JP2008109485A - Imaging apparatus and imaging control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus which has an improved detection rate of a particular object such as a face and enables the power consumption thereof to be reduced, and to provide an imaging control method. <P>SOLUTION: When a through image is displayed on an image display device 26 when a face detection function is set in off, a CPU 10 controls a vertical synchronizing signal to be added to a vertical driver 36V to set a CCD driving mode to a through image reading mode, and the number of horizontal lines to be read out of a CCD 36 is thinned to 1/8. When the face detection function is set to on, the CPU 10 controls the vertical synchronizing signal to be added to the vertical driver 36V to switch the CCD driving mode to a high-resolution mode, and the number of horizontal lines to be read out of the CCD 36 is thinned to 1/4. When the face detection function is switched from on to off, the CPU 10 controls the vertical synchronization signal to be added to the vertical driver 36 V to switch the CCD driving mode to a through image reading mode. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an imaging apparatus and an imaging control method, and more particularly to a technique for detecting a face area from a captured image.

Conventionally, techniques for detecting a face area from a captured image and performing automatic focusing control and automatic exposure control on the detected face area have been proposed (Patent Documents 1 and 2).
JP 2003-107335 A JP 2003-107555 A

  In the techniques of Patent Documents 1 and 2 described above, in order to accurately detect a face area and perform processing based on the detected face area in real time corresponding to the face detection process, it is necessary to acquire an image with high speed and high resolution. There is. However, if the drive mode of the image sensor is switched so as to read a high-resolution image and the clock frequency for reading an image from the image sensor is increased, the power consumption of the apparatus increases.

  The present invention has been made in view of such circumstances, and provides an imaging apparatus and an imaging control method capable of improving the detection rate of a specific object such as a face and reducing power consumption. Objective.

  In order to solve the above problems, an imaging apparatus according to the first aspect of the present invention includes an imaging element that captures an image, an image reading unit that reads an image from the imaging element, and a specific object from the image that is read from the imaging element. Detection means for detecting, object detection function on / off setting means for setting on / off of an object detection function for detecting the specific object by the detection means, and setting the object detection function on The image reading unit is configured to read a high resolution image from the image sensor, and to read a normal resolution image from the image sensor when the object detection function is set to off. Read control means for controlling, and image processing means for processing an image picked up by the image sensor, and when the object detection function is on, the specific object Characterized in that it comprises an image processing means for processing the image based on the image.

  According to the present invention 1, when detecting a specific object (for example, a human face, animal, car, etc.) from an image captured by the image sensor, by increasing the resolution of the image read from the image sensor, The detection accuracy of a specific object can be increased. Furthermore, according to the first aspect of the present invention, the power consumption of the imaging apparatus can be reduced by performing control so as to increase the resolution of an image to be read only when a specific object is detected.

  Invention 2 of the present application further includes display means for displaying a live view image read from the image sensor in the imaging apparatus of Invention 1 of the present application, wherein the detection means detects the specific object from the live view image, The readout control means reads out a high-resolution live view image from the imaging device when the object detection function is set to on, while the imaging control unit reads out the imaging when the object detection function is set to off. The image reading unit is controlled so as to read a live view image having a normal resolution from the element.

  According to the second aspect of the present invention, when a specific object is detected from a live view image read out at a lower resolution than a recording image, the specific object from the live view image is increased by increasing the live view image resolution. Detection accuracy can be increased.

  Invention 3 of the present application increases the imaging clock frequency for driving the image sensor when reading the image when the object detection function is set to on in the imaging apparatus of Invention 1 or 2, and the object When the object detection function is set to OFF, the image pickup clock control means for lowering the image pickup clock frequency is further provided.

  According to the third aspect of the present invention, the time required to read out a high-resolution image can be shortened by increasing the imaging clock frequency when detecting a specific object. As a result, the time required to read the image can be kept constant between the case where the high resolution image is read and the case where the normal resolution image is read.

  Invention 4 of the present application, in the imaging device of Invention 3 of the present application, further includes a battery that supplies operating power for the image sensor, and a battery remaining amount detection unit that detects the remaining amount of the battery, and the imaging clock control unit includes When the object detection function is set to ON, the imaging clock frequency is increased when the remaining amount of the battery is equal to or greater than a predetermined value.

  According to the fourth aspect of the present invention, when detecting a specific object, the imaging clock frequency is increased only when the remaining amount of the battery is greater than or equal to a predetermined value. The battery can be saved by reducing the power consumption required to drive the battery.

  Invention 5 of the present application is the imaging device according to Inventions 1 to 4 of the present application, in which the image processing means is configured to perform focus control, exposure control, or exposure control based on the image of the specific object when the object detection function is on. At least one process of white balance control is performed.

