JP6223160B2 - Imaging device, control method thereof, and control program - Google Patents

Description

  The present invention relates to an imaging apparatus, a control method thereof, and a control program, and more particularly to an imaging apparatus that obtains an evaluation value related to photometry or distance measurement according to an image signal and performs focus control.

  2. Description of the Related Art Conventionally, in an imaging apparatus, when obtaining subject position information for use in focus control, position information is obtained in accordance with an image signal output from an imaging element. In addition, an optical signal indicating a subject is directly input to a dedicated detection device, and position information of the subject is obtained according to a phase difference in an image indicated by the optical signal. When position information is obtained according to the image signal, a dedicated detection device is not necessary, and the imaging device can be downsized.

  FIG. 7 is a diagram for explaining the timing of an autofocus imaging operation (AF evaluation imaging) during live view in a conventional imaging apparatus.

  In a conventional imaging apparatus, imaging timing is defined by a vertical synchronizing signal (VD). When the AF control signal is turned on, an AF evaluation image (an AF evaluation image) is captured by the imaging device in accordance with VD after the live view imaging period. When the AF control signal is turned off, the live view imaging period starts again.

  As described above, since the live view imaging period for obtaining the live view image and the AF operation period for obtaining the AF evaluation image exist serially along the time axis, the live view image and the AF evaluation image are simultaneously captured. It is not possible.

  For this reason, as shown in the figure, an AF evaluation image is picked up in an AF operation period located between the live view periods (frames), and is unavoidable between the live view image and the AF evaluation image. There is a time lag.

  In addition, the live view image is displayed even when the AF evaluation image is captured. At this time, the live view image is displayed according to the AF evaluation image. As shown in FIG. 7, when an AF evaluation image is captured, the frame rate is set higher than that of the live view imaging period. Will be lower. Therefore, it is difficult to avoid a sense of incongruity due to a reduction in image quality and a change in image quality of the live view image.

  In order to avoid this state, there is an image pickup apparatus in which focus detection pixels are provided separately from image pickup signal pixels in a pixel portion provided in the image pickup element. As an example of the AF operation using this focus detection pixel, a contrast detection method (contrast AF) that detects a focus position according to a subject image obtained by a normal pixel (that is, an imaging signal pixel) A so-called phase difference detection method (phase difference AF) is known.

  In contrast AF, focusing on the output signal of the image sensor, in particular, high frequency components (contrast information), the position of the photographing lens having the largest evaluation value (contrast evaluation value) is set as the in-focus position. In contrast AF, the contrast evaluation value is obtained while moving the photographic lens by a small amount. In contrast AF, it is necessary to drive the photographic lens until the position of the photographic lens where the contrast evaluation value is maximized is known.

  On the other hand, in the phase difference AF, the light beam that has passed through the exit pupil of the photographing lens is divided into two, and the two divided light beams are received by a pair of focus detection sensors (that is, focus detection pixels). Then, the amount of deviation of the image signal output according to the amount of received light, that is, the amount of relative positional deviation in the beam splitting direction is detected to directly determine the amount of deviation of the photographing lens in the focus direction.

  Therefore, in the phase difference AF, once the charge accumulation operation is performed by the focus detection sensor, the focus shift amount and the direction can be obtained, and the focus adjustment operation can be performed at high speed.

  Note that in order to achieve both image quality and focus detection accuracy in a live view image, there is an image pickup apparatus having an image pickup element in which focus detection pixels are discretely arranged to change the drive of the image pickup element (patent) Reference 1). Here, a first thinning readout mode and a second thinning readout mode in which at least one of the thinning rate and the thinning phase is different are provided, and the first thinning readout mode and the second thinning readout mode according to the state of the imaging device. To choose.

JP 2010-181751 A

  However, in the imaging device described in Patent Document 1, it is necessary to handle focus detection pixels as defective pixels in a captured image when reading pixels. For this reason, in consideration of the image quality such as a still image using all pixels, it is difficult to arrange the focus detection images at high density in all regions of the image sensor.

  Therefore, it is difficult to perform AF control with high accuracy by covering a sufficient field angle area with only focus detection pixels. To improve AF control performance, phase difference AF using focus detection pixels is difficult. It is necessary to use together contrast AF using an image signal. In this case, in contrast AF, the time lag due to the drive switching described above occurs, and further, the image quality of the live view image is reduced. If phase difference AF and contrast AF are used together, the time lag and the image quality reduction can be improved. Will be difficult.

  In addition, when phase difference AF and contrast AF are used in combination, the burden on both the driving of the image sensor and the image data processing circuit increases. Then, the combined use of the phase difference AF and the contrast AF inevitably increases the power consumption, and the power source such as a battery is consumed in a short time.

  Accordingly, an object of the present invention is to provide an imaging apparatus, a control method thereof, and a control program capable of reducing power consumption by avoiding a deterioration in image quality of a live view image while performing high-speed and high-precision focus control. It is to provide.

