JP2009139423A - Imaging apparatus and subject distance calculating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image pickup apparatus and a subject distance calculating method by which a subject distance can be calculated by utilizing an existing mechanism without using a special means. <P>SOLUTION: When a through-image is captured, camera shake (shift shake (X-shift, Y-shift)) and rotation shake (yaw pitch) are detected by a sensor and the like. At the same time as this, an amount of movement, which is an amount of difference between image data before and after the camera shake, is detected. The effect of rotation shake is removed from the amount of movement. Based on the amount of movement obtained from image data from which the effect of the rotation shake is removed, the shift shake, and a focal distance, the distance of a subject is calculated, thereby capturing distance measurement information by the use of an existing mechanism with no cost. The calculated distance of the subject is used for limiting an AF search range or adjusting a quantity of light suitable for flash. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an imaging device and a subject distance calculation method, and more particularly to an imaging device and a subject distance calculation method that can estimate a subject distance without using special means.

  Patent Document 1 describes a technique for acquiring images with different phases using a lens driving mechanism for camera shake correction, and calculating a distance to a subject from a lens driving amount, an image correlation amount, and a focal length. Yes.

  In Patent Document 2, a first AF area image of a frame imaged at a certain arbitrary focus lens position and a second AF area image of a frame imaged by moving the focus lens slightly are acquired. The point spread coefficients of the AF area image and the second AF area image are obtained, and the focal position and direction are calculated from the point image radius of the first AF area image and the point image radius of the second AF area image. The technology to do is described.

Patent Document 3 describes a technique that includes a plurality of imaging units and calculates a distance to a subject based on a phase difference, a base line length, and a focal length of images captured by the respective imaging units. Yes.
JP 2002-296491 A JP 2000-199845 A Japanese Patent Laid-Open No. 2005-43225

  However, the technique described in Patent Document 1 has a problem in that a live view image (through image) is displayed in a greatly blurred manner because an image having a phase difference is obtained by moving the lens greatly.

  Further, the technique described in Patent Document 3 has a problem that since an image having a phase difference is acquired using a plurality of imaging units, it can only be applied to an apparatus including a plurality of imaging units. In addition, there is a problem that the size of the apparatus becomes large by providing a plurality of imaging means.

  Note that the technique described in Patent Document 2 estimates the subject distance from the lens position when focused, and cannot directly calculate the distance to the subject.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an imaging device and a subject distance calculation method capable of calculating a subject distance using an existing mechanism without using a special means. To do.

  In order to achieve the object, the imaging apparatus according to claim 1 forms an image on the imaging element by a shift amount detection unit that detects a shift amount in a direction orthogonal to the imaging optical axis of the imaging apparatus and a shooting optical system. An acquisition unit that acquires image data of a captured subject image, and an amount of movement of an image on the image sensor according to the shift amount of the imaging device detected by the shift amount detection unit from the image data acquired by the acquisition unit Subject distance based on the motion amount detection means, the motion amount detected by the motion amount detection means, the shift amount of the imaging device detected by the shift amount detection means, and the focal length of the photographing optical system Subject distance calculating means for calculating

  According to the imaging apparatus of the first aspect, the shift amount of the imaging apparatus, that is, the direction and amount of shift blur (X shift, Y shift) of the imaging apparatus is detected, and shift blur occurs in the imaging apparatus, so The amount of movement of the image on the image sensor generated in the image data of the subject image formed on the image sensor by the system is detected. The subject distance is calculated based on the shift amount of the imaging device, the motion amount of the image data, and the focal length of the photographing optical system. Thereby, it is possible to acquire distance measurement information without using a special means and using an existing mechanism without cost.

  The image pickup apparatus according to claim 2 is the image pickup apparatus according to claim 1, wherein camera shake detection means for detecting rotational shakes in the vertical and horizontal directions of the image pickup apparatus, and rotation detected by the camera shake detection means. Based on the shake, at least a part of the optical member of the photographing optical system or the image pickup device is driven to correct the camera shake of the image pickup apparatus, and the camera shake correction means corrects the camera shake of the image pickup apparatus. And an image data acquisition control unit that causes the acquisition unit to acquire the image data corrected in the above-described manner.

  According to the image pickup apparatus of the second aspect, the rotational shake of the image pickup apparatus is obtained from the image data acquired by the image pickup element by the mechanical shake correcting unit that moves the optical member or the image pickup element that is movably disposed. Remove the effects of. Image data from which rotational blur is removed is acquired, and a subject distance is calculated based on the image data. In this way, by using the camera shake correction mechanism that is an existing mechanism, distance measurement information can be acquired without cost. In addition, an accurate subject distance can be calculated by removing the influence of rotational blur (yaw, pitch) of the imaging device from the image data acquired by the imaging device.

  The image pickup apparatus according to claim 3 is the image pickup apparatus according to claim 1 or 2, wherein the camera shake detection means includes the shift amount detection means.

  The imaging device according to claim 4 is the imaging device according to any one of claims 1 to 3, wherein a face detection unit that detects a human face from image data acquired by the imaging device, and the face detection unit. Image data acquisition control means for causing the acquisition means to acquire image data of a region in which a person's face has been detected.

  According to the imaging apparatus of the fourth aspect, the face of a person is detected from the image data acquired by the imaging device, and the subject distance is calculated based on the image data of the area where the face is detected. Thus, accurate distance measurement can be performed by calculating the subject distance based on the main subject.

