JP2012235325A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of excellently detecting a flicker.SOLUTION: An imaging apparatus includes: a charge storage type photometric element (137); a storage time control part (172) for transmitting a first storage time for photometry or a second storage time for the detection of a flicker due to the periodical luminance change of a light source to the photometric element thereby to allow the photometric element to perform charge storage in the first storage time or the second storage time; an acquisition part (171) for acquiring an output from the photometric element; a photometric part (173) for performing photometry on the basis of an output from the photometric element, which is stored in the first storage time; and a flicker detection part (175) for detecting the flicker on the basis of an output from the photometric element, which is stored in the second storage time.

Description

  The present invention relates to an imaging apparatus.

  2. Description of the Related Art Conventionally, in an imaging apparatus, an attempt has been made to detect flicker caused by AC lighting and suppress the influence of flicker. For example, Patent Document 1 discloses a technique for detecting flicker based on an output from a focus detection sensor using a phase difference method.

JP 2007-306093 A

  However, in the case of detecting flicker based on the output from the focus detection sensor using the phase difference method as described in Patent Document 1, the focus detection sensor using the phase difference method can be used for photographing with the image sensor. Since the luminance information cannot be obtained for the entire range, the flicker detection accuracy is insufficient.

  An object of the present invention is to provide an imaging apparatus that can detect flicker well.

  The present invention solves the above problems by the following means. In the following description, the reference numerals corresponding to the drawings showing the embodiments of the present invention are used for explanation, but these reference numerals are only for facilitating the understanding of the present invention and are not intended to limit the invention. Absent.

  [1] The imaging device of the present invention includes a charge accumulation type photometric element (137), a first accumulation time for photometry, and a second accumulation for detecting flicker caused by a periodic luminance change of the light source. An accumulation time control unit (172) for causing the photometric element to accumulate electric charge during the first accumulation time or the second accumulation time by sending any one of the times to the photometric element; and the photometric element Based on the output from the photometric element accumulated in the first accumulation time, the photometric unit (173) that performs photometry based on the output from the photometric element accumulated in the first accumulation time, and accumulated in the second accumulation time And a flicker detection unit (175) for performing flicker detection based on the output from the photometric element.

  [2] In the imaging apparatus of the present invention, the acquisition unit (171) outputs an output from the photometric element when the charge is accumulated by the photometric element (137) in the second accumulation time. , It can be configured to read by thinning.

  [3] In the imaging apparatus of the present invention, the accumulation time control unit (172) periodically switches between the first accumulation time and the second accumulation time and sends the first accumulation time to the photometric element (137). Can be configured.

  [4] The imaging apparatus of the present invention further includes a scene recognizing unit (174) for recognizing a type of a shooting scene based on an output from the photometric element (137), and the accumulation time control unit (172) includes: In the case where the scene recognition unit recognizes the type of the photographic scene, when the photometry element accumulates charges during the first accumulation time, the timing of charge accumulation by the photometry element is the flicker of the flicker. The accumulation time of the photometric element can be controlled so that the timing is different from the timing at which the light amount of the light source is minimized.

  [5] In the imaging apparatus of the present invention, the flicker detection unit (175) repeatedly performs flicker cycle detection based on the output from the photometric element (137) accumulated in the second accumulation time. The detected flicker cycle can be corrected.

  ADVANTAGE OF THE INVENTION According to this invention, the imaging device which can detect a flicker favorably can be provided.

FIG. 1 is a block diagram showing a single-lens reflex digital camera 1 according to this embodiment. FIG. 2 is a view showing a light receiving surface of the photometric sensor according to the present embodiment. FIG. 3 is a block diagram showing a circuit configuration of the camera 1 according to the present embodiment. FIG. 4A is a diagram illustrating an example of luminance change of a flicker light source such as a fluorescent lamp or a mercury lamp, and FIG. 4B is a diagram illustrating an example of intensities of a red R component and a blue B component of the flicker light source. is there. FIG. 5 is a flowchart showing the operation of the camera 1 according to this embodiment. FIG. 6 is a flowchart showing photometric processing according to the present embodiment. FIG. 7 is a diagram illustrating execution timings of peak AGC control, subject-oriented AGC control, and flicker detection control according to the present embodiment. FIG. 8 is a flowchart of flicker detection control in the present embodiment. FIG. 9 is a diagram showing an example of a scene when a flicker light source exists within the light receiving range of the photometric sensor. FIG. 10 is a diagram illustrating an example of a change in average luminance value of each divided region in the scene example illustrated in FIG. 9. FIG. 11 is a diagram showing another example of the scene when the flicker light source exists within the light receiving range of the photometric sensor. FIG. 12 is a diagram showing the relationship between the luminance change due to flicker and the luminance value of flicker detection data by the photometric sensor.

  In the following, an embodiment in which the present invention is applied to a single-lens reflex digital camera will be described with reference to the drawings. However, the present invention can also be applied to other imaging devices such as a silver salt film camera.

  FIG. 1 is a block diagram showing a single-lens reflex digital camera 1 according to this embodiment, and illustration and description of a general configuration of the camera other than the configuration related to the imaging apparatus of the present invention are partially omitted.

  The single-lens reflex digital camera 1 of this embodiment (hereinafter simply referred to as the camera 1) includes a camera body 100 and a lens barrel 200, and the camera body 100 and the lens barrel 200 are detachably coupled. In the camera 1 of the present embodiment, the lens barrel 200 is replaceable depending on the purpose of shooting.

  The lens barrel 200 incorporates a photographing optical system including lenses 211, 212, 213 and a diaphragm 220.