  The imaging control method according to the sixth aspect of the present invention includes an image reading step of reading an image from an image pickup device that picks up an image, a detection step of detecting a specific object from the image read from the image pickup device, An object detection function on / off setting step for setting on / off of an object detection function for performing detection, and reading out a high-resolution image from the image sensor when the object detection function is set to on. When the object detection function is set to OFF, a read control step for controlling reading of the image so as to read an image with a normal resolution from the image sensor, and when the object detection function is ON And an image processing step of processing the image based on the image of the specific object.

  Invention 7 of the present application is the imaging control method of Invention 6 of the present invention, wherein in the detection step, the specific object is detected from a live view image, and in the readout control step, the object detection function is turned on. In addition, the high-resolution live view image is read from the image sensor, and when the object detection function is set to ON, the image reading is performed so that the normal-resolution live view image is read from the image sensor. It is characterized by controlling.

  Invention 8 of the present application increases the imaging clock frequency for driving the image sensor when reading the image when the object detection function is set to ON in the imaging control method of Invention 6 or 7, An imaging clock control step of lowering the imaging clock frequency when the object detection function is set to OFF is further provided.

  A ninth aspect of the present invention is the imaging control method according to the eighth aspect of the present invention, further comprising a remaining battery level detecting step of detecting a remaining amount of a battery that supplies an operating power supply of the imaging device, When the function is set to ON, the imaging clock frequency is increased when the remaining amount of the battery is a predetermined value or more.

  Invention 10 of the present application is the imaging control method according to Inventions 6 to 9 of the present invention, in the image processing step, when the object detection function is on, focusing control and exposure control based on the image of the specific object Alternatively, at least one process of white balance control is performed.

  According to the present invention, only when detecting a specific object (for example, a human face, animal, car, etc.) from an image captured by the image sensor, by increasing the resolution of the image read from the image sensor, The detection accuracy of a specific object can be increased, and the power consumption of the imaging apparatus can be reduced. In addition, according to the present invention, when a specific object is detected from a live view image read out at a lower resolution than a recording image, the specific object from the live view image is increased by increasing the live view image resolution. Object detection accuracy can be increased.

  Hereinafter, preferred embodiments of an imaging apparatus and an imaging control method according to the present invention will be described with reference to the accompanying drawings.

[Overall configuration of imaging device]
FIG. 3 is a block diagram showing the main configuration of the imaging apparatus according to the first embodiment of the present invention. As shown in FIG. 3, the imaging device 1 is an electronic camera having a function of recording and playing back still images and moving images, and the overall operation of the imaging device 1 is controlled by a central processing unit (CPU) 10. The CPU 10 functions as a control unit that controls the camera system according to a predetermined program, and performs various calculations such as an automatic exposure (AE) calculation, an automatic focusing control (AF) calculation, and a white balance (WB) adjustment calculation. Functions as a calculation means. The power supply circuit 12 supplies power to each block of the camera system.

  A ROM (Read Only Memory) 16 and an EEPROM (Electronically Erasable and Programmable Read Only Memory) 18 are connected to the CPU 10 via a bus 14. The ROM 16 stores programs executed by the CPU 10, various data necessary for control, and the like, and the EEPROM 18 stores CCD pixel defect information, various constants / information related to camera operation, and the like.

  A memory (SDRAM, Synchronous Dynamic Random Access Memory) 20 is used as a program development area and a calculation work area for the CPU 10, and is also used as a temporary storage area for image data and audio data. A video random access memory (VRAM) 22 is a temporary storage memory dedicated to image data, and includes an A area and a B area. The memory 20 and the VRAM 22 can be shared.

  The image pickup apparatus 1 includes operation switches 24 such as a power switch, a mode selection switch, an image pickup mode changeover switch (80), a face detection function ON / OFF switch (82), a release button, a menu / OK key, a cross key, and a cancel key. Is provided. Signals from these various operation switches are input to the CPU 10, and the CPU 10 controls each circuit of the imaging apparatus 1 based on the input signals. For example, lens driving control, imaging operation control, image processing control, image data recording / recording Playback control, display control of the image display device 26, and the like are performed.

  The power switch is an operation unit for controlling on / off of the power supply of the imaging apparatus 1.

  The mode selection switch is an operation means for switching between the imaging mode and the reproduction mode.

  The imaging mode switch 80 functions as a switch for switching the imaging mode of the imaging apparatus 10, and depending on the setting position, the scene position (for example, natural photo, person, landscape, sports, night view, underwater imaging, close-up (flowers, etc.) or text text The scene position mode for optimizing the focus and exposure according to the imaging), the auto mode for automatically setting the focus and exposure, the manual mode in which the focus and exposure can be set manually, or the video imaging mode can be switched. .

  The face detection function ON / OFF switch 82 controls ON / OFF of a face detection function for detecting a face from a captured image.