  In order to achieve the above object, an imaging apparatus according to the present invention includes a plurality of images, an imaging element that outputs an image signal corresponding to an optical image, and readout control of a first pixel group among the plurality of pixels. Reading means for performing a first reading for obtaining a first image signal and performing a second reading for obtaining a second image signal by performing a reading control of a second pixel group among the plurality of pixels; Display control means for displaying an image corresponding to the first image signal on the display unit, and when displaying an image corresponding to the first image signal obtained by the first reading on the display unit, Control that performs second focus control based on the second image signal obtained by the second reading when the in-focus state cannot be obtained by the first focus control performed based on the first image signal. And means.

  A control method according to the present invention is a control method of an imaging apparatus that includes an image sensor that includes a plurality of images and outputs an image signal corresponding to an optical image, and performs readout control of a first pixel group among the plurality of pixels. Performing a first readout step for obtaining a first image signal, a second readout step for obtaining a second image signal by performing readout control of a second pixel group among the plurality of pixels, When a display control step of displaying an image corresponding to one image signal on the display unit and an image corresponding to the first image signal obtained by the first reading step are displayed on the display unit, When the in-focus state cannot be obtained by the first focus control performed based on the first image signal, the second focus control is performed based on the second image signal obtained by the second readout step. Do And having a control step.

  A control program according to the present invention is a control program used in an imaging apparatus that includes a plurality of images and includes an imaging element that outputs an image signal corresponding to an optical image, and the computer included in the imaging apparatus includes the plurality of pixels. A first readout step of performing a readout control of the first pixel group to obtain a first image signal, and performing a readout control of a second pixel group of the plurality of pixels to obtain a second image signal. A second reading step to be obtained, a display control step for displaying an image according to the first image signal on a display unit, and an image according to the first image signal obtained by the first reading step. When the in-focus state is not obtained by the first focus control performed based on the first image signal when displayed on the display unit, the second readout step obtains the in-focus state. A control step of performing a second focus control based on the second image signal, characterized in that to the execution.

  According to the present invention, it is possible to reduce power consumption by avoiding deterioration of the image quality of a live view image while performing high-speed and high-precision focus control.

1 is a block diagram illustrating a configuration of an example of an imaging apparatus according to a first embodiment of the present invention. It is a perspective view which shows the structure of the image pick-up element shown in FIG. It is a block diagram for demonstrating an example of a structure of the image pick-up element shown in FIG. FIG. 4 is a diagram for explaining pixel selection in a column signal line in the first chip shown in FIG. 3. FIG. 2 is a timing diagram for illustrating imaging timing in an AF evaluation mode in the camera shown in FIG. 1. 3 is a flowchart for explaining focus control in the camera shown in FIG. 1. It is a figure for demonstrating the timing of the autofocus imaging operation in the case of live view in the conventional imaging device.

  Hereinafter, an example of an imaging apparatus according to an embodiment of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram showing the configuration of an example of an imaging apparatus according to the first embodiment of the present invention.

  The illustrated imaging apparatus is, for example, an electronic still camera or video camera with a moving image function (hereinafter simply referred to as a camera). The camera 100 includes an optical barrel 101, an image sensor 102, a drive circuit 103, a signal processing unit 104, a compression / decompression unit 105, a control unit 106, a light emitting unit 107, an operation unit 108, an image display unit 109, and an image recording unit 110. Have.

  The optical barrel 101 includes a photographic lens unit (not shown, hereinafter simply referred to as a photographic lens) and an optical mechanism unit 1011. The photographic lens collects light (optical image) from the subject on the image sensor 102 (that is, forms an image).

  Although not shown, the optical mechanism unit 1011 includes an AF mechanism, a zoom drive mechanism, a mechanical shutter mechanism, a diaphragm mechanism, and the like. The optical mechanism unit 1011 is driven by the drive circuit 103 under the control of the control unit 106.

  The image sensor 102 includes a pixel unit 201 and an A / D converter (not shown) which will be described later, and is, for example, a so-called XY readout type CMOS image sensor. The image sensor 102 is driven by a drive circuit 103 that operates under the control of the control unit 106, performs an imaging operation such as exposure, signal readout, and reset, and outputs an imaging signal (also referred to as an image signal). .

  The signal processing unit 104 performs predetermined signal processing such as white balance adjustment processing, color correction processing, and AE (Auto Exposure) processing on the image signal output from the image sensor 102 under the control of the control unit 106. Go to output image data. Further, the signal processing unit 104 includes a contrast AF evaluation value detection unit 1041 and a phase difference AF evaluation value detection unit 1042 described later.

  The contrast AF evaluation value detection unit 1041 obtains contrast information indicating the contrast of image data based on an image signal (here, image data) that is an output of the image sensor 102. The contrast AF evaluation value detection unit 1041 detects a contrast AF evaluation value (autofocus evaluation value) at a timing controlled by the control unit 106 based on the contrast information.

