JP2013134403A - Focus adjustment device and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To acquire image data focusing on a main subject when carrying out continuous shooting at high speed.SOLUTION: The imaging apparatus includes: a subject detection section for detecting a subject; a setting section for setting regions respectively cut out from images which are continuously outputted from an imaging element as an object domain based on a result of the subject detection by the subject detection section; a compression section for carrying out compression processing for the images of the object domain which are respectively cut out from the images which are continuously outputted from the imaging element; and a control section for controlling a focus position of an imaging optical system forming a subject image on the imaging element based on the variation in the data amount of the images of the object domain having undergone compression processing.

Description

  The present invention relates to a focus adjustment device and an imaging device.

  Examples of autofocus (AF) control mounted on a digital camera include phase control and contrast detection focus control. In a digital camera equipped with such AF control, it has been devised to execute high-speed continuous shooting.

JP 2006-201282 A

  Since it is difficult to perform AF control between shots in high-speed continuous shooting, shooting with a fixed focus position adjusted at the start of continuous shooting is performed. However, even if the focus adjustment is focused on the main subject at the start of continuous shooting, it is assumed that the main subject may not be in focus during the continuous shooting process, resulting in an image that is not focused on the main subject. There is a risk of data being acquired.

  An object of the present invention is to provide a focus adjustment device and an imaging device that can acquire image data that focuses on a main subject when performing high-speed continuous shooting.

  The focus adjustment apparatus according to the present invention sets, as a target region, a subject detection unit that detects a subject and a region that is cut out from each of the images that are continuously output from the image sensor based on the result of subject detection by the subject detection unit. A setting unit that performs compression processing on the image of the target region cut out from each of the images continuously output from the imaging device, and a data amount of the image of the target region that has been compressed And a control unit that controls a focus position of an image pickup optical system that forms a subject image on the image pickup element based on the change in the image pickup element.

  Further, the imaging apparatus of the present invention continuously captures the subject image formed by the imaging optical system, sequentially outputs the image, and the imaging optical system based on the images sequentially output from the imaging element. And a focus adjusting device for controlling the focus position of the camera.

  According to the present invention, it is possible to acquire image data that focuses on a main subject when performing high-speed continuous shooting.

It is a functional block diagram which shows the structure of the digital camera of this invention. (A) The figure which shows the comparison object area | region set when the size of a face area is smaller than the magnitude | size of one division area, and a face area is settled in one division area, (b) The magnitude | size of a face area The figure which shows the comparison object area | region set when it is smaller than the size of one division area, and a face area straddles several division areas, (c) When the size of a face area is larger than the magnitude | size of one division area It is a figure which shows the comparison object area | region set to. (A) The figure which shows the comparison object area | region set when the largest face area is selected among several face areas, (b) The face area superimposed on AF area was selected among several face areas It is a figure which shows the comparison object area | region set in the case. (A) The figure which shows the comparison object area | region set when there is one AF area which focuses, and this AF area is settled in one division area, (a) There is one AF area which focuses, Also, it is a diagram showing a comparison target area that is set when the AF area extends over a plurality of divided areas. (A) The figure which shows the comparison object area | region set when the some AF area which focuses is contained in one division area, (b) The case where the some AF area which focuses is straddling the several division area which adjoins FIG. 4C is a diagram showing a comparison target area set in (c), and FIG. 4C is a diagram showing a comparison target area set when a plurality of in-focus AF areas fit in each of divided areas. It is a flowchart which shows the flow of a series of processes in continuous imaging | photography. It is a flowchart which shows the flow of a series of processes in continuous imaging | photography. It is a flowchart which shows the flow of a series of processes in continuous imaging | photography.

  Hereinafter, a digital camera 10 will be described as an example of an embodiment of the present invention. The digital camera 10 of the present invention can perform continuous shooting for acquiring a plurality of still images by continuously performing imaging processing in addition to still image shooting for acquiring still images by one imaging processing. . For this continuous shooting, high-speed continuous shooting such as 30 frames / second, 50 frames / second, and 60 frames / second can be performed.

  As shown in FIG. 1, the digital camera 10 includes an imaging optical system 15, a quick return mirror 16, a mechanical shutter 17, an image sensor 18, an analog front end (AFE) circuit 19, a timing generator (TG) 20, and a lens driving mechanism 21. , Shutter drive mechanism 22, buffer memory 25, image processing circuit 26, compression / expansion circuit 27, display control circuit 28, display device 29, connection I / F 30, CPU 40, nonvolatile memory 41, work memory 42, focus detection unit 43, a release button 44, an operation unit 45, and the like. The AFE circuit 19, the buffer memory 25, the image processing circuit 26, the compression / decompression circuit 27, the display control circuit 28, the connection I / F 30, and the CPU 40 are electrically connected via a bus 46.

  The imaging optical system 15 forms an object scene light beam and forms an object scene image near the imaging surface of the image sensor 18. In FIG. 1, the imaging optical system 15 is described as a single lens, but in actuality, the imaging optical system 15 includes a plurality of lenses including a focusing lens. The focusing lens is moved in the optical axis direction via the lens driving mechanism 21. Focus control is executed by moving the focusing lens in the optical axis direction.