  The release button is an operation button for inputting an instruction to start imaging, and is composed of a two-stroke switch having an S1 switch that is turned on when half-pressed and an S2 switch that is turned on when fully pressed. The menu / OK key is an operation having both a function as a menu button for instructing to display a menu on the screen of the image display device 26 and a function as an OK button for instructing confirmation and execution of selection contents. Key. The cross key is an operation unit for inputting instructions in four directions, up, down, left, and right, and functions as a button (cursor moving operation means) for selecting an item from the menu screen or instructing selection of various setting items from each menu. To do. The up and down keys of the cross key function as a zoom switch for shooting or a playback zoom switch for playback, and the left and right keys function as a frame advance (forward / reverse feed) button in playback mode. To do. The cancel key is used to delete a desired target such as a selection item, cancel an instruction content, or return to the previous operation state. The flash button functions as a button for switching the flash mode, and the flash mode is set to each mode of flash emission / emission prohibition by pressing the flash button under the imaging mode.

  The image display device 26 is composed of a liquid crystal monitor capable of color display. The image display device 26 can be used as an electronic viewfinder for checking the angle of view at the time of imaging, and is used as means for reproducing and displaying a recorded image. The image display device 26 is also used as a display screen for a user interface, and displays information such as menu information, selection items, and setting contents. In addition to the liquid crystal monitor, other types of display devices such as organic EL (electro-luminescence) can be used as the image display device 26.

  The imaging apparatus 1 includes a media socket (media mounting unit) 28, and a recording medium 30 can be mounted on the media socket 28. The form of the recording medium 30 is not particularly limited, and various types such as a xD picture card (registered trademark), a semiconductor memory card represented by smart media (registered trademark), a portable small hard disk, a magnetic disk, an optical disk, a magneto-optical disk, etc. Media can be used. The media controller 32 performs necessary signal conversion in order to transfer input / output signals suitable for the recording medium 30 mounted in the media socket 28.

  Further, the imaging apparatus 1 includes an external connection interface unit (external connection I / F) 34 as a communication unit for connecting to a personal computer or other external devices. The imaging device 1 can exchange data with the external device by connecting the imaging device 1 and the external device using a USB cable or the like (not shown). Note that the communication method between the imaging apparatus 1 and the external device is not limited to USB, and IEEE1394, Bluetooth (registered trademark), and other communication methods may be applied.

[Imaging mode]
Next, the imaging function of the imaging device 1 will be described. When the imaging mode is selected by the mode selection switch, power is supplied to the imaging unit including the color CCD solid-state imaging device 36 (hereinafter, referred to as CCD 36), and imaging is possible.

  The lens unit 38 is an optical unit that includes an imaging lens 44 that includes a focus lens 40 and a zoom lens 42, and a mechanical shutter 46 that also serves as an aperture. Focusing of the imaging lens 44 is performed by moving the focus lens 40 by the focus motor 40A, and zooming is performed by moving the zoom lens 42 by the zoom motor 42A. The focus motor 40A and the zoom motor 42A are driven and controlled by the focus motor driver 40B and the zoom motor driver 42B, respectively. The CPU 10 controls the focus motor driver 40B and the zoom motor driver 42B by outputting control signals.

  The diaphragm 46 is a so-called turret-type diaphragm, and changes the diaphragm value (F value) by rotating a turret plate in which diaphragm holes of F2.8 to F8 are formed. The diaphragm 46 is driven by an iris motor 46A. The iris motor 46A is driven and controlled by an iris motor driver 46B. The CPU 10 controls the iris motor driver 46B by outputting a control signal.

  The light that has passed through the lens unit 38 forms an image on the light receiving surface of the CCD 36. A number of light receiving elements (for example, photodiodes) are two-dimensionally arranged on the light receiving surface of the CCD 36, and primary colors of red (R), green (G), and blue (B) correspond to the respective light receiving elements. The filters are arranged in a predetermined arrangement structure. The CCD 36 has an electronic shutter function for controlling the charge accumulation time (shutter speed) of each light receiving element. The CPU 10 controls the charge accumulation time in the CCD 36 via a timing generator (TG) 48 based on a signal having a predetermined frequency generated in the oscillation element 47. Further, the CPU 10 controls the potential of an OFD (Overflow Drain) with respect to the CCD 36 to adjust the upper limit value of the signal charge accumulated in the light receiving elements constituting the CCD 36.

  The subject image formed on the light receiving surface of the CCD 36 is converted into a signal charge of an amount corresponding to the amount of incident light by each light receiving element. The signal charges accumulated in each light receiving element correspond to the signal charges by the vertical driver 36V and the horizontal driver 36H based on drive pulses (readout pulse, vertical synchronization signal, horizontal synchronization signal) given from the TG 48 in accordance with a command from the CPU 10. It is sequentially read out as an analog voltage signal. Details of driving the CCD will be described later.

  The analog voltage signal read from the CCD 36 is sent to an analog processing unit (CDS / AMP) 50 where the R, G, and B signals for each pixel are sampled and held (correlated double sampling processing) and amplified. Thereafter, it is added to the A / D converter 52 and A / D converted. The dot sequential R, G, B signals converted into digital signals by the A / D converter 52 are stored in the memory 20 via the image input controller 54. The amplification gains of the R, G, and B signals in the analog processing unit 50 correspond to imaging sensitivity (ISO sensitivity), and the CPU 10 sets the imaging sensitivity by adjusting the amplification gain. The imaging sensitivity control method will be described later.