  The focus lens 212 is provided so as to be movable along the optical axis L1 of the lens barrel 200, and its position is adjusted by the focus lens drive motor 230 while its position is detected by the encoder 260. Then, the current position information of the focus lens 212 detected by the encoder 260 is sent to the camera control unit 170 described later via the lens control unit 250. Then, the drive amount Δd of the focus lens 212 calculated based on this information is sent from the lens drive control unit 165 via the lens control unit 250, and based on this, the focus lens drive motor 230 is driven.

  The aperture 220 has an aperture diameter centered on the optical axis L1 in order to limit the amount of light flux that passes through the imaging optical system and reaches the image sensor 110 provided in the camera body 100 and adjusts the amount of blur. It is configured to be adjustable. The adjustment of the aperture diameter by the diaphragm 220 is performed, for example, by sending an appropriate aperture diameter calculated in the automatic exposure mode from the camera control unit 170 via the lens control unit 250. Further, the set aperture diameter is input from the camera control unit 170 to the lens control unit 250 by a manual operation by the operation unit 150 provided in the camera body 100. The aperture diameter of the aperture 220 is detected by an aperture sensor (not shown), and the lens controller 250 recognizes the current aperture diameter.

  On the other hand, the camera body 100 includes a mirror system 120 for guiding the light flux from the subject to the image sensor 110, the finder 135, the photometric sensor 137, and the focus detection module 161. The mirror system 120 includes a quick return mirror 121 that rotates by a predetermined angle between the observation position and the photographing position of the subject around the rotation axis 123, and the quick return mirror 121 that is pivotally supported by the quick return mirror 121. And a sub mirror 122 that rotates in accordance with the rotation. In FIG. 1, a state where the mirror system 120 is at the observation position of the subject is indicated by a solid line, and a state where the mirror system 120 is at the photographing position of the subject is indicated by a two-dot chain line.

  The mirror system 120 is inserted on the optical path of the optical axis L1 in the state where the subject is in the observation position, while rotating so as to retract from the optical path of the optical axis L1 in the state where the subject is in the photographing position.

  The quick return mirror 121 is composed of a half mirror, and in a state where the subject is at the observation position, the quick return mirror 121 reflects a part of the light flux (optical axes L2 and L3) from the subject (optical axis L1). Then, the light is guided to the finder 135 and the photometric sensor 137, and a part of the light beam (optical axis L4) is transmitted and guided to the sub mirror 122. On the other hand, the sub mirror 122 is configured by a total reflection mirror, and guides the light beam (optical axis L4) transmitted through the quick return mirror 121 to the focus detection module 161.

  Therefore, when the mirror system 120 is at the observation position, the light beam (optical axis L1) from the subject is guided to the finder 135, the photometric sensor 137, and the focus detection module 160, and the subject is observed by the photographer and exposure calculation is performed. And the focus adjustment state of the focus lens 212 is detected. When the photographer fully presses a release button (not shown), the mirror system 120 is rotated to the photographing position, and all the light flux (optical axis L1) from the subject is guided to the image sensor 110, and the photographed image data is illustrated. Do not save to memory.

  The light beam from the subject reflected by the quick return mirror 120 forms an image on a focusing screen 131 disposed on a surface optically equivalent to the image sensor 110 and can be observed through the pentaprism 133 and the eyepiece lens 134. It has become. At this time, the transmissive liquid crystal display 132 superimposes and displays a focus detection area mark on the subject image on the focusing screen 131 and relates to shooting such as the shutter speed, aperture value, and number of shots in an area outside the subject image. Display information. As a result, the photographer can observe the subject, its background, and photographing related information through the finder 135 in the photographing preparation state.

  The photometric sensor 137 is composed of a two-dimensional color CMOS image sensor or the like, and divides the photographing screen into a plurality of regions and outputs an output signal corresponding to the luminance of each region in order to calculate an exposure value at the time of photographing. The photometric sensor 137 also serves as an image sensor for scene recognition and an image sensor for flicker detection. An output signal corresponding to the subject image formed on the focusing screen 131 by the photographing optical system, and flicker detection The output signal is output. The signal detected by the photometric sensor 137 is output to the camera control unit 170 and used for automatic exposure control, scene recognition processing, and flicker detection processing.

  FIG. 2 is a view showing the light receiving surface 137a of the photometric sensor 137. As shown in FIG. The photometric sensor 137 is configured by arranging a plurality of pixels (for example, 22 rows and 14 columns), each pixel including a red R, green G, and blue B filter and a photometric unit, and a red R component. , The photometric values of the green G component and the blue B component are output. The photometric sensor 137 is divided into 15 divided regions as shown in FIG. However, the number of the divided regions is not limited to 15 and can be set as appropriate.

  Returning to FIG. 1, the focus detection module 160 is fixed at a position on the optical axis L4 of the light beam reflected by the sub mirror 122 and optically equivalent to the image pickup surface of the image pickup device 110. Automatic focusing control is executed by the phase difference detection method used.

  The image sensor 110 is provided on the optical axis L1 of the light beam from the subject of the camera body 100 and at a position that is a planned focal plane of the photographing optical system including the lenses 211, 212, and 213, and a shutter 111 is provided on the front surface thereof. Is provided. The image sensor 110 is a two-dimensional array of a plurality of photoelectric conversion elements, and can be constituted by a two-dimensional CCD image sensor, MOS sensor, CID, or the like. The electrical image signal photoelectrically converted by the image sensor 110 is subjected to image processing by the camera control unit 170 and then stored in a memory (not shown). Note that the memory for storing the photographed image can be constituted by a built-in memory or a card-type memory.

