JP5661248B2 - Imaging device and light emitting device control method - Google Patents

Description

  The present invention relates to an imaging device and a method for controlling a light emitting device used together with the imaging device.

  Conventionally, in shooting with an imaging device such as a digital camera, when the shooting target is dark, the brightness of the shot subject is made appropriate by slowing the shutter speed. However, when the shutter speed is slowed down, there is a possibility of causing adverse effects such as camera shake and subject blur. For example, as described in Cited Document 1, it is generally performed to compensate for the shortage of light amount by flash. .

  Here, the light emission amount of the flash is normally adjusted so that an appropriate brightness can be maintained when the distance between the subject and the camera is within a certain range (light control range).

Japanese Patent Laid-Open No. 08-006113

  However, for example, if the subject has moved beyond the flash dimming range and moved closer to the near side, the amount of light emission becomes excessive, causing the subject to overshoot, and conversely by performing imaging using the flash. Image quality may be degraded.

  The present invention has been made in view of the above problems, and an object of the present invention is to make it possible to capture a better image when performing flash shooting when the subject is outside the flash light control range. .

In order to achieve the above object, the imaging apparatus of the present invention capable of imaging using a light emitting device is a subject detection that detects a subject from image data obtained by imaging using an imaging means without using the light emitting device. Imaging using the light emitting device, a distance detecting unit for obtaining a distance to the detected subject, an exposure control unit for obtaining an exposure condition including an exposure time based on luminance information of the image data, and Determining means for determining whether the light emitting device emits light based on the luminance information when the determining means determines that the light emitting device is used for imaging. has a motion detection means for detecting a motion amount of the subject, the determination unit is longer than the exposure time the exposure time is set in advance determined by the exposure control means, to the subject If the distance is outside the range of light control of the light emitting device, based on whether or not exceeding the first threshold amount of motion of said object is predetermined, whether to perform imaging by using the light emitting device to decide.

The control method of the present invention of a light emitting device for use with an imaging apparatus, from the image data obtained by imaging by the imaging means without using the pre-Symbol emitting device, a subject detection step of detecting an object, before Symbol Detection a distance detection step of determining the distance to the object that is, based on the luminance information before Symbol image data, the exposure control step of determining the exposure conditions including exposure time, whether to perform imaging by using a pre-Symbol emitting device a determination step of determining, when it is determined that performs imaging by using the light emitting device by the previous SL determining step, based on the luminance information, a calculation step of obtaining the light emission amount for light emitting the light emitting device, wherein a motion detection step of detecting a movement amount of the object, and in the determination step, exposure time obtained based on the luminance information of the image data is longer than the preset exposure time, the subject If the distance at is outside the range of light control of the light emitting device, based on whether or not exceeding the first threshold amount of motion of said object is predetermined, whether or not to perform imaging by using the light emitting device Determine whether .

  According to the present invention, when performing flash photography, a better image can be taken when the subject is outside the flash light control range.

1 is a block diagram showing a schematic configuration of a digital camera according to a first embodiment of the present invention. 3 is a flowchart for explaining an outline of an imaging operation of the digital camera according to the first embodiment of the present invention. It is a flowchart which shows the flash light emission judgment process in the 1st Embodiment of this invention. It is a figure which shows an example of the light control range of a flash. It is a block diagram which shows schematic structure of the digital camera concerning the 2nd Embodiment of this invention. It is a flowchart which shows the flash light emission judgment process in the 2nd Embodiment of this invention.

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

<First Embodiment>
Configuration of Imaging Device In the first embodiment, a case where a digital camera is used as the imaging device will be described. FIG. 1 is a block diagram illustrating a functional configuration of the digital camera 100 according to the first embodiment.