  The image signal processing circuit 56 includes a synchronization circuit (a processing circuit that converts a color signal into a simultaneous expression by interpolating a spatial shift of the color signal associated with the color filter array of a single CCD), a white balance adjustment circuit, a gradation It functions as an image processing means including a conversion processing circuit (for example, a gamma correction circuit), a contour correction circuit, a luminance / color difference signal generation circuit, and the like, and the R stored in the memory 20 is used while utilizing the memory 20 in accordance with a command from the CPU 10. , G and B signals are subjected to predetermined signal processing.

  The R, G, and B signals input to the image signal processing circuit 56 are converted into a luminance signal (Y signal) and a color difference signal (Cr, Cb signal) by the image signal processing circuit 56, and a gradation conversion process (for example, , Gamma correction) and the like are performed. The image data processed by the image signal processing circuit 56 is stored in the VRAM 22.

  When the captured image is output to the image display device 26 on a monitor, the image data is read from the VRAM 22 and sent to the video encoder 58 via the bus 14. The video encoder 58 converts the input image data into a predetermined video signal for display (for example, an NTSC color composite image signal) and outputs the video signal to the image display device 26.

  Image data representing an image for one frame is rewritten alternately between the A area and the B area of the VRAM 22 by the image signal output from the CCD 36. Of the A area and B area of the VRAM 22, the written image data is read from an area other than the area where the image data is rewritten. In this way, the image data in the VRAM 22 is periodically rewritten, and an image signal generated from the image data is supplied to the image display device 26, whereby the image being captured is displayed on the image display device 26 in real time. Is done. The photographer can check the angle of view of the captured image with a live view image (hereinafter referred to as a through image) displayed on the image display device 26.

  The face detection circuit 100 performs face detection processing on the image data output from the CCD 36 when the face detection function is set to ON. As a face detection processing method, for example, there is a method in which a pixel having a color close to a color designated as a skin color is extracted from an original image, and the extracted region is detected as a face region. In this face detection process, for example, in a color space for distinguishing skin color from other colors, a range of skin color on the color space is determined from pre-sampled skin color information, and the color of each pixel falls within the determined range. It is performed by determining whether or not.

  When the release button is pressed halfway and S1 is turned on, the imaging apparatus 1 starts AE and AF processing. That is, the image signal output from the CCD 36 is input to the AF detection circuit 60 and the AE / AWB detection circuit 62 via the image input controller 54 after A / D conversion.

  The AE / AWB detection circuit 62 includes a circuit that divides one screen into a plurality of divided areas (for example, 8 × 8 or 16 × 16) and integrates R, G, and B signals for each divided area. A value is provided to the CPU 10. The CPU 10 detects the brightness of the subject (subject luminance) based on the integrated value obtained from the AE / AWB detection circuit 62, and calculates an exposure value (imaging EV value) suitable for imaging. The CPU 10 determines an aperture value and a shutter speed according to the obtained exposure value and a predetermined program diagram, and controls the electronic shutter and iris of the CCD 36 according to this to obtain an appropriate exposure amount.

  Further, the CPU 10 sends a command to the flash control circuit 64 to operate it when the flash emission mode is set. The flash control circuit 64 includes a main capacitor for supplying a current for causing the flash light emitting unit 66 (discharge tube) to emit light. In accordance with a flash light emission command from the CPU 10, the main capacitor charging control and the flash light emitting unit 66 are performed. The discharge (light emission) timing and discharge time are controlled. As the flash light emitting means, it is also possible to use an LED instead of the discharge tube.

  Further, the AE / AWB detection circuit 62 calculates an average integrated value for each color of the R, G, and B signals for each divided area during automatic white balance adjustment, and provides the calculation result to the CPU 10. The CPU 10 obtains an integrated value of R, an integrated value of B, and an integrated value of G, obtains a ratio of R / G and B / G for each divided area, and calculates R / G and R / G of the values of B / G. The light source type is determined based on the distribution in the color space of the G and B / G axis coordinates, and the gain value (white balance gain) for the R, G, and B signals of the white balance adjustment circuit is determined according to the determined light source type. Control and correct the signal of each color channel.

  For example, contrast AF for moving the focus lens 40 so that the high-frequency component of the G signal of the image signal is maximized is applied to the AF control in the imaging apparatus 1. In other words, the AF detection circuit 60 cuts out a signal in a focus target area set in advance in a high-pass filter that passes only a high-frequency component of the G signal, an absolute value processing unit, and a screen (for example, the center of the screen). An area extraction unit and an integration unit that integrates absolute value data in the AF area are configured.