  The operation unit 150 is a shutter release button, a zoom button, and an input switch for a photographer to set various operation modes of the camera 1, and switches between an automatic exposure mode / manual exposure mode, an auto focus mode / manual focus mode, and the like. Can be set. The shutter release button switch includes a first switch SW1 that is turned on when the button is half-pressed and a second switch SW2 that is turned on when the button is fully pressed.

  The camera body 100 is provided with a camera control unit 170. The camera control unit 170 includes peripheral components such as a microprocessor, an ASIC, and a RAM, and is electrically connected to the lens control unit 250. From the lens control unit 250, information on the focus adjustment range of the lens barrel 200 is included. The lens information is received and information such as an aperture control signal is transmitted to the lens control unit 250.

  Further, as shown in FIG. 3, the camera control unit 170 of the present embodiment includes an A / D converter 171, a photometric sensor control unit 172, a photometric calculation unit 173, a scene recognition unit 174, a flicker detection unit 175, and a focus detection calculation. Part 176 is provided.

The photometric sensor control unit 172 controls the charge accumulation time and the amplifier gain of the photometric sensor 137. Specifically, the photometric sensor control unit 172 detects photometry accumulation time T _p for performing photometry of the object scene, scene recognition accumulation time T _S for performing scene recognition, and light source flicker detection. An accumulation time _TF for flicker detection for performing the above is set. Then, the photometric sensor control unit 172 switches the photometric storage time T _p , the scene recognition storage time T _S, and the flicker detection storage time T _F and outputs the result together with the amplifier gain to the photometric sensor 137. Thus, the photometric sensor 137 performs photometric charge accumulation, scene recognition charge accumulation, or flicker detection charge accumulation.

For example, when performing photometry of the object scene, the photometry sensor control unit 172 causes the maximum luminance of the object scene to be the target photometry value, that is, the maximum output of the photometry sensor 137 is the target value. set the accumulation time T _p for photometry, with amplifier gain accumulation time T _p for photometry, by outputting the photometric sensor 137, controls the charge storage time and the amplifier gain of the photometric sensor 137. In the present embodiment, such control of the photometric sensor 137 is referred to as “peak AGC control”.

When performing scene recognition, the photometric sensor control unit 172 performs scene recognition so that the average luminance of the object scene becomes the target photometric value, that is, the average output of the photometric sensor 137 becomes the target value. storing sets the time T _S of the storage time T _S for scene recognition with amplifier gain, by outputting the photometric sensor 137, controls the charge storage time and the amplifier gain of the photometric sensor 137. In the present embodiment, such control of the photometric sensor 137 is referred to as “subject-oriented AGC control”.

Furthermore, when performing flicker detection, photometric sensor control unit 172, so as to be able to detect a period of the flicker, to set the accumulation time T _F for flicker detection, the accumulation time T _F of the flicker detection with amplifier gain By outputting to the photometric sensor 137, the charge accumulation time and amplifier gain of the photometric sensor 137 are controlled. In the present embodiment, such control of the photometric sensor 137 is referred to as “flicker detection control”.

4A shows an example of luminance change of a flicker light source such as a fluorescent lamp or a mercury lamp, and FIG. 4B shows an example of intensity of red R component and blue B component of the flicker light source. It is. As shown in FIG. 4A, the flicker light source repeats blinking periodically at a predetermined flicker cycle. For example, when the flicker light source uses a commercial power source as a power source, the flicker cycle is 10.0 ms with a 50 Hz power source, and the flicker cycle is 8.3 ms with a 60 Hz power source. Therefore, in the present embodiment, the flicker detection accumulation time _TF is set to such a time that such a flicker cycle can be detected. In the flicker light source, as shown in FIG. 4B, the red R component and the blue B component have different intensity change levels according to the flicker cycle. In such a portion, the intensity difference between them becomes the maximum, and the image picked up in the blinking valley portion becomes a yellowish image.

As described above, when the flicker light source is present and the charge accumulation time of the photometry sensor 137 or the charge accumulation time of the image sensor 110 is short, the luminance of the subject to be detected and imaged or the subject is influenced by the flicker light source. May change the color of. When subject-oriented AGC control for scene recognition is performed by the photometric sensor 137 in such a blinking valley portion, scene recognition accuracy may be reduced. Therefore, in this embodiment, in order to remove the influence of such a flicker light source, flicker detection control is performed by causing the photometric sensor 137 to accumulate charges during the flicker detection accumulation time _TF . Details of the flicker detection control will be described later.

  In addition, the photometric sensor control unit 172 includes a first timer (not shown) for switching the above-described peak AGC control, subject-oriented AGC control, and flicker detection control, and the count value of the first timer is determined in advance. Until the predetermined value is exceeded, the peak AGC control and the subject-oriented AGC control are repeatedly executed. When the predetermined value is exceeded, the count value of the first timer is reset to zero and flicker detection control is executed. That is, the photometric sensor control unit 172 switches between execution of peak AGC control and subject-oriented AGC control and execution of flicker detection control according to the count value of the first timer.

Further, the output signal from the photometric sensor 137 is converted into a digital signal by the A / D converter 171 and then input to the photometric sensor control unit 172. The photometric sensor control unit 172 On the basis of the output signal from, the accumulation time T _p for photometry, the accumulation time T _S for scene recognition, and the accumulation time T _F for flicker detection are set by feedback control.

The photometric calculation unit 173 receives an output signal from the photometric sensor 137 converted into a digital signal by the A / D converter 171 when charge is accumulated by the photometric sensor 137 according to the photometric accumulation time T _p. Then, based on the output signal from the photometric sensor 137, photometric calculation is performed, the subject brightness is calculated, and the shutter speed and aperture value corresponding to the brightness are determined.