  Similarly, the phase difference AF evaluation value detection unit 1042 obtains phase difference information indicating a phase difference in accordance with a focus detection image signal obtained from focus detection pixels provided in the image sensor 102. The phase difference AF evaluation value detection unit 1042 detects a phase difference AF evaluation value (autofocus evaluation value) at a timing controlled by the control unit 106 based on the phase difference information.

  The contrast AF evaluation value and the phase difference AF evaluation value are sent from the contrast AF evaluation value detection unit 1041 and the phase difference AF evaluation value detection unit 1042 to the control unit 106, respectively.

  The compression / decompression unit 105 operates under the control of the control unit 106. The compression / decompression unit 105 performs compression encoding processing on the image data output from the signal processing unit 104 in a predetermined still image data format such as the JPEG method, and generates encoded image data. JPEG is an abbreviation for Joint Photographic Coding Experts Group. Further, the compression / decompression unit 105 decompresses and decodes the encoded image data sent from the control unit 106 to generate decoded image data.

  Note that the compression / decompression unit 105 may perform compression encoding / decompression decoding processing on moving image data using an MPEG (Moving Picture Experts Group) method or the like.

  The control unit 106 is a microcontroller including, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The CPU 100 executes the program stored in the ROM to control the entire camera 100 as a whole.

  When the control unit 106 determines that the exposure value of the subject is low according to the AE processing by the signal processing unit 104, the control unit 106 controls the light emitting unit 107 to emit light to illuminate the subject. As the light emitting unit 107, for example, a strobe device using a xenon tube or an LED light emitting device is used.

  The operation unit 108 includes, for example, various operation keys such as a shutter release button, a lever, and a dial, and gives an operation signal corresponding to a user input operation to the control unit 106. The image display unit 109 includes, for example, a display device such as an LCD (Liquid Crystal Display) and an interface circuit for the display device, and displays an image according to the image data sent from the control unit 106 on the display device.

  The image recording unit 110 is a recording medium such as a portable semiconductor memory, an optical disc, an HDD (Hard Disk Drive), or a magnetic tape. The image recording unit 110 stores encoded image data that has been compression-encoded by the compression / decompression unit 105 as an image file. Further, the image recording unit 110 reads the image file designated by the control unit 106 and outputs the image file to the control unit 106. Then, the control unit 106 decompresses and decodes the read encoded image data in the compression / decompression unit 105 to obtain decoded image data.

  Here, the basic operation of the camera 100 shown in FIG. 1 will be described.

  For example, when capturing a still image, before the still image is captured (that is, before the actual capturing), the image sensor 102 sequentially performs CDS processing and AGC processing on the image signal that is the output of the pixel unit 201. A digital image signal is converted by an A / D converter. The digital image signal is sent to the signal processing unit 104.

  In the signal processing unit 104, a contrast AF evaluation value detection unit 1041 obtains a contrast AF evaluation value (contrast control information) according to contrast information obtained from an image signal obtained by live view imaging and AF evaluation value detection imaging described later. . Then, the contrast AF evaluation value is output to the control unit 106.

  Similarly, the phase difference AF evaluation value detection unit 1042 obtains a phase difference AF evaluation value (control information) according to phase difference information obtained from a focus detection pixel in an image signal obtained by live view imaging described later. The phase difference AF evaluation value is output to the control unit 106.

  As will be described later, the control unit 106 determines a control amount of the optical mechanism unit 1011 based on these AF evaluation values, and controls the drive circuit 103 according to the control amount. As a result, the optical mechanism unit 1011 is driven by the drive circuit 103.

  Further, the control unit 106 performs AF mode determination processing by determining whether or not an AF evaluation value detection imaging described later is necessary based on the AF evaluation value. The control unit 106 determines whether or not to perform AF evaluation value detection imaging according to the determination result, and controls the drive circuit 103.

  The signal processing unit 104 performs, for example, image quality correction processing on the digital image signal that is the output of the image sensor 102 to generate a camera-through image signal. Then, the signal processing unit 104 sends the camera through signal to the image display unit 109 via the control unit 106. As a result, a camera-through image (live view image) corresponding to the camera-through image signal is displayed on the image display unit 109, and the user can adjust the angle of view while viewing the camera-through image.

  When the camera release image is displayed on the image display unit 109, when the shutter release button of the operation unit 108 is pressed, the control unit 106 controls the drive circuit 103 to capture an image signal for one frame from the image sensor 102. (Digital image signal) is taken into the signal processing unit 104. The signal processing unit 104 performs image quality correction processing on the digital image signal for one frame, and sends the processed digital image signal (image data) to the compression / decompression unit 105.

  The compression / decompression unit 105 compresses and encodes the image data, and sends the encoded image data to the image recording unit 110 via the control unit 106. As a result, an image file related to the captured still image is recorded in the image recording unit 110.