  An operation unit 101 includes switches and buttons that are operated by an operator of the digital camera 100 to input various instructions. The operation unit 101 also includes a shutter button. When the shutter button is half-pressed, SW1 is turned on, and the control unit 102 is notified from the operation unit 101. When the shutter button is fully pressed, SW2 is turned on, and the control unit 102 is notified from the operation unit 101. As an example of processing executed by half-pressing (SW1 ON) and full-pressing (SW2 ON), there is processing for capturing a captured image by locking the focus and exposure by half-pressing and then continuously pressing fully.

  Reference numeral 103 denotes an image pickup device represented by a CCD or CMOS sensor, and reference numeral 108a denotes a lens. In FIG. 1, it is represented by a single lens for the sake of convenience, but actually it is composed of a plurality of lenses including a focus lens. An exposure mechanism 109a includes a mechanical shutter. The image sensor 103 receives incident light through the lens 108a and the exposure mechanism 109a, and accumulates electric charges according to the amount of light. The accumulated charge is read out to the shift register and sequentially read out as a voltage signal by the transfer pulse.

  The A / D conversion unit 104 performs sampling, gain adjustment, A / D conversion, and the like on the analog image signal output from the image sensor 103, and outputs digital image data.

  The image processing unit 105 performs various kinds of image processing on the digital image data output from the A / D conversion unit 104, and outputs processed digital image data. For example, digital image data received from the A / D conversion unit 104 is converted into YUV image data and output.

  Reference numeral 102 denotes a control unit that controls the operation of each unit of the digital camera 100 shown in FIG. 1 and controls each unit in accordance with an instruction from the operation unit 101.

  The luminance detection unit 106 uses the digital image data output from the A / D conversion unit 104 to obtain luminance information for each predetermined block.

  The subject detection unit 115 detects a subject such as a face from the digital image data. The information related to the detected subject (subject information) includes the position on the screen, the range, and the reliability (probability as the shape of the face). The subject detection unit 115 holds subject information in time series and compares the subject information before and after to determine whether the subject is moving in the screen, and calculates the position, range, and amount of motion of the subject. Such information is also included in the subject information.

  The distance detection unit 116 calculates the distance to the subject from the distance information obtained by performing the AF process. The obtained distance to the subject is sent to the AF processing unit 108 via the control unit 102, and the AF processing unit 108 performs focus adjustment by controlling the focus lens of the lens 108a based on the distance to the subject.

  The light emission determination unit 117 determines the necessity of flash emission based on the luminance information obtained by the luminance detection unit 106, the subject information obtained by the subject detection unit 115, and the distance information obtained by the distance detection unit 116. At that time, the light emission determination unit 117 obtains an exposure condition including a shutter speed (exposure time) and an aperture amount based on the luminance information, and notifies the obtained exposure condition to the AE processing unit 109 via the control unit 102. . The AE processing unit 109 controls the exposure mechanism 109a based on the notified exposure condition. The process related to the determination of flash emission will be described later in detail with reference to FIG. When it is determined that the flash is necessary, the EF processing unit 110 is instructed to flash on. When the EF processing unit 110 receives a flash-on instruction, the EF processing unit 110 calculates a light emission amount based on the luminance information obtained by the luminance detection unit 106, and transmits an appropriate light emission amount to the flash unit 111 (light emitting device) to emit light.

  The display unit 107 is configured with a small liquid crystal screen or the like, and displays an image according to the image data processed by the image processing unit 105.

  The format conversion unit 112 converts the format of the digital image data (image data) output from the image processing unit 105 into a format such as JPEG and outputs it to the image recording unit 113. The image recording unit 113 performs processing for recording the format-converted image data received from the format conversion unit 112 in a memory (not shown) in the digital camera 100, an external memory inserted in the digital camera 100, or the like.

  The external connection unit 114 functions as an interface for connecting the digital camera 100 to an external device such as a PC (personal computer) or a printer.

Process Flow Next, the operation of the digital camera 100 having the above configuration in the first embodiment will be described.

  FIG. 2 is a flowchart showing the imaging operation of the digital camera 100 according to the first embodiment, which is executed when the power switch included in the operation unit 101 is turned on and the imaging mode is selected.

