D image signal are used in combination. During standby AF control, readout is performed using vertical decimation readout mode, and only the correlation calculation result (horizontal focus detection) between the A image signal and the B image signal is used.

[0035] The imaging signal processing unit 124 performs predetermined image processing, such as gamma conversion, white balance processing, and various correction processing, on the imaging signal output from the CDS / AGC / AD circuit 123, and stores the processed image data in the SDRAM 136 via the bus 131.

[0036] Display image data stored in the SDRAM 136 is read by the display control unit 132 via the bus 131 and displayed on the display unit 133. Recording image data is recorded on the recording medium 135 by the recording medium control unit 134 when the system is in recording mode.

[0037] Furthermore, the image data for brightness determination is used for measuring the brightness of the subject (photometry) in the photometering unit 142, and the photometry result is output to the camera control unit 141.

[0038] The exposure setting (AE) is determined based on the metering results and camera control values ​​such as charge accumulation time, shooting sensitivity, and aperture value.

[0039] The vibration detection unit 143 uses a vibration sensor such as a gyro sensor to detect angular velocity around a predetermined axis and outputs it to the camera control unit 141. Based on these detection signals, the camera control unit 141 drives the correction optical system for image stabilization and detects the orientation of the camera body.

[0040] ROM 137 stores the control program executed by the camera control unit 141 and various data necessary for control, while flash ROM 138 stores various setting information related to the operation of the camera body 102, such as user setting information.

[0041] The shooting preparation switch (SW1) 139 is turned ON by, for example, half-pressing a shutter release button (not shown), and instructs the start of shooting preparation operations such as AF and AE (hereinafter referred to as "SW1"). The shooting switch (SW2) 140 is turned ON after SW1 is turned ON by, for example, fully pressing a shutter release button (not shown), and instructs the camera to take a picture (hereinafter referred to as "SW2").

[0042] The camera control unit 141 determines the lens drive amount based on the defocus amount and reliability information output from the focus detection signal processing unit 125. The lens drive amount is transmitted to the focus control unit 116 via the lens control unit 117, and the focus control unit 116 drives the focus lens 114 to achieve autofocus (AF).

[0043] Next, the shooting process performed by the camera body 102 will be explained with reference to Figure 3. This process is achieved by the camera control unit 141 executing the control program stored in the ROM 137. The operation of the other flowcharts that follow is similar.

[0044] First, in step S301, the camera control unit 141 performs initialization processing such as camera settings, and then proceeds to step S302. In this embodiment, the scene change flag and the vertical focus flag are also initialized here. The scene change flag is set in step S401, which will be described later, to determine whether the user has changed the shooting scene, and its initial state is set to zero. The vertical focus flag is set in step S306, which will be described later, to determine whether the camera is in focus using vertical focus detection, and its initial state is set to zero.

[0045] In step S302, the camera control unit 141 sets the readout mode to vertical decimation readout mode and proceeds to step S303.

[0046] In step S303, the standby AF control process is executed, and the process proceeds to step S304. In the standby AF control process in step S303, the readout mode is set to vertical decimation readout mode, so the horizontal focus detection result is used for AF control. Details will be described later with reference to Figure 4.

[0047] In step S304, the camera control unit 141 determines whether or not SW1 has been pressed. If it has not been pressed, the process returns to step S303 and the standby operation (steps S303 and S304) is repeated. If it has been pressed, the process proceeds to step S305.

[0048] In step S305, the camera control unit 141 sets the readout mode to the no-decimation readout mode and proceeds to step S306.

[0049] In step S306, the camera control unit 141 performs AF control processing and proceeds to step S307. In the AF control processing of step S306, since the readout mode is set to the no-decimation readout mode, the horizontal focus detection result and the vertical focus detection result are used in combination to perform AF control. Details will be described later with reference to Figure 7.

[0050] In step S307, the camera control unit 141 determines whether or not the camera is in focus. If it is not in focus, the process returns to step S306 and the AF operation (steps S306 and S307) is repeated. If the camera is in focus, in step S308, SW2 becomes available to press, and pressing SW2 executes still image capture.

[0051] After capturing a still image, the process returns to step S302, switches the readout mode to vertical decimation readout mode, and transitions to standby operation (steps S303, S304).

