JP4554529B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus, and more particularly to an imaging apparatus that switches a shooting mode depending on a subject.

The imaging apparatus includes a face recognition unit that recognizes whether or not the subject includes a face, and a moving body detection unit that detects whether or not the subject is moving, based on output information of the face recognition unit and the moving body detection unit. There is known a photographing mode automatic setting camera that automatically sets the photographing mode of the camera (for example, Patent Document 1). There is also known an imaging apparatus that determines whether or not a person is photographed and automatically performs strobe light emission suitable for portrait photography (Patent Document 2).
JP 2003-344891 A JP 2003-107567 A

  The inventions described in Patent Documents 1 and 2 do not consider the case of a child whose subject is small. For example, in a child whose movement is quick, camera shake and subject blur increase, or conversely, for a baby who is sleeping quickly, There is a problem that it is easy to make a mistake such as waking up by shutter sound or strobe light emission.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an imaging apparatus that can photograph a child without failure.

  An imaging apparatus according to the present invention includes an imaging element that photographs a subject through a photographing lens, a face detection unit that detects a face of the subject based on an image signal output from the imaging element, and the subject by the face detection unit. After the face is detected, the in-screen face size detection unit detects the size of the face of the subject in the shooting screen, and the distance to the subject is determined based on the focal length and focus position information of the shooting lens. A subject distance calculation unit to be calculated; an actual face size calculation unit that calculates the actual face size of the subject from the face size and the subject distance occupied in the shooting screen; and a subject based on the actual face size A child determination unit that determines whether or not a child is a child, and a child shooting mode that is suitable for child shooting from a normal shooting mode that is suitable for general shooting when the child determination unit determines that the subject is a child In Characterized in that a Ri replacing controller.

  In the child shooting mode, an automatic for child shooting that determines the relationship between the aperture and the shutter speed so that a higher shutter speed is preferentially used than in the normal shooting mode according to the luminance signal of the image signal. An exposure control program is selected.

  In addition, a strobe device that automatically emits strobe light when the brightness signal of the image signal falls below a predetermined brightness threshold is provided. In the child shooting mode, the strobe light is emitted on the higher brightness side than in the normal shooting mode. The brightness threshold value is changed so that is performed.

  In addition, a camera shake warning unit that displays a camera shake warning on a display unit when a shutter speed determined based on a luminance signal of the image signal is slower than a predetermined speed threshold is provided. The threshold value is changed to a value faster than that in the normal photographing mode.

  In addition, a sound generation unit that artificially emits a shutter sound in accordance with the shutter release operation is provided, and generation of the shutter sound by the sound generation unit is stopped in the child photographing mode.

  According to the imaging device of the present invention, the size of the face of the subject is detected based on the image signal output from the imaging device, and it is determined whether the subject is a child based on the size of the face. When it is determined that the subject is a child, the normal shooting mode is switched to the child shooting mode, so that the child can be shot without failure.

  In the child shooting mode, an automatic exposure control program for child shooting that determines the relationship between the aperture and the shutter speed is selected so that a higher shutter speed is preferentially used than in the normal shooting mode. It is preferable to do this.

  In the child photographing mode, it is preferable to change the luminance threshold value as a criterion for determining whether or not to emit the strobe light so that the strobe light is emitted on the higher luminance side than in the normal photographing mode.

  In the child photographing mode, it is preferable to change the speed threshold value for determining whether or not to display a camera shake warning to a value faster than that in the normal photographing mode. In the child photographing mode, it is preferable to stop the generation of the shutter sound by the sound generator.

  In FIG. 1 showing the external appearance of a digital camera according to the first embodiment of the present invention, a photographing lens 12, which is a zoom lens, a flash light emitting unit 14, and an autofocus (AF) assist are provided on the front surface of a camera body 11 of the digital camera 10. A light projection window 15 and a light control sensor 16 are provided. Although not shown, a card slot for mounting a memory card 80 (see FIG. 3) is provided on the left hand side of the camera body 11.