  In a state where the power switch is ON, when power is supplied to each part of the digital camera 100, the shutter included in the exposure mechanism 109a opens, and light enters the image sensor 103 through the lens 108a and the exposure mechanism 109a. To do. In this state, an imaging process is performed in step S11. Here, first, the electric charge accumulated for a predetermined time by the electronic shutter control is read and output to the A / D converter 104 as an analog image signal. The A / D conversion unit 104 performs sampling, gain adjustment, A / D conversion, and the like on the analog image signal output from the image sensor 103 and outputs the digital image data to the image processing unit 105. The image processing unit 105 performs various types of image processing on the digital image data, and outputs processed digital image data.

  Next, in step S12, the digital image data that has been processed is subjected to format conversion so that the format conversion unit 112 has a format suitable for display, and is displayed on the display unit 107 (through display). As described above, by sequentially displaying the image data sequentially obtained at a predetermined frame rate on the display unit 107, an electronic viewfinder (EVF) function can be realized.

  In addition, the digital image data processed by the image processing unit 105 is displayed on the display unit 107, and the AE processing unit 109 controls the exposure mechanism 109a so that the screen is optimally exposed. Further, the AF processing unit 108 operates the lens 108a so as to focus on the subject (step S13). Note that the processing order of steps S12 and S13 is not particularly limited, and whichever is first may be performed in parallel. For example, when the subject detection unit 115 detects a face and adjusts the exposure and focus on the face, for example, a method described in Japanese Patent Application Laid-Open No. 2003-107555 or Japanese Patent Application Laid-Open No. 2004-184508 is used. be able to.

  Then, the state of the shutter button included in the operation unit 101 is checked. If the shutter button is not pressed and SW1 is OFF (OFF in step S14), the process returns to step S11 and the above processing is repeated.

  On the other hand, if SW1 is ON, the process proceeds to step S15 to prepare for actual photographing. During preparation for shooting, first, in step S15, imaging is performed in the same manner as in step S11 using the exposure conditions obtained in the immediately preceding step S13, and the image obtained in the next step S16 is displayed through as in step S12. In step S17, the subject detection unit 115 detects the subject from the digital image data obtained in step S15.

  Next, in step S18, photometry and focus adjustment processing are performed. Here, in the focus adjustment process, an edge in the screen is detected based on the digital signal of the subject area detected in step S17, and is calculated from the focal length information of the focus lens operated in the AF processing unit 108. The obtained distance information is acquired. Then, based on the obtained distance, the focus lens of the lens 108a is controlled to adjust the focus.

  Next, in step S19, the light emission determination unit 117 determines whether or not to emit the flash. This determination of flash emission will be described later in detail with reference to FIG.

  When the flash light emission determination process of step S19 is completed, the process proceeds to step S20 to determine the state of SW2, and if SW2 is OFF, the process returns to step S14. If SW1 is ON, the above-described steps S15 to S19 are performed. Repeat the process. If it is determined in step S14 that SW1 is also OFF, the process returns to step S11. On the other hand, if SW2 is ON (ON in step S20), the process proceeds to step S21, and actual shooting is performed according to the imaging conditions set in steps S18 and S19.

  In step S 22, the format conversion unit 112 converts the format of the digital image data output from the image processing unit 105 into a format such as JPEG, and outputs it to the image recording unit 113. The image recording unit 113 records the format-converted image data in a predetermined memory.

  When the recording process (step S22) ends, the control unit 102 determines the state of SW2 (step S23), waits for SW2 to turn off, and returns to step S14 when turned off.

  Next, the flash emission determination process performed in step S19 by the emission determination unit 117 will be described in detail with reference to FIG.

  First, the luminance detection unit 106 divides the digital image data obtained by imaging in step S15 into blocks, and calculates an average luminance value (luminance information) for each block (step S201). Then, the light emission determination unit 117 acquires the calculated luminance information.

