WO2010044227A1 - Imaging device - Google Patents

Imaging device Download PDF

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Publication number
WO2010044227A1
WO2010044227A1 PCT/JP2009/005250 JP2009005250W WO2010044227A1 WO 2010044227 A1 WO2010044227 A1 WO 2010044227A1 JP 2009005250 W JP2009005250 W JP 2009005250W WO 2010044227 A1 WO2010044227 A1 WO 2010044227A1
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WIPO (PCT)
Prior art keywords
image
flicker
shutter
accumulation time
flicker detection
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PCT/JP2009/005250
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French (fr)
Japanese (ja)
Inventor
佐藤　▲琢▼也
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株式会社ニコン
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Publication of WO2010044227A1 publication Critical patent/WO2010044227A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/70—Circuitry for compensating brightness variation in the scene
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/70—Circuitry for compensating brightness variation in the scene
    • H04N23/745—Detection of flicker frequency or suppression of flicker wherein the flicker is caused by illumination, e.g. due to fluorescent tube illumination or pulsed LED illumination
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
    • H04N25/50—Control of the SSIS exposure
    • H04N25/53—Control of the integration time
    • H04N25/531—Control of the integration time by controlling rolling shutters in CMOS SSIS

Definitions

  • the present invention relates to an imaging apparatus such as an electronic camera.
  • CMOS Complementary Metal-Oxide Semiconductor
  • flicker luminance unevenness
  • an object of the present invention is to provide an imaging apparatus that can suppress the occurrence of flicker due to a fluorescent lamp and can acquire a moving image with less frame dropping.
  • An image pickup apparatus includes an image pickup device, an electronic shutter, an image pickup device drive unit, a flicker detection exposure control unit, a flicker detection unit, and an accumulation time control unit.
  • the imaging element can two-dimensionally arrange a plurality of pixels and perform line reading by addressing.
  • the electronic shutter has a plurality of shutter functions for electronically controlling exposure to the image sensor.
  • the image sensor driving unit causes the image sensor to capture a moving image at a predetermined frame rate, and also detects a flicker detection image for detecting flicker due to a periodic change in luminance of the light source between consecutive moving image capturing.
  • the image sensor is caused to take an image using
  • the flicker detection exposure control unit sequentially switches the exposure between the first shutter speed and the second shutter speed at which the shutter speed of the electronic shutter is different for each predetermined line by address designation when capturing a flicker detection image.
  • the flicker detection unit detects the presence or absence of flicker based on a flicker detection image composed of a first image captured at the first shutter speed and a second image captured at the second shutter speed.
  • the accumulation time control unit controls the accumulation time of the image sensor for capturing a moving image using an electronic shutter according to the detection result of the flicker detection unit.
  • the accumulation time control unit controls the accumulation time by reading all pixel signals at once.
  • the accumulation time control unit controls the accumulation time by sequentially releasing the shutter for each line and reading the pixel signal for each line when the flicker detection unit does not detect flicker. To do.
  • the accumulation time control unit calculates the power supply frequency of the light source based on the flicker detection image, and sets the accumulation time as an arbitrary power supply frequency.
  • the accumulation time is controlled by setting an integral multiple and sequentially releasing the shutter for each line and reading the pixel signal for each line.
  • the exposure control unit performs the first shutter speed and the second shutter speed for each predetermined line with respect to the number of readout lines that are pre-addressed and capable of detecting at least flicker. Are alternately switched to sequentially control exposure.
  • the first shutter speed is n / 100 sec
  • the second shutter speed is m / 120 sec
  • n and m are arbitrary integers. It is.
  • the number of bits of the output signal of the analog / digital conversion is reduced when the flicker detection image is captured as compared with the time when the moving image is captured and output.
  • a bit number control unit is further provided.
  • the image pickup apparatus of the present invention it is possible to suppress the occurrence of flicker due to a fluorescent lamp and to obtain a moving image with less frame dropping.
  • FIG. 1 is a block diagram illustrating the configuration of an electronic camera 1 that is an imaging apparatus according to an embodiment
  • a flowchart showing an example of an operation example in the flicker suppression mode The figure which shows an example of the video recording using the flicker detection in 1st Embodiment.
  • the figure which shows the process of step S103 and step S104 notionally Diagram explaining the flow of flicker extraction The figure explaining an example of a window reading function
  • FIG. 1 is a block diagram illustrating a configuration of an electronic camera 1 that is an imaging apparatus according to the present embodiment.
  • the electronic camera 1 includes a photographing optical system 11, an image sensor 12, a timing generator (TG) 13, an A / D converter 14, a signal processor 15, and a RAM (Random Access Memory).
  • a recording interface (recording I / F) 17 a display unit 18, an operation unit 19, a CPU (Central processing Unit) 20, a ROM (Read Only Memory) 21, and a bus 22.
  • the signal processing unit 15, the RAM 16, the recording interface (recording I / F) 17, the display unit 18, the CPU 20, and the ROM 21 are connected to each other via a bus 22.
  • the operation unit 19 is connected to the CPU 20.
  • the photographing optical system 11 includes a plurality of lens groups including a focus lens and a zoom lens.
  • FIG. 1 shows the photographing optical system 10 as a single lens.
  • the image sensor 12 generates an image by photoelectrically converting a subject image formed on the imaging surface.
  • the image sensor 12 uses a CMOS in which a plurality of pixels are two-dimensionally arranged and line reading is possible by address designation.
  • the image pickup device 12 selects a global shutter (not shown) that sequentially releases the shutter for each line and reads all pixel signals at once, and a rolling shutter (not shown) that reads the pixel signal for each line.
  • a global shutter (not shown) that sequentially releases the shutter for each line and reads all pixel signals at once
  • a rolling shutter (not shown) that reads the pixel signal for each line.
  • the timing generator (TG) 13 sends a drive signal to each of the image sensor 12 and the A / D converter 14 according to an instruction from the CPU 20, thereby controlling the drive timing of both. More specifically, the timing generator (TG) 13 causes the image sensor 12 to capture a moving image at a predetermined frame rate in accordance with an instruction from the CPU 20, and continuously generates flicker detection images for flicker detection. The image pickup device 12 is caused to take an image using the interval between the image pickup operations.
  • the A / D converter 14 converts the analog signal generated by the image sensor 12 into a digital signal and outputs it.
  • the digital signal output from the A / D converter 14 is temporarily stored in the frame memory of the RAM 16 as a moving image or flicker detection image.
  • the signal processing unit 15 reads a digital signal (RGB signal distribution) stored in the frame memory of the RAM 16 and performs predetermined signal processing. For example, the signal processing unit 15 converts image data of RGB signals into image data of YC signals represented by luminance (Y) and color (C) as necessary. The reverse conversion is also performed.
  • RGB signal distribution digital signal distribution
  • the signal processing unit 15 is provided with an image changeover switch, an image separation circuit, an image subtraction circuit, and a determination circuit (not shown) separately from a circuit used for normal signal processing such as a clamp circuit. .
  • the image switching switch is a switch for switching between a moving image read from the RAM 16 and a flicker detection image at a predetermined timing in accordance with an instruction from the CPU 20.
  • the image changeover switch is set to a moving image, the moving image is sequentially recorded on the recording medium 23 via the bus 22, or the moving image is sequentially displayed on the display unit 18 as a through image.
  • the flicker detection image is sent to the image separation circuit.
  • the image separation circuit separates the flicker detection image into a first image (YC signal image data) captured at the first shutter speed and a second image (YC signal image data) captured at the second shutter speed. .
  • the image subtraction circuit calculates a difference in luminance value between the first image and the second image (details will be described later).
  • the determination circuit detects the presence or absence of flicker based on the difference in luminance value between the first image and the second image, and notifies the detection result to a flicker detection unit 20b described later.
  • the recording interface (recording I / F) 17 provides a communication interface so that a moving image can be recorded on the recording medium 23.
  • the display unit 18 displays an operation menu of the electronic camera 1 and the like. In the live view mode, a live image of the image sensor 12 is displayed.
  • the operation unit 19 is a release button, a command dial, or the like, and gives a signal to the CPU 20 in accordance with the operation content by the user.
  • the CPU 20 is a processor that performs overall control of the electronic camera 1.
  • the CPU 20 controls each part of the electronic camera 1 by executing a sequence program stored in advance in the ROM 21. Further, the CPU 20 of this embodiment also functions as an exposure control unit 20a for flicker detection, a flicker detection unit 20b, an accumulation time control unit 20c, and a bit number control unit 20d.
  • the exposure control unit 20a sequentially performs exposure control by alternately switching the first shutter speed and the second shutter speed for each predetermined line by addressing the image sensor 12.
  • the first shutter speed is n / 100 sec
  • the second shutter speed is m / 120 sec
  • n and m are arbitrary integers.
  • the flicker detection unit 20b instructs the signal processing unit 15 to perform flicker detection processing using the image separation circuit, the image subtraction circuit, and the determination circuit, and receives the determination result of the determination circuit.
  • the hardware configuration of the flicker detection unit 20b is handled by the signal processing unit 15.
  • the accumulation time control unit 20c controls the accumulation time of the image sensor for capturing a moving image via the timing generator (TG) 13 according to the detection result of the flicker detection unit 20b. For example, the accumulation time control unit 20c controls the accumulation time using a global shutter when the flicker detection unit 20b detects flicker.
  • the accumulation time control unit 20c controls the accumulation time using a rolling shutter when the flicker detection unit 20b does not detect flicker.
  • the bit number control unit 20d outputs an instruction to the A / D conversion unit 14, and reduces the number of bits of the output signal of the A / D conversion unit 14 when capturing a flicker detection image compared to when capturing a moving image.
  • FIG. 2 is a flowchart showing an example of an operation example in the flicker suppression mode.
  • the flowchart shown in FIG. 2 starts when the user sets the flicker suppression mode to ON and selects moving image shooting or live view display.