  The integrated value data obtained by the AF detection circuit 60 is notified to the CPU 10. The CPU 10 calculates a focus evaluation value (AF evaluation value) at a plurality of AF detection points while moving the focus lens 40 by controlling the focus motor driver 40B, and adjusts the lens position where the calculated focus evaluation value is maximized. Determine as the focal position. Then, the CPU 10 controls the focus motor driver 40B so as to move the focus lens 40 to the obtained in-focus position. The calculation of the AF evaluation value is not limited to a mode using the G signal, and a luminance signal (Y signal) may be used.

  When the release button is half-pressed, AE / AF processing is performed when S1 is turned on, the release button is fully pressed, and when S2 is turned on, a recording imaging operation is started. The image data acquired in response to S2 ON is converted into a luminance / color difference signal (Y / C signal) in the image signal processing circuit 56, subjected to predetermined processing such as gamma correction, and then stored in the memory 20. The

  The Y / C signal stored in the memory 20 is compressed according to a predetermined format by the compression / decompression circuit 68 and then recorded on the recording medium 30 via the media controller 32. For example, still images are recorded as JPEG (Joint Photographic Experts Group) format, and moving images are recorded as AVI (Audio Video Interleaving) format image files.

[Playback mode]
When the playback mode is selected by the mode selection switch, the compressed data of the final image file (last recorded image file) recorded on the recording medium 30 is read. When the image file related to the last recording is a still image file, the read image compression data is expanded to an uncompressed Y / C signal via the compression / decompression circuit 68, and the image signal processing circuit 56 and the video encoder After being converted to a display signal via 58, it is output to the image display device 26. As a result, the image content of the image file is displayed on the screen of the image display device 26.

  Switching the playback target image file by operating the right or left key of the four-way controller during single-frame playback of a still image (including the playback of the first frame of a movie) (forward frame reverse / reverse frame forward) Can do. The image file at the frame-advanced position is read from the recording medium 30, and still images and moving images are reproduced and displayed on the image display device 26 in the same manner as described above.

  When an external display such as a personal computer or a television is connected to the imaging apparatus 1 via the video input / output terminal 70 in the playback mode, the image file recorded on the recording medium 30 is the video output circuit 72. Is processed and reproduced and displayed on the external display.

[Imaging control method]
Next, the imaging control method according to the first embodiment of the present invention will be described. FIG. 1 is a timing chart showing a driving control method of the CCD 36 when reading an image signal, and FIG. 2 is a diagram schematically showing image data.

  As shown in FIG. 2A, the number of pixels in the vertical direction (number of horizontal lines) of the image formed on the light receiving surface of the CCD 36 is 1536, and the number of pixels in the horizontal direction is 2048.

  When a through image is displayed on the image display device 26 when the face detection function is set to OFF, the vertical synchronization signal applied to the vertical driver 36V is controlled by the CPU 10 as shown in FIG. The drive mode is set to the through image read mode, and the number of horizontal lines read from the CCD 36 is thinned out to 1/8. Then, as shown in FIG. 2B, the number of horizontal lines read out from the CCD 36 is thinned out to 1/8, and 192 lines out of 1536 horizontal lines are read out. As a result, the time required to read the through image 1 field (192 × 2048) is 1/60 second, and the frame rate of the through image is 30 frames / second (fps). As shown in FIG. 2B, when the number of pixels of the image display device 26 is 240 × 320, a through image with sufficiently high visibility can be obtained.

  When the face detection function is set to ON, as shown in FIG. 1, the vertical synchronization signal applied to the vertical driver 36V is controlled by the CPU 10 to switch the CCD drive mode to the high resolution mode and read out from the CCD 36. The number of horizontal lines is reduced to 1/4. Then, as shown in FIG. 2C, the number of horizontal lines read out from the CCD 36 is thinned out to 1/4, and 384 lines out of 1536 lines in the horizontal direction are read out. Thereby, the resolution of the image read from the CCD 36 is increased, and the detection accuracy of the face area can be increased.

  When the face detection function is switched from ON to OFF, as shown in FIG. 1, the vertical synchronization signal applied to the vertical driver 36V is controlled by the CPU 10, and the CCD driving mode is switched to the through image reading mode.

  The numerical values such as the number of pixels of the image and the number of horizontal lines thinned out at the time of reading are not limited to the above values.

  Next, the imaging control method of the present embodiment will be described with reference to the flowchart of FIG. First, when the power of the imaging apparatus 1 is turned on and the face detection function is set to ON (Yes in step S10), the CCD drive mode is switched to the high resolution mode (step S12), and from the CCD 36 to 384 × 2048. The high-resolution image is read and detection of the face area is started (step S14). In step S24, a face detection frame indicating the detected face area is displayed on the through image of the image display device 26.

  Next, when the release button is pressed halfway and S1 is turned on (Yes in step S16), it is determined whether a face area is detected from the image read from the CCD 36 (step S18). If it is determined in step S18 that no face area has been detected, normal AE control and AF control are performed (step S20).

