JP2008090059A - Imaging apparatus and autofocus control method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus which is capable of high-speed autofocus control without blurring of images, even when a child runs toward the person photographing, and to provide an autofocus control method thereof. <P>SOLUTION: When the apparatus is focused on a subject by video autofocus is successful in face extraction after a first release, a face extraction means 12 outputs face detection size in matching with the number of pixels, CCD size, and lens focal length. A subject distance calculation means 14 calculates subject distance information, from the face detection size and face size information stored in a storage means 16 and outputs the subject distance information to a focus lens target position calculation means 18. The focus lens target position calculation means 18 outputs a lens driving target position to a focus lens driving means 20, on the basis of this distance information to achieve continuous autofocus. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an imaging apparatus, and more specifically to an imaging apparatus capable of performing autofocus control at high speed.

  In recent years, technological progress of digital cameras has been remarkable, and various devices have been made so that anyone can easily shoot with a camera. In particular, since there are many cases where the subject of camera photography is generally a person, various functions have been proposed to prevent person photography from failing.

For example, in Patent Document 1, in order to prevent a photographer from deviating the timing of pressing a shutter and taking a photo opportunity, a conventional technique of an image pickup apparatus that automatically takes a picture after detecting a face image as a trigger. Is disclosed. This prior art describes a technique for automatically performing screen size and backlight processing from a detected face image.
Further, Patent Document 2 discloses a conventional imaging apparatus having an autofocus function that prevents camera shake even when a child camera shooting mode such as a young mother is selected, or automatically focuses even at a short distance. Technology is disclosed.

Furthermore, Patent Document 3 extracts a feature point of a subject's face in human photographing, determines the size of the extracted feature point, sets an optimum autofocus area according to the determination result, and The prior art of the imaging device which calculates the distance to the subject based on the feature points is disclosed. In other words, this conventional technique limits the autofocus drive range based on this distance by calculating a rough distance from the face and eye spacing of the captured image that is the subject and the size of a general human. This speeds up autofocus.
JP 2003-92700 A JP 2005-184246 A JP 2004-317699 A

  However, Patent Document 1 or 2 does not disclose any autofocus speed. For this reason, for example, when a child runs and approaches, the autofocus speed cannot follow and the image is blurred. Occurs. Further, Patent Document 3 discloses a high-speed autofocus, but the autofocus disclosed in this document detects an edge of an image while moving a focus lens at a predetermined step every 1/30 seconds, for example. This is video autofocus control. For this reason, when the child runs and comes close to the photographer as described above, the image is blurred because the autofocus process cannot follow the child's speed as in Patent Document 1 or 2. Even Patent Document 3 could not solve the problem.

  The present invention solves such a problem of the prior art, and an image pickup apparatus capable of high-speed autofocus control without blurring an image even when a child runs and approaches the photographer, and its auto It is an object to provide a focus control method.

  In order to solve the above-described problems, the invention described in claim 1 is directed to an image forming surface of an image pickup element via an image pickup optical system while driving a focus lens included in the image pickup optical system in a focus adjustment direction. In an imaging apparatus having a first focus adjustment unit that detects a focus position based on an image of a subject formed on the object, subject data representing the size of all or part of a desired object is stored in advance. Storage means, external image recognition means for recognizing an external image corresponding to all or part of the object from the image of the subject at the in-focus position detected by the first focus adjustment means, and external image recognition Based on all or part of the outline image of the object recognized by the means and the subject data read from the storage means, the distance calculating means for calculating the distance to the subject, and the distance calculating means With respect to the release, characterized in that it comprises a second focusing adjusting means drives the focus lens in the focusing direction to detect a new focus position.

According to the first aspect of the present invention, the focus lens is driven in the focus adjustment direction based on the distance calculated by the distance calculation means for calculating the distance to the subject, and a new in-focus position is detected. By providing the second focus adjustment means, the focus adjustment can be performed even on a fast-moving subject that cannot be adjusted by the conventional technique.
Therefore, even an amateur can take a beautiful image in focus.