  On the upper surface of the camera body 11, a ring-shaped mode switching dial 18 for switching modes by rotating, a shutter button 19 provided at the center, and a power switch 20 are disposed. The shutter button 19 is configured in a two-stage manner, and in the “half-pressed” state where the shutter button 19 is lightly pressed and stopped, AF and automatic exposure control (AE) are activated to lock the AF and AE, and further press from the “half-press” “full press” In this state, shooting is performed.

  As shown in FIG. 2, a liquid crystal display (LCD) 22, a zoom button 24, a multi-function cross button 26, a menu / execution button 27, a liquid crystal display / return button 28, and a playback mode button 31 are provided on the back of the camera body 11. , A photo mode button 32 is provided.

  The LCD 22 displays a through image on the screen 22a before shooting and is used as an electronic viewfinder. In addition to a preview image of the shot image and a reproduced image read from the memory card 80, there is a risk of camera shake, for example. In some cases, for example, a camera shake warning sentence 33 “There is a risk of camera shake. Zoom to the wide-angle side or switch to flash photography” (see FIG. 5) is displayed.

  In FIG. 3 showing the electrical configuration of the digital camera 10, the CPU 50 controls each unit of the camera body 11 via the I / O bus 52 in accordance with various operation signals input from the operation unit 51. The operation unit 51 includes the mode switching dial 18, the shutter button 19, the power button 20, the zoom button 24, and the like.

  The photographing lens 12 includes a lens 52 and a diaphragm 53. The lens 52 includes a front lens group that is a variator lens and a rear lens group that is a compensator lens having a focusing function. The lens 52 is driven by a lens driving mechanism 54 including a stepping motor to change the optical zoom magnification and adjust the focus. The aperture 53 is driven by an aperture drive mechanism 55 including a motor to switch the aperture diameter. The lens driving mechanism 54 and the aperture driving mechanism 55 are driven by motor drivers 56 and 57 controlled by the CPU 50.

  A CCD image sensor (hereinafter simply referred to as “CCD”) 58 is disposed behind the photographing lens 12. The CCD 58 images subject light that has passed through the photographing lens 12 and is imaged on its light receiving surface, and outputs an analog imaging signal. The CCD 58 is provided with an electronic shutter function for performing a shutter release operation in response to an operation of the shutter button 19. This electronic shutter function is controlled based on a timing signal (clock pulse) input from the CCD drive unit 59.

  When displaying a through image, an imaging signal of a field image (even field or odd field) is read from the CCD 58 and input to the CDS / AMP circuit 60. Further, at the time of actual shooting, the image signal of the frame image is read from the CCD 58 and input to the CDS / AMP circuit 60.

  The CDS / AMP circuit 60 includes a correlated double sampling circuit (CDS) and an amplifier (AMP). The CDS generates R, G, B analog image signals from the imaging signals. The AMP amplifies the R, G, B analog image signals.

  The imaging signal output from the CDS / AMP circuit 60 is converted into digital image data by the A / D converter 61 and then sent to the image input controller 63 of the DSP 62. The image input controller 63 is connected to the CPU 50 via the bus 52, and controls the CCD 58, the CDS / AMP circuit 60, and the A / D converter 61 in accordance with a control command from the CPU 50.

  In addition to the CPU 50 and image input controller 63, the DSP 62 includes an image signal processing circuit 64, compression / decompression processing circuit 65, video encoder 66, SDRAM 70, media controller 71, AE detection circuit 72, AF detection circuit 74, flash memory 75, face A detection processing circuit 76, a subject distance detection circuit 77, a timer circuit 78, and a sound reproduction circuit 79 are connected via the I / O bus 52.

  The image processing circuit 64 performs various image processing such as gradation conversion, white balance correction, and γ correction processing and YC conversion processing on digital R, G, and B image data. Before the shooting process is executed in the shooting mode, the image data (field image) of the through image input to the image signal processing circuit 64 is subjected to simple image processing and YC conversion processing and temporarily stored in the SDRAM 70. Written in.