  An imaging apparatus according to a fifth aspect is the imaging apparatus according to any one of the first to fourth aspects, further comprising an acquisition control unit that causes the acquisition unit to acquire image data of a live view image.

  According to the imaging device of the fifth aspect, the subject distance is calculated based on the image data of the live view image. Thus, by calculating the subject distance before shooting, the calculated distance measurement information can be used during shooting.

  The imaging apparatus according to claim 6 is the imaging apparatus according to any one of claims 1 to 5, wherein the imaging optical system is moved over a focus adjustment range, and the imaging element is moved every time the imaging optical system moves by a predetermined amount. Is an automatic focusing control unit that outputs an image signal from the image signal and performs focusing control of the photographing optical system based on a contrast component of the subject obtained from the output image signal, and is calculated by the subject distance calculating unit. And an automatic focusing control means for performing focusing control by limiting a range in which the photographing optical system is moved based on the subject distance.

  According to the imaging device of the sixth aspect, the imaging optical system is moved over a limited focus adjustment range based on the calculated subject distance, and an image is captured from the imaging element each time the imaging optical system moves by a predetermined amount. A signal is output, and focusing control of the photographing optical system is performed based on the contrast component of the subject obtained from the output image signal. In this way, by using the calculated subject distance and performing focus control with a limited focus adjustment range, the time required for focus control can be shortened. Further, by shortening the time required for focusing control, it is possible to capture an image according to the operator's intention without missing a photo opportunity.

  The imaging device according to claim 7 controls the light emission of the flash light source based on the flash light source and the subject distance calculated by the subject distance calculation means in the imaging device according to any one of claims 1 to 6. And a light emission control means.

  According to the imaging device of claim 7, the flash light source emits light based on the subject distance calculated based on the parallel movement amount of the image data, the direction and amount of the parallel movement of the imaging device, and the focal length. To control. Thereby, the subject can be irradiated with a flash having an appropriate amount of light according to the subject distance. Further, when the subject distance is a short distance, white stripes can be prevented by emitting a flash.

  An imaging apparatus according to an eighth aspect of the present invention is the imaging apparatus according to the seventh aspect, wherein the light from the flash light source reaches the subject based on the subject distance calculated by the subject distance calculating means. And a warning unit that issues a warning when the determination unit determines that the light from the flash light source does not reach the subject.

  According to the imaging apparatus of the eighth aspect, it is determined whether or not the light from the flash light source reaches the subject, and if not, the photographer is warned. Thereby, appropriate flash photography can be performed.

  The subject distance calculation method according to claim 9, in synchronization with the step of detecting the direction and amount of translation and rotation of the imaging device, and the detection of the direction and amount of translation and rotation of the imaging device, Based on the step of acquiring image data of the subject image formed on the image sensor by the imaging optical system and the detected direction and amount of rotation of the imaging device, Removing the influence of rotation, detecting the parallel movement amount of the image data from which the influence of the rotation of the imaging device has been removed, and detecting the parallel movement amount of the subsequent image with respect to the preceding image; Calculating a subject distance based on the detected parallel movement amount, the detected direction and amount of the parallel movement of the imaging device, and the focal length of the photographing optical system, You .

  According to the present invention, the subject distance can be calculated using an existing mechanism without using any special means.

  The best mode for carrying out a camera according to the present invention will be described below in detail with reference to the accompanying drawings.

<First Embodiment>
FIG. 1 is a front perspective view showing an embodiment of an electronic apparatus according to the present invention, and FIG. 2 is a rear perspective view thereof. This electronic device is a digital camera that receives light passing through a lens with an imaging device, converts the light into a digital signal, and records it on a recording medium.

  The camera body 12 of the digital camera 10 is formed in a horizontally-long rectangular box shape, and as shown in FIG. 1, a photographing lens 13, a flash 16, an AF auxiliary light lamp 18 and the like are provided on the front surface. On the top surface, a shutter button 22, a mode lever 24, a power button 26, and the like are provided. A slot cover 11 that can be freely opened and closed is provided on the side surface. Inside the slot cover 11, a memory card slot 14 for mounting a memory card is provided.

  On the other hand, as shown in FIG. 2, a monitor 28, a zoom button 30, a playback button 32, a function button 34, a cross button 36, a MENU / OK button 38, a DISP / BACK button 40, etc. are provided on the back of the camera body 12. It has been.

  Note that a bottom surface (not shown) is provided with a tripod screw hole and an openable / closable battery cover for housing the battery inside.

  The lens 13 is constituted by a retractable zoom lens, and is extended from the camera body 12 when the power of the digital camera 10 is turned on by the power button 26. In addition, since the zoom mechanism and the retracting mechanism of the lens 13 are well-known techniques, description of the specific configuration is omitted here.

  The memory card slot 14 is a connection unit for mounting a memory card in which various data such as image data and audio data of a photographed subject are recorded.

  The flash 16 is configured using, for example, a xenon tube as a light source, and is formed so that the amount of light emission can be adjusted. In addition to a xenon tube, a flash using a high-luminance LED as a light source can also be used.

  The AF auxiliary light lamp 18 is configured, for example, as a high-intensity LED, and emits light as necessary during AF.