  • Step S101 First, the CPU 20 acquires a moving image. That is, the CPU 20 drives the timing generator (TG) 13 to cause the image sensor 12 to capture a moving image at a predetermined frame rate.
  • TG timing generator
  • this processing routine starts, it is assumed that a moving image is first picked up by the rolling shutter.
  • the line reading by the rolling shutter is performed every two lines in consideration of the RGB Bayer arrangement of the image sensor 12.
  • Step S102 The CPU 20 acquires a flicker detection image. That is, the CPU 20 drives the timing generator 13 to cause the image sensor 12 to capture the flicker detection image.
  • the exposure control unit 20a sequentially controls the exposure by alternately switching the first shutter speed and the second shutter speed every two lines by the rolling shutter. Since the frame rate is defined by the frame rate of the moving image, the exposure control unit 20a appropriately adjusts the flicker detection image accumulation time using a blanking time or the like.
  • FIG. 3 is a diagram showing an example of moving image shooting using flicker detection in the first embodiment.
  • the horizontal direction represents elapsed time
  • the vertical direction represents each horizontal line.
  • FIG. 3A is a diagram illustrating moving image shooting by a rolling shutter when flicker detection is not performed as a comparative example. As shown in FIG. 3A, images are taken at different times when signal charge accumulation starts for each line direction of the image sensor 12. Then, moving images are sequentially acquired at a predetermined frame rate.
  • FIG. 3B shows imaging in the case of flicker detection disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2007-329658) as a comparative example.
  • Patent Document 1 Japanese Patent Laid-Open No. 2007-329658
  • FIG. 3B shows imaging in the case of flicker detection disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2007-329658) as a comparative example.
  • FIG. 3B shows imaging in the case of flicker detection disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2007-329658) as a comparative example.
  • FIG. 3B shows imaging in the case of flicker detection disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2007-329658) as a comparative example.
  • FIG. 3B shows imaging in the case of flicker detection disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2007-329658) as a comparative example.
  • FIG. 3C illustrates an example of flicker detection according to the first embodiment of the present invention.
  • the bit number control unit 20d performs processing for reducing the number of bits of the output signal of the A / D conversion unit 14 when capturing the flicker detection image compared to when capturing the moving image.
  • the A / D converter 14 outputs a 12-bit output signal when capturing a moving image, and outputs an 8-bit output signal when capturing a flicker detection image.
  • FIG. 4 is a diagram illustrating an example of capturing the flicker detection image illustrated in FIG.
  • the horizontal direction represents elapsed time
  • the vertical direction represents each horizontal line.
  • the exposure control unit 20a controls the rolling shutter by alternately switching the first shutter speed (1/100 sec) and the second shutter speed (1/120 sec) every two lines as described above. That is, under the control of the exposure control unit 20a, images of 1/100 sec and 1/120 sec are alternately captured on one image. 3 (d) and 3 (e) will be described later.
  • Step S103 The CPU 20 sends a predetermined timing signal to the signal processing unit 15, and sorts the moving image and the flicker detection image by the image changeover switch.
  • the image separation circuit of the signal processing unit 15 separates the flicker detection image into a first image captured at the first shutter speed (1/100 sec) and a second image captured at the second shutter speed (1/120 sec). To do.
  • Step S104 First, the CPU 20 calculates the difference between the luminance values of the first image and the second image. This will be specifically described below.
  • FIG. 5 is a diagram conceptually showing the processing of step S103 and step S104.
  • FIG. 5A is an image diagram of the flicker detection image 100.
  • FIG. 5B is an image diagram of the first image 101 captured at the first shutter speed (1/100 sec) and the second image 102 captured at the second shutter speed (1/120 sec).
  • solid lines and dotted lines represent flicker components.
  • the dotted line portion represents a line with a thick flicker component
  • the solid line represents a line with a thin flicker component.
  • the first image 101 and the second image 102 are compressed images captured with half the number of lines as compared to the flicker detection image 100.
  • the accumulation time of the image sensor 12 is the second shutter speed (1/120 sec)
  • this accumulation time is not an integral multiple of the double power supply frequency (1/100 sec). Accordingly, the accumulated brightness (brightness) is not constant for each line, and a light and dark stripe pattern is generated as flicker (brightness unevenness).
  • the image subtracting circuit of the signal processing unit 15 extracts the flicker by taking the difference between the first image 101 and the second image 102.
  • FIG. 5C shows an image 103 from which flicker is extracted. Further details will be described with reference to FIG.
  • FIG. 6 is a diagram for explaining the flow of flicker extraction.
  • the horizontal axis represents lines, and the vertical axis represents the luminance value for each line.
  • FIG. 6A shows the case of an image (second image 102) when there is flicker.
  • FIG. 6B shows an image (first image 101) when there is no flicker.
  • the image subtraction circuit of the signal processing unit 15 calculates the difference between the luminance value in the line direction of the second image 102 and the luminance value in the line direction of the first image 101. In this case, for example, a luminance value is obtained for each pixel of the line, and a difference between the average values is calculated. Since a difference between two images having different exposure times is taken, correction such as increasing the gain is performed on an image having a short exposure time. If both the first image 101 and the second image 102 are dark, the gain is appropriately increased so that flicker can be detected.
  • FIG. 6C shows the state after the difference is calculated.
  • the determination circuit of the signal processing unit 15 determines that flicker exists if the difference value is greater than or equal to a certain value.
  • the above-described flicker detection method is an example, and is not limited to the above-described method.
  • the flicker detection unit 20b receives the determination result of the determination circuit of the signal processing unit 15. If there is flicker (step S104: Yes), the processing routine proceeds to step S105.
  • Step S105 The accumulation time control unit 20c of the CPU 20 issues an instruction to the timing generator (TG) 13 and performs all pixel batch reset processing by the global shutter. As shown in FIG. 3D, the accumulation time control unit 20c switches from the rolling shutter to the global shutter. Then, the processing routine proceeds to step S107.
  • TG timing generator
  • Step S107 The CPU 20 determines the presence / absence of a shooting end command based on a user input. If the photographing end command is not accepted (step S107: No), the process returns to step S101. On the other hand, when the photographing end command is received (step S107: Yes), this processing routine ends.
  • step S104 determines whether flicker has been flicker. If there is no flicker in step S104 (step S104: No), the processing routine proceeds to step S106.
  • Step S106 The accumulation time control unit 20c instructs the timing generator (TG) 13 to perform reset processing for each line by the rolling shutter. In this case, the state of FIG. 3C continues continuously.
  • FIG. 3E shows a state in which, after switching to the global shutter, flicker is not detected, so that switching to the rolling shutter is performed again.
  • This is applied, for example, when the illumination is changed from a fluorescent lamp to tungsten light while shooting a moving image under a fluorescent lamp.
  • the present invention is applied to a case where a subject moves out of the room into the garden while shooting a moving image under sunlight, while shooting a moving image of the subject in the room under a fluorescent lamp.
  • the bit number control unit 20d compares the number of bits of the output signal of the A / D conversion unit 14 when capturing a flicker detection image as compared to when capturing a moving image. Since the output is reduced, the data processing speed can be increased.
  • the flicker detection unit 20b determines the presence or absence of flicker detection from an image of one frame. For example, when flicker is detected continuously for three frames, the accumulation time control unit 20c switches from the rolling shutter to the global shutter. It may be. That is, the number of frames used for flicker detection may be set arbitrarily.
  • the CPU 20 captures a flicker detection image with a rolling shutter using a window detection function for reading a predetermined number of lines by addressing.
  • the exposure control unit 20a sets a first shutter speed and a second shutter speed with different shutter speeds for each predetermined line with respect to the number of readout lines addressed in advance at which flicker can be detected at least. The exposure is sequentially controlled by switching alternately.
  • FIG. 7 is a diagram for explaining an example of the window reading function.
  • FIG. 7 shows a moving image (one frame) captured at a shutter speed n / 100 sec, for example.
  • flicker does not occur under a 50 Hz fluorescent lamp.
  • flickering occurs under a 60 Hz fluorescent lamp.
  • the dotted line portion represents a dark line with a flicker component
  • the solid line represents a thin line with a flicker component.
  • a plurality of flickers occur in one screen according to the frame rate at the time of moving image shooting.
  • step S102 shown in FIG. 2 the flicker detection image is not captured for one screen, but at least the number of lines capable of detecting flicker is captured.
  • the number of lines varies depending on the frequency of the fluorescent lamp and the frame rate, but can be calculated by a known method.
  • the flicker detection unit 20b captures the flicker detection image captured with at least the number of lines capable of detecting flicker at the first shutter speed (1/100 sec) and the second shutter speed (1/120 sec). After being divided into captured images, the presence or absence of flicker is detected based on the difference in luminance values.
  • FIG. 8 is a diagram showing an example of moving image shooting using flicker detection in the first modification.
  • the horizontal direction represents elapsed time, and the vertical direction represents each horizontal line.
  • a flicker detection image is captured in which at least the number of lines capable of detecting flicker is captured.
  • the accumulation time control unit 20c switches to the global shutter. Further, when flicker is not detected thereafter, the accumulation time control unit 20c switches to the rolling shutter as shown in FIG.
  • flicker can be detected by shortening the imaging time of the flicker detection image, so that the frame rate is higher than that of the electronic camera 1 of the first embodiment. It is possible to raise. Therefore, even in the first modified electronic camera 1, it is possible to suppress the occurrence of flicker due to a fluorescent lamp and obtain a moving image with few frames dropped.
  • the accumulation time control unit 20c when the flicker detection unit 20b detects flicker, the accumulation time control unit 20c first calculates the power supply frequency of the fluorescent lamp based on the flicker detection image. Subsequently, the accumulation time control unit 20c is characterized in that the accumulation time is set to an arbitrary integer multiple of the power supply frequency and the accumulation time is controlled by a rolling shutter.