  According to a second aspect of the present invention, in the first aspect of the present invention, when the first-stage pressing state of the shutter button is detected, the first-stage pressing state of the shutter button is detected. , The external image recognition means until the time when the second focus state of the shutter button is detected after the processing by the first focus adjustment means is started and after the processing is finished by the first focus adjustment means. A series of processing by the distance calculation unit and the second focus adjustment unit is repeated, and the photographing operation is started when the second-stage pressing state of the shutter button is detected.

  According to the second aspect of the present invention, when the first-stage pressing state of the shutter button is detected, the processing by the first focus adjustment unit is started and the subject to be focused is specified. Since a series of processes by the second focus adjustment unit is repeated until the time when the second stage of the button is pressed is detected, high-speed focus adjustment is possible. Also, if the first-pressed state of the shutter button is released, the series of processing by the second focus adjustment means is also released, so that even if the subject is selected incorrectly, the correct subject can be selected immediately. It becomes possible.

  The invention described in claim 3 is the invention described in either claim 1 or 2, further comprising a sensitivity adjustment means for adjusting the sensitivity of the image sensor, wherein the sensitivity adjustment means is a second focus adjustment means. At the time of focusing adjustment according to, the sensitivity of the image sensor is adjusted to be higher than a preset optimum value at the time of shooting.

  According to the third aspect of the present invention, the sensitivity of the image sensor is adjusted so as to be higher than the optimum value at the time of shooting at the time of focus adjustment by the second focus adjustment unit. The depth of field can be secured, and the movement of the subject in the optical axis direction can be quickly followed.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the switching means that selectively switches the photographing mode or the object measurement mode according to an external operation, and the object measurement mode is selected. , A photographing means for photographing a subject whose shape and size are set in advance together with a desired subject, and all or a part of the subject based on the shape and size of the subject photographed by the photographing means Size calculation means for calculating the size of the image, and the calculation result of the size calculation means is stored in the storage means as subject data.

  According to the fourth aspect of the present invention, it is possible to calculate the size of all or a part of a subject by simply photographing a subject whose shape and size are preset together with a desired subject, and storing it in the storage means. Since it can be memorized, it is possible to easily register and register a desired subject.

  The invention described in claim 5 is the invention described in any one of claims 1 to 4, wherein all or part of a desired object is a human face.

  The invention described in claim 6 is based on the image of the subject imaged on the imaging surface of the imaging element via the imaging optical system while driving the focus lens included in the imaging optical system in the focus adjustment direction. In the imaging method for executing the first focus adjustment step for detecting the focus position, subject data representing the size of all or part of a desired object is stored in advance, and the first focus adjustment is performed. An outline image recognition step for recognizing an outline image corresponding to all or part of the object from the image of the subject at the in-focus position detected by the step, an outline image of all or part of the recognized object, and the object Based on the data, a distance calculation step for calculating the distance to the subject and a new focus position is detected by driving the focus lens in the focus adjustment direction based on the calculated distance. And executes a second focusing adjustment step that.

  According to the sixth aspect of the invention, the focus lens is driven in the focus adjustment direction based on the distance calculated by the distance calculating step for calculating the distance to the subject, and a new in-focus position is detected. By providing the second focus adjustment step, the focus adjustment can be performed even for a fast-moving subject that cannot be adjusted by the conventional technique. Therefore, even an amateur can take a beautiful image in focus.

  According to a seventh aspect of the present invention, in the invention described in the sixth aspect of the invention, the first focus adjustment is performed when the first pressing state of the shutter button in which the pressing state is set to two levels is detected. The processing by the step is started, and after the processing by the first focus adjustment step is finished, the outer shape image recognition step, the distance calculation step, and the second time until the time when the second-stage pressing state of the shutter button is detected. A series of processing by the focusing adjustment step is repeated, and the photographing operation is started when the second-pressed state of the shutter button is detected.

  According to the seventh aspect of the present invention, the first focus adjustment step is started when the first pressing state of the shutter button is detected, and the subject to be focused is specified. Since a series of processes by the second focus adjustment step is repeated until the time when the second-stage button pressing state is detected, high-speed focus adjustment is possible. Also, if the first-pressed state of the shutter button is released, the series of processes in the second focus adjustment step is also released, so that even if the subject is selected incorrectly, the correct subject can be selected immediately. It becomes possible.

