JP2006033440A - Digital camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve detection accuracy for detecting a feature such as the face of an object in a digital camera. <P>SOLUTION: The digital camera is provided with a feature detector for detecting the feature of an object, a memory for storing the feature information detected by the feature detector, and a photographing control unit for performing photographing control on the basis of the feature detected by the feature detector. If the feature detector cannot detect the feature when photographing a recording image, the photographing control unit performs photographing control on the basis of the feature information stored in the memory. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a digital camera that captures an image of a subject, and more particularly to a digital camera that can detect a characteristic part of a subject such as face detection.

  In order to focus on the face portion of a person when the subject is a person, a camera that detects the face portion of the person in the object scene captured by the camera and performs AF on the detected face area has been proposed.

  However, when a face is detected, problems such as a face cannot be detected or detection accuracy is poor depending on the face detection method or environment. An object of the present invention is to improve detection accuracy for detecting a characteristic part of a subject such as a face in a digital camera.

  According to the first aspect of the present invention, in the digital camera, a feature part detection unit that detects a feature part of a subject, a memory that stores feature part information detected by the feature part detection unit, and detection by the feature part detection unit An imaging control unit configured to perform imaging control based on the feature part, and the imaging control unit is stored in the memory when the feature part detection unit cannot detect the feature part when capturing a recorded image. It was set as the structure which performs imaging | photography control based on characteristic part information.

  According to a second aspect of the present invention, in the digital camera according to the first aspect, the imaging control unit is configured to execute autofocus control using the characteristic part as an autofocus area.

  According to a third aspect of the present invention, the imaging control unit includes a feature part detection unit that detects a feature part of a subject, and an imaging control unit that performs imaging control based on the feature part detected by the feature part detection unit. Is configured to perform imaging control based on a predetermined part in the object scene when the characteristic part cannot be detected by the characteristic part detection unit when a recorded image is taken.

  According to a fourth aspect of the present invention, in the digital camera according to the third aspect, the imaging control unit is configured to execute autofocus using the characteristic part as an autofocus area.

  According to a fifth aspect of the present invention, in the digital camera according to the third aspect, the imaging control unit autofocuses the central part in the object scene when the characteristic part cannot be detected by the characteristic part detection unit. The area is configured to execute autofocus control.

  Even when a characteristic part is not formed when the recorded image is captured, the recorded image can be captured.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the configuration of the digital camera 1 according to the embodiment of the present invention will be described.

  FIG. 1 is an external view of a digital camera 1 according to an embodiment of the present invention. In FIG. 1, the digital camera 1 includes a shutter button 101, a cross key 102, a monitor 103, and an enter button 104.

  The shutter button 101 is a button that can detect two stages, a half-pressed stage and a fully-pressed stage. The shutter button 101 is operated for the user to instruct the start of shooting. The cross key 102 is operated to move a cursor or the like on the monitor 103. The decision button 104 is operated when the item selected with the cross key 102 is decided. The enter button 104 is operated to switch the monitor 103 between the on state and the off state.

  FIG. 2 is a block diagram showing functions of the digital camera 1 according to the embodiment of the present invention. In FIG. 2, the digital camera 1 includes a CPU 111, a face detection unit 112, a built-in memory 113, an operation circuit 114, a display circuit 115, a monitor 103, an image processing circuit 116, an image sensor 117, a zoom lens 118, a zoom driver 119, and a focus lens. 120, a focus driver 121, an aperture 122, an aperture driver 123, and a memory card slot 124. Of course, there are other circuits for realizing the functions of the digital camera, but they are not related to the present invention and will not be described.

  The CPU 111 is a circuit that processes programs for realizing various functions executed by the digital camera 1. The CPU 111 executes programs stored in the memory in the CPU 111 and the built-in memory 113 and controls various circuits in the digital camera 1. The face detection unit 112 extracts a feature portion of image data captured by the image sensor 117 and detects a face area, a face size, and the like of the subject. For the sake of explanation, the functional block of the face detection unit 112 is described, but in the present embodiment, the face detection function is realized by software obtained by executing the face detection program by the CPU 111. It is also possible to assemble and implement hardware circuits.