  • FIG. 9 is a diagram illustrating an example of moving image shooting using flicker detection in the second embodiment.
  • the horizontal direction represents elapsed time, and the vertical direction represents each horizontal line.
  • the power frequency of the fluorescent lamp can be calculated from the flicker detection image.
  • the electronic camera 1 if the accumulation time for capturing moving images is set to an integral multiple of the power supply frequency of the fluorescent lamp, there is no need to switch to the global shutter when flicker is detected. It becomes possible to raise compared to the camera 1. Therefore, also in the electronic camera 1 of the second embodiment, it is possible to suppress the occurrence of flicker due to a fluorescent lamp and to acquire a moving image with few frames dropped.

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Abstract

An imaging device which is capable of capturing moving images with a minimum of lost frames by inhibiting the occurrence of flickers otherwise caused by a fluorescent lamp. The imaging device is provided with an imaging element, an electronic shutter, an imaging element driving section, an exposure control section, a flicker detecting section, and an accumulation time control section.  The imaging element picks up the images of a subject.  The electronic shutter is provided with a plurality of shutter functions.  The imaging element driving section lets the imaging element pick up moving images and lets the imaging element pick up flicker detecting images by using the intervals between the continuing picking-ups of moving images.  When the flicker detecting images are picked up, the exposure control section alternately switches between a first shutter speed and a second shutter speed for every predetermined line of the imaging element to sequentially effect an exposure control.  The flicker detecting section detects the presence or absence of a flicker on the basis of a first image picked up at the first shutter speed and a second image picked up at the second shutter speed.  The accumulation time control section controls the accumulation time of the imaging element used for picking up moving images.

Description

撮像装置Imaging device
　本発明は、電子カメラなどの撮像装置に関する。 The present invention relates to an imaging apparatus such as an electronic camera.
　従来より、ＣＭＯＳ（Ｃｏｍｐｌｅｍｅｎｔａｒｙ　Ｍｅｔａｌ－Ｏｘｉｄｅ　Ｓｅｍｉｃｏｎｄｕｃｔｏｒ）型の撮像素子を備える撮像装置において、蛍光灯下の動画撮影では、交流電源（５０Ｈｚ若しくは６０Ｈｚ）による蛍光灯（光源）の周期的な輝度変化に起因するフリッカが発生することがある。例えば、撮像素子のライブ映像を液晶モニタに表示するライブビューモードで、撮像素子のライン（画素行）ごとに順次シャッタを切るローリングシャッタ制御を行った場合を想定する。この場合、交流電源の周波数と撮像素子の蓄積時間との兼ね合いによっては、１つの画面内において、周期的にフリッカ（輝度むら）が生じる。 Conventionally, in an imaging apparatus equipped with a CMOS (Complementary Metal-Oxide Semiconductor) type imaging device, in moving image shooting under a fluorescent lamp, it is caused by a periodic luminance change of the fluorescent lamp (light source) by an AC power supply (50 Hz or 60 Hz). Flicker may occur. For example, it is assumed that rolling shutter control is performed in which a shutter is sequentially released for each line (pixel row) of the image sensor in a live view mode in which a live image of the image sensor is displayed on a liquid crystal monitor. In this case, depending on the balance between the frequency of the AC power supply and the storage time of the image sensor, flicker (luminance unevenness) occurs periodically in one screen.
　そこで、このフリッカを抑止する撮像装置が提案されている（例えば、特許文献１参照）。 Therefore, an imaging apparatus that suppresses the flicker has been proposed (for example, see Patent Document 1).
　特許文献１の撮像装置では、先ず、ローリングシャッタ使用時に、連続する動画像の撮像の合間を利用してシャッタ速度１／１００ｓｅｃと１／１２０ｓｅｃとの画像を２枚連続して取得し、共通する画像領域の輝度値を比較する。続いて、この撮像装置では、比較結果からフリッカを検出すると、全ての画素信号を一括して読み出すグローバルシャッタ制御を行う。これにより、フリッカの発生を抑止する。（なお、蛍光灯は、電源周波数の各サイクルに輝度変化を２回起こす。つまり、この輝度変化は、電源周波数の２倍の周波数に相当する周期で繰り返される。そのため、５０Ｈｚの場合は、１／１００ｓｅｃ、６０Ｈｚの場合は、１／１２０ｓｅｃの周期になる。） In the imaging apparatus of Patent Document 1, first, when using a rolling shutter, two images with shutter speeds of 1/100 sec and 1/120 sec are acquired continuously using the interval between successive moving image imaging, and they are common. Compare brightness values of image areas. Subsequently, in this imaging apparatus, when flicker is detected from the comparison result, global shutter control for reading all pixel signals at once is performed. Thereby, the occurrence of flicker is suppressed. (Note that the fluorescent lamp causes a luminance change twice in each cycle of the power supply frequency. In other words, this luminance change is repeated in a cycle corresponding to a frequency twice the power supply frequency. (In the case of / 100 sec and 60 Hz, the cycle is 1/120 sec.)
特開２００７－３２９６５８号公報JP 2007-329658 A
　しかしながら、特許文献１の撮像装置では、ローリングシャッタ使用時にフリッカ検出のために２枚の画像を連続して取得するため、フレームレートの低下に繋がる。そのため、動きのある被写体の場合には、不自然に見えるという問題が生じるおそれがある。 However, in the imaging apparatus of Patent Document 1, two images are continuously acquired for flicker detection when a rolling shutter is used, which leads to a decrease in frame rate. Therefore, in the case of a moving subject, there may be a problem that it looks unnatural.
　本発明は、上記事情に鑑み、蛍光灯によるフリッカの発生を抑止し、コマ落ちの少ない動画像の取得を行うことができる撮像装置を提供することを目的とする。 In view of the above circumstances, an object of the present invention is to provide an imaging apparatus that can suppress the occurrence of flicker due to a fluorescent lamp and can acquire a moving image with less frame dropping.
　第１の発明に係る撮像装置は、撮像素子と、電子シャッタと、撮像素子駆動部と、フリッカ検出用の露光制御部と、フリッカ検出部と、蓄積時間制御部と、を備える。撮像素子は、複数の画素を２次元的に配列し、アドレス指定によりライン読み出しが可能である。電子シャッタは、撮像素子への露光を電子的に制御する複数のシャッタ機能を有する。撮像素子駆動部は、所定のフレームレートで動画像を撮像素子に撮像させるとともに、光源の周期的な輝度変化に起因するフリッカを検出するためのフリッカ検出画像を、連続する動画像の撮像の合間を利用して撮像素子に撮像させる。フリッカ検出用の露光制御部は、フリッカ検出画像の撮像時には、アドレス指定により所定のラインごとに、電子シャッタのシャッタ速度が異なる第１シャッタ速度と第２シャッタ速度とを交互に切り替えて順次露光制御する。フリッカ検出部は、第１シャッタ速度で撮像した第１画像と第２シャッタ速度で撮像した第２画像とで構成されるフリッカ検出画像に基づいて、フリッカの有無を検出する。蓄積時間制御部は、フリッカ検出部の検出結果に応じて、動画像を撮像するための撮像素子の蓄積時間を電子シャッタにより制御する。 An image pickup apparatus according to a first aspect of the present invention includes an image pickup device, an electronic shutter, an image pickup device drive unit, a flicker detection exposure control unit, a flicker detection unit, and an accumulation time control unit. The imaging element can two-dimensionally arrange a plurality of pixels and perform line reading by addressing. The electronic shutter has a plurality of shutter functions for electronically controlling exposure to the image sensor. The image sensor driving unit causes the image sensor to capture a moving image at a predetermined frame rate, and also detects a flicker detection image for detecting flicker due to a periodic change in luminance of the light source between consecutive moving image capturing. The image sensor is caused to take an image using The flicker detection exposure control unit sequentially switches the exposure between the first shutter speed and the second shutter speed at which the shutter speed of the electronic shutter is different for each predetermined line by address designation when capturing a flicker detection image. To do. The flicker detection unit detects the presence or absence of flicker based on a flicker detection image composed of a first image captured at the first shutter speed and a second image captured at the second shutter speed. The accumulation time control unit controls the accumulation time of the image sensor for capturing a moving image using an electronic shutter according to the detection result of the flicker detection unit.
　第２の発明は、第１の発明において、蓄積時間制御部は、フリッカ検出部がフリッカを検出した場合、全ての画素信号を一括して読み出すことにより蓄積時間を制御する。 In a second aspect based on the first aspect, when the flicker detection unit detects flicker, the accumulation time control unit controls the accumulation time by reading all pixel signals at once.
　第３の発明は、第１の発明において、蓄積時間制御部は、フリッカ検出部がフリッカを検出しない場合、ラインごとに順次シャッタを切り、ラインごとの画素信号を読み出すことにより、蓄積時間を制御する。 In a third aspect based on the first aspect, the accumulation time control unit controls the accumulation time by sequentially releasing the shutter for each line and reading the pixel signal for each line when the flicker detection unit does not detect flicker. To do.
　第４の発明は、第１の発明において、蓄積時間制御部は、フリッカ検出部がフリッカを検出した場合、フリッカ検出画像に基づいて光源の電源周波数を算出し、蓄積時間を電源周波数の任意の整数倍に設定するとともに、ラインごとに順次シャッタを切り、ラインごとの画素信号を読み出すことにより、蓄積時間を制御する。 In a fourth aspect based on the first aspect, when the flicker detection unit detects flicker, the accumulation time control unit calculates the power supply frequency of the light source based on the flicker detection image, and sets the accumulation time as an arbitrary power supply frequency. The accumulation time is controlled by setting an integral multiple and sequentially releasing the shutter for each line and reading the pixel signal for each line.