  The invention described in claim 8 is the invention described in any of claims 6 and 7, wherein the sensitivity of the image sensor is set in advance at the time of focus adjustment in the second focus adjustment step. A sensitivity adjustment step is performed to adjust the value to be higher than the optimum value at the time of shooting.

  According to the eighth aspect of the present invention, the sensitivity of the image sensor is adjusted to be higher than the optimum value at the time of shooting at the time of focus adjustment in the second focus adjustment step. The depth of field can be secured, and the movement of the subject in the optical axis direction can be quickly followed.

  The invention described in claim 9 is the invention described in any one of claims 6 to 8, wherein the photographing mode or the object measurement mode is selectively switched according to an external operation, and the object measurement mode selection is performed. Sometimes, based on the photographing step of photographing a subject whose shape and size are set in advance together with a desired subject and the shape and size of the photographed subject, the size of all or part of the subject And a size calculation step for calculating the size, and the calculation result of the size calculation step is stored as subject data.

  According to the ninth aspect of the present invention, it is possible to calculate and store the size of all or a part of a subject simply by photographing a subject whose shape and size are preset together with a desired subject. Therefore, setting registration of a desired subject can be easily performed.

  The invention described in claim 10 is the invention described in any one of claims 6 to 9, wherein all or part of a desired object is a human face.

  According to the present invention, high-speed autofocus processing is performed on a subject in a predetermined shooting mode. As a result, it is possible to take a picture in a focused state even in the case where, for example, a person rushes away, for example, when the conventional autofocus process is not in time and the image is out of focus. Therefore, it is possible to take a photograph that is in focus even in such a scene that has been difficult for an amateur to shoot.

Next, an embodiment of an imaging apparatus and an autofocus control method thereof according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 2 is a functional block diagram showing an embodiment when the imaging apparatus according to the present invention is applied to a digital still camera. Hereinafter, the imaging apparatus 10 of the present embodiment will be described in detail with reference to FIG.

  The photographic lens 100 is a photographic lens for forming a subject image on the CCD 102, and is an imaging optical system including a zoom lens, an autofocus lens, and a diaphragm mechanism. The CCD 102 is an image sensor that photoelectrically converts the subject imaged by the photographing lens 100, and outputs a photoelectrically converted video signal to the analog front end 104.

  The analog front end 104 is a processing unit that converts an analog video image from the CCD 102 into a digital video signal. Specifically, the analog front end 104 inputs a control signal from an MPU 118 (to be described later) via a serial / parallel converter 112 in addition to a function of converting an analog video image into a digital signal. The analog front end 104 includes an auto gain control 106, an analog / digital converter 108, and a timing generation circuit 110. These circuits are controlled by the MPU 118.

  The auto gain control 106 is an image brightness adjustment circuit that receives a video signal photoelectrically converted by the CCD 102 and automatically adjusts the value when the video signal exceeds a predetermined adjustment range. The video signal adjusted by the auto gain control 106 is sent to the analog / digital converter 108.

  The analog / digital converter 108 is a converter that converts a photoelectrically converted analog video signal into a digital video signal, and performs noise removal, signal amplification, and the like. The analog / digital converter 108 outputs the processed digital video signal to the bus 200. The timing generation circuit 110 is a timing generator that outputs a clock for synchronizing the analog front end 104 and the CCD 102.

  The serial / parallel converter 112 is a converter that converts parallel data input via the bus 200 into serial data. Specifically, the serial / parallel converter 112 outputs a control signal from the MPU 118 that controls the entire imaging apparatus 10 to the analog front end 104 and the motor driver 114.

  The motor driver 114 is a drive circuit that performs automatic exposure and autofocus control by inputting a control signal from the MPU 118 from the serial / parallel converter 112 and controlling the photographing lens 100 in accordance with the contents. This autofocus control is based on the subject image formed on the imaging surface of the CCD 102 via the imaging lens 100 while driving the focus lens included in the photographing lens 100 in the focus adjustment direction. This is a focus control method for detecting a focal position.

  The flash memory 116 is a non-volatile memory, and stores firmware of the imaging device 10 that is an operation program of the MPU 118. The flash memory 116 also stores registration information set by the user. Specifically, the size of the face that is referred to when performing continuous autofocus control to be described later is stored.