  The SDRAM 70 has a through-image memory area for storing two consecutive field fractions, and writes to the other while reading from one. The video encoder 66 converts the image data written in the SDRAM 70 into a composite signal and displays it as a through image on the LCD 22.

  When the photographing process is executed, the image data of the frame image input to the image signal processing circuit 64 is subjected to full-scale image processing and YC conversion processing and temporarily stored in the SDRAM 70. After being subjected to compression processing by the compression / decompression processing circuit 65, it is stored in the memory card 80 via the media controller 71.

  The AE detection circuit 72 integrates the luminance signal of the imaging signal and sends the luminance integration value as the obtained photometric data to the CPU 50. In addition, the AF detection circuit 74 decomposes the imaging signal into spatial frequency components, and sends contrast data of high frequency components to the CPU 50. The CPU 50 controls the lens driving mechanism 55 via the motor driver 57 to advance and retract the focusing lens in the optical axis direction and stop it at a position where the contrast of the high frequency component of the subject image is the highest.

  The flash memory 75 is a known nonvolatile memory, and stores various programs and data, various control parameters, and the like.

  The face detection processing circuit 76 reads the image data of the through image (field image) from the SDRAM 70, and detects the subject's face by detecting both eyes of the object from this image data (hereinafter referred to as the through image data).

  When detecting both eyes of the subject, the image of the through image data is divided into a grid (for example, 16 × 16), and the skin and skin are determined from the signal levels of the R, G, and B color signals included in each divided region. A divided area including many estimated skin color pixels is selected. Furthermore, a region having white pixels of the eye part and a black pixel estimated to be a pupil is selected from a region containing many skin-colored pixels, and the position coordinates of both eyes of the subject on the image are obtained from the region, The face position is obtained using the midpoint of the position coordinates as a representative point.

  The face detection processing circuit 76 regards an area including a lot of surrounding skin-colored pixels as a face area from the detected position coordinates of both eyes of the subject. When a plurality of face areas are detected (when two or more pairs of eyes of the subject are detected), the face area near the center of the shooting screen is regarded as the face area of the main subject.

  The subject distance detection circuit 77 uses the flash memory 75 based on the focal length information of the photographing lens 12 (determined by the magnification information (zoom position) of the lens 52) and the focus position information (position information of the rear lens group of the lens 52). The distance to the subject is obtained with reference to a lookup table as shown in Table 1 below stored in advance. This is performed in the subject distance detection circuit 77.

  The CPU 50 detects the length in the vertical direction that the face area obtained from the face detection processing circuit 76 occupies in the entire area of the through image, calculates the length a on the imaging plane of the CCD 58, and From the distance x from the lens 52 to the imaging surface of the CCD 58, as shown in FIG. 4, the subject distance obtained from the subject distance detection circuit 77 is y, and the subject face size (vertical length) is b. Then, since a: b = x: y holds, the face size b of the subject is obtained by b = a · y / x. Note that the distance x from the lens 52 to the imaging surface of the CCD 58 is a constant value determined when the digital camera 10 is designed.

  After obtaining the face size b of the subject, the CPU 50 compares the face size b with a predetermined face size threshold, and if the face size b is smaller than the face size threshold, the subject is a small child. After the determination, the program diagram for shutter control used by reading from the flash memory 75 and the luminance threshold value for strobe light emission are changed for child photographing. The small child is, for example, a child under 5 years old, and the face size threshold is obtained by measuring the face lengths of 100 children under 5 years old, and excluding extremely short faces and long faces. For example, 160 mm.

  Here, the program diagram will be described. The program diagram includes a program diagram (see FIG. 6) of the normal photographing program AE used in the normal photographing mode and a program diagram (see FIG. 7) of the child photographing program AE used in the child photographing mode. It is prepared.

  The values of the aperture and shutter speed shown in FIGS. 6 and 7 are values when the sensitivity (gain) of the CCD 58 is equivalent to ISO200. The aperture value of the aperture 53 is changed by about 1/3 aperture in the range of F2.9 to F8.