　第５の発明は、第１の発明において、露光制御部は、フリッカを少なくとも検出可能な予めアドレス指定された読み出しライン数に対して、所定のラインごとに、第１シャッタ速度と第２シャッタ速度とを交互に切り替えて順次露光制御する。 In a fifth aspect based on the first aspect, the exposure control unit performs the first shutter speed and the second shutter speed for each predetermined line with respect to the number of readout lines that are pre-addressed and capable of detecting at least flicker. Are alternately switched to sequentially control exposure.
　第６の発明は、第１から第５のいずれか１の発明において、第１シャッタ速度は、ｎ／１００ｓｅｃであり、第２シャッタ速度は、ｍ／１２０ｓｅｃであり、ｎ及びｍが任意の整数である。 In a sixth aspect based on any one of the first to fifth aspects, the first shutter speed is n / 100 sec, the second shutter speed is m / 120 sec, and n and m are arbitrary integers. It is.
　第７の発明は、第１から第６のいずれか１の発明において、アナログ／デジタル変換の出力信号のビット数を、動画像の撮像時と比較してフリッカ検出画像の撮像時には減らして出力させるビット数制御部をさらに備える。 According to a seventh aspect of the invention, in any one of the first to sixth aspects, the number of bits of the output signal of the analog / digital conversion is reduced when the flicker detection image is captured as compared with the time when the moving image is captured and output. A bit number control unit is further provided.
　本発明の撮像装置によれば、蛍光灯によるフリッカの発生を抑止し、コマ落ちの少ない動画取得を行うことができる。 According to the image pickup apparatus of the present invention, it is possible to suppress the occurrence of flicker due to a fluorescent lamp and to obtain a moving image with less frame dropping.
本実施形態の撮像装置である電子カメラ１の構成を説明するブロック図1 is a block diagram illustrating the configuration of an electronic camera 1 that is an imaging apparatus according to an embodiment フリッカ抑止モードでの動作例の一例を表すフローチャートA flowchart showing an example of an operation example in the flicker suppression mode 第１実施形態におけるフリッカ検出を用いた動画撮影の一例を示す図The figure which shows an example of the video recording using the flicker detection in 1st Embodiment. 図３（ｃ）に示すフリッカ検出画像の撮像の一例を示す図The figure which shows an example of imaging of the flicker detection image shown in FIG.3 (c). ステップＳ１０３及びステップＳ１０４の処理を概念的に示す図The figure which shows the process of step S103 and step S104 notionally フリッカの抽出の流れを説明する図Diagram explaining the flow of flicker extraction 窓読み出し機能の一例を説明する図The figure explaining an example of a window reading function 第１の変形例におけるフリッカ検出を用いた動画撮影の一例を示す図The figure which shows an example of the video recording using the flicker detection in a 1st modification. 第２実施形態におけるフリッカ検出を用いた動画撮影の一例を示す図The figure which shows an example of the video recording using the flicker detection in 2nd Embodiment.
　以下、図面に基づいて本発明の実施の形態を詳細に説明する。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
　図１は本実施形態の撮像装置である電子カメラ１の構成を説明するブロック図である。図１に示す通り電子カメラ１には、撮影光学系１１と、撮像素子１２と、タイミングジェネレータ（ＴＧ）１３と、Ａ／Ｄ変換部１４と、信号処理部１５と、ＲＡＭ（Ｒａｎｄｏｍ　Ａｃｃｅｓｓ　Ｍｅｍｏｒｙ）１６と、記録インターフェース（記録Ｉ／Ｆ）１７と、表示部１８と、操作部１９と、ＣＰＵ（Ｃｅｎｔｒａｌ　ｐｒｏｃｅｓｓｉｎｇ　Ｕｎｉｔ）２０と、ＲＯＭ（Ｒｅａｄ　Ｏｎｌｙ　Ｍｅｍｏｒｙ）２１と、バス２２とが備えられる。このうち信号処理部１５、ＲＡＭ１６、記録インターフェース（記録Ｉ／Ｆ）１７、表示部１８、ＣＰＵ２０及びＲＯＭ２１は、バス２２を介して互いに接続されている。また、操作部１９は、ＣＰＵ２０に接続されている。 FIG. 1 is a block diagram illustrating a configuration of an electronic camera 1 that is an imaging apparatus according to the present embodiment. As shown in FIG. 1, the electronic camera 1 includes a photographing optical system 11, an image sensor 12, a timing generator (TG) 13, an A / D converter 14, a signal processor 15, and a RAM (Random Access Memory). 16, a recording interface (recording I / F) 17, a display unit 18, an operation unit 19, a CPU (Central processing Unit) 20, a ROM (Read Only Memory) 21, and a bus 22. Among them, the signal processing unit 15, the RAM 16, the recording interface (recording I / F) 17, the display unit 18, the CPU 20, and the ROM 21 are connected to each other via a bus 22. The operation unit 19 is connected to the CPU 20.
　撮影光学系１１は、フォーカスレンズやズームレンズを含む複数のレンズ群で構成されている。なお、簡単のため、図１では、撮影光学系１０を１枚のレンズとして図示する。 The photographing optical system 11 includes a plurality of lens groups including a focus lens and a zoom lens. For the sake of simplicity, FIG. 1 shows the photographing optical system 10 as a single lens.
　撮像素子１２は、その撮像面に形成された被写体像を光電変換することにより、画像を生成する。なお、本実施形態では、撮像素子１２は、複数の画素を２次元的に配列し、アドレス指定によりライン読み出しが可能なＣＭＯＳを用いている。 The image sensor 12 generates an image by photoelectrically converting a subject image formed on the imaging surface. In the present embodiment, the image sensor 12 uses a CMOS in which a plurality of pixels are two-dimensionally arranged and line reading is possible by address designation.
　この撮像素子１２は、ラインごとに順次シャッタを切り、全ての画素信号を一括して読み出すグローバルシャッタ（不図示）と、ラインごとに画素信号を読み出すローリングシャッタ（不図示）とが選択されることにより、被写体像を撮像する。なお、グローバルシャッタやローリングシャッタの詳細は、公知技術と同様であるので説明を省略する。 The image pickup device 12 selects a global shutter (not shown) that sequentially releases the shutter for each line and reads all pixel signals at once, and a rolling shutter (not shown) that reads the pixel signal for each line. Thus, a subject image is captured. The details of the global shutter and the rolling shutter are the same as those of the known art, and thus the description thereof is omitted.
　タイミングジェネレータ（ＴＧ）１３は、ＣＰＵ２０からの指示に従い、撮像素子１２及びＡ／Ｄ変換部１４の各々へ向けて駆動信号を送出し、それによって両者の駆動タイミングを制御する。より具体的には、タイミングジェネレータ（ＴＧ）１３は、ＣＰＵ２０からの指示に従い、所定のフレームレートで動画像を撮像素子１２に撮像させるとともに、フリッカの検出用のフリッカ検出画像を、連続する動画像の撮像の合間を利用して撮像素子１２に撮像させる。 The timing generator (TG) 13 sends a drive signal to each of the image sensor 12 and the A / D converter 14 according to an instruction from the CPU 20, thereby controlling the drive timing of both. More specifically, the timing generator (TG) 13 causes the image sensor 12 to capture a moving image at a predetermined frame rate in accordance with an instruction from the CPU 20, and continuously generates flicker detection images for flicker detection. The image pickup device 12 is caused to take an image using the interval between the image pickup operations.
　Ａ／Ｄ変換部１４は、撮像素子１２が生成するアナログ信号をデジタル信号に変換して出力する。このＡ／Ｄ変換部１４が出力するデジタル信号は、動画像やフリッカ検出画像として、ＲＡＭ１６のフレームメモリに一時的に記憶される。 The A / D converter 14 converts the analog signal generated by the image sensor 12 into a digital signal and outputs it. The digital signal output from the A / D converter 14 is temporarily stored in the frame memory of the RAM 16 as a moving image or flicker detection image.
　信号処理部１５は、ＲＡＭ１６のフレームメモリに記憶されたデジタル信号（ＲＧＢ信号の分布）を読み出して所定の信号処理を行う。例えば、信号処理部１５は、必要に応じて、ＲＧＢ信号の画像データを輝度（Ｙ）と色（Ｃ）とで表されるＹＣ信号の画像データに変換する。また、その逆の変換も行う。 The signal processing unit 15 reads a digital signal (RGB signal distribution) stored in the frame memory of the RAM 16 and performs predetermined signal processing. For example, the signal processing unit 15 converts image data of RGB signals into image data of YC signals represented by luminance (Y) and color (C) as necessary. The reverse conversion is also performed.
　また、この信号処理部１５には、クランプ回路などといった、通常の信号処理に用いられる回路とは別に、画像切り替えスイッチ、画像分離回路、画像減算回路及び判別回路（不図示）が設けられている。 Further, the signal processing unit 15 is provided with an image changeover switch, an image separation circuit, an image subtraction circuit, and a determination circuit (not shown) separately from a circuit used for normal signal processing such as a clamp circuit. .
　画像切り替えスイッチは、ＣＰＵ２０の指示に従い、所定のタイミングで、ＲＡＭ１６から読み出される動画とフリッカ検出画像とを切り替えるスイッチである。画像切り替えスイッチが動画像の設定の場合には、動画像はバス２２を介して記録媒体２３に順次記録されたり、表示部１８に動画像がスルー画像として順次表示されたりする。 The image switching switch is a switch for switching between a moving image read from the RAM 16 and a flicker detection image at a predetermined timing in accordance with an instruction from the CPU 20. When the image changeover switch is set to a moving image, the moving image is sequentially recorded on the recording medium 23 via the bus 22, or the moving image is sequentially displayed on the display unit 18 as a through image.