  The imaging optical system 15 includes a diaphragm (not shown). The diaphragm diameter is adjusted according to the Av value set by the CPU 40. This Av value may be a value input by the user or a value calculated by automatic exposure calculation.

  The quick return mirror 16 is disposed on the optical path of the field light beam between the imaging optical system 15 and the imaging element 18. The quick return mirror 16 is switched between a mirror-down state and a mirror-up state. When the quick return mirror 16 is in the mirror-down state, the subject light flux is guided by the quick return mirror 16 to the focus detection unit 43 and a photometry unit (not shown). On the other hand, when the quick return mirror 16 is in the mirror-up state, the subject light flux is guided to the image sensor 18 by the quick return mirror 16.

  The mechanical shutter 17 is disposed on the optical path of the field light beam between the quick return mirror 16 and the image sensor 18. The mechanical shutter 17 is opened and closed by a shutter drive mechanism 22 that has received a drive signal from the TG 20.

  The image sensor 18 is composed of a CCD image sensor, a CMOS image sensor, or the like. The image sensor 18 accumulates signals and reads signals in accordance with the drive signal supplied from the TG 20.

  The TG 20 outputs a drive signal to the image sensor 18 and the shutter drive mechanism 22 in response to an instruction from the CPU 40. Further, the TG 20 supplies a synchronization signal to the AFE circuit 19 and the CPU 40. Here, the TG 20 controls the exposure time per frame by a combination of the pattern of the drive signal supplied to the image sensor 18 and the pattern of the drive signal supplied to the mechanical shutter 17. The exposure time is set to a value corresponding to the Tv value designated by the CPU 40. Here, the Tv value may be a value input by the user or a value calculated by automatic exposure calculation. Here, when performing high-speed continuous shooting described later, drive control (signal accumulation and signal readout) of the image sensor 18 is performed while the mechanical shutter 17 is in an open state. In this case, the exposure time is controlled only by the drive signal supplied to the image sensor 18. That is, when performing high-speed continuous shooting, an electronic shutter is used instead of the mechanical shutter 17.

  The AFE circuit 19 includes a CDS circuit, a gain circuit, an A / D conversion circuit, and the like. The CDS circuit removes the noise component of the analog signal output from the image sensor 18 by correlated double sampling. The gain circuit amplifies the analog signal from which noise has been removed. The A / D conversion and output conversion circuit converts the amplified analog signal into a digital signal.

  Here, the signal amplification factor (gain) used when the signal is amplified by the gain circuit is a value based on the Sv value from the CPU 40. This Sv value is a sensitivity at the time of photographing (ISO sensitivity), and this Sv value may be a value designated by the user or a value calculated by automatic exposure calculation.

  The focus detection unit 43 generates a defocus signal of the imaging optical system 15 for the imaging element 18 by dividing the pupil of the field light beam guided from the quick return mirror 16 in the mirror-down state and then reintegrating it. Consists of a phase difference detection type focus detection unit. Here, the defocus signal of the imaging optical system 15 is generated in each of a plurality of AF areas arranged in a plurality with respect to the imaging range.

  In the buffer memory 25, the digital signal output from the AFE circuit 19 is written. In the buffer memory 25, the digital signal output from the AFE circuit 19 is written, and other digital signals transferred from the image processing circuit 26 are written. Here, the buffer memory 25 can store digital signals for a plurality of frames.

  The image processing circuit 26 includes a white balance processing circuit, a pixel interpolation circuit, a matrix processing circuit, a non-linear transformation (γ correction) processing circuit, an edge enhancement processing circuit, and the like, and performs white balance, pixel interpolation, matrix, Processing such as nonlinear transformation (γ correction) and edge enhancement is performed. The image processing circuit 26 includes a trimming unit 47. The trimming unit 47 trims an area corresponding to a comparison target area, which will be described later, from each of the image data obtained by continuous shooting. The trimmed image data (target image data) is stored in the buffer memory 25.

  The compression / decompression circuit 27 performs compression processing on the image data that has undergone image processing and the target image data. The compressed image data is written to the storage medium 48 via the connection I / F 30. Here, examples of the storage medium 48 include a memory card made of a nonvolatile memory, an optical disk, and a magnetic disk. Further, the compression / decompression circuit 27 performs decompression processing on the compressed image data read from the storage medium 48. The display control circuit 28 converts the input image data into a predetermined signal for display and displays it on the display device 29.

  The CPU 40 controls each unit using the work memory 42 as a temporary storage work area according to a control program stored in the nonvolatile memory 41. In the CPU 40, the functions of the face detection unit 51, the region setting unit 52, the data comparison unit 53, and the focus control unit 54 become effective during continuous shooting.