Scene recognition unit 174, the storage time T _S for scene recognition, if the charge accumulation is performed by the photometry sensor 137, receiving the output signal from the photometry sensor 137 that has been converted by the A / D converter 171 into a digital signal Then, based on an output signal from the photometric sensor 137, color information and luminance information of a photographed image photographed by the photometric sensor 137 are detected, and based on these information, main subjects such as human faces in the image are detected. Recognize the area and detect the position and movement of the main subject. Then, the scene recognition unit 174 outputs information on the position and movement of the main subject such as a person to the focus detection calculation unit 176.

The flicker detection unit 175 receives an output signal from the photometric sensor 137 that has been converted into a digital signal by the A / D converter 171 when the photometric sensor 137 accumulates charges according to the flicker detection accumulation time _TF. The flicker cycle is detected based on the output signal from the photometric sensor 137.

  Further, the flicker detection unit 175 controls the timing at which the subject-focused AGC control is executed in order to suppress the influence of the flicker when the subject-focused AGC control is performed based on the calculated flicker cycle. A second timer (not shown) is provided. The second timer is reset when counted up to the flicker period based on the calculated flicker period (for example, see FIG. 4), and the timing of this reset is the flicker valley (the luminance is minimum) in the flicker period. Are set so as to be shifted by a time α (where α <flicker cycle). In other words, the second timer is periodically reset at “timing that becomes the flickering valley in the flicker cycle + α”, in other words, at the reset timing, it always shifts from the flickering valley in the flicker cycle. Is set as follows.

  The focus detection calculation unit 176 focuses on the main subject based on the position and motion information of the main subject obtained from the scene recognition unit 174 and the defocus amount of the focus detection area obtained from the focus detection module 160. The lens driving amount Δd is calculated. Then, the focus detection calculation unit 176 sends a drive command to the focus lens drive motor 230 via the lens control unit 250 and moves the focus lens 212 by the lens drive amount Δd, thereby adjusting the focus of the optical system. .

  Next, an operation example of the camera 1 according to this embodiment will be described. FIG. 5 is a flowchart showing the operation of the camera 1 according to this embodiment. The operation described below starts when the shooting mode is selected by the operation unit 150 and is executed by the camera control unit 170.

  First, in step S1, it is determined whether or not the photographer has pressed the shutter release button halfway (the first switch SW1 is turned on). When the first switch SW1 is turned on, the process proceeds to step S2. On the other hand, if the first switch SW1 is not turned on, the process proceeds to step S11. If the predetermined time has not elapsed since the shooting mode was selected (step S11 = No), the process proceeds to step S1. If the operation for turning on the first switch SW1 is not performed for a predetermined time or longer (step S11 = Yes), the imaging control is terminated.

  In step S2, photometric processing is performed. The photometry process will be described later.

  In step S <b> 3, the focus detection calculation unit 176 performs focus detection processing based on the output signal from the focus detection module 160.

  In step S4, it is determined whether the photographer has fully pressed the shutter release button (second switch SW2 is turned on). When the second switch SW2 is turned on, the process proceeds to step S5. When the second switch SW2 is not turned on, the process returns to step S1, and as long as the first switch SW1 is kept on (step S1 = Yes), Steps S1 to S4 are repeated.

  In step S5, the quick return mirror 121 and the sub mirror 122 constituting the mirror system 21 are rotated in the direction of retracting from the optical path of the optical axis L1, and the imaging element 110 is initialized in the subsequent step 6.

  In step S <b> 7, the image sensor 110 is caused to accumulate electric charges, and an image signal is read from the image sensor 110. In this charge accumulation for imaging, the exposure is adjusted by controlling the shutter 111 and the diaphragm 214 so that the control exposure obtained by the photometric calculation result by the photometric process described later is obtained. If the charge accumulation time for imaging is shorter than the flicker cycle calculated in step S213 described later, the reset timing of the second timer set in step S214 described later (that is, the blinking valley in the flicker cycle). Control is performed such that charge accumulation for imaging is started at time α (where α <flicker cycle) is deviated from the time point when the luminance becomes the minimum).

  In step S8, the quick return mirror 121 and the sub mirror 122 constituting the mirror system 21 are returned to the optical path of the optical axis L1, and in a subsequent step S9, predetermined processing is performed on the image signal to generate an image. Thereafter, in step S10, an image is recorded on a recording medium (not shown), and the photographing control is terminated.

  Next, the photometric process in step S2 will be described. FIG. 6 is a flowchart showing photometric processing according to the present embodiment.

  First, in step S101, the photometric sensor control unit 172 determines whether or not the count value of the first timer is equal to or greater than a predetermined value. When the count value of the first timer is not equal to or greater than the predetermined value, the process proceeds to step S102, and when the count value of the first timer is equal to or greater than the predetermined value, the process proceeds to step S118. Note that, as described above, the first timer is a timer for switching execution of peak AGC control, subject-oriented AGC control, and flicker detection control. For example, in step S1 of FIG. When the 1 switch SW1 is turned on, the count is started. In the present embodiment, until the count value of the first timer becomes equal to or greater than a predetermined value, the process proceeds to step S102 where peak AGC control and subject-oriented AGC are performed, while the count of the first timer is equal to or greater than the predetermined value. Only when it becomes, the process proceeds to step S118, the count of the first timer is reset to zero, the process proceeds to step S119, and flicker detection control is performed. Note that the predetermined value in this case is not particularly limited, but may be a time at which flicker detection control is executed instead of peak AGC control at intervals of about once every 50 times.