　一方、画像切り替えスイッチがフリッカ検出画像の設定の場合には、フリッカ検出画像は、画像分離回路に送出される。画像分離回路は、フリッカ検出画像を、第１シャッタ速度で撮像した第１画像（ＹＣ信号の画像データ）と、第２シャッタ速度で撮像した第２画像（ＹＣ信号の画像データ）とに分離する。 On the other hand, if the image changeover switch is set to flicker detection image, the flicker detection image is sent to the image separation circuit. The image separation circuit separates the flicker detection image into a first image (YC signal image data) captured at the first shutter speed and a second image (YC signal image data) captured at the second shutter speed. .
　画像減算回路は、第１画像と第２画像との輝度値の差分を算出する（詳細は後述する）。判別回路は、第１画像と第２画像との輝度値の差分に基づいて、フリッカの有無を検出し、検出結果を後述するフリッカ検出部２０ｂに通知する。 The image subtraction circuit calculates a difference in luminance value between the first image and the second image (details will be described later). The determination circuit detects the presence or absence of flicker based on the difference in luminance value between the first image and the second image, and notifies the detection result to a flicker detection unit 20b described later.
　記録インターフェース（記録Ｉ／Ｆ）１７は、動画像を記録媒体２３に記録できるように通信インターフェースを提供する。 The recording interface (recording I / F) 17 provides a communication interface so that a moving image can be recorded on the recording medium 23.
　表示部１８は、電子カメラ１の操作メニュー等を表示する。また、ライブビューモードでは撮像素子１２のライブ映像を表示する。 The display unit 18 displays an operation menu of the electronic camera 1 and the like. In the live view mode, a live image of the image sensor 12 is displayed.
　操作部１９は、レリーズボタン、コマンドダイヤルなどであり、ユーザによる操作内容に応じてＣＰＵ２０へ信号を与えるものである。 The operation unit 19 is a release button, a command dial, or the like, and gives a signal to the CPU 20 in accordance with the operation content by the user.
　ＣＰＵ２０は、電子カメラ１の統括的な制御を行うプロセッサである。ＣＰＵ２０は、ＲＯＭ２１に予め格納されたシーケンスプログラムを実行することにより電子カメラ１の各部を制御する。また、本実施形態のＣＰＵ２０は、フリッカ検出用の露光制御部２０ａと、フリッカ検出部２０ｂと、蓄積時間制御部２０ｃと、ビット数制御部２０ｄとしても機能する。 The CPU 20 is a processor that performs overall control of the electronic camera 1. The CPU 20 controls each part of the electronic camera 1 by executing a sequence program stored in advance in the ROM 21. Further, the CPU 20 of this embodiment also functions as an exposure control unit 20a for flicker detection, a flicker detection unit 20b, an accumulation time control unit 20c, and a bit number control unit 20d.
　露光制御部２０ａは、フリッカ検出画像の撮像時には、撮像素子１２のアドレス指定により所定のラインごとに、第１シャッタ速度と第２シャッタ速度とを交互に切り替えて順次露光制御する。なお、第１シャッタ速度は、ｎ／１００ｓｅｃであり、第２シャッタ速度は、ｍ／１２０ｓｅｃであり、ｎ及びｍが任意の整数である。ここでは、説明の便宜上、ｎ＝１、ｍ＝１とする。 When the flicker detection image is captured, the exposure control unit 20a sequentially performs exposure control by alternately switching the first shutter speed and the second shutter speed for each predetermined line by addressing the image sensor 12. The first shutter speed is n / 100 sec, the second shutter speed is m / 120 sec, and n and m are arbitrary integers. Here, for convenience of explanation, it is assumed that n = 1 and m = 1.
　フリッカ検出部２０ｂは、信号処理部１５に指示を出し、画像分離回路、画像減算回路及び判別回路を用いてフリッカ検出処理を行わせて、判別回路の判定結果を受信する。なお、フリッカ検出部２０ｂのハード構成は、信号処理部１５で担っている。 The flicker detection unit 20b instructs the signal processing unit 15 to perform flicker detection processing using the image separation circuit, the image subtraction circuit, and the determination circuit, and receives the determination result of the determination circuit. The hardware configuration of the flicker detection unit 20b is handled by the signal processing unit 15.
　蓄積時間制御部２０ｃは、フリッカ検出部２０ｂの検出結果に応じて、タイミングジェネレータ（ＴＧ）１３を介して、動画像を撮像するための撮像素子の蓄積時間を制御する。例えば、蓄積時間制御部２０ｃは、フリッカ検出部２０ｂがフリッカを検出した場合、グローバルシャッタにより蓄積時間を制御する。 The accumulation time control unit 20c controls the accumulation time of the image sensor for capturing a moving image via the timing generator (TG) 13 according to the detection result of the flicker detection unit 20b. For example, the accumulation time control unit 20c controls the accumulation time using a global shutter when the flicker detection unit 20b detects flicker.
　また、蓄積時間制御部２０ｃは、フリッカ検出部２０ｂがフリッカを検出しない場合、ローリングシャッタにより蓄積時間を制御する。 Further, the accumulation time control unit 20c controls the accumulation time using a rolling shutter when the flicker detection unit 20b does not detect flicker.
　ビット数制御部２０ｄは、Ａ／Ｄ変換部１４に指示を出し、Ａ／Ｄ変換部１４の出力信号のビット数を、動画像の撮像時と比較してフリッカ検出画像の撮像時には減らして出力させる。 The bit number control unit 20d outputs an instruction to the A / D conversion unit 14, and reduces the number of bits of the output signal of the A / D conversion unit 14 when capturing a flicker detection image compared to when capturing a moving image. Let
　次に、本実施形態の電子カメラ１において、フリッカを抑止するフリッカ抑止モードでの動作例を説明する。 Next, an operation example in the flicker suppression mode for suppressing flicker in the electronic camera 1 of the present embodiment will be described.
　図２は、フリッカ抑止モードでの動作例の一例を表すフローチャートである。この図２に示すフローチャートは、ユーザが、フリッカ抑止モードをオンに設定して、動画撮影若しくはライブビュー表示を選択すると開始される。 FIG. 2 is a flowchart showing an example of an operation example in the flicker suppression mode. The flowchart shown in FIG. 2 starts when the user sets the flicker suppression mode to ON and selects moving image shooting or live view display.
　ステップＳ１０１：ＣＰＵ２０は、先ず、動画像の取得を行う。すなわち、ＣＰＵ２０は、タイミングジェネレータ（ＴＧ）１３を駆動させ、所定のフレームレートで動画像を撮像素子１２に撮像させる。ここで、この処理ルーチンが開始したときには、先ずローリングシャッタにより動画像が撮像されるものとする。また、ローリングシャッタによるラインの読み出しとしては、撮像素子１２のＲＧＢのＢａｙｅｒ配列を考慮して、２ラインごとに読み出すものとする。 Step S101: First, the CPU 20 acquires a moving image. That is, the CPU 20 drives the timing generator (TG) 13 to cause the image sensor 12 to capture a moving image at a predetermined frame rate. Here, when this processing routine starts, it is assumed that a moving image is first picked up by the rolling shutter. In addition, the line reading by the rolling shutter is performed every two lines in consideration of the RGB Bayer arrangement of the image sensor 12.
　ステップＳ１０２：ＣＰＵ２０は、フリッカ検出画像の取得を行う。すなわち、ＣＰＵ２０は、タイミングジェネレータ１３を駆動させ、フリッカ検出画像を撮像素子１２に撮像させる。この際、露光制御部２０ａは、ローリングシャッタにより、２ラインごとに、第１シャッタ速度と第２シャッタ速度とを交互に切り替えて順次露光制御する。なお、フレームレートは動画像のフレームレートで規定されるので、露光制御部２０ａは、フリッカ検出画像の蓄積時間について、ブランキング時間などで時間の調節を適宜行う。 Step S102: The CPU 20 acquires a flicker detection image. That is, the CPU 20 drives the timing generator 13 to cause the image sensor 12 to capture the flicker detection image. At this time, the exposure control unit 20a sequentially controls the exposure by alternately switching the first shutter speed and the second shutter speed every two lines by the rolling shutter. Since the frame rate is defined by the frame rate of the moving image, the exposure control unit 20a appropriately adjusts the flicker detection image accumulation time using a blanking time or the like.
　図３は、第１実施形態におけるフリッカ検出を用いた動画撮影の一例を示す図である。水平方向が経過時間を表し、垂直方向が、各水平ラインを表している。 FIG. 3 is a diagram showing an example of moving image shooting using flicker detection in the first embodiment. The horizontal direction represents elapsed time, and the vertical direction represents each horizontal line.
　図３（ａ）は、比較例として、フリッカ検出を行わない場合のローリングシャッタによる動画撮影を説明する図である。図３（ａ）に示すように、撮像素子１２のライン方向ごとに信号電荷の蓄積を開始する時刻がずれて撮像される。そして、所定のフレームレートで、動画像が順次取得される。 FIG. 3A is a diagram illustrating moving image shooting by a rolling shutter when flicker detection is not performed as a comparative example. As shown in FIG. 3A, images are taken at different times when signal charge accumulation starts for each line direction of the image sensor 12. Then, moving images are sequentially acquired at a predetermined frame rate.
　図３（ｂ）は、比較例として、特許文献１（特開２００７－３２９６５８号公報）に開示されているフリッカ検出の場合の撮像を示している。図３（ｂ）に示すように、動画像のフレームを１枚取得した後、フリッカ検出のため、シャッタ速度１／１００ｓｅｃと１／１２０ｓｅｃとの画像を２枚連続して取得している。既に、上述した通り、ローリングシャッタ使用時にフリッカ検出のために２枚の画像を連続して取得するため、フレームレートの低下に繋がる。そのため、動きのある被写体の場合には、不自然に見えるという問題が生じるおそれがある。 FIG. 3B shows imaging in the case of flicker detection disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2007-329658) as a comparative example. As shown in FIG. 3B, after acquiring one moving image frame, two images with shutter speeds of 1/100 sec and 1/120 sec are acquired continuously for flicker detection. As described above, since two images are continuously acquired for flicker detection when the rolling shutter is used, the frame rate is lowered. Therefore, in the case of a moving subject, there may be a problem that it looks unnatural.