  The face detection unit 51 detects the face of a person included in the image. As the process for detecting the face, for example, a skin color area included in the image is detected, and a process for determining whether the face is a feature from the feature amount included in the skin color area, or a plurality of face shape templates. For example, a process for detecting a face region from the correlation between the template and the image is prepared. When a face is detected, the face detection unit 51 extracts a rectangular area including the detected face as a face area, and obtains position data of the face area. Here, the position data of the face area is address data indicating the position coordinates of the four corner vertices of the face area.

  The area setting unit 52 sets an area (comparison target area) used for data comparison executed by the data comparison unit 53 described later. First, the area setting unit 52 divides an image obtained by the first imaging process in continuous shooting into a total of m × n areas of m in length and n in width. Data relating to this area division is stored in the work memory 42, for example. Hereinafter, an area obtained by dividing an image will be described as a divided area.

  When a face is detected in the face detection process by the face detection unit 51 described above, any one of the plurality of divided regions is compared with the comparison target region using the position data of the extracted face region. Set as. On the other hand, in the face detection process by the face detection unit 51, when a face is not detected, the region setting unit 52 performs a plurality of divided regions based on the result of focus adjustment executed in the first imaging process. Is set as a comparison target area.

  When the comparison target area is set, the area setting unit 52 obtains position data of the comparison target area. The obtained position data of the comparison target area is address data indicating the position coordinates of the vertices at the four corners of the comparison target area. The position data of the comparison target area is output to the image processing circuit 26. The image processing circuit 26 performs a trimming process on each image data obtained at the time of continuous shooting based on the position data of the comparison target region.

  The data comparison unit 53 compares the data amounts of the target image data subjected to the above-described compression processing. For example, the data amounts of two images taken of the same scene are approximated. However, the data amount of an image with high sharpness tends to be larger than the data amount of an image with low sharpness. Here, the higher the sharpness in the image, the more focused the image. In addition, since the comparison target area described above is an area including the face area of a person as a main subject or an AF area in focus, comparing the data amount of target image data that has been subjected to compression processing allows the image to be compared. Focus control can be performed so that the region to be noticed is focused on, and other regions can be prevented from being focused.

  The focus control unit 54 executes each focus control in continuous shooting. The focus control of the first imaging process in the continuous shooting is focus control using the detection result in the focus detection unit 43 described above. Further, the second and subsequent focus control in the continuous shooting is focus control based on the comparison result by the data comparison unit 53. Note that the second and subsequent focus control is feedback control using the relationship between the sharpness of the target image obtained by trimming the comparison target region and the data amount of the target image.

  Next, setting of the comparison target area will be described.

As described above, the comparison target region is set based on the result of the face detection process by the face detection unit 51. Hereinafter, four images P ₁ obtained by the first imaging processing vertical, if divided into horizontal 6 total 24 regions A ₁ to A ₂₄ will be described. When a face is detected by the face detection unit 51, the region setting unit 52 determines whether the detected face is single (one) or plural (two or more).

  For example, when the number of detected faces is one, the area setting unit 52 determines whether or not the extracted face area is smaller than one divided area. When it is determined that the face area is smaller than the divided area, the area setting unit 52 determines whether the extracted face area fits in any one of the plurality of divided areas or straddles the plurality of divided areas.

As shown in FIG. 2A, when the extracted face area FR ₁ is smaller than one divided area and the face area FR ₁ fits in the divided area A ₁₇ , the area setting unit 52 uses the divided area A _17. Is set as the comparison target area.

As shown in FIG. 2B, even when the extracted face area FR ₂ is smaller than one divided area, the face area FR ₂ is divided into a plurality of divided areas A ₁₀ , A ₁₁ , A ₁₆ , A There are times when it straddles ₁₇ . In such a case, the area setting unit 52 sets the divided areas A ₁₀ , A ₁₁ , A ₁₆ , and A ₁₇ as comparison target areas. FIG. 2B illustrates a case where the face area FR ₂ extends over a plurality of divided areas A ₁₀ , A ₁₁ , A ₁₆ , A ₁₇ , but the face area is adjacent in the vertical direction or the horizontal direction 2. When straddling two divided areas, two divided areas straddling the face area may be set as the comparison target areas.

On the other hand, as shown in FIG. 2C, when the face area FR ₃ is larger than one divided area, the face area FR ₃ extends over a plurality of divided areas. In such a case, the area setting unit 52 Sets the divided areas A ₁₀ , A ₁₁ , A ₁₂ , A ₁₆ , A ₁₇ , A ₁₈ , A ₂₂ , A ₂₃ , A ₂₄ that the face area FR ₃ straddles as the comparison target areas.

When there are a plurality of faces detected by the face detection unit 51, the area setting unit 52 first determines whether there is a face area larger than one divided area among the face areas based on the detected faces. Determine whether or not. FIG. 3A shows a case where three face regions FR ₄ , FR ₅ , FR ₆ are extracted. When the face area FR ₆ is the largest face area among the face areas FR ₄ , FR ₅ , and FR ₆ , the area setting unit 52 selects the face area FR ₆ . Then, the area setting unit 52 sets the divided areas A ₁₆ , A ₁₇ , A ₂₂ , A ₂₃ that the selected face area FR ₆ spans as comparison target areas.