Next, in step S102, peak AGC control is performed. More specifically, in order to perform the photometry of the subject field, the photometric sensor control unit 172, the accumulation time T _p for photometry, and outputs the photometry sensor 137 together with the amplifier gain, the accumulation time for photometry photometry sensor 137 Charge accumulation is performed at T _p , and photometric data is read from the photometric sensor 137. As the accumulation time _{T p} for photometry in the previous process, calculated in step S104 to be described later, the next photometric accumulation time _{T p_next} is used. Alternatively, in the first photometry, since the next photometry accumulation time T _{p_next} cannot be calculated in step S104 described later, the photometry accumulation time T _p is set to a predetermined time (for example, 5 ms).

  In step S103, it is determined whether or not the photometric data read from the photometric sensor 137 is valid data. In this validity determination, it is determined whether or not the maximum photometric value is close to the target value and is suitable for performing photometric calculation.

In step S104, the photometric sensor control unit 172 calculates the next photometric accumulation time T _{p_next} for performing accumulation for the next photometry according to the following formula (1), and based on the calculated next photometric accumulation time T _{p_next.} Set the amplifier gain.
T _p — _next = V _agc / V _omax · T _p (1)
In the above equation (1), T _p is the next metering accumulation time, T _p is the metering accumulation time at the current processing, V _agc is the target value (target AGC level), and V _omax is the photometric sensor 137 at the current processing. Maximum output value.

  In step S105, the photometric calculation unit 173 calculates the average photometric value in the entire region of the photometric sensor 137, calculates the average photometric value for each divided region shown in FIG. Extraction of the minimum region is performed.

  In step S106, if it is determined in step S103 described above that the photometric data is not valid data, the process returns to step S102, and the processes in steps S102 to S105 described above are performed once again. On the other hand, if it is determined that the photometric data is valid data, the process proceeds to step S107.

  In step S107, the photometric sensor control unit 172 determines whether to execute subject-oriented AGC control for scene recognition. Specifically, it is determined whether or not the difference between the maximum value and the minimum value among the average photometric values for each divided region calculated in step S105 is equal to or greater than a predetermined value. When these differences are smaller than a predetermined value, the subject is a uniform subject with a small difference in luminance, and is not suitable for subject-oriented AGC control in which the average luminance becomes the target photometric value. Is determined not to be executed. On the other hand, since luminance information and color information are used for scene recognition, if the difference between the maximum value and the minimum value of the average photometric value for each divided region is a predetermined value or more, charge accumulation by subject-oriented AGC control is performed. It is determined that scene recognition is performed based on the photometric value of the accumulation result.

In step S108, the photometric sensor control unit 172 calculates the scene recognition accumulation time T _S for performing subject-oriented AGC control according to the following equation (2), and calculates the calculated scene recognition accumulation time T _S. Based on the above, the amplifier gain is set.
T _S = V _agc SC / V _ave · T _p (2)
In the above equation (2), T _S is the accumulation time for scene recognition, T _p is the accumulation time for photometry during the current process, V _agc SC is the target value (target AGC level) of the subject-oriented AGC, and V _ave is the peak It is the average value of the output value of the photometry sensor 137 in AGC control.

  In step S109, the photometric sensor control unit 172 performs photometric calculation based on photometric data obtained by peak AGC control, and calculates the shutter speed and aperture value.

  In step S110, if subject-focused AGC control is executed according to the determination result in step S107 described above, the process proceeds to step S111. If subject-focused AGC control is not performed, the process proceeds to step S115.

  When subject-focused AGC control is executed, the process proceeds to step S111, and it is determined whether or not flicker is detected in flicker detection control in step S119 described later. If flicker is detected, the process proceeds to step S112. If flicker is not detected, the process proceeds to step S113.

  If it is determined in step S111 that flicker has been detected, the process proceeds to step S112, where the reset timing of the second timer set in step S214 (to be described later) (that is, the blinking valley in the flicker cycle (the luminance is minimized). The process waits for a time α (where α <flicker cycle) is deviated from the point of time), and then proceeds to step S113.

In step S113, subject-oriented AGC control is performed. More specifically, in order to perform the scene recognition, photometry sensor control unit 172, the accumulation time T _S for scene recognition, with amplifier gain, and outputs the photometry sensor 137, the photometry sensor 137, storage for scene recognition and to perform the charge accumulation time T _S, reads the photometric data from the photometric sensor 137. In addition, as the accumulation time T _S for scene recognition, the one calculated in step S108 described above can be used. If it is determined in step S111 that flicker has been detected, charge accumulation by the photometric sensor 137 is started at the reset timing of the second timer. According to the present embodiment, the timing of charge accumulation by the photometric sensor 137 when performing subject-oriented AGC control is thus started by starting the charge accumulation by the photometric sensor 137 at the reset timing of the second timer. Can be shifted from the period.

  In step S114, it is determined whether or not the photometric data read from the photometric sensor 137 is valid data, that is, whether or not the sensor output is normal.

  In step S115, it is determined whether the currently set focus mode is the tracking mode or the auto area AF mode. If the focus mode is the tracking mode, the process proceeds to step S116. If the focus mode is the auto area AF mode, the process proceeds to step S117. In step S116, the focus detection calculation unit 176 performs template matching between a captured image in subject-oriented AGC control by the photometric sensor 137 and a template image of a specific subject set in advance, and tracks the specific subject to focus on the specific subject. An appropriate lens drive amount Δd is calculated, and the focus lens 212 is moved by the lens drive amount Δd, thereby adjusting the focus of the optical system. On the other hand, in step S117, an area of a subject such as a background and a person is extracted from a captured image in subject-oriented AGC control by the photometric sensor 137, and a lens driving amount Δd that focuses on the subject such as a person is calculated. The focus adjustment of the optical system is performed by moving the focus lens 212 by the drive amount Δd.