　図３（ｃ）は、本発明の第１実施形態におけるフリッカ検出の一例を説明する図である。図３（ｃ）に示すように、動画像のフレームを１枚取得した後、フリッカ検出画像を１枚取得している。ここで、ビット数制御部２０ｄは、Ａ／Ｄ変換部１４の出力信号のビット数を、動画像の撮像時と比較してフリッカ検出画像の撮像時には減らして出力させる処理を行う。これにより、Ａ／Ｄ変換部１４は、例えば、動画像の撮像時には１２ビットの出力信号を出力し、フリッカ検出画像の撮像時には８ビットの出力信号を出力する。 FIG. 3C illustrates an example of flicker detection according to the first embodiment of the present invention. As shown in FIG. 3C, after one frame of the moving image is acquired, one flicker detection image is acquired. Here, the bit number control unit 20d performs processing for reducing the number of bits of the output signal of the A / D conversion unit 14 when capturing the flicker detection image compared to when capturing the moving image. Thereby, for example, the A / D converter 14 outputs a 12-bit output signal when capturing a moving image, and outputs an 8-bit output signal when capturing a flicker detection image.
　図４は、図３（ｃ）に示すフリッカ検出画像の撮像の一例を示す図である。水平方向が経過時間を表し、垂直方向が、各水平ラインを表している。 FIG. 4 is a diagram illustrating an example of capturing the flicker detection image illustrated in FIG. The horizontal direction represents elapsed time, and the vertical direction represents each horizontal line.
　露光制御部２０ａは、上述した通り、２ラインごとに、第１シャッタ速度（１／１００ｓｅｃ）と第２シャッタ速度（１／１２０ｓｅｃ）とを交互に切り替えてローリングシャッタを制御する。つまり、露光制御部２０ａの制御により、１枚の画像には、１／１００ｓｅｃと１／１２０ｓｅｃとの画像が交互に撮像されることとなる。なお、図３（ｄ）、図３（ｅ）については後述する。 The exposure control unit 20a controls the rolling shutter by alternately switching the first shutter speed (1/100 sec) and the second shutter speed (1/120 sec) every two lines as described above. That is, under the control of the exposure control unit 20a, images of 1/100 sec and 1/120 sec are alternately captured on one image. 3 (d) and 3 (e) will be described later.
　ステップＳ１０３：ＣＰＵ２０は、信号処理部１５に所定のタイミング信号を送出することにより、画像切り替えスイッチにより、動画像とフリッカ検出画像とを振り分ける。信号処理部１５の画像分離回路では、フリッカ検出画像を、第１シャッタ速度（１／１００ｓｅｃ）で撮像した第１画像と、第２シャッタ速度（１／１２０ｓｅｃ）で撮像した第２画像とに分離する。 Step S103: The CPU 20 sends a predetermined timing signal to the signal processing unit 15, and sorts the moving image and the flicker detection image by the image changeover switch. The image separation circuit of the signal processing unit 15 separates the flicker detection image into a first image captured at the first shutter speed (1/100 sec) and a second image captured at the second shutter speed (1/120 sec). To do.
　ステップＳ１０４：ＣＰＵ２０は、先ず、画像減算回路は、第１画像と第２画像との輝度値の差分を算出する。以下、具体的に説明する。 Step S104: First, the CPU 20 calculates the difference between the luminance values of the first image and the second image. This will be specifically described below.
　図５は、ステップＳ１０３及びステップＳ１０４の処理を概念的に示す図である。図５（ａ）は、フリッカ検出画像１００のイメージ図である。図５（ｂ）は、第１シャッタ速度（１／１００ｓｅｃ）で撮像した第１画像１０１と、第２シャッタ速度（１／１２０ｓｅｃ）で撮像した第２画像１０２のイメージ図である。図中、実線及び点線は、フリッカ成分を表している。ここで、点線の部分がフリッカ成分の濃いラインを表しており、実線がフリッカ成分の薄いラインを表している。 FIG. 5 is a diagram conceptually showing the processing of step S103 and step S104. FIG. 5A is an image diagram of the flicker detection image 100. FIG. 5B is an image diagram of the first image 101 captured at the first shutter speed (1/100 sec) and the second image 102 captured at the second shutter speed (1/120 sec). In the figure, solid lines and dotted lines represent flicker components. Here, the dotted line portion represents a line with a thick flicker component, and the solid line represents a line with a thin flicker component.
　図５（ａ）、図５（ｂ）に示すように、第１画像１０１と第２画像１０２とは、フリッカ検出画像１００に比べて、半分のライン数で撮像された圧縮画像となる。 As shown in FIGS. 5A and 5B, the first image 101 and the second image 102 are compressed images captured with half the number of lines as compared to the flicker detection image 100.
　一例として、５０Ｈｚの蛍光灯下で撮像する場合を想定する。例えば、撮像素子１２の蓄積時間が第１シャッタ速度（１／１００ｓｅｃ）の場合、この蓄積時間は、電源周波数の２倍周波数（１／１００ｓｅｃ）の整数倍（１倍）となる。したがって、蓄積される明るさ（輝度）は、ライン単位で一定となる。そのため、フリッカは生じない。 As an example, assume a case where an image is captured under a 50 Hz fluorescent lamp. For example, when the accumulation time of the image sensor 12 is the first shutter speed (1/100 sec), this accumulation time is an integral multiple (1 time) of the frequency twice the power supply frequency (1/100 sec). Therefore, the accumulated brightness (luminance) is constant for each line. Therefore, no flicker occurs.
　一方、撮像素子１２の蓄積時間が第２シャッタ速度（１／１２０ｓｅｃ）の場合、この蓄積時間は、電源周波数の２倍周波数（１／１００ｓｅｃ）の整数倍とならない。したがって、蓄積される明るさ（輝度）は、ライン単位で一定とならず、フリッカ（輝度むら）として、濃淡の縞模様が発生してしまう。 On the other hand, when the accumulation time of the image sensor 12 is the second shutter speed (1/120 sec), this accumulation time is not an integral multiple of the double power supply frequency (1/100 sec). Accordingly, the accumulated brightness (brightness) is not constant for each line, and a light and dark stripe pattern is generated as flicker (brightness unevenness).
　そこで、信号処理部１５の画像減算回路は、第１画像１０１と第２画像１０２との差分をとることで、フリッカを抽出する。図５（ｃ）は、フリッカを抽出した画像１０３を表している。図６でさらに詳細について説明する。 Therefore, the image subtracting circuit of the signal processing unit 15 extracts the flicker by taking the difference between the first image 101 and the second image 102. FIG. 5C shows an image 103 from which flicker is extracted. Further details will be described with reference to FIG.
　図６は、フリッカの抽出の流れを説明する図である。横軸は、ラインを表しており、縦軸は、ラインごとの輝度値を表している。 FIG. 6 is a diagram for explaining the flow of flicker extraction. The horizontal axis represents lines, and the vertical axis represents the luminance value for each line.
　図６（ａ）は、フリッカがある場合の画像（第２画像１０２）の場合を表している。図６（ｂ）は、フリッカがない場合の画像（第１画像１０１）を表している。ここで、信号処理部１５の画像減算回路は、第２画像１０２のライン方向の輝度値と第１画像１０１のライン方向の輝度値との差分を算出する。この場合、例えば、ラインの画素ごとに輝度値を求めて、その平均値の差分を算出する。なお、露光時間が異なる２つの画像の差分をとることになるので、露光時間の短い画像に対してゲインを上げるなどの補正を行う。また、第１画像１０１、第２画像１０２ともに画像が暗い場合には、適宜ゲインを上げて、フリッカが検出できるレベルにする。 FIG. 6A shows the case of an image (second image 102) when there is flicker. FIG. 6B shows an image (first image 101) when there is no flicker. Here, the image subtraction circuit of the signal processing unit 15 calculates the difference between the luminance value in the line direction of the second image 102 and the luminance value in the line direction of the first image 101. In this case, for example, a luminance value is obtained for each pixel of the line, and a difference between the average values is calculated. Since a difference between two images having different exposure times is taken, correction such as increasing the gain is performed on an image having a short exposure time. If both the first image 101 and the second image 102 are dark, the gain is appropriately increased so that flicker can be detected.
　図６（ｃ）は、差分の算出後の状態を表している。信号処理部１５の判別回路は、差分値がある値以上であれば、フリッカが存在すると判定する。上述したフリッカ検出の方法は、一例であって、上述した方法に限定されるものではい。 FIG. 6C shows the state after the difference is calculated. The determination circuit of the signal processing unit 15 determines that flicker exists if the difference value is greater than or equal to a certain value. The above-described flicker detection method is an example, and is not limited to the above-described method.
　このようにして、フリッカ検出部２０ｂは、信号処理部１５の判別回路の判定結果を受信する。そして、フリッカがある場合には（ステップＳ１０４：Ｙｅｓ）、この処理ルーチンは、ステップＳ１０５に進む。 In this way, the flicker detection unit 20b receives the determination result of the determination circuit of the signal processing unit 15. If there is flicker (step S104: Yes), the processing routine proceeds to step S105.
　ステップＳ１０５：ＣＰＵ２０の蓄積時間制御部２０ｃは、タイミングジェネレータ（ＴＧ）１３に指示を出し、グローバルシャッタにより、全画素一括リセット処理を行う。図３（ｄ）に示すように、蓄積時間制御部２０ｃは、ローリングシャッタから、グローバルシャッタに切り替える。そして、この処理ルーチンは、ステップＳ１０７に進む。 Step S105: The accumulation time control unit 20c of the CPU 20 issues an instruction to the timing generator (TG) 13 and performs all pixel batch reset processing by the global shutter. As shown in FIG. 3D, the accumulation time control unit 20c switches from the rolling shutter to the global shutter. Then, the processing routine proceeds to step S107.