  The shutter button 22 is composed of a two-stroke switch composed of so-called “half press” and “full press”. When the shutter release button 22 is half-pressed, the digital camera 10 performs shooting preparation processing, that is, each of AE (Automatic Exposure), AF (Auto Focus), and AWB (Automatic White Balance). When the image is processed and fully pressed, the image is captured and recorded.

  The mode lever 24 functions as a shooting mode setting means for setting the shooting mode of the digital camera 10, and the shooting mode of the digital camera 10 is set to various modes according to the setting position of the mode dial. For example, an “auto shooting mode” in which an aperture, a shutter speed, etc. are automatically set by the digital camera 10, a “movie shooting mode” for moving image shooting, a “person shooting mode” suitable for portrait shooting, and a moving subject shooting “Sports shooting mode”, “Scenery shooting mode” suitable for landscape shooting, “Night scene shooting mode” suitable for sunset and night scene shooting, the scale of the aperture is set by the photographer, and the shutter speed is automatically set by the digital camera 10 The photographer sets the “aperture priority shooting mode” to be set automatically, the shutter speed is set by the photographer, and the “shutter speed priority shooting mode” in which the digital camera 10 automatically sets the aperture scale, the aperture, the shutter speed, etc. “Manual shooting mode” to be set, “Camera shake correction mode” for automatically detecting and correcting camera shake.

  The power button 26 is used to turn on / off the power of the digital camera 10, and is turned on / off when pressed for a predetermined time (for example, 2 seconds).

  The monitor 28 is composed of a liquid crystal display capable of color display. The monitor 28 is used as an image display panel for displaying a photographed image in the reproduction mode, and is used as a user interface display panel for performing various setting operations. In the shooting mode, a live view image (through image) is displayed as necessary, and is used as an electronic viewfinder for viewing angle confirmation.

  The zoom button 30 is used for a zoom operation of the photographic lens 13 and includes a zoom tele button for instructing zooming to the telephoto side and a zoom wide button for instructing zooming to the wide-angle side.

  The playback button 32 is used for an instruction to switch to the playback mode. That is, the digital camera 10 is switched to the playback mode when the playback button 32 is pressed during shooting. When the playback button 32 is pressed while the power is off, the digital camera 10 is activated in the playback mode.

  The function button 34 is used to call up various setting screens for shooting and playback functions. That is, when this function button 34 is pressed during shooting, a setting screen for image size (number of recorded pixels), sensitivity, etc. is displayed on the monitor 28. When this function button 34 is pressed during playback, the image is erased on the monitor 28. A print reservation (DPOF) setting screen is displayed.

  The cross button 36 functions as direction instruction means for inputting instructions in four directions, up, down, left, and right, and is used, for example, for selecting a menu item on a menu screen.

  The MENU / OK button 38 functions as a button (MENU button) for instructing transition from the normal screen to the menu screen in each mode, and functions as a button (OK button) for instructing selection confirmation, execution of processing, and the like. To do.

The DISP / BACK button 40 is used for a display content switching instruction (DISP function) of the monitor 28 and an instruction for canceling an input operation (BACK function), and is assigned according to the setting state of the digital camera 10. The function is switched.
[Internal configuration of digital camera 10]
FIG. 3 is a block diagram showing an electrical configuration of the digital camera 10 of the present embodiment. As shown in the figure, the digital camera 10 includes a CPU 110, an operation unit (shutter button 22, mode lever 24, power button 26, zoom button 30, play button 32, function button 34, cross button 36, MENU / OK button 38. , DISP / BACK button 40, etc.) 112, ROM 114, RAM 116, buffer memory 118, imaging optical system 124, aperture / focus / zoom control unit 126, image sensor 128, imaging control unit (timing generator) 130, image signal processing unit 132 , Subject distance calculation unit 134, AE / AWB detection unit 136, AF detection unit 138, camera shake correction control unit 140, flash control unit 142, AF auxiliary light lamp control unit 144, image recording unit 146, display control unit 150, face It comprises a detection unit 152 and the like.

  The CPU 110 functions as a control unit that performs overall control of the overall operation of the digital camera 10, and also functions as a calculation unit that performs various types of calculation processing. The CPU 110 is configured according to a predetermined control program based on an input from the operation unit 112. Control each part.

  The ROM 114 stores firmware, which is a control program executed by the CPU 110, various data necessary for control, camera setting values, captured image data, and the like. As will be described later, the captured image data is normally recorded on the memory card. However, when the user selects it, the memory card is not loaded, or the memory card has insufficient capacity, the ROM 114 To be recorded.

  The RAM 116 is used as a work area for the CPU 110 and as a temporary storage area for image data.

  The buffer memory 118 is used as a temporary storage area dedicated to display image data.

  The photographing optical system 124 includes a photographing lens 13, a diaphragm, and a shutter, and each component is operated by being driven by a driving unit configured by an actuator such as a motor. For example, the focus lens group constituting the photographing lens 13 is driven by a focus motor to move in the front-rear direction, and the zoom lens group is driven by the zoom motor to move in the front-rear direction. The diaphragm is driven by a diaphragm motor to expand and contract, and the shutter is driven by a shutter motor to open and close.