  The photometric process is performed as described above. When the photometry process is completed, after the focus detection process is performed in step S3 shown in FIG. 5, the second switch SW2 is not turned on (step S4 = No), and the first switch SW1 is continued. If it is turned on (step S1 = Yes), the process again proceeds to step S101 shown in FIG. Until the count value of the first timer becomes equal to or greater than the predetermined value, the above-described peak AGC control and subject-oriented AGC control are repeatedly performed (step S101 = No), while the count of the first timer is equal to or greater than the predetermined value. When it becomes (step S101 = Yes), the count value of the first timer is reset to zero in step S118, and the process proceeds to step S119, where flicker detection control is performed instead of peak AGC control. That is, in the present embodiment, as shown in FIG. 7, the peak AGC control and the subject-oriented AGC control are performed until the first switch SW1 is continuously turned on and the second switch SW2 is turned on. Are repeatedly executed, and flicker detection control is executed instead of peak AGC control at a predetermined interval (that is, an interval at which the count value of the first timer is equal to or greater than a predetermined value). Although FIG. 7 shows an example in which flicker detection control is executed instead of peak AGC control at intervals of once every five times, the interval at which flicker detection control is executed is particularly limited. For example, the flicker detection control may be executed at an interval of about once every 50 times.

  Hereinafter, flicker detection control in this embodiment will be described. FIG. 8 is a flowchart of flicker detection control in the present embodiment.

First, in step S201, it is determined whether or not the next photometric accumulation time T _{p_next} in the peak AGC control calculated in step S104 described above is less than 10 ms. If the next photometric accumulation time T _{p_next} in peak AGC control is less than 10 ms, it is determined that flicker detection is necessary, and the process proceeds to step S202. On the other hand, when the next photometry accumulation time T _{p_next} in the peak AGC control is 10 ms or more, the next photometry accumulation time T _{p_next} in the peak AGC control is longer than the flicker cycle, and therefore the influence of flicker is small. It is determined that it is not necessary to detect, and the flicker detection control is terminated. In the present embodiment, assuming that the power source of the flicker light source is a 50 Hz or 60 Hz power source, it is determined whether or not the next photometric accumulation time T _{p_next} is less than 10 ms. _However , the length of the next photometric accumulation time T _{p_next} when making such a determination is not particularly limited to 10 ms, and can be appropriately changed according to the frequency of the power source of the flicker light source.

In step S202, the photometric sensor control unit 172 sets the flicker detection accumulation time _TF for causing the photometric sensor 137 to perform measurement for flicker detection. The flicker detection accumulation time _TF is set to such a time that the flicker cycle can be detected, for example, about 1/8 to _1/16 of the next photometric accumulation time T _{p_next} in peak AGC control. The photometric sensor control unit 172 also sets the amplifier gain of the photometric sensor 137 in accordance with the flicker detection accumulation time _TF as well as the flicker detection accumulation time _TF . The amplifier gain is set to 4 times or 8 times the amplifier gain in the peak AGC control, for example.

In step S203, the photometric sensor control unit 172 outputs the flicker detection accumulation time _TF set in step S202, together with the amplifier gain, to the photometric sensor 137, and accumulates charges for flicker detection in the photometric sensor 137. Accordingly, flicker detection data is read from the photometric sensor 137. In this case, in order to increase the reading speed of flicker detection data from the photometric sensor 137, the data from the photometric sensor 137 may be read out. By reading out the data from the photometric sensor 137, the reading time of flicker detection data can be shortened, and the interval of charge accumulation for flicker detection by the photometric sensor 137 can be shortened. It is possible to collect flicker detection data.

  In step S204, the flicker detection unit 175 determines whether or not the photometry sensor 137 has performed charge accumulation for flicker detection and reading of flicker detection data from the photometry sensor 137 a predetermined number of times. Is done. If the charge accumulation for flicker detection and the reading of the data for flicker detection are executed a predetermined number of times, the process proceeds to step S205. If the number is less than the predetermined number, the process returns to step S203 and flicker detection is performed until the predetermined number of times is reached. Charge storage and flicker detection data are repeatedly read out. Note that the predetermined number of times in this case is not particularly limited, but may be the number of times that data that can sufficiently detect the flicker period can be collected. Further, instead of whether or not the charge accumulation for flicker detection and the reading of the data for flicker detection have been executed a predetermined number of times, the charge accumulation for flicker detection and the reading of the data for flicker detection are performed for a predetermined time. It may be configured to make the above determination based on whether or not.

  In step S205, a variable N indicating the number of the frame to be processed is set to N = 1. In subsequent step S206, the flicker detection data repeatedly measured and read in steps S203 and S204 by the flicker detection unit 175. Among them, processing for calculating an average luminance value for each divided region of the light receiving surface 137a of the photometric sensor 137 shown in FIG. That is, for example, when N = 1, the average luminance value for each divided area of the light receiving surface 137a is calculated for the flicker detection data measured and read out in the first frame.

  In step S207, the flicker detection unit 175 performs processing for extracting a region where the average luminance value for each divided region calculated in step S205 is maximum for the flicker detection data measured and read in the Nth frame. Here, FIG. 9 shows an example of a scene in the case where a flicker light source exists within the light receiving range of the photometric sensor 137, and FIG. 10 shows an example of a change in average luminance value of each divided area in the example of scene shown in FIG. Show. The scene example shown in FIG. 9 shows a scene in which a flicker light source exists across the area A and the area B among the 15 divided areas of the light receiving surface 137a of the photometric sensor 137.