  When playing back an image file recorded in the image recording unit 110, the control unit 106 reads an image file selected according to an operation input from the operation unit 108 from the image recording unit 110. Then, the control unit 106 sends the image file to the compression / decompression unit 105, and the compression / decompression unit 105 decompresses and decodes the image file to obtain decoded image data. The control unit 106 sends the decoded image data to the image display unit 109, and reproduces and displays a still image corresponding to the decoded image data on the image display unit 109.

  On the other hand, when recording moving image data, the control unit 106 controls the drive circuit 103 to capture the digital image signal output from the image sensor 102 into the signal processing unit 104. The signal processing unit 104 sequentially processes the digital image signal to generate image data (that is, moving image data). The moving image data is compression-encoded by the compression / decompression unit 105, and the encoded moving image data is sequentially transferred to the image recording unit 110 and recorded as a moving image file.

  When playing back a moving image file recorded in the image recording unit 110, the control unit 106 reads the selected moving image file from the image recording unit 110 in accordance with an operation input from the operation unit 108. Then, the control unit 106 sends the moving image file to the compression / decompression unit 105, and the compression / decompression unit 105 decompresses and decodes the moving image file to obtain decoded moving image data. The control unit 106 sends the decoded moving image data to the image display unit 109 and reproduces and displays the moving image corresponding to the moving image data on the image display unit 109.

  FIG. 2 is a perspective view showing the structure of the image sensor 102 shown in FIG.

  In FIG. 2, the image sensor 102 includes a first chip (pixel unit) 20 and a second chip 21, and the first chip (first element) is placed on the second chip (second element unit) 21. Element portion) 20 is laminated. The first chip 20 has a plurality of pixels 201 arranged in a matrix, and the first chip 20 is disposed on the light incident side (that is, located on the light receiving side of the optical image). . The second chip 21 is formed with pixel driving circuits such as column scanning circuits 213-a and 213-b and a row scanning circuit 212 described later.

  In this manner, if the pixel 201 is formed on the first chip 20 and the pixel driving circuit is formed on the second chip 21, the manufacturing process of the peripheral circuit and the pixel portion of the image sensor 102 can be divided. For this reason, it is possible to achieve high speed, miniaturization, and high functionality by thinning and increasing the density of wiring in the peripheral circuit.

  FIG. 3 is a block diagram for explaining an example of the configuration of the image sensor 102 shown in FIG.

  In the first chip 20, the pixels 201 are arranged in a two-dimensional matrix. The pixel 201 is connected to the transfer signal line 203, the reset signal line 204, and the row selection signal line 205 in the horizontal direction (row direction), and connected to the column signal lines 202-a and 202-b in the vertical direction (column direction). ing. The column signal lines 202-a and 202-b have different connection destinations depending on the read row unit.

  As illustrated, each of the pixels 201 includes a photodiode PD, which is a photoelectric conversion element, a transfer transistor M1, a reset transistor M2, an amplification transistor M3, a selection transistor M4, and a floating diffusion FD.

  In the illustrated example, each of the transistors is an n-channel MOSFET (MOS Field-Effect Transistor).

  A transfer signal line 203, a reset signal line 204, and a row selection signal line 205 are connected to the gates of the transfer transistor M1, the reset transistor M2, and the selection transistor M4, respectively. These signal lines 203 to 205 extend in the horizontal direction, and pixels in the same row are driven simultaneously. As a result, the operation of the line sequential operation type rolling shutter or the all row simultaneous operation type global shutter can be controlled. Further, the column signal line 202-a or 202-b is connected to the source of the selection transistor M4 in units of rows.

  The photodiode PD accumulates electric charges generated by photoelectric conversion. The P side of the photodiode PD is grounded, and the N side is connected to the source of the transfer transistor M1. When the transfer transistor M1 is turned on, the charge of the photodiode PD is transferred to the FD, and since there is a parasitic capacitance in the FD, the charge transferred to the FD is accumulated.

  A power supply voltage Vdd is applied to the drain of the amplification transistor M3, and its gate is connected to the FD. The amplification transistor M3 amplifies the charge (that is, voltage) of the FD and converts it into a voltage signal. The selection transistor M4 is for selecting a pixel from which a signal is read out in units of rows, and its drain is connected to the source of the amplification transistor M3. The source of the selection transistor M4 is connected to the column signal line 202.

  When the selection transistor M4 is turned on, a voltage signal corresponding to the voltage of the FD is output to the column signal line 202. A power supply voltage Vdd is applied to the drain of the reset transistor M2, and its source is connected to the FD. When the reset transistor M2 is turned on, the voltage of the FD is reset to the power supply voltage Vdd.

  The second chip 21 is provided with a column ADC block 211, and the column ADC 211 is connected to the column signal line 202-a or 202-b. Furthermore, the second chip 21 includes a row scanning circuit 212, column scanning circuits 213-a and 213-b, a timing control circuit 214, and horizontal signal lines (output means) 215-a and 215-b. .