On the other hand, as shown in FIG. 3B, any of the detected three face regions FR ₇ , FR ₈ , FR ₉ may be smaller than one divided region. In such a case, the area setting unit 52 determines whether there is a face area to be superimposed on any of the AF areas based on the position of the face area and the position of the AF area. If there is a face area to be superimposed on any of the AF areas, the area dividing unit 52 selects the face area, and sets a divided area in which the selected face area fits or a divided area that spans the face area as a comparison target area. To do. In FIG. 3B, since the face area FR ₈ is superimposed on the AF area, the area setting unit 52 selects the face area FR ₈ . Then, the area setting unit 52 sets the divided regions A ₉ the face area FR ₈ falls as a comparison target area. If none of the detected face areas is superimposed on the AF area, the divided area where the largest face area is located among the detected face areas may be set as the comparison target area, or the focused AF is performed. A divided region including an area may be set as a comparison target region.

  Next, a case where no face is detected in the face detection process by the face detection unit 51 will be described. When a face is not detected in the face detection process by the face detection unit 51, the region setting unit 52 selects one of a plurality of divided regions based on the result of focus adjustment executed when continuous shooting is started. The area is set as a comparison target area. In the first imaging process described above, focus control using a defocus signal for each AF area obtained by the focus detection unit 43 is executed. The area setting unit 52 sets a comparison target area using an AF area in focus among these AF areas.

As shown in FIG. 4 (a), among the plurality of AF areas, if one of the AF area _{B 1} as the AF area in focus falls, the area setting unit 52, an AF area _{B 1} which in focus is one It is determined whether it falls within a divided area or straddles a plurality of divided areas. In this case, since the AF area _{B 1} represents fit in divided areas _{A 10,} region setting unit 52 sets the divided regions _{A 10} as comparison regions.

For example, a plurality of AF areas may not necessarily fall within the divided areas and may extend over adjacent divided areas. As shown in FIG. 4B, when the AF area B ₂ extending over the divided areas A ₉ , A ₁₀ , A ₁₅ , A ₁₆ is an in-focus AF area, the area setting unit 52 includes the divided areas A ₉ , A ₁₀ , A ₁₅ , and A ₁₆ are set as comparison target areas.

On the other hand, when there are a plurality of in-focus AF areas, the area setting unit 52 determines whether or not each of the in-focus AF areas fits in one divided area. FIG. 5A shows a case in which a plurality of in-focus AF areas fall within one divided area, and the in-focus AF area is shown in a solid color. In this case, the area setting unit 52 sets the divided area A ₁₀ that is the AF area in focus falls as a comparison target area.

On the other hand, when there are a plurality of in-focus AF areas and each AF area fits in a plurality of divided areas, the area setting unit 52 sets all the divided areas including the in-focus AF areas as comparison target areas. . In the case of FIG. 5B, the AF area indicated by filling is an in-focus AF area. In this case, the area setting unit 52 sets the divided areas A ₉ , A ₁₀ , A ₁₅ , and A ₁₆ where the focused AF area is located as the comparison target area.

As shown in FIG. 5C, the focused AF areas may not be located close to each other but may be located discretely. In such a case, the area setting unit 52 sets the divided area A ₈ and the divided areas A ₁₀ and A ₁₁ including the focused AF area as the comparison target areas.

  6 to 8 are flowcharts showing the flow of processing when continuous shooting is performed.

  Step S101 is processing for determining whether or not the release button has been pressed halfway. The release button 44 is provided with a detection switch for detecting the half-pressing operation and the full-pressing operation. When the release button 44 is half-pressed, a detection switch that detects the half-press operation is turned on, and a signal (hereinafter, half-press signal) is output to the CPU 40. In response to the input of the half-press signal, the CPU 40 determines Yes in step S101. In this case, the process proceeds to step S102.

  On the other hand, when the half-press signal is not input, the CPU 40 determines No in step S101. In this case, the determination process of step S101 is executed until the determination process of step S101 becomes Yes.

  Step S102 is processing for executing AE processing and AF processing. The CPU 40 executes AE processing based on a signal output from a photometry device (not shown). When the CPU 40 executes the AE process, a combination of the Tv value, the Av value, and the Sv value is determined. In addition, the CPU 40 performs AF processing based on the defocus signal output from the focus detection unit. In this AF process, the CPU 40 selects a defocus signal for the set focus area from among the defocus signals input from the focus detection unit, and then obtains the driving amount of the focusing lens from the selected defocus signal.

  Step S103 is processing for determining whether or not the half-press operation of the release button has been released. As described above, when the release button 44 is half-pressed, a half-press signal is input to the CPU 40. Further, when the half-press operation of the release button 44 is released, the output of the half-press signal to the CPU 40 is stopped. That is, in this step S103, the CPU 40 determines whether or not the half-press operation of the release button 44 has been released depending on whether or not the output of the half-press signal has been stopped.