  The MPU 118 is a main processor that controls each component of the imaging device 10 connected via the bus 200 by executing firmware stored in the flash memory 116. In particular, in this embodiment, the MPU 118 selects the portrait mode, which is the portrait shooting mode, as the shooting mode, and when a specific person registered in advance by the “kid shooting mode selection of person” is selected, the normal video auto focus is selected. After the above operation, subject focus control is performed by continuous autofocus. The continuous autofocus will be described in detail later with reference to FIG.

  The SDRAM 120 is a volatile memory that is used as a frame memory for temporarily storing image data and used as a work memory when the MPU 118 performs various calculations. That is, the SDRAM 120 temporarily stores images for a plurality of frames output in real time from the analog / digital converter to the bus 200, processed by the image processing unit 122, and then stored in the SDRAM 120 again. An image when a shutter button (not shown) is pressed is processed by an image compression / decompression unit 124 described later. At this time, image compression is performed via the SDRAM 120, and the compressed image is again displayed. Stored in the SDRAM 120.

  The image processing unit 122 is a circuit that performs, for example, pixel interpolation, color balance control, γ correction, and the like on an image that is output from the analog front end 104 to the bus 200 and stored in the SDRAM 120 under the control of the MPU 118. It is.

  Similarly, the image compression / decompression unit 124 is a circuit that performs image compression such as JPEG compression on an image whose shutter button is pressed under the control of the MPU 118. The image compression / decompression unit 124 also performs decompression processing of an image stored in the memory card 128 when the imaging apparatus 10 is in the reproduction mode under the control of the MPU 118, and stores it in the SDRAM 120.

  The memory card 128 is a detachable card type storage device that employs a flash memory or the like as a storage medium. The memory card 128 stores an image compressed by the image compression / decompression unit 124 via the card interface 126.

  The liquid crystal display 132 is a display provided with a function as an electronic viewfinder that displays an image at the time of photographing in real time and a function as a display screen for confirming the image taken at the playback mode. The video output from the analog front end 104 to the bus 200 at the time of shooting is processed by the image processing unit 122 under the control of the MPU 118, stored in the SDRAM 120, and displayed on the liquid crystal display 132 in real time via the video interface 130. Is done. In the playback mode, the image stored in the memory card 128 is decompressed by the image compression / decompression unit 124 under the control of the MPU 118 and stored in the SDRAM 120, and then displayed on the liquid crystal display 132 via the video interface 130. The

  The operation key 136 is an operation unit of the imaging apparatus 10 for a user to perform an external operation. The operation keys 136 include a power button of the imaging apparatus 10, a cross key for specifying various settings such as designation of a shooting mode and a playback mode, and a face size, a zoom button, a shutter button, and the like. This shutter button is a button having a detection function for detecting a pressed state in two steps. In the present embodiment, the first step is referred to as a 1st release and the second step is referred to as a 2nd release. The operation key 136 is connected to the bus 200 via the key interface 134, and when the operation key 136 is operated, the MPU 118 is detected via the bus 200 and processing corresponding to the key operation is executed.

  FIG. 1 is a functional block diagram for performing continuous autofocus control of the imaging apparatus 10 shown in FIG. The continuous autofocus control is a control method for performing autofocus by registering a specific part of a subject, in this embodiment, the face size of a person, and calculating the distance to the subject based on this.

  The face extraction unit 12 is a unit that extracts a face from a photographed image focused by video autofocus by edge extraction or pattern extraction, and is executed by the MPU 118. When the face extraction unit 12 extracts the face of the subject, the face extraction unit 12 notifies the subject distance calculation unit 14 of the detected face size as the detected face size.

The subject distance calculation unit 14 is a calculation unit that calculates the number of face pixels extracted by the face extraction unit 12, the CCD size, the lens focal length, and the distance from the face size stored in the storage unit 16 that is the SDRAM 120 to the subject. is there. Specifically, when f: object focal length, Z: object distance, and M: vertical magnification,
M = f / Z. . . . . . (1)
It becomes. The object focal length f is determined by the zoom position, and the vertical magnification M can be calculated by dividing the number of pixels obtained by the face extraction unit 12 × CCD pitch by the face size stored in the storage unit 16. Therefore, it is possible to calculate the object distance Z (subject distance information indicating the distance to the subject) of the equation (1). Note that the subject distance calculation means 14 is also executed by the MPU 118.