  The timing control circuit 214 controls the operation timing of the row scanning circuit 212, the column scanning circuits 213-a and 213-b, and the column ADC block 211 under the control of the control unit 106. The row scanning circuit 212 scans each row, and the column scanning circuits 213a and 213b scan each column.

  The horizontal signal lines 215-a and 215-b transfer the output signal (image signal) of the column ADC block 211 according to the timing controlled by the column scanning circuits 213-a and 213-b, respectively.

  As will be described later, the image signal transferred to the horizontal signal line 215-a is given to the signal processing unit 104 as an image signal for live view. On the other hand, the image signal transferred to the horizontal signal line 215-b is given to the signal processing unit 104 as an image signal for AF evaluation value detection.

  FIG. 4 is a diagram for explaining pixel selection in the column signal lines 202-a or 202-b in the first chip 20 shown in FIG.

  In FIG. 3, a pixel portion of 6 rows × 8 columns is shown, and here, each pixel is arranged in a Bayer array. When AF evaluation value detection imaging (second imaging mode) is required as a result of the AF mode determination processing, live view imaging (first imaging mode) and AF evaluation value detection imaging (second imaging mode) are performed. Are separately read out in the image sensor 102. The AF mode determination process will be described later.

  At this time, an image signal for live view (first image signal, that is, an image display signal) is output to the column signal line 202-a, and an image signal for AF evaluation detection (second image signal) is a column signal. Output to line 202-b.

  In FIG. 3, row numbers 1 and 2 are rows for AF evaluation value detection imaging (second pixel group), and row numbers 3 to 8 are rows for live view imaging (first pixel group). ). In the illustrated example, readout scanning is sequentially performed in units of rows, and readout scanning is repeatedly performed in units of 8 rows. The first pixel group is provided with focus detection pixels (not shown) for phase difference AF at a predetermined cycle, and phase difference AF processing can be performed simultaneously with live view display.

  In AF evaluation value detection imaging, 3 pixels out of 4 pixels of the same vertical color are skipped and read out in order to emphasize the frame rate. On the other hand, in live view imaging, in order to emphasize image quality, 1 pixel out of 4 pixels of the same vertical color is thinned and 3 pixels are added.

  In other words, in the AF evaluation value detection imaging, the second pixel group is read at the second frame rate. In live view imaging, the first pixel group is read out at a first frame rate slower than the second frame rate.

  As described above, by dividing AF scanning imaging and live view imaging for each selected row, it is possible to acquire image signals of different frame rates with different data sizes in different charge accumulation times.

  Next, the voltage signals (analog signals) output to the column signal lines 202-a and 202-b are converted from analog signals to digital signals (image signals) in the column ADC block 211 shown in FIG.

  The image signal which is the output of the column ADC block 211 is read from the column ADC block 211 to the horizontal signal line 215-a or 215-b by the column scanning circuit 213-a or 213-b. The image signals read out to the horizontal signal lines 215-a and 215-b are sent to the signal processing unit 104.

  When AF evaluation value detection imaging (second imaging mode) becomes unnecessary as a result of AF mode determination processing described later, live view imaging (first imaging mode) is performed, but AF evaluation value detection imaging ( The second shooting mode) does not operate (is not performed). That is, the image signal is not read out to the column signal line 202-b, and the column scanning circuit 213-b does not operate, so there is no output from the horizontal signal line 215-b. Therefore, when the AF evaluation value detection imaging is unnecessary, the power consumption is reduced.

  In the above example, the case where the image signal is not read out to the column signal line 202-b has been described. However, when the AF evaluation value detection imaging (second imaging mode) is not performed, the signal processing unit 104 does not calculate the AF evaluation value (that is, the phase difference AF evaluation value). In which block the power is stopped is arbitrary.

  In the following description, during imaging, the output path by the column signal line 202-a and the horizontal signal line 215-a is called a channel Ch1, and the output path by the column signal line 202-b and the horizontal signal line 215-b is a channel Ch2. Call it.

  FIG. 5 is a timing chart for explaining the imaging timing in the AF evaluation mode in the camera 100 shown in FIG.

  As shown in the figure, the imaging timing is defined by the vertical synchronization signal (VD). Here, for the sake of simplification, the frame rate of the AF evaluation value detection imaging is three times that of the live view imaging. To do. The image signal obtained by live view imaging is used for live view display, and here, live view imaging is always performed. At the start of live view imaging, image signals are not read out by AF evaluation value detection imaging.

  In the frames in the period T0 to T1, the image signal (first image signal) obtained by the live view imaging is used for live view display. Further, an image signal (referred to as first image information) obtained by the focus detection pixel (that is, the phase difference detection pixel) is input to the phase difference AF evaluation value detection unit 1042 and obtained by the remaining pixels. An image signal (referred to as second image information) is input to the contrast AF evaluation value detection unit 1041.