  Here, as shown in FIG. 10, in the case where the flicker light source exists within the light receiving range of the photometric sensor 137, when the average luminance of all areas is calculated, the areas other than the areas A and B where the flicker light source exists are calculated. Due to the influence of the area, the luminance change caused by the flicker light source becomes small. On the other hand, in region A and region B where the flicker light source exists, particularly in region B where the luminance value shows the maximum value, the luminance change due to the flicker light source is large. By using the data, the flicker cycle can be detected satisfactorily. Therefore, in the present embodiment, in order to detect the flicker cycle using such data, the flicker detection data measured / read out in the Nth frame is the region where the average luminance value for each divided region is maximum. Perform the extraction process. In the present embodiment, the region where the average luminance value is maximum is referred to as “maximum luminance region”. For example, in the example shown in FIGS. 9 and 10, the maximum luminance area is area B.

  In step S208, the flicker detection unit 175 determines whether or not the composition has been changed. In the present embodiment, whether or not the composition has been changed is determined based on whether or not the maximum luminance area of the Nth frame is the same as the maximum luminance area of the (N−1) th frame. That is, when the maximum brightness area of the Nth frame and the maximum brightness area of the (N-1) th frame are the same, it can be determined that the composition has not been changed, and the maximum brightness area of the Nth frame. If the maximum brightness area of the (N−1) th frame is different, it can be determined that the composition has been changed. For example, when the position of the flicker light source is changed from the position shown in FIG. 9 to the position shown in FIG. 11, the maximum luminance area is also changed from the area B to the area A. That is, in such a case, since the maximum luminance area is different, it can be determined that the composition has been changed. If it is determined that the composition has not been changed, the process proceeds to step S209. On the other hand, if it is determined that the composition has been changed, it is determined that it is not appropriate to perform flicker detection, and the flicker detection control is terminated. If N = 1, there is no data for the (N−1) th frame, so the process proceeds to step S209 without performing this process.

  In step S209, the flicker detection unit 175 determines whether or not the luminance value of the maximum luminance region shows a minimum value in the (N-1) th frame. When the luminance value of the maximum luminance area in the N-1th frame shows a minimum value, the frame number of the N-1th frame is stored, and the flicker flicker valley (the point at which the luminance is minimized) is stored. ) The counter starts to detect the period. If the counter for detecting the flicker flickering cycle has already been started, the count number up to the (N-2) th frame is saved, the counter value is reset, and a new count is added. Start. Whether or not the luminance value of the maximum luminance area in the N-1 frame is a minimum value is determined by, for example, the luminance value of the maximum luminance area in the N frame and the maximum luminance in the N-1 frame. This can be done by comparing the brightness value of the region. Specifically, when the luminance value of the maximum luminance region in the Nth frame is larger than the luminance value of the maximum luminance region in the N−1th frame, the maximum luminance region in the N−1th frame. It is possible to determine that the luminance value of is a minimum value. If the maximum luminance area in the N-1th frame indicates a minimum value, the process proceeds to step S210. On the other hand, if the maximum luminance area in the N-1th frame does not indicate a minimum value, the process proceeds to step S210. The process proceeds to step S213. If N = 1, there is no data in the (N−1) th frame, and the process proceeds to step S211 without performing this process.

  In step S210, the flicker detection unit 175 performs an interpolation operation based on the luminance value of the maximum luminance area extracted in step S207, and detects flicker flickering valleys (points at which the luminance is minimized). Done. FIG. 12 shows the relationship between the luminance change due to flicker and the luminance value of flicker detection data by the photometric sensor 137. As shown in FIG. 12, the flicker detection data measured by the photometric sensor 137 is not necessarily data in the flickering valley of the flicker. Therefore, in this embodiment, the frame in which the luminance value in the maximum luminance region is minimal. On the basis of the luminance value of the maximum luminance region at and the luminance value of the maximum luminance region in the surrounding frames, an interpolation operation is performed to detect a flicker flicker valley.

  In step S211, the flicker detection unit 175 determines whether N has reached a predetermined number. If N is not a predetermined number, the process proceeds to step S214, where N = N + 1, and the processes of steps S206 to S210 described above are repeated until N reaches the predetermined number. On the other hand, if N reaches a predetermined number, the process proceeds to step S212. In this case, the predetermined number can be set to a number that can obtain a sufficient sample for flicker detection.

  Next, in step S212, the flicker detection unit 175 compares the maximum value and the minimum value of the luminance values in the maximum luminance region, and determines that the flicker light source is present when the difference is equal to or greater than a predetermined value. The process proceeds to step S213. On the other hand, if the difference is less than the predetermined value, it is determined that there is no flicker light source, and the flicker detection control is terminated.

Next, in step S213, the flicker detection unit 175 calculates the flicker cycle. The flicker cycle can be calculated based on the following formula (3).
Flicker cycle = (sampling cycle by photometric sensor 137) × [(number of samples in the blinking valley) + (interpolated value)] (3)
Note that as the number of samplings between the blinking valleys, the counter value of the counter for detecting the flickering valley period described above can be used. In addition, as the interpolation value, a value after the decimal point of the calculation value calculated by the interpolation calculation in step S210 can be used. If data for a plurality of flicker cycles is obtained, the flicker cycle may be calculated by averaging the data for the plurality of flicker cycles.

  Next, in step S214, the flicker detection unit 175 performs processing for starting the second timer based on the flicker cycle calculated in step S213. In the present embodiment, when starting the second timer, it is reset when counted up to the flicker cycle calculated in step S213, and the reset timing is the flicker valley (in the flicker cycle calculated in step S212). The timing is set so as to be shifted by a time α (where α <flicker cycle) from the time point when the luminance becomes the minimum. In other words, the second timer is periodically reset at “timing that becomes the flickering valley in the flicker cycle + α”, in other words, at the reset timing, it always shifts from the flickering valley in the flicker cycle. Is set as follows. In this embodiment, if the second timer has already been started, the reset timing of the second timer is corrected based on the newly calculated flicker cycle in step S213.