  The built-in memory 113 is a memory for storing image data, a control program, and the like. For example, a nonvolatile semiconductor memory is used. The built-in memory 113 stores a face detection program that is executed to detect the face area of the subject. The built-in memory 113 can store face information such as a face position and a face size obtained by face detection. The operation circuit 114 is a circuit that detects the operation of operation buttons such as the release button 101, the cross key 102, and the determination button 104 provided in the digital camera 1 and transmits them to the CPU 111. The operation circuit 114 detects a half-press operation and a full-press operation of the release button 101. The display circuit 115 is a circuit that generates screen data to be displayed on the monitor 103. The monitor 103 is a liquid crystal display provided on the back surface of the digital camera 1 and displays the screen data generated by the display circuit 115.

  The photographing lens is composed of a zoom lens 118, a focus lens 120, and the like, and is an optical lens for forming a subject image on the light receiving surface of the image sensor 117. The zoom lens 118 is a lens that is moved by a motor to realize an enlargement and reduction of an optical image formed on the image sensor 117 among lenses constituting the photographing lens. The zoom driver 119 is a circuit for driving a motor according to a command from the CPU 111 and moving the zoom lens 118 to a predetermined position. The focus lens 120 is a lens that is moved by a motor in order to adjust the focus among the lenses constituting the photographing lens. The focus driver 121 is a circuit for driving a motor according to a command from the CPU 111 and moving the focus lens 120 to a predetermined position.

  The diaphragm 122 is for adjusting the amount of light of the object scene incident on the image sensor 117. The aperture driver 123 is a circuit that drives a motor in response to a command from the CPU 111 and controls the open / close state of the aperture 122. The imaging element 117 is an element configured by a CCD or the like that converts an optical image input via a photographing lens into an electric image signal. The image processing circuit 116 performs analog / digital conversion on the electrical signal output from the image sensor 117 to generate a digital signal. Further, the image processing circuit 116 performs interpolation processing or the like on the digital signal that has been digitally converted, and generates image data. The memory card slot 124 is a slot for inserting a memory card, writing data such as image data into the memory card, and erasing the data.

  Next, the operation of the digital camera 1 according to the embodiment of the present invention will be described.

  A setting operation for using the face detection function in the digital camera 1 will be described. When the main subject is a person, the camera user wants to focus on the face portion obtained by the face detection. The digital camera 1 uses the result of face detection as one of the options for determining the area to be AF. Therefore, the digital camera 1 includes face detection as one of AF area selection items that can be selected by the user.

  3 and 4 are diagrams showing menu screens related to the focus displayed on the monitor 103 of the digital camera 1.

  FIG. 3 is a diagram showing a screen displayed when setting the “AF area” in the selection items of the menu screen. In the selection item “AF area”, any one of “auto”, “manual”, “center”, and “face detection” can be selected. When “Auto” is selected, control is performed using all the AF areas to focus on the subject closest to the digital camera 1 among the subjects overlapping any of the AF areas. When “Manual” is selected, control is performed so as to focus using only the AF area selected by the user from among a plurality of AF areas. When “center” is selected, control is performed so that focusing is performed using only the central AF area among the plurality of AF areas. When “Face detection” is selected, control is performed so that the closest face portion among the detected faces is in focus.

  FIG. 4 is a diagram showing a screen displayed when the “AF mode” in the selection items of the menu screen is set. In the selection item “AF mode”, “always AF” and “single AF” can be selected, but when “face detection” is selected, the mode is automatically switched to “always AF”. When “always AF” is selected, regardless of the operation of the shutter button 101, focusing by AF is repeated, and the AF lock is performed by half-pressing the shutter button 101. When “single AF” is selected, control is performed so that AF is focused only while the shutter button 101 is half-pressed, and AF lock is performed when focus is achieved.