[0052] Furthermore, if SW2 is not pressed in step S308 and SW1 is released (not shown), the process returns to step S302, the read mode is switched to vertical decimation read mode, and the process transitions to standby operation (steps S303, S304).

[0053] This process is repeated until the shooting process is stopped. The shooting process is stopped when the power to the camera body 102 is turned off, or when an interrupt process for an operation other than shooting occurs, such as camera user setting processing or playback processing for checking captured images and videos.

[0054] Next, the standby AF control process performed in step S303 in Figure 3 will be explained with reference to the flowchart in Figure 4.

[0055] In step S401, the camera control unit 141 performs a scene change determination process to determine whether or not the shooting scene has changed.

[0056] Here, the processing for scene change detection in step S401 will be explained with reference to Figure 5.

[0057] In step S501, the camera control unit 141 compares the detection results from the photometering unit 142 and the vibration detection unit 143 with the detection results from the previous determination to determine whether there has been a change. If it is determined in step S501 that there has been a change in the camera's posture or brightness, it means that the user has changed the shooting scene and the subject has also changed, so it is necessary to perform focus detection again. Therefore, in step S502, the camera control unit 141 sets the scene change flag to 1 and simultaneously resets (sets to zero) the vertical focus status flag and terminates the process.

[0058] If it is determined in step S501 that there was no change in the camera's orientation or brightness, the camera control unit 141 terminates the process in step S503 by setting the scene change flag to zero. In this case, the vertical focus state must be maintained, so the flag is not set.

[0059] When determining the continuity of changes in posture and brightness, it is preferable to consider hand shake and other factors to establish a threshold. For example, the detection results from the photometer 142 and the vibration detection unit 143 are stored in a dedicated memory, and if multiple stored results exceed a predetermined threshold a predetermined number of times, it is determined that a change has occurred.

[0060] In this embodiment, we have described, as an example, how to determine a change in the shooting scene based on changes in posture and brightness, but it is also possible to determine this based on changes in the subject detection state. If there is a detected subject, it is useful because it is easier to reflect the user's intention. Changes in the subject detection state refer to cases where the subject can no longer be detected, another subject is selected when there are multiple subjects, or the subject moves. Subject movement can be determined by whether or not the change in the size and position of the subject relative to the field of view exceeds a certain amount.

[0061] Once step S401, which is the scene change detection process, is completed, the camera control unit 141 proceeds to the focus detection process in step S402.

[0062] The focus detection process in step S402 will be explained with reference to the flowchart in Figure 6.

[0063] First, in step S601, the camera control unit 141 sets the vertical calculation flag i to zero and the calculation result to an initial value, and proceeds to step S602. The vertical calculation flag i is a flag that determines whether or not it is a vertical focus detection calculation (or a horizontal focus detection calculation).

[0064] In step S602, the camera control unit 141 extracts the focus detection signal within the focus detection region from the focus detection signal output from the image sensor 121. From the extracted focus detection signal, it generates a pair of image signals (image A and image B when the vertical calculation flag i=0, and image C and image D when the vertical calculation flag i=1). Then, the process proceeds to step S603.

[0065] In step S603, the camera control unit 141 performs an averaging process on each of the pair of image signals generated in step S602 in a direction orthogonal to the pupil division direction (y-direction when vertical calculation flag i=0, and x-direction when vertical calculation flag i=1). After that, the process proceeds to step S604. The averaging process in step S603 can reduce the influence of noise on the image signal.

[0066] In step S604, the camera control unit 141 performs filtering to extract signal components of a predetermined frequency band from the pair of image signals obtained by the averaging process in step S603, and proceeds to step S605. Here, a low-pass filter that extracts low-frequency components of the signal and a high-pass filter that extracts high-frequency components may be used, or a mid-pass filter that can extract frequency components between the low-pass and high-pass filters may be used, or three or more types of filters may be used.

[0067] In step S605, the camera control unit 141 calculates a correlation amount using the pair of image signals that were filtered in step S604.

[0068] In step S606, the camera control unit 141 calculates the correlation change amount from the correlation amount calculated in step S605.

[0069] In step S607, the camera control unit 141 calculates the image displacement amount from the correlation change amount calculated in step S606.