  The motion amount detection unit 120 translates the parallel movement amount between the previously acquired through-image image data (previous image) and the next acquired through-image image data (subsequent image). Is detected. That is, as shown in FIG. 4, the motion amount detection unit 120 firstly combines the previous image f (i, j) with the subsequent image g (i, j) f (i, j) + g (i , j). After that, the correlation value between the previous image f (i, j) and the subsequent image g (i, j) is calculated while moving (shifting) the previous image f (i, j) little by little. Is detected as the amount of movement of the image between the preceding image f (i, j) and the subsequent image g (i, j).

  The camera shake amount detection unit 122 detects rotation (rotation blur) of the digital camera 10 with a gyro sensor or the like, and detects parallel movement (shift blur) of the digital camera 10 with a speed sensor or the like. The rotation blur is the direction and blur amount (hereinafter referred to as rotational blur amount) of the yaw and pitch shown in FIG. 5, and is added, that is, the direction and blur amount of X shift and Y shift shown in FIG. ). Note that the sensor used in the camera shake amount detection unit 122 is not limited to the above-described sensor, and various means can be used.

  A diaphragm / focus / zoom control unit 126 controls the driving unit of the photographing optical system 124 in accordance with a command from the CPU 110, and controls the operations of the photographing lens 13, the diaphragm, and the shutter.

  The imaging device 128 is configured by, for example, a color CCD having a predetermined color filter array, and electronically captures an image of a subject formed by the photographing optical system 124.

  The imaging control unit (timing generator, TG) 130 outputs a timing signal for driving the imaging element 128 in response to a command from the CPU 110.

  The image signal processing unit 132 is for the purpose of reducing correlated double sampling processing (noise (particularly thermal noise) included in the output signal of the image sensor) and the like for the image signal output from the image sensor 128. The process of obtaining accurate pixel data by taking the difference between the feed-through component level and the pixel signal component level included in the output signal for each pixel is amplified, and output. The image signal processing unit 132 has a built-in line buffer with a predetermined capacity, converts the output R, G, B analog image signals into digital image signals, and outputs one image according to a command from the CPU 110. Minute image signals are accumulated and recorded in the RAM 116.

  In addition, the image signal processing unit 132 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 the single CCD), a white balance correction circuit, A gamma correction circuit, a contour correction circuit, a luminance / color difference signal generation circuit, and the like are included, and the input image signal is subjected to necessary signal processing in accordance with a command from the CPU 110 to obtain luminance data (Y data) and color difference data (Cr, Image data (YUV data) composed of (Cb data).

  The subject distance calculation unit 134 calculates the estimated subject distance based on the motion amount detected by the motion amount detection unit 120, the shift amount detected by the camera shake amount detection unit 122, and the focal length of the photographing optical system 124. . Hereinafter, a method for calculating the estimated subject distance in the subject distance calculation unit 134 will be described. FIG. 6 is a flowchart showing a flow of processing for calculating the estimated subject distance, and FIG. 7 is a functional diagram showing a data flow when calculating the estimated subject distance.

  Camera shake (rotational shake and shift shake) that occurs during through-image shooting (details will be described later) is detected by the camera shake amount detection unit 122 (step S1). At the same time, the image data of the through image output from the imaging device 128 is acquired immediately before and immediately after the camera shake is detected by the camera shake amount detection unit 122, and the motion amount between the previous image and the subsequent image is moved. The amount is detected by the amount detection unit 120 (step S2). The rotational blur amount and shift blur amount detected in step S1 and the information on the motion amount detected by the motion amount detection unit 120 are input to the subject distance detection unit 134, respectively.

  The CPU 110 detects whether or not the camera shake correction mode is set (step S3). When the camera shake correction mode is set (YES in step S3), the camera shake correction control unit 140 (described later) removes the influence of the rotational shake from the image data that is the basis for detecting the motion amount in step S2. Therefore, the process proceeds to step S5 as it is.

  When the camera shake correction mode is not set (NO in step S3), the subject distance calculation unit 134 uses the amount of motion detected in step S2 to detect the previous image and the rear image by the rotational shake detected in step S1. The amount of motion that has occurred between the two images is removed (step S4), and the process proceeds to step 5.

  Here, the reason why the influence of the rotational blur is removed from the amount of motion in steps S3 and S4 will be described. FIG. 8 is a graph showing the relationship between the rotational blur amount and the motion amount when the subject distance is different, and FIG. 9 is a graph showing the relationship between the shift blur amount and the motion amount when the subject distance is different.

  As shown in FIG. 8, the rotational blur and the amount of motion are in a proportional relationship, but the proportionality coefficient is constant regardless of the subject distance. Therefore, the subject distance cannot be obtained from the relationship between the rotational blur amount and the motion amount. On the other hand, since the shift blur amount and the motion amount are in a proportional relationship, and the proportionality coefficient varies depending on the subject distance, the subject distance can be calculated if the shift blur amount and the motion amount are known. Therefore, the amount of motion used in step S5 needs to be the amount of motion due to only shift blur by removing the influence of rotational blur.

Finally, based on the amount of movement due to the shift blur obtained in step S3 or S4, the shift blur amount detected in step S2, and the focal length of the photographing optical system 124 output from the aperture / focus / zoom control unit 126, FIG. The estimated subject distance is calculated based on the obtained mathematical formula 1 (step S5). The calculated estimated subject distance is output from the subject distance calculation unit 134 to the CPU 110, the AF detection unit 138, the flash control unit 142, and the like.
[Equation 1]
Estimated subject distance = f (zoom value, shift blur amount, motion amount)
= A x (shift blur / motion)
Note that a is a coefficient and takes a different value depending on the zoom value (focal length of the photographing optical system 124).