  On the other hand, when it is determined that a face area is detected (Yes in step S18), AE control and AF control based on the detected face area are performed (step S22). As a method of AE control based on the face area, for example, there is a method in which the AE control is performed based on the integrated value of the image signal of the face area with the face area as a photometric area. Further, as an AF control method based on the face area, for example, there is a method in which the detected face area is used as an AF detection area and AF control is performed so that the face is focused. When a plurality of face areas are detected, for example, the detected face area having the largest size, the face area closest to the imaging device 1, or the face region designated by the user of the imaging device 1 is used. AE control and AF control may be performed based on the above. Furthermore, in the present embodiment, AWB control optimized for the face area may be performed.

  Next, when the release button is fully pressed and S2 is turned on (Yes in step S24), an image is formed on the light receiving surface of the CCD 36 and main exposure is performed (step S26). The recording image signal read from the CCD 36 is subjected to a predetermined process in the image signal processing circuit 56 (step S28), compressed according to a predetermined format by the compression / decompression circuit 68, and then a predetermined file format. Is recorded on the recording medium 30 (step S30).

  According to the present embodiment, when detecting a face area, by increasing the number of horizontal lines read from the CCD 36, the resolution of the image read from the CCD 36 can be increased and the detection accuracy of the face area can be increased. Furthermore, in this embodiment, the power consumption of the imaging apparatus 1 can be reduced by controlling the number of horizontal lines read from the CCD 36 to be increased only when detecting a face area.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  FIG. 5 is a block diagram showing a CCD drive unit of an imaging apparatus according to the second embodiment of the present invention.

  The clock generator 82 generates an imaging clock having a predetermined frequency (for example, 36 MHz) from the pulse output from the oscillation element 47.

  The changeover switch 84 switches the imaging clock transmission path in accordance with the imaging clock switching control signal input from the CPU 10. In FIG. 5, the changeover switch 84 is illustrated as a mechanical switch, but an electrical switch may be used. When the face detection function is set to ON, the CPU 10 switches the changeover switch 84 by the imaging clock switching control signal so that the imaging clock having an imaging clock frequency of 36 MHz is directly input to the timing generator (TG) 48. To do. On the other hand, when the face detection function is set to OFF, the imaging clock is input to the ½ divider 86 and the imaging clock frequency is divided into 18 MHz and then input to the TG 48.

  The timing generator (TG) 48 generates a vertical synchronization signal and a horizontal synchronization signal from the imaging clock output from the clock generator 82, and outputs them to the vertical driver 36V and the horizontal driver 36H, respectively.

  FIG. 6 is a timing chart showing the drive control method of the CCD 36 according to this embodiment. As shown in FIG. 6, when a through image is displayed on the image display device 26 when the face detection function is set to OFF, the imaging clock is divided by the ½ divider 86 to 18 MHz. After that, the input to the TG 48, and the CCD drive mode is set to the through image read mode for reading out the number of horizontal lines by １ ／. As a result, 192 lines are read out at the imaging clock frequency of 18 MHz, and the frame rate of the through image becomes 30 fps.

  When the face detection function is set to ON, as shown in FIG. 6, the changeover switch 84 is switched and a 36 MHz imaging clock is input to the TG 48, and the CCD driving mode reduces the number of horizontal lines to 1 /. It is switched to the high resolution mode by thinning out by 4. As a result, when the number of horizontal lines read from the CCD 36 is 384 lines double that when the face detection function is set to OFF, by setting the imaging clock frequency to 36 MHz, the frame rate of the through image is 30 fps. Will remain.

  When the face detection function is switched from ON to OFF, the changeover switch 84 is switched, and the imaging clock is frequency-divided to 18 MHz by the 1/2 frequency divider 86 and then input to the TG 48 and is driven by the CCD. The mode is set to the through image readout mode.

  The numerical values such as the number of pixels of the image, the number of horizontal lines thinned out at the time of reading, and the imaging clock frequency are not limited to the above values.

  Next, the imaging control method of this embodiment will be described with reference to the flowchart of FIG. First, when the power of the imaging apparatus 1 is turned on and the face detection function is set to ON (Yes in step S50), the imaging clock is input directly to the TG 48 without passing through the 1/2 frequency divider 86. The changeover switch 84 is switched to switch the imaging clock frequency from 18 MHz to 36 MHz (step S52). Then, the CCD drive mode is switched to the high resolution mode (step S54), and a high resolution image of 384 × 2048 is read from the CCD 36 and the detection of the face area is started (step S56).

  Next, when the release button is pressed halfway and S1 is turned on (Yes in step S58), it is determined whether a face area is detected from the image read from the CCD 36 (step S60). If it is determined in step S60 that no face area has been detected, normal AE control and AF control are performed (step S62).

  On the other hand, when it is determined that a face area is detected (Yes in step S60), AE control and AF control based on the detected face area are performed (step S64). Note that the AE control and AF control based on the face area are the same as those in the first embodiment.