[0070] In step S608, the camera control unit 141 obtains either Defocus_0 (horizontal calculation result) or Defocus_1 (vertical calculation result) by multiplying the image displacement amount by a conversion coefficient to convert it into a defocus amount. This conversion coefficient is a value held by the camera, corresponding to the zoom lens position, aperture value, and image height of the image sensor. In step S609, the camera control unit 141 obtains Reliability_0 (evaluation result of horizontal calculation) or Reliability_1 (evaluation result of vertical calculation), which are reliability evaluation results indicating how reliable the defocus amount calculated in step S608 is, and proceeds to step S610.

[0071] Reliability is determined by estimating the standard deviation of the defocus amount based on the values ​​calculated in steps S605 and S606, and setting stepped thresholds for that standard deviation. However, the method for determining reliability is not limited to this method, and other known methods may be used.

[0072] Furthermore, in this embodiment, the reliability evaluation result is expressed as "high" when reliability is good (reliability is above a predetermined value: the defocus amount can be used for focusing), and "low" when reliability is poor (reliability is below a predetermined value: the defocus amount cannot be used for focusing). Here, reliability is expressed in two stages for the sake of clarity, but intermediate reliability levels between high and low may be used, or it may be divided into three or more stages.

[0073] In step S610, the camera control unit 141 determines whether vertical focus detection calculation is required (readout mode is readout mode without decimation).

[0074] In step S401 of Figure 4, vertical focus detection calculation is unnecessary during standby AF (the readout mode is vertical decimation readout mode). Therefore, if the process proceeds from step S401 to the flow shown in Figure 6, the camera control unit 141 determines that the vertical focus detection calculation in step S610 is unnecessary, terminates the processing of this flow, and returns to step S403 of Figure 4. The case where vertical focus detection calculation is necessary (the readout mode is non-decimation readout mode) will be explained in the focus detection processing in step S701 of Figure 7, including steps S611 and S612.

[0075] In step S403 of Figure 4, the camera control unit 141 determines the reliability obtained in step S609, and if the reliability of the horizontal focus detection calculation is high, it proceeds to step S404. In this case, the reliability of the result of the horizontal focus detection calculation is high, and there is a high possibility that the subject can be focused. Therefore, in step S404, the camera control unit 141 sets the lens drive amount to the defocus amount obtained from the horizontal focus detection calculation in step S608. Then, since it has switched to the result of the horizontal focus detection calculation, it sets the vertical focus status flag to zero and proceeds to step S408.

[0076] On the other hand, if in step S403 the reliability obtained in step S609 is determined to be low, the camera control unit 141 proceeds to step S405 to determine whether or not the camera is in vertical focus and whether or not there is a scene change. If the camera control unit 141 is in vertical focus and there is no scene change, it proceeds to step S406.

[0077] In this case, the defocus amount obtained in the horizontal focus detection calculation in step S608 is unreliable, and the scene has not changed, so the vertical focus state is maintained. Therefore, in step S406, the camera control unit 141 sets the lens drive amount to zero and proceeds to step S408.

[0078] If vertical focus is not achieved in step S405, or if there is a scene change, the process proceeds to step S407. In this case, the defocus amount obtained in the horizontal focus detection calculation in step S608 is also unreliable, so the lens drive amount is set to the search drive amount, and the process moves to a search operation to find the subject (focus position). The camera control unit 141 sets the vertical focus flag to zero, cancels the vertical focus state, and proceeds to step S408.

[0079] In step S408, the camera control unit 141 determines whether the lens drive amount set in the previous step is greater than the focus monitoring width. The focus monitoring width is a threshold that prevents unnecessary lens movement when the lens is already in focus, and it is desirable to set it to approximately 1Fδ. If the lens drive amount is greater than the focus monitoring width, the camera control unit 141 proceeds to step S409, drives the lens by the set lens drive amount, and terminates the process. If it is less than or equal to the focus monitoring width, the process terminates without driving the lens.

[0080] Next, the AF control in step S306 of Figure 3 will be explained with reference to the flowchart in Figure 7.

[0081] First, the focus detection process in step S701 will be explained with reference to the flowchart in Figure 6. Steps S601 to S609 are the same as the focus detection process in step S402 in Figure 4 mentioned above, so the explanation will be omitted.