  Next, the light emission determination unit 117 acquires subject information as a result of subject detection performed in step S17 by the subject detection unit 115 (step S202). The subject information acquired here includes subject position information such as face center coordinates and face size, gender, face reliability information, and the like. Here, the subject information is also stored in the time series in the past, and the movement of the subject is detected by comparing with the latest information.

  And the light emission determination part 117 acquires the distance information obtained by AF process of step S18. Here, since the AF processing is performed based on the coordinates obtained by subject detection, distance information of the detected main subject can be acquired (step S203).

  Next, an exposure condition including a shutter speed (exposure time), an aperture amount, and the like in the case of shooting without flash is calculated (step S204). The subject luminance obtained when the image is taken under the exposure condition obtained here is calculated from the block luminance and subject position information, and further, an exposure condition with this as the appropriate luminance is calculated.

  It is determined whether the shutter speed (Tv) is faster than the preset threshold value Tvth among the calculated exposure conditions (step S205). If it is fast, it is determined that the subject is sufficiently bright without the use of a flash and the influence of camera shake is small, and a non-flash determination is made (step S210).

  On the other hand, if the shutter speed (Tv) is not faster than the threshold value Tvth among the calculated exposure conditions, it is determined whether the distance to the subject is within the flash light control range (step S206). In the example shown in FIG. 4, when the subject is closer than 80 cm, the possibility of overexposure due to the flash increases, and therefore, the case where the subject is out of the light control range is shown.

  If it is within the dimming range, it is possible to perform proper dimming with a flash, so light emission is judged (step S211), and the light emission conditions are calculated (step S212). Here, when performing flash emission, the control unit 102 controls the EF processing unit 110 to cause the flash unit 111 to perform pre-emission, and performs processing such as calculation of the emission amount and weighting of the EF frame.

  If it is out of the light control range, the movement information of the subject is confirmed (step S207). Here, information on the transition of the subject position over a certain period obtained by subject detection is used. If the transition of the subject position is not within 5% of the angle of view, it is determined that the subject may move during the main photographing (NO in step S207), and the light emission determination is made (step S211). The light emission condition is calculated (step S212).

  If it is determined that the subject is stationary (the amount of motion of the subject is equal to or less than the first threshold value) (YES in step S207), the exposure condition for non-light emission is recalculated (step S209). Here, in consideration of subject movement information, the shutter speed Tv is finely adjusted according to the amount of movement of the subject, and the exposure is recalculated.

  When the reset exposure condition does not reach the limit of exposure control and is within the appropriate exposure range, that is, when the exposure condition is within the predetermined exposure condition range, the non-emission judgment is made. (Step S210), and the process proceeds to the main photographing process under the reset exposure conditions. If it is out of the proper exposure range, a light emission judgment is made (step S211) and a light emission condition is calculated (step S212) in order to maintain appropriate luminance.

  As described above, according to the first embodiment, based on the distance to the subject, the presence or absence of the subject's movement, etc., the shortage of light amount is compensated for by the flash, or the exposure condition is controlled without using the flash. It is determined whether to adjust the brightness of the subject. As a result, it is possible to adjust the amount of light using the flash more appropriately.

  In the first embodiment, the case where the movement of the subject is added to the flash emission determination has been described. However, when the subject is dark, the distance to the subject is adjusted to the flash light control without taking the movement of the subject into consideration. You may make it judge based on whether it is settled in the range.

<Second Embodiment>
Configuration of Imaging Device As an imaging device according to the second embodiment, a configuration of a digital camera 100 ′ is shown in FIG. The configuration shown in FIG. 5 is a configuration in which a camera motion detection unit 218 configured to detect the motion of the digital camera 100 ′ is added to the configuration shown in FIG. Since the other configuration is the same as the configuration of FIG. 1, the same reference numerals are given, and the description thereof is omitted here. The camera motion detection unit is not particularly limited to a gyro sensor, for example, an acceleration sensor, an HV sensor, or the like as long as the amount and direction of camera motion can be known.

Process Flow Next, the operation of the digital camera 100 ′ having the above configuration in the second embodiment will be described.