  Selection and determination on the menu screen can be performed by the user operating the cross key 102 and the determination button 104.

  Next, the face detection operation in the digital camera 1 according to the embodiment of the present invention will be described.

The digital camera 1 executes face detection control by switching to a still image shooting mode that enables still image shooting in a state where “face detection” is selected on the menu screen shown in FIG. In the digital camera 1, face detection is performed using a moving image (through image) captured by the image sensor 117 displayed on the monitor 103 in order to confirm a subject image to be captured. Further, the digital camera 1 performs control so that the brightness of the through image is increased when face detection is performed, compared to when face detection is not performed. The face can be easily detected by increasing the brightness of the through image.

  Further, the digital camera 1 repeatedly performs face detection using the through image until the shutter button 101 is half-pressed. At that time, if a face cannot be detected, center area AF and multi-area AF are executed to focus on the subject and assist face detection.

  Further, the digital camera 1 repeatedly stores the face detection information such as the face position and the face size as face detection results in the built-in memory 113 while overwriting the latest one time until the shutter button 101 is half-pressed. Thereby, even if the face cannot be detected when the half-press operation is performed, the previous detection result stored in the built-in memory 113 can be read and used. If face detection information is not obtained during the half-press operation, AF using another area such as the central area is forcibly executed.

  Hereinafter, photographing control by face detection will be specifically described with reference to a flowchart.

  FIG. 5 is a flowchart showing the control executed by the CPU 111. The flow shown in FIG. 5 starts when “Face Detection” is selected on the menu screen shown in FIG. 3 and the still image shooting mode is set.

  First, in step S101, it is detected whether the monitor 103 is in a lighting state. When it is in the lighting state, the process proceeds to step S102, and when it is not in the lighting state, the process proceeds to step S118. Here, when the monitor 103 is not in the lit state, the user cannot confirm the face detection result, so there is a possibility that the face is erroneously detected. In the digital camera 1, the AF area setting by face detection is invalidated when the face detection result cannot be confirmed by the user. In the digital camera 1, when the monitor 103 is not in the lighting state, the face detection is not performed by controlling so as not to output the through image.

  In step S102, the field luminance is measured using the image captured by the image sensor 117. Subsequently, in step S <b> 103, brightness adjustment is performed based on the photometric field brightness, and a through image is displayed on the monitor 103. In addition, processing for increasing the depth of field is executed. The process executed in this step will be described later with reference to the flowchart shown in FIG.

  In step S104, face detection is performed using the through image. Subsequently, in step S105, it is determined whether a face has been detected. If a face is detected, the process proceeds to step S106, and if no face is detected, the process proceeds to step S108. In step S106, an area is set according to the detected face position and face size, and AF is executed in the area. A display example on the monitor 103 when a face is detected is shown in FIG. Subsequently, in step S107, the detected face information is temporarily stored in the built-in memory 113. By storing the face information detected here, the face information stored in the built-in memory 113 is used to determine the AF area when a face cannot be detected during the half-press operation for finally determining the AF area. decide. The face information stored in the built-in memory 113 is overwritten with new face information when the next face is detected.

In step S108, AF with the central area as the AF area is executed. Even if a person is in the field, the face may be too blurry to detect the face. Assist. In step S109, it is determined again whether a face has been detected. If no face is detected, the process proceeds to step S110. If a face is detected, the process proceeds to step S106. In step S110, multi-area AF is executed. In step S108, as in AF in the central area, a face when a person is present in a region other than the central portion can be detected.