[0082] In step S701 of the focus detection process in Figure 7, since the readout mode is the non-decimation readout mode, it is determined in step S610 that a vertical focus detection calculation is required, and the camera control unit 141 proceeds to step S611.

[0083] In step S611, the camera control unit 141 determines whether the vertical focus detection calculation has been completed. If the vertical calculation flag i is zero, the vertical focus detection calculation has not been completed, and the process proceeds to step S612.

[0084] In step S612, the camera control unit 141 sets the vertical calculation flag i to 1, returns to step S602, and performs the vertical focus detection calculation. When the process proceeds to step S611 again, the vertical calculation flag is 1, so the process ends and returns to step S702 in Figure 7.

[0085] In this case, steps S608 and S609 obtain the horizontal calculation result (Defocus_0, Reliability_0) and the vertical calculation result (Defocus_1, Reliability_1).

[0086] Next, in step S702, the camera control unit 141 determines the reliability of the vertical focus detection calculation result and the horizontal focus detection calculation result. If the reliability of both is low, the camera control unit 141 proceeds to step S706.

[0087] In this case, since the amount of defocus obtained in step S608 is unreliable, in step S706, the camera control unit 141 sets the lens drive amount to a search drive amount and proceeds to a search operation to find the subject. The vertical focus flag is set to zero, the vertical focus state is released, and the process proceeds to step S707.

[0088] On the other hand, in step S702, if the reliability of either the vertical or horizontal calculation result is lower than expected, the camera control unit 141 proceeds to step S703 to compare the reliability and determine which calculation result to use. If the reliability of the vertical focus detection calculation is higher, the camera control unit 141 sets the vertical focus detection calculation result to the lens drive amount in step S704, sets the vertical focus flag to 1, and proceeds to step S707.

[0089] Furthermore, if the reliability of the horizontal focus detection calculation result is higher, in step S705 the lens drive amount is set to the horizontal focus detection calculation result (allowing transition to the horizontal calculation result), the vertical focus flag is set to zero, and the process proceeds to step S707.

[0090] In step S707, the camera control unit 141 determines whether the lens drive amount set in the previous step is greater than the focus management width. The focus management width is a threshold for determining whether or not the camera is in focus, and it is desirable to set it to a value of about 0.25 to 0.5Fδ, which is smaller than the focus monitoring width (about 1Fδ) in step S408.

[0091] If the lens drive amount is greater than the focusing control range, the camera control unit 141 proceeds to step S708, drives the lens by the set lens drive amount, and terminates the process.

[0092] If the lens drive amount is less than or equal to the focus control range, the camera control unit 141 proceeds to step S709, determines that focus is achieved, and terminates the process.

[0093] Here, the effects of this embodiment will be explained using Figure 3, with the example of focusing on a subject with horizontal stripes.

[0094] In the case of a subject with horizontal stripes, the vertical thinning mode is set in step S302, so focus detection is not possible, and during the standby operation immediately after camera startup (steps S303, S304), the image will be blurred while in standby mode.

[0095] When SW1 is pressed in step S304 and the system switches to the no-decimation readout mode in step S305, focus detection becomes possible using vertical focus detection calculation. Therefore, during AF operation (steps S306 and S307), the system enters a vertical focus state (vertical focus flag = 1 in step S704 in Figure 7), and the process proceeds to step S308, enabling still image capture.

[0096] After taking a still image in step S308, returning to step S302 and switching to vertical decimation mode would cause the camera to lose focus detection again. Previously, even though the subject had not changed, the camera would switch to a search operation to find the subject, resulting in a sudden blurring of the image.

[0097] In this embodiment, when the vertical focus flag is 1, step S405 in Figure 4 determines that the vertical focus state is maintained, and since the lens is not moved, the state in focus on the horizontally striped subject is maintained. This state is maintained until the scene change determination in step S401 in Figure 4 determines that the shooting scene has changed (the user has switched subjects), or until the reliability (Reliability_0) of the waiting horizontal focus detection calculation result is determined to be high in step S403 in Figure 4. Therefore, as long as the subject does not change from a horizontally striped subject, the state in focus on the horizontally striped subject can be stabilized.

[0098] As described above, this embodiment makes it possible to perform AF control stably even when the phase difference detection direction is switched.