  As shown in FIG. 6, the program diagram of the normal photographing program AE shows that the aperture diameter of the aperture 53 decreases stepwise (the aperture value increases) and the shutter speed increases as the subject brightness (EV) increases. Is displaced within a range of 1/2 TV to 1 TV for each aperture value, and as a whole, both the aperture value and the shutter speed sequentially increase as the subject brightness increases.

  Further, in a shooting environment where the subject brightness is lower than 9.5 EV (dark), the aperture 53 cannot be opened more than the aperture value F2.9, so that the sensitivity (gain) of the CCD 58 is increased by one step as the darkness increases. (+1 SV (2 times)) up to 2 steps (+2 SV (4 times)), the shutter speed is between 1/250 (second) and 1/500 (second) to 1/8 (second) Change with.

  As shown in FIG. 7, the program diagram of the child photographing program AE shows that the shutter speed is 9.65 to 10 TV (1/3 of 1/2000 (seconds) in the luminance range of the subject luminance of 13 to 16 EV. The shutter 53 is within the range of slow shutter speed to 1/2000 (second)), and the aperture 53 changes by about 1/3 aperture within the range of F2.9 to F8. In other words, in a relatively bright shooting environment, the shutter speed is always 1/3 steps slower than 1/2000 (seconds), which is a very high shutter speed to 1/2000 (seconds). Even when chasing and shooting, camera shake and subject blur are extremely unlikely.

  Further, in the luminance range of the subject luminance of 9.5 to 13 EV, the shutter speed is an intermediate speed between 1/125 (second) and 1/500 (second) to 1/2000 (second) with F2.9 (open aperture). ), The camera shake is less likely to occur. When the subject brightness becomes darker than 9.5 EV, the sensitivity (gain) of the CCD 58 is increased to 1 step (+1 SV (2 times)) to 2 steps (+2 SV (4 times)) as the darkness increases, and the shutter is released. The speed is changed between an intermediate speed of 1/250 (second) and 1/500 (second) to 1/8 (second).

  Further, the program diagram of the child photographing program AE is not limited to the above example, and as shown in FIG. 8, from the early stage (when the subject brightness becomes darker than 12 EV), as the darkness increases, The sensitivity (gain) is increased by 1 step (+1 SV (2 times)) to 2 steps (+2 SV (4 times)), and the shutter speed is changed between 1/2000 (seconds) and 1/8 (seconds). It may be.

  In addition, when the sensitivity of the CCD 58 is equivalent to ISO 200, the luminance threshold value used when determining whether or not to perform strobe shooting is, for example, 9 EV when it is determined that the subject is not a child, and the subject is a child. Is determined to be 10 EV, for example.

  Further, when the shutter speed becomes slower than the reciprocal of the focal length of the taking lens 12, the CPU 50 displays the camera shake warning sentence 33 (see FIG. 5) to prompt the user to zoom to the wide angle side. The reciprocal of the focal length of the photographic lens 12 is referred to as a camera shake limit speed (a speed threshold that is a criterion for determining whether or not to perform a camera shake warning). If it is determined that the subject is a child, the camera shake limit speed is shifted one step to the high speed side, and a camera shake warning is displayed at an early stage.

  The timer circuit 78 measures a time during which the change amount of the photometric value does not change to a predetermined value or more during live view display. The sound reproduction circuit 79 reads from the flash memory 75 sound effect data such as a pseudo shutter sound that simulates the mechanical shutter drive sound in accordance with a command signal from the CPU 50 and a beep sound that indicates an operation error. Play by. Note that a plurality of types of pseudo shutter sound and beep sound are prepared, and the user can freely select them.

  Next, the operation of the above embodiment will be described. In order to use the digital camera 10, first, the power button 20 is pressed. Thereby, the photographing lens 12 protrudes from the retracted position, and the preparation for photographing is completed. Next, when the still image shooting mode is set, through image display is started (st1) and the timer circuit 78 is reset (st2).