  Thereby, it is possible to acquire distance measurement information without incurring costs by applying the camera shake correction mechanism which is an existing mechanism without using a special mechanism. The image data used for distance measurement is desirably performed when the digital camera 10 is largely moved, that is, immediately before the obtained through image becomes a stable image. In this case, since the amount of motion of the through image increases, the estimated subject distance can be calculated with high accuracy.

  The AE / AWB detection unit 136 calculates a physical quantity necessary for AE control and AWB control from the input image signal in accordance with a command from the CPU 110. For example, as a physical quantity required for AE control, one screen is divided into a plurality of areas (for example, 16 × 16), and an integrated value of R, G, and B image signals is calculated for each divided area. The CPU 110 detects the brightness of the subject (subject brightness) based on the integrated value obtained from the AE / AWB detection unit 136, and calculates an exposure value (shooting EV value) suitable for shooting. Then, an aperture value and a shutter speed are determined from the calculated shooting EV value and a predetermined program diagram. Further, as a physical quantity necessary for AWB control, one screen is divided into a plurality of areas (for example, 16 × 16), and an average integrated value for each color of R, G, and B image signals is calculated for each divided area. . The CPU 110 obtains the ratio of R / G and B / G for each divided area from the obtained R accumulated value, B accumulated value, and G accumulated value, and R of the obtained R / G and B / G values. The light source type is discriminated based on the distribution in the color space of / G and B / G. Then, according to the white balance adjustment value suitable for the determined light source type, for example, the value of each ratio is approximately 1 (that is, the RGB integration ratio is R: G: B≈1: 1: 1 in one screen). Then, a gain value (white balance correction value) for the R, G, and B signals of the white balance adjustment circuit is determined.

  The AF detection unit 138 calculates a physical quantity necessary for AF control from the input image signal in accordance with a command from the CPU 110. In the digital camera 10 of the present embodiment, AF control is performed based on the contrast of the image obtained from the image sensor 128 (so-called contrast AF), and the AF detection unit 138 shows a focus indicating the sharpness of the image from the input image signal. An evaluation value is calculated. The CPU 110 detects a position where the focus evaluation value calculated by the AF detection unit 138 is maximized, and moves the focus lens group to that position. That is, the focus lens group is moved in a predetermined step (hereinafter referred to as an AF search range) from a close range to infinity, and a focus evaluation value is obtained at each position. The focus lens group is moved to the position where the maximum position is the in-focus position.

  The camera shake correction control unit 140 detects the shake of the digital camera 10 with a gyro sensor, and moves the image sensor 128 in the direction opposite to the shake, thereby correcting the camera shake of the subject image formed on the image sensor 128.

  The flash control unit 142 controls light emission of the flash 16 according to the command from the CPU 110 and according to the subject distance calculated by the subject distance calculation unit 134.

  The AF auxiliary light lamp controller 144 controls the light emission of the AF auxiliary light lamp 18 in accordance with a command from the CPU 110. That is, if the CPU 110 determines that the subject is dark during AF or determines that the subject has a low contrast, the CPU 110 causes the AF auxiliary light lamp 18 to emit light via the AF auxiliary light lamp controller 144 and emits AF auxiliary light to the subject. Irradiate and execute AF control.

  The image recording unit 146 performs compression processing of a predetermined format on the input image data in accordance with a command from the CPU 110, and generates compressed image data. Further, in accordance with a command from the CPU 110, the input compressed image data is subjected to a decompression process in a predetermined format to generate uncompressed image data. The image recording unit 146 controls reading / writing of data with respect to the memory card 148 loaded in the memory card slot 14 in accordance with a command from the CPU 110.

  The display control unit 150 controls display on the monitor 28 in accordance with a command from the CPU 110. That is, in accordance with a command from the CPU 110, the input image signal is converted into a video signal (for example, NTSC signal, PAL signal, SCAM signal) for display on the monitor 28 and output to the monitor 28. The graphic information is output to the monitor 28.

The face detection unit 152 extracts a face area in the image from the input image data in accordance with a command from the CPU 110, and detects the position (for example, the center of gravity of the face area). In this face area extraction, for example, skin color data is extracted from an original image, and a cluster of photometric points determined to be in the skin color range is extracted as a face. In addition, as a method for extracting a face area from an image, a method for determining a face area by converting photometric data into hue and saturation, creating a two-dimensional histogram of the converted hue / saturation, and analyzing it. Or a method for extracting a face candidate region corresponding to the shape of a human face and determining the face region from the feature amount in the region, extracting a human face outline from an image, and determining a face region, There are known methods for extracting a human face by preparing a template having the shape of a human face, calculating the correlation between the template and an image, and using the correlation value as a face candidate region. Can be extracted.
[Shooting, recording and playback operations of the digital camera 10]
When the power button 26 is pressed and the power of the digital camera 10 is turned on, the digital camera 10 is activated under the shooting mode.