[0099] (Second embodiment) Next, the shooting process performed by the camera body 102 in the second embodiment will be described with reference to Figures 8 to 10. In the first embodiment, when the phase difference detection direction was switched, the focus adjustment was stabilized by not moving the lens until there was a scene change or until the reliability of focus detection in the detection direction after the switch was increased.

[0100] In the second embodiment, focus adjustment is stabilized by maintaining a state where focus detection is possible without changing the readout mode. Steps that are the same as those in the flowchart of the first embodiment described in Figures 3 to 7 are given the same reference numerals and their explanations are omitted.

[0101] In Figure 8, in step S301, the camera control unit 141 performs initialization processing and proceeds to step S801.

[0102] In step S801, the camera control unit 141 sets the readout mode and proceeds to step S802.

[0103] In step S802, the camera control unit 141 performs standby AF control and proceeds to step S304. Steps S304 onward are the same as those shown in Figure 3.

[0104] Here, the read mode setting in step S801 will be explained with reference to the flowchart in Figure 9.

[0105] In step S401, the camera control unit 141 performs the scene change detection process (Figure 5) and proceeds to step S901.

[0106] In step S901, the camera control unit 141 determines whether or not the camera is in focus in the vertical direction and whether or not there is a scene change. If the camera is in focus in the vertical direction and there is no scene change, the camera control unit 141 proceeds to step S902. In this case, in order to continue the vertical focus detection calculation, the readout mode is set to the no-decimation readout mode and the process ends, and the process proceeds to step S802 in Figure 8.

[0107] Furthermore, if it is determined in step S901 that the camera is not in focus vertically, or that there is a scene change, the camera control unit 141 does not need to perform vertical calculations, so it sets the readout mode to vertical decimation readout mode, terminates the process, and proceeds to step S802.

[0108] Next, the standby AF control process in the second embodiment of step S802 will be described with reference to the flowchart in Figure 10.

[0109] In step S701, the camera control unit 141 performs focus detection processing (Figure 6). In step S701, if the readout mode was set to the no-decimation readout mode in step S801, the horizontal calculation results (Defocus_0, Reliability_0) and vertical calculation results (Defocus_1, Reliability_1) are obtained in steps S608 and S609 of Figure 6.

[0110] On the other hand, if the read mode is set to vertical decimation read mode in step S801, only the horizontal calculation results (Defocus_0, Reliability_0) are obtained in steps S608 and S609, and initial values ​​are assigned to the vertical calculation results (Defocus_1, Reliability_1).

[0111] In step S1001, the camera control unit 141 determines whether the defocus amount (Defocus_1) of the vertical focus detection calculation result is an initial value. If the vertical decimation readout mode was set to the readout mode in step S801, an initial value is set for Defocus_1, and the process proceeds to step S1002.

[0112] In step S1002, the camera control unit 141 determines the reliability of the horizontal calculation result obtained in step S609. If the reliability is high, the process proceeds to step S1003.

[0113] In step S1003, the camera control unit 141 sets the lens drive amount to the defocus amount (Defocus_0) acquired in step S608 and proceeds to step S408.

[0114] Furthermore, if in step S1002 the reliability of the horizontal calculation result obtained in step S609 is determined to be low, the camera control unit 141 proceeds to step S1004.

[0115] In step S1004, the camera control unit 141 determines that the defocus amount (Defocus_0) obtained in step S608 is unreliable, so it sets the lens drive amount to the search drive amount and proceeds to step S408.

[0116] On the other hand, if the readout mode is set to the no-decimation readout mode in step S801, the camera control unit 141 proceeds to step S1005 because the defocus amount (Defocus_1) of the vertical focus detection calculation result is not the initial value in step S1001.

[0117] In step S1005, the camera control unit 141 determines the reliability of the vertical focus detection calculation result obtained in step S609. If the reliability is low, the process proceeds to step S1006 to release the vertical focus state, sets the vertical focus flag to zero, and proceeds to step S1002.

[0118] In step S1002, as described above, the camera control unit 141 determines the reliability of the horizontal calculation result, sets the lens drive amount, and proceeds to step S408.

[0119] Furthermore, if the reliability of the vertical focus detection calculation result obtained in step S609 is determined to be high in step S1005, the camera control unit 141 proceeds to step S1007.