  Next, when the release button is fully pressed and S2 is turned on (Yes in step S66), an image is formed on the light receiving surface of the CCD 36 and main exposure is performed (step S68). The recording image signal read from the CCD 36 is subjected to a predetermined process in the image signal processing circuit 56 (step S70), compressed according to a predetermined format by the compression / decompression circuit 68, and then a predetermined file format. Is recorded on the recording medium 30 (step S72).

  According to the present embodiment, when detecting a face area, it is necessary to increase the number of horizontal lines read from the CCD 36 and simultaneously increase the imaging clock frequency to read a high-resolution image with a large number of horizontal lines. Time can be shortened. As a result, the detection accuracy of the face area can be improved, and at the same time, the frame rate of the through image display can be made the same as when reading an image with normal resolution. Furthermore, in the present embodiment, the power consumption of the imaging apparatus 1 can be reduced by increasing the number of horizontal lines read from the CCD 36 and increasing the imaging clock frequency only when detecting the face area.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. In the following description, the same components as those in the above embodiment are denoted by the same reference numerals and description thereof is omitted.

  FIG. 8 is a block diagram showing a main configuration of an image pickup apparatus according to the third embodiment of the present invention, and FIG. 9 is a block diagram showing a CCD drive unit of the image pickup apparatus of FIG. The imaging apparatus 1 according to the present embodiment further includes a remaining battery level check circuit 102 that detects the remaining battery level of the power supply circuit 12. In the present embodiment, when the face detection function is set to ON, the imaging clock frequency is increased when the remaining battery level is greater than or equal to a predetermined value.

  Next, the imaging control method of the present embodiment will be described with reference to the flowchart of FIG. First, when the power of the imaging apparatus 1 is turned on and the face detection function is set to ON (Yes in step S80), the remaining battery level is detected by the remaining battery level check circuit 102, and the remaining battery level is predetermined. It is determined whether the value is greater than or equal to the value (step S82). In step S82, when the remaining battery level is equal to or greater than the predetermined value, the changeover switch 84 is switched so that the imaging clock is directly input to the TG 48 without passing through the 1/2 divider 86, and the imaging clock frequency is changed. Is switched from 18 MHz to 36 MHz (step S84). On the other hand, when the remaining amount of the battery is less than the predetermined value (No in step S82), the process proceeds to step S86. Then, the CCD drive mode is switched to the high resolution mode (step S86), a high resolution image of 384 × 2048 is read from the CCD 36, and the detection of the face area is started (step S88).

  Next, when the release button is pressed halfway and S1 is turned on (Yes in step S90), it is determined whether a face area is detected from the image read from the CCD 36 (step S92). If it is determined in step S92 that no face area has been detected, normal AE control and AF control are performed (step S94).

  On the other hand, when it is determined that a face area has been detected (Yes in step S92), AE control and AF control based on the detected face area are performed (step S96). Note that the AE control and AF control based on the face area are the same as in the above embodiment.

  Next, when the release button is fully pressed and S2 is turned on (Yes in step S98), an image is formed on the light receiving surface of the CCD 36 and main exposure is performed (step S100). The recording image signal read from the CCD 36 is subjected to a predetermined process in the image signal processing circuit 56 (step S102), compressed according to a predetermined format by the compression / decompression circuit 68, and then a predetermined file format. Is recorded on the recording medium 30 (step S104).

  According to the present embodiment, when the face detection function is set to ON, the imaging clock frequency is increased only when the remaining amount of the battery is greater than or equal to a predetermined value. The battery can be saved by reducing the power consumption required to drive the battery.

  In the above embodiment, the number of horizontal lines read from the CCD 36 is switched to two stages, but may be switched to three or more stages. For example, when a face area is not detected when the face detection function is set to ON, the number of horizontal lines read from the CCD 36 may be further increased to increase the image resolution. Further, when an operation input indicating that the face area detected by the user of the imaging apparatus 1 is incorrect is performed, the number of horizontal lines may be further increased. In the above case, the imaging clock frequency may be increased in multiple steps in proportion to the number of horizontal lines.

  In the above embodiment, the number of horizontal lines read from the CCD 36 is increased in the face area detection imaging mode. For example, when AF is performed (for example, when S1 is on), a frame used for AF detection is used. The accuracy of AF can be improved by reading in the high resolution mode. Moreover, when performing AE, the precision of AE can be improved by reading the flame | frame used for calculation of an integrated value in high resolution mode. Furthermore, the same control may be performed when detecting a specific object other than the face (for example, an animal, a car, etc.). For example, when the imaging mode is set to the scene position mode (sports), the accuracy of AF and AE with respect to a moving subject can be increased by driving the CCD 36 in the high resolution mode.

  Note that the imaging drive method according to the above-described embodiment can also be provided as a program for an electronic camera.