  The phase difference AF evaluation value detection unit 1042 calculates a phase difference AF evaluation value AFP_1 according to the first image information. Further, the contrast AF evaluation value detection unit 1041 calculates the contrast AF evaluation value AFC_1 according to the second image information. The control unit 106 performs AF mode determination processing based on the phase difference AF evaluation value AFP_1 and the contrast AF evaluation value AFC_1. The control unit 106 activates AF evaluation value detection imaging only when AF evaluation value detection imaging is required by the AF mode determination processing.

  Subsequently, in the frames of the periods T1 to T2, the image signal obtained by the live view imaging is used for live view display. Similarly, the phase difference AF evaluation value detection unit 1042 and the contrast AF evaluation value detection unit 1041 calculate the phase difference AF evaluation value AFP_1 and the contrast AF evaluation value AFC_1AF, respectively. Then, the control unit 106 performs the above-described AF mode determination processing, and when the AF evaluation value detection imaging is necessary, reading in the AF evaluation value detection imaging (that is, for AF evaluation value detection) is performed at time T2. To start.

  In the frame of the period T2 to T3, the image signal (second image signal) obtained by the AF evaluation value detection imaging (that is, the channel Ch2) is input to the contrast AF evaluation value detection unit 1041. The contrast AF evaluation value detection unit 1041 calculates a contrast AF evaluation value AFC_2 based on the image signal (second image signal) obtained by AFAF evaluation value detection (channel Ch2).

  The control unit 106 performs an AF mode determination process according to the contrast AF evaluation value AFC_2, and determines whether or not it is in a focused state. If it is determined that the in-focus state is not obtained, the control unit 106 continues the readout by the AF evaluation value detection imaging and the AF operation.

  On the other hand, the result of the AF operation by the AF evaluation value detection imaging (that is, the result of the AF operation according to the contrast AF evaluation value AFC_2), for example, at time T4, the control unit 106 performs the AF operation by the AF evaluation value detection imaging. Assume that it is determined that the camera is in focus. Accordingly, the control unit 106 confirms the AF evaluation values (that is, the phase difference AF evaluation value AFP_1 and the contrast AF evaluation value AFC_1) corresponding to the image signal for live view imaging. If the control unit 106 determines that the in-focus state is based on these AF evaluation values, the control unit 106 stops reading by AF evaluation value detection imaging at time T5.

  FIG. 6 is a flowchart for explaining the focus control in the camera 100 shown in FIG. The illustrated flowchart is performed under the control of the control unit 106.

  When the power of the camera 100 is turned on and the camera 100 is set to the shooting mode by the operation unit 108, the control unit 106 starts live view imaging as described above (step S502). In this live view imaging, as described with reference to FIG. 4, a live view selection row is read out, and this readout includes focus detection pixels for phase difference AF.

  Note that in step S502, an image signal obtained by live view imaging is subjected to image processing and screen display as a live view or a moving image for recording, but the description thereof is omitted here.

  Subsequently, the control unit 106 confirms whether the AF evaluation value detection imaging presence / absence flag Sub_ON is “1” (step S503). It is assumed that the AF evaluation value detection imaging presence / absence flag Sub_ON is “0” at the time when live view imaging starts.

  If the AF evaluation value detection imaging presence / absence flag Sub_ON is not “1” (NO in step S503), that is, if the AF evaluation value detection imaging presence / absence flag Sub_ON is “0”, under the control of the control unit 106, The phase difference AF evaluation value detection unit 1042 obtains a phase difference AF evaluation value AFP_1 (first phase difference evaluation value which is a first evaluation value) according to an image signal obtained from the focus detection pixel in live view imaging. Calculate (step S504). Then, the control unit 106 obtains a feedback control amount according to the phase difference AF evaluation value AFP_1, and drives and controls the drive circuit 103 according to the feedback control amount to drive the AF mechanism provided in the optical mechanism unit 1011. It will be.

  Next, the control unit 106 determines whether or not the phase difference AF evaluation value AFP_1 is within a range (phase difference threshold range) defined by a preset minimum phase difference threshold P_Min and maximum phase difference threshold P_Max. . That is, the control unit 106 determines whether or not P_Min <AFP_1 <P_Max (step S505).

  Here, in the AF mode determination process, the control unit 106 determines whether or not the phase difference AF evaluation value AFP_1 is in a range defined by the phase difference minimum threshold P_Min and the phase difference maximum threshold P_Max. If it is within the range, the control unit 106 assumes that the in-focus position can be estimated by the phase difference AF (that is, the first focus control is possible), and further high-speed AF operation is not necessary. .

  If P_Min <AFP_1 <P_Max (YES in step S505), control unit 106 shifts to shooting of the next frame by vertical synchronization signal VD (step S506). Note that shooting of the next frame starts from the process of step S502.