  The second timer thus set controls the charge accumulation start timing by the photometric sensor 137 when performing subject-oriented AGC control in step S113 described above, and the image sensor 110 in step S7 described above. This is used to control the start timing of charge accumulation for imaging when performing imaging.

  The camera 1 of this embodiment operates as described above.

In the present embodiment, photometric accumulation time T _p for photometry of the object scene, scene recognition accumulation time T _S for scene recognition, and flicker detection for detecting light source flicker. set the accumulation time T _F of the use, storage time T _p for these _photometry switch the accumulation time T _F for storage time T _S and flicker detection for scene recognition, along with the amplifier gain, and outputs the photometry sensor 137 This causes the photometric sensor control unit 172 to perform charge accumulation for photometry (peak AGC control), charge accumulation for scene recognition (subject-oriented AGC control), or charge accumulation for flicker detection (flicker detection control). Therefore, according to the present embodiment, the flicker cycle can be satisfactorily detected by one sensor (photometric sensor 137) without providing a new sensor.

  In particular, according to the present embodiment, as shown in FIG. 7, peak AGC control and subject-oriented AGC control are repeatedly executed, and flicker detection control is executed instead of peak AGC control at predetermined intervals. By adopting such a configuration, it is possible to satisfactorily detect flicker while appropriately performing photometry and exposure control. Further, with such a configuration, flicker detection control can be repeatedly executed at a predetermined interval, whereby the calculated flicker cycle can be corrected sequentially, and based on this, the flicker cycle can be corrected. The second timer based on can be sequentially corrected, and as a result, the flicker cycle detection accuracy can be improved.

  Further, according to the present embodiment, based on the detected flicker cycle, the timing of charge accumulation for scene recognition (subject-oriented AGC control) and charge accumulation for imaging is set to the flicker valley (the luminance is minimum) in the flicker cycle. Therefore, it is possible to effectively prevent a decrease in scene recognition accuracy and a decrease in the quality of a captured image due to flicker.

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  For example, in the above-described embodiment, a configuration in which the peak AGC control, the subject-focused AGC control, and the flicker detection control are performed by the photometric sensor 137 is illustrated. However, these configurations are performed by the image sensor 110. Also good.

  In the above-described embodiment, the configuration in which the peak AGC control, the subject-focused AGC, and the flicker detection control are switched based on whether the count of the first timer is equal to or greater than the predetermined value is exemplified. The flicker detection control may be executed when the peak AGC control and the subject-oriented AGC are repeated and executed a predetermined number of times.

  Further, in the above-described embodiment, when calculating the flicker cycle, it is determined whether the flicker cycle of the 50 Hz power source is 10.0 ms or the 60 Hz power source flicker cycle is 8.3 ms, A configuration may be adopted in which the closer cycle (that is, 10.0 ms or 8.3 ms) is calculated as the flicker cycle.

  Note that the imaging apparatus 1 of the present embodiment is not limited to the single-lens reflex digital camera described above, and can also be applied to a lens-integrated digital still camera. Further, the present invention can also be applied to a small camera module, a surveillance camera, a robot visual recognition device, and the like built in a mobile phone.

DESCRIPTION OF SYMBOLS 1 ... Single-lens reflex digital camera 100 ... Camera body 110 ... Image pick-up element 137 ... Photometric sensor 150 ... Operation part 160 ... Focus detection module 170 ... Camera control part 171 ... A / D converter 172 ... Photometric sensor control part 173 ... Photometric calculation part 174 ... Scene recognition unit 175 ... Flicker detection unit 176 ... Focus detection calculation unit 200 ... Lens barrel 212 ... Focus lens 230 ... Focus lens drive motor 250 ... Lens control unit

Claims (5)

A charge storage photometric element;
Sending either one of the first accumulation time for photometry and the second accumulation time for detecting flicker due to the periodic luminance change of the light source to the photometry element, the first accumulation time or An accumulation time control unit for causing the photometric element to accumulate charges in the second accumulation time;
An acquisition unit for acquiring an output from the photometric element;
A photometric unit that performs photometry based on the output from the photometric element accumulated in the first accumulation time;
An imaging apparatus comprising: a flicker detection unit that performs flicker detection based on an output from the photometry element accumulated in the second accumulation time. The imaging device according to claim 1,
The acquisition unit is characterized in that, when charge accumulation by the photometric element is performed in the second accumulation time, the output from the photometric element is read out and read out. The imaging device according to claim 1 or 2,
The image capturing apparatus, wherein the accumulation time control unit periodically switches between the first accumulation time and the second accumulation time and sends the first accumulation time to the photometric element. In the imaging device in any one of Claims 1-3,
A scene recognizing unit for recognizing the type of the shooting scene based on the output from the photometric element;
In the case where the scene recognition unit recognizes the type of the photographic scene, the accumulation time control unit accumulates charges by the photometric element when the photometric element accumulates charges during the first accumulation time. An image pickup apparatus that controls the accumulation time of the photometric element so that the timing becomes different from the timing at which the light amount of the light source becomes the smallest in the flicker cycle. In the imaging device according to any one of claims 1 to 4,
The image pickup apparatus, wherein the flicker detection unit corrects the detected flicker cycle by repeatedly detecting the flicker cycle based on the output from the photometric element accumulated in the second accumulation time.

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