[0120] In step S1007, the camera control unit 141 determines the reliability of the horizontal focus detection calculation result obtained in step S609. If the reliability is low, the vertical focus state continues, so the process proceeds to step S1008, where the defocus amount (Defocus_1) obtained in step S608 is set as the lens drive amount, and the process proceeds to step S408.

[0121] Furthermore, if the reliability of the horizontal calculation result obtained in step S609 is determined to be high in step S1007, the process proceeds to step S1009, where the camera control unit 141 determines whether the phase difference detection direction can be switched.

[0122] In step S1009, it is determined whether the absolute value of the difference in the defocus amount between the horizontal focus detection calculation result and the vertical focus detection calculation result obtained in step S608 (|Defocus_0-Defocus_1|) is greater than the threshold Th. The threshold Th for switching the phase difference detection direction is a threshold used to determine whether there is no unnaturalness when switching from the vertical focus detection calculation to the horizontal focus detection calculation result, so it is preferable to set it to about 1Fδ.

[0123] If, in step S1009, it is determined that the absolute value of the difference in the defocus amount is greater than the threshold Th, the camera control unit 141 proceeds to step S1008 in order to maintain the vertical focus state. Then, it sets the lens drive amount to the defocus amount (Defocus_1) obtained in step S608 as the result of the vertical focus detection calculation, and proceeds to step S408.

[0124] If, in step S1009, the absolute value of the difference in the amount of defocus is determined to be less than or equal to the threshold Th, the camera control unit 141 proceeds to step S1010. Then, in order to switch to the horizontal focus detection calculation result, the vertical focus flag is set to zero, the vertical focus state is released, and the process proceeds to step S1003.

[0125] In step S1003, the camera control unit 141 sets the lens drive amount to the defocus amount (Defocus_0) obtained in step S608 as the result of the horizontal focus detection calculation, and proceeds to step S408.

[0126] Steps S408 and S409 are the same as the steps in Figure 4, so their explanation is omitted.

[0127] Here, the effects of this embodiment will be explained using Figure 8, with an example of performing focus detection on a horizontally striped subject.

[0128] In the case of a subject with horizontal stripes, the vertical decimation mode is set in step S801 immediately after camera startup. Therefore, focus cannot be detected during the standby operation immediately after camera startup (steps S303 and S304), and the image remains blurred during standby. When SW1 is pressed in step S304, and the camera switches to the no-decimation readout mode in step S305, focus detection becomes possible using vertical calculation. As a result, during AF operation (steps S306 and S307), the camera enters a vertical focus state (vertical focus flag = 1 set in step S704 in Figure 7), and the process proceeds to step S308, enabling still image capture.

[0129] After taking a still image in step S308, the system returns to step S801. If the vertical focus state is achieved (vertical focus flag = 1), then in step S901 in Figure 9, it is determined that vertical calculation is necessary. Then, in step S902, the system is set to readout mode without decimation, and vertical calculation continues, allowing the system to maintain focus on the horizontally striped subject. This state is maintained, as in the first embodiment, until the scene change determination in step S401 in Figure 9 determines that the shooting scene has changed (the user has switched subjects), or until the reliability (Reliability_1) of the waiting vertical calculation result in step S1005 in Figure 10 becomes low. Therefore, as long as the subject does not change from a horizontally striped subject, the system can maintain stable focus on the horizontally striped subject.

[0130] Alternatively, in step S1009 of Figure 10, the system maintains the defocus result of the horizontal calculation (Defocus_0) and the defocus result of the vertical calculation (Defocus_1) until they are determined to be of similar quality, i.e., to be transferable to the horizontal calculation result. If it is determined that the system can transfer to the horizontal calculation result, the system can perform focus driving using the defocus result of the horizontal calculation (Defocus_0) in step S1003 of Figure 10, and even if the readout mode is switched to the vertical decimation readout mode in step S903 of Figure 9, stable focus control can be achieved.

[0131] As described above, this embodiment allows for stable AF control even when the phase difference detection direction is switched.

[0132] The disclosures herein include the following imaging devices and their control methods, programs, and storage media.