  Next, in step S111, it is determined whether the face has been detected again. If no face is detected, the process proceeds to step S112. If a face is detected, the process proceeds to step S106. In step S112, it is detected whether the shutter button 101 is half-pressed. If it is detected that the half-press operation has been performed, the process proceeds to step S114. If the half-press operation is not detected, the process proceeds to step S113. In step S113, the face information stored in the built-in memory 113 is deleted, and the process returns to step S101.

  In step S114, it is determined whether a face has been detected in order to identify the face to be the final AF area. If a face is detected, the process proceeds to step S115, and if no face is detected, the process proceeds to step S116. In step S115, an area set according to the detected face position and size is set as the final AF area, and AF control is executed. A display example on the monitor 103 is shown in FIG. In step S116, it is detected whether the face information stored in step S107 exists in the memory. When it exists, it progresses to step S117, and when it does not exist, it progresses to step S118.

  In step S117, an area based on the stored face information is set as an AF area, and AF control is executed. As a result, even when a face cannot be detected during a half-press operation, the most recently detected face area with a small time difference can be used as the AF area, so that the face can be focused almost without error. In particular, it is possible to cope with a single press operation of pressing the shutter button 101 all the way down. In step S118, AF control with the central area as the AF area is executed. As a result, when the face cannot be detected, the central area, which is an area where the main subject is likely to exist automatically, is automatically used as the AF area, so that the main subject is likely to be focused. Further, since it is not necessary to return to the menu screen and reset the AF area, a photo opportunity is not missed.

  In step S119, it is detected whether the shutter button 101 has been fully pressed. If the full press operation has been performed, the process proceeds to step S120, and if the full press operation has not been performed, the process proceeds to step S121. In step S120, shooting and recording processing is executed. In step S121, it is detected whether the shutter button 101 is half-pressed. If the shutter button 101 is half-pressed, the process returns to step S119. If the shutter button 101 is not half-pressed, the process returns to step S101.

  6 and 7 are diagrams showing display examples at the time of face detection control displayed on the monitor 103 of the digital camera 1. The monitor display during face detection control will be described with reference to FIGS. A display example before the half-pressing operation of the shutter button 101 is shown in FIG. 6, and a table example after the full-pressing operation is shown in FIG. As shown in FIGS. 6 and 7, a frame set as an AF area according to the detected position and size of the face is displayed superimposed on the through image. When a plurality of faces are detected, a frame is displayed for each face. When a half-press operation is performed, the largest or closest face frame detected at the time of the half-press operation is switched from a yellow frame (thin line frame in FIG. 6) to a red frame (thick line frame in FIG. 7). The area indicated by the red frame in FIG. 7 is set as the AF area at the time of the full press operation.

  Next, the brightness adjustment process executed in step S103 in FIG. 5 will be described.

The purpose of this processing is to improve the accuracy of detecting the face portion. Although it differs depending on the detection algorithm of the face detection program for detecting the face, control is performed so that the brightness of the image used for detection is adjusted to a brightness that is easy for the face detection program to detect the face. In the digital camera 1 of the present embodiment, an example is shown in which a face detection program that makes it easier to detect a face when the brightness is increased than during normal shooting is shown.

  In addition, the possibility that a face can be detected increases when the depth of field is wider. Therefore, the depth of field is controlled to be wider than that of a normal through image. When face detection is selected, an operation of reducing the aperture as much as possible or moving the zoom to the wide angle side is executed. Of course, it is not necessary to widen the depth of field more than a predetermined depth of field, and when the face cannot be detected, the width may be gradually increased.

  Specific control will be described with reference to FIG. FIG. 8 is a flowchart showing the control executed in step S103 of FIG.

  First, in step S301, the brightness setting is set to be brighter than the appropriate brightness setting for a normal through image. Subsequently, in step S302, the diaphragm 122 is driven so as to have a predetermined depth of field. Next, in step S303, it is determined whether the brightness can be secured with the current state of the aperture 122. If it has been secured, this flow is terminated, and if it has not been secured, the process proceeds to step S304. In step S304, the image processing circuit 116 performs processing for increasing the sensitivity of the through image. Subsequently, in step S305, it is determined again whether the luminance is secured. If it has been secured, this flow is terminated, and if it has not been secured, the process proceeds to step S306.