  For example, when the output of the half-press signal is continued, the CPU 40 determines that the half-press operation of the release button 44 has not been released. In this case, the determination process in step S103 is No, and the process proceeds to step S104. On the other hand, when the output of the half-press signal is stopped, the CPU 40 determines that the half-press operation of the release button 44 has been released. In this case, the determination process in step S103 is Yes, and the process returns to step S101.

  Step S104 is processing for determining whether or not the release button has been fully pressed. When the release button 44 is fully pressed, a detection switch for detecting the full press operation is turned on, and a signal (full press signal) is output to the CPU 40. In response to the input of the full-press signal, the CPU 40 determines Yes in step S104. In this case, the process proceeds to step S105. On the other hand, when the full-press signal is not input, the CPU 40 determines No in step S104. In this case, the process returns to step S103.

  Step S105 is an imaging process (first time). The CPU 40 designates the Tv value, Av value, and Sv value determined in step S102 to the lens driving mechanism 21, the TG 20, and the AFE circuit 19. At the same time, the CPU 40 switches the quick return mirror 16 to the mirror-up state. Then, the CPU 40 outputs an imaging start signal to the TG 20. Thereby, an imaging process is performed.

  By performing this imaging process, an image signal is output from the imaging element 18. This image signal is stored in the buffer memory 25 via the AFE circuit 19. Then, it is read by the image processing circuit 26. The image processing circuit 26 performs image processing such as white balance adjustment, color interpolation, gradation conversion, and color conversion. The image data that has been subjected to various types of image processing by the image processing circuit 26 is stored in the buffer memory 25 again.

  Step S106 is face detection processing. The CPU 40 reads the image processed image data stored in the buffer memory 25 and executes face detection processing. When a face is detected by this face detection process, the CPU 40 extracts a rectangular area including the detected face as a face area and then obtains position data of the face area.

  Step S107 is processing to determine whether or not a face has been detected. If a face is detected in the face detection process in step S106, the CPU 40 sets the determination process in step S107 to Yes. In this case, the process proceeds to step S108. On the other hand, when the face is not detected in the determination process of step S106, the CPU 40 sets the determination process of step S107 to No. In this case, the process proceeds to step S109.

  Step S108 is a process of setting a comparison target area based on the position data of the face area. For example, when one face is detected, the CPU 40 compares the size of the face area with the size of the divided area. For example, when the size of the face area is smaller than the size of one divided area, the CPU 40 determines whether the face area fits in one divided area or straddles a plurality of divided areas. When the face area fits in one divided area, the CPU 40 sets the divided area in which the face area fits as a comparison target area. On the other hand, when the face region extends over a plurality of divided regions, the CPU 40 sets the divided region over which the face region extends as a comparison target region. When the size of the face area is larger than the size of one divided area, the CPU 40 sets a plurality of divided areas across the face area as comparison target areas.

  When a plurality of faces are detected, the CPU 40 determines whether or not there is a face area larger than the size of one divided area among the plurality of detected face areas. When there is a face area larger than the size of one divided area, the CPU 40 sets a divided area that the face area spans as a comparison target area.

  On the other hand, if any of the detected face areas is smaller than the size of one divided area, the CPU 40 sets the divided area where the face area superimposed on the AF area is located as the comparison target area. Here, the divided area where the face area superimposed on the AF area is located is a divided area where the face area superimposed on the AF area fits, or a divided area straddling the face area superimposed on the AF area.

  Step S109 is processing for setting a comparison target area based on the AF area.

  As described above, the process of step S109 is executed when no face is detected in step S106. The CPU 40 identifies an AF area in focus among the AF areas. Then, the CPU 40 sets a divided area where the identified AF area is located or a divided area where the AF area is straddled as a comparison target area.

  Step S110 is processing for saving image data. The compression / decompression circuit 27 duplicates (copies) the image processed image data stored in the buffer memory 25 onto the buffer memory 25. Then, compression processing is performed on the copied image data. The compressed image data is stored in the buffer memory 25. The CPU 40 stores the compressed image data stored in the buffer memory 25 in the storage medium 48 via the connection I / F 30. By this step S110, the image data in the first shooting is stored in the storage medium 48.

  Step S111 is a trimming process. The image processing circuit 26 reads the image processed image data stored in the buffer memory 25. Then, the image processing circuit 26 performs a trimming process based on the comparison target area. Note that the target image data is generated by performing the trimming process. By this step S111, target image data in the first shooting is generated and stored in the buffer memory 25.

  Step S112 is a compression process. The compression / decompression circuit 27 reads the target image data stored in the buffer memory 25. Then, compression processing is executed on the target image data. The CPU 40 stores the data amount of the target image data subjected to the compression process in the work memory in association with the number of shot frames. Thereby, the data amount when the target image data in the first shooting is compressed is acquired. Here, the compressed target image data may be stored in the buffer memory 25 or may be deleted without being stored.