Timing chart showing drive control method of CCD 36 when reading image signal Diagram showing image data 1 is a block diagram showing the main configuration of an imaging apparatus according to a first embodiment of the present invention. 1 is a flowchart showing an imaging control method according to the first embodiment of the present invention. FIG. 5 is a block diagram showing a CCD drive unit of an imaging apparatus according to a second embodiment of the present invention. Timing chart showing the drive control method of the CCD 36 according to the second embodiment of the present invention The flowchart which shows the imaging control method which concerns on the 2nd Embodiment of this invention. The block diagram which shows the main structures of the imaging device which concerns on the 3rd Embodiment of this invention. FIG. 5 is a block diagram showing a CCD drive unit of an imaging apparatus according to a third embodiment of the present invention. 7 is a flowchart showing an imaging control method according to the third embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Imaging device, 10 ... Central processing unit (CPU), 12 ... Power supply circuit, 14 ... Bus, 16 ... ROM, 18 ... EEPROM, 20 ... Memory (SDRAM), 22 ... VRAM, 24 ... Operation switch, 26 ... Image Display device 28 ... Media socket 30 ... Recording medium 32 ... Media controller 34 ... External connection interface (external connection I / F) 36 ... CCD 38 ... Lens unit 40 ... Focus lens 42 ... Zoom lens 44 ... Imaging lens, 46 ... Mechanical shutter combined with aperture, 47 ... Oscillating element, 48 ... Timing generator (TG), 50 ... Analog processing unit (CDS / AMP), 52 ... A / D converter, 54 ... Image input controller 56 ... Image signal processing circuit, 58 ... Video encoder, 60 ... AF detection circuit, 62 ... AE / A B detection circuit, 64 ... flash light emitting unit, 66 ... flash control circuit, 68 ... compression / decompression circuit, 70 ... video input / output terminal, 72 ... video output circuit, 80 ... imaging mode switch, 82 ... clock generator, 84 ... switch Switch, 86 ... 1/2 frequency divider, 100 ... Face detection circuit, 102 ... Battery remaining amount check circuit

Claims (10)

An image sensor for capturing an image;
Image reading means for reading an image from the image sensor;
Detecting means for detecting a specific object from an image read from the image sensor;
An object detection function on / off setting means for setting on / off of an object detection function for detecting the specific object by the detection means;
When the object detection function is set to ON, a high resolution image is read from the image sensor, while when the object detection function is set to OFF, a normal resolution image is read from the image sensor. A reading control means for controlling the image reading means so as to read;
Image processing means for processing an image picked up by the image pickup device, wherein the image processing means for processing the image based on the image of the specific object when the object detection function is on;
An imaging apparatus comprising: Further comprising display means for displaying a live view image read from the image sensor;
The detection means detects the specific object from the live view image,
The readout control means reads out a high-resolution live view image from the imaging device when the object detection function is set to on, while the imaging control unit reads out the imaging when the object detection function is set to off. 2. The image pickup apparatus according to claim 1, wherein the image reading unit is controlled so as to read a live view image having a normal resolution from the element.   When the object detection function is set on, the imaging clock frequency for driving the image sensor when reading the image is increased, and when the object detection function is set off, the imaging clock The imaging apparatus according to claim 1, further comprising imaging clock control means for reducing the frequency. A battery for supplying operating power of the image sensor;
A battery remaining amount detecting means for detecting the remaining amount of the battery;
The said imaging clock control means raises the said imaging clock frequency when the remaining amount of the said battery is more than predetermined value, when the said object detection function is set to ON. Imaging device.   The image processing means performs at least one of focus control, exposure control, and white balance control based on an image of the specific object when the object detection function is on. The imaging device according to any one of claims 1 to 4. An image reading step of reading an image from an image pickup device that picks up an image;
A detection step of detecting a specific object from an image read from the image sensor;
An object detection function on / off setting step for setting on / off of an object detection function for detecting the specific object;
When the object detection function is set to ON, a high resolution image is read from the image sensor, while when the object detection function is set to OFF, a normal resolution image is read from the image sensor. A reading control step for controlling reading of the image so as to read;
An image processing step of processing the image based on the image of the specific object when the object detection function is on;
An imaging control method comprising: In the detection step, the specific object is detected from a live view image,
In the readout control step, when the object detection function is set to ON, a high-resolution live view image is read from the imaging element, while when the object detection function is set to ON, the imaging The imaging control method according to claim 6, wherein reading of the image is controlled so as to read a live view image having a normal resolution from the element.   When the object detection function is set on, the imaging clock frequency for driving the image sensor when reading the image is increased, and when the object detection function is set off, the imaging clock The imaging control method according to claim 6 or 7, further comprising an imaging clock control step of decreasing the frequency. A battery remaining amount detecting step of detecting a remaining amount of a battery that supplies an operation power source of the image sensor;
9. The imaging clock frequency control step according to claim 8, wherein, in the imaging clock control step, when the object detection function is set to ON, the imaging clock frequency is increased when the remaining amount of the battery is equal to or greater than a predetermined value. Imaging control method.   In the image processing step, when the object detection function is on, at least one of focus control, exposure control, and white balance control is performed based on the image of the specific object. The imaging control method according to any one of claims 6 to 9.

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