  The subject distance calculation unit 14 outputs the calculated subject distance information to the focus lens target position calculation unit 18. The focus lens target position calculation unit 18 is a unit executed by the MPU 118, calculates a lens drive target position based on the subject distance information, and outputs this to the focus lens drive unit 20. The focus lens driving unit 20 corresponds to the motor driver 114 in FIG. 1, and performs continuous autofocus control by controlling the photographing lens 100 in accordance with the input lens drive target position.

  FIG. 3 is a flowchart showing the photographing operation of the image pickup apparatus 10 shown in FIG. Here, the operation when the photographer sets the photographing mode to the child photographing mode, selects a pre-registered child and performs photographing will be described. When the child selected in the child photographing mode is positioned at the center of the liquid crystal display 132, which is an electronic viewfinder, the photographer performs the first release, which is a half-press of the shutter button (S300).

  By this first release operation, an automatic exposure process is performed in which the shutter speed for shooting, the aperture, the ISO sensitivity, and the presence or absence of flash emission are determined (S302). Next, the normal video autofocus is operated to detect the edge of the image located at the center of the liquid crystal display 132, and the focus is adjusted by detecting the peak (S304). As described above, the video autofocus is a method of automatically focusing by detecting the edge of the image while moving the focus lens of the photographing lens 100 by predetermined steps and searching for the peak.

  When the subject is in focus by the video auto focus, face recognition processing is executed (S306). There are various face recognition processing methods at this time, but in the present embodiment, it is only necessary to recognize the outer shape of the head, and this is possible by a relatively simple recognition method such as a static two-dimensional method. When face recognition processing is performed, for example, the inclination of the face can be obtained from the characteristics of the eyes and nose and corrected more accurately than the size of the face.

  Next, as a result of determining whether or not there is a face in the subject focused by video autofocus, if the face cannot be detected as a result of the face recognition process, the process returns to step S306 to repeat the face recognition process. Execute. On the other hand, when the face can be detected, the distance to the subject is calculated by the method described with reference to FIG. 1 (S310), and continuous autofocus control for driving the focus lens based on the distance is executed (S312). . The continuous autofocus control described in FIG. 1 is executed until the 2nd release is performed (S314) or until the 1st release is released. When the 2nd release is performed, shooting processing is performed (S316), and the image is stored in the memory card (S318).

  Video autofocus control takes time because it detects a peak by moving the focus lens to detect the edge of the image. Therefore, the video autofocus control is performed stepwise, for example, every 1/30 seconds. On the other hand, since continuous autofocus control drives the focus lens from the distance to the subject, it is possible to focus continuously in real time. As a result, high-speed autofocus is possible, and thus autofocus control can be performed with high follow-up performance even when shooting a child who is approaching in a conventional manner.

  By the way, the 2nd release in step S314 is performed, and the photographing process in step S316 is performed. The photographing conditions at this time are similar to the conditions determined in step S302, and the continuous autofocus control is performed. It is different from the time. This is because images in the continuous autofocus control video mode with face recognition are preferred to have a fast shutter speed in order to reduce motion blur in children, but conversely, the aperture is reduced to ensure the depth of field. It is also important to follow the movement of the subject in the optical axis direction.

  Therefore, when switching to continuous autofocus control, a program diagram for increasing the ISO sensitivity shown in FIG. 4 is applied instead of the program diagram used for actual photographing. That is, since the moving image reading mode of the CCD 102 provides an output in which pixels are added, higher sensitivity is possible than in the normal reading mode. For this reason, as shown in FIG. 4, when the brightness Bv of the subject becomes −1 or more, the ISO sensitivity is set to ISO 1600, which is the maximum value that is normally used. Even if the brightness Bv of the subject becomes brighter, the ISO 1600 is fixed and the open Fno and the shutter speed are changed.