　ステップＳ１０７：ＣＰＵ２０は、ユーザ入力により、撮影終了コマンドの有無を判定する。撮影終了コマンドを受けつけない場合には（ステップＳ１０７：Ｎｏ）、ステップＳ１０１の処理に戻る。一方、撮影終了コマンドを受けつけた場合には（ステップＳ１０７：Ｙｅｓ）、この処理ルーチンは終了する。 Step S107: The CPU 20 determines the presence / absence of a shooting end command based on a user input. If the photographing end command is not accepted (step S107: No), the process returns to step S101. On the other hand, when the photographing end command is received (step S107: Yes), this processing routine ends.
　一方、ステップＳ１０４にて、フリッカがない場合には（ステップＳ１０４：Ｎｏ）、この処理ルーチンは、ステップＳ１０６に進む。 On the other hand, if there is no flicker in step S104 (step S104: No), the processing routine proceeds to step S106.
　ステップＳ１０６：蓄積時間制御部２０ｃは、タイミングジェネレータ（ＴＧ）１３に指示を出し、ローリングシャッタにより、ラインごとにリセット処理を行う。この場合は、図３（ｃ）の状態が連続して続くことになる。 Step S106: The accumulation time control unit 20c instructs the timing generator (TG) 13 to perform reset processing for each line by the rolling shutter. In this case, the state of FIG. 3C continues continuously.
　このようにして、動画像の取得において、蓄積時間制御部２０ｃは、フリッカの有無に応じてグローバルシャッタとローリングシャッタとを適宜切り替える。図３（ｅ）では、一旦、グローバルシャッタに切り替わった後、フリッカを検出しないため、再度、ローリングシャッタに切り替わった様子を表している。これは、例えば、蛍光灯下での動画を撮影中、照明が蛍光灯からタングステン光になった場合などに適用される。また、例えば、蛍光灯下で部屋の中にいる被写体の動画を撮影中、被写体が部屋から庭に出て、太陽光下での動画の撮影になった場合などに適用される。 In this way, in acquiring moving images, the accumulation time control unit 20c appropriately switches between the global shutter and the rolling shutter according to the presence or absence of flicker. FIG. 3E shows a state in which, after switching to the global shutter, flicker is not detected, so that switching to the rolling shutter is performed again. This is applied, for example, when the illumination is changed from a fluorescent lamp to tungsten light while shooting a moving image under a fluorescent lamp. In addition, for example, the present invention is applied to a case where a subject moves out of the room into the garden while shooting a moving image under sunlight, while shooting a moving image of the subject in the room under a fluorescent lamp.
　以上、第１実施形態の電子カメラ１によれば、蛍光灯によるフリッカの発生を抑止し、コマ落ちの少ない動画像の取得を行うことができる。また、第１実施形態の電子カメラ１によれば、ビット数制御部２０ｄが、Ａ／Ｄ変換部１４の出力信号のビット数を、動画像の撮像時と比較してフリッカ検出画像の撮像時には減らして出力させるため、データ処理の高速化を実現できる。 As described above, according to the electronic camera 1 of the first embodiment, it is possible to suppress the occurrence of flicker due to a fluorescent lamp and to acquire a moving image with few frame dropping. Further, according to the electronic camera 1 of the first embodiment, the bit number control unit 20d compares the number of bits of the output signal of the A / D conversion unit 14 when capturing a flicker detection image as compared to when capturing a moving image. Since the output is reduced, the data processing speed can be increased.
　なお、フリッカ検出部２０ｂは、フリッカ検出の有無を１フレームの画像で判定したが、例えば、３フレーム分連続してフリッカを検出したら、蓄積時間制御部２０ｃが、ローリングシャッタからグローバルシャッタに切り替えるようにしてもよい。すなわち、フリッカ検出に用いるフレーム数を任意に設定してもよい。
（第１の変形例）
　次に、第１の変形例について説明する。第１の変形例では、ＣＰＵ２０は、アドレス指定により所定のライン数を読み出す窓検出機能を用いて、フリッカ検出画像をローリングシャッタにより撮像する。具体的には、露光制御部２０ａは、フリッカを少なくとも検出可能な予めアドレス指定された読み出しライン数に対して、所定のラインごとに、シャッタ速度が異なる第１シャッタ速度と第２シャッタ速度とを交互に切り替えて順次露光制御する。 Note that the flicker detection unit 20b determines the presence or absence of flicker detection from an image of one frame. For example, when flicker is detected continuously for three frames, the accumulation time control unit 20c switches from the rolling shutter to the global shutter. It may be. That is, the number of frames used for flicker detection may be set arbitrarily.
(First modification)
Next, a first modification will be described. In the first modification, the CPU 20 captures a flicker detection image with a rolling shutter using a window detection function for reading a predetermined number of lines by addressing. Specifically, the exposure control unit 20a sets a first shutter speed and a second shutter speed with different shutter speeds for each predetermined line with respect to the number of readout lines addressed in advance at which flicker can be detected at least. The exposure is sequentially controlled by switching alternately.
　図７は、窓読み出し機能の一例を説明する図である。図７は、例えば、シャッタ速度ｎ／１００ｓｅｃで撮像した動画像（１フレーム）を表している。この場合、上述した通り、５０Ｈｚの蛍光灯下であるとフリッカは、発生しない。しかしながら、６０Ｈｚの蛍光灯下であるとフリッカが発生する。図７では、点線の部分がフリッカ成分の濃いラインを表しており、実線がフリッカ成分の薄いラインを表している。このように、動画撮影時のフレームレートに応じて、１画面中にフリッカが複数本発生することとなる。 FIG. 7 is a diagram for explaining an example of the window reading function. FIG. 7 shows a moving image (one frame) captured at a shutter speed n / 100 sec, for example. In this case, as described above, flicker does not occur under a 50 Hz fluorescent lamp. However, flickering occurs under a 60 Hz fluorescent lamp. In FIG. 7, the dotted line portion represents a dark line with a flicker component, and the solid line represents a thin line with a flicker component. As described above, a plurality of flickers occur in one screen according to the frame rate at the time of moving image shooting.
　そこで、フリッカの有無を検出する場合、１画面分を撮像しなくても、窓読み出し機能を用いて、フリッカを少なくとも検出可能なライン数だけ撮像すればよいことがわかる。 Therefore, when detecting the presence or absence of flicker, it is understood that it is sufficient to capture at least the number of lines that can detect flicker using the window readout function without imaging one screen.
　したがって、図２に示すステップＳ１０２において、フリッカ検出画像を１画面分、撮像するのではなく、フリッカを少なくとも検出可能なライン数だけ撮像する。このライン数は、蛍光灯の周波数やフレームレートに応じて変化するが、公知の方法で算出することができる。 Therefore, in step S102 shown in FIG. 2, the flicker detection image is not captured for one screen, but at least the number of lines capable of detecting flicker is captured. The number of lines varies depending on the frequency of the fluorescent lamp and the frame rate, but can be calculated by a known method.
　そして、フリッカ検出部２０ｂは、フリッカを少なくとも検出可能なライン数で撮像されたフリッカ検出画像を、第１シャッタ速度（１／１００ｓｅｃ）で撮像した画像と、第２シャッタ速度（１／１２０ｓｅｃ）で撮像した画像とに分けた後、輝度値の差分に基づいて、フリッカの有無を検出する。 Then, the flicker detection unit 20b captures the flicker detection image captured with at least the number of lines capable of detecting flicker at the first shutter speed (1/100 sec) and the second shutter speed (1/120 sec). After being divided into captured images, the presence or absence of flicker is detected based on the difference in luminance values.
　図８は、第１の変形例におけるフリッカ検出を用いた動画撮影の一例を示す図である。水平方向が経過時間を表し、垂直方向が、各水平ラインを表している。 FIG. 8 is a diagram showing an example of moving image shooting using flicker detection in the first modification. The horizontal direction represents elapsed time, and the vertical direction represents each horizontal line.
　図８（ａ）に示すように、動画像を１フレーム撮像した後、フリッカを少なくとも検出可能なライン数だけ撮像したフリッカ検出画像を撮像する。ここで、フリッカを検出した場合には、図８（ｂ）に示すように蓄積時間制御部２０ｃは、グローバルシャッタに切り替える。さらに、その後、フリッカを検出しなくなった場合には、図８（ｃ）に示すように蓄積時間制御部２０ｃは、ローリングシャッタに切り替える。 As shown in FIG. 8A, after one frame of a moving image is captured, a flicker detection image is captured in which at least the number of lines capable of detecting flicker is captured. Here, when flicker is detected, as shown in FIG. 8B, the accumulation time control unit 20c switches to the global shutter. Further, when flicker is not detected thereafter, the accumulation time control unit 20c switches to the rolling shutter as shown in FIG.
　以上より、第１の変形例の電子カメラ１によれば、フリッカ検出画像の撮像時間を短縮してフリッカを検出することができるので、第１実施形態の電子カメラ１に比べて、フレームレートを上げることが可能となる。そのため、第１の変形の電子カメラ１においても、蛍光灯によるフリッカの発生を抑止し、コマ落ちの少ない動画像の取得を行うことができる。 As described above, according to the electronic camera 1 of the first modification, flicker can be detected by shortening the imaging time of the flicker detection image, so that the frame rate is higher than that of the electronic camera 1 of the first embodiment. It is possible to raise. Therefore, even in the first modified electronic camera 1, it is possible to suppress the occurrence of flicker due to a fluorescent lamp and obtain a moving image with few frames dropped.
　（第２実施形態）
　次に、本発明の第２実施形態について説明する。なお、本発明の第１実施形態と本発明の第２実施形態とでは、同じ要素については同じ符号を付して説明を省略する。 (Second Embodiment)
Next, a second embodiment of the present invention will be described. In the first embodiment of the present invention and the second embodiment of the present invention, the same elements are denoted by the same reference numerals and description thereof is omitted.