  The contrast AF evaluation value detection unit 1041 operates under the control of the control unit 106. When AFP_1 ≦ P_Min or P_Max ≦ AFP_1 is satisfied (NO in step S505), the contrast AF evaluation value detection unit 1041 calculates a contrast AF evaluation value AFC_1 (step S507). Here, the contrast AF evaluation value AFC_1 (the first contrast evaluation value which is the first evaluation value) is calculated according to the image signal obtained by the live view imaging. Then, the control unit 106 obtains a feedback control amount according to the contrast AF evaluation value AFC_1, drives the drive circuit 103 according to the feedback control amount, and drives the AF mechanism provided in the optical mechanism unit 1011. become.

  Subsequently, the control unit 106 determines whether or not the contrast AF evaluation value AFC_1 is within a range (contrast threshold range) defined by a preset minimum contrast threshold C_Min and maximum contrast threshold C_Max. That is, the control unit 106 determines whether or not C_Mim <AFC_1 <C_Max (step S508).

  Here, the control unit 106 determines whether or not the contrast AF evaluation value AFC_1 is in a range defined by the minimum contrast threshold P_Min and the maximum contrast threshold P_Max. If it is within the range, it is assumed that the control unit 106 can estimate the in-focus position by contrast AF (assuming that the first focus control is possible), and further high-speed AF operation is not necessary.

  If C_Min <AFC_1 <C_Max (YES in step S508), control unit 106 proceeds to the process in step S506. On the other hand, if AFC_1 ≦ C_Min or C_Max ≦ AFC_1 (NO in step S508), the control unit 106 determines that the current frame is not in focus. Then, the control unit 106 sets the AF evaluation value detection imaging presence / absence flag Sub_ON to “1” to perform high-speed AF operation by AF evaluation value detection imaging from the next frame (step S509). That is, the control unit 106 determines to perform the second focus control. And the control part 106 progresses to the process of step S506.

  When AF evaluation value detection imaging presence / absence flag Sub_ON is “1” (YES in step S503), control unit 106 resets variable n indicating the AF evaluation value detection imaging count to “0” (step S510). . Here, since the AF evaluation value detection imaging has a frame rate three times that of the live view imaging, if the variable n is 0, 1, or 2, the AF evaluation value detection imaging is performed.

  Subsequently, the control unit 106 performs AF evaluation value detection imaging as described above (step S511). In AF evaluation value detection imaging, the AF selected row shown in FIG. 4 is read, and an image signal different from the live view image is read. That is, the AF evaluation value detection imaging is performed at a timing independent of the live view imaging.

  Next, under the control of the control unit 106, the contrast AF evaluation value detection unit 1041 determines the contrast AF evaluation value AFC_2 (the second evaluation value is the second evaluation value) according to the image signal obtained by the AF evaluation value detection imaging. The contrast evaluation value is calculated (step S512). Then, the control unit 106 obtains a feedback control amount according to the contrast AF evaluation value AFC_2, and drives and controls the drive circuit 103 according to the feedback control amount to drive the AF mechanism provided in the optical mechanism unit 1011. .

  Subsequently, the control unit 106 determines whether or not the contrast AF evaluation value AFC_2 is within a range defined by the minimum contrast threshold C_Min and the maximum contrast threshold (step S513). Here, the control unit 106 determines whether or not the contrast AF evaluation value AFC_2 is within a range defined by the minimum contrast threshold C_Min and the maximum contrast threshold. If it is within the range, the control unit 106 is assumed to be able to estimate the in-focus position by contrast AF, and it is assumed that no further high-speed AF operation is necessary after the next frame.

  If C_Min <AFC_2 <C_Max (YES in step S513), the control unit 106 sets the AF evaluation value detection imaging presence / absence flag Sub_ON to “0” (step S514). Then, the control unit 106 increments the variable n indicating the number of times of AF evaluation value detection imaging (step S515). On the other hand, if AFC_2 ≦ C_Min or C_Max ≦ AFC_2 (NO in step S513), the control unit 106 proceeds to the process of step S509.

  Subsequently, the control unit 106 confirms whether or not the variable n is “3” (step S516). If the variable n is not “3” (NO in step S516), the control unit 106 returns to the process of step S511 to perform AF evaluation value detection imaging again. On the other hand, if variable n is “3” (YES in step S516), control unit 106 proceeds to the process in step S504, and phase difference AF evaluation value detection unit 1042 sets AF evaluation value AFP_1 as described above. calculate.

  As described above, in the embodiment of the present invention, if the phase difference AF evaluation value and the contrast AF evaluation value do not reach predetermined levels in live view imaging, AF evaluation value detection is performed at a higher frame rate than in live view imaging. Imaging is performed to obtain a contrast AF evaluation value. Further, in the AF evaluation value detection imaging, the pixel is read simultaneously with the live view imaging using a different pixel from the live view imaging. As a result, it is possible to avoid degradation of the image quality of the live view image and to reduce the time lag when performing AF evaluation.

  Furthermore, in the embodiment of the present invention, since the AF evaluation imaging is performed only when necessary, the power consumption during the AF operation can be reduced.