  In the through image display, a field image (even field or odd field) is read from the CCD 58, subjected to simple image processing and YC conversion processing by the image processing circuit 64, and then temporarily written in the SDRAM 70. The video encoder 66 converts the image data written in the SDRAM 70 into a composite signal and displays it as a through image on the LCD 22.

  While the through image is displayed, AF control and AE control are performed at regular time intervals. The luminance signal of the imaging signal is acquired by the AE detection circuit 72, this is integrated, and the obtained luminance integration value (photometric value) is sent to the CPU 50 (st3).

  When the difference between the photometric value of the field image read first from the CCD 58 and the photometric value of the field image read next is calculated, that is, when the change of the photometric value is smaller than a predetermined value (for example, 1 EV) In (st4), since the luminance of the subject has hardly changed, the timer circuit 78 starts operating (st5).

  The through image written in the SDRAM 70 is read into the face detection processing circuit 76, and the face of the subject is detected (st6). If the subject's face is not detected (st7), the AF area is set as the center area of the image (st8). If the subject's face is detected (st7), the AF area is set as the face area of the image (st9). Then, AF processing is executed (st10). In this AF process, the focusing lens in the lens 52 is advanced and retracted in the optical axis direction, and stopped at the position where the contrast of the high frequency component of the subject image is the highest.

  When the shutter button 19 is half-pressed (S1) (st11), the face detection processing circuit 76 detects the face again (st12) and confirms whether or not the face area is in focus (st13). Thereby, there is no possibility that the child who has stopped at the time of displaying the through image suddenly starts moving immediately before shooting and fails.

  If the face area is in focus, the position of the front lens group at that time, that is, the zoom position is detected (st14). From the zoom position and focus position information (position information of the rear lens group of the lens 52), the subject distance detection circuit 77 refers to the lookup table shown in Table 1 to obtain the subject distance (st15).

  The CPU 50 determines the subject face size b (vertical length) by b = a · y / x from the vertical length a of the face area and the subject distance x obtained from the subject distance detection circuit 77. Is obtained (st16).

  The face size b is compared with a predetermined size (face size threshold) (st17), and if the face size b is smaller than the face size threshold, it is determined that the subject is a child. Thereby, the program diagram (see FIG. 7) of the child photographing program AE is read from the flash memory 75 (st18), and the combination of the aperture and shutter speed in the subsequent photographing is determined according to this program diagram.

  Further, the luminance threshold value for strobe light emission is set to 10 EV for child photography (st19), and strobe photography is performed from an early stage when it becomes dark. Further, the camera shake limit speed is shifted one step to the high speed side (st20). At this time, when the shutter speed determined by the program diagram of the child photographing program AE is lower than the hand movement limit speed for the child, the hand movement warning sentence 33 is immediately displayed on the LCD 22.

  When the change in the photometric value is smaller than the predetermined value and the measurement time (timer value) of the timer circuit 78 starting from step 5 is equal to or longer than a predetermined value (for example, 10 seconds). (St21), the sound setting is set to “no sound” to stop the reproduction of the sound effect data such as the pseudo shutter sound and the beep sound by the sound reproduction circuit 79 (st22). This prevents, for example, surprises of a sleeping baby.

  In step 17 (st17), if the face size b is greater than or equal to the face size threshold, it is determined that the subject is an adult. As a result, the program diagram (see FIG. 6) of the normal photographing program AE is read from the flash memory 75 (st23), and the combination of the aperture and shutter speed in the subsequent photographing is determined according to this program diagram. Further, the luminance threshold value for strobe light emission is set to 9 EV for normal photographing (st24). Further, the camera shake limit speed is set for normal use (st25). In addition, the sound setting is set to “sound is present” in which a pseudo shutter sound or a beep sound of a type selected in advance by the user is reproduced (st26).

  Subsequently, when the shutter button 15 is fully pressed, actual shooting is performed by setting the aperture and operating the electronic shutter of the CCD 34 according to the program diagram of the child shooting program AE or the normal shooting program AE. The frame image shot in the actual shooting is subjected to various image processing in the image signal processing circuit 64 through the CDS / AMP circuit 60 and the A / D converter 61, and then compressed in the compression / decompression processing circuit 65. Then, it is recorded on the memory card 80 via the media controller 71.