  FIG. 6 is a flowchart showing the flash emission determination process in the second embodiment, which is a process performed in step S19 of FIG. 2 instead of FIG. In the following description, the same steps as those in FIG.

  In the second embodiment, in addition to the luminance information (step S201), the subject information (step S202), and the distance information (step S203), the motion information of the digital camera 100 ′ is received from the camera motion detection unit 218 in step S301. To get. The camera motion detection unit 218 (blur detection unit) acquires angular velocity information in the camera rotation direction from the gyro sensor, and acquires the amount of fluctuation for a certain period. Then, an average value of the obtained fluctuation amounts is calculated, and it is determined that the camera is moving when a certain threshold value is exceeded.

  Next, it is determined whether or not the shutter speed (Tv) is faster than a preset first threshold value Tvth1 among the exposure conditions obtained in step S204 when shooting with the flash being non-lighted (step S302). . In the second embodiment, it is assumed that the first threshold value Tvth1 is set to a different value according to the angle of view variation such as zoom.

  In the second embodiment, when the shutter speed Tv obtained in step S204 is not faster than the preset first threshold value Tvth1, in addition to determining the distance to the subject and the stationary state of the subject, Whether the camera is stationary is determined (step S303). If it is determined that the camera 100 'is moving, a light emission determination is made (step S211), and a light emission condition is calculated (step S212).

On the other hand, if the camera is Ru stationary Tei, the process proceeds to step S207, to check the motion information of the subject. When it is determined that the subject is stationary, the exposure condition when no light is emitted is recalculated (step S208). If the reset exposure condition does not reach the limit of exposure control and is within the appropriate exposure range (YES in step S209), the reset shutter speed (Tv) is preset in step S304. It is determined whether or not it is faster than the second threshold value Tvth2. Here, the second threshold value Tvth2 is a shutter speed at which there is a possibility that the influence of camera shake occurs in a stable state with little camera movement, and is different from the first threshold value Tvth1.

  If the reset shutter speed (Tv) is faster than the second threshold value Tvth2, a non-emission determination is made, and the process proceeds to the main exposure process under the reset exposure conditions (step S210). On the other hand, if it is not faster than the second threshold value Tvth2, in order to maintain appropriate luminance, a light emission judgment is made (step S211), and a light emission condition is calculated (step S212).

  As described above, according to the second embodiment, in addition to the first embodiment described above, when the subject is out of the dimming range, if the movement of the digital camera and the movement of the subject are small, the shutter speed Increase the exposure adjustment time. As a result, it is possible to adjust the amount of light using the flash more appropriately.

  In the above two embodiments, whether or not the shutter speed (Tv) is faster than a preset threshold value is taken into account in the flash emission determination, but the flash emission determination is made without taking the shutter speed (Tv) into consideration. You may make it perform.

Further, although a plurality of conditions are provided for the determination of flash emission, the order used for the determination is not limited to the described order, and the flash emission determination may be performed in an order different from the described order.
Further, although a plurality of conditions are provided for the determination of flash emission, the conditions to be used may be changed according to the selected shooting mode as long as the shooting mode can be selected from a plurality of modes. For example, when the night view mode for shooting that specializes in night scenes is selected, it is assumed that the subject is moving in a small shooting scene. Therefore, whether or not the subject is stationary is not taken into consideration in the flash emission determination condition. You may do it. Alternatively, when the tripod mode is selected to perform shooting that is specialized for tripod shooting with the camera body mounted on a tripod, it is assumed that there is a shooting scene with a small camera movement. You may make it not consider in the conditions of judgment. Even when other shooting modes are selected, the conditions used for the flash emission determination may be combined according to the shooting scene in which each shooting mode is assumed to be used. However, whether or not the distance to the subject is within the light control range of the flash is taken into consideration in the flash emission determination condition.

  In addition, although the flash unit which is a light emitting device is built in the digital camera, an external flash device which can be attached to and detached from the digital camera may be used as the light emitting device.