[0133] (Item 1) A phase difference detection means for detecting the phase difference in a first direction of the light image caused by light passing through different pupil regions of the optical system, and the phase difference in a second direction different from the first direction, A focus detection means that detects the focus state and obtains its reliability based on at least one of the phase difference in the first direction and the phase difference in the second direction, An adjustment means that drives the optical system to adjust the focus based on the focus state detected by the focus detection means, When transitioning from a first state in which focus adjustment is performed based on the phase difference in the first direction to a second state in which focus adjustment is performed based on the phase difference in the second direction, a control means controls the adjustment means so as not to perform the focus adjustment based on the phase difference in the second direction until the reliability of the focus state detected based on the phase difference in the second direction becomes higher than a predetermined value. An imaging device characterized by comprising:

[0134] (Item 2) The imaging apparatus according to item 1, characterized in that, when transitioning from the first state to the second state, the control means permits the focus adjustment based on the phase difference in the second direction after the reliability of the focus state detected based on the phase difference in the second direction has become higher than a predetermined value.

[0135] (Item 3) The imaging apparatus according to item 1 or 2, characterized in that, when transitioning from the first state to the second state, the control means stops driving the optical system after transitioning to the second state until the reliability of the focal state detected based on the phase difference in the second direction becomes higher than a predetermined value.

[0136] (Item 4) The imaging apparatus according to item 1, characterized in that, when transitioning from the first state to the second state, the control means controls the transition so as not to the second state until the reliability of the focal state detected based on the phase difference in the second direction becomes higher than a predetermined value.

[0137] (Item 5) The imaging apparatus according to item 4, characterized in that, when transitioning from the first state to the second state, the control means permits the transition to the second state when the difference between the focal state detected based on the phase difference in the first direction and the focal state detected based on the phase difference in the second direction becomes smaller than a threshold.

[0138] (Item 6) The imaging device according to item 4 or 5, characterized in that the control means permits a transition to the second state when there is a change in the shooting scene.

[0139] (Item 7) The imaging device according to item 6, characterized in that the control means determines the change in the shooting scene based on the change in the posture of the imaging device.

[0140] (Item 8) The imaging apparatus according to item 6, characterized in that the control means determines the change in the shooting scene by the change in the brightness of the image.

[0141] (Item 9) The imaging device according to item 6, characterized in that the control means determines the change in the shooting scene based on the detected change in the subject.

[0142] (Item 10) The imaging apparatus according to any one of items 1 to 9, characterized in that the control means controls the optical system to perform a search drive to search for a focal position when there is a change in the shooting scene.

[0143] (Item 11) The imaging device according to any one of items 1 to 10, characterized in that, in the second state, the focus detection means detects the focus state based on a signal obtained by downsampling the signals of pixels in a direction orthogonal to the second direction.

[0144] (Item 12) The imaging apparatus according to any one of items 1 to 11, characterized in that the focus detection means is capable of detecting a focus state based on a phase difference in the first direction and a focus state based on a phase difference in the second direction in the first state, and is capable of detecting a focus state based on a phase difference in the second direction in the second state.

[0145] (Item 13) A phase difference detection process that detects the phase difference in a first direction of the light image caused by light passing through different pupil regions of the optical system, and the phase difference in a second direction different from the first direction, A focus detection step that detects the focus state and obtains its reliability based on at least one of the phase difference in the first direction and the phase difference in the second direction, Based on the focus state detected in the focus detection step, an adjustment step is performed to drive the optical system and adjust the focus; A control step controls the adjustment process so as not to perform the adjustment based on the phase difference in the second direction when transitioning from a first state in which focus adjustment is performed based on the phase difference in the first direction to a second state in which focus adjustment is performed based on the phase difference in the second direction, until the reliability of the focus state detected based on the phase difference in the second direction becomes higher than a predetermined value. A control method for an imaging device, characterized by having the following features.

[0146] (Item 14) A program that causes a computer to execute each step of the control method described in item 13.

[0147] (Item 15) A computer-readable storage medium containing a program that causes a computer to execute each step of the control method described in item 13.

[0148] (Other embodiments) Furthermore, the present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by a process in which one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions.