  In the embodiment described above, when a plurality of face areas are detected, the face area near the center of the shooting screen is regarded as the face area of the main subject. However, the present invention is not limited to this. Instead, for example, the face area detected first or the face area having the largest area in the shooting screen may be regarded as the face area of the main subject.

  Further, in the above embodiment, when no sound is set, it is not particularly set to prohibit strobe light emission, but it is more preferable because it is considered a scene of photographing a sleeping baby or pet. In addition to sound, set the flash to be prohibited.

  Moreover, in the said embodiment, although "child" was 5 years old or less, this invention is not limited to this, For example, it is good also as 4 years old or less or 6 years old or less. Moreover, although the face size threshold value used as a criterion for determining whether or not a child is 160 mm, the present invention is not limited to this, and may be 150 mm or 165 mm, for example.

  Further, the program diagram is an example, and it is only necessary to preferentially use a shutter speed higher than usual for child photographing, and it is needless to say that the program diagram is not limited thereto. The above warning text is an example, and another warning text may be used as long as it represents the same purpose.

  In the above embodiment, the CCD is used as the image sensor. However, the present invention is not limited to this, and a CMOS image sensor, for example, may be used. In the above embodiment, a digital camera is used as the imaging device, but a camera-equipped mobile phone, a camera-equipped PDA, or the like may be used.

It is a perspective view which shows the digital camera which is embodiment of this invention from the front side. It is a top view which shows the back surface of a digital camera. It is a block diagram which shows the electric constitution of a digital camera. It is explanatory drawing which shows how to obtain | require the face size of a to-be-photographed object. It is explanatory drawing which shows an example of a warning sentence. It is a program diagram of the normal photographing program AE. It is a program diagram of program AE for child photography. It is a program diagram of another child photographing program AE. It is a flowchart which shows the main sequences of this invention.

Explanation of symbols

10 Digital Camera 12 Shooting Lens 14 Flash Unit 22 LCD
33 Warning text 50 CPU
58 CCD
76 face detection processing circuit 77 subject distance detection circuit 78 timer circuit 79 audio reproduction circuit

Claims (5)

An image sensor for photographing a subject through a taking lens;
A face detection unit that detects the face of the subject based on the image signal output from the image sensor;
After the face of the subject is detected by the face detection unit, an in-screen face size detection unit that detects the size of the face of the subject in the shooting screen;
A subject distance calculation unit for obtaining a distance to a subject based on information on a focal length and a focus position of the photographing lens;
An actual face size calculation unit that calculates the actual face size of the subject from the size of the face occupied in the shooting screen and the subject distance;
A child determination unit that determines whether the subject is a child based on the actual face size;
An imaging device comprising: a control unit that switches from a normal shooting mode suitable for general shooting to a child shooting mode suitable for child shooting when the child determination unit determines that the subject is a child .   In the child photographing mode, for automatic exposure for child photographing, the relationship between the aperture and the shutter speed is determined so that a higher shutter speed is preferentially used than in the normal photographing mode according to the luminance signal of the image signal. The imaging apparatus according to claim 1, wherein a control program is selected.   A strobe device that automatically emits strobe light when the brightness signal of the image signal falls below a predetermined brightness threshold is provided. In the child photography mode, strobe light is emitted on the higher brightness side than in the normal photography mode. The imaging apparatus according to claim 1, wherein the luminance threshold value is changed so as to be displayed.   A camera shake warning unit for displaying a camera shake warning on a display unit when a shutter speed determined based on a luminance signal of the image signal is slower than a predetermined speed threshold is provided. In the child photographing mode, the speed threshold is set. 4. The imaging device according to claim 1, wherein the imaging device is changed to a value faster than that in the normal photographing mode.   5. A sound generation unit that artificially emits a shutter sound in accordance with a shutter release operation is provided, and generation of a shutter sound by the sound generation unit is stopped in the child photographing mode. Imaging device.

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