　第２実施形態では、フリッカ検出部２０ｂがフリッカを検出した場合、先ず、蓄積時間制御部２０ｃは、フリッカ検出画像に基づいて蛍光灯の電源周波数を算出する。続いて、蓄積時間制御部２０ｃは、蓄積時間を電源周波数の任意の整数倍に設定するとともに、ローリングシャッタにより蓄積時間を制御することを特徴とする。 In the second embodiment, when the flicker detection unit 20b detects flicker, the accumulation time control unit 20c first calculates the power supply frequency of the fluorescent lamp based on the flicker detection image. Subsequently, the accumulation time control unit 20c is characterized in that the accumulation time is set to an arbitrary integer multiple of the power supply frequency and the accumulation time is controlled by a rolling shutter.
　図９は、第２実施形態におけるフリッカ検出を用いた動画撮影の一例を示す図である。水平方向が経過時間を表し、垂直方向が、各水平ラインを表している。 FIG. 9 is a diagram illustrating an example of moving image shooting using flicker detection in the second embodiment. The horizontal direction represents elapsed time, and the vertical direction represents each horizontal line.
　説明をわかりやすくするため、５０Ｈｚの蛍光灯下で、第２シャッタ速度（１／１２０ｓｅｃ）の整数倍で動画撮影している場合を想定する。この場合、５０Ｈｚの蛍光灯下では、フリッカ検出画像において、１／１２０ｓｅｃで撮像した第２の画像にフリッカが生成することになる。この場合、第１の画像と第２の画像の差分をとった差分画像において、フリッカ成分の濃淡が周期的に変化することから、この周期より電源周波数を算出することができる。つまり、この例では電源周波数は、５０Ｈｚとなる。 In order to make the explanation easy to understand, it is assumed that a movie is being shot at a multiple of the second shutter speed (1/120 sec) under a 50 Hz fluorescent lamp. In this case, under a 50 Hz fluorescent lamp, flicker is generated in the second image captured at 1/120 sec in the flicker detection image. In this case, in the difference image obtained by taking the difference between the first image and the second image, the density of the flicker component changes periodically, so that the power supply frequency can be calculated from this cycle. That is, in this example, the power supply frequency is 50 Hz.
　そこで、図９に示すように、動画撮影のシャッタ速度を第１シャッタ速度（１／１００ｓｅｃ）の整数倍に切り替えて動画撮影を行えば、動画像のフレームには、フリッカは現れなくなる。 Therefore, as shown in FIG. 9, if moving image shooting is performed by switching the shutter speed for moving image shooting to an integral multiple of the first shutter speed (1/100 sec), flicker does not appear in the frame of the moving image.
　以上より、第２実施形態の電子カメラ１によれば、フリッカ検出画像から、蛍光灯の電源周波数を算出することができる。これにより、電子カメラ１では、動画像の撮像の蓄積時間を蛍光灯の電源周波数の整数倍に設定すれば、フリッカ検出時にグローバルシャッタに切り替える必要がなくなるため、フレームレートを第１実施形態の電子カメラ１に比べて上げることが可能となる。そのため、第２実施形態の電子カメラ１においても、蛍光灯によるフリッカの発生を抑止し、コマ落ちの少ない動画像の取得を行うことができる。 As described above, according to the electronic camera 1 of the second embodiment, the power frequency of the fluorescent lamp can be calculated from the flicker detection image. As a result, in the electronic camera 1, if the accumulation time for capturing moving images is set to an integral multiple of the power supply frequency of the fluorescent lamp, there is no need to switch to the global shutter when flicker is detected. It becomes possible to raise compared to the camera 1. Therefore, also in the electronic camera 1 of the second embodiment, it is possible to suppress the occurrence of flicker due to a fluorescent lamp and to acquire a moving image with few frames dropped.
１・・・電子カメラ、１２・・・撮像素子、１５・・・信号処理部、２０ａ・・・露光制御部、２０ｂ・・・フリッカ検出部、２０ｃ・・蓄積時間制御部、２０ｄ・・・ビット数制御部
  DESCRIPTION OF SYMBOLS 1 ... Electronic camera, 12 ... Image sensor, 15 ... Signal processing part, 20a ... Exposure control part, 20b ... Flicker detection part, 20c .... Accumulation time control part, 20d ... Bit number control part

Claims (7)

  1. 　複数の画素を２次元的に配列し、アドレス指定によりライン読み出しが可能な撮像素子と、
    　前記撮像素子への露光を電子的に制御する複数のシャッタ機能を有する電子シャッタと、
    　所定のフレームレートで動画像を前記撮像素子に撮像させるとともに、光源の周期的な輝度変化に起因するフリッカを検出するためのフリッカ検出画像を、連続する前記動画像の撮像の合間を利用して前記撮像素子に撮像させる撮像素子駆動部と、
    　前記フリッカ検出画像の撮像時には、前記アドレス指定により所定のラインごとに、前記電子シャッタのシャッタ速度が異なる第１シャッタ速度と第２シャッタ速度とを交互に切り替えて順次露光制御する、フリッカ検出用の露光制御部と、
    　前記第１シャッタ速度で撮像した第１画像と前記第２シャッタ速度で撮像した第２画像とで構成される前記フリッカ検出画像に基づいて、前記フリッカの有無を検出するフリッカ検出部と、
    　前記フリッカ検出部の検出結果に応じて、前記動画像を撮像するための前記撮像素子の蓄積時間を前記電子シャッタにより制御する蓄積時間制御部と、
    　を備えることを特徴とする撮像装置。     An image sensor that two-dimensionally arranges a plurality of pixels and can read lines by addressing;
    An electronic shutter having a plurality of shutter functions for electronically controlling exposure to the image sensor;
    A flicker detection image for detecting a flicker caused by a periodic change in luminance of a light source is captured using the interval between successive capturing of the moving image while causing the image sensor to capture a moving image at a predetermined frame rate. An image sensor driving unit that causes the image sensor to image;
    When capturing the flicker detection image, the first shutter speed and the second shutter speed with different shutter speeds of the electronic shutter are alternately switched for each predetermined line according to the address designation, and exposure control is performed sequentially. An exposure control unit;
    A flicker detection unit configured to detect the presence or absence of the flicker based on the flicker detection image composed of a first image captured at the first shutter speed and a second image captured at the second shutter speed;
    An accumulation time control unit that controls an accumulation time of the image sensor for capturing the moving image by the electronic shutter according to a detection result of the flicker detection unit;
    An imaging apparatus comprising:
  2. 　請求項１に記載の撮像装置において、
    　前記蓄積時間制御部は、前記フリッカ検出部が前記フリッカを検出した場合、全ての画素信号を一括して読み出すことにより前記蓄積時間を制御することを特徴とする撮像装置。     The imaging device according to claim 1,
    The image pickup apparatus, wherein the accumulation time control unit controls the accumulation time by reading all pixel signals at once when the flicker detection unit detects the flicker.
  3. 　請求項１に記載の撮像装置において、
    　前記蓄積時間制御部は、前記フリッカ検出部が前記フリッカを検出しない場合、前記ラインごとに順次シャッタを切り、前記ラインごとの画素信号を読み出すことにより、前記蓄積時間を制御することを特徴とする撮像装置。     The imaging device according to claim 1,
    The accumulation time control unit controls the accumulation time by sequentially releasing a shutter for each line and reading a pixel signal for each line when the flicker detection unit does not detect the flicker. Imaging device.
  4. 　前記蓄積時間制御部は、前記フリッカ検出部が前記フリッカを検出した場合、前記フリッカ検出画像に基づいて前記光源の電源周波数を算出し、前記蓄積時間を前記電源周波数の任意の整数倍に設定するとともに、前記ラインごとに順次シャッタを切り、前記ラインごとの画素信号を読み出すことにより、前記蓄積時間を制御することを特徴とする撮像装置。 When the flicker detection unit detects the flicker, the accumulation time control unit calculates a power frequency of the light source based on the flicker detection image, and sets the accumulation time to an arbitrary integer multiple of the power frequency. In addition, the accumulation time is controlled by sequentially releasing the shutter for each line and reading the pixel signal for each line.
  5. 　請求項１に記載の撮像装置において、
    　前記露光制御部は、予めアドレス指定された、前記フリッカを少なくとも検出可能な読み出しライン数に対して、前記所定のラインごとに、前記第１シャッタ速度と前記第２シャッタ速度とを交互に切り替えて順次露光制御することを特徴とする撮像装置。     The imaging device according to claim 1,
    The exposure control unit alternately switches the first shutter speed and the second shutter speed for each predetermined line with respect to the number of readout lines that are pre-addressed and capable of detecting at least the flicker. An image pickup apparatus that performs sequential exposure control.
  6. 　請求項１から請求項５のいずれか１項に記載の撮像装置において、
    　前記第１シャッタ速度は、ｎ／１００ｓｅｃであり、前記第２シャッタ速度は、ｍ／１２０ｓｅｃであり、前記ｎ及び前記ｍが任意の整数であることを特徴とする撮像装置。     In the imaging device according to any one of claims 1 to 5,
    The first shutter speed is n / 100 sec, the second shutter speed is m / 120 sec, and the n and the m are arbitrary integers.
  7. 　請求項１から請求項６のいずれか１項に記載の撮像装置において、
    　アナログ／デジタル変換の出力信号のビット数を、前記動画像の撮像時と比較してフリッカ検出画像の撮像時には減らして出力させるビット数制御部をさらに備えることを特徴とする撮像装置。     The imaging apparatus according to any one of claims 1 to 6,
    An image pickup apparatus, further comprising: a bit number control unit configured to reduce and output the number of bits of an output signal of analog / digital conversion when a flicker detection image is captured compared to when capturing a moving image.
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