  Specifically, for example, when the brightness Bv is −1, the spot is lowered along an oblique dotted line, that is, the exposure Ev is 8, the shutter speed is 1/30, the Tv is 5, the aperture Av is 3, and the aperture is open. Fno is 2.8. Similarly, when the brightness Bv is 9, the exposure Ev is 18, the shutter speed is 1/1000, the Tv is 10, the aperture Av is 8, and the open Fno is 16. Above ISO 1600, noise increases and the accuracy of edge extraction decreases. Therefore, this is used when the brightness Bv, which is not supported with a shutter speed of Fno 2.8 and 1/30, is −1 or less. Further, when the brightness Bv is 9 or more, the shutter speed is 1/1000, Tv10, the aperture Av8, and the open Fno16 as in Bv9, and the ISO sensitivity is lowered.

  FIG. 5 is a program diagram at the time of the 2nd release, and shows a case where actual photographing is performed. At the time of 2nd release, the ISO sensitivity is not increased at a stretch considering the deterioration of image quality (noise characteristics), but by setting the aperture value to a value close to that at the 1st release, the aperture drive after 2nd release is minimized and the release time lag is reached. Make sure that does not grow.

  For this reason, ISO is set to 400 when Ev is 8 or less (brightness Bv is 1 or less), and proper exposure is obtained by flash emission with an aperture of F2.8 and a shutter speed of 1/30. When the brightness Bv exceeds 1, the aperture Fno and the shutter speed are increased, and when the brightness Bv exceeds 5 to 7, the aperture Fno and the shutter speed are fixed and the ISO sensitivity is decreased to ISO100. When the brightness Bv is 7 or more, it is fixed at ISO 100 and the shutter speed is increased with Fno.

  Next, a child shooting mode that is a shooting mode in which continuous autofocus control is performed will be described. When performing continuous autofocus control, the imaging apparatus 10 needs to store the size of the face (head) in advance. A setting procedure for registering the face size in the imaging apparatus 10 will be described below with reference to FIG.

  First, an initial screen of “Face size setting” for setting the face size by operating the cross key in the operation key 136 (see FIG. 1) is displayed on the liquid crystal display 132 (D400). Although the cross key is not specifically shown, there are four switches, up, down, left, and right, and one switch in the center, and these switches can be used to move and confirm the screen. In addition, the portion selected by the cross key is highlighted so that the user can know that it is currently selected. As shown on the screen D400, in the present embodiment, the face sizes of up to three persons can be registered in the imaging apparatus 10. Since no one has been registered on the screen D400, “person A”, “person B”, “person C” and temporary names are displayed.

  When “person A” is selected, a face size registration screen is displayed on the liquid crystal display 132 (D402). In this embodiment, there are two types of methods for registering the face size. First, a method for directly specifying the face size will be described. When the face size is directly input, the cross key is operated to highlight the vertically symmetrical triangle mark 402a. In that state, use the vertical switch of the cross key to input the face size by pressing the upper side to increase the size and pressing the lower side to decrease the size. The input face size is displayed on the display sections 402b and 402c. If this is acceptable, the cross button is used to move to the OK button 410 to highlight it, and then the center button of the cross key is operated to operate the next face size. The name registration screen is displayed (D404).

  On the name registration screen D404, the name is set by selecting the alphabet in the alphabet selection section 404b with the cross key. Specifically, by pressing the up / down / left / right buttons of the cross key, one character in the alphabet is highlighted, and by pressing the center button of the cross key, the highlighted character is added to the name setting unit 404a. Is done. In addition, when correcting the character added to the name setting part 404a, it moves to the delete button 404c with a cross key and highlights it, Then, the name setting part 404a is pressed by pressing the center button of a cross key. One character added at the end of is deleted.

  When the name setting is completed, the OK button 410 is operated with the cross key to return to the initial screen of “face size setting” (D406). The initial screen at this time is changed to the name “TARO” in which the part originally displayed as “person A” is registered as shown in a screen D406.

  FIG. 7 shows an example of a screen displayed on the liquid crystal display 132 when the child shooting mode in the person shooting mode is selected when the shooting mode is selected. In the example of the screen D500, the face sizes of three children are registered together with names, and the face size of the child selected with the cross key is used as face size information used in continuous autofocus.

  FIG. 8 shows an example of a marker attached to the imaging apparatus 10 that is used when “marker imaging” is selected. Since the actual size of the marker 510 is registered in advance in the flash memory 116 of the imaging apparatus 10, if the marker 510 is photographed by placing it next to the face to be registered, the size of the face can be calculated from the actual size of the marker 510. Can do.