  Step S113 is processing for determining whether or not the operation of the release button has been released. As described above, when the release button 44 is operated, a signal (half-press signal, full-press signal) based on the operation of the release button 44 is input to the CPU 40. In this step S113, it is determined whether or not the operation of the release button 44 is released depending on whether or not the output of the signal based on the operation of the release button 44 is stopped. For example, if the output of the signal based on the operation of the release button 44 is continued, the CPU 40 determines that the operation of the release button 44 has not been released. In this case, the determination in step S113 is No, and the process proceeds to step S114. On the other hand, when the output of the signal based on the operation of the release button 44 is stopped, the CPU 40 determines that the operation of the release button 44 has been released. In this case, the determination in step S113 is Yes. In this case, the process related to continuous shooting ends.

  Step S114 is an imaging process (second time). In this imaging process, the position of the focusing lens constituting the imaging optical system is the same as that of the first imaging process, that is, the second imaging process is executed while the position of the focusing lens is fixed. By executing the second imaging process, the image signal output from the imaging device 18 is stored in the buffer memory 25 via the AFE circuit 19. Then, it is read by the image processing circuit 26. The image processing circuit 26 performs image processing such as white balance adjustment, color interpolation, gradation conversion, and color conversion. The image data that has been subjected to various types of image processing by the image processing circuit 26 is stored in the buffer memory 25 again.

  Step S115 is processing to store image data. The process of step S115 is the same process as step S110. The image data in the second shooting is stored in the storage medium 48 by the processing in step S115.

  Step S116 is a trimming process. The process of step S116 is the same process as step S111. The target image data in the second shooting is generated by the processing in step S116.

  Step S117 is a compression process. The process of step S117 is the same process as step S112. By the processing in step S117, the data amount when the target image data in the second shooting is compressed is acquired.

Step S118 is processing for calculating the amount of change in the data amount. CPU40 from the data amount D ₂ of the target image data based on the stored second imaging processing at step S117, the data amount D ₁ of the target image data based on the first imaging processing stored at step S112 By subtracting, the change amount ΔD ₁₂ of the data amount in the comparison target region is calculated. Here, since the first imaging process focuses on the subject, the target image data based on the first imaging process becomes the reference target image data.

Step S119 is processing for determining whether or not the amount of change in the data amount is outside the predetermined range. When the change amount ΔD ₁₂ of the data amount obtained in step S118 is out of the predetermined range, the CPU 40 sets the determination process in step S119 to Yes, and proceeds to step S120.

On the other hand, if the data amount of change in the amount [Delta] D ₁₂ determined in step S118 it is within a predetermined range, and No the determination process in step S119. In this case, the process proceeds to step S123. Here, the predetermined range used in step S119 is preferably a range obtained in advance by experiments, statistics, and the like.

That is, when the determination processing is No, in step S119, can be presumed that the change amount [Delta] D ₁₂ of data amount is included for example in the range of error. For this reason, the focusing lens is fixed at the position of the focusing lens in the second imaging process.

S120 is processing for determining whether or not the data amount has decreased. In step S118, the change amount [Delta] D ₁₂ of data quantity is calculated. If this amount of data [Delta] D ₁₂ is a negative value, CPU 40 determines that the data amount is reduced. In this case, the determination process in step S120 is Yes, and the process proceeds to step S121.

On the other hand, when the data amount [Delta] D ₁₂ becomes a positive value, CPU 40 determines that the data amount is increased. In this case, the determination process in step S120 is No, and the process proceeds to step S123. As described above, the amount of image data that is in focus is larger than the amount of image data that is out of focus. That is, when the data amount ΔD ₁₂ is a positive value, the image data obtained by the second imaging process is focused on the main subject more than the image data obtained by the first imaging process. It can be estimated that. In this case, the focusing lens is fixed at the position of the focusing lens in the second imaging process.

Step S121 is processing for calculating the amount of movement of the focusing lens. CPU40 uses the data amount of the variation [Delta] D ₁₂ obtained in step S119, calculates the movement amount of the focusing lens. In the calculation of the focusing lens, characteristics unique to the imaging optical system 15 such as a focal length are taken into consideration.

  Step S122 is processing to move the focusing lens. The CPU 40 moves the focusing lens via the lens driving mechanism 21 based on the movement amount obtained in step S121. At this time, the moving direction of the focusing lens is set in advance in either the closest end direction or the infinite end direction. The CPU 40 moves the focusing lens in the set moving direction.

  Step S123 is processing for determining whether or not the operation of the release button has been released. Note that the process of step S123 is the same process as step S113. For example, if the output of the signal based on the operation of the release button 44 is continued, the CPU 40 determines that the operation of the release button 44 has not been released. In this case, the determination in step S123 is No, and the process proceeds to step S124. That is, the second imaging process is completed, and the third and subsequent imaging processes are executed.

  On the other hand, when the output of the signal based on the operation of the release button 44 is stopped, the CPU 40 determines that the operation of the release button 44 has been released. In this case, the determination in step S123 is Yes. In this case, the process related to continuous shooting ends.

  Step S124 is an imaging process (third time). By this imaging process, the image signal output from the image sensor 18 is stored in the buffer memory 25 via the AFE circuit 19. Then, it is read by the image processing circuit 26. The image processing circuit 26 performs image processing such as white balance adjustment, color interpolation, gradation conversion, and color conversion. The image data that has been subjected to various types of image processing by the image processing circuit 26 is stored in the buffer memory 25 again.