  First, the driving unit of the photographing optical system 124 is driven via the aperture / focus / zoom control unit 126, and the photographing lens 13 is extended to a predetermined position. Then, when the photographing lens 13 is extended to a predetermined position, the imaging element 128 performs photographing for a through image, and the through image is displayed on the monitor 28. That is, images are continuously picked up by the image pickup device 128 and the image signals are continuously processed to generate image data for a through image. The generated image data is sequentially added to the display control unit 150 via the buffer memory 118, converted into a signal format for display, and output to the monitor 28. As a result, the image captured by the image sensor 128 is displayed through on the monitor 28.

  At the same time, based on the image data of the through image acquired by the image sensor 128, the subject distance calculation unit 134 calculates the estimated subject distance. When a human face is detected by the face detection unit 152, image data of an area where the face is detected is input to the subject distance calculation unit 134, and an estimated subject distance is calculated based on the image data. Thus, accurate distance measurement can be performed by calculating the subject distance based on the main subject.

  The photographer determines the composition by looking at the through image displayed on the monitor 28 and presses the shutter button 22 halfway.

  When the shutter button 22 is half-pressed, an S1 ON signal is input to the CPU 110. In response to the S1 ON signal, the CPU 110 executes shooting preparation processing, that is, AE, AF, and AWB processing.

  First, the image signal output from the image sensor 128 is taken into the RAM 116 via the image signal processing unit 132 and added to the AE / AWB detection unit 136 and the AF detection unit 138.

  The AE / AWB detection unit 136 calculates a physical quantity necessary for AE control and AWB control from the input image signal, and outputs it to the CPU 110. Based on the output from the AE / AWB detection unit 136, the CPU 110 determines an aperture value and a shutter speed and also determines a white balance correction value.

  At the same time, it is determined whether or not the flash 16 needs to emit light and the amount of light emitted from the flash 16 is adjusted. When it is determined that the flash 16 needs to emit light, the appropriate light amount of the flash 16 is adjusted based on the flowchart shown in FIG. FIG. 10 is a flowchart showing a flow of processing for adjusting the appropriate light amount of the flash 16, and FIG. 11 is a functional diagram showing a data flow when adjusting the appropriate light amount of the flash 16.

  The estimated subject distance calculated in steps S1 to S5 is input from the subject distance detection unit 134 to the flash control unit 142 (step S11), and the subject determined based on the reflected light obtained by pre-flashing the flash 16 And the estimated subject distance input in step S11, the flash control unit 142 determines the light emission amount of the flash 16 during the main photographing based on the graph shown in FIG. 12 (step S12). When the flash control unit 142 determines that the subject distance calculated by the subject distance calculation unit 134 is a distance that the flash 16 does not reach based on the graph shown in FIG. 12, the flash 28 reaches the monitor 28. A warning message such as “No” is displayed (step S13).

  Thereby, the subject can be irradiated with a flash having an appropriate amount of light according to the subject distance. Further, when the subject distance is a short distance, it is possible to prevent a white stripe caused by a flash. Further, by giving a warning when the flash does not reach, the photographer can be guided to perform appropriate flash photography. The warning is not limited to the message, but may be performed by sound, voice, or the like.

  Thereafter, the AF detection unit 138 calculates a physical quantity necessary for AF control from the input image signal, and outputs it to the CPU 110. The present embodiment is characterized in that AF control is performed by limiting the AF search range based on the subject distance calculated by the subject distance calculation unit 134. Hereinafter, a method for executing AF control by limiting the AF search range based on the subject distance calculated by the subject distance calculation unit 134 will be described. FIG. 13 is a flowchart showing a flow of processing for limiting the AF search range, and FIG. 14 is a functional diagram showing a data flow when limiting the AF search range.

  The estimated subject distance calculated in steps S1 to S5 is input from the subject distance detection unit 134 to the AF detection unit 138 (step S15), and the focal length of the photographing optical system 124 output from the aperture / focus / zoom control unit 126, Based on the estimated subject distance input in step S11 and focus characteristic information created in advance, the AF detection unit 138 sets an AF search range that is limited to a predetermined range from close to infinity. (Step S16). The focus characteristic information in the present embodiment indicates the relationship between the reciprocal of the subject distance for each focal length and the in-focus position, whereby the position of the lens to be in focus can be calculated.

  The CPU 110 controls the drive of the drive unit of the photographing optical system 124 via the aperture / focus / zoom control unit 126 based on the output from the AF detection unit 138 to move the focus lens in predetermined steps, and at each position. A focus evaluation value is acquired (step S17). The position where the obtained focus evaluation value is the maximum is taken as the in-focus position, and the focus lens group is moved to that position (step S18).

  Here, the limited AF search range will be described. FIG. 15 shows the state of AF search when the subject distance is 1 m, normal brightness, and zooming.

  In a normal AF search, an AF evaluation value is calculated while performing a rough search that takes a large search step (about 30 pulses). The range of the rough search is determined for each focal length, and the rough search is performed in the range in focus in each case from the vicinity to infinity. When the AF evaluation value of the rough search decreases twice, a detailed search is performed in a detailed search step (about 6 pulses) in the opposite direction to the rough search.

  The limited AF search range is the AF search range of this detailed search. In this embodiment, since the estimated subject distance is calculated, a detailed search can be performed without performing a rough search by setting the estimated subject distance as the position of the maximum AF evaluation value in the rough search. The range of the detailed search is, for example, a range of about five detailed search steps centered on the position of the estimated subject distance.