[0149] The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, claims are attached to disclose the scope of the invention. [Explanation of symbols]

[0150] 101: Lens unit, 102: Camera body, 111: Imaging lens, 112: Fixed lens, 113: Aperture, 114: Focus lens, 115: Aperture control unit, 116: Focus control unit, 117: Lens control unit, 121: Image sensor, 122: Timing generator, 123: CDS / AGC / AD circuit, 124: Image signal processing unit, 125: Focus detection signal processing unit, 131: Bus, 132: Display control unit, 133: Display unit, 134: Recording medium control unit, 135: Recording medium, 136: SDRAM, 137: ROM, 138: Flash ROM, 139: SW1, 140: SW2, 141: Camera control unit

Claims

1. In order to perform phase difference detection based on light beams passing through different pupil regions of the optical system, an image sensor is provided in which a plurality of pixels capable of outputting a pair of focus detection signals are arranged two-dimensionally in a first direction and a second direction, Control means for controlling the readout mode of the signal from the image sensor, The system includes a focus detection means for detecting phase difference information in the first direction and phase difference information in the second direction based on a signal output from the image sensor, The control means sets the readout mode of the image sensor to the first readout mode during the standby period when no instruction to start shooting preparation operation is input, and when an instruction to start shooting preparation operation is input, switches the readout mode of the image sensor from the first readout mode to the second readout mode. The imaging device is characterized in that the focus detection means detects phase difference information in the first direction during the standby period, and detects the phase difference information in the first direction and the phase difference information in the second direction when an instruction to start the shooting preparation operation is input.

2. The imaging apparatus according to claim 1, characterized in that the first direction is horizontal and the second direction is vertical.

3. When transitioning from a first state in which phase difference information in the first direction is detected in the first reading mode to a second state in which phase difference information in both the first and second directions is detected in the second reading mode, The imaging apparatus according to claim 1, characterized in that it does not transition to the second state until the reliability of the focal state detected based on the phase difference in the second direction becomes higher than a predetermined value.

4. When transitioning from a first state in which phase difference information in the first direction is detected in the first reading mode to a second state in which phase difference information in both the first and second directions is detected in the second reading mode, The imaging apparatus according to claim 1, characterized in that the control means permits a transition to the second state when the difference between the focal state detected based on the phase difference in the first direction and the focal state detected based on the phase difference in the second direction becomes smaller than a threshold.

5. When transitioning from a first state in which phase difference information in the first direction is detected in the first reading mode to a second state in which phase difference information in both the first and second directions is detected in the second reading mode, The imaging apparatus according to claim 1, characterized in that the control means permits a transition to the second state when there is a change in the shooting scene.

6. The imaging apparatus according to claim 5, characterized in that the control means determines the change in the shooting scene based on the change in the posture of the imaging apparatus.

7. The imaging apparatus according to claim 5, characterized in that the control means determines the change in the shooting scene based on the change in the brightness of the image.

8. The imaging apparatus according to claim 5, characterized in that the control means determines the change in the shooting scene based on the detected change in the subject.

9. The imaging apparatus according to claim 1, characterized in that the control means controls the optical system to perform a search drive to search for a focal position when there is a change in the shooting scene.

10. When transitioning from a first state in which phase difference information in the first direction is detected in the first reading mode to a second state in which phase difference information in both the first and second directions is detected in the second reading mode, The imaging apparatus according to claim 1, characterized in that, in the second state, the focus detection means detects the focus state based on a signal obtained by downsampling the signals of pixels in a direction orthogonal to the second direction.

11. A focus detection step in which, in order to perform phase difference detection based on light beams passing through different pupil regions of the optical system, a plurality of pixels capable of outputting a pair of focus detection signals are arranged two-dimensionally in a first direction and a second direction, and phase difference information in the first direction and the second direction is detected using signals from an image sensor. The system includes a readout mode control step that sets the readout mode of the signal from the image sensor to a first readout mode during the standby period when no instruction to start shooting preparation is input, and switches to a second readout mode when an instruction to start shooting preparation is input. A control method for an imaging device, characterized in that, in the focus detection step, phase difference information in the first direction is detected during the standby period, and when an instruction to start the shooting preparation operation is input, phase difference information in the first direction and the second direction is detected.

12. A program for causing a computer to execute each step of the control method described in claim 11.

13. A computer-readable storage medium storing the program described in claim 12.

Images