  Step S125 is processing to store image data. The process of step S125 is the same process as S115. As a result, the image data obtained by the third imaging process is stored in the storage medium 48.

  Step S126 is a trimming process. The process of step S126 is the same process as step S116. By the processing in step S126, target image data in the third imaging process is generated.

  Step S127 is a compression process. The process of step S127 is the same process as step S112. By the processing in step S127, the data amount when the target image data in the third shooting is compressed is acquired.

Step S128 is processing for calculating the amount of change in the data amount. The CPU 40 calculates the amount of change in the data amount using the data amount of the target image data when the compression process is performed. CPU40 from the data amount D3 of the compression processed target image data obtained by the imaging processing of the third, subtracting the data amount D ₁ of the compression processed target image data obtained by the first imaging process, A change amount ΔD ₁₃ is obtained. Further, CPU 40 is third subtracting the data amount D ₂ compression processed target image data obtained from the data amount D ₃ compression processed target image data by the second imaging processing obtained by the imaging processing of the Then, the change amount ΔD ₂₃ is obtained.

Step S129 is a predetermined step for determining whether or not the amount of change in the data amount exceeds a predetermined range. When the change amount ΔD ₁₃ of the data amount obtained in step S128 is out of the predetermined range, the CPU 40 determines Yes in step S119 and proceeds to step S130.

On the other hand, if the change amount ΔD ₁₃ of the data amount obtained in step S128 is within the predetermined range, the determination process in step S129 is No. In this case, the process proceeds to step S135. That is, when the determination processing in step S129 is No, can be assumed that the change amount [Delta] D ₁₃ of data amount is included for example in the range of error. For this reason, the focusing lens is fixed at the position of the focusing lens in the third imaging process.

Step S130 is processing to determine whether or not the amount of change in data amount has decreased. The CPU 40 determines whether or not the data amount change amount ΔD ₁₃ is smaller than the data amount change amount ΔD ₁₂ using the data amount change amount ΔD ₁₃ and the change amount ΔD ₁₂ obtained in step S128. . For example, when the change amount ΔD ₁₃ of the data amount is equal to or less than the change amount ΔD _{12 of the} data amount, the CPU 40 determines Yes in step S130. In this case, the process proceeds to step S131. On the other hand, when the data amount change amount ΔD ₁₃ exceeds the data amount change amount ΔD ₂₃ , the CPU 40 determines No in step S 130. In this case, the process proceeds to step S133.

  As described above, when the determination result of step S130 is Yes, the process proceeds to step S131.

Step S131 is processing for calculating the amount of movement of the focusing lens. The CPU 40 calculates the moving amount of the focusing lens using the data amount change amount ΔD ₂₃ .

  Step S132 is a process of moving the focusing lens in the same direction. The CPU 40 moves the focusing lens in the same direction as the moving direction of the focusing lens in step S122 via the lens driving mechanism 21. Here, the moving amount of the focusing lens is the moving amount obtained in step S131. When this process is executed, the process proceeds to step S135.

  On the other hand, when the determination result of step S130 is No, the process proceeds to step S133.

  Step S133 is processing for calculating the amount of movement of the focusing lens. The process of step S133 is the same process as step S131.

  Step S134 is a process of moving the focusing lens in the reverse direction. The CPU 40 moves the focusing lens through the lens driving mechanism 21 in the direction opposite to the moving direction of the focusing lens in step S122. Here, the moving amount of the focusing lens is the moving amount obtained in step S131. When this process is executed, the process proceeds to step S135.

Step S135 is processing to determine whether or not the operation of the release button has been released. The process of step S135 is the same process as steps S113 and S123. That is, if the CPU 40 determines that the operation of the release button 44 has been released, the determination process in step S135 is Yes. In this case, a series of processes related to continuous shooting ends. The quick return mirror 16 is switched from the mirror-up state to the mirror-down state based on the end of a series of processes related to continuous shooting.
On the other hand, if the CPU 40 determines that the operation of the release button 44 has not been released, the determination process in step S135 is No. In this case, returning to the process of step S124, the fourth imaging process is executed. And the process of step S124-step S134 is performed. Thereafter, the processing from step S124 to step S134 is repeatedly executed until the processing of step S135 becomes Yes. That is, the fourth and subsequent shootings are executed.

  As described above, the focus control of the present embodiment is executed based on a change in the data amount of the target image data that has been subjected to compression processing that is obtained by performing compression processing on the target image data corresponding to the comparison target region. Here, since the comparison target area is an area based on the main subject at the time of shooting or the focused area, appropriate focus control is performed on the focused area when continuous shooting is started. It can be carried out. That is, when comparing the amount of change in the amount of data when the entire image data is compressed, not the image data focused on the main subject but also the image data focused on other subjects can be obtained. There is a fear, but with the configuration of the present invention, it is possible to acquire only image data that is focused on the main subject.