  In step S306, it is determined whether or not the zoom lens 118 is in a zoomed state. If it is zoomed, the process proceeds to step S307, and if it is not zoomed, the process proceeds to step 309. In step S307, the zoom lens 118 is moved to the wide angle side. Subsequently, in step S308, it is determined whether a predetermined depth and luminance are secured. If it has been secured, this flow ends. If it has not been secured, the process proceeds to step S309. In step S309, the diaphragm 122 is driven to the open side to ensure brightness.

  Next, another embodiment of face detection control executed by the digital camera 1 will be described.

  In the control shown in FIG. 5, an example is shown in which AF is performed using the center area and the multi-area when face detection cannot be performed to assist face detection.

  In the control in the present embodiment, when a face is not detected, AF is not performed but the focus lens 120 is moved to a predetermined position. For example, first, the focus lens 120 is moved to the closest side. This is to give priority to the closest face. Then, until the face is detected, the focus lens 120 is moved from the closest side by a predetermined movement amount (movement step), and when the face is detected, the lens driving is stopped.

  The moving step of the focus lens 120 is set to the same moving amount as the minimum moving step that can be moved during manual focusing.

  Hereinafter, an example of control in the digital camera 1 of the present embodiment will be specifically described with reference to FIG. FIG. 9 is a flowchart showing the control executed by the CPU 111. The flow shown in FIG. 9 starts when “FACE DETECTION” is selected on the menu screen shown in FIG. 3 and the still image shooting mode is set.

  First, in step S201, it is detected whether the monitor 103 is in a lighting state. When it is in the lighting state, the process proceeds to step S203, and when it is not in the lighting state, the process proceeds to step S202. In step S202, if the monitor 103 is not in the lighting state, the user cannot confirm the face detection result, and thus the monitor 103 is forcibly turned on.

  In step S203, the field luminance is measured using an image captured by the image sensor 117. Subsequently, in step S <b> 204, brightness adjustment is performed based on the photometric field brightness, and a through image is displayed on the monitor 103. In addition, processing for increasing the depth of field is executed. The processing executed in this step has been described with reference to the flowchart shown in FIG.

  In step S205, face detection is performed using the through image. In step S206, it is determined whether a face has been detected. If a face is detected, the process proceeds to step S211, and if no face is detected, the process proceeds to step S207. In step S207, the focus lens 120 is moved to the closest side. Next, in step S208, it is determined again whether a face has been detected. If a face is detected, the process proceeds to step S211, and if no face is detected, the process proceeds to step S209. In step S209, the focus lens 120 is moved in a predetermined movement step. Subsequently, in step S210, it is determined again whether a face has been detected. If a face is detected, the process proceeds to step S211. If no face is detected, the process returns to step S209.

  In step S211, an area is set according to the detected face position and face size, and AF is executed in the area. A display example on the monitor 103 when a face is detected is shown in FIG. In step S212, the detected face information is temporarily stored in the built-in memory 113. By storing the face information detected here, the face information stored in the built-in memory 113 is used to determine the AF area when a face cannot be detected during the half-press operation for finally determining the AF area. decide. The face information stored in the built-in memory 113 is overwritten with new face information when the next face is detected.

  In step S213, it is detected whether the shutter button 101 has been pressed halfway. If it is detected that the half-press operation has been performed, the process proceeds to step S215. If the half-press operation is not detected, the process proceeds to step S214. In step S214, the face information stored in the built-in memory 113 is deleted, and the process returns to step S201.