  Specifically, on the screen D402 in FIG. 6, if the marker photographing 408 is selected with the cross key and a confirmation operation is performed, the imaging device 10 is switched to the marker photographing mode. Here, the marker 510 is placed beside the face of the person who is the subject, and shooting is performed by the same operation as in normal shooting.

  FIG. 9 is a processing flow showing an operation when registering a child's face size by marker photographing. When the first release is performed after the marker photographing mode is selected and the imaging apparatus 10 is switched to the photographing mode, automatic exposure processing (S602) and autofocus processing (S604) are performed. As a result, the shutter speed, aperture, ISO sensitivity, and whether or not the flash is emitted are determined, and when the 2nd release is performed with the subject (in this case, the child's face) in focus (S606), face recognition is performed. Processing is executed (S608).

  A face is extracted from the image captured by the face recognition processing in step S608. As a result, when a face is not detected or a plurality of faces are detected (S610), the process proceeds to error processing (S620). . On the other hand, when one face is detected (S610), a recognition process for a marker placed beside the face is executed (S612), but when a marker is not detected or a plurality of markers are detected (S612). The process proceeds to error processing (S620).

  When one face and one marker are detected, face size calculation processing is performed (S616). When performing the face size calculation process, first, the size of the photographed marker is acquired. The distance from an arbitrary point on the circumference to the center point of the marker is acquired in units of pixels, and the maximum value of the acquired values is set as the marker size. Next, the size detected by face detection is acquired in pixel units. Since the size of the marker is determined in advance, the face size is calculated from these ratios. When the face size is calculated, it is displayed as shown on the screen D402 in FIG. 6 (S618). Thereafter, as described in FIG. 6, the name is registered and the setting is completed.

  The marker 500 may be attached as an accessory of the imaging device 10, but for example, in the case of a camera with a lens cap, the marker 500 can be used as a marker by printing the pattern of the marker 500 on the back side of the cap. is there.

  The embodiments of the imaging apparatus according to the present invention have been described in detail with reference to the drawings. However, the present invention is not limited to these embodiments, and various modifications or corrections having the same technical idea can be made. It is included in the category of the invention. That is, in the present embodiment, the face size is the size of the entire face, but it may be a part instead of the whole face. In the present embodiment, the present invention is applied to a digital still camera. However, the present invention is not particularly limited to this, and can be applied to a digital video camera, a mobile phone with an imaging device, or the like. For example, when the present invention is applied to a digital video camera, since there is no first release operation, the focus control is performed by switching to the continuous autofocus when the face can be recognized from the subject in focus by the video focus. . As a result, high-speed autofocus control can be realized even in the case of a digital video camera, so that it is possible to take a clear image even in the case of conventional out-of-focus.

  Furthermore, in the present embodiment, the case where the present invention is applied to the person shooting mode has been described. However, the present invention is not particularly limited to only the person shooting, and focusing can be performed in the conventional technique in which the subject approaches. It is effective for difficult subjects. Even in this case, if the size of the specific part of the subject is registered and the imaging device can extract the specific part of the subject in the first release, the continuous autofocus control is performed after the video autofocus control. It is possible to continue focusing.

The functional block diagram which shows embodiment when the imaging device by this invention is applied to a digital still camera. FIG. 2 is a functional block diagram obtained by blocking continuous autofocus control for each function in the imaging apparatus shown in FIG. 1. 4 is a processing flow showing an embodiment of an autofocus control method in an imaging apparatus according to the present invention. FIG. 4 is a program diagram when continuous autofocus control is performed after the first release shown in FIG. 3. FIG. 4 is a program diagram when shooting is actually performed at the 2nd release shown in FIG. 3. The screen transition figure which shows the operation procedure when registering face size. The example of a display screen when selecting portrait mode as photography mode of an imaging device, and also selecting child photography mode. Marker example used when marker shooting is selected when registering face size. The processing flow which shows embodiment when marker imaging | photography is selected when registering a face size.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Imaging device 12 Face extraction means 14 Subject distance calculation means 16 Storage means 18 Focus lens target position calculation means 20 Focus lens drive means 100 Shooting lens 102 CCD
104 Analog Front End 106 Auto Gain Control 108 Analog / Digital Converter 110 Timing Generation Circuit 112 Serial / Parallel Converter 114 Motor Driver 116 Flash Memory 118 MPU
120 SDRAM
122 image processing unit 124 image compression / decompression unit 126 card interface 128 memory card 130 video interface 132 liquid crystal display 134 key interface 136 operation key