  In the present embodiment, face detection processing and processing for setting a comparison target region are performed on the image data obtained by the first imaging processing when continuous shooting is started, but it is necessary to limit to this. Rather, it is also possible to perform in advance a face detection process and a process for setting a comparison target region using an image (through image) output from the image sensor before continuous shooting is performed.

  In this embodiment, when a plurality of faces are detected by the face detection process, the divided area including the largest face or the face to be superimposed on the AF area is set as the comparison target area. However, the present invention is not limited to this. Instead, it is also possible to designate a main subject in advance based on an input operation using the operation unit 45 by the user, and set a divided region including the designated face as a comparison target region. If no face is detected by the face detection process, if the user has previously designated an AF area to be used for focus detection, a divided area including the AF area designated by the user may be set as a comparison target area.

  In the present embodiment, immediately after the imaging process, a process for saving image data obtained by the imaging process is performed (step S110, step S115, and step S125). However, the present invention is not limited to this, and the release button 44 is operated. In response to the release of, the image data obtained by each imaging process in the continuous shooting may be stored.

  In this embodiment, image data obtained by each imaging process is used. However, the present invention is not limited to this, and in a digital camera, face detection processing is performed using image data obtained by reducing the obtained image data. Therefore, the focus control of this embodiment can be performed using reduced image data.

  In this embodiment, the image is divided into a plurality of divided areas in advance, and the face area of the subject included in the image or the divided area including the focused AF area is used as the comparison target area. For example, when a face is detected by the face detection process, a rectangular area including the detected face area is set as a comparison target area, and a face is not detected by the face detection process. A region having a predetermined size including the focused AF area can be set as a comparison target region.

  In this embodiment, the face of a person is taken as an example. However, the present invention is not limited to this. In addition to a person, a transport device such as an animal, a car, or a ship, a building, or the like may be used as a subject.

  In the present invention, the focus control in the digital camera is the phase difference detection type focus control. However, the present invention is not limited to this and may be the contrast detection type focus control. In addition, it is possible to perform focus control based on an operation by a user during the first imaging process in continuous shooting.

  Although a single-lens flex camera has been described as the digital camera of the present invention, the present invention can also be used for a compact camera, a mobile phone having a camera function, a camera mounted on or connected to a computer, and the like.

  DESCRIPTION OF SYMBOLS 10 ... Digital camera, 18 ... Image pick-up element, 27 ... Compression / decompression circuit, 36 ... Image processing circuit, 40 ... CPU, 41 ... Non-volatile memory, 42 ... Work memory, 47 ... Trimming part, 51 ... Face detection part, 52 ... Area setting unit, 53 ... Data comparison unit, 54 ... Focus control unit

Claims (10)

A subject detection unit for detecting a subject;
A setting unit that sets a region to be cut out from each of the images continuously output from the image sensor based on the result of subject detection by the subject detection unit;
A compression unit that performs compression processing on the image of the target area cut out from each of the images continuously output from the imaging device;
A control unit that controls a focus position of an imaging optical system that forms a subject image on the imaging device based on a change in the data amount of the compressed image of the target area;
A focus adjustment device comprising: The focus adjustment apparatus according to claim 1,
The focus adjustment apparatus, wherein the setting unit sets a region of the largest subject among the plurality of subjects as the target region when the subject detection unit detects a plurality of subjects. The focus adjustment apparatus according to claim 1,
A focus detection unit that detects a focus state of the imaging optical system using a plurality of focus detection areas arranged in an imaging range at the time of image acquisition,
The setting unit sets, as the target region, an area including a subject to be superimposed on the focus detection area among the plurality of subjects when the focus detection unit detects a plurality of subjects. Focus adjustment device. The focus adjustment apparatus according to claim 1,
A focus detection unit that detects a focus state of the imaging optical system using a plurality of focus detection areas arranged in an imaging range at the time of image acquisition,
The setting unit is configured to set, as the target region, a region including a focus detection area in focus among the plurality of focus detection areas when no subject is detected by the subject detection unit. apparatus. The focus adjustment apparatus according to claim 1,
The setting unit divides an image continuously output from the image sensor into a plurality of regions,
The focus adjustment apparatus, wherein the setting unit sets any one of the plurality of regions as the target region based on a result of the subject detection. The focus adjustment apparatus according to claim 1,
The focus detection apparatus, wherein the subject detection unit detects a human face included in an image as a subject. The focus adjustment apparatus according to claim 1,
The focus adjustment apparatus, wherein the control unit performs initial adjustment of the focus position in accordance with an instruction from a user. The focus detection apparatus according to claim 7,
The focus adjustment apparatus, wherein the control unit performs initial adjustment of the focus position by a phase difference detection method. The focus detection apparatus according to claim 1,
The focus adjustment apparatus, wherein the control unit displaces the focus position when a change amount of the data amount exceeds a reference range. An image sensor that continuously captures the subject image formed by the imaging optical system and sequentially outputs the images;
The focus adjustment apparatus according to any one of claims 1 to 9, wherein a focus position of the imaging optical system is controlled based on images sequentially output from the imaging element.
An imaging apparatus comprising:

Images