  In step S215, it is determined whether a face has been detected in order to identify the face to be the final AF area. If a face is detected, the process proceeds to step S216. If no face is detected, the process proceeds to step S217. In step S216, an area set according to the detected face position and size is set as a final AF area, and AF control is executed. A display example on the monitor 103 is shown in FIG. In step S217, it is detected whether the face information stored in step S212 exists in the memory. When it exists, it progresses to step S218, and when it does not exist, it progresses to step S219.

  In step S218, an area based on the stored face information is set as an AF area, and AF control is executed. As a result, even when a face cannot be detected during a half-press operation, the most recently detected face area with a small time difference can be used as the AF area, so that the face can be focused almost without error. In particular, it is possible to cope with a single press operation of pressing the shutter button 101 all the way down. In step S219, AF control with the central area as the AF area is executed. As a result, when the face cannot be detected, the central area, which is an area where the main subject is likely to exist automatically, is automatically used as the AF area, so that the main subject is likely to be focused. Further, since it is not necessary to return to the menu screen and reset the AF area, a photo opportunity is not missed.

In step S220, it is detected whether the shutter button 101 is fully pressed. If the full press operation has been performed, the process proceeds to step S221. If the full press operation has not been performed, the process proceeds to step S222. In step S221, shooting and recording processing is executed. In step S222, it is detected whether the shutter button 101 is half-pressed. If the shutter button 101 is half-pressed, the process returns to step S220. If the shutter button 101 is not half-pressed, the process returns to step S201.

  By executing the above-described control described above, the accuracy of face detection can be improved.

FIG. 1 is an external view of a digital camera 1 according to an embodiment of the present invention. FIG. 2 is a block diagram showing functions of the digital camera 1 according to the embodiment of the present invention. FIG. 3 is a diagram showing a menu screen related to focus displayed on the monitor 103 of the digital camera 1. FIG. 4 is a diagram showing a menu screen related to focus displayed on the monitor 103 of the digital camera 1. FIG. 5 is a flowchart showing the control executed by the CPU 111. FIG. 6 is a diagram illustrating a display example at the time of face detection control displayed on the monitor 103 of the digital camera 1. FIG. 7 is a diagram illustrating a display example during face detection control displayed on the monitor 103 of the digital camera 1. FIG. 8 is a flowchart showing the control executed in step S103 of FIG. FIG. 9 is a flowchart showing the control executed by the CPU 111.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Digital camera 101 ... Shutter button 102 ... Cross key 103 ... Monitor 104 ... Decision button 111 ... CPU
DESCRIPTION OF SYMBOLS 112 ... Face detection part 113 ... Built-in memory 114 ... Operation circuit 115 ... Display circuit 116 ... Image processing circuit 117 ... Image sensor 118 ... Zoom lens 119 ... Zoom driver 120 ... Focus lens 121 ... Focus driver 122 ... Aperture 123 ... Aperture driver 124 ... Memory card slot

Claims (5)

A feature part detector for detecting a feature part of the subject;
A memory for storing feature part information detected by the feature part detection unit;
An imaging control unit that performs imaging control based on the feature part detected by the feature part detection unit;
The imaging control unit performs imaging control based on feature part information stored in the memory when the feature part cannot be detected by the feature part detection unit when taking a recorded image. . The digital camera according to claim 1, wherein
The digital camera according to claim 1, wherein the imaging control unit executes autofocus control using the feature portion as an autofocus area. A feature part detector for detecting a feature part of the subject;
An imaging control unit that performs imaging control based on the feature part detected by the feature part detection unit;
The imaging control unit performs imaging control based on a predetermined predetermined part in the object scene when the characteristic part cannot be detected by the characteristic part detection unit when a recorded image is captured. Digital camera. The digital camera according to claim 3, wherein
The digital camera according to claim 1, wherein the imaging control unit executes autofocus using the feature portion as an autofocus area. The digital camera according to claim 3, wherein
The digital camera according to claim 1, wherein the imaging control unit executes autofocus control using the central part in the object scene as an autofocus area when the feature part cannot be detected by the feature part detection unit.

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