  Further, instead of calculating the distance to the subject from the distance information obtained by performing the AF process, the distance to the subject may be calculated by other methods. For example, the distance to the subject may be calculated from the detected face size of the subject detected by the subject detection unit.

106 luminance detection unit 110 EF processing unit 111 flash unit 115 subject detection unit 116 distance object detection unit 117 light emission determination unit 218 camera motion detection unit

Claims (7)

An imaging device capable of imaging using a light emitting device,
Subject detection means for detecting a subject from image data obtained by imaging by an imaging means without using the light emitting device;
Distance detecting means for obtaining a distance to the detected subject;
Exposure control means for obtaining an exposure condition including an exposure time based on luminance information of the image data;
Determining means for determining whether to perform imaging using the light emitting device;
A calculation unit for obtaining a light emission amount to be emitted from the light emitting device based on the luminance information when the determination unit determines to perform imaging using the light emitting device ;
Movement detecting means for detecting the amount of movement of the subject;
Have
When the exposure time obtained by the exposure control means is longer than a preset exposure time and the distance to the subject is outside the dimming range of the light emitting device, the determining means determines the amount of movement of the subject in advance. An image pickup apparatus that determines whether or not to perform image pickup using the light emitting device based on whether or not a predetermined first threshold value is exceeded .   The determination unit uses the light emitting device when the exposure time obtained by the exposure control unit is longer than the preset exposure time and the distance to the subject is within the light control range of the light emitting device. The imaging apparatus according to claim 1, wherein it is determined that imaging is performed. Before SL determining means, said exposure control longer than the exposure time the exposure time the preset determined by means if that is outside the dimming range of the distance is the light emitting device to the subject, the movement of the object if the amount exceeds the first threshold value, the imaging apparatus according to claim 1 or 2, characterized in that it is determined that performs imaging by using the light emitting device. Before Symbol exposure control means is longer than the exposure time the exposure time the preset determined by the exposure control means, when the distance to the subject is Ru dimming range near the light-emitting device, of the subject if the motion amount is less than the first threshold value, adjusted in accordance with said exposure time obtained based on the luminance information to the motion amount of the subject,
Said determination means, said adjusted based on the exposure time after imaging as claimed in any one of claims 1 to 3, wherein the determining whether to perform imaging by using the light emitting device apparatus. Further comprising a shake detection means for detecting the amount of movement of the imaging device,
Said determination means, said exposure control longer than the exposure time the exposure time the preset determined by means, if the distance to the subject is out of the dimming range of the light emitting device, by the shake detection means if more than a second threshold amount of motion detected the imaging device is predetermined, any one of claims 1 to 3, characterized in that it is determined that performs imaging by using the light emitting device The imaging device described in 1.   2. The determination unit according to claim 1, wherein when the exposure time obtained by the exposure control unit is not longer than the preset exposure time, the determination unit determines to perform imaging without using the light emitting device. The imaging device according to any one of 1 to 5. A method for controlling a light emitting device used together with an imaging device,
From the image data obtained by imaging by the imaging means without using the pre-Symbol emitting device, a subject detection step of detecting an object,
A distance detection step of determining the distance to the object that has been pre-Symbol detection,
Based on the luminance information before Symbol image data, the exposure control step of determining the exposure conditions including exposure time,
A determination step of determining whether to perform imaging by using a pre-Symbol emitting device,
If it is determined that performs imaging by using the light emitting device by the pre-Symbol decision step, a calculation step on the basis of the luminance information, obtains the light emission amount for light emitting the light emitting device,
A motion detection step of detecting the amount of motion of the subject;
Have
In the determining step, when the exposure time obtained based on the luminance information of the image data is longer than a preset exposure time and the distance to the subject is outside the dimming range of the light emitting device , the subject A method for controlling a light-emitting device, comprising: determining whether or not to perform imaging using the light-emitting device based on whether or not a movement amount of the light exceeds a predetermined first threshold value .

Images