  In this way, the AF control can be speeded up by limiting the AF search range and performing the AF control. Also, even when the subject is dark or the conditions are short, such as when the distance is short, the time required for AF control can be made equal to the time required for normal AF control, and stable AF control can be performed. For example, when the subject is dark, the AF method takes about 1 to 2 seconds in the normal method, but the time required for the AF control is 0.4 to 0.6 by using the method of the present embodiment. It can be shortened to about seconds. Further, since the macro setting is automatically switched based on the estimated subject distance, the user can easily perform the operation without switching to the macro setting for short-distance shooting. Further, by shortening the time required for focusing control, it is possible to capture an image according to the operator's intention without missing a photo opportunity. Note that the CPU 110 performs AF control by causing the AF auxiliary light lamp 20 to emit light as necessary.

  The photographer confirms the focus state of the photographing lens 13 by looking at the through image displayed on the monitor 28 and executes photographing. That is, the shutter button 22 is fully pressed.

  When the shutter button 22 is fully pressed, an S2 ON signal is input to the CPU 110. The CPU 110 executes photographing and recording processing in response to the S2ON signal.

  First, the image sensor 128 is exposed at the aperture value and shutter speed obtained in the above AE process, and a recording image is captured. At this time, when the flash 16 is caused to emit light, the flash 16 is caused to emit light based on the light emission amount of the flash 16 obtained from the result of the pre-emission via the flash emission control unit 156.

  The recording image signal output from the image sensor 128 is captured by the image signal processing unit 132 and stored in the RAM 116. The image signal stored in the RAM 116 is added to the image signal processing unit 132 under the control of the CPU 110. The image signal processing unit 132 performs predetermined signal processing on the input image signal to generate image data (YUV data) including luminance data and color difference data.

  The image data generated by the image signal processing unit 132 is temporarily stored in the RAM 116 and then added to the image recording unit 146. The image recording unit 146 performs a predetermined compression process on the input image data to generate compressed image data.

  The compressed image data is stored in the RAM 116 and recorded on the memory card 148 via the image recording unit 146 as a still image file (for example, Exif) in a predetermined format. If there is no free space in the memory card 148 where the image file can be stored, or if the operator selects it, the image data stored in the RAM 116 is a still image file (eg, Exif) in a predetermined format. It is stored in the ROM 114. When image data is stored in the ROM 114, the image data is stored in a plurality of clusters, usually a plurality of consecutive clusters.

  The image data recorded in the memory card 148 or the ROM 114 in this manner is reproduced and displayed on the monitor 28 by setting the mode of the digital camera 10 to the reproduction mode. Transition to the playback mode is performed by pressing the playback button 32.

  When the play button 32 is pressed, the CPU 110 reads the compressed image data of the last recorded image file. When the last recorded image file is recorded on the memory card 148, the CPU 110 reads the compressed image data of the image file recorded last on the memory card 148 via the image recording unit 146. When the last recorded image file is recorded in the ROM 114, the CPU 110 can directly read the compressed image data of the image file from the ROM 114.

  The compressed image data read from the memory card 148 or the ROM 114 is added to the image recording unit 146, converted into uncompressed image data, and then added to the buffer memory 118. Then, the data is output from the buffer memory 118 to the monitor 28 via the display control unit 150. As a result, the image recorded in the memory card 148 or the ROM 114 is reproduced and displayed on the monitor 28.

  Image frame advance is performed by operating the left and right keys of the cross button 36. When the right key is operated, the next image file is read from the memory card 160 and reproduced and displayed on the monitor 28. Further, when the left key of the cross button 36 is operated, the previous image file is read from the memory card 148 or the ROM 114 and reproduced and displayed on the monitor 28.

  While confirming the image reproduced and displayed on the monitor 28, the image recorded on the memory card 148 or the ROM 114 can be deleted as necessary. The image is erased by pressing the function button 34 while the image is reproduced and displayed on the monitor 28.

  When the function button 34 is pressed, the CPU 110 displays, via the display control unit 150, a message informing the image erasure such as “Are you sure you want to erase this photo” superimposed on the image on the monitor 28. When the MENU / OK button 38 is pressed, the image is erased. When image data is recorded on the memory card 148, the CPU 110 deletes the image file recorded on the memory card 148 via the image recording unit 146. When image data is recorded in the ROM 114, the CPU 110 can delete the image file directly from the ROM 114.

  According to the present embodiment, since the subject distance is calculated based on the image data of the through image, the calculated distance measurement information can be used for setting shooting conditions such as AF control and flash emission control. Further, by applying the camera shake correction mechanism, which is an existing mechanism, to calculate the estimated subject distance, distance measurement information can be acquired without cost.

  Further, according to the present embodiment, it is possible to reduce the time required for focusing control by performing focusing control with a limited focus adjustment range using the calculated subject distance. Further, by shortening the time required for focusing control, it is possible to capture an image according to the operator's intention without missing a photo opportunity.

  Further, according to the present embodiment, appropriate flash photography can be performed by performing light emission control so that the flash emission amount is appropriate using the calculated subject distance.

  In this embodiment, the case where contrast AF is performed has been described as an example. However, the present invention is not limited to contrast AF, and can be applied to other AF control such as hill climbing search.

  Note that the application of the present invention is not limited to a digital camera, and is similarly applied to an electronic device capable of updating firmware such as an imaging device such as a mobile phone with a camera or a video camera, a portable music player, or a PDA. be able to.