  In other words, when an image corresponding to the first image signal is displayed, if the in-focus state is not obtained by the first focus control performed based on the first image signal, the image is obtained by the second readout. Second focus control is performed based on the second image signal. That is, it is determined whether or not an in-focus state is obtained together with the live view display, and it is determined whether or not to read out the second pixel group according to the determination result. Accordingly, it is possible to reduce power consumption by avoiding deterioration of the image quality of the live view image while performing high-speed and high-precision focus control.

  In the above-described embodiment, an example in which the AF operation is performed at the time of live view display has been described. However, the AF operation is performed not only at the time of live view display but also at other video shooting timings. You may do it.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to these embodiment, Various forms of the range which does not deviate from the summary of this invention are also contained in this invention. .

  As is clear from the above description, in the example shown in FIG. 1, the control unit 106 and the drive circuit 103 function as a reading unit. The control unit 106 and the image display unit 109 function as a display control unit, and the control unit 106 and the drive circuit 103 function as a control unit.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to these embodiment, Various forms of the range which does not deviate from the summary of this invention are also contained in this invention. .

  For example, the function of the above embodiment may be used as a control method, and this control method may be executed by the imaging apparatus. Further, a program having the functions of the above-described embodiments may be used as a control program, and the control program may be executed by a computer included in the imaging apparatus. The control program is recorded on a computer-readable recording medium, for example.

  Each of the control method and the control program has at least a first reading step, a second reading step, a display control step, and a control step.

  The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various recording media, and a computer (or CPU, MPU, etc.) of the system or apparatus reads the program. It is a process to be executed.

DESCRIPTION OF SYMBOLS 101 Optical barrel 102 Image pick-up element 103 Drive circuit 104 Signal processing part 106 Control part 108 Operation part 109 Image display part 1011 Optical mechanism part 1041 Contrast AF evaluation value detection part 1042 Phase difference AF evaluation value detection part

Claims (8)

An image sensor that includes a plurality of images and outputs an image signal corresponding to the optical image;
Of the plurality of pixels, the first pixel group performs read control to obtain a first image signal, and among the plurality of pixels, the second pixel group performs read control and the second pixel group is read out. Reading means for performing second reading to obtain an image signal;
Display control means for displaying an image corresponding to the first image signal on a display unit;
When an image corresponding to the first image signal obtained by the first readout is displayed on the display unit, an in-focus state is obtained by the first focus control performed based on the first image signal. If not, control means for performing second focus control based on the second image signal obtained by the second readout;
An imaging device comprising:   When the first evaluation value obtained based on the first image signal is not within a preset range, the control means performs a second operation based on the second image signal obtained by the second reading. The imaging apparatus according to claim 1, wherein focus control is performed. The first pixel group includes a phase difference detection pixel for detecting a phase difference,
The control means is configured such that the first phase difference evaluation value obtained based on the image signal obtained from the phase difference detection pixel is not within a predetermined phase difference threshold range and is not the phase difference detection pixel. When the first contrast evaluation value obtained according to the image signal obtained from the pixel is not within the predetermined contrast threshold range, the second contrast signal is obtained based on the second image signal obtained by the second readout. The imaging apparatus according to claim 1, wherein focus control is performed.   When the control means performs the second focus control based on the second image signal obtained by the second readout, the second contrast evaluation value obtained based on the second image signal The imaging apparatus according to any one of claims 1 to 3, wherein the second focus control is performed in accordance with the frequency.   The imaging apparatus according to claim 4, wherein the control unit stops the second reading by the reading unit when the second contrast evaluation value is in a predetermined contrast threshold range. In the first readout, the first pixel group is read out at a first frame rate,
6. The imaging according to claim 1, wherein in the second readout, the second pixel group is read out at a second frame rate that is faster than the first frame rate. apparatus. A control method of an imaging apparatus including an image sensor that includes a plurality of images and outputs an image signal corresponding to an optical image,
A first readout step of performing readout control of a first pixel group among the plurality of pixels to obtain a first image signal;
A second readout step of obtaining a second image signal by performing readout control of a second pixel group among the plurality of pixels;
A display control step of displaying an image according to the first image signal on a display unit;
When an image corresponding to the first image signal obtained in the first readout step is displayed on the display unit, the in-focus state is achieved by the first focus control performed based on the first image signal. Is not obtained, a control step of performing second focus control based on the second image signal obtained by the second readout step;
A control method characterized by comprising: A control program for use in an imaging apparatus that includes a plurality of images and includes an imaging device that outputs an image signal corresponding to an optical image,
In the computer provided in the imaging device,
A first readout step of performing readout control of a first pixel group among the plurality of pixels to obtain a first image signal;
A second readout step of obtaining a second image signal by performing readout control of a second pixel group among the plurality of pixels;
A display control step of displaying an image according to the first image signal on a display unit;
When an image corresponding to the first image signal obtained in the first readout step is displayed on the display unit, the in-focus state is achieved by the first focus control performed based on the first image signal. Is not obtained, a control step of performing second focus control based on the second image signal obtained by the second readout step;
A control program characterized by causing

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