Claims (10)

A focus position is detected based on an image of a subject imaged on the imaging surface of the imaging device via the imaging optical system while driving a focus lens included in the imaging optical system in a focus adjustment direction. In the imaging apparatus having one focusing adjustment unit,
Storage means for storing subject data representing the size of all or part of a desired object in advance;
An outline image recognition means for recognizing an outline image corresponding to all or part of the object from the image of the subject at the in-focus position detected by the first focus adjustment means;
Distance calculating means for calculating a distance to the subject based on all or part of the outer shape image recognized by the outer shape image recognizing means and the subject data read from the storage means;
An imaging apparatus comprising: a second focus adjustment unit configured to detect a new focus position by driving the focus lens in a focus adjustment direction based on the distance calculated by the distance calculation unit. A detecting means for detecting the pressing state of the two-stage shutter button;
When the first-pressed state of the shutter button is detected, processing by the first focus adjustment unit is started,
After the processing is completed by the first focus adjustment unit, the outline image recognition unit, the distance calculation unit, and the second focus adjustment are performed until the time when the second-stage pressing state of the shutter button is detected. Repeat a series of processing by means,
The imaging apparatus according to claim 1, wherein a photographing operation is started when a second-stage pressing state of the shutter button is detected. A sensitivity adjusting means for adjusting the sensitivity of the image sensor;
The sensitivity adjustment unit adjusts the sensitivity of the image sensor so that the sensitivity of the image sensor is higher than a preset optimum value at the time of focusing when the second focus adjustment unit adjusts the focus. The imaging device according to claim 1, wherein: Switching means for selectively switching the shooting mode or the object measurement mode according to an external operation;
A photographing means for photographing a subject whose shape and size are set in advance together with the desired subject when the object measurement mode is selected;
Size calculating means for calculating the size of all or part of the subject based on the shape and size of the object photographed by the photographing means, and the calculation result of the size calculating means as the subject data It memorize | stores in the said memory | storage means. The imaging device in any one of Claims 1-3 characterized by the above-mentioned. The imaging apparatus according to claim 1, wherein all or part of the desired object is a human face. A focus position is detected based on an image of a subject imaged on the imaging surface of the imaging device via the imaging optical system while driving a focus lens included in the imaging optical system in a focus adjustment direction. In the imaging method for executing one focus adjustment step,
Object data representing the size of all or part of a desired object is stored in advance, and from the image of the object at the in-focus position detected by the first in-focus adjustment step, all of the object or An outline image recognition step for recognizing an outline image corresponding to a part;
A distance calculating step for calculating a distance to the subject based on the whole or part of the recognized outline image of the object and the subject data;
And a second focus adjustment step of detecting a new focus position by driving the focus lens in a focus adjustment direction on the basis of the calculated distance. When the first pressing state of the shutter button whose pressing state is set to two steps is detected, the processing by the first focus adjustment step is started.
After the end of the processing in the first focus adjustment step, the outline image recognition step, the distance calculation step, and the second focus adjustment are performed until the time when the second-stage pressing state of the shutter button is detected. Repeat a series of steps,
The imaging method according to claim 6, wherein a photographing operation is started when a second-stage pressing state of the shutter button is detected. Executing a sensitivity adjustment step of adjusting the sensitivity of the image sensor so that the sensitivity of the image sensor is higher than a preset optimum value at the time of shooting during the focus adjustment in the second focus adjustment step; The imaging method according to claim 6, wherein: A photographing mode or an object measurement mode is selectively switched in accordance with an external operation, and an object to be photographed together with the desired subject is photographed with a shape and size set in advance when the object measurement mode is selected. Steps,
A size calculation step of calculating the size of all or a part of the subject based on the shape and size of the photographed object, and storing the calculation result of the size calculation step as the subject data. The imaging method according to claim 6, wherein: The imaging method according to claim 6, wherein all or part of the desired object is a human face.

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