1 is a front perspective view showing an external configuration of a first embodiment of an electronic apparatus (digital camera) 10 to which the present invention is applied. 2 is a rear perspective view showing an external configuration of the first embodiment of the digital camera 10. FIG. 1 is a block diagram showing an electrical configuration of a first embodiment of the digital camera 10. FIG. It is a figure explaining the method of calculating a motion amount. It is a figure explaining camera shake. It is a flowchart which shows the flow of a process which calculates an estimation subject distance. It is a functional diagram showing a data flow of processing for calculating an estimated subject distance. It is a graph which shows the relationship between rotation blur and a motion amount. It is a graph which shows the relationship between shift blur and a motion amount. It is a flowchart which shows the flow of the process which adjusts the suitable light quantity of a flash using an estimated to-be-photographed object distance. It is a functional diagram showing a data flow of processing for adjusting an appropriate light amount of a flash using an estimated subject distance. It is a graph which shows the relationship between a to-be-photographed object distance and the suitable light quantity of a flash. It is a flowchart which shows the flow of a process which restricts AF search range using estimated object distance, and performs AF. FIG. 6 is a functional diagram showing a data flow of processing for performing AF while limiting an AF search range using an estimated subject distance. It is a figure explaining the limited AF search range.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Digital camera, 11 ... Slot cover, 12 ... Camera body, 13 ... Shooting lens 1, 14 ... Memory card slot, 16 ... Flash, 18 ... AF auxiliary light lamp, 26 ... Power button, 28 ... Monitor, 30 ... Zoom Buttons 32 ... Play button 34 ... Function button 36 ... Cross button 38 ... MENU / OK button 40 ... DISP / BACK button 110 110 CPU 114 ROM 116 116 RAM 118 Buffer memory 124 Imaging optical system, 126 ... Aperture / focus / zoom control unit, 128 ... Image sensor, 130 ... Imaging control unit (timing generator), 132 ... Image signal processing unit, 134 ... Subject distance calculation unit, 136 ... AE / AWB detection unit 138: AF detection unit, 140: Camera shake correction control unit, 142: Flash Control unit, 144 ... AF assist lamp control unit, 146 ... image recording section, 148 ... memory card, 150 ... display controller, 152 ... face detecting unit

Claims (9)

Shift amount detection means for detecting a shift amount in a direction orthogonal to the imaging optical axis of the imaging device;
Acquisition means for acquiring image data of a subject image formed on an image sensor by a photographing optical system;
A motion amount detection means for detecting a motion amount of the image on the image sensor in accordance with the shift amount of the imaging device detected by the shift amount detection means from the image data acquired by the acquisition means;
Subject distance calculation means for calculating a subject distance based on the motion amount detected by the motion amount detection means, the shift amount of the imaging device detected by the shift amount detection means, and the focal length of the photographing optical system When,
An imaging apparatus comprising: Camera shake detection means for detecting rotational shake in the vertical and horizontal directions of the imaging device;
A camera shake correction unit configured to drive at least a part of the optical member of the imaging optical system or the imaging device based on the rotational shake detected by the camera shake detection unit, and to correct the camera shake of the imaging device;
Image data acquisition control means for causing the acquisition means to acquire image data in which camera shake of the imaging apparatus is corrected by the camera shake correction means;
The imaging apparatus according to claim 1, further comprising:   The imaging apparatus according to claim 1, wherein the camera shake detection unit includes the shift amount detection unit. Face detection means for detecting a human face from the image data acquired by the image sensor;
Image data acquisition control means for causing the acquisition means to acquire image data of a region in which a human face is detected by the face detection means;
The imaging apparatus according to claim 1, further comprising:   The imaging apparatus according to claim 1, further comprising an acquisition control unit that causes the acquisition unit to acquire image data of a live view image.   The photographic optical system is moved over the focus adjustment range, and an image signal is output from the imaging device every time the photographic optical system moves by a predetermined amount, and the photographic optical system is output based on the contrast component of the subject obtained from the output image signal. An automatic focusing control unit that performs focusing control of the optical system, and that performs focusing control by limiting a range in which the photographing optical system is moved based on the subject distance calculated by the subject distance calculating unit. 6. The imaging apparatus according to claim 1, further comprising a focusing control unit. A flash light source,
Light emission control means for controlling light emission of the flash light source based on the subject distance calculated by the subject distance calculation means;
The imaging apparatus according to claim 1, further comprising: Determining means for determining whether light from the flash light source reaches the subject based on the subject distance calculated by the subject distance calculating means;
Warning means for giving a warning when it is determined by the determination means that the light from the flash light source does not reach the subject;
The imaging apparatus according to claim 7, further comprising: Detecting the direction and amount of translation and rotation of the imaging device;
Acquiring image data of a subject image formed on an image sensor by a photographing optical system in synchronization with detection of the direction and amount of parallel movement and rotation of the imaging device;
Removing the influence of the rotation of the imaging device from the acquired image data based on the detected direction and amount of rotation of the imaging device;
Detecting the parallel movement amount of the image data from which the influence due to the rotation of the imaging device is removed, and the parallel movement amount of the subsequent image with respect to the preceding image;
Calculating a subject distance based on the detected parallel movement amount, the detected direction and amount of the parallel movement of the imaging device, and the focal length of the photographing optical system;
A subject distance